Control Valve Apparatus

Abstract

In a hydraulic system equipped with a main flow passage for feeding oil to each of lubricated engine parts and a branch passage branched from the main flow passage, a control valve apparatus is provided for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point. The control valve apparatus is configured to control openings of a large flow control section and a small flow control section, depending on a position of a valve element, and further configured to close the opening of the small flow control section, at least in a specified state where the opening of the large flow control section is fully opened with a maximum opening area.

Description

TECHNICAL FIELD

The present invention relates to a control valve apparatus configured to control fluid flow (lubricating and/or working oil flow).

BACKGROUND ART

It is generally known that, in a hydraulic system with a main fluid-flow passage for feeding oil (lubricating oil) to moving parts of an internal combustion engine requiring lubrication and a branch passage branched from the main flow passage for feeding oil (working oil) to a hydraulic actuator, a control valve apparatus is disposed in the main flow passage downstream of a branched point of the branch passage from the main flow passage, for controlling a flow rate of oil flowing through the main flow passage downstream of the branched point. One such control valve apparatus has been disclosed in Japanese Patent Provisional Publication No. 57-173513 (hereinafter is referred to as “JP57-173513”), corresponding to U.S. Pat. No. 4,452,188, issued on Jun. 5, 1984. In the control valve apparatus (the oil-feed control apparatus) disclosed in JP57-173513, when the flow rate of oil fed into the main flow passage is limited, the flow rate of oil flowing through the main flow passage downstream of the branched point is limited to an amount of oil passing through a bypass passage (an orifice) by means of the control valve apparatus. As a result of this, oil can be preferentially fed into the branch passage, thereby enhancing the responsiveness of a hydraulic actuator, to which oil (working oil) is delivered by way of the branch passage.

SUMMARY OF THE INVENTION

However, in the case of the apparatus as disclosed in JP57-173513, there is a risk of the insufficient flow-rate adjustment.

It is, therefore, in view of the previously-described disadvantages of the prior art, an object of the invention to provide a control valve apparatus capable of enhancing a function of flow-rate adjustment.

In order to accomplish the aforementioned and other objects of the present invention, in a hydraulic system equipped with a main flow passage for feeding oil, discharged from an oil pump driven by an internal combustion engine, to each of lubricated engine parts, a branch passage branched from the main flow passage at a branched point, and a hydraulic actuator operated by a hydraulic pressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point,

the control valve apparatus configured to control an opening of a large flow control section and an opening of a small flow control section whose opening area is less than that of the large flow control section, depending on a position of a valve element disposed in the portion of the main flow passage downstream of the branched point, and

the control valve apparatus further configured to close the opening of the small flow control section, at least in a specified state where the opening of the large flow control section is fully opened with a maximum opening area.

According to another aspect of the invention, in a hydraulic system equipped with a main flow passage for feeding oil, discharged from an oil pump driven by an internal combustion engine, to each of lubricated engine parts, a branch passage branched from the main flow passage at a branched point, and a hydraulic actuator operated by a hydraulic pressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point,

the control valve apparatus comprising a sliding-contact bore into which an inlet of the main flow passage opens and from which an outlet of the main flow passage opens, and a spool installed to axially move in the sliding-contact bore only as needed, the sliding-contact bore and the spool both disposed in the portion of the main flow passage downstream of the branched point, and the spool has a first communication passage intercommunicating the inlet and the outlet and a second communication passage intercommunicating the inlet and the outlet and having an opening area less than an opening area of the first communication passage,

the control valve apparatus configured to bring the first communication passage to a communicated state and simultaneously to bring the second communication passage to a non-communicated state, in a first state where the spool has moved with a maximum displacement in one axial direction of the spool, and

the control valve apparatus further configured to bring the second communication passage to a communicated state and simultaneously to bring the first communication passage to a non-communicated state, in a second state where the spool has moved with a maximum displacement in the opposite axial direction of the spool.

According to a further aspect of the invention, in a hydraulic system equipped with a main flow passage for feeding oil, discharged from an oil pump driven by an internal combustion engine, to each of lubricated engine parts, a branch passage branched from the main flow passage at a branched point, and a hydraulic actuator operated by a hydraulic pressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point,

the control valve apparatus comprising a sliding-contact bore into which an inlet of the main flow passage opens and from which an outlet of the main flow passage opens, and a spool installed to axially move in the sliding-contact bore selectively between two opposite axial positions only as needed, the sliding-contact bore and the spool both disposed in the portion of the main flow passage downstream of the branched point, and the spool has a first communication passage intercommunicating the inlet and the outlet and a second communication passage intercommunicating the inlet and the outlet and having an opening area less than an opening area of the first communication passage,

the control valve apparatus configured to bring the first communication passage to a communicated state and simultaneously to bring the second communication passage to a non-communicated state, in a first state where the spool has moved to one of the two opposite axial positions, and

the control valve apparatus further configured to bring the second communication passage to a communicated state and simultaneously to bring the first communication passage to a non-communicated state, in a second state where the spool has moved to the opposite axial position.

The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic system diagram illustrating a hydraulic system configuration of the embodiment, including a main fluid-flow passage, a branch passage, a hydraulic actuator such as a variable valve timing control (VTC) device (cross-sectioned along the line I-I of FIG. 2), and a control valve apparatus.

FIG. 2 is a front elevation view illustrating the VTC device incorporated in the hydraulic system of the embodiment and kept at its maximum phase-retard position.

FIG. 3 is a front elevation view illustrating the VTC device incorporated in the hydraulic system of the embodiment and kept at its maximum phase-advance position.

FIG. 4 is a partial cross-section of the control valve apparatus of the embodiment, whose spool is controlled to a large flow-rate side.

FIG. 5 is a partial cross-section of the control valve apparatus of the embodiment, whose spool is controlled to a small flow-rate side.

FIG. 6 is a partial cross-section of a control valve apparatus of a second comparative example, whose spool is controlled to a small flow-rate side.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, particularly to FIG. 1, a control valve apparatus 1 of the embodiment can be applied to a hydraulic system of an internal combustion engine of an automotive vehicle.

As can be seen from the hydraulic system configuration of FIG. 1, the hydraulic system is comprised of a hydraulically-operated variable valve timing control (VTC) device for variably controlling engine valve timing (valve open timing and/or valve closure timing), moving engine parts requiring lubrication (hereinafter is referred to as “lubricated engine parts”), and an oil supply-and-exhaust mechanism 5 for supplying and exhausting pressure oil (lubricating/working oil) to and from each of lubricated engine parts and the VTC device. The upper-right cross-section of FIG. 1 shows the partial cross-section taken along the line I-I of FIG. 2, passing through the rotation axis “O” of the VTC device of the intake valve side.

The VTC device is a hydraulically-operated phase-converter that continuously varies a relative angular phase of a camshaft 65 to a crankshaft of the engine, by hydraulic pressure of working oil fed to the VTC device. The VTC device includes a sprocket 91 driven by the crankshaft via a timing chain and configured to be relatively rotatable with respect to the camshaft 65, and a phase-change mechanism installed between sprocket 91 and camshaft 65 to change a relative angular phase of camshaft 65 to sprocket 91 (the crankshaft). The VTC device is a hydraulic actuator, which is hydraulically operated by supplying and exhausting working oil to and from the phase-change mechanism via the oil supply-and-exhaust mechanism 5.

The phase-change mechanism includes a phase-converter housing HSG (a housing member) and a vane member 6 accommodated in the housing HSG. A plurality of working oil chambers (exactly, phase-advance chambers A1-A4, which are collectively referred to as “phase-advance chamber A”, and phase-retard chambers R1-R4, which are collectively referred to as “phase-retard chamber R”,) are defined by vanes 61-64 and housing HSG. A change in working oil pressure, acting on each of the vanes, takes place by the oil supply or oil exhaust to or from the working oil chambers. As a result, vane member 6 (the camshaft side) is relatively rotated with respect to housing HSG (the crankshaft side) by a given angle. Under this condition, torque transmission between them is made. In this manner, a phase of rotation of camshaft 65 to a phase of rotation of the crankshaft can be changed.

Oil supply-and-exhaust mechanism 5 is configured to hydraulically operate the VTC device by adjusting the working oil supply-and-exhaust to and from the phase-change mechanism. That is, a volume change in each of the plurality of working oil chambers occurs by selectively supplying working oil to either phase-advance chambers A1-A4 or phase-retard chambers R1-R4 or by selectively exhausting working oil from either phase-advance chambers A1-A4 or phase-retard chambers R1-R4 by means of oil supply-and-exhaust mechanism 5, with the result that vane member 6 can be relatively rotated with respect to housing HSG by a predetermined angle in a normal-directional direction or in a reverse-rotational direction. The working oil supply and exhaust, achieved through the oil supply-and-exhaust mechanism 5, is controlled by control means (concretely, a central processing unit) incorporated in an electronic control unit CU (hereinafter referred to as “controller”).

Oil supply-and-exhaust mechanism 5 includes an oil pump P (serving as a hydraulic pressure source), fluid-flow passages (oil passages) and various valves.

Oil pump P (hereinafter referred to as “pump”) is driven by power transmitted from the engine crankshaft, for discharging engine oil (hereinafter referred to as “oil”). For instance, a variable displacement single-direction vane pump that allows for only one direction of pump rotation, can be used as the pump P. It will be appreciated that pump P is not limited to such a rotary type vane pump. In lieu thereof, a gear-type oil pump, such as an external gear pump or an internal gear pump, may be used.

As the oil passages, oil supply-and-exhaust mechanism 5 includes an inlet passage 52, a supply passage 53 for feeding oil to each of lubricated engine parts, a supply passage 54 for feeding oil to the VTC device, and an exhaust passage 57 for exhausting (draining) oil from the VTC device.

As the various valves, oil supply-and-exhaust mechanism includes the control valve apparatus 1, a pressure relief valve 58, and a directional control valve 59. Inlet passage 52 is configured to interconnect an inlet of pump P and an oil pan O/P detachably installed as a lower part of an engine block EB. Supply passage 53 is configured to interconnect an outlet of pump P and each of lubricated engine parts.

Pump P draws oil from the oil pan O/P via the inlet passage 52 during operation (during rotation), and then discharges (feeds) a pressurized high-pressure oil to the supply passage 53. That is, pump P is provided to force-feed oil in the oil pan O/P to the supply passage 53.

Assume that, regarding an oil flow line, the side of pump P, which supplies oil, is called “upstream side”, and the opposite side, to which oil is supplied, is called “downstream side”.

Supply line 53 is a main fluid-flow passage to which oil discharged from pump P is introduced and which is configured to feed the oil to each of lubricated engine parts.

An oil filter O/F is disposed in the supply passage 53 to remove any impurities from the oil discharged from pump P.

One end of a bypass passage 55 is connected to a midpoint of the portion of supply passage 53 between oil filter O/F and pump P, whereas the other end of bypass passage 55 is connected to the inlet passage 52. Relief valve 58 is disposed in the bypass passage 55. Relief valve 58 is a normally-closed valve, which is automatically opened when a pressure of the oil, discharged from pump P into supply passage 53, exceeds a specified limit (a set pressure of relief valve 58), to relieve the oil from the supply passage 53 back to the oil pan O/P, thereby preventing the pressure in supply passage 53 (the internal pressure of the hydraulic system) from increasing beyond the specified value.

Supply passage 54 for oil supply to the VTC device is branched from a branched point 530 of supply passage 53 at the downstream side of oil filter O/F. In other words, supply passage 53, extending from pump P, is branched into an oil supply line for lubricating-oil supply to each of lubricated engine parts and an oil supply line (i.e., supply passage 54) for working/lubricating oil supply to the VTC device.

Control valve apparatus 1 is disposed in the supply passage 53 downstream of the branched point 530. The portion of supply passage 53, extending from control valve apparatus 1 toward the upstream side, is hereinafter represented as “supply passage 53a”, whereas the portion of supply passage 53, extending from control valve apparatus 1 toward the downstream side, is hereinafter represented as “supply passage 53b”.

The upstream supply passage 53a communicates the outlet of pump P. That is, the upstream supply passage 53a serves as a pump-flow introductory portion.

The downstream supply passage 53b is connected to the upstream supply passage 53a and also connected to a main oil gallery formed in the engine. In lieu thereof, the downstream supply passage 53b in itself may be a main oil gallery. That is, the downstream supply passage 53b serves as a lubricating oil passage for feeding the oil in the upstream supply passage 53a to each of lubricated engine parts. Supply passage 54 is a branch passage, which is branched from the supply passage 53a for feeding the oil in supply passage 53a to the VTC device. Control valve apparatus 1 is provided to adjust or control a flow rate of oil flowing through the supply passage 53 downstream of the branched point 530, in other words, a flow rate of oil flowing through the downstream supply passage 53b.

The downstream end of supply passage 54 is connected to the directional control valve 59. Directional control valve 59 is connected to the VTC device through a dual hydraulic-circuit system, namely, a phase-retard passage 50 provided for working/lubricating oil supply-and-exhaust to and from each of phase-retard chambers R1-R4, and a phase-advance passage 51 provided for working/lubricating oil supply-and-exhaust to and from each of phase-advance chambers A1-A4. Additionally, an oil-exhaust passage (simply, a drain passage) 57 is connected to the directional control valve 59. The downstream end of drain passage 57 communicates the oil pan O/P.

Directional control valve 59 is a direct-operated electromagnetic solenoid valve (a four-port three-position spring-offset directional control valve) that is configured to control switching between fluid-communication of supply passage 54 and phase-retard passage 50 and fluid-communication of supply passage 54 and phase-advance passage 51, and simultaneously to control switching between fluid-communication of exhaust passage 57 and phase-advance passage 51 and fluid-communication of exhaust passage 57 and phase-retard passage 50.

Directional control valve 59 is comprised of a valve body fixedly connected to a cylinder head of the engine, a solenoid SOL fixedly installed on the valve body, and a spool (a valve element) slidably accommodated in the valve body. The valve body has four ports formed therein, that is, a supply port 590 communicating the supply passage 54, a first port 591 communicating the phase-retard passage 50, a second port 592 communicating the phase-advance passage 51, and an exhaust port 593 communicating the exhaust passage 57

Solenoid SQL is connected to controller CU via a harness, so as to shift (move) the spool, when solenoid SQL is energized. Under a de-energized state of solenoid SQL, by the spring force of a return spring RS, the spool is forced (biased) to its original position (a spring offset position) at which fluid-communication between supply port 590 (supply passage 54) and first port 591 (phase-retard passage 50) is established and fluid-communication between second port 592 (phase-advance passage 51) and exhaust port 593 (exhaust passage 57) is established. Conversely under an energized state of solenoid SOL, responsively to a control current from controller CU, the spool can be moved against the spring force of return spring RS apart from the spring-offset position, and then held at its fully-energized position at which fluid-communication between supply port 590 (supply passage 54) and second port 592 (phase-advance passage 51) is established and fluid-communication between first port 591 (phase-retard passage 50) and exhaust port 593 (exhaust passage 57) is established, or held at a given intermediate position within its entire stroke range. With the spool held at the given intermediate position, first and second ports 591 and 592 are both closed.

Controller CU (the electronic control unit) generally comprises a microcomputer. Controller CU includes an input/output interface (I/O), memories (RAM, ROM), and a microprocessor or a central processing unit (CPU). The input/output interface (I/O) of controller CU receives input information from various engine/vehicle sensors, namely, a crank angle sensor (a crankshaft position sensor), an airflow meter (an airflow sensor), a throttle opening sensor (a throttle position sensor), and an engine temperature sensor (such as an engine coolant temperature sensor). The crank angle sensor is provided for detecting engine speed, and the airflow meter is provided for detecting a quantity of intake air. Within controller CU, the central processing unit (CPU) allows the access by the I/O interface of input informational data signals from the previously-discussed engine/vehicle sensors. For instance, on the basis of sensor signals from the engine/vehicle sensors, the more recent engine operating condition can be detected.

Controller CU is also configured to output a pulse control current, which is determined depending on the detected engine operating condition, to the solenoid SOL of directional control valve 59, to change the path of flow through the directional control valve (in other words, to carry out flow-path switching control among fluid-flow passages 50, 51, 54, and 57), thus enabling oil to be selectively supplied to either phase-advance chambers A1-A4 or phase-retard chambers R1-R4 or enabling oil to be selectively exhausted from either phase-advance chambers A1-A4 or phase-retard chambers R1-R4. In this manner, a working pressure for the VTC device can be controlled.

Controller CU is further configured to output a control current, which is determined depending on the detected engine operating condition, to a solenoid 34 of a pilot valve 3 (described later) of control valve apparatus 1, to carry out switching control (fluid-flow restricting control) between fluid-flow passages 53 and 54, thus enabling more improved fine control of flow for a flow rate of oil, which is fed to each of lubricated engine parts and/or the VTC device.

The construction of the intake-valve side VTC device incorporated in the hydraulic system of the embodiment is hereinafter described in reference to FIGS. 1-3.

Assuming that the direction of the rotation axis “O” of the VTC device, that is, the direction of the rotation axis of the intake-port camshaft (camshaft 65) is taken as an “X-axis”, a direction of the “X-axis”, directed from the camshaft to the side of installation of the VTC device on the camshaft end, is a positive X-axis direction, whereas the opposite direction of “X-axis” is a negative X-axis direction.

FIGS. 2-3 are front elevation views (as viewed from the positive X-axis direction) illustrating the internal construction of the VTC device incorporated in the hydraulic system of the embodiment, but with a front plate 8 removed. In other words, each of FIGS. 2-3 is a partially-assembled view that a housing body 10 of housing HSG and vane member 6 are assembled and installed on a rear plate 9 of housing HSG. In FIGS. 1 to 3, oil passages formed in the vane member 6, are indicated by the broken line. In the shown embodiment, control valve apparatus 1 can be used for oil-flow control for working oil to be fed to the intake-valve side VTC device. Control valve apparatus 1 may be used for oil-flow control for working oil to be fed to the exhaust-valve side VTC device.

The VTC device is installed on the axial end 65a of camshaft 65, facing in the positive X-axis direction, by means of one cam bolt 66. Cam bolt 66 has a head 660 and a shank 661 consisting of an unthreaded shank portion and a male-screw-threaded portion.

Camshaft end 65a is formed therein with a bolt hole 650 into which the male-screw-threaded portion of shank 661 is screwed. Bolt hole 650 is formed to axially extend from the end face 653 of camshaft end 65a, facing in the positive X-axis direction, to a predetermined depth in the negative X-axis direction. Bolt hole 650 is constructed by a large-diameter cylindrical bore portion 651 and a small-diameter cylindrical bore portion 652, both bored in the camshaft end 65a in that order from the end face 653. The inner periphery of small-diameter cylindrical bore portion 652 is formed with a female-screw-threaded portion into which the male-screw-threaded portion of shank 661 of cam bolt 66 is screwed. Camshaft end 65a has a disk-shaped flanged portion 654 formed at a specified position corresponding to an axial distance measured from the end face 653 in the negative X-axis direction.

The VTC device (the VTC unit) includes the housing HSG, vane member 6, and an oil-passage structural member 5a. Housing HSG is laid out at the camshaft end 65a. Housing HSG has a timing sprocket 91 (a first sprocket described later) formed integral therewith. Sprocket 91 has a driven connection with the crankshaft so that torque is transmitted from the crankshaft to the timing sprocket. Vane member 6 is fixedly connected to the camshaft end 65a by means of cam bolt 66. Vane member 6 is accommodated in the housing HSG, so that relative rotation of vane member 6 to housing HSG is permitted. Oil-passage structural member 5a is a substantially cylindrical block in which a portion of phase-retard passage 50 and a portion of phase-advance passage 51 are formed.

Housing HSG includes front plate 8, rear plate 9, and housing body 10.

Housing body 10 is formed as a cylindrical hollow housing member, opened at both ends in the opposite X-axis directions. Housing body 10 is made of sintered alloy materials, such as iron-based sintered alloy materials. Housing body 10 is integrally formed on its inner periphery with a plurality of radially-inward protruded shoes 11, 12, 13, and 14. Concretely, the four shoes 11-14 are spaced from each other by approximately 90 degrees in the direction around the rotation axis “O” (that is, in the circumferential direction). As seen in FIG. 2, each of shoes 11-14 is formed as a radially-inward protruded partition wall portion extending in the X-axis direction of housing HSG. Each of shoes 11-14 has a substantially trapezoidal shape in lateral cross section, taken in the direction perpendicular to the X-axis direction, and tapered radially inwards. As viewed in the X-axis direction, both side faces of each of shoes 11-14, facing in the circumferential direction, are formed as substantially flat surfaces configured to be conformable to straight lines extending radially (i.e., in the radial direction of housing body 10) outwards from the rotation axis “O”. As viewed from the positive X-axis direction, each of the innermost ends of the radially-inward protruded shoes 11-14, opposing to the rotation axis “O”, are formed as somewhat concave circular-arc end faces, which are configured to be substantially conformable to the shape of the outer periphery of a vane rotor 60 (described later) of vane member 6. As seen in FIG. 2, shoes 11-14 are formed substantially at their centers in trapezoidal lateral cross section with respective bolt insertion holes 110, 120, 130, and 140 (through holes extending in the X-axis direction) into which bolts b are inserted. Front plate 8 is fixedly installed on the left-hand axial end faces (viewing FIG. 1) of shoes 11-14, facing in the positive X-axis direction, whereas rear plate 9 is fixedly installed on the right-hand axial end faces of shoes 11-14, facing in the negative X-axis direction. As seen in FIG. 2, the innermost ends of shoes 11-14 have respective axially-elongated seal retaining grooves 111, 121, 131, and 141, formed substantially in their centers in the circumferential direction and extending in the X-axis direction. Four seal retaining grooves 111, 121, 131, and 141 are formed into a substantially rectangle. Each of seal retaining grooves 111, 121, 131, and 141 is formed over the entire axial length of the associated shoe. Four oil seal members 112, 122, 132, and 142, each having a substantially square lateral cross section, are fitted into respective seal retaining grooves 111, 121, 131, and 141. Additionally, four seal springs, concretely, four leaf springs (not shown), are retained in respective seal retaining grooves 111, 121, 131, and 141, in a manner so as to force four seal members 112, 122, 132, and 142 into abutment (sliding-contact) with the outer peripheral surface of vane rotor 60 over the entire axial length in the X-axis direction. During relative rotation of vane rotor 60 to housing HSG, four seal members 112, 122, 132, and 142 are kept in sliding-contact with the outer peripheral surface of vane rotor 60 by the spring forces of the seal springs. As viewed from the positive X-axis direction, a substantially rectangular cut-out portion 114 is formed in the innermost end of the side face 113 of the first shoe 11, facing in the clockwise direction.

Front plate 8 is a housing member that hermetically closes the opening end of housing body 10, facing in the positive X-axis direction, in other words, the leftmost ends (viewing FIG. 1) of phase-advance chamber A and phase-retard chamber R, facing in the positive X-axis direction. Front plate 8 is formed into a substantially disk shape by press-working steel materials. Front plate 8 has a centrally-bored, large-diameter bolt insertion hole (an axial through hole) 80 into which cam bolt 66 and oil-passage structural member 5a are both inserted during assembling of the VTC device. Additionally, front plate 8 is formed with circumferentially equidistant-spaced, four bolt holes (through holes extending in the X-axis direction), which are configured to be opposed to respective bolt insertion holes 110, 120, 130, and 140 of housing body 10 in the X-axis direction.

Rear plate 9 is a housing member that hermetically closes the opening end of housing body 10, facing in the negative X-axis direction, in other words, the rightmost ends (viewing FIG. 1) of phase-advance chamber A and phase-retard chamber R, facing in the negative X-axis direction, while permitting a rotor shaft portion 60b (described later) of vane rotor 60 to be inserted through the central bore of rear plate 9. Rear plate 9 is made of sintered alloy materials, such as iron-based sintered alloy materials. Rear plate 9 includes a plate body 90, and first and second sprockets 91 and 92.

Plate body 90 includes a disk-shaped portion (on the side of the positive X-axis direction) and a cylindrical portion (on the side of the negative X-axis direction). Plate body 90 is formed with a central stepped bore 93 arranged coaxially with the rotation axis “O”. Stepped bore 93 serves as a rotor supporting bore into which the rotor shaft 60b of vane rotor 60 (vane member 6) is inserted so that rotor shaft 60b is rotatably supported. Concretely, stepped bore 93 is comprised of a main supporting portion (a bearing bore portion) 93a and a rightmost opening end portion 93b (the rightmost end of the negative X-axis direction of stepped bore 93, viewing FIG. 1) whose inside diameter is dimensioned to be greater than that of the main supporting portion 93a.

The inside diameter of main supporting portion 93a of stepped bore 93 is dimensioned to be slightly greater than the outside diameter of rotor shaft 60b.

The inside diameter of rightmost opening end portion 93b of stepped bore 93 is dimensioned to be greater than the outside diameter of the flanged portion 654 of camshaft 65, such that a portion of the flanged portion 654 can be inserted into the rightmost opening end portion 93b.

Plate body 90 of rear plate 9 is formed with circumferentially equidistant-spaced, four bolt holes (female screw-threaded portions formed in the X-axis direction), which are configured to be opposed to respective bolt insertion holes 110, 120, 130, and 140 of housing body 10 in the X-axis direction.

Front plate 8, housing body 10, and rear plate 9 are integrally connected to each other by tightening four bolts b. In more detail, each of four bolts b is inserted into the associated bolt hole of front plate 8 and also inserted into the associated bolt insertion hole of housing body 10 from the positive X-axis direction, and then screwed into the associated female-screw-threaded portion of rear plate 9. In this manner, front plate 8 and rear plate 9 are fixedly connected to housing body 10.

The disk-shaped portion (the side of the positive X-axis direction) of plate body 90 is integrally formed on its outer periphery with the first sprocket 91. The cylindrical portion (the side of the negative X-axis direction) of plate body 90 is integrally formed on its outer periphery with the second sprocket 92.

The outer periphery of first sprocket 91 is formed integral with a toothed portion in meshed-engagement with a first timing chain. In a similar manner, the outer periphery of second sprocket 92 is formed integral with a toothed portion in meshed-engagement with a second timing chain. First sprocket 91 is driven clockwise (viewing FIG. 2) by the crankshaft via the first chain, so that rear plate 9 (housing HSG), integrally formed with first sprocket 91, is rotated in the same rotation direction (i.e., clockwise). Second sprocket 92, together with rear plate 9, is rotated clockwise, so that an exhaust-valve side VTC device is driven via the second chain.

As best seen in FIG. 3, a cylindrical bore 900, which is closed at one axial end and has a predetermined depth in the X-axis direction, is formed at a position of plate body 90 adjacent to the side face of the first shoe 11, facing clockwise.

Vane member 6 serves as a driven rotational member that is rotatable relative to housing HSG. That is, vane member 6, together with camshaft 65, rotates clockwise (viewing FIG. 2). Vane member 6 is comprised of four radially-extending vane blades 61-64 that receive working oil pressure, and vane rotor 60. Vane rotor 60 has an axially-extending central bore 602 (described later) into which cam bolt (vane mounting bolt) 66 is inserted for bolting vane rotor 60 to the camshaft end 65a by axially tightening the cam bolt. The axis of vane rotor 60 is coaxially aligned with the axis of camshaft 65.

Rotor 60 is formed into a substantially cylindrical shape, and comprised of a rotor body 60a and a rotor shaft 60b both coaxially aligned with each other. Rotor body 60a and four vane blades 61-64 are integrally formed with each other. Rotor shaft 60b is integrally formed with the rotor body 60a in such a manner as to extend from the rotor body 60a in the negative X-axis direction.

The outside diameter of rotor body 60a is dimensioned to be slightly greater than the inside diameter of main supporting portion 93a of stepped bore 93 of rear plate 9 and the inside diameter of bolt insertion hole 80 of front plate 8. The outside diameter of rotor shaft 60b is dimensioned to be slightly less than the inside diameter of main supporting portion 93a of stepped bore 93 of rear plate 9.

Rotor 60 has a substantially cylindrical bore 600, extending coaxially with the rotation axis “O”, and opening in the positive X-axis direction and closed at the opposite side. The entire axial length of cylindrical bore 600 is dimensioned to reach a predetermined depth of rotor shaft 60b in the negative X-axis direction. Cylindrical bore 600 is an oil-path configuration bore into which oil-passage structural member 5a of the VTC device is inserted and installed. The left-hand side opening end (viewing FIG. 1) of cylindrical bore 600 is machined as a tapered portion (a beveled or chamfered portion) 604.

Also, rotor 60 has a substantially cylindrical bore 601, extending coaxially with the rotation axis “O”, and opening in the negative X-axis direction and closed at the opposite side. The entire axial length of cylindrical bore 601 is dimensioned to reach a predetermined depth of rotor shaft 60b in the positive X-axis direction. Cylindrical bore 601 is a camshaft insertion bore into which camshaft end 65a is inserted and installed. The axial length of cylindrical bore 601 is dimensioned to be slightly greater than the distance from the end face 655 of camshaft flanged portion 654, facing in the positive X-axis direction, to the end face 653 of camshaft end 65a, facing in the positive X-axis direction. Central bore 602 (a through hole through the rotation axis “O”) is formed in the partition wall through which cylindrical bores 600-601 are divided. Central bore 602 serves as a cam-bolt insertion hole into which cam bolt 66 is inserted.

The head 660 of cam bolt 66 is positioned in cylindrical bore 600, whereas the shank 661 of cam bolt 66 is inserted through central bore 602 into the bolt hole 650 of camshaft 65. Then, the male-screw-threaded portion of shank 661 of cam bolt 66 is screwed into the female-screw-threaded portion of cylindrical bore portion 652 of bolt hole 650. In this manner, rotor 60 is integrally connected to the camshaft end 65a by tightening the cam bolt 66. At this time, the end face 603 of rotor 60, facing in the negative X-axis direction, is brought into abutted-engagement with the end face 655 of camshaft flanged portion 654, facing in the positive X-axis direction.

Rotor 60 is rotatably supported on the housing HSG, while being kept in sliding-contact with each of oil seal members 112, 122, 132, and 142, which are fitted into respective seal retaining grooves 111, 121, 131, and 141 the innermost ends of four shoes 11-14.

Rotor 60 has radially-outward protruded, circumferentially-equidistant spaced four vane blades 61-64 formed on its outer periphery.

Four blades 61-64 are formed integral with rotor body 60a. The axial length of each of blades 61-64, measured in the X-axis direction, is dimensioned to be approximately equal to that of rotor body 60a. With vane member 6 installed in the housing HSG, the axial end face of each of blades 61-64, facing in the positive X-axis direction, and the axial end face of front plate 8, facing in the negative X-axis direction, are opposed to each other by a very small clearance space. In a similar manner, the axial end face of each of blades 61-64, facing in the negative X-axis direction, and the axial end face of rear plate 9 (plate body 9a), facing in the positive X-axis direction, are opposed to each other by a very small clearance space.

As best seen in FIG. 2, in the hydraulically-operated four-blade vane member equipped VTC device, the areas of the outside circumferences of four blades 61-64 of the four-blade vane member 6, in other words, the circumferential widths of four blades 61-64 are dimensioned to be somewhat different from each other. Four blades 61-64 are classified into two sorts, namely a maximum-width blade (that is, the first blade 61) and the remaining narrow-width blades 62-64. The remaining narrow-width blades 62-64 have almost the same circumferential width and the same radial length. Three narrow-width blades 62-64 are configured to be substantially rectangular in lateral cross section. As viewed in the X-axis direction, rounded corners of both side faces of the root of each of narrow-width vane blades 62-64 are further recessed. The first blade 61 is formed as a maximum-width blade whose circumferential width is dimensioned to be greater than that of each of three narrow-width blades 62-64, so as to be able to accommodate a lock mechanism (described later) in the first blade 61. The first blade 61 is configured to have an inverted trapezoidal shape in lateral cross section.

Four blades 61-64 have respective axially-elongated seal retaining grooves 611, 621, 631, and 641, formed in their outermost ends (apexes) and extending in the X-axis direction. Each of four seal retaining grooves 611, 621, 631, and 641 is formed into a substantially rectangle, as viewed in the X-axis direction. Four oil seal members (four apex seals) 612, 622, 632, and 642, each having a substantially square lateral cross section, are fitted into respective seal retaining grooves 611, 621, 631, and 641. Additionally, four seal springs, concretely, four leaf springs (not shown), are retained in respective seal retaining grooves 611, 621, 631, and 641, in a manner so as to force four seal members 612, 622, 632, and 642 into abutment (sliding-contact) with the inner peripheral surface of housing body 10.

As seen in FIG. 2, the first blade 61 has a cylindrical bore 70 formed as a through hole extending in the X-axis direction. The bore 70 serves as a lock-piston sliding-motion permitting bore (simply, a lock-piston bore) in which a retractable lock piston (described later) of a lock mechanism 7 is slidably installed. Lock-piston bore 70 is comprised of a small-diameter chamber 701 formed on the side of the negative X-axis direction and a large-diameter chamber 702 formed on the side of the positive X-axis direction.

The anticlockwise edge of the outermost end of the first blade 61 is formed as a rounded edge having a circular-arc curved surface, whose center is identical to the center of lock-piston bore 70, and which has a radius of curvature greater than the radius of lock-piston bore 70 and is configured to be curved along the circumference of lock-piston bore 70. The circular-arc curved surface of the rounded edge is formed to be continuous with the side face 613 of the first blade 61.

A radial groove 605 is formed in the axial end face of the first blade 61, facing in the positive X-axis direction. Radial groove 605 is a cut-out groove interconnecting the opening end of the positive X-axis direction of lock-piston bore 70 and the opening end of the positive X-axis direction of cylindrical bore 600 of rotor 60.

As viewed in the X-axis direction, four oil chambers are defined by four pairs of two adjacent shoes (11, 12; 12, 13; 13, 14; 14, 11). Each of the four oil chambers is divided into phase-advance chamber A and phase-retard chamber R by the blade disposed between the two adjacent shoes. For instance, the first phase-advance chamber A1 is defined between the side face 113 of the first shoe 11, facing in the clockwise direction, and the side face 613 of the first blade 61, facing in the anticlockwise direction, whereas the first phase-retard chamber R1 is defined between the side face 614 of the first blade 61, facing in the clockwise direction, and the side face 123 of the second shoe 12, facing in the anticlockwise direction. Phase-advance chamber A and phase-retard chamber R are partitioned from each other in a fluid-tight fashion with a less oil leakage by means of oil seal members 112, 122, 132, and 142.

As viewed from the positive X-axis direction, when vane member 6 rotates anticlockwise relative to housing HSG by a predetermined angle or more, the side face 113 of the first shoe 11, facing in the clockwise direction, and the side face 613 of the first blade 61, facing in the anticlockwise direction, are brought into wall-contact with each other (see FIG. 2). With the first-shoe side face 113 and the first-blade side face 613 kept in wall-contact with each other, there is a slight aperture between two opposed side walls of shoe 12 and blade 62, there is a slight aperture between two opposed side walls of shoe 13 and blade 63, and there is a slight aperture between two opposed side walls of shoe 14 and blade 64. The maximum rotary motion of vane member 6 relative to housing HSG in the anticlockwise direction (i.e., in the phase-retard direction), can be restricted by abutment between the side face 113 of the first shoe 11 and the side face 613 of the first blade 61. That is, the side face 113 of the first shoe 11 and the side face 613 of the first blade 61 cooperate with each other to provide a first stopper (an anticlockwise rotary-motion stopper for vane member 6).

Conversely when vane member 6 rotates clockwise relative to housing HSG from the maximum phase-retard position of vane member 6 shown in FIG. 2, the side face 123 of the second shoe 12, facing in the anticlockwise direction, and the side face 614 of the first blade 61, facing in the clockwise direction, are brought into wall-contact with each other (see FIG. 3). With the second-shoe side face 123 and the first-blade side face 614 kept in wall-contact with each other, there is a slight aperture between two opposed side walls of shoe 13 and blade 62, there is a slight aperture between two opposed side walls of shoe 14 and blade 63, and there is a slight aperture between two opposed side walls of shoe 11 and blade 64. The maximum rotary motion of vane member 6 relative to housing HSG in the clockwise direction (i.e., in the phase-advance direction), can be restricted by abutment between the side face 123 of the second shoe 12 and the side face 614 of the first blade 61. That is, the side face 123 of the second shoe 12 and the side face 614 of the first blade 61 cooperate with each other to provide a second stopper (a clockwise rotary-motion stopper for vane member 6).

As discussed above, the maximum anticlockwise rotary motion of vane member 6 relative to housing HSG and the maximum clockwise rotary motion of vane member 6 relative to housing HSG are restricted by means of the first stopper (113, 613) and the second stopper (123, 614).

As can be seen in FIGS. 2-3 shoes 11-14 of housing body 10 and blades 61-64 of vane member 6 are configured so that, over the entire range of relative rotation of vane member 6 to housing HSG, the volume of phase-retard chamber R and the volume of phase-advance chamber A can be both kept at a value greater than “0”, and thus the opening area of a phase-retard oil passage (e.g., a phase-retard oil passage 501 described later), opening into phase-retard chamber R, and the opening area of a phase-advance oil passage (e.g., a phase-advance oil passage 511 described later), opening into phase-advance chamber A, can be ensured. For instance, as seen in FIG. 2, the volume of the first phase-advance chamber A1 and the opening area of the phase-advance oil passage 511 are ensured by a space, defined by the cut-out portion 114 of the first shoe 11. For instance, as seen in FIG. 3, the volume of the first phase-retard chamber R1 and the opening area of the phase-retard oil passage 501 are ensured by an aperture, formed by the difference of radius of curvature between the anticlockwise rounded edge of the innermost end of the second shoe 12 and the clockwise rounded corner of the root of the first blade 61.

A portion of phase-retard passage 50 and a portion of phase-advance passage 51 are formed in each of oil-passage structural member 5a and vane member 6.

Axial passages 50a and 51a, extending in the X-axis direction, are opened at the end face of the negative X-axis direction of oil-passage structural member 5a. The opening end (the rightmost axial end, viewing FIG. 1) of axial passage 51a is hermetically closed by a press-fit ball B1. An internal space 50b is defined between the end face of the negative X-axis direction of oil-passage structural member 5a and the inner peripheral surface of cylindrical bore 600. A groove 51c is an annular circumferential groove formed in the outer peripheral surface of oil-passage structural member 5a at a predetermined axial position somewhat spaced apart from the end face of the negative X-axis direction of oil-passage structural member 5a. A radial passage 51b is formed in oil-passage structural member 5a in a manner so as to intercommunicate axial passage 51a and groove 51c. Axial passage 50a and space 50b construct a portion of phase-retard passage 50, whereas axial passage 51a, radial passage 51b, and groove 51c construct a portion of phase-advance passage 51.

Oil-passage structural member 5a has three circumferential grooves formed in its outer peripheral surface. Oil seals S1-S3 are fitted into the respective circumferential grooves. Oil-passage structural member 5a is installed in cylindrical bore 600 of rotor 60, so that relative rotation of oil-passage structural member 5a to vane member 6 is permitted. The outer peripheral surface of each of oil seals S1-S3 is kept in sliding-contact with the inner peripheral surface of cylindrical bore 600. Oil seals S1-S2 are laid out in a manner so as to sandwich the groove 51c between them, thus ensuring a high fluid-tightness of phase-advance passage 51. Oil seal S3 is laid out near the end face of the negative X-axis direction of oil-passage structural member 5a to ensure a high fluid-tightness of phase-retard passage 50 (in particular, space 50b).

Rotor 60 has radial oil holes 501-504 and radial oil holes 511-514 formed therein. Oil holes 501-504 and 511-514 are radially-extending through holes formed in rotor body 60a. These oil holes intercommunicate the inner peripheral surface of cylindrical bore 600 and the outer peripheral surface of rotor body 60a. Oil holes 501-504 construct a portion of phase-retard passage 50, whereas oil holes 511-514 construct a portion of phase-advance passage 51.

As viewed from the positive X-axis direction, oil holes 501-504 are laid out adjacent to the respective clockwise sides of the roots of the first, second, third, and fourth blades 61-64 (see FIG. 2). The axial positions of oil holes 501-504 are placed near the axial end of the negative X-axis direction of rotor body 60a (see FIG. 1).

As viewed from the positive X-axis direction, oil holes 511-514 are laid out adjacent to the respective anticlockwise sides of the roots of the first, second, third, and fourth blades 61-64 (see FIG. 2). The axial positions of oil holes 511-514 are placed to be slightly offset from the midpoint of rotor body 60a toward the positive X-axis direction (see FIG. 1).

In a state where oil-passage structural member 5a is inserted and installed into cylindrical bore 600 of rotor 60, the inside opening ends of phase-retard side radial oil holes 501-504 are placed in the negative X-axis direction from the oil seal S3 and open into the space 50b. On the other hand, the outside opening ends of phase-retard side radial oil holes 501-504 open into respective phase-retard chambers R1-R4. The inside opening ends of phase-advance side radial oil holes 511-514 are sandwiched between oil seals S1-S2, and opposed to and open into the groove 51c. The outside opening ends of phase-advance side radial oil holes 511-514 open into respective phase-advance chambers A1-A4.

Phase-retard passage 50, extending from directional control valve 59, is communicated with each of phase-retard chambers R1-R4 through axial passage 50a of oil-passage structural member 5a (a non-rotary member), space 50b, and radial oil holes 501-504 of vane member 6 (a rotary member).

Phase-advance passage 51, extending from directional control valve 59, is communicated with each of phase-advance chambers A1-A4 through axial passage 51a of oil-passage structural member 5a, radial passage 51b, groove 51c, and radial oil holes 511-514 of vane member 6.

Lock mechanism 7 is disposed between vane member 6 (exactly, the first blade 61) and rear plate 9 of housing HSG, for disabling rotary motion of vane member 6 relative to rear plate 9 by locking and engaging vane member 6 with housing HSG, and for enabling rotary motion of vane member 6 relative to rear plate 9 by unlocking (or disengaging) vane member 6 from housing HSG. The VTC device is configured in a manner so as to be locked by the lock mechanism 7 at the maximum phase-retard position at which rotary motion of vane member 6 relative to housing HSG is restricted by the first stopper (113, 613).

Lock mechanism 7 is comprised of a retractable lock piston 71, a concavity 730 of rear plate 9, and an engaging-and-disengaging mechanism. The engaging-and-disengaging mechanism operates to engage the lock piston 71 with the concavity 730 via an extension stroke of lock piston 71, depending on an engine operating condition. The engaging-and-disengaging mechanism also operates to disengage the lock piston 71 from the concavity 730 via a retraction stroke of lock piston 71, depending on an engine operating condition.

Lock piston 71 is an iron taper-pin-shaped engaging member, which is formed into a substantially cylindrical hollow shape and closed at one axial end. Lock piston 71 is slidably installed in the lock-piston bore 70 of the first blade 61, so that lock piston 71 can reciprocate or slide in the X-axis direction.

Lock piston 71 is comprised of a cylindrical sliding portion 710 accommodated in the lock-piston bore 70 so that a sliding motion of sliding portion 710 relative to lock-piston bore 70 is permitted, and a tapered head portion 714 going in and out of the lock-piston bore 70. Sliding portion 710 is comprised of a small-diameter portion 711 formed on the side of the negative X-axis direction and a large-diameter portion 712 formed on the side of the positive X-axis direction. Small-diameter portion 711 is formed into a substantially cylindrical hollow shape and closed at one axial end, and opened in the positive X-axis direction. Small-diameter portion 711 is slidably installed in small-diameter chamber 701 of lock-piston bore 70. The substantially circular-truncated-cone-shaped (frusta-conical), tapered head portion 714 is integrally formed on the side of the negative X-axis direction of the bottom (the right-hand closed end, viewing FIG. 1) 713 of small-diameter portion 711. Head portion 714 has a trapezoidal longitudinal cross-section and has a curved surface (a tapered surface) that the diameter of the circle of the frustum decreases in the negative X-axis direction from the bottom (the root of head portion 714) to the top (the tip of head portion 714). Large-diameter portion 712 is a basal portion of lock piston 71, that is, an annular flanged portion formed at the leftmost end of sliding portion 710 in the positive X-axis direction. The outside diameter of large-diameter portion 712 is dimensioned to be greater than that of small-diameter portion 711. Large-diameter portion 712 is slidably installed in large-diameter chamber 702 of lock-piston bore 70.

On the other hand, the previously-discussed concavity 730, which is closed at one axial end, is formed in the end face of rear plate 9, facing in the positive X-axis direction. Concavity 730 is a lock-piston engaging hole into which the head portion 714 of lock piston 71 can be inserted at the maximum phase-retard position of vane member 6 shown in FIG. 2.

Engaging concavity 730 is constructed by an inner periphery of a sleeve 73 (a substantially cylindrical cup-shaped engaging-concavity structural member closed at one axial end). Rear plate 9 is formed with an axially-bored retaining hole 900. That is, sleeve 73 (the cup-shaped engaging-concavity structural member) is press-fitted into the retaining hole 900 of rear plate 9, such that engaging concavity 730 is defined in the cup-shaped sleeve 73.

Engaging concavity 730 has a substantially trapezoidal axial cross section, cut along a plane through the axis of the cup-shaped sleeve 73. Engaging concavity 730 is formed as a tapered hole whose inside diameter gradually increases toward the opening end of the positive X-axis direction. In other words, engaging concavity 730 has a curved surface that the diameter of the circle of the frustum decreases in the negative X-axis direction from the opening end of engaging concavity 730 to the bottom face of cup-shaped sleeve 73. The cone angle of the inner peripheral surface engaging concavity 730 is dimensioned to be approximately identical to that of the outer peripheral surface of head portion 714 of lock piston 71.

When rotary motion of vane member 6 relative to housing HSG in the phase-retard direction occurs and then the maximum rotary motion of vane member 6 in the phase-retard direction is restricted by the first stopper (113, 613), that is, when the volume of phase-advance chamber A1 becomes minimum, as viewed in the X-axis direction, the circumferential position of head portion 714 of lock piston 71 becomes identical to that of engaging concavity 730 of rear plate 9. In other words, the circumferential position of engaging concavity 730 is determined or designed so that, when the head portion 714 of lock piston 71 is brought into engagement with the engaging concavity 730 of rear plate 9, the angular position of vane member 6 relative to housing HSG is brought into an optimal angular position (i.e., the maximum phase-retard position) suited to an engine-startup period.

Fully taking account of the slight difference between the slightly tapering diameter of the inner periphery of engaging concavity 730 and the slightly tapering diameter of the outer periphery of lock-piston head portion 714, that is, in order to reliably keep the locked state of vane member 6 with rear plate 9 (housing HSG) at the maximum phase-retard position, the circumferential position of the axis of engaging concavity 730 of the rear plate side is designed to be slightly offset anticlockwise (viewing FIG. 2) from the axis of lock-piston head portion 714.

A back-pressure chamber 72 for lock piston 71 is also defined in the lock-piston bore 70. Back-pressure chamber 72 is a low-pressure chamber partitioned by lock piston 71 to face in the positive X-axis direction with respect to lock piston 71. Concretely, back-pressure chamber 72 is defined by the axial end face (the inside face) of front plate 8, facing in the negative X-axis direction, the inner peripheral surface of lock-piston bore 70, and the inner peripheral surface of cylindrical sliding portion 710 of lock piston 71.

The engaging-and-disengaging mechanism is comprised of a coiled compression spring 74, serving as an engaging (locking) biasing member, and a communication hole 75 and a communication groove 76, both serving as disengaging (unlocking) oil passages.

A spring retainer 74a is disposed in the back-pressure chamber 72. The basal portion (the head portion) of the positive X-axis direction of spring retainer 74a is kept in sliding-contact with the inside face of front plate 8, whereas the axially-protruding portion of the negative X-axis direction of spring retainer 74a is loosely fitted into the inner periphery of coil spring 74.

Coil spring 74 is disposed in back-pressure chamber 72 under preload. The left-hand axial end of coil spring 74, facing in the positive X-axis direction, is kept in abutted-engagement with the left-hand annular end of the head portion of spring retainer 74a, facing in the negative X-axis direction. The right-hand axial end of coil spring 74, facing in the negative X-axis direction, is kept in abutted-engagement with the bottom (the right-hand closed end, viewing FIG. 1) 713 of small-diameter sliding portion 711 of lock piston 71. Coil spring 74 is a spring-bias member that permanently forces the lock piston 71 in the negative X-axis direction, that is, toward the engaging concavity 730 of rear plate 9.

Also defined in the lock-spring bore 70 are two pressure-receiving chambers, each of which produces a hydraulic pressure acting on the lock piston 71. The first pressure-receiving chamber 77 is defined in the large-diameter chamber 702 of lock-piston bore 70 by the annular end face of small-diameter chamber 701 of lock-piston bore 70, facing in the positive X-axis direction, the annular end face of large-diameter portion 712 of lock piston 71, facing in the negative X-axis direction, the outer peripheral surface of small-diameter sliding portion 711, and the inner peripheral surface of large-diameter chamber 702 of lock-piston bore 70. The second pressure-receiving chamber 78 is defined by the outer peripheral surface of the tapered head portion 714, facing in the negative X-axis direction, and the inner peripheral surface of cup-shaped sleeve 73, facing in the positive X-axis direction.

The first blade 61 is formed with oil passages therein, for introducing hydraulic pressure in the working oil chamber (phase-retard chamber R or phase-advance chamber A) into either the first pressure-receiving chamber 77 or the second pressure-receiving chamber 78. Concretely, the first blade 61 is formed with the circumferentially-extending communication hole 75 through which the first phase-retard chamber R1 and the first pressure-receiving chamber 77 are always intercommunicated to introduce hydraulic pressure in the first phase-retard chamber R1 into the first pressure-receiving chamber 77. In a similar manner, the first blade 61 is also formed with the circumferentially-extending communication groove 76 through which the first phase-advance chamber A1 and the second pressure-receiving chamber 78 are always intercommunicated to introduce hydraulic pressure in the first phase-advance chamber A1 into the second pressure-receiving chamber 78 (into the engaging concavity 730 in the locked state of vane member 6). By the way, even at the maximum phase-retard position, the opening area of the communication groove 76 opening into the first phase-advance chamber A1 is ensured by the space, defined by the cut-out portion 114 of the first shoe 11.

A part of working oil, supplied to the first phase-retard chamber R1, and then introduced through the communication hole 75 into the first pressure-receiving chamber 77, produces a hydraulic pressure that forces lock piston 71 in its retracting direction (i.e., in the positive X-axis direction). In the same manner, a part of working oil, supplied to the first phase-advance chamber A1, and then introduced through the communication groove 76 into the second pressure-receiving chamber 78, also produces a hydraulic pressure that forces lock piston 71 in its retracting direction (i.e., in the positive X-axis direction).

At the maximum phase-retard position of vane member 6, with an extending stroke of the head portion 714 of lock piston 71 out of the first blade 61 (the lock-piston bore 70) by the spring force of coil spring 74, the head portion 714 is inserted into and engaged with the engaging concavity 730. With lock piston 71 engaged with the engaging concavity 730, relative rotation between rear plate 9 and vane member 6, that is, relative rotation between housing HSG and camshaft 65 is restricted (disabled).

On the other hand, the large-diameter portion 712 of lock piston 71 is forced in the positive X-axis direction by hydraulic pressure of working oil fed from the first phase-retard chamber R1 through the communication hole 75 to the first pressure-receiving chamber 77. Additionally, the tapered head portion 714 of lock piston 71 is forced in the positive X-axis direction by hydraulic pressure of working oil fed from the first phase-advance chamber A1 through the communication groove 76 to the second pressure-receiving chamber 78. As a result, the tapered head portion 714 of lock piston 71 goes out of the engaging concavity 730, and then lock piston 71 retracts into the lock-piston bore 70 of the first blade 61, and thus lock piston 71 becomes disengaged from the engaging cavity 730 of rear plate 9. Back-pressure chamber 72 communicates with the bolt insertion hole 80 of front plate 8 through the radial groove 605. Thus, hack-pressure chamber 72 is opened to the exterior space of the VTC device (i.e., to the atmosphere), in other words, to a low-pressure space (see FIG. 1).

The operation of the VTC device including the VTC control system is hereunder described in detail.

In an engine stopped state, pump P is kept inoperative, and thus oil supply to the working oil chambers (phase-advance chamber A and phase-retard chamber R) is also stopped. Additionally, there is no application of control current (exciting current) from controller CU to the solenoid SOL of directional control valve 59, and thus fluid-communication of supply passage 54 and phase-retard passage 50 and fluid-communication of phase-advance passage 51 and exhaust passage 57 are established.

Just before the engine has been stopped, owing to the alternating torque acting on the camshaft 65, vane member 6 becomes held at its initial position, i.e., the maximum phase-retard position (see FIG. 2). Also, at this maximum phase-retard position, the lock piston 71 of lock mechanism 7 is kept in engagement with the engaging concavity 730 of rear plate 9, so that relative rotation of vane member 6 to housing HSG is restricted.

Thereafter, when the engine is cranked and started by turning the ignition key ON, the pump P begins to operate. Just after the engine has been started, oil supply to the VTC device (i.e., a working oil pressure) becomes still insufficient. At this time, by virtue of lock mechanism 7, vane member 6 is restricted or held at its initial position (the maximum phase-retard position suited to an engine startup, i.e., a smooth cranking operation). As a result of this, it is possible to enhance an engine startability, while avoiding undesirable collision-contact (noise) between vane member 6 (concretely, the side face 613 of the first blade 61) and housing HSG (concretely, the side face 113 of the first shoe 11 of housing body 10), which may occur owing to the alternating torque.

When the engine has been started but any control current has not yet been inputted from controller CU to the solenoid SOL of directional control valve 59, fluid-communication of supply passage 54 and phase-retard passage 50 and fluid-communication of phase-advance passage 51 and exhaust passage 57 remain established. Under these conditions, oil, fed from pump P to supply passage 54, is delivered to each of phase-retard chambers R1-R4.

As previously described, a part of working oil in the first phase-retard chamber R1 is introduced through communication hole 75 of lock mechanism 7 into the first pressure-receiving chamber 77. The hydraulic pressure of working oil, introduced into the first pressure-receiving chamber 77, serves to force lock piston 71 in its retracting direction (i.e., in the positive X-axis direction). As soon as the hydraulic pressure in the first phase-retard chamber R1, in other words, the hydraulic pressure in supply passage 54, becomes greater than or equal to a specified pressure value, the head portion 714 of lock piston 71 becomes completely disengaged from the engaging concavity 730 of rear plate 9. As, a result, the locked state of vane member 6 becomes released, so that relative rotation of vane member 6 to housing HSG becomes permitted and an arbitrary change in engine valve timing (valve open timing and/or valve closure timing) becomes enabled. After a transition of vane member 6 to its unlocked state has occurred, during operation of the engine at low speeds, vane member 6 is still maintained at its maximum phase-retard position by a comparatively low working oil pressure supplied to each of phase-retard chambers R1-R4.

Thereafter, suppose that the engine operating condition shifts to a middle speed range, and thus the spool of directional control valve 59 shifts to the fully-energized position, responsively to a pulse control current having a given duty ratio from controller CU. Fluid-communication between supply passage 54 and phase-advance passage 51 and fluid-communication between phase-retard passage 50 and exhaust passage 57 are established. As a result, oil in each of phase-retard chambers R1-R4 is exhausted and then returned to oil pan O/P, whereas oil, fed from pump P to supply passage 54, is delivered to each of phase-advance chambers A1-A4.

Owing to a rise in hydraulic pressure in each of phase-advance chambers A1-A4, vane member 6 begins to rotate apart from the maximum phase-retard position, so that rotary motion of vane member 6 relative to housing HSG in the clockwise direction (i.e., in the phase-advance direction) occurs. Under these conditions, the hydraulic pressure in the first pressure-receiving chamber 77 of lock mechanism 7 tends to fall, but a part of working oil, supplied to the first phase-advance chamber A1, is introduced through the communication groove 76 into the second pressure-receiving chamber 78 of lock mechanism 7. The working oil, introduced into the second pressure-receiving chamber 78, produces a hydraulic pressure that forces lock piston 71 in its retracting direction (i.e., in the positive X-axis direction). Thus, the unlocked state, in which the head portion 714 of lock piston 71 is completely disengaged from the engaging concavity 730 of rear plate 9, can be maintained.

A relative angular phase of camshaft 65 to the crankshaft becomes changed to the phase-advance side, so that intake-valve open timing (IVO) and intake-valve closure timing (IVC) can be both phase-advanced. As a result, a valve overlap period, during which the open periods of intake and exhaust valves are overlapped, tends to increase, thus enhancing a combustion efficiency.

Thereafter, suppose that due to a further engine speed rise the engine operating condition shifts to a high speed range, and thus the spool of directional control valve 59 is continuously kept at the fully-energized position, responsively to a pulse control current having a given duty ratio from controller CU. High-pressure working oil can be continuously supplied to each of phase-advance chambers A1-A4. As a result, a further clockwise rotational motion of vane member 6 relative to housing HSG occurs, and thus a relative angular phase of camshaft 65 to the crankshaft is further phase-advanced. Finally, the relative angular phase of vane member 6 reaches its maximum phase-advance position at which the volume of each of phase-advance chambers A1-A4 becomes maximum (see FIG. 3). As a result, a valve overlap period, during which the open periods of intake and exhaust valves are overlapped, becomes maximum.

After this, suppose that, owing to an engine speed fall, the hydraulic pressure in each of phase-advance chambers A1-A4 tends to gradually fall and thus a relative angular phase of camshaft 65 to the crankshaft is returned back to the phase-retard side. Thus, the previously-discussed valve overlap period becomes small. At this time, the hydraulic pressure in supply passage 54, remains kept at a pressure level above the specified pressure value, and hence the unlocked state, in which the head portion 714 is completely disengaged from the engaging concavity 730, remains maintained.

The construction of control valve apparatus 1 is hereunder described in detail in reference to FIGS. 4-5. The cross-section of each of FIGS. 4-5 shows the partial cross-section passing through the centerline “Q” of control valve apparatus 1 of the embodiment (that is, the axis of sliding motion of a spool 20 described later in detail and constructing a part of control valve apparatus 1). The centerline “Q” of control valve apparatus 1 is hereinafter referred to as “axis Q”.

Assume that the direction, perpendicular to one side face 100 of engine block EB, is taken as an “x-axis”, the direction, parallel to the side face 100 of engine block EB, is taken as a “y-axis”, a direction of the “x-axis”, directed apart from engine block EB is a positive x-axis direction, and a direction of the “y-axis”, facing apart from the supply passage 53a with respect to an annular groove 561, is a positive y-axis direction.

First of all, the oil-path configuration of the side of engine block BB, on which control valve apparatus 1 is installed, is described.

Supply passage 53 (that is, the upstream supply passage 53a and the downstream supply passage 53b) and supply passage 54 are formed in the engine block EB by machining (concretely, drilling). The upstream supply passage 53a is formed to extend approximately straight in the y-axis direction, while being spaced from the end face 100 of engine block EB by a predetermined distance. The end of the negative y-axis direction of supply passage 53a is connected to the outlet of pump P. Supply passage 54 for working/lubricating oil supply to the VTC device is branched from the branched point 530 of the positive y-axis direction of supply passage 53a. The supply passage 54 is hereinafter referred to as “branch passage 54”. Branch passage 54 is formed to extend approximately straight in the x-axis direction. The end of the negative x-axis direction of branch passage 54 is connected to directional control valve 59. The downstream supply passage 53b is formed to extend approximately straight in the x-axis direction. The downstream supply passage 53b is connected, on the side of the negative x-axis direction, to each of lubricated engine parts. The end of the positive y-axis direction of supply passage 53a and the end of the positive x-axis direction of supply passage 53b are connected to each other in a unit mounting portion 56 formed in the engine block EB.

Unit mounting portion 56 is a mounting hole drilled in the engine block EB for mounting a valve unit including the control valve apparatus 1. Unit mounting portion 56 is comprised of a housing retaining bore 560, an annular groove 561, and a seal retaining bore 562. Seal retaining bore 562, annular groove 561, and housing retaining bore 560 are substantially cylindrical bores formed inside of the side face 100 of engine block EB, and aligned substantially coaxially with the downstream supply passage 53b with respect to the axis “Q”. Seal retaining bore 562, annular groove 561, and housing retaining bore 560 are laid out in that order, in the negative x-axis direction. Regarding the inside diameters of seal retaining bore 562, annular groove 561, and housing retaining bore 560, the inside diameter of seal retaining bore 562 is dimensioned to be greater than that of annular groove 561, and the inside diameter of annular groove 561 is dimensioned to be greater than that of housing retaining bore 560. That is, unit mounting portion 56 is formed as a two-stepped bore. Regarding the dimensions of seal retaining bore 562, annular groove 561, and housing retaining bore 560, measured in the x-axis direction, the seal retaining bore 562 is dimensioned to be shorter than the annular groove 561, and the annular groove 561 is dimensioned to be shorter than the housing retaining bore 560. Annular groove 561 is connected, on the side of the negative y-axis direction, to the supply passage 53a. The width of annular groove 561, measured in the x-axis direction, is dimensioned to be greater than the inside diameter of supply passage 53a. The end of the positive y-axis direction of supply passage 53a opens from the inner peripheral surface of annular groove 561 into the internal space. Supply passage 53b is connected to the end of the negative x-axis direction of housing retaining bore 560. The inside diameter of housing retaining bore 560 is dimensioned to be greater than that of supply passage 53b. The end of the positive x-axis direction of supply passage 53b opens at the end of negative x-axis direction of housing retaining bore 560. Seal retaining bore 562 opens from the side face 100 of engine block EB.

Component parts of control valve apparatus 1 are hereunder described in detail.

Control valve apparatus 1 is comprised of a spool valve 2 (serving as a flow-path selector) and a pilot valve 3 (provided for a pilot operation), both accommodated in a single housing (the same valve casing) 4 common to these two valves 2-3. As a valve unit with both the spool valve 2 and the pilot valve 3, control valve apparatus 1 is installed in the unit mounting portion 56 of engine block EB. Control valve apparatus 1 is configured to produce a control hydraulic pressure by the electromagnetically-operated pilot valve 3. Spool valve 2 is operated (opened or closed) by the control hydraulic pressure. That is, as the control valve apparatus 1, a pilot-operated type is adopted.

Spool valve 2 has a spool (a main valve element) 20. Spool valve 2 is a directional control valve configured to change the path of flow through the valve element (i.e., with a sliding motion of spool 20). The spool valve 2 functions as a two-way valve that performs switching action of the path of flow by opening and closing action of the valve element (spool 20), and also functions as a flow control valve that controls a flow rate of oil through the valve element by a flow-constricting orifice action. Pilot valve 3 is a control valve configured to operate the spool valve 2 (the main valve) by a pilot pressure.

Housing 4 is a support member serving to support or mount both spool valve 2 and pilot valve 3. Housing 4 is installed on the unit mounting portion 56. Housing 4 is made of aluminum alloy materials by die-casting. Housing 4 is comprised of a spool valve body (a spool valve housing) 4a, a flanged portion 4b, and a pilot valve body (a pilot valve housing) 4c, all formed integral with each other.

Spool valve body 4a of housing 4 has a back-pressure portion 41 formed on the side of the positive x-axis direction and a flow-passage portion 42 formed on the side of the negative x-axis direction. The inner periphery of spool valve body 4a is formed as a substantially cylindrical-hollow sliding-contact bore 40 that serves as a guide surface designed to ensure a smooth sliding motion of spool 20.

Back-pressure portion 41 is formed into a substantially cylindrical shape. The end of the positive x-axis direction of back-pressure portion 41 is formed as an opening end. The end of the negative x-axis direction of back-pressure portion 41 is formed to be continuous with the flow-passage portion 42. The inner peripheral surface of back-pressure portion 41 has a female-screw-threaded portion 410 formed on the side of positive x-axis direction. The inner peripheral surface of back-pressure portion 41 is formed as a large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40 for spool 20). The end of the positive x-axis direction of large-diameter bore 40a has an annular groove 411 (see FIG. 5) formed in the inner periphery of bore 40a in close proximity to the end of the negative x-axis direction of female-screw-threaded portion 410.

The end of the negative x-axis direction of back-pressure portion 41 is integrally formed with the flanged portion 4b radially-outward extending along the plane perpendicular to the axis “Q” and located in close proximity to the flow-passage portion 42.

Flanged portion 4b has a bolt hole 43 formed as a through hole extending in the x-axis direction. A mounting bolt is inserted into the bolt hole 43 from the side of the positive x-axis direction. By screwing and tightening the mounting bolt into a female-screw-threaded portion formed in the side face 100 of engine block EB, housing 4 is fixedly connected to and mounted on the engine block EB. An O ring (an oil seal member) S4 is fitted into the seal retaining bore 562 of engine block EB. Under a state where housing 4 has been bolted to the side face 100 of engine block EB, O ring S4 is sandwiched and compressed between the end face of the negative x-axis direction of flanged portion 4b of housing 4 and the end face of the positive x-axis direction of seal retaining bore 562, thus ensuring a high fluid-tightness of the interior space of unit mounting portion 56.

Back-pressure portion 41 has an oblique hole 412 formed on the side of the positive y-axis direction and the negative x-axis direction. Oblique hole 412 is formed as a substantially-straight through hole penetrating the inner and outer peripheries of back-pressure portion 41. Oblique hole 412 is opened to the exterior space of engine block EB through the outer peripheral surface of back-pressure portion 41 on the side of the positive x-axis direction of flanged portion 4b. Oblique hole 412 is also opened to the interior space of sliding-contact bore 40 through the inner peripheral surface of large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40 for spool 20) at a given position, somewhat overlapping with the flanged portion 4b in close proximity to the end of the negative x-axis direction of back-pressure portion 41. Oblique hole 412, intercommunicating the interior and exterior spaces of back-pressure portion 41 (spool valve body 4a), serves as an air breather that functions to facilitate a change in volume of the internal space defined between the outer periphery of spool 20 and the inner periphery of large-diameter bore 40a of sliding-contact bore 40.

A threaded plug 413 is screwed into the female-screw-threaded portion 410 of back-pressure portion 41, so as to hermetically close the opening end of back-pressure portion 41, facing in the positive x-axis direction. That is, the side of the backface of spool 20 is closed in a fluid-tight fashion by the threaded plug 413.

Flow-passage portion 42 of spool valve body 4a is formed into a substantially cylindrical bore closed at one end and having a diameter smaller than a diameter of back-pressure portion 41. Flow-passage portion 42 is formed with communication holes (for example, communication holes (through holes) 421 and 423).

The inner peripheral surface of flow-passage portion 42 is formed as a small-diameter bore 40b (a small-diameter portion of sliding-contact bore 40 for spool 20). The inside diameter of small-diameter bore 40b is dimensioned to be less than that of large-diameter bore 40a. The end of the positive x-axis direction of small-diameter bore 40b and the end face of the negative x-axis direction of flanged portion 4b are aligned with each other in the x-axis direction, in a manner so as to form a stepped annular portion in cooperation with large-diameter portion 40a. The outside diameter of the outer peripheral surface of flow-passage portion 42 is dimensioned to be approximately equal to that of large-diameter bore 40a. The outer peripheral surface of the left-hand half (viewing FIGS. 4-5) of flow-passage portion 42 is formed to be continuous with the end face of the negative x-axis direction of flanged portion 4b, while drawing a moderately curved surface.

The end of the negative x-axis direction of flow-passage portion 42 is inserted and fitted into the housing retaining bore 560. As a result, sliding-contact bore 40 (large-diameter bore 40a and small-diameter bore 40b) and annular groove 561 are accurately positioned and aligned coaxially with each other with respect to the axis “Q”. By way of such an accurate positioning and fitting process, it is possible to suppress an undesirable fluid-communication between annular groove 561 and housing retaining bore 560 via the outer peripheral aide of flow-passage portion 42.

A plurality of circumferentially-equidistant spaced circular holes (four holes 421-424 in the shown embodiment) are formed in the basal end of the positive x-axis direction of flow-passage portion 42. Each of holes 421-424 is formed as a through hole radially penetrating the inner and outer peripheries of flow-passage portion 42. Each of through holes 421-424 is a communication hole that opens from the outer peripheral surface of flow-passage portion 42 and also opens from the inner peripheral surface of sliding-contact bore 40 (especially, small-diameter bore 40b). In the shown embodiment, although flow-passage portion 42 has four circular through holes 421-424, it will be appreciated that the number of through holes is not limited to “4”. The shape and the number of through holes may be modified.

The diameters of through holes 421-424 are dimensioned to be approximately equal to each other, and also dimensioned to be less than the diameter of supply passage 53a. The openings (i.e., through holes 421-424) of housing 4, installed in unit mounting portion 56, are located at the inner peripheral side of annular groove 561. In other words, annular groove 561 is located at the outer peripheral side of the openings (i.e., through holes 421-424) of housing 4. The axial position of the center of the x-axis direction of each of through holes 421-424 is laid out to be approximately identical to the position of the x-axis direction of the centerline of supply passage 53a. Of four through holes 421-424, the first through hole 421 is located to open in the negative y-axis direction, in a manner so as to be opposed to the supply passage 53a in the y-axis direction.

The end (a bottom 425) of the negative x-axis direction of flow-passage portion 42 is formed with a hole 420. Hole 420 is formed as a through hole penetrating the inner and outer peripheries of the bottom 425 and extending in the x-axis direction and aligned substantially coaxially with the axis “Q”. Hole 420 is a communication hole that opens into the exterior space of flow-passage portion 42 (i.e., the inner peripheral side of housing retaining bore 550) on the side of the negative x-axis direction of bottom 425 in a manner so as to be opposed to the supply passage 53b in the x-axis direction, and also opens into the interior space of flow-passage portion 42 (i.e., the inner peripheral side of small-diameter bore 40b of sliding-contact bore 40) on the side of the positive x-axis direction of bottom 425. The inside diameter of through hole 420 is dimensioned to be slightly greater than one-half of the inside diameter of small-diameter bore 40b of sliding-contact bore 40, and also dimensioned to be less than the inside diameter of supply passage 53b.

Pilot valve body 4c is formed as a substantially cylindrical portion that extends in the negative y-axis direction from the outer periphery of back-pressure portion 41 of spool valve body 4a. Pilot valve body 4c and spool valve body 4a are formed integral with each other.

Pilot valve body 4c is a pilot-valve mounting bore for pilot valve 3. Pilot valve body 4c has a large-diameter bore 440 that opens into the exterior space of housing 4 on the side of the negative y-axis direction, and a small-diameter bore 441 formed substantially coaxially with the large-diameter bore 440 in close proximity to the side of the positive y-axis direction of large-diameter bore 440. The inside diameter of small-diameter bore 441 is dimensioned to be less than that of large-diameter bore 440.

Additionally, pilot valve body 4c has an axial passage 442 and a radial passage 443 both formed therein, for supplying or exhausting oil (for a pilot operation) to or from back-pressure portion 41 of spool valve body 4a. Axial passage 442 is formed to extend in the y-axis direction. The end of the positive y-axis direction of axial passage 442 opens into the sliding-contact bore 40 of back-pressure portion 41 (i.e., the annular groove 411 of large-diameter bore 40a shown in FIG. 5). The end of the negative y-axis direction of axial passage 442 is connected to a relay passage 303 of pilot valve 3. Radial passage 443 is formed to extend in the x-axis direction. The end of the negative x-axis direction of radial passage 443 opens from the end face of the negative x-axis direction of flanged portion 4b in a manner so as to communicate the annular groove 561 and the seal retaining bore 562 of unit mounting portion 56. The end of the positive x-axis direction of radial passage 443 opens into the end of the positive y-axis direction of small-diameter bore 441 in a manner so as to be connected to the axial passage 442 through the relay passages 302-303.

Pilot valve 3 has an oil passage 30, a ball 31, a spring 32, an armature 33, and a solenoid 34.

Oil passage 30 is constructed by an axial passage 301, and relay passages 302-305. Axial passage 301 is formed to extend in the y-axis direction. The end of the positive y-axis direction of axial passage 301 communicates the radial passage 443 of pilot valve body 4c of housing 4, whereas the end of the negative y-axis direction of axial passage 301 communicates the relay passage 302. Relay passage 302 is formed to extend in the y-axis direction. The end of the negative y-axis direction of relay passage 302 communicates the relay passage 303. Relay passage 303 is formed to extend in the direction perpendicular to the y-axis. The end of the positive y-axis direction of relay passage 303 communicates the axial passage 442 of pilot valve body 4c of housing 4, whereas the end of the negative y-axis direction of relay passage 303 communicates the relay passage 304. Relay passage 304 is formed to extend in the y-axis direction. The side of the negative y-axis direction of relay passage 304 communicates the relay passage 305. Relay passage 305 is connected through an exhaust passage (not shown) to the oil pan O/P, and thus opened to the atmosphere.

Ball 31 is installed on the side of the negative y-axis direction of axial passage 301. Ball 31 is permanently biased in the negative y-axis direction by means of the spring 32 installed in the axial passage 301 in a manner so as to close the opening of relay passage 302. Armature 33 has a needle-shaped pointed portion that extends in the y-axis direction in a manner so as to penetrate all of relay passages 302-304. The end of the positive y-axis direction of the needle-shaped pointed portion of armature 33 is installed to be kept in abutment with the ball 31. A sealing surface is provided at the end of the negative y-axis direction of armature 33, that is, the root of the needle-shaped pointed portion of armature 33. By bringing the sealing surface of armature 33 into abutted-engagement with a sealing surface formed in the opening of the negative y-axis direction of relay passage 304, fluid-communication between two relay passages 304 and 305 can be blocked. Solenoid 34 is connected via a connector 35 to an electric power source. When solenoid 34 is energized, the electric coil of solenoid 34 creates a magnetic force that forces armature 33 in the positive y-axis direction.

Spool 20 is a piston slidably accommodated in sliding-contact bore 40 of spool valve body 4a. Spool 20 is made of iron-based metal materials, and formed into a substantially cylindrical shape by cold forging. Spool 20 is partitioned into a back-pressure portion 21 defined on the side of the positive x-axis direction and a flow-passage portion 22 defined on the side of the negative x-axis direction by a partition wall portion 23.

Back-pressure portion 21 is formed into a substantially cylindrical hollow shape, but closed at one axial end. The end of the positive x-axis direction of back-pressure portion 21 is formed as an opening end. The end of the negative x-axis direction of back-pressure portion 21 is closed by the partition wall portion 23. In other words, the inner peripheral side of back-pressure portion 21 is formed as a recessed portion, concretely, a substantially cylindrical bore 210 whose bottom (closed end) is the partition wall portion 23 (see FIG. 4).

The end of the positive x-axis direction of back-pressure portion 21, that is, the perimeter of the left-hand side opening (viewing FIGS. 4-5) of back-pressure portion 21 is formed integral with a flanged portion 211. Flanged portion 211 is formed as a large-diameter annular ring-shaped flange radially-outward extending from the outer peripheral surface of spool 20 and having an outside diameter greater than the outside diameter of the other cylindrical portion of spool 20. The dimension (the axial length) of the x-axis direction of flanged portion 211 is dimensioned to be greater than that of annular groove 411 of housing 4.

The end face of the positive x-axis direction of flanged portion 211 is formed with a groove 214 having a predetermined depth in the x-axis direction. Groove 214 is a straight radial groove extending in the radial direction of spool 20 in a manner so as to intercommunicate the inner peripheral side (cylindrical bore 210) and the outer peripheral side of flanged portion 211.

The length of back-pressure portion 21 in the x-axis direction, that is, the distance between the end of the positive x-axis direction of back-pressure portion 21 and the end face of the positive x-axis direction of partition wall portion 23 is dimensioned to be approximately equal to the axial length of large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40).

The outside diameter of the circumference of flanged portion 211 is dimensioned to be slightly less than the inside diameter of large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40).

Flow-passage portion 22 is formed into a substantially cylindrical hollow shape, but closed at one axial end. The end of the negative x-axis direction of flow-passage portion 22 is formed as an opening end. The end of the positive x-axis direction of flow-passage portion 22 is closed by the partition wall portion 23. In other words, the inner peripheral side of flow-passage portion 22 is formed as a substantially cylindrical bore 220 whose bottom (closed end) is the partition wall portion 23 (see FIG. 4).

Flow-passage portion 22 has a first groove 221 and a second groove 222, both formed in the outer periphery of flow-passage portion 22.

The first groove 221 is an annular groove (of a constant width in the x-axis direction) located to be slightly offset from the midpoint of flow-passage portion 22 toward the negative x-axis direction and formed around the entire circumference of flow-passage portion 22. The dimension of the first groove 221 (in the x-axis direction) is dimensioned to be slightly less than the diameter of each of through holes 421-424 of housing 4.

The second groove 222 is an annular groove (of a constant width of approximately one-third the width of the first groove 221 in the x-axis direction) located at the position sandwiched between the first groove 221 and the partition wall portion 23 and formed around the entire circumference of flow-passage portion 22. The distance between the end of the negative x-axis direction of the second groove 222 and the end of the negative x-axis direction of spool 20 is dimensioned to be approximately equal to the distance between the end of the negative x-axis direction of each of through holes 421-424 of housing 4 and the end of the positive x-axis direction of the bottom 425. Also, the distance between the end of the negative x-axis direction of the second groove 222 and the end of the negative x-axis direction of spool 20 is dimensioned to be approximately equal to the distance between the end of the positive x-axis direction of each of through holes 421-424 of housing 4 and the end of the negative x-axis direction of the threaded plug 413.

The depths of first and second grooves 221 and 222 in the radial direction of spool 20 are approximately equal to each other.

A plurality of circumferentially-equidistant spaced circular holes (four holes 223, 224, 225, and 226 in the shown embodiment) are further formed in the grooved portion of flow-passage portion 22 that the first groove 221 is formed. Each of holes 223-226 is formed as a through hole radially penetrating the inner and outer peripheries of flow-passage portion 22. Each of holes 223-226 is a communication hole that opens from the bottom (the inside groove surface) of the first groove 221 and also opens from the inner peripheral surface of cylindrical bore 220. In the shown embodiment, although flow-passage portion 22 has four through holes 223-226, it will be appreciated that the number of through holes is not limited to “4”. The shape and the number of through holes may be modified.

The diameters of through holes 223-226 are dimensioned to be approximately equal to each other, and also dimensioned to be slightly less than the dimension of the first groove 221, measured in the x-axis direction.

A hole 227 is further formed in the grooved portion of flow-passage portion 22 that the second groove 222 is formed. Hole 227 is formed as a through hole radially penetrating the inner and outer peripheries of flow-passage portion 22. Hole 227 is a communication hole that opens from the bottom (the inside groove surface) of second groove 222 and also opens from the inner peripheral surface of cylindrical bore 220. Hole 227 constructs an orifice. That is, through hole 227 is a flow-constriction orifice that intercommunicates the inner and outer peripheries of flow-passage portion 22 with a flow-constricting action. In the shown embodiment, although flow-passage portion 22 has one through hole 227, it will be appreciated that the number of a through hole is not limited to “1”. The shape and configuration and the number of a through hole may be modified. For instance, two or more through holes (i.e., two or more flow-constriction orifices) may be formed to adjust a fluid-flow passage area (i.e., an orifice area) through an orifice constriction.

The diameter of through hole 227 is dimensioned to be less than the dimension of the second groove 222, measured in the x-axis direction, and also dimensioned to be approximately equal to one-fourth of the inside diameter of each of through holes 223-226.

The length of flow-passage portion 22 in the x-axis direction, that is, the distance between the end of the negative x-axis direction of flow-passage portion 22 and the end face of the negative x-axis direction of partition wall portion 23 is dimensioned to be less than the length of flow-passage portion 42 of housing 4 in the x-axis direction, and also dimensioned to be approximately equal to the length of annular groove 561 in the x-axis direction.

The outside diameter of the outer peripheral surface of flow-passage portion 22 is dimensioned to be slightly less than the inside diameter of small-diameter bore 40b (a small-diameter portion of sliding-contact bore 40).

(Installation State of Spool Valve)

Flanged portion 211 of spool 20 is slidably installed in back-pressure portion 41 of housing 4 so that the outer peripheral surface of flanged portion 211 slides in the x-axis direction with respect to the inner peripheral surface of large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40). Back-pressure portion 21 and flow-passage portion 22 of spool 20 are slidably installed in housing 4, so that the outer peripheral surface of back-pressure portion 21 and flow-passage portion 22, except for the flanged portion 211 of spool 20, slides in the x-axis direction with respect to the inner peripheral surface of small-diameter bore 40b (a small-diameter portion of sliding-contact bore 40).

The first pressure chamber is defined by the inner peripheral surface of small-diameter bore 40b (a small-diameter portion of sliding-contact bore 40) and all sidewall surfaces of flow-passage portion 22, facing in the negative x-axis direction, whereas the second pressure chamber (i.e., a back-pressure chamber of spool 20) is defined by the inner peripheral surface of large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40), the end face of the negative x-axis direction of threaded plug 413, and all sidewall surfaces of back-pressure portion 21, facing in the positive x-axis direction.

The first group of sidewall surfaces of flow-passage portion 22, facing in the negative x-axis direction, constructs a first pressure-receiving surface for receiving a hydraulic pressure (in the first pressure chamber) acting on the spool 20 from the side of the negative x-axis direction so as to force the spool 20 in the positive x-axis direction.

The second group of sidewall surfaces of back-pressure portion 21, facing in the positive x-axis direction, constructs a second pressure-receiving surface for receiving a hydraulic pressure (in the second pressure chamber) acting on the spool 20 from the side of the positive x-axis direction so as to force the spool 20 in the negative x-axis direction.

An area D1 of the first pressure-receiving surface is set or formed to be less than an area D2 of the second pressure-receiving surface by an area of the sidewall surface of flanged portion 211, facing in the positive x-axis direction, that is, D1<D2.

An annular space α1 is defined by the first groove 221 between the outer peripheral surface of flow-passage portion 22 and the inner peripheral surface of small-diameter bore 40b (a small-diameter portion of sliding-contact bore 40). In a similar manner, an annular space α2 is defined by the second groove 222 between the outer peripheral surface of flow-passage portion 22 and the inner peripheral surface of small-diameter bore 40b. Through holes 223-226, opening at the bottom (the inside groove surface) of the first groove 221, communicate the annular space α1, whereas through hole 227, opening at the bottom (the inside groove surface) of second groove 222, communicates the annular space a2.

Rotary motion of spool 20 about the axis “Q” with respect to the sliding-contact bore 40 is not restricted. Sliding motion of spool 20 in the positive x-axis direction is restricted by abutment between the end face of the positive x-axis direction of spool 20 (flanged portion 211) and the end face of the negative x-axis direction of threaded plug 413 (see FIG. 4). The restricted position of spool 20 is hereinafter referred to as “position A”. That is, the end face of the positive x-axis direction of spool 20 (flanged portion 211) and the end face of the negative x-axis direction of threaded plug 413 cooperate with each other to provide a first stopper (a sliding-motion stopper for spool 20 in the positive x-axis direction).

Also, sliding motion of spool 20 in the negative x-axis direction is restricted by abutment between the end face of the negative x-axis direction of spool 20 (flow-passage portion 22) and the inside face of bottom 425 of flow-passage portion 42 of housing 4, facing in the positive x-axis direction (see FIG. 5). The restricted position of spool 20 is hereinafter referred to as “opposite position B”. That is, the end face of the negative x-axis direction of spool 20 (flow-passage portion 22) and the inside face of bottom 425 of flow-passage portion 42 of housing 4, facing in the positive x-axis direction, cooperate with each other to provide a second stopper (a sliding-motion stopper for spool 20 in the negative x-axis direction).

At the position “A” (see FIG. 4), back-pressure portion 21 of spool 20 is positioned within the back-pressure portion 41 of housing 4, whereas flow-passage portion 22 is positioned within the flow-passage portion 42 of housing 4 in a manner so as to almost accord with the annular groove 561 of unit mounting portion 56. As viewed in the radial direction of housing 4, at the position “A”, the entire range of the grooved area of flow-passage portion 22, in which first groove 221 is formed, is positioned to almost accord with the area of flow-passage portion 42 of housing 4, in which through holes 421-424 are formed. On the other hand, the second groove 222 is positioned to be slightly offset from the end of the positive x-axis direction of each of through holes 421-424 toward the positive x-axis direction. The entire range of the grooved area of flow-passage portion 22, in which second groove 222 is formed, is positioned within the remaining area (i.e., a root 426 of flow-passage portion 42 of housing 4 corresponding to the side of the positive x-axis direction of flow-passage portion 42), in which through holes 421-424 are not formed.

At the position “A” (see FIG. 4), the volume of an annular space β defined between the outer peripheral surface of back-pressure portion 21 (and the end face of the negative x-axis direction of flanged portion 211) and the inner peripheral surface of large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40) becomes maximum.

At the opposite position “B” (see FIG. 5), most of back-pressure portion 21 and flow-passage portion 22 are positioned within the flow-passage portion 42 of housing 4. As viewed in the radial direction of housing 4, at the opposite position “B”, the entire range of the grooved area of flow-passage portion 22, in which the first groove 221 is formed, is positioned within the remaining area (i.e., a tip of flow-passage portion 42 of housing 4 corresponding to the side of the negative x-axis direction of flow-passage portion 42), in which through holes 421-424 are not formed. On the other hand, the end of the negative x-axis direction of the second groove 222 and the end of the negative x-axis direction of each of through holes 421-424 are positioned to almost accord with each other. The entire range of the grooved area of flow-passage portion 22, in which the second groove 222 is formed, is positioned within the area of flow-passage portion 42 of housing 4, in which through holes 421-424 are formed.

At the opposite position “B” (see FIG. 5), the volume of annular space β becomes minimum. The end of the negative x-axis direction of flanged portion 211 is positioned to be slightly offset from the end of the negative x-axis direction of the inward opening of oblique hole 412, which opens into the interior space of sliding-contact bore 40 through the inner peripheral surface of large-diameter bore 40a, toward the positive x-axis direction.

Depending on a change in the axial position of spool 20, arising from a sliding motion of spool 20 in the x-axis direction, the volume of annular space β changes (increases or decreases). Movement of air in and out of the annular space β, occurring as a result of the sliding motion of spool 20, can be smoothly achieved through the oblique hole 412, thus ensuring a smooth operation (a smooth sliding motion) of spool 20.

(Opening and Closing Action of Spool Valve)

In the shown embodiment, a plurality of circumferentially-equidistant spaced through holes (four through holes 421-424) are formed in housing 4. Additionally, annular groove 561 of unit mounting portion 56 is formed in a manner so as to surround the entire circumference of a portion of flow-passage portion 42 having through holes 421-424. Therefore, it is possible to more efficiently supply a large amount of oil from the supply passage 53a through the plurality of through holes 421-424 to the spool 20. As previously discussed, in the shown embodiment, annular groove 561 is provided and formed in the engine block EB and flow-passage portion 42 of housing 4 has four through holes 421-424. In lieu thereof, annular groove 561 may be eliminated and also only the first through hole 421, opposed to the supply passage 53a in the y-axis direction, may be formed (in other words, the other three through holes 422-424 may be eliminated).

Through holes 223-227 of spool 20 and through holes 421-424 of housing 4 are configured such that fluid-communication between the first group of through holes 223-226 and the second group of through holes 421-424 can be established or blocked and that fluid-communication between through hole 227 and the second group of through holes 421-424 can be blocked or established, depending on the axial position of spool 20, arising from a sliding motion of spool 20 in the x-axis direction.

As viewed in the radial direction of housing 4, at an axial position of spool 20 that the first groove 221 of spool 20 and the through holes 421-424 overlap each other, for instance, at the position “A” (see FIG. 4), annular space α1 is communicated with the through holes 421-424, and thus fluid-communication between the first group of through holes 223-226 and the second group of through holes 421-424 is established. Hence, even when the first group of through holes 223-226 of the spool side and the second group of through holes 421-424 of the housing side do not overlap each other in the circumferential direction owing to rotary motion of spool 20 (flow-passage portion 22) about the axis “Q” with respect to the sliding-contact bore 40 (in other words, with respect to the flow-passage portion 42 of spool valve body 4a of housing 4), by virtue of the first groove 221 (in other words, annular space α1), fluid-communication between the first group of through holes 223-226 and the second group of through holes 421-424 cannot be blocked. Therefore, at the overlapping position of the first groove 221 and through holes 421-424, it is possible to reliably intercommunicate the first group of through holes 223-226 and the second group of through holes 421-424, regardless of the presence or absence of rotary motion of spool 20 about the axis “Q” with respect to the sliding-contact bore 40. Additionally, by the formation of the plurality of through holes 223-226 and the plurality of through holes 421-424, it is possible to increase the total opening area (i.e., the total flow passage area), thus enabling a large amount of oil to be more efficiently supplied from the second group of through holes 421-424 via the first group of through holes 223-226 to the inner peripheral side of spool 20. Instead of forming the first groove 221 in the flow-passage portion 22 of spool 20, the number and shape of through holes 223-226 and/or the number of shape of through holes 421-424 may be properly modified, such that, at least at the position “A”, fluid-communication between the first group of through holes 223-226 and the second group of through holes 421-424 can be established even if spool 20 is positioned in any rotation position with respect to sliding-contact bore 40.

By the way, the second group of through holes 421-424 always communicates the annular groove 561 of unit mounting portion 56. Hence, at the overlapping position of the first groove 221 and through holes 421-424, the first group of through holes 223-226 can be communicated with the supply passage 53a, which opens into the annular groove 561. The inner peripheral side (the first pressure chamber) of flow-passage portion 22, into which the through holes 223-226 open, always communicates the supply passage 53b via the through hole 420 of housing 4. Thus, at the overlapping position at which the first groove 221 of spool 20 and the through holes 421-424 overlap each other, supply passage 53a can be communicated with supply passage 53b via the through holes 223-226. That is, at the overlapping position, the first group of through holes 223-226 serves as a first communication passage intercommunicating supply passages 53a and 53b. The first group of through holes 223-226 is a large flow control section whose opening area is greater than that of through hole 227 and through which a large amount of fluid flow can be distributed.

In contrast, at a non-overlapping position at which the first groove 221 and the through holes 421-424 do not overlap each other, for instance, at the opposite position “B” (see FIG. 5), annular space α1 is not communicated with the through holes 421-424, and thus there is no fluid-communication between the first group of through holes 223-226 and the second group of through holes 421-424. As a result, fluid-communication between supply passages 53a and 53b via the through holes 223-226 is blocked. That is, at the opposite position “B” of FIG. 5, the opening of the large flow control section is closed and thus the first communication passage (through holes 223-226) is kept in non-communicated state.

As viewed in the radial direction of housing 4, an area of the first groove 221, which opens into the through holes 421-424, in other words, a flow-passage area that annular space α1 is communicated with the through holes 421-424 becomes maximum at the position “A”. Roughly speaking, the flow-passage area tends to gradually reduce, as the spool 20 moves (slides) in the negative x-axis direction from the position “A”, in other words, as the annular space α1 moves in the negative x-axis direction with respect to the through holes 421-424. More concretely, immediately after a first intermediate position “A1” of spool 20 has been reached with spool 20 sliding in the negative x-axis direction from the position “A”, the flow-passage area becomes less than the total opening area of through holes 223-226, which open into the first groove 221, in other words, a flow-passage area that the annular space α1 always communicates the through holes 223-226. Thereafter, from a second intermediate position “B1” of spool 20 immediately before the opposite position “B”, the flow-passage area becomes zero. Within a range of sliding motion of spool 20 between the second intermediate position “B1” and the opposite position “B”, the flow-passage area remains kept at zero.

Hence, regarding the flow passage by way of the first communication passage (through holes 223-226), within a range of sliding motion of spool 20 between the position “A” and the second intermediate position “B1”, fluid-communication between two supply passages 53a-53b can be established. Conversely, within a range of sliding motion of spool 20 between the second intermediate position “B1” and the opposite position “B” (because of zero-overlapping of the first group of through holes 223-226 and the second group of through holes 421-424), fluid-communication between two supply passages 53a-53b can be blocked. Within a range of sliding motion of spool 20 from the first intermediate position “A1” to the second intermediate position “B1”, the flow-passage area by way of the first communication passage (through holes 223-226) tends to gradually reduce (because of gradual overlapping of the first group of through holes 223-226 and the second group of through holes 421-424), as the spool 20 moves in the negative x-axis direction from the first intermediate position “A1”.

In this manner, by an axial displacement of spool 20, it is possible to perform switching between the open state and the closed state of the large flow control section, in other words, switching between the established (enabled) state and the blocked (disabled) state of fluid-communication between two supply passages 53a-53b by way of the first communication passage (through holes 223-226).

In a similar manner, as viewed in the radial direction of housing 4, at an axial position of spool 20 that the second groove 222 of spool 20 and the through holes 421-424 overlap each other, for instance, at the position “B” (see FIG. 5), annular space a2 is communicated with the through holes 421-424, and thus fluid-communication between the through hole 227 and the second group of through holes 421-424 is established. Hence, even when the through hole 227 of the spool side and the second group of through holes 421-424 of the housing side do not overlap each other in the circumferential direction owing to rotary motion of spool 20 (flow-passage portion 22) about the axis “Q” with respect to the sliding-contact bore 40 (in other words, with respect to the flow-passage portion 42 of spool valve body 4a of housing 4), by virtue of the second groove 222 (in other words, annular space a2), fluid-communication between the through hole 227 and the second group of through holes 421-424 cannot be blocked. Therefore, at the overlapping position of the second groove 222 and through holes 421-424, it is possible to reliably intercommunicate the through hole 227 and the second group of through holes 421-424, regardless of the presence or absence of rotary motion of spool 20 about the axis “Q” with respect to the sliding-contact bore 40.

At the overlapping position of the second groove 222 and through holes 421-424, the through hole 227 communicates the supply passage 53a, and also the inner peripheral side (the first pressure chamber) of flow-passage portion 22, into which the through hole 227 opens, always communicates the supply passage 53b via the through hole 420 of housing 4. Thus, at the overlapping position at which the second groove 222 of spool 20 and the through holes 421-424 overlap each other, supply passage 53a can be communicated with supply passage 53b via the through hole 227. That is, at the overlapping position, the through hole 227 serves as a second communication passage intercommunicating supply passages 53a and 53b. The through hole 227 is a small flow control section whose opening area is less than that of the first group of through holes 223-226 and through which a small amount of fluid flow can be distributed.

In contrast, at a non-overlapping position at which the second groove 222 and the through holes 421-424 do not overlap each other, for instance, at the position “A” (see FIG. 4), annular space a2 is not communicated with the through holes 421-424, and thus there is no fluid-communication between the through hole 227 and the second group of through holes 421-424. As a result, fluid-communication between supply passages 53a and 53h via the through hole 227 is blocked. That is, at the position “A” of FIG. 4, the opening of the small flow control section is closed and thus the second communication passage (through hole 227) is kept in its non-communicated state.

As viewed in the radial direction of housing 4, an area of the second groove 222, which opens into the through holes 421-424, in other words, a flow-passage area that annular space α2 is communicated with the through holes 421-424 becomes zero at the position “A”. Roughly speaking, the flow-passage area tends to gradually increase, as the spool 20 (i.e., annular space α2) moves (slides) in the negative x-axis direction from the position “A”. More concretely, immediately after a third intermediate position “A0” of spool 20 has been reached with spool 20 sliding in the negative x-axis direction from the position “A”, the flow-passage area becomes greater than zero. Thereafter, the flow-passage area remains kept at a value greater than zero, until the opposite position “B” has been reached.

Hence, regarding the flow passage by way of the second communication passage (through hole 227), within a range of sliding motion of spool 20 between the position “A” and the third intermediate position “A0” (because of zero-overlapping of the through hole 227 (the second groove 222) and the second group of through holes 421-424), fluid-communication between two supply passages 53a-53b can be blocked. Conversely, within a range of sliding motion of spool 20 between the third intermediate position “A0” and the opposite position “B”, fluid-communication between two supply passages 53a-53b can be established.

In this manner, by an axial displacement of spool 20, it is possible to perform switching between the open state and the closed state of the small flow control section, in other words, switching between the established (enabled) state and the blocked (disabled) state of fluid-communication between two supply passages 53a-53b by way of the second communication passage (through hole 227).

By the way, a flow-passage area that the second group of through holes 421-424 is communicated with the annular space α2 varies depending on the axial displacement of spool 20 in the negative x-axis direction from the third intermediate position “A0”. The flow-passage area is configured to be greater than an area of the through hole 227, which opens into the second groove 222, (i.e., a flow-passage area that annular space α2 is communicated with the through hole 227). In other words, the flow-passage area of the oil flow path, directed from the supply passage 53a via the through hole 227 to the supply passage 53b, becomes minimum at the through hole (orifice) 227, regardless of the axial position of spool 20. That is, the oil flow is constricted by means of the through hole (orifice) 227.

As discussed above, regarding supply passage 53, its inlet (supply passage 53a) opens from the sliding-contact surface of sliding-contact bore 40 (flow-passage portion 42 of housing 4) in sliding-contact with spool 20, whereas its outlet (supply passage 53b) opens from one axial end (i.e., the end of the negative x-axis direction) of sliding-contact bore 40. Additionally, the first communication passage (through holes 223-226) and the second communication passage (through hole 227) are provided on the side of the sliding-contact surface of spool 20 in sliding-contact with sliding-contact bore 40. The first communication passage (through holes 223-226) and the second communication passage (through hole 227) are merged with each other by the axial passage (i.e., the first pressure chamber) formed along the axis “Q”, and then communicated with the outlet of supply passage 53, that is, the downstream supply passage 53b. Within a range of axial displacement (sliding motion) of spool 20 from the position “A” (see FIG. 4) to the opposite position “B” (see FIG. 5), the flow-passage area of the oil flow path, directed from the supply passage 53a through the annular groove 561, through holes 421-424 and through holes 223-227 to the inner peripheral side (the first pressure chamber) of flow-passage portion 22, becomes a maximum value (i.e., a summed value of the opening areas of through holes 223-226) at the position “A”. Within a range of axial displacement (sliding motion) of spool 20 from the position “A” to the first intermediate position “A1”, the flow-passage area remains kept approximately maximum. As the spool 20 shifts from the first intermediate position “A1” to the second intermediate position “B1”, the flow-passage area gradually decreases with a change in opening area (orifice area) of through holes 223-226. Within a range of axial displacement (sliding motion) of spool 20 from the second intermediate position “B1” to the opposite position “B”, the flow-passage area becomes a minimum value, corresponding to the opening area of the through hole 227, by a maximum flow-constricting orifice action of through hole 227.

Owing to the throttled (constricted) flow-passage area, the flow rate of oil flowing to the downstream side (i.e., supply passage 53b) tends to decrease. Assuming that the flow rate of oil, fed into the upstream supply passage 53a, is constant, the flow rate of oil, fed into the branch passage 54, tends to increase by the decreased flow rate of oil flowing to the downstream supply passage 53b. At the position “A”, the flow rate of oil, fed from the supply passage 53a via the spool valve 2 to the supply passage 53b, becomes maximum. In contrast, at the opposite position “B”, oil, fed from the supply passage 53a via the spool valve 2 to the supply passage 53b, is limited to oil, flowing via only the through hole (orifice) 227. Thus, at the opposite position “B”, the flow rate of oil, flowing through the downstream supply passage 53b, becomes minimum. That is, most of oil (except for oil flowing via the through hole 227 to the supply passage 53b), fed from pump P into supply passage 53a, is delivered into the branch passage 54.

In this manner, control valve apparatus 1 is configured to control switching between the opening of the large flow control section (through holes 223-226) whose opening area is comparatively great and the opening of the small flow control section (through hole 227) whose opening area is less than that of the large flow control section, depending on the position of the valve element (spool 20). At least in a specified state where the opening of the large flow control section (through holes 223-226) is fully opened with a maximum opening area (corresponding to the position “A”), the small flow control section (through hole 227) is closed. Concretely, in a first state (i.e., at the position “A” of FIG. 4) corresponding to a maximum axial displacement of spool 20 in one axial direction, the first communication passage (through holes 223-226) is kept in its communicated state, whereas the second communication passage (through hole 227) is kept in its non-communicated state. Conversely, in a second state (i.e., at the opposite position “B” of FIG. 5) corresponding to a maximum axial displacement of spool 20 in the other axial direction, the second communication passage (through hole 227) is kept in its communicated state, whereas the first communication passage (through holes 223-226) is kept in its non-communicated state.

(Control System Configuration)

Control valve apparatus 1 is configured to selectively switch one of the position “A” and the opposite position “B” to the other by an electrical signal output from controller CU to pilot valve (electromagnetic solenoid valve) 3. That is, an axial displacement of spool 20 occurs responsively to a control signal input into the pilot valve 3, and then switching between a full fluid-communication state of supply passages 53a-53b (i.e., the position “A” of FIG. 4) and a maximum flow-constriction state (i.e., the opposite position “B” of FIG. 5) is made. In this manner, the flow rate of oil, fed into the downstream supply passage 53b, can be adjusted or controlled responsively to a control signal from controller CU to pilot valve 3.

The hydraulic pressure in the first pressure chamber, acts on each surface of the sidewall surfaces of flow-passage portion 22 of spool 20, all facing in the negative x-axis direction, namely, on the first pressure-receiving surface. This hydraulic pressure, acting on the first pressure-receiving surface, creates a first force F1 that forces or biases spool 20 in the positive x-axis direction. Conversely, the hydraulic pressure in the second pressure chamber, acts on each surface of the sidewall surfaces of back-pressure portion 21 of spool 20, all facing in the positive x-axis direction, namely, on the second pressure-receiving surface. This hydraulic pressure, acting on the second pressure-receiving surface, creates a second force F2 that forces or biases spool 20 in the negative x-axis direction.

As previously discussed, the area D1 of the first pressure-receiving surface is set to be less than the area D2 of the second pressure-receiving surface, that is, D1<D2. For the same hydraulic pressure, acting on each of the first and second pressure-receiving surfaces, the first force F1 is less than the second force F2. Hence, the sliding force, produced as a result of the force difference (F2−F1) between the second force F2 acting in the negative x-axis direction and created by hydraulic pressure on the second pressure-receiving surface of the area D2 and the first force F1 acting in the positive x-axis direction and created by hydraulic pressure on the first pressure-receiving surface of the area D1, acts on spool 20 so as to force the spool 20 in the negative x-axis direction.

The hydraulic pressure in the first pressure chamber is approximately equal to the hydraulic pressure in supply passage 53b. At least at the position “A”, the hydraulic pressure in a portion of supply passage 53a downstream of the branched point 530 and the hydraulic pressure in supply passage 53b can be regarded as to be approximately equal to each other. Thus, the hydraulic pressure in the first pressure chamber can also be regarded as to be approximately equal to the hydraulic pressure in a portion of supply passage 53a downstream of the branched point 530.

When a signal “A” is outputted from controller CU to pilot valve 3, the pilot valve 3 operates to connect the second pressure chamber to the oil pan O/P (that is, to the atmosphere), thus realizing a state where the hydraulic pressure in supply passage 53b acts on only the first pressure-receiving surface. Hence, by the first force F1, spool 20 is forced in the positive x-axis direction (i.e., in a direction that increases the flow-passage area of the flow path between supply passages 53a-53b). In this manner, the position “A” can be realized. Conversely when a signal “B” is outputted from controller CU to pilot valve 3, the pilot valve 3 operates to connect a portion of supply passage 53a downstream of the branched point 530 to the second pressure chamber, thus realizing a state where a hydraulic pressure approximately equal to the hydraulic pressure in supply passage 53b (or the hydraulic pressure in supply passage 53a) acts on both the first and second pressure-receiving surfaces. Hence, by a force corresponding to the difference (F2−F1) between the second force F2 and the first force F1, spool 20 is forced in the negative x-axis direction (i.e., in a direction that decreases or throttles the flow-passage area of the flow path between supply passages 53a-53b). In this manner, the position “B” can be realized.

More concretely, when a signal “A” (i.e., an OFF signal) is outputted from controller CU to pilot valve 3, the solenoid 34 of pilot valve 3 becomes de-energized. Thus, ball 31, which is forced in the negative y-axis direction by the spring force of spring 32, acts to block fluid-communication between axial passage 301 and relay passage 302. Simultaneously, the sealing surface of armature 33 moves apart from the sealing surface formed in the opening of the negative y-axis direction of relay passage 304, and as a result fluid-communication between relay passages 304-305 is established. Hence, oil in a portion of supply passage 53a downstream of the branched point 530 is not fed into the second pressure chamber. Also, oil in the second pressure chamber is drained through the axial passage 442, relay passages 303-305, and the exhaust passage (not shown) to the oil pan O/P. Thus, the hydraulic pressure in the second pressure chamber drops to a pressure level substantially corresponding to atmospheric pressure. Owing to the hydraulic pressure acting on the second pressure-receiving surface, remarkably less than the hydraulic pressure acting on the first pressure-receiving surface, the first force F1 becomes greater than the second force F2. As a result of this, spool 20 is forced in the positive x-axis direction, thus realizing the position “A”.

In contrast, when a signal “B” (i.e., an ON signal) is outputted from controller CU to pilot valve 3, the solenoid 34 of pilot valve 3 becomes energized. Thus, armature 33 moves in the positive y-axis direction against the spring force of spring 32 by a magnetic force. Hence, ball 31 moves apart from the opening of the positive y-axis direction of relay passage 302, and as a result fluid-communication between axial passage 301 and relay passage 302 is established. Simultaneously, the sealing surface of armature 33 is brought into abutted-engagement with the sealing surface formed in the opening of the negative y-axis direction of relay passage 304, and as a result fluid-communication between relay passages 304-305 is blocked. Hence, oil in a portion of supply passage 53a downstream of the branched point 530 is fed into the second pressure chamber through radial passage 443, axial passage 301, relay passage 303 and axial passage 442. Also, oil in the second pressure chamber is not drained through the relay passages (e.g., relay passage 304) to the oil pan O/P. Thus, the hydraulic pressure in the second pressure chamber becomes approximately equal to the hydraulic pressure in a portion of supply passage 53a downstream of the branched point 530. Owing to the hydraulic pressures acting on the first and second pressure-receiving surfaces, approximately equal to each other, the second force F2 becomes greater than the first force F1. As a result of this, spool 20 is forced in the negative x-axis direction, thus realizing the opposite position “B”.

In the embodiment, the signal “A” inputted to pilot valve 3 is an OFF (de-energization) signal, whereas the signal “B” inputted to pilot valve 3 is an ON (energization) signal. The control valve apparatus of the embodiment is configured so that the axial position of spool 20 can be selectively shifted from one of two different positions (namely, the position “A” and the opposite position “B”) to the other.

Controller CU carries out switching action between the signal “A” (an OFF signal of solenoid 34) and the signal “B” (an ON signal of solenoid 34) appropriately depending on latest up-to-date information about the engine operating condition (e.g., the current engine load and the current valve-timing control state). Hereby, the throttled (constricted) state of the flow path, through which supply passages 53a-53b are communicated with each other, can be adjusted, and thus the flow rate of oil flowing through the supply passage 53b and the flow rate of oil flowing through the branch passage 54 can be controlled.

OPERATION AND EFFECTS OF EMBODIMENT

(Effects Obtained by Electronic Control)

In the shown embodiment, control valve apparatus 1 is electronically controlled in response to an electric signal (an electronic signal). That is, by outputting a selected one of signals “A” and “B” from controller CU to pilot valve 3, the axial position of spool 20 (a valve element) of control valve apparatus 1 can be electronically controlled from one of the position “A” (i.e., a full fluid-communication state) and the opposite position “B” (i.e., a maximum flow-constriction state) to the other with a high responsiveness, only as needed.

As a modification, a spring-offset, external-pilot-pressure operated type may be adopted as the control valve apparatus 1. For instance, one axial end of the spool is permanently biased in the positive x-axis direction by a biasing member (e.g., a coiled spring), whereas the opposite end of the spool is forced in the negative x-axis direction by a hydraulic pressure in the supply passage, in other words, an external pilot pressure. In such a spring-offset, external-pilot-pressure operated type, the spool valve can be opened or closed depending on the hydraulic pressure in the supply passage. However, the spring-offset, external-pilot-pressure operated type has difficulty in arbitrarily varying a flow rate of lubricating oil flow into the downstream supply passage (toward each of lubricated engine parts) and a flow rate of working oil flow into the upstream supply passage (toward the VTC device). The spring-offset, external-pilot-pressure operated spool valve type is inferior to the electronically-controlled spool valve type, in controllability.

In the case of the electronically-controlled type control valve apparatus 1 of the embodiment, it is possible to optimally control a fluid-communication state of the flow path between supply passages 53a-53b (in other words, both a supply flow rate of lubricating oil to each of lubricated engine parts and a supply flow rate of working oil to the VTC device) through all engine operating conditions as well as during an engine startup.

By the way, in the embodiment, control valve apparatus 1 is operated by way of two-position control, in other words, ON/OFF control, that is, switching between the position “A” (a large opening degree of the flow path between supply passages 53a-53b via spool valve 2) and the opposite position “B” (a small opening degree of the flow path between supply passages 53a-53b via spool valve 2). As compared to a continuously variable solenoid-operated control valve system in which the axial position of the spool (in other words, the opening degree of the flow path between supply passages 53a-53b) can be continuously varied, depending on a duty cycle of a pulse-width modulated signal of energization of the solenoid, control valve apparatus 1 of the embodiment, which is operated by way of two-position control, is superior with respect to simplified and downsized control valve system configuration.

In the embodiment, switching between the position “A” and the opposite position “B” of spool valve 2 is performed by ON-OFF control (energization/de-energization control) for the solenoid 34 of pilot valve 3. In this manner, the opening degree of pilot valve 3 (i.e., the position of armature 33) can be varied directly by solenoid 34. In lieu thereof, the ON/OFF controlled spool valve system may be replaced by a continuously variable solenoid-operated control valve system in which the axial position of the spool (in other words, the opening degree of the flow path between supply passages 53a-53b) can be continuously varied, depending on a duty cycle of a pulse-width modulated signal of energization of the solenoid. The duty-ratio-controlled continuously variable solenoid-operated control valve system is superior with respect to reduced whole size of the spool valve system, but inferior with respect to simplified control valve system configuration. Also, in the embodiment, sliding motion of spool 20 can be controlled by a control pressure (a pilot pressure) created by pilot valve 3 and applied to the back-pressure chamber (i.e., the second pressure-receiving surface) of spool valve 2. In lieu thereof, the spool may be operated directly by a magnetic force of a solenoid, that is, the pilot-operated spool valve may be replaced by a solenoid-operated spool valve. The solenoid-operated spool valve is superior with respect to a higher responsiveness, but inferior with respect to reduced whole size of the spool valve system.

(Optimization of Engine Lubricating Action and VTC Operability)

Controller CU is configured to output the signal “A” during high engine load operation that requires a high lubricating-oil flow rate and a high hydraulic pressure for engine lubrication, so that spool 20 is controlled to the position “A”. For instance, to determine whether the engine load is high or low, the processor of controller CU can use information from the crank angle sensor. With control valve apparatus 1 controlled to the position “A”, the flow path between supply passages 53a-53b is kept fully open but not throttled. Thus, lubricating oil of a large flow rate and a high hydraulic pressure can be fed into supply passage 53b (toward each of lubricated engine parts). Each of lubricated engine parts can be smoothly operated depending on engine load.

Under a high engine-load state, the engine speed often becomes high, and thus the hydraulic pressure, supplied from pump P to supply passage 53a, also becomes high. Hence, even with the flow path controlled to the fully-open state, a sufficient amount of oil can be also supplied to the branch passage 54 (toward the VTC device).

Controller CU is further configured to output the signal “B” when a rapid operation of the VTC device (i.e., a high responsiveness of valve timing control) is required for a superior operability of the VTC device, so that spool 20 is controlled to the opposite position “B”. With control valve apparatus 1 controlled to the opposite position “B”, the flow path between supply passages 53a-53b is throttled. The flow rate of lubricating oil fed to supply passage 53b (toward each of lubricated engine parts) is limited, and therefore most of the oil, discharged and force-fed from pump P to supply passage 53a, is fed into branch passage 54 (toward the VTC device). Thus, high-pressure working oil can be preferentially fed into the VTC device. Even under the above-mentioned fully-throttled state (i.e., the maximum flow-constriction state), oil can be fed via only the through hole 227 formed in spool 20 to supply passage 53b (toward lubricated engine parts). The flow rate of oil, flowing via only the through hole 227 to supply passage 53b, is set to a flow rate equal to or slightly greater than a minimum flow rate needed to lubricate moving engine parts.

By the way, controller CU is further configured to output the signal “A” to the pilot valve 3 for a predetermined time delay (a set time of a delay timer incorporated in controller CU) after the engine has been started. Thus, the position “A” of spool valve 2 is realized, and thus a flow rate of oil flowing through the supply passage 53b can be increased so as to preferentially feed most of oil, discharged and force-fed from pump P to supply passage 53a, into supply passage 53b (i.e., toward lubricated engine parts), and simultaneously to limit oil supply to the hydraulic actuator (the VTC device). Hereby, it is possible to enhance a lubrication performance when restarting the engine after the vehicle (the engine) was left for a long time in the engine stopped state, and also to suppress a stability of operation and a startability of the VTC device from deteriorating owing to oil including a lot of air bubbles and fed to the VTC device immediately after an engine startup.

In this manner, in the embodiment, switching between the signal “A” and the signal “B” is made depending on the engine operating condition (e.g., the current engine load and the current valve-timing control state). As a result of this, shifting of the axial position of spool 20 between the position “A” and the opposite position “B”, in other words, switching of the flow path between supply passages 53a-53b from one of a large opening degree of the flow path between supply passages 53a-53b and a small opening degree of the flow path between supply passages 53a-53b to the other is made, so as to optimally control a flow rate of oil flow into the downstream supply passage (toward each of lubricated engine parts) and a flow rate of oil flow into the upstream supply passage (toward the VTC device). Thus, two requirements, namely, a superior engine lubricating action and a superior VTC operability can be optimally balanced to each other at a high level.

(Enhancement of Function of Flow-Rate Adjustment)

The apparatus as disclosed in JP57-173513 (hereinafter referred to as “first comparative example”) can also be applied to the same hydraulic system to which the control valve apparatus 1 of the embodiment can be applied. In the apparatus as disclosed in the first comparative example, in order to realize the enhanced responsiveness of a hydraulic actuator, while suppressing an increase in capacity (an increase in discharge) of an oil pump, when the discharge pressure of the oil pump is low and thus the flow rate of oil fed into a supply passage is limited, the control valve apparatus is closed and as a result the flow rate of oil flowing through the supply passage downstream of the branched point is limited to an amount of oil passing through a bypass passage (an orifice). Hereby, oil can be preferentially fed into the branch passage (toward the hydraulic actuator). Conversely when the discharge pressure of the oil pump becomes high, the control valve apparatus is opened so as to increase an amount of oil fed into each of lubricated engine parts. However, in the apparatus as disclosed in the first comparative example, there is a risk of the deterioration of a function of flow-rate adjustment. That is, the orifice of the apparatus as disclosed in the first comparative example is configured to open responsively to the inflow of oil into the orifice. Contaminants probably exist within the oil flowing into the orifice. There is an increased tendency for the orifice, whose opening area is small, to be choked by such contaminants (debris and/or dusts). Thus, there is a risk of deteriorating the oil supply to the downstream side of the orifice (toward each of lubricated engine parts).

More concretely, there is a possibility that debris, arising from machining (drilling), still remains within the supply passage to be connected to the control valve apparatus, at least before the first oil flow through the supply passage. Also, due to wear of each of moving engine parts during operation of the engine, dusts are produced. There is a risk that the opening of the orifice is choked due to the produced dusts and/or debris.

Also, when the oil was left for a long time under a state where there is no oil flow, that is, with zero oil-flow velocity, or with low oil-flow velocity, in other words, with stagnant oil, oil clot, having a high viscosity, may be produced. Such oil clot often stays in the oil passage. For instance, when the oil pump comes into operation and thus oil begins to flow into the oil passage, the oil clot, sticking in the oil passage, falls away from the inner peripheral wall of the oil passage and then mixed with the circulating oil. Thus, there is a risk that the opening of the orifice is choked due to the fallen oil clot.

By the way, generally, the opening area of the orifice is less than the area of one mesh of a usual oil filter. In the case that such a usual oil filter is used, it is difficult to remove or purify almost all of contaminants (debris and dusts). It is difficult to certainly avoid the opening of the orifice from being choked due to the contaminants. To certainly remove contaminants, a contaminant-purifying filter must be installed separately from the usual oil filter. This leads to the demerit of increased manufacturing costs.

In contrast to the above, control valve apparatus 1 of the embodiment is configured to control, depending on the axial position of the valve element (spool 20), switching between the opening of the large flow control section (through holes 223-226) whose maximum opening area is comparatively large and the opening of the small flow control section (through hole 227) whose maximum opening area is comparatively small. At least in a specified state where the opening of the large flow control section is fully opened with a maximum opening area, the opening of the small flow control section (serving as an orifice) is closed. Concretely, at the position “A” of spool 20, the first communication passage (through holes 223-226) is kept in its communicated state and simultaneously the opening of through hole 227, which opens from the bottom of second groove 222, is blocked by the root 426 of flow-passage portion 42 of housing 4 such that the second communication passage (through hole 227) is kept in its non-communicated state.

For the reasons discussed above, even when contaminants are mixed with the oil, there is a less possibility the opening of the second communication passage (through hole 227) may be choked due to the contaminants, because of no distribution of oil through the small flow control section (through hole 227) at least during the large flow control with spool 20 held at the position “A”. Thus, it is possible to effectively suppress the through hole 227 from being undesirably choked due to contaminants. Thereafter, when spool 20 has been shifted to the opposite position “B”, the small flow control cannot be prevented.

There is a slight tendency that contaminants stay in the opening of through hole 227, which opens from the inner peripheral surface of cylindrical bore 220 of flow-passage portion 22 of spool valve 2, due to oil flow within the first pressure chamber even during the large flow control. In such a case, there is a less possibility that the contaminants are press-fitted into the opening of through hole 227. This is because the opening of through hole 227, which opens from the bottom of second groove 222, is blocked by the root 426 of flow-passage portion 42 of housing 4. Thereafter, when the flow control mode has been switched to the small flow control, the contaminants, sticking in the opening of through hole 227, can be easily pushed and swept away by oil flown out of the opposite opening of through hole 227, which opens from the bottom of second groove 222. Hence, there is no problem.

Therefore, during the small flow control (i.e., during the throttled control) with spool 20 held at the opposite position “B”, it is possible to feed a desired amount of oil into the downstream supply passage 53b as well as the upstream supply passage 53a. Hereby, it is possible to enhance the function of flow-rate adjustment of control valve apparatus 1.

Suppose that the axial position of the valve element (spool 20) is continuously controlled within the entire range of axial stroke of spool 20. This eliminates the necessity for opening the second communication passage (through hole 227), during the flow control with the first communication passage (though holes 223-226) opened. From the viewpoint of a reduction of contaminants staying in the opening of through hole 227, it is preferable to maintain the opening of the second communication passage (through hole 227) at its blocked state. For instance, suppose that the layout (the relative-position relationship) among the first group of through holes 223-226, the second group of through holes 421-424, and the through hole 227 is preset such that the second communication passage (through hole 227) becomes kept in its non-communicated state within a stroke range (in the x-axis direction) in which the valve element (spool 20) is positioned with greater frequency during flow control according to a predetermined control logic for reconciling an enhancement in lubrication performance and an enhancement in operability of the VTC device. The optimal setting of the layout of the through holes can provide the same effect as discussed above, that is, an enhancement in the function of flow-rate adjustment.

According to the shown embodiment, at least in a specified state where the large flow control section (through holes 223-226) is fully opened with a maximum opening area, the small flow control section (through hole 227) is closed. Concretely, at the position “A corresponding to a maximum axial displacement of spool 20 in the positive x-axis direction, the second communication passage (through hole 227) becomes kept in its non-communicated state.

Thus, according to the control valve apparatus of the embodiment in which the axial position of spool 20 can be selectively shifted (or switched) between two different positions, namely, the position “A” and the opposite position “B”, but, basically, spool 20 cannot be positioned at a certain intermediate position between these two positions “A” and “B”, the opening of through hole 227 is kept in its blocked state, except when selecting the opposite position “B”. In particular, during the large flow control that the position “A” is selected and thus through holes 223-226 are opened, the opening of through hole 227 is closed (blocked). For this reason, it is possible to eliminate or avoid a bad influence on the second communication passage (through hole 227) due to contaminants, thus enhancing the function of flow-rate adjustment.

Even assuming that the axial position of spool 20 continuously controlled, it is possible to effectively suppress the second communication passage (through hole 227) from being choked due to contaminants, at least in a specified state where the opening of the large flow control section is fully opened with a maximum opening area (that is, at least during a time period during which spool 20 is kept in the position “A”). In particular, in the case of adoption of a control logic that spool 20 is controlled to the position “A” and thus the opening of the large flow control section is fully opened with a maximum opening area at least for the purpose of enhancing a lubrication performance immediately after an engine startup, it is possible to eliminate or avoid a bad influence on the second communication passage (through hole 227) due to contaminants (oil clot), produced immediately after an engine startup (an oil pump startup), as much as possible.

Even in the event that the through hole 227 has been choked due to contaminants (oil clot), according to the shown embodiment in which control valve apparatus 1 can be electronically controlled in response to an electric signal (an electronic signal), it is possible to provide a fail-safe control function. For instance, during a signal output for controlling spool 20 to the opposite position “B”, controller CU receives information from an oil pressure sensor, on whether an oil supply to the downstream supply passage 53b (toward each of lubricated engine parts) is insufficient, and then determines, based on the information from the oil pressure sensor, whether the through hole 227 is choked. When it is determined that the second communication passage (through hole 227) has been choked due to contaminants, controller CU executes a fail-safe flow control by which the first communication passage (through holes 223-226) is opened by moving the spool 20. By virtue of such a fail-safe flow control, the flow control of oil by way of the second communication passage (through hole 227) is replaced with the flow control of oil by way of the first communication passage (through holes 223-226). By way of the first communication passage, it is possible to certainly assume an appropriate flow rate of oil fed into the downstream supply passage 53b (toward each of lubricated engine parts).

(Operation and Effects Obtained by Flow Path Layout of One Supply Passage Connected to Side Face of Spool and the Other Supply Passage Connected to Axial End of Spool)

In connecting supply passage 53 to spool 20, suppose that inlet and outlet ports of spool valve 2, are provided on the same side face of spool 20 in a manner so as to communicate the opening end of upstream supply passage 53a and the opening end of downstream supply passage 53b, respectively, such that the opening degree (i.e., the flow-passage area) of the flow path between supply passages 53a-53b can be adjusted depending on the axial position (sliding motion) of spool 20. In this case, generally, the opening end of upstream supply passage 53a and the opening end of downstream supply passage 53b must be laid out to be axially spaced from each other. This results in an increase in overall axial length of spool valve 2. Alternatively, inlet and outlet ports of spool valve 2, are provided on the same axial end of spool 20 in a manner so as to communicate the opening end of upstream supply passage 53a and the opening end of downstream supply passage 53b, respectively, such that the opening degree (i.e., the flow-passage area) of the flow path between supply passages 53a-53b can be adjusted depending on rotary motion of spool 20. In this case, generally, the opening end of upstream supply passage 53a and the opening end of downstream supply passage 53b must be laid out to be radially spaced from each other. This results in an increase in outside diameter of spool valve 2.

In contrast to the above, in the embodiment, one of the two ports of spool 20 is provided on the side of the sliding-contact surface of spool 20 in a manner so as to communicate the opening end of upstream supply passage 53a, while the other port is provided on the axial end of spool 20 in a manner so as to communicate the opening end of downstream supply passage 53b. Concretely, the inlet (i.e., supply passage 53a) of supply passage 53 opens from the sliding-contact surface of sliding-contact bore 40 (flow-passage portion 42 of housing 4) in sliding-contact with spool 20, whereas the outlet (i.e., supply passage 53b) of supply passage 53 opens from one axial end (i.e., the end of the negative x-axis direction) of sliding-contact bore 40. This contributes to the reduced radial dimension and reduced axial length of spool valve 2. Thus, it is possible to compactify the whole size of control valve apparatus 1.

In the case of supply passage 53 (supply passages 53a-53b) of the shown embodiment, the direction (i.e., the y-axis direction) that the upstream supply passage 53a extends and the direction (i.e., the x-axis direction) that the downstream supply passage 53b extends, differ from each other and intersect with each other at an approximately right angle. In the shown embodiment, the control valve structure is designed so that spool 20 slides in the x-axis direction. In lieu thereof, the control valve structure may be designed so that spool 20 slides in the y-axis direction, and that the opening degree (i.e., the flow-passage area) of the flow path between supply passages 53a-53b can be adjusted depending on sliding motion of spool 20 in the y-axis direction.

Even with the above-discussed construction that the directions that the upstream and downstream supply passages 53a-53b extend, differ from each other and intersect with each other at an approximately right angle, the provision of annular groove 561, formed to surround the entire circumference of the flow-passage portion, is advantageous with respect to smooth oil flow from one port of spool valve 2 (i.e., supply passage 53a) to the other port (i.e., supply passage 53b).

(Operation and Effects Obtained by Pressure-Receiving Surface Area Difference D2−D1)

Generally, a sliding spool type control valve is superior from a viewpoint that its valve element (a spool) can be smoothly operated (moved) by a comparatively small force without being affected by a hydraulic pressure of fluid flowing through the spool valve, rather than control valves of another type. Thus, the spool type control valve is suited to reliable control of flow for a high-pressure hydraulic circuit.

However, in the control valve structure of the embodiment, a hydraulic pressure acts on each of axial ends of spool 20. For instance, suppose that spool 20 is operated directly by a magnetic force of a solenoid. Such an electromagnetic-solenoid-operated control valve system requires a comparatively large magnetic force, overcoming the hydraulic pressure. This means an enlargement in the whole size of the solenoid-operated control valve system.

For the reasons discussed above, in the embodiment, pilot valve 3 is further provided and spool 20 is operated by applying a hydraulic pressure (a pilot pressure), concretely, a hydraulic pressure in supply passage 53a to the second pressure-receiving surface of spool 20 by way of the pilot valve 3. In comparison with the solenoid-operated control valve system, the control valve apparatus 1 of the embodiment facilitates switching of a high-pressure hydraulic circuit, concretely, smooth adjustment of flow of oil flowing through the flow path (i.e., supply passage 53b) downstream of the branched point 530, while suppressing the control valve system from being enlarged.

Also, in the embodiment, there is an area difference (D2−D1) between the second pressure-receiving surface of spool 20 and the first pressure-receiving surface of spool 20. The control valve apparatus of the embodiment is configured to operate (shift) spool 20 by the force difference (F2−F1) of two opposite forces F2 and F1, acting on respective axial ends of spool 20, which force difference is created by the area difference (D2−D1). Hence, it is possible to reduce the size of spool 20, while ensuring a smooth sliding motion (a high responsiveness of operation) of spool 20 laid out at a portion in which supply passages 53a-53b intersect with each other at an approximately right angle.

Conversely, suppose that there is no area difference between the first and second pressure-receiving surfaces and thus sliding motion of spool 20 is created by the hydraulic pressure difference of hydraulic pressures acting on respective axial ends of spool 20. On the one hand, it is necessary to let the magnitudes of hydraulic pressures acting on respective axial ends of spool 20 be different. Simultaneously, suppose that spool 20 is installed at a portion in which supply passages 53a-53b intersect with each other at an approximately right angle. On the other hand, a hydraulic pressure the downstream end of supply passage (i.e., the downstream supply passage 53b) always acts on the first axial end of spool 20 (i.e., the first pressure-receiving surface) during operation of the engine. For instance, assuming that spool 20 has to be moved in the negative x-axis direction in which the first axial end of spool 20 faces, the magnitude of hydraulic pressure acting on the second axial end of spool 20 (i.e., the second pressure-receiving surface) has to be increased than the magnitude of hydraulic pressure acting on the first axial end of spool 20 (i.e., the first pressure-receiving surface). In this case, a hydraulic pressure in the upstream end of supply passage 53 (i.e., the upstream supply passage 53a) can be just used as a hydraulic pressure acting on the second axial end of spool 20 (i.e., the second pressure-receiving surface). However, a hydraulic pressure in the downstream end of supply passage 53 (i.e., the downstream supply passage 53b) to be used as a hydraulic pressure acting on the first axial end of spool 20 (i.e., the first pressure-receiving surface) must be adjusted (dropped) by means of a flow-constriction device or a pressure control valve. This leads to the problem of a pressure loss.

For the reasons discussed above, in order for spool 20 to move without producing any pressure loss, the area difference (D2−D1) between the second pressure-receiving surface of the area D2 and the first pressure-receiving surface of the area D1 is necessary.

Alternatively, suppose that there is no area difference between the first and second pressure-receiving surfaces and thus the force difference between forces acting on respective axial ends of spool 20 is created by the spring force of a biasing means (e.g., a spring-load means). For instance, suppose that, to move the spool 20 in the negative x-axis direction, the spring force, produced by the biasing means, acts on the second axial end of spool 20 (i.e., the second pressure-receiving surface) instead of using the hydraulic pressure difference. In such a case, immediately after an engine startup there is a less development of hydraulic pressure in supply passage 53, spool 20 can be held at the opposite position “B”, in which the flow path is conditioned in the maximum flow-constriction state of supply passages 53a-53b, by the spring force of the biasing means. Under these condition, when shifting spool 20 from the opposite position “B” to the position “A”, there is a lag time between (i) the point of time of switching from the signal “B” to the signal “A” and (ii) the point of time of a sufficient development of hydraulic pressure in supply passage 53, overcoming the spring force of the biasing means. Thus, it is necessary to wait, until, the hydraulic pressure in supply passage 53 develops sufficiently. However, such a spring-offset type control valve system has difficulty in enhancing a lubrication performance by opening the flow path between supply passages 53a-53b during an engine startup. Spool 20 has to be moved in the positive x-axis direction by the hydraulic pressure, while overcoming the spring force of the biasing means during the engine startup. There is a possibility that spool 20 cannot be operated (shifted) with a high responsiveness. Also, by the addition of the biasing means (spring-load means), a working oil pressure range, within which spool 20 can be operated, tends to become narrow, and as a result it is difficult to ensure a smooth sliding motion (a high responsiveness of operation) of spool 20.

Conversely, suppose that, in order for spool 20 to move in the positive x-axis direction, the spring force, produced by the biasing means, acts on the first axial end of spool 20 (i.e., the first pressure-receiving surface) instead of using the hydraulic pressure difference. In such a case, immediately after an engine startup, spool 20 can be held at the position “A”, in which the flow path is conditioned in the full fluid-communication state of supply passages 53a-53b, by the spring force of the biasing means. Under these conditions, when shifting spool 20 from the position “A” to the opposite position “B”, in other words, for switching to the maximum flow-constriction state of supply passages 53a-53b, spool 20 has to be moved in the negative x-axis direction by a sufficient hydraulic pressure acting on the second axial end of spool 20 (i.e., the second pressure-receiving surface), overcoming the spring force of the biasing means. To produce the sufficient hydraulic pressure, which acts on the second pressure-receiving surface, higher than the hydraulic pressure, which acts on the first pressure-receiving surface, the area difference between the second pressure-receiving surface and the first pressure-receiving surface is necessary.

In contrast, in the embodiment, spool 20 can be operated by the force difference (F2−F1) of two opposite forces F2 and F1, acting on respective axial ends of spool 20, which force difference is created by the pressure-receiving surface area difference (D2−D1), without any biasing means (e.g., without any spring-load means) acting on spool 20.

Thus, it is unnecessary to wait, until the hydraulic pressure in supply passage 53 develops sufficiently. Even when hydraulic pressures acting respective axial ends of spool 20 are still low, it is possible to produce a force needed to axially move the spool 20 by virtue of the area difference (D2−D1). A working oil pressure range, within which spool 20 can be operated, is comparatively wide and also it is unnecessary to move the spool 20 against the spring force, because of no addition of biasing means (spring-load means). Thus, it is possible to ensure a smooth sliding motion (a high responsiveness of operation) of spool 20. Therefore, at an early stage after the engine has been started, switching of the flow path between a full fluid-communication state of supply passages 53a-53b (i.e., the large flow control mode corresponding to the position “A” of FIG. 4) and a maximum flow-constriction state (i.e., the small flow control mode corresponding to the opposite position “B” of FIG. 5) can be made with a high responsiveness, and thus flow control can be rapidly accurately performed.

Additionally, there is no biasing means (no sprang-load means) acting on spool 20, the number of component parts can be reduced. Also, only the hydraulic pressure acts on each of the first and second pressure-receiving surfaces of spool 20, and additionally the magnitude of hydraulic pressure acting on the first pressure-receiving surface and the magnitude of hydraulic pressure acting on the second pressure-receiving surface are approximately equal to each other. Hence, even in the case of a slight pressure-receiving surface area difference (D2−D1), it is possible to operate spool 20, utilizing the force difference (F2−F2) created by the slight pressure-receiving surface area difference (D2−D1). As a result, spool valve 2 (especially, the radial size of spool 20) can be downsized. In other words, control valve apparatus 1 of the embodiment can reconcile both the reduced size of spool 20 and the same high responsiveness as the previously-discussed spring-offset type control valve system.

Furthermore, the hydraulic pressure in the downstream end of supply passage 53 (i.e., the downstream supply passage 53b) is just used as a hydraulic pressure acting on the first axial end of spool 20 (i.e., the first pressure-receiving surface), while the hydraulic pressure in the upstream end of supply passage 53 (i.e., the upstream supply passage 53a) is just used as a hydraulic pressure acting on the second axial end of spool 20 (i.e., the second pressure-receiving surface). Thus, there is a less wasteful pressure loss.

In particular, control valve apparatus 1 of the embodiment is configured to selectively introduce oil of the upstream side of supply passage 53 (i.e., the upstream supply passage 53a) into the second pressure chamber (the side of the second pressure-receiving surface) without introducing oil of the downstream side of supply passage 53 (i.e., the downstream supply passage 53b) into the second pressure chamber. As compared to another type of control valve system in which oil of the downstream side of supply passage 53 (i.e., the downstream supply passage 53b) is introduced into the second pressure chamber, in the control valve apparatus 1 of the embodiment that selectively introduces oil of the upstream side of supply passage 53 (i.e., the upstream supply passage 53a) into the second pressure chamber, there is a less pressure loss of hydraulic pressure introduced into the second pressure chamber (the side of the second pressure-receiving surface). Hence, the pressure difference between hydraulic pressure introduced into the second pressure chamber and hydraulic pressure introduced into the first pressure chamber tends to become less. As a result, spool 20 can be effectively shifted by virtue of the area difference (D2−D1) between the area D2 of the second pressure-receiving surface (the second axial end of spool 20) and the area D1 of the first pressure-receiving surface (the first axial end of spool 20), in other words, by the sliding force (i.e., F2−F1), produced as a result of the force difference between the axial force F2 acting in the negative x-axis direction and created by hydraulic pressure on the second pressure-receiving surface of the area D2 and the axial force F1 acting in the positive x-axis direction and created by hydraulic pressure on the first pressure-receiving surface of the area D1. Thus, it is possible to ensure a smooth sliding motion (a high responsiveness of operation) of spool 20.

(Operation and Effects Obtained by Flow Path Layout of Upstream Supply Passage Connected to Side Face of Spool and Downstream Supply Passage Connected to Axial End of Spool)

In the embodiment, spool 20 is laid out to slide in the direction (i.e., in the x-axis direction) that the downstream supply passage 53b extends. In other words, the inlet port of spool 20 is provided on the side of the sliding-contact surface of spool 20 in a manner so as to communicate the opening end of upstream supply passage 53a, while the outlet port of spool 20 is provided on the axial end of spool 20 in a manner so as to communicate the opening end of downstream supply passage 53b.

Thus, the direction of flow of oil flowing via the inlet port of spool 20 (i.e., the opening end of upstream supply passage 53a) into spool valve 2 is substantially perpendicular to the direction of sliding motion of spool 20. The direction of flow of oil flowing via the spool inlet port into spool valve 2 is not the axial direction of spool 20. Thus, it is possible to suppress the operation (the sliding motion) of spool 20 from being affected by dynamic pressure, which may be created by the flow velocity of oil flowing through spool 20. In particular, even when the oil-flow velocity is high, it is possible to suppress unintended sliding motion of spool 20, thus enabling stable operation of spool 20, that is, more accurate flow control.

Furthermore, annular groove 561 is provided to surround the entire circumference of the flow-passage portion of spool valve 2, and thus oil, supplied from supply passage 53a to spool valve 2, is necessarily distributed into annular groove 561. This contributes to equalization of the supplied oil pressure, thus more certainly enabling stable operation of spool 20 and more accurate flow control.

Moreover, the inlet port of spool 20 (i.e., the opening end of upstream supply passage 53a) is provided on the side of the sliding-contact surface of spool 20 rather than on the axial end of spool 20. The distance between the opening end of upstream supply passage 53a and the second axial end of spool 20 (i.e., the second pressure-receiving surface) is shorter than the distance between both axial end faces of spool 20. In the case of the embodiment in which the flow path is configured to selectively introduce oil of the upstream side of supply passage 53 (i.e., the upstream supply passage 53a) into the second pressure chamber (the side of the second pressure-receiving surface), it is possible to simplify the flow-passage structure among the spool inlet port, the opening end of upstream supply passage 53a, and the second pressure chamber. Concretely, the system of the embodiment does not require the addition of a hydraulic line interconnecting the upstream supply passage 53a and the oil passage (i.e., radial passage 443) formed in pilot valve body 4c. This is because seal retaining bore 562 of engine block EB also serves as a hydraulic line interconnecting the upstream supply passage 53a and the radial passage 443. This contributes to smaller space requirements of overall system, reduced manufacturing costs and simplified control valve apparatus.

Additionally, the length of the hydraulic line interconnecting the upstream supply passage 53a (i.e., the inlet side of spool 20) and the second axial end of spool 20 (i.e., the second pressure-receiving surface) can be shortened. This contributes to a less pressure loss of oil, which is introduced from the former (supply passage 53a) to the latter (the second pressure-receiving surface), that is, a smooth sliding motion (a high responsiveness of operation) of spool 20.

(Operation and Effects Obtained by Layout of Pilot Valve)

Suppose that the centerline of pilot valve 3 is laid out in the x-axis direction, for example, coaxially with the centerline of spool valve 2 such that these centerlines pass through the axis “Q” of sliding motion of spool 20. In such a case, pilot valve 3 is located to protrude from the side face 100 of engine block EB in the positive x-axis direction, thus deteriorating the layout flexibility of control valve apparatus 1. Also, the distance between supply passage 53 and axial passage 301, which axial passage is formed in pilot valve 3 for intercommunicating the supply passage 53 and the second axial end of spool 20 (i.e., the second pressure-receiving surface), tends to become longer. Such a control valve structure requires the addition of a hydraulic line formed in housing 4 for interconnecting the supply passage 53 and the axial passage 301.

In contrast, in the embodiment, the axis of pilot valve 3 is laid out in the y-axis direction in such a manner as to extend parallel to the side face 100 of engine block EB. Thus, it is possible to suppress control valve apparatus 1 from protruding from the side face 100, thus enhancing the layout flexibility of control valve apparatus 1. Also, the axis of pilot valve 3 is laid out close to the side face 100 of engine block BB, and thus it is possible to shorten the distance between axial passage 301 and supply passage 53 (concretely, upstream supply passage 53a, annular groove 561, and seal retaining bore 562, all formed in engine block EB). Therefore, it as possible to simplify the flow-passage structure interconnecting the axial passage 301 and the supply passage 53. More concretely, as the hydraulic line interconnecting these passages 301 and 53, control valve apparatus 1 of the embodiment requires only the radial passage 443 formed in pilot valve body 4c of housing 4. This contributes to reduced manufacturing costs and simplified, downsized control valve apparatus.

(Operation and Effects Obtained by a Valve Unit Formed by Integrating Two Valve Components)

As a valve unit with both the spool valve 2 and the pilot valve 3 (in other words, with all of spool 20, pilot valve 3, and housing 4, which defines therein the sliding-contact bore 40), control valve apparatus 1 is easily assembled into the unit mounting portion 56 of engine block EB. Such a valve unit contributes to lower hydraulic system installation time and costs, reduced service time, and smaller space requirements of overall system.

(Operation and Effects Obtained by Flow-Constriction Orifice Structure)

The operation and effects, obtained by the flow-constriction orifice structure of control valve apparatus 1 of the embodiment is hereunder described, while comparing with the apparatus of the second comparative example shown in FIG. 6.

Referring now to FIG. 6, there is shown a partial cross-section of control valve apparatus 1 of the second comparative example, in which a flow-constriction device, which is provided for throttling or constricting the flow-passage area of the flow path between supply passages 53a-53b, is constructed by the apertures defined between the inner peripheral surfaces of through holes 421-424 of housing 4 and one axial end of spool 20, instead of forming a through hole (radial through hole 227) in the spool 20. The cross-section of FIG. 6 shows the partial cross-section passing through the centerline “Q” of control valve apparatus 1 of the second comparative example (that is, the axis of sliding motion of spool 20), under a state of the maximum displacement of spool 20 in the negative x-axis direction.

As clearly shown in FIG. 6, in the second comparative example, spool 20 does not have flow-passage portion 22. Spool 20 is formed into a substantially cylindrical hollow shape, but closed at one axial end such that partition wall portion 23 constructs the bottom of spool 20. The axial length of spool 2 of the second comparative example is dimensioned to be shorter than that of the embodiment. Notice that spool 20 of the second comparative example does not have through holes 223-227.

Spool 20 has an intermediate stepped portion 213 formed integral with the flanged portion 211 in such a manner as to extend from the side face of flanged portion 211 in the negative x-axis direction by a predetermined axial length. Intermediate stepped portion 213 is formed into an annular shape. The outside diameter of intermediate stepped portion 213 is dimensioned to be slightly less than that of flanged portion 211 and also dimensioned to be slightly greater than the inside diameter of small-diameter bore 40b.

In a similar manner to the embodiment (see FIGS. 4-5), in the second comparative example (see FIG. 6), sliding motion of spool 20 in the positive x-axis direction is restricted by abutment between the end face of the positive x-axis direction of flanged portion 211 and the end face of the negative x-axis direction of threaded plug 413. On the other hand, sliding motion of spool 20 in the negative x-axis direction is restricted by abutment between the end face of the negative x-axis direction of intermediate stepped portion 213 and the leftmost end face (viewing FIG. 5) of flow-passage portion 42 of housing 4, facing in the positive x-axis direction. That is, the end face of the negative x-axis direction of intermediate stepped portion 213 and the leftmost end face of flow-passage portion 42 of housing 4, facing in the positive x-axis direction, cooperate with each other to provide a second stopper (a sliding-motion stopper for spool 20 in the negative x-axis direction) by which the opposite restricted position “B” shown in FIG. 6 is realized.

Intermediate stepped portion 213 is formed to have its outside diameter slightly less than that of flanged portion 211. Even with the spool 20 held at the position “B”, an annular space can be defined between the outer peripheral surface of intermediate stepped portion 213 and the inner peripheral surface of large-diameter bore 40a (a large-diameter portion of sliding-contact bore 40). Thus, the inward opening of oblique hole 412, which opens into the interior space of sliding-contact bore 40 through the inner peripheral surface of large-diameter bore 40a, is not closed but always open. This enables the smooth movement of air in and out of the annular space through the oblique hole 412 during sliding motion of spool 20, thus ensuring a smooth operation (a smooth sliding motion) of spool 20.

With spool 20 held at the position “A”, the end face of spool 20, facing in the negative x-axis direction, that is, the right-hand side face of the bottom 23 is positioned to close approximately one-half (the left-hand half) of each of through holes 421-424 by the outside cylindrical surface of spool 20. In other words, at the position “A”, each of through holes 421-424 is approximately half-opened. At this restricted position “A”, the opening degree of through holes 421-424 becomes maximum, and thus the flow-passage area of the oil flow path, directed from the supply passage 53a through the annular groove 561 and through holes 421-424 to the inner peripheral side of flow-passage portion 42 (supply passage 53b), becomes a maximum value.

The opening area (the flow-passage area) of the through holes 421-424 tends to gradually reduce (because of gradual overlapping of the outside cylindrical surface of spool 20 and the through holes 421-424), as spool 20 moves from the position “A” to the opposite position “B” in the negative x-axis direction and thus the axial displacement of spool 20 in the negative x-axis direction increases.

With spool 20 held at the opposite position “B” (see FIG. 6), the end face of spool 20, facing in the negative x-axis direction, that is, the right-hand side face of the bottom 23 is positioned to be slightly offset from the end of the negative x-axis direction of each of through holes 421-424 toward the positive x-axis direction. In other words, at the opposite position “B”, spool 20 and the through holes 421-424 of flow-passage portion 42 of housing 4 largely overlap each other. At this restricted position “B” (i.e., the largely overlapping position of FIG. 6), the opening degree of through holes 421-424 becomes minimum, and thus the flow-passage area of the oil flow path, directed from the supply passage 53a through the annular groove 561 and through holes 421-424 to the inner peripheral side of flow-passage portion 42 (supply passage 53b), becomes a minimum value.

As discussed above, in the second comparative example of FIG. 6, the apertures defined between the inner peripheral surfaces of through holes 421-424 of housing 4 and the first axial end of spool 20, facing in the negative x-axis direction, serve as a flow-constriction device (a variable orifice). When spool 20 is positioned at the opposite position “B” (see FIG. 6), the apertures (the variable orifice) provide a maximum flow-constricting orifice action. Also, at the opposite position “B” (see FIG. 6), corresponding to the maximum axial displacement of spool 20 in the negative x-axis direction, the first axial end of spool 20, facing in the negative x-axis direction, exists within the through holes 421-424, as viewed in the radial direction of housing 4. More concretely, in the second comparative example of FIG. 6, at the position “A” as well as at the opposite position “B”, the first axial end of spool 20, facing in the negative x-axis direction, exists within the through holes 421-424, as viewed in the radial direction of housing 4. That is, the first axial end of spool 20, facing in the negative x-axis direction, is not supported by the entire inner periphery of small-diameter bore 40b.

The other construction of the second comparative example of FIG. 6 is exactly the same as the embodiment of FIGS. 4-5.

In contrast to the flow-path configuration of the embodiment (see FIGS. 4-5) in which oil can be fed from annular groove 561 through the second group of through holes 421-424 and the first group of through holes 223-226 to the inner peripheral side of flow-passage portion 42 (supply passage 53b), according to the flow-path configuration of the second comparative example (see FIG. 6), oil is fed into the inner peripheral side of flow-passage portion 42 directly through the through holes 421-424. Thus, it is easy to enlarge the flow-passage area of the oil flow path, directed from the supply passage 53a through the annular groove 561 and through holes 421-424 to the inner peripheral side of flow-passage portion 42 (supply passage 53b), as compared to the flow-path configuration of the embodiment (see FIGS. 4-5). Hence, a pressure loss of oil flowing through the control valve apparatus 1 can be easily suppressed, thus enabling oil to be more rapidly fed to each of lubricated engine parts, after the engine has been started.

In the shown embodiment of FIGS. 4-5, differing from the second comparative example of FIG. 6, through hole 227 is further formed in the grooved portion of flow-passage portion 22 of spool 20 at which the second groove 222 is formed. Especially, at the opposite position “B” (see FIG. 5), through hole 227, bored in spool 20, serves as a flow-constriction orifice (an orifice) that throttles or constricts the flow-passage area of the flow path between supply passages 53a-53b with a maximum flow-constricting orifice action. That is, spool 20 is formed with two kinds of holes, namely, the first communication hole (or the first communication passage, concretely, through holes 223-226) whose opening area is large and the second communication hole (or the second communication passage, concretely, through hole 227) whose opening area is small. When a flow rate of oil to be fed into supply passage 53b (toward each of lubricated engine parts) has to be increased, the first communication passage is opened so as to feed oil to supply passage 53b by way of the first communication passage. Conversely when a flow rate of oil to be fed into branch passage 54 (toward the VTC device) has to be increased, the first communication passage is closed and simultaneously the second communication passage (the orifice) is opened so as to throttle the flow path between supply passages 53a-53b. Instead of throttling the flow path between supply passages 53a-53b by reducing the opening area of one kind of hole (see the second comparative example of FIG. 6), control valve apparatus 1 of the embodiment uses two kinds of holes so as to throttle the flow path between supply passages 53a-53b by switching from the closed state of the second communication hole (through hole 227) to the open state and by simultaneously switching from the open state of the first communication hole (through holes 223-226) to the closed state. In the second comparative example of FIG. 6, in which, especially at the opposite position “B”, the flow-constriction device is constructed in the form of a variable orifice (i.e., the apertures defined between the inner peripheral surfaces of through holes 421-424 of housing 4 and the first axial end of spool 20), utilizing the relative-position relationship between the axially sliding spool 20 and the stationary spool valve body 4a of housing 4, spool 20 (having back-pressure portion 21 but not having flow-passage portion 22) and spool valve body 4a (especially, through holes 421-424 formed in housing 4) both have to be more accurately machined and produced. In contrast, the embodiment requires accurate machining of only the through hole 227 (especially, an orifice bore of through hole 227 formed in spool 20), but not require very accurate machining of two different components, namely, spool 20 and spool valve body 4a of housing 4. That is, by accurate machining of only the orifice bore of through hole 227, it is possible to easily realize an accurate flow-passage area (i.e., an accurate orifice area) of the second communication passage, thus enabling the function of flow-rate adjustment to be enhanced, while largely suppressing individual differences of flow-constriction orifices machined and manufactured and also reducing manufacturing costs. That is, with spool 20 shifted to the opposite position “B”, the flow rate of oil flowing into the downstream supply passage 53b can be more accurately controlled or throttled by virtue of only the accurately-machined orifice bore of through hole 227. Thus, it is possible to intendedly realize preferential feed of most of oil, discharged from pump P to supply passage 53a, into branch passage 54 (i.e., toward the VTC device) and distribution of a minimum amount of oil, needed for lubricating action, to each of lubricated engine parts.

Also, in the embodiment, spool 20 is supported at both sides of through holes 421-424 of spool valve body 4a of housing 4 within its entire stroke range from the position “A” to the opposite position “B”. Concretely, at the side of the positive x-axis direction of through holes 421-424, spool 20 is supported by the entire inner periphery of sliding-contact bore 40 (both large-diameter bore 40a and small-diameter bore 40b). Also, at the side of the negative x-axis direction of through holes 421-424, spool 20 is supported by the entire inner periphery of sliding-contact bore 40 (small-diameter bore 40b). Thus, it is possible to suppress the centerline of spool 20 from being undesirably inclined with respect to the axis “Q” (i.e., the axis of sliding motion of spool 20).

Suppose that spool 20 is supported at one side of through holes 421-424 of spool valve body 4a of housing 4 either at the side of the positive x-axis direction of through holes 421-424 or at the side of the negative x-axis direction of through holes 421-424. For instance, suppose that, only at the side of the positive x-axis direction of through holes 421-424, spool 20 is supported by the inner periphery of sliding-contact bore 40 (see spool 20 of the second comparative example of FIG. 6 and having back-pressure portion 21 but not having flow-passage portion 22). In such a one-side support (see FIG. 6), the first axial end of spool 20, facing in the negative x-axis direction, tends to be somewhat inclined toward the inside of each of through holes 421-424, in other words, in the radial direction. In contrast, in the both-side support of the embodiment shown in FIGS. 4-5, it is possible to suppress each axial end of spool 20 from being inclined in the radial direction. This contributes to a smooth operation (a smooth sliding motion) of spool 20.

(Operation and Effects Obtained by Stopper)

In the embodiment, the inside diameter of the opening (i.e., through hole 420) of the negative x-axis direction of flow-passage portion 42 of housing 4 is dimensioned to be less than that of small-diameter bore 40b (a small-diameter portion of sliding-contact bore 40 for spool 20), in such a manner as to form the bottom 425 of the negative x-axis direction of flow-passage portion 42. The inside face of bottom 425 of flow-passage portion 42 of housing 4 cooperates with the end face of the negative x-axis direction of spool 20 (flow-passage portion 22) to provide a second stopper (a sliding-motion stopper for spool 20 in the negative x-axis direction). This eliminates the necessity of providing or forming an additional stopper structure, thus ensuring reduced number of component parts, lower machining time and costs, and compact control valve apparatus. Instead of using the second stopper, constructed by the end face of the negative x-axis direction of spool 20 and the inside face of bottom 425 of flow-passage portion 42 of housing 4, in a similar manner to the second comparative example of FIG. 6, the spool 20 of control valve apparatus 1 of the embodiment may have an intermediate stepped portion 213 formed integral with the flanged portion 211 in a manner so as to construct the second stopper by the intermediate stepped portion 213 in cooperation with the leftmost end face of flow-passage portion 42 of housing 4, facing in the positive x-axis direction.

(Operation and Effects Obtained by Cylindrical Bore and Radial Groove)

In the embodiment, cylindrical bore (recessed portion) 210 is formed in the back-pressure portion 21 of spool 20. This contributes to lightening of spool 20 (that is, reduced inertial mass of the valve element), and a smooth sliding motion (a high responsiveness of operation) of spool 20, in other words, a rapid switching action between the position “A” and the opposite position “B”. This also contributes to minimizing the area difference (D2−D1) between the area D2 of the second pressure-receiving surface (the second axial end of spool 20) and the area D1 of the first pressure-receiving surface (the first axial end of spool 20), in other words, the sliding force (i.e., F2−F1), produced as a result of the force difference between the axial force F2 acting in the negative x-axis direction and created by hydraulic pressure on the second pressure-receiving surface of the area D2 and the axial force F1 acting in the positive x-axis direction and created by hydraulic pressure on the first pressure-receiving surface of the area D1, as much as possible.

Furthermore, it is possible to install a biasing member (e.g., a spring) within the internal space (i.e., the second pressure chamber) defined by cylindrical bore 210 of the back-pressure portion 21, thus ensuring expanded design flexibility. For instance, suppose that an extension spring is installed in the cylindrical bore 210 (in other words, the second pressure chamber) to permanently force the spool 20 in the positive x-axis direction with respect to housing 4. The modification can provide the same operation and effects as a different modification in which a coiled compression spring is installed in the first pressure chamber to permanently force the spool 20 in the positive x-axis direction with respect to housing 4.

Conversely, suppose that the end face of spool 20, facing in the positive x-axis direction, is not formed with cylindrical bore (recessed portion) 210, but formed as a flat end face (a closed flat face). When, with spool 20 held at the position “A”, spool 20 is further forced in the positive x-axis direction by the hydraulic pressure in the first pressure chamber (supply passage 53), the flat end face of spool 20 and the inside end face of threaded plug 413 may adhere to each other with a less aperture between them. In such a case, it is difficult to deliver oil via pilot valve 3 through the flat end face of spool 20, facing in the positive x-axis direction to the second pressure-receiving surface (i.e., the second pressure chamber).

In contrast, in the embodiment, the end face of spool 20, facing in the positive x-axis direction, is formed with the cylindrical bore (recessed portion) 210. Thus, it is possible to suppress the end face of the positive x-axis direction of spool 20 and the inside end face of threaded plug 413 from adhering to each other. Even with the flanged portion 211 of spool 20 kept in wall-contact with the inside end face of threaded plug 413, cylindrical bore (recessed portion) 210 facilitates axial movement of the flanged portion 211 apart from the threaded plug 413 when delivering oil to the wall-contact portion. That is, when oil is fed via pilot valve 3 to the second axial end of spool 20 held at the position “A”, it is possible to easily catch or receive oil introduced via pilot valve 3 to the side of the second pressure-receiving surface by the cylindrical bore (recessed portion) 210. This enables a rapid sliding motion of spool 20 in the negative x-axis direction by rapidly generating a large magnitude of the second force F2, created by hydraulic pressure acting on the second pressure-receiving surface of the area D2.

By the way, when oil is fed via pilot valve 3 to the second pressure chamber of spool 20 held at the position “A”, first of all, oil introduced from axial passage 442 of pilot valve body 4c is fed into annular groove 411 formed in the inner periphery of sliding-contact bore 40 (large-diameter bore 40a). Hence, oil can be fed into the cylindrical bore (recessed portion) 210, while being distributed around the entire circumference of spool 20, thus ensuring more smooth introduction of oil into the second pressure chamber. In this manner, annular groove 411 contributes to a rapid sliding motion of spool 20 from the position “A” to the opposite position “B” (i.e., in the negative x-axis direction).

Additionally, in the embodiment, the end face of the positive x-axis direction of flanged portion 211 is formed with the radial groove 214. When spool 20 is positioned at the position “A”, oil can be delivered from annular groove 411 via radial groove 214 to the cylindrical bore (recessed portion) 210. This ensures smooth oil supply to the second pressure-receiving surface (the second pressure chamber), thereby further enhancing the above-mentioned effects obtained by the formation of cylindrical bore (recessed portion) 210.

Even when the angular position of radial groove 214 is arbitrarily changed owing to rotary motion of spool 20 (back-pressure portion 21) about the axis “Q” with respect to the sliding-contact bore 40, oil can be delivered by way of annular groove 411 via radial groove 214 to the cylindrical bore (recessed portion) 210.

Suppose that spool 20 is formed with only the radial groove 214 but not formed with the cylindrical bore (recessed portion) 210. The end face of spool 20, facing in the positive x-axis direction, can receive hydraulic pressure only within an area corresponding to radial groove 214, until movement of the flanged portion 211 out of abutted-engagement with the threaded plug 413 occurs. In contrast, in the embodiment, spool 20 is formed with the cylindrical bore (recessed portion) 210 as well as the radial groove 214, thus enabling the increased pressure-receiving surface even when the flanged portion 211 is in abutted-engagement with the threaded plug 413.

In the shown embodiment, although the flanged portion 211 has one radial groove 214, it will be appreciated that the number of a radial groove is not limited to “1”. The shape and the number of a radial groove formed in the flanged portion may be modified. Instead of forming the radial groove 214 in the flanged portion 211 of spool 20, a communication groove, intercommunicating the annular groove 411 and the cylindrical bore (recessed portion) 210, may be formed in the threaded plug 413. Instead of forming a communication groove (i.e., radial groove 214), intercommunicating the annular groove 411 and the cylindrical bore (recessed portion) 210, a ridged portion may be formed on either the flanged portion 211 or the threaded plug 413. When the flanged portion 211 is brought into abutted-engagement with the threaded plug 413 at the position “A”, an aperture (a communication passage) can be defined between them by the ridged portion.

As will be appreciated from the above, control valve apparatus 1 of the embodiment can provide the following significant effects.

(1) In a hydraulic system equipped with a main flow passage (supply passage 53) for feeding oil, discharged from an oil pump driven by an internal combustion engine, to each of lubricated engine parts, a branch passage 54 branched from the main flow passage at a branched point 530, and a hydraulic actuator (e.g., a VTC device) operated by a hydraulic pressure in the branch passage 54, the combination of:

a control valve apparatus 1 for adjusting a flow rate of the oil flowing through a portion (supply passage 53b) of the main flow passage downstream of the branched point 530, the control valve apparatus 1 configured to control an opening of a large flow control section (through holes 223-226) and an opening of a small flow control section (through hole 227) whose opening area is less than that of the large flow control section, depending on a position of a valve element (spool 20), and

the control valve apparatus 1 further configured to close the opening of the small flow control section, at least in a specified state where the opening of the large flow control section is fully opened with a maximum opening area.

Thus, it is possible to enhance the function of flow-rate adjustment, while suppressing the opening of the small flow control section, whose opening area is small, from being choked due to contaminants (debris and dusts).

The above-mentioned expression “adjustment of a flow rate of the oil flowing through a portion (supply passage 53b) of the main flow passage downstream of the branched point 530” is synonymous with “adjustment of a flow rate of the oil flowing through the branch passage 54”. This is because the greater the flow rate of oil flowing through supply passage 53b that can be controlled by control valve apparatus 1, the smaller the flow rate of oil flowing through branch passage 54, and vice versa.

Also, in the shown embodiment, although control valve apparatus 1 is applied to the variable valve timing control (VTC) device serving as a hydraulic actuator, it will be appreciated that control valve apparatus 1 may be applied to a hydraulic system with a hydraulic actuator of another type that requires a working pressure above a predetermined pressure level. For instance, control valve apparatus 1 may be applied to a hydraulic system with another type of hydraulically-operated variable valve operating device, such as a variable valve lift (VVL) system or a continuously variable valve event and lift control (VEL) system, or to a hydraulic system with a floating-bearing lubrication system (e.g., a turbine-bearing lubrication system of a turbocharger).

(2) The valve element (spool 20) is disposed in the portion (supply passage 53b) of the main flow passage downstream of the branched point 530.

That is, in the embodiment, control valve apparatus 1 is disposed in the main flow passage (supply passage 53) downstream of the branched point 530, for controlling or adjusting a flow rate of oil flowing through the main flow passage downstream of the branched point 530. In lieu thereof, control valve apparatus 1 may be disposed either in the branched point 530 or in the branch passage 54, for flow-rate distribution between oil distributed to each of lubricated engine parts and oil distributed to the hydraulic actuator. For instance, suppose that control valve apparatus 1 of a three-way type is disposed in the branched point 530, the downstream end of passage 54 is connected to each of lubricated engine parts such that passage 54 serves as a main flow passage, and the downstream end of passage 53b is connected to the VTC device such that passage 53b serves as a branch passage. In such a case, by throttling the opening degree of the three-way valve, a flow rate of oil flowing through the branch passage (passage 53b) can be controlled to a small flow-rate side. Conversely, by enlarging the opening degree of the three-way valve, a flow rate of oil flowing through the branch passage (passage 53b) can be controlled to a large flow-rate side. However, from the following viewpoints, the embodiment is superior to this modification.

In the embodiment, as previously described, the valve element (spool 20) is disposed in the portion (supply passage 53b) of the main flow passage downstream of the branched point 530. In other situations, except for in the presence of a sufficient lubricating requirement, such as during an engine startup in which lubricating action for moving engine parts is largely rapidly required, it is possible to throttle or control the flow rate of oil distributed to each of lubricated engine parts to a minimum. Thus, it is possible to suppress oil, discharged from the oil pump, from being wastefully exhausted, thus minimizing energy loss. Additionally, by throttling or controlling the flow rate of oil distributed to each of lubricated engine parts (to supply passage 53b) to a minimum value, needed for lubricating action, it is possible to distribute most of oil, discharged and force-fed from the oil pump, toward the hydraulic actuator (the VTC device) as much as possible. The responsiveness of the hydraulic actuator can be effectively enhanced. Control valve apparatus 1 of the embodiment uses a two-way valve. Thus, as compared to the use of a three-way valve having a more complicated structure, the two-way valve is simple, thus ensuring the increased design flexibility.

In the embodiment, control valve apparatus 1 is constructed by the pilot-operated type two-way spool valve 2. That is, as a valve element that can control or adjust the valve opening depending on its axial position, spool 20 is used. It will be appreciated that control valve apparatus 1 is not limited to such a pilot-operated type two-way spool valve. In lieu thereof, a control valve of another type may be used. That is, the spool valve may be replaced with another type, such as a rotary valve, a needle valve, or a slide valve.

(3) Control valve apparatus 1 comprises a sliding-contact bore 40 into which an inlet (supply passage 53a) of the main flow passage opens and from which an outlet (supply passage 53b) of the main flow passage opens, and a spool 20 installed to axially move in the sliding-contact bore 40 only as needed, the sliding-contact bore 40 and the spool 20 both disposed in the portion (supply passage 53b) of the main flow passage downstream of the branched point 530. The spool 20 has a first communication passage (through holes 223-226) intercommunicating the inlet (supply passage 53a) and the outlet (supply passage 53b) and a second communication passage (through hole 227) intercommunicating the inlet and the outlet and having an opening area less than an opening area of the first communication passage. Control valve apparatus 1 is configured to bring the first communication passage to a communicated state and simultaneously to bring the second communication passage to a non-communicated state, in a first state where the spool 20 has moved with a maximum displacement in one axial direction (i.e., the position “A” of FIG. 4) of the spool 20. Control valve apparatus 1 is further configured to bring the second communication passage to a communicated state and simultaneously to bring the first communication passage to a non-communicated state, in a second state where the spool 20 has moved with a maximum displacement in the opposite axial direction (i.e., the position “B” of FIG. 5) of the spool 20.

Thus, by the use of spool 20, it is possible to simply realize smooth switching (smooth flow-rate adjustment) for a high-pressure hydraulic circuit, through which, oil, discharged from the oil pump, flows. Additionally, in the maximum-displacement state of spool 20 (i.e., either in the first state (the position “A”) or the second state (the opposite position “B”)), switching action of the first communication passage from one of the communicated state and the non-communicated state to the other and switching action of the second communication passage from one of the non-communicated state and the communicated state to the other can be simultaneously made. This contributes to the simplified control system configuration. Furthermore, the second communication passage, serving as the small flow control section (the flow-constriction orifice), is formed in the spool 20 in the form of a through hole (hole 227). By accurate machining of only the second communication passage (an orifice bore of through hole 227 formed in spool 20), it is possible to enhance the function of flow-rate adjustment.

(4) Control valve apparatus 1 comprises a sliding-contact bore 40 into which an inlet (supply passage 53a) of the main flow passage opens and from which an outlet (supply passage 53b) of the main flow passage opens, and a spool 20 installed to axially move in the sliding-contact bore 40 selectively between two opposite axial positions (the position “A” and the opposite position “B”) only as needed, the sliding-contact bore 40 and the spool 20 both disposed in the portion (supply passage 53b) of the main flow passage downstream of the branched point 530. The spool 20 has a first communication passage (through holes 223-226) intercommunicating the inlet and the outlet and a second communication passage (through hole 227) intercommunicating the inlet and the outlet and having an opening area less than an opening area of the first communication passage Control valve apparatus 1 is configured to bring the first communication passage to a communicated state and simultaneously to bring the second communication passage to a non-communicated state, in a first state where the spool 20 has moved to one (the position “A”) of the two opposite axial positions. Control valve apparatus 1 is further configured to bring the second communication passage to a communicated state and simultaneously to bring the first communication passage to a non-communicated state, in a second state where the spool 20 has moved to the opposite axial direction “B”.

This contributes to the simplified and downsized control valve system configuration.

(5) The inlet (supply passage 53a) of the main flow passage is configured to open from a sliding-contact surface of the sliding-contact bore 40 in sliding-contact with the spool 20, whereas the outlet (supply passage 53b) of the main flow passage is configured to open from a first axial end of two opposite axial ends of the sliding-contact bore 40. The first communication passage (through holes 223-226) and the second communication passage (through hole 227) are formed separately from each other in a sliding-contact surface of the spool 20 in sliding-contact with the sliding-contact bore 40. The first communication passage (through holes 223-226) and the second communication passage (through hole 227) are configured to be merged with each other by an axial passage (the first pressure chamber) formed in the spool 20 along a centerline (the axis “Q”) of the spool 20, and then communicated with the outlet (supply passage 53b) of the main flow passage.

Thus, it is possible to enhance the stability of operation (sliding motion) of spool 20, while compactifying the whole size of control valve apparatus 1.

(6) The displacement of the spool 20 is electronically controlled.

Thus, it is possible to optimally control or adjust the flow rate of oil distributed to each of lubricated engine parts and the flow rate of oil distributed to the hydraulic actuator. Additionally, it is possible to ensure an appropriate flow rate of oil fed toward each of lubricated engine parts by a fail-safe flow control.

(7) The axial passage (the first pressure chamber) is configured to open from only the first axial end of two opposite axial ends of the spool 20. A pressure-receiving surface area D2 of the second axial end (back-pressure portion 21) of the spool 20 is dimensioned to be greater than a pressure-receiving surface area D1 of the first axial end (flow-passage portion 22) formed with the axial passage (the first pressure chamber). A hydraulic pressure in the main flow passage is selectively supplied or exhausted to or from the second axial end (back-pressure portion 21) of the spool 20 by an electromagnetic valve (pilot valve 3).

Thus, it is possible to reconcile the high responsiveness of operation (sliding motion) of spool 20 and the downsized spool 20.

(8) The second axial end (back-pressure portion 21) of the spool 20 has a cylindrical bore (recessed portion 210) formed therein.

Thus, it is possible to realize light-weight and enhanced operability of spool 20, thus reducing the whole size of control valve apparatus 1.

(9) The oil in the inlet (supply passage 53a) of the main flow passage is introduced into the second axial end (back-pressure portion 21) of the spool 20.

Thus, it is possible to enhance the responsiveness of operation of spool 20.

(10) The sliding-contact bore 40, the spool 20, and the electromagnetic valve are installed in the internal combustion engine in the form of a valve unit with the spool 20, the electromagnetic valve (pilot valve 3), and a housing 4, which defines therein the sliding-contact bore 40.

Thus, it is possible to realize lower hydraulic system installation time and costs, reduced service time, and smaller space requirements of overall system.

The entire contents of Japanese Patent Application No. 2010-033193 (filed Feb. 18, 2010) are incorporated herein by reference.

While the foregoing is a description of the preferred embodiments carried out the invention, it will be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope or spirit of this invention as defined by the following claims.

Claims

1. In a hydraulic system equipped with a main flow passage for feeding oil, discharged from an oil pump driven by an internal combustion engine, to each of lubricated engine parts, a branch passage branched from the main flow passage at a branched point, and a hydraulic actuator operated by a hydraulic pressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point,

the control valve apparatus configured to control an opening of a large flow control section and an opening of a small flow control section whose opening area is less than that of the large flow control section, depending on a position of a valve element disposed in the portion of the main flow passage downstream of the branched point, and

the control valve apparatus further configured to close the opening of the small flow control section, at least in a specified state where the opening of the large flow control section is fully opened with a maximum opening area.

2. In a hydraulic system equipped with a main flow passage for feeding oil, discharged from an oil pump driven by an internal combustion engine, to each of lubricated engine parts, a branch passage branched from the main flow passage at a branched point, and a hydraulic actuator operated by a hydraulic pressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point,

the control valve apparatus comprising a sliding-contact bore into which an inlet of the main flow passage opens and from which an outlet of the main flow passage opens, and a spool installed to axially move in the sliding-contact bore only as needed, the sliding-contact bore and the spool both disposed in the portion of the main flow passage downstream of the branched point, and the spool has a first communication passage intercommunicating the inlet and the outlet and a second communication passage intercommunicating the inlet and the outlet and having an opening area less than an opening area of the first communication passage,

the control valve apparatus configured to bring the first communication passage to a communicated state and simultaneously to bring the second communication passage to a non-communicated state, in a first state where the spool has moved with a maximum displacement in one axial direction of the spool, and

the control valve apparatus further configured to bring the second communication passage to a communicated state and simultaneously to bring the first communication passage to a non-communicated state, in a second state where the spool has moved with a maximum displacement in the opposite axial direction of the spool.

3. The control valve apparatus as claimed in claim 2, wherein:

the inlet of the main flow passage is configured to open from a sliding-contact surface of the sliding-contact bore in sliding-contact with the spool, whereas the outlet of the main flow passage is configured to open from a first axial end of two opposite axial ends of the sliding-contact bore,

the first and second communication passages are formed separately from each other in a sliding-contact surface of the spool in sliding-contact with the sliding-contact bore, and

the first and second communication passages are configured to be merged with each other by an axial passage formed in the spool along a centerline of the spool, and then communicated with the outlet of the main flow passage.

4. The control valve apparatus as claimed in claim 3, wherein:

the displacement of the spool is electronically controlled.

5. The control valve apparatus as claimed in claim 4, wherein:

the axial passage is configured to open from only a first axial and of two opposite axial ends of the spool,

a pressure-receiving surface area of the second axial end of the spool is dimensioned to be greater than a pressure-receiving surface area of the first axial end formed with the axial passage, and

a hydraulic pressure in the main flow passage is selectively supplied or exhausted to or from the second axial end of the spool by an electromagnetic valve.

6. The control valve apparatus as claimed in claim 5, wherein:

the second axial end of the spool has a cylindrical bore formed therein.

7. The control valve apparatus as claimed in claim 5, wherein:

the oil in the inlet of the main flow passage is introduced into the second axial end of the spool.

8. The control valve apparatus as claimed in claim 5, wherein:

the sliding-contact bore, the spool, and the electromagnetic valve are installed in the internal combustion engine in the form of a valve unit with the spool, the electromagnetic valve, and a housing, which defines therein the sliding-contact bore.

9. The control valve apparatus as claimed in claim 3, wherein:

the first axial end of the sliding-contact bore, from which the outlet of the main flow passage opens, is formed with a through hole whose inside diameter is dimensioned to be less than an inside diameter of the sliding-contact bore in sliding-contact with the spool to form a small-diameter bottom, and the small-diameter bottom constructs a stopper that restricts the maximum displacement of the spool in the opposite axial direction.

10. In a hydraulic system equipped with a main flow passage for feeding oil, discharged from an oil pump driven by an internal combustion engine, to each of lubricated engine parts, a branch passage branched from the main flow passage at a branched point, and a hydraulic actuator operated by a hydraulic pressure in the branch passage, the combination of:

a control valve apparatus for adjusting a flow rate of the oil flowing through a portion of the main flow passage downstream of the branched point,

the control valve apparatus comprising a sliding-contact bore into which an inlet of the main flow passage opens and from which an outlet of the main flow passage opens, and a spool installed to axially move in the sliding-contact bore selectively between two opposite axial positions only as needed, the sliding-contact bore and the spool both disposed in the portion of the main flow passage downstream of the branched point, and the spool has a first communication passage intercommunicating the inlet and the outlet and a second communication passage intercommunicating the inlet and the outlet and having an opening area less than an opening area of the first communication passage,

the control valve apparatus configured to bring the first communication passage to a communicated state and simultaneously to bring the second communication passage to a non-communicated state, in a first state where the spool has moved to one of the two opposite axial positions, and

the control valve apparatus further configured to bring the second communication passage to a communicated state and simultaneously to bring the first communication passage to a non-communicated state, in a second state where the spool has moved to the opposite axial position.