VALVE TIMING CONTROL APPARATUS OF INTERNAL COMBUSTION ENGINE

Abstract

In a valve timing control apparatus employing a helical torsion spring attached at one end to a vane rotor and attached at the other end to a housing, for biasing the vane rotor relative to the housing in a specified phase-change direction under a preload, adjacent coils of the torsion spring being brought into contact with each other at a part of the torsion spring in a circumferential direction under a state where the torsion spring is loaded, a back-pressure relief passage is configured to discharge working oil in a back-pressure chamber of a lock mechanism. The back-pressure relief passage is provided at a predetermined circumferential position that goes across a coil-to-coil contact part that the adjacent coils of the torsion spring are brought into contact with each other when the vane rotor rotates relative to the housing by a maximum angular displacement.

Description

TECHNICAL FIELD

The present invention relates to a valve timing control apparatus of an internal combustion engine configured to variably control valve timing of an engine valve (intake and/or exhaust valves) depending on an operating condition of the engine.

BACKGROUND ART

One such valve timing control (VTC) apparatus has been disclosed in Japanese Patent Provisional Publication No. 2005-325749 (hereinafter is referred to as “JP2005-325749”). In the VTC apparatus disclosed in JP2005-325749, a helical torsion spring is interleaved between a housing and a vane rotor such that the centerline of the helical torsion spring is arranged to be substantially coaxial with the rotation axis of the rotor, for enabling a biasing force of the torsion spring to act the rotor to oppose the rotating load of the rotor relative to the housing, produced by a valve-spring reaction force (i.e., a force acting to phase-retard an angular phase of a camshaft relative to an engine crankshaft) during operation of the valve operating system of the engine. This contributes to superior operating characteristic and enhanced responsiveness of the VTC apparatus.

SUMMARY OF THE INVENTION

However, when the helical torsion spring is loaded in its winding direction, the torsion spring deforms, so that the distance between adjacent coils (adjacent turns of wire) of a certain circumferential part of the coiled spring portion of the torsion spring narrows and the distance between the adjacent coils of the diametrically-opposed part of the coiled spring portion widens. At this time, the deformed helical torsion spring tends to incline with respect to the axis (the centerline) of the torsion spring. As a result of this, in the case of the prior-art VTC apparatus, a coil-to-coil contact tends to occur at the circumferential part of the coiled spring portion having the narrowed coil-to-coil distance. Such a coil-to-coil contact leads to the problem of undesirable wear of the helical torsion spring.

It is, therefore, in view of the previously-described drawbacks of the prior art, an object of the invention to provide a valve timing control (VTC) apparatus of an internal combustion engine configured to suppress a helical torsion spring from being worn owing to a coil-to-coil contact, even in the presence of occurrences of the coil-to-coil contact of the torsion spring, loaded and deformed during operation of the VTC apparatus.

In order to accomplish the aforementioned and other objects of the present invention, a valve timing control apparatus of an internal combustion engine comprises a housing adapted to be driven by a crankshaft of the engine, and configured to define a plurality of working-fluid chambers therein by partitioning an internal space by a plurality of shoes protruding radially inward from an inner peripheral surface of the housing, a vane rotor having a rotor adapted to be fixedly connected to a camshaft and a plurality of radially-extending vanes formed on an outer periphery of the rotor for partitioning each of the working-fluid chambers of the housing by the shoes and the vanes to define phase-advance working chambers and phase-retard working chambers, the vane rotor being configured to phase-advance relative to the housing by supplying hydraulic pressure to each of the phase-advance working chambers and by discharging working oil in each of the phase-retard working chambers and configured to phase-retard relative to the housing by supplying hydraulic pressure to each of the phase-retard working chambers and by discharging working oil in each of the phase-advance working chambers, and also configured to have a cylinder structural bore formed in at least one of the plurality of vanes as a through hole extending in a direction of a rotation axis of the vane rotor, a lock mechanism having a lock member slidably installed in the cylinder structural bore and a biasing member for biasing the lock member in its extended direction from the vane rotor, the lock mechanism being configured to permit the lock member to be displaced in its retracted direction against a biasing force of the biasing member by hydraulic pressure acting on the lock member, an engaging recess formed in the housing so as to oppose the lock member, for restricting rotary motion of the vane rotor relative to the housing by bringing the lock member into engagement with the engaging recess with sliding motion of the lock member in the extended direction, a helical torsion spring attached at one end to the vane rotor and attached at the other end to the housing, for exerting a biasing force on the vane rotor and for biasing the vane rotor relative to the housing in a specified phase-change direction under a preload of the torsion spring, adjacent coils of the torsion spring being brought into contact with each other at a part of the torsion spring in a circumferential direction under a state where the torsion spring is loaded, and a back-pressure relief passage through which a back-pressure chamber, configured to install the biasing member of the lock mechanism, is communicated with an exterior space of the housing, the back-pressure relief passage configured to open toward the torsion spring, wherein the back-pressure relief passage is provided at a predetermined circumferential position that goes across a coil-to-coil contact part that the adjacent coils of the torsion spring are brought into contact with each other when the vane rotor rotates relative to the housing by a maximum angular displacement.

According to another aspect of the invention, a valve timing control apparatus of an internal combustion engine comprises a driving rotary member adapted to be driven by a crankshaft of the engine, a driven rotary member adapted to be fixedly connected to a camshaft and configured to phase-change relative to the driving rotary member by supplying or discharging working oil, and also configured to have a cylinder structural bore formed to extend in a direction of a rotation axis of the driven rotary member, a lock mechanism having a lock member slidably installed in the cylinder structural bore and a biasing member for biasing the lock member in its extended direction from the vane rotor, the lock mechanism being configured to permit the lock member to be displaced in its retracted direction against a biasing force of the biasing member by hydraulic pressure acting on the lock member, an engaging recess formed in the driving rotary member so as to oppose the lock member, for restricting rotary motion of the driven rotary member relative to the driving rotary member by bringing the lock member into engagement with the engaging recess with sliding motion of the lock member in the extended direction, a helical torsion spring attached at one end to the driven rotary member and attached at the other end to the driving rotary member, for exerting a biasing force on the vane rotor and for biasing the vane rotor relative to the housing in a specified phase-change direction under a preload of the torsion spring, adjacent coils of the torsion spring being brought into contact with each other at a part of the torsion spring in a circumferential direction under a state where the torsion spring is loaded, a spring guide provided to surround an outer periphery of the torsion spring, and a back-pressure relief passage through which a back-pressure chamber, configured to install the biasing member of the lock mechanism, is communicated with an inner periphery of the spring guide, wherein the back-pressure relief passage is provided at a predetermined circumferential position that goes across a point of contact between the spring guide and the torsion spring at which the outer periphery of the torsion spring is most strongly brought into contact with the inner periphery of the spring guide when the driven rotary member rotates relative to the driving rotary member by a maximum angular displacement.

According to a further aspect of the invention, a valve timing control apparatus of an internal combustion engine comprises a housing adapted to be driven by a crankshaft of the engine, and configured to define a plurality of working-fluid chambers therein by partitioning an internal space by a plurality of shoes protruding radially inward from an inner peripheral surface of the housing, a vane rotor having a rotor adapted to be fixedly connected to a camshaft and a plurality of radially-extending vanes formed on an outer periphery of the rotor for partitioning each of the working-fluid chambers of the housing by the shoes and the vanes to define phase-advance working chambers and phase-retard working chambers, the vane rotor being configured to phase-advance relative to the housing by supplying hydraulic pressure to each of the phase-advance working chambers and by discharging working oil in each of the phase-retard working chambers and configured to phase-retard relative to the housing by supplying hydraulic pressure to each of the phase-retard working chambers and by discharging working oil in each of the phase-advance working chambers, and also configured to have a cylinder structural bore formed in at least one of the plurality of vanes as a through hole extending in a direction of a rotation axis of the vane rotor, a lock mechanism having a lock member slidably installed in the cylinder structural bore and a biasing member for biasing the lock member in its extended direction from the vane rotor, the lock mechanism being configured to permit the lock member to be displaced in its retracted direction against a biasing force of the biasing member by hydraulic pressure acting on the lock member, an engaging recess formed in the housing so as to oppose the lock member, for restricting rotary motion of the vane rotor relative to the housing by bringing the lock member into engagement with the engaging recess with sliding motion of the lock member in the extended direction, a helical torsion spring attached at one end to the vane rotor and attached at the other end to the housing, for exerting a biasing force on the vane rotor and for biasing the vane rotor relative to the housing in a specified phase-change direction under a preload of the torsion spring, adjacent coils of the torsion spring being brought into contact with each other at a part of the torsion spring in a circumferential direction under a state where the torsion spring is loaded, and a back-pressure relief passage through which a back-pressure chamber, configured to install the biasing member of the lock mechanism, is communicated with an exterior space of the housing, the back-pressure relief passage configured to open toward the torsion spring, wherein the back-pressure relief passage is provided at a predetermined circumferential position that goes across a given angular position displaced from a spring-retainer position at which the other end of the torsion spring is attached to the housing by approximately 90 degrees in a direction opposite to a spring-loaded direction of the torsion spring.

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 disassembled view illustrating an embodiment of a valve timing control (VTC) apparatus.

FIG. 2 is a front elevation view illustrating the VTC apparatus of the embodiment.

FIG. 3 shows a longitudinal cross section of the VTC apparatus shown in FIG. 2 and also shows a schematic hydraulic circuit for controlling the VTC apparatus.

FIG. 4 is an explanatory view illustrating the essential part of the internal structure of the VTC apparatus of FIG. 2, controlled to a maximum phase-advance angular position of a vane rotor relative to a housing.

FIG. 5 is an explanatory view illustrating the essential part of the internal structure of the VTC apparatus of FIG. 2, controlled to a maximum phase-retard angular position of the rotor relative to the housing.

FIG. 6 is an enlarged cross section illustrating the essential part of the lock mechanism shown in FIG. 3.

FIG. 7A is a front elevation view illustrating only the helical torsion spring shown in FIG. 3, whereas FIG. 7B is a cross section of the helical torsion spring, taken along the line A-A of FIG. 7A.

FIG. 8 is an enlarged cross section illustrating the essential part of the VTC apparatus shown in FIG. 3 with the helical torsion spring in the assembled state.

FIGS. 9A-9B are explanatory views illustrating assembling processes of the helical torsion spring shown in FIG. 3, FIG. 9A showing the disassembled state of the helical torsion spring, and FIG. 9B showing the assembled state of the helical torsion spring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, the valve timing control apparatus of the embodiment is exemplified in a hydraulically-operated rotary vane type variable valve timing control (VTC) apparatus installed in an internal combustion engine of an automotive vehicle.

As shown in FIG. 3, the hydraulically-operated rotary vane type VTC apparatus is interleaved between a timing sprocket 1, which sprocket is driven by an engine crankshaft, and a camshaft 2, whose one axial end is rotatably fitted to a central bore of sprocket 1, such that rotary motion of camshaft 2 relative to sprocket 1 is permitted. The operation of the VTC apparatus is controlled by means of a hydraulic supply-and-drain means 4 (described later), for phase-conversion of the angular phase of camshaft 2 relative to sprocket 1.

Concretely, as shown in FIGS. 3-5, the VTC apparatus is mainly constructed by a vane rotor 10 and a housing 20 configured to accommodate the vane rotor 10 in an internal space defined in the housing 20 such that rotary motion of vane rotor 10 relative to housing 20 is permitted. Vane rotor 10 is comprised of a cylindrical rotor body 15 fixedly connected to the one axial end of camshaft 2 for co-rotation with the camshaft 2 and a plurality of vane blades (simply, vanes), radially-outward protruding from the outer periphery of rotor body 15. In the shown embodiment, the plurality of vanes are four vanes 11-14. As described later, housing 20 is a substantially cylindrical driving rotary member which is comprised of a front plate 26, a substantially cylindrical housing body 25, and a rear plate 27 (see FIG. 3). The rear plate 27 of housing 20 is integrally formed with the sprocket 1. A plurality of radially-inward protruding shoes (four shoes 21-24 in the shown embodiment), associated with respective vanes 11-14 of vane rotor 10, are integrally formed on the inner periphery of the housing body 25. Four vanes 11-14 of vane rotor 10 and four shoes 21-24 of housing 20 cooperate with each other to define four variable-volume phase-advance working chambers (simply, phase-advance chambers) Ad and four variable-volume phase-retard working chambers (simply, phase-retard chambers) Re. The operation of the VTC apparatus is controlled by supplying hydraulic pressure (working oil) selectively to either one of each of phase-retard chambers Re and each of phase-advance chambers Ad via the hydraulic supply-and-drain means 4.

As shown in FIGS. 1-3, a helical torsion spring 30 is interleaved between the vane rotor 10 and the housing 20, such that one end 30a of helical torsion spring 30 is retained or held on the vane rotor 10 and the other end 30b of helical torsion spring 30 is retained or held on the housing 20. With the torsion spring 30 interleaved between the vane rotor 10 and the housing 20 under a preload, vane rotor 10 is forced or biased in a phase-advance direction (clockwise with respect to the housing 20, viewing FIGS. 4-5). Torsion spring 30 is configured such that a biasing force of torsion spring 30 acts to force or bias the vane rotor 10 in the phase-advance direction against so-called alternating torque, transmitted through the camshaft 2 and acting to phase-retard the camshaft 2 (i.e., the vane rotor 10) relative to the crankshaft (i.e., the housing 20), immediately before the engine is put into a stopped state where there is a less hydraulic-pressure supply to each of phase-advance and phase-retard chambers Ad and Re. By the way, as best seen from the cross section of FIG. 7B showing one example of the torsion spring, torsion spring 30 of the shown embodiment is a helical torsion spring having a substantially rectangular longitudinal cross section and made from a flat square wire having a substantially rectangular lateral cross section, more precisely, a lateral cross section of a long side in a radial direction of the helical torsion spring and a short side in an axial direction of the helical torsion spring. By the use of the helical torsion spring made from a flat square wire, it is possible to reduce the axial length of torsion spring 30. This contributes to the reduced axial dimension of the torsion-spring equipped VTC apparatus.

As best seen in FIG. 3, vane rotor 10 has a central cylindrical-hollow fitting groove 15a formed on the right-hand side facing the one axial end of camshaft 2. Vane rotor 10 is fitted onto the one axial end of camshaft 2 via the cylindrical-hollow fitting groove 15a. Also, vane rotor 10 has an axially-extending central bore 15b (a through hole) into which a cam bolt (vane mounting bolt) 5 is inserted for bolting the vane rotor 10 to the one axial end of camshaft 2 by axially tightening the cam bolt, for co-rotation with the camshaft 2. With this arrangement, the angular phase of camshaft 2 relative to the crankshaft can be changed by relatively rotating the vane rotor 10, which rotor is configured to rotate in synchronism with rotation of the camshaft 2, with respect to the housing 20, which housing is configured to rotate in synchronism with rotation of the engine crankshaft. This enables the engine valve timing (valve open timing and valve closure timing) to be changed.

As can be seen in FIGS. 3-5, a plurality of radial communication bores (four radial through holes 16, 16, 16, 16 in the shown embodiment) are formed at predetermined circumferential positions of vane rotor 10 and located adjacent to the roots of respective vanes 11-14. The outermost ends of radial communication bores 16 are configured to open into respective phase-advance chambers Ad (see FIGS. 4-5). On the other hand, the innermost ends of radial communication bores 16 are configured to communicate with a phase-advance side oil passage 52 (described later) formed in the camshaft 2. Hence, phase-advance chambers Ad are always communicated with the phase-advance side oil passage 52 through respective radial communication bores 16. Thus, hydraulic-pressure supply to respective phase-advance chambers Ad via the hydraulic supply-and-drain means 4 and hydraulic-pressure discharge from respective phase-advance chambers Ad via the hydraulic supply-and-drain means 4 are achieved through the radial communication bores 16 as well as the phase-advance side oil passage 52.

As shown in Figs.1-5, rotor body 15 of vane rotor 10 has a substantially ring-shaped flat-faced collar-head-bolt seat 17 formed on the left-hand side (viewing FIG. 3) facing the front plate 26 in a manner so as to surround the axially-extending central bore 15b of vane rotor 10. When assembling, a collar head 5a of cam bolt 5 is seated on the collar-head-bolt seat 17. An annularly-grooved torsion-spring seat 18 (an annular groove constructing part of a spring guide 41 described later) is recessed or formed in the outer periphery of collar-head-bolt seat 17. The one end 30a of torsion spring 30 is seated on the annularly-grooved torsion-spring seat 18. The outside diameter of collar-head-bolt seat 17 is set or dimensioned to be slightly less than the coil inside diameter of a coiled spring portion 30c of torsion spring 30, so as to ensure a clearance fit (a loose fit) between the outer periphery of collar-head-bolt seat 17 and the inner periphery of the coiled spring portion 30c. As best seen from the front elevation view of FIG. 2, the circumference of the flat top face of collar-head-bolt seat 17 is formed as a rounded edge portion or a frusto-conical chamfered (tapered) edge portion 17a, machined in the circumferential direction. This chamfered edge portion 17a suppresses a part of the coiled spring portion 30c from being caught on the edge of the circumference of collar-head-bolt seat 17 when the torsion spring 30 is loaded or twisted so as to cause a deformation of the coiled spring portion 30c in the winding direction, thus ensuring a smooth torsional deformation of torsion spring 30.

As clearly shown in FIGS. 1-3, the substantially ring-shaped flat-faced collar-head-bolt seat 17 has a radially-recessed groove 19 formed or machined to be continuous with the annularly-grooved torsion-spring seat 18 in a manner so as to communicate the central bore 15b with the annularly-grooved torsion-spring seat 18 through the radially-recessed groove. The radially-recessed groove 19 serves as a first spring retainer that retains or holds the one end 30a (exactly, a radially-inward bent short arm (hereunder described in detail) of the one spring end 30a) of torsion spring 30. Concretely, the one end 30a of torsion spring 30 is bent radially inward from the outer peripheral side of collar-head-bolt seat 17 to the center such that the radially-inward bent short arm of the one spring end 30a is configured to be substantially conformable to the shape of the first spring retainer 19 (i.e., the radially-recessed groove of collar-head-bolt seat 17) and thus the radially-inward bent short arm of the one spring end 30a can be certainly retained in the first spring retainer 19. The collar head 5a of cam bolt 5, which bolt is screwed into the front end of camshaft 2 through the axially-extending central bore 15b of vane rotor 10, also overlaps with the axial opening end of the first spring retainer 19 (i.e., the radially-recessed groove of collar-head-bolt seat 17) in a manner so as to close most of the axial opening end (the left-hand opening end, viewing FIG. 3) of the first spring retainer 19. This prevents the one end 30a of torsion spring 30 from falling out of the first spring retainer 19. The utilization of the existing structure, such as the collar head 5a of cam bolt 5, eliminates the necessity of having a separate spring retainer for retaining the one end 30a of torsion spring 30. This contributes to lower assembling/installation time and costs and reduced production costs.

As shown in FIGS. 1, and 4-5, each of vanes 11-14 has an axially-elongated seal groove formed in its apex along the axial direction of rotor body 15. Four elongated oil seals S1 are fitted into and retained in the respective seal grooves of vanes 11-14. By sliding-contact between each of oil seals S1 of vanes 11-14 and the inner peripheral wall surface of the housing body 25, four spaces, defined among four shoes 21-24, are partitioned into four pairs of phase-advance and phase-retard chambers (Ad, Re), (Ad, Re), (Ad, Re), and (Ad, Re). A given one (hereinafter is referred to as “wide vane”) of four vanes 11-14 is configured as a wide vane having an inverted trapezoidal shape in lateral cross section, whereas the remaining vanes 12-14 are configured to be substantially rectangular in lateral cross section. The remaining three vanes 12-14 have almost the same circumferential width and the same radial length. The circumferential width of the wide vane 11 having the inverted trapezoidal shape is dimensioned to be greater than that of each of the remaining vanes 12-14. The maximum angular displacement of vane rotor 10 relative to housing 20 in the phase-advance direction is restricted by abutment of the wide vane 11 with the shoe 21 of the two adjacent shoes 21 and 24. Conversely, the maximum angular displacement of vane rotor 10 relative to housing 20 in the phase-retard direction is restricted by abutment of the wide vane 11 with the shoe 24 of the two adjacent shoes 21 and 24. Also, a lock mechanism 31 (interlocking means) is installed in the wide vane 11 for holding the angular phase of vane rotor 10 relative to housing 20 at a given angular-phase position such as a maximum phase-advance position when the engine is shifted to a stopped state.

As shown in FIGS. 3-6, particularly, as best seen from the longitudinal cross section of FIG. 3, lock mechanism 31 is mainly comprised of a substantially cylindrical lock pin 32 and a return spring (a coiled compression spring) 33. Lock pin 32 is slidably installed in a lock-pin accommodation bore, simply, a lock-pin bore 34 (a cylinder structural bore) formed in the wide vane 11 as an axially-extending stepped through hole. Lock pin 32 is configured to be substantially conformable to the shape of lock-pin bore 34. By engaging the lock pin 32 with an engaging hole 35 formed in the rear plate 27, constructing a part of housing 20, rotary motion of vane rotor 10 relative to housing 20 can be restricted. Return spring 33 is interleaved between the lock pin 32 and the front plate 26, constructing a part of housing 20, under preload, for permanently forcing or biasing the lock pin 32 toward the rear plate 27.

More concretely, as clearly shown in FIG. 6, lock pin 32 is formed as a hollow stepped cylinder that the root (the left-hand side of pin 32, viewing FIG. 6) is formed as a large-diameter portion 32a and the other (the right-hand side of pin 32) is formed as a small-diameter portion 32b. In a similar manner, lock-pin bore 34 is formed as a stepped through hole that the left-hand half (viewing FIG. 6) is formed as a large-diameter bore 34a and the right-hand half is formed as a small-diameter bore 34b. When assembling, the large-diameter portion 32a of lock pin 32 is kept in sliding-contact with the large-diameter bore 34a of lock-pin bore 34, whereas the small-diameter portion 32b of lock pin 32 is kept in sliding-contact with the small-diameter bore 34b of lock-pin bore 34. A back-pressure chamber 36 is defined by the large-diameter portion 32a in sliding-contact with the large-diameter bore 34a. Return spring 33 is elastically installed into a spring-retainer bore formed in the lock pin 32 through the back-pressure chamber 36. By the way, hydraulic pressure in the phase-retard chamber Re, defined between the wide vane 11 and the shoe 21, is supplied into the engaging hole 35 of the rear plate 27 through a recessed communication groove 37 (see FIGS. 1 and 4-5, in particular, see FIG. 1) formed in the right-hand sidewall (viewing FIG. 1) of the wide vane 11, facing the rear plate 27. Hence, the lock mechanism is configured so that the lock pin 32 can be brought into and out of engagement with the engaging hole 35 depending on the hydraulic pressure in the phase-retard chamber Re.

Also, as seen from the enlarged cross section of FIG. 6, an annular space 38 is defined between the stepped portion 32c (formed between the large-diameter portion 32a and the small-diameter portion 32b of lock pin 32) and the stepped portion 34c (formed between the large-diameter bore 34a and the small-diameter bore 34b of lock-pin bore 34). The annular space 38 is configured to communicate with the phase-advance chamber Ad, defined between the wide vane 11 and the shoe 24, through a through hole 39 (see FIGS. 4-5 and 6, in particular, see FIG. 6) formed in the wide vane 11 in a manner so as to extend from the lock-pin bore 34 to this phase-advance chamber Ad. That is, the hydraulic pressure in the phase-advance chamber Ad is always introduced or supplied via the through hole 39 into the annular space 38. When the hydraulic pressure in the phase-advance chamber Ad exceeds a predetermined high-pressure level, a lock-pin disengagement state where the lock pin 32 is out of engagement with the engaging hole 35 can be maintained.

As clearly shown in FIGS. 1, 3-6, and 8, a recessed communication groove 40a is formed in the left-hand sidewall (viewing FIG. 1) of the wide vane 11, facing the front plate 26, for communicating the lock-pin bore 34 with the annularly-grooved torsion-spring seat 18 through the recessed communication groove 40a. That is, the axial opening end (the left-hand opening end, viewing FIGS. 3 and 6) of the recessed communication groove 40a is closed by the front plate 26 to define a back-pressure relief passage 40 for discharging or relieving working oil, leaked from the annular space 38 into the back-pressure chamber 36 through a very small radial clearance space defined between the outer peripheral surface of the large-diameter portion 32a of lock pin 32 and the inner peripheral surface of the large-diameter bore 34a of lock-pin bore 34, toward the side of annularly-grooved torsion-spring seat 18. Notice that the back-pressure relief passage 40 (i.e., the recessed communication groove 40a) is configured or formed at a predetermined circumferential position that the back-pressure relief passage 40 (i.e., the recessed communication groove 40a) goes across a coil-to-coil contact part “T” (see FIG. 8) of the coiled spring portion 30c of torsion spring 30, that has a narrower coil-to-coil distance and that the adjacent coils are brought into contact with each other, when the vane rotor 10 rotates relative to the housing 20 by a maximum angular displacement from one of the maximum phase-advance angular position and the maximum phase-retard angular position to the other. This permits working oil, leaked into the back-pressure chamber 36 and discharged by way of the back-pressure relief passage 40 (i.e., the recessed communication groove 40a), to be discharged or directed toward the coil-to-coil contact part “T”. More concretely, the previously-noted predetermined circumferential position, going across the coil-to-coil contact part “T”, corresponds to a circumferential position that goes across a given angular position displaced from a spring-retainer position (an angular position of a second spring retainer 45 described later), at which the radially-outward bent short arm of the other end 30b of torsion spring 30 is retained, by approximately 90 degrees in the direction (i.e., the load-released direction) opposite to the twist direction (i.e., the spring-loaded direction) of torsion spring 30. On the assumption that the housing 20 (sprocket 1) is actually rotating during operation of the engine but the housing 20 is stationary, the load-released direction of torsion spring 30 corresponds to the clockwise direction in FIGS. 4-5, whereas the spring-loaded direction of torsion spring 30 corresponds to the counterclockwise direction in FIGS. 4-5. This is based on the fact that a twisting force, acting on torsion spring 30, causes the deformed torsion spring to be inclined with respect to the axis of torsion spring 30 about the other end 30b forming the fulcrum or the pivot, and hence owing to the twisting force, the given angular position displaced from a spring-retainer position, at which the radially-outward bent short arm of the other end 30b is retained, by approximately 90 degrees in the direction opposite to the twist direction (i.e., the spring-loaded direction) of torsion spring 30 becomes the previously-discussed coil-to-coil contact part “T”.

By the way, regarding the layout of back-pressure relief passage 40, it is more preferable that the back-pressure relief passage 40 is laid out at a predetermined circumferential position going across a press-contact part “P” (described later by reference to the enlarged cross section of FIG. 8) that the outer periphery of the coiled spring portion 30c is most strongly brought into press-contact with the inner periphery of a spring guide 41 (described later) with contact pressure due to an inclination of the coiled spring portion 30c with respect to the axis (the centerline) of the torsion spring, when the vane rotor 10 rotates relative to the housing 20 by a maximum angular displacement from one of the maximum phase-advance angular position and the maximum phase-retard angular position to the other. With the more preferable layout of back-pressure relief passage 40, working oil, leaked into the back-pressure chamber 36 and discharged by way of the back-pressure relief passage 40 (i.e., the recessed communication groove 40a) can be directed toward the press-contact part “P” of the coiled spring portion 30c with the spring guide 41 as well as the coil-to-coil contact part “T” of the coiled spring portion 30c.

As shown in FIGS. 1-5, particularly, as best seen from the longitudinal cross section of FIG. 3, housing 20 is comprised of the substantially cylindrical-hollow housing body 25, the front plate 26, and the rear plate 27. As previously noted, housing body 25 has four radially-inward protruding shoes 21-24 integrally formed on the inner periphery. Front plate 26 is configured to close the front opening end of the housing body 25, whereas rear plate 27 is configured to close the rear opening end of the housing body 25. Housing body 25 and front and rear plates 26-27 are axially fastened together and integrally connected to each other with four bolts 6.

In a similar manner to the four oil seals S1 fitted into the respective seal grooves of shoes 11-14, as shown in FIGS. 1, and 4-5, each of shoes 21-24 has an axially-elongated seal groove formed in its apex along the axial direction of vane rotor 10. Four elongated oil seals S2 are fitted into and retained in the respective seal grooves of shoes 21-24. By sliding-contact between each of oil seals S1 of vanes 11-14 and the inner peripheral wall surface of the housing body 25 and by sliding-contact between each of oil seals S2 of shoes 21-24 and the outer peripheral wall surface of the rotor body 15, four spaces, defined among four shoes 21-24, are partitioned into four pairs of phase-advance and phase-retard chambers (Ad, Re), (Ad, Re), (Ad, Re), and (Ad, Re). Additionally, regarding a pair of shoes 21 and 24, located adjacent to the wide vane 11, as clearly shown in FIGS. 4-5, each of shoes 21 and 24 is integrally formed at its root with a circumferentially-protruding, partially thick-walled portion 28, such that the partially thick-wall portion 28 of shoe 21 and the partially thick-walled portion 28 of shoe 24 are circumferentially opposed to each other. When the vane rotor 10 is displaced relative to the housing 20 in the phase-advance direction, the partially thick-wall portion 28 of shoe 21 functions to restrict the maximum angular displacement in the phase-advance direction by abutment with the wide vane 11, while ensuring the phase-retard chamber Re between the wide vane 11 and the shoe 21. Conversely when the vane rotor 10 is displaced relative to the housing 20 in the phase-retard direction, the partially thick-wall portion 28 of shoe 24 functions to restrict the maximum angular displacement in the phase-retard direction by abutment with the wide vane 11, while ensuring the phase-advance chamber Ad between the wide vane 11 and the shoe 24.

As shown in FIGS. 1-3, front plate 26 is formed as a comparatively thin-walled disc. Front plate 26 has an axially-forward-protruding central cylindrical portion 43 (constructing part of the spring guide 41 described later). Cam bolt 5 and torsion spring 30 can be installed through a central through hole 43a of cylindrical portion 43 of front plate 26 from the outside (see FIGS. 9A-9B). By the way, as best seen from the enlarged cross section of FIG. 8, the inside diameter of the central through hole 43a of cylindrical portion 43 of front plate 26 is set or dimensioned to be approximately equal to the inside diameter of the radially-outside circumferentially-extending curved peripheral wall surface of annularly-grooved torsion-spring seat 18 of vane rotor 10 such that the central through hole 43a of cylindrical portion 43 is configured to be continuous with the radially-outside circumferentially-extending curved peripheral wall surface of annularly-grooved torsion-spring seat 18. That is, the inner peripheral wall of cylindrical portion 43 of front plate 26 together with the curved peripheral wall of annularly-grooved torsion-spring seat 18 of vane rotor 10 is formed as a continuous smooth curved peripheral wall that constructs the spring guide 41 for torsion spring 30. The internal space, defined in the spring guide 41 (i.e., the curved peripheral wall of annularly-grooved torsion-spring seat 18 of vane rotor 10 and the inner peripheral wall of central through hole 43a of front plate 26), serves as a spring accommodation bore 42 (a torsion spring chamber) in which the coiled spring portion 30c of torsion spring 30 is accommodated. With the previously-discussed arrangement, the coiled spring portion 30c of torsion spring 30 can be installed in the spring accommodation bore 42 in a manner so as to enable or permit smooth torsional motion of torsion spring 30 in both directions of winding and unwinding. This ensures smooth deformation of the coiled spring portion 30c during application of torque to the torsion spring 30.

As clearly shown in FIGS. 1-2, a substantially ring-shaped axially-forward-protruding end 43b of cylindrical portion 43 has a cutout 44 partially cut out in its circumferential direction. The root of one sidewall 44a of circumferentially-opposed sidewalls 44a-44b of cutout 44, is further cut out partially in the circumferential direction so as to form a radially-cutout groove. The further radially-cutout groove 45 serves as a second spring retainer that retains or holds the other end 30b (exactly, a radially-outward bent short arm (hereunder described in detail) of the other spring end 30b) of torsion spring 30. Concretely, the other end 30b of torsion spring 30 is bent radially outward, such that the radially-outward bent short arm of the other spring end 30b is configured to be substantially conformable to the shape of the second spring retainer 45 (i.e., the further radially-cutout groove of cutout 44 of cylindrical portion 43 of front plate 26) and thus the radially-outward bent short arm of the other spring end 30b can be certainly retained in the second spring retainer 45. In this manner, by constructing or machining the second spring retainer 45 in the form of the further radially-cutout groove configured to open at the ring-shaped axially-forward-protruding end 43b of cylindrical portion 43, as can be seen from the explanatory views of FIGS. 9A-9B, it is possible to easily assemble or install the torsion spring 30 on the annularly-grooved torsion-spring seat 18 of rotor body 15 through the central through hole 43a of cylindrical portion 43 of front plate 26 from the outside. As a result of this, it is possible to avoid a complicated assembling work that other component parts are installed, while relatively rotating the vane rotor 10 with respect to the housing 20 against the biasing force of torsion spring 30 after the torsion spring 30 has been installed. This contributes to the good productivity of the torsion-spring equipped VTC apparatus. In the shown embodiment, as best seen in FIG. 2, the circumferentially-opposed sidewalls 44a-44b of cutout 44 are configured to be substantially parallel with each other. In order for a straight line “L1”, obtained by radially inwardly extending the end face 45a of the second spring retainer 45 (i.e., the further radially-cutout groove of cutout 44), which end face is configured to face in the circumferential direction and at which the radially-outward bent short arm of the other end 30b of torsion spring 30 is retained, to pass through the vicinity of the center “C” of cylindrical portion 43 of front plate 26, the straight line “L1” is arranged in close proximity to the center “C” of cylindrical portion 43, rather than a straight line “L2”, obtained by radially inwardly extending the other sidewall 44b of circumferentially-opposed sidewalls 44a-44b of cutout 44. More concretely, the cutout 44 is radially pierced or cut and formed with a punching tool at a given position at which the end face 45a of the second spring retainer 45 is offset toward a straight line “L0” passing through the center “C” of cylindrical portion 43 relatively to the other sidewall 44b of cutout 44. The cutout 44 is configured such that the angle “θ” between the other sidewall 44b and a tangential line “L3” at the intersection point “X” of the other sidewall 44b and the inner peripheral wall surface of cylindrical portion 43 is an obtuse angle.

Additionally, the second spring retainer 45 is configured as the radially-cutout groove formed or machined by further cutting out partially only the root of the one sidewall 44a of cutout 44. Hence, the circumferential width “W1” of the cutout 44 at the tip of the ring-shaped axially-forward-protruding end 43b is dimensioned to be narrower than the circumferential width “W2” of the cutout 44 at the root of the ring-shaped axially-forward-protruding end 43b. The inside face 45b of the second spring retainer 45, which inside face is configured to face in the axial direction, functions as a fall-out prevention spring short-arm retainer for restricting axial movement of the other end 30b of torsion spring 30 and for retaining the radially-outward bent short arm of the other end 30b in place. By means of the fall-out prevention spring short-arm retainer 45b, it is possible to restrict or suppress the torsion spring 30 from falling out, thus stably retaining the torsion spring in place.

As shown in FIGS. 1 and 3-5, rear plate 27 is formed as a comparatively thick-wall disc. Rear plate 27 is integrally formed at its outer periphery with the sprocket 1. As best seen in FIG. 1, rear plate 27 has a central through hole 27a into which the front end of camshaft 2 is inserted. Also, rear plate 27 has four circumferentially-equidistant-spaced female-screw threaded portions 27b in to which respective bolts 6 are screwed. Furthermore, a plurality of radial communication grooves (four radial communication grooves 46, 46, 46, 46 in the shown embodiment) are formed in the inside face of rear plate 27 and arranged to be cut out at predetermined circumferential positions of rear plate 27 and located along the peripheral edge of central through hole 27a. The outermost ends of radial communication grooves 46 are configured to open into respective phase-retard chambers Re (see FIGS. 4-5). On the other hand, the innermost ends of radial communication grooves 46 are configured to communicate with a phase-retard side oil passage 51 (described later) formed in the camshaft 2. Hence, phase-retard chambers Re are always communicated with the phase-retard side oil passage 51 through respective radial communication grooves 46. Thus, hydraulic-pressure supply to respective phase-retard chambers Re via the hydraulic supply-and-drain means 4 and hydraulic-pressure discharge from respective phase-retard chambers Re via the hydraulic supply-and-drain means 4 are achieved through the radial communication grooves 46 as well as the phase-retard side oil passage 51.

Additionally, as described previously, rear plate 27 has the engaging hole 35 (see FIGS. 1, 3, and 6) formed in the inside face of rear plate 27 and brought into engagement with the lock pin 32 slidably installed in the lock-pin bore 34 of vane rotor 10 when vane rotor 10 is positioned at its maximum phase-advance position (see FIG. 4), so as to restrict rotary motion of vane rotor 10 relative to housing 20. As seen from the enlarged cross section of FIG. 6, engaging hole 35 is formed as a comparatively shallow stepped recessed groove that the left-hand half (viewing FIG. 6) is formed as a large-diameter circular recessed groove 35a and the right-hand half (viewing FIG. 6) is formed as a small-diameter circular recessed groove 35b. The inside diameter of large-diameter circular recessed groove 35a is dimensioned to be greater than the outside diameter of small-diameter portion 32b of lock pin 32. On the other hand, the inside diameter of small-diameter circular recessed groove 35b (the bottom groove) is dimensioned to be less than the outside diameter of small-diameter portion 32b of lock pin 32. When the angular phase of vane rotor 10 relative to housing 20 has been held at the maximum phase-advance state (see FIG. 4), rotary motion of vane rotor 10 relative to housing 20 can be restricted by engagement of the lock pin 32 with the large-diameter circular recessed groove 35a.

Moreover, as clearly shown in FIGS. 1, and 4-5, rear plate 27 has an axially-protruding positioning pin 48 formed on the inside face of rear plate 27. On the other hand, housing body 25 has an axially-elongated engaging groove 47 cut in the outer periphery of housing body 25. Engaging the positioning pin 48 of rear plate 27 with the engaging groove 47 of housing body 25, ensures the proper positioning of the rear plate 27 on the housing body 25. The provision of the positioning pin 48 ensures a good engagement relationship of the lock pin 32 with the engaging hole 35 after three housing members, namely housing body 25, and front and rear plates 26-27 have been assembled each other and integrally connected to each other with four bolts 6.

As shown in FIG. 3, hydraulic supply-and-drain means 4 is provided for selectively supplying and draining hydraulic pressure (working oil) to and from either one of each phase-advance chamber Ad and each phase-retard chamber Re. Hydraulic supply-and-drain means 4 is mainly comprised of the phase-retard side oil passage 51 connected to each of radial communication grooves 46, the phase-advance side oil passage 52 connected to each of radial communication bores 16, an oil pump 53, and a drain passage 54. Oil pump 53 serves as a hydraulic pressure source for supplying hydraulic pressure (working oil) to a selected one of the oil passages 51-52 through the use of a generally-known electromagnetic solenoid-operated directional control valve 55. Drain passage 54 is configured for draining or directing hydraulic pressure (working oil) from the unselected oil passage of the oil passages 51-52 through the use of the electromagnetic directional control valve 55 to an oil pan 56. By the way, electromagnetic directional control valve 55 of the shown embodiment is a so-called three-position, spring-offset, four-way solenoid-operated directional control valve. Electromagnetic directional control valve 55 uses a sliding spool to change the path of flow through the directional control valve. As seen from the hydraulic circuit diagram of FIG. 3, for a given position of the spool, a unique flow path configuration exists within the directional control valve. Directional control valve 55 is designed to operate with either three positions of the spool. The flow path configuration for each unique spool position can be controlled responsively to a control signal from an electronic control unit ECU (not shown).

The operation and effects of the VTC apparatus of the internal combustion engine of the embodiment are hereunder described in detail in reference to FIGS. 3-5.

During an engine startup, as shown in FIGS. 3-4, vane rotor 10 is held at the given angular-phase position (i.e., the maximum phase-advance position) suited to the engine startup by engagement of the tip of small-diameter portion 32b of lock pin 32 with the large-diameter circular recessed groove 35a of engaging hole 35, thus ensuring smooth cranking operation, that is, better startup, immediately when an ignition switch (not shown) is turned ON.

During operation of the engine in a first predetermined load range after the engine has been started up, directional control valve 55 becomes energized (ON) responsively to a control signal from the ECU. Hence, fluid-communication between the phase-retard side oil passage 51 and the oil pump 53 becomes established and simultaneously fluid-communication between the phase-advance side oil passage 52 and the drain passage 54 becomes established. That is, working oil, discharged from the oil pump 53, is flown into each of phase-retard chambers Re through the phase-retard side oil passage 51, and thus hydraulic pressure in each of phase-retard chambers Re becomes high. At this time, working oil in each of phase-advance chambers Ad is directed through the phase-advance side oil passage 52 and the drain passage 54 to the oil pan 56, and thus hydraulic pressure in each of phase-advance chambers Ad becomes low. By the way, part of working oil, flown into the phase-retard chamber Re, defined between the wide vane 11 and the shoe 21, is further flown or supplied into the engaging hole 35. Hence, the lock pin 32 is brought out of engagement with the engaging hole 135, thereby permitting free rotary motion of vane rotor 10 relative to housing 20. As a result, owing to an increase in the volume of each phase-retard chamber Re, arising from hydraulic-pressure supply (working-oil supply) to each phase-retard chamber Re, vane rotor 10 rotates counterclockwise and therefore the angular phase of camshaft 2 relative to the crankshaft is converted to a phase-retard side (see FIG. 5).

In contrast, when the engine operating condition has been shifted to a second predetermined load range, directional control valve 55 becomes de-energized (OFF) responsively to a control signal from the ECU. Hence, fluid-communication between the phase-advance side oil passage 52 and the oil pump 53 becomes established and simultaneously fluid-communication between the phase-retard side oil passage 51 and the drain passage 54 becomes established. That is, working oil in each of phase-retard chambers Re is directed through the phase-retard side oil passage 51 and the drain passage 54 to the oil pan 56, and thus hydraulic pressure in each of phase-retard chambers Re becomes low. At this time, working oil, discharged from the oil pump 53, is flown into each of phase-advance chambers Ad through the phase-advance side oil passage 52, and thus hydraulic pressure in each of phase-advance chambers Ad becomes high. Owing to hydraulic-pressure supply to each phase-advance chamber Ad, there is an increased tendency for the hydraulic pressure in the phase-advance chamber Ad, defined between the wide vane 11 and the shoe 24, to be positively supplied via the through hole 39 into the annular space 38. With the hydraulic pressure supplied to the annular space 38 and exceeding the predetermined high-pressure level, the lock-pin disengagement state where the lock pin 32 is out of engagement with the engaging hole 35 can be maintained. As a result, owing to an increase in the volume of each phase-advance chamber Ad, arising from hydraulic-pressure supply (working-oil supply) to each phase-advance chamber Ad, vane rotor 10 rotates clockwise and therefore the angular phase of camshaft 2 relative to the crankshaft is converted to a phase-advance side (see FIG. 4).

Immediately before the engine becomes put into a stopped state, hydraulic-pressure supply to each of phase-advance and phase-retard chambers Ad-Re becomes stopped, and hence there is an increased tendency for the angular phase of vane rotor 10 relative to housing 20 to be shifted to the phase-retard side by alternating torque acting on the camshaft 2. However, by virtue of the biasing force (i.e., the opposing torque) of torsion spring 30, interleaved between the vane rotor 10 and the housing 20, as shown in FIG. 4, the vane rotor 10 rotates relative to the housing 20 toward the phase-advance side against the alternating torque (the torque applied from the valve springs via the camshaft to the vane rotor), and then the tip of small-diameter portion 32h of lock pin 32 is brought into engagement with the large-diameter circular recessed groove 35a of engaging hole 35 by the spring force of return spring 33. Hence, vane rotor 10 is held again at the given angular-phase position (i.e., the maximum phase-advance position).

As discussed above, in the VTC apparatus of the embodiment, free rotary motion of vane rotor 10 relative to housing 20 can be ensured or maintained by introducing or supplying hydraulic pressure to the lock-pin engaging hole 35 or to the annular space 38. At the same time, working oil, supplied to the engaging hole 35 or to the annular space 38, is considerably flown or leaked into the back-pressure chamber 36 through the very small radial clearance space defined between the outer peripheral surface of the large-diameter portion 32a of lock pin 32 and the inner peripheral surface of the large-diameter bore 34a of lock-pin bore 34, and then the working oil, flown or leaked into the back-pressure chamber 36, is discharged through the back-pressure relief passage 40 (i.e., the recessed communication groove 40a) into the spring accommodation bore 42.

By the way, as described previously, the back-pressure relief passage 40 is configured or formed at a predetermined circumferential position that the back-pressure relief passage 40 goes across the coil-to-coil contact part “T” of the coiled spring portion 30c of helical torsion spring 30. Hence, working oil, discharged through the back-pressure relief passage 40, is directed to the coil-to-coil contact part “T”, thereby enabling the coil-to-coil contact part “T” of torsion spring 30 to get a proper amount of lubrication, and consequently suppressing undesirable wear of the coil-to-coil contact part “T”. In particular, in the case of the embodiment using a helical torsion spring having a substantially rectangular longitudinal cross section and made from a flat square wire, when torsion spring 30 is loaded or twisted due to the applied torque and thus a twisted deformation of torsion spring 30 having the substantially rectangular longitudinal cross section takes place, the twisted, deformed torsion spring tends to easily incline in the axial direction. Hence, in the case of the use of such a helical torsion spring having a substantially rectangular longitudinal cross section, there is an increased tendency for an undesirable coil-to-coil contact to occur, during operation of the VTC apparatus. For the reasons discussed above, the proper amount of lubrication of the coil-to-coil contact part “T” is effective in smooth, low-friction torsional motion of torsion spring 30. By the way, in the case of the embodiment using a helical torsion spring made from a flat square wire having a lateral cross section of a long side in the radial direction, when subjected to torque, the twisted, deformed torsion spring tends to more easily incline in the axial direction, and thus there is a further increased tendency for an undesirable coil-to-coil contact to occur, during operation of the VTC apparatus. Hence, the proper amount of lubrication of the coil-to-coil contact part “T” is more effective in smooth, low-friction torsional motion of torsion spring 30 during operation of the VTC apparatus.

In addition to the above, due to the inclination of the coiled spring portion 30c, occurring when subjected to torque, the outer periphery of the coil-to-coil contact part “T” is most strongly brought into press-contact with the inner peripheral surface of the spring guide 41 (i.e., the curved peripheral wall of annularly-grooved torsion-spring seat 18 of vane rotor 10 and the inner peripheral wall of central through hole 43a of front plate 26) with contact pressure. The back-pressure relief passage 40 (i.e., the recessed communication groove 40a) is configured to open through the inner peripheral wall surface of spring guide 41 into the spring accommodation bore 42. Hence, working oil, discharged through the back-pressure relief passage 40, is also directed to the press-contact part “P”, thereby enabling the press-contact part “P” of torsion spring 30 to get a proper amount of lubrication, and consequently suppressing undesirable wear and scoring of the press-contact part “P”. That is to say, the proper amount of lubrication of the press-contact part “P” is effective in smooth, low-friction sliding-motion of torsion spring 30 relative to the inner periphery of spring guide 41 during operation of the VTC apparatus.

As will be appreciated from the above, according to the torsion-spring equipped VTC apparatus of the internal combustion engine of the embodiment, the back-pressure relief passage 40 is provided at a predetermined circumferential position going across a circumferential portion of the coiled spring portion 30c of torsion spring 30 that (i) the previously-discussed coil-to-coil contact between the adjacent coils (the adjacent turns of wire) and/or (ii) the previously-discussed press-contact of the outer periphery of the coiled spring portion 30c with the inner periphery of the spring guide 41 with contact pressure occurs due to an inclination of the coiled spring portion 30c when subjected to torque during rotary motion of vane rotor 10 relative to housing 20. More concretely, the previously-noted predetermined circumferential position, going across the coil-to-coil contact part “T” and/or the press-contact part “P”, corresponds to a circumferential position that goes across a given angular position displaced from the angular position of the second spring retainer 45, at which the radially-outward bent short arm of the other end 30b of torsion spring 30 is retained, by approximately 90 degrees in the direction opposite to the spring-loaded direction of torsion spring 30. By virtue of working oil, introduced into the back-pressure relief passage 40, and then directed to the coil-to-coil contact part “T” and/or the press-contact part “P”, the coil-to-coil contact part “T” and the press-contact part “P” can be properly lubricated. As a result, it is possible to effectively suppress undesirable wear, occurring at the coil-to-coil contact part “T” and/or the press-contact part “P” of the coiled spring portion 30c due to friction.

In the shown embodiment, back-pressure relief passage 40 is constructed by the recessed communication groove 40a formed in the sliding-contact surface of the wide vane 11 of vane rotor 10, in sliding-contact with the inside face of front plate 26. In lieu thereof, back-pressure relief passage 40 may be constructed as a radial through hole formed in the wide vane 11 in a manner so as to communicate the back-pressure chamber 36 with the spring accommodation bore 42. As compared to the back-pressure relief passage 40, constructed as a radial through hole formed in the wide vane 11, the back-pressure relief passage 40, constructed by the recessed communication passage 40a, is superior in easier machining, in other words, good productivity of the torsion-spring equipped VTC apparatus.

By the way, for the purpose of introducing working oil (lubricating oil) into the spring accommodation bore 42 through the use of the back-pressure relief passage 40, the torsion-spring equipped VTC apparatus of the embodiment adopts a specific clearance-space fluid-flow path configuration that, first of all, working oil is introduced into the annular space 38 adjacent to the back-pressure chamber 36, and then the introduced working oil is leaked from the annular space 38 through the very small radial clearance space defined between the lock pin 32 and the lock-pin bore 34 into the back-pressure chamber 36. The annular space 30 adjacent to the back-pressure chamber 36 functions to properly promote working-oil leakage through the very small radial clearance space into the back-pressure chamber 36. This ensures an adequate amount of working oil (lubricating oil) to be supplied through the back-pressure relief passage 40 to the spring accommodation chamber 42, thus enabling the coil-to-coil contact part “T” and/or the press-contact part “P” to get a proper amount of lubrication.

Furthermore, back-pressure relief passage 40 is positioned on the phase-advance side with respect to an circumferential position (an angular position) of the coil-to-coil contact part “T” of the coiled spring portion 30c of torsion spring 30 under a locked state where the lock pin 32 of lock mechanism 31 is kept in locked-engagement with the lock-pin bore 34 for restricting rotary motion of vane rotor 10 relative to housing 20. This ensures more certain lubrication of the coil-to-coil contact part “T”, during operation of the VTC apparatus.

The entire contents of Japanese Patent Application Nos. 2012-179732 (filed Aug. 14, 2012) and 2013-091054 (filed Apr. 24, 2013) 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. A valve timing control apparatus of an internal combustion engine comprising:

a housing adapted to be driven by a crankshaft of the engine, and configured to define a plurality of working-fluid chambers therein by partitioning an internal space by a plurality of shoes protruding radially inward from an inner peripheral surface of the housing;

a vane rotor having a rotor adapted to be fixedly connected to a camshaft and a plurality of radially-extending vanes formed on an outer periphery of the rotor for partitioning each of the working-fluid chambers of the housing by the shoes and the vanes to define phase-advance working chambers and phase-retard working chambers, the vane rotor being configured to phase-advance relative to the housing by supplying hydraulic pressure to each of the phase-advance working chambers and by discharging working oil in each of the phase-retard working chambers and configured to phase-retard relative to the housing by supplying hydraulic pressure to each of the phase-retard working chambers and by discharging working oil in each of the phase-advance working chambers, and also configured to have a cylinder structural bore formed in at least one of the plurality of vanes as a through hole extending in a direction of a rotation axis of the vane rotor;

a lock mechanism having a lock member slidably installed in the cylinder structural bore and a biasing member for biasing the lock member in its extended direction from the vane rotor, the lock mechanism being configured to permit the lock member to be displaced in its retracted direction against a biasing force of the biasing member by hydraulic pressure acting on the lock member;

an engaging recess formed in the housing so as to oppose the lock member, for restricting rotary motion of the vane rotor relative to the housing by bringing the lock member into engagement with the engaging recess with sliding motion of the lock member in the extended direction;

a helical torsion spring attached at one end to the vane rotor and attached at the other end to the housing, for exerting a biasing force on the vane rotor and for biasing the vane rotor relative to the housing in a specified phase-change direction under a preload of the torsion spring, adjacent coils of the torsion spring being brought into contact with each other at a part of the torsion spring in a circumferential direction under a state where the torsion spring is loaded; and

a back-pressure relief passage through which a back-pressure chamber, configured to install the biasing member of the lock mechanism, is communicated with an exterior space of the housing, the back-pressure relief passage configured to open toward the torsion spring,

wherein the back-pressure relief passage is provided at a predetermined circumferential position that goes across a coil-to-coil contact part that the adjacent coils of the torsion spring are brought into contact with each other when the vane rotor rotates relative to the housing by a maximum angular displacement.

2. The valve timing control apparatus as claimed in claim 1, further comprising:

a spring guide provided to surround an outer periphery of the torsion spring.

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

the housing comprises: a cylindrical housing body formed integral with the plurality of shoes protruding radially inward from the inner peripheral surface of the cylindrical housing body; a front plate configured to close one axial end of the housing body; and a rear plate configured to close the other axial end of the housing body, facing the camshaft;

the spring guide comprises: an axially-protruding cylindrical portion formed integral with the front plate; and an annular groove recessed in the vane rotor.

4. The valve timing control apparatus as claimed in claim 1, wherein:

the vane rotor has the back-pressure relief passage, which is a recessed groove formed in a sliding-contact surface of the vane rotor in sliding-contact with the front plate.

5. The valve timing control apparatus as claimed in claim 1, wherein:

the torsion spring is made from a flat square wire having a substantially rectangular lateral cross section.

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

the torsion spring is made from the flat square wire having the lateral cross section of a longer side in a radial direction of the torsion spring.

7. The valve timing control apparatus as claimed in claim 1, wherein:

the back-pressure relief passage is positioned on a phase-advance side with respect to the coil-to-coil contact part of the torsion spring under a locked state where the lock member of the lock mechanism has been engaged with the engaging recess.

8. The valve timing control apparatus as claimed in claim 1, wherein:

the lock member is a stepped lock pin having a stepped portion formed between a large-diameter portion and a small-diameter portion; and

the lock mechanism is configured so that hydraulic pressure acts on at least the stepped portion.

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

two hydraulic pressures act on the large-diameter portion and the small-diameter portion separately from each other.

10. A valve timing control apparatus of an internal combustion engine comprising:

a driving rotary member adapted to be driven by a crankshaft of the engine;

a driven rotary member adapted to be fixedly connected to a camshaft and configured to phase-change relative to the driving rotary member by supplying or discharging working oil, and also configured to have a cylinder structural bore formed to extend in a direction of a rotation axis of the driven rotary member;

a lock mechanism having a lock member slidably installed in the cylinder structural bore and a biasing member for biasing the lock member in its extended direction from the vane rotor, the lock mechanism being configured to permit the lock member to be displaced in its retracted direction against a biasing force of the biasing member by hydraulic pressure acting on the lock member;

an engaging recess formed in the driving rotary member so as to oppose the lock member, for restricting rotary motion of the driven rotary member relative to the driving rotary member by bringing the lock member into engagement with the engaging recess with sliding motion of the lock member in the extended direction;

a helical torsion spring attached at one end to the driven rotary member and attached at the other end to the driving rotary member, for exerting a biasing force on the vane rotor and for biasing the vane rotor relative to the housing in a specified phase-change direction under a preload of the torsion spring, adjacent coils of the torsion spring being brought into contact with each other at a part of the torsion spring in a circumferential direction under a state where the torsion spring is loaded;

a spring guide provided to surround an outer periphery of the torsion spring; and

a back-pressure relief passage through which a back-pressure chamber, configured to install the biasing member of the lock mechanism, is communicated with an inner periphery of the spring guide,

wherein the back-pressure relief passage is provided at a predetermined circumferential position that goes across a point of contact between the spring guide and the torsion spring at which the outer periphery of the torsion spring is most strongly brought into contact with the inner periphery of the spring guide when the driven rotary member rotates relative to the driving rotary member by a maximum angular displacement.

11. A valve timing control apparatus of an internal combustion engine comprising:

a housing adapted to be driven by a crankshaft of the engine, and configured to define a plurality of working-fluid chambers therein by partitioning an internal space by a plurality of shoes protruding radially inward from an inner peripheral surface of the housing;

a vane rotor having a rotor adapted to be fixedly connected to a camshaft and a plurality of radially-extending vanes formed on an outer periphery of the rotor for partitioning each of the working-fluid chambers of the housing by the shoes and the vanes to define phase-advance working chambers and phase-retard working chambers, the vane rotor being configured to phase-advance relative to the housing by supplying hydraulic pressure to each of the phase-advance working chambers and by discharging working oil in each of the phase-retard working chambers and configured to phase-retard relative to the housing by supplying hydraulic pressure to each of the phase-retard working chambers and by discharging working oil in each of the phase-advance working chambers, and also configured to have a cylinder structural bore formed in at least one of the plurality of vanes as a through hole extending in a direction of a rotation axis of the vane rotor;

a lock mechanism having a lock member slidably installed in the cylinder structural bore and a biasing member for biasing the lock member in its extended direction from the vane rotor, the lock mechanism being configured to permit the lock member to be displaced in its retracted direction against a biasing force of the biasing member by hydraulic pressure acting on the lock member;

an engaging recess formed in the housing so as to oppose the lock member, for restricting rotary motion of the vane rotor relative to the housing by bringing the lock member into engagement with the engaging recess with sliding motion of the lock member in the extended direction;

a helical torsion spring attached at one end to the vane rotor and attached at the other end to the housing, for exerting a biasing force on the vane rotor and for biasing the vane rotor relative to the housing in a specified phase-change direction under a preload of the torsion spring, adjacent coils of the torsion spring being brought into contact with each other at a part of the torsion spring in a circumferential direction under a state where the torsion spring is loaded; and

a back-pressure relief passage through which a back-pressure chamber, configured to install the biasing member of the lock mechanism, is communicated with an exterior space of the housing, the back-pressure relief passage configured to open toward the torsion spring,

wherein the back-pressure relief passage is provided at a predetermined circumferential position that goes across a given angular position displaced from a spring-retainer position at which the other end of the torsion spring is attached to the housing by approximately 90 degrees in a direction opposite to a spring-loaded direction of the torsion spring.