VALVE TIMING CONTROLLER

Abstract

A control valve is provided with a spool and a supply port through which an operating oil is supplied. The spool is provided with an advance check valve and a retard check valve. The advance check valve restricts an operating oil flow flowing from the advance chamber to the supply port and permits an operating oil flow flowing from the supply port to the advance chamber when the advance chamber communicates with the supply port. The retard check valve restricts the operating oil flow flowing from the retard chamber to the supply port and permits the operating oil flow flowing from the supply port to the retard chamber when the retard chamber communicates with the supply port. When a rotational phase of the camshaft is held at a target phase region, the advance chamber and the retard chamber communicate with the supply port respectively.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2007-277960 filed on Oct. 25, 2007, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a valve timing controller which adjusts a valve timing of an inlet valve and/or an exhaust valve of an internal combustion engine.

BACKGROUND OF THE INVENTION

A valve timing controller includes a housing rotating with a crankshaft and a vane rotor rotating with a camshaft. An advance chamber and a retard chamber are defined by a shoe of the housing and a vane of the vane rotor. Operating oil is supplied to the advance chamber or the retard chamber in order to drive the camshaft in an advance direction or a retard direction with respect to the crankshaft, whereby a valve timing is adjusted.

In the valve timing controller, as shown in JP-2006-63835A, a fluctuation torque is arisen in an advance direction or a retard direction of the camshaft. While the engine is running, the fluctuation torque is always arisen due to a reaction spring force of an intake/exhaust valve which is driven by a camshaft. In such a hydraulic valve timing controller, a rotational phase of the camshaft relative to the crankshaft, which is referred to as an engine rotational phase, is determined according to a balance between the fluctuation torque, a driving torque generated by supplying an operating oil to the advance chamber and the retard chamber, and a torque applied to the camshaft.

In a case that an operating oil supply is controlled by an electromagnetic spool as shown in JP-2006-63835A, the electromagnetic spool can be controlled so as to stop the operating oil supply to each chamber in order to hold the engine rotational phase at a target rotational phase region, whereby the valve timing is substantially hold at a suitable timing. If the operating oil is flown out from one of the advance chamber and the retard chamber due to the large fluctuation torque, a negative pressure is arose in the other chamber to draw air through a clearance gap, which may cause a large fluctuation of the vane rotor relative to the housing. Such a fluctuation of the vane rotor may deteriorate a control accuracy of a valve timing.

SUMMARY OF THE INVENTION

The present invention is made in view of the above matters, and it is an object of the present invention to provide a valve timing controller which can realize a valve timing suitable for the internal combustion engine.

A valve timing controller adjusts a valve timing of a valve opened/closed by a torque transmitted from a crankshaft to a camshaft of an internal combustion engine. The valve timing controller includes a first rotating member rotating along with the crankshaft and a second rotating member rotating along with the camshaft. The second rotating member defines an advance chamber and a retard chamber in cooperation with the first rotating chamber in a rotating direction thereof. The second rotating member drives the camshaft in an advance direction or a retard direction relative to the crankshaft by receiving an operating fluid into the advance chamber or the retard chamber. The valve timing controller further includes a control valve provided with a spool and a supply port through which the operating fluid is supplied from a fluid supply source. The spool slidably moves so as to control a communicating condition of the advance chamber and the retard chamber to the supply port. The spool is provided with an advance check valve and a retard check valve. The advance check valve restricts an operating fluid flow flowing from the advance chamber to the supply port and permits the operating fluid flow flowing from the supply port to the advance chamber when the advance chamber communicates with the supply port. The retard check valve restricts an operating fluid flow flowing from the retard chamber to the supply port and permits the operating fluid flow flowing from the supply port to the retard chamber when the retard chamber communicates with the supply port. The control valve moves the spool to a position in which both of the advance chamber and the retard chamber are communicated with the supply port so that an engine rotational phase is held at a target rotational phase region.

Even if the operating fluid in the advance chamber is compressed by a fluctuation torque which retards the camshaft, the advance check valve restricts the operating fluid flow flowing from the advance chamber to the supply port and the retard check valve permits the operating fluid flow flowing from the supply port to the retard chamber so that an inner pressure of the retard chamber can be held positive. Further, even if the operating fluid in the retard chamber is compressed by a fluctuation torque which advances the camshaft, the retard check valve restricts the operating fluid flow flowing from the retard chamber to the supply port and the advance check valve permits the operating fluid flow flowing from the supply port to the advance chamber so that an inner pressure of the advance chamber can be held positive.

Hence, when the engine rotational phase is held at the target phase region, it can be restricted that the operating fluid flows out from the advance chamber and the retard chamber. Furthermore, it can be restricted that the inner pressure of the advance chamber and the retard chamber becomes negative. Thereby, a fluctuation of the second rotating member relative to the first rotating member can be restricted. Therefore, the engine rotational phase can be held at the target phase region so that a suitable valve timing can be achieved.

According to another aspect of the present invention, the control valve is provided with an advance port and a retard port which respectively communicates with the advance chamber and the retard chamber. The spool is provided with an advance connecting passage connecting the advance port with the supply port, and a retard connecting passage connecting the retard port with the supply port. The advance check valve is arranged in the advance connecting passage in such a manner that the operating fluid flow flowing from the advance port to the supply port is restricted. The retard check valve is arranged in the retard connecting passage in such a manner that the operating fluid flow flowing from the retard port to the supply port is restricted.

When the advance port is communicated with the supply port through the advance connecting passage, the advance check valve restricts the operating fluid flow flowing from the advance port to the supply port and permits the reverse flow of the operating fluid. When the retard port is communicated with the supply port through the retard connecting passage, the retard check valve restricts the operating fluid flow flowing from the retard port to the supply port and permits the reverse flow of the operating fluid.

According to the another aspect, the control valve moves the spool to a position in which the advance port communicates with the supply port in a case that the rotational phase of the camshaft relative to the crankshaft is advanced. In a case that the rotational phase of the camshaft relative to the crankshaft is retarded, the control valve moves the spool to a position in which the retard port communicates with the supply port. In a case that the rotational phase of the camshaft relative to the crankshaft is held at the target rotational phase region, the control valve moves the spool to a position in which an opening degree of the advance port is restricted more than a case where the rotational phase of the camshaft is advanced and an opening degree of the retard port is restricted more than a case where the rotational phase of the camshaft is retarded.

In a case that the camshaft is advanced, the operating fluid is reliably introduced into the advance chamber and the outflow of the operating fluid from the advanced chamber is reliably restricted even if the operating fluid in the advance chamber is compressed by the fluctuation torque.

In a case that the camshaft is retarded, the operating fluid is reliably introduced into the retard chamber and the outflow of the operating fluid from the retard chamber is reliably restricted even if the operating fluid in the retard chamber is compressed by the fluctuation torque.

In a case that the engine rotational phase is held at the target phase region, the opening degree of the advance port and the opening degree of the retard port are restricted. Thus, even if the pressure of the operating fluid is abruptly changed, the fluctuation in driving torque can be restricted.

According to another aspect of the invention, the control valve is provided with a drain port through which the operating fluid is discharged. The control valve moves the spool to a position in which the supply port communicates with the advance chamber and the drain port communicates with the retard chamber in a case that the rotational phase of the camshaft relative to the crankshaft is advanced. The control valve moves the spool to a position in which the supply port communicates with the retard chamber and the drain port communicates with the advance chamber in a case that the rotational phase of the camshaft relative to the crankshaft is retarded.

In a case that the camshaft is advanced, the advance chamber communicates with the supply port and the retard chamber communicates with the drain port. Thus, when the operating fluid in the retard chamber is compressed by the fluctuation torque, the operating fluid in the retard chamber can be discharged through the drain port. When the operating fluid in the advance chamber is compressed by the fluctuation torque, the advance check valve restricts the operating fluid flow flowing from the advance chamber to the supply chamber, whereby the outflow of the operating fluid from the advance chamber can be restricted. Therefore, a variation speed of the engine rotational phase in an advance direction can be enhanced, so that the suitable valve timing can be early achieved.

In a case that the camshaft is retarded, the retard chamber communicates with the supply port and the advance chamber communicates with the drain port. Thus, when the operating fluid in the advance chamber is compressed by the fluctuation torque, the operating fluid in the advance chamber can be discharged through the drain port. When the operating fluid in the retard chamber is compressed by the fluctuation torque, the retard check valve restricts the operating fluid flow flowing from the retard chamber to the supply chamber, whereby the outflow of the operating fluid from the retard chamber can be restricted. Therefore, a variation speed of the engine rotational phase in a retard direction can be enhanced, so that the suitable valve timing can be early achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 is a schematic view showing the valve timing controller according to an embodiment of the present invention;

FIG. 2 is a diagram for explaining the fluctuation torque applied to a control unit;

FIG. 3A and FIG. 3B are cross sectional views schematically showing a structure and an operation condition of a control valve;

FIG. 4A and FIG. 4B are cross sectional views schematically showing a structure and an operation condition of a control valve;

FIG. 5A and FIG. 5B are cross sectional views schematically showing a structure and an operation condition of a control valve;

FIG. 6 is a graph showing a variation speed of an engine rotational phase; and

FIG. 7 is a graph showing a fluctuation of the engine rotational phase.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereafter, a first embodiment of the present invention is described.

FIG. 1 shows a first embodiment of a valve timing controller 1 which is applied to an internal combustion engine for a vehicle. The valve timing controller 1 is driven by an operating fluid such as operating oil to adjust a valve timing of an intake valve.

(Basic Structure)

A basic structure of the valve timing controller 1 will be described hereinafter. The valve timing controller 1 includes a driving unit 10 and a control unit 30. The driving unit 10 transmits a driving force of a crankshaft (not shown) to a camshaft 2. The control unit 30 controls an operating oil supply to the driving unit 10.

(Driving Unit)

In the driving unit 10, a housing corresponding to a first rotating member includes a cylindrical sprocket 12a and a plurality of shoes 12b, 12c, 12d as partitioning portions.

The sprocket 12a rotates along with a crankshaft through a timing chain (not shown). While the engine is operated, the driving force is transmitted from the crankshaft to the sprocket 12a so that the housing 12 rotates in a clockwise direction in FIG. 1.

Each shoe 12b-12d protrudes radially inwardly from an inner surface of the sprocket 12a at regular intervals in a rotational direction. An inner tip end of each shoe 12b-12d is concavely arc-shaped to slidably contact with an outer surface of a boss portion 14a of a vane rotor 14. Three accommodation chambers 50 are defined between adjacent shoes 12b-12d.

The vane rotor 14 corresponding to a second rotating member is accommodated in the housing 12. The vane rotor 14 includes the columnar boss portion 14a and three vanes 14b, 14c, 14d.

The boss portion 14a is coaxially fixed on the camshaft 2 by a bolt (not shown). The vane rotor 14 rotates in a clockwise direction along with the camshaft 2. The vane rotor 14 can relatively rotate relative to the housing 12. Each of the vanes 14b-14d protrudes radially outwardly from the boss portion 14a at regular intervals and is accommodated in the corresponding accommodation chamber 50 respectively. An outer tip end of each vane 14b-14d is convexly arc-shaped to slidably contact with an inner surface of the sprocket 12a.

Each of the vanes 14b-14d divides the accommodation chamber 50 into an advance chamber and a retard chamber. Specifically, an advance chamber 52 is defined between the shoe 12b and the vane 14b, an advance chamber 53 is defined between the shoe 12c and the vane 14c, and an advance chamber 54 is defined between the shoe 12d and the vane 14d, respectively. Furthermore, a retard chamber 56 is defined between the shoe 12c and the vane 14b, a retard chamber 57 is defined between the shoe 12d and the vane 14c, and a retard chamber 58 is defined between the shoe 12b and the vane 14d, respectively.

When the operating oil is supplied to each of the advance chambers 52-54, the vane rotor 14 rotates in an advance direction relative to the housing 12 so that the camshaft 2 is driven in the advance direction relative to the crankshaft. Thus, the valve timing is advanced. When the operating oil is supplied to each of the retard chambers 56-58, the vane rotor 14 rotates in a retard direction relative to the housing 12 so that the camshaft 2 is driven in the retard direction relative to the crank shaft. Thus, the valve timing is retarded.

(Control Unit)

In the control unit 30, a first advance passage 72 is formed in the camshaft 2, and a second advance passage 73 is formed in a journal 3 which supports the camshaft 2. The first advance passage 72 communicates with the second advance passage 73 and communicates with each of the advance chambers 52-54. A first retard passage 76 is formed in the camshaft 2, and a second retard passage 77 is formed in the journal 3. The first retard passage 76 communicates with the second retard passage 77 and communicates with each of the retard chambers 56-58.

A supply passage 80 communicates with a discharge port of an oil pump 4. The operating oil in an oil pan 5 is pumped up by the oil pump 4 and is discharged to the supply passage 80. The oil pump 4 is a mechanical pump which is driven by the crankshaft. While the engine is operated, the operating oil is continuously supplied to the supply passage 80. Drain passages 82, 83 is provided in such a manner as to discharge the operating oil to the oil pan 5.

A control valve 100 is an electromagnetic spool valve which reciprocates a spool 120 in a sleeve 110 by use of an electromagnetic driving force generated by a solenoid 130. The sleeve 110 is provided with an advance port 112 communicating to the second advance passage 73, a retard port 114 communicating to the second retard passage 77, a supply port 116 communicating to the supply passage 80, and drain ports 118, 119 communicating to the drain passage 82, 83. The control valve 100 reciprocates the spool according to an energization of the solenoid 130, whereby the communication of the advance port 112 and the retard port 114 to the supply port 116 and the drain ports 118, 119 are controlled.

A control circuit 200 includes a microcomputer which is electrically connected with the solenoid 130 of the control valve 100. The control circuit 200 controls an energization of the solenoid 130 and an operation of the internal combustion engine.

When the advance port 112 communicates with the supply port 116, the operating oil is supplied to the advance chambers 52-54 through the supply passage 80 and the first and second advance passages 72, 73. When the retard port 114 communicates with the supply port 116, the operating oil is supplied to the retard chambers 56-58 through the supply passage 80 and the first and second retard passages 76, 77. When the advance port 112 communicates with the drain port 118, the operating oil in the advance chambers 52-54 is discharged to the oil pan 5 through the advance passages 72, 73 and the drain passage 82. When the retard port 114 communicates with the drain port 119, the operating oil in the retard chambers 56-58 is discharged to the oil pan 5 through the retard passages 76, 77 and the drain passage 83.

The basic structure of the valve timing controller 1 has been described above. A feature of the valve timing controller 1 will be described in detail hereinafter.

(Fluctuation Torque)

While the engine is running, a fluctuation torque caused by a spring reactive force of the intake valve is applied to the vane rotor 14 through the camshaft 2. As shown in FIG. 2, the fluctuation torque is periodically fluctuates between negative torque which advances the camshaft 2 relative to the crankshaft and positive torque which retards the camshaft 2 relative to the crankshaft. In this embodiment, a positive peak torque “T+” is substantially equal to a negative peak torque “T−”. Alternatively, the positive peak torque “T+” is slightly greater than the negative peak torque “T−”. Hence, an average torque of the fluctuation torque is substantially zero, or slightly biased to the positive torque (that is, the camshaft 2 is biased to the retard direction). Such a fluctuation torque is generated in a case that the internal combustion engine is provided with a roller-rocker type valve or a friction slightly exists between the camshaft 2 and the journal 3.

(Control Valve)

As shown in FIGS. 3A and 3B, the control valve 100 includes the sleeve 110 in which a return spring 140 is accommodated. The return spring 140 is a compression coil spring made from metallic material. The return spring 140 is disposed between the spool 120 and an end portion 110a of the sleeve 110. The return spring 140 biases the spool 120 toward the solenoid 130. When the solenoid 130 is energized to generate electromagnetic force, the spool 120 is biased toward the return spring 140. The position of the spool 120 is determined based on the biasing force of the return spring 140 and the electromagnetic force generated by the solenoid 130.

The sleeve 110 made from metallic material is provided with the drain port 118, the advance port 112, the supply port 116, the retard port 114 and the drain port 119 in this series in a direction from the return spring 140 to the solenoid 130. The spool made from metallic material is provided with an advance support land 122, an advance switch land 123, an advance valve built-in land 124, a retard valve built-in land 125, a retard switch land 126, and a retard support land 127 in this series in a direction from the return spring 140 to the solenoid 130.

The advance support land 122 is slidably supported in the sleeve 110 at the end portion 110a. The advance valve built-in land 124 is slidably supported in the sleeve 110 between the advance port 112 and the supply port 116. The advance switch land 123 is slidably supported in the sleeve 110 between the supply port 116 and the drain port 118. When the spool 120 slides so that the advance switch land 123 is supported between the advance port 112 and the advance port 112 and the supply port 116 as shown in FIGS. 4A and 4B the advance port 112 communicates with the drain port 118 through a space between the advance switch land 123 and the advance support land 122. When the advance switch land 123 is supported between the drain port 118 and the supply port 116, the advance port 112 communicates with a space between the advance switch land 123 and the advance valve built-in land 124.

As shown in FIG. 3, the retard valve built-in land 125 is slidably supported between the supply port 116 and the retard port 114. The retard support land 127 is slidably supported in the sleeve 110 between the drain port 119 and the solenoid 130. The retard switch land 126 is slidably supported between the retard port 114 and the drain port 119. As shown in FIG. 5, when the retard switch land 126 is slidably supported between the retard port 114 and the supply port 116, the retard port 114 communicates with the drain port 119 through a space between the retard switch land 126 and the retard support land 127. On the other hand, as shown in FIGS. 3 and 4, when the retard switch land 126 is supported between the retard port 114 and the drain port 119, the drain port 114 communicates with the space between the retard switch land 126 and the retard valve built-in land 125.

When a reference electric current “Ib” is supplied to the solenoid 130, as shown in FIGS. 3A and 3B, the advance port 112 communicates with the space between the lands 123 and 124, and the retard port 114 communicates with the space between the lands 126 and 125. When an electric current greater than the reference current “Ib” is supplied to the solenoid, as shown in FIG. 5, the advance port 112 communicates with the space between the lands 123 and 124, and the retard port communicates with the drain port 119. When an electric current less than the reference current “Ib”, as shown in FIG. 4, the advance port 112 communicates with the drain port 118 and the retard port 114 communicates with the space between the lands 126 and 125.

As shown in FIGS. 3A and 3B, the advance valve built-in land 124 and the retard valve built-in land 125 respectively include a check valve 150, 160 therein.

Specifically, the advance valve built-in land 124 and the retard valve built-in land 125 are connected to each other by a connecting shaft portion 128 which is provided with a common connecting passage 170. The common connecting passage 170 always communicates with the supply port 116.

The advance valve built-in land 124 is provided with an advance connecting passage 152 which connects the space between the advance valve built-in land 124 and the advance switch land 123 to the common connecting passage 170. As shown in FIG. 5A, when the advance port 112 communicates with the space between the advance valve built-in land 124 and the advance switch land 123, the advance port 112 communicates with the supply port 116 through the advance connecting passage 152 and the common connecting passage 170.

An advance check valve 150 is provided in the advance connecting passage 152 in such a manner as to prevent a fluid flow flowing from the advance port 112 toward the supply port 116. The advance check valve 150 is comprised of a valve seat 154, a valve body 156, and a valve spring 158.

The valve seat 154 is formed by decreasing an inner diameter of the advance connecting passage 152 toward the common connecting passage 170.

The valve seat 154 has a circular conical surface. The valve body 156 is a ball valve made of metallic material and is arranged at opposite side of the common connecting passage 170 across the valve seat 154. The valve body 156 axially moves with respect to the valve seat 154. The valve spring 158 is a compression coil spring made of metallic material and is arranged between a wall 159 and the valve body 156. The valve spring 158 biases the valve body 156 toward the valve seat 154.

In a case that the advance port 112 communicates with the supply port 116, the advance check valve 150 restricts a fluid flow flowing from the advance port 112 toward the supply port 116 as shown in FIG. 3A and FIG. 5B, and permits a fluid flow flowing from the supply port 116 to the advance 112 as shown in FIG. 3B and FIG. 5A.

As shown in FIGS. 3A and 3B, the retard valve built-in land 125 is provided with a retard connecting passage 162 which connects the space between the retard valve built-in land 125 and the retard switch land 126 to the common connecting passage 170. As shown in FIG. 4A, when the retard port 114 communicates with the space between the retard valve built-in land 125 and the retard switch land 126, the retard port 114 communicates with the supply port 116 through the retard connecting passage 162 and the common connecting passage 170.

A retard check valve 160 is provided in the retard connecting passage 162 in such a manner as to prevent a fluid flow flowing from the retard port 114 toward the supply port 116. The retard check valve 160 is comprised of a valve seat 164, a valve body 166, and a valve spring 168.

The valve seat 164 is formed by decreasing an inner diameter of the retard connecting passage 162 toward the common connecting passage 170. The valve seat 164 has a circular conical surface. The valve body 166 is a ball valve made of metallic material and is arranged at opposite side of the common connecting passage 170 across the valve seat 164. The valve body 156 axially moves with respect to the valve seat 164. The valve spring 168 is arranged between a wall 169 and the valve body 166, and biases the valve body 166 toward the valve seat 164.

In a case that the retard port 114 communicates with the supply port 116, the retard check valve 160 restricts a fluid flow flowing from the retard port 114 toward the supply port 116 as shown in FIG. 3B and FIG. 4B, and permits a fluid flow flowing from the supply port 116 to the retard 114 as shown in FIG. 3A and FIG. 4A.

(Valve Timing Adjust Operation)

While the engine is running to drive the oil pump 4, the control circuit 200 computes an actual phase and a target phase of the camshaft 2 relative to the crankshaft. Based on the computed phases, the electric current supplied to the solenoid 130 is controlled. The energization of the solenoid 130 moves the spool 120. According to the position of the spool 120, an operating oil supply or an operating oil discharge to or from the advance chambers 52-55 and the retard chambers 56-58 is conducted, whereby the valve timing is adjusted. The valve timing adjust operation will be described in detail hereinafter.

(1) Advance Operation

An advance operation will be described in detail hereinafter. In the advance operation, a rotational phase of the camshaft 2 is advanced relative to the crankshaft so that the valve timing is advanced.

When the accelerator pedal is not stepped, or when the vehicle is running in low speed and high load to require high output torque, the electric current greater than the reference current “Ib” is supplied to the solenoid 130. The spool 120 moves to a position in which the supply port 116 communicates with the advance port 112 and the retard port 114 communicates with the drain port 119, as shown in FIG. 5A.

Hence, while the negative torque is applied to the vane rotor 14, the advance check valve 150 permits the operating oil flow flowing from the supply port 116 to the advance port 112, whereby the operating oil supply from the oil pump 4 to the advance chambers 52-54 is maintained. The operating oil in the retard chambers 56-58 is compressed by the vane rotor 14 receiving the negative torque, and is discharged to the oil pan 5 through the retard port 114 and the drain port 119 as shown in FIG. 5A.

When the positive torque is applied to the vane rotor 14 to compress the operating oil in the advance chambers 52-54, the operating oil flow flowing from the advance port 112 to the supply port 116 is restricted by the advance check valve 150, as shown in FIG. 5B. Hence, the outflow of the operating oil from the advance chambers 52-54 is restricted.

As shown in FIGS. 5A and 5B, whichever the fluctuation torque is the negative torque or the positive torque, the retard check valve 160 is opened by the operating oil flowing from the supply port 116. The space between the retard valve built-in land 125 and the retard switch land 126 is closed with respect to the retard port 114, so that no operating oil is supplied to the retard chambers 56-58 from the oil pump 4.

As shown in FIG. 6, according to the present embodiment, an advance speed of the camshaft 2 is higher than that of a conventional control valve which does not have an advance check valve in a spool. Therefore, the valve timing can be early advanced to a timing which is suitable for a current engine condition.

(2) Retard Operation

A retard operation will be described in detail hereinafter. In the retard operation, a rotational phase of the camshaft 2 is retarded relative to the crankshaft so that the valve timing is retarded.

When the vehicle is running in low load, the electric current lower than the reference current “Ib” is supplied to the solenoid 130. The spool 120 moves to a position in which the supply port 116 communicates with the retard port 114 and the advance port 118 communicates with the drain port 119, as shown in FIG. 4A.

Hence, while the positive torque is applied to the vane rotor 14, the retard check valve 160 permits the operating oil flow flowing from the supply port 116 to the retard port 114, whereby the operating oil supply from the oil pump 4 to the retard chambers 56-58 is maintained. The operating oil in the advance chambers 52-54 is discharged to the oil pan 5 through the advance port 112 and the drain port 118 as shown in FIG. 4A.

When the negative torque is applied to the vane rotor 14 to compress the operating oil in the retard chambers 56-58, the operating oil flow flowing from the retard port 114 to the supply port 116 is restricted by the retard check valve 150, as shown in FIG. 4B. Hence, the outflow of the operating oil from the retard chambers 56-58 is restricted.

As shown in FIGS. 4A and 4B, whichever the fluctuation torque is the negative torque or the positive torque, the advance check valve 150 is opened by the operating oil flowing from the supply port 116. The space between the advance valve built-in land 124 and the advance switch land 123 is closed with respect to the advance port 114, so that no operating oil is supplied to the advance chambers 52-54 from the oil pump 4.

According to the present embodiment, a retard speed of the camshaft 2 is higher than that of a conventional control valve which does not have a retard check valve in a spool. Therefore, the valve timing can be early retarded to a timing which is suitable for a current engine condition.

(3) Hold Operation

In a hold operation, the engine rotational phase is held at the target rotational phase, so that the valve timing is substantially held at the target valve timing.

When a stable engine driving condition is established, the reference current “Ib” is supplied to the solenoid 130. The spool 120 moves a position shown in FIGS. 3A and 3B in which the advance port 112 and the retard port 114 communicate with the supply port 116.

When the positive torque is applied to the vane rotor 14 to compress the operating oil in the advance chambers 52-54, as shown in FIG. 3A, the advance check valve 150 restricts the operating oil flow flowing from the advance port 112 to the supply port 116 so as to keep the operating oil in the advance chambers 52-54. Although the retard check valve 160 permits the operating oil flow flowing from the supply port 116 to the retard port 114, an opening degree of the retard port 114 is restricted by the spool 120 more than the retard operation shown in FIGS. 4A and 4B. Thus, irrespective of the variation in the operating oil pressure, while the oil pressure in the retard chambers 56-58 is kept positive to hold the engine rotational phase, the operating oil supply to the retard chambers 56-58 can be realized.

When the negative torque is applied to the vane rotor 14 to compress the operating oil in the retard chambers 56-58, as shown in FIG. 3B, the retard check valve 160 restricts the operating oil flow flowing from the retard port 114 to the supply port 116 so that the operating oil pressure in the retard chambers 56-58 is held. Although the advance check valve 150 allows the operating oil flow flowing from the supply port 116 to the advance port 112, the advance port 112 is restricted by the spool more than the advance operation shown in FIGS. 5A and 5B. Thus, irrespective of the variation in the operating oil pressure, while the oil pressure in the advance chambers 52-54 is kept positive to hold the engine rotational phase, the operating oil supply to the retard chambers 52-54 can be realized.

According to the above embodiment, the outflow of the operating oil from the advance chambers 52-54 and the retard chambers 56-58 can be restricted. Furthermore, it can be restricted that the pressure in the advance chambers 52-54 and the retard chambers 56-58 become negative. Hence, an oscillating movement of the vane rotor 14 relative to the housing 12 can be restricted. Therefore, as shown in FIG. 7, a variation width of the engine rotational phase becomes smaller than that in a conventional structure which does not have the check valves in the spool. According to the present embodiment, the engine rotational phase can be held at the target phase region and a suitable valve timing can be obtained.

Other Embodiment

The present invention should not be limited to the disclosure embodiment, but may be implemented in other ways without departing from the sprit of the invention.

Specifically, it can be configured that the fluctuation torque of which average torque is biased to the positive torque may be applied to the driving unit 10 through the camshaft 2. In such a case, the driving unit 10 may be provided with an assist spring which biases the camshaft 2 in a direction of the negative torque. Furthermore, the housing 12 may rotate along with the camshaft 2, and the vane rotor 14 may rotates along with the crankshaft.

The control valve 100 may be comprised of a piezo actuator or a hydraulic actuator in stead of the solenoid 130 for moving the spool 120.

And the present invention is applicable also to the apparatus which adjusts the valve timing of the exhaust valve, and the apparatus which adjusts the valve timing of the intake valve and the exhaust valve.

Claims

1. A valve timing controller which adjusts a valve timing of a valve opened/closed by a torque transmitted from a crankshaft to a camshaft of an internal combustion engine, the valve timing controller comprising:

a first rotating member rotating along with the crankshaft;

a second rotating member rotating along with the camshaft, and defining an advance chamber and a retard chamber in cooperation with the first rotating member in a rotating direction thereof, the second rotating member driving the camshaft in an advance direction or a retard direction relative to the crankshaft by receiving an operating fluid into the advance chamber or the retard chamber; and

a control valve provided with a spool and a supply port through which the operating fluid is supplied from a fluid supply source, the spool slidably moving so as to control a communicating condition of the advance chamber and the retard chamber to the supply port, wherein

the spool includes: an advance check valve which restricts an operating fluid flow flowing from the advance chamber to the supply port and permits the operating fluid flow flowing from the supply port to the advance chamber when the advance chamber communicates with the supply port; and a retard check valve which restricts an operating fluid flow flowing from the retard chamber to the supply port and permits the operating fluid flow flowing from the supply port to the retard chamber when the retard chamber communicates with the supply port, and

the control valve moves the spool to a position in which both of the advance chamber and the retard chamber are communicated with the supply port so that a rotational phase of the camshaft relative to the crankshaft is held at a target rotational phase region.

2. A valve timing controller according to claim 1, wherein

the control valve is provided with an advance port and a retard port which respectively communicates with the advance chamber and the retard chamber, and

the spool is provided with an advance connecting passage which connects the advance port with the supply port, in which the advance check valve is arranged in such a manner that the operating fluid flow flowing from the advance port to the supply port is restricted, and a retard connecting passage which connects the retard port with the supply port, in which the retard check valve is arranged in such a manner that the operating fluid flow flowing from the retard port to the supply port is restricted.

3. A valve timing controller according to claim 2, wherein

the control valve moves the spool to a position in which the advance port communicates with the supply port in a case that the rotational phase of the camshaft relative to the crankshaft is advanced,

the control valve moves the spool to a position in which the retard port communicates with the supply port in a case that the rotational phase of the camshaft relative to the crankshaft is retarded, and

the control valve moves the spool to a position in which an opening degree of the advance port is restricted more than a case where the rotational phase of the camshaft is advanced and an opening degree of the retard port is restricted more than a case where the rotational phase of the camshaft is retarded in a case that the rotational phase of the camshaft relative to the crankshaft is held at the target rotational phase region.

4. A valve timing controller according to claim 1, wherein

the control valve is provided with a drain port through which the operating fluid is discharged,

the control valve moves the spool to a position in which the supply port communicates with the advance chamber and the drain port communicates with the retard chamber in a case that the rotational phase of the camshaft relative to the crankshaft is advanced, and

the control valve moves the spool to a position in which the supply port communicates with the retard chamber and the drain port communicates with the advance chamber in a case that the rotational phase of the camshaft relative to the crankshaft is retarded.