Valve timing control apparatus

An advancing check valve is placed in an advancing connection passage of a spool to enable a flow of hydraulic fluid in a first direction from a retarding port side toward an advancing port side upon placement of the spool in an advancing position and to limit a flow of hydraulic fluid in a second direction from the advancing port side toward the retarding port side upon placement of the spool in the advancing position. A retarding check valve is placed in a retarding connection passage of the spool to enable a flow of hydraulic fluid in the second direction upon placement of the spool in a retarding position and to limit a flow of hydraulic fluid in the first direction upon placement of the spool in the retarding position.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2007-307989 filed on Nov. 28, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve timing control apparatus that controls valve timing of at least one valve, which is driven by a camshaft through transmission of a torque from a crankshaft of an internal combustion engine.

2. Description of Related Art

A known valve timing control apparatus of a fluid drive type has a housing and a vane rotor. The housing serves as a driving-side rotator, which is rotated synchronously with a crankshaft. The vane rotor serves as a driven-side rotator, which is rotated synchronously with a camshaft. Japanese Unexamined Patent Publication No. 2006-63835 discloses this type of valve timing control apparatus, in which hydraulic fluid is supplied to advancing chambers or retarding chambers, each of which extends in a rotational direction and is defined between a corresponding shoe of the housing and a corresponding vane of the vane rotor, so that the camshaft is driven relative to the crankshaft in the advancing direction or the retarding direction to adjust the valve timing.

Here, in the valve timing control apparatus of Japanese Unexamined Patent Publication No. 2006-63835, a spool valve is used to change communication of a supply passage, into which the hydraulic fluid is supplied from a pump, to the advancing chambers or the retarding chambers. Specifically, at the time of changing the phase (hereinafter, referred to as an engine phase) of the camshaft relative to the crankshaft toward the advancing side, a port, which is communicated with the supply passage, is communicated with a port, which is communicated with the advancing chambers, by moving a spool of the spool valve to a corresponding position. Furthermore, at the time of changing the engine phase toward the retarding side, the port, which is communicated with the supply passage, is communicated with a port, which is communicated with the retarding chambers, by moving the spool to a corresponding position.

In the valve timing control apparatus of Japanese Unexamined Patent Publication No. 2006-63835, the variable torque is varied between the negative torque side for advancing the camshaft relative to the crankshaft and the positive torque side for retarding the camshaft relative to the crankshaft. Here, the variable torque is always applied during the operation of the internal combustion engine by, for example, a spring reaction force of the valves, which are driven by the camshaft. The amount of the variable torque changes depending on the rotational state of the internal combustion engine.

Therefore, in the case of changing the engine phase toward the advancing side, when the amount of supply of the hydraulic fluid from the pump is relatively small at the time of applying the negative torque as the variable torque, the hydraulic fluid becomes deficient in the advancing chambers, the volume of which is increased by the action of the negative torque. Thus, when the variable torque is reversed from the negative torque to the positive torque, the retardation of the camshaft cannot be limited due to the deficient of the working fluid. As a result, the response at the time of advancing the engine phase is disadvantageously deteriorated. The deterioration of the response also occurs at the time of changing the engine phase toward the retarding side. Therefore, it is desirable to take appropriate measures for both of the advancing side change and the retarding side change of the engine phase.

SUMMARY OF THE INVENTION

The present invention is made in view of the above disadvantage. Thus, it is an objective of the present invention to provide a valve timing control apparatus, which exhibits improved response. According to the present invention, there is provided a valve timing control apparatus that controls valve timing of at least one valve of an internal combustion engine, which is driven by a camshaft through transmission of a torque from a crankshaft of the internal combustion engine to open and close the at least one valve. The valve timing control apparatus includes a driving-side rotator, a driven-side rotator and a spool valve. The driving-side rotator is rotatable synchronously with the crankshaft. The driven-side rotator is rotatable synchronously with the camshaft. The driving-side rotator and the driven side rotator form an advancing chamber and a retarding chamber therebetween. The camshaft is driven relative to the crankshaft in one of an advancing direction and a retarding direction when hydraulic fluid is supplied to corresponding one of the advancing chamber and the retarding chamber. The spool valve includes an advancing port, a retarding port, a supply port, a spool, an advancing connection passage, an advancing check valve, a retarding connection passage and a retarding check valve. The advancing port is communicated with the advancing chamber. The retarding port is communicated with the retarding chamber. The supply port receives hydraulic fluid from an external fluid supply source. The spool is reciprocally drivable. The spool is driven to an advancing position to communicate the advancing port to the supply port at time of advancing a phase of the camshaft relative to the crankshaft and is driven to a retarding position to communicate the retarding port to the supply port at time of retarding the phase of the camshaft relative to the crankshaft. The advancing connection passage is formed in the spool and connects between the advancing port and the retarding port at the time of placing the spool in the advancing position. The advancing check valve is placed in the advancing connection passage to enable a flow of hydraulic fluid in a first direction from the retarding port side toward the advancing port side upon placement of the spool in the advancing position and to limit a flow of hydraulic fluid in a second direction from the advancing port side toward the retarding port side upon placement of the spool in the advancing position. The retarding connection passage is formed in the spool and connects between the advancing port and the retarding port upon placement of the spool in the retarding position. The retarding check valve is placed in the retarding connection passage to enable a flow of hydraulic fluid in the second direction upon placement of the spool in the retarding position and to limit a flow of hydraulic fluid in the first direction upon placement of the spool in the retarding position.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a valve timing control apparatus1of the first embodiment installed to an internal combustion engine of a vehicle. The valve timing control apparatus1is of a hydraulically controlled type, which uses hydraulic oil as working fluid to adjust the valve timing of intake valves.

Hereinafter, a basic structure of the valve timing control apparatus1will be described. The valve timing control apparatus1includes a drive device10and a control device30. The drive device10is driven by the hydraulic oil and is provided in a drive force transmission system, which transmits a drive force of a crankshaft (not shown) of the internal combustion engine to a camshaft2of the internal combustion engine. The control device30controls supply of the hydraulic oil to the drive device10.

In the drive device10, a housing12, which serves as a driving-side rotator, includes a generally cylindrical sprocket portion12aand a plurality of shoes (serving as partitions)12b-12e.

The sprocket portion12ais connected to the crankshaft through a timing chain (not shown). With the above construction, at the time of driving the internal combustion engine, the drive force is transmitted from the crankshaft to the sprocket portion12a, and thereby the housing12is rotated synchronously with the crankshaft in a clockwise direction inFIG. 1.

The shoes12b-12eare arranged one after another along the sprocket portion12aat generally equal intervals in the rotational direction of the sprocket portion12aand radially inwardly project. A projecting end surface of each shoe12b-12eforms an arcuate concave surface when it is viewed in a direction perpendicular to the plane ofFIG. 1. The projecting end surface of each shoe12b-12eslidably engages an outer peripheral wall surface of a boss14aof a vane rotor14. A receiving chamber50is formed between each adjacent two of the shoes12b-12e, which are adjacent to each other in the rotational direction.

The vane rotor14, which serves as a driven-side rotator, is received in the housing12and slidably engages the housing12in the axial direction. The vane rotor14includes the cylindrical boss14aand a plurality of vanes14b-14e.

The boss14ais coaxially fixed to the camshaft2with a bolt. Thereby, the vane rotor14rotates in the clockwise direction inFIG. 1synchronously with the camshaft2and can rotate relative to the housing12.

The vanes14b-14e, which are placed one after another at the generally equal intervals in the rotational direction at the boss14a, radially outwardly project from the boss14aand are received in the receiving chambers50, respectively. A projecting end surface of each vane14b-14dforms an arcuate convex surface as viewed in the direction perpendicular to the plane ofFIG. 1and is slidably engaged with the inner peripheral wall surface of the sprocket portion12a.

Each vane14b-14edivides the corresponding receiving chamber50to form an advancing chamber and a retarding chamber relative to the housing12. Specifically, the advancing chamber52is formed between the shoe12band the vane14b, and the advancing chamber53is formed between the shoe12cand the vane14c. Furthermore, the advancing chamber54is formed between the shoe12dand the vane14d, and the advancing chamber55is formed between the shoe12eand the vane14e. Also, the retarding chamber56is formed between the shoe12cand the vane14b, and the retarding chamber57is formed between the shoe12dand the vane14c. Also, the retarding chamber58is formed between the shoe12eand the vane14d, and the retarding chamber59is formed between the shoe12band the vane14e.

In the drive device10, when the hydraulic oil is supplied to the respective advancing chambers52-55, the vane rotor14is rotated in the advancing direction relative to the housing12, so that the camshaft2is driven in the advancing direction relative to the crankshaft. Therefore, in this case, the engine phase, which determines the valve timing, is changed in the advancing direction. Furthermore, in the drive device10, when the hydraulic oil is supplied to the respective retarding chambers56-59, the vane rotor14is rotated in the retarding direction relative to the housing12, so that the camshaft2is driven in the retarding direction relative to the crankshaft. Therefore, in this case, the engine phase is changed in the retarding direction.

In the control device30, an advancing passage72, which extends through the camshaft2and a bearing (not shown) thereof, is communicated with the advancing chambers52-55. Furthermore, a retarding passage76, which extends through the camshaft2and the bearing thereof, is communicated with the retarding chambers56-59.

A supply passage80is communicated with an outlet opening of a pump (a fluid supply source)4to receive the hydraulic oil, which is pumped from an oil pan5by the pump4. The pump4of the present embodiment is a mechanical pump, which is driven by the crankshaft. At the time of driving the internal combustion engine, the hydraulic oil is continuously supplied to the supply passage80.

The spool valve100is a solenoid control valve, which linearly and reciprocally drives a spool through use of an electromagnetic drive force generated from a solenoid120. The spool valve100includes an advancing port112, a retarding port114and a supply port116. The advancing port112is communicated with the advancing chambers52-55through the advancing passage72. The retarding port114is communicated with the retarding chambers56-59through the retarding passage76. The supply port116receives the hydraulic oil from the pump4through the supply passage80. Thus, in the spool valve100, the spool is reciprocally driven through energization of the solenoid120to change the port, which is communicated with the supply port116, between the advancing port112and the retarding port114.

A control circuit200includes, for example, a microcomputer and is electrically connected to the solenoid120of the spool valve100. The control circuit200controls the energization of the solenoid120and the operation of the internal combustion engine.

In the control device30, the spool of the spool valve100is driven through the energization of the solenoid120, which is controlled by the control circuit200, so that the communicating states of the ports112,114relative to the supply port116are controlled. Thereby, when the advancing port112is communicated with the supply port116, the hydraulic oil, which is supplied from the pump4to the supply passage80, is provided to the advancing chambers52-55through the advancing passage72. Furthermore, when the retarding port114is communicated with the supply port116, the hydraulic oil, which is supplied from the pump4to the supply passage80, is provided to the retarding chambers56-59through the retarding passage76.

Hereinafter, characteristics of the valve timing control apparatus1will be described.

At the time of driving the internal combustion engine, the variable torque, which is generated due to, for example, a spring reaction force applied from the intake valves that are opened and closed by the camshaft2, is applied to the vane rotor14of the drive device10through the camshaft2. As shown inFIG. 2, the variable torque periodically varies between a negative torque, which causes the advancing of the camshaft2relative to the crankshaft, and a positive torque, which causes the retarding of the camshaft2relative to the crankshaft. For example, the variable torque can be set such that an absolute value of a peak T+ of the positive torque is substantially equal to an absolute value of a peak T− of the negative torque, so that an average torque becomes substantially zero. Alternatively, the variable torque can be set such that the absolute value of the peak T+ of the positive torque is larger than the absolute value of the peak T− of the negative torque, so that an average torque is deviated on the positive torque side.

As shown inFIG. 3, the spool valve100of the present embodiment includes a sleeve110, the solenoid120, the spool130, a drive shaft139and a return spring140.

The sleeve110is made of metal and is configured into a generally cylindrical body. The solenoid120is fixed to one end portion110aof the sleeve110. In the sleeve110, the retarding port114, the supply port116and the advancing port112are arranged in this order from the one end portion110aside to the other end portion110bside.

The spool130is made of metal and is configured into a rod-shaped body and is coaxially received in the sleeve110. The drive shaft139, which is electromagnetically driven by the solenoid120, is coaxially connected to one end portion130aof the spool130, and thereby the spool130is axially reciprocally driven together with the drive shaft139. In the spool130, an advancing support land132, an advancing change land134, a retarding change land and a retarding support land138are arranged in this order from the other end portion130bside to the one end portion130aside

The advancing support land132is always slidably supported by the sleeve110on the end portion110bside of the advancing port112. The advancing change land134is always slidably supported by the sleeve110on at least one of the end portion110bside of the advancing port112and the supply port116side of the advancing port112. As shown inFIG. 3, when the advancing change land134is supported by the sleeve110only on the end portion110bside of the advancing port112, the advancing port112is communicated with the supply port116through the gap between the advancing change land134and the retarding change land136. Furthermore, as shown inFIG. 4, when the advancing change land134is supported by the sleeve110only on the supply port116side of the advancing port112, the advancing port112is communicated with the gap between the advancing support land132and the advancing change land134. In addition, as shown inFIG. 5, when the advancing change land134is supported by the sleeve110on the end portion110bside of the advancing port112and also the supply port116side of the advancing port112, the advancing port112is closed.

As shown inFIG. 3, the retarding support land138is always slidably supported by the sleeve110on the end portion110aside of the retarding port114. The retarding change land136is slidably supported by the sleeve110on at least one of the supply port116side of the retarding port114and the end portion110aside of the retarding port114. As shown inFIG. 4, when the retarding change land136is supported by the sleeve110only on the end portion110aside of the retarding port114, the retarding port114is communicated with the supply port116through the gap between the advancing change land134and the retarding change land136. Furthermore, as shown inFIG. 3, when the retarding change land136is supported by the sleeve110only on the supply port116side of the retarding port114, the retarding port114is communicated with the gap between the retarding change land136and the retarding support land138. In addition, as shown inFIG. 5, when the retarding change land136is supported by the sleeve110on the end portion110aside of the retarding port114and also the supply port116side of the retarding port114, the retarding port114is closed.

In the present embodiment, the supply port116is always communicated with the gap between the advancing change land134and the retarding change land136.

The return spring140is constructed as a compression coil spring made of metal in the present embodiment and is received coaxially within the sleeve110. The return spring140is interposed between the end portion110band the advancing support land132in the sleeve110at the side opposite from the solenoid120. The return spring140is compressively deformable to exert a restoring force for urging the spool130toward the solenoid120side in the axial direction. Furthermore, when the solenoid120is energized, the solenoid120exerts the electromagnetic drive force to urge the spool130toward the return spring140side in the axial direction. Therefore, in the spool valve100, the spool130is driven in response to the balance between the restoring force, which is exerted by the return spring140, and the electromagnetic drive force, which is exerted by the solenoid120.

As shown inFIGS. 1 and 3, according to the present embodiment, two check valves210,230are provided in two connection passages220,240, respectively, of the spool valve100.

Specifically, as shown inFIG. 3, one end portion221of the advancing connection passage220, which is formed in the spool130, opens to an outer peripheral surface of the spool130at a plurality of locations between the advancing change land134and the retarding change land136. Therefore, as shown inFIG. 3, when the advancing port112is communicated with the supply port116through the gap between the advancing change land134and the retarding change land136, the end portion221of the advancing connection passage220is communicated with the advancing port112through the gap between the advancing change land134and the retarding change land136.

The other end portion222of the advancing connection passage220opens to the outer peripheral surface of the spool130at a plurality of locations between the retarding change land136and the retarding support land138. Therefore, as shown inFIG. 3, when the retarding port114is communicated with the gap between the retarding change land136and the retarding support land138, the end portion222of the advancing connection passage220is communicated with the retarding port114through the gap between the retarding change land136and the retarding support land138.

The advancing check valve210is placed such that a direction from the one end portion221toward the other end portion222at the advancing connection passage220coincides with a valve closing direction of the advancing check valve210, and an opposite direction from the other end portion222toward the one end portion221at the advancing connection passage220coincides with a valve opening direction of the advancing check valve210. The advancing check valve210of the present embodiment includes an advancing valve seat212, an advancing valve member214, an advancing retainer215and a resilient member216.

The advancing valve seat212is configured into a generally conical surface, which has an inner diameter that is progressively reduced toward an end portion222side of an inner peripheral wall surface of the advancing connection passage220. The advancing valve member214is made of metal and is configured into a ball. The advancing valve member214is placed on an end portion221side of the advancing valve seat212in the advancing connection passage220and is axially seatable and liftable with respect to the advancing valve seat212. The advancing retainer215is made of metal and is configured into a cup shaped cylindrical body. The advancing retainer215is placed on a side of the advancing valve member214, which is opposite from the advancing valve seat212, in the advancing connection passage220. An outer peripheral surface of a peripheral wall215aof the advancing retainer215is axially reciprocally supported by an inner peripheral wall surface of the advancing connection passage220. Furthermore, an inner peripheral surface of the peripheral wall215aof the advancing retainer215holds the advancing valve member214. The resilient member216is a compression coil spring made of metal in the present embodiment. The resilient member216is placed on a side of the advancing retainer215, which is opposite from the advancing valve member214. The resilient member216is interposed between the retarding check valve230and the advancing retainer215, which are axially opposed to the advancing valve seat212. The resilient member216is compressively deformable to exert a restoring force to urge the advancing valve member214toward the advancing valve seat212side through the advancing retainer215. Specifically, the resilient member216serves as an advancing urging member of the advancing check valve210.

In the advancing check valve210, as shown inFIG. 6, when the advancing valve member214is moved in the valve opening direction toward the end portion221side and is thereby lifted away from the advancing valve seat212, the flow of the hydraulic oil in the valve opening direction is permitted. In contrast, in the advancing check valve210, as shown inFIG. 3, when the advancing valve member214is moved in the valve closing direction toward the end portion222side and is thereby seated against the advancing valve seat212, the flow of the hydraulic oil in the valve closing direction is limited.

As shown inFIG. 3, the retarding connection passage240is formed in the spool130to share the end portion221of the advancing connection passage220. Specifically the end portion221is the common end portion221, which is common to the advancing connection passage220and the retarding connection passage240. Therefore, as shown inFIG. 4, when the retarding port114is communicated with the supply port116through the gap between the advancing change land134and the retarding change land136, the common end portion221is communicated with the retarding port114through the gap between the advancing change land134and the retarding change land136.

The other end portion242of the retarding connection passage240opens to the outer peripheral surface of the spool130at a plurality of locations between the advancing support land132and the advancing change land134. Therefore, as shown inFIG. 4, when the advancing port112is communicated with the gap between the advancing support land132and the advancing change land134, the end portion242of the retarding connection passage240is communicated with the advancing port112through the gap between the advancing support land132and the advancing change land134.

The retarding check valve230is placed such that a direction from the common end portion221toward the other end portion242at the retarding connection passage240coincides with a valve closing direction of the retarding check valve230, and an opposite direction from the other end portion242toward the common end portion221at the retarding connection passage240coincides with a valve opening direction of the retarding check valve210. Here, similar to the advancing check valve210, the retarding check valve230of the present embodiment includes a retarding valve seat232, a retarding valve member234, a retarding retainer235and the resilient member216.

In the retarding check valve230, the retarding valve seat232is configured into a generally conical surface, which has an inner diameter that is progressively reduced toward an end portion242side of an inner peripheral wall surface of the retarding connection passage240. The retarding valve member234is provided on a common end portion221side of the retarding valve seat232in the retarding connection passage240and is axially seatable and liftable with respect to the retarding valve seat232. The retarding retainer235is provided on a side of the retarding valve member234, which is opposite from the retarding valve seat232in the retarding connection passage240. Furthermore, an inner peripheral surface of the peripheral wall235aof the retarding retainer235, which is supported by the inner peripheral wall surface of the retarding connection passage240, holds the retarding valve member234. The resilient member216, which is common to the advancing check valve210, is provided on a side of the retarding retainer235, which is opposite from the retarding valve member234, in the retarding connection passage240. The resilient member216is installed between the retarding valve member234and the advancing valve member214through the retainers235,215. Here, the retarding valve member234is placed on the forward side of the common end portion221in the valve closing direction of the retarding check valve230, and the advancing valve member214is placed on the forward side of the common end portion221in the valve closing direction of the advancing check valve210. The resilient member216is compressively deformable to exert the restoring force to urge the retarding valve member234toward the retarding valve seat232side through the retarding retainer235. That is, the resilient member216also functions as a retarding urging member of the retarding check valve230. With this construction, the structure is simplified, and the manufacturing costs are reduced.

In the retarding check valve230, as shown inFIG. 7when the retarding valve member234is moved in the valve opening direction toward the common end portion221side and is thereby lifted away from the retarding valve seat232, the flow of the hydraulic oil in the valve opening direction is permitted. In contrast, in the retarding check valve230, as shown inFIG. 4, when the retarding valve member234is moved in the valve closing direction toward the end portion242side and is thereby seated against the retarding valve seat232, the flow of the hydraulic oil in the valve closing direction is limited.

As shown inFIGS. 1 and 3, a supply check valve250is provided in the supply passage80, which communicates between the pump4and the supply port116. When the supply check valve250is opened in the manner shown inFIG. 5, the flow of the hydraulic oil from the pump4side toward the supply port116, i.e., toward the downstream side of the supply passage80is permitted. When the supply check valve250is closed in the manner shown inFIG. 3, the flow of the hydraulic oil from the supply port116side toward the pump4side, i.e., the backflow of the hydraulic oil from the downstream side of the supply passage80can be limited.

At the time of driving the internal combustion engine, during which the pump4is driven, the control circuit200computes an actual engine phase of the camshaft2relative to the crankshaft and a target engine phase thereof. Then, based on the result of the computation, the control circuit200controls the electric power supply to the solenoid120of the spool valve100. Thereby, the spool130of the spool valve100is moved to implement the corresponding supply of the hydraulic oil relative to the advancing chambers52-55and the retarding chambers56-59, which corresponds to the operational position of the spool130,50that the valve timing is adjusted. The valve timing adjusting operation of the valve timing control apparatus1of the present embodiment will now be described in detail.

Hereinafter, the operation for advancing the valve timing by advancing the engine phase of the camshaft2relative to the crankshaft will be described.

Upon satisfaction of a predetermined operational condition of the internal combustion engine, which indicates an off state of an accelerator of the vehicle or a state of a low to middle rotational speed and a high load of the internal combustion engine, the control circuit200controls the electric current supplied to the solenoid120to a value larger than a predetermined reference value Ib. Therefore, the spool130is moved to the advancing position shown inFIGS. 3 and 6to communicate the advancing port112to the supply port116. In this advancing position of the spool130, the advancing connection passage220communicates between the advancing port112, which is communicated with the common end portion221, and the retarding port114, which is communicated with the other end portion222.

Therefore, as shown inFIG. 6, when the negative torque is applied to the vane rotor14, the hydraulic oil, which is supplied from the pump4to the supply passage80, is supplied to the advancing chambers52-55through the supply port116and the advancing port112. At that time, the compressed hydraulic oil of the retarding chambers56-59, which is compressed by the vane rotor14that receives the negative torque, is supplied from the retarding port114to the advancing connection passage220. At this time, in the advancing check valve210, the advancing valve member214is moved toward the common end portion221side against the pressure of the hydraulic oil supplied to the supply port116and the restoring force of the resilient member216, so that the flow of the hydraulic oil from the retarding port114side to the advancing port112side is permitted. Therefore, when the amount of supply of the hydraulic oil from the pump4is reduced, the hydraulic oil can be supplemented from the retarding port114side. Therefore, it is possible to limit the shortage of the hydraulic oil at the advancing chambers52-55, the volume of which is increased by the action of the negative torque. The hydraulic oil, which is supplied from the pump4, flows into the retarding connection passage240, which is communicated with the advancing port112at the common end portion221. At this time, the flow of the hydraulic oil toward the end portion242side is limited by the retarding check valve230.

When the positive torque is applied to the vane rotor14to compress the advancing chambers52-55with the vane rotor14, the hydraulic oil tries to flow backward from the advancing port112toward the respective connection passages220,240and the supply passage80, as shown inFIG. 3. However, at this time, the flow of the hydraulic oil toward the retarding port114side in the advancing connection passage220is limited by the advancing check valve210, and the flow of the hydraulic oil toward the end portion242side in the retarding connection passage240is limited by the retarding check valve230. Furthermore, in the supply passage80, the flow of the hydraulic oil toward the pump4side is limited by the supply check valve250. Therefore, the outflow of the hydraulic oil from the advancing chambers52-55is limited while the erroneous supply of the hydraulic oil to the retarding chambers56-59is avoided.

When the above advancing operation is executed, the function of the respective check valves210,230is appropriately implemented to drain the hydraulic oil from the retarding chambers56-59, and at the same time, the sufficient amount of the hydraulic oil can be supplied to the advancing chambers52-55. Thereby, the high advancing response can be achieved.

Hereinafter, the operation for retarding the valve timing by retarding the engine phase of the camshaft2relative to the crankshaft will be described.

Upon satisfaction of an operational condition, which indicates a normal operational state of the internal combustion engine with the low load of the internal combustion engine, the control circuit200controls the electric current supplied to the solenoid120to a lower value that is lower than the reference value Ib. Therefore, the spool130is moved to the retarding position shown inFIGS. 4 and 7to communicate the retarding port114to the supply port116. In this retarding position of the spool130, the retarding connection passage240communicates between the retarding port114, which is communicated with the common end portion221, and the advancing port112, which is communicated with the other end portion242.

Therefore, as shown inFIG. 7, when the positive torque is applied to the vane rotor14, the hydraulic oil, which is supplied from the pump4to the supply passage80, is supplied to the retarding chambers56-59through the supply port116and the retarding port114. At that time, the compressed hydraulic oil of the advancing chambers52-55, which is compressed by the vane rotor14that receives the positive torque, is supplied from the advancing port112to the retarding connection passage240. At this time, in the retarding check valve230, the retarding valve member234is moved toward the common end portion221side against the pressure of the hydraulic oil supplied to the supply port116and the restoring force of the resilient member216, so that the flow of the hydraulic oil from the advancing port112side to the retarding port114side is permitted. Therefore, when the amount of supply of the hydraulic oil from the pump4is reduced, the hydraulic oil can be supplemented from the advancing port112side. Therefore, it is possible to limit the shortage of the hydraulic oil at the retarding chambers56-59, the volume of which is increased by the action of the positive torque. The hydraulic oil, which is supplied from the pump4, flows into the advancing connection passage220, which is communicated with the retarding port114at the common end portion221. At this time, the flow of the hydraulic oil toward the end portion222side is limited by the advancing check valve210.

When the negative torque is applied to the vane rotor14to compress the retarding chambers56-59with the vane rotor14, the hydraulic oil tries to flow backward from the retarding port114toward the respective connection passages220,240and the supply passage80, as shown inFIG. 4. However, at this time, the flow of the hydraulic oil toward the advancing port112side in the retarding connection passage240is limited by the retarding check valve230, and the flow of the hydraulic oil toward the end portion222side in the advancing connection passage220is limited by the advancing check valve210. Furthermore, in the supply passage80, the flow of the hydraulic oil toward the pump4side is limited by the supply check valve250. Therefore, the outflow of the hydraulic oil from the retarding chambers56-59is limited while the erroneous supply of the hydraulic oil to the advancing chambers52-55is avoided.

When the above retarding operation is executed, the function of the respective check valves230,210is appropriately implemented to drain the hydraulic oil from the advancing chambers52-55, and at the same time, the sufficient amount of the hydraulic oil can be supplied to the retarding chambers56-59. Thereby, the high retarding response can be achieved.

Hereinafter, the operation for substantially holding the valve timing by holding the engine phase within a predetermined target phase range will be described.

When a predetermined operational condition, which indicates a stable operational state of the internal combustion engine (e.g., the holding sate of the accelerator of the vehicle), the control circuit200controls the current supplied to the solenoid120to the reference value Ib. Therefore, the spool130is moved to a holding position shown inFIG. 5to block both of the advancing port112and the retarding port114relative to the supply port116. In this holding position of the spool130, the common end portion221of the advancing connection passage220and of the retarding connection passage240is communicated with the supply port116through the gap between the advancing change land134and the retarding change land136. However, the other end portion222of the advancing connection passage220and the other end portion242of the retarding connection passage240are blocked from both of the advancing port112and the retarding port114.

Therefore, the hydraulic oil, which is supplied from the pump4to the supply passage80, is not supplied to both of the advancing chambers52-55and the retarding chambers56-59, and also the outflow of the hydraulic oil from the advancing chambers52-55and the outflow of the hydraulic fluid from the retarding chambers56-59are limited. As a result, the change in the engine phase is limited, and thereby the valve timing is substantially maintained. The hydraulic oil, which is supplied from the pump4, flows from the supply port116into the common end portion221of the advancing connection passage220and of the retarding connection passage240. However, at this time, the flow of the hydraulic oil toward the other end portions222,242is both limited by the check valves210,230.

According to the present embodiment, the valve timing adjustment, which is suitable for the internal combustion engine, is rapidly and appropriately performed.

The present invention has been described with respect to the embodiment of the present invention. However, the present invention is not limited to the above embodiment, and the above embodiment may be modified in various ways within a spirit and scope of the present invention.

Specifically, in the drive device10, it is possible to provide a resilient member (e.g., an assist spring), which urges the camshaft2toward the opposite side that is opposite from the biased side of the average torque of the variable torque. Furthermore, in the drive device10, the housing12may be rotated synchronously with the camshaft2to rotate the vane rotor14synchronously with the crankshaft.

In the spool valve100of the control device30, as shown inFIG. 8, a retarding urging member236of the retarding check valve230may be provided separately from the resilient member216, which serves as the advancing urging member of the advancing check valve210. In such a case, the retarding urging member236may be constructed by the metal compression coil spring, which is interposed between the inner wall surface248of the retarding connection passage240and the retarding retainer235, to generate the restoring force toward the retarding valve seat232side. Furthermore, the resilient member216, which serves as the advancing urging member, is interposed between the inner wall surface228of the advancing connection passage220and the advancing retainer215to generate the restoring force toward the advancing valve seat212side. Furthermore, although not depicted in the drawings, the opposite end portion of the retarding connection passage240, which is opposite from the end portion242, may be separated from the opposite end portion of the advancing connection passage220, which is opposite from the end portion222.

Also, in the above embodiment, the spool valve100is constructed to drive the spool130by the solenoid120. Alternatively, the spool130of the spool valve may be driven by, for example, a piezoelectric actuator. Furthermore, the spool valve100may be modified such that the port114is communicated with the advancing chambers52-55through the advancing passage72, and the port112is communicated with the retarding chambers56-59through the retarding passage76. In such a case, the position shown inFIGS. 3 and 6becomes the retarding position for the retarding operation. Furthermore, the position shown inFIGS. 4 and 7becomes the advancing position for the advancing operation.

Furthermore, the present invention is also applicable to any other type of valve timing control apparatus, which controls valve timing of exhaust valves or which controls both of the valve timing of the intake valves and the valve timing of the exhaust valves.