JP2010209780A - Variable valve train for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable valve train certainly performing locking in an intermediate phase when an engine is stopped in a VTC (variable valve train) with an intermediate locking mechanism. <P>SOLUTION: This so-called vane type variable valve train includes: the locking mechanism 15 prohibiting the relative rotation of a vane member 4 and a sprocket 2 in the intermediate phase between a most advance angle phase and a most retard angle phase; circuits 20, 23 supplying hydraulic pressure for unlocking from an advance chamber 5 and a retard chamber 6 respectively; and a check valve 14 provided in the middle of the circuits 20 to 22 supplying the hydraulic pressure to the locking mechanism 15 from the retard chamber 6 in a direction with the vane member 4 pressed by a pressing means, and opened and closed according to the hydraulic pressure in the circuits. The valve opening pressure of the check valve 14 is so set that the check valve is not opened by the hydraulic pressure in the retard chamber 6 when the engine rotates at low speed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a variable valve mechanism for an internal combustion engine, and more particularly to a variable valve mechanism having a lock mechanism that is fixed at an intermediate phase between a most advanced angle phase and a most retarded angle phase.

  As a mechanism for improving engine output performance, exhaust performance, fuel consumption performance, etc., the valve shaft timing of the intake and exhaust valves can be changed by changing the rotational phase of the camshaft relative to the crankshaft according to the operating state A valve timing mechanism is known.

  For example, there is a so-called vane type variable valve timing mechanism that includes a vane fixed to rotate integrally with a camshaft and a housing fixed to a sprocket that rotates synchronously with a crankshaft, and rotates the housing and vane relative to each other by hydraulic pressure. Generally well known.

  Patent Document 1 discloses that the vane is in a state intermediate between the most advanced angle and the most retarded angle in order to improve the engine startability and expand the variable range of the valve timing to improve the output at the time of high rotation. The structure which provides the lock pin which controls the motion of this is disclosed. Specifically, in a state where no hydraulic pressure is applied, the lock pin is urged by a spring to engage with the lock pin recess, and the movement of the vane is restricted. On the other hand, when the hydraulic pressure exceeds the urging force of the spring, the lock pin is disengaged from the recess for the lock pin, and the vane can rotate relative to the housing. The state regulated by the lock pin is a valve timing suitable for starting the engine.

  According to this configuration, the variable range of the valve timing can be expanded, so that, for example, by changing the valve timing further to the retard side than the valve timing suitable for starting the engine at high engine speed while ensuring engine startability. , Volume efficiency can be improved.

Japanese Patent No. 3211713

  By the way, in the above configuration, it is necessary to apply a hydraulic pressure (release hydraulic pressure) that allows at least the lock pin to be removed from the recess for the lock pin during normal operation. This is to prevent the lock pin from engaging with the recess for the lock pin in the middle of changing the valve timing according to the operating state.

  In this regard, in Patent Document 1, both the advance chamber hydraulic pressure and the retard chamber hydraulic pressure can be used as the release hydraulic pressure.

  However, when the engine is stopped, when the vane rotates toward the initial position by a cam reaction force or a spring that biases the vane, the oil chamber on the vane traveling direction side (for example, when the initial position is the most retarded angle) In the advance chamber, the remaining hydraulic oil is pushed by the vanes to generate hydraulic pressure. As a result, the lock pin is released, and the vane may be rotated to the most advanced angle or most retarded angle state without being locked in the intermediate phase. In this case, at the next start, since the valve timing is not suitable for the start, startability is deteriorated.

  Therefore, an object of the present invention is to provide a variable valve timing mechanism in which a lock pin is surely locked when the engine is stopped and reliably released during normal operation.

  The variable valve mechanism for an internal combustion engine according to the present invention includes a sprocket that is driven to rotate by a crankshaft, a camshaft that is provided to be rotatable relative to the sprocket, and is fixed to one end of the camshaft and is rotatable within a housing of the sprocket. A vane member provided in the housing, an advance angle chamber and a retard angle chamber defined by the vane member inside the housing, and an urging force to urge the vane member to rotate in either the advance angle direction or the retard angle direction. And the phase of the crankshaft and the camshaft is changed by controlling the supply of hydraulic pressure to the advance chamber and the retard chamber. A lock mechanism that can be in a locked state that prohibits relative rotation of the vane member and the sprocket at an intermediate phase between the most advanced angle phase and the most retarded angle phase, and a hydraulic pressure for releasing the locked state. And a circuit for supplying hydraulic pressure to the lock mechanism from the oil chamber in the direction in which the vane member is urged by the urging means in the advance chamber or the retard chamber. And a check valve that opens and closes according to the hydraulic pressure in the circuit. Further, the check valve is not opened by the hydraulic pressure at the time of engine low rotation of the oil chamber of the advance chamber or the retard chamber in the direction in which the vane member is urged by the urging means. Is set.

  According to the present invention, when the engine is stopped, even if the oil pressure is generated in the oil chamber in the rotation direction by rotating the vane, the oil pressure can be prevented from acting on the lock mechanism. Therefore, when the engine is stopped, the lock mechanism can be reliably locked.

It is a block diagram of the variable valve timing system to which 1st Embodiment is applied. It is sectional drawing along the AA line of FIG. It is a block diagram of the lock pin and check valve periphery of 2nd Embodiment. It is a block diagram of the lock pin and check valve periphery of 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a variable valve timing system to which a first embodiment of the present invention is applied. 1 is a variable valve mechanism (VTC), 7 is an oil pump, 8 is an oil pan, 9 is a VTC conversion angle positioning controller, 10 is a solenoid valve, 14 is a check valve, and 15 is a lock pin.

  The VTC conversion angle positioning controller 9 measures the conversion angle of VTC 1 (described later) based on the detection values of the crank angle sensor 11 and the camshaft position sensor 12, and detects the detection value of the water temperature sensor 13, the accelerator opening of the driver, and the like. Accordingly, the target conversion angle is calculated, and a current command value corresponding to the target conversion angle is output to the solenoid valve 10 to control the conversion angle.

  The oil pump 7 pumps up the oil in the oil pan 8 and supplies it to the solenoid valve 10. The solenoid valve 10 adjusts the hydraulic pressure supplied to the VTC 1 based on the current command value from the VTC conversion angle positioning controller 9, Switch over.

  The VTC 1 includes a plurality of vanes 4 fixed to one end of a camshaft 3 of an engine so as to be integrally rotatable with the camshaft 3, and a camshaft attached coaxially to the camshaft 3 and rotatable in the circumferential direction with respect to the camshaft 3. And a drive sprocket 2.

  The camshaft drive sprocket 2 is provided with a hydraulic chamber inside the housing, and the hydraulic chamber is divided into an advance chamber 5 and a retard chamber 6 by a vane 4. Further, a timing chain (not shown) is wound around the camshaft driving sprocket 2 and rotates synchronously with a crankshaft (not shown) via this timing chain. Here, the rotation direction of the camshaft driving sprocket 2 is clockwise in the figure. When the camshaft driving sprocket 2 rotates, the camshaft 3 rotates with a relative phase angle (hereinafter referred to as a conversion angle) with respect to the camshaft driving sprocket 2.

  In the configuration as described above, the conversion angle of the advance side or the retard side is controlled depending on whether the hydraulic pressure is supplied to the advance chamber 5 or the retard chamber 6, and the supplied hydraulic pressure is controlled. The size of the conversion angle is controlled by the size. For example, when hydraulic pressure is supplied to the retarding chamber 6, the vane 4 rotates relative to the camshaft driving sprocket 2 counterclockwise, so that the valve opening / closing timing is retarded relatively.

  On the contrary, when the hydraulic pressure is supplied to the advance chamber 5, the vane 4 rotates relative to the camshaft drive sprocket 2 in the clockwise direction, so that the valve opening / closing timing is advanced relatively. The amount of advance or retard, that is, the magnitude of the conversion angle is controlled by adjusting the amount of hydraulic pressure supplied to the advance chamber 5 or the retard chamber 6. For example, the advance amount or retard amount increases as the supplied hydraulic pressure increases, and the advance amount or retard amount decreases as the supplied hydraulic pressure decreases.

  Further, the VTC of the present embodiment includes a spring (not shown) that urges the vane 4 in the advance direction. For this reason, when the engine stops and the hydraulic pressure in the advance chamber 5 and the retard chamber 6 decreases, the vane 4 rotates in the advance direction, and the most advanced angle is obtained unless the vane 4 is locked in an intermediate phase by a lock pin 15 described later. It becomes a state.

  Such a VTC that is in the most advanced state in the initial state and can rotate only in the retard direction is referred to as “retard angle VTC”.

  On the other hand, a VTC that can rotate only in the advance angle direction in the initial state with the most retarded angle is referred to as an advance angle VTC.

  Next, the lock pin 15 and the check valve 14 will be described with reference to FIG.

  FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 and shows a state in which the position of the lock pin 15 overlaps the lock pin recess 16. 30 is a front plate of the VTC 1 and 31 is a rear plate. A rear plate 31 is located on the engine side in the axial direction of the camshaft 3. In the vehicle mounted state, a front cover that covers the entire VTC 1 is attached to the engine front portion.

  The vane 4 has a first cylinder 32 in which the lock pin 15 is slidably accommodated, a second cylinder 33 in which the check valve 14 is slidably accommodated, and an oil passage 20 that communicates the second cylinder 33 and the retard chamber 6. And an oil passage 22 that communicates the two cylinders, an oil passage 23 that communicates the first cylinder 32 and the advance chamber 5, and an oil passage 21 that communicates the second cylinder 33 and the oil passage 22.

  The cylinder axes of the first cylinder 32 and the second cylinder 33 coincide with the longitudinal axis of the cam shaft 3. The oil passage 20 and the oil passage 23 are formed between the rear plate 31 and the vane 4.

  The lock pin 15 has a so-called stepped shape in which the outer diameter is narrowed over a predetermined range from the end on the rear plate 31 side. And it is urged | biased by the spring 18 toward the rear plate 31 direction from the front plate 30 side. Therefore, if there is no hydraulic action described later, the rear end portion 15a of the lock pin 15 is housed in the lock pin recess 16, and the vane 4 cannot rotate relative to the sprocket 2 (hereinafter referred to as a locked state).

  The lock pin recess 16 is provided at a position between the most advanced angle state and the most retarded angle state at a valve timing suitable for engine start.

  On the other hand, the check valve 14 has a stepped shape with a small outer diameter over a predetermined range from the front end on both the front plate 30 side and the rear plate 31 side. Like the lock pin 15, the spring 19 is biased toward the rear plate 31.

  The distance between the bottom surface of the oil passage 22 on the rear plate 31 side, the tip portion 14a of the check valve 14 and the stepped portion of the body portion 14c is a. The distance between the stepped portion 34 formed by the second cylinder 33 and the oil passage 21, the rear end portion 14b of the check valve 14 and the stepped portion of the body portion 14c is b. At this time, the dimensions of the check valve 14 and the oil passage 22 are set so that a is larger than b.

  A relief passage 17 that penetrates the front plate 30 and the vane 4 is provided on the end surface of the second cylinder 33 on the front plate 30 side.

  Next, lock / release of the lock pin 15 in the above configuration will be described.

  When the hydraulic pressure of the advance chamber 5 is increased, the lock pin 15 is pushed up against the urging force of the spring 18 by the hydraulic pressure of the hydraulic oil flowing into the oil passage 23, and the locked state is released.

  On the other hand, when the hydraulic pressure of the retard chamber 6 is increased, the check valve 14 is pushed up against the urging force of the spring 19 by the hydraulic pressure of the hydraulic oil flowing into the oil passage 20. When the check valve 14 is pushed up by the distance a, the oil passage 20, the oil passage 21, and the oil passage 22 communicate with each other, so that the oil pressure in the oil passage 22 increases and the lock pin 15 is pushed up.

  Since the distance a is larger than the distance b as described above, the communication between the oil passage 21 and the second cylinder 33 is blocked by the body portion 14c of the check valve 14 when the oil passage 20 and the oil passage 21 communicate with each other. . Therefore, the hydraulic pressure of the hydraulic oil flowing in from the retard chamber 6 is used for unlocking the lock pin 15 without being released in the relief passage 17.

  In this way, the lock pin 15 can be released with any hydraulic pressure in the advance chamber 5 or the retard chamber 6. Therefore, during operation in which the hydraulic pressure of either the advance chamber 5 or the retard chamber 6 is increasing, the lock pin 15 is released, and the lock pin 15 is locked even if it passes through the lock pin recess 16 when the valve timing is changed. There is no state.

  The spring constant of the spring 19 is set to a value that can shut off the hydraulic pressure in the retard chamber 6 when the engine is running at a low speed.

  Further, in order to prevent the locked state during operation more reliably, the valve timing may not be set so that the lock pin 15 and the lock pin recess 16 overlap each other during normal operation. .

  Next, the behavior of the lock pin 15 when the engine is stopped will be described.

  When stopping the engine, the engine is stopped in a state in which the engine is on the retard side with respect to the recess 16 for the lock pin. Then, the hydraulic pressure in the advance chamber 5 and the retard chamber 6 decreases, and the vane 4 rotates in the advance direction (the retard chamber 6 direction in FIG. 2). At this time, if the hydraulic pressure applied to the lock pin 15 is lower than the urging force of the spring 18, the lock state is reached when the lock pin recess 16 is reached. However, if the lock pin 15 reaches the lock pin recess 16 before the hydraulic pressure decreases, the lock pin 15 does not enter the locked state and passes through the lock pin recess 16.

  In this embodiment, since the advance chamber 5 becomes negative pressure by rotating the vane 4 in the direction of the retard chamber 6, the hydraulic pressure of the advance chamber 5 quickly decreases.

  On the other hand, when the operating oil remains in the retarding chamber 6, the vane 4 rotates in the retarding chamber 6 direction, whereby hydraulic pressure is generated in the retarding chamber 6.

  However, since the check valve 14 is urged toward the rear plate 31 by the spring 19, the hydraulic pressure generated in the retard chamber 6 is shut off. Further, when the check valve 14 moves to the rear plate 31 side so as to cut off the hydraulic pressure from the retard chamber 6, the oil passage 21 and the cylinder 33 communicate with each other. Therefore, the hydraulic oil remaining in the oil passage 21 and the oil passage 22 is discharged from the relief passage 17. Therefore, the lock pin 15 is not locked by the hydraulic pressure generated in the retard chamber 6.

  That is, the vane 4 is reliably locked in the intermediate phase when the engine is stopped.

  The retardation VTC1 having the above-described configuration is used as an exhaust side, that is, an exhaust valve driving device. In the locked state, the position of the lock pin recess 16 is set so that the valve timing is suitable for starting the engine.

  The valve timing at the start is set, for example, for the purpose of reducing the HC emission amount at the cold start. Then, in a scene where output is required as in acceleration, the angle is advanced from this. On the other hand, at the time of middle / high rotation and partial load operation, the valve timing is retarded from that at the start in order to increase the internal EGR and improve the fuel efficiency.

  That is, immediately after the engine is started, there is no scene where the valve timing of the exhaust valve is retarded, and when the valve timing is changed, the valve timing is advanced. Therefore, as shown in FIG. 2, even when the hydraulic pressure from the retarded angle chamber 6 is cut off at the start and in the low rotation range, the hydraulic pressure in the advanced angle chamber 5 acts on the lock pin 15 and locks. Can be released and the valve timing can be advanced, so that engine performance is not deteriorated due to a delay in changing the valve timing.

  As described above, in the present embodiment, the following effects can be obtained.

  (1) In the vane-type VTC 1, a lock pin 15 that prohibits relative rotation of the vane 4 and the sprocket 2 in an intermediate phase, oil passages 20 to 23 that supply hydraulic pressure for releasing the locked state, and the vane 4 is a spring And a check valve 14 provided in the middle of oil passages 20 to 22 for supplying hydraulic pressure to the lock pin 15 from the retard chamber 6 in the direction urged by the valve, and the valve opening pressure of the check valve 14 is retarded. The hydraulic pressure at the time of engine low rotation of the chamber 6 is set so as not to open. For this reason, when the engine is stopped, even if hydraulic pressure is generated in the retarded angle chamber 6 by rotating the vane 4 in the advanced angle direction before the hydraulic oil in the retarded angle chamber 6 is completely drained, the hydraulic pressure is not locked. 15 can be prevented. Therefore, it is possible to prevent the vane 4 from rotating to the most advanced angle phase while the locked state is released when the engine is stopped.

  (2) When the lock pin 15 changes from the unlocked state to the locked state and the check valve 14 changes from the open state to the closed state, the oil pressure in the oil passages 21 and 22 provided in the vane 4 is relieved. Since the relief passage 17 is provided, the lockable state can be quickly achieved when the engine is stopped.

  (3) The relief passage 17 is configured such that when the check valve 14 is closed, the oil passage 21 communicates with the outside of the sprocket 2 and when the check valve 14 is opened, this communication is blocked. Therefore, the hydraulic pressure in the retard chamber 6 is not directly relieved into the atmosphere.

  (4) Since the engine is not operated in the intermediate phase where the lock pin 15 and the lock pin recess 16 overlap after the engine is started, the lock pin 15 may be accidentally The locked state can be prevented.

  In this embodiment, the retard angle VTC has been described, but the same applies to the advance angle VTC. However, the positions of the advance chamber 5 and the retard chamber 6 in FIG. 2 are reversed. In other words, since the hydraulic pressure is generated when the engine is stopped, the advance chamber 5 is provided, so the check valve 14 is provided so as to shut off the hydraulic pressure from the advance chamber 5.

  Further, although the exhaust side VTC 1 has been described, the present invention can also be applied to the case where it is provided on the intake side. In this case, the advance angle VTC is desirable. During acceleration or the like, the intake valve closing timing is delayed to increase charging efficiency, and during mid-high rotation / partial load operation, the intake valve opening timing is advanced to extend the overlap period. Therefore, the advance angle is not made immediately after starting, and the hydraulic pressure from the advance chamber 5 may be cut off.

  A second embodiment will be described.

  FIG. 3 is a configuration diagram around the lock pin 15 and the check valve 14 of the VTC 1 of the present embodiment. The difference from FIG. 2 is the configuration of the check valve 14 and the surrounding oil passage.

  The body portion of the check valve 14 is provided with a small-diameter portion with a reduced outer diameter. An oil passage 42 is formed by the small diameter portion and the wall surface of the cylinder 33 facing the small diameter portion.

  An oil passage 40 and an oil passage 41 are provided in the vane 4 so as to open to positions facing the oil passage 42 in a state where the check valve 14 is in contact with the rear plate 31.

  The oil passage 40 has an opening at a position facing the oil passage 42, and then joins between the cylinder 33 side opening and the cylinder 32 side opening of the oil passage 22. The oil passage 41 penetrates the inside of the vane 4 and communicates the oil passage 42 with the outside of the VTC 1.

  When the check valve 14 rises due to the hydraulic pressure from the retard chamber 6 and the oil passage 22 and the cylinder 33 communicate with each other, the opening on the cylinder 33 side of the oil passage 40 and the oil passage 41 is blocked by the body portion 14c of the check valve 14. The That is, as in the configuration of FIG. 2, the hydraulic pressure from the retard chamber 6 is not directly relieved. Further, when the engine is stopped, the hydraulic oil in the oil passage 22 is released from the oil passage 40 to the outside through the oil passage 42 and the oil passage 41 when the check valve 14 comes into contact with the rear plate 31.

  Thus, even with the configuration shown in FIG. 3, the same effects as those of the first embodiment can be obtained.

  In addition, since the cylinder 33 communicates with the outside by providing the relief passage 17, it is possible to prevent the movement of the check valve 14 from being hindered by pressure fluctuations in the cylinder 33.

  A third embodiment will be described.

  FIG. 4 is a configuration diagram around the lock pin 15 and the check valve 14 of the VTC 1 of the present embodiment. In this embodiment, the check valve 14 and the lock pin 15 are arranged coaxially.

  The vane 4 is provided with a cylinder 57 extending in the camshaft direction in which the check valve 14 and the lock pin 15 are slidably accommodated.

  The cylinder 57 accommodates the lock pin 15 on the rear plate 31 side and the check valve 14 on the front plate 30 side.

  The lock pin 15 is urged toward the rear plate 31 by a spring 18. The spring 18 is fixedly supported at one end by the lock pin 15 and at the other end by a support member 56 fixed between the lock pin 15 in the cylinder 57 and the check valve 14.

  The check valve 14 is urged toward the rear plate 31 by a spring 19. One end of the spring 19 is fixedly supported on the check valve 14, and the other end is fixedly supported on the inner wall surface of the cylinder 57.

  The vane 4 is provided with an oil passage 50 communicating with the retard chamber 6 and the cylinder 57 so that the opening on the cylinder 57 side is between the support member 56 and the check valve 14. Furthermore, an oil passage 54 extending in the camshaft direction, an oil passage 52, an oil passage 53, and an oil passage 55 communicating with the cylinder 57 and the oil passage 54 are provided.

  The oil passage 52 and the oil passage 53 are both provided such that the opening on the cylinder 57 side is opened and closed by the check valve 14. Specifically, the oil passage 52 is provided at a position where the cylinder 57 side opens when the check valve 14 comes into contact with the support member 56. The oil passage 53 is provided at a position where the cylinder 57 side opens when the check valve 14 moves to the front plate 30 side by the hydraulic pressure from the retard chamber 6.

  The oil passage 55 is provided so that the opening on the cylinder 57 side is near the position where the stepped portion of the lock pin 15 is seated.

  With this configuration, when the hydraulic pressure in the retard chamber 6 increases, the hydraulic oil that has flowed into the cylinder 57 from the oil passage 50 pushes up the check valve 14, and the oil passage 53 opens. Then, the hydraulic oil that has flowed into the oil passage 54 from the oil passage 53 pushes up the lock pin 15 through the oil passage 55.

  On the other hand, when the hydraulic pressure in the advance chamber 5 increases, the hydraulic oil that has passed through the oil passage 51 pushes up the lock pin 15.

  Further, when the engine is stopped, when the hydraulic pressure is reduced and the check valve 14 is seated on the support member 56, the oil passage 52 is opened, so that the hydraulic oil remaining in the oil passage 54 is quickly transferred from the vane 4. To be discharged. For this reason, the lock pin 15 can be quickly locked, and reliably engages with the lock pin recess 16.

  Here, the formation method of the oil path 52-the oil path 55 is demonstrated.

  The oil passage 54 is formed by drilling from the front plate 30 side of the vane 4, and the plug 60 closes the vicinity of the front plate 30 side end portion.

  The oil passage 52, the oil passage 53, and the oil passage 55 are drilled from the advance chamber 5 side toward the cylinder 57, and then the portion closer to the advance chamber 5 than the oil passage 54 is closed with a plug 60.

  As described above, the same effects as those of the first and second embodiments can be obtained with the configuration of FIG. Furthermore, by arranging the check valve 14 and the lock pin 15 coaxially, it is possible to make a compact configuration in the radial direction of the vane 4.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

1 Variable valve mechanism (VTC)
2 sprocket 3 cam shaft 4 vane 5 advance chamber 6 retard chamber 7 oil pump 8 oil pan 9 VTC conversion angle positioning controller 10 solenoid valve 11 crank angle sensor 12 camshaft position sensor 13 water temperature sensor 14 check valve 15 lock pin 17 relief Passage 30 Front plate 31 Rear plate

Claims (4)

A sprocket that is rotationally driven by a crankshaft of an internal combustion engine;
A camshaft provided to be rotatable relative to the sprocket;
A vane member fixed to one end of the camshaft and rotatably provided in the sprocket housing;
An advance chamber and a retard chamber partitioned by the vane member inside the housing;
Urging means for urging the vane member to rotate in either the advance angle direction or the retard angle direction;
With
In a variable valve mechanism for an internal combustion engine that changes the phase of the crankshaft and the camshaft by controlling the supply of hydraulic pressure to the advance chamber and the retard chamber,
A locking mechanism that can be in a locked state that prohibits relative rotation of the vane member and the sprocket at an intermediate phase between a most advanced angle phase and a most retarded angle phase;
A circuit for supplying hydraulic pressure for releasing the locked state from each of the advance chamber and the retard chamber;
Of the advance chamber or the retard chamber, the vane member is provided in the middle of a circuit for supplying hydraulic pressure to the lock mechanism from an oil chamber in a direction in which the vane member is biased by the biasing means. A check valve that opens and closes according to the hydraulic pressure;
Have
The valve opening pressure of the check valve is opened at the oil pressure at the time of engine low rotation of the oil chamber in the direction in which the vane member is urged by the urging means in the advance chamber or the retard chamber. A variable valve mechanism for an internal combustion engine, characterized in that it is set so as not to occur.   Provided between the check valve and the lock mechanism inside the vane when the lock mechanism changes from the unlocked state to the locked state and the check valve changes from the open state to the closed state. The variable valve mechanism for an internal combustion engine according to claim 1, further comprising a relief mechanism for relieving hydraulic pressure in the circuit.   The relief mechanism is configured such that when the check valve is closed, a circuit provided between the check valve and the lock mechanism communicates with the outside of the housing, and when the check valve is opened, the check valve The variable valve mechanism for an internal combustion engine according to claim 2, wherein communication between a circuit provided between the valve and the lock mechanism and the outside is cut off.   A phase setting means for setting a phase of the crankshaft and the camshaft according to an engine operating state is provided, and the phase setting means does not set an intermediate phase that becomes the locked state after the engine is started. Item 5. The variable valve mechanism for an internal combustion engine according to any one of Items 1 to 3.

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