JPH02305305A - Lavel timing controller for engine - Google Patents

Abstract

PURPOSE:To constantly maintain effective lubrication by bypassing a hydraulic selector valve and forcing the small quantity of leakage hydraulic pressure to act on a bubble timing variable mechanism, in a system in which the hydraulic selector valve is operated so as to force hydraulic pressure to act on the bubble timing variable mechanism. CONSTITUTION:A hydraulic selector valve G is provided in an oil supply passage F for guiding engine lubricating oil to a valve timing variable mechanism A mounted on the cam shaft C of an engine E through a cam shaft bearing part B. During the specific operation of the engine E, the valve timing variable mechanism A is change over by hydraulic pressure through the operation of the hydraulic selector valve G, thereby valve timing being changed by a valve timing changing means D. In this device, a leakage passage H for bypassing the hydraulic selector valve G and guiding a small quantity of hydraulic pressure to the valve timing variable mechanism A is provided. The lubrication of the cam shaft bearing part B is maintained by leakage hydraulic pressure during non-specific operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine valve timing control device that changes valve timing by supplying hydraulic pressure to a variable valve timing mechanism mounted on a camshaft of the engine. It is something.

(Prior Art) Conventionally, a hydraulically driven variable valve timing mechanism is mounted on the camshaft of an engine, and a passage is formed in the variable valve timing mechanism to introduce engine lubricating oil through the camshaft bearing. A technique for changing the valve timing by applying hydraulic pressure to the variable valve timing mechanism using a valve timing changing means during a specific operation is disclosed in, for example, Japanese Patent Laid-Open No. 62-1911.
This is known as seen in Japanese Patent No. 336.

(Problem to be solved by the invention) However, in the valve timing control device as described above,
If the operating state continues for a long time in which no hydraulic pressure is applied to the variable valve timing mechanism, poor lubrication of the bearing portion of the camshaft may occur, which may pose a problem in terms of engine durability.

That is, a portion of engine lubricating oil is supplied from the engine body side to the variable valve timing mechanism mounted on the camshaft through the bearing section of the camshaft, and the variable valve timing mechanism is operated. The bearing portion of the camshaft is lubricated by a portion of the oil that supplies hydraulic pressure to the variable valve timing mechanism. For example, if the valve timing variable mechanism is configured to change the valve timing so as to increase the overlap between intake and exhaust by introducing hydraulic pressure to the variable valve timing mechanism under high load or high rotation conditions, it is possible to change the valve timing at low load and low rotation to reduce the overlap. If the operating state continues for a long time, no oil pressure will be applied to the variable valve timing mechanism during that time, and oil supply to the bearing portion of the camshaft will stop, potentially resulting in insufficient lubrication.

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides an engine valve timing control device that eliminates the lack of lubrication of the camshaft bearing even if the operating state continues for a long time in which no hydraulic pressure is applied to the variable valve timing mechanism. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the valve timing control device of the present invention has the basic configuration shown in FIG.
A hydraulic switching valve G is interposed in an oil supply passage F that introduces engine lubricating oil through a camshaft bearing B to a variable valve timing mechanism A mounted on a camshaft C of A valve timing changing means is provided which changes the valve timing by switching the hydraulic pressure to the variable valve timing mechanism A upon operation, and a small amount of hydraulic pressure is used to vary the valve timing by bypassing the hydraulic pressure switching valve G of the valve timing changing mechanism. It is constructed by providing a drainage passage H that is introduced into the mechanism A.

(Function) In the valve timing control device as described above, the valve timing is changed by introducing hydraulic pressure to the variable valve timing mechanism by the valve timing changing means during specific operations such as high load or high rotation conditions. Lubricating oil is supplied to the camshaft bearing by supplying hydraulic pressure to ensure lubrication. In addition, in a non-specific operating state other than the above-mentioned specific operating state, a small amount of oil pressure is introduced into the variable valve timing mechanism by the leak passage formed by bypassing the hydraulic switching valve installed in the oil supply passage, and this non-specific operating state Even if this continues, lubricating oil is supplied to the camshaft bearing to ensure lubrication.

(Example) The present invention will be described in detail below with reference to the drawings.

Embodiment 1 FIG. 2 shows a schematic configuration of an engine equipped with a valve timing control device according to an embodiment.

In the cylinder 1a of the engine 1, an intake port 5 opened and closed by an intake valve 4 and an exhaust port 7 opened and closed by an exhaust valve 6 are opened in a combustion chamber 3 formed above the piston 2. 8 is connected to the exhaust port 7, and an exhaust passage 9 is connected to the exhaust port 7.

An overhead intake side camshaft 11 for driving the opening and closing of the intake valve 4 of each cylinder 1a is provided, and
An overhead exhaust side camshaft 12 is provided to open and close the exhaust valve 6 of each cylinder 1a. Both camshafts 11, 12 are rotationally driven via a timing belt 14 by a synchronous drive mechanism 13 installed at each end in synchronization with the rotation of an engine output shaft 15.

On the other hand, an air cleaner 18, an intake air amount sensor 19, and a throttle valve 20 are interposed in the intake passage 8 communicating with the intake port 5 from the upstream side, and a mechanical supercharger 21 is disposed downstream of the throttle valve 20. ing. Furthermore, the intake passage 8 on the downstream side of the supercharger 21 is formed into an independent intake passage 8a whose downstream side of the surge tank 22 is connected to each cylinder 1a, and an injector 23 that injects fuel into the independent intake passage 8a. is installed.

Further, a supercharging bypass passage 24 is connected to bypass the supercharger 21, and a supercharging bypass valve 25 is interposed in this supercharging bypass passage 24.

The supercharging bypass valve 25 is opened in response to the intake pressure downstream of the throttle valve 20, and simultaneously supplies intake air through the supercharging bypass passage 24 in a state where supercharging by the supercharger 21 is insufficient. When the pressure becomes high, it opens and relieves the supercharging air, regulating the upper limit of the supercharging pressure and reducing the driving load.

Furthermore, an exhaust side camshaft 12 for the exhaust valve 6
A variable valve timing mechanism 27 is installed to change the opening/closing timing of the valve timing and the overlap period with the intake valve 4. The details of this variable knob timing mechanism 27 will be described later with reference to FIG. 4, but it is hydraulically operated.
Engine lubricating oil from an oil pump (not shown) of the engine is supplied through an oil supply passage 28, and a hydraulic pressure switching valve 29 is interposed in the middle of the oil supply passage 28 to supply hydraulic pressure and return release. can be switched.

Additionally, a leakage passage 26 is provided that bypasses the hydraulic switching valve 29 and connects the oil supply passage 28 on the upstream side and the downstream side of the hydraulic switching valve 29, and supplies a small amount of hydraulic pressure to the variable valve timing mechanism 27 side. A throttle 26a is interposed in the drainage passage 26 as necessary, and a drainage opening/closing valve 30 for opening and closing the drainage passage 26 is provided.

As shown in FIG. 3, a specific structural example of the hydraulic switching valve 29 (three-way solenoid valve) includes a spool valve 32 inserted into a cylinder 31, a return spring 33 compressed at one end, and a drive spring 33 at the other end. Rod 34a of solenoid 34
When the spool valve 32 moves, the C port that communicates with the oil supply passage 28 for the variable valve timing mechanism 27 is communicated with the return B port that opens into the cylinder head or with the oil pump for engine lubrication. It is configured to switch communication to the C port. Note that the C port is opened to the return side to allow movement of the spool valve 32. The solid line indicates the OFF state, and the chain line indicates the ON state. In the OFF state, the C port and the B port communicate, and oil is not supplied to the variable valve timing mechanism 27. On the other hand, in the ON state, the spool valve 32
As a result of this movement, the C port and the C port are brought into communication, and oil from the oil pump is supplied to the variable valve timing mechanism 27, thereby introducing a predetermined hydraulic pressure.

Then, a drive signal is output from the engine controller 36 to the drive solenoid 34 of the hydraulic switching valve 29 according to the operating state, and an on signal is output during a specific operation (high load, high rotation region) to control the valve timing variable mechanism. 27 to extend the valve overlap period. Further, a drive signal is outputted to the drain opening/closing valve 30 from the engine controller 36 according to the operating state, and while it is normally operated in the open state, the hydraulic switching valve 29 is switched from the on state to the off state. When the hydraulic switching valve 29 is operated, it is operated in a closed state for a predetermined period of time to ensure lubricity in non-specific operating conditions and to improve the operational response of the hydraulic switching valve 29.

Further, the engine controller 36 outputs a fuel injection signal for adjusting the amount of fuel supplied to the injector 23 of the intake passage 8, and also outputs an ignition signal for adjusting the ignition timing to the spark plug 37 of the cylinder 1a. The engine controller 36 receives an intake air amount signal from the intake air amount sensor 19 in order to detect the operating state, a signal from the throttle sensor 38 that detects the throttle opening,
Signals and the like from a rotation sensor 40 that detects engine rotation are respectively input.

The detailed structure of the variable valve timing mechanism 27 is as shown in the fourth
As shown in the figure, a cylindrical spacer 53 is fixed to the end of the exhaust side camshaft 12, and a drive pulley 54 is attached to the outside of this spacer 53. This pulley 54
is in sliding contact with the outer periphery of the tip of the spacer 53 at the tip of the boss portion 55, and the cylindrical connecting member 5 rotatably attached to the exhaust side camshaft 12 is attached to the base end side of the boss portion 55.
It is fixed at 6. A first gear 57 is spline-coupled to the other end of the connecting member 56 and the lock nut 5
It is fixed by 8. A second gear 59 fixed to the tip of the intake side camshaft 11 is meshed with the first gear 57 .

The spacer 53 is provided inside the boss portion 55 of the pulley 54.
An annular piston 60 is installed between the two. The piston 60 has a structure in which it is divided into two parts in the axial direction, and both parts are fixed to each other by a plurality of pins 61 arranged at equal intervals in the circumferential direction. Helical splines 62 and 63 in opposite directions are formed on the inside and outside of the piston 60. A helical spline 64 is formed on the outside of the spacer 53 with respect to the spline 62 of the inner extension 1 of the piston 60, and a helical spline 65 is formed on the outer periphery of the boss portion 55 of the pulley 54 with respect to the spline 63 on the outside of the piston 60. It is formed. piston 6
0 is biased toward the distal end side by a spring 66 installed between the connecting member 56 and the end surface thereof.

An oil passage 67 is formed in the exhaust side camshaft 12 along its axis. One end of this oil passage 67 is a passage 67a formed in the radial direction of the camshaft 12 at a portion of the bearing portion 72 that supports the camshaft 12.
An annular groove 72a is formed on the inner periphery of the bearing portion 72 in alignment with the opening of the shaft outer peripheral surface of the passage 67a, and the oil supply passage 28 from the oil pump via the hydraulic switching valve 29 connects the bearing portion 72. It passes through and communicates with the annular groove 72a.

On the other hand, the cylindrical spacer 53 is fixed to the exhaust side camshaft 12 with a fixing bolt 69 via a stopper member 68. The fixing bolt 69 is provided with an axial through hole 70 that communicates with the oil passage 67. Furthermore, a pressure chamber 71 is provided at the tip of the boss portion 55 of the pulley 54, facing the head of the piston 60, for introducing the hydraulic pressure from the oil passage 67. Hydraulic pressure is introduced into these pressure chambers 71 through the oil passage 67, and the spring 66
When the piston 60 moves in the axial direction by compressing the Rotate to . This changes the phase of the exhaust side camshaft 12 and the pulley 54, which are integrated with the spacer 53, that is, the valve timing.

The introduction control of the oil pressure is performed by an engine controller 36 that outputs a drive signal to the oil pressure switching valve 29, but this controller 36 controls the engine load (e.g. throttle opening) and engine speed. Based on this, the operating range of the variable valve timing mechanism 27 (see Fig. 5) corresponding to the current operating state is determined and the communication state of the hydraulic pressure switching valve 29 is switched. This is done in conjunction with the operation of the

The control characteristics of the operating range of the variable valve timing mechanism 27 are set according to the engine load Q a /as shown in FIG.
The high-speed, high-load region ■ (specific operating region) where the relationship between N and the engine speed N is outside the setting line Lo is the region where hydraulic pressure is introduced into the variable valve timing mechanism 27, and when this hydraulic pressure is introduced, as shown in FIG. As shown by the solid line in the valve timing, the opening/closing timing of the exhaust valve 6 is delayed to increase the overlap period OLI during which both the exhaust valve 6 and the intake valve 4 are open. In addition, low load low rotation region I (non-specific operation region) inside the above setting line Lo
is the region where the introduction of hydraulic pressure to the variable valve timing mechanism 27 is stopped, and when the introduction of hydraulic pressure is stopped, the opening/closing timing of the exhaust valve 6 is advanced and the timing of opening and closing of the exhaust valve 6 is advanced as shown by the broken line in the valve timing of FIG. This is to reduce the overlap period OL2 in which both are open at the same time.

The specific operating region I of the above-mentioned small overlap is the supercharger 2
1 corresponds to a non-supercharging region in which it is not driven, while a non-specific operation region (2) with large overlap corresponds to a region in which the supercharger 21 is driven to perform supercharging. The above-mentioned overlap period OLI is large in the region where the supercharger 21 is driven and supercharging is performed, and this is due to the fact that the overlap period OLI is large in the region where the supercharger 21 is driven and supercharging is performed.
Reducing the amount of residual exhaust gas remaining in the exhaust valve 6 lowers the temperature inside the cylinder and is advantageous in knocking resistance.
The overlap period between the intake valve 4 and the intake valve 4 is set to be long, and during this period, the exhaust gas is pushed out of the cylinder 1a by pressurized air by the supercharger 21 to obtain a scavenging effect. In addition, the overlap period OL in the low load and low rotation region I
The reason for shortening 2 is that when moving to a low load and low speed range with the valve overlap set long as described above, the boost pressure will decrease as the engine speed decreases, and the exhaust pressure will be higher. This is to shorten the overlap period and improve combustion stability, whereas the exhaust gas would blow back into the intake passage 8, increasing the amount of exhaust gas brought in in the low rotation range and reducing combustibility. .

The processing of the engine controller 36 will be explained based on the flowchart of FIG. The routine in Figure 7 is
The operation control of the hydraulic pressure switching valve 29 and the leakage on/off valve 30 corresponding to the determination of the operating region will be described.

After the control starts, a valve timing determination flag F is initialized in step S1, and a timer T, which will be described later, is reset in step S2. Then, in step S3, various data such as the intake air amount Q a % and the engine speed N are read, and in step S4, based on the characteristics of the map (Fig. 5), it is determined whether the operating state is in a specific operating region of high load and high rotation. Determine whether or not.

If this determination is YES and the specific operating region ■ (large overlap region) is detected, the process proceeds to step S5 and the hydraulic switching valve 2
9 outputs an on signal to the solenoid 34, introduces hydraulic pressure to the variable valve timing mechanism 27, delays the valve timing of the exhaust valve 6 to increase the overlap, and resets the flag F to 0 in step S6, In step 813, the on-off valve 30 is opened.

On the other hand, if the determination in step S4 is NO and the operation is in the low-load, low-speed non-specific operation region I (small overlap region), the drive signal to the solenoid 34 of the hydraulic pressure switching valve 29 is turned off in step S7. The supply of hydraulic pressure to the variable timing mechanism 27 is stopped, and the valve timing of the exhaust valve 6 is advanced to reduce the overlap. Then, in step S8, it is determined whether the flag F is 0, that is, whether the hydraulic pressure switching valve 29 was in the ON state last time.

If the determination in step S8 is YES and the hydraulic pressure switching valve 29 has been switched from the on state to the off state this time, step S9
The timer T is added in step SIO, and the drain on-off valve 30 is closed in step SIO. Then, in step Sll, the controller waits for the value of the timer T to reach a predetermined value T1, and closes the on-off valve 30 until the predetermined period T1 has elapsed.

If the determination in step Sll is YES and if the determination in step S8 is NO and the hydraulic switching valve 29 continues to be off, the process advances to step S12, where the flag F is set to 1, and then In step S13, the on-off valve 30 is opened.

A time chart of the above control is shown in FIG. 8. When the operating state reaches the high load, high rotation region (■) at point 8, an ON signal is output to the hydraulic pressure switching valve 29 (B), and the hydraulic pressure is applied to the variable valve timing mechanism 27. introduced to increase overlap. Then, when the operating state shifts to low load and low rotation region I at point b, an off signal is output to the hydraulic switching valve 29,
The introduction of hydraulic pressure to the variable valve timing mechanism 27 is stopped, but at that time, the leakage opening/closing valve 30 (A) is closed for a predetermined period T1 up to point C, and the variable valve timing mechanism 27 is reset by the leakage oil pressure. I try not to interfere with that. When the point C is reached, the drain on/off valve 30 is opened again and a small amount of hydraulic pressure is supplied within the range in which the variable valve timing mechanism 27 does not operate even if the hydraulic switching valve 29 is off, thereby controlling the bearing portion 72 of the camshaft 12. This ensures lubrication.

According to the above-described embodiment, when the operation is in the specific operating range (3) in a high-load, high-speed state, the hydraulic switching valve 29
By this switching operation, oil pressure is supplied to the variable valve timing mechanism 27, and the bearing portion 72 of the camshaft 12 is sufficiently lubricated. On the other hand, even if operation continues in the non-specific operating state I, hydraulic pressure is supplied through the leakage passage 26 to ensure lubrication, and the variable valve timing mechanism 2
7 to obtain good operation.

Further, the variable valve timing mechanism 27 having the structure shown in FIG. 4 can be formed compactly, and in addition to making the phase of the exhaust valve 6 variable, the phase of the intake valve 4 may also be made variable. Further, the variable valve timing mechanism 27 can be modified to other configurations as appropriate.

Embodiment 2 This embodiment is an example of application to the V-type engine shown in FIGS. 9 and 10.

The V-type engine 81 has left and right banks 8 inclined at a predetermined angle.
Equipped with 1L and 81R, each bank 81L.

The combustion chambers 3, 3 formed above the pistons 2゜2 in the cylinders 81a, 81b of the 81R have intake valves 4,
The intake port 5.5 is opened and closed by the exhaust valve 6, and the exhaust port 7.7 is opened and closed by the exhaust valve 6.
is opened. The downstream portion of an intake passage 8 configured in the same manner as in the previous example is connected to the intake ports 5, 5 of each bank 81L, 81R by branch passages 8a, 8b, which are branched to the banks 81L, 81R on both sides, respectively. Exhaust passages 9,9 are connected to ports 7.7.

The overhead intake side camshaft 11.1 drives the intake valves 4°4 of both banks 81L and 81R to open and close.
1 is disposed, and overhead exhaust side camshafts 12 and 12 for driving the opening and closing of the exhaust valves 6, 6 of both banks 81L and 81R are disposed, respectively. Both intake and exhaust side camshafts 11, 1.2 are connected to the engine output shaft 85.
It is driven to rotate in synchronization with the rotation of.

Furthermore, each exhaust side camshaft 12.12 in the left and right banks 81L, 81R is equipped with a valve timing variable mechanism 27. 27 have been installed. and.

Engine lubricating oil from an oil pump is supplied to each variable valve timing mechanism 27.27 of the left and right banks 81L, 81R through an oil supply passage 88 formed through its bearing portion 72.72. A hydraulic switching valve 29 similar to the previous example is interposed in the middle of this oil supply passage 88. That is, the oil supply passage 88 passing through the hydraulic switching valve 29 is connected to the exhaust side camshaft 1 of the left bank 81L.
The oil supply passage 88 is connected to the variable valve timing mechanism 27 via the bearing part 72 of the left bank 81L to the camshaft bearing part 72 of the right bank 81R. It is extended so as to communicate with the banks 81L and 81R, and communicates with the variable valve timing mechanism 27 of the right bank 81R via the bearing part 72 of the exhaust side camshaft 12, so that the left and right banks are connected in accordance with the operation of the hydraulic switching valve 29. The variable valve timing mechanisms 27 and 27 of 81L and 81R operate simultaneously.

On the other hand, the right bank 8 is located downstream of the oil supply passage 88.
1R camshaft bearing part 72 part bleed passage 89
The draining passage 89 is connected to the oil supply passage 88 on the upstream side via the draining on/off valve 30, bypassing the hydraulic pressure switching valve 29.

The rest of the structure is the same as that of the previous example, and the same structures are given the same reference numerals.

A drive signal is outputted from the controller 36 to the hydraulic switching valve 29 and the draining on/off valve 30, and the operation is controlled according to the operating state and switching timing as in the previous example. In other words, during specific operation ■ (high load, high rotation area)
Then, an ON signal is output to the hydraulic switching valve 29, and hydraulic pressure is introduced into the left and right valve timing variable mechanisms 27, 27 to delay the timing of the exhaust valve 6 and increase the overlap.

On the other hand, the drain on/off valve 30 is normally operated in an open state,
Even when the hydraulic switching valve 29 is off, a small amount of hydraulic pressure is introduced, and when the hydraulic switching valve 29 is switched from the on state to the off state, it is operated in the closed state for a predetermined period T1, and the variable valve timing mechanism is activated. 27. This speeds up the discharge of hydraulic pressure from 27 to ensure switching responsiveness.

Embodiment 3 This embodiment is another embodiment applied to a V-type engine as shown in FIG. 11, and differs from Embodiment 2 in the connection structure of the oil supply passage.

Variable valve timing mechanism for left and right banks 81L and 81R of V-type engine 81 configured in the same manner as the previous example 27.27
On the other hand, the oil supply passage 91 passing through the hydraulic switching valve 29 is
It is branched for the left and right banks 81L and 81R, and one branch passage 91a is connected to the camshaft bearing portion 72 of the left bank 81L.
The other branch passage 91b communicates with the variable valve timing mechanism 27 via the camshaft bearing portion 72 of the right bank 81R.
It is connected to 7. A drain passage 92 equipped with a drain opening/closing valve 30 is connected to a branch passage 91b for the right bank 81R of the oil supply passage 91 on the downstream side of the oil pressure switching valve 29, and the drain passage 89 has a throttle 9.
3 is interposed.

The rest of the structure is the same as that of the previous example, and the hydraulic switching valve 29 and the drain opening/closing valve 30 are also operated and controlled in the same manner to obtain the same functions, and the same components are given the same reference numerals.

In each of the above embodiments, the on/off operation of the supercharger 21 and the overlap switching are set to be changed based on the determination of the same operating region, but the non-supercharging region is set to be narrower than the small overlap region. It may be possible to use a wide range of characteristics, or vice versa.

(Effects of the Invention) According to the present invention as described above, engine lubricating oil is introduced into the variable valve timing mechanism attached to the camshaft of the engine via the camshaft bearing, and the hydraulic switching valve is actuated during a specific operation. In order to change the valve timing by introducing hydraulic pressure into the variable valve timing mechanism, a leakage passage is provided that bypasses the hydraulic pressure switching valve and introduces a small amount of oil pressure into the variable valve timing mechanism, so that the leakage passage can be used even under non-specific operating conditions. By applying a small amount of oil pressure to the variable valve timing mechanism, the non-specific operating state continues and becomes the operating state. Depending on the corresponding valve timing change control, lubricating oil may be supplied to the camshaft bearing. Even if the camshaft bearing continues to be in an operating state in which the camshaft bearing is not energized, the lubrication of the camshaft bearing can be ensured by supplying the leakage oil pressure, thereby preventing seizure or the like from occurring.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the basic configuration of the present invention, FIG. 2 is an overall configuration diagram of an engine equipped with a valve timing control device in the first embodiment, and FIG. 3 is a configuration example of a hydraulic switching valve. Figure 4 is a cross-sectional view of the main parts showing a specific example of the variable valve timing mechanism, Figure 5 is a characteristic diagram showing the control range of the variable valve timing mechanism, Figure 6 is the overlap between the exhaust valve and intake valve. FIG. 7 is a flowchart for explaining the processing of the controller, FIG. 8 is a time chart of the operation of the hydraulic switching valve and the drain on/off valve, and FIG. 9 is a diagram of the second embodiment. An overall configuration diagram of an engine equipped with a valve timing control device, FIG. 10 is a configuration diagram showing the hydraulic pressure supply system in the example of FIG. 9, and FIG. 11 is a configuration diagram showing the hydraulic pressure supply system in the third embodiment. . E.1. 81...Engine, C, 11,
12...Camshaft, A, 27...
Valve timing variable mechanism, B, 72...Camshaft bearing section, D...Valve timing changing means, F, 28,88°91...Oil supply passage, G, 29...Hydraulic switching valve, H, 2'6, 8
9.92...Drainage passage, 4...Intake valve, 36...Controller.憚4tj ;J ■ (N KotoL Naruko

Claims (2)

[Claims] (1) A hydraulic switching valve is installed in the oil supply passage that introduces engine lubricating oil to the variable valve timing mechanism attached to the engine camshaft via the camshaft bearing,
In a valve timing control device comprising a valve timing changing means for changing valve timing by switching hydraulic pressure to a variable valve timing mechanism by operating the hydraulic switching valve during a specific operation, the hydraulic switching valve of the valve timing changing means is bypassed. A valve timing control device for an engine, characterized in that a leakage passage is provided for introducing a small amount of hydraulic pressure into a variable valve timing mechanism. (2) Engine valve timing control according to claim 1, characterized in that the drain passage is temporarily closed in synchronization with a switching operation of a hydraulic pressure switching valve that stops introducing hydraulic pressure to the variable valve timing mechanism. Device.