JPS62203911A - Valve timing change gear for diesel engine - Google Patents

Abstract

PURPOSE:To improve drivability, by equipping an engine with a driving piston, which reciprocates in the axial direction cooperatively with a tappet, and a working piston, which drives intake and exhaust valves by the hydraulic pressure, and enabling valve timing of the intake and exhaust valves to be changed in accordance with a load. CONSTITUTION:An engine, when it is in high loaded operation, opens a solenoid valve 14 to supply working fluid to a supply oil part 10 while moves a switching piston 11 rightward against a spring 15 to open a check valve 13. In this way, the working fluid is supplied into an oil pressure generating chamber A through an oil path 30 and a check valve 16, and the engine, in which a control rod 28 is lifted against a spring 29, is set to valve timing when the engine is high loaded. While the engine, when it is in low loaded operation, closes the solenoid valve 14 to move the switching piston 11 leftward by the spring 15, and the engine is set to valve timing, when the engine is low loaded, by closing the check valve 13 while pressing the control rod 28 to be lowered by the spring 29. And the valve timing can be changed by pressing a driving piston 6 by a tappet 3 and lifting a working piston 7.

Description

[Detailed Description of the Invention] Industry↓Emperor and Industry... The present invention relates to a valve timing changing device for internal combustion engines, particularly diesel engines, and more specifically, to a valve timing changing device for internal combustion engines, particularly diesel engines, and more specifically, for changing valve timing during high-load operation and low-load operation of a highly supercharged diesel engine. The present invention relates to a valve timing changing device for automatically changing the opening timing of an intake or exhaust valve in correspondence with each other to maintain the diesel engine in the best operating condition at all times.

Conventionally, the opening and closing timings of the intake and exhaust valves installed in diesel engines are normally set to the optimal state within a certain range according to the output and rotation speed, but as the engine output increases As supercharging increases due to this, it is necessary to increase the period during which the intake and exhaust valves are open at the same time, that is, the overramp period, in order to increase the scavenging effect and suppress the heat load during high-load operation.

For this reason, during low-load operation close to non-supercharging, due to the excessive overlap period, exhaust gas blows back into the combustion chamber and intake system, resulting in dirt, and exhaust color due to a drop in compression temperature and piston temperature due to a drop in supply air pressure. Problems such as defects and E-shift defects occur.

Therefore, it is desirable to shorten the overlap period when the load is low in order to maintain the best operating condition of the engine.

For example, when the load is high, the intake valve opens at position A, approximately 80 degrees before the piston's top dead center [TDc], as shown by the solid line in Fig. 6(a), and closes to the bottom dead center CB D C. ) after about 45
Close the exhaust valve at position B at 50°, and open the exhaust valve at about 50° before the piston bottom dead center CB D C) as shown by the broken line.
The intake valve is set to close at a position approximately 60 degrees after top dead center (TDC), and when the load is low, the intake valve is set at a position approximately 20" before top dead center (TDC) as shown in Figure 6 (b). The overlap period can be shortened by setting the exhaust valve to open at A°.Also, as shown in Figure 6(c), the exhaust valve can be set to open at bottom dead center (B
DC) may be set to open at a position C'' approximately 30° forward, and the expansion pressure of the combustion gas may be effectively utilized.

As mentioned above, as a device for automatically changing valve timing during high load and low load, there is a device disclosed in Japanese Utility Model Application Publication No. 50-59808, and this device is driven by an engine. The hydraulic pressure generated by the fluid pump is supplied to the valve opening device of the intake/exhaust valve through the switching valve, and the switching of the switching valve is performed by the switching valve operating device using the timing cam as the driving source. The actuator incorporates a valve opening/closing timing adjustment mechanism.

Also, as another example, British Patent No. 1224168
The patent specification consists of a pump having a piston that reciprocates in the axial direction in cooperation with a cam, and a plunger that is actuated by hydraulic pressure generated by this pump to drive a pulse valve, which rotates the piston. A valve timing changing device that can change valve timing is disclosed.

By the way, the former valve timing changing device [Utility Model Application Publication No. 59808/1983] requires a fluid pump to constantly generate high pressure, so there is no energy loss. Since it is large and uses a fluid pump, switching valve, etc., the entire device is complicated and expensive.Furthermore, the cam lift upward curve must be gentle because both valves open and close during the cam lift upward stroke. Therefore, the valve opens slowly, and there is a drawback that a sufficient valve opening area cannot be obtained, so that it is still not sufficient.

Furthermore, the latter valve timing changing device [British Patent No. 1224168] has only one hydraulic control hole, and control notches are provided at both axial ends of one land of the piston. Because of this, the lower notch opens the hydraulic control hole before the end of the piston's upward stroke.
This causes the hydraulic pressure acting on the plunger to be released, and therefore, the valve opening/closing timing is no longer controlled by the downward lift of the cam, and even though the cam is reciprocating the piston up and down, the upward stroke of the piston by the cam does not control the valve opening/closing timing at all. Since the valve only controls the opening and closing of the valve, there is a disadvantage that there is a lot of wasted movement in the piston, making it difficult to increase the valve opening area, and also making it difficult to set the valve closing timing accurately. .

That is, in the above two examples, since the valves are controlled to open and close only during the upward stroke of the cam lift, it is unreasonable and causes a large energy loss, and furthermore, the device itself inevitably becomes larger and more complicated.

By the way, in a diesel engine, by increasing the overlap period, residual gas in the combustion chamber can be cleaned, increasing the amount of intake air, and cooling the combustion chamber.In addition, by opening the exhaust valve earlier, the turbocharger can be By increasing the amount of energy supplied to the combustion chamber and increasing the amount of air into the combustion chamber,
Combustion efficiency can be increased.

Therefore, during high-load operation, the engine can be operated in the best condition by advancing the opening timing of the intake or exhaust valves, so changing only the opening timing of the intake or exhaust valves is a simple and inexpensive valve timing change. equipment is required.

The present invention includes a driving piston that reciprocates in the axial direction in cooperation with a tappet, and an operating piston that drives an intake or exhaust valve through hydraulic pressure generated by the tappet and the driving piston. A valve timing changing device configured to change the valve timing of an intake or exhaust valve by changing the operation timing of a driving piston with respect to the tappet, the valve timing changing device being defined by the tappet and the driving piston. a hydraulic pressure generating chamber, an oil passage for supplying oil to the hydraulic pressure generating chamber and discharging hydraulic oil from the hydraulic pressure generating chamber, and an outflow of hydraulic oil from the hydraulic pressure generating chamber to the oil passage. and a control rod that operates the check valve by hydraulic pressure in the oil passage and opens the check valve after the operating piston has risen by a specified amount and when the load is low. By switching on and off the supply of hydraulic oil to the oil passage, the hydraulic oil in the hydraulic pressure ordering chamber is discharged or retained through the check valve, thereby changing the timing at which the drive piston starts operating with respect to the tappet, thereby reducing the load on the diesel engine. This is a valve timing changing device for a diesel engine that changes the valve timing of an intake or exhaust valve according to the engine speed.

The valve timing changing device for a diesel engine according to the present invention presses a control rod using the pressure of hydraulic oil supplied to an oil passage to operate a check valve when the load is high. The driving piston and the operating piston are raised integrally with the tappet, and when the load is low, the control rod opens the check valve to discharge the hydraulic oil in the oil pressure generation chamber from the oil passage, and the hydraulic oil is discharged for a predetermined time. After that, the opening timing of the intake or exhaust valve is changed by directly pressing the driving piston with the tappet and raising the working piston.

1 to 3 are drawings showing an embodiment of a valve timing changing device for a diesel engine according to the present invention.

In the drawings, (1) is a cam shirt I, (2) is a timing cam integrally formed on the camshaft (1),
(3) is a tappet that moves up and down by a timing cam (2), (4) is a device body installed upright on a cylinder block (5), and the tappet (3) is connected to the lower end of the inside of this device body (4). Sliding.

Inside the device body (4), above the tappet (3),
A drive piston (6) that interlocks with this tappet (3) is slidably fitted, and furthermore, an operating piston (7) that interlocks with the drive piston (6) is slidable above this drive piston (6). The lower part of the drive piston (6) is slidably inserted into the upper part of the tappet (3) to define a hydraulic pressure generating chamber (A).

A spring (8) is compressed and interposed between the device main body (4) and the tappet (3), and presses the tappet (3) downward so that it always comes into contact with the timing cam (2). (9) is a spring compressed and interposed between the tappet (3) and the drive piston (6), which constantly presses the drive piston (6) upward to eliminate the tappet 1 clearance of the valve drive system. (10) is an oil supply section provided approximately at the center of the side surface of the device main body (4), (11) is a switching piston disposed within the oil supply section (10), and (12) is a drive piston (6). Oil supply hole for supplying hydraulic oil inside (
13) is a check valve disposed in the middle of this oil supply hole (12), and (14) is a solenoid valve that connects and disconnects the supply of hydraulic oil to the oil supply part (10), which is connected to the switching piston (11). When there is no hydraulic oil supplied to the oil supply section (10), the check valve (13)
is pushed open by the elastic restoring force of the spring (15),
The hydraulic oil in the oil supply hole (12) is discharged.

(16) is a check valve disposed in the hollow part of the drive piston (6), and the hydraulic oil from the oil supply hole (11) passes through the check valve (16) to the oil pressure generation chamber (A). When the tappet (3) is raised, the spring (17) blocks the hydraulic oil from flowing out from the hydraulic pressure generating chamber (A), thereby increasing the hydraulic oil pressure in the hydraulic pressure generating chamber (A). (18)
(19) is a bushing rod whose lower end spherical portion is supported by the operating cylinder (7), and (19) is a bushing rod (18).
), (20) is an intake or exhaust valve (hereinafter simply referred to as a valve) that is opened and closed by the rocker arm (19), and (21) is a valve spring.

(22) is a control piston fitted on the outer periphery of the working piston (7) so as to be slidable in the axial direction, and (23) is a control rod that is housed inside the working piston (7) so as to be slidable in the axial direction. , (24) is a spring that always elastically biases the control rod (23) upward, (25) is a long hole formed along the axial direction in the actuating piston (7), and (26) is the long hole (
The control piston (22) and the control rod (2
3) is a pin that integrally connects the control piston (
22) moves the control rod (23) against the elastic restoring force of the spring (24) when the actuating piston (7) rises by a predetermined amount and comes into contact with the inner upper end surface (27) of the device body (4). and press down.

On the 2nd, a control rod is inserted into the center of the upper part of the driving piston (6) so as to be movable in the axial direction, and the spring (29) pushes the check valve (16) downward to open it. being oppressed. (30) is an oil passage formed between the control rod (28) and the check valve (16), and this oil passage (
30) is an oil outlet (
31) and the oil supply hole (12) are communicated with each other. (32)
is a pressure regulating valve provided at the oil outlet (31), which regulates the hydraulic pressure from the check valve (16) to a constant level, as will be described later.
Preventing a sudden drop in oil pressure inside the drive piston (6),
Hunting in the system from the drive piston (6) to the valve (20) is prevented.

The operating procedure of the valve timing changing device having the above configuration will be explained below.

First, in the state shown in FIG. 1, the solenoid valve (14) opens,
Hydraulic oil is supplied to the oil supply section (10), and the pressure of this hydraulic oil causes the switching piston (11) to move against the spring (15).
The check valve (1) is moved to the right in the figure against the elastic restoring force of
3) Push open. Then, this hydraulic oil passes through the oil passage (30) from the oil supply hole (12), pushes open the check valve (16), and flows into the oil pressure generation chamber (A), and the control rod (28) is driven by the oil pressure. It is pushed upward against the elastic restoring force of the spring (29) to set the valve timing at high load.

In this state, the timing cam (2) controls the tappet (3).
) is pushed up, the hydraulic oil is compressed between the tappet (3) and the drive piston (6), the pressure of the hydraulic oil in the hydraulic pressure generating chamber (A) increases, and the check valve (16) closes. As a result, the driving piston (6) rises together with the tappet (3), and the operating piston (7) is pushed by the driving piston (6) and rises together, causing the bushing rod (18) and the rocker arm ( 19) to open the valve (20).

The operating piston (7) rises to a predetermined position, and the control piston (22) is moved to the inner upper end surface (27) of the device body (4).
When abutting the control piston (22), the pin (26)
The control rod (23) is pushed down via the control rod (23).
) further pushes down the control rod (28) on the drive piston (6) side. Control rod (28) on the drive piston (6) side
When the control rod (28) is pushed down, the lower end of the control rod (28) pushes open the check valve (16), and the hydraulic oil in the oil pressure generation chamber (A) is transferred from the oil passage (30) to the oil outlet (31) and the KFm pressure valve. ζ3
2), the drive piston (6)
If the tappet (3) rises further, only the tappet (3) will rise and the opening degree of the valve (20) will be kept constant, and the tappet (3) will rise further.
The relative distance X between the drive piston (6) and the drive piston (6) is zero.

At this time, the pressure of the hydraulic oil at the oil outlet (31) is controlled by the pressure regulating valve (
32), hunting in the valve drive system is prevented. In other words, the pressure regulating valve (32
) is not provided, when the operating screw (7) rises to a predetermined position and the check valve (16) is opened, the hydraulic oil pressure in the oil pressure generation chamber (A) will drop to Okg / rd, and the drive screw (6) and operating piston (7) are pushed back by the elastic restoring force of the valve spring (21), causing the valve (20) to swing. However, if the pressure regulating valve (32) is arranged as described above, the hydraulic oil pressure at the oil outlet (31) is kept constant, so the oil pressure in the oil pressure generation chamber (A) does not drop, and therefore, , drive piston (6) and drive piston (7
) is not pushed back (maintained at a constant position, so the valve (20) does not swing).

Then, as the timing cam (2) rotates, the tappet (3) is pushed down by the elastic restoring force of the spring (8) and begins to descend, the pushing force against the drive piston (6) disappears and the valve spring (21) Due to the elastic restoring force of the driving piston (6) and the actuating piston (7
) is pushed down in accordance with the amount of descent of the tappet (3).

Tappet (3) and drive piston (6) under high load
The operating characteristics of the tappet (3) are shown in FIG. 3. The tappet (3) is interlocked with the timing cam (2) and exhibits the operating characteristics shown by the dashed line. ), it stops rising at a predetermined position and stands still, and when descending, it descends following the tappet (3).

Next, the operation at low load will be explained.

In this case, as shown in Fig. 2, the solenoid valve (14) is switched to interrupt the supply of hydraulic oil to the oil supply section (10), and the switching piston (11) is activated by the elastic restoring force of the spring (15).
) to the left in the figure to open the check valve (13),
In addition, the elastic restoring force of the spring (29) pushes the control rod (28) downward and pushes the check valve (16) open against the elastic restoring force of the spring (17), allowing the valve to open under low load. Set the timing.

In this state, the tappet (
3) is pushed up, the hydraulic oil in the hydraulic pressure generating chamber (A) flows through the check valve (16), the oil passage (30), and the oil supply hole (
12) The hydraulic oil is discharged from the oil supply part (10) via the check valve (13), and therefore the pressure of the hydraulic oil in the oil pressure generation chamber (A) does not rise, so the drive piston (6) does not rise and the above-mentioned tappet (3) rises while compressing the springs (8) and (9) until the relative distance X with the drive piston (6) becomes O, that is, until it comes into contact with the drive piston (6), then the drive piston (6) is directly pressed by tappet (3) and rises. The drive piston (6) is therefore connected to the tappet (3).
) and rises after a predetermined time delay compared to the operating piston (7).
is pushed up to open the valve (20) via the Buchcheronde (18) and the rocker arm (19). Then, the timing cam (2) rotates further, and the tappet (3)
) becomes stronger, the tappet (3) is pushed down by the elastic restoring force of the spring (7) and begins to descend, and the driving piston (6) and operating piston (7) move toward the valve spring (21). Due to the elastic restoring force, the tappet (3) begins to descend as the tappet (3) descends, closing the valve (20).

Fig. 3 shows the operating characteristics of the tappet (3) and the drive piston (6) during this low load state. As mentioned above, the tappet (3) works in conjunction with the timing cam (2) to achieve the operating characteristics shown by the dashed line. The drive piston (6) lags behind the tappet (3) by a predetermined angle and exhibits an operating characteristic as shown by the chain line.

Therefore, when the load is low, the valve (20) is opened a predetermined time later than when the load is high, until the tappet (3) and the driving piston (6) come into contact with each other.

4 and 5 are drawings showing other embodiments of the valve timing changing device for a diesel engine according to the present invention,
Components that are the same as those in FIGS. 1 and 2 are given the same reference numerals or symbols, and their explanations will be omitted.

In this embodiment, the device main body (4゛) is the upper main body (4゛).
It has a two-part structure consisting of a) and a lower body (4b),
An operating piston (7) is slidably fitted in the upper body (4a), and a tappet (3) is fitted in the lower body (4b).
A driving piston (6゛) is also slidably fitted therein.

A flange (40) is formed at the upper end of the drive piston (6''), and this flange (4o) is connected to the lower body (4b).
It engages with a counterbore (41) formed in the upper end opening of the drive piston (6') to restrict the lowest position of the drive piston (6'). On the other hand, the lower end opening of the upper body (4a) has a diameter larger than the flange (40) of the drive piston (6') and a length corresponding to the maximum stroke amount of the drive piston (6'). An annular groove (42) is formed.

That is, the flange (40) moves between the counterbore (41) of the lower body (4b) and the annular groove (42) of the upper body (4a) as the drive piston (6゛) moves up and down. Move up and down.

Furthermore, in this embodiment, the oil supply hole (12) and the oil outlet (3
1') is shifted up and down. That is, in the state shown in FIG. 4, the oil supply hole (12) and the drive piston (6"
) is in communication with the oil 1i'8 (30), and when the drive piston (6゛) rises by a predetermined amount and the oil passage (30) reaches the position shown by the two-point stop in Fig. 4, the above The oil passage (30) and the oil outlet (31'') communicate with each other.

Therefore, in this embodiment, by forming the flange (40) at the upper end of the drive piston (6゛), the flange (40) is arranged between the tappet (3) and the drive piston (6) in the previous embodiment. The spring (9) is omitted and the oil supply hole (
12) and the oil outlet (31') are vertically shifted in height, so that the oil supply part (10) in the previous embodiment is omitted.

The operating procedure of the valve timing changing device having the above configuration will be explained below.

First, in the state shown in Fig. 4, the solenoid valve (4) is opened,
Hydraulic oil is supplied to the oil supply hole (12), and this hydraulic oil passes from the oil supply hole (12) to the check valve (12) through the oil passage (30).
6) is pushed open and flows into the hydraulic pressure generating chamber (A), and the control rod (28) is moved by the spring (29) by the hydraulic pressure.
) is pushed upward against the elastic restoring force, and the valve timing is set for high loads.

In this state, the timing cam (2) controls the tappet (3).
) is pushed up, the hydraulic oil is compressed between the tappet (3) and the drive piston (6″), and the hydraulic pressure generation chamber (A)
As the pressure of the hydraulic oil increases and the check valve (16) is closed, the driving piston (6') rises together with the tappet (3), and the working piston (7) moves upward from the driving piston (16). 6') and rise together to open the valve (20) via the bush rod (18) and the Rosoka man (19).

The operating piston (7) rises to a predetermined position, and the control piston (22) is moved to the inner upper end surface (27) of the device body (4).
When abutting the control piston (22), the pin (26)
The control rod (23) is pushed down via the control rod (23).
) further includes the control rod (2) of the drive piston (6') OtlJ.
8) Press down. When the control rod (28) on the drive piston (6°) side is pushed down, the lower end of this control rod (28) pushes open the check valve (16) and opens the hydraulic pressure generation chamber (A).
In order to discharge the hydraulic oil inside the system from the oil passage (30) through the oil outlet (31') and the pressure regulating valve (32), the drive piston (6°) does not rise any further and only the tappet (3) increases, the opening degree of the valve (20) is kept constant, and the relative distance X between the tappet (3) and the drive piston (6'') becomes zero.

Then, as the timing cam (2) rotates, the tappet (3) is pushed down by the elastic restoring force of the spring (8) and begins to descend, the pushing force against the drive piston (6') disappears and the valve spring (21 ), the driving piston (6') and the operating piston (7) are pushed down in accordance with the amount of descent of the tappet (3).

Next, the operation at low load will be explained.

In this case, as shown in Figure 5, the solenoid valve (14) is switched to interrupt the supply of hydraulic oil to the oil supply hole (12), and the elastic restoring force of the spring (29) allows the control rod (2 days) to By pressing downward, the check valve (16) is pushed open against the elastic restoring force of the spring (17), and the valve timing is set at low load.

In this state, the tappet (
3) is pushed up, the hydraulic oil in the oil pressure generation chamber (A) is discharged from the oil supply hole (12) via the check valve (16) and the oil passage (30), so that the oil pressure generation chamber (A) is discharged from the oil supply hole (12). ) does not increase the pressure of the hydraulic oil in the drive piston (6″).
does not rise, and the tappet (3) moves toward the drive piston (6
After rising while compressing the spring (8) until the relative distance X with respect to
3) is directly pressed and rises. Therefore, the driving piston (
6) rises after a predetermined time delay compared to the tappet (3), pushes up the operating piston (7), and pushes the bushing rod (1) up.
8) and the valve (2) via the rocker arm (19).
0) is opened. When the timing cam (2) further rotates and the pushing force on the tappet (3) increases, the tappet (3) is pushed down by the elastic restoring force of the spring (7) and begins to descend, and the drive piston (6° ), and the operating piston (7) begins to descend as the tappet (3) descends due to the elastic restoring force of the valve spring (21), closing the valve (20).

Therefore, when the load is low, the valve (20) is opened a predetermined time later than when the load is high, that is, the time required for the tappet 7) (3) and the drive piston (6') to come into contact with each other.

As explained above, the valve timing change device for a diesel engine according to the present invention presses the control rod using the pressure of the hydraulic oil supplied to the oil passage to operate the check valve when the load is high. The drive piston and the operating piston are raised integrally with the tappet by the hydraulic oil pressure in the oil pressure generation chamber, and when the load is low, the control rod opens the check valve to discharge the hydraulic oil in the oil pressure generation chamber from the oil passage. After draining the hydraulic oil for a predetermined period of time, the tappet directly presses the drive screw 1 to raise the operating piston, so that no air intake or exhaust air can be used at both high and low loads. By changing the opening timing of the valve as appropriate and adjusting the overlap period of the intake and exhaust valves or the opening timing of the exhaust valve, it is possible to always operate the engine in the best condition. The working oil pressure of
Since the hydraulic pressure is generated by the hydraulic pressure generation chamber defined by the drive piston and the tappet, a separate hydraulic pump is not required, and the device is simple in structure and inexpensive.

Furthermore, the diesel engine valve timing changing device according to the present invention intermittently generates the working hydraulic pressure of the intake or exhaust valve only when the intake or exhaust valve is operated, and furthermore, this working hydraulic pressure is generated only under high load. Because we are letting
Especially when the load is low, energy loss is extremely small and the ti
This is very reasonable and can also realize fuel efficiency of the engine itself.

[Brief explanation of drawings]

1 to 3 are drawings showing one embodiment of a valve timing changing device for a diesel engine according to the present invention, and FIG.
The figure is a longitudinal side view showing the state when the tappet starts to rise under high load, Figure 2 is a longitudinal side view showing the state when the tappet starts to rise under low load, and Figure 3 shows the operating characteristics of the tappet and drive piston. FIG. 4 and 5 are drawings showing other embodiments of the pulp timing changing device for a diesel engine according to the present invention,
FIG. 4 is a longitudinal side view showing the state when the tappet starts to rise under a high load, and FIG. 5 is a longitudinal side view showing the state when the tappet starts rising under a low load. FIGS. 6(a), 6(b), and 6(c) are diagrams showing an example of valve timing during high-load operation and low-load operation of a typical diesel engine. (3)-m-tappet, (6) (6')--driving piston, (7)--actuating piston, (16)--check valve, (20)-
m-valve [intake valve or exhaust valve], (23)
(2B)...-control rod, (30)-oil line,
(A) - Hydraulic pressure generation chamber. Patent applicant: Daihatsu Diesel Co., Ltd.: Osamu Hayashi, Gangwon Province,
:,1,-.

Claims (1)

[Claims] (1) Consisting of a drive piston that reciprocates in the axial direction in cooperation with a tappet, and an operating piston that drives an intake or exhaust valve via hydraulic pressure generated by the tappet and the drive piston, the drive piston for the tappet A valve timing changing device capable of changing the valve timing of an intake or exhaust valve by changing the operation timing of the hydraulic pressure generating chamber defined by the tappet and the driving piston; an oil passage for supplying hydraulic oil to the chamber and discharging the hydraulic oil from the oil pressure generation chamber; a check valve for blocking the flow of hydraulic oil from the oil pressure generation chamber to the oil passage; and an oil passage in the oil passage. The control rod is equipped with a control rod that operates the check valve by hydraulic pressure and opens the check valve after the operating piston has risen by a specified amount and during low load, and disconnects and disconnects the supply of hydraulic oil to the oil passage. According to
By discharging or stopping the hydraulic oil in the oil pressure generation chamber through a check valve, the timing at which the driving piston starts operating relative to the tappet is changed, and the valve timing of the intake or exhaust valve is changed according to the load of the diesel engine. A valve timing change device for a diesel engine, which is characterized by the following: