JPH08312316A - Variable timing type valve driving device - Google Patents

Abstract

PURPOSE: To provide a variable timing type valve driving device capable of performing sure shifting between high-speed and low-speed cams and having high durability. CONSTITUTION: Low-speed and high-speed locker arms 15 and 16 having valve driving arms are engaged and disengaged by an engaging arm 17 and a hydraulic plunger device 18 and a hydraulic oil chamber 30 and a spring chamber 33 are formed in both side of a piston 28 with a projectingly provided needle 29 for opening and closing a stop valve 31 attached to a locking oil chamber 27 between the cylinder 21 of a plunger body 19 having a spring 25 and the plunger. A spring 32 and an air passage 35 are provided in the spring cheer 33, and when a hydraulic oil pressure declines, a directional control valve changes the pressing direction of the piston 28 by shutting off the hydraulic oil chamber 30, a hydraulic oil supply path 11a and the air passage 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable timing valve drive device, and more particularly, to a cam drive device for an internal combustion engine, which is formed by two cams and two rocker arms. The present invention relates to a variable timing valve drive device that changes the valve timing by changing hydraulic pressure.

[0002]

2. Description of the Related Art As a means for controlling an internal combustion engine, a variable timing valve drive system in which two cams having different cam profiles are attached to a camshaft and the cams to be used are switched according to operating conditions The device is already known. For example, the method described in Japanese Patent Laid-Open No. 4-219409 will be described with reference to FIG. In FIG. 9, another rocker arm 3 is pivotally supported by a hinge pin 2 on the free end side of the end pivot rocker arm 1, a hydraulic actuator 5 is attached to the rocker shaft 4 side of the end pivot rocker arm 1, and a push rod 5
The rocker arm 3 is attached so that the free end side can be pushed up by a.

Two cams 7 and 8 having different cam profiles are attached to a cam shaft 6 arranged above the free end side of the end pivot rocker arm 1, one cam 7 is in contact with the end pivot rocker arm 1 and the other is The cam 8 is attached so as to contact the rocker arm 3. A roller 1a is attached to the lower side of the end pivot rocker arm 1, and the valve stem 9 is pushed down via this roller 1a.

Therefore, the cam profiles of the cams 7 and 8 lift the valve stem 9 according to the cam profile of the cam 7 with which the rocker arm 3 is in contact when the free end side of the rocker arm 3 is pushed up by the hydraulic actuator 5. When the pushing down is released, the end pivot rocker arm 1 contacts the cam 8,
The valve stem 9 lifts according to the cam profile of the cam 8.

The actuator 5 comprises an automatic non-return valve 5b and a hydraulic distributor 10. The automatic non-return valve 5b includes a ball plug 5c and a spring 5e for urging the ball plug 5c in the closing direction. The hydraulic distributor 10 forms a seat 10a and a protrusion 10c on the rocker shaft 4 and connects the rocker shaft 4 to the rocker shaft 4. Has a plurality of through holes 4a communicating between the oil passage 11 formed in the hollow portion and the seat 10a.

The hydraulic selector 12 is formed so that the hydraulic oil is supplied from the pressurized oil supply pipe 12a and the hydraulic oil is discharged by the discharge pipe 12b. Now operate the hydraulic selector 12 to connect the pressurized oil supply pipe 12a to the oil passage 11, and
When the rocker shaft 4 is rotated so that the seat 10a faces the ball plug 5c, the hydraulic oil flows into the hydraulic selector 12, and the push rod 5a moves to the hydraulic actuator 5
Is extruded from.

Further, the hydraulic selector 12 is operated to operate the oil passage 11
When the rocker shaft 4 is rotated so that the projection 10c faces the ball plug 5c while the discharge pipe 12b is in communication with the ball plug 5c, the ball plug 5c is pushed up, the hydraulic oil in the hydraulic actuator 5 is discharged, and the push rod 5a is removed. Can be retracted. By the way, the variable timing valve drive device described with reference to FIG. 9 still requires improvement in the following points. That is, 1. Due to the friction between the rocker arm 3 and the rocker shaft 4, a rotational force acts on the shaft, which causes a problem such as a phase shift with the ball plug 5c.

2. The oil tightness between the outer surface of the push rod 5a and the inner surface of the hollow body 5a depends on the material of the end pivot rocker arm 1. 3. Since the stroke of the push rod 5a is large and the axial direction is fixed, an oblique force is applied, the clearance due to wear increases, and the oil tightness deteriorates.

4. Since the hydraulic distributor 10 is controlled by rotating the rocker shaft 4, the structure becomes complicated. 5. It is difficult to process the rocker shaft 4, especially the protrusion 10c. 6. Since the space between the rocker arm 3 and the cam 7 is opened during the operation of the cam 8, the rocker arm 3 may move up and down without permission, and the cam 7 and the rocker arm 3 may collide and be damaged.

7. Due to the structure, the only way to increase the rocker ratio is to raise the cam peak. 8. Due to the structure, the rocker shaft 4 becomes a sliding rotation, and a large force is required to rotate it in an engine having four or more tilts. Due to the above, application to large engines for trucks and the like has problems in durability and reliability, and cannot be used.

In the variable timing valve drive device disclosed in Japanese Utility Model Laid-Open No. 57-182205, one rocker arm is provided with abutting portions in contact with two cams having different cam profiles. An actuator for adjusting the protrusion length of the abutting portion from the arm is attached according to the conditions. The means for varying the protrusion length is configured so that the plunger attached to the contact portion and the stopper attached to the arm side are supported by the cylinder by making the plunger non-rotatable and the stopper rotatable. In this case, a spring is formed which is formed into a meshable concavo-convex and biases the plunger in the direction of extending from the cylinder.

A spring, which urges the piston fitted in the hydraulic cylinder in the pulling direction, is attached, a lever fixed to the stopper is pivotally supported on the piston rod, and the stopper rotates when the piston strokes. . The piston is locked on the lock plate. Further, a timing rod for detecting a relative position to the rocker shaft is attached to the rocker arm, and the lock plate is operated by the timing rod.

Therefore, when the unevenness of the abutting surface of the stopper is rotated by the hydraulic actuator to a position where it meshes with the unevenness of the abutting surface of the plunger, the plunger penetrates into the stopper when it is pushed down by the cam and does not function as a rocker arm. The fixed contact portion contacts the low speed cam, and the valve is lifted by the low speed cam. Further, when the stopper is rotated to a position where the convex portions of the concavities and convexities are brought into contact with each other, the valve is lifted by the high speed cam.

The means described in this utility model publication are as follows: The piston is twisted by the vibration of the rod attached to the piston of the hydraulic actuator, and the oil tightness is reduced. 2. The overall structure has many parts and has a complicated structure. 3. Since the timing rod is in contact with the rocker shaft and relatively moves, it is worn, lock and unlock operations are likely to be incomplete, and the rocker arm receives thrust force.

4. Since the timing rod is arranged in the recess of the rocker shaft, the rocker arm is less easily assembled to the rocker shaft. 5. The plunger receives a rotational force generated by processing accuracy of a cam, a plunger, a rocker arm, or the like. Therefore, there is a problem that durability of the rotation stopper of the plunger is reduced.

6. Many processing parts require high processing accuracy, resulting in high cost. Due to the above, application to large engines for trucks and the like has problems in durability and reliability, and cannot be used. Further, in any of the variable timing valve drive devices described above, there is no durability measure because the rollers do not have oil supply means, or the plunger is brought into contact with the cam to move up and down, and no countermeasure is taken against the lateral force. There is.

[0017]

As described above,
The conventional variable timing valve drive device using two cams and a rocker arm has drawbacks such as difficulty in maintaining durability due to a structural reason, and further improvement is required. The present invention has been made in view of the above problems, and uses a rocker arm that makes contact with each of two cams, a high-speed cam and a low-speed cam, to reliably switch these cams. Moreover, it is an object of the present invention to provide a variable timing valve drive device having high durability, which does not apply an excessive force due to switching.

[0018]

SUMMARY OF THE INVENTION To achieve the above object, the variable timing valve drive system of the present invention has a rocker arm for each of a low speed cam and a high speed cam mounted on a camshaft. Mounting, forming a valve to be pushed down by a rocker arm in contact with a low speed cam, attaching an engaging arm to one rocker arm, and attaching a hydraulic plunger device for engaging a plunger body to the engaging arm on the other rocker arm , A spring for urging the engaging arm side is attached to the plunger body, and a plunger made of a hollow body is fitted to the cylinder extending from the plunger body into the hydraulic plunger device to form a lock oil chamber in the cylinder. The plunger is equipped with a shutoff valve at the opening on the front end, the rear end is opened, and the piston is projected from this opening. The needle is inserted into the plunger so that the closing valve can be biased in the opening direction, a first oil chamber is formed on the needle side of the piston, and a spring that biases the opposite side piston to the needle side is provided, and When a spring chamber opened to the atmosphere is formed and the pressure of the hydraulic oil decreases, the first oil chamber is shut off from the hydraulic oil supply path,
The spring chamber is cut off from the atmosphere so that the urging direction of the piston can be switched.

When the switching valve is formed of a spool valve with a spring, and when high-pressure hydraulic oil acts on the spool valve, the spool valve is stroked against the spring to move the first oil chamber to the hydraulic oil supply oil passage. When the hydraulic pressure of the hydraulic oil drops below the urging force of the spring while communicating with the atmosphere, the spring chamber can be stroked in the opposite direction to interrupt the communication.

The closing valve provided in the lock oil chamber is not particularly limited, but a preferable valve is a ball valve. Since an oil supply passage for easily supplying oil can be formed in the rotating portion and the sliding portion of the rocker arm, it is easy to prevent deterioration of durability and operability due to friction. The variable timing valve drive device can be applied to both the intake valve drive and the exhaust valve drive.

[0021]

Operation: Two cams, a high-speed cam profile and a low-speed cam profile, are provided, and the valve is driven by a rocker arm that contacts the low-speed cam, and the rocker arm and the rocker arm that contacts the high-speed cam are connected to each other. , When the hydraulic plunger device is engaged with the engagement arm and the valve for low speed is lifted by the cam, the lock oil chamber is opened by the piston with needle, and when the valve is lifted by the high speed cam, the valve is closed. The means for closing the valve can control the engagement and disengagement of the two rocker arms only by controlling the hydraulic pressure, and prevent the generation of prying force as much as possible.
Moreover, the assembling work can be facilitated.

When high-pressure hydraulic oil is supplied by the switching valve, the first oil chamber and the hydraulic oil supply passage are communicated with each other, the spring chamber is opened from the atmosphere, and the hydraulic pressure of the hydraulic oil is supplied to the spring attached to the switching valve. If the elastic force is reduced below,
The means for switching the urging direction of the piston by shutting off the oil chamber from the hydraulic oil supply passage and the spring chamber from the atmosphere prevents the free movement of the high-speed rocker arm during the lost motion, and stabilizes it. It is possible to reliably perform the valve drive operation and the switching between the high speed cam and the low speed cam.

The means for forming the switching valve by the spool valve can promptly perform the switching operation between the high speed cam and the low speed cam by the hydraulic pressure. Further, the means for forming the stop valve attached to the lock oil chamber by the ball valve is
The certainty and durability of the opening / closing operation of the valve can be obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings with reference to the accompanying drawings. First, the structure of the variable timing valve drive device of the embodiment will be described with reference to FIGS. As shown in FIG. 1, the variable timing valve drive device 13 of the present embodiment is formed by a low speed rocker arm 15 and a high speed rocker arm 16 for intake valves (not shown).

Then, the low-speed rocker arm 15 to the engaging arm
By extending 17 and attaching the hydraulic plunger device 18 to the rocker arm 16 for high speed, and the pad 17a attached to the engaging arm 17 is brought into contact with the plunger body 19,
The low speed rocker arm 15 and the high speed rocker arm 16 are engaged with each other. 1 to 4, reference numeral 20a is a pin hole for attaching the adjusting screw 20 (shown in and after FIG. 2), 20b is a placket, 22 is a high speed cam, and 23 is a low speed cam. Moreover, in FIGS. 1 to 5, the same members as those in FIG. An oil supply passage 24 (only shown in FIGS. 2 and 3) is provided in each sliding portion of the variable timing valve drive device 13 of this embodiment to prevent wear.

Next, the lash adjust portion will be described with reference to FIGS. The plunger body 19 is formed in a flange shape around its periphery, and is brought into contact with a spring 25 that biases the pad 17a side, and a portion in contact with the pad 17a is formed into a slightly spherical shape. Rocker arm
It is designed to minimize the influence of prying when the 16 and 16 make different rotational movements. The spring 25 is used when the high-speed rocker arm 16 tries to rotate more than the low-speed rocker arm 15.
Has the effect of absorbing the force of 16 rotating masses.

Then, the cylinder body 21 is attached to the plunger body 19.
And a cylindrical plunger 26 is fitted therein, and the cylinder 21 and the plunger 26 form a lock oil chamber 27. The lock oil chamber 27 is one that seals high-pressure oil here, and cannot lock the plunger body 19 into the housing 18a, that is, locks it. The cylinder 21 is attached so as to move back and forth in contact with a sleeve housing 18b extending from the high speed rocker arm 16 side into the hydraulic plunger device 18.

The oil passage 26a shown in FIG. 6 is an oil passage provided in the flange portion of the plunger 26, and is used to circulate the working oil inside and outside the plunger 26. The sliding length of the sleeve housing 18b and the cylinder 21 of the plunger body 19 is slightly inclined at the contact between the pad 17a and the plunger body 19 to improve the prying resistance when prying force is generated. Made it longer

A needle 29 protruding from a piston 28 is fitted in the hollow portion of the plunger 26, and a working oil chamber 30 is formed by the space around the needle 29 and the space of the piston 28 on the needle 29 side. A stop valve 31 formed of a ball valve is provided between the lock oil chamber 27 and the lock oil chamber 27. A guide 31a (FIG. 6) that allows passage of hydraulic oil is attached around the stop valve 31.

A spring chamber 33 in which a spring 32 is fitted is formed on the opposite side of the hydraulic oil chamber 30 with respect to the piston 28. The spring chamber 33 and the spring 32 constantly urge the piston 28 toward the closing valve 31 side, and the compression spring 26b is mounted in the lock oil chamber 27 between the plunger 26 and the plunger body 19. Further, the high speed rocker arm 16 is provided with an air passage 35 for communicating the spring chamber 33 with the atmosphere.

A switching valve 34 formed of a spool valve is provided between the hydraulic oil chamber 30 and the hydraulic oil supply passage 11a and the air passage 35.
Attached to the middle part of the valve body 34a (Fig. 6)
(FIG. 6), the hydraulic oil supply passage 11a is biased. The hydraulic oil supply passage 11a is formed in the high-speed rocker arm 16 so as to communicate with the oil passage 11 formed in the hollow portion of the rocker shaft 4.

When a high pressure acts on the switching valve 34, the valve body 34a is retracted against the spring 36 so that the hydraulic fluid chamber 30 and the hydraulic fluid supply passage 11a are communicated with each other, and at the same time, in the circumferential direction of the body portion of the valve body 34a. The ring chamber 34b of FIG. 6 (FIG. 6) allows the spring chamber 33 to communicate with the atmosphere through the air passage 35. When the hydraulic pressure becomes lower than the elastic force of the spring 36, the valve body 34a makes a stroke by the elastic force of the spring 36 to disconnect the hydraulic oil chamber 30 from the hydraulic oil supply passage 11a and the spring chamber 33 from the atmosphere.

As shown in FIG. 4, the control system for operating the variable timing valve drive device 13 pumps up the operating oil in the engine oil tank 37 by the pump 38 and supplies it to the oil gallery 39. The oil gallery 39 is branched into a line 39a for supplying engine oil to each part of an internal combustion engine (not shown) and a line 39b for supplying engine oil to the hydraulic / oil amount control valve 40. Hydraulic oil is supplied from the above to the oil passage 11. Oil pressure / oil quantity control valve
The electronic control unit (ECU) 41 that controls the internal combustion engine is used to control 40.

Next, the operation of the variable timing valve drive device 13 of this embodiment will be described with reference to FIGS. In FIGS. 5 and 6A, the state of the hydraulic plunger device 18 is shown in FIG.
4 shows a state similar to 4, that is, a state in which high-pressure hydraulic oil is supplied into the oil passage 11, and the high-speed rocker arm 16 rides on the cam mountain of the high-speed cam 22. Therefore, the adjusting screw 20 attached to the low speed rocker arm 15 pushes down the valve (not shown),
34 is a hydraulic oil supply path that moves backward by receiving the high-pressure hydraulic oil.
11a and the air passage 35 are open.

The high-speed rocker arm 16 is a high-speed cam
In the state of riding on the cam lobe of No. 22, the reaction force of the valve spring (not shown) acts on the low speed rocker arm 15, the engaging arm 17 pushes the plunger body 19, and the hydraulic oil in the lock oil chamber 27 is operated. A force that pushes the oil chamber 30 side acts. Therefore, the stop valve 31 receives a force in the closing direction, the high-pressure hydraulic oil in the lock oil chamber 27 is trapped inside the chamber, and the hydraulic pressure rises,
It cannot be compressed.

As described above, the low-speed rocker arm 15 does not seem to freely rotate, and the high-speed rocker arm 16 does not move freely.
Following this, a valve (not shown) lifts according to the cam profile of the high speed cam 22. When the roller 1a is located on the base diamond of the high-speed cam 22, the engaging arm
The pressing force of 17 on the plunger body 19 is lost, and the hydraulic fluid chamber 30 is filled with high-pressure hydraulic fluid. Therefore, when the oil pressure in the lock oil chamber 27 decreases, the shutoff valve 31 is opened by the oil pressure and the working oil is replenished.

Next, when the engine is operating at a low speed, the spring 36
The operating hydraulic pressure in the oil passage 11 is controlled so that the hydraulic pressure is lower than the elastic force of. Therefore, the switching valve 34 is connected to the hydraulic oil supply passage.
Strokes to the 11a side, the internal pressure of the hydraulic oil chamber 30 decreases, the oil supply is stopped, and the spring chamber 33 is sealed. Then, the force that pushes the piston 28 toward the spring chamber 33 is the spring.
When the piston 28 falls below the urging force of 32, the piston 28 strokes toward the hydraulic oil chamber 30 side, and the needle 29 pushes the closing valve 31 open (B in FIGS. 5 and 6).

When the shut-off valve 31 is opened, the lock oil chamber 27 is opened, the hydraulic oil in the chamber flows out to the hydraulic oil chamber 30 side where the pressure becomes low, the plunger body 19 is unlocked, and the stroke is made possible. Become. That is, in this state, high speed / low speed cam 2
When the roller 1a is located at the ridges 2 and 23, as shown in FIG. 5B, the low speed cam 22 has a speed corresponding to the difference between the height of the high speed cam 22 and that of the low speed cam. The rocker arm 15 rotates for a larger amount than the rocker arm 16 for high speed.

Therefore, since the plunger body 19 is pushed into the hydraulic plunger device 18 by being pushed by the engaging arm 17, the hydraulic oil in the lock oil chamber 17 is pushed out into the hydraulic oil chamber 30, so that the low speed rocker. The engagement between the arm 15 and the high-speed rocker arm 16 is released, and the high-speed rocker arm 16 enters a so-called play state (lost motion). By the way, when the roller 1a is located on the base diamonds of the high speed / low speed cams 22 and 23 in the low speed state, the lift difference between the cams disappears,
The plunger body 19 receives the push-back force (rightward in the figure) by the spring 25, but since the hydraulic oil chamber 30 and the spring chamber 33 are sealed by switching the switching valve 34 as described above, the stop valve 31 is opened. Despite the valve state, the plunger body 19 does not make a stroke toward the engagement arm 17 side, and the valve can be lifted by the low speed cam 23.

Next, when the hydraulic pressure of the hydraulic oil supplied to the oil passage 11 is returned to a high pressure, the switching valve 34 is resisted against the elastic force of the spring 36.
Strokes, high-pressure hydraulic oil is supplied to the hydraulic oil chamber 30, and the spring chamber 33 is opened to the atmosphere. Therefore, while the high-pressure hydraulic oil flows into the lock oil chamber 27, the force that pushes the piston 28 on the hydraulic oil chamber 30 side is the spring.
As the elastic force of 36 is overcome, the piston 28 strokes toward the spring chamber 33, and the needle 29 that has opened the stop valve 31 retracts.

Therefore, when the locking oil chamber 27 is compressed by the engagement arm 17 pushing the plunger body 19 while the high-pressure hydraulic oil is being supplied to the first oil chamber, as described above. The stop valve 31 closes and the plunger body 19 is locked again. FIG. 7 shows the crank angle CA and the valve lift amount L of the variable timing valve drive device 13 of the first embodiment.
It shows the relationship with
Only you can close it early.

The variable timing valve drive device 13 of the present embodiment described above 1) ensures oil tightness by reducing the number of parts and preventing uneven wear by increasing the meshing length of the sliding portion. Therefore, it is easy to supply oil to the roller 1a. 2) The position of the roller 1a with respect to the rocker arms 15 and 16 ensures the degree of freedom in selecting the rocker ratio, so that the cam lift need not be extremely large.

3) Since the volumes of the lock oil chamber 27 and the hydraulic oil chamber 30 can be reduced, the reduction of the valve lift due to the compression of oil can be reduced and the interior of the chamber can be filled with oil in a short time. , High speed cam 22 and low speed cam
It is possible to increase the responsiveness of switching 23. 4) Since the lock oil chamber 27 and the hydraulic oil chamber 30 are filled with the hydraulic oil even during the lost motion, the switching of the cams 22 and 23 can be completed only by hydraulic control.

5) Moreover, since the rocker arm does not freely move at the time of the lost motion, there is no possibility that the rocker arms 15 and 16 and the cams 22 and 23 collide with each other and are damaged. 6) Since the closing valve 31 is opened by driving the needle 29 only by the elastic force of the spring 32, the switching operation due to the decrease in hydraulic pressure is reliable.

7) The workability of the rocker shaft 4 is good. 8) Excellent in ease of assembly. 9) The switching operation of the cams 22 and 23 due to the fluctuation of the hydraulic pressure is performed by making the plunger body 19, the plunger 26, the piston 28 and the needle 29 all stroke on the same axis, so the switching time is short and the reliability is high. Can be increased.

10) Since the switching valve 34 is formed by the spool valve, the switching mechanism is simplified. FIG. 8 shows the relationship between the crank angle CA and the valve lift amount L when the variable timing valve drive device 13 of the present invention is applied to the other stage exhaust.

[0047]

The variable timing valve drive device of the present invention described above can achieve the following effects. When the low-speed rocker arm drives the valve, the low-speed rocker arm and the high-speed rocker arm are engaged by the hydraulic plunger device and the engaging arm, and the low-speed cam lifts the valve, the needle is attached. When the lock oil chamber is opened by the piston and the valve is lifted by the high speed cam, the closing valve is closed.Therefore, only by controlling the hydraulic pressure, the relationship between the low speed rocker arm and the high speed rocker arm can be increased. It is possible to control the disengagement, prevent the generation of the twisting force as much as possible, and there is no part that slides due to the rotation of the rocker arm, so that the assembly work can be facilitated.

When high-pressure hydraulic oil is supplied by the switching valve, the first oil chamber and the hydraulic oil supply passage are communicated with each other, the spring chamber is opened to the atmosphere, and the hydraulic pressure of the hydraulic oil is attached to the switching valve. If the elastic force of the spring is reduced below,
Since the oil chamber is cut off from the hydraulic oil supply path, the spring chamber is cut off from the atmosphere, and the urging direction of the piston is switched, the free movement of the high-speed rocker arm is prevented during the lost motion. It is possible to ensure stable valve drive operation and switching between high-speed cam and low-speed cam.

The means for forming the switching valve by the spool valve can promptly perform the switching operation between the high speed cam and the low speed cam by the hydraulic pressure. Further, the means for forming the shutoff valve attached to the lock oil chamber by the ball valve can improve the reliability and durability of the opening / closing operation of the valve.

[Brief description of drawings]

FIG. 1 is a plan view of a variable timing valve driving device according to an exemplary embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is a perspective view and a control system diagram of a main part of FIG. 1 partially cut away.

5 is an operation explanatory view of the variable timing valve drive device shown in FIGS. 1 to 4, in which A shows a high speed cam operation, and B shows
Indicates the operation of the low speed cam.

6 is an enlarged view of a main part of A of FIG. 5, and B is an enlarged view of a main part of B of FIG.

FIG. 7 is a graph showing a relationship between a crank angle and a cam lift amount according to the embodiment shown in FIGS.

FIG. 8 is a graph showing a relationship between a crank angle and a cam lift amount when the variable timing valve drive device of the present invention is applied to an exhaust valve.

FIG. 9 is a vertical cross-sectional view for explaining an outline of a variable timing valve drive device according to a conventional example.

[Explanation of symbols]

13 Variable timing valve drive device 15 Low speed rocker arm 16 High speed rocker arm 17 Engaging arm 18 Hydraulic plunger device 19 Plunger body 20 Adjust screw 21 Cylinder 22 High speed cam 23 Low speed cam 25 Spring 26 Plunger 27 Locking oil chamber 28 Piston 29 Needle 30 First oil chamber 31 Stop valve 32 Spring 33 Spring chamber 34 Switching valve 35 Air passage 36 Spring 37 Engine oil tank 38 Hydraulic oil pump 39 Oil gallery 40 Hydraulic / oil quantity control valve 41 Electronic control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Teruichi Nishimura Inventor Teruichi, Fujisawa City, Kanagawa 8 Isuzu Motors Co., Ltd. Fujisawa Plant (72) Inventor, Shinichi Nakanishi, No. 8, Fujisawa, Kanagawa Prefecture Isuzu Motors Fujisawa Co., Ltd. Inside the factory (72) Inventor Kotoku Kawamoto 2400 Kamigo, Ebina City, Kanagawa Prefecture Automotive Department, Ltd. (72) Inventor Hisao Iijima 2400 Kamigo, Ebina City, Kanagawa Prefecture Automotive Department, Ltd.

Claims (4)

[Claims] 1. A rocker arm is attached to each of a low speed cam and a high speed cam attached to a cam shaft, and a valve is driven by the rocker arm in contact with the low speed cam. Attach a joint arm, attach a hydraulic plunger device that engages the plunger body with the engagement arm on the other rocker arm, attach a spring that urges the engagement arm side to the plunger body, and remove the plunger body from the hydraulic plunger device. A hollow plunger is fitted into the cylinder that extends to the inside to form a lock oil chamber in the cylinder.The plunger has a stop valve at the tip opening and the rear end is opened. The needle protruding from the piston is inserted into the plunger so that the closing valve can be biased in the opening direction,
Forming a working oil chamber on the needle side of the piston, forming a first spring chamber for urging the opposite side piston to the needle side, and cutting off the working oil chamber from the working oil supply passage when the hydraulic pressure of the working oil decreases, A variable timing valve drive device provided with a switching valve that causes the needle to stroke toward the closing valve side by the urging force of the first spring. 2. When the switching valve is urged to one side by a second spring, and high-pressure hydraulic oil acts on the switching valve,
This hydraulic pressure drives the switching valve against the second spring to communicate the hydraulic oil chamber with the hydraulic oil supply oil passage and open the first spring chamber to the atmosphere so that the hydraulic pressure of the hydraulic oil is equal to that of the second spring. When the pressure drops below the urging force, the second spring drives the switching valve against the hydraulic pressure to shut off the hydraulic oil chamber from the hydraulic oil supply passage, and at the same time shut off the switching valve to shut off the first spring chamber from the atmosphere. The variable timing valve drive device according to claim 1, which is formed. 3. The variable timing valve drive device according to claim 1, wherein the switching valve is a spool valve. 4. The variable timing valve drive device according to claim 1, wherein the shutoff valve provided in the lock oil chamber is formed by a ball valve.