JPH0141811B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve drive device for driving intake and exhaust valves (hereinafter collectively referred to as on-off valves) provided in a combustion chamber of an internal combustion engine, and particularly to a valve drive device with a valve stop function. Regarding.

In order to improve the high-speed performance of internal combustion engines, four-valve engines, six-valve engines, eight-valve engines, etc., which are provided with a plurality of intake valves and a plurality of exhaust valves, are well known. In an internal combustion engine equipped with such multiple on-off valves, all the on-off valves are driven at high speeds to ensure a sufficient opening area for the intake and exhaust passages, while at medium to low speeds some of the on-off valves are deactivated and the remaining open/close valves are driven. It is known that a valve drive device is combined with a valve deactivation device in order to prevent the air-fuel mixture from blowing through due to so-called overlapping by driving only the on-off valve of the engine, thereby ensuring operational performance at medium and low speeds. There is. On the other hand, an example of a valve drive device equipped with a valve stop device is disclosed in Japanese Patent Application Laid-Open No. 54-36415.

However, such conventional valve drive devices
The problem was that the structure was quite complex and lacked durability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a valve drive device that has a simple structure and is highly durable.

In the valve drive device according to the present invention, a cam follower that engages with a cam that rotates with the rotation of the crankshaft and drives an on-off valve to open and close intermittently is pivotally supported by a hydraulic tappet mechanism, and the hydraulic tappet mechanism is rotated in the direction of its central axis. The hydraulic tappet mechanism is configured to be selectively positionable in either the raised position or the lowered position to position the hydraulic tappet mechanism in the lowered position to effect valve rest.

Hereinafter, a valve driving device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a part of a cylinder head of an internal combustion engine using a valve drive device according to the present invention, in which an opening of an intake or exhaust passage 2 formed in a cylinder block 1 into a combustion chamber 3 is shown. An on-off valve 4 consisting of a valve body 5 forming an intake or exhaust valve and a valve rod 5a connected to the valve body 5 is slidably guided by a valve guide 6. The on-off valve 4 is biased in the direction of closing by a known valve spring mechanism 7. The tip of the valve rod 5a is in contact with one end of a cam follower 9 that is engaged with a cam 8. The other end of the cam follower 9 is a piston plunger 1 forming an oil tappet mechanism 10.
The valve rod 5 is pivoted by a spherical head 1 and can be pressed by the rotation of a cam 8 that rotates in response to the rotation of a crankshaft (not shown), thereby pressing the valve rod 5. The piston plunger 11 is formed into a cylindrical shape as a whole, and has two holes on the periphery of the opening end.
two protrusions 12a, 12 protruding outward in the radial direction;
A piston plunger 11 is slidably inserted into a tappet cylinder 12 having an opening end thereof, thereby forming a hydraulic chamber 13. The piston plunger 11 has a through passage 11a therein, and the through passage 11a communicates with the hydraulic chamber 13 via an orifice 11b at the bottom of the piston plunger 11.
Further, an opening is provided at the tip of the spherical head of the piston plunger 11 so that lubricating oil can be supplied between the cam follower 9 and the spherical head.
The through passage 11a further communicates with an orifice 11c provided in the side wall of the piston plunger 11. Tappet cylinder 12 has an orifice 12c in its side wall that communicates with orifice 11c of piston plunger 11. Tappet cylinder 1
2 is slidably inserted into the support cylinder 14.

On the other hand, a compression spring 15 is provided within the hydraulic chamber 13 and urges the piston plunger 11 in a direction to push it out of the tappet cylinder 12. Further, a spherical valve body 16 is provided in a retainer 17 at the bottom of the piston plunger 11 in the hydraulic chamber 13, and the orifice 11 is pressed by a pressing spring 18.
b and forms a check valve.

As is clear from FIGS. 2B and 2C, the support cylinder 14 has a pair of notches 14a, 14b at its upper peripheral edge, into which the protrusions 12a, 12b of the tapepet cylinder 12 engage. This notch 14
a and 14b are A forming a valley and a shelf, respectively.
It consists of side, B side, and C side. A latching recess is formed at the deepest part of the D surface which faces the B surface and forms a trough, and the shape is such that a part of the A surface bites into the D surface.

As is clear from FIG. 3, the tip 12aa of the protrusion 12a is shaped like a disk, and is held by a holding member 20 supported by the shift rod 19. In response to movement in the direction of the central axis, for example in the direction of arrow P, the tapepet cylinder 12 rotates in the direction of arrow Q. The shift rod 19 is operated by a suitable drive device (not shown) so as to be positioned in either the valve operating position or the valve resting position depending on the operating state of the engine.
driven by. That is, shift rod 1
9. The drive mechanism for the clamping member 20 and the shift rod 19 serves as a tappet cylinder positioning means.

On the other hand, a hydraulic pressure supply passage 14c is formed in the side wall of the support cylinder 14, and can communicate with the orifice 12c only when the tappet cylinder 12 is in the valve operating position, and communicates with an external hydraulic power source via the hydraulic passage 21. ing. Further, the tapepet cylinder 12 is connected to the support cylinder 14 by a return spring 22.
The cam follower 9 is energized in the direction of pulling out from the cam follower 9, that is, in the direction of pushing up the cam follower 9.

The cam follower 9 is guided by a cam follower guide 23 so as to properly abut the tip of the valve rod 5a.

In the valve drive device according to the present invention configured as described above, when operating the on-off valve normally,
The relative position of tappet cylinder 12 with respect to support cylinder 14 is positioned by shift rod 19 to the valve operating position shown in solid lines in FIG. 2C. That is, the protrusions 12a and 12b of the tapepet cylinder 12 are in contact with the C surface of the support cylinder 14, the piston plunger 11 is in the raised position, and the swinging motion of the cam follower 9 is transmitted to the valve rod 5a.

Next, in this valve driving device, when the on-off valve is to be stopped despite the rotation of the cam 8, the shift rod 19 is moved, for example, in the P direction in FIG. 3, and the tappet cylinder 12 is rotated in the Q direction. This rotation of the tappet cylinder 12 in the Q direction corresponds to the movement in the Q direction in FIG.
a, 12b are valley portions 14a, 1 of the support cylinder 14
4b (the position indicated by the dotted line in FIG. 2C). At this time, when the cam follower 9 is pressed by the cam 8, the tappet cylinder 12
are also pressed, and the protrusions 12a, 12b are pressed against the troughs 14a,
14b, and by the force of the shift rod 19, the protrusion 12 is further pushed into the latch recess on the D side.
Parts a and 12b are engaged. FIG. 4 shows such a state. In such a situation,
Despite the rotation of the cam 8, the cam follower 9 is maintained in the state shown in FIG. 4, and no pressing force is applied to the valve rod 5a, so that the on-off valve 4 is at rest.

Note that in this embodiment, the support cylinder 14
A latch recess is provided on the D side of the tappet so that the tappet cylinder 12 is latched when pushed into the support cylinder 14 by the pressing force of the cam follower 9. However, even if the latch recess is not formed, An on-off valve deactivation effect can be obtained, and the latching recess can be omitted in some cases.

Next, when the shift rod 19 is moved in the direction opposite to the P direction in FIG.
2 is pushed up along the B plane in the direction of coming out of the support cylinder 14, and further rotated in the direction opposite to the Q direction by the biasing force of the shift rod 19, so that the protrusions 12a and 12b move as shown by the solid line in FIG. 2C. reach the position. In such a state, the operation of the on-off valve according to the rotation of the cam 8 is restarted.

As is clear from the above, the support cylinder 14, hydraulic circuit 21, return spring 22
and the tappet cylinder positioning means form a tappet cylinder support mechanism that supports the tappet cylinder 12 in the raised or lowered position.

As described above, according to the present invention, when the valve is switched from rest to operation, the shock is alleviated by the buffering effect of the hydraulic oil in the hydraulic chamber, resulting in a highly durable stop mechanism with less noise during switching.

In addition, when the valve is in the rest state, the force acting on the piston plunger 11 becomes almost zero, and if the hydraulic pressure continues to be supplied to the hydraulic chamber 13, the total height of the oil tappet becomes slightly higher, and when the valve rest state is released, the force acting on the piston plunger 11 becomes almost zero. There is a possibility that the tappet cylinder 12 is pushed in by the pressing force of the cam follower 9 before it is completely raised, resulting in a delay in returning to the valve operating state. However, in the valve driving device according to the present invention,
When the tappet cylinder 12 is lowered to the valve rest position, the hydraulic pressure supply to the hydraulic chamber 13 is cut off, so that the above-mentioned problem does not occur.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a part of a cylinder head of an internal combustion engine including a valve drive device according to the present invention;
2A and 2B are perspective views showing the main parts of the valve driving device shown in FIG. 1, FIG. 2C is a developed view of the members shown in FIG. 2B, and FIG. FIG. 4 is a partial plan view of the valve driving device shown in the figure, and is a sectional view showing the valve driving device shown in FIG. 1 in a valve rest state. Explanation of symbols of main parts 1...Cylinder head,
2... Intake or exhaust passage, 3... Combustion chamber, 4... Open/close valve, 5... Valve body, 5a... Valve rod, 7... Valve spring mechanism, 8... Cam, 9... Cam follower, 10... Oil tappet mechanism, 11... Piston plunger, 12... Tappet cylinder, 14... Support cylinder, 19... Shift rod, 20... Clamping member.

Claims (1)

[Scope of Claims] 1. A cam that rotates in accordance with rotation of a crankshaft of an internal combustion engine, a cam follower that responds to the cam and drives an on-off valve of the internal combustion engine at one end thereof, and a cam follower that rotates in response to the rotation of the crankshaft of an internal combustion engine; a tappet cylinder that receives the piston plunger and forms a hydraulic chamber; and a tappet cylinder support mechanism that supports the tappet cylinder in either a raised position or a lowered position. A valve driving device characterized by: 2. The valve drive device according to claim 1, wherein the cam follower engages with the cam at its center and is intermittently pressed to drive the on-off valve. 3. The tappet cylinder has at least one radial protrusion around the opening for receiving the piston plunger, and the tappet cylinder support mechanism is configured such that the tappet cylinder is slidably inserted therein and connected to the internal combustion engine. a support cylinder fixed to the tappet cylinder, the support cylinder having a recess at the periphery of the opening for receiving the tapepet cylinder that can engage with the radial projection of the tappet cylinder; The mechanism further engages the tappet cylinder and positions the tappet cylinder in an angular position where the radial protrusion of the tappet cylinder and the recess of the support cylinder engage to provide valve rest. A valve driving device according to claim 1, characterized in that the valve driving device comprises means.