JPH0243004B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Purpose of the Invention (1) Field of Industrial Application The present invention is directed to a motor which is rotatably driven in synchronization with the rotation of an engine and has a cam integrated therein corresponding to an intake valve or an exhaust valve. The present invention relates to a valve operating device for an internal combustion engine that includes a camshaft and a rocker arm for opening and closing the intake valve or the exhaust valve according to the rotation of the cam.

(2) Prior art In such a valve train, the valve diameter and valve lift amount are set with emphasis on high speed so that when the amount of air-fuel mixture necessary to output maximum horsepower is sucked in, horsepower will not decrease due to inflow resistance. It is common to set the

By the way, if the intake valve is driven with the same valve timing and the same lift amount from low speed range to high speed range, the intake amount will differ depending on each rotation speed, so
The air-fuel mixture inflow speed into the combustion chamber is different. That is, at low speeds, the air-fuel mixture inflow speed decreases, the turbulence of the air-fuel mixture within the combustion chamber becomes small, and the combustion speed also slows down. For this reason, fuel consumption increases due to a decrease in combustion efficiency, and the knocking limit decreases due to a decrease in combustion speed.

Therefore, in order to solve this problem, there is a system in which a part of the intake valve or exhaust valve is closed and paused during low-speed operation, and the intake valve or exhaust valve is opened during high-speed operation.
It is disclosed in the publication No. 59-226216.

(3) Problems to be Solved by the Invention In the above-mentioned conventional technology, the intake valve, which is inactive during low-speed operation, may remain inactive for a long period of time depending on the operating conditions. If an intake valve or an exhaust valve remains inactive for a long period of time, carbon produced by combustion will accumulate between the valve and the valve seat, causing the valve to stick to the valve seat. Therefore, when shifting to high-speed operation and opening the valve, the valve is forcibly peeled off from the valve seat, resulting in a sealing problem between the valve and the valve seat. Further, when the intake valve is closed and rests, a fuel stagnation may occur, and the mixture concentration may become rich when the intake valve is opened.

The present invention has been made in view of the above circumstances, and solves the problems associated with stoppage by opening and closing the intake valve or exhaust valve with valve timing and valve lift according to the low-speed operation even during low-speed operation. It is an object of the present invention to provide a valve operating system for an internal combustion engine that solves the above problems, reduces fuel consumption, and prevents knocking.

B. Structure of the Invention (1) Means for Solving the Problems According to the present invention, in order to achieve the above object, the camshaft includes a low-speed cam having a shape suitable for low-speed operation of the engine, and a cam for high-speed operation of the engine. A first rocker arm that contacts the intake valve or the exhaust valve and slides on the low-speed cam, and a second rocker arm that slides on the high-speed cam are arranged adjacent to each other, 1st and 2nd
A connection switching means is provided between the rocker arms, which can switch between connection and disconnection between the rocker arms.

(2) Effect When the first and second rocker arms are connected by the connection switching means during high-speed operation of the engine, the first and second rocker arms swing in accordance with the shape of the high-speed cam, and the intake valve or exhaust valve is closed. It opens and closes at the timing and lift amount determined by the high-speed cam. Furthermore, when the connection between the first and second rocker arms is released during low-speed operation of the engine, the first rocker arm swings due to the low-speed cam, and therefore the intake valve or exhaust valve is opened at the timing determined by the low-speed cam. It opens and closes depending on the amount of lift.

(3) Embodiments Below, embodiments of the present invention will be described with reference to the drawings. First, in FIGS. 1 and 2 showing an embodiment of the present invention, a pair of intake valves 1a, 1b is a camshaft 2 that is driven at a rotation ratio of 1/2 in synchronization with the rotation of the engine.
It is driven to open and close by the functions of a low-speed cam 3 and a high-speed cam 5 that are integrally provided with the camshaft 2 and the first and second rocker arms 7 and 8 that are pivotally supported by a rocker shaft 6 that is parallel to the camshaft 2. Further, the engine body is equipped with a pair of exhaust valves (not shown), and these exhaust valves also have the aforementioned intake valve 1.
It is driven to open and close in the same way as a and 1b.

The camshaft 2 is rotatably disposed above the engine body, and the low-speed cam 3 is connected to both intake valves 1a,
The camshaft 2 is provided integrally with the camshaft 2 at a position corresponding to the middle of the camshaft 1b. In addition, the high-speed cam 5 is connected to the intake valve 1.
It is integrally provided on the camshaft 2 at a position corresponding to b. Furthermore, the low-speed cam 3 has a shape suitable for low-speed operation of the engine, and has a high portion 3a that protrudes outward in the radial direction of the camshaft 2 by a relatively small amount. The high-speed cam 5 has a shape suitable for high-speed operation of the engine, and has a radially outward protrusion of the camshaft 2 larger than the high portion 3a and a center wider than the high portion 3a. It has a high portion 5a extending over a corner range.

The rocker shaft 6 is fixedly arranged below the camshaft 2. This locking shaft 6 has a first locking arm 7 corresponding to the low speed cam 3.
and a second rocker arm 8 corresponding to the high-speed cam 8.
Cam slippers 10 and 11 are provided on the upper portions of both rocker arms 7 and 8, on which the low-speed and high-speed cams 3 and 5 slide, respectively. Also the first
The lock arm 7 has two intake valves 1 that are branched into two.
Arms 7a and 7b extending above a and 1b are integrally provided. Tappet screws 12 and 13 which can abut the upper ends of the respective intake valves 1a and 1b are screwed into the tips of these arms 7a and 7b so as to be movable forward and backward.

On the other hand, a flange 1 is provided at the upper part of both intake valves 1a and 1b.
4, 15 are provided, and these collar parts 14,
Valve springs 16 and 17 surrounding the intake valves 1a and 1b are interposed between 15 and the engine body, and the valve springs 16 and 17 direct each intake valve 1a and 1b upward, that is, in the valve closing direction. energized.

A bottomed cylindrical lifter 19 is in contact with the lower surface of the end of the second rocker arm 8 as a pressing means, and this lifter 19 is urged upward by a lifter spring 20 interposed between it and the engine body. Ru. As a result, the cam slipper 11 of the second rocker arm 8 is always resiliently in sliding contact with the high-speed cam 5. Moreover, the spring force of the lifter spring 20 is set to be relatively weak.

In FIG. 3, the first and second rocker arms 7, 8 are in sliding contact with each other, allowing relative angular displacement, and both rocker arms 7, 8
A connection switching means 21 is provided between the first and second rocker arms 7 and 8, which can switch between the state in which the two rocker arms are integrally connected.

This connection switching means 21 includes a piston 23 that is movable between a position where the first and second rocker arms 7 and 8 are connected and a position where the connection is released, and a stopper 24 that restricts the movement of the piston 23.
and a spring 25 that biases the stopper 24 to move the piston 23 toward the disconnection position.

The first locking arm 7 has a second locking arm 8.
While opening towards the side, the lock shaft 6
A first guide hole 26 parallel to the first guide hole 26 is bored, and a small diameter portion 28 is provided at the closed end side of the first guide hole 26 via a stepped portion 27. First guide hole 26
A piston 23 is slidably engaged with the piston 23 , and a hydraulic chamber 29 is defined between the piston 23 and the closed end of the first guide hole 26 .

An oil passage 30 communicating with the hydraulic chamber 29 is bored in the first rocker arm 7, and an oil passage 31 communicating with a hydraulic pressure supply source (not shown) is bored in the rocker shaft 6. Further, both oil passages 30 and 31 are connected to each other via a communication hole 32 bored in the side wall of the rock shaft 6.
Communication is always maintained regardless of the swinging state of the first rocker arm 7.

The second rocker arm 8 is provided with a second guide hole 35 that is open toward the first rocker arm 7 and corresponds to the first guide hole 26.
A disc-shaped stopper 24 is slid into the guide hole 35 . A regulating step 3 is provided on the closed end side of the second guide hole 35.
A small diameter portion 37 is provided through the hole 6, and an insertion hole 38 coaxial with the small diameter portion 37 is bored at the closed end. Moreover, a guide rod 39 coaxially and integrally provided with the stopper 24 is inserted into the insertion hole 38. Furthermore, a coiled spring 25 surrounding the guide rod 39 is interposed between the stopper 24 and the closed end of the second guide hole 35 .

The length of the piston 23 in the axial direction is such that when one end comes into contact with the stepped portion 27, the other end is located between the first and second rocker arms 7 and 8, and the stopper 24 is placed against the regulating step 36. The setting is such that one end remains in the first guide hole 26 when the second guide hole 35 is entered until the contact is made. Further, a spring 33 that biases the piston 23 toward the second rocker arm 8 is housed in the hydraulic chamber 29 of the first rocker arm 7, and the set load of this spring 33 is set to be smaller than that of the spring 25. be done.

Next, the operation of this embodiment will be explained. When the engine is operated at low speed, the connection switching means 21 releases the connection between the first and second rocker arms 7 and 8, as shown in FIG. That is, hydraulic chamber 2
When the hydraulic pressure at 9 is released, the stopper 24 releases the spring 25.
Moves to the first rocker arm 7 side by the spring force of
The piston 23 is retracted until it abuts the stepped portion 27. In this state, the contact surfaces of the piston 23 and the stopper 24 are at positions corresponding to the sliding surfaces of the first and second rocker arms 7, 8, so the first and second rocker arms 7, 8 are in sliding contact with each other. It is in a state where relative angular displacement is possible.

In such a disconnected state, the first rocker arm 7 swings in sliding contact with the low-speed cam 3 due to the rotational movement of the camshaft 2, and both intake valves 1a and 1b are brought into contact with the first rocker arm 7. Therefore, it is driven to open and close. At this time, the second rocker arm 8 also swings in response to sliding contact with the high-speed cam 5, but this swinging action does not affect the operation of both intake valves 1a, 1b. Moreover, the second rocker arm 8 has a lifter spring 20.
Since it is only in sliding contact with the high-speed cam 5 due to a relatively weak spring force, friction loss in the valve train can be suppressed to a low level.

In this way, when the engine is operating at low speed, both intake valves 1a and 1b are driven to open and close at a timing and lift amount that corresponds to the shape of the low-speed cam 3, that is, the low-speed operation, and the optimum air-fuel mixture inflow speed is obtained. It is possible to reduce fuel consumption and prevent knocking.

When operating the engine at high speed, the connection switching means 21
As a result, the first and second rocker arms 7, 8 are connected as shown in FIG. That is, by supplying hydraulic pressure to the hydraulic chamber 29, the piston 2
3 fits into the second guide hole 35 while pressing the stopper 24 against the spring force of the spring 25, and the stopper 24 is pressed against the regulating step 36. In this state, the first and second rocker arms 7, 8 are prevented from relative rotation and swing integrally.

In this connected state, the amount of swing of the second rocker arm 8 that is in sliding contact with the high-speed cam 5 is the same as that of the first rocker arm 7.
Since the first rocker arm 7 is larger than the second rocker arm 8, the first rocker arm 7 swings following the second rocker arm 8. Therefore, both intake valves 1a and 1b are driven to open and close at the timing and lift amount defined by the high-speed cam 5, and high output and high torque can be obtained by improving intake efficiency.

In the above embodiment, one cylinder has a pair of intake valves 1a,
1b, the present invention can also be applied to an internal combustion engine having a single intake valve 1 or exhaust valve in one cylinder, as shown in FIG. The same effects as in the above embodiment can be achieved.

C. Effects of the Invention As described above, according to the present invention, the camshaft is provided with a low-speed cam having a shape suitable for low-speed operation of the engine and a high-speed cam having a shape compatible with high-speed operation of the engine, A first rocker arm that abuts the intake valve or the exhaust valve and slides on the low-speed cam, and a second rocker arm that slides on the high-speed cam are arranged adjacent to each other, and the first and second rocker arms are arranged adjacent to each other.
A connection switching means is provided between the rocker arms to connect and disconnect between them.
When driving at low speeds, the intake and exhaust valves can be opened and closed at timings and lifts appropriate for low speed driving to reduce fuel consumption and prevent knocking. Also, during high speed driving, the intake and exhaust valves can be opened and closed at timings and lifts appropriate for low speed driving. It is possible to obtain high output and high torque by opening and closing with the timing and lift amount according to the situation. Moreover, since the intake valve or exhaust valve does not stop during operation, there is no risk of carbon depositing between the valve and the valve seat and causing the valve to stick to the valve seat. It is also possible to prevent the concentration from becoming too high.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, in which FIG. 1 is a vertical side view and a sectional view taken along the line - in FIG. 2, FIG. 2 is a plan view of FIG. 1, FIG. 3 is an enlarged sectional view taken along the line of FIG. 1 to show the connection state, FIG. 4 is an enlarged sectional view corresponding to FIG. 3 when the connection is released, and FIG. 5 shows another embodiment of the present invention. FIG. 2 is a plan view corresponding to FIG. 2; 1a, 1b...Intake valve, 2...Camshaft, 3...
Low-speed cam, 5... High-speed cam, 7... First rocker arm, 8... Second rocker arm, 19... Lifter as pressing means, 21... Connection switching means.

Claims (1)

[Scope of Claims] 1. A camshaft 2 which is rotationally driven in synchronization with the rotation of the engine and has cams 3 and 5 integrated therein corresponding to the intake valves 1a and 1b or the exhaust valves, and the cams 3 and 5. In a valve train for an internal combustion engine, which is equipped with rocker arms 7 and 8 for opening and closing the intake valves 1a and 1b or the exhaust valves according to rotation, the camshaft 2 has a shape suitable for low-speed operation of the engine. A first rocker arm 7 includes a low-speed cam 3 and a high-speed cam 5 having a shape suitable for high-speed operation of the engine and is in contact with the intake valve 1a; 1b or the exhaust valve and also slides against the low-speed cam 3. and a second rocker arm 8 that is in sliding contact with the high-speed cam 5 are arranged adjacent to each other, and a connection switching means 21 is provided between the first and second rocker arms 7 and 8 that can switch between connection and disconnection. A valve train for an internal combustion engine, characterized in that it is provided with: 2 The second rocker arm 8 has a high-speed cam 5.
2. The valve train for an internal combustion engine according to claim 1, wherein a pressing means 19 is brought into contact for resiliently biasing the valve gear toward the valve. 3 The first rocker arm 7 has a pair of intake valves 1
The valve operating device for an internal combustion engine according to claim 1, wherein the valve operating device is brought into contact with a; 1b or an exhaust valve.