JPH0765485B2 - Valve drive for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention relates to a valve train of an internal combustion engine, and in particular, it is interposed between an intake valve and an intake cam of an intake camshaft. The fulcrum of the intake cam follower is swingably fitted to a seat member fixed to the cylinder head, and the fulcrum of the exhaust cam follower is interposed between the exhaust valve and the exhaust cam of the exhaust cam shaft. The present invention relates to an improvement of a valve operating device of a type in which a cam portion is fitted in a seat member fixed to a cylinder head so as to be swingable, and both cam shafts are rotated in the same direction.

(2) Conventional Technology Conventionally, in a valve train of this type, the intake cam follower and the exhaust cam follower are arranged symmetrically with respect to the cylinder axis, and the intake cam shaft and the exhaust cam shaft are common to the crankshaft. There is known one in which rotation is performed in the same direction via a timing belt.

(3) Problems to be Solved by the Invention In the conventional valve operating system, the lift curves of the intake and exhaust cams have the same gradient in the buffer portions on the valve opening side and the valve closing side.

However, of the intake and exhaust cam followers, the cam follower that receives the lateral component of the pressing force from the cam in the direction of the seat member during the lift operation of the cam is the lift operation of the cam compared to the other cam followers. At the time of starting, since the pressing force is received from the cam at a position relatively far from the seat member,
The thrust load exerted on the seat member by the spherical fulcrum portion of the one cam follower (that is, the pressing force of the spherical fulcrum portion on the seat member) is greater than the thrust load exerted on the seat member by the spherical fulcrum portion of the other cam follower. Therefore, even if the lateral components of the pressing force applied from the cams corresponding to both cam followers are equal, the one cam follower moves relatively more laterally than the other cam follower. There is a problem in that the tapping sound is likely to occur at the fitting portion between the fulcrum portion of the one cam follower and the receiving member.

An object of the present invention is to provide a valve operating system for an internal combustion engine which can solve such a problem and can secure a predetermined valve overlapping angle.

B. Configuration of the Invention (1) Means for Solving the Problems To achieve the above object, the present invention provides a fulcrum portion of an intake cam follower interposed between an intake valve and an intake cam of an intake camshaft. Is swingably fitted to an intake seat member fixed to the cylinder head, and the fulcrum of the exhaust cam follower interposed between the exhaust valve and the exhaust cam of the exhaust cam shaft is In a valve operating system of an internal combustion engine, which is swingably fitted to an exhaust receiving member fixed to a head so as to rotate both cam shafts in the same direction, the intake cam is lifted when the intake cam is lifted. Determines the rotation direction of the intake cam shaft so that the intake cam follower slides toward the intake valve, while the exhaust cam exhausts the exhaust cam follower toward the exhaust seat member during lift operation of the exhaust cam. The direction of rotation of the camshaft for The gradient of the valve-opening side buffer portion of the arm of the lift curve, characterized by being smaller than the gradient of the valve-opening side buffer portion of the lift curve of the intake cam.

(2) Action Since the gradient of the valve opening side buffer portion of the lift curve of the exhaust cam is set to be smaller than the gradient of the valve opening side buffer portion of the intake cam lift curve, the lift operation of the exhaust cam is quietly started, The increase in the pressing force that acts on the exhaust cam follower from the exhaust cam slows down, and the exhaust cam follower does not abruptly move laterally, and a tapping sound is generated at the fitting part between the fulcrum of the cam follower and the seat Can be prevented.

Moreover, the valve opening side buffer part of the lift curve of the exhaust cam sucks,
Since the valve stacking angle of the exhaust valve is not affected at all, a proper valve stacking angle can be secured.

(3) Example Hereinafter, an example of the present invention will be described with reference to the drawings. In FIG. 1, a cylinder head 2 is superposed and bonded on the upper surface of a cylinder block 1. The cylinder head 2 is provided with a combustion chamber 4 facing the upper surface of the piston 3 in the cylinder block 1, and intake and exhaust ports 5i, 5e opening to the combustion chamber 4, and these ports 5i, 5e are connected to each other. Intake and exhaust valves 6i and 6e for opening and closing are provided.

The intake and exhaust valves 6i, 6e are arranged so that the valve heads of the intake and exhaust valves 6i, 6e are widened to increase the axial distance, and the valve guides are provided.
It is movably supported by the cylinder head 2 via 7i and 7e, and is opened and closed by the valve operating device 8.

The valve operating device 8 is a valve that is contracted between retainers 9i and 9e attached to the upper ends of intake and exhaust valves 6i and 6e and the cylinder head 2 to urge the valves 6i and 6e in the closing direction. The base ends of the springs 10i, 10e and the seat members 11i, 11e fixed to the cylinder head 2 are swingably supported to suck the tip ends of the exhaust valves 6i, 6e. , Exhaust cam follower 12i, 12
e, the rotatably supported by the cylinder head 2, sucking, sucking on the slipper surface of the upper surface of the exhaust cam followers 12i, 12e, engaging the exhaust cams 14i, 14e respectively, the exhaust camshaft 13
It is composed of i and 13e in the so-called DOHC type.

The base ends of the cam followers 12i and 12e are spherical fulcrums 1 of the adjusting bolts 15i and 15e that are screwed to the respective cam followers.
The cam followers 12i, 12e are constituted by 6i, 16e, and these spherical fulcrums 16i, 16e are fitted into the spherical recesses 17i, 17e of the receiving members 11i, 11e screwed to the cylinder head 2.
Is rotatably supported by the seat members 11i, 11e. The cam followers 12i and 12e are arranged symmetrically with respect to the cylinder axis 18 with the spherical fulcrums 16i and 16e directed toward the cylinder axis 18.

The intake and exhaust camshafts 13i, 13e are rotationally driven in the same direction from a crankshaft (not shown) via a common timing belt. The rotation direction of the intake camshaft 13i is such that the intake cam 14i is the intake cam follower. 12i is set to the direction A that slides toward the intake valve 6i, and the exhaust cam shaft 13e has the exhaust cam 14e.
Is the direction B in which the exhaust cam follower 12e slides toward the seat member 11e.

Thus, the intake cam 14i of the intake camshaft 13i performs a lift action in the intake stroke of the engine, swings the intake cam follower 12i downward around the spherical fulcrum 16i, and causes the intake valve 6i to be a valve spring. It opens against the force of 10i, and the exhaust cam 14e of the exhaust cam shaft 13e performs a lift action in the exhaust stroke, so that the spherical fulcrum 1
The exhaust cam follower 12e can be swung downward around the 6e, and the exhaust valve 6e can be opened against the force of the valve spring 10e.

The intake and exhaust cams 14i, 14e have their respective profiles formed by the lift curves I, E as shown in FIG. 2, and the intake lift curve I and the exhaust lift curve E are closed. And are overlapped with a predetermined valve stacking angle α.

Lift curves I and E are both on the valve opening side and the valve closing side.
Buffer portions a, b; a ', b' are provided to absorb the suction and exhaust of the exhaust cams 14i, 14e and the opening / closing impact force on the exhaust valves 6i, 6e.

In this case, the gradients of the valve opening-side buffer portion a of the intake lift curve I and the valve closing-side buffer portion b'of the exhaust lift curve E are uniquely determined by the predetermined valve overlap angle α, but for the exhaust gas The slope of the lift curve E of the valve opening side cushioning part a ′ that is not related to the valve overlap angle α is set sufficiently smaller than the slope of the valve opening side cushioning part a of the intake lift curve I. FIG. 3 shows specific examples of these gradients.

Incidentally, in the present invention, the spherical fulcrum portion 1 of each cam follower 12i, 12e
6i, 16e may be formed as concave portions, and spherical convex portions that fit into the concave portions may be formed on the receiving members 11i, 11e, and both cam followers 1
2i, 12e have their spherical fulcrums 16i, 16e on both camshafts 13i, 1e.
It may be placed on both sides of 3e.

Next, the operation of this embodiment will be described. The intake and exhaust camshafts
By taking the rotation directions A and B as described above, 13i and 13e,
The intake cam 14i presses the intake cam follower 12i at a position close to the seat member 11i at the start of the lift,
The exhaust cam 14e presses the exhaust cam follower 12e at a position close to the exhaust valve 6e at the time of starting the lift. The spherical fulcrum 16i on the 6i side is larger. Therefore, the spherical fulcrum portion 16i on the intake valve 6i side does not easily move laterally with respect to the seat member 11i, but the spherical fulcrum portion 16e on the exhaust valve 6e side easily moves laterally with respect to the seat member 11e.
Therefore, even if the lateral components of the pressing force applied to the intake and exhaust cam followers 12i, 12e from the intake and exhaust cams 14i, 14e are equal, the exhaust cam follower 12e causes the above-described lateral components at the start of the lift of the exhaust cam 14e. Is moved by the spherical support point 16e of the cam follower 12e and the seat member 11e.
A tapping sound is likely to be generated at the fitting portion of and.

However, in the present invention, as described above, the exhaust cam 14
Since the gradient of the valve opening side buffer portion a ′ of the lift curve E of e is set to be smaller than the gradient of the valve opening side buffer portion a of the lift curve I of the intake cam 14i, the lift operation of the exhaust cam 14e starts quietly. As a result, the increase in the pressing force acting on the exhaust cam follower 12e from the exhaust cam 14e slows down.
The sudden lateral movement of 12e does not occur, and as a result, it is possible to prevent the tapping sound from being generated at the fitting portion between the spherical fulcrum portion 16e and the seat member 11e.

Moreover, since the valve opening side cushioning portion a'of the lift curve E of the exhaust cam 14e does not affect the valve overlap angle α, the proper valve overlap angle α is secured to improve the high speed output of the engine and Exhaust port 5e of fresh air supplied to the combustion chamber 4
The exhaust emission can be reduced by suppressing the blow-through to the exhaust.

C. Effects of the Invention As described above, according to the present invention, the rotation direction of the intake camshaft is determined so that the intake cam follows the intake cam follower toward the intake valve during lift operation of the intake cam, while Since the direction of rotation of the exhaust cam shaft is determined so that the cam slides toward the exhaust cam follower toward the exhaust seat member during the lift operation, the exhaust cam follower is more likely than the intake cam follower when the cam lift is started. Also becomes easy to move in the lateral direction, and a relatively large hammering sound is likely to be generated at the fitting portion between the fulcrum portion of the exhaust cam follower and the exhaust seat member. Since the gradient of the side buffer portion is set to be smaller than the gradient of the valve opening side buffer portion of the lift curve of the intake cam so as to suppress the abrupt lateral movement of the exhaust cam follower, the exhaust cam follower fulcrum portion and the seat member Mating with Can effectively prevent the occurrence of striking sound, the
Moreover, in this way, even if the valve opening side buffer section of the lift curve of the exhaust cam is made a gentler gradient than that of the intake cam, it does not affect the valve stacking angle of the exhaust valve at all, so ensure a proper valve stacking angle. As a result, it is possible to contribute to the reduction of the operating noise of the valve operating device while suppressing the deterioration of the output performance of the engine.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of an internal combustion engine equipped with the valve operating device of the present invention, and FIG. 2 is a lift curve diagram for intake and exhaust of the valve operating device. FIG. 3 is a gradient comparison diagram of the valve opening side buffer section of the intake / exhaust lift curve. a, b; a ', b' ... buffer, A ... rotation direction of intake camshaft, B ... rotation direction of exhaust camshaft, α ... valve overlap angle,
I, E ... lift curve, 6i ... intake valve, 6e ... exhaust valve, 8 ... valve operating device, 11i, 11
e ... seat member, 12i, 12e ... intake and exhaust cam followers,
13i, 13e …… Suction / exhaust camshaft, 14i, 14e …… Suction, exhaust cam, 16i, 16e …… Spherical fulcrum, 17i, 17e …… Spherical recess

Claims (1)

[Claims] 1. A fulcrum portion (16i) of an intake cam follower (12i) interposed between an intake valve (6i) and an intake cam (14i) of an intake camshaft (13i) is attached to a cylinder head (2). ) Is fitted to an intake seat member (11i) fixed to the exhaust valve (6e) and an exhaust cam (1e) of the exhaust cam shaft (13e).
The fulcrum part (16e) of the exhaust cam follower (12e) interposed between the exhaust cam seat and the 4e) is swingably fitted to the exhaust seat member (11e) fixedly mounted on the cylinder head (2). In a valve operating system of an internal combustion engine in which both cam shafts (13i, 13e) are rotated in the same direction, the intake cam (14i) is moved by the intake cam follower (12i) during lift operation of the intake cam (14i).
i) Slide the intake camshaft (1i) toward the intake valve (6i).
3i) direction of rotation (A) is determined, while exhaust cam (14e)
The exhaust cam (14e) determines the rotation direction (B) of the exhaust cam shaft (13e) so that the exhaust cam (14e) slides on the exhaust cam follower (12e) toward the exhaust seat member (11e). The slope of the valve opening-side buffer section (a ') of the lift curve (E) of (14e) is set smaller than the slope of the valve opening-side buffer section (a) of the lift curve (I) of the intake cam (14i). A valve operating system for an internal combustion engine, comprising: