JPH0235844B2 - - Google Patents

Description

Detailed Description of the Invention A. Purpose of the Invention (1) Industrial Field of Application The present invention relates to a valve train for an internal combustion engine, in particular, to a valve train and a camshaft for driving the valve, so that their axes are perpendicular to each other. The present invention relates to a valve train of a type in which a free end of a cam follower is disposed between the two and is pivotally supported on an engine body so as to be swingable.

(2) Prior Art Such a valve train is already known as described in Japanese Utility Model Publication No. 52-21389.

(3) Problems to be solved by the invention In such a valve train, the lever ratio of the cam follower is approximately 1, and the reciprocating inertial mass of the cam follower is minimized, so the cam follower follows the camshaft well and the engine It is possible to accurately open and close the valve even when the engine rotates at high speed, making it suitable for high-speed engines.

However, in conventional valve train systems, the imaginary straight line connecting the center of swing of the cam follower and the contact point between the cam follower and the valve is perpendicular to the valve axis when the valve is fully closed. As a result, the valve moves greatly on the upper end surface of the valve, in other words, the abutting portion of the cam follower and the valve slides relatively largely, and the frictional resistance at that time acts on the valve as a side load, causing the valve to move at high speeds. The inventors of the present invention have discovered that this affects the followability of the camshaft.

Therefore, the present invention provides a valve train in which the relative sliding amount between the cam follower and the valve is kept as small as possible to reduce the side load on the valve, and the valve's ability to follow the camshaft during high-speed operation is improved. The purpose is to provide.

B. Structure of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention arranges a valve and a camshaft that drives it so that their axes are perpendicular to each other, and In a valve train for an internal combustion engine, in which a free end of a cam follower pivotally supported by the engine body is interposed between the cam shafts and a free end of the cam follower, a virtual line connecting the center of swing of the cam follower and the contact point of the cam follower and the valve. so that the straight line swings approximately equiangularly in one direction and the other direction as the valve opens and closes from a position perpendicular to the valve axis.
In addition, the cam follower is arranged so that the contact points alternately move to one side and the other side of the axis of the valve as the valve opens and closes.

(2) Effect According to the above configuration, the imaginary straight line connecting the center of swing of the cam follower and the contact point between the cam follower and the valve approximately moves in one direction and the other direction as the valve opens and closes from a position perpendicular to the axis of the valve. Since the cam follower and the valve swing at equal angles, the amount of relative sliding between the cam follower and the valve is minimized, and the side load acting on the valve is reduced.

In addition, since the contacts between the cam follower and the valve alternately move to one side and the other side of the axis of the valve as the valve opens and closes, the pressing force of the cam follower against the valve is always applied to the area near the axis of the valve. The side load acting on the side is further reduced. Moreover, since the axis of the cam is perpendicular to the axis of the valve, the pressing force that the cam follower receives from the camshaft,
The pressure reaction force received from the valve can be canceled out without being offset from each other, and almost no bending load acts on the cam follower.

(3) Embodiment An embodiment of the present invention will be described below with reference to the drawings. In FIG.
A cylinder head 2 is polymerized and bonded to the upper surface of the engine via a gasket 3, and an engine body E is constituted by these components.

The cylinder head 2 is formed with a combustion chamber 5 that faces the top surface of the piston 4 sliding inside the cylinder block 1, and an intake (exhaust) port 6 that opens into the combustion chamber 5. A valve 7 for opening and closing the air port 6 is provided so as to be movable up and down via a valve guide 8. The valve 7 is driven by a valve train 9.

The valve train 9 includes a camshaft 10 rotatably supported by the cylinder head 2 and driven by a crankshaft (not shown), and a camshaft 10 supported by the cylinder head 2 via a support shaft 11 so as to be swingable in the opening/closing direction of the valve 7. The cam follower 12 is compressed between the cylinder head 2 and the retainer 13 at the upper end of the valve 7.
The valve spring 14 biases the valve toward the closing side. The camshaft 10 is arranged above the valve 7 so that the axis X of the camshaft 10 and the axis Y of the valve 7 are perpendicular to each other, and the cam follower 12 has its free end connected to the cam 10a of the camshaft 10 and the axis Y of the valve 7. It is interposed between the upper end surface and the upper end surface. At this time, the upper end of the valve 7 is covered with a cap 15 for adjusting the gap, and in this embodiment, the upper end surface of the valve 7 refers to the upper end surface of the cap 15.

Therefore, when the cam shaft 10 is rotated, the cam 10a
When the peak of the cam 10a presses the cam follower 12, the cam follower 12 swings downward to open the valve 7 against the force of the valve spring 14, and then when it is released from the peak of the cam 10a, the valve 7 opens. It is closed by the force of the valve spring 14 and the cam follower 12 is swung upward. When the cam follower 12 is oscillated in this manner, the free end of the cam follower 12 that contacts the upper end surface of the valve 7 moves in an arc, so that relative sliding occurs at the abutting portions of the cam follower 12 and the valve 7.

In order to reduce the relative sliding amount s as much as possible, the swing center O of the cam follower 12 and the cam follower 12
and the contact point P of the valve 7, as shown in FIG. The cam follower 12 is arranged so that the angle β by which the valve 7 swings upward to the fully closed position C is approximately equal to each other. At that time, valve 7
The axis Y of the valve 7 is divided into two by the relative sliding amount s, that is, the contact point P
Since the valve 7 of the cam follower 12 is arranged so as to move alternately to one side and the other side of the axis Y of the cam follower
A pressing force is always applied to the vicinity of the axis Y of the valve 7, so that the side load acting on the valve 7 is further reduced. Moreover, as mentioned above, the axis Y of the valve 7
Since the axis X of the camshaft 10 is orthogonal to , the pressing force that the cam follower 12 receives from the camshaft 10 is
The pressing reaction force received from the valve 7 can be canceled out without being offset from each other, and almost no bending load acts on the cam follower 12 due to the pressing force and the pressing reaction force.

Next, to explain the operation of this embodiment, the camshaft 1
Since the valve opening force of the camshaft 10 is directly transmitted to the valve 7 via the cam follower 12, the lever ratio of the cam follower 12 is approximately It becomes 1. Therefore, the reciprocating inertial mass of the cam follower 12 is minimized, and the ability of the cam follower 12 to follow the cam 10a is ensured even during high-speed operation of the engine, so that the valve 7 can be opened and closed accurately.

Furthermore, since the virtual curve L of the cam follower 12 swings downward and upward at approximately equal angles α and β from a position A orthogonal to the axis Y of the valve 7 as the valve 7 opens and closes, the cam follower 12 and the valve 7 come into contact with each other. The relative sliding amount s of the valve 7 can be suppressed to a substantially minimum value (approximately half that of the conventional one), and therefore the side load on the valve 7 caused by the relative sliding is significantly reduced, and the cam 10a of the valve 7 is Not only can the followability of the valve guide 8 be further improved, but also the wear of the valve guide 8 that guides the opening/closing operation of the valve 7 can be reduced, and its durability can also be improved.

C. Effects of the Invention As described above, according to the present invention, the valves and the camshafts that drive the valves are arranged so that their axes are perpendicular to each other, and the valves and the camshafts are provided between the valves and the camshafts so as to be able to swing freely relative to the engine body. In a valve train for an internal combustion engine in which a free end of a pivotally supported cam follower is interposed, a virtual straight line connecting the center of swing of the cam follower and a contact point between the cam follower and the valve is orthogonal to the axis of the valve to open and close the valve. Since the cam follower is arranged so that it swings at approximately equal angles in one direction and the other direction, the amount of relative sliding between the cam follower and the valve abutment part is kept to a minimum, and the valve movement caused by that relative sliding is minimized. The side load can be reduced, and the reciprocating inertial mass of the cam follower is therefore small, and the followability of the valve to the camshaft can be greatly improved, resulting in improved high-speed performance and durability of the engine. can contribute greatly.

In particular, the cam follower is arranged so that the contact point between it and the valve alternately moves to one side and the other side of the axis of the valve as the valve opens and closes, so that the pressing force of the cam follower against the valve is always on the same side. Since it is added near the axis of the valve,
The side load acting on the valve can be further reduced. Furthermore, as mentioned above, since the axis of the camshaft is orthogonal to the axis of the valve, it is possible to cancel out the pressing force that the cam follower receives from the camshaft and the pressing reaction force that it receives from the valve without offseting each other. Because of this, almost no bending load acts on the cam follower, which can contribute to reducing the weight and improving the durability of the cam follower.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view showing an embodiment of the present invention;
FIG. 2 is a schematic diagram showing the relative position of the cam follower and the valve. E...engine body, L...virtual straight line, O...cam follower swing center, P...contact, X...camshaft axis, Y...valve axis, α...downward swing angle, β ...Upward swing angle, 1...Cylinder block, 2...Cylinder head, 6...Intake (exhaust) port, 7...Valve, 8...Valve guide, 9...
... Valve gear, 10... Camshaft, 10a... Cam,
12...Cam follower, 14...Valve spring.

Claims (1)

[Claims] 1 The valve 7 and the camshaft 10 that drives it,
The axes Y and X are arranged to be perpendicular to each other, and a free end of a cam follower 12 is interposed between the valve 7 and the camshaft 10, and the free end of the cam follower 12 is pivotally supported on the engine body E. In the valve device, a virtual straight line L connecting the swing center O of the cam follower 12 and the contact point P of the cam follower 12 and the valve 7 moves in one direction and the other direction as the valve 7 opens and closes from a position perpendicular to the axis Y of the valve 7. The cam follower 12 is arranged so that the cam follower 12 swings approximately at equal angles, and so that the contact P moves alternately to one side and the other side of the axis Y of the valve 7 as the valve 7 opens and closes. A valve train for an internal combustion engine.