JPS6059407B2 - Internal combustion engine valve train - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a valve control device for an internal combustion engine using a rocker arm.

FIGS. 1 and 2 show an example of a rocker shaft type of the so-called O, H, C (overhead camshaft) type valve train in which the camshaft 1 is disposed above the cylinder head. The rocker arm 3 rotatably supported by the rocker shaft 2 has one end 3a in contact with the cam 4,
The other end 3 is brought into contact with the valve stem end 5a of the intake/exhaust valve 5, so that the lift of the cam 4 is transmitted to the intake/exhaust valve 5 at a predetermined rocker ratio.

Conventionally, a separate tip 6 having a semi-cylindrical shape and having excellent wear resistance was fixed to the portion that came into contact with the cam 4 by means such as brazing. Therefore, as the cam 4 rotates, the cam surface 4a and the convex abutting surface 6a slide, producing a large abrasion noise and causing a large friction loss. In addition, since wear is accelerated, the valve opening and closing characteristics tend to change over time, which tends to cause deterioration in engine performance, increase in noise, and the like. This invention was made in view of the above-mentioned drawbacks of the prior art, and is an improvement to internal combustion engines of the type in which a rotatably supported rocker arm contacts a cam and pushes a valve stem through the rocker arm. The purpose of this device is to reduce friction noise and friction loss that occur between a rocker arm and a cam. That is, in the internal combustion engine safety valve device according to the present invention, a tappet having a convex spherical cam contact surface is rotatably disposed at one end of the rocker arm, and the contact point between the cam surface and the tappet is centered on the tappet. It is characterized by being set at a position offset from.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

3 and 4 show the present invention applied to an OHC type valve train (rocker shaft type) similar to the conventional example, in which a rocker arm 12 rotatably supported by a rocker shaft 11 has a cam A tappet 14 is attached to one end 12a of the 13 side.
The other end 12b is adapted to abut against a valve stem end (not shown) via an adjusting screw 23 for adjusting valve clearance, as in the conventional case.

The tappet 14, as shown in FIG. The tappet mounting hole 18 is rotatably fitted into the hole 18, and the opening surface 22 of the tappet mounting hole 18 is formed into a smooth surface so that the seat surface of the seat portion 16 is in contact with the tappet mounting hole 18. In addition, the tappet 14
The cam contact surface 14a of the cam abutment surface 14a is formed into a gently convex spherical surface, and the cam 13 facing this has its cam surface 13a slightly ( As a result, the contact point A between the cam surface 13a and the contact surface 14a is oriented in the axial direction of the camshaft 19 with respect to the center of rotation of the tappet 14. It is set to an offset position. Further, a lubricating oil passage 20 is formed in the rocker arm 12, and lubricating oil is supplied from the lubricating oil passage 21 in the rocker shaft 11 into the tappet mounting hole 18. Therefore, in the above configuration, when the cam 13 is rotationally driven, the tappet 14 rotates as the cam 13 moves.

In other words, avoid contacts of the same part during operation,
By constantly changing the contact surface and making contact in the form of rolling contact, the friction generated between the two is extremely small.
On the other hand, the tappet 14 has a seat portion 16 and a shaft portion 1.
7 makes sliding contact with the rocker arm 12, but since a lubricating oil film made of the lubricating oil supplied from the lubricating oil passage 20 is well maintained here, the friction generated is the same. small. Therefore, the friction noise and friction loss accompanying the rotation of the cam 13 are significantly smaller than those of the conventional cam. The oil film interposed between the seating surface of the tappet 14 and the rocker arm 12 exerts a so-called squeeze effect, causing the cam 13 to lift! The impact applied to the tappet 14 at the time of starting can be alleviated, and the noise caused by the impact can also be reduced. Further, since the tappet 14 can be configured to be sufficiently small, the inertial mass does not increase significantly compared to a conventional rocker arm.
As shown in FIG. 4, it is substantially sufficient for the cam surface 13a of the cam 13 to be tapered only in the cam lift portion excluding the base circle portion. Of course, the entire circumference of the cam 13 including the portion may be formed into a tapered shape.

The present invention is also applicable to other types of 0, H, and C type valve gears, that is, the so-called pivot type in which the valves are opened and closed via a rocker arm that swings with a cam lift of a camshaft as a fulcrum. It goes without saying that it can be done.

As described in detail above, in the valve operating system for an internal combustion engine according to the present invention, friction noise and friction loss generated between the rocker arm and the cam can be significantly reduced.

Furthermore, wear of various parts due to friction is reduced, so desired characteristics can be maintained over a long period of time. Furthermore, since there is an oil film between the tappet and the rocker arm, its squeezing effect can reduce the shock during cam lift.Moreover, since the tappet part is simple, it can be constructed lightweight, reducing the increase in inertial mass. It has the effect of not inviting people.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional valve train, and Figure 2 is its
3 is a sectional view showing the valve train according to the present invention, FIG. 4 is a sectional view taken along the line 1, and 5 is a perspective view of the tappet. . 11...Rocker shaft, 12...Rocker arm,
13...Cam, 14...Tappet, 19...Camshaft, 20...Lubricating oil passage.

Claims (1)

[Claims] 1. In a valve operating system for an internal combustion engine in which a rotatably supported rocker arm contacts a cam and pushes a valve stem through the rocker arm, a tappet equipped with a lubricating oil passage is attached to one end of the rocker arm. A shaft portion of a tappet having a hole and a convex spherical cam contact surface is rotatably fitted into the tappet mounting hole, and the back surface of the tappet is coated with an oil film on the smooth surface around the tappet mounting hole. A valve train for an internal combustion engine, characterized in that the cam contact surface and the tappet are brought into contact with each other through the tappet, and a contact point between the cam contact surface and the tappet is set at a position offset from the center of the tappet.