JPH04262007A - Locker arm of overhead cam type engine - Google Patents

Abstract

PURPOSE:To prevent the speedy abrasion of the slide contact part between a cam engagement part and a cam because of the error generated at each part of a valve system, and sufficiently secure the abrasion resistance effect when the cam engagement part is constituted of ceramics material so as to improve abrasion resistance. CONSTITUTION:When a locker arm 12 is constituted of a locker arm body 13 supported on a locker shaft 10 and a cam engagement part 17 which is cam-engaged with the cam 24 of a camshaft 22, the cam engagement part 17 is pivotally supported in turnable manner around the axis center 18, on the locker arm body 13, and when the cam engagement part 17 and the cam 24 are cam-engaged, the cam engagement part 17 is turned so that the surfaces 17a and 24a of the cam engagement part 17 and the cam 24 surface-contact, viewed from the longitudinal direction of the axis center 18. Further, the cam engagement part 17 uses the ceramic material in a sintered state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a rocker arm for an overhead cam type engine.

0002

2. Description of the Related Art Conventionally, there is a valve operating mechanism for an overhead cam type engine as disclosed in, for example, Japanese Patent Laid-Open No. 2-123206. According to this, the rocker arm is rotatably supported on the cylinder head by the rocker shaft. This rocker arm includes a rocker arm body that is supported by the rocker shaft and is rotatable around the axis of the rocker shaft, and a rocker arm body that is supported by the rotating end of the rocker arm body and engaged with the cam of the camshaft. The camshaft is operatively connected to the crankshaft. The rocker arm rotates in conjunction with the rotation of the crankshaft through the cam engagement, thereby opening and closing the intake valve and the exhaust valve as appropriate.

0003

[Problems to be Solved by the Invention] However, the above-mentioned valve train mechanism has the following problems. That is, firstly, the parallelism of the rocker shaft and the camshaft, the straightness of the rocker shaft itself, and furthermore, the parallelism of each surface at the sliding contact part between the cam engaging part and the cam and the bearing part of the same rocker arm. Errors occur in each case. Therefore, due to these accumulated tolerances, the respective surfaces of the sliding contact portion between the cam engaging portion and the cam may be inclined to each other, and the surface pressure of this sliding contact portion may become partially large. When this occurs, there is a problem in that wear progresses quickly and the life of the engine is shortened. In addition, in the above-mentioned valve train mechanism, lubricating oil is supplied to the above-mentioned sliding contact parts in order to prevent the above-mentioned wear, but this is especially true when this type of engine is used as a drive source for a gas heat pump for air conditioning. Since the lubricating oil is used exclusively at low speed rotation, the thickness of the lubricating oil film on the sliding contact portion becomes thinner, which causes the problem that the wear progresses more markedly.

Secondly, in view of the above points, in order to improve the wear resistance, it is conceivable to form the cam engaging part by firing a ceramic material and use it by polishing it with a grindstone. . However, in this case, the surface roughness of the polishing wheel is transferred to the cam engaging part to be polished, which causes the cam to wear out. Therefore, even if the cam engaging part is simply molded from a ceramic material, There is a problem that the effect of wear cannot be sufficiently obtained.

[0005]

OBJECTS OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances. Firstly, due to errors occurring in various parts of the valve mechanism, sliding contact between the cam engaging portion and the cam is prevented. Second, when the cam engaging part is molded with ceramic material to improve wear resistance, it is possible to sufficiently obtain this wear resistance effect. The purpose is to

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the first invention provides a method for moving the cam shaft around an axis substantially perpendicular to a virtual plane including the sliding contact portion between the cam engaging portion and the cam, and the axial center of the camshaft. The cam engaging portion is pivotally supported on the rocker arm body so that it can rotate freely. Further, in the second invention, the cam engaging portion is molded from a ceramic material, and the shape of the surface at the sliding contact portion with the cam is the same shape as the ceramic material is fired in the mold. .

[0007]

[Operation] The operation of the above configuration is as follows. According to the first invention, the sliding contact portion 25 between the cam engaging portion 17 and the cam 24 and the axis 23 of the camshaft 22 are rotatable about the axis 18 that is substantially perpendicular to the virtual plane 26 . The cam engaging portion 17 is pivotally supported on the rocker arm main body 13 so that the cam engaging portion 17 is shown as (arrow B in each figure). Therefore, due to errors occurring in each part of the valve mechanism 8, the cam engaging portion 17 and the cam 2
Even if the respective surfaces 17a and 24a of the sliding contact portion 25 with 4 are inclined to each other when viewed from the longitudinal direction of the axis 18,
At this time, the cam engaging portion 17 rotates around the axis 18, and the two surfaces 17a and 24a come into surface contact with each other. Therefore, the surface pressure of each part of the sliding contact portion 25 is equalized.

Further, according to the second invention, the cam engaging portion 1
7 is molded from a ceramic material, and the shape is the same as that of the ceramic material fired in the mold.In other words, the cam engaging portion 17 is formed as it is after firing. The surface roughness of the grinding wheel due to polishing is not transferred to 17, and therefore, the cam engaging portion 17 having a smooth surface on the inner surface of the mold is used as is, and the cam engaging portion 17 and the cam 24 The cam engages smoothly.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings. In the figure, code 1 is a gas heat pump for air conditioning (G
．． H. P. This engine 1 has a cylinder 2, a piston 3, and a cylinder head 4. An intake port 5 is formed in the cylinder head 4, and an intake valve 6 for opening and closing the intake port 5 is provided. This intake valve 6 is biased by a spring 7 in a direction to close the intake port 5, and is provided with a valve operating mechanism 8 that opens this intake valve 6.

The valve mechanism 8 has a rocker shaft 10, which is supported by a bearing and is rotatable about its axis 11. Further, a rocker arm 12 is attached to the rocker shaft 10 in the shape of a bell crank. This rocker arm 12
The rocker arm body 13 is supported by the rocker shaft 10 and is rotatable together with the rocker shaft 10 as shown by arrow A in FIG. A bolt 14 is screwed to the left rotational end of the rocker arm body 13 (referring to the direction as viewed in FIG. It is joined. In addition, the same rocker arm body 13
There is a pivot shaft 16 protruding rightward on the right rotation end side of the
is integrally molded, and a cam engaging portion 17 is pivotally supported on this pivot shaft 16, and the cam engaging portion 17 is rotatable around the axis 18 of the same pivot shaft 16 (see each figure). Middle arrow B). 1
9 is a washer, and 20 is a circlip.

On the other hand, 22 is a camshaft made of aluminum or steel that is arranged parallel to the rocker shaft 10, and this camshaft 22 is supported by a bearing and is rotatable around its axis 23. There is. Then, the cam engaging portion 1
The lower rotating end of 7 is cam-engaged with the cam 24 of the camshaft 22. The camshaft 22 is interlocked with the crankshaft, and through the cam engagement, the rocker arm 12 rotates in conjunction with the rotation of the crankshaft, thereby resisting the spring 7 and causing the intake valve 6 is operated to open the valve.

In the above case, as shown in FIG.
The axis 18 of 6 is the sliding contact portion 2 of the cam engaging portion 17 and the cam 24.
5 and the axis 23 of the camshaft 22.
It is said that it is almost perpendicular to 6. For this reason, the valve mechanism 8
Even if the surfaces 17a and 24a of the sliding contact portion 25 between the cam engaging portion 17 and the cam 24 tend to tilt toward each other when viewed from the longitudinal direction of the shaft center 18 due to errors occurring in each portion, in this case, the cam The engaging portion 17 rotates around the axis 18, and the surfaces 17a and 24a come into surface contact with each other. Therefore, since the surface pressure of each part of the sliding contact portion 25 is approximately equal, wear can be suppressed to a low level compared to the conventional case where the surface pressure is partially large.

The cam engaging portion 17 includes a cam engaging portion main body 28 made of aluminum or cast iron which is pivotally supported on the pivot shaft 16, and a ceramic material attached to the rotating end of the cam engaging portion main body 28. The tip 29 is attached to the cam engaging part main body 28 by a casting when the cam engaging part main body 28 is cast. Then, the surface 17a of the sliding contact portion 25 is formed on this chip 29.

In the above case, the tip 29 of the cam engaging portion 17
The shape was the same as the ceramic material was fired in the mold, that is, the cam engaging part 17 was made as it was after firing, so the surface 1 of the cam engaging part 17
The surface roughness of the grinding wheel during polishing is not transferred to 7a, and the cam engaging portion 1 has a smooth inner surface of the mold.
7 will be molded. Therefore, this cam engaging portion 1
7 and the cam 24 are smoothly engaged with each other, so that the wear-resistant effect of the cam engaging portion 17 formed of a ceramic material can be sufficiently obtained. Although the above is based on the illustrated example, the above embodiment may also be applied to an exhaust valve provided in the cylinder head 4.

[0015]

[Effects of the Invention] According to the first invention, it is possible to freely rotate around an axis that is substantially perpendicular to a virtual plane that includes the sliding contact portion between the cam engaging portion and the cam and the axis of the camshaft. Since the cam engaging part is pivotally supported on the rocker arm body, due to errors occurring in various parts of the valve mechanism, each surface of the sliding contact part between the cam engaging part and the cam is Even if they are inclined to each other when viewed from the direction, the cam engaging portion rotates around the axis and the two surfaces come into surface contact with each other. Therefore, since the surface pressure of each part of the sliding contact portion is equalized, the wear of the sliding contact portion can be suppressed to a low level compared to the conventional case where the surface pressure was locally large.

Further, according to the second invention, the shape of the surface of the cam engaging portion at the sliding contact portion with the cam is the same shape as the ceramic material is fired in the mold, that is, after firing. Since the cam-engaging part was made as it is, the surface roughness of the grinding wheel due to polishing is not transferred to this cam-engaging part, and therefore a cam-engaging part with a smooth surface on the inner surface of the mold is formed. The Rukoto. As a result, the cam engaging portion and the cam are smoothly engaged with each other, and the wear resistance effect of the cam engaging portion molded from a ceramic material can be sufficiently obtained. These inventions are extremely beneficial, particularly in terms of extending the lifespan of gas heat pump engines, which are used at low speeds and are subject to severe wear on their sliding parts.

[Brief explanation of the drawing]

FIG. 1 is an overall side sectional view.

FIG. 2 is a view taken along the line 2-2 in FIG. 1;

[Explanation of symbols]

1 Engine 8 Valve mechanism 10 Rocker shaft 11 Axial center 12 Rocker arm 13 Rocker arm body 16 Pivot axis 17 Cam engagement part 17a side 18 Axial center 22 Camshaft 23 Axial center 24 Cam 24a side 25 Sliding contact part 26 Virtual plane

Claims (2)

[Claims] 1. A rocker arm body supported by a rocker shaft and rotatable around the axis of the rocker shaft, and a cam engaging portion supported at a rotating end of the rocker arm body, A rocker arm for an overhead cam type engine in which the cam engaging portion engages with a cam of a camshaft, the rocker arm including a sliding contact portion between the cam engaging portion and the cam, and an axis of the camshaft. A rocker arm for an overhead cam type engine in which a cam engaging portion is pivoted to a rocker arm body so as to be rotatable around an axis substantially perpendicular to an imaginary plane. 2. A rocker arm body supported by a rocker shaft and rotatable around the axis of the rocker shaft, and a cam engaging portion supported at a rotating end of the rocker arm body, In a rocker arm for an overhead cam type engine in which the cam engaging portion engages with the cam of the camshaft, the cam engaging portion is molded from a ceramic material, and the surface of the sliding contact portion with the cam is molded from a ceramic material. A rocker arm for an overhead cam engine that has the same shape as the ceramic material fired in the mold.