JPH0533611A - Rocker arm for engine valve system - Google Patents

Abstract

PURPOSE:To provide improved strength and weight reduction by preventing internal defects form being caused by forming the rocker arm of an engine valve system by means of casting. CONSTITUTION:A rocker arm 1 is formed by means of casting, its arm part 1d is formed so that the sectional area of the arm part 1d to the valve contact part 1b side is smaller than the one on the end pivot part 1a, and the center of gravity for the whole area comes to the end pivot part 1a side. Because the rocker arm 1 is formed by means of casting, it is possible to prevent internal defect such as the void around the central part of the arm part 1d, especially around a shaft hole 1e which supports a roller 8 from being produced, and the void from being produced at the shaft hole 1e which is formed by drilling at a successive process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocker arm of an OHC engine valve train, for example, and more particularly to a rocker arm formed by casting.

[0002]

2. Description of the Related Art A conventional rocker arm for an OHC engine valve operating system is, for example, one shown in FIG. O
The HC, end pivot (swinging arm) type rocker arm (101) has an end pivot part (101a) pivotally supported by a spherical head-shaped pivot (103) provided on a cylinder head (102). A valve contact part (102) that is formed at one end and that opens and closes the valve by contacting the engine valve (104)
b) is formed at the other end, connects the end pivot part (101a) and the valve contact part (102b), and has a shaft hole (101c) at approximately the center.
A pair of arm portions (101d) formed by post-processing are formed in the middle portion, and further between the end pivot portion (101a) and the valve contact portion (101), and both arm portions (101d). A roller (105) contacting the cam (106) is provided in the roller housing (101e) between the shaft hole to reduce friction with the cam (106).
It is rotatably supported by a shaft (107) fixed to (101c). The rocker arm is generally formed by precision manufacturing such as die casting or shell molding in order to manufacture the main body at low cost.

[0003]

However, the rocker arm having the roller (105) as described above is not suitable for the roller (10
In order to withstand the load acting on 5), it is necessary to increase the strength and rigidity.In addition, casting molding tends to cause internal defects such as mixing of impurities and voids. It is necessary to take extra safety and take extra wall thickness in the arm part (101d) .If this is done, the weight of the entire rocker arm will increase and the inertial mass during operation will become large, making it difficult to apply for high speed rotation. , It becomes an obstacle to increase the allowable engine speed.

Further, when the rocker arm (101) is formed by casting, as shown in FIG. 7, the end pivot portion (101
a) The material that has flowed in from the valve contact part as shown by the arrow.
Although it flows into (101b), since the cross-sectional area of the central part that pivotally supports the roller (105) of the arm part (101d) is larger than other parts, voids are likely to occur around the shaft hole (101c). ,
In particular, the shaft hole (101) of the arm (101d) that supports the roller (105)
Since stress concentrates on c), strength is reduced and the arm part
There is a problem that an extra wall thickness of (101d) is required, which further promotes weight increase.

In view of the above problems of the prior art, the present invention aims to improve the strength by suppressing the occurrence of internal defects due to casting and to reduce the weight of the rocker arm of the engine valve system. The purpose is to provide.

[0006]

In order to achieve the above object, the device of the present invention has a valve contact portion that can contact an engine valve formed at one end, and an end that is pivotally supported on the cylinder head side. A pivot part is formed at the other end, and a pair of arm parts connecting the valve contact part and the end pivot part are formed in the intermediate part, and a roller that can contact the cam can be rotated between both arm parts. In the rocker arm of the engine valve system pivotally supported by the above, the sectional area of the arm portion is gradually reduced from the pivot portion toward the valve contact portion.

[0007]

In the arm portion of the rocker arm, the cross-sectional area near the valve contact portion is formed smaller than the cross-sectional area near the end pivot portion, so that the center of gravity of the entire body is near the end pivot portion, and at the time of casting the rocker arm, By pouring the material from the end pivot part toward the valve abutting part side, the material is gradually compressed, near the center of the arm part,
In particular, it is possible to suppress the generation of internal defects such as voids around the shaft hole that supports the roller, and it is possible to suppress the generation of voids in the shaft hole that is bored by post-processing.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS. (1) is a rocker arm formed by precision casting, and at one end, a pivot groove that is swingably fitted to a pivot (5) fitted to a cylinder head (2)
An end pivot portion (1a) having (1c) is guided at the other end to the cylinder head (2) so as to be movable up and down and is urged in a valve closing direction by a valve spring (3). ) Valve contact part (1b) that can contact the shaft end of
However, a pair of arm portions (1d) on both sides for connecting the valve contact portion (1b) and the end pivot portion (1a) are formed at the intermediate portion.

A shaft hole (1e) is formed in the middle of the arm portion (1d) by post-processing, and both arm portions (1d) between the valve contact portion (1b) and the end pivot portion (1a) are formed. A roller (8) capable of contacting the cam (9) rotating with the camshaft is provided in the roller housing (6) in the space between the shaft holes (1e).
It is rotatably accommodated by a shaft (7) which is non-rotatably fitted in.

The cam (9) rotates and the ridges (9
When a) contacts the roller (8), the rocker arm
(1) is rotated so that the valve contact portion (1b) swings downward about the end pivot portion (1a) as a fulcrum, and the valve contact portion (1b) rotates the engine valve (4). The valve is opened by pushing against the urging force of the valve spring (3).

The rocker arm (1) is formed so that its width and thickness gradually decrease from the end pivot (1a) toward the valve contact portion (1b) as a whole.
(1d) cross section near the valve contact part (1a) (BB in FIG. 2)
The cross-sectional area (D) of (shown by the cross-sectional line) is the cross-sectional area (E) of the cross-sectional portion near the end pivot part (1a) (shown by the CC cross-sectional line in FIG. 2).
It is smaller, and the center of gravity of the whole is the end pivot part.
(1a) It is formed so as to be closer.

As described above, the arm portion (1d) of the rocker arm (1) is connected to the valve contact portion from the end pivot (1a) side.
When the rocker arm (1) is formed by casting, the material flowing from the sprue is formed from the end pivot (1a) to the arm portion (1d) when the rocker arm (1) is formed by casting so that the cross-sectional area gradually decreases toward the (1b) side. Through the valve abutment part (1b)
Flowing toward the valve abutment portion (1b), the sectional area of the arm portion (1d) becomes smaller toward the valve contact portion (1b). It is possible to suppress the occurrence of internal defects such as voids, and it is possible to suppress the occurrence of voids in the shaft hole (1e) formed by post-processing.

Also, the end pivot (1) of the arm portion (1d)
a) Since the cross-sectional area of the rocker arm (1) is large, the center of gravity of the rocker arm (1) is located near the end pivot (1a), so the inertial weight does not have a large effect on the valve train movement. It can be lowered, the followability with the cam (9) at the time of high speed rotation is improved, and the allowable rotation speed and maximum output of the engine can be increased,
The strength of the arm portion (1d) is improved, the overall shape can be made thinner, and the weight can be reduced.

[0014]

As described above, the present invention has the following effects. (a) Since an internal defect is less likely to occur around the shaft hole that pivotally supports the roller of the arm portion, the strength of the arm portion can be improved. (b) Since the strength of the arm portion is improved, and the cross-sectional area of the arm portion is gradually reduced from the end pivot portion toward the valve contact portion so that the center of gravity is located closer to the pivot portion as a whole, Since the inertial weight during operation can be reduced and the arm can be made thin, the weight of the rocker arm as a whole is reduced, the followability with the cam at high speed rotation is improved, and the allowable engine speed and The maximum output can be increased.

[Brief description of drawings]

FIG. 1 is a schematic view of a mounted state of a rocker arm.

FIG. 2 is a plan view of a rocker arm.

3 is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is a sectional view taken along line BB in FIG.

5 is a cross-sectional view taken along the line CC in FIG.

FIG. 6 is a schematic view of a conventional OHC end pivot type rocker arm in a mounted state.

FIG. 7 is a plan view of a conventional rocker arm.

[Explanation of symbols]

(1) Rocker arm (1a) End pivot part (1b) Valve contact part (1c) Pivot groove (1d) Arm part (1e) Shaft hole (2) Cylinder head (3) Valve spring (4) Engine valve (5) Pivot (6) Roller housing (7) Shaft (8) Roller (9) Cam (9a) Crest

Claims (1)

Claim: What is claimed is: 1. A valve contact portion capable of contacting an engine valve is formed at one end, and an end pivot portion pivotally supported on the cylinder head side is formed at the other end. A pair of arm portions that connect the contact portion and the end pivot portion are formed in the intermediate portion, and between the both arm portions, a roller that is capable of contacting the cam is rotatably supported and rotatably supported. A rocker arm for an engine valve system, characterized in that a cross-sectional area of the rocker arm is gradually reduced from a pivot part toward a valve contact part.