JP2807932B2 - Rocker arm for engine valve system - Google Patents

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, for example, an OHC engine valve train, and more particularly to a rocker arm formed by casting.

[0002]

2. Description of the Related Art As a conventional rocker arm of an OHC engine valve train, there is, for example, one shown in FIG. O
HC, end pivot (swinging arm) type rocker arm (101) has an end pivot portion (101a) pivotally supported by a ball-shaped pivot (103) provided on a cylinder head (102) so as to be swingable. A valve contact portion (102) formed at one end and in contact with the engine valve (104) to open and close the valve.
b) is formed at the other end, and connects the end pivot part (101a) and the valve contact part (102b), and the shaft hole (101c) is almost at the center.
A pair of arms (101d) formed by post-processing are formed in the middle part, and between the end pivot part (101a) and the valve contact part (101), and both arm parts (101d) A roller (105) abutting on the cam (106) has a shaft hole in the roller storage portion (101e) between the rollers 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
5) It is necessary to increase the strength and rigidity so that it can withstand the load acting on 5) .In addition, since casting tends to cause internal defects such as mixing of impurities and voids, it is necessary to further increase the strength of the material by design. It is necessary to take extra safety and take extra thickness of the arm part (101d), and if this is done, the weight of the entire rocker arm will increase, and the inertial mass during operation will increase, making it difficult to apply to high-speed rotation. However, this becomes an obstacle in increasing the allowable rotation speed of the engine.

Further, when the rocker arm (101) is formed by casting, as shown in FIG.
a) The material that has flowed in from the valve abutment as indicated by the arrow
(101b), but since the cross-sectional area of the central part of the arm (101d) pivotally supporting the roller (105) is larger than other parts, voids are likely to be generated around the shaft hole (101c). ,
In particular, the shaft hole (101) of the arm (101d) supporting the roller (105)
In c), the concentration of stress causes a decrease in strength,
There is a problem that an extra thickness of (101d) is required, and the weight is further increased.

The present invention has been made in consideration of the above-mentioned problems of the prior art, and has been developed in consideration of the above-described problems, thereby suppressing the occurrence of internal defects due to casting, thereby improving strength and reducing the weight of an engine valve train rocker arm. The purpose is to provide.

[0006]

In order to achieve the above object, the present invention is directed to an apparatus having a valve contact portion formed at one end and capable of contacting an engine valve, and an end pivotally supported on a cylinder head side. A pivot portion is formed at the other end, and a pair of arm portions connecting the valve contact portion and the end pivot portion are formed at an intermediate portion, and a roller capable of contacting the cam can be rotated between both arm portions. In the rocker arm of the engine valve train, which is pivotally supported, the cross-sectional area of the arm portion is gradually reduced from the pivot portion toward the valve contact portion.

[0007]

Since the cross-sectional area of the arm portion of the rocker arm near the valve contact portion is smaller than the cross-sectional area of the rocker arm near the end pivot portion, the center of gravity of the entire arm is closer to the end pivot portion, and at the time of casting the rocker arm, The material is gradually compressed by flowing the material from the end pivot part toward the valve contact part side, near the center of the arm part,
In particular, the generation of internal defects such as voids around the shaft hole supporting the roller can be suppressed, and the generation of voids in the shaft hole formed by post-processing can be suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. (1) is a rocker arm formed by precision casting. One end of the rocker arm is pivotally fitted to a pivot (5) fitted to a cylinder head (2).
An end pivot portion (1a) having an end (1c) is guided at the other end thereof in a vertically movable manner by a cylinder head (2), and is urged in a valve closing direction by a valve spring (3). ) Valve contact part (1b) that can contact the shaft end
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 in the intermediate portion, respectively.

A shaft hole (1e) is formed substantially at 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) that can abut on a cam (9) that rotates together with the camshaft has a shaft hole (1e) in a roller storage portion (6) in the space between (1) and (2).
It is rotatably housed by a shaft (7) which is non-rotatably fitted into the shaft.

[0010] The cam (9) rotates, and the ridge (9)
a) comes into contact with the roller (8), so that the rocker arm
(1) is rotated about the end pivot portion (1a) as a fulcrum so that the valve contact portion (1b) swings downward, and the engine valve (4) is rotated by the valve contact portion (1b). The valve is opened by being pushed 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) A cross-sectional area near the valve contact portion (1a) (BB in FIG. 2)
The cross-sectional area (D) of the section (shown by the cross-sectional line) is closer to the end pivot portion (1a) (E).
Smaller and the overall center of gravity is at the end pivot
(1a) It is formed so as to be closer.

As described above, the arm portion (1d) of the rocker arm (1) is moved from the end pivot (1a) side to the valve contact portion.
When the rocker arm (1) is formed by casting by forming the sectional area so as to gradually decrease toward the (1b) side, the material that has flowed from the gate is moved from the end pivot (1a) to the arm portion (1d). Via the valve contact part (1b)
, And at this time, the cross-sectional area of the arm (1d) becomes smaller toward the valve contact portion (1b), so that the material is compressed and the vicinity of the center of the arm (1d), especially around the shaft hole (1e) In addition, the occurrence of internal defects such as voids can be suppressed, and the occurrence of voids in the shaft hole (1e) formed by post-processing can be suppressed.

Further, the end pivot (1) of the arm (1d) is provided.
a) Since the overall cross-sectional area is large, the entire center of gravity of the rocker arm (1) is located near the end pivot (1a), so the influence of the inertial weight on the valve train motion is not greatly affected. It is possible to increase the allowable rotation speed and the maximum output of the engine while improving the followability with the cam (9) during high-speed rotation,
The strength of the arm (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 a shaft hole pivotally supporting the roller of the arm portion, the strength of the arm portion can be improved. (b) As the strength of the arm is improved, and the cross-sectional area of the arm is gradually reduced from the end pivot to the valve contact portion so that the center of gravity is positioned closer to the pivot as a whole shape. The inertial weight during operation can be reduced, and the arm section can be made thinner, so the weight of the entire rocker arm is reduced, and the followability with the cam during high-speed rotation is improved, and the allowable rotation speed of the engine and The maximum output can be increased.

[Brief description of the 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.

FIG. 3 is a sectional view taken along line AA in FIG. 2;

FIG. 4 is a sectional view taken along line BB in FIG. 2;

FIG. 5 is a sectional view taken along line CC in FIG. 2;

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

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 storage (7) Shaft (8) Roller (9) Cam (9a) Crest

Claims (1)

(57) [Claims] 1. A valve contact portion capable of contacting an engine valve is formed at one end, an end pivot portion pivotally supported on a cylinder head side is formed at the other end, and the valve contact portion and the end pivot are formed. In a rocker arm of an engine valve system, a pair of arms that are connected to each other are formed at an intermediate portion and a roller that can contact a cam is rotatably supported between the two arms. A rocker arm for an engine valve operating system, wherein a sectional area is gradually reduced from a pivot portion to a valve contact portion.