JP2001129633A - Rocker arm and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high efficiency manufacturing method for a light-weight rocker-arm capable of forming a valve stem guide groove with enough depth precisely and easily. SOLUTION: In the manufacturing method for a rocker arm with press working, a semi-finished product 20C is first produced which is equipped with a pair of side walls 22, a valve stem contact wall 30 connecting both-side walls 22 at one end in a longitudinal direction, and a push-in margin 25 longitudinally protruding at one end of the valve stem contact wall 30. Secondly, the valve stem contact wall 30 is increased in thickness by compressing and pressing the push-in margin 25b of the semi-finished product 20C into the calve stem contacting wall 30. Then, valve stem guide groove 40 is formed by driving a grooving punch underneath the thick valve stem contact wall 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocker arm for opening and closing a valve provided on a cylinder head with rotation of a cam in a valve operating mechanism of an internal combustion engine of a vehicle, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 9 is a sectional view showing a valve train in an internal combustion engine of a vehicle. As shown in the figure, a cam (3) that rotates in conjunction with a crankshaft (2) is provided in the valve mechanism.
A rocker arm (1) for converting the rotational movement of the valve stem into a reciprocating linear movement of a valve stem (5) in a valve (4) such as an intake valve or an exhaust valve is provided.

As shown in FIGS. 9 and 10, the rocker arm (1) has a pair of side walls (1) arranged in parallel.
1) and a valve stem contact wall (12) and a pivot contact wall (13) connecting between one end and the other end in the longitudinal direction of both side walls (11). And both side walls (1
1) A support shaft (8) of a roller (7) is fixed to a shaft fixing hole provided in an intermediate region in the longitudinal direction, and the roller (7) and the cam (3) can make rolling contact. It is configured as follows. Further, on the lower surface side of the pivot contact wall (13) in the rocker arm (1), a pivot engaging concave portion (13a) is formed, and in this concave portion (13a),
The pivot portion (6) fixed to the cylinder head is disposed in the engaged state, and the valve stem contact wall (12)
The tip of the valve stem (5) is arranged in contact with the lower surface of the. A valve stem guide groove (12a) is formed on the lower surface side of the valve stem abutting wall (12), and the distal end of the valve stem (5) is housed in the guide groove (12a). Locking the rocker arm (1) by locking the tip to the groove wall (lower edge of both side walls 11)
However, with the pivot portion (6) side as a fulcrum, the position of the roller supporting shaft (8) is prevented from being displaced in the axial direction.

In such a rocker arm (1), a valve stem guide groove (12a) is formed on the lower surface side of the valve stem contact wall (12), and the inner surface of the guide groove (12a) is connected to the valve stem. (5) It is necessary to form on a predetermined finished surface for smooth sliding contact with it, and high dimensional accuracy is required and the shape of the rocker arm itself is complicated. It has been customary to manufacture by forging using a material such as carbon steel or precision casting such as a lost wax method. However, in forging and precision casting, it is certainly possible to deal with higher precision and more complicated shapes, but the production efficiency is low, and in order to secure a certain rigidity, etc., the weight must be increased. May come.

On the other hand, in the technical field of valve trains in recent years, as the speed and output of an internal combustion engine increase, the weight of the rocker arm itself has been keenly reduced in order to reduce the inertial weight. That is the current situation. For this reason, in recent years, many techniques for manufacturing a rocker arm by pressing a steel plate or the like have been proposed so as to cope with a reduction in the weight of the rocker arm.

[0006]

However, since the rocker arm (1) is required to have high precision in the valve stem guide groove (12a) and the groove finishing treatment as described above, the rocker arm (1) is formed by press molding. When manufacturing an arm, there is a problem that many man-hours are required in high-precision grooving and the like, and the manufacturing becomes difficult.

On the other hand, the present applicant has previously filed Japanese Patent Application No.
No. 6930 proposes a rocker arm manufacturing technique by press working. In this proposed technique, a predetermined valve stem guide groove is formed on the lower surface side of the valve stem contact wall by pressing with a pressing punch, and a highly accurate guide groove can be formed.

However, when the pressing punch is driven into the valve stem abutting wall, a crack may occur in the valve stem abutting wall due to a shearing phenomenon, so that it is difficult to make the guide groove deep. In some cases, there is still room for improvement, for example, the tip of the valve stem may not be stably accommodated in the guide groove.

In the above-mentioned proposed technique, if a thicker material is used, the valve stem guide groove can be formed deeper. However, this increases the thickness of the entire rocker arm, resulting in an increase in weight. Occurs.

According to the present invention, a rocker arm capable of reducing the weight, forming a valve stem guide groove having a sufficient depth with high accuracy and ease, and further efficiently manufacturing the same, and a method of manufacturing the same. The purpose is to provide.

[0011]

In order to achieve the above object, a method for manufacturing a rocker arm according to the first aspect of the present invention is directed to a method for manufacturing a rocker arm, comprising a pair of side walls and a valve stem connecting between one end in the longitudinal direction of the both side walls. A step of obtaining an intermediate product having a tongue-shaped push-in allowance protruding in the longitudinal direction at a longitudinal edge of the valve stem contact wall, and a press-in allowance of the intermediate product. Compression molding so as to be pushed into the inside of the valve stem abutting wall by processing to increase the thickness of the valve stem abutting wall; and forming a valve on the lower surface side of the increased valve stem abutting wall. And forming a stem guide groove.

In the method for manufacturing a rocker arm according to the first aspect of the present invention, the valve stem contact wall is formed into a thick and high strength by compression molding, and then the valve stem guide groove is formed in the contact wall. Therefore, even if the guide groove is formed deeply by pressing or the like, generation of cracks due to a shear phenomenon can be effectively prevented.

Further, since the valve stem guide groove can be formed without any trouble by pressing processing by driving the pressing punch or the like, the guide groove can be accurately formed in accordance with the shape of the pressing punch, and a highly accurate guide groove can be formed. Can be formed.

Also, unlike forging or precision casting using alloy steel, carbon steel, or the like, the rocker arm can be manufactured only by press working using a steel plate as a material, so that the rocker arm itself can be reduced in weight. Production efficiency can be improved.

In the first aspect of the invention, as described above, the valve stem guide groove can be formed with high accuracy by pressing such as driving a groove pressing punch. Therefore, in the first aspect of the present invention, it is preferable that the valve stem guide groove is formed by driving a groove forming pressing punch into the lower surface side of the valve stem contact wall.

In the first aspect of the present invention, it is preferable that the bottom surface of the valve stem guide groove is formed to have a predetermined curved surface simultaneously with the driving of the pressing punch for groove formation. That is, when the rocker arm is assembled to the valve train,
The tip of the valve stem can be smoothly brought into sliding contact with the bottom surface of the guide groove, and the opening and closing operation of the valve can be performed smoothly. Further, since it is not necessary to finish the guide groove bottom surface into a curved surface in a separate step, the curved surface can be formed more efficiently.

On the other hand, the second invention specifies a rocker arm obtained by implementing the first invention. That is, the gist of the rocker arm of the second invention is that manufactured by the rocker arm manufacturing method according to any one of claims 1 to 3.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method of manufacturing a rocker arm according to an embodiment of the present invention will be described in detail according to a manufacturing procedure with reference to the drawings. In the following drawings, the rocker arm (including the intermediate product) is shown in a state in a manufacturing process, that is, a state in which the rocker arm is turned upside down with respect to the actual use state. The “upper side” of the drawing will be described as “lower side” according to the description.

First, as shown in FIG. 1, a predetermined area of a steel sheet is punched out, and arc-shaped convex portions (22a) are integrally formed on both side edges, and a tongue piece projecting forward at a center position of one end edge. To obtain a first intermediate product (20A) integrally formed with the pushing allowance (25).

Next, as shown in FIG. 2, the intermediate region at the other end of the first intermediate product (20A) is recessed by bulging to form a hemispherical pivot engaging concave portion (24). After that, the central region is punched out to form a drum-shaped hole (26) to obtain a second intermediate product (20B).

Subsequently, as shown in FIG. 3, by bending the second intermediate product (20B), a third intermediate product (30B) corresponding to the intermediate product of the present invention is obtained.

The third intermediate product (20C) is formed in a substantially U-shape when viewed from the end face, and has a pair of both side walls (22) opposed to each other, and a lower end of one end of each side wall (22). It has a valve stem contact wall (30) for connecting between them, and a pivot contact wall (23) for connecting between lower ends of the other ends.

In the third intermediate product (20C),
The pushing allowance (25) is arranged on one end edge of the valve stem contact wall (30) so as to protrude along the longitudinal direction. Further, the pivot engagement concave portion (24) is arranged at the center of the lower surface side of the pivot contact wall (23),
The drum-shaped hole (26) is provided between the valve stem contact wall (30) and the pivot contact wall (2) between the pair of side walls (22).
3) and is configured as an opening disposed therebetween.

The third intermediate product (20C) thus obtained
As shown in FIG. 4, the valve stem contact wall (30) of
The fourth intermediate product (20D) is obtained by increasing the thickness by pressing.

That is, both sides (22) of the third intermediate product (20C) are set in a predetermined mold so as to restrain the edge of the valve stem contact wall (30) on the opening (26) side. Then, by pressing the front end surface of the pushing allowance (25) from the front side in the longitudinal direction to the rear, the pushing allowance (2) is obtained.
5) is compression molded in the longitudinal direction so as to be pushed into the valve stem contact wall (30), and the valve stem contact wall (30) is pressed.
To increase the wall thickness.

For reference, in this embodiment,
By this pressing, the valve stem contact wall (30)
Can increase the wall thickness by about 40%.

Next, if necessary, the fourth thickened
The intermediate product (20D) is subjected to a soft annealing treatment to remove the internal stress of the valve stem contact wall (30).

Subsequently, as shown in FIG. 5, a valve stem guide groove (40) is formed on the lower surface side of the valve stem contact wall (30) of the fourth intermediate product (20D) by pressing (coining). Thus, a fifth intermediate product (20E) is obtained.

That is, the inner side, the outer side, and the front end of the two side walls (22) at one end (the end on the valve stem contact side) are set in a predetermined mold so as to be restrained, and pressing for groove formation is performed. The punch is pressed against a predetermined area on the lower surface side of the valve stem contact wall (30), and the lower surface side of the valve stem contact wall (30) is plastically deformed into a shape corresponding to the pressed punch surface. As a result, the lower surface side intermediate region of the valve stem contact wall (30) is concavely deformed upward, and both sides of the concave portion are deformed so as to bulge downward, and the guide walls (41) are provided on both sides. A guide groove (40) having the same is formed.

Further, at the same time as the pressing process for forming a groove, the bottom surface of the guide groove (40) is made to correspond to the driving surface of the pressing punch for forming a groove so that the bottom surface of the guide groove (40) can smoothly slide on the tip of the valve stem. It is formed on a curved surface (42) having a curvature.

Finally, as shown in FIG. 6, holes are formed in both side walls (22) of the fifth intermediate product (20E) in the longitudinal middle portions (portions corresponding to the arc-shaped convex portions 22a) from both sides. Punching is performed to form shaft fixing holes (21) at predetermined positions on both side walls (22) so that their axes coincide with each other.

Thus, the rocker arm (20) according to the present embodiment is manufactured.

As described above, according to the manufacturing method of the present embodiment, the rocker arm (20) is manufactured only by pressing such as outer diameter punching, bending, pressing, and punching. Therefore, unlike manufacturing by forging or precision casting using alloy steel, carbon steel, or the like, it is possible to reduce the weight of the rocker arm (20) itself, and to improve production efficiency and reduce costs. Can be planned.

Further, since the valve stem guide groove (40) is formed by pressing, the guide groove (40) can be accurately formed in accordance with the shape of the groove forming pressing punch, and there is no variation in dimensional accuracy. , A highly accurate guide groove (40) can be formed.

Moreover, the valve stem contact wall (30) is
After forming into a sufficient thickness and high strength by increasing the thickness, the valve stem contact wall (30) is formed by pressing.
Since the guide groove (40) is formed in the groove, even if the deep guide groove (40) is formed, it is possible to effectively prevent the occurrence of cracks due to the shear phenomenon. As described above, the guide groove (40) having a sufficient depth can be formed with high accuracy without any trouble. For example, when the rocker arm (20) is assembled to the valve operating mechanism, the tip of the valve stem is inserted into the guide groove (40). Can be accommodated in a stable state, and the operation reliability can be reliably improved.

Further, since the bottom surface of the guide groove (40) is formed as a curved surface (42) having a predetermined radius of curvature, when the guide groove (40) is assembled to the valve operating mechanism, The tip of the valve stem can be smoothly slid and the opening and closing operation of the valve can be performed smoothly.

In the present embodiment, in particular, the formation of the guide groove (40) and the formation of the curved surface (42) are performed at the same time by driving the pressing punch at the time of the grooving pressing process. Compared to the case of performing in a process, it can be manufactured more efficiently, and furthermore, since low-efficiency machining such as cutting is not used, it can be manufactured more efficiently.

In the above embodiment, the pushing allowance (25) is formed at one end of the valve stem contact wall (30). However, the present invention is not limited to this, and as shown in FIG. Alternatively, a pushing allowance (25) may be formed at the other end edge of the valve stem contact wall (30), and the press allowance (25) may be compression molded so as to be pushed into the valve stem contact wall. Further, as shown in FIG. 10, the valve contact wall (30)
The pressing margin (25) may be formed on both the one end edge and the other end edge, and both the pressing margins (25) may be compression molded so as to be pressed into the inside of the valve contact wall from both sides. In particular, when the compression is performed from both sides, the thickness of the valve stem contact wall (30) can be increased in a well-balanced manner.

In the present invention, needless to say,
The shape of the pushing allowance is not limited to the above.

[0040]

As described above, according to the rocker arm manufacturing method of the first aspect of the present invention, the pushing allowance provided on the valve stem contact wall is pushed into the valve stem contact wall by pressing. Since the valve stem contact wall is formed to be thick and high-strength after compression molding, the guide groove is formed in the contact wall. Cracks due to the phenomenon can be effectively prevented. For this reason, for example, when the valve stem is assembled to the valve operating mechanism, the distal end of the valve stem can be sufficiently accommodated in the guide groove in a stable state, and the operation reliability can be reliably improved. Further, since the guide groove can be formed by pressing processing such as driving of a pressing punch, the guide groove can be formed accurately in accordance with the shape of the pressing punch, and a highly accurate guide groove can be formed. In addition, unlike forging and precision casting, rocker arms can be manufactured only by pressing using steel plates as materials, so that the rocker arms themselves can be reduced in weight, while improving production efficiency and reducing costs. There is an effect that can be.

In the first aspect of the present invention, when the bottom surface of the valve stem guide groove is formed into a predetermined curved surface at the same time as the pressing process for forming the groove, the guide is provided when the rocker arm is assembled to the valve mechanism. The end of the valve stem can be smoothly slid on the bottom of the groove, and the opening and closing operation of the valve can be performed smoothly, and the operation reliability can be further improved, and the curved surface on the bottom of the guide groove can be formed efficiently. There is an advantage that it can be performed well.

According to the second aspect of the invention, since the rocker arm manufactured by the manufacturing method of the first aspect of the invention is specified, the same effect as described above can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first intermediate product in a rocker arm manufacturing method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a second intermediate product in the manufacturing method according to the embodiment.

FIG. 3 is a perspective view showing a third intermediate product in the manufacturing method of the embodiment.

FIG. 4 is a perspective view showing a fourth intermediate product in the manufacturing method according to the embodiment.

FIG. 5 is a perspective view showing a fifth intermediate product in the manufacturing method of the embodiment.

FIG. 6 is a perspective view showing a rocker arm obtained by the manufacturing method of the embodiment.

FIG. 7 is a perspective view showing a third intermediate product in a rocker arm manufacturing method according to a modification of the present invention.

FIG. 8 is a perspective view showing a third intermediate product in a rocker arm manufacturing method according to another modification of the present invention.

FIG. 9 is a cross-sectional view showing a valve mechanism of an internal combustion engine in a conventional vehicle.

FIG. 10 is a sectional view showing a valve stem contact portion of a rocker arm applied to a conventional valve train.

[Explanation of symbols]

 Reference Signs List 20: Rocker arm 20C: Intermediate product (third intermediate product) 22: Side walls 25: Push-in allowance 30: Valve stem contact wall 40: Valve stem guide groove 42: Curved surface (bottom surface)

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yoshio Kawatake 3-3-5 Tenmabashi, Kita-ku, Osaka-shi F-term in Nakanishi Kinzoku Kogyo Co., Ltd. 3G016 BB09 CA04 CA13 EA03 FA00 FA06 FA12 GA00 GA01 4E087 CA31 HA67

Claims (4)

[Claims] 1. A valve stem abutting wall connecting a pair of both side walls and one end in a longitudinal direction of the both side walls, and a longitudinal edge of the valve stem abutting wall has a longitudinal direction. A step of obtaining an intermediate product having a tongue-shaped pushing allowance protruding into the valve stem, and press-forming the pushing allowance of the intermediate product into the inside of the valve stem contact wall by a pressing process. A method for manufacturing a rocker arm, comprising: a step of increasing a thickness of a contact wall; and a step of forming a valve stem guide groove on a lower surface side of the valve stem abutting wall having the increased thickness. 2. The method of manufacturing a rocker arm according to claim 1, wherein the valve stem guide groove is formed by driving a groove pressing punch into the lower surface of the valve stem contact wall. 3. The method for manufacturing a rocker arm according to claim 2, wherein the bottom surface of the valve stem guide groove is formed into a predetermined curved surface simultaneously with the driving of the pressing punch for groove formation. 4. A rocker arm manufactured by the method for manufacturing a rocker arm according to claim 1. Description: