Rocker arm and method of manufacturing same

Abstract

A rocker arm 6 that is rockably attached to a cylinder head 1 actuates a valve 4 by means of a guide groove 73b that is formed at an end thereof engaging with an upper end of a valve stem 41, and a roller 8 that is mounted in a roller housing portion 72 of the arm main unit 7 contacting against a cam 31 and rocking. The guide groove 73b is formed by press working ends of the arm main unit 7 in the thickness direction of the plate material to form a pair of walls 73d, and thereafter applying sandwiching pressure in the lateral direction to the walls 73d to increase the height thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative aspects in accordance with the invention will be described in detail with reference to the following figures wherein:

FIG. 1 is a sectional view illustrating a valve gear of an internal combustion engine that applies the rocker arm according to one illustrative aspect;

FIG. 2 is an enlarged view of the principal parts shown in FIG. 1;

FIG. 3 is a side view of the rocker arm shown in FIG. 2;

FIG. 4 is a plane view of the rocker arm shown in FIG. 2;

FIG. 5 is a plane view of an punched material that was formed by punching a plate material to form an arm main unit;

FIG. 6 is a plane view illustrating a state in which the side edges of an punched material are bent upward to form a roller housing portion;

FIG. 7 is a plane view illustrating a state in which a receiving protrusion of a rocking support is further formed at one end;

FIG. 8 is a sectional view illustrating the state of the other end before forming a guide groove in the arm main unit;

FIG. 9 is a sectional view illustrating a method that forms an initial groove at the other end of the arm main unit; and

FIG. 10 is a sectional view illustrating a method that forms a guide groove by applying sandwiching pressure to the initial groove.

Claims

1. A method of manufacturing a rocker arm comprising the following steps, wherein the rocker arm is a cold-formed rocker arm of a cam follower type that is attached to a cylinder head of an internal combustion engine, has a guide groove that accepts a top end of a valve stem of the internal combustion engine, and rocks to actuate a valve of the internal combustion engine: a punching step that punches a plate material into a predetermined shape having a pair of side edges;a press step that forms an initial groove having an opposing pair of guide walls by depressing the punched plate material by a predetermined amount in a thickness direction thereof by pressing a punch against the plate material; anda sandwich pressure step that increases heights of the pair of guide walls by applying sandwiching pressure to the guide walls in a direction from the outside toward the inside using a sandwich pressure punch (the guide groove is defined between the pair of guide walls).

2. The method of manufacturing a rocker arm according to claim 1, wherein in the sandwich pressure step, the punch that is used in the press step is left between the guide walls and the guide walls are clamped between the punch and the sandwich pressure punch.

3. The method of manufacturing a rocker arm according to claim 1, wherein a pair of the sandwich pressure punches is provided and the two respective guide walls are clamped between one of the punches from an external side of the pair of guide walls at substantially the same time.

4. The method of manufacturing a rocker arm according to claim 2, wherein a pair of the sandwich pressure punches is provided and the two respective guide walls are clamped between one of the punches from an external side of the pair of guide walls at substantially the same time.

5. The method of manufacturing a rocker arm according to claim 1, wherein after executing the punching step and before executing the press step, a bending step is executed that bends the side edges of the punched plate material upward.

6. The method of manufacturing a rocker arm according to claim 2, wherein after executing the punching step and before executing the press step, a bending step is executed that bends the side edges of the punched plate material upward.

7. The method of manufacturing a rocker arm according to claim 3, wherein after executing the punching step and before executing the press step, a bending step is executed that bends the side edges of the punched plate material upward.

8. The method of manufacturing a rocker arm according to claim 4, wherein after executing the punching step and before executing the press step, a bending step is executed that bends the side edges of the punched plate material upward.

9. A rocker arm that is a cold-formed rocker arm of a cam follower type that is attached to a cylinder head of an internal combustion engine having a valve stem, comprising the following elements: a metal arm main unit that includes a first edge and a second edge;a rocking support that is formed at the first edge side of the arm main unit; anda pair of guide walls that are formed at the second edge side of the arm main unit (these guide walls are formed in the main unit by pressing a punch against the main unit in the thickness direction thereof to depress the main unit by a predetermined amount to form an initial groove that is surrounded by a pair of walls, and thereafter increasing heights of the walls by applying sandwiching pressure to the walls in a direction from the outside toward the inside using a sandwich pressure punch);and wherein a guide groove that accepts an upper edge of a valve stem of the internal combustion engine is formed between the guide walls, and the arm main unit rocks to actuate a valve of the internal combustion engine.

10. The rocker arm according to claim 9, wherein a pair of retainer walls that are bent upward on an opposite side to the guide walls are formed at a side edge of the arm main unit, and a roller is rotatably mounted between the retainer walls.