JPH0534098B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a method of manufacturing a camshaft for an internal combustion engine.

B. PRIOR ART Conventional camshafts for internal combustion engines include those that are integrally formed by casting, those that are formed by combining individually shaped component parts by casting, and those that are integrally constructed by welding or the like. Camshafts manufactured by these methods are heavy and have high manufacturing costs, so they use a single metal tube.
A method of simultaneously molding the cam part, journal part, and shaft part by bulge molding (Japanese Patent Application Laid-Open No.
58−98608) has been proposed.

As shown in Figs. 3 and 4, this method involves placing a metal tube b in a divisible mold a having a recess corresponding to the external shape of the camshaft to be molded, and inserting an inlet c into the metal tube b. The pressurizing fluid d is introduced into the hollow part of the metal tube b and then pressurized. As a result, as shown in FIG. 4, a camshaft is obtained in which a cam portion, a journal portion, and a shaft portion that bulge into a predetermined shape are formed along the recessed portion of the mold a.

The camshaft thus molded is subjected to a predetermined heat treatment after molding. For example, portions where surface hardening is required, such as the cam portion and the journal portion, are irradiated with a laser beam or an electron beam to perform partial heat treatment.

c. Problems to be Solved by the Invention Camshafts formed by bulge forming as described above have a drawback in that the tube thickness of the cam surface, which is the bulging portion, is thin. There is also the problem that deformation and bending occur due to heat treatment. Furthermore, when irradiating a laser beam, the surfaces of the cam part, journal part, shaft part, etc. are not on the same plane, so it is difficult to focus the laser beam, so the intensity is not constant and a homogeneous product cannot be obtained. The problem is that there is no.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a camshaft which eliminates the problems of the conventional method.

d Means for Solving the Problems The present invention achieves the above object by the means described below.

That is, in the case of manufacturing a camshaft in which a cam part, a journal part, etc. are integrally press-molded using a tube material, the present invention applies the above-mentioned molding to the parts of the camshaft to be partially hardened, such as the cam part and journal part. A camshaft is characterized in that the camshaft is subjected to this hardening treatment prior to the hardening process, and then a pressurized fluid is introduced into the inside of the camshaft and pressurized to mainly deform the parts other than the hardened part to form the camshaft. This is the manufacturing method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1, 1 shows a part of the raw material pipe before the bulge forming, and FIG. 2 shows the pipe after the same forming. Prior to forming the pipe 1, the pipe 1 is set in a laser hardening device (not shown).
The heat-treated portion 3 on the surface that is to become the cam portion 2 and the heat-treated portion 5 on the portion that is to become the journal portion 4 are irradiated with a laser beam to heat them, and then rapidly cooled and subjected to surface hardening treatment.

Next, as in the conventional method, as shown in FIG. 3, the raw material pipe 1 which has been treated in the same manner as the metal pipe b is set in the mold a, and the inside of the raw material pipe 1 is pressurized from the inlet c. A fluid is introduced and pressurized to form a predetermined shape.

The parts other than the parts that have been surface hardened in advance, such as the cam part 2 and the journal part 4, are mainly involved in the deformation, and are deformed as shown in Figure 4, and in detail, in the state shown in Figure 2. The camshaft is formed.

e Effects As described above, according to the method of the present invention, when forming a camshaft from a single pipe by bulge processing, the parts to be surface hardened, such as the cam part and the journal part, are not affected by the forming process. Since the surface is first hardened by heat treatment using a laser beam or the like, and then the molding process is performed, the bending, deformation, etc. of the product caused by the heat treatment can be corrected. Furthermore, since the cam part is hardened in advance, it is possible to prevent the surface of the cam part from becoming thinner during molding. Furthermore, since the laser beam is irradiated onto the same surface before molding, there is no problem such as difficulty in focusing the laser beam or inconsistency due to differences in the unevenness of the surfaces of the cam part and journal part. The problem of uneven quality caused by this can also be resolved.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can also be applied to other molding methods and other partial hardening treatment methods in which a partial hardening treatment is performed on the camshaft prior to press molding. Needless to say.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of the method for manufacturing a camshaft according to the present invention, FIG. 1 is an explanatory diagram of the processing procedure before molding, and FIG. 2 is an explanatory diagram of the process after molding,
FIGS. 3 and 4 are explanatory diagrams of the molding procedure performed using a mold. DESCRIPTION OF SYMBOLS 1...Material pipe, 2...Cam part, 3...Heat-treated part on the cam part, 4...Journal part, 5...
The heat treated area on the journal part.

Claims (1)

[Claims] 1. When manufacturing a camshaft in which a cam part, a journal part, etc. are integrally press-molded using a tube material, the parts to be partially hardened, such as the cam part and journal part, of the camshaft, prior to said molding, After this hardening treatment, pressurized fluid is introduced and pressurized inside the camshaft,
A method for manufacturing a camshaft, characterized in that the camshaft is formed by mainly deforming parts other than the hardened part.