JPS6264428A - Manufacture of assembly cam shaft - Google Patents

Abstract

PURPOSE:To prevent a crack of a cam frame, etc., by forming a hardened layer on a cam frame surface layer part, also fitting it into a hollow shaft, and subsequently, expanding a diameter of the hollow shaft, and thereafter, grinding the outside periphery of a cam frame and finishing it. CONSTITUTION:A cam frame 3 is formed by forging a steel material, and thereafter, a hardened layer 31 of a roughly uniform depth is formed by hardening on the whole periphery of a surface layer part. Subsequently, the cam frame 3 and a journal 6 are inserted into a prescribed position of a hollow shaft 2, and closed in upper and lower metallic dies 20, 21. In this state, an emulsion liquid, etc. are injected into the hollow shaft 2, and also the emulsion liquid is compressed and pressed. In this case, the hollow shaft 2 contracts as to its overall length and also expands to the outside, the inside peripheral surface of the cam frame 3, the journal frame 6, etc. are brought to a plastic deformation, and a deformation of a cam pfofile is prevented. Subsequently, a cam frame outside periphery 34, etc. are ground and finished, and a cam shaft 1 is obtained. In this way a crack of the cam frame 3 is prevented, and also its finish margein can also be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention uses a hollow tube material as a camshaft of an internal combustion engine, and utilizes tube expansion processing such as bulge processing to form a separate cam portion, shaft end member, etc. Concerning a stuck assembled camshaft.

2. Description of the Related Art A method for manufacturing an assembled camshaft of this type is disclosed in Japanese Patent Application Laid-Open No. 57-149655.

Problems to be Solved by the Invention In the conventional manufacturing method, there was a problem in that the sintered cam piece or the cast iron cam piece broke during pressurization during bulge processing.

In addition, if a cam piece made of forged steel is bulge-joined in an unhardened state or with only the lift part quenched, the cam will fit within the clearance previously provided between the die surface of the bulge mold and the outer periphery of the cam piece. The bridge was enlarged in diameter, which caused the cam profile to collapse.

Another way to solve the problem is to forge a steel material to form a cam piece, harden the cam piece to form a hardened layer of approximately uniform depth all around the surface layer of the cam piece, and then fit it into a hollow shaft. Next, expand the diameter of the hollow shaft and connect the two.
Thereafter, the outer periphery of the cam piece is further ground to give a desired profile, and a predetermined hardened layer is left on the surface layer of the cam piece.

The radial expansion force is alleviated in the non-hardened portion inside the working cam piece, and the cam profile is prevented from being deformed by the radial expansion force in the outer quenched hardened layer.

Example Embodiments of the present invention will be described below based on the drawings.

Fig. 1 shows the cam piece 3, and Fig. 2 shows the assembled camshaft 1 that has been completely connected in the bulge mold. 2 is a hollow shaft such as a steel pipe, 4 and 5 are shaft end members, and 6 is a journal piece. It is.

The cam piece 3 is formed by forging a steel material, and is then subjected to heat treatment such as induction hardening or carburizing hardening to form a hardened layer 31 of approximately uniform depth all around the surface layer of the cam piece.

This cam piece 3 has a substantially desired cam profile formed on its outer periphery 34 by forging, and is provided with a through hole 30 through which the hollow shaft 2 before diameter expansion can be inserted.

The through hole 30 is given a polygonal shape, such as a hexagonal cross section, for the purpose of preventing relative rotation after coupling with the hollow shaft 2.

Next, the assembly of the assembled camshaft 1 will be explained.

First, to explain the bulge mold, the bulge mold is divided into upper and lower parts, 20 is an upper mold, and 21 is a lower mold. The upper and lower molds 20.21 have a mold holder 22.
Received by 23.

The inner peripheries of the upper and lower molds 20 and 21- are carved into the shape of the desired camshaft, and at both ends of the die-cutting are injection nozzles 25 that also serve as a shaft end part 24 and a shaft end part part. are placed facing each other.

The shaft end part 24 and the injection nozzle 25 are designed to be pressed against the hydraulic pressure filling the inner periphery of the hollow shaft 2 by a hydraulic cylinder (not shown). First, the cam piece 3 and the journal piece are inserted into the hollow shaft 20 at a predetermined position, and then the shaft end members 4 and 5 are fitted onto the hollow shaft end.

Then, place this in the bulge mold and close the mold by applying pressure in the direction of the arrow.

Then, with the mold closed, emulsion-1-I was poured into the hollow shaft.
e) and pressurize the emulsion.

Then, as shown in FIG. 2, the hollow shaft 2 contracts in its entire length and expands outward, along the inner peripheral surfaces of the cam piece 3, journal piece 6, shaft end members 4 and 5, and the mold surface of the bulge mold. plastically deforms.

At this time, the cam piece 3 simply increases the outer circumference 34 with respect to the expansion of the diameter of the hollow shaft 2.
Not only is it supported by the bulge mold to prevent its own deformation, but the unquenched part inside the cam piece relieves the expansion force.
The outer hardened layer 31 prevents deformation of the cam profile due to diameter expansion force.

Then, after taking it out from the bulge mold, the cam piece outer periphery 34
Then, the desired camshaft 1 is completed by grinding the journal portion and machining oil holes and the like.

In addition, on the cam piece outer circumference 34 after grinding, a predetermined portion of the hardened layer 31 formed when the cam piece 3 was used as a single unit is left on the entire circumference of the surface layer of the sword piece to increase the durability when the cam shaft is used. . As a result, there is no need to harden the camshaft assembly to the outer periphery of the cam later, and the process becomes more rational.

Effects As described above, according to the present invention, the diameter expansion force is alleviated in the unhardened portion inside the cam piece, and the deformation of the cam profile due to the diameter expansion force is prevented in the outside hardened layer, thereby preventing cracking of the cam piece. It is possible to prevent this and reduce the amount of grinding and finishing allowance for the cam piece.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a plan view of a cam piece. FIG. 2 is a cross-sectional plan view showing the assembled camshaft that has been assembled within the bulge mold. (Explanation of symbols) l...Assembly camshaft. 2...-...Medium
Empty axis. , 3... Cam piece. 31...
... Quenched hardened layer, -334 ... Cam piece outer periphery.

Claims (1)

[Claims] A cam piece 3 is formed by forging a steel material, and the cam piece 3 is hardened to form a hardened layer 31 with a substantially uniform depth all around the surface layer of the cam piece.Then, the cam piece 3 is fitted into the hollow shaft 2, and then the hollow An assembled cam characterized in that the diameter of the shaft 2 is enlarged and the two are joined together, and then the cam piece outer periphery 34 is further ground to give a desired profile, and a predetermined quenched hardened layer 31 is left on the surface layer of the cam piece. How to manufacture the shaft.