JPH0310683B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of manufacturing an assembly type camshaft used in internal combustion engines and the like.

<Prior Art> A method of manufacturing an assembled camshaft by sintering and fixing assembly parts such as a cam and a journal of a separately manufactured sintered alloy powder molded body to a camshaft of a hollow steel rod is known. At this time, it is well known that if the camshaft and the assembled parts are positioned using hollow pins or spring pins, the pins used for positioning during assembly will serve as oil passages after assembly. However, when using a hollow pin without a slit, if the degree of fit between the hollow pin and the pin hole of the assembled part before sintering is too loose, the pin and the sintered alloy assembly part will not come into close contact and the pin will fall off. There is a risk that the assembly position may shift, and conversely, if it is too tight, there will be a problem that the assembled parts will crack during sintering and become unusable. Even if a spring pin with a slit is used, the pin may lose its elasticity at high temperatures during sintering and fall off, so the problem of misalignment of the assembly position still remains.

<Object of the invention> The present invention attempts to solve the above problem by providing a method in which the hollow pin that determines the position of the sintered metal assembly part with respect to the camshaft of the steel hollow rod does not fall off during sintering. .

<Technical means to achieve the objective> As a technical means to achieve the above objective,
The method of the present invention uses a hollow pin consisting of a slitted upper part and a non-slitted lower part to position the assembled part of the powder compact onto the camshaft of a steel-clad hollow rod. That is, the hollow pin is press-fitted into a pin hole formed in the camshaft, and the upper part is inserted into the pin hole formed in the sintered alloy powder molded body.

Before the assembly parts of the sintered alloy powder molded body are sintered, the lower part of the hollow pin is press-fitted into the camshaft and the upper part snaps into the assembly part, so there is no risk of the hollow pin falling out. The position of the assembled parts will not shift. While the assembly parts of the sintered alloy powder molded body are sintered and fixed to the camshaft of the steel hollow rod, the hollow pin is exposed to high temperature, and the upper part of the hollow pin contracts together with the sintered molded body, but there is a slit. No cracking occurs. At this time, the lower part of the hollow pin pressed by the steel camshaft thermally expands along with the camshaft, but normally there is almost no difference in the coefficient of thermal expansion between the two, so the press-fit state is maintained as it is, so the hollow pin It can be said that it almost never falls out of the pin hole of the camshaft.

<Example> The method of the present invention will be explained based on an example shown in the drawings. The camshaft 10 shown in FIG. 1 is manufactured by the method of the present invention, and includes a camshaft 11 made of a hollow steel rod, a cam 12 made of a sintered alloy, and a journal 1.
Consists of 3. The sintered alloy powder molded body of the cam 12 and the journal 13 is attached to the cam shaft 11 by a hollow pin 14.
and then fixed in that position by sintering. Since the hollow pin 14 communicates with the hollow part of the camshaft 11, it is used together with the hollow part of the camshaft as a passage for lubricating oil.

As shown in FIG. 2, the camshaft 11 is pre-drilled with a pin hole 12 extending from the outer peripheral surface to the inner peripheral surface, and a pin hole 22 is also pre-drilled in the powder molded cam 12 shown by the chain line. camshaft 11
After the cam 12 of the powder molded body is loosely fitted into the cam 12, the pin holes 21 and 22 of both are made to communicate with each other, and the hollow pin 14 is inserted into the pin hole. The inner diameters of the pin holes 21 and 22 are slightly smaller than the outer diameter of the hollow pin 14. There is no slit in the lower part of the hollow pin 14, and a slit extending in the axial direction is present in the upper part. Therefore, the lower part of the hollow pin 14 is press-fitted into the pin hole 21 of the camshaft 11, and the upper part is inserted into the pin hole 22 of the powder molded body. When sintered in this state, the powder compact shrinks and becomes the camshaft shown by the solid line.

As shown in FIG. 3, if the sintering shrinkage rate of the powder molded body of the assembly part is small, the number of axial slits 15 provided at the top of the hollow pin 14 may be just one.
When the sintering shrinkage rate of the powder compact is large, the slits 15 in the axial direction are made into two as shown in FIG. 4, or the slits 15 in the axial direction are made into two as shown in FIG. An arcuate slit 16 is provided perpendicular to the slit 16 to facilitate contraction. When the sintering shrinkage rate of the powder compact is very large, two axial slits 15 are provided as shown in FIG.
A circumferential slit 16 perpendicular to each axial slit is provided to further enhance shrinkability. In order to facilitate press-fitting into the pin hole, it is desirable to provide a tapered portion 17 on the outer periphery of the lower end of the hollow pin 14, as shown in FIG.

Since the lower part of the hollow pin 14 is press-fitted into the pin hole of the camshaft 11, there is no fear that the hollow pin 14 will fall off before sintering. If the coefficient of thermal expansion of the hollow pin 14 is the same as or larger than the coefficient of thermal expansion of the camshaft 11, the press-fit condition will not change even at high temperatures, so there is no fear that the hollow pin 14 will fall off during sintering. An axial slit 15 and a circumferential slit 16 are provided in the upper part of the hollow pin 14 in accordance with the shrinkage rate of the powder molded product, so that the upper part of the hollow pin 14 comes into close contact with the powder molded product and shrinks together. do. Therefore, there is no risk that the powder molded body will crack during sintering.

As shown in FIG. 7, the pin hole 21 of the camshaft 11
is formed in two stages and the inner diameter of the inner stepped hole portion 21a is smaller than the inner diameter of the hollow pin 14. Even if the coefficient of thermal expansion of the hollow pin 14 is smaller than that of the camshaft 11, the It is possible to prevent the hollow pin from falling into the hollow part of the camshaft 11.
Also in this case, the inner diameter of the outer stepped hole portion 21b is made slightly smaller than the outer diameter of the hollow pin 14, as in the previous embodiment.

<Effects of the Invention> As described above, the method of the present invention uses a hollow pin to position an assembly part made of a sintered alloy on the camshaft of a hollow steel rod and then sinter and fix it. is provided only on the upper part that is inserted into the pin hole of the sintered metal assembly part, and there is no slit on the lower part that is inserted into the pin hole of the steel camshaft, so it does not work like a conventional hollow pin without a slit. The sintered alloy assembly parts will not crack during sintering and become unusable, nor will they become plastic and fall off during sintering like spring pins do, and the hollow pin will always fit into the pin hole of the camshaft. . Therefore, the method of the present invention prevents the misalignment and damage of assembled parts that have conventionally occurred during sintering, and has the excellent effect of significantly reducing the occurrence of defective products.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an assembled camshaft manufactured by the method of the present invention, FIG. 2 is a sectional view showing the positioning of the cam in FIG. 1, FIG. 3 is a perspective view showing the hollow pin in FIG. 4 to 6 are perspective views showing different embodiments of the hollow pin, and FIG. 7 is a diagram corresponding to FIG. 2 of another embodiment. In the figure, 10 is a camshaft, 11 is a camshaft, 12 is a cam (assembly part), 14 is a hollow pin,
21 is a cam shaft pin hole, and 22 is a cam pin hole.

Claims (1)

[Scope of Claims] 1. Fitting a powder molded body of assembly parts such as a cam and journal onto a camshaft of a hollow steel rod, and aligning pin holes drilled in the camshaft and the powder molded body, respectively; A method of inserting a hollow pin into the pin hole to determine the position of the powder molded body with respect to the camshaft, and then sintering and fixing the powder molded body to the camshaft, the hollow pin having an upper portion having a slit. and a lower part without a slit, and the hollow pin is inserted into the pin hole such that the upper part is located in the pin hole of the powder compact, and the lower part is located in the pin hole of the camshaft. Manufacturing method of assembled camshaft. 2. The method for manufacturing an assembly type camshaft according to claim 1, wherein the hollow pin comprises an axial slit and an arcuate slit orthogonal to the axial slit at the boundary between the upper and lower parts. 3. The pin hole of the camshaft is formed in two stages, inside and outside, and the diameter of the outer hole that opens on the outer circumferential surface is slightly smaller than the outer diameter of the hollow pin, and the diameter of the inner hole that opens on the inner circumferential surface is smaller than the diameter of the hollow pin. Claim 1 or 2, characterized in that the diameter is equal to or smaller than the inner diameter of
A method for manufacturing an assembly type camshaft as described in .