JPH0323601B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a camshaft that is a solid or hollow steel shaft, and a set of separately manufactured sintered cam lobes, journals, gears, etc. on the outside of the camshaft. The present invention relates to a method for manufacturing an assembly type camshaft in which attached parts are assembled and integrated by liquid phase sintering.

[Prior art] Conventionally, when this type of assembly parts were joined to a camshaft by liquid phase sintering, the assembly positions of the assembly parts varied from part to part, and the assembly dimensions were not uniform. Ta.

The inventors of the present invention have conducted extensive research to find out the cause of this problem, and have found that the uneven assembly dimensions are due to the following causes. That is, Figures 1 and 2
As shown in the figure, when the cam lobe 10, which is a sintered assembly part, is fitted and assembled onto the camshaft 11 and put into a sintering furnace and subjected to liquid phase sintering, the cam lobe 10 is attached to the camshaft 11. It has become clear that the dimensions of the assembled parts after sintering are not uniform because the cam lobe 10 contracts around the position where joining was first started, and this position is not constant for each cam lobe 10.

For example, when the cam lobe 10 is assembled to the camshaft 11, as shown in FIG.
If the cam lobe 10 is first joined to the camshaft 11 at a point, after liquid phase sintering, the cam lobe 10 will contract around this point A as shown by the imaginary line in FIG. If the cam lobe 10 is first joined to the cam shaft 11, the cam lobe 10 will contract around point B after liquid phase sintering, as shown by the imaginary line in FIG. The above shrinkage phenomenon occurs not only in the cam lobe but also in other assembled parts such as sintered journals and gears. Therefore, the position of the assembled parts relative to the camshaft after liquid phase sintering changes depending on the initial joining point and is not constant.

The inventors of the present invention have focused on the fact that the above-mentioned drawbacks can be solved by actively creating the joining starting point of the assembled parts at a desired position by utilizing the above-mentioned shrinkage characteristics of the assembled parts. The invention was completed.

[Object of the invention] The present invention provides a method for assembling parts such as sintered cam lobes, journals, and gears to be joined at predetermined positions on a camshaft.
An object of the present invention is to provide a method for manufacturing a camshaft with uniform assembly dimensions.

[Structure of the Invention] The method of manufacturing a camshaft according to the present invention provides a method of manufacturing a camshaft by forming a part of the inner circumferential surface of a fitting hole of a sintered assembly part to be fitted and joined to a camshaft approximately at the outer diameter of the camshaft. After forming camshaft circumferential parts with equal inner diameters and bringing only the camshaft circumferential parts into contact with the camshaft, the sintered assembly parts are liquid-phase sintered and joined to the camshaft. It is characterized by

At this time, the gap between the maximum inner diameter of the fitting hole of the assembled part before sintering and the outer diameter of the camshaft is set to 0.3 in order to improve the degree of adhesion between the camshaft and the assembled part after liquid phase sintering.
It is desirable to keep it below mm.

Further, the circumferential surface of the camshaft circumferential portion of the assembly part is desirably formed parallel to the outer circumferential surface of the camshaft in order to maintain stability during assembly.

[Example] Next, an example of the present invention will be described in detail based on the drawings.

FIG. 6 is a longitudinal cross-sectional view of a cam lobe and a cam shaft joined together in the method of manufacturing a camshaft according to the first embodiment of the present invention. The characteristic feature of the first embodiment is that the inner circumferential surface of the fitting hole 12 of the cam lobe 10 is tapered to form only the left end of the fitting hole 12 as a cam shaft circumferential part, and the maximum inner diameter of the fitting hole 12 is The gap t between the inner diameter of the right end and the outer diameter of the camshaft 11 is the average shrinkage amount of the cam lobe 10. The reason is that it is 0.3mm or less. Here, the camshaft circumferential portion has an inner diameter approximately equal to the outer diameter of the camshaft 11.

If the cam lobe 10 having such a configuration is fitted to the camshaft 11 and the left end of the fitting hole 12 is aligned with a predetermined position of the camshaft 11, the left end of the fitting hole 12, which is the camshaft circumferential contact area, Only the camshaft 11 contacts the camshaft 11. Next, if liquid phase sintering is performed in this state, this fitting hole 12
Since the cam lobe 10 contracts in a fixed direction with respect to the left end of the cam lobe 10, the assembled dimensions of the cam lobe 10 do not always change and become uniform. At the same time, by setting the gap t between the inner diameter of the right end of the fitting hole 12 and the outer diameter of the camshaft 11 to 0.3 mm or less, the cam lobe 10 can be removed after liquid phase sintering.
The camshaft 11 and the camshaft 11 are tightly joined to each other, and a decrease in joint strength due to the provision of the camshaft circumferential portion in the fitting hole 12 can be prevented.

FIG. 7 is a longitudinal sectional view of a cam lobe and a camshaft joined together in a method of manufacturing a camshaft according to a second embodiment of the present invention. The characteristic feature of the second embodiment is that, like the first embodiment, the inner peripheral surface of the fitting hole 12 of the cam lobe 10 is tapered, and only the left end portion of the fitting hole 12 is formed as a camshaft circumferential part. In addition, the circumferential surface of the camshaft circumferential portion is formed parallel to the outer circumferential surface of the camshaft 11.

After the cam lobe 10 having such a configuration matches a predetermined position on the camshaft 11, it is stably held at a predetermined position on the camshaft 11 until it is liquid-phase sintered.

FIG. 8 is a longitudinal sectional view of a cam lobe and a cam shaft joined together in a method for manufacturing a camshaft according to a third embodiment of the present invention. The characteristic feature of the third embodiment is that the fitting hole 12 of the cam lobe 10 is shaped like a drum, and only the center portion of the fitting hole 12 is formed as a circumferential portion of the camshaft.

If the cam lobe 10 having such a structure is liquid-phase sintered with its center position aligned with the predetermined position of the camshaft 11, the assembled dimensions of the cam lobe 10 will not change at all times, as in the first embodiment. It will be like that.

FIG. 9 is a longitudinal sectional view of a cam lobe and a camshaft joined together in a method of manufacturing a camshaft according to a fourth embodiment of the present invention. The characteristic feature of the fourth embodiment is that, like the third embodiment, the fitting hole 12 of the cam lobe 10 is shaped like a drum, and only the center portion of the fitting hole 12 is formed as a circumferential portion of the camshaft. Furthermore, the circumferential surface of this camshaft circumferential portion is formed parallel to the outer circumferential surface of the camshaft 11.

After the cam lobe 10 having such a configuration matches the predetermined position of the camshaft 11 as in the second embodiment,
It is stably held at a predetermined position on the camshaft 11 until liquid phase sintering.

Although a cam lobe is shown as an example of the above-mentioned sintered assembly part, other sintered assembly parts such as journals and gears can be used in the same manner.

[Effects of the Invention] As described above, according to the present invention, a camshaft circumferential contact portion is formed on a part of the inner circumferential surface of a fitting hole of a sintered assembly part that fits into a camshaft. After bringing only this camshaft circumferential contact part into contact with the camshaft, the assembled parts are liquid-phase sintered and bonded to the camshaft, so that the assembled parts can be assembled based on the camshaft circumferential contact part. Because it contracts in a fixed direction, the assembled dimensions of the assembled parts do not always change.
It is possible to make the camshafts uniform without causing variations.

In addition, if the gap between the maximum inner diameter of the fitting hole of the assembled parts before sintering and the outer diameter of the camshaft is kept below 0.3 mm, which is the average shrinkage of the assembled parts, the camshaft after liquid phase sintering will The degree of adhesion between the assembled parts is improved, and a decrease in the bonding strength of the assembled parts to the camshaft due to the provision of the camshaft circumferential portion can be prevented.

Furthermore, if the circumferential surface of the camshaft circumferential portion of the assembly part is formed parallel to the outer peripheral surface of the camshaft, stability during assembly of the assembly part can be maintained.

[Brief explanation of drawings]

Figure 1 is a vertical sectional view of the assembled camshaft, Figure 2 is an enlarged cross-sectional view of Figure 1, and Figure 3 is the joining of the cam lobe and camshaft before liquid phase sintering in the conventional camshaft manufacturing method. 4 and 5 are longitudinal cross-sectional views of the cam lobe and camshaft before and after sintering in FIG. 3, and FIG. 6 is a cross-sectional view of the camshaft before and after liquid phase sintering in the method for manufacturing a camshaft according to the first embodiment of the present invention. FIG. 7 is a longitudinal sectional view of the cam lobe and camshaft bonded together before liquid phase sintering in the method for manufacturing a camshaft according to the second embodiment of the present invention, and FIG. A longitudinal cross-sectional view of the cam lobe and camshaft joined together before liquid phase sintering in the manufacturing method of the camshaft according to the embodiment. FIG. FIG. 10: Cam lobe, 11: Cam shaft, 12: Fitting hole.

Claims (1)

[Scope of Claims] 1. A part of the inner circumferential surface of the fitting hole of the sintered assembly part to be fitted and joined to the camshaft is provided with a camshaft circumferential surface having an inner diameter approximately equal to the outer diameter of the camshaft. A method for manufacturing a camshaft, in which the sintered assembly part is liquid phase sintered to join the sintered assembly part to the camshaft after the camshaft circumferential part is brought into contact with the camshaft. 2. The method of manufacturing a camshaft according to claim 1, wherein the gap between the maximum inner diameter of the fitting hole of the assembled part and the outer diameter of the camshaft before sintering is 0.3 mm or less. 3. The method for manufacturing a camshaft according to claim 1 or 2, wherein the circumferential surface of the camshaft circumferential portion is formed parallel to the outer circumferential surface of the camshaft.