JPH0432923B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a valve stem for an intake valve or an exhaust valve of an internal combustion engine.

[Conventional technology]

In the intake valve or exhaust valve of an internal combustion engine that is driven to open and close by a cam, the valve spring 1A,
The spring seat 2 receiving the spring seat 1B is supported on the valve stem 4 via a holder 3 which is vertically divided into two parts, and the holder 3 connects the convex part 3A on the upper part of the inner peripheral surface to the circumferential groove-like recess 4A of the valve stem 4. The inner peripheral surface 3a is brought into frictional contact with the peripheral surface 4a of the valve stem 4.

[Problem to be solved by the invention]

By the way, since the valve stem 4 moves in the axial direction while being guided by the valve guide 6 on the side of the cylinder head 5, the portion in contact with the valve guide 6 has generally been hard chrome plated. valve stem 4
The circumferential surface 4a is machined to a surface roughness of 5 to 10 microns (Fig. 2a), and when chrome plating, the circumferential surface 4a is covered with a cap or the like. Figure 3 is a graph showing the relationship between the surface roughness of the circumferential surface 4a and the shaft sliding load, and the curve shows the frictional force withstanding the shaft sliding load when the surface roughness of the peripheral surface 4a is 5 to 10 μ. target level
This shows that it exceeds Fo.

In recent years, there has been a trend toward soft nitriding treatment to reduce costs (see Japanese Patent Application Laid-Open No. 117310/1983).
When the entire valve stem 4 is immersed in the soft nitriding treatment liquid, a hardened layer 7 (Fig. 2b) is formed of nitrides, and if only the scale 8 attached to the surface is removed, the surface of the hardened layer 7 becomes hard and hard. Because it is relatively smooth, it is not possible to obtain a frictional force that can withstand the shaft sliding load (curve in Figure 3).

If processing such as grinding is performed to further roughen the peripheral surface 4a on which the hardened layer 7 is formed, the third
As shown by the curve in the figure, the necessary frictional force can be obtained, but the nitrocarburized valve stem 4 is difficult to process, making surface roughening work difficult.

When carrying out nitrocarburizing treatment, if a cap or the like is placed over the peripheral surface 4a, performance equivalent to that shown by the curve in Fig. 3 can be obtained, but since the work of attaching and removing the cap is involved for each product, nitrocarburizing treatment is adopted. The benefits of this will be diminished.

The present invention was invented in order to solve the above-mentioned problems with the conventional valve stem of an internal combustion engine, and the entire valve stem is subjected to soft nitriding treatment without covering the peripheral surface of the valve stem end with a cap etc., and after the soft nitriding treatment, It is an object of the present invention to provide a method of manufacturing a valve stem for an internal combustion engine that can obtain a necessary frictional force without performing processing such as grinding to make the valve stem end peripheral surface rough.

[Means to solve the problem]

In order to achieve the above object, the method for manufacturing a valve stem for an internal combustion engine of the present invention has a method for manufacturing a valve stem for an internal combustion engine.
After processing the valve stem to a surface roughness of ~30μ, the entire valve stem is subjected to soft nitriding treatment, and scale on the contact surface of the socket is further removed by shot blasting.

[Effect]

According to the above-mentioned manufacturing method of the present invention, during the soft-nitriding process, it is not necessary to cover the circumferential surface, which is the contact surface of the valve stem near the end of the valve stem, with a cap, etc., and after the soft-nitriding process, the limited stem By simply shot blasting the parts, you can obtain a valve stem that has a large friction with the valve stem and is highly reliable against tensile loads during operation.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In an easy-to-process state before nitrocarburizing, the circumferential surface 4a of the valve stem 4, which will be the contact surface of the valve stem near the end of the valve stem, is processed with a grinder to a surface roughness of 10 to 35μ. The hardened layer 7 is formed by nitrocarburizing the entire structure, and the scale to be removed is removed by highly efficient sandblasting, so the labor and time required for processing can be shortened.

The curve in FIG. 3 is a graph showing the relationship between the surface roughness of the valve stem obtained by the method of the present invention and the shaft sliding load, and it can be seen that the curve has almost the same performance as the curve.

As is clear from the above description, according to the manufacturing method of the present invention, during soft nitriding treatment, there is no need to cover the circumferential surface 4a, which is the contact surface of the valve stem near the end of the valve stem, with a cap or the like. After nitrocarburizing treatment, by simply shot blasting a limited portion of the stem, a valve stem with large friction with the valve stem and highly reliable against tensile loads during operation can be obtained, making it extremely inexpensive and efficient. be.

〔Effect of the invention〕

As described above, in the method of manufacturing a valve stem for an internal combustion engine according to the present invention, after processing the cotter contact surface to a surface roughness of 10 to 35μ, the entire valve stem is subjected to soft nitriding treatment, and then the cotter contact surface is subjected to soft nitriding treatment. It is characterized by removing scale by shot blasting, so by just shot blasting a limited portion of the stem after nitrocarburizing treatment, the friction with the stem is large and it is reliable against tensile loads during operation. This has the effect of providing a valve stem with high properties.

Furthermore, during soft nitriding treatment, it is not necessary to cover the circumferential surface, which is the contact surface of the valve stem near the end of the valve stem, with a cap or the like, making the manufacturing method extremely efficient and inexpensive.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view showing the structure of the intake and exhaust valves, Figure 2a is an enlarged cross-sectional view showing the contact surface of the kotsuta with a surface roughness of 5 to 10μ, and Figure 2b is an enlarged sectional view showing the contact surface of the kotsuta with a surface roughness of 5 to 10μ. An enlarged sectional view showing a state in which a hardened layer has been formed by soft nitriding on the contact surface. Figure c shows a state in which a hardened layer has been formed by soft nitriding on a contact surface with a surface roughness of 15 to 30μ. The enlarged sectional view, FIG. 3, is a diagram showing the relationship between surface roughness and shaft sliding load. 1... Valve spring, 2... Spring seat, 3... Kotta, 4... Valve stem, 4a
...Surrounding surface, 7...Hardened layer of nitride, 8...Scale.

Claims (1)

[Claims] 1. For use in internal combustion engines, the valve stem is machined to have a surface roughness of 15 to 30 μm, the entire valve stem is subjected to nitrocarburizing treatment, and scale on the contact surface of the valve stem is removed by shot blasting. Valve stem manufacturing method.