JPH0645066B2 - Manufacturing method of overlay valve for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a build-up valve for an internal combustion engine, and more particularly, to forming a wear-resistant build-up part on a face portion of an engine valve for an internal combustion engine. Regarding the method.

2. Description of the Related Art FIG. 1 schematically shows the structure of an engine valve. The illustrated engine valve has a round bar-shaped shaft portion (stem) 1,
The shaft end portion 3 is formed at one end thereof, and the umbrella-shaped neck portion 6 and the umbrella portion 7 are formed at the other end. Face part 4 of the umbrella part 7
A built-up portion 5 is formed on the surface to ensure wear resistance. The engine valve manufacturing method includes an electric shrinking method and a hot squeezing method, and in either case, primary molding is performed by hot forging. The end surface portion of the umbrella portion 7 is called an umbrella table 9 and is usually not subjected to a post-treatment by machining after the above forging.

With the improvement of the performance of internal combustion engines, it has been desired to improve the durability of the face portion of engine valves, that is, wear resistance. Conventionally, in order to secure the wear resistance of the face portion, Co-based stellite alloy overlay is used. A powder overlay material such as a material was overlay welded by oxygen-acetylene gas welding to form an overlay portion. However, in this method, unless the surface of the base material is melted to some extent and then the buildup is performed, the formed buildup portion is easily separated from the base material. Therefore, it is necessary to perform overlay welding while visually inspecting the melting of the surface of the base material, and automation of the work cannot be achieved.

Therefore, by using an inert gas shield welding such as plasma welding, laser welding, TIG welding, etc.
A method of forming a weld overlay by welding an overlay weld of a powder overlay such as a base Stellite alloy overlay has been introduced.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, in the method of forming a built-up portion by the above-mentioned oxygen-acetylene gas welding, since the entire umbrella portion is heated, the umbrella surface is not thermally deformed, but the work is automated. However, there is a problem that the manufacturing cost becomes high because it is not possible.

Further, in the method of forming the build-up portion by the above-mentioned inert gas shield powder welding, the work can be fully automated easily and labor saving can be achieved, but the umbrella surface becomes convex due to local heating of the umbrella portion. There is a problem in that the manufacturing cost becomes high because post-treatment is required, in which the surface of the umbrella is flattened by mechanical processing after heat deformation and overlaying.

Therefore, it is an object of the present invention to provide a method for forming a built-up surface of an engine valve face, which enables complete automation of work and does not require post-processing such as machining of an umbrella surface.

Means for Solving the Problems The inventors of the present invention have focused on the fact that an engine valve is primarily formed by hot forging in both cases of the electric forging method and the hot squeezing method, and overlay welding is performed. It was found that if the engine valve canopy surface is forged in advance to a shape that almost cancels out the thermal deformation amount of the above, and then overlay welding is performed, a nearly flat umbrella table can be obtained as a result of thermal deformation due to welding. Invented.

That is, according to the present invention, in a method for manufacturing a built-up valve for an internal combustion engine, which comprises forming a built-up portion on a face portion of an engine valve by welding a built-up powder material by plasma welding, laser welding or TIG welding. A method is provided in which the umbrella table of the engine valve is previously forged into a concave shape and then overlay welding is performed so that the umbrella table becomes substantially flat due to thermal deformation caused by overlay welding.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a schematic view schematically showing thermal deformation of the umbrella surface when formed by conventional inert gas shield powder welding. Deformation amount A shown in the figure generally depends on parameters such as valve size, valve material, overlay material, and welding conditions. Generally, the larger the valve size, the larger the amount of deformation. In any case, if the above parameters are set, the amount of thermal deformation can be known in advance by a test.

FIG. 3 is a schematic view showing an umbrella surface that is previously forged into a concave shape according to the present invention. As described above, since the amount of thermal deformation caused by overlay welding can be known in advance, it is preferable to form the concave portion in a shape that substantially cancels the amount of thermal deformation.
In the present embodiment, the illustrated recess is formed in a truncated cone shape whose bottom surface is the end surface of the umbrella surface. The depth of the recess, that is, the height B of the truncated cone is set to be substantially equal to the deformation amount A, and the angle between the side generatrix of the truncated cone and the bottom surface,
That is, the illustrated angle C is approximated to the thermal deformation.

By the way, depending on parameters such as valve material, overlay material, welding conditions, etc., when the neck diameter is 35 mm, the deformation amount is about 0.10 to 0.25 mm, and the angle C is 1
It is about 3 degrees. In this manner, when the frusto-conical recess is forged on the umbrella surface of the engine valve and then the overlay welding is performed, a substantially flat umbrella surface is obtained as a result of thermal deformation due to welding.

In this embodiment, the concave portion of the umbrella surface has a frusto-conical shape, but it can be formed with another shape that substantially cancels the amount of thermal deformation.

Effect of the Invention As described above, according to the method for manufacturing a built-up valve for an internal combustion engine according to the present invention, since the built-up portion is formed by plasma welding, laser welding or TIG welding, the work can be completely automated, and Since a substantially flat umbrella surface can be obtained after the build-up portion is formed, no post-treatment such as machining is required, so that an engine valve with low manufacturing cost can be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an engine valve, and FIG. 2 is a schematic diagram showing thermal deformation of an umbrella surface when formed by conventional inert gas shield powder welding, and FIG. [FIG. 3] is a schematic view showing an umbrella surface that has been previously forged into a concave shape according to the present invention. 1 ... Shaft part (stem), 5 ... Overlay part, 3 ... Shaft end part, 4 ... Face part, 7 ... Umbrella part, 9 ... Umbrella table.

Claims (1)

[Claims] 1. A method for manufacturing a built-up valve for an internal combustion engine, which comprises forming a built-up portion on a face portion of an engine valve by laminating a built-up powder material by plasma welding, laser welding or TIG welding. A method, characterized in that the umbrella surface of the valve is forged in advance into a concave shape, and then overlay welding is performed so that the umbrella table becomes substantially flat due to thermal deformation accompanying the overlay welding.