JPH0465734B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing lightweight engine valves and hollow engine valves for use in internal combustion engines.

BACKGROUND OF THE INVENTION With the demand for high-speed, high-output engines, engine valves for internal combustion engines are desired not only to withstand high-temperature atmospheres but also to be as lightweight as possible to avoid adverse effects caused by inertia of the valves. There is.

As one measure to reduce weight, attempts have been made to make the valve stem portion thinner than the umbrella portion, and this has been put into practical use, but there is a limit to the weight reduction due to the strength limit of the shaft diameter. Another attempt to reduce the weight of the valve is to make the valve itself hollow. For example, the specification of Utility Model Publication No. 60-34725 is
This patent discloses an engine valve in which a steel material or a preformed product having a valve head and a valve stem is made hollow by drilling a hole, and a core made of aluminum alloy or magnesium alloy is charged and fixed into the hole. Also, the specification of Special Publication No. 51-29106 or Special Publication No. 51-
Specification No. 29506 states that the pipe is manufactured by using a pipe material, inserting an insert to serve as a waste core inside the pipe, or inserting and adhering a core insert, and then performing upset forging and hot pressing. Engine valves are disclosed. Furthermore, it has also been practiced to prepare the cap, stem, and shaft end portions of a hollow valve separately and then weld them together. Another attempt to reduce the weight of the valve is to make the valve itself from a light metal.

Problems to be Solved by the Invention However, when attempting to reduce the weight of engine valves in this way, accurate and precise drilling is required to make them hollow, and the process results in waste cores. The process is complicated and difficult, and the manufacturing cost is high because the insert must be removed by cutting or leaching with corrosive acid, or the core insert and each part of the valve must be welded. The problem was that it was easy. In addition, when manufacturing engine valves from light metals, the material is expensive, difficult to process, and the surface needs to be hardened by nitriding, so there is a problem that it is not common except for special engines. It was hot.

An object of the present invention is to provide a method for manufacturing a lightweight engine valve that eliminates the above-mentioned problems and can be manufactured without complicated processing.

In manufacturing engine valves, the present invention involves forming a hole in the center of a cylindrical material made of heat-resistant steel by backward extrusion, and using materials such as graphite, carbon ceramics, etc., which do not melt and solidify during hot forming and easily flow and deform. A core material made of is loaded into the hole, and the core material loaded material is heated, and then a valve stem portion containing the core material is formed by hot extrusion molding on the side opposite to the opening of the hole of the material, Next, the remaining part of the material is subjected to hot press upsetting to form an umbrella part, and then, after taking out part or all of the core material from the hole, the opening of the hole is sealed by welding with a plug. That is.

The present invention will be explained below with reference to the drawings.

Embodiment FIG. 1 is a schematic sectional view of an example showing the manufacturing process of a lightweight engine valve according to the present invention. A bar material of heat-resistant steel or titanium alloy is prepared and cut into a predetermined size to obtain a material 4. This is inserted into the recess 6 of the die 1 as shown in Fig. 2, the stock pin 5 is set to the normal position shown in the figure, and the punch 2 is used to perform warm or hot backward extrusion processing. A hole 3 with one end closed is formed in the center of the material 4. The material 4 having the hole 3 formed therein can be extracted from the die 1 by moving the stock pin 5 to the left.

Next, as shown in FIG. 1a, the core material 7 is loaded into the hole 3 of the material 4. This core material 7 needs to be a material that does not melt and easily flows and deforms during subsequent hot forming. Therefore, graphite, carbon ceramic, etc. are preferable as the core material, and graphite is used in this example.

Next, the material 4 with the core material 7 loaded into the hole 3 is heated to a predetermined temperature suitable for hot extrusion molding, the heated material 4 is inserted into the extrusion molding die 8 shown in FIG. Then, compression is applied to the material 4 from the opening side of the hole 3, and hot forward extrusion is performed from the opposite end to form the valve stem 10. When the valve stem 10 is extruded to a predetermined length, a portion 11 that will become the valve head remains in the die. Figure 1b
As shown in the figure, the core graphite in the material is extruded together with the material, and as a result, it uniformly enters the center of the stem 10.

Next, in order to use this as an engine valve, as shown in FIG. 4, it is inserted into a die 12 and hot press upsetting is performed on the portion 11 using a punch 13 to form a cap portion 14 having a predetermined shape. The umbrella part 14 is shown in Fig. 1c.
The engine valve taken out from the die 12 after upsetting is shown.

Next, as shown in FIG. 1d, a part of the core material is taken out from the opening of the hole 3 in the umbrella part 14, and the opening of the hole 3 is hermetically sealed with a plug 15 made of heat-resistant steel by welding. As this welding, resistance welding, TIG welding, friction welding, etc. can be applied. Finally, the shaft end 16 is formed on the engine valve.

FIG. 5 is a partial cross-sectional view of a lightweight engine valve manufactured by another example of the engine valve manufacturing method according to the present invention. Since this method differs from the embodiment shown in FIG. 1 only in the sealing step, the same explanation as in FIG. 1 will be omitted. As before, the engine valve is made through hot extrusion molding and hot press upsetting, and all of the graphite 7 that is the core material is crushed and taken out from the opening of the hole 3 on the surface of the umbrella part 14, and the engine valve is made. Hollow out. Then, plug 1 is made by welding.
5' is fixed to the umbrella part 14 and sealed tightly.

In the case of a hollow lightweight engine valve, metallic sodium can be sealed inside the hollow space to improve the cooling effect.

Effects As is clear from the above explanation, according to the method of manufacturing a lightweight engine valve according to the present invention, a core material such as graphite, carbon, or ceramic is loaded into the center of a heat-resistant steel material, and then the valve stem portion is formed by hot extrusion molding. A cap is formed on the other end by hot press upsetting, and then part or all of the core material is removed and the opening of the hole is tightly plugged with a plug.
Extremely light engine valves can be manufactured easily and at low cost.

[Brief explanation of the drawing]

Figures 1 a to d are schematic cross-sectional views of an example of a method for manufacturing a lightweight engine valve according to the present invention, and Figure 2 is a schematic cross-sectional view of an example of a method for manufacturing a lightweight engine valve according to the present invention. FIG. 3 is a schematic diagram showing a die and punch for forming the valve stem of a lightweight engine valve by hot forward extrusion; FIG. FIG. 5 is a schematic view showing a die and punch for forming a cap portion by press upsetting, and FIG. 5 is a partially cutaway sectional view showing a lightweight engine valve according to another example of the method for manufacturing an engine valve of the present invention. be. 4...Material, 14...Umbrella part, 7...Core material, 1
5...Plug, 10...Valve stem part.

Claims (1)

[Claims] 1. In manufacturing engine valves, a hole is formed in the center of a material made of heat-resistant steel by backward extrusion, and a core material made of a material such as graphite or carbon ceramics that does not melt and easily flows and deforms during hot forming is used as described above. After the core material and the material loaded in the hole are heated, a valve stem portion containing the core material is formed by hot extrusion on the opposite side of the hole opening of the material, and then The remaining part of the material is subjected to hot press upsetting to form an umbrella part, and then, after taking out part or all of the core material from the hole, the opening of the hole is sealed by welding with a plug. A method for manufacturing lightweight engine valves.