JPH0465735B2 - - Google Patents

Description

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

BACKGROUND TECHNOLOGY Engine valves are required not only to withstand high-temperature atmospheres, but also to be as lightweight as possible to avoid damage caused by valve inertia due to high-speed operation, as engines are now required to operate at high speeds and with high output. It is rare.

As one of the measures to reduce weight, attempts have been made to make the valve slam portion thinner than the valve head 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 Japanese Utility Model Publication No. 60-34725 discloses that a steel material or a preformed product with a valve head and a valve stem is made hollow by drilling, and an aluminum alloy or magnesium alloy core is loaded and fixed in the created hole. This shows the engine valve that has been removed. 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 is also practiced to separately prepare a hollow umbrella portion, a stem portion, and a shaft end portion and then weld them together. Another attempt to reduce the weight of the valve is to make the valve itself out of light metal.

Problems to be Solved by the Invention However, when attempting to reduce the weight of engine valves by making them hollow, it is difficult to make the engine valves hollow, which requires accurate and precise drilling, or the use of discarded cores. Processing is complicated and difficult, and manufacturing costs are high because the core 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 is that it tends to get expensive. In addition, manufacturing engine valves from light alloys is an expensive material, difficult to process, and requires hardening of the surface through window treatment, etc.
The problem was that it was not common except for special engines.

The purpose of the present invention is to eliminate the above-mentioned problems, and eliminate the need for precise drilling inside the engine valve at a stage close to the final process, and the need to appropriately thicken the pipe material at the valve head portion. It is an object of the present invention to provide a method for manufacturing a hollow engine valve, which allows the valve to be manufactured easily and at low cost with a small number of processing steps.

The method of manufacturing a hollow engine valve according to the present invention involves drilling a hole in the center of a material made of heat-resistant steel, heating the material, inserting a mandrel whose surface is coated with a lubricant into the hole, and then inserting the mandrel of the material into the hole. Immediately hot extrusion molding is performed on the end opposite to the inserted side to form the valve stem part, and then hot press molding is performed with the mandrel inserted on the mandrel insertion side of the material to form the umbrella part. After upsetting, the mandrel is removed by cutting, and the openings of the umbrella portion and the valve stem portion are hermetically sealed.

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

Embodiment FIG. 1 is a schematic cross-sectional view of an example showing the manufacturing process of a lightweight engine valve according to the present invention. A cylindrical heat-resistant steel rod material 1 is prepared, and a hole is drilled in the center to form a through hole 2 as shown in FIG. 1a. Next, this heat-resistant steel bar material is heated, and a mandrel 3 is inserted into the hole 2 of the material 1, as shown in FIG. 1b. As shown in FIG. 2, the mandrel 3 has a lubricant 4 made of a heat-resistant material such as copper or graphite on the surface of the shaft, and a collar 5 is provided at the end of the shaft to prevent it from falling. There is. The mandrel 3 itself requires a certain level of strength and hardness because it is affected by heat, and is made of high carbon steel or alloy steel.

Next, as shown in FIG. 1c, the material 1 with the mandrel attached is inserted into the extrusion molding die 6 shown in FIG. 3, and the punch 7 applies compression to the material 4 from the end opposite to the opening of the hole 3. Then hot forward extrusion is performed to form the valve stem 8, leaving a blank portion 9 which is to become the valve head as a remainder in the die. During this extrusion, the entire mandrel enters into the material 1, and the collar 5 of the mandrel becomes flush with the end surface of the part 9, but the lubricant 4 prevents slippage between the extruded part of the material and the mandrel. secured and prevents movement of the mandrel.

Next, as shown in FIG. 1d, the extruded material 1 is inserted into a die 10 as shown in FIG. An umbrella portion 12 is formed.
Hot extrusion and hot pressing must be carried out quickly so that the insertion mandrel does not lose its strength due to heat.

Next, the mandrel 3 and the lubricant 4 are taken out and removed by cutting from the opening of the hole 2 in the valve head portion 12. Therefore, the engine valve is a hollow structure with both ends open.

Finally, if necessary, metallic sodium is loaded into the engine valve space 13 to enhance the cooling effect, and the opening of the valve head is welded and sealed with a plug 14.
The opening of the valve stem portion is welded and sealed by the shaft end 15. As a method of sealing the opening of the valve stem portion, as shown in FIG. 5, the end portion may be drawn to close off the space 13.

Effects As is clear from the above description, according to the present invention, a hollow material having a through hole is prepared, a mandrel surrounded by a lubricant is inserted into the material, and then hot forward extrusion is performed on the side opposite to the insertion side of the mandrel. The stem part is formed by processing, the valve head part is formed by hot pressing on the mandrel insertion side, and the mandrel is then removed to manufacture the hollow engine valve. A hollow engine valve can be manufactured easily and at low cost with a small number of machining steps without the need for complicated machining such as drilling.

[Brief explanation of drawings]

1A to 1E are schematic cross-sectional views of an example of the manufacturing process of the hollow engine valve according to the present invention, FIG. 2 is a cross-sectional view showing a mandrel used for manufacturing the engine valve of the present invention, and FIG. , a schematic diagram showing a die and punch for hot extrusion used for manufacturing a hollow engine valve according to the present invention, No. 4
The figure is a schematic diagram showing a die and punch for hot press forming used in manufacturing a hollow engine valve according to the present invention, and FIG. 5 shows a hollow engine valve as another example of the method for manufacturing an engine valve according to the present invention. FIG. 2 is a partially cutaway sectional view. 2... hole, 3... mandrel, 4... lubricant,
8... Valve stem portion, 12... Valve head portion, 1
3... Space.

Claims (1)

[Claims] 1. When manufacturing a hollow engine valve, a hole was made in the center of a material made of heat-resistant steel, the material was heated, a mandrel whose surface was coated with a lubricant was inserted into the hole, and then a mandrel of the material was inserted. Immediately hot extrusion molding is performed on the opposite end portion to form the valve stem portion, and then hot press molding is performed with the mandrel inserted into the mandrel insertion side of the material to upset the umbrella portion. 1. A method for manufacturing a hollow engine valve, which comprises removing the mandrel by cutting and sealing the openings of the umbrella portion and the valve stem portion.