JPS63109203A - Manufacturing method for lightweight engine valve - Google Patents

Abstract

PURPOSE:To manufacture a lightweight engine valve easily by filling a slot of a heat-resistant steel block with coring powder, tapping the slot of the block and then defining both a valve stem part and a skirt part thereon. CONSTITUTION:The slot 3 of a heat-resistant steel block 4 is filled with coring powder of titanium alloy. After the opening of the block 4 is closed with a tap 8 made of heat-resistant steel, the block 4 is subjected to the hot forward extrusion to define a stem part 11 at one side thereof. The block 4 is then subjected to the hot press and swaging to define a skirt part 15 at the other side thereof. Thus, a lightweight valve may be manufactured easily.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing lightweight engine valves for use in internal combustion engines.

[Conventional technology]

Nowadays, as engines are required to operate at higher speeds and higher outputs, engine valves are desired to not only withstand high-temperature atmospheres, but also to be as lightweight as possible in order to avoid adverse effects caused by inertia of the valves due to high-speed operation.

As one measure to reduce weight, attempts have been made to make the stem portion thinner than the umbrella portion, and this has been put to practical use, but there is a limit to the weight reduction due to the strength limit of the shaft diameter. Another attempt to reduce weight is to make the valve itself hollow. For example, in the specification of Japanese Utility Model Publication No. 60-34725, a steel material or a preformed product forming a valve head and a valve shaft is drilled to make it hollow, and an aluminum alloy or magnesium alloy core is loaded and fixed into the created hole. The engine valves are exposed. Also special public service 51-2910
Specification No. 6 or Japanese Patent Publication No. 51-29506 discloses that a pipe material is used, and an insert serving as a core is inserted inside the pipe, or an insert serving as a core is inserted and bonded and then an upset is made. Also disclosed is an engine valve manufactured by performing hot pressing. 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 body from a light metal.

[Problem that the invention seeks to solve]

However, such attempts to reduce the weight of engine valves require accurate and precise drilling to make them hollow, or the inserts that will become waste cores must be cut out or leached by corrosive acids. The problem is that the core insert and the various parts of the valve must be welded together, making the process complicated and difficult and resulting in high manufacturing costs.

Another problem with manufacturing light alloy engine valves is that they are not common except for special engines because the materials are expensive, processing is difficult, and the surface needs to be hardened by window treatment. there were.

The purpose of the present invention is to eliminate the above-mentioned problems, and to provide an easy-to-manufacture product that has a lightweight core material such as titanium alloy integrated from the stem part to the cap part, and has a lid made of heat-resistant steel on the cap part surface. An object of the present invention is to provide a method for manufacturing a lightweight engine valve.

[Means for solving problems]

Therefore, the present invention provides the following advantages when manufacturing an engine valve:
A hole is formed in the center of the material made of heat-resistant steel by backward extrusion processing, and the material has a lower specific gravity and coefficient of thermal expansion than the material, does not melt at hot forging temperatures, and does not expand or contract in volume due to hot forging. A small amount of the core material is loaded into the hole, and a disk-shaped lid made of heat-resistant steel is inserted into the hole so that its outer surface is flush with the open end surface of the material, and then the core material and the lid are inserted into the hole. After heating the loaded material and the lid, a stem portion containing a core material is formed in the material by hot forward extrusion on the side opposite to the opening of the hole, and then a stem portion containing the core material is formed in the remaining material by hot press upsetting. The feature is that the umbrella portion is formed by.

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 heat-resistant steel bar is prepared and cut into a predetermined size to obtain a material 4. As shown in FIG. 2, the material 4 is inserted into the recess 6 of the die 1, the stock pin 5 is set at the normal position shown in the figure, and the punch 2 is used to perform warm or hot backward extrusion processing. As a result, a hole 3 with one end closed is formed in the material 4. The material 4 formed with the hole 3 in the center can be extracted from the die 1 by moving the stock pin to the left.

Next, as shown in FIG. 1(a), a predetermined amount of core material 7 made of an appropriate material is inserted into the hole 3 of the material 4, and a disk-shaped lid 8 made of the same heat-resistant steel as the material 4 is attached to its outer surface. After inserting the lid 8 into the hole 3 so that it is flush with the open end of the material 4,
Weld to. The core material is a material that is lighter than the raw material, has a lower coefficient of thermal expansion than the raw material, does not melt at hot forging temperatures, and has less volumetric expansion and contraction due to hot forging, such as titanium alloy, foundry sand, etc. , ceramic powder is suitable.

Next, the raw material 4 loaded with the lid 8 and the core material 7 is heated to a predetermined temperature for hot extrusion molding, and then this heated raw material is inserted into the die 9 for extrusion molding 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 to form the valve stem 11 from the opposite end. When the valve stem 11 is extruded to a predetermined length, a blank portion 12 that will become the valve head remains in the die 9. As shown in Fig. 1 et al., the core material is also extruded together with the material, so that the core material uniformly enters the center of the stem portion.

Next, in order to use this as an engine valve, as shown in FIG. 4, it is inserted into a die 13 and hot press upsetting is performed on the portion 12 using a punch 14 to form an umbrella portion 15 having a predetermined shape. FIG. 1(C) shows the engine valve taken out from the die 12 after upsetting the umbrella portion 15. The lid 8 is stretched out and placed on the surface of the umbrella part 15.

Finally, the shaft end portion 16 is formed on the engine valve as shown in FIG. 1(d).

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a suitable core material such as titanium alloy is loaded in the center of a heat-resistant steel material, a heat-resistant steel lid is inserted into a hole in the material, welded, and then the hot front Since the stem part is formed by extrusion molding, and then the umbrella part is formed by hot press upsetting, the core material can be inserted into the center of the stem part, without any additional processing after forging. Since a heat-resistant steel lid can be placed on the surface of the cap that is directly exposed to the combustion chamber of the engine, an extremely lightweight engine valve that can be used over a wide range of temperatures can be manufactured easily and at low cost. In particular, according to the manufacturing method of the present invention, since the core material is loaded before hot forging,
After forging, the core material can be sealed inside the material with no gaps (particularly powdered core materials are extremely tightly sealed.Also, lightweight valves with core material (particularly titanium alloy) sealed inside the material can withstand harsh engine conditions. However, it has excellent rigidity and durability.

[Brief explanation of the drawing]

Figures 1 (a) to (d) are schematic cross-sectional views showing an example of the manufacturing process of the lightweight engine valve of the present invention, and Figure 2 is a backward extrusion process for the material used to manufacture the lightweight engine valve of the present invention. FIG. 3 is a diagram showing the gougs and punches used to hot-extrude a lightweight engine valve formed according to the present invention; FIG. FIG. 2 is a diagram showing a goug and punch for hot press forming an engine valve. 4...Material, 7...Core material, 8...
... Lid, 11 ... Stem part, 15 ...
・Umbrella part.

Claims (1)

[Claims] In manufacturing engine valves, a hole is formed in the center of a material made of heat-resistant steel by backward extrusion processing, and the material has a lower specific gravity and coefficient of thermal expansion than the material, does not melt at hot forging temperatures, and is made of heat-resistant steel. A core material material whose volume expands and contracts less due to heat is loaded into the hole, and a disk-shaped lid made of heat-resistant steel is inserted into the hole so that its outer surface is flush with the opening side end surface of the material. Then, after heating the core material, the material loaded with the core material, and the lid, a stem portion containing the core material is formed in the material by hot front extrusion on the side opposite to the opening of the hole, and then the remaining material is heated. A method for manufacturing a lightweight engine valve, characterized in that an umbrella portion is formed by hot press upsetting.