JPH0621529B2 - Lightweight engine valve manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a lightweight engine valve used during an internal combustion period.

[Conventional technology]

At present, when high-speed and high-power output of an engine is required, it is desired that the engine valve not only withstand a high-temperature atmosphere but also be as light as possible in order to avoid a harmful effect caused by inertia of the valve due to high-speed operation.

As one of the measures for reducing the weight, an attempt has been made to make the stem portion thinner than the umbrella portion, and it has been put into practical use. However, there is a limit to the weight reduction due to the limit in strength of the shaft diameter. Another attempt to reduce the weight is to make the valve itself hollow. For example, in Japanese Utility Model Publication No. 60-34725, a steel material or a preformed product having a valve head and a valve shaft is perforated to be hollow, and an aluminum alloy or magnesium alloy core is loaded and fixed in the resulting hole. The disclosed engine valve is disclosed. In addition, Japanese Patent Publication Sho 51-2910
No. 6 or Japanese Patent Publication No. 51-29506 discloses that a pipe material is used, and an insert that serves as a waste core is inserted inside the pipe, or an insert that serves as a core is inserted and bonded, and then upset forging and heat treatment. An engine valve manufactured by performing hot pressing is disclosed. Further, it is also practiced to separately prepare a hollow umbrella portion, a stem portion and a shaft end portion and then weld these. As yet another attempt to reduce the weight of the valve, the valve itself is made of light metal.

[Problems to be solved by the invention]

However, in such attempts to reduce the weight of engine valves, precise and precise drilling is required to make them hollow, or the inserts that are the cores are cut out or eluted by corrosive acid. Therefore, there is a problem in that machining is complicated and difficult, and the manufacturing cost is likely to be high, because machining for removal is required or each part of the core insert or valve has to be welded. In addition, manufacturing a light alloy engine valve has the problem that it is not common except for special engines because the material is expensive, it is difficult to process, and it is necessary to harden the surface by windowing etc. there were.

The object of the present invention is to eliminate the above-mentioned problems, to have a lightweight core material such as a titanium alloy inside from the stem portion to the umbrella portion integrally, and to dispose a lid of heat-resistant steel on the surface of the umbrella portion, which is easy to manufacture. It is to provide a method for manufacturing a lightweight engine valve.

[Means for solving problems]

Therefore, the present invention, when manufacturing an engine valve,
A hole is formed in the center of the heat-resistant steel material by the backward extrusion process, has a smaller specific gravity and coefficient of thermal expansion than the material, does not melt at the hot forging temperature, and does not expand or contract in volume due to hot forging. A small amount of 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 end surface on the opening side of the material. After heating the loaded material and the lid, a stem portion containing a core material is formed on the material on the side opposite to the opening of the hole by hot front extrusion molding, and then hot press upsetting on the rest of the material. It is characterized in that the umbrella portion is formed by.

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

EXAMPLE FIG. 1 is a schematic sectional view of an example showing a manufacturing process of a lightweight engine valve according to the present invention. A bar material of heat-resistant steel is prepared and cut into a predetermined size to obtain a material 4. As shown in FIG. 2, the blank 4 is inserted into the recess 6 of the die 1, the stock pin 5 is set to the normal position shown in the figure, and the punch 2 is used for warm or hot endwise extrusion. As a result, a hole 3 having one end closed is formed in the material 4. The material 4 having the hole 3 formed at the center can be removed from the die 1 by moving the stock pin to the left.

Then, as shown in FIG. 1 (a), a predetermined amount of a core material 7 of a suitable 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 placed on the outside of the material. After inserting the hole 3 so that the surface thereof is flush with the end of the material 4 on the opening side, the lid 8 is welded to the material 4. The core material is lighter than the material, has a smaller coefficient of thermal expansion than the material, does not melt at the hot forging temperature, and is a substance that has less volume expansion and shrinkage due to hot forging,
Titanium alloys, foundry sands, ceramic powders are suitable, for example.

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 heating raw material is inserted into the extrusion die 9 shown in FIG. Then, compression is applied to the material 4 from the opening side of the hole 3, and hot front extrusion molding is performed as the valve stem 11 from the opposite end. When the valve stem 11 is extruded for a predetermined length, a material portion 12 to be a valve head remains in the die 9 as a remaining portion. Since the core material is also extruded together with the material as shown in FIG. 1 (b), 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 a punch 14 performs hot press upsetting on the portion 12 to form an umbrella portion 15 having a predetermined shape. FIG. 1 (c) shows the engine valve taken out from the die 12 after the upsetting of the umbrella portion 15. The lid 8 is stretched and arranged on the surface of the umbrella portion 15.

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

〔The invention's effect〕

As apparent from the above description, according to the present invention, a suitable core material such as titanium alloy is loaded in the center of the heat-resistant steel material, the heat-resistant steel lid is inserted into the hole of the material, and after welding, the hot front Since the stem part is formed by extrusion molding and then the umbrella part is formed by hot press upsetting molding, the core material can be inserted into the center of the stem part, while any processing is required after forging. Since the lid of heat-resistant steel can be arranged on the surface of the umbrella portion that is directly exposed to the combustion chamber of the engine, an extremely light engine valve having a wide operating temperature range 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, the core material after forging can be enclosed inside the material without any gaps, and particularly with the powder core material, it can be enclosed very densely. In addition, a lightweight valve with a core material (particularly titanium alloy) enclosed inside has excellent rigidity and durability even under severe engine conditions.

[Brief description of drawings]

1 (a) to 1 (d) are schematic cross-sectional views showing an example of the manufacturing process of the lightweight engine valve according to the present invention, and FIG. FIG. 3 is a diagram showing a die and a punch to be applied, FIG. 3 is a diagram showing a die and a punch to which a lightweight engine valve formed according to the present invention is subjected to hot extrusion molding, and FIG. 4 is a light weight formed according to the present invention. It is a diagram showing a die and a punch for performing hot press molding on an engine valve. 4 ... material, 7 ... core material, 8 ... lid, 11 ... stem portion, 15 ... umbrella portion.

Claims (1)

[Claims] 1. When manufacturing an engine valve, a hole is formed in the center of a material made of heat-resistant steel by backward extrusion, has a smaller specific gravity and thermal expansion coefficient than the material, and does not melt at the hot forging temperature, And the volume expansion due to hot forging,
A core material with less shrinkage 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 end surface on the opening side of the material. After heating the material loaded with this and the lid, a stem portion containing the core material is formed on the material on the side opposite to the opening of the hole by hot front extrusion molding, and then hot press installation is performed on the rest of the material. A method for manufacturing a lightweight engine valve, characterized in that the umbrella portion is formed by in-molding.