JPH0656090B2 - Hollow engine valve manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a hollow engine valve used in an internal combustion engine.

2. Description of the Related Art The engine valve of an internal combustion engine, of course, withstands a high heat atmosphere in response to the demand for high speed and high output of the engine,
It is desired to be as light as possible in order to avoid the adverse effect caused by the inertia of the valve.

As one of measures to reduce the weight, an attempt has been made to make the valve stem portion thinner than the umbrella portion, and it has been put into practical use, but there is a limit to the weight reduction due to the limit in strength of the shaft diameter.
As another attempt to reduce the weight of the valve, the valve itself is made hollow. For example, Jitsuko Sho 60-3
Japanese Patent No. 4725 discloses an engine valve in which a steel material or a preform 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 formed hole. ing. See also
No. 1-29106 or Japanese Patent Publication No. 51-29506
In the specification, it is manufactured by using a pipe material and inserting an insert which becomes a core inside the pipe or inserting and bonding an insert which becomes a core and then performing upset forging and hot pressing. An engine valve is disclosed. Further, the umbrella portion, the stem portion and the shaft end portion of the hollow valve are separately prepared and then welded. As another attempt to reduce the weight, the valve itself is made of a light metal.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such an attempt to reduce the weight of the engine valve, accurate and precise drilling is required to make the valve hollow, and it becomes a waste core. Processing is complicated and difficult and the manufacturing cost tends to be high because the insert must be machined or removed by elution with corrosive acid, or the core insert and each part of the valve must be welded There was a problem. In addition, manufacturing a light alloy engine valve has a problem that it is not common except for a special engine because the material is expensive, the processing is difficult, and the surface needs to be hardened by nitriding or the like. It was

An object of the present invention is to eliminate the above-mentioned problems, and to manufacture a hollow engine valve which can be manufactured easily and at low cost without drilling the engine valve and without using a pipe material. To provide.

Means for Solving the Problems The present invention, in manufacturing a hollow engine valve, forms a hole in the center of a heat-resistant steel material by backward extrusion,
A core rod made of high-strength alloy is loaded in the hole so that its axis is located on the axis of the material, and the core material is made of graphite, carbon, ceramic powder or the like that does not melt and solidifies strongly during hot forming. To the hole loaded with the core rod,
After that, the material is heated, and the valve stem portion containing the core material and the core rod is formed by hot front extrusion molding on the side opposite to the opening of the hole of the material, and then hot press upset molding is performed on the rest of the material. The umbrella is formed by, and the core rod is removed from the material by pulling out the core rod from the umbrella end to form a hollow portion, and the opening of the umbrella is hermetically sealed.

The present invention will be described in detail 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, insert this material 4 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 warmly extruded backward, whereby the material 4
A hole 3 having one end closed is formed in the. 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.

Next, as shown in FIG. 1 (a), the core rod 7 is inserted into the hole 3 of the material 4.
Is loaded so that its axis is located on the axis of the material, and the core material 8 is filled inside the hole 3 in which the core rod 7 is loaded. The core rod 7 is made of stainless steel or titanium alloy having a high tensile strength, and its tip is enlarged so that the core material 8 can be easily removed in a later step. It may be a cylindrical core rod 7'as shown in FIG. The core rod is for taking out the core material, and therefore, even after the core material is loaded into the raw material 4, the rear end thereof protrudes from the hole 3.

The core material 8 needs to be a material that does not melt or strongly solidify during the subsequent hot forming, is easily deformed and fluidized, and is easily crushed. Therefore, graphite, carbon, ceramic powder or the like is desirable as the core material, and graphite is used in this example.

Next, the core material filled with this core rod is heated to a temperature suitable for hot extrusion molding, and then this heating material is inserted into the extrusion molding die 9 shown in FIG. A punch 10 having a recess 10 'for accommodating the protruding portion of the core rod 7 compresses the material from the opening side of the hole, and hot front extrusion molding is performed as a valve stem 11 from the opposite end. When the valve stem is extruded for a specified length,
In the die, the material portion 12 to be the valve head remains as the rest. During this extrusion molding, the diameter of the core rod 7 is reduced as shown in FIG. 1 (b), and the enlarged tip portion of the core rod is
It is located at the most tip of the hole in the stem portion, expands in the valve stem while deforming to a diameter almost equal to the inner diameter of the hole, and enters the central portion of the valve stem portion 11 together with graphite.

Subsequent to this hot extrusion molding, this is inserted into a die 13 as shown in FIG. 5 to form an engine valve, and a punch 14 having a concave portion 14 'for accommodating the protruding portion of the core rod 7 is provided at a tip portion 12 thereof. Then, hot press upsetting is performed to form the umbrella portion 15 having a predetermined shape. The umbrella portion 15 is shown in FIG. 1 (c).
The engine valve taken out from the die 13 after the upsetting of FIG. Next, as shown in FIG. 1 (d), the rear end of the core rod 7 protruding from the umbrella portion 15 is pulled out from the opening of the hole 3 of the material 4.
Therefore, in the process in which the core rod arranged in the graphite is linearly pulled out so as to scratch the inside of the hole 3 of the stem portion at the enlarged end portion, the graphite around the core rod is crushed and is easily broken from the hole 3. It is taken out to form a hollow 16 in the engine valve.

Finally, plug the hollow portion 16 of the engine valve shown in FIG.
7. Weld tightly with 7 and the shaft end 1 on the valve stem.
8 is provided. The shaft end portion 18 does not have to be directly formed on the stem portion as shown in FIG. 1 (e), and as shown in FIG. 6, a shaft end component 18 'different from the stem portion may be welded. Metallic sodium that enhances the cooling effect of the valve can be enclosed in the hollow portion 16 if necessary.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the method for manufacturing a hollow engine valve of the present invention, the core material having the core rod arranged at the center is filled in the holes of the raw material, these are heated, and the post heat treatment is performed. In order to form the valve stem by front extrusion molding,
The core material and core rod enter the valve stem part as they are, and after forming the umbrella part by hot press upsetting, the entire stem part from the engine valve made of heat-resistant steel can be covered by simply pulling out the coil. Further, the core material can be removed from the umbrella portion, so that the hollow valve can be manufactured easily and at low cost without performing complicated processing. Further, since the core rod is relatively thick and made of a high tensile strength material, there is an advantage that the core rod is not cut in the core material removing step.

[Brief description of drawings]

1 (a) to 1 (e) are schematic cross-sectional views showing an example of a manufacturing process of a hollow engine valve according to the present invention, and FIG. 2 is a rear extrusion process of a material used for manufacturing the hollow engine valve according to the present invention. FIG. 3 is a schematic view showing a die and a punch formed by the method, FIG. 3 is a view showing another example of a core rod used for manufacturing the hollow engine valve according to the present invention, and FIG. 4 is a stem of the hollow engine valve according to the present invention. FIG. 5 is a schematic view showing a die and a punch for forming a portion by hot front extrusion molding, and FIG. 5 is a schematic view showing a die and a punch for forming an umbrella portion of a hollow engine valve according to the present invention by hot press upsetting. FIG. 6 is a partially cutaway partial sectional view showing another example of the shaft end portion of the hollow engine valve of FIG. 1 (e). 3 ... hole, 4 ... material, 7 ... core rod, 8 ... core material, 11 ... valve stem part, 15 ... umbrella part, 17 ... plug.

Claims (1)

[Claims] 1. When manufacturing a hollow engine valve,
A hole is formed in the center of the heat-resistant steel material by backward extrusion, and a core rod made of a high-tensile alloy is loaded into the hole so that its axis is located on the axis of the material and melted during hot forming. Core material made of graphite, carbon, ceramic powder, etc., which does not solidify strongly, is filled in the hole in which the core rod is loaded, and then the material is heated, and the material is heated forward on the side opposite to the opening of the hole. Form the valve stem part containing the core material and core rod by extrusion molding, then mold the umbrella part by hot press upset molding on the rest of the material, and pull out the core rod from the umbrella end part from the material A method of manufacturing a hollow engine valve, characterized in that a core is removed to form a hollow portion, and an opening of the umbrella portion is sealed and sealed.