JPH07102917A - Sodium-enclosed hollow engine valve manufacturing method - Google Patents

Abstract

PURPOSE:To reduce material costs by making a non-through round hole by means of a hot static water pressure press in a round bar raw material, forming a tapered section in a part of the outer peripheral area of an opening end, forming a valve shaft section with the raw material extruded without filling a filler in the round hole, forming a bevel section in plasticity processing, and enclosing the raw material with a metal Na bar inserted from an opening end side. CONSTITUTION:A raw material 1a is a heat resistant steel bar and has large diameter than the diameter of a valve shaft. A partially fabricated item having a round hole 10 with a bottom and a tapered section wherein the wall thickness of a part in the area of an opening end gradually increases downward is made with a hot static water press. In the next step, a shaft section 12 is formed by extruding the raw material without filling a filler in the round hole 10, and a bevel section 3a is formed by giving plasticity processing to a part of the bottom of the hole, and a shaft end is cut off, and after cleaning it, a metal Na bar, which becomes a heating medium, is inserted in the hole, forming a metal Na16a with space left at the bottom part, and a shaft end enclosing member 5 is friction welded. A raw material cost can be reduce by deforming the hole 10 using a thick round raw material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a metal sodium sealed engine valve applied to an automobile engine.

[0002]

2. Description of the Related Art In order to achieve high output and high performance of an automobile engine, it is necessary to supercharge the engine and burn a large amount of fuel. In that case, it is necessary to solve the problem of engine cooling. There is. When attempting to increase the output of the engine, problems such as seizure of the piston and piston ring, gas leakage from the engine valve seat, and melting of the valve head portion occur. Since the present invention relates to an engine valve, only the engine valve will be described below. There is no problem because the intake valve of the engine valve is cooled by the intake gas flowing around the valve during the intake stroke, but the exhaust valve is continuously heated by the exhaust gas,
The seizure of engine valves becomes a big problem. The heat of the engine valve flows out from the valve seat and the valve stem into the cylinder head, but in the engine valve in which metallic sodium is sealed, metallic sodium is liquefied at high temperature,
Since it causes convection in the engine valve to promote the heat flow in the engine valve and the temperature of each part of the valve is averaged, it is possible to completely solve those troubles that occur when the engine valve is used. You can

The engine valve in which metallic sodium is sealed as described above is an extremely effective means for increasing the output of the engine. Therefore, it was also used in fighters during World War II. In addition, in order to increase the output of the engine, the engine valve stem is made hollow to reduce the weight of the valve and to facilitate the design of the valve spring. To prevent this, a 4-valve engine tends to be adopted, and the diameter of the engine valve is becoming smaller.

Next, three conventional examples will be described below with reference to FIGS. FIG. 4 is a sectional view showing a method for manufacturing a Na-filled hollow engine valve by the upset method of the first conventional example, and FIG. A round bar material 1b having a predetermined length (outer diameter d ₀ , total length l ₀ ) is upset-molded (resistive current heating compression) to form a spherical portion 2b, and then the umbrella portion 3b is forged. After that, the hollow portion 4 is formed from the shaft end portion by electric discharge machining or a gun drill or the like, and metallic sodium 13 serving as a heat transfer accelerating medium is inserted as necessary, and then sealed by friction welding or the like by the shaft end sealing member 5. 6 is a welded joint.

FIG. 5 is a sectional view showing a manufacturing process of a Na-filled hollow engine valve by the pipe method of the second conventional example, and FIG. One end of a pipe material (outer diameter d ₀ , total length l ₀ ) 1c having a predetermined length is joined by friction welding or the like with the shaft end sealing member 5. 6 is a welded joint. afterwards,
The hollow sphere portion 2c is molded by upset molding (resistive current heating compression) to the opening at the other end, and then the umbrella portion 3c is hot forged. Subsequently, after machining and removing the extra thickness portion 14 and the inner diameter portion 7 of the umbrella portion that obstruct the hollow, after inserting the metallic sodium 13 as a heat transfer accelerating medium as necessary, the projection is performed by the umbrella front side sealing member 8. Seal by welding, etc., and finish the protrusion on the front side of the umbrella by machining.

FIG. 6 is a cross-sectional view showing a manufacturing process of a hollow core material-containing hollow engine valve by the conventional extruded forging method and the conventional extruded forging method.
“Japanese Patent Application No. 61-256203 Fuji Valve (KK)” A large diameter short material (outer diameter = D ₀ , total length: L ₀ ) 1d is provided with a hole 10 which is opened at one end in advance, and a titanium alloy is used as a lightweight core material 14 in the hole. Fill with graphite powder. Then, the opening side end 1
5 is formed by drawing, and then the valve stem portion (outer diameter: d ₀ ) 12 is formed by hot extrusion molding *, and then the non-open large diameter portion (outer diameter: D ₀ ) is hot forged to form the umbrella portion. Mold 3a. The tip of the stem portion marked with * is forged and sealed by hot extrusion molding.

[0007]

[Problems to be Solved by the Invention]

(A) Problem of upset method (Fig. 4) As a result of the progress of multi-valve engine, the shaft diameter (d ₀ ) and the umbrella diameter became smaller. As a result, the diameter (d ₀ ) of the material becomes thin, and (1) there is a drawback that an economically expensive material having a small diameter is used. [The valve material is a difficult-to-work material because it uses heat-resistant alloy steel, and the large-diameter material (8φ to 10φ) is a small-diameter material (6 to 7).
(2) In addition, (2) Also, when drilling hollow holes 4 with a small diameter material using a gun drill, etc., drill breakage and eccentricity occur, defective rate increases, and expensive electric discharge machining is applied. There are drawbacks that cannot be avoided.

(B) Problems of pipe construction method (Fig. 5) As the number of valves increases, the outer diameter (d ₀ ) and inner diameter of the pipe material become smaller, and (1) pipes made of heat-resistant alloy steel are not available in the current technology. Beyond, expensive and difficult. (2) In addition, the welding points are two, that is, the shaft end portion 6 and the umbrella surface portion 8, and the inspection process for ensuring reliability becomes complicated,
As a result, it is difficult to provide an inexpensive hollow valve.

(C) Problems of the exclude forging method (FIG. 6) The exclude forging method has been widely adopted mainly in the United States since the prewar period as a method for manufacturing solid engine valves. Since this method starts with a cheap large-diameter material (D ₀ ) as the diameter of the multi-valve immediate shaft diameter (d ₀ ) becomes smaller, it becomes an economically more advantageous method than the upset method. is there. On the other hand, in the "lightweight engine valve and manufacturing method thereof" disclosed in Japanese Patent Application No. 61-256203, D ₀
After forming the hole 10 in the large-diameter material 1d, the light-weight core material 14 such as Ti alloy or graphite is filled and the opening is drawn.
Here, the use of the lightweight filler 14 means that the stem portion 12
However, it has the following drawbacks.

(1) The deformation resistance at the time of molding increases, a large molding machine is required, and (2) the die life is shortened. (3) The Ti alloy and graphite not only hinder the forge welding seal at the time of sealing the shaft tip, but also the welding hindrance in the case where the welding sealing is performed in the subsequent process. (4) Since Ti alloy and graphite have low thermal conductivity, heat transfer from the cap portion during valve operation is lower than that of a solid valve. (5) Since the filling material is completely filled in the valve, tensile stress is generated in the valve material on the outer periphery, which is not preferable in terms of fatigue strength unless it is annealed to completely remove the stress, and contributes to weight reduction. The degree is low.

The object of the present invention is to solve the above problems, to significantly reduce the material cost, to uniform the deformation resistance during the molding process, to extend the life of the mold, the reliability of the joint portion, and the valve umbrella portion. The heat transfer from the valve shaft to the valve shaft is improved and the weight is reduced. Furthermore, the tensile stress does not remain on the valve shaft.
It is to provide a method for manufacturing an enclosed hollow engine valve.

[0012]

The method for manufacturing a Na-filled hollow engine valve according to the present invention comprises a completed valve by hot isostatic pressing at the center of one end of a round material having a diameter larger than the shaft diameter of the completed engine valve. After forming a non-through circular hole having a diameter larger than the inner diameter of the hollow portion and forming a taper portion in which the wall thickness of a part of the outer diameter region of the opening end gradually increases inward, filling is performed in the circular hole. Without pressing, the outer diameter region of the material is extruded from the opening end side to a predetermined region to form the valve shaft portion, and the umbrella portion is formed by hot plastic working on the large diameter portion of the material on the non-opening end side. After that, a metallic sodium rod is inserted from the opening end side leaving a partial space, and then the opening end is sealed by a sealing member.

[0013]

[Action] destination Dzu outer diameter d of the outer diameter D ₀ by hot isostatic pressing than the outer diameter d ₀ of the large diameter of the material of the finished valve complete valve
A semi-finished product having a circular hole 10 having a bottom larger than ₀ and larger than the inner diameter d _{2 of the} completed valve and having a taper portion in which the wall thickness of a partial region of the upper opening end gradually increases downward is produced.
Further, a predetermined region on the opening end side is extruded without filling the inside of the circular hole 10 to form a valve shaft portion. Next, the remaining bottom portion is subjected to hot plastic working to form an umbrella portion of the valve.
After inserting the rod, the open ends are joined to form a Na-filled hollow engine valve.

[0014]

Embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a manufacturing process of a Na-encapsulated hollow engine valve of the embodiment, FIG. 2 is a cross-sectional view showing the outline of the hydrostatic press molding of the embodiment, and FIG. 3 is a cross-section of a material of the hydrostatic press-molding of the embodiment. It is a figure. In the figure, 1a is a material, 10
Is a hole, 11 is a tapered portion of the opening of the hydrostatic press-formed material,
Reference numeral 12 is a valve shaft portion, 2a is a head portion, 3a is an umbrella portion, 5 is a shaft end sealing material, 16a is metal Na, 16b is metal Na, 6 is a joint portion, 17 is a lower die assembly, and 17a is a lower die ( Cemented carbide hereinafter), 17b is a lower die holder (made of die steel), 18 is an upper die assembly, 18a is an upper die (made of cemented carbide), 18
Reference numeral b is an upper die holder (made of die steel), 18c is a wall thickness tapered portion forming member of the opening of the upper die material, and 19 is a knockout pin (made of cemented carbide).

The operation of the above embodiment will be described. (1) Material 1a is JIS G4311 heat-resistant steel bar SUH3
5 (21Cr · 4Ni · 9Mn) with an outer diameter D ₀ = 17 mm, which is larger than the valve shaft diameter, and a total length L ₀ = 25.1 mm.
7a, the upper mold assembly 18 is lowered at a speed of 60 mm / s, and the outer diameter D ₀ = 17 mm, the total length 30.5 mm, the hole diameter d ₁ = 9 mm, the hole depth 7.5 mm, and the bottom thickness 3 mm. After finishing and molding, the knockout pin 19 pushes it out from the lower mold 17a. (2) The semi-finished product formed as described above is heated again to 1250 ° C. by high-frequency heating, and then, at the second station of the hydrostatic press, a pair of upper and lower molds (not shown) is used to form a hollow part with the tip of the opening of the material at the beginning. Pore size without packing in 6.
Extrude from a 5 mm mold to form the shaft portion 12,
The head 2a is formed while leaving the original diameter D ₀ of the material 18 mm in length. The above-mentioned molded product has a total length of 125 mm, and the shaft has an outer diameter d ₀ =
6.5 mm, inner diameter d ₂ = 3.45 mm, length 107 m
m, the head has an outer diameter of 17 mm and a length of 18 mm.

(3) Next, at the third station of the hydrostatic press, a pair of upper and lower umbrella part forming dies for the head 2a (not shown)
To form an umbrella portion 3a having an outer diameter of 31.6 mm. (4) Then, the member obtained in (3) above is 22 mm from the shaft end.
Cut to a length of 102 mm at the position of, and wash with a hot water jet from the opening, and after drying, outer diameter 3.0 mm, total length 60 mm
After inserting metal Na, which is the heat transfer medium of
The shaft end sealing material 5 of mm was friction-welded and bonded so that the total length was 119 mm. Then, heat treatment, finishing, nitriding, etc. were performed to complete a Na-filled hollow engine valve.

[0017]

Since the present invention is constructed as described above, the following effects are produced. (1) Large diameter material D ₀ (6.5φ → 17.0)
Since φ) is used and the hole 10 is formed by plastic working, the material cost can be significantly reduced. (2) The synergistic effect of using a hydrostatic press, gradually increasing the wall thickness of the opening from the end surface, and not filling the hole with a lightweight core material at the stage of the valve plastic working does not produce The deformation resistance is made uniform, and the life of the die is improved. (3) The reliability of the joint is improved by not using a filler such as Ti alloy or graphite. (4) Metallic Na, which has better heat transfer coefficient than Ti alloy or graphite
Therefore, heat transfer from the umbrella portion to the shaft end side is improved when the valve is operated. (5) Since the metal Na, which has a smaller specific gravity than Ti alloy or graphite, is inserted inside the hole leaving a space, the degree of weight reduction is large. Further, since the filling is incomplete, no tensile stress remains in the outer wall material of the valve during the molding of the valve, which is advantageous in terms of fatigue strength.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a Na-filled hollow valve according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the essentials of isostatic press molding of the same example.

FIG. 3 is a sectional view of a material formed by the hydrostatic press of the same example.

FIG. 4 is a cross-sectional view showing the manufacturing process of the Na-filled hollow engine valve by the upset method of the first conventional example.

FIG. 5 is a cross-sectional view showing the process of manufacturing a Na-filled hollow engine valve using the pipe of the second conventional example.

FIG. 6 is a cross-sectional view showing the process of manufacturing a lightweight core material-containing engine valve by the extruded forging method of the third conventional example.

[Explanation of symbols]

1a ... Material, 2a ... Head, 3a ... Umbrella part, 5 ... Shaft end sealing material, 6 ... Joining part, 10 ... Hole, 11 ... Tapered part, 12 ... Valve shaft part, 16a ... Na, 16b ... Na, Reference numeral 17 ... Lower mold assembly, 17a ... Lower mold, 17b ... Lower mold holder, 18 ... Upper mold assembly, 18a ... Upper mold, 18b ... Upper mold holder, 18c ... Upper mold material opening tapered portion forming portion .

Claims (1)

[Claims] 1. A non-penetrating circular hole (10) larger than the inner diameter of the hollow portion of the completed valve is formed by hot isostatic pressing at the center of one end of a round material having a diameter larger than the diameter of the valve shaft, and one of the open ends is formed. After forming the tapered portion (11) in which the thickness of the outer diameter region gradually increases, without filling the circular hole (10) with a filling material,
The material is extruded from the opening end side to a predetermined area to form the outer shape of the valve shaft portion (12), and the large diameter portion on the non-opening end side is formed with the umbrella portion (3a) by hot plastic working. After that, a metal sodium rod (16a) is inserted from the open end side leaving a partial space, and then the open end is sealed by a sealing member (5), which is a method for manufacturing a Na-filled hollow engine valve. .