JPH0557388A - Method for forming engine valve - Google Patents

Abstract

PURPOSE:To provide a forming method for engine valve which can be easily formed even in the case of using a difficult-to-work material. CONSTITUTION:By using rolls 1, 2, 3 for rolling forming a recessed part 7 for forming valve part in an engine valve at an outer peripheral face and arranged with plural pieces in parallel in a radial direction, a round bar-like raw material is rolled in isothermal atmosphere, and the projecting part 12 is formed with the recessed part 7 at the center part of the raw material 11. Further, after forming the both side parts 13, 13 to almost the same size as shaft parts in the engine valve, the formed material is bisected at the projecting part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding an engine valve, which is capable of easily molding a material which is difficult to process.

[0002]

2. Description of the Related Art An engine valve for a vehicle is composed of a valve portion 21 and a shaft portion 22 as shown in FIG. 6, and is conventionally made of a high alloy steel material. As the forming method, as shown in FIG. 7, a round bar material 23 having substantially the same diameter as the shaft portion 22 is subjected to several steps (A),
It is generally formed by hot upsetting of (B) and (C). In the figure, 24 is a forming die and 25 is a pressure punch.

[0003]

However, recently, a lighter weight and heat-resistant material has been demanded, and one example thereof is Ti-A.
There are intermetallic compounds. This type of intermetallic compound is lightweight and excellent in heat resistance, but it has extremely poor workability, and
It can be molded only at a high temperature of 00 ° C and at a low strain rate (10 ^-2 to 10 ^-4 / sec). Therefore, when the conventional hot upsetting is applied, high-speed processing cannot be performed, the temperature is lowered, and molding is difficult.

That is, in the conventional hot upsetting, the material is preheated and then processed in several steps in a short time, and it is difficult to perform high temperature and low speed processing. Further, since the diameter ratio between the valve portion 21 and the shaft portion 22 of the valve is generally about 3 to 5, when the valve portion 21 is installed from the round bar material 23 having the same diameter as the shaft portion 22, the deformation amount becomes extremely large. , Difficult to process materials such as Ti-Al cause cracks.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for molding an engine valve which is easy to mold even a difficult-to-machine material.

[0006]

According to the forming method of the present invention, the outer peripheral surface is formed with a concave portion for forming a valve portion of an engine valve, and a plurality of rolling rolls are arranged parallel to the radial direction in a constant temperature atmosphere. After rolling a round bar-shaped material with the above-mentioned method, a convex portion is formed in the central portion of the material by the concave portion and both side portions thereof are formed to have substantially the same dimensions as the shaft portion of the engine valve, and then the molding material is divided into two by the convex portion. ..

[0007]

In the constant temperature atmosphere, rolling is repeatedly subjected to compressive deformation, so that it is possible to process at a low speed while maintaining the temperature, and to form a difficult-to-process material without causing cracks. Also, after rolling one material, the molding material is divided into two by the convex portion, so that it is possible to improve the production efficiency, and by molding the convex portion in the central portion,
It can facilitate the flow of material in the axial direction of the material,
Excellent moldability.

[0008]

First, a molding apparatus for carrying out the present invention will be described. FIG. 1 shows the main part of the molding apparatus,
The three forming rolls 1, 2, 3 are radially arranged so that their axes are parallel to each other, and a pair of bearing members 4, 4, 5, 5, 6, 6 are arranged in front of and behind the body of the roll. It is rotatably supported by. The bearing member 4 of the upper roll 1 is fixed. On the other hand, the bearing members 5 and 6 of the lower rolls 2 and 3 are configured to be movable back and forth by a hydraulic cylinder, an electric cylinder, etc. along the radial direction, and as shown in FIG.
The diameter of the inscribed circle of each roll 1,2,3 is adjusted by moving forward and backward. A concave portion 7 for forming the valve portion is formed on the outer peripheral surface of the body of the rolls 1, 2, 3 and its cross-sectional shape is almost the same as that of the end surfaces of the valve portion 21 which are adjacent to each other with a constant gap. It is a cross section. Generally, the roll is ceramic and the bearing box is N
i-base super heat-resistant alloy, bearing is made of graphite,
Any material can be used as long as it has heat resistant strength without being limited to the above materials. The forming rolls 1, 2 and 3 are installed in a heating device and heated together with the round bar-shaped material up to 1200 ° C. Incidentally, it goes without saying that the drive unit 8 of the forming rolls 1, 2, 3 and the drive cylinders of the bearing members 5, 6 are installed outside the heating device. Further, in FIGS. 1 and 2, reference numeral 11 denotes a round bar-shaped forming intermediate material.

In order to carry out the present invention, the lower forming rolls 2, 3 are opened outward in the radial direction, a round bar-shaped material is placed inside thereof, and then the heating device is heated to a predetermined temperature. After raising the temperature, bring the molding rolls 1, 2, and 3 into close proximity while rotating,
Start molding. FIG. 3 shows a state of forming the material 11 at the initial stage of forming. Both side portions 13 and 13 except the convex portion 12 corresponding to the concave portion 7 of the roll are radially reduced by the rolls 2 and 3 approaching while rotating. As a result, the film is stretched in the axial direction. Figure 4 shows the state of forming the material 11 at the end of forming.
The convex portion 12 is molded to the outer dimension of the material, and the both side portions 13 and 13 are molded to the dimension of the engine valve shaft portion. The molding material after molding is
As shown in FIG. 5, the protrusion 12 is cut in the direction perpendicular to the axial center. Therefore, two molding engine valves 14 and 14 are obtained by one molding.

According to the above procedure, φ-50 mm Ti-50at%
Round bar material of Al, temperature 1100 ℃, strain rate 1 × 10 ^-2 / se
As a result of molding with c, two products with a valve diameter of 35 mm and a shaft diameter of 9 mm were obtained by molding once. The heating atmosphere may be in the air, but may be a vacuum or an inert atmosphere for preventing oxidation depending on the material of the roll material or the material to be processed. Further, the number of forming rolls is not limited to that in the embodiment, and a backup roll may be provided to prevent the roll from bending. Further, as the roll supporting means, instead of using the bearing member, a structure for supporting the entire body of the roll may be adopted.

[0011]

According to the method of molding an engine valve of the present invention, since it is possible to repeatedly apply compressive deformation in a constant temperature atmosphere by using a molding roll, it is possible to perform processing at a low strain rate and cause cracking. It can be easily molded into a predetermined shape without causing it. Moreover, since the predetermined concave portion is formed on the outer peripheral surface of the roll, it is possible to mold two products at the same time, and it is possible to easily cause a material flow in the axial direction of the material, which is excellent in productivity.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a molding apparatus for carrying out the present invention.

FIG. 2 is a cross-sectional view of a forming roll body of the forming apparatus.

FIG. 3 is a cross-sectional explanatory view showing a molded state of a rod-shaped material in the initial stage of molding.

FIG. 4 is an explanatory cross-sectional view showing the same molding state at the final stage of molding.

FIG. 5 is a front view showing a state in which a molding material is divided into two.

FIG. 6 is a front view of an engine valve to be molded.

FIG. 7 is a cross-sectional explanatory view showing an upsetting process of an engine valve.

[Explanation of symbols]

 1 Forming Roll 2 Forming Roll 3 Forming Roll 7 Recess 11 Material 12 Convex 13 Both Sides

Claims (1)

[Claims] 1. A round bar-shaped material is rolled in a constant temperature atmosphere by a rolling roll having a concave portion for molding a valve portion of an engine valve formed on an outer peripheral surface thereof and arranged in plural in parallel with a radial direction. A method for molding an engine valve, characterized in that a convex portion is formed by the concave portion and both side portions thereof are formed to have substantially the same dimensions as a shaft portion of the engine valve, and then a molding material is divided into two by the convex portion.