JPH0246942A - Forge-compression compact for forming engine valve and forming thereof - Google Patents

Abstract

PURPOSE:To prevent a defect from being generated in a valve bevel neck lower part by forming an inclination angle of the outer peripheral surface of a bulge part of a forge-compression compact to an angle being almost the same as an inclination angle of the forming surface of a forging forming die or above. CONSTITUTION:In the latter half process in which one end of a rod-like stock is brought to forge-compression forming between an anvil electrode and a clamp electrode, forming is executed by reducing gradually the forge-compression forming quantity. In this case, forming is executed by setting the inclination angle theta of the outer peripheral surface of a compact bulge part 3 to almost the same as the inclination angle theta0 of the bevel neck lower part forming surface of a forging forming die 4, or controlling the former to the latter or below. In such a manner, at the time of forming the bevel neck lower part of the valve bulge part 3, the void quantity to the forge-compression compact in the vicinity of the forming surface is reduced. Accordingly, the adhesion of the compact in this part is improved, and the generation of such defects as a fold, a crack, etc., in the valve bevel neck lower part is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a preformed forged body used for forging an engine valve and a method for forming the same.

(Prior art) Conventionally, engine valves have been made by preforming a rod-shaped body with an electric upsetter into a molded body with a forging-formed bulge at one end, and then using this forging to form a predetermined shape. molded engine valves.

Since this rod-shaped material uses a material that is difficult to form, such as heat-resistant steel or heat-resistant superalloy, there are various problems in forming it.

In other words, defects such as wrinkles, scratches, uneven thickness, and buckling that occur during electric upsetter forming, uneven thickness due to poor forging shape that occurs during forging forming, and cranks due to temperature drops affect the quality of molded products. Various improvements have been attempted to provide this. However, a problem that is surprisingly not recognized is that
Wrinkles that occur at the bottom of the molded engine valve head (
When it gets bigger, it becomes a crank).

In engine valves, the strength of the lower part of the cap is important, but the stem, face, and outer diameter of the cap are functionally important and are polished and processed. It is not considered important and is not processed, so if there are wrinkles or cranks in the lower part of the canopy, they will remain as they are and cause problems.

As a result of studying this point, the inventors found that there is a close relationship between the shape of the forged product before forging and the forging mold.

That is, as shown in FIG. 4, which shows the relationship between the shape of the forged body X before forging and the forging mold A, the forged body X formed by the electric upsetter
The inclination angle θ of the outer peripheral surface where the bulging portion Y connects to the rod-shaped base end Z
is the inclination angle θ of the molding surface B that molds the lower part of the engine valve head in the forging mold A. When the size is larger, a large gap is created between the forged body X and the forged body X in the vicinity of the forming surface B, and as a result, the adhesion of the forged body X to the forged body B is poor in this area, resulting in a gap during forming. The flesh of the molded body X is likely to be rolled inward, and wrinkles X are likely to occur at the bottom of the canopy, as shown in Figure 5, which shows a molded engine valve.

(Problems to be Solved) The present invention eliminates such inconveniences and provides a forging molded body formed by an electric upsetter that does not cause wrinkles or cracks in the lower part of the canopy when forming engine valves by forging molding, and The purpose is to provide a molding method.

(Means for Solving the Problems) In order to achieve the above object, the forging molded product of the present invention has the following features:
A forged or contracted body for forming an engine valve, which has a bulge formed by forging at one end of a rod-shaped material, and the angle of inclination of the outer peripheral surface where the bulge extends to the base end of the rod-shaped material is determined by the angle of inclination of the outer circumferential surface of the engine valve. It is characterized in that the lower part of the head of the engine valve in the forging mold for molding is formed at an angle that is approximately the same as or smaller than the inclination angle of the molding surface.

Further, the forming method of the present invention uses an electric upsetter that applies electricity between an anvil electrode, which one end of the rod-shaped material contacts, and a clamp electrode that grips the rod-shaped material, and directly heats the rod-shaped material while pushing it into forge-forming. In the latter half of the molding process,
The method is characterized in that the forged body for molding engine valves is formed by gradually reducing the amount of forging formed on the rod-shaped material.

In the latter half of the process of molding the electric upsetter, the set voltage and pushing force are kept constant, and the pushing speed is gradually reduced.

(Function) When forging an engine valve using the forging molded body of the present invention, the angle of inclination of the outer circumferential surface where the bulging part of the forging molded body is connected to the rod-shaped base end is determined by the forging mold. Since the angle of inclination is approximately the same as or smaller than the inclination angle of the molding surface that molds the lower part of the canopy of the engine valve, the gap between the molded body and the forged body in the vicinity of the molding surface is reduced,
For this reason, the adhesion of the forged molded product in this area is good (and the wrinkles that occur in the lower part of the canopy as in the past do not occur).

Further, according to the above-mentioned forming method, by gradually reducing the forging amount in the latter half of the forming process of the electric upsetter, the bulging part of the forging formed body is formed at an angle of inclination of the outer circumferential surface where the bulge part is connected to the rod-shaped base end. It becomes possible to mold the angle of inclination of the molding surface for molding the lower part of the head of the engine valve in the forging mold to be approximately the same or smaller than the angle of inclination.

Then, in order to gradually reduce the forging amount, the set voltage and pushing force are kept constant, and the pushing speed is gradually reduced.

(Example) An example of the present invention will be explained in detail using FIGS. 1 to 3.

Fig. 1 is a sectional view for explaining the relationship between the forging formed body and the forging mold of this example, Fig. 2 is an explanatory drawing for explaining forging forming by an electric upsetter, and Fig. 3 FIG. 2 is a diagram for explaining control of the amount of forging.

Reference numeral 1 denotes a forged body formed by the electric upsetter of this embodiment, and the forged body 1 has a bulge 3 connected to a rod-shaped base end 2 of the portion forming the lower part of the bare neck of the engine valve. The inclination angle θ of the outer circumferential surface is the inclination angle θ of the molding surface 5 for molding the lower part of the bare neck of the engine valve of the forging mold 4, as shown in the first diagram. It was formed to be approximately equal to or smaller than that.

Therefore, the gap between the bulging portion 3 and the molding surface 5 is reduced, and when an engine valve is forged using the forging molded body 1, wrinkles and cracks are generated in the lower part of the molded bare neck. It no longer occurs.

An embodiment of a method for forming a forged body l having such a shape using an electric upsetter will be described with reference to FIGS. 2 and 3.

As shown in the second diagram, forge forming using an electric upsetter is
Electricity is supplied between an anvil electrode 7 on which one end of the rod-shaped material 6 comes into contact and a clamp electrode 8 that grips the rod-shaped material 6, and the rod-shaped material 6 is directly heated and pushed into the rod-shaped material 6 by a hydraulic cylinder 9 to forge-form.

At this time, the inclination angle e of the outer circumferential surface of the portion of the bulging portion 3 to be molded that is continuous with the rod-shaped base end 2 is set to be approximately the same as or smaller than the inclination angle e0 of the molding surface 5 of the forging mold 4 described above. In order to achieve this, the amount of forging is gradually reduced in the latter half of the forging process.

That is, in the latter half of the molding process, the portion of the bulging portion 3 that is continuous with the rod-shaped base end 2 is likely to be molded, and by gradually reducing the amount of molding at this time, the inclination angle θ becomes small.

In this way, in order to reduce the forging amount in the latter half of the forging process, as shown in the third diagram, when the set voltage and pushing force are kept constant, the pushing speed is gradually reduced.

(Effects) As is clear from the above description, according to the present invention, when forging an engine valve, the engine valve molding method is provided with a bulge formed by forging at one end of a rod-shaped material as a preform. The inclination angle of the outer circumferential surface where the bulging part is connected to the base end of the rod-shaped material is the same as that of the forming surface for forming the lower part of the bare neck of the engine valve in a forging mold for engine valve forming. Since it is formed at an angle that is approximately the same as or smaller than the inclination angle, when it is formed into an engine valve, it can be made to have excellent strength without causing wrinkles or cranks in the lower part of the bare neck.

Further, the forged body for molding engine valves of the present invention can be easily manufactured by gradually reducing the amount of forged molding in the latter half of the process of molding the electric upsetter.

[Brief explanation of the drawing]

Fig. 1 is a sectional view for explaining the relationship between the forging formed body and the forging mold of this example, Fig. 2 is an explanatory drawing for explaining forging forming by an electric upsetter, and Fig. 3 4 is a diagram for explaining the control of the amount of forging, FIG. 4 is a sectional view for explaining the relationship between a conventional forged body and a forging die, and FIG. It is a sectional view showing zinc molding. ■... Forging molded body for engine valve molding 2... Base end part 3... Swelling part 4... Forging mold 5... Molding surface 7... Anvil electrode 8...
Clamp electrode θ. ...Inclination angle θ of molding surface ...Inclination angle stroke of molded object

Claims (1)

[Scope of Claims] 1. A forging molded body for engine valve molding, which has a bulge formed by forging on one end of a rod-shaped material, the outer circumferential surface of which the bulge extends to the base end of the rod. The forging for engine valve forming is characterized in that the angle of inclination is approximately the same as or smaller than the inclination angle of the forming surface for forming the lower part of the head of the engine valve in the forging mold for forming engine valves. Molded object. 2. In the latter half of the forming process of the electric upsetter, which applies electricity between the anvil electrode that one end of the rod-shaped material comes into contact with and the clamp electrode that grips the rod-shaped material, the rod-shaped material is directly heated and pushed into forge-forming. 3. A method for forming a forged body for engine valve forming according to claim 1, characterized in that the forging formed body for engine valve forming according to claim 1 is formed by gradually reducing the amount of forging formed on a rod-shaped material, The method for forming a forged compact for engine valve forming according to claim 2, characterized in that in the latter half of the forming process, the set voltage and pushing force are kept constant and the pushing speed is gradually reduced.