JPS606730B2 - Closed forging method for bevel gears - Google Patents

Description

[Detailed description of the invention] The present invention relates to a closed forging method for bevel gears.

The closed forging method is an extremely efficient production method that can mass produce products with complex shapes at high speed. However, when forging a bevel gear 2 with teeth 1 protruding from the outside as shown in Fig. 1, under the forging force within the permissible range of the punch, the outer end, especially the back conical surface 3, may be underfilled. Therefore, it was not possible to form a good shape, and in order to form a good shape without underfilling, the forging force of the punch had to be increased beyond the allowable range. Therefore, the durability of the mold and punch cannot be obtained, and it has been difficult to practically perform closed forging of a good bevel gear without underfilling. The present invention was developed in view of the above points, and the forging pressure of the conventional flat-headed punch restricts the flow of the forging material at the roots of the teeth of the bevel gear, resulting in increased flow resistance. Eliminate the
The forging material can be smoothly filled up to the outer end of the cavity, and the forging force of the punch can be maintained at a small load within the allowable range without causing any underfilling on the back conical surface of the outer end. To provide a closed forging method for bevel gears, etc., which can practically mass-produce bevel gears having a desired shape.

Hereinafter, the present invention will be explained with reference to examples. FIG. 2 shows an example of a bevel gear 2 forged according to the present invention, in which the back conical surface 3 of a portion of the tooth 1 does not become underfilled as shown in FIG. 1, and can be formed into a desired shape. FIG. 3 and the following are embodiments of the present invention, and are an example of closed forging of the bevel gear 2 as shown in FIG. 2 above.

Mold 4 is an upper mold 5 which is divided into upper and lower halves by one tooth of bevel gear 2.
and a lower mold 6, and an upper punch 7 and a lower punch 8 are freely retractable in the center of each, and a desired bevel gear 2 is formed.
The cavity 9 can be formed. The entire forging surface of the end surface of the upper punch 7 on the small diameter gear side on the upper mold 6 side for forming the upper part of the teeth 1 of the bevel gear 2 has an apex angle of 120 as shown in the figure.
The forging surface 10' has a conical height shape with an obtuse angle of 100 degrees, and the root part 11 of the tooth 1 is widened so that the flow of the forging material 12 is not narrowly restricted but is shaped like a mountain wisteria. I allow it to flow. The lower punch 8 is of a normal flat head shape and is used to form the ball portion 13 of the bevel gear 2 and pass the forging material 12 to the outer end of the cavity 9 to the outer end of the back conical surface of the bevel gear. It is made to flow by forging with a forging load that supports this.
An example of closed forging of the bevel gear 2 will be described.

After completing the upper punch from mold 4, press the lower punch 8 into the specified forging press (
As shown in FIG. 3, the cylindrical forged material 12 in a warm state is mounted on the lower punch 8 which is retracted downward, and housed in the cavity 9. Then, as shown in Fig. 4, the upper die 5 and the upper punch 7 are lowered to bring the upper die 5 into close contact with the lower die 6.
First, press. At this time, the forged material 2 is conically depressed at one end as shown in the figure, and bulges out slightly toward the outer periphery of the cavity 9 and the like. Next, when the lower punch 8 is raised and the forged material 12 is forged, the forged material 2 shrinks as shown in FIG. 5, forms a bag portion 13, and flows toward the outer circumference of the cavity 9. Since the forging surface 10 of the upper punch 7 has a conical height shape, the root portion li of the tooth 1 is
As shown in the figure, the forging material 12 flows smoothly along the forging surface 10 to the outer end without becoming narrow and causing the flow of the forging material 12 to be in a constricted state, thereby reliably forming the back conical surface 3 of the bevel gear 2. be. Therefore, the forging force of the lower punch 8 can be set to a small load within the allowable range, and even though the forging force is small, the back conical surface 3 does not become under-filled as in the conventional case, and a good condition as shown in Fig. 2 is achieved. The cage gear 2 can be pressed into a desired shape. When the lower punch 8 finishes forging, the upper die 5 and the upper punch 7 are raised as shown in Fig. 6, and the lower punch 8 is further raised to carry out the forged bevel gear 2 and then the next forged material 12. It is to be housed and closed forged in the same manner as above. Note that the drilling process is performed in a later process. In the above example, the outer diameter of the overflow state of 300 to 50,000 is 35
When forging a bevel gear with an outer end diameter of 65 mm from willow forging material, the compressive stress of the punch is reduced to 180 to 206 kg, which is sufficiently within the allowable range, whereas in the conventional method the compressive stress of the punch was 300 kg or more. This is a 40% reduction, and the durability of the punch can be put to practical use in the mass production of bevel gears.

In the above example, the forging surface of the upper punch was made into a conical peak shape with an apex angle of 120 degrees, but even if the apex angle was set to 60 degrees, the forging force was within the allowable range, and the shape of the bevel gear was However, an apex angle in the range of approximately 60 to 160 degrees to, more preferably, an obtuse angle range is sufficient for practical use.

In addition, the shape of the forging surface of the upper punch is not limited to a conical shape, but can also be a mountain shape or a spherical shape that is easy to process. It is more preferable to have a shape.

Furthermore, according to the present invention, forging, which was previously impossible with the closed forging method described above, can be performed within a predetermined tolerance range by setting the apex angle of the forging surface to an appropriate angle as described above. It can be closed forged using forging pressure, and cold closed forging of bevel gears can also be put to practical use.

As described above, in the present invention, all end faces of the punch on the small diameter gear side of the bevel gear to be forged have a predetermined inclination angle and are not perpendicular to the punch axis, and furthermore, the flow of the forging material is prevented. This eliminates the constriction at the root of the bevel gear teeth, which increases flow resistance, and enables smooth flow filling all the way to the outer edge of the cavity.Also, even though the hoeing pressure is applied at temperatures below the interstitial state, First, the forging force of the punch can be made as small as possible within the allowable range, thereby increasing the durability of the punch and die.Moreover, it is possible to fluidly fill the forging material without causing underfilling of the back cone of the bevel gear. Therefore, it is possible to practically produce bevel gears and the like having a good desired shape.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a conventional closed forged bevel gear, Fig. 2 is a side sectional view of an example of a closed forged bevel gear of the present invention, and Figs. 3 to 6 are an embodiment of the same as above. FIG. 3 is a side sectional view of a main part for explaining each process of closed forging. Tortoise: Teeth 2: Bevel gear, 3: Back conical surface, 4: Mold, 5: Upper mold, 6: Lower mold, 7. ... Upper punch, 8... Lower punch, 9... Cavity, 10... Forging surface. 11... Root part, j2
...Forged material. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. In a closed forging method for bevel gears in which a forging material is stored in a predetermined cavity formed by a die and a punch and the forging material is filled into the cavity by forging, the punch that appears in the cavity on the small diameter gear side of the bevel gear to be forged is All end faces are formed into a conical or hemispherical raised shape with an apex angle of approximately 60 to 160 degrees, and the punch side with this raised shape is first entered into the cavity to press the forged material, and then the other opposing punch is inserted into the cavity. Closure of a bevel gear, characterized in that the forged material is pushed with a forging load to the extent that it comes into contact with the outer end surface of the back conical surface of the bevel gear in the cavity, and the forged material is forged at a temperature below the warm state. Forging method.