JP3254777B2 - Split mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a split mold for molding, and more particularly to a split mold suitable for forging a bevel gear.

[0002]

2. Description of the Related Art For example, in forging a bevel gear, a material is put into a female mold having a tooth profile, and the material is pressed against the female mold by a punch to form a tooth profile. FIG. 2 shows an example of a conventional bevel gear forging die. 2A is a cross-sectional view of a female mold, and FIG. 2B is a plan view of a part. In the female mold 21, a large number of tooth forming parts 22 are radially formed as concave parts, and between each tooth forming part 22, a convex part 2 for forming the bottom of the product is formed.
4 are integrally formed. When forging is performed using this bevel gear forging die, since the diameter of the bottom portion 23 of the female die is reduced, stress generated by a load during forging concentrates on the bottom portion 23, and the die is damaged. In particular, stress is locally concentrated on the small-diameter portion 25 inside the convex portion 24 that forms the bottom of the product, and a crack is generated in this portion 25 of the mold 21.

[0003] In order to disperse the concentration of stress generated in the mold and to facilitate the manufacture of the mold, various types of divided molds have been proposed. FIG. 3 shows an example of a split type bevel gear forging die. FIG. 3A is a cross-sectional view of a female mold, and FIG. 3B is a plan view of a part. In this split mold, a tooth forming portion 32 is formed in a mold body 31, and an inner portion from an inner diameter portion 35 of an umbrella-shaped small diameter portion of a product bevel gear at a bottom portion 33 is fitted as a hollow cylindrical split mold 30. The mold body 31 and the split mold 30 are separated from each other by a circular dividing line 3.
6 corresponds to the one obtained by dividing the integrated female mold 21 of FIG. In this split mold, a stress at the bottom 33 is received by the mold body 31 and the split mold 30 at the time of forging, but the stress is locally applied to the small-diameter portion 37 inside the convex portion 34 that forms the tooth bottom of the product. concentrate.

FIG. 4 shows another example of a split type bevel gear forging die. 4A is a cross-sectional view of a female mold, and FIG. 4B is a plan view of a part. In this split mold, the inside from the outer diameter portion (umbrella-shaped large-diameter portion) of the product bevel gear is fitted into a mold body 41 as a split mold 40, and the tooth forming shape portion 42 is fitted into the fitted mold body. 41 and the split mold 40. In this case, the two dividing lines are circular dividing lines 43 as shown in FIG. 4B. In this split die, stress is applied to the die bottom by the split die 40 at the time of forging, and the stress is locally concentrated on the small diameter portion 45 inside the convex portion 44 that forms the tooth bottom of the product. Further, Japanese Patent Application No. 1-197029 discloses a mold in which the split mold 40 shown in FIG. 4 is further divided inside from the inner diameter of the product bevel gear.

[0005] In the above-mentioned integrated mold and split mold, when the forging load increases, stress concentrates on the bottom of the mold and the mold is damaged. In particular, stress is locally concentrated on the small diameter portion (25 in FIG. 2, 37 in FIG. 3, and 45 in FIG. 4) inside the convex portion of the mold for molding the tooth bottom of the product. Cracks occur.
The cracking site of this die is the site of the root bottom end K of the tooth profile G of the forged product bevel gear W shown in FIG. 5, and molding failure occurs at this site of the forged product.

In order to solve the problems of the integral type and the split type, there is a split type as shown in FIG. FIG.
6A is a cross-sectional view of a female mold, FIG. 6B is a plan view of a part, and FIG. 6C is a cross-sectional view taken along line YY of FIG. 6A. In the female mold body 51, a large number of tooth forming portions 52 are radially formed as concave portions, and an inner portion extends from a bottom corner 53 (corresponding to a tip portion of a tooth-shaped small diameter portion of a product bevel gear). A petal-shaped hollow cylindrical split mold 50, and a female main body 5
Carve a recess along the petal-shaped dividing line 55 in 1
Both are fitted.

[0007]

In the split mold of this type, the concentration of stress on the inner convex portion at the bottom of the conventional mold is reduced, but the stress on the corner 53 of the bottom of the female mold body 51 during forging is reduced. Concentration occurs, and cracks occur at both ends 54 of the recess. The cracks in the die are located at both ends E of the tooth tips of the tooth shape G of the forged product bevel gear W shown in FIG. 7, and a molding failure occurs in this portion of the forged product. Further, since this portion E is a joint portion between the female mold main body 51 and the split mold 50, it is not rounded, and the product bevel gear W has a sharp edge, so that the engagement with the mating bevel gear becomes poor. Furthermore, it is difficult to process the female mold body 51 and the split mold 50 along the petal-shaped dividing line 55, and to accurately process the phases of the two, the mold becomes expensive, and the phase matching becomes impossible. If it is accurate, burrs will occur on the product during forging along the parting line of both molds.

The present invention solves the above problems of the split mold, eliminates local stress concentration of molding pressure, greatly increases the life of the mold, and provides a split mold that can be manufactured at low cost. Aim.

[0009]

According to the present invention, a molded part for forming a convex part of a product on a female mold body is formed as a concave part,
A rounded corner is formed at the bottom corner of the concave portion, and an inner portion separated from the corner by a small distance is formed into a petal-shaped tubular split type, and the female main body is also formed into a split-type petal-shaped external shape. A split mold in which the combined concave portion is carved and the female mold body and the split mold are fitted.

[0010]

In this split mold, the mold bottom where the stress due to the molding pressure is concentrated at the time of molding is formed as a split mold and the bottom corner is rounded, so that local stress concentration at the mold bottom can be prevented. In addition, since the position of the petal-shaped dividing line between the female main body and the split mold is slightly shifted inward from the bottom corner, a slight phase shift in the fitting portion between the female main body and the split mold can be tolerated.

[0011]

FIG. 1 shows an embodiment of the present invention.
1B is a cross-sectional view of a female mold, FIG. 1B is a plan view of a part, FIG. 1C is a cross-sectional view taken along line XX of FIG. 1A, and FIG. 1D is a perspective view of a part of a forged product bevel gear. The female mold body 1 has a large number of tooth-forming portions 12 formed radially as recesses, and between each tooth-forming portion 12, a convex portion 14 for forming the bottom of a product is formed. Corner 1 of molded part 12
3 (corresponding to the tip of the tooth-shaped small-diameter portion of the product bevel gear) has a roundness R, and the inner portion from the inner portion 20 separated from the corner 13 by a small distance L (about 0.5 to 1.5 mm), The outer shape is a hollow cylindrical split mold 2 having a petal shape, and a concave portion along the petal split line 10 is engraved in the female mold body 1 and both are fitted together. Reference numeral 3 denotes a product die-cutting hole. .

In this split mold, since the corner 13 of the tooth forming portion 12 is formed in the female body 1, the corner 13 can be rounded, and the female body 1
Since the corner 13 is rounded, concentration of local stress on this portion can be prevented, and the life of the mold can be greatly increased. In addition, since the position of the maximum diameter 20 of the petal-shaped parting line 10 is slightly shifted inside the corner 13 of the tooth forming part 12, a slight phase shift between the female body 1 and the parting mold 2 can be tolerated. Therefore, processing of the mold becomes easy, and the mold can be manufactured at low cost. Even if there is a gap between the fitting portion between the female mold body 1 and the split mold 2 and a burr occurs on the product forged with the split mold, the burr generated on the product is indicated by a broken line 1 in FIG. 1D.
Since it occurs on the end face of the product W along the dividing line of the mold indicated by 0, there is no effect on the meshing surface of the product gear.

In the above embodiment, the forging die for a bevel gear has been described. However, the present invention is not limited to this, and the present invention can be applied to a molding die for a product having a shape having irregularities in the inner circumferential direction. .

[0014]

According to the present invention, in a mold having irregularities in the circumferential direction, local stress concentration due to molding pressure during molding is eliminated, the life of the mold is greatly increased, and the mold can be manufactured at low cost.

[Brief description of the drawings]

1A and 1B are cross-sectional views, FIG. 1B is a partial plan view, FIG. 1C is a cross-sectional view taken along line XX of FIG. 1A, and FIG. 1D is a perspective view of a part of a product. FIG.

FIG. 2 shows a conventional forging die, and FIG.
FIG. 2B is a plan view of one part.

3A and 3B show a conventional split mold, FIG. 3A is a cross-sectional view, and FIG. 3B is a plan view of a part.

4A and 4B show another example of a conventional split mold, where FIG. 4A is a cross-sectional view and FIG. 4B is a plan view of a part.

FIG. 5 is a partial perspective view showing a molded product using a conventional mold.

6A and 6B show another example of a conventional split mold, FIG. 6A is a cross-sectional view, FIG. 6B is a plan view of a part, and FIG. 6C is YY in FIG. 6A.
Sectional view along the line.

FIG. 7 is a partial perspective view showing a molded body formed by a split mold according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Female type main body 2 Split type 10 Petal-shaped parting line 12 Teeth forming part 13 Tooth forming part bottom corner

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Claims (1)

(57) [Claims] 1. A molded part for forming a convex part of a product in a female mold body is formed as a concave part, a rounded part is formed at a bottom corner of the concave part, and an inner part separated from the corner by a small distance is formed. The split is characterized in that the external shape is a petal-shaped cylindrical split type, and the female main body is carved with a concave portion corresponding to the split-type petal-shaped external shape, and the female main body and the split type are fitted. Mold.