JP2001073003A - Method for compacting helical gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of cracks on the root parts of teeth at the time of compacting a helical gear. SOLUTION: At the time of engaging the outer circumferential helices (p) of a lower punch 7 and the outer circumferential helices (q) of an upper punch 8 to the inner circumferential helices (r) of an intermediate die 10, applying a compressive load on raw material powder G charged to the space between the upper punch 8 and the lower punch 7 to form a compacted body of a helical gear, the lower faces of the tip parts of the outer circumferential helices (q) of the upper punch 8 and the upper faces of the tip parts of the outer circumferential helices (p) of the lower punch 7 are formed with inclined projecting parts (t), and, at the time of compacting, a part of the raw material powder at the tip parts (a) is pushed to the root parts (b) to increase the density of the root parts (b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for enhancing the strength of a tooth root when compacting a helical gear.

[0002]

2. Description of the Related Art Conventionally, as a compacting technique for producing a helical gear as a sintered product, for example, a technique such as Japanese Patent Application Laid-Open No. H11-58087 proposed by the present applicant has been known. In this technique, the inner periphery of the floating die (intermediate die) is meshed with the outer periphery of the upper and lower punches, and the raw material powder filled in the space surrounded by the floating die and the upper and lower punches is A compression load is applied by the upper and lower punches to perform compacting.

[0003]

However, in the above-mentioned compacting method, for example, when the torsion angle of the helical body is to be deepened, or when the tooth profile having a small tooth thickness is to be formed. However, there is a problem that when the intermediate die is released after the compacting is completed, cracks are likely to be generated particularly in the tooth roots of the teeth of the molded product.

Accordingly, the present invention provides a method for forming cracks in the tooth root portion of a powder compact, even when the torsion angle of the helical piece becomes deep or when gear parts having a small tooth thickness are formed. The purpose is to make it difficult.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an intermediate die formed by an intermediate die and a lower punch, wherein an inner peripheral portion of the lower punch is engaged with an outer peripheral portion of the lower punch. After the raw material powder is filled in the concave space, the inner periphery of the intermediate die is meshed with the outer periphery of the upper punch on the upper part of the base, and then a compression load is applied to the raw material powder by the upper and lower punches. In the powder compacting method of a helical gear, which is formed by powder molding, the outer periphery of the upper punch and the lower punch is used for pushing a part of the raw material powder on the tip side to the root side of the helical tooth. An inclined convex portion was formed, and the density of the root portion was increased by the inclined convex portion to perform compacting.

Here, the reason why cracks are generated in the root portion when the intermediate die is released after the completion of the compacting is that, for example, a compact of about 420 tons is applied from the upper punch to the compact after the compacting. When the upper die is shifted laterally when the intermediate die which has been restrained around the load is reduced to about 4 tons and then the intermediate die is released, the lower surface of the upper punch drags the upper surface of the molded product. I think that the.
Therefore, the density of the root portion is increased to increase the strength, and the occurrence of cracks in the root portion is prevented.

Here, the outer periphery of the upper punch and the lower punch is formed as an inclined convex portion formed on the tip of the skirt, for example, on the lower surface of the tip of the upper punch and on the upper surface of the tip of the lower punch. The convex shape of the inclined surface is formed so that the amount of protrusion gradually increases, so that a part of the raw material powder on the tooth tip automatically flows toward the tooth root when a compressive load is applied. To On this occasion,
The inclined surface may be a linearly inclined surface or a curvedly inclined surface.

[0008]

Embodiments of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 is a schematic diagram of the structure of a powder compacting apparatus to which the method of compacting a helical gear according to the present invention is applied, and FIG. FIG. 3 is an explanatory diagram of the reason for the occurrence of cracks, and FIG. 4 is an explanatory diagram of the locations where the cracks occur.

A method for compacting a helical gear according to the present invention is applied to compacting a helical gear in a compacting apparatus 1 as shown in FIG. A lower plate 3 fixed to the base 2, a guide post 4 erected on the machine base 2, an intermediate plate 5 floatingly supported by a floating mechanism (not shown) with respect to the guide post 4, and a guide post 4 An upper plate 6 that can be moved up and down by a press mechanism (not shown) is provided.

Then, on the upper part of the machine base 2 and the lower plate 3,
The lower punch 7 is fixed. The lower punch 7 includes an outer lower outer punch 7a and an inner lower inner punch 7b, and a rim p is formed on an outer peripheral portion of the lower outer punch 7a. ing.

An upper outer punch 8 is provided below the upper plate 6, and the upper outer punch 8 is fixed to the upper plate 6 by an upper inner punch 8b.
And an upper outer punch 8a rotatable around the vertical axis around the upper inner punch 8b, and a rim q is formed on an outer peripheral portion of the upper outer punch 8a.

An intermediate die 10 is provided at the center of the intermediate plate 5 so as to be rotatable about a vertical axis. An inner periphery of the intermediate die 10 is formed with a rim r. I have. The inner circumference of the intermediate die 10 is
The outer periphery of the lower outer punch 7a is
Are engaged with each other so that a concave portion for filling the raw material powder is formed in a space surrounded by the lower outer punch 7a and the intermediate die 10.

The inner periphery of the intermediate die 10 is located above the upper punch 8a when the upper punch 8 is lowered.
The outer periphery of the upper outer punch 8a is provided with a phase guide 11 so that the outer periphery of the upper outer punch 8a and the inner periphery of the intermediate die 10 are in phase with each other. The outer periphery of the upper outer punch 8a meshes with the rim s, and the inner periphery of the phase guide 11 meshes with the rim s.

When the upper punch 8 descends, the upper outer punch 8a rotates while the inner periphery of the phase guide 11 is guided by the sub-square s, and the lower surface of the upper outer punch 8a is
0, the upper outer punch 8a
The outer circumference of the intermediate die 10 is made to coincide with the phase of the rim q, and the inner circumference of the intermediate die 10 is made to coincide with the phase of the rim r.

The outer periphery of the upper outer punch a is a lower surface of the tip of the helical q, and the outer periphery of the lower outer punch 7a is
An inclined convex portion t as shown in FIG.

The inclined convex portion t is formed as an inclined surface such that the amount of protrusion gradually increases outward (toward the tip of the tooth tip). When a compressive load is applied to the raw material powder G in the manner described below, Part of the raw material powder G on the tooth tip side can be pushed to the tooth root side.

The above compacting apparatus 1 has the same structure as that of the conventional compacting apparatus except for the inclined projections t of the upper outer punch 8a and the lower outer punch 7a. The cause of crack generation and the like will be described again.

First, the raw material powder G is filled in a concave space surrounded by the intermediate die 10 and the lower punch 7, and the upper punch 8 is lowered. The upper outer punch 8a rotates while rotating around the axis of the upper inner punch 8b. Descends and its outer circumference is q
However, the inner periphery of the intermediate die 10 meshes with the upper end of the base r.
Then, the upper punch 8 is further lowered, and the raw material powder G
Approximately 420 tons of compressive load is applied.

At this time, as shown in FIG. 3 (a), due to the vertical load F of the upper punch 8, the inclined outer periphery of the upper outer punch 8a is the rim q, and the inner periphery of the intermediate die 10 is the upper end of the rim r. The upper punch 8 has a load of about 4
A similar state is maintained after the holding load is reduced to tons.

Then, as shown in FIG. 3 (b), when the intermediate die 10 starts to descend, the outer periphery of the upper outer punch 8a loses its support and starts to shift laterally, dragging the upper surface of the tooth portion of the molded product. As a result, cracks c are likely to occur at the root of the molded product as shown in FIG.

In view of the above, according to the present invention, the density of the root portion of the molded product is increased at the time of compacting to increase the strength.
As shown in FIG. 2 (a) to FIG. 2 (b), when a compressive load is applied by the upper punch 8, a part of the raw material powder G of the tooth tip part a is pushed toward the tooth root part b by the inclined convex part t. I'm trying to get it done. For this reason, as shown in FIG.
When the intermediate die 10 is released and the mold is opened, a molded product having no crack at the root portion b is taken out.

The present invention is not limited to the above embodiment. Those having substantially the same configuration as those described in the claims of the present invention and exhibiting the same operation and effect belong to the technical scope of the present invention. For example, the shape or the like of the inclined convex portion t may be an inclined surface that is linearly inclined toward the tooth tip side, and the specific configuration of the powder compacting apparatus 1 is also an example.

[0023]

As described above, in the method for compacting a helical gear according to the present invention, the outer periphery of the upper punch and the lower punch is provided with the part of the raw material powder on the tip side at the tip of the helical part. Since the inclined convex portion for pushing to the root side is formed, when a compressive load is applied to the raw material powder, the density of the root can be increased and the powder compacting can be performed, which is effective in preventing cracks.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a powder compacting apparatus to which a method for compacting a helical gear according to the present invention is applied.

FIG. 2 is an explanatory view for explaining the action of a slanted convex portion of the outer periphery of an upper punch and a lower punch;

FIG. 3 is an explanatory diagram of the reason for the occurrence of cracks.

FIG. 4 is an explanatory view of a location where a crack occurs.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compacting machine, 7 ... Lower punch, 8 ... Upper punch, 10
… Intermediate dies, p… The outer periphery is rim, q… The outer periphery is rim, r…
The inner periphery is t, and the slope is a convex part.

Claims (1)

[Claims] An inner periphery of an intermediate die is meshed with a lower portion of a lower punch, and an outer periphery of a lower punch is meshed with a lower portion of the lower die. After filling the raw material powder into a concave space formed by the intermediate die and the lower punch,
The inner periphery of the intermediate die is meshed with the outer periphery of the upper punch from the upper part of the helical gear, and then the compression of the helical gear is performed by applying a compressive load to the raw material powder with the upper and lower punches. In a powder molding method, the outer periphery of the upper punch and the lower punch is formed at the tip of the helical portion with an inclined convex portion for pushing a part of the raw material powder on the tip side toward the root. A powder compacting method for a helical gear, wherein the compacting is performed by increasing the density of the root portion by using the inclined convex portion.