JP2819930B2 - Forming method for internal teeth - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an internal tooth profile.

[0002]

2. Description of the Related Art A method of forming a tooth profile by forging or the like is disclosed, for example, in Japanese Patent Application Laid-Open No. 60-115342. There, the molding material is filled between the inner cavity side forming punch and the lower die on which the forming tooth profile on the outer side is formed, and a compression load is applied by the main punch in the axial direction to perform closed forging. Then, the forming material of the annular body is expanded in the radial direction, and a tooth shape which is regarded as the tooth shape of the lower die is formed on the outer peripheral side. However, this is a method in which an axial force is applied to the annular body to radially expand the annular body to form an external tooth profile.

[0003]

When the above-mentioned closed forging method of the external teeth is applied to the plastic forming of the internal teeth, the annular body expands radially outward when an axial force is applied. In the case of the internal tooth profile in which the tooth profile is formed, the filling of the tooth tip with the material is insufficient, and molding failure occurs. Since the molding load must be increased in order to fill the tip of the internal tooth profile, the device may be damaged.

Therefore, conventionally, the formation of the internal tooth profile has been performed by machining such as cutting. In particular, it has been considered impossible to cut a helical internal tooth except for cutting.
However, formation of a tooth profile by machining has a long cycle time and poor productivity. Further, since a broaching machine is usually used, there is a problem that equipment costs are increased.

An object of the present invention is to provide a method of forming an internal tooth profile which can fill the material to the tooth tip with a relatively small forming load and therefore can plastically form an internal tooth profile which has been considered impossible in the past. Aim.

[0006]

According to the present invention, the above object is achieved by the following method for forming an internal tooth profile. That is, the first step of forming a tooth on a material by a predetermined processing amount by closed forging, and a part of the material other than the tooth forming part is set as a free surface, and the meat of the material protrudes from a part of the free surface. A second step of applying a compressive force to the material to form the internal teeth while allowing the material to be formed, and a third step of removing the protruding portion of the free surface portion generated in the second step by cutting. A method for forming an internal tooth profile comprising:

[0007]

According to the method of the present invention described above, in the first step, a tooth forming shape having a predetermined processing amount, for example, a fill-up rate of 80% is performed by closed forging. Since the fill-up rate is about 80% or less, it can be performed with a relatively small compressive load, and no mold breakage occurs. Next, in a second step, a contour shape that is difficult to finish is formed by plastic working by applying a so-called split flow method, which is a type of precision die forging. In the split flow method, the molding is performed while flowing the material in two directions (the outer peripheral direction and the inner peripheral direction), so that the material can be easily filled in the molded part, and since there is a free surface in a part, abruptly, An increase in load can be avoided, and tooth formation can be performed with a relatively small forming load. In the third step, the excess portion of the free surface portion is scraped off.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for forming an internal tooth profile according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a case in which the method of the present invention is applied to forming an internal helical tooth profile in the order of processing steps. In FIG. 1, (A) shows an annular blank 2 for forming a tooth from which a tooth is to be formed, and (B) shows an intermediate product 4 in which a predetermined amount of an internal helical tooth is formed by closed forging in a first step. (C), in the second step, the internal tooth helical tooth profile 6 was formed by applying the so-called split flow method to form the flange 8 by protruding the flesh into the free surface portion provided on a part of the intermediate product. (D) shows an internal helical tooth profile product 12 after the flange 8 has been cut in the third step.

The material 2 in FIG. 1A is a metal, for example, aluminum. After the end of the first step, for example, the thickness is 7 mm, the outer diameter is 40 mm, and the valley diameter of the internal teeth is 2 mm.
In order to obtain a coarse intermediate tooth profile intermediate product with a 3.55 mm internal tooth ridge diameter of 17.69 mm, a raw material 2 having a thickness of 10 mm, an outer diameter of 40 mm, and an inner diameter of 23.6 mm is prepared at the raw material stage.

The closed forging in the first step of FIG. 1B is performed, for example, as shown in FIG. In FIG. 2, the material 2 is compressed between the restraining container 14, the upper punch 16, and the lower punch 18 to form an internal tooth profile.

In the closed forging, the fill-up rate of the tooth height is 8
Mold to about 0%. The fill-up rate of the tooth height is the filling ratio of the material to the tooth profile, and the total height of the tooth to be molded is t ₀ ,
If the height of the filled tooth is t, it is defined as t / t ₀ . When the fill-up rate is 80% or more, the molding load increases sharply, causing mold breakage.

FIG. 3 shows the relationship between the tooth height fill-up rate (%) and the closed forging load (TON). As can be seen from FIG. 3, as the molding load increases, the rate of increase in the tooth-length fill-up rate decreases, and the load must be rapidly increased in order to fill the material with a narrow tooth tip. It is shown that. Therefore, there is a limit in closed forging in order to fill the material with a narrow tooth tip.

In the second step shown in FIG. 1C, molding is performed by applying a split flow method. The split flow method is a method in which a contour shape that is difficult to finish is formed by plastic working, material flow to a portion having a simple shape is allowed, and cutting is performed later. In the split flow method, molding is performed while causing the material to flow in two directions, and a free surface is partially provided, so that a sudden increase in load can be avoided.

FIG. 4 shows a mold structure of the split flow method. At the center, a mandrel 20 having a tooth profile formed on the outer peripheral portion is provided, and the intermediate product 4 is compressed by the upper punch 22 and the lower punch 24. 26 is an upper restraining container that restrains the upper part of the intermediate product 4, and 28 is a lower restraining container that restrains the lower part of the intermediate product 4. Container 26 for upper restraint and container 2 for lower restraint
8, there is a gap, and this gap provides a free surface to a part of the outer peripheral surface of the intermediate product 4.

When the intermediate product 4 is compressed between the upper punch 22 and the lower punch 24, the material of the intermediate product 4 flows in two directions, radially inward and outward. The flesh flowing outward is flange 8
Is formed, and the material flowing inward fills the internal teeth and is precisely formed.

FIG. 5 shows that the teeth are substantially formed by the split flow method.
The contact ratio (%) of the tooth tip of the material whose length is filled up
The relationship with the forming load (TON) is shown. In the figure, K
d and Ku are the predetermined restraint amounts of containers 28 and 26
(See FIG. 6). In addition, the tooth contact ratio of the tooth tip
As shown in FIG. 7, the length l per mold is the total tooth length l in the tooth trace direction.
₀FIG. 5 shows that in percentage, ie, 1 /
l₀× 100 shown. As can be seen from FIG.
When the forming load of closed forging in the process was 50 TON
However, in the second step of the split flow method, the forming load is increased too much.
It is possible to fill the tooth tip without filling. for example
For example, in the split flow method, the forming load is 60 TON and almost
Is satisfied and the tip contact ratio of the tooth tip can be 80% or more.
it can. In addition, as the molding load increases,
The rate of increase in the forging rate tends to increase.
The reverse of the case). Therefore, make the molding load too large
Without, it can get close to 100% of the tip contact
You.

In the third step shown in FIG. 1D, the flange 8 is removed by cutting in the forming by the split flow method to obtain a product 12.

Next, the operation will be described. The method of the present invention performs plastic working of an internal tooth profile by applying the working principle of the split flow method. In the second step by the split flow method, as the material is compressed, the material protrudes toward the inner diameter side, that is, toward the mandrel 20. At this time, the overhang of the material to the outer peripheral side is limited to a predetermined amount or less by a predetermined constraint amount (Kd, Ku in FIG. 6).

By flowing the material also to the outer peripheral side,
The inner peripheral side (tooth portion) can be easily filled with the material, and the helical tooth shape of the internal teeth can be formed with a relatively low forming load.

[0021] As described above, the tooth shape of the internal tooth formed by the plastic working is increased by about 20% as compared with the tooth profile formed by the mechanical processing because the tooth flow of the plastic processed tooth shape is continued. I have.

[0022]

According to the present invention, the internal tooth profile is formed into a predetermined amount of tooth formation by closed forging, and then the compression force is applied while allowing the material to flow out from the free surface provided on a part thereof. Since the tooth forming shape (shaping by the so-called split flow method) is performed, the internal tooth shape can be plastically processed with a relatively small forming load.

[Brief description of the drawings]

FIG. 1 is a sectional view of a raw material, an intermediate product, and a product in a process order in a method of forming an internal tooth profile according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a mold used in a closed forging step of the present invention.

FIG. 3 is a diagram of tooth height fill-up rate versus forming load in closed forging.

FIG. 4 is a schematic cross-sectional view of a mold used in a forming step of a split flow method of the present invention.

FIG. 5 is a diagram showing a relationship between a tooth height increase ratio and a molding load in molding by a split flow method.

FIG. 6 is an enlarged sectional view of a part A of the mold of FIG. 4;

FIG. 7 is a schematic perspective view and a partial cross-sectional view showing a definition of a mold contact ratio of a tooth tip.

[Explanation of symbols]

 2 Material 4 Intermediate product 6 Internal tooth shape 8 Flange 10 Intermediate product 12 Product 20 Mandrel 22 Upper punch 24 Lower punch 26 Upper restraining container 28 Lower restraining container

Claims (1)

(57) [Claims] 1. A first step of forming a tooth on a material by a predetermined processing amount by closed forging, and setting a part of the material other than the tooth-forming part as a free surface, and starting from a portion of the free surface to a meat of the material. A second step of forming an internal tooth by applying a compressive force to the material while allowing the material to protrude, and a third step of removing the protruding portion of the free surface portion generated in the second step by cutting. And a process for forming an internal tooth profile.