JPH0833940A - Cold heading tool - Google Patents

Abstract

PURPOSE:To provide a cold heading tool capable of suppressing the wear and damages of an ejector pin or its peripheral part and enabling the continuous use for a long time with an inexpensive and simple constitution. CONSTITUTION:A cold heading tool 1 is provided with a cemented carbide die 3 where a forming hole 3a which is made to the shape of a bolt shaft, and a through hole 3b which is communicated with the forming hole 3a and is through in the axial direction, a die case 5 in which the cemented carbide 3 is fitted, and an ejector pin 7 which is slidably inserted in the through hole 3b. The ejector pin 7 is of the projecting shape where the tip surface 7a is projected out of the peripheral margin at the axial center, and a tapered projecting part 7b where the axial center position is projected is formed on the rear end side. An intermediate pin 13 which is slidably supported in the axial direction by a liner 11 is abutted on the rear end side of the ejector pin 7. A tapered recessed part 13a where the projecting part 7b on the rear end side of the ejector pin 7 is fitted with its axial center being aligned therewith is formed at the axial center position on the tip side of the intermediate pin 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold forging tool used for cold forging a machine element blank.

[0002]

2. Description of the Related Art Conventionally, blanks of machine elements such as bolts and nuts (hereinafter referred to as "machine element blanks") have been cold headed using a cold heading tool. This cold forging tool is provided with a forming hole that is hollowed out in the shape of a machine element blank, a through hole that communicates with the forming hole and penetrates in the axial direction, and an ejector pin that is inserted into the through hole. When punching, the tip surface of the ejector pin forms a part of the wall surface of the forming hole, and after forming, the ejector pin slides in the axial direction to push out the machine element blank in the forming hole. There is.

[0003]

By the way, when ejecting a machine element blank, the ejector pin is struck by a knockout mechanism via an intermediate pin or the like, is sandwiched between the machine element blank and the intermediate pin, and receives a load from both ends. . Here, if the arrangement position and the end face shape of the ejector pin are ideal, the end face of the ejector pin is uniformly loaded in the axial direction with respect to the entire face.

However, in practice, there are slight tolerances in the disposition position of the ejector pin and the shape of the end face, and in many cases the load is applied to the position where the end face is biased (hereinafter, the bias load is applied). With such an unbalanced load applied,
Since a shearing force acts on the ejector pin, the ejector pin is pushed into the through hole in a tilted or distorted state, increasing the frictional resistance between the ejector pin and the through hole. Wear or damage on the machine becomes severe.

Therefore, parts such as ejector pins have to be replaced frequently, resulting in an increase in the cost of the replacement parts. Further, the continuous operation of the forging machine cannot be performed, and the production efficiency of machine element blanks decreases. It was also the cause. Therefore, an object of the present invention is to provide a cold heading tool which is inexpensive and has a simple structure, which suppresses wear and damage of the ejector pin and its peripheral portion and enables continuous use for a long time.

[0006]

In order to achieve the above-mentioned object, the present invention provides, as claimed in claim 1, a forming hole hollowed in the shape of a machine element blank and an axial direction communicating with the forming hole. And a machine element blank that is inserted into the through hole and has a tip end surface that forms a part of the wall surface of the forming hole and that slides in the axial direction and is cold forged in the forming hole. In the cold forging tool including an ejector pin for pushing out, the tip end surface of the ejector pin is shaped so as to protrude from the peripheral edge at the axial center.

According to a second aspect of the present invention, a forming hole that is hollowed out in the shape of a machine element blank, a through hole that communicates with the forming hole and penetrates in the axial direction, and is inserted into the through hole and has a tip surface. While forming a part of the wall surface of the forming hole, in the cold forging tool provided with an ejector pin that slides in the axial direction and pushes out the machine element blank that has been cold forged in the forming hole, at the tip side. It has an intermediate pin that abuts on the rear end side of the ejector pin and pushes out the ejector pin in the axial direction, and on the rear end side of the ejector pin, while forming a convex portion whose axial center position is projected, At the axial center position on the tip end side of the intermediate pin, a concave portion is formed in which the convex portion fits with its axial center aligned.

Further, as described in claim 3, in the cold forging tool according to claim 2, the tip end surface of the ejector pin is shaped so as to protrude from the peripheral edge at the axial center.

[0009]

According to the cold forging tool according to the first aspect of the present invention, the tip end surface of the ejector pin, that is, the surface of the ejector pin that abuts the machine element blank in the forming hole is formed in a shape projecting more axially than the peripheral edge. There is. Therefore, when the mechanical element blank is extruded, the load is likely to concentrate particularly on the axial center position even within the tip end face, and shearing force that tilts or distorts the ejector pin is unlikely to occur.

Further, according to the cold forging tool of the second aspect, a convex portion protruding at the axial center is formed on the rear end side of the ejector pin. Therefore, when the mechanical element blank is pushed out, the load is likely to be concentrated particularly on the axial center position even on the rear end side of the ejector pin, and shearing force that tilts or distorts the ejector pin is unlikely to occur. Further, since the convex portion fits into the concave portion on the tip end side of the intermediate pin with the axial center aligned, the ejector pin can be centered without making the length of the through hole longer than in the conventional case, and the ejector pin can be accurately attached. It can be supported at the axial center position, and the through hole can be easily processed. Furthermore, since the length of the through hole does not have to be made longer than in the past, the length of the ejector pin itself can be shortened accordingly.
The ejector pin is less likely to be distorted, and the ejector pin itself can be easily processed.

In particular, according to the third aspect, when the mechanical element blank is pushed out, the load is applied between the axial center of the front end and the axial center of the rear end, and the ejector pin is tilted or distorted. Very unlikely to generate shearing force.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG. 1, the cold forging tool 1 is a bolt blank B that is hollowed into the shape of a bolt shaft and has been rough pressed.
A cemented carbide die 3 having a molding hole 3a into which a hole is inserted and a through hole 3b communicating with the molding hole 3a and penetrating in the axial direction.
And a die case 5 into which the cemented carbide die 3 is fitted, and an ejector pin 7 slidably inserted into the through hole 3b.

The ejector pin 7 is, as shown in FIG.
The tip surface 7a is formed in a convex shape that protrudes at the axial center from the peripheral edge. In the embodiment, the tip end surface 7a is a conical surface whose apex is the axis and the taper angle α of the apex is in the range of about 160 ° to 180 °. Further, on the rear end side of the ejector pin 7, a tapered convex portion 7b whose axial center position is projected is formed. In the embodiment, in order to prevent the ejector pin 7 from entering the through hole 3b more than a predetermined amount, the flange portion 7c is provided on the rear end side of the ejector pin 7.
Is formed on the bottom surface of the flange portion 7c,
It has a conical shape with the axis at the apex and the angle β of 30 °.
Further, the vertex portion 7d has a rounded shape.

As shown in FIG. 1, the rear end side of the ejector pin 7 is in contact with the intermediate pin 13 which is axially slidably supported by the liner 11. This intermediate pin 13
At the axial center position on the front end side, a convex portion 7b on the rear end side of the ejector pin 7 is formed with a tapered concave portion 13a into which the axial center is fitted and fitted. This recess 13a is shown in FIG.
As shown in FIG. 5, in the embodiment, the conical shape having an angle γ of 30 ° is used, and the diameter D2 of the opening is set to the diameter D1 of the convex portion 7b.
It is made 1.2 mm larger than (see FIG. 2) so that the convex portion 7b fits completely into the concave portion 13a. In addition, since air, oil, and the like escape to the axial center of the intermediate pin 13,
A through hole 13b is formed by reducing the diameter D3 to half the diameter D1.

In the above structure, the ejector pin 7 closes the through hole 3b as shown in FIG.
The tip surface 7a forms a part of the wall surface of the forming hole 3a, and the bolt shaft of the rough-pressed bolt blank B is inserted into the forming hole 3a. Then, in this state, the punch 21 press-forms the bolt head. After the head of the bolt is press-formed, the intermediate pin 13 is struck by a knockout mechanism (not shown) and slides in the direction of arrow A in the drawing, and as shown in FIG. 4, the ejector pin 7 slides in the axial direction. Then, the bolt blank B is pushed out of the forming hole 3a.

At this time, the ejector pin 7 is sandwiched between the bolt blank B and the intermediate pin 13 and receives a load from both ends. Since the tip end surface 7a that abuts the bolt blank B is a convex surface from which the shaft center projects, the load is concentrated especially on the shaft center. On the other hand, the convex portion 7b on the rear end side of the ejector pin 7 also has the axial center protruding and is fitted into the concave portion 13a of the intermediate pin 13, so that the load is particularly concentrated on the axial center. Therefore, the ejector pin 7 receives a load at each axial center of both ends. In this way, ejector pin 7
Since an unbalanced load is not applied to, the shearing force that tilts or distorts the ejector pin 7 is extremely unlikely to occur.

The convex portion 7b is the concave portion 13 of the intermediate pin 13.
Since the shaft center is fitted in a and fitted, the ejector pin 7 can be centered and the ejector pin 7 can be accurately supported at the shaft center position without making the length of the through hole 3b longer than in the conventional case. Therefore, the ejector pin 7 is connected to the through hole 3
It can slide more smoothly than before in b, and wear of the ejector pin 7 and the through hole 3b is suppressed.

Further, as for the ejector pin 7, the length of the through hole 3b does not have to be made longer than in the conventional case, so that the length of the ejector pin 7 itself can be shortened. Damage is prevented. As a result, parts such as the ejector pin 7 do not have to be replaced more frequently than in the conventional case.
The cost of replacement parts can be reduced, and since the replacement of parts does not hinder the continuous operation of the forging machine, the production efficiency of bolt blanks is improved.

Furthermore, since the ejector pin 7 can be shortened, the ejector pin 7 itself can be easily processed, and the through hole 3b to be formed with high precision can be shortened, so that the cemented carbide die 3 can be easily processed. Therefore, the cost for manufacturing the cold heading tool 1 itself is also reduced.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various embodiments can be adopted without departing from the scope of the present invention. For example, in the embodiment, the bolt shaft is inserted into the molding hole 3a, but the present invention is also applicable to the case where the molding hole 3a has a shape for molding a bolt head, a shape for molding a nut, and the like. The configuration of can be adopted.

In the embodiment, the tip surface 7a of the ejector pin 7 is a conical surface, but it may have a shape other than the conical surface (for example, a spherical surface) as long as it projects at the axial center position. Furthermore, in the embodiment, the convex portion 7b and the concave portion 13a are formed into a conical shape that fits snugly, but if the convex portion fits into the concave portion and the ejector pin 7 can be centered, a shape other than the conical shape (for example, a pyramid) can be used. Shape).

[0022]

As described above, according to the cold forging tool according to the first aspect of the present invention, when the machine element blank is extruded, the ejector pin is sheared so as to tilt or distort the ejector pin. Since force is less likely to be generated, the ejector pin slides smoothly in the through hole, and wear and damage of the ejector pin is suppressed.

According to the cold forging tool of the second aspect, when the machine element blank is extruded, a shearing force that tilts or distorts the ejector pin is unlikely to occur, and the length of the through hole is reduced. Since the ejector pin can be accurately supported at the axial center position without making it longer than before, the ejector pin smoothly slides in the through hole, and wear and damage of the ejector pin are suppressed. In addition, the length of the through hole does not have to be longer than in the past, the length of the ejector pin itself can be shortened, the ejector pin becomes less likely to be distorted, and the through hole and the ejector pin itself can be easily processed. Cost can be reduced.

Further, according to the cold forging tool of the third aspect, when the machine element blank is extruded, a shearing force that tilts or distorts the ejector pin is extremely unlikely to occur, so that the ejector pin is worn. It is highly effective in suppressing damage.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a cold heading tool as an example.

FIG. 2 is an enlarged front view showing the ejector pin of the embodiment.

FIG. 3 is an enlarged cross-sectional view showing the main parts of the intermediate pin of the embodiment.

FIG. 4 is a cross-sectional view showing a state in which a bolt blank is extruded in the cold heading tool of the embodiment.

[Explanation of symbols]

1 ... Cold forging tool, 3 ... Carbide die, 3a ...
・ Molding hole, 3b ... Through hole, 5 ... Die case,
7 ... Ejector pin, 7a ... Tip surface, 7b.
..Convex portion, 7c ... Flange portion, 11 ... Liner, 13 ... Intermediate pin, 13a ... Recessed portion, 13b
..Punching through holes, 21 ...

Claims (3)

[Claims] 1. A molding hole that is hollowed out in the shape of a machine element blank, a through hole that communicates with the molding hole and penetrates in the axial direction, and a front end surface of a wall surface of the molding hole that is inserted into the through hole. In a cold forging tool comprising an ejector pin that forms a part and slides in the axial direction to push out a machine element blank that has been cold forged in the forming hole, wherein the tip surface of the ejector pin is A cold forging tool characterized in that it also has a shape that protrudes at the axial center. 2. A molding hole which is hollowed out in the shape of a machine element blank, a through hole which communicates with the molding hole and penetrates in the axial direction, and a front end face of a wall surface of the molding hole which is inserted into the through hole. A cold forging tool, which forms a part and ejects a cold-forged machine element blank that slides in the axial direction in the axial direction, and a cold forging tool, wherein the tip end side is the rear end side of the ejector pin Has an intermediate pin that pushes out the ejector pin in the axial direction, and at the rear end side of the ejector pin, a convex portion whose axial center position is projected is formed, and at the end side of the intermediate pin. A cold heading tool, characterized in that at the axial position, a concave portion is formed in which the convex portion fits with the axial center thereof aligned. 3. The cold forging tool according to claim 2, wherein the tip surface of the ejector pin is shaped so as to protrude from the peripheral edge at the axial center.