JP2021079398A - Press die and press working method using the die - Google Patents

Abstract

To provide a simple method for processing part of a pipe into a complete flat surface in a single process.SOLUTION: A press die for pressing an outer periphery of a pipe to process part of the outer periphery of the pipe into a flat surface includes a step of forming a bead-shape protrusions at predetermined intervals in a direction substantially orthogonal to an axial direction of a pipe at a surface of the pipe to be pressed.SELECTED DRAWING: Figure 2

Description

The present invention relates to a die for pressurizing a part of the outer circumference of a steel pipe such as an automobile exhaust pipe to make it flat, and a press working method using the die.

It may be necessary to process a part of the pipe to form a flat part. For example, in order to avoid interference with other parts, a part of the exhaust pipe for an automobile is processed flat. In that case, when pressure is applied using a mold having a flat pressure surface, a dent is generated in the central portion as shown in the photograph of FIG.

The reason for this is that when the pipe is pressed with a mold whose pressure surface is a flat surface, the arc-shaped part is deformed to be linear and the circumference is reduced by processing, so the stress to maintain the circumference is stressed. Is generated inside, and as a result, it is presumed that it deforms to the inside of the pipe without being restrained by the mold in order to maintain the circumference.

A method of forming a flat portion while avoiding the dent generated in the central portion is proposed in Japanese Patent Application Publication No. 49-8794. This is a method of avoiding a dent generated in the central portion by bending the pressurizing surface of the die with a radius of about 5 times the pipe diameter and pressurizing with an arcuate die.

As shown in FIGS. 4 (A) and 4 (B), when the pipe as the workpiece is set in the lower mold along the pipe shape and pressed by the mold g formed by the plane f, FIG. 4 (C) ), It is shown that a dent is formed in the central portion and the upper end portion of the pipe is not flat. On the other hand, as shown in FIGS. 5A and 5B, when the pressurizing die is pressurized with an arc-shaped upper die curved with a radius of about 5 times the pipe diameter, FIG. 5C is shown. The shape of the upper end surface of the pipe can be obtained along the shape of the upper die having a substantially arc shape as shown in.

According to this method, since the above-mentioned stress for maintaining the total length acts in the direction along the upper mold in an arc shape, the deformed pipe does not leave the mold and generate a central dent. That is, molding of a pipe along a curved surface can be realized.

Publication No. 49-8794

However, although the problem of the dent generated in the central portion can be avoided by using this method, since the upper mold is curved, only machining on a curved surface can be realized.
When a flat surface is required to be machined due to design requirements, it is machined once with a curved die to avoid a dent in the center, and then processed again with a flat die. Is required. That is, when a part of the pipe is to be machined flat, there is a problem of the prior art that the machining process of a plurality of steps must be set in order to realize the machining on a flat surface.

The present invention has been made in consideration of such a problem, and an object of the present invention is to provide a simple method for processing a part of a pipe into a flat surface in one step.

The invention according to claim 1 is a press die for pressurizing the outer circumference of a pipe to process a part of the outer circumference of the pipe into a flat surface, the first mold for holding the pipe, and the first mold. It has a second mold that pressurizes the pipe in close proximity to the mold, and the second mold has a bead shape at predetermined intervals in a direction substantially orthogonal to the axial direction of the pipe on the surface that pressurizes the pipe. It is characterized in that protrusions are formed.

The press die according to the first aspect of the present invention has bead-shaped protrusions formed at predetermined intervals in a direction substantially perpendicular to the pipe axial direction on the pressure-pressing surface. When the pipe is pressurized with this mold, the pressure is started on the line orthogonal to the pipe axial direction by the protrusions, so that minute grooves are formed at predetermined intervals in the direction substantially perpendicular to the pipe axial direction at the initial stage of pressurization. Orthogonal. This groove suppresses the generation of an axial dent in the central part, and while forming a minute groove, the intermediate part of the unpressurized protrusion is also uniform due to deformation due to pressure around the protrusion. It transforms into a flat shape.

Therefore, according to this press die, although a minute groove is formed, a flat portion can be formed in a part of the pipe in one step without forming an axial dent in the central portion of the pipe.

The invention according to claim 2 is a press working method in which the outer periphery of the pipe is pressurized to process a part of the outer periphery of the pipe into a flat surface, the step of holding the pipe in the first mold, and the above-mentioned first. The second mold has a pressurizing step in which the second mold is brought close to the first mold to pressurize the pipe, and the second mold has a direction substantially orthogonal to the axial direction of the pipe on the surface for pressurizing the pipe. Bead-shaped protrusions are formed at predetermined intervals, and the pipe is pressurized by the plurality of bead-shaped protrusions.

According to the press working method according to the second aspect, the pipe is pressurized by bead-shaped protrusions formed at predetermined intervals in a direction substantially perpendicular to the pipe axial direction. Since pressurization is started on a line orthogonal to the pipe axial direction by the protrusions, minute grooves are formed at predetermined intervals in a direction substantially perpendicular to the pipe axial direction at the initial stage of pressurization. This groove suppresses the generation of an axial dent in the central part, and while forming a minute groove, the intermediate part of the unpressurized protrusion is also uniform due to deformation due to pressure around the protrusion. It transforms into a flat shape.

Therefore, according to this press working method, although minute grooves are formed, a flat portion can be formed in a part of the pipe in one step without forming an axial dent in the central portion of the pipe.

In the invention according to claim 3, in addition to the structure of the press die according to claim 1, the end portion of the bead-shaped protrusion that abuts on the outer circumference of the pipe is formed in a rounded shape having a radius of 0.1 mm to a radius of 4 mm. It is characterized by being.

If the radius of the bead-shaped protrusion end is less than 0.1 mm, the protrusion top may damage the pipe surface, which may deteriorate the appearance quality of the pipe and the strength of the pipe. Further, if the radius of the protrusion end portion exceeds 4 mm, the groove formed at the top of the protrusion portion in the direction orthogonal to the pipe axial direction is too shallow, and the formation of a dent in the pipe axial direction generated in the central portion of the pipe cannot be prevented. Therefore, the proper range of the radius of the bead-shaped protrusion end is 0.1 mm to 4 mm.

The invention according to claim 4 is characterized in that, in addition to the structure of the press die according to claim 1 or 3, the interval between the bead-shaped protrusions is 15 mm to 30 mm.

According to the experiment, when the distance between the bead-shaped protrusions is less than 15 mm, it becomes close to the state of being pressurized by a flat mold, and there is a possibility that an axial dent is formed in the central portion. Further, if the distance between the protrusions exceeds 30 mm, the intermediate portion where the pressing force of the protrusions does not act directly becomes too long, so that sufficient stress is not indirectly generated in the intermediate portion, so that the intermediate portion is deformed to a flat surface. Will be inadequate.
Therefore, the appropriate range of the spacing between the bead-shaped protrusions is 15 mm to 30 mm.

According to the present invention, a part of the pipe can be processed into a flat surface in one step without using a plurality of steps.

It is a side view which shows the whole structure of the press apparatus which concerns on this invention. It is a perspective view which shows the 1st mold (lower mold) and 2nd mold (upper mold) which concerns on this invention. It is a perspective view which inverted the 2nd mold (upper mold) which concerns on this invention. It is a figure which showed the deformation of the pipe when the pipe was pressed by the mold composed of the plane, which was shown in the publication of the publication No. 49-8794. It is a figure which showed the deformation of the pipe when the pipe was pressurized by the structure shown in the publication of the publication No. 49-8794. It is a photograph which shows the part of the pipe which was pressed by using the mold which made the pressure surface flat. It is a photograph which shows the part of the pipe which was pressed by using the press working die which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following description of the embodiment is merely an essential example, and is not intended to limit the present invention, its application, or its use.

As shown in FIG. 1, the upper die 20 is mounted on the slide of the press device 1, the lower die 10 is mounted on the bolster, and the support surface 11 supporting the pipe 2 of the lower die 10 is processed into a shape that conforms to the shape of the pipe. There is. Further, a pressurizing surface 21 for pressurizing the pipe 2 is configured on the lower surface of the upper die 20.

Further, the pipe 2 is a steel pipe used for an exhaust pipe for a passenger car, and a part of the exhaust pipe is processed flat in order to avoid interference with other parts. In this embodiment, the pipe used is a ferritic stainless steel pipe having an outer diameter of 60.5 mm and a plate thickness of 1.2 mm.

The slide is lowered by the operation of the press device 1, and the pressing surface 21 pressurizes the upper surface of the pipe 2 supported by the lower mold 10 to perform processing. In the processing in the present embodiment, the processed surface is processed so as to stay on the surface above the center line of the pipe 2.

When the pressurizing surface 21 is pressurized by the upper mold 20 having a simple flat surface, a dent is formed in the central portion of the pipe 2 toward the inside of the pipe as shown in FIG. 4C, and the upper end portion of the pipe is formed. It does not become a flat surface. This is because when the pipe is pressed with a mold composed of a flat surface, the arc-shaped part is deformed so that the circumference is reduced in a straight line, so stress to maintain the circumference is generated inside the pipe. As a result, it is presumed that it tries to deform to the inside of the pipe without being restrained by the mold in order to maintain the circumference.

In the present embodiment, as shown in FIG. 3, bead-shaped protrusions 22 are formed on the pressurizing surface 21 at predetermined intervals in a direction substantially orthogonal to the axial direction of the pipe to be pressurized. In FIG. 3, the upper die 20 is shown upside down for easy illustration. As for the protrusion shape, for example, as shown in the detailed view of FIG. 3, the protrusion base end portion 24 has a trapezoidal shape, the protrusion top portion 23 has an arc shape, and in the present embodiment, the protrusion height is 3 mm. Generally, the cross-sectional shape is such that the height of the protrusion is approximately 1 mm or more.

The reason why a dent toward the inside of the pipe does not occur in the center of the pipe when pressure is applied by a pressure surface having bead-shaped protrusions will be described below.

When the bead-shaped protrusion 22 comes into contact with the upper end of the pipe due to the lowering of the pressure surface 21, the bead-shaped protrusion 22 first forms a minute groove corresponding to the protrusion shape in a direction substantially orthogonal to the pipe axial direction. When the pressure surface is further lowered, the pressure from the protrusions does not act directly between the protrusions formed at predetermined intervals, but the pressure is similarly deformed due to the deformation of the pipe part directly pressed from the protrusions. To go.

According to the experiment, there is a slight difference in shape between the part in contact with the bead-shaped protrusion 22 that directly receives the pressure of the protrusion and the intermediate part of the protrusion 22 that receives the pressure indirectly, but only a slight difference of about 1 mm or less. Does not occur. According to an actual experiment, as shown in the photograph of FIG. 7, in a pipe pressurized by a pressure surface having bead-shaped protrusions, indentations pressed by the protrusions remain as a pattern in a direction substantially orthogonal to the pipe axis direction. Processing is performed on a substantially flat surface.

The minute groove in the direction substantially orthogonal to the pipe axial direction generated at the initial stage of the above-mentioned processing prevents the occurrence of a dent in the central portion of the pipe. That is, even if a dent is formed in the central portion of the pipe in the pipe axial direction, a minute groove formed in a direction substantially orthogonal to the pipe axial direction acts to prevent the dent from being generated.

There is an appropriate range in the radius of the top of the protrusion. The radius is too small, if it is less than approximately specifically 0.1 mm, since the apex damage the pipe surface is not preferable from the viewpoint of appearance quality and strength of the pipe of the pipe. On the other hand, if the radius is too large, specifically, if it becomes larger than about 4 mm, the groove formed at the top in the direction orthogonal to the pipe axial direction is too shallow, and the dent in the pipe axial direction generated in the center of the pipe is formed. The formation cannot be prevented. Therefore, the appropriate range of the radius of the top of the protrusion is a range of approximately 0.1 mm to 4 mm.

There is also an appropriate range for the spacing between the bead-shaped protrusions. If the distance between the protrusions is less than 15 mm, it will be close to being pressurized on a flat surface without protrusions, and the groove formed by the top of the protrusions in the direction orthogonal to the pipe axis direction will become shallower, which will occur in the center of the pipe. It becomes impossible to prevent the dent in the pipe axis direction.

On the other hand, if the distance between the protrusions exceeds approximately 30 mm, the intermediate portion where the pressing force of the protrusions does not act directly becomes too long, so that sufficient stress does not act on the intermediate portion and the deformation of the intermediate portion becomes insufficient. .. That is, while the part where the protrusions come into contact is processed into a flat surface along the part where the protrusions come into contact, the intermediate part is sufficiently flat because the pressing force hardly acts even indirectly because the distance is large. No deformation is done. If the depth of the flat part formed on the pipe is larger than the height of the protrusion, the flat part of the pressure surface directly pressurizes the pipe in the middle part of the protrusion, so the pipe is placed in the center of the pipe at that part. A dent toward the center will be generated. As described above, the appropriate range of the spacing between the bead-shaped protrusions is approximately 15 mm to approximately 30 mm.

1 Press device 2 Pipe 10 Lower mold (1st mold)
11 Support surface 20 Upper mold (second mold)
21 Pressurized surface 22 Bead-shaped protrusion 23 Protrusion top 24 Protrusion base end

Claims (4)

A press die that pressurizes the outer circumference of a pipe to process a part of the outer circumference of the pipe into a flat surface.
The first mold to hold the pipe and
Having a second mold that pressurizes the pipe in close proximity to the first mold
The second mold is characterized in that bead-shaped protrusions are formed on the surface for pressurizing the pipe at predetermined intervals in a direction orthogonal to the axial direction of the pipe.
Press die.
It is a press working method that pressurizes the outer circumference of a pipe and processes a part of the outer circumference of the pipe into a flat surface.
The process of holding the pipe in the first mold,
It has a pressurizing step of pressurizing the pipe by bringing the second mold close to the first mold.
In the second mold, bead-shaped protrusions are formed on the surface for pressurizing the pipe at predetermined intervals in a direction orthogonal to the axial direction of the pipe, and the pipe is pressurized by the plurality of bead-shaped protrusions. Characterized by that
Press processing method.
The top of the bead-shaped protrusion that abuts on the outer circumference of the pipe is formed in a rounded shape having a radius of 0.1 mm to a radius of 4 mm.
The press die according to claim 1.
The distance between the bead-shaped protrusions is 15 mm to 30 mm.
The press die according to claim 1 or 3.

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