JP2000061539A - Pipe folding-back method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a folding-back method of a pipe capable of forming a folding-back part of a long size replaceing a double pipe structure. SOLUTION: In a pipe folding-back method wherein a folding-back pipe A1 having a pipe main body part 1, a bending part 2 and a folding-back part 3 is formed from a pipe stock having the same diameter, a stepped pipe forming process wherein a stepped pipe 6 having a pipe part 6a having a large diameter, a stepped and inclined part 6b and a pipe part 6c having a small diameter is formed of the pipe stock having the same diameter and an outside thrusting process wherein a pipe end surface of the pipe part 6a having the large diameter is thrust toward the pipe part 6c having the small diameter in the axial direction of the pipe, the pipe part 6c having the small diameter is formed into the pipe main body part 1, a part weakened by forming the stepped and inclined part 6b is made to be the bending part 2, and a part overlapped by longitudinal buckling is made to be the outside folding-back part 3 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a pipe folding method which is applied to an exhaust pipe of an automobile or the like and improves the strength of a pipe end.

[0002]

2. Description of the Related Art Conventionally, as a method for improving the strength of a pipe end, a collar is provided on the inner or outer surface of the pipe end and the pipe end has a double pipe structure. In this case, there is a problem that the number of parts and the number of steps are increased, resulting in high cost.

Therefore, it is conceivable to fold the end of the pipe inward or outward to form an integral type double pipe structure. As a method of inward fold, an arc groove is formed as shown in FIG. It is known to push the pipe end into the mold and curl the pipe end.

[0004]

However, in the above-mentioned conventional pipe folding method, the tip of the pipe is rounded due to the property of the material, and the U-shaped folding cannot be performed. In addition, as shown in FIG. 8B, that is, even if the conventionally known processing method of the pipe end is adopted, it is possible to form the curl at the pipe end, and to replace the high-strength double pipe structure with a long length. The problem remains that the folded-back portion of the scale cannot be formed.

The problem to be solved by the present invention is to provide a pipe folding method capable of forming a long folding portion which is an alternative to the double pipe structure.

[0006]

[Means for Solving the Problems] (Solution Means 1) A means for solving the above problems (claim 1) is a pipe for forming a folded pipe having a pipe main body portion, a bent portion and a folded portion from a pipe material of the same diameter. In the folding method, a step pipe forming step of forming a step pipe having a large-diameter pipe portion, a step slope portion, and a small-diameter pipe portion from the same-diameter pipe material; and a pipe end face of the large-diameter pipe portion facing the small-diameter pipe portion. An outward pushing process in which the small-diameter pipe portion is pushed in the axial direction, the pipe main body portion is used, the weakened portion due to the formation of the step sloped portion is the bent portion, and the portion folded by the vertical buckling is the outer folded portion, It is characterized by having. (Solution Means 2) Means 2 for solving the above problems (claim 2) is
The pipe folding method according to claim 1, wherein the outer pushing step is a step of pushing stroke up to an intermediate position of the folding portion to form a flange folding pipe having an outer bending portion at an end of the folding portion. A flange is inserted into the folded-back portion of the flange-folded pipe, and the flange is fixed by using a gap portion secured between the flange and the outer bent portion as a welding portion. (Solution Means 3) Means 3 for solving the above problems (claim 3) is
In a pipe folding method for molding a folded pipe having a pipe main body portion, a bent portion and a folded portion from the same diameter pipe material, a stepped pipe having a large diameter pipe portion, a step slope portion and a small diameter pipe portion is formed from the same diameter pipe material. Step of forming a stepped pipe, and pushing the pipe end surface of the small diameter pipe part toward the large diameter pipe part in the pipe axial direction, making the large diameter pipe part the pipe body part, and folding the part weakened by forming the step sloped part An inner pushing step in which the bent portion is folded inward by vertical buckling and is used as an inner folded portion. (Solution means 4) Solution means 4 (claim 4) for solving the above problems is
The pipe folding method according to claim 3, wherein the inner pushing step is a step of stopping the inner pushing in the middle of folding so that the first pipe main body portion, the first bending portion, the folding portion, and the second bending portion. And a vibration absorbing pipe having a second pipe body.

[0007]

(Embodiment 1) Embodiment 1 is a pipe folding method corresponding to the invention described in claims 1 and 2. [Regarding a basic example of a method for returning a pipe to the outside] Fig. 1
FIG. 2 is a diagram showing an outward pipe turning method which is the basis of the first embodiment, and FIG. 2 is a cross-sectional view showing an outer turning pipe formed by the method of the first embodiment.
A1 is an outer folded pipe, 1 is a pipe main body, 2 is a bent portion, 3 is an outer folded portion, 4 is a pipe expanding type, 5 is an outer pushing type, 6 is a step pipe, 6a is a large diameter pipe section, and 6b is a step. The inclined portion 6c is a small diameter pipe portion.

The method of folding back the pipe to the outside is to use a pipe material of the same diameter, a pipe body 1, a bent portion 2 and an outer folded portion 3.
2 is a method of molding the outer folded pipe A1 shown in FIG. 2, and the steps of the step pipe molding step, the first outer pushing step, and the second outer pushing step, which constitute this method, will be described.

In the step pipe forming step, as shown in FIG. 1 (a), the pipe expanding die 4 is pushed in from one end of the pipe member of the same diameter, and the large diameter pipe portion 6a, the step inclined portion 6b and the small diameter pipe portion 6c are inserted. This is a step of forming the stepped pipe 6 that has.

In the first outside pushing step, as shown in FIG. 1B, the outside pushing die 5 is used to make a large diameter pipe portion 6
This is a step of pushing the end face of the pipe a toward the small-diameter pipe portion 6c halfway in the pipe axial direction.

In the second outer pushing step, as shown in FIG. 1C, the outer pushing die 5 is pushed further in the axial direction of the pipe, and the small diameter pipe portion 6c is used as the pipe body portion 1.
The portion weakened by forming the step sloped portion 6b is bent to the bent portion 2
In this step, the portion folded in by vertical buckling is used as the outer folded portion 3.

As described above, the step pipe forming step for forming the step pipe 6 is set in advance before the outer pushing step. Since the step inclined portion 6b is formed in this step pipe forming step, the step inclined portion is formed. When the material of 6b is formed, a thin portion of the material is generated due to the elongation of the material, and when a buckling stress is applied in the first outer pushing step, the stress is concentrated on the thin portion and the bending deformation starts. To do. Since the large-diameter pipe portion 6a and the small-diameter pipe portion 6c are formed so as to sandwich the step sloped portion 6b, when the pushing force is applied in the first and second outer pushing steps, the pipe portions 6a and 6b interfere with each other. It will be folded by vertical buckling without doing.

Therefore, it is possible to obtain the outer folded pipe A1 in which the long outer folded portion 3 is formed instead of the double pipe structure. [Application example of the method of turning the pipe outwards] Fig. 3
Is a cross-sectional view showing an outside folded pipe with a flange according to an application example of the outward pipe folding method of Embodiment 1,
Fig. 4 (a) is an enlarged sectional view of the welded part of the flanged outer folded pipe, and Fig. 4 (b) is an enlarged sectional view of the welded part of the conventional flanged pipe, in which A2 is the folded pipe for flange and 1 is the The pipe body portion, 2 is a bent portion, 3 is an outer folded portion, 7 is an outer bent portion, 8 is a flange, and 9 is a welded portion.

An example of application of this outward pipe turning method is to stop in the stepped pipe forming step → first outside pushing step, that is, the step of pushing stroke to the middle position of the outside turning portion 3 to stop the outside turning portion. The flange turn-back pipe A2 having the outer bent portion 7 at the end of 3 is molded, and the flange 8 is inserted and attached to the outer turn-back portion 3 of the flange turn-back pipe A2. As shown in FIG. In this example, the gap 8 (about 3 to 5 mm) secured between the outer bent portion 7 and the outer bent portion 7 is used as the welded portion 9 and the flange 8 is fixed.

In the conventional flanged pipe, as shown in FIG. 4B, a flange is attached to the end of the pipe, and the base end of the flange and the corner of the pipe are welded. In this case, when a force is applied to the flange, stress concentrates in the vicinity of the weld bead, and cracks easily occur in this portion. That is, there is a problem that the strength of the welded portion is low.

On the other hand, as shown in FIG. 4 (a), the flanged outer folded pipe of the first embodiment has a gap (3 to 5 m) secured between the flange 8 and the outer bent portion 7.
m) is used as the welded portion 9 and the flange 8 is fixed,
The weld bead is applied to the outer bent portion 7 to increase the welding strength, and the contact of the outer bent portion 7 with the pipe body 1 is an arc contact due to the bent portion, so that stress is less likely to be concentrated.

Therefore, it is possible to provide the flanged outer folded pipe in which the strength of the welded portion 9 is significantly increased. (Embodiment 2) Embodiment 2 is a pipe folding method corresponding to the invention described in claims 3 and 4. [Regarding a basic example of a method of folding a pipe inward] Fig. 5
FIG. 6 is a diagram showing a method of folding back an inner pipe, which is the basis of the second embodiment, and FIG. 6 is a cross-sectional view showing an inner folding pipe molded by the method of the second embodiment.
B1 is an inner folded pipe, 11 is a pipe body, and 12
Is a bent portion, 13 is an inner folded portion, 14 is a drawing type, 15
Is an inward push type, 16 is a stepped pipe, 16a is a large-diameter pipe part, 16b is a stepped inclined part, 16c is a small-diameter pipe part,
Reference numeral 17 is a pipe holding type.

The inward pipe return method is a method of forming an inner return pipe B1 shown in FIG. 6 having a pipe main body portion 11, a bent portion 12 and an inner return portion 13 from a pipe material of the same diameter. Each step of the stepped pipe forming step, the first inward pushing step, and the second inward pushing step which constitute the step will be described.

In the step of forming the stepped pipe, as shown in FIG. 5 (a), a large-diameter pipe portion 16a, a stepped inclined portion 16b, and a small-diameter pipe portion 16c are formed from a pipe material of the same diameter using a drawing die 14.
It is a step of forming the step pipe 16 having the step.

In the first inward pushing step, as shown in FIG. 5B, the inward pushing die 15 and the pipe holding die 17 are pressed.
Is a step of pushing the pipe end surface of the small-diameter pipe portion 16c toward the large-diameter pipe portion 16a halfway in the pipe axial direction.

In the second inward pushing step, as shown in FIG. 5C, the inner pushing die 15 is pushed further in the axial direction of the pipe so that the large diameter pipe portion 6a becomes the pipe main body portion 11 and the step inclined portion 6b. In this step, the portion weakened by molding is used as the bent portion 12, and the portion folded in by vertical buckling is used as the inner folded portion 13.

As described above, the step pipe forming step for forming the step pipe 16 is set in advance before the inward pushing step. In the step pipe forming step, the step inclined portion 16 is formed.
Since b is formed, when the step sloped portion 16b is formed, a portion of the material with a small thickness is generated due to the elongation of the material, and when a buckling stress is applied in the first inward pushing step, the portion with a small thickness is formed. The stress concentrates and the bending deformation starts. Since the large-diameter pipe portion 16a and the small-diameter pipe portion 16c are formed so as to sandwich the step sloped portion 16b, when the pushing force is applied in the first and second inner pushing steps, both pipe portions 16a,
16b will be folded by vertical buckling without interfering with each other.

Therefore, it is possible to obtain the inner folded pipe B1 in which the long inner folded portion 13 is formed instead of the double pipe structure. [Example of application of inward pipe folding method] Fig. 7
2B is a cross-sectional view showing a vibration absorbing pipe formed by applying an inward pipe folding method according to the second embodiment.
Is a vibration absorbing pipe, 11a is the first pipe body, 11b
Is a second pipe body portion, 12a is a first bent portion, 12b is a second bent portion, and 13 is an inner folded portion.

An example of application of this pipe folding method to the inner side is a step pipe forming step → first inner pushing step, that is, a step by pushing stroke to an intermediate position of the inner inner folding portion 13 This is an example of molding a vibration absorbing pipe B2 including a pipe body 11a, a first bent portion 12a, an inner folded portion 13, a second bent portion 12b, and a second pipe body 11b.

Therefore, when vibration is input from the member connected to the first pipe body 11a and the second pipe body 11b in the expansion / contraction direction, the bending direction, the twisting direction, etc., the first bent portion 12a and the inner folded portion are folded back. This can be absorbed by the deformation of the portion 13 and the second bent portion 12b. (Other Embodiments) In the first embodiment, an example of forming a stepped pipe by expansion is shown, and in the second embodiment, an example of forming a stepped pipe by drawing is shown. May be used as an example.

[0026]

According to the invention of claim 1, in a pipe folding method for molding a folded pipe having a pipe body portion, a bent portion and a folded portion from a pipe material of the same diameter, a pipe material of the same diameter and a large diameter is formed. A step pipe forming step of forming a step pipe having a pipe portion, a step slope portion, and a small diameter pipe portion, and pushing the pipe end surface of the large diameter pipe portion toward the small diameter pipe portion in the pipe axial direction, and the small diameter pipe portion. And an outer pushing step in which a portion weakened by forming the step sloped portion is used as a bent portion and a portion folded by vertical buckling is used as an outer folded portion. It is possible to obtain an effect that a long outer folded portion can be formed.

According to the invention of claim 2, claim 1
In the pipe folding method described, the outer pushing step is a step by a pushing stroke up to an intermediate position of the folding portion, thereby forming a flange folding pipe having an outer bending portion at an end of the folding portion, and folding the flange portion. Since the flange is inserted into the folded portion of the pipe and the gap is secured between the flange and the outer bent portion as the welded portion, the flange is fixed. It is possible to provide an outer folded pipe with a flange that plays a good role.

According to the third aspect of the invention, in the pipe folding method for forming a folded pipe having a pipe body, a bent portion and a folded portion from a pipe material of the same diameter,
A step pipe forming step of forming a step pipe having a large-diameter pipe portion, a step slope portion and a small-diameter pipe portion from the same-diameter pipe material, and pushing the pipe end surface of the small-diameter pipe portion toward the large-diameter pipe portion in the pipe axial direction, An inner pushing step in which a large-diameter pipe portion is used as a pipe main body, a portion weakened by forming a stepped slope portion is used as a bent portion, and a portion folded by vertical buckling is used as an inner folded portion. For,
The effect that a long inner folded portion can be formed instead of the double pipe structure can be obtained.

According to the invention of claim 4, claim 3
In the pipe turning-back method described above, the inner pushing step is a step of stopping the inner pushing in the middle of turning back, so that the first pipe body portion, the first bending portion, the turning portion, the second bending portion, and the second bending portion Since the vibration absorbing pipe provided with the pipe main body is molded, it is possible to provide the vibration absorbing pipe exhibiting the vibration absorbing performance by applying the folding-back molding in addition to the effect of the third aspect of the invention.

[Brief description of drawings]

FIG. 1 is a diagram showing an outward pipe turning method which is the basis of the first embodiment.

FIG. 2 is a cross-sectional view showing an outer folded pipe molded by the method of the first embodiment.

FIG. 3 is a cross-sectional view showing an outside folded pipe with a flange according to an application example of the outward pipe folding method according to the first embodiment.

FIG. 4 (a) is an enlarged sectional view of a welded portion of a flanged outer folded pipe, and FIG. 4 (b) is an enlarged sectional view of a welded portion of a conventional flanged pipe.

FIG. 5 is a diagram showing a method of folding back an inward pipe, which is the basis of the second embodiment.

FIG. 6 is a cross-sectional view showing an inner folded pipe formed by the method of the second embodiment.

FIG. 7 is a cross-sectional view showing a vibration absorbing pipe formed by an application example of the method of folding back a pipe according to the second embodiment.

FIG. 8 is a diagram illustrating a conventional method for curling a pipe end.

[Explanation of symbols]

A1 Outer folded pipe 1 Pipe body 2 Folding section 3 Outside fold 4 Expansion type 5 Push-out type 6 step pipe 6a Large diameter pipe section 6b Step slope 6c Small diameter pipe A2 Folded pipe for flange 7 Outside bend 8 flange 9 welds B1 Inner folded pipe 11 Pipe body 12 Folding section 13 Inner folded part 14 aperture type 15 Push-in type 16 step pipe 16a Large diameter pipe 16b step slope 16c small diameter pipe 17 Pipe holding type B2 Vibration absorption pipe 11a First pipe main body 11b Second pipe body portion 12a First bent portion 12b Second bent portion 13 Inner folded part

Claims (4)

[Claims] 1. A folded pipe (A1) having a pipe body (1), a bent portion (2) and a folded portion (3) made of a pipe material of the same diameter.
In the pipe folding method for molding, a step pipe forming step of forming a step pipe (6) having a large diameter pipe portion (6a), a step inclination portion (6b) and a small diameter pipe portion (6c) from the same diameter pipe material, The pipe end face of the large diameter pipe portion (6a) is connected to the small diameter pipe portion (6c).
Push in the axial direction of the pipe toward the small diameter pipe section (6c)
Is the pipe body (1), the part weakened by forming the step sloped part (6b) is the bent part (2), and the part folded by vertical buckling is the outer folded part (3) A pipe folding method, comprising: a pushing step. 2. The pipe folding method according to claim 1, wherein the outer pushing step is a step of pushing stroke up to an intermediate position of the folding portion (3), so that the end portion of the folding portion (3) is outside. Mold the flange turn-back pipe (A2) having the bent portion (7), insert the flange (8) into the turn-back portion (3) of the flange turn-up pipe (A2), and then attach the flange (8) and the outer bent portion. (7)
The gap secured between the flange and the welded part (9)
(8) The method of folding a pipe, characterized in that it is fixed. 3. A folded pipe (B1) having a pipe body (11), a bent portion (12) and a folded portion (13) made of a pipe material of the same diameter.
In the pipe folding method for molding, the same-diameter pipe material is used to form the large-diameter pipe section (16a) and the step slope section (16a).
b) the step pipe forming step of forming the step pipe (16) having the small diameter pipe section (16c), and the pipe end surface of the small diameter pipe section (16c) is
6a) and push it in the axial direction of the pipe,
(16a) is the pipe body (11), the weakened part due to the molding of the step sloped part (16b) is the bent part (12), and the part folded by vertical buckling is the inner folded part (13) The method of folding a pipe, comprising: 4. The pipe folding method according to claim 3, wherein the inward pushing step is a step of stopping the inward pushing in the middle of folding back the first pipe body portion (1).
1a), the first bent portion (12a), the folded portion (13), and the second bent portion
A method of folding a pipe, characterized in that a vibration absorbing pipe (B2) including a (12b) and a second pipe body (11b) is molded.