JPH07224987A - Metallic bent pipe - Google Patents

Abstract

PURPOSE:To reduce passage resistance and disperse stress concentration by disposing a thick-walled part, satisfying a specific condition, on the inside of a bent part, disposing shift parts of specific length on both sides of the thick- walled part, and forming the outer peripheral shape of the bent part into almost the same shape as an element pipe. CONSTITUTION:A metallic bent pipe 30 has a bent part of R<=D/2 and theta=60-120 deg., where R is a bend inner radius, theta is a bending angle. and D is the outer diameter of the metallic pipe. In this case, a thick-walled part 31 satisfying the following condition is disposed at the inner surface of the bending angle thetapart on the inside of the bent part, whereas shift parts 31-1, 31-2 of wall thickness gradually approaching the wall thickness of the element pipe and 1/D or more in length are disposed on both sides of the thick-walled part 31, and the outer peripheral shape of the bent part is formed into almost the same shape as the element pipe, that is, 2.0t>=T2<=1.5t, where T2 is the inner wall thickness (mm) of the bending angle theta part, and (t) is the wall thickness (mm) of the element pipe. The passage resistance of a fluid is thereby reduced, and the stress concentration of the bent part is dispersed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality bent metal tube which is free from crushing, cracking, breakage, etc. at a bent portion due to stress concentration in the tube.

[0002]

2. Description of the Related Art In engine rooms and cooler mechanisms of automobiles, the use of miniaturized parts is increasing, and in order to connect these parts arranged at a high disposition density,
There is a need for a bent metal tube with a small radius of curvature. A metal bending tube with a relatively large radius of curvature can be manufactured by holding the tip of the work piece with a clamp and pressing it in a bending die to bend it, but the radius of curvature is larger than the diameter of the work piece of the tubular body. When it becomes smaller, in this manufacturing method, the tip of the work piece slides backward during rotation of the bending die, the circular cross section of the bending portion cannot be maintained, and the metal bending pipe is crushed,
Alternatively, there is a tendency that wrinkles and buckling occur inside the bent portion and damage occurs outside.

FIG. 5 shows an example of a metal bending pipe in which processing defects have occurred. (A) shows the outside of the bending portion crushed so that the passage of the bending portion has a flat cross section (b). Cracks are formed on the outside of the part, and (c) is buckling on the inner wall of the bent part. It is natural that the metal pipe parts with cracks are not preferable because the fluid leaks to the outside, but even if the metal pipe parts have a flat cross section or buckle, the inside of the metal pipe is The passage resistance of the flowing fluid increases, which is not preferable, and stress concentration may occur in the buckling portion, which may cause cracks or the like in the portion.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the current state of the metal bending pipe of this kind as described above, and it is possible to prevent crushing, cracking, buckling, cracking or the like at the bent portion. It is intended to provide a metal bend tube with a small radius of curvature.

[0005]

According to the present invention, when the outer diameter of the metal pipe is D, the bending inner radius is R, and the bending angle is θ, the bending inner radius R ≦ D / 2, the bending angle θ = 60 to. In a metal bent pipe having a bent portion of 120 degrees, a thick wall portion satisfying the following condition is provided on the inner surface of the θ portion inside the bent portion, and the wall thickness gradually increases on both sides of the thick wall portion. The gist of the present invention is that it has a transitional portion having a length of 1 / 3D or more that approaches the wall thickness t, and that the outer peripheral shape of the bent portion is substantially the same as that of the raw pipe. Note 2.0t ≦ T ₂ ≦ 1.5t T ₂ : inner wall thickness of the θ portion (mm) t: wall thickness of the raw tube (mm)

[0006]

1 is an explanatory view of a metal bending pipe according to the present invention, showing a state in which a bending portion is cross-sectioned, 30 is a metal bending pipe, 31 is a thick wall portion, 31-1 and 31-2 are transitions. Department,
l ₁ and l ₂ are the lengths of the transition portions, T ₁ and T ₃ are the wall thicknesses of the transition portions, and R is the bending radius inside the pipe.

In the present invention, the reason why the thickness T ₂ of the thick portion 2 of the θ portion is limited to satisfy the above condition is that when the inner thickness T ₂ of the θ portion exceeds 2.0 t, the flow path resistance is increased. Occurs,
On the other hand, if it is less than 1.5 t, it is not possible to exert the stress concentration prevention (stress dispersion effect) generated in the bent portion. Further, the lengths l ₁ and l ₂ of the transitional parts 3-1 and 3-2, which gradually approach the wall thickness t of the raw pipe, are limited to 1 / 3D or more. This is because the stress dispersion effect cannot be obtained when the length is less than 1 / 3D. This transition section 3-1, 3
Since the wall thicknesses T ₁ and T ₃ of −2 gradually approach the wall thickness t of the raw pipe, T ₁ > t and T ₃ > t, respectively.

Bending inner radius R ≦ D / which is the object of the present invention
2. In the case of a bend pipe having a small radius of curvature or a minimum radius of curvature having a bend portion with a bend angle θ = 60 to 120 degrees, stress tends to concentrate on the bend portion because the bend inner radius R is small.
2.0t ≦ T ₂ ≦ 1.5t in the θ portion inside the bent portion
The thick portion 2 satisfying the condition of 1 and the transition portion having a length of ⅓D or more that gradually approaches the wall thickness t of the raw pipe are provided on both sides of the thick portion, and the outer peripheral shape of the bent portion is changed. By making the shape substantially the same as that of the base pipe, not only the passage resistance of the fluid flowing inside the metal pipe can be reduced, but also the stress concentration generated in the bent portion can be dispersed.

The method for manufacturing the metal bending tube according to the present invention is not particularly limited, but for example, the metal tube is held in a bending die having a split structure, the core metal is inserted from the fixed side, and the metal tube is pushed from the movable side. It is possible to use a means for performing bending while applying a compressive force to the metal tube with a rod. According to this method, bending is performed along the guide surface of the core metal with a small radius of curvature, and the large axial force in the compression direction generated from the other end of the pipe to the bending portion causes plastic flow to the bending portion. It is possible to obtain a high-quality bent pipe without fear of crushing, cracking, breakage, etc. due to the increase in wall thickness.

[0010]

FIG. 2 is a schematic plan view showing an example of an apparatus for manufacturing a metal bending pipe according to the present invention, FIG. 3 is a schematic front view showing a state before bending a work by the same apparatus, and FIG. It is a schematic front view which shows the state after bending.

That is, in the apparatus for manufacturing a metal bending pipe illustrated here, the second clamp 11b is formed by the lower mold 1 and the upper mold 2, and the first clamp 11a is formed by the lower mold 3 and the upper mold 4.
Is formed, and the pipe guide grooves 12 and 12 'are formed on the first clamp 11a and the second clamp 11b so as to extend on the mutual extension, and the recess 12a is formed on the pipe guide groove 12 side. It is provided. In the pipe guide groove 12, a terminal processing portion 10a including a spool or a flare formed on the workpiece 10 side of the pipe body to be processed.
Is installed from the first clamp 11a side in a state in which the first clamp 11a is positioned inside the recess 12a, and at the same time, the guide surface 7a formed at the tip from the first clamp 11a side is the first clamp 1a.
It is attached and set on a cored bar 7 which is located at a specified length protruding from a boundary surface formed by 1a and the second clamp 11b. And by the cylinder 15 by the first clamp 11a,
Alternatively, the work 10 is fixed to the cored bar 7 by holding it by pressing the work piece 10 onto the core metal 7, and further, by the cylinder 16 on the side of the second clamp 11b, the other end side of the work 10 is guided near the guide groove 12 '. It is held loosely on the part.

On the other hand, a push rod 6 is provided in contact with the other end of the work 10, and the push rod 6 can be pushed by a push cylinder 5. And the second clamp 11b
Are arranged so as to be rotatable about a rotation center C provided at an end of a surface facing the first clamp 11a. That is, the rotating body 20 provided with the rotating shaft 18 at the rotation center C is fixed to the second clamp 11b, and the rotating shaft 18 is supported by the bearing 21 fixed to the first clamp 11a. There is.

From this state, the pressing cylinder 5
While the push rod 6 presses the other end of the work 10, the rotary shaft 1
When the rotating body 20 is rotated by rotating 8, the second clamp 11b moves with respect to the first clamp 11a.
It rotates about the center of rotation C. This state is shown in FIG. 3, and when the rotary body 20 is rotated from the state of FIG. 3, the second clamp 11b fixed to the rotary body 20 rotates, and a 90 ° bent pipe, for example. In the case of processing, the second clamp 11b rotates to the state shown in FIG. At this time, one end of the work 10 is fixed by the clamp 11a, and the other end is constantly pressed by the push rod 6, so that the work 10 moves along the guide groove 12 'of the second clamp 11b. The inner wall surface is bent while being guided by the guide surface 7a. At this time, the other end side of the work is kept pressed by the push rod 6 along the guide groove 12 'of the second clamp 11b.
Bending part of high quality with a small radius of curvature that does not cause crushing, cracking or damage at the bending part due to thickening due to plastic flow on the pipe wall of the bending part at all times due to axial force Will be processed efficiently.

According to the data obtained experimentally by the present inventors, the second clamp 11b covers about half of the outer bent portion of the work 10 at the end of bending of the work 10. When the shape of the second clamp 11b is set,
It was possible to manufacture a high-quality bent tube with the least amount of crushing and wrinkling at the bent portion.

According to the above bending apparatus, it is possible to process a high-quality bent pipe having a small radius of curvature without crushing, cracking, breaking, wrinkling, or buckling at the bent portion, and in a short time, the metal bending Since the pipe is processed, it is also advantageous in terms of processing cost.

[0016]

As described above, the metal bending pipe having a small radius of curvature or a very small radius of curvature according to the present invention has a thick wall portion satisfying a predetermined condition on the inner side of the bent portion, and a metal wall on both sides of the thick wall portion. The passage resistance of the fluid flowing inside the metal pipe is reduced by having a transition part of a predetermined length that gradually approaches the wall thickness of the raw pipe and making the outer peripheral shape of the bent portion almost the same as the raw pipe. In addition to being able to do so, it is possible to disperse the stress concentration generated in the bent portion, so that both rigidity and durability are excellent, and a great effect is achieved especially for automobile parts.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a bent portion for explaining a metal bent tube according to the present invention.

FIG. 2 is a schematic plan view showing an example of a metal bending pipe manufacturing apparatus according to the present invention.

FIG. 3 is a schematic front view showing a state before bending of a work by the same apparatus.

FIG. 4 is a schematic front view showing a state after the work is also bent.

5A and 5B are cross-sectional views illustrating a conventional metal bending pipe in which a processing defect has occurred, where FIG. 5A is a view in which the outside of the bending portion is crushed and the passage of the bending portion has a flat cross section, and FIG. 5B is bending. A crack is generated on the outer side of the portion, and (c) is a buckle on the inner wall of the bent portion.

[Explanation of symbols]

1 Lower Die 2 Upper Die 3 Lower Die 4 Upper Die 5 Cylinder 6 Push Bar 7 Core Bar 7a Guide Surface 10 Workpiece 11a First Clamp 11b Second Clamp 12 Pipe Guide Groove 12 'Guide Groove 30 Metal Bent Pipe 31 Thick Section 31 - transition l _{1, l 2} migration length of the portion T _{1, T 3} transition thick R bend inside radius

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[Procedure amendment]

[Submission date] March 28, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

According to the present invention, when the outer diameter of the metal pipe is D, the bending inner radius is R, and the bending angle is θ, the bending inner radius R ≦ D / 2, the bending angle θ = 60 to. In a metal bent pipe having a bent portion of 120 degrees, a thick wall portion satisfying the following condition is provided on the inner surface of the θ portion inside the bent portion, and the wall thickness gradually increases on both sides of the thick wall portion. The gist of the present invention is that it has a transitional portion having a length of 1 / 3D or more that approaches the wall thickness t, and that the outer peripheral shape of the bent portion is substantially the same as that of the raw pipe. Note 2.0t ≧ T ₂ ≧ 1.5t T ₂ : inner thickness of the θ portion (mm) t: thickness of the raw tube (mm)

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

Bending inner radius R ≦ D / which is the object of the present invention
2. In the case of a bend pipe having a small radius of curvature or a minimum radius of curvature having a bend portion with a bend angle θ = 60 to 120 degrees, stress tends to concentrate on the bend portion because the bend inner radius R is small.
2.0t ≧ T ₂ ≧ 1.5t in the θ portion inside the bent portion
The thick portion 2 satisfying the condition of 1 and the transition portion having a length of ⅓D or more that gradually approaches the wall thickness t of the raw pipe are provided on both sides of the thick portion, and the outer peripheral shape of the bent portion is changed. By making the shape substantially the same as that of the base pipe, not only the passage resistance of the fluid flowing inside the metal pipe can be reduced, but also the stress concentration generated in the bent portion can be dispersed.

Claims (1)

[Claims] 1. The outer diameter of the metal tube is D, the inner radius of bending is R,
When the bending angle is θ, the following condition is satisfied on the inner surface of the θ portion inside the bending portion in a metal bending pipe having a bending inner radius R ≦ D / 2 and a bending angle θ = 60 to 120 degrees. It has a thick wall portion, and a transition portion having a length of ⅓D or more that gradually approaches the wall thickness t of the raw tube on both sides of the thick wall portion, and the outer peripheral shape of the bent portion is the raw tube. A metal bent tube characterized by having almost the same shape as. Note 2.0t ≦ T ₂ ≦ 1.5t T ₂ : inner wall thickness of the θ portion (mm) t: wall thickness of the raw tube (mm)