JPH1071428A - Method for bending pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a thickness reducing rate on the outer peripheral side of bending even when a pipe to be worked is longer and thinner in a method for bending the pipe by a rotary pull bending method. SOLUTION: The side of one end part of the pipe P to be worked is held with a bend roll 1, the outer peripheral side of the bending part of the pipe P to be worked is engaged with the groove 31 of a die 3. After respectively clamping the inner peripheral side of bending and outer peripheral side of bending on the side of the other end part of the pipe P to be worked with an inside clamp 4 and outside clamp 5 and, in the state in which compressive load is applied to the outer peripheral side of bending in the bending part of the pipe P to be worked with the outside clamp 5 and also tensile load is applied to the inner peripheral side of bending in the bending part of the pipe P to be worked with the inside clamp 4, the bend roll 1 is rotated and, by pulling out the bending part of the pipe P to be worked from the groove 31 of the die 3 and mating the bending part with the bend roll 1, the pipe is bent into a bend radius in accordance with the circular-arc of the bend roll 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a pipe bending method applied to the manufacture of exhaust pipes and the like of automobiles.

[0002]

2. Description of the Related Art As one of pipe bending methods applied to the manufacture of automobile exhaust pipes and the like, there is a method called a rotary drawing method. In this method, one end of a pipe to be processed is engaged with a groove of a bend roll rotatably supported and held by a clamper, and the other end of the pipe to be processed is engaged with a groove of a die. Then, the bend roll is rotated in a predetermined direction, the bent portion of the pipe to be processed is extracted from the groove of the die, and is bent along the bend roll to a bending radius corresponding to the arc of the bend roll. It is.

[0003] However, in the bending method of the rotary pulling bending method as described above, the bent portion of the pipe is formed such that the bending inner circumferential side is separated from the neutral shaft which is not affected by the stress due to the axial stress. The thickness increases, and the outer peripheral side of the bending decreases in thickness. This is because, as shown in FIG.
The compression load F1 acts on the bending inner circumference side from −X, and the tensile load F2 acts on the bending outer circumference side from the neutral axis XX. Therefore, the range in which the tensile load F2 acts is the pipe circle. It occupies almost 2/3 of the circumference. It has also been found that thinning and thickening of a pipe are proportional to the bending angle of the pipe.

By the way, in order to satisfy the required forming characteristics, it is necessary to reduce the thickness reduction on the bending outer peripheral side. For that purpose, it is necessary to move the neutral shaft to the bending outer peripheral side.

Accordingly, the present inventor has disclosed in, for example,
As described in JP-A-295024, a boost cylinder is arranged on an extension of the axial center of a pipe, and a pipe pusher is connected to a tip of a piston rod of the boost cylinder. By cutting one end of the pipe diagonally, the pipe pressing tool can press the bending outer peripheral side of the end face of the pipe, and the pipe pressing tool applies a compressive load to the bending outer peripheral side of the bent part of the pipe. I tried to bend. That is, by applying a compressive load to the bending outer peripheral side of the bent portion of the pipe, the tensile load substantially acting on the bending outer peripheral side of the bent portion at the time of the bending process is alleviated, and an attempt is made to reduce the thickness reduction.

[0006]

However, when the end face of the pipe is pressed, a compressive load is applied to the entire length of the pipe from one end to the portion held by the bend roll. When the distance from one end of the pipe P pressed by the pipe pressing tool a to the bent portion of the pipe P held by the bend roll b is long and the wall thickness of the pipe P is relatively thin, Due to the compressive load F3 by the tool a, problems such as deformation as shown in part A of FIG. 5 occur. As a result, it becomes impossible to apply a necessary compressive load to the bending outer peripheral side of the bending portion, and it becomes difficult to reduce the wall thickness of the pipe P.

An object of the present invention is to provide a method of bending a pipe by a rotary drawing method, which can be applied to a case where a pipe to be processed is long and thin, and that the thickness of the outer peripheral side of the bending is reduced. In order to achieve a reduction in

[0008]

[Means for Solving the Problems]

(Solution 1) Solution 1 of the above problem (Claim 1)
One end of the pipe to be processed is held by the bend roll,
The bending outer peripheral side of the bending portion of the pipe to be processed is engaged with the groove of the die, and the inner and outer bending sides of the bending at the other end of the pipe to be processed are gripped by the inner clamp and the outer clamp, respectively. After that, the bend roll is rotated in a state where a compressive load is applied to the bending outer peripheral side of the bent portion of the pipe to be processed by the outer clamp, and the bent portion of the pipe to be processed is pulled out from the groove of the die. A bend roll is formed to have a bending radius corresponding to the arc of the bend roll by being arranged along the bend roll.

(Solution 2) In the pipe bending method according to the first aspect, when the pipe to be processed is bent, the pipe is bent by the inner clamp. It is characterized in that a tensile load is applied to the bending inner peripheral side of the bending portion of the processing pipe.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Embodiment 1 is a pipe bending method corresponding to Solution 1 and Solution 2.

FIG. 2 is a side view showing a bending apparatus used in the pipe bending method according to the first embodiment, and FIG.
First, the configuration of the bending apparatus A will be described with reference to FIG. 2 and FIG.

In the drawing, reference numeral 1 denotes a bend roll. The bend roll 1 has an arc portion 11 having an outer shape formed by a circumferential surface, and a corner portion 12 having an outer shape formed by a right angle surface. It is supported rotatably around the center 11 s of the part 11. Further, a semicircular groove 13 substantially matching the outer diameter of the pipe P to be processed is continuously formed on the circumferential surface of the arc portion 11 and one surface of the corner portion 12.

In the drawing, reference numeral 2 denotes a clamp provided opposite to the groove 13 of the corner portion 12 of the bend roll 1.
Has a semi-circular groove 21 substantially matching the outside diameter of the bend roll 1 so that one end side of the pipe to be processed P can be held in the groove 13 of the corner 12 of the bend roll 1.

In the drawing, reference numeral 3 denotes a die for guiding a bent portion of the pipe P to be processed, that is, a die for guiding a bent portion, which is arranged on a bending outer peripheral side of the bent portion. The die 3 is also provided with a semicircular groove 31 substantially matching the outer diameter of the pipe P to be processed.

In the figure, reference numerals 4 and 5 denote an inner clamp and an outer clamp for gripping the other end of the pipe P to be processed, which are provided on the inner bending side and the outer bending side of the pipe P to be processed, respectively. Semi-circular grooves 41 and 51 which are substantially the same as the outer diameter of the pipe to be processed P are formed on each of the opposing surfaces. The inner clamp 4 and the outer clamp 5 can be moved from the clamp position to the unclamped position or from the unclamped position to the clamp position by the clamp cylinders 6 and 7.
The compression and pressurizing cylinders 8 and 9 can move in the axial direction of the pipe to be processed P.

FIG. 1 is a diagram showing a method for bending a pipe according to the first embodiment. Hereinafter, a method for bending a pipe will be described with reference to FIG.

First, as shown in (i), one end of a pipe to be processed P is held by a bend roll 1 by a clamp 2, and a bent outer peripheral side of a bent portion of the pipe to be processed P is formed into a groove of a die 3. The inner clamp 4 and the outer clamp 5 grip the other end of the pipe P to be processed. At this time, the distance between the bend roll 1 and the inner clamp 4 and the outer clamp 5 needs to be longer than the substantial length of the pipe to be processed P required for bending.
It is preferable not to make it longer than necessary. That is, the distance between the bend roll 1 and the inner clamp 4 and the outer clamp 5 is preferably adjusted not according to the length of the pipe P to be processed but according to the bending angle or the bending radius.

Next, as shown in (ii), the bend roll 1 is rotated, the bent portion of the pipe to be processed P is pulled out from the groove 31 of the die 3, and is bent along the groove 13 of the bend roll 1. The bending process is performed to a bending radius corresponding to the arc of the bend roll 1. At this time, the outer clamp 5 is moved in the direction of the arrow at a speed higher than the speed of extracting the die 3 from the groove 31 to apply a compressive load to the bending outer peripheral side of the bent portion of the pipe P to be processed, and 3 by moving the inner clamp 4 in the direction of the arrow at a speed lower than the speed of withdrawal from the groove 31.
A tensile load is applied to the inner bend of the bend. As a result, the pipe P to be processed can relieve the tensile load substantially acting on the bending outer peripheral side of the bent portion at the time of bending, and the compressive load substantially acting on the bending inner peripheral side of the bent portion. Therefore, the thickness reduction on the bending outer peripheral side of the bent portion is reduced, and the thickness increase on the bending inner peripheral side of the bent portion is reduced.

As described above, according to the pipe bending method of the first embodiment, the thickness reduction on the bending outer peripheral side of the bent portion can be reduced, so that the required forming characteristics can be satisfied.

Further, since a compressive load is applied to the bending outer peripheral side of the bent portion of the pipe to be processed P by the outer clamp 5 gripping the outer peripheral side of the bending of the pipe to be processed P, depending on the position of the outer clamp, By adjusting the range in the longitudinal direction of the pipe to be processed P on which the compressive load is applied, it is possible to prevent a problem such as deformation from occurring when the compressive load is applied. In other words, the present invention can be applied to a case where a long and thin pipe P to be processed is bent, and even in such a case, the reduction in wall thickness can be sufficiently reduced.

Furthermore, since the increase in the thickness of the bent inner peripheral side of the bent portion can be reduced, wrinkles and buckling do not occur on the bent inner peripheral side of the bent portion, and the appearance is improved.

(Other Embodiments) In the first embodiment, the die 3 is provided only on the outside of the pipe P to be processed, and the bending is performed. The pipe to be processed P may be bent while the gold is inserted. FIG. 1 shows an example in which the pipe to be processed P is bent at an angle of 90 degrees, but the bending angle of the pipe to be processed P is not limited to 90 degrees and can be set arbitrarily.

[0023]

According to the first aspect of the present invention, in a method of bending a pipe by a rotary drawing method, one end of the pipe to be processed is held by a bend roll, and the pipe is bent. The outer peripheral side of the part is engaged with the groove of the die, and the other end of the pipe to be processed is gripped by the inner clamp and the outer clamp provided on the inner side and the outer side of the pipe to be bent. After that, the bend roll is rotated in a state where a compressive load is applied to the bending outer peripheral side of the bent portion of the pipe to be processed by the outer clamp, and the bent portion of the pipe to be processed is pulled out from the groove of the die. A method of bending the bend roll to a bending radius corresponding to the arc of the bend roll by following the bend roll reduces the tensile load substantially acting on the bending outer peripheral side of the bent portion of the pipe to be processed during the bending process. , It is possible to reduce the wastage of bending outer peripheral side of the bent portion. In addition, since a compressive load is applied to the bending outer peripheral side of the bent portion of the pipe to be processed by the outer clamp, the range of the length of the pipe to be processed in which the compressive load is applied is adjusted according to the position of the outer clamp. In addition, when a compressive load is applied, problems such as deformation can be prevented. In other words, the present invention can be applied to a case where a long and thin pipe to be processed is bent, and even in such a case, the effect of sufficiently reducing the wall thickness can be obtained.

According to the second aspect of the present invention, the first aspect is provided.
In the pipe bending method described, when bending the bent portion of the pipe to be processed, a method of applying a tensile load to the bending inner peripheral side of the bent portion of the pipe to be processed with the inner clamp, The compressive load substantially acting on the bending inner peripheral side of the bent portion of the pipe to be processed can be reduced, and the increase in the thickness of the bent inner peripheral side of the bent portion can be reduced. Therefore, in addition to the above effects, wrinkles and buckling do not occur on the bending inner peripheral side of the bending portion, and an effect of improving aesthetic appearance can be obtained.

[Brief description of the drawings]

FIG. 1 is a process chart showing a pipe bending method according to a first embodiment.

FIG. 2 is a side view showing a bending apparatus used in the pipe bending method according to the first embodiment.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a diagram showing stress characteristics during bending of a pipe.

FIG. 5 is a view showing a problem in a conventional pipe bending method.

[Explanation of symbols]

 P Pipe for processing 1 Bend roll 2 Clamp 3 Die 31 Groove 4 Inner clamp 5 Outer clamp

Claims (2)

[Claims] An end of a pipe to be processed is held by a bend roll, and a bent outer peripheral side of a bent portion of the pipe to be processed is engaged with a groove of a die. After the inner and outer bends are gripped by an inner clamp and an outer clamp, respectively, the bend roll is applied in a state where a compressive load is applied to a bent outer peripheral side of a bent portion of the pipe to be processed by the outer clamp. The pipe is characterized in that a bent portion of the pipe to be processed is extracted from the groove of the die and is bent along the bend roll to a bending radius corresponding to the arc of the bend roll. Bending method. 2. The method according to claim 1, wherein, when bending the pipe to be processed, a tensile load is applied to the bending inner peripheral side of a bent portion of the pipe to be processed by the inner clamp. Pipe bending method.