JP2005161325A - Pipe bending machine and pipe bending method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pipe bending machine and a pipe bending method capable of preventing buckling and wall thickness reduction by controlling the pressure of a pressing die by a simple method. <P>SOLUTION: The pipe bending machine has: a bending die 1 having a turnable body part and a groove part formed on the circumferential surface of the body part and having a shape corresponding to the bending shape of a pipe p; a clamp to hold the pipe p; a pressing die 3; a pressing means to press the pressing die 3; a control means; and a spacing limiting means to limit the spacing u between the groove part and the pressing die 3. The spacing limiting means has: a bending die side limiting part 11 fixed to the bending die 1; and a pressing die side limiting part 31 which is abutted on the circumferential surface of the bending die side limiting part 11 to limit the movement of the pressing die 3 to the bending die 1 and which is fixed to the pressing die 3. By controlling the spacing u between the groove part and pressing die 3, the pressure applied from the pressing die to the pipe can be controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pipe bending apparatus and a pipe bending method for bending a pipe by plastic working.

  Pipe parts that have been subjected to minimal bending (for example, a bending radius of 1.5 DR or less) are widely used in automobiles, air conditioners, and the like. As a bending apparatus for bending a pipe into a predetermined shape, a rotary pull bending apparatus as shown in FIGS. 4 and 5 is widely used. 5 is a cross-sectional view taken along line bb of FIG.

  The rotary pull bending apparatus holds a rotatable bending die 91 having a bending guide groove, a clamp 92 for fixing a part of the pipe p to the bending die 91, and a bending outer peripheral surface of the pipe p. A pressing die 93, a wiper 94 that holds the inner peripheral surface of the pipe p, a mandrel 95 that is held inside the pipe p, and a pipe booster 96 that urges the pipe p in the axial direction from the rear end of the pipe p. Have.

  The pressing die 93 is supported by a holder 97 so as to be movable in the axial direction of the pipe p, and the holder 97 can be adjusted in the radial position of the bending die 1 by a position adjusting screw 7a. In general, the position of the pressing die 93 is often fixed when the pipe p is processed.

  In order to bend the pipe p, a part of the pipe p is fixed to the bending die 91 by the clamp 92, and the pressing die 93 is moved to a desired position by the position adjusting screw 97a, and the bending die 91, the wiper 94, By rotating the bending die 91 while holding the pipe p with the mandrel 95 and the pressing die 93, the pipe p is bent into a shape following the groove shape of the bending die 91. Further, if necessary, the pipe is boosted by the pipe booster 96 from the rear end of the pipe p.

  In the above-described bending apparatus for the pipe p, the bending behavior of the pipe differs between the inside and outside of the bending around the geometric neutral axis of the bending of the pipe p. That is, since the trajectory length is long with respect to the neutral axis on the outer side of the bend, the thickness is increased in the axial direction and the thickness after bending becomes thinner than the original thickness t. Since the trajectory length is shorter with respect to the neutral axis on the inner side of the bend, the thickness is reduced in the axial direction and the thickness after bending becomes thicker than the original thickness t.

  Therefore, cracks are likely to occur on the outer side of the bend and buckling on the inner side of the bend. In addition, the cross section after bending is made elliptical. Conventionally, in order to prevent buckling on the inner side of bending and prevention of ovalization of the pipe p, bending is performed in a state where a mandrel 95 is provided on the inner side of the pipe p as shown in FIGS. That is, buckling prevention has been achieved by bending the pipe wall on the inner side of the pipe p with the bending die 91, the wiper 94, and the mandrel 95.

  However, since the outer pipe wall is subjected to ironing deformation by the mandrel 95, there has been a disadvantage that thinning of the outer bending side is promoted.

  As a method for suppressing buckling in such bending, in the conventional technique, the rotary pulling bending device controls the bending start point and the processing speed so that the neutral axis of the bending portion is controlled from the geometric axis. Has also been proposed to be moved to the back side by 5 to 10% (Patent Document 1).

  Then, a mandrel is inserted into the pipe, a pipe rear end hooking convex portion is provided on the push die, and the rear end of the pipe is hooked on the convex portion, and the pipe is bent along the bending die. At the same time as bending the part, it has been proposed to push the pushing die forward and push the rear end of the pipe hooked on the convex portion forward together with the pushing die by a predetermined length (Patent Document 2).

  Further, in the prior art, the peripheral surface on the pressing die 93 side of the pipe is kept substantially the same as the pipe radius, the peripheral surface on the bending die 91 side is deformed to a radius larger than the pipe radius, and the entire circumference of the pipe is A pipe bending method for reducing the length by several percent is disclosed (Patent Document 3).

  By the way, the pressing die must be pressed against the bending die with an appropriate pressure. For example, it is necessary to press the mold relatively strongly for the purpose of preventing buckling, etc. for the part where pipe bending is performed, but for the part where bending is not performed, the pressing mold is strongly pressed against the bending mold. Not required.

As a method for controlling the pressing force for pressing the pressing die against the bending die, a method for controlling the pressing force by controlling the pressing means (Patent Document 4), or a method for controlling the displacement of the pressing die by controlling the pressing means. (Patent Document 5) is disclosed.
JP 2001-353530 A Japanese Patent Laid-Open No. 5-96332 Japanese Patent Laid-Open No. 55-5180 JP-A-3-204120 JP-A-3-297517

  However, pressure control is complicated and the equipment becomes large, and the displacement control of the pressing die needs to synchronize the rotation of the bending die with the displacement of the pressing die. When the mechanism is complicated and the displacement is large, there is a problem that the bending die bites the pushing die.

  In this invention, it is set as the problem which should be solved to provide the pipe bending apparatus and method which can control the pressurizing force of a pressing die by a simple method. In the present invention, it is an object to be solved to provide a pipe bending apparatus and method capable of preventing buckling and thinning during pipe bending. It is another object of the present invention to provide a pipe bending apparatus and method that can freely change the circumference of the pipe.

(1) A pipe bending apparatus of the present invention that solves the above-described problems includes a bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending apparatus having control means for controlling the pressurizing means,
It has a space | interval restriction | limiting means which restrict | limits the magnitude | size of the space | interval between this groove part and this pressing die (Claim 1).

And the pipe bending method of the present invention that solves the above-mentioned problems is a bending die having a rotatable main body and a groove formed on the peripheral surface of the main body and having a shape corresponding to the bending shape of the pipe,
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending method using a control means for controlling the pressurizing means,
An interval limiting means for limiting the interval according to the bending shape and / or the amount of diameter reduction of the portion of the pipe held by the groove and the pressing die, the interval between the groove and the pressing die;
The pipe is bent and reduced in diameter (claim 9).

  In other words, by controlling the distance between the groove and the pressing die by the interval limiting means, it is possible to easily limit the pressing force applied from the pressing die to the pipe without precisely controlling the pressing force of the pressurizing means. Thus, the feed amount of the pressing die can be precisely controlled. In the device according to the present invention, since the distance between the groove and the pressing die is controlled, there is an effect that the control becomes easier as compared with the case where the displacement of the pressing die is controlled independently.

  According to the present invention, the necessary pressing force can be applied to the groove (pipe) by the pressing die without precisely controlling the pressing force on the pressing die. In other words, the pressing force applied to the pressing die by the pressurizing means is applied to the pipe until it is limited by the interval limiting means, so that the gap between the groove and the pressing die is controlled to be small in a portion where a large pressing force needs to be applied to the pipe By doing so, a large pressure can be applied to the pipe.

  And it is preferable to make the circumference of the part which combined the said groove part and the said pressing die shorter than the circumference of the said pipe (Claim 2). Furthermore, it is preferable that the said space | interval restriction | limiting means is a means to restrict | limit the said space | interval according to the bending shape and / or diameter reduction amount of the corresponding part of the said pipe (Claim 3). The pipe can be effectively reduced in diameter by applying a large force to the portion of the pipe where bending and diameter reduction are performed.

  Further, the spacing limiting means limits the amount of movement of the pressing die to the bending die by contacting a bending die side limiting portion fixed to the bending die and a peripheral surface of the bending die side limiting portion. It is preferable to have a pressing die side restricting portion fixed to the pressing die. By controlling the length of the state in which the bending die side limiting portion and the pressing die side limiting portion are in contact with each other, the pressure applied to the pipe by the pressing die can be easily controlled.

  The sum of the peripheral length of the portion combining the groove and the pressing die and the size of the interval limited by the interval limiting means is preferably 85% to 97% with respect to the peripheral diameter of the pipe. Item 5, 12). By controlling the sum of the circumferential length of the combined portion of the groove and the pressing die and the size of the interval limited by the interval limiting means within the above range, the pipe is held between the groove and the bending die and contracted. Diameter. If the diameter of the pipe is reduced, an appropriate value of compressive stress is applied in the circumferential direction of the pipe, so that it is difficult for thickness reduction or cracking to occur.

(2) A pipe bending apparatus of the present invention that solves the above-described problems includes a bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending apparatus having control means for controlling the pressurizing means,
The circumferential length of the portion combining the groove and the pressing die is a circumferential length according to the bent shape and / or the amount of diameter reduction of the sandwiched portion of the pipe,
The pressing die abuts on the groove to pinch the pipe (Claim 6).

  That is, the circumferential length of the portion where the groove portion and the pressing die are combined is the circumferential length according to the bending shape and / or the diameter reduction amount of the holding portion of the pipe, so that the function of the above-mentioned distance limiting means can be achieved. Since it can be given to the mold itself, the same effect as the above-described invention can be exhibited. Here, it is preferable that the circumferential length of the portion combining the groove and the pressing die is 85% to 97% with respect to the circumferential diameter of the pipe.

  (3) In (1) and (2), in the linear direction, the pressurizing means has a point where a straight line passing through the point where the bending mold and the pipe abut and the rotation center of the main body intersect the pressing mold. A means for applying pressure is preferred (claims 8 and 11).

  As a pressurizing means, an unnecessary moment is applied to the pipe by using a means that pressurizes the point where the straight line passing through the point where the bending die and the pipe abut and the rotation center of the main body intersect the push die in the linear direction. And no extra force is applied to the pipe being processed. Since no extra force is applied, no extra deformation occurs on the pipe wall.

[First Embodiment]
(Constitution)
A schematic configuration of the pipe bending apparatus of the present embodiment is shown in FIG. FIG. 2 is a sectional view taken along the line aa in FIG. The pipe bending apparatus of this embodiment includes a bending die 1, a clamp 2, a pressing die 3, a pressurizing means (not shown), a control means (not shown), and a distance limiting means.

  The bending die 1 has a main body portion and a groove portion. The main body is rotatably held on a rotation shaft (rotation center) o. The groove is formed on the peripheral surface of the main body, and has a shape corresponding to the bent shape of the pipe p.

  The pressing die 3 is means for pressing the pipe p against the groove and plastically deforming it. The pressing die 3 holds the pipe p and is supported so as to be movable in the axial direction of the pipe p together with the pipe p. The circumferential length of the portion where the groove portion and the pressing die 3 are combined is shorter than the circumferential length of the pipe.

  In addition, the apparatus has spacing limiting means. The interval limiting unit is a unit that limits the interval between the groove and the pressing die 3. The interval limiting means has a bending die side limiting portion and a pressing die side limiting portion.

  As shown in FIG. 2, the bending die side limiting portions 11 are integrally formed as convex portions on both sides of the groove portion of the bending die 1. On both sides of the portion of the pressing die 3 corresponding to the groove portion of the bending die 1, a pressing die side limiting portion 31 is integrally formed as a recess. When the groove portion and the pressing die 3 are combined, the peripheral surface of the bending die side limiting portion 11 and the pressing die side limiting portion 31 are brought into contact with each other and combined to limit the distance between the groove portion and the pressing die 3. Limit 3 moves.

  Specifically, the difference between the height h1 of the bending die side limiting portion 11 from the peripheral surface of the bending die 1 and the depth h2 from the surface of the pressing die side limiting portion 31 facing the groove portion of the pressing die 3 is the groove portion. And the distance u from the pressing die. The difference between the height h1 and the depth h2 (= the distance u between the groove and the pressing die 3) is changed according to the degree of pipe bending and the diameter of the pipe (the degree of bending or the diameter reduction). The difference between the height h1 and the depth h2 is reduced in a portion where the degree of the height is large, and either the height h1 or the depth h2 may be changed. If the pressing die 3 is sufficiently pressurized by the pressing means, until the sum of the circumferential length of the portion combining the groove and the pressing die 3 and the interval (u × 2) limited by the interval limiting means is obtained. The circumference of the pipe is reduced in diameter.

  That is, by combining the bending die side limiting portion and the pressing die side limiting portion, an effect similar to a cam is exhibited and the interval u between the groove portion and the pressing die 3 is limited. Here, both the bending die side limiting portion and the pressing die side limiting portion do not need to be integrated with the bending die 1 and the pressing die 3, and may restrict the movement of the bending die 1 and the pressing die 3 in which the interval u changes. Any means may be used. For example, instead of providing the space limiting means (bending mold side limiting portion and 11 and the pressing mold side limiting portion 31) between the bending die 1 and the pressing die, the bending die side limiting portion and 11 are provided between the bending die 1 and the pressing means. An interval limiting means similar to the push mold side limiting portion 31 can be provided.

  The sum of the peripheral length of the combined portion of the groove portion and the pressing die 3 and the interval limited by the interval limiting means depends on properties such as the elongation of the pipe, but is preferably 97% or less with respect to the peripheral length of the pipe, More preferably, it is 95% or less. Furthermore, the circumferential length of the portion where the groove portion and the pressing die 3 are combined is preferably 85% or more. That is, buckling, cracking, thinning, etc. that occur during pipe bending can be effectively prevented by reducing the diameter of the pipe to a length corresponding to these values.

  The clamp 2 is a means for holding a part of the pipe p. Preferably, it is means for fixing one end of the pipe p to a part of the peripheral surface of the bending die 1. The pipe p is bent by using a portion fixed to the clamp 2 as one of the support points.

  The pressurizing means is means for pressing the pressing die 3 against the bending die 1 by applying pressure. As the pressurizing means, general means such as a hydraulic mechanism and a crank mechanism can be adopted. The pressurizing means is a means controlled by hydraulic pressure. The pressurizing means controls the pressurizing force and the feed amount based on the control signal input from the control means. If necessary, the pressing force and / or feed amount of the pressurizing means can be measured and output as a signal to the control means.

  The control means is means for controlling the pressurizing means. It is preferable that the pressurizing means is controlled so that sufficient pressure can be exerted even at a site where the applied pressure is required, such as a site where the interval u is the smallest and a site where the pipe is bent. For example, the control means can make the applied pressure constant. Even if the pressure is constant, the degree of diameter reduction varies depending on the part of the pipe due to the action of the interval limiting means.

(Function and effect)
Since it has the above-described configuration, the pipe bending apparatus of the present embodiment has the following operational effects. That is, the present processing apparatus holds the pipe p to be bent by the clamp 2 and fixes it on the peripheral surface of the bending die 1. The clamp 2 rotates together with the bending die 1. The pipe p is bent by the clamp 2, the bending die 1 and the pressing die 3 according to the shape of the groove on the peripheral surface of the bending die 1. The control means controls the pressurizing means.

  As a result, since the interval u between the groove and the pressing die 3 is limited by the interval limiting means, the groove and the pressing die 3 come close to the limited interval u, and the diameter of the pipe p is reduced. That is, the diameter reduction amount of the pipe p can be controlled by the interval limiting means.

  When the part of pipe p whose diameter is reduced is a part to be bent, the part where the pipe wall is extended by the bending process is compensated by the remaining pipe wall due to the reduced diameter, and the thinning outside the pipe p is reduced. Can be prevented. Further, since the compressive stress is applied in the circumferential direction of the pipe p when the diameter is reduced, the stress that presses the pipe wall of the pipe p against the groove portion and the pressing die 3 is generated. Ovalization due to bending can be suppressed.

  As described above, according to the configuration of the bending apparatus of the present embodiment, it is possible to easily control the pressing force that presses the pressing die 3 against the groove, and can suppress the thinning of the outer side of the bending, and there is no buckling on the inner side of the bending. This makes it possible to manufacture pipes having different circumferential lengths in the axial direction.

[Second Embodiment]
(Constitution)
A schematic configuration of the pipe bending apparatus of the present embodiment is shown in FIG. The aa cross-sectional view in FIG. 3 is almost the same as FIG. The pipe bending apparatus of the present embodiment includes a bending die 1, a clamp 2, a pressing die 3, a pressurizing means 8, a control means 6, and an interval limiting means. Furthermore, it has a pressing die urging means 4. In addition, the code | symbol attached | subjected to each component was made into the same code | symbol about what has a substantially the same effect as the component of 1st Embodiment.

  Since the bending die 1, the pressing die 3, the control means 6, and the interval limiting means are the same as those in the first embodiment, description thereof is omitted.

  The pressurizing unit 8 is a unit that pressurizes a point where a straight line passing through a point where the bending die 1 and the pipe p abut and a rotation center of the main body of the bending die 1 intersects the pressing die 3. The direction of pressurization is the direction toward the center of rotation of the main body. The pressurizing means 8 always pressurizes the pressing die 3 through the holder 7 in order to make the position and direction of pressurization constant. As shown in the drawing, the holder 7 restrains the pressing die 3 in the radial direction of the bending die 1 and the rotation axis direction of the bending die 1 and holds the bending die 1 movably in the axial direction of the pipe p. Means.

  A force acts on the pipe p in a direction opposite to the rotation center of the main body from the point of contact with the bending die 1. By applying a force opposite to this force to the pipe p, the force is balanced and it is possible to prevent a rotational moment from being applied to the pipe p. Further, a member for holding the pipe p such as a wiper necessary for preventing buckling in the conventional pipe bending apparatus from the opposite side of the pressing die 3 becomes unnecessary. Adjustment of the setting position of the wiper requires skill and is a consumable item that wears out, so the advantage of eliminating the need for the wiper is great.

  The pressing die urging means 4 is a means for urging the pressing die 3 in the axial direction of the pipe p. Since the pressing die 3 and the pipe p move as the bending die 1 rotates, the force applied to the bending die 1 increases as the size of the pipe p increases. By urging the pressing die 3 by the pressing die urging means 4, the force for rotating the bending die 1 can be reduced. Further, a pipe booster that has been conventionally used may be used in place of the push-type urging means 4. Since the pipe booster needs to hold the end of the pipe p, the push-type urging means 4 for directly urging the push-type 3 is preferable because there is room for downsizing the apparatus.

(Function and effect)
Since it has the above-described configuration, the pipe bending apparatus of this embodiment has the following functions and effects in addition to the functions and effects of the apparatus of the first embodiment. That is, the pressure means 8 is a means for pressurizing the point where the straight line passing through the point where the bending die and the pipe abut and the rotation center of the main body intersect the push die in the direction of the straight line. Will not be applied and no extra force will be applied to the pipe being processed. Since no extra force is applied, no extra deformation occurs on the pipe wall.

  The pressing die urging means 4 can suppress the inertial force of the pressing die 3 from being applied to the bending die 1 by urging the pressing die 3 in the axial direction of the pipe p. The movement in the axial direction can be performed smoothly. In addition, since the slip between the pressing die 3 and the pipe p can be reduced, it is possible to suppress the thinning due to ironing that may remain slightly on the bent outer side of the pipe p.

[Third Embodiment]
(Constitution)
The pipe bending apparatus of the present embodiment includes a bending die, a clamp, a pressing die, a pressurizing unit, and a control unit. It is almost the same as the first embodiment except that there is no interval limiting means. That is, during bending of the pipe, the groove portion and the pressing die always come into contact with each other, and the circumferential length of the portion combining the groove portion and the pressing die is necessary for the pipe p sandwiched by the groove portion and the pressing die. The length can only be reduced.

(Function and effect)
Since it has the above-described configuration, the pipe bending apparatus of the present embodiment has the same functions and effects as those of the apparatus of the first embodiment.

(Test 1)
The pipe used was a carbon steel electric resistance welded steel pipe with an outer diameter (D) of φ70 mm and a wall thickness (t) of 2.6 mm. It was. The bending process applied to this pipe was a bending radius (R) of 180 mm, a bending angle of 90 °, and a pressing force of 16 ton.

  Pipe bending is performed using the pipe bending apparatus shown in FIG. 3 (the apparatus of the present invention) and the pipe bending apparatus shown in FIG. 3 without the space limiting means 11 and 31 (comparative example apparatus). It was. After bending the pipe, the appearance was observed. The appearance was observed with the naked eye and examined for the occurrence of buckling.

(result)
The pipe that was bent using the comparative apparatus had buckling. On the other hand, the pipe bent using the apparatus of the present invention did not buckle and was able to obtain a good product. It is considered that the buckling that occurred in the pipe processed by the comparative apparatus was caused by reducing the diameter of the pipe more than necessary.

  That is, in the apparatus of the present invention, it is possible to set an appropriate interval between the bending die and the pressing die so that buckling does not occur without performing complicated control of the pressing means. Therefore, it has been found that a pipe bending apparatus that does not cause inconvenience such as buckling due to pipe bending can be provided at low cost. Furthermore, the dimensional accuracy is good, and the product yield and productivity can be improved.

(Test 2)
The state of bending of the pipe was examined by changing the circumference of the portion where the groove portion and the pressing die 3 were combined. The circumference was changed by grinding the groove portion and the flange portion of the stamping die portion. The pipe used was a carbon steel ERW steel pipe with an outer diameter (D) of φ70 mm, a circumference of 220 mm, and a wall thickness (2.0 mm) of the pipe wall (t). ) Was 460 MPa, and the elongation was 55%. The bending process applied to this pipe had a bending radius (R) of 180 mm (≈2.6D) and a bending angle of 90 °. A mandrel, a wiper, and a pressing die urging means were not used, and the pressure applied to press the pressing die was 12.5 ton. FIG. 6 shows the peripheries of the pressing die, the bending die, and the pressing die, and the maximum thickness reduction rate of the pipe after processing.

  As apparent from FIG. 6, the appearance of the pipe after processing was good by setting the peripheral lengths of the bending die and the pressing die in the range of 85% to 98% with respect to the peripheral length of the pipe. Moreover, the maximum thickness reduction rate was able to be reduced to about 7% by making the circumference of a bending die and a pressing die into the range of 85%-97% with respect to the circumference of a pipe. Furthermore, by setting it to 85% to 95%, the maximum thickness reduction can be extremely reduced to 5% or less.

It is the schematic which showed one Embodiment of the pipe bending apparatus of this invention. It is the aa cross-sectional schematic of the pipe bending apparatus shown in FIG. It is the schematic which showed one Embodiment of the pipe bending apparatus of this invention. It is the schematic which showed the pipe bending apparatus of the prior art. It is a bb cross-sectional schematic diagram of the pipe bending apparatus shown in FIG. 6 is a graph showing the results of Test 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,91 ... Bending die 11 ... Space | interval restriction | limiting means (bending die side restriction | limiting part)
2, 92 ... Clamp 3, 93 ... Push mold 31 ... Interval limiting means (push mold side limiting portion)
4 ... Pushing type urging means 6 ... Control means 7, 97 ... Holder 8 ... Pressurizing means 9 ... Hydraulic control means 94 ... Wiper 95 ... Mandrel 96 ... Pipe booster o ... Rotation center (rotating shaft) of the bending die

Claims (12)

A bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending apparatus having control means for controlling the pressurizing means,
An apparatus for bending a pipe, characterized by having interval limiting means for limiting the size of the interval between the groove and the pressing die.   The pipe bending apparatus according to claim 1, wherein a circumferential length of a portion where the groove portion and the pressing die are combined is shorter than a circumferential length of the pipe.   3. The pipe bending apparatus according to claim 1, wherein the interval limiting unit is a unit that limits the interval according to a bending shape and / or a diameter reduction amount of a corresponding portion of the pipe.   The spacing limiting means limits the amount of movement of the pressing die to the bending die by contacting a bending die side limiting portion fixed to the bending die and a peripheral surface of the bending die side limiting portion. The pipe bending apparatus according to any one of claims 1 to 3, further comprising a pressing die side restricting portion fixed to the pipe.   The sum of the peripheral length of the portion combining the groove and the pressing die and the size of the interval limited by the interval limiting means is 85% to 97% with respect to the peripheral length of the pipe. The pipe bending apparatus according to any one of the above. A bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending apparatus having control means for controlling the pressurizing means,
The circumferential length of the portion combining the groove and the pressing die is a circumferential length according to the bent shape and / or the amount of diameter reduction of the sandwiched portion of the pipe,
The pipe bending apparatus characterized in that the pressing die abuts on the groove portion to pinch the pipe.   The pipe bending apparatus according to claim 6, wherein a circumferential length of a portion where the groove portion and the pressing die are combined is 85% to 97% with respect to a circumferential length of the pipe.   The pressurizing means is means for pressurizing, in the linear direction, a point where a straight line passing through the point where the bending die and the pipe abut and the rotation center of the main body intersect the pressing die. A pipe bending apparatus according to claim 1. A bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending method using a control means for controlling the pressurizing means,
An interval limiting means for limiting the interval according to the bending shape and / or the amount of diameter reduction of the portion of the pipe held by the groove and the pressing die, the interval between the groove and the pressing die;
A pipe bending method characterized by bending the pipe and reducing the diameter.   The pipe bending method according to claim 9, wherein a circumferential length of a portion where the groove portion and the pressing die are combined is shorter than a circumferential length of the pipe.   The pressure means is means for pressurizing a point where a straight line passing through a point where the bending die and the pipe abut and a rotation center of the main body part intersects the push die in the linear direction. Pipe bending method.   The pipe bending method according to any one of claims 9 to 11, wherein a circumferential length of a portion where the groove portion and the pressing die are combined is 85% to 97% with respect to a circumferential length of the pipe.

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