JP2006043765A - Method and apparatus for bending pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for bending a pipe by which the occurrence of wrinkles on the bent inner side of the thin-wall pipe is prevented during the bending in a comparatively large bend radius, and to provide an apparatus for bending the pipe which is suitable to carry out the method. <P>SOLUTION: In this method for bending the pipe W by pressing the pipe W onto a bending mold 2 to be copyed into its bend shape, the pipe is pressed against the bending mold 2 while adding tube-axis tensile load to both ends of the pipe and adding drawing in the bending part of the pipe. By holding and pressing the pipe with the receiving groove part 2U of the bending mold 2 and the pressing groove part 3U of a pressing mold 3 and moving the abutting point of the pipe on the pressing groove part along the bending shape, bending and drawing are simultaneously added. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pipe bending method and apparatus.

In a bending method in which a pipe is pressed against a bending die to follow the bending shape of the bending die, as a means to reduce the variation in spring back of the product, tension is applied while bending more than the yield strength in the tube axis direction. A bending method (Patent Document 1) is known. In addition, as a means of further reducing the variation in springback, the tension applied in the tube axis direction during tensile bending is based on the bending radius dependence of the springback and changes in the bending radius of the part to be bent. There is known a method (Patent Document 2) in which the change is made accordingly.
Japanese Patent Laid-Open No. 11-290962 JP 2003-39117 A

However, when a thin pipe (particularly having a wall thickness to outer diameter ratio t / D of 0.03 or less) is bent by the conventional tensile bending method, the bending radius R is, for example, about 600 mm or more. Even when it is relatively large, there is a problem that wrinkles are generated on the inner side of the bend (inner side of the bend).
The present invention solves this problem, and provides a pipe bending method that does not generate wrinkles inside a thin pipe being bent to a relatively large bending radius, and a pipe bending apparatus suitable for carrying out the method. The purpose is to provide.

The present inventors have intensively studied to achieve the above object, and as a result, while applying tension in the pipe axis direction to the pipe (pipe), let it follow the bending portion (that is, the bending die) of the pipe. It was found that the wrinkle generation on the inner surface side of the bending can be suppressed by performing drawing processing (diameter reduction processing) on the portion). That is, the present invention is as follows.
(Invention Item 1) In a pipe bending method in which a pipe is pressed against a bending die to follow the bending shape of the bending die, a pipe axial tensile load is applied to both ends of the pipe, and the bending portion of the pipe A pipe bending method, wherein the pipe is pressed against a bending die while drawing is added to the pipe.

(Invention 2) The tube axis tensile load is added so that the tube axis direction tension ratio defined by the following equation (1) is 0.01 or more, and the drawing is defined by the following equation (2). 2. The pipe bending method according to claim 1, wherein the bending portion circumferential length drawing ratio is 0.5% or more.
Tube axis tension ratio = tube axis tensile load / (element tube cross-sectional area x element tube yield strength) (1)
Bending part circumference drawing ratio = (Round pipe circumference-Pipe circumference after bending) / Raw pipe circumference x 100 (%) (2)
Here, the elementary pipe refers to a pipe before bending.

  (Invention Item 3) In a pipe bending apparatus that presses a pipe against a bending die and imitates the bending shape of the bending die, the receiving groove portion provided in the bending shape portion of the bending die and both end portions of the pipe are gripped. A pair of tension applying mechanisms that can apply a pipe axial tension to the pipe by urging the chuck with a tension applying actuator, and support the pair of tension applying mechanisms individually, and approximately line according to the bending angle A pair of tension-adding swivel arms that can pivot symmetrically, and a pair of pressurizing actuators that press the pipe in contact with the pipe with a pressurizing groove and urge the pipe against the bending mold with a pressurizing actuator. A pipe bending apparatus comprising: a pressurizing mechanism section; and a pair of pressurizing swivel arms that individually support the pair of pressurizing mechanism sections and are capable of swiveling in a substantially line symmetrical manner according to a bending angle. .

(Invention 4) The pipe according to Invention 3, wherein the sum of the arc length of the receiving groove portion of the bending die and the arc length of the pressing groove portion of the pressing die is smaller than the circumferential length of the pipe before bending. Bending machine.
(Invention 5) The pipe bending apparatus according to Claim 3 or 4, wherein the chuck or the tension applying actuator is rotatably supported on the tension applying swivel arm.

(Invention 6) The pressing die is composed of a rail-shaped shoe, and is supported between the shoe and the pressurizing actuator and is moved by rolling in the longitudinal direction of the shoe while pressing the shoe. The pipe bending apparatus according to any one of claims 3 to 5, further comprising a pressing point moving roller.
(Invention 7) The invention according to any one of Inventions 3 to 5, wherein the pressing die includes a pressing roller, and the pressing roller is supported by the pressurizing actuator and rolls and moves in the tube axis direction while pressing the pipe. The pipe bending apparatus according to any one of the above.

  According to the bending method of the present invention (the method of the present invention), the pipe is pressed against the bending die while applying a pipe axis tensile load to both ends of the pipe and applying a drawing process to the bending portion of the pipe. By doing so, tensile stress in the tube axis direction is generated inside the bend due to drawing applied to the bending portion, and this tensile stress effectively reduces the compressive stress in the tube axis direction inside the bend due to bending. Therefore, when the thin pipe is bent to a relatively large bending radius, it is possible to effectively prevent wrinkling from occurring inside the bending.

  According to the bending apparatus of the present invention (the apparatus of the present invention), the method of the present invention can be advantageously carried out with a relatively simple apparatus configuration.

  As described above, according to the method of the present invention, when a thin pipe is bent to a relatively large bending radius, it is possible to effectively prevent wrinkling from occurring inside the bend. At this time, the pipe axis tensile load is added so that the pipe axis direction tension ratio defined by the following formula (1) is 0.01 or more, and the drawing is defined by the following formula (2). It is preferable to add the bent portion circumferential length drawing ratio to be 0.5% or more because the wrinkle generation suppressing effect becomes more remarkable.

Tube axis tension ratio = tube axis tensile load / (element tube cross-sectional area x element tube yield strength) (1)
Bending part circumference drawing ratio = (Round pipe circumference-Pipe circumference after bending) / Raw pipe circumference x 100 (%) (2)
Here, the elementary pipe refers to a pipe before bending.

However, if an attempt is made to add a pipe shaft tensile load so that the pipe shaft direction tension ratio exceeds 1.0, a large-scale facility including the capability of a hydraulic cylinder or the like as a power source for applying the load is required. Therefore, the tension ratio in the tube axis direction is preferably 1.0 or less.
Also, in the drawing process where the bending part circumference drawing ratio exceeds 5.0%, the pipe outer diameter after the bending process becomes too small and the practicality of the product becomes poor. It is preferably 5.0% or less.

The method of the present invention can be advantageously implemented with a relatively simple device configuration when the device of the present invention as exemplified below is used.
FIG. 1 is a plan view showing an embodiment of the device of the present invention, where (a) is before the start of bending and (b) is after the end of bending. In this apparatus, a bending die 2 is disposed on the apparatus base 1, and a receiving groove 2 </ b> U is provided in a bent shape portion (a portion where the pipe W is pressed) of the bending die 2.

  Both ends of the pipe W are gripped by a pair of chucks 6, and each chuck 6 is urged by an attractive force from the tension applying actuator 5, so that a pipe axial tension can be applied to the pipe W. That is, a pair of a chuck 6 that grips one end of the pipe W and a tension applying actuator 5 that biases the chuck 6, and a chuck 6 that grips the other end of the pipe W and a tension applying actuator 5 that biases the chuck W A tension applying mechanism is configured.

  The pair of tension applying mechanisms are individually supported by one ends of the pair of tension applying turning arms 8. Each of the pair of tension applying swivel arms 8 is individually supported by a pair of rotating shafts 11 arranged at the other end of the apparatus base 1 and can be swiveled around the pivoting rotating shaft 11. . The pair of rotating shafts 11 is substantially symmetrical with respect to the width center line of the bending die 2 (a straight vertical bisector connecting the length ends of the bent portion), and the pipe of the pipe W when the bending die 2 is set. It is arranged in the vicinity of the axial position. Accordingly, the pair of tension applying swivel arms 8 is substantially a line with respect to the width center line of the bending die 2 in accordance with the bending angle of the pipe W in a state where the tension applying mechanism portion applies a pipe axial tension to the pipe W. It can pivot symmetrically.

  The push groove portion 3U of the pair of push dies 3 provided with the push groove portions 3U is brought into contact with a portion of the outer periphery of the pipe W opposite to the bending die 2. Each pressing die 3 is biased by a pressing force from the pressurizing actuator 4, and the pipe W can be pressed in the pipe circumferential direction by pressing the pipe W against the receiving groove 2U of the bending die 2 by the pressing groove 3U. . That is, a pair of pressurizing mechanism sections are constituted by a pair of press molds 3 that are in contact with the pipe W by the push groove sections 2U and pressurizing actuators 4 that individually bias the press molds 3 toward the bending mold 2. .

  The pair of pressurizing mechanisms are individually supported by one end portions of the pair of pressurizing swivel arms 7. Each of the pair of pressurizing swivel arms 7 is individually supported by a pair of rotating shafts 10 disposed at the other end of the apparatus base 1, and can be swung around the pivoting rotating shaft 10. The pair of rotary shafts 10 are substantially line-symmetric with respect to the width center line of the bending die 2 and in the vicinity of the width center line, and on the opposite side of the pressurizing mechanism portion with respect to the bent portion (receiving groove portion 2U) of the bending die 2. Has been placed. Therefore, the pair of pressurizing swivel arms 7 are substantially line symmetrical with respect to the width center line of the bending die 2 in accordance with the bending angle of the pipe W in a state where the pressurizing mechanism presses the pipe W in the pipe circumferential direction. It is possible to turn.

However, if the sum of the arc lengths of the receiving groove portion 2U and the push groove portion 3U is equal to or greater than the circumference of the raw tube, drawing is performed so that the bending portion circumference length drawing ratio of the formula (2) is 0.5% or more. Therefore, it is preferable that the sum of the arc lengths of the receiving groove portion 2U and the push groove portion 3U is less than the circumferential length of the raw tube.
Further, during the turning of the tension applying swivel arm 8, generally, the angle formed between the tube axis direction of the unbent portion of the pipe W and the longitudinal direction of the tension adding swivel arm 8 changes according to the bending angle. If the tension applying mechanism is fixed to the tension applying swivel arm 8, an excessive torque may act on the tension applying mechanism and the chuck 6 or the tension applying actuator 5 may be damaged. In order to eliminate this fear, for example, as shown in FIG. 1, the tension applying actuator 5 is rotatably supported by the rotating shaft 12 provided on the tension applying swivel arm 8, and the tension applying mechanism portion applies the tension. It is preferable to freely rotate on the turning arm 8 and to follow the change in the pipe axis direction of the unbent portion of the pipe W. Although the tension applying actuator 5 is pivotally supported in FIG. 1, the chuck 6 may be pivotally supported instead.

  For example, as shown in FIG. 1, the pressing die 3 can be configured by a rail-shaped shoe. In the case of a shoe, the surface of the pipe W may be damaged if the push groove portion slides on the outer peripheral surface of the pipe W. Therefore, as shown in FIG. 1, a pressing point moving roller 9 is provided between the shoe and the pressing actuator 4 so as to roll and move in the longitudinal direction of the shoe while pressing the shoe while being supported by the pressing actuator. Good. Accordingly, the shoe rotates in the bending direction while changing the contact portion with the pipe W as the push point moving roller 9 rolls, and the push groove portion can be prevented from sliding on the outer peripheral surface of the pipe W.

The pressing die 3 may be constituted by a pressing roller (see FIG. 2) instead of the shoe. It is assumed that the pressing die 3 constituted by a pressing roller has a pressing groove portion 3U on the entire periphery thereof, and is supported by the pressurizing actuator 4 so as to roll and move in the tube axis direction while pressing the pipe W. In this case, of course, the pushing point moving roller 9 is unnecessary.
In order to perform bending using the apparatus of the present invention illustrated in FIG. 1, first, the pipe W is set as shown in FIG. 1 (a), and both ends of the pipe W are gripped by the chuck 6, and the tension applying actuator 5 is applied. Apply tensile load with. The state where the tensile load is applied is maintained until the end of the bending process. Next, it is only necessary to press the shoe (pressing die 3) against the pipe W with the pressurizing actuator 4.

The pipe W is first pressed against the midpoint of the bent shape portion of the bending die 2, but the pushing force transmitted through the push point moving roller 9 acts on both sides of the midpoint of the bent shape portion. The pipe W starts to bend with fulcrum as the fulcrum.
Once the pipe W begins to bend, the pair of shoes follow the bend (bending angle), and the opposite ends (opposing ends) of the pair of shoes are separated from the bending die 2, and the opposite ends (anti-opposing ends) are bent. Rotate to approach mold 2. In response to the moment generated by this rotation, the push point moving roller 9 rolls and moves to the opposite side of the shoe, and the pair of pressurizing swivel arms 7 swivel substantially symmetrically. On the other hand, according to the bending angle of the pipe W, the pair of tension applying actuators 5 rotate and the pair of tension applying swivel arms 8 are rotated so that the rotary shaft 12 passes on the tube axis of the unbent portion of the pipe W. It turns in a line symmetry. At this time, the bending portion of the pipe W is subjected to a pressing force via the pressing point moving roller 9 and is bent, and is pressed between the receiving groove portion 2U and the pressing groove portion 3U and drawn in the pipe circumferential direction. Is done. This series of movement processes proceeds continuously until the end of the bending process shown in FIG.

  In order to perform bending using the apparatus of the present invention illustrated in FIG. 2, first, the pipe W is set as shown in FIG. 2 (a), and both ends of the pipe W are gripped by the chuck 6, and the tension applying actuator 5 is applied. Apply tensile load with. The state where the tensile load is applied is maintained until the end of the bending process. Next, it is only necessary to press the pressing roller (pressing die 3) against the pipe W with the pressurizing actuator 4.

The pipe W is first pressed against the midpoint of the bent portion of the bending die 2, but the pushing force transmitted through the push roller acts on both sides of the midpoint of the bent portion, so that the pipe is set with this midpoint as a fulcrum. W begins to turn.
Once the pipe W begins to bend, the pair of push rollers follow this bend (bending angle) and move in a direction away from the middle point (a direction away from each other), and follow this to follow a pair of press turns. The arm 7 turns in a substantially line symmetry. On the other hand, according to the bending angle of the pipe W, the pair of tension applying actuators 5 rotate and the pair of tension applying swivel arms 8 are rotated so that the rotary shaft 12 passes on the tube axis of the unbent portion of the pipe W. It turns in a line symmetry. At this time, the bending portion of the pipe W is subjected to a pressing force through the pressing roller and is bent, and is pressed between the receiving groove portion 2U and the pressing groove portion 3U and drawn in the pipe circumferential direction. This series of movement processes proceeds continuously until the end of the bending process shown in FIG.

  Table 1 shows the results of bending the target pipe shown in Table 1 under the conditions shown in Table 1 and examining the degree of wrinkling inside the bend using the apparatus of the present invention illustrated in FIG. Here, hydraulic cylinders were used as the actuators for pressurization and tension application. The tension ratio in the tube axis direction was changed by changing the setting of the tension applying actuator. The bending portion circumferential length drawing ratio was changed by changing the arc length of the receiving groove portion and the pushing groove portion and adjusting the pressure applied by the pressurizing actuator.

As shown in Table 1, the wrinkles exceeding the allowable range were generated in the comparative example, while the wrinkles occurred in the comparative example were within the allowable range. No wrinkles were generated in the pipe formed with a tension ratio in the range of 0.01 or more and a bending portion circumferential length drawing ratio in the range of 0.5% or more.
Of the comparative examples, those with a tension ratio of 0 or less in the tube axis direction are neutral (zero) or compressed instead of the urging force of the hydraulic cylinder used as the tension applying actuator being the tension side (+ side). Bending is performed on the side (− side).

  INDUSTRIAL APPLICABILITY The present invention can be used in a wide range of industrial fields such as piping that requires bent pipes, mechanical parts, and electrical parts.

It is a top view which shows one form (form which comprised the pressing die with the shoe) of this invention apparatus, (a) is before a bending process start, (b) is after a bending process completion | finish. It is a top view which shows another form (form which comprised the press type | mold with the press roller) of this invention apparatus, (a) is before a bending process start, (b) is after completion | finish of a bending process.

Explanation of symbols

W pipe
DESCRIPTION OF SYMBOLS 1 Apparatus stand 2 Bending type | mold 2U Receiving groove part 3 Push type | mold 3U Pushing groove part 4 Pressurizing actuator 5 Tension applying actuator 6 Chuck 7 Pressurizing turning arm 8 Tension applying turning arm 9 Push point moving roller 10, 11, 12 Rotating shaft

Claims (7)

  In a pipe bending method in which a pipe is pressed against a bending die to follow the bending shape of the bending die, a pipe shaft tensile load is applied to both ends of the pipe and a drawing process is added to the bending portion of the pipe. A method for bending a pipe, wherein the pipe is pressed against a bending die. The tube shaft tensile load is added so that the tube axis direction tension ratio defined by the following equation (1) is 0.01 or more, and the drawing is performed at the bent portion circumferential length defined by the following equation (2). 2. The pipe bending method according to claim 1, wherein the ratio is added so as to be 0.5% or more.
Tube axis tension ratio = tube axis tensile load / (element tube cross-sectional area x element tube yield strength) (1)
Bending part circumference drawing ratio = (Round pipe circumference-Pipe circumference after bending) / Raw pipe circumference x 100 (%) (2)
Here, the elementary pipe refers to a pipe before bending.   In a pipe bending apparatus that presses a pipe against a bending die to follow the bending shape of the bending die, tension is applied to a receiving groove provided in the bending shape portion of the bending die and a chuck that grips both ends of the pipe. A pair of tension applying mechanisms that can be applied with an axial force to the pipe by being urged by an actuator, and the pair of tension applying mechanisms can be individually supported and swiveled substantially line-symmetrically according to the bending angle. A pair of tension applying swivel arms, and a pair of pressurizing mechanisms capable of pressurizing the pipe in the tube circumferential direction by urging a pressing mold contacting the pipe with a pressing groove toward the bending mold with a pressurizing actuator; A pipe bending apparatus comprising: a pair of pressurizing swivel arms that individually support the pair of pressurization mechanism portions and are capable of swiveling substantially line-symmetrically in accordance with a bending angle.   4. A pipe bending apparatus according to claim 3, wherein the sum of the arc length of the receiving groove portion of the bending die and the arc length of the pressing groove portion of the pressing die is smaller than the circumferential length of the pipe before bending.   The pipe bending apparatus according to claim 3 or 4, wherein the chuck or the tension applying actuator is rotatably supported on the tension applying swivel arm.   The push die is composed of a rail-shaped shoe, and is supported between the shoe and the pressurizing actuator, and is supported by the pressurizing actuator to roll and move in the longitudinal direction of the shoe while pushing the shoe. 6. The pipe bending apparatus according to claim 3, further comprising a roller.   The said pressing die consists of a pressing roller, and this pressing roller is supported by the said pressurization actuator, and rolls and moves to a pipe-axis direction, pressing the said pipe. Pipe bending machine.