JP4993951B2 - Pipe bending method and apparatus - Google Patents

Description

  The present invention relates to a pipe bending method and apparatus. The pipe includes a high-strength thin-walled steel pipe (TS: 590 MPa or more, wall thickness / outer diameter ratio: 5% or less steel pipe) that is applied to an automobile underbody or body application member.

  As a pipe bending means, a part of the pipe is fixed to a rotatable bending die, the pipe is clamped between the bending die and a pressure die, and the pressure applied to the pipe in the clamping area is reduced. A so-called push rotary bending method is known in which the bending die is rotated while feeding the pressure die in the pipe entry direction into the clamping region while adding to the die (see Patent Documents 1 and 2). .

The push rotary bending method suppresses thinning of the outside of the bend, even in the case of a small R bending process where R / D (R: neutral axis bending radius, D: pipe outer diameter) is smaller than 2, and the core metal and wrinkle Rotational pull bending, which has been widely used before, in that it prevents buckling inside the bend without using a tool such as a restraint, and allows the circumference of the bend to be easily controlled in the longitudinal direction. This is more advantageous than the law (see Patent Documents 3, 4, 5, etc.).
JP 2005-161324 A Japanese Patent Application No. 2005-153465 (public number not yet issued) Japanese Patent No. 2554001 Japanese Patent Publication No. 2-15291 JP-A-3-204120

  FIG. 5 is a side view showing a conventional example of the push rotary bending method (at the time of pipe setting). In FIG. 5, reference numeral 1 denotes a bending mold that can rotate around a fixed rotation center axis A. A groove having a shape corresponding to the bent shape of one half of the pipe 10 is provided on the outer peripheral portion of the bending mold 1. Reference numeral 2 denotes a clamp die for fixing a part of the pipe 10 to the bending die 1. 3 is a linear pressure die which clamps the pipe 10 in cooperation with the bending die 1. A groove having a shape corresponding to the bent shape of the other half circumference of the pipe 10 is provided on the holding side of the pressure die 3.

Reference numeral 4 denotes a reduction hydraulic cylinder that applies a reduction force to the pressure die 3 to reduce 12 the pipe 10 in the clamping portion.
The intersection of the reduction force action line of the reduction hydraulic cylinder 4 and the pipe 10 at the time of pipe setting is defined as the origin O, and the axis that coincides with the action line of the reduction force and in which the reaction direction of the reduction force is positive is defined as the y axis. An Oxy coordinate system is used in which the axis passing through the origin O is parallel to the central axis of the cross section of the pipe 10 when the pipe is set and the direction from the origin O toward the opposite side of the clamp 2 is the positive direction (hereinafter the same). In this Oxy coordinate system, the bending mold 1 is rotated in the xy plane (the rotation center axis is perpendicular to the xy plane), the acting direction of the rolling force is the -y direction, and the pipe 10 is bent during the bending process. The approaching direction to the clamping part is the -x direction. The y-axis intersects with the rotation center axis A of the bending mold 1 (see Patent Document 1) or intersects with an axis that is shifted from the rotation center axis A by a distance δ (0 <δ ≦ D) in the x direction (Patent Document 2). Reference) is fixedly arranged.

Reference numeral 5 denotes an axial feed cylinder for feeding the pressure die 3 in the -x direction. Note that one and the other of the contact surfaces of the pressure die 3 and the reduction hydraulic cylinder 4 are configured to be slidable in the direction parallel to the x-axis.
Bending is started from the pipe setting state of FIG. The state during bending is shown in FIG. The bending mold 1 is in rotation 11 with the clamp die 2. The pressure die 2 receives a reduction force from the reduction hydraulic cylinder 4, and the pipe 10 portion (in the holding region of the pipe 10) in the holding region (the region where the pipe 10 is held between the pressure die 2 and the bending die 1). Part) is being reduced and is being fed in the -x direction by the axial feed cylinder 5. This feed speed is controlled so as to coincide with the peripheral speed of the bending die 1 by the rotation 11 as much as possible. That is, the speed difference between the pipe 10 and the pressure die 3 is controlled to be as zero as possible. However, an appropriate speed difference may be provided as necessary.

  Since a part of the clamping area exit side portion of the pipe 10 is fixed to the bending mold 1 by the clamp die 2, the pipe 10 is pulled out of the clamping area by the rotation 11 of the clamping die 2 and is rotated by the rotation 11 of the bending mold 1. The bending shape of the bending mold 1 is made to follow the bending force. A bending reaction force that opposes this bending force is applied to the sandwiching area entrance side portion of the pressure die 3 by the reduction 12 from the reduction hydraulic cylinder 4.

  However, the clamping area entry side portion of the pressure die 3 becomes shorter as the bending process proceeds. Therefore, at the final stage of the bending process, the bending reaction force moment acting on the pressure die 3 from the holding region entry side portion of the pipe 10 overcomes the reverse moment derived from the reduction force of the reduction 12, and the pressure die 3 is held. There was a problem that the inward side portion was pushed back in the y direction, and as a result, the bending angle became smaller and the apparent spring back might become larger. This springback can be reduced by increasing the reduction force of the reduction 12, but this reduction force is limited to the shaft member deformation resistance of the rotation center axis A, and is excessively even within this limit range. If it is increased, the cross-sectional flatness in the clamping area becomes larger than necessary, which is not preferable.

  An object of the present invention is to solve the above-mentioned problems and to provide a pipe bending method and apparatus capable of reducing springback while making a reduction force to a pressure die moderate in a push rotary bending method.

The present invention that has achieved the above object is as follows.
1. Some rotatable bending molds (1) pipe (10) is fixed at the clamping die (2), sandwiching de the pipe (10) the bending mold (1) is and the pressure die (3) and, while applying the to the pressure die (3) at該挟lifting region of the pipe (10) a pressure (12) to pressure force reduction hydraulic cylinder (4), the axial feed cylinder the pressure die (3) In the pipe bending method in which the bending mold (1) is rotated while being fed in the pipe entry direction into the clamping area in (5), the pipe end on the clamping area entry side is connected to the pipe end clamp (6). Thus , the spring is held in such a manner that it cannot be displaced in the direction opposite to the reduction (12) and can be displaced (13) in the same direction and in the same size as the pressure die (3) by the reduction (12). and characterized in that to reduce the back Pipe bending how.

2. Rotatable bending die (1), in cooperation with the clamping die (2) is a fixing means for fixing the part of the pipe (10) in the bending mold (1), said bending mold (1) and a pressure die (3) forming a clamping area, a pressure means for applying the clamping region of the pressure pipe (10) (12) rolling force to said pressure die (3) reduction of the pipe (10) Te In the pipe bending apparatus, the hydraulic cylinder (4) and the axial feed cylinder (5) which is a feeding means for feeding the pressure die (3) in the pipe entry direction into the clamping area as gripping means to reduce the frequency entry side of the pipe end portion grasped by the spring back, moving the pipe approach direction, said the movement direction and rotation in the rolling direction, pressure die by the pressure (12) (3) Displacement and synchronization Pipe bending apparatus characterized by having a displacement in the same direction and the same magnitude (13) and capable of tube end clamp (6).

According to the present invention, it is possible to hold the pipe end portion on the clamping area entry side so that it cannot be displaced in the opposite direction to the pipe section in the clamping area, so that the rolling force on the pressure die does not become excessively large. The pressure die can be prevented from being pushed back by the bending reaction force moment of the pipe, and the spring back can be reduced.
In addition to this, the pipe being bent is gripped by gripping the end of the pipe on the clamping area entry side in the same direction, preferably the same size, in synchronism with the displacement of the pressure die due to the reduction. Therefore, it is possible to reduce the displacement in the rolling direction between the pressure die contact portion and the gripped portion, to prevent occurrence of reverse warping of the bending end portion, and to further reduce the spring back.

  FIG. 2 is a side view showing an example of the embodiment of the present invention (during pipe setting). In the figure, reference numeral 6 denotes a tube end clamp (gripping means), which is the same as or equivalent to those in the previously described figures (FIGS. 4 and 5), and a description thereof is omitted. The pipe end clamp 6 is a gripping means for gripping the end of the pipe 10 portion on the inlet side (the area where the pipe 10 is clamped between the pressure die 2 and the bending die 1) as shown in the drawing, Movement in the direction (-x direction) (including both forward and backward movements) and rotation from the moving direction to the reduction direction (-y direction) (rotation in the xy plane, including both forward rotation and reverse rotation); Is configured to be possible.

  Therefore, during the bending process, as shown in FIG. 3, the tube end clamp 6 grips the end of the pipe 10 portion on the clamping area entry side so that it cannot be displaced in the direction opposite to the reduction 12 (y direction). Therefore, even if the clamping part entry side portion of the pressure die 3 is pushed back by the bending reaction force of the pipe 10, the y-direction displacement amount due to the pushing-back is suppressed to be smaller than the −y-direction displacement amount due to the reduction 12. Reduction of bending angle at the end of processing can be suppressed, and spring back can be reduced.

Since the tube end clamp 6 is rotatable in the xy plane, the tube end clamp 6 can follow the deflection in the xy plane of the gripped portion of the pipe 10.
However, when the tube end clamp 6 cannot be displaced in the same direction in synchronization with the displacement of the pressure die 3 due to the reduction 12, depending on the reduction amount of the reduction 12, the pressure to be applied to the pipe 10 being bent is reduced. Due to the displacement in the rolling direction between the die contact portion and the gripped portion, the reverse warp introduced into the bending end portion becomes large, and it becomes difficult to sufficiently suppress the decrease in the bending angle. Therefore, as shown in FIG. 1, it is preferable that the tube end clamp 6 has a configuration capable of further displacement 13 in the same direction in synchronization with the displacement of the pressure die 3 due to the reduction 12. In order to obtain the tube end clamp 6 in such a form that the displacement 13 is possible, the tube end clamp 6 can be moved by a predetermined distance in the −y direction in synchronization with the reduction 12 to the tube end clamp. What is necessary is just to add the biasing means (illustration omitted) which consists of cylinders.

  The size of the displacement 13 is most preferably the same as the displacement of the pressure die 3 due to the reduction 12. In this case, during bending, the y-direction position of the gripped portion of the pipe 10 is kept the same as that of the pressure die contact portion, the pressure die 2 is not pushed back, and the reverse warp does not occur. The back is kept to a minimum.

Using a pipe having an outer diameter of 70 mm, a wall thickness of 2.6 mm, and a length of 1000 mm made of a TS780 MPa class steel pipe, bending was performed at 90 degrees under the following conditions. In any of the conditions, the bending die 1 having a bending radius R = 140 mm was used, and the reduction force (pressure die load) of the reduction 12 was set to 20 tonf (196 kN).
・ Condition 1 (Comparative example): Processing in the embodiment of FIG.
Condition 2 (Invention Example 1): Processing in the embodiment of FIG. 3 (the y-direction position of the tube end clamp 6 is fixed)
Condition 3 (Example 2 of the present invention): Processing in the embodiment of FIG. 1 (the displacement 13 of the tube end clamp 6 is synchronized with the displacement in the −y direction of the pressure die 3 due to the reduction 12, and the reduction in both direction and size is performed. Set to the same as the -y direction displacement of the pressure die 3 by 12)
The bending angle of the pipe after processing (spring-backed state) was measured. The results are 83.2 degrees in the comparative example, 86.5 degrees in the inventive example 1, and 88.1 degrees in the inventive example 2. The bending angle of the pipe after processing is higher in the inventive example than in the comparative example. Is close to the target bending angle (90 degrees here). That is, according to the present invention, it can be seen that springback can be reduced. In addition, the invention example 2 which is a more preferred embodiment has a smaller spring back than the invention example 1.

It is a side view which shows one example (during bending process; more suitable than FIG. 3) of embodiment of this invention. It is a side view which shows one example (at the time of pipe setting) of embodiment of this invention. It is a side view which shows one example (during a bending process) of embodiment of this invention. It is a side view which shows the prior art example (during bending process) of the push rotary bending method. It is a side view which shows the prior art example (at the time of pipe setting) of the push rotary bending method.

Explanation of symbols

1 Bending mold 2 Clamp die (fixing means)
3 Pressure die 4 Hydraulic cylinder for reduction (reduction means)
5 Axial feed cylinder (feeding means)
6 Tube end clamp (gripping means)
10 pipe 11 rotation 12 reduction 13 displacement A rotation center axis O origin of Oxy coordinate system

Claims (2)

Some rotatable bending molds (1) pipe (10) is fixed at the clamping die (2), sandwiching de the pipe (10) the bending mold (1) is and the pressure die (3) and, while applying the to the pressure die (3) at該挟lifting region of the pipe (10) a pressure (12) to pressure force reduction hydraulic cylinder (4), the axial feed cylinder the pressure die (3) In the pipe bending method in which the bending mold (1) is rotated while being fed in the pipe entry direction into the clamping area in (5), the pipe end on the clamping area entry side is connected to the pipe end clamp (6). Thus , the spring is held in such a manner that it cannot be displaced in the direction opposite to the reduction (12) and can be displaced (13) in the same direction and in the same size as the pressure die (3) by the reduction (12). and characterized in that to reduce the back Pipe bending how. Rotatable bending die (1), in cooperation with the clamping die (2) is a fixing means for fixing the part of the pipe (10) in the bending mold (1), said bending mold (1) and a pressure die (3) forming a clamping area, a pressure means for applying the clamping region of the pressure pipe (10) (12) rolling force to said pressure die (3) reduction of the pipe (10) Te In the pipe bending apparatus, the hydraulic cylinder (4) and the axial feed cylinder (5) which is a feeding means for feeding the pressure die (3) in the pipe entry direction into the clamping area as gripping means to reduce the frequency entry side of the pipe end portion grasped by the spring back, moving the pipe approach direction, said the movement direction and rotation in the rolling direction, pressure die by the pressure (12) (3) Displacement and synchronization Pipe bending apparatus characterized by having a displacement in the same direction and the same magnitude (13) and capable of tube end clamp (6).

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