JPH0247287B2 - KINZOKUKANNOATSUSHUKUMAGEHOHOOYOBISONOSOCHI - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention heats a metal tube annularly and locally, and applies a bending moment to the metal tube while moving the heating section in the longitudinal direction of the metal tube. The present invention relates to a method and apparatus for applying and continuously bending a metal tube, and more particularly to a method and apparatus for bending a metal tube to a bending radius that is different from the effective length of the bending arm used to apply a bending moment.

[Conventional technology]

As a method for bending a metal tube (hereinafter simply referred to as a tube), as shown in FIG. It is gripped by a clamp 4A of a bending arm or arm 4 that can pivot around the center, and the pivot shaft 3 is moved in the longitudinal direction of the pipe 1 by a drive device (for example, a hydraulic cylinder) 5 connected to the pivot shaft 3 via a boom or the like. This applies a bending moment to the tube 1, and at the same time heats the tube 1 locally and annularly with a heater (for example, a high-frequency inductor) 6 to deform the tube 1 in this area, and further deforms the tube 1 in this heated area. A method is known in which the tube 1 is continuously bent by moving the tube 1 in the longitudinal direction and cooling it immediately thereafter. In this bending method, if the heater 6 is always positioned on the straight line If the tube 1 is always kept at the same position in the longitudinal direction, the bending radius of the tube 1 becomes the effective length L of the arm, and if this position is changed, the bending radius becomes different from the effective length L of the arm. Also,
In order to prevent the tube wall thickness from decreasing at the bending part, arm 4
A method is also known in which a constant counterclockwise torque is applied to the tube 1 to apply an axial compressive force to the tube 1, thereby increasing the thickness of the tube. The conventional torque applying device used here is
It is composed of a compression wheel 8 that is rotatable around a pivot shaft 3 together with an arm 4, a wire 9 with one end fixed to the outer periphery of the compression wheel 8, and a drive device 10 that applies tension to the wire 9. A constant tension is applied to the wire 9 by the drive device 10, and the compression wheel 8
Therefore, a constant torque is always applied to arm 4,
A constant compressive force can be applied to the tube 1 via the arm.

[Problem that the invention seeks to solve]

However, with the method of bending the tube while applying compressive force as described above, no particular problem occurred when the tube was bent to the same bending radius as the effective length of the arm, but when the tube was bent to a different radius. A problem arose in that the thickness of the tube wall at the bent portion varied in the axial direction.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a compression bending method and apparatus capable of reducing axial variations in tube wall thickness at the bending portion when bending a tube to a bending radius different from the effective length of the arm. It is to be.

[Means for solving problems]

The inventor of the present invention investigated the reasons for variations in tube wall thickness in conventional methods and found the following.

When bending with a bending radius different from the effective arm length using the apparatus shown in FIG. 1, the pivot shaft 3 and heater 6 are moved at different speeds in the longitudinal direction of the tube 1, as shown in FIG. , as the bending progresses, the center of the pivot shaft 3 returns to the position O at the start of the bending.
to position O', and the distance y between the center of the pivot shaft 3 and the axis of the tube 1 also changes. This variation in distance y causes a change in the compressive force P applied to the tube 1 via the arm 4, causing a variation in the wall thickness of the tube.

The present invention has been made based on such knowledge, and when bending a pipe while applying compressive force, the torque applied to the arm 4 is adjusted according to the distance y, and the compression applied to the pipe 1 during bending is adjusted. The feature is that the force P is adjusted so that the thickness increase rate does not fluctuate.

The present invention will be explained in more detail below. Now, the second
In the state shown in the figure, it is assumed that the pipe 1 is being bent at a constant bending radius R while increasing its wall thickness by μ times. At this time, the tension applied to the pivot shaft 3 is _P1 The tension applied to the compression wheel 8 is _P2 The axial compression force applied to the pipe 1 is P The bending moment applied to the pipe 1 is M.

In addition, in the following explanation, θ: Bending angle R: Bending radius L: Arm effective length r: Compression wheel radius C: Center of bending.

From Fig. 2, the distance y is y=R+(L-R)cosθ...(1) Also, each tension force P, _P1 ,
The relationship between P ₂ , bending moment M, etc. is P = P ₁ + P ₂ ... (2) M = yP ₁ + (y-r) P ₂ ... (3) By the way, when bending without increasing the thickness, When the compressive force P ₀ applied to the pipe 1 and the bending moment applied to the pipe 1 at this time are M ₀ , the following equation holds true between the two.

P ₀ =M ₀ /R (4) Here, M ₀ is a constant determined by the physical properties of the pipe 1, the section modulus, etc.

As mentioned above, compressive force P, bending moment M
Since the bending process is performed while increasing the thickness by μ times, if the compressive force P at this time is P ₀ times m, then P=mP ₀ ...(5) M=μM ₀ ...(6) Substituting equations (4) to (6) into equations (2) and (3) and rearranging, P=R/y(μP ₀ +r/RP ₂ )=r/yP ₂ m/m−μ
...(7) P ₁ = P (1-y/r m-μ/m) = M ₀ /R{m-y
/r(m-μ)}...(8) _P2 =y/rPm-μ/m= _yM0 /rR(m-μ)...(9)

This means that the tension P, which satisfies equations (7) to (9) above,
Bending at P ₁ and P ₂ means that bending is performed with a constant thickness increase rate. As can be clearly seen from equation (9), in order to perform bending with a constant thickness increase rate, the tension P ₂ applied to the compression wheel 8 is a function of the distance y, and it is necessary to change it according to the distance y. Since the tension _P2 was constant, wall thickness variations occurred at the bent portion of the tube.

The present invention is based on this knowledge, and P ₁ , P ₂
is adjusted as y changes based on equations (8) and (9). In addition, the tension P ₁ applied to the rotation axis 3 is
If the turning axis 3 is moved in the longitudinal direction of the tube 1 at the speed necessary for the prescribed bending process, the speed will be automatically determined according to the physical properties of the tube 1, the bending radius, etc., so there is no need to control it in particular. The tension applied to the compression wheel 8 without
Only P ₂ needs to be adjusted according to equation (9). This tension
P ₂ causes the arm 4 to generate a torque around the pivot axis 3, and if this torque is T, then T=rP ₂ =yM ₀ /R(m-μ)...(10) Therefore, The present invention adjusts the torque T applied to the arm 4 according to the distance y between the center of the pivot shaft 3 and the axis of the tube 1 based on equation (10). In addition, formula (9),
(10) is a theoretical formula that does not take into account external disturbances such as machine friction at all, but since external disturbances such as friction are included in actual bending, it is not necessary to follow equations (9) and (10) exactly. In fact, the tension or torque obtained by equations (9) and (10) may be appropriately corrected and used.

〔Example〕

FIG. 3 is a block diagram schematically showing an example of an apparatus for carrying out the method of the present invention. In this figure, the same reference numerals are used for the same parts as in FIG. 1. The torque applying device that applies torque to the arm 4 includes a compression wheel 8 that is rotatable together with the arm 4 and a drive device 10 that applies tension P ₂ to the compression wheel 8 via a wire 9. In this example, a hydraulic cylinder is used as the drive device 10. Hydraulic pressure is supplied to the hydraulic cylinder 10 via an electromagnetic proportional valve 12 .
The electromagnetic proportional valve 12 is controlled by a signal from a control device 13 with an arithmetic function. A tension detector 14 such as a load cell is attached to the wire 9 at an appropriate position, and its output signal is input to the control device 13. Rotating axis 3
A pivot axis position measuring device 15 is attached to the rotary shaft position measuring device 15 , which measures the distance y between the center of the pivot shaft 3 and the axis of the tube 1 and outputs it to the control device 13 . In addition,
Although not shown, a drive device 5 that moves the pivot shaft 3 in the longitudinal direction of the tube 1 and a drive device (not shown) that moves the heater 6 in the longitudinal direction of the tube 1 are also included.
It is configured to be controlled by a control device 13.

In the apparatus configured as described above, the pivot shaft 3 and the heater 6 move in the longitudinal direction of the tube 1 at speeds controlled by the control device 13, thereby performing continuous bending. At this time, at the same time, a tension force P ₂ is applied to the compression wheel 8 by the drive device 10, and therefore a torque is applied to the arm 4, and a compression force is applied to the tube 1. The tension P ₂ caused by the drive device 10 is calculated using the signal y from the measuring device 15 and equation (9), and the tension P 2 caused by the electromagnetic proportional valve 12 is
and is controlled to an accurate value by a feedback signal from the load cell 14. Thus, during bending, a predetermined compressive force P acts on the tube 1, and a bent tube with a uniform wall thickness in the axial direction is obtained. Note that as mentioned above, equation (9) is a theoretical one that does not take into account any external disturbances such as mechanical friction, so the tension P ₂ calculated using equation (9)
may be used with appropriate correction.

In the above device, the position of the rotation axis 3 is measured and the tension applied to the compression wheel is controlled according to the position.
Alternatively, the change in tension applied to the compression wheel over time may be programmed in advance, and the control may be performed according to that program. That is, when the bending radius is specified, the distance y with respect to the bending angle is determined as shown in FIG. 4, and therefore the tension P ₂ for performing the bending process at a constant thickness increase rate is also determined from equation (9). On the other hand, the bending angle over time is determined according to the moving speed of the rotating shaft 3 and the heater 6, so if the moving speed of the rotating shaft 3 with respect to the tube 1 and the moving speed of the heater 6 with respect to the tube 1 are determined, the tension P Changes in ₂ over time will also be determined. Thus, by programming these in advance and controlling the moving speed of the pivot shaft 3, the moving speed of the heater 6, and the tension force P2 applied to the compression wheel 8 according to the program, the compressive force _P2 applied to the pipe 1 can be controlled. can be made constant, and the tube wall can be bent to have a uniform thickness in the axial direction.

In addition, although the above description has shown that the torque applying device that applies torque to the arm 4 includes the compression wheel 8 and the drive device 10 that applies tension to the compression wheel 8, the present invention is limited to this type of torque applying device. However, other types of known devices capable of applying torque to the arm 4 may be used. Furthermore, in the above explanation, the tube 1 is fixed and the pivot shaft 3 and the heater 6 are moved in the longitudinal direction of the tube 1.
The pivot shaft 3 and the heater 6 only have to be relatively movable in the longitudinal direction of the tube 1. Therefore, the tube 1 may be moved and the pivot shaft 3 and the heater 6 may be fixed.

Furthermore, although the above description is based on the case where the bending radius R is constant, the present invention is also applicable to cases where the bending radius R changes. That is, since equations (9) and (10) hold true even when the bending radius R changes, processing can be performed by substituting equations for changes in the bending radius into equations (9) and (10).

〔Effect of the invention〕

As described above, in the present invention, when bending a tube to a bending radius different from the effective length of the bending arm (arm 4), the bending arm is Since a corresponding torque is applied during the bending process, the tube wall thickness can be uniformly increased in the axial direction regardless of the position of the arm during the bending process. As a result, it is possible to produce bent tubes with bends that have a uniform wall thickness in the axial direction.

[Brief explanation of drawings]

Fig. 1 is a top view schematically showing a device that performs thickening bending, Fig. 2 is a diagram showing the positional relationship, tension, moment, etc. of each part during bending, and Fig. 3 is an apparatus used in the method of the present invention. A block diagram showing an example of
Figure 4 shows the bending angle, compressive force P, tension P ₂ and distance y.
It is a graph showing the relationship between. 1...Pipe, 2...Fixing device, 3...Swivel axis, 4
... Arm, 5 ... Drive device, 6 ... Heater, 8
. . . Compression wheel, 9 . . . Wire, 10 . . . Drive device, 12 . . . Electromagnetic proportional valve, 13 .

Claims (1)

[Claims] 1. A metal tube to be bent is locally heated in an annular shape by a heater, the heater is moved relatively in the longitudinal direction of the metal tube, and at the same time a part of the metal tube is heated. The pivot axis of the bending arm, which can be gripped and turned, is moved in a direction substantially parallel to the longitudinal direction of the metal tube and relative to the metal tube to apply a bending moment to the metal tube, and the bending arm bends the metal tube. A method for compression bending a metal tube, the method comprising bending the metal tube to a bending radius different from the length, the method comprising applying a torque to the bending arm according to the distance between the pivot axis and the axis of the metal tube to be bent. 2. The scope of claims characterized in that the relative moving speed of the heater, the rotating shaft, and the metal tube, and the torque applied to the bending arm are programmed in advance, and the bending process is performed according to the program. 2. The method for compression bending a metal tube according to item 1. 3 The distance between the pivot axis and the axis of the metal tube to be bent is measured, the torque to be applied to the bending arm is calculated according to the measured value, and the torque is controlled according to the calculated value. Claim 1
Compression bending method for metal tubes as described in Section 1. 4. A heater that locally heats the metal tube to be bent in an annular shape, a drive device that relatively moves the heater in the longitudinal direction of the metal tube, and a device that grips the metal tube and rotates it around a rotation axis. A possible bending arm, a drive device that relatively moves the pivot axis in the longitudinal direction of the metal tube, a torque applying device that applies torque to the bending arm, and a distance between the pivot axis and the metal tube axis. It is characterized by having a measuring device for measuring, and a control device with an arithmetic function that calculates the torque to be applied to the bent arm based on the measured value of the measuring device, and controls the torque applying device based on the calculated value. Compression bending equipment for metal tubes.