JP3594262B2 - Metal tube bending method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a bending method suitable for use in manufacturing a metal bent pipe having straight pipe portions at both ends using a metal pipe.
[0002]
[Prior art]
Conventionally, the control at the time of bending a metal pipe is performed by a method of controlling a bending radius in a hot bending apparatus disclosed in JP-A-57-26171 and the control of a bending radius by the apparatus, or according to the above-described method and apparatus. Only the control of the bending angle is performed, and the control of the pipe length required for forming the bent portion is not performed.
[0003]
For example, a bending method by a compression control described in Japanese Patent Application Laid-Open Publication No. 62-13216, a method and apparatus for compressing and bending a metal tube, or a method of compressing and bending a metal tube disclosed in Japanese Patent Application Laid-Open No. 62-13216. However, since the purpose of the control is to always keep the wall thickness at a desired value, the length of the pipe required for the bent portion is slightly longer or shorter, and a straight pipe portion of a required length is formed in the bent portion. The bending process in which the entire length of the bending tube was maintained at the required length could not be performed. For this reason, in the above-mentioned prior art, post-processing or post-setup, in which the entire length of the pipe before processing is longer than necessary beforehand and unnecessary length portions are cut after processing, is indispensable.
[0004]
To avoid such post-processing cuts, select the required processing means after conducting test bending and examining the conditions such as how long the pipe length required for forming the bent portion is necessary. Must. However, adopting the conventional methods as described above causes an increase in processing time and cost in any of the methods.
[0005]
[Problems to be solved by the invention]
Accordingly, the problem to be solved by the present invention is to develop a bending method capable of setting the length of a raw tube required for a bent portion of a metal tube to a desired value in the conventional bending method. It is an object of the present invention to provide a new bending method which does not require cutting work after bending or trial bending before main processing.
[0006]
[Means for Solving the Problems]
An object of the present invention, which has been made to solve the above-mentioned problems, is to provide an arm which is capable of rotating a metal tube to be bent through an appropriate heating means for locally heating the metal tube in a circular manner at a processing tip side. Immediately after the metal tube is heated by the heating means and the heating section is relatively moved by the moving means in the longitudinal direction of the pipe to impart bending moment and deformed, the heating section is cooled. In the method of bending a metal pipe, the turning angle of the arm and the length of the pipe required to generate the turning angle during the bending are measured, and the deviation between the length of the pipe and its predetermined value is detected. By adding a control operation for adjusting the thickness of the bending deformation progressing portion in a direction in which the deviation decreases, the length of the raw tube consumed for forming the bent portion is controlled.
[0007]
【Example】
Next, an embodiment of the method of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing the concept of a known compression bending apparatus to which the method of the present invention is applied, FIG. 2 is a plan view showing the concept of a known normal bending apparatus to which the method of the present invention is applied, and FIG. FIG. 4 is a plan view of an example in which the method of the present invention is applied to the side where the bending radius is reduced, and FIG. 4 is a plan view of an example in which the method of the present invention is applied to the apparatus of FIG.
[0008]
In FIG. 1, reference numeral 1 denotes a metal pipe which is propelled in the axial direction of the pipe 1 (to the right in FIG. 1) at a moving speed Vp by an appropriate propelling means or moving means, for example, a moving means using a hydraulic cylinder or the like. The tube 1 is grasped by the clamp 3 of the arm 2 rotating about the fulcrum 0 with the bending radius set to R. Numeral 4 is disposed adjacent to the arm 2 before the clamp 3 (in the moving direction of the tube) when the tube 1 is in a posture orthogonal to the tube 1, and is formed in an annular shape to locally heat the tube 1 in an annular shape. The high-frequency inductor 5 is a compression wheel arranged at the fulcrum of the arm 2, that is, at the center of rotation 0, with the arm 2 and the center of rotation coaxial with each other, and has a radius of rb. The compression wheel 5 controls the circumferential speed Vb so that a force opposing a thrust that causes the tube 1 to move at the moving speed Vp is applied to the tube 1 as a compressive force or a tensile force. The above members 1 to 5 constitute an example of a known compression bending apparatus.
[0009]
Now, in the bending apparatus of FIG. 1, when the peripheral speed of the compression wheel 5 when the bending is performed without applying a driving force to the compression wheel 5 is Vbo, the compression bending and the normal bending are classified as follows. Is done.
When Vbo = Vb: This is a known normal bending, and the bending thrust P acts as a compressive force. This bending is expressed as a bending of a compressive force 1P for convenience of explanation.
When Vbo> Vb: This is a known compression bending, and a compression force of 1 P or more acts.
When Vbo <Vb, the compressive force is 1 P or less, so that the bending is performed.
[0010]
When the above-described normal bending or compression bending is performed, the pipe 1 receives a compressive force while being bent. Therefore, the feed amount of the pipe 1 by the thrust of the moving device, that is, the straight pipe portion (base pipe) of the pipe 1 The amount of movement does not coincide with the length of the bent portion of the tube 1 formed by the moved portion (hereinafter, referred to as a bent portion).
[0011]
That is, assuming that the tube 1 does not expand or contract at all in the normal bending or the compression bending, the moving amount (feed amount) L of the tube 1 and the turning angle of the arm 2, that is, the bending angle θ Is represented by an equation of L = Rθ. However, since the tube length of the bent portion is actually reduced due to the compressive force, that is, it is consumed to increase the thickness of the compressed portion inside the bent portion or to reduce the thickness of the bent portion outside the bent portion. Assuming that the ratio of the length of the raw tube required to perform the above process (the expected value) to the length of the raw tube compressed during generation of the actual bent portion pipe length is a compression ratio (reduction ratio) ρ, The moving amount L of the pipe 1 for obtaining the bent pipe length is expressed by the following equation (1).
[0012]
L = R · θ (1 + ρ) (1)
[0013]
The compression ratio ρ when the bending is performed with the bending radius R, the moving speed Vp of the pipe 1, and the peripheral speed Vb of the compression wheel 5 is expressed by the following equation (2) from FIG.
[0014]
ρ = rb / R · Vp / Vb−1 (2)
[0015]
From this, in the present invention, the turning angle θ of the arm 2 and the actual movement amount of the pipe 1 fed for turning at this angle θ, that is, the length of the straight pipe portion fed, are measured. A deviation between the actual movement amount and a predetermined value of the movement amount set in advance based on the above equation (1) to generate the turning angle θ is calculated, and the deviation of the bending portion is reduced. Adjust the wall thickness. That is, in the compression bending illustrated in FIG. 1, the peripheral speed Vb of the compression wheel 5 is controlled to adjust the compression force, and the compression ratio ρ is controlled to form a bent portion having a predetermined bending angle. The length of the tube to be fed is controlled so as to be a predetermined value. Note that, even when compression bending is performed, if bending is performed with a thrust close to 1P, tensile bending may be performed with a thrust of 1P or less depending on conditions.
[0016]
In the apparatus shown in FIG. 1, the adjustment of the compression force is performed by operating one or both of the peripheral speed Vb of the compression wheel 5 and the moving speed Vp of the moving device operating on the pipe 1 by the thrust. At the same time as the adjusting operation, an operation of moving the inductor 4 forward and backward with respect to the longitudinal direction of the tube 1 so that the relative speed between the tube 1 and the inductor 4 becomes constant may be added.
[0017]
In the above example, the method of the present invention is applied to the compression bending shown in FIG. 1. However, the above method of the present invention can be applied to the normal bending method in which no compressive force is applied as shown in FIG. This point is described below.
[0018]
In the normal bending apparatus illustrated in FIG. 2, the compression ratio is adjusted without applying an external force as in the compression bending in FIG. That is, the thickness of the bent portion of the pipe 1 is adjusted by changing the bending radius R in the above equation (2), that is, the bending curvature. This point will be described with reference to FIGS.
[0019]
In order to change the bending curvature in the arm bending mechanism shown in FIG. 2, which is a typical example of the normal bending method in which the rotation center O of the bending arm 2 is fixed, a method disclosed in Japanese Patent Application Laid-Open No. 57-26171 is used. The control method of the bending radius in the inter-bending device and the technique described in the device are applied. That is, assuming that the minute arc length is dS and the minute angle is dθ, the bending radius R is expressed by the following equation (3).
[0020]
R = dS / dθ (3)
[0021]
Therefore, if the minute arc length dS is adjusted, the bending radius R changes. This is realized by changing the position of the inductor 4 relative to the rotation center O of the arm 2. That is, as shown in FIG. 3, when the inductor 4 is advanced from the original position, the curvature increases, that is, the bending radius R becomes smaller and the compression ratio becomes larger. , The bending radius R is enlarged and the compression ratio is reduced.
[0022]
From this, in the present invention, the turning angle θ of the arm 2 and the actual movement of the pipe 1 fed for turning at this angle θ, that is, the length of the fed straight pipe section, are measured. In order to generate the actual movement amount and the turning angle θ, a deviation between a predetermined movement amount set in advance based on the above equation (1) is calculated, and the thickness of the bent portion is reduced on the side to reduce the deviation. Adjust the thickness. That is, in the normal bending illustrated in FIG. 2, the inductor 4 is advanced or retracted in the longitudinal direction of the tube 1 to control the compression ratio ρ, so that the inductor 4 is fed to form a bent portion having a predetermined bending angle. The length of the raw pipe to be controlled is controlled so as to be a predetermined value.
[0023]
In the present invention, in the bending process by the bending device shown in FIG. B is displaced (moved) from B. When displacing (moving) the inductor 4, the relative speed V generated by the moving speed Vp of the tube 1 and the speed Vc for the displacement of the inductor 4 is kept constant. The moving speed Vp of the tube 1 may be adjusted simultaneously with the displacement of the inductor 4.
[0024]
【The invention's effect】
As described above, the present invention measures the turning angle of a bending arm and the length of a pipe fed to bend the pipe to that angle in bending, and measures the measured pipe length and the fed pipe length. By controlling the bending so as to adjust the wall thickness of the bent portion of the pipe in the direction in which the deviation is reduced and the deviation is detected, the length of the pipe to be fed and the length of the bent portion are controlled. Conventionally, the extra pipe length generated in the bent portion was conventionally taken for bending, so the extra work of cutting the extra straight pipe as post-processing after bending is completely eliminated. The effect is obtained.
[Brief description of the drawings]
FIG. 1 is a plan view showing the concept of a known compression bending apparatus to which the method of the present invention is applied.
FIG. 2 is a plan view showing the concept of a known normal bending apparatus to which the method of the present invention is applied.
FIG. 3 is a plan view showing an example in which the method of the present invention is applied to the apparatus of FIG. 2 on the side where the bending radius is reduced.
FIG. 4 is a plan view of an example in which the method of the present invention is applied to the apparatus of FIG. 2 on the side where the bending radius is enlarged.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bending pipe 2 Bending arm 3 Arm 2 clamp 4 Heating inductor 5 Compression wheel

Claims (4)

The metal tube to be bent is passed through an appropriate heating means for locally heating the metal tube in a ring shape, and the processing end is clamped to a rotatable arm, and the metal tube is heated by the heating means. Immediately after being deformed by imparting a bending moment by relatively moving the pipe in the longitudinal direction of the pipe by a moving means, in a bending method of a metal pipe for cooling a heating section, an arc is formed during bending. Measuring the turning angle of the system and the tube length required for generating the turning angle, detecting the deviation between the tube length and the predetermined value, and adjusting the thickness of the bending deformation progressing portion in a direction in which the deviation decreases. A metal pipe length consumed in forming a bent portion by adding a control operation for bending the metal pipe. 2. The metal according to claim 1, wherein the thickness of the bending deformation progressing portion is adjusted by connecting a device for rotating and driving the arm to the arm and adjusting the turning speed of the arm or the moving speed of the metal tube. Pipe bending method. 2. The bending method for a metal pipe according to claim 1, wherein the heating means is movably provided to advance or retreat in a longitudinal direction of the metal pipe to adjust the thickness of the bending deformation advancing part. 4. The bending method according to claim 2, wherein the thickness of the bending deformation progressing portion is adjusted by relatively moving the heating means and the metal pipe before bending while keeping the relative speed constant.

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