JP4920502B2 - Method and apparatus for bending metal pipe - Google Patents

Description

  The present invention relates to a method and apparatus for bending a metal tube, and more particularly, to a method and apparatus for rotating and bending a metal tube.

  The method of rotating and bending metal pipes basically involves fixing the bending start end of the tube material to a rotatable bending die with a clamp, and pushing the outer bending side of the unbent straight pipe portion of the pipe material with a pushable die. This is a processing method in which a pipe is pulled by a clamp and bent along the bending die by rotating the bending die. This processing method is suitable for parts that are used by bending steel pipes, such as pipes, structural steel pipes, and automobile exhaust steel pipes. By reducing local wrinkles and reducing wall thickness, the parts can be made thinner and smaller R Bending (for example, t / D is 4.0% or less, R / D is 1.5 or less) can be achieved.

  As means for suppressing the occurrence of local wrinkles and thinning, the pressing force (pressing force) of the pressing die is controlled within a range in which a buckling limit gap cannot be formed between the pipe material and the bending die (Patent Literature). 1) For small R-bending, the tube axis direction pressurizing means (pipe booster) of the pipe material, the bending inner holding means (wiper), and the mandrel to be inserted inside the pipe material are used together. Apply the lubricant to the inner surface of the pipe material by optimizing the clearance between them, or further optimizing the timing of pressurization by the tube booster (Patent Documents 2 and 3) and the lubricant application means provided in the mandrel (Patent Document 4) is known.

In addition, it is possible to use a pulling means (chuck, pulling actuator) capable of adding a pipe axis tensile load by grasping the processing end of the pipe material (Patent Document 5), or within the tube material holding groove between the bending die and the push die. It is known that the sum of the perimeters is made smaller than the perimeter of the pipe material, and bending is performed while applying a restriction to the pipe material (Patent Documents 6 and 7).
Japanese Patent Laid-Open No. 2005-161342 JP 2003-290838 A JP 2003-290839 A JP 2005-186143 A JP 2006-88178 A JP 2006-289488 A JP 2006-315077 A

If there is no variation in the material characteristics and thickness of the tube material, the product bending angle of the rotary pull bending process is determined by the shape of the bending die and the set bending angle. Therefore, conventionally, when pipes of the same standard / nominal size are bent to the same product bending angle, the bending is performed using the same bending mold and the same set bending angle.
However, depending on the material characteristics and wall thickness variation due to differences in tube production lots, etc., the variation in springback when the processed product is removed from the bending machine becomes large, and the product bending angle matches the target bending angle. There may not be. In such a case, until the product bend angle matches the target bend angle, the adjustment of the set bending angle must be repeated by trial and error. Therefore, there is a problem that it is difficult to improve the product yield and processing productivity. .

The present invention is a means for solving the above-mentioned problems, and measures the wall thickness and the pressing load during bending (load applied to the pressing die) for each pipe material, and measures these. Based on the results, the set bending angle is corrected during the machining.
That is, the present invention measures the wall thickness of an unbent straight pipe portion for each metal tube, and measures the pressing load during the bending process, and performs these measurements. This is a method of bending a metal tube (the method of the present invention) characterized in that a corrected set bending angle is derived on the basis of a value and a predetermined reference value, and this is used as an end point of bending.

In the present invention (the present invention method), it is preferable to calculate the corrected set bending angle by the following equations (1) and (2).
Η = α × (P × t ₀ ² ) / (P ₀ × t ² ) (1)
Θ = η × θ ₀ (2)
Where, Θ: corrected set bending angle, θ ₀ : set bending angle reference value, t: wall thickness measurement value, t ₀ : wall thickness reference value, P: pressing load measurement value, P ₀ : pressing load reference value , Α: coefficient (depending on the use conditions of the bending apparatus), η: bending angle correction coefficient.

Note that the bending angle (bending mold rotation angle) β at the time of measuring the pressing load during bending is the same as that at the measuring time of the pressing load. The bending angle β may be appropriately selected from the range of (1/3) to (2/3) of the initial setting bending angle.
In carrying out the method of the present invention, a rotatable bending die, a clamp for fixing a bending start end portion of the metal tube to the bending die, and the metal tube are sandwiched in cooperation with the bending die, and the metal tube is not yet attached. In a bending apparatus for a metal tube having a pressing die movable in the axial direction of the bent straight pipe portion, a thickness meter for measuring the thickness of the unbent straight pipe portion of the metal tube, and a pressing die being bent It is preferable to use a metal tube bending device (the device of the present invention) characterized by including a load meter for measuring the load.

The device according to the present invention is further described in any one of Patent Documents 1 to 7, such as a metal tube direction pressurizing means (tube booster), a bent inner holding means (wiper), and a core metal core (mandrel). One or two or more of the tube axial direction tension means may be included.
The apparatus of the present invention preferably further includes, from each measured value t of the thickness meter and a measured value P of the load cell at a predetermined bending angle β during bending, for each metal tube, the following formula (1) , (2) calculates a corrected set bending angle Θ, and includes an arithmetic controller that uses this as an end point of bending.

Η = α × (P × t ₀ ² ) / (P ₀ × t ² ) (1)
Θ = η × θ ₀ (2)
Where, Θ: corrected set bending angle, θ ₀ : set bending angle reference value, t: wall thickness measurement value, t ₀ : wall thickness reference value, P: pressing load measurement value, P ₀ : pressing load reference value , Α: coefficient (varies depending on use conditions of the bending apparatus), η: angle correction coefficient.

  According to the present invention, even if the wall thickness and material characteristics change somewhat due to differences in the production lots of metal tubes, etc., the variation in bending angle after bending can be suppressed, and the product yield and processing productivity are improved. .

  For example, as shown in FIG. 1, the device of the present invention includes a rotatable bending die (bending die) 1, a clamp (clamp die) 2 that fixes a bending start end of a pipe material (metal tube) 10 to the bending die 1, A pressing die 3 (pressure die) 3 is provided which can move in the axial direction of the unbent straight pipe portion of the pipe member 10 by sandwiching the pipe member 10 in cooperation with the bending die 1. The pressing die 3 is supported by the pressing die supporting means 3A so as to be movable in the axial direction of the unbent straight pipe portion of the tube material 10.

  The apparatus of the present invention further includes a wall thickness meter 4 for measuring the wall thickness of the unbent straight pipe portion of the tube material 10. As the thickness gauge 4, for example, an ultrasonic thickness gauge or a rotary micrometer may be installed online and used. Moreover, the load meter 5 which measures the pressing die load (load applied to the pressing die 3) during bending is provided. As the load meter 5, for example, a load cell or the like is preferably installed online.

In addition, although illustration is abbreviate | omitted, even if it is an apparatus provided with 1 type or 2 types or more among the pipe | tube booster, a wiper, a mandrel, and a pipe axial direction tension | pulling means described in the said patent documents 1-7. Good.
The method of the present invention is preferably carried out using the apparatus of the present invention as described above. An example of a preferred implementation procedure is shown in FIG. This execution procedure is executed for each pipe.

First, the thickness of the unbent straight pipe portion of the pipe material is measured with the thickness gauge 4 (step 100). Next, bending is started (step 110). At this time, the (initial) set bending angle may be set as the angle of the set bending angle reference value θ _{0 in} the equation (2). Then, the pressing load P when the predetermined bending angle β is reached during the bending is detected (measured) by the load meter 5 (step 120). As the predetermined bending angle β, an appropriate constant value may be selected from the range of (1/3) to (2/3) of the initial setting bending angle. Next, the bending angle correction coefficient η is calculated from the equation (1) (step 130). Finally, the corrected set bending angle Θ is calculated by equation (2) (step 140), and the bending process ends when the bending process proceeds to this angle Θ (step 150).

  From the viewpoint of efficiently executing the above procedure, in the apparatus of the present invention, for example, as shown in FIG. 3, the measured value t of the wall thickness meter 4 and the measured value P of the load cell 5 at a predetermined bending angle β during bending. Therefore, it is preferable to provide an arithmetic controller 6 that calculates the corrected set bending angle Θ by the above formulas (1) and (2) and controls the rotation of the bending die 1 so that the angle Θ becomes the end point of the bending process. . Such an arithmetic controller 6 can be easily configured using a normal measurement control system.

The coefficient α in the equation (1) can be determined by conducting a preliminary experiment of bending with various steel types, wall thicknesses, and set bending angles, and statistically analyzing the collected stamping load data. The coefficient α varies depending on the usage conditions of the bending apparatus (bending radius of the bending die, usage conditions of the tube booster, mandrel, wiper, etc.), and it is therefore preferable to obtain the coefficient α for each usage condition.
Further, the thickness reference value t ₀ is the thickness of the reference material, and the set bending angle reference value θ ₀ is the bending angle θ _s (see FIG. 4) of the reference material bending product after being taken out from the bending apparatus. The set bending angle is adjusted so as to be within the target tolerance range, and the stamping load reference value P ₀ is set under the bending angle condition where the bending angle θ _s of the reference material bending product is within the target tolerance range. It is a pressing load measurement value when a predetermined bending angle β is reached during bending of the reference material. These values are preferably obtained by using about three pipes randomly extracted from the same lot at the stage of adjusting (conditioning) the bending apparatus before the actual bending process according to the method of the present invention for each processing lot of the pipe material. It is good to decide.

  In the example, the bending machine shown in Fig. 3 was used, and one lot (2000) of STKM15A equivalent steel pipe (outer diameter D = 48.6mm, wall thickness t = 2.0mm (tolerance ± 5%)) in JIS. On the other hand, bending was performed according to the method of the present invention. The bending radius R of the bending die was 2.0 × D. Bending was performed for each tube material according to the flow shown in FIG. The target bend angles here are three levels of 45 °, 60 °, and 90 °, and each pipe was processed continuously for each level corresponding to about 1/3 lot.

As the coefficient α in the equation (1), a value determined by a preliminary experiment in the above manner was used. In addition, the set bending angle reference value θ ₀ , the wall thickness reference value t ₀ , and the pressing die load reference value P ₀ in the expressions (1) and (2) are adjusted at the adjustment stage before bending for each of the three levels. Two or three pipe materials selected for the same level of processing were randomly selected as reference materials and obtained by trial bending using these. The bending angle at the time of P, P ₀ measurement during processing is 1/2 of the target bending angle, and the initial bending angle in the actual bending process is the set bending angle reference value θ ₀ (the level of the target bending angle Different for each).

  As a result, the product yield for all three levels of processing was about 93%. This is significantly higher than the actual product yield (about 72%) at the time when bending was performed by the conventional method (the method in which the initial bending angle is not corrected and the bending end point is used as it is). In addition, the processing productivity of this example (the number of products manufactured per unit time of bending products (excluding disqualified products)) was improved by about 10% compared to the past results.

It is a schematic diagram which shows one example of this invention apparatus. It is a flowchart which shows an example of the implementation procedure of this invention method. FIG. 2 is a schematic diagram showing an example of the device of the present invention. It is explanatory drawing which shows the bending angle of the reference | standard material bending process product after taking out from a setting bending angle reference value and a bending process apparatus.

Explanation of symbols

1 Bending die (bending die)
2 Clamp (clamp die)
3 Pressing die (pressure die)
3A Pushing die support means 4 Thickness gauge (ultrasonic thickness gauge, micrometer, etc.)
5 Load cell (load cell, etc.)
6 Arithmetic controller
10 Metal pipe (pipe material)

Claims (4)

  When rotating and bending a metal tube, measure the thickness of the unbent straight pipe part for each metal tube and measure the pressing load during the bending process. A modified bending method for a metal tube, wherein a corrected setting bending angle is derived based on the value and used as an end point of bending. 2. The method of bending a metal pipe according to claim 1, wherein the corrected set bending angle is calculated by the following formulas (1) and (2).
Η = α × (P × t ₀ ² ) / (P ₀ × t ² ) (1)
Θ = η × θ ₀ (2)
Where, Θ: corrected set bending angle, θ ₀ : set bending angle reference value, t: wall thickness measurement value, t ₀ : wall thickness reference value, P: pressing load measurement value, P ₀ : pressing load reference value , Α: coefficient, η: bending angle correction coefficient.   A rotatable bending die, a clamp for fixing the bending start end of the metal tube to the bending die, and the metal tube sandwiched in cooperation with the bending die and moved in the axial direction of the unbent straight tube portion of the metal tube In a bending apparatus for a metal tube having a possible stamping die, a thickness meter for measuring the thickness of an unbent straight pipe portion of the metal tube and a load meter for measuring a stamping load during bending are provided. A metal tube bending apparatus characterized by the above. Furthermore, from the measured value t of the wall thickness meter and the measured value P of the load cell at a predetermined bending angle β during bending for each one of the metal tubes, it is corrected by the following formulas (1) and (2) The metal pipe bending apparatus according to claim 3, further comprising an arithmetic controller that calculates a bending angle Θ and sets the bending end point as an end point of the bending process.
Η = α × (P × t ₀ ² ) / (P ₀ × t ² ) (1)
Θ = η × θ ₀ (2)
Where, Θ: corrected set bending angle, θ ₀ : set bending angle reference value, t: wall thickness measurement value, t ₀ : wall thickness reference value, P: pressing load measurement value, P ₀ : pressing load reference value , Α: coefficient, η: angle correction coefficient.

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