JP2005161324A - Pipe bending machine and pipe bending method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pipe bending machine capable of preventing buckling and wall thickness reduction when a pipe is bent, and a pipe bending machine capable of freely changing the circumferential length of the pipe. <P>SOLUTION: The pipe bending machine has a bending die 1 having a groove part of a shape corresponding to the bending shape, a clamp 2, a pressing die 3, a pressing means 8 and a control means 6. The pressing means 8 presses, in the direction of the line, the pipe at a point at which the line passing through a point where the bending die 1 abuts on a pipe p and the center of rotation o intersects with the pressing die 3. No moment unnecessary for the pipe p is applied to the pressing position of the pressing means 8. In addition, by setting the circumferential length of a combined portion of the groove part and the pressing die 3 to be smaller than that of the pipe p, the compressive stress is applied to the pipe p, and buckling on the inner bending side and wall thickness reduction on the outer bending side can be effectively prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pipe bending apparatus and a pipe bending method for bending a pipe by plastic working.

  Pipe parts that have been subjected to minimal bending (for example, a bending radius of 1.5 D or less) are widely used in automobiles, air conditioners, and the like. As a bending apparatus for bending a pipe into a predetermined shape, a rotary drawing bending apparatus as shown in FIGS. 9 and 10 is widely used. 10 is a cross-sectional view taken along line bb of FIG.

  The rotary pull bending apparatus holds a rotatable bending die 91 having a bending guide groove, a clamp 92 for fixing a part of the pipe p to the bending die 91, and a bending outer peripheral surface of the pipe p. A pressing die 93, a wiper 94 that holds the inner peripheral surface of the pipe p, a mandrel 95 that is held inside the pipe p, and a pipe booster 96 that urges the pipe p in the axial direction from the rear end of the pipe p. Have.

  The pressing die 93 is supported by a holder 97 so as to be movable in the axial direction of the pipe p, and the holder 97 can be adjusted in the radial position of the bending die 1 by a position adjusting screw 7a. In general, the position of the pressing die 93 is often fixed when the pipe p is processed.

  In order to bend the pipe p, a part of the pipe p is fixed to the bending die 91 by the clamp 92, and the pressing die 93 is moved to a desired position by the position adjusting screw 97a, and the bending die 91, the wiper 94, By rotating the bending die 91 while holding the pipe p with the mandrel 95 and the pressing die 93, the pipe p is bent into a shape following the groove shape of the bending die 91. Further, if necessary, the pipe is boosted by the pipe booster 96 from the rear end of the pipe p.

  In the above-described bending apparatus for pipe p, as shown in FIG. 11, the bending behavior of the pipe differs between the inside and outside of the bending around the geometric neutral axis of the bending of pipe p. That is, since the trajectory length is long with respect to the neutral axis on the outer side of the bend, the thickness is increased in the axial direction and the thickness after bending becomes thinner than the original thickness t. Since the trajectory length is shorter with respect to the neutral axis on the inner side of the bend, the thickness is reduced in the axial direction and the thickness after bending becomes thicker than the original thickness t.

  Therefore, cracks are likely to occur on the outer side of the bend and buckling on the inner side of the bend. In addition, as shown in FIG. 12, the cross section after bending is made elliptical. Conventionally, in order to prevent buckling on the inner side of bending and prevention of ovalization of the pipe p, bending is performed in a state where a mandrel 95 is provided on the inner side of the pipe p as shown in FIGS. That is, buckling prevention has been achieved by bending the pipe wall on the inner side of the pipe p with the bending die 91, the wiper 94, and the mandrel 95.

  However, since the outer pipe wall is subjected to ironing deformation by the mandrel 95, there is a drawback that the outer wall thickness of the bent outer side is promoted and further cracking is liable to occur.

  As a method for suppressing such defects in cracking and buckling in bending, in the prior art, a bending speed detector of a bending die 91 and a pushing speed detector of a pipe booster 96 are attached to a rotary drawing bending apparatus, and the bending speed is increased. It has been proposed to adopt a synchronous control that makes the bending speed pattern and the pressing speed pattern similar by controlling acceleration / deceleration of the bending speed or the pressing speed based on signals from the detector and the pressing speed detector ( For example, Patent Document 1).

Further, in the prior art, the peripheral surface on the pressing die 93 side of the pipe is kept substantially the same as the pipe radius, the peripheral surface on the bending die 91 side is deformed to a radius larger than the pipe radius, and the entire circumference of the pipe is A pipe bending method for reducing the length by several percent is disclosed (for example, Patent Document 2).
Japanese Patent No. 2544001 Japanese Patent Laid-Open No. 55-5180

  However, even if these techniques are adopted, the mandrel 95 for preventing the flattening of the pipe p and the buckling of the inner side of the bending causes the squeezing deformation to the inner surface of the pipe p as described above. Meat is inevitable, and in addition, when mandrel 95 is removed and minimal bending (1.5 DR or less) is performed to prevent thinning due to ironing deformation, there is a drawback that buckling occurs inside the bend.

  Further, as a trend of pipe parts used in recent automobile parts, members obtained by processing pipes by hydraulic forming have been widely used. In general, the hydraulic forming is performed after preforming such as bending, and the circumference of the member after the hydraulic forming is often changed for each part in the longitudinal direction.

  If the thinning after bending as a pipe preform used for such hydraulic forming is significant, cracking tends to occur during the hydraulic forming. Therefore, it is very important to suppress the thinning. Furthermore, it is very important to provide a circumference corresponding to a change in circumference of the hydraulic molding die during bending. In particular, in hydroforming performed at a low pressure, if the circumference after bending is longer than the circumference of the hydroforming mold, buckling will occur during hydroforming, and conversely if the circumference is short, molding will occur. This is because a defect such as a lack of shape (for example, R portion) occurs.

  Further, when hydraulic forming is performed on a pipe, it is often performed to reduce the diameter of both ends of the pipe prior to the hydraulic forming. In that case, the mandrel cannot be inserted into the pipe, and effective buckling cannot be prevented.

  Moreover, in the hydraulic forming, the cross-sectional shape is different at each site in the longitudinal direction, and there may be a location where the cross-sectional width is narrower than the raw tube diameter. For this reason, the pipe p that has been bent by a conventional bending apparatus may not be able to be inserted into the hydroformed hole mold. In that case, after bending by a conventional apparatus, the part where the pipe p interferes with the hydraulic forming hole mold is crushed by press molding and then generally inserted into the hydraulic forming hole mold. Yes. In other words, the processing steps are (1) a bending step, (2) a press forming step, and (3) a hydraulic forming step, which is also unreasonable from the viewpoint of increasing manufacturing time, processing equipment, and mold preparation.

  Therefore, an object of the present invention is to provide a pipe bending apparatus and method that can prevent buckling and thinning during pipe bending. Furthermore, it is an object of the present invention to provide a pipe bending apparatus and method that can freely change the circumference of the pipe.

The pipe bending apparatus of the present invention includes a bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending apparatus having control means for controlling the pressurizing means,
The pressurizing means is means for pressurizing a point where a straight line passing through a point where the bending die and the pipe abut and a rotation center of the main body part intersects the push die in the linear direction. Item 1).

  As a pressurizing means, an unnecessary moment is applied to the pipe by using a means that pressurizes the point where the straight line passing through the point where the bending die and the pipe abut and the rotation center of the main body intersect the push die in the linear direction. And no extra force is applied to the pipe being processed. Since no extra force is applied, no extra deformation occurs on the pipe wall.

  Then, by reducing the diameter of the pipe by making at least a part of the circumference of the combined portion of the groove and the pressing die shorter than the circumference of the pipe, a compressive stress is applied to the pipe to cause buckling inside the bend. It can be effectively prevented. Therefore, a wiper or the like necessary for a conventional pipe bending apparatus is no longer necessary. Also, the mandrel that holds the pipe from the inside together with the wiper is not an essential element.

  Further, by reducing the diameter of the pipe, the material is supplied to the outside of the bending where it is easy to reduce the thickness, and the thickness reduction can be prevented.

  And it is preferable that the circumference of the part which combined the said bending die and the said press die is shorter than the circumference of the said pipe (Claim 2). The control means is preferably means for controlling the pressurizing means in accordance with the bending shape of the pipe. By pressurizing the pressing die with the pressurization means, the diameter of the pipe can be increased, and inconveniences (buckling, thinning, etc.) due to bending of the pipe can be prevented, but the pipe is not bent. It is not only the case that it is generally preferable to reduce the diameter.

  Therefore, it is preferable to control the pressurizing means so as not to reduce the diameter except for the bent portion of the pipe. Even if the circumferential length of the portion where the groove portion and the pressing die are combined is shorter than the circumferential length of the pipe, the diameter reduction of the pipe can be controlled depending on the degree of pressing of the pressing die by the pressurizing means.

  In addition, the pipe diameter after processing needs to be different in the axial direction as in the case of pipe bending as the preforming of the hydraulic forming described above. The diameter can be changed in the axial direction.

  As a particularly preferred form, the apparatus has a rotation angle detection means for detecting the rotation angle of the bending mold, and the control means controls the pressurizing means based on the rotation angle detected by the rotation angle detection means. (Claim 4).

  Since the pipe is bent following the shape of the groove formed in the peripheral surface of the bending die main body, the degree of bending of the pipe is determined based on the rotation angle of the bending die. Therefore, by controlling the pressurizing means based on the detected rotation angle of the bending mold, the diameter of the pipe can be reduced by a necessary amount (for example, a part where the pipe is bent).

  And it is preferable that the said control means controls the said pressurizing means so that the feed amount of the said pressing die may become predetermined value (Claim 5). The amount of diameter reduction of the pipe is determined by the distance between the pressing die and the bending die, that is, the feeding amount of the pressing die. Therefore, the amount of diameter reduction of the pipe can be controlled more precisely by controlling the feed amount of the pressing die.

  Further, it is preferable to have a pressing die urging means for urging the pressing die in the moving direction of the pipe. As the outer diameter and bending radius of the pipe become larger, the push die also becomes larger. By urging the push die in the pipe movement direction (axial direction), the inertia of the push die during operation of this device can be reduced. .

  And it is preferable not to arrange a mandrel inside the portion of the pipe held between the bending die and the pressing die. By not placing a mandrel, it is possible to suppress the thinning due to ironing from inside the pipe. In the apparatus of the present invention, buckling is unlikely to occur inside the pipe even if there is no mandrel.

The pipe bending method of the present invention includes a bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending method using a control means for controlling the pressurizing means,
The pressurizing means is a means for pressurizing in the linear direction a point where a straight line passing through the point where the bending mold and the pipe abut and a rotation center of the main body part intersects the pressing mold,
The pipe is bent and reduced in diameter (claim 8).

  And it is preferable that the circumference of the part which combined the said groove part and the said pressing die is shorter than the circumference of the said pipe (Claim 9). Moreover, it is preferable to reduce the diameter of the pipe according to the bending shape of the pipe. Further, it is preferable that a rotation angle detection unit that detects a rotation angle of the bending die is provided, and the pipe is reduced in diameter based on the rotation angle detected by the rotation angle detection unit. Furthermore, it is preferable not to arrange a mandrel inside the portion of the pipe that is sandwiched between the bending die and the pressing die.

(Constitution)
A schematic configuration of the pipe bending apparatus of the present embodiment is shown in FIG. FIG. 2 is a sectional view taken along the line aa in FIG. The pipe bending apparatus according to the present embodiment includes a bending die 1, a clamp 2, a pipe position detecting unit 5, a pressing die 3, a pressurizing unit 8, and a control unit 6. Furthermore, it can have the push type urging means 4 as needed.

  The bending die 1 has a main body portion and a groove portion. The main body is rotatably held on a rotation shaft (rotation center) o. The groove is formed on the peripheral surface of the main body, and has a shape corresponding to the bent shape of the pipe. The perimeter of the bending die 1 is determined in accordance with the length of the processed portion of the pipe to be processed. Further, the widths of the groove and the main body are determined corresponding to the diameter of the pipe.

  The clamp 2 is a means for holding a part of the pipe p. Preferably, it is means for fixing one end of the pipe p to a part of the peripheral surface of the bending die 1. The pipe p is bent by using a portion fixed to the clamp 2 as one of the support points.

  The pipe position detecting means 5 is a means for detecting the position where the pipe p is held between the bending die 1 and the pressing die 3. The position of the pipe p sandwiched between the bending die 1 and the pressing die 3 is detected for the purpose of detecting and controlling the position where the diameter of the pipe p is reduced. In particular, it is preferable to detect a portion where the pipe p is bent. As will be described later, it is preferable to reduce the diameter of the pipe p with respect to the portion to be bent. Therefore, the position of the pipe p is detected and the pressure is applied in accordance with the degree of bending corresponding to the detected position. It is preferable to control the means 8.

  As means for detecting the position of the pipe p, means for detecting the position of the clamp 2 holding the pipe p and the position of the pressing die 3, means for directly measuring the position of the pipe p, and detecting the rotation angle of the bending die 1. Means can be adopted. Since the shape of the groove portion of the bending die 1 changes depending on the rotation angle corresponding to the bending shape of the pipe p, the groove shape of the bending die 1, that is, the bending shape of the pipe p is detected by detecting the rotation angle of the bending die 1. Can be detected.

  The method for detecting the position of the pipe p and the like and the method for detecting the rotation angle are not particularly limited. General detection means such as a linear encoder and a rotary encoder can be employed. Further, the elapsed time from the start of bending can also be used for pipe position detection. The pipe position information detected by the pipe position detection means 5 is output to the control means 6 as a pipe position signal.

  The pressing die 3 is means for pressing the pipe p against the groove and plastically deforming it. The pressing die 3 holds the pipe p and is supported so as to be movable in the axial direction of the pipe p together with the pipe p. Of the portion where the groove portion and the pressing die 3 are combined, at least the portion where the diameter of the pipe p is reduced, the peripheral length of the portion where the groove portion and the pressing die 3 are combined is shorter than the peripheral length of the pipe. Further, the circumferential length of the portion where the groove portion and the pressing die 3 are combined depends on properties such as the elongation of the pipe, but is preferably 97% or less, more preferably 95% or less with respect to the circumferential length of the pipe. Furthermore, the circumferential length of the portion where the groove portion and the pressing die 3 are combined is preferably 85% or more, and more preferably 85%.

  As a result, it is possible to efficiently reduce the diameter of the portion of the pipe p that requires a reduced diameter. For example, as shown in FIG. 2, when the pipe p is sandwiched between the bending die 1 and the pressing die 3, a gap u is formed, so that the bending die 1 and the pressing die 3 are The circumference of the combined part is shorter than the circumference of the pipe p.

  Moreover, the circumference of the part which combined the groove part and the press die 3 can also be made shorter than the circumference of a pipe. In this case, as will be described later, the control unit 6 controls the pressurizing unit 8 so that the pressurizing unit 8 is operated only at a portion where the diameter reduction is required until the pipe p is contracted. This part can be reduced in diameter. In addition, the diameter can be reduced in all parts of the pipe p.

  The pipe p, which is pressed against the groove and reduced in diameter, is easily bent with the groove as a force point due to plastic deformation.

  The cross-sectional shape of the portion where the groove portion and the pressing die 3 are combined can be selected according to the finally required cross-sectional shape of the pipe p. Furthermore, when this apparatus is used as a pre-forming apparatus for hydraulic forming, it is possible to select the cross-sectional shape of the portion where the groove portion and the pressing die 3 are combined regardless of the cross-sectional shape of the pipe p that is finally required. is there. For example, the cross-sectional shape can be selected in accordance with the shape of a hydraulic forming mold.

  The pressurizing means 8 is means for pressing the pressing die 3 against the bending die 1 by applying pressure. As the pressurizing means 8, general means such as a hydraulic mechanism and a crank mechanism can be adopted. The pressurizing means 8 in FIG. 1 is a means controlled by a hydraulic control means 9. The pressurizing means 8 controls the pressurizing force and the feed amount based on the control signal input from the control means 6. The pressing force and / or feed amount of the pressurizing means 8 can be measured and output as a signal to the control means 6 as required.

  The pressurizing unit 8 is a unit that pressurizes a point where a straight line passing through a point where the bending die 1 and the pipe p abut and a rotation center of the main body of the bending die 1 intersects the pressing die 3. The direction of pressurization is the direction toward the center of rotation of the main body. The pressurizing means 8 always pressurizes the pressing die 3 through the holder 7 in order to make the position and direction of pressurization constant. As shown in the drawing, the holder 7 restrains the pressing die 3 in the radial direction of the bending die 1 and the rotation axis direction of the bending die 1 and holds the bending die 1 movably in the axial direction of the pipe p. Means.

  A force acts on the pipe p in a direction opposite to the rotation center of the main body from the point of contact with the bending die 1. By applying a force opposite to this force to the pipe p, the force is balanced and it is possible to prevent a rotational moment from being applied to the pipe p. Further, a member for holding the pipe p such as a wiper necessary for preventing buckling in the conventional pipe bending apparatus from the opposite side of the pressing die 3 becomes unnecessary. Adjustment of the setting position of the wiper requires skill and is a consumable item that wears out, so the advantage of eliminating the need for the wiper is great.

  The control means 6 is means for controlling the pressurizing means 8 based on the pipe position signal inputted from the pipe position detecting means 5. As a method for controlling the pressurizing means 8, there are a method for controlling the pressing force of the pressing die 3 and a method for controlling the feed amount of the pressing die 3. For example, a method of measuring the relationship between the pressing force or the feed amount and the diameter reduction amount of the pipe p in advance and controlling the pressurizing means 8 so that the necessary diameter reduction can be performed at a necessary portion based on the relationship. Can be considered. As described above, control signals such as pressure and feed amount can be input from the pressurizing means 8 or the like as necessary. Controlling the feed amount of the pressing die 3 is preferable because it directly adjusts the diameter reduction of the pipe p. Note that it is preferable to control the applied pressure in terms of simplicity. In addition, it is considered that the degree of diameter reduction is different in a portion accompanying pipe bending even if the pressure is constant.

  The relationship between a pipe position signal and control of the pressurizing means 8 is illustrated. First, the bending shape at the position of the pipe detected by the pipe position detection means 5 is obtained, and the larger the bending curvature of that portion, the greater the pressing force (and / or feed amount) by the pressurizing means 8 to reduce the diameter. Increase the amount. By increasing the applied pressure according to the curvature, it is possible to effectively prevent buckling, thinning, ovalization, etc. associated with bending.

  Further, when the present apparatus is used as a pre-formation in hydraulic forming or the like, it is necessary to change the diameter of the pipe p regardless of the position of the bending process. Also for such a part, the diameter can be reduced to a necessary part by controlling the pressing force and the like.

  The pressing die urging means 4 is a means for urging the pressing die 3 in the axial direction of the pipe p. Since the pressing die 3 and the pipe p move as the bending die 1 rotates, the force applied to the bending die 1 increases as the size of the pipe p increases. By urging the pressing die 3 by the pressing die urging means 4, the force for rotating the bending die 1 can be reduced. Further, a pipe booster that has been conventionally used may be used in place of the push-type urging means 4. Since the pipe booster needs to hold the end of the pipe p, the push-type urging means 4 for directly urging the push-type 3 is preferable because there is room for downsizing the apparatus.

(Function and effect)
Since it has the above-described configuration, the pipe bending apparatus of the present embodiment has the following operational effects. That is, the present processing apparatus holds the pipe p to be bent by the clamp 2 and fixes it on the peripheral surface of the bending die 1. The clamp 2 rotates together with the bending die 1. The pipe p is bent by the clamp 2, the bending die 1 and the pressing die 3 according to the shape of the groove on the peripheral surface of the bending die 1.

  The control means 6 controls the pressurizing means 8 based on the position detected by the pipe position detecting means 5 and where the pipe p is held between the bending die 1 and the push die 3. Specifically, the pressurizing means 8 is controlled based on the degree of bending at the position of the pipe p held by the bending die 1 and the pressing die 3 and the required pipe diameter. In other words, when the position of the pinched pipe p is a portion where the degree of bending is large and a portion where the required diameter is small, the pressure means 8 is operated to a greater extent to reduce the diameter of the pipe p. Increase the degree of

  As a result, when the pressing die 3 is brought close to the bending die 1, the pipe p sandwiched therebetween is crushed in the circumferential direction, and the pressing die 3 and the bending die 1 are combined in accordance with the degree of proximity. The diameter is reduced to. When the part of pipe p whose diameter is reduced is a part to be bent, the part where the pipe wall is extended by the bending process is compensated by the remaining pipe wall due to the reduced diameter, and the thinning outside the pipe p is reduced. Can be prevented. Further, since the compressive stress is applied in the circumferential direction of the pipe p when the diameter is reduced, the stress that presses the pipe wall of the pipe p against the groove portion and the pressing die 3 is generated. Ovalization due to bending can be suppressed.

  The pressing die urging means 4 can suppress the inertial force of the pressing die 3 from being applied to the bending die 1 by urging the pressing die 3 in the axial direction of the pipe p. The movement in the axial direction can be performed smoothly. In addition, since the slip between the pressing die 3 and the pipe p can be reduced, it is possible to suppress the thinning due to ironing that may remain slightly on the bent outer side of the pipe p.

  As described above, according to the configuration of the bending apparatus of the present invention, it is possible to suppress the thinning of the outer side of the bending, and there is no buckling on the inner side of the bending, making it possible to manufacture pipes having different circumferential lengths in the axial direction.

(Test conditions)
Using the pipe bending apparatus of the present invention and the conventional pipe bending apparatus, pipe bending was performed under various conditions. The processing conditions were changed by changing the presence or absence of a mandrel, the presence or absence of a wiper, the presence or absence of a pipe booster (pushing die urging means in the device of the present invention), and the pressing force of the pushing die. After bending the pipe, the appearance, maximum thinning rate, and minimum peripheral length after processing were measured. The appearance was observed with the naked eye and examined for the occurrence of buckling, cracking, and meat sink. The maximum thinning rate is the thinning rate from the wall thickness of the unprocessed pipe for the minimum value of the wall thickness measured at every 10 ° bending angle using a point micrometer for the pipe after processing [ = {(Thickness after processing) − (Thickness of raw pipe)} ÷ (Thickness of raw pipe) × 100 (%)] The minimum perimeter after processing was the minimum value of the perimeter measured in order in the pipe axis direction for the processed pipe. In many tests, pipe bending conditions included minimum bending, and many processing conditions that could not be completely bent by conventional processing equipment were selected.

(Test 1)
The pipe used was a carbon steel ERW steel pipe with an outer diameter (D) of φ65 mm, a circumference of 204 mm, and a wall thickness of the pipe wall (t) of 2.3 mm. ) Was 840 MPa, and the elongation was 22%. The bending process applied to this pipe had a bending radius (R) of 90 mm (≈1.4D) and a bending angle of 90 °. Other processing conditions and test results are shown in Table 1.

  In Test Examples 8 to 9 in which bending was performed using a conventional apparatus, it was difficult to obtain a good product depending on the presence or absence of a mandrel and a wiper and the presence or absence of a pipe booster. On the other hand, in Test Examples 1 to 7 in which bending was performed using the apparatus of the present invention, a good product could be obtained without buckling or cracking even without a mandrel and a wiper.

  As is clear from the results of Test Examples 1 to 5, the maximum thickness reduction rate decreased as the pressing force for pressing the pressing die against the bending die was increased, and a pipe that was bent more uniformly could be obtained. . In this test, the effect of reducing the maximum thickness reduction is saturated when the pressing force for pressing the pressing die is 25 tons or more. This is because the perimeter of the bending die and the push die is 192 mm, whereas the minimum perimeter after processing for the pipes of Test Examples 4 and 5 is 193 mm. It is considered that the maximum thickness reduction rate could not be reduced.

  Further, as is clear from the results of Test Examples 5 to 7, it is found that the maximum thickness reduction rate can be reduced by urging the pressing die with the pressing die urging means even if the pressing force of the pressing die is the same. It was.

(Test 2)
The test was performed using a pipe having a smaller elongation than the pipe used in Test 1. The pipe used was a carbon steel ERW steel pipe with an outer diameter (D) of φ70 mm, a circumference of 220 mm, and a wall thickness (2.0 mm) of the pipe wall (t). ) Was 900 MPa, and the elongation was 8%. The bending process applied to this pipe had a bending radius (R) of 180 mm (≈2.6D) and a bending angle of 90 °. Other processing conditions and test results are shown in Table 2.

  As is clear from the results of Test Examples 11 and 12 shown in Table 2, it was found that the use of the apparatus of the present invention can provide good processing results even for materials with low elongation.

(Test 3)
The state of bending of the pipe was examined by changing the circumference of the portion where the groove portion and the pressing die 3 were combined. The circumference was changed by grinding the groove portion and the flange portion of the stamping die portion. The pipe used was a carbon steel ERW steel pipe with an outer diameter (D) of φ70 mm, a circumference of 220 mm, and a wall thickness (2.0 mm) of the pipe wall (t). ) Was 460 MPa, and the elongation was 55%. The bending process applied to this pipe had a bending radius (R) of 180 mm (≈2.6D) and a bending angle of 90 °. A mandrel, a wiper, and a pressing die urging means were not used, and the pressure applied to press the pressing die was 12.5 ton. FIG. 3 shows the peripheries of the pressing die, the bending die, and the pressing die, and the maximum thickness reduction rate of the pipe after processing.

  As apparent from FIG. 3, the appearance of the pipe after processing was good by setting the circumferences of the bending die and the pressing die in the range of 85% to 98% with respect to the circumference of the pipe. Moreover, the maximum thickness reduction rate was able to be reduced to about 7% by making the circumference of a bending die and a pressing die into the range of 85%-97% with respect to the circumference of a pipe. Furthermore, by setting it to 85% to 95%, the maximum thickness reduction can be extremely reduced to 5% or less.

(Test 4)
We investigated the change in the circumference of the pipe by changing the pressure applied to the pressing die during bending of the same pipe. The pipe used was a carbon steel ERW steel pipe with an outer diameter (D) of φ65 mm, a circumference of 204 mm, and a wall thickness of the pipe wall (t) of 2.3 mm. ) Was 840 MPa, and the elongation was 22%. The bending process applied to this pipe had a bending radius (R) of 180 mm (≈2.8D) and a bending angle of 90 °. The mandrel, the wiper and the pressing die urging means were not used, and the peripheral length of the portion combining the groove portion and the pressing die 3 was 184 mm.

  FIG. 4 shows a graph showing the relationship between the pressure applied to the pressing die and the circumference of the pipe after processing. As is apparent from FIG. 4, it was found that the circumference of the pipe becomes smaller as the pressing force is increased with respect to the pressing die. That is, it has become clear that the circumference of the pipe can be controlled by changing the pressure applied to the pressing die even on a single pipe.

(Test 5)
The state of bending of the pipe was examined by changing the circumference of the portion where the groove portion and the pressing die 3 were combined. Thereafter, hydraulic forming was performed.

  The pipe used is an electric-welded steel pipe made of carbon steel, and the tensile strength (TS) is JIS No. 11 pipe (round pipe) with a 390 MPa, outer diameter (D) is 70 mm, circumference is 220 mm, elongation is 55%, The wall thickness (t) of the tube wall was 2.0 mm. Concentric diameter reduction processing (50 mm) was made at both ends of the pipe.

  The bending process applied to this pipe had a bending radius (R) of 180 mm (≈2.6D) and a bending angle of 90 °. A mandrel, a wiper, and a pressing die urging means were not used, and the pressure applied to press the pressing die was 12.5 ton. FIG. 5 shows the cross-sectional shapes of the pressing die and the bending die. The bending mold 11 and the pressing mold 31 were used in place of the bending mold 1 and the pressing mold 3 of the apparatus of the present invention. Table 3 shows the peripheries of the bending die and the pressing die, the appearance of the pipe after processing, and the maximum thickness reduction rate.

  Thereafter, the pipes after processing of each test example were subjected to hydroforming under two conditions (circumferential length 200 mm, 204 mm), and the appearance was inspected. The results are also shown in Table 3.

  As is apparent from Table 3, in Test Examples 26 to 32 in which the perimeters of the bending die and the pressing die were made as short as possible with respect to the perimeter of the pipe, no buckling occurred in the processed pipe. Furthermore, Test Examples 26 to 31 in which the perimeters of the bending die and the pressing die are in the range of about 88% to 98.5% with respect to the perimeter of the pipe have good appearance without occurrence of buckling and buildup. It was.

  In the subsequent hydroforming, in Examples 27 to 32 when the circumference was 200 mm, and in Examples 26 to 32 where the circumference was 204 mm, no meat sink occurred and the tube had a good appearance and tube wall state. . In the case of the circumference of 200 mm, the circumference of the bending die and the pressing die of Test Example 27 is 106% with respect to the circumference of 200 mm of the hydraulic forming hole die in the hydraulic forming. The peripheral length of the die and the pressing die is 108% with respect to the peripheral length of 204 mm of the hydraulic forming hole die in the hydraulic forming, and the peripheral length of the bending die and the pressing die is 108 of the peripheral length of the hydraulic forming hole die. It became clear that if it was less than%, good hydraulic forming without meat sink could be performed. In Test Example 32, no sink marks occurred, but folding occurred due to the hydraulic forming at the build-up portion.

(Test 6)
Pipe bending and hydraulic forming were performed under conditions close to actual processing conditions. The pipe used was a carbon steel ERW steel pipe with an outer diameter (D) of φ65 mm, a circumference of 204 mm, and a wall thickness of the pipe wall (t) of 2.3 mm. TS) was 840 MPa, and the elongation was 22%.

  The bending process applied to this pipe has a bending angle of 90 °, the bending radius (R) is 90 mm from 0 to 12.5 °, straight from 12.5 to 30 °, and bending. The angle ranged from 30 to 90 ° was 180 mm.

  FIG. 6 shows the cross-sectional shapes of the pressing die and the bending die. The bending mold 12 and the pressing mold 32 were used in place of the bending mold 1 and the pressing mold 3 of the apparatus of the present invention. The peripheral length of the combined portion of the bending die 12 and the pressing die 32 was 188 mm. A mandrel, wiper and pusher biasing means were not used.

  FIG. 7 is a graph showing the pressing force of the pressing die 32, the peripheral length of the pipe after processing, and the peripheral length of the hydroformed hole die with respect to the bending angle. FIG. 8 is a graph showing the pressing force of the pressing die 32, the width of the processed pipe, and the width of the hydroformed hole die with respect to the bending angle.

  As is apparent from FIGS. 7 and 8, by sequentially changing the pressing force of the pressing die 32 during the bending process, the peripheral length and width matched to the hydroforming hole die having different peripheral lengths in the axial direction of the pipe. You can get a pipe with.

  The cross section of the pipe after bending was a shape corresponding to the cross sectional shape of the bending die and the pressing die shown in FIG. In other words, the width of the pipe can be narrowed by partially smashing the pipe wall of the pipe by the straight portion provided in the pressing die 32.

  Since the width of the pipe can be made narrower than the width of the hydraulic forming hole mold, the pipe can be inserted without interfering with the hydraulic forming hole mold. That is, it is possible to omit the press forming step that has been conventionally performed after bending.

  As described in detail above, the pipe cross-sectional shape that can be inserted into the composite R shape by a single bending process, and can be inserted without interfering with the hydroforming hole mold, as the pipe ends of both pipes are reduced in diameter. Can be formed. The cross-sectional shape of the pipe can be easily controlled in the axial direction of the pipe by controlling the pressure applied to the pressing die, and changing the shape of the bending die groove and the pressing die.

It is the schematic which showed one Embodiment of the pipe bending apparatus of this invention. It is the aa cross-sectional schematic of the pipe bending apparatus shown in FIG. 6 is a graph showing the results of Test 3. 6 is a graph showing the results of Test 4. 6 is a partial cross-sectional view of a bending die and a pressing die used in Test 5. FIG. FIG. 6 is a partial cross-sectional view of a bending die and a pressing die used in Test 6. 10 is a graph showing the results of Test 6. 10 is a graph showing the results of Test 6. It is the schematic which showed the pipe bending apparatus of the prior art. It is the bb cross-sectional schematic of the pipe bending apparatus shown in FIG. It is a figure explaining the thinning of the bending outer side of the pipe in a prior art. It is a figure explaining the ovalization of the pipe in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11, 12, 91 ... Bending die 2, 92 ... Clamp 3, 31, 32, 93 ... Push die 4 ... Push die biasing means 5 ... Pipe position detection means 6 ... Control means 7, 97 ... Holder 8 ... Addition Pressure means 9 ... Hydraulic control means 94 ... Wiper 95 ... Mandrel 96 ... Pipe booster o ... Bending center of rotation (rotating shaft)

Claims (12)

A bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending apparatus having control means for controlling the pressurizing means,
The pipe bending means characterized in that the pressurizing means is a means for pressurizing a point where a straight line passing through a point where the bending die and the pipe abut and a rotation center of the main body part intersects the push die in the linear direction. Processing equipment.   The pipe bending apparatus according to claim 1, wherein a peripheral length of a portion where the bending die and the pressing die are combined is shorter than a peripheral length of the pipe.   The pipe bending apparatus according to claim 1 or 2, wherein the control means is means for controlling the pressurizing means in accordance with a bending shape of the pipe. A rotation angle detecting means for detecting a rotation angle of the bending mold;
The pipe bending apparatus according to any one of claims 1 to 3, wherein the control means controls the pressurizing means based on the rotation angle detected by the rotation angle detection means.   The pipe bending apparatus according to any one of claims 1 to 4, wherein the control means controls the pressurizing means so that a feed amount of the pressing die becomes a predetermined value.   The pipe bending apparatus according to any one of claims 1 to 5, further comprising a pushing die urging unit that urges the pushing die in a moving direction of the pipe.   The pipe bending apparatus according to any one of claims 1 to 6, wherein a mandrel is not disposed inside a portion of the pipe sandwiched between the bending mold and the pressing mold. A bending die having a rotatable main body portion and a groove portion formed on the peripheral surface of the main body portion and having a shape corresponding to the bending shape of the pipe;
A clamp that holds a portion of the pipe;
A pressing die that can be sandwiched between the bending portion and the groove, and is movable in the axial direction of the sandwiched pipe;
Pressurizing means for pressurizing the pressing mold toward the bending mold;
A pipe bending method using a control means for controlling the pressurizing means,
The pressurizing means is a means for pressurizing in the linear direction a point where a straight line passing through the point where the bending mold and the pipe abut and a rotation center of the main body part intersects the pressing mold,
A pipe bending method characterized by bending the pipe and reducing the diameter.   The pipe bending method according to claim 8, wherein a circumferential length of a portion where the groove portion and the pressing die are combined is shorter than a circumferential length of the pipe.   The pipe bending method according to claim 8 or 9, wherein the pipe is reduced in diameter according to a bending shape of the pipe. A rotation angle detecting means for detecting a rotation angle of the bending mold;
The pipe bending method according to any one of claims 8 to 10, wherein the diameter of the pipe is reduced based on a rotation angle detected by the rotation angle detection means.   The pipe bending method according to any one of claims 8 to 11, wherein a mandrel is not disposed inside a portion of the pipe sandwiched between the bending die and the pressing die.

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