JP3739751B2 - Metal bending tube manufacturing method and bending apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method for producing a bent metal pipe by bending a straight metal pipe and a bending apparatus for a metal pipe used for carrying out the method.
[0002]
[Prior art]
[Patent Document 1]
  Japanese Patent Publication No.58-2726
[Patent Document 2]
  Japanese Patent Publication No.54-28155
[Patent Document 3]
  Japanese Patent Publication No. 1-1870
[Patent Document 4]
  JP-A 61-199521
  2. Description of the Related Art Conventionally, as a method for manufacturing a metal bent tube, a method of bending a metal straight tube hot or cold is known. Then, as a typical method of hot bending, as shown in FIG. 20 (a), the straight pipe 1 to be bent is passed through the induction coil 2 arranged at a fixed position, and the tip is attached to the fulcrum O. A front clamp 4 provided on a pivotable bending arm 3 as a center is gripped, a rear end is gripped by a rear clamp 5, and an intermediate portion is set to be guided by a guide roller 6. A heating section 7 is formed by induction heating a small section in the tube axis direction of 1 to a temperature at which plastic deformation is easy, and at the same time, the rear clamp 5 is pushed in the tube axis direction by a propulsion device (not shown) to move the tube 1 in the tube axis direction. As shown in FIG. 20 (b), the heating unit 7 formed by the induction coil 2 is moved relative to the tube axis direction, and the heating unit 7 is caused by the turning of the bending arm 3. Apply bending moment to the song A method of performing a bending operation on the desired region of the tube 1 is known in which a cooling medium 8 such as cooling water is sprayed from the induction coil 2 to cool and harden immediately after being deformed. As shown in FIG. 20 (c), a metal bent tube 1A including a bent tube portion 1a and straight tubular tube ends 1b and 1c at both ends thereof is manufactured.
[0003]
  In this bending method, as shown in an exaggerated cross section of the curved pipe portion 1a in FIG. 20 (d), the bending wall (neutral axis) N-N is used as a boundary to bend the tube wall on the inner side (C side). The compression force acts to increase the thickness, and the bending outside (T side) tube wall acts on the tube wall to reduce the thickness. Therefore, in order to suppress thinning of the bending outer peripheral tube wall, a method of bending the tube 1 while applying a compressive force in the tube axis direction is also known. Will be further expanded. During bending, when a large compressive force acts on the bending inner tube wall and a large increase in thickness is about to occur, the deformation of the tube wall becomes unstable, and as shown in FIG. 21, the bending inner tube wall 1aa Unstable deformations called “Jabara” may occur. Therefore, conventionally, measures have been taken such as suppressing the bending speed or limiting the bending radius R to a certain level or less so as not to cause looseness.
[0004]
  Further, in the bending method described above, at the start of bending, the thrust applied to the tube acts as a compressive force on the tube wall before the inner wall of the bend is thickened. Likely to happen. Therefore, prior to bending, the straight pipe part located in front of the bent pipe part is subjected to hot upsetting to increase the thickness of the straight pipe part.Keep it bigger and thenIt is also known that by starting the bending process, the compressive stress generated on the inner tube wall at the start of bending is reduced and the occurrence of looseness is prevented (for example, Japanese Patent Publication No. 58-2726 of Patent Document 1). reference).
[0005]
  Further, in the bending method described above, the bending outer peripheral side wall wall and the bending inner side tube wall are deformed so as to approach the bending neutral portion NN at the time of bending, and the outer diameter of the neutral position is increased accordingly. The tube is flattened. Therefore, in order to prevent this flattening, as shown in FIGS. 22A and 22B, the flattening prevention jig 10 is manually attached to the bent pipe portion 1a after passing through the induction coil 2 during bending. A method for preventing flattening by successively attaching and regulating the outer diameter on the bending neutral portion NN of the bent pipe portion 1a is known (see, for example, Japanese Patent Publication No. 54-28155 of Patent Document 2). ).
[0006]
  In the above-described conventional hot bending method, in most cases, the induction coil 2 that locally heats the tube 1 is disposed outside the tube 1 and heated from the outer surface of the tube. In order to preferentially heat-treat the surface, an induction coil may be arranged in the pipe (see Japanese Patent Publication No. 1-18970 of Patent Document 3).
[0007]
  As a cold bending method, as shown in FIG. 23, a clamp 4 that holds the tip of a pipe 1 to be bent is attached to a partial disk-shaped foam guide 11 that rotates around a fulcrum O, and the foam is formed. A method is known in which a regulating surface 11a for regulating the outer circumferential surface of the tube 1 is formed on the outer circumferential surface of the guide 11, and the tube 1 is bent so as to be wound around the regulating surface 11a of the foam guide 11 in the cold state. (For example, see Japanese Patent Application Laid-Open No. 61-199521 of Patent Document 4).
[0008]
[Problems to be solved by the invention]
  However, all of these conventional techniques have problems. That is, in the hot bending method as shown in FIGS. 20 and 22, there is a possibility that the inner wall of the bent inner wall may be loosened, and the straight pipe portion is thickened before the bending process to prevent the looseness. Even if the method is adopted, when the bending speed is increased, a looseness is still generated, so that the bending speed cannot be increased very much (for example, 1.5 mm / sec is the limit at a bending radius of 1.5 DR). There was a problem that the cost could not be reduced by increasing the bending speed. Moreover, in order to prevent flattening of a curved pipe part, the method of attaching a flattening prevention jig manually requires a troublesome work, and a work burden becomes large. Moreover, even if the above-mentioned problem of looseness can be solved and the bending speed can be increased, in that case, it becomes extremely difficult to attach the flattening prevention jig due to the increased speed, and the number of attachments can be reduced or Additional personnel may be required and may not be installed. If the bending speed is increased, the number of flattening prevention jigs must be reduced or become unusable despite the increase in flatness. Increases, and therefore the quality decreases. Moreover, when flattening occurs in the bent pipe part, a flattening in the direction rotated 90 degrees (called reverse flattening) occurs at the pipe end part. Therefore, it is often necessary to heat and correct the end of the tube in a perfect circle shape, which increases the cost.
[0009]
  Furthermore, because the induction coil is arranged on the outer surface side of the pipe for heating during bending, the clamp for gripping the pipe must be arranged at an appropriately separated position so as not to interfere with the induction coil. The straight tubular tube ends 1b and 1c that are left on both sides of the bent tube portion 1a of the bent tube 1A thus manufactured become long and do not meet the required standard values. Therefore, conventionally, after the bending process is completed, a part of the straight tubular pipe ends 1b and 1c is cut off and adjusted to a desired length, and extra cost is required for this work. Moreover, since the pipe end portions 1b and 1c must be cut after the bending process, it is necessary to perform groove processing and flange attachment to the pipe end after the bending process, which is extremely difficult and expensive. In other words, in the case of groove processing and flange mounting on curved pipes, unlike straight pipes, it takes time to certify the pipe end axis, or it does not adapt to centering by rotation, and it takes time to center the flange. The cost is high.
[0010]
  On the other hand, since the cold bending method is a draw bending method, it is not possible to suppress the thinning of the bending outer peripheral side. In addition, since it is cold work, the allowable elongation on the outer periphery side after bending is the value obtained by subtracting the elongation due to bending from the allowable elongation of the material. If the bending radius is small), the allowable elongation after bending becomes small, and the standard value required for the pipe cannot be satisfied. For this reason, it is difficult to use a cold bending product of 2DR or less for general industrial plant piping. Furthermore, because of cold working, the deformation resistance during machining is extremely large, which requires a large power for bending and a mechanical structure with high rigidity according to the power, increasing the equipment cost. . In a thin tube, the inner wall of the bent inner wall is often uneven, and in order to prevent this, it is necessary to insert a metal core into the tube and bend it.
[0011]
  The present invention has been made in view of the above problems, and is not suitable for a straight metal pipe.And flatBending can be performed at high speed without causing flatness, and the straight pipe parts left on both sides of the curved pipe part are shortened to meet the standard values required for metal bent pipes. Therefore, an object of the present invention is to provide a technique capable of significantly reducing the manufacturing cost of the metal bent pipe.
[0012]
[Means for Solving the Problems]
  In order to avoid the problems in cold bending when manufacturing the metal bent pipe by bending, the present inventors adopt hot bending to prevent looseness and flattening that occurs during the hot bending. As a result of study, in the region where the bending deformation of the tube occurs (referred to as bending deformation progressing portion), the outer peripheral surface of the bending inner portion of the tube and the outer peripheral surfaces of both sides of the bending neutral portion are regulated by appropriate tools. It was found that flattening can be prevented.
[0013]
  The present invention has been made on the basis of such knowledge. The invention according to claim 1 of the present application is such that a small section in the tube axis direction of a pipe is made to a temperature at which plastic deformation is easy by induction heating. Heating and moving the heating part formed by the heating relative to the pipe axis direction, giving a bending moment to the heating part to bend and deform it, and then cooling it immediately, In a method of manufacturing a bent metal pipe having straight pipe ends at both ends thereof, an induction coil for induction heating is arranged only inside the pipe, and bending of the outer peripheral surface of the pipe is performed. Of deformation progressionThe outer peripheral surface of the bending inner part and the outer peripheral surface of both sides of the bending neutral partPerform bending operations while restricting with permanent toolPrior to the bending operation for the pipe, the pipe is compressed in the direction of the pipe axis to increase the wall thickness before the bending start point of the pipe. Upsetting The operation of gradually increasing the tube wall thickness toward the bending start point by the operation, and then shifting to the bending operation following this operationIt is what. By arranging the induction coil only inside the pipe in this way, it becomes possible to arrange the permanent tool outside the area heated by the induction coil of the pipe without any trouble, and the permanent tool can bend the pipe. By regulating the outer peripheral surface of both sides of the bending neutral part of the deformation progression part, flattening can be effectively prevented.Moreover, the occurrence of looseness can be effectively prevented by regulating the outer peripheral surface of the bent inner portion.In addition, the configuration in which the induction coil is disposed only inside the tube is advantageous for preventing the occurrence of looseness (the reason will be described later). For this reason, the bending speed can be increased, and the cost can be reduced. In addition, since it is not necessary to use a conventionally used anti-flattening jig, the troublesome work of manually attaching the anti-flattening jig is not necessary, and the cost can be reduced from this point. Furthermore, as a result of preventing the bent pipe portion from being flattened, it is possible to prevent reverse flattening that may have occurred at the pipe end and to eliminate the need for correcting the pipe end. In addition, since the induction coil is arranged in the pipe, the clamp for gripping the pipe end does not interfere with the induction coil. Therefore, the clamp can be positioned in the vicinity of the position where the induction coil is arranged. The straight pipe part left on both sides of the pipe part can be bent with a short length required for the finished product. For this reason, after the bending process is finished, there is no need to cut off a part of the straight tubular pipe end portion and adjust it to a desired length, and a flange is attached to the pipe end at the straight pipe stage prior to the bending process. In addition, groove processing can be performed, and the manufacturing cost of the metal bent pipe can be further reduced. In carrying out this invention, the bending deformation progressing portion of the pipe with a permanent tool is used.The outer peripheral surface of the bending inner part and the outer peripheral surfaces of both sides of the bending neutral partThe period that regulates the period should be the entire period from the start of bending to the end of bending.And preventionIt is preferable because it can maximize the effects ofAnd preventionIf it is within the range where the effect of is not reduced so much, a part of the bending process may be in a state without restriction by the permanent tool. Specifically, a period of about 70% or more of the total bending process period may be regulated with a permanent tool.
[0014]
[0015]
[0016]
  Furthermore, the invention according to claim 1Prior to the bending operation for the pipe, by a hot upsetting process that compresses the pipe in the direction of the pipe axis to increase the thickness of the pipe with respect to the straight pipe portion adjacent to the end of the bending start point of the pipe. An operation of gradually increasing the tube thickness toward the bending start point is performed, and the operation is shifted to the bending operation operation following this operation.ByBecause the bending process is started after the thickness of the straight pipe part is increased, a sudden change in thickness occurs between the inner wall of the bent inner pipe and the pipe wall of the straight pipe part. This prevents the occurrence of looseness. In addition, in the manufactured metal bent pipe, the thickness of the straight pipe portion on the bending start point side gradually increases toward the bent pipe portion, so that it is between the thickened pipe wall of the bent inner portion of the bent pipe portion. Therefore, there is no occurrence of stress concentration or high resistance to the fluid in the pipe.
[0017]
  Claim2The invention of claim1In the method for producing a bent metal pipe, the bending operation is performed on the pipe, and when the bending end point of the pipe is reached, the pipe is compressed in the axial direction with respect to the straight pipe portion adjacent to the rear of the pipe. In this configuration, the tube thickness is gradually decreased from the bending end point by hot upsetting to increase the thickness. With this structure, the thickness of the straight pipe part on the bending end point side of the manufactured metal bent pipe gradually decreases from the bent pipe part. Therefore, there is no occurrence of stress concentration or high resistance to the fluid in the pipe.
[0018]
  Claim3The invention of claim 1Or 2In the method of manufacturing a bent metal pipe described above, hot upsetting is performed on the straight pipe portion positioned behind the bending end point of the pipe to increase the pipe thickness by pushing the pipe end in the pipe axis direction. In this case, the position of the tube end in the manufactured metal bent tube is adjusted by adjusting the pushing end point position of the tube end. With this configuration, even if there is an error in the length of the straight pipe used for the bending process or an error in the bending radius formed by the bending process, the position of the pipe end of the manufactured metal bending pipe can be set to a predetermined value. Adjustment can be made to match the standard value, and the dimensional accuracy of the product can be improved.
[0019]
  Claim4The invention of claim 1 starts from claim 1.34. The method of manufacturing a metal bent pipe according to claim 1, wherein at the start of bending of the pipe, the bending arm is turned and the induction coil is bent from a position farther from the predetermined bending position to the pipe tip side. The bending arm turning speed and the induction coil moving speed at the time are moved in the direction of the tube axis, and the ratio of the relative moving speed of the heating unit to the tube with respect to the bending arm turning speed (that is, the heating unit) Is set so that the bending radius gradually decreases with the progress of the bending process, so that the bending is performed so that the bending radius gradually decreases from the large bending radius. After reaching the bending position, bending is performed with a constant bending radius while the induction coil is stopped at the bending position. With this configuration, bending is started by starting bending with a large bending radius, then gradually reducing the bending radius to a predetermined bending radius, and then continuing the bending with the predetermined bending radius. Therefore, the occurrence of looseness can be prevented, and a metal bent tube having a structure in which the transition portion from the straight tube portion to the bent tube portion is smoothly curved can be obtained.
[0020]
  Claim5The invention of claim 1 starts from claim 1.4In the metal bending tube manufacturing method according to any one of the above, when the induction coil is stopped at a predetermined bending position, bending with a constant bending radius is continued, and when approaching the end of bending, In this state, the bending coil pivoting is continued and the induction coil is moved from the predetermined bending position toward the tube rearward in the direction of the tube axis, and the bending arm pivoting speed and the induction coil moving speed at that time are bent. By setting the ratio of the relative movement speed of the heating unit to the tube with respect to the arm rotation speed (that is, the relative movement speed of the heating unit to the tube / the bending arm rotation speed) to gradually increase as the bending process proceeds. The bending process is performed so that the bending radius gradually increases from a predetermined bending radius. With this configuration, it is possible to perform so-called blur bending, in which bending is performed while gradually increasing the bending radius from a predetermined bending radius at the end of bending, and the transition from the bent pipe portion to the straight pipe portion is performed. A metal bent tube having a smoothly curved structure can be obtained.
[0021]
  Claim6The invention of claim 1 starts from claim 1.5In the manufacturing method of a metal bent pipe according to any one of the above, the bending operation is performed in a state where a compressive force in the direction of the pipe axis is applied to the pipe. It is possible to suppress the thinning of the bent outer portion tube wall.
[0022]
  Claim7The invention of claim 1 starts from claim 1.6The method of manufacturing a metal bent pipe according to any one of the above, wherein the pipe is provided with a flange at a straight pipe stage at the pipe end and then subjected to the bending operation to obtain a bent pipe with a flange. is there. As described above, the flange is attached to the pipe end at the straight pipe stage, so that the flange can be attached much more easily than the case where the flange is attached to the bent pipe after bending. A bent metal pipe can be manufactured at low cost. Also, if bending is performed with the flange attached to the pipe end, the pipe end is held in a perfect circle by the flange, so there is no reverse flattening that has occurred at the pipe end during conventional bending, From this point, it is possible to manufacture a curved pipe with good quality.
[0023]
  Claim8The invention of claim 1 starts from claim 1.6The method of manufacturing a metal bent pipe according to any one of claims 1 to 3, wherein the pipe is subjected to the bending operation after forming a welding groove at a straight pipe stage at a pipe end thereof. It is set as the structure which obtains. In this way, by forming the welding groove at the straight pipe stage at the pipe end, the groove formation is performed as compared with the case where the welding groove is formed at the pipe end of the bent pipe after bending. The work can be simplified and a metal bent pipe with a grooved end can be manufactured at low cost.
[0024]
[0025]
[0026]
  Claim9 inventionsA bending apparatus for use in the implementation of a method for manufacturing a metal bent pipe, wherein a bending position of a metal straight pipe to be bent advances through a predetermined bending position in the pipe axis direction. A pipe restricting means for holding the straight pipe portion at the rear of the pipe in a predetermined travel path, a clamp for gripping the tip of the pipe, a bending arm that can turn around a predetermined fulcrum, and inserted into the pipe, An induction coil that induction-heats a small section in the tube axis direction located at the bending position of the tube, and a cooling means that blows and cools a cooling medium on the tube tip side of the region heated by the induction coil of the tube; Driving means for turning the bending arm directly, through the pipe, or a combination of both so that a bending moment is applied to the pipe by turning the bending arm, and the outer periphery of the pipe during the bending operation. Is obtained by bending the inner portion outer peripheral surface and bending the neutral section on both sides the outer peripheral surface of the bending deformation progress portion of and a permanent-type device to regulate the configured that comprises a. With this configuration, the tube can be hot-bended, and during the bending process, the outer peripheral surface of the bending inner portion and the outer peripheral surface of both sides of the bending neutral portion of the tube are regulated by a permanent tool. Bending operation can be performed, and bending can be performed at high speed without causing looseness and flatness.
[0027]
  Further, the invention of claim 9 is in addition to the above structure.The permanent tool is configured to include a shape-retaining guide provided so as to rotate integrally with the bending arm, and the shape-retaining guide includes a bending deformation progressing portion of the tube and a bending connected thereto. For the deformed curved pipe part, the loosen regulation surface that prevents the occurrence of looseness by regulating the outer peripheral surface of the bending inner part, and the flat restriction surface that prevents the flattening of the pipe by regulating the outer peripheral surfaces on both sides of the bending neutral part It is set as the structure provided with. The shape maintaining guide having this configuration can regulate not only the bending deformation progressing portion of the tube but also the bent tube portion that has been bent and deformed during the bending process, so that the occurrence of looseness and flatness can be further prevented.
[0028]
  Claim10The invention of claim9In the bending apparatus, the shape maintaining guide includes a main shaft that rotates integrally with the bending arm, a loose prevention member provided with the loose restriction surface, and two flattening prevention plates provided with the flat restriction surface, The looseness prevention member and the two flattening prevention plates are configured to be attached to the main shaft in a detachable form. In this way, the looseness prevention member and the anti-flat plate can be attached to and detached from the main shaft, so that an appropriate liner and anti-flat plate can be bent according to bending conditions such as the outer diameter and bending radius of the pipe to be bent. It can be attached at a position according to the conditions, and can easily cope with changes in bending conditions.
[0029]
  Claim11The invention of claim10In the bending apparatus, the looseness restricting surface of the looseness preventing member is constituted by an arcuate surface that conforms to the outer peripheral surface of the bent inner portion of the bent tube portion formed by bending, and the flattening restriction surface of the flattening prevention plate is formed. It is composed of a flat surface. If the looseness restricting surface of the looseness prevention member is an arcuate surface that conforms to the outer peripheral surface of the bent inner portion of the curved pipe portion, a good looseness prevention effect can be exhibited. Further, when the flattening restriction surface of the flattening prevention plate is a flat surface, the structure becomes simple and the cost of the equipment can be reduced.
[0030]
  Claim12The invention of claim10Or11In the bending apparatus, the flattening prevention plate has a structure including a flat regulating surface that is widened in the bending radius direction so that the flattening prevention plate can be used for bending with different pipe outer diameters and different bending radii. A plurality of members are prepared corresponding to bending processes with different pipe outer diameters and different bending radii, and a member suitable for the bending process conditions is attached. With this configuration, when changing the bending process conditions, only the loose prevention member can be replaced and the same flat prevention plate can be used, and the equipment cost can be further reduced.
[0031]
[0032]
  Claim13The invention of claim9From12The bending apparatus according to any one of claims 1 to 4, further pressing the rear end of a pipe whose tip is constrained by a clamp of the bending arm so as to reduce the length of the pipe to the clamp in the pipe axis direction. It is set as the structure provided with the apparatus. With this configuration, a compressive force in the direction of the tube axis can be applied to the tube during bending, and various measures such as bending can be performed while suppressing the thinning of the bent outer portion of the tube wall.
[0033]
  Claim14The invention of claim9From13The bending apparatus according to any one of the above, further includes means for moving the induction coil in the tube axis direction in a region before and after the bending position. By adopting a configuration in which the induction coil can be moved in this manner, bending by various methods can be performed. For example, if the tube is used in combination with a pressing device that compresses the tube in the tube axis direction, the induction coil is heated while heating the straight tube portion adjacent to the tip of the bending start point of the tube with the induction coil prior to the bending operation. Move toward the bending start point in the tube axis direction, and at the same time, push the tube end in the tube axis direction by pressing means, and apply a compressive force in the tube axis direction to the tube to increase the tube thickness in the straight pipe part Hot upsetting can be performed, and the tube wall thickness can be gradually increased toward the bending start point by appropriately changing the moving speed of the induction coil and / or the pushing speed of the pipe at that time. And when the induction coil reaches the bending start point, stop the movement of the induction coil and start bending.And thenIt is possible to perform a bending process that further prevents the occurrence of looseness. In addition, when the bending process is continued and the end point of bending of the tube is reached, the tube thickness is reduced by moving the induction coil in the tube axis direction and in the direction away from the bent tube portion while the pushing to the tube end is continued. Hot upsetting can be performed to increase the thickness, and the pipe thickness is gradually reduced from the bending end point by appropriately changing the moving speed of the induction coil and / or the pushing speed of the pipe. Inwear. Further, with respect to the straight pipe portion positioned behind the end point of bending of the pipe, hot installation is performed in which the pipe end is pushed in the pipe axis direction by a pressing device while the pipe is heated by an induction coil to increase the pipe wall thickness. It is possible to adjust the pushing end point position of the pipe end at that timewear. In addition, since the induction coil can be moved in the tube axis direction in the region before and after the bending position, bending can be performed while moving the induction coil from the front of the bending position toward the bending position. The bending method can be adopted in which the bending is started (starting the turning of the bending arm), and when the induction coil reaches the bending position, the induction coil is stopped at that position and the bending is continued.wear. In addition, when reaching the bending end region, the bending arm can be moved backward from the bending position while the bending arm continues to pivot.wear.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention shown in the drawings will be described. FIG. 1 is a schematic plan view of a metal pipe bending apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view thereof. 1 and 2, reference numeral 13 denotes a metal pipe to be bent, such as a steel pipe, which is set at a predetermined position of the bending apparatus. In this embodiment, as shown in FIG. 3 (a), the pipe 13 to be subjected to bending processing is used in which flanges 14 are fixed to both ends in advance by welding. In FIGS. 1 and 2, 15 is a machine body, 16 is attached to the machine body 15, a main shaft rotatably held around a vertical axis OO, and 17 is attached to the main shaft 16 so as to rotate integrally. The bending arm 18 is a clamp (hereinafter referred to as a front clamp) which is attached to the bending arm 17 and holds the tip of the tube 1. With this configuration, when the tube 13 moves in the tube axis direction as indicated by the arrow E and the bending arm 17 pivots about the axis OO, a bending moment can be applied to the tube 13 to bend and deform. . Here, in the case where the bending moment is applied by the bending arm 17 while the tube 13 is advanced, the tube is continuously bent and deformed, the bending deformation progressing portion of the tube passes through the fulcrum O of the bending arm, and the axis of the tube 13 In this specification, the straight line OA is referred to as a “bending position” because the bending process can be performed stably and efficiently. Further, in this specification, expressions such as “front end”, “rear end”, “front”, “rear”, and the like regarding the tube 13 are based on the moving direction of the tube indicated by the arrow E. The structure of the front clamp 18 for gripping the tip of the tube 13 is arbitrary as long as it can grip the tube 13 directly and / or through the flange 14 with the required strength. It is preferable to have a structure that can grip the outer surface of the region adjacent to the flange and the flange because the tube 13 can be gripped with high strength.
[0035]
  Reference numeral 20 denotes drive means for rotating the bending arm 17 for bending the pipe. The pinion 21 is attached to the main shaft 16, the rack 22 is arranged so as to be engaged with the pinion 21, and the rack 22 is reciprocated. The main bending cylinder 23 is provided. Reference numeral 25 denotes a rear clamp for gripping the rear end of the pipe 13, and reference numeral 26 denotes a rear clamp support base for holding the clamp 25, which is held movably in the pipe axis direction of the pipe 13 by an appropriate support guide (not shown). ing. 28 is a pressing device for pressing the rear end of the tube 13 in the tube axis direction and approaching the front clamp 18 holding the tube tip to compress the tube in the tube axis direction. A movable table 29 movably held in a guide (not shown) in the tube axis direction, a connecting plate 30 for coupling the movable table 29 so as to move together with the rack 22, and the rear clamp support table 26 are moved to the movable table. 29 is provided with a compression cylinder 31 or the like that is driven so as to approach or separate from the 29.
[0036]
  Reference numeral 35 denotes an induction coil that is inserted into the tube 13 and inductively heats a small section in the tube axis direction of the tube, and a cooling medium 36 such as cooling water (see FIG. 3) on the tube tip side of the heated region. The cooling means which cools by spraying is provided. 37 is a relay lead that holds the induction coil 35 and supplies power and a cooling medium, 38 is a high-frequency transformer that holds the relay lead 37 and is movable in the tube axis direction, and 39 is a tube shaft that supports the high-frequency transformer 38. This is a transformer moving motor that reciprocates in the direction. The induction coil 35 can be moved in the tube 13 in the tube axis direction by moving the high-frequency transformer 38 by the transformer moving motor 39. Here, the moving range of the induction coil 35 by the transformer moving motor 39 is set to be a desired range before and after the straight line OA (bending position). In this specification, when describing the position of the induction coil 35 in the tube axis direction, the induction medium 35 is slightly closer to the induction coil 35 than the position (cooling line) where the cooling medium 36 sprayed from the induction coil 35 is sprayed onto the tube 13. It is described with reference to a close position (a position where bending deformation or thickening deformation ends by cooling). Therefore, for example, as shown in FIG. 5, when the cooling medium 36 from the induction coil 35 is at a position slightly beyond the bending position OA, the induction coil 36 is described as being on the bending position OA.
[0037]
  Reference numeral 40 denotes a permanent tool that regulates the outer peripheral surface of the bending inner portion and the outer peripheral surfaces of both sides of the bending neutral portion of the tube 13 at least in the region where the bending processing position OA is located during the bending operation. The permanent tool 40 in this embodiment includes a shape-retaining guide 41 attached by a nut 44 so as to rotate integrally with the bending arm 17, and the shape-retaining guide 41 has a substantially U-shaped cross section. The control surface 42 is in the form of an integral structure formed in an arc shape with the turning center O as the center. As shown in an enlarged view in FIG. 6 (b), the restricting surface 42 is formed in a shape that fits the bent inner peripheral surface 13aa of the bent tube 13, and regulates the bent inner peripheral surface 13aa. A loose regulation surface 42a for preventing the occurrence of looseness and flat regulating surfaces 42b and 42b for preventing the flatness by regulating the outer peripheral surfaces 13ab and 13ab on both sides on the bending neutral portion NN of the pipe 13; At the time of bending the tube 13, as shown in FIG. 6A, the bent tube 13 can be restrained by the restricting surface 42 to prevent occurrence of looseness and flattening. In FIG. 1, the formation position and the circumferential length of the regulating surface 42 are at least during the rotation of the bending arm 17 from the position shown in FIG. 1 (position for setting the pipe to be bent) to the end of bending. The regulation surface 42 is always positioned on the bending position OA. Therefore, during the bending process, the regulating surface 42 can always regulate the region of the pipe 13 at the bending position OA and the bent pipe portion formed by the bending process.
[0038]
  46 is a pipe regulating means for holding a straight pipe portion behind the bending position of the pipe 13 in a predetermined travel path when the pipe 13 is bent. It is used.
[0039]
  In FIG. 2, when the machine body 15 is installed, the axis of the tube 13 set in the apparatus is inclined so that the tip side of the tube is lowered by 2 to 3 °. This is so that the cooling medium injected into the pipe is quickly discharged out of the pipe. Instead of inclining the machine body 15 at the time of installation, each part for holding the tube 13 with respect to the machine body 15 may be attached to the machine body so that the tube 13 is inclined.
[0040]
  Next, a method for manufacturing the metal bent tube 13A shown in FIG. 7 using the bending apparatus having the above-described configuration will be described. This metal bent tube 13A includes a bent tube portion 13a having a bending angle θ and straight tube end portions 13b and 13c having lengths b and c at both ends thereof, and a flange 14 is attached to each tube end. ing. Moreover, each pipe | tube edge part 13b, 13c is equipped with transition part 13bd, 13ce which thickness increases gradually toward a curved pipe part in the area | region of length d, e adjacent to the curved pipe part 13a.
[0041]
  In manufacturing the metal bent tube 13A, first, as shown in FIG. 3A, a metal straight tube 13 is prepared, and the straight tube is subjected to hot bending and hot upsetting described later. Thus, the length is adjusted so that the metal bent tube 13A having a desired length is obtained, and the flanges 14 are welded and fixed to both ends thereof. Since the welding and fixing work of the flange 14 is performed on a straight pipe, it can be performed very easily and with good workability as compared to the case of welding and fixing to a bent pipe after bending as in the prior art. Next, as shown in FIGS. 1, 2, and 3 (b), the straight pipe 13 with the flanges 14 fixed at both ends is set at a predetermined position of the bending apparatus, and the front end 18 is a front clamp 18 of the bending arm 17. The rear end is held by the rear clamp 25, and the induction coil 35 is inserted into the tube 13. Here, the position of the front clamp 18 is set so that the distance b from the tip of the straight pipe 13 to the bending position OA is equal to the length b of the pipe end 13b on the front side of the metal bent pipe 13A shown in FIG. is doing. Normally, the length b required for the tube end portion 13b of the metal bent tube 13A is relatively short, so that the tube end of the tube 13 gripped by the front clamp 18 is separated from the bending position OA by a distance b. In order to achieve this, it is necessary to arrange the front clamp 18 at a position close to the bending position OA. However, since the induction coil 35 is located in the pipe as illustrated, the induction coil 35 interferes with the front clamp 18. Therefore, the front clamp 18 can be disposed at a desired position without any trouble.
[0042]
  Next, in FIG. 3B, the induction coil 35 is positioned at a position separated by a distance d from the bending position OA to the tube tip side. Here, the distance d is set equal to the length d of the transition portion 13bd formed in the metal bent tube 13A shown in FIG. From this state, first, hot upsetting for the tube 13 is started. That is, as shown in FIGS. 3B and 3C, heating by the induction coil 35 is started in a state where the bending arm 17 is not rotated and the front clamp 18 is held at a fixed position, and the induction coil of the tube 13 is started. The induction coil 35 is bent to a bending position OA while the small section facing 35 is heated to a temperature at which plastic deformation is easy, for example, a red hot temperature, the temperature is increased, and the cooling medium 36 is sprayed to a position closer to the tube tip than the heating region. At the same time, the rear clamp 25 is advanced by the compression cylinder 31 (see FIG. 1) to push the rear end of the tube 13 toward the front end. As a result, the heated region of the tube 13, that is, the heated portion is increased in thickness, and immediately after the increase in thickness, the tube 13 moves in the direction of the tube axis while being cooled and cured, so that hot upsetting is continuously performed. . The thickness increase rate of the tube wall at this time is determined by the ratio of the pushing speed of the rear clamp 25 and the moving speed of the induction coil 35. In this embodiment, the moving speed of the induction coil 35 is constant, and the pushing speed of the rear clamp 25 is gradually increased. Thereby, the thickness increase rate increases as the induction coil 35 moves, and the transition portion 13bd is formed.
[0043]
  Then, when the induction coil 18 reaches the bending position OA, the induction coil 35 is stopped and the bending operation is started. That is, with the heating and cooling medium spraying by the induction coil 35 continued, the operation of the main bending cylinder 23 (see FIG. 2) is started, the bending arm 17 is swung through the rack 22 and the pinion 21, and at the same time the compression cylinder 31 is activated. As a result, as shown in FIGS. 3D and 4A, the tube 13 is continuously bent and a bent tube portion 13a is formed. At this time, the operating speed of the compression cylinder 31 is pushed at a speed at which the rear end of the tube 13 can secure a desired compression rate compared to the bending speed (the speed at which the pipe 13 passes the bending position OA). It is determined as follows. Thereby, compression of a desired compression rate can be added to the pipe 13 of a bending process position during bending, and the thinning of a bending outer peripheral side pipe wall can be suppressed. Here, in setting the operating speed of the compression cylinder 31, the compression cylinder 31 itself is moved together with the rack 22 for turning the bending arm 17, and the moving speed v is relative to the bending speed V.
  v = V × Rs / R
  (Where Rs is the pitch circle radius of the pinion 21 and R is the bending radius of the pipe)
This should be determined in consideration of this.
[0044]
  In the above bending process, at the start of the bending process, as shown in FIG. 3 (d), the tube wall is in a thickened state, and in this state, the bending process is started. Even when the thickness of the inner tube wall is increased, there is no sudden thickness difference between the tube wall of the previous straight tube portion. For this reason, unstable deformation such as looseness hardly occurs. Moreover, the region of the tube 13 at the bending position OA is always bent during the bending process, as shown in FIG. Since the outer peripheral surface on N is regulated, stable bending deformation occurs, and the occurrence of looseness and flattening can be prevented. Further, since the bent pipe portion 13a formed by bending deformation is always regulated by the regulating surface 42 of the shape maintaining guide 41, the occurrence of unevenness and flattening can be prevented from this point. Furthermore, by arranging the induction coil 35 in the pipe, it is possible to further prevent the occurrence of looseness compared to the case where the induction coil 35 is arranged outside the pipe. This is due to the following reason. That is, as shown in an enlarged view in FIG. 5, when the tube 13 is heated by the induction coil 35 disposed in the tube, the tube inner surface side mainly generates heat, and the outer surface side is heated by heat transfer from the inner surface. For this reason, the temperature on the inner surface of the tube is higher than that on the outer surface of the tube, and the temperature unevenness is also increased. For example, when the inner surface of the tube is heated to 950 ° C. and the temperature is raised, the temperature range on the inner surface of the tube is about 950 ± 20 ° C., whereas it is about 920 ± 5 ° C. on the outer surface of the tube. . If the temperature is high and the unevenness is large, the unevenness is likely to occur, so that the unevenness is more likely to occur on the inner surface side of the tube than on the outer surface side of the tube. However, the bending radius R on the tube inner surface side₂Is the bending radius R on the tube outer surface side₁Therefore, the compression rate accompanying bending is smaller than that of the outer surface side, and therefore, it is difficult to generate a jumble. On the other hand, when heating by an induction coil is performed from the outside of the tube as in the prior art, the temperature on the outer surface side of the tube is high and the temperature unevenness is liable to occur, and the unevenness is likely to occur on the outer surface side of the tube. Since the compression ratio associated with is larger than that on the inner surface side, looseness is more likely to occur. Thus, the occurrence of looseness can be further suppressed by arranging the induction coil in the tube.
[0045]
  As described above, in this embodiment, occurrence of looseness and flattening can be suppressed by using the shape maintaining guide and adopting heating from the inside of the tube. For this reason, for example, 1.5DR bending can be performed at 3 to 6 mm / second at a bending speed that is significantly increased as compared with the prior art. In addition, since it is not necessary to attach a flattening prevention jig by manual work, which is conventionally performed, there is no problem in increasing the bending speed.
[0046]
  As shown in FIG. 4A, when the bending process proceeds and the bending arm 17 turns to the position where the predetermined bending angle θ is reached, the turning of the bending arm 17 is stopped. Next, as shown in FIG. 4B, with the heating by the induction coil 35 and the blowing of the cooling medium 36 being continued, the induction coil 35 is moved in the tube axis direction and toward the rear end of the tube, and at the same time for compression. The cylinder 31 pushes the rear end of the pipe 13 in the pipe axis direction. Thereby, a hot upsetting process will be given to the straight pipe part following the curved pipe part 13a. Also at this time, the moving speed of the induction coil 35 and the pushing speed of the tube end are set so that the thickness increase rate of the tube wall gradually decreases as the distance from the curved tube portion 13a increases. Thereby, as shown in FIG.4 (c), the transition part 13be whose thickness decreased gradually is formed. Further, when the pipe end is pushed, the rear end of the pipe 13 held by the rear clamp 25 is moved from the bending position OA to a predetermined distance c (to the straight pipe end 13c of the metal bent pipe 13A shown in FIG. Push in until it reaches a length equal to the required length c). As a result, even if there is a dimensional error during the production of the straight pipe 13 or a dimensional error that occurs during bending, it can be absorbed and a product with extremely accurate dimensions can be obtained. As described above, the flanged metal curved pipe 13A having the shape shown in FIG. 7 can be manufactured.
[0047]
  The obtained metal bent tube 13A has almost no looseness or flatness and is excellent in dimensional accuracy. Further, since the flanges 14 are attached to both ends of the pipe at the time of bending, the flange 14 holds the pipe 13 in a perfect circle, and this exhibits the effect of suppressing flatness that may occur in the bent pipe portion 13a. In this respect, flattening is also suppressed. In addition, there is no large step between the bent inner tube wall and the straight tube portion connected to it, so there is no stress concentration, excellent strength characteristics, and no great resistance to fluid flowing inside. It has characteristics.
[0048]
  In the above embodiment, the bending process is performed on the flanged straight pipe 13, but the straight pipe 13 used for the bending process is not limited thereto, and may be performed on a flangeless pipe. Even in this case, processing that needs to be performed on the pipe end, for example, groove processing, is performed at the straight tube stage prior to bending, which is far more processing than when performing after bending. Since it becomes easy, it is preferable.
[0049]
  In the above-described embodiment, the shape maintaining guide 41 having an integral structure is used. However, the shape maintaining guide is not limited to the one having the integral structure, and components can be appropriately selected so that different bending radii and different tube diameters can be easily handled. You may make it comprise combining. FIG. 8 shows a shape maintaining guide 41A according to an embodiment in that case. This shape maintaining guide 41A can be used for pipes 50a, 50b and 50c having different outer diameters, and a plurality of anti-flat plates 51a and 51b are provided on the main shaft 16 of the bending arm 17 from the bending arm 17 side. 51c, the attachment plate 52, the looseness prevention member 53a, the attachment plate 52, the plurality of flattening prevention plates 51c, 51b, 51a, and the presser 54 are attached in a stacked form and fastened with a nut 55 to be fixed. As shown in FIG. 9 (a), the looseness prevention member 53a has a partial disk shape as a whole, and a fitting groove 57 for fitting to the main shaft 16 is formed in the central region, and an arcuate circumferential surface is formed. A loose regulating surface 58 for regulating the outer peripheral surface of the bent inner portion of the bent pipe portion of the tube 50a is formed. As shown in FIG. 9B, the loose regulating surface 58 is formed of an arcuate surface that conforms to the outer peripheral surface of the bent inner portion of the bent tube portion. If the width and the central angle α of the loose regulation surface 58 are too small, the effect of preventing looseness is insufficient, and thus a certain size or more is necessary. However, if the width is too large, the looseness prevention member 53a becomes large and the equipment cost increases. Increasing or handling becomes difficult. Therefore, the center angle α is preferably selected to be about 30 to 150 °. The looseness prevention member 53a shown in the figure is used for a large-diameter pipe 50a, and is made to have a size corresponding to the outer diameter and bending radius of the pipe 50a. In addition, a looseness prevention member having a size corresponding to the pipes 50b and 50c having other outer diameters is prepared, and can be used by replacing the looseness prevention member 53a.
[0050]
  As shown in FIGS. 10A and 10B, the flattening prevention plate 51 a is formed as a whole by a partial disk-like flat plate, and has a hole 60 into which the main shaft 16 is inserted at the center. And the arc-shaped area | region 61 shown by hatching in Fig.10 (a) forms the flat control surface which controls the outer peripheral surface on the bending neutral part NN of the curved pipe part of the pipe | tube 50a. In this embodiment, the flat regulating surface 61 is simply a flat surface, but may be an arcuate surface adapted to the outer peripheral surface of the curved pipe portion of the tube, if necessary. In FIG. 8 (b), the anti-flat plates 51b and 51c have the same structure as the anti-flat plate 51a, but the outer diameters are set to be small so as not to interfere with the pipe having a larger diameter than the pipe to be used. Yes.
[0051]
  When bending the large-diameter pipe 50a using the shape maintaining guide 41A having the above-described configuration, the parts are assembled and used as shown in FIG. As a result, in the bent tube 50a, the region at the bending deformation position and the formed bent pipe portion are regulated by the loose restriction surface 58 of the loose prevention member 53a at the outer peripheral surface of the bent inner portion. In addition, the outer peripheral surface of the bending neutral portion is regulated by the anti-flat plates 51a and 51a on both sides to prevent flattening. Next, when bending the minimum diameter pipe 50c using the shape maintaining guide 41A, as shown in FIG. 11A, a looseness prevention member 53c for the pipe 50c is attached, and the pipe 50c is attached. Only the anti-flat plate 53c is disposed on the upper side of the plate. Thereby, it is possible to perform a bending process on the small-diameter pipe 50c while restricting the outer peripheral surface of the bending inner portion and the outer peripheral surface of the neutral position. Further, when the bending process is performed with the small-diameter pipe 50c but with a large bending radius, as shown in FIG. 11 (b), the looseness prevention member 53d for the pipe 50c and corresponding to the one with a large bending radius is used. Are attached, and large-diameter flattening prevention plates 51a and 51a are arranged at positions where they contact the tube 50c. Thereby, it is possible to perform a bending process while regulating the outer peripheral surface of the bending inner portion and the outer peripheral surface of the neutral position with a large bending radius with respect to the small-diameter pipe 50c. As described above, the shape maintaining guide 41A having this configuration can cope with changes in bending processing conditions such as a pipe diameter and a bending radius by exchanging some parts. Compared with the case of using, it has the advantage that the condition changing work is easy and the equipment cost can be reduced.
[0052]
  FIGS. 12-14 shows the shape maintenance guide 41B which concerns on other embodiment. The shape maintaining guide 41B uses wide flattening prevention plates 51 and 51 that can be used in common for pipes having different pipe diameters and different bending radii. As the looseness preventing member, when the bending radius is small, as shown in FIG. 12, a cylindrical body 65 having a loosening restriction surface 66 formed on the outer periphery of the cylindrical surface is used, and when the bending radius is large, as shown in FIG. As shown in FIG. 14, the arc-shaped member 67 having the irregular regulating surface 68 formed on the outer periphery of the arc-shaped member is used, and even when the pipe diameter is large, as shown in FIG. An arcuate member 70 having a loosely restricting surface 71 is used. In addition, cylindrical spacers 72, 73, 74 and the like are attached to the main shaft 16 for adjusting the positions of the anti-flat plates 51, 51. The shape maintaining guide 41B having this configuration can easily cope with different bending conditions such as different pipe diameters and different bending radii by exchanging some parts.
[0053]
  In any of the above embodiments, the permanent mold 40 used for preventing looseness and flattening includes the shape maintaining guides 41, 41A, 41B and the like that rotate integrally with the bending arm 17. It is not always necessary to rotate together with the bending arm 17, and it may be configured to be fixedly arranged at the bending position. FIG. 15 (a) shows a permanent tool 40A fixed at a fixed position. The permanent mold 40A includes a support arm 80, and a die-shaped mold 81 held by the support arm 80 so as to be positioned on the bending position OA of the tube 13. The mold 81 is The tube 13 includes a regulating surface 82 that regulates the outer circumferential surface of the bending inner portion and the outer circumferential surfaces of both sides of the bending neutral portion in the region located at the bending position. By using this permanent mold 40A, it is possible to prevent fluttering and flattening at the time of bending of the pipe, and it is possible to perform bending at high speed.
[0054]
  The tool 81 used for the permanent tool 40A is not limited to an integral structure as shown in FIG. 15 (b), and the outer peripheral surface of the bent inner portion of the tube 13 is shown in FIG. 15 (c). Two anti-flat plates 86, 86 each provided with a loose prevention member 84 having a loose restriction surface 85 for preventing looseness and a flat restriction surface 87 for restricting the outer peripheral surface of the bending neutral portion of the tube 13. It can be set as the structure provided with. With this configuration, it is possible to easily cope with a change in bending process conditions by replacing the looseness prevention member 84 or the flattening prevention plate 86, changing the position, and the like. Further, in the permanent tool 40A shown in FIG. 15 (c), instead of the loose prevention member 84, a roll having a loose restriction surface formed on the circumferential surface is used, or a roll is used instead of the flattening prevention plate 86, etc. It is also possible to make changes.
[0055]
  In the bending method of the embodiment shown in FIGS. 3 and 4, the induction coil 35 is stopped at the bending position OA during the period in which the pipe 13 is bent, and the obtained metal bent pipe 13A is obtained. The bent pipe portion 13a (see FIG. 7) has a constant bending radius R over the entire angle range. However, the present invention is not limited to this bending method, and the bending start region of the bent pipe portion is gradually decreased so that the bending radius becomes a predetermined bending radius R from a bending radius larger than the predetermined bending radius R. The bending end region can also be applied to a method of bending so that the bending radius gradually increases from a predetermined bending radius R, that is, blur bending. Hereinafter, an embodiment in this case will be described. FIG. 16 shows a bent metal tube 13B manufactured by blur bending, and this bent metal tube 13B has a bent tube portion 13Ba (angle θ).₀) And straight tubular tube ends 13Bb and 13Bc (length b) at both ends thereof₁, C₁Area). The curved pipe portion 13Ba formed here has a blurred bent portion (angle θ₁, Θ₂Region and angle θ_Four, Θ_FiveArea) and the central bend (angle θ)_ThreeArea). The steady bending portion is a region having a constant bending radius R, and the blur bending portions on both sides of the steady bending portion are bent radius R as the distance from the steady bending portion increases._GIs a region gradually increasing from a predetermined bending radius R. Further, the blurred bending portion is provided with an instruction angle θ (an angle when the entire bending tube portion is set to a constant bending radius R, that is, straight pipe end portions 13b and 13c having lengths b and c shown in FIG. An area (angle θ) set within a range of the sandwiched curved pipe portion 13a equal to the angle θ.₂, Θ_FourAnd an area (angle θ) set on the outer side (in the area corresponding to the straight tubular tube ends 13b and 13c shown in FIG. 7).₁, Θ_FiveTherefore, the angle θ of the curved pipe portion 13Ba₀Is wider than the indicated angle θ.
[0056]
  Next, a method of manufacturing the metal bent pipe 13B by bending a metal straight pipe will be described. The bending apparatus shown in FIGS. 1 and 2 may be used as it is for manufacturing the metal bent pipe 13B, but in order to prevent the occurrence of looseness better, the shape maintaining guide 41C shown in FIG. Is preferably used. The shape maintaining guide 41C includes, on its outer peripheral surface, a regulating surface 42C that regulates the outer circumferential surface of the bent inner portion and both sides of the bent neutral portion of the bent tube portion 13Ba, and the bottom of the regulating surface 42C is In a plane perpendicular to the rotation axis of the shape maintaining guide 41C, the shape is adapted to the outer peripheral surface of the bent inner portion of the bent tube portion 13Ba. That is, the portion corresponding to the steady bent portion at the bottom of the regulating surface 42C has a constant radius R.₁The portions corresponding to the blurred bent portions on both sides thereof have a shape in which the radius gradually changes.
[0057]
  At the time of bending, first, the straight pipe 13 to be bent is set as shown in FIG. 18A, and the induction coil 35 is directed from the pipe tip side toward the bending position OA while energizing the induction coil 35. Move at a predetermined speed. And the induction coil 35 is at a distance b from the tube end.₁When reaching a position separated by (a distance equal to the length of the straight tubular tube end portion 13Bb formed on the metal bent tube 13B), bending is started while the movement of the induction coil 35 continues. That is, the feeding of the tube 13 in the tube axis direction is started, and the bending arm 17 is swung while gradually increasing the swirling speed to reach a constant swirling speed. At the same time, the movement speed of the induction coil 35 is gradually decreased in such a way as to compensate for the increase in the rotation speed of the swivel arm (so that the relative movement speed of the heating section formed on the pipe by the induction coil 35 is constant). go. Thereby, the pipe 13 is bent. The bending radius at this time is the ratio of the relative moving speed of the heating unit to the tube (= the moving speed of the induction coil 35 + the moving speed of the tube according to the turning speed of the turning arm 17) to the turning speed of the bending arm (that is, (Relative movement speed of the heating section with respect to the tube / bending arm turning speed), the turning speed of the bending arm 17 is gradually increased as described above, and the moving speed of the induction coil 35 is gradually reduced. Thus, the bending radius is considerably larger than the predetermined bending radius R at the start of bending, and gradually decreases as the bending process proceeds. Here, the turning of the bending arm 17 and the movement of the induction coil 35 cause the bending arm 17 to move at an angle θ as shown in FIG.₂The turning speed is set to a constant speed at the time of turning, and the induction coil 35 is set to stop at the bending position OA in synchronization with the turning speed. Thereby, the bending radius becomes the predetermined bending radius R when the induction coil 35 reaches the bending position OA. As described above, the blurred bending portion on the bending start side (angle θ of the metal bending tube 13B in FIG. 16).₁, Θ₂Region) is formed. By forming the blur bending portion in the bending start region in this way, it is avoided that the tube wall of the bending inner portion is suddenly increased in thickness, and unstable deformation such as looseness is less likely to occur. Further, at the time of this bending process, the induction coil 35 is located at a position farther from the bending end position OA toward the distal end side of the pipe. Therefore, the bending deformation progressing portion of the pipe is located away from the bending position OA. However, since the regulating surface 42C of the shape-retaining guide 41C exists at a position facing the bending deformation progression portion, it is the outer circumferential surface on both sides of the bending inner portion and the bending neutral portion of the bending deformation progression portion. To regulate. For this reason, looseness and flatness are prevented. Strictly speaking, the bottom surface of the regulating surface 42C of the shape maintaining guide 41C is bent inside the bending deformation progressing portion of the pipe as the blur bending portion is bent (with the rotation of the shape maintaining guide 41C). Although it is away from the outer peripheral surface of the part, the amount thereof is small, so that it is possible to suppress the bulging of the tube wall when the jaggedness is generated, and to exhibit the jumble prevention effect. Further, in order to further prevent the looseness, the center position of the shape-retaining guide 41 is moved with the rotation of the shape-retaining guide 41C, and the bottom surface of the regulating surface 42C is the bending inner portion of the bending deformation progressing portion of the pipe. The outer peripheral surface may always be regulated accurately.
[0058]
  After the induction coil 35 reaches the bending position OA, the bending process is continued with the induction coil 35 stopped at that position. Thereby, the bending process with the fixed radius R is performed. Then, as shown in FIG. 18C, the bending arm 17 further has an angle θ_ThreeAt this point, while gradually reducing the turning speed of the bending arm 17, the movement of the induction coil 35 in the tube axis direction toward the rear end of the pipe is started, and the moving speed at that time is changed to the turning of the bending arm. Increase gradually to compensate for the decrease in speed. As a result, the bending process is performed while the bending radius is gradually increased, and the blurred bending portion on the bending end side is formed. Then, as shown in FIG. 19, the bending arm 17 has an angle θ_FourThe induction coil 35 is c from the rear end of the pipe₁It is set so that the bending process is completed by reaching a position separated by (a distance equal to the length of the straight pipe end 13Bc formed on the metal bent tube 13B). Thereby, the blur bending part of a predetermined angle range is formed. Even in this blur bending, since the regulating surface 42C exists at a position facing the bending deformation progressing portion of the tube, the occurrence of unevenness and flatness are prevented. As described above, the bent metal pipe 13A having the shape shown in FIG. 16 can be manufactured.
[0059]
  In addition, in embodiment shown in FIGS. 16-19, as shown in FIG. 17, the bottom part of the control surface 42C currently formed in the shape maintenance guide 41C is made into the bending inner part outer peripheral surface of the curved pipe part which should be formed. Although the shape is adapted, the shape of the bottom of the regulating surface 42C does not necessarily need to be exactly the shape that fits the outer peripheral surface of the bent inner side of the bent tube portion, and may be slightly shifted. For example, the region facing the blur bending portion may be approximated by a straight line shape or a simple arc shape, thereby reducing the manufacturing cost of the shape maintaining guide 41C. In addition, as a shape maintenance guide in the case of performing the blur bending shown in FIGS. 18 and 19, an assembly type shape maintenance guide as shown in FIGS. 8 to 14 may be used, and further, the shape maintenance guide may be used. Instead of the guide, a permanent tool 40A provided separately from the bending arm 17 as shown in FIG. 15 may be used. In that case, it is preferable that the mold 81 that regulates the bending deformation progressing portion of the pipe is configured to be able to move in the tube axis direction in conjunction with the movement of the induction coil and to always restrict the bending deformation progressing portion. Further, in the above embodiment, when performing blur bending, the moving speed of the induction coil 35 is increased or decreased to compensate for the increase or decrease of the swing speed of the swing arm, and the tube of the heating unit formed on the tube by the induction coil 35 The relative movement speed with respect to is constant. This is preferable because an advantage that the amount of heat that the induction coil 35 should input to the tube can be made constant is preferable, but it is not an essential requirement when performing blur bending. Therefore, the moving speed of the induction coil 35 and the turning speed of the bending arm 17 are not necessary. Can be appropriately changed.
[0060]
【The invention's effect】
  According to the method and the apparatus of the present invention, it is difficult to bend at the time of bending a metal pipe.as well asThe bending speed can be increased while preventing flattening, and the manufacturing cost of the metal bent pipe can be reduced. In addition, it is possible to bend a pipe with a flange attached to the pipe end at the straight pipe stage, or to bend a pipe with a grooved pipe end at the straight pipe stage. Compared with the case of groove processing, it is possible to greatly reduce the costs of flange mounting and groove processing, and from this point, the manufacturing cost of the metal bent pipe can be greatly reduced. Thus, the present invention has an effect that a high-quality metal bent pipe can be manufactured at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a bending apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of the bending apparatus shown in FIG.
3 (a), (b), (c), and (d) are schematic cross-sectional views for explaining a bending operation by the bending apparatus shown in FIG.
4A, 4B, and 4C are schematic cross-sectional views for explaining a bending operation performed by the bending apparatus shown in FIG.
5 is an enlarged schematic cross-sectional view showing a region in which bending deformation of a pipe occurs in the bending apparatus of FIG.
FIG. 6A is a schematic cross-sectional view at a bending position between the forming and maintaining guide and the pipe.
  (B) is a schematic cross-sectional view showing the same part as (a) with the tube away from the shape maintenance guide.
7 is a schematic cross-sectional view of a metal bent pipe manufactured by the bending apparatus shown in FIG.
8A is a schematic plan view showing a modification of the shape maintaining guide used in the bending apparatus shown in FIG. 1. FIG.
  (B) is a schematic sectional view taken along line FF in (a).
9A is a schematic plan view of a looseness prevention member used in the shape maintenance guide of FIG.
  (B) is a schematic cross-sectional view taken along line GG in (a).
10A is a schematic plan view of an anti-flat plate used in the shape maintenance guide of FIG.
  (B) is a schematic cross-sectional view taken along line HH in (a).
FIGS. 11A and 11B are schematic cross-sectional views of the same part as FIG. 8B, showing a state in which the shape-retaining guide of FIG. 8 is used under different bending conditions.
12A is a schematic plan view showing still another modified example of the shape maintaining guide used in the bending apparatus of FIG. 1. FIG.
  (B) is a schematic sectional view taken along line JJ of (a).
13A is a schematic plan view showing a state in which the shape maintenance guide of FIG. 12 is used under different bending conditions.
  (B) is a schematic sectional view taken along the line KK in (a).
14A is a schematic plan view showing a state in which the shape maintenance guide of FIG. 12 is used under further bending conditions.
  (B) is the MM arrow schematic sectional drawing of (a).
FIG. 15A is a schematic plan view of a bending apparatus using a modification of a permanent tool.
  (B) is a schematic cross-sectional view taken along the line PP in (a).
  (C) is schematic sectional drawing which shows the modification of the tool 81 shown in (b)
FIG. 16 is a schematic cross-sectional view showing another example of a metal bent pipe manufactured in an embodiment of the present invention.
17 is a schematic cross-sectional view of a shape-retaining guide used for manufacturing the metal bent pipe shown in FIG.
18 (a), (b), and (c) are schematic cross-sectional views for explaining a bending operation for manufacturing the metal bent pipe shown in FIG.
19 is a schematic cross-sectional view for explaining a bending operation for manufacturing the metal bent pipe shown in FIG.
FIG. 20A is a schematic plan view of a conventional bending apparatus.
  (B) is a schematic plan view showing the bending apparatus of (a) in a state during bending.
  (C) is a schematic plan view of a bent pipe manufactured by this bending apparatus.
  (D) is a schematic cross-sectional view taken along line BB in (a).
FIG. 21 is a schematic cross-sectional view of a bending region for explaining problems in conventional bending processing.
FIG. 22 (a) is a schematic plan view showing another example of a conventional bending apparatus.
  (B) is a schematic cross-sectional view taken along the line CC of (a).
FIG. 23A is a schematic plan view showing still another example of a conventional bending apparatus.
  (B) is a schematic cross-sectional view taken along the line DD in (a).
[Explanation of symbols]
  13 tubes
  13A bent metal pipe
  13a Curved pipe
  13b, 13c Pipe end
  15 Machine body
  16 Spindle
  17 Bending arm
  18 Front clamp
  20 Drive means
  23 Main bending cylinder
  25 Rear clamp
  26 Rear clamp support
  28 Pressing device
  30 connecting plate
  31 Cylinder for compression
  35 induction coil
  36 Cooling medium
  38 high frequency transformer
  39 Motor for moving transformer
  40,40A Permanent tool
  41, 41A, 41B, 41C Shape maintenance guide
  42,42C Regulatory aspects
  42a Jabara regulation
  42b Flat regulating surface
  46 Pipe control means
  47 Presser roller
  50a, 50b, 50c pipe
  51a, 51b, 51c Flatness prevention plate
  53a, 53c, 53d
  58 Jabara Regulation
  61 Flat regulation surface

Claims (14)

For a straight pipe made of metal, a small section in the tube axis direction of the tube is heated to a temperature at which plastic deformation is easy by induction heating, and the heating part formed by the heating is moved relative to the tube axis direction. In a method for producing a metal bent pipe having a bent pipe portion and straight pipe end portions at both ends thereof by applying a bending operation to bend and deform immediately after applying a bending moment to the heating portion, The induction coil for the induction heating is disposed only inside the tube, and the outer peripheral surface of the bending inner portion of the outer peripheral surface of the tube and the outer peripheral surface of both sides of the bending neutral portion are formed by a permanent tool. Before the bending operation for the pipe, the pipe is compressed in the axial direction with respect to the straight pipe portion adjacent to the tip of the bending start point of the pipe. The pipe wall thickness is increased by hot upsetting to increase the wall thickness. Do gradually increasing toward the lower starting point, method for producing a metal bent tube, characterized in that where the structure moves to the bending operation subsequent to the operation. When the bending operation is performed on the pipe and the end point of bending of the pipe is reached, hot upsetting is performed to compress the pipe in the axial direction of the straight pipe portion adjacent to the rear to increase the wall thickness. The manufacturing method of the metal bending pipe of Claim 1 which performs operation which reduces pipe | tube thickness gradually from the said bending end point by a process. For the straight pipe portion located behind the bending end point of the pipe, a hot upsetting process is performed to increase the pipe wall thickness by pushing the pipe end in the pipe axis direction, and the pushing end position of the pipe end at that time The manufacturing method of the metal bending pipe of Claim 1 or 2 which adjusts positioning of the pipe end in the manufactured metal bending pipe by adjusting . At the start of the bending process for the pipe, the bending arm is turned and the induction coil is moved in the direction of the pipe axis from the position farther from the distal end side of the pipe than the predetermined bending position toward the bending position. By setting the arm turning speed and the moving speed of the induction coil so that the ratio of the relative moving speed of the heating unit to the bending arm turning speed gradually decreases as the bending process proceeds, the bending radius is reduced. Bending to gradually decrease from a large bending radius, and after the induction coil reaches the bending position, perform bending with a constant bending radius with the induction coil stopped at the bending position. The manufacturing method of the metal curved pipe of any one of Claim 1 to 3 . Bending with a constant bending radius is continued with the induction coil being stopped at a predetermined bending position, and when approaching the end of the bending process, the bending coil continues to rotate and the induction coil is moved to the predetermined position. Move from the bending position toward the rear end of the pipe in the direction of the pipe axis, and change the turning speed of the bending arm and the moving speed of the induction coil at the relative movement speed of the heating part to the pipe with respect to the turning speed of the bending arm. The metal according to any one of claims 1 to 4, wherein the bending is performed so that the bending radius gradually increases from a predetermined bending radius by setting the ratio to gradually increase as the bending progresses. A manufacturing method for curved pipes. The method of manufacturing a metal bent pipe according to any one of claims 1 to 5, wherein the bending operation is performed in a state in which a compressive force in a pipe axis direction is applied to the pipe . The method of manufacturing a metal bent pipe according to any one of claims 1 to 6, wherein a flanged bent pipe is obtained by attaching the flange to the pipe end at a straight pipe stage and then subjecting the pipe to the bending operation . The said pipe | tube is used for the said bending process after forming the groove for welding in the pipe end in the pipe end, The curved pipe with a welding groove | channel is obtained in any one of Claim 1-6 . A method of manufacturing a metal bent pipe. A pipe restricting means for holding a straight pipe portion behind the bending position in a predetermined travel path when a metal straight pipe to be bent advances in the pipe axis direction through a predetermined bending position; A clamp arm that holds the tip of the tube, and a bending arm that can pivot about a predetermined fulcrum, and a small section in the tube axis direction that is inserted into the tube and located at the bending position of the tube is induction-heated. An induction coil, cooling means for cooling the tube by spraying a cooling medium on the tube tip side of the region heated by the induction coil, and the bending arm so as to apply a bending moment to the tube by turning the bending arm Driving means for rotating the tube directly or through the tube or a combination of both, and during bending operation, the outer peripheral surface of the bending deformation portion of the outer peripheral surface of the tube and the outer periphery on both sides of the bending neutral portion surface A permanent mold that regulates the shape of the pipe, and the permanent mold includes a shape-retaining guide provided so as to pivot integrally with the bending arm. For the deformation advancing part and the bent pipe part that has been bent and deformed, the outer peripheral surface of the bending inner part is restricted to prevent the occurrence of looseness, and the outer peripheral surfaces on both sides of the bending neutral part are restricted. An apparatus for bending a metal pipe, comprising a flat regulating surface for preventing flattening . The shape maintaining guide includes a main shaft that rotates integrally with the bending arm, a loose prevention member provided with the loose restriction surface, two anti-flat plates provided with the flat restriction surface, the loose prevention member, and The metal tube bending apparatus according to claim 9, further comprising means for attaching the two flattening prevention plates to the main shaft in a detachable form . The looseness restricting surface of the looseness preventing member is composed of an arcuate surface that conforms to the outer peripheral surface of the bent inner portion of the bent pipe portion formed by bending, and the flatness restricting surface of the antiflattening plate is composed of a flat surface. The metal pipe bending apparatus according to claim 10 . The anti-flat plate has a flat regulating surface that is also widened in the bending radius direction so that the anti-flat plate can be commonly used for bending with different pipe outer diameters and different bending radii. The metal tube bending apparatus according to claim 10 or 11, wherein a plurality of bending processes corresponding to bending processes with different bending radii are prepared, and those suitable for bending conditions are attached . The pressure device further comprises a pressing device that presses the rear end of the tube whose tip is constrained by the clamp of the bending arm so as to reduce the tube length in the tube axis direction and to the clamp. A bending apparatus for a metal pipe according to claim 1 . The metal tube bending apparatus according to any one of claims 9 to 13, further comprising means for moving the induction coil in a tube axis direction in a region before and after a bending position .

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