Mold and processing method using the same

Abstract

Provided is a mold capable of suppressing the occurrence of breakage and wrinkles of a workpiece during bending processing, and a processing method using the mold. The mold is a mold for bending processing a plate-shaped workpiece (100). The mold includes a lower mold (20) on which the workpiece (100) is placed, and an upper mold (30) formed with a pressing surface (32) that presses the workpiece (100) toward the lower mold (20). The lower mold (20) includes a lower side movable portion (60) that is slidable in the same direction as the moving direction of the upper mold (30), a reaction force generating member (70) that elastically supports the lower side movable portion (60) from below, and a receiving member (54) located at both side portions of the lower side movable portion (60). The pressing surface (32) is convex in cross-sectional circular arc shape toward the lower mold (20) and extends in the long side direction of the workpiece (100). The deepest position of the lower end portion of the pressing surface is a position deeper than a position obtained by subtracting the finish machining dimension of the inner diameter of the workpiece from the upper surface of the lower mold.

Description

Technical Field

[0001] This invention relates to a mold for bending a plate-shaped workpiece into a tubular shape, and a processing method using the mold. Background Technology

[0002] Conventionally, a UO bending processing method is known as a processing method for such molds. This UO bending processing method includes a first step of processing a workpiece into a U-shape and a second step of processing the U-shaped workpiece into an O-shape. The above processing method involves placing a metal sheet, which is the workpiece, above a mold (fixed part) with a groove, and pressing it from above using a punch (movable part) (see, for example, Patent Documents 1 and 2).

[0003] Patent document 1 discloses the following processing method: placing a sheet material on a lower mold with a concave die and pressing the sheet material with an upper mold with a convex die to form a U-shape.

[0004] Furthermore, Patent Document 2 discloses an apparatus in which, when forming using a punch with a protrusion and a die with a concave portion, the forming is performed while the steel plate is pressed toward the punch side and pressure is applied by a control device.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 58-107220

[0008] Patent Document 2: Japanese Patent Application Publication No. 2004-195504 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] In recent years, it has become known to produce bent products from plate-shaped metal-based composites made of metals such as aluminum and ceramics. Such metal-based composites, especially those made of aluminum and ceramics, are characterized by low ductility. Therefore, if bending is performed using existing methods, tensile stress (hereinafter also referred to as tension) acts on the outer side of the bent portion, easily leading to fracture and cracks. Furthermore, compressive force is easily applied to the inner side of the bent portion, and wrinkles are easily formed.

[0011] When such a metal-based composite (workpiece) is machined into a U-shape, in the processing method described in Patent Document 1, the tension generated from the bending point of the workpiece along the outer side when the workpiece is pressurized using the upper punch may cause the workpiece to break.

[0012] Furthermore, in the processing method described in Patent Document 2, processing can be performed simultaneously by pressing the workpiece in from below using upper and lower punches. However, since the concave end face of the die head is not a rounded surface, there is a technical problem that the tension generated from the bending point of the workpiece can easily escape into the gap and cause the workpiece to break.

[0013] Therefore, the present invention was created to solve the technical problem of providing a mold capable of suppressing the breakage and wrinkling of a workpiece during bending processing, and a processing method using the mold.

[0014] Technical solutions adopted to solve technical problems

[0015] To solve the aforementioned technical problems, the mold of the present invention is a mold for bending plate-shaped workpieces. The mold has a lower mold and an upper mold. The lower mold holds the workpiece, and the upper mold has a pressing surface that presses the workpiece towards the lower mold. The lower mold includes: a lower movable portion capable of sliding in the same direction as the movement direction of the upper mold; a reaction force generating member that elastically supports the lower movable portion from below; and receiving members located on both sides of the lower movable portion. The pressing surface faces the lower mold and has a convex, arc-shaped cross-section, extending along the long side of the workpiece. The maximum pressing position of the lower end of the pressing surface is deeper than the position after the inner diameter of the workpiece has been precisely machined down from the upper surface of the lower mold.

[0016] In this invention, when the upper die is moved downwards and the workpiece is pressed using a pressing surface, the workpiece is pressed against the lower die while a compressive force is applied to the workpiece from the vertical direction, thereby performing a U-shaped bending process. At this time, since the lower end of the pressing surface is pressed into a position deeper than the position after the workpiece's inner diameter has been machined down from the upper surface of the lower die, the workpiece is fixed in a holding manner throughout the entire range of the U-shape bending along the circular pressing surface. This allows sufficient stress to be applied to the workpiece while preventing slippage or misalignment. Therefore, breakage and wrinkling of the workpiece during bending can be suppressed.

[0017] Furthermore, it is preferable that the aforementioned reaction force generating component is a gas spring. By using a gas spring, the initial reaction force is stronger compared to using other reaction force generating components such as springs, and the workpiece can be firmly held by the upper and lower dies. Therefore, the workpiece is firmly held in a manner where it is gripped by a pressing surface with a circular cross-section, thereby applying sufficient stress to the workpiece while preventing slippage and misalignment. This improves formability.

[0018] Furthermore, it is preferable that multiple reaction force generating components are arranged along the long side of the lower die. With this configuration, even if the workpiece is elongated, a uniform reaction force can be generated along the long side, and the same bending process can be performed in each portion along the long side. Moreover, by arranging multiple gas springs along the long side of the lower die, a die of a length adapted to the long side dimension of the workpiece can be constructed.

[0019] Furthermore, it is preferable that the reaction force generating member described above can adjust the magnitude of the reaction force. With this configuration, the required reaction force can be appropriately set according to the size and strength of the workpiece, the pressing pressure of the upper die, etc., and sufficient reaction force can be generated relative to the bending stress required for bending processing.

[0020] Furthermore, preferably, the lower movable part includes a curved, concave pressing surface opposite to the pressing surface of the upper mold, wherein the difference between the diameter of the pressing surface and the diameter of the pressing surface of the upper mold is smaller than the thickness of the workpiece. With this configuration, the workpiece is pressed against the lower mold while ideally applying compressive force from above and below, thereby firmly holding the workpiece in a manner where it is held by the pressing surface, which has a circular cross-sectional shape. Therefore, formability is improved.

[0021] Furthermore, preferably, the pressing surface of the upper mold is formed by a cylindrical core member extending along the long side of the lower mold. This configuration allows for easy formation of the pressing surface. Additionally, by configuring the core member to be detachable, core members with different outer diameters can be easily provided according to the workpiece's thickness.

[0022] Furthermore, preferably, the lower movable part is housed inside the receiving member, and its movable range is the same as the maximum stroke distance of the reaction force generating member. With this configuration, it is possible to further press the upper die toward the workpiece after the full stroke of the reaction force generating member, thereby improving the formability of the workpiece.

[0023] Furthermore, it is preferable that the inner edge of the aforementioned receiving member is rounded with a radius smaller than that of the aforementioned pressing surface. This configuration helps to mitigate stress concentration during bending processes.

[0024] Furthermore, it is preferable that a hard chrome plating layer is formed on the surface of the lower movable part and the edge of the receiving member. This configuration can prevent wear on the mold.

[0025] Alternatively, the processing method preferably includes: a step of placing the workpiece in the lower mold; a step of pressing the workpiece with the upper mold; and a step of moving the lower movable part and the upper mold downward while applying force to the workpiece in the opposite direction to the moving direction of the upper mold using the reaction force generating member.

[0026] Alternatively, the processing method preferably includes: a step of placing the workpiece protected by the protective sheet on the lower mold; a step of pressing the workpiece using the upper mold; and a step of moving the lower movable part and the upper mold downwards while applying force to the workpiece in the opposite direction to the moving direction of the upper mold using the reaction force generating member.

[0027] Alternatively, preferably, the processing method includes a step of further bending the U-shaped member, which has been processed using the above-mentioned mold, into an O-shape and then finishing it into a pipe.

[0028] Invention Effects

[0029] According to the present invention, it is possible to obtain a mold capable of suppressing the occurrence of breakage or wrinkling of a workpiece during bending processing, and a processing method using the mold. Attached Figure Description

[0030] Figure 1 This is a perspective view showing the overall structure around the mold to which an embodiment of the present invention is applied, and the processing method using the mold.

[0031] Figure 2 This is a top view showing the lower mold in the mold.

[0032] Figure 3 It is along Figure 2 The section along line III-III represents a side view of the overall structure of the lower mold.

[0033] Figure 4 This is a longitudinal sectional view showing the process of U-shaped bending.

[0034] Figure 5 This is an enlarged longitudinal sectional view showing the main parts of the U-shaped bending process.

[0035] Figure 6A This is a flowchart illustrating the process of placing the workpiece in the lower die during U-bending machining.

[0036] Figure 6B This is a flowchart illustrating the process of pressing the workpiece with an upper die during U-shaped bending.

[0037] Figure 6CThis is a flowchart illustrating the process of pressing the workpiece with an upper die during U-shaped bending.

[0038] Figure 6D It is a process diagram showing the state of the component that generates the reaction force after it has completed its full stroke during the U-bending process.

[0039] Figure 6E This is a process diagram showing the state in which the upper die retracts during the U-shaped bending process.

[0040] Figure 7 This is a longitudinal sectional view showing the process of bending an O-shape.

[0041] Figure 8A This is a process diagram showing the process of placing a U-shaped component in the lower die of an O-shape during O-shaped bending.

[0042] Figure 8B This is a process diagram showing the process of moving the upper die of the O-shape downwards toward the U-shaped component during the O-shape bending process.

[0043] Figure 8C This is a process diagram showing the middle of the O-shaped bending process, in which the upper die of the O-shape moves downward toward the U-shaped component.

[0044] Figure 8D This is a process diagram showing the process of machining a U-shaped component into an O-shaped pipe during O-bending.

[0045] Figure 8E This is a process diagram showing the state in which the upper die of the O-shape retracts during the bending process of the O-shape. Detailed Implementation

[0046] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a perspective view of the mold 10 used in the bending machine 1 of the embodiment. Hereinafter, firstly, the mold 10 for processing the workpiece 100 into a U-shaped component 110 and the processing method will be described, and secondly, the mold 10A for processing the U-shaped component 110 into a pipe 120 and the processing method will be described.

[0047] The mold 10 bends the plate-shaped workpiece 100 into a U-shape. The mold 10 includes a lower mold 20 for placing the workpiece 100 and an upper mold 30 for pressing the workpiece 100.

[0048] like Figure 5As shown, the workpiece 100, which is the object of processing, mainly consists of a core portion 101 and skin portions 102, 102 disposed on the front and back sides of the core portion 101. The core portion 101 is made of a mixture of aluminum powder and tungsten powder, gadolinium oxide powder, or boron (B4C), thereby possessing shielding properties against radiation or neutron rays. The core portion 101 (workpiece 100) is in the form of a flat plate before processing (see reference). Figure 6A Such composite parts have lower ductility compared to aluminum alloys.

[0049] The skin portion 102 is configured to cover the front and back sides of the core portion 101 over approximately the entire surface area. The skin portion 102 is made of a highly ductile aluminum alloy. Each skin portion 102 is formed such that its thickness dimension is smaller than that of the core portion 101.

[0050] The upper mold 30 is configured to move vertically via a drive mechanism (not shown). The upper mold 30 includes a lower end portion 30a with a concave cross-section (see reference). Figure 5 The upper mold 30 has a base 38 and a core member 31 mounted on its lower end 30a. The core member 31 has a pressing surface 32 opposite to the lower mold 20. The core member 31 is a cylindrical member extending along the long side direction of the upper mold 30 (the extension direction of the workpiece 100). Figure 4 As shown, the core member 31 is fixed to the lower end 30a of the base 38 by a plurality of mounting bolts 33 (only one is shown in the figure) arranged at intervals along the long side of the upper mold 30. The core member 31 can be installed and removed by screwing in the mounting bolts 33. For example, by changing the core member 31 to a different outer diameter, the finishing inner diameter (outer diameter) of the tube formed from the workpiece 100 can be changed.

[0051] The pressing surface 32 faces the lower die 20 and has a convex cross-section arc shape, extending along the long side of the workpiece 100. For example... Figure 5 As shown, the maximum pressing position P1 of the lower end 32a of the pressing surface 32 is a position deeper than the position P2 after the workpiece 100 has been lowered from the upper surface 20a of the lower die 20 by the inner diameter finishing dimension L1. In other words, the pressing dimension L2 of the pressing surface 32 pressing into the upper surface 20a of the lower die 20 is set to be larger than the inner diameter finishing dimension L1 of the workpiece 100.

[0052] The upper mold 30 is positioned in a ready position for retraction upwards, located on the upper surface 54a of the receiving member 54 constituting the lower mold 20 (see reference). Figure 5The upper mold 30 is positioned further up and a specified space is provided between the upper mold 30 and the receiving member 54 to accommodate the workpiece 100. In addition, the upper mold 30 is configured such that, in the downward pressing position, the pressing surface 32 approaches the inner side of the receiving members 54, 54 of the lower mold 20 and then inserts between the receiving members 54, 54.

[0053] like Figure 1 , Figure 4 As shown, the lower mold 20 includes a mounting portion 50 fixed to the base portion 40, a lower movable portion 60, and a gas spring 70 as a reaction force generating member that supports the lower movable portion 60 from below. Specifically, in the mounting portion 50, along the long side direction A (refer to...) Figure 1 A concave groove 52 is formed. Receiving members 54, 54 are accommodated on both sides of the groove 52. The receiving members 54, 54 are then detachably fixed to the mounting portion 50 by a plurality of bolts 56 inserted from both sides into the mounting portion 50 (see reference). Figure 4 ).

[0054] The receiving member 54 sandwiches the lower movable part 60. The inner edge 54b of each receiving member 54 is formed into an inverted round shape (cylindrical surface) with a radius smaller than the radius L1 / 2 of the core member 31 (see reference). Figure 5 ).

[0055] The lower movable part 60 is configured to slide vertically between the receiving components 54. Figure 5 As shown, the lower movable part 60 includes a curved concave pressing bearing surface 62 opposite to the pressing surface 32 of the upper mold 30. The radius L3 of the pressing bearing surface 62 is set to be greater than or equal to the radius L1 / 2 of the pressing surface 32. In this embodiment, the difference (L3 - L1 / 2) between the radius L3 of the pressing bearing surface 62 and the radius L1 / 2 of the pressing surface 32 of the upper mold 30 is set to be smaller than the thickness L4 of the workpiece 100.

[0056] The cross-sectional shape of the two ends 62f, 62f of the pressing bearing surface 62 is an upwardly convex arc. The radius r3 of this end 62f is set to be smaller than the radius r4 of the inner edge 54b of the receiving member 54 (r3 < r4). In this way, the space formed by the clamping of the three members—the end 62f of the lower movable part 60, the inner edge 54b of the receiving member 54, and the workpiece 100—can be reduced. As a result, the tensile pressure generated in the workpiece 100 can be reduced, and fracture can be suppressed.

[0057] In addition, such as Figure 4As shown, when the lower movable part 60 is at its lowest point, it abuts against the bottom 20e of the lower mold 20. In other words, the lower movable part 60 abuts against the bottom 20e of the lower mold 20 to restrict its downward movement. The movable range of the lower movable part 60 is set to be the same as the maximum stroke distance of the gas spring 70.

[0058] like Figure 2 or Figure 3 As shown, there are multiple gas springs 70 arranged in a row directly below the lower movable part 60, with a predetermined interval along the long side direction A of the lower mold 20 (the extension direction of the workpiece 100). There are seven of them in this arrangement.

[0059] Each gas spring 70 has a cylinder 71 and a piston 72. Furthermore, the piston 72 is configured to adjust the reaction force according to the pressure of the gas filling the cylinder 71. For example, nitrogen is used as the filling gas. However, it is not limited to this; other types of gases or mixtures of these gases may also be used.

[0060] like Figure 4 As shown, the upper end face 73 of the piston 72 abuts against the lower surface 61 of the lowest end of the lower movable part 60. Furthermore, the gas spring 70 is configured to provide elastic support to the lower movable part 60 from below.

[0061] Next, along Figures 6A-6E The steps shown illustrate the processing method of the U-shaped component 110 using mold 10.

[0062] First, a protective film 103 is attached to the lower surface of the workpiece 100. The protective film 103... Figure 6A As shown in the figure, omitted in other figures. Figure 6A The process of placing the workpiece 100 onto the lower mold 20 is shown. In this process, as... Figure 6A As shown, the workpiece 100 is placed on the upper surface of the lower mold 20, with the protective film 103 facing downwards. Furthermore, the positioning fixture 80 is pre-fixed to the lower mold 20 using bolts 81. This facilitates the positioning of the workpiece 100. By using the positioning fixture 80, the center of the workpiece 100 in the width direction (short side direction) can be easily positioned at the center of the lower mold 20 in the width direction (short side direction). Therefore, the formability of the tube is excellent, and the processing accuracy is improved. By ensuring that the surface with the protective film is in contact with the lower mold 20, damage to the workpiece 100 during bending processing can be prevented.

[0063] If the workpiece 100 is placed on the upper surface of the lower mold 20, the two ends 62f, 62f of the lower movable part 60 and the upper surface parts 54a, 54a of the receiving member 54 abut against the lower surface of the workpiece 100. Additionally, the upper mold 30 is in a retracted position, which is omitted from the figure.

[0064] Figures 6B to 6D This is a process diagram showing the process of pressing the workpiece 100 using the upper mold 30. In this process, as... Figure 6B As shown, the upper mold 30 moves downward and presses the workpiece 100 using the pressing surface 32 of the core member 31. In this case, the pressing surface 32 of the upper mold 30 presses the workpiece 100 from the upper surface side and clamps the workpiece 100 between it and the pressing bearing surface 62 of the lower movable part 60. At this time, the gas spring 70 begins to move downward under the pressing force of the upper mold 30.

[0065] As the upper mold 30 moves further downward, such as Figure 6C As shown, with the movement of the upper die 30, the two sides of the workpiece 100 are bent so as to stand upright between the core member 31 and the receiving members 54, 54, and the central part of the workpiece 100 is gradually bent around the pressing surface 32 of the core member 31 in a circumferential direction. This suppresses deformation that would generate rapid tension, and the workpiece 100 is bent and deformed along the bending shape of the pressing bearing surface 62 and the pressing surface 32. In other words, with the bending deformation, the workpiece 100 is compressed along the thickness direction, centered on the portion abutted by the pressing bearing surface 62 of the lower movable part 60. Therefore, the skin portion 102 of the lower surface of the workpiece 100 moves along the extension direction together with the material of the adjacent core portion 101, thereby reducing tension. Therefore, since the workpiece 100's tension is eased due to the deformation during bending, breakage of the workpiece 100 at the lower surface is suppressed. In addition, it alleviates the compressive force on the upper surface of the workpiece 100, thereby suppressing the formation of wrinkles.

[0066] Thus, during the downward movement of the upper mold 30, the reaction force of the gas spring 70 is constantly applied to the lower movable part 60. Therefore, the workpiece 100 is always subjected to force in the opposite direction to the downward movement of the upper mold 30, i.e., upward. Here, the initial reaction force of the gas spring 70 is stronger than that of other reaction force mechanisms such as springs. Therefore, the workpiece 100 is firmly held between the lower mold 20 and the upper mold 30. That is, when the upper mold 30 presses the workpiece 100 disposed on the lower mold 20, the reaction force from the lower mold 20 constrains the workpiece 100. Thus, from the point of pressing with the upper mold 30 until the lower movable part 60 reaches its lowest point, a compressive force in the thickness direction is applied to the workpiece 100. This compressive force suppresses slippage between the mold 10 and the workpiece 100 and reduces tension in the direction of the portion abutting the pressing surface 62.

[0067] Furthermore, since the workpiece 100 is kept confined in a vertical direction during bending, the bending initiation point moves along the lower surface of the workpiece 100, preventing a concentration of bending stress on the workpiece 100. In other words, the bending initiation point of the workpiece 100 in the initial stage of bending is the portion where the pressing surface 32 abuts against the upper surface of the workpiece 100 and the portion where the workpiece 100 contacts the inner edges 54b of each of the supporting members 54. When the workpiece 100 is confined, if the upper die 30 and the lower movable part 60 slide downwards, the portion of the workpiece 100 that contacts the inner edge 54b moves downwards along the inner edge 54b, thereby preventing a concentration of bending stress on the workpiece 100.

[0068] Furthermore, the inner edges 54b of each receiving member 54 are formed into a rounded shape (cylindrical surface) with a radius smaller than the radius L1 / 2 of the core member 31. Therefore, while ensuring the contact area of ​​the workpiece 100 with respect to the inner edges 54b, it is possible to allow the workpiece 100 to move smoothly downward on the inner edges 54b. Thus, throughout the entire range of the U-shape bend, the workpiece 100 is gradually embraced by the core member 31, thereby applying sufficient stress to the workpiece 100 while preventing slippage or misalignment. In other words, the bending proceeds gradually, preventing the workpiece 100 from bending abruptly.

[0069] Then, as Figure 6D As shown, the upper mold 30 is moved further downwards, causing the lower surface 61 of the lowest end of the lower movable part 60 to abut against the bottom 20e of the lower mold 20. In this embodiment, as... Figure 5As shown, the maximum pressing position P1 of the lower end 32a of the pressing surface 32 is pressed deeper than the position P2 after the inner diameter L1 of the workpiece 100 has been machined down from the upper surface 20a of the lower mold 20. Thus, the workpiece 100 is fixed in a holding manner throughout the entire range of the pressing surface 32, which is bent into a U-shape along its circular cross-section, thereby applying sufficient stress to the workpiece 100 while preventing slippage or misalignment. Furthermore, the core member 31 is inserted entirely into the inner side of the lower mold 20.

[0070] Then, starting from the aforementioned contact state, the core member 31 is pressed further downward using the upper mold 30. In other words, an additional load is applied to the workpiece 100 to improve formability. As a result, a U-shaped member 110 that can be bent into the desired U-shape can be obtained.

[0071] Figure 6E The process of moving the upper die 30 upward and placing it in a retracted position is shown. When the upper die 30 moves upward, a gap is formed between the lower die 20 and the upper die 30. Since the pressing force of the upper die 30 no longer acts on the lower movable part 60 of the lower die 20, the reaction force of the gas spring 70 acts as a force to lift the workpiece 100 from the base part 40. Therefore, by retracting the upper die 30, the U-bent workpiece 100 can be easily removed from the bending machine 1.

[0072] Next, the mold 10A for machining the U-shaped component 110 into the pipe fitting 120 and the machining method will be described. For example... Figure 7 As shown, mold 10A bends the U-shaped component 110 into an O-shape. Mold 10A includes a lower O-shaped mold 20A for holding the U-shaped component 110 and an upper O-shaped mold 30A for pressing the U-shaped component 110.

[0073] The O-shaped upper mold 30A is configured to move vertically via a drive mechanism (not shown), and includes a base 37 and a pressing member 35 mounted on the base 37. Figure 7 As shown, a concave pressing surface 30g is formed at the lower part of the pressing member 35. The pressing member 35 is fixed to the base 37 by a plurality of mounting bolts 34 (only one is shown in the figure) arranged at intervals along the long side of the base 37. The pressing member 35 can be installed and removed by screwing in the mounting bolts 34. The pressing surface 30g has a cross-sectional arc shape extending along the long side of the U-shaped member 110. The radius of curvature of the pressing surface 30g corresponds to the radius of curvature of the outer diameter of the U-shaped member 110.

[0074] On both sides of the pressing surface 30g, inclined surfaces (opening surfaces) 36, 36 with a cross-section cone shape are formed in a manner continuous with the pressing surface 30g.

[0075] In the upward retracting preparation position, the upper O-shaped mold 30A forms a predetermined space between itself and the mounting portion 55 of the lower O-shaped mold 20A, allowing the U-shaped member 110 to be mounted. Furthermore, in the downward pressing position, the upper O-shaped mold 30A is configured such that the two upper ends 26, 26 of the lower O-shaped mold 20A (described later) are inserted into the inside of the inclined surfaces 36, 36, facing each other in a non-abutting state.

[0076] The lower O-shaped mold 20A includes a mounting portion 55 fixed to the base portion 40 by bolts 44. The mounting portion 55 has a generally trapezoidal cross-section. At the upper end of the mounting portion 55, there is a curved concave pressing bearing surface 57 that holds the U-shaped member 110. The radius of curvature of the pressing bearing surface 57 corresponds to the radius of curvature of the outer diameter of the U-shaped member 110. On both sides of the pressing bearing surface 57, there are upper end portions 26, 26 protruding toward the inclined surfaces 36, 36 of the upper O-shaped mold 30A.

[0077] Next, along Figures 8A to 8E The steps shown illustrate the processing method of the pipe fitting 120 using mold 10A.

[0078] Figure 8A The process of placing the U-shaped member 110 on the mounting portion 55 of the O-shaped lower mold 20A is shown. In this process, as... Figure 8A As shown, a U-shaped member 110 is positioned on the pressing surface 57 of the lower O-shaped mold 20A. Then, a cylindrical member 90, which acts as a core, is positioned inside the U-shaped member 110. The radius of curvature of the cylindrical member 90 is set to be the same as or slightly smaller than the radius of curvature of the inner diameter of the U-shaped member 110.

[0079] After the cylindrical member 90 is positioned inside the U-shaped member 110, the U-shaped member 110 is positioned using the positioning member 85. The positioning member 85 is approximately L-shaped and is detachably mounted relative to the outer side of the mounting portion 55. The positioning member 85 includes a reference plate 86 for positioning the two ends 115, 115 of the U-shaped member 110 at the same height. By using the positioning member 85, the U-shaped member 110 is positioned approximately horizontally on the mounting portion 55. After positioning, the positioning member 85 is removed from the mounting portion 55. Alternatively, by means of a mechanism not shown, the positioning member 85 can be configured to retract to a position where it does not interfere with the upper O-die 30A during O-shaped bending processing.

[0080] Figures 8B to 8D This is a process diagram showing the process of pressing the U-shaped component 110 using the O-shaped upper mold 30A. In this process, firstly, as... Figure 8BAs shown, the upper O-shaped mold 30A is moved downwards, and the two ends 115, 115 of the U-shaped member 110 approach and abut against the pressing surface 30g of the pressing member 35.

[0081] like Figure 8C As shown, when the O-shaped upper mold 30A moves further downward, the two ends 115, 115 of the U-shaped member 110 bend inward along the curved concave pressing surface 30g of the pressing member 35, and bend in a manner that embraces the outer peripheral surface of the cylindrical member 90. This suppresses deformation that would generate sharp tension, and simultaneously bends and deforms the straight portion of the U-shaped member 110 along the curved shape of the pressing surface 30g and the outer peripheral surface of the cylindrical member 90.

[0082] Then, as Figure 8D As shown, the O-shaped upper mold 30A is moved further downward, and in the final stage of bending deformation, the tube 120 is pressed by the pressing surface 30g, the pressing bearing surface 57, and the cylindrical member 90. Thus, the tube 120 bent into an O-shape can be obtained.

[0083] Figure 8E The process of moving the O-shaped upper die 30A upward and placing it in a retracted position is shown. By moving the O-shaped upper die 30A upward and retracting it, the tube 120 after O-bending can be easily removed from the bending machine 1 together with the cylindrical component 90. Then, the processing step of the tube 120 is completed by performing an operation to pull the cylindrical component 90 from the tube 120. The tube 120 is formed as a product with its ends 121 having a gap between them and facing each other.

[0084] In the mold 10 of this embodiment described above, when the workpiece 100 is bent into a U-shape, the lower end of the pressing surface 32 is pressed into a position P1 deeper than the position P2 after the inner diameter of the workpiece 100 has been machined down from the upper surface (upper surface portion 54a) of the lower mold 20 by the same machining dimension L1. Therefore, the workpiece 100 is fixed in a holding manner throughout the entire range of the U-shape bent along the circular pressing surface 32, thereby applying sufficient stress to the workpiece 100 while preventing slippage or misalignment. This suppresses breakage and wrinkling of the workpiece 100 during bending.

[0085] Furthermore, since the reaction force generating component is a gas spring 70, the initial reaction force is stronger compared to cases using other reaction force generating components such as springs, and the workpiece 100 can be firmly held by the upper mold 30 and the lower mold 20. Therefore, the workpiece 100 is firmly held in a gripping manner along the circular pressing surface 32, thereby applying sufficient stress to the workpiece 100 while preventing slippage or misalignment. This improves formability.

[0086] Furthermore, since multiple gas springs 70 are arranged along the long side of the lower die 20, even if the workpiece 100 is elongated, a uniform reaction force can be generated along the long side, and the same bending process can be performed in each part along the long side. In addition, by arranging multiple gas springs 70 along the long side of the lower die 20, a die 10 (lower die 20) of a length adapted to the long side dimension of the workpiece 100 can be constructed.

[0087] Furthermore, since the gas spring 70 can adjust the magnitude of the reaction force, the required reaction force can be appropriately set according to the size and strength of the workpiece 100, the pressing force of the upper die 30, etc., and sufficient reaction force can be generated relative to the bending stress required for bending processing.

[0088] Furthermore, the difference between the diameter L3 of the pressing surface 62 of the lower movable part 60 and the diameter L1 / 2 of the pressing surface 32 of the upper mold 30 is smaller than the thickness L4 of the workpiece 100. Therefore, while ideally applying compressive force to the workpiece 100 from the vertical direction, the workpiece 100 is pressed against the lower mold 20, and thus the workpiece 100 is firmly held in a manner where it is held within the pressing surface 32, which has a circular cross-sectional shape. This improves formability.

[0089] Furthermore, the pressing surface 32 of the upper mold 30 is formed by a cylindrical core member 31 extending along the long side of the lower mold 20, thus the pressing surface 32 can be easily formed. In addition, since the core member 31 is detachable, core members 31 with different outer diameters can be easily set according to the plate thickness L4 of the workpiece 100.

[0090] Furthermore, the movable range of the lower movable part 60 is the same as the maximum stroke distance of the gas spring 70. Therefore, it is possible to further press the upper die 30 into the workpiece 100 after the gas spring 70 has completed its full stroke. As a result, the formability of the workpiece 100 is improved.

[0091] In addition, since the inner edge 54b of the receiving member 54 is rounded with a radius smaller than the radius L1 / 2 of the core member 31, it can ideally mitigate the stress concentration during bending processing.

[0092] In addition, since a hard chrome plating layer is formed on the surface of the lower movable part 60 and the edge of the receiving member 54, wear of the lower mold 20 can be prevented.

[0093] Furthermore, since the process includes further O-shaped bending to finish the U-shaped member 110, which has been processed using the mold 10, into a tube 120, it is possible to obtain a tube 120 that suppresses the occurrence of breakage and wrinkling of the workpiece 100 (U-shaped member 110).

[0094] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and can be modified in various ways. The above embodiments are illustrative for the purpose of easily understanding the present invention and are not limited to including all the structures described. For example, in the above embodiments, a gas spring 70 is used as a reaction force generating member, but it is not limited to this. It can also be a member composed of other mechanisms such as a hydraulic cylinder or a metal spring, or a soft and elastic member such as a foamed synthetic resin material such as polyurethane or a rubber member, or it can be a member generating reaction force of other structures. That is to say, it is preferred to have a member that elastically supports the lower movable part 60 from below, especially a member in which the reaction force increases as it is compressed. If such a member generates reaction force, the shape, number and material of the reaction force generating member are not particularly limited.

[0095] In addition, in the above embodiment, the core member 31 is used as a member including the pressing surface 32, but it is not limited to this. Other pressing members with other shapes having the pressing surface 32 integrally formed in the lower part can also be used.

[0096] Furthermore, various sizes can be used if the size (width or area) of the pressing bearing surface 62 of the lower movable part 60 is sufficient to hold the workpiece 100 between it and the core member 31 during bending processing, and is introduced between it and the inner edges 54b, 54b of the receiving members 54, 54 in a manner that allows the workpiece 100 to be held into the core member 31.

[0097] Symbol Explanation

[0098] 10. Molds;

[0099] 10A mold;

[0100] 20 Lower molds;

[0101] 20A O-shaped lower die (lower die);

[0102] 30 upper mold;

[0103] 30A O-shaped upper mold (upper mold);

[0104] 31. Core-rib components;

[0105] 32 pressing surfaces;

[0106] 54. Supporting components;

[0107] 54b Inner edge;

[0108] 60. Lower movable part;

[0109] 62. Pressing bearing surface;

[0110] 70 gas spring;

[0111] 100 workpieces;

[0112] 110 U-shaped components;

[0113] 120 pipe fittings;

[0114] L1 is the precision-machined inner diameter dimension;

[0115] P1 is the maximum pressing position at the lower end of the pressing surface;

[0116] P2 is the position after the inner diameter has been reduced to the precision-machined dimension.

Claims

1. A mold for bending a workpiece in a plate shape, characterized by comprising a lower mold on which the workpiece is placed and an upper mold which is formed with a pressing surface that presses the workpiece toward the lower mold, wherein the lower mold comprises: a lower movable portion that is slidable in the same direction as the moving direction of the upper mold; a reaction force generating member that elastically supports the lower movable portion from below; and a receiving member that is located at both sides of the lower movable portion, the pressing surface is convex in cross section and extends in the longitudinal direction of the workpiece, the both side portions of the workpiece are bent in a manner that stands between the upper mold and the receiving member, and the central portion of the workpiece is gradually bent in a manner that is further embraced in the circumferential direction along the pressing surface, whereby the workpiece is bent in a U shape, the deepest position of the lower end portion of the pressing surface is deeper than the position after the inner diameter finish dimension of the workpiece is lowered from the upper surface of the lower mold, and the inner edge portion of the receiving member is rounded with a smaller radius than the radius of the pressing surface.

2. The mold according to claim 1, characterized in that the difference between the radius dimension of the bending concave pressing receiving surface of the lower mold and the radius dimension of the pressing surface of the upper mold is smaller than the thickness dimension of the workpiece, and the cross sectional shape of the both end portions of the pressing receiving surface is in the shape of an arc that protrudes upward, and the radius of the end portion is set to be smaller than the radius of the inner edge portion of the receiving member.

3. The mold according to claim 1 or 2, characterized in that the reaction force generating member is a gas spring.

4. The mold according to claim 1 or 2, characterized in that the reaction force generating member is arranged in a plurality along the longitudinal direction of the lower mold.

5. The mold according to claim 1 or 2, characterized in that the reaction force generating member is capable of adjusting the magnitude of the reaction force.

6. The mold according to claim 1 or 2, characterized in that the pressing surface of the upper mold is formed by a cylindrical core member that extends in the longitudinal direction of the lower mold.

7. The mold according to claim 1 or 2, characterized in that the lower movable portion is housed inside the receiving member, and the movable range of the lower movable portion is the same as the maximum stroke distance of the reaction force generating member.

8. The mold according to claim 1 or 2, characterized in that a hard chrome plating layer is formed on the surface of the edge portion of the lower movable portion and the receiving member. The processing method comprises: a step of placing the workpiece on the lower mold; a step of pressing the workpiece with the upper mold; and a step of advancing the lower movable portion and the upper mold downward while applying a force to the workpiece in the direction opposite to the moving direction of the upper mold by the reaction force of the reaction force generating member. The processing method comprises: a step of placing the workpiece protected by a protective sheet on the lower mold; ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 9. A processing method which is a processing method using the mold according to any one of claims 1 to 8, characterized by, ​ ​ ​ ​ 10. A processing method which is a processing method using the mold according to any one of claims 1 to 8, characterized by, ​ ​ a process of pressing the workpiece with the upper die; a process of advancing the lower movable portion and the upper die downward while applying a force to the workpiece in a direction opposite to the moving direction of the upper die using the reaction force of the reaction force generating member.

11. A processing method characterized by comprising: the processing method includes a process of further bending processing an O-shaped member from a U-shaped member to which the processing using the mold according to any one of claims 1 to 8 is applied and finish processing into a pipe.

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