Eccentric tube shortening method and device for pipe material

Abstract

To provide an eccentric pipe contraction method and an eccentric pipe contraction device of a pipe material which can mold an eccentric pipe contraction part in the target shape in an end of the pipe material.SOLUTION: An eccentric pipe contraction method of a pipe material molds an eccentric pipe contraction part 82 in an end 80 of a pipe material 8 by processing the end 80 of the pipe material 8 with a molding hole 30 of a die 3. The eccentric pipe contraction method of the pipe material uses the die 3 having a front side escape part 31, a depth side escape part 33 and a molding part 32 in the molding hole 30. The front side escape part 31 and the depth side escape part 33 are formed in the internal diameter retracting from the pipe material 8 in a hole end in the axial direction L of the molding hole 30. The molding part 32 is formed into the shape of contracting the diameter of the end 80 of the pipe material 8 in the eccentric state in the axial direction L between the front side escape part 31 and the depth side escape part 33 of the molding hole 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for eccentrically reducing a pipe material. [Background technology]

[0002] Pipe materials are used for a variety of purposes. Depending on the application of the pipe material, an eccentrically reduced pipe section may be formed at the end of the pipe material, where the diameter is reduced eccentrically in a specific radial direction. Methods for processing pipe material include, for example, bulge forming (hydroforming), in which hydrostatic pressure such as oil or water pressure is applied to the inside of the pipe material, and spinning (spatula drawing), in which a tool is applied to a rotating pipe material to process it. On the other hand, to overcome the drawbacks of bulge forming and spinning, such as the need for large-scale equipment and long processing times, press forming using a die may be performed on the end of the pipe material.

[0003] One example of a method for eccentrically drawing the end of a pipe material by press working is the eccentrically drawing method for a pipe described in Patent Document 1. In this eccentrically drawing method, when eccentrically drawing the end of the pipe to form a drawn portion, the diameter of the drawn portion is gradually reduced and a plurality of dies are used that gradually shift the central axis of the drawn portion relative to the central axis of the pipe. In this way, eccentric drawing is performed on the end of the pipe using a simple device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 57-187119 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it has been found that, for example, when the pipe material has a higher hardness and a larger diameter, it is difficult to form an eccentrically reduced portion (eccentrically drawn portion) at the end of the pipe material using conventional processing methods such as those described in Patent Document 1. In this case, buckling or the like occurs at the end of the pipe material, and it may not be possible to form it into the desired shape. Therefore, it has been found that further improvements are needed in the forming hole of the die to enable processing of the ends of various pipe materials.

[0006] The present invention has been made in consideration of such problems, and aims to provide an eccentrically shortening method and an eccentrically shortening device for pipe material that can form an eccentrically shortened portion of the desired shape at the end of the pipe material. [Means for solving the problem]

[0007] One aspect of the present invention is A method for eccentrically reducing a pipe material, comprising processing an end of the pipe material through a forming hole of a die to form an eccentrically reduced portion at the end of the pipe material, the diameter of which is reduced in an eccentric state in a specific radial direction, The forming hole has a front relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a front side in the axial direction into which the end of the pipe material is inserted, and a rear relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a rear side in the axial direction located opposite the front side, and has a forming portion between the front relief portion and the rear relief portion in the axial direction that reduces the diameter of the end of the pipe material in an eccentric state. death, With respect to the plurality of types of dies, the forming hole of the die used in the final stage of processing the end of the pipe material has an elliptical shape with the largest inner diameter including the specific radial direction, and the forming hole of the die used in other stages of processing the end of the pipe material has a perfect circular shape. The present invention relates to an eccentric tube shortening method for pipe material. Another aspect of the present invention is A method for eccentrically reducing a pipe material, comprising processing an end of the pipe material through a forming hole of a die to form an eccentrically reduced portion at the end of the pipe material, the diameter of which is reduced in an eccentric state in a specific radial direction, the forming hole has a front relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a front side in the axial direction into which the end of the pipe material is inserted, and a rear relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a rear side in the axial direction located opposite the front side, and a forming portion that reduces the diameter of the end of the pipe material in an eccentric state between the front relief portion and the rear relief portion in the axial direction, When an upper die plate approaches a lower die plate on which the die is disposed in a vertical direction, the die moves in a horizontal direction intersecting the vertical direction, thereby processing the end of the pipe material disposed along the horizontal direction, using an eccentric tube reduction device; the upper die plate has a pressing portion that presses the pipe material by the pressing force of a pressing member, The method for eccentrically shortening a pipe material includes a pressing portion provided with an ejection member that generates an ejection force for ejecting the end of the formed pipe material from the forming hole of the die when the die approaches the pressing portion.

[0008] Another aspect of the present invention is a lower die plate on which the pipe material is arranged in a horizontal direction; a die disposed on the lower die plate and having a forming hole for processing an end of the pipe material; an upper mold plate that can be lowered in a vertical direction perpendicular to the horizontal direction relative to the lower mold plate, An eccentric tube reduction device for a pipe material, in which when the upper die plate approaches the lower die plate in the vertical direction, the die moves in the horizontal direction, and an eccentric tube reduction portion is formed at the end of the pipe material by the forming hole of the die, the diameter of which is reduced in an eccentric state in a specific radial direction, The forming hole is a front-side relief portion formed on an inner diameter of the hole at a front end in the axial direction into which the end of the pipe material is inserted, the front-side relief portion being retracted from the pipe material; a deep relief portion formed on an inner diameter side of the pipe material at an end portion of the hole on a deep side in the axial direction located opposite to the front side; The eccentric tube reduction device for pipe material has a forming section that reduces the diameter of the end of the pipe material in an eccentric state between the front side relief section and the rear side relief section in the axial direction. [Effects of the Invention]

[0009] (One embodiment of a method for eccentrically shortening a pipe material) In the above-described method for eccentrically reducing a pipe material, a die is used in which a forming hole is formed with a front relief portion and a rear relief portion in addition to the forming portion. The front relief portion and the rear relief portion are configured to prevent a part of the forming hole from contacting the outer periphery of the end of the pipe material when the end of the pipe material is eccentrically reduced in diameter by the forming portion of the forming hole of the die.

[0010] When the end of the pipe is eccentrically reduced, the circumferential position of the end of the pipe close to a specific radial direction is hardly processed, while the circumferential position of the end of the pipe close to the opposite side of the specific radial direction is heavily processed. Therefore, when the end of the pipe is processed, a distribution of stress occurs in the circumferential direction of the end.

[0011] At this time, the formation of a front side relief portion and a rear side relief portion in the forming hole of the die allows the stress generated at the end of the pipe material to be appropriately released. This makes it possible to prevent buckling or the like at the end of the pipe material even if stress is distributed in the circumferential direction. Furthermore, even if the pipe material has a higher hardness or a larger diameter, it is possible to prevent buckling or the like at the end of the pipe material.

[0012] Therefore, according to the method for eccentrically shortening a pipe material of the one aspect described above, an eccentrically shortened portion of a desired shape can be formed at the end of the pipe material in various cases.

[0013] (Other embodiments of eccentric pipe shortening device) In the eccentric tube shortening device for pipe material of the other embodiment, the movement of the upper die plate approaching the lower die plate in the vertical direction is converted into the movement of the die in the horizontal direction, and the eccentric tube shortening portion is formed at the end of the pipe material by the forming hole of the die. This makes it possible to process the end of the pipe material, for example, even if the length of the pipe material is longer, without using a device with a large height.

[0014] Therefore, according to the eccentric tube shortening device for a pipe material of the other aspect, an eccentric tube shortening portion of a desired shape can be formed at the end of the pipe material using a simple device. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is an explanatory diagram showing a cross section of a die for performing a first stage of processing in a specific radial direction of a pipe material according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing a cross section perpendicular to the axial direction of the pipe material, illustrating a die for performing the first stage of processing according to an embodiment. [Figure 3] FIG. 10 is an explanatory diagram showing a cross section of a die for performing final processing in a specific radial direction of a pipe material according to an embodiment. [Figure 4]FIG. 2 is an explanatory diagram showing a cross section perpendicular to the axial direction of the pipe material, illustrating a die that performs the final processing step according to an embodiment. [Figure 5] 1 is an explanatory diagram showing a cross section of the periphery of an end portion of a pipe material taken along a specific radial direction according to an embodiment. FIG. [Figure 6] 1 is an explanatory diagram showing an eccentric pipe shortening device for a pipe material in an embodiment, with the upper die plate at the top dead center. FIG. [Figure 7] 1 is an explanatory diagram showing an eccentric pipe shortening device for a pipe material in an embodiment, with the upper die plate in the middle of descending. FIG. [Figure 8] 1 is an explanatory diagram showing an eccentric pipe shortening device for a pipe material in an embodiment, with the upper die plate at the bottom dead center. [Figure 9] An explanatory diagram showing an eccentric tube reduction device for pipe material according to an embodiment, with the upper die plate at the bottom dead center, in a cross section perpendicular to the axial direction of the pipe material. DETAILED DESCRIPTION OF THE INVENTION

[0016] A preferred embodiment of the above-mentioned method and device for eccentrically reducing a pipe material will be described with reference to the drawings. <Embodiment> In the eccentric tube reduction method for pipe material 8 of this embodiment, as shown in Figures 1 to 5, the end 80 of the pipe material 8 is processed through a forming hole 30 of a die 3 to form an eccentric tube reduction portion 82 in the end 80 of the pipe material 8, which is reduced in diameter in an eccentric state in a specific radial direction R0. In the eccentric tube reduction method for pipe material 8, a die 3 is used in the forming hole 30, which has a front relief portion 31, a back relief portion 33, and a forming portion 32. Details will be described later, but Figures 1 and 2 show a die 3A that performs the first stage of processing, and Figures 3 and 4 show a die 3B that performs the final stage of processing.

[0017] The front relief portion 31 is formed with an inner diameter that is retracted from the pipe material 8 at the front hole end in the axial direction L of the forming hole 30, into which the end 80 of the pipe material 8 is inserted. The rear relief portion 33 is formed with an inner diameter that is retracted from the pipe material 8 at the rear hole end in the axial direction L of the forming hole 30, located on the opposite side from the front side. The forming portion 32 is formed in a shape that reduces the diameter of the end 80 of the pipe material 8 in an eccentric state between the front relief portion 31 and the rear relief portion 33 in the axial direction L of the forming hole 30.

[0018] The eccentric pipe shortening method and eccentric pipe shortening device 1 of this embodiment will be described in detail below. (Pipe material 8) FIG. 5 shows a cross section of the periphery of the end 80 of the pipe material 8 taken along a specific radial direction R0. As shown in FIG. 5, the pipe material 8 manufactured by the eccentric tube reduction method has a cylindrical main tube portion 81 and an eccentric tube reduction portion 82 formed at one end of the main tube portion 81. The eccentric tube reduction portion 82 may be formed at both ends of the main tube portion 81. The eccentric tube reduction portion 82 has a cylindrical tube reduction portion 821 formed at the tip of the pipe material 8 and parallel to the axial direction L, and an inclined tube portion 822 formed eccentrically inclined between the main tube portion 81 and the inclined tube portion 821. In FIG. 5, the central axes of the pipe material 8 and the main tube portion 81 are indicated by symbol O1, and the central axis of the eccentric tube reduction portion 82 is indicated by symbol O2.

[0019] The inclined tube portion 822 is formed into an outer peripheral shape in which the inclination angle θ of the inclined inner peripheral surface 823 with respect to the axial direction L increases as it moves from the specific radial direction R0 toward the opposite side of the specific radial direction R0 (the side 180° out of phase) in the circumferential direction C. At the position in the specific radial direction R0, the eccentric tube reduction portion 82 is not eccentric to the inner peripheral side from the main body tube portion 81. At the position in the specific radial direction R0, the eccentric tube reduction portion 82 has a linear shape that is continuous with the main body tube portion 81 and parallel to the axial direction L.

[0020] The eccentric tube shortening method and eccentric tube shortening device 1 for a pipe material 8 of this embodiment can form an eccentric tube shortening portion 82 at the end 80 of a pipe material 8 having a large outer diameter of φ50 mm to φ70 mm. In addition, the eccentric tube shortening method and eccentric tube shortening device 1 for a pipe material 8 of this embodiment can form an eccentric tube shortening portion 82 at the end 80 of a pipe material 8 having a large outer diameter of φ50 mm to φ70 mm. 2 ~490N / mm 2 The eccentrically reduced tube portion 82 can be formed at the end portion 80 of the pipe material 8 having a strength of 1000 MPa. The outer diameter and tensile strength of the pipe material 8 may be outside these values.

[0021] (Eccentric tube contraction device 1) As shown in Figures 6 to 9, in the eccentric tube shortening method for pipe material 8, an eccentric tube shortening device 1 for pipe material 8, which includes a lower die plate 2, a die 3, and an upper die plate 5, is used to process the end 80 of the pipe material 8. Figure 6 shows the eccentric tube shortening device 1 in a state 101 where the upper die plate 5 is at the top dead center, Figure 7 shows the eccentric tube shortening device 1 in a state where the upper die plate 5 is in the middle of descending, and Figure 8 shows the eccentric tube shortening device 1 in a state 102 where the upper die plate 5 is at the bottom dead center. Figure 9 shows the eccentric tube shortening device 1 in a state 102 where the upper die plate 5 is at the bottom dead center, in a cross section perpendicular to the axial direction L of the pipe material 8.

[0022] In the eccentric tube shortening device 1, when the upper die plate 5 approaches the lower die plate 2 in the vertical direction H, the die 3 on the lower die plate 2 moves in the horizontal direction W that intersects with the vertical direction H, to process the end 80 of the pipe material 8 arranged along the horizontal direction W. The eccentric tube shortening method for the pipe material 8 and the eccentric tube shortening device 1 process the end 80 of the pipe material 8 by so-called press forming.

[0023] In this embodiment of the eccentric tube reduction device 1, the direction parallel to the horizontal direction and in which the axial direction of the pipe material 8 is directed is called the horizontal direction W, and the direction parallel to the vertical direction and perpendicular to the horizontal direction W is called the vertical direction H.

[0024] The axial direction L of the pipe material 8 refers to the direction in which the central axis O1 of the pipe material 8 passes, and the axial direction L of the pipe material 8 and the axial direction L of the forming hole 30 are the same direction. The circumferential direction C of the pipe material 8 refers to the direction around the central axis O1 of the pipe material 8, and the circumferential direction C of the pipe material 8 and the circumferential direction C of the forming hole 30 are the same direction. The radial direction R of the pipe material 8 refers to a radial direction centered on the central axis O1 of the pipe material 8, and the radial direction R of the pipe material 8 and the radial direction R of the forming hole 30 are the same direction.

[0025] As shown in Figures 6, 8 and 9, a pipe receiving portion 4 on which a pipe material 8 is placed along the horizontal direction W is disposed on the upper surface of the lower mold plate 2. A semicircular receiving surface 41 that holds the outer periphery of the pipe material 8 is formed on the upper surface of the pipe receiving portion 4. An end portion 80 of the pipe material 8 is disposed in a state that protrudes in the horizontal direction W from the end face of the pipe receiving portion 4. A die 3 for processing the end portion 80 of the pipe material 8 is disposed on the upper surface of the lower mold plate 2.

[0026] The die 3 is disposed to the side of the pipe material receiving portion 4 of the lower die plate 2 so as to be slidable relative to the lower die plate 2, and can move toward and away from the pipe material 8 in the pipe material receiving portion 4. A return force is applied to the die 3 by a return member 34 such as a spring in a direction away from the pipe material receiving portion 4. The lower die plate 2 is also provided with a stopper 43 that comes into contact with the end face of the pipe material 8 opposite the end 80 where the eccentric tube reduction portion 82 is formed, and receives the pipe material 8 pressed in the lateral direction W by the die 3.

[0027] The eccentric tube reduction device 1 can be used by installing the upper die plate 5 on the bolster of the press equipment and the lower die plate 2 on the table of the press equipment. The upper die plate 5 can be raised and lowered in the vertical direction H relative to the lower die plate 2 by the press equipment or the like. A cam 51 is disposed on the lower surface of the upper die plate 5. When the upper die plate 5 descends toward the lower die plate 2, the cam 51 abuts against the die 3 on the lower die plate 2, causing the die 3 to slide in the horizontal direction W. The die 3 is provided with a cam receiver 35 having an abutment surface 351 that abuts against the inclined surface 511 of the cam 51.

[0028] 6, 8, and 9, a pressing section 6 is disposed on the lower surface of the upper plate 5, which presses the pipe material 8 with the pressing force (elastic force) of a pressing member 61. The pressing section 6 is slidable in the vertical direction H of the upper plate 5 by a guide or the like (not shown), and is slidable so as to approach the lower surface of the upper plate 5 while elastically deforming the pressing member 61. The pressing member 61 is constituted by a spring or the like, and is disposed between the lower surface of the upper plate 5 and the pressing section 6.

[0029] A semicircular pressing surface 63 that holds the outer periphery of the pipe material 8 is formed on the underside of the pressing part 6. When the upper die plate 5 is closest to the lower die plate 2 (when the upper die plate 5 reaches the bottom dead center), the entire periphery of the pipe material 8, excluding the ends, is held by the receiving surface 41 of the pipe material receiving part 4 of the lower die plate 2 and the pressing surface 63 of the pressing part 6.

[0030] The pressing unit 6 is provided with an upper ejection member 62 that generates an ejection force for ejecting the end 80 of the formed pipe material 8 from the forming hole 30 of the die 3 when the die 3 approaches the pressing unit 6. The upper ejection member 62 is composed of a gas cushion, a spring, or the like. At least a portion of the upper ejection member 62 is arranged so as to protrude from the side surface of the pressing unit 6 in the lateral direction W toward the die 3 in the lateral direction W.

[0031] In addition, a lower ejection member 42 is provided on the pipe material receiving portion 4 of the lower die plate 2. At least a portion of the lower ejection member 42 of the pipe material receiving portion 4 is arranged so as to protrude from the side surface of the pipe material receiving portion 4 in the lateral direction W toward the die 3 in the lateral direction W. When the die 3 approaches the pipe material receiving portion 4, an ejection force for ejecting the end portion 80 of the formed pipe material 8 from the forming hole 30 of the die 3 is also generated by the lower ejection member 42 of the pipe material receiving portion 4.

[0032] The eccentric tube shortening device 1 for pipe material in this embodiment is a hydraulic type that uses a hydraulic cylinder to raise and lower the upper die plate 5. The eccentric tube shortening device 1 is configured to maintain the upper die plate 5 at the bottom dead center for a predetermined time and detect the pressurized state when the upper die plate 5 descends to the bottom dead center relative to the lower die plate 2. The eccentric tube shortening device 1 may also be a mechanical type that uses a servo motor to raise and lower the upper die plate 5.

[0033] (3 dice) As shown in Figures 1 and 2, the forming hole 30 of the die 3 is open in the lateral direction W facing the pipe material receiving portion 4. The forming hole 30 is formed in a shape that squeezes the end 80 of the pipe material 8 in an eccentric manner when the end 80 of the pipe material 8 is inserted. The front relief portion 31 of the forming hole 30 has, at the front end of the hole in the axial direction L where the end 80 of the pipe material 8 is inserted, a front parallel portion 311 that is parallel to the axial direction L of the forming hole 30, and a front inclined portion 312 that decreases in diameter as it goes deeper in the axial direction L. The front parallel portion 311 is formed with an inner diameter that does not contact the outer periphery of the end 80 of the pipe material 8, and the front inclined portion 312 is formed as an inclined surface that connects the front parallel portion 311 and the forming portion 32.

[0034] The rear relief portion 33 of the forming hole 30 has, at the hole end on the rear side in the axial direction L located opposite the front side, a rear parallel portion 331 parallel to the axial direction L of the forming hole 30 and a rear inclined portion 332 whose diameter decreases as it goes rearward in the axial direction L. The rear parallel portion 331 is formed with an inner diameter that does not contact the outer periphery of the end portion 80 of the pipe material 8, and the rear inclined portion 332 is formed as an inclined surface that connects the rear parallel portion 331 and the forming portion 32.

[0035] The molding portion 32 of the molding hole 30 is formed between the front inclined portion 312 of the front relief portion 31 and the rear inclined portion 332 of the rear relief portion 33 in the axial direction L of the molding hole 30. The molding portion 32 has a linear shape along the axial direction L at a specific radial position R0 in the circumferential direction C of the molding hole 30, and has a tapered shape in which the inner diameter decreases from the front side in the axial direction L toward the rear side in the axial direction L at positions in the circumferential direction C other than the specific radial position R0.

[0036] In other words, the forming portion 32 has a contact parallel portion 321 formed parallel to the axial direction L and in contact with the outer periphery of the end portion 80 of the pipe material 8; a contact inclined portion 322 that contacts the outer periphery of the end portion 80 of the pipe material 8 on the far side of the contact parallel portion 321 in the axial direction L and whose inner diameter decreases as it goes farther away except for a position in the specific radial direction R0; and a minimum diameter reduction portion 323 formed parallel to the axial direction L and connected to the far side of the contact inclined portion 322 in the axial direction L. The minimum diameter reduction portion 323 is the part where the inner diameter of the forming portion 32 in the forming hole 30 is the smallest. The contact inclined portion 322 is formed into an inner circumferential shape in which the inclination angle θ1 of the inclined inner circumferential surface with respect to the axial direction L increases as it goes from the specific radial direction R0 toward the opposite side of the specific radial direction R0 (the side 180° out of phase) in the circumferential direction C.

[0037] 1 and 3, an R-shape (curved surface shape) is formed at the corner between the contact parallel portion 321 and the contact inclined portion 322. The end portion on the far side in the axial direction L of the narrowest diameter portion 323 is connected to the far inclined portion 332 of the far relief portion 33. Except for a specific position in the radial direction R0, the contact inclined portion 322 and the narrowest diameter portion 323 of the molded portion 32 and the far inclined portion 332 of the far relief portion 33 form a mountain-shaped inclined inner circumferential surface.

[0038] In the eccentric tube shortening method and eccentric tube shortening device 1, the end 80 of a pipe material 8 is inserted multiple times into the forming holes 30 of multiple types of dies 3 to form an eccentric tube shortening portion 82 on the end 80 of the pipe material 8. Figures 1 and 2 show a die 3A that performs the first stage of processing, and Figures 3 and 4 show a die 3B that performs the final stage of processing. The other dies 3 besides the first stage die 3A and the final stage die 3B are not shown.

[0039] When the position where the inner diameter of the forming portion 32 in the forming hole 30 is the smallest is defined as the narrowest diameter portion 323, a plurality of types of dies 3 are used, each with a different inner diameter of the narrowest diameter portion 323. In the eccentric tube reduction device 1, the dies 3 arranged on the lower mold plate 2 can be replaced so that the inner diameter of the narrowest diameter portion 323 changes stepwise from larger to smaller.

[0040] In the eccentric tube reduction method and eccentric tube reduction device 1, the end 80 of the pipe material 8 is sequentially inserted into the forming holes 30 of multiple types of dies 3 so that the inner diameter of the narrowest diameter portion 323 of the die 3 used to process the end 80 of the pipe material 8 is gradually reduced. Furthermore, the amount of reduction in the diameter of the end 80 of the pipe material 8 gradually achieved by the narrowest diameter portion 323 of the multiple types of dies 3 is the greatest by the narrowest diameter portion 323 of the first-stage die 3A. The reduction amount is indicated as the amount by which the outer diameter of the end 80 of the pipe material 8 is reduced by the narrowest diameter portion 323. Furthermore, the difference between the inner diameter of the narrowest diameter portion 323 of the second-stage die 3 and the narrowest diameter portion 323 of the first-stage die 3A is greater than the difference between the inner diameters of the narrowest diameter portions 323 of the second-stage die 3 and the first-stage die 3A.

[0041] When processing the end 80 of the pipe material 8, work hardening is likely to occur more severely in the early stages of processing. By making the amount of forming by the narrowest diameter portion 323 of the die 3A in the first stage greater than the amount of forming by the narrowest diameter portion 323 of the die 3 in the second stage and subsequent stages, the end 80 of the pipe material 8 can be effectively processed into the desired shape before the end 80 of the pipe material 8 is work hardened.

[0042] The end 80 of the pipe material 8 is machined into an eccentrically reduced diameter shape, and therefore the inner peripheral surface in particular is slightly deformed from a perfect circle to an elliptical shape. Specifically, when the forming hole 30 of the die 3 is formed into a perfect circle, when the eccentrically reduced portion 82 is formed in the end 80 of the pipe material 8, the inner diameter at a position in the circumferential direction C including the specific radial direction R0 in the end 80 of the pipe material 8 tends to be smaller than the inner diameter at a position in the circumferential direction C that is 90° out of phase with the specific radial direction R0. In other words, when the forming hole 30 of the die 3 is formed into a perfect circle, the end 80 of the pipe material 8 is formed with an elliptical inner peripheral surface in which the inner diameter at a position in the circumferential direction C including the specific radial direction R0 is the minor diameter portion.

[0043] Therefore, in this embodiment, for multiple types of dies 3, the shape of the forming hole 30 of the die 3B used in the final stage of processing the end 80 of the pipe material 8 is changed so that the elliptical inner circumferential surface of the end 80 of the pipe material 8 becomes an inner circumferential surface that is close to a perfect circle. Specifically, as shown in Figure 4, the forming portion 32 of the forming hole 30 of the die 3B used in the final stage of processing the end 80 of the pipe material 8 is formed into an elliptical shape with the largest inner diameter including a specific radial direction R0. In Figure 4, the elliptical shape is shown exaggerated.

[0044] That is, the forming portion 32 of the forming hole 30 of the die 3B in the final stage has an elliptical shape in which the inner diameter at a position in the circumferential direction C including the specific radial direction R0 (a position shown in the vertical direction in FIG. 4) is larger than the inner diameter at a position in the circumferential direction C that is 90° out of phase with the specific radial direction R0. In other words, the forming portion 32 of the forming hole 30 of the die 3B in the final stage has an elliptical inner peripheral surface in which the inner diameter at a position in the circumferential direction C including the specific radial direction R0 is the major diameter.

[0045] The forming holes 30 of the remaining dies 3, except for the final-stage die 3B, are formed with inner peripheral surfaces that are perfectly circular. By devising the shape of the forming hole 30 of the final-stage die 3B, the shape of the inner peripheral surface of the eccentric tube-reducing portion 82 formed on the end portion 80 of the pipe material 8 can be made to be close to a perfect circle.

[0046] (Tube shrinkage forming method) The pipe shrinking method involves a lowering process in which the upper die plate 5 is lowered relative to the lower die plate 2 and the end 80 of the pipe material 8 is processed through the forming hole 30 of the die 3, and an ascent process in which the upper die plate 5 is raised relative to the lower die plate 2 and the end 80 of the pipe material 8 is pulled out from the forming hole 30 of the die 3. In addition, before the lowering process, as a preparation process, lubricating oil is applied to the forming hole 30 of the die 3 and the end 80 of the pipe material 8 to make it easier for the end 80 of the formed pipe material 8 to be pulled out from the forming hole 30 of the die 3.

[0047] 6 and 7, in the lowering process, when the upper plate 5 descends relative to the lower plate 2, the inclined surface 511 of the cam 51 of the upper plate 5 abuts against the abutment surface 351 of the cam receiving portion 35 of the die 3 of the lower plate 2. At this time, the die 3 approaches the pipe material receiving portion 4 against the return force of the return member 34, and the end portion 80 of the pipe material 8 is inserted into the forming hole 30 of the die 3, and the pressing portion 6 abuts against the outer periphery of the pipe material 8 against the pressing force of the pressing member 61.

[0048] Then, as shown in FIG. 8 , the cam 51 moves the die 3 closer to the pipe material receiving portion 4, and the end portion 80 of the pipe material 8 is inserted from the front relief portion 31 of the forming hole 30 of the die 3 into the forming portion 32, and the end portion 80 of the pipe material 8 is processed by the forming portion 32. At this time, the formation of the front relief portion 31 relieves stress that occurs in the portion of the end portion 80 of the pipe material 8 that is closer to the front side than the portion that will be processed into the forming portion 32. Furthermore, the formation of the rear relief portion 33 also relieves stress that occurs in the portion of the end portion 80 of the pipe material 8 that is closer to the rear side than the portion that will be processed into the forming portion 32. In other words, when the end portion 80 of the pipe material 8 is processed by the forming portion 32, stress that occurs in the end portion 80 of the pipe material 8 is appropriately relieved, making it less likely that defects such as buckling will occur in the end portion 80 of the pipe material 8.

[0049] When the end 80 of the pipe material 8 is machined by the forming portion 32 of the forming hole 30 of the die 3, the upper ejection member 62 provided on the pressing portion 6 of the upper die plate 5 and the lower ejection member 42 provided on the pipe material receiving portion 4 of the lower die plate 2 come into contact with the die 3. In addition, when the upper die plate 5 descends to the bottom dead center relative to the lower die plate 2, the upper die plate 5 remains at the bottom dead center for a predetermined period of time.

[0050] Next, in the raising step, the upper die plate 5 is raised relative to the lower die plate 2. Then, the die 3 is moved by the return member 34 in the lateral direction W away from the pipe material 8. At this time, the pipe material 8 is held in position by the receiving surface 41 of the pipe material receiving portion 4 and the pressing surface 63 of the pressing portion 6, which receives the pressing force of the pressing member 61. In addition, the ejection force of the upper ejection member 62 of the pressing portion 6 and the ejection force of the lower ejection member 42 of the pipe material receiving portion 4 act to move the die 3 away from the end 80 of the pipe material 8 in the lateral direction W. Furthermore, the lubricating oil applied to the forming hole 30 of the die 3 and the end 80 of the pipe material 8 makes it easier for the end 80 of the pipe material 8 to be removed from the forming hole 30. With these configurations, when the die 3 moves away from the pipe material receiving portion 4, the end 80 of the pipe material 8 is smoothly extracted from the forming hole 30 of the die 3, and the return member 34 returns the die 3 to its original position away from the pipe material receiving portion 4.

[0051] Next, the pipe material 8 that has undergone the first stage of processing of the eccentric tube reduction section 82 is held on the receiving surface 41 of the pipe material receiving section 4 that faces the die 3 that performs the second stage of processing. Then, in the lowering process, as the upper mold plate 5 descends relative to the lower mold plate 2, the end 80 of the pipe material 8 that has undergone the first stage of processing is subjected to the second stage of processing through the forming hole 30 of the die 3 that performs the second stage of processing. Next, in the raising process, the upper mold plate 5 rises from the lower mold plate 2, and the end 80 of the pipe material 8 that has undergone the second stage of processing is pulled out from the forming hole 30 of the die 3.

[0052] Thereafter, the lowering and ascending steps are repeated until the end 80 of the pipe material 8 is processed by the forming hole 30 of the die 3B, which performs the final processing stage. Then, an eccentrically reduced tube portion 82 is formed in the end 80 of the pipe material 8, and the eccentrically reduced tube portion 82 is extracted from the forming hole 30.

[0053] (Action and effect) In the eccentric tube reduction method and eccentric tube reduction device 1 for a pipe material 8 of this embodiment, a die 3 is used in which a forming hole 30 is formed with a front relief portion 31 and a rear relief portion 33 in addition to a forming portion 32. The front relief portion 31 and the rear relief portion 33 are designed to prevent a part of the forming hole 30 from contacting the outer periphery of the end portion 80 of the pipe material 8 when the forming portion 32 of the forming hole 30 of the die 3 reduces the diameter of the end portion 80 of the pipe material 8 in an eccentric state. In addition, the movement of the upper die plate 5 approaching the lower die plate 2 in the vertical direction H is converted into the movement of the die 3 moving in the horizontal direction W, and an eccentric tube reduction portion 82 is formed in the end portion 80 of the pipe material 8 by the forming hole 30 of the die 3.

[0054] When the end 80 of the pipe material 8 is reduced in diameter in an eccentric state, a position close to the specific radial direction R0 in the circumferential direction C of the end 80 of the pipe material 8 is hardly processed, while a position close to the opposite side of the specific radial direction R0 in the circumferential direction C of the end 80 of the pipe material 8 is heavily processed. Therefore, when the end 80 of the pipe material 8 is processed, a distribution of stress occurs in the end 80 in the circumferential direction C.

[0055] At this time, since the forming hole 30 of the die 3 has a front side relief portion 31 and a rear side relief portion 33 formed therein, stress generated in the end portion 80 of the pipe material 8 is appropriately released. This makes it possible to prevent buckling or the like from occurring in the end portion 80 of the pipe material 8 even if stress is distributed in the circumferential direction C. Furthermore, even if the hardness of the pipe material 8 is higher or the diameter of the pipe material 8 is larger, it is possible to prevent buckling or the like from occurring in the end portion 80 of the pipe material 8.

[0056] Therefore, according to the present embodiment of the eccentric shortening method and eccentric shortening device 1 for pipe material 8, it is possible to form an eccentric shortening portion 82 of the desired shape at the end 80 of the pipe material 8 in various cases.

[0057] The present invention is not limited to the embodiments, and various other embodiments can be configured without departing from the spirit of the present invention. The present invention also includes various modifications, modifications within the scope of equivalents, etc. [Explanation of symbols]

[0058] 1. Pipe material eccentric reduction device 2 Lower die plate 3 dice 30 forming holes 31 Front relief 311 Front parallel section 312 Front slope 32 Molding section 321 Contact parallel part 322 Contact slope part 323 Most reduced diameter part 33 Back side relief 331 Back side parallel part 332 Back slope part 34 Return member 35 Cam receiver 4 Pipe receiving part 41 Receiving surface 42 Lower extraction member 43 Stopper 5 Upper plate 51 Cam 6 Pressing part 61 Pressing member 62 Upper extraction member 63 Pressing surface 8 Pipe material 80 End 81 Main body pipe 82 Eccentric constriction section 821 Constriction section 822 Inclined pipe section

Claims

1. A method for eccentrically reducing a pipe material, comprising processing an end of the pipe material through a forming hole of a die to form an eccentrically reduced portion at the end of the pipe material, the diameter of which is reduced in an eccentric state in a specific radial direction, the forming hole has a front relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a front side in the axial direction into which the end of the pipe material is inserted, and a rear relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a rear side in the axial direction located opposite the front side, and a forming portion that reduces the diameter of the end of the pipe material in an eccentric state between the front relief portion and the rear relief portion in the axial direction, A method for eccentrically shortening a pipe material, wherein, for multiple types of dies, the forming hole of the die used for the final stage of processing the end of the pipe material has an elliptical shape with the largest inner diameter including the specific radial direction, and the forming hole of the die used for other stages of processing the end of the pipe material has a perfect circular shape.

2. A method for eccentrically reducing a pipe material, comprising processing an end of the pipe material through a forming hole in a die to form an eccentrically reduced portion at the end of the pipe material, the eccentrically reduced portion reducing the diameter in an eccentric state in a specific radial direction, the forming hole has a front relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a front side in the axial direction into which the end of the pipe material is inserted, and a rear relief portion formed in an inner diameter that is retracted from the pipe material at a hole end on a rear side in the axial direction located opposite the front side, and a forming portion that reduces the diameter of the end of the pipe material in an eccentric state between the front relief portion and the rear relief portion in the axial direction, When an upper die plate approaches a lower die plate on which the die is disposed in a vertical direction, the die moves in a horizontal direction intersecting the vertical direction, thereby processing the end of the pipe material disposed along the horizontal direction, using an eccentric tube reduction device; the upper die plate has a pressing portion that presses the pipe material by the pressing force of a pressing member, The method for eccentrically shortening a pipe material, wherein the pressing portion is provided with an ejection member that generates an ejection force to eject the end of the formed pipe material from the forming hole of the die when the die approaches the pressing portion.

3. 3. An eccentric tube shortening method for pipe material as described in claim 1 or 2, wherein the forming portion has a linear shape along the axial direction at the specific radial corresponding position in the circumferential direction of the forming hole, and has a tapered shape in which the inner diameter decreases from the front side in the axial direction toward the back side in the axial direction at positions other than the specific radial corresponding position in the circumferential direction.

4. When the part of the forming hole where the inner diameter of the forming portion is reduced the most is defined as the narrowest diameter part, a plurality of types of dies having different inner diameters at the narrowest diameter part are used, The end of the pipe material is sequentially inserted into the forming holes of the plurality of types of dies so that the inner diameter of the narrowest diameter portion of the die used to process the end of the pipe material becomes smaller in a stepwise manner; An eccentric tube reduction method for pipe material as described in any one of claims 1 to 3, wherein the amount of forming by which the end of the pipe material is gradually reduced in diameter by the narrowest diameter portion of the multiple types of dies is the largest amount of forming by the narrowest diameter portion of the die in the first stage.

5. a lower die plate on which the pipe material is arranged in a horizontal direction; a die disposed on the lower die plate and having a forming hole for processing an end of the pipe material; an upper mold plate that can be lowered in a vertical direction perpendicular to the horizontal direction relative to the lower mold plate, When the upper die plate approaches the lower die plate in the vertical direction, the die moves in the horizontal direction, and the forming hole of the die forms an eccentric tube reduction portion at the end of the pipe material, the diameter of which is reduced in an eccentric state in a specific radial direction, The forming hole is a front-side relief portion formed on an inner diameter of the hole at a front end in the axial direction into which the end of the pipe material is inserted, the front-side relief portion being retracted from the pipe material; a deep relief portion formed on an inner diameter side of the pipe material at an end portion of the hole on a deep side in the axial direction located opposite to the front side; an eccentric tube reduction device having a forming section that reduces the diameter of the end of the pipe material in an eccentric state between the front side relief section and the rear side relief section in the axial direction.

6. the upper die plate has a pressing portion that presses the pipe material by the pressing force of a pressing member, An eccentric tube reduction device as described in claim 5, wherein the pressing portion is provided with an ejection member that generates an ejection force to eject the end of the formed pipe material from the forming hole of the die when the die approaches the pressing portion.

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