Apparatus for manufacturing a branching structure of a metal pipe and method for manufacturing a branching structure of a metal pipe

Abstract

This device for producing a branch part structure comprises: a die 10 that is formed in a spherical shape and has a long diameter A1 and a short diameter B1 which is shorter than the long diameter A1; and a drawing jig 20 that can connect to the die 10. When the die 10, having been inserted into a pipe 30 in which a burred portion 32 is to be formed, is extracted by the drawing jig 20 connected to the die 10, a first burring process is performed by the die on a lower hole 31 that is formed at a branch part formation position in the pipe 30 and passes radially through the body of the pipe 30. The drawing jig 20 then rotates the extracted die 10 by a prescribed angle about a center axis, and a second burring process is performed on the lower hole 31 by the rotated die 10 from the exterior of the pipe 30.

Description

[Technical field]

[0001] The present invention relates to an apparatus for manufacturing a branched portion structure of a metal pipe and a method for manufacturing a branched portion structure of a metal pipe. [Background technology]

[0002] As an example of a branch structure manufacturing apparatus for manufacturing a branch structure of a metal pipe used for various piping applications, there is known a branch structure manufacturing apparatus for a metal pipe described in Patent Document 1. In the branch structure manufacturing apparatus described in Patent Document 1, a pilot hole is drilled in a pipe, which is a metal pipe, and a burring process is performed in which a spherical die inserted in the pipe is pulled out from the inside to the outside at the location where the pilot hole is drilled, thereby branching a branch side pipe from a main pipe. In other words, the pipe diameter of the branch side pipe is determined by the diameter of the spherical die. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-209889 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the branch structure manufacturing device of Patent Document 1, if the diameter of the spherical mold is the same as the diameter of the main pipe, it is difficult to insert the mold into the inside of the main pipe, which causes a problem that it is difficult to perform burring so that the pipe diameter of the branch side and the pipe diameter of the main pipe are the same.

[0005] The present invention has been made to solve such problems, and has an object to provide an apparatus for manufacturing a branching structure for a metal pipe, and a method for manufacturing a branching structure for a metal pipe, which are capable of manufacturing a branching structure having a branched side pipe with the same pipe diameter as the main pipe diameter of the metal pipe. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides an apparatus for manufacturing a branched portion structure of a metal pipe, the apparatus comprising: a spherical mold having a central axis and extending in a direction perpendicular to the direction in which the central axis extends, the spherical mold having a first diameter and a second diameter shorter than the first diameter; and a connecting member connectable to the mold. The die has a front curved surface portion, a maximum diameter portion, and a rear curved surface portion, which are provided in this order along the direction in which the central axis extends. When the die in which the connecting member is connected to the die is inserted into the metal pipe is removed to the outside of the metal pipe, the connecting member is connected to the die with respect to a pilot hole formed at a branch portion forming position of the metal pipe and passing through the body of the metal pipe in a radial direction, Front curved surface The first burring process is performed by rotating the removed die around the central axis by a specified angle, Rear curved section From the outside of the metal pipe After the first burring A second burring process is performed on the pilot hole.

[0007] The mold may also be a truncated sphere having a pair of opposing flat surfaces extending parallel to the central axis. The mold may also be ellipsoidal.

[0008] In order to solve the above problems, a manufacturing method of a branching portion structure of a metal pipe according to the present invention includes a first step of forming a pilot hole that radially penetrates a body of the metal pipe at a branching portion formation position of the metal pipe, and a second step of forming a pilot hole having a central axis and extending in a direction perpendicular to the extension direction of the central axis, the pilot hole having a first diameter and a second diameter shorter than the first diameter. A front curved surface portion, a maximum diameter portion, and a rear curved surface portion are provided in this order along the direction in which the central axis extends. A second step of inserting a spherical mold having the above-mentioned shape into the inside of the metal tube and moving the mold to the position of the pilot hole; and a second step of removing the mold to the outside of the metal tube. Front curved surface The third process is to perform the first burring process on the pilot hole by rotating the die by a specified angle around the central axis. Rear curved section From the outside of the metal pipe After the first burring and a fourth step of performing a second burring process on the pilot hole.

[0009] Furthermore, the method may include a fifth step between the second step and the third step of inserting a connecting member into the pilot hole and connecting the die and the connecting member, the third step being performed by pulling the connecting member connected to the die radially outward of the metal tube, and the fourth step being performed by rotating the connecting member connected to the die by a predetermined angle around the central axis and pushing the connecting member radially inward of the metal tube. Effect of the Invention

[0010] The manufacturing device for a branching structure of a metal pipe and the manufacturing method for a branching structure of a metal pipe according to the present invention comprise a spherical mold having a first diameter and a second diameter shorter than the first diameter extending perpendicularly to the direction in which a central axis extends, which is used to perform a first burring process on a pilot hole that radially penetrates the body of the metal pipe and then remove it from the metal pipe, rotate the removed mold a predetermined angle around the central axis, and use the rotated mold to perform a second burring process on the pilot hole from outside the metal pipe, thereby making it possible to manufacture a branching structure having a branch side tube with the same diameter as the main pipe diameter of the metal pipe. [Brief description of the drawings]

[0011] [Figure 1] 1 is a front view of a mold for a branching structure manufacturing apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is a right side view of a mold for the branching structure manufacturing apparatus according to the first embodiment of the present invention. FIG. [Diagram 3] 1 is a plan view of a mold for a branching structure manufacturing apparatus according to a first embodiment of the present invention. [Figure 4] 1 is a front view of a pulling jig of the branching section structure manufacturing apparatus according to the first embodiment of the present invention. [Diagram 5] FIG. 4 is a front cross-sectional view showing a pilot hole forming step of the branching portion structure of the metal pipe according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a front view, partially in section, showing a die insertion step in the manufacturing method for the branch portion structure of a metal pipe according to the first embodiment. [Figure 7] 3 is a front view, partially in cross section, showing a drawing jig coupling step of the manufacturing method for the branched portion structure of the metal pipe according to the first embodiment of the present invention. FIG. [Figure 8] 8 is a right side view, partially in section, of the pipe shown in FIG. 7. [Figure 9] 8 is a plan sectional view of the pipe of FIG. 7 taken along line LL. [Figure 10] 1 is a front view, partially in section, showing a first burring process step in the manufacturing method for a branched portion structure of a metal pipe according to a first embodiment of the present invention. FIG. [Figure 11] 1 is a right side view, partially in section, showing a first burring process step in the manufacturing method for a branched portion structure of a metal pipe according to a first embodiment of the present invention. FIG. [Figure 12] 1 is a front view, partially in cross section, showing a state after a first burring process step in the manufacturing method for a branching portion structure of a metal pipe according to a first embodiment of the present invention. FIG. [Figure 13] 13 is a right side view, partially in section, of the pipe shown in FIG. 12. [Figure 14] 13 is a plan sectional view of the burred portion of the pipe shown in FIG. 12 taken along line MM. [Figure 15] 3 is a plan view, partially in cross section, showing a die rotating step in the manufacturing method for the branch portion structure of the metal pipe according to the first embodiment of the present invention. FIG. [Figure 16] 4 is a front view, partially in section, showing a second burring process step in the manufacturing method for a branched portion structure of a metal pipe according to the first embodiment of the present invention. FIG. [Figure 17] 17 is a right side view, partially in section, of the pipe shown in FIG. 16. [Figure 18] 4 is a right side view, partially in section, showing a second state of a second burring process step in the manufacturing method for a branching portion structure of a metal pipe according to the first embodiment of the present invention. FIG. [Figure 19] 19 is a plan sectional view of the burring processed portion of FIG. 18 taken along line NN. [Figure 20] FIG. 11 is a front view of a mold according to a second embodiment of the present invention. [Figure 21] FIG. 21 is a right side view of the mold shown in FIG. 20. [Figure 22] FIG. 21 is a plan view of the mold shown in FIG. 20. [Diagram 23] FIG. 11 is a plan view of a mold according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Embodiment 1 Hereinafter, a branch structure manufacturing apparatus according to the first embodiment of the present invention will be described with reference to the attached drawings, FIGS. 1 to 4. FIG. 1 is a front view of a mold of the branch structure manufacturing apparatus according to the first embodiment. The mold 10 is a mold made of metal such as stainless alloy, special steel, and tool steel, and is formed in a substantially spherical shape. It has a maximum diameter portion 12 between a front portion 11 and a rear portion 14, where the diameter is a maximum value. The diameter at the maximum diameter portion is called a major diameter A1. The direction in which the major diameter A1 extends, that is, the left-right direction of the drawing of FIG. 1, is called the left-right direction of the mold 10. A rear flat portion 15 is formed in the rear portion 14. In addition, a front curved surface portion 13 is formed between the front portion 11 and the maximum diameter portion 12, and a rear curved surface portion 19 is formed between the rear portion 14 and the maximum diameter portion 12. Furthermore, a through hole 16 extending from the front portion 11 to the rear portion 14 is formed in the mold 10. That is, the through hole 16 extends in a direction perpendicular to the major diameter A1. As will be described in detail later, in the burring process using the die 10, the front portion 11 is the front direction and the rear portion 14 is the rear direction, so the direction in which the through hole 16 extends is called the front-rear direction. A threaded portion 17 is formed on the inner peripheral surface of the through hole 16.

[0013] Fig. 2 is a right side view of the mold 10 of the branching structure manufacturing apparatus according to the first embodiment, and Fig. 3 is a plan view of the mold 10 of the branching structure manufacturing apparatus according to the first embodiment. The mold 10 has a minimum diameter portion 18 between the front portion 11 and the rear portion 14. The minimum diameter portion 18 is a flat portion formed by cutting out a part of one outer diameter portion of the substantially spherical mold 10 and a part of the other outer diameter portion facing the one outer diameter portion in parallel to the direction in which the central axis P extends. The distance between the one minimum diameter portion 18 and the other minimum diameter portion 18 is called the minor axis B1. The maximum diameter portion 12 (see Fig. 1) and the minimum diameter portion 18 form a central portion 40 in the front-rear direction of the mold 10.

[0014] 4 is a front view of the extraction jig 20 of the branch structure manufacturing apparatus according to the first embodiment. The extraction jig 20 is made of a metal such as stainless alloy, special steel, or tool steel, and has a cylindrical tip portion 21, a cylindrical main body portion 25 having a diameter larger than that of the tip portion 21, and a tapered portion 23 connecting the tip portion 21 and the main body portion 25. The tip portion 21 is formed with a jig thread portion 22 that can be screwed into the thread portion 17 (see FIG. 1) of the mold 10. The diameter of the main body portion 25 is called a jig diameter C1. The extraction jig 20 constitutes a connecting member.

[0015] Next, a manufacturing method of the branched portion structure of a metal pipe according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a front cross-sectional view showing a pilot hole forming step of the manufacturing method of the branch structure of the metal pipe of the first embodiment. The pipe 30 is a metal pipe made of any metal, such as stainless alloy, special steel, and tool steel, used for piping various fluids. FIG. 5 shows a cross section of the pipe 30 cut along the center of the inner diameter in the longitudinal direction. The size of the inner diameter of the pipe 30 is called the pipe inner diameter A2. First, a known pilot hole processing machine (not shown) forms an oval spline-shaped pilot hole 31 that connects the inside and outside of the pipe 30 at the branch structure manufacturing location of the pipe 30. Here, the long axis length of the pilot hole 31 is called the long axis length C2. The long axis A1 (see FIG. 1) of the die 10 is formed to be approximately the same length as the pipe inner diameter A2 of the pipe 30, but the long axis A1 is slightly smaller. In addition, the jig diameter C1 (see FIG. 4) of the main body 25 of the drawing jig 20 is formed to be smaller than the long axis length C2.

[0016] 6 is a front view partially in cross section showing a die insertion step of the manufacturing method of a branch structure of a metal pipe according to the first embodiment, and the pipe 30 is shown in the same cross section as in FIG. 5. The die 10 is inserted into the pipe 30 and moved to a position where the pilot hole 31 is formed. At this time, the die 10 is inserted so that the extension direction of the through hole 16 of the die 10 coincides with the extension direction of the pilot hole 31 and the radial centers of the through hole 16 and the pilot hole 31 coincide with each other. At this time, the die 10 is inserted so that the maximum diameter portion 12 of the die 10 faces the longitudinal direction of the pipe 30 and the minimum diameter portion 18 faces the direction perpendicular to the longitudinal direction of the pipe 30, i.e., faces the inner surface of the pipe 30.

[0017] 7 is a front view, partially in cross section, showing a drawing jig coupling step of the manufacturing method for a branch structure of a metal pipe according to the present embodiment 1. The tip 21 of the drawing jig 20 is inserted from the outside into the pilot hole 31 of the pipe 30. The tip 21 inserted inside the pipe 30 is then inserted into the through hole 16 of the die 10. Then, the jig threaded portion 22 of the tip 21 is screwed into the threaded portion 17 of the through hole 16 of the die 10, whereby the tip 21 of the drawing jig 20 is coupled to the die 10.

[0018] FIG. 8 is a right side view showing a partial cross section of the pipe 30 shown in FIG. 7. The front curved surface portion 13 and the rear curved surface portion 19 of the mold 10 are substantially along the inner curved surface of the pipe 30. FIG. 9 is a plan cross-sectional view of the pipe 30 of FIG. 7 cut along the line LL. Referring to FIGS. 8 and 9, the minor axis B1 of the minimum diameter portion 18 of the mold 10 is smaller than the pipe inner diameter A2 of the pipe 30, and a gap 33 is formed between the minimum diameter portion 18 and the inner curved surface of the pipe 30. Compared to a case where a substantially spherical mold 10 without the minimum diameter portion 18 is used, the mold 10 of this embodiment has a gap 33 formed between the minimum diameter portion 18 and the inner surface of the pipe 30, so that the mold 10 can be easily inserted into the inside of the pipe 30 even if the major axis A1 of the mold 10 and the pipe inner diameter A2 of the pipe 30 are substantially the same length.

[0019] Fig. 10 is a front view partially in cross section showing the first burring process of the manufacturing method of the branch structure of a metal pipe according to the first embodiment, and Fig. 11 is a right side view partially in cross section. A known burring machine (not shown) pulls out the drawing jig 20 in the radially outward direction along the extension direction of the pilot hole 31 of the pipe 30, i.e., in the direction of the arrow Z1. As a result, the edge of the pilot hole 31 (see Fig. 7) is pulled out in the direction of the arrow Z1 by the front curved surface portion 13 of the die 10 connected to the drawing jig 20, and the die 10 is pulled out in the direction of the arrow Z1 while forming the burred portion 32.

[0020] Fig. 12 is a front view, partially in cross section, showing a state after a first burring process in the manufacturing method of a branch structure of a metal pipe according to the first embodiment. When the die 10 is removed from the pipe 30, the burring process portion 32 is pushed and spread toward the maximum diameter portion 12 of the die 10 in the direction along the longitudinal direction of the pipe 30, forming an opening having the same length as the major axis A1. Fig. 13 is a right side view, partially in cross section, showing the pipe 30 of Fig. 12. The burring process portion 32 is pushed and spread toward the minimum diameter portion 18 of the die 10 in the direction perpendicular to the longitudinal direction of the pipe 30, forming an opening having the same length as the minor axis B1.

[0021] Fig. 14 is a plan sectional view of the burred portion 32 of the pipe 30 in Fig. 12 taken along line MM. The burred portion 32 has a major axis A1 and a minor axis B1, and is formed as a partially cut circular opening by a straight line portion 32a.

[0022] 15 is a plan view partially in cross section showing a rotation step of the die 10 in the manufacturing method of the branch structure of a metal pipe according to the present embodiment 1. A burring machine (not shown) rotates the drawing jig 20 (see FIG. 12) 90 degrees clockwise, thereby rotating the die 10 90 degrees clockwise. As a result, the maximum diameter portion 12 of the die 10 is positioned perpendicular to the longitudinal direction of the pipe 30, i.e., facing the inner surface of the pipe 30, and the minimum diameter portion 18 of the die 10 is positioned facing the longitudinal direction of the pipe 30.

[0023] Fig. 16 is a front view, partially in cross section, showing a second burring process step in the manufacturing method for a branch structure of a metal pipe according to the first embodiment, and Fig. 17 is a right side view, partially in cross section, of the pipe 30 shown in Fig. 16. A burring machine (not shown) moves the extraction jig 20 to the inside of the pipe 30, i.e., in the direction of the arrow Z2. Then, the die 10 is inserted again into the burring processing section 32 by the movement of the extraction jig 20 in the direction of the arrow Z2.

[0024] Fig. 18 is a right side view, partially in cross section, showing a second state of the second burring process step shown in Fig. 17. When the removal jig 20 moves in the direction of the arrow Z2 to insert the die 10 further into the pipe 30, the straight portions 32a come into contact with the rear curved surface portion 19 of the die 10 and are pushed apart from the maximum diameter portion 12. The straight portions 32a are then pushed apart until the distance between the opposing straight portions 32a becomes equal to the major axis A1, which is the length of the maximum diameter portion 12.

[0025] Fig. 19 is a plan sectional view of the burring processing part 32 shown in Fig. 18 cut along the line NN. The distance between the straight parts 32a (see Fig. 18) is expanded until it is equal to the major axis A1, so that the inner diameter of the burring processing part 32 (see Fig. 16) in the direction along the longitudinal direction of the pipe 30 and the inner diameter of the burring processing part 32 in the direction along the radial direction of the pipe 30 are both equal to the major axis A1. That is, the burring processing part 32 is formed into a circular shape whose diameter is equal to the major axis A1. Next, a burring processing machine (not shown) pulls out the drawing jig 20 and the die 10 to the outside of the pipe 30, thereby completing the burring processing of the burring processing part 32, which is the pipe on the branch side of the branch structure of the pipe 30.

[0026] In this manner, the branch structure manufacturing apparatus according to the first embodiment includes a mold 10 having a central axis P and a spherical shape having a major axis A1 and a minor axis B1 shorter than the major axis A1, the mold 10 extending perpendicularly to the direction in which the central axis P extends, and an extraction jig 20 connectable to the mold 10. When the extraction jig 20 connected to the mold 10 removes the mold 10 inserted into the pipe 30 in which the burring processing portion 32 is to be formed, the mold 10 performs a first burring process on the pilot hole 31 formed at the branch formation position of the pipe 30 and penetrating the body of the pipe 30 in the radial direction, and the extraction jig 20 rotates the removed mold 10 by a predetermined angle around the central axis, and the rotated mold 10 performs a second burring process on the pilot hole 31 from the outside of the pipe 30. As a result, a branch structure having a burring processing portion 32, which is a branch side pipe having the same diameter as the pipe diameter of the main pipe side of the pipe 30, can be manufactured.

[0027] Furthermore, since the mold 10 is a truncated sphere having a pair of opposing minimum diameter portions 18 extending parallel to the central axis P, the spherical mold 10 having a major diameter A1 and a minor diameter B1 can be formed by simple processing.

[0028] In this way, the manufacturing method for the branching structure of a metal pipe according to the first embodiment includes a first step of forming a pilot hole 31 that radially penetrates the body of the pipe 30 at a branching position of the pipe 30; a second step of inserting a spherical mold 10 having a central axis P and extending perpendicularly to the direction in which the central axis P extends, and having a major axis A1 and a minor axis B1 shorter than the major axis A1, into the inside of the pipe 30 and moving the mold 10 to the position of the pilot hole 31; a third step of performing a first burring process on the pilot hole by the mold 10 when removing the mold 10 to the outside of the pipe 30; and a fourth step of rotating the orientation of the mold 10 by a predetermined angle around the central axis and performing a second burring process on the pilot hole 31 from the outside of the pipe 30 by the mold 10. Therefore, a branching structure having a burring process portion 32, which is a pipe on the branching side having the same diameter as the pipe diameter on the main pipe side of the pipe 30, can be manufactured.

[0029] In addition, between the second and third steps, there is a fifth step of inserting the extraction jig 20 into the pilot hole 31 and connecting the die 10 and the extraction jig 20. The third step is performed by pulling the extraction jig 20 connected to the die 10 outward in the radial direction of the pipe 30, and the fourth step is performed by rotating the extraction jig 20 connected to the die 10 by a predetermined angle around the central axis and pushing the extraction jig 20 into the radial direction of the pipe. Therefore, with a simple configuration, the die 10 can be pulled out from the pipe 30 to perform the first burring process, and the die 10 can be pushed into the pipe 30 to perform the second burring process.

[0030] Embodiment 2 Next, a branching structure manufacturing device according to a second embodiment of the present invention will be described with reference to Figures 20, 21 and 22. In the following embodiments, the same reference characters as those in Figures 1 to 19 denote the same or similar components as those in the first embodiment, and detailed descriptions thereof will be omitted. In the branching structure manufacturing device according to the second embodiment, the shape of the mold in the first embodiment is changed from a truncated sphere to an ellipsoid. FIG. 20 is a front view of a mold 10a of the second embodiment. The mold 10a has a maximum diameter portion 12a, a front curved surface portion 13a, and a rear curved surface portion 19a. FIG. 21 is a right side view of the mold 10a shown in FIG. 20, and FIG. 22 is a plan view of the mold 10a shown in FIG. 20. The mold 10a is formed in an ellipsoid shape having a maximum diameter portion 12a and a minimum diameter portion 18a formed at a position rotated 90 degrees in the circumferential direction around the central axis P with respect to the maximum diameter portion 12a. The diameter of the maximum diameter portion 12a is a major axis A1. The diameter of the minimum diameter portion 18a is a minor axis B1. The other configurations are the same as those of the first embodiment.

[0031] In this way, even though the mold 10a is ellipsoidal, it has a major axis A1 and a minor axis B1 in the direction perpendicular to the central axis P, as in embodiment 1, so that it is possible to manufacture a branch structure having a burring processing portion 32, which is a branch side tube having the same diameter as the main tube diameter of the pipe 30, as in embodiment 1.

[0032] Embodiment 3 Next, a branching structure manufacturing device according to a third embodiment of the present invention will be described with reference to Fig. 23. In this third embodiment, the same reference characters as those in Figs. 20 to 22 denote the same or similar components as those in the second embodiment, and detailed descriptions thereof will be omitted. The branching structure manufacturing device of the third embodiment is obtained by modifying the shape of the maximum diameter portion 12a of the mold 10a of the second embodiment. 23 is a plan view of a mold 10b according to the third embodiment. A notch 41 is formed at a position rotated 90 degrees circumferentially around the through hole 16 with respect to the minimum diameter portion 18a of the mold 10b. The notch 41 is formed along the outer periphery of the mold 10b from the front to the rear portion 14 of the mold 10b. The maximum diameter portions 12b of the mold 10b are formed at positions on both sides of the notch 41 in the central portion 40. The distance from one maximum diameter portion 12b to the other maximum diameter portion 12b across the through hole 16 is the major axis A1. The other configurations are the same as those of the second embodiment.

[0033] In this way, even though the mold 10b is ellipsoidal with the notch 41 formed along its outer periphery, it has a major axis A1 and a minor axis B1 in the direction perpendicular to the central axis as in embodiment 1, so that it is possible to manufacture a branch structure having a burring processed portion 32, which is a branch side tube having the same diameter as the main tube diameter of the pipe 30, as in embodiment 1.

[0034] In the first and second embodiments of the present invention, the shapes of the dies 10, 10a, and 10b are described, but these shapes are merely examples and are not limited to these. Also, the length of the maximum diameter part of the dies 10, 10a, and 10b is the major axis A1, which is approximately the same as the pipe inner diameter A2 of the pipe 30, but the major axis A1 of the dies 10, 10a, and 10b may be any other length as long as it is equal to or less than the pipe inner diameter A2 of the pipe 30.

[0035] In the first and second embodiments of the present invention, the dies 10, 10a, 10b and the extraction jig 20 are made of metals such as stainless steel alloy, special steel, and tool steel, but may be made of any other metal. Also, the pipe 30 is made of metals such as stainless steel alloy, special steel, and tool steel, but may be made of any other metal such as copper.

[0036] In the first and second embodiments of the present invention, the major axis A1 and the minor axis B1 of the dies 10, 10a, and 10b are perpendicular to each other, but the shapes of the dies 10, 10a, and 10b are not limited to this. In the first and second embodiments of the present invention, the dies 10, 10a, and 10b are rotated by 90 degrees after the first burring process, but if the major axis A1 and the minor axis B1 of the dies 10, 10a, and 10b do not intersect perpendicularly, the angle by which the dies 10, 10a, and 10b are rotated after the first burring process may be changed appropriately according to the angle between the major axis A1 and the minor axis B1. [Explanation of symbols]

[0037] 10, 10a, 10b mold, 18 smallest diameter portion (flat portion), 20 pulling jig (connecting member), 30 pipe (metal pipe), 31 pilot hole, A1 major diameter (first diameter), B1 minor diameter (second diameter), P central axis.

Claims

1. A mold having a spherical shape with a central axis and a first diameter and a second diameter that is shorter than the first diameter, the first diameter extending perpendicularly to a direction in which the central axis extends; A connecting member connectable to the mold; The die includes a front curved surface portion, a maximum diameter portion, and a rear curved surface portion, which are provided in this order along the direction in which the central axis extends. Equipped with When a connecting member connected to the die is removed from the die inserted inside the metal pipe to the outside of the metal pipe, the front curved portion performs a first burring process on a pilot hole that is formed in the metal pipe at a branch formation position of the metal pipe and radially penetrates a body of the metal pipe, and the connecting member rotates the removed die by a predetermined angle about the central axis, and the rear curved portion performs a second burring process from the outside of the metal pipe on the pilot hole after the first burring process.

2. 2. The manufacturing device for a branched portion structure of a metal pipe according to claim 1, wherein the die is a partially cut sphere having a pair of opposing flat surfaces extending parallel to the central axis.

3. 2. The manufacturing apparatus for a branched portion structure of a metal pipe according to claim 1, wherein the die is ellipsoidal.

4. a first step of forming a pilot hole at a branch portion formation position of the metal pipe, the pilot hole passing through a body of the metal pipe in a radial direction; a second step of inserting a spherical mold having a central axis and a first diameter extending perpendicularly to a direction in which the central axis extends, the first diameter being shorter than the first diameter, and the mold having a front curved surface portion, a maximum diameter portion, and a rear curved surface portion, which are provided in that order along the direction in which the central axis extends, into the metal tube, and moving the mold to the position of the pilot hole; a third step of performing a first burring process on the pilot hole by the front curved surface portion when the die is removed to the outside of the metal tube; a fourth step of rotating the orientation of the die by a predetermined angle around the central axis, and performing a second burring process on the pilot hole after the first burring process from the outside of the metal tube by the rear curved surface portion; A method for manufacturing a branched portion structure of a metal pipe, comprising:

5. a fifth step between the second step and the third step of inserting a connecting member into the pilot hole and connecting the die and the connecting member; the third step is performed by drawing the connecting member connected to the die outward in a radial direction of the metal pipe, 5. The method for manufacturing a branched portion structure of a metal pipe according to claim 4, wherein the fourth step is performed by rotating the connecting member connected to the die through a predetermined angle around the central axis and pushing the connecting member radially inwardly into the metal pipe.

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