Extrusion forming method and extrusion forming device for pipes with different thicknesses

Abstract

The inner side of a pipe material is provided with a small inner diameter region having an inner diameter smaller than the outer diameter of the pipe material and a large inner diameter region having an inner diameter larger than the outer diameter of the pipe material on the front end side and the base end side. A mandrel (metal core) having a small outer diameter region having an outer diameter corresponding to the inner diameter of the pipe material and a large outer diameter region having an outer diameter larger than the inner diameter of the pipe material is press-fitted on the tip side and the base end side, respectively, and the base end side end of the pipe material is expanded in diameter, and then the base end side end of the pipe material is pressed by a sleeve. The pipe into which the mandrel is inserted is pressed into the small-inner-diameter region of the extrusion container, and the diameter of the pipe is reduced. As a result, it is possible to provide an extrusion molding method and an extrusion molding device for an unequal-thickness pipe in which the diameter difference between a large-diameter section (ear section) and a small-diameter section (unequal-thickness section formed by reducing the diameter) can be set to be large without an excessive increase in the machining load, and in which the length in the axial direction can be set arbitrarily.

Description

Technical Field

[0001] The invention relates to an extrusion molding method and an extrusion molding device for tubes of unequal thickness. Background Art

[0002] In this technical field, there is known a tube of unequal thickness (also called "butted pipe" and "butted tube") in which a thick wall portion is formed in a part of the tube in the axial direction for the purpose of achieving desired mechanical strength in the thick wall portion and achieving weight reduction in the thin wall portion (portion other than the thick wall portion).

[0003] As an extrusion molding method for obtaining the above-mentioned unequal thickness tube, for example, the method described in Japanese Patent Gazette No. 6933762 (Patent Document 1) of the present applicant is known. According to this method, a large diameter portion (ear portion) maintaining the outer diameter of the tube and a small diameter portion reduced in diameter and extending in the axial direction (extrusion direction) can be integrally formed from a tube having a constant outer diameter and wall thickness, and two portions (unequal thickness portions) having different wall thicknesses can be formed in the small diameter portion.

[0004] In the above method, in order to obtain an unequal thickness tube having a large diameter portion with a larger outer diameter, it is necessary to make the outer diameter of the tube larger accordingly. In this case, if the outer diameter of the small diameter portion of the unequal thickness tube is maintained unchanged, the result is that the reduction rate (reduction amount) in the extrusion molding of the unequal thickness tube becomes larger, and the processing load increases. Therefore, due to the processing limit of the extrusion molding device determined by, for example, the material constituting the tube material and the material of the components constituting the extrusion molding device and the extrusion performance of the extrusion molding device, it may be difficult or impossible to achieve the target reduction rate. In addition, even if the reduction processing (extrusion processing) is within the processing limit, the greater the reduction amount, the greater the extrusion resistance, so it is inevitable to reduce the extrusion amount, and it may be difficult or impossible to form a small diameter portion with a desired shape (such as the length in the axial direction, etc.).

[0005] On the other hand, Japanese Patent No. 6256668 (Patent Document 2) proposes a forming method in which a mandrel is pressed into a pipe from the base end side of the pipe while the end of the mandrel on the front end side of the pipe in the direction of the mandrel being pressed into the pipe is blocked so as not to move further toward the front end side and the relative position of the pipe with respect to the die in the longitudinal direction is fixed (for example, see paragraph

[0022] , etc.). Thus, the end of the base end side of the pipe is made into an expanded diameter portion with an expanded outer diameter, and the outer diameter of the portion closer to the front end side of the expanded diameter portion of the pipe (non-expanded diameter portion) is maintained unchanged, and the inner diameter of the region adjacent to the front end side of the expanded diameter portion is expanded, so that the wall thickness of the non-expanded diameter portion can be changed (uneven thickness) by performing ironing and drawing.

[0006] However, in the above method, since the end portion of the front end side of the pipe material is blocked, the material constituting the non-expanded portion whose inner diameter is expanded as the mandrel moves forward flows in the direction opposite to the moving direction of the mandrel, that is, toward the base end side, so that the non-expanded portion extends toward the base end side, and the contact area with the mandrel increases. As a result, the friction between the non-expanded portion and the mandrel increases, causing the processing load to increase as the mandrel moves forward, so the above method is not suitable for forming a long workpiece (axially long tube of uneven thickness).

[0007] Patent Document 1: Japanese Patent No. 6933762

[0008] Patent Document 2: Japanese Patent No. 6256668

[0009] As described above, in this technical field, there is a need for an extrusion molding method for unequal thickness tubes that can set the diameter difference between the large diameter portion (ear portion) and the small diameter portion (unequal thickness portion formed by diameter reduction) to be larger without excessive increase in processing load and can also arbitrarily set the axial length. Summary of the invention

[0010] In view of the above-mentioned problems, the inventors conducted in-depth research and found that: a mandrel (metal core) having a small outer diameter area with an outer diameter corresponding to the inner diameter of the tube and a large outer diameter area with an outer diameter larger than the inner diameter of the tube on the front end side and the base end side, respectively, is pressed into the interior of an extrusion cylinder (mold) provided with a small inner diameter area with an inner diameter smaller than the outer diameter of the tube and a large inner diameter area with an inner diameter larger than the outer diameter of the tube on the front end side and the base end side, respectively, so that the end part of the base end side of the tube is expanded in diameter, and then the end part of the base end side of the tube is extruded by a sleeve, and the tube with the mandrel inserted inside is pressed into the small inner diameter area of ​​the extrusion cylinder to reduce its diameter, thereby solving the above-mentioned problems.

[0011] Specifically, the extrusion molding method of the unequal thickness tube involved in the present invention (hereinafter referred to as "the method of the present invention") includes the first step to the third step performed in an extrusion molding device. The extrusion molding device has: a mandrel, which is a metal core having a predetermined shape; a sleeve, which is a cylindrical member coaxially arranged outside the mandrel; an extrusion cylinder, which is a die formed with a through hole having a predetermined shape, i.e., an extrusion cylinder hole; and a driving mechanism configured to press the mandrel and the sleeve into the extrusion cylinder hole.

[0012] The first step is to place a tube having a predetermined shape at a predetermined position inside the hole of the extrusion cylinder. The second step is to press the mandrel into the tube by a driving mechanism to expand the diameter of the upstream side, i.e., the base end side, of the tube in the extrusion direction. The third step is to press the tube into the downstream side, i.e., the front end side, of the extrusion cylinder hole by extruding the end of the base end side of the tube through the sleeve at a time later than the start time of the second step, i.e., the first time, to perform extrusion processing, thereby reducing the diameter of the front end side of the tube.

[0013] The pipe material is a cylindrical part having a first outer diameter of a prescribed outer diameter, a first inner diameter of a prescribed inner diameter, and a first wall thickness of a prescribed wall thickness. The unequal thickness pipe formed according to the method of the present invention includes a first small diameter region, a second small diameter region, and a large diameter region in order from the front end side toward the base end side. The first small diameter region is a region having a second outer diameter of a prescribed outer diameter smaller than the first outer diameter, a second inner diameter of an inner diameter equal to the first inner diameter, and a second wall thickness of a prescribed wall thickness smaller than the first wall thickness. The second small diameter region is a region having a third outer diameter of an outer diameter equal to the second outer diameter and a third wall thickness of a prescribed wall thickness smaller than the second wall thickness. The large diameter region is a region having a fourth outer diameter of a prescribed outer diameter larger than the first outer diameter and a fourth wall thickness of a prescribed wall thickness.

[0014] The mandrel includes a small cross-sectional area, a large cross-sectional area, and a cross-sectional expansion area. The small cross-sectional area is a cylindrical area formed on the front end side and having a first cross-sectional area, wherein the first cross-sectional area is a circular cross-sectional area having a fifth outer diameter and an outer diameter corresponding to the first inner diameter and the second inner diameter. The large cross-sectional area is a columnar area formed on the base end side and having a second cross-sectional area, wherein the second cross-sectional area is a cross-sectional area corresponding to the cross-sectional area of ​​the internal space of the second small diameter area and the large diameter area. The cross-sectional expansion area is an area formed between the small cross-sectional area and the large cross-sectional area and whose cross-sectional area expands from the first cross-sectional area to the second cross-sectional area as it approaches from the small cross-sectional area to the large cross-sectional area.

[0015] The sleeve includes an extruded region which is a cylindrical region formed on the front end side and having a seventh outer diameter equal to the fourth outer diameter and a columnar internal space having a third cross section corresponding to the second cross section.

[0016] In addition, the shapes of the cross-sections of the inner spaces of the second small diameter region and the large diameter region of the unequal thickness tube are not particularly limited, and can be various shapes such as polygonal, elliptical, and circular. In other words, the shapes of the inner spaces of the second small diameter region and the large diameter region are not particularly limited, and can be various shapes such as polygonal, elliptical, and cylindrical.

[0017] For example, the inner space of the second small diameter region may have a cylindrical shape having a third inner diameter having a predetermined inner diameter larger than the first inner diameter, and the inner space of the large diameter region may have a cylindrical shape having a fourth inner diameter having an inner diameter equal to the third inner diameter. In this case, the large cross-sectional region of the mandrel has a cylindrical shape having a sixth outer diameter having an outer diameter corresponding to the fourth inner diameter, and the cross-sectional expansion region of the mandrel has a truncated cone shape whose outer diameter increases from the fifth outer diameter of the small cross-sectional region to the sixth outer diameter of the large cross-sectional region as it approaches the small cross-sectional region. In addition, the extrusion region of the sleeve has a cylindrical shape having a seventh outer diameter and a seventh inner diameter having an inner diameter equal to the third inner diameter and the fourth inner diameter.

[0018] The extrusion cylinder hole includes a large inner diameter region, a small inner diameter region, and a reduced inner diameter region. The large inner diameter region is a region of the sixth inner diameter formed on the base end side and having an inner diameter corresponding to the fourth outer diameter. The small inner diameter region is a region of the seventh inner diameter formed on the front end side and having an inner diameter corresponding to the second outer diameter and the third outer diameter. The reduced inner diameter region is a region formed between the large inner diameter region and the small inner diameter region and whose inner diameter decreases from the sixth inner diameter to the seventh inner diameter as it approaches from the large inner diameter region to the small inner diameter region.

[0019] Furthermore, in the method of the present invention, at the moment when the third step begins, that is, the second moment, the end of the front end side of the mandrel in the extrusion direction reaches the end of the front end side of the tube or a position closer to the front end side than the end of the front end side of the tube, and the end of the base end side of the small cross-sectional area of ​​the mandrel is located at a position closer to the base end side than the end of the base end side of the small inner diameter area of ​​the extrusion barrel hole.

[0020] Another aspect of the method of the present invention is an extrusion molding method for forming a tube of unequal thickness by pressing a tube of a predetermined shape into an extrusion cylinder hole through a sleeve in an extrusion molding device. The extrusion molding device used in the method of the present invention in this aspect comprises: a mandrel, which is a metal core of a predetermined shape; a sleeve, which is a cylindrical component coaxially arranged outside the mandrel; an extrusion cylinder, which is a die formed with a through hole of a predetermined shape, i.e., an extrusion cylinder hole; and a drive mechanism, which is configured to at least press the sleeve into the extrusion cylinder hole.

[0021] The pipe is a cylindrical part having an 11th outer diameter of a specified outer diameter, an 11th inner diameter of a specified inner diameter, and an 11th wall thickness of a specified wall thickness. The unequal thickness pipe includes an 11th small outer diameter region, an 11th large outer diameter region, and an 11th outer diameter increase region. The 11th small outer diameter region is a region formed on the downstream side, i.e., the front end side, in the direction in which the pipe is pressed into the hole of the extrusion cylinder, i.e., in the extrusion direction, and has a 12th outer diameter of a specified outer diameter smaller than the 11th outer diameter, a 12th inner diameter of an inner diameter equal to the 11th inner diameter, and a 12th wall thickness of a specified wall thickness smaller than the 11th wall thickness. The 11th large outer diameter region is a region formed on the upstream side, i.e., the base end side, in the extrusion direction, and has a 13th outer diameter of a specified outer diameter larger than the 11th outer diameter, a 13th inner diameter of an inner diameter equal to the 11th inner diameter, and a 13th wall thickness of a specified wall thickness larger than the 11th wall thickness. The 11th outer diameter increased region is formed between the 11th small outer diameter region and the 11th large outer diameter region and the outer diameter increases from the 12th outer diameter to the 13th outer diameter as approaching the 11th small outer diameter region toward the 11th large outer diameter region, the wall thickness increases from the 12th wall thickness to the 13th wall thickness, and the inner diameter is a constant 14th inner diameter equal to the 11th inner diameter.

[0022] The mandrel includes a basic outer diameter region, which is a cylindrical region of the 14th outer diameter formed on the front end side and having an outer diameter corresponding to the 11th inner diameter. The sleeve includes an 11th extrusion region, which is a cylindrical region of a cylindrical inner space having a 15th outer diameter formed on the front end side and having an outer diameter equal to the 13th outer diameter and a 15th inner diameter having an inner diameter corresponding to the 14th outer diameter. The extrusion barrel hole includes an 11th large inner diameter region, an 11th small inner diameter region, and an 11th reduced inner diameter region. The 11th large inner diameter region is a region of the 16th inner diameter formed on the base end side and having an inner diameter corresponding to the 13th outer diameter. The 11th small inner diameter region is a region of the 17th inner diameter formed on the front end side and having an inner diameter corresponding to the 12th outer diameter. The 11th reduced inner diameter region is a region formed between the 11th large inner diameter region and the 11th small inner diameter region and has an inner diameter that decreases from the 16th inner diameter to the 17th inner diameter as it approaches the 11th large inner diameter region.

[0023] The method of the present invention according to this aspect includes the 11th to 13th steps listed below.

[0024] The eleventh step is a step of placing the tube at a predetermined position inside the extrusion cylinder hole by bringing the end of the front end side of the tube into contact with the reduced inner diameter region of the extrusion cylinder hole.

[0025] The twelfth step is a step of extruding the end of the base end of the tube through the sleeve while the mandrel is inserted into the tube, causing the material constituting the tube to plastically flow and fill the space between the extrusion cylinder and the mandrel in the 11th large inner diameter area and the 11th inner diameter reduction area of ​​the extrusion cylinder hole, thereby maintaining the inner diameter of the tube at the 11th inner diameter and expanding the outer diameter of the tube to the 13th outer diameter.

[0026] The 13th process is a process of reducing the diameter of the front end side of the tube by performing an extrusion process. In the above extrusion process, when the mandrel is inserted into the tube, the end of the base end side of the tube is further extruded by the sleeve, and the material constituting the tube is extruded toward the 11th small inner diameter area of ​​the extrusion tube hole through the gap between the end of the base end side of the 11th small inner diameter area of ​​the extrusion tube hole and the mandrel.

[0027] Furthermore, at the time when the 12th process starts, that is, the 11th time, the end of the front end side of the mandrel reaches the same position as the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole in the extrusion direction, that is, the 11th position, or a position closer to the front end side than the 11th position. Furthermore, at the time when the 13th process starts, that is, the 12th time, the end of the front end side of the mandrel reaches a position closer to the front end side by a predetermined distance in the extrusion direction than the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, that is, the 12th position, or a position closer to the front end side than the 12th position.

[0028] In addition, the present invention also relates to an extrusion molding device for unequal thickness tubes (hereinafter referred to as "the device of the present invention") for molding unequal thickness tubes by executing the above-mentioned method of the present invention.

[0029] In the method of the present invention, as described above, in the first step, a pipe is placed in an extrusion barrel formed with an extrusion barrel hole, and the extrusion barrel hole has a small inner diameter region having an inner diameter smaller than the outer diameter of the pipe and a large inner diameter region having an inner diameter larger than the outer diameter of the pipe on the front end side and the base end side, respectively. Then, in the second step, a mandrel having a small outer diameter region having an outer diameter corresponding to the inner diameter of the pipe and a large outer diameter region having an outer diameter larger than the inner diameter of the pipe on the front end side and the base end side, respectively, is pressed into the inside of the pipe to expand the diameter of the end portion of the base end side of the pipe. Furthermore, in the third step, the end portion of the base end side of the pipe is extruded by the sleeve, and the pipe with the mandrel inserted inside is pressed into the small inner diameter region of the extrusion barrel to reduce its diameter.

[0030] Therefore, according to the present invention, compared with the case where the diameter difference between the large diameter part and the small diameter part of the unequal thickness tube is increased by increasing the outer diameter of the tube material, the increase in processing load can be reduced. In addition, as described in detail later, the increase in processing load accompanying the elongation of the unequal thickness tube to be formed can be reduced. That is, according to the present invention, it is possible to provide an extrusion molding method and an extrusion molding device for unequal thickness tubes, which can set the diameter difference between the large diameter part (ear part) and the small diameter part (unequal thickness part formed by reducing the diameter) to be larger without excessive increase in processing load and can also arbitrarily set the length in the axial direction.

[0031] In addition, in the unequal thickness tube formed by the method of the present invention according to another embodiment, the 11th large outer diameter region is formed by thickening the tube material, and the 11th small outer diameter region is formed by thinning the tube material. Therefore, compared with the case where the large outer diameter region is formed while maintaining the outer diameter of the tube material and the small outer diameter region is formed by greatly reducing the outer diameter of the tube material, a larger diameter difference can be achieved with a smaller processing load. In addition, the wall thickness of the large outer diameter region can be increased, so that, for example, an unequal thickness tube suitable for applications requiring high mechanical strength in the large diameter portion can be formed.

[0032] In addition, the axial lengths of the 11th large outer diameter region and the 11th small outer diameter region vary according to the axial length of the tube, the diameter expansion amount in the 12th step, the diameter reduction amount in the 13th step, and the amount of the sleeve pressed into the tube. That is, the axial lengths of the 11th large outer diameter region and the 11th small outer diameter region of the unequal thickness tube can be arbitrarily set.

[0033] Other objects, other features and incidental advantages of the present invention will be easily understood from the description of the embodiments of the present invention described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flowchart showing the flow of each step included in the extrusion molding method (first method) of a tube of unequal thickness according to the first embodiment of the present invention.

[0035] Figure 2 This is a schematic cross-sectional view showing an example of the structure of the pipe material used in the first method and the unequal thickness pipe formed from the pipe material.

[0036] Figure 3 This is a schematic cross-sectional view showing an example of the structure of the mandrel, sleeve, and extrusion cylinder used in the first method.

[0037] Figure 4 This is a schematic cross-sectional view showing an example of a change in the shape of the pipe material accompanying the execution of the first method.

[0038] Figure 5This is a photograph showing the smoothing of the inner peripheral surface of the pipe material accompanying the execution of the second step included in the first method.

[0039] Figure 6 This is a schematic cross-sectional view showing an example of a change in the shape of a pipe material when a unequal thickness pipe having a second small diameter region including two portions having different shapes is formed by the first method according to the modification.

[0040] Figure 7 It is a schematic cross-sectional view of an extrusion cylinder used in the first method according to another modification and a tube of unequal thickness molded using the extrusion cylinder.

[0041] Figure 8 This is a schematic cross-sectional view showing an example of the structure of a tube material used in the extrusion molding method of a tube of uneven thickness (fifth method) according to the fifth embodiment of the present invention and a tube of uneven thickness molded from the tube material.

[0042] Fig. 9 This is a schematic cross-sectional view showing an example of the structure of the mandrel, sleeve, and extrusion cylinder used in the fifth method.

[0043] Fig.10 This is a flowchart showing the flow of each step included in the fifth method.

[0044] Fig.11 This is a schematic cross-sectional view showing an example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder, and unequal thickness pipe as the fifth method proceeds.

[0045] Fig.12 This is a schematic cross-sectional view showing another example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder, and unequal thickness pipe as the fifth method is performed.

[0046] Fig.13 This is a schematic cross-sectional view showing an example of the structure of a tube material used in one form of an extrusion molding method of a tube of uneven thickness (sixth method) according to a sixth embodiment of the present invention and a tube of uneven thickness molded from the tube material.

[0047] Fig.14 This is a schematic cross-sectional view showing an example of the structure of a mandrel, a sleeve, and an extrusion cylinder used in the sixth method involved in the first aspect.

[0048] Fig.15 This is a schematic cross-sectional view showing an example of changes in the positional relationship and shape of the pipe, mandrel, sleeve, extrusion cylinder, and unequal thickness pipe as the sixth method involved in the first embodiment is carried out.

[0049] Fig.16 This is a schematic cross-sectional view showing an example of changes in the positional relationship and shape of the tube, mandrel, sleeve, extrusion cylinder and unequal thickness tube accompanying the modification of the sixth method involved in the first form.

[0050] Fig.17 This is a schematic cross-sectional view showing an example of the structure of a pipe material used in the sixth method involved in the second aspect and a tube of unequal thickness formed from the pipe material.

[0051] Fig.18 This is a schematic cross-sectional view showing an example of the structure of a mandrel, a sleeve, and an extrusion cylinder used in the sixth method involved in the second aspect.

[0052] Fig.19 This is a schematic cross-sectional view showing an example of changes in the positional relationship and shape of the pipe, mandrel, sleeve, extrusion cylinder, and unequal thickness pipe as the sixth method involved in the second embodiment is carried out.

[0053] Fig. 20 This is a schematic cross-sectional view showing an example of the structure of a tube material used in the extrusion molding method of a tube of uneven thickness (the seventh method) according to the seventh embodiment of the present invention and a tube of uneven thickness molded from the tube material.

[0054] Fig.21 This is a schematic cross-sectional view showing an example of the structure of a mandrel, a sleeve, and an extrusion cylinder used in the seventh method.

[0055] Fig. 22 This is a schematic cross-sectional view showing an example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe as the seventh method is carried out.

[0056] Fig.23 This is a schematic cross-sectional view showing an example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe as the process is carried out when the seventh method is applied to the sixth method involved in the second form.

[0057] Fig.24 Yes means Fig.23 Schematic front view of the appearance of the pipe 111 ′ and the uneven thickness pipe 121 ′ shown in FIG.

[0058] Fig.25 is Fig.24 A cross-sectional view of the portion enclosed by the thick dotted line.

[0059] Fig.26This is a schematic cross-sectional view showing an example of the structure of a tube material used in the extrusion molding method of a tube of uneven thickness (eighth method) according to the eighth embodiment of the present invention and a tube of uneven thickness molded from the tube material.

[0060] Fig. 27 This is a schematic cross-sectional view showing an example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe as the eighth method is carried out. DETAILED DESCRIPTION

[0061] 《First Implementation Method》

[0062] Hereinafter, an extrusion molding method of a tube of unequal thickness according to a first embodiment of the present invention (hereinafter sometimes referred to as a “first method”) will be described with reference to the drawings.

[0063] <structure>

[0064] The first method includes the first step to the third step performed in an extrusion molding device. The extrusion molding device comprises: a mandrel, which is a metal core having a predetermined shape; a sleeve, which is a cylindrical member coaxially arranged outside the mandrel; an extrusion cylinder, which is a die formed with a through hole having a predetermined shape, i.e., an extrusion cylinder hole; and a driving mechanism configured to press the mandrel and the sleeve into the extrusion cylinder hole.

[0065] The basic structure of the extrusion molding device is well known to those skilled in the art, so a detailed description is omitted. The components represented by the mandrel, sleeve, and extrusion barrel are made of materials having properties (such as mechanical strength and durability, etc.) that can withstand processing conditions such as loads acting on the components in the extrusion process described later. In addition, the driving mechanism for pressing the mandrel and sleeve into the extrusion barrel hole can be appropriately selected from various driving mechanisms known in the technical field according to the properties of the material constituting the pipe to be extruded (such as mechanical strength and hardness, etc.). Typically, a press such as a hydraulic press can be used as the driving mechanism.

[0066] Figure 1 1 is a flowchart showing the flow of each process included in the first method. The first process performed in step S01 is a process of setting a pipe having a predetermined shape at a predetermined position inside the extrusion cylinder hole. Specifically, in the first process, the pipe is set at a predetermined position inside the extrusion cylinder hole by making the end of the front end side of the pipe abut against the inner diameter reduction area formed between the large inner diameter area and the small inner diameter area of ​​the extrusion cylinder hole formed in the extrusion cylinder (the above-mentioned areas will be described later).

[0067] In addition, in order to form a tube of unequal thickness having a predetermined shape by the first method, the tube needs to be coaxially arranged with respect to the mandrel, the sleeve and the extrusion cylinder. The method for arranging the tube in this way is not particularly limited, and for example, by arranging a tapered portion at the end of the front end side of the mandrel, and inserting the tapered portion into the tube when the diameter expansion of the tube is to be started in the second step, the tube can be coaxially arranged with respect to the mandrel, the sleeve and the extrusion cylinder.

[0068] The second process performed in step S02 is a process of expanding the diameter of the upstream side, i.e., the base end side, of the pipe in the extrusion direction by pressing the mandrel into the pipe by a driving mechanism. The third process performed in step S03 is a process of performing extrusion processing by pressing the end of the base end side of the pipe by a sleeve at a time later than the time when the second process starts, i.e., the first time, to press the pipe into the downstream side, i.e., the front end side, of the extrusion direction of the extrusion cylinder hole, thereby reducing the diameter of the front end side of the pipe. As described in detail later, by performing the above-mentioned first to third processes included in the first method, a pipe of unequal thickness having a specified shape can be formed.

[0069] Hereinafter, details of the pipe material, mandrel, sleeve, and extrusion cylinder used in the first method, and the unequal thickness pipe formed by executing the first method will be described with reference to the drawings.

[0070] Figure 2 FIG. 1 is a schematic cross-sectional view showing an example of the structure of a pipe material used in the first method and a pipe of unequal thickness formed from the pipe material. Figure 2 As shown in (a) of FIG. 1 , the pipe material 11 is a cylindrical member having a first outer diameter DO1 of a predetermined outer diameter, a first inner diameter DI1 of a predetermined inner diameter, and a first wall thickness T1 of a predetermined wall thickness.

[0071] In addition, the shape of the pipe is not necessarily limited to Figure 2 The illustrated simple cylindrical shape may be provided with a portion having a different structure at the end of the front end side of the pipe material, for example, as long as it does not hinder the execution of the first method. Specifically, for example, a cylindrical portion having a prescribed outer diameter smaller than the outer diameter of the small inner diameter region of the extrusion cylinder hole, a prescribed inner diameter less than the first inner diameter DI1, which is the inner diameter of the pipe material, and a prescribed wall thickness smaller than the first wall thickness T1, which is the wall thickness of the pipe material, may be provided at the end of the front end side of the pipe material.

[0072] The material constituting the tube 11 is not particularly limited as long as it can be formed into a desired shape by plastic deformation during extrusion. Typically, the material constituting the tube 11 is a metal represented by lead, tin, aluminum, copper, zirconium, titanium, molybdenum, vanadium, niobium, and steel.

[0073] Next, if Figure 2As shown in (b), the unequal thickness tube 21 formed by the first method includes a first small diameter region RSD1, a second small diameter region RSD2, and a large diameter region RLD in order from the front end side (the lower side in the drawing) toward the base end side (the upper side in the drawing). The first small diameter region RSD1 is a region having a second outer diameter DO2 (DO2<DO1) having a specified outer diameter smaller than the first outer diameter DO1, a second inner diameter DI2 (DI2=DI1) having an inner diameter equal to the first inner diameter DI1, and a second wall thickness T2 (T2<T1) having a specified wall thickness smaller than the first wall thickness T1. The second small diameter region RSD2 is a region having a third outer diameter DO3 (DO3=DO2) having an outer diameter equal to the second outer diameter DO2, and a third wall thickness T3 (T3<T2) having a specified wall thickness smaller than the second wall thickness T2. The large diameter region RLD is a region having a fourth outer diameter DO4 of a predetermined outer diameter greater than the first outer diameter DO1 and a fourth wall thickness T4 of a predetermined wall thickness. In addition, the internal spaces of the second small diameter region RSD2 and the large diameter region RLD are both formed by expanding the internal space of the pipe 21 by a large cross-sectional area of ​​a mandrel described later, so the shapes of the cross sections of the internal spaces of the second small diameter region RSD2 and the large diameter region RLD are the same.

[0074] In addition, a first tapered region RtDI1 is formed between the first small diameter region RSD1 and the second small diameter region RSD2, and the first tapered region RtDI1 is a portion where the wall thickness decreases from the second wall thickness T2 to the third wall thickness T3 and the cross section of the internal space expands (but the outer diameter remains unchanged) as the first small diameter region RSD1 approaches the second small diameter region RSD2. In addition, a second tapered region RtDI2 is formed between the second small diameter region RSD2 and the large diameter region RLD, and the second tapered region RtDI2 is a portion where the wall thickness increases from the third wall thickness T3 to the fourth wall thickness T4 and the outer diameter increases (but the cross section of the internal space remains unchanged) as the second small diameter region RSD2 approaches the large diameter region RLD. Details of the first tapered region RtDI1 and the second tapered region RtDI2 will be described later.

[0075] In addition, as described above, the shape of the cross section of the internal space of the second small diameter region RSD2 and the large diameter region RLD is not particularly limited, and can be set to various shapes such as polygonal, elliptical and circular. In other words, the shape of the internal space of the second small diameter region RSD2 and the large diameter region RLD is not particularly limited, and can be set to various shapes such as polygonal, elliptical and cylindrical. Therefore, as long as the shape of the cross section of the internal space of the first small diameter region RSD1 (circular) approaches the shape of the cross section of the internal space of the second small diameter region RSD2 and the cross section expands as it approaches from the first small diameter region RSD1 to the second small diameter region RSD2, the shape of the internal space of the first tapered region RtDI1 is not particularly limited. In addition, as described above, the shapes of the cross sections of the internal spaces of the second small diameter region RSD2 and the large diameter region RLD are the same. Therefore, the cross-sectional shape of the internal space of the second tapered region RtDI2 formed between the second small-diameter region RSD2 and the large-diameter region RLD is also entirely identical to the cross-sectional shapes of the internal spaces of the second small-diameter region RSD2 and the large-diameter region RLD.

[0076] The mandrel includes a small cross-sectional area, a large cross-sectional area, and a cross-sectional expansion area. The small cross-sectional area is a cylindrical area formed on the front end side and having a first cross-sectional area, wherein the first cross-sectional area is a circular cross-sectional area having a fifth outer diameter corresponding to the second inner diameter. The large cross-sectional area is a columnar area formed on the base end side and having a second cross-sectional area, wherein the second cross-sectional area is a cross-sectional area corresponding to the cross-sectional area of ​​the internal space of the second small diameter area and the large diameter area. The cross-sectional expansion area is an area formed between the small cross-sectional area and the large cross-sectional area and whose cross-sectional area expands from the first cross-sectional area to the second cross-sectional area as it approaches from the small cross-sectional area to the large cross-sectional area.

[0077] The sleeve includes an extruded area, which is a cylindrical area formed on the front end side and having a seventh outer diameter equal to the fourth outer diameter and a columnar internal space having a third cross-section corresponding to the second cross-section.

[0078] The extrusion cylinder hole includes a large inner diameter region, a small inner diameter region, and a reduced inner diameter region. The large inner diameter region is a region of the sixth inner diameter formed on the base end side and having an inner diameter corresponding to the fourth outer diameter. The small inner diameter region is a region of the seventh inner diameter formed on the front end side and having an inner diameter corresponding to the second outer diameter and the third outer diameter. The reduced inner diameter region is a region formed between the large inner diameter region and the small inner diameter region and whose inner diameter decreases from the sixth inner diameter to the seventh inner diameter as it approaches from the large inner diameter region to the small inner diameter region.

[0079] In addition, as described above, the shapes of the internal spaces of the second small diameter region RSD2 and the large diameter region RLD of the unequal thickness tube 21 are not particularly limited, and can be various shapes such as polygonal prisms, elliptical columns, and cylinders. However, in the following description, for the purpose of easy understanding of the present invention, the case where the internal spaces of the second small diameter region RSD2 and the large diameter region RLD of the unequal thickness tube 21 have cylindrical shapes will be described. Specifically, the following case will be described: Figure 2 As indicated by brackets in (b), the internal space of the second small diameter region RSD2 of the uneven thickness tube 21 has a cylindrical shape having a third inner diameter DI3 (DI3>DI1) having a predetermined inner diameter larger than the first inner diameter DI1, and the internal space of the large diameter region RLD of the uneven thickness tube 21 has a cylindrical shape having a fourth inner diameter DI4 (DI4=DI3) having an inner diameter equal to the third inner diameter DI3. In this case, as shown below with reference to Figure 3 As described in (a), the large cross-sectional area of ​​the mandrel and the internal space of the sleeve also have cylindrical shapes.

[0080] Figure 3 This is a schematic cross-sectional view showing an example of the structure of the mandrel, sleeve, and extrusion cylinder used in the first method. Figure 3 (a) is a schematic cross-sectional view showing an example of the structure of the mandrel and the sleeve used in the first method. Figure 3 As shown in (a), the mandrel 31 includes a small cross-sectional area RSC, a large cross-sectional area RLC, and a cross-sectional expansion area ReC. The small cross-sectional area RSC is a cylindrical area formed on the front end side and having a first cross-sectional area, wherein the first cross-sectional area is a circular cross-sectional area having a fifth outer diameter DO5 with an outer diameter corresponding to the second inner diameter DI2. The large cross-sectional area RLC is a cylindrical area formed on the base end side and having a second cross-sectional area, wherein the second cross-sectional area is a circular cross-sectional area having a sixth outer diameter DO6 with an outer diameter corresponding to the third inner diameter DI3 and the fourth inner diameter DI4 (i.e., a cross-sectional area corresponding to the cross-sectional area of ​​the internal space of the second small diameter area RSD2 and the large diameter area RLD). The cross-sectional expansion area ReC is an area formed between the small cross-sectional area RSC and the large cross-sectional area RLC and having a truncated cone-shaped shape whose outer diameter increases from the fifth outer diameter DO5 to the sixth outer diameter DO6 as it approaches from the small cross-sectional area RSC to the large cross-sectional area RLC (i.e., an area whose cross-sectional area expands from the first cross-sectional area to the second cross-sectional area). In the second step, by inserting the small cross-sectional area RSC of the mandrel 31 having such a shape into the internal space of the tube 11 from the base end side (the upper side in the drawing) and pressing the cross-sectional expansion area ReC and the large cross-sectional area RLC toward the front end side (the lower side in the drawing), the base end side of the tube 11 can be expanded to form the large diameter area RLD of the unequal thickness tube 21.

[0081] The sleeve 41 includes a pressing region RP, which is a cylindrical region formed on the front end side and having a seventh outer diameter DO7 having an outer diameter equal to the fourth outer diameter DO4 and a fifth inner diameter DI5 having an inner diameter corresponding to the sixth outer diameter DO6 (i.e., a cylindrical region having a columnar internal space having a third cross section having a cross section corresponding to the second cross section). In the third step, the end of the base end side (upper side in the drawing) of the tube 11 is pressed into the front end side of the extrusion cylinder hole by pressing the end of the front end side (lower side in the drawing) of the pressing region RP having such a shape against the end of the base end side (upper side in the drawing) of the tube 11, thereby enabling the extrusion process to be performed.

[0082] Next, Figure 3 (b) is a schematic cross-sectional view of an example of the structure of the extrusion cylinder used in the first method. Figure 3 As shown in (b), the extrusion cylinder hole 51a formed in the extrusion cylinder 51 includes a large inner diameter region RLDI, a small inner diameter region RSDI and a reduced inner diameter region RsDI. The large inner diameter region RLDI is a region formed on the base end side and having a 6th inner diameter DI6 with an inner diameter corresponding to the 4th outer diameter DO4. The small inner diameter region RSDI is a region formed on the front end side and having a 7th inner diameter DI7 with an inner diameter corresponding to the 2nd outer diameter DO2 and the 3rd outer diameter DO3. The reduced inner diameter region RsDI is a region formed between the large inner diameter region RLDI and the small inner diameter region RSDI and whose inner diameter decreases from the 6th inner diameter DI6 to the 7th inner diameter DI7 as it approaches from the large inner diameter region RLDI to the small inner diameter region RSDI. In the third step, the tube 11 is pressed into the extrusion cylinder hole 51a having such a shape through the sleeve 41, so that the first small diameter region RSD1, the first tapered region RtDI1, the second small diameter region RSD2 and the second tapered region RtDI2 of the unequal thickness tube 21 can be formed.

[0083] In addition, during the formation of the first small diameter region RSD1 of the uneven thickness tube 21, it is necessary to perform the extrusion process through a gap corresponding to the wall thickness of the first small diameter region RSD1, that is, the second wall thickness T2. Therefore, in the first method, at the time when the third process starts, that is, the second time, the end of the front end side of the mandrel 31 in the extrusion direction reaches the end of the front end side of the tube 11 or a position closer to the front end side than the end of the front end side of the tube 11. In other words, when the end of the front end side of the sleeve 41 abuts against the end of the base end side of the tube 11, the end of the front end side of the mandrel 31 reaches the end of the front end side of the tube 11 or has passed the end of the front end side of the tube 11. In addition, at the second time, the end of the base end side of the small cross-sectional region RSC of the mandrel 31 is located at a position closer to the base end side than the end of the base end side of the small inner diameter region RSDI of the extrusion cylinder hole 51a. Thus, the material of the first small diameter region RSD1 to be formed into the unequal thickness tube 21 can be extruded toward the front end side through the gap corresponding to the wall thickness of the first small diameter region RSD1, i.e., the second wall thickness T2, i.e., the gap between the small cross-sectional region RSC of the mandrel 31 and the small inner diameter region RSDI of the extrusion tube hole 51a. That is, the extrusion processing of the first small diameter region RSD1 of the unequal thickness tube 21 can be performed. In addition, the distance between the end of the base end side of the small cross-sectional region RSC of the mandrel 31 and the end of the base end side of the small inner diameter region RSDI of the extrusion tube hole 51a can be appropriately determined based on, for example, the length in the extrusion direction and the wall thickness, i.e., the second wall thickness T2, of the first small diameter region RSD1 of the unequal thickness tube 21 to be formed.

[0084] In addition, the length of the small cross-sectional area RSC of the mandrel 31 can also be appropriately determined based on, for example, the length in the extrusion direction of the first small diameter area RSD1 of the unequal thickness tube 21 to be formed. Specifically, for example, when the length of the small cross-sectional area RSC of the mandrel 31 is too short, when the material of the first small diameter area RSD1 of the unequal thickness tube 21 to be formed reaches the end of the base end side of the small inner diameter area RSDI of the extrusion cylinder hole 51a, the end of the front end side of the small cross-sectional area RSC of the mandrel 31 does not reach the end of the base end side of the small inner diameter area RSDI of the extrusion cylinder hole 51a, it is possible that the material detours to a position closer to the front end side than the small cross-sectional area RSC of the mandrel 31, and the wall thickness of the front end side of the first small diameter area RSD1 of the unequal thickness tube 21 becomes thicker than the second wall thickness T2. From the viewpoint of avoiding such problems, it is preferred that: at the latest when the material of the first small diameter region RSD1 that is to form the unequal thickness tube 21 reaches the end of the base end side of the small inner diameter region RSDI of the extrusion tube hole 51a, the end of the front end side of the small cross-sectional region RSC of the core shaft 31 reaches the end of the base end side of the small inner diameter region RSDI of the extrusion tube hole 51a or a position closer to the front end side than the end of the base end side of the small inner diameter region RSDI of the extrusion tube hole 51a.

[0085] Figure 4 1 is a schematic cross-sectional view showing an example of a change in the shape of a pipe material accompanying the execution of the first method. Figure 4 In order to make the drawings simple, Figure 2 and Figure 3 The reference numerals for the various parts shown in FIG. Figure 4 In the following descriptions, for the sake of accuracy, the Figure 2 and Figure 3 Please refer to the reference numerals shown in the figure as needed. Figure 2 and Figure 3 .

[0086] Figure 4 (a) shows a state where the first step included in the first method is completed, the tube 11 is inserted into the large inner diameter region RLDI of the extrusion cylinder hole 51a formed in the extrusion cylinder 51, and the end of the front end side of the tube 11 abuts against the inner diameter reduction region RsDI. That is, the tube 11 is set at a predetermined position inside the extrusion cylinder hole 51a. In addition, Figure 4 In the example shown in (a), the tube 11 is inserted through the small cross-sectional area RSC of the mandrel 31, and the tube 11 is coaxially arranged with respect to the mandrel 31, the sleeve 41 and the extrusion cylinder 51.

[0087] Next, in Figure 4 In (b), in the second step included in the first method, the mandrel 31 is pressed into the tube 11 by a driving mechanism (not shown) so that the base end of the tube 11 is expanded through the large cross-sectional area RLC of the mandrel 31, and the end of the front end side of the sleeve 41 abuts against the end of the base end side of the tube 11. That is, Figure 4 (b) shows the state at the second moment when the third step is to be started. Figure 4In the example shown in (b), the end of the front end side of the mandrel 31 reaches a position closer to the front end side than the end of the front end side of the tube 11. Therefore, in the third step performed later, during the formation of the first small diameter region RSD1 of the uneven thickness tube 21, the first small diameter region RSD1 of the uneven thickness tube 21 is extruded through the gap corresponding to the wall thickness of the first small diameter region RSD1, that is, the second wall thickness T2, that is, the gap between the small cross-sectional region RSC of the mandrel 31 and the small inner diameter region RSDI of the extrusion tube hole 51a. Therefore, as described above, it is possible to avoid the problem that the material detours to a position closer to the front end side than the small cross-sectional region RSC of the mandrel 31, and the wall thickness of the front end side of the first small diameter region RSD1 of the uneven thickness tube 21 becomes thicker than the second wall thickness T2. In addition, the end of the base end side of the small cross-sectional region RSC of the mandrel 31 is located closer to the base end side than the end of the base end side of the small inner diameter region RSDI of the extrusion tube hole 51a. Therefore, the material to form the first small diameter region RSD1 of the unequal thickness tube 21 can be squeezed toward the front end through the gap between the small cross-sectional region RSC of the mandrel 31 and the small inner diameter region RSDI of the extrusion tube hole 51a to form the first small diameter region RSD1 of the unequal thickness tube 21.

[0088] In the second step, if the mandrel 31 and the sleeve 41 are further pressed toward the front end side and the extrusion process is further performed, the material constituting the tube 11 is extruded toward the front end side through the gap between the cross-sectional expansion area ReC of the mandrel 31 and the small inner diameter area RSDI of the extrusion tube hole 51a to form the first tapered area RtDI1 of the unequal thickness tube 21. Then, the material constituting the tube 11 is extruded toward the front end side through the gap between the large cross-sectional area RLC of the mandrel 31 and the small inner diameter area RSDI of the extrusion tube hole 51a to form the second small diameter area RSD2 of the unequal thickness tube 21.

[0089] Figure 4 (c) shows a state where the extrusion processing of the first small diameter region RSD1 and the second small diameter region RSD2 of the uneven thickness tube 21 in the third step is completed and the molding of the uneven thickness tube 21 is completed. Figure 4 As shown in the portion surrounded by the thick dotted line in (c), the inclination of the inner circumference of the first tapered region RtDI1 of the unequal thickness tube 21 is gentler than the inclination of the outer circumference of the cross-sectional expansion region ReC of the mandrel 31. This is because: as the cross-sectional expansion region ReC of the mandrel 31 passes through the position opposite to the end of the base end of the small inner diameter region RSDI of the extrusion cylinder hole 51a, the gap between the end of the base end of the small inner diameter region RSDI and the mandrel 31 gradually narrows, and accordingly, the flow rate of the material extruded toward the front end side increases, so the inclination of the inner circumference of the first tapered region RtDI1 is a longer and gentler inclination in the extrusion direction than the cross-sectional expansion region ReC.

[0090] In addition, a gap is generated between the portion adjacent to the base end side of the first tapered region RtDI1 of the unequal thickness tube 21 and the mandrel 31. This is because: as the cross-sectional enlarged region ReC of the mandrel 31 passes through the position opposite to the end of the base end side of the small inner diameter region RSDI of the extrusion cylinder hole 51a, the gap between the end of the base end side of the small inner diameter region RSDI and the mandrel 31 gradually narrows, and the cross-sectional area of ​​the gap between the large cross-sectional region RLC of the mandrel 31 and the small inner diameter region RSDI of the extrusion cylinder hole 51a becomes smaller than the cross-sectional area of ​​the tube 11 pressed into the gap (expanded to the large diameter region RLD of the unequal thickness tube 21), so the flow rate of the material extruded toward the front end side increases, and the first tapered region RtDI1 and the second small diameter region RSD2 of the unequal thickness tube 21 become longer in the extrusion direction.

[0091] The above-mentioned gap becomes longer as the extrusion process of the second small diameter region RSD2 of the uneven thickness tube 21 in the third process proceeds, and the contact area between the uneven thickness tube 21 and the mandrel 31 decreases. As a result, according to the first method, as the extrusion process of the second small diameter region RSD2 of the uneven thickness tube 21 in the third process proceeds, the processing load decreases, so it is suitable for forming a long workpiece (an uneven thickness tube that is long in the axial direction).

[0092] <Effect>

[0093] As described above, in the first method, in the first step, the tube is set in an extrusion tube formed with an extrusion tube hole, and the extrusion tube hole has a small inner diameter region with an inner diameter smaller than the outer diameter of the tube and a large inner diameter region with an inner diameter larger than the outer diameter of the tube on the front end side and the base end side, respectively. Then, in the second step, a mandrel is pressed into the inside of the tube to expand the diameter of the end of the base end side of the tube, and the mandrel has a small outer diameter region with an outer diameter corresponding to the inner diameter of the tube and a large outer diameter region with an outer diameter larger than the inner diameter of the tube on the front end side and the base end side, respectively. Then, in the third step, the end of the base end side of the tube is extruded by the sleeve, and the tube with the mandrel inserted inside is pressed into the small inner diameter region of the extrusion tube to reduce its diameter.

[0094] Therefore, according to the first method, the increase in processing load can be reduced compared to the case where the diameter difference between the large diameter portion and the small diameter portion of the unequal thickness tube is increased by increasing the outer diameter of the tube. In addition, the increase in processing load accompanying the elongation of the unequal thickness tube to be formed can be reduced. That is, according to the first method, the diameter difference between the large diameter portion (ear portion) and the small diameter portion (unequal thickness portion formed by reducing the diameter) can be set larger without excessive increase in processing load, and the length in the axial direction can also be set arbitrarily.

[0095] In addition to the above, in the second step included in the first method, the mandrel is pressed into the pipe as described above, and the base end side of the pipe is expanded through the large cross-sectional area of ​​the mandrel. In this process, the inner circumference of the pipe is processed by the mandrel, so that, for example, processing marks (tool marks) generated when punching the hole (internal space) of the pipe are crushed and the inner circumference of the pipe is smoothed. Figure 5 This is a photograph showing the smoothing of the inner peripheral surface of the pipe material accompanying the execution of the second step included in the first method. Figure 5 (a) is a photograph of the inner surface of the tube before the second step is performed or in a processing method in which the base end of the tube is expanded without passing through the large cross-sectional area of ​​the mandrel. It can be seen that the processing marks produced when the holes of the tube are punched. Such processing marks may become the starting point for defects such as cracks when the extrusion processing and / or uneven thickness tube forming performed in the subsequent third step is used, such as when subjected to tensile stress or other stress. On the other hand, Figure 5 (b) is a photograph of the inner circumference of the first small diameter region of the unequal thickness tube formed by the first method, as shown in FIG. Figure 5 That is, according to the first method, the possibility of defects such as cracks being generated when the tube is subjected to stress such as tensile stress during use after the extrusion process and / or uneven thickness tube forming performed in the third step is reduced.

[0096] 〈Variation Example〉

[0097] As reference Figure 2 As described in (b), the unequal thickness tube 21 formed by the first method includes, in order from the front end side to the base end side, a first small diameter region RSD1, a second small diameter region RSD2, and a large diameter region RLD. The second small diameter region RSD2 of the unequal thickness tube 21 is composed of a portion having: a third outer diameter DO3 having an outer diameter equal to the second outer diameter DO2 smaller than the outer diameter of the tube 11, i.e., the first outer diameter DO1, an internal space having a cross section corresponding to the cross section of the large cross section region RLC of the mandrel 31, and a third wall thickness T3 having a wall thickness smaller than the wall thickness of the first small diameter region RSD1, i.e., the second wall thickness T2. However, the second small diameter region of the unequal thickness tube does not necessarily need to be composed of a single portion, and may also include a plurality of portions having different shapes of cross sections of the internal space.

[0098] Figure 6 This is a schematic cross-sectional view showing an example of a change in the shape of a pipe material when a unequal thickness pipe having a second small diameter region including two portions having different shapes is formed by the first method according to the modification. Figure 6 (a) to (c) show the same as those referred to in the description of the first method. Figure 4 The states (a) to (c) correspond to. Figure 6In, also with Figure 4 Similarly, in order to make the drawings simple, Figure 2 and Figure 3 The reference numerals for the various parts shown in FIG. Figure 6 In the following descriptions, for the sake of accuracy, the Figure 2 and Figure 3 Please refer to the reference numerals shown in the figure as needed. Figure 2 and Figure 3 .in addition, Figure 6 (d) is a schematic cross-sectional view of a tube 21 ′ of uneven thickness formed by the first method according to the modification.

[0099] exist Figure 6 In the example shown, the large cross-sectional area RLC of the mandrel 31' includes: a portion formed on the base end side having a cross section corresponding to the cross section of the inner space of the large diameter area RLD of the unequal thickness tube 21' being formed; and a portion formed on the base end side having a cross section corresponding to the cross section of the inner space of the second small diameter area RSD2 of the unequal thickness tube 21' being formed. Figure 6 As shown in (b), in the second step included in the first method, two parts having internal spaces with different cross-sections are formed in the area on the base end side of the tube 11 that has been expanded by the large cross-section area RLC of the mandrel 31' (and a part formed between the two parts and whose cross-section expands as the cross-section of the internal space approaches from the front end side to the base end side). Thereafter, the first small diameter area RSD1 and the second small diameter area RSD2 of the uneven thickness tube 21' are formed by performing the extrusion process in the third step, as shown in FIG. Figure 6 As illustrated in (c), the forming of the unequal thickness tube 21' is completed.

[0100] In the second small diameter region RSD2 of the unequal thickness tube 21' formed as described above, Figure 6 As shown in (d), a portion PSD2 having a columnar internal space having the same cross section as the cross section of the internal space of the large diameter region RLD (a cylindrical internal space having a fourth inner diameter DI4 when the cross section is circular) is formed on the base end side, and a portion PSD1 having a columnar internal space having an intermediate cross section between the cross section of the internal space of the large diameter region RLD and the cross section of the internal space of the first small diameter region RSD1 (a cylindrical internal space when each cross section is circular) is formed on the front end side. In addition, between the above two portions PSD1 and PSD2, a tapered portion PtDI is formed whose cross section expands from the cross section of PSD1 to the cross section of PSD2 as the cross section of the internal space approaches from the front end side to the base end side.

[0101] As described above, according to the first method involved in the modification, it is possible to form a tube of uneven thickness having a second small diameter region having a plurality of portions having different shapes of cross sections including an internal space. In addition, when a plurality of portions having different cross sections are formed in the large cross section region RLC of the mandrel 31' as described above, it is necessary to form the large cross section region RLC in such a manner that the cross section of the portion on the front end side is smaller than the cross section of the portion on the base end side.

[0102] In addition, in the above-mentioned modification, the case where the second small diameter region of the unequal thickness tube is multi-staged into a plurality of parts having different shapes of the cross section including the internal space is described. However, the multi-stage of the unequal thickness tube is not limited to the above-mentioned example, and for example, it is also possible to provide a plurality of parts having different inner diameters in the large inner diameter region and / or the small inner diameter region of the extrusion barrel, so as to multi-stage the outer peripheral surface of the first small diameter region, the second small diameter region or / and the large diameter region of the unequal thickness tube to be formed.

[0103] Figure 7 1 is a schematic cross-sectional view of an extrusion cylinder used in the first method according to another variation as described above and a tube of unequal thickness formed using the extrusion cylinder. Figure 7 In the extrusion cylinder hole 51a' formed in the extrusion cylinder 51' illustrated in (a), the large inner diameter region RLDI is multi-staged (two-staged) into a portion having a sixth inner diameter DI6 formed on the front end side and a portion having an inner diameter DI6' larger than the sixth inner diameter DI6 formed on the base end side. By using the extrusion cylinder 51' having such a structure and a sleeve (not shown) corresponding to the extrusion cylinder 51' to perform the first method, it is possible to form a Figure 7 As shown in (b) of the example, the unequal thickness tube 21" has a large diameter region RLD which is multi-leveled (two-staged) into a portion having a fourth outer diameter DO4 formed on the front end side and a portion having an outer diameter DO4' larger than the fourth outer diameter DO4 formed on the base end side. Although not shown in the figure, as described above, if the small inner diameter region RSDI of the extrusion cylinder is multi-leveled, an unequal thickness tube 21" having a multi-leveled first small diameter region RSD1 and / or second small diameter region RSD2 can be formed.

[0104] <<Second Implementation Method>>

[0105] Hereinafter, an extrusion molding method of a tube of unequal thickness according to a second embodiment of the present invention (hereinafter sometimes referred to as a “second method”) will be described with reference to the drawings.

[0106] As described in the description of the first method, in the third step, as the cross-sectional enlargement area of ​​the mandrel passes through a position opposite to the end of the base end of the small inner diameter area of ​​the extrusion tube hole, the gap between the end of the base end of the small inner diameter area and the mandrel gradually narrows. In addition, the cross-sectional area of ​​the gap between the large cross-sectional area of ​​the mandrel and the small inner diameter area of ​​the extrusion tube hole is smaller than the cross-sectional area of ​​the tube pressed into the gap (expanded to the large diameter area of ​​the unequal thickness tube). As a result, the flow rate of the material squeezed from the gap between the large cross-sectional area of ​​the mandrel and the small inner diameter area of ​​the extrusion tube hole to the front end side increases, and the first tapered area and the second small diameter area of ​​the unequal thickness tube become longer in the extrusion direction. Therefore, a gap is generated between the portion adjacent to the base end of the first tapered area of ​​the unequal thickness tube and the mandrel.

[0107] In the above process, the first tapered region and the second small diameter region of the unequal thickness tube extend toward the front end faster than the mandrel, so the mandrel is pulled toward the front end by the first small diameter region of the unequal thickness tube. Therefore, if the mandrel is fixed to the sleeve so that the mandrel does not move toward the front end faster than the sleeve, the sleeve is pulled toward the front end by the first tapered region and the second small diameter region of the unequal thickness tube via the mandrel. That is, a part of the processing load required for extrusion processing by extruding the tube material by the sleeve in the third step can be provided by the tensile stress generated by the first tapered region and the second small diameter region of the unequal thickness tube extending faster toward the front end.

[0108] <structure>

[0109] Therefore, the second method is an extrusion molding method for unequal thickness tubes in which the mandrel and the sleeve are fixed in such a manner that the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve in the extrusion direction is not larger than the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve at the second moment, based on the above-mentioned first method.

[0110] Here, reference is made to the description related to the first method. Figure 3 (a). Figure 3 The mandrel 31 illustrated in (a) is inserted into the columnar internal space formed in the sleeve 41. That is, the sleeve 41 is coaxially arranged outside the mandrel 31. A portion having a larger cross section than the cross section of the internal space of the sleeve 41 (an outer diameter larger than the fifth inner diameter DI5) is formed at the end of the base end side of the mandrel 31, and this portion abuts against the sleeve 41 at the end of the base end side of the internal space of the sleeve 41. Therefore, the mandrel 31 cannot move forward to a greater distance than the sleeve 41. Figure 3 That is, the mandrel 31 and the sleeve 41 are fixed so that the distance between the end of the front end of the mandrel 31 and the end of the front end of the sleeve 41 does not increase further.

[0111] <Effect>

[0112] In summary, when the first tapered region and the second small diameter region of the unequal thickness tube are extruded in the third step, as described above, the mandrel is pulled from the first small diameter region of the unequal thickness tube toward the front end, so the mandrel 31 drives the sleeve 41 toward the front end. As a result, a part of the processing load required for extrusion processing by extruding the tube material through the sleeve 41 in the third step can be provided by the tensile stress generated by the first tapered region and the second small diameter region of the unequal thickness tube extending faster toward the front end, so the processing load in the third step can be reduced. This effect is extremely effective in the case of molding a long unequal thickness tube.

[0113] Furthermore, in order to achieve the above-mentioned effect, it is sufficient as long as the mandrel and the sleeve are fixed in such a manner that the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve in the extrusion direction is not greater than the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve at the second moment. However, from the viewpoint of reducing the manufacturing cost due to the simplification of the structure of the extrusion molding device, the positional relationship between the mandrel and the sleeve may be always fixed.

[0114] 《Third Implementation Method》

[0115] In addition, as described at the beginning of this specification, the present invention also relates to an extrusion molding device for unequal thickness tubes, and not only to an extrusion molding method for unequal thickness tubes represented by the above-mentioned first method and second method. Therefore, the extrusion molding device for unequal thickness tubes involved in various embodiments of the present invention will be described below.

[0116] First, an extrusion-molding apparatus for unequal-thickness tubes according to a third embodiment of the present invention (hereinafter sometimes referred to as a "third apparatus") will be described.

[0117] <structure>

[0118] The third device is an extrusion molding device for unequal thickness tubes, which comprises: a mandrel, which is a metal core having a predetermined shape; a sleeve, which is a cylindrical component coaxially arranged outside the mandrel; an extrusion cylinder, which is a die formed with a through hole having a predetermined shape, i.e., an extrusion cylinder hole; and a driving mechanism configured to press the mandrel and the sleeve into the extrusion cylinder hole. The third device is configured to mold a unequal thickness tube having a predetermined shape by performing the first step to the third step.

[0119] For details of the first to third steps and the mandrel, sleeve, and extrusion barrel, refer to the description related to the first method. Figures 1 to 4 It has already been described, so the explanation is omitted here.

[0120] In addition, as described above, the cross-sectional shapes of the internal spaces of the second small diameter region RSD2 and the large diameter region RLD of the unequal thickness tube are not particularly limited, and can be various shapes such as polygonal, elliptical, and circular. Typically, as described in the description of the first method, Figure 2 and Figure 3 As described above, the internal space of the second small diameter region RSD2 of the unequal thickness tube 21 has a cylindrical shape having a third inner diameter DI3 (DI3>DI1) having a predetermined inner diameter larger than the first inner diameter DI1, and the internal space of the large diameter region RLD of the unequal thickness tube 21 has a cylindrical shape having a fourth inner diameter DI4 (DI4=DI3) having an inner diameter equal to the third inner diameter DI3. In this case, the shapes of the internal spaces of the large cross-sectional region RLC of the mandrel 31 and the sleeve 41 also have cylindrical shapes.

[0121] <Effect>

[0122] By performing the first to third steps in the third device having the above-described structure, the increase in processing load can be reduced compared to the case where the diameter difference between the large diameter portion and the small diameter portion of the unequal thickness tube is increased by increasing the outer diameter of the tube. In addition, the increase in processing load accompanying the elongation of the unequal thickness tube to be formed can be reduced. That is, according to the third device, the diameter difference between the large diameter portion (ear portion) and the small diameter portion (unequal thickness portion formed by reducing the diameter) can be set larger without excessive increase in processing load, and the length in the axial direction can also be set arbitrarily.

[0123] 《Fourth Implementation Method》

[0124] Next, an extrusion-molding apparatus for unequal-thickness tubes according to a fourth embodiment of the present invention (hereinafter sometimes referred to as a "fourth apparatus") will be described.

[0125] <structure>

[0126] The fourth device is an extrusion molding device for unequal thickness tubes in which the mandrel and the sleeve are fixed in such a manner that the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve in the extrusion direction is not larger than the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve at the second moment, based on the above-mentioned third device.

[0127] <Effect>

[0128] According to the fourth device, when the first tapered region and the second small diameter region of the unequal thickness tube are extruded in the third step, as described above, the mandrel is pulled from the first small diameter region of the unequal thickness tube toward the front end, so the mandrel 31 drives the sleeve 41 toward the front end. As a result, a part of the processing load required for extrusion processing by extruding the tube material through the sleeve 41 in the third step can be provided by the tensile stress generated by the first tapered region and the second small diameter region of the unequal thickness tube extending more quickly toward the front end, so that the processing load in the third step can be reduced. This effect is extremely effective when a long unequal thickness tube is to be formed.

[0129] Furthermore, in order to achieve the above-mentioned effect, it is sufficient as long as the mandrel and the sleeve are fixed in such a manner that the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve in the extrusion direction is not greater than the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve at the second moment. However, from the viewpoint of reducing the manufacturing cost due to the simplification of the structure of the extrusion molding device, the positional relationship between the mandrel and the sleeve may be always fixed.

[0130] 《Fifth Implementation Method》

[0131] Next, the extrusion molding method of the unequal thickness tube involved in the fifth embodiment of the present invention (hereinafter referred to as the "fifth method") is described. In addition, please note that the drawings referred to in the following description are only schematic diagrams for the purpose of explaining the present invention, and the dimensions, size relationships, and positional relationships of the various components depicted in the drawings do not strictly and accurately show the constituent elements of the present invention. The above content is also the same for other embodiments of the present invention described later.

[0132] In the extrusion molding method (first method and second method) of the unequal thickness tube according to the first embodiment and the second embodiment of the present invention, after the mandrel including the region with an outer diameter larger than the inner diameter of the tube is pressed into the inside of the tube to expand the diameter of the end portion on the base end side of the tube, the tube is pressed into the small inner diameter region of the extrusion cylinder by extruding the end portion on the base end side of the tube through the sleeve to reduce the diameter. Thus, compared with the case where the diameter difference between the large diameter portion and the small diameter portion of the unequal thickness tube is increased by increasing the outer diameter of the tube, the diameter difference between the large diameter portion and the small diameter portion (the unequal thickness portion formed by the reduced diameter) can be set larger without excessive increase in the processing load, and the length in the axial direction can also be set arbitrarily.

[0133] However, in the above method, not only the outer diameter of the large diameter portion but also the inner diameter is expanded by the mandrel, so the wall thickness of the large diameter portion is naturally reduced. However, for example, in applications where a high mechanical strength is required for the large diameter portion, it is preferred to maintain the wall thickness of the pipe material in the large diameter portion or to increase the wall thickness of the pipe material further.

[0134] <structure>

[0135] Therefore, the fifth method is an extrusion molding method for forming a tube of unequal thickness having a predetermined shape by pressing a tube material of a predetermined shape into an extrusion cylinder hole through a sleeve in an extrusion molding device. The extrusion molding device used in the fifth method comprises: a mandrel, which is a metal core having a predetermined shape; a sleeve, which is a cylindrical member coaxially arranged outside the mandrel; an extrusion cylinder, which is a die formed with a through hole of a predetermined shape, i.e., an extrusion cylinder hole; and a driving mechanism, which is configured to at least press the sleeve into the extrusion cylinder hole.

[0136] As described in the description of the first method, the basic structure of the extrusion molding device is well known to those skilled in the art, and therefore a detailed description is omitted. The components represented by the mandrel, sleeve, and extrusion barrel are made of materials having properties (such as mechanical strength and durability) that can withstand processing conditions such as loads acting on the components in each process described later. In addition, the driving mechanism for pressing the mandrel and sleeve into the hole of the extrusion barrel can be appropriately selected from various driving mechanisms known in the technical field according to the properties of the material constituting the pipe to be extruded (such as mechanical strength and hardness). Typically, a press such as a hydraulic press can be used as the driving mechanism.

[0137] Hereinafter, details of the pipe material, mandrel, sleeve, and extrusion cylinder used in the fifth method, and the unequal thickness pipe formed by executing the fifth method will be described with reference to the drawings.

[0138] Figure 8 FIG. 1 is a schematic cross-sectional view showing an example of the structure of a pipe material used in the fifth method and a pipe of unequal thickness formed from the pipe material. Figure 8 As shown in (a) of FIG. 1 , the pipe material 111 is a cylindrical member having an 11th outer diameter DO11 which is a predetermined outer diameter, an 11th inner diameter DI11 which is a predetermined inner diameter, and an 11th wall thickness T11 which is a predetermined wall thickness.

[0139] In addition, the shape of the pipe is not necessarily limited to Figure 8 The illustrated simple cylindrical shape may be provided with a portion having a different structure at the end of the front end side and / or the base end side of the pipe material, for example, as long as it does not hinder the execution of the fifth method. The method of forming a tube of unequal thickness having a predetermined shape from such a pipe material is described in detail in the description of other embodiments of the extrusion molding method of unequal thickness pipes involved in the present invention (the method of the present invention).

[0140] The material constituting the tube 111 is not particularly limited as long as it can be formed into a desired shape by plastic deformation in the extrusion process, similar to the tube 11 used in the first method. Typically, the material constituting the tube 111 is a metal represented by lead, tin, aluminum, copper, zirconium, titanium, molybdenum, vanadium, niobium, and steel.

[0141] Next, if Figure 8 As shown in (b), the unequal thickness tube 121 formed by the fifth method includes an 11th small outer diameter region RSDO11, an 11th large outer diameter region RLDO11, and an 11th outer diameter increase region ReDO11. The 11th small outer diameter region RSDO11 is formed on the downstream side, i.e., the front end side, in the direction in which the tube 111 is pressed into the hole of the extrusion cylinder, i.e., in the extrusion direction, and has a 12th outer diameter DO12 (DO12<DO11) of a specified outer diameter smaller than the 11th outer diameter DO11, a 12th inner diameter DI12 (DI12=DI11) of an inner diameter equal to the 11th inner diameter DI11, and a 12th wall thickness T12 (T12<T11) of a specified wall thickness smaller than the 11th wall thickness T11. The 11th large outer diameter region RLDO11 is formed on the upstream side in the extrusion direction, i.e., the base end side, and has a 13th outer diameter DO13 (DO13>DO11) having a specified outer diameter larger than the 11th outer diameter DO11, a 13th inner diameter DI13 (DI13=DI11) having an inner diameter equal to the 11th inner diameter DI11, and a 13th wall thickness T13 (T13>T11) having a specified wall thickness larger than the 11th wall thickness T11.

[0142] The 11th outer diameter increase region ReDO11 is formed between the 11th small outer diameter region RSDO11 and the 11th large outer diameter region RLDO11, and the outer diameter increases from the 12th outer diameter DO12 to the 13th outer diameter DO13 as it approaches from the 11th small outer diameter region RSDO11 to the 11th large outer diameter region RLDO11, the wall thickness increases from the 12th wall thickness T12 to the 13th wall thickness T13, and the inner diameter is constant at the 14th inner diameter DI14 (DI14=DI11) which is equal to the 11th inner diameter DI11. That is, the cross section of the internal space of the unequal thickness tube 121 is the same and constant as the cross section of the internal space of the tube 111 throughout the entire area of ​​the 11th small outer diameter region RSDO11, the 11th outer diameter increase region ReDO11, and the 11th large outer diameter region RLDO11.

[0143] Therefore, by executing the fifth method, the wall thickness of the tube 111 is reduced from the 11th wall thickness T11 to the 12th wall thickness T12, and the region where the outer diameter of the tube 111 is reduced from the 11th outer diameter DO11 to the 12th outer diameter DO12 becomes the 11th small outer diameter region RSDO11 of the unequal thickness tube 121. In addition, by executing the fifth method, the wall thickness of the tube 111 is increased from the 11th wall thickness T11 to the 13th wall thickness T13, and the region where the outer diameter of the tube 111 is increased from the 11th outer diameter DO11 to the 13th outer diameter DO13 becomes the 11th large outer diameter region RLDO11 of the unequal thickness tube 121. In this way, according to the fifth method, the inner diameter of the tube 111 can be maintained in the 11th large outer diameter region RLDO11 of the unequal thickness tube 121, and the outer diameter can be increased by thickening. Therefore, the fifth method is suitable for forming unequal thickness tubes for applications requiring high mechanical strength in large diameter portions, for example.

[0144] Fig. 9 This is a schematic cross-sectional view showing an example of the structure of the mandrel, sleeve, and extrusion cylinder used in the fifth method. Fig. 9 (a) is a schematic cross-sectional view showing an example of the structure of the mandrel and the sleeve used in the fifth method. Fig. 9 As shown in (a), the mandrel 131 includes a basic outer diameter region RBDO, which is a cylindrical region formed on the front end side and has an outer diameter corresponding to the inner diameter of the tube 111, that is, the 11th inner diameter DI11, and the 14th outer diameter DO14.

[0145] The sleeve 141 includes an 11th extrusion area RP11, which is a tubular area formed on the front end side and has a cylindrical internal space with a 15th outer diameter DO15 having an outer diameter equal to the outer diameter of the 11th large outer diameter area RLD11 of the unequal thickness tube 121, i.e., the 13th outer diameter DO13, and a 15th inner diameter DI15 having an inner diameter corresponding to the outer diameter of the basic outer diameter area RBDO of the core shaft 131, i.e., the 14th outer diameter DO14.

[0146] Next, Fig. 9 (b) is a schematic cross-sectional view showing an example of the structure of the extrusion cylinder used in the fifth method. Fig. 9As shown in (b), the extrusion cylinder hole 151a formed in the extrusion cylinder 151 includes the 11th large inner diameter region RLDI11, the 11th small inner diameter region RSDI11 and the 11th reduced inner diameter region RsDI11. The 11th large inner diameter region RLDI11 is a region formed on the base end side and having the 16th inner diameter DI16 with an inner diameter corresponding to the 13th outer diameter DO13. The 11th small inner diameter region RSDI11 is a region formed on the front end side and having the 17th inner diameter DI17 with an inner diameter corresponding to the 12th outer diameter DO12. The 11th reduced inner diameter region RsDI11 is a region formed between the 11th large inner diameter region RLDI11 and the 11th small inner diameter region RSDI11 and whose inner diameter decreases from the 16th inner diameter DI16 to the 17th inner diameter DI17 as it approaches from the 11th large inner diameter region RLDI11 to the 11th small inner diameter region RSDI11.

[0147] In the fifth method, by executing the 11th to 13th steps described below, the core shaft 131 is inserted into the internal space of the tube 111 from the base end side (the upper side in the drawing), and the end of the base end side of the tube 111 is extruded through the 11th extrusion area RP11 of the sleeve 141 to press the tube 111 into the extrusion cylinder hole 151a, thereby forming the above-mentioned unequal thickness tube 121.

[0148] Fig.10 1 is a flowchart showing the flow of each process included in the fifth method. The 11th process performed in step S11 is a process of setting a pipe having a predetermined shape at a predetermined position inside the extrusion cylinder hole. Specifically, in the 11th process, the pipe 111 is set at a predetermined position inside the extrusion cylinder hole 151a by making the end of the front end side of the pipe 111 abut against the first inner diameter reduction area RsDI11 formed between the 11th large inner diameter area RLDI11 and the 11th small inner diameter area RSDI11 formed in the extrusion cylinder hole 151a of the extrusion cylinder.

[0149] Next, the 12th process performed in step S12 is a process of expanding the diameter of the tube by squeezing the base end side of the tube with the mandrel inserted into the tube. Specifically, in the 12th process, the base end of the tube 111 is squeezed by the sleeve 141 with the mandrel 131 inserted into the tube 111. As a result, the material constituting the tube 111 plastically flows and is filled in the space between the extrusion cylinder 151 and the mandrel 131 in the 11th large inner diameter region RLDI11 and the 11th reduced inner diameter region RsDI11 of the extrusion cylinder hole 151a. As a result, the inner diameter of the tube 111 can be maintained at the 11th inner diameter DI11 and the outer diameter of the tube 111 can be expanded to the 13th outer diameter DO13.

[0150] Next, the 13th process performed in step S13 is a process of further squeezing the base end side of the tube through the sleeve, pressing the front end side of the tube 111 into the 11th small inner diameter area of ​​the extrusion tube hole, and reducing its diameter. Specifically, in a state where the mandrel 131 is inserted into the tube 111, the end of the base end side of the tube 111 is further squeezed by the sleeve 141. Thus, an extrusion process is performed in which the material constituting the tube 111 is squeezed into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a through the gap between the end of the base end side of the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a and the mandrel 131. As a result, the front end side of the tube 111 can be reduced in diameter. By performing the 11th to 13th processes included in the fifth method in this way, an unequal thickness tube having a predetermined shape can be formed.

[0151] In addition, as described above, both the 12th step and the 13th step are performed in a state where the mandrel 131 is inserted into the tube 111. The insertion of the mandrel 131 into the tube 111 only needs to be completed at the latest when the 12th step is started. Therefore, the mandrel 131 may be inserted into the tube 111 after the tube 111 is set inside the extrusion cylinder hole 151a in the 11th step, or the tube 111 with the mandrel 131 inserted therein may be set inside the extrusion cylinder hole 151a in the 11th step.

[0152] In addition, in order to fill the material constituting the tube 111 in the space between the extrusion cylinder 151 and the mandrel 131 by extruding the base end side of the tube 111 through the sleeve 141 in the 12th step as described above to expand the diameter of the tube 111, the front end of the mandrel needs to reach the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole in the extrusion direction. Therefore, in the fifth method, at the time when the 12th step starts, that is, the 11th time, the end of the front end side of the mandrel reaches the same position as the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole in the extrusion direction, that is, the 11th position or a position closer to the front end side than the 11th position.

[0153] Furthermore, in the 13th step, as described above, the base end side of the tube 111 is further squeezed by the sleeve 141 so that it passes through the gap between the end of the base end side of the 11th small inner diameter area RSDI11 of the extrusion cylinder hole 151a and the mandrel 131, and the front end side of the tube 111 is pressed into the 11th small inner diameter area RSDI11 of the extrusion cylinder hole 151a to reduce its diameter. At this time, if the protrusion amount of the mandrel 131 from the end of the base end side of the 11th small inner diameter area RSDI11 in the extrusion direction is too small, there is a case where the material constituting the tube 111 pressed into the 11th small inner diameter area RSDI11 detours inward in the radial direction, and the 11th small outer diameter area RSDO11 of the unequal thickness tube 121 is not formed into a desired shape.

[0154] Therefore, in the fifth method, at the time when the 13th step starts, that is, at the 12th time, the end of the front end side of the mandrel reaches a position that is a predetermined distance closer to the front end side than the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole in the extrusion direction, that is, the 12th position or a position closer to the front end side than the 12th position. In addition, the so-called "predetermined distance" here is a distance that can prevent the material constituting the tube 111 pressed into the 11th small inner diameter region RSDI11 from detouring inward in the radial direction and forming the 11th small outer diameter region RSDO11 of the uneven thickness tube 121 into a desired shape. The specific size of such a distance can be appropriately determined based on, for example, preliminary experiments conducted by making various changes to the distance that the end of the front end side of the mandrel protrudes toward the front end side than the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole in the extrusion direction and / or the results of simulation analysis using the finite element method.

[0155] In addition, the configuration of the mandrel in the 12th step and the 13th step included in the fifth method is not particularly limited as long as the above conditions are met. For example, the mandrel and the sleeve may be formed integrally and both may be driven integrally by a driving mechanism. On the contrary, when the mandrel and the sleeve are formed relatively independently, both may be driven integrally by a driving mechanism, or may be driven independently of each other, or the mandrel may be fixed at a position that meets the above conditions and only the sleeve may be driven by the driving mechanism.

[0156] Fig.11 This is a schematic cross-sectional view showing an example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe accompanying the progress of the fifth method. Fig.11 In order to make the drawings simple, Figure 8 and Fig. 9 The reference numerals for the various parts shown in FIG. Fig.11 In the following descriptions, for the sake of accuracy, the Figure 8 and Fig. 9 Please refer to the reference numerals shown in the figure as needed. Figure 8 and Fig. 9 .

[0157] Fig.11 (a) shows a state where the tube 111 is set at a predetermined position inside the extrusion cylinder hole 151 a and the mandrel 131 is inserted into the tube 111 by executing the eleventh step. Fig.11 (b) shows a state where, through the execution of the twelfth step, the base end side of the tube 111 is squeezed by the sleeve 141 so that the material constituting the tube 111 fills the space between the extrusion cylinder 151 and the mandrel 131 and the diameter of the tube 111 is expanded. Fig.11(c) shows that through the execution of the 13th process, the base end side of the tube 111 is further squeezed by the sleeve 141, and the front end side of the tube 111 is pressed into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a through the gap between the end of the base end side of the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a and the core shaft 131, and the diameter is reduced.

[0158] like Fig.11 As illustrated, in the fifth method, the region where the outer diameter of the tube 111 is enlarged from the 11th outer diameter DO11 to the 13th outer diameter DO13 by increasing the wall thickness of the tube 111 from the 11th wall thickness T11 to the 13th wall thickness T13 becomes the 11th large outer diameter region RLDO11 of the unequal thickness tube 121. In addition, the region where the outer diameter of the tube 111 is reduced from the 11th outer diameter DO11 to the 12th outer diameter DO12 by decreasing the wall thickness of the tube 111 from the 11th wall thickness T11 to the 12th wall thickness T12 becomes the 11th small outer diameter region RSDO11 of the unequal thickness tube 121. In this way, in the fifth method, the inner diameter of the tube 111 can be maintained in the 11th large outer diameter region RLDO11 of the unequal thickness tube 121, and the outer diameter can be increased by increasing the thickness. Therefore, according to the fifth method, compared with the case where the diameter difference between the large diameter portion and the small diameter portion of the unequal thickness tube is increased by increasing the outer diameter of the tube, for example, an unequal thickness tube having a diameter difference (of the 11th large outer diameter region RLDO11 and the 11th small outer diameter region RSDO11) suitable for uses requiring higher mechanical strength in the large diameter portion can be formed without an excessive increase in the processing load.

[0159] In addition, the axial lengths of the 11th large outer diameter region RLDO11 and the 11th small outer diameter region RSDO11 vary according to the axial length of the tube 111, the diameter expansion amount in the 12th step (the difference between the outer diameter of the tube 111, i.e., the 11th outer diameter DO11, and the inner diameter of the 11th large inner diameter region RLDI11 of the extrusion cylinder hole 151a, i.e., the 16th inner diameter DI16), the diameter reduction amount in the 13th step (the difference between the outer diameter of the tube 111, i.e., the 11th outer diameter DO11, and the inner diameter of the 11th small inner diameter region RSDI11 of the extrusion cylinder hole 151a, i.e., the 17th inner diameter DI17), and the amount of the sleeve 141 pressed into the tube 111. That is, according to the fifth method, the axial lengths of the 11th large outer diameter region RLDO11 and the 11th small outer diameter region RSDO11 of the uneven thickness tube 121 can be arbitrarily set.

[0160] In addition, Fig.11In the state shown in (b) of FIG. 11 , in which the diameter expansion of the tube 111 is completed by the execution of the 12th process, the material constituting the tube 111 has not yet started to flow into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a. However, for example, depending on the ease of plastic flow of the material constituting the tube 111, the structure of the mandrel, sleeve and extrusion tube of the extrusion molding device used in the fifth method, and the extrusion speed of the sleeve driven by the driving mechanism, there is a case where the material constituting the tube 111 starts to flow into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a before the diameter expansion of the tube 111 is completed. That is, there is a case where the 13th process is started before the execution of the 12th process is completed.

[0161] In addition, as in Fig.11 As shown by the dotted line in Fig.11 In the fifth method illustrated, the mandrel 131 is fixed to a position (the 12th position) at a predetermined distance d1 closer to the front end side in the extrusion direction than the end of the 11th smaller inner diameter region RSDI11 of the extrusion tube hole 151a, and only the sleeve 141 is driven by a driving mechanism not shown. However, as described above, the mandrel 131 and the sleeve 141 may be driven integrally by the driving mechanism.

[0162] Fig.12 This is a schematic cross-sectional view showing another example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe as the fifth method is carried out. Fig.12 In order to make the drawings simple, the Figure 8 and Fig. 9 The reference numerals for the various parts shown in FIG. Fig.12 In the following descriptions, for the sake of accuracy, the Figure 8 and Fig. 9 Please refer to the reference numerals shown in the figure as needed. Figure 8 and Fig. 9 .

[0163] Fig.12 The left side of the center axis AX of (a) shows the state of each component at the 11th moment, when the tube 111 is set at the specified position inside the extrusion cylinder hole 151a and the core shaft 131 is inserted into the tube 111 and the 12th step starts. Fig.12The right side of the center axis AX of (a) shows that through the execution of the 12th and 13th processes, the base end side of the tube 111 is extruded by the sleeve 141, and the material constituting the tube 111 is filled in the space between the extrusion cylinder 151 and the core shaft 131, and the tube 111 is expanded in diameter, and the front end side of the tube 111 is pressed into the 11th small inner diameter area RSDI11 of the extrusion cylinder hole 151a through the gap between the core shaft 131 and the base end side of the 11th small inner diameter area RSDI11 of the extrusion cylinder hole 151a, and is reduced in diameter, thereby forming the desired state of the unequal thickness tube 121.

[0164] In addition, Fig.12 In the example shown, the amount of the sleeve 141 pressed into the tube 111 is Fig.11 As a result, the axial length of the eleventh largest outer diameter region RLDO11 of the uneven thickness tube 121 is greater than Fig.11 The example shown is short and has a flange-shaped 11th largest outer diameter area RLDO11. Fig.12 In the example shown, the spindle 131 and the sleeve 141, which are formed relatively independently, are integrally driven by a driving mechanism (not shown).

[0165] Fig.12 (b) is in Fig.12 The enlarged view of the portion enclosed by the thick dashed line in (a). Fig.12 In (b), the mandrel 131 and the sleeve 141 are omitted for the purpose of easily understanding the shape change from the tube 111 to the uneven thickness tube 121. Fig.12 As shown in (b), by executing the fifth method, in the 11th large outer diameter region RLDO11 of the unequal thickness tube 121, the outer diameter of the tube 111, which is drawn by the thin dotted line, i.e., the 11th outer diameter DO11, is expanded to the 13th outer diameter DO13 (expansion amount = ΔDe). On the other hand, in the 11th small outer diameter region RSDO11 of the unequal thickness tube 121, the outer diameter of the tube 111, which is drawn by the thin dotted line, i.e., the 11th outer diameter DO11, is reduced to the 12th outer diameter DO12 (reduction amount = ΔDs).

[0166] Fig.12 (c) is in Fig.12 The enlarged view of the portion surrounded by the thick dashed line in (b). Fig.12 In (c), in order to easily understand the change in shape from the tube 111 to the unequal thickness tube 121, not only the mandrel 131 and the sleeve 141, but also the extrusion cylinder 151 are omitted. Fig.12As shown in (c), by executing the fifth method, in the 11th largest outer diameter region RLDO11 of the unequal thickness tube 121, the wall thickness of the tube 111 depicted by the thin dotted line, that is, the 11th wall thickness T11, increases toward the 13th wall thickness T13 (thickening amount = ΔTe). On the other hand, in the 11th smallest outer diameter region RSDO11 of the unequal thickness tube 121, the wall thickness of the tube 111 depicted by the thin dotted line, that is, the 11th wall thickness T11, decreases toward the 12th wall thickness T12 (thinning amount = ΔTs).

[0167] <Effect>

[0168] As described above, in the unequal thickness tube formed by the fifth method, the 11th large outer diameter region is formed by thickening the tube material, and the 11th small outer diameter region is formed by thinning the tube material. Therefore, compared with the case where the large outer diameter region is formed while maintaining the outer diameter of the tube material and the small outer diameter region is formed by greatly reducing the outer diameter of the tube material, a larger diameter difference can be achieved with a smaller processing load. In addition, according to the fifth method, the wall thickness of the large outer diameter region can be increased, so that, for example, an unequal thickness tube suitable for use in which a high mechanical strength is required for the large diameter portion can be formed.

[0169] Furthermore, as described above, the axial lengths of the 11th large outer diameter region and the 11th small outer diameter region vary according to the axial length of the tube, the amount of diameter expansion in the 12th step, the amount of diameter reduction in the 13th step, and the amount of the sleeve pressed into the tube. That is, according to the fifth method, the axial lengths of the 11th large outer diameter region and the 11th small outer diameter region of the unequal thickness tube can be arbitrarily set.

[0170] 《Sixth Implementation Method》

[0171] Next, a method for extrusion molding of a tube of uneven thickness according to a sixth embodiment of the present invention (hereinafter sometimes referred to as a “sixth method”) will be described.

[0172] The 11th small outer diameter region of the unequal thickness tube formed by the fifth method is a region having a straight tube shape having a 12th outer diameter, a 12th inner diameter, and a 12th wall thickness. However, depending on the use of the unequal thickness tube, there is a case where two portions (unequal thickness portions) having different wall thicknesses need to be formed in the small diameter portion (small outer diameter region), as in the unequal thickness tube formed by the first method.

[0173] <structure>

[0174] Therefore, the sixth method is an extrusion molding method for unequal thickness tubes, based on the fifth method, in which a 12th small outer diameter region is formed at the end of the front end side of the unequal thickness tube, and the mandrel also includes a 13th small outer diameter region and a 12th outer diameter increase region. The 12th small outer diameter region is a region having a 16th outer diameter equal to the 12th outer diameter, an 18th inner diameter smaller than the 12th inner diameter, and a 14th wall thickness greater than the 12th wall thickness. The 13th small outer diameter region is a cylindrical region formed at a position closer to the front end side than the basic outer diameter region of the mandrel and having an outer diameter corresponding to the 18th inner diameter, which is the inner diameter of the 12th small outer diameter region of the unequal thickness tube. The 12th outer diameter increase region is a region formed between the 13th small outer diameter region and the basic outer diameter region of the mandrel and whose outer diameter increases from the 18th outer diameter to the 14th outer diameter as it approaches from the 13th small outer diameter region to the basic outer diameter region.

[0175] Furthermore, in the sixth method, at the moment when the 13th process starts, i.e., the 12th moment, the end of the base end side of the 13th small outer diameter region of the mandrel is located at a position closer to the base end side than the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, i.e., the 11th position, in the extrusion direction. As described above, the 13th small outer diameter region is formed on the front end side of the mandrel. That is, at the 12th moment, the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole is opposite to the 13th small outer diameter region of the mandrel. Therefore, at the 12th moment, the material constituting the tube 111 begins to flow into the 11th small inner diameter region RSDI11 of the extrusion cylinder hole 151a through the gap between the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole and the 13th small outer diameter region of the mandrel. Thus, a region having a 16th outer diameter equal to the 12th outer diameter, an 18th inner diameter having a specified inner diameter smaller than the 12th inner diameter, and a 14th wall thickness having a specified wall thickness greater than the 12th wall thickness, i.e., the 12th small outer diameter region, is formed at the end portion on the front end side of the unequal thickness tube.

[0176] <Sixth method according to the first aspect>

[0177] In addition, the shape of the uneven thickness tube formed by the sixth method changes according to the position of the mandrel at the time when the 13th step is completed, that is, at the 13th moment. For example, in the sixth method involved in the first form, at the 13th moment, the end of the front end side of the basic outer diameter region of the mandrel is located at a position closer to the front end side than the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, that is, the 11th position. The uneven thickness tube formed as a result includes: the 11th large outer diameter region; the 11th outer diameter increase region; the 11th small outer diameter region; the 12th small outer diameter region formed at a position closer to the front end side than the 11th small outer diameter region; and the 11th inner diameter increase region. The 11th inner diameter increased region is formed between the 12th small outer diameter region and the 11th small outer diameter region of the unequal thickness tube and the inner diameter increases from the 18th inner diameter to the 12th inner diameter as approaching the 12th small outer diameter region toward the 11th small outer diameter region, and the wall thickness decreases from the 14th wall thickness to the 12th wall thickness, and the outer diameter is constant at the 17th outer diameter equal to the 12th outer diameter.

[0178] Fig.13 This is a schematic cross-sectional view showing an example of the structure of a pipe material used in the sixth method involved in the first aspect and a tube of unequal thickness formed from the pipe material. Fig.13 The pipe 111 illustrated in (a) and the fifth method are referred to in the related description. Figure 8 The pipe material 111 illustrated in (a) is similarly a cylindrical member having an 11th outer diameter DO11 which is a predetermined outer diameter, an 11th inner diameter DI11 which is a predetermined inner diameter, and an 11th wall thickness T11 which is a predetermined wall thickness.

[0179] Next, if Fig.13 As shown in (b), the unequal thickness tube 121 formed by the sixth method involved in the first form has the same characteristics as those referred to in the relevant description of the fifth method, except that it also includes the 12th small outer diameter area RSDO12 and the 11th inner diameter increased area ReDI11 at a position closer to the front end side than the 11th small outer diameter area RSDO11. Figure 8 As described above, the 12th small outer diameter region RSDO12 is formed at a position closer to the front end side than the 11th small outer diameter region RSDO11 of the unequal thickness tube 121 and has a 16th outer diameter DO16 (DO16=DO12) equal to the 12th outer diameter DO12, an 18th inner diameter DI18 (DI18<DI12) smaller than the 12th inner diameter DI12, and a 14th wall thickness T14 (T14>T12) greater than the 12th wall thickness T12.

[0180] The 11th inner diameter increase area ReDI11 is formed between the 12th small outer diameter area RSDO12 and the 11th small outer diameter area RSDO11 of the unequal thickness tube 121 and the inner diameter increases from the 18th inner diameter DI18 to the 12th inner diameter DI12 as it approaches the 12th small outer diameter area RSDO12 toward the 11th small outer diameter area RSDO11, and the wall thickness decreases from the 14th wall thickness T14 to the 12th wall thickness T12, and the outer diameter is a constant area with the 17th outer diameter DO17 (DO17=DO12) equal to the 12th outer diameter DO12.

[0181] Fig.14 This is a schematic cross-sectional view showing an example of the structure of a mandrel, a sleeve, and an extrusion cylinder used in the sixth method involved in the first aspect. Fig.14 (a) is a schematic cross-sectional view of an example of the structure of the mandrel and the sleeve used in the sixth method involved in the first embodiment. Fig.14 As shown in (a), the mandrel 131 used in the sixth method involved in the first form has the same structure as that referred to in the description of the fifth method except that it also includes a 13th small outer diameter area RSDO13 and a 12th outer diameter increased area ReDO12. Fig. 9 The structure is the same as the mandrel 131 illustrated in (a). As described above, the 13th small outer diameter region RSDO13 is a cylindrical region formed at a position closer to the front end side than the basic outer diameter region RBDO of the mandrel 131 and having an outer diameter corresponding to the inner diameter of the 12th small outer diameter region RSDO12 of the unequal thickness tube 121, that is, the 18th inner diameter DI18. The 12th outer diameter increase region ReDO12 is a region formed between the 13th small outer diameter region RSDO13 of the mandrel 131 and the basic outer diameter region RBDO and the outer diameter increases from the 18th outer diameter to the 14th outer diameter as it approaches from the 13th small outer diameter region RSDO13 to the basic outer diameter region RBDO.

[0182] The sleeve 141 used in the sixth method according to the first aspect and the fifth method are referred to in the related description. Fig. 9 The core shaft 131 illustrated in (a) also includes the 11th extrusion area RP11, which is a tubular area formed on the front end side and has a cylindrical internal space with a 15th outer diameter DO15 having an outer diameter equal to the outer diameter of the 11th large outer diameter area RLD11 of the unequal thickness tube 121, i.e., the 13th outer diameter DO13, and a 15th inner diameter DI15 having an inner diameter corresponding to the outer diameter of the basic outer diameter area RBDO of the core shaft 131, i.e., the 14th outer diameter DO14.

[0183] Next, Fig.14(b) is a schematic cross-sectional view showing an example of the structure of an extrusion cylinder used in the sixth method according to the first embodiment. Fig.14 The extrusion cylinder hole 151a formed in the extrusion cylinder 151 illustrated in (b) is similar to the one referred to in the related description of the fifth method. Fig. 9 Similarly, the extrusion cylinder hole 151a formed in the extrusion cylinder 151 illustrated in (b) includes the 11th large inner diameter area RLDI11, the 11th small inner diameter area RSDI11, and the 11th reduced inner diameter area RsDI11. The details of each area of ​​the extrusion cylinder hole 151a have been described in the description related to the fifth method, so the description is omitted here.

[0184] Even in the sixth method involved in the first form, by executing the same 11th to 13th steps as the fifth method, the above-mentioned unequal thickness tube 121 can be formed by extruding the end of the base end side of the tube 111 through the 11th extrusion area RP11 of the sleeve 141, while the mandrel 131 is inserted into the internal space of the tube 111 from the base end side (the upper side in the drawing).

[0185] Fig.15 This is a schematic cross-sectional view showing an example of the positional relationship and shape change of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe accompanying the sixth method involved in the first embodiment. Fig.15 In order to make the drawings simple, Fig.13 and Fig.14 The reference numerals for the various parts shown in FIG. Fig.15 In the following descriptions, for the sake of accuracy, the Fig.13 and Fig.14 Please refer to the reference numerals shown in the figure as needed. Fig.13 and Fig.14 .

[0186] Fig.15 (a) shows the state where the mandrel 131 is to be inserted into the tube 111 at a predetermined position inside the extrusion cylinder hole 151a by executing the 11th process. The outer diameter DO18 of the 13th small outer diameter area RSDO13 formed at the front end of the mandrel 131 is smaller than the 11th inner diameter DI11 of the tube 111, and the inner diameter DI18 of the 11th large inner diameter area RLDI11 of the extrusion cylinder hole 151a is larger than the 11th outer diameter DO11 of the tube 111. Therefore, Fig.15 In the state shown in (a), there are gaps both outside the outer peripheral surface and inside the inner peripheral surface of the tube 111.

[0187] Fig.15(b) shows the state where the base end of the tube 111 is squeezed by the sleeve 141 at the start of the twelfth step, the material constituting the tube 111 is filled in the space between the extrusion cylinder 151 and the mandrel 131, and the diameter of the tube 111 is gradually expanded. Fig.15 In the state shown in (b), the gap between the 13th small outer diameter region RSDO13 formed at the front end of the mandrel 131 and the inner peripheral surface of the tube 111, and the gap between the end near the front end side of the 11th large inner diameter region RLDI11 of the extrusion cylinder hole 151a and the outer peripheral surface of the tube 111 have not been filled with the material constituting the tube 111. However, the base end side of the tube 111 is further extruded by the sleeve 141, and the above-mentioned gaps are also filled with the material constituting the tube 111, and the diameter expansion of the tube 111 is completed, and the second step is completed.

[0188] Fig.15 (c) shows a state where the base end of the tube 111 is further squeezed by the sleeve 141 through the execution of the 13th step, and the front end of the tube 111 is pressed into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a through the gap between the end of the base end of the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a and the mandrel 131, and the diameter is reduced. Fig.15 As shown in (c), the material constituting the tube 111 flows into the 11th small inner diameter region RSDI11 of the extrusion tube hole 151a through the gap between the end portion on the base end side of the 11th small inner diameter region RSDI11 of the extrusion tube hole 151a and the 13th small outer diameter region RSDO13 and the 12th increased outer diameter region ReDO12 formed at the front end of the core shaft 131, and forms the 12th small outer diameter region RSDO12 and the 11th increased inner diameter region ReDI11 having thicker walls than the 11th small outer diameter region RSDO11 at a position closer to the front end side than the 11th small outer diameter region RSDO11 of the unequal thickness tube 121. In other words, in the unequal thickness tube 121 formed by the sixth method involved in the first form, the outer diameter of the large diameter portion (large outer diameter region) is expanded as a whole by thickening toward the outside while the inner diameter remains unchanged, the outer diameter of the base end side of the small diameter portion (small outer diameter region) is reduced by thinning while the inner diameter remains unchanged, and the outer diameter of the portion from the middle of the small diameter portion to the front end side is reduced by thinning while the inner diameter is reduced by thickening.

[0189] As described above, the mandrel used in the sixth method further includes: a 13th small outer diameter region, which is a cylindrical region thinner than the basic outer diameter region and formed at a position closer to the front end than the basic outer diameter region; and a 12th outer diameter increasing region, which is a region formed between the 13th small outer diameter region and the basic outer diameter region and whose outer diameter increases as it approaches the basic outer diameter region from the 13th small outer diameter region. In addition, in the sixth method, at the moment when the 13th process starts, that is, at the 12th moment, the end of the base end side of the 13th small outer diameter region of the mandrel is located at a position closer to the base end side than the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, that is, the 11th position, in the extrusion direction. In addition, in the sixth method involved in the first form, at the 13th moment, the end of the base end side of the basic outer diameter region of the mandrel is located at a position closer to the front end side than the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, that is, the 11th position, at the 13th moment. Therefore, according to the sixth method involved in the first aspect, a unequal thickness tube having a 12th small outer diameter region thicker than the 11th small outer diameter region and an 11th inner diameter increased region formed at the front end can be formed.

[0190] <Variation of the sixth method according to the first aspect>

[0191] As reference Figures 13 to 15 As described above, the unequal thickness tube 121 formed by the sixth method according to the first embodiment further includes: a 13th small outer diameter region, which is a cylindrical region thinner than the basic outer diameter region and formed at a position closer to the front end than the basic outer diameter region; and a 12th outer diameter increase region, which is a region formed between the 13th small outer diameter region and the basic outer diameter region and whose outer diameter increases as it approaches the basic outer diameter region from the 13th small outer diameter region. That is, Figures 13 to 15 The small diameter portion (small outer diameter region) of the unequal thickness tube 121 illustrated in the example has two small outer diameter regions with different inner diameters and wall thicknesses. However, the small diameter portion (small outer diameter region) of the unequal thickness tube formed by the sixth method involved in the first embodiment can also be formed by Figure 6 The unequal thickness tube formed by the first method according to the modification example illustrated in the figure has three or more small outer diameter regions.

[0192] Fig.16 This is a schematic cross-sectional view showing an example of the change in positional relationship and shape of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe accompanying the modification of the sixth method involved in the first form. Fig.16 In order to make the drawings simple, the Fig.13 and Fig.14 The reference numerals for the various parts are shown in FIG. Fig.16 In the following descriptions, for the sake of accuracy, the Fig.13 and Fig.14Please refer to the reference numerals shown in the figure as needed. Fig.13 and Fig.14 wait.

[0193] like Fig.16 As illustrated on the left side of the center axis AX of (a), in the mandrel 131 used in the above-mentioned form of the 6th method involved in the modified example, the 13th small outer diameter region is divided into the above-mentioned RSDO13, and RSDO13' which is formed at a position closer to the front end side than RSDO13 and is thinner than the above-mentioned RSDO13. If the mandrel 131 having such a structure is used to perform the 13th process, during the process in which the material constituting the tube 111 flows into the 11th small inner diameter region RSDI11 of the extrusion cylinder hole 151a, the portion of the mandrel 131 opposite to the end portion on the base end side of the 11th small inner diameter region RSDI11 changes from RSDO13' of the 13th small outer diameter region via RSDO13 to the basic outer diameter region RBDO. Along with this, the size of the gap between the end portion on the base end side of the 11th small inner diameter region RSDI11 and the mandrel 131 is gradually reduced, so that as shown in FIG. Fig.16 As illustrated on the right side of the central axis AX in (a), the wall thickness of the small diameter portion (the unequal thickness portion formed by reducing the diameter) of the uneven thickness tube 121 also decreases stepwise as it goes from the distal end side to the proximal end side.

[0194] Fig.16 (b) is in Fig.16 An enlarged view of the portion enclosed by the thick dashed line in (a). Fig.16 As illustrated in (b), the small diameter portion (the unequal thickness portion formed by reducing the diameter) of the unequal thickness tube 121 formed by the above-mentioned form of the sixth method involved in the modified example includes, in order from the front end side toward the base end side: a small diameter region RSDO12' having a maximum wall thickness T14'; a 12th small diameter region RSDO12 having an intermediate wall thickness T12; and an 11th small diameter region RSDO11 having a minimum wall thickness T12.

[0195] As described above, according to the modification of the sixth method involved in the first form, it is possible to form a "multi-stage" unequal thickness tube having a small diameter portion (unequal thickness portion formed by reducing the diameter) divided into a plurality of small diameter regions with different wall thicknesses and inner diameters. In addition, the multi-stage unequal thickness tube is not limited to the above case, for example, it can also be based on the mechanical strength of the material constituting the tube, the degree of work hardening and / or the ease of plastic flow, and / or the mechanical strength of the components constituting the extrusion molding device and / or the processing capacity of the extrusion molding device, as referred to in the description related to the first method involved in another modification. Figure 7As shown in the example, by providing multiple parts with different inner diameters in the 11th large inner diameter region and / or the 11th small inner diameter region of the extrusion cylinder, the outer peripheral surface of the 11th small outer diameter region, the 12th small outer diameter region and / or the 11th large outer diameter region of the unequal thickness tube to be formed can be multi-leveled.

[0196] <Sixth method according to the second aspect>

[0197] As described above, the shape of the uneven thickness tube formed by the sixth method changes according to the position of the mandrel at the time when the 13th process is completed, that is, at the 13th moment. For example, in the sixth method involved in the second form, at the 13th moment, the end of the base end side of the 13th small outer diameter region of the mandrel is located at a position closer to the base end side than the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, that is, the 11th position. As a result, the uneven thickness tube formed includes the 12th small outer diameter region, the 11th large outer diameter region, the 12th large outer diameter region, the 13th outer diameter increased region, and the 12th inner diameter increased region.

[0198] The 12th largest outer diameter region is a region formed between the 12th small outer diameter region and the 11th large outer diameter region and has a 19th outer diameter equal to the 13th outer diameter, a 19th inner diameter equal to the 18th inner diameter, and a 15th wall thickness of a predetermined wall thickness greater than the 13th wall thickness. The 13th outer diameter increasing region is a region formed between the 12th small outer diameter region and the 12th largest outer diameter region and has an outer diameter increasing from the 16th outer diameter to the 19th outer diameter as it approaches from the 12th small outer diameter region to the 12th largest outer diameter region, a wall thickness increasing from the 14th wall thickness to the 15th wall thickness, and an inner diameter being constant at the 20th inner diameter equal to the 18th inner diameter. The 12th inner diameter increased region is formed between the 12th largest outer diameter region and the 11th largest outer diameter region and the inner diameter increases from the 19th inner diameter to the 13th inner diameter as it approaches the 12th largest outer diameter region toward the 11th largest outer diameter region, and the wall thickness decreases from the 15th wall thickness to the 13th wall thickness, and the outer diameter is constant at the 20th outer diameter equal to the 13th outer diameter.

[0199] Fig.17 This is a schematic cross-sectional view showing an example of the structure of a pipe material used in the sixth method involved in the second aspect and a tube of unequal thickness formed from the pipe material. Fig.17 The pipe material 111 illustrated in (a) is the same as the pipe material 111 referred to in the description of the fifth method and the sixth method. Figure 8 (a) and Fig.13 The pipe material 111 illustrated in (a) is similarly a cylindrical member having an 11th outer diameter DO11 which is a predetermined outer diameter, an 11th inner diameter DI11 which is a predetermined inner diameter, and an 11th wall thickness T11 which is a predetermined wall thickness.

[0200] Next, if Fig.17As shown in (b), the unequal thickness tube 121 formed by the sixth method involved in the second form includes a 12th small outer diameter region RSDO12, an 11th large outer diameter region RLDO11, a 12th large outer diameter region RLDO12, a 13th outer diameter increase region ReDO13 and a 12th inner diameter increase region ReDI12.

[0201] The 12th large outer diameter region RLDO12 is formed between the 12th small outer diameter region RSDO12 and the 11th large outer diameter region RLDO11 and has the 19th outer diameter DO19 (DO19=DO13) which is equal to the 13th outer diameter DO13, the 19th inner diameter DI19 (DI19=DI18) which is equal to the 18th inner diameter DI18, and the 15th wall thickness T15 (T15>T13) which is a specified wall thickness greater than the 13th wall thickness T13. The 13th outer diameter increased region ReDO13 is formed between the 12th small outer diameter region RSDO12 and the 12th large outer diameter region RLDO12 and the outer diameter increases from the 16th outer diameter DO16 to the 19th outer diameter DO19 as it approaches the 12th small outer diameter region RSDO12 toward the 12th large outer diameter region RLDO12, the wall thickness increases from the 14th wall thickness T14 to the 15th wall thickness T15, and the inner diameter is a constant region with the 20th inner diameter DI20 (DI20=DI18) which is equal to the 18th inner diameter DI18. The 12th inner diameter increase region ReDI12 is formed between the 12th largest outer diameter region RLDO12 and the 11th largest outer diameter region RLDO11 and the inner diameter increases from the 19th inner diameter DIO19 to the 13th inner diameter DI13 as it approaches the 12th largest outer diameter region RLDO12 toward the 11th largest outer diameter region RLDO11, and the wall thickness decreases from the 15th wall thickness T15 to the 13th wall thickness T13, and the outer diameter is a constant region with the 20th outer diameter DO20 (DO20=DO13) which is equal to the 13th outer diameter DO13.

[0202] Fig.18 This is a schematic cross-sectional view showing an example of the structure of a mandrel, a sleeve, and an extrusion cylinder used in the sixth method involved in the second aspect. Fig.18 (a) is a schematic cross-sectional view showing an example of the structure of the mandrel and the sleeve used in the sixth method involved in the second aspect. Fig.18 As shown in (a), the mandrel 131 used in the sixth method involved in the second form has the same characteristics as those referred to in the description of the sixth method involved in the first form, except that the 13th small outer diameter region RSDO13 accounts for a higher proportion (longer) of the total length in the axial direction and the basic outer diameter region RBDO accounts for a lower proportion (shorter). Fig.14 The structure is the same as the spindle 131 illustrated in (a).

[0203] The sleeve 141 used in the sixth method according to the second aspect is the same as the sleeve 141 referred to in the description of the fifth method and the sixth method according to the first aspect. Fig. 9 (a) and Fig.14 The sleeve 141 illustrated in (a) also includes the 11th extrusion area RP11, which is a tubular area formed on the front end side and has a cylindrical internal space with a 15th outer diameter DO15 having an outer diameter equal to the outer diameter of the 11th large outer diameter area RLD11 of the unequal thickness tube 121, i.e., the 13th outer diameter DO13, and a 15th inner diameter DI15 having an inner diameter corresponding to the outer diameter of the basic outer diameter area RBDO of the core shaft 131, i.e., the 14th outer diameter DO14.

[0204] Next, Fig.18 (b) is a schematic cross-sectional view showing an example of the structure of an extrusion cylinder used in the sixth method involved in the second aspect. Fig.18 The extrusion cylinder hole 151a formed in the extrusion cylinder 151 illustrated in (b) is similar to the one referred to in the related description of the sixth method involved in the fifth method and the first form. Fig. 9 (b) and Fig.14 Similarly, the extrusion cylinder hole 151a formed in the extrusion cylinder 151 illustrated in (b) includes the 11th large inner diameter area RLDI11, the 11th small inner diameter area RSDI11, and the 11th reduced inner diameter area RsDI11. The details of each area of ​​the extrusion cylinder hole 151a have been described in the description related to the fifth method, so the description is omitted here.

[0205] In the sixth method involved in the second form, by executing the same 11th to 13th steps as the fifth method, with the mandrel 131 inserted into the internal space of the tube 111 from the base end side (the upper side in the drawing), the end of the base end side of the tube 111 is extruded through the 11th extrusion area RP11 of the sleeve 141 to press the tube 111 into the extrusion cylinder hole 151a, thereby forming the above-mentioned unequal thickness tube 121.

[0206] Fig.19 This is a schematic cross-sectional view showing an example of the positional relationship and shape change of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe accompanying the sixth method involved in the second form. Fig.19 In order to make the drawings simple, Fig.17 and Fig.18 The reference numerals for the various parts shown in FIG. Fig.19 In the following descriptions, for the sake of accuracy, the Fig.17 and Fig.18 The reference numerals are shown, so please refer to them as needed. Fig.17 and Fig.18 .

[0207] Fig.19 (a) shows a state where the mandrel 131 is inserted through the pipe 111 at a predetermined position set inside the extrusion cylinder hole 151a by executing the 11th process. The outer diameter DO18 of the 13th small outer diameter area RSDO13 formed at the front end of the mandrel 131 is smaller than the 11th inner diameter DI11 of the pipe 111, and the inner diameter DI18 of the 11th large inner diameter area RLDI11 of the extrusion cylinder hole 151a is larger than the 11th outer diameter DO11 of the pipe 111. Fig.19 In the state shown in (a), there are gaps both outside the outer peripheral surface and inside the inner peripheral surface of the tube 111.

[0208] Fig.19 (b) shows the state where the base end of the tube 111 is squeezed by the sleeve 141 at the start of the twelfth step, the material constituting the tube 111 is filled in the space between the extrusion cylinder 151 and the mandrel 131, and the diameter of the tube 111 is gradually expanded. Fig.19 In the state shown in (b), the gap between the 13th small outer diameter region RSDO13 formed at the front end of the mandrel 131 and the inner peripheral surface of the tube 111, and the gap between the end near the front end side of the 11th large inner diameter region RLDI11 of the extrusion cylinder hole 151a and the outer peripheral surface of the tube 111 have not been filled with the material constituting the tube 111. However, the base end side of the tube 111 is further extruded by the sleeve 141, and the above-mentioned gaps are also filled with the material constituting the tube 111, and the diameter expansion of the tube 111 is completed, and the second step is completed.

[0209] Fig.19 (c) shows that the execution of the 13th process is completed, the base end side of the tube 111 is further squeezed by the sleeve 141, and the front end side of the tube 111 is pressed into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a through the gap between the end of the base end side of the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a and the mandrel 131, and the diameter is reduced. As described above, in the sixth method involved in the second form, at the moment when the 13th process is completed, that is, at the 13th moment, the end of the base end side of the 13th small outer diameter area RSDO13 of the mandrel 131 is at a position closer to the base end side than the position of the end of the base end side of the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a, that is, the 11th position.

[0210] Therefore, in the sixth method according to the second embodiment, during the entire period of the 13th step, the material constituting the tube 111 flows into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a through the gap between the end portion on the base end side of the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a and the 13th small outer diameter area RSDO13 formed at the front end of the mandrel 131. Therefore, the small diameter portion (small outer diameter area) of the unequal thickness tube 121 is composed only of the 16th outer diameter DO16 having an outer diameter smaller than the 11th outer diameter DO11, which is the outer diameter of the tube 111, the 18th inner diameter DI18 having an inner diameter smaller than the 11th inner diameter DI11, which is the inner diameter of the tube 111, and the 12th small outer diameter area RSDO12 having a region with a predetermined 14th wall thickness T14.

[0211] Furthermore, at the 13th moment, the end of the base end side of the 13th small outer diameter region RSDO13 of the mandrel 131 is located at a position closer to the base end side than the position of the end of the base end side of the 11th small inner diameter region RSDI11 of the extrusion tube hole 151a, that is, the 11th position, so the front end side portion of the large diameter portion (large outer diameter region) of the unequal thickness tube 121 is also thickened toward the inside to form the 12th large outer diameter region RLDO12. In other words, in the unequal thickness tube 121 formed by the sixth method involved in the second form, the base end side portion of the large diameter portion (large outer diameter region) is expanded in outer diameter by thickening toward the outside and the inner diameter remains unchanged, the portion from the middle of the large diameter portion to the front end side is expanded in outer diameter by thickening toward the outside and the inner diameter is reduced by thickening toward the inside, and the small diameter portion (small outer diameter region) is reduced in outer diameter by thinning as a whole and the inner diameter is reduced by thickening.

[0212] As described above, the mandrel used in the sixth method further includes: a 13th small outer diameter region, which is a cylindrical region thinner than the basic outer diameter region and formed at a position closer to the front end than the basic outer diameter region; and a 12th outer diameter increasing region, which is a region formed between the 13th small outer diameter region and the basic outer diameter region and whose outer diameter increases as it approaches the basic outer diameter region from the 13th small outer diameter region. In addition, in the sixth method, at the moment when the 13th process starts, that is, at the 12th moment, the end of the base end side of the 13th small outer diameter region of the mandrel is located at a position closer to the base end side than the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, that is, the 11th position, in the extrusion direction. In addition, in the sixth method involved in the second form, at the 13th moment, the end of the base end side of the 13th small outer diameter region of the mandrel is located at a position closer to the base end side than the position of the end of the base end side of the 11th small inner diameter region RSDI11 of the extrusion cylinder hole 151a, that is, the 11th position. Therefore, according to the sixth method involved in the second form, the inner diameter of the range from the middle of the large diameter part (large outer diameter region) whose outer diameter is expanded by thickening toward the outside to the end of the front end side of the small diameter part (small outer diameter region) can be reduced by thickening.

[0213] <Effect>

[0214] As described above, according to the sixth method, by appropriately adjusting the size and / or length of the 12th small outer diameter region, which is a portion thinner than the inner diameter of the tube material formed on the front end side of the mandrel, and the position of the mandrel at the time of completion of the 13th step, the range in which the inner diameter is reduced by thickening in the uneven thickness tube formed by the sixth method can be changed. Therefore, for example, the shape and wall thickness distribution of the uneven thickness tube can be designed with a high degree of freedom according to the application.

[0215] 《Seventh Implementation Method》

[0216] Next, a method for extruding a tube of unequal thickness according to a seventh embodiment of the present invention (hereinafter sometimes referred to as a “seventh method”) will be described.

[0217] As described above, the shape of the pipe material used in the extrusion molding method of the unequal thickness pipe involved in the fifth embodiment and the sixth embodiment of the present invention (the fifth method and the sixth method) is not necessarily limited to the shape of the pipe material. Figure 8 , Fig.13 as well as Fig.17 The simple cylindrical shape exemplified in the above, for example, may also be provided with a portion having a different structure at the end of the front end side and / or the base end side of the pipe material, as long as it does not hinder the execution of the fifth method. By forming a unequal thickness pipe from such a pipe material, the structure provided at the end of the front end side and / or the base end side of the pipe material can be brought into the unequal thickness pipe.

[0218] <structure>

[0219] Therefore, the seventh method is a method for molding a tube of uneven thickness by the fifth method or the sixth method using a tube having a portion having an outer diameter smaller than the outer diameter of the tube and an inner diameter larger than the inner diameter of the tube at the end portion on the base end side. Specifically, the seventh method is a method for extruding a tube of uneven thickness from the eleventh step to the thirteenth step using a tube having an eleventh thin-walled portion at the end portion on the base end side on the basis of the fifth method or the sixth method described above, wherein the eleventh thin-walled portion is a portion having a 21st outer diameter smaller than the 11th outer diameter, which is the outer diameter of the tube, a 21st inner diameter larger than the 11th inner diameter, which is the inner diameter of the tube, and a 16th wall thickness smaller than the 11th wall thickness, which is the wall thickness of the tube.

[0220] The sleeve used in the seventh method has a receiving portion, which is a space having an opening on the end surface on the front end side and having a shape corresponding to the 11th thin-walled portion. In the seventh method, the 12th step and the 13th step are performed in a state where the 11th thin-walled portion of the pipe material is received in the receiving portion of the sleeve, and the 11th thin-walled portion remains at the end portion on the front end side of the pipe material. As a result, the uneven thickness tube formed by the seventh method also includes the 11th thin-walled portion at the end portion on the base end side.

[0221] Fig. 20 This is a schematic cross-sectional view showing an example of the structure of a pipe material used in the seventh method and a pipe of uneven thickness formed from the pipe material. Fig. 20 The pipe material 111' illustrated in (a) has the same characteristics as those mentioned in the description of the fifth method and the sixth method except that the pipe material 111' further has an eleventh thin-walled portion PST11 at the end portion on the base end side. Figure 8 (a) Fig.13 (a) and Fig.17 The 11th thin-walled portion PST11 has a 21st outer diameter DO21 (DO21<DO11) which is smaller than the outer diameter of the tube 111', i.e., the 11th outer diameter DO11, and a 21st inner diameter DI21 (DI21≥DI11) which is the inner diameter of the tube 111', i.e., the 11th inner diameter DI11. However, Fig. 20 DI21 = DI11) and a portion of the 16th wall thickness T16 (T16 < T11) which is smaller than the wall thickness of the tube 111', i.e., the 11th wall thickness T11. Fig. 20 As shown in (b), the uneven thickness tube 121' formed by the seventh method has the same characteristics as those mentioned in the description of the fifth method except that the end portion on the base end side also includes the eleventh thin-walled portion PST11. Figure 8 The same structure as the unequal thickness tube 121 illustrated in (b).

[0222] Fig.21 This is a schematic cross-sectional view showing an example of the structure of a mandrel, a sleeve, and an extrusion cylinder used in the seventh method. Fig.21 (a) is a schematic cross-sectional view showing an example of the structure of the mandrel and the sleeve used in the seventh method. Fig.21 As shown in (a), the mandrel 131 used in the seventh method is the same as that referred to in the description of the first method. Fig. 9 The mandrel 131 illustrated in (a) similarly includes a basic outer diameter region RBDO which is a cylindrical region formed at the front end side and having an outer diameter corresponding to the 11th inner diameter DI11 which is the inner diameter of the tube 111 ′.

[0223] The sleeve 141′ used in the seventh method has the same structure as that described in the fifth and sixth methods except that the sleeve 141′ has a receiving portion PC which is open at the end surface on the front end side and has a space having a shape corresponding to the 11th thin-walled portion PST11. Fig. 9 (a) Fig.14 (a) and Fig.18 The same structure as the sleeve 141 illustrated in (a).

[0224] Next, Fig.21 (b) is a schematic cross-sectional view showing an example of the structure of an extrusion cylinder used in the seventh method. Fig.21 The extrusion cylinder hole 151a formed in the extrusion cylinder 151 illustrated in (b) is similar to the one referred to in the related description of the fifth method and the sixth method. Fig. 9 (b) Fig.14 (b) and Fig.18 Similarly, the extrusion cylinder hole 151a formed in the extrusion cylinder 151 illustrated in (b) includes the 11th large inner diameter area RLDI11, the 11th small inner diameter area RSDI11, and the 11th reduced inner diameter area RsDI11. The details of each area of ​​the extrusion cylinder hole 151a have been described in the description related to the fifth method, so the description is omitted here.

[0225] In the seventh method, the above-mentioned tube 111', mandrel 131, sleeve 141' and extrusion cylinder 151 are used to perform the same 11th to 13th steps as in the fifth method, so that the end of the base end side of the tube 111' can be pressed into the extrusion cylinder hole 151a by extruding the end of the base end side of the tube 111' through the 11th extrusion area RP11 of the sleeve 141', thereby forming the above-mentioned unequal thickness tube 121'. In addition, as described above, in the seventh method, the 12th and 13th steps are performed in a state where the 11th thin-walled portion PST11 of the tube 111' is accommodated in the accommodation portion PC of the sleeve 141'. As a result, the 11th thin-walled portion PST11 is retained at the end of the front end side of the tube 111'. As a result, the uneven thickness tube 121 ′ formed by the seventh method further includes the eleventh thin-walled portion PST11 at the end portion on the base end side.

[0226] Fig. 22 This is a schematic cross-sectional view showing an example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe as the seventh method is carried out. Fig. 22 In order to make the drawings simple, Fig. 20 and Fig.21 The reference numerals for the various parts shown in FIG. Fig. 22In the following descriptions, for the sake of accuracy, the Fig. 20 and Fig.21 Please refer to the reference numerals shown in the figure as needed. Fig. 20 and Fig.21 .

[0227] Fig. 22 The left side of the central axis AX shows a state where the tube 111' having the 11th thin-walled portion PST11 at the end of the base end side is set at a predetermined position inside the extrusion cylinder hole 151a by executing the 11th process, the mandrel 131 is inserted into the tube 111', and the 11th thin-walled portion PST11 is accommodated in the accommodation portion PC of the sleeve 141'. In this state, the 12th process is started, and the end of the base end side of the tube 111' is extruded by the sleeve 141'. As a result, the material constituting the tube 111' plastically flows and is filled in the space between the extrusion cylinder 151 and the mandrel 131 in the 11th large inner diameter region RLDO11 and the 11th reduced inner diameter region RsDI11 of the extrusion cylinder hole 151a, so that the inner diameter of the tube 111' is maintained at the 11th inner diameter DI11, and the outer diameter of the tube 111' is expanded from the 11th outer diameter DO11 to the 13th outer diameter DO13.

[0228] Then, in the 13th step, the base end side of the tube 111' is further squeezed by the sleeve 141', and the front end side of the tube 111' is pressed into the 11th small inner diameter area RSDI11 of the extrusion cylinder hole 151a to reduce its diameter. As a result, the outer diameter of the front end side of the tube 111' is reduced from the 11th outer diameter DO11 to the 12th outer diameter DO12. Fig. 22 The right side of the central axis AX shows the state where the 13th step is completed and the desired unequal thickness tube 121' is formed. Fig. 22 As illustrated in the figure, according to the seventh method, the uneven thickness tube 121 ′ having the 11th thin-walled portion PST11 at the end portion on the proximal end side can be easily and reliably formed from the tube material 111 ′ having the 11th thin-walled portion PST11 at the end portion on the proximal end side.

[0229] In addition, Fig. 22 In the unequal thickness tube 121' shown in the example, the wall thickness of the 11th thin-walled portion PST11 formed at the end portion on the base end side (the 16th wall thickness T16) and the wall thickness of the 11th small outer diameter region RSDO11 formed at the end portion on the front end side (the 12th wall thickness T12) appear to be almost equal, but the 16th wall thickness T16 and the 12th wall thickness T12 may be the same or different, and both may be appropriately designed according to the purpose of the unequal thickness tube 121'. In addition, Fig. 22The inner diameter of the unequal thickness tube 121' shown in the example is the same as the inner diameter of the tube 111, i.e., the 11th inner diameter DI11, throughout the 11th small outer diameter region RSDO11, the 11th outer diameter increase region ReDO11, the 11th large outer diameter region RLDO11, and the 11th thin-walled portion PST11. However, for example, the 7th method can also be applied to the 6th method mentioned above to form a plurality of regions with different inner diameters in the unequal thickness tube 121'. Alternatively, as shown in FIG. Figure 7 As described in the first method according to another modified example, the large inner diameter region and / or small inner diameter region of the extrusion cylinder hole may be multi-staged to form a plurality of regions with different outer diameters in the uneven thickness tube 121'.

[0230] Fig.23 It is a schematic cross-sectional view of an example of the positional relationship and shape changes of the tube, mandrel, sleeve, extrusion cylinder and unequal thickness tube accompanying the progress of the process when the seventh method is applied to the sixth method involved in the above-mentioned second form. Fig.23 The states on the left and right sides of the central axis AX are respectively Fig. 22 The states on the left and right sides of the central axis AX are the same, so the description is omitted here. Fig.23 In the unequal thickness tube 121 ′ illustrated in FIG, the inner diameter of the range from the 11th large outer diameter region RLDO11 to the end portion on the front end side of the unequal thickness tube 121 ′ is reduced by increasing the thickness by applying the seventh method to the sixth method according to the second embodiment.

[0231] Fig.24 Yes means Fig.23 Schematic front view of the appearance of the pipe 111' and the unequal thickness pipe 121' shown in FIG. Fig.23 The seventh method illustrated in the example can be performed as follows Fig.24 The 11th pipe material 111' having the 11th thin-walled portion PST11 at the end portion on the base end side as shown in (a) is formed as follows Fig.24 As shown in (b), the uneven thickness tube 121' includes the 11th thin-walled portion PST11 at the end portion on the base end side. Fig.23 and Fig.24 In the uneven thickness tube 121 ′ illustrated in FIG. 1 , the axial length of the eleventh large outer diameter region RLDO11 is short, and the eleventh large outer diameter region RLDO11 has a flange-like shape.

[0232] Fig.25 is Fig.24 A cross-sectional view of the portion enclosed by the thick dotted line. Fig.25 (a) is Fig.24 A cross-sectional view of the pipe 111' illustrated in (a), Fig.25 (b) is Fig.24141' is a cross-sectional view of the uneven thickness tube 121' illustrated in (b). As described above, in the seventh method, the 12th step and the 13th step are performed in a state where the 11th thin-walled portion PST11 of the tube 111' is accommodated in the accommodation portion PC of the sleeve 141'. As a result, in the uneven thickness tube 121', the 11th thin-walled portion PST11 is also maintained at the end portion on the base end side.

[0233] As mentioned above, in Fig.23 In the example shown, the seventh method is applied to the sixth method according to the second embodiment, and the inner diameter of the range from the eleventh largest outer diameter region RLDO11 of the unequal thickness tube 121' to the end portion on the front end side is reduced by increasing the thickness. Fig.25 As shown in (b), in the 11th largest outer diameter region RLDO11 of the unequal thickness tube 121', the outer diameter is expanded by thickening toward the outside, and the inner diameter is reduced by thickening toward the inside, and the wall thickness is greatly increased. In addition, in the 11th small outer diameter region RSDO11 located closer to the front end side than the 11th largest outer diameter region RLDO11 of the unequal thickness tube 121', the outer diameter is reduced by the extrusion process performed in the third step, and the inner diameter is reduced by thickening toward the inside, becoming thicker than the wall of the tube 111'. In this way, according to the forming method of the unequal thickness tube involved in the present invention, including the fifth method to the seventh method, unequal thickness tubes with various structures can be formed.

[0234] <Effect>

[0235] As described above, in the seventh method, the 11th to 13th steps are performed using a pipe material that further includes the 11th thin-walled portion at the end portion on the base end side, the 11th thin-walled portion being a portion having a 21st outer diameter that is a predetermined outer diameter smaller than the 11th outer diameter of the pipe material, a 21st inner diameter that is a predetermined inner diameter greater than the 11th inner diameter of the pipe material, and a 16th wall thickness that is a predetermined wall thickness smaller than the 11th wall thickness of the pipe material. The sleeve used in the seventh method includes a receiving portion that is a space that opens at the end surface on the front end side and has a shape corresponding to the 11th thin-walled portion. Therefore, in the seventh method, by performing the 12th and 13th steps in a state where the 11th thin-walled portion of the pipe material is received in the receiving portion of the sleeve, the 11th thin-walled portion remains at the end portion on the base end side of the pipe material. As a result, according to the seventh method, an unequal thickness pipe that further includes the 11th thin-walled portion at the end portion on the base end side can be easily and reliably formed.

[0236] 《Eighth Implementation Method》

[0237] Next, an extrusion molding method for a tube of unequal thickness according to an eighth embodiment of the present invention (hereinafter sometimes referred to as “eighth method”) will be described.

[0238] As described above, the shape of the pipe material used in the extrusion molding method of the unequal thickness pipe involved in the fifth embodiment and the sixth embodiment of the present invention (the fifth method and the sixth method) is not necessarily limited to the shape of the pipe material. Figure 8 , Fig.13 as well as Fig.17 The simple cylindrical shape exemplified in the above, for example, may be provided with a portion having a different structure at the end portion on the distal end side and / or the proximal end side of the tube as long as it does not hinder the execution of the fifth method.

[0239] Furthermore, as described above, the shape of the pipe material used in the extrusion molding method of the unequal thickness pipe (the first method) according to the first embodiment of the present invention is not necessarily limited to the shape of the pipe material. Figure 2 The simple cylindrical shape exemplified in the embodiment may also be provided with a portion having a different structure at the end of the front end side of the pipe material, for example, as long as it does not hinder the execution of the first method. By forming a unequal thickness pipe from such a pipe material, the structure provided at the end of the front end side and / or the base end side of the pipe material can be brought into the unequal thickness pipe.

[0240] <structure>

[0241] Therefore, the eighth method is a method for molding a tube of uneven thickness by using the first method, the second method, and any one of the fifth method to the seventh method, using a tube having a portion having an outer diameter smaller than the minimum inner diameter in the extrusion cylinder hole and an inner diameter larger than the tube inner diameter at the end portion on the front end side. Specifically, the eighth method is a method for extruding a tube of uneven thickness by performing the eleventh to thirteenth steps using a tube having a twelfth thin-walled portion at the end portion on the front end side on the basis of the above-mentioned first method, the second method, and any one of the fifth method to the seventh method, wherein the twelfth thin-walled portion is a portion having a 22nd outer diameter smaller than a prescribed outer diameter corresponding to the minimum inner diameter in the extrusion cylinder hole, a 22nd inner diameter larger than the 11th inner diameter, which is the inner diameter of the tube, and a 17th wall thickness smaller than the 11th wall thickness, which is the wall thickness of the tube.

[0242] In the 8th method, when the 12th thin-walled portion at the end of the tube on the front end side meets the above requirements, no special structural changes are required for the mandrel, sleeve and extrusion cylinder. By using the tube to perform steps 11 to 13, a tube of unequal thickness that also includes the 12th thin-walled portion at the end on the front end side can be formed.

[0243] Fig.26 This is a schematic cross-sectional view showing an example of the structure of a pipe material used in the eighth method and a pipe of uneven thickness formed from the pipe material. Fig.26 The pipe material 111" illustrated in (a) has the same characteristics as those described in the fifth and sixth methods except that the pipe material 111" has a twelfth thin-walled portion PST12 at the end portion on the front end side. Figure 8 (a) Fig.13 (a) and Fig.17 The 12th thin-walled portion PST12 has a 22nd outer diameter DO22 (DO22≤DI17) having a prescribed outer diameter less than the outer diameter corresponding to the minimum inner diameter (e.g., the 17th inner diameter DI17) in the extrusion cylinder hole 151a, and a 22nd inner diameter DI22 (DI22≥DI11) having an inner diameter greater than the 11th inner diameter DI11. However, Fig.26 DI22 = DI11) and the 17th wall thickness T17 (T17 < T11) of the pipe 111″, which is smaller than the 11th wall thickness T11. Fig.26 As shown in (b), the unequal thickness tube 121" formed by the eighth method has the same characteristics as those mentioned in the description of the fifth method except that the end portion on the front end side also includes a twelfth thin-walled portion PST12. Figure 8 The same structure as the unequal thickness tube 121 illustrated in (b).

[0244] On the other hand, as described above, the mandrel, sleeve, and extrusion cylinder used in the eighth method do not require any special structural changes and can be used in the eighth method using the pipe material 111" having the above-mentioned structure. Therefore, in the eighth method, for example, the mandrel, sleeve, and extrusion cylinder referred to in the description related to the fifth method can be used. Fig. 9 The mandrel 131, sleeve 141 and extrusion cylinder 151 are exemplified in the figure. Therefore, the description of the mandrel, sleeve and extrusion cylinder used in the eighth method is omitted here.

[0245] In the 8th method, by using the above-mentioned tube 111", mandrel 131, sleeve 141 and extrusion cylinder 151 to perform the same 11th to 13th steps as the 5th method, the mandrel 131 is inserted into the internal space of the tube 111" from the base end side (the upper side in the drawing), and the end of the base end side of the tube 111" is squeezed by the 11th extrusion area RP11 of the sleeve 141 to press the tube 111" into the extrusion cylinder hole 151a, thereby forming the above-mentioned unequal thickness tube 121". That is, the unequal thickness tube 121" formed by the 8th method also includes the 12th thin-walled portion PST12 at the end on the front end side.

[0246] Fig. 27 This is a schematic cross-sectional view showing an example of the positional relationship and shape changes of the pipe, mandrel, sleeve, extrusion cylinder and unequal thickness pipe as the eighth method is carried out. Fig. 27 In order to make the drawings simple, Fig.26 and Fig. 9The reference numerals for the various parts are shown in FIG. Fig. 27 In the following descriptions, for the sake of accuracy, the Fig.26 and Fig. 9 Please refer to the reference numerals shown in the figure as needed. Fig.26 and Fig. 9 wait.

[0247] Fig. 27 The left side of the center axis AX shows a state in which the tube 111" having the 12th thin-walled portion PST12 at the end on the front end side is set at a specified position inside the extrusion cylinder hole 151a, and the mandrel 131 is inserted into the tube 111' through the execution of the 11th process. In this state, the 12th process starts, and the end on the base end side of the tube 111" is extruded by the sleeve 141. As a result, the material constituting the tube 111" plastically flows and is filled in the space between the extrusion cylinder 151 and the mandrel 131 in the 11th large inner diameter region RLDO11 and the 11th reduced inner diameter region RsDI11 of the extrusion cylinder hole 151a, so that the inner diameter of the tube 111" is maintained at the 11th inner diameter DI11, and the outer diameter of the tube 111" is expanded from the 11th outer diameter DO11 to the 13th outer diameter DO13.

[0248] Then, in the 13th process, the base end side of the tube 111" is further squeezed by the sleeve 141, and the front end side of the tube 111" is pressed into the 11th small inner diameter area RSDI11 of the extrusion tube hole 151a to reduce its diameter. As a result, the outer diameter of the front end side portion of the tube 111" is reduced from the 11th outer diameter DO11 to the 12th outer diameter DO12. Fig. 27 The right side of the central axis AX shows the state where the 13th step is completed and the desired unequal thickness tube 121" is formed. Fig. 27 As shown in the example, according to the eighth method, a tube 111'' having a 12th thin-walled portion PST12 at the end portion on the front end side can be easily and reliably formed into an uneven thickness tube 121'' having a 12th thin-walled portion PST12 at the end portion on the front end side.

[0249] also, Fig. 27 The inner diameter of the unequal thickness tube 121" shown in the example is the same as the inner diameter of the tube 111, i.e., the 11th inner diameter DI11, and is constant throughout the 12th thin-walled portion PST12, the 11th small outer diameter region RSDO11, the 11th outer diameter increased region ReDO11, and the 11th large outer diameter region RLDO11. However, for example, the 8th method can also be applied to the 6th method mentioned above to form a plurality of regions with different inner diameters in the unequal thickness tube 121". Alternatively, as shown in FIG. Figure 7As described in the first method according to another variation, the large inner diameter region and / or the small inner diameter region of the extrusion tube hole may be multi-leveled to form a plurality of regions with different outer diameters in the unequal thickness tube 121".

[0250] <Effect>

[0251] As described above, in the eighth method, the eleventh to thirteenth steps are performed using a pipe material having a twelfth thin-walled portion at the end of the front end side, the twelfth thin-walled portion being a portion having a 22nd outer diameter which is a prescribed outer diameter less than the outer diameter corresponding to the minimum inner diameter in the hole of the extrusion cylinder, a 22nd inner diameter which is a prescribed inner diameter greater than the 11th inner diameter which is the inner diameter of the pipe material, and a 17th wall thickness which is a prescribed wall thickness less than the 11th wall thickness which is the wall thickness of the pipe material. In the eighth method, when the twelfth thin-walled portion at the end of the front end side of the pipe material satisfies the above requirements, no special structural changes are required for the mandrel, the sleeve, and the extrusion cylinder, and even when the eleventh to thirteenth steps are performed using the pipe material, the twelfth thin-walled portion remains at the end of the front end side of the pipe material. As a result, according to the eighth method, a unequal thickness pipe having a twelfth thin-walled portion at the end of the front end side can be easily and reliably formed.

[0252] <<Ninth Implementation Method>>

[0253] As mentioned at the beginning of this specification, the present invention not only relates to the extrusion molding method of unequal thickness tubes represented by the above-mentioned methods 5 to 8, but also relates to the extrusion molding device of unequal thickness tubes. Therefore, the extrusion molding device of unequal thickness tubes involved in various embodiments of the present invention is described below.

[0254] First, an extrusion molding apparatus for unequal thickness tubes according to a ninth embodiment of the present invention (hereinafter referred to as a "ninth apparatus") will be described.

[0255] <structure>

[0256] The ninth device is an extrusion molding device for unequal thickness tubes, which comprises: a mandrel, which is a metal core having a predetermined shape; a sleeve, which is a cylindrical member coaxially arranged outside the mandrel; an extrusion cylinder, which is a die formed with a through hole having a predetermined shape, i.e., an extrusion cylinder hole; and a driving mechanism configured to at least press the sleeve into the extrusion cylinder hole. The ninth device is configured to press a tube having a predetermined shape into the extrusion cylinder hole through the sleeve to mold a unequal thickness tube having a predetermined shape.

[0257] Regarding the structure of the tube, mandrel, sleeve and extrusion cylinder, refer to the description related to the fifth method. Figures 8 to 12 It has been described in detail, so the explanation is omitted here.

[0258] Furthermore, the ninth device is configured to form a tube of unequal thickness by executing the 11th step, the 12th step, and the 13th step. The 11th step to the 13th step have been described in detail in the description of the fifth method, so the description thereof is omitted here.

[0259] Furthermore, the ninth device is configured such that, at the time when the 12th step is started, that is, at the 11th time, the end of the front end side of the mandrel reaches the same position as the position of the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole in the extrusion direction, that is, the 11th position, or a position closer to the front end side than the 11th position. Furthermore, the ninth device is configured such that, at the time when the 13th step is started, that is, at the 12th time, the end of the front end side of the mandrel reaches the position closer to the front end side by a predetermined distance in the extrusion direction than the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole, that is, the 12th position, or a position closer to the front end side than the 12th position.

[0260] <Effect>

[0261] By performing the 11th to 13th steps in the 9th device having the above-mentioned structure, the 11th large outer diameter region is formed by thickening the tube material, and the 11th small outer diameter region is formed by thinning the tube material. Therefore, compared with the case where the large outer diameter region is formed while maintaining the outer diameter of the tube material and the small outer diameter region is formed by greatly reducing the outer diameter of the tube material, a larger diameter difference can be achieved with a smaller processing load. In addition, according to the 9th device, the wall thickness of the large outer diameter region can be increased, so that, for example, an unequal thickness tube suitable for use in which a high mechanical strength is required for the large diameter portion can be formed.

[0262] In addition, the axial lengths of the 11th large outer diameter region and the 11th small outer diameter region vary according to the axial length of the pipe material, the amount of diameter expansion in the 12th step, the amount of diameter reduction in the 13th step, and the amount of the sleeve pressed into the pipe material. That is, according to the ninth device, the axial lengths of the 11th large outer diameter region and the 11th small outer diameter region of the unequal thickness pipe can be arbitrarily set.

[0263] 《10th Implementation Method》

[0264] Next, an extrusion-molding apparatus for unequal-thickness tubes according to a tenth embodiment of the present invention (hereinafter sometimes referred to as a "tenth apparatus") will be described.

[0265] <structure>

[0266] The tenth device is based on the ninth device, and is configured to form a unequal thickness tube having a 12th small outer diameter region thickened inwardly and having a wall thickness greater than that of the 11th small outer diameter region at a position closer to the front end side than the 11th small outer diameter region by executing the sixth method. The 12th small outer diameter region is formed at the end of the front end side of the unequal thickness tube formed by the tenth device, and the 12th small outer diameter region is a region having a 16th outer diameter equal to the 12th outer diameter, an 18th inner diameter smaller than the 12th inner diameter, and a 14th wall thickness greater than the 12th wall thickness.

[0267] In order to form the 12th small outer diameter region as described above, the mandrel provided by the 10th device further includes a 13th small outer diameter region and a 12th outer diameter increase region. The 13th small outer diameter region is a cylindrical region of the 18th outer diameter formed at a position closer to the front end side than the basic outer diameter region and having an outer diameter corresponding to the 18th inner diameter. The 12th outer diameter increase region is a region formed between the 13th small outer diameter region and the basic outer diameter region and whose outer diameter increases from the 18th outer diameter to the 14th outer diameter as it approaches from the 13th small outer diameter region to the basic outer diameter region.

[0268] Furthermore, the tenth device is configured such that, at the twelfth time, the end portion on the proximal side of the thirteenth small outer diameter region is located closer to the proximal side than the eleventh position.

[0269] In addition, the tenth device may be configured to execute the sixth method according to the first aspect. In this case, the tenth device is configured so that at the 13th time when the 13th step is completed, the end of the front end of the basic outer diameter region is located closer to the front end than the 11th position.

[0270] The unequal thickness tube formed by executing the sixth method according to the first embodiment in the tenth device includes: an eleventh large outer diameter region; an eleventh increased outer diameter region; an eleventh small outer diameter region; a twelfth small outer diameter region formed at a position closer to the front end side than the eleventh small outer diameter region; and an eleventh increased inner diameter region. The eleventh increased inner diameter region is a region formed between the twelfth small outer diameter region and the eleventh small outer diameter region, and the inner diameter increases from the eighteenth inner diameter to the twelfth inner diameter as it approaches from the twelfth small outer diameter region to the eleventh small outer diameter region, and the wall thickness decreases from the fourteenth wall thickness to the twelfth wall thickness, and the outer diameter is constant at the seventeenth outer diameter equal to the twelfth outer diameter.

[0271] In addition, the tenth device may be configured to execute the sixth method according to the second aspect. In this case, the tenth device is configured so that at the 13th time when the 13th step is completed, the end of the base end of the 13th small outer diameter region is located closer to the base end than the 11th position.

[0272] The unequal thickness tube formed by performing the sixth method according to the second embodiment in the tenth device includes a 12th small outer diameter region, an 11th large outer diameter region, a 12th large outer diameter region, a 13th increased outer diameter region, and a 12th increased inner diameter region. The 12th large outer diameter region is a region formed between the 12th small outer diameter region and the 11th large outer diameter region and having a 19th outer diameter equal to the 13th outer diameter, a 19th inner diameter equal to the 18th inner diameter, and a 15th wall thickness greater than the 13th wall thickness. The 13th increased outer diameter region is a region formed between the 12th small outer diameter region and the 12th large outer diameter region and having an outer diameter increasing from the 16th outer diameter to the 19th outer diameter as it approaches from the 12th small outer diameter region to the 12th large outer diameter region, a wall thickness increasing from the 14th wall thickness to the 15th wall thickness, and an inner diameter constant at a 20th inner diameter equal to the 18th inner diameter. The 12th inner diameter increased region is formed between the 12th largest outer diameter region and the 11th largest outer diameter region and the inner diameter increases from the 19th inner diameter to the 13th inner diameter as it approaches the 12th largest outer diameter region toward the 11th largest outer diameter region, and the wall thickness decreases from the 15th wall thickness to the 13th wall thickness, and the outer diameter is constant at the 20th outer diameter equal to the 13th outer diameter.

[0273] For details of the sixth method performed in the tenth device and the unequal thickness tube formed by performing the sixth method in the tenth device, refer to the description related to the sixth method. Figures 13 to 19 It has been described in detail, so the explanation is omitted here.

[0274] <Effect>

[0275] As described above, according to the tenth device, by appropriately adjusting the size and / or length of the twelfth small outer diameter region, which is a portion thinner than the inner diameter of the tube formed on the front end side of the mandrel, and the position of the mandrel at the time of the end of the thirteenth step, the range in which the inner diameter is reduced by increasing the thickness of the uneven thickness tube formed by executing the sixth method in the tenth device can be changed. Therefore, for example, the shape of the uneven thickness tube and the distribution of the wall thickness can be designed with a high degree of freedom according to the application.

[0276] 《11th Implementation Method》

[0277] Next, an extrusion-molding apparatus for tubes of unequal thickness according to an eleventh embodiment of the present invention (hereinafter referred to as “eleventh apparatus”) will be described.

[0278] <structure>

[0279] The 11th device is based on the above-mentioned 9th device or 10th device, and is constructed by executing the above-mentioned 7th method to form an unequal thickness tube having an 11th thin-walled portion with a specified shape at the end portion on the base end side.

[0280] The 11th device is configured to perform the 11th to 13th steps using a pipe material further having an 11th thin-walled portion at the end portion on the base end side in addition to the 9th or 10th device described above. The 11th thin-walled portion is a portion having a 21st outer diameter which is a prescribed outer diameter smaller than the 11th outer diameter, a 21st inner diameter which is a prescribed inner diameter greater than the 11th inner diameter, and a 16th wall thickness which is a prescribed wall thickness smaller than the 11th wall thickness.

[0281] The sleeve provided by the 11th device has a receiving portion which is open at the end face on the front end side and has a space having a shape corresponding to the 11th thin-walled portion. Furthermore, the 11th device is configured to perform the 12th step and the 13th step in a state where the 11th thin-walled portion is received in the receiving portion of the sleeve. Thus, the 11th thin-walled portion is retained at the end portion on the front end side of the pipe material. As a result, the unequal thickness tube formed by the 11th device also includes the 11th thin-walled portion at the end portion on the base end side.

[0282] For details of the seventh method performed in the eleventh apparatus and the unequal thickness tube formed by performing the seventh method in the eleventh apparatus, refer to the description related to the seventh method. Figure 20 to Figure 25 It has been described in detail, so the explanation is omitted here.

[0283] <Effect>

[0284] As described above, in the 11th device, the 11th to 13th steps are performed using a pipe material that further includes the 11th thin-walled portion at the end portion on the base end side, the 11th thin-walled portion being a portion having a 21st outer diameter that is a specified outer diameter smaller than the 11th outer diameter, which is the outer diameter of the pipe material, a 21st inner diameter that is a specified inner diameter greater than the 11th inner diameter, which is the inner diameter of the pipe material, and a 16th wall thickness that is a specified wall thickness smaller than the 11th wall thickness, which is the wall thickness of the pipe material. The sleeve provided in the 11th device includes a receiving portion that is open at the end surface on the front end side and has a space with a shape corresponding to the 11th thin-walled portion. Therefore, in the 11th device, by performing the 12th and 13th steps in a state where the 11th thin-walled portion of the pipe material is received in the receiving portion of the sleeve, the 11th thin-walled portion remains at the end portion on the base end side of the pipe material. As a result, according to the 11th device, an unequal thickness pipe that further includes the 11th thin-walled portion at the end portion on the base end side can be easily and reliably formed.

[0285] 《12th Implementation Method》

[0286] Next, an extrusion-molding apparatus for unequal-thickness tubes according to a twelfth embodiment of the present invention (hereinafter sometimes referred to as a "twelfth apparatus") will be described.

[0287] <structure>

[0288] The 12th device is based on any one of the above-mentioned 3rd device, 4th device, 9th device and 10th device, and is constructed by executing the above-mentioned 8th method to form an unequal thickness tube having a 12th thin-walled portion at the end portion on the front end side from a tube having a 12th thin-walled portion having a specified shape at the end portion on the front end side.

[0289] The 12th thin-walled portion is a portion having a 22nd outer diameter which is a prescribed outer diameter less than the outer diameter corresponding to the minimum inner diameter in the extrusion cylinder hole, a 22nd inner diameter which is a prescribed inner diameter greater than the 11th inner diameter, and a 17th wall thickness which is a prescribed wall thickness less than the 11th wall thickness. The 12th device is based on any one of the above-mentioned 3rd, 4th, 9th and 10th devices, and is configured to perform the 11th to 13th steps using a pipe material further having the 12th thin-walled portion at the end portion on the front end side. Thus, the unequal thickness pipe formed by the 12th device further includes the 12th thin-walled portion at the end portion on the front end side.

[0290] For details of the eighth method performed in the twelfth apparatus and the unequal thickness tube formed by performing the eighth method in the twelfth apparatus, refer to the description related to the eighth method. Fig.26 and Fig. 27 It has been described in detail, so the explanation is omitted here.

[0291] <Effect>

[0292] As described above, in the 12th device, the 11th to 13th steps are performed using a pipe material having a 12th thin-walled portion at the end of the front end side, the 12th thin-walled portion being a portion having a 22nd outer diameter which is a prescribed outer diameter less than the outer diameter corresponding to the minimum inner diameter in the hole of the extrusion cylinder, a 22nd inner diameter which is a prescribed inner diameter greater than the 11th inner diameter which is the inner diameter of the pipe material, and a 17th wall thickness which is a prescribed wall thickness less than the 11th wall thickness which is the wall thickness of the pipe material. In the 12th device, when the 12th thin-walled portion at the end of the front end side of the pipe material satisfies the above requirements, no special structural changes are required for the mandrel, the sleeve, and the extrusion cylinder, and even when the 11th to 13th steps are performed using the pipe material, the 12th thin-walled portion remains at the end of the front end side of the pipe material. As a result, according to the 12th device, an unequal thickness pipe having a 12th thin-walled portion at the end of the front end side can be easily and reliably formed.

[0293] In the above, for the purpose of illustrating the present invention, several embodiments and modifications with specific structures have been described, sometimes with reference to the accompanying drawings, but the scope of the present invention should not be interpreted as being limited to the above-mentioned illustrative embodiments and modifications, and can of course be appropriately modified within the scope of the claims and the description.

[0294] Description of Reference Numerals

[0295] 11… pipe material; DO1… 1st outer diameter; DI1… 1st inner diameter; T1… 1st wall thickness; 21, 21', 21"… unequal thickness pipe; RSD1… 1st small diameter area; DO2… 2nd outer diameter; DI2… 2nd inner diameter; T2… 2nd wall thickness; RSD2… 2nd small diameter area; DO3… 3rd outer diameter; DI3… 3rd inner diameter; T3… 3rd wall thickness; PSD1, PSD2… multi-stage part; PtDI… tapered part; RLD… large diameter area; DO4… 4th outer diameter; DI4… 4th inner diameter; T4… 4th wall thickness; RtDI1… 1st tapered area; RtDI2… 2nd tapered area; 31, 31'… mandrel; RSC… small cross-section area; DO5… 5th outer diameter; RLC… large cross-section area domain; DO6…6th outer diameter; ReC…cross-section expansion area; 41…sleeve; RP…extrusion area; DO7…7th outer diameter; DI5…5th inner diameter; 51, 51'…extrusion barrel; 51a, 51a'…extrusion barrel hole; RLDI…large inner diameter area; DI6…6th inner diameter; RSDI…small inner diameter area; DI7…7th inner diameter; RsDI…inner diameter reduction area; 111, 111', 111"…tube; DO11…11th outer diameter; DI11…11th inner diameter; T11…11th wall thickness; PST11…11th thin wall portion; DO21…21st outer diameter; DI21…21st inner diameter; T16…16th wall thickness; PST12…12th thin wall portion; DO22…22nd outer diameter; DI22…22nd inner diameter; T17…17th wall thickness; 121, 121', 121"…different thickness tubes; RSDO11…11th smallest outer diameter area; DO12…12th outer diameter; DI12…12th inner diameter; T12…12th wall thickness; RSDO12, RSDO12'…12th smallest outer diameter area; DO16…16th outer diameter; DI18…18th inner diameter; T14, T14'…14th wall thickness; RLDO11…11th largest outer diameter area; DO13…13th outer diameter; DI13…13th inner diameter; T13…13th wall thickness; RLDO12…12th largest outer diameter area; DO19…19th outer diameter; DI19…19th inner diameter; T15…15th wall thickness; ReDO1 1…11th outer diameter increase area; DI14…14th inner diameter; ReDO13…13th outer diameter increase area; DI20…20th inner diameter; ReDi11…11th inner diameter increase area; DO17…17th outer diameter; ReDi12…12th inner diameter increase area; DO20…20th outer diameter; 131…mandrel; RBDO…basic outer diameter area; DO14…14th outer diameter; RSDO13, RSDO13'…13th small outer diameter area; DO18…18th outer diameter; ReDO12…12th outer diameter increase area; 141, 141'…sleeve; RP11…11th extrusion area; DO15…15th outer diameter; DI15…15th inner diameter; PC…housing part; 151…extrusion cylinder;151a…extrusion cylinder hole; RLDI11…11th largest inner diameter area; DI16…16th inner diameter; RSDI11…11th small inner diameter area; DI17…17th inner diameter; RsDI11…11th reduced inner diameter area. ;

Claims

1. An extrusion molding method for unequal thickness tubes, comprising a first step, a second step and a third step performed in an extrusion molding device, The extrusion molding device comprises: a mandrel, which is a metal core having a predetermined shape; The sleeve is a cylindrical component coaxially arranged outside the mandrel; the extrusion cylinder is a die formed with a through hole of a predetermined shape, i.e., an extrusion cylinder hole; and a driving mechanism configured to press the mandrel and the sleeve into the extrusion cylinder hole, The first step is a step of placing a tube having a predetermined shape at a predetermined position inside the extrusion cylinder hole. The second step is a step of pressing the mandrel into the tube by the driving mechanism to expand the diameter of the upstream side, that is, the base end side, in the extrusion direction of the tube. The third step is a step of performing an extrusion process by extruding the end of the base end side of the tube by the sleeve at a time later than the time when the second step is started, i.e., the first time, to press the tube into the downstream side, i.e., the front end side, of the extrusion cylinder hole in the extrusion direction, thereby reducing the diameter of the front end side of the tube. The extrusion molding method of the unequal thickness tube is characterized in that: The pipe is a cylindrical member having a first outer diameter of a predetermined outer diameter, a first inner diameter of a predetermined inner diameter, and a first wall thickness of a predetermined wall thickness. The unequal thickness tube includes, in order from the front end side toward the base end side: a first small diameter region, which is a region having a second outer diameter with a specified outer diameter smaller than the first outer diameter, a second inner diameter with an inner diameter equal to the first inner diameter, and a second wall thickness with a specified wall thickness smaller than the first wall thickness; a second small diameter region, which is a region having a third outer diameter with an outer diameter equal to the second outer diameter, and a third wall thickness with a specified wall thickness smaller than the second wall thickness; and a large diameter region, which is a fourth outer diameter with a specified outer diameter larger than the first outer diameter, and a fourth wall thickness with a specified wall thickness, The core shaft includes: a small cross-sectional area, which is a cylindrical area formed on the front end side and has a first cross-sectional area, wherein the first cross-sectional area is a circular cross-sectional area having a fifth outer diameter corresponding to the second inner diameter; a large cross-sectional area, which is a columnar area formed on the base end side and has a second cross-sectional area, wherein the second cross-sectional area is a cross-sectional area corresponding to the cross-sectional area of ​​the internal space of the second small diameter area and the large diameter area; and a cross-sectional expansion area, which is formed between the small cross-sectional area and the large cross-sectional area, and the cross-sectional area expands from the first cross-sectional area to the second cross-sectional area as it approaches from the small cross-sectional area to the large cross-sectional area. The sleeve includes an extrusion area, which is a cylindrical area formed on the front end side and having a seventh outer diameter equal to the fourth outer diameter and a columnar internal space having a third cross section corresponding to the second cross section, The extrusion cylinder hole includes: a large inner diameter region, which is a region of the sixth inner diameter formed on the base end side and having an inner diameter corresponding to the fourth outer diameter; a small inner diameter region, which is a region of the seventh inner diameter formed on the front end side and having an inner diameter corresponding to the second outer diameter and the third outer diameter; and an inner diameter reduction region, which is formed between the large inner diameter region and the small inner diameter region and has an inner diameter that decreases from the sixth inner diameter to the seventh inner diameter as it approaches from the large inner diameter region to the small inner diameter region. At the moment when the third process starts, that is, the second moment, the end of the front end side of the mandrel in the extrusion direction reaches the end of the front end side of the tube or a position closer to the front end side than the end of the front end side of the tube, and the end of the base end side of the small cross-sectional area is located closer to the base end side than the end of the base end side of the small inner diameter area.

2. The extrusion molding method of unequal thickness tubes according to claim 1, characterized in that: The internal space of the second small diameter region of the unequal thickness tube has a cylindrical shape having a third inner diameter that is a predetermined inner diameter larger than the first inner diameter. The internal space of the large diameter region of the unequal thickness tube has a cylindrical shape having a fourth inner diameter equal to the third inner diameter. The large cross-sectional area of ​​the mandrel has a cylindrical shape with a sixth outer diameter corresponding to the fourth inner diameter, The cross-sectional expansion region of the mandrel has a truncated cone shape in which the outer diameter increases from the fifth outer diameter to the sixth outer diameter as approaching from the small cross-sectional region to the large cross-sectional region, The extrusion region of the sleeve has a cylindrical shape having the seventh outer diameter and a seventh inner diameter corresponding to the sixth outer diameter.

3. The extrusion molding method of unequal thickness tubes according to claim 1 or 2, characterized in that: The mandrel and the sleeve are fixed in such a manner that the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve in the extrusion direction is not larger than the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve at the second moment.

4. An extrusion molding device for tubes of unequal thickness, comprising: a mandrel, which is a metal core having a prescribed shape; The sleeve is a cylindrical component coaxially arranged outside the mandrel; the extrusion cylinder is a die formed with a through hole of a predetermined shape, i.e., an extrusion cylinder hole; and the driving mechanism is configured to press the mandrel and the sleeve into the extrusion cylinder hole. The unequal thickness tube extrusion molding device is configured to mold the unequal thickness tube having a specified shape by performing the following steps: The first step is to place a tube having a predetermined shape at a predetermined position inside the extrusion cylinder hole; The second step is a step of pressing the mandrel into the tube by the driving mechanism to expand the diameter of the upstream side, that is, the base end side, in the extrusion direction of the tube. as well as The third step is a step of performing an extrusion process by extruding the end of the base end side of the tube by the sleeve at a time later than the time when the second step is started, i.e., the first time, to press the tube into the downstream side, i.e., the front end side, of the extrusion cylinder hole in the extrusion direction, thereby reducing the diameter of the front end side of the tube. The extrusion forming device for unequal thickness tubes is characterized in that: The pipe is a cylindrical member having a first outer diameter of a predetermined outer diameter, a first inner diameter of a predetermined inner diameter, and a first wall thickness of a predetermined wall thickness. The unequal thickness tube includes, in order from the front end side toward the base end side: a first small diameter region, which is a region having a second outer diameter with a specified outer diameter smaller than the first outer diameter, a second inner diameter with an inner diameter equal to the first inner diameter, and a second wall thickness with a specified wall thickness smaller than the first wall thickness; a second small diameter region, which is a region having a third outer diameter with an outer diameter equal to the second outer diameter, and a third wall thickness with a specified wall thickness smaller than the second wall thickness; and a large diameter region, which is a fourth outer diameter with a specified outer diameter larger than the first outer diameter, and a fourth wall thickness with a specified wall thickness, The core shaft includes: a small cross-sectional area, which is a cylindrical area formed on the front end side and has a first cross-sectional area, wherein the first cross-sectional area is a circular cross-sectional area having a fifth outer diameter corresponding to the second inner diameter; a large cross-sectional area, which is a columnar area formed on the base end side and has a second cross-sectional area, wherein the second cross-sectional area is a cross-sectional area corresponding to the cross-sectional area of ​​the internal space of the second small diameter area and the large diameter area; and a cross-sectional expansion area, which is formed between the small cross-sectional area and the large cross-sectional area, and the cross-sectional area expands from the first cross-sectional area to the second cross-sectional area as it approaches from the small cross-sectional area to the large cross-sectional area. The sleeve includes an extrusion area, which is a cylindrical area formed on the front end side and having a seventh outer diameter equal to the fourth outer diameter and a columnar internal space having a third cross section corresponding to the second cross section, The extrusion cylinder hole includes: a large inner diameter region, which is a region of the sixth inner diameter formed on the base end side and having an inner diameter corresponding to the fourth outer diameter; a small inner diameter region, which is a region of the seventh inner diameter formed on the front end side and having an inner diameter corresponding to the second outer diameter and the third outer diameter; and an inner diameter reduction region, which is formed between the large inner diameter region and the small inner diameter region and has an inner diameter that decreases from the sixth inner diameter to the seventh inner diameter as it approaches from the large inner diameter region to the small inner diameter region. At the moment when the third process starts, that is, the second moment, the position of the end portion of the front end side in the extrusion direction of the mandrel, that is, the first position, is equal to the position of the end portion of the front end side of the tube, that is, the second position, or is located at a position which is a specified distance closer to the front end side than the second position, that is, the third position.

5. The extrusion forming device for unequal thickness tubes according to claim 4, characterized in that: The internal space of the second small diameter region of the unequal thickness tube has a cylindrical shape having a third inner diameter that is a predetermined inner diameter larger than the first inner diameter. The internal space of the large diameter region of the unequal thickness tube has a cylindrical shape having a fourth inner diameter equal to the third inner diameter. The large cross-sectional area of ​​the mandrel has a cylindrical shape with a sixth outer diameter corresponding to the fourth inner diameter, The cross-sectional expansion region of the mandrel has a truncated cone shape in which the outer diameter increases from the fifth outer diameter to the sixth outer diameter as approaching from the small cross-sectional region to the large cross-sectional region, The extrusion region of the sleeve has a cylindrical shape having the seventh outer diameter and a seventh inner diameter that is equal to the third inner diameter and the fourth inner diameter.

6. The extrusion molding device for unequal thickness tubes according to claim 4 or 5, characterized in that: The mandrel and the sleeve are fixed in such a manner that the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve in the extrusion direction is not larger than the distance between the end of the front end side of the mandrel and the end of the front end side of the sleeve at the second moment.

7. An extrusion molding method for unequal thickness tubes, in which a tube having a specified shape is pressed into an extrusion barrel hole through a sleeve in an extrusion molding device, thereby forming a unequal thickness tube having a specified shape, the extrusion molding device comprising: a mandrel, which is a metal core having a specified shape; the sleeve, which is a tubular component coaxially arranged outside the mandrel; an extrusion barrel, which is a die formed with a through hole having a specified shape, i.e., the extrusion barrel hole; and a driving mechanism, which is configured to at least press the sleeve into the extrusion barrel hole, The extrusion molding method of the unequal thickness tube is characterized in that: The pipe is a cylindrical member having an 11th outer diameter of a specified outer diameter, an 11th inner diameter of a specified inner diameter, and an 11th wall thickness of a specified wall thickness, The unequal thickness tube comprises: The 11th small outer diameter region is formed on the downstream side, i.e., the front end side, in the direction in which the tube is pressed into the extrusion cylinder hole, i.e., the extrusion direction, and has a 12th outer diameter of a prescribed outer diameter smaller than the 11th outer diameter, a 12th inner diameter of an inner diameter equal to the 11th inner diameter, and a 12th wall thickness region of a prescribed wall thickness smaller than the 11th wall thickness; the 11th large outer diameter region is formed on the upstream side, i.e., the base end side, in the extrusion direction, and has a 13th outer diameter of a prescribed outer diameter larger than the 11th outer diameter, a 14th inner diameter of an inner diameter equal to the 15th inner diameter, and a 15th outer diameter of a prescribed wall thickness smaller than the 11th wall thickness. 13th inner diameter equal to the inner diameter of the 11th inner diameter, and a 13th wall thickness area with a prescribed wall thickness greater than the 11th wall thickness; and an 11th outer diameter increasing area, which is formed between the 11th small outer diameter area and the 11th large outer diameter area, and the outer diameter increases from the 12th outer diameter to the 13th outer diameter as it approaches from the 11th small outer diameter area to the 11th large outer diameter area, and the wall thickness increases from the 12th wall thickness to the 13th wall thickness, and the inner diameter is constant at a 14th inner diameter equal to the 11th inner diameter, The mandrel includes a basic outer diameter region, which is a cylindrical region formed on the front end side and having an outer diameter of a 14th outer diameter corresponding to the 11th inner diameter. The sleeve includes an 11th extrusion area, which is a cylindrical area formed on the front end side and has a cylindrical internal space with a 15th outer diameter equal to the 13th outer diameter and a 15th inner diameter corresponding to the 14th outer diameter, The extrusion cylinder hole includes: an 11th large inner diameter region, which is a region of the 16th inner diameter formed on the base end side and having an inner diameter corresponding to the 13th outer diameter; an 11th small inner diameter region, which is a region of the 17th inner diameter formed on the front end side and having an inner diameter corresponding to the 12th outer diameter; and an 11th inner diameter reduction region, which is formed between the 11th large inner diameter region and the 11th small inner diameter region, and the inner diameter of which decreases from the 16th inner diameter to the 17th inner diameter as it approaches from the 11th large inner diameter region to the 11th small inner diameter region. The extrusion molding method of the unequal thickness tube comprises: The eleventh step is a step of placing the tube at a predetermined position inside the extrusion tube hole by bringing the end of the front end side of the tube into contact with the reduced inner diameter region of the extrusion tube hole; The twelfth step is a step of extruding the end of the base end of the tube by the sleeve while the mandrel is inserted into the tube, so that the material constituting the tube plastically flows and fills the space between the extrusion cylinder and the mandrel in the 11th large inner diameter region and the 11th inner diameter reduction region of the extrusion cylinder hole, thereby maintaining the inner diameter of the tube at the 11th inner diameter and expanding the outer diameter of the tube to the 13th outer diameter; and The 13th step is a step of reducing the diameter of the front end side of the tube by performing an extrusion process, in which, while the mandrel is inserted into the tube, the end of the base end side of the tube is further extruded by the sleeve, and the material constituting the tube is extruded toward the 11th small inner diameter region of the extrusion cylinder hole through a gap between the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole and the mandrel. At the moment when the 12th step starts, that is, the 11th moment, the end of the front end side of the mandrel reaches the same position as the position of the end of the base end side of the 11th small inner diameter area of ​​the extrusion cylinder hole in the extrusion direction, that is, the 11th position or a position closer to the front end side than the 11th position. At the moment when the 13th process starts, that is, the 12th moment, the end of the front end side of the core shaft reaches a position that is a specified distance from the front end side in the extrusion direction than the end of the base end side of the 11th smaller inner diameter region of the extrusion cylinder hole, that is, the 12th position or a position closer to the front end side than the 12th position.

8. The extrusion molding method of unequal thickness tubes according to claim 7, characterized in that: A 12th small outer diameter region is formed at the end of the front end side of the unequal thickness tube, and the 12th small outer diameter region is a region having a 16th outer diameter equal to the 12th outer diameter, an 18th inner diameter having a predetermined inner diameter smaller than the 12th inner diameter, and a 14th wall thickness having a predetermined wall thickness greater than the 12th wall thickness, The spindle further includes: a 13th small outer diameter region, which is a cylindrical region of an 18th outer diameter formed at a position closer to the front end side than the basic outer diameter region and having an outer diameter corresponding to the 18th inner diameter; and a 12th outer diameter increase region, which is formed between the 13th small outer diameter region and the basic outer diameter region and has an outer diameter that increases from the 18th outer diameter to the 14th outer diameter as it approaches from the 13th small outer diameter region to the basic outer diameter region. At the twelfth time, the end portion on the proximal end side of the thirteenth small outer diameter region is located closer to the proximal end side than the eleventh position.

9. The extrusion molding method of unequal thickness tubes according to claim 8, characterized in that: At the 13th time point when the 13th step is finished, the end portion of the front end side of the basic outer diameter region is located closer to the front end side than the 11th position. The unequal thickness tube includes: the 11th large outer diameter region; the 11th outer diameter increase region; the 11th small outer diameter region; the 12th small outer diameter region formed at a position closer to the front end side than the 11th small outer diameter region; and the 11th inner diameter increase region, which is formed between the 12th small outer diameter region and the 11th small outer diameter region, and the inner diameter increases from the 18th inner diameter to the 12th inner diameter as it approaches from the 12th small outer diameter region to the 11th small outer diameter region, and the wall thickness decreases from the 14th wall thickness to the 12th wall thickness, and the outer diameter is constant at the 17th outer diameter equal to the 12th outer diameter.

10. The extrusion molding method of unequal thickness tubes according to claim 8, characterized in that: At the 13th time when the 13th step is finished, the end of the 13th small outer diameter region on the proximal side is located closer to the proximal side than the 11th position. The unequal thickness tube includes: the 12th small outer diameter region; the 11th large outer diameter region; the 12th large outer diameter region is formed between the 12th small outer diameter region and the 11th large outer diameter region, and has a 19th outer diameter equal to the 13th outer diameter, a 19th inner diameter equal to the 18th inner diameter, and a 15th wall thickness region with a prescribed wall thickness greater than the 13th wall thickness; the 13th outer diameter increasing region is formed between the 12th small outer diameter region and the 12th large outer diameter region, and as it approaches from the 12th small outer diameter region to the 12th large outer diameter region The outer diameter increases from the 16th outer diameter to the 19th outer diameter, the wall thickness increases from the 14th wall thickness to the 15th wall thickness, and the inner diameter is a region with a constant 20th inner diameter equal to the 18th inner diameter; and the 12th inner diameter increasing region is formed between the 12th largest outer diameter region and the 11th largest outer diameter region, and the inner diameter increases from the 19th inner diameter to the 13th inner diameter as it approaches from the 12th largest outer diameter region to the 11th largest outer diameter region, the wall thickness decreases from the 15th wall thickness to the 13th wall thickness, and the outer diameter is a region with a constant 20th outer diameter equal to the 13th outer diameter.

11. The extrusion molding method of unequal thickness tubes according to any one of claims 7 to 10, characterized in that: The 11th to 13th steps are performed using the pipe material further having an 11th thin-walled portion at the end portion on the base end side, wherein the 11th thin-walled portion is a portion having a 21st outer diameter having a prescribed outer diameter smaller than the 11th outer diameter, a 21st inner diameter having a prescribed inner diameter greater than the 11th inner diameter, and a 16th wall thickness having a prescribed wall thickness smaller than the 11th wall thickness, The sleeve includes a housing portion, which is a space opened at the end surface on the front end side and having a shape corresponding to the 11th thin-walled portion. By performing the twelfth step and the thirteenth step in a state where the eleventh thin-walled portion is accommodated in the accommodation portion, the eleventh thin-walled portion remains at the end portion on the front end side of the pipe material. The uneven thickness tube further includes the eleventh thin-walled portion at the end portion on the base end side.

12. The extrusion molding method of unequal thickness tubes according to any one of claims 1 to 3 or 7 to 11, characterized in that: The 11th to 13th steps are performed using the tube material further having a 12th thin-walled portion at the end portion on the front end side, wherein the 12th thin-walled portion is a portion having a 22nd outer diameter which is a prescribed outer diameter less than the outer diameter corresponding to the minimum inner diameter in the extrusion cylinder hole, a 22nd inner diameter which is a prescribed inner diameter greater than the 11th inner diameter, and a 17th wall thickness which is a prescribed wall thickness smaller than the 11th wall thickness, The unequal thickness tube further includes the 12th thin-walled portion at the end portion on the front end side.

13. An extrusion molding device for tubes of unequal thickness, comprising: a mandrel, which is a metal core having a prescribed shape; The sleeve is a cylindrical component coaxially arranged outside the mandrel; the extrusion cylinder is a die formed with a through hole of a predetermined shape, i.e., an extrusion cylinder hole; and a driving mechanism configured to at least press the sleeve into the extrusion cylinder hole, The structure is to press a tube having a prescribed shape into the hole of the extrusion cylinder through the sleeve, thereby forming a tube of unequal thickness having a prescribed shape. The extrusion forming device for unequal thickness tubes is characterized in that: The pipe is a cylindrical member having an 11th outer diameter of a specified outer diameter, an 11th inner diameter of a specified inner diameter, and an 11th wall thickness of a specified wall thickness, The unequal thickness tube includes: an 11th small outer diameter region, which is formed on the downstream side, i.e., the front end side, in the direction in which the tube is pressed into the extrusion cylinder hole, i.e., the extrusion direction, and has a 12th outer diameter with a specified outer diameter smaller than the 11th outer diameter, a 12th inner diameter with an inner diameter equal to the 11th inner diameter, and a 12th wall thickness region with a specified wall thickness smaller than the 11th wall thickness; an 11th large outer diameter region, which is formed on the upstream side, i.e., the base end side, in the extrusion direction, and has a 13th outer diameter with a specified outer diameter larger than the 11th outer diameter, a 13th inner diameter having an inner diameter equal to the 11th inner diameter, and a 13th wall thickness region having a prescribed wall thickness greater than the 11th wall thickness; and an 11th outer diameter increasing region, which is formed between the 11th small outer diameter region and the 11th large outer diameter region, and in which the outer diameter increases from the 12th outer diameter to the 13th outer diameter and the wall thickness increases from the 12th wall thickness to the 13th wall thickness as the area from the 11th small outer diameter region to the 11th large outer diameter region approaches, and the inner diameter is constant at a 14th inner diameter equal to the 11th inner diameter, The mandrel includes a basic outer diameter region, which is a cylindrical region formed on the front end side and has an outer diameter corresponding to the 11th inner diameter, that is, a 14th outer diameter. The sleeve includes an 11th extrusion area, which is a cylindrical area formed on the front end side and has a cylindrical internal space with a 15th outer diameter equal to the 13th outer diameter and a 15th inner diameter corresponding to the 14th outer diameter, The extrusion cylinder hole includes: an 11th large inner diameter region, which is a region of the 16th inner diameter formed on the base end side and having an inner diameter corresponding to the 13th outer diameter; an 11th small inner diameter region, which is a region of the 17th inner diameter formed on the front end side and having an inner diameter corresponding to the 12th outer diameter; and an 11th inner diameter reduction region, which is formed between the 11th large inner diameter region and the 11th small inner diameter region, and the inner diameter of which decreases from the 16th inner diameter to the 17th inner diameter as it approaches from the 11th large inner diameter region to the 11th small inner diameter region. The extrusion forming device of the unequal thickness tube is configured to form the unequal thickness tube by performing the following steps: The eleventh step is a step of placing the tube at a predetermined position inside the extrusion tube hole by bringing the end of the front end side of the tube into contact with the reduced inner diameter region of the extrusion tube hole; The twelfth step is a step of extruding the end of the base end of the tube by the sleeve while the mandrel is inserted into the tube, so that the material constituting the tube plastically flows and fills the space between the extrusion cylinder and the mandrel in the 11th large inner diameter region and the 11th inner diameter reduction region of the extrusion cylinder hole, thereby maintaining the inner diameter of the tube at the 11th inner diameter and expanding the outer diameter of the tube to the 13th outer diameter; and The 13th step is a step of reducing the diameter of the front end side of the tube by performing an extrusion process, in which, while the mandrel is inserted into the tube, the end of the base end side of the tube is further extruded by the sleeve, and the material constituting the tube is extruded toward the 11th small inner diameter region of the extrusion cylinder hole through a gap between the end of the base end side of the 11th small inner diameter region of the extrusion cylinder hole and the mandrel. At the moment when the 12th step starts, that is, the 11th moment, the end of the front end side of the mandrel reaches the same position as the position of the end of the base end side of the 11th small inner diameter area of ​​the extrusion cylinder hole in the extrusion direction, that is, the 11th position or a position closer to the front end side than the 11th position. At the moment when the 13th process starts, that is, the 12th moment, the end of the front end side of the core shaft reaches a position that is a specified distance from the front end side in the extrusion direction than the end of the base end side of the 11th smaller inner diameter region of the extrusion cylinder hole, that is, the 12th position or a position closer to the front end side than the 12th position.

14. The extrusion forming device for tubes of unequal thickness according to claim 13, characterized in that: A 12th small outer diameter region is formed at the end of the front end side of the unequal thickness tube, and the 12th small outer diameter region is a region having a 16th outer diameter equal to the 12th outer diameter, an 18th inner diameter having a predetermined inner diameter smaller than the 12th inner diameter, and a 14th wall thickness having a predetermined wall thickness greater than the 12th wall thickness, The spindle further includes: a 13th small outer diameter region, which is a cylindrical region of an 18th outer diameter formed at a position closer to the front end side than the basic outer diameter region and having an outer diameter corresponding to the 18th inner diameter; and a 12th outer diameter increase region, which is formed between the 13th small outer diameter region and the basic outer diameter region and has an outer diameter that increases from the 18th outer diameter to the 14th outer diameter as it approaches from the 13th small outer diameter region to the basic outer diameter region. At the twelfth time, the end portion on the proximal end side of the thirteenth small outer diameter region is located closer to the proximal end side than the eleventh position.

15. The extrusion forming device for tubes of unequal thickness according to claim 14, characterized in that: At the 13th time point when the 13th step is finished, the end portion of the front end side of the basic outer diameter region is located closer to the front end side than the 11th position. The unequal thickness tube includes: the 11th large outer diameter region; the 11th outer diameter increase region; the 11th small outer diameter region; the 12th small outer diameter region formed at a position closer to the front end side than the 11th small outer diameter region; and the 11th inner diameter increase region, which is formed between the 12th small outer diameter region and the 11th small outer diameter region, and the inner diameter increases from the 18th inner diameter to the 12th inner diameter as it approaches from the 12th small outer diameter region to the 11th small outer diameter region, and the wall thickness decreases from the 14th wall thickness to the 12th wall thickness, and the outer diameter is constant at the 17th outer diameter equal to the 12th outer diameter.

16. The extrusion forming device for tubes of unequal thickness according to claim 14, characterized in that: At the 13th time when the 13th step is finished, the end of the 13th small outer diameter region on the proximal side is located closer to the proximal side than the 11th position. The unequal thickness tube includes: the 12th small outer diameter region; the 11th large outer diameter region; the 12th large outer diameter region is formed between the 12th small outer diameter region and the 11th large outer diameter region, and has a 19th outer diameter equal to the 13th outer diameter, a 19th inner diameter equal to the 18th inner diameter, and a 15th wall thickness region with a prescribed wall thickness greater than the 13th wall thickness; the 13th outer diameter increasing region is formed between the 12th small outer diameter region and the 12th large outer diameter region, and as it approaches from the 12th small outer diameter region to the 12th large outer diameter region The outer diameter increases from the 16th outer diameter to the 19th outer diameter, the wall thickness increases from the 14th wall thickness to the 15th wall thickness, and the inner diameter is a region with a constant 20th inner diameter equal to the 18th inner diameter; and the 12th inner diameter increasing region is formed between the 12th largest outer diameter region and the 11th largest outer diameter region, and the inner diameter increases from the 19th inner diameter to the 13th inner diameter as it approaches from the 12th largest outer diameter region to the 11th largest outer diameter region, the wall thickness decreases from the 15th wall thickness to the 13th wall thickness, and the outer diameter is a region with a constant 20th outer diameter equal to the 13th outer diameter.

17. The extrusion molding device for tubes of unequal thickness according to any one of claims 13 to 16, characterized in that: The 11th step to the 13th step are performed using the tube material further having an 11th thin-walled portion at the end portion on the base end side, wherein the 11th thin-walled portion is a portion having a 21st outer diameter having a prescribed outer diameter smaller than the 11th outer diameter, a 21st inner diameter having a prescribed inner diameter greater than the 11th inner diameter, and a 16th wall thickness having a prescribed wall thickness smaller than the 11th wall thickness, The sleeve includes a housing portion, which is a space opened at the end surface on the front end side and having a shape corresponding to the 11th thin-walled portion. By performing the twelfth step and the thirteenth step in a state where the eleventh thin-walled portion is accommodated in the accommodation portion, the eleventh thin-walled portion remains at the end portion on the front end side of the pipe material. The uneven thickness tube further includes the eleventh thin-walled portion at the end portion on the base end side.

18. The extrusion molding device for unequal thickness tubes according to any one of claims 4 to 6 or 13 to 17, characterized in that: The 11th to 13th steps are performed using the tube material further having a 12th thin-walled portion at the end portion on the front end side, wherein the 12th thin-walled portion is a portion having a 22nd outer diameter which is a prescribed outer diameter less than the outer diameter corresponding to the minimum inner diameter in the extrusion cylinder hole, a 22nd inner diameter which is a prescribed inner diameter greater than the 11th inner diameter, and a 17th wall thickness which is a prescribed wall thickness smaller than the 11th wall thickness, The unequal thickness tube further includes the 12th thin-walled portion at the end portion on the front end side.

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