JP7627451B2 - Manufacturing apparatus and manufacturing method - Google Patents

Description

The present invention relates to a socket, a manufacturing device for manufacturing the socket, and a manufacturing method.

The following Patent Document 1 discloses a hose coupling in which a hose is inserted between a nipple and a sleeve formed on the outside of the nipple, and the sleeve is tightened from the outside in the radial direction to fix the hose between the nipple and the socket.

Japanese Utility Model Application Publication No. 4-132289

In the hose coupling described in Patent Document 1, multiple ring-shaped grooves are formed at intervals in the axial direction on the inner peripheral surface of the sleeve (see Figure 2). However, there is no description of a method for forming multiple ring-shaped grooves on the inner peripheral surface of the sleeve. For example, a method of forming multiple ring-shaped grooves by cutting the inner peripheral surface of the sleeve is conceivable. However, this method requires cutting multiple grooves at intervals on the inner peripheral surface of the sleeve using a cutting tool or the like, which makes the work complicated and wastes the cut material.

In consideration of the above, the present invention aims to provide a socket that can efficiently form a spiral groove on the inner surface of the cylindrical portion without wasting material, as well as a manufacturing device and method for manufacturing the socket.

The manufacturing device described in the first aspect is a manufacturing device that manufactures sockets using a cylindrical workpiece, and has a cylindrical workpiece mounting part onto which the inside of the workpiece is extrapolated, a spiral uneven part formed on the outer peripheral surface of the workpiece mounting part, and a plurality of cylindrical dies that are arranged around the workpiece mounting part so as to be able to approach and move away from the workpiece mounting part, come into contact with the outer peripheral surface of the workpiece mounted on the workpiece mounting part to press the inner peripheral surface of the workpiece against the uneven part, and rotate around an axis.

According to the manufacturing device of the first aspect, the inside of the workpiece is fitted onto the cylindrical workpiece mounting part. A spiral concave-convex portion is formed on the outer peripheral surface of the workpiece mounting part. A plurality of cylindrical dies are provided around the workpiece mounting part so that they can approach and move away from the workpiece mounting part. The plurality of dies contact the outer peripheral surface of the workpiece mounted on the workpiece mounting part, press the inner peripheral surface of the workpiece against the concave-convex portion, and rotate around the axis. As a result, the inner peripheral surface of the workpiece is pressed against the spiral concave-convex portion of the workpiece mounting part while rotating, so that the workpiece advances in the axial direction from the tip of the workpiece mounting part, and a spiral groove is formed on the inner peripheral surface of the workpiece by forging at the concave-convex portion. Therefore, compared to forming a groove on the inner peripheral surface of the workpiece by cutting, it is possible to efficiently form a spiral groove on the inner peripheral surface of the cylindrical workpiece without wasting material.

The manufacturing device described in the second aspect is the manufacturing device described in the first aspect, in which three dies are provided around the work mounting section and rotate around an axis in the same direction.

According to the manufacturing device described in the second aspect, three dies are provided around the work mounting portion and rotate in the same direction around the axis. Therefore, by pressing the inner peripheral surface of the work against the spiral concave-convex portion of the work mounting portion while the three dies rotate in the same direction around the axis, a spiral groove can be efficiently formed on the inner peripheral surface of the work by pressing at the concave-convex portion.

The manufacturing method described in the third aspect is a method for manufacturing a socket using the manufacturing device described in the first or second aspect, and includes a setting process for inserting the inside of the workpiece onto the workpiece mounting portion, and a forging process for pressing the inner peripheral surface of the workpiece against the uneven portion by bringing the multiple dies into contact with the outer peripheral surface of the workpiece and rotating the dies around an axis to form a spiral groove on the inner peripheral surface of the workpiece by forging.

According to the manufacturing method described in the third aspect, in the setting step, the inside of the workpiece is extrapolated to the workpiece mounting portion. Furthermore, in the forging step, multiple dies are brought into contact with the outer peripheral surface of the workpiece to press the inner peripheral surface of the workpiece against the spiral uneven portion, while the dies are rotated around the axis. As a result, the workpiece is advanced along the axial direction of the workpiece mounting portion, and a spiral groove portion is formed on the inner peripheral surface of the workpiece by forging at the spiral uneven portion. Therefore, compared to forming a groove portion on the inner peripheral surface of the workpiece by cutting, a spiral groove portion can be efficiently formed on the inner peripheral surface of a cylindrical workpiece without wasting material.

The socket described in the fourth aspect has a through hole that penetrates in the axial direction, a cylindrical portion provided at one end in the axial direction, and a spiral groove portion formed on the inner surface of the cylindrical portion.

The socket described in the fourth aspect has a through hole penetrating in the axial direction, a cylindrical portion provided at one end in the axial direction, and a spiral groove portion formed on the inner peripheral surface of the cylindrical portion. Therefore, compared to forming a groove portion on the inner peripheral surface of the cylindrical portion by cutting, the manufacturing device or method described above can efficiently form a spiral groove portion on the inner peripheral surface of the cylindrical portion of the socket without wasting material. In addition, when the hose is inserted into the inner peripheral side of the socket and the socket is crimped to fix the hose, the spiral groove portion formed on the inner peripheral surface of the socket can maintain adhesion between the socket and the hose.

The socket, manufacturing device, and manufacturing method for the socket disclosed herein can efficiently form a spiral groove on the inner surface of the cylindrical portion without wasting material.

FIG. 1 is a schematic perspective view showing a manufacturing apparatus according to a first embodiment. 1A is a front view showing the workpiece, and FIG. 1B is a cross-sectional view showing the workpiece in half. 1A is a front view showing a work mounting section used in the manufacturing apparatus according to the first embodiment, and FIG. 1B is a side view showing the work mounting section. 5A to 5C are cross-sectional views showing a process of forming a spiral groove on the inner peripheral surface of a cylindrical portion of a workpiece using the manufacturing apparatus according to the first embodiment. 1A is a front view showing a socket manufactured by the manufacturing apparatus, and FIG. 1B is a side view showing the socket manufactured by the manufacturing apparatus. FIG. 4 is a cross-sectional view showing a state in which a hose is fixed to a joint having a socket.

The following describes the socket according to the first embodiment of the present invention, as well as the manufacturing apparatus and method for manufacturing this socket, using Figures 1 to 6.

Figure 1 shows a perspective view of a manufacturing apparatus 10 according to the first embodiment. As shown in Figure 1, the manufacturing apparatus 10 is an apparatus that supplies a cylindrical workpiece 100 and processes the workpiece 100 to manufacture a socket 120. The workpiece 100 having a cylindrical portion 102 is an example of a cylindrical workpiece.

In this embodiment, we will first explain the workpiece 100.

2(A) and (B) show a front view and a half-cut cross-sectional view of the workpiece 100. As shown in FIG. 2(A) and (B), the workpiece 100 has a cylindrical portion 102 formed on one end side in the axial direction, a cylindrical intermediate portion 104 formed continuous with the cylindrical portion 102, and a cylindrical small diameter portion 106 provided continuous with the intermediate portion 104 and formed on the other end side in the axial direction. The workpiece 100 is formed of, for example, a metal.

The cylindrical portion 102 has a circular through hole 108 that penetrates in the axial direction, and the through hole 108 forms an inner peripheral surface 110 on the inside of the cylindrical portion 102. The inner diameter of the inner peripheral surface 110 is almost constant in the axial direction, and the inner peripheral surface 110 has a smooth shape. The through hole 108 is formed on the side of the tip portion 102A in the axial direction of the cylindrical portion 102 (the side opposite the small diameter portion 106). In addition, the outer diameter of the outer peripheral surface 112 of the cylindrical portion 102 is almost constant in the axial direction, and the outer peripheral surface 112 has a smooth shape.

The outer diameter of the intermediate portion 104 is smaller than the outer diameter of the cylindrical portion 102. The axial length of the intermediate portion 104 is shorter than the axial length of the cylindrical portion 102. The intermediate portion 104 has a circular through hole 114 that penetrates in the axial direction. The through hole 114 is formed across the intermediate portion 104 and a part of the cylindrical portion 102, and the through hole 114 is connected to the through hole 108. The inner diameter of the through hole 114 is smaller than the inner diameter of the through hole 108.

The small diameter portion 106 has an outer diameter smaller than the outer diameter of the intermediate portion 104. The axial length of the small diameter portion 106 is greater than the axial length of the intermediate portion 104. The small diameter portion 106 has a circular through hole 116 that penetrates in the axial direction. The through hole 116 is connected to the through hole 114. The inner diameter of the through hole 116 is slightly smaller than the inner diameter of the through hole 114.

Next, we will explain the manufacturing device 10.

As shown in FIG. 1, the manufacturing device 10 includes a cylindrical workpiece mounting section 14 onto which the inside of the cylindrical section 102 of the workpiece 100 is extrapolated, and a plurality of cylindrical dies 12 arranged around the workpiece mounting section 14 so that they can move toward and away from the workpiece mounting section 14. In the manufacturing device 10, the workpiece 100 is supplied in the direction of the workpiece mounting section 14 as indicated by arrow B, and the inside of the cylindrical section 102 of the workpiece 100 is extrapolated onto the workpiece mounting section 14. In FIG. 1, the workpiece 100 and the socket 120 are shown diagrammatically, and the shapes of the workpiece 100 and the socket 120 differ from the actual shapes.

Three dies 12 are provided around the work mounting section 14. The three dies 12 have the same configuration. The die 12 includes a shaft portion 12A, a tubular portion 12B formed around the shaft portion 12A, and an outer tubular portion 12C formed around the tubular portion 12B. The outer tubular portion 12C of the die 12 is circular and contacts the outer circumferential surface 112 of the cylindrical portion 102 of the work 100.

The shaft portion 12A is connected to a motor (not shown), which allows the dies 12 to rotate. The three dies 12 rotate around the shaft when the workpiece 100 is supplied. In this embodiment, the three dies 12 rotate in the same predetermined direction (the direction of arrow A) when the workpiece 100 is supplied. More specifically, the three dies 12 rotate in the same direction at a position facing the workpiece mounting portion 14. That is, when the workpiece 100 is supplied in the direction of arrow B, the three dies 12 rotate in the same direction at the contact portion with the outer circumferential surface 112 of the cylindrical portion 102 of the workpiece 100.

The three dies 12 are supported by an actuator (not shown) so that they can move toward and away from the work mounting portion 14, for example. That is, when the work 100 is supplied in the direction of arrow B, the three dies 12 advance and retreat in the radial direction of the cylindrical portion 102 of the work 100. As a result, the three dies 12 come into contact with the outer peripheral surface 112 of the cylindrical portion 102 of the work 100 mounted on the work mounting portion 14, causing the work mounting portion 14 to press the inner peripheral surface 110 of the work 100, and rotate around the axis. The dies 12 are formed, for example, from a metal. The shaft portion 12A, the cylindrical portion 12B, and the outer cylindrical portion 12C may be formed from the same material, or may be formed from different materials.

3(A) and (B) show a front view and a side view of the work mounting part 14. As shown in FIG. 3(A) and (B), the work mounting part 14 has a cylindrical core part 20 and a cylindrical tube part 22 provided around the core part 20. The axial length of the tube part 22 is shorter than the axial length of the core part 20. The tube part 22 is provided on the tip part 20A side of the core part 20 in the axial direction, but the tube part 22 is not provided at the terminal part of the tip part 20A of the core part 20. A spiral uneven part 24 is formed on the outer peripheral surface of the tube part 22 along the axial direction. The uneven part 24 is configured such that the convex part 24A and the concave part 24B are arranged in a spiral shape. That is, when viewed from a direction perpendicular to the axial direction of the work mounting part 14, the convex part 24A and the concave part 24B are arranged alternately.

In this embodiment, a single continuous spiral convex portion 24A is provided on the outer peripheral surface of the tubular portion 22. When viewed from a direction perpendicular to the axial direction of the tubular portion 22, the convex portion 24A is a peak portion protruding in a substantially triangular shape, and the concave portion 24B is a valley portion recessed in a substantially triangular shape between adjacent convex portions 24A. As shown in FIG. 3(B), when viewed from a direction perpendicular to the axial direction of the work mounting portion 14, the tubular portion 22 has multiple peak portions formed by the convex portion 24A and multiple valley portions formed by the concave portion 24B alternately arranged in parallel in a diagonal direction relative to the axial direction. As an example, the concave-convex portion 24 is formed in a male screw shape.

At the end of the core 20 opposite the axial tip 20A, an attachment portion 26 is provided for fixing the core 20 to the manufacturing device 10. The attachment portion 26 is formed in a rectangular shape when viewed from the axial direction of the core 20 by cutting the outer peripheral surface of the core 20 into four parts. The work mounting portion 14 is configured not to rotate by fixing the attachment portion 26 of the core 20 to the manufacturing device 10. The work mounting portion 14 is formed, for example, from a metal. It is preferable that the work mounting portion 14 is formed from a metal harder than the metal constituting the work 100.

The manufacturing device 10 is provided with a push-out section (not shown) that supplies the work 100 to a position where the inside of the cylindrical section 102 of the work 100 is extrapolated onto the tip section 20A of the core section 20 of the work mounting section 14. The push-out section can advance and retreat toward the work mounting section 14 by an actuator. The push-out section supplies the work 100 to the tip section 20A of the work mounting section 14, so that the inside of the end of the cylindrical section 102 of the work 100 is extrapolated onto the tip section 20A of the core section 20 of the work mounting section 14.

In the manufacturing device 10, as shown in FIG. 4, the three dies 12 (see FIG. 1) are rotated in the direction of the arrow A while pressing the outer peripheral surface 112 of the cylindrical portion 102 of the workpiece 100 in the radially inward direction (the direction of the arrow F). Then, the three dies 12 press the inner peripheral surface 110 of the cylindrical portion 102 against the spiral uneven portion 24 of the workpiece mounting portion 14. At this time, the workpiece 100 may be supported by a pushing portion (not shown). As a result, the cylindrical portion 102 of the workpiece 100 is advanced in the axial direction from the tip portion 20A of the workpiece mounting portion 14, and a spiral groove portion 126 (see FIG. 4) is formed on the inner peripheral surface 110 of the cylindrical portion 102 of the workpiece 100 by pressing (in this embodiment, rolling) at the spiral uneven portion 24. Here, pressing refers to a metal processing method in which a strong force is applied to a material to form it (i.e., plastic processing).

In the manufacturing device 10, the workpiece 100 is machined to produce the socket 120. For example, the socket 120 may be rotated in a direction opposite to the direction of arrow A to rotate the spiral groove portion 126 of the socket 120 in a direction to remove it from the uneven portion 24, thereby ejecting the socket 120 from the workpiece mounting portion 14.

Figures 5(A) and (B) show a front view and a half-cut cross-sectional view of a socket 120 manufactured by the manufacturing apparatus 10 (see Figure 1). As shown in Figures 5(A) and (B), the socket 120 has a cylindrical portion 122 formed on one end side in the axial direction, an intermediate portion 104 formed continuous with the cylindrical portion 122, and a small diameter portion 106 formed continuous with the intermediate portion 104. A spiral groove portion 126 is formed on the inner peripheral surface 110 of the cylindrical portion 122.

In this embodiment, the inner surface 110 of the cylindrical portion 102 of the workpiece 100 is pressed against the helical uneven portion 24 of the workpiece mounting portion 14 while rotating the three dies 12 (see FIG. 1). As a result, a helical groove portion 126 is formed on the inner surface 110 of the cylindrical portion 102 by pressing at the helical uneven portion 24 (see FIG. 4). Therefore, in the socket 120, the outer diameter of the cylindrical portion 102 of the workpiece 100 is reduced by the three dies 12, forming a cylindrical portion 122 with an outer diameter smaller than the outer diameter of the cylindrical portion 102, and forming a helical groove portion 126 on the inner surface 110 of the cylindrical portion 122.

Figure 6 shows a joint 170 using the socket 120 (see Figure 5) of this embodiment. The joint 170 is composed of a connection member 172 and a socket 120. The connection member 172 has a cylindrical axial core portion 174 through which a through hole 176 is formed. The through hole 176 is provided in a direction intersecting the axial direction of the socket 120 (in this embodiment, a direction perpendicular to the axial direction). The inner peripheral surface of the through hole 176 is formed with an annular groove 178 that expands the diameter of the through hole 176. The groove 178 is connected to a mounting hole 180 drilled from the outer peripheral surface of the connection member 172. The cylindrical small diameter portion 106, which is one end side of the socket 120, is inserted into the mounting hole 180, and the small diameter portion 106 and the wall portion of the mounting hole 180 are joined by copper brazing.

A through hole 116 is formed in the small diameter portion 106 of the socket 120, and a through hole 114 with a larger diameter than the through hole 116 is formed in the middle portion 104 of the socket 120. The tip of the nipple 160 is inserted into the through hole 114 from the opening 122B side of the cylindrical portion 122 of the socket 120, and the tip of the nipple 160 and the wall surface of the through hole 114 are joined by copper brazing.

In addition, a hose (flexible hose) 188 is inserted between the socket 120 and the nipple 160 from the opening 122B side of the cylindrical portion 122 of the socket 120, and then the socket 120 is tightened from the outside to connect the hose 188 to the fitting 170. The nipple 160 is inserted into the hose 188, and a plurality of annular grooves 162 are formed on the outer circumferential surface of the nipple 160 at intervals in the axial direction, thereby preventing the hose 188 from slipping out of the nipple 160 when internal pressure acts on the fitting 170.

In addition, a spiral groove 126 is formed on the inner circumferential surface of the cylindrical portion 122 of the socket 120, which maintains the close contact between the socket 120 and the hose 188 and prevents the hose 188 from slipping out of the socket 120.

Such a coupling 170 is, for example, a coupling for a hydraulic hose, and is used in the brake system of an automobile. The other end of the hose 188 is connected to a master cylinder (not shown). Furthermore, the connection member 172 is fixed to the cylinder block of a brake caliper (not shown) by a mounting fixture.

This allows the brake oil delivered by the hose 188 to be sent to the cylinder section via the through hole 116 of the socket 120, the groove 178, and a communication passage formed in the cylinder block (not shown).

Next, the operation and effects of this embodiment will be explained.

In the manufacturing device 10 of this embodiment, the workpiece 100 is supplied to the workpiece mounting section 14, and the inside of the cylindrical section 102 of the workpiece 100 is extrapolated onto the workpiece mounting section 14. A spiral uneven section 24 is formed on the outer peripheral surface of the workpiece mounting section 14. A plurality of cylindrical dies 12 (three in this embodiment) are arranged around the workpiece mounting section 14, and the dies 12 contact the outer peripheral surface 112 of the cylindrical section 102 of the workpiece 100 to press the uneven section 24 against the inner peripheral surface 110 of the workpiece 100, while the dies 12 rotate in the same direction (arrow A direction). That is, the three dies 12 rotate in the same direction at the contact portion with the outer peripheral surface 112 of the workpiece 100.

In the manufacturing device 10, the inner surface 110 of the cylindrical portion 102 of the workpiece 100 is pressed against the spiral concave-convex portion 24 of the workpiece mounting portion 14 while rotating the multiple dies 12. As a result, as shown in FIG. 4, the workpiece 100 advances in the axial direction from the tip portion 20A side of the workpiece mounting portion 14, and a spiral groove portion 126 is formed on the inner surface 110 of the cylindrical portion 102 of the workpiece 100 by pressing at the concave-convex portion 24. By processing the workpiece 100 with such a manufacturing device 10, a cylindrical portion 122 having an outer diameter smaller than the outer diameter of the cylindrical portion 102 is obtained, and a socket 120 having a spiral groove portion 126 on the inner surface 110 of the cylindrical portion 122 is manufactured. Therefore, in the manufacturing device 10, the spiral groove portion 126 can be efficiently formed on the inner surface 110 of the cylindrical portion 102 of the workpiece 100 without wasting material, compared to the case where a groove portion is formed on the inner surface of the workpiece by cutting.

In addition, in the manufacturing device 10, three dies 12 are provided around the work mounting portion 14 and rotate in the same direction (arrow A direction) around the axis. Therefore, while the three dies 12 rotate, the inner surface 110 of the cylindrical portion 102 of the work 100 is pressed against the spiral uneven portion 24 of the work mounting portion 14, and a spiral groove portion 126 can be efficiently formed on the inner surface 110 of the cylindrical portion 102 of the work 100 by pressing at the uneven portion 24. In addition, in this embodiment, the work mounting portion 14 is provided with one continuous spiral convex portion 24A that constitutes the uneven portion 24, so that one spiral groove portion 126 can be efficiently formed on the inner surface 110 of the cylindrical portion 102 of the work 100 by pressing.

In addition, in the manufacturing method for manufacturing the socket 120 using the manufacturing device 10, in the setting process, the inside of the cylindrical portion 102 of the work 100 is extrapolated to the tip portion 102A of the work mounting portion 14. Furthermore, in the pressing process, a plurality of dies 12 are brought into contact with the outer peripheral surface 112 of the cylindrical portion 102 of the work 100 to press the inner peripheral surface 110 of the cylindrical portion 102 of the work 100 against the spiral uneven portion 24, and the die 12 is rotated around the axis. As a result, as shown in FIG. 4, the work 100 is advanced along the axial direction of the work mounting portion 14, and a spiral groove portion 126 is formed on the inner peripheral surface 110 of the cylindrical portion 102 of the work 100 by pressing with the spiral uneven portion 24. By processing the work 100 through such a process, a socket 120 having a spiral groove portion 126 on the inner peripheral surface 110 of the cylindrical portion 122, which has a reduced outer diameter than the cylindrical portion 102, is manufactured. Therefore, in the above manufacturing method, the spiral groove 126 can be efficiently formed on the inner surface 110 of the cylindrical portion 102 of the workpiece 100 without wasting material, compared to forming the groove on the inner surface of the workpiece by cutting.

The socket 120 of this embodiment has a through hole 108 penetrating in the axial direction, a cylindrical portion 122 provided at one end side in the axial direction, and a spiral groove portion 126 formed on the inner peripheral surface 110 of the cylindrical portion 122. Therefore, compared to forming a groove portion on the inner peripheral surface of the cylindrical portion by cutting, the above manufacturing device or manufacturing method can efficiently form the spiral groove portion 126 on the inner peripheral surface 110 of the cylindrical portion 122 of the socket 120 without wasting material. In addition, in the joint 170 equipped with the socket 120, the cylindrical portion 122 of the socket 120 is crimped with the hose 188 inserted into the inner peripheral side of the cylindrical portion 122 of the socket 120 to fix the hose 188 to the joint 170. At this time, the spiral groove portion 126 formed on the inner peripheral surface 110 of the cylindrical portion 122 of the socket 120 can maintain the close contact between the socket 120 and the hose 188.

In the manufacturing device 10 of this embodiment, three dies 12 are provided, but any number of dies may be used, and the number of dies can be changed.

In addition, in the manufacturing device 10 of this embodiment, the shape of the work mounting portion 14 can be changed. In this embodiment, the uneven portion 24 has one continuous spiral convex portion 24A on the work mounting portion 14, but the spiral convex portion 24A may be provided in multiple portions or may be provided in separate portions.

In addition, the overall shape of the workpiece 100 of this embodiment can be changed as long as it has a cylindrical portion. The diameter and length of the cylindrical portion of the workpiece can also be changed.

Furthermore, although the present invention has been described in detail with respect to a specific embodiment, the present invention is not limited to such an embodiment, and it will be apparent to those skilled in the art that various other embodiments are possible within the scope of the present invention.

10 Manufacturing device 12 Die 14 Workpiece mounting portion 24 Concave and recessed portion 100 Workpiece 102 Cylindrical portion 102A Tip portion 108 Through hole 110 Inner peripheral surface 112 Outer peripheral surface 120 Socket 122 Cylindrical portion 122A Tip portion 126 Groove portion

Claims (4)

A manufacturing apparatus for machining a cylindrical workpiece, comprising:
A work mounting portion ;
A spiral uneven portion is formed on the outer peripheral surface of the work mounting portion , and the inner peripheral surface of the work is inserted as the work moves in the axial direction ;
A plurality of cylindrical dies are arranged around the work mounting portion so as to be able to approach and move away from the work mounting portion, contact the outer peripheral surface of the work inserted onto the work mounting portion to press the inner peripheral surface of the work against the concave and convex portions, and rotate around an axis;
A manufacturing apparatus having the above structure. 2. The manufacturing apparatus according to claim 1, wherein the plurality of dies are configured to simultaneously advance in a radially inward direction of the workpiece, contact an outer peripheral surface of the workpiece, and rotate about an axis . 3. The manufacturing apparatus according to claim 1 , wherein three of the dies are provided around the work mounting portion and rotate in the same direction around an axis. A manufacturing method for manufacturing a socket by machining a workpiece using the manufacturing apparatus according to any one of claims 1 to 3, comprising the steps of :
A supply step of supplying the workpiece to a workpiece mounting portion ;
a workpiece moving step in which the workpiece moves in an axial direction so that an inner peripheral surface of the workpiece is extrapolated onto the spiral concave-convex portion formed on the outer peripheral surface of the workpiece mounting portion;
a forging process in which a plurality of the dies are brought into contact with an outer peripheral surface of the workpiece that is extrapolated onto the workpiece mounting portion to press an inner peripheral surface of the workpiece against the concave-convex portion, and the dies are rotated around an axis to form a spiral groove portion on the inner peripheral surface of the workpiece by forging;
The manufacturing method comprising the steps of: