Shaft manufacturing method

Abstract

To provide a shaft enabling the omission of post-processing to a coupling portion that is a production object of a knurling, and a method of manufacturing the shaft.SOLUTION: In a coupling portion 32 of an output shaft 23 that is a production object of a knurling, a recessed portion 33 is provided between a large-diameter part 32b of the coupling portion 32 and a body portion 23a of the output shaft 23. An inclined aspect of an outer peripheral surface 32c of the coupling portion 32 toward an outer peripheral surface 23b of the body portion 23a of the output shaft 23 is formed in a shape in the process of inclining in the setting of the recessed portion 33, the large-diameter part 32b of the coupling portion 32 is located on the inner side from the outer peripheral surface 23b of the body portion 23a of the output shaft 23.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention is a tapered flat knurled Rusi This relates to a method for manufacturing a shaft. [Background technology]

[0002] Shafts used in wiper devices include the output shaft of a wiper motor connected to a crank constituting a wiper link mechanism, a pivot shaft connected to a wiper arm, etc. The output shaft, pivot shaft, etc. are subjected to, for example, a tapered flat knurling process on their axial ends in order to connect them to the mounting members such as the crank and wiper arm so as not to rotate relative to each other.

[0003] An example of a shaft having a connecting portion formed of a tapered flat knurl at an axial end is disclosed in, for example, Patent Document 1. In Patent Document 1, the pivot shaft and the knurl are described as the drive shaft and the serration, respectively. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 2614394 Summary of the Invention [Problem to be solved by the invention]

[0005] To create a tapered flat knurled joint at the axial end of a shaft, for example, a rolling die is placed at an angle against the intended site at the axial end of the shaft. The unevenness of the die bites into the intended site of the joint, causing plastic deformation, and creating the unevenness of the knurl.

[0006] At this time, the material of the concave portion of the knurling moves to create a convex portion, so that at the boundary with the shaft body, a part of the convex portion may protrude further outward from the outer circumferential surface of the shaft body. In the subsequent shaft assembly process, when the shaft is inserted into a cylindrical bearing from the end side having the connecting portion, the part protruding from the outer circumferential surface of the shaft body may hit the bearing, which may lead to damage to the bearing or the inability to insert the bearing. Therefore, post-processing such as removing unnecessary parts protruding from the outer circumferential surface of the shaft body that may occur when the knurling is made is required, which makes the manufacture of the shaft complicated.

[0007] The present invention has been made to solve the above problems. That is, an object of the present invention is to omit post-processing of a connecting portion to be formed with a knurl. Rusi The object of the present invention is to provide a method for manufacturing a shaft. [Means for solving the problem]

[0008] The shaft that solves the above problem is a shaft (23, 14, 15) for a wiper device having a connecting portion (32) with a tapered flat knurling on its outer peripheral surface (32c) for attaching a workpiece (27, 18, 19) so that the workpiece cannot rotate relative to the connecting portion, and a recess (33) is provided between the large diameter portion of the connecting portion and the main body of the shaft so that the inclination of the outer peripheral surface of the connecting portion toward the outer peripheral surface (23b, 14b, 15b) of the main body of the shaft is a mid-inclination shape and the large diameter portion (32b) of the connecting portion is positioned inward from the outer peripheral surface of the main body of the shaft.

[0009] According to the above configuration, a recess is provided between the large diameter portion of the connecting portion and the main body of the shaft at the connecting portion of the shaft on which the knurling is to be made. The inclination of the outer circumferential surface of the connecting portion toward the outer circumferential surface of the main body of the shaft is set to a shape that is midway inclined by setting the recess, so that the large diameter portion of the connecting portion is located inside the outer circumferential surface of the main body of the shaft. In other words, no unnecessary portion that protrudes from the outer circumferential surface of the main body of the shaft is generated at the connecting portion, and post-processing such as cutting off the unnecessary portion can be omitted. In addition, since the recess can be made at the same time as the planned production site of the connecting portion where the knurling is to be made is produced in advance in the shaft material, the feared increase in the number of new processes for producing the recess can be suppressed.

[0010] A method for manufacturing a shaft that solves the above problem is a shaft (23, 14, 15) for a wiper device that has a connecting portion (32) having an outer circumferential surface (32c) with a tapered flat knurling for mounting a mounted member (27, 18, 19) such that the mounted member cannot rotate relative to the shaft, and a method for manufacturing a shaft (23, 14, 15) for a wiper device that has a large diameter portion (32b) of the connecting portion formed on an outer circumferential surface (32c) of the shaft body (23a, 14a, 15a) of the shaft, the large diameter portion (32b) of the connecting portion being inclined toward the outer circumferential surface (23b, 14b, 15b) of the shaft body (23a, 14a, 15a ... The method for manufacturing a shaft further comprises a recess (33) formed by recessing radially inward between the large diameter portion of the connecting portion and the main body of the shaft so as to be positioned inward from the outer circumferential surface of the main body of the shaft, the method comprising: a first step of producing both a portion (32α) where the connecting portion is to be made and the recess in a shaft material (36) for making the shaft; and a second step of performing tapered flat knurling on the portion where the connecting portion is to be made.

[0011] According to the above-mentioned configuration, a recess is provided between the large diameter part of the connecting part and the main body part of the shaft so that an unnecessary part that protrudes from the outer circumferential surface of the main body part of the shaft is not generated in the connecting part where the knurl is to be made. In this case, the recess is made at the same time as the planned production site of the connecting part where the knurl is to be made is produced in advance in the shaft material, so that the feared increase in the number of new processes for producing the recess is suppressed. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating an overall configuration of a wiper device according to an embodiment; [Diagram 2] FIG. 4 is a diagram showing an assembled state of the shaft in the embodiment. [Diagram 3] FIG. 4 is an exploded view showing a state before the shaft is assembled in the embodiment. [Figure 4] 11A to 11C are explanatory diagrams for explaining a manufacturing process of the shaft in the same embodiment. [Diagram 5] 11A to 11C are explanatory diagrams for explaining a manufacturing process of the shaft in the same embodiment. [Figure 6] FIG. 11 is a configuration diagram showing an assembled state of a shaft in a comparative example. [Figure 7] FIG. 11 is an exploded view showing a state before assembly of a shaft in a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of a shaft and a method for manufacturing the shaft will now be described. [Overall structure of wiper system] A wiper device 10 of this embodiment shown in FIG. 1 is intended to wipe a windshield (not shown) of an automobile, and is installed on a mounting portion (not shown) on the vehicle body side below the windshield.

[0014] The wiper device 10 includes a pair of pivot holders 11 and 12. The pivot holders 11 and 12 are integrally formed by being connected to each other via a connecting frame 13. The pivot holders 11 and 12 each have a mounting portion 11a and 12a. The pivot holders 11 and 12 are attached to a vehicle body side mounting portion at the mounting portion 11a and 12a.

[0015] Each pivot holder 11, 12 rotatably supports a pivot shaft 14, 15 in a manner that the pivot shaft 14, 15 is inserted therethrough. A first end of a pivot lever 16, 17 is fixed to a base end of each pivot shaft 14, 15. Each pivot shaft 14, 15 rotates back and forth based on the swinging of each pivot lever 16, 17 within a predetermined angle range. A base end of a wiper arm 18, 19 is attached to a tip end of each pivot shaft 14, 15. Each wiper arm 18, 19 swings back and forth based on the swinging of each pivot shaft 14, 15, and a reciprocating wiper action of the windshield is performed by a wiper blade (not shown) connected to the tip end of each wiper arm 18, 19.

[0016] A wiper motor 20, which is a drive source of the wiper device 10, is attached to the connecting frame 13. The wiper motor 20 is formed by integrally assembling a motor section 21 and a speed reducer section 22. The wiper motor 20 reduces the rotational drive of the motor section 21 in the speed reducer section 22 and outputs the rotational drive from an output shaft 23 provided in the speed reducer section 22. The wiper motor 20 is configured such that an axis L2 of the output shaft 23 of the speed reducer section 22 is perpendicular to an axis L1 of the motor section 21 in a side view. The wiper motor 20 is disposed such that an axis L1 of the motor section 21 is aligned along the longitudinal direction of the connecting frame 13 and an axis L2 of the output shaft 23 is oriented in substantially the same direction as the pivot shafts 14, 15. A housing 24 of the speed reducer section 22 is fixed to the connecting frame 13 by using a fastening member 25 and a mounting plate 26. Further, the housing 24 of the speed reducer portion 22 is provided with, in addition to the mounting portions 11a, 12a of the pivot holders 11, 12, a mounting portion 20a for mounting the wiper motor 20 to a mounting portion on the vehicle body side.

[0017] A first end of a crank 27 is attached to the tip of the output shaft 23. A first end of a drive rod 28 is connected to a second end of the crank 27. A second end of the drive rod 28 is connected to a second end of the pivot lever 16. The second ends of the pivot levers 16, 17 are connected to each other by a link rod 29.

[0018] When the crank 27 rotates in one direction by the drive of the output shaft 23 of the wiper motor 20, the pivot lever 16 swings via the drive rod 28. When the pivot lever 16 swings, the pivot lever 17 also swings via the link rod 29. The pivot shafts 14, 15 rotate together based on the synchronized swinging of the pivot levers 16, 17, and the wiper arms 18, 19 swing together to perform a wiping operation of the wiper.

[0019] [Output shaft detailed configuration] As shown in Figures 2 and 3, the tip portion of the output shaft 23 in this embodiment is provided with a threaded portion 31, a connecting portion 32, and a recessed portion 33 in this order from the tip side, and the recessed portion 33 is adjacent to the main body portion 23a of the output shaft 23.

[0020] The threaded portion 31 is configured as a male screw having a thread formed on its outer circumferential surface 31a. After the crank 27, which is a member to be attached, is attached to the connecting portion 32 adjacent to the threaded portion 31, a nut 34 is attached to the threaded portion 31. By attaching the nut 34 to the threaded portion 31, the crank 27 is attached so as to be sandwiched between the connecting portion 32, which has a tapered shape (more specifically, a truncated cone shape), and the nut 34.

[0021] The connecting portion 32 is configured with a tapered flat knurling. That is, the connecting portion 32 is tapered with a small diameter portion 32a on the side where the threaded portion 31 is present and a large diameter portion 32b on the side where the recessed portion 33 is present. The small diameter portion 32a of the connecting portion 32 is substantially flush with the crank 27 in the attached state. The large diameter portion 32b of the connecting portion 32 is set to be smaller radially inward by a dimension D1 than the main body portion 23a of the output shaft 23. The taper angle θ1 of the connecting portion 32 is set to the same angle as the taper angle θ2 of the connecting hole 27a of the crank 27. The connecting portion 32 has triangular projections and recesses on its outer circumferential surface 32c, which are alternately configured at equal intervals in the circumferential direction. The projections and recesses of the knurling created on the outer circumferential surface 32c of the connecting portion 32 extend linearly along the axial direction when viewed from the side of the output shaft 23. The concave and convex stripes of the knurling of the connecting portion 32 are formed continuously over the entire area from the small diameter portion 32a to the large diameter portion 32b. A method for forming the knurling of the connecting portion 32 will be described later.

[0022] In addition, the connecting hole 27a of the crank 27 connected to the connecting portion 32 also has a tapered flat knurling formed on the inner peripheral surface 27b. The crank 27 is attached so that the concave and convex knurling of its own connecting hole 27a and the connecting portion 32 of the output shaft 23 mesh with each other. In this case, the concave and convex knurling of the connecting portion 32 are completely formed over the entire area from the small diameter portion 32a to the large diameter portion 32b, so that the meshing with the connecting hole 27a of the crank 27 is deep and the connection between them is strong. In this way, the crank 27 is attached to the connecting portion 32 of the output shaft 23 so as to be unable to rotate relative to it.

[0023] The recessed portion 33 is recessed from the outside to the inside in the radial direction of the output shaft 23 between the large diameter portion 32b of the connecting portion 32 where the knurling is made and the main body portion 23a of the output shaft 23. By providing the recessed portion 33 between the connecting portion 32 and the main body portion 23a of the output shaft 23, the large diameter portion 32b of the connecting portion 32 is located inward from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 by a dimension D1 without changing the taper angle θ1 of the connecting portion 32. In other words, when the connecting portion 32 is knurled, plastic deformation occurs in which the convex portion rises, but even the convex portion of the large diameter portion 32b of the connecting portion 32, which has the largest diameter, does not protrude from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23. In addition, since the taper angle θ1 of the connecting portion 32 is not changed, the output shaft 23 is highly versatile.

[0024] 6 and 7 show an output shaft 23x of a comparative example. The output shaft 23x does not have the recessed portion 33 of the output shaft 23 of this embodiment, and is provided with a threaded portion 31 and a connecting portion 32 in this order from the tip side, and the connecting portion 32 is adjacent to the main body portion 23a of the output shaft 23x. In other words, the output shaft 23x of the comparative example has a commonly used configuration. A tapered flat knurl is formed on the connecting portion 32. The connecting portion 32 has the same taper angle θ1 as this embodiment.

[0025] In the comparative example, when the knurling is made on the connecting portion 32, a part of the convex portion of the knurling may further protrude outward from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23x at the boundary with the main body portion 23a of the output shaft 23x. Therefore, post-processing such as cutting off the unnecessary portion 32x protruding from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23x at the connecting portion 32 is necessary. That is, in the later assembly process of the output shaft 23x in the wiper motor 20, when the cylindrical bearing 35 fixed to the housing 24 is inserted from the tip side of the output shaft 23x, the unnecessary portion 32x hits the bearing 35. Incidentally, it is also conceivable to stop making the concave portion of the knurling before the boundary so that the unnecessary portion 32x does not protrude from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23, thereby suppressing the rise of the convex portion. In this case, however, it may happen that the grooves of the knurling do not extend all the way through in the longitudinal direction, and therefore the engagement of the crank 27 with the connecting portion 32 at the ends of the grooves will be shallow.

[0026] In contrast to the above, the output shaft 23 of this embodiment shown in Figs. 2 and 3 allocates a part of itself, which was the connecting portion 32 in the comparative example, to the recessed portion 33. In other words, when the taper angle θ1 of the connecting portion 32 is maintained, the inclination mode of the outer peripheral surface 32c of the connecting portion 32 toward the outer peripheral surface 23b of the main body portion 23a of the output shaft 23 becomes a shape in the middle of the inclination due to the setting of the recessed portion 33, and the outer diameter of the large diameter portion 32b is set to be smaller than that of the comparative example. Therefore, even if the connecting portion 32 is knurled, the convex portion of the large diameter portion 32b of the connecting portion 32 does not protrude from the outer peripheral surface 23b of the main body portion 23a of the output shaft 23. In other words, the dimensions of the recessed portion 33 are set so that the convex portion of the large diameter portion 32b of the connecting portion 32 does not protrude from the outer peripheral surface 23b of the main body portion 23a of the output shaft 23. In the output shaft 23 of this embodiment, even if the connecting portion 32 is knurled, no unnecessary portion that protrudes from the outer circumferential surface 23b of the main body 23a of the output shaft 23 is generated in the connecting portion 32. As a result, even when the bearing 35 fixed to the housing 24 is inserted from the tip side of the output shaft 23 in the subsequent assembly process of the output shaft 23, the output shaft 23 can be inserted without post-processing.

[0027] [Output shaft manufacturing] As shown in FIG. 4, when producing the tip portion of the output shaft 23, a rod-shaped shaft material 36 for producing the output shaft 23 is used.

[0028] In the first step, the planned region 31α of the threaded portion 31, the planned region 32α of the connecting portion 32, and the recessed portion 33 are all produced in one step using turning, cold forging, etc. on the tip portion of the shaft material 36. The planned region 31α of the threaded portion 31 is produced in a cylindrical shape with a smooth outer circumferential surface 31a0. The planned region 32α of the connecting portion 32 is also produced in a tapered shape with a smooth outer circumferential surface 32c0.

[0029] The taper angle θ0 of the planned preparation portion 32α of the connecting portion 32 is set to be smaller than the taper angle θ1 of the connecting portion 32 after the knurling is prepared as shown in Fig. 5. The planned preparation portion 32α of the connecting portion 32 has a shape that is continuous with the recessed portion 33 without any step. That is, the large diameter portion 32b0 of the planned preparation portion 32α of the connecting portion 32 is located inward from the outer circumferential surface 23b of the main body 23a of the output shaft 23 by a dimension D0, which is larger than the dimension D1 of the large diameter portion 32b of the connecting portion 32 after the knurling is prepared as shown in Fig. 5.

[0030] 4 and 5, in the second step, the threaded portion 31 is formed in the intended formation portion 31α. The threaded portion 31 may be formed after the knurling is formed in the intended formation portion 32α of the connecting portion 32.

[0031] In addition, after or before the threaded portion 31 is produced, a tapered flat knurling process is performed on the planned production portion 32α of the connecting portion 32, and a knurl is produced in the connecting portion 32. A known rolling die (not shown) is applied to the outer peripheral surface 32c0 of the planned production portion 32α of the connecting portion 32 to perform the knurling process. In the outer peripheral surface 32c0 of the connecting portion 32, plastic deformation occurs in which the material of the concave portion of the knurl moves to the convex portion, and the unevenness of the knurl is produced. After the knurling is produced, the connecting portion 32 protrudes radially outward due to the rise of the convex portion of the knurl.

[0032] At this time, since the output shaft 23 of this embodiment is provided with the recessed portion 33 in advance, even the protruding portion of the large diameter portion 32b, which has the largest diameter, of the connecting portion 32 does not protrude from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23. Therefore, no unnecessary portion is generated in the connecting portion 32 of this embodiment, and it is possible to omit the post-processing step of cutting off the unnecessary portion, which was performed in the comparative example. The manufacturing process of the output shaft 23 is simplified. In this manner, the output shaft 23 of this embodiment is manufactured.

[0033] [Effects of this embodiment] The effects of this embodiment will be described. (1) In the connecting portion 32 of the output shaft 23 on which the knurling is to be produced, a recessed portion 33 is provided between the large diameter portion 32b of the connecting portion 32 and the main body portion 23a of the output shaft 23. The inclination of the outer circumferential surface 32c of the connecting portion 32 toward the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 is set to a shape that is midway inclined by setting the recessed portion 33, so that the large diameter portion 32b of the connecting portion 32 is positioned inward from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23. In other words, no unnecessary portion that protrudes from the outer circumferential surface 23b of the main body portion 23a of the output shaft 23 is generated in the connecting portion 32, and post-processing such as cutting off the unnecessary portion can be omitted.

[0034] (2) The recess 33 is produced in parallel with the production of the planned site 32α of the connecting portion 32 where the knurling is to be produced in advance in the shaft blank 36. Therefore, it is possible to prevent the anticipated increase in the number of steps required for producing the recess 33.

[0035] (3) The planned preparation portion 32α of the connecting portion 32 and the recessed portion 33 are prepared to have a continuous shape without any step. In other words, the shape of the connecting portion 32 spanning the planned preparation portion 32α of the connecting portion 32 and the recessed portion 33 is a relatively simple shape, which can facilitate processing.

[0036] (4) The taper angle θ0 of the planned preparation portion 32α of the connecting portion 32 is set to be smaller than the taper angle θ1 of the connecting portion 32 after the knurling is prepared. In other words, the shape of the connecting portion 32 spanning the planned preparation portion 32α and the recessed portion 33 can be made relatively simple, and the knurling can be more appropriately prepared for the connecting portion 32.

[0037] [Example of change] This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0038] The shapes of the output shaft 23 having the connecting portion 32 and the recessed portion 33 in the above embodiment, and the planned portion 32α of the connecting portion 32 to be manufactured from the shaft material 36, etc. are merely examples and may be changed as appropriate.

[0039] While the above embodiment has been described with respect to application to the output shaft 23, the tip portions of the pivot shafts 14, 15 shown in FIGS. 1 to 3 may be manufactured using the same configuration and manufacturing process as the tip portion of the output shaft 23.

[0040] Specifically, as the same reference numerals are given to each of the pivot shafts 14, 15, a threaded portion 31, a connecting portion 32, and a recessed portion 33 are provided in this order from the tip side, and each recessed portion 33 is adjacent to the main body portion 14a, 15a of each of the pivot shafts 14, 15. The connecting portion 32 of each of the pivot shafts 14, 15 is formed with a tapered flat knurl on the outer circumferential surface 32c. The wiper arms 18, 19, which are the members to be attached, are attached to the connecting portion 32 of each of the pivot shafts 14, 15 so that they cannot rotate relative to each other. The wiper arms 18, 19 are provided with connecting holes 18a, 19a, which are also formed with a tapered flat knurl on the inner circumferential surface 18b, 19b. The wiper arms 18, 19 are attached so that the knurled projections and recesses of the connecting holes 18a, 19a and the connecting portion 32 of each of the pivot shafts 14, 15 mesh with each other.

[0041] Furthermore, the connecting portion 32 of each pivot shaft 14, 15 does not have unnecessary portions that protrude from the outer circumferential surfaces 14b, 15b of the main bodies 14a, 15a. Therefore, even when the bearings 35 fixed to the pivot holders 11, 12 are inserted into each pivot shaft 14, 15 from the tip side in a later assembly process, each pivot shaft 14, 15 can be inserted without post-processing. The same effects as those of the output shaft 23 described above can be obtained for each pivot shaft 14, 15.

[0042] The wiper device 10 in the above embodiment is configured to connect the output shaft 23 of the wiper motor 20 to the crank 27 of the link mechanism, but the wiper device 10 may be configured to directly connect the output shaft 23 of the wiper motor 20 to the wiper arm 18 (, 19).

[0043] The wiper device 10 in the above embodiment is configured to perform a typical arc-shaped wiping action, but it may be a wiper device that performs a non-arc-shaped wiping action by incorporating a four-link mechanism. In that case, it may be applied to the shaft for mounting the wiper arm 18 (19) provided on the four-link mechanism.

[0044] [Note] The technical ideas that can be understood from the above-described embodiment and modified examples will be described. (A) A shaft having a connecting portion having a tapered knurled outer surface for mounting a workpiece so as to prevent the workpiece from rotating relative to the workpiece, A shaft having a recess formed by recessing the area between the large diameter portion of the connecting part and the main body of the shaft radially inward so that the inclination pattern of the outer circumferential surface of the connecting part toward the outer circumferential surface of the main body of the shaft is an intermediate inclination shape and the large diameter portion of the connecting part is positioned inward from the outer circumferential surface of the main body of the shaft.

[0045] (B) A shaft having a connecting portion having a tapered flat knurl on its outer circumferential surface for mounting a workpiece so as to prevent the workpiece from rotating relative to the workpiece. a recessed portion is further provided by recessing a portion between the large diameter portion of the connecting portion and the main body of the shaft radially inward so that the inclination of the outer circumferential surface of the connecting portion toward the outer circumferential surface of the main body of the shaft is an intermediate inclination shape and the large diameter portion of the connecting portion is located inward from the outer circumferential surface of the main body of the shaft, A first step of forming a portion for forming the connection portion and the recessed portion in a shaft material for producing the shaft; A second step of performing a tapered flat knurling process on the portion to be manufactured of the connecting portion; A method for manufacturing a shaft comprising:

[0046] The above-described shaft and the method of manufacturing the shaft can be applied not only to a shaft for a wiper device but also to a shaft for use in a device other than a wiper device, and similar functions and effects can be obtained. [Explanation of symbols]

[0047] 14, 15 pivot shaft (shaft), 14a, 15a main body, 14b, 15b outer circumferential surface, 18, 19 wiper arm (attached member), 23 output shaft (shaft), 23a main body, 23b outer circumferential surface, 27 crank (attached member), 32 connecting portion, 32b large diameter portion, 32c outer circumferential surface, 33 recessed portion

Claims

1. A shaft (23, 14, 15) for a wiper device, comprising a connecting portion (32) having a tapered flat knurl on an outer circumferential surface (32c) for mounting a mounting member (27, 18, 19) such that the mounting member cannot rotate relative to the connecting portion, a recess (33) is further provided by recessing a portion between the large diameter portion (32b) of the connecting portion and the main body portion of the shaft radially inward so that the inclination mode of the outer circumferential surface of the connecting portion toward the outer circumferential surface (23b, 14b, 15b) of the main body portion (23a, 14a, 15a) of the shaft is an intermediate inclination shape and the large diameter portion (32b) of the connecting portion is located inward from the outer circumferential surface of the main body portion of the shaft, and the shaft is configured such that the recess is adjacent to the main body portion of the shaft, A first step of preparing a portion (32α) for preparing the connection portion and the recessed portion in a shaft material (36) for preparing the shaft; A second step of performing a tapered flat knurling process on the portion to be manufactured of the connecting portion; Equipped with A method for manufacturing a shaft, wherein a taper angle (θ0) of a planned portion of the connecting portion to be created in the first step is set to be smaller than a taper angle (θ1) of the connecting portion after the knurling is created in the second step.

2. The method for manufacturing a shaft according to claim 1 , wherein in the first step, the planned production site of the connecting portion and the recessed portion are produced to have a shape that is continuous without any step.

3. A method for manufacturing a shaft as described in claim 1 or claim 2, wherein the shaft is provided with a threaded portion (31) consisting of a male thread from the tip, the connecting portion, and the recessed portion, in that order.

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