JP2023017270A - shaft structure - Google Patents

Abstract

To provide a shaft structure which can be used for a constant velocity universal joint which is used under a comparatively-severe load condition by being designed to a specification using back wave welding which does not cause the disadvantage of a weld factor of a tip part.SOLUTION: An inside joint member of a constant velocity universal joint comprises a stub shaft which is inserted with a tip-side insertion shaft part, and a hollow pipe body to which a large-diameter part arranged at a base end side of the stub shaft is connected. A circumferential counterbore groove which is opened in an outside-diameter direction is formed at a large-diameter part of the stub shaft, and a tip side of an opening part of the circumferential counterbore groove is covered with an outside-diameter flange part. An opening end part of the hollow pipe body and an end edge part of the outside-diameter flange part of the stub shaft are brought into an abutment state by fitting the large-diameter part into an opening of the hollow pipe body at the stub shaft side, and the opening end part and the end edge part are integrated to each other by a bevel weld part being back wave welding.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a shaft structure, and more particularly to a shaft structure that is an intermediate shaft connected to a constant velocity universal joint as a power transmission mechanism for automobiles and various industrial machines.

2. Description of the Related Art Constant velocity universal joints that are applied as power transmission mechanisms for automobiles and various industrial machines are described in Patent Document 1, Patent Document 2, and the like. The constant velocity universal joint described in Patent Document 1, as shown in FIG. An inner joint member 6 in which a pair of track grooves 5 is formed, a ball 7 interposed between the track groove 2 of the outer joint member 3 and the track groove 5 of the inner joint member 6 and transmitting torque, and an outer joint A retainer 8 is interposed between the inner diameter surface 1 of the member 3 and the outer diameter surface 4 of the inner joint member 6 to retain the balls 7 .

A female spline 10 is formed on the inner diameter surface of the axial hole of the inner joint member 6, and a male spline 12 at the tip of the stub shaft 11 is fitted into the axial hole. Thereby, the female spline 10 and the male spline 12 are fitted. Retaining rings 13 and 14 are attached to the distal and proximal ends of the male spline 12, respectively. That is, a circumferential groove 12a is formed at the distal end of the male spline 12, a circumferential groove 12b is formed at the proximal end of the male spline 12, and snap rings 13 and 14 are mounted in the respective circumferential grooves 12a and 12b. .

At this time, the retaining ring 13 abuts on one end face 6a of the inner joint member 6 (the end face on the adapter side, which will be described later), and the retaining ring 14 contacts the inner diameter of the other end face 6b of the inner joint member 6 (the end face on the side opposite to the adapter). It is fitted in a notch 15 provided in the part. Therefore, the axial movement of the shaft 11 with respect to the inner joint member 6 is restricted.

A pipe material (steel pipe) 16 is continuously provided on the base end side of the stub shaft 11 . That is, a boss portion 11b is formed at the base end portion of the stub shaft 11, and a pipe material 16 is connected to the boss portion 11b to form an intermediate shaft (shaft structure) S. As shown in FIG. In this case, a fitting portion 17 is formed on the boss portion 11b, and this fitting portion 17 is fitted into the opening of the pipe material 16, and the large diameter portion 18 of the boss portion 11b and the pipe material 16 are welded. etc.

The outer joint member 3 is a disk type, and an adapter 20 is attached to one end surface 3a side, and a boot fixing plate 21 is attached to the other end surface 3b side. That is, the adapter 20 is formed of a tubular body having a key groove 20a formed on its inner diameter surface, and a fitting concave portion 20b into which the end portion of the outer joint member 3 on the adapter 20 side is fitted is formed on the end surface on the side of the joint body. A packing 9a is mounted between the end surface 3a and the end surface 3a. The boot fixing plate 21 is formed of a flat plate ring body, and is provided with a fitting concave portion 21a in the end face on the side of the joint body, into which the end portion of the outer joint member 3 on the side opposite to the adapter is fitted. A packing 9b is mounted therebetween.

Through holes 22 and 23 are provided in the boot fixing plate 21 and the outer joint member 3 , and a screw hole 24 is provided in the adapter 20 . Therefore, the end of the outer joint member 3 on the side opposite to the adapter is fitted into the fitting recess 20 b of the adapter 20 and the end of the outer joint member 3 on the side opposite to the adapter is fitted into the fitting recess 21 a of the boot fixing plate 21 . match. In this state, the bolt member 25 is inserted into the through hole 22 of the boot fixing plate 21 and the through hole 23 of the outer joint member 3, and the threaded portion 25a of the bolt member 25 is screwed into the threaded hole 24 of the adapter 20. For example, the boot fixing plate 21, the outer joint member 3 and the adapter 20 are integrated.

The shaft-side opening of the constant velocity universal joint is sealed with a sealing device 30 . The sealing device in this case includes a metal inner diameter side tubular portion 30a, a metal outer diameter side tubular portion 30b, and a U-shaped cross section connecting the inner diameter side tubular portion 30a and the outer diameter side tubular portion 30b. and a bent portion 30c made of a flexible material.

The inner diameter side tubular portion 30 a is fitted onto the shaft 11 , and the outer diameter side tubular portion 30 b is fixed to the outer joint member 3 via the boot fixing plate 21 . That is, a collar portion 26 extending in the outer diameter direction is provided at the joint-side end portion of the outer diameter side cylindrical portion 30b. It fits into the directional recess 27 .

A grease nipple 28 for replenishing grease is arranged on the boot fixing plate 21 . That is, the grease nipple 28 is in communication with the interior of the joint body.

By the way, in industrial fixed joints, a constant velocity universal joint shown in FIG. 7 can be used for low-angle, high-speed rotation. However, there are cases where impact torque is frequently input in places of use such as rolling and winding processes of steel equipment, and the intermediate shaft (the shaft formed by connecting the stub shaft 11 and the hollow tubular body 16) Due to the applied bending stress, it may be difficult to ensure the strength of the welded portion W between the large-diameter portion 18 of the boss portion 11b and the hollow tubular body 16 .

Welding of such a weld W is performed by arc welding, as shown in FIG. In this case, V-groove welding is performed. Strength is ensured by reducing the notch factor by cutting the outer diameter bead, improving penetration by securing the root of the butt surface, and increasing the steel pipe diameter. Also in Patent Document 2, the connection between the stub shaft 11 of the intermediate shaft and the hollow tubular body 18 is performed by arc welding or the like.

JP 2017-227224 A JP 2016-217365 A

However, increasing the diameter of the steel pipe may cause a problem of interference with surrounding parts in placement, so it is not preferable to increase the diameter. That is, it is preferable to ensure the required strength without increasing the diameter.

Therefore, in view of such circumstances, the present invention is designed to a specification using Uranami welding that does not disadvantageously affect the welding coefficient of the groove, so that it can be used for constant velocity universal joints that are used under relatively severe load conditions. An object of the present invention is to provide a shaft structure capable of

A shaft structure of the present invention is a shaft coupled to a constant velocity universal joint including an outer joint member, an inner joint member, and a ball as a torque transmission member interposed between the outer joint member and the inner joint member. A hollow structure in which a stub shaft into which an insertion shaft portion on the distal end side is inserted and a large diameter portion provided on the proximal end side of the stub shaft are connected to the inner joint member of the constant velocity universal joint. a tubular body, wherein a circumferential counterbore groove that opens in the outer diameter direction is provided in the large diameter portion of the stub shaft, and the tip end side of the opening of the circumferential counterbore groove is covered with an outer diameter flange. and inserting the large-diameter portion into the opening of the hollow tubular body on the stub shaft side so that the open end of the hollow tubular body and the edge of the outer diameter flange of the stub shaft are butted against each other. As a shape, the opening end and the edge are integrated at the groove welded portion which is Uranami welding. Here, Uranami welding is a welding method in which a bead is formed on the back surface (inner surface) by welding from the surface (outer surface).

According to the shaft structure of the present invention, the open end portion of the hollow tubular body and the edge portion of the outer diameter flange portion of the stub shaft are butted, and the open end portion and the edge portion are welded by Uranami welding. Since they are integrated at the groove welded portion, it is possible to improve the joint strength of the joint portion between the open end portion of the hollow tubular body and the edge portion of the outer diameter collar portion of the stub shaft.

The stub shaft is provided with an axial hole, and the axial hole and the circumferential counterbore groove are communicated with each other through a communicating hole, and the communicating hole and the axial hole are used as an air vent during Uranami welding. preferable. By configuring in this way, it is possible to suppress an increase in internal pressure during welding, and to stably form the Uranami bead portion (the bead portion on the back side).

The inner diameter surface of the opening of the hollow tubular body into which the large diameter portion of the stub shaft is fitted and the outer diameter surface of the large diameter portion facing the inner diameter surface are joined by a joining means before welding the welded portion. is preferred. With this configuration, the hollow tube and the stub shaft can be firmly connected while leaving a gap at the joint between the open end of the hollow tube and the edge of the outer diameter flange of the stub shaft. , allowing the weld to be welded while maintaining the proper clearance.

It is preferable that the joint portion joined by the joining means and the groove weld portion are shifted in the axial direction. By adopting such a configuration, a space can be secured by counterbore on the inner diameter side of the welded portion, and Uranami welding capable of forming a Uranami bead portion (a bead portion on the back surface side) can be performed. That is, since the strength of the shaft structure that constitutes the intermediate shaft can be ensured, an excessive increase in diameter can be prevented, and interference with peripheral parts can be avoided.

The joining means may be shrink fitting. Here, shrink fitting is a joining method in which a hole on the side of receiving a shaft is heated to expand and widen, the shaft is fitted in, and then cooled. For this reason, there is a strong joining force and no generation of chips. In addition, the root spacing of butt may be determined by sandwiching a steel plate or the like corresponding to a specified value at the time of shrink fitting and positioning.

It is preferable that the outer diameter portion of the groove welded portion be a cylindrical surface that is flush with the outer diameter surface of the outer diameter flange portion. With this configuration, even if ultrasonic waves are applied to the outer diameter surface of the welded portion, irregular reflection does not occur, and inspection by ultrasonic flaw detection can be performed.

The constant velocity universal joint may be a sliding constant velocity universal joint that allows axial displacement and operating angle displacement, or a fixed constant velocity universal joint that allows only operating angle displacement. . Sliding type constant velocity universal joints include double offset type, tripod type, cross groove type and the like, and fixed type constant velocity universal joints include Rzeppa type, undercut free type and the like.

INDUSTRIAL APPLICABILITY The shaft structure of the present invention can improve the fatigue strength of joints (welded parts), and is used as a constant velocity universal joint for industrial machinery in steel equipment and the like, where impact torque is frequently input. It can be effectively used for structures (intermediate axes).

1 is a cross-sectional view of a constant velocity universal joint to which a shaft structure of the present invention is connected; FIG. FIG. 2 is a sectional view taken along the line XX of FIG. 1; FIG. 4 is an exploded cross-sectional view of a main portion of the shaft structure; FIG. 4 is a cross-sectional view of the integrated state of the shaft structure; FIG. 4 is a cross-sectional view of the shaft structure just before welding; It is a simplified cross-sectional view showing a groove shape. FIG. 10 is a cross-sectional view of a constant velocity universal joint to which a conventional shaft structure is connected; FIG. 3 is an enlarged view of a main portion of a conventional shaft structure;

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 and 2 show a constant velocity universal joint to which a shaft structure according to the present invention is connected. Between the inner joint member 36 in which the track groove 35 paired with the track groove 32 of the outer joint member 33 is formed on the radial surface 34 and the track groove 32 of the outer joint member 33 and the track groove 35 of the inner joint member 36 It is provided with balls 37 interposed to transmit torque, and retainers 38 interposed between the inner diameter surface 31 of the outer joint member 33 and the outer diameter surface 34 of the inner joint member 36 to hold the balls 37 .

A hollow tubular body 46 made of a pipe material is connected to the base end side of the stub shaft 41 . That is, a large-diameter portion 41a is formed at the proximal end portion of the stub shaft 41, and this large-diameter portion 41a is fitted into an opening portion 46a of the hollow tubular body 46 on the stub shaft side. In this case, as will be described later, the stub shaft 41 and the hollow tubular body 46 are integrated to form a shaft structure S according to the present invention.

A female spline 40 is formed on the inner diameter surface of the axial hole of the inner joint member 36, and a male spline 42, which is an insertion shaft portion on the distal end side of the stub shaft 41, is fitted into the axial hole. Thereby, the female spline 40 and the male spline 42 are fitted. Retaining rings 43 are attached to the distal ends of the male splines 42 to prevent them from coming off. That is, the retaining ring 43 is attached to the inner joint member 36 via a bolt member 44 screwed onto the tip surface of the inner joint member 36 .

The outer joint member 33 is a disk type, and an adapter 50 is attached to one end surface 33a side, and a boot fixing plate 51 is attached to the other end surface 33b side. That is, the adapter 50 has a cylindrical adapter main body 50a and a flat ring-shaped end plate portion 50b integrated with the adapter main body 50a on the constant velocity universal joint side. An end face of the end plate portion 50b is provided with a fitting recess 50b1 into which the end of the outer joint member 33 on the side of the adapter 50 is fitted. is equipped with packing 39a. The boot fixing plate 51 is formed of a flat plate ring body, and is provided with a fitting concave portion 51a on the end face of the joint main body side, into which the end portion of the outer joint member 33 on the side opposite to the adapter is fitted. A packing 39b is mounted between the other end face 33b and the fitting recess 51a. The packings 39a and 39b are molded from a synthetic material of paper and resin. The packings 39a and 39b can be made of metal (iron, stainless steel, aluminum, etc.) or liquid gaskets depending on the usage conditions and environment.

Through holes 52 and 53 are provided in the boot fixing plate 51 and the outer joint member 33, and a screw hole 54 is provided in the end plate portion 50b of the adapter 50. As shown in FIG. Therefore, the end of the outer joint member 33 on the side opposite to the adapter is fitted into the fitting recess 50 b 1 of the adapter 50 and the end of the outer joint member 33 on the side opposite to the adapter is fitted into the fitting recess 51 a of the boot fixing plate 51 . match. In this state, the bolt member 55 is inserted into the through hole 52 of the boot fixing plate 51 and the through hole 53 of the outer joint member 33 , and the threaded portion 55 a of the bolt member 55 is screwed into the threaded hole 54 of the adapter 50 . For example, the boot fixing plate 51, the outer joint member 33 and the adapter 50 are integrated.

A grease nipple 58 for replenishing grease is arranged on the boot fixing plate 51 . That is, the grease nipple 58 is in communication with the interior of the joint body.

A sealing device 60 seals the opening of the constant velocity universal joint on the shaft side. In this case, the sealing device 60 has a U-shaped cross section connecting the inner diameter side cylindrical portion 60a made of metal, the outer diameter side cylindrical portion 60b made of metal, and the inner diameter side cylindrical portion 60a and the outer diameter side cylindrical portion 60b. and a bent portion 60c made of a flexible material. In this case, the bent portion 60c is vulcanized and bonded to the metal rings of the inner diameter side tubular portion 60a and the outer diameter side tubular portion 60b. The metal material of the inner diameter side cylindrical portion 60a and the outer diameter side cylindrical portion 60b and the flexible material of the bending portion 60c are those that can be used in the environment in which this constant velocity universal joint is used. good.

The inner diameter side tubular portion 60 a is fitted onto the shaft 41 , and the outer diameter side tubular portion 60 b is fixed to the outer joint member 33 via the boot fixing plate 51 . That is, a collar portion 56 extending in the outer diameter direction is provided at the joint-side end portion of the outer diameter side cylindrical portion 60b, and the collar portion 56 is formed on the inner diameter portion of the joint-side end surface 51a of the boot fixing plate 51. It fits in the circumferential recess.

Next, a method of connecting the stub shaft 41 and the hollow tubular body 46 will be described. In this case, as shown in Figs. The side is covered with the outer diameter flange portion 71 . In addition, a radial end surface portion 72a on the circumferential counterbore groove 70 side and a tapered surface portion 72b on the opening side are formed at the edge portion of the outer diameter flange portion.

The hollow tubular body 46 has a shaft insertion portion 46a whose inner diameter is slightly larger than that of other portions at the opening on the stub shaft 41 side. A radial end surface portion 73a on the inner diameter side and a tapered surface portion 73b on the outer diameter side, which are symmetrical with the edge portion of the collar portion 71, are formed.

For this reason, the large-diameter portion 41a of the stub shaft 41 is fitted into the shaft insertion portion 46a of the hollow tubular body 46 and butted against each other as shown in FIG. In this case, a predetermined gap is set between the facing radial end face portions. Here, the predetermined gap is set to, for example, approximately 1.5 mm to 2.5 mm.

That is, the abutting surfaces of the radial end face portions facing each other serve as grooves for performing V-groove welding, and the root interval is about 1.5 mm to 2.5 mm, which is the above-mentioned predetermined gap. Further, the root surface length is set to, for example, about 1.0 mm to 2.0 mm, the inclination angles θ1 and θ2 of the tapered surface portion are set to be the same, and the groove angle θ is set to about 50° to 70°. be.

When the large diameter portion 41a of the stub shaft 41 is fitted into the shaft insertion portion 46a of the hollow tubular body 46, the inner diameter surface 46a1 of the shaft insertion portion 46a and the large diameter portion of the stub shaft 41 are connected via a joining means. The outer diameter surface 41a1 of 41a is joined together to form a joint J between the inner diameter surface 46a1 and the outer diameter surface 41a1. As a joining means in this case, shrink fitting is employed in this embodiment. Here, shrink fitting is a joining method in which a hole on the side of receiving a shaft is heated to expand and widen, the shaft is fitted in, and then cooled. For this reason, there is a strong joining force and no generation of chips.

By the way, both the corner portions 75 and 76 of the bottom surface 70a of the circumferential counterbore groove 70 of the stub shaft 41 are rounded portions, and the corner portion 77 between the outer diameter flange portion 71 and the circumferential counterbore groove 70 is also rounded. Earl part. Further, the side of the circumferential counterbore groove opposite to the outer diameter flange portion is a portion (body portion) 78 that is joined to the inner diameter surface 46a1 of the shaft insertion portion 46a by shrink fitting. Chamfered portions 78a and 78b are formed, and the joint range H of the joint portion J is between the chamfered portions.

As shown in FIGS. 1 and 3 , the stub shaft 41 is provided with an axial hole 80 , and the communication hole 81 communicates between the circumferential counterbore groove 70 and the axial hole 80 . The communication hole 81 extends radially from the bottom surface 70 a of the circumferential counterbore groove 70 and reaches the axial hole 80 .

It is for welding (V-groove welding) to the groove portion. They are integrated at the groove welded portion W, which is wave welded. Here, Uranami welding is welding from the surface (outer surface), and is a welding method for forming a bead 82 on the back surface (inner surface) as shown in FIG. In this case, the communication hole 81 and the axial hole 80 serve as air vent holes during Uranami welding.

Normally, if such welding is performed, a weld bulge Wa (see FIG. 8) is formed on the surface side. The outer diameter portion of the welded portion W is a cylindrical surface flush with the outer diameter surface 71 a of the outer diameter flange portion 71 .

In the shaft structure of the present invention, the open end of the hollow tubular body 46 and the edge of the outer diameter collar portion 71 of the stub shaft 41 are butted together, and the open end and the edge are welded by Uranami welding. Since they are integrated at the groove welded portion, the joint strength of the joint (welded portion) W between the open end portion of the hollow tubular body 46 and the edge portion of the outer diameter flange portion 71 of the stub shaft 41 can be improved. can be planned.

For this reason, the shaft structure of the present invention can improve the fatigue strength of the joint (welded portion) W, and can be used as a constant velocity universal joint for industrial machinery in steel equipment and the like at a high frequency of impact torque. It can be effectively used for the input shaft structure (intermediate shaft).

The stub shaft 41 is provided with an axial hole 80, and the axial hole 80 and the circumferential counterbore groove 70 are communicated with each other through a communicating hole 81. The communicating hole 81 and the axial hole 80 are used for air bleeding during Uranami welding. Since it can be formed as a hole, it is possible to suppress an increase in internal pressure during welding, and moreover, it is possible to stably form the Uranami bead portion (bead portion on the back side).

An inner diameter surface 46a1 of the opening (shaft insertion portion 46a) of the hollow tubular body 46 into which the large diameter portion 41a of the stub shaft 41 is fitted, and an outer diameter surface 41a1 of the large diameter portion 41a facing the inner diameter surface 46a1. are joined by a joining means before welding of the welded part. For this reason, the hollow pipe 46 and the stub shaft 41 are firmly attached to each other while leaving a gap at the junction H between the open end of the hollow pipe 46 and the edge of the outer diameter collar portion 71 of the stub shaft 41 . It is possible to weld the weld while maintaining an appropriate gap.

Since the joint J joined by the joining means and the groove weld W are offset in the axial direction, a space can be secured by the counterbore groove 70 on the inner diameter side 46 a of the weld, and the Uranami bead portion 82 (back surface Uranami welding that can form a bead portion on the side) is possible. That is, since the strength of the shaft structure S constituting the intermediate shaft can be ensured, it is possible to prevent an excessive increase in diameter and avoid interference with peripheral parts.

Since the joining means is shrink fitting, there are advantages such as strong joining force and no generation of cutting chips.

The outer diameter portion of the groove welded portion W is a cylindrical surface that is flush with the outer diameter surface 71 a of the outer diameter flange portion 71 . That is, by grinding or cutting the weld bulge formed on the outer diameter side, even if ultrasonic waves are irradiated to the outer diameter surface of the welded part, the ultrasonic waves are not diffusely reflected because of the flush cylindrical surface. Inspection by flaw detection can be performed.

By the way, as a constant velocity universal joint that can be connected to the present shaft structure S, even if it is a sliding constant velocity universal joint that allows axial displacement and operating angle displacement, only operating angle displacement is possible. , or a combination of a sliding constant velocity universal joint and a fixed universal joint. Sliding type constant velocity universal joints include double offset type, tripod type, cross groove type and the like, and fixed type constant velocity universal joints include Rzeppa type, undercut free type and the like.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be modified in various ways. When performing V-groove welding, it is not limited to arc welding, Other welding methods capable of Uranami welding (for example, electron beam welding, laser welding, etc.) may be used. Also, a joint for joining the inner diameter surface 46a1 of the opening 46a of the hollow tubular body 46 into which the large diameter portion 41a of the stub shaft 41 is fitted and the outer diameter surface 41a1 of the large diameter portion 41a facing the inner diameter surface 46a1. The means is not limited to shrink fitting, and other joining methods (for example, electromagnetic pressure welding, ultrasonic pressure welding, etc.) may be used.

The groove shape may be Y-shaped, I-shaped, V-shaped, L-shaped, K-shaped, J-shaped, X-shaped, U-shaped, double-sided J-shaped, H (double-sided U)-shaped, or the like.

33 outer joint member 36 inner joint member 37 ball 41 stub shaft 41a large diameter portion 41a1 outer diameter surface 46 hollow tubular body 46a opening (shaft insertion portion)
46a1 inner diameter surface 70 circumferential counterbore groove 71 outer diameter collar portion 80 shaft center hole 81 communicating hole
J Joint W Groove weld

Claims (9)

A shaft structure connected to a constant velocity universal joint comprising an outer joint member, an inner joint member, and a ball as a torque transmission member interposed between the outer joint member and the inner joint member,
The inner joint member of the constant velocity universal joint comprises a stub shaft into which an insertion shaft portion on the distal end side is inserted, and a hollow tubular body to which a large diameter portion provided on the proximal end side of the stub shaft is connected, The large-diameter portion of the stub shaft is provided with a circumferential counterbore groove that opens in the outer diameter direction, and the front end side of the opening of the circumferential counterbore groove is covered with an outer diameter flange, and the hollow tubular body The large-diameter portion is inserted into the opening on the stub shaft side of the stub shaft, and the opening end of the hollow tubular body and the edge of the outer diameter flange of the stub shaft are butted together, and the opening end is A shaft structure characterized in that a portion and an edge portion are integrated at a groove welded portion that is Uranami welding. The stub shaft is provided with an axial hole, the axial hole and the circumferential counterbore groove are communicated with each other through a communication hole, and the communication hole and the axial hole are used as air vent holes during Uranami welding. The shaft structure of Claim 1. The inner diameter surface of the opening of the hollow tubular body into which the large diameter portion of the stub shaft is fitted and the outer diameter surface of the large diameter portion facing the inner diameter surface are joined by a joining means before welding the welded portion. 3. The shaft structure according to claim 1 or 2, characterized by: 4. The shaft structure according to claim 3, wherein the joint portion joined by the joining means and the groove weld portion are axially displaced. 5. The shaft structure according to claim 3, wherein said joining means is shrink fitting. 6. The shaft structure according to any one of claims 1 to 5, wherein the outer diameter portion of the groove welded portion is a cylindrical surface that is flush with the outer diameter surface of the outer diameter flange portion. . The shaft structure according to any one of claims 1 to 6, wherein the constant velocity universal joint is a sliding constant velocity universal joint that allows axial displacement and operating angle displacement. body. The shaft structure according to any one of claims 1 to 6, wherein the constant velocity universal joint is a fixed constant velocity universal joint that allows only a change in operating angle. 7. The shaft structure according to claim 1, wherein the constant velocity universal joint is a combination of a sliding constant velocity universal joint and a fixed universal joint.

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