JP2011237018A - Fixed constant velocity universal joint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixed constant velocity universal joint which ensures excellent durability by ensuring the stable contact state of balls with a forged track and a finished track, and which has track shapes facilitating quality control of a forging mold and products just as in a conventional one.SOLUTION: At least either of a track groove 12 of an outer joint member 13 and a track groove 15 of an inner joint member 16 is formed by means of finishing with cold forging. The cross sectional shapes of the track grooves 12, 15 on the bottom sides thereof are shaped like a gothic arch, and those on the opening sides thereof are shaped like an oval. The joint angle for the gothic arch shape and the oval shape is gradually reduced from the open angle side of the track groove toward the bottom side of the joint.

Description

  The present invention relates to a fixed type constant velocity universal joint, and more particularly to a fixed type constant velocity universal joint that can be used for a drive shaft, a propeller shaft, and the like of an automobile.

  Fixed constant velocity universal joints include fixed constant velocity universal joints such as a Barfield type (BJ) and an undercut free type (UJ).

  Barfield's fixed type constant velocity universal joints have an outer joint member in which a plurality of track grooves are formed along the axial direction at equal intervals in the circumferential direction on the inner spherical surface, and a track groove of the outer joint member is paired on the outer spherical surface. A plurality of track grooves formed between the inner joint member formed along the axial direction at equal intervals in the circumferential direction, and a plurality of torque grooves interposed between the track grooves of the outer joint member and the track grooves of the inner joint member. And a cage for holding the ball interposed between the inner spherical surface of the outer joint member and the outer spherical surface of the inner joint member.

  The outer joint member and the inner joint member in such a fixed type constant velocity universal joint are manufactured by the following method. First, a cylindrical billet is formed into an approximate shape of an outer joint member or an inner joint member by hot forging, warm forging, or cold forging, and is turned into an arbitrary shape. After that, heat treatment is performed, and the outer sphere, inner sphere and track groove are finished by grinding or quenching steel cutting.

  In this way, finishing track grooves after forging, turning, and heat treatment increases the cost of equipment, tools, etc. required for finishing track grooves, and requires time for finishing and materials. Has the disadvantage of poor yield. Therefore, there is a method of forming at least one or both of the track groove of the outer joint member and the track groove of the inner joint member by cold forging (Patent Document 1). As described above, since the track groove is formed only by cold forging because it is formed by cold forging, a lot of machining such as cutting and grinding after conventional cold forging is omitted. Therefore, the yield can be improved and the cost of the fixed type constant velocity universal joint can be reduced.

JP 2008-2624 A

  By the way, the cross-sectional shape of the track groove of such a fixed type constant velocity universal joint is desirably a structure in which the ball is in angular contact with the ball so as to stabilize the contact state of the ball with the track groove. The cross-sectional shape of the track groove is an elliptical shape depending on the tool and the processing method in the finishing method by grinding or hardened steel cutting, whereas the cross-sectional shape of the track groove in the cold forging finish is formed by forging. From the viewpoint of ease and quality control, the shape is usually Gothic arch.

  Inside the fixed constant velocity universal joint subjected to a torque load, the load is transmitted from the inner joint member (outer joint member) to the ball → outer joint member (inner joint member), and the PCD clearance between the inner joint member and the outer joint member. Depending on the magnitude of the torque, the contact point between the ball and the track moves to the spherical surface side (the ball climbs up the track slope), and the contact angle changes.

  Compared to the above-mentioned cold forged finish track groove (gothic arch shape) and machining track groove (elliptical shape) of the above prior art, the movement distance of the contact point (change amount of contact angle) is different due to the shape difference, so the outer joint member There is a concern that the contact angle between the ball, the outer joint member, and the inner joint member track may deviate from the target value, resulting in variations in durability.

  FIG. 10 shows the cross-sectional shape of a conventional forged molding track, and FIG. 11 shows the cross-sectional shape of a finishing track. The track groove cross-sectional shape of a normal forging molding is a shape in which a simple R is projected onto the vertical axis, so that a VC (Vertical Clearance) formed on the track groove bottom 2 side (the groove bottom 2 of the track groove 1 and The dimension between the ball 3 and the groove bottom corresponding portion 3a) can be increased, and shape management by VC measurement is facilitated. However, the cross-sectional shape of the finished track groove 1 is elliptical, and the VC on the track groove bottom 2 side is small. That is, when the VC amount of the forged track is VC1 and the VC amount of the finishing track is VC2, VC1> VC2. For this reason, when applying the shape of the finished track to a forged track that is not finished, it is more difficult to manage the shape of the mold or forged product than in the case of simple R.

  The object of the present invention is to secure a stable contact state between the forged molding track and the ball of the finishing track to ensure superior durability, and forging molds and product quality control are as easy as before. We propose a fixed type constant velocity universal joint with a track shape.

  The fixed type constant velocity universal joint of the present invention includes an outer joint member having a track groove formed on the inner diameter surface, an inner joint member having a track groove formed on the outer diameter surface, a track groove of the outer joint member, and an inner side corresponding thereto. A fixed type constant velocity universal joint provided with a torque transmission ball disposed on a torque transmission ball track formed in cooperation with a track groove of a joint member, and a cage for holding the torque transmission ball. At least one of the track groove of the joint member and the track groove of the inner joint member is molded by cold forging, and the cross-sectional shape thereof is a gothic arch shape on the track groove bottom side, and the track groove opening side is an elliptical shape. In addition, the connecting angle between the Gothic arch shape and the elliptical shape is gradually reduced from the opening angle side of the track groove toward the joint back side.

  In the fixed type constant velocity universal joint of the present invention, the side close to the spherical surface (track groove opening side) can have an elliptical shape similar to that of the finishing track groove. That is, the track range necessary for the function is an elliptical shape, and the track range necessary for the management is a Gothic arch shape.

  Since the joint angle (joint position) between the Gothic arch shape and the elliptical shape is gradually reduced from the open angle side (joint opening side) of the track groove to the joint back side, the contact ellipse is also on the joint back side. The protrusion is less likely to occur. In this case, the contact angle can be set to gradually decrease from the opening angle side of the track groove on the joint opening side toward the joint back side.

  The connecting position of the Gothic arch shape and the elliptical shape is located on the groove opening side in the range of 30 ° to 45 ° around the straight line connecting the ball center and the track groove bottom center, or 20 ° to 35 It can be positioned on the groove opening side within a range of °. If it is less than 20 °, the amount of VC for shape management is insufficient, and if it exceeds 45 °, the track surface (range) in the range exceeding 45 ° is small, and the effect of making an ellipse is small (advantage) Is not demonstrated).

  A track chamfer is formed at each of the boundary portion between the inner diameter surface and the track groove in the outer joint member and the boundary portion between the outer diameter surface and the track groove in the inner joint member, and the track groove is formed on the track groove side of the track chamfer. A rounded portion to be connected can be formed. Further, the boundary portion between the inner diameter surface and the track groove in the outer joint member and the boundary portion between the outer diameter surface and the track groove in the inner joint member can be a rounded track chamfer.

  Furthermore, an inlet chamfer formed along the entire circumference of the opening edge of the outer joint member, a track chamfer at the boundary between the inner diameter surface and the track groove in the outer joint member, and a track inlet at the boundary between the inlet chamfer and the track groove The chamfer can be formed by cold forging.

  The inlet chamfer formed along the opening end face or the entire periphery of the opening edge of the outer joint member may be formed by cold forging. Also, the track groove and the track inlet chamfer of the outer joint member are formed by simultaneous cold forging, or the track groove and the track chamfer of the outer joint member and the track groove and the track chamfer of the inner joint member are simultaneously cold forged. Respectively.

  The fixed type constant velocity universal joint may be a bar field type in which the track groove bottom is only an arc portion or an undercut free type fixed constant velocity universal joint in which the track groove bottom is an arc portion and a straight portion.

  It can be used for a fixed type constant velocity universal joint for a drive shaft of an automobile or a fixed type constant velocity universal joint for an automobile propeller shaft.

  The number of torque transmitting balls is preferably 10 or less.

  In the fixed type constant velocity universal joint of the present invention, the track range necessary for the function is an elliptical shape, the track range necessary for the management is a Gothic arch shape, and the quality control of the forging die and product is easy. It is possible to achieve both stabilization of the contact state between the ball and the track groove. In addition, the contact ellipse does not easily protrude even at a shallow portion of the joint in the track groove, and higher durability can be secured.

  For connecting the Gothic arch shape and the elliptical shape with the straight line connecting the ball center and the track groove bottom center in the range of 20 ° to 45 ° on the groove opening side, A sufficient amount of VC can be secured, and a sufficient track surface necessary for the function can be secured.

  After conventional cold forging by cold forging the inlet chamfer of the outer joint member, the track chamfer of the outer joint member, the track chamfer of the inner joint member, the track chamfer of the inlet chamfer and the track groove, etc. Cutting, grinding, etc. can be omitted. As a result, the yield can be improved and the manufacturing cost of the fixed type constant velocity universal joint can be reduced.

  In particular, the track groove and track chamfer of the outer joint member are formed by simultaneous cold forging finish, the track groove and track chamfer of the outer joint member, and the track groove and track chamfer of the inner joint member by simultaneous cold forging finish. Thus, productivity can be improved.

  Since it is sufficient that the number of the torque transmission balls is 10 or less, the degree of freedom in design is great and the design is excellent. Moreover, it can respond to various types of fixed type constant velocity universal joints.

It is sectional drawing of the track groove of the outer joint member of the 1st fixed type constant velocity universal joint of this invention. It is sectional drawing of the track groove of the inner joint member of the said fixed type constant velocity universal joint. The track groove shape of the said fixed type constant velocity universal joint is shown, (a) is explanatory drawing of (theta) 1 in the range of 30-45deg, (b) is explanatory drawing of the range of (theta) 2 20-35deg. It is sectional drawing of the said fixed type constant velocity universal joint. It is a simplified development view of the track groove of the outer joint member of the fixed type constant velocity universal joint. FIG. 5 is a half cut sectional view of an outer joint member of the fixed type constant velocity universal joint. The track groove of the said outside joint member is shown, (a) is A section of FIG. 6, (b) B section of FIG. 6, (c) is C section. The track groove | channel when the connection angle of an outer joint member is not changed is shown, (a) is A section of FIG. 6, (b) B section of FIG. 6, (c) is C section. It is sectional drawing of the 2nd fixed type constant velocity universal joint of this invention. It is sectional drawing which shows the cross-sectional shape of a forge molding track groove. It is sectional drawing which shows the cross-sectional shape of a finishing process track groove.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 4 shows an undercut free type fixed type constant velocity universal joint which is a fixed type constant velocity universal joint of the present invention. This fixed type constant velocity universal joint includes an outer joint member 13 in which a plurality of track grooves 12 are formed on an inner spherical surface (inner diameter surface) 11 along the axial direction at equal intervals in the circumferential direction, and an outer spherical surface (outer diameter surface). 14, an inner joint member 16 in which a plurality of track grooves 15 paired with the track groove 12 of the outer joint member 13 are formed along the axial direction at equal intervals in the circumferential direction, and the track groove 12 and the inner side of the outer joint member 13 are formed. A plurality of balls 17 that are interposed between the track grooves 15 of the joint member 16 and transmit torque, and are interposed between the inner spherical surface 11 of the outer joint member 13 and the outer spherical surface 14 of the inner joint member 16. And a cage 18 for holding. The cage 18 is provided with a plurality of pockets 18a for accommodating the balls 17 along the circumferential direction.

  Further, the track groove 12 of the outer joint member 13 has an arcuate portion 12a on the back side and a straight portion 12b on the opening side. The track groove 15 of the inner joint member 16 has a straight portion 15a on the back side and an arc portion 15b on the opening side. The center of curvature O1 of the track groove 15 of the inner joint member 16 and the center of curvature O2 of the track groove 12 of the outer joint member 13 are offset from the joint center O by an equal distance F, F in the opposite axial direction.

  The inner joint member 16 is provided with a shaft insertion hole 19, and a female spline 23 is formed on the inner diameter surface of the shaft insertion hole 19. An end male spline 25 a of the shaft 25 is fitted into the shaft insertion hole 19 of the inner joint member 16, and the end male spline 25 a is fitted to the female spline 23 of the inner joint member 16. A circumferential groove 26 is provided at the end of the end male spline 25a, and a retaining ring 27 is attached to the circumferential groove 26.

  In the outer joint member 13, as shown in FIG. 5, an inlet chamfer (cup inlet chamfer) 30 formed along the entire circumference of the opening edge is formed, and a track is formed at the boundary between the inner diameter surface 11 and the track groove 12. A chamfer 31 is formed, and a track inlet chamfer 32 is formed at the boundary between the track groove 12 and the cup inlet chamfer 30.

  In the inner joint member 16, a track chamfer 33 (see FIG. 2) is formed at the boundary between the outer diameter surface 14 and the track groove 15.

  As shown in FIG. 1, the cross-sectional shape of the track groove 12 of the outer joint member 13 is a gothic arch shape on the track groove bottom side and an elliptical shape on the track groove opening side. That is, the track groove 12 of the outer joint member 13 is formed with a simple R track shape portion 35 on the track groove bottom side and with elliptic track shape portions 36, 36 on the track groove opening side. The track chamfer 31 at the boundary between the inner diameter surface 11 and the track groove 12 in the outer joint member 13 is constituted by a rounded portion 31a as shown in FIG.

  As shown in FIG. 2, the cross-sectional shape of the track groove 15 of the inner joint member 16 is also a gothic arch shape on the track groove bottom side and an elliptical shape on the track groove opening side. That is, the track groove 15 of the inner joint member 16 is formed with a simple round track shape portion 38 on the track groove bottom side and with elliptic track shape portions 39, 39 on the track groove opening side. As shown in FIG. 2, the track chamfer 33 at the boundary between the outer diameter surface 14 and the track groove 15 in the inner joint member 16 includes a tapered surface 33 a, and the track chamfer 33 and the track groove 15 have a small round portion 40. It is connected through.

  The track chamfer 31 in the outer joint member 13 may have the shape of the track chamfer 33 as shown in FIG. 2, or the track chamfer 33 in the inner joint member 16 may have the shape of the track chamfer 31 as shown in FIG.

  By the way, as shown in FIGS. 3A and 3B, the connecting position 22 between the simple R track shape portion 35 (38) and the elliptical track shape portion 36 (39) is formed between the ball center Ob and the track groove bottom center. Centering on the connected straight line L, it is located on the groove opening side in the range of θ (θ1, θ2). That is, as shown in FIGS. 1 and 2, the simple R track shape portion 35 (38) is provided in the range H, and the elliptic track shape portion 36 (39) is provided in the range H1. In FIG. 3A, the θ is θ1 (30 ° to 45 °), and in FIG. 3B, the θ is θ2 (20 ° to 35 °).

  In the outer joint member 13, the track groove 12, the inlet chamfer (cup inlet chamfer) 30, the track chamfer 31, the track inlet chamfer 32, and the open end face 13a are formed by cold forging. In particular, the track groove 12 and the track inlet chamfer 32 of the outer joint member 13 are formed by simultaneous cold forging, and the track groove 12 and the track chamfer 31 of the outer joint member 13 are formed by simultaneous cold forging.

  By the way, forging finishing of the outer joint member 13 can be performed by an existing manufacturing apparatus (for example, a manufacturing apparatus disclosed in Japanese Patent Laid-Open No. 2009-185933). In this case, the shape of the track groove forming portions of the plurality of divided punches may be changed to a shape capable of forming the simple R track shape portion 35 and the elliptic track shape portions 36 and 36.

  Also in the inner joint member 16, the track groove 15 and the track chamfer 33 are formed by simultaneous cold forging finishing. The forging of the inner joint member 16 can be performed with an existing manufacturing apparatus (for example, a manufacturing apparatus disclosed in Japanese Patent Application Laid-Open No. 2007-260698). In this case, the shape of the track groove forming portion of the die may be changed to a shape capable of forming the simple R track shape portion 38 and the elliptic track shape portions 39, 39.

  In the fixed type constant velocity universal joint of the present invention, the side close to the spherical surface (track groove opening side) can have an elliptical shape similar to that of the finishing track groove. That is, the track range necessary for the function is an elliptical shape, and the track range necessary for the management is a Gothic arch shape. For this reason, it becomes possible to achieve both easy quality control of the forging die and product and stabilization of the contact state between the ball 17 and the track groove 12 (15).

  Further, the connecting position between the Gothic arch shape and the elliptical shape is located on the groove opening side in the range of 20 ° to 45 ° with the straight line connecting the ball center Ob and the track groove bottom center as the center. Therefore, a VC (Vertical Clearance) amount for shape management can be sufficiently secured as shown in VC3 and VC4 as shown in FIGS. 1 and 2, and a track surface necessary for function can be sufficiently secured.

  By cold forging the inlet chamfer 30 of the outer joint member 13, the track chamfer 31 of the outer joint member 13, the track inlet chamfer 32 of the outer joint member 13, the track chamfer 33 of the inner joint member 16, etc. The cutting and grinding after the cold forging can be omitted. As a result, the yield can be improved and the manufacturing cost of the fixed type constant velocity universal joint can be reduced.

  In particular, the track groove 12 and the track inlet chamfer 32 of the outer joint member 13 are formed by simultaneous cold forging, or the track groove 12 and the track chamfer 31 of the outer joint member 13 and the track groove 17 of the inner joint member 16 are formed. Further, productivity can be improved by forming the track chamfer 33 by simultaneous cold forging.

  The torque transmission balls may be 10 or less. For this reason, the degree of design freedom is large and the design is excellent.

  By the way, in this type of fixed type constant velocity universal joint, as shown in FIG. 6, the track groove 12 of the outer joint member 13 is gradually shallower from the track opening angle side (joint opening side) toward the joint back side. Become. For this reason, if the connection position 22 of the simple R track shape part 35 (38) and the elliptical track shape part 36 (39) is the same position along the joint back side from the opening angle side, the connection position is closer to the joint back side. The distance from 22 to the track edge E (the boundary line between the track groove and the inner diameter surface) (see FIGS. 7 and 8) becomes shorter toward the joint back side.

  That is, θ in the A cross section of FIG. 6 (cross section cut along a straight line connecting the center O2 and A portion of the track groove 12) and the B cross section of FIG. 6 (center O2 and B portion of the track groove 12) Θ in a cross section cut along a straight line connecting the two and the C in FIG. 6 (cross section cut along a straight line connecting the center O2 and the C portion of the track groove 12) in FIG. 8 (a), (b) and (c) are the same.

  In this case, as shown in FIG. 8A, the distance from the connection position 22 in the A cross section to the track edge E is La, and as shown in FIG. 8B, the track from the connection position 22 in the B cross section is tracked. The distance to the edge E is Lb, and as shown in FIG. 8C, the distance from the connecting position 22 on the C cross section to the track edge E is Lc. In this case, La <Lb <Lc. For this reason, when a torque larger than imagined is applied, the contact ellipse protrudes and the life is shortened.

  Therefore, in the present invention, the connecting angle θ (θa, θb, θc) between the Gothic arch shape and the elliptical shape is shown in FIG. 7 from the opening angle side (joint opening side) of the track groove to the joint back side. It is gradually getting smaller. Thus, if set, the distance from the connection position 22 in the A section to the track edge E is La ′ (see FIG. 7A), and the distance from the connection position 22 in the B section to the track edge E is Lb ′ (see FIG. 7B), and the distance from the connection position 22 to the track edge E in the C cross section is Lc ′ (see FIG. 7C). In this case, La <La ′, Lb <Lb ′, and Lc <Lc ′.

  This makes it difficult for the contact ellipse to protrude even in a shallow part of the track groove on the deeper side of the joint, thereby ensuring higher durability. In this case, the contact angle may not change from the joint opening side to the joint back side, or may gradually decrease from the joint opening side to the joint back side.

  Next, FIG. 9 shows a bar field type fixed type constant velocity universal joint. This fixed type constant velocity universal joint has a plurality of track grooves 42 on the inner diameter surface 41 along the axial direction at equal intervals in the circumferential direction. The formed outer joint member 43 and a plurality of track grooves 45 that are paired with the track grooves 42 of the outer joint member 43 on the outer diameter surface 44 are formed along the axial direction at equal intervals in the circumferential direction. A torque transmission ball 47 disposed on a ball track formed by cooperation of the track groove 42 of the outer joint member 43 and the track groove 45 of the inner joint member 46, and the inner diameter surface 41 of the outer joint member 43. A cage 48 is provided between the outer joint surface 46 of the inner joint member 46 and holds the ball 47.

  Also in this case, as shown in FIGS. 1 and 2, the track grooves 42 and 45 form simple round track shape portions 35 and 38 on the track groove bottom side, and elliptic track shape portions 36 and 36 on the track groove opening side. , 39, 39. Moreover, the connecting angle between the Gothic arch shape and the elliptical shape is gradually reduced from the opening angle side of the track groove toward the joint back side.

  Furthermore, an inlet chamfer (cup inlet chamfer) 30 formed along the entire periphery of the opening edge is formed in the outer joint member 43, and a track chamfer is formed at the boundary between the inner diameter surface 41 and the track groove 42. A track inlet chamfer is formed at the boundary between the track groove 42 and the cup inlet chamfer 30. In the inner joint member 46, a track chamfer is formed at the boundary between the outer diameter surface 44 and the track groove 45.

  Also in this case, the track groove 42, the inlet chamfer (cup inlet chamfer), the track chamfer, the track inlet chamfer, and the open end face 43a of the outer joint member 43 are formed by cold forging. In particular, the track groove 42 and the track inlet chamfer of the outer joint member 43 are formed by simultaneous cold forging, and the track groove 12 and the track chamfer of the outer joint member 43 and the track groove 45 and the track chamfer of the inner joint member 46 are simultaneously formed. Formed by cold forging finish.

  Even such a barfield type fixed type constant velocity universal joint has the same effects as the undercut free type fixed type constant velocity universal joint shown in FIG. For this reason, the fixed type constant velocity universal joint of the present invention can be used for a fixed type constant velocity universal joint for a drive shaft of an automobile or a fixed type constant velocity universal joint for a propeller shaft of an automobile.

  As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above-described embodiment, each track of the outer joint member and the inner joint member Although the groove is formed by cold forging, the track groove of only one of the outer joint member and the inner joint member may be formed by cold forging. The radius of curvature of the round portion of the chamfer can be variously changed as long as the track groove and the inner diameter surface (or outer diameter surface) are smoothly continuous. Further, the displacement amounts such as θa, θb, and θc in FIG. 7 can be variously changed within a range in which the protrusion of the contact ellipse hardly occurs even in a shallow portion of the track groove on the back side of the joint.

11 inner diameter surface 12 track groove 13 outer joint member 14 outer diameter surface 15 track groove 16 inner joint member 17 torque transmission ball 18 cage 30 cup inlet chamfer 31 track chamfer 32 track inlet chamfer 33 track chamfer 41 inner spherical surface (inner diameter surface)
42, 45 Track groove 43 Outer joint member 44 Outer spherical surface 46 Inner joint member 47 Ball 48 Cage

Claims (15)

The outer joint member having a track groove formed on the inner diameter surface, the inner joint member having a track groove formed on the outer diameter surface, the track groove of the outer joint member, and the track groove of the corresponding inner joint member cooperated. A fixed type constant velocity universal joint comprising a torque transmission ball disposed on a formed torque transmission ball track and a cage for holding the torque transmission ball,
At least one of the track groove of the outer joint member and the track groove of the inner joint member is molded by cold forging, and the cross-sectional shape thereof is a gothic arch shape on the track groove bottom side and an elliptical shape on the track groove opening side. A fixed type constant velocity universal joint characterized in that the connecting angle between the Gothic arch shape and the elliptical shape is gradually reduced from the opening angle side of the track groove to the joint back side.   The fixed constant velocity universal joint according to claim 1, wherein the contact angle gradually decreases from the opening angle side of the track groove, which is the joint opening side, toward the joint back side.   2. The connecting position between the Gothic arch shape and the elliptical shape is located on the groove opening side in a range of 30 ° to 45 ° with a straight line connecting the ball center and the track groove bottom center as a center. Or the fixed type constant velocity universal joint of Claim 2.   2. The connecting position between the Gothic arch shape and the elliptical shape is located on the groove opening side in a range of 20 ° to 35 ° with a straight line connecting the ball center and the track groove bottom center as a center. Or the fixed type constant velocity universal joint of Claim 2.   A track chamfer is formed at each of the boundary portion between the inner diameter surface and the track groove in the outer joint member and the boundary portion between the outer diameter surface and the track groove in the inner joint member, and the track groove is formed on the track groove side of the track chamfer. The fixed type constant velocity universal joint according to any one of claims 1 to 4, wherein a rounded portion to be connected is formed.   The boundary portion between the inner diameter surface and the track groove in the outer joint member and the boundary portion between the outer diameter surface and the track groove in the inner joint member are rounded track chamfers. Fixed fixed-velocity universal joint of any one of Claims.   An inlet chamfer formed along the entire circumference of the opening edge of the outer joint member, a track chamfer at the boundary between the inner diameter surface and the track groove in the outer joint member, and a track inlet chamfer at the boundary between the inlet chamfer and the track groove The fixed constant velocity universal joint according to any one of claims 1 to 6, wherein the fixed constant velocity universal joint is formed by cold forging.   The fixed type or the like according to any one of claims 1 to 7, wherein an inlet chamfer formed along the opening end face or the entire periphery of the opening edge of the outer joint member is formed by cold forging. Fast universal joint.   The fixed type constant velocity universal joint according to any one of claims 1 to 8, wherein the track groove and the track entrance chamfer of the outer joint member are formed by simultaneous cold forging.   The track groove and the track chamfer of the outer joint member, and the track groove and the track chamfer of the inner joint member, respectively, are formed by simultaneous cold forging finishing, respectively. Fixed constant velocity universal joint.   The fixed constant velocity universal joint according to any one of claims 1 to 10, wherein the track groove bottom is only an arc portion.   The fixed constant velocity universal joint according to any one of claims 1 to 10, wherein the track groove bottom includes an arc portion and a straight portion.   The fixed type constant velocity universal joint according to claim 11 or 12, which is used for a fixed type constant velocity universal joint for a drive shaft of an automobile.   The fixed type constant velocity universal joint according to claim 11 or 12, which is used for a fixed type constant velocity universal joint for a propeller shaft of an automobile.   The fixed type constant velocity universal joint according to any one of claims 1 to 14, wherein the number of torque transmission balls is 10 or less.

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