Shaft coming-off preventing structure for constant velocity universal joint, and constant velocity universal joint

Abstract

To stably pull out a shaft by applying a predetermined axial force in a coming-off prevention structure in which the shaft is separably prevented from coming off from an inner joint member.SOLUTION: The retaining ring 7 mounted in the retaining ring groove 63 of the shaft 6 is locked to the locking surface 36 formed on the inner surface of the shaft hole 33 of the inner joint member 3, A retaining structure for retaining a shaft 6 with respect to an inner joint member 3, wherein a retaining surface 36 is formed in a tapered surface shape whose diameter is gradually reduced in the direction of pulling out the shaft 6 from an axial hole 3, and an annular groove 38 whose groove width y is smaller than the wire diameter d of a wire constituting the retaining ring 7 is provided in a region on the inner diameter side of a contact part P with the retaining ring 7 retained with respect to the retaining surface 36.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a retaining structure for a shaft connected to an inner joint member of a constant velocity universal joint so as to be able to transmit torque, and to a constant velocity universal joint provided with this retaining structure. [Background technology]

[0002] As is well known, automobiles equipped with a drive source such as an engine or an electric motor on their chassis are equipped with a power transmission device such as a drive shaft or a propeller shaft to transmit the output (torque) of the drive source to the wheels. This power transmission device is equipped with a constant velocity universal joint that connects two shafts, a drive shaft and a driven shaft, and is capable of transmitting torque at a constant velocity even if the two connected shafts are angularly displaced relative to each other. Constant velocity universal joints are broadly divided into fixed-type constant velocity universal joints that allow only angular displacement of the two connected shafts, and sliding-type constant velocity universal joints that allow angular and axial displacement of the two connected shafts.

[0003] For example, a drive shaft includes a fixed constant velocity universal joint and a sliding constant velocity universal joint that are arranged at an interval, and a shaft (also referred to as an "intermediate shaft") that connects the inner joint members of both constant velocity universal joints so as to be able to transmit torque. One end of the shaft on one axial side (the outer side in the vehicle width direction when mounted on a vehicle) is connected to the inner joint member so as to be able to transmit torque by so-called spline fitting in which a male spline formed on the outer peripheral surface of the shaft is fitted into a female spline formed on the inner diameter of the shaft hole of the inner joint member of the fixed constant velocity universal joint, and is further prevented from coming off from the inner joint member by a predetermined retaining structure.

[0004] As the retaining structure for the shaft from the inner joint member, a separable structure is preferably adopted that can prevent separation of the inner joint member and the shaft (disengagement of the shaft) when an axial static load acts on the shaft, such as when the automobile is being driven, while allowing separation of the inner joint member and the shaft when an axial impact load is applied to the shaft, such as when performing maintenance work (for example, replacement of a boot provided between the shaft and a constant velocity universal joint). By adopting such a structure, it is possible to realize a drive shaft that allows the automobile to be driven safely and allows maintenance work to be performed efficiently. For example, Patent Document 1 listed below describes such a separable retaining structure.

[0005] The separable retaining structure described in Patent Document 1 has a basic structure in which a retaining ring is attached in an elastically contractible state to an annular retaining ring groove provided on the outer periphery of the tip end of the shaft so as to be positioned within the shaft insertion hole of the inner joint member, and the retaining ring is engaged in the axial direction (the direction in which the shaft is removed) with an abutting portion provided in the axial hole. The retaining ring is characterized by the angle difference (β - α) between the angle β that the tapered surface constituting the abutting portion makes with respect to a direction perpendicular to the axial direction (radial direction) and the angle α that the inclined surface provided on the inner wall surface of the retaining ring groove near the tip end of the shaft makes with respect to the radial direction, being set to greater than 19°. Note that a difference of 19° or less results in a non-separable retaining structure in which separation of the inner joint member and the shaft is not permitted. Therefore, when the angle difference exceeds 19°, it can be said that the greater the angle difference, the easier it is to remove the shaft. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4964417 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when an attempt is made to adjust the axial pull-out force (axial force) required to pull out the shaft by changing the relative angle difference between the inclined surfaces provided on each of the two members (the inner joint member and the shaft) that are connected to each other, as in the technical means described in Patent Document 1, the axial force required to pull out the shaft is likely to vary between individual members, which may make it difficult to carry out maintenance work, including shaft pull-out, efficiently.

[0008] In view of the above circumstances, the present invention aims to provide a constant velocity universal joint in which a shaft retention structure is used to separably retain the shaft in the inner joint member of the constant velocity universal joint using a retaining ring, and which enables the shaft to be stably pulled out when a predetermined pulling force is applied to the shaft, thereby enabling maintenance work including shaft removal to be carried out efficiently. [Means for solving the problem]

[0009] The present invention, which has been devised to achieve the above object, A shaft retaining structure for a constant velocity universal joint comprising: an inner joint member of a constant velocity universal joint having an axial hole for inserting a shaft; a shaft having an annular retaining ring groove formed on its outer diameter surface and positioned within the axial hole; and a retaining ring attached to the retaining ring groove in a state in which the retaining ring can be elastically contracted in diameter, wherein the retaining ring is engaged with an engaging surface provided on the inner surface of the axial hole to prevent the shaft from coming off the inner joint member, and the engaging surface has a tapered shape whose diameter gradually decreases in a direction in which the shaft is pulled out of the axial hole, A feature of this invention is that an annular groove having a groove width smaller than the wire diameter of the wire material constituting the retaining ring is formed in the region of the retaining surface that is on the inner diameter side of the contact portion with the retaining ring that is retained against the retaining surface.

[0010] In a constant velocity universal joint to which the above-described retaining structure according to the present invention is applied, when an axial pull-out force exceeding the locking force (static friction force) of the retaining ring on the inner joint member (locking surface) is applied to the shaft connected to the inner joint member, the retaining ring attached to the shaft gradually reduces in diameter along the locking surface while maintaining contact with the locking surface. When the retaining ring reduces in diameter until its outer diameter becomes equal to or smaller than the minimum inner diameter of the locking surface, the retaining ring is released from contact with the locking surface, allowing the shaft to be pulled out from the inner joint member. However, in the present invention, an annular groove is provided in the locking surface in an area that is on the inner diameter side of the contact portion with the retaining ring locked on the locking surface, and therefore, in order to release the retaining ring from contact with the locking surface and pull out the shaft, it is necessary to reduce the diameter of the retaining ring so that it goes over the annular groove. Conversely, if the retaining ring cannot get over the annular groove and cannot be released from its state of being stuck in the annular groove when the diameter of the retaining ring is reduced along the locking surface, the shaft cannot be pulled out from the inner joint member, and the connected state between the shaft and the inner joint member is maintained.

[0011] Therefore, in the case of the retaining structure according to the present invention, it is only necessary to set the groove width of the annular groove and the formation position of the annular groove within the locking surface according to the axial force that enables the shaft to be pulled out from the shaft hole, and there is no need to devise a shape for the retaining ring groove provided in the shaft or to precisely control the shape accuracy of the inner wall surface of the retaining ring groove. Therefore, it is possible to prevent individual variations in the axial force required to pull out the shaft from the inner joint member as much as possible, and it is possible to stably pull out the shaft when a predetermined pull-out force is applied to the shaft.

[0012] In the above configuration, when the wire diameter of the metal wire constituting the retaining ring is d, the groove width y of the annular groove is set within the range of 0.08d to 0.4d (to satisfy the relational expression 0.08d≦y≦0.4d). This makes it possible to appropriately realize the separable retaining structure according to the present invention.

[0013] Furthermore, when the diameter of the wire material constituting the retaining ring is d, it is preferable that the groove depth z of the annular groove be 0.005d or more (z≧0.005d). In other words, the above-mentioned effects that can be obtained by the retaining structure according to the present invention can be obtained by intentionally forming an annular groove on the locking surface, rather than by fine machining marks (grooves) that inevitably occur when machining a workpiece, such as cutting or turning.

[0014] In a direction along the locking surface in an axial-parallel cross section of the joint, when the distance between the inner diameter end of the locking surface and the contact portion between the locking surface and the retaining ring is defined as w and the distance between the inner diameter end of the locking surface and the groove width center of the annular groove is defined as x, it is preferable to form the annular groove in the locking surface so as to satisfy the relational expression 0.2w≦x≦0.4w.

[0015] It is preferable to provide a rounded portion at the boundary between the annular groove and the locking surface, so that the annular groove and the locking surface are continuous via the rounded portion. This reduces or prevents wear on the retaining ring, which repeatedly slides against the locking surface (contacts the boundary between the annular groove and the locking surface) as a pull-out force is applied to the shaft, and makes it possible to stably maintain the shaft retained state. [Effects of the Invention]

[0016] From the above, according to the present invention, in a shaft retention structure in which a retaining ring is used to separably retain the shaft from the inner joint member of a constant velocity universal joint, it is possible to stably pull out the shaft when a predetermined pull-out force is applied to the shaft. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a longitudinal sectional view of a constant velocity universal joint to which a retaining structure according to an embodiment of the present invention is applied, in a state where the operating angle is 0°. [Figure 2] FIG. 2 is a partially enlarged view of FIG. [Figure 3] FIG. 3 is an enlarged view of FIG. [Figure 4] FIG. 2 is a schematic plan view of a retaining ring in a natural state. [Figure 5]FIG. 10 is a cross-sectional view showing a state in which the shaft is being pulled out from the inner joint member. [Figure 6] FIG. 1(a) is a schematic diagram illustrating the relationship between the wire diameter of the retaining ring and the groove width of the annular groove, and FIG. 1(b) is a partially enlarged view of FIG. 1(a). DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] FIG. 1 is a longitudinal cross-sectional view (axial cross-sectional view parallel to the axis) of a constant velocity universal joint 1 to which a retaining structure according to the present invention is applied, when the operating angle is 0°. FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a partially enlarged view of FIG. 2. The constant velocity universal joint 1 shown in FIG. 1 is a fixed-type constant velocity universal joint that allows only relative angular displacement between two shafts (a drive shaft and a driven shaft) to be connected, and includes an outer joint member 2, an inner joint member 3, a plurality of balls 4, and a cage 5. This constant velocity universal joint 1, together with a shaft 6 also called an "intermediate shaft" and a sliding-type constant velocity universal joint (not shown), constitutes a drive shaft of an automobile, and is disposed on the drive wheel side (outboard side) when the drive shaft is assembled in the automobile. Note that in FIG. 1, the left side of the paper is the outboard side, and the right side of the paper is the inboard side (drive source side).

[0020] The outer joint member 2 integrally has a bottomed, bowl-shaped mouth portion 21 and a shaft portion 22 extending axially outward (outboard side) from the bottom of the mouth portion 21, and a plurality of outer track grooves 24 corresponding to the number of balls 4 are formed at equal intervals in the circumferential direction on the spherical inner peripheral surface 23 of the mouth portion 21.

[0021] The inner joint member 3 is formed in an annular shape having an axial hole 33 for inserting the shaft 6, and is disposed on the inner periphery of the mouth portion 21 of the outer joint member 2. A plurality of inner track grooves 32 corresponding to the number of balls 4 are formed at equal intervals in the circumferential direction on the spherical outer peripheral surface 31 of the inner joint member 3, and torque is transmitted between the two joint members 2, 3 by the balls 4 interposed between pairs of track grooves 24, 32. The number of balls 4 is generally six or eight, but may be ten or more.

[0022] The cage 5 is made of metal or resin material and has an annular shape, and is disposed between the spherical inner peripheral surface 23 of the mouth portion 21 of the outer joint member 2 and the spherical outer peripheral surface 31 of the inner joint member 3. The cage 5 has a plurality of pockets 51 formed at equal intervals in the circumferential direction, each of which individually accommodates (holds) the balls 4.

[0023] A cylindrical boot 10 functioning as a sealing member is provided between the mouth portion 21 of the outer joint member 2 and the shaft 6, and a large-diameter cylindrical portion 10a and a small-diameter cylindrical portion 10b provided at one and the other axial ends of the boot 10 are fastened and fixed to the outer diameter surfaces of the mouth portion 21 and the shaft 6 using boot bands 11. This prevents leakage of lubricant such as grease sealed in the internal space of the mouth portion 21 and the intrusion of foreign matter into the internal space.

[0024] A tip end 61 on one axial side (outboard side) of the shaft 6 is inserted into the axial hole 33 of the inner joint member 3. A male spline 62 is formed on the outer diameter surface of the tip end 61, and the male spline 62 is made up of a plurality of axially extending convex portions and concave portions alternately arranged in the circumferential direction. The male spline 62 is fitted (spline fitted) with a female spline 34 formed on the inner diameter surface of the axial hole 33. As a result, torque is transmitted between the inner joint member 3 and the shaft 6.

[0025] An annular retaining ring groove 63 is formed on the outer diameter surface of the tip end 61 of the shaft 6 and is disposed inside the axial hole 33, and a retaining ring 7 that prevents the shaft 6 from coming off from the inner joint member 3 is attached to this retaining ring groove 63 in a state in which the diameter can be elastically contracted. Two inner wall surfaces that are spaced apart in the axial direction and define the retaining ring groove 63 (that hold the retaining ring 7 from both axial sides) are each formed as a flat surface that extends in a radial direction perpendicular to the axial direction.

[0026] An abutment portion against which a retaining ring 7 fitted in the retaining ring groove 63 abuts is provided on the inner diameter surface of the shaft hole 33 in a region on one axial side of the region where the female spline 34 is formed. This abutment portion has a cylindrical surface 35 extending substantially parallel to the axial direction and a locking surface 36 provided between the cylindrical surface 35 and the female spline 34. The cylindrical surface 35 is located on the outer diameter side of the bottom of the axially extending recess that constitutes the female spline 34, and the locking surface 36 is formed as a tapered surface whose diameter gradually decreases in the direction in which the shaft 6 inserted in the shaft hole 33 is pulled out of the shaft hole 33 (to the right on the paper surface of FIGS. 1-3 ). The retaining ring 7 is locked (in axial contact) at a predetermined position on the locking surface 36 to prevent the shaft 6 from coming out.

[0027] As shown in Fig. 4, for example, a C-shaped metal part having a slit 7a in a portion of the circumferential direction is used as the retaining ring 7. Such a retaining ring 7 is also called a "circlip" or a "snap ring." The retaining ring 7 has an outer diameter D in its natural state that is set larger than the diameter D1 (see Fig. 2) of the inscribed circle of the female spline 34 (a circular orbit connecting the inner diameter ends of the convex portions constituting the female spline 34) formed on the inner diameter surface of the insertion hole 33, the diameter D2 (see Fig. 2) of the circumscribed circle of the male spline 62 (a circular orbit connecting the outer diameter ends of the convex portions constituting the male spline 62), and the diameter D3 (see Fig. 2) of the cylindrical surface 35 constituting the abutting portion, and is elastically deformable to reduce in diameter until its outer diameter becomes equal to or smaller than the diameter D1 of the inscribed circle.

[0028] Due to the structure of the constant velocity universal joint 1, the shaft 6 is assembled to the inner joint member 3 after the inner joint member 3, the plurality of balls 4, and the cage 5 are assembled into the mouth portion 21 of the outer joint member 2. Specifically, a retaining ring 7 is fitted to a retaining ring groove 63 provided in the tip end portion 61 of the shaft 6, and then the tip end portion 61 is inserted into the shaft hole 33 from the inboard opening of the shaft hole 33 in a state where the retaining ring 7 is elastically contracted in diameter, and the retaining ring 7 is positioned within the axial range of the abutment portion. As a result, the retaining ring 7 expands in diameter due to its own elastic restoring force, and its outer diameter portion abuts against the cylindrical surface 35. Therefore, when no pull-out force is acting on the shaft 6 connected to the inner joint member 3 so as to be able to transmit torque, the retaining ring 7 fitted in the retaining ring groove 63 of the shaft 6 abuts against (the abutment portion provided on) the inner joint member 3 in the radial and axial directions. This configuration increases the pull-out strength of the shaft 6.

[0029] The retaining structure for the shaft 6 using the retaining ring 7 employed in this embodiment is a so-called separable type, which can prevent the shaft 6 from coming out of the axial hole 33 of the inner joint member 3 when an axial force (axial pull-out force) of the order of the static load that is unavoidably applied to the shaft 6 while the automobile is being driven, etc., but can also allow the shaft 6 to come out of the axial hole 33 when an axial impact load (instantaneous large load) is applied to the shaft 6 during maintenance work (for example, replacement of the boot 10), etc. Hereinafter, a characteristic configuration employed in the separable retaining structure of this embodiment will be described.

[0030] As shown in Figs. 2 and 3, of the tapered locking surface 36 provided on the inner diameter of the axial hole 33 of the inner joint member 3, an annular groove 38 having a semicircular cross section and a groove width y (see Fig. 6) smaller than the linear dimension d (see Fig. 6) of the wire material constituting the retaining ring 7 is formed in an area on the inner diameter side of a contact portion P with the retaining ring 7 locked onto the locking surface 36 (the contact point of the retaining ring 7 with the locking surface 36 when no pull-out force is applied to the shaft 7).

[0031] In the retaining structure of the present embodiment, the retaining ring 7 attached to the retaining ring groove 63 of the shaft 6 is brought into contact with (the cylindrical surface 35 and the locking surface 36 provided on) the inner joint member 3, thereby preventing the shaft 6 from coming off from the inner joint member 3. When an axial pulling force exceeding the static friction force of the retaining ring 7 against the inner joint member 3 is applied to the shaft 6, the retaining ring 7 gradually reduces in diameter along the locking surface 36 while maintaining contact with the locking surface 36 of the inner joint member 3.

[0032] 5, when the outer diameter of the retaining ring 7 is reduced to a value equal to or smaller than the minimum inner diameter of the locking surface 36 (here, the diameter D1 of the inscribed circle of the female spline 34: see FIG. 2), the retaining ring 7 is released from contact with the locking surface 36, and the shaft 7 can be pulled out of the axial hole 33 of the inner joint member 3. However, in this embodiment, as described above, the annular groove 38 is provided in the region of the locking surface 36 that is on the inner diameter side of the contact portion P with the retaining ring 7 engaged with the locking surface 36. Therefore, in order to release the contact state of the retaining ring 7 with the locking surface 36 and pull out the shaft 6, it is necessary to reduce the diameter of the retaining ring 7 so that it gets over the annular groove 38. Conversely, if the retaining ring 7 cannot get over the annular groove 38 and cannot be released from its fitted state in the annular groove 38 when the retaining ring 7 is reduced in diameter along the locking surface 36, the shaft 6 cannot be pulled out of the axial hole 33 of the inner joint member 3, and the connected state therebetween is maintained.

[0033] For this reason, in the case of the separable retaining structure employed in this embodiment, when an axial force of the same magnitude as the static load inevitably applied to the shaft 6 when the automobile is driven is applied to the shaft 6 (when the retaining ring 7 moves at a low speed on the retaining surface), the retaining ring 7 cannot overcome the annular groove 38, but when an axial impact load for pulling out is applied to the shaft 6 (when the speed at which the retaining ring 7 moves on the retaining surface is faster and the kinetic energy is greater than when an axial force of the same magnitude as the static load is applied to the shaft 6), the retaining ring 7 can overcome the annular groove 38. Therefore, it is sufficient to set the groove width (y) of the annular groove 38 and the position of the annular groove 38 within the retaining surface 36, and there is no need to modify the shape of the retaining ring groove 63 of the shaft 6 or precisely control the shape accuracy of the inner wall surface of the retaining ring groove 63. Therefore, it is possible to prevent individual variations in the axial force required to pull out the shaft 6 as much as possible, and the shaft 6 can be stably pulled out by applying a predetermined pulling force.

[0034] A preferred embodiment (configuration) employed in the retaining structure of this embodiment will be described below.

[0035] First, if the annular groove 38 is too close to the inner diameter end 36a of the locking surface 36 (the inner diameter end of the convex portion that constitutes the female spline 34), there is a high possibility that the locking surface 36 (the female spline 34 provided on one axial end face) will be partially damaged. Conversely, if the annular groove 38 is too far from the inner diameter end 36a of the locking surface 36, the separation distance between the contact portion P and the annular groove 38 will be shortened, and therefore it will be impossible to ensure a sufficient travel distance (run-up distance) for the retaining ring 7, which reduces in diameter along the locking surface 36, to reach the annular groove 38. Therefore, even if a predetermined axial force that enables the shaft 6 to be pulled out is applied to the shaft 6, it may not be possible for the retaining ring 7 to reduce in diameter so as to overcome the annular groove 38. For this reason, as shown in Figure 3, in a direction B along the locking surface 36 in an axial cross section (longitudinal cross section) of the joint, when the distance between the inner diameter end 36a of the locking surface 36 and the contact portion P is defined as w and the distance between the inner diameter end 36a of the locking surface 36 and the groove width center of the annular groove 38 is defined as x, it is preferable to form the annular groove 38 in the locking surface 36 so as to satisfy the relational expression 0.2w≦x≦0.4w.

[0036] Furthermore, if the groove width of the annular groove 38 is too small, the retaining ring 7 may overcome the annular groove 38 as it contracts along the locking surface 36, even if the axial pull-out force applied to the shaft 6 is approximately the same as the static load input to the shaft 6 when the vehicle is being driven. Conversely, if the groove width of the annular groove 38 is too large, the retaining ring 7 may not be able to be released from the annular groove 38 as it contracts along the locking surface 36, even if an axial force for pulling out the shaft 6 is applied to the shaft 6. Therefore, as shown in FIG. 6 , when the wire diameter of the wire material constituting the retaining ring 7 is d, the groove width y of the annular groove 38 is preferably set within a range of 0.08d to 0.4d (so as to satisfy the relational expression 0.08d≦y≦0.4d).

[0037] 6(a), when the wire diameter of the wire material constituting the retaining ring 7 is d, the groove depth z of the annular groove 38 provided in the locking surface 36 is preferably 0.005d or more (z≧0.005d). That is, to realize the retaining structure according to the present embodiment described above, it is necessary to intentionally form a groove (annular groove 38) in the locking surface 36, rather than leaving minute machining marks (grooves) that inevitably occur when a workpiece is machined, for example, by cutting or turning. The locking surface 36 including the annular groove 38 can be formed, for example, by turning the base material of the inner joint member 3 using a forming tool (for example, a forming tool) that corresponds to the shape of the locking surface 36.

[0038] 6(b), in this embodiment, a rounded portion 39 is provided at the boundary between the annular groove 38 and the locking surface 36, and (the inner surface of) the annular groove 38 and the locking surface 36 are continuous via the rounded portion 39. This makes it possible to suppress or prevent wear of the retaining ring 7, which repeatedly slides against the locking surface 36 (contact between the inner surface of the annular groove 38 and the boundary between the locking surface 36) as axial force is applied to the shaft 6, and therefore makes it possible to stably maintain a retained state of the shaft 6.

[0039] Although the constant velocity universal joint (fixed type constant velocity universal joint 1) including the shaft retaining structure according to the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this. For example, the shaft retaining structure according to this embodiment can be applied not only to fixed type constant velocity universal joints, but also to retaining the shaft from the inner joint member constituting a sliding type constant velocity universal joint.

[0040] The present invention is not limited to the above-described embodiments, and may be embodied in various forms without departing from the spirit of the present invention. The scope of the present invention is defined by the claims, and includes the equivalent meanings of the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0041] 1 Fixed constant velocity universal joint 2 Outer joint member 3 Inner joint member 4 balls 5 Cage 6 shafts 7 Retaining ring 35 Cylindrical Surface 36 Locking surface 38 Annular groove 39 R-bu 63 Retaining ring groove d Wire diameter D Outer diameter of retaining ring in natural state P contact part y Annular groove width z Annular groove depth

Claims

1. A shaft retaining structure for a constant velocity universal joint comprising: an inner joint member of a constant velocity universal joint having an axial hole for inserting a shaft; a shaft having an annular retaining ring groove formed on its outer diameter surface and positioned within the axial hole; and a retaining ring attached to the retaining ring groove in a state in which the retaining ring can be elastically contracted in diameter, wherein the retaining ring is engaged with an engaging surface provided on the inner surface of the axial hole to prevent the shaft from coming off the inner joint member, and the engaging surface has a tapered shape whose diameter gradually decreases in a direction in which the shaft is pulled out of the axial hole, A shaft retention structure for a constant velocity universal joint, characterized in that an annular groove having a groove width smaller than the wire diameter of the wire constituting the retaining ring is formed in an area of ​​the retaining surface that is on the inner diameter side of the contact portion with the retaining ring that is engaged with the retaining surface.

2. 2. A shaft retaining structure for a constant velocity universal joint according to claim 1, wherein the groove width of said annular groove is within a range of 0.08d to 0.4d, where d is the wire diameter of said wire material.

3. 2. A shaft retaining structure for a constant velocity universal joint according to claim 1, wherein the depth of said annular groove is 0.005d or more, where d is the diameter of said wire rod.

4. 2. A shaft anti-slip structure for a constant velocity universal joint as described in claim 1, wherein, in a direction along the locking surface in an axial cross section of the joint, when the distance between the inner diameter end of the locking surface and the contact point of the locking surface with the retaining ring is w and the distance between the inner diameter end of the locking surface and the groove width center of the annular groove is x, the relationship 0.2w≦x≦0.4w is satisfied.

5. 2. A shaft retaining structure for a constant velocity universal joint according to claim 1, wherein a rounded portion is provided at the boundary between said annular groove and said locking surface.

6. A constant velocity universal joint comprising the shaft retaining structure for a constant velocity universal joint according to claim 1.

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