Torque transmission device and constant velocity universal joint

Abstract

To provide a torque transmission device in which the degree of freedom of a shaft processing system corresponding to a non-disassembly type coming-off prevention structure is enhanced.SOLUTION: The torque transmission device 2 includes a shaft 19 having a male spline 21, an inner joint member 12 having a female spline 22 and coupled to the shaft 19 in a torque transmittable manner by fitting of the male spline 21 and the female spline 22, and a retaining ring 24 housed in an annular recessed groove 23 formed in the shaft 19. The retaining ring 24 comes into contact with an end surface 22a of the female spline 22 and a side surface 23a of the annular recessed groove 23 on the shaft tip side, so that the shaft 19 is prevented from coming off. The 22a of the end face of the female spline 22 is expanded toward the tip side of the shaft. A groove bottom surface 23c of the annular recessed groove 23 is inclined so as to be diametrically expanded toward the shaft tip side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a torque transmission device used in the power transmission systems of automobiles, aircraft, ships, various industrial machines, etc., which transmits torque by fitting a male spline with a female spline, and to a constant velocity universal joint having such a torque transmission device. [Background technology]

[0002] A known example of a mechanical element using the torque transmission device described above is a constant velocity universal joint that allows angular displacement between two shafts on a driving side and a driven side. For example, in the drive shaft of an automobile, it is necessary to accommodate angular displacement and axial displacement due to changes in the relative positional relationship between the engine (or motor) and the wheels. Therefore, a sliding type constant velocity universal joint that allows both angular displacement and relative axial movement between the two shafts is used on the inboard side (the center side in the vehicle width direction), and a fixed type constant velocity universal joint that allows angular displacement between the two shafts but does not allow relative axial movement between the two shafts is used on the outboard side (the outside in the vehicle width direction).

[0003] In a drive shaft, a sliding type constant velocity universal joint and a fixed type constant velocity universal joint are connected via a shaft. The torque transmission devices described above are provided between the shaft and the inner joint member of the sliding type constant velocity universal joint, and between the shaft and the inner joint member of the fixed type constant velocity universal joint, respectively.

[0004] This type of torque transmission device typically includes a retaining structure to prevent the shaft from slipping out of the inner joint member. In this retaining structure, an annular groove is formed in the tip end of the shaft, and an abutment portion is formed at the end of the axial hole of the inner joint member. With an elastically contractible retaining ring attached to the annular groove of the shaft, the tip end of the shaft is inserted into the axial hole of the inner joint member. When the contracted retaining ring reaches the abutment portion of the inner joint member, the retaining ring is expanded in diameter by its elastic restoring force and abuts against the abutment portion of the inner joint member, thereby preventing the shaft from slipping out.

[0005] In this type of retaining structure, a non-disassembly structure is known in which the inner joint member and the shaft cannot be disassembled after the shaft is retained (Patent Document 1 and Patent Document 2).

[0006] In the anti-slip structure of Patent Document 1, an annular groove step is provided closer to the tip of the shaft than the annular groove of the shaft, and when an axial pulling force is applied, the retaining ring is pressed against the edge between the annular groove step and the side surface of the annular groove to prevent the shaft from slipping out.

[0007] Patent Document 2 discloses a retaining structure in which the side of the annular groove at the tip end of the shaft is formed with a locking surface that extends from the outer circumference of the shaft toward the inner diameter and is inclined with respect to a plane perpendicular to the axial direction, and a wall surface that is formed adjacent to the locking surface and extends toward the inner diameter and is parallel to the plane perpendicular to the axial direction. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 4964146 [Patent Document 2] Patent No. 6284712 Summary of the Invention [Problem to be solved by the invention]

[0009] The anti-slip structures described in Patent Documents 1 and 2 are both non-disassembly type anti-slip structures achieved by changing the shape of the outer diameter region of the side surface of the annular groove provided in the shaft at the tip end of the shaft.

[0010] There are two possible machining procedures for shafts compatible with a retaining structure: forming an annular groove in the shaft material by turning or other processes, then forming a male spline in the shaft material by plastic processing, such as rolling or press forming; or forming a male spline in the shaft material by plastic processing, and then forming the annular groove by turning. However, the former procedure has the problem that the outer diameter region of the side surface of the annular groove at the tip of the shaft, which is important for achieving a non-disassembly retaining structure, is deformed during plastic processing, reducing the precision of that region. This makes it difficult to consistently ensure the non-disassembly of the retaining structure. To avoid this, the latter procedure is necessary, which restricts the processing sequence and reduces the flexibility of the processing sequence.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a torque transmission device that increases the degree of freedom in the processing sequence of the inner member (shaft) that is compatible with a non-disassembly type retaining structure. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, the present invention provides a torque transmission device comprising an inner member having a male spline, an outer member having a female spline and coupled to the inner member so as to be able to transmit torque by fitting the male spline to the female spline, and a retaining ring housed in an annular groove formed in the inner member, wherein the retaining ring contacts an end face on one axial side of the female spline and a side face on one axial side of the annular groove to prevent the inner member from coming off, and the end face of the female spline is inclined so as to expand in diameter toward one axial side, characterized in that the groove bottom surface of the annular groove is inclined so as to expand in diameter toward one axial side.

[0013] With this configuration, when a pull-out force is applied to the inner member, the resultant force of the reaction force acting on the retaining ring from the end face of the female spline and the reaction force acting on the retaining ring from the groove bottom of the annular groove acts in the radially outward direction. This direction corresponds to the narrowing side of the wedge gap formed by the end face of the female spline and the side surface on one axial side of the annular groove. Therefore, even if a large pull-out force is applied to the inner member, the retaining ring does not elastically deform in the radially expanding direction. This restricts disassembly of the inner member and the outer member, resulting in a non-disassembly retaining structure. Even when plastic processing is performed to form the male spline on the inner member, the groove bottom is less susceptible to plastic flow. Furthermore, annular grooves with inclined groove bottoms can be easily formed by turning or other processes. Therefore, when manufacturing the inner member, it is possible to select either a procedure of forming the annular groove in the blank and then forming the male spline, or a procedure of forming the male spline in the blank and then forming the annular groove, depending on the situation. This increases the flexibility of the inner member's processing sequence.

[0014] It is preferable that the angle of inclination of the groove bottom surface of the annular groove relative to a plane perpendicular to the axial direction be larger than the angle of inclination of the end surface of the female spline relative to a plane perpendicular to the axial direction.

[0015] The bottom surface of the annular groove may be formed of a separate member that is detachable from the inner member, thereby enabling the retaining structure to be switched between a non-detachable type and a detachable type.

[0016] The inner member may be a shaft, and the outer member may be an inner joint member of a constant velocity universal joint.

[0017] The inner member may be a stem portion provided on an outer joint member of a constant velocity universal joint, and the outer member may be a side gear of a differential.

[0018] The constant velocity universal joint can be provided with the torque transmission device described above. [Effects of the Invention]

[0019] As described above, according to the present invention, it is possible to increase the degree of freedom in the processing sequence of the inner member corresponding to the non-disassembly type retaining structure. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view of a constant velocity universal joint equipped with a torque transmission device. [Figure 2] FIG. 2 is an enlarged cross-sectional view of part A in FIG. [Figure 3] FIG. 10 is a cross-sectional view showing an insertion step of inserting a shaft into the inner periphery of the inner joint member. [Figure 4] FIG. 10 is a cross-sectional view showing a state after a shaft has been inserted into the inner periphery of the inner joint member. [Figure 5] FIG. 10 is a cross-sectional view showing a state in which a pulling force is applied to the shaft. [Figure 6] FIG. 10 is a cross-sectional view showing another embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing another embodiment. [Figure 8] FIG. 4 is a front view of the ring member as viewed from the axial direction. [Figure 9] FIG. 10 is a cross-sectional view showing another example of a mechanism having a torque transmission device. DETAILED DESCRIPTION OF THE INVENTION

[0021] Fig. 1 shows a cross-sectional view in the joint axis direction of a constant velocity universal joint 1 equipped with a torque transmission device 2 according to the present invention. In Fig. 1, a Rzeppa constant velocity universal joint (BJ), which is a type of fixed constant velocity universal joint, is shown as an example of constant velocity universal joint 1, but constant velocity universal joint 1 may be a fixed constant velocity universal joint other than the Rzeppa type (for example, an undercut-free constant velocity universal joint (UJ)), or may be a double offset constant velocity universal joint (DOJ), which is a sliding constant velocity universal joint, a tripod constant velocity universal joint (TJ), or a cross groove constant velocity universal joint, etc.

[0022] 1 , the constant velocity universal joint 1 is mainly composed of an outer joint member 11, an inner joint member 12, and balls 13 as torque transmission members that transmit torque between the outer joint member 11 and the inner joint member 12. The constant velocity universal joint of this embodiment has a structure including: the outer joint member 11, which is cup-shaped with one open end and has track grooves 15 extending in the axial direction formed at a plurality of positions on a spherical inner peripheral surface 16 at equal intervals in the circumferential direction; the inner joint member 12, which has track grooves 17 extending in the axial direction formed at a plurality of positions on a spherical outer peripheral surface 18 at equal intervals in the circumferential direction, paired with the track grooves 15 of the outer joint member 11; balls 13 disposed between the track grooves 15 of the outer joint member 11 and the track grooves 17 of the inner joint member 12; and a cage 14 interposed between the spherical inner peripheral surface 16 of the outer joint member 11 and the spherical outer peripheral surface 18 of the inner joint member 12 to hold the balls 13. The number of balls 13 can be selected arbitrarily, such as six or eight.

[0023] A shaft 19 is coupled to the inner joint member 12. In the case of, for example, an automobile drive shaft, the shaft 19 serves to transmit torque from a sliding-type constant velocity universal joint (not shown) to the fixed-type constant velocity universal joint 1 shown in FIG. 1. A male spline 21 is formed on the outer peripheral surface of the shaft 19, and a female spline 22 is formed on the inner peripheral surface of the inner joint member 12. As shown in FIG. 2, an annular groove 23 whose bottom has a smaller diameter than the small-diameter portion (valley portion) of the male spline 21 is formed in a region on one axial side of the male spline 21 (the side opposite to the direction in which a pull-out force F acts on the shaft 19: hereinafter referred to as the "shaft tip side"), and a retaining ring 24 is accommodated in this annular groove 23. The male spline 21 and the female spline 22 are fitted together to couple the inner joint member 12 and shaft 19 so as to transmit torque. The term "spline" also includes serrations.

[0024] In this embodiment, the torque transmission device 2 is composed of a shaft 19 (inner member) having a male spline 21 and an inner joint member 12 (outer member) having a female spline 22. The torque transmission device 2 is provided with a retaining ring 24. The retaining ring 24 is elastically contractible in diameter and has a C-shape when viewed from the axial direction. A circlip, for example, can be used as the retaining ring 24.

[0025] 2, an end face 22a of the female spline 22 on the shaft tip side forms a tapered surface that is inclined so that the diameter increases toward the shaft tip side. Side faces 23a, 23b on both axial sides of the annular groove 23 extend in a direction perpendicular to the axial direction, and when a pull-out force F is applied to the shaft 19, the end face 22a of the female spline 22 is located between the both side faces 23a, 23b. On the inner circumferential surface of the inner joint member 12, a cylindrical relief portion 25 having a diameter larger than the large-diameter portion 22b (valley portion) of the female spline 22 is formed on the shaft tip side of the end face 22a of the female spline 22.

[0026] When the shaft 19 is assembled into the inner joint member 12, the shaft 19 is inserted into the inner periphery of the inner joint member 12 in a state in which the maximum outer diameter dimension S (radial dimension) of the retaining ring 24 housed in the annular groove 23 is reduced to be equal to or smaller than the minor diameter dimension Ds (radial dimension) of the female spline 22, as shown in Fig. 3 . When the shaft 19 is pushed forward in the direction of the arrow, the retaining ring 24 elastically expands in diameter until it comes into contact with the inner periphery of the recess 25 when it faces the recess 25, as shown in Fig. 4 . In this state, when a pull-out force F is applied to the shaft 19 in the direction of the arrow, as shown in Fig. 5 , the retaining ring 24 comes into contact with the end face 22 a of the female spline 22 and the side face 23 a of the annular groove 23 on the shaft tip side, thereby preventing the shaft 19 from coming out of the inner joint member 12.

[0027] In this embodiment, as shown in FIG. 2, the groove bottom surface 23c of the annular concave groove 23 is inclined with respect to the axial direction so that the diameter increases toward the tip end side of the shaft. In this case, the groove bottom surface 23c has a conical surface shape with a larger diameter toward the tip end side of the shaft. The inclination angle θ of the groove bottom surface 23c of the annular concave groove 23 with respect to the plane orthogonal to the axial direction is larger than the inclination angle ω of the end surface 22a of the female spline 22 with respect to the plane orthogonal to the axial direction (θ > ω).

[0028] In the state shown in FIG. 5, when a pulling force F is applied to the shaft, the resultant force P1 of the reaction force acting on the retaining ring 24 from the end surface 22a of the female spline 22 and the reaction force acting on the retaining ring 24 from the side surface 23a on the tip end side of the shaft of the annular concave groove 23 acts in the inner diameter direction. Therefore, the retaining ring 24 elastically contracts in diameter, and as shown in FIG. 2, the retaining ring 24 comes into contact with the groove bottom surface 23c of the annular concave groove 23. That is, the retaining ring 24 contacts the shaft 19 at three points: the end surface 22a of the female spline 22, the side surface 23a on the tip end side of the shaft of the annular concave groove 23, and the groove bottom surface 23c.

[0029] In the state shown in FIG. 2, the resultant force P2 of the reaction force acting on the retaining ring 24 from the end surface 22a of the female spline 22 and the reaction force acting on the retaining ring from the groove bottom surface 23c acts in the outer diameter direction, and this direction is the narrowing side of the wedge clearance formed by the end surface 22a of the female spline 22 and the side surface 23a on the tip end side of the shaft of the annular concave groove 23. Therefore, even if the pulling force F is increased, the retaining ring 24 does not deform in the diameter expansion direction or the diameter contraction direction, and the state shown in FIG. 2 is maintained. Therefore, even when an excessive pulling force F acts on the shaft 19, the disassembling of the shaft 19 and the inner joint member 12 is restricted. Thereby, the retaining structure of the shaft 19 becomes non-detachable.

[0030] In addition, in the embodiment shown in FIG. 2, the minimum outer diameter dimension d min (radius dimension) of the groove bottom surface 23c is smaller than the value obtained by subtracting the wire diameter dimension R (diameter dimension) of the retaining ring 24 from the small diameter dimension Ds of the female spline 22 (d min < Ds - R). The maximum outer diameter dimension d maxis smaller than the minor diameter dimension Ds of the female spline 22 and is larger than the value obtained by subtracting the wire diameter dimension R (diameter dimension) of the retaining ring 24 from the minor diameter dimension Ds (Ds-R <d max <Ds)。

[0031] In the above configuration, the only shape change required to achieve a non-disassembly retaining structure is the shape of the groove bottom surface 23c of the annular groove 23. As shown in FIG. 2, the entire groove bottom surface 23c has a smaller diameter than the small-diameter portion 21a of the male spline 21, so the groove bottom surface 23c is less susceptible to plastic flow when plastic processing is performed to form the male spline 21. Furthermore, the annular groove 23 with an inclined groove bottom surface 23c can be easily formed by turning or other processing. Therefore, when manufacturing the shaft 19, it is possible to select either a procedure in which the annular groove 23 is formed in the shaft material and then the male spline 21 is formed, or a procedure in which the male spline 21 is formed in the shaft material and then the annular groove 23 is formed, depending on the situation. This increases the flexibility of the processing sequence for the shaft 19.

[0032] Another embodiment is shown in Figures 6 and 7. In this embodiment, the bottom surface 231 of the annular groove 23 is formed into a cylindrical surface. A ring member 26 having an outer peripheral surface formed into a conical surface is fitted into this annular groove 23. The inclination direction of the outer peripheral surface of the ring member 26 conforms to the groove bottom surface 23c shown in Figure 2. Other configurations of this embodiment are common to the embodiment shown in Figures 1 to 5.

[0033] In this embodiment, the tapered groove bottom surface 23c of the annular groove 23 is formed on the outer peripheral surface of the ring-shaped member 26. This makes it possible to provide a non-disassembly type retaining structure that allows for a high degree of freedom in processing sequences, similar to the embodiment shown in Figures 1 to 5.

[0034] On the other hand, as shown in Fig. 7, when the ring member 26 is removed from the annular groove 23, the annular groove 23 has the same shape as a conventional general annular groove, with both side surfaces 23a, 23b perpendicular to the axial direction and a bottom surface 231 that is cylindrical. Therefore, when a pull-out force F is applied to the shaft 19, a resultant force P3 of the reaction force acting on the retaining ring 24 from the end surface of the female spline 22 and the reaction force acting on the retaining ring 24 from the side surface 23a of the annular groove 23 on the shaft tip side acts in the inner diameter direction. In this case, the application of the pull-out force F allows the retaining ring 24 to elastically contract to or below the minor diameter dimension Ds of the female spline 22. Therefore, by increasing the pull-out force F, the shaft 19 can be pulled out from the inner joint member 12. This makes it possible to realize a disassembly-type retaining structure that allows the inner joint member 12 and the shaft 19 to be disassembled. As described above, according to this embodiment, by attaching and detaching the ring member 26, it is possible to switch the retaining structure between a non-disassembly type and a disassembly type.

[0035] 8, it is preferable that the ring member 26 has a notch 26a formed in a portion of its circumference so that the diameter can be elastically expanded and contracted. This allows the ring member 26 to be attached to and detached from the annular groove 23. For example, a circlip (retaining ring) can be used as the ring member 26.

[0036] Although the torque transmission device 2 including the shaft 19 and the inner joint member 12 of the fixed type constant velocity universal joint 1 has been described above, the scope of application of the present invention is not limited thereto. For example, as shown in FIG. 9 , when the stem portion 31 a of the outer joint member 31 of the inboard constant velocity universal joint 3 (sliding type constant velocity universal joint) constituting the drive shaft is coupled to the inner periphery of the side gear 41 of the differential gear 4, the side gear 41 (outer member) and the stem portion 31 a (inner member) are coupled by the engagement of the male spline 21 and the female spline 22. A retaining ring 24 is accommodated in an annular groove 23 provided on the tip side of the stem portion 31 a, and the retaining ring 24 is brought into contact with the end face of the female spline 22, thereby preventing the stem portion 31 a from coming off. In this torque transmission device 2, by inclining the groove bottom of the annular groove 23 as shown in FIG. 2 , a non-disassembly retaining structure with increased flexibility in processing sequences can be obtained. 6 can be attached to and detached from the annular groove 23. The retaining structure can be switched between a non-detachable type and a detachable type. Reference numeral 42 in FIG. 9 denotes a differential case. [Explanation of symbols]

[0037] 1 Fixed constant velocity universal joint 2. Torque transmission device 3 Sliding constant velocity universal joint 11 Outer joint member 12 Inner joint member (outer member) 19 Shaft (inner member) 21 male spline 22 female splines 22a End face 23 Circular groove 23a side 23b Side 23c Groove bottom surface 24 retaining ring

Claims

1. a retaining ring received in an annular groove formed in the inner member, wherein the retaining ring contacts an end face of the female spline on one axial side and a side face of the annular groove on one axial side, thereby preventing the inner member from slipping out; and a torque transmission device comprising: an inner member having male splines; an outer member having female splines and coupled to the inner member so as to be able to transmit torque by fitting the male splines with the female splines; and a retaining ring received in an annular groove formed in the inner member, wherein the retaining ring contacts an end face of the female spline on one axial side and a side face of the annular groove on one axial side, the end face of the female spline being inclined so as to increase in diameter toward the one axial side, A torque transmission device characterized in that the groove bottom surface of the annular groove is inclined so that the diameter increases toward one side in the axial direction.

2. 2. The torque transmission device according to claim 1, wherein the inclination angle of the groove bottom surface of the annular groove relative to a plane perpendicular to the axial direction is larger than the inclination angle of the end surface of the female spline relative to a plane perpendicular to the axial direction.

3. 2. The torque transmission device according to claim 1, wherein the bottom surface of the annular groove is formed by a separate member that is detachable from the inner member.

4. 2. The torque transmission device according to claim 1, wherein said inner member is a shaft and said outer member is an inner joint member of a constant velocity universal joint.

5. 2. A torque transmission device according to claim 1, wherein the inner member is a stem portion provided on an outer joint member of a constant velocity universal joint, and the outer member is a side gear of a differential.

6. A constant velocity universal joint comprising the torque transmission device according to any one of claims 1 to 5.

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