Tripod type constant velocity universal joint

Abstract

To provide a tripod type constant velocity universal joint that is improved in workability in fitting to a fitting groove of a snap ring.SOLUTION: A tripod type constant velocity universal joint 1 of a double roller type includes snap rings 14, 15 for regulating movement of an inner ring 12 in an axial direction of a leg shaft 32 which are provided in an inner periphery of an outer ring 11. The snap rings 14, 15 are fitted to a fitting groove 11a formed in an inner peripheral surface of the outer ring 11. A first tapered surface 11d1 and a second tapered surface 11d2 having different inclination angles are provided in a corner part between an end surface 11c and an inner peripheral surface 11b of the outer ring 11.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a tripod-type constant velocity universal joint used for power transmission in automobiles and various industrial machines. [Background technology]

[0002] In driveshafts used in automotive power transmission systems, a sliding-type constant velocity universal joint is often connected to the inboard side (the center side in the vehicle width direction) of the intermediate shaft, and a fixed-type constant velocity universal joint is connected to the outboard side (the end side in the vehicle width direction).The sliding-type constant velocity universal joint here allows both angular displacement and relative axial movement between the two shafts, while the fixed-type constant velocity universal joint allows angular displacement between the two shafts but does not allow relative axial movement between the two shafts.

[0003] A tripod-type constant velocity universal joint is well known as a sliding-type constant velocity universal joint. This tripod-type constant velocity universal joint is available in single roller and double roller types. The single roller type has rollers inserted into track grooves of an outer joint member, which are rotatably attached to the trunnions of the tripod members via multiple needle rollers. The double roller type has rollers inserted into track grooves of an outer joint member and inner rings fitted onto the trunnions of the tripod members to rotatably support the rollers. The double roller type allows the rollers to oscillate relative to the trunnions, which has the advantage of reducing induced thrust (axial force induced by friction between parts inside the joint) and sliding resistance compared to the single roller type.

[0004] An example of a double-roller tripod constant velocity universal joint is disclosed in Patent Document 1 listed below. In such a double-roller tripod constant velocity universal joint, the rollers are rotatably arranged on the outer periphery of an inner ring via needle rollers. The needle rollers and inner ring are prevented from coming off by a pair of snap rings attached to the inner circumferential surface of the rollers. That is, a pair of mounting grooves are formed on the inner circumferential surface of the rollers, spaced apart in the leg axis direction at a distance corresponding to the length of the needle rollers, and a snap ring is fitted into each of these mounting grooves.

[0005] This snap ring is fitted into the mounting groove of the roller by elastically contracting its diameter. As shown in Fig. 18, Patent Document 2 below discloses that when fitting the snap ring into the mounting groove 111a, the edge portion 115 has an R-curved cross-sectional shape with tangents to the inner peripheral surface 111b of the roller 111 and the inner wall surface 111a1 of the mounting groove 111a so that the snap ring does not get caught on the edge portion 115 of the mounting groove 111a. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-320563 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-97853 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with the configuration of Patent Document 2, depending on the shape of the end S of the inner peripheral surface, which is the entrance side when the snap ring is inserted into the inner periphery of the roller, the snap ring may get caught on the roller, preventing the snap ring from being smoothly assembled into the mounting groove. Also, because the snap ring is made of soft steel and the roller is made of hardened hard steel, burrs may be generated from the snap ring if it gets caught during installation, and these may become foreign matter and impair the operability of the tripod type constant velocity universal joint.

[0008] While it is possible to avoid these problems by sufficiently reducing the diameter of the snap ring when it is installed into the mounting groove, if the snap ring is excessively reduced in diameter when automating the installation process, it will undergo plastic deformation and become unusable. Therefore, the amount of reduction in the diameter of the snap ring during installation must be kept to a minimum. Because there is a limit to the amount of reduction that can be tolerated in a snap ring, it is difficult to solve the above problems with the current configuration.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a tripod-type constant velocity universal joint in which the workability of attaching a snap ring to an attachment groove is improved. [Means for solving the problem]

[0010] The present invention, which has been made based on the above findings, provides an outer joint member having track grooves at three locations in the circumferential direction of the joint, each of the track grooves having a pair of roller guideways arranged opposite to each other in the circumferential direction of the joint; a tripod member having a body portion having a center hole and three trunnions protruding in the radial direction of the body portion; rollers attached to the trunnions; and an inner ring fitted onto the trunnions and supporting the rollers rotatably, wherein the rollers are movable in the axial direction of the outer joint member along the roller guideways, and the rollers and the inner ring constitute a roller unit that can swing with respect to the trunnion, a snap ring is provided on the inner periphery of the roller to restrict movement of the inner ring in the axial direction of the trunnion, and the snap ring is fitted into a mounting groove formed on the inner periphery of the roller, in a tripod type constant velocity joint, a first tapered surface and a second tapered surface having different inclination angles are provided at a corner between the end face and the inner periphery of the roller, and the first tapered surface is connected to the end face of the roller, and the second tapered surface is connected to the cylindrical inner periphery of the roller, When the snap ring is in its natural state, the outer peripheral surface of the snap ring is located on the outer diameter side of the outer diameter end of the first tapered surface, an arc portion is provided between the first tapered surface and the second tapered surface, and the first tapered surface and the second tapered surface are arranged in tangential directions to both ends of the arc portion. It is characterized by:

[0011] With this configuration, the angle between the end face of the roller and the first tapered surface, the angle between the first tapered surface and the second tapered surface, and the angle between the second tapered surface and the inner circumferential surface of the roller are all large obtuse angles, which prevents the snap ring from getting caught on an edge when it moves between two adjacent surfaces, improving the ease of assembly of the snap ring.

[0012] Also, This makes it possible to more effectively prevent the snap ring from getting caught while it transitions from the first tapered surface to the second tapered surface.

[0013] It is preferable that the inclination angle of the first tapered surface relative to the end face of the outer ring and the inclination angle of the second tapered surface relative to the inner peripheral surface of the outer ring are both set to 10° to 25°. This increases the inter-plane angles at the boundary between the first tapered surface and the end face and at the boundary between the second tapered surface and the inner peripheral surface, and also increases the inter-plane angles between the first tapered surface and the second tapered surface, making it even more difficult for the snap ring to get caught.

[0014] It is preferable that the inner surface of the inner ring is formed into an arc-shaped convex surface in a longitudinal section of the inner ring, the outer surface of the trunnion is straight in a longitudinal section including the axis of the trunnion and is approximately elliptical in a cross section perpendicular to the axis of the trunnion, and the outer surface of the trunnion abuts against the inner surface of the inner ring in a direction perpendicular to the axis of the joint, and a gap is formed between the outer surface of the trunnion and the inner surface of the inner ring in the axial direction of the joint.

[0015] It is preferable to dispose a plurality of rolling elements between the inner ring and the roller, and needle rollers, for example, can be used as the rolling elements. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a tripod type constant velocity universal joint in which the workability of attaching a snap ring to an attachment groove is improved. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view of a double-roller type tripod constant velocity universal joint taken along the joint axis. [Figure 2] FIG. 2 is a cross-sectional view taken along line KK in FIG. 1. [Figure 3] FIG. 2 is a cross-sectional view taken along line LL in FIG. [Figure 4] 2 is a cross-sectional view showing a state in which the tripod constant velocity universal joint of FIG. 1 has an operating angle. [Figure 5] 3 is a plan view of the roller unit attached to the leg shaft as viewed from the direction A in FIG. 2. FIG. [Figure 6] FIG. 4 is a cross-sectional view of the roller unit taken along the axial direction of the leg shaft. [Figure 7] FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along line MM in FIG. 7. [Figure 9] FIG. 4 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of the outer ring. [Figure 10] 10A to 10C are cross-sectional views taken along the axial direction of the trunnion, illustrating the process of attaching a snap ring to a roller unit. [Figure 11] FIG. 4 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of the outer ring. [Figure 12] FIG. 4 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of the outer ring. [Figure 13] FIG. 4 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of the outer ring. [Figure 14] FIG. 4 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of the outer ring. [Figure 15] FIG. 4 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of the outer ring. [Figure 16] FIG. 10 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of an outer ring in a comparative example. [Figure 17] FIG. 10 is an enlarged cross-sectional view showing an inner diameter corner portion on one axial side of an outer ring in a comparative example. [Figure 18] FIG. 10 is a cross-sectional view showing a conventional outer ring. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of a tripod type constant velocity universal joint according to the present invention will be described with reference to FIGS.

[0019] The tripod type constant velocity universal joint 1 of this embodiment shown in Figures 1 to 4 is of a double roller type. Note that Figure 1 is an axial cross-sectional view of the double roller type tripod type constant velocity universal joint, and Figure 2 is a cross-sectional view taken along line KK in Figure 1. Figure 3 is a cross-sectional view taken along line LL in Figure 1, and Figure 4 is an axial cross-sectional view showing the tripod type constant velocity universal joint when an operating angle is taken. Note that in the following description, the joint axial direction and joint circumferential direction respectively refer to the axial direction and circumferential direction of the tripod type constant velocity universal joint when the operating angle is set to 0°.

[0020] As shown in Figures 1 and 2, the tripod type constant velocity universal joint 1 is mainly composed of an outer joint member 2, a tripod member 3 as an inner joint member, and a roller unit 4 as a torque transmission member. The outer joint member 2 is cup-shaped with one end open, and has three linear track grooves 5 extending in the joint axial direction formed on its inner peripheral surface at equal intervals in the joint circumferential direction. Each track groove 5 is formed with a roller guide surface 6 that is arranged opposite to each other in the joint circumferential direction of the outer joint member 2 and extends in the joint axial direction. The tripod member 3 and the roller unit 4 are housed inside the outer joint member 2.

[0021] The tripod member 3 integrally comprises a body portion 31 (trunnion body portion) having a center hole 30, and three trunnion journals 32 protruding radially from positions equally dividing the outer circumferential surface of the body portion 31 in the joint circumferential direction. The tripod member 3 is coupled to the shaft 8 so as to be able to transmit torque, by fitting a male spline 81 formed on the shaft 8 serving as an axis into a female spline 34 formed in the center hole 30 of the body portion 31. The tripod member 3 is fixed to the shaft 8 in the joint axial direction by engaging an end face on one side of the tripod member 3 in the joint axial direction with a shoulder portion 82 provided on the shaft 8, and engaging a retaining ring 10 attached to the tip of the shaft 8 with an end face on the other side of the tripod member 3 in the joint axial direction.

[0022] The roller unit 4 is mainly composed of an outer ring 11, which is an annular roller centered on the axis of the trunnion 32, an annular inner ring 12 arranged on the inner diameter side of the outer ring 11 and fitted around the trunnion 32, and a large number of rolling elements 13 interposed between the outer ring 11 and the inner ring 12. In this embodiment, full-complement needle rollers without cages are used as an example of the rolling elements 13. The roller unit 4 is housed in the track grooves 5 of the outer joint member 2. As will be described in detail later, the roller unit 4, which is made up of the outer ring 11, inner ring 12, and needle rollers 13, is structured to not disassemble naturally by means of steel snap rings 14 and 15.

[0023] In this embodiment, the outer peripheral surface of the outer ring 11 (see FIG. 2) is a convex curved surface whose generating line is an arc having a center of curvature on the axis of the trunnion 32. The outer peripheral surface of the outer ring 11 is in angular contact with the roller guideway 6.

[0024] The needle rollers 13 are arranged rollably between the cylindrical inner peripheral surface of the outer ring 11 as the outer raceway surface and the cylindrical outer peripheral surface of the inner ring 12 as the inner raceway surface.

[0025] The outer peripheral surface of each trunnion 32 of the tripod member 3 has a straight shape in the axial direction of the trunnion 32 in a cross section in any direction including the axis of the trunnion 32. Also, as shown in FIG. 3, the outer peripheral surface of the trunnion 32 has a substantially elliptical shape in a cross section perpendicular to the axis of the trunnion 32. The outer peripheral surface of the trunnion 32 contacts the inner peripheral surface 12a of the inner ring 12 in a direction perpendicular to the joint axial direction, i.e., in the direction of the major axis a. In the joint axial direction, i.e., in the direction of the minor axis b, a gap m is formed between the outer peripheral surface of the trunnion 32 and the inner peripheral surface 12a of the inner ring 12.

[0026] As shown in FIGS. 1 and 2, an intermediate portion 33 between the body portion 31 and the leg shaft 32 of the tripod member 3 is formed so as to describe a concave curve in any cross section including the axis of the leg shaft 32.

[0027] The inner peripheral surface 12a of the inner ring 12 forms a convex arc shape in any cross section including the axis of the inner ring 12. Because of this, and because the cross section of the trunnion 32 is generally elliptical as described above and a predetermined gap m is provided between the trunnion 32 and the inner ring 12, the inner ring 12 is able to swing relative to the trunnion 32. As described above, the inner ring 12 and the outer ring 11 are assembled via the needle rollers 13 so as to be relatively rotatable, and therefore the outer ring 11 can swing integrally with the inner ring 12 relative to the trunnion 32. In other words, the axes of the outer ring 11 and the inner ring 12 can tilt relative to the axis of the trunnion 32 within a plane including the axis of the trunnion 32 (see Figure 4).

[0028] As shown in Figure 4, when the tripod type constant velocity universal joint 1 rotates through an operating angle, the axis of the tripod member 3 is inclined relative to the axis of the outer joint member 2, but because the roller unit 4 is swingable, it is possible to prevent the outer ring 11 and the roller guideway 6 from intersecting at an angle. As a result, the outer ring 11 rolls horizontally relative to the roller guideway 6, which makes it possible to reduce induced thrust and sliding resistance, thereby enabling the tripod type constant velocity universal joint 1 to achieve low vibration.

[0029] As already mentioned, the cross section (transverse section) of the trunnion 32 is substantially elliptical and the cross section (longitudinal section) of the inner peripheral surface 12a of the inner ring 12 is an arc-shaped convex cross section, so that the outer peripheral surface of the trunnion 32 on the torque load side and the inner peripheral surface 12a of the inner ring 12 come into point contact (including contact over a small area close to point contact) at contact point X, as shown in Figure 3. This reduces the force that tends to tilt the roller unit 4, improving the stability of the posture of the outer ring 11.

[0030] 5 is a plan view of the roller unit 4 attached to the trunnion 32 as viewed from the direction A in FIG. 2, and FIG. 6 is a cross-sectional view of the roller unit 4 along the axial direction of the trunnion 32. As shown in FIG.

[0031] 5 and 6, in the roller unit 4, mounting grooves 11a are formed on the inner peripheral surface of the outer ring 11 so as to be spaced apart in the axial direction of the trunnion 32. Snap rings 14, 15 are fitted into these mounting grooves 11a and attached to the inner peripheral surface 11b of the outer ring 11 so as to be spaced apart in the axial direction of the trunnion 32. These snap rings 14, 15 face the end faces of the needle rollers 13 and the inner ring 12 on both sides in the axial direction of the trunnion 32, and the snap rings 14, 15 restrict relative movement of the needle rollers 13 and the inner ring 12 with respect to the outer ring 11 in the axial direction of the trunnion 32. Therefore, the snap rings 14, 15 restrict spontaneous disassembly of the roller unit 4.

[0032] FIG. 7 is a plan view of the snap rings 14, 15, and FIG. 8 is a cross-sectional view of the snap rings 14, 15 taken along line MM in FIG. 7. As shown in FIG. 7, the snap rings 14, 15 have a slit C (a gap in the circumferential direction) and are formed as ended rings divided by the slit C. The snap rings 14, 15 have a shape in which a strip plate is wound around an axis extending in the thickness direction of the snap ring. The slit C extends in a direction inclined relative to the radial direction of the snap rings 14, 15. As shown in FIG. 8, the snap rings 14, 15 have a width b and a thickness t, and are formed as a rectangular cross section where b>t.

[0033] The characteristic configuration of this embodiment will be described below. FIG. 9 is an enlarged cross-sectional view of an inner diameter corner portion on one axial side of the outer ring 11. As shown in FIG. 9, a boundary surface 11d is formed between the cylindrical inner peripheral surface 11b of the outer ring 11 and an end face 11c on one axial side of the outer ring 11. The boundary surface 11d includes two annular tapered surfaces 11d1 and 11d2 having different inclination angles with respect to a common reference plane (e.g., end face 11c), and an annular first arc portion 11d3 interposed between the two tapered surfaces 11d1 and 11d2. The first tapered surface 11d1 and the second tapered surface 11d2 are located at different positions in the axial direction of the outer ring 11 (hereinafter referred to as the "ring axial direction"), and the two tapered surfaces 11d1 and 11d2 are arranged so as to form a mountain. The first tapered surface 11d1 and the second tapered surface 11d2 both extend in a tangential direction of the first arc portion 11d3.

[0034] The first tapered surface 11d1 is connected to an end face 11c on one side in the ring axial direction, and the second tapered surface 11d2 is connected to an inner peripheral surface (flange surface) 11b of the outer ring 11. A boundary 11e between the first tapered surface 11d1 and the end face 11c forms an edge, and a boundary 11f between the second tapered surface 11d2 and the inner peripheral surface 11c also forms an edge. The inclination angle α1 of the first tapered surface 11d1 with respect to the end face 11c and the inclination angle α2 of the second tapered surface 11d2 with respect to the inner peripheral surface 11b are both set in the range of 10° to 25°.

[0035] The mounting groove 11a is formed with a pair of inner wall surfaces 11a1, 11a2 that face each other in the ring axial direction. A second circular arc portion 11g is formed between the inner peripheral surface 11b of the outer ring 11 and the inner wall surface 11a1 on one side in the ring axial direction of the mounting groove 11a. The boundary between the second circular arc portion 11g and the inner peripheral surface 11b and the boundary between the second circular arc portion 11g and the inner wall surface 11a1 on one side in the ring axial direction both form edges.

[0036] The inner peripheral surface 11b and the boundary surface 11d of the outer ring 11 are turned surfaces finished by turning, or grinding surfaces finished by grinding. The first tapered surface 11d1, the second tapered surface 11d2, and the first arc portion 11d3 are formed by turning or simultaneously ground by a form grinding wheel having a shape corresponding to these surfaces. In the case of simultaneous grinding by a form grinding wheel, the boundary surface 11d can be formed as a smooth surface (a surface without an edge). The groove bottom surface and the inner wall surface 11a1 of the mounting groove 11a, and the second arc portion 11g are turned surfaces finished by turning.

[0037] The length dimension P of the boundary surface 11d in the ring axis direction is preferably smaller than the thickness dimension t of the snap ring 14 (P < t). Specifically, the length dimension P of the boundary surface 11d is preferably about 0.2 mm to 0.6 mm. The width dimension Q of the boundary surface 11d in the ring radial direction is preferably about 0.2 mm to 0.6 mm, similar to the length dimension P. Further, the radius of curvature of the first arc portion 11d3 is preferably about 0.1 mm to 0.6 mm.

[0038] In the above description, the shape near the inner diameter corner on one side in the ring axis direction of the outer ring 11 has been described. However, the shape near the inner diameter corner on the other side in the ring axis direction of the outer ring 11 also has the same shape as that in FIG. 9. That is, on both sides in the ring axis direction of the outer ring 11, the contours of the mounting groove 11a, the inner peripheral surface 11b, and the boundary surface 11d are in a line-symmetrical relationship with the center line O-O (see FIG. 6) in the width direction of the outer ring 11 as the axis of symmetry.

[0039] FIG. 10 shows the mounting process of the snap ring 14 to the roller unit 4 in a cross-sectional view along the axial direction of the leg shaft 32. Hereinafter, the mounting process of the snap ring 14 on the outer diameter side of the joint will be described. However, the snap ring 15 on the inner diameter side of the joint is also mounted through the same mounting process.

[0040] As shown in FIG. 10 , the snap ring 14 is attached to the mounting groove 11a on the inner circumferential surface 11b of the outer ring 11 by applying a radially reducing force to the snap ring 14 using a jig 51 placed on the end face 11c of the outer ring 11 while applying an axial pressing force F to the snap ring 14 using an actuator or the like, while the outer ring 11, the inner ring 12, and the needle rollers 13 are assembled together. In this embodiment, this attachment process is automated. By applying a radially reducing force to the snap ring 14 from the jig 51, the snap ring 14 elastically contracts in the direction of arrow Y and deforms into a spiral shape until both ends 21, 22 (see FIG. 7 ) overlap and the outer diameter φD of the snap ring 14 (the diameter dimension in its natural state when no external force is applied) becomes equal to or smaller than the inner diameter φd of the outer ring 11. In this state, the snap ring 14 is inserted into the inner periphery of the outer ring 11, whereby the snap ring 14 is attached to the mounting groove 11a. It should be noted that the jig 51 in FIG. 10 is conceptually shown and differs from the actual configuration.

[0041] The detailed process for attaching the snap ring 14 will be described below with reference to Figures 11 to 15. Figures 11 to 15 are enlarged cross-sectional views showing an inner diameter corner portion on one axial side of the outer ring 11, and the jig 51 is not shown in any of the figures.

[0042] First, as shown in FIG. 11 , the snap ring 14 in its natural state is accommodated on the inner periphery of a jig 51, and the snap ring 14 is positioned on one axial end face 11c of the outer ring 11. In this state, the outer peripheral surface of the snap ring 14 is positioned on the outer diameter side of the outer diameter end of the first tapered surface 11d1. Next, the snap ring 14 is reduced in diameter by the jig 51 while applying an axial pressing force F to the snap ring 14. As a result, as shown in FIG. 12 , the snap ring 14 reduces in diameter and moves over the edge-like boundary 11e between the first tapered surface 11d1 and the end face 11c, sliding over the first tapered surface 11d1. Even when the snap ring 14 moves over the edge-like boundary 11e between the first tapered surface 11d1 and the end face 11c, the snap ring 14 moves over the first tapered surface 11d1 without getting caught on the boundary 11e because the angle between the first tapered surface 11d1 and the end face 11c is an obtuse angle (less than 180°).

[0043] By further reducing the diameter of snap ring 14 using jig 51 while applying axial pressing force F to snap ring 14, snap ring 14 passes over first circular arc portion 11d3 and slides on second tapered surface 11d2, as shown in Fig. 13. Even when snap ring 14 passes over first circular arc portion 11d3, because the angle between first tapered surface 11d1 and second tapered surface 11d2 is an obtuse angle and, further, first circular arc portion 11d3 is interposed between the two tapered surfaces, with both tapered surfaces 11d1 and 11d2 as its tangent, snap ring 14 can reduce its diameter without getting caught on first circular arc portion 11d3 and move onto second tapered surface 11d2.

[0044] When the snap ring 14 is further reduced in diameter by the jig 51 while applying an axial pressing force F to the snap ring 14, the snap ring 14 moves over the edge-like boundary 11f and slides on the inner circumferential surface 11b of the outer ring 11, as shown in FIG. 14. Even when the snap ring 14 moves over the boundary 11f between the second tapered surface 11d2 and the inner circumferential surface 11b, the snap ring 14 is able to reduce in diameter and move to the inner circumferential surface 11b without getting caught on the boundary 11f, because the angle between the second tapered surface 11d2 and the inner circumferential surface 11b is an obtuse angle. The application of a diameter-reducing force to the snap ring 14 by the jig 51 ends at this stage.

[0045] Further application of axial pressing force F to snap ring 14 causes snap ring 14 to slide on second arcuate portion 11g and elastically expand its diameter to fit into mounting groove 11a, as shown in Figure 15. This completes the installation of snap ring 14. After installation, the outer peripheral surface of snap ring 14 comes into contact with the bottom surface of mounting groove 11a.

[0046] Next, the roller unit 4 is turned over in the axial direction, and the snap ring 15 on the other axial side is attached to the attachment groove 11a on the other axial side in the same manner, completing the roller unit 4. Note that the order in which the snap ring 14 on the outer diameter side of the joint and the snap ring 15 on the inner diameter side of the joint shown in Figure 1 are attached to the outer ring 11 is arbitrary; one of the snap rings can be attached first, and then the other snap ring can be attached.

[0047] In the installation process described above, the radial reduction force applied to the snap rings 14, 15 is dominated by the radial reduction force applied by the jig 51, but the horizontal component of the pressing force F generated by pressing the snap rings 14, 15 against the first tapered surface 11d1 and the second tapered surface 11d2 also constitutes part of the radial reduction force.

[0048] As described above, in this embodiment, the boundary surface 11d, which includes a first tapered surface 11d1 and a second tapered surface 11d2, is provided at the corner between the inner circumferential surface 11b and the end face 11c of the outer ring 11. Furthermore, both tapered surfaces 11d1 and 11d2 are arranged so that the inner diameter of the outer ring 11 gradually decreases from the first tapered surface 11d1 to the second tapered surface. In this case, the angle between the end face 11c and the first tapered surface 11d1, the angle between the first tapered surface 11d1 and the second tapered surface 11d2, and the angle between the second tapered surface 11d2 and the inner circumferential surface 11b are all large obtuse angles less than 180°. This prevents the snap ring 14 from getting caught on an edge when moving between adjacent surfaces, improving the ease of assembly of the snap ring 14.

[0049] In particular, in this embodiment, the first arc portion 11d3 is positioned between the first tapered surface 11d1 and the second tapered surface 11d2, and the first tapered surface 11d1 and the second tapered surface 11d2 are positioned along the tangential directions of both ends of the first arc portion 11d3, which makes it possible to more effectively prevent the snap ring 14 from getting caught while it transitions from the first tapered surface 11d1 to the second tapered surface 11d2.

[0050] 16 and 17 show comparative examples of this embodiment. Fig. 16 shows a comparative example in which the inner peripheral surface 11b' and the end surface 11c' of the outer ring 11' are directly connected without an intervening boundary surface, while Fig. 17 shows a comparative example in which a chamfer 53 is provided between both surfaces 11b' and 11c'.

[0051] In the comparative example shown in FIG. 16 , when inserting the snap ring 14, the snap ring 14′ is likely to get caught on the edge E1 between the inner circumferential surface 11b′ and the end face 11c′. In the comparative example shown in FIG. 17 , the angle between the chamfer 53 and the end face 11c′ and the angle between the chamfer 53 and the inner circumferential surface 11b′ are small, so the snap ring is likely to get caught on the respective edges E2 and E3 during installation. In contrast, in this embodiment, by providing a boundary surface 11d including a first tapered surface 11d1 and a second tapered surface 11d2 between the inner circumferential surface 11b and the end face 11c of the outer ring 11, the angle between the boundary surface 11e between the first tapered surface 11d1 and the end face 11c and the angle between the second tapered surface 11d2 and the inner circumferential surface 11b are larger than the angles between the edges E2 and E3 in the comparative example shown in FIG. 17 . Therefore, it becomes even more difficult for the snap ring 14 to get caught at the boundaries 11e and 11f.

[0052] In order to increase the inter-surface angle at the boundary 11e between the first tapered surface 11d1 and the end face 11c and at the boundary 11f between the second tapered surface 11d2 and the inner peripheral surface 11b, and further to increase the inter-surface angle between the first tapered surface 11d1 and the second tapered surface 11d2, it is preferable to set the inclination angle α1 of the first tapered surface 11d1 relative to the end face 11c and the inclination angle α2 of the second tapered surface 11d2 relative to the inner peripheral surface 11b in the range of 10° to 25°.

[0053] The above-described embodiments of the present invention can also be applied to double-roller type tripod constant velocity universal joints having other configurations.

[0054] For example, the outer peripheral surface of the trunnion 32 can be formed into a convex curved surface (e.g., a convex arc-shaped cross section), and the inner peripheral surface 12a of the inner ring 12 can be formed into a cylindrical surface. Alternatively, the outer peripheral surface of the trunnion 32 can be formed into a convex curved surface (e.g., a convex arc-shaped cross section), and the inner peripheral surface 12a of the inner ring 12 can be formed into a concave spherical surface that fits into the outer peripheral surface of the trunnion. In this case, by providing a flange on at least one of the two end portions of the outer ring, one of the snap rings 14 can be made unnecessary.

[0055] The application of the tripod constant velocity universal joint 1 described above is not limited to the drive shaft of an automobile, but can be widely used in power transmission paths of automobiles, industrial equipment, and the like. [Explanation of symbols]

[0056] 1 Tripod-type constant velocity universal joint 2 Outer joint member 3 Tripod member 4 Roller unit 5 Track groove 6 Roller guideway 11 Laura (Outering) 11a Mounting groove 11b Inner surface 11c End face 11d Boundary surface 11d1 First tapered surface 11d2 Second tapered surface 11d3 Arc section (first arc section) 12 Inner Ring 13 Needle roller 14 Snap ring 15 snap ring 31 Torso 32 Leg axis

Claims

1. an outer joint member provided with track grooves extending in a joint axial direction at three positions in a circumferential direction, each of the track grooves having a pair of roller guide surfaces arranged opposite to each other in the joint circumferential direction; a tripod member including a body portion having a central hole and three leg shafts protruding in a radial direction of the body portion; a roller attached to each of the leg shafts; an inner ring fitted onto the trunnion shaft and supporting the roller rotatably; the rollers are movable in the axial direction of the outer joint member along the roller guide surfaces, the roller and the inner ring constitute a roller unit that can swing relative to the trunnion; A tripod-type constant velocity universal joint in which a snap ring is provided on an inner periphery of the roller to restrict movement of the inner ring in the axial direction of the trunnion, and the snap ring is fitted into a mounting groove formed on the inner periphery of the roller, a first tapered surface and a second tapered surface having different inclination angles are provided at a corner between the end face and the inner peripheral surface of the roller, the first tapered surface being connected to the end face of the roller, and the second tapered surface being connected to the cylindrical inner peripheral surface of the roller; a tripod-type constant velocity universal joint characterized in that, in a natural state of the snap ring, the outer peripheral surface of the snap ring is located on the outer diameter side of the outer diameter end of the first tapered surface, an arc portion is provided between the first tapered surface and the second tapered surface, and the first tapered surface and the second tapered surface are arranged in tangential directions to both ends of the arc portion.

2. 2. The tripod-type constant velocity universal joint according to claim 1, wherein the inclination angle of the first tapered surface relative to the end face of the roller and the inclination angle of the second tapered surface relative to the inner peripheral surface of the roller are both set to 10° to 25°.

3. 3. A tripod-type constant velocity universal joint according to claim 1, wherein the inner peripheral surface of the inner ring is formed into an arc-shaped convex surface in a longitudinal section of the ring, the outer peripheral surface of the trunnion is straight in a longitudinal section including the axis of the trunnion and is substantially elliptical in a cross section perpendicular to the axis of the trunnion, the outer peripheral surface of the trunnion abutting against the inner peripheral surface of the inner ring in a direction perpendicular to the axis of the joint, and a gap is formed between the outer peripheral surface of the trunnion and the inner peripheral surface of the ring in the axial direction of the joint.

4. 4. The tripod type constant velocity universal joint according to claim 1, wherein a plurality of rolling elements are disposed between said inner ring and said rollers.

5. 5. A tripod type constant velocity universal joint according to claim 4, wherein said rolling elements are needle rollers.

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