Tripod-type constant-velocity universal joint

Abstract

A tripod-type constant-velocity universal joint comprises: an outer joint member provided with three circumferentially spaced, axially extending track grooves, each of the track grooves having a pair of roller guide surfaces that are arranged opposite each other in the circumferential direction; a tripod member provided with three leg shafts that protrude in a radial direction; and rollers inserted into the track grooves, the rollers being configured to be capable of moving in the axial direction of the outer joint member along the roller guide surfaces. In the outer peripheral surface of each roller, cylindrical parts having cylindrical surface shapes are provided on both sides sandwiching the widthwise center of the roller, and a recess that is recessed relative to the outer peripheral surfaces of the cylindrical parts is provided between the cylindrical parts. In each roller guide surface, flat surface parts having flat surface shapes are provided on both sides sandwiching the widthwise center of the roller, and a protrusion that protrudes relative to the end surfaces of the flat surface parts and engages with the recesses of the rollers is provided between the flat-surface parts.

Description

Tripod constant velocity joint

[0001] The present invention relates to a tripod constant velocity joint.

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

[0003] A tripod constant velocity joint is known as a sliding constant velocity joint. As this tripod constant velocity joint, there are a single roller type and a double roller type. An example of the double roller type tripod constant velocity joint is described in, for example, Patent Document 1 and Patent Document 2. The double roller type tripod constant velocity joint includes a roller inserted into a track groove of an outer joint member and an inner ring that fits externally onto a leg shaft of a tripod member and rotatably supports the roller, and has an advantage that it can achieve reduction of induced thrust (axial force induced by friction between components inside the joint) and slide resistance compared to the single roller type.

[0004] Japanese Patent Application Laid-Open No. 2000-320563 Japanese Patent Application Laid-Open No. 2019-132316

[0005] In a conventional double roller type tripod constant velocity joint, the outer peripheral surface of the roller is substantially spherical or substantially annular, and the roller guide surface (rolling surface of the roller) of the track groove of the outer ring has a circular contact with a contact ratio following the shape of the roller outer diameter, or an angular contact shape having a contact ratio and a contact angle.

[0006] Therefore, due to its structure, when the tripod-type constant velocity universal joint rotates at an operating angle, the unit 104 (roller unit) including the roller 111 and inner ring 112 may tilt to the left or right on a cross section perpendicular to the joint axis direction, as shown in Figure 13, or it may tilt to the front or back on a cross section parallel to the joint axis direction, as shown in Figure 14.

[0007] When tilting occurs from side to side or front to back, the direction of travel of the roller 111 may differ from the orientation of the roller 111, or the outer diameter end face 111a of the roller 111 may come into contact with the bottom of the track groove 105, or the outer circumference of the roller 111 may come into contact with the unloaded roller guide surface 106' of the track groove 105 (the direction of rotation is indicated by arrows in Figure 13). As a result, rolling resistance increases, and the induced force and sliding resistance of the constant velocity universal joint increase. All of these factors worsen the NVH characteristics of the automobile.

[0008] Furthermore, in the case of circular contact or angular contact shapes, when the torque applied to the coupling becomes unloaded (or nearly unloaded) during high-speed rotation, the centrifugal force pushes the roller 111 toward the outer diameter side. As shown in Figure 15, a wedge effect occurs at the wedge angle between the roller 111 and the roller guide surface 106, causing the roller 111 and the roller guide surface 106 to bite together, which raises concerns about increased rolling resistance.

[0009] As shown in Patent Document 2, some rollers have a cylindrical outer surface to suppress lateral tilting, but since they do not have a mechanism to suppress front-to-back tilting, front-to-back tilting is more likely to occur, which can actually increase rolling resistance.

[0010] Therefore, the present invention aims to reduce the rolling resistance of the rollers and reduce vibration in a double-roller type tripod-type constant velocity universal joint.

[0011] The first tripod-type constant velocity universal joint of the present invention comprises an outer joint member having track grooves extending axially at three locations in the circumferential direction, each track groove having a pair of roller guide surfaces arranged opposite to each other in the circumferential direction, a tripod member having three leg shafts projecting radially, a roller inserted into the track grooves, and an inner ring fitted onto the leg shafts and supporting the roller rotatably, wherein the roller is configured to move in the axial direction of the outer joint member along the roller guide surfaces, characterized in that cylindrical portions are provided on both sides of the outer circumferential surface of the roller, sandwiching the center in the width direction of the roller, and recesses are provided between the cylindrical portions, recesses that are recessed from the outer circumferential surface of the cylindrical portions, and flat portions are provided on both sides of the roller guide surface, sandwiching the center in the width direction of the roller, and protrusions are provided between the flat portions, protruding from the end faces of the flat portions and engaging with the recesses.

[0012] In the first tripod-type constant velocity universal joint described above, when a torque load is applied, the cylindrical portion of the roller and the flat surface portion of the outer joint member make line contact, thereby suppressing the lateral tilting phenomenon of the roller. Furthermore, as the roller rolls on the track of the outer joint member, the recess of the roller's outer diameter and the convex portion of the outer joint member come into contact, correcting the forward and backward tilt of the roller. In this case, when the roller rolls toward the outer diameter side of the outer joint member, the inner diameter side of the convex portion of the outer joint member comes into contact with the recess of the roller's outer diameter, and the frictional force acts as a brake, changing the direction of the roller, thus avoiding further contact and preventing an increase in rolling resistance. When the roller rolls in the opposite direction (i.e., toward the inner diameter of the outer joint member), the outer diameter side of the convex portion of the outer joint member comes into contact with the recess of the roller's outer diameter, changing the direction of the roller. This makes it possible to keep the roller horizontal to the track groove, preventing unnecessary contact between the roller and the outer joint member outside of the torque transmission points, and thus avoiding a further increase in rolling resistance.

[0013] The second tripod-type constant velocity universal joint of the present invention comprises an outer joint member having track grooves extending axially at three locations in the circumferential direction, each track groove having a pair of roller guide surfaces arranged opposite to each other in the circumferential direction, a tripod member having three leg shafts projecting radially, a roller inserted into the track grooves, and an inner ring fitted onto the leg shafts and supporting the roller rotatably, wherein the roller is configured to move in the axial direction of the outer joint member along the roller guide surfaces, characterized in that cylindrical portions are provided on both sides of the outer circumferential surface of the roller, sandwiching the widthwise center of the roller, and protrusions are provided between the cylindrical portions, protruding from the outer circumferential surface of the cylindrical portions, and flat portions are provided on both sides of the roller guide surface, sandwiching the widthwise center of the roller, and recesses are provided between the flat portions, recessed from the end faces of the flat portions, into which the protrusions engage.

[0014] In the second tripod-type constant velocity universal joint described above, when a torque load is applied, the cylindrical portion of the roller and the flat surface portion of the outer joint member make line contact, thereby suppressing the lateral tilting phenomenon of the roller. Furthermore, as the roller rolls on the track of the outer joint member, the convex portion of the roller's outer diameter contacts the concave portion of the outer joint member, thereby correcting the forward and backward tilt of the roller. In this case, when the direction of travel of the roller is toward the outer diameter side of the outer joint member, the outer diameter side of the convex portion of the roller's outer diameter contacts the concave portion of the outer joint member, changing the orientation of the roller, avoiding further contact, and preventing an increase in rolling resistance. When the roller rolls in the opposite direction (i.e., toward the inner diameter of the outer joint member), the inner diameter side of the convex portion of the roller's outer diameter contacts the concave portion of the outer joint member, changing the orientation of the roller. This makes it possible to keep the roller horizontal to the track groove, preventing unnecessary contact between the roller and the outer joint member outside of the torque transmission point, and preventing a further increase in rolling resistance.

[0015] In the above configuration, it is preferable that the contact angle between the side surface of the protrusion and the recess be 20° or more and 60° or less, and more preferably 35° or more and 45° or less. If the contact angle is less than 20°, when the roller moves towards the outer diameter side due to centrifugal force in an unloaded state, the non-loaded side also makes contact, and there is a concern that the rolling resistance of the roller will increase due to the occurrence of a wedge effect. If it exceeds 60°, the wedge effect is reduced, but the forging formability of the outer joint member deteriorates, and there is a concern that shape defects and a reduction in mold life may occur.

[0016] As a tripod-type constant velocity universal joint, it is also possible to use one in which the outer surface of the leg shaft is formed as a convex curved surface and the inner surface of the inner ring is formed as a cylindrical surface, or one in which the outer surface of the leg shaft is formed as a convex curved surface and the inner surface of the inner ring is formed as a concave curved surface.

[0017] In the above configuration, a guide surface may be provided within the track groove of the outer joint member to guide the axial outer end surface of the roller. When the axial outer end surface of the roller and the guide surface come into contact, the restraining force against changes in the roller's posture is increased, so that even if the gap between the convex and concave portions is large, for example, the forward and backward tilt of the roller can be suppressed. In other words, the deterioration of the roller's rolling resistance and NVH can be suppressed more stably. In addition, by reducing the volume inside the outer joint member, the amount of lubricating grease contained can be reduced, and the overall mass and cost can be reduced.

[0018] According to the present invention, in a double-roller type tripod-type constant velocity universal joint, it is possible to reduce the rolling resistance of the rollers and achieve low vibration.

[0019] This is a longitudinal cross-sectional view of the first embodiment of a tripod-type constant velocity universal joint. This is a partial transverse cross-sectional view taken along the line K-K in Figure 1. This is a transverse cross-sectional view taken along the line L-L in Figure 1. This is a longitudinal cross-sectional view of the tripod-type constant velocity universal joint in Figure 1 in the operating angle position. This is an enlarged transverse cross-sectional view showing the contact area between the outer ring and the roller guide surface in Figure 2. This is an enlarged transverse cross-sectional view showing the main part of the contact area between the outer ring and the roller guide surface in Figure 5. This is an enlarged transverse cross-sectional view showing the contact area between the outer ring and the roller guide surface of a tripod-type constant velocity universal joint of the second embodiment. This is an enlarged transverse cross-sectional view showing the contact area between the outer ring and the roller guide surface when the guide surface is provided in the track groove of the outer joint member in Figure 5. This is a partial enlarged view showing another form of the guide surface, when it is provided on the roller guide surface side. This is a partial enlarged view showing another form of the guide surface, when it is provided at a position spaced apart from the roller guide surface. This is an enlarged transverse cross-sectional view showing the contact area between the outer ring and the roller guide surface, showing a different form from the concave and convex parts in Figure 5. This is a transverse cross-sectional view of a tripod-type constant velocity universal joint according to another embodiment. This is a cross-sectional view of a tripod-type constant velocity universal joint according to another embodiment. This is a cross-sectional view of a tripod-type constant velocity universal joint illustrating left-right tilt. This is a longitudinal cross-sectional view of a tripod-type constant velocity universal joint illustrating front-back tilt. This is a cross-sectional view of a tripod-type constant velocity universal joint illustrating wedge angle.

[0020] A first embodiment of the tripod-type constant velocity universal joint according to the present invention will be described with reference to Figures 1 to 6.

[0021] The tripod-type constant velocity universal joint 1 of this embodiment is a double-roller type. As shown in Figures 1 and 2, the main parts of this tripod-type constant velocity universal joint 1 consist 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 three linear track grooves 5 extending axially are formed on its inner circumferential surface at equal intervals in the circumferential direction. Each track groove 5 has a roller guide surface 6 that is positioned opposite to the outer joint member 2 in the circumferential direction and extends axially from the outer joint member 2. The tripod member 3 and the roller unit 4 are housed inside the outer joint member 2.

[0022] The tripod member 3 has three radially protruding leg shafts 7. The tripod member 3 is coupled to the shaft 9 in a torque-transmitting manner by fitting a male spline 24 formed on the shaft 9 into a female spline 23 formed in the central hole 8. The tripod member 3 is fixed axially to the shaft 9 by engaging a retaining ring 10 attached to the tip of the shaft 9 with the end face of the tripod member 3.

[0023] The roller unit 4 mainly consists of an outer ring 11 which is a roller, a cylindrical inner ring 12 which is positioned inside the outer ring 11 and fitted onto the leg shaft 7, and a number of needle-shaped rollers 13 interposed between the outer ring 11 and the inner ring 12, and is housed in the track groove 5 of the outer joint member 2.

[0024] The inner circumferential surface 12a of the inner ring 12 is convex, specifically, it is convex in the shape of a circular arc in a longitudinal cross-section including the axis of the inner ring 12. The roller unit 4, consisting of the inner ring 12, needle rollers 13, and outer ring 11, is designed to remain inseparable by washers 14 and 15.

[0025] The outer circumferential surface of each leg shaft 7 of the tripod member 3 is straight in a longitudinal cross-section that includes the axis O-O of the leg shaft 7. Also, as shown in Figure 3, the outer circumferential surface of the leg shaft 7 is substantially elliptical in a cross-section perpendicular to the axis O-O of the leg shaft 7. The outer circumferential surface of the leg shaft 7 is in contact with the inner circumferential surface 12a of the inner ring 12 in a direction perpendicular to the axis of the joint, i.e., in the direction of the major axis a. In the direction of the axial direction of the joint, i.e., in the direction of the minor axis b, a gap m is formed between the outer circumferential surface of the leg shaft 7 and the inner circumferential surface 12a of the inner ring 12.

[0026] The outer ring 11 of the roller unit 4, which is mounted on the leg shaft 7 of the tripod member 3, is rotatably supported by the inner ring 12 via needle rollers 13. When the tripod-type constant velocity universal joint 1 rotates at an operating angle, the outer ring 11 rolls on the roller guide surface 6 of the track groove 5 of the outer joint member 2. Since the cross-section of the leg shaft 7 is substantially elliptical, as shown in Figure 4, when the tripod-type constant velocity universal joint 1 takes an operating angle, the axis of the tripod member 3 is inclined with respect to the axis of the outer joint member 2, but the roller unit 4 can be inclined with respect to the axis of the leg shaft 7 of the tripod member 3. Therefore, it is possible to avoid a state in which the outer ring 11 of the roller unit 4 and the roller guide surface 6 are obliquely aligned. As a result, the outer ring 11 rolls correctly with respect to the roller guide surface 6, which reduces induced thrust and sliding resistance, and enables low vibration of the joint.

[0027] As shown in an enlarged view in Figure 5, cylindrical portions 11a1 and 11a2 are formed on both sides of the outer circumferential surface of the outer ring 11, straddling the center line (P-P) in the width direction of the outer ring 11 (hereinafter referred to as the roller width direction). In the cross-section of Figure 5, the cylindrical portion 11a1 on the outer diameter side of the joint and the cylindrical portion 11a2 on the inner diameter side of the joint are symmetrical with respect to the center line (P-P) in the roller width direction.

[0028] Furthermore, on the outer circumferential surface of the outer ring 11, a recess 16 is provided between the cylindrical portions 11a1 and 11a2, which is recessed from the outer circumferential surfaces of the cylindrical portions 11a1 and 11a2. The recess 16 is continuously recessed in the circumferential direction. In this embodiment, as shown in Figure 6, the side portion 16a of the recess 16 is a tapered surface that narrows in width towards the bottom side of the recess 16, and its cross-section is trapezoidal. The recess 16 is symmetrical with respect to the center line (P-P) in the roller width direction.

[0029] As shown in Figure 5, the roller guide surface 6 has flat surface portions 6a1 and 6a2 formed on both sides of the center line (P-P) in the width direction (hereinafter referred to as the roller width direction) of the outer ring 11. In the cross-section of Figure 5, similar to the outer circumferential surface of the outer ring 11, the flat surface portion 6a1 on the outer diameter side of the joint and the flat surface portion 6a2 on the inner diameter side of the joint are symmetrical with respect to the center line (P-P) in the roller width direction.

[0030] A protrusion 17 is provided between the flat surfaces 6a1 and 6a2, projecting from the end faces of the flat surfaces 6a1 and 6a2. In this embodiment, as shown in Figure 6, the side surface 17a of the protrusion 17 is a tapered surface that narrows in width towards the tip of the protrusion 17, and its cross-section is trapezoidal. The protrusion 17 is symmetrical with respect to the center line (P-P) in the roller width direction.

[0031] In this embodiment, in the cross-section shown in Figure 5, the contours of the flat surfaces 6a1 and 6a2 of the roller guide surface 6 coincide with the contours of the cylindrical portions 11a1 and 11a2 of the outer ring 11, and the outer circumferential surface of the roller guide surface 6 is shaped to match the shape of the outer circumferential surface of the outer ring 11. Furthermore, the convex portion 17 provided on the roller guide surface 6 engages with the concave portion 16 provided on the outer ring 11.

[0032] As described above, a surface hardened layer is formed on both the outer circumferential surface of the outer ring 11 and the roller guide surface 6 by high-frequency induction hardening or the like.

[0033] During rotation of the tripod-type constant velocity universal joint 1 having the above configuration, on the load side, the cylindrical portion 11a1 on the joint outer diameter side of the outer ring 11 makes line contact with the flat surface portion 6a1 on the joint outer diameter side of the roller guide surface 6, and the cylindrical portion 11a2 on the joint inner diameter side of the outer ring 11 makes line contact with the flat surface portion 6a2 on the joint inner diameter side of the roller guide surface 6. As a result, torque is transmitted at each contact point.

[0034] Even when an operating angle is applied, the cylindrical portions 11a1 and 11a2 of the outer ring 11 make line contact with the flat surfaces 6a1 and 6a2 of the roller guide surface 6, thus suppressing the left-right tilt of the outer ring 11. Furthermore, as the outer ring 11 rolls on the track of the outer joint member, the recess 16 and the protrusion 17 come into contact, suppressing the front-back tilt of the outer ring 11. In this case, when the outer ring 11 rolls toward the outer diameter side of the joint, as shown in Figure 6, the inner diameter side of the protrusion 17 comes into contact with the recess 16, and the frictional force acts as a brake, changing the orientation of the outer ring 11, thus avoiding further contact and preventing an increase in rolling resistance. When the outer ring 11 rolls in the opposite direction (i.e., toward the inner diameter side of the joint), the outer diameter side of the protrusion 16 comes into contact with the recess 17, changing the orientation of the outer ring 11. This makes it possible to keep the roller unit 4 horizontal to the track groove 5, preventing unnecessary contact between the outer ring 11 and the outer joint member 2 at points other than the torque transmission point, thus avoiding a further increase in rolling resistance and resulting in low vibration.

[0035] If the contact angle θ between the side surface 17a of the convex portion 17 and the recess 16 is less than 20°, when the outer ring 11 moves toward the outer diameter side of the joint due to centrifugal force under no load, the non-load side also comes into contact, raising concerns about an increase in the rolling resistance of the outer ring 11 due to the wedge effect. If it exceeds 60°, the wedge effect is reduced, but the forging formability of the outer joint member deteriorates, raising concerns about shape defects and a decrease in mold life. Here, the contact angle θ refers to the angle that the tangent P2 of the contact point C between the side surface 17a of the convex portion 17 and the recess 16 makes with respect to the axis P1 of the outer surface of the cylindrical portions 11a1 and 11a2, as shown in Figure 6. Therefore, it is preferable to set the contact angle θ between the side surface 17a of the convex portion 17 and the recess 16 in the range of 20° to 60°, and more preferably to 35° to 45°.

[0036] Next, a second embodiment of the tripod-type constant velocity universal joint according to the present invention will be described with reference to Figure 7. As shown in Figure 7, in the tripod-type constant velocity universal joint of the second embodiment, similar to the first embodiment, cylindrical portions 11a1 and 11a2 are formed on both sides of the outer circumferential surface of the outer ring 11, straddling the center line (P-P) in the width direction of the outer ring 11. In addition, flat portions 6a1 and 6a2 are formed on both sides of the roller guide surface 6, straddling the center line (P-P) in the width direction of the outer ring 11.

[0037] On the other hand, in the second embodiment, as shown in Figure 7, a protrusion 18 is provided on the outer circumferential surface of the outer ring 11, between the cylindrical portions 11a1 and 11a2, protruding from the outer circumferential surfaces of the cylindrical portions 11a1 and 11a2. In the second embodiment as well, the protrusion 18 has a trapezoidal cross-section and protrudes continuously in the circumferential direction. Also, on the roller guide surface 6, a recess 19 is provided between the flat surface portions 6a1 and 6a2, recessed from the end faces of the flat surface portions 6a1 and 6a2. In the second embodiment as well, the recess 19 has a trapezoidal cross-section. In the second embodiment as well, the protrusion 18 and the recess 19 are symmetrical with respect to the center line (P-P) in the roller width direction.

[0038] In the second embodiment as well, when the operating angle is set, the cylindrical portions 11a1 and 11a2 of the outer ring 11 make line contact with the flat surfaces 6a1 and 6a2 of the roller guide surface 6, thereby suppressing the left-right tilt of the outer ring 11. Furthermore, when the outer ring 11 rolls on the track of the outer joint member, the convex portion 18 and the concave portion 19 come into contact, suppressing the front-back tilt of the outer ring 11, avoiding further contact and preventing an increase in rolling resistance. When the outer ring 11 rolls in the opposite direction (i.e., towards the inner diameter side of the joint), the inner diameter side of the convex portion 18 comes into contact with the concave portion 19, changing the orientation of the outer ring 11.

[0039] Except for the matters described above, the configuration and functions of each part of the second embodiment are the same as those of the first embodiment, so the explanation of the overlapping parts will be omitted.

[0040] FIG. 8 shows that in the first embodiment shown in FIG. 5, a guide surface 20 for guiding the axial outer end surface 11b of the outer ring 11 is provided in the track groove of the outer joint member 2. That is, in the track groove 5 of the outer joint member 2, the surface with which the axial outer end surface 11b of the outer ring 11 abuts is formed in a straight shape.

[0041] By providing the guide surface 20, when the axial outer end surface 11b of the outer ring 11 contacts the guide surface 20, the restraining force against the attitude change of the outer ring 11 increases. Therefore, for example, even when the gap between the convex portion 17 and the concave portion 16 is large, the front and rear tilting of the outer ring 11 can be suppressed. That is, the deterioration of the rolling resistance of the outer ring 11 and the deterioration of NVH can be more stably suppressed. Further, by reducing the volume inside the outer joint member, the amount of lubricating grease contained can also be reduced, and the overall mass and cost can be reduced.

[0042] As another form of the guide surface, it may be provided at a position separated from the roller guide surface 6, like the guide surface 20a shown in FIG. 9A, or may be provided only on the side of the roller guide surface 6, like the guide surface 20b shown in FIG. 9B. Also, in the second embodiment shown in FIG. 7, a guide surface as shown in FIGS. 8, 9A, and 9B may be provided.

[0043] The concave and convex portions are not limited to the trapezoidal shape as in the first and second embodiments, and other shapes may be used. For example, as shown in FIG. 10, the convex portion 21 and the concave portion 22 may be formed in an R shape. However, the contact angle θ between the convex and concave portions is preferably in the range of 20° or more and 60° or less, and more preferably 35° or more and 45° or less. Although FIG. 10 shows a case where the guide surface 20 is provided in the track groove of the outer joint member 2, even when there is no guide surface 20 as shown in FIGS. 5 and 7, the shapes of the concave and convex portions can be various shapes.

[0044] Further, the present invention is not limited to the embodiments described above, and can be widely applied to other tripod constant velocity joints having other configurations as long as they are of the double roller type

[0045] For example, as shown in the embodiment in Figure 11, the outer circumferential surface 7a of the leg shaft 7 can be formed as a convex curved surface (for example, a convex arc in cross-section), and the inner circumferential surface 12a of the inner ring 12 can be formed as a cylindrical surface. Alternatively, as shown in the embodiment in Figure 12, the outer circumferential surface 7a of the leg shaft 7 can be formed as a convex curved surface (for example, a convex arc in cross-section), and the inner circumferential surface 12a of the inner ring 12 can be formed as a concave spherical surface that fits with the outer circumferential surface 7a of the leg shaft (washers 14 and 15 can be made unnecessary by providing flanges at both ends of the inner diameter of the outer ring). In any embodiment, except for the differences described above, the same reference numerals are used for members and elements common to the first and second embodiments described in Figures 1 to 10, and redundant explanations are omitted.

[0046] The tripod-type constant velocity universal joint 1 described above is not limited to automobile drive shafts, but can be widely used in power transmission paths for automobiles, industrial equipment, and the like.

[0047] This is a double-roller tripod-type constant velocity universal joint with an outer ring and an inner ring. Its applications are not limited to automobile drive shafts; it can also be used in power transmission paths for automobiles and industrial equipment.

[0048] 1 Tripod type constant velocity universal joint 2 Outer joint member 3 Tripod member 4 Roller unit 5 Track groove 6 Roller guide surface 6a1 Cylindrical section 6a2 Cylindrical section 7 Leg shaft 7a Outer surface of leg shaft 8 Center hole 11 Roller (outer ring) 11a1 Flat surface section 11a2 Flat surface section 12 Inner ring 16, 19, 22 Recessed section 17, 18, 21 Protruding section 20, 20a, 20b Guide surface O Axis of leg shaft P Center in the width direction of the roller θ Contact angle

Claims

1. A tripod-type constant velocity universal joint comprising: an outer joint member having track grooves extending axially at three locations in the circumferential direction, each track groove having a pair of roller guide surfaces arranged opposite to each other in the circumferential direction; a tripod member having three leg shafts projecting radially; a roller inserted into the track grooves; and an inner ring fitted onto the leg shafts and supporting the roller rotatably, wherein the roller is configured to move in the axial direction of the outer joint member along the roller guide surfaces, characterized in that cylindrical portions are provided on both sides of the outer circumferential surface of the roller, sandwiching the center in the width direction of the roller, and recesses are provided between the cylindrical portions, recesses that are recessed from the outer circumferential surface of the cylindrical portions; and flat portions are provided on both sides of the roller guide surface, sandwiching the center in the width direction of the roller, and protrusions are provided between the flat portions, protruding from the end faces of the flat portions and engaging with the recesses.

2. A tripod-type constant velocity universal joint comprising: an outer joint member having track grooves extending axially at three locations in the circumferential direction, each track groove having a pair of roller guide surfaces arranged opposite to each other in the circumferential direction; a tripod member having three leg shafts projecting radially; a roller inserted into the track grooves; and an inner ring fitted onto the leg shafts and supporting the roller rotatably, wherein the roller is configured to move in the axial direction of the outer joint member along the roller guide surfaces, characterized in that cylindrical portions are provided on both sides of the outer circumferential surface of the roller, sandwiching the center in the width direction of the roller, and protrusions are provided between the cylindrical portions, protruding from the outer circumferential surface of the cylindrical portions; and flat portions are provided on both sides of the roller guide surface, sandwiching the center in the width direction of the roller, and recesses are provided between the flat portions, recessed from the end faces of the flat portions, into which the protrusions engage.

3. The tripod-type constant velocity universal joint according to claim 1 or 2, characterized in that the contact angle between the side surface of the convex portion and the concave portion is 20° or more and 60° or less.

4. The tripod-type constant velocity universal joint according to claim 3, characterized in that the contact angle is 35° or more and 45° or less.

5. The tripod-type constant velocity universal joint according to claim 1 or 2, characterized in that the outer circumferential surface of the leg shaft is formed as a convex curved surface and the inner circumferential surface of the inner ring is formed as a cylindrical surface.

6. The tripod-type constant velocity universal joint according to claim 1 or claim 2, characterized in that the outer circumferential surface of the leg shaft is formed as a convex curved surface and the inner circumferential surface of the inner ring is formed as a concave spherical surface.

7. A tripod-type constant velocity universal joint according to claim 1 or 2, characterized in that a guide surface is provided in the track groove of the outer joint member for guiding the axial outer end surface of the roller.

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