Tripod type constant velocity joint

Abstract

To provide a tripod-type constant velocity universal joint which allows a roller to smoothly slide to a roller guide face in a state that torque is not imposed on the joint.SOLUTION: A tripod-type constant velocity universal joint 1 is composed of: an outside joint member 2 in which three track grooves 5 having roller guide faces 6 which are arranged while opposing a circumferential direction are formed; a tripod member 3 having three leg shafts 7 protruding in a radial direction; rollers 11; and a roller unit 4 having inner rings 12 for rotatably supporting the rollers 11. External peripheral faces 11a of the rollers 11 are formed of partial spherical faces each having a curvature center on an axial line 7x of the leg shaft 7, the roller guide faces 6 are formed of partial cylinder faces each having a curvature center on a horizontal line X-X which passes through a cross point T between pitch circles PC of the track grooves 5 and center lines 5x of the track grooves 5, and end parts 11e of the external peripheral faces 11a of the rollers 11 abut on the roller guide faces 6 in a state that torque is not imposed on the joint.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tripod-type constant velocity universal joint. [Background technology]

[0002] Constant velocity universal joints that constitute the power transmission systems of automobiles and various industrial machines connect two shafts, one on the driving side and one on the driven side, in a manner that allows torque transmission, and can transmit rotational torque at a constant speed regardless of the operating angle of the two shafts. Constant velocity universal joints are broadly divided into fixed type constant velocity universal joints that allow only angular displacement, and sliding type constant velocity universal joints that allow both angular displacement and axial displacement. For example, in a drive shaft that transmits power from an automobile engine to driving wheels, a sliding type constant velocity universal joint is used on the differential side (inboard side), and a fixed type constant velocity universal joint is used on the driving wheel side (outboard side).

[0003] One type of sliding type constant velocity universal joint is the tripod type constant velocity universal joint. This tripod type constant velocity universal joint is known to have rollers as torque transmission members of single roller type and double roller type, but the present invention is directed to a double roller type tripod type constant velocity universal joint shown in Patent Document 1, for example. This double roller type tripod type constant velocity universal joint (hereinafter also simply referred to as tripod type constant velocity universal joint) is mainly composed of an outer joint member, a tripod member as an inner joint member, and a roller unit as a torque transmission member.

[0004] The outer joint member has three linear track grooves extending in the axial direction formed on its inner peripheral surface at equal intervals in the circumferential direction, and roller guide surfaces extending in the axial direction are formed on both sides of each track groove, arranged opposite each other in the circumferential direction. A tripod member and a roller unit are housed inside the outer joint member. The tripod member has three trusses protruding in the radial direction. The roller unit is mainly composed of a roller, an inner ring arranged inside the roller and fitted onto the truss, and a plurality of needle rollers interposed between the roller and the inner ring, and is housed in the track grooves of the outer joint member. The inner peripheral surface of the inner ring forms an arc-shaped convex surface in a vertical cross section including the axis of the inner ring.

[0005] The outer peripheral surface of each trunnion of the tripod member has a straight shape in a vertical section including the axis of the trunnion, and has a substantially elliptical shape in a cross section perpendicular to the axis of the trunnion, and contacts 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 inner peripheral surface of the inner ring in the axial direction of the joint. In this tripod-type constant velocity universal joint, the rollers of the roller units attached to the trunnions of the tripod member roll on the roller guideways of the track grooves of the outer joint member. Since the cross section of the trunnion is substantially elliptical, when the tripod-type constant velocity universal joint takes an operating angle, the axis of the tripod member is inclined with respect to the axis of the outer joint member, but the roller units can be inclined with respect to the axis of the trunnion of the tripod member. Therefore, the rollers roll correctly on the roller guideways, and thus it is possible to reduce induced thrust and sliding resistance, and to realize low vibration of the joint. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-132766 A Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, when a drive shaft assembly having a tripod type constant velocity universal joint attached to one end is installed in a vehicle, it is desirable for the rollers, which are internal parts of the tripod type constant velocity universal joint, to slide smoothly relative to the outer joint member when no torque is applied to the joint (hereinafter sometimes abbreviated as "unloaded").

[0008] The tripod-type constant velocity universal joint proposed in Patent Document 1 allows the rollers to tilt in the track grooves by making the outer peripheral surface of the roller a partial spherical surface with the center of curvature on the axis of the leg shaft of the tripod member and making the roller guideway a partial cylindrical surface parallel to the axis of the outer joint member. When the roller and the roller guideway are in circular contact, the roller comes into contact with the roller guideway at one point, but when the ratio R / r of the radius of curvature R of the roller guideway to the radius of curvature r of the outer spherical surface of the roller is large, the contact angle between the roller and the roller guideway in the above-mentioned no-load state becomes small, and the frictional force generated between the outer spherical surface of the roller and the roller guideway becomes large. As a result, it was found that there is a risk of impeding smooth sliding of the roller in the no-load state.

[0009] In view of the above problems, an object of the present invention is to provide a tripod-type constant velocity universal joint that enables the rollers to slide smoothly against the roller guideways when no torque is applied to the joint. [Means for solving the problem]

[0010] As a result of extensive investigations into achieving the above-mentioned objective, the inventors came up with the new idea of ​​setting large the contact angle between the outer peripheral surface of the roller and the roller guideway in a double-roller type tripod constant velocity universal joint when no load is applied, and arrived at the present invention.

[0011] As technical means for achieving the above-mentioned object, the present invention provides a roller unit comprising an outer joint member in which three track grooves having roller guideways arranged opposite to each other in the circumferential direction are formed, a tripod member having three trunnions protruding in the radial direction, a roller and an inner ring supporting the roller so as to be able to rotate, the inner ring being fitted onto the trunnion and the roller being movable along the roller guideways of the track grooves, the inner peripheral surface of the inner ring being formed into an arc-shaped convex surface in a longitudinal section of the inner ring, and the outer peripheral surface of the trunnion being formed into an arc-shaped convex surface in a longitudinal section including the axis of the trunnion. in a tripod-type constant velocity joint, the outer circumferential surface of the trunnion is in a straight shape in a cross section perpendicular to the axis of the trunnion and is substantially elliptical in a cross section perpendicular to the axis of the trunnion, the outer circumferential surface of the trunnion abuts against the inner circumferential surface of the inner ring in a direction perpendicular to the axis of the joint, and a gap is formed between the inner circumferential surface of the inner ring in the axial direction of the joint, and the roller can tilt within the track groove, the outer circumferential surface of the roller is formed by a partial spherical surface having a center of curvature on the axis of the trunnion, and the roller guideway is formed by a partial cylindrical surface having a center of curvature on a horizontal line passing through an intersection of a pitch circle of the track groove and a center line of the track groove, a center of curvature of the partial cylindrical surface of the roller guideway is shifted from a center line of the track groove, and a track gap is provided between the roller guideway and an outer circumferential surface of the roller; The contact ratio R / r between the radius of curvature R of the partial cylindrical surface of the roller guideway and the radius of curvature r of the partial spherical surface of the roller's outer circumferential surface is set in the range of 0.95≦R / r≦1.08, so that when no torque is applied to the joint, the end of the outer circumferential surface of the roller , on both sides of the roller diameter It is characterized in that it abuts against the roller guide surface.

[0012] With the above configuration, it is possible to set a large contact angle between the outer peripheral surface of the roller and the roller guideway when there is no load, thereby realizing a tripod-type constant velocity universal joint that enables the roller to slide smoothly against the roller guideway when there is no load.

[0013] Specifically, it is desirable to set the contact ratio R / r between the radius of curvature R of the partial cylindrical surface of the roller guideway and the radius of curvature r of the partial spherical surface of the roller's outer circumferential surface in the range of 0.95≦R / r≦1.08. This makes it possible to realize a tripod-type constant velocity universal joint that is highly practical in terms of manufacturing as well as in terms of performance, in which the rollers slide smoothly along the roller guideway under no load. Here, in this specification and claims, the contact ratio is defined as the ratio R / r of the radius of curvature R of the partial cylindrical surface of the roller guideway and the radius of curvature r of the partial spherical surface of the roller's outer circumferential surface.

[0014] By disposing a plurality of rolling elements between the inner ring and the roller, the relative rotation between the inner ring and the roller can be made smooth.

[0015] By using needle rollers as the rolling elements, the relative rotation between the inner ring and the rollers can be made smooth, and the internal components can be made compact.

[0016] The roller outer circumferential surface can be formed at both ends with rounded portions having a radius of curvature smaller than the radius of curvature r of the partial spherical surface of the roller outer circumferential surface, thereby making it possible to effectively avoid edge load and improve the durability of the roller guideway.

[0017] The outer circumferential surface of the roller can be partially spherical in the widthwise central region, and recesses can be formed in the regions from the widthwise central region to both ends to form a convex shape, thereby reducing the contact pressure during torque transmission and improving the durability of the roller guideway.

[0018] For reference,A tripod-type constant velocity universal joint includes an outer joint member in which three track grooves having roller guideways arranged opposite to each other in the circumferential direction are formed, a tripod member having three trunnions protruding in the radial direction, and a roller unit including a roller and an inner ring for rotatably supporting the roller, the inner ring of the roller unit being fitted onto the trunnions, the roller unit being tiltable with respect to the trunnions, the roller being movable along the roller guideways of the track grooves, and the roller being tiltable within the track grooves, wherein the outer peripheral surface of the roller is formed of a partial spherical surface having a center of curvature on the axis of the trunnions, the roller guideway is formed of a partial cylindrical surface having a center of curvature on a horizontal line passing through an intersection point between a pitch circle of the track groove and a center line of the track groove, and the contact ratio R / r between a radius of curvature R of the partial cylindrical surface of the roller guideway and a radius of curvature r of the partial spherical surface of the roller is set to 0. By setting R / r within the range of .95≦R / r≦1.08, when a torque load is applied, the outer peripheral surface of the roller and the roller guideway come into contact over almost the entire width direction of the outer peripheral surface of the roller, thereby reducing the induced thrust of the joint. Effect of the Invention

[0019] According to the present invention, it is possible to set the contact angle between the outer peripheral surface of the roller and the roller guideway when there is no load large, thereby realizing a tripod-type constant velocity universal joint that enables the roller to slide smoothly against the roller guideway even when there is no load. [Brief description of the drawings]

[0020] [Figure 1] 1 is a vertical sectional view of a tripod type constant velocity universal joint according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] 2 is a plan view of a roller unit and a trunnion as viewed along line BB in FIG. 1. [Figure 4] 4 is a vertical cross-sectional view of the roller unit taken along line EE in FIG. 3. [Diagram 5]2 is a vertical sectional view showing a state in which the tripod type constant velocity universal joint of FIG. 1 is at a normal operating angle. [Figure 6] 2 is a vertical sectional view showing a state in which the tripod type constant velocity universal joint of FIG. 1 has an operating angle larger than a normal operating angle. [Figure 7] 3A is a cross-sectional view of the upper 1 / 3 of FIG. 2, where FIG. 3A shows the radius of curvature of the partial cylindrical surface of the roller guideway, and FIG. 3B shows the radius of curvature of the partial spherical surface of the outer circumferential surface of the roller. [Figure 8] FIG. 3 is an enlarged cross-sectional view of part D in FIG. 2. [Figure 9] 5A and 5B are schematic diagrams showing the state of the rollers and the roller guideways during torque transmission; [Figure 10] FIG. 4 is a schematic diagram showing the state of the roller and the roller guideway when no load is applied; [Figure 11] 4 is a schematic diagram showing the relationship between the load, the contact angle, and the frictional force between the roller and the roller guideway when no load is applied; FIG. [Figure 12] FIG. 13 is a diagram showing modeling of a roller with respect to the wedge effect. [Figure 13] 1 is a graph showing the relationship between contact angle θ and frictional force f. [Figure 14] 1 is a schematic diagram showing the relationship between the contact ratio R / r and the contact angle θ1. [Figure 15] 1 is a schematic diagram showing the relationship between the contact ratio R / r and the contact angle θ2. [Figure 16] 9 is a cross-sectional view showing a state where the contact ratio R / r is changed in FIG. 8. [Figure 17] 17 is a partial cross-sectional view showing a state in which the outer circumferential surface of the roller and the roller guideway in FIG. 16 are in contact with each other. FIG. [Figure 18] 18 is a cross-sectional view showing the contact state between the outer circumferential surface of the roller and the roller guideway in FIG. 17, with the center line of the track groove and the axis of the trunnion also shown. [Figure 19] FIG. 11 is a partial cross-sectional view showing a first modified example of the roller. [Figure 20] FIG. 11 is a partial cross-sectional view showing a second modified example of the roller. [Figure 21]21 is a partial cross-sectional view showing a state in which the outer circumferential surface of the roller in FIG. 20 is in contact with a roller guideway. FIG. [Figure 22] FIG. 11 is a partial cross-sectional view showing a tripod-type constant velocity universal joint according to a second embodiment of the present invention, illustrating the state in which the outer peripheral surface of the roller and the roller guideway in FIG. 8 used to explain the first embodiment are in contact under torque load. [Figure 23] 1 is a partial cross-sectional view of a conventional example in which the outer peripheral surface of a roller and a roller guideway are in angular contact with each other. [Figure 24] 13 is a partial cross-sectional view of a second embodiment in which the outer peripheral surface of the roller and the roller guide surface are in contact with each other over substantially the entire width direction of the outer peripheral surface of the roller. FIG. [Diagram 25] 24 is a diagram for explaining the resistance when the roller in angular contact in the conventional example shown in FIG. 23 is inclined. FIG. [Figure 26] 25 is a diagram illustrating the resistance of the roller in the second embodiment of FIG. 24 when inclined. FIG. [Figure 27] 13 is a graph showing measurement results of induced thrust in the conventional example and the second embodiment. [Figure 28] 13 shows the second embodiment with different contact rates R / r, where (a) shows the contact rate R / r=1.00 and (b) shows the contact rate R / r=0.95. [Figure 29] FIG. 11 is a cross-sectional view of a tripod type constant velocity universal joint according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] A tripod type constant velocity universal joint according to a first embodiment of the present invention is shown in Figs. 1 to 18. First, the overall configuration of the tripod type constant velocity universal joint of this embodiment will be described with reference to Figs. 1 to 6. Fig. 1 is a longitudinal sectional view of the tripod type constant velocity universal joint according to this embodiment, and Fig. 2 is a transverse sectional view taken along line AA in Fig. 1. However, in Fig. 2, the tripod member 3 and the two lower roller units 4 are not shown in cross section, and the shaft 9 is not shown. Fig. 3 is a plan view of the roller units and trunnions taken along line BB in Fig. 1, and Fig. 4 is a longitudinal sectional view of the roller units taken along line EE in Fig. 3. Fig. 5 is a longitudinal sectional view showing a state in which the tripod type constant velocity universal joint of Fig. 1 has a normal operating angle, and Fig. 6 is a longitudinal sectional view showing a state in which the tripod type constant velocity universal joint of Fig. 1 has a larger operating angle than the normal operating angle.

[0022] 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 axial direction formed on its inner circumferential surface at equal intervals in the circumferential direction, and roller guide surfaces 6 extending in the axial direction are formed on both sides of each track groove 5, arranged opposite each other in the circumferential direction. The tripod member 3 and the roller unit 4 are housed inside the outer joint member 2.

[0023] The tripod member 3 has three trunnions 7 protruding in the radial direction. A shaft 9 is spline-fitted into a central hole 8 of the tripod member 3 and is fixed in the axial direction by a retaining ring 10. The roller unit 4 is mainly composed of a roller 11, an inner ring 12 disposed inside the roller 11 and fitted onto the trunnion 7, and a plurality of needle rollers 13 interposed between the roller 11 and the inner ring 12. The roller unit 4 is housed in a track groove 5 of the outer joint member 2, and the center of the roller unit 4 (roller 11) in the width direction is located on the pitch circle PC of the track groove 5.

[0024] As shown in Fig. 4, the needle rollers 13 are arranged between the cylindrical inner peripheral surface 11b of the roller 11 and the cylindrical outer peripheral surface 12b of the inner ring 12 in a so-called full roller state without a cage, with the cylindrical inner peripheral surface 11b of the roller 11 being the outer raceway surface and the cylindrical outer peripheral surface 12b of the inner ring 12 being the inner raceway surface. The inner peripheral surface 12a of the inner ring 12 forms an arc-shaped convex surface in a vertical cross section including the axis of the inner ring 12. This arc-shaped convex surface has a radius of curvature ri of, for example, about 30 mm to allow for an inclination of about 2 to 3° of the truss 7 with respect to the inner ring 12 caused by the whirling that is unique to tripod-type constant velocity universal joints.

[0025] The outer peripheral surface 11a of the roller 11 is formed as a partial sphere with a radius of curvature r whose center of curvature is located on the axis 4x of the roller unit 4, in other words, on the axis 7x of the leg shaft 7 shown in Fig. 3. The roller unit 4, consisting of the inner ring 12, needle rollers 13 and rollers 11 of the roller unit 4, is structured so as not to be separated by washers 14 and 15. The washers 14 and 15 are separated at one point in the circumferential direction (see Fig. 3) and are fitted into the annular groove of the cylindrical inner peripheral surface 11b of the roller 11 in an elastically contracted state.

[0026] As shown in Fig. 1 and Fig. 2, the outer peripheral surface 7a of each trunnion 7 of the tripod member 3 has a straight shape in a vertical section including the axis 7x of the trunnion 7 (see Fig. 3). Also, as shown in Fig. 3, the outer peripheral surface 7a of the trunnion 7 has a substantially elliptical shape in a cross section perpendicular to the axis 7x of the trunnion 7, and contacts the inner peripheral 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, and forms a gap m between the outer peripheral surface 7a and the inner peripheral surface 12a of the inner ring 12 in the axial direction of the joint, i.e., in the direction of the minor axis b. In the tripod-type constant velocity universal joint 1, the rollers 11 of the roller units 4 attached to the trunnions 7 of the tripod member 3 roll on the roller guide surfaces 6 of the track grooves 5 of the outer joint member 2.

[0027] Since the cross section of the trunnion 7 is substantially elliptical, at a relatively small operating angle commonly used, the axis of the tripod member 3 is inclined to the axis of the outer joint member 2 as shown in Fig. 5, but the roller unit 4 can be inclined to the axis of the trunnion 7 of the tripod member 3. Therefore, the rollers 11 of the roller unit 4 and the roller guideway 6 are prevented from being in an oblique state and roll correctly, so that it is possible to reduce induced thrust and sliding resistance, and to realize low vibration of the joint. In this specification and claims, the substantially elliptical shape is not limited to a literal elliptical shape, but includes shapes generally called egg shapes, oval shapes, etc.

[0028] Torque is transmitted by contact between the truss axle 7, whose cross section is approximately elliptical, and the inner ring 12, which has a circular inner peripheral surface 12a, so the ellipticity b / a of the major axis a and minor axis b of the approximately elliptical shape of the truss axle 7 and the curvature radius ri of the inner peripheral surface 12a of the inner ring 12 (see Figure 4) are set to reduce the surface pressure at the contact area between the truss axle 7 and the inner ring 12 and to ensure the strength of the truss axle 7. Therefore, at a relatively small operating angle that is commonly used, the roller unit 4 can be inclined with respect to the truss axle 7, as described above in Figure 5, so that the rollers 11 of the roller unit 4 can roll without intersecting the roller guideway 6 at an angle.

[0029] On the other hand, when the angle becomes larger than a predetermined angle (for example, about 15°) exceeding the normal operating angle, the outer peripheral surface 7a of the truss axle 7 and the inner peripheral surface 12a of the inner ring 12 shown in Fig. 3 interfere with each other, and the roller unit 4 (roller 11) cannot tilt any further with respect to the truss axle 7. Since the angle at which the roller unit 4 can tilt with respect to the truss axle 7 is limited, if the angle is larger than the predetermined angle exceeding the normal operating angle, the roller unit 4 needs to tilt by the missing angle with respect to the track groove 5. However, as shown in Fig. 4, the outer peripheral surface 11a of the roller 11 is formed as a partial sphere with a curvature radius r whose center of curvature is located on the axis 7x of the truss axle 7, so that the roller unit 4 can tilt within the track groove 5 as shown in Fig. 6, and can also accommodate a large operating angle.

[0030] The overall configuration of the tripod type constant velocity universal joint 1 of this embodiment is as described above. Next, the characteristic configurations will be described. The characteristic configurations are as follows (1) to (3). (1) The outer circumferential surface 11a of the roller 11 is formed as a partial sphere having a center of curvature on the axis 7x of the leg shaft 7. (2) The roller guideway 6 is formed as a partial cylindrical surface having a center of curvature located on a horizontal line passing through the intersection of the pitch circle PC of the track groove 5 and the center line of the track groove 5. (3) When no torque is applied to the joint, the end of the outer circumferential surface 11a of the roller 11 abuts against the roller guideway 6.

[0031] The characteristic features (1) and (2) will be specifically described with reference to Fig. 7(a), Fig. 7(b), and Fig. 8. Fig. 7(a) is a cross-sectional view of the upper 1 / 3 of Fig. 2, showing the radius of curvature of the partial cylindrical surface of the roller guideway, and Fig. 7(b) is a cross-sectional view of the upper 1 / 3 of Fig. 2, showing the radius of curvature of the partial spherical surface of the roller's outer circumferential surface. Fig. 8 is an enlarged cross-sectional view of part D in Fig. 2. Hatching of the cross-sectional portions has been omitted in Figs. 7(a), 7(b), and 8.

[0032] 7(a), 7(b), and 8 show the state in which the center line 5x of the track groove 5 and the axis line 7x of the trunnion 7 are aligned. As shown in FIG. 7(b), the outer circumferential surface 11a of the roller 11 is formed of a partial spherical surface with a curvature radius r, the center of curvature Or (see FIG. 8) being located on the axis line 7x of the trunnion 7. As shown in FIG. 7(a), the roller guideway 6 is formed of a partial cylindrical surface with a curvature radius R, the center of curvature being located on a horizontal line XX passing through an intersection point T between the pitch circle PC of the track groove 5 and the center line 5x of the track groove 5, and extends parallel to the axis line of the joint. In this embodiment, the curvature radius R of the roller guideway 6 is shaped according to the curvature radius r of the outer circumferential surface 11a of the roller 11. That is, the curvature radius R of the partial cylindrical surface of the roller guideway 6 and the curvature radius r of the partial spherical surface of the outer circumferential surface 11a of the roller 11 are set to R=r, and the contact ratio is R / r=1.00.

[0033] 8, the relationship between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 of the track groove 5 will be described in more detail. With the center line 5x of the track groove 5 and the axis 7x of the trunnion 7 aligned, a gap δ / 2 is provided between the outer peripheral surface 11a of the roller 11, which is a partial spherical surface formed with a curvature radius r, and the roller guideway 6, which is a partial cylindrical surface formed with a curvature radius R. In this embodiment, the curvature radius R is set to r (contact ratio R / r=1.00), so that the center of curvature OR of the partial cylindrical surface formed with the curvature radius R of the roller guideway 6 is shifted by the gap δ / 2 from the center line 5x of the track groove 5 on the horizontal line XX.

[0034] When the outer peripheral surface 11a of the left half roller 11 not shown in Fig. 8 is pressed against the roller guideway 6, the gap δ / 2 between the outer peripheral surface 11a of the right half roller 11 and the roller guideway 6 becomes twice as large as δ (see Fig. 9), and this gap δ is called the track gap. The track gap δ is a very small value, for example, on the order of several tens of µm to several hundred µm.

[0035] The characteristic configuration of the tripod-type constant velocity universal joint 1 of this embodiment is as described above in that (1) the outer peripheral surface 11a of the roller 11 is formed as a partial spherical surface having a center of curvature on the axis 7x of the leg axle 7, and (2) the roller guideway 6 is formed as a partial cylindrical surface having a center of curvature on the horizontal line XX passing through the intersection T of the pitch circle PC of the track groove 5 and the center line 5x of the track groove 5.

[0036] Next, the characteristic configuration (3) of the tripod type constant velocity universal joint 1 of this embodiment, in which the end of the outer circumferential surface 11a of the roller 11 abuts against the roller guideway 6 when no torque is applied to the joint, will be described with reference to Fig. 9 to Fig. 13. Fig. 9 is a schematic diagram showing the state of the roller and the roller guideway when torque is transmitted, and Fig. 10 is a schematic diagram showing the state of the roller and the roller guideway when no load is applied.

[0037] As shown in Fig. 9, when torque is applied counterclockwise to the tripod member 3 (see Fig. 2), the outer peripheral surface 11a of the roller 11 abuts against the roller guideway 6 on the left side of Fig. 9 and receives the load, but since there is a track gap δ between the roller guideway 6 on the right side of Fig. 9 and the outer peripheral surface 11a of the roller 11, the roller 11 rolls smoothly on the roller guideway 6. Corresponding to the track gap δ, the axis 11x of the roller 11 is slightly misaligned in the direction of the horizontal line XX from the center line 5x of the track groove 5. In Figs. 9 and 10, the track gap δ is exaggerated for ease of understanding.

[0038] On the other hand, as shown in Fig. 10, when no torque is applied to the joint, the roller 11 is not constrained by the roller guideway 6 and can move either upward or downward in the radial direction. As a result, the outer peripheral surface 11a of the roller 11 comes into contact with the roller guideway 6 on both diametrical sides. Fig. 10 shows a state in which the roller 11 has moved downward, and the widthwise center line 11y of the roller 11 is shifted downward from the horizontal line XX of the track groove 5.

[0039] In this embodiment, the contact ratio between the radius of curvature R of the partial cylindrical surface of the roller guideway 6 and the radius of curvature r of the partial spherical surface of the outer circumferential surface 11a of the roller 11 is set to R / r = 1.00, so that the end 11e of the outer circumferential surface 11a of the roller 11 abuts against the roller guideway 6. This increases the contact angle θ between the outer circumferential surface 11a of the roller 11 and the roller guideway 6, allowing the roller 11 to slide smoothly along the roller guideway 6 when no load is applied. The relationship between the contact angle θ between the outer circumferential surface 11a of the roller 11 and the roller guideway 6 when no load is applied and the sliding characteristics of the roller 11 along the roller guideway 6, as well as the practical range of the contact ratio R / r, will be described later in detail.

[0040] Fig. 10 shows the roller 11 in a horizontal position shifted downward so that the center line 5x of the track groove 5 overlaps with the axis 11x of the roller 11, but the roller 11 may also be in an inclined position. Also, Fig. 10 shows the roller 11 moving downward, but the same applies when the roller 11 moves upward. Furthermore, in Fig. 10, the track gap δ is exaggerated, so the amount of deviation between the width direction center line 11y of the roller 11 and the horizontal line XX of the track groove 5 is also shown large.

[0041] As described above, the characteristic configuration (3) of the tripod-type constant velocity universal joint 1 of this embodiment is that when no torque is applied to the joint, the end 11e of the outer circumferential surface 11a of the roller 11 abuts against the roller guide surface 6.

[0042] The relationship between the contact angle θ between the outer peripheral surface 11a of roller 11 and roller guideway 6 when there is no load, and the sliding characteristics of roller 11 relative to roller guideway 6 will be described with reference to Fig. 11 to Fig. 13. Fig. 11 is a schematic diagram showing the relationship between the load, contact angle, and frictional force between the roller and roller guideway when there is no load, Fig. 12 is a diagram showing a model of the roller in terms of the wedge effect, and Fig. 13 is a graph showing the relationship between the contact angle θ and frictional force f.

[0043] As shown in FIG. 11, when the roller 11 moves downward relative to the roller guideway 6, a frictional force f is generated between the outer peripheral surface 11a of the roller 11 and the roller guideway 6. The frictional force f is a factor that hinders the smooth sliding of the roller 11 when no load is applied. In FIG. 11, the load from the roller 11 is F, the vertical load on the roller guideway 6 is P, and the angle between the straight line connecting the center Or of the roller 11 and the contact point C on the roller guideway 6 and the horizontal line 11y (which is also the center line of the roller 11 in the width direction) passing through the center Or of the roller 11 is the contact angle θ, and is expressed as the frictional force f on the roller guideway 6. In addition to the case where this frictional force f acts on the paper surface of the drawing as shown in the figure, when a drive shaft assembly having the tripod type constant velocity universal joint 1 attached to one end is assembled to a vehicle, the frictional force f acts in the axial direction of the roller guideway 6, but is expressed on the paper surface of the drawing for convenience in order to simplify the relationship with the load, the contact angle, etc.

[0044] In order to express the friction force f generated between the outer peripheral surface 11a of roller 11 and roller guideway 6 shown in FIG. 11, FIG. 12 shows an example of a model in which a wedge J is driven into object M. Wedge J corresponds to roller 11. Here, F: load, P: normal load, θ: contact angle, f: friction force, μ: friction coefficient. The wedge angle is 2 × contact angle θ. From the balance of forces, the relationship between contact angle θ and friction force f is expressed by the following equation.

number

[0045] The relationship between the contact angle θ and the frictional force f is shown in a graph in Figure 13. The larger the contact angle θ, the smaller the frictional force f. Therefore, it was confirmed that by increasing the contact angle θ and reducing the frictional force f, the roller 11 can slide smoothly.

[0046] Based on the above findings, the contact angle θ that provides good sliding characteristics of the roller 11 under no load was verified, and the relationship between the contact angle θ and the contact ratio R / r was also verified. The verification results will be described with reference to Figs. 14 to 18. Fig. 14 is a schematic diagram showing the relationship between the contact ratio R / r and the contact angle θ1, and Fig. 15 is a schematic diagram showing the relationship between the contact ratio R / r and the contact angle θ2. Fig. 16 is a cross-sectional view in Fig. 8 with the contact ratio R / r changed. Fig. 17 is a partial cross-sectional view showing the state in which the outer peripheral surface of the roller and the roller guideway are in contact with each other in Fig. 16, and Fig. 18 is a cross-sectional view showing the contact state between the outer peripheral surface of the roller and the roller guideway in Fig. 17 with the center line of the track groove and the axis of the leg shaft added. However, in Fig. 18, the roller and the tripod member are not in a cross-sectional view but in a side view.

[0047] FIG. 14 shows an example in which the contact ratio R / r is greater than 1.08. The contact angle θ1 when no load is applied is smaller as the contact ratio R / r is greater than 1. As shown in the figure, the widthwise center line 11y of the roller 11 is significantly shifted downward from the horizontal line XX of the track groove 5, and the contact point C between the outer peripheral surface 11a of the roller 11 and the roller guide surface 6 is shifted away from the end 11e of the outer peripheral surface 11a of the roller 11 and is located closer to the center of the roller 11. As a result of testing and design consideration, it was confirmed that if the contact ratio R / r exceeds 1.08 (R / r>1.08), the smooth sliding of the roller 11 when no load is applied is hindered, and problems may occur in practical use. Therefore, it is preferable that the contact ratio is R / r≦1.08. The track gap δ is also shown slightly exaggerated in FIGS. 14 to 16.

[0048] 15 shows the case where the contact ratio R / r=1.00. As shown in the figure, the widthwise center line 11y of the roller 11 is only slightly deviated from the horizontal line XX of the track groove 5, and the contact point C between the outer circumferential surface 11a of the roller 11 and the roller guideway 6 is located at the end 11e of the outer circumferential surface 11a of the roller 11. The contact angle θ2 when no load is applied becomes large, allowing the roller 11 to slide smoothly when no load is applied.

[0049] 16 and 17 show an example where the contact ratio R / r<1.00. Although not shown, in this case, similar to Fig. 15, the end 11e of the outer circumferential surface 11a of the roller 11 abuts against the roller guideway 6 when no load is applied. For this reason, the contact angle θ can be set large, enabling the roller 11 to slide smoothly when no load is applied.

[0050] In the case where the contact ratio R / r<1.00, when the roller 11 is pressed against the roller guideway 6 as shown in Fig. 17, both ends 11e of the outer circumferential surface 11a of the roller 11 come into contact with the roller guideway 6. In the state where both ends 11e of the outer circumferential surface 11a of the roller 11 come into contact with the roller guideway 6, the axis 7x of the trunnion 7 is shifted by 1 / 2 of the track gap δ from the center 5x of the track groove 5 as shown in Fig. 18. Then, during torque transmission, the roller 11 comes into contact over the entire width W of the outer circumferential surface 11a including the portion with the gap γ1 near the center of the roller 11 as shown in Figs. 17 and 18, and the contact surface pressure tends to be particularly large at the ends 11e of the outer circumferential surface 11a of the roller 11. As a result of testing and design considerations, in the range of contact ratio R / r<1.00, it is desirable for the contact ratio R / r≧0.95 to suppress an extreme increase in contact surface pressure at the end 11e of the outer circumferential surface 11a of the roller 11 and ensure the durability of the roller guideway 6. Figures 16 to 18 show an example where the contact ratio is set to R / r=0.95. In this case, as shown in Figure 16, the reduction in the radius of curvature R is added, and the intersection point XX is on the horizontal line XX. T or The deviation of the center of curvature OR of the radius of curvature R from these values ​​is larger than that in Fig. 8. For ease of understanding, Figs. 16 and 18 exaggerate the curved state of the partial cylindrical surface with respect to the radius of curvature R of the partial cylindrical surface of the roller guideway 6 with the center of curvature OR.

[0051] Therefore, as an advantageous configuration of the present invention, it is desirable to set the contact ratio R / r between the radius of curvature R of the partial cylindrical surface of the roller guideway 6 and the radius of curvature r of the partial spherical surface of the outer circumferential surface 11a of the roller 11 in the range of 0.95≦R / r≦1.08. This makes it possible to realize a tripod-type constant velocity universal joint 1 that is highly practical in terms of manufacturing as well as in terms of performance, in which the rollers 11 slide smoothly along the roller guideway 6 when no load is applied.

[0052] Next, a first modified example of roller 11 will be described with reference to FIG. 19. FIG. 19 is a partial cross-sectional view showing the first modified example of the roller. In this modified example, the shape of outer peripheral surface 11a of roller 11 is different from that of roller 11 in the first embodiment shown in FIGS. 16 to 18 described above. The other configurations are the same as those in the first embodiment, so the same reference numerals are used for parts having the same functions, and the contents described in the first embodiment apply mutatis mutandis. Below, the differences of this modified example from roller 11 in the first embodiment will be described.

[0053] In this modification, in order to avoid the above-mentioned edge contact when the contact ratio R / r<1.00, the end 11e of the outer circumferential surface 11a of the roller 11 is rounded with a radius of curvature ra, as shown in Fig. 19. This results in a form in which the rounded portion Q with the radius of curvature ra of the end 11e of the outer circumferential surface 11a of the roller 11 comes into contact with the roller guideway 6, making it possible to effectively avoid edge load and leading to improved durability of the roller guideway 6.

[0054] The relationship between the radius of curvature r of the partial spherical surface of the outer peripheral surface 11a of the roller 11 and the radius of curvature ra of the rounded portion Q is r>ra. In FIG. 19, the width W1 of the outer peripheral surface 11a of the roller 11 includes the area of ​​the partial spherical surface of the radius of curvature r and the area of ​​the rounded portion Q of the radius of curvature ra. It is desirable that the radius of curvature r and the radius of curvature ra are connected by a smooth tangent line. Furthermore, the width W1 of the outer peripheral surface 11a of the roller 11 is generally finished by grinding or hardened steel cutting (referring to cutting after hardening), but in particular, when finishing by grinding, it is desirable to finish the area of ​​the radius of curvature r and the area of ​​the radius of curvature ra as one unit by using, for example, a forming grindstone that transfers the radius of curvature r and the radius of curvature ra together. In this modification, when the contact ratio R / r<1.00, the rounded portion Q with the curvature radius ra is provided at the end 11e of the outer circumferential surface 11a of the roller 11, but the present invention is not limited to this, and in order to avoid unavoidable edge load, the rounded portion Q may be provided even when 1.00≦R / r≦1.08. In this modification, too, it is preferable that the contact ratio R / r is in the range of 0.95≦R / r≦1.08.

[0055] Further, a second modified example of the roller 11 will be described with reference to Figs. 20 and 21. Fig. 20 is a partial cross-sectional view showing the second modified example of the roller, and Fig. 21 is a partial cross-sectional view showing the state in which the outer peripheral surface of the roller in Fig. 20 is in contact with the roller guide surface. In the first modified example described above, the rounded portion Q with a radius of curvature ra is provided only at the end 11e of the outer peripheral surface 11a of the roller 11, but in this modified example, the widthwise central region of the outer peripheral surface 11a of the roller 11 is made into a partial spherical surface with a radius of curvature r, and a retreat portion K with a radius of curvature rb is provided in the region from the widthwise central region to the end 11e of the outer peripheral surface 11a of the roller 11. This point is different from that of the outer peripheral surface 11a of the roller 11 in the first modified example.

[0056] The configuration other than the outer circumferential surface 11a of the roller 11 is the same as that of the first embodiment, so the same reference numerals are used for parts having the same functions, and the contents described in the first embodiment apply mutatis mutandis. The following describes the differences of this modification from the roller 11 in the first embodiment.

[0057] As shown in Fig. 20, the widthwise central region Lc of the outer peripheral surface 11a of the roller 11, which includes the horizontal line XX, is formed by a partial spherical surface with a curvature radius r and a center of curvature Or on the axis 7x of the leg axle 7, and the region Le from the widthwise central region Lc to the end 11e of the outer peripheral surface 11a of the roller 11 is formed with a retreated portion K with a curvature radius rb and a center of curvature Orb. The retreated amount of the retreated portion K is about several tens of µm at the end 11e with respect to the curvature radius r. The curvature radius r of the partial spherical surface with a curvature center Or on the axis 7x of the leg axle 7 and the curvature radius rb of the retreated portion K with a curvature center Orb are smoothly connected by a tangent.

[0058] The outer peripheral surface 11a of the roller 11 has a recessed portion K with a radius of curvature rb in the region Le from the widthwise central region Lc to both ends 11e, so that the roller 11 has a convex shape. Therefore, as shown in FIG. 21, the recessed portion K of the outer peripheral surface 11a of the roller 11 is in surface contact with the roller guideway 6, and the gap γ2 near the center of the roller 11 is smaller than the gap γ1 shown in FIG. 18 of the first embodiment. As a result, the contact surface pressure during torque transmission is reduced, and the durability of the roller guideway 6 can be improved. In this modification, the recessed portion K is formed with one radius of curvature rb, but this is not limited to this, and the region of the radius of curvature rb may be formed with multiple curves with different radii of curvature. In this modification, it is also preferable that the contact ratio R / r is in the range of 0.95≦R / r≦1.08.

[0059] Next, a tripod type constant velocity universal joint according to a second embodiment of the present invention will be described. The tripod type constant velocity universal joint according to this embodiment was discovered as a technical means for solving a new technical problem during experimental confirmation of the practical level of smooth sliding characteristics between the rollers and the roller guideways of the tripod type constant velocity universal joint according to the first embodiment under no load.

[0060] The above-mentioned new technical problem will be outlined first. For example, in a drive shaft that transmits power from an engine to driving wheels of an automobile, a sliding type constant velocity universal joint is used on the differential side (inboard side), and a tripod type constant velocity universal joint is often used as one of the sliding type constant velocity universal joints. In the double roller type sliding type tripod type constant velocity universal joint that is the subject of this embodiment, a roller unit is attached to the truss of the tripod member, and the roller unit includes a spherical roller, an inner ring disposed inside the roller and externally attached to the truss, and a plurality of needle rollers are interposed between the roller and the inner ring in a full roller state without a cage. When torque is transmitted with a working angle taken, repeated axial force due to induced thrust is generated during rotation due to mutual friction between the internal parts. A typical NVH phenomenon of an automobile involving induced thrust is the lateral vibration of the vehicle body while traveling.

[0061] The key to solving the NVH problem in automobiles is to reduce the magnitude of the induced thrust of the joint. In general, the induced thrust of the joint tends to depend on the magnitude of the working angle. For this reason, when applied to the drive shaft of an automobile, it leads to a design constraint that the working angle cannot be made large. Therefore, in order to increase the freedom of designing the suspension of an automobile, it is necessary to stabilize the induced thrust at a low level. The above-mentioned double roller type tripod type constant velocity universal joint is designed to reduce the induced thrust by making the roller unit inclineable with respect to the axis of the leg shaft of the tripod member even if the axis of the tripod member is inclined with respect to the axis of the outer joint member when the working angle is taken, and the rollers roll correctly on the roller guideway. However, it is an important technical issue to further reduce and stabilize the induced thrust.

[0062] A tripod type constant velocity universal joint according to a second embodiment of the present invention will be specifically described with reference to Fig. 1, Fig. 2, and Fig. 22 to Fig. 28. Fig. 22 shows a tripod type constant velocity universal joint according to the second embodiment, and is a partial cross-sectional view showing a state in which the outer peripheral surface of the roller and the roller guideway in Fig. 8 used to explain the first embodiment are in contact with each other under torque load. Fig. 23 is a partial cross-sectional view of a conventional example in which the outer peripheral surface of the roller and the roller guideway are in angular contact, and Fig. 24 is a partial cross-sectional view of this embodiment in which the outer peripheral surface of the roller and the roller guideway are in contact with each other over substantially the entire width direction of the outer peripheral surface of the roller.

[0063] The tripod type constant velocity universal joint according to the second embodiment has a new technical objective of further reducing and stabilizing induced thrust, but the overall configuration of the tripod type constant velocity universal joint according to the second embodiment is the same as that of the first embodiment based on Fig. 1 and Fig. 2, so the description thereof applies mutatis mutandis. The main points will be described below.

[0064] The contact form between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 of the tripod type constant velocity universal joint 1 according to the second embodiment will be described with reference to Fig. 22. The outer peripheral surface 11a of the roller 11 is formed of a partial spherical surface with a radius of curvature r and a center of curvature Or on the axis 7x of the truss 7. The roller guideway 6 is formed of a partial cylindrical surface with a radius of curvature R and a center of curvature Or on a horizontal line XX passing through an intersection T between the pitch circle PC of the track groove 5 and the center line 5x of the track groove 5. The radius of curvature R of the partial cylindrical surface of the roller guideway 6 and the radius of curvature r of the partial spherical surface of the outer peripheral surface 11a of the roller 11 are R = r, and the contact ratio R / r = 1.00. The center of curvature OR of the partial cylindrical surface formed by the radius of curvature R of the roller guideway 6 is offset by a gap δ / 2 from the center line 5x of the track groove 5 on the horizontal line XX, and when torque is loaded, coincides with the center of curvature Or located on the axis 7x of the leg shaft 7 of the partial spherical surface formed by the radius of curvature r of the outer peripheral surface 11a of the roller 11.

[0065] In this embodiment, when the radius of curvature R is set to R (contact ratio R / r = 1.00), when the joint is subjected to a torque load, as shown in Figure 22, the outer peripheral surface 11a of the roller 11 and the roller guide surface 6 come into contact with each other over the entire width direction of the outer peripheral surface 11a of the roller 11.

[0066] The contact form between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 will be described by comparing the tripod type constant velocity universal joint 1 of the second embodiment with a current product as a conventional example. In the conventional example, as shown in Fig. 23, the contact form between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 is angular contact. The angular contact has two contact areas a with a certain contact angle. An apex gap VC is formed between the two contact areas a, which also serves as a lubricant oil reservoir, and the conventional example follows a proven contact form.

[0067] In contrast, in the present embodiment shown in FIG. 24, a large contact area b can be provided in the width direction of the outer peripheral surface 11a of the roller 11. Therefore, the contact area b of the present embodiment shown in FIG. 24 is 2a < b with respect to the total 2a of the two-point contact areas a of the conventional example shown in FIG. 23. In FIG. 24, an example is illustrated in which the contact ratio R / r is set to a value close to 1.00 but exceeding 1.00.

[0068] Next, the difference in the resistance of the roller 11 during inclination between the conventional example and the present embodiment will be considered with reference to FIGS. 25 to 27. FIG. 25 is a diagram for explaining the resistance of the roller during inclination in the conventional example with angular contact as shown in FIG. 23, and FIG. 26 is a diagram for explaining the resistance of the roller during inclination in the present embodiment shown in FIG. 24. FIG. 27 is a graph showing the measurement results of the induced thrust of the conventional example and the present embodiment.

[0069] As shown in FIG. 25, in the conventional example where the contact form between the outer peripheral surface 11a of the roller 11 and the roller guide surface 6 is angular contact, the resistance during the inclination of the roller 11 is considered to be represented by the area 2A of the hatched portion A. In contrast, as shown in FIG. 26, in the present embodiment in which a large contact area is provided in the width direction of the outer peripheral surface 11a of the roller 11, the resistance during the inclination of the roller 11 is considered to be represented by the area 2B of the hatched portion B. As a result, the roller 11 of the present embodiment is more likely to be held in the horizontal direction of the roller guide surface 6 of the track groove 5 when a torque load is applied, compared with the conventional example. That is, it is considered that the roller 11 is less likely to incline with respect to the roller guide surface 6 of the track groove 5, and by promoting the horizontal movement, the induced thrust can be reduced.

[0070] Figure 27 shows the measurement results of induced thrust (third-order component) versus joint angle for the conventional example and this embodiment. Compared to the conventional example in which the contact form between the outer circumferential surface 11a of the roller 11 and the roller guideway 6 is angular contact, this embodiment, in which a larger contact area is provided in the width direction of the outer circumferential surface 11a of the roller 11, exhibits a low and stable induced thrust even when the joint angle is large. The tripod-type constant velocity universal joint 1 of this embodiment also has the effect of enabling the roller 11 to slide smoothly against the roller guideway 6 when no load is applied.

[0071] Fig. 28 shows different contact ratios R / r in this embodiment, with Fig. 28(a) showing the contact ratio R / r = 1.00 and Fig. 28(b) showing the contact ratio R / r = 0.95. However, even in this embodiment, it is desirable that the contact ratio R / r between the radius of curvature R of the partial cylindrical surface of the roller guideway 6 and the radius of curvature r of the partial spherical surface of the outer circumferential surface 11a of the roller 11 be in the range of 0.95 ≦ R / r ≦ 1.08.

[0072] The technical means for reducing and stabilizing the induced thrust in the tripod type constant velocity universal joint 1 according to the second embodiment can be summarized as follows. (1) A tripod-type constant velocity universal joint in which an inner ring of a roller unit is fitted onto a trunnion, the roller unit is tiltable relative to the trunnion, the rollers are movable along the roller guide surfaces of the track grooves, and the rollers are tiltable within the track grooves, (2) The outer peripheral surface of the roller is formed as a partial sphere with the center of curvature on the axis of the leg shaft. (3) The roller guideway is formed of a partial cylindrical surface having a center of curvature on a horizontal line passing through the intersection of the pitch circle of the track groove and the center line of the track groove. (4) The induced thrust of the joint is reduced by setting the contact ratio R / r between the radius of curvature R of the partial cylindrical surface of the roller guideway and the radius of curvature r of the partial spherical surface of the roller's outer circumferential surface in the range of 0.95≦R / r≦1.08.

[0073] The technical means for reducing and stabilizing the induced thrust in the tripod type constant velocity universal joint according to the second embodiment can also be applied to the tripod type constant velocity universal joint according to the third embodiment. The tripod type constant velocity universal joint according to the third embodiment will be described with reference to FIG. 29, which is a cross-sectional view thereof.

[0074] As shown in Fig. 29, the tripod type constant velocity universal joint 1' of this embodiment is different from the second embodiment in that the outer peripheral surface 7a' of the trunnion 7' ​​of the tripod member 3' is formed as a spherical surface, the inner ring 12' of the roller unit 4' has a cylindrical inner peripheral surface 12a', and the cylindrical inner peripheral surface 12a' of the inner ring 12' is slidably fitted to the spherical outer peripheral surface 7a' of the trunnion 7' ​​of the tripod member 3'. The other configurations are the same as those of the second embodiment, so that the same reference numerals (with primes) are used for parts having the same functions, and the main points will be described.

[0075] The roller unit 4' is mainly composed of a roller 11', an inner ring 12', and a number of needle rollers 13' assembled between the roller 11' and the inner ring 12' in a full-complement state. The roller unit 4' is housed in a track groove 5' of the outer joint member 2', and the center of the width of the roller unit 4' (roller 11') is located on the pitch circle PC of the track groove 5'. The outer peripheral surface 11a' of the roller 11' is formed as a partial spherical surface of radius of curvature r' with the center of curvature Or' located on the axis 7x' of the truss axle 7'.

[0076] The tripod member 3' has three trunnions 7' protruding in the radial direction. The outer peripheral surface 7a' of the trunnions 7' is formed as a sphere with a center of curvature on the axis 7x' of the trunnions 7', and the cylindrical inner peripheral surface 12a' of the inner ring 12' of the roller unit 4' is slidably fitted to the spherical outer peripheral surface 7a'. When the joint forms an operating angle, the roller unit 4' can be tilted with respect to the axis of the trunnions 7' of the tripod member 3'. This prevents the rollers 11' of the roller unit 4' from being obliquely intersecting with the roller guideway 6', allowing the rollers to roll correctly.

[0077] The roller guide surface 6' is an intersection point between the pitch circle PC of the track groove 5' and the center line 5x' of the track groove 5'. T A horizontal line passing through X - X The roller guideway 6' is formed of a partial cylindrical surface with a radius of curvature R' having a center of curvature on the roller guideway 6' and extends parallel to the axis of the joint. In this embodiment, too, it is preferable that the contact ratio R' / r' between the radius of curvature R' of the partial cylindrical surface of the roller guideway 6' and the radius of curvature r' of the partial spherical surface of the outer circumferential surface 11a' of the roller 11' is in the range of 0.95≦R' / r'≦1.08. In this embodiment, too, a large contact area is formed in the width direction of the outer circumferential surface 11a' of the roller 11', so that the induced thrust is stabilized at a low level. In addition, it has the effect of enabling the roller 11' to slide smoothly against the roller guideway 6' when no load is applied.

[0078] The present invention is not limited to the above-described embodiments, and can of course be embodied in various other forms without departing from the spirit of the present invention. The scope of the present invention is indicated by the claims, and further includes the equivalent meanings set forth in the claims, and all modifications within the scope of the claims. [Explanation of symbols]

[0079] 1 Tripod type constant velocity joint 2 Outer joint member 3 Tripod member 4 Roller unit 5 Track groove 5x track groove centerline 6 Roller guideway 7 Leg axis 7x leg axis 9 Shaft 11. Lola 11a Outer surface 11e End 12 Inner Ring 12a Inner surface 13 Needle roller C Contact point K Retreat section Lc width center area PC track groove pitch circle Q Rounded part R, R’ Radius of curvature of the cylindrical surface of the roller guideway T intersection XX Horizontal line a long axis b Minor axis m Gap r, r’ Radius of curvature of the partial sphere of the outer periphery of the roller θ contact angle δ Track gap

Claims

1. A tripod-type constant velocity joint comprising an outer joint member in which three track grooves having roller guideways arranged opposite to each other in the circumferential direction are formed, a tripod member having three trunnions protruding in the radial direction, and a roller unit including a roller and an inner ring rotatably supporting the roller, the inner ring being fitted onto the trunnion and the roller being movable along the roller guideways of the track grooves, the inner surface of the inner ring being formed into an arc-shaped convex surface in a longitudinal section of the inner ring, the outer surface of the trunnion having a straight shape in a longitudinal section including the axis of the trunnion and a substantially elliptical shape in a transverse section perpendicular to the axis of the trunnion, the outer surface of the trunnion abutting against the inner surface of the inner ring in a direction perpendicular to the axis of the joint and a gap being formed between the inner surface of the inner ring and the outer surface of the trunnion in the axial direction of the joint, and the roller is tiltable within the track grooves, the outer circumferential surface of the roller is formed as a partial spherical surface having a center of curvature on the axis of the trunnion, the roller guideway is formed by a partial cylindrical surface having a center of curvature on a horizontal line passing through an intersection point between a pitch circle of the track groove and a center line of the track groove, a center of curvature of the partial cylindrical surface of the roller guideway is shifted from a center line of the track groove, a track gap is provided between the roller guideway and the outer circumferential surface of the roller; The contact ratio R / r between the radius of curvature R of the partial cylindrical surface of the roller guideway and the radius of curvature r of the partial spherical surface of the roller outer circumferential surface is set in the range of 0.95≦R / r≦1.08, A tripod-type constant velocity universal joint, characterized in that when no torque is applied to the joint, the ends of the outer peripheral surfaces of the rollers abut against the roller guide surfaces on both sides in the roller diameter direction.

2. 2. 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.

3. 3. A tripod type constant velocity universal joint according to claim 2, wherein said rolling elements are needle rollers.

4. 2. A tripod-type constant velocity universal joint according to claim 1, wherein said rollers have rounded portions at both ends of their outer peripheral surfaces, said rounded portions having a radius of curvature smaller than the radius of curvature r of the partial spherical surface of said outer peripheral surfaces.

5. The tripod-type constant velocity universal joint according to claim 1, characterized in that the outer peripheral surface of the roller has a partially spherical surface in its widthwise central region, and a recess is formed in the region from the widthwise central region to the end portion to form a convex shape.

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