JP7664728B2 - Tripod type constant velocity joint - Google Patents

Description

This invention relates to a tripod-type constant velocity universal joint.

Constant velocity universal joints, which make up the power transmission systems of automobiles and various industrial machines, connect two shafts, one driving side and one driven side, so that torque can be transmitted, 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, which allow only angular displacement, and sliding type constant velocity universal joints, which allow both angular displacement and axial displacement. For example, in a drive shaft that transmits power from an automobile engine to the 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).

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

The outer joint member has three linear track grooves formed on its inner peripheral surface at equal intervals in the circumferential direction, and roller guideways 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 multiple 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.

The outer peripheral surface of each trunnion of the tripod member has a straight shape in a longitudinal section including the axis of the trunnion, and has a substantially elliptical shape in a cross section perpendicular to the axis of the trunnion. The outer peripheral surface of the trunnion 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 unit attached to the trunnion of the tripod member roll on the roller guideway of the track groove 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 unit can be inclined with respect to the axis of the trunnion of the tripod member. Therefore, the rollers roll correctly on the roller guideway, which reduces induced thrust and sliding resistance and realizes low vibration of the joint.

JP 2001-132766 A

When assembling a drive shaft assembly with a tripod-type constant velocity universal joint attached to one end onto a vehicle, it is desirable for the rollers, which are internal components of the tripod-type constant velocity universal joint, to slide smoothly against the outer joint member when no torque is applied to the joint (hereinafter sometimes abbreviated as "unloaded").

The tripod-type constant velocity universal joint proposed in Patent Document 1 allows the roller to tilt within the track groove 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 that the smooth sliding of the roller in the no-load state may be hindered.

In view of the above problems, the present invention aims to provide a tripod-type constant velocity universal joint that allows the rollers to slide smoothly against the roller guideways when no torque is applied to the joint.

After extensive research to achieve the above objective, the inventors came up with the novel idea of setting a large contact angle between the outer circumferential surface of the roller and the roller guideway in a double-roller type tripod constant velocity universal joint when no load is applied, which led to the present invention.

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 freely rotatable, 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, the outer peripheral surface of the trunnion being straight in a longitudinal section including the axis of the trunnion and being substantially elliptical in a transverse section perpendicular to the axis of the trunnion, the outer peripheral surface of the trunnion being in contact with the inner peripheral surface of the inner ring in a direction perpendicular to the axis of the joint, and being in contact with the inner peripheral surface of the inner ring in the axial direction of the joint. and a clearance is formed between the roller and the roller, and the roller can tilt within the track groove. The outer circumferential surface of the roller is formed of a partial spherical surface having a center of curvature on the axis of the trunnion, the roller guideway is formed of 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, the center of curvature of the partial cylindrical surface of the roller guideway is at a position shifted from the center line of the track groove, a track clearance is provided between the roller guideway and the outer circumferential surface of the roller, and a contact rate 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 in a range of 0.95≦R/r≦1.08, so that when no torque is loaded on the joint, the end of the outer circumferential surface of the roller abuts against the roller guideway on both sides in the roller diameter direction .

The above configuration makes it possible to set a large contact angle between the outer circumferential surface of the roller and the roller guideway when no load is applied, realizing a tripod-type constant velocity universal joint that allows the roller to slide smoothly against the roller guideway when no load is applied.

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 roller slides smoothly against 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.

By placing multiple rolling elements between the inner ring and the roller, the relative rotation between the inner ring and the roller can be made smooth.

By using needle rollers as the rolling elements, the relative rotation between the inner ring and the rollers can be made smoother, and the internal parts can be made more compact.

A rounded portion having a radius of curvature smaller than the radius of curvature r of the partial spherical surface of the roller's outer circumferential surface can be formed at both ends of the outer circumferential surface of the roller. This makes it possible to effectively avoid edge loads and improve the durability of the roller guideway.

The outer peripheral 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 give it a convex shape. This reduces the contact pressure during torque transmission and improves the durability of the roller guideway.

A reference example is a tripod-type constant velocity universal 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 supporting the roller so as to be able to rotate, the inner ring of the roller unit being fitted onto the trunnion, the roller unit being tiltable with respect to the trunnion, the roller being movable along the roller guideway of the track groove, and the roller being tiltable within the track groove, wherein the outer peripheral surface of the roller is formed by 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 the intersection of the pitch circle of the track groove and the center line of the track groove, and 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 is 0. By setting R/r in the range of 95≦R/r≦1.08, the outer circumferential surface of the roller and the roller guideway come into contact over almost the entire width direction of the outer circumferential surface of the roller when a torque is applied, thereby reducing the induced thrust of the joint.

According to the present invention, 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, and it is possible to realize a tripod-type constant velocity universal joint that allows the roller to slide smoothly against the roller guideway even when there is no load.

1 is a longitudinal sectional view of a tripod type constant velocity universal joint according to a first embodiment of the present invention. 2 is a cross-sectional view taken along line AA in FIG. 1. 2 is a plan view of the roller unit and the truss taken along line BB in FIG. 1. 4 is a vertical cross-sectional view of the roller unit taken along line EE in FIG. 3. 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. 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. 3A is a cross-sectional view of the upper 1/3 portion of FIG. 2, FIG. 3A showing the radius of curvature of the partial cylindrical surface of the roller guideway, and FIG. 3B showing the radius of curvature of the partial spherical surface of the outer circumferential surface of the roller. FIG. 3 is an enlarged cross-sectional view of part D in FIG. 2 . 5A and 5B are schematic diagrams showing the state of the rollers and the roller guideways during torque transmission; FIG. 4 is a schematic diagram showing the state of the roller and the roller guideway when no load is applied; 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. FIG. 13 is a diagram showing modeling of a roller with respect to the wedge effect. 1 is a graph showing the relationship between the contact angle θ and the frictional force f. 1 is a schematic diagram showing the relationship between a contact ratio R/r and a contact angle θ1. FIG. 1 is a schematic diagram showing the relationship between the contact ratio R/r and the contact angle θ2. 9 is a cross-sectional view showing a state where the contact ratio R/r is changed in FIG. 8 . 17 is a partial cross-sectional view showing a state in which the outer circumferential surface of the roller in FIG. 16 is in contact with a roller guideway. FIG. 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. FIG. 4 is a partial cross-sectional view showing a first modified example of the roller. FIG. 11 is a partial cross-sectional view showing a second modified example of the roller. 21 is a partial cross-sectional view showing a state in which the outer peripheral surface of the roller in FIG. 20 is in contact with a roller guideway. FIG. 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. 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. 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 over substantially the entire width direction of the outer peripheral surface of the roller. FIG. FIG. 24 is a diagram for explaining the resistance when the roller in angular contact in the conventional example shown in FIG. 23 is inclined. 25 is a diagram illustrating the resistance of the roller of the second embodiment of FIG. 24 when inclined. FIG. 13 is a graph showing measurement results of induced thrust in the conventional example and the second embodiment. 13 shows the second embodiment with different contact rates R/r, with FIG. 13(a) showing the contact rate R/r=1.00 and FIG. 13(b) showing the contact rate R/r=0.95. FIG. 11 is a cross-sectional view of a tripod type constant velocity universal joint according to a third embodiment of the present invention.

A tripod type constant velocity universal joint according to the 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 based on Figs. 1 to 6. Fig. 1 is a vertical cross-sectional view of the tripod type constant velocity universal joint according to this embodiment, and Fig. 2 is a horizontal cross-sectional view taken along line A-A 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 B-B in Fig. 1, and Fig. 4 is a vertical cross-sectional view of the roller units taken along line E-E in Fig. 3. Fig. 5 is a vertical cross-sectional view showing the tripod type constant velocity universal joint of Fig. 1 in a state where it has a normal operating angle, and Fig. 6 is a vertical cross-sectional view showing the tripod type constant velocity universal joint of Fig. 1 in a state where it has a larger operating angle than the normal operating angle.

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

The tripod member 3 has three trunnions 7 protruding in the radial direction. A shaft 9 is spline-fitted into the center 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 arranged inside the roller 11 and fitted onto the trunnion 7, and a number of needle rollers 13 interposed between the roller 11 and the inner ring 12. The roller unit 4 is housed in the 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.

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 a 2-3° inclination of the truss 7 relative to the inner ring 12 caused by the whirling that is unique to tripod-type constant velocity universal joints.

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 on the axis 4x of the roller unit 4, in other words, on the axis 7x of the leg shaft 7 shown in Figure 3. The roller unit 4, consisting of the inner ring 12, needle rollers 13 and rollers 11, is structured so that it cannot be separated by washers 14 and 15. The washers 14 and 15 are separated at one point in the circumferential direction (see Figure 3) and are fitted into the annular groove of the cylindrical inner peripheral surface 11b of the roller 11 in an elastically contracted state.

As shown in Figures 1 and 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 Figure 3). Also, as shown in Figure 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 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 roller 11 of the roller unit 4 attached to the trunnion 7 of the tripod member 3 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 approximately elliptical, at a relatively small operating angle commonly used, the axis of the tripod member 3 is inclined relative to the axis of the outer joint member 2 as shown in FIG. 5, but the roller unit 4 can be inclined relative to the axis of the leg shaft 7 of the tripod member 3. Therefore, the roller 11 of the roller unit 4 and the roller guideway 6 are prevented from being in an oblique state and roll correctly, which reduces induced thrust and sliding resistance and achieves low vibration of the joint. In this specification and claims, the approximately elliptical shape is not limited to a literal elliptical shape, but includes shapes generally referred to as egg shapes, oval shapes, etc.

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

On the other hand, if the angle exceeds a predetermined angle (for example, about 15°) that exceeds 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 relative to the truss axle 7. Since the angle at which the roller unit 4 can tilt relative to the truss axle 7 is limited, if the angle is greater than the predetermined angle that exceeds the normal operating angle, the roller unit 4 must tilt by the missing angle relative 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 large operating angles.

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 peripheral 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 of 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 11 a of the roller 11 abuts against the roller guideway 6 .

The characteristic configurations (1) and (2) will be specifically described with reference to Figs. 7(a), 7(b), and 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.

In each of Figs. 7(a), 7(b), and 8, the center line 5x of the track groove 5 and the axis 7x of the leg shaft 7 are shown in the same state. As shown in Fig. 7(b), the outer peripheral 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 7x of the leg shaft 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 X-X 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, and extends parallel to the axis 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 peripheral 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 peripheral surface 11a of the roller 11 are R = r, and the contact ratio R/r = 1.00.

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 reference to FIG. 8. With the center line 5x of the track groove 5 and the axis 7x of the leg shaft 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 radius of curvature r, and the roller guideway 6, which is a partial cylindrical surface formed with a radius of curvature R. In this embodiment, the radius of curvature R is set to r (contact ratio R/r = 1.00), so the center of curvature OR of the partial cylindrical surface formed with the radius of curvature R of the roller guideway 6 is shifted from the center line 5x of the track groove 5 on the horizontal line X-X by a gap δ/2.

When the outer peripheral surface 11a of the roller 11 on the left half (not shown in Figure 8) is pressed against the roller guideway 6, the gap δ/2 between the outer peripheral surface 11a of the roller 11 on the right half and the roller guideway 6 becomes twice as large as δ (see Figure 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 and several tens of μm.

The characteristic configuration of the tripod-type constant velocity universal joint 1 of this embodiment is as follows: (1) the outer circumferential surface 11a of the roller 11 is formed as a partial spherical surface with a center of curvature located on the axis 7x of the leg shaft 7, and (2) the roller guideway 6 is formed as a partial cylindrical surface with a center of curvature located on the horizontal line X-X passing through the intersection T between the pitch circle PC of the track groove 5 and the center line 5x of the track groove 5.

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 Figures 9 to 13. Figure 9 is a schematic diagram showing the state of the roller and roller guideway when torque is being transmitted, and Figure 10 is a schematic diagram showing the state of the roller and roller guideway when no load is applied.

As shown in Figure 9, when torque is applied counterclockwise to the tripod member 3 (see Figure 2), the outer peripheral surface 11a of the roller 11 abuts against the roller guideway 6 on the left side of Figure 9 and receives the load, but because there is a track gap δ between the roller guideway 6 on the right side of Figure 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 horizontal line X-X direction from the center line 5x of the track groove 5. In Figures 9 and 10, the track gap δ is exaggerated to make it easier to understand.

On the other hand, as shown in Figure 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 sides in the diameter direction. Figure 10 shows the state in which the roller 11 has moved downward, with the widthwise center line 11y of the roller 11 deviating downward from the horizontal line X-X of the track groove 5.

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 against 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 against the roller guideway 6, as well as the practical range of the contact ratio R/r, will be described later.

Figure 10 shows the roller 11 in a horizontal position shifted downward, with the center line 5x of the track groove 5 overlapping with the axis 11x of the roller 11, but the roller 11 may also be in an inclined position. Also, while Figure 10 shows the roller 11 moving downward, the same applies when it moves upward. Furthermore, in Figure 10, the track gap δ is exaggerated, so the amount of deviation between the widthwise center line 11y of the roller 11 and the horizontal line X-X of the track groove 5 is also shown large.

Characteristic configuration of the tripod-type constant velocity universal joint 1 of this embodiment (3) As described above, 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.

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

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 (which is also the widthwise center line of the roller 11) 11y passing through the center Or of the roller 11 is the contact angle θ, and is expressed as the frictional force f of the roller guideway 6. In addition to the case where this frictional force f acts on the paper surface of the drawing as shown, when a drive shaft assembly having a 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, contact angle, etc.

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

Figure 13 shows a graph of the relationship between the contact angle θ and the frictional force f. The larger the contact angle θ, the smaller the frictional force f. Therefore, it was confirmed that by increasing the contact angle θ and decreasing the frictional force f, the roller 11 can slide smoothly.

Based on the above findings, we verified the contact angle θ that provides good sliding characteristics of the roller 11 under no load, and also verified the relationship between this contact angle θ and the contact ratio R/r. The verification results will be explained based on Figures 14 to 18. Figure 14 is a schematic diagram showing the relationship between the contact ratio R/r and the contact angle θ1, and Figure 15 is a schematic diagram showing the relationship between the contact ratio R/r and the contact angle θ2. Figure 16 is a cross-sectional view in Figure 8 with different contact ratios R/r. Figure 17 is a partial cross-sectional view showing the state in which the outer circumferential surface of the roller and the roller guideway are in contact with each other in Figure 16, and Figure 18 is a cross-sectional view showing the contact state between the outer circumferential surface of the roller and the roller guideway in Figure 17, with the center line of the track groove and the axis of the leg shaft added. However, in Figure 18, the roller and tripod member are shown in a side view rather than a cross-sectional view.

Figure 14 shows an example where the contact ratio R/r is greater than 1.08. The larger the contact ratio R/r is, the smaller the contact angle θ1 when no load is applied. As shown in the figure, the widthwise center line 11y of the roller 11 is significantly shifted downward from the horizontal line X-X of the track groove 5, and the contact point C between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 is located near the center of the roller 11, away from the end 11e of the outer peripheral surface 11a 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 desirable for the contact ratio to be R/r≦1.08. The track gap δ is also slightly exaggerated in Figures 14 to 16.

Figure 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 X-X of the track groove 5, and the contact point C between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 is located at the end 11e of the outer peripheral surface 11a of the roller 11. The contact angle θ2 when there is no load becomes large, allowing the roller 11 to slide smoothly when there is no load.

Figures 16 and 17 show an example where the contact ratio R/r<1.00. Although not shown, in this case, similar to Figure 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, allowing the roller 11 to slide smoothly when no load is applied.

In the case where the contact ratio R/r is less than 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 consideration, in the range of the contact ratio R/r<1.00, it is desirable to set the contact ratio R/r≧0.95 in order to suppress an extreme increase in the 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 the case where the contact ratio R/r is set to 0.95. In this case, as shown in Figure 16, the amount of deviation of the center of curvature OR of the radius of curvature R from the intersection point T on the horizontal line X-X is increased compared to Figure 8 due to the reduction in the radius of curvature R. For ease of understanding, Figures 16 and 18 show 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 emphasized.

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 roller 11 slides smoothly against the roller guideway 6 when no load is applied.

Next, a first modified example of the 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 the outer peripheral surface 11a of the roller 11 is different from that of the roller 11 in the first embodiment shown in FIGS. 16 to 18 described above. The rest of the configuration is the same as in the first embodiment, so parts having the same functions are given the same reference numerals and the contents described in the first embodiment apply mutatis mutandis. Below, the differences of this modified example compared to the roller 11 in the first embodiment will be described.

In this modified example, in order to avoid the above-mentioned edge contact when the contact ratio R/r is < 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 a 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, which effectively avoids edge load and leads to improved durability of the roller guideway 6.

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. In addition, the width W1 of the outer peripheral surface 11a of the roller 11 is generally finished by grinding or hardened steel cutting (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 using, for example, a forming grindstone in which the radius of curvature r and the radius of curvature ra are transferred together. In this modified example, when the contact ratio R/r is less than 1.00, the end 11e of the outer circumferential surface 11a of the roller 11 is provided with a rounded portion Q having a radius of curvature ra. However, this is not limited to this, and in order to avoid unavoidable edge loads, the rounded portion Q may be provided even when 1.00≦R/r≦1.08. In this modified example, it is also desirable to set the contact ratio R/r in the range of 0.95≦R/r≦1.08.

Furthermore, 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, a 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 of the outer peripheral surface 11a of the roller 11 to the end 11e. This is different from the outer peripheral surface 11a of the roller 11 in the first modified example.

The configuration other than the outer peripheral 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. Below, the differences of this modified example compared to the roller 11 in the first embodiment are described.

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 X-X, is formed by a partial spherical surface of a radius of curvature r with the 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 of a radius of curvature rb with the center of curvature Orb. The amount of retreat of the retreated portion K is about several tens of μm at the end 11e with respect to the radius of curvature r. The radius of curvature r of the partial spherical surface with the center of curvature Or on the axis 7x of the leg axle 7 and the radius of curvature rb of the retreated portion K with the center of curvature Orb are smoothly connected by a tangent.

The outer peripheral surface 11a of the roller 11 has a recessed portion K of a radius of curvature rb in the region Le from the central region Lc in the width direction 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 modified example, 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 composed of multiple curves with different radii of curvature. In this modified example, it is also preferable that the contact ratio R/r is in the range of 0.95≦R/r≦1.08.

Next, we will explain a tripod-type constant velocity universal joint according to a second embodiment of the present invention. The tripod-type constant velocity universal joint according to this embodiment was discovered as a technical means for solving new technical problems while experimentally confirming the practical level of smooth sliding characteristics between the rollers and the roller guideways when no load is applied to the tripod-type constant velocity universal joint according to the first embodiment.

First, an overview of the new technical problems mentioned above will be provided. For example, in a drive shaft that transmits power from an automobile engine to the driving wheels, a sliding 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 type of sliding constant velocity universal joint. In the double roller type sliding tripod type constant velocity universal joint that is the subject of this embodiment, a roller unit is attached to the pedestal of the tripod member, and the roller unit is composed of a spherical roller, an inner ring disposed inside the roller and externally attached to the pedestal, and multiple 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 runout of the vehicle body while it is running.

The key to solving the NVH problem in automobiles is to reduce the magnitude of induced thrust in the joint. In general, induced thrust in a joint tends to depend on the magnitude of the working angle. For this reason, when applied to the drive shaft of an automobile, this leads to design constraints that do not allow the working angle to be 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 constant velocity universal joint is designed to reduce induced thrust by allowing the roller unit to tilt with respect to the axis of the leg shaft of the tripod member even if the axis of the tripod member is tilted 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.

A tripod-type constant velocity universal joint according to a second embodiment of the present invention will be specifically described with reference to Figures 1, 2, and 22 to 28. Figure 22 shows a tripod-type constant velocity universal joint according to the second embodiment, and is a partial cross-sectional view showing the state in which the outer peripheral surface of the roller and the roller guideway in Figure 8 used to explain the first embodiment are in contact with each other under torque load. Figure 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 Figure 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 over almost the entire width of the outer peripheral surface of the roller.

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 described for the first embodiment based on Figures 1 and 2, so the description applies mutatis mutandis. The main points are described below.

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 Figure 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 X-X 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. 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 X-X, and when torque is applied, it 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.

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

The contact form between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 will be explained 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. 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 lubricating oil reservoir, and the conventional example follows a proven contact form.

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 circumferential surface 11a of the roller 11. Therefore, compared to the total of 2a for the two contact areas a in the conventional example shown in FIG. 23, the contact area b in the present embodiment shown in FIG. 24 satisfies 2a<b. FIG. 24 shows an example in which the contact ratio R/r is set to a value close to but exceeding 1.00.

Next, the difference in resistance when the roller 11 is tilted between the conventional example and this embodiment will be considered based on Figs. 25 to 27. Fig. 25 is a diagram explaining the resistance when the roller is tilted in the conventional example with angular contact shown in Fig. 23, and Fig. 26 is a diagram explaining the resistance when the roller is tilted in this embodiment shown in Fig. 24. Fig. 27 is a graph showing the measurement results of induced thrust in the conventional example and this embodiment.

As shown in FIG. 25, in the conventional example in which the contact form between the outer peripheral surface 11a of the roller 11 and the roller guideway 6 is angular contact, the resistance when the roller 11 is tilted 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 when the roller 11 is tilted is considered to be represented by the area 2B of the hatched portion B. As a result, the roller 11 of this embodiment is more likely to be held in the horizontal direction of the roller guideway 6 of the track groove 5 under torque load than the conventional example. In other words, it is considered that the roller 11 is less likely to tilt relative to the roller guideway 6 of the track groove 5, and the induced thrust can be reduced by promoting horizontal movement.

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, which provides a larger contact area in the width direction of the outer circumferential surface 11a of the roller 11, has 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 allowing the roller 11 to slide smoothly against the roller guideway 6 when no load is applied.

Figure 28 shows this embodiment with different contact ratios R/r, with Figure 28(a) showing a contact ratio R/r = 1.00 and Figure 28(b) showing a contact ratio R/r = 0.95. However, even in this embodiment, 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.

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 having a center of curvature on the axis of the leg shaft.
(3) The roller guideway is formed as 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 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, thereby reducing the induced thrust of the joint.

The technical means for reducing and stabilizing 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.

As shown in FIG. 29, the tripod-type constant velocity universal joint 1' of this embodiment differs from the second embodiment in that the outer peripheral surface 7a' of the leg shaft 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 leg shaft 7' of the tripod member 3'. The rest of the configuration is the same as in the second embodiment, so the same reference numerals (with primes) are used for parts having the same functions, and the main points will be explained.

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 roller state. The roller unit 4' is housed in the 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 by a partial sphere of a radius of curvature r' with the center of curvature Or' located on the axis 7x' of the truss axle 7'.

The tripod member 3' has three leg shafts 7' protruding in the radial direction. The outer peripheral surface 7a' of the leg shafts 7' is formed as a sphere with the center of curvature on the axis 7x' of the leg shafts 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 is at an operating angle, the roller unit 4' can be tilted with respect to the axis of the leg shafts 7' of the tripod member 3'. This prevents the roller 11' of the roller unit 4' from being obliquely intersecting with the roller guide surface 6', allowing it to roll correctly.

The roller guideway 6' is formed of a partial cylindrical surface with a curvature radius R', the center of curvature of which is located on a horizontal line X - X 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 of the joint. In this embodiment as well, it is desirable to set the contact ratio R'/r' between 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' in the range of 0.95≦R'/r'≦1.08. In this embodiment as well, 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 also has the effect of enabling the roller 11' to slide smoothly against the roller guideway 6' when no load is applied.

The present invention is not limited to the above-described embodiment, 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.

Reference Signs List 1 Tripod type constant velocity universal joint 2 Outer joint member 3 Tripod member 4 Roller unit 5 Track groove 5x Center line of track groove 6 Roller guideway 7 Leg 7x Leg axis 9 Shaft 11 Roller 11a Outer peripheral surface 11e End 12 Inner ring 12a Inner peripheral surface 13 Needle roller C Contact point K Retraction portion Lc Width direction central region PC Pitch circle Q of track groove Rounded portion R, R' Radius of curvature T of partial cylindrical surface of roller guideway Intersection point X-X Horizontal line a Major axis b Minor axis m Gap r, r' Radius of curvature θ of partial spherical surface of outer peripheral surface of roller Contact angle δ Track gap

Claims (5)

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 . The tripod-type constant velocity universal joint according to claim 1, characterized in that multiple rolling elements are arranged between the inner ring and the roller. The tripod-type constant velocity universal joint according to claim 2, characterized in that the rolling elements are needle rollers. The tripod-type constant velocity universal joint according to claim 1, characterized in that rounded portions having a radius of curvature smaller than the radius of curvature r of the partial spherical surface of the outer circumferential surface of the roller are formed at both ends of the outer circumferential surface of the roller. The tripod-type constant velocity universal joint according to claim 1, characterized in that the outer peripheral surface of the roller is partially spherical 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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