Tripod constant velocity universal joint

Abstract

To provide a tripod constant velocity universal joint capable of performing smooth rotating operation by loosening concentration of a stress acting on a needle roller to improve durability at the time of rotating operation while an operation angle is maintained.SOLUTION: In a tripod constant velocity universal joint 1, a roller assembly 4 comprises: an inner ring 12 externally fitted with a leg shaft 7; a roller 11 fitted and inserted in a roller guide face 6; plural needle-like rollers 13 arranged between a cylindrical outer periphery 12b of the inner ring 12 and a cylindrical inner periphery 11b of the roller 11; and a pair of washers 14, 15 arranged on both axial sides of the needle-like roller 13 and the inner ring 12 and mounted to the inner periphery of the roller 11 at an outer peripheral edge. An annular projection part 12c is formed at least at a root side axial end of the leg shaft 7 of a tripod member 3 among axial ends of the cylindrical outer periphery 12b of the inner ring 12. When the needle-like roller 13 relatively moves in an axial direction to the cylindrical outer periphery 12b of the inner ring 12, an end of the needle-like roller 13 interferes the annular projection part 12c and does not come into contact with the washer 14.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Constant velocity universal joints, which make up the power transmission systems of automobiles and various industrial machines, connect two shafts, one on a driving side and one on a driven side, so that torque can be transmitted, and can transmit rotational torque at a constant velocity even when the two shafts have an operating angle. 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 and axial displacement. For example, in a drive shaft that transmits power from an automobile engine to the drive 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 drive wheel side (outboard side). Constant velocity universal joints installed in automobiles are required to have the basic function of transmitting rotational torque from the engine / motor at a constant velocity when the joint angle is set, as well as durability equivalent to the life of the automobile and NVH characteristics that suppress engine / motor vibration.

[0003] One type of sliding type constant velocity universal joint is the tripod constant velocity universal joint. This tripod constant velocity universal joint is known to have rollers, which are torque transmission members, of either the single roller type or the double roller type. A double roller type tripod constant velocity universal joint (hereinafter simply referred to as a tripod constant velocity universal joint) is mainly composed of an outer joint member, a tripod member as an inner joint member, and a roller assembly as a torque transmission member. In recent years, particularly with the shift to motors as power sources, there have been increasing demands for improved durability and lifespan due to higher output and for quieter vehicles, and when tripod constant velocity universal joints are applied to the engine / motor side, the application rate of double roller type tripod constant velocity universal joints has been increasing.

[0004] The outer joint member has three linear track grooves formed on its inner circumference at three equally spaced positions in the circumferential direction, extending in the axial direction, and roller guideways arranged circumferentially opposite each other on both sides of each track groove, each extending in the axial direction. A tripod member and a roller assembly are housed inside the outer joint member. The tripod member has three trunnions protruding in the radial direction. The roller assembly is mainly composed of a roller, an inner ring arranged inside the roller and fitted onto the trunnion, 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.

[0005] A typical design for a double-roller tripod constant velocity universal joint is a combination of a roller assembly and a tripod member. To achieve compactness and cost reduction, the roller assembly is constructed with a pair of upper and lower washers securing the needle rollers between the outer roller and the inner ring. The pair of washers prevents the roller assembly, consisting of the inner ring, needle rollers, and rollers, from separating. The washer has a slit for assembly purposes, and is fitted into the annular groove on the cylindrical inner surface of the roller while reducing its diameter during assembly. The inner surface of the inner ring forms a convex arc in a longitudinal cross section including the axis of the inner ring.

[0006] The outer peripheral surface of each trunnion of the tripod members has a straight shape in a longitudinal cross section including the axis of the trunnion and a generally elliptical shape in a cross section perpendicular to the axis of the trunnion. The outer peripheral surface 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, rollers of the roller assemblies attached to the trunnions of the tripod members roll on roller guideways of the track grooves of the outer joint member. Because the cross section of the trunnion is generally elliptical, when the tripod-type constant velocity universal joint has an operating angle, the axis of the tripod members is inclined relative to the axis of the outer joint member, but the roller assemblies can tilt relative to the axes of the trunnions of the tripod members. Therefore, the rollers roll properly on the roller guideways, thereby reducing induced thrust and sliding resistance and achieving low vibration in the joint (see, for example, Patent Documents 1 and 2). The three track grooves having roller guideways formed in the outer joint member are mainly of angular contact or circular contact shape. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-320563 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-132766 Summary of the Invention [Problem to be solved by the invention]

[0008] During operation of a double-roller type tripod constant velocity universal joint, the end faces of the needle rollers in the rotating roller assembly are transferred over the slits in the washer, which impairs the smooth rotation of the needle rollers, resulting in a deterioration in NVH performance such as induced thrust, and a shortened lifespan due to early wear of the needle roller end faces and washer.

[0009] Additionally, when a double-roller tripod constant velocity joint is used, the center of the joint, the center of the tripod member, and the center of the shaft do not geometrically coincide with each other when the operating angle is taken. As a result, the axis of the tripod member's trunnion is rotated while tilting slightly relative to the center line of the track grooves, which are formed in three equal 120-degree increments around the circumferential direction. During rotation, the inner ring of the roller assembly moves vertically relative to the trunnion of the tripod member. This study focused on the relationship between the vertical load at this time and the tilt of the roller assembly in the rotational direction (also known as left-right tilt) relative to the center of the roller guideway of the outer joint member.

[0010] In addition to the above-mentioned loading condition in which the vertical load and the biased load are interrelated, the inner ring of the roller assembly moves vertically relative to the trunnion of the tripod member during operation, causing the thrust load of the needle rollers to be applied more to the lower washer than to the upper washer, which can cause damage particularly to the lower washer, and it was discovered that it is important to change the relationship between the lower washer and the needle rollers. Patent Documents 1 and 2 do not pay attention to this problem.

[0011] In view of the above problems, an object of the present invention is to provide a double roller type tripod constant velocity universal joint that is excellent in durability and NVH characteristics. [Means for solving the problem]

[0012] In order to achieve the above object, the inventors investigated the behavior of roller assembly components when a double-roller tripod constant velocity universal joint is at an operating angle. As a result, they came to the conclusion that although the amount of rolling of the roller assembly components of a tripod constant velocity universal joint is small compared to a typical rolling bearing, the relative movement of the roller assembly components is extremely severe compared to a typical rolling bearing. Based on this result, and taking into consideration the above-mentioned relative movement of the roller assembly components, they arrived at a new idea for the relationship between the roller assembly's washer and needle roller, which led to the present invention. Detailed operation and behavior, as well as the findings from the development process that led to the present invention, will be described later.

[0013] As technical means for achieving the above-mentioned object, the present invention provides an outer joint member having three track grooves formed at three equally spaced positions in the circumferential direction of an inner circumference thereof and having roller guideways arranged to face the track grooves in the circumferential direction, a tripod member having three trunnions protruding radially outward from the three equally spaced positions in the circumferential direction, and a roller assembly externally fitted to the trunnions, wherein the roller assembly includes an inner ring externally fitted to the trunnions, rollers inserted in the roller guideways, and a cylindrical outer peripheral surface of the inner ring and a cylindrical inner peripheral surface of the roller. and a pair of washers arranged on both axial sides of the needle rollers and the inner ring, with their outer peripheral edges attached to the inner periphery of the rollers, characterized in that, of the axial ends of the cylindrical outer peripheral surface of the inner ring, at least the axial end on the root side of the trunnion of the tripod member is formed with annular protrusions, so that when the needle rollers move axially relative to the cylindrical outer peripheral surface of the inner ring, the ends of the needle rollers interfere with the annular protrusions and do not contact the washers. With the above configuration, it is possible to realize a double-roller type tripod constant velocity universal joint that enables smooth rotation of the needle rollers and has excellent durability and NVH characteristics.

[0014] The annular protrusions are formed on both axial ends of the cylindrical outer peripheral surface of the inner ring, thereby enabling smooth rotation of the needle rollers and realizing a double roller type tripod constant velocity universal joint with excellent durability and NVH characteristics, as well as preventing incorrect assembly of the inner ring into the roller assembly and improving ease of assembly.

[0015] The inner peripheral surface of the inner ring is formed into an arc-shaped convex surface in a longitudinal section of the inner ring, the outer peripheral surface of the trunnion is straight in a longitudinal section including the axis of the trunnion and is generally elliptical in a cross section perpendicular to the axis of the trunnion, the outer peripheral surface of the trunnion abuts against the inner peripheral surface of the inner ring in a direction perpendicular to the axis of the joint, and a gap is formed between the outer peripheral surface of the trunnion and the inner peripheral surface of the inner ring in the axial direction of the joint, so that the rollers can tilt within the track grooves. This smooths the tilting movement of the rollers within the track grooves, promoting smooth rotation of the needle rollers in the roller assembly, further reducing induced thrust and sliding resistance and achieving low vibration of the joint.

[0016] The contact form between the roller and the roller guide surface can be either angular contact or circular contact. [Effects of the Invention]

[0017] According to the present invention, it is possible to realize a double-roller type tripod constant velocity universal joint that is excellent in durability and NVH characteristics. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a longitudinal sectional view of a tripod type constant velocity universal joint according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. [Figure 3] 2 is a plan view of the roller assembly and the trunnion as viewed along the line BB in FIG. 1. [Figure 4] FIG. 4 is a vertical cross-sectional view of the roller assembly taken along line EE in FIG. 3. [Figure 5] 3 is a cross-sectional view illustrating one roller assembly shown on the upper side of FIG. 2 and a state of contact between a roller and a roller guideway at approximately 1 / 3 of the circumference of the outer joint member. FIG. [Figure 6] 2 is a longitudinal sectional view showing a state in which the tripod type constant velocity universal joint of FIG. 1 has an operating angle. [Figure 7]1A and 1B are diagrams showing a characteristic configuration of a roller assembly of a first embodiment, in which FIG. 1A is a longitudinal cross-sectional view of a part of the roller assembly, and FIG. 1B is an enlarged longitudinal cross-sectional view of part G. [Figure 8] 1A and 1B are diagrams showing a modified example of the characteristic configuration of the roller assembly of the first embodiment, in which FIG. 1A is a longitudinal cross-sectional view of a portion of the roller assembly, and FIG. 1B is an enlarged longitudinal cross-sectional view of part H. [Figure 9] This is a longitudinal cross-sectional view of the roller assembly of an existing tripod-type constant velocity universal joint that was the subject of the study. (a) is a standard roller assembly with a pair of washers on both ends of the inner ring, and (b) is a roller assembly using a flanged roller and a washer. [Figure 10] FIG. 10 is a plan view showing both the roller assemblies and trunnions of FIGS. 9(a) and 9(b). [Figure 11] 1A and 1B are diagrams illustrating the state, operation, and behavior of the trunnion and roller assembly when they are positioned in the track groove at the top dead center (0° phase) of the outer joint member with the operating angle taken, where FIG. 1A is a longitudinal cross-sectional view and FIG. 1B is a transverse cross-sectional view. [Figure 12] 11(b) is a diagram for explaining the state, operation, and behavior of the roller assembly 4'(1) when rotated clockwise to a 90° phase, where FIG. 11(a) is a vertical cross-sectional view and FIG. 11(b) is a horizontal cross-sectional view. [Figure 13] 11(b) is a diagram illustrating the state, operation, and behavior of the roller assembly 4'(1) when it has further rotated clockwise to a phase of 180°, where FIG. 11(a) is a longitudinal cross-sectional view and FIG. 11(b) is a transverse cross-sectional view. [Figure 14] (a) is a diagram showing the combined operation and behavior of the roller assembly in the track groove with left and right tilt, (b) is a cross-sectional view showing the left and right tilt in clockwise rotation, (c) is a cross-sectional view showing the horizontal state, and (d) is a cross-sectional view showing the left and right tilt in counterclockwise rotation. [Figure 15] 10 is a partial cross-sectional view showing a modification in which the contact state between the roller and the roller guideway of the first embodiment is circular contact. FIG. [Figure 16]FIG. 5 is a cross-sectional view of a tripod type constant velocity universal joint according to a second embodiment of the present invention. [Figure 17] FIG. 10 is a cross-sectional view of a modified example of a tripod type constant velocity universal joint according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] A tripod-type constant velocity universal joint according to a first embodiment of the present invention is shown in FIGS. 1 to 7. First, the overall configuration of the tripod-type constant velocity universal joint according to this embodiment will be described with reference to FIGS. 1 to 6. FIG. 1 is a longitudinal cross-sectional view of the tripod-type constant velocity universal joint according to this embodiment, and FIG. 2 is a transverse cross-sectional view taken along line AA in FIG. 1. However, in FIG. 2, the tripod member and the two lower roller assemblies are not shown in cross section, and the shafts are not shown. The two lower roller assemblies in FIG. 2 do not appear in FIG. 1, which is a longitudinal cross-sectional view. FIG. 3 is a plan view of the roller assemblies and trunnions taken along line BB in FIG. 1, and FIG. 4 is a longitudinal cross-sectional view of the roller assemblies taken along line EE in FIG. 3. FIG. 5 is a cross-sectional view of one upper roller assembly and the outer joint member at approximately one-third of the circumference in FIG. 2, illustrating the contact state between the rollers and the roller guideways. Cross-sectional hatching is omitted. FIG. 6 is a longitudinal cross-sectional view showing the tripod-type constant velocity universal joint of FIG. 1 at an operating angle.

[0020] As shown in Figures 1 and 2, the tripod type constant velocity universal joint 1 is mainly composed of an outer joint member 2, a tripod member 3 as an inner joint member, and a roller assembly 4 as a torque transmission member. The outer joint member 2 has a cup portion 2a with one open end, and three linear track grooves 5 extending in the axial direction are formed on its inner circumference at three equal circumferential positions, and on both sides of each track groove 5, roller guideways 6 are formed, arranged circumferentially opposite each other and extending in the axial direction. The roller guideways 6 have a substantially partially cylindrical cross section. The tripod member 3 and roller assembly 4 are housed inside the outer joint member 2.

[0021] The tripod member 3 has three trunnions 7 that protrude radially outward from three equally spaced positions in the circumferential direction. A shaft 9 is spline-fitted into a center hole 8 of the tripod member 3 and is fixed in the axial direction by a retaining ring 10. The roller assembly 4 is mainly composed of rollers 11, an inner ring 12 that is disposed inside the rollers 11 and fitted onto the trunnions 7, and a plurality of needle rollers 13 that are interposed between the rollers 11 and the inner ring 12. The roller assembly 4 is housed in the track groove 5 of the outer joint member 2, and the center Cr (see Figure 4) of the roller assembly 4 (roller 11) is located on the pitch circle PC of the track groove 5.

[0022] As shown in FIG. 4, needle rollers 13 are arranged between the cylindrical inner peripheral surface 11b of roller 11 and the cylindrical outer peripheral surface 12b of inner ring 12 in a so-called full-complement configuration without a cage, with the cylindrical inner peripheral surface 11b of roller 11 serving as the outer raceway surface and the cylindrical outer peripheral surface 12b of inner ring 12 serving as the inner raceway surface. Annular protrusions 12c are formed on both axial ends of the cylindrical outer peripheral surface 12b (inner raceway surface) of inner ring 12. Details will be described later. The inner peripheral surface 12a of inner ring 12 forms an arc-shaped convex surface in a vertical cross section including the axis of inner ring 12. This arc-shaped convex surface has a radius of curvature ri of, for example, approximately 30 mm to allow for left and right tilt of trunnion 7 relative to inner ring 12 due to whirling, which is unique to tripod-type constant velocity universal joints. As shown in FIG. 3, torque is transmitted by contact between the trunnion 7, which has an approximately elliptical cross section, and the inner ring 12, which has a circular inner surface 12a. Therefore, in order to reduce the surface pressure at the contact point between the trunnion 7 and the inner ring 12 and to ensure the strength of the trunnion 7, the ellipticity b / a of the major axis a and minor axis b of the approximately elliptical shape of the trunnion 7 and the radius of curvature ri of the inner surface 12a of the inner ring 12 (see FIG. 4) are set.

[0023] As shown in FIG. 4, the outer peripheral surface 11a of the roller 11 is formed as a partial sphere with a curvature radius ro whose center of curvature is located on the axis 4x of the roller assembly 4, in other words, on the axis 7x of the trunnion 7 shown in FIG. 3. The roller assembly 4, consisting of the inner ring 12, needle rollers 13, and rollers 11, is structured to be inseparable by washers 14 and 15. The washers 14 and 15 are divided at a single point in the circumferential direction (see FIG. 3) and are fitted into an annular groove in the cylindrical inner peripheral surface 11b of the roller 11 in an elastically contracted state. The divided slits 14a and 15a of the washers 14 and 15 of this embodiment are divided in the radial direction. The washers 14 and 15 of this embodiment are easier to process and can reduce manufacturing costs compared to washers of roller assemblies having slits divided obliquely relative to the radial direction (see FIG. 10).

[0024] 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 cross 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 is in contact with 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 a gap m is formed 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 assemblies 4 attached to the trunnions 7 of the tripod member 3 roll on the roller guideways 6 of the track grooves 5 of the outer joint member 2.

[0025] As shown in Figure 5, the outer peripheral surface 11a of the roller 11 is formed as a partial sphere with a curvature radius ro and a center of curvature Or located on the axis 7x of the trunnion 7. The center of curvature Or is also the center Cr of the roller assembly. The roller guideway 6 is formed as a Gothic arch-shaped cross section with a curvature radius Rt. The center of curvature ORt passes through the intersection T of 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 on a line with a contact angle α, beyond the center line 5x of the track groove 5. The curvature radius Rt is appropriately set larger than the curvature radius ro. Therefore, the outer peripheral surface 11a of the roller 11 and the roller guideway 6 are in angular contact at two points with a contact angle α relative to a horizontal line XX passing through the intersection T. A small track gap δ is provided between the roller guideway 6 and the outer peripheral surface 11a of the roller 11. In Figure 5, the center line 5x of the track groove and the axis 7x of the trunnion 7 are shown aligned. Therefore, the track gap on one side is δ / 2.

[0026] Because the cross section of the trunnion 7 is approximately elliptical, at a commonly used relatively small operating angle, the axis of the tripod member 3 is inclined with respect to the axis of the outer joint member 2 as shown in Figure 6, but the roller assembly 4 can be inclined with respect to the axis of the trunnion 7 of the tripod member 3. Therefore, the rollers 11 of the roller assembly 4 and the roller guideways 6 are prevented from intersecting obliquely and roll correctly, which reduces induced thrust and sliding resistance and enables low vibration of the joint. In this specification and claims, the term "approximately elliptical shape" is not limited to a literal elliptical shape, but also includes shapes generally referred to as egg shapes, oval shapes, etc.

[0027] 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 trunnion 7 and the inner peripheral surface 12a of the inner ring 12 shown in Figure 3 interfere with each other, and the roller assembly 4 (roller 11) cannot tilt any further relative to the trunnion 7. Because the angle at which the roller assembly 4 can tilt relative to the trunnion 7 is limited, if the angle is greater than the predetermined angle that exceeds the normal operating angle, the roller assembly 4 must tilt by the missing angle relative to the track groove 5. However, as shown in Figure 4, the outer peripheral surface 11a of the roller 11 is formed as a partial sphere with a radius of curvature ro whose center of curvature is on the axis 7x of the trunnion 7, so the roller assembly 4 can tilt within the track groove 5 and can also accommodate large operating angles.

[0028] The overall configuration of the tripod type constant velocity universal joint 1 of this embodiment is as described above. Next, the characteristic configuration will be described. The characteristic configuration is as follows. (1) In a double roller type tripod constant velocity universal joint, an annular protrusion is formed on at least the axial end of the cylindrical outer surface of the inner ring of the roller assembly, on the axial end on the base side of the leg shaft of the tripod member. (2) When the needle rollers move axially relative to the cylindrical outer peripheral surface of the in-ring, the ends of the needle rollers interfere with the annular projections and do not come into contact with the washers.

[0029] Before specifically explaining the above characteristic configuration, the roller assemblies of the existing tripod-type constant velocity universal joint that was the subject of study will be explained with reference to Figures 9 and 10. Figure 9 is a longitudinal cross-sectional view of the roller assemblies of the existing tripod-type constant velocity universal joint that was the subject of study, with Figure 9(a) being a standard roller assembly with a pair of washers on both ends of the inner ring, and Figure 9(b) being a roller assembly using a flanged roller and a washer. Figure 10 is a plan view showing both roller assemblies and trunnions in Figures 9(a) and 9(b).

[0030] As roller assemblies for existing tripod-type constant velocity universal joints, we will show two examples: a standard roller assembly with a pair of washers on both axial ends of the inner ring, and a flanged roller assembly using a single flanged roller and a single washer. As shown in Figure 9(a), the standard roller assembly 4' has a structure in which washers 14' and 15' fitted in annular grooves on the cylindrical inner peripheral surface 11'b of the roller 11' come into contact with the end faces of the needle roller 13' and the inner ring 12', preventing the roller assembly 4' from separating.

[0031] As shown in Figure 10, a standard roller assembly 4' is designed to achieve compactness and cost reduction by fastening a needle roller 13', which is installed between a roller 11' and an inner ring 12', with upper and lower washers 14' and 15'. The divided slits 14'a in the washer 14' are formed at an angle to the radial direction, allowing the end faces of the needle rollers 13' to easily roll through the slits 14'a. The divided slits in the washer 15' are not shown. However, the slits 14'a formed at an angle to the radial direction increase the processing load and lead to increased manufacturing costs.

[0032] As shown in Figure 9(b), the flanged roller assembly 4" has a flange 11"c formed on one axial end (towards the base of the trunnion) of the cylindrical inner circumferential surface 11"b of the roller 11", and a washer 14' fitted in an annular groove on the other axial end of the cylindrical inner circumferential surface 11"b of the roller 11". The flange 11"c and washer 14' come into contact with the end faces of the needle roller 13" and the inner ring 12", preventing the roller assembly 4" from separating. The flanged roller assembly 4" differs from the standard roller assembly 4' described above in that it does not have the lower washer 15' and has a flange 11"c on the underside of the roller 11". However, because the required flange length is long, the flange reduces the manufacturing yield of the roller 11", which is disadvantageous in terms of cost, and the flange end face bears the downward load on the inner ring 12", which is disadvantageous in terms of strength.

[0033] Using the standard roller assembly 4' in Figure 9(a) as an example, the results and findings of investigations into operation and behavior during the development process are explained with reference to Figures 11 to 14. Figure 11 is a diagram explaining the state, operation, and behavior when the trunnion and roller assembly are positioned in the track groove at the top dead center (0° phase) of the outer joint member with the operating angle set; Figure 11(a) is a longitudinal cross-sectional view, and Figure 11(b) is a transverse cross-sectional view. Figure 12 is a diagram explaining the state, operation, and behavior when the roller assembly 4'(1) in Figure 11(b) has rotated clockwise to a 90° phase; Figure 12(a) is a longitudinal cross-sectional view, and Figure 12(b) is a transverse cross-sectional view. Figure 13 is a diagram explaining the state, operation, and behavior when the roller assembly 4'(1) in Figure 11(b) has further rotated clockwise to a 180° phase; Figure 13(a) is a longitudinal cross-sectional view, and Figure 13(b) is a transverse cross-sectional view. Figure 14(a) is a diagram showing the combined operation and behavior of the roller assembly in the track groove with left and right tilt, Figure 14(b) is a cross-sectional view showing the left and right tilt in clockwise rotation, Figure 14(c) is a cross-sectional view showing the horizontal state, and Figure 14(d) is a cross-sectional view showing the left and right tilt in counterclockwise rotation.

[0034] In Figure 11(b), the axis 7x of the leg shaft of the tripod member is shown by a thick dashed line, and the outline of the tripod member is not shown. The two roller assemblies 4'(2) and 4'(3) on the lower side of Figure 11(b) do not appear in Figure 11(a), which is a vertical cross section.

[0035] When the joint has an operating angle θ, a plane F including the axis 7x of the trunnion 7 of the tripod member 3 is tilted by the operating angle θ. The tripod member 3 rotates on this plane F. Even when the joint has an operating angle θ, the center Cr of the roller assembly 4' (see FIG. 4) is located on the axis 7x of the trunnion 7 of the tripod member 3 and is constrained on the pitch circle PC of the track groove 5. As shown in FIGS. 11(a) and 11(b), the upper roller assembly 4'(1) is located at a 0° phase (ψ = 0°) on the opening side I of the cup portion 2a of the outer joint member 2. This state is called the 0° phase state. In this state, the upper roller assembly 4'(1) is in a horizontal position, and the axis 4x of the roller assembly 4'(1) is not tilted left or right with respect to a vertical plane including the center line 5x of the track groove 5. Furthermore, the axis 7x of the upper trunnion 7 of the tripod member 3 is not tilted left or right with respect to a vertical plane including the center line 5x of the track groove 5. The arrows shown on the radially outer side of the outer joint member 2 indicate that a rotational torque in the direction of the arrow is applied to the outer joint member 2. In other words, the left side of the roller assembly 4' is the load side. The same applies to Figures 12(b) and 13(b) described below.

[0036] The three trunnions 7 of the tripod member 3 are formed to protrude radially outward from three equally spaced positions in the circumferential direction, and the relative positions of the three trunnions are fixed. The center Cr of each roller assembly 4' (see FIG. 4) is located on the axis 7x of the trunnion 7 of the tripod member 3 and is constrained on the pitch circle PC of the track groove 5. Therefore, as shown in FIG. 11(b), when an operating angle θ is taken, the axes 7x of the three trunnions 7 are located on an inclined plane F, and the center Ct of the tripod member 3 shifts downward with respect to the joint center Cj, causing the tripod member 3 to tilt by the operating angle θ. As a result, the roller assembly 4'(1) and the axis 7x of the trunnion 7 on which the roller assembly 4'(1) is mounted do not tilt left or right with respect to a vertical plane including the center line 5x of the track groove 5, but relative axial movement occurs between the inner ring 12' of the roller assembly 4'(1) and the trunnion 7.

[0037] On the other hand, the axis 4x of the two lower roller assemblies 4'(2) and 4'(3) and the axis 7x of the trunnion 7 on which these roller assemblies 4'(2) and 4'(3) are mounted are tilted left and right as the trunnion 7 moves axially relative to the inner ring 12'. Depending on the direction of the left and right tilt of the axis 7x of the trunnion 7 and the direction of the axial relative movement of the trunnion 7 with respect to the inner ring 12', the lower right roller assembly 4'(2) is tilted left and right as shown by the arrow, and the lower left roller assembly 4'(3) is tilted right and left as shown by the arrow.

[0038] The joint center Cj is the center of curvature of the pitch circle radius PCR of the track grooves 5 of the outer joint member 2. The center Ct of the tripod member 3 and the center Cs of the shaft coincide with each other. This state is also the same in Figures 12(b) and 13(b) described later. For ease of understanding, Figure 11(b) is a schematic diagram in which the operating angle θ is approximately 30°, and the deviation amount and lateral tilt β of the center Ct of the tripod member 3 with respect to the joint center Cj are exaggerated. This is also shown in Figures 12(b) and 13(b) described later.

[0039] The state in which the joint is rotated clockwise and the roller assembly 4'(1) is positioned at a 90° phase will be described with reference to Figure 12. Figure 12 is a diagram illustrating the state, operation, and behavior of the roller assembly 4'(1) in Figure 11(b) when rotated clockwise to the 90° phase. As shown in Figure 12(b), when the roller assembly 4'(1) is positioned at a 90° phase (ψ=90°), the axis 4x of the roller assembly 4'(1) is not inclined left or right with respect to the horizontal plane containing the center line 5x of the track groove 5. Furthermore, the axis 7x of the trunnion 7 is not inclined left or right with respect to the horizontal plane containing the center line 5x of the track groove 5.

[0040] The center Cr (see FIG. 4) of each roller assembly 4' is located on the axis 7x of the trunnion 7 of the tripod member 3 and is constrained on the pitch circle PC of the track groove 5. Therefore, as shown in FIG. 12(b), when the roller assembly 4'(1) is in a 90° phase position, the center Ct of the tripod member 3 is shifted to the right in the drawing with respect to the joint center Cj. As a result, the axis 4x of the roller assembly 4'(1) and the axis 7x of the trunnion 7 on which this roller assembly 4'(1) is mounted do not tilt left or right with respect to the horizontal plane containing the center line 5x of the track groove 5, but there is relative axial movement between the inner ring 12' of the roller assembly 4'(1) and the trunnion 7. When the roller assembly 4'(1) is in a 90° phase position, the amount of deviation of the center Ct of the tripod member 3 from the joint center Cj increases, and the amount of relative axial movement between the inner ring 12' of the roller assembly 4'(1) and the trunnion 7 increases. A clockwise lateral tilt β90, as indicated by the arrow, occurs between the axis 4x of the diagonally lower roller assembly 4'(2) and the axis 7x of the trunnion 7, as the trunnion 7 moves axially relative to the inner ring 12'. A counterclockwise lateral tilt β90, as indicated by the arrow, occurs between the axis 4x of the diagonally upper roller assembly 4'(3) and the axis 7x of the trunnion 7, as the trunnion 7 moves axially relative to the inner ring 12'.

[0041] The state in which the roller assembly 4'(1) is positioned at the 180° phase after the joint is further rotated clockwise will be described with reference to Figure 13. Figure 13 is a diagram illustrating the state, operation, and behavior of the roller assembly 4'(1) in Figure 11(b) after it has rotated clockwise to the 180° phase on the far side II of the cup portion 2a of the outer joint member 2. The center Cr (see Figure 4) of each roller assembly 4' is located on the axis 7x of the trunnion 7 of the tripod member 3 and is constrained on the pitch circle PC of the track groove 5. Therefore, as shown in Figure 13(b), when the roller assembly 4'(1) is positioned at the 180° phase (ψ = 180°), the roller assembly 4'(1) returns to a horizontal position, and the axis 4x of the roller assembly 4'(1) does not tilt left or right with respect to the vertical plane including the center line 5x of the track groove 5. Furthermore, the axis 7x of the trunnion 7 on which the roller assembly 4'(1) is mounted does not tilt left or right with respect to the vertical plane including the center line 5x of the track groove 5.

[0042] Because the center Ct of the tripod member 3 is shifted upward relative to the joint center Cj, the roller assembly 4'(1) and the truss axle 7 on which this roller assembly 4'(1) is externally mounted do not tilt left or right relative to a vertical plane containing the center line 5x of the track groove 5, but relative axial movement occurs between the inner ring 12' of the roller assembly 4'(1) and the truss axle 7. The axis 4x of the upper left roller assembly 4'(2) and the axis 7x of the truss axle 7 on which this roller assembly 4'(2) is externally mounted undergo a left or right tilt β180 in a counterclockwise direction as indicated by the arrow, along with the axial relative movement of the truss axle 7 with respect to the inner ring 12'. Furthermore, the axis 4x of the upper right roller assembly 4'(3) and the axis 7x of the truss axle 7 on which this roller assembly 4'(3) is externally mounted undergo a right or left tilt β180 in a clockwise direction as indicated by the arrow, along with the axial relative movement of the truss axle 7 with respect to the inner ring 12'.

[0043] For ease of understanding, the above has specifically explained that the axis 4x of the roller assembly 4' and the axis 7x of the trunnion 7 on which this roller assembly 4' is externally disposed tilt left and right, and that the trunnion 7 moves axially relative to the inner ring 12', corresponding to the states in which the roller assembly 4'(1) is positioned at the 0° phase (ψ=0°), 90° phase (ψ=90°), and 180° phase (ψ=180°). In reality, in the double-roller type tripod constant velocity universal joint 1 under consideration, while the joint rotates once with the operating angle set, the left and right tilt of the axis 4x of the roller assembly 4' and the axis 7x of the trunnion 7 on which this roller assembly 4' is externally disposed, and the relative axial movement of the trunnion 7 with respect to the inner ring 12', occur repeatedly and continuously while fluctuating.

[0044] The relative axial movement and left-right tilt behavior of the roller assembly in the track groove will be summarized with reference to Figure 14. Figure 14(a) is a diagram showing the combined left-right tilt behavior of the roller assembly in the track groove, Figure 14(b) is a cross-sectional view showing the left-right tilt during clockwise rotation, Figure 14(c) is a cross-sectional view showing the horizontal state, and Figure 14(d) is a cross-sectional view showing the left-right tilt during counterclockwise rotation.

[0045] As shown in Figure 14(a), the roller assembly 4' undergoes relative axial movement and tilts to the left or right, resulting in a horizontal position, clockwise rotation, or counterclockwise rotation, depending on the phase described above. The horizontal position of the roller assembly 4' in Figure 14(c) will be explained in more detail, for example, in the state of phase 0° (ψ = 0°) shown in Figures 11(a) and 11(b). The trunnion 7 is tilted by an operating angle θ (see also Figure 6). When the roller assembly 4'(1) rotates from a phase just before phase 0° (ψ = 0°) to phase 0° (ψ = 0°), the roller assembly 4'(1) assumes a horizontal position. Although the trunnion 7 is tilted by the operating angle θ, it assumes a horizontal position relative to the trunnion 7 when viewed in a cross section perpendicular to the axis of the outer joint member. This means that the moment the phase reaches 0° (ψ = 0°), the relative axial movement of the trunnion 7 relative to the inner ring 12' of the roller assembly 4'(1) becomes zero instantaneously, and the load of the trunnion 7 moving the inner ring 12' up and down disappears. As a result, the roller assembly 4'(1) assumes the horizontal position as described above, with the inner ring 12' and needle roller 13' positioned axially at the center between the washers 14' and 15'. An axial gap is formed between both ends of the inner ring 12' and the washers 14' and 15', dividing them into two equal parts. The roller assembly 4'(1) can also assume a horizontal position in which the axis 7x of the trunnion 7 and the axis 4x of the roller assembly 4'(1) coincide, as shown in Figures 12(a) and 12(b) when the phase is 90° (ψ = 90°).

[0046] To further explain the left-right tilt of the roller assembly 4' in FIG. 14(b), for example, when the inner ring 12' of the roller assembly 4' (3) on the lower left side of FIG. 11(b) moves relative to the truss 7 of the tripod member 3 due to rotation of the outer joint member in the direction of the arrow, the truss 7 pulls the inner ring 12' of the roller assembly 4' (3) downward, causing left-right tilt of the right rotation. At the same time, the lower end faces of the inner ring 12' and the needle rollers 13' abut against the lower washer 15', and the upper end faces of the inner ring 12' and the needle rollers 13' move away from the upper washer 14', creating an axial gap (axial movement Ia). The axial movement Ia of the inner ring 12' is an appropriate dimension taking into account mass productivity and past performance.

[0047] To further explain the left-right tilt of the roller assembly 4' in Figure 14(d), for example, when the inner ring 12' of the roller assembly 4' on the lower right side shown in Figure 11(b) moves relative to the truss axle 7 of the tripod member 3 due to rotation of the outer joint member in the direction of the arrow, the truss axle 7 pushes the inner ring 12' of the roller assembly 4'(2) upward, causing left-right tilt of the roller assembly 4' in Figure 14(d). The upper end face of the inner ring 12' and the upper end faces of the needle rollers 13' come into contact with the upper washer 14', and the lower end faces of the inner ring 12' and the lower end faces of the needle rollers 13' move away from the lower washer 15', creating an axial clearance (axial movement amount Ia).

[0048] Although the components of the roller assembly 4' of the tripod-type constant velocity universal joint 1 have a small amount of rolling compared to a typical rolling bearing, the relative movement of the components of the roller assembly 4' is significantly different and extremely severe compared to a typical rolling bearing. The axial load generated when the inner ring 12' of the roller assembly 4' repeatedly moves relative to the axial direction on the truss 7 of the tripod member 3, and the uneven contact between the cylindrical outer peripheral surface 12'b of the inner ring 12', the needle roller 13', and the cylindrical inner peripheral surface 11'b of the roller 11', result in a large axial load acting on the needle roller 13'. In particular, as mentioned above, when the roller assembly 4'(1) is in a 90° phase position, the amount of relative axial movement between the inner ring 12' of the roller assembly 4'(1) and the truss 7 becomes large, and the axial load on the needle roller 13' toward the base of the truss 7 of the tripod member 3, i.e., toward the washer 15', becomes large. It was discovered that under such a load condition, the end faces of the needle rollers 13' roll on the slits in the washer 15', which may impair the smooth rotation of the needle rollers 13', deteriorate NVH characteristics such as induced thrust, and shorten the lifespan of the needle rollers 13' and washer 15' due to premature wear.

[0049] The above-mentioned relative axial movement and left-right tilt behavior of the roller assembly within the track grooves is similar between the existing tripod constant velocity universal joint that was the subject of study and the tripod constant velocity universal joint of this embodiment. Based on this result, and taking into consideration the above-mentioned relative movements of the components of the roller assembly, a new idea was reached regarding the relationship between the washer and needle roller of the roller assembly, leading to the following characteristic configuration of this embodiment. (1) In a double roller type tripod constant velocity universal joint, an annular protrusion is formed on at least the axial end of the cylindrical outer surface of the inner ring of the roller assembly, on the axial end on the base side of the leg shaft of the tripod member. (2) When the needle rollers move axially relative to the cylindrical outer peripheral surface of the in-ring, the ends of the needle rollers interfere with the annular projections and do not come into contact with the washers.

[0050] The characteristic features of the first embodiment will be described in detail with reference to FIG. 7. FIG. 7 shows the characteristic features of the roller assembly of this embodiment, with FIG. 7(a) being a longitudinal cross-sectional view of a portion of the roller assembly and FIG. 7(b) being an enlarged longitudinal cross-sectional view of portion G in FIG. 7(a). The roller assembly 4 is primarily 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 inner ring 12 has a cylindrical outer peripheral surface 12b, and annular protrusions 12c are formed on both axial ends of the cylindrical outer peripheral surface 12b. Because the annular protrusions 12c are formed, the cylindrical outer peripheral surface 12b, which forms the inner raceway of the needle rollers 13, is recessed in a groove-like shape. The corner radius r2 between the cylindrical outer peripheral surface 12b and the annular protrusion 12c is appropriately set in consideration of the contact state with the end face radius r1 of the needle rollers 13, and is approximately 1 to 5 mm.

[0051] Washers 14, 15 fitted in annular grooves formed in the cylindrical inner peripheral surface 11b of roller 11 contact both axial end surfaces of inner ring 12, and needle rollers 13 are arranged on the grooved cylindrical outer peripheral surface 12b of inner ring 12. When needle rollers 13 move axially relative to cylindrical outer peripheral surface 12b of inner ring 12, the ends of needle rollers 13 interfere with annular protrusions 12c, and an axial gap is maintained between the ends of needle rollers 13 and washers 14, 15, so that the ends of needle rollers 13 do not come into contact with washers 14, 15. This structure in which the needle rollers and washers do not come into contact with each other is a new idea.

[0052] The ends of needle rollers 13 are configured not to come into contact with washers 14, 15, so the end faces of needle rollers 13 do not roll over the slits in washers 14, 15, eliminating the risk of impairing the smooth rotation of needle rollers 13, worsening NVH characteristics such as induced thrust, and shortening the lifespan of needle rollers 13 due to early wear of the end faces of needle rollers 13 and washers 14, 15.

[0053] In the roller assembly 4 of this embodiment, the ends of the needle rollers 13 are configured not to come into contact with the washers 14, 15, so the divided slits 14a, 15a of the washers 14, 15 are divided in the radial direction. The washers 14, 15 of this embodiment are easier to process than washers of roller assemblies having slits divided obliquely relative to the radial direction (see FIG. 10), and manufacturing costs can be reduced. However, the washers 14, 15 of this embodiment may also have slits divided obliquely relative to the radial direction.

[0054] A modified example of the characteristic configuration of the roller assembly of the first embodiment will be described with reference to FIG. 8. FIG. 8 shows a modified example of the characteristic configuration of the roller assembly of this embodiment, with FIG. 8(a) being a longitudinal cross-sectional view of a portion of the roller assembly and FIG. 8(b) being an enlarged longitudinal cross-sectional view of portion H in FIG. 8(a). In this modified example, an annular protrusion 12c is formed only on one axial end of the cylindrical outer peripheral surface 12b of the inner ring 12 of the roller assembly 4. This axial end of the cylindrical outer peripheral surface 12b of the inner ring 12 is on the root side of the trunnion 7 of the tripod member 3, i.e., on the washer 15 side. As mentioned above, this is in consideration of the large axial load on the needle rollers 13 directed toward the root side of the trunnion 7 of the tripod member 3, toward the washer 15 side. Since the axial load of the needle roller 13 toward the side opposite the base of the trunnion 7, i.e., the washer 14 side, is relatively small, no annular protrusion 12 is formed at the other axial end of the cylindrical outer surface 12b of the inner ring 12.

[0055] The case of circular contact is shown in Figure 15. Figure 15 is a partial cross-sectional view showing a modified example in which the contact state between the roller and roller guideway of the first embodiment is circular contact. In the case of circular contact, the roller guideway 6 of the track groove 5 is formed into a partially cylindrical shape with a radius of curvature Rt' whose center of curvature ORt' is located on a horizontal line XX that passes through an intersection T between the center line 5x of the track groove 5 and the pitch circle PC of the track groove 5. The roller guideway 6 and roller 11 come into contact with each other around the horizontal line XX that passes through the intersection T. The case of circular contact can be applied in the same way as the case of angular contact.

[0056] A tripod type constant velocity universal joint according to a second embodiment of the present invention will be described with reference to FIG. 16. FIG. 16 is a cross-sectional view of the tripod type constant velocity universal joint of this embodiment. However, the two lower rollers and the tripod member are not shown in cross section, and the shaft is not shown. This embodiment is a double roller type tripod type constant velocity universal joint, but differs from the double roller type tripod type constant velocity universal joint 1 of the first embodiment in the shape of the trunnion and the shape of the roller assembly. Parts having similar functions are assigned the same reference numerals, and the main points will be described.

[0057] As shown in FIG. 16 , in the tripod-type constant velocity universal joint 1 of this embodiment, the outer peripheral surfaces 7a of the trunnions 7 of the tripod members 3 are formed in a spherical shape, and the inner rings 12 of the roller assemblies 4 have cylindrical inner peripheral surfaces 12a that are slidably fitted to the spherical outer peripheral surfaces 7a of the trunnions 7 of the tripod members 3. The outer peripheral surfaces 11a of the rollers 11 are formed in an annular shape with a relatively small radius of curvature ro″ and a center of curvature at a position Or″ that is radially offset from the axis 7x of the trunnions 7. As the other configurations are the same as those of the first embodiment, parts having similar functions are designated by the same reference numerals, and the main points will be described below.

[0058] The roller assembly 4 is mainly composed of a roller 11, an inner ring 12, and a number of needle rollers 13 fitted between the rollers 11 and the inner ring 12 in a full complement state. The roller 11 has a cylindrical inner circumferential surface 11b. Washers 14 and 15 are fitted into annular grooves in the cylindrical inner circumferential surface 11b of the roller 11 in an elastically contracted state, and the roller assembly 4 consisting of the inner ring 12, needle rollers 13, and roller 11 is structured to not separate due to the washers 14 and 15. The inner ring 12 has a cylindrical outer circumferential surface 12b, and annular protrusions 12c are formed on both axial ends of the cylindrical outer circumferential surface 12b. In the roller assembly 4 of this embodiment, when the needle rollers 13 move axially relative to the cylindrical outer peripheral surface 12b of the in-ring 12, the ends of the needle rollers 13 interfere with the annular protrusions 12c, and an axial gap is maintained between the ends of the needle rollers 13 and the washers 14, 15, so that the ends of the needle rollers 13 do not come into contact with the washers 14, 15. Because the ends of the needle rollers 13 are configured not to come into contact with the washers 14, 15, the end faces of the needle rollers 13 do not roll on the slits of the washers 14, 15, eliminating the risk of impairing the smooth rotation of the needle rollers 13, deteriorating NVH characteristics such as induced thrust, and reducing the lifespan of the end faces of the needle rollers 13 and the washers 14, 15 due to premature wear. The roller assembly 4 is housed in the track grooves 5 of the outer joint member 2, and the center of the roller assembly 4 (rollers 11) in the width direction is located on the pitch circle PC of the track groove 5.

[0059] The tripod member 3 has three trunnions 7 protruding in the radial direction. The outer peripheral surface 7a of each trunnion 7 is spherical with its center of curvature located on the axis 7x of the trunnion 7, and a cylindrical inner peripheral surface 12a of an inner ring 12 of the roller assembly 4 is slidably fitted to the spherical outer peripheral surface 7a. When the joint forms an operating angle, the roller assembly 4 can tilt with respect to the axis of the trunnions 7 of the tripod member 3 and can move in the axial direction. This prevents the rollers 11 of the roller assembly 4 from intersecting the roller guideway 6 at an angle, allowing them to roll correctly.

[0060] The roller guideway 6 is formed by a partial cylindrical surface of a relatively small radius of curvature Rt" whose center of curvature is located 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, at a position ORt" radially offset from the center line 5x of the track groove 5, and extends parallel to the axis of the joint. In this embodiment, the track groove 5 is provided with a flange 5a on one side thereof, but as in a modified example shown in FIG. 17, it is also possible not to provide a flange on one side of the track groove 5.

[0061] In the tripod constant velocity universal joint 1 according to the second embodiment shown in Fig. 16 and the modified example shown in Fig. 17, a plurality of 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, and the needle rollers 13 are arranged in a so-called full-complement state without a cage. A characteristic configuration is that, in the roller assembly 4 of this embodiment, the inner ring 12 also has annular protrusions 12c formed on both axial ends of the cylindrical outer peripheral surface 12b. When the needle rollers 13 move axially relative to the cylindrical outer peripheral surface 12b of the inner ring 12, the ends of the needle rollers 13 interfere with the annular protrusions 12c, and an axial gap is maintained between the ends of the needle rollers 13 and the washers 14, 15, so that the ends of the needle rollers 13 do not come into contact with the washers 14, 15. The ends of needle rollers 13 are configured so as not to come into contact with washers 14, 15, and therefore the end faces of needle rollers 13 do not roll on the slits of washers 14, 15, eliminating the risk of impairing smooth rotation of needle rollers 13, worsening NVH characteristics such as induced thrust, and shortening the lifespan due to early wear of the end faces of needle rollers 13 and washers 14, 15. The above-mentioned characteristic configuration explained in relation to the tripod type constant velocity universal joint of the first embodiment is also applicable to the tripod type constant velocity universal joint of this embodiment, and so applies mutatis mutandis.

[0062] 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]

[0063] 1 Tripod-type constant velocity universal joint 2 Outer joint member 3 Tripod member 4 Roller Assembly 5 Track groove 5x track groove centerline 6 Roller guideway 7 Leg axis 7x Leg axis 11 Laura 11a Outer surface 11b Cylindrical inner surface 12 Inner Ring 12a Inner surface 12b Cylindrical outer surface 12c Annular protrusion 13 Needle roller 14, 15 Washers Cr Center of inner ring Ct Center of tripod member Or center of curvature Or” center of curvature ORt center of curvature ORt' center of curvature ORt” center of curvature PC track groove pitch circle Rt radius of curvature Rt' radius of curvature Rt” radius of curvature T intersection XX Horizontal line a Long axis b Minor axis m gap ro radius of curvature ro” radius of curvature α contact angle β Left / right tilt θ Working angle δ Track gap

Claims

1. a tripod-type constant velocity universal joint comprising an outer joint member having three axially extending track grooves formed at three equally spaced positions in the circumferential direction of its inner circumference and having roller guideways arranged circumferentially opposite the track grooves; a tripod member having three trunnions protruding radially outward from the three equally spaced positions in the circumferential direction; and a roller assembly externally fitted to the trunnions, wherein the roller assembly comprises an inner ring externally fitted to the trunnions, rollers inserted in the roller guideways, a plurality of needle rollers arranged between the cylindrical outer peripheral surface of the inner ring and the cylindrical inner peripheral surface of the rollers, and a pair of washers arranged on both axial sides of the needle rollers and the inner ring and with outer peripheral edges attached to the inner circumference of the rollers, an annular protrusion is formed at least on an axial end portion of a cylindrical outer peripheral surface of the inner ring that is closer to the base of the trunnion of the tripod member; a tripod-type constant velocity universal joint characterized in that, when the needle rollers move axially relative to the cylindrical outer peripheral surface of the in-ring, the ends of the needle rollers interfere with the annular protrusions and do not come into contact with the washer.

2. 2. A tripod-type constant velocity universal joint according to claim 1, wherein the annular projections are formed on both axial ends of the cylindrical outer peripheral surface of the inner ring.

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

4. 4. The tripod type constant velocity universal joint according to claim 1, wherein the rollers and the roller guideways are in angular contact with each other.

5. 4. The tripod type constant velocity universal joint according to claim 1, wherein the rollers and the roller guideways are in circular contact with each other.

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