Tripod type constant velocity universal joint

Abstract

The invention provides a tripod type constant velocity universal joint that can restrain generation of an excessive frictional force inside the joint because of the rotation phase angle of the inner joint member, thereby suppressing vibration and achieving higher rotation durability. The tripod type constant velocity universal joint includes an outer roller rotatably located inside the roller guide section of the outer joint member, and an inner roller spherically fitted to the trunnion of the inner joint member so as to be pivotally rotatable, and to support the outer roller permitting relative rotation and relative axial movement, so that when a torque is applied with the outer joint member and the inner joint member oriented with an operating angle θ, a facet of the outer roller inclined along with the rotation of the inner joint member is sustained by the track groove bottom portion formed in a flat plane.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a tripod type constant velocity universal joint to be incorporated in for example a driving system of an automobile, for transmission of a rotational force mainly between non-linearly oriented rotating shafts. [0003] 2. Description of the Related Art [0004]FIG. 8 is a cross-sectional view showing a conventional tripod type constant velocity universal joint 41, for example disclosed in JP-A No. 2002-147482, including an inner joint member 44 having three trunnions 45 radially projecting from its outer circumferential surface, respectively engaged via a roller assembly 46 in each of three track grooves 43 provided on an inner circumferential surface of an outer joint member 42, so as to transmit a torque between the outer joint member 42 and the inner joint member 44, while allowing angular and axial displacement with respect to each other. [0005] The tripod type constant velocity univ...

AI Technical Summary

Benefits of technology

[0011] The present invention has been conceived in view of the foregoing problem, with an object to provide a tripod type constant velocity universal joint that can restrain generation of an excessive frictional force inside the joint because of the rotation phase angle of the inner joint member, thereby suppressing vibration and achieving higher rotation durability.

[0015] Further, since the track groove bottom portion is formed in a flat plane, the contact point between the outer roller and the track groove bottom portion moves along a predetermined arc along with the rotation of the inner joint member. Because of such motion, the distance between contact point and center, i.e. from the contact point between the outer roller and the track groove bottom portion to the center of moment is maintained at a predetermined length despite the change in rotation phase angle of the inner joint member. By contrast in the conventional structure, the distance between contact point and center L is maintained at a predetermined length while a facet of the outer roller 48 is contacting the flange portion 52 via the points in a region opposing the flange portion 52 (such as A1, A2, A3), however during a period after the outer roller 48 has made one-point contact with a facet of the flange portion 52 via the point B1, until the outer roller 48 makes two-point contact with a facet of the flange portion 52 at the points B1 and B2, the distance between contact point and center L gradually becomes shorter. Accordingly, in the tripod type constant velocity universal joint according to the present invention, provided that a clearance between a facet of the outer roller and the track groove bottom portion in an unloaded state is the same as the clearance between a facet of the outer roller 48 and the flange portion 52, the distance between contact point and center becomes longer than in the conventional structure, when the contact point between the outer roller and the track groove bottom portion is located in a region corresponding to between the flange portions 52 in the conventional structure, and therefore a frictional force generated at this stage between the outer roller and the track groove bottom portion is alleviated.

[0016] As already stated, in the tripod type constant velocity universal joint according to the present invention, the bottom portion of the track groove between the roller guide sections of the outer joint member is formed in a flat plane, so that the facet of the outer roller is supported by the track groove bottom portion. Such a structure suppresses an increase in rolling resistance of the outer roller with respect to the non-load side roller guide section, as well as an increase in frictional force between the outer roller and the track groove bottom portion, originating from an environment of use or a rotation phase angle of the inner joint member. Consequently, a frictional force inside the joint is restrained and a tertiary rotational axial force is reduced, which results in upgrading the rotation durability of the joint.

[0018] In the tripod type constant velocity universal joint thus constructed, the second reduced-thickness portion is formed in a groove shape having a rectangular or a curved cross-section. Accordingly, reducing the thickness in the same amount as a conventional structure, wherein a region on an outer periphery of the outer joint member corresponding to the track groove is scraped off to be flat, can increase the circumferential length of a maximum rotation radius portion of the outer joint member. The thickness reduction amount herein referred to means a volume of space enclosed by a cylinder having a radius equal to the maximum rotation radius of the outer joint member and the second reduced-thickness portion. The increase in circumferential length of the maximum rotation radius portion of the outer joint member leads to an increase in inner circumferential length of a maximum inner diameter portion of the boot fitted to the outer joint member, and hence in circumferential length of a mechanism that prevents a position shift in an axial direction between the outer joint member and the boot. Consequently, the boot acquires improved retention capability and upgraded sealing effect between the outer joint member and the boot.

[0019] As stated above, in the tripod type constant velocity universal joint according to the present invention, the track groove bottom portion of the outer joint member is formed in a flat plane and located close to a facet of the outer roller, and besides the outer joint member includes the second reduced-thickness portion on an outer periphery thereof in a region corresponding to the region where the track grooves are located. Therefore, the weight of the tripod type constant velocity universal joint can be reduced, yet securing sufficient retention capability of the boot.

Problems solved by technology

This incurs an excessive frictional force inside the joint, which leads to an increase in tertiary rotational axial force.

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