Tripod CVJ Trunnion Corner Design for Compact Joints
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Solution Overview
Problem
Existing tripod type constant velocity universal joints face challenges in reducing joint outer diameter while maintaining strength and life, as they struggle to achieve a compact and lightweight design due to limitations in pitch circle diameter reduction and increased risk of edge loads and instability from recess shapes at the root portion.
Innovation Solution
A tripod type constant velocity universal joint design featuring a corner portion without a recess shape at the root portion of the trunnion journal, ensuring contact over the entire length except for the end surface corner, which restricts needle roller movement and maintains load balance, allowing for radial inward positioning of needle rollers and reducing the number of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inner washer is provided at the root portion of the trunnion journal, then the needle roller movement is restricted, but the pitch circle diameter cannot be reduced and the joint outer diameter cannot be minimized
Solution Approach 1:
The invention removes the inner washer component entirely and replaces it with a corner portion structure integrated into the trunnion journal. This extraction of the separate washer component allows for radial inward positioning of needle rollers, reducing the pitch circle diameter and joint outer diameter while maintaining the needle roller movement restriction function through the corner portion geometry.
Solution Approach 2:
The invention merges the function of the inner washer into the corner portion of the trunnion journal structure. The corner portion is formed by continuous material from the cylindrical outer peripheral surface without a recess, integrating the movement restriction function directly into the journal geometry rather than requiring a separate component.
2Volume of moving object
If a recess is provided at the root portion to eliminate the inner washer, then the joint outer diameter is reduced, but the root portion thickness is reduced decreasing strength and the needle roller rolling fatigue life is reduced
Solution Approach 1:
The corner portion is formed with a continuous curved surface transitioning from the cylindrical outer peripheral surface without a sharp recess. This curvature design maintains material continuity and structural integrity at the root portion, preserving strength while enabling the reduced outer diameter configuration.
3Volume of moving object
If a recess is provided at the root portion to eliminate the inner washer, then the joint outer diameter is reduced, but the needle roller rolling fatigue life is reduced due to shortened inner raceway surface
Solution Approach 1:
By removing the recess entirely and using the corner portion structure, the inner raceway surface is extended to contact the needle roller over a longer axial length. This extraction of the recess feature directly increases the rolling contact length, thereby extending the needle roller rolling fatigue life while maintaining the compact joint outer diameter.
4Volume of moving object
If the needle roller is positioned radially inward to reduce joint outer diameter, then the joint is more compact, but the number of components cannot be reduced without additional structures
Solution Approach 1:
The invention extracts and removes the inner washer component from the design, allowing the needle rollers to be positioned radially inward without requiring this additional component. The corner portion structure provides the necessary movement restriction function, enabling component reduction while achieving the compact joint outer diameter.
Solution Approach 2:
The corner portion of the trunnion journal serves multiple functions: it restricts needle roller movement axially, maintains structural strength at the root portion, and enables the compact configuration. This self-service approach eliminates the need for separate components like the inner washer.
Data Source
AI summary
A tripod type constant velocity universal joint includes an outer joint member having track grooves, a tripod member including trunnion journals, and spherical rollers each fitted in a rotatable manner about each of the trunnion journals through intermediation of a plurality of needle rollers. A corner portion is formed at a root portion of each of the trunnion journals so as to restrict movement of the plurality of needle rollers in the axial direction toward the root portion of each of the trunnion journals by interference between an end surface corner rounded portion of each of the plurality of needle rollers and the corner portion at the root portion.