Tripod Constant Velocity Joint Angular Contact Stress Distribution
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Solution Overview
Problem
Conventional tripod constant velocity joints face challenges in achieving a compact design while maintaining sufficient torsional strength and durability, particularly due to increased stresses at reduced pitch circle radii, which can lead to torsional fatigue and reduced joint life.
Innovation Solution
The design incorporates an angular contact type joint with specific ratios between key dimensions, such as the length of contact points, curvature ratios, and trunnion diameters, to distribute stress evenly and reduce concentration at central points, enhancing the joint's compactness and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pitch circle radius is reduced to achieve a compact design, then the joint size is reduced, but the stress concentration increases leading to reduced durability and torsional fatigue
Solution Approach 1:
The contact area between the spherical roller and tripod housing groove is segmented into multiple discrete contact points rather than a single central contact point. This segmentation distributes the transmitted force across multiple locations, reducing stress concentration at any single point and thereby improving durability while maintaining the compact pitch circle radius design
Solution Approach 2:
The groove curvature radius is specifically optimized to create an angular contact pattern with distinct contact points. By adjusting the local geometric properties of the groove (its curvature radius relative to the spherical roller), the contact stress is redistributed to multiple points, enhancing the local stress distribution quality and preventing premature fatigue failure
2Device complexity
If the spherical roller and tripod housing groove are designed with circular contact type, then the structure is simple, but stress concentrates at the central contact point reducing joint life
Solution Approach 1:
The groove curvature radius is designed to be asymmetric relative to the spherical roller radius, creating an angular contact pattern rather than a symmetric circular contact. This asymmetry in geometric proportions causes the contact to occur at multiple points offset from the center, distributing stress and extending joint life without significantly increasing design complexity
Data Source
AI summary
A constant velocity joint for a drive system comprises: a tripod housing coupled to the first rotating shaft and having a plurality of guide grooves therein, each guide groove extending in an axial direction of the tripod housing; a spider coupled to the second rotating shaft and having a plurality of trunnions, each trunnion positioned in a corresponding guide groove of the tripod housing; and a spherical roller disposed between the trunnion and the guide groove of the tripod housing, and a plurality of needle rollers disposed between the trunnion and spherical roller. Each spherical roller is in angular contact with the guide groove of the tripod housing with two contact points displaced relative to a pitch circle diameter line of the tripod housing. The ratio of the length (CL) between two contact points of tripod housing groove to the length (SL) between two edges of spherical roller is between 0.5 and 0.85, and the ratio of the radius (TGR2) of the guide groove of the tripod housing to the radius (SRR) of the spherical roller is between 1.1 and 1.4.