Tripod CV Joint Roller Geometry for Smooth No-Torque Sliding
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Solution Overview
Problem
Existing tripod type constant velocity universal joints experience increased frictional force and hindered smooth sliding of rollers under no torque conditions due to a reduced contact angle between the roller and roller guide surfaces, leading to potential issues in assembly and operation.
Innovation Solution
The design sets a large contact angle between the outer peripheral surface of the roller and the roller guide surface by forming the roller with a partially spherical surface and the guide surface with a partially cylindrical surface, with a specific contact ratio of 0.95≤R/r≤1.08, allowing the roller to smoothly slide even under no torque conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the roller guide surface is formed with a large curvature radius R and the roller has a small curvature radius r (large R/r ratio), then the roller can be inclined in the track groove, but the contact angle between the roller and roller guide surface is reduced, increasing frictional force and hindering smooth sliding under no torque conditions
Solution Approach 1:
The patent changes the geometric parameters of the roller and roller guide surface by setting a specific contact ratio range (0.95 ≤ R/r ≤ 1.08) between the curvature radius R of the roller guide surface and the curvature radius r of the roller. This parameter optimization ensures a sufficiently large contact angle while maintaining roller inclination capability, thereby resolving the contradiction between adaptability and ease of operation.
2Adaptability or versatility
If the contact angle between the roller and roller guide surface is small, then the roller can accommodate inclination, but the frictional force increases and smooth sliding is hindered
Solution Approach 1:
The patent optimizes the contact angle by controlling the contact ratio R/r within the specific range of 0.95 to 1.08. This parameter change ensures that the contact angle is sufficiently large to minimize frictional force while still allowing the roller to accommodate inclination requirements, thus resolving the contradiction between adaptability and force reduction.
3Device complexity
If the roller contacts the roller guide surface at a small contact angle, then the joint structure is compact, but edge loads occur and durability is reduced
Solution Approach 1:
The patent changes the contact geometry parameters by setting the contact ratio R/r within 0.95 ≤ R/r ≤ 1.08, which ensures a sufficiently large contact angle. This distributes the contact load over a larger area, preventing edge loads and improving durability while maintaining relatively compact joint structure.
Solution Approach 2:
The patent employs curved surfaces for both the roller (with curvature radius r) and the roller guide surface (with curvature radius R). This spheroidality design, optimized through the contact ratio parameter, ensures smooth contact and load distribution, preventing edge loads and enhancing durability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enables smooth sliding of the roller on the guide surfaces, reducing frictional forces and enhancing durability by avoiding edge loads, thus improving the joint's performance and practicality.
Implementation Method 1
the roller rolls on the roller guide surfaces properly, and thus induced thrust and sliding resistance can be reduced
Implementation Method 2
under a state in which no torque is applied to the joint, smooth sliding of the roller on the guide surfaces
Data Source
AI summary
A tripod type constant velocity universal joint includes an outer joint member having three track grooves each including roller guide surfaces opposing each other in a circumferential direction of each of the track grooves, a tripod member including three leg shafts, and roller units each including a roller and an inner ring to support the roller. An outer peripheral surface of the roller has a partially spherical surface having a curvature center on an axis of each of the leg shafts. The roller guide surfaces are each formed of a partially cylindrical surface having a curvature center on a horizontal line passing an intersection of a pitch circle of the track grooves and a center line of each of the track grooves, and when no torque is applied to the joint, an end portion of the outer peripheral surface of the roller abuts against the roller guide surfaces.