Tripod CV Joint Curved Guide Surfaces for Smooth No-Torque Sliding
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Solution Overview
Problem
Existing tripod type constant velocity universal joints experience increased frictional forces 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 operational issues.
Innovation Solution
The design incorporates a configuration where the outer peripheral surface of the roller is partially spherical with a curvature center on the leg shaft axis, and the roller guide surfaces are partially cylindrical with a curvature center aligned with the track groove intersection, setting a contact ratio of 0.95≤R/r≤1.08 to ensure a large contact angle and smooth sliding under no torque conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the roller guide surfaces are formed with a large curvature radius R, then the roller can accommodate axial displacement, but the contact angle between the roller and roller guide surface is reduced, increasing frictional force under no torque conditions
Solution Approach 1:
The roller guide surface is designed with different curvature radii in different regions: a large curvature radius R1 in the axial direction to accommodate axial displacement, and a small curvature radius R2 in the radial direction to maintain a large contact angle and reduce frictional force under no torque conditions. This local differentiation of geometric properties resolves the contradiction between axial adaptability and friction reduction.
2Adaptability or versatility
If the roller guide surfaces are formed with a large curvature radius R, then the roller can accommodate axial displacement, but smooth sliding under no torque conditions is hindered
Solution Approach 1:
The roller guide surface is designed with different curvature radii in different regions: a large curvature radius R1 in the axial direction to accommodate axial displacement, and a small curvature radius R2 in the radial direction to maintain a large contact angle and reduce frictional force under no torque conditions. This local differentiation of geometric properties resolves the contradiction between axial adaptability and friction reduction.
3Device complexity
If the roller and roller guide surface contact at one point (circular contact), then the structure is simple, but edge loads and contact pressure increase under no torque conditions
Solution Approach 1:
The roller guide surface is designed with curved surfaces having specific curvature radii (R1 in axial direction, R2 in radial direction) to transform the contact from point contact to surface contact. This curvature design increases the contact area between the roller and guide surface, distributing the load and reducing contact pressure and edge loads under no torque conditions.
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 allows the rollers to smoothly slide on the guide surfaces even when no torque is applied, reducing frictional forces and enhancing durability by minimizing edge loads and contact pressure.
Implementation Method 1
the roller rolls on the roller guide surfaces properly
Implementation Method 2
a plurality of needle rollers interposed between the roller and the inner ring
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Provided is a tripod type constant velocity universal joint (1), including: an outer joint member (2) having three track grooves (5) each including roller guide surfaces (6) arranged so as to be opposed to each other in a circumferential direction of each of the track grooves; a tripod member (3) including three leg shafts (7) projecting in a radial direction of the tripod member; and roller units (4) each including a roller (11) and an inner ring (12) configured to support the roller (11) in a freely rotatable manner, in which an outer peripheral surface (1 1a) of the roller (11) is formed of a partially spherical surface having a curvature center on an axis (7x) of each of the leg shafts (7), in which the roller guide surfaces (6) are each formed of a partially cylindrical surface having a curvature center on a horizontal line (X-X) passing an intersection (T) of a pitch circle (PC) of the track grooves (5) and a center line (5x) of each of the track grooves (5), and in which under a state in which no torque is applied to the joint, an end portion (11e) of the outer peripheral surface (11a) of the roller (11) is held in abutment against the roller guide surfaces (6).