Fixed CV Joint Track Groove Design for Torque Loss
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Solution Overview
Problem
Conventional fixed type constant velocity universal joints face challenges in suppressing torque loss and heat generation, especially at frequently used operating angles, due to insufficient effective track length and imbalance in forces applied to the balls, which affects their efficiency and durability.
Innovation Solution
The design incorporates circular-arc first track groove portions with a curvature center not offset in the axial direction and second track groove portions with a straight part to increase effective track length, allowing for higher operating angles while maintaining stability and reducing torque loss and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the curvature center of the track groove is offset to the opening side to increase the maximum operating angle, then the maximum operating angle is improved, but the effective track length becomes insufficient causing balls to drop off the track groove
Solution Approach 1:
The track groove is divided into two distinct portions: a first track groove portion with a curvature center offset to the opening side (for high operating angles) and a second track groove portion with a curvature center at the joint center (for effective track length). This segmentation allows each portion to optimize for its specific function, resolving the contradiction between maximum operating angle and effective track length.
Solution Approach 2:
Different portions of the track groove are given different local qualities through different curvature center positions. The first portion has offset curvature for high-angle operation while the second portion has centered curvature for maintaining ball engagement. This local differentiation allows the single track groove structure to satisfy both contradictory requirements at different locations.
2Adaptability or versatility
If a large inlet chamfer is formed to accommodate high operating angles, then the operating angle capability is improved, but the effective track length of the outer joint member becomes insufficient
Solution Approach 1:
The track groove structure is segmented into two portions with different curvature characteristics. The first portion compensates for the space consumed by the inlet chamfer by having its curvature center offset further, while the second portion ensures sufficient effective track length. This segmentation allows the system to accommodate both large inlet chamfers for high operating angles and maintain adequate ball engagement length.
3Adaptability or versatility
If the track grooves are designed for high operating angles, then the operating angle range is improved, but torque loss and heat generation increase due to force imbalance on the balls
Solution Approach 1:
Different portions of the track groove provide different local qualities for force distribution. The first portion with offset curvature handles the high operating angle geometry while the second portion with centered curvature optimizes force balance on the balls. This local differentiation allows the joint to achieve both high operating angle capability and reduced torque loss through improved force distribution.
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3c
AI summary
In a fixed type constant velocity universal joint (1), track grooves (7) of an outer joint member (2) comprise first track groove portions (7a) each located on a depth side and second track groove portions (7b) each located on an opening side. The first track groove portions (7a) each comprise a circular-arc ball-raceway center line (Xa) having a curvature center that is not offset in an axial direction with respect to a joint center (O). Planes (M) defined in the first track groove portions (7a) that are adjacent to each other in a circumferential direction, the planes (M) each comprising at least the ball-raceway center line (Xa) and the joint center (O), are inclined with respect to a joint axial line (N-N) with their inclination directions opposite to each other. The second track groove portions (7b) each comprise a ball-raceway center line (Xb) comprising a straight part so as to increase an effective track length at a maximum operating angle. The ball-raceway center line (Xa) of each of the first track groove portions (7a) comprises an end portion (A) located on the opening side with respect to the joint center (O) in the axial direction. The ball-raceway center line (Xb) of each of the second track groove portions (7b) is connected to the end portion (A). Track grooves (9) of an inner joint member (3) each comprise a ball-raceway center line (Y) formed to be mirror-image symmetrical with a ball-raceway center line (X) of the paired track groove (7) of the outer joint member (2) with respect to a plane (P) comprising the joint center (O) at an operating angle of 0°.