Rear-Wheel Drive Shaft CV Joint Geometry for Lower Weight
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Solution Overview
Problem
Current rear-wheel drive shafts with constant velocity universal joints face challenges in reducing weight and size while maintaining torque load capacity, as they are often designed with larger operating angles that increase component thickness and weight.
Innovation Solution
The design incorporates a fixed type and plunging type constant velocity universal joint with reduced maximum operating angles of 20° or less, featuring eight track grooves and balls with specific pitch circle diameters and ball diameters ratios, and an intermediate shaft with increased spline hole diameters to enhance torsional strength and reduce overall weight and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the maximum operating angle of constant velocity universal joints is reduced to 20° or less, then weight and size of the rear-wheel drive shaft are reduced, but load capacity and durability may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the ratio of pitch circle diameter to ball diameter within specific ranges (4.0 ≤ PCDBALL/DBALL ≤ 4.5 for fixed type, 3.5 ≤ PCDBALL/DBALL ≤ 4.0 for plunging type). This parameter optimization allows the joint to maintain sufficient load capacity with reduced operating angles, resolving the contradiction between weight reduction and load capacity maintenance
Solution Approach 2:
The patent utilizes the dynamic characteristic of plunging type constant velocity universal joints that can displace axially while forming operating angles. This dynamic capability allows the joint to accommodate varying operating conditions with smaller angular deviations, enabling weight reduction while maintaining performance
2Strength
If the number of torque transmission balls is increased from six to eight, then strength and load capacity are improved, but weight and size increase
Solution Approach 1:
The patent optimizes the pitch circle diameter to ball diameter ratio parameter to compensate for the increased number of balls. By controlling this ratio within specific ranges, the patent achieves sufficient load capacity with eight balls while minimizing the weight increase that would otherwise result from adding two additional balls
Solution Approach 2:
The patent uses eight balls instead of the conventional six, providing excessive torque transmission capability. This allows for reduced ball diameter or reduced joint size while maintaining the required load capacity, ultimately achieving weight reduction despite the increased ball count
3Strength
If the diameter of spline holes in intermediate shaft is increased to enhance torsional strength, then strength is improved, but weight and size increase
Solution Approach 1:
The patent optimizes the spline hole diameter parameter to achieve sufficient torsional strength with minimal material. By precisely controlling this dimension, the patent enhances strength while avoiding excessive weight gain that would result from oversized spline holes
Solution Approach 2:
The patent employs composite construction with the intermediate shaft having different wall thicknesses at different sections. The spline hole diameter is optimized to create a composite structure that provides high torsional strength where needed while reducing material usage and weight in other areas
Data Source
AI summary
A rear-wheel drive shaft (1) includes a fixed type constant velocity universal joint (3), a plunging type constant velocity universal joint (2), and an intermediate shaft (4) coupling both the constant velocity universal joints to each other. A ratio (PCDBALL(f)/DBALL(f)) of a pitch circle diameter (PCDBALL(f)) of balls (33) of the fixed type constant velocity universal joint (3) to a diameter (DBALL(f)) of each of the balls (33) is set from 3.70 to 3.87. A ratio (PCDBALL(s)/DBALL(s)) of a pitch circle diameter (PCDBALL(s)) of balls (23) of the plunging type constant velocity universal joint (2) to a diameter (DBALL(s)) of each of the balls (23) is set from 3.3 to 3.6.