Rear-Wheel CV Joint Geometry for Lower Weight Without Torque Loss
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Solution Overview
Problem
Current fixed type constant velocity universal joints, such as the Rzeppa type with eight balls, do not adequately address the need for further reduction in weight and size while maintaining strength and durability for rear-wheel drive shafts, particularly due to their universal application across both front and rear-wheel drive shafts.
Innovation Solution
A fixed type constant velocity universal joint with an outer and inner joint member featuring eight track grooves and balls, a cage with reduced radial thickness and pitch circle diameter, and a spline hole design optimized for a reduced maximum operating angle of 20° or less, allowing for a more compact and lightweight configuration by distributing load evenly and reducing component thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fixed type constant velocity universal joint with eight balls is used, then torque load capacity and durability are improved, but weight and size increase
Solution Approach 1:
The patent optimizes specific geometric parameters including the pitch circle diameter ratio (PCDBALL/DBALL) set to 3.70-3.87 and cage radial thickness ratio (TC/DBALL) set to 0.22-0.25. These parameter changes enable weight reduction while maintaining the torque load capacity provided by eight balls, resolving the contradiction between strength and weight
2Weight of moving object
If component thickness is reduced to achieve weight reduction, then weight and size decrease, but strength and load capacity deteriorate
Solution Approach 1:
The patent determines optimal thickness ratios for the cage radial thickness (TC/DBALL = 0.22-0.25) and pitch circle diameter ratio (PCDBALL/DBALL = 3.70-3.87). These parameter changes ensure that components maintain sufficient strength and load capacity even with reduced thickness, resolving the contradiction between weight reduction and strength maintenance
3Ease of manufacture
If the same universal joint specifications are used for front and rear-wheel drive shafts, then manufacturing cost is reduced, but weight and size cannot be optimized for rear-wheel application
Solution Approach 1:
The patent applies local quality by optimizing the universal joint specifically for rear-wheel drive shafts with different parameters (PCDBALL/DBALL = 3.70-3.87, TC/DBALL = 0.22-0.25, maximum operating angle of 20° or less) compared to front-wheel applications. This allows weight optimization for rear-wheel use while maintaining manufacturing efficiency through targeted design
4Strength
If a larger pitch circle diameter is used, then torque load capacity is improved, but size and weight increase
Solution Approach 1:
The patent optimizes the pitch circle diameter ratio (PCDBALL/DBALL) to 3.70-3.87, which determines the optimal balance between torque load capacity and size. This parameter change enables the joint to achieve sufficient torque capacity with a compact size, resolving the contradiction between load capacity and volume
Data Source
AI summary
A fixed type constant velocity universal joint (3) includes an outer joint member (31), an inner joint member (32), eight balls (33), and a cage (34). A curvature center (O31d) of track grooves (31d) of the outer joint member (31) and a curvature center (O32e) of track grooves (32e) of the inner joint member (32) are offset to opposite sides in an axial direction of the joint with respect to a joint center (O(f)) by an equal distance. A ratio (PCDBALL/DBALL) of a pitch circle diameter (PCDBALL) of the balls (33) to a diameter (DBALL) of each of the balls (33) is set from 3.70 to 3.87. A ratio (TC/DBALL) of a radial thickness (TC) of the cage (34) to the diameter (DBALL) of each of the balls (33) is set from 0.22 to 0.25.