Rear-Drive Fixed CV Joint Geometry for Lower Weight and Size
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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 for rear-wheel drive shafts is designed with specific internal specifications, including a reduced pitch circle diameter of balls and radial thickness of the cage, optimized to reduce maximum loads on components, allowing for a smaller size and weight without compromising torque load capacity or durability, by setting the pitch circle diameter of the balls between 3.70 to 3.87 and the radial thickness of the cage between 0.22 to 0.25 times the ball diameter, and increasing the spline hole diameter for enhanced torsional strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same fixed type constant velocity universal joint specifications are used for both front-wheel and rear-wheel drive shafts, then mass production cost is reduced, but weight and size cannot be further reduced for rear-wheel drive applications
Solution Approach 1:
The patent applies local quality by creating a specialized version of the universal joint optimized for rear-wheel drive shafts with smaller operating angles. The curvature offset distance is specifically tuned for maximum operating angles of 20° or less, allowing weight and size reduction while maintaining constant velocity characteristics. This localized optimization resolves the contradiction by having different design parameters for different application scenarios.
2Weight of moving object
If the pitch circle diameter of balls and radial thickness of cage are reduced to decrease weight and size, then material usage is reduced, but load capacity and durability may be compromised
Solution Approach 1:
The patent applies parameter changes by establishing specific ratio ranges: pitch circle diameter of balls to ball diameter ratio of 3.70-3.87, and radial thickness of cage to ball diameter ratio of 0.22-0.25. These optimized parameters allow reduction in absolute dimensions while maintaining sufficient load capacity through mathematically determined proportional relationships, resolving the contradiction between weight reduction and strength maintenance.
3Adaptability or versatility
If a fixed type constant velocity universal joint with large operating angle is used for rear-wheel drive shaft, then it can accommodate larger angles, but it increases weight and size unnecessarily
Solution Approach 1:
The patent applies partial action by providing exactly the operating angle capability needed for rear-wheel drive shafts (20° or less), without the excess capacity of larger angle joints designed for front-wheel steering applications. The curvature offset distance is optimized for this specific range, eliminating unnecessary weight and size while maintaining sufficient adaptability for the intended application.
Data Source
Figure 1
Figure 2
Figure 3A~3B
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.