Eight-Ball Sliding CV Joint Geometry for Lighter Rear Drive Shafts
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Solution Overview
Problem
Current plunging type constant velocity universal joints, particularly those with eight balls, face challenges in reducing weight and size while maintaining torque load capacity and durability, especially when used exclusively for rear-wheel drive shafts where the maximum operating angle can be minimized.
Innovation Solution
The design reduces the maximum operating angle of the plunging type constant velocity universal joint to 20° or less by optimizing internal specifications such as the pitch circle diameter of the balls, radial thickness of the inner joint member, and cage dimensions, allowing for a smaller size and weight reduction without compromising load capacity or durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the number of balls is increased to eight to ensure strength and load capacity, then torque load capacity and durability are improved, but weight and size of the universal joint increase
Solution Approach 1:
The patent applies parameter changes by optimizing the pitch circle diameter of the balls, radial thickness of the inner joint member, and cage dimensions. By changing these parameters and reducing the maximum operating angle to 20° or less, the design achieves weight and size reduction while maintaining the torque load capacity provided by eight balls
Solution Approach 2:
The patent uses partial action by reducing the maximum operating angle to 20° or less, which is smaller than conventional designs. This partial reduction in operating angle allows for smaller component dimensions while the eight balls provide sufficient torque load capacity for rear-wheel drive applications
2Volume of moving object
If the pitch circle diameter of balls and radial thickness of inner joint member are reduced to decrease size, then weight and size are reduced, but torque load capacity may be compromised
Solution Approach 1:
The patent simultaneously optimizes multiple parameters including pitch circle diameter of balls, radial thickness of inner joint member, and maximum operating angle. These coordinated parameter changes allow size reduction while maintaining torque load capacity through the eight-ball configuration
Solution Approach 2:
The patent employs composite construction by combining eight torque transmission balls with an optimized cage structure and inner joint member. This composite design distributes loads effectively across multiple components, allowing reduced individual component sizes while maintaining overall load capacity
3Weight of moving object
If the maximum operating angle is reduced to 20° or less for rear-wheel drive shafts, then weight and size are reduced, but the joint must maintain equivalent torque load capacity
Solution Approach 1:
The patent changes the maximum operating angle parameter to 20° or less, which enables smaller component dimensions. This parameter change is compensated by optimizing the eight-ball configuration and other dimensional parameters to maintain equivalent torque load capacity for rear-wheel drive applications
Solution Approach 2:
The patent applies local quality by optimizing specific regions and components of the universal joint, such as the pitch circle diameter of balls and radial thickness of the inner joint member, to achieve weight reduction while maintaining overall reliability and torque load capacity
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Provided is a plunging type constant velocity universal joint (2) comprising an outer joint member (21), an inner joint member (22), eight balls (23), and a cage (24). A curvature center (O24b) of a spherical portion (24b) of an outer peripheral surface of the cage (24) and a curvature center (O24d) of a spherical portion (24d) of an inner peripheral surface of the cage (24) are offset to opposite sides in the axial direction with respect to a joint center (O(s)) by an equal distance . A ratio PCDBALL/DBALL of a pitch circle diameter PCDBALL of the balls (23) to a diameter DBALL of each of the balls (23) is set from 3.3 to 3.6. A ratio TI/DBALL of a radial thickness TI of the inner joint member (22) to the diameter DBALL of each of the balls (23) is set from 0.30 to 0.45.