Constant Velocity Joint Journal Stiffness Optimization
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Solution Overview
Problem
In constant velocity universal joint assemblies, the elasticity of the journal leads to relative movements between the outer joint part and the inner bearing race under torque, causing noise and fretting corrosion, and the goal is to minimize the size of the wheel bearing and wheel carrier for cost and size considerations.
Innovation Solution
The outer joint part is redesigned with a shorter and thicker journal, altering the characteristic size ratios to increase stiffness and reduce relative movements, including a central threaded bore for clamping the wheel hub, with specific ratios for journal diameter to length and end face to journal length to enhance torsional strength and prevent relative movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the journal diameter is minimized to reduce wheel bearing size and cost, then the size of wheel bearing and wheel carrier is reduced, but the journal elasticity increases causing relative movements between outer joint part and inner bearing race under torque
Solution Approach 1:
The patent applies parameter changes by modifying the journal's dimensional parameters - specifically increasing the journal diameter and decreasing the journal length. This changes the diameter-to-length ratio from conventional values to a higher ratio, fundamentally altering the journal's stiffness characteristics and eliminating the need for large wheel bearings while maintaining reliability
2Ease of manufacture
If the journal diameter is minimized for cost reduction, then manufacturing cost is reduced, but relative movements occur between outer joint part and inner bearing race leading to noise and fretting corrosion
Solution Approach 1:
The patent resolves this contradiction by changing the journal's dimensional parameters to achieve optimal stiffness. The increased diameter and decreased length create a shorter, thicker journal that is sufficiently stiff to prevent harmful relative movements and associated noise and fretting corrosion, while still allowing for cost-effective manufacturing
3Volume of moving object
If the journal is designed with minimum strength requirements, then the wheel bearing inner diameter can be reduced, but the journal becomes elastic causing torque-induced relative movements
Solution Approach 1:
The patent applies parameter changes by fundamentally altering the journal's diameter-to-length ratio. This creates a shorter, thicker journal configuration that provides sufficient torsional strength to prevent elastic deformation and relative movements, while still enabling a compact wheel bearing design with reduced inner diameter
Data Source
AI summary
An outer joint part of a constant velocity universal joint for a wheel hub-constant velocity fixed joint unit wherein a wheel hub (60, 90) with a through-aperture (59, 89) carrying inner shaft teeth (44, 74) is clamped relative to the outer joint part (46, 76) of a constant velocity universal joint (42, 72), to which outer joint part (46, 76) there is formed on a journal (53, 83) with outer shaft teeth (54, 84), wherein the inner shaft teeth (44, 74) of the through-aperture (59, 89) and the outer shaft teeth (54, 84) of the journal (53, 83) engage one another and wherein a double-row wheel bearing (43, 73) is slid on to the wheel hub (60, 90) which wheel bearing comprises an inner bearing race (64, 94) which directly supports an end face (52, 82) of the outer joint part (46, 76), wherein the ratio of the journal diameter at the journal base (DZ) and the journal length (LZ) is greater than 0.95.