Ball Joint Assembly With Elastomeric Preload to Prevent Memory Steer
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Solution Overview
Problem
In four-wheel drive vehicle systems, ball joints with limited axial movement can lead to 'memory steer' due to improper installation, causing the vehicle to continue turning in the same direction after a turn, as the ball stud binds with the housing.
Innovation Solution
A ball joint assembly with a housing and a ball stud featuring elastomeric preload members that provide a clearance fit, allowing axial movement without binding, and are designed with a corrugated shape and tapered surfaces for efficient biasing, reducing torque requirements and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ball joint uses a fixed fit between the ball stud and housing, then the ball joint maintains stable positioning, but the ball stud binds during axial movement causing memory steer
Solution Approach 1:
The patent changes the fit parameter from a fixed interference fit to a clearance fit between the ball stud and housing, allowing controlled axial movement while maintaining radial stability through the elastomeric preload members
Solution Approach 2:
The elastomeric preload members act as intermediaries between the ball stud and housing, providing a compliant connection that allows axial movement while maintaining stable positioning and preventing binding
2Ease of operation
If the ball joint allows axial movement of the ball stud, then memory steer is prevented, but the torque required for articulation increases
Solution Approach 1:
The patent uses elastomeric materials with specific durometer ratings to optimize the balance between allowing axial movement and minimizing articulation torque, changing the material parameter to achieve both goals
3Ease of manufacture
If traditional ball joint designs are used, then manufacturing is simple, but axial binding occurs during installation
Solution Approach 1:
The patent introduces a clearance fit parameter and elastomeric preload members that can be manufactured using conventional processes, maintaining manufacturing simplicity while enabling axial movement
Solution Approach 2:
The patent segments the connection into distinct functional elements: the clearance fit housing, the elastomeric preload members, and the ball stud, allowing each to be manufactured separately and assembled
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the ball stud to move axially without binding, minimizing torque needed for articulation and rotation, while maintaining cost-effectiveness and preventing 'memory steer' issues.
Implementation Method 1
The preload members are of an elastomeric material. At least one of the preload members is compressed to urge the ball portion to a central location.
Implementation Method 2
each of the preload members has a corrugated top with a plurality of peaks and a plurality of valleys, and each of the preload members has a corrugated bottom with a plurality of peaks and a plurality of valleys
Implementation Method 3
the inner surface is tapered radially outwardly on the peaks
Data Source
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AI summary
The ball joint assembly includes a housing with an inner wall which surrounds an inner bore that extends along a central axis. The ball joint assembly further includes a ball stud with a ball portion and a shank portion. The ball portion is received in the inner bore of the housing, and the shank portion projects out of the inner bore through an open end of the housing. First and second preload members are disposed in the inner bore on opposite axial sides of the ball portion and are in contact with the ball portion. The preload members are of an elastomeric material. At least one of the preload members is compressed to urge the ball portion to a central location.