Anti-Lash Bushing for Vehicle Power Steering Ball Nut
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Solution Overview
Problem
Existing vehicle power steering assemblies experience 'lash' due to clearances between components, leading to detectable rattles or noises when the direction of motion is reversed, which is undesirable.
Innovation Solution
An anti-lash assembly is introduced, comprising a steering member with a screw portion, a ball nut, and a bushing with different lead spacings, where the bushing is connected to the screw portion to bias the ball nut, reducing lash by creating a preload that minimizes movement discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ball nut and rack member assembly is used to transmit force in a power steering system, then force transmission and steering control are achieved, but clearances between components cause lash and rattling noises when direction is reversed
Solution Approach 1:
The bushing is pre-installed on the screw portion with a different lead spacing than the ball nut, creating a preliminary biasing force that opposes the development of lash. This preliminary anti-action prevents clearance issues before they occur during direction reversals, eliminating rattle noise while maintaining force transmission capability
Solution Approach 2:
The invention changes the lead spacing parameter of the bushing screw thread convolution to be different from the ball nut screw thread convolution. This parameter difference creates the necessary biasing action that eliminates lash, transforming the clearance problem into a controlled interference fit that prevents rattling during steering operations
2Object-generated harmful factors
If a bushing with different lead spacing is added to bias the ball nut against the screw portion, then lash is reduced, but device complexity increases
Solution Approach 1:
The bushing serves multiple functions simultaneously: it acts as a mounting component for the ball nut assembly, provides the biasing force to eliminate lash through its different lead spacing, and maintains structural support for the screw portion. This multi-functionality reduces the need for separate components, offsetting the apparent complexity increase with functional consolidation
Data Source
AI summary
A vehicle power steering assembly comprises a steering member having a screw portion. The screw portion has an external screw thread convolution with a first lead spacing. A ball nut is operatively connected to the screw portion. A bushing is operatively connected to the screw portion. The bushing has a bushing screw thread convolution with a second lead spacing. The second lead spacing is different than the first lead spacing. The bushing biases the ball nut against the screw portion.