Steering Rack Bush Load Distribution
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Solution Overview
Problem
In rack and pinion steering systems, the rack bush closer to the guide member often experiences distortion or abrasion due to long-term or sudden large loads, leading to deterioration, as it bears the pressing force and sliding friction between the gear housing and rack shaft.
Innovation Solution
A steering system design that includes a pinion shaft, a rack shaft with meshing teeth, a housing, a guide member, an opposed member, a biasing member, a first rack bush, a second rack bush positioned closer to the guide member, and an elastic member, which together support the rack shaft for sliding motion while distributing loads to minimize backlash and pressure on the second rack bush.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the rack bush is disposed close to the guide member to absorb backlash, then the steering precision is improved, but the rack bush is subjected to large loads and deteriorates due to distortion or abrasion
Solution Approach 1:
The invention divides the single rack bush into two separate rack bushes: a first rack bush disposed close to the guide member to absorb backlash, and a second rack bush disposed away from the guide member to bear large loads. This segmentation allows each rack bush to have specialized functions, improving both steering precision and durability.
Solution Approach 2:
The first rack bush acts as an intermediary element between the guide member and the second rack bush. It absorbs backlash and reduces the impact of large loads on the second rack bush, thereby protecting the load-bearing component from deterioration while maintaining steering precision.
2Manufacturing precision
If the rack bush is disposed close to the guide member to reduce backlash, then the meshing accuracy between pinion and rack is improved, but the rack bush bears large loads from rough roads or curb impacts
Solution Approach 1:
The invention segments the load-bearing function from the precision-meshing function by placing the first rack bush close to the guide member for backlash absorption and meshing accuracy, while the second rack bush bears the large loads from rough roads or curb impacts.
Solution Approach 2:
Different portions of the rack shaft are provided with different rack bushes having different functions: the first rack bush at the backlash-critical location ensures meshing accuracy, while the second rack bush at the load-critical location ensures strength and load capacity.
3Device complexity
If a single rack bush is used to support the rack shaft, then the device complexity is reduced, but the rack shaft experiences backlash and the rack bush deteriorates under long-term or sudden loads
Solution Approach 1:
The invention uses two rack bushes instead of one to segment the functional requirements: backlash absorption and load bearing. This increases component count but resolves the reliability issues caused by using a single rack bush for both functions.
Solution Approach 2:
The first rack bush provides beforehand cushioning by absorbing backlash and reducing the impact of sudden loads before they reach the second rack bush, thereby protecting the rack shaft system from deterioration and maintaining stability.
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
This design suppresses the deterioration of the second rack bush by distributing loads and reducing pressure, maintaining the bush's resilience and preventing creep or abrasion, even under heavy use, thus ensuring consistent performance and reduced wear.
Implementation Method 1
an elastic member disposed between the inner surface and the second rack bush and that can be elastically deformed
Data Source
AI summary
In a steering system, a guide member faces the rack shaft on the opposite side of the rack shaft from the pinion shaft, and an opposed member faces the guide member at a first distance. The rack shaft is supported by the first rack bush so as to be slidable in the axial direction. The rack shaft is supported so as to be slidable in the axial direction X at a position closer to the guide member than the first rack bush is by the second rack bush disposed away from the inner surface. An elastic member that can be elastically deformed is disposed between the inner surface and the second rack bush. The second rack bush has an opposed portion disposed on the opposite side of the rack shaft from the pinion shaft and facing the inner surface at a second distance that is larger than the first distance.