Steering Device Rack Guide Backlash Elimination
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Solution Overview
Problem
Conventional steering devices experience differences in steering feel between turning and turning back due to backlash caused by gaps between the engagement projection and groove, leading to inconsistent steering performance.
Innovation Solution
Incorporating a rack guide with a protrusion and elastic spacers that contact the rack shaft and housing, allowing for precise guidance and minimizing the impact of backlash, ensuring consistent steering feel by maintaining the position of the rack guide and allowing smooth movement during steering operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a gap is formed between the engagement projection and engagement groove for assembly purposes, then assembly ease is improved, but steering feel consistency deteriorates due to backlash
Solution Approach 1:
A rack guide member is introduced as an intermediary component between the rack shaft and rack housing. The rack guide has a protrusion that fits into a recess of the rack housing, while the rack shaft contacts the rack guide. This intermediary structure transmits steering force while maintaining positional accuracy, eliminating the direct gap between engagement projection and groove that causes backlash.
Solution Approach 2:
The invention changes the dimensional parameters by making the protrusion width smaller than the recess width in the axial direction, creating a controlled gap that allows assembly while the rack guide maintains steering precision. The elastic member further adjusts parameters by providing compliance to absorb minor misalignments without creating backlash.
2Ease of manufacture
If the rack bush engages through a gap, then assembly is facilitated, but steering operation smoothness deteriorates due to backlash influence
Solution Approach 1:
The rack guide member serves as a mediator that separates the engagement functions. The protrusion-recess engagement provides structural support and positioning, while the rack shaft-rack guide contact provides smooth steering operation. This mediation eliminates the direct transmission of gap-induced backlash to the steering operation.
Solution Approach 2:
The steering mechanism is segmented into distinct functional zones: the protrusion-recess engagement zone for structural support and positioning, and the rack shaft-rack guide contact zone for smooth steering operation. This segmentation allows each zone to optimize its function without the negative effects of the other.
3Adaptability or versatility
If tolerance variation is allowed in gap size, then manufacturing flexibility is improved, but steering feel difference between turning directions increases
Solution Approach 1:
The rack guide member acts as a mediator that decouples the tolerance variations in the protrusion-recess gap from the steering operation. Since the rack shaft contacts the rack guide rather than engaging directly through the gap, variations in gap size do not translate to variations in steering feel between turning directions.
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 eliminates the difference in steering feel between turning and turning back, providing a consistent and smooth steering experience by reducing the need for excessive stress and preventing sudden movements of the rack shaft, thus enhancing the overall steering operation.
Implementation Method 1
The spacer may be an elastic member having elasticity
Data Source
AI summary
A steering device includes: a pinion shaft that has a pinion on an outer circumferential surface thereof; a rack shaft that has a rack that engages with the pinion; a rack housing that has a recess on an inner circumferential surface thereof and accommodates the rack shaft; a rack guide that has a protrusion smaller than a width of the recess in axial directions of the rack shaft, and is disposed inside the recess, the rack guide contacting an outer circumferential surface of the rack shaft and an inner circumferential surface of the rack housing, and guiding the rack shaft along an axis of the rack shaft; and a spacer that contacts one side and the other side of the protrusion in the axial directions of the rack shaft, and is disposed between an inner surface of the recess and an outer surface of the protrusion.