Steering Rack Thrust Piece Structure for Lower Housing Friction
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Solution Overview
Problem
High friction forces between the thrust piece and housing in motor vehicle steering systems due to high forces acting on the toothed rack during driving, leading to reduced mobility of the thrust piece.
Innovation Solution
A thrust piece with a circumferential wall featuring depressions that reduce contact area with the housing, combined with ribs for stiffness and potentially a glass-fiber-reinforced plastic material, and a slide element with a low-friction material for the toothed rack contact surface, to minimize friction and enhance mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thrust piece is pressed against the housing wall by high forces during driving operation, then the toothed rack remains engaged with the drive pinion, but high friction force arises at the contact surface between the thrust piece and housing, adversely affecting the mobility of the thrust piece
Solution Approach 1:
The patent extracts material from the thrust piece by creating depressions in its circumferential wall, removing portions of the material to reduce the contact area with the housing. This extraction of material directly reduces the friction force while maintaining the structural integrity through strategic placement of ribs, thereby improving thrust piece mobility without compromising engagement reliability
Solution Approach 2:
The patent creates a porous-like structure on the thrust piece surface through depressions, transforming the solid circumferential wall into a structure with reduced material presence. This porous configuration reduces the effective contact area with the housing, lowering friction forces and improving mobility while the ribs provide necessary structural support
2Ease of operation
If depressions are formed on the circumferential wall of the thrust piece to reduce contact area, then friction force is reduced and mobility is improved, but the stiffness of the thrust piece may be compromised
Solution Approach 1:
The patent segments the circumferential wall of the thrust piece by creating multiple depressions separated by ribs. This segmentation approach allows material removal for friction reduction while the ribs act as structural dividers that maintain overall stiffness. The segmented structure achieves both reduced contact area and preserved mechanical strength
Solution Approach 2:
The patent employs a composite structure combining depression regions (for friction reduction) and rib regions (for structural support) within the same thrust piece. This composite approach integrates two conflicting requirements - low friction surface and high stiffness structure - into a single unified component, achieving both mobility improvement and strength maintenance
Data Source
AI summary
A device for a steering system of a motor vehicle for pressing a toothed rack against a drive pinion is specified, the device having a housing and a thrust piece which is mounted displaceably in the housing and which has a circumferential wall which is in contact with the housing, the thrust piece having, on its circumferential wall, at least one depression which runs in a circumferential direction at least in certain portions and which delimits a hollow chamber arranged between thrust piece and housing.