Steering Column Bushing Design for Friction and Rigidity
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Solution Overview
Problem
Conventional steering column support apparatuses for electric power steering systems face challenges in maintaining stable friction forces during steering wheel height adjustment while supporting assist reaction forces, often resulting in uncomfortable operation and reduced support rigidity.
Innovation Solution
The apparatus features bushings with thinned sections on circumferential or side surfaces, allowing main and sub contact surfaces to engage only under assist force, reducing contact area and friction in the neutral state, and enhancing support rigidity through specific surface geometries and materials like polyamide resin and elastomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If bushings with large contact surfaces are used to support assist reaction forces, then support rigidity is improved, but friction resistance during steering wheel adjustment increases
Solution Approach 1:
The bushing is designed with non-uniform thickness, creating different contact surface areas in different radial positions. The thinner portion provides reduced friction contact for adjustment operations, while the thicker portion provides enhanced support rigidity for assist reaction forces. This local variation in geometry allows simultaneous optimization of both conflicting requirements.
Solution Approach 2:
The bushing design allows dynamic adaptation of contact characteristics based on loading conditions. Under assist reaction forces, the thicker portions engage to provide rigid support. During steering wheel adjustment, the thinner portions reduce friction resistance. The elastic material properties further enable dynamic response to different operational states.
2Stability of the object's composition
If bushings with thick sections are used to maintain support capability, then support rigidity is improved, but friction force during adjustment increases
Solution Approach 1:
The bushing incorporates local thickness variations where thinner sections are positioned at locations where friction reduction is critical during adjustment, while thicker sections are positioned where support rigidity is needed for assist reaction forces. This localized geometric differentiation resolves the contradiction between support capability and friction force.
Solution Approach 2:
The bushing can be considered as having functionally segmented zones with different thickness characteristics. Each zone serves its specific purpose: some zones optimize for friction reduction during adjustment, while others optimize for support capability. This functional segmentation allows both requirements to be satisfied simultaneously.
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 stabilizes friction forces during steering wheel adjustment, improves operational workability, and maintains support rigidity by reducing friction resistance and preventing abnormal wear, thus enhancing the overall driving experience.
Implementation Method 1
a pair of bushings (30c) made of an elastic material or a low-friction material
Implementation Method 2
stabilizes friction forces during steering wheel adjustment, improves operational workability, and maintains support rigidity by reducing friction resistance
Data Source
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AI summary
A steering column support apparatus for an electric power-steering apparatus with a tilt mechanism is achieved that is capable of sufficiently maintaining support rigidity of a tilt pivot shaft 15a to support a pivot bracket 28, and keeping the resistance when performing a tilt operation low with the durability of the side plate sections 32c of a pair of bushings 30c sufficiently maintained The portions of the outer circumferential surface of the tilt pivot shaft 15a and the inner circumferential surface of the through hole 29 that hold the cylindrical sections 31 of the bushings 30c are cylindrical surfaces. Moreover, main contact surface sections 36, which come in contact with the inner side surfaces of support plate sections 23 in the neutral state in which there is no assist reaction force, and sub contact surface sections 37, which do not come in contact with the support plate sections 23 in the neutral state, and come in contact with the inside surfaces of the support plate sections 23 only when there is elastic deformation due to the occurrence of an assist reaction force, are formed on outside surfaces of the side plate sections 32c of the bushings 30c.