Steering Column Bearing Inner Ring Local Quality Design
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Solution Overview
Problem
Existing radial support bearing assemblies for steering columns face challenges in reducing the thickness and outer diameter while maintaining the service life and preventing damage during assembly, especially when increasing the outer diameter of the steering shaft.
Innovation Solution
The radial support bearing assembly features an inner ring with a circular cross-section in direct contact with the shaft, or disposed in an annular groove, and a plurality of roller elements between the inner and outer rings, allowing for reduced thickness and outer diameter while maintaining smooth operation through elastomeric preload rings and annular grooves for axial fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of the inner ring is reduced to reduce the overall thickness of the support bearing, then the radial space between the steering shaft and steering tube is reduced, but the inner ring becomes more prone to fracturing during press-fit assembly and the core may unintentionally harden
Solution Approach 1:
The inner ring is designed with non-uniform thickness: the core portion (at the center) has greater thickness to maintain softness and prevent fracturing during assembly, while the raceway surface portion has reduced thickness to minimize overall bearing thickness. This local quality variation allows the bearing to simultaneously achieve compact size and reliable service life.
Solution Approach 2:
The inner ring employs a composite structure combining a soft core material with a harder raceway surface material. The soft core prevents fracturing during press-fit assembly, while the harder surface provides durable rolling contact. This composite approach resolves the contradiction between thinning the ring and maintaining service life.
2Length of moving object
If the outer diameter of the steering shaft is increased while maintaining the outer diameter of the steering tube constant, then the radial space for the radial support bearing is reduced, but the bearing must still provide adequate support life and resistance to assembly damage
Solution Approach 1:
The inner ring's non-uniform thickness distribution allows the bearing to be thinner overall while maintaining adequate material at critical locations. The raceway surface is sufficiently thick to provide service life, while the core is thinned to reduce overall bearing thickness, enabling the bearing to fit in reduced radial space without sacrificing reliability.
3Reliability
If the inner ring is superficially heat treated to increase the service life of the raceway surface, then the surface hardness is improved, but the core may unintentionally harden and become prone to fracturing during press-fit assembly
Solution Approach 1:
The heat treatment process is controlled to affect only the raceway surface, creating a hard surface layer while leaving the core relatively soft. This local quality differentiation ensures the surface has high hardness for durable rolling contact, while the soft core remains ductile and resistant to fracturing during assembly.
Solution Approach 2:
The heat treatment parameters (temperature, time, atmosphere) are optimized to achieve case hardening - increasing surface hardness while maintaining core softness. This parameter control allows the surface to withstand rolling contact stresses while the core absorbs assembly shocks without fracturing.
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 configuration enables a thinner, more compact support bearing assembly with enhanced service life and reduced risk of damage during assembly, maintaining smooth operation and extending the service life of the raceway surface.
Implementation Method 1
a plurality of roller elements disposed between the at least one inner ring and the at least one outer ring in rolling contact with the inner raceway and the outer raceway
Implementation Method 2
maintaining smooth operation through elastomeric preload rings
Data Source
AI summary
A radial support bearing assembly for use within a steering column assembly having an outer tube and a shaft, including at least one inner ring defining an inner raceway, the inner ring being axially fixed relative to the shaft, at least one outer ring defining an outer raceway, and a plurality of roller elements disposed between the at least one inner ring and the at least one outer ring in rolling contact with the inner raceway and the outer raceway. The inner ring is in direct contact with the shaft and has a circular cross-section as taken in a plane parallel to a longitudinal center axis of the shaft.