Steering Column Intermediate Shaft Sleeve for Raceway Stability
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Solution Overview
Problem
Existing intermediate shaft assemblies for steering columns experience deformations due to heat treatment processes, leading to non-linear raceways and increased axial forces or slippage, which reduces the assembly's lifespan.
Innovation Solution
A shaft assembly design featuring a first shaft with a cavity and a second shaft partially within it, a sleeve on the second shaft with a bearing raceway, and a bearing assembly with rolling elements and a cage, where the sleeve is heat-treated and secured via an interference fit or direct rotational connection, allowing for axial adjustment and oscillation while maintaining radial clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment is applied to shafts during formation processes to provide surface hardness for rolling element raceways, then the requisite surface hardness is achieved, but deformations occur in the rolling element raceway causing non-linearity and radial clearance out of specification
Solution Approach 1:
The invention divides the bearing support structure into separate components: the first bearing raceway remains on the first shaft, while the second bearing raceway is transferred to a separate sleeve component. This segmentation allows the second shaft to be heat treated without requiring its raceway to maintain dimensional stability, as the sleeve can be separately manufactured and fitted to achieve the required precision.
Solution Approach 2:
The second bearing raceway is extracted from the second shaft and placed on a separate sleeve component. This extraction allows the second shaft to undergo heat treatment processes without compromising raceway linearity, while the sleeve can be precisely manufactured and heat treated independently to provide the required surface hardness and dimensional stability.
2Strength
If shaft geometry and heat treatment processes are used to provide surface hardness, then the requisite surface hardness is achieved, but radial clearance becomes out of specification
Solution Approach 1:
By segmenting the bearing support into separate shaft and sleeve components, each can be optimized independently. The sleeve can be manufactured with precise radial clearance specifications and heat treated to achieve surface hardness without the deformations that would occur if the entire shaft assembly were heat treated.
Solution Approach 2:
The second bearing raceway is extracted from the heat-treated shaft and placed on a separately manufactured sleeve. This allows the sleeve to be precisely controlled for radial clearance during manufacturing, while still achieving the required surface hardness through controlled heat treatment of the sleeve alone.
3Strength
If rolling element raceways become non-linear due to deformations, then heat treatment provides surface hardness, but axial forces increase for relative axial displacement
Solution Approach 1:
Segmenting the bearing support into separate shaft and sleeve components prevents the propagation of deformation-induced non-linearity throughout the entire bearing assembly. The sleeve can be manufactured with precise raceway geometry that maintains proper rolling element alignment, thereby reducing abnormal axial forces during operation.
4Strength
If rolling element raceways become non-linear due to deformations, then heat treatment provides surface hardness, but slippage of rolling elements occurs on the raceways
Solution Approach 1:
By extracting the second bearing raceway from the heat-treated shaft and placing it on a separately manufactured sleeve, the raceway geometry can be precisely controlled to ensure proper rolling element engagement. This prevents slippage by maintaining the correct raceway profile and surface hardness without the deformations that would cause rolling elements to slip.
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 enhances the reliability and durability of the steering column assembly by maintaining radial clearance and reducing axial forces, thereby extending the assembly's lifespan and preventing slippage.
Implementation Method 1
The sleeve is heat treated
Implementation Method 2
The sleeve is secured to the axial end of the second shaft by an interference fit
Data Source
AI summary
An intermediate shaft assembly for a steering column is disclosed herein. The assembly includes a first shaft defining a cavity and a first bearing raceway, a second shaft arranged at least partially within the cavity of the first shaft, a sleeve arranged on an axial end of the second shaft and defining a second bearing raceway, and a bearing assembly including at least two rows of rolling elements and a cage. The rolling elements are supported between the first bearing raceway of the first shaft and the second bearing raceway of the sleeve. The sleeve can be heat treated, and formed from sheet metal. The sleeve can be secured to the axial end of the second shaft by a direct rotational connection such that the sleeve is rotationally fixed to the second shaft.