Telescopic Steering Column Bearing Assembly NVH
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Solution Overview
Problem
Conventional steering column assemblies with integrated electric power steering units face challenges in achieving the minimum natural vibration frequency due to resistance to bending, leading to steering wheel shake from engine vibrations or road roughness, and recent manufacturers' higher targets for automatic engine stop-start strategies.
Innovation Solution
A telescopic steering column assembly with a support bearing assembly comprising a separate first bearing race, a resilient spacer applying radial biasing force, and a cage locating bearings relative to the first bearing race, allowing the bearings to slide or roll during adjustment, which removes radial play while maintaining low frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the upper column shaft is supported by a ball bearing at the upper end and a splined sliding interface with the EPS input shaft, then the structure is economical and allows telescopic movement, but the natural vibration frequency cannot achieve the minimum target of 50 Hz due to bending stiffness limitations
Solution Approach 1:
The bearing assembly is segmented into distinct functional components: a ball bearing for radial support, a resilient spacer for axial positioning and vibration isolation, and a splined interface for telescopic movement. This segmentation allows each component to be optimized for its specific function while working together to achieve both economic manufacturing and high natural vibration frequency
Solution Approach 2:
The bearing assembly combines different material properties: the ball bearing provides rigid radial support, the resilient spacer provides elastic compliance for vibration isolation, and the splined interface provides controlled sliding. This composite approach enables the assembly to simultaneously achieve structural economy and high natural vibration frequency by leveraging the complementary properties of different materials and components
2Ease of operation
If the sliding interface has clearances to allow free telescopic movement, then the upper column can telescope smoothly, but the resistance to bending is reduced making it difficult to achieve minimum natural vibration frequency target
Solution Approach 1:
The resilient spacer dynamically adjusts the axial position and preload of the ball bearing based on operational conditions. During telescopic movement, the spacer allows sufficient clearance for smooth operation. When vibration occurs, the spacer compresses to increase radial preload on the bearing, thereby increasing bending stiffness and natural vibration frequency without compromising telescopic ease of operation
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 solution enhances the natural frequency of the steering column assembly, reducing noise, vibration, and harshness (NVH) by eliminating radial play and maintaining low frictional resistance, effectively addressing the challenges of steering wheel shake and vibration.
Implementation Method 1
a resilient spacer that applies a biasing force that is directed in a radial direction from the axis of the shaft
Implementation Method 2
the second bearing face permitting the bearings to slide or roll in the direction of adjustment of the steering column assembly
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A telescopic steering column assembly comprises an upper and a lower shroud portion (1, 2) able to move relatively during telescopic adjustment, a telescopic steering shaft (3, 4) that passes through and is supported by the shroud portions (1, 2) through at least one support bearing assembly (7, 8) that acts between an upper portion (4) of the telescopic steering shaft (3, 4) and a lower portion of the shroud (2) that move relative to one another axially during telescopic adjustment. The at least one support bearing assembly (7, 8) comprises a first bearing race which is separate from the shroud portions (1, 2) and the steering shaft (3, 4), a resilient spacer (12) that applies a biasing force that is directed in a radial direction from the axis of the shaft (3, 4) and that is located between the first race and an adjacent face of one of the lower shroud portion (2) and the upper shaft portion (3); a set of bearings (11), and a cage (10) that locates the bearings (11) relative to the first bearing race (9). The bearings (11) bear onto a second bearing race that is defined by a surface of the other one of the lower shroud portion (2) and the upper shaft portion (3), the second bearing face permitting the bearings (11) to slide or roll in the direction of adjustment of the steering column assembly when it is adjusted for reach.