Steering Column Bearing Assembly Vibration Control

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Solution Overview

Problem

Conventional steering column assemblies with electric power steering units face challenges in achieving the minimum natural vibration frequency due to resistance to bending, which results in steering wheel shake from engine vibrations or road roughness, and recent targets for higher frequencies to accommodate automatic engine stop-start strategies.

Innovation Solution

A telescopic steering column assembly with a support bearing assembly comprising inner and outer bearing races, ball bearings, and a biasing means that applies axial thrust to convert into radial thrust, ensuring rigid radial contact between the shaft and shroud, reducing unwanted movement due to vibration while allowing easy adjustment for reach.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a telescopic steering column assembly is used to allow adjustment for reach and absorb crash energy, then adjustability and crash energy absorption are improved, but the natural vibration frequency decreases leading to steering wheel shake

Engineering Contradiction:

ImproveadjustabilityVSAvoidnatural vibration frequency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The bearing assembly is segmented into two separate bearing races (inner and outer) that can move independently relative to each other along the telescopic shaft, allowing the system to maintain rigidity while permitting controlled movement

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention converts axial movement (one dimension) into radial support (another dimension) by using the relative axial movement of the two bearing races to maintain constant radial contact between the ball bearings and the races, thereby providing rigid support in the radial direction while allowing telescopic adjustment

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of operation

If ball bearings are used to support the upper column shaft to allow free telescopic movement, then ease of adjustment is improved, but the bending stiffness decreases making it difficult to achieve minimum natural vibration frequency

Engineering Contradiction:

Improveease of adjustmentVSAvoidbending stiffness

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The bearing assembly is designed to be dynamic rather than static, with two bearing races that can move relative to each other to maintain optimal contact under varying loads, thereby adapting to both adjustment movements and vibration conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The second bearing race acts as an intermediary element between the ball bearings and the outer structure, providing an additional contact surface that enhances radial support while allowing axial movement for telescopic adjustment

Inventive Principle:

Principle #24Intermediary (Mediator)

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

The solution significantly reduces steering assembly movement due to vibration, maintaining low axial friction for driver-adjustable reach and increasing the minimum natural frequency, thereby improving NVH performance.

Implementation Method 1

a set of ball bearings that are located between the inner bearing race and the outer bearing race and are free to roll along bearing surfaces defined by the bearing races

Methodology Applied

Scientific EffectBall bearing rolling: Ball Bearing

Implementation Method 2

a biasing means that in use applies an axially directed thrust between a first one of the annular support sleeves and one of the respective bearing race parts, and in which the bearing assembly is arranged such that the axial thrust applied by the biasing means is converted into a radial thrust that is applied to the inner bearing race and outer bearing race

Methodology Applied

Scientific EffectMechanical thrust conversion: Mechanical Force

Data Source

PatentUS10137925B2Improvements to steering column assemblies

Publication Date: 2018.11.27 TRW LIMITED

AI summary

A telescopic steering column assembly includes at least one support bearing assembly that comprises an inner bearing race which is located on the steering shaft, an outer bearing race that is located on an inner face of a shroud, and a set of ball bearings that are located between the inner bearing race and the outer bearing race and are free to roll along bearing surfaces defined by the bearing races. Each of the bearing races comprises a pair of annular bearing race parts, defining a circumferentially extending bearing surface arranged coaxially and spaced apart from each other axially such that varying the spacing between the two parts varies the effective radius of the bearing race. The support bearing assembly further comprising an inner annular support sleeve that is located between the inner bearing race and the inner shaft, an outer annular support sleeve that is located between the outer bearing race and the shroud, and a biasing means that in use applies an axially directed thrust between a first one of the annular support sleeves and one of the respective bearing race parts, and the bearing assembly is arranged such that the axial thrust applied by the biasing means is converted into a radial thrust that is applied to the inner bearing race and outer bearing race to force them into engagement with the inner and outer sleeves respectively.