Radially Preloaded Rack Bearing for Steering Noise Reduction

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Solution Overview

Problem

Rack and pinion steering systems in the automotive industry often suffer from undesirable noise, suboptimal steering feel, and increased maintenance complexity due to the meshed connection between the pinion gear and the steering rack.

Innovation Solution

A radially preloaded rack bearing is introduced, supported by a housing and preloaded to the rack, which includes semi-cylindrical segments that radially expand and contract, and a resilient member to maintain a line-to-line fit and compensate for thermal expansion, reducing noise and improving steering feel.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional rack bearing designs are used to support the meshed connection between pinion gear and rack, then the system structure is simple, but undesirable noise is generated and steering feel performance deteriorates

Engineering Contradiction:

Improvesystem noiseVSAvoidbearing structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The rack bearing is divided into two separate semi-cylindrical segments that can independently expand and contract radially. This segmentation allows each segment to adapt to thermal expansion and maintain optimal contact with the rack, reducing noise while preserving structural simplicity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bearing segments are designed to be dynamically adjustable through radial expansion and contraction. This dynamic capability enables the bearing to maintain optimal fit under varying thermal and operational conditions, eliminating noise without requiring complex fixed-geometry structures

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If conventional rack bearing designs are used, then manufacturing is simpler, but steering feel performance is suboptimal

Engineering Contradiction:

Improvesteering feelVSAvoidmanufacturing complexity

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

Dividing the bearing into two semi-cylindrical segments enables each segment to be manufactured using cost-effective processes like injection molding, while the segmented design itself delivers superior steering feel through adaptive radial expansion and contraction

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bearing segments are designed to change their radial dimensions in response to thermal expansion and operational loads. This parameter change capability improves steering feel by maintaining optimal contact conditions without requiring complex manufacturing processes

Inventive Principle:

Principle #35Parameter changes

3Ease of repair

If conventional rack bearing designs are used, then the structure is less complex, but maintenance complexity increases

Engineering Contradiction:

Improvemaintenance complexityVSAvoidbearing structure complexity

Core Design Contradiction:

Ease of repairVSDevice complexity

Solution Approach 1:

The two semi-cylindrical segments are designed as independent, interchangeable components that can be easily replaced without affecting the other segment or requiring complex disassembly procedures, thereby reducing maintenance complexity despite the segmented structure

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each bearing segment is designed to perform multiple functions: supporting radial loads, accommodating thermal expansion, and maintaining optimal meshed connection. This multi-functionality reduces the need for additional maintenance components and procedures

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Stability of the object's composition

If conventional rack bearing designs are used, then initial manufacturing costs may be lower, but thermal expansion compensation is insufficient leading to fit instability

Engineering Contradiction:

Improvefit stabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The bearing segments are explicitly designed to accommodate thermal expansion through their ability to radially expand and contract. This thermal adaptation mechanism maintains stable fit and contact conditions across temperature variations without requiring complex compensation structures

Inventive Principle:

Principle #37Thermal expansion

Solution Approach 2:

The dynamic radial expansion and contraction capability of the bearing segments provides automatic compensation for thermal effects and operational variations, ensuring fit stability under varying conditions while maintaining manufacturing simplicity

Inventive Principle:

Principle #15Dynamics

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 minimizes system noise, enhances steering feel, and optimizes robustness by maintaining a stable fit under varying temperatures and operational conditions, reducing manufacturing costs and complexity while eliminating the need for secondary machining operations.

Implementation Method 1

a resilient member to maintain a line-to-line fit and compensate for thermal expansion

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10618544B2Radially preloaded rack bearing

Publication Date: 2020.04.14 STEERING SOLUTIONS IP HOLDING CORP

AI summary

A rack and pinion steering system includes a housing, a rack, a pinion gear, and a radially preloaded rack bearing. The rack is supported by the housing, and the pinion gear is meshed to the rack. The radially preloaded rack bearing is supported and preloaded to the housing and is preloaded to the rack.