PTFE Composite Sliding Member for Low-Torque Rack Steering
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Solution Overview
Problem
Multi-layer sliding members used in rack-and-pinion steering apparatuses experience torque loss due to a significant difference between static and kinetic friction coefficients, affecting steering smoothness.
Innovation Solution
A multi-layer sliding member with a coating layer composed of a tetrafluoroethylene resin matrix containing thermotropic liquid crystal polymer, polyarylketone resin, melt moldable fluororesin, and polyimide resin additives, which minimizes the difference between static and kinetic friction coefficients, enhancing friction and wear characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a multi-layer sliding member with a coating layer formed from a synthetic resin composition containing PTFE as a main component is used, then low friction properties are achieved under dry friction conditions or with a lubricant, but a significant difference between static friction coefficient and kinetic friction coefficient causes torque loss and affects steering smoothness
Solution Approach 1:
The patent applies composite materials by formulating a synthetic resin composition containing PTFE as the main component (50-90 mass%) combined with specific additives: polyimide resin (1-10 mass%), polyarylketone resin (5-15 mass%), and melt moldable fluororesin (5-15 mass%). This composite composition creates a coating layer that minimizes the difference between static and kinetic friction coefficients while maintaining low friction properties, thereby reducing torque loss and improving steering smoothness.
2Force
If a multi-layer sliding member with a coating layer is used to support the rack bar, then sliding functionality is achieved, but wear resistance is insufficient due to the soft nature of PTFE
Solution Approach 1:
The patent resolves the contradiction between low friction properties and wear resistance by creating a composite coating layer where PTFE (50-90 mass%) provides low friction characteristics while being reinforced with polyimide resin (1-10 mass%), polyarylketone resin (5-15 mass%), and melt moldable fluororesin (5-15 mass%). The polyarylketone resin and melt moldable fluororesin specifically enhance wear resistance, while the polyimide resin improves adhesion to the porous sintered metal layer, achieving a balance between sliding performance and durability.
Solution Approach 2:
The patent applies local quality by creating a multi-component coating layer where each additive serves a specific function: PTFE provides low friction, polyimide resin enhances adhesion to the substrate, polyarylketone resin improves wear resistance, and melt moldable fluororesin provides both wear resistance and processability. This localized functional distribution within the coating layer achieves overall performance optimization.
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 provides a multi-layer sliding member with reduced torque loss and improved wear resistance, enabling smooth steering feel in rack-and-pinion steering apparatuses by minimizing the difference between static and kinetic friction coefficients.
Implementation Method 1
the thermotropic liquid crystal polymer helps low friction properties of the matrix
Implementation Method 2
the polyarylketone resin, the melt moldable fluororesin, and the polyimide resin reinforce the matrix to contribute to an improvement in wear resistance of the matrix
Implementation Method 3
a porous sintered metal layer integrally bonded to one surface of the backing plate
Data Source
AI summary
A multi-layer sliding member (1) includes a backing plate (2) formed from a steel plate, a copper-plated or nickel-plated layer (4) formed on one surface (3) of the backing plate (2), a porous sintered metal layer (5) integrally bonded to the surface (3) of the backing plate (2) through the layer (4), and a coating layer (8) filling pores (6) and coating on the surface (7) of the porous sintered metal layer (5) and formed from a synthetic resin composition. The synthetic resin composition contains a PTFE as a main component and further contains, as additives, 5 to 30% by mass of a thermotropic liquid crystal polymer, 5 to 12% by mass of a polyarylketone resin, 5 to 12% by mass of a melt moldable fluororesin, and 1 to 5% by mass of a polyimide resin.