Multilayered Sliding Member for Rack-and-Pinion Steering
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Solution Overview
Problem
Multilayered sliding members used in various applications face challenges with wear resistance and load-bearing capability, particularly in rack-and-pinion type steering apparatus for automobiles, due to environmental concerns with lead-based additives and limitations of polytetrafluoroethylene (PTFE) coatings.
Innovation Solution
A multilayered sliding member comprising a backing plate with a porous metal sintered layer and a coating layer containing 50-75% PTFE and 10-40% metal metaphosphate, along with 3-20% heat-resistant resin, to enhance wear resistance and load-bearing capability, while avoiding environmentally harmful additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead or lead oxide is used as an additive in the coating layer, then wear resistance and load bearing capability are improved, but environmental contamination and pollution increase
Solution Approach 1:
The invention replaces lead-based additives with alternative materials (polymer particles, metal particles, or ceramic particles) that have appropriate size ranges (0.1-10 μm, 1-5 μm, or 3-7 μm respectively). This parameter change in material composition and particle size maintains wear resistance while eliminating environmental contamination from lead
Solution Approach 2:
The invention converts the harmful effect of lead-based additives into a beneficial solution by using environmentally friendly alternative particles. The polymer, metal, or ceramic particles not only eliminate pollution but also provide enhanced wear resistance and load bearing capability through their specific mechanical properties and size-controlled distribution in the PTFE coating matrix
2Object-affected harmful factors
If phosphate or barium sulfate, magnesium silicate or mica is used as additives, then environmental concerns are addressed, but load bearing capability and wear resistance are insufficient
Solution Approach 1:
The invention creates a composite coating layer where PTFE serves as the base matrix and is combined with polymer particles, metal particles, or ceramic particles as reinforcement. This composite structure leverages the low friction properties of PTFE while the dispersed particles provide enhanced wear resistance and load bearing capability, achieving both environmental friendliness and superior mechanical performance
Solution Approach 2:
The invention applies local quality by distributing particles of specific sizes (0.1-10 μm polymer particles, 1-5 μm metal particles, or 3-7 μm ceramic particles) throughout the coating layer. This localized distribution ensures that the beneficial properties of each particle type are optimally utilized at the contact surface, providing enhanced wear resistance and load bearing capability while maintaining environmental compatibility
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 improves wear resistance and load-bearing capability of the multilayered sliding members, making them suitable for rack-and-pinion type steering apparatus, with improved frictional properties and reduced wear, thus addressing the limitations of PTFE coatings alone.
Implementation Method 1
a porous metal sintered layer formed on one surface of the backing plate
Implementation Method 2
a coating layer filling pores of, and coating a surface of, the porous metal sintered layer
Implementation Method 3
the coating layer including a PTFE and 10 to 40% by mass of a metal metaphosphate
Data Source
AI summary
A rack-and-pinion type steering apparatus 1 comprises a gear case 3 made of aluminum or an aluminum alloy and having a hollow portion 2; a steering shaft 6 rotatably supported by the gear case 3 through rolling bearings 4 and 5; a pinion 7 which is provided integrally on a shaft end portion of the steering shaft 6 and is rotatably supported in the hollow portion 2 by the gear case 3 through the steering shaft 6; a rack bar 9 on which rack teeth 8 meshing with the pinion 7 are formed; a rack guide 10 which is disposed in the hollow portion 2 of the gear case 3 and supports the rack bar 9 slidably; and a spring 11 constituted by a coil spring for pressing the rack guide 10 toward the rack bar 9.