Resin Sliding Layer with Mixed Graphite for Low-Oil Wear Control
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Solution Overview
Problem
Conventional sliding members with spherical graphite particles in synthetic resin compositions suffer from surface scratches and wear issues due to insufficient oil feeding during start-up and variable load conditions, leading to deterioration in sliding performance.
Innovation Solution
A sliding member with a back metal layer and a sliding layer comprising synthetic resin and a combination of spheroidal and flake-like graphite particles, where the spheroidal particles have a curved cross-sectional structure and the flake-like particles are anisotropically dispersed to reduce wear and prevent scratches by minimizing direct contact with the shaft surface during low oil conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flake-like graphite particles are used in the sliding layer, then the sliding performance is improved through shearing between AB planes, but the particles break and drop off during machining, increasing surface roughness
Solution Approach 1:
The patent applies spheroidality by transforming the conventional flake-like graphite particles into spherical graphite particles. This curvature change eliminates the thin plate structure that is prone to breaking, while maintaining the lubricating function through the curved AB planes that can still shear under load. The spherical shape provides mechanical strength during machining while preserving sliding performance during operation.
Solution Approach 2:
The patent changes the morphological parameter of graphite particles from flake-like to spherical shape. This parameter change fundamentally alters the mechanical properties (increasing strength and resistance to breaking) while maintaining the functional properties (shearing between AB planes) through controlled transformation processes.
2Manufacturing precision
If spherical graphite particles are used to improve surface roughness, then the surface quality is improved, but the counterpart shaft surface is easily scratched under insufficient oil feeding conditions
Solution Approach 1:
The patent applies local quality by creating a composite particle structure where spherical graphite particles are coated or combined with flake-like graphite particles on their surface. This local differentiation allows the spherical core to provide mechanical strength and the flake-like surface layer to provide lubrication and prevent scratching, with each component performing its specific function locally.
Solution Approach 2:
The patent uses composite materials by combining spherical graphite particles with flake-like graphite particles or applying flake-like graphite coating on spherical particles. This composite structure integrates the advantages of both particle types: the spherical shape provides strength and resistance to breaking, while the flake-like component provides enhanced lubrication and protection against shaft surface scratching.
3Reliability
If flake-like graphite particles are used as solid lubricant, then the shearing function is effective, but the particles are brittle and break under variable load conditions
Solution Approach 1:
The patent applies spheroidality by transforming the conventional flake-like graphite particles into spherical graphite particles. This curvature change eliminates the thin plate structure that is prone to breaking, while maintaining the lubricating function through the curved AB planes that can still shear under load. The spherical shape provides mechanical strength during machining while preserving sliding performance during 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
The combination of spheroidal and flake-like graphite particles effectively reduces wear and prevents scratches on the counterpart shaft surface, maintaining sliding performance even under conditions of insufficient oil feeding and variable loads, by promoting shearing between graphite planes and reducing direct contact with the shaft.
Implementation Method 1
A bonding strength, by van der Waals force, is much weak between the laminated AB planes compared with an in-plane direction of the AB plane. Thus, shearing easily occurs between the AB planes.
Implementation Method 2
A bonding strength, by van der Waals force, is much weak between the laminated AB planes compared with an in-plane direction of the AB plane.
Data Source
AI summary
A sliding member includes a back metal layer and a sliding layer on the back metal layer. The sliding layer includes a synthetic resin matrix and graphite particles dispersed in the matrix in a volume ratio of 5-50% of that of the sliding layer. The graphite particles are composed of spheroidal and flake-like particles. The flake-like particles have a volume ratio of 10-40% of total graphite particles. The spheroidal particles have a cross-sectional structure with a plurality of AB planes of a graphite crystal laminated along a curved particle surface, from the surface toward a center direction. The flake-like graphite particles have a cross-sectional structure with the plurality of AB planes laminated in a thickness direction of the thin plate shape. The spheroidal particles have an average particle size of 3-50 μm, and the flake-like graphite particles have an average particle size of 1-25 μm.