Lead-Free Sliding Layer Composition for Static-Dynamic Friction Control
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Solution Overview
Problem
Current sliding members in shock absorbers face challenges in controlling the relationship between static and dynamic friction forces, which affects ride quality, as they either focus on reducing dynamic friction coefficient without addressing static friction or fail to optimize the balance between the two.
Innovation Solution
Incorporating a predetermined amount of pitch-based carbon fibers in a lead-free resin composition for the sliding layer, which includes a metallic substrate, a porous metal or alloy layer, and a sliding layer made of a resin composition comprising pitch-based carbon fibers, fluororesin, and optional additives like aramid fiber, iron oxide, molybdenum disulfide, graphite, and zinc, to control static and dynamic friction forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resin composition containing PTFE and carbon fibers is used to reduce dynamic friction coefficient, then slidability is improved, but static friction force cannot be increased and the relationship between static and dynamic friction force cannot be controlled
Solution Approach 1:
The patent changes the compositional parameters of the resin material by precisely controlling the ratio of PTFE to carbon fibers (1:0.03 to 1:0.2 by weight) and adding specific additives like zinc stearate and calcium carbonate. This parameter optimization simultaneously achieves low dynamic friction coefficient and increased static friction force, resolving the contradiction between slidability and static friction control
Solution Approach 2:
The patent creates a composite resin material combining PTFE (for low dynamic friction) with carbon fibers (for structural reinforcement and static friction enhancement) and additional additives. This composite approach allows the material to exhibit both low dynamic friction coefficient for good slidability and increased static friction force for improved ride quality
2Reliability
If carbon fibers and calcium compounds are blended to improve abrasion resistance, then durability is enhanced, but the relationship between static friction force and dynamic friction force is not optimized
Solution Approach 1:
The patent optimizes the concentration parameters of carbon fibers (0.03 to 0.2 parts by weight per 1 part PTFE) and calcium compounds (calcium carbonate at 0.1 to 2 parts by weight per 1 part PTFE) to achieve the dual effect of enhanced abrasion resistance and optimized friction force relationship. This precise parameter control ensures that the material maintains durability while achieving the desired static and dynamic friction characteristics
3Ease of operation
If lead is added to Cu-based alloy powder to ensure good slidability, then dynamic friction is reduced, but harmful effects to human health occur
Solution Approach 1:
The patent completely removes lead (Pb) from the resin composition, extracting this harmful substance from the material system. The resulting lead-free resin composition achieves good slidability through the optimized PTFE-carbon fiber composite structure without any harmful effects to human health, while maintaining the necessary friction characteristics
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
This approach increases static friction force and reduces the rate of change of dynamic friction force relative to static friction, thereby enhancing abrasion resistance and improving ride quality by optimizing the frictional characteristics.
Implementation Method 1
the static friction force can become large and the relationship between the static friction force and the dynamic friction force can be controlled, by containing a predetermined amount of pitch-based carbon fibers in a resin composition forming a sliding layer
Implementation Method 2
the resin composition consists of a pitch-based carbon fiber and a fluororesin
Implementation Method 3
a porous layer formed on a surface of the metallic substrate
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Provided is a sliding member that makes it possible to control the relationship between static friction force and kinetic friction force, and a bearing using said sliding member. A sliding member 1 is provided with a metal base 2, a porous layer 3 formed on one surface of the metal base 2, and a sliding layer 5 covering the porous layer 3. The sliding layer 5 is formed of a resin composition 4 that does not contain lead. The resin composition 4 contains more than 10 up to 35 wt% pitch-based carbon fiber, where the weight of the resin composition is 100, the remainder being fluororesin. The pitch-based carbon fiber has a fiber diameter of 5 to 20 µm, a fiber length of 10 to 150 µm, and an aspect ratio of 2 to 20.