Lead-Free Sliding Layer for Balanced Bushing Friction
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Solution Overview
Problem
In shock absorbers, the friction forces generated by guide bushings affect vehicle ride quality, with existing sliding members failing to effectively control the relationship between static and dynamic friction forces, leading to suboptimal ride quality due to unbalanced friction coefficients.
Innovation Solution
A sliding member with a lead-free resin composition containing pitch-based carbon fibers, along with optional additives like aramid fiber, iron oxide, molybdenum disulfide, graphite, and zinc, is used to form a sliding layer on a metallic substrate, optimizing the static friction force and minimizing the rate of change in dynamic friction force relative to static friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If lead (Pb) is added to Cu-based alloy powder to improve slidability, then dynamic friction coefficient is reduced, but Pb usage is limited due to harmful effects to human health
Solution Approach 1:
The invention extracts and removes lead (Pb) from the sliding member composition entirely, replacing it with a lead-free resin composition containing fluororesin and pitch-based carbon fibers. This extraction eliminates the harmful effects to human health while maintaining sliding functionality through the alternative material composition.
Solution Approach 2:
The invention uses a composite material system consisting of lead-free resin composition (fluororesin + pitch-based carbon fibers) as the sliding layer. This composite replaces the traditional Cu-based alloy with Pb, achieving both health safety and sliding performance through the synergistic combination of fluororesin (providing low friction) and pitch-based carbon fibers (providing structural integrity and controlled friction characteristics).
2Ease of operation
If dynamic friction coefficient is reduced to enhance slidability, then sliding performance improves, but the relationship between static and dynamic friction forces becomes unbalanced, affecting ride quality
Solution Approach 1:
The invention changes the friction characteristics by adjusting the composition parameters of the sliding layer, specifically incorporating pitch-based carbon fibers in optimized amounts (5-50 wt%, preferably 10-30 wt%). This parameter adjustment modifies both static and dynamic friction forces to achieve a balanced relationship, improving ride quality while maintaining sliding performance. The pitch-based carbon fibers specifically influence the static friction component, creating a more favorable friction profile.
3Reliability
If carbon fibers are blended into resin composition to improve abrasion resistance, then durability increases, but the control over static and dynamic friction force relationship becomes insufficient
Solution Approach 1:
The invention optimizes the concentration parameter of pitch-based carbon fibers within a specific range (5-50 wt%, preferably 10-30 wt%) to simultaneously achieve adequate abrasion resistance and proper control over the static-dynamic friction force relationship. This precise parameter control allows the pitch-based carbon fibers to contribute to both durability and friction balance, unlike conventional carbon fiber additions that focus only on abrasion resistance.
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 increases static friction force and reduces the rate of change in dynamic friction force, thereby enhancing abrasion resistance and improving vehicle ride quality by balancing friction forces.
Implementation Method 1
containing a predetermined amount of pitch-based carbon fibers... the static friction force can become large
Implementation Method 2
the resin composition consists of a pitch-based carbon fiber and a fluororesin... good slidability is ensured
Implementation Method 3
a porous layer formed on a surface of the metallic substrate... made of a metal itself or an alloy composition
Data Source
AI summary
A sliding member includes a metallic substrate, a porous layer formed on a surface of the metallic substrate, and a sliding layer that covers the porous layer. The porous layer is made of a metal itself or an alloy composition. The sliding layer is made of a lead-free resin composition. The resin composition consists of a pitch-based carbon fiber and a fluororesin, and assuming weight of the resin composition as 100, more than 10 weight % and 35 weight % or less of the pitch-based carbon fiber is contained.