Shock Absorber Rod Coating for Hardness and Low Friction
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Solution Overview
Problem
Existing shock absorbers face challenges in achieving both high hardness and low frictional force, particularly with trivalent chromium plating films, which are needed for components like suspension rods, without using hexavalent chromium that poses environmental and health risks.
Innovation Solution
A shock absorber design incorporating a hard layer on the piston rod with a trivalent chromium plating film containing both crystalline and amorphous materials, along with specific additives, is manufactured using a plating bath with controlled pH and current density conditions to enhance hardness and reduce friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard trivalent chromium plating film is formed to achieve high hardness (800 HV or greater), then hardness and abrasion resistance are improved, but slidability such as frictional force is insufficient
Solution Approach 1:
The invention changes the chemical composition parameters of the plating bath by introducing specific organic compounds (carboxylic acid and its ester) alongside traditional inorganic additives. This parameter change transforms the plating film structure to contain both crystalline and amorphous regions, where the amorphous regions provide low friction coefficients while crystalline regions maintain hardness, thereby resolving the contradiction between hardness and slidability
Solution Approach 2:
The plating film is designed as a composite material containing both crystalline chromium structures (providing hardness) and amorphous organic-inorganic hybrid structures (providing low friction). The combination of inorganic chromium compounds with organic carboxylic acid derivatives creates a composite plating film that simultaneously achieves high hardness and excellent slidability
2Strength
If hexavalent chromium plating is used to achieve excellent abrasion resistance and corrosion resistance, then hardness is improved, but environmental and health hazards increase
Solution Approach 1:
The invention fundamentally changes the oxidation state parameter of chromium from +6 (hexavalent) to +3 (trivalent), transforming the plating chemistry from hexavalent chromium-based to trivalent chromium-based. This parameter change eliminates the toxic and carcinogenic properties of hexavalent chromium while maintaining plating effectiveness through the addition of organic complexing agents that enable stable trivalent chromium plating
Solution Approach 2:
The invention converts the previously harmful hexavalent chromium system into a beneficial trivalent chromium system. By using trivalent chromium with appropriate organic additives, the invention achieves comparable or superior performance while eliminating environmental and health hazards, effectively turning a harmful technology into a safe one
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 shock absorber achieves high hardness and low frictional force, meeting or exceeding the performance of hexavalent chromium systems while avoiding environmental and health hazards.
Implementation Method 1
a plating step of forming a plating film including a hard layer mainly containing chromium obtained from a trivalent chromium plating bath
Data Source
AI summary
Provided is a shock absorber in which trivalent chromium is used to achieve both high hardness and low frictional force at a high level without using hexavalent chromium which is suspected of causing damage to the human body and the environment, and a method for manufacturing the shock absorber.A shock absorber (100) of the present invention includes: a cylinder (1) which is filled with hydraulic oil (3); a piston rod (2) which is movable in the cylinder (1); and an oil seal (8) which is fixed to the cylinder (1) and slides on the piston rod (2), in which a hard layer mainly containing chromium obtained from a trivalent chromium plating bath is provided on a surface of the piston rod (2), and the hard layer contains both a crystalline material and an amorphous material, and also contains an additive other than chromium.