Coil Spring End-Turn Softening for Corrosion Fatigue Resistance
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Solution Overview
Problem
Existing coil springs for vehicle suspension devices face challenges in achieving optimal settling resistance and corrosion fatigue resistance, as the same layer structure is applied uniformly across the wire, which can lead to inconsistent performance across different portions of the spring, and existing production methods struggle to control temperature distribution during high-frequency induction heating.
Innovation Solution
A coil spring design featuring a helically wound wire with a softer surface area in the end turn portion and a uniform surface hardness in the effective portion, achieved by locally applying laser light to soften specific areas of the wire, creating a first and second layer configuration that enhances corrosion fatigue resistance while maintaining settling resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the hardness of the wire is increased as a whole, then settling resistance is improved, but corrosion fatigue resistance deteriorates due to fast crack development
Solution Approach 1:
The wire is designed with non-uniform hardness distribution: the end turn portion has lower hardness to prevent crack development and improve corrosion fatigue resistance, while the effective portion maintains high hardness for settling resistance. This local differentiation resolves the contradiction by optimizing each region's properties according to its functional requirements.
2Ease of manufacture
If the same layer structure is applied uniformly across the wire, then manufacturing is simplified, but performance consistency across different portions deteriorates
Solution Approach 1:
The wire features different layer structures in different regions: the end turn portion has a first layer structure optimized for corrosion fatigue resistance, while the effective portion has a second layer structure optimized for settling resistance. This local differentiation ensures each region's performance requirements are met while maintaining manufacturing feasibility through a controlled production process.
3Productivity
If high-frequency induction heating is used to create layer configuration, then productivity is improved, but temperature distribution control deteriorates
Solution Approach 1:
The patent modifies the heating parameters and process conditions of high-frequency induction heating to achieve precise temperature distribution control. By optimizing factors such as heating power, heating time, and wire feeding speed, the process creates the desired hardness differentiation in the wire structure while maintaining high production efficiency.
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 coil spring exhibits improved settling resistance and corrosion fatigue resistance, with the localized softening process allowing for precise control of hardness distribution, effectively delaying crack development and maintaining overall spring performance.
Implementation Method 1
achieved by locally applying laser light to soften specific areas of the wire
Data Source
AI summary
According to an embodiment, a coil spring is formed of a wire which is helically wound, and includes an end turn portion and an effective portion, and a surface of the wire in the end turn portion includes an area which is softer than a surface of the wire in the effective portion.