Automobile Suspension Coil Spring Sag Resistance
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Solution Overview
Problem
Conventional coil spring manufacturing methods for automobile suspensions, where hot setting is performed before warm shot peening, result in weakened oriented residual stress, compromising sag resistance and durability.
Innovation Solution
Reversing the sequence by performing warm shot peening before hot setting to maintain surface compressive stress and impart oriented residual stress, enhancing sag resistance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If hot setting is performed before warm shot peening, then oriented residual stress is generated to improve sag resistance, but the oriented residual stress is weakened by subsequent warm shot peening
Solution Approach 1:
The patent inverts the conventional sequence of hot setting and warm shot peening. Instead of performing hot setting first to generate oriented residual stress and then warm shot peening which weakens it, the patent performs warm shot peening first to generate surface compressive stress, followed by hot setting to generate oriented residual stress. This inversion allows both types of residual stress to coexist and reinforce each other, simultaneously improving sag resistance and durability.
2Reliability
If warm shot peening is performed after hot setting, then surface compressive stress is generated to improve durability, but the oriented residual stress from hot setting is weakened
Solution Approach 1:
The patent applies preliminary action by performing warm shot peening before hot setting. The warm shot peening is performed first to establish surface compressive stress, which serves as a foundation that will be preserved and enhanced by the subsequent hot setting process. This preliminary action ensures that the surface compressive stress is not weakened by the hot setting process, and both stress types work together to improve both durability and sag resistance.
3Ease of manufacture
If the sequence of hot setting then warm shot peening is used, then manufacturing process is simple, but the ratio of residual stress along critical directions deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the sequence parameter of the manufacturing process. By changing the order of operations from hot setting then warm shot peening to warm shot peening then hot setting, the patent achieves a significant improvement in the residual stress ratio parameter. This parameter change allows both manufacturing feasibility and optimal stress distribution to be achieved, as the process remains relatively simple while producing superior stress 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
The new method significantly improves sag resistance and durability by maintaining a favorable ratio of residual stresses along specific directions, ensuring the coil spring can handle tensile stresses even when the surface is worn, thus extending its service life.
Implementation Method 1
the coil spring is subjected to warm shot peening
Implementation Method 2
the heat treated, coil-shaped steel wire is subjected to hot setting
Data Source
AI summary
A manufacturing method of a coil spring for an automobile suspension includes forming a material into a coil shape; performing a heat treatment step on the material; performing a warm shot peening step on the material, and performing a hot setting step on the material. By performing the warm shot peening step prior to the hot setting step, a stronger compressive residual stress is imparted in a direction along which a large tensile stress acts during actual use of the coil spring, thereby improving sag resistance and durability of the coil spring. A coil spring is also manufactured according to this method.