Eddy Current Inspection of Spring Members Using AC Bridge Circuit
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Solution Overview
Problem
Current methods for inspecting the surface properties of spring-shaped members after surface treatments like shot-peening and heat treatment are time-consuming and destructive, leading to inefficiencies in the inspection and sorting process, particularly for spring-shaped members where cycle times are short.
Innovation Solution
A surface property inspection and sorting apparatus using an AC bridge circuit with a variable resistor and an inspection detector coil to evaluate surface properties non-destructively by exciting eddy currents, allowing for continuous evaluation and sorting of spring-shaped members without stopping, facilitated by a guide member and sorting device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal emission effects are used for surface property inspection, then measurement precision is improved, but inspection time increases significantly
Solution Approach 1:
The patent applies periodic action by using AC power supply with variable frequency to excite eddy currents in the spring-shaped member. The inspection device measures impedance changes at different frequencies, allowing rapid assessment of surface properties without requiring prolonged thermal emission measurement. This periodic excitation method enables quick detection of residual stress and hardness variations.
Solution Approach 2:
The patent implements parameter changes by varying the frequency of AC power supplied to the inspection detector coil. By measuring impedance frequency response characteristics at multiple frequencies, the system can evaluate surface properties rapidly. The variable resistor in the AC bridge circuit also allows adjustment of excitation parameters to optimize measurement speed and precision.
2Measurement precision
If destructive inspection methods are used, then measurement precision is improved, but productivity decreases due to inability to inspect all parts
Solution Approach 1:
The patent replaces mechanical destructive testing methods with an electromagnetic non-destructive inspection system. The inspection detector coil generates AC magnetic fields that induce eddy currents in the spring-shaped member, and impedance changes in the AC bridge circuit reveal surface property information without physical contact or damage. This substitution enables 100% inspection of all produced parts while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces an AC bridge circuit as an intermediary measurement system. Instead of directly measuring mechanical properties that would require destructive testing, the system measures electrical impedance changes caused by eddy current variations. This intermediary electrical measurement method provides accurate surface property evaluation without destroying the inspected parts.
3Productivity
If continuous inspection without stopping is implemented, then productivity is improved, but measurement precision may deteriorate due to motion effects
Solution Approach 1:
The patent applies preliminary action by guiding the spring-shaped member through a standardized path using the guide member before inspection. The guide member ensures proper positioning and orientation of the member relative to the inspection detector coil, maintaining consistent measurement conditions even during continuous motion. This preliminary positioning action enables accurate measurements without stopping the production flow.
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 enables high-precision, efficient inspection and sorting of spring-shaped members, reducing evaluation and judgment time to match short cycle times and ensuring reliable differentiation between good and bad parts, thus optimizing the overall process rate.
Implementation Method 1
an inspection detector comprising a coil capable of exciting an AC magnetic field, formed so that said coil can be disposed to excite an eddy current in the spring-shaped member
Implementation Method 2
the inspection detector detects electromagnetic property of the spring-shaped members
Data Source
AI summary
To provide a surface property inspection sorting apparatus, system, and method capable of efficiently performing steps to evaluate the surface properties of spring-shaped members. A surface property inspection and sorting apparatus 1 includes a surface property inspection device, a measuring member for measuring the surface properties of the spring-shaped members M, and a sorting means for sorting the spring-shaped members into good and bad parts. The measuring member is constituted so that spring-shaped members can pass through an inspection detector, and the surface properties of the spring-shaped member can be evaluated and a pass/fail judgment made by a surface property inspection device based on output signals output from an AC bridge circuit while the spring-shaped member passes through the inspection detector.