Resonant Coil Layout for Accurate Foreign Matter Detection
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Solution Overview
Problem
Existing contactless power transmission systems face challenges in accurately detecting foreign matters, such as metal, between transmission and reception coils, which can lead to malfunction or ignition due to heat generation, and positional fluctuations affecting coupling efficiency.
Innovation Solution
A foreign matter detection device is implemented with a plurality of detection coils arranged at different positions, each forming a resonance circuit with a capacitor, and a power feeding coil for electromagnetic coupling, supplying AC power at a specific frequency to detect voltage changes caused by foreign matters, with adjacent coils overlapping to ignore mutual coupling, ensuring accurate detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple detection coils are arranged closely to improve detection coverage, then detection coverage is improved, but electromagnetic coupling between adjacent coils increases causing detection accuracy to deteriorate
Solution Approach 1:
The detection area is segmented into multiple independent detection coils arranged in a matrix pattern. Each detection coil operates independently with its own resonance circuit, allowing individual detection and measurement without mutual interference from adjacent coils.
Solution Approach 2:
A capacitor is introduced as an intermediary component to form a resonance circuit with each detection coil. This resonance circuit acts as a frequency-selective mediator that enhances the detection signal while suppressing electromagnetic coupling interference from adjacent coils by operating at a specific resonance frequency.
2Measurement precision
If detection coils are arranged to overlap significantly to enhance detection sensitivity, then detection sensitivity is improved, but mutual electromagnetic coupling between coils increases making it difficult to identify individual foreign matter
Solution Approach 1:
The detection coils are segmented into discrete units with controlled partial overlap. This segmentation allows each coil to maintain its individual detection characteristics while providing overlapping coverage areas, enabling both sensitive detection and spatial localization of foreign matter.
Solution Approach 2:
Each detection coil is designed with specific local characteristics including its own resonance frequency and detection sensitivity. The overlapping regions are controlled to ensure that each location in the detection area is primarily influenced by one dominant detection coil, preserving location information while maintaining sensitivity.
3Measurement precision
If detection coils are arranged with large spacing to reduce electromagnetic coupling, then detection accuracy is improved, but detection coverage area decreases
Solution Approach 1:
The harmful electromagnetic coupling effect is extracted and isolated by introducing capacitors to form resonance circuits. This allows the detection coils to be placed closer together for increased coverage while the resonance circuits extract and suppress the interfering coupling signals, preserving detection accuracy.
Solution Approach 2:
The operating frequency of each detection coil is changed to its resonance frequency determined by the coil inductance and capacitor value. This parameter change optimizes the signal-to-noise ratio and minimizes electromagnetic coupling between adjacent coils operating at different resonance frequencies, enabling closer spacing without sacrificing accuracy.
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 device enhances the accuracy of detecting foreign matters by isolating the effect of each detection coil from others, allowing for precise identification of foreign objects even if they are smaller than the transmission or reception coils, thereby preventing malfunctions and ensuring reliable power transmission.
Implementation Method 1
each forming a resonance circuit with a capacitor
Implementation Method 2
a power feeding coil arranged to be electromagnetically coupled with each of the plurality of detection coils
Implementation Method 3
a power feeding coil arranged to be electromagnetically coupled with each of the plurality of detection coils; supplying AC power having a predetermined frequency to each of the plurality of detection coils via the power feeding coil
Data Source
AI summary
A foreign matter detection device includes: a plurality of detection coils (43-1 to 43-n) between a transmission coil (12) of a power transmission device (2) and a reception coil (21) of a power reception device (3), through which power is transmitted in a contactless manner; a plurality of capacitors (44-1 to 44-n) forming, for each of the detection coils, a resonance circuit together with the detection coil; a power supply circuit (41) supplying AC power having a predetermined frequency to each detection coil; and a detection circuit (45) detecting a voltage output from each detection coil and detecting a foreign matter entering between the transmission coil (12) and the reception coil (21) according to the voltage detected. Then, each detection coil is arranged to overlap by a predetermined amount that allows electromagnetic coupling between adjacent two of the detection coils (43-1 to 43-n) to be ignored.