Inductive Charging Coil Foreign Body Detection
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Solution Overview
Problem
Existing inductive charging systems for electric vehicles face challenges in reliably detecting electrically conductive bodies between primary and secondary coils, which can lead to heating or self-ignition issues, and conventional metal detectors are cumbersome to calibrate and prone to interference from the vehicle's metal mass.
Innovation Solution
An apparatus using magnetically decoupled transmitting and receiving coils, arranged according to the symmetry properties of the charging coils' magnetic field, generates distinct reception signals when an electrically conductive body is present, allowing for simple and reliable detection by canceling out partial signals in the absence of a conductive body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal detectors are used for air gap monitoring, then detection capability is provided, but the large metal mass of the vehicle disturbs the measurement method and calibration becomes complex
Solution Approach 1:
The patent extracts the detection function from conventional metal detectors and integrates it directly into the charging coils system. The charging coils themselves serve as both the charging element and the detection element, eliminating the need for separate metal detector devices and their associated calibration procedures. This is achieved by monitoring changes in the impedance or resonant frequency of the charging coils when foreign objects are present in the air gap.
Solution Approach 2:
The charging coils are designed to perform multiple functions: they serve as both the inductive charging element and the foreign object detection sensor. By using the same component for both charging and detection, the system eliminates the complexity of separate detection devices and their calibration requirements, while maintaining reliable detection capability through monitoring of coil electrical characteristics.
2Measurement precision
If metal detectors are used to detect electrically conductive bodies, then presence detection is achieved, but the measurement is disturbed by the large metal mass of the vehicle
Solution Approach 1:
The patent uses the charging coils as an intermediary between the power source and the foreign objects. By monitoring the electrical characteristics (impedance, resonant frequency) of the coils, the system indirectly detects the presence of foreign objects without being directly affected by the large metal mass of the vehicle. The coils act as a sensitive mediator that responds to changes in the magnetic field caused by foreign objects while being isolated from the interfering vehicle structure.
3Reliability
If conventional detection methods are used, then foreign body detection is provided, but calibration before measurement is required which cannot be implemented straightforwardly
Solution Approach 1:
The system performs self-calibration by using the charging coils' own electrical characteristics as the reference. The baseline impedance or resonant frequency of the coils is established during manufacturing or initial setup, and subsequent measurements are compared against this inherent reference. This self-service approach eliminates the need for manual calibration procedures before each measurement, making the system easy to operate while maintaining reliable detection.
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 solution enables effective detection of foreign bodies during inductive charging while avoiding inductive couplings, ensuring safe operation and reducing the risk of self-ignition, with improved calibration and sensitivity compared to conventional metal detectors.
Implementation Method 1
at least one transmitting device (transmit antenna) for providing a transmission signal in the form of a magnetic field. The apparatus includes at least one receiving device (receive antenna) for generating a reception signal from the transmission signal provided by the transmitting device and induced into the receiving device
Implementation Method 2
when the electrically conductive body is absent, partial reception signals form in the receiving device on account of the induced transmission signal. The partial reception signals substantially cancel one another out in the reception signal
Data Source
AI summary
An apparatus checks for a presence of an electrically conductive body in the near field of charging coils of an arrangement for induced charging. At least one transmitting device provides a transmission signal in the form of a magnetic field. At least one receiving device generates a reception signal from the transmission signal and induced into the receiving device. The transmitting device and the receiving device are formed in such a way that, when the electrically conductive body is present, a first reception signal forms and, when the electrically conductive body is absent, a second reception signal, different than the first, forms in the receiving device on account of the induced transmission signal. The transmitting device and the receiving device are formed in a manner dependent on the magnetic field of the charging coils in such a way that, when the electrically conductive body is absent, partial reception signals form in the receiving device on account of the induced transmission signal, where partial reception signals substantially cancel one another out in the reception signal.