Inductive Charging Coil Ratio for Foreign Object Heating Prevention
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Solution Overview
Problem
Existing inductive charging systems for handheld tool battery devices face challenges in preventing foreign objects from heating up due to high magnetic field intensity, which can damage the system and pose a risk to operators, especially with small foreign objects in the contact area.
Innovation Solution
The system optimizes the ratio between the main coil extension and the minimum clearance between the charging coil and the contact area, ensuring a low field intensity by using a secondary induction charging unit in the battery device and a primary induction charging unit in the charging device, with ratios ranging from 7/1 to 30/1, to achieve efficient energy transmission while minimizing heating risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the main coil extension is increased to improve energy transmission efficiency, then the charging power is improved, but the magnetic field intensity in the contact area increases causing foreign objects to heat up
Solution Approach 1:
The patent applies parameter changes by optimizing the ratio between the main coil extension and the minimum clearance to specific ranges (7/1 to 30/1). This adjusts the magnetic field distribution parameters to achieve efficient energy transmission while preventing excessive field intensity that would cause foreign object heating.
Solution Approach 2:
The patent introduces a new dimensional parameter - the clearance distance between the charging coil and contact area - to resolve the contradiction. By controlling the ratio between coil extension (horizontal dimension) and clearance (vertical dimension), the system achieves both high power transfer and low foreign object heating risk.
2Productivity
If the magnetic field intensity is increased to improve charging speed, then the productivity is improved, but the temperature of foreign objects increases causing safety risks
Solution Approach 1:
The patent changes the magnetic field distribution parameters by establishing specific ratios between coil dimensions and clearance distances. This allows high charging speed through adequate field intensity while preventing foreign object temperature rise by limiting peak field concentrations.
Solution Approach 2:
The patent converts the potentially harmful effect of magnetic fields on foreign objects into a beneficial design constraint. By using the foreign object heating risk as a design parameter (maintaining ratio between 7/1 and 30/1), the system achieves efficient charging while inherently preventing overheating issues.
3Object-affected harmful factors
If the clearance between charging coil and contact area is increased to reduce magnetic field intensity, then foreign object heating is prevented, but the energy transmission efficiency decreases
Solution Approach 1:
The patent optimizes the clearance parameter within specific ratio ranges (7/1 to 30/1 relative to coil extension). This finds the optimal balance point where clearance is sufficient to prevent foreign object heating but not so large as to significantly reduce energy transmission efficiency.
Solution Approach 2:
The patent creates a dynamic design space by defining a range of acceptable ratios rather than a fixed value. This allows the system to adapt the clearance distance based on specific application requirements while maintaining both safety and efficiency within the specified ratio boundaries.
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 configuration effectively prevents foreign objects from heating up, ensuring the safety of the system and operator by maintaining a low magnetic field intensity and enabling efficient energy transfer during charging.
Implementation Method 1
a charging device (14), which in a charging operation is provided to transmit a charging energy inductively to the battery device (12)
Implementation Method 2
at least one induction charging unit (16, 18), which has at least one charging coil (20, 22)
Data Source
AI summary
A charging system for a battery device of a handheld tool includes a charging device provided to inductively charge the battery device in a charging operation, the charging device having at least one induction charging unit which has at least one charging coil having a main coil extension. A gap is provided between the battery device and the charging device in a charging operation. A ratio between (i) the at least one main coil extension and (ii) a minimum clearance between the at least one charging coil and a surface defining the gap is at most 30/1.