Inductive Displacement Sensor for Power Tools
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Solution Overview
Problem
Existing power tool displacement sensors face issues such as large size, complex circuitry, high power consumption, maintenance difficulties, costliness, sensitivity to external magnetic fields, and low accuracy, making them unsuitable for use in power tools.
Innovation Solution
A robust and accurate displacement sensor using a stator and rotor element with mutually inductive conductive patterns, employing a high-frequency excitation signal with constant amplitude to measure relative displacement, which is less sensitive to electromagnetic interferences and allows for simpler circuitry and reduced size, weight, and production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inductive detector arrangements are used, then displacement sensing capability is achieved, but the device size becomes large and circuit complexity increases
Solution Approach 1:
The detector arrangement is segmented into a stator element with first conductive patterns and a rotor element with second conductive patterns. This segmentation allows each element to be optimized independently, reducing overall circuit complexity while maintaining displacement sensing capability through the distributed conductive pattern configuration.
Solution Approach 2:
The patent replaces complex mechanical contact-based displacement sensing mechanisms with an inductive coupling system using conductive patterns. This substitution eliminates mechanical wear and reduces circuit complexity by using electromagnetic field interaction instead of physical contact and wiring.
2Measurement precision
If traditional detector arrangements are used, then displacement measurement is possible, but power consumption becomes high
Solution Approach 1:
The detector uses periodic excitation signals applied to the conductive patterns to induce currents in the rotor element. This periodic action allows for efficient energy transfer through mutual inductance, reducing continuous power consumption while maintaining accurate displacement measurement capability.
Solution Approach 2:
The rotor element generates its own signal through mutual induction from the stator's excitation signal, without requiring external power supply to the rotor. This self-service mechanism reduces overall power consumption while enabling displacement sensing.
3Measurement precision
If traditional detector arrangements are used, then displacement sensing is achieved, but sensitivity to external magnetic fields increases
Solution Approach 1:
The patent converts the potential harmful effect of external magnetic fields into a beneficial evaluation mechanism. By monitoring changes in mutual inductance that affect the phase relationship between excitation and induced signals, the system can distinguish between displacement-induced changes and external field interference, thereby improving robustness against magnetic interference while maintaining measurement accuracy.
4Measurement precision
If traditional detector arrangements are used, then displacement measurement capability is provided, but manufacturing cost increases
Solution Approach 1:
The conductive patterns on the stator and rotor elements can be manufactured using standard PCB tracing techniques, copying proven manufacturing processes from the electronics industry. This approach significantly reduces manufacturing cost compared to traditional encoder mechanisms while maintaining displacement measurement capability.
Solution Approach 2:
The invention changes the fundamental parameters of the detector from mechanical components to electrical conductive patterns, allowing manufacturing using low-cost PCB processes. This parameter change from mechanical to electrical implementation dramatically reduces manufacturing cost while preserving measurement functionality.
5Measurement precision
If traditional detector arrangements are used, then displacement sensing is achieved, but the device becomes difficult to maintain
Solution Approach 1:
The patent replaces mechanical contact components with inductive coupling between conductive patterns, eliminating mechanical wear and contact degradation. This substitution dramatically improves ease of maintenance as there are no moving parts requiring lubrication or replacement, while maintaining displacement sensing capability through electromagnetic interaction.
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 solution provides a compact, cost-effective, and accurate displacement sensor with improved robustness against disturbances and misalignment, capable of operating near power cables with high currents, and effectively suppresses noise and external magnetic field interference.
Implementation Method 1
The first conductive pattern and the second conductive pattern are mutually inductively coupled. The first conductive pattern is configured to receive an excitation signal. The second conductive pattern is configured to generate an intermediate signal therein caused due to mutual induction between the first conductive pattern and the second conductive pattern.
Data Source
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AI summary
The invention pertains to an inductive displacement sensor and associated method for sensing relative displacement between two relatively moveable parts of a power tool. The displacement sensor comprises a stator element and a rotor element configured for relative movement, said stator element having a first conductive pattern, wherein said rotor element having a second conductive pattern. The first conductive pattern and the second conductive pattern are mutually inductively coupled. The first conductive pattern is configured to receive a high- frequency excitation signal having substantially constant amplitude. The high-frequency excitation signal causes due to mutual induction, between the first conductive pattern and the second conductive pattern, an intermediate signal to be generated in the second conductive pattern. The intermediate signal is indicative of the relative displacement between the stator element and the rotor element.