Speed Detecting Device Stray Magnetic Field Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional speed sensors struggle to accurately detect the speed of completely flat moving bodies without discontinuity characteristics, as they rely on optical or magnetic discontinuities, and eddy current-based sensors face inefficiencies due to magnetic flux leakage and optimization challenges in coil arrangements and yoke shapes.
Innovation Solution
A speed detecting device with an excitation coil and two detection coils disposed on a yoke, where the coils are wound on convex portions to minimize magnetic flux leakage, and a stray magnetic field is suppressed using multiple excitation coils with alternating currents, concentrating magnetic flux and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a yoke is provided around the excitation coil and detection coils to prevent magnetic flux leakage, then magnetic efficiency is improved, but stray magnetic fields are generated and power consumption increases
Solution Approach 1:
The excitation coil system is segmented into multiple coils (first excitation coil and second excitation coil) positioned at different locations. Each coil generates magnetic flux that links with the detection coils, allowing the system to achieve both magnetic flux concentration and stray field cancellation through coordinated operation of the segmented excitation sources
Solution Approach 2:
The patent converts the harmful stray magnetic field into a beneficial effect by using the same excitation coils to generate both the useful magnetic flux for detection and the compensating flux for stray field cancellation. The second excitation coil specifically generates flux oriented to cancel stray fields from the first coil, turning what would be waste energy into a useful cancellation mechanism
2Measurement precision
If the proportion of magnetic fluxes failing to be linked with detection coils increases, then magnetic flux leakage occurs, but eddy current magnitude decreases and speed detection accuracy deteriorates
Solution Approach 1:
The patent applies different spatial arrangements and orientations to different excitation coils. The first excitation coil is positioned to optimize magnetic flux linkage with detection coils for accurate speed detection, while the second excitation coil is positioned and oriented specifically to address stray field cancellation. This local optimization of each coil's function resolves the contradiction between flux linkage and stray field generation
3Adaptability or versatility
If conventional speed sensors use optical or magnetic discontinuity characteristics, then they can detect moving bodies with discontinuities, but they fail to detect completely flat moving bodies without discontinuity characteristics
Solution Approach 1:
The patent replaces optical or magnetic discontinuity-based detection with an electromagnetic induction system that detects speed through induced voltages in detection coils. This substitution of detection mechanism enables the system to measure speed on completely flat surfaces by detecting the motion-induced changes in magnetic flux linkage, rather than relying on surface discontinuities
Solution Approach 2:
The patent changes the detection parameter from optical/magnetic discontinuity characteristics to electromagnetic induction parameters (induced voltage, magnetic flux linkage). By using the relationship between motion, magnetic flux, and induced voltage described by Faraday's law, the system can detect speed on flat surfaces where no discontinuities exist, expanding adaptability while maintaining measurement precision
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 accurately detects the speed of flat moving bodies by enhancing magnetic efficiency and reducing stray magnetic fields, improving detection sensitivity and power efficiency.
Implementation Method 1
a magnetic flux produced by an eddy current generated on a moving body 6 as a result of the moving body 6 moving through a magnetic flux generated by an excitation coil 2 is detected by two detection coils 3
Implementation Method 2
a magnetic flux produced by an eddy current generated on a moving body 6 as a result of the moving body 6 moving through a magnetic flux generated by an excitation coil 2
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A speed detecting device (1) includes n (n is an integer of 3 or greater) excitation coils (2) for generating magnetic fluxes corresponding to alternating currents, a plurality of detection coils (3) each generating an induced voltage corresponding to a magnetic flux produced by an eddy current generated on a conductive relative moving body (6), the eddy current being generated so as to correspond to a moving speed of the relative moving body (6), and a speed estimation portion (4) for estimating, based on the induced voltage generated in each of the plurality of detection coils (3), the moving speed of the relative moving body (6). The n excitation coils (2) and the plurality of detection coils (3) are disposed so that magnetic fluxes generated by the alternating currents flowing through the n excitation coils (2) are linked with at least one of the plurality of detection coils (3). In this way the usable magnetic field at the location of the detection coils is increased, while stray magnetic fields which cannot contribute to the detection signals are reduced.