Magnetic Detection Device Direction Discrimination
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Solution Overview
Problem
Conventional magnetic detection devices face challenges in accurately detecting the moving direction of a tooth-shaped magnetic moving body, often resulting in erroneous detections, especially during alternate forward and backward rotations caused by vibrations.
Innovation Solution
The magnetic detection device employs first and second magnetoelectric conversion elements in a biasing magnetic field, with an output signal processing circuit generating distinct pulses for forward and backward movements, ensuring accurate detection by comparing these pulses with different comparison levels to prevent erroneous discrimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic detection devices use simple magnetoresistance elements to detect tooth-shaped magnetic moving body, then the device structure is simple, but detection accuracy deteriorates due to erroneous detections during alternate forward and backward rotations caused by vibrations
Solution Approach 1:
The patent divides the detection function into multiple magnetoresistance elements (first, second, and third MR elements) arranged at different positions. Each element detects magnetic field changes from the tooth-shaped magnetic moving body, and their outputs are processed separately through bridge circuits and comparison circuits to determine rotation direction, thereby improving detection accuracy through segmented measurement
Solution Approach 2:
The patent introduces a magnet 1 as an intermediary component that generates a biasing magnetic field between the magnetoresistance elements and the tooth-shaped magnetic moving body. This intermediary magnetic field enables the MR elements to detect position changes accurately by modulating their resistance based on the magnetic field strength, which varies as teeth and recesses pass by
2Measurement precision
If the device uses multiple magnetoresistance elements and complex signal processing circuits to improve detection accuracy, then detection precision is improved, but the device complexity increases
Solution Approach 1:
The patent makes the magnetoresistance elements serve multiple functions: they detect both the presence of teeth and recesses as well as the direction of rotation. By arranging three MR elements at specific positions and processing their outputs through bridge circuits and comparison circuits, the system universally handles both position detection and direction determination without requiring separate dedicated sensors for each function
Solution Approach 2:
The patent uses bridge circuits (23 and 30) to create balanced measurement configurations where the magnetoresistance elements are paired with resistors in Wheatstone bridge arrangements. This equipotential approach cancels out common-mode errors and provides stable reference levels, allowing accurate detection of small resistance changes caused by magnetic field variations while maintaining circuit simplicity
3Adaptability or versatility
If conventional devices use single-level comparison circuits, then the circuit design is simple, but the ability to differentiate between forward and backward rotations during alternate operations deteriorates
Solution Approach 1:
The patent transitions from single-level comparison to multi-level comparison by introducing two distinct comparison levels (first and second comparison levels) in the comparison circuits. This dimensional expansion in the signal processing domain allows the system to differentiate between forward and backward rotations by comparing the output signals against multiple reference thresholds, providing robust direction detection even during alternate operations caused by vibrations
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 enables precise detection of the moving direction without errors, even during alternate operations, enhancing the device's ability to differentiate between forward and backward rotations.
Implementation Method 1
three magnetoresistance elements as magnetic detection elements (magnetoelectric conversion elements) are integrated
Implementation Method 2
a rectangular-parallelepiped magnet 1 for generating a biasing magnetic field
Data Source
AI summary
A magnetic detection device is provided in which a first signal is outputted in accordance with the mutual phase relationship between the output of a first magnetoelectric conversion output circuit and the output of a second magnetoelectric conversion output circuit that are based on the movement, in forward direction, of a detection subject, thereby generating a pulse of a high level 1 and a low level 1; a second signal is outputted in accordance with the mutual phase relationship between the output of the first magnetoelectric conversion output circuit and the output of the second magnetoelectric conversion output circuit that are based on the movement, in forward direction, of the detection subject; an output signal processing circuit for generating a pulse of a high level 2 and a low level 2 is provided; and not only the pulse of the high level 1 and the low level 1 does not cross the other comparison level, but also the pulse of the high level 2 and the low level 2 does not cross the one comparison level.