Magnetoresistive Position Detector with Opposing Bias Fields
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Solution Overview
Problem
Existing position detectors using magnetoresistive elements are limited in detecting positions over a wide area, particularly around the center of a magnet, due to their inability to distinguish between magnetic field components and the complexity of their circuits, leading to inaccurate position determination and the need for larger magnets.
Innovation Solution
A position detector employing magnetoresistive elements with bias magnetic fields acting in opposite directions, allowing for accurate detection of movement positions in both X and Y directions using a single magnet, which cancels out the effect of orthogonal magnetic field components and stabilizes detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Hall element is used to detect magnetic field intensity, then the position can be detected, but the detection area is limited and the circuit becomes complex
Solution Approach 1:
The patent replaces Hall elements with magnetoresistive elements that directly convert magnetic field effects into resistance changes, eliminating the need for complex signal conditioning circuits. The magnetoresistive elements provide direct electrical resistance variation in response to magnetic field changes, simplifying the overall detector circuit while maintaining position detection capability
Solution Approach 2:
The patent changes the detection parameter from magnetic field intensity (scalar) to magnetic field direction and intensity components (vector). By using magnetoresistive elements sensitive to magnetic field direction, the system can detect both X and Y position coordinates simultaneously, expanding the detection area without increasing circuit complexity
2Area of stationary object
If the size of the magnet is increased to expand the detection area, then the position can be detected over a wider area, but the device becomes larger and heavier
Solution Approach 1:
The patent changes the detection approach from scalar magnetic field intensity to vector magnetic field components. By using magnetoresistive elements that detect magnetic field direction, a small magnet can provide sufficient detection coverage across a wide area. The directional sensitivity allows the system to distinguish position information that would otherwise require a larger magnet
Solution Approach 2:
The patent adds the dimension of magnetic field direction detection to the traditional intensity-only detection. By measuring both the direction and intensity of magnetic field components, the system achieves wide-area detection with a compact magnet, as the directional information provides additional position discrimination capability
3Measurement precision
If giant magnetoresistive elements are used to detect magnetic flux components, then the position can be detected, but the magnetization becomes unstable when orthogonal magnetic field components are present
Solution Approach 1:
The patent segments the detection function into multiple magnetoresistive elements, each with pinned magnetic layers oriented in different directions. This segmentation allows each element to be optimized for detecting specific magnetic field components while being less susceptible to interference from orthogonal components, thereby maintaining magnetization stability
Solution Approach 2:
The patent applies local quality by giving each magnetoresistive element a specific pinned magnetic layer orientation tailored to its detection function. Elements detecting X-direction components have pinned layers oriented to reject Y-direction interference, while elements detecting Y-direction components have pinned layers oriented to reject X-direction interference, ensuring local magnetization stability
4Device complexity
If only magnetic field intensity is detected, then the detector structure is simple, but the position cannot be distinguished on both sides of the center
Solution Approach 1:
The patent changes the detection from scalar magnetic field intensity to vector magnetic field components by using magnetoresistive elements sensitive to magnetic field direction. This allows the detector to distinguish between positions on opposite sides of the magnet center by detecting the direction of magnetic field components, providing unambiguous position information
Solution Approach 2:
The patent transitions from one-dimensional intensity detection to two-dimensional vector detection by measuring both X and Y components of the magnetic field. This dimensional expansion enables the system to distinguish positions in all quadrants around the magnet center, resolving the ambiguity inherent in intensity-only 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
Enables precise position detection over a wide area with a compact and lightweight design, reducing the number of required magnets and improving detection accuracy by using a single magnet for both X and Y direction components.
Implementation Method 1
each of the first X-direction detecting element, the second X-direction detecting element, the first Y-direction detecting element, and the second Y-direction detecting element is a magnetoresistive element whose electrical resistance changes on the basis of the relationship between the direction of the magnetization of a pinned magnetic layer and the direction of the magnetization of a free magnetic layer
Implementation Method 2
in the first X-direction detecting element and the second X-direction detecting element, bias magnetic fields provided to the free magnetic layers act in opposite directions parallel to the Y axis, and in the first Y-direction detecting element and the second Y-direction detecting element, bias magnetic fields provided to the free magnetic layers act in opposite directions parallel to the X axis
Data Source
AI summary
A circular top surface of a magnet is magnetized to the N-pole, and a back surface thereof is magnetized to the S-pole. A detector moves within the X-Y plane at positions located away from the top surface of the magnet. A pair of X-direction detecting elements and a pair of the Y-direction detecting elements are provided in the detector. In the X-direction detecting elements, the directions of a bias magnetic field provided to free magnetic layers are opposite to each other. When the detector moves in the Y direction, a decrease in the sensitivity of one of the X-direction detecting elements is compensated for by an improvement in the sensitivity of the other element. This also applies to the Y-direction detecting elements. Accordingly, position detection outputs of the X direction and the Y direction can be accurately obtained from the detector.