Magnetic Sensor Asymmetric Magnetization for Angle Detection
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Solution Overview
Problem
Existing magnetic sensors for rotational angle detection face challenges in achieving equal output values and reducing device size, with difficulties in accurately disposing magnetic detection elements and maintaining output consistency due to slight shifts and differences in sensor characteristics.
Innovation Solution
A magnetic sensor design featuring two magnetic detection element groups with self-pinned magnetoresistive effect elements, where the fixed magnetic layers have antiparallel magnetization directions and are arranged symmetrically to ensure equal output values, allowing for reliable detection even with slight distortions in the magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetic detection elements are disposed in the vicinity of the rotating body, then rotational angle detection can be performed, but output values from different detection elements become unequal due to slight shifts and characteristic differences
Solution Approach 1:
The patent employs asymmetric magnetization direction arrangement where detection elements have different magnetization orientations (e.g., +X and -X directions) to compensate for positional variations. This asymmetric configuration ensures that even with slight shifts in disposition, the output values from different detection elements remain equal by balancing their sensitivity characteristics through opposite magnetization directions.
Solution Approach 2:
The patent changes the magnetization direction parameter of the magnetic detection elements to resolve the output equality issue. By configuring elements with opposite magnetization directions (positive and negative X directions), the sensitivity characteristics are modified to compensate for positional discrepancies, thereby maintaining equal output values despite manufacturing variations in element disposition.
2Measurement precision
If magnetic detection elements are accurately disposed at predetermined positions, then equal output values can be obtained, but device size increases due to the need for precise positioning structures
Solution Approach 1:
The asymmetric magnetization configuration allows the detection elements to be disposed at non-symmetric positions while still achieving equal output values. This eliminates the need for precise symmetric positioning structures, thereby reducing device size while maintaining output consistency through the compensating effect of opposite magnetization directions.
Solution Approach 2:
By changing the magnetization direction parameter to opposite orientations, the system becomes tolerant to positional variations. This parameter change allows relaxed positioning requirements, eliminating the need for complex precision positioning structures and reducing overall device volume while maintaining measurement precision.
3Measurement precision
If self-pinned magnetoresistive effect elements with antiparallel magnetization are used, then equal output values are achieved, but manufacturing complexity increases
Solution Approach 1:
The magnetoresistive effect element is segmented into distinct functional layers: a fixed magnetic layer with pinned magnetization direction and a free magnetic layer with switchable magnetization. This segmentation allows independent optimization of each layer's properties, simplifying the manufacturing of the overall structure while achieving the desired antiparallel magnetization configuration for equal output values.
Solution Approach 2:
The patent uses identical magnetoresistive effect element structures for both detection elements, copying the same layered configuration (fixed layer + free layer). This copying approach simplifies manufacturing by using the same fabrication process for both elements, while the antiparallel magnetization configuration ensures equal output values are achieved without increasing structural complexity.
4Adaptability or versatility
If a single magnet body with alternating N and S poles is used, then rotational angle detection is enabled, but output values from multiple detection elements become unequal due to magnetic field distortions
Solution Approach 1:
The asymmetric magnetization direction configuration of the detection elements compensates for the magnetic field distortions generated by the single alternating pole magnet body. By having elements with opposite magnetization directions, the system can tolerate the asymmetric magnetic field distribution and still achieve equal output values, thereby maintaining measurement precision while using a compact single magnet body structure.
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 design achieves equal output values from both detection element groups, enhancing reliability and allowing for smaller device sizes while maintaining accurate rotational angle detection, even with distortions in the magnetic field.
Implementation Method 1
a first magnetic detection element group and a second magnetic detection element group each of which includes a plurality of magnetoresistive effect elements
Implementation Method 2
a fixed magnetic layer which is of a self-pinned type in which a first magnetic layer and a second magnetic layer are laminated with a non-magnetic intermediate layer interposed therebetween and magnetization directions of the first magnetic layer and the second magnetic layer are fixed to be antiparallel to each other
Implementation Method 3
configured to respectively process detection signals detected from a magnetic field by the magnetoresistive effect elements
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
A magnetic sensor includes: a first magnetic detection element group G11 and a second magnetic detection element group G12 each of which including a plurality of self-pinned magnetoresistive effect elements; and a first control unit and a second control unit configured to respectively process detection signals detected from a magnetic field by the magnetoresistive effect elements M of the first magnetic detection element group G11 and the second magnetic detection element group G12, in which pinned magnetization directions (D1, D2, D3, and D4) of at least two magnetoresistive effect elements M in the first magnetic detection element group G11 and the second magnetic detection element group G12 are different from each other, and the plurality of magnetoresistive effect elements M of the first magnetic detection element group G11 and the plurality of magnetoresistive effect elements M of the second magnetic detection element group G12 are arranged so that the magnetization directions (D1, D2, D3, and D4) thereof are symmetrical.