Magnetic Sensor Position Detection Using MR Elements
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Solution Overview
Problem
Existing magnetic position detection devices face challenges in maintaining detection accuracy due to unnecessary magnetic fields and magnetic hysteresis characteristics, especially when the direction of the applied magnetic field changes, leading to a drop in detection accuracy.
Innovation Solution
A position detection device is designed with a magnetic sensor that includes at least one magnetoresistive element with a first magnetic layer having magnetization that can change direction within a specific plane. The magnetic sensor is configured such that the magnetic field to be detected can be divided into in-plane and perpendicular components, ensuring that the detection value is generated while maintaining accuracy even when the magnetic field direction changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a soft magnetic body is used to convert magnetic field direction, then the magnetic sensor can detect magnetic fields in different directions, but detection accuracy drops due to unnecessary magnetic fields and magnetic hysteresis characteristics
Solution Approach 1:
The patent removes the soft magnetic body from the magnetic sensor structure. Instead of using a soft magnetic body to convert magnetic field directions, the invention uses multiple magnetoresistive elements with different sensitivity directions to directly detect magnetic field components, thereby eliminating the harmful effects of unnecessary magnetic fields and hysteresis characteristics while maintaining the ability to detect magnetic fields in multiple directions.
Solution Approach 2:
The patent employs multiple magnetoresistive elements with different sensitivity directions (e.g., in-plane and out-of-plane sensitivity) to perform multiple detection functions simultaneously. This allows the sensor to detect magnetic field components in different directions without requiring a soft magnetic body, achieving both versatility in detection direction and precision in measurement.
2Device complexity
If a magnetoresistive element with sensitivity to magnetic field in a specific plane is used, then the element structure is simple, but detection accuracy drops when magnetic field direction changes outside that plane
Solution Approach 1:
The patent combines multiple magnetoresistive elements with different sensitivity characteristics (in-plane and out-of-plane sensitivity) into a single integrated magnetic sensor. This merging approach maintains relatively simple individual element structures while achieving accurate detection of magnetic fields in three-dimensional space through the combined output of multiple elements.
Solution Approach 2:
The patent uses a composite structure of multiple magnetoresistive elements with different magnetic sensitivity orientations. By combining elements with in-plane sensitivity and out-of-plane sensitivity, the sensor achieves comprehensive magnetic field detection capability while maintaining the simplicity of individual magnetoresistive element designs.
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 proposed solution effectively suppresses the drop in detection accuracy by ensuring that the strength of the in-plane component remains non-zero, even when the magnetic field direction changes, thereby maintaining reliable position detection.
Implementation Method 1
a magnetic sensor that detects a magnetic field generated by the magnet and generates a detection value
Implementation Method 2
The spin-valve magnetoresistive element includes a magnetization pinned layer having a magnetization whose direction is fixed, a free layer having a magnetization whose direction is variable depending on the direction of an applied magnetic field
Implementation Method 3
The soft magnetic body converts a magnetic field on an XZ plane, generated by the magnet, into a magnetic field on an XY plane to which the two magnetic sensor elements have sensitivity
Implementation Method 4
a rotating body including a magnet. In this device, as the rotating body rotates, the direction of a magnetic field generated by the rotating body changes within a plane of variation perpendicular to the slope
Data Source
AI summary
A position detection device includes a magnet that generates a magnetic field to be detected, and a magnetic sensor. The magnetic sensor detects the magnetic field to be detected and generates a detection value corresponding to the position of the magnet. The magnetic field to be detected has a first direction that changes within a first plane, at a reference position in the first plane. The magnetic sensor includes four MR elements. Each of the MR elements includes a first magnetic layer having first magnetization that can change in direction within a second plane corresponding to the each of the MR elements. The first plane and the second plane intersect at a dihedral angle α other than 90°. A detection value depends on the direction of the first magnetization.