Magnetic Sensor System with Pre-Imprinted Anisotropy for Angle Error Correction
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Solution Overview
Problem
Magnetic sensors employing spin-valve MR elements face errors in detected angles due to induced magnetic anisotropy occurring after installation, which can be exacerbated by temperature changes and external magnetic fields, leading to inaccuracies in rotational or linear position detection.
Innovation Solution
A magnetic sensor system with a magnetic field generation unit and a magnetic sensor featuring a magnetic detection element with pre-imparted induced magnetic anisotropy, combined with shape magnetic anisotropy and an arithmetic circuit for error correction, ensures reduced errors by orienting the easy axis of magnetization to minimize induced anisotropy effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spin-valve MR element is used as the magnetic detection element, then the magnetic sensor can detect the target magnetic field, but an induced magnetic anisotropy occurs in the free layer after installation causing error in the detected angle
Solution Approach 1:
The patent applies preliminary anti-action by imparting induced magnetic anisotropy to the magnetic layer before installation in a predetermined direction. This pre-imparted anisotropy counteracts the a posteriori induced magnetic anisotropy that would otherwise occur after installation due to temperature changes and external magnetic fields, thereby maintaining detection accuracy throughout the sensor's operational life.
Solution Approach 2:
The patent implements preliminary action by performing the magnetic anisotropy imparting process during manufacturing, before the sensor is installed and subjected to operational conditions. This ensures that the magnetic layer is pre-conditioned to resist future anisotropy changes, eliminating the need for post-installation calibration or adjustment.
2Temperature
If the temperature of the MR element is lowered from high temperature while an external magnetic field is applied, then the magnetic sensor operates in cold conditions, but induced magnetic anisotropy occurs in the free layer causing detection error
Solution Approach 1:
The patent applies preliminary anti-action by pre-imparting induced magnetic anisotropy in a predetermined direction during manufacturing. This pre-conditioning counteracts the anisotropy changes that occur during temperature cycling and external magnetic field exposure, ensuring that the magnetic layer maintains its magnetic properties and detection accuracy across the full operational temperature range.
3Ease of manufacture
If no induced magnetic anisotropy is imparted in advance to the magnetic layer, then the manufacturing process is simpler, but the magnetic sensor exhibits large errors after installation due to a posteriori induced magnetic anisotropy
Solution Approach 1:
The patent implements preliminary action by incorporating the induced magnetic anisotropy imparting process into the manufacturing sequence. This ensures that the magnetic layer is pre-conditioned with the necessary magnetic properties before the sensor is assembled and installed, guaranteeing accurate detection performance without requiring complex post-installation calibration procedures.
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 system effectively reduces errors in detected values by stabilizing the magnetic layer's anisotropy, maintaining accuracy across varying operational conditions, and correcting for angle errors caused by induced magnetic anisotropy.
Implementation Method 1
magnetic sensors that employ a spin-valve magnetoresistive (MR) element as the magnetic detection element
Implementation Method 2
an induced magnetic anisotropy that occurs on an a posteriori basis in the free layer of the MR element
Data Source
AI summary
A magnetic sensor system includes a magnetic field generation unit for generating a target magnetic field and a magnetic sensor for detecting the target magnetic field, and is selectable between an operating state and a non-operating state. The magnetic sensor has a magnetic detection element including a magnetic layer whose magnetization direction varies according to the direction of the target magnetic field in a reference position. When in the operating state, the direction of the target magnetic field in the reference position varies when viewed from the magnetic sensor. When in the non-operating state, the direction of the target magnetic field in the reference position does not vary when viewed from the magnetic sensor and the magnetization direction of the magnetic layer is pinned in a first direction. The magnetic layer has an induced magnetic anisotropy that is imparted in advance to the magnetic layer.