Magnetic Sensor Bias Magnet Layout for Accurate Field Detection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing magnetic sensors face challenges in accurately detecting external magnetic fields due to bias magnets that are not effectively aligned to cancel external magnetic fields, leading to reduced accuracy, complex algorithms, and increased memory consumption.

Innovation Solution

The magnetic sensor employs bias magnets with an elongate cross section parallel to the external magnetic field, magnetized perpendicularly to the longitudinal direction, ensuring the bias magnetic field effectively cancels the external field, improving detection accuracy and reducing computational complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a bias magnet with an elongate cross section is magnetized in a direction perpendicular to the longitudinal direction, then the bias magnetic field can be applied in a direction perpendicular to the longitudinal direction, but the magnetization direction is easily directed (bent) in the longitudinal direction due to shape anisotropy

Engineering Contradiction:

Improvemagnetic field detection accuracyVSAvoidmagnetization direction stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The bias magnet is designed with an elongate cross-section where the surface extending in the longitudinal direction is longer than the other sides. This asymmetric geometry creates shape anisotropy that stabilizes the magnetization direction perpendicular to the longitudinal direction, preventing it from bending in the longitudinal direction while maintaining the desired magnetic field orientation.

Inventive Principle:

Principle #4Asymmetry

2Area of stationary object

If a common bias magnet is used for multiple magneto-resistive effect elements, then space efficiency is improved, but the bias magnetic field changes for each element making it difficult to enhance detection accuracy

Engineering Contradiction:

Improvesensor module areaVSAvoidmagnetic field intensity detection accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The bias magnet is divided into multiple independent bias magnets, with each magneto-resistive effect element having its own dedicated bias magnet. This segmentation ensures that each element receives a consistent and stable bias magnetic field, improving detection accuracy while maintaining compact design through efficient spatial arrangement of the individual bias magnets.

Inventive Principle:

Principle #1Segmentation

3Area of stationary object

If bias magnets with elongate cross sections are used, then space efficiency is improved, but the magnetization direction is easily directed in the longitudinal direction due to shape anisotropy

Engineering Contradiction:

Improvebias magnet areaVSAvoidmagnetization direction stability

Core Design Contradiction:

Area of stationary objectVSStability of the object's composition

Solution Approach 1:

The bias magnet employs an elongate cross-section with the surface extending in the longitudinal direction being longer than the other sides. This asymmetric configuration creates shape anisotropy that specifically stabilizes the magnetization direction perpendicular to the longitudinal direction, preventing unwanted bending while maintaining compact footprint.

Inventive Principle:

Principle #4Asymmetry

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 enhances the accuracy of magnetic field detection, simplifies algorithms, reduces memory requirements, and minimizes the influence of offset temperature characteristics.

Implementation Method 1

a bias magnet that is provided near the magneto-resistive effect element and that applies a bias magnetic field to the magneto-resistive effect element, the bias magnetic field having a component in a direction such that the component cancels the external magnetic field that is applied to the magneto-resistive effect element and a component that is perpendicular to the external magnetic field

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

a magneto-resistive effect element that generates a magnetic resistance change in accordance with the change of the external magnetic field

Methodology Applied

Scientific EffectMagneto-resistive effect: Magnetoresistance

Data Source

PatentUS12467988B2Magnetic sensor and camera module

Publication Date: 2025.11.11 TDK CORP

AI summary

A pair of bias magnets applies a bias magnetic field to the magneto-resistive effect element, the bias magnetic field having a component in a direction such that the component cancels the external magnetic field that is applied to the magneto-resistive effect element and a component that is perpendicular to the external magnetic field. The bias magnet has an elongate cross section in a plane that is parallel both to the external magnetic field and to the bias magnetic field. In a projection plane that is parallel to the cross section and onto which the bias magnets and the magneto-resistive effect element are projected, the bias magnet includes an element facing side that is opposite to the magneto-resistive effect element and that extends in a longitudinal direction. The bias magnet is magnetized in a direction that is perpendicular to the longitudinal direction. The element facing side is longer than other sides.