Differential Magnetic Sensor for Leakage Field Immunity

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Solution Overview

Problem

Magnetic sensors in automotive applications are susceptible to magnetic leakage fields, which can lead to inaccurate wheel speed measurements due to the increasing electrification and hybridization of vehicles, requiring improved insensitivity to such fields.

Innovation Solution

A sensor device comprising a magnet with a differential magnetic field sensor having two sensor elements spaced apart perpendicular to the magnetization direction, designed to detect magnetic field components perpendicular to both the magnetization and sensor element directions, effectively canceling out magnetic leakage fields by utilizing a differential scanning principle.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a magnetic sensor is used to measure wheel speeds in automotive applications, then wheel speed measurement is enabled, but the sensor becomes susceptible to magnetic leakage fields causing inaccurate measurements

Engineering Contradiction:

Improvewheel speed measurement accuracyVSAvoidmagnetic leakage field susceptibility

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The sensor device is segmented into two separate sensor elements (first sensor element and second sensor element) spaced apart in a specific direction. Each element detects magnetic field components, and their differential output cancels out leakage field effects while maintaining measurement accuracy for wheel speed

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A magnet is introduced as an intermediary component between the sensor elements and the wheel. This magnet generates a magnetic field that enables the sensor elements to detect wheel rotation while the differential arrangement of sensor elements cancels out the harmful leakage field effects

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the air gap width is reduced to improve measurement resolution, then measurement precision improves, but magnetic leakage field interference increases

Engineering Contradiction:

Improvemeasurement resolutionVSAvoidmagnetic leakage field interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

By segmenting the sensor into two spatially separated elements and arranging them perpendicular to the magnetization direction, the device can operate at small air gap widths for high resolution while the differential measurement cancels the increased leakage field interference that would otherwise occur at such small gaps

Inventive Principle:

Principle #1Segmentation

3Object-affected harmful factors

If a differential magnetic field sensor with sensor elements spaced apart is used, then insensitivity to magnetic leakage fields is improved, but device complexity increases

Engineering Contradiction:

Improvemagnetic leakage field insensitivityVSAvoidsensor structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The differential magnetic field sensor integrates two sensor elements, a magnet, and associated structures into a single combined device. This merging achieves leakage field insensitivity through the differential arrangement while maintaining manageable overall device complexity through integrated design

Inventive Principle:

Principle #5Merging (Combining)

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 solution enhances the performance of sensor devices in the presence of magnetic leakage fields, ensuring accurate wheel speed measurements even at small air gap widths, thereby improving reliability in safety-critical automotive applications.

Implementation Method 1

the first sensor element and the second sensor element are designed to detect a magnetic field component in a third direction perpendicular to the first direction and perpendicular to the second direction

Methodology Applied

Scientific EffectHall effect: Hall Effect

Implementation Method 2

such magnetic sensors are used in safety-relevant applications

Methodology Applied

Scientific EffectMagnetoresistance effect: Magnetoresistance

Implementation Method 3

a magnet having a magnetization in a first direction

Methodology Applied

Scientific EffectMagnetism: Magnetism

Data Source

PatentUS11150260B2Sensor devices and methods for producing sensor devices

Publication Date: 2021.10.19 INFINEON TECHNOLOGIES AG

AI summary

A sensor device comprises a magnet having a magnetization in a first direction. Furthermore, the sensor device comprises a differential magnetic field sensor arranged on the magnet and having a first sensor element and a second sensor element, wherein the sensor elements are spaced apart in a second direction perpendicular to the first direction. The first sensor element and the second sensor element are designed to detect a magnetic field component in a third direction perpendicular to the first direction and perpendicular to the second direction.