Magnetic Sensor Device With Shielded Case For External Field Immunity
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Solution Overview
Problem
Existing magnetic sensor devices lack magnetic shielding, leading to variations in performance due to external magnetic fields and low electromagnetic immunity, causing electromagnetic interference and instability in detection.
Innovation Solution
A magnetic sensor device with a magnetic shield covering the case, except for the surface with the magnetic-resistance-effect-element mounted substrate, featuring side walls that extend along the longitudinal direction of the magnet to minimize external magnetic field interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If no magnetic shield is provided, then the device structure is simple, but the performance varies due to external magnetic fields
Solution Approach 1:
A magnetic shield body is introduced as an intermediary component between the permanent magnet and external environment. This magnetic shield body, having higher magnetic permeability than the permanent magnet, acts as a mediator that preferentially conducts magnetic flux through itself, thereby protecting the permanent magnet from external magnetic field interference while maintaining device functionality
2Object-affected harmful factors
If the magnetic shield body is electrically independent, then the magnetic shielding function is achieved, but electromagnetic interference increases
Solution Approach 1:
The magnetic shield body is electrically connected to the case, merging the magnetic shielding function with the structural case. This electrical connection grounds the magnetic shield body, preventing it from functioning as an antenna and thereby eliminating electromagnetic interference while maintaining effective magnetic shielding
3Ease of operation
If the permanent magnet is exposed to lateral magnetic field, then the device structure is open, but electromagnetic immunity decreases
Solution Approach 1:
The magnetic shield body is positioned specifically at the lateral sides of the permanent magnet, providing localized magnetic shielding exactly where lateral magnetic field interference occurs. This targeted approach protects the permanent magnet from side-directional magnetic fields while maintaining device accessibility and not interfering with the primary detection function
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 magnetic sensor device achieves reduced susceptibility to external magnetic field variations, enhanced electromagnetic immunity, and stable performance by effectively shielding the internal components from external magnetic flux.
Implementation Method 1
a magnetic shield to cover the case except for the surface of the magnetic-resistance-effect-element mounted substrate on which the magnetic-resistance-effect-element mounted body is mounted
Implementation Method 2
outputs a variation in resistance value that indicates a variation in the transport direction component of the cross magnetic field caused by the magnetic component of the object-to-be-detected transported in the cross magnetic field
Data Source
AI summary
A magnetic sensor device includes: a magnet; a magnetic-resistance-effect-element mounted substrate on which a magnetic-resistance-effect-element mounted body is mounted on a surface thereof opposite to a surface thereof facing the magnet, the magnetic-resistance-effect-element mounted body extending in the longitudinal direction of the magnet; a case that accommodates or retains the magnet and the magnetic-resistance-effect-element mounted substrate; and a magnetic shield that covers the case except for the surface of the magnetic-resistance-effect-element mounted substrate on which is mounted the magnetic-resistance-effect-element mounted body. The magnetic shield covers the case at a position corresponding to the surface of the magnetic-resistance-effect-element mounted substrate facing the magnet, or from the position corresponding to the surface of the magnetic-resistance-effect-element mounted substrate facing the magnet to a side of the case opposite to the magnet.