Magnetic Sensor Device with Asymmetric Shielding for Uniform Flux
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Solution Overview
Problem
Conventional magnetic sensor devices experience uneven magnetic flux in the longitudinal direction, leading to reduced sensitivity at the ends and susceptibility to external magnetic flux due to inadequate shielding, which affects the accuracy and coherence of magnetic field detection.
Innovation Solution
A magnetic sensor device with a magnetic sensor unit, a magnet extending in the longitudinal direction, and a magnetic shield unit that includes side surfaces with varying lengths to optimize magnetic flux distribution, along with a cover for electrical shielding, ensuring uniform magnetic flux density and reduced external interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a magnetic shield unit is added to block external magnetic flux, then shielding effectiveness is improved, but device complexity increases
Solution Approach 1:
The magnetic shield unit is integrated with the housing structure, merging the shielding function into the existing device framework. The shield unit shares spatial and structural elements with the housing, eliminating the need for a completely separate shielding component and reducing overall device complexity.
Solution Approach 2:
The housing structure serves multiple functions: it provides mechanical support, defines the device boundary, and simultaneously acts as a magnetic shield when the shield unit is integrated into it. This multi-functionality reduces the number of separate components needed.
2Measurement precision
If the magnet length in vertical direction is increased at ends to apply bias magnetic flux, then sensitivity uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The magnet is designed with asymmetric dimensions where the vertical length varies along the longitudinal direction, being longer at the ends and shorter at the center. This asymmetric geometry creates the desired non-uniform magnetic flux distribution to improve sensitivity uniformity across the sensing target.
Solution Approach 2:
Different portions of the magnet have different vertical lengths tailored to local requirements: longer sections at the ends provide bias flux for improved sensitivity, while the shorter central portion maintains appropriate flux density for the central sensing region.
3Adaptability or versatility
If anisotropic magnetoresistive elements are arranged linearly, then sensitivity to tilted magnetic patterns is improved, but device complexity increases
Solution Approach 1:
The linear arrangement of anisotropic magnetoresistive elements creates a dynamic response to magnetic fields at various angles. The elements collectively detect tilted patterns through their combined resistance changes, allowing the system to adapt to different magnetic pattern orientations without requiring complex individual element configurations.
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 achieves uniform magnetic flux distribution and enhanced sensitivity across the magnetic sensor unit, suppressing sensitivity reduction at the ends while providing effective magnetic shielding against external flux.
Implementation Method 1
a magnet extending in a longitudinal direction
Implementation Method 2
outputs, as a change in a resistance value, a change in the component of the cross field
Implementation Method 3
the smallest length of a length of the third side surface and a length of the fourth side surface in a perpendicular direction is smaller than the largest length of a length of the first side surface and a length of the second side surface
Implementation Method 4
a cover that is disposed between the magnetic sensor unit and the sensing target and that covers the magnetic shield unit
Data Source
AI summary
A magnetic sensor device (10) includes a magnetic sensor unit including a magnetoresistive element mounted on a sensor board extending in a longitudinal direction and a magnet (3) located on a surface of the sensor board opposite to a surface on which the magnetoresistive element is mounted, a housing supporting the magnetic sensor unit, a magnetic shield unit (4) covering side surfaces and a bottom surface of the housing, and a cover covering an upper portion of the housing. The magnetic shield unit (4) has an opening (4o) facing in Z-axis direction from the magnetoresistive element toward a transport path of a sensing target. The opening (4o) is defined by two long sides in the longitudinal direction and two short sides in a lateral direction. The two long sides of the magnetic shield unit (4) are nearer to the sensing target in Z-axis direction than the two short sides.