Magnetic Sensor Unit with Nested Shield and Yoke for Compact Angle Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing magnetic sensor units for detecting rotation angles face challenges in effectively shielding external magnetic fields while maintaining a compact size, leading to inaccuracies in high magnetic field strength regions and increased device size due to magnetic saturation.
Innovation Solution
A magnetic sensor unit design incorporating a magnet with opposing magnetized regions, a magnetic yoke to enhance magnetic flux density, and a strategically positioned magnetic shield that satisfies specific distance relations to minimize size and maximize shielding, utilizing anisotropic magnetoresistors for improved angle detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a magnetic shield is added to suppress external magnetic fields, then magnetic shielding performance is improved, but device size increases
Solution Approach 1:
The magnetic shield is positioned inside the magnetic yoke structure, with the shield's outer peripheral surface facing the inner peripheral surface of the yoke. This nested arrangement allows the magnetic shield to be contained within the existing yoke boundaries, providing shielding functionality without proportionally increasing the overall device volume.
Solution Approach 2:
The magnetic shield is strategically positioned only in regions where external magnetic field interference is most critical, rather than providing uniform shielding throughout the entire device. The shield's location is optimized to protect the magnetic sensor from harmful fields while minimizing material usage and device size.
2Volume of stationary object
If the magnetic shield is positioned closer to the magnet to reduce size, then device size is reduced, but magnetic saturation occurs reducing accuracy
Solution Approach 1:
The magnetic yoke serves as an intermediary structure between the magnet and the magnetic shield. The yoke's inner peripheral surface is positioned between the magnet and shield, creating an optimal magnetic flux path that prevents direct interaction between the shield and magnet. This intermediary arrangement allows the shield to be positioned close to the magnet for compactness while avoiding magnetic saturation through the yoke's flux management.
Solution Approach 2:
The distance relationships between components are precisely controlled to optimize performance. Specifically, the distance from the magnet center to the shield (LB) is kept smaller than the distance from the magnet center to the yoke inner surface (LA), creating an optimized magnetic circuit that prevents saturation while maintaining compact dimensions.
3Measurement precision
If a magnetic yoke is added to increase magnetic flux density, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The magnetic yoke performs multiple functions simultaneously: it concentrates magnetic flux to improve the signal-to-noise ratio, provides structural support for mounting the magnetic shield, and defines the geometric boundaries of the magnetic circuit. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity despite adding the yoke structure.
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 provides enhanced magnetic shielding, reduced size, and high accuracy in detecting rotation angles with a large signal-to-noise ratio, even in high magnetic field strengths, by effectively managing magnetic field distribution and saturation.
Implementation Method 1
The magnet includes a first magnetized region magnetized along the up and down direction, and a second magnetized region magnetized in a direction opposite to a direction of magnetization of the first magnetized region
Implementation Method 2
a magnetic yoke covering an upper surface and a side surface of the magnet
Implementation Method 3
a magnetic shield surrounding the magnetic sensor in a lateral direction crossing up and down directions of the magnetic sensor
Implementation Method 4
utilizing anisotropic magnetoresistors for improved angle detection accuracy
Data Source
AI summary
A magnetic sensor unit includes a magnet, a magnetic sensor facing a lower surface of the magnet, a magnetic shield surrounding the magnetic sensor in a lateral direction crossing up and down directions of the magnetic sensor, and a magnetic yoke covering an upper surface and a side surface of the magnet. The magnet includes a first magnetized region magnetized along the up and down direction, and a second magnetized region magnetized in a direction opposite to a direction of magnetization of the first magnetized region. The first and second magnetized regions have first and second magnetic poles provided on the lower surface of the magnet. A distance LA between a center of the first magnetic pole and a center of the second magnetic pole, a distance LB between the magnetic shield and the center of the first magnetic pole, a distance LC between the magnetic shield and the center of the second magnetic pole satisfy a relation of LA<LB+LC. This magnetic sensor unit has magnetic shielding properties and has a small size.