Magnetic Shield Structure for Stray Field Suppression
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Solution Overview
Problem
Magnetic field sensor systems face errors in angular position measurement due to stray magnetic fields superimposed on the sensing axis, which cannot be distinguished from actual rotation, leading to inaccurate readings.
Innovation Solution
A system comprising an encoder magnet and a magnetic field sensor with a shield structure that surrounds both components to suppress stray magnetic fields, using high permeability materials and varied geometric configurations to redirect stray fields without affecting the measurement magnetic field, and is attachable to secondary structures for integration in applications like throttle valves and BLDC motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shield structure is introduced to suppress stray magnetic fields, then measurement precision is improved, but device complexity increases
Solution Approach 1:
A shield structure made of high permeability material is introduced as an intermediary component between the encoder magnet and the magnetic field sensor. This shield redirects stray magnetic fields away from the sensing axis, allowing the sensor to measure only the measurement magnetic field from the encoder magnet, thereby improving angular position measurement accuracy without complicating the core sensing mechanism
Solution Approach 2:
The shield structure utilizes materials with high magnetic permeability to change the magnetic field distribution parameters. By selecting materials with specific permeability characteristics, the shield effectively redirects stray magnetic fields while maintaining the integrity of the measurement magnetic field, achieving improved measurement precision through material parameter optimization rather than structural complexity
2Measurement precision
If high permeability shield materials are used to redirect stray fields, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the permeability parameter of the shield material to achieve the minimum necessary shielding effectiveness. By carefully selecting materials with appropriate (but not excessively high) permeability values, the shield achieves adequate stray field redirection while controlling material costs and maintaining ease of manufacture
Solution Approach 2:
The shield structure is designed to provide sufficient but not excessive shielding. The dimensions and material properties are optimized to achieve the required measurement precision with the minimum necessary shielding capability, avoiding over-engineering that would increase manufacturing costs without providing additional measurement accuracy benefits
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 shield structure effectively suppresses stray magnetic fields, ensuring accurate angular position measurement by isolating the measurement magnetic field, thus enhancing the reliability and precision of magnetic field sensing without requiring additional electronic circuitry, while allowing for cost-effective manufacturing and integration in various automotive and industrial applications.
Implementation Method 1
a shield structure at least partially surrounding the encoder magnet and/or the magnetic field sensor for shielding against stray magnetic fields
Data Source
AI summary
A system includes an encoder magnet, a magnetic field sensor, and a shield structure. The encoder magnet is configured to rotate about an axis of rotation and is configured to produce a measurement magnetic field. The magnetic field sensor is axially displaced away from the encoder magnet and is configured to detect the measurement magnetic field. The shield structure at least partially surrounds both of the encoder magnet and the magnetic field sensor for shielding against stray magnetic fields. The shield structure attaches to a secondary structure. The shield structure and the encoder magnet may be coupled via the secondary structure so that they are commonly rotational. Alternatively, the sensor package and the shield structure are coupled via the secondary structure so that they are nonrotational relative to the encoder magnet.