Back-Biased Magnetoresistance Sensor for Gear Tooth Detection
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Solution Overview
Problem
Conventional magnetic field sensors in back-biased arrangements face challenges in accurately differentiating between gear teeth and gear valleys due to variations in relative positions, magnetic field strengths, and temperature changes, often requiring complex and expensive magnets to avoid magnetic saturation of magnetoresistance elements.
Innovation Solution
A magnetic field sensor design utilizing one or more magnetoresistance elements with a simpler magnet, where the substrate is positioned to minimize magnetic field interference and saturation, allowing for accurate differentiation between gear teeth and valleys without magnetic saturation, using a magnet with at least two poles and a cavity to optimize magnetic field sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a complex magnet with special core material is used to provide a low baseline magnetic field, then the ability to differentiate gear teeth from valleys is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the core material from the magnet structure, using only magnetic poles without a complex core. This simplifies the magnet design while maintaining the ability to generate the necessary magnetic field for differentiation, resolving the contradiction between measurement precision and device complexity
Solution Approach 2:
The patent changes the magnetic field parameters by positioning the sensor in a back-biased arrangement where it experiences a baseline magnetic field from the magnet. This allows accurate differentiation of gear features without requiring complex magnet structures, addressing both differentiation accuracy and simplifying the magnet design
2Measurement precision
If a magnetoresistance element is used to achieve high sensitivity and signal-to-noise ratio, then measurement precision is improved, but the element becomes saturated at larger magnetic fields requiring complex magnets to control field strength
Solution Approach 1:
The patent changes the operating parameters by using a back-biased arrangement that provides a controlled baseline magnetic field. This allows the magnetoresistance element to operate in its high-sensitivity range without saturation, maintaining measurement precision while avoiding the need for complex magnet structures to control field strength
3Measurement precision
If the substrate is positioned closer to the magnet to improve sensing, then measurement precision is improved, but magnetic field saturation of the magnetoresistance element occurs
Solution Approach 1:
The patent changes the spatial parameters by positioning the substrate at an optimized distance and orientation relative to the magnet. The back-biased arrangement creates a baseline field that allows close positioning for high sensing accuracy while preventing saturation of the magnetoresistance element
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 enables accurate and cost-effective differentiation between gear teeth and valleys, maintaining sensor performance across varying conditions without magnetic saturation, using a less expensive magnet and optimizing sensor placement for improved sensitivity.
Implementation Method 1
one or more magnetoresistance elements disposed upon the substrate, the one or more magnetoresistance elements having respective major response axes parallel to the x-axis, the one or more magnetoresistance elements configured to generate one or more respective magnetic field signals
Implementation Method 2
a magnet disposed proximate to the substrate, the magnet having at least two poles to generate a magnetic field parallel to the major planar surface of the substrate
Data Source
AI summary
A magnetic field sensor includes one or more magnetic field sensing elements and a back-biased magnet arranged to avoid saturation of the one or more magnetic field sensing elements, particularly when the one or more magnetic field sensing elements comprise one or more magnetoresistance elements. The one or more magnetoresistance elements can be arranged in a resistor bridge.