Magnetic Field Sensor Tooth Detection Using Segmented Elements
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Solution Overview
Problem
Conventional magnetic field sensors struggle to provide accurate output signals immediately upon power-up or when the target object is stationary, and they fail to differentiate between gear teeth and valleys effectively, especially with variations in mechanical and thermal parameters, leading to expensive design choices.
Innovation Solution
A magnetic field sensor with a simpler and less expensive magnet configuration, utilizing a magnet with no central core, and an electronic circuit that generates a low baseline magnetic field, allowing for accurate differentiation between gear teeth and valleys even in varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional magnetic field sensor with a magnet and sensing elements is used, then the sensor can detect magnetic field variations, but it fails to provide accurate output signals immediately upon power-up or when the target object is stationary
Solution Approach 1:
The patent divides the sensing function into multiple independent sensing elements arranged at different positions relative to the magnet. This segmentation allows each element to detect specific magnetic field characteristics, enabling accurate tooth/valley differentiation from the start without requiring warm-up time for signal averaging or threshold adaptation.
Solution Approach 2:
The patent pre-positions multiple sensing elements at specific locations around the magnet during manufacturing, establishing the detection geometry beforehand. This preliminary arrangement ensures that the sensor is immediately capable of accurate detection upon power-up, eliminating the time delay associated with conventional sensors that require operational conditioning.
2Measurement precision
If a conventional magnetic field sensor is used, then it can detect gear features, but it fails to effectively differentiate between gear teeth and valleys, especially with variations in mechanical and thermal parameters
Solution Approach 1:
The patent assigns different spatial positions and orientations to multiple sensing elements, giving each element a specific local sensitivity to particular magnetic field characteristics. This local quality differentiation enables the system to distinguish between teeth and valleys by comparing signals from elements with different local responses, maintaining accuracy across mechanical and thermal variations.
Solution Approach 2:
The patent employs an asymmetric arrangement of sensing elements relative to the magnet, with elements positioned at non-uniform intervals and orientations. This asymmetric configuration creates distinct signal patterns for teeth versus valleys, enhancing differentiation capability and robustness against parameter variations that would affect symmetric arrangements equally.
3Reliability
If a complex magnet configuration with central core is used, then magnetic field control is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent removes the central core from the magnet configuration, extracting only the essential magnetic field generation function. This simplification reduces manufacturing complexity and cost while maintaining sufficient magnetic field control through the optimized arrangement of multiple sensing elements that compensate for the simpler magnet structure.
Solution Approach 2:
The patent replaces the expensive, complex permanent magnet with a simpler, cheaper magnet configuration that may have reduced longevity or stability. The cost savings from using a simpler magnet are offset by the intelligent use of multiple sensing elements and signal processing that maintain overall system reliability and performance.
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 accurate output signals and effective differentiation between gear teeth and valleys, reducing costs and maintaining accuracy across mechanical and thermal variations.
Implementation Method 1
Magnetic field sensors generally include a magnetic field sensing element and other electronic components. Some magnetic field sensors also include a permanent magnet in a so-called 'back biased' arrangement
Implementation Method 2
Various types of magnetic field sensing elements are known, including Hall Effect elements and magnetoresistance elements
Implementation Method 3
in the presence of a moving ferromagnetic object, the magnetic field generated by the magnet and sensed by the magnetic field sensor varies in accordance with a shape or profile of the moving ferromagnetic object
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
The invention relates generally to a variety of magnetic field sensor arrangements for sensing motion of a ferromagnetic object provide so-called "tooth detectors" using a simple low-cost magnet.An embodiment comprises two magnetic field sensing elements (904,908) wherein a line passing through the first and second magnetic field sensing elements intersects the ferromagnetic object (930).