Magnetic Field Sensor Gear Tooth Differentiation
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Solution Overview
Problem
Conventional magnetic field sensors face challenges in accurately differentiating between gear teeth and gear valleys, especially when using simpler and less expensive magnets, and they struggle with variations in mechanical and thermal parameters, leading to inaccurate output signals, particularly at low rotation speeds or when the ferromagnetic target object is stationary.
Innovation Solution
A magnetic field sensor design featuring a substrate with a first and second full bridge circuit, each comprising magnetoresistance elements, generating differential signals that are combined to produce feature and edge signals, allowing for accurate differentiation between gear teeth and valleys, even with simpler magnets, and providing accurate output signals at low rotation speeds and when stationary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional magnetic field sensors use simpler and less expensive magnets, then manufacturing cost is reduced, but measurement precision deteriorates due to inaccurate differentiation between gear teeth and valleys
Solution Approach 1:
The sensor output signal is segmented into multiple components representing different physical phenomena. The first output signal component corresponds to a first physical phenomenon (e.g., magnetic field changes due to gear tooth presence), while the second output signal component corresponds to a second physical phenomenon (e.g., magnetic field changes due to gear valley presence). By separately processing these segmented signal components, the sensor achieves accurate differentiation between gear teeth and valleys even with simpler magnets.
Solution Approach 2:
The sensor utilizes changes in magnetic field parameters (strength, direction, distribution) as the ferromagnetic target object moves through different positions relative to the magnet and sensing elements. By detecting and processing these parameter changes across multiple sensing elements, the system can distinguish between gear teeth and valleys using less expensive magnet configurations.
2Use of energy by moving object
If conventional magnetic field sensors operate at low rotation speeds or stationary states, then energy consumption is reduced, but measurement precision deteriorates due to inability to provide accurate output signals
Solution Approach 1:
The sensor performs preliminary signal processing and component separation in advance, preparing the output signal components for accurate interpretation regardless of rotation speed. This preliminary action enables the sensor to provide accurate measurements even when the ferromagnetic target object is stationary or moving slowly, as the signal components are already prepared for differentiation without requiring multiple rotation cycles.
Solution Approach 2:
The sensor dynamically adjusts its signal processing based on the motion state of the ferromagnetic target object. By continuously monitoring and adapting to changes in rotation speed and position, the sensor maintains measurement precision across varying operational conditions, from stationary states to high-speed rotation.
3Measurement precision
If conventional magnetic field sensors require multiple rotation cycles to provide accurate signals, then measurement precision improves, but productivity deteriorates due to delayed accurate output
Solution Approach 1:
The sensor performs preliminary signal processing and component separation in advance, preparing the output signal components for accurate interpretation regardless of rotation speed. This preliminary action enables the sensor to provide accurate measurements even when the ferromagnetic target object is stationary or moving slowly, as the signal components are already prepared for differentiation without requiring multiple rotation cycles.
4Measurement precision
If conventional magnetic field sensors use complex magnet configurations, then measurement precision improves, but device complexity increases
Solution Approach 1:
The sensor segments the measurement function across multiple sensing elements rather than relying on a complex single magnet configuration. Each sensing element detects specific magnetic field parameters, and the combined output provides accurate differentiation between gear teeth and valleys using a simpler overall magnet structure.
Solution Approach 2:
The magnet configuration is designed to serve multiple functions simultaneously: generating the magnetic field for sensing, providing reference signals for differentiation, and enabling detection across various operational conditions. This multi-functionality reduces the need for separate complex magnet structures while maintaining measurement precision.
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 sensor achieves accurate differentiation between gear teeth and valleys, ensuring reliable operation across varying mechanical and thermal conditions, including low rotation speeds and stationary states, using a simpler and less expensive magnet configuration.
Implementation Method 1
A magnetic field sensor includes a substrate, a first full bridge circuit disposed upon the substrate and proximate to the ferromagnetic target object, the first full bridge circuit including a first magnetoresistance element
Implementation Method 2
In some embodiments that have the magnet (back-biased arrangements), the sensed magnetic field is a magnetic field generated by the magnet
Implementation Method 3
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
Figure 1A
Figure 2
AI summary
A magnetic field sensor operates as a motion detector for sensing a movement of a ferromagnetic target object having features. The magnetic field sensor has a plurality of magnetoresistance elements to generate, in a first channel, a feature signal indicative of a proximity of a feature of a ferromagnetic target object and, in a second channel, an edge signal indicative of a proximity of an edge of a feature of a ferromagnetic target object.