Magnetic Sensor Device Hysteresis Stabilization
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Solution Overview
Problem
Magnetoresistive elements in magnetic sensor devices exhibit hysteresis in their magnetic flux-resistance characteristics, leading to unstable output signals due to differential effects on bridge-connected elements after reading a paper sheet medium.
Innovation Solution
The magnetic sensor device incorporates a magnetic field generator that applies a magnetic field with components in both the transport and longitudinal directions to magnetoresistive elements arranged in sets with increasing distances between them, ensuring stable bias magnetic fields and reducing hysteresis effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two bridge-connected magnetoresistive elements are placed adjacent to each other in the transport direction to improve detection sensitivity, then detection sensitivity is improved, but hysteresis effects cause unstable output signals
Solution Approach 1:
The patent transitions from arranging magnetoresistive elements only in the transport direction (X-direction) to arranging them in both transport direction (X-direction) and width direction (Y-direction), forming a two-dimensional array. This dimensional expansion allows the magnetic field generator to apply bias fields from multiple directions, effectively counteracting hysteresis effects while maintaining detection sensitivity.
Solution Approach 2:
The patent applies different spatial arrangements and magnetic field orientations to different regions of the magnetoresistive element array. Specifically, elements in different Y-direction positions receive magnetic fields with different Y-direction components, allowing localized compensation for hysteresis effects based on position-specific conditions.
2Reliability
If magnetoresistive elements are arranged with increasing distance from one end in the reading width direction to apply stable bias magnetic field, then hysteresis effects are reduced, but the structure becomes more complex
Solution Approach 1:
The patent divides the magnetoresistive element array into multiple sets arranged in the Y-direction, with each set containing elements at different X-direction positions. This segmentation allows independent optimization of each set's distance from the magnetic field generator, simplifying the overall design by breaking down the complex single-array problem into manageable subsets.
3Reliability
If a micro magnet is added at the end of a magnet in the longitudinal direction to forcibly apply magnetic field in the non-magnetosensitive direction, then output stability is improved, but the magnet structure becomes complicated
Solution Approach 1:
Instead of modifying the magnet's longitudinal structure by adding micro magnets, the patent introduces a new dimension (Y-direction arrangement of magnetoresistive elements) to achieve the same goal of applying bias fields in the non-magnetosensitive direction. This approach avoids complicating the existing magnet structure while achieving the desired field distribution.
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
This configuration stabilizes the output signals of the magnetoresistive elements by ensuring a consistent magnetic field in the longitudinal direction, thereby reducing the impact of hysteresis and providing a more stable detection process.
Implementation Method 1
a magnetic field generator that generates a magnetic field intersecting with a detection object
Implementation Method 2
A magnetoresistive element has the applied magnetic flux-resistance characteristics showing hysteresis
Implementation Method 3
multiple magnetoresistive elements with resistances that change in accordance with magnetic flux density
Data Source
AI summary
A magnetic sensor device includes a magnet that generates a magnetic field and sets of magnetoresistive elements arranged in a longitudinal direction that is perpendicular to a transport direction. Each of the sets of magnetoresistive elements includes a first and a second resistor. A midpoint of the first and the second resistor is matched with a center axis of the magnet in the transport direction. The first and the second resistor are arranged such that the distance therebetween increases from a distance between first ends of the first and the second resistor in the longitudinal direction to a distance between second ends of the first and the second resistor in the longitudinal direction. At least two sets of the first and the second resistor are arranged so as to be axisymmetric with respect to an imaginary line that is perpendicular to the longitudinal direction of the magnet.