MR Sensor Position Switch for External Magnetic Field Rejection
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Solution Overview
Problem
Position detecting switches are prone to erroneous detection of piston position due to external magnetic fields, particularly in environments with strong magnetic interference like welding machines, especially when the spacing between magnetic sensors is small and piston velocity is low.
Innovation Solution
A position detecting switch utilizing first through third MR sensors to determine piston area transitions and distinguish between continuous and discontinuous areas, incorporating an area transition information generating unit and a switch signal generating unit to reliably differentiate between cylinder magnetic fields and external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the placement spacing between two magnetic sensors is increased to avoid simultaneous detection of external magnetic field, then the ability to distinguish external magnetic field from cylinder magnetic field is improved, but the detection capability when piston velocity is small deteriorates because the two magnetic sensors will not be capable of simultaneously receiving an external magnetic field of the same strength
Solution Approach 1:
The patent divides the detection function into three separate magnetic sensors instead of using two sensors, allowing for more flexible spatial arrangement and detection logic to distinguish between external and cylinder magnetic fields while maintaining detection capability at low velocities
Solution Approach 2:
The patent introduces a new dimension of analysis by evaluating magnetic field detection patterns across multiple sensors simultaneously, using the spatial distribution and temporal characteristics of magnetic field signals to differentiate between external and cylinder magnetic fields
2Measurement precision
If two magnetic sensors are placed at separate positions to detect magnetic field with time interval, then the ability to detect piston position is improved, but the system becomes vulnerable to external magnetic field interference from welding machines
Solution Approach 1:
The patent uses feedback from multiple magnetic sensors to continuously monitor and analyze magnetic field patterns, comparing expected cylinder magnetic field patterns with actual readings to detect and compensate for external magnetic field interference
Solution Approach 2:
The patent introduces a control unit that acts as an intermediary, processing magnetic field signals from multiple sensors and applying logical operations to distinguish between cylinder magnetic fields and external magnetic fields before generating position detection results
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 switch accurately determines piston position and operating range, distinguishing between cylinder and external magnetic fields, ensuring precise control and reducing erroneous detections.
Implementation Method 1
first to third MR sensors that detect a magnetic field of a magnet (52)
Data Source
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AI summary
An area transition information generation unit (20) determines a piston area on the basis of the outputs of first to third MR sensors (12, 14, 16), updates area transition information when the piston area transitions between two continuous areas, and does not update the area transition information when the piston area jumps and transitions between two non-continuous areas. A switch signal generation unit (28) switches a switch signal on the basis of at least the area transition information.