Magnetic Load Sensor for Linear Actuator Axial Force Detection
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Solution Overview
Problem
Existing linear motion actuators in electric brake systems face challenges in accurately detecting axial loads due to temperature influences on strain-based sensors and reliability issues with hydraulic pressure chambers, which affect detection accuracy and long-term reliability.
Innovation Solution
A magnetic load sensor unit is introduced, comprising a magnetic target and a magnetic sensor that changes position relative to each other with axial load, providing a deformation-based detection method that is less susceptible to temperature variations and external vibrations, using a Hall IC for high accuracy and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a strain gauge is mounted to the caliper body to detect axial load, then the detection system is simple to implement, but the detection accuracy deteriorates due to temperature influence and local strain measurement
Solution Approach 1:
The patent replaces the strain gauge (mechanical/electrical resistance-based sensor) with a magnetic sensor system consisting of a Hall element and a magnet. This substitution eliminates the temperature sensitivity and local strain measurement issues of strain gauges, as the Hall element measures magnetic field changes that are directly related to the axial load through the deflection of the support member, providing more accurate and temperature-stable measurements.
Solution Approach 2:
The patent introduces a magnet as an intermediary element that couples the mechanical deflection of the support member to the electrical Hall element. The magnet converts the physical displacement into a magnetic field change, which the Hall element then detects. This intermediary mechanism provides a more reliable transmission of the load information compared to direct strain measurement.
2Device complexity
If electrodes are embedded in the linear motion member to detect axial load through resistance change, then the sensor structure is compact, but detection accuracy deteriorates due to temperature influence and local strain measurement
Solution Approach 1:
The patent replaces the electrode-based resistance measurement system with a magnetic sensor system. The Hall element and magnet configuration substitutes the electrical resistance measurement approach, eliminating the temperature dependence and local strain measurement limitations while maintaining a compact structure. The magnetic field interaction provides a more accurate measure of the overall support member deflection.
3Device complexity
If a hydraulic pressure chamber is used to detect axial load through pressure measurement, then the detection mechanism is simple, but long-term reliability deteriorates due to hydraulic fluid leakage
Solution Approach 1:
The patent replaces the hydraulic pressure chamber system with a magnetic sensor system. This substitution eliminates the need for hydraulic fluid and sealing mechanisms, thereby removing the leakage problem entirely. The Hall element and magnet provide a contactless, maintenance-free detection method that maintains simplicity while dramatically improving long-term reliability.
4Reliability
If additional seal structures are added to maintain hydraulic pressure chamber liquid tightness, then reliability improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and removes the hydraulic pressure chamber and its associated sealing structures from the system. By replacing the hydraulic detection mechanism with a magnetic sensor system, the patent eliminates the source of leakage problems and the need for complex seal structures, achieving reliability improvement through simplification rather than added complexity.
Solution Approach 2:
The patent substitutes the hydraulic mechanical system with a magnetic field-based detection system. This replacement removes the need for liquid-tight sealing and complex pressure chamber structures, achieving high reliability through a fundamentally different detection approach that is inherently leak-free.
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 magnetic load sensor unit achieves high accuracy in detecting axial loads with reduced temperature influence and enhanced reliability, eliminating the need for complex seal structures and expensive components, thus improving the overall performance and longevity of the electric brake system.
Implementation Method 1
a magnetic sensor configured such that a position of the magnetic sensor relative to the magnetic target changes corresponding to the axial load
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A magnetic load sensor unit (1) is provided which can detect the magnitude of an axial load applied by a linear motion actuator (14) to a friction pad (22). The magnetic load sensor unit (1) includes a magnetic target (4) which generates a magnetic field, and a magnetic sensor (5) designed to move relative to the magnetic target (4) corresponding to the axial load.