Magnetic Sensor Load Determination for Rolling Element Bearings
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Solution Overview
Problem
Existing load determining systems for rolling element bearings, such as those used in hub units, face challenges in accurately sensing load variations due to their low sensitivity to distance changes and inability to account for thermal expansions, with non-contact magnetic sensors being insensitive to load changes and strain gauges struggling to provide absolute load measurements.
Innovation Solution
A load determining system with a magnetic sensor and deformation sensor integrated into a rolling element bearing, featuring a target ring with a pitch wavelength of 4 mm or less, and a signal processing unit that combines magnetic and deformation sensor outputs to calculate bearing loads, effectively increasing sensitivity and canceling drift induced by friction heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard target ring with wavelength of 8 mm or more is used for wheel speed detection, then the signal-to-noise ratio is sufficient and pulses are neatly detectable, but the sensitivity to distance changes is too low for accurate load sensing
Solution Approach 1:
The patent changes the wavelength parameter of the target ring from 8 mm or more (standard for wheel speed detection) to 4 mm or less (optimized for load sensing). This parameter change increases the sensitivity of the magnetic sensor to distance changes, enabling accurate load detection while the signal processing unit compensates to maintain sufficient signal-to-noise ratio
2Measurement precision
If strain gauges are attached to measure elastic deformations, then local deformation can be measured, but absolute load values cannot be derived due to temperature and thermal gradient effects
Solution Approach 1:
The patent introduces a magnetic sensor and target ring as an intermediary measurement system. Instead of directly measuring strain with temperature-sensitive gauges, the system measures the magnetic field interaction between the sensor and target ring, which is unaffected by temperature. This intermediary approach allows accurate load measurement without temperature interference
3Adaptability or versatility
If non-contact magnetic sensors are used for wheel speed detection, then the system is simple and reliable, but the sensors are insensitive to load changes
Solution Approach 1:
The patent modifies the target ring wavelength parameter to 4 mm or less, which fundamentally changes the magnetic sensor's response characteristics. This parameter change makes the sensor sensitive to both wheel speed (frequency) and load (amplitude), enabling dual functionality from the same non-contact magnetic sensing system
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 system achieves improved sensitivity for detecting bearing deformations caused by cornering forces, allowing for accurate measurement of load vectors and overcoming the limitations of existing methods by enhancing distance resolution and accounting for thermal effects.
Implementation Method 1
The amplitude of the magnetic field acting between a magnetic sensor and an angle target ring depends on the axial distance between these elements and is used to determine the relative axial position of the rings
Data Source
AI summary
The invention provides a load determining system including a sensorized rolling element bearing in a hub unit for wheels. The bearing includes a first ring and a second ring as an inner ring and an outer ring. Either one of the first and second ring may be the inner ring, the other ring being the outer ring. The system includes at least one magnetic sensor attached to the first ring that interacts with a target wheel attached to the second ring. Further, the system includes a signal processing unit configured to receive the magnetic sensor output of the at least one magnetic sensor. The signal processing unit is configured to determine at least axial forces acting on the bearing based on the amplitude of the magnetic sensor output. It is proposed that a pitch wavelength of the target ring is 4 mm or less.