Electric Bicycle Torque Sensor Using Hall Effect and Isolation Transformer
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Solution Overview
Problem
Existing electric bike torque sensors suffer from nonlinear and continuous signal output, poor stability, sensitivity issues, complex mechanical structures, and lead wire entanglement problems, leading to decreased performance and accuracy.
Innovation Solution
An electric bike torque sensor design featuring a deformed frame with torque-sensing steel magnets and a linear Hall element, combined with an isolation transformer and speed-sensing components, which includes a stationary and rotating part assembly to prevent lead wire entanglement and enhance signal stability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional torque sensor is used to convert foot pedal force into voltage signal, then the output power of the motor can be controlled, but the signal output is nonlinearly continuous, easy to be off, and hysteretic, resulting in poor work stability and sensitivity
Solution Approach 1:
The patent replaces the traditional mechanical torque sensor with a magnetic field-based detection system. Two torque-sensing steel magnets are fixed on the inner ring, and a linear Hall element is fixed on the outer ring. When torque is applied, the relative position between the magnets and Hall element changes, causing the Hall element to output a voltage signal that is linearly proportional to the torque, thereby eliminating the nonlinear, hysteretic characteristics of mechanical sensors.
Solution Approach 2:
The patent introduces a deformed frame structure including an outer ring and an inner ring connected through radial connecting bars as an intermediary mechanism. The inner ring is secured to the crank and the outer ring to the chain wheel. This deformed frame transmits torque-induced relative displacement to the Hall element-magnet system, enabling accurate torque measurement while improving signal linearity and stability.
2Ease of operation
If the lead wire is connected to the rotating central shaft for signal transmission, then the sensor can function, but the lead wire is easy to be wound to the central shaft of the bike
Solution Approach 1:
The patent converts the stationary signal receiving board into a rotating component that rotates together with the chain wheel and deformed frame. The lead wire is now stationary while the signal board rotates, reversing the dynamic relationship. This dynamic inversion eliminates lead wire winding issues while maintaining signal transmission functionality.
Solution Approach 2:
The patent introduces an isolation transformer with primary and secondary windings as an intermediary for signal transmission. The primary winding is electrically connected with an alternating-current generator on the signal receiving board, and the secondary winding is connected with the signal output board. This transformer intermediary enables wireless-like signal transmission without physical lead wire connection to the rotating shaft.
3Ease of manufacture
If the mechanical structure of the torque sensor is simplified, then the device becomes easier to manufacture, but the sensitivity and measurement accuracy may deteriorate
Solution Approach 1:
The patent replaces complex mechanical torque sensing mechanisms with a magnetic field-based Hall element detection system. The torque-sensing steel magnets and linear Hall element provide direct magnetic coupling for torque measurement, eliminating the need for complex mechanical linkages while enhancing measurement accuracy and sensitivity.
Solution Approach 2:
The deformed frame structure serves multiple functions: it transmits torque from the crank to the chain wheel, provides mounting surfaces for the magnets and Hall element, and enables relative displacement for torque sensing. This multi-functionality simplifies the overall mechanical structure 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 solution provides improved work stability and sensitivity, preventing lead wire entanglement and enhancing measurement accuracy by using a deformed frame with torque-sensing magnets and an isolation transformer, resulting in better torque and speed detection.
Implementation Method 1
a signal output board, on which is installed a linear Hall element, is fixed on the outer ring, the sensing face of the linear Hall element being opposite to the outer surface of the two steel magnets
Implementation Method 2
the rotating part of the present invention is provided with some speed-sensing steel magnets having a circular distribution, and the signal receiving board with a switching Hall element, the switch Hall element having its sensing face opposite to the surface of the speed-sensing steel magnet
Implementation Method 3
the primary and secondary windings together form an isolation transformer, the primary winding being electrically connected with an alternating-current generator arranged on the signal receiving board, the secondary winding being electrically connected with the signal output board
Data Source
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AI summary
The present invention discloses an electric-bike torque sensor, which comprises a central shaft, a chain wheel, and a crank fixed on the central shaft, as well as a deformed frame including an outer ring and an inner ring connected with each other through a number of radial connecting bars, the inner ring being secured to the crank, the outer ring being secured to the chain wheel; two torque-sensing steel magnets, their outer surfaces having the opposite polarity, are fixed on the inner ring, and a signal output board, on which is installed a linear Hall element, is fixed on the outer ring, the sensing face of the linear Hall element being opposite to the outer surface of the two steel magnets; the electric-bike torque sensor further includes a rotating part, on which is fixed a secondary winding, and a stationary part, on which are fixed a primary winding and a signal receiving board, assembled coaxially on the central shaft, the primary and secondary windings together forming an isolation transformer, the primary winding being electrically connected with an alternating-current generator arranged on the signal receiving board provided with a lead wire, the secondary winding being electrically connected with the signal output board. The present invention has good work stability and sensitivity.