Electric Bicycle Drive Torque Sensor Segmentation
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Solution Overview
Problem
Existing pedelec drive devices can only determine the magnitude of cyclist torque, not whether the torque is induced by the first or second pedal crank, leading to inaccurate torque measurement and motor control.
Innovation Solution
A drive device for electric bicycles with a sensor assembly comprising a first torque sensor cooperating with the bottom bracket shaft and a second torque sensor cooperating with a summing hollow shaft, allowing for accurate measurement of torque induced by each pedal crank, improving motor control and detecting riding states like out-of-saddle conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single torque sensor cooperates with the bottom bracket shaft to determine cyclist torque, then the device complexity is reduced, but the measurement precision of torque source identification deteriorates
Solution Approach 1:
The patent divides the torque measurement function into two separate sensors: a first torque sensor that measures torque from the first pedal crank and a second torque sensor that measures torque from the second pedal crank. This segmentation allows independent measurement of each crank's contribution, resolving the contradiction by maintaining simple device architecture while achieving precise torque source identification.
2Ease of operation
If torque measurement only determines magnitude without source identification, then the ease of operation is improved, but the reliability of motor control deteriorates
Solution Approach 1:
The patent introduces a control unit as an intermediary that receives torque magnitude data from both sensors and determines the active pedal crank based on the combination of measurements. This intermediary processes the simple magnitude readings into reliable source identification, maintaining operational simplicity while ensuring accurate motor control.
Data Source
AI summary
A drive device for an electric bicycle includes a drive housing rigidly connected to a frame of the electric bicycle and a bottom bracket shaft arranged to rotate in the drive housing. First and second pedal cranks are arranged at respective ends of the bottom bracket shaft. The first and second pedal cranks are arranged to rotate with the bottom bracket shaft. A summing hollow shaft is rotatably supported in the drive housing. The summing hollow shaft is directly connected to the bottom bracket shaft via a cyclist's freewheel and, via a motor freewheel, to a gear driven by an electric motor. The summing hollow shaft is connected to a chain wheel for rotation therewith. A sensor assembly fixedly arranged in the drive housing includes a first torque sensor which cooperates with the bottom bracket shaft, and a second torque sensor which cooperates with the summing hollow shaft.