Torque Sensor for Electric Bicycle Drive Device
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Solution Overview
Problem
Existing torque sensors for electric bicycles, particularly pedelecs, face challenges such as complex integration, susceptibility to abrasion and dirt, and high maintenance requirements when attached directly to the pedal crank.
Innovation Solution
A drive device with a sensor system that includes a deflection device with a pivotable arm and an elastic element, supported on a housing, which generates sensor data based on the deflection of a load strand in the power transmission means, allowing for instantaneous torque measurement and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are attached directly to the pedal crank to measure torque, then measurement precision is improved, but device complexity and maintenance requirements increase due to integration complexity and susceptibility to abrasion and dirt
Solution Approach 1:
The sensor is extracted from the pedal crank and relocated to the power transmission means (chain or belt). This separates the measurement function from the complex integration location, allowing the sensor to measure chain/belt deflection which correlates to torque without requiring direct attachment to the crank. The sensor measures the deflection of the power transmission means under load, which provides torque information without the integration complexities of direct crank mounting.
Solution Approach 2:
The power transmission means (chain or belt) serves as an intermediary between the torque source and the sensor. Instead of measuring torque directly at the crank, the sensor measures the deflection of this intermediary element, which transmits the torque information in a form that is easier to measure and less susceptible to contamination.
2Measurement precision
If strain gauges are attached directly to the pedal crank, then torque measurement is achieved, but reliability decreases due to susceptibility to abrasion and dirt requiring frequent maintenance
Solution Approach 1:
The sensor is extracted from the direct torque path at the crank and placed on the power transmission means. This location is more accessible and less exposed to direct contamination from pedaling forces, sweat, and dirt. The chain or belt environment, while still mechanical, provides a measurement point that is easier to protect and maintain.
Solution Approach 2:
Instead of measuring torque directly at its source (crank), the system measures the effect of torque on the power transmission means (deflection of chain/belt). This inverted approach measures the consequence of torque application rather than the torque itself, providing equivalent information with improved reliability.
3Loss of time
If the sensor is located on the load strand of the power transmission means, then response time is improved for torque measurement, but the sensor becomes exposed to harsher conditions
Solution Approach 1:
The power transmission means acts as an intermediary that immediately transmits torque information to the sensor on the load strand. The deflection of the chain or belt under load provides instantaneous torque measurement data. While the load strand does experience higher forces, the measurement is taken on the element itself rather than requiring additional transmission components, reducing overall system delay.
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 accurate, low-delay torque measurement with minimal maintenance requirements, enhancing the performance and reliability of electric bicycle drive systems.
Implementation Method 1
The elastic element has a piezoelectric crystal
Data Source
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AI summary
The invention relates, inter alia, to a drive device (10) for a vehicle (100). The drive device (100) comprises a first drive (1) for providing a first drive force, an electric motor (2) for providing a second drive force, and an output (3). The output (3) is configured to receive the first and/or the second drive force and transmit it to at least one driven wheel (110) of the vehicle (100). Furthermore, the drive device (10) according to the invention comprises a power transmission element (4) arranged between the first drive (1) and the output (3), and a sensor (5) arranged in the load-bearing section (7) of the power transmission element (4), which is configured to generate sensor data as a function of a pivotable deflection (65) of the power transmission element (4).