Electric Bicycle Drive Device Torque Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric bicycle drive systems face challenges in accurately measuring rider torque due to error-prone sensors and increased construction and manufacturing costs associated with additional gear stages, as well as potential falsification of measurement results when the electric motor is not a hub motor.
Innovation Solution
The drive device separates torque transmission and force measurement, using three non-coaxial shafts to isolate the bearing force generated by the rider, allowing for precise measurement of pedaling torque without influence from other forces, and employs a bearing sensor to determine the torque applied by the rider, minimizing gear parts and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are provided directly at exposed locations to determine torque applied by the driver, then torque measurement can be performed, but the sensors are error-prone and measurement reliability deteriorates
Solution Approach 1:
The patent introduces an intermediary bearing structure that indirectly measures the torque applied by the driver. Instead of placing sensors directly at exposed locations on the pedal shaft, the bearing sensor measures bearing forces on the output shaft, which are influenced by the driver's torque through the transmission system. This intermediary measurement approach protects the sensor from harsh environments while maintaining measurement capability.
2Measurement precision
If an additional gear stage is introduced to transmit torque to a sensor shaft, then torque measurement becomes possible, but construction and manufacturing costs increase
Solution Approach 1:
The patent merges the torque transmission function and the measurement function into a single bearing structure. The bearing that supports the output shaft simultaneously serves to transmit torque from the pedal shaft through the drive shaft and to provide a measurement point for the bearing sensor. This eliminates the need for separate sensor shafts and additional gear stages, reducing device complexity while maintaining measurement capability.
3Measurement precision
If change in chain force is measured to determine torque applied by the driver, then torque measurement can be achieved, but measurement results may be falsified when the electric motor is not a hub motor
Solution Approach 1:
The patent extracts the measurement point from the chain drive system and relocates it to the bearing structure of the output shaft. By measuring bearing forces directly at the output shaft rather than inferring torque from chain force changes, the system eliminates the reliability issue caused by the electric motor's torque transmission through the chain. The bearing force measurement directly reflects the driver's torque input independent of the motor's operation mode.
4Measurement precision
If bearing forces of the sensor shaft are used to control the drive motor, then torque measurement is achieved, but additional gear parts are required increasing manufacturing costs
Solution Approach 1:
The output shaft bearing structure is designed to serve multiple functions simultaneously: it supports the output shaft, transmits torque from both the pedal shaft and drive shaft, and provides a measurement point for the bearing sensor. This multi-functional design eliminates the need for dedicated sensor shafts and additional gear components, reducing manufacturing complexity and cost while maintaining accurate torque measurement capability.
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
This solution provides a reliable and cost-effective method for determining rider torque, reducing measurement errors and construction costs, while ensuring accurate control of the electric motor, enhancing driving comfort and performance.
Implementation Method 1
the bearing force measured according to the invention is generated practically exclusively by the driver, the electric motor has almost no influence
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The drive device (1) has an output shaft (2) with a bearing (25), where a transmission device transmits a torque on a wheel of an electric bike and acts a bearing force in a direction on the bearing. A drive shaft (3) is provided, on which a torque generated by an electric motor (30) acts, where another transmission device transmits a torque from the drive shaft on the output shaft. A controller (11) is mounted in a housing (10) and is configured to control the electric motor as a function of the signal of a bearing sensor (26). An independent claim is included for a controller with a return force.