E-bike Torque Detection via Differential Gear Ratios
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Solution Overview
Problem
Existing mechanisms for detecting torque in electric bicycles are prone to errors and complexity, particularly in systems where sensors are directly exposed and attached to elements that transmit torque, leading to inaccurate readings and complex data analysis.
Innovation Solution
A transmission system where torque from the pedal crankshaft is transmitted to a sensor axis parallel to the pedal crank axis, using sensor gears with different transmission ratios, resulting in a total force that is directly proportional to the torque, allowing for accurate detection using a force sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are directly attached to torque transmission elements, then torque detection is achieved, but measurement precision deteriorates due to errors from exposed locations and direct torque transmission
Solution Approach 1:
The patent introduces a sensor shaft with sensor gears as an intermediary between the pedal crankshaft and the force sensor. This mediator transmits torque through gear mechanisms rather than direct attachment, isolating the force sensor from direct exposure to high torque forces while maintaining measurement capability through the relationship between gear ratios and applied force.
Solution Approach 2:
The patent replaces direct mechanical attachment of sensors to torque transmission elements with a gear-based mechanical system. The sensor gears with different transmission ratios convert torque into measurable force on the sensor shaft, substituting a complex direct measurement approach with a gear-mediated mechanical transformation that improves reliability.
2Measurement precision
If optical or magnetic sensing is used to detect phase shift, then torque detection is achieved, but device complexity increases due to soft drive mechanisms and complex data analysis
Solution Approach 1:
The patent replaces optical or magnetic sensing systems with a purely mechanical force detection approach. By using sensor gears with different transmission ratios on a sensor shaft, the system converts torque directly into measurable force through mechanical means, eliminating the need for complex optical/magnetic sensors and their associated data analysis systems.
Solution Approach 2:
The patent extracts the sensing function from complex optical or magnetic systems and isolates it to a simple force sensor on the sensor shaft. By separating the torque transmission path (pedal crankshaft through sensor gears) from the measurement point (force sensor), the system achieves torque detection using only simple force measurement without complex auxiliary systems.
3Measurement precision
If sensor gears with different transmission ratios are used, then torque transmission to sensor axis is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses sensor gears with deliberately different transmission ratios as a key parameter change. By selecting specific gear ratios that create a known relationship between input torque and output force on the sensor shaft, the system transforms the manufacturing challenge into a calculable parameter relationship. The force sensor measures the resulting force, which can be mathematically related back to the original torque through the known gear ratio relationship.
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 simple and accurate method for torque detection, reducing errors and complexity by using a force sensor to measure the total force, which is directly related to the gear ratios and torque, enabling easy integration into existing systems without radial misalignment issues.
Implementation Method 1
a force sensor connected to the sensor shaft, which detects a force exerted by the sensor shaft, which corresponds to the torque to be detected
Data Source
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AI summary
The invention relates to a transmission for electrical bicycles for detecting a torque which acts upon a crank axle. The transmission comprises the crank axle on which the torque acts, a hollow shaft configured for connection to an output shaft through which hollow shaft the crank axle coaxially extends, and which is mounted rotatably with respect to the crank axle, a sensor shaft offset parallel to the crank axle and a power sensor connected to the sensor shaft. The transmission further comprises a drive-side sensor transmission and an output-side sensor transmission. The drive-side sensor transmission connects the crank axle to the sensor shaft and the output-side sensor transmission connects the sensor shaft to the hollow shaft. The hollow shaft is configured to be connected to an output shaft and the drive-side sensor transmission has a gear ratio which differs from the gear ratio of the output-side sensor transmission. The invention further relates to a corresponding method.