Compact Torque Sensor for Electric Bicycles Using Flexible Arm
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Solution Overview
Problem
Conventional devices for monitoring torque in electric bicycles are often too large, exposed to the elements, and capture torque values too slowly to effectively complement the rider's driving force.
Innovation Solution
An electric bicycle system featuring a compact torque sensor with a flexible arm and sensing member that engages the drive chain between the electric motor's output shaft and the pedal crank, allowing for real-time torque measurement and adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional torque monitoring devices are used, then torque measurement is achieved, but the device size becomes too large for compact electric motors
Solution Approach 1:
The torque sensor is segmented into distinct functional components: a flexible arm that engages the drive chain, a sensing member at the extremity, and a base mounted to the frame or motor. This segmentation allows each component to be optimized independently, resulting in a compact overall size suitable for integration with electric motors while maintaining torque measurement capability.
Solution Approach 2:
The torque sensor utilizes the spatial dimension by positioning the sensing member to engage the drive chain laterally rather than requiring axial space. The flexible arm extends perpendicular to the motor axis, allowing torque measurement in a direction that does not interfere with the compact motor housing, effectively using unused spatial dimensions for sensor placement.
2Measurement precision
If conventional torque monitoring devices are used, then torque measurement is achieved, but the device becomes exposed to the elements and susceptible to damage
Solution Approach 1:
The flexible arm acts as an intermediary between the drive chain and the sensing mechanism. It transmits torque information from the chain to the sensing member while remaining protected within the motor housing or frame mounting, shielding the sensitive measurement components from direct exposure to environmental elements such as moisture, dust, and temperature extremes.
Solution Approach 2:
The torque sensor components are nested within the existing motor housing structure. The base is mounted to either the frame or the motor housing, with the flexible arm and sensing member contained within this protective enclosure. This nesting approach allows the torque sensor to operate within the protected internal volume of the motor, eliminating direct exposure to external elements.
3Measurement precision
If conventional torque monitoring devices are used, then torque measurement is achieved, but the torque values are captured too slowly to be effective
Solution Approach 1:
The torque sensor replaces complex mechanical torque measurement mechanisms with a simplified flexible arm and sensing member system. This substitution reduces mechanical friction and inertia, allowing for faster response times. The direct engagement of the sensing member with the drive chain via the flexible arm enables real-time torque capture without the lag associated with conventional mechanical sensors.
Solution Approach 2:
The flexible arm is designed with specific material properties and geometric parameters that optimize its response characteristics. By changing parameters such as arm thickness, length, and material stiffness, the sensor achieves optimal balance between flexibility for accurate measurement and rigidity for fast response. This parameter optimization enables the sensor to capture torque values at high speeds while maintaining measurement accuracy.
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
Enables quick and accurate torque readings, allowing the electric motor to provide timely assistance to the rider, improving the overall performance and efficiency of the bicycle.
Implementation Method 1
the torque sensor having a flexible arm extending from the base and a sensing member mounted to an extremity of the flexible arm, the extremity being displaceable relative to the base, the sensing member engaging the drive chain
Data Source
AI summary
An electric bicycle having an electric motor mounted to a frame of the bicycle and which includes a motor output shaft defining an output end engaging a drive chain of the bicycles drive train to transmit the drive of the electric motor thereto. A torque sensor includes a base mounted in fixed relation to the frame and/or the electric motor. The torque sensor has a flexible arm extending from the base and a sensing member mounted to an extremity of the flexible arm that is displaceable relative to the base. The sensing member engages the drive chain along a segment thereof and is displaceable thereby. The segment of the drive chain extends from the output end of the motor output shaft to the pedal crank of the drive train.