Bicycle Hub Torque Sensor Using Inductive Position Detection
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Solution Overview
Problem
Existing bicycle wheel hub power meters using torque tubes and diagonal strain gauges add weight and rotational inertia, and face calibration challenges due to the need to measure small strains accurately.
Innovation Solution
A bicycle wheel hub design featuring a torque element with a radial distance difference between input and output portions, utilizing inductive sensors and a wireless data transmission system, along with an automatic zeroing mechanism for torque sensor calibration during exercise, to measure torque without the need for manual calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque tube is used in the rear hub to measure torque, then power measurement capability is achieved, but weight and rotational inertia of the rear wheel increase
Solution Approach 1:
The patent removes the torque tube from the hub assembly and replaces it with a torque sensor that measures torque directly at the interface between the cog and hub flange. This extraction of the torque measurement function from the wheel structure eliminates the need for a heavy torque tube while maintaining power measurement capability.
Solution Approach 2:
The patent replaces the mechanical torque tube measurement system with an electronic torque sensor that uses strain gauges or similar transducers to measure torque directly. This substitution allows for accurate torque measurement without the structural modifications and added weight of a torque tube.
2Measurement precision
If a diagonal strain gage is positioned on a torque tube to measure torque, then power measurement is enabled, but calibration difficulty increases due to the need to measure extremely small strains
Solution Approach 1:
The patent extracts the torque measurement function from the torque tube structure and places it directly at the torque input interface. By measuring torque where it is applied rather than through a torque tube, the system avoids the need to measure extremely small strains and simplifies calibration significantly.
Solution Approach 2:
The patent introduces a dedicated torque sensor as an intermediary device between the cog and hub flange. This sensor directly measures torque at the point of application using strain gauges or other transducers, eliminating the need to measure small strains in a torque tube and greatly simplifying the measurement and calibration process.
3Measurement precision
If manual calibration of torque sensors is required, then measurement accuracy can be maintained, but ease of operation decreases due to the need for user intervention
Solution Approach 1:
The patent implements an automatic calibration system that uses the bicycle's own operation to calibrate the torque sensor. By detecting when the cyclist is coasting (no torque applied) and automatically zeroing the sensor at that moment, the system maintains measurement accuracy without requiring manual user intervention or specialized calibration procedures.
Solution Approach 2:
The patent performs calibration automatically during normal cycling operation by detecting coasting conditions. This preliminary automatic calibration ensures the sensor is ready for accurate measurement without requiring separate manual calibration steps, improving ease of operation while maintaining precision.
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 design reduces weight and rotational inertia while improving calibration accuracy and convenience by enabling on-the-fly torque sensor recalibration during cycling, providing precise power measurement without user intervention.
Implementation Method 1
the displacement sensor comprises an inductive sensor
Data Source
AI summary
A bicycle having a rear wheel including an axle, a hub shell, a torque element including a torque output portion and a torque input portion, and a rear cog coupled to the torque input portion. The torque output portion is a first radial distance from the torque input portion. The position sensor measures a rotational position of the torque input portion relative to the torque output portion. In one embodiment, the position sensor includes a displacement indicator (e.g., a radial tab mounted to the torque output portion) and a displacement sensor (e.g., an inductive sensor mounted to the torque input portion). The inductive sensor preferably has two sensing coils positioned on each side of the displacement indicator. The hub assembly can further comprise a wireless transmitter adapted to transmit data from the position sensor. The hub shell preferably includes a window that facilitates data transmission from the wireless transmitter.