Contactless eBike Torque Sensor Using Inductive Coil Sensing
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Solution Overview
Problem
Existing torque sensors for electric bicycles, such as strain gauges, are expensive, incompatible with concentric motors, and do not allow for contactless sensing, limiting accurate and cost-effective torque measurement for electric pedal assist control and automatic shifting.
Innovation Solution
A torque sensor design featuring a support around the bicycle's device with an excitation coil and sense coil separated by an air gap, utilizing a magnetic circuit with multiple coils and shields to induce voltage related to torque, allowing for accurate and cost-effective torque measurement without physical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used for torque sensing, then torque measurement capability is provided, but cost increases and compatibility with concentric motors is lost
Solution Approach 1:
The patent replaces mechanical strain gauges with an electromagnetic sensing system consisting of excitation coils and sense coils that measure torque through magnetic field interactions with the clutch mechanism, eliminating the need for mechanical contact and strain gauge installation
Solution Approach 2:
The patent introduces magnetic fields as an intermediary between the torque measurement system and the clutch mechanism, allowing torque to be sensed indirectly through the effect of torque on the magnetic circuit rather than through direct mechanical measurement
2Measurement precision
If contact-based sensing is used, then torque measurement is achieved, but the system becomes more complex and less adaptable to concentric motor configurations
Solution Approach 1:
The patent replaces mechanical contact-based sensing with electromagnetic field-based sensing, allowing the sensor to function without physical contact with the rotating components, thereby enabling installation on concentric motor configurations where mechanical sensors cannot be mounted
Solution Approach 2:
The patent transitions from mechanical dimension (physical contact) to electromagnetic dimension (magnetic field interaction), creating a new measurement dimension that is not constrained by mechanical mounting requirements and can adapt to various motor configurations including concentric designs
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 robust, accurate, and cost-effective torque sensing for electric bicycles, enabling proportional control of electric assist and automatic shifting by determining torque through induced voltage differences, improving riding efficiency and control.
Implementation Method 1
The excitation coil is configured to induce a voltage in the sense coil via the device of the bicycle when the support is disposed around the device of the bicycle. The induced voltage is related to a torque in the device.
Data Source
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AI summary
A torque sensor for a bicycle includes a coil. The torque sensor may include a support that is disposable around a device of the bicycle, such that the support and the device of the bicycle are separated by an air gap. The torque sensor may also include an excitation coil supported by the support, and a sense coil supported by the support at a distance away from the excitation coil in an axial direction of the support. The excitation coil is configured to induce a voltage and/or current in the sense coil via the device of the bicycle when the support is disposed around the device of the bicycle. The induced voltage is related to a torque in the device.