Cycle Torque Sensor Using Single-Point Magnetic Detection
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Solution Overview
Problem
Existing torque sensors for electric bicycles suffer from bulkiness, high cost, sensitivity to external interference, and mechanical robustness issues due to complex designs requiring electrical contact or large deformations, which are unsuitable for mass production and ergonomic pedaling.
Innovation Solution
A torque sensor system with a bottom bracket axle and chainring connection, utilizing a magnetosensitive probe to measure magnetic field changes via elastically deformable elements and concentric rings with air gaps, providing torque and cadence information without rotating parts, thus reducing size and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic contactless solutions are used for torque measurement, then reliability and lifespan are improved, but device complexity increases due to additional components like coils and signal processing electronics
Solution Approach 1:
The patent extracts and eliminates the complex signal processing electronics and additional transmitting/receiving coils from the system. By using a single permanent magnet and a single magnetosensitive probe, the invention removes the need for electromagnetic induction components and their associated complex electronics, while maintaining contactless measurement and reliability.
Solution Approach 2:
The invention uses a permanent magnet to create a magnetic field pattern that can be detected by the magnetosensitive probe. This magnetic field copying approach replaces complex electromagnetic induction systems, providing a simpler way to transmit rotational position information without physical contact or complex electronics.
2Reliability
If Hall effect sensors with permanent magnets and ferromagnetic markers are used, then contactless measurement is achieved, but measurement precision deteriorates due to small flux change per degree rotation requiring large angular deformation
Solution Approach 1:
The patent applies local quality by concentrating the magnetic field in a specific air gap region between the permanent magnet and the magnetosensitive probe. This localized field concentration ensures that even small angular deformations of the bottom bracket axle produce detectable changes in magnetic flux density at the probe location, improving measurement precision without requiring large angular movements.
Solution Approach 2:
The invention replaces the mechanical contact-based measurement systems with a magnetic field-based detection system. The magnetosensitive probe detects changes in magnetic flux density caused by angular deformation of the bottom bracket axle, substituting mechanical contact with magnetic field sensing to achieve both contactless operation and high precision.
3Measurement precision
If multiple magnets and coaxial coils are added to transmit signals, then measurement capability is improved, but weight and size increase
Solution Approach 1:
The patent extracts and removes the heavy coaxial coils and multiple magnets from the system. By using a single permanent magnet and a single magnetosensitive probe that can detect both magnetic field strength and direction, the invention achieves torque and cadence detection without the weight penalty of multiple electromagnetic components.
Solution Approach 2:
The single magnetosensitive probe in the invention serves multiple functions: it detects the magnetic field to determine rotational position, measures cadence through rotation speed, and enables torque measurement through angular deformation detection. This multi-functionality eliminates the need for separate sensors and coils, reducing overall weight.
4Ease of manufacture
If soft ferromagnetic materials with low remanence are used for shaft magnetization, then ease of manufacture is improved, but measurement precision deteriorates due to very weak magnetic field generation
Solution Approach 1:
Instead of magnetizing the shaft with soft ferromagnetic materials that generate weak fields, the invention inverts the approach by using a permanent magnet that generates a strong, stable magnetic field. This permanent magnet is positioned in the bottom bracket axle to cooperate with the magnetosensitive probe, providing a robust magnetic field that is not susceptible to demagnetization or field weakness issues.
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
The solution offers precise torque measurement with reduced size, weight, and power consumption, enhancing mechanical integration and reliability, suitable for mass production and ergonomic pedaling assistance.
Implementation Method 1
a magnetosensitive probe fixed with respect to the frame and measuring a magnetic field generated by the permanent magnet as a function of the relative angular position of the first and second sections
Implementation Method 2
The Hall effect sensor detects a change in position between the permanent magnet and the marker during a torsion of the shaft
Data Source
Figure 1~2
Figure 3~4
Figure 4~5
AI summary
The invention relates to a cycle driving device having a torque sensor, comprising a crank axle (130) or a hub connected to a plate (250) by a coupling, driving and measuring member, having a first section (100) which rotates as one with the crank axle (130) or hub and a second section (200) connected to the plate (250), a magnetic field source supported by one of the sections (100, 200), the coupling member incorporating a torque detection device. The first and second sections cooperate through an elastically deformable element (400), the torque detection device comprising a fixed magneto-sensitive element (456) which measures a magnetic field according to the relative angular position of the first and second sections and is capable of converting the magnetic field into an electrical signal, the magnetic field measurement being performed at a single axial position in the periphery of the first and second sections independently of the rotation of the crank axle (130) or hub.