Central Shaft Torque Sensing for E-Bike Center Motor
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Solution Overview
Problem
Current central shaft torque sensing systems for electric bicycles with center-mounted motors fail to provide proportional assistance to riders as they do not accurately reflect the actual pedal situation, leading to unbalanced foot detection and potential motor actuation errors.
Innovation Solution
A central shaft torque sensing system comprising a strain sleeve connected to a sprocket bracket and a central shaft, with a torque sensor transmitting signals to a controller to adjust motor output based on pedal force, incorporating a dual-ratchet clutch and planetary reduction mechanism for precise torque measurement and transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a constant power motor driving system is used, then the motor can provide stable power output, but it cannot provide corresponding assistance based on the specific requirements of a rider
Solution Approach 1:
The patent installs a torque sensor on the strain sleeve before the system operates, which preliminarily detects the pedal torque and transmits the signal to the controller. This preliminary detection enables the controller to adjust motor assistance according to actual riding conditions, resolving the contradiction between constant power output and adaptive assistance requirements.
2Measurement precision
If the torque sensor is mounted on the strain sleeve connected to the central shaft, then the actual pedal situation is accurately reflected, but the system complexity increases
Solution Approach 1:
The strain sleeve serves multiple functions: it transmits torque from the central shaft, provides a mounting surface for the torque sensor, and enables accurate pedal situation detection. By making the strain sleeve multi-functional, the patent reduces overall system complexity while maintaining high measurement precision.
3Reliability
If the strain sleeve is fixedly connected to the central shaft with inner surface fitting, then torque transmission is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise dimensional parameters for the strain sleeve and central shaft fitting, including the inner surface of the strain sleeve fitting with the outer surface of the central shaft. By carefully controlling these geometric parameters within specified tolerances, the system achieves reliable torque transmission while maintaining feasible manufacturing precision requirements.
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 system provides aligned assistance to riders by accurately measuring pedaling force, preventing unbalanced foot detection and ensuring smooth riding, while minimizing motor actuation errors during abnormal pedal situations.
Implementation Method 1
a signal is produced by a torque sensor which is on the surface of the strain sleeve
Implementation Method 2
a magnetic steel part is inserted into the rotor
Data Source
AI summary
A central shaft torque sensing system for an electric bicycle having a center-mounted motor. The system comprises a central shaft, a center-mounted motor and a controller, and also comprises a torque sensor and a strain sleeve. The controller is respectively connected to the torque sensor and the center-mounted motor, and the motor comprises a main housing, a coil stator, a rotor, a motor output gear shaft, a planetary reduction mechanism and a dual-ratchet clutch, one end of the strain sleeve being connected to the dual-ratchet clutch, the other end being sleeved on the central shaft and fixedly connected thereto, the torque sensor being mounted on the sleeve. The motor output gear shaft is sleeved on the central shaft and forms an integrated structure with the rotor of the motor, the coil stator is fixed on the main housing, the rotor is wrapped on the outside of the coil stator and fixedly connected to the motor output gear shaft, the planetary reduction mechanism is arranged within the main housing, and the gear shaft engages with the planetary reduction mechanism via a gear. The present motor driving system provides corresponding assistance according to the specific requirements of a rider.