Power-Split E-Bike Driveline With One-Way Clutches for Motor Decoupling
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Solution Overview
Problem
Existing power-split hybrid drivelines for electric bicycles face inefficiencies due to the torque from pedals always reacting with the ratio controlling motor at low speeds, leading to motor inefficiency and heat loss, and at high speeds, the ratio controlling motor turns quickly, delivering mechanical power and requiring the traction motor to generate electrical energy, potentially causing damage.
Innovation Solution
An electric auxiliary drive system with an epicyclic gearing mechanism, including first and second one-way clutches, to control the transmission ratio and disconnect the assist motor when not needed, using a control motor to maintain pedaling speed and a traction motor to assist in forward motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ratio controlling motor reacts against pedal torque at low speeds, then the transmission ratio can be controlled, but the motor becomes inefficient and generates excessive heat
Solution Approach 1:
The patent extracts the ratio control function from the continuous operation of the ratio controlling motor by introducing a one-way clutch. The clutch allows the motor to disengage when not needed, taking out the unnecessary motor operation that causes energy loss while maintaining the ability to control transmission ratio when required.
Solution Approach 2:
The system dynamically engages and disengages the ratio controlling motor based on operating conditions through the one-way clutch mechanism. The clutch allows the motor shaft to rotate freely in the forward direction (disengaging the motor) while preventing reverse rotation (maintaining engagement), creating a dynamic connection state that adapts to operational needs.
2Reliability
If the ratio controlling motor operates at high speeds to maintain pedal speed, then transmission ratio control is maintained, but the traction motor generates electrical energy that may damage electronic systems
Solution Approach 1:
The patent extracts the traction motor from the power transmission path when it is not needed for assistance, using the second one-way clutch. This prevents the traction motor from generating harmful electrical energy during regenerative braking or coasting conditions while maintaining its assistance function when power is needed.
Solution Approach 2:
The one-way clutches act as intermediary devices between the motors and the epicyclic gearing mechanism. They mediate the connection, allowing power transmission when needed and disconnection when not needed, thereby preventing harmful effects while maintaining beneficial functions.
3Power
If the assist motor is continuously connected to the output shaft, then power assistance can be provided, but the system cannot prevent the motor from generating electrical energy during reverse rotation
Solution Approach 1:
The second one-way clutch extracts the assist motor from the output shaft connection when the motor is not providing assistance or when reverse rotation occurs. This allows the motor to be disconnected while the output shaft continues to rotate, preventing harmful electrical energy generation while maintaining power assistance capability when needed.
Data Source
AI summary
An electric auxiliary drive system for a bicycle having a pedal crankshaft, an epicyclic gearing mechanism, an assist motor for driving an output shaft, and a control motor for controlling, through the epicyclic gearing mechanism, a transmission ratio between the pedal crankshaft and the output shaft is provided. A first one-way clutch operatively connected to the control motor is configured for blocking a rotation of a rotatable member of the epicyclic gearing mechanism in a forward direction of rotation while allowing the rotation of the rotatable member of the epicyclic gearing mechanism in a reverse direction of rotation. A second one-way clutch is configured for drivingly connecting the assist motor to the output shaft when the assist motor is switched on, and for disengaging the assist motor from the output shaft when the assist motor is switched off but the output shaft continues rotation in the forward direction.