Mid-Mounted Motor Speed Control for E-Bike Gear Shifting
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Solution Overview
Problem
Traditional pedal-assisted bicycles experience issues with unmatched teeth, chain breakage, and derailleur damage during gear shifting due to high assisting forces, and the motor's shutdown and restart process is too lengthy, causing delays in the return of assisting force.
Innovation Solution
A gear shifting system that lowers the motor rotational speed during gear shifting by using a micro-computer to control the mid-mounted motor's speed, maintaining a lower rotational speed similar to idle rotation, and quickly returning to the original speed after shifting, thereby preventing damage and reducing delay in assisting force return.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the motor provides enough assisting force during gear shifting, then the rider experiences easier pedaling, but it causes unmatched teeth without smooth engagement, chain breakage, or derailleur damage
Solution Approach 1:
The micro-computer temporarily shuts down the motor before gear shifting occurs, preventing the motor from providing assisting force during the critical gear transition period. This preliminary action eliminates the risk of chain breakage and derailleur damage while maintaining ease of pedaling during normal operation
2Reliability
If the motor is shut down during gear shifting, then chain breakage and derailleur damage are prevented, but the time required for the motor to stop and restart causes delays in returning assisting force
Solution Approach 1:
The motor is shut down in advance before gear shifting begins, and the micro-computer immediately restarts it after shifting completes. This timing strategy minimizes the motor's non-operational period while ensuring safe gear transition, thereby reducing time delay in assisting force return
3Reliability
If the motor rotational speed is reduced during gear shifting, then smooth engagement and prevention of damage are achieved, but the assisting force is temporarily reduced
Solution Approach 1:
The motor rotational speed is temporarily reduced immediately before gear shifting occurs, ensuring smooth engagement and prevention of damage. The micro-computer quickly restores full rotational speed after shifting completes, minimizing the duration of reduced assisting force
Data Source
AI summary
A gear shifting system (10)(10')(50) for lowering a motor rotational speed during gear shifting of a pedal-assisted bicycle, comprising: a power module (11); a micro-computer (21)(21')(61); a gear shift driver (31) and a vehicle speed sensor module (41); the micro-computer (21)(21')(61) having a motor rotational speed control logic (22)(22')(62)(62') and a vehicle speed/motor rotational speed correspondence table (24); during gear shifting, the micro-computer (21)(21')(61) executing the motor rotational speed control logic (22); a process of the micro-computer (21)(21')(61) executing the motor rotational speed control logic (22) including: finding a motor driven rotational speed corresponding to a current vehicle speed based on the vehicle speed/motor rotational speed correspondence table (24); controlling the mid-mounted motor (91) to be of a rotational speed lower than the motor driven rotational speed corresponding to the current vehicle speed but still maintaining a rotation of the mid-mounted motor (91); after gear shifting completed, controlling the mid-mounted motor (91) to return back to a motor driven rotational speed prior to gear shifting.