Electric Bicycle Drive Assembly Using Controlled Speed for Low-Wear Shifting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric bicycles with drive assemblies face challenges in performing automatic shift operations efficiently and with low wear, particularly when the bicycle is stationary or not being pedaled.
Innovation Solution
A method for operating a drive assembly that involves determining the current drive load, incrementally increasing motor speed to an engagement speed, and shifting at a controlled speed just below engagement to minimize wear and ensure smooth gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If automatic shift operations are performed when the bicycle is stationary or not being pedaled, then shifting capability is improved, but wear on the drive train increases
Solution Approach 1:
The control unit initiates drive unit rotation before the shift operation is actually needed. By rotating the drive unit in advance (without torque transmission to the drive train), the system prepares the drivetrain for upcoming shifts, ensuring smooth transitions while minimizing wear during the actual shifting moment.
Solution Approach 2:
The system dynamically adjusts the operating state of the drive unit by switching between rotation modes (with and without torque transmission). The control unit manages the transition between these dynamic states, allowing the drive unit to rotate freely for shift preparation and then engage for power transmission, thereby reducing wear during shift operations.
2Speed
If the drive unit is rotated quickly to engage the drive train, then response time is improved, but wear during engagement increases
Solution Approach 1:
The drive unit is rotated in advance at controlled speeds below engagement threshold to prepare for upcoming shifts. This preliminary rotation occurs without engaging the drive train, allowing the system to respond quickly to shift commands while avoiding wear-associated high-speed engagement.
Solution Approach 2:
The control unit modifies the rotational speed parameter of the drive unit, maintaining it below the engagement speed threshold during preparatory phases. By controlling the speed parameter to stay below the threshold that would cause drive train engagement, the system achieves fast response without the wear consequences of high-speed engagement.
3Productivity
If the drive unit operates at high speed for quick shifting, then shifting speed is improved, but wear on transmission elements increases
Solution Approach 1:
Shift preparation operations are performed in advance at controlled lower speeds. The control unit rotates the drive unit and positions transmission elements before the actual shift is needed, allowing the main shift operation to execute quickly while minimizing wear through reduced-speed preparatory movements.
Solution Approach 2:
The drive unit alternates between rotation phases (with and without torque transmission) in periodic cycles. During non-torque transmission phases, the drive unit rotates to prepare for shifts at controlled speeds, then engages for power delivery, creating a periodic pattern that enables fast shifting while reducing cumulative wear on transmission elements.
Data Source
AI summary
A method of operating a drive assembly of an electric bicycle is disclosed, wherein the drive assembly has a drive unit and a shift control which can be actuated in a controlled manner. The method includes (i) determining a current drive load of the drive unit, (ii) increasing a motor speed of the drive unit in a controlled manner to an engagement speed at which the drive load reaches a predetermined engagement load, and (iii) performing controlled shifting via the shift control while operating the drive unit at a maximum of the engagement speed.