Coactive Bicycle Transmission Shifting for Synchronized Gear Changes
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Solution Overview
Problem
Bicycle transmission systems experience noticeable time delays between gear shift initiation and completion, leading to asynchronous shifts that can feel out of sync, especially in synchronous shift mechanisms, causing rider discomfort.
Innovation Solution
A method for upshifting and downshifting a bicycle transmission system involving a coactive shift sequence where a first transmission is downshifted before upshifted, or vice versa, to account for time delays and ensure predictable gear changes, using an actuation unit to coordinate clutch actuators in a series-connected transmission system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If synchronous shift mechanism is used to shift multiple transmissions simultaneously, then gear shifting efficiency is improved, but time delay between shift initiation and completion causes asynchronous shifts that feel out of sync to the rider
Solution Approach 1:
The control unit initiates shift commands for multiple transmissions simultaneously, but accounts for known time delays by sequencing the actual execution. The system performs preliminary timing calculations to ensure that despite different completion times, the shifts are coordinated to provide a synchronized rider experience.
Solution Approach 2:
The system uses feedback from sensors monitoring transmission state and shift progression to dynamically adjust shift timing. The control unit receives real-time data on clutch engagement, gear position, and rotational speed to optimize the sequencing of shift operations across multiple transmissions.
2Reliability
If time delay between clutch actuator activation and gear shift is accounted for by sequencing shifts, then shift predictability is improved, but rider experiences temporary disconnection during the sequencing process
Solution Approach 1:
The system employs periodic clutch engagement and disengagement cycles that are timed to create smooth, rhythmic power delivery. By using multiple clutches that engage and disengage in a periodic sequence rather than all at once, the system maintains continuous power transmission while achieving the desired gear ratio change, reducing rider-perceived discontinuities.
3Speed
If multiple transmissions are shifted simultaneously in synchronous shift step, then overall transmission ratio change is achieved faster, but noticeable time delay causes shifts to feel out of sync
Solution Approach 1:
The control system segments the simultaneous shift operation into sequential phases, controlling each transmission's shift independently but in coordination. By dividing the multi-transmission shift into manageable segments with carefully timed execution, the system achieves both speed and synchronization, as each segment completes its shift without interfering with others while maintaining overall coherence.
Data Source
AI summary
A method for upshifting a bicycle transmission system including a first transmission and a second transmission each having at least two different transmission ratios, and an actuation unit configured for, upon receiving an upshift input, upshifting the bicycle transmission according to an upshift sequence, wherein the upshift sequence comprises one or more coactive shifts of upshifting the bicycle transmission by coactively downshifting a first one of the first transmission and the second transmission and upshifting a second one of the first transmission and the second transmission. The method comprises, for one or more of the one or more coactive shifts of the upshift sequence, downshifting the first one of the first transmission and the second transmission and subsequently upshifting the second one of the first transmission and the second transmission.