Electric Bicycle Propulsion Unit with Selective Chain Engagement
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Solution Overview
Problem
Existing electric bicycles with regenerative braking systems have complex, bulky, and heavy structures due to the use of multiple chains and clutches, leading to unwanted mechanical power recirculation and potential chain breakage.
Innovation Solution
A propulsion unit with a movable member that selectively engages one of two toothed wheels, connected to an electric motor, allowing independent operation of each chain, and an electronic circuit to control energy conversion and member positioning, optimizing mechanical and electrical power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multiple chains and clutches are used to connect the rear wheel to the motor for regenerative braking, then energy recovery is enabled, but the structure becomes complex, bulky, and heavy
Solution Approach 1:
The system segments the power transmission path into two independent chain loops, each with its own toothed wheel (22, 24). The movable member (50) selectively engages one toothed wheel at a time, creating distinct mechanical pathways for propulsion and regenerative braking operations.
Solution Approach 2:
The movable member (50) dynamically shifts between two operating positions to selectively engage either the first toothed wheel (22) for propulsion or the second toothed wheel (24) for regenerative braking. This dynamic reconfiguration allows the system to adapt its mechanical connection based on operational requirements.
2Use of energy by moving object
If multiple chains and clutches are used for regenerative braking, then energy recovery is enabled, but the system becomes bulky and heavy
Solution Approach 1:
The system merges the propulsion and regenerative braking functions into a single integrated mechanism. The electric motor (M) serves dual purposes: providing assistive torque during pedaling and functioning as a dynamo during regenerative braking. The movable member (50) and selective toothed wheel engagement combine multiple functions into one compact arrangement.
Solution Approach 2:
The electric motor (M) is designed with multi-functionality, serving as both a motor for assistive pedaling and a dynamo for energy recovery. The same motor housing, shaft, and control electronics are utilized for both propulsion and regenerative braking operations, eliminating the need for separate dedicated components.
3Reliability
If two chains connect to both toothed wheels simultaneously, then power transmission is redundant, but mechanical power recirculation and chain breakage occur
Solution Approach 1:
The system extracts the harmful recirculation pathway by ensuring that only one toothed wheel is engaged at any given time. The movable member (50) physically disconnects one chain loop while engaging the other, eliminating the possibility of mechanical power recirculation between both chains simultaneously.
Solution Approach 2:
The movable member (50) acts as an intermediary switching mechanism that controls the engagement between the motor shaft and the two toothed wheels. This intermediary component selectively connects or disconnects each chain loop, preventing simultaneous engagement and the resulting harmful recirculation effects.
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 solution provides a compact, efficient, and reliable system that avoids mechanical power recirculation, reduces bulk, and enhances performance by optimizing energy recovery and motor assistance, while allowing energy storage during downhill riding.
Implementation Method 1
an electric motor to assist pedaling
Implementation Method 2
electric energy is regeneratively recovered during braking and the battery is recharged
Data Source
Figure 1~2
Figure 3
AI summary
An electric bicycle is described with a propulsion unit comprising two pedals (12), an electric motor (M) to assist pedaling, a first drive toothed wheel (22) connected via a free wheel to the pedals, and a second drive toothed wheel (24) which is coaxial to the first toothed wheel and connected to the motor to receive drive torque, Two chains transfer drive torque from the first and second wheels to two gears of a bicycle wheel. An electronic circuit controls electrical power generated by the electric motor, and preferably stores it in a battery.