E-bike Drive Unit Asymmetric Rear Arm and One-Way Clutch
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Solution Overview
Problem
Existing bicycles with integrated electric motors and human power systems face maintenance challenges due to obstructive rear arms that hinder access to the electric motor and rear wheel, complicating maintenance operations.
Innovation Solution
A drive unit design where the rear arm is positioned only on one side of the rear wheel, allowing easy access for maintenance, and incorporates a power transmission mechanism that includes a one-way clutch to prevent power loss when using the electric motor alone, with a supporting shaft structure that simplifies assembly and supports the rear hub.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rear arms are disposed on both sides of the rear wheel to support the wheel axle, then the structural stability and support for the electric motor are improved, but the accessibility for maintenance operation deteriorates
Solution Approach 1:
The patent extracts the power transmission mechanism from the space between the rear arms and relocates it to the right side of the rear wheel. This allows the right rear arm to be positioned away from the electric motor, improving accessibility for maintenance while the left rear arm continues to provide structural support. The transmission mechanism is specifically extracted and placed in a dedicated space on the right side.
Solution Approach 2:
The patent employs asymmetric positioning of the power transmission mechanism and rear arms. The transmission mechanism is disposed only on the right side of the rear wheel, creating an asymmetric layout that allows the right rear arm to be positioned for better accessibility while the left rear arm maintains structural support. This asymmetric arrangement resolves the contradiction between stability and maintenance accessibility.
2Device complexity
If the power transmission mechanism is positioned between the rear arms to support the electric motor, then the compactness and integration are improved, but the accessibility for maintenance operation deteriorates
Solution Approach 1:
The power transmission mechanism is extracted from the space between the rear arms and relocated to the right side of the rear wheel. This extraction allows maintenance personnel to access the electric motor and transmission mechanism easily from the right side, while the left rear arm continues to provide structural support. The mechanism is specifically positioned in the space on the right side of the rear wheel.
3Device complexity
If the crank shaft is coupled to the rear hub directly for simple power transmission, then the device complexity is reduced, but power loss occurs during electric motor only operation
Solution Approach 1:
The patent introduces a one-way clutch mechanism that enables dynamic power transmission. The one-way clutch allows power to be transmitted from the crank shaft to the rear hub when human power is applied, but automatically disengages when the electric motor operates alone. This dynamic mechanism prevents power loss during electric-only operation while maintaining a relatively simple overall structure.
Solution Approach 2:
The one-way clutch acts as an intermediary mechanism between the crank shaft and the rear hub. It mediates the power transmission by allowing it in one direction (crank to hub) while blocking it in the opposite direction, thereby preventing the crank shaft from being driven backward by the electric motor and causing power loss.
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
This design enhances maintenance workability by providing clear access to the electric motor and rear wheel, reduces power loss during electric-only operation, and simplifies the assembly process while maintaining efficient power transmission.
Implementation Method 1
a power transmission mechanism that transmits power from the crank shaft to the rear hub, and comprises a one-way clutch
Data Source
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AI summary
A drive unit 10 includes a first power system having an electric motor 30 and a second power system having a crank shaft 61 to which pedals are attached. The second power system transmits rotation of the crank shaft 61 to a rear hub 41 through a second transmission shaft 27 and a first transmission shaft 21. A rear arm 50 and the second transmission shaft 27 are disposed leftward of a rear wheel 40. The first transmission shaft 21 is disposed inside a stator 31, and coupled to the rear hub 41 on the opposite side to the second transmission shaft 27. This improves workability of maintenance operation of a bicycle.