Quick-Connect Hub Drive for Retrofit Power-Assist Bicycles
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Solution Overview
Problem
Conventional power-assist systems for vehicles, such as bicycles, face challenges including difficulty in retrofitting, limited gearing and wheel size options, high rotational inertia affecting braking and acceleration, and inefficiency due to frictional losses in friction-drive systems, as well as compatibility issues with certain tire types.
Innovation Solution
A power-assist drive system featuring a drive unit with a quick-connect system, an electric motor, and a drivetrain that can be easily installed or removed, integrated with a driven gear attached to the wheel hub or brake disc, allowing for adjustable power assistance and regeneration, suitable for various vehicle types, including bicycles, scooters, and cars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a mid-drive power-assist system is used, then power is transferred to the crankset to drive the rear wheel through the drivetrain, but the system is difficult to retrofit onto a non-power-assisted bicycle and can render the vehicle inoperable should a failure occur
Solution Approach 1:
The power-assist system is divided into independent modules: a drive unit with motor and drivetrain components that can be separately installed and removed. The drive unit connects to the bicycle's existing drivetrain through standardized interfaces, allowing modular installation without modifying the entire bicycle system.
Solution Approach 2:
The drive unit is designed with universal mounting capabilities that can interface with various bicycle frame types and drivetrain configurations. The system can be installed on different bicycle models and can be easily removed or replaced, providing multi-functionality across different vehicle applications.
2Ease of operation
If a hub-drive power-assist system is used, then power is transferred directly to the hub for direct power delivery, but the system has limited gearing and wheel size options and includes a rotating mass with high rotational inertia that adversely impacts braking, acceleration, and top speed
Solution Approach 1:
The motor and high-inertia rotating components are extracted from the wheel hub and placed in a separate drive unit mounted on the bicycle frame. This removes the heavy rotating mass from the wheel assembly, reducing rotational inertia while maintaining direct power delivery capability through the drivetrain.
Solution Approach 2:
The drivetrain components (chain, sprockets, gears) serve as intermediaries between the motor and the rear wheel. This allows power transfer without requiring the motor to be directly integrated into the hub, enabling use of standard bicycle wheels and drivetrains while maintaining efficient power delivery.
3Ease of manufacture
If a friction-drive power-assist system is used, then power input is provided directly to the tire, but the system is incompatible with heavily treaded tires and is limited in the amount of torque that can be transferred
Solution Approach 1:
The friction-based mechanical contact system is replaced with a positive-drive mechanical system using gears and chains. Instead of relying on friction between a roller and tire surface, the system uses interlocking gear teeth and chain links to transfer power, eliminating dependency on tire tread characteristics and significantly increasing torque capacity.
4Ease of manufacture
If a friction-drive power-assist system is used, then power is transferred through friction between the friction roller and the tire, but the system suffers from frictional losses and inefficiency
Solution Approach 1:
The friction-based power transfer mechanism is replaced with a positive-drive gear and chain system. The interlocking teeth of gears and chain links provide direct mechanical engagement that minimizes energy loss to friction, significantly improving overall system efficiency compared to friction-based roller contact.
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 system provides efficient power assistance, flexibility in installation, and improved usability by reducing rotational inertia and frictional losses, while enabling freewheeling and regeneration features for enhanced performance and battery charging.
Implementation Method 1
a drive unit configured to transmit power to rotate a driven wheel... an electric motor
Implementation Method 2
a drivetrain that can be easily installed or removed, integrated with a driven gear attached to the wheel hub or brake disc
Data Source
AI summary
A power-assist drive system for a vehicle (e.g., a bicycle) is provided. The system includes a drive unit assembly attached to a frame of a vehicle and a motor having an output shaft, and a drive gear rotatably associated with the output shaft. The system further includes a driven unit assembly including a driven gear configured to be attached to a wheel hub of the vehicle, and a brake disc coaxially attached to the driven gear. The drive gear may be configured to operably engage the driven gear to transmit power from the motor to the wheel hub. A brake caliper may be integrated with the drive unit assembly. The system may further include a battery and a speed controller configured to receive an input signal to selectively direct electrical power from the battery to the motor to drive the wheel via the drive gear and the driven gear.