Power-Assisted Drive Assembly with One-Way Sprag Clutch
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Solution Overview
Problem
Conventional in-wheel or hub motor power-assisted drive units for bicycles suffer from limited torque output, lack of gear shifting capability, and integration of torque sensing, making them unsuitable for varied terrains and requiring complex retrofits, especially when maintenance is needed.
Innovation Solution
A power-assisted drive assembly fitted to a bicycle's bottom bracket shell, featuring a sprocket assembly, drive spindle, motor, gear mechanism with one-way sprag clutches, and torque sensing assembly, allowing for adjustable gearing and freewheeling, enabling enhanced torque output and compatibility with multi-speed bicycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an in-wheel motor is used to simplify the drive unit structure, then manufacturing simplicity is improved, but torque output is limited and gear shifting capability is lost
Solution Approach 1:
The drive system is segmented into separate functional modules: the in-wheel motor handles propulsion, while a separate gear mechanism (derailleur, sprockets, chain) handles shifting. This allows the motor to remain simple while gaining versatility through the independent gear system.
Solution Approach 2:
The patent merges the in-wheel motor with a conventional bicycle gear shifting mechanism into a hybrid system. The motor provides direct propulsion while the gear mechanism provides variable ratio transmission, combining the simplicity of hub motors with the versatility of multi-speed bicycles.
2Device complexity
If an in-wheel motor is used to eliminate gear mechanism, then device complexity is reduced, but torque output is limited for varied terrains
Solution Approach 1:
The system dynamically adjusts the gear ratio through the derailleur mechanism to match terrain conditions. The motor provides base torque while the variable gear ratios amplify torque output for climbing or provide speed for flat terrain, making the system adaptable to varied conditions.
3Adaptability or versatility
If an in-wheel motor is installed on existing bicycles, then retrofitting is enabled, but wheel removal is required which disables the bicycle
Solution Approach 1:
The motor is extracted from the wheel assembly and mounted separately on the bicycle frame. This separates the motor function from the wheel function, allowing the wheel to remain functional for both manual and powered operation while the motor is independently installed and maintained.
4Ease of repair
If an in-wheel motor is used, then wheel replacement is simplified, but the wheel cannot be rotatable for manual pedaling after motor failure
Solution Approach 1:
The drive system is segmented into motor function and wheel function. The motor is a separate replaceable component mounted on the frame, while the wheel remains a separate functional unit. This allows the motor to be replaced without affecting wheel rotatability for manual operation.
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 more versatile and efficient power-assisted drive system with adjustable gearing, improved torque output, and integrated torque sensing, enabling better performance on various terrains and simplifying maintenance and retrofitting processes.
Implementation Method 1
a drive spindle drivably connected to the sprocket assembly through a first one-way sprag clutch
Implementation Method 2
a reduction gear set arranged between the rotor of the motor and the drive gear
Implementation Method 3
a motor mounted on the motor mounting portion and drivably connected to the sprocket assembly
Data Source
AI summary
A power-assisted drive assembly comprising a sprocket assembly, a drive spindle drivably connected to the sprocket assembly through a first one-way sprag clutch, a main housing rotatably supporting the drive spindle and defining a spindle axis, the main housing comprising a spindle supporting portion and a motor mounting portion, a motor mounted on the motor mounting portion and drivably connected to the sprocket assembly, the motor having a drive axis offset to the spindle axis, a gear mechanism drivably connecting the motor and the sprocket assembly. The gear mechanism comprises a second one-way sprag clutch and a drive gear mounted concentrically with the sprocket assembly. The motor comprises a stator surrounded by a rotor, a pinion gear is provided on the rotor drivably connects with the gear mechanism for driving the drive gear and the sprocket assembly, the gear mechanism further includes a reduction gear set arranged between the rotor of the