Crank Variable-Speed Gear Device for Bicycle Power Transmission
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Solution Overview
Problem
Existing bicycle power transmission devices are complex, suffer from friction-related efficiency losses, and complicate gear ratio changes, making them difficult to achieve desired performance and compactness.
Innovation Solution
A crank variable-speed gear device featuring a gear assembly with a sun gear, planetary gears, and a latch assembly that allows for gear ratio adjustment from 1.6:1 to 1.8:1 and 1:1, utilizing a housing with a chain ring mounting part, splines, and anti-rotation units for efficient power transmission and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate rotating drum and multiple planetary gears are provided to change gear ratio, then gear ratio change capability is improved, but device complexity increases and power transmission efficiency deteriorates due to friction
Solution Approach 1:
The patent combines the drum structure and planetary gears into an integrated unit where the drum serves as both a structural component and a gear carrier. The planetary gears are directly mounted on the drum without requiring separate installation plates, merging multiple functions into a single compact assembly that reduces part count and structural complexity.
Solution Approach 2:
The drum structure performs multiple functions simultaneously: it serves as a mounting support for the planetary gears, acts as a structural framework for the power transmission device, and provides a platform for chain ring installation. This multi-functionality eliminates the need for separate rotating drums and installation plates, simplifying the overall structure.
2Adaptability or versatility
If multiple planetary gears and separate installation plates are used, then gear ratio adjustment range is improved, but manufacturing complexity and assembly difficulty increase
Solution Approach 1:
The patent divides the power transmission device into modular components: the drum assembly with integrated planetary gears, the chain ring assembly, and the housing. Each module can be manufactured and assembled independently, then combined to form the complete device. This segmentation simplifies manufacturing processes and assembly operations while maintaining gear ratio adjustment capability.
Solution Approach 2:
The planetary gears are designed with movable mounting positions on the drum, allowing their radial positions to be adjusted dynamically. This enables gear ratio changes without requiring complete disassembly of the system, facilitating easier manufacturing and assembly while maintaining a wide adjustment range.
3Adaptability or versatility
If a complex power transmission structure with multiple components is used, then gear ratio change capability is improved, but transmission efficiency deteriorates due to friction between components
Solution Approach 1:
By merging the drum and planetary gear mounting functions into a single integrated structure, the patent reduces the number of interfaces and contact points between components. This minimizes friction losses at interfaces while maintaining the capability for gear ratio adjustment through positional changes of the planetary gears on the drum.
4Adaptability or versatility
If separate rotating drum and multiple planetary gears are provided, then gear ratio increase effect is improved, but device weight and size increase
Solution Approach 1:
The drum structure serves multiple purposes: structural support, gear mounting platform, and space-efficient component arrangement. By making the drum multi-functional, the patent achieves gear ratio increase effects without adding separate weight-bearing structures, thereby reducing overall device weight while maintaining the desired gear ratio adjustment range.
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 device achieves excellent transmission efficiency, simplifies gear manipulation, and provides a compact and lightweight bicycle by optimizing gear ratio adjustment and reducing friction through its innovative design.
Implementation Method 1
planetary gears disposed so as to revolve about the sun gear while being engaged with the sun gear through one side of a radial outer surface of each thereof
Implementation Method 2
a ring gear disposed outside the planetary gears so as to be engaged with a remaining side of the radial outer surface of each of the planetary gears
Data Source
AI summary
Disclosed is a crank variable-speed gear device (100) wherein the gear ratio can be increased to 1.6:1 to 1.8:1 through a gear assembly and a latch assembly, and the gear ratio can also be changed to 1:1, if necessary, thereby providing an excellent transmission efficiency, facilitating the manipulation thereof, and making it possible to provide a compact and lightweight bicycle.