Bicycle CVT With Variable-Radius Coupling for Wide Gear Range
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Solution Overview
Problem
Current bicycle transmission systems, particularly in racing bicycles, rely on derailleurs or gear hubs with limited gear ratios, which can be cumbersome and inefficient for achieving a wide range of transmission ratios.
Innovation Solution
A continuously variable transmission (CVT) unit is designed with first and second drive elements that are rotatable about parallel axes, allowing for torque transfer through movable coupling elements at constant and variable radii, enabling various transmission ratios by adjusting the relative displacement between the axes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional derailleurs or gear hubs with limited gear ratios are used, then the transmission system is simpler in structure, but the range of transmission ratios is limited and the system becomes cumbersome
Solution Approach 1:
The patent employs a continuously variable transmission mechanism where the second drive element can be dynamically positioned at different radial distances from the second axis. This dynamic adjustment allows the transmission ratio to vary continuously rather than being fixed at discrete values, thereby achieving a wide range of transmission ratios without requiring multiple fixed gear sets or complex derailleur mechanisms
Solution Approach 2:
The invention introduces a radial dimension for position adjustment of the second drive element, in addition to the rotational dimension. By allowing the second drive element to move radially inward or outward from the second axis, the system creates a new degree of freedom that enables continuous variation of the effective radius ratio,从而实现连续可变的传动比
2Ease of operation
If multiple gear ratios are achieved through fixed gear wheels and derailleurs, then the transmission ratios are discrete, but the actuation force required for shifting is high and the mechanism is cumbersome
Solution Approach 1:
The patent replaces fixed gear ratios with a dynamic transmission system where the second drive element can be continuously repositioned radially. This dynamic capability allows smooth transition between different effective transmission ratios without requiring high-force derailleur mechanisms to jump between fixed gear positions, significantly reducing the actuation force needed
Solution Approach 2:
The invention changes the transmission ratio by varying the radial position parameter of the second drive element rather than switching between discrete gear wheels. This continuous parameter adjustment enables smooth transmission ratio variation with minimal actuation force, eliminating the need for high-force shifting mechanisms
3Reliability
If conventional transmission systems with multiple components are used, then the gear ratios are fixed, but the system requires extensive lubrication and maintenance
Solution Approach 1:
The patent integrates the functions of multiple separate components (drive elements, coupling elements, position adjustment mechanisms) into a unified continuously variable transmission system. By merging these functions into a single integrated mechanism rather than using separate fixed gear wheels and derailleurs, the system reduces the number of moving parts requiring lubrication and maintenance
Solution Approach 2:
The invention employs self-lubricating materials and surfaces in the coupling elements and drive elements. The coupling elements are designed with self-lubricating properties that reduce friction and wear without requiring external lubrication, thereby improving reliability and reducing maintenance requirements
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 CVT unit provides a compact and efficient means to achieve a wide range of transmission ratios, reducing actuation force and allowing for gearless operation with minimal lubrication, enhancing the performance and efficiency of bicycle transmissions.
Implementation Method 1
The first coupling elements are coupled to the first drive element in a radial direction at the first radius, and movable relative to the first drive element in a first tangential direction... The first coupling elements are provided for transferring torque between the first drive element and the second drive element
Data Source
AI summary
The disclosure relates to a continuously variable transmission (CVT) unit. The CVT unit comprises a first drive element that is rotatable about a first axis and a second drive element that is rotatable about a second axis parallel to the first axis, wherein the first drive element and the second drive element are movable relative to each other in a direction transverse to the first and second axis. The CVT unit further comprises first coupling elements provided at a constant first radius from the first axis and at a variable second radius from the second axis, for transferring torque between the first drive element and the second drive element.