Bicycle Continuously Variable Transmission Pivot Mechanism
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Solution Overview
Problem
Conventional bicycle transmissions are limited to discrete gear ratios, prone to malfunction, chain slippage, and derailment, especially under full load, and are difficult to operate for stepless shifting.
Innovation Solution
A continuously variable transmission system with a driver assembly pivotable about a first axis and a driven assembly rotatable about a second axis, where the engagement distance between them is infinitely adjustable, allowing for stepless shifting with infinitely selectable gear ratios between high and low gear, using a pivot assembly and roller assembly to maintain relative positioning and adjust gear ratios without lag or chain derailment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional discrete sprockets and chain are used, then the transmission structure is simple, but the gear ratio selection is limited to predetermined discrete values only
Solution Approach 1:
The patent applies the dynamics principle by replacing static discrete sprockets with dynamic friction elements that can continuously adjust their engagement distance. The driver and driven assemblies pivot about fixed axes while maintaining variable engagement distances, enabling continuous gear ratio adjustment rather than discrete steps. This dynamic adjustment mechanism resolves the contradiction by providing infinite gear ratio selectability without requiring complex multi-sprocket systems.
Solution Approach 2:
The patent implements parameter changes by varying the engagement distance between driver and driven assemblies as a continuous parameter. By changing this geometric parameter (engagement distance) rather than discrete sprocket sizes, the system achieves continuous gear ratio variation. The engagement distance can be adjusted smoothly throughout the gear ratio range, transforming the transmission from discrete to continuous parameter control.
2Reliability
If conventional chain and sprocket system is used, then the transmission is compact, but chain slippage and derailment occur under full load
Solution Approach 1:
The patent replaces the chain-sprocket mechanical system with a friction-based contact system. Instead of relying on chain links engaging with sprocket teeth, the system uses friction elements that maintain continuous contact through pivotable assemblies. This substitution eliminates chain slippage and derailment by creating a more reliable friction-based power transmission that maintains stable engagement under full load conditions.
Solution Approach 2:
The dynamic pivotable assemblies allow the transmission to adapt to load variations in real-time. The driver and driven assemblies can pivot to maintain optimal engagement distances, ensuring continuous reliable power transmission even under varying full load conditions. This dynamic adaptation prevents the chain slippage and derailment issues that plague static chain systems under load.
3Ease of operation
If conventional derailleur shifting mechanism is used, then gear ratio changes are possible, but shifting under full load causes damage and torque loss
Solution Approach 1:
The patent replaces the complex derailleur mechanism with a simpler friction-based pivot system. The shifting action is achieved through pivotable driver and driven assemblies that adjust engagement distances, eliminating the need for chain-guiding derailleurs. This substitution allows smooth gear ratio changes without the mechanical stress and torque loss associated with conventional derailleur systems under full load.
Solution Approach 2:
The patent enables continuous gear ratio adjustment without interruption to power transmission. The friction-based pivot system allows smooth transitions between gear ratios while maintaining continuous engagement, eliminating the torque loss and shifting lag inherent in conventional derailleur systems. This continuity of useful action ensures reliable operation during full load shifting conditions.
4Measurement precision
If multiple sprockets are used to achieve better gear ratio control, then incremental control improves, but the transmission becomes more complex and prone to malfunction
Solution Approach 1:
The patent achieves precise gear ratio control by continuously varying a single parameter - the engagement distance between driver and driven assemblies. Instead of using multiple discrete sprockets to achieve precision, the system varies the engagement distance as a continuous parameter, providing infinite gear ratio selectability with a simpler single-pair assembly structure.
Solution Approach 2:
The dynamic pivotable assemblies provide precise gear ratio control through continuous adjustment of engagement distances. The pivot mechanism allows smooth, precise variation of the gear ratio without requiring multiple discrete components. This dynamic adjustment provides better incremental control than conventional multi-sprocket systems while reducing overall transmission complexity.
Data Source
AI summary
A transmission for a bicycle having a driver assembly with a torque band, the driver assembly being pivotable about a first axis. A driven assembly rotatable about a second axis, the second axis spaced a distance from the first axis. The torque band is rotatable about the second axis. An input source engaged with the driver assembly such that the input source causes the torque band to rotate about the second axis. The driver assembly principally engages said driven assembly along an engagement path at a first distance from the first axis and at a second distance from the second axis whereby the driven assembly is caused to rotate about the second axis, the second distance being infinitely adjustable throughout a gear ratio range. A rotatable output member is engaged with the driven member wherein rotation of the driven member causes the output member to rotate.