Rear Wheel Sprocket Assembly for Wide Gear Range in Tight Hub Space
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Solution Overview
Problem
Modern bicycle rear wheel sprocket arrangements face challenges in providing a wide range of transmission ratios that are finely graduated while efficiently utilizing the limited space on the rear wheel hub, particularly in 1-speed derailleur systems, where existing solutions either offer rough gradation over large space or fine gradation in less space, failing to meet the demand for both high gear range and packing density.
Innovation Solution
A bicycle rear wheel sprocket arrangement with a gear range packing coefficient greater than 1.25, achieved by using sprockets with high numbers of teeth and optimized axial spacing, allowing for a large range of transmission ratios with fine gradation in a compact space, reducing chain loads and improving ride comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of sprockets in the rear wheel sprocket arrangement is increased to achieve finer gradation of transmission ratios, then the gear range quotient improves, but the axial installation space required increases
Solution Approach 1:
The patent transitions from traditional lateral arrangement of sprockets to an axial stacking arrangement, utilizing the axial dimension more effectively. By stacking sprockets along the axial direction with optimized spacing, the design achieves higher gear range quotient (≥1.25) while controlling the axial installation space through precise spacing optimization.
Solution Approach 2:
The patent optimizes the axial spacing parameter between sprockets to achieve the desired gear range quotient while minimizing axial installation space. By carefully selecting and adjusting the axial distance parameter, the design resolves the contradiction between achieving fine gradation (higher gear range) and space efficiency.
2Adaptability or versatility
If the number of sprockets is increased to achieve finer gradation of transmission ratios, then the packing density quotient improves, but the device complexity increases
Solution Approach 1:
The patent divides the sprocket arrangement into axially stacked segments, where each sprocket is independently positioned at optimized axial intervals. This segmentation allows for fine gradation of transmission ratios (high packing density quotient) while managing complexity through modular, standardized sprocket designs and systematic axial spacing.
Solution Approach 2:
The patent employs parameter optimization of axial spacing to achieve high packing density quotient. By systematically adjusting the axial distance parameter between sprockets, the design achieves fine transmission ratio gradation while controlling overall complexity through standardized spacing intervals and modular sprocket configurations.
3Adaptability or versatility
If sprockets with high numbers of teeth are used to increase gear range quotient, then the transmission ratio range improves, but the chain loads increase
Solution Approach 1:
The patent optimizes the tooth count parameter of sprockets to achieve the required gear range quotient (≥1.25) while controlling chain loads. By carefully selecting tooth numbers and their distribution across the axial stack, the design balances the need for wide transmission ratio range with the constraint of acceptable chain loading forces.
Data Source
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AI summary
A bicycle rear wheel sprocket assembly (10) rotatable about a sprocket rotation axis (R) comprises a plurality of sprockets (12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34) of different numbers of teeth arranged coaxially with respect to the sprocket rotation axis (R) and at axial distances from one another, which are designed for positive engagement with a bicycle chain (76). The pinion arrangement (10) has a pitch range quotient, which is formed by dividing the number of teeth of the largest diameter pinion (12) by the number of teeth of the smallest diameter pinion (34), and has a packing density quotient, formed by dividing the number of pinions (12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34) in the pinion arrangement (10) by the axial distance (A), measured in millimeters, of the axially outermost pinions from each other.According to the invention, the pinion arrangement (10) has a pitch range packing coefficient formed from the product of the pitch range quotient and the packing density quotient, which is greater than 1.25, preferably greater than 1.3, particularly preferably greater than 1.35, most preferably greater than 1.4.