Friction Damper for Bicycle Rear Derailleur Chain Tension
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Solution Overview
Problem
Existing bicycle rear derailleurs with roller clutch-based friction damping systems are heavy, complex, and costly, failing to effectively manage chain tension during rough terrain rides, leading to chain slack and slapping against the frame.
Innovation Solution
A friction damper system is introduced, utilizing a torsion spring with a tab positioned within a recess in the movable member, applying a radial spring force to resist chain tensioner rotation in the slackening direction while allowing free rotation in the tensioning direction, eliminating the need for roller clutches and reducing weight and manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If roller clutch-based friction damping systems are used, then chain tensioner rotation is resisted in the slackening direction, but the system becomes heavy and complex
Solution Approach 1:
The invention extracts and eliminates the roller clutch component from the damping system, retaining only the essential friction-based damping function. The friction member directly engages with the chain tensioner body without requiring roller clutches, significantly simplifying the construction while maintaining the ability to resist chain tensioner rotation in the slackening direction
Solution Approach 2:
The invention replaces the complex roller clutch mechanical system with a simpler friction-based damping mechanism. The friction member, biased against the chain tensioner body by a spring, provides damping forces through direct frictional engagement, eliminating the need for roller clutches and their associated complexity
2Reliability
If roller clutch-based friction damping systems are used, then chain tensioner rotation is resisted in the slackening direction, but the weight increases
Solution Approach 1:
The invention removes the roller clutch components from the damping system, eliminating their weight contribution. The simplified friction-based damping mechanism uses only essential components (friction member, spring, biasing mechanism), significantly reducing the overall weight of the rear derailleur while maintaining effective chain tension maintenance
3Reliability
If roller clutch-based friction damping systems are used, then damping function is provided, but manufacturing cost increases
Solution Approach 1:
The invention extracts the roller clutch assembly from the damping system, eliminating multiple parts and numerous manufacturing steps. The simplified design with direct frictional engagement requires fewer components and less complex assembly processes, making the rear derailleur easier and less expensive to manufacture
Solution Approach 2:
The invention merges the damping function directly into the chain tensioner structure through the friction member that engages with the chain tensioner body. This integration eliminates the need for separate roller clutch assemblies and reduces the number of parts, simplifying both manufacturing and assembly
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 friction damper system provides higher damping torque in the slackening direction, limiting chain oscillation and maintaining tension without increasing the size or weight of the rear derailleur, while being easier and less expensive to manufacture and install.
Implementation Method 1
a friction member having at least one friction surface biased against and in frictional engagement with the pivot member
Implementation Method 2
a biasing device configured to bias the chain guide assembly in a first rotational direction relative to the movable member
Data Source
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AI summary
A bicycle rear derailleur (80) includes a movable member (90) and a chain guide assembly (92) rotatably connected to the movable member (90). The bicycle rear derailleur (80) also includes a pivot member (126) non-rotatably coupled to the chain guide assembly (92) and having an outer annular surface (170), a biasing device (142) configured to bias the chain guide assembly (92) in a first rotational direction (T) relative to the movable member (90), and a damper device (120) disposed between the chain guide assembly (92) and the movable member (90). The damper device (120) is operable to apply a damping force to the chain guide assembly (92) when the chain guide assembly (92) rotates in a second rotational direction (D) relative to the movable member (90). The damper device (120) includes a friction device that is radially inner relative to the biasing device (142) and is configured as a spring clutch.