Rear Derailleur Friction Damper Without Roller Clutches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bicycle rear derailleurs with roller clutch based friction damping systems are heavy, complex, and expensive, leading to increased weight and cost, while failing to effectively manage chain slackening during rough terrain.
Innovation Solution
A friction damper system for bicycle rear derailleurs that uses a torsion spring with a friction member to apply higher damping forces in the chain slackening direction and lower forces in the tensioning direction, eliminating the need for roller clutches and reducing weight and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If roller clutch based friction damping systems are used, then chain slackening is controlled, but weight increases
Solution Approach 1:
The patent removes the roller clutch mechanism from the damping system, extracting only the essential friction-based damping function. This eliminates the complex roller clutch components while retaining the core capability to control chain slackening through friction between the friction member and pivot member.
Solution Approach 2:
The patent changes the damping mechanism from a mechanical roller clutch system to a friction-based system using a friction member with adjustable friction characteristics. By modifying the friction coefficient and contact pressure parameters, the system achieves effective chain slack control without the weight penalty of roller clutches.
2Reliability
If roller clutch based friction damping systems are used, then chain slackening is controlled, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the roller clutch mechanism, retaining only the essential friction-based damping function. This simplifies the overall device structure by removing complex mechanical components while preserving the core chain slack control capability.
Solution Approach 2:
The friction member is integrated directly into the existing derailleur structure, merging the damping function with the chain tensioner assembly. This consolidation eliminates the need for separate roller clutch mechanisms and reduces the overall number of components.
3Reliability
If roller clutch based friction damping systems are used, then chain slackening is controlled, but manufacturing cost increases
Solution Approach 1:
The patent removes the roller clutch mechanism, extracting only the essential friction-based damping function. This simplification reduces manufacturing steps and part count, leading to lower production costs while maintaining chain slack control effectiveness.
Solution Approach 2:
The friction member is manufactured as an integrated component of the chain tensioner assembly, combining multiple functions into a single part. This merging reduces the number of manufacturing operations and assembly steps, thereby reducing overall manufacturing cost.
4Reliability
If higher damping forces are applied in chain slackening direction, then chain oscillation is limited, but chain tensioning freedom is restricted
Solution Approach 1:
The friction member is designed with asymmetric friction characteristics that provide higher damping forces during chain slackening (when the chain pulls the derailleur forward) while allowing freer movement during chain tensioning (when the spring pulls the derailleur backward). This asymmetry is achieved through the friction contact geometry and biasing direction.
Solution Approach 2:
The damping force is made dynamic rather than fixed, automatically adjusting based on the direction and magnitude of chain forces. The friction-based system provides variable damping that adapts to different riding conditions, providing strong oscillation control during rough terrain while maintaining smooth operation during normal shifting.
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 effectively limits chain oscillation during rough terrain, reduces weight, and simplifies manufacturing, while maintaining chain tension without increasing the size or cost of the derailleur.
Implementation Method 1
A friction member is provided. The friction member has a friction surface. A first portion of the friction surface is biased against and in frictional engagement with the outer annular surface of the pivot member
Implementation Method 2
A chain tensioner is provided. The chain tensioner includes a biasing device. The biasing device is configured to bias the chain guide assembly in a first rotational direction relative to the movable member
Data Source
AI summary
A rear derailleur includes a base member mountable to a bicycle frame, a movable member movably coupled to the base member, and a pivot member rotatably coupled to the movable member. The rear derailleur also includes a chain guide assembly rotatably connected to the movable member via the pivot member. The rear derailleur includes a damper device disposed within the movable member. The damper device is operable to apply a damping force to the chain guide assembly when the chain guide assembly rotates. The damper device includes a friction member having a friction surface. A first portion of the friction surface is in frictional engagement with the pivot member, and a second portion of the friction surface is in frictional engagement with the movable member. The friction device is disposed within the movable member at a distance relative to the biasing device in an axial direction along the pivot member.