Bicycle Rear Derailleur Linkage for Consistent Shifting Force
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Solution Overview
Problem
Existing bicycle rear derailleurs require significant operational energy for shifting between gear positions, leading to inefficient energy usage and varying force requirements for shifting between adjacent gears.
Innovation Solution
A motorized rear derailleur design featuring a cable-operated structure with a biasing member and link members that minimizes the rate of change in operating energy between shift stage positions, using a four-bar parallelogram linkage to maintain consistent shifting force across multiple gear positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional cable operated rear derailleur is used, then the shifting mechanism is simple and reliable, but the operating energy varies significantly between different shift stage positions
Solution Approach 1:
The patent applies asymmetry by strategically positioning the biasing member connection points outside the quadrilateral formed by the four pivot axes. This asymmetric arrangement creates a mechanical advantage that balances the operating energy across different shift positions, resolving the energy inconsistency problem without requiring complex additional components
Solution Approach 2:
The patent changes the geometric parameters of the linkage system by defining specific relationships between link lengths, pivot positions, and biasing member attachment points. These parameter adjustments optimize the energy distribution across shift stages, maintaining consistent operating energy while preserving the simplicity of the cable-operated mechanism
2Device complexity
If the biasing member is connected at standard positions, then the linkage structure is simple, but the rate of change in operating energy between adjacent shift positions exceeds acceptable thresholds
Solution Approach 1:
The patent applies local quality by making the biasing member connection points distinct from standard positions, placing them specifically outside the quadrilateral formed by pivot axes A1-A4. This localized modification to the linkage geometry creates the necessary mechanical advantage to reduce energy rate of change while keeping the overall structure simple and cable-operated
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
This design reduces the percentage of rate of change in operating energy between shift stage positions, ensuring a consistent shifting force and balancing energy usage, thereby enhancing the efficiency and user experience of gear shifting.
Implementation Method 1
A biasing member (e.g., a spring) is operatively connected between the first and second link members such that the movable member is biased towards the top shift stage position
Implementation Method 2
The inner wire is slidably disposed within an outer casing and coupled to one of the first link member and the second link member for moving the movable member and the chain guide laterally relative to the base member
Implementation Method 3
The first link member has a first end pivotally mounted to the base member about a first pivot axis and a second end pivotally mounted to the movable member about a second pivot axis. The second link member has a first end pivotally mounted to the base member about a third pivot axis and a second end pivotally mounted to the movable member about a fourth pivot axis
Data Source
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AI summary
A bicycle rear derailleur (12) is basically provided with a base member (32), a cable operated structure (34, 36), a movable member (38) and a biasing member (46). The movable member(38) is movably supported to the base member (32) by the cable operated structure (34, 36) to move between a plurality of shift stage positions with respect to the base member (32). The biasing member (46) is interposed between the first and second link members such that the movable member (38) is biased towards one of a top shift stage position and a low shift stage position. The cable operated structure (34, 36) and the biasing member (46) configured balance an operation energy used for shifting between each of the shift stage positions.