Segmented Bicycle Sprocket Gearbox for In-Plane Shifting
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Solution Overview
Problem
Existing bicycle gearbox technologies face challenges in efficiently shifting gears without displacing the chain out of its plane, leading to potential chain drop issues and reduced durability due to exposure to elements and impacts.
Innovation Solution
A gearbox design featuring segmented sprocket clusters and a shifting system with a wedge mechanism that allows gear ratio changes by pivoting inboard gear segments into and out of the plane without displacing the chain, maintaining chain alignment and reducing exposure to external factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional gear shifting mechanisms are used, then gear ratio changes can be achieved, but the chain is displaced out of its plane causing chain drop issues
Solution Approach 1:
The inboard gear is divided into multiple segments that can independently pivot relative to the chain plane. Each segment can be selectively engaged or disengaged from the chain while maintaining the chain's overall planar alignment, enabling gear ratio changes without chain drop
Solution Approach 2:
The gear segments are designed to pivot in a dimension perpendicular to the chain plane, allowing them to enter and exit the chain's plane without displacing the chain itself. This dimensional movement enables gear shifting while maintaining chain alignment stability
2Ease of repair
If the gearbox is exposed to external environment, then accessibility for maintenance is improved, but durability decreases due to exposure to elements and impacts
Solution Approach 1:
The gear clusters are nested within the gearbox housing, with the segmented inboard gear contained within the protected interior. This nested arrangement shields the critical gear components from external environmental factors like dirt and moisture while maintaining structural integrity
Solution Approach 2:
The gearbox housing acts as a protective shell enclosing the internal gear mechanisms. This shell structure provides a barrier against environmental contaminants and physical impacts, enhancing durability while allowing controlled access for maintenance
3Reliability
If segmented gear clusters with pivoting segments are used, then gear shifting without chain displacement is achieved, but device complexity increases
Solution Approach 1:
The inboard gear is segmented into multiple independent sections, each capable of pivoting on its own axis. This segmentation allows each segment to be controlled independently, enabling precise gear ratio changes while maintaining overall system manageability
Solution Approach 2:
The gear segments are designed with dynamic pivoting capability, allowing them to transition between engaged and disengaged states. This dynamic behavior enables flexible gear ratio changes while the segments return to a neutral position, maintaining chain alignment when not 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
This design enhances gear shifting reliability, reduces chain drop risk, improves durability by maintaining chain alignment under load, and protects the gearbox from environmental factors, while allowing for efficient motor operation and easier maintenance.
Implementation Method 1
a shifting system including a shifting wedge configured to pivot the inboard segments into and out of the plane
Implementation Method 2
each of which has a respective pin protruding transversely from an inboard face
Data Source
AI summary
A gearbox may include a drive spindle and several interconnected gear clusters arranged in a housing. A first of the gear clusters is coaxially fastened to the spindle, and has an outboard gear and an inboard gear. The first gear cluster drives a chain to operate one or more of the other gear clusters, and the inboard gear is physically divided into a plurality of segments. A shifting system for the gearbox includes an actuator configured to urge the segments of the inboard gear of the first gear cluster into and out of the plane of the chain, such that a gear ratio of the gearbox is changeable without displacing the chain out of the plane.