Variable Ratio Sprocket Mechanism for Load Shifting
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Solution Overview
Problem
Existing power transmission systems, such as those in bicycles, face challenges with derailleur gears due to increased friction, material fatigue, and the inability to shift during load operation, as well as high weight and space requirements in sprocket gear systems, and issues with sector alignment and jamming in multistage gear systems.
Innovation Solution
A control mechanism that uses sectored, divided, or interrupted sprockets with thrust elements connected via resilient connections, allowing for axial movement or pivotal displacement without constant contact between stationary and rotating parts, enabling smooth shifting and reduced friction and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If derailleur gears are used to change transmission ratio, then transmission ratio can be adjusted, but chain friction increases and material fatigue occurs
Solution Approach 1:
The sprocket is divided into multiple independent sector blades that can be selectively positioned. Each sector blade can be independently engaged or disengaged from the chain, allowing smooth transitions between different transmission ratios without forcing the chain to operate in misaligned positions, thereby reducing friction and material fatigue
Solution Approach 2:
The sector blades are designed to be dynamically positionable along the axial direction, enabling them to be engaged or disengaged from the chain during rotation. This dynamic adjustment allows the transmission system to optimize chain alignment and engagement at different transmission ratios, minimizing harmful friction and wear effects
2Adaptability or versatility
If derailleur gears are used for transmission ratio change, then variable transmission is achieved, but shifting during load operation becomes impossible
Solution Approach 1:
The sprocket is segmented into multiple independent sector blades that can be selectively engaged. This segmentation allows individual sectors to be positioned and engaged without requiring the entire sprocket to be disengaged, enabling smooth shifting even during load operation by progressively engaging or disengaging specific sectors
Solution Approach 2:
The sector blades can be dynamically adjusted during rotation and load, allowing the transmission ratio to be changed without stopping or reducing power transmission. The resilient connection enables the sectors to flex and engage smoothly under load conditions
3Adaptability or versatility
If multiple axially adjacently arranged chain blades are used to realize large transmission ratios, then transmission ratio range increases, but space requirements increase
Solution Approach 1:
Multiple sector blades are arranged axially adjacent to each other on the same sprocket, creating a nested configuration where different transmission ratio components occupy the same radial space. This allows a wide transmission ratio range to be achieved without proportionally increasing the overall space occupation, as the different gear ratios are stacked axially rather than radially
4Stability of the object's composition
If sectored sprockets with constant contact between stationary and rotating parts are used, then sector positioning is maintained, but friction and noise increase
Solution Approach 1:
The resilient connection allows the sector blades to periodically engage and disengage from the chain during rotation rather than maintaining constant contact. This periodic action reduces continuous friction and noise generation while still maintaining stable positioning when engaged, as the sectors are spring-loaded to automatically engage with the chain teeth
Solution Approach 2:
The resilient connection changes the contact parameter from constant to intermittent by introducing elastic deformation. The spring-loaded sectors can deflect and absorb impacts, maintaining positioning stability through elastic forces rather than constant mechanical contact, thereby reducing friction and noise
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 solution allows for shifting during load operation with reduced friction and noise, minimizes space and weight requirements, and prevents sector jamming, resulting in a more efficient and durable power transmission system.
Implementation Method 1
each of the wheel rim sectors is connected to the respectively associated thrust element via a resilient connection so as to be rotationally fixed relative to the rotation about the wheel axle
Data Source
AI summary
A control mechanism (800) for setting a transmission ratio between a traction means (812), in particular chain, and a wheel set that is rotatable about a wheel axle and includes two or more wheel blades (810, 820, 830), in particular sprocket blades, adjusts the wheel rim sectors relative to a fixed plane of the traction means in a direction transverse to the plane of alignment. At least one of the wheel blades is composed of a plurality of independently adjustable wheel rim sectors (802, 803). By means of a control component (807) mounted decoupled from a rotary movement of the wheel set, a plurality of co-rotating thrust elements (804, 805) are each displaced via rotation-free couplings between a first and a second position at least in the axial direction, wherein each of the wheel rim sectors is connected in a rotationally fixed manner to a respectively associated thrust element. The first position of a thrust element corresponds to the position of the associated wheel rim sector outside the plane of alignment, whereas a thrust element located in the second position exerts on the respective wheel rim sector, at least as long the latter is outside the plane of the traction means, a force for displacing the respective wheel rim sector into the plane of alignment, thus shifting the same into the plane.