Bicycle Shifting Device Planetary Mechanism Torque Management
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Solution Overview
Problem
Existing bicycle shifting devices have complex configurations for changing transmission ratios, particularly when increasing the ratio in a stepped manner, which can lead to complications and inefficiencies due to the need to switch between sun gears with different numbers of teeth, affecting torque transmission and shifting performance.
Innovation Solution
A bicycle shifting device with a simplified configuration that uses multiple planetary mechanisms and a setting mechanism to establish distinct shifting paths, allowing rotational speed changes without altering the first planetary mechanism in higher transmission ratios, thereby reducing complexity and torque issues during ratio changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transmission ratio is increased by switching between sun gears with different numbers of teeth, then the transmission ratio changes in a stepped manner, but the configuration of shifting paths becomes complicated and torque transmission is adversely affected
Solution Approach 1:
The shifting mechanism is divided into multiple independent planetary mechanisms (first, second, third, and fourth planetary mechanisms), each capable of independently changing transmission ratios. This segmentation allows each mechanism to handle specific ratio changes without requiring complex interactions between mechanisms, thereby simplifying the overall shifting path configuration while maintaining versatile transmission ratio adjustment capability.
Solution Approach 2:
A carrier mechanism is introduced as an intermediary component that connects the planetary mechanisms and facilitates smooth transitions between different transmission ratios. The carrier mechanism acts as a mediator that coordinates the engagement and disengagement of different planetary mechanisms, eliminating the need for complex direct switching between sun gears and simplifying the shifting path configuration.
2Adaptability or versatility
If multiple planetary mechanisms are used to achieve multiple transmission ratios, then the transmission ratio can be changed in multiple steps, but the device complexity increases
Solution Approach 1:
Multiple planetary mechanisms are merged into a single integrated hub structure, sharing common components such as the carrier mechanism and housing. This merging approach allows the system to achieve multiple transmission ratios through coordinated operation of the planetary mechanisms while avoiding the complexity of completely separate mechanisms, thereby reducing overall device complexity while maintaining versatile ratio change capability.
3Adaptability or versatility
If the shifting mechanism switches between different sun gears, then the transmission ratio changes, but torque transmission is adversely affected during the switching process
Solution Approach 1:
The carrier mechanism is designed to pre-position and pre-engage the appropriate planetary mechanism before the actual transmission ratio change is required. This preliminary action ensures that the switching between different sun gears occurs smoothly without sudden torque interruptions, thereby maintaining torque transmission stability while enabling transmission ratio adjustment.
Solution Approach 2:
The shifting mechanism employs dynamic engagement and disengagement of planetary mechanisms through the carrier mechanism, allowing continuous torque transmission during ratio changes. The dynamic design enables smooth transitions between different transmission ratios by progressively engaging or disengaging planetary mechanisms based on the required ratio, preventing torque interruptions and maintaining reliability during switching.
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 device effectively changes transmission ratios in a simplified manner, reducing the adverse effects on shifting performance even under high torque conditions, and maintains efficient operation with motor-assisted human driving force.
Implementation Method 1
The plurality of shifting mechanisms includes a first shifting mechanism (62A). The first shifting mechanism (62A) includes a first planetary mechanism (64) and a second planetary mechanism (66)
Data Source
AI summary
A bicycle shifting device includes a first shifting mechanism, a transmission mechanism, and a setting mechanism. The setting mechanism sets paths in the transmission mechanism to transmit rotation from an input body to an output body at transmission ratios of at least three steps. The transmission mechanism establishes a first path transmitting the rotation at one of first and second transmission ratios by changing a rotational speed with the first shifting mechanism, and a second path transmitting the rotation at a greater transmission ratio than the first and second transmission ratios by changing the rotational speed with a different shifting mechanism from the first shifting mechanism. The first path includes first and second planetary mechanisms. The setting mechanism sets the transmission mechanism so that the rotational speed is not changed by the first planetary mechanism in the second path.