Bicycle Continuously Variable Transmission Automatic Ratio Adjustment
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Solution Overview
Problem
Conventional bicycle transmission systems allow speed changes only within a limited number of options corresponding to the number of sprockets, requiring user operation to adjust the speed ratio, whereas an automatic adjustment of speed ratio according to load would enhance convenience, similar to an automobile's automatic transmission.
Innovation Solution
A continuously variable transmission system incorporating an input rotor, output rotor, planetary rollers, guide member, movable ring, and elastic member, where the angle of inclination of the planetary rollers' rotation shaft changes with load, adjusting the contact positions between the input and output rotors to automatically alter the speed change ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional transmission system with multiple sprockets is used, then the speed change ratio can be adjusted, but the adjustment is limited to a fixed number of options and requires user operation
Solution Approach 1:
The transmission system automatically adjusts the speed change ratio based on the load applied to the planetary rollers, eliminating the need for user operation. The elastic member (spring) automatically responds to load changes, causing the planetary rollers to tilt and change the contact positions on the conical surfaces, thereby self-regulating the transmission ratio according to driving conditions
Solution Approach 2:
The system transitions from a static transmission ratio (fixed sprockets) to a dynamic transmission ratio that continuously varies with load. The planetary rollers are designed to tilt dynamically in response to applied load, and the elastic member provides dynamic response to load changes, enabling continuous adjustment of the speed change ratio rather than discrete steps
2Adaptability or versatility
If a continuously variable transmission with ball-leg assembly is used, then the speed change ratio can be continuously varied, but it still requires user operation to change the ratio
Solution Approach 1:
The transmission system automatically adjusts the speed change ratio based on the load applied to the planetary rollers, eliminating the need for user operation. The elastic member (spring) automatically responds to load changes, causing the planetary rollers to tilt and change the contact positions on the conical surfaces, thereby self-regulating the transmission ratio according to driving conditions
3Ease of operation
If an automatic transmission system is implemented, then user convenience is improved, but the device complexity increases
Solution Approach 1:
The system changes the physical state and orientation of the planetary rollers from fixed to tiltable, allowing the rotation shafts to change their inclination angles in response to load. This parameter change enables automatic transmission functionality through a relatively simple mechanical structure involving elastic members and conical surfaces, avoiding the need for complex electronic control systems
Solution Approach 2:
The transmission system is divided into modular components: input rotor, output rotor, planetary rollers with rotation shafts, guide members, movable rings, and elastic members. This segmentation allows each component to perform a specific function and simplifies the overall design and manufacturing while enabling automatic operation
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
Enables automatic adjustment of the speed change ratio without user intervention, providing enhanced convenience and efficiency by changing the speed ratio based on applied load, similar to an automatic transmission system.
Implementation Method 1
The elastic member is capable of expanding and contracting in the axial direction. The elastic member is arranged to apply a pressure to the movable ring in the axial direction.
Data Source
AI summary
A continuously variable transmission includes an input rotor, an output rotor, a plurality of planetary rollers, a guide member, a movable ring, and an elastic member. The input rotor is arranged to rotate about a main axis at a rotation rate before a speed change. The output rotor is arranged to rotate about the main axis at a rotation rate resulting from the speed change. The planetary rollers are arranged around the main axis, and each planetary roller is capable of rotating about a rotation shaft. The guide member is arranged to restrict positions of both end portions of the rotation shaft. The movable ring is capable of rotating about the main axis between the main axis and the planetary rollers. The movable ring is annular, and is capable of moving in an axial direction. The elastic member is capable of expanding and contracting in the axial direction. Each planetary roller includes a first slanting surface, a second slanting surface, and an annular recessed portion or annular projecting portion. The guide member is arranged to hold the end portions of the rotation shaft at different circumferential positions such that each end portion of the rotation shaft is capable of shifting a position thereof in a radial direction with respect to the main axis. The elastic member is arranged to apply a pressure to the movable ring in the axial direction.