Bicycle Transmission Layout for Shifting Under Pedaling Load
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Solution Overview
Problem
Existing bicycle transmission systems often require the rider to stop pedaling to shift gears, limiting the ability to up- or downshift based on pedal force or electromotor torque.
Innovation Solution
A transmission system with two serially connected transmissions, each with its own clutch, allowing for four distinct system transmission ratios, enabling gear shifting without the need to stop pedaling by using load-shifting clutches that can be coupled or decoupled under load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional gear hub shifting mechanisms or single-transmission systems are used, then the structure is simpler, but up- and downshifting cannot always be possible depending on rider pedal force
Solution Approach 1:
The transmission system is divided into two separate transmissions connected in series, each capable of providing two different transmission ratios through its own clutch mechanism. This segmentation allows independent control of each transmission stage, enabling gear shifting under load without requiring the rider to stop pedaling.
Solution Approach 2:
Two transmissions are combined in series configuration, where the first transmission has a first clutch and the second transmission has a second clutch. The combination of these two transmissions with their respective clutches creates a four-speed transmission system that can shift gears independently of pedal force, resolving the contradiction between shifting capability and structural complexity.
2Ease of operation
If conventional clutch systems are used, then the structure is simpler, but gear shifting requires stopping pedaling or torque application
Solution Approach 1:
The clutch mechanisms are designed to be dynamically controllable during torque transmission. The first clutch in the first transmission and the second clutch in the second transmission can be engaged or disengaged independently while the system is under load, allowing gear shifts without requiring the rider to stop pedaling. This dynamic control capability enables seamless gear changing during operation.
3Adaptability or versatility
If a single transmission with multiple ratios is used, then the structure is simpler, but the range and precision of transmission ratios are limited
Solution Approach 1:
The transmission system is segmented into two independent transmissions, where the first transmission provides two different transmission ratios and the second transmission also provides two different transmission ratios. This segmentation multiplies the available gear ratios (2×2=4), providing a broader and more precise range of transmission options compared to a single transmission system.
Solution Approach 2:
Each transmission stage serves multiple functions by providing two different transmission ratios through its respective clutch mechanism. The first transmission can operate in first or second ratio modes, and the second transmission can operate in third or fourth ratio modes, creating a universal four-speed transmission system that adapts to various riding conditions.
Data Source
AI summary
Disclosed is a transmission system for a vehicle, particularly for a bicycle. The system comprises an input and an output, and a first transmission and a second transmission between the input and the output, wherein the first transmission and the second transmission are connected in series. The first transmission is selectively operable according to a first transmission ratio or a second transmission ratio, and has a first load-shifting clutch for switching the first transmission from the first transmission ratio to the second transmission ratio and/or vice versa. The second transmission is selectively operable according to a third transmission ratio or a fourth transmission ratio, and has a second load-shifting clutch for switching the second transmission from the third transmission ratio to the fourth transmission ratio and/or vice versa.