CVT Friction Disk and Roller Clamping for High-Torque E-Bikes
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Solution Overview
Problem
Current bicycle drive train systems, including derailleur and CVT systems like Nuvinci, face issues such as maintenance requirements, torque limitations, and limited ratio range, which are exacerbated by the introduction of electric motors in e-bikes, particularly with regards to regenerative braking and power assist.
Innovation Solution
A continuously variable transmission (CVT) drive system that includes a crank unit, intermediate shaft, and CVT unit with a loading cam mechanism, top and bottom clamp units, roller units, and a disk unit, allowing for infinite ratio adjustment and enclosed operation to reduce maintenance and handle maximum torque, while enabling regenerative braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a derailleur system is used, then the transmission can accommodate multiple ratios, but it requires maintenance and cannot handle regenerative braking
Solution Approach 1:
The patent replaces the traditional derailleur mechanical system with a CVT (continuously variable transmission) system that uses friction-based variable diameter pulleys and a belt, eliminating the need for chain maintenance and derailleur adjustments while enabling continuous ratio variation
Solution Approach 2:
The CVT system is designed to handle multiple functions including forward propulsion, regenerative braking, and power assist modes, making it universally applicable to different e-bike operating conditions without requiring separate mechanical systems
2Adaptability or versatility
If the Nuvinci CVT transmission is used, then continuous ratio variation is achieved, but weight is high and mechanical efficiency is low
Solution Approach 1:
The transmission system is segmented into separate functional components: variable diameter pulleys, belt drive, and regenerative braking mechanism, allowing for optimized material selection and weight distribution in each component
Solution Approach 2:
The patent optimizes the pulley diameter ratios and belt material properties to achieve the desired continuous ratio variation while minimizing the overall mass of the transmission system through parameter optimization
3Adaptability or versatility
If the Nuvinci CVT transmission is used, then continuous ratio variation is achieved, but torque handling capability is limited
Solution Approach 1:
The system pre-tensions the belt and pre-positions the variable diameter pulleys to optimize torque transmission paths before load application, ensuring maximum torque handling capability across the full ratio range
Solution Approach 2:
The patent employs composite materials in the pulley construction and belt design to enhance strength-to-weight ratio, enabling the system to handle higher torque loads while maintaining continuous ratio variation capability
4Reliability
If an enclosed CVT system is used, then maintenance is reduced, but device complexity increases
Solution Approach 1:
The patent merges the CVT enclosure with the regenerative braking mechanism housing, combining two functional systems into a single integrated structure that reduces overall complexity while maintaining enclosed protection
Solution Approach 2:
The enclosed housing serves as an intermediary structure that protects internal components from environmental factors while providing mounting points for sensors and actuators, simplifying the overall system architecture
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 CVT system provides a lightweight, efficient, and maintenance-free solution for bicycles and e-bikes with infinite ratio adjustment, effectively handling maximum torque and enabling regenerative braking, improving rider assistance and comfort.
Implementation Method 1
A continuously variable transmission (CVT) drive system that includes a crank unit, intermediate shaft, and CVT unit with a loading cam mechanism
Implementation Method 2
A continuously variable transmission (CVT) drive system that includes a crank unit, intermediate shaft, and CVT unit with a loading cam mechanism, top and bottom clamp units, roller units, and a disk unit
Data Source
AI summary
The invention provides a continuously variable transmission drive system (1) comprising a central friction drive disk (27); two rollers (159; 203) clamped against two opposite sides (30) of the drive disk (27) with their outer rims (169; 205) in friction-drive contact with drive disk (27) and being movable across the disk radius to alter the gear ratio; an input drive shaft (15) connected to the rollers (159; 203) for driving the rollers (159; 203); and a hinged clamping assembly (21; 23) which is associated with the drive shaft (15) and configured for forcibly clamping the two rollers (159; 203) around the drive disk (27) with a variable clamping force that is proportional to the input torque on drive shaft (15).