Segmented Pulley CVT for Wide-Ratio Torque Transmission
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Solution Overview
Problem
Existing continuously variable transmissions (CVTs) face limitations in efficiency, lubrication challenges, and shock-load tolerance due to reliance on contact friction and mechanical limitations, which restrict their ability to transmit torque effectively over a wide range of ratios.
Innovation Solution
A mechanical belt-drive system with segmented pulleys that vary diameters simultaneously to maintain a constant belt circumference, allowing for continuous variation of speed and torque ratios without lubrication, utilizing a controller to move pulleys in opposite directions for smooth ratio changes, and featuring a constraining cage for radial motion control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If contact friction mechanisms are used to transmit torque in CVT, then torque transmission capability is improved, but efficiency decreases and lubrication challenges increase
Solution Approach 1:
The pulleys are divided into multiple segments that can move independently relative to each other. This segmentation allows the pulley diameter to vary continuously while maintaining a rigid structure for torque transmission, resolving the contradiction between needing friction for torque and maintaining efficiency through reduced mechanical complexity
Solution Approach 2:
The pulley diameter is made dynamically adjustable through the movement of segments along the shaft. This dynamic capability enables continuous ratio variation without the need for complex friction-based mechanisms, improving efficiency while maintaining torque transmission through the belt drive system
2Force
If contact friction mechanisms are used to transmit torque in CVT, then torque transmission capability is improved, but lubrication requirements become more difficult
Solution Approach 1:
The patent replaces friction-based torque transmission with a positive engagement belt drive system. The belt engages with the segmented pulleys through mechanical interlocking rather than friction, eliminating the need for lubrication while maintaining effective torque transmission across the variable ratio range
3Force
If contact friction mechanisms are used to transmit torque in CVT, then torque transmission capability is improved, but shock-load tolerance decreases
Solution Approach 1:
The segmented pulley design allows individual segments to move independently to accommodate sudden torque changes. This segmentation provides shock absorption capability while maintaining positive belt engagement, improving shock-load tolerance without sacrificing torque transmission capability
4Adaptability or versatility
If pulley diameters are varied to change speed ratio in CVT, then continuous ratio variation is achieved, but device complexity increases
Solution Approach 1:
The pulleys are segmented into multiple movable sections that can independently adjust their position along the shaft. This segmentation simplifies the mechanism for achieving continuous diameter variation compared to traditional single-piece pulley designs, reducing device complexity while maintaining continuous ratio variation capability
Solution Approach 2:
The dynamic adjustment of segmented pulley positions along the shaft provides continuous ratio variation. The segments move smoothly relative to each other, creating a simple yet effective mechanism for continuous adaptation of the speed ratio without complex control systems
Data Source
AI summary
A continuously variable transmission including an input pulley having a first subassembly supported upon a first rotatably driven shaft and an output pulley having a second subassembly supported upon a second rotatable shaft. Each subassembly includes a plurality of left link elements extending from segmented pulley segments to a first shaft supported rotating element, along with a plurality of right link elements extending from the segmented pulley segments to a second shaft supported rotated element for positioning the segmented pulley segments in an outwardly circumferentially arrayed fashion about each of the first and second shafts. Axial displacement of a first and second pairs of said first and second shaft supporting elements in each of the input and output pulley subassemblies inversely varying a collective diameter formed by said arrangements of segmented pulley segments in order to maintain a constant circumference of a belt supported about the segmented pulley segments for each of the input and output pulleys.