CVT Roll Surface Geometry to Eliminate Prying Motion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current continuously variable transmissions suffer from prying motion at contact points, leading to wear and dissipative losses, which compromise efficiency and limit the usable range of transmission ratios.
Innovation Solution
A continuously variable transmission system with two main shafts and an auxiliary shaft, where the roll surfaces are designed to ensure pure rolling without prying motion by having double curvature and specific geometric profiles, allowing the auxiliary shaft to move along a reference plane to vary the transmission ratio through tangential force and normal force at contact points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional continuously variable transmission uses rolling surfaces with single curvature or point contact, then the structure is simpler, but prying motion occurs causing wear and dissipative losses
Solution Approach 1:
The invention applies double curvature to the roll surfaces of both the auxiliary shaft and main shafts. The roll surfaces are formed by rotating generatrix curves around the shaft axes, creating surfaces with curvature in two directions. This double curvature ensures that the contact between rolling surfaces maintains pure rolling without prying motion, eliminating the harmful relative rotation that occurs with single curvature or point contact surfaces.
2Adaptability or versatility
If the transmission ratio range is expanded, then the versatility improves, but wear and prying motion increase limiting the usable range
Solution Approach 1:
The double curvature roll surfaces enable pure rolling contact across the entire transmission ratio range. By ensuring that the contact between the auxiliary shaft and main shafts maintains rolling without prying motion throughout the full range of motion, the invention eliminates wear that would otherwise limit the usable transmission ratio range, thereby expanding the reliable operational envelope.
Solution Approach 2:
The invention changes the geometric parameters of the roll surfaces by implementing double curvature instead of single curvature or point contact. This parameter change in the surface geometry fundamentally alters the contact mechanics, eliminating prying motion and enabling the transmission to operate reliably across a wider range of transmission ratios without increased wear.
3Reliability
If pure rolling without prying motion is achieved through double curvature surfaces, then wear and dissipative losses are reduced, but the manufacturing complexity increases
Solution Approach 1:
The double curvature roll surfaces are generated by rotating generatrix curves around the shaft axes. This rotational generation method provides a systematic approach to creating the complex double curved surfaces, making them more manufacturable than arbitrary complex geometries while still achieving the pure rolling contact necessary to eliminate wear and dissipative losses.
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 system achieves efficient motion transmission with reduced wear and losses, enabling a wider range of variable transmission ratios without prying motion, thus enhancing the durability and efficiency of the transmission system.
Implementation Method 1
During use of the transmission, the roll surfaces of the auxiliary shaft roll without rubbing on the corresponding roll surfaces of the main shafts
Data Source
AI summary
A continuously variable transmission includes a first main shaft and a second main shaft and at least one auxiliary shaft, rotatable around a rotation axis and interposed between the first and second main shafts. The auxiliary shaft has two secondary roll surfaces. Each secondary roll surface is shaped as a solid of revolution and is placed in contact with a respective primary roll surface of the first and second main shafts. The primary and secondary roll surfaces are shaped so that straight lines tangential thereto in contact points between the auxiliary shaft and the first and second main shafts pass through two distinct intersection points between the axes of the first and second main shafts.