Metallic Belt Element for CVT Misalignment Prevention
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Solution Overview
Problem
Existing continuously variable transmission systems with metallic belts experience misalignment and decreased friction coefficient in small diameter states, leading to uneven wear and reduced durability.
Innovation Solution
The system incorporates a metallic belt with a constant-angle inclined generatrix portion on the inner side and a curved generatrix portion on the outer side of the pulley grooves, featuring a locking edge and a projecting portion that bends inward, ensuring line contact and enhanced friction force, particularly in small diameter states, and a curved shape for improved durability and contact area in large diameter states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a smooth convex curved surface is used at the boundary portion of the pulley to prevent misalignment, then misalignment is reduced, but gear change control becomes difficult when the element contacts the boundary portion
Solution Approach 1:
The pulley groove is divided into three distinct generatrix portions along the radial direction: a constant-angle inclined generatrix portion on the inner radius side, a curved generatrix portion in the middle, and another constant-angle inclined generatrix portion on the outer radius side. This segmentation allows each portion to serve different functions - the constant-angle portions ensure stable line contact for friction, while the curved portion facilitates smooth transition during gear change control.
Solution Approach 2:
Different sections of the pulley groove are given different geometric properties tailored to their specific functions. The constant-angle inclined portions provide consistent friction characteristics for power transmission, while the curved generatrix portion in the boundary region enables easy gear change control by allowing the element to transition smoothly between different contact points without abrupt angular changes.
2Device complexity
If point contact is used between the element and pulley, then the structure is simple, but the friction coefficient decreases in small diameter states
Solution Approach 1:
The side edges of the element are formed with curved surfaces that correspond to the curved generatrix portion of the pulley groove. This curvature matching ensures line contact between the element and pulley surface, particularly in the small diameter state where the curved generatrix portion is engaged. The line contact significantly increases the friction coefficient compared to point contact, while the curved geometry maintains structural simplicity.
3Reliability
If the generatrix angle changes abruptly at the boundary portion, then misalignment is prevented, but control during gear change becomes difficult
Solution Approach 1:
The curved generatrix portion dynamically adapts the contact angle between the element and pulley during gear change operations. As the movable pulley half moves to change gears, the curved surface allows the element to follow the changing radius smoothly, maintaining optimal contact angles throughout the transition. This dynamic adaptation prevents misalignment while enabling easy gear change control, avoiding abrupt angle changes.
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
This configuration effectively prevents misalignment, maintains a high friction coefficient in small diameters, and enhances durability by ensuring stable line contact and reducing surface pressure, while allowing for efficient gear change control.
Implementation Method 1
when the element and the curved generatrix portion on the radial outer side of any of the drive pulley and the driven pulley contact each other, the projecting portion bends inward in an axial direction of the pulley
Data Source
AI summary
An element 40 for a metallic belt in a belt-type continuously variable transmission has a structure in which: a belt radial outer portion 46b of a metallic belt 7 is linearly shaped to come into line contact with a pulley radial inner portion 11a which is a constant-angle inclined generatrix portion of a pulley 5 or 8; a projecting portion 48 located below a locking edge portion 44a and extending inward in the belt radial direction is provided at each of the lower ends of both side edges of the element 40; and when the element 40 and a pulley radial outer portion 11b which is a curved generatrix portion of the pulley 5 or 8 contact each other, the projecting portion 48 bends inward in the axial direction of the pulley 5 or 8.