Metallic Belt Element for CVT Misalignment and Friction
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Solution Overview
Problem
Existing continuously variable transmission systems face issues with misalignment of metallic belts, leading to uneven wear and decreased durability, particularly in small diameter states where friction coefficients are low and surface pressure is high, and conventional solutions either struggle with gear change control or result in point contact that reduces durability.
Innovation Solution
The system incorporates a metallic belt element with a constant-angle inclined generatrix portion for line contact in small diameters and a curved generatrix portion for point contact in large diameters, along with oil drain grooves to prevent slipping and ensure smooth gear changes, maintaining friction and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a smooth convex curved surface is used for the boundary portion of the pulley to prevent misalignment, then misalignment is reduced, but gear change control becomes difficult due to large angle changes
Solution Approach 1:
The pulley groove is divided into three distinct generatrix portions along the radial direction: a constant-angle inclined generatrix portion (first portion) for line contact, a curved generatrix portion (second portion) for point contact, and a boundary portion (third portion) connecting them. This segmentation allows each portion to serve a specific function, resolving the contradiction between misalignment prevention and gear change control.
Solution Approach 2:
Different regions of the pulley groove are given different geometric properties: the constant-angle inclined portion provides line contact for friction maintenance, the curved portion provides point contact for misalignment reduction, and the boundary portion with gradual angle change ensures smooth transitions. This local differentiation resolves the contradiction by optimizing each region for its specific purpose.
2Stability of the object's composition
If point contact is used between the element and pulley, then misalignment is reduced, but the friction coefficient decreases in small diameter states
Solution Approach 1:
The contact type between the element and pulley is made dynamic rather than static. The boundary between line contact and point contact regions is designed to shift along the generatrix as the pulley diameter changes. In small diameter states, the contact occurs in the constant-angle inclined portion providing line contact for high friction, while in large diameter states, contact shifts to the curved portion providing point contact for misalignment prevention.
Solution Approach 2:
The solution adds a radial dimension to the contact geometry by creating a boundary portion that gradually transitions the angle along the radial direction. This allows the system to utilize both line contact and point contact characteristics by transitioning between them in the radial dimension, resolving the contradiction between friction maintenance and misalignment prevention.
3Stability of the object's composition
If the generatrix angle changes rapidly in the boundary portion, then misalignment is prevented, but gear change control becomes difficult
Solution Approach 1:
The boundary portion is designed with a gradual angle change that acts as a cushioning transition zone between the constant-angle inclined portion and the curved generatrix portion. This gradual transition prevents sudden angle changes that would cause difficult gear change control, while still achieving misalignment prevention through the overall curved geometry.
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 design effectively reduces misalignment, maintains friction force, and enhances durability by adjusting contact types based on pulley diameter, preventing slipping and wear, while ensuring smooth gear changes through the use of oil drain grooves.
Implementation Method 1
a failure to properly discharge lubricating oil present between the element and the pulley causes a fluid lubrication state and puts the belt in danger of slip
Implementation Method 2
the friction coefficient between the element and the pulley decreases in a small diameter state where the element contacts the inner diameter side of the pulley
Data Source
AI summary
An element for a metallic belt in a continuously variable transmission capable of reducing misalignment while ensuring friction force in a small diameter state is provided. An element 40 for a metallic belt in a belt-type continuously variable transmission has a structure in which a side edge of the element 40 of a metallic belt 7 that contacts a drive pulley 5 and a driven pulley 8 includes: a belt radial outer portion 46b that is located on a radial outer side of the metallic belt 7 and linearly shaped to follow a radial inner portion 11a as a constant-angle inclined generatrix portion; and a belt radial inner portion 46a that is located on a radial inner side of the metallic belt 7 and curved to taper inward in the belt radial direction to gradually increase an inclination angle.