Pneumatic Tire Load Support Layer Width Ratio
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Solution Overview
Problem
Run-flat tires face challenges in maintaining durability while ensuring ride comfort and controlling weight, as increased load support layer thickness enhances durability but compromises ride comfort and increases weight, leading to higher rolling resistance.
Innovation Solution
The pneumatic tire design includes load support layers extending from the side portions to the radially inner side of the belt, with a specific width ratio that increases bending stiffness and reduces buckling, maintaining ride comfort and appropriate weight without significantly affecting vertical stiffness or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of load support layers is increased to improve run-flat durability, then run-flat durability is improved, but the vertical stiffness constant increases which impairs ride comfort
Solution Approach 1:
The load support layer is designed with non-uniform thickness: thicker at the shoulder portions (axial direction outer edges) to provide run-flat support where needed, and thinner at the central portion to maintain ride comfort. This local differentiation allows the tire to have excellent run-flat durability without excessive vertical stiffness that would impair ride comfort.
Solution Approach 2:
Instead of uniformly increasing thickness in one dimension, the invention varies the thickness in the axial direction to create a three-dimensional thickness distribution. The load support layer has maximum thickness at the shoulders and minimum thickness at the center, effectively using dimensional variation to resolve the contradiction between durability and comfort.
2Reliability
If the thickness of load support layers is increased to improve run-flat durability, then run-flat durability is improved, but the weight of the tire increases which increases rolling resistance
Solution Approach 1:
The load support layer thickness is optimized locally: thicker regions are placed only where structural support is critical (shoulder portions), while the central portion uses thinner construction. This localized thickening provides run-flat durability without the penalty of uniformly increasing tire weight, thereby controlling rolling resistance.
Solution Approach 2:
The invention changes the thickness parameter of the load support layer from a uniform value to a variable value that depends on the radial and axial position. By adjusting the thickness parameter strategically (thicker at shoulders, thinner at center), the tire achieves improved run-flat durability with minimal weight increase.
3Reliability
If the load support layer extends too far radially inward to improve run-flat durability, then run-flat durability is improved, but the belt position during run-flat running may not be optimally positioned above the ground contact surface
Solution Approach 1:
The load support layer is designed with differentiated radial extension: it extends further radially inward at the shoulder portions where run-flat support is needed, while maintaining appropriate extension at the center. This local differentiation ensures that during run-flat running, the belt remains optimally positioned above the ground contact surface, maximizing the ground contact area and improving durability.
Data Source
AI summary
In a tire 2, each load support layer 22 extends from a side portion 24 of the tire 2 to a radially inner side of a belt 14 at an inner side of a carcass 12. A ratio (SP/WB) of a width SP from an equator plane to an outer edge 48 of the load support layer 22, relative to a width WB from the equator plane to an edge of the belt 14, in an axial direction is equal to or greater than 0.1 and equal to or less than 0.6.