Run-Flat Tire Sidewall Reinforcement Thickness Optimization
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Solution Overview
Problem
Conventional run-flat tire designs face challenges in achieving both durability and ride comfort due to the shift in carcass ply position and thickness of the sidewall reinforcing rubber layer, which affects the tire's vertical spring constant and bending rigidity.
Innovation Solution
The carcass ply is shifted axially outward in the bead portions, reducing the thickness from the carcass ply to the outer tire surface, and the sidewall reinforcing rubber layer's thickness is optimized between 29% to 35% of the tire thickness to enhance run-flat durability while maintaining ride comfort by controlling the vertical spring constant and bending rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the carcass ply is shifted toward the axially outside in the bead portions, then the thickness from the carcass ply to the outer surface of the tire is reduced, but the sidewall reinforcing rubber layer thickness relative to tire thickness must be increased to maintain run-flat durability
Solution Approach 1:
The invention changes the parameter of sidewall reinforcing rubber layer thickness to a specific range (29-35% of tire thickness) to resolve the contradiction between reduced overall thickness and maintained run-flat durability. This parameter optimization allows the tire to achieve both compactness and reliability.
2Reliability
If the sidewall reinforcing rubber layer thickness is increased to improve run-flat durability, then the vertical spring constant increases, but ride comfort deteriorates
Solution Approach 1:
The invention optimizes the sidewall reinforcing rubber layer thickness within the specific range of 29-35% of tire thickness. This parameter change prevents excessive increase in vertical spring constant while maintaining sufficient bending rigidity for run-flat durability, thus balancing reliability and ride comfort.
Solution Approach 2:
The invention applies different rubber layer thickness configurations to different regions: the sidewall reinforcing rubber layer is positioned and sized specifically (29-35% of tire thickness) to provide local reinforcement where needed for run-flat durability, while maintaining appropriate flexibility in other areas for ride comfort.
Data Source
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AI summary
A run-flat tire (T) comprising a tread portion (2), sidewall portions (3), bead portions (4), a carcass ply (6A), a sidewall reinforcing rubber layer (10) provided in each sidewall portion (3) and disposed on the axially inside of the carcass ply (6A) and a rim protector (12) provided on the axially outer surface of each sidewall portion (3) and projecting axially outward, wherein the bead portions (4) are each provided therein with an axially inside core (5i) and an axially outside core (5o) between which a radially inner edge portion of the carcass ply (6A) is secured and when measured along a normal line drawn normally to the carcass ply (6A) from an apex (12a) of the rim protector (12), the thickness of the sidewall reinforcing rubber layer (10) is in a range of from 29 % to 35 % of the thickness of the tire.