Run-flat Tire with Crescent Side Reinforcing Rubber
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Solution Overview
Problem
Run-flat tires with crescent-like side reinforcing rubber face a trade-off between high fuel efficiency and durability due to weight increase, necessitating a design that improves both performance metrics.
Innovation Solution
A run-flat tire design featuring a tread portion, sidewall portions with crescent-like side reinforcing rubbers, a toroidally arranged carcass, and belt layers, where the sectional width to outer diameter ratio and belt layer configuration optimize fuel efficiency and durability by reducing buckling and enhancing rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If side reinforcing rubber with crescent-like cross section is added to ensure run-flat durability, then run-flat durability is improved, but weight increases causing deteriorated fuel efficiency
Solution Approach 1:
The side reinforcing rubber is positioned specifically in the lower portion of the sidewall (from 0° to 90° from the ground contact point), providing run-flat support only where needed rather than uniformly throughout the entire sidewall. This localized reinforcement reduces overall weight while maintaining run-flat durability in the critical load-bearing region.
Solution Approach 2:
The tire employs a composite structure combining side reinforcing rubber with specific carcass cord arrangements (diagonal and radial plies at different angles) and belt layers. This composite design optimizes the distribution of reinforcement materials, providing run-flat capability through strategic material placement rather than uniform thickening, thereby controlling weight while ensuring durability.
2Use of energy by moving object
If narrow-width, large-diameter tire configuration is used to improve fuel efficiency, then fuel efficiency is improved, but run-flat travelling performance deteriorates
Solution Approach 1:
The invention optimizes specific geometric parameters including the sectional width to outer diameter ratio (SW/OD ≤ 0.26 for SW < 165mm, or OD ≥ 2.135×SW+282.3 for SW ≥ 165mm), the angular position of side reinforcing rubber (0° to 90° from ground contact), and belt layer angles (20° to 75°). These parameter optimizations enable narrow-width tires to achieve run-flat performance through precise dimensional control rather than increased size or weight.
Solution Approach 2:
The tire design incorporates dynamic considerations for run-flat operation by positioning the side reinforcing rubber to accommodate sidewall deformation during run-flat travel. The reinforcement is placed in the lower sidewall region where dynamic stresses occur during run-flat conditions, allowing the narrow tire to adapt to run-flat demands while maintaining its fuel-efficient geometry during normal operation.
Data Source
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AI summary
The run-flat tire of this disclosure includes a tread portion, a pair of sidewall portions, bead portions, side reinforcing rubbers with crescent-like cross section, and a carcass formed of plies of radially arranged cords, wherein: when the tire is mounted to a rim, and an internal pressure of 250 kPa or more is applied to the tire, in a case where a sectional width SW of the tire is less than 165 mm, a ratio of the sectional width SW to an outer diameter OD of the tire, SW/OD, is 0.26 or less; in a case where the sectional width SW of the tire is 165 mm or more, the sectional width SW and the outer diameter OD of the tire satisfy a relation expression OD≥2.135×SW+282.3 (mm); and the relation expression 0.5≤WG/WB≤0.8 is satisfied.