Run-flat Tire Width-Diameter Ratio and Bead Filler Placement
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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 increases, necessitating a design that improves both performance metrics.
Innovation Solution
A run-flat tire design featuring a narrow-width, large-diameter configuration with specific ratios of sectional width to outer diameter, bead filler placement, and carcass structure, which includes radially arranged cords and bead cores, to optimize fuel efficiency and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If side reinforcing rubber with crescent-like cross section is added to improve 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 (with the lower end located at a position lower than the upper end in the tire radial direction), concentrating reinforcement where it is most needed for run-flat performance while minimizing overall weight addition. This localized placement provides structural support during run-flat conditions without uniformly increasing tire weight.
Solution Approach 2:
The bead filler is positioned at the lower end of the side reinforcing rubber in advance, creating a pre-configured support structure that engages during run-flat conditions. This preliminary arrangement of materials ensures that when a puncture occurs, the structured configuration immediately provides the necessary support without requiring additional weight or complex mechanisms.
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 durability becomes insufficient
Solution Approach 1:
The invention specifies precise geometric parameters for the side reinforcing rubber and bead filler configurations (including positional relationships and dimensional ratios) that optimize the balance between fuel efficiency and run-flat durability. By carefully controlling parameters such as the location of the lower end of side reinforcing rubber and the dimensions of bead filler, the tire achieves improved fuel efficiency through reduced rolling resistance while maintaining sufficient run-flat capability.
Data Source
Figure 1
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, 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); the bead portions have bead cores, and further have bead fillers on a tire radial outer side of the bead cores; and the relation expression 1.8≤H1/H2≤3.5 is satisfied.