Run-Flat Tire Variable Thickness Side Reinforcement
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Solution Overview
Problem
Run-flat tires with large tire section heights experience buckling issues when internal pressure is reduced, leading to excessive tension forces on the side reinforcement layer during steering, which can cause damage and reduce durability.
Innovation Solution
A run-flat tire design with a carcass bridging between bead portions, a tire side portion linking bead and tread portions, and a side reinforcement layer positioned at the tire width direction inner side, where the thickness at 40% of the tire section height is no more than 65% of the maximum width position, effectively reducing tension forces on the side reinforcement layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a side-reinforcing rubber is provided to reinforce the tire side portion in a run-flat tire with large section height, then run-flat endurance is improved, but tension forces act on the side-reinforcing rubber during buckling when slip angle is applied
Solution Approach 1:
The side-reinforcing rubber is designed with non-uniform thickness distribution, being thickest at the carcass maximum width position and progressively thinner toward the bead and tread portions. This local variation in thickness provides reinforcement exactly where needed to prevent buckling while reducing tension forces in regions where the rubber would otherwise be overstressed during slip angle conditions.
Solution Approach 2:
The invention changes the geometric parameter of the side-reinforcing rubber from uniform thickness to variable thickness. By controlling the thickness to be at most 65% of the maximum thickness at the carcass maximum width position, the design optimizes the balance between providing sufficient reinforcement for run-flat capability and minimizing tension forces during buckling events.
2Reliability
If the thickness of side reinforcement layer is increased to suppress tension forces during buckling, then durability is improved, but weight increases and riding comfort deteriorates
Solution Approach 1:
Instead of uniformly increasing the thickness of the side-reinforcing rubber throughout the entire tire side portion, the invention applies variable thickness distribution. The rubber is thickest at the carcass maximum width position where reinforcement is most needed, and gradually thinner toward the bead and tread portions. This localized approach provides the necessary durability improvement while minimizing overall weight increase.
Solution Approach 2:
The invention optimizes the thickness parameter of the side-reinforcing rubber by establishing that the thickness at the position at 40% of the tire section height should be at most 65% of the thickness at the carcass maximum width position. This parameter control ensures sufficient durability without excessive weight gain.
Data Source
AI summary
A run-flat tire includes a carcass, a tire side portion and a side reinforcement layer. The carcass bridges between a pair of bead portions. The tire side portion links between a bead portion and a tread portion. A carcass maximum width position of the tire side portion, at which the width of the carcass is at a maximum, is provided at the tire radial direction outer side relative to a position that is at 40% of the tire section height. The side reinforcement layer is provided at the tire width direction inner side of the carcass. A thickness of the side reinforcement layer at the position that is at 40% of the tire section height is not more than 65% of a thickness of the side reinforcement layer at the carcass maximum width position.