Run-flat tire rigidity reducing portion for comfort and durability
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Solution Overview
Problem
Conventional run-flat radial tires with reinforcing rubber layers face a trade-off between durability during run-flat travel and comfort during normal pressure travel, as the high rigidity required for durability leads to an uncomfortable ride.
Innovation Solution
A run-flat radial tire design featuring a reinforcing rubber layer with a substantially-crescent-shaped cross section, incorporating a rigidity reducing portion on the tread portion, which reduces tire rigidity by positioning the inner end of the reinforcing rubber layer on the outer side of the road-contacting end and the belt end, and using circumferential grooves or holes to distribute stress effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reinforcing rubber layer with high rigidity is used to maintain tire shape during run-flat travel, then durability during run-flat travel is improved, but ride comfort during normal pressure travel deteriorates
Solution Approach 1:
The patent applies local quality by creating a rigidity reducing portion with a specific cross-sectional area ratio in the tread portion. This localized modification allows the tire to have different effective rigidity characteristics in different regions: the reinforcing rubber layer maintains high rigidity for run-flat durability, while the rigidity reducing portion in the tread area provides lower rigidity for comfort during normal operation. The cross-sectional area ratio of 5-30% optimizes this local differentiation to balance both requirements.
2Reliability
If the thickness of the reinforcing rubber layer is increased to improve run-flat durability, then reliability during run-flat travel is improved, but the spring constant increases resulting in less comfortable ride
Solution Approach 1:
The patent applies local quality by creating a rigidity reducing portion with a specific cross-sectional area ratio in the tread portion. This localized modification allows the tire to have different effective rigidity characteristics in different regions: the reinforcing rubber layer maintains high rigidity for run-flat durability, while the rigidity reducing portion in the tread area provides lower rigidity for comfort during normal operation. The cross-sectional area ratio of 5-30% optimizes this local differentiation to balance both requirements.
3Reliability
If a fiber reinforced layer is added to enhance run-flat durability, then reliability during run-flat travel is improved, but device complexity and weight increase
Solution Approach 1:
The patent applies parameter changes by modifying the cross-sectional area ratio of the reinforcing rubber layer to create a rigidity reducing portion. This approach changes the geometric parameters of the existing rubber layer rather than adding a separate fiber reinforced layer. By controlling the cross-sectional area ratio between 5-30%, the patent achieves the desired rigidity reduction for comfort while maintaining the structural simplicity and avoiding the complexity and weight increase associated with adding fiber reinforced layers.
Data Source
AI summary
Provided is a run-flat tire having a substantially-crescent-shaped cross section, which makes it possible to achieve both durability at the time of run-flat travel and ride comfort at the time of travel at a normal inner pressure. A rigidity reducing portion that reduces a tire rigidity in the width direction extends in the circumferential direction on a surface of a tread rubber in an area located on the inner side than an end of a belt in the tire width direction and on the outer side than a road-contacting end in the tire width direction under a 75% load state.