Shoulder-Groove Tire Structure for Low Rolling Resistance
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Solution Overview
Problem
Existing tires face a challenge in achieving reduced rolling resistance without compromising wet road surface grip performance, and forming narrow grooves on shoulder land portions can lead to belt edge loosening and other damages.
Innovation Solution
A tire design with circumferential grooves and a circumferential narrow groove on the shoulder land portion, where the groove width is smaller than the shoulder circumferential groove, positioned between the shoulder circumferential groove and the end of the outer layer, with specific ratios to minimize compressive strain and maintain grip performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a crosslinked rubber with low heat generation properties is used for the cap portion, then rolling resistance is reduced, but wet road surface grip performance is decreased
Solution Approach 1:
The invention applies different rubber compositions to different regions of the cap portion. Specifically, the shoulder land portions use a first crosslinked rubber with low heat generation properties (low rolling resistance), while the central land portion uses a second crosslinked rubber optimized for wet grip performance. This local differentiation allows the tire to achieve both low rolling resistance and good wet grip simultaneously.
2Loss of energy
If a narrow groove is formed on each shoulder land portion, then rolling resistance is reduced, but belt edge loosening and other damages may occur
Solution Approach 1:
The invention changes the groove width parameter in the shoulder land portions to be 2mm or less (narrow grooves), which reduces rolling resistance by minimizing strain in the shoulder land portions. However, to prevent belt edge loosening, the groove depth is controlled to be 0.5mm or less, and the grooves are positioned at specific locations that avoid the belt edge region, thus maintaining reliability while achieving the rolling resistance reduction.
3Strength
If the outer layer of the belt extends axially outward beyond the inner layer, then structural integrity is improved, but manufacturing complexity increases
Solution Approach 1:
The invention employs an asymmetric belt structure where the outer layer extends axially outward beyond the inner layer at the shoulder regions. This asymmetric design improves structural integrity by providing additional reinforcement where the tire experiences higher stresses during cornering and steering operations, while the specific extension pattern is designed to align with the natural stress distribution in the tire.
Data Source
AI summary
A tire 2 includes a tread 4 and a belt 14 including inner and outer layers 38 and 40. Each end of the outer layer 40 is located axially inward of an end of the inner layer 38. A circumferential narrow groove 48 is formed on each shoulder land portion 46s so as to continuously extend in a circumferential direction. A groove width of the circumferential narrow groove 48 is smaller than that of a shoulder circumferential groove 44s. The circumferential narrow groove 48 is located between the shoulder circumferential groove 44s and the end of the outer layer 40 in an axial direction. A ratio of a distance in the axial direction from the shoulder circumferential groove 44s to the circumferential narrow groove 48 to a distance in the axial direction from the shoulder circumferential groove 44s to the end of the outer layer 40 is 15% to 55%.