Shoulder Rib Arc Geometry for Tire Wear and Stability
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Solution Overview
Problem
Heavy-duty tires for trucks and buses experience excessive wear and reduced steering stability due to uneven circumferential lengths of shoulder ribs, leading to increased contact pressure and slipping, which compromises cornering power and wear resistance.
Innovation Solution
The tire design features a tread with a crown rib and shoulder rib, where the outer surface of the shoulder rib is shaped as a second arc with a specific chord length and distance from its center, maintaining a ratio between 0.03 and 0.05, to reduce wear and prevent warping during cornering, thereby enhancing steering stability without compromising wear resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer surface of the shoulder rib is formed into an arc with a large radius to reduce circumferential length difference, then wear resistance is improved, but the outer surface warps during cornering causing high contact pressure at ends and low contact pressure at center, reducing cornering power and steering stability
Solution Approach 1:
The patent changes the geometric parameters of the shoulder rib outer surface by specifying a precise arc shape with a radius of curvature between 150mm to 300mm and a specific arc height to chord length ratio (0.03-0.05). This parameter optimization balances the reduction of circumferential length difference (improving wear resistance) while preventing excessive warping during cornering (maintaining steering stability and cornering power).
Solution Approach 2:
The patent applies curvature by forming the outer surface of the shoulder rib as a circular arc rather than a straight line or large-radius arc. This specific curved shape reduces the circumferential length difference between inner and outer portions of the shoulder rib, improving wear resistance, while the controlled curvature radius prevents excessive warping during cornering operations.
2Ease of operation
If a large steering angle is used to improve cornering power, then steering responsiveness is improved, but the region of the tire that slips relative to the road surface increases, accelerating wear
Solution Approach 1:
The patent optimizes the arc shape parameters of the shoulder rib to achieve a balance where adequate cornering power is obtained without requiring excessive steering angles. The specific radius of curvature (150-300mm) and arc height to chord length ratio (0.03-0.05) allow the tire to maintain better contact with the road surface during cornering, reducing slip-induced wear while preserving steering responsiveness.
Data Source
AI summary
In a tire 2 according to the present invention, an outer surface 52 of a crown rib 48e and an outer surface 54 of a shoulder rib 48s form a part of a tread surface 28. On a cross-section of the tire 2 along a plane that includes a rotation axis of the tire 2, an outline of the outer surface 52 of the crown rib 48e is represented as a first arc. A center of a circle to which the first arc belongs is disposed on the equator plane. An outline of the outer surface 54 of the shoulder rib 48s is represented as a second arc. A ratio of a distance from a center of a chord of the second arc to the second arc relative to a length of the chord of the second arc is not less than 0.03 and not greater than 0.05.