Tire sidewalls for heavy civil engineering vehicles

Abstract

The present invention relates to radial tires (10) for heavy civil engineering vehicles, and more particularly to their sidewalls (20), and seeks to reduce surface cracks on the sidewall of the tire on the one hand and to slow the propagation of cracks through the thickness of the sidewall on the other hand. The tire (10) comprises two sidewalls (20), each sidewall (20) consisting of a layered structure comprising at least a first and a second sidewall layer (21, 22), the Said first and second sidewall layers (21, 22) overlap axially and have a total thickness E, said first sidewall layer (21) being axially outermost has a thickness E1 and is composed of a first elastomer compound Composed of M1, the axially innermost said second sidewall layer (22) has a thickness E2 and consists of a second elastomeric compound M2. According to the invention, the thickness E1 of the first sidewall layer (21) is at most equal to 0.9 times the total thickness E, and the thickness E2 of the second sidewall layer (22) is at least equal to 3 mm or 0.1 times the total thickness E, whichever is the smallest, The first elastomeric compound M1 has a cycle number before failure NR1 equal to at least 150,000 cycles, the second elastomeric compound M2 has a cycle number NR2 at least equal to 300,000 cycles and the crack is located between the first and second elastomeric compounds. The respective velocity ratio VP1 / VP2 of propagation in the mixture (M1, M2) is at least equal to 1.25.

Description

technical field [0001] The present invention relates to radial tires intended to be fitted to heavy vehicles of the construction site type, and more particularly to the sidewalls of such tires. Background technique [0002] According to the European Tire and Rim Technical Organization or ETRTO standard, radial tires for heavy vehicles of the construction site type are intended to be fitted to rims with a diameter at least equal to 25 inches. It is usually fitted to heavy vehicles intended to carry relatively high loads and to travel on rough terrain such as stone-covered roads. [0003] Typically, since a tire has a geometry that rotates with respect to the axis of rotation, its geometry is described in a meridian plane that contains the axis of rotation of the tire. For a given meridian plane, radial, axial and circumferential directions denote directions perpendicular to the axis of rotation, parallel to the axis of rotation and perpendicular to the meridian plane, respec...

AI Technical Summary

Problems solved by technology

Crack propagation on the surface may cause degradation of aesthetic appearance that may be noticed by the user

Crack propagation radially inward through the sidewall may reach the carcass reinforcement and lead to the inner wall of the tire, causing rapid pressure loss of the tire

This pressure loss requires tire replacement

[0020] Considering the increase in mine production, the tires of construction site vehicles are subjected to increasingly higher mechanical stresses due to transport speeds or due to transported loads, which makes them more sensitive to the propagation of cracks in the sidewalls, able to lead to a degradation of the aesthetic appearance and rapid pressure loss in extreme cases

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