Tire for Heavy Vehicles Comprising Layers of Peripheral Reinforcement Elements
A tire with radial carcass reinforcement comprising a crown reinforcement formed of at least two working crown layers, itself radially capped by a tread, the said tread being connected to two beads by two sidewalls, and the crown reinforcement comprising at least one layer of circumferential reinforcing elements. The reinforcing elements of the layer of circumferential reinforcing elements are stranded cords exhibiting, between their initial state and their state when extracted from the tire, a reduction greater than 15 GPa and preferably greater than 20 GPa in the maximum tangent modulus.
1 . A tire with radial carcass reinforcement comprising a crown reinforcement formed of at least two working crown layers of inextensible reinforcing elements, which are crossed from one ply to the other making angles of between 10° and 45° with the circumferential direction, itself radially capped by a tread, said tread being connected to two beads by two sidewalls, the crown reinforcement comprising at least one layer of circumferential reinforcing elements, wherein the reinforcing elements of the layer of circumferential reinforcing elements are stranded cords exhibiting, between their initial state and their state when extracted from the tire, a reduction greater than 15 GPa and preferably greater than 20 GPa in the maximum tangent modulus.
2 . The tire according to claim 1 , wherein the reinforcing elements of at least one layer of circumferential reinforcing elements are metal reinforcing elements having a secant modulus at 0.7% elongation comprised between 10 and 120 GPa and a maximum tangent modulus of less than 150 GPa.
3 . The tire according to claim 2 , wherein the secant modulus of the reinforcing elements at 0.7% elongation is less than 100 GPa, preferably greater than 20 GPa and more preferably still, comprised between 30 and 90 GPa.
4 . The tire according to claim 2 , wherein the maximum tangent modulus of the reinforcing elements is less than 130 GPa and preferably less than 120 GPa.
5 . The tire according to claim 1 , wherein the reinforcing elements of the said layer of circumferential reinforcing elements are metal reinforcing elements exhibiting a tensile stress/relative elongation curve that has shallow gradients for small elongations and a substantially constant and steep gradient for greater elongations.
6 . The tire according to characterized in that claim 1 , wherein the ratio of the distance between the extreme wear surface and the reinforcing elements of the layer of circumferential reinforcing elements in the circumferential median plane to the distance between the extreme wear surface and the reinforcing elements of the layer of circumferential reinforcing elements at the ends of the said layer of circumferential reinforcing elements is comprised between 0.95 and 1.05.
7 . The tire according to claim 1 , wherein the axially widest working crown layer is radially on the inside of the other working crown layers.
8 . The tire according to claim 1 , wherein the difference between the axial width of the axially widest working crown layer and the axial width of the axially narrowest working crown layer is comprised between 10 and 30 mm.
9 . The tire according to claim 1 , wherein the axial width of at least one layer of circumferential reinforcing elements is less than the axial width of the axially widest working crown layer.
10 . The tire according to claim 1 , wherein at least one layer of circumferential reinforcing elements is laid radially between two working crown layers.
11 . The tire according to claim 10 , wherein the axial widths of the working crown layers radially adjacent to the layer of circumferential reinforcing elements are greater than the axial width of the said layer of circumferential reinforcing elements.
12 . The tire according to claim 11 , wherein the working crown layers adjacent to the layer of circumferential reinforcing elements are, on each side of the equatorial plane and in the immediate axial continuation of the layer of circumferential reinforcing elements, coupled over an axial width and then decoupled by profiled elements of rubber compound at least over the remainder of the width common to the said two working layers.
13 . The tire according to claim 1 , wherein the crown reinforcement is supplemented radially on the outside by at least one additional ply, known as a protective ply, of reinforcing elements that are said to be elastic, which are directed at an angle comprised between 10° and 45° with respect to the circumferential direction and in the same direction as the angle formed by the inextensible elements of the working ply radially adjacent to it.
14 . The tire according to claim 1 , wherein the crown reinforcement further comprises a triangulation layer formed of metal reinforcing elements that make angles greater than 60° with the circumferential direction.