Tire Comprising An Improved Tread

摘要

Tire tread has a central rib (411-413) and two lateral ribs (421-422) which are separated by circumferential grooves (141-144). A first lateral rib (421) adjacent to the outer axial edge of the tread and a central rib have a first portion (4211, 4111, 4121, 4131) the axial width of which exceeds 20% of the axial width of the relevant rib made from a first rubber composition containing an elastomer and a reinforcing filler consisting predominantly of carbon black, and an axially adjacent second portion (4212, 4112, 4122, 4132) made of a second rubber composition containing an elastomer and a reinforcing filler a minority proportion of which consists of carbon black. The second rubber composition has a tan d0 value which is less than the tan d0 value of the first rubber composition, the tan d0 values being measured at a temperature of 0 C and under a stress of 0.7 MPa.

主权项

1. A tire adapted to be mounted on a mounting rim of a wheel of a vehicle and having a predetermined direction of mounting on the vehicle, comprising a tread extending between an outer axial edge and an inner axial edge, the inner axial edge being the edge intended to be mounted on the vehicle body shell side when the tire is mounted on the vehicle in the said predetermined direction of mounting, the axial distance between the outer axial edge and the inner axial edge defining an axial width L of the tread;
wherein the tread comprises, in any radial section, at least one central rib and two lateral ribs, the lateral ribs being positioned one on each side of the said at least one central rib, the ribs being separated by circumferential grooves each having two lateral walls; wherein each central rib is axially delimited by an outer boundary and by an inner boundary, each boundary being formed by a lateral wall of a circumferential groove, the inner boundary being axially closer to the inner axial edge of the tread than the inner boundary, the axial distance, on the tread surface in the new state, between the outer boundary and the inner boundary defining an axial width LC of the central rib; wherein a first lateral rib is adjacent to the outer axial edge of the tread and delimited axially by an outer boundary and an inner boundary, the outer boundary being situated, over the entire radial depth of the first lateral rib, an axial distance DE1 from the inner axial edge of the tread, the distance DE1 being greater than or equal to 0.95·L, the inner boundary being formed, at least in part, by a lateral wall of a circumferential groove, the axial distance between the outer boundary and the inner boundary defining an axial width LL1 of the first lateral rib; wherein the first lateral rib and at least one of the central ribs comprise a first portion made of a rubber composition containing at least one elastomer and at least one reinforcing filler containing a carbon black, the carbon black representing a percentage greater than or equal to 50% and less than or equal to 100% of the weight of all the reinforcing filler, and a second portion made of a rubber composition containing at least one elastomer and at least one reinforcing filler, the carbon black representing a percentage greater than or equal to 0% and less than or equal to 50% of the weight of all the reinforcing filler; wherein the first portion of the first lateral rib extends from the outer boundary of the first lateral rib axially inwards, the axial width LP1 of this portion being, over the entire radial depth of the central rib, greater than or equal to 20% of the axial width LL1 of the first lateral rib, and in which the second portion of the first lateral rib is axially adjacent to the first portion of the first lateral rib; wherein the first portion of the central rib extends axially from the outer boundary of the central rib, the axial width LPC of this portion being, over the entire radial depth of the central rib, greater than or equal to 20% of the axial width LC of the central rib, and wherein the second portion of the central rib is axially adjacent to the first portion of the central rib; wherein the rubber compositions that make up the second portion of the first lateral rib and the second portion of the central rib all have a tan d0 value which is less than the tan d0 value of the rubber compositions that form the first portion of the first lateral rib and the first portion of the central rib, where tan d0 denotes the value of tan d measured at a temperature of 0 C and under a stress of 0.7 MPa.