Pneumatic tire having an improved belt structure

摘要

A pneumatic tire having a belt structure includes: a first belt layer; a second belt layer in a radially inner position with respect to the first belt layer, a third belt layer in a radially inner position with respect to the first and second belt layers, each belt layer including a plurality of elongated reinforcing elements disposed at a first, second and third belt angle respectively. The first and second belt angles have an absolute value of 15 to 40 degrees; the second angle is of opposite sign with respect to the first belt angle; and the third belt angle has an absolute value of 40 to 90 degrees and is of opposite sign with respect to the second belt angle. The belt structure also includes a zero degree belt layer placed in a radially outer position with repeat to the first belt layer including elongated reinforcing elements arranged such as to form a belt angle which is substantially zero.

主权项

1. A four-wheeled vehicle comprising a front axle and a rear axle, the front axle being equipped with a first tire and a second tire, the rear axle being equipped with a third and a fourth tire, wherein each of said first to fourth tires comprises:
a toroidal carcass structure comprising at least one carcass ply, said carcass structure comprising a crown portion and two axially opposite side portions, each side portion being associated with a respective bead structure for mounting the tire on a rim; a tread band in a position radially external to the carcass structure; a belt structure interposed between the carcass structure and the tread band; a pair of sidewalls applied to the carcass structure in axially opposite positions, wherein said belt structure comprises: a first belt layer comprising a plurality of substantially parallel elongated metal reinforcing elements disposed at a first belt angle; a second belt layer in a radially inner position with respect to said first belt layer, comprising a plurality of substantially parallel elongated metal reinforcing elements disposed at a second belt angle of opposite sign with respect to said first belt angle; wherein said first and second belt angles have an absolute value of 15 to 40 degrees; a zero degree belt layer placed in a radially outer position with respect to the first belt layer, said zero degree belt layer comprising elongated reinforcing elements which are substantially parallel to each other and arranged such as to form a belt angle which is substantially zero; and a third belt layer in a radially inner position with respect to said first and second belt layers, said third belt layer comprising a plurality of substantially parallel elongated reinforcing elements disposed at a third belt angle; wherein said third belt angle is of opposite sign with respect to said second belt angle; wherein the third belt angle of the first tire and of the second tire has an absolute value of 50 to 75 degrees; wherein the third belt angle of the third tire and of the fourth tire has an absolute value of 75 to 90 degrees; and wherein the absolute value of the third belt angle of the third and fourth tires is larger than the absolute value of the third belt angle of the first and second tires by at least five degrees.