Patent ID: 7461679
Filing Date: 2008-12-09
Classification: B60C,Y10T

Abstract:
1. A heavy duty tire comprising: a tread portion; a pair of sidewall portions; a pair of bead portion each with a bead core; a carcass ply which extends between the bead portions through the tread portion and the sidewall portions and is turned up around the bead cores from the axially inward to the axially outward of the tire to form a pair of turnup portions and a carcass main portion therebetween, each of the turnup portions including a radially inner main part which is curved along the axially inner surface, radially inner surface and axially outer surface of the bead core, and a radially outer sub-part which extends axially inwardly from the curved radially inner main part toward the carcass main portion in a region near the radially outer surface of the bead core with a gradient with respect to the radially outer surface of the bead core; a bead reinforcing layer disposed in each of the bead portions, and including a curved portion which passes radially inward of the carcass turnup portion, an axially outer portion which is located on the axially outer side of the curved portion and extends radially outwardly from the curved portion, separating from the carcass turnup portion, with slightly slanting toward the axially outward of the tire, and an axially inner portion which is located on the axially inner side of the curved portion and extends radially outwardly from the curved portion along the axially inner surface of the carcass main portion, wherein the radial height of the axially outer portion of the bead reinforcing layer from the radially outer end thereof to a bead base line is from 25 to 40 mm, and the distance between the axially outer portion of the bead reinforcing layer and a point on the carcass main portion apart from the radially outer surface of the bead core by a distance of 5 mm is from 14 to 20 mm; an axially inner rubber disposed between the carcass main portion and the axially outer portion of the bead reinforcing layer in each of the bead portions, the axially inner rubber including a portion made of a first low modulus rubber having a complex elastic modulus E* wherein said portion made of the first low modulus rubber extends radially outwardly beyond the radially outer end of the axially outer portion, the thickness Ti of the axially inner rubber measured along a first base line drawn from the radially outer end of the axially outer portion of the bead reinforcing layer at a right angle with respect to the carcass main portion is from 7.0 to 13.0 mm, and the ratio ti/Ti of a thickness ti of the first low modulus rubber portion measured along the first base line to the thickness Ti is at least 0.9; and an axially outer rubber which is located between the axially outer portion of the bead reinforcing layer and the axially outer surface of the tire, the axially outer rubber including an axially inner layer made of a second low modulus rubber having a complex elastic modulus E* an axially outer layer made of a higher modulus rubber having a complex elastic modulus E* wherein the axially inner layer extends radially outwardly beyond the radially outer end of the axially outer portion, whereby the radially outer end of the axially outer portion is sandwiched between the portion made of the first low modulus rubber and the axially inner layer made of the second low modulus rubber, the axially outer layer extends radially outwardly from the bead bottom so as to cover the axially outer surface of the axially inner layer, the thickness To of the axially outer rubber measured along a second base line drawn from the radially outer end of the axially outer portion of the bead reinforcing layer at a right angle with respect to the axially outer surface of the tire is from 5.0 to 11.0 mm, and the ratio to/To of a thickness to of the axially inner layer measured along the second base line to said thickness To is at least 0.4.