US 12,227,029 B2
Pneumatic tire
Hiroshi Fujii, Hiratsuka (JP)
Assigned to The Yokohama Rubber Co., LTD., Tokyo (JP)
Appl. No. 17/055,481
Filed by The Yokohama Rubber Co., LTD., Tokyo (JP)
PCT Filed Dec. 25, 2018, PCT No. PCT/JP2018/047665
§ 371(c)(1), (2) Date Nov. 13, 2020,
PCT Pub. No. WO2019/220680, PCT Pub. Date Nov. 21, 2019.
Claims priority of application No. 2018-093906 (JP), filed on May 15, 2018.
Prior Publication US 2021/0221177 A1, Jul. 22, 2021
Int. Cl. B60C 11/00 (2006.01); B60C 11/03 (2006.01); B60C 11/04 (2006.01)
CPC B60C 11/005 (2013.01) [B60C 11/0008 (2013.01); B60C 11/033 (2013.01); B60C 11/04 (2013.01); B60C 2011/0025 (2013.01); B60C 2011/0033 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A pneumatic tire, comprising:
a carcass including at least one carcass ply;
a belt including a belt layer including cords, the belt being disposed on an outer side in a tire radial direction of the carcass; and
a tread rubber disposed on the outer side in the tire radial direction of the belt, the tread rubber constituting a portion of a tread portion, at least one circumferential main groove being formed in the tread portion, a sum of groove widths of the at least one circumferential main groove being 15% or greater of a ground contact width,
the tread rubber including an undertread rubber and a cap tread rubber formed on the outer side in the tire radial direction of the undertread rubber, the cap tread rubber being formed from rubber having a hardness higher than that of the undertread rubber,
in a state in which the pneumatic tire is mounted on a specified rim, inflated to 92% of a specified internal pressure, and loaded with a load of 75% of a maximum load capacity, when two regions at a center in a tire width direction obtained by dividing a tire ground contact width into four regions in a tire meridian cross-sectional view are a center region and remaining two regions are shoulder regions, an average thickness of the undertread rubber in the center region being greater than that of each shoulder region and the average thickness of the undertread rubber on a tire equatorial plane is greater than that of any location of each shoulder region,
a loss tangent tan δ at 60° C. of the cap tread rubber being higher than that of the undertread rubber,
in a region of the center region, located closer to an inner side in the tire radial direction than an imaginary line that extends in parallel to a tire profile line at a position located 1.6 mm on the outer side in the tire radial direction from a groove bottom of the circumferential main groove, a ratio CAI/UAI of a cross-sectional area CAI of the cap tread rubber to a cross-sectional area UAI of the undertread rubber being not less than 0.15 and not greater than 0.50, and
a maximum thickness of the undertread rubber in each of the shoulder regions being less than a maximum thickness of the undertread rubber in the center region;
wherein axially outer boundaries of the center region are defined on an axially inner side of axially outermost circumferential main grooves.
 
12. A pneumatic tire, comprising:
a carcass including at least one carcass ply;
a belt including a belt layer including cords, the belt being disposed on an outer side in a tire radial direction of the carcass; and
a tread rubber disposed on the outer side in the tire radial direction of the belt, the tread rubber constituting a portion of a tread portion, at least one circumferential main groove being formed in the tread portion, a sum of groove widths of the at least one circumferential main groove being 15% or greater of a ground contact width,
the tread rubber including an undertread rubber and a cap tread rubber formed on the outer side in the tire radial direction of the undertread rubber, the cap tread rubber being formed from rubber having a hardness higher than that of the undertread rubber,
in a state in which the pneumatic tire is mounted on a specified rim, inflated to 92% of a specified internal pressure, and loaded with a load of 75% of a maximum load capacity, when two regions at a center in a tire width direction obtained by dividing a tire ground contact width into four regions in a tire meridian cross-sectional view are a center region and remaining two regions are shoulder regions, an average thickness of the undertread rubber in the center region being greater than that of each shoulder region,
a loss tangent tan δ at 60° C. of the cap tread rubber being higher than that of the undertread rubber,
in a region of the center region, located closer to an inner side in the tire radial direction than an imaginary line that extends in parallel to a tire profile line at a position located 1.6 mm on the outer side in the tire radial direction from a groove bottom of the circumferential main groove, a ratio CAI/UAI of a cross-sectional area CAI of the cap tread rubber to a cross-sectional area UAI of the undertread rubber being not less than 0.51 and not greater than 0.95, and
a maximum thickness of the undertread rubber in each of the shoulder regions being less than a maximum thickness of the undertread rubber in the center region.
 
13. A pneumatic tire, comprising:
a carcass including at least one carcass ply;
a belt including a belt layer including cords, the belt being disposed on an outer side in a tire radial direction of the carcass; and
a tread rubber disposed on the outer side in the tire radial direction of the belt, the tread rubber constituting a portion of a tread portion, at least one circumferential main groove being formed in the tread portion, a sum of groove widths of the at least one circumferential main groove being 15% or greater of a ground contact width,
the tread rubber including an undertread rubber and a cap tread rubber formed on the outer side in the tire radial direction of the undertread rubber, the cap tread rubber being formed from rubber having a hardness higher than that of the undertread rubber,
in a state in which the pneumatic tire is mounted on a specified rim, inflated to 92% of a specified internal pressure, and loaded with a load of 75% of a maximum load capacity, when two regions at a center in a tire width direction obtained by dividing a tire ground contact width into four regions in a tire meridian cross-sectional view are a center region and remaining two regions are shoulder regions, an average thickness of the undertread rubber in the center region being greater than that of each shoulder region,
a loss tangent tan δ at 60° C. of the cap tread rubber being higher than that of the undertread rubber,
in a region of the center region, located closer to an inner side in the tire radial direction than an imaginary line that extends in parallel to a tire profile line at a position located 1.6 mm on the outer side in the tire radial direction from a groove bottom of the circumferential main groove, a ratio CAI/UAI of a cross-sectional area CAI of the cap tread rubber to a cross-sectional area UAI of the undertread rubber being not less than 0.15 and not greater than 0.95, and
a maximum thickness of the undertread rubber in each of the shoulder regions being less than a maximum thickness of the undertread rubber in the center region; wherein the undertread rubber extends to and forms a part of an outer surface of a sidewall of the pneumatic tire.