US 12,251,966 B2
Run-flat tire
Shunya Harada, Hiratsuka (JP)
Assigned to The Yokohama Rubber Co., LTD., Tokyo (JP)
Appl. No. 16/981,683
Filed by The Yokohama Rubber Co., LTD., Tokyo (JP)
PCT Filed Feb. 15, 2019, PCT No. PCT/JP2019/005713
§ 371(c)(1), (2) Date Sep. 16, 2020,
PCT Pub. No. WO2019/176445, PCT Pub. Date Sep. 19, 2019.
Claims priority of application No. 2018-050172 (JP), filed on Mar. 16, 2018.
Prior Publication US 2021/0031562 A1, Feb. 4, 2021
Int. Cl. B60C 11/00 (2006.01); B60C 3/04 (2006.01); B60C 17/00 (2006.01); B60C 11/03 (2006.01)
CPC B60C 11/005 (2013.01) [B60C 3/04 (2013.01); B60C 17/0009 (2013.01); B60C 2011/0033 (2013.01); B60C 2011/0355 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A run-flat tire, comprising:
a reinforcing rubber layer having a roughly crescent-shaped meridian cross-section and being disposed in sidewall portions at both sides in a tire width direction,
a tread portion being provided formed of a tread rubber that comprises a cap tread rubber and an undertread rubber, the undertread rubber being disposed on an inner side of the cap tread rubber in a tire radial direction and having a higher hardness than the cap tread rubber, and
in a meridian cross-section, a gauge of the undertread rubber on a shoulder land portion on an outer side of an outermost main groove located furthest outward in the tire width direction being thicker than a gauge of the undertread rubber of a center land portion closest to a tire equatorial plane, wherein
a cross-sectional profile of the cap tread rubber is symmetrical across the tire equatorial plane and a cross-sectional profile of the undertread rubber is symmetrical across the tire equatorial plane,
a ratio Ga_ce/GD of a gauge Ga_ce of the undertread rubber at the center land portion to a groove depth GD of the outermost main groove is from 0.2 to 0.4,
a ratio Ga_sh/GD of a gauge Ga_sh of the undertread rubber at the shoulder land portion to the groove depth GD of the outermost main groove is from 0.4 to 0.6,
the gauge Ga_ce of the undertread rubber at the center land portion and the gauge Ga_sh of the undertread rubber at the shoulder land portion have a relationship Ga_ce<Ga_sh,
the gauge of the undertread rubber gradually decreases from the outermost main groove toward the tire equatorial plane,
a ratio W1/Wg of a width W1 in the tire width direction of a portion of the undertread rubber where the gauge of the undertread rubber gradually decreases from the outermost main groove toward the tire equatorial plane to a groove width Wg of the outermost main groove is from 1.0 to 3.0, and
the gauges of the undertread rubber Ga_ce and Ga_sh are determined by measuring groove bottoms of the outermost main groove and other main grooves using an imaginary line as a reference, and finding an average gauge within the land portion or a block, excluding the portion of the outermost main groove and the other main grooves.