Pneumatic tire
View Patent ↗A pneumatic tire includes: a rim cushion rubber disposed in a bead portion where the bead portion and a rim are in contact with each other; an electrically conductive rubber disposed in the rim cushion rubber, the electrically conductive rubber having an electrical resistance value lower than that of the rim cushion rubber, and including a first end exposed on an outer surface of the rim cushion rubber in contact with the rim, and a second end disposed in contact with a tire component adjacent to the rim cushion rubber; and an ground tread rubber disposed in a tread portion passing through a cap tread rubber and an undertread rubber of the tread portion, the ground tread rubber having an electrical resistance value lower than that of the cap tread rubber.
1. A pneumatic tire, comprising:
a rim cushion rubber disposed in a bead portion where the bead portion and a rim are in contact with each other when the pneumatic tire is mounted on the rim;
an electrically conductive rubber disposed in the rim cushion rubber, the electrically conductive rubber having an electrical resistance value lower than that of the rim cushion rubber, and including
a first end exposed on an outer surface of the rim cushion rubber in contact with the rim, and
a second end disposed in contact with a tire component adjacent to the rim cushion rubber; and
a ground tread rubber disposed in a tread portion passing through a cap tread rubber and an undertread rubber of the tread portion, the ground tread rubber having an electrical resistance value lower than that of the cap tread rubber, and including
a first end exposed on a tread surface, and
a second end disposed in contact with a belt layer or a belt reinforcing layer,
in a meridian cross-section, a width of the second end in a thickness direction being greater than a width of the first end; wherein
the cap tread rubber has a loss tangent tan δ at 60° C. of 0.20 or greater, and the undertread rubber has a loss tangent tan δ at 60° C. of 0.20 or less, and
the electrically conductive rubber has a greater loss tangent tan δ at 60° C. than that of the ground tread rubber.
2. The pneumatic tire according to claim 1 , wherein the electrically conductive rubber has a greater value than that of the ground tread rubber for: carbon black volume fraction×dibutyl phthalate oil absorption number/100.
3. The pneumatic tire according to claim 2 , wherein the ground tread rubber is disposed on opposite sides of a tire equatorial plane in a tire width direction in a range starting at the tire equatorial plane which is from 0% to 50% of a ground contact width.
4. The pneumatic tire according to claim 1 , wherein the ground tread rubber is disposed on opposite sides of a tire equatorial plane in a tire width direction in a range starting at the tire equatorial plane which is from 0% to 50% of a ground contact width.