Pneumatic tire and method of making tire

A vulcanized pneumatic tire comprising;

• a tread portion including a surface rubber layer, which has a specific resistance of 108Ω·cm or more after curing by vulcanization, said surface rubber layer provided at least at a tire radial direction outer side region of a tire tread portion, and portions of the tread portion being replaced by plural conductive rubber members formed from a rubber composition whose specific resistance is 106Ω·cm or less, a layer radially beneath said tread portion,
• wherein each of the conductive rubber members has the shape of a column having a small diameter, and is provided from a tire radial direction outer side surface of the tread portion to a tire radial direction inner surface of the tread portion, and is electrically connected to said layer which is beneath the tread portion, and exposed portions of the respective conductive rubber members are disposed at separate locations in the tire radial direction outer side surface of the surface rubber layer, wherein the tread portion has at least a two layer structure comprising the surface rubber layer which is disposed in an outer portion of the tread portion in the radial direction of said tire and an inner rubber layer which is disposed in an inner portion of the tread portion in the radial direction of said tire and has a specific resistance of 106Ω·cm or less after curing by vulcanization, such that the inner rubber layer has a relatively large specific resistance in the range of 106Ω·cm or less after curing by vulcanization, the conductive rubber members have better conductivity than the inner rubber layer, and each conductive rubber member extends through the surface rubber layer and the inner rubber layer with substantially the same thickness as the total thickness of the surface rubber layer and the inner rubber layer.

A vulcanized pneumatic tire comprising:

• a tread portion including surface rubber layer, which has a specific resistance of 108Ω·cm or more after curing by vulcanization, said surface rubber layer provided at least at a tire radial direction outer side region of the tread portion, and at least one portion of the tread portion being replaced by at least one conductive rubber member formed from a rubber composition whose specific resistance is 106Ω·cm or less, a layer radially beneath said tread portion
• wherein each conductive rubber member is disposed from a tire radial direction outer side surface of the tread portion to a tire radial direction inner surface of the tread portion and is electrically connected to said layer which is beneath the tread portion, and elongated exposed portions of each conductive rubber member at the tire radial direction outer side surface of the surface rubber layer are formed such that a longitudinal direction of the elongated exposed portions extends along a circumferential direction of the tire and are aligned discontinuously along the circumferential direction of the tire, and each conductive rubber member is formed such that a continuous lower portion thereof are electrically connected along the circumferential direction of the tire at a tire radial direction inner side region of the tread portion, wherein the tread portion has at least a two layer structure comprising the surface rubber layer which is disposed in an outer portion of the tread portion in the radial direction of said tire and an inner rubber layer which is disposed in an inner portion of the tread portion in the radial direction of said tire and has a specific resistance of 106Ω·cm or less after curing by vulcanization, such that the inner rubber layer has a relatively large specific resistance in the range of 106 Ω·cm or less after curing by vulcanization, the conductive rubber members have better conductivity than the inner rubber layer, and each conductive rubber member extends through the surface rubber layer and the inner rubber layer with substantially the same thickness as the total thickness of the surface rubber layer and the inner rubber layer.

In a method of manufacturing a vulcanized tire having a tread portion and a layer radially beneath the tread portion wherein the tread includes a surface rubber layer, the improvement comprising:

• forming cavities in the tread portion such that the cavities are provided discontinuously along the tire circumferential direction, wherein each cavity extends from a tire radial direction outer side surface of the tread portion to a tire radial direction inner surface of the tread portion;
• pouring and filling, into the cavities, a rubber cement;
• and vulcanizing the tread portion such that the rubber cement forms a plurality of conductive rubber members which are electrically connected to the layer beneath the tread portion, wherein the vulcanized surface rubber layer has a specific resistance of 108Ω·cm or more and the vulcanized conductive rubber members have a specific resistance of 106Ω·cm or less wherein the tread portion has at least a two layer structure comprising the surface rubber layer which is disposed in an outer portion of the tread portion in the radial direction of said tire and an inner rubber layer which is disposed in an inner portion of the tread portion in the radial direction of said tire and has a specific resistance of 106Ω·cm or less after curing by vulcanization, such that the inner rubber layer has a relatively large specific resistance in the range of 106Ω·cm or less after curing by vulcanization, the conductive rubber members have better conductivity than the inner rubber layer, and each conductive rubber member extends through the surface rubber layer and the inner rubber layer with substantially the same thickness as the total thickness of the surface rubber layer and the inner rubber layer.