1. Field of the Invention
The present invention relates to a pneumatic tire which can discharge a static electricity generated in a vehicle body and a tire, to a road surface, and a manufacturing method of the pneumatic tire.
2. Description of the Related Art
In recent years, there has been proposed a pneumatic tire in which a rubber member such as a tread rubber or a side wall rubber is formed by a nonconductive rubber which is blended with a silica at a high ratio, in order to reduce rolling resistance of the tire which has a close relationship with fuel consumption efficiency. However, compared to a conventional rubber member blended with carbon black at a high ratio, such a rubber member has a higher electric resistance, and therefore static charge generated on a vehicle body or a tire is prevented from being released to a road surface. As a result, a problem such as radio noises tends to occur.
Accordingly, there has been developed a pneumatic tire which can achieve electrical conduction performance by setting a conductive portion which is made of a conductive rubber blended with carbon black or the like, while forming a tread rubber and a side wall rubber by a nonconductive rubber. For example, in a pneumatic tire described in Japanese Unexamined Patent Publication No. 2008-296634, a conductive path for releasing static charge is formed by setting a band-like rubber strip which is formed by a conductive rubber and extends in a tire diametrical direction on an outer surface of a side wall rubber. Further, Japanese Unexamined Patent Publication Nos. 2004-268863 and 48-57302 describe a tire formed with a conductive path in the same manner as above.
However, in the tire in which the band-like conductive portion extending in the tire diametrical direction is provided on the outer surface of the side wall rubber as mentioned above, the conductive path is disconnected by an external damage of the side wall rubber caused by contact with a curb, which may deteriorate electrical conduction performance.
USPTO Backgrounds
USPTO Backgrounds