Resilient tires and wheels – Tires – resilient – With electrical conducting means
Reexamination Certificate
1997-10-17
2001-08-07
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
With electrical conducting means
C152S209500, C152SDIG002
Reexamination Certificate
active
06269854
ABSTRACT:
The present invention relates to a pneumatic tire improved in the rolling resistance and electrical conductivity between the tread and road surface.
In recent years, to decrease fuel consumption and exhaust gas of the automobiles, there is a strong demand for a tire having a low rolling resistance.
In Japanese patent application No. JP-A-8-120120 and U.S. Pat. No. 5,518,055, tires are disclosed, wherein the tread rubber contains silica as a reinforcing agent for the rubber instead of carbon black to decrease the rolling resistance. However, since the rubber with a silica base is very high in electrical resistance, which is almost insulation, the vehicle body is liable to have static electricity of a high voltage during running. Thus, there are problems: for example, there is a danger of sparking when the fuel lid is opened; the driving control computers become out of order; the radio becomes noisy and the like. In the disclosed tires, therefore, to provide an electrical conductivity, a thin layer made of rubber reinforced by carbon black is disposed outside the silica base tread rubber along the tread face. In this arrangement, however, as the thin outer layer is worn out, tire performance is greatly altered. Especially, when the worn states are different among the four wheels of a vehicle, handling of the vehicle during cornering and at the time of breaking and the like become unstable and very dangerous. Further, after the thin outer layer is completely worn out, the electrical resistance becomes very high and the situation returns to that wherein the primary problem is not solved.
It is therefore, an object of the present invention to provide a pneumatic tire, in which the rolling resistance is decreased, and a good electrical conductivity of the tire is maintained from beginning to end of the tread wear life.
According to one aspect of the present invention, a pneumatic tire includes
a tread portion,
a pair of sidewall portions,
a pair of bead portions with a bead core therein,
a carcass extending between the bead portions through the tread portion and the sidewall portions,
a belt disposed radially outside the carcass and inside the tread portion,
the tread portion comprising
a tread cap rubber defining the tread face and
a tread base rubber disposed radially inside the tread cap rubber,
the tread base rubber comprising
a collector part disposed radially inside the tread cap rubber and
discharge terminal parts extending radially outwardly from the collector part to the tread face, penetrating the tread cap rubber,
the tread cap rubber made of an insulation rubber material the volume resistivity of which is not less than 1×10
8
ohm cm,
the insulation rubber material compounded from
100 parts by weight of a rubber base comprising one or more materials selected from diene rubber and
copolymers of a conjugated diene monomer and
an aromatic vinyl compound,
30 to 100 parts by weight of silica, and
3 to 20 parts by weight of carbon black,
the tread base rubber made of a first electrically conductive rubber material the volume resistivity of which is not more than 1×10
7
ohm cm,
the first electrically conductive rubber material compounded from
100 parts by weight of a rubber base comprising one or more materials selected from
diene rubber and
copolymers of a conjugated diene monomer and
an aromatic vinyl compound,
0 to 50 parts by weight of silica, and
not less than 25 parts by weight of carbon black,
the hardness Hs1 of the insulation rubber material being not more than the hardness Hs2 of the first electrically conductive rubber material at a temperature of 25 degrees C., and
an electrical conductor extending from the collector part to the bead portions.
Accordingly, the rolling resistance and wet performance are improved by mainly the tread cap rubber, and a good electrical conductivity is provided by the tread base rubber. Such improved characteristics can be maintained from beginning to end of the tread wear life, without sacrificing the steering stability and the like.
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Matsuo Toshio
Nakagawa Yoshiki
Birch & Stewart Kolasch & Birch, LLP
Maki Steven D.
Sumitomo Rubber Industries Ltd.
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