Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1998-07-09
2001-04-10
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S548000, C152S556000
Reexamination Certificate
active
06213182
ABSTRACT:
The present invention relates to a pneumatic tire having a sidewall structure being capable of improving the tire weight, rolling resistance and road noise without deteriorating the maneuverability.
In general, in the sidewall portions of pneumatic tires, a sidewall rubber made of a hard rubber compound is disposed axially outside the carcass. The sidewall rubber has a minimum thickness which usually occurs around the maximum tire section width point and which is conventionally at least 2 to 4 mm. Generally speaking, the minimum thickness is at least 2 times the carcass cord diameter.
By the way, in various types of pneumatic tires, especially passenger car tires, the tire aspect ratio has a tendency to decrease, and the above-mentioned minimum thickness has a tendency to relatively increase as the aspect ratio decreases.
In such a sidewall structure, when the sidewall portion is bent with a relatively heavy tire load, the carcass cords are subjected to a large compressive force. As a cord has little resistance to a compressive force, there are problems with cord buckling, cord cut and cord separation from the surrounding rubber.
These problems can be solved by further increasing the thickness of the sidewall rubber. However, the tire weight inevitably increases. The rolling resistance is liable to increase because the energy loss in the sidewall rubber increases. Further, a noise during running is liable to increase because the transmission of vibrations from the tread potion to the bead potions is increased by the thick sidewall rubber. Further, if the sidewall rubber thickness is insufficient, the sidewall portions tend to be short of rigidity, causing a shortage of the tire stiffness, cornering power and cornering force. As a result, the steering stability is not good.
It is therefore an object of the present invention to provide a pneumatic tire, in which the tire weight, rolling resistance and noise are decreased, without decreasing the tire stiffness and deteriorating the steering stability and the like.
According to one aspect of the present invention, a pneumatic tire comprises
a tread portion,
a pair of sidewall portions,
a pair of bead portions with a bead core therein,
a carcass comprising at least one carcass ply of cords, and
a belt disposed radially outside the carcass in the tread portion and having axial edges,
the at least one carcass ply comprising an axially innermost part extending through one of the sidewall portions from one of the edges of the belt to the axial inside of one of the bead cores, and an axially outermost part extending through the sidewall potion from the edge of the belt to the axial outside of the bead core, and
the rubber thickness measured at the maximum tire section width point in the sidewall portion from the outer surface of the tire to the carcass cords in the axially outermost part being not less than 0.2 mm but not more than 1.5 times the diameter of the carcass cords.
Therefore, the neutral line between the tensile strain and compressive strain produced in a sidewall portion during bending deformation shifts axially inwards. Accordingly, the stress acting on the axially outmost carcass cords turns to a tensile stress. As a result, the carcass cords can be prevented from the cord buckling, cutting and separation. Further, as the carcass cords display their full resistance to a tensile stress, the tire stiffness is maintained or increased, although the rubber thickness is decreased. Furthermore, as the rubber thickness is decreased, the rolling resistance and noise can be improved.
REFERENCES:
patent: 4096899 (1978-06-01), Kitazawa et al.
patent: 4408648 (1983-10-01), Ohashi
patent: 4462447 (1984-07-01), Siefert et al.
patent: 4955417 (1990-09-01), Igarashi
patent: 5119857 (1992-06-01), Kukimoto
patent: 5411068 (1995-05-01), Kogure
patent: 128852 (1984-12-01), None
patent: 0652118 (1995-05-01), None
patent: 09300922 (1997-11-01), None
Hanya Masahiro
Suzuki Kazuya
Birch & Stewart Kolasch & Birch, LLP
Maki Steven D.
Sumitomo Rubber Industries Ltd.
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