Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2001-07-02
2004-09-28
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209800, C152S209180, C152S209220, C152SDIG003
Reexamination Certificate
active
06796347
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pneumatic tire and, more particularly, to a pneumatic tire which is provided with a plurality of substantially quadrilateral land portions arranged on a tread and defined by two sets of main grooves of different angles with respect to a tire equatorial plane.
BACKGROUND ART
In the prior art, there is a pneumatic tire which is provided with a plurality of substantially quadrilateral land portions arranged on a tread and defined by two sets of main grooves of different angles with respect to a tire equatorial plane.
In this pneumatic tire, it is conceivable to form auxiliary grooves such as sipes in the land portions so as to improve the wet performance.
The auxiliary grooves such as the sipes are formed in the land portions, so that the edge factors are increased to improve the wet performance, but the rigidity of the land portions may be degraded and the deterioration of the dry performance may be caused.
In
FIG. 13A
, for example, a pair of main grooves
100
extending in the circumferential directions (i.e., in the directions as indicated by arrows A and B) and a pair of main grooves
102
intersecting the main grooves
100
define land portions
104
having generally parallelogram shapes. When the land portions
104
are halved in the tire circumferential directions by forming auxiliary grooves
106
in parallel with the main grooves
102
, there arises a problem that the rigidity of the land portions
104
in the tire circumferential directions decreases.
On the other hand, when the auxiliary grooves
106
are formed in the generally parallelogram land portions
104
along the longer diagonal lines, as shown in
FIG. 13B
, there are formed two small land portions each of which has a substantially slender triangular shape. This formation raises a problem that the rigidity of the land portions
104
in the directions (i.e., in the directions of arrow C) perpendicular to the longitudinal direction of the auxiliary grooves
106
seriously decreases.
Considering the aforementioned facts, the invention has an object to provide a pneumatic tire which can improve the wet performance while keeping the rigidity of the land portions.
MEANS FOR SOLVING THE PROBLEMS
According to a first aspect of the invention, there is provided a pneumatic tire, in which a plurality of substantially quadrilateral land portions are arranged on a tread and defined by two sets of main grooves having different angles with respect to a tire equatorial plane and in which auxiliary grooves are arranged in said land portions, characterized: in that said land portions have diagonal lines of different lengths; and in that said auxiliary grooves are arranged at the central portions of said land portions and substantially along the shorter diagonal lines.
According to a second aspect of the invention, a pneumatic tire is characterized in that said auxiliary grooves are not opened in said main grooves.
According to a third aspect of the invention, a pneumatic tire is characterized in that said auxiliary groove have a length of no less than 30% but less than 70% of the length of said shorter diagonal lines.
According to a fourth aspect of the invention, a pneumatic tire is characterized in that the angle formed between said shorter diagonal lines and said auxiliary grooves is within ±20 degrees.
According to a fifth aspect of the invention, a pneumatic tire is characterized in that said auxiliary grooves are arranged substantially on said shorter diagonal lines.
According to a sixth aspect of the invention, a pneumatic tire is characterized in that said auxiliary grooves have a depth of no less than 30% of the depth of said main grooves.
According to a seventh aspect of the invention, a pneumatic tire is characterized in that end portion grooves opened in said main grooves are connected to the end portions of said auxiliary grooves.
According to an eighth aspect of the invention, a pneumatic tire is characterized in that said end portion grooves are opened in said main grooves which are the closet to the end portions auxiliary grooves.
According to a ninth aspect of the invention, a pneumatic tire is characterized in that the angle formed between said end portion grooves and said auxiliary grooves is obtuse.
According to tenth aspect of the invention, a pneumatic tire is characterized in that the angle formed between said end portion grooves and the neighborhood main grooves, in which said end portion grooves are not opened, is no more than 30 degrees.
According to an eleventh aspect of the invention, a pneumatic tire is characterized: in that said end portion grooves are formed on the two end portions of said auxiliary grooves; and in that one auxiliary groove is opened in one of the main grooves opposed to each other whereas the other auxiliary groove is opened in the other of the main opposed to each other.
According to a twelfth aspect of the invention, a pneumatic tire is characterized in that said end portion grooves are as deep as or shallower than said auxiliary grooves.
According to a thirteenth aspect of the invention, a pneumatic tire is characterized in that the depth of said end portion grooves is no less than 10% and no more than 30% of the depth of said main grooves.
According to a fourteenth aspect of the invention, a pneumatic tire is characterized in that the shortest distance between the end portions of said auxiliary grooves and said main grooves which are the closest to said end portions is no less than 15% of the length of said shorter diagonal lines.
According to a fifteenth aspect of the invention, there is provided a pneumatic tire, in which a plurality of substantially quadrilateral land portions are arranged on a tread and defined by two sets of main grooves having different angles with respect to a tire equatorial plane and in which auxiliary grooves are arranged in said land portions, characterized: in that said land portion has an auxiliary groove extending throughout from one side to another side; and in that said auxiliary groove includes: a central auxiliary groove portion inclined in the same direction as that of the shorter diagonal line of the land portion and arranged at the central portion of said land portion; end portion auxiliary groove portions extending in directions different from that of said central auxiliary groove portion and opened in the closest main grooves; and connection portions for smoothly joining said central auxiliary groove portion and said end portion auxiliary groove portions.
According to a sixteenth aspect of the invention, a pneumatic tire is characterized in that said connection portions are formed into arcuate shapes having a radius of curvature of no less than 3 mm and no more than 10 mm.
According to a seventeenth aspect of the invention, a pneumatic tire is characterized in that said central auxiliary groove portion has a length of less than 70% of the length of said shorter diagonal line.
According to an eighteenth aspect of the invention, a pneumatic tire is characterized in that the angle formed between said shorter diagonal line and said central auxiliary groove portion is within ±20 degrees.
According to a nineteenth aspect of the invention, a pneumatic tire is characterized in that said central auxiliary groove portion is arranged substantially on said shorter diagonal line.
According to a twentieth aspect of the invention, a pneumatic tire is characterized in that said central auxiliary groove portion has a depth of no less than 30% of the depth of said main grooves.
According to a twenty-first aspect of the invention, a pneumatic tire is characterized in that the angle formed between said end portion auxiliary groove portions and the neighborhood main grooves, in which said end portion auxiliary groove portions are not opened, is no more than 30 degrees.
According to a twenty-second aspect of the invention, a pneumatic tire is characterized in that said end portion auxiliary groove portions are as deep as or shallower than said central auxiliary groove portion.
According to
Fukunaga Takayuki
Ishiyama Makoto
Matsuzaki Jun
Bridgestone Corporation
Maki Steven D.
Sughrue & Mion, PLLC
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