Resilient tires and wheels – Tires – resilient – Anti-skid devices
Patent
1997-06-05
1998-09-08
Maki, Steven D.
Resilient tires and wheels
Tires, resilient
Anti-skid devices
152DIG3, B60C 1112, B60C10100, B60C10300, B60C10500
Patent
active
058040005
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a pneumatic radial tire which can drastically improve noise performance while securing excellent wet performance (water draining performance) by two thick main grooves.
BACKGROUND ART
As tires for passenger cars have come to have a low profile in recent years, the ground contact width of the tread surface tends to become greater. However, when the ground contact width of the tread surface becomes great, water draining performance drops. Therefore, a tread pattern so designed as to put particular emphasis on water draining performance has been employed for the low-profile tires. The tread pattern having such high water draining performance generally has a block pattern comprising a plurality of straight main grooves extending on the tread surface in a tire circumferential direction and sub-grooves so extending in a tire width-wise direction as to cross these straight main grooves.
In the block pattern having such a large number of straight main grooves and sub-grooves, however, the pattern noise increases remarkably, and it is extremely difficult to simultaneously secure wet performance and to reduce the pattern noise. Particularly because the grade of the cars has become higher and higher in recent years, the market demand for the reduction of a high frequency pattern noise in the range of 800 to 1,000 Hz has become stronger, but the conventional block patterns cannot reduce such pattern noises.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a pneumatic radial tire which can drastically improve noise performance, and more particularly, can reduce a high frequency pattern noise in the range of 800 to 1,000 Hz, while securing satisfactory wet performance.
The pneumatic radial tire according to the present invention for accomplishing the object described above is characterized in that one each wide main groove having a groove width of at least 10 mm is disposed on each side of a tire equator on the tread surface, the area interposed between these right and left two main grooves is used as ribs, two kinds of large and small sub-grooves having mutually different groove widths and extending from these main grooves toward the ground contact end in a tire width-wise direction are alternately disposed throughout one circumference of the tire in both outside areas of the main grooves, sub-main grooves extending in a tire circumferential direction are disposed between the main grooves and the ground contact end in the tire width-wise direction, and the groove width a of the main grooves, the distance b from the tire equator to the groove center of the main grooves, the ground contact half width W of the tread surface, the groove width cw and the groove depth cd of the sub-groove having a smaller groove width, the groove width dw and the groove depth dd of the sub-grooves having a greater groove width, and the groove depth ed of the sub-main grooves satisfy the following relation:
In the present invention, the term "main groove" represents those grooves which have a groove width of at least 5 mm. As such main grooves, the present invention disposes only two main grooves having a groove width a of at least 10 mm and having a width satisfying the relation described above with respect to the ground contact half width W of the tread surface in such a manner as to interpose the tire equator between them, but does not dispose any other main grooves, in order to improve wet performance. The area interposed between these two main grooves is used as ribs having high rigidity so as to increase the ground contact pressure of the center area of the tread and to secure maneuvering stability during driving on a wet road surface.
On the other hand, two kinds of sub-grooves having mutually different groove widths extending from the main grooves to the ground contact end in the tire width-wise direction are alternately disposed throughout one circumference of the tire so as to improve wet performance and to disperse the noise (pattern noise). Further, th
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Shirai Kenichi
Suzuki Toshihiko
Maki Steven D.
The Yokohama Rubber Co. Ltd.
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