Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
1998-11-19
2001-11-13
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152SDIG003, C152S903000
Reexamination Certificate
active
06315018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pneumatic tire in which deterioration in wet performance of the tire due to wear of the tire can be suppressed.
2. Description of the Related Art
Conventionally, in pneumatic radial tires, especially tires for passenger cars, in order to improve the ground-contact performance, the wet performance, and wear resistance, and in order to reduce noise, a method in which sipes are provided in block-shaped land portions or in ribs formed on a tread surface of the tire has been employed. Accordingly, edge components can be increased, and the rigidity of the blocks can be controlled.
Ordinarily, in the case of improving wet performance, narrow sipes are formed in the block-shaped land portions. By making narrow sipes, the edge components can be increased and the rigidity of the block-shaped land portions can be ensured. However, in the case in which narrow sipes are formed in the block-shaped land portions, although the edge components can be ensured sufficiently, there is a problem with draining performance. Namely, in a tire having such sipes formed therein, at the initial stage of wear of the tire, sufficient draining performance can be obtained by main grooves or the like which are formed in the tread surface. However, in a later stage of wear of the tire, because the draining performance of the main grooves or the like deteriorates, the sipes must also exhibit the ability to drain. However, if the sipes are narrow, the draining performance is low, and it is thus difficult to ensure a sufficient wet performance.
In order to improve the draining performance of the sipes, it is desirable to increase the widths of the sipes. However, in this case, there is the concern that the rigidity of the blocks may decrease, and accordingly, the stability and controllability performance may deteriorate greatly. Further, if the width of the sipe is increased, the amount of noise may increase.
A tire in which sipes are made wider only at portions of the sipes which are exposed in the final stage of wear of the tire has been proposed. However, with this tire, there is the drawback that the draining performance of the sipes deteriorates at the intermediate stage of wear and the wet performance deteriorates.
SUMMARY OF THE INVENTION
In view of the aforementioned, it is an object of the present invention to provide a pneumatic tire in which deterioration in wet performance due to wear of the tire is suppressed, and noise is also suppressed.
The first aspect of the present invention is a pneumatic tire having a tread on which a plurality of block-shaped land portions which are demarcated by a plurality of grooves intersecting each other are formed, and in which a sipe is provided in the block-shaped land portion, wherein the sipe is structured by a narrow groove portion, which is formed at a tire ground contact surface side of the sipe and has a first width, and a wide groove portion, which is formed at a bottom portion side of the sipe and has a second width greater than the first width, and toward the bottom portion of the sipe, the proportion of the sipe accounted for by the narrow groove portion in a longitudinal direction of the sipe which is orthogonal to a depthwise direction of the sipe decreases, while the proportion of the sipe accounted for by the wide groove portion in the longitudinal direction of the sipe which is orthogonal to the depthwise direction of the sipe increases.
In accordance with the first aspect of the present invention, when the vehicle travels with such pneumatic tires installed thereon, at the initial stage of wear, sufficient depths of the respective grooves (main grooves, lug grooves and the like) are ensured, and an excellent draining performance is exhibited. Further, because the proportion of the exposed portion of the sipe accounted for the narrow groove portion is large, the surface area of the exposed portion of the sipe is small, and there is little noise. At the intermediate stage of wear of the tire, the depths of the grooves decrease, and the draining performance deteriorates. However, because the proportion of the exposed portion of the sipe accounted for the wide groove portion increases, the exposed surface area of the sipe increases. The deterioration in the draining performance of the grooves can be compensated for by the improvement in the draining performance of the sipes, and the excellent wet performance of the tire can be maintained. At the final stage of wear of the tire in which the depths of the grooves decrease even more, most of the exposed portion of the sipe is occupied by the wide groove portion, and the exposed surface area of the sipe is thereby increased. Thus, the deterioration in the draining performance of the respective grooves can be compensated for even more. In this case, although the surface area of the exposed portion of the sipe increases, noise can be suppressed because the depth of the sipe is small.
In this way, when a vehicle on which pneumatic tires according to the first aspect of the present invention are mounted travels, a good draining performance (wet performance) can be maintained throughout the stages of wear of the tire, and noise can be suppressed.
The second aspect of the present invention is a pneumatic tire, wherein the sipe is an open sipe in which at least one of the longitudinal direction end portions of the sipe is open at a groove of the plurality of grooves, and the wide groove portion is formed continuously in the longitudinal direction of the sipe from the at least one of the end portions of the sipe.
In accordance with the second aspect of the present invention, the wide groove portion is continuously formed from at least one end portion of the sipe open at a groove of the grooves which section the block-shaped land portions. Accordingly, the water which is absorbed by the sipe is drained into the groove or grooves quickly. Therefore, the draining performance in the sipe is further improved.
The third aspect of the present invention is a pneumatic tire in which the sipe is a one-side-open sipe in which one of the longitudinal direction end portions of the sipe is open at a groove of the plurality of grooves, and in the longitudinal direction of the sipe, the proportion of the sipe accounted for by the wide groove portion in the depthwise direction of the sipe increases toward the one end portion of the sipe.
In accordance with the third aspect of the present invention, in a case in which a one-side-open sipe is formed at the block-shaped land portion, the proportion of the sipe occupied by the wide groove portion in the depthwise direction of the sipe increases toward the one longitudinal direction end portion of the sipe which is open at a groove. Namely, the water which is absorbed by the sipe is drained quickly from the one end portion into the groove. Accordingly, an excellent draining performance of the one-side-open sipe can be ensured.
The fourth aspect of the present invention is a pneumatic tire in which the sipe is a both-sides-open sipe in which both longitudinal direction end portions of the sipe are open at grooves of the plurality of the grooves, and the proportion accounted for by the wide groove portion of the sipe in the depthwise direction of the sipe increases toward the end portions from an intermediate portion between the end portions of the sipe in the longitudinal direction thereof.
In accordance with the fourth aspect of the present invention, in the case in which a both-sides-open sipe is formed in the block-shaped land portion, the proportion of the sipe occupied by the wide groove portion in the depthwise direction of the sipe increases toward the end portions, from the intermediate portion between the end portions in the longitudinal direction of the sipe. Namely, the water which is absorbed by the sipe drains rapidly from the end portions of the sipe into the grooves. As a result, an excellent draining performance of the both-sides-open sipe can be ensured.
The fifth aspect of the present
Bridgestone Corporation
Maki Steven D.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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