Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-03-30
2001-08-07
Johnstone, Adrienne C. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S554000, C152S555000
Reexamination Certificate
active
06269857
ABSTRACT:
BACKGROUND OF THE INVENTION
Background
The present invention relates to a run-flat tire, which is capable of running for some time even after the tire has become uninflated or flat.
The run-flat tire is the kind of tire that has a wall-rigidity capable of bearing the load of the vehicle until reaching the nearest service station even when the pneumatic pressure of the tire becomes insufficient or zero due to a puncture or other causes.
Various kinds of structures have been proposed for such run-flat tires. A typical run-flat tire is disclosed in JP-A-62 279107(1987) for example. This tire has a side-reinforcing rubber pad which is crescent in vertical section (a section including the tire axis) and which is attached to the inner surface of a carcass layer extending from near the upper end of a rim flange to one end of a belt layer thereby reinforcing the side wall of the tire. This side-reinforcing rubber pad which is also called a lunette gives a “self supporting capability” to an flat tire and is usually formed of a rubber layer of high rigidity.
In the tire disclosed in EP 385192A1 (1990, counterpart of JP-A-02 283508), a single fibrous layer
103
formed of a fibrous cord ply extends from one side of the tire to the opposite side of the tire, that is, from one rim-fitting portion to another rim-fitting portion at opposite end. The fibrous layer
103
is inserted into a side-reinforcing rubber pad
102
along the center of the thickness of the rubber pad
102
as shown in FIG.
6
. Such fibrous layer
103
is adapted to rigidify the side-reinforcing rubber pad so that when the tire gets punctured, generation of a crack in the side-reinforcing rubber pad resulting from an excessive compressive deformation is prevented.
Further, in the structure of the tire disclosed JP-A-05310013(1993), the fibrous layer
103
is arranged on the interface between an inner liner
105
and the side-reinforcing rubber pad
102
so that the fibrous layer
103
wraps up the inner surface of the side-reinforcing rubber pad
102
as shown in FIG.
7
. Thus, it is described in the specification that with such structure, the durability life (a distance for which the tire is capable of running under a rated load, hereinafter referred to as the run-flat durability) of the tire in the flat condition can be increased.
However, since the fibrous layer which is strong against a tensile force is arranged on the inner surface of the tire subject to a compressive deformation, the effect of improving the durability of the tire has not been sufficient.
Further, inview of the rigidity of the side-reinforcing rubber pad due to the provision of the fibrous layer, the ride quality or ride comfortableness becomes worse.
In addition, in order to give the tire a sufficient degree of rigidity and durability, it has been necessary for the side-reinforcing rubber pad and the fibrous layer to have sufficiently large sizes which results in increasing the weight of the tire.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described prior art problems and an object of the invention is to provide a run-flat tire which is capable of increasing its mileage or traveling distance when flat and which can improve the ride quality of the vehicle.
A first feature of the run-flat tire according to the present invention resides in that the run-flat tire is provided with a bead portion; at least one carcass ply turned up around the bead portion; a side-reinforcing rubber pad which is crescent-shaped in section including the tire axis and which is arranged on the side of the carcass ply that is adjacent to the inner surface of the tire; and a fibrous layer for reinforcing the side-reinforcing rubber pad. The carcass ply is turned up from tire's-inner-surface side toward tire's-outer-surface side so as to wrap up the bead portion and then toward the tread with its turn-up end reaching one end of a belt layer. The side-reinforcing rubber pad comprises a tire's-outer-surface-side rubber pad and a tire's-inner-surface-side rubber pad, both of which rubber pads are laid one above another, with the fibrous layer being sandwiched therebetween, and with the tire's-inner-surface-side rubber pad having a thickness larger than that of the tire's-outer-surface-side rubber pad.
With the above-described structure, since the carcass turn-up end reaches one end of the belt layer, the tensile force for inhibiting the deformation of the side wall portion acts on the outer side of the carcass layer when the tire is uninflated so that the deformation of the tire due to a load on the tire can be restrained without increasing the rigidity of the rubber of the side wall portion. Consequently, it is possible to improve the run-flat durability without worsening the ride quality.
Further, since the fibrous layer for reinforcing the side-reinforcing rubber pad is arranged close to the outer surface of the side-reinforcing rubber pad, the compressive deformation to which the fibrous layer is subjected is mitigated, thereby improving the durability of the tire. Accordingly, the durability of the tire at the time of normal use and at the time of the tire is running flat can be increased. Further, by the arrangement of such fibrous layer, it is possible to control the manifestation of an excessive degree of rigidity at the time of minor deformation of the tire while keeping the resistance against a major deformation of the tire side wall portion, as compared to a case where the fibrous layer is arranged on the inner surface of the side-reinforcing rubber pad. Consequently, the worsening of the ride quality due to the arrangement of the fibrous layer can be mitigated.
Thus, with the structure of the first feature of the present invention, the run-flat durability of the tire can be increased and the ride quality of the tire both at the time of normal use of the tire and at the time when the tire is in the uninflated condition can be improved.
A second feature of the run-flat tire according to the present invention resides in that the upper end of the fibrous layer is located under one end of the belt layer while the lower end of the fibrous layer is located on the inner-surface side of the tire.
With the above structure, the increase of the weight of the tire due to the presence of the fibrous layer can be minimized. Further, since the stress resulting from any cause other than the deformation of the side-reinforcing rubber pad is prevented from being applied on the fibrous layer, it is possible to enhance the durability of the fibrous layer.
A third feature of the run-flat tire according to the present invention resides in that the carcass layer comprises a single ply.
With the above structure, the weight of the tire can be reduced.
A fourth feature of the run-flat tire according to the present invention resides in that the fiber cords of the fibrous layer are arranged substantially in the radial direction of the tire.
A fifth feature of the run-flat tire according to the present invention resides in that a separate carcass ply is laid over the above-described at least one carcass ply, on the tire's-outer-surface side of the side-reinforcing rubber pad, and this separate carcass ply is turned up from the tire inner surface side toward the tire outer surface side at the bead portion in such a manner that the turn-up end of the carcass ply is located within the range from the lower end to the upper end of the bead filler rubber.
With the above structure, the tire can have a sufficient degree of run-flat durability even when the tire is used for large-sized passenger cars, minivans and the like.
A sixth feature of the run-flat tire according to the present invention resides in that a separate carcass ply is provided on the tire's-inner-surface side of the side-reinforcing rubber pad; and this separate carcass ply is turned up from the tire's-inner-surface side toward tire's-outer-surface side at the bead portion in such a manner that the turn-up end of the carcass ply is located within th
Guo Wuyun
Iwagase Tomoyuki
Kanai Masayuki
Miyazaki Yuji
Nakayama Rinichi
Johnstone Adrienne C.
Jordan and Hamburg LLP
Toyo Tire & Rubber Co., Ltd.
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