Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Patent
1997-07-14
1999-02-16
Johnstone, Adrienne
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
152527, 152531, 152533, 152534, 152535, 152536, B60C 918, B60C 920, B60C 1300, B60C 1700
Patent
active
058716017
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pneumatic radial tire, and more specifically, to a pneumatic radial tire which is strengthened by providing, at the sidewall of the tire, a rubber reinforcing layer having a crescent moon shaped cross-section, such that when the pneumatic tire installed on a vehicle is punctured during running, the tire can run for a considerable distance in the punctured state.
BACKGROUND ART
Conventionally, various measures have been devised for safely continuing running, without damaging the tire further and without disadvantages such as poor steering. This occurs over a distance from the place where the tire was punctured to a place desired by the driver, e.g., a service station where the tire can be changed, at the time when the internal pressure decreases or becomes zero (hereinafter, "punctured") for some reason, and in many cases, due to a foreign object such as a nail or a metal piece piercing the tire, during traveling of the pneumatic tire installed on a vehicle.
Among these measures, as a simple and effective measure for radial tires for passenger vehicles in particular, Japanese Patent Application Publication No. 52-41521 discloses art relating to a so-called side reinforced run-flat tire in which a rubber reinforcing layer having a crescent moon shaped crosssection is made to line the carcass inner peripheral surface of the sidewall, which is the region in the tire having the lowest rigidity, so that the entire sidewall has approximately the same thickness and so as to provide rigidity.
In this side reinforced run-flat tire, in an ordinary state, the load is mainly supported by internal pressure. When the tire is punctured, the supporting of the load is taken over by the rigidity inherent in the reinforced sidewall.
However, in this side reinforced run-flat tire, as illustrated in FIG. 2, when the tire is punctured, buckling of a sidewall S is avoided, but a crown portion 21 exhibits the phenomenon known as buckling, and a tread 22 is thereby lifted up from a road surface R. As a result, a portion 23 of the sidewall separated from the tread 22 contacts the ground.
In this ground-contacting state, obviously, stress concentrates and defects arise at an early stage at portions at which there is much bending deformation. As a result, in order to increase the durability of the run-flat tire, buckling of the crown portion 21 must be suppressed, and tire deformation must, as much as possible, be maintained the same as before the puncture.
Japanese Patent Application Laid-Open No. 6-191243 and Japanese Patent Application Laid-Open No. 6-191244 disclose techniques in which at least one organic fiber cord layer, which is effective for weight reduction, is disposed at the outer periphery of the belt layer, so as to increase the rigidity of the tread base portion.
However, these disclosed techniques do not exhibit sufficient effects for suppressing buckling, and the current situation is that, even if the rigidity of the tread base portion is increased even more, by winding a plurality of layers, the effects are small in proportion to the increase in cost and in weight.
DISCLOSURE OF THE INVENTION
The present invention has taken into consideration the above-described problematic points, and an object thereof is to provide a pneumatic tire in which, when the tire is punctured, buckling of the crown portion is suppressed, and durability is increased.
The present invention is a pneumatic radial tire equipped with a belt, which includes a plurality of metal cord layers, and a tread successively placed on a crown portion periphery of a toroidal radial carcass, and equipped with, at a side portion inner peripheral surface of the carcass, a rubber reinforcing layer having a crescent moon shaped cross-section and bearing and supporting load, comprising: an auxiliary belt disposed between the carcass and the belt and including organic fiber cords which are oriented to substatially cross the cords of the carcass and the cords of the belt with respect to a central equatorial
REFERENCES:
patent: 5427176 (1995-06-01), Hayashi et al.
Bridgestone Corporation
Johnstone Adrienne
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