Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Patent
1997-02-19
1998-12-22
Knable, Geoffrey L.
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
152548, 152549, B60C 514
Patent
active
058513230
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pneumatic tire, more particularly, it relates to a pneumatic tire which is lightened in weight without detracting from the durability of the belt portion, without allowing damage due to local strain caused near the carcass cord in the tire side portion, and without detracting from the retention of air pressure due to fine cracks caused in the inner liner layer due to deformation of the tire at the time of use.
BACKGROUND ART
Reduction of fuel consumption is one of the major technical issues in automobiles. As one of the means for solving this issue, demands have been strongly increased for reduction of the weight of pneumatic tires. From this viewpoint, tires using an air permeation preventive layer made by a film composed of a plastic or plastic/rubber have been proposed to lighten the tire weight (for example, see Japanese Unexamined Patent Publication (Kokai) No. 5-329961 etc.)
An inner liner layer or other air permeation preventive layer composed of a halogenated butyl rubber or other rubber having a low air permeability is conventionally provided at the inner surface of the pneumatic tire. However, a halogenated butyl rubber has a large hysteresis loss, and therefore, after vulcanization of the tire, when rippling is caused in the rubber of the inner surface of the carcass layer and the air permeation preventive layer, the air permeation preventive layer deforms along with deformation of the carcass layer. Thus, there is the problem of an increase in the rolling resistance. Therefore, in general, a rubber sheet called a "tie rubber" having a small hysteresis loss has been inserted between the air permeation preventive layer (halogenated butyl rubber) and rubber of the inner surface of the carcass layer for joining the two. Accordingly, in addition to the thickness of the air permeation preventive layer of the halogenated butyl rubber, the thickness of the tie rubber is added and the layer overall becomes a thickness of over 1 mm (1,000 .mu.m). As a result, this has become a factor increasing the weight of the final tire.
Techniques have been proposed for using various materials in place of the low air permeability rubber such as butyl rubber as the air permeation preventive layer of a pneumatic tire. For example, Japanese Unexamined Patent Publication (Kokai) No. 6-40207 proposes providing an air permeation preventive layer at the inside of the tire by laminating a low air permeability layer composed of a polyvinylidene chloride film or ethylene-vinyl alcohol copolymer film and an adhesive layer composed of a polyolefinic film, aliphatic polyamide film, or polyurethane film to form a thin film and laminating that thin film on the inner surface of a green tire composed of unvulcanized rubber so that the adhesive layer contacts the carcass layer, then vulcanizing and molding the green tire. By using this multilayer film for the air permeation preventive layer, it is possible to reduce the weight of the tire without detracting from the retention of the air pressure. However, when forming the inner liner or other air permeation preventive layer from such a thermoplastic multilayer film, there is insufficient elongation of the thermoplastic film in the face of the repeated deformation at the time of tire use, and therefore, the film cannot keep up with this deformation and a large number of cracks occur in the film. As a result, there is a risk of a decline in the sealability of the air.
On the other hand, as shown in FIG. 1, at the air permeation preventive layer 1 of the tire, the lift h at the time of the secondary molding of the tire causes the circumferential length of the bottom portion 2 of the belt to become longer by the amount of the lift. The gauge becomes thinner by that amount, and therefore, air permeates from that portion and the problem occurs of a drop in durability of the belt portion due to oxygen deterioration. Accordingly, the practice has been to extrude the belt thicker giving consideration to the thinning of the gauge or to extr
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Hashimura Yoshiaki
Kaido Hiroyuki
Shida Zenichiro
Watanabe Jiro
Yamakawa Kazuto
Knable Geoffrey L.
The Yokohama Rubber Co. Ltd.
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