Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Patent
1998-02-25
2000-05-09
Johnstone, Adrienne C.
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
152528, 152533, 152534, 152536, B60C 918, B60C 920, B60C 926
Patent
active
060589973
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a pneumatic radial tire and more particularly, to a pneumatic radial tire which improves straight driving stability while improving edge separation resistance of belt layers.
BACKGROUND ART
Generally, belt layers of pneumatic radial tires for passenger cars have the construction in which two belt layers having steel cords aligned obliquely in a tire circumferential direction and having cut ends of the steel cords at both end portions thereof are laminated in such a fashion that the steel cords cross one another between the layers. The belt layers having such a construction involve the problem that because a stress is likely to concentrate on the cut end portions of the steel cords due to a load during driving, so-called "edge separation" or in other words, peel of the steel cord ends from the rubber layer, is likely to occur. The same problem develops also in heavy load pneumatic radial tires for small trucks and for trucks and buses having three or more belt layers.
The belt layers of the conventional pneumatic radial tires have the two-layered structure wherein a belt layer having steel cords inclined to the right in a tire circumferential direction and a belt layer having steel cords inclined to the left are laminated. For this reason, the belt layers having such a two-layered structure inevitably generates a spiral torsion due to the tensile strength in the tire circumferential direction that occurs when the tire rolls. Since this torsion of the belt layers generates a lateral force to the tire, the tire undergoes drift or runs toward one side at the time of straight driving and straight driving stability is impeded.
DISCLOSURE OF INVENTION
It is a main object of the present invention to provide a pneumatic radial tire which makes it possible to improve straight driving stability while improving an edge separation resistance of belt layers.
The object of the present invention described above can be accomplished by a pneumatic radial tire having at least two belt layers at a tread portion thereof, characterized in that the two belt layers are constituted by inclining a strip each being formed by aligning a plurality of reinforcing cords relative to a tire circumferential direction and extending them zigzag in the tire circumferential direction in such a fashion that the reinforcing cords are turned back from the inner belt layer to the outer belt layer at both end portions of the belt layers and zone portions in which the reinforcing cords incline to the right in the tire circumferential direction and zone portions in which the reinforcing cords incline to the left are alternately disposed.
Since the belt layers are formed by arranging the reinforcing cords obliquely to the tire circumferential direction and turning back them zigzag, the cut ends of the reinforcing cords are not formed at both end portions of the belt layers. Therefore, the edge separation which occurs due to the stress concentration on the portions of the reinforcing cords near their cut ends can be avoided.
Moreover, those outer and inner two belt layers do not extend around the full circumference in the tire circumferential direction under the state where their reinforcing cords incline in the same direction, but the portions in which the reinforcing cords incline to the right and the portions in which they incline to the left are arranged alternately at predetermined pitches in the tire circumferential direction. In consequence, the two belt layers can offset the spiral torsion that results from the tensile strength in the tire circumferential direction, and the ply steer due to the torsion of the belt layers when the tire rolls, that is, the side run of the tire, can be inhibited and its straight driving stability can be improved.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a tire meridian sectional view showing an example of a pneumatic radial tire used for a passenger car according to the present invention.
FIG. 2 is a plan view of principal portions of the belt layers shown in FIG.
REFERENCES:
patent: 2895525 (1959-07-01), Lugli
patent: 2982327 (1961-05-01), Vanzo et al.
patent: 3563296 (1971-02-01), Wells
patent: 5535801 (1996-07-01), Iseki et al.
Horie Hitoshi
Kabe Kazuyuki
Morikawa Tsuneo
Nishida Kenichiro
Takahashi Shuji
Johnstone Adrienne C.
The Yokohama Rubber Co. Ltd.
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