Pneumatic tire and manufacturing method of the same

Abstract

In a pneumatic tire of the present invention provided with a pair of bead cores, a troidal-shaped carcass surrounding said bead cores, a tread rubber, a carcass, a plurality of belt layers 6 reinforced by a steel cords 7, wherein in at least one of said belt layers 6, the maximum value of deviation of an angle θc of said steel cords 7 is not greater than 3 degrees with respect to the angle made by said steel cords 7 at the center in the tire width direction and the tire circumferential direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic half section view including the shoulder region of a tread of a pneumatic tire according to the present invention.

FIG. 2 is an expansion view of a belt layer used for a pneumatic tire of the present invention.

FIG. 3 is a graph showing the angle deviation of steel cords in a belt layer used for a pneumatic tire of the present invention.

FIG. 4 is a view showing the changes in a shape of a tread as a driving distance of a tire increases.

FIG. 5 is a half section view of a die mold showing the manufacturing process of a pneumatic tire of the present invention.

FIG. 6 is a graph showing the angle deviation of steel cords in a belt layer by the changes in an underbelt diameter (L2/L1-1).

FIG. 7 is a graph showing the growth amount of an inner surface of a tire after driving 20,000 km.

FIG. 8 is a view showing the manufacturing process of a pneumatic tire by sector molds provided with divided pieces.

FIG. 9 is a view explaining the space between segments.

FIG. 10 is a graph showing the relationship between the segment division number N and the space between segments AL.

Claims

1. A pneumatic tire provided with a pair of bead cores, a troidal-shaped carcass surrounding said bead cores, a tread rubber, a carcass, a plurality of belt layers reinforced by steel cords, wherein in at least one of said belt layers, the maximum value of angle deviation of said steel cords is not greater than 3 degrees with respect to the angle made by said steel cords at the center in the tire width direction and the tire circumferential direction.

2. The pneumatic tire as set forth in claim 1, wherein said pneumatic tire is molded by a plurality of sector molds divided in the tire circumferential direction and side molds, the difference between thickness of the tread rubber at the position corresponding to the divided position of said sector molds and average thickness of the tread rubber over whole circumference of the tire is not greater than 0.4 mm.

3. A manufacturing method of a pneumatic tire by a die mold for vulcanization molding, wherein said method of manufacturing a pneumatic tire comprises the steps of; molding a green tire so that the formula 0≦L2/L1-1≦0.02 is satisfied, where an underbelt diameter of the green tire is represented as L1, and an underbelt diameter of the vulcanized tire as L2, and molding to make the underbelt diameter of the vulcanized green tire L2.

4. A manufacturing method of a pneumatic tire with a die mold provided with a plurality of sector molds divided in the tire circumferential direction and a pair of side molds, wherein said sector molds are provided with a plurality of pieces movable in the tire circumferential direction and with repulsive means between said adjacent pieces comprising the step of sandwiching a green tire with the side molds, wherein the green tire is molded so that the formula 0≦L2/L1-1≦0.02 is satisfied, where an underbelt diameter of the green tire is represented as L1, and an underbelt diameter of the vulcanized tire as L2, and that an underbelt diameter of the vulcanized green tire is L2, followed by shrinking the diameter of said sector molds gradually decreasing the spaces between said pieces, closing the die mold, thereby molding said green tire.