JPH09226320A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve high speed durability by preventing outer peripheral growth at the time of high speed travelling. SOLUTION: A pneumatic radial tire with at least two layers of belt layers 3u, 3d cords of which cross with each other between plies and having cutoff end surfaces on both side ends in the cross direction arranged on the outside of a carcass layer 2 on a tread 1 is constituted by forming a cross section flat cylindrical continuous tube 10 by spirally and continuously winding a plural number of rubberized reinforced cords 12 paralleled in parallel with each other at a specified angle in the longitudinal direction and forming belt cover layers 4 by spirally and continuously winding the continuous tube 10 around on an outer periphery of at least both side parts of the extreme outside belt layer by a plural number of times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having improved high speed durability.

[0002]

2. Description of the Related Art In recent years, flatness of heavy vehicles such as trucks and buses and radial tires of light trucks has been increasing. However, as the tire becomes flatter, the load on the tire belt portion increases, and separation of the belt edge, growth of the outer periphery, and the like occur, resulting in a problem that the durability is significantly reduced.

Conventionally, as a measure against such a load on the belt portion, as is often used in radial tires for passenger cars, a belt cover is provided so as to cover both sides or the entire surface in the width direction of the outermost belt layer. Layers are provided. However, in the nylon fiber cord with a large elongation used as the cord of the belt cover layer of the tire for passenger cars,
The effect of the belt cover layer in the circumferential direction of the tire was not sufficient, so that the growth of the outer circumference could not be sufficiently suppressed.

Therefore, when steel cords or aromatic polyamide fiber cords having a large elastic modulus are used for the cords of the belt cover layer, since these cords have a small elongation, the belt cover layer follows the lift (expanded diameter) during vulcanization. However, there is a problem in that it is impossible to manufacture a tire. Further, when the cords are arranged in the bias direction, cut end faces are formed at both widthwise ends of the belt cover layer, which causes a problem that edge separation occurs from the end faces.

[0005]

The object of the present invention is to achieve high-speed running without causing the above-mentioned problems even when the tire is flattened, particularly when the tire is a heavy-duty tire. It is an object of the present invention to provide a pneumatic radial tire in which outer peripheral growth is prevented and high-speed durability is improved.

[0006]

SUMMARY OF THE INVENTION According to the present invention, at least two cords are provided on the outer side of a carcass layer in a tread, the cords crossing each other between plies and having cut end faces at both widthwise ends.
In a pneumatic radial tire in which belt layers of layers are arranged, a plurality of rubberized reinforcing cords aligned in parallel with each other are continuously wound spirally at a predetermined angle with respect to the longitudinal direction, and have a flat tubular cross section. Of the outermost belt layer, and the belt cover layer is formed by spirally winding the continuous tube around the outer circumference of at least both sides in the width direction of the outermost belt layer.

As described above, since the continuous tube having a flat cross section is spirally wound around the outer circumference of at least the widthwise side of the outermost belt layer a plurality of times continuously to form the belt cover layer, the belt cover layer is formed. Since there is no cut end surface at both widthwise ends, separation does not occur between the rubber and the cord at both ends. Further, the belt cover layer is made of a continuous tube having a flat cross section, and this continuous tube can be stretched because it is formed by spirally winding a rubberized reinforcing cord at a predetermined angle with respect to the longitudinal direction. The belt cover layer can follow the lift during vulcanization.

Furthermore, since there are no cut end faces on both widthwise ends of the belt cover layer, the tensile rigidity of the belt cover layer in the tire circumferential direction is high, and the belt cover layer has a sufficient hoop effect in the tire circumferential direction to grow the outer circumference. Therefore, even when the tire is flattened so that the load on the belt layer increases, excellent high-speed durability can be improved.

[0009]

1 shows a cross section in the meridian direction of an example of a pneumatic radial tire of the present invention, FIG. 2 shows its belt structure, and FIG.
The belt part planarly viewed in (B) is shown. 1 and 2
In (A) and (B), two belt layers including a lower belt layer 3d and an upper belt layer 3u are arranged outside the carcass layer 2 in the tread 1. Each of these belt layers is made of a polyester fiber cord, an organic fiber cord such as an aromatic polyamide fiber cord, or a steel cord. Further, in these belt layers, cords intersect with each other between plies and have cut end faces at both widthwise ends. The cord angle of each of these belt layers is 15 ° to 35 °. In addition, CL in FIG. 1 represents a tire equator line.

Of these belt layers, a belt cover layer 4 is disposed on the outer circumference of both sides in the width direction of the upper belt layer 3u, which is the outermost belt layer, so as to cover the both sides.
As shown in FIG. 3, the belt cover layer 4 may be arranged over the entire surface of the upper belt layer 3u so as to cover the entire surface thereof. The belt cover layer 4 is formed by continuously connecting the continuous tube 10 having a flat tubular cross-section shown in FIG. 4 to the outer circumferences of the upper belt layer 3u in the width direction on both sides or to the entire outer circumference of the upper belt layer 3u in a spiral manner. It is formed by winding. This continuous tube 10 has a rubberized reinforcing cord formed by embedding a plurality of reinforcing cords 12 (organic fiber cords) in rubber, preferably 5 to 100 in parallel with each other at a predetermined angle (10 °) with respect to the longitudinal direction. It can be formed by continuously spirally winding at about 30 °) into a tubular body, and crushing the tubular body along its longitudinal direction. Also, using a die capable of inserting a predetermined number of reinforcing cords into a tuber (extruding device) capable of forming a tubular rubber sheet, the reinforcing cords are extruded while being embedded in the tubular rubber sheet, and It is also possible to form the continuous tube 10 by rotating the and arranging the reinforcing cords in a spiral state and then crushing them with a roller or the like.

The width of the continuous tube 10 is 5 mm to 60 m.
m. If it is less than 5 mm, the width will be too narrow and the productivity of the tubular body will be reduced.
This is because the width of the terminal portion of 0 becomes too long, which deteriorates tire uniformity and durability. Reinforcement cord 1
No. 2 has a tensile elastic modulus of 3000 kgf / mm ² or more and a tensile strength of 150 kgf / mm ² or more. Tensile modulus is 3
If it is less than 000 kgf / mm ² , sufficient effect cannot be obtained on outer peripheral growth property, and if it is less than 150 kgf / mm ² , sufficient effect cannot be obtained on high-speed durability.

The organic fiber cords constituting the reinforcing cords 12 are, for example, aromatic polyamide fibers, polyarylate fibers, polyparaphenylenebenzbisoxazole fibers,
A twisted yarn obtained by twisting one or more fibers selected from polyvinyl alcohol fibers. The cord angle of the belt cover layer 4 with respect to the tire circumferential direction is 10 ° to 30 °.
It should be °. Belt cover layer 4 for lift during vulcanization
This is because it is possible to easily follow. In order to set the cord angle of the belt cover layer 4 to 10 ° to 30 °, as described above, the rubberized reinforcing cord is continuously spirally wound at a predetermined angle with respect to the longitudinal direction to form the continuous tube 10. At this time, the predetermined angle may be set to 10 ° to 30 °. This is because the longitudinal direction of the continuous tube 10 becomes substantially the tire circumferential direction when the belt cover layer 4 is formed.

A core material made of a rubber sheet may be inserted inside the continuous tube 10 along the longitudinal direction thereof.
This is to increase the rigidity of the belt cover layer 4. When the continuous tube 10 is wound around the outer periphery of the upper belt layer 3u, the adjacent side portions of the continuous tube 10 are butted against each other, slightly overlapped (about -5 mm) with a step, or slightly spaced. It may be opened (+5 mm or so). The present invention described above can be applied not only to passenger car tires, but can also exhibit particularly excellent high-speed durability when applied to flattened heavy-duty tires.

[0014]

[Examples] With respect to the tire of the present invention and the conventional tire having the following belt structure, high-speed durability and outer peripheral growth were evaluated under the following conditions. Table 1 shows the results. Tire of the present invention Reinforcing cord; Kevlar (aromatic polyamide fiber cord)
1500d / 2, number of ends: 51 / 5cm, width 15m
A continuous tube having a cord angle of 20 ° and a width of 30 mm is continuously wound spirally a plurality of times on the outer circumferences of the outermost belt layers on both sides in the width direction while adjoining mutually adjacent sides of the continuous tube. A cover layer is formed (FIGS. 1 and 2 (A) and (B)).

Conventional tire reinforcing cord; Kevlar (aromatic polyamide fiber cord)
1500d / 2, number of ends: 51 / 5cm, width 30m
A two-layer rubberized sheet having a cord angle of 0 ° and a cord angle of about 0 ° is arranged on the outer circumference of both outermost belt layers in the width direction to form a belt cover layer. Conditions Air pressure: 875KPa, rim: 22.5 × 9.00, load: 30.89kN Tire size: 285/60 R22.5 Other than the belt cover layer, other tire structures, dimensions, etc. are common.

High-speed durability : After the JATMA high-speed durability test with a drum diameter of 1707 mm, the test was continued by accelerating every 50 km / hr until the tire broke. This result is 100 for comparison tire 1
It shows with the index. Larger numbers are better. Peripheral growth : Internal pressure 50Kpa after rim assembly to JATMA standard rim
The outer circumference at the time of and the outer circumference at the maximum air pressure of JATMA were compared.
The result is shown by an index with the comparative tire 1 being 100. The smaller the number, the better. As is clear from Table 1, the tire of the present invention is excellent in outer peripheral growth property and high-speed durability.

[0017]

As described above, according to the present invention, outside the carcass layer in the tread, at least two belt layers having cords intersecting each other between plies and having cut end faces on both widthwise ends are arranged. In the pneumatic radial tire described above, a plurality of rubberized reinforcing cords aligned in parallel with each other are continuously wound spirally at a predetermined angle with respect to the longitudinal direction to form a continuous tube having a flat tubular cross section. In order to form a flat cover of the tire, a high load is applied to the belt layer because the continuous tube is spirally wound around the outer periphery of the outermost belt layer at least on both sides in the width direction to form a belt cover layer. Even when advanced, high-speed durability can be improved by preventing growth of the outer periphery during high-speed running, and moreover, the belt cover layer can follow the lift during vulcanization.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view in the meridian direction of an example of a pneumatic radial tire of the present invention.

2A and 2B show a belt structure of the pneumatic radial tire of FIG. 1, in which FIG. 2A is a sectional explanatory view thereof, and FIG. 2B is a plan view explanatory view thereof.

FIG. 3 is an explanatory plan view showing a belt structure of another example of the pneumatic radial tire of the present invention.

FIG. 4 is a perspective explanatory view showing an example of a continuous tube forming a belt cover layer in the present invention.

[Explanation of symbols]

1 tread 2 carcass layer 3d lower belt layer 3u upper belt layer 4 belt cover layer 10
Continuous tube 12 Reinforcement cord

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B60C 9/20 B60C 9/20 B D02G 3/48 D02G 3/48 (72) Inventor Masamichi Seiyanagi 2-1, Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Factory (72) Inventor Kazuyuki Kabe 2-1, Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Factory (72) Inventor Eiji Igarashi Kanagawa 2-1, Oiwake, Hiratsuka-shi, Japan Yokohama Rubber Co., Ltd. Hiratsuka Factory

Claims (5)

[Claims] 1. Outside the carcass layer in the tread,
In a pneumatic radial tire in which cords cross each other between plies and at least two belt layers having cut end faces on both widthwise ends are arranged, a plurality of rubberized reinforcing cords aligned in parallel with each other are provided in a longitudinal direction. To form a continuous tube having a flat tubular cross-section, which is continuously wound in a spiral shape at a predetermined angle with respect to the outermost belt layer at least in the width direction on both side outer circumferences. A pneumatic radial tire with a belt cover layer wound around it. 2. The reinforcing cord has a tensile elastic modulus of 3000 k.
The pneumatic radial tire according to claim 1, which has a gf / mm ² or more and a tensile strength of 150 kgf / mm ² or more. 3. The reinforcing cord is a twisted yarn in which one or more kinds of organic fibers selected from aromatic polyamide fibers, polyarylate fibers, polyparaphenylenebenzbisoxazole fibers, and polyvinyl alcohol fibers are twisted together. The pneumatic radial tire according to claim 2. 4. The pneumatic radial tire according to any one of claims 1 to 3, wherein a core material made of a rubber sheet is inserted inside the continuous tube along a longitudinal direction thereof. 5. The pneumatic radial tire according to claim 1, wherein a cord angle of the belt cover layer with respect to a tire circumferential direction is 10 ° to 30 °.