JPH08127984A - Steel cord for reinforcing rubber article and pneumatic radial tire - Google Patents

Abstract

PURPOSE: To obtain a steel cord having improved corrosion resistance without damaging fatigue resistance of the steel cord and a pneumatic radial tire having raised durability by using the steel cord as a reinforcing material. CONSTITUTION: In steel cord of twisted two or three layers comprising a core composed of three or four filaments, at least one filament among filaments in each layer of the core, a first sheath and a second sheath is wound with a spiral.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber article reinforcing steel cord used as a reinforcing material for rubber articles such as pneumatic radial tires and conveyor belts, and a pneumatic radial tire using the steel cord as a reinforcing material. It is a thing.

[0002]

2. Description of the Related Art Steel cord is widely used as a reinforcing material for rubber articles such as pneumatic radial tires because it has higher strength than organic fibers and has a low elongation. As a steel cord used for tires, in order to increase the cord cutting load per diameter of the cord and obtain good fatigue resistance,
Steel cord of 2-3 layers twisted by twisting filaments of the same wire diameter by changing the twist pitch for each layer, or multiple strands by twisting multiple filaments and then twisting multiple strands The structure's Ceil code is used.

Further, in the case of a steel cord used for a heavy-duty tire, a steel cord having a close-packed structure in which steel filaments are twisted in the same direction and at the same pitch is also used to increase the cord cutting load.

[0004]

However, in the above-mentioned conventional steel cord, there is a problem that the rubber does not easily penetrate into the cord, so that the corrosion permeability is remarkably inferior. In particular, in a two- to three-layer twisted cord, in the case where the number of cores is 3 to 4, the rubber does not penetrate into the center of the core, so that if water enters from the cut portion of the tire caused by running on a rough road, Moisture propagated from the center of the core in the lengthwise direction of the cord, corroding the cord.

In order to avoid such problems, in order to allow the rubber to penetrate into the inside of the core, there is a steel cord in which a gap is provided between the filaments by corrugating the core filaments, etc. With steel cords having a complicated twist structure such as a double twist and a double twist, there is a problem that the contact shape between filaments is large and the cord shape becomes unstable, resulting in poor fatigue resistance.

Therefore, an object of the present invention is to improve the corrosion resistance of a steel cord without impairing the fatigue resistance of the cord, and a pneumatic radial tire whose durability is enhanced by using the steel cord as a reinforcing material. To provide.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventor impairs the fatigue resistance of the cord when a spiral is wound around at least one of the filaments constituting the steel cord. It has been found that the corrosion propagation resistance can be improved without the need to complete the present invention.

That is, the steel cord (1) for reinforcing rubber articles according to the present invention is a steel cord of two to three layers twisted in which the number of filaments in the core is 3 to 4,
The spiral is wound around at least one of the filaments of the respective layers of the first sheath and the second sheath.

The steel cord (2) for reinforcing a rubber article according to the present invention comprises a filament having a closest packing structure, and in a steel cord twisted in the same direction and at the same pitch, a spiral is wound around at least one of the filaments. It is attached.

The rubber cord reinforcing steel cord (3) of the present invention has a double twist structure in which the above rubber cord reinforcing steel cord (1) or (2) is used as a strand and a plurality of the strands are twisted.

The material of the spiral is steel or organic fiber.

It is preferable that the diameter of the circumscribing circle containing the spiral of the filament wound with the spiral is substantially the same as the diameter of the filament not wound with other spirals.

The diameter of the spiral is preferably 25% or less of the diameter of the filament on which the spiral is not wound.

The cross-sectional shape of the spiral is preferably elliptical.

The twist angle of the spiral wound around the filament with respect to the filament is 30 to 60.
It is preferably in the range of °.

The present invention also relates to a pneumatic radial tire using any one of the steel cords (1) to (3) for reinforcing a rubber article described above in a belt layer.

[0017]

[Function] The number of filaments in the core is 3 to 4
In a three-layer twisted steel cord (1), at least one filament in each layer of the core, the first sheath, and the second sheath, and in a close-packed steel cord (2), at least one filament. To
Further, in the steel cord (3) having a multi-twisted structure, a spiral is wound around at least one filament in the strand, so that the rubber to the center of the cord such as the core is not impaired without damaging the fatigue resistance of the cord. It is possible to enhance the infiltration property of. The filament of the core is preferably straight from the viewpoint of productivity. When two or more spirally wound filaments are arranged, it is preferable that the filaments are symmetrically dispersed in the cord cross section.

Any material such as steel or organic fiber may be used as the material of the spiral. However, steel is preferably used because the spiral is less likely to be broken by the contact pressure between filaments in the twisting process of the cord and the shape of the cord is stabilized. It is preferable.

It is preferred that the diameter of the circumscribing circle containing the spiral of the filament wound with the spiral and the diameter of the filament not wound with the other spiral are substantially the same when they are not the same. This is because the contour of the cord becomes distorted and the stress distribution when the cord undergoes bending deformation becomes non-uniform, which leads to a reduction in the fatigue resistance of the cord.

Further, it is preferable that the diameter of the spiral is 25% or less of the diameter of the filament in which the spiral is not wound, and when it is larger than 25%, the diameter of the filament in which the spiral is wound and the spiral itself. Since the diameter of the cord gets closer, stress concentrates on the spiral when the cord undergoes bending deformation, and it becomes difficult to wind the spiral in a neat spiral shape, and the contour of the cord becomes distorted shape, which is also the resistance of the cord. This is because the fatigue property is lowered.

Further, it is preferable that the cross-sectional shape of the spiral is an ellipse, because if it is an ellipse, the contact pressure on the filament is lowered and fretting can be prevented.

Furthermore, the twist angle of the spiral wound around the filament with respect to the filament is 3
It is preferably within the range of 0 to 60 °, 30 °
If it is smaller than 60 °, the fretting resistance and rubber penetration between the spirals are deteriorated. On the other hand, if it is larger than 60 °, the adjacent filaments are likely to fall and the rubber penetration is deteriorated and the cord shape becomes resistant to distortion. This is because the fatigue property is deteriorated.

In the steel cords (1) and (2) for reinforcing rubber articles according to the present invention, spirals are wound between core filaments and sheath filaments not wound with spirals, and between strands and in strands. It is preferable that the filaments have the same filament diameter, but different filament diameters are also acceptable.

Next, in the pneumatic radial tire of the present invention, the cord gap is within the range of 0.70 to 1.10 mm, and the interlayer gauge of the belt layer is 0.75 to 1.1.
It is preferably within the range of 5 mm. The reason why the preferable cord gap is within the range of 0.70 to 1.10 mm is that the belt separation resistance is optimal in this range, and the preferable belt interlayer gauge is 0.75 to 1.15 m.
The reason for being in the range of m is that the heat generation durability and the belt separation resistance are optimal in this range.

[0025]

EXAMPLES The present invention will be specifically described below based on examples. Various steel cords were manufactured by twisting under the conditions shown in Table 1 and Table 2 below. Examples 1 to 3 are shown in FIGS. 1 to 3, and conventional examples 1 to 3 are shown in FIGS.
6 is shown. This steel cord is applied to the belt layer at a driving number of 18.6 lines / 5 cm, and the size is 10.00R2.
Radial tires for trucks and buses of 0 14 PR were manufactured as prototypes, and the following evaluations were performed on these tires.

Rubber penetration into the inside of the cord Take out the steel cord from the belt layer of the test tire,
The state where no rubber penetrated into the steel cord was regarded as 0% and evaluated in%.

Separation resistance test tires were mounted on 10-ton trucks, repeated running on bad roads until the tire tread was completely worn, and then the tires were dissected and the presence or absence of separation in the belt layer was visually inspected. The obtained results are shown in Tables 1 and 2 below.

[0028]

[Table 1] * Compact structure

[0029]

[Table 2]

* 1 Compact structure * 2 Straight core filament * 3 Spiral cross section is elliptical

[0031]

As described above, the steel cord for reinforcing rubber articles of the present invention can improve the permeability of rubber into the cord without impairing the fatigue resistance of the cord. Good corrosion resistance. Further, since the cord made of the filament of the closest packing structure is twisted in the same direction and at the same pitch, the productivity is good. Therefore, the pneumatic radial tire in which such a steel cord is applied to the belt layer exhibits an excellent durability effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a steel cord for reinforcing a rubber article according to a first embodiment.

FIG. 2 is a cross-sectional view of a steel cord for reinforcing a rubber article according to a second embodiment.

FIG. 3 is a sectional view of a steel cord for reinforcing a rubber article according to a third embodiment.

FIG. 4 is a cross-sectional view of a steel cord for reinforcing a rubber article of Conventional Example 1.

FIG. 5 is a sectional view of a steel cord for reinforcing a rubber article of Conventional Example 2.

FIG. 6 is a sectional view of a steel cord for reinforcing a rubber article of Conventional Example 3.

Claims (8)

[Claims] 1. In a steel cord with a two- to three-layer twist in which the number of filaments of the core is 3 to 4, at least one of the filaments of the core, the first sheath and the second sheath has a spiral. Steel cord for reinforcing the wrapped rubber articles. 2. A steel cord for reinforcing a rubber article, which comprises a filament having a closest packing structure and is twisted in the same direction and at the same pitch, in which a spiral is wound around at least one of the filaments. 3. A steel cord for reinforcing rubber articles, wherein the steel cord for reinforcing rubber articles according to claim 1 or 2 is used as a strand, and a plurality of the strands are twisted to form a double twist structure. 4. The steel cord for reinforcing rubber articles according to claim 1, wherein the material of the spiral is steel cord or organic fiber. 5. The spiral wound filament has a diameter of a circumscribing circle including the spiral that is substantially the same as the diameter of a filament not wound with another spiral. A steel cord for reinforcing a rubber article according to any one of claims. 6. The steel cord for reinforcing rubber articles according to claim 1, wherein a diameter of the spiral is 25% or less of a diameter of a filament around which the spiral is not wound. 7. The twist angle of the spiral wound around the filament with respect to the filament is 30 to 6
The steel cord for reinforcing a rubber article according to any one of claims 1 to 6, which is within a range of 0 °. 8. A pneumatic radial tire using the steel cord for reinforcing a rubber article according to claim 1 in a belt layer.