JPH10131067A - Steel cord for reinforcing rubber article and pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord of a plural lay structure improved in corrosion fatigue and breaking resistances and to provide a pneumatic radial tire respec tively raised both in belt separation resistance by applying the steel cord to a belt and in breaking resistance of cord filaments by applying the steel cord to a carcass ply. SOLUTION: This steel cord for reinforcing a rubber article is obtained by laying seven strands 3 of a ply lay structure composed of one core filament 1 and four or five sheath filaments 2 and further winding a spiral filament 4 around the strands. In the steel cord, the filament diameter of the strands 3 is 0.20-0.30mm. The pneumatic radial tire is prepared by using the steel cord for reinforcing the rubber article as a reinforcing material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord for reinforcing a rubber article, and more particularly, to a water resistance of a steel cord for reinforcing a rubber article having a multi-twist structure in which a strand in which a plurality of steel filaments are twisted is further twisted. Also, the present invention relates to a pneumatic radial tire with improved durability against filament breakage, thereby greatly improving durability.

[0002]

2. Description of the Related Art Steel cords used for carcass plies and belts of large steel radial tires, such as construction vehicle tires, are required to have high strength, and strands obtained by twisting a plurality of steel filaments are further twisted. The steel cord of the double twist structure is used,
For example, as shown in FIG. 3, seven strands 3 (filament diameter: 0.21 mm) having a layered structure composed of one core filament 1 and six sheath filaments 2 are twisted, and a spiral filament 4 is further surrounded therearound.
(7 × (1 + 6) × 0.21 + 1 × 0.15) A teal cord (filament diameter: 0.15 mm) wound around
And steel cords with different filament diameters (7 × (1
+6) × 0.25 + 1 × 0.15) are known.

[0003]

The above-mentioned conventionally known steel cords have no particular problem in terms of durability and various performances of a large steel radial tire.
There is room for improvement in the following points, and improvement in that point has been desired. First, when such a conventional steel cord is applied to a tire belt, the rubber does not penetrate into the inside of the strand of the cord, so that water easily propagates in the strand, so that a cut wound reaching the tread portion was received. In some cases, separation may occur between the steel cord and the rubber.

Further, when such a conventional steel cord is applied to a carcass ply of a tire, the carcass ply also receives a compression input when a large compression input is applied in the radial direction of the tire tread due to a dangerous turn or the like, and the cord is constituted. There is a concern that the filaments may break due to fatigue. That is,
This is because in the conventional steel cord, the filaments constituting the strand are in direct contact with each other.

Accordingly, an object of the present invention is to solve such a problem, to improve the water resistance and the rupture resistance of a multi-twisted steel cord, and to improve the belt separation resistance by applying the steel cord to a belt. Another object of the present invention is to provide a pneumatic radial tire in which the breakage resistance of a cord filament is increased by applying to a carcass ply.

[0006]

The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and as a result, has found that the conventional 7 × (1 + 6) +
In a single-structured teal cord, the filament diameter is set within a predetermined range, the number of sheath filaments around the core filament in each strand is changed from 6 to 4 or 5, and the gap between the sheath filaments is 0.02 mm.
As a result, when the steel cord is applied to a tire belt, even if the tread has a cut wound reaching the belt, the propagation of water from the cut scratch is suppressed, the belt separation resistance is improved, and the carcass ply is applied. At times, even when a large compression input is received in the radial direction of the tire tread, it has been found that since the contact between the filaments is relaxed by the rubber, the fatigue fracture of the filament is suppressed, and the present invention has been completed.

That is, the steel cord for reinforcing a rubber article of the present invention is obtained by twisting seven strands having a layered structure composed of one core filament and four or five sheath filaments, and further comprising a spiral filament around the strand. A wound steel cord for reinforcing a rubber article having a multi-twist structure, wherein the filament diameter of the strand is 0.20 to 0.30 mm.

[0008] The present invention also relates to a steel cord for reinforcing a rubber article, wherein the tensile strength of a filament constituting the strand is 290 kgf / mm ² or more.

Further, the present invention provides the above-mentioned steel cord for reinforcing rubber articles, wherein the cord has a twist pitch of 20 to 3.
0 mm, and the ratio (S / C) of the twist pitch (S) of the strand to the twist pitch (C) of the cord is 0.5 to 0.6.
7 is a steel cord for reinforcing a rubber article.

Further, the present invention is a pneumatic radial tire using the above steel cord for reinforcing rubber articles as a reinforcing material.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the steel cord for reinforcing a rubber article of the present invention, the filament diameter of the strand is 0.1 mm.
It is in the range of 20 to 0.30 mm. If the filament diameter is less than 0.20 mm, sufficient strength as a cord cannot be ensured. On the other hand, if it exceeds 0.30 mm, the filament distortion at the time of tire input increases, and the fatigue resistance of the cord decreases. Getting worse.

In the steel cord for reinforcing rubber articles of the present invention, the number of sheath filaments in each strand is reduced by one or two compared to a conventional 7 × (1 + 6) +1 structure teal cord. Although the strength is reduced, this reduction in strength can be covered by increasing the strength of the steel material or increasing the pitch of the strands. However, when the number of sheath filaments is reduced by 3 to form a 7 × (1 + 3) +1 structure, it is difficult to secure the strength.

In the present invention, the tensile strength of the filament is preferably 290 kgf / mm ² or more. Such tensile strength is the strength of the steel material converted from the cord strength and the filament diameter. This tensile strength is 290 kgf / mm ²
If it is less than, sufficient strength as a cord cannot be secured. On the other hand, if it exceeds 350 kgf / mm ² , the current cord manufacturing technology will cause disconnection during manufacture, which is not practical.

In the present invention, the twist pitch of the cord is preferably 20 to 30 mm. Conventional 7
In the case of the teal cord having the × (1 + 6) +1 structure, the twist pitch of the cord was 18.5 mm, but by making it longer, the cord strength can be increased. However, if the length of the strand exceeds 30 mm, or if the ratio (S / C) of the twist pitch (S) of the strand to the cord pitch (C) exceeds 0.67, when the cord receives a compression input, Protrusion occurs and fatigue resistance deteriorates. On the other hand, when the ratio (S / C) is less than 0.5, the strength of the strand is reduced, and the cord strength is reduced.

As described above, the steel cord for reinforcing rubber articles of the present invention does not substantially reduce the cord strength as compared with the conventional 7 × (1 + 6) +1 structure multi-twisted steel cord, and does not cause a substantial decrease in the cord strength. By allowing the rubber to penetrate, when such a steel cord is applied to a tire belt, even if the tread has a cut wound that reaches the belt, the propagation of water from the cut scratch is suppressed and the resistance to water is reduced. The belt separation property is improved, and when applied to a carcass ply, the contact between filaments is alleviated by rubber even when a large compression input is applied in the tire tread radial direction, so that fatigue fracture of the filaments is suppressed. Is done. As a result, the durability of the pneumatic radial tire of the present invention in which the rubber cord for reinforcing a rubber article is used as a reinforcing material for a belt or a carcass ply is greatly improved.

[0016]

Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Various steel cords according to the cord structure, twist pitch, twist direction, and ratio (S / C) of the twist pitch (S) of the strand and the twist pitch (C) of the cord shown in Table 1 below were experimentally manufactured. In the table, 7 × (1
Fig. 1 shows a steel cord of +5) +1 structure, and 7x
FIG. 2 shows a steel cord having a (1 + 4) +1 structure, and FIG. 3 shows a conventional steel cord having a 7 × (1 + 6) +1 structure. In addition, such a steel cord has a size of 29.
5R25 radial tire carcass ply and first
Various test tires were manufactured by applying the test belts to ５5 belts.

For these prototype steel cords, S-
An S tensile test was performed. Specifically, an S-shaped chuck was set with an Instron and an autograph tester, a cord or filament taken out of the tire was set, and the cord or filament was pulled at a pulling speed of 20 mm / min, and the breaking strength at that time was determined. . The obtained cord strength and converted filament tensile strength are also shown in Table 1 below.

The test tire was subjected to a water resistance test of a belt and a compression fatigue test of a carcass ply. The test methods are as follows. (A) Water resistance test of belts Prototype tires were mounted on an actual vehicle, and rough roads including wet road surfaces were
After running 0000 km, dissection was performed and the length of water penetration in the cord longitudinal direction from the cut wound that reached the fifth belt was measured.

(B) Compression fatigue resistance test of carcass ply A vehicle equipped with a prototype tire having a normal internal pressure is repeatedly turned sharply on a constant zigzag path to dissect the tire after traveling 5,000 km and disassemble the carcass ply on the tread portion. Code 1
Zero filaments were pulled out, and the broken state of the filament was observed. The evaluation was represented by a breaking rate of the filament based on the following equation. Breaking rate = [(total number of broken filaments) / (total number of filaments)] × 100 The obtained results are also shown in Table 1 below.

[0020]

[Table 1] * This is a calculated value assuming that the gaps between sheath filaments in each strand are uniformly arranged.

[0021]

As described above, in the steel cord for reinforcing rubber articles of the present invention, a 7 × (1 + 5) +1 structure or a 7 × (1+
4) Due to the +1 structure, the rubber penetrates into the inside of the strand during vulcanization of the tire. Therefore, when such a steel cord is applied to a tire belt, even if a cut wound that reaches the belt is made on the tread, the cut is applied. The propagation of water from the wound is suppressed and the belt separation resistance is improved, and when applied to a carcass ply, even when a large compression input is received in the tire tread radial direction, the contact between filaments is relaxed by rubber. Therefore, fatigue fracture of the filament is suppressed. Further, by reducing the tensile strength of the filament to 290 kgf / mm ² or more, or setting the twist pitch of the cord and the twist pitch ratio of the strand to the cord within a predetermined range, the strength reduction accompanying the decrease in the sheath filament of the strand is sufficiently compensated. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a steel cord having a 7 × (1 + 5) +1 structure.

FIG. 2 is a sectional view of a steel cord having a 7 × (1 + 4) +1 structure.

FIG. 3 is a sectional view of a steel cord having a 7 × (1 + 6) +1 structure.

[Explanation of symbols]

 1 core filament 2 sheath filament 3 strand 4 spiral filament

Claims (4)

[Claims] 1. One core filament and four or five core filaments
A steel cord for reinforcing a rubber article having a multiply-twisted structure in which seven strands of a layer-twisted structure composed of two sheath filaments are twisted and a spiral filament is wound therearound, wherein the filament diameter of the strand is 0.20 A steel cord for reinforcing rubber articles, characterized by having a diameter of 0.30 mm. 2. The steel cord for reinforcing rubber articles according to claim 1, wherein the tensile strength of the filament constituting the strand is 290 kgf / mm ² or more. 3. The twist pitch of the cord is 20 to 30 mm, and the ratio (S / C) of the twist pitch (S) of the strand and the twist pitch (C) of the cord is 0.5 to 0.67. Item 3. A steel cord for reinforcing rubber articles according to item 1 or 2. 4. A pneumatic radial tire using the steel cord for reinforcing rubber articles according to claim 1 as a reinforcing material.