JPH09228270A - Steel cord for reinforcing rubber article and pneumatic radial tire using the steel cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject steel cord excellent in rubber infiltrativity despite having three-layer multiply laid structure hard for rubber to infiltrate into the inward of the cord, and excellent in resistance to corrosion propagation and buckling fatigue, and to obtain a pneumatic tire using the above steel cord. SOLUTION: This steel cord for reinforcing rubber articles has three-layer multiply laid structure. The core 1 is a strand A composed of three filaments arranged in nearly parallel with one another, at least one of them being subjected to preforming or postforming in the form of wave, helix or combination thereof. For each sheath layer, at least one sheath among the three sheaths adjacent to one another consists of strand A, or strand B composed of two filaments arranged in nearly parallel with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber cord for reinforcing rubber articles used as a reinforcing material for rubber articles such as pneumatic tires and industrial belts, and a pneumatic tire using the same.

[0002]

2. Description of the Related Art Conventionally, for reinforcement of rubber products such as pneumatic tires, in steel cords that are used by being embedded in rubber, moisture propagates in the longitudinal direction of the cord when a cut is made in the rubber product, Rubber has been required to penetrate into the cord to prevent corrosion from spreading.

In the conventional technology, (a) the number of sheaths and the wire diameter are larger than the wire diameters of the open twisted cord in which the filaments are excessively shaped and the gaps between the filaments are provided, and (b) the core strand. Cords with gaps between filaments by specifying, (C) 1x2, 2+
Cords having an improved twist structure such as 2, 4 × 2 are mainly known as a method for enhancing rubber penetration.

[0004]

However, since it is difficult to obtain the cord strength with the cord structure (a) or (c) described above, it is used as a reinforcing layer for protecting the inner layer from small tires and external damage. However, it was unsuitable as a reinforcing layer for a medium-sized or larger tire. Further, although the cord strength is easily obtained by the method (b), there is a problem that the arrangement of the constituent filaments is apt to be biased and the penetration of the rubber into the cord is not stable.

Therefore, an object of the present invention is to reinforce a rubber article which is excellent in rubber permeability, corrosion propagation and buckling fatigue resistance, even though it has a three-layer double twist structure in which rubber hardly penetrates into the inside. To provide a steel cord and a pneumatic tire using the same.

[0006]

In order to achieve the above-mentioned object, a steel cord for reinforcing rubber articles having a three-layer double twist structure of the present invention has three cores whose cores are aligned substantially parallel to each other. At least one filament has a pitch P (5Dt ≦ P ≦ 40Dt: Dt is a filament wire diameter) and a die attachment amount R (0.3Dt ≦ R ≦ 3D).
The corrugated or spiral shape of t), or a combination of the strands (A) having a pattern, and each sheath layer includes at least one of three adjacent sheaths,
The strand (A), or a strand (B) composed of two filaments that are aligned in parallel (however,
When the number of sheaths in each sheath layer is two, at least one is the strand (A) or the strand (B)).

In the present invention, all of the sheaths constituting each sheath layer can be either the strand (A) or the strand (B).

Further, after the sheaths forming the respective sheath layers,
The diameter of the filament of the sheath consisting of one filament is Dm, and the diameter of the filament of the strand (A) is D
t, when the filament diameter of the strand (B) is Dd, it is preferable that the following equation be satisfied: Dd ≦ Dm ≦ 2Dd Dt ≦ Dm ≦ (1 + 2 / √3) Dt, and more preferably the filament diameter. Dt and the filament diameter Dd are set to satisfy the following equation: Dd = Dt.

The present invention also relates to a pneumatic tire in which the steel cord for reinforcing a rubber article is applied to a belt.

In a conventional steel cord having a three-layer double-twisted structure and having a core composed of three filaments, the core strand has symmetry and the shape is stable, and one or two The number of sheaths can be increased as compared with the case of the core filament, which is advantageous for expressing the cord strength. However, in this case, since the central part of the core strand is shielded from the outside, the rubber does not permeate into the central part, and since it continues in the longitudinal direction, a corroded part when water enters due to cutting etc. It has the problem of spreading. On the other hand, in the steel cord of the present invention, the core is composed of the strand (A), and the sheath (A) or the strand (B) is also used in each sheath layer, so that the cord strength is impaired. It is possible to permeate rubber without.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In a steel cord for reinforcing rubber articles according to the present invention, the cores are aligned in parallel with each other.
Pitch P (5Dt ≤ P ≤ 40Dt: Dt is the filament wire diameter) and die attachment amount R (0.3Dt ≤ R ≤ 3D) among at least one of the filaments.
It is composed of a corrugated or spiral shape of t) or a strand (A) having a pattern formed by combining them. here,
The molding amount R is defined as the amplitude amount of the molding.

The reason why at least one filament of the filaments of the strand (A) is imprinted is to allow the rubber to penetrate into the portion surrounded by the three filaments. When the pitch P and the molding amount R of this molding become P <5Dt or R> 3Dt, the alignment becomes poor when a tensile input is applied to the cords, and the strength decreases. On the other hand, when P> 40 Dt and R <0.3 Dt, the effect of molding becomes small and the rubber penetration becomes poor.

Further, the steel cord of the present invention has advantages such as good productivity and less loss of strength because it is not necessary to twist the strand beforehand.

Next, in the steel cord of the present invention, at least one of the three adjoining sheaths in each sheath layer is the above-mentioned strand (A), or two filaments aligned substantially in parallel. Strand (B). However, when the number of sheaths constituting each sheath layer is two, at least one sheath is the strand (A) or the strand (B). The reason for this is that, as shown in FIG. 7, when three adjacent sheaths are ordinary monofilaments, a void portion a in which rubber cannot penetrate is generated, which easily becomes connected in the longitudinal direction of the cord, resulting in rubber permeability. Is worse.

In the present invention, in order to make it easier for the rubber to penetrate into the inside of the cord, each filament or strand itself constituting the sheath may be corrugated or spiral-shaped.

Further, in the present invention, after the sheaths forming the respective sheath layers, the filament diameter of the sheath consisting of one filament is Dm, the filament diameter of the strand (A) is Dt, and the strand (B) is When the diameter of the filament is Dd, it is preferable from the viewpoint of the heavy load between the filaments and the production of the cord that the following formula is satisfied: Dd ≦ Dm ≦ 2Dd Dt ≦ Dm ≦ (1 + 2 / √3) Dt. = Dt is more preferable.

[0017]

Next, the present invention will be described in detail with reference to examples. Steel cords were produced according to Table 1 below. Regarding these steel cords, the cord cross sections of Examples 1 to 4 are shown in FIGS. 1 to 4, respectively, and the cord cross sections of Comparative Examples 1 and 2 are shown in FIGS. 5 and 6, respectively.

Next, radial tires for trucks and buses of size 10.00R20 equipped with such a belt made of steel cord were prototyped, and each tire was tested for corrosion propagation resistance and buckling fatigue resistance. It was The results are also shown in Table 1 below. The corrosion propagation resistance is a maximum value of the length of the corroded portion extending from the cut portion of the damaged portion, measured in the cord direction, of the tire that has been completely worn due to running on rough roads.

[0019]

[Table 1] * 1 cr + 2 represents one strand (A).

[0020]

INDUSTRIAL APPLICABILITY The steel cord for reinforcing a rubber article of the present invention has a three-layer double-twisted structure, which is advantageous for exhibiting cord strength, and has good rubber permeability, corrosion resistance and corrosion resistance. Excellent in buckling fatigue. Further, by applying the cord to the belt layer of the pneumatic radial tire, a pneumatic tire excellent in durability and weight reduction can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a steel cord according to a first embodiment.

FIG. 2 is a sectional view of a steel cord according to a second embodiment.

FIG. 3 is a sectional view of a steel cord according to a third embodiment.

FIG. 4 is a sectional view of a steel cord according to a fourth embodiment.

5 is a cross-sectional view of a normal 1 + 5 structure steel cord of Comparative Example 1. FIG.

6 is a cross-sectional view of a steel cord having a normal 1 + 6 + 12 structure of Comparative Example 2. FIG.

FIG. 7 is a cross-sectional view of a steel cord having a three-layer double twist structure in which three adjacent sheaths are normal monofilaments.

[Explanation of symbols]

 1 Core Filament 2 Core Strand 3 First Sheath Filament 4 First Sheath Strand 5 Second Sheath Filament 6 Second Sheath Strand a Void

Claims (5)

[Claims] 1. In a steel cord for reinforcing a rubber article having a three-layer double twist structure, a core is composed of three filaments aligned substantially in parallel, and at least one of the filaments has a pitch P.
(5Dt ≦ P ≦ 40Dt: Dt is the filament wire diameter) and a corrugated or spiral shape with a die amount R (0.3Dt ≦ R ≦ 3Dt) or a strand (A) provided with a die having a combination thereof, Each of the sheath layers has at least one of three adjacent sheaths, the strand (A), or a strand (B) composed of two filaments aligned substantially in parallel (however, in each sheath layer). When the number of sheaths is 2, at least one of the strands is the strand (A) or the strand (B)). 2. All of the sheaths constituting each sheath layer are the strands (A) or the strands (B).
The steel cord for reinforcing a rubber article according to claim 1, which is any one of the strands. 3. The diameter of the filament of a sheath consisting of one filament after the sheath constituting each sheath layer is D
m, the diameter of the filament of the strand (A) is Dt,
The steel for reinforcing rubber articles according to claim 1 or 2, wherein when the diameter of the filament of the strand (B) is Dd, the following formula is satisfied: Dd ≤ Dm ≤ 2Dd Dt ≤ Dm ≤ (1 + 2 / √3) Dt. code. 4. The steel cord for reinforcing rubber articles according to claim 3, wherein the filament diameter Dt and the filament diameter Dd satisfy the following equation: Dd = Dt. 5. A pneumatic tire in which the steel cord for reinforcing a rubber article according to any one of claims 1 to 4 is applied to a belt.