JP5692749B2 - Steel cords for rubber article reinforcement and rubber-steel cord composites - Google Patents

Description

  The present invention relates to a steel cord for rubber article reinforcement and a rubber-steel cord composite (hereinafter also simply referred to as “cord” and “composite”), and more particularly, for reinforcement of rubber articles including tires, The present invention relates to a steel cord for reinforcing rubber articles and a rubber-steel cord composite useful as a carcass ply cord for a tire.

  Conventionally, a rubber-steel cord composite formed by coating a steel cord with rubber has been generally used as a reinforcing material for rubber articles such as tires. In particular, the carcass ply cord, which is a skeleton material for tires for large vehicles such as trucks and buses, is repeatedly bent at the tire side, so if the tire air pressure is low, the curvature of the tire side becomes severe, leading to the cord This increases the load.

  As a carcass ply cord generally used in a tire for a large vehicle, there is a 3 + 9 + 1 structure having a single spiral filament on the outer periphery of a 3 + 9 two-layer twist structure made of filaments having the same wire diameter. In a cord having such a 3 + 9 + 1 structure, fretting occurs between nine sheath filaments in contact with the spiral filament due to repeated bending input, which causes the cord to break.

  On the other hand, for example, Patent Document 1 proposes a technique for reducing fretting between the spiral filament and the sheath filament by making the twist direction of the spiral filament and the outermost sheath filament the same. . However, in consideration of the manufacturing aspect, if the twist direction of the sheath filament and the twist direction of the spiral filament are the same direction, the cord body is the same unless the sheath is tightened in an extreme torsional direction. A desired torsion cannot be obtained with a spiral filament wound in a twisted direction. In this case, if the torsion of the cord is forced out, an excessive brazing process is required on the sheath filament, and the twisting property may be disturbed.

  In Patent Document 2, the spiral filament is removed in order to eliminate fretting between the spiral filament and the outermost sheath filament, and a rubber penet is secured in order to restrain the sheath filament from being loosened during large bending input. A 3 + 8 steel cord is proposed. However, in the case of a 3 + 8 ply cord having no spiral filament, the bead core and the outermost sheath filament come into contact with each other when being wound around the bead core, and fretting occurs in the outermost sheath filament during traveling. There was a risk of breaking.

  Further, for a 1 × 12 compact twisted cord, a technique for changing the diameter of the outermost sheath filament is disclosed in Patent Documents 3 and 4, for example.

JP-A-6-17384 (Claims etc.) Japanese Patent Laid-Open No. 7-109685 (claims, etc.) Japanese Utility Model Publication 5-85898 (Claims) JP-A-5-279975 (Claims etc.)

  As described above, in the prior art, in the layer twist cord having a spiral filament, it is not possible to sufficiently suppress the occurrence of fretting between the spiral filament and the sheath filament without causing other problems such as productivity. There wasn't.

  Accordingly, an object of the present invention is to provide a rubber article that can more effectively suppress the occurrence of fretting between a spiral filament and a sheath filament without solving the above problems and causing problems such as productivity. It is to provide a reinforcing steel cord and rubber-steel cord composite.

  As a result of diligent study, the present inventor has determined that the outermost layer sheath is composed of two types of sheath filaments having different wire diameters in a two-layer twisted cord having spiral filaments, It has been found that the above-mentioned problems can be solved by arranging them uniformly in the circumferential direction of the cord.

That is, the steel cord for reinforcing rubber articles of the present invention is a steel cord for reinforcing rubber articles having an m + n + 1 structure in which spiral filaments are wound around the outer periphery of a two-layer twisted cord formed by twisting a plurality of steel filaments. ,
The sheath is composed of two types of sheath filaments having different wire diameters, and each of the two types of sheath filaments is arranged at three or more locations at equal intervals in the cord circumferential direction. When the twisting pitch is different, and the wire diameter of the thick one of the two types of sheath filaments is φa and the wire diameter of the thin sheath filament is φb,
0.65 ≦ φb / φa <1.0
It is characterized by satisfying.

  In the cord of the present invention, it is preferable that the twisting directions of the sheath filament and the spiral filament are different.

The rubber-steel cord composite of the present invention is a rubber-steel cord composite in which the steel cord for reinforcing rubber articles of the present invention is coated with rubber.
The rubber is contained between the two types of sheath filaments having a small diameter and the spiral filament.

  According to the present invention, the above configuration makes it possible to more effectively suppress the occurrence of fretting between the spiral filament and the sheath filament without causing problems such as productivity. Steel cords and rubber-steel cord composites can be realized.

It is sectional drawing of the width direction which shows an example of the steel cord for rubber article reinforcement of this invention. It is sectional drawing of the width direction which shows the other example of the steel cord for rubber article reinforcement of this invention. It is sectional drawing of the width direction which shows the further another example of the steel cord for rubber article reinforcement of this invention. It is explanatory drawing which shows the outline | summary of the fatigue test in an Example. It is sectional drawing of the width direction which shows an example of the conventional steel cord for rubber article reinforcement. It is width direction sectional drawing which shows the other example of the conventional steel cord for rubber article reinforcement.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The steel cord for reinforcing rubber articles of the present invention is a two-layer twisted cord having an m + n + 1 structure in which a spiral filament is wound around the outer periphery of a layer twisted cord formed by twisting a plurality of steel filaments. In the present invention, m and n in the m + n + 1 structure can be appropriately selected within a range of m = 1 to 4 and n = 6 to 12.

  FIG. 1 is a cross-sectional view in the width direction showing an example of a steel cord for reinforcing rubber articles according to the present invention. The steel cord for reinforcing rubber articles of the present invention shown in the figure is a one-layer sheath 2 comprising a core 1 in which three core filaments 11 having the same diameter are twisted together and nine sheath filaments 12 wound around the core 1. A 3 + 9 + 1 structure in which a spiral filament 13 is wound around the outer periphery of a layer twisted cord 3 made of In the cord of the present invention, as shown, the sheath 2 is composed of two types of sheath filaments 12A and 12B having different wire diameters, and each of the two types of sheath filaments 12A and 12B is equally spaced in the cord circumferential direction. It is important that it is arranged at three or more places, particularly 3 to 6 places.

  FIG. 5 shows a cross-sectional view in the width direction of a steel cord having a conventional 3 + 9 + 1 structure in which all sheath filaments have the same wire diameter. In this case, as shown in the drawing, since the spiral filament is wound around the nine outermost sheath filaments 102, the spiral filament 103 comes into contact with the nine sheath filaments 102 and fretting occurs. On the other hand, when the two types of sheath filaments 12A and 12B are arranged at three or more positions at equal intervals in the cord circumferential direction as in the present invention, the spiral filament 13 is wound around the outer circumference. In this case, mainly three or more large-diameter sheath filaments 12A support the spiral filament. Therefore, although the fretting occurs in the large-diameter sheath filament 12A as in the conventional case, the rubber sufficiently penetrates between the small-diameter sheath filament 12B and the spiral filament 13, so the fretting between them is slight. It will be something. Therefore, fretting can be reduced by comparing the 3 + 9 + 1 structure cord using the same wire diameter sheath filament having a spiral filament, and the cord fatigue property can be improved. Moreover, since the cord of the present invention does not have a restriction on the twisting direction, there is no problem in manufacturing. In particular, in the cord of the present invention, it is preferable in terms of manufacturing that the twist directions of the sheath filament and the spiral filament are different.

  In the present invention, the arrangement method of the two different-diameter sheath filaments 12A and 12B is not particularly limited as long as they are arranged at three or more locations at equal intervals in the cord circumferential direction. For example, in the example shown in the figure, the large-diameter sheath filaments 12A are arranged at three locations at 120 ° intervals in the cord circumferential direction, and the two small-diameter sheath filaments 12B are arranged at three locations therebetween. .

  In addition, as shown in FIG. 2, the thin sheath filaments 12B are arranged at three locations at 120 ° intervals in the cord circumferential direction, and the two large sheath filaments 12A are arranged at three locations between them. You may do. In this case, the six large diameter sheath filaments 12 </ b> A support the spiral filament 13. Therefore, fretting occurs between the spiral filament 13 and the large-diameter sheath filament 12A, but fretting between the small-diameter sheath filament 12B is reduced, and the cord fatigue property is improved. Further, for example, in the case of a cord of 3 + 8 + 1 structure, as shown in FIG. 3, one large filament filament 12A and one small sheath filament 12B are alternately arranged at four positions at 90 ° intervals in the cord circumferential direction. In this case, the four large-diameter sheath filaments 12 </ b> A support the spiral filament 13. Therefore, fretting occurs between the spiral filament 13 and the large-diameter sheath filament 12A, but fretting between the small-diameter sheath filament 12B is reduced, and the cord fatigue property is improved.

Here, in the present invention, the two different-diameter sheath filaments constituting the sheath 2 have the following formulas when the wire diameter of the large-diameter sheath filament is φa and the wire diameter of the small-diameter sheath filament is φb:
0.65 ≦ φb / φa <1.0
Is preferably satisfied. If the ratio φb / φa is less than 0.65, the dispersibility of the sheath filament is deteriorated, and the cross-sectional shape of the cord may be disturbed.

  In the present invention, it is preferable that the twist pitch of the core 1 and the twist pitch of the sheath 2 are different. Thereby, since the sheath filament does not fall into the gap between the cores, it becomes easy to ensure the dispersibility of the sheath filament.

  The rubber-steel cord composite of the present invention is obtained by coating the steel cord for reinforcing rubber articles with rubber, and between the thin sheath filament 12B and the spiral filament 13 of the two types of sheath filaments. , Rubber is in the way. Since the sheath 2 has a cord structure composed of two types of sheath filaments 12A and 12B having different wire diameters, rubber sufficiently enters between the thin sheath filament 12B and the spiral filament 13, so Therefore, the fretting suppression effect can be obtained with certainty.

  In the cord and composite of the present invention, specific conditions such as the wire diameter, cord diameter, and twist pitch of each filament are not particularly limited, and can be appropriately selected as desired. The present invention can be applied to all cords having a two-layer twist structure having spiral filaments other than a so-called compact structure in which a core filament and a sheath filament are twisted simultaneously.

Hereinafter, the present invention will be described in more detail with reference to examples.
Steel cords of cord structure 3 + 9 × 0.22 mm + 0.15 mm and 3 + 8 × 0.22 mm + 0.15 mm are used as Conventional Example 1 and Conventional Example 2 respectively, and two types of sheath filaments having different wire diameters under the conditions shown in the following table Steel cords of each example in which were arranged were prepared.

<Fatigue resistance>
The test cords were arranged in parallel at intervals of 2.0 mm, and the arranged cords were coated with rubber sheets from the upper and lower sides, and vulcanized under conditions of 145 ° C. × 40 minutes. As shown in FIG. 4, the sample 10 obtained by cutting a bundle of three cords after vulcanization is passed through a pulley 20 having a diameter of 22 mm, and the sample is moved up and down with a tension of 8.0% cord strength applied. A fatigue test was performed, and the number of repetitions until the sample broke was measured. The result was converted into an index display with each conventional example as 100. A larger index value indicates higher fatigue.

<Fretting properties>
In the same fatigue test as described above, the sample was driven up and down 1 million times in a state where a cord strength of 8.0% was applied through a pulley having a diameter of 50 mm and stopped. Next, the sample is dissected, one cord is extracted, the spiral filament is removed, the fretting depth of all the sheath filaments and the spiral filament is measured with a microscope, and the total value is calculated for each conventional example. The index was converted to 100. A smaller index value indicates better fretting properties.

<Cord shape>
Each test cord was embedded in the resin, and the disorder of the cord cross section was observed with a microscope, and judged in three stages of ◯, Δ, and ×. ○ indicates a state in which the dispersion of the sheath filament is good, Δ indicates a state in which the dispersion of the sheath filament is partially biased, and x indicates a state in which the dispersion of the sheath filament is biased as a whole.
These results are also shown in the table below.

  As shown in the above table, the sheath is composed of two types of sheath filaments having different wire diameters, and each of the two types of sheath filaments is arranged at three or more locations at equal intervals in the cord circumferential direction. As compared with Examples 1 and 2, it was confirmed that the fretting property between the spiral filament and the sheath filament was improved and the fatigue property was improved. Further, in the range where the wire diameter φa of the large sheath filament and the wire diameter φb of the small sheath filament satisfy 0.65 ≦ φb / φa <1.0, the dispersibility of the sheath filament is ensured and the cord shape It can be seen that is improved. In each of the rubber-steel cord composite samples of each example, a state where the rubber sufficiently entered between the thin sheath filament and the spiral filament was ensured.

DESCRIPTION OF SYMBOLS 1 Core 2 Sheath 3 Layer twisted cord 10 Sample 11, 101 Core filament 12A, 12B, 102 Sheath filament 13, 103 Spiral filament 20 Pulley

Claims (3)

In a steel cord for reinforcing rubber articles having an m + n + 1 structure in which a spiral filament is wound around the outer periphery of a two-layer twisted cord formed by twisting a plurality of steel filaments,
Sheath consists of two sheath filaments having different diameter, each of the two sheath filaments, Ri your code circumferential direction are arranged at equal intervals in three places or more, the core of the twist pitch and the and twist pitch of the sheath Ri is Do different, and, among the two kinds of sheath filaments, when the wire diameter of the ones of the large diameter .phi.a, and φb the diameter of the small diameter ones, the following equation,
0.65 ≦ φb / φa <1.0
A steel cord for reinforcing rubber articles characterized by satisfying The sheath filaments and twist direction of the spiral filaments different claims 1 steel cord for reinforcement of rubber articles according. A rubber-steel cord composite in which the steel cord for reinforcing rubber articles according to claim 1 or 2 is coated with rubber,
A rubber-steel cord composite, wherein the rubber enters between a thin filament of the two types of sheath filaments and the spiral filament.

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