JP3043891B2 - Steel cord for reinforcing elastomer products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord used as a reinforcing material for elastomer products such as pneumatic tires and industrial belts, and more particularly to an improvement in cord break resistance.

[0002]

2. Description of the Related Art For example, as a steel cord for reinforcing a tire, a so-called 1 × 4 or 1 × 5 structure in which 4 to 5 steel filaments are twisted has been widely used. However, in recent years, there has been a strong demand for weight reduction and further cost reduction of tires, particularly for contributing to lower fuel consumption of automobiles. To meet this demand, steel cords having a 1 × 3 or 1 × 2 structure have been used. Is starting to be.

[0003] These 1x3 or 1x2 steel cords have a simple twist structure in which the number of filaments is simply reduced, and in order to obtain appropriate belt strength, the filaments need to be thickened. . However, if excessive input is applied to the tire during cornering or the like, the so-called buckling deformation occurs on the tread of the tire that is outside during cornering, and the cord is buckled, so compressive stress is applied to the cord, Eventually, the cord breaks. This phenomenon occurs remarkably especially when the filament is thick.

Conventionally, in order to avoid such a cord breaking phenomenon, means for adding a new reinforcing member to a tire product or the like has been adopted, but this is a factor that greatly impedes the reduction in weight and cost of the product. Therefore, the merit of applying the steel cord having the 1 × 3 or 1 × 2 structure to the reinforcing material is greatly reduced.

Further, regarding a 1 × 3 structure code, Japanese Patent Publication No. 3-29914 discloses a space in which a single wire is removed from a 1 × 4 structure code as an interval between the wires. The structure is disclosed. It is believed that cords according to this structure exhibit good properties when compressive stress is applied to the cord. However, a code sequence that is originally a 1 × 4 structure must be maintained in a 1 × 3 structure,
In particular, it is very difficult to maintain this structure even after high-stress molding, such as vulcanization molding of a tire, so that application on an industrial scale has been impossible.

On the other hand, steel cords used for reinforcing belts of tires are disclosed in JP-A-56-31090 and JP-A-56-13140.
No. 4 describes a code having a 1 + 3 structure. The cords disclosed therein are advantageous in that they have relatively high tensile stiffness, but they are inferior in cord breaking resistance because buckling occurs easily.

[0007]

Accordingly, an object of the present invention is to provide a steel cord having a 1 + 3 structure excellent in cord breakage resistance, which can be expected to improve not only in weight saving but also in cost reduction. Is what you do.

According to the present invention, there is provided a steel cord formed by twisting a sheath made of three filaments having the same diameter around one core filament shaped into a waveform that changes on one plane. In a cross section orthogonal to the longitudinal direction of the cord, the maximum angle of a triangle formed by connecting the center points of the respective sheath filaments is 90 ° or more.
The apex that is less than 0 ° and forms the maximum angle is always on the same sheath filament, and furthermore, the center-to-center distance between the sheath filament and an adjacent sheath filament is
A steel cord for reinforcing an elastomer product, characterized in that the sheath filaments are arranged so that the diameter thereof is 1.0 to 1.3 times the sheath filament diameter.

[0009] The steel cord has a capacity of 0.80 to 0.
It is advantageous to use a filament containing 90% by weight of carbon. That is, in order to reduce the weight, which is one of the objects of the present invention, when the carbon content of the filament is increased, the cord strength is increased, and the durability of the cord itself can be improved. In this case, the strength can be maintained by the cord without using another reinforcing body, and the amount of the cord itself can be reduced, which can help to reduce the weight of the tire.

FIG. 1 shows a cross section of a steel cord for reinforcing an elastomer product according to the present invention. In the figure, reference numeral 1 denotes a core filament shaped in a waveform that changes on one plane. The core filament 1 is formed by twisting sheath filaments 2 to 4 having a diameter larger than that of the core filament 1.

The sheath filaments 2 to 4 are
In any cross section perpendicular to the longitudinal direction of the
Form by connecting the center points 2a, 3a and 4a of the sheath filament
The maximum angle α of the triangle formed is 90 ° or more and less than 180 °,
And the apex forming the maximum angle is always on the sheath filament 3
And the sheath filament 3 and adjacent thereto
The distance L between the centers of the sheath filaments 2 and 4 is
Thread filament diameter d _s1.0 to 1.3 times
Is important.

[0012] By arranging the sheath filaments according to the above, when a predetermined shaping is performed on the sheath,
The phase between each sheath filament is substantially the same,
The cord breakage resistance is improved.

The diameter of the core filament is preferably in the range of 40 to 85% of the sheath filament diameter, more preferably 40 to 85%.
By setting it to about 60%, the tensile rigidity of the cord is improved,
Consequently, it is preferable to avoid belt end separation. Further, if the twist pitch of the sheath filament is less than 9.5 mm, it is economically disadvantageous. On the other hand, if it exceeds 28 mm, the cord rupture resistance deteriorates.

Further, in producing the steel cord of the present invention, a required molding amount is given by a preformer, and the three sheath filaments are made substantially the same in phase, and are wound around the core filament. It may be twisted, or it may be produced by twisting around the core filament by giving a predetermined amount of molding to the three bundles by a preformer. Further, the cord can be flattened with a press roll or the like to produce an elliptical cord.

[0015]

In the present invention, the maximum angle of the triangle formed by connecting the center points of the sheath filaments of the cord is set to 90 degrees.
° or more, and the distance L between the sheath filament and the sheath filaments adjacent thereto located maximum angle, to a 1.0 to 1.3 times the sheath filament diameter d _s for the following reason. That is, in the conventional 1 × 3 twisted structure and 1 + 3 twisted structure cord as shown in FIGS.
When there is a compression bending input, as shown in FIG. 4, a compression buckling phenomenon that occurs at a critical point where a large bending deformation occurs is recognized, whereas in the case of the cord according to the present invention shown in FIG. No buckling phenomenon was observed as shown in FIG.

This is because, by adopting the cord arrangement shown in FIG. 1, the phases between the sheath filaments are substantially the same, so that even if the cord has a compressive bending input, the three sheath filaments will buckle. The input can be absorbed without causing the core filament, and since the core filament is shaped into a corrugated shape, the core filament accompanying the sheath filament does not buckle and can absorb the compression bending input. It is considered that buckling does not occur.

However, when the maximum angle of the triangle formed in the cross section of the cord is less than 90 °, the buckling phenomenon appears similarly to the conventional cord shown in FIGS.
An arrangement of 90 ° or more is required.

On the other hand, the reason why the maximum angle is less than 180 ° is that three sheath filaments are arranged in a straight line.
That is, when the maximum angle is 180 °, the resistance to breakage of the belt cord is reduced, so that this is prevented.

Further, the distance L between the sheath filament located at the maximum angle and the sheath filament adjacent thereto is
And was a 1.0 to 1.3 times the sheath filament diameter d _s for the following reason. That is, in order to improve the resistance to cord breakage resistance, be L = d _s, i.e. three filaments be adjacent, is advantageous, contacting with each other the sheath filaments of three twisting,
Since the production is extremely difficult, a substantial effect can be obtained if the ratio is 1.3 times or less.

The steel cord having the above structure can be suitably used as a reinforcing material for a carcass, a belt and a chafer of a pneumatic tire.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Steel cords having a 1 + 3 structure shown in FIG. 1 were prototyped according to Table 1, and these cords were sized to 175/70.
R13 was applied to a two-layer belt in a radial tire for passenger cars. The prototype belt has a cord angle:
At 68 °, the width is 140mm (first belt) and 130mm (second belt)
Belt). As a comparison, a steel cord having the structure shown in FIGS. 2 and 3 was prototyped according to Table 1, and applied under the same conditions. Here, the maximum angle α of each steel cord and the distance between adjacent filaments are the results of measurements on arbitrary 20 cord sections in the belt, shown in the upper and lower limits.

After the prototype tire thus obtained was run on a drum of 10,000 km under a low internal pressure and a high load, the cords of the tires were taken out, and the number of broken cords was examined. Table 1 also shows the results. .

[0023]

[Table 1]

[0024]

According to the steel cord for reinforcing an elastomer product of the present invention, the durability against compression deformation applied to the cord is remarkably improved, so that the durability of the elastomer product can be remarkably improved. In particular, when applied to a tire that frequently undergoes compression deformation, not only can the durability be naturally improved, but also the weight and cost of the tire can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a steel cord according to the present invention.

FIG. 2 is a cross-sectional view of a conventional steel cord.

FIG. 3 is a cross-sectional view of a conventional steel cord.

Fig. 4 Compressive strain (%) and compressive stress (kg) of steel cord
It is a graph which shows the relationship with f).

[Explanation of symbols]

 1 core filament 2 sheath filament 3 sheath filament 4 sheath filament

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) D07B 1/06

Claims (2)

(57) [Claims] 1. A steel cord formed by twisting a sheath made of three filaments of the same diameter around one core filament shaped into a waveform that changes on one plane, wherein the sheath is In a cross section orthogonal to the longitudinal direction of the cord, the maximum angle of the triangle formed by connecting the center points of the sheath filaments is 90 ° or more and less than 180 °, and the apex forming the maximum angle is always on the same sheath filament, A steel cord for reinforcing an elastomer product, characterized in that the sheath filaments are arranged such that the center-to-center distance between the sheath filament and the sheath filament adjacent thereto is 1.0 to 1.3 times the sheath filament diameter. 2. The steel cord according to claim 1, wherein the filament contains 0.80 to 0.90% by weight of carbon.