JP2002227081A - Steel cord for reinforcing rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel cord which has a high cord strength-exhibiting rate and excellent durability and is used for reinforcing rubbers. SOLUTION: This steel cord that is used for reinforcing a rubber article, is formed from a core comprising two core element wires which have the same diameter (d) and are arranged in parallel to each other in the longitudinal direction without being twisted, and a mono-layered sheath comprising four sheath element wires which have the same diameter as that of the core element wire and are twisted around the core, and has a flat cross-sectional outline is characterized in that a wave-shaped spiral deformation having an amplitude (Lw, Lh) comprising (a) 2.5d>=Lw>=1.3d (Lw is a width in the direction for binding the centers of the core elements to each other) and (b) 2.0d>=Lh>=1.1d (Lh is a width in the direction rectangular to the direction for binding the centers of the core elements to each other) is applied to the core element wire and in that the twist pitch P of the sheath is 90d>=P>=45d. Therein, 1... the core element wire, 2... the sheath element wire, Lw... the width in the direction for binding the centers of the core elements to each other, Lh... the width in the direction rectangular to the direction for binding the centers of the core elements to each other.

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 for reinforcing rubber, and more particularly, to provide a steel cord having a high cord strength and a high durability. Aim.

[0002]

2. Description of the Related Art In a rubber article represented by a tire, a steel cord is usually buried as a reinforcing layer in the rubber. The penetrated moisture propagates through the cavity and spreads inside the steel cord, causing rust on the steel cord, resulting in a decrease in strength and a decrease in adhesion to rubber. Therefore, a method has been proposed in which a plurality of core wires are twisted or twisted into a waveform without being twisted, and a sheath wire having a smaller number of wires than the fine filling is wound around the outside.

[0003] Further, Japanese Patent Application Laid-Open No. 9-156314 discloses a steel in which two core wires having the same diameter are arranged in parallel without twisting, and a sheath wire having substantially the same diameter as this is spirally wound. Code has been proposed. According to the invention proposed herein, a steel cord with reduced cost and improved corrosion resistance is obtained because there is no step of hammering the core element wire, and when this is used for a belt layer of a radial tire, Although the effect can be expected by tightening the carcass, on the other hand, there is no room for the core strand, so the load difference between the sheath strand and the load increases, and the strength of the steel cord is inferior to the strength .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a steel cord having a high cord strength and a high durability.

[0005]

The gist of the present invention is to provide a core in which two untwisted core strands having the same diameter d are arranged in parallel in the longitudinal direction, and a core having the same diameter as the core strand. And a single-layered sheath formed by twisting four sheath strands having the following structure around the core: (A)
The width Lw in the direction connecting the core strands is 2.5d ≧ Lw ≧
1.3d, (b) an amplitude (Lw, Lw) in which the width Lh in the direction perpendicular to the direction connecting the centers of the core strands is 2.0d ≧ Lh ≧ 1.1d.
h) The corrugated spiral is formed and the twist pitch P of the sheath is 90d ≧ P ≧ 45d.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The steel cord of the present invention is as described above. Here, the reasons for the limitation on the helical shaping amplitude of the core wire and the twist pitch of the sheath will be further described.

[0007] Spiral knitting amplitude of the core wire diameter is generally formed by corrugating the core wire diameter into a waveform by using an ordinary shaping machine, and bundling them in parallel to form a core. (A) The width Lw in the direction connecting the centers of the core strands is 2.3d.
.Gtoreq.Lw.gtoreq.1.4d, and (b) the width Lh in the direction perpendicular to the direction connecting the centers of the core wires is 1.8d.gtoreq.Lh.gtoreq.1.2d.
The reason why the helical shaping amplitude is specified in this manner is that the load of the tension applied to the steel cord is almost equally applied to the core and the sheath, and the strength of the core and the sheath wire is effectively exerted.

More specifically, when the diameter of the core wire and the sheath wire is d, the width Lw in the direction connecting the center of the core wire is 1.4d, or the width Lw in the direction connecting the center of the core wire. When the width Lh in the perpendicular direction is smaller than 1.2 d, when tension is applied to the steel cord, the core wire having low elongation breaks first and the strength of the steel cord decreases, which is not preferable. On the other hand, Lw is 2.3.
When d or Lh is larger than 1.8 d, the rubber is easy to penetrate, but on the contrary, the sheath is broken first. In addition, the shape of the steel cord becomes unstable, which adversely affects the workability during tire production, which is not preferable.

(Sheet Twist Pitch) Next, the sheath twist pitch is 45 to 90 times, preferably 50 to 70 times the wire diameter d. When the twist pitch of the sheath is shortened, the weight of the steel cord tends to be heavy and the strength tends to decrease, and when it is shorter than 45 times the strand diameter d, the effect of exerting the strength of the steel cord having the above-mentioned core strand amplitude is significantly impaired. Therefore, the diameter is preferably 50 times the wire diameter d. However, if the twist pitch is too large, the shape retention of the sheath after twisting deteriorates, so that the wire diameter d is preferably 90 times or less, and more preferably 70 times or less.

(Strand) Regarding the strand, the tensile strength of the strand is preferably 300 kg / mm ² or more, and 330 kg / mm ^2.
mm ² or more is more preferable. The material of the strand is preferably a brass-plated steel wire. Note that the tensile strength of the wire may be different between the core and the sheath.

[0011]

The present invention will be described in more detail with reference to the following examples. FIG. 1 is a sectional view (2+) of a steel cord according to the present invention.
4), 1 is a core strand, 2 is a sheath strand, and two core strands 1 are corrugated within a range indicated by an approximately ellipse (dotted line) and are parallel to each other. Is kept. On the other hand, the four sheath wires are formed by twisting the outer layer of the core wire at a predetermined pitch. The core and sheath wires used here were brass-plated steel wires. Table 1 shows the structure and characteristics of the steel cord.

To verify Example 1 and Comparative Examples 1 to 5,
This is an example in which an experiment was performed using the same strand (d = 0.225 mm). That is, Example 1 is an example that satisfies all the conditions, Comparative Examples 1 and 2 are out of the range of the condition specified by Lw, Comparative Examples 3 and 4 are out of the range of the condition specified by Lh, and Comparative Example 5 is In each example, the twist pitch is out of the range of the specified condition. The breaking strength of each of these steel cords was measured.
And the comparative examples were found to be inferior to this.

Examples 2 to 4 are examples in which the strands are changed, and all satisfy the conditions of the present invention.
It was found that the breaking strength of each of these steel cords was superior to that of the comparative example.

[0014]

[Effect] The steel cord of the present invention can suppress the drop in strength caused by using a steel cord in which a sheath strand is twisted in a conventional core strand non-twisted structure, and effectively reduce the potential strength of the strand. In this way, it is possible to supply more powerful steel cords at a lower cost. And, when embedded in rubber, of course, each element wire is entirely covered with rubber, thereby improving corrosion resistance and cord breakage resistance.

[0015]

[Table 1]

[Brief description of the drawings]

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

[Description of Signs] 1 ‥ core wire, 2 ‥ sheath wire, Lw ‥ width in the direction connecting the center of the core wire, Lh ‥ width in the direction perpendicular to the direction connecting the center of the core wire.

Claims (5)

[Claims] 1. A core comprising two untwisted core strands having the same diameter d arranged in parallel in the longitudinal direction, and four sheath strands having the same diameter as the core strand. In a steel cord for reinforcing a rubber article having a flat cross-sectional profile constituted by a single-layer sheath twisted around a core, the core strands arranged in parallel include (a) Width Lw in the direction connecting the core strands
2.5d ≧ Lw ≧ 1.3d, (b) The width Lh in the direction perpendicular to the direction connecting the centers of the core wires is 2.0d ≧ Lh ≧ 1.1d
A steel cord for rubber reinforcement, which is provided with a waveform spiral habit of an amplitude (Lw, Lh) and a twist pitch P of the sheath is 90d ≧ P ≧ 45d. 2. A width Lw in a direction connecting the centers of the core wires.
2. The steel cord for rubber reinforcement according to claim 1, wherein 2.3d ≧ Lw ≧ 1.4d. 3. The steel cord for rubber reinforcement according to claim 1, wherein (b) a width Lh in a direction perpendicular to a direction connecting the centers of the core wires satisfies 1.8d ≧ Lh ≧ 1.2d. 4. The twist pitch P of the sheath is 70d ≧ P ≧
The steel cord for rubber reinforcement according to claim 4, which is 50d. 5. The tensile strength of the core strand and the sheath strand is 30.
0 kg / mm ² or more of claims 1 rubber reinforcing steel cord, wherein the brass plated steel wire.