JP2000273775A - Steel cord and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive steel cord with high rubber infiltrativeness thereinto despite being of simple structure, capable of preventing the core from slipping off as well. SOLUTION: This steel cord is obtained by arranging n side wires (n is 5-7) around a single core wire followed by stranding them together; wherein the core wire consists of a flat wire 60-90% in flatness (minor axis/major axis) having waves in the direction of the minor axis and twisted with nearly equal strand length to that of this cord.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord suitable for reinforcing a rubber molded product and a radial tire using the same.

[0002]

2. Description of the Related Art Steel cords are widely used as reinforcing materials for rubber molded products such as radial tires and conveyor belts. Among them, a 3 + 6 structure is used as a belt material for large vehicles such as trucks and buses. Such a structure has a gap between wires on each side as shown in FIG. Although improved, this alone has a cavity in the center of the three strands in the core. For this reason, there is a problem that a so-called separation phenomenon occurs in which moisture penetrates into the core portion, corrodes the wire, and separates the rubber from the wire. Further, the steel cord of the 3 + 6 structure has a problem in that the manufacturing cost is increased because the core strand is twisted and the sides are twisted in two steps. In order to solve these two problems, as shown in FIG. 2, a 1 + 6 structure is employed, and the diameter of the core wire is relatively increased in order to improve rubber permeability. The wire is easy to get out of the cord terminal,
Therefore, there is a problem that the life of the tire is significantly reduced.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a simple structure having a good rubber permeability and a good core. It is an object of the present invention to provide an inexpensive steel cord that can prevent detachment. Another object of the present invention is to provide a radial tire which is less prone to corrosion and has a long life.

[0004]

In order to achieve the above-mentioned object, the present invention provides a method in which n wires (n = 5 to 7) around one core wire.
Is a steel cord in which the side wires are arranged and twisted together, wherein the core wire is a flat wire having a flattening ratio (short diameter / long diameter) of 60 to 90%, and the flat wire has a wave in the short diameter direction. It is characterized by being twisted with the same twist length as the cord. Preferably, the core wire has a pitch of 1 to 15 mm and a wave height of 0.01 to 0.3 m so that the gap amount between the side wires is 0.02 to 0.10 mm.
It consists of m waves. In order to achieve the second object, the present invention is characterized in that the steel cord is embedded in a rubber molded body as a belt ply or a carcass ply.

[0005]

In the present invention, the number of side wires selected from 5 to 7 is arranged around one core wire 1 and the wires are twisted all together, so that they can be manufactured in one process. As a result, the manufacturing cost can be reduced. The core wire is flattened and corrugated in its short diameter direction. According to the present invention, the side wire is arranged around the flat wire as a center and twisted all at once. Since the fibers are twisted, a gap that allows rubber to penetrate between the side wires can be freely and reliably formed by adjusting the flatness and the wave height of the core wire. In addition, since the core wire has a flat cross section and has a wave in the minor diameter direction as described above, and has a torsion that occurs during stranded wire, the core wire has a core wire between the side wire compared to a round wire having a circular cross section. , A large resistance can be obtained in the pulling-out direction, whereby the resistance to centering can be remarkably improved.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 shows an embodiment of the steel cord according to the present invention at predetermined intervals (approximately 1 / in the longitudinal direction of the cord).
(Every four pitches). Reference numeral 1 denotes a single core wire, and reference numerals 2 and 2 ′ denote a plurality of (six in the drawing) side wires that are arranged so as to surround the core wire 1 and are collectively twisted by a buncher type twisting machine. The carbon content of the core wire 1 and the side wires 2 and 2 ′ is 0.70 to 1.00 wt%.
Made of high tensile steel wire with a tensile strength of 280
It is preferably 450 kgf / mm ² , and the surface is plated with brass or the like having good adhesion to rubber.

The number of the side wires 2 and 2 'is 5 or more and 7 or less. The reason is that the four wires make the core wire easily jump out to the side, and the eight wires need to have a large core wire diameter in order to provide a sufficient gap between the side wires 2 and 2 ', thereby resulting in fatigue. This is because the property is reduced. In FIG. 3, the steel cord has a 1 + 6 structure, but is not limited to this. A plurality of gaps s of 0.02 to 0.10 mm, which are sufficient for rubber penetration, are formed between the side wires and between the core wire and the side wire. If the size of the gap is less than 0.02 mm, it is impossible to achieve a rubber permeability of 80% or more, which is not possible. On the other hand, if the gap is larger than 0.10 mm, it is not appropriate because the poor twisting in which the core wire 1 protrudes from between the side wires 2 and 2 'easily occurs.

Each of the side wires 2 and 2 'is formed of a round wire having the same diameter, but the core wire 1 has a flat cross section. As shown in FIG. 4, assuming that the major axis is W and the minor axis is D, D / W is preferably 0.6 to 0.90. The reason for this is that when the D / W is 0.90 or more, it is not the same as a round wire, and the corelessness resistance is deteriorated. When the D / W is 0.6 or less, it is difficult to flatten the wire. . The cross-sectional shape of the core wire 1 is substantially oval as shown in the figure, but is not limited thereto, and may be elliptical, oval, or track-like. In the illustrated example, the core wire 1 has a larger wire diameter (cross-sectional area) than the side wires 2 and 2 ′, but is not necessarily limited to this.

Further, the core wire 1 has a continuous wave 10 in the minor axis direction in the cross section as shown in FIG. This wave 10 is for widening the interval between the side wires 2 and 2 'and improving the rubber permeability to the cord core. The wave 10 may be a crimped shape in which a bent portion and a straight line portion are repeated, or may be a wave composed of only a smoothly continuous curved portion without including a linear component in one plane. This wave consisting only of a continuous curved part is not only a combination of continuous arcs,
It may be a sinusoidal curve, a continuous arc of a cycloid, a continuous arc of a cardioid, a continuous arc of a tratrix, and the like. The core wire 1 may have a twist before being twisted.

The two-dimensional wave 10 has a wave pitch P in the range of 1.0 to 15.0 mm and a wave height h of 0.01.
It is preferably in the range of 0.30 mm. Wave height h
Is less than 0.01 mm, the effect of widening the gap between the side wires 2 and 2 ′ becomes poor, and the rubber permeability decreases. Further, the effect of preventing the loss of heart becomes insufficient, so that it is impossible.
However, if the wave height h exceeds 0.30 mm, the peak of the wave is too high, and the core wire 1 jumps out of the gap between the side wires 2 and 2 ′, which is not appropriate.

In the steel cord, since the core wire 1 having a flat cross section and having the wave 10 in the short diameter direction and the surrounding side wires 2 and 2 'are twisted together, FIG. As shown in (d), the core wire 1 is twisted and deformed at a rotation angle substantially equal to the twist pitch in the longitudinal direction of the cord. That is, the side wire is tentatively twisted around the circular circumscribed circle as shown in FIG. For this reason, the gap s is reliably formed, and the core wire 1 partially contacts the side wires 2 and 2 ′, whereby a frictional resistance action is generated when a tensile force is applied in the axial direction. Due to the permeation of the rubber from the gap s, the movement (extraction) of the core wire 1 in the axial direction is suppressed.

Incidentally, the diameter of the core wire 1 is changed to the side wires 2 and 2 '.
When the diameter is larger than the diameter, the gap between the side wires due to the wave 10 and the twisting can be widened, and the gap can be formed by increasing the diameter, so that the rubber permeability to the cord core can be further improved. Also, the wave 10 of the core wire 1 is
In the case of a wave composed of only smoothly curved portions without a linear component in one plane, fatigue resistance can be improved.

FIG. 5 shows an example of a radial tire according to the present invention. Reference numeral 5 denotes an outermost rubber sheet on which a tread is formed, and reference numerals 6a and 6b denote lower-layer rubber sheets for a lower-layer rubber sheet. The steel cord A according to the present invention is embedded in the rubber sheets 6a and 6b for use.

Next, an example of a method for producing a steel cord according to the present invention will be described. The core wire 1 is formed by quenching a high-strength steel wire having a predetermined diameter, brass plating, wire drawing, flattening, and then corrugating with a gear having a large number of pins at the tooth tip. Made by doing. The flattening is performed using a pair of rolls or more, and the rolls can be adjusted in a gap so that a predetermined flattening ratio can be obtained. Said gear is arranged on the pass line and bends the wire by means of a pin, thus producing a core wire 1 having a flat cross section and having a wave 10 in its minor axis direction.

FIG. 5 shows an example in which the processing of the core wire 1 and the production of the steel cord are performed in a continuous line. Six supply reels 3 and 3 'are arranged upstream, and one reel 3' in the center. From round wire 1 'for core wire 1
However, from the other five reels 3, the side wires 2 are continuously supplied to the buncher-type twisting machine 7 via the head plate 4 and the voice 6, respectively. The buncher type twisting machine 7 includes a plurality of turn rollers 70,
Guide roll 70 ', a pair of fryers 71, a cradle 72, a capstan 73 and a winding drum 74
And

On the pass line between the reel 3 ′ and the end plate 4, the above-mentioned rolling rolls 9, 9 and special gears 8, 8 are arranged, so that the round wire 1 ′ is separated from the reel 3 ′. When it is fed out, it is compressed from the symmetrical position by 180 degrees by the rolling rolls 9 and 9 and flattened upstream of the end plate 4, and then the wave 10 is formed by the engagement of the pins 80 and 80 of the gears 8 and 8. The obtained core wire 1 passes through the end plate 4 and the voice 6 together with the side wire 2, and the side wire 2 is arranged so as to surround the core wire 1 at the center. The steel gorge A of the present invention is obtained by twisting all together by rotation.

Next, specific examples of the present invention will be described. And strength is 300 kgf / mm ² class different diameters one round wire of tensile, tensile strength using 300 kgf / mm ² grade diameter various six round wires, 1+ by stranding machine shown in FIG. 6
Six steel cord structures were prepared. As shown in FIG. 4, a core wire having a crimped wave was used. As shown in Table 1, the thickness, flatness, wave height, and wave pitch of the core wire were variously measured, and the obtained steel cords were tested for breaking force, side wire gap, rubber permeability, and resistance to centering. Are shown in Table 2.

The rubber permeability was determined by visual inspection using a score system. 5 points where the rubber has completely penetrated, 2.5 points where the rubber has completely penetrated, and 0 points where the rubber has not penetrated. A total of 50 points were checked. By displaying this in 100 minutes, the permeability of the comb is evaluated,
Those with 80% or more were judged as good. Two types of corelessness resistance were evaluated. The first is the coreless resistance in the state of the bare cord. The end of the 300 mm cord is gripped, and in this state, the core wire on the free end side is pulled out, and the maximum value at that time is determined by the breaking force of the core wire. The divided value was expressed as a percentage. Second
Species are rubberized cords that are resistant to centering.
The value divided by the breaking force of the core wire when the core wire was pulled out in this state was expressed in percentage. The case where the core wire was cut and did not come off was defined as 100%.

[0019]

[Table 1]

[0020]

[Table 2]

As is clear from Tables 1 and 2, the flatness of the core wire is 0.60 to 0.90, the wave height of the core wire is 0.01 to 0.3 mm, and the wave pitch of the core wire is 1 to
It can be seen that each effect of rubber penetration and prevention of core slippage is excellent because it is 15 mm.

[0022]

According to the first aspect of the present invention described above, an inexpensive steel cord which has a simple structure and can be manufactured by one-step twisting, yet has good rubber permeability and can prevent slippage. An excellent effect is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conventional steel cord having a 3 + 6 structure.

FIG. 2 is a sectional view of a conventional steel cord having a 1 + 6 structure.

3 (a), 3 (b), 3 (c), and 3 (d) are enlarged cross-sectional views showing different positions in the longitudinal direction of the steel cord according to the present invention.

FIG. 4A is a schematic perspective view showing an example of a core wire in the steel cord of the present invention, FIG. 4B is an enlarged sectional view,
(C) is an explanatory view showing a state when the core wire and the side wire are twisted.

FIG. 5 is a sectional view showing an example of a radial tire according to the present invention.

FIG. 6 is a side view illustrating a steel cord manufacturing apparatus of the present invention.

[Explanation of symbols]

 1 core wire 2, 2 'side wire 10 waves

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Muneyoshi Chiba 2-3-14 Nihonbashi Muromachi, Chuo-ku, Tokyo F-term in Tokyo Seimitsu Corporation (reference) 3B153 AA10 AA19 AA32 BB08 BB13 CC52 FF16 GG05 GG40

Claims (3)

[Claims] (1) n wires (n = 5 to 5) around one core wire;
7) A steel cord in which the side wires are arranged and twisted together, and the core wire has a flattening ratio (short diameter / long diameter) of 60 to 90.
% Flat wire, wherein the flat wire has a wave in the minor axis direction and is twisted with a twist length substantially equal to that of the cord. 2. A gap between side wires is 0.02 to 0.10.
The steel cord according to claim 1, wherein 3. A radial tire, wherein the steel cord according to claim 1 or 2 is embedded as a belt ply or a carcass ply in a rubber molded body.