JPH08302577A - Steel cord for reinforcing rubber and radial tire - Google Patents

Abstract

PURPOSE: To form a steel cord for reinforcing a rubber excellent in rubber permeability and fatigue resistance by winding a wire having a different preforming ratio spirally around the outer circumference of plural wires having a specific preforming ratio and to obtain a radial tire by using the steel cord to reinforce its belt part. CONSTITUTION: This steel cord for reinforcing a rubber, having its wires twisted each other in a loose state, is obtained by binding 2 wires having 110-150% preforming ratio almost in parallel to a bundle and winding a wire having 103-140% preforming ratio spirally around the circumference of the wires. By using the steel cord for reinforcing belt part, a radial tire is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord and a radial tire used for reinforcing rubber products such as vehicle tires and conveyor belts.

[0002]

2. Description of the Related Art In order to reinforce a belt layer in a passenger car tire, a steel cord having a 1 × n structure such as 1 × 3 to 1 × 5 in which three to five strands are twisted in the same direction at the same time has been conventionally used. Was used. However, in this structure, as shown in FIG. 1, since there is almost no gap between the strands of the cord, it is difficult to infiltrate the rubber into the void inside the cord during the vulcanization step after tire molding.
It is unavoidable that the voids are continuous in the longitudinal direction of the cord. Therefore, when a flaw reaches the reinforcing cord by stepping on a stone, a metal piece, or the like on the road surface while using such a tire, water is transmitted through the void portion inside the cord and rust is propagated to the entire cord. In such a state, not only the cord strength is lowered, but also the adhesive layer is broken at the interface between the cord surface and the rubber, so-called separation phenomenon occurs, the function as a tire is remarkably deteriorated, and its life is shortened. Will end up.

In order to improve such a defect, Japanese Patent Publication No. 2-29408 discloses that n strands are wound and twisted around a strand bundle in which n strands are aligned substantially in parallel. A combined n + n structure steel cord is disclosed. FIG. 2 shows a steel cord of such a 2 + 2 structure according to the prior art, which includes two strands 1a arranged in parallel.
The other two strands 2a, 2a are twisted together so as to be wound around 1a. In this structure, since the continuous void portion where the rubber does not penetrate is not formed in the center of the cord, the above-mentioned drawbacks of the 1 × n structure can be considerably improved.

[0004]

[Problems to be Solved by the Invention]
Even in the +2 structure steel cord, in the cross-sectional portions of (a) and (c) of FIG.
Since the same voids as in the 1 × 4 structure of (b) are generated, and in particular, there is a portion where the two aligned strands are in close contact with each other, the rubber permeability is still insufficient. There was a problem. Furthermore, when various stresses are applied to the cords in the tire, the wires are in close contact with each other in the prior art, so if there is no rubber in this part, a fretting phenomenon occurs in which the wires rub against each other, resulting in fatigue resistance. There was a problem that it was not enough.

The present invention was devised in order to solve the above problems. The purpose of the present invention is to prevent the wires from coming into direct contact with each other, and not to mention the central part of the cord, but to The rubber can be sufficiently penetrated into the circumference,
An object of the present invention is to provide a steel cord for rubber reinforcement which has improved corrosion resistance and high fretting resistance due to prevention of fretting between strands. Another object of the present invention is to provide a high performance and long life radial tire.

[0006]

In order to achieve the above-mentioned object, the present invention provides a wavy shape which is greater than the wave height generated in the wire when tightly wound before winding. It consists of three strands, two of which are bundled almost in parallel, and one strand is wound around the two strands in a spiral shape, so that the strands become loose. It has a structure. The patterning rate is such that the patterning rate PF _{2 of two} wires to be bundled is 110 to 15
It is preferable that the embossing rate PF _{1 of} 0% and one strand to be wound around the outer periphery is in the range of 103 to 140%. Further, in order to achieve another object, the present invention uses the steel cord having the above-mentioned configuration for reinforcing the belt portion.

[0007]

In the present invention, the number of strands is three, and the steel cord has a 2 + 1 structure in which one strand is spirally wound around two strands that are bundled substantially in parallel. . For this reason, no large void is formed in the center of the cord. Moreover, the strands including the bundle of strands are continuously given a wavy pattern of excessive height before being twisted. This allows
The length of continuous contact between the two strands that make up the bundle is extremely small, and a gap is created between the two strands, so that the strands are partially in the longitudinal direction of the cord. , And the closed contour portion is not formed by being surrounded by three strands at any position along the length of the cord.
Therefore, since the rubber is sufficiently spread and adhered to the periphery of each element wire, the steel cord is excellent in touch resistance, fretting resistance and fatigue resistance. In addition,
There is no problem with the decrease in the cord strength due to the number of strands being three because it can be compensated by increasing the diameter of the strands and increasing the strength.
Further, by using the steel cord having such a structure to reinforce the belt portion of the tire, a tire having a strong corrosion resistance and separation resistance and a long life can be obtained.

The present invention will be described below with reference to the accompanying drawings.
FIG. 3 schematically shows one embodiment of a rubber-reinforcing steel cord according to the present invention. Reference numerals 1a, 1a and 1b are strands, and carbon steel wire rods are drawn, and rubber such as brass is formed on the surface. It has been plated with good adhesion with, and has a diameter of, for example, 0.80 to 2.50 mm and a tensile strength of 110.
It is 135 kgf / mm ² . The three strands may all have the same diameter or may differ by one or more. 2 of the 3 wires 1a, 1a, 1b
The single strands 1a, 1a form a bundle that is aligned substantially parallel to the longitudinal direction, and the remaining single strand 1b is spirally wound around the outer periphery of the bundle strands 1a, 1a. The winding pitch is arbitrarily set to 10 to 18 mm.

Moreover, the bundled wires 1a and 1a and the other wire 1b are continuously formed with waviness of an excessive height at a molding rate of more than 100% before being made into a cord. ing. That is, the patterning rate of the bundled wires 1a, 1a is set to PF.
₂ and the patterning rate of _one strand 1b to be wound is PF ₁ , PF ₂ = 110-150%, PF ₁ =
The range of 103 to 140% is preferable. The reason for this is PF
_{When both 2} and PF ₁ are below the lower limit, the rubber permeability becomes almost the same as the conventional example, while when it is above the upper limit, the balance of the twisted-in length of the wire becomes poor and the fatigue resistance decreases. This is because the characteristics such as damage will occur.

With this configuration, as shown in FIGS. 3 (a) and 3 (b),
The bundle strands 1a, 1a and the other strand 1b only come into contact locally in the cord longitudinal direction, and a gap S is created between the bundle strands 1a, 1a and the other strand 1b. To be done. Moreover, the two strands 1a, 1a forming the bundle are also parallel to each other, but there are few regions in continuous contact with each other.
A gap S'is also created between a and 1a. Therefore, at any cross-section in the longitudinal direction of the cord, there is always one or more gaps and no closed contour.

The steel cord according to the present invention can be manufactured by using, for example, the buncher type twisted wire device shown in FIG. This twisted wire device has guide rolls 11, 12, 13, 14 on the central axis of rotation of the twisted wire device body 23.
Is provided, and a disk roll 15a that rotates in the same manner as the guide roll is provided outside the central axis of rotation,
15b, 16a, 16b are provided. Further, one element wire supply bobbin 19 which keeps a fixed position regardless of the rotation of the disc roll is arranged inside the disc roll. Two strands of wire supply bobbins 20 and 21 are provided outside the stranded wire device body 23. Further, in the stranded wire device main body 23, there are provided mold-forming devices 18a and 18b for imparting excessive slack to each strand.

In the production of the cord, the two wire strands 1a and 1a which should form a bundle are pulled out from the wire feed bobbins 20 and 21, and these wire strands 1a and 1a are guided by the guide rolls 11.
→ 15a, 15b → guide roll 12 → first molding device 18a → guide roll 13 → disc roll 16a,
16b → removing bobbin 22 passing through the guide roll 14
To be wound up. Further, the winding wire 1b is drawn out from the wire bobbin 19, and the wire 1b is formed by the second molding device 18b → guide roll 13 → disk roll 16
a, 16b → Passes through the guide roll 14 and is wound on the winding bobbin 22. And the disk rolls 15a, 15
Under the condition that b, 16a, 16b rotate, the winding bobbin 22 rotates and the cord 3 is continuously wound around the winding bobbin 22.

In the above process, the wire bobbins 20, 21
The strands 1a, 1a drawn out from the above are twisted in one direction until they pass through the guide roll 11, the disc rolls 15a, 15b and the guide roll 12, and when passing through the first molding device 18a, the PF ₂ Excessive squeezing is given by. On the other hand, the wire 1b drawn out from the wire bobbin 19 is excessively curled by the above-mentioned PF ₁ when passing through the second molding device 18b, and is drawn on the two wire 1a, 1a. It Since the two wires 1a and 1a are untwisted in the opposite direction before passing through the guide rolls 13 and 14, the wires 1a and 1a are almost twisted so that the waviness of the first molding device 18a remains. There is no state. Wire 1b is guide roll 1
The bobbin 2 is wound around the wires 1a and 1a when passing through the wires 3 and 14 and is a steel cord 3 having a 2 + 1 structure.
It is wound up to 2. The steel cord of the present invention can of course be manufactured not only by the buncher type twisted wire device but also by the tubular type twisted wire device.

[0014]

EXAMPLES Examples of the present invention will be described below. Diameter 0.28m
Steel cords having a 2 + 1 structure according to the present invention were manufactured by using three strands of m and changing the wave height (molding ratio) in various ways. Further, as a comparative example, the same strand as that of the example was used to fabricate a tightly twisted 2 + 1 structure steel cord. As a conventional example, a steel cord having a 2 + 2 structure was manufactured using the same strands as those of the example. Table 1 shows manufacturing conditions and code characteristics of the above-mentioned examples, comparative examples, and conventional examples. In Table 1, "rubber permeability" means that a linear cord is vulcanized in rubber to prepare a sample, the cord in this rubber is decomposed in the longitudinal direction, and the rubber permeability is visually determined. It depends on the method. 100% of the cord was completely covered with rubber. Further, the "fatigue resistance index" was obtained by vulcanizing a linear cord in rubber to prepare a cylindrical sample, and using a Hunter type rotary bending fatigue tester with a fatigue limit of 10 ⁷ times, The conventional example was expressed as an index with 100.

[0015]

[Table 1]

As is clear from Table 1, Examples 1 to 1
It can be seen that the steel cord of No. 5 has a stable and good rubber permeability, has less fretting and is excellent in fatigue resistance as compared with the conventional 2 + 2 structure.

[0017]

According to the first aspect of the present invention described above, a wavy pattern is formed in advance before winding so that the wave height becomes larger than the wave height generated in the wire when the cord is tightly wound. It consists of three strands, two of which are bundled almost in parallel, and one strand is wound around the two strands in a spiral shape so that the strands become loose. Therefore, there is a gap between the strands at any position in the longitudinal direction of the cord, and the rubber is sufficiently spread around the periphery of each of the three strands. Therefore, stable and good rubber permeability is ensured, fretting is small, and fatigue resistance is excellent. Further, according to claim 2, since the an embossed rate PF ₁ of one strand to be wound on the typing rate PF ₂ and the outer circumference of the two wires to be bundled with the optimum range, corrosion resistance and The excellent effect of achieving well-balanced fatigue is obtained. According to the third aspect, since the steel cord is used to reinforce the belt portion, it is possible to provide an excellent effect that a long-life radial tire excellent in corrosion resistance and fatigue resistance can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a conventional steel cord.

FIG. 2 is an explanatory view schematically showing a conventional steel cord.

3A and 3B schematically show an example of a steel cord according to the present invention, FIG. 3A is a side view thereof, and FIG. 3B is a sectional view of each portion for one pitch.

FIG. 4 is an explanatory view showing an example of a steel cord manufacturing apparatus and a manufacturing method of the present invention.

[Explanation of symbols]

 1a, 1a bundle of wires 1b winding wire

Claims (3)

[Claims] 1. A three-strand wire, which is pre-wound before being wound, having a wave height that is greater than the wave height of the wire when tightly wound. A steel cord for rubber reinforcement, characterized in that the strands are loose by bundling the strands substantially in parallel and winding one strand around the two strands in a spiral shape. 2. A patterning rate PF of two wires to be bundled.
_{2. The} steel cord for rubber reinforcement according to claim 1, wherein ₂ is 110 to 150%, and the patterning rate PF _{1 of one} strand to be wound around the outer periphery is in the range of 103 to 140%. 3. A radial tire comprising the steel cord according to claim 1 for reinforcing a belt portion.