JP2600770Y2 - Steel cord for reinforcing rubber 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 for reinforcing rubber products used as a reinforcing material for rubber products such as automobile tires and conveyor belts.

[0002]

2. Description of the Related Art Generally, steel cords of this kind are used as reinforcing materials for rubber products such as automobile tires, conveyor belts, etc., in which a large number of steel cords are covered in parallel in a straight line. . Therefore, indispensable conditions for steel cord are not only excellent mechanical strength, but also good chemical adhesion with rubber material and good penetration of rubber material into steel cord. ,. That is, in order for the steel cord to sufficiently serve as a reinforcing material for a rubber product, it must be a complete composite with the rubber material.

[0003] A conventional steel cord has a so-called closed twist structure in which four to five strands are closely adhered to each other and twisted. This kind of steel cord has a hollow part in the center of the cord, so when forming a composite sheet using a steel cord and two rubber sheets, the rubber material does not penetrate to the above-mentioned hollow part, Simply covering the outer periphery of the cord cannot form a complete composite with the rubber material.

[0004] Therefore, in a rubber product using the steel cord, for example, an automobile tire, the rubber material and the steel cord are not sufficiently adhered to each other, and the rubber material and the steel cord are separated during running of the automobile, a so-called separation phenomenon. Causes significant impairment of the function of the tire, as well as moisture in the rubber material and moisture penetrating from the cuts in the tire reach the interior of the cord and propagate in the longitudinal direction of the cord, corroding the steel cord, The mechanical strength will be greatly reduced.

[0005] For this reason, recently, a steel cord in which a rubber material penetrates into the inside of the steel cord and is adhered to the entire circumference of each strand has been considered. This steel cord has a so-called open twist structure in which wires are twisted while providing a gap between the wires.

[0006]

However, in a steel cord having an open twist structure, in order for the rubber material to adhere to the entire circumference of each strand and sufficiently penetrate into the cord, a gap between the strands is required. Is required to be a sufficient interval for the rubber material to enter, that is, 0.02 mm or more. However, if a sufficient gap is provided between the strands as described above, the twisted structure is likely to be unstable during the production of the steel cord, and the strands are deflected or twisted in the longitudinal direction of the steel cord. There is a disadvantage that it becomes uniform.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and the rubber material surely penetrates between the strands to form a complete composite, and buckling and fretting are caused by repeated bending stress. An object of the present invention is to provide a steel cord for reinforcing rubber products which does not easily wear and has excellent fatigue properties.

[0008]

In order to achieve the above object, a steel cord for reinforcing a rubber product of the present invention is provided at one center.
N core wires and n wires around the core wire (n = 3 to 5)
In the steel cord of 1 + n structure formed by twisting by disposing side wire, wire diameter Shinmotosen d ₁ = 0.20~0.
In 40 mm, a pitch P ₁ = 4d ₁ ~35d _1, the outer diameter of the apparent d ₀ = 1.08d ₁ ~1.3d ₁ and which have substantially the habit spiral small consisting, P ₁ is P ₁ = 0 .3P
０．７0.7 P (P is the twist pitch), and the ratio d ₁ / d ₂ of the wire diameter d _{1 of the} core wire to the wire diameter d _{2 of the} side wire =
0.75 to 1.0.

By the way, the numerical limitation in the above configuration is a result obtained by a number of experiments, respectively, for the following reason.

[0010] The number n of the side strands constituting the cord is 3 to 5
The reason is that if the number of side strands is two or less, the shape of the cord tends to be unstable, and the strength of the cord is reduced. This is because the gap becomes too narrow or it becomes difficult to arrange the side strands evenly around the core strand.

If the wire diameter d ₁ of the core element wire is too small, the mechanical strength is inferior. If the wire diameter d ₁ is too large, the flexibility is inferior and the cord diameter increases. preferable.

Further, if the small spiral pitch P _{1 in} a substantially spiral shape of the core wire is smaller than four times the wire diameter d ₁ , an excessive plastic deformation is applied to the core wire at the time of the warp, and the core wire becomes hard. It breaks easily and productivity decreases. If it is larger than 35 times, the gap between the wires decreases due to the tensile force due to the flow of the rubber material during the molding of the rubber product or the ironing force applied to the cord surface, and the penetration of the rubber material becomes insufficient. ₁ = was 4d ₁ ~35d _1. Incidentally, 0 stability of the code twist pitch P of the steel cord twist is preferably 8~12mm the plane of the productivity, P ₁ in the range from substantially the same reason as the reason.
It is preferably 3 P to 0.7 P.

The apparent outer diameter d ₀ is 1.08 of d ₁ .
If it is smaller than twice, even if a rubber material having good fluidity is used, penetration into the inside of the steel cord during pressure vulcanization will not be sufficient, and if it is larger than 1.3, the stability of twist will deteriorate, and Not only is the fatigue property reduced, but the cord elongation under extremely low load is increased, and the workability is poor, so that d ₀ = 1.08
was d ₁ ~1.3d _1.

Here, a substantially spiral small habit is not limited to a precise spiral shape, but also a simple wavy shape can provide substantially the same effect, and thus includes such a shape.

By the way, the wire diameter ratio d ₁ / d ₂ = 0.75 to 1.0 of the central core wire and the n side wires around it.
The reason is that if the wire diameter ratio is smaller than 0.75, the width of the gap between the strands is reduced, so that the desired rubber material cannot be sufficiently penetrated, and if it is larger than 1.0, the shape is poor. Become
This is because adverse effects such as popping out of the core strands are caused.

By the way, it is conceivable to make the wire diameter ratio smaller than 0.75 and increase the apparent outer diameter d _{0. In} this case, the rubber product is formed into a substantially spiral shape by the tension applied to the steel cord during molding. It is not preferable because a small habit is easily deformed and rubber infiltration becomes difficult.

[0017]

When the rubber cord for reinforcing a rubber product according to the present invention having the above structure is vulcanized under pressure between two rubber sheets, a core wire and a side wire formed by a substantially spiral small habit are obtained. The rubber material penetrates into the minute gaps therebetween, and the circumference of all the wires is covered with the rubber material to form a complete composite with the rubber material.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The steel cord for reinforcing rubber products of the present invention will be specifically described below with reference to embodiments.

Embodiment 1 In FIG. 1, a small spiral pitch P ₁ =
Around a single core element wire 2 having a diameter d ₁ = 0.20 mm having an outer diameter d ₀ = 0.24 mm of 3.5 mm, three side elements having a diameter d ₂ = 0.20 mm The wire 3 is provided, and the steel cord 1 is configured by twisting with a twist pitch P = 10.5 mm and S twist. This embodiment is shown in Table 1 of the present invention 1.
Shown in

Embodiment 2 In FIG. 2, a small spiral pitch P ₁ =
Around one core element wire 5 having a diameter d ₁ = 0.22 mm having an outer diameter d ₀ = 0.26 mm of 3.5 mm, five lateral elements having a diameter d ₂ = 0.22 mm The steel cord 4 is formed by providing the wire 6 and twisting in the S twist direction with a pitch P = 10.5 mm. This embodiment is shown in Table 2 of the present invention. Also, P ₁ = 3.5 mm and d ₀ = 0.26 m
m around a single core wire having a wire diameter d ₁ = 0.22 mm
_{The invention} 3 of Table 1 shows a case where five side strands of ₂ = 0.28 mm are twisted in the same direction and at the same pitch. Furthermore,
P ₁ = 4.0 mm, wire diameter d ₁ = d ₀ = 0.40 mm
D ₂ = 0.38 m around one core strand of 0.35 mm
The present invention 4 in Table 1 shows a case where four side strands of m are similarly twisted.

By the way, as shown in Japanese Patent Publication No. 63-63293, the small twisting of the core strands 2 and 5 is carried out by means of a twisting device which rotates with the supplied strand as an axis. than Te, it is intended to impart an outer diameter d ₀ of the apparent and desired habit pitch P _1. In this case in order to impart the outer diameter d ₀ of the apparent and desired habit pitch P ₁ adjusts the rotational speed of the rotation interval of the imprint pins, the dimensions and strand as axial.

As the wires constituting the steel cord, a steel wire having a carbon content of 0.70 to 0.90 wt% is usually used. However, in order to impart high strength and good toughness to the steel cord, each wire is used. The wire has a carbon content of 0.80
It is more preferable to use 0.85 wt% steel wire.

Further, in order to improve the adhesion between the rubber material and the steel cord, it is preferable that each of the above-mentioned wires is plated with brass plating, bronze plating or the like. The wires constituting each cord used in the test were all made to have a carbon content of 0.82 wt%, and the surface thereof was subjected to brass plating.

Next, in order to confirm the performance characteristics of the steel cord of the present invention, a comparative test was conducted between the steel cords of the present invention 1 to 4 described in the above embodiment and the conventional steel cord, and the breaking load, rubber penetration The results shown in Table 1 were obtained when the ratio, compression fatigue property, and workability were evaluated.

It should be noted, in the table BL is the breaking load, RP rubber penetration property, RF compression fatigue, HW handling workability, habit pitch, d ₀ of P ₁ is wire with peculiarities substantially smaller spirally apparent outer diameter of, d ₁ is diameter of Shinmotosen, d ₂ denotes the wire diameter of Side Element wire.

[0026]

[Table 1]

At the time of this evaluation, the breaking load BL (kg
f) indicates the breaking load of only the steel cord, and this kind of steel cord requires at least 40 kgf or more.

The infiltration rate RP (%) of the rubber material is a rubber material having a 100% modulus of 35 kg / cm ² under a tensile load of 5 kg applied to each cord (used for tire breakers in which steel cords are embedded). The steel cord is taken out after vulcanization under pressure, the cord is disassembled, a certain length between the wires is observed, and the rubber material is compared to the observed length. The ratio of the lengths of the traces of contact was determined as a percentage, and the average value was displayed. This value needs to be 60 or more.

For the compression fatigue RF (%), a composite sheet is formed by embedding a plurality of steel cords in a rubber material having a 100% modulus of 35 kg / cm ² , and using this sheet to form a three-point pulley. Using a bending fatigue tester, the number of repetitions until the cord was broken after fretting wear, buckling and the like was determined, and the index of the cord of Conventional Example 1 was set to 100 and expressed as an index.

The handling workability HW is an evaluation of the complexity of the work during the production of the steel cord and the formation of the composite sheet and the handling of the cord. X was evaluated as very poor compared with the code, Δ as slightly inferior, and ○ as no difference.

FIG. 3 is a graph showing the ratio of the elongation to the load of the steel cord of the invention 1 and the steel cord of the conventional example 2 in a graph.

In Table 1, Conventional Example 1 is 1 × 5 × 0.2
5 A steel cord with a closed twist structure, with extremely stable twist, good compression fatigue properties and good workability but poor rubber penetration rate.

Conventional Example 2 is a steel cord having an open stranded structure of 1 × 5 × 0.25, which is excellent in rubber penetration rate and compression fatigue property, but inferior in handling workability. Further, in FIG. 3, the elongation with respect to the load is larger than that of the first invention.

In Comparative Example 1, each wire diameter is smaller than that of the present invention, and in Comparative Example 2, the wire diameter d ₂ of the side strand is larger than 0.3 mm. Moreover, Comparative Example 3 is greater than 35 times the value of the pitch P ₁ of Shinmotosen is wire diameter d ₁ of Shinmotosen with habit substantially spiral small, Comparative Example 4 has a number of Side Element Wire In Comparative Example 5, the apparent outer diameter d ₀ of the core _element having a substantially spiral small habit is larger than 1.3 times the diameter d ₁ of the core element. The test results did not satisfy all of the evaluation items.

On the other hand, the steel cords of the present inventions 1-4 satisfy all of the breaking load, the rubber penetration rate, the compression fatigue property, and the handling workability, and are optimal as a reinforcing material for rubber products. There was found.

[0036]

[Effect of the Invention] The steel cord for reinforcing rubber products of the present invention has no hollow portion inside the cord over almost the entire area in the longitudinal direction of the cord, and the cord has a small elongation under an extremely low load, so that the handling work can be performed. The properties are also good. In addition, when the steel cord is covered with rubber material, the rubber material surely spreads between the wires constituting the steel cord, forming a complete complex with the rubber material. Can be prevented from separating from the cord. Therefore, buckling does not easily occur even when a repeated bending stress is applied, and the wear due to the fretting phenomenon is small, so that the fatigue property is excellent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a steel cord according to a first embodiment.

FIG. 2 is a sectional view showing a steel cord according to a second embodiment.

FIG. 3 is a graph showing a ratio of elongation to load of the steel cord of the present invention 1 and the steel cord of the conventional example 2;

[Explanation of symbols]

 1,4 Steel cord 2,5 Core wire with small spiral shape, almost spiral 3,6 Side wire

Claims (1)

(57) [Scope of request for utility model registration] A steel cord having a 1 + n structure in which one (1) core element wire and n (n = 3 to 5) side element wires are arranged and twisted around the core element wire. The core element wire has a wire diameter d ₁ = 0.20 to 0.40 mm and a pitch P ₁ = 4d ₁
３５35 d ₁ , apparent outer diameter d ₀ = 1.08 d ₁ １1.3
has a substantially spiral small habit of d ₁ ,
P ₁ is P ₁ = 0.3P~0.7P of (P is twisting pitch)
Within the range, and the wire diameter d _{1 of the} core wire and the wire diameter d _{2 of the} side wire
Rubber products steel cord for reinforcing, which is a ratio d ₁ / d ₂ = 0.75~1.0 with.