JPH08284079A - Steel cord - Google Patents

Abstract

PURPOSE: To obtain a steel cord used as a reinforcing material for elastomer products such as pneumatic tires, and to improve the fatigue resistance of tires reinforced with the cord. CONSTITUTION: At least a part of strands is made up of core consisting of a single steel filament and sheath five steel filaments. The core filament is a wire which is so designed that the locus of its section perpendicular to the longer direction of the cord stands ellipsoidally preformed or postformed, having the following parameters: the ratio of the major axis (a) to minor axis (b) for the ellipsoid is 1.1<=(a/b)<=2.3; preformed or postformed rate Rc expressed by the ratio of the preformed or postformed amplitude Lc to the wire diameter (dc):(Lc/dc) is 0.12<=Rc<=1.0; and the preformed or postformed pitch Pc satisfies the relationship: 3.0(dc)/0.34<=Pc<=8.0(dc)/0.34.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel cord which is widely used for industrial purposes, and particularly used as a reinforcing material for belts, tires and the like.

[0002]

2. Description of the Related Art Conventionally, steel cords used for reinforcement of tires for construction vehicles and reinforcement of conveyor belts are required to have high strength and have a double twist structure in which strands obtained by twisting filaments are further twisted. Steel cords are widely used.

[0003]

However, when the steel cord having such a double twist structure is used, for example, for reinforcing a rubber article, rubber hardly penetrates into the cord and external damage reaches the reinforcing steel cord. Then, there is a problem that moisture penetrates, propagates inside the cord, propagates in the longitudinal direction, and corrodes the cord, which shortens the durable life of the product. Further, even if there was no external damage, the filament that was not bonded to the rubber inside the cord was not restrained by the rubber, so that it repeatedly jumped out of the composite due to bending input, leading to a failure.

Therefore, it is conceivable to use a 1 × 5 open twisted cord having good rubber permeability inside the strand, but when the open twisted cord is further twisted, the steel cord is closed due to the contact pressure with the adjacent strand. It is in a state and the expected effect cannot be obtained.

An object of the present invention is to provide a steel cord having sufficient durability without the cord being closed due to pressure during vulcanization.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has made a 1 + 5 structure in which a core filament is appropriately modeled into one strand, and twists the strands together. It was found that sufficient rubber can be stably permeated into the steel cord after pressure vulcanization, and the present invention was completed.

That is, the present invention is as follows: (1) At least a part of the strands comprises a core made of one steel filament and a sheath made of five steel filaments arranged around the core, The filament has an elliptical shape with a locus of a cross section perpendicular to the longitudinal direction of the cord, and the ratio of the major axis a to the minor axis b of the ellipse is in the range of 1.1 ≦ a / b ≦ 2.3. Further, the molding ratio Rc (= Lc / dc) represented by the ratio of the molding amplitude Lc of the core filament to the strand diameter dc of the core filament is 0.12 ≦ Rc ≦ 1.0, and the core The filament pitch Pc is 3.
It is a steel cord for reinforcing a rubber article having a multi-twist structure using a strand of 0 dc / 0.34 ≦ Pc ≦ 8.0 dc / 0.34.

(2) In a multi-twisted steel cord consisting of one core strand and six sheath strands arranged around the core strand, at least one strand of each strand is described in (1). Is a steel cord for reinforcing rubber articles.

(3) In a multi-twisted steel cord consisting of one core strand and six sheath strands arranged around the core strand, all strands have the structure described in (1), and a rubber article is reinforced. It is a steel cord for.

(4) In a multi-twisted steel cord in which 2 to 5 strands are twisted in a single layer, at least one of the strands is a steel cord for reinforcing rubber articles having the constitution described in (1). is there.

(5) In a multi-twisted steel cord in which 2 to 5 strands are twisted in a single layer, all the strands are steel cords for reinforcing rubber articles having the structure described in (1).

(6) In a multi-twisted steel cord consisting of two core strands and 6 to 8 sheath strands arranged around the core strands, at least one of the strands is described in (1). Is a steel cord for reinforcing a rubber article having the above structure.

(7) In a multi-twisted steel cord composed of two core strands and 6 to 8 sheath strands arranged around the core strands, all the strands have the structure described in (1). A steel cord for reinforcing goods.

(8) A steel cord for reinforcing a rubber article having the structure described in (6) to (7), characterized in that two core strands are aligned in parallel.

(9) The steel cord for reinforcing rubber articles according to (1) to (8), wherein the core filament diameter dc and the sheath filament diameter ds are substantially dc = ds in the structure of at least a part of the strands. is there.

[0016]

The present invention will be described in detail below. In the core filament of the strand of the 1 + 5 structure in the present invention, the cross-sectional locus drawn in the direction perpendicular to the cord longitudinal direction is an ellipse, and the ratio of the major axis a and the minor axis b of the ellipse is in a specific range. In addition, it is important to have a specific range of amplitude and pitch, which secures a gap for rubber penetration between the sheath filaments. Also, if the core filament is shaped within the scope of the present application, the strand itself becomes flat, and if this is used for the core strand, the arrangement of the sheath strands will be appropriately dispersed, the permeability of rubber inside the cord will be good, and corrosion resistance will be improved. This is because it has advantages such as increased sex.

As a result, in the conventional multi-twisted cord, the permeability of rubber was insufficient and there was a problem in corrosion resistance. However, when the strand of the present invention is used, the sheath strand has a dense structure. Even when they are in contact with each other, the effect of sufficient rubber permeability is exhibited.

In the present invention, the core filament has an elliptical section locus drawn in the direction perpendicular to the longitudinal direction of the cord, but if the ratio a / b of the major axis a and the minor axis b of the ellipse is less than 1.1. The arrangement of the sheath becomes uniform, the effect of permeating the rubber into the cord is insufficient, and when it exceeds 2.30, the core filament pops out from between the sheath filaments and the cord properties deteriorate.

When the number of sheath filaments in the strand is 5, that is, in the case of the 1 + 5 structure, the molding ratio Rc of the core filament (= Lc / dc, where Lc is the amplitude of the core filament, and dc is the diameter of the core filament). 0.12 ≦ Rc ≦ 1.0. When Rc is less than 0.12, the arrangement of the sheath is dispersed, the sheath gap cannot be properly secured, and the effect of permeating the rubber into the cord is insufficient, and when Rc exceeds 1.0, the cord properties are poor, This is because the stress is not evenly applied when a tensile load is applied to the cord and the cord strength is reduced.

The pitch Pc of the core filament of the strand is 3.0 dc / 0.34≤Pc≤
It is set to 8.0 dc / 0.34. Pc is 8.0 dc / 0.
If it is larger than 34, the sheath gap cannot be properly secured, the effect of permeating the rubber into the cord is insufficient, and Pc is 3.
If it is less than 0 dc / 0.34, the strength is reduced due to the load on the core filament during molding, and the core filament and sheath filament are not evenly loaded during tensile load on the cord, resulting in insufficient cord strength. become.

Here, the amplitude of the core filament in defining the patterning ratio Rc is to consider the portion forming the major axis in the elliptical cross-sectional shape formed by the core filament, and not the minor axis side.

In the present invention, in particular, in the case of the double twist structure having one core strand and six sheath strands, it was difficult for the conventional rubber to penetrate into the inside, but by using the strand of the structure of the present invention, it is possible to obtain sufficient rubber. Invades.

Also, in the case of a double twist structure in which 2 to 5 strands are twisted in a single layer, it has been difficult for the rubber to intrude into the inside, but by using the strand of the structure of the present invention, the rubber sufficiently intrudes. To do.

Also in the case of a double twist structure consisting of two core strands and 6 to 8 sheath strands, it has been difficult for the conventional rubber to penetrate into the inside, but by using the strand of the structure of the present invention, it is possible to obtain sufficient rubber. Invades. Further, this effect is obtained even when the core strand is in a straight shape in which the strands are not twisted.

When the core filament diameter of the strand is made smaller than the sheath filament diameter, the spacing between the sheath filaments becomes narrow, rubber is difficult to enter, and the rigidity of the core becomes weak, so that the effect of molding is deteriorated.
Further, when the core filament diameter is made larger than the sheath filament diameter, there are problems such as an increase in cord weight and deterioration in productivity. Therefore, it is preferable that the core filament diameter dc and the sheath filament diameter ds have substantially the same diameter from the viewpoint of improving the productivity in the manufacturing process.

As a reinforcing material, in order to secure the strength of the rubber composite and reduce the weight thereof, the carbon content is 0.80 to 0.80.
It is preferable to use a steel cord made of 0.85% by weight of high-pitched steel.

Even if a spiral filament is added to the multi-twisted cord of the present invention, the same effect as described above can be obtained.

[0028]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The cord structure, the elliptical shape of the core, and the core embedding ratio R described in Table 1, Table 2, Table 3, and Table 4.
c, a core pitch Pc, a sheath twist pitch Ps, a core filament diameter dc, a radial tire for construction vehicles of size 3600R51 equipped with a belt in which a steel cord made of a strand having a sheath filament diameter ds is embedded, and each tire is endured. The corrosion propagation property (separation resistance) and the cord strength were examined. The results are also shown at the bottom of Tables 1 to 4. 2 × of Example 10
(1 + 5) + 6 × (1 + 5) indicates that two core strands are aligned in parallel.

For corrosion resistance, the belt cord with rubber covered was taken out from the tire for 100 mm, the side surface was covered with silicon celite, and one end of the cord was immersed in a 10% NaOH aqueous solution to form an aqueous solution only from the cut surface. Was infiltrated and then penetrated for 24 hours. Then, the rubber was pinched with a pair of pliers and peeled off. The exposed portion of the metal was defined as a corrosion propagation portion, and the length (mm) was evaluated. The smaller the length (mm), the better the corrosion propagation resistance.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

EFFECT OF THE INVENTION The steel cord using the strand of the present invention has good productivity, is less affected by variations in the process, and has good rubber permeability so that it has good corrosion propagation resistance and cord strength. Since it can be held, it can be used as a rubber reinforcing material to improve the durability of a rubber composite pair such as a tire and to greatly improve its service life.

[Brief description of drawings]

FIG. 1 is a part of a cross-sectional view of a steel cord having a 1 + 5 structure strand of the present invention.

FIG. 2 is a part of a cross-sectional view of a steel cord having a conventional 1 + 6 structure strand (having a large core diameter and not having a mold).

FIG. 3 is a side view of an ellipse-shaped core filament of the present invention, and is an explanatory diagram of a core wire diameter dc, an amplitude Lc, and a pitch Pc.

[Explanation of symbols]

 1, 3 Core filament 2, 4 Sheath filament a Long axis b Short axis dc Core wire diameter Lc Core waveform amplitude Pc Core waveform pitch

Claims (9)

[Claims] 1. The composition of at least some of the strands comprises:
A core made of one steel filament and a sheath made of five steel filaments arranged around the core are provided, and the core filament has an elliptical shape with a locus of a cross section perpendicular to the longitudinal direction of the cord. , The ratio of the major axis a to the minor axis b of the ellipse is in the range of 1.1 ≦ a / b ≦ 2.3, and the shaping amplitude Lc of the core filament is
And the die diameter Rc (= Lc / dc) represented by the ratio of the core filament diameter dc is 0.12 ≦ Rc ≦ 1.
0, and the pitch Pc of the molding of the core filament
However, 3.0 dc / 0.34 ≦ Pc ≦ 8.0 dc / 0.3
A steel cord for reinforcing a rubber article having a double-twisted structure using a strand of No. 4. 2. In a multi-twisted steel cord comprising one core strand and six sheath strands arranged around the core strand, at least one of the strands has the structure according to claim 1. A steel cord for reinforcing certain rubber articles. 3. A multi-twisted steel cord comprising one core strand and six sheath strands arranged around the core strand, all strands having the structure according to claim 1 for reinforcing a rubber article. Steel cord. 4. A multi-twisted steel cord in which 2 to 5 strands are twisted in a single layer, and at least one of the strands is a steel cord for reinforcing rubber articles, wherein the strand has the structure according to claim 1. 5. A steel cord for reinforcing rubber articles, wherein in a multi-twisted steel cord in which 2 to 5 strands are twisted together in a single layer, all the strands have the structure according to claim 1. 6. A multi-twisted steel cord comprising two core strands and 6 to 8 sheath strands arranged around the core strands, wherein at least one of the strands is one of the strands. Steel cord for reinforcing rubber articles, which is a component. 7. A multi-twisted steel cord comprising two core strands and 6 to 8 sheath strands arranged around the core strands, all strands having the structure according to claim 1. Steel cord for reinforcement. 8. A steel cord for reinforcing a rubber article having a structure according to claim 6, wherein two core strands are aligned in parallel. 9. The steel cord for reinforcing a rubber article according to claim 1, wherein the core filament diameter dc and the sheath filament diameter ds are substantially dc = ds in the constitution of at least a part of the strands.