JPH05272081A - Steel cord - Google Patents

Abstract

PURPOSE:To produce a steel cord improved in life time by alternately arranging plural cords composed of two intertwisted wires and strands, twisting the cords together with the strands and effectively improving fatigue properties and rubber permeability. CONSTITUTION:This invented steel cord has a characteristic structure formed by alternately arranging two to six cords (a) composed of two intertwisted wires and strands (2) and twisting the cords together with the strands. The plural cords (a) composed of two intertwisted wires are intertwisted together with the strands 2 characteristically in the opposite direction to that of the twisting of the cord (a) itself. The twist of the cord (a) itself is characterized by its twist length within a range of >=20 times and <=80 times the strand diameter.

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 as a reinforcing material for radial tires.

[0002]

2. Description of the Related Art From the viewpoints of global environment preservation, tire performance, etc., it is required to reduce the weight and extend the life of tires. In order to solve this problem, the role of steel cord as a reinforcing material for tires is extremely important. large. Conventionally, for example, in truck and bus tires, a steel having a 3 + 9 structure or the like is composed of an inner layer formed by twisting three strands and an outer layer formed by tightly twisting nine strands around the strand. The code was used. However, in the steel cord, when rubber is vulcanized, a central portion of the inner layer and a gap between the inner layer and the outer layer where the rubber does not penetrate are formed, and moisture penetrates into the gap to cause a cord corrosion-separation trouble. As a countermeasure against this, a steel cord with increased rubber permeability inside the cord has been developed by increasing the diameter of the inner layer strands or decreasing the number of outer layer strands to form gaps between the outer layer strands. Has been done.

[0003]

In all of the above-mentioned steel cords, there is a big drawback that the inner layer wire and the outer layer wire are in a point contact which is sharp and promotes fretting corrosion. As described above, when the wire diameter of the inner layer is increased, a wire diameter difference occurs, and fatigue progresses from the wire having the larger inner layer. Further, as described above, the wire diameter of the inner layer is increased or the number of wire strands of the outer layer is reduced, and the gaps between the wire strands of the outer layer tend to be concentrated in one place. Variations occur and rubber does not penetrate into the central voids of the inner layer, and there is a limit to improving their fatigue properties and rubber permeability.

The present invention was developed in order to solve the above-mentioned problems, and its object is to arrange a plurality of two-stranded cords and strands alternately and twist them at the same time. The purpose of the present invention is to provide a steel cord with improved fatigue life as well as effective rubber penetration to improve cord life.

[0005]

According to the present invention, two or more two-twisted cords and strands are alternately arranged and twisted at the same time to form a loose point contact state between strands. To reduce wear and effectively form a gap open to the outside up to the center of the cord to improve rubber penetration.

Further, the twisting of a plurality of two-stranded cords and the strands of wire is configured by twisting in a direction opposite to the twisting direction of the two-stranded cord itself, and further, the twist length of the cord itself is made from the two twisted cords. By making the wire diameter 20 to 80 times as large, the fatigue characteristics and rubber permeability are further enhanced.

[0007]

Operation: Two to six double-stranded cords and strands are alternately arranged and twisted at the same time, and each strand is contacted in a loose point contact state to effectively reduce wear and A large uniform open gap is formed between the double-stranded cord and each strand to improve rubber penetration and effectively reduce cord corrosion. In addition, the two-stranded cord and the strand are twisted in a direction opposite to the twisting direction of the two-stranded cord itself, and the twist length of the two-stranded cord itself is 20 Double to 80 times, each wire is in a state of loose point contact, the formation of the gap is further improved, wear is reduced, and rubber penetration is further enhanced to improve fatigue characteristics and rubber penetration. ing.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are shown in FIGS.
In the figure, a is a two-strand cord formed by previously twisting two strands 1 and 2 is a strand twisted by alternately arranging between the two-strand cords a, which is a steel cord of the present invention. Is a two-strand cord a prepared by twisting two strands 1 in advance.
2 to 6 two-stranded cords a and the wires 2 are alternately arranged as shown in the drawing and simultaneously twisted to form a final cord. For example, as in the embodiment shown in FIG. 1A,
3 × 2 + with 3 two twisted cords a and 3 strands 2
The steel cord has three structures, and theoretically has a cross-sectional structure as shown in FIG. 1A, specifically, a cross-sectional structure as shown in FIGS. 2A to 2D. Further, as in the embodiment shown in FIG. 1B, a steel cord having a 4 × 2 + 4 structure is constructed by four two-stranded cords a and four strands 2 and theoretically has a cross section as shown in FIG. 1B. The structure is specifically a cross-sectional structure as shown in FIGS. 3A to 3D.

As is clear from the drawings, in each of the above steel cords, a closed space is not formed in each two-stranded cord a itself, and each strand 1 of each two-stranded cord a is sequentially formed. The structure is arranged in the center, and each two-stranded cord a
A large air gap that is open to the outside as shown in the drawing is effectively formed between each of the strands of wire and each of the strands 2, and the gap is relatively large as is clear from the cross-sectional views of FIGS. In addition to being formed regularly, the contact between each of the wires 1 and 2 is in a state of point contact which is considerably looser than that of the conventional multi-layer twisted steel cord. Therefore, there is a feature that the progress of wear of each strand is gradually reduced, and furthermore, the rubber is effectively penetrated completely into the center of the cord due to the gap.

[0010] Each two-stranded cord a and each strand 2 are preferably braided to an appropriate degree when they are simultaneously twisted together to increase their openness. Further, it is preferable that the number N of the two-stranded cord a and the number of the strands 2 be 2 ≦ N ≦ 6. N = 2 is the required minimum number, and when N = 7 or more, each two-stranded cord a is arranged inside the seven strands 2, and the alternate arrangement structure is impaired. A uniform twist structure is not formed. Within the range of the basic structure as described above, 2 cords are provided between the two twisted cords a, respectively.
A structure in which the strands 2 of the book are arranged is also possible.

Further, in the steel cord of the present invention, the twisting of a plurality of double twisted cords a and the strands 2 is carried out in a direction opposite to the twisting direction of the double twisted cord a itself. That is, the SZ twist structure further enhances the gap formation between each two-strand cord a and each strand 2, and further enhances the rubber permeability and its reliability.

Further, in the steel cord of the present invention, the twist length (twist pitch) P2 of the two-strand cord a itself is set to 20 times or more and 80 times or less of the wire diameter of the wire 1. By changing the twist length P2, it is possible to change the degree of penetration of the rubber. If P2 is made small, the rubber penetration condition will be good but the fatigue properties will decrease.
2 is preferably 20 times or more the wire diameter. If P2 is increased, the permeation condition of the rubber becomes worse, and the degree of permeation differs depending on the type of rubber. Therefore, it is necessary to determine P2 while confirming the permeation degree. 80 times or less of the wire diameter is desirable.

In each of the sectional views A to D shown in FIG. 3, a brass-plated wire (0.22 mmφ, element wire) has a twist length P 2 = 10.
mm (45 times as large as the wire diameter), two wires are twisted together to make a two-stranded cord a, and four of these two-stranded cords and four of the brass-plated wires (0.22 mmφ, strands) are alternated. The steel cords of 4 × 2 + 4 structure, which are arranged and simultaneously twisted in the SZ direction with a twist length P1 = 20 mm (91 times the wire diameter), are embedded in a transparent liquid thermosetting resin and cured. The cross-sectional structures of the twist length P2 cut at substantially equal intervals are shown. In each of the sectional views A to D shown in FIG. 2, the steel cord having the 3 × 2 + 3 structure formed in the same manner has the same sectional structure.

Brass plated wire (0.22mmφ, bare wire)
Steel cord with 3 × 2 + 3 structure (SZ twist) (invention) -Sample No. 1, steel cord with 3 × 2 + 3 structure (twist in the same direction) (invention) -Sample No. 2, 4 ×
Steel cord of 2 + 4 structure (SZ twist) (present invention)-
Sample No. 3 and steel cord with 3 + 9 structure (twist in the same direction) (conventional example) -Sample No. 4 was manufactured, the steel cord of each sample was embedded in rubber, the rubber block was placed in water, and the air of each steel cord was placed. The amount of permeation was measured and the results shown in Table 1 were obtained. Further, the sample No.
3, the twist length P1 of the two-stranded cord a and the strand 2 is set to 20 mm, and the twist length P of the two-stranded cord a itself is set.
2 = 5 mm to 20 mm was changed, and the air permeation amount and the fatigue characteristics were measured using two kinds of rubbers, and the results in Table 2 were obtained.

[0015]

[Table 1]

[0016]

[Table 2]

Each steel cord of the present invention is shown in FIGS.
As is clear from FIGS. 3A to 3D, large gaps open to the outside are formed substantially uniformly between the two twisted cords a and the individual strands of the individual strands 2, as shown in Table 1. To
The steel cords (Samples 1 to 3) of the present invention have a significantly reduced air permeation amount as compared with the conventional example (Sample 4).
In the case of Z twist, air hardly permeates. That is, no residual void is formed inside the steel cord embedded in the rubber, and excellent rubber permeability is confirmed.

Further, as is apparent from Table 2, depending on the twist length P2 of the double twisted cord a itself and the kind of rubber,
Although the amount of air permeation and the fatigue property change, good results can be obtained for both the amount of air permeation (rubber permeability) and the fatigue property when P2 is approximately 20 to 80 times the wire diameter. It has been confirmed.

[0019]

The present invention has the above-mentioned structure.
Two to six two-stranded cords and strands are alternately arranged and twisted at the same time, and each strand is contacted in a loose point contact state to effectively reduce wear, and
A large, substantially open gap, which is open to the outside, is formed between the main-twisted cord and each strand to improve rubber penetration and effectively reduce cord corrosion. In addition, the two-stranded cord and the strand are twisted in a direction opposite to the twisting direction of the two-stranded cord itself, and the twist length of the two-stranded cord itself is 20 times the strand diameter. Or 80 times, the wear reduction and the rubber penetration are further enhanced, and the fatigue characteristics and the rubber penetration are remarkably improved.

[Brief description of drawings]

FIG. 1 is a theoretical cross-sectional mechanism diagram (A), (B) showing each embodiment of the present invention.

2A to 2D are cross-sectional mechanical views of concrete parts of the steel cord shown in FIG. 1A.

3A to 3D are cross-sectional mechanical views (A) to (D) of specific portions of the steel cord shown in FIG. 1B.

[Explanation of symbols]

 a 2 strand cords 1, 2 strands

Claims (3)

[Claims] 1. A steel cord comprising two to six double-stranded cords and strands arranged alternately and twisted at the same time. 2. The steel cord according to claim 1, wherein a plurality of two-stranded cords and the strands are twisted together,
A steel cord characterized by being twisted in a direction opposite to the twisting direction of the two-strand cord itself. 3. The steel cord according to claim 1 or 2, wherein the twisted length of the two-strand cord itself is 20 times or more and 80 times or less of a wire diameter. ..