JP2564507Y2 - 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 a rubber product having a novel twist structure (hereinafter referred to as a steel cord) used as a rubber reinforcing material for automobile tires and conveyor belts.

[0002]

2. Description of the Related Art Conventionally, as a steel cord of this type, 1 ×, as shown in FIGS.
Those with a 3, 1 × 4, 1 × 5 configuration were common. However, since the steel cord (12) having the above-described structure has a close-twisted structure in which a plurality of strands (11) are closely adhered and twisted, rubber is formed at the center of the steel cord during pressure vulcanization. The hollow portion D does not penetrate into the hollow portion D, and the continuous hollow portion D in the longitudinal direction of the cord remains. For this reason, in a tire using such a steel cord, when the tire is injured while the vehicle is running, moisture that has entered through the wound or moisture in the rubber causes the hollow portion D of the steel cord to be removed.
The steel cord penetrates and propagates in the longitudinal direction of the steel cord, corroding the steel cord, causing a decrease in the adhesion between the steel cord and the rubber, causing a separation phenomenon, that is, a so-called separation phenomenon, thereby significantly shortening the life of the tire.

In recent years, with the development of high-strength wires, it has become possible to reduce the number of constituent wires of a steel cord, and a steel cord (22) having a 1 × 2 structure as shown in FIG. 5 has been developed. (For example, see JP-A-62-234).
921, JP-A-62-117893). Further, as shown in FIG. 6, a steel cord (32) having a 1 × 2 configuration and an open twist structure has been proposed (for example, Japanese Utility Model Laid-Open No. 63-110102).

[0004] The steel cord (22) (3)
In the case of 2), since there is no hollow portion D closed by the strand as in the steel cord (12), corrosion of the steel cord due to intrusion of moisture can be prevented.

[0005]

The corrosion resistance of the steel cords (22) and (32) has been greatly improved.
However, it cannot be said that the recent demands for quality improvement such as speeding up, riding comfort, and weight reduction of automobiles are still sufficient, and there is a demand for further improvement in durability and flexibility of steel cords.

Incidentally, the steel cord (22)
Since the wires (21) are in line contact with each other, fretting wear is likely to occur, and rubber does not penetrate into the contacting surface, so that the two wires are united as if they were flat. Not only did the wire have a twisted configuration, but because the cross-sectional shape was circular, buckling was liable to occur with repeated compression-tension bending fatigue, and the fatigue life and flexibility were poor.

In the steel cord (32), since there is always a space between the strands (31) and (31), the twisted structure is likely to be unstable. In addition to the increase in thickness, there was the same problem as the above-mentioned steel cord (22) against repeated compression-tensile bending fatigue.

The present invention has been made to solve the above-mentioned problems of the conventional 1 × 2 steel cord, and has a stable twist structure, high flexibility, a thin rubber thickness, and a fatigue life. It is an object of the present invention to provide a steel cord that improves the tire weight and contributes to reducing the weight of the tire.

[0009]

In order to achieve the above object, a steel cord according to the present invention is a steel cord obtained by twisting two strands, and has a wire diameter of 0.25 to 0.5 mm.
35 mm, a strand having a carbon content of 0.75 to 0.85% by weight, a twist pitch of 9.0 to 16.0 mm, and an average shaping rate of 10
Twisted at 5-150%, the cross-sectional shape, and the substantially elliptical shape of the substantially same direction in the longitudinal direction is the ratio of the major diameter D ₁ and the minor axis D ₂ is _{1.1 ≦ D 1 / D 2 ≦} 2.2 Consisting of

[0010] Here, the average shaping ratio is, as shown in Fig. 2, a code diameter when two strands are densely twisted, dc, and a small gap C between the strands. cord diameter when twisted do (Incidentally, do is D ₁ + D _2/2, the value of do is the average value of the plurality of positions measured values in the code length.) and the time table by the following formula Say the number to be. Average shaping rate (%) = do / dc × 100

Incidentally, the numerical limitation of the present invention is a result obtained by a number of experiments, for the following reason.

[0012] The wire diameter of each strand is 0.25 mm or more and 0.35
mm or less, when used for tires and the like, since the number of strands is smaller than in the past, 0.25 mm is the minimum required to obtain appropriate strength, and if it exceeds 0.35 mm Poor flexibility.

The carbon content is required to be 0.75% by weight or more in order to use a high tension wire.
Is exceeded, wire breakage occurs frequently in the drawing and twisting steps.

[0014] If the twist pitch is too long, twisting failures occur frequently and handling work becomes difficult. For this reason,
It is necessary to be 16.0 mm or less. But,
If it is less than 9.0 mm, the elongation becomes too large, and it is not suitable as a rubber reinforcing material for general tires and the like.

If the average shaping ratio is less than 105%, rubber penetration between the strands becomes insufficient, and if it exceeds 150%,
The cord is easily stretched, and it is difficult to maintain the dimensions during the molding process, and the workability when calendering with a rubber sheet is also deteriorated.

Further, by making the cross-sectional shape substantially elliptical in the same direction in the longitudinal direction of the cord, it is possible to promote the infiltration of rubber between the strands while improving the stability of the twisted structure, It is also effective against bending fatigue, and can reduce the thickness of the rubber sheet.

However, if the ratio of D ₁ / D ₂ is less than 1.1, the effect cannot be expected, and if it exceeds 2.2, it tends to buckle when subjected to compression in the longitudinal direction, resulting in fatigue resistance. It becomes inferior in sex.

[0018]

When the steel cord configured as described above is used, there is a place where the wires substantially contact each other in the short axis direction, so that the twisted structure is stable and the handling workability is good.
A gap between wires is prevented from being reduced at the time of molding a rubber sheet, and good rubber infiltration into the cord is maintained. In addition, since the cross-sections are substantially elliptical in the same direction in the longitudinal direction, they have high flexibility in the short-axis direction, are not subjected to excessive plastic deformation, are unlikely to buckle, and have improved fatigue life. .

[0019]

Next, examples of the present invention, conventional examples, and comparative examples will be specifically described.

Table 1 shows various steel cords obtained by twisting two strands of which the surface is subjected to brass plating while varying the strand diameter, the carbon content, the twist pitch, the average shape ratio, and the cross-sectional shape in various ways. It shows the test results.

Experiment Nos. 1 and 2 are conventional steel cords shown in FIG. Experiment Nos. 8 to 10 are the steel cords of the present invention shown in FIG. Experiment number 3
7 are steel cords of comparative examples.

The average shaping rate can be adjusted by adjusting the spacing and dimensions of the twisting pins of the twisting machine, and by straightening small-diameter flat rollers in a staggered manner to make the cross-sectional shape substantially elliptical. It can be easily done by passing through a machine. A buncher type was used as a stranded wire machine. Then, the steel cord (2) of the present invention was covered with a rubber sheet (5) from above and below as shown in FIG. 3 (a) to prepare a composite sheet (6). Note that composite sheets were prepared in the same manner as in the conventional example and the comparative example. This composite sheet (6) was used for a belt portion (7) of a tire (8) as shown in FIG.

The breaking strength of each of the various steel cords in each state, the rubber penetration rate between the strands when the rubber is vulcanized, the compression-tensile bending fatigue resistance as a composite with rubber, 5 k
The elongation under load and the handling workability during rubber product processing were evaluated as follows.

(Strength at break) This is the breaking load of only the steel cord, and this kind of steel cord requires at least 25 kgf or more. (Rubber penetration rate) After embedding in rubber and vulcanizing, pull out the steel cord, peel off the strand, and determine the percentage of rubber that has penetrated into the surface where the two strands are in contact. Show. (Compression-Tension Bending Fatigue) A plurality of steel cords were embedded in a rubber sheet, and this sheet was used to evaluate with a three-point pulley bending fatigue tester. The results were indexed with the experiment number 1 as 100. Ultimately, fretting wear, buckling, etc., may lead to breakage, but the number of repetitions until this state is evaluated. (Handling workability) This refers to the workability of handling steel cords during the production of steel cords, embedding in rubber sheets, and the molding process of rubber products such as tires. Flare properties of steel cords, low load elongation, between steel cords Entanglement and straightness are involved. X was evaluated as very poor as compared with the conventional product, Δ as slightly inferior, and ○ as no difference.

[0025]

[Table 1]

As is clear from Table 1, the steel cord of the present invention has a sufficient breaking load of 25 kgf or more, rubber well penetrates between the wires, and has improved fatigue resistance. The handling workability was almost the same as that of the closed twist.
In addition, as a result of using the steel cord of the present invention for a tire, the thickness of the rubber sheet can be reduced, the weight of the tire can be reduced, the life of the tire can be greatly extended, and the riding comfort has been improved.

[0027]

[Effect of the Invention] The steel cord of the present invention has the above-mentioned structure, so that the rubber surely penetrates between the strands, has a sufficient strength as a steel cord, has a stable twist structure, and is easy to handle. Good and corrosion resistance has been improved. Also, when used for tires, the thickness of the tire can be reduced,
Reduces tire weight, reduces stress on steel cord even when riding on uneven roads, pebbles, curbs, etc. when driving a car, does not apply excessive plastic deformation to steel cord, fatigue resistance, ride comfort And has an excellent effect such that the life can be greatly improved.

[Brief description of the drawings]

1A is a schematic plan view showing one embodiment of the steel cord of the present invention, FIG. 1B is a front view thereof, and FIG. 1C is a line AA to GG of FIG. It is sectional drawing.

FIG. 2A is a cross-sectional view of a steel cord having a gap between wires, and FIG. 2B is a cross-sectional view of a densely twisted steel cord.

FIG. 3A is a cross-sectional view of a composite sheet in which a steel cord of the present invention is embedded, and FIG. 3B is a cross-sectional view of a main part of a tire using the composite sheet for a belt portion.

FIG. 4A is a cross-sectional view of a conventional 1 × 3 close-twisted steel cord, FIG. 4B is a cross-sectional view of a conventional 1 × 4 close-twisted steel cord, and FIG. It is sectional drawing of the steel cord of a 1x5 close twist structure.

FIGS. 5A and 5B are cross-sectional views of a conventional 1 × 2 closed twisted steel cord. FIG.

FIG. 6 is a cross-sectional view of a conventional composite sheet using a steel cord having a 1 × 2 open twist structure.

[Explanation of symbols]

 1, 11, 21, 31 strand 2, 12, 22, 32 steel cord 5 rubber sheet 6 composite sheet 7 belt part 8 tire

Claims (1)

(57) [Scope of request for utility model registration] 1. In a steel cord formed by twisting two strands, a strand having a wire diameter of 0.25 to 0.35 mm and a carbon content of 0.75 to 0.85% by weight has a twist pitch of 9. 0-16.0 mm, twisted at an average shaping rate of 105-150%, and the cross-sectional shape is such that the ratio of the major axis D ₁ to the minor axis D ₂ is 1.1 ≦ D ₁ / D ₂ ≦ 2.2. A steel cord for reinforcing rubber products, which has a substantially elliptical shape having substantially the same direction.