JPH09217286A - Steel cord for reinforcing rubber and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord for reinforcing a rubber excellent in rubber penetrating property, suppressing elongation thereof low at a low loading and suitable for reinforcing the belt part of a radial tire by twisting plural number of excessively patterned wires simultaneously in a same direction at a same pitch. SOLUTION: This steel cord for reinforcing a rubber is obtained by twisting (n)-lines (n=3-6) of wires patterned at 105-125% patterning ratio simultaneously in a same direction at a same pitch for forming a loose open cord which has among the wires constituting the cord, at least one and at most (n-1) wires are constituted by wires Wb having ripple curls 10 smaller than the twisting pitch P of the cord and at least one wire Wa has no ripple curl 10, and satisfies the relationship among the wave height h of the ripple curl 10, pitch p thereof, wire diameter d and the cord pitch P;1.05<=h/d<=1.45, 0.25<=p/P<=0.55. By using the steel cord for reinforcing the 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 used for reinforcing a rubber product such as a radial tire for an automobile or a conveyor belt, and a radial tire using the same.

[0002]

2. Description of the Related Art As a reinforcing means for rubber products such as radial tires for passenger cars and conveyor belts, steel cords having a plurality of brass-plated wires twisted together are used. Among them, in radial tires for passenger cars, as the steel cord of the belt part,
As shown in FIGS. 6 (a) (b) (c), those having a 1 × n structure in which 3 to 5 strands are twisted at a time have been mainly used.
However, in such a steel cord, as is clear from the cross-sectional shape, the strands are tightly twisted together so that there is almost no gap between the individual strands. There is almost no rubber permeation, and in the tire of the product, a space not filled with rubber exists continuously in the longitudinal direction. As a result,
If the tire gets scratched during driving, water penetrates into the tire through the scratch, reaches the reinforcing layer, travels through the continuous hollow inside the steel cord, and water penetrates the entire length of the cord. Rust propagates along the entire length of the cord. As the rust progresses, the strength of the steel coat decreases and the adhesive surface between the cord and rubber is destroyed, so-called separation phenomenon occurs and the integrity of the steel cord and rubber is lost, and the reinforcing effect of the cord is lost. However, there has been a problem that the function of the tire is greatly deteriorated and the life is shortened remarkably.

As a countermeasure against this, a steel cord having a loose open structure whose cross section is shown in FIGS. 7 (a) (b) (c) is partially used. In this steel cord, each strand forming the cord is oversized, and the strands are twisted together under this condition to form a gap between the strands to allow rubber to permeate intentionally. Further, as another steel cord, a flat cord is proposed in which the open cord is further crushed in one direction as shown in the cross section of FIGS. 8 (a) (b) (c). However, although the loose open cord itself has a gap between the strands in the cord itself, when tension is applied in the longitudinal direction of the cord, the cord greatly expands and contracts in the radial direction, and the steel twisted tightly. The shape of the cord is approximated, and as a result, the gap between the wires is substantially narrowed. That is, for example, as shown in FIG. 9A, there is a gap s between the wires in the unloaded state. However, when tension is applied, it shrinks in the diametrical direction as shown in FIG. 9 (b), and the gap s between the strands disappears or becomes very small, even if it does not disappear. From this,
1.To the cord during the vulcanization process in the mold in tire manufacturing.
There was a drawback that it became difficult for rubber to penetrate into the inside of the cord when a tension of about 5 kgf was applied.

[0004] Therefore, as a countermeasure against this, the dimensional ratio of the wires is set to be excessive (usually exceeds 130%), and the cord cross-sectional shape is intentionally changed by twisting the wires due to uneven length or phase shift. In some cases, even when tension is applied to the cord during vulcanization, it is difficult for the cord to contract in the radial direction and the gap is prevented from disappearing. But,
It is difficult to maintain a constant quality for cords with a particularly high die-casting rate, as the low load elongation becomes significantly large and the twisting becomes unstable during the production of the cord. However, there is a problem in that variations in characteristics such as low load elongation and patterning rate become very large. Further, the flat cord has a drawback that the flattening reduces the cord strength. Further, in the calendering process during tire manufacturing, a large number of steel cords are aligned in parallel while applying a predetermined low load tension, and the rubber compound is attached to a sheet by applying pressure from above and below using a roll. A rubber sheet (calender sheet) is manufactured, and then this sheet is cut at regular intervals and joined so as to form a bias. During this cutting, the tension remaining in the cord is released and the cord shrinks, so if there is variation in the amount of shrinkage of each steel cord, the cut surfaces will become uneven, or the cut sheet will become uneven, Since the joining of the cutting sheets becomes inaccurate, defects such as unbalanced rolling when tires are formed tend to occur.

[0005]

SUMMARY OF THE INVENTION The present invention was devised to solve the above problems, and its object is to loosen open cords having a high type ratio or to flatten them. Improved instability in the code,
It is to provide a steel cord having a stable rubber permeability even when the die-casting rate is low and having a high rubber reinforcing effect. Another object of the present invention is to provide a radial tire having good corrosion resistance and excellent rolling stability.

[0006]

In order to achieve the above object, the present invention is to provide n (n = 3 to 6) strands with excessively over 100% of the wires at the same pitch in the same direction. A twisted 1 × n loose-open steel cord, in which one or more and n-1 or less of the strands forming the cord have a small waviness smaller than the waviness caused by twisting. It is configured to have continuously. And, preferably, the patterning ratio of the wire is 105 to 105.
125%, height h of the wavelet of the wire and pitch length p
Is a configuration satisfying the following formula in relation to the wire diameter d and the cord twist pitch length P. 1.05 ≦ h / d ≦ 1.45 0.25 ≦ p / P ≦ 0.55 The small wave pattern of the strand may be spiral or planar.

[0007]

The steel cord according to the present invention has a loose open cord of 1.times.n in which three or six oversized wires are twisted in the same direction at the same pitch. Only a part of the strands, that is, one or more strands and an arbitrary number of strands in the range up to n-1 have a wavelet having a pitch smaller than that of the cord twist. For this reason, a gap as shown in FIG. 5 (a) is formed between the wires due to the continuous peaks and valleys of the wires Wb with the small wave habit 10, and tension is applied to the cord during vulcanization. Even when the cord is contracted in the radial direction, as shown in FIG. 5 (b), the gap s between the strands is surely left due to the ridges and valleys between the strands, and the rubber can penetrate through the gap s. it can. Therefore, even if the molding rate is smaller than that of the conventional loose open structure, stable rubber permeability can be secured. Further, since at least one strand Wa of the strands in the cord is not given a small wave,
Combined with the low molding rate, low load elongation can be suppressed to a low level. In addition, the strength of the cord is not significantly reduced, and the strength equivalent to that of the conventional loose open cord can be maintained.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an outline of a steel cord for rubber reinforcement having a 1 × 3 structure to which the present invention is applied. Also,
FIG. 2 schematically shows a cross section of the steel cord of FIG. 1 at a pitch pitch of 1/4 for one twist pitch. Wa, Wb, and Wb are wires having a diameter of 0.20 to 0.40 mm, the surface of which is brass-plated. Each strand is 1
It has a spiral shape due to over-molding of more than 00%, but two strands Wb, Wb of them are subjected to a continuous small wave pattern 10 at a pitch p shorter than the cord twist pitch P before twisting. The other one of the strands Wa is not given a small wave, and the three strands are simultaneously twisted in the same direction at the same twist pitch P. Therefore, as shown in FIG. 1 and FIG. 2, loose stranded wires form a gap s between the wires, and gaps s are formed between the wires due to the continuous ridges and valleys formed by the small wave patterns 10.

FIG. 3 shows another example of the present invention (a).
Shows a cross section of a 1 × 4 loose open structure, (b) shows a 1 × 5 loose open structure, and (c) shows a cross section of a 1 × 6 loose open structure. In the illustrated embodiment, three wires Wb,
Wb and Wb each have a minute wave habit 10. Of course, the present invention uses only 1
The number of books may be two or two. 4 in Figure 5 (b)
It may be a book or four or five in FIG. 5 (c). The strands with a small wavy pattern may be arranged adjacent to each other, or may be alternately arranged with the strands without a small wavy pattern as shown in FIG. 3 (c). In addition, in each of the illustrated embodiments, all the wires constituting the cord have the same diameter.
Wires having different diameters of more than one kind may be used. The strands having different diameters may be strands having the small wave habit 10 or may be strands having no small wave habit.

In any case, the small wave habit 10 of the wire is
As shown in FIG. 4 as a representative of one strand of wire taken out of the cord, the height h is 1.05d to the strand diameter d.
The range of 1.45d and the pitch length p are preferably in the range of 0.25P to 0.55P with respect to the twist pitch P of the cord.
The reason for this is that if the height h is less than 1.05, the gap between the strands becomes too narrow when the cord is tensioned, and the rubber penetration effect due to the small wave pattern becomes poor. Is too large, the breaking load is reduced, and the fatigue resistance is also reduced. On the other hand, if the pitch length p is less than 0.25P, it is difficult to process, and the breaking load due to scratches due to processing is reduced, or the fatigue resistance of the cord is reduced. This is because when it becomes easier and the tension is applied to the cord, the small wave habit is practically eliminated, and the gap between the strands is narrowed.

[0011] As for the molding rate, if the diameter (circumscribing circle diameter) of the steel cord when twisted tight is D and the mountain height of the wire measured by dividing the cord is H, then (H / D) x 100% It is a value represented by. This type ratio is 105 in the case of the present invention.
It is preferably in the range of to 125%. The reason for this is that if the molding rate is less than 105%, the gap required for rubber penetration cannot be formed, and if it exceeds 125%, the elongation at low load becomes large like the conventional loose open cord, which is preferable. Because there is no.

The minute wavelike habit 10 as described above usually has a spiral shape. In order to obtain this, the wire drawn from the supply bobbin may be applied in front of the stranding machine main body. This can be done, for example, on a pass line between the supply bobbin and the stranding machine main body in parallel or in a staggered manner with 3 to 5
A method of arranging a corrugating device with two pins and revolving it around the strand in the direction opposite to the rotation direction of the twisting machine, or fixing the corrugating device in position and placing the strand before and after this device. There is a method of rotating in the same direction as the rotating direction of the twisting machine.
In the case of the latter method, lead the wire twister immediately downstream of the corrugating device, revolve the wire twister with respect to the strand in the same direction as the rotation direction of the stranding machine main body, and twist the strand. It is possible to apply a spiral small wave pattern to each of the strands, apply a predetermined shaping to all the strands using a fixed shaping device, and twist the strands in the stranding machine body. In addition, depending on the case, the small wave pattern of the wire may be two-dimensional. In this case, a pair of gears may be used, and a two-dimensional minute wave pattern may be imparted by passing a wire between them, and then twisted in the same manner. The steel cord of the present invention can be manufactured by either a buncher type twisting machine or a tubular type twisting machine.

[Specific Example 1] An ultra-high-strength wire having a diameter of 0.28 mm and a brass-plated surface (tensile strength = 356 kgf / m
Using 3 m ² ), a 1 × 3 steel cord was twisted in the S direction with a twist pitch of 12.5 mm. In Examples 1 and 2, a spiral small wave pattern was applied, and a steel cord having a loose open structure was manufactured by using the same strands, and Comparative Examples 1 and 3 were obtained. Further, a flattened cord (short diameter / long diameter = 0.70) was manufactured, and used as Comparative Example 2. Table 1 shows these conditions and characteristics.

[Specific Example 2] Five high-strength wires (tensile strength = 330 kgf / mm ² ) having a diameter of 0.23 mm were used and twisted in the S direction at a twist pitch of 12.5 mm, 1 × 5. It was a steel cord. Of these, 3 with a spiral wavelet
Examples of the types are Examples 3 to 5. Further, steel cords having a loose open structure were manufactured by using the same strands, which were set as Comparative Examples 4 and 5, respectively. Table 2 shows these conditions and characteristics.

In Tables 1 and 2, the "cord elongation index under low load" means the elongation amount of the cord between a load of 0.3 kgf and 1.63 kgf. In Table 1, Comparative Example 3 is 1
00 in Table 2, and Comparative Example 5 as 100 in Table 2. The "strength utilization factor" is defined as (Y / A) x 100%, where A is the aggregate strength of the strands before twisting and Y is the breaking strength of the cord. The "fatigue resistance index" is a cord-shaped rubber vulcanized strip-shaped sample that is stretched over three rolls of a fixed diameter arranged in a zigzag pattern, and the cord is subjected to a tensile load of 10% of the breaking load. Is a result of measuring the number of repetitions until the cord is broken by repeatedly bending the roll to the left and right to repeatedly bend the sample, and in Table 1, Comparative Example 3 is 100, and in Table 2, comparison is made. It is expressed as an index with Example 5 as 100. "Rubber permeability" means that one cord is vulcanized in rubber while applying a tension of 100 gr to prepare a sample, and then the cord in the rubber is taken out, and this cord is disassembled in the longitudinal direction. The degree of penetration into the cord was visually observed, and the degree of complete penetration was judged to be 100%.

[0016]

[Table 1]

[0017]

[Table 2]

From Tables 1 and 2, it is clear that the steel cord of the present invention has stable and good rubber permeability even though the elongation under low load is smaller than that of the loose open cord. Further, it can be seen that it is excellent as a reinforcing material without the decrease in cord strength (low rate of strength utilization of strands) as seen in flat cords. Further, it can be seen that since the elongation amount under a low load is small, it becomes easy to handle in the production of cords and tires.

[0019]

According to claim 1 of the present invention, the number of strands is 3
~ In 6 loose open cords, some of the strands are continuously provided with a small wave pattern smaller than the wavy pattern caused by twisting the cords, so even though it is a loose open cord, there is a gap between the strands even when tension is applied. Is ensured,
It is possible to realize stable rubber permeability. Moreover, not all the strands are subjected to the small wave habit, but at least one strand not subjected to the small wave habit is included, so the excellent effect that the elongation at low load can be suppressed to a low level can be obtained. . According to claim 2, since the stranding rate is low, the twisting stability is good and the variation in the shape and quality important for the cord can be reduced, and the pitch and height of the wavelet are within the predetermined range. The excellent effect that the features of claim 1 can be fully exerted is obtained. According to the third aspect, it is possible to obtain an excellent effect that the low load elongation can be further reduced by thickening a part of the wires. According to the fourth aspect, an excellent effect that a radial tire having good corrosion resistance and rolling stability can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged side view schematically showing an example of a steel cord according to the present invention.

FIG. 2 is a schematic enlarged sectional view in which one twist pitch of the steel cord of FIG. 1 is cut at regular intervals.

FIG. 3 is a schematic cross-sectional view showing another example of the present invention.

FIG. 4 is an explanatory diagram showing a wave state of an element wire which is unwound and extracted in the present invention.

5A is an enlarged cross-sectional view showing a state of the cord according to the present invention when no load is applied, and FIG. 5B is an enlarged cross-sectional view showing a state when tension is applied.

FIG. 6 is an enlarged sectional view showing an example of a conventional compact type steel cord.

FIG. 7 is an enlarged sectional view showing an example of a conventional open steel cord.

FIG. 8 is an enlarged cross-sectional view showing an example of a conventional flat open steel cord.

FIG. 9A is an enlarged sectional view showing a conventional open cord in a non-loaded state, and FIG. 9B is an enlarged sectional view showing a state in which a tension load is applied.

[Explanation of symbols]

 Wa Elementary wire without wavelet Wb Elemental wire with wavelet 10 Gap P Cord twist pitch length p Wavelet pitch length h Wavelet wave height d Element wire diameter

Claims (4)

[Claims] 1. A 1 × n loose-open steel cord obtained by simultaneously twisting n (where n = 3 to 6) excessively typed wires exceeding 100% in the same direction at the same pitch. And a rubber reinforcement characterized in that one or more and n-1 or less of the strands constituting the cord continuously have small wave patterns smaller than the wave patterns resulting from twisting. For steel cord. 2. The stranding ratio of the strands is 105 to 125%, and the height h of the wavelets of the strands and the pitch length p are the strand diameter d.
The steel cord for rubber reinforcement according to claim 1, wherein the following formula is satisfied in relation to the cord twist pitch length P. 1.05 ≦ h / d ≦ 1.45 0.25 ≦ p / P ≦ 0.55 3. The steel cord for rubber reinforcement according to claim 1, including a case where the wires have different diameters. 4. A radial tire comprising the steel cord according to claim 1 for reinforcing a belt portion.