JPH09195186A - Steel cord for reinforcing rubber and radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a steel cord of open structure, good in rubber penetrability, easy to be handled with little elongation under a low loading and suitable for reinforcing the belt part of a radial tire by twisting plural wires in the same direction with the same pitch at a same time. SOLUTION: A steel cord having an open structure is obtained by twisting 3 wires 1a, 1b and 1b, excessively formed over than 100%, in the same direction with the same pitch P mm, so that one wire 1a among the wires 1a, 1b and 1b has a smaller degree of formation in >=5% in the absolute value compared with that of other two wires 1b and 1b and a minute wave form 10 different from the wave form formed by the twisting, to satisfy the relations, 0.30<=p/P<=0.55 [(p) is a pitch in mm of the minute wave form) and 1.05<=h/d<=1.85 [(d) is a diameter in mm of the wire, (h) is a wave height in mm] and forming spaces (s) between the 2 wires 1b and 1b. A radial tire is formed by using the above cord for reinforcing the belt part of the radial tire.

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 for transportation, and a radial tire for an automobile.

[0002]

2. Description of the Related Art Steel cords (tight twisted cords) which are tightly twisted as shown in FIGS. 1 (a), (b) and (c) are used for belt reinforcing layers of passenger car tires. . However, in such a tight-twisted cord, there is almost no gap between the individual strands, as is clear from the cross-sectional shape, so when used in the belt part of a tire, rubber penetrates into the center of the cord. There will be continuous spaces in the longitudinal direction. As a result, the rubber-steel cord is not sufficiently adhered, and the rubber-cord and composite are not sufficient, especially when a part of the tire is damaged and water enters the inside from this part and reaches the cord, Water is transmitted through the space inside the cord, and along with this, rust progresses. This rust has a drawback that the adhesion surface between the cord and the rubber is destroyed and a so-called separation phenomenon occurs, the function of the tire is significantly reduced, and the life is remarkably shortened.

As a countermeasure against this, a steel cord (open twist cord) having a structure shown in FIGS. 2 (a) (b) (c) is partially used. However, since this open-twisted cord is loosely twisted by excessively shaping each wire in order to improve rubber penetration, it has a large elongation at low load and is applied in the mold during tire manufacturing. When the cord is stretched in the longitudinal direction by applying a tension of about 1.5 kgf during the vulcanization process, the cord is compressed in the radial direction and the gap between the strands narrows, making it difficult for rubber to actually penetrate into the cord. Become. Therefore, by giving the strands a higher sizing rate, the cord cross-sectional shape is intentionally made uneven due to uneven lengths of strands and phase shifts during twisting, so that the tension on the cords during vulcanization is increased. Even if it is applied, it is generally used that it is difficult to shrink in the radial direction of the cord and the gap is prevented from disappearing. However, such a cord with a particularly high rate of shaping must have an unstable twist during the production of the cord, and it is difficult to maintain a constant quality, and variations in characteristics are extremely high. There is a problem of getting bigger. 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 the sheet while 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 pressed together 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.

[0004]

DISCLOSURE OF THE INVENTION The present invention was made by research to solve the above problems, and its object is to have stable and good rubber permeability, Moreover, it is to provide a practical steel cord for rubber reinforcement which has an open structure, has little elongation under low load, is easy to handle, and has excellent durability. A second object of the present invention is to provide a radial tire having excellent separation resistance and good rolling balance.

[0005]

In order to achieve the above object, the present invention provides an open structure steel cord in which three strands having more than 100% patterning are simultaneously twisted in the same direction and at the same pitch. One of the wires has an absolute value of 15% or less in absolute value compared to the other two wires, and has a minute wavy pattern different from the wavy pattern caused by twisting. It was done. Preferably, the pitch p (mm) of minute waviness and the wave height h (mm)
Is the wave pitch P (mm) due to twisting, and the wire diameter d (mm)
In relation to, the following formula is satisfied.
0.30 ≦ p / P ≦ 0.55 1.05 ≦ h / d ≦ 1.85 In order to achieve the second object, the present invention uses one of the above steel cords for reinforcing the belt portion. It was done. The patterning ratio of the two wires is usually 150.
% Or less, the patterning rate of one strand is over 100 to 120
% Is preferable.

[0006]

In the present invention, in a single-layer open-twisted steel cord consisting of three strands having a pattern of more than 100%, the three strands constituting the cord are not shaped equally but The patterning rate of the strands is set to be 15% or more lower than the patterning rates of the other two strands. Moreover, since one strand having a low patterning ratio continuously has minute waviness different from the waviness caused by twisting, a large inter-strand gap due to two loose strands. Is formed and a gap is formed between the element wire and other strands due to the slight waviness, so that the rubber permeability can be improved. Then, it becomes a form in which two strands of loose twist are bound by one strand having a slight waviness and a low molding rate in absolute value, and thereby a good balance is obtained between the strands. In addition, due to the presence of the wire with a low molding rate, the elongation of the cord under low load is in a proper small range, that is, 0.30 to 1.63 kg.
It can be kept below 0.190% between f loads. Further, even if radial tension is applied due to the tension applied to the cord during vulcanization, the gap between the strands is accurately secured, and thus stable rubber permeability can be secured despite the open cord structure. Also, since the low load elongation is small, the cord is easy to handle and the flatness of the sheet is good. Furthermore, when stress is applied to the cord, the stress load of one strand having a low patterning rate becomes large. However, since the strand has minute wavy patterns formed continuously, the fine wavy pattern causes The stress load is relieved and the durability of the cord can be improved. In particular, when the fine wave pitch pitch p is 0.30 ≦ p / P ≦ 0.55 and the fine wave patter height h is 1.05 ≦ h / d ≦ 1.85, the breaking load is Good rubber permeability can be obtained without lowering. It should be noted that each of the strands may have a normal high strength, or may have an ultrahigh strength with a tensile strength Z of -200d + 400 (kgf / mm ² ) or more. A strong reinforcing effect can be achieved.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 3 to 5 show an embodiment of a steel cord for rubber reinforcement according to the present invention. FIG. 3 shows a steel cord to which the present invention is applied, and FIG. 4 schematically shows a cross-sectional shape obtained by cutting five points corresponding to one pitch in FIG. 3 at right angles to the longitudinal direction. In FIGS. 3 and 4, 1
Reference numerals a, 1b and 1b are strands. Each strand 1a, 1
b and 1b have a brass plated surface with a diameter of 0.
It is made of steel wire of about 25 to 0.35 mm and is twisted in the same direction and at the same pitch P at the same time. Each of the strands 1a, 1b, 1b has a spiral shape with a patterning rate of more than 100%.
Only have different typing rates. That is, the molding rate is smaller than that of the other two wires 1b and 1b by 15% or more. Here, the molding ratio is the diameter of a 1x3 steel cord when tightly twisted (circumscribed circle diameter)
Let D be D, and let the peak height of the spiral wire measured by disassembling the cord be H, this is a value represented by (H / D) × 100%.

In the usual case, it is preferable that the molding rate of one strand 1b is more than 100 to 120%, and the molding rate of the other two strands 1b and 1b is 150% or less. The reason is that if the molding rate of one strand 1b exceeds 120%, the elongation of the cord under a low load increases, and the two strands 1b
It is not possible for the b and 1b mold ratios to exceed 150% because the elongation at low load becomes large, the elongation balance between the strands becomes poor, the breaking load decreases, and the fatigue resistance also decreases. In addition, one strand 1a and the other two strands 1b,
If the difference in the molding rate of 1b is less than 15%, the elongation under low load increases, which is not suitable. If the molding ratio is in the above range, the elongation under low load is 0.1 which is suitable for the cord.
It can be 90% or less.

Further, the single strand 1a is formed with continuous minute wavy patterns 10 at a pitch p shorter than the cord twisting pitch P. Therefore, the two strands 1b, 1b having a high typing rate and the one strand 1a having a low typing rate
As shown in FIGS. 3 and 4, a large gap S is formed between the two strands 1b, 1b by simultaneously twisting the two strands, and one strand 1a having a low molding rate is loose. The strands 1b, 1b are relatively tightly tightened, and even if the cord is tensioned by the continuous ridges and valleys of the minute wavy lines 10 provided on the single strand 1a, the other strands 1b, A large number of small gaps s are created with 1b.

The minute wavy habit 10 is applied to the strand 1a in advance before twisting, and the minute wavy habit 10 is a twist pitch of cords, that is, a wave caused by twisting as shown in FIG. With respect to the relationship between the pitch P and the wire diameter d, it is preferable to have a predetermined pitch p and a predetermined height h. Specifically, p / P is 0.30
It is preferably about 0.55 and h / d is about 1.05 to 1.85. The reason for this is that if p / P is less than 0.30, the pitch is too fine and it is difficult to process, and the breaking load is also reduced, which is not desirable. When tension is applied to the cord at the time of vulcanization, the strands of wire will stretch, and the minute wave curl 10 that has been attached will practically disappear,
This is because the rubber permeability is reduced. Moreover, h / d is 1.
If it is less than 05, the rubber penetration effect due to the imparting of a slight wave becomes poor, and if it exceeds 1.85, the balance between the strands is deteriorated, the breaking load tends to decrease, and the fatigue resistance also decreases. is there.

The micro wave habit 10 is usually spiral, but it may be two-dimensional in some cases. In order to obtain the former mode, the strand drawn from the supply bobbin may be applied in front of the stranding machine main body. For example, a corrugating device having three or five pins in a zigzag pattern is arranged on the path line between the supply bobbin and the main body of the twisting machine, and the corrugating machine is arranged in the direction opposite to the rotating direction of the twisting machine. There is a method of revolving with respect to the wire, or a method of fixing the position of the corrugating device and rotating the wire before and after this device 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. The spiral small wave pattern is applied to the three strands, and then all three strands are subjected to predetermined shaping using a fixed shaping device and twisted in the twisting machine body. In the latter case, use a pair of gears,
After passing a wire between them to give a two-dimensional minute wave pattern, the wires may be twisted in the same manner. The steel cord of the present invention can be manufactured by a buncher type twisting machine and a tubular type twisting machine.

In the above embodiment, the diameters of the three strands are the same. However, in some cases, the two strands 1b, 1b having a large casting rate and the one strand 1a having a low casting rate are used. The diameters may be different. The strands 1a, 1b, 1b are
Tensile strength before twisting: Z = -200d + 365 (k
gf / mm ² ) to Z = −200d + 385 (kgf / mm ² ), a high strength wire may be used, but the tensile strength is Z ≧ −20.
You may use the thing of 0d + 400 (kgf / mm < ² >).

[0013]

[Specific example 1]

(1) Equivalent to JIS G 3502 piano wire as raw wire material,
Chemical composition (wt%) C: 0.82, Si: 0.21, Mn: 0.51 Steel wire consisting of balance iron and unavoidable impurities is used, and this steel wire is continuously dry-drawn by heat treatment-Brass plating-
Diameter 0.28mm (tensile strength:
325 kgf / mm ² ) of high-strength wire, and the 1 × 3 steel cords of Examples 1 to 3 and Comparative Examples 1 to 5 were variously changed by using the wire with different shaping ratio and spiral micro wave curling. Obtained. Further, using the same strand as above, a steel cord of Conventional Example 1 having an open structure shown in FIG. 2 (a) was obtained. The twist direction is the S direction and the twist pitch is 1 in both Examples and Comparative Examples.
4 mm. (2) A buncher type stranding machine is used as the stranding machine
In Example 3, and in Comparative Examples 1 to 4, the minute wave pattern to one strand is arranged with a corrugating device (fixed) having three pins in a zigzag pattern upstream of the buncher type stranding machine main body. At the same time, arrange a wire twister immediately downstream of the wire twister, and revolve the wire twister in the same direction as the rotation direction of the twisting machine main body to twist the wire and pass it through the corrugating device. The spiral microwave was applied at. After that, the three strands of wire were passed through another fixed mold making device to be subjected to predetermined molding, and then introduced into a wire twisting machine and twisted. The characteristics of these steel cords are shown in Table 1 together with the embossing ratio and the spiral micro wave curl.

SPECIFIC EXAMPLE 2 Using the same high-strength element wire diameter of 0.32 mm (tensile strength: 313 kgf / mm ² ) as the specific example 1, the conditions for the molding ratio and the spiral micro wave squeezing are used. The steel cords of Examples 4 and 5 and Comparative Examples 6 to 9 were manufactured by various methods. In each case, the twisting direction was the S direction and the twisting pitch was 16 mm. In addition, a steel cord of Conventional Example 2 having an open structure shown in FIG. 2A was also obtained by using the same strands. These characteristics are shown in Table 2 together with the patterning ratio and the spiral micro wave habit. Table 1 and Table 2
In the above, the die attachment rate is measured by dividing the circumscribed circle diameter (D) of the cord twisted tightly and the cord height (H) by disassembling the cord as described above, and expressing it in (H / D) × 100. It was done. The pitch p and the wave height h of the slight wave habit were measured by disassembling the cord. "Rubber permeability" is 100g of straight cord
After vulcanizing in rubber under tension of r to make a sample,
The cord was divided in the longitudinal direction, and the degree of rubber penetration into the cord was visually observed. The cord completely covered with rubber up to the cord central portion was determined as 100%. “Fatigue resistance” means that a belt-shaped sample obtained by vulcanizing a cord in rubber is stretched over three rolls of a constant diameter arranged under a load of 10% of the cord breaking load, and the roll is rolled left and right. Repeatedly reciprocate to repeatedly bend the sample,
It is the result of measuring the number of repetitions until the cord breaks, and in Tables 1 and 2, the conventional example was set to 100 and expressed as an index.

[0015]

[Table 1]

[0016]

[Table 2]

As is clear from Table 1 and Table 2, Example 1
According to the fifth embodiment, the magnitude of the shaping ratio is appropriate, the difference in the shaping ratio between one strand and the other two strands is appropriate, and the fine wave applied to one strand has an appropriate pitch. And because of the wave height, elongation at low load, rubber permeability and fatigue resistance are achieved in a well-balanced manner. In particular, good rubber permeability was obtained even when the molding ratio was made smaller than in Conventional Examples 1 and 2, which means that the cord has a stable twist and little variation. On the other hand, in Comparative Example 1, the pitch and the wave height of the minute wave are unsuitable, so that the rubber permeability is poor, and in Comparative Example 2, the breaking load due to the excessively large type ratio of the two wires, Elongation at low load, rubber permeability and fatigue resistance are poor. Comparative Example 3 has an inadequate micro wave pitch and thus is inferior in rubber permeability, and Comparative Example 4 has an inadequate micro wave wave height and thus is inferior in breaking load and fatigue resistance. Since Comparative Examples 5 and 9 do not form the micro wave habit, the rubber permeability is inferior. Comparative Example 6 is inferior in rubber permeability and elongation under low load because the pitch of the fine wave and the patterning ratio of the two strands are inadequate, and Comparative Example 7
Is improper in the pitch and wave height of the slight wave pattern and the imprinting ratio of the two strands, so the breaking load, elongation at low load,
Poor rubber penetration and fatigue resistance. Comparative Example 8 is 2
Since the difference in the molding rate between the single strand and the single strand is inappropriate, the rubber permeability is poor.

[0018]

As described above, according to claim 1 of the present invention, in a steel cord having a 1 × 3 open twist structure, one of the three strands is replaced with the other two strands. Compared with this, since the type forming rate is reduced by 15% or more in absolute value, the elongation of the cord under a low load can be set to an appropriate range of 0.190% or less, and moreover, one element with a small type forming rate can be used. Since the wires are continuously provided with small wave patterns that are different from the waves generated by twisting the cords, gaps are created by the resulting valleys, and excellent rubber permeability can be obtained while maintaining a stable twisted state as a cord. In addition, it is possible to reduce the stress applied to a single wire with a small molding rate due to the slight wave habit, and the durability is also good. The handleability for compounding with rubber is good, and the sheet is cut after calendering. Sometimes Excellent effect capable of flatness of the sheet to may be accurate fit joint of the sheet be obtained. According to the second aspect, since the pitch and the wave height of the slight wave are defined in a specific range, in addition to the effect of the first aspect, the processing is easy, and the rubber permeability, the breaking load and the fatigue resistance are high. The excellent effect of being able to improve the balance in a good manner is obtained. Claim 3
According to this, there is an effect that it is possible to obtain a radial tire having a separation resistance, a long life, and excellent rolling stability.

[Brief description of the drawings]

1A, 1B, and 1C are cross-sectional views of a conventional tight-twisted steel cord.

2 (a), (b) and (c) are cross-sectional views of conventional steel cords having an open twist structure.

FIG. 3 is an enlarged side view showing an embodiment of a steel cord for rubber reinforcement according to the present invention.

4 is a cross-sectional view schematically showing each part of the cord of FIG. 3 for one twist pitch.

FIG. 5 is a side view schematically showing a strand of wire taken out by disassembling a cord according to the present invention.

[Explanation of symbols]

 1a Strands with a low embossing ratio 1b, 1b Strands with a high embossing ratio 10 Micro wave habit P Cord twist pitch (wave pitch due to twisting) p Micro wave habit pitch d Element wire diameter H Element wire height h Wave height of slight wave habit

Claims (3)

[Claims] 1. A steel cord having an open structure in which three strands having a patterning rate of more than 100% are simultaneously twisted in the same direction and at the same pitch, and one of the strands is the other two strands. A steel cord for rubber reinforcement, which has a small crease ratio of 15% or more in absolute value compared to the above-mentioned wire and has a minute wavy pattern different from the wavy pattern caused by twisting. 2. The steel cord for rubber reinforcement according to claim 1, wherein the pitch p and the wave height h of the minute waviness satisfy the following expressions. 0.30 ≤ p / P ≤ 0.55 1.05 ≤ h / d ≤ 1.85 where P: wave pitch (mm) due to twisting, d: strand diameter (mm) 3. A radial tire using the steel cord according to claim 1 or 2 for reinforcing a belt portion.