JP2920477B2 - Steel cord for rubber reinforcement and radial tire - 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 used for reinforcing automobile tires and conveyor belts, and a radial tire using the same as a reinforcing material.

[0002]

2. Description of the Related Art A steel cord formed by twisting a plurality of strands is used as a reinforcing material in a belt portion of a radial tire for an automobile. This steel cord is required to have high strength and high durability, but not only adheres well between the cord surface and the rubber, but also penetrates well into the inside of the cord and adheres well between the inside and outside of the cord and the rubber Is required to be a complex. The reason is that while the vehicle is running, the tires step on stones or metal pieces and are scratched, and when this scratch reaches the steel cord, water enters from this scratch and rusts the steel cord, but the steel cord If there is a continuous hollow part in which rubber does not penetrate inside, water will propagate through this hollow part and rust will spread, causing a separation phenomenon between the cord and rubber in the tire, increasing the function of the tire. This is because the lifetime is shortened or its life is shortened.

Conventionally, as a steel cord of a radial tire for a passenger car, as shown in FIGS. 1 (a), 1 (b) and 1 (c), three to five strands are tightly twisted simultaneously in the same direction at the same pitch in the same direction. A 1.times.n structure (especially 1.times.4, 1.times.5) is common. However, since these steel cords have almost no gap between the wires as is evident from their cross-sectional shapes, it is difficult for the rubber to penetrate into the cord in the vulcanization process after tire molding, and a hollow portion is formed inside. It remains continuously. For this reason, the above-described problem has occurred. In order to solve this problem, steel cords having a so-called 1 × n open twist structure in which all strands are over-molded by more than 100% and the strands are loosely twisted have been proposed. 2
(a), (b), and (c). However, in this structure, the strands are loosely twisted with each other, and the looseness is increased by increasing the molding rate to ensure rubber penetration. It becomes bigger than.

[0004] In addition, the open twisted steel cord has a fundamental problem that it is difficult to control the cord to have a uniform elongation at low load in the manufacturing process. Furthermore, in the tire manufacturing process, a large number of cords are aligned in parallel in a calendering process while applying a predetermined tension (low load), and a rubber compound is applied from above and below using a roll, and the cord is attached in a sheet shape while applying pressure. A rubber sheet is produced, and then the calender sheet is cut at regular intervals, and the sheets are connected to form a bias.
Since the tension remaining in the cord at the time of this cutting is released and the cord shrinks, the amount of shrinkage is large, and if there is a variation in the amount of shrinkage of each steel cord, the cut section becomes uneven or the cut rubber sheet Becomes uneven, and cutting sheets cannot be joined accurately.
When it becomes a radial tire, defects such as a poor rolling balance are likely to occur.

[0005] In addition, a method of using a pair of gears, as shown in Fig. 3 (a), and passing a wire between them to form a zigzag shape is often used for the hammering. As shown in FIG. 3 (b), the peak portion of the wave is sharply curved and the portion is apt to be damaged. For this reason, when a cord is manufactured using a buncher-type twisted wire machine, etc., the strands are twisted many times, stress is concentrated on the top of the wave, and the wire breaks, and the fatigue resistance of the cord also deteriorates There was a problem.

[0006]

SUMMARY OF THE INVENTION The present invention has been made by researching to solve the drawbacks of the conventional open twisted steel cord. The first object of the present invention is to provide a steel cord having a stable rubber permeability. An object of the present invention is to provide a steel cord which is good, has low elongation under a low load, has no problem with fatigue resistance, is easy to handle, and is easily processed at the time of tire production. A second object of the present invention is to provide a radial tire having a good balance and a long life.

[0007]

In order to achieve the first object, the present invention provides a 1 + 2 structure in which two side strands are spirally wound around one linear core strand. In steel cord, the core strand has a molding rate A of 80.0-9.
5.0%, and at least one of the side strands has a wave pitch p in the range of p / P = 0.30 to 0.60 in relation to the winding pitch P; h is in the range of h / d = 1.05 to 1.85 in terms of the ratio to the element wire diameter d, and the radius of curvature r at the top of the wave has a continuous wave habit of 3.50 d or more before winding. And
The configuration is such that the cord elongation between 0.30 kgf and 1.63 kgf load is 0.15% or less. It is preferable to obtain the wavy shape of the above specification by a pair of gear-shaped members provided with a cylindrical pin having a smooth surface on each tooth tip in a direction perpendicular to the rotation direction. Further, in order to achieve the second object, the present invention is configured such that any one of the steel cords is used as a reinforcing material for a belt portion.

[0008]

[Function] The steel cord consists of three strands, one strand is arranged in the center, and two strands are helically twisted around this, so that it has a 1 + 2 structure. As a result, a closed contour portion in which three strands are adjacent to each other does not occur. Moreover, in this 1 + 2 structure, at least one of the side strands has a wave pitch p in the range of p / P = 0.30 to 0.60 in relation to the winding pitch P before winding. , And h / d =
It has a wave height h in the range of 1.05 to 1.85, and has a wave habit continuously having a radius of curvature r of 3.50 d or more. For this reason, a gap is formed not only between the core strand and the side strands but also between the two side strands due to the short-ranged wavy waves in the specific range. Therefore, the rubber can well penetrate into the cord, and the corrosion resistance is improved. The core strand has a molding rate A of 80.0 to 95.0%, and is not subjected to a wavy shape. Therefore, when an external force is applied, the core strand and the side strand do not show the same behavior, When tension is applied to the steel cord at the time of vulcanization or the like, elongation of the entire steel cord, particularly at low load, can be suppressed low by the core strand, and a gap between the strands is firmly secured.
In addition, the twisted length of the side strands is well balanced, and portions that are separated from each other in the longitudinal direction of the cord always occur.
For this reason, the gap between the strands is stable, the rubber spreads well around each of the core strand and the side strand, and the adhesion area with the rubber can be increased, and the corrosion resistance and the separation resistance are excellent. It will be. Also, since the side strands are not sharp at the top of the wavy curve and have a smooth radius of curvature r of 3.50 d or more, excessive stress is applied to the crests when twisted in the stranded wire process. It is not concentrated, so that the stranded wire is good and no break occurs, and the problem of scratches is eliminated, so that the fatigue resistance is also good. Elongation of cord at low load
(Elongation between 0.30kgf-1.63kgf load) is kept low, resulting in good handling.

[0009] In particular, the wavy curving of the side strands is expressed as p / P =
Since it is in the range of 0.30 to 0.60, the workability of the wire is good, the reduction of the strength of the wire is suppressed, and the tension between the wires when the cord is tensioned at the time of vulcanizing rubber or the like. The gap does not become too narrow. Further, since the wave height h is in the range of h / d = 1.05 to 1.85 in terms of the ratio to the strand diameter d, there is an advantage that the rubber permeability is good and the elongation under a low load is not increased. Radius of curvature r of the wave
Is greater than or equal to 3.50 d in relation to the wire diameter d, so that stress concentration can be prevented well and the occurrence of scratches can be avoided.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 4 to 7 schematically show an example of a steel cord for rubber reinforcement according to the present invention. 1a is one core strand, 1b and 1b are two side strands, and the core strand 1a
Is arranged at the center, and the side strands 1b, 1b are spirally wound around this at a predetermined pitch in a 1 + 2 structure. In this example, the strands have the same diameter in the range of about 0.20 to 0.40 mm in diameter. However, the present invention is not necessarily limited to this. For example, the core strand 1a may have a different diameter such as a relatively small diameter or a large diameter than the side strands 1b, 1b. Included in the present invention. The winding direction may be either the S direction or the Z direction, and the winding pitch P is usually preferably about 40 to 60 d (d is the element diameter).

The core element wire 1a is hardly twisted and has a substantially linear shape with a molding ratio A of 80.0 to 95.0%. The "molding ratio" is defined as the value obtained by measuring the mountain height H of the wire as shown in FIG.
H / D × 100 (%), where D is the diameter (circumscribed circle diameter) of the × 3 tight twisted cord. The reason why the molding rate was limited was that the molding rate of the core strand Wa was 8
If it is less than 0%, the rubber permeability becomes unstable and deteriorates, while if the molding rate exceeds 95%, the elongation under a low load suddenly increases.

On the other hand, both or one of the side strands 1b and 1b are continuously corrugated at a short pitch p different from the winding wave before winding, and in this state, the core strand 1a It is a cord that is spirally wound around it. The wave patterns of the side strands 1b, 1b will be described in detail. In the state of the waves attached to the strands when the cord is disassembled as shown in FIGS. 6 and 7, the pitch is p, and the wave height is h. , The winding pitch P and the wire diameter d are in a range satisfying the following expression. 0.30 ≦ p / P ≦ 0.60 1.05 ≦ h / d ≦ 1.85 The reason for this is that p / P is set to 0.1 in order to improve the wavy workability and to suppress a decrease in strand strength. It is required to be 30 or more. However, in order to prevent the gap between the strands from becoming too narrow when tension is applied to the cord at the time of vulcanization after molding of the tire, it is preferable to set the value to 0.3.
It is set to 60 or less. Further, the wave height h is required to be 1.05 or more in order to maintain a good state with stable rubber permeability. However, if the wave is too high, the elongation under a low load becomes large, so that the wave height h is 1.85 or less. That is.

Due to such a cord structure, the corrugation of the side strands and the shaping ratio of the core strands, the core strand 1a and the side strands 1b, 1b do not show the same behavior when subjected to an external force.
When a low load is applied, that is, 0.30 kgf and 1.63 kgf
The elongation of the steel cord between the cords is about 0.10 to 0.15%, which can be extremely reduced as compared with the open twist cord. For this reason, even if tension is applied to the steel cord in the vulcanizing step at the time of tire molding, the gap between the cord strands is accurately secured, and stable rubber permeability can be realized. In addition, a tire having a stable dimensional accuracy and a well-balanced tire structure can be obtained.

FIG. 4 (b) schematically shows the cross-sectional shape at each position where one pitch of the steel cord according to the present invention is divided into four. When three wires are simply twisted at a time, the cross-sectional shape becomes as shown in FIG. 1, but in the present invention, two side wires 1b, 1b are surrounded around one core wire 1a. Is spirally wound, so that no closed contour portion in which three strands 1a, 1b, 1b are adjacent to each other at any cross-sectional position, and a gap s is always formed at one or more locations. You. Moreover, since at least one of the side strands 1b is pre-curved at a pitch and height in the above-described range, there are portions that are separated from each other even in the longitudinal direction of the cord as shown in the figure, thereby creating a gap s. Is done. Therefore, a gap s is formed between the core strand 1a and the side strands 1b, 1b, or between the two side strands 1b, 1b.

The vertices of the side strands 1b, 1b are:
The round part 10 is formed as shown in FIG. The radius of curvature r of the radius portion 10 is preferably 3.50 d or more in relation to the strand diameter d from the viewpoint of preventing stress concentration and preventing generation of scratches. Means for obtaining a wavy shape having such a radius portion includes gear-shaped members 3, 3 as shown in FIG.
May be used. That is, the teeth 30, 30 meshing with each other are provided at regular intervals on the outer periphery of the pair of gear members 3, 3, and the teeth 30, 30 have a pair of plate portions 30a, 30a, respectively, and are opposed to each other. Plate part 3
A cylindrical pin 31 made of a metal having a smooth surface, for example, a cemented carbide, is laid across the tips (tooth tips) of the reference numerals 0a and 30a. The wave pitch p is set by the circular pitch of the gear,
The wave height h is set by the interval between the pair of gears. Pin 3
In order to obtain the radius of curvature r, 1 preferably has a thickness having a radius of 3.35d or more. The pin 31 may be exchangeably fixed to the plate portions 30a, 30a by screws or the like, but is preferably rotatable by a bearing. When a pair of gear-shaped members 3, 3 having such pins 31, 31 at the tooth tip are used, the strand 1b is periodically bent and deformed in the longitudinal direction by the pins 31, 31, so that the top portion is Is continuously provided with a wavy portion having a round portion 10. Moreover, the radius portion 10 having an arbitrary radius of curvature can be obtained by selecting the thickness of the pins 31 and 31 and exchanging the pins 31 with various diameters. Furthermore, unlike conventional gears, only the pins need to have abrasion resistance, so they are inexpensive, and by using cemented carbide or the like for the pins, the life can be extended with respect to wear.

The wires 1a constituting the steel cord,
For 1b and 1b, a carbon steel wire having a C content of 0.80 to 0.95% by weight is used, and the wire is drawn to a predetermined intermediate diameter.
An ultra-high strength strand obtained by performing dry drawing after plating and plating diffusion and then performing wet drawing to a target wire diameter is suitable. Specific chemical component compositions include C:
0.80 to 0.95%, Si: 0.15 to 0.35%,
Mn: 0.3 to 0.9%, the balance being composed of iron and unavoidable impurities.
And the like may be added in a predetermined amount as an alloy element.

The steel cord according to the present invention can be manufactured by a tubular type twisting machine, but also by a buncher type twisting machine. FIG. 9 shows this example. In the stranded wire device, guide rolls 11, 12, 13, and 14 are provided on the center axis of rotation of the stranded wire device main body 23, and inside the disc roll, Two side wire supply bobbins 1 that keep a fixed position regardless of the rotation of the disc roll
9, 19 'are arranged. 8 is provided between the side wire supply bobbins 19, 19 'and the voice 21 to form a wave on the side wire. It has a structure shown in FIG. In this example, the warping device 18 is provided in the path of each of the side wire supply bobbins 19 and 19 '. One or a wavy device 18 may be provided and separated so as not to mesh with the pair of gear members 3. A single core element supply bobbin 20 is provided outside the stranded wire device main body 23.

In manufacturing the cord, a core wire 1a is pulled out from the core wire supply bobbin 20, and this core wire 1a is guided by a guide roll 11, a guide roll 12, a voice 21, a guide roll 13, a guide roll. It passes through 14 and is wound on a winding bobbin 22. In this example, the side strands 1b for winding are drawn out from the side strand bobbins 19, 19 ', and the strands 1b, 1b are respectively corrugated devices 18, 18 → voice 21 → guide roll 13 → guide roll. It passes through 14 and is wound on a winding bobbin 22.

In the above process, the core wire 1a drawn from the core wire bobbin 20 is twisted by passing through the guide rolls 11 and 12, while being drawn from the side wire supply bobbins 19 and 19 '. Is the strand 1b,
1b is a wave pattern of a short pitch in which the round portions 10 and 10 are provided by the pins 31 and 31 and the pitch and height are defined as described above, respectively, as the pair of gear-shaped members 3 and 3 mesh with each other and rotate. In this state, the voice 21 is drawn on one core element wire 1a. 1
Since the core strand 1a is twisted back in the opposite direction before passing through the guide rolls 13 and 14, the strand 1a is almost straight. The two side strands 1b, 1b are wound around the core strand 1a when passing through the guide rolls 13, 14, and the bobbin 22 is formed as a steel cord B having a 1 + 2 structure.
It is wound up.

[0020]

Next, embodiments of the present invention will be described. As shown in FIG. 9, a core wire and a side wire having a diameter of 0.28 mm are used.
Using a buncher-type stranded wire machine shown in (1), a steel cord having a 1 + 2 (winding direction: S, pitch P: 16 mm) structure was manufactured. As shown in FIG. 8, the wavy braiding of the side strands is performed by using a device having a pair of gear-shaped members having a 2.0 mm (about 7.14 d) pin made of cemented carbide attached to the tooth tip. Done. In Examples 1 and 2, only one side strand was corrugated, and in Example 3, two side strands were corrugated.
In Comparative Examples 1 to 3, the two side strands were corrugated, and the corrugated pitch p / P or the wave height h / d was excluded from the present invention. Comparative Example 4 was the side strand. Two of the gears are sharply corrugated using the gears shown in FIG. The conventional example uses the same strands as in the first embodiment, and
This is an open code having a × 3 structure. Table 1 shows the manufacturing specifications and code characteristics of the above-described examples, comparative examples, and conventional examples.

In Table 1, ○ in “Twistability” indicates no problem, and Δ indicates disconnection. "Low load elongation"
Elongation between 0.30 kgf and 1.63 kgf load.
"Rubber permeability" means that a straightened cord is vulcanized in rubber under a tension of 100 gf to prepare a sample, and then the cord is disassembled in the longitudinal direction, and the rubber permeability is visually observed. The rubber completely covered to the center was determined as 100%. The "fatigue resistance index" is calculated by applying a strip-shaped sample obtained by vulcanizing a steel cord in rubber to three rolls each having a constant diameter and arranged in a staggered manner.
%, And the roll was repeatedly reciprocated left and right to repeatedly bend the sample to determine the number of repetitions until the cord was broken. It was expressed by.
The "flexural rigidity index" is a value obtained by giving a constant-angle bending to a cord sample having a length of 70 mm and calculating the magnitude of the bending moment required for each.

[0022]

[Table 1]

As is clear from Table 1, Examples 1 to 3 have good rubber permeability and low elongation under a low load. This is because even if tension is applied to the cord due to the cord structure, the core strand with a small molding rate keeps the cord elongation low, so that the gap between the strands can be secured, and the side strands have the proper pitch and height. This is because the gap is within the stable optimum range.
In addition, Examples 1 to 3 have good stranded wire properties and fatigue resistance. This is because the radius of curvature of the wave is 3.50 d or more due to the corrugating process. On the other hand, in Comparative Example 1, the rubber pitch was not sufficiently improved because the corrugated pitch was too large, and in Comparative Example 2, the elongation at low load was large because the corrugated height was too large. Comparative Example 3 has a small corrugated height and is inferior in rubber permeability. In Comparative Example 4, since the corrugation was sharp, the strandedness and fatigue resistance were insufficient. The conventional example has a large elongation at low load and is inferior in fatigue resistance.

[0024]

According to the first aspect of the present invention, in the steel cord having a 1 + 2 structure in which two side wires are spirally wound around one linear core wire, Since the strand A has a molding rate A of 80.0 to 95.0%, the rubber permeability does not become an unstable region and the elongation under a low load can be suppressed. , At least one of the side strands has a wave pitch p
Is p / P = 0.30 in relation to the winding pitch P
０．６0.60, the wave height h is in the range of h / d = 1.05 to 1.85 in the ratio to the strand diameter d, and the radius of curvature r at the top is a continuous wavy wave of 3.50 d or more. Before winding, and 0.30 kgf of the cord and 1.63
Since the elongation between the kgf loads is 0.15% or less, the rubber permeability is stable with a secure and stable gap between the strands. Is easy to handle at the time of compound work, and the wavy shape has a curvature radius r of a top portion of 3.50 d or more.
An excellent effect of good stranded wire properties and good fatigue resistance is obtained. According to the second aspect, since the wavy shape is formed by a pair of gear-shaped members provided on each tooth tip with a cylindrical pin having a smooth surface perpendicular to the rotation direction, a continuous curvature with a stable curvature is provided. An excellent effect is obtained in that a wave shape having a desired radius of curvature can be freely and easily formed depending on the pin diameter. According to the third aspect, there is obtained an excellent effect that a radial tire having good corrosion resistance, a long life, and a good balance can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a conventional steel cord.

FIG. 2 is a sectional view of a conventional steel cord.

FIG. 3A is a partial cross-sectional view of a conventional device for corrugating steel cord, and FIG. 3B is an enlarged side view showing a corrugated state.

4 (a) is an enlarged side view schematically showing a steel cord according to the present invention, and FIG. 4 (b) is one of the steel cords shown in FIG.
It is sectional drawing of each position which divided the pitch into four.

FIG. 5 is an explanatory diagram of a molding rate of a core strand.

FIG. 6 is a schematic side view showing a state where a side strand is disassembled from a cord.

FIG. 7 is a partially enlarged side view of FIG. 6;

8 (a) is a partial cross-sectional view of a wavy device used in the present invention, and FIG. 8 (b) is a perspective view of the same.

FIG. 9 is an explanatory view schematically showing a steel cord manufacturing apparatus and steps of the present invention.

[Explanation of symbols]

 1a Core strand 1b Side strand s Gap 10 Round part p Wave pitch h Wave height P Winding pitch d Element diameter r Wave radius radius of curvature

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-90784 (JP, A) JP-A-5-140882 (JP, A) JP-A-51-43446 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) D07B 1/06 B29D 30/38 B60C 9/00-9/08

Claims (3)

(57) [Claims] 1. A steel cord having a 1 + 2 structure in which two side strands are spirally wound around one linear core strand, the core strand has a molding rate A of 80.0 to 95. .0
%, And at least one of the side strands is
The relationship between the wave pitch p and the winding pitch P is p / P
= 0.30 to 0.60, the wave height h is in the range of h / d = 1.05 to 1.85 in terms of the ratio to the strand diameter d, and the radius of curvature r of the top of the wave is A rubber reinforcement characterized by having a continuous wavy of 3.50 d or more before winding and having a cord elongation between 0.30 kgf and 1.63 kgf load of 0.15% or less. For steel cord. 2. The rubber reinforcement according to claim 1, wherein the wavy shape is provided by a pair of gear-shaped members provided on each tooth tip with a cylindrical pin having a smooth surface and orthogonal to the rotation direction. For steel cord. 3. A radial tire using the steel cord according to claim 1 for reinforcing a belt portion.