JPH06294083A - Steel cord for reinforcing rubber article and its production - Google Patents

Abstract

PURPOSE:To improve fatigue resistance, corrosion resistance, etc., desired to steel cord used as a reinforcing material for rubber article such as pneumatic tire or industrial belt used for heavy load vehicles such as truck and bus. CONSTITUTION:This steel cord for reinforcing rubber articles is obtained by twisting a core 1 obtained by twisting 1-4 raw wires with a sheath 3 consisting of 6-9 raw wires arranged around this core. A wavy form satisfying the formulas L<=(p1), 5d1<=L<=30d1 and 1.05d1<=H<=2.0d1 between a wavelength L and wave height H and the raw wire diameter (d1) and twist pitch (p1) is formed on either one raw wire constituting the sheath to improve impregnation of rubber to the space between sheath raw wires.

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 as a reinforcing material for rubber articles such as pneumatic tires and industrial belts used in heavy-duty vehicles such as trucks and buses, and particularly steel for heavy-duty tires. It is intended to improve the fatigue resistance and corrosion resistance desired for the cord.

[0002]

2. Description of the Related Art For example, a steel cord used in a heavy-duty tire is required to have many characteristics. Above all, rubber adhesion is an important characteristic because it greatly affects fatigue resistance and corrosion resistance. Regarding this improvement of rubber adhesion,
In the 56-14396 publication, a core wire is formed in a helical shape, and a plurality of side wires are twisted around the outer circumference of the core wire without touching each other, so that rubber penetrates even into the inside of the cord to improve rubber adhesion. The improvement is described together with the improvement of the rustproof property of the steel cord itself due to rubber penetration even inside the cord.

Further, layer-twisted steel cords having a 3 + 9 or 3 + 9 + 15 structure have been widely used as reinforcing materials for heavy duty tires because of their excellent fatigue resistance. However, in these layer-twisted steel cords, when the wire diameters of the respective strands are made substantially the same, the strands of each layer are in contact with each other, it becomes difficult for rubber to enter the inside of the cord, and the corrosion resistance of the cord is poor.

To solve this problem, Japanese Patent Laid-Open No. 223503/1984 proposes a 4 + 9 + 14 structure in which the number of wires in the intermediate layer and the outer layer is smaller than that of the close-packed structure to provide a gap between the wires. ing. However, in a cord in which the core wire is formed in a helical shape and multiple side wires are twisted around it, the wire of the intermediate layer may fall into the circle formed in the helical shape, and as a result, The rubber penetration is impaired, the alignment of the wires in the middle and outer layers is deteriorated, and the cord strength and fatigue resistance are deteriorated. If the number of strands in the middle and outer layers is small, rubber penetration into the cord is poor.However, if the number of strands is reduced to improve this, the cord strength decreases and the tire reinforcement material Would be unsuitable as

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, in the above-mentioned three-layer twisted cord and two-layer twisted cord having excellent fatigue resistance, it is extremely easy for rubber to penetrate into the inside of the cord without lowering the cord strength. It is an object of the present invention to propose a steel cord for reinforcing rubber articles having improved durability and a method for manufacturing the same.

[0006]

According to the present invention, a core formed by twisting 1 to 4 strands and a sheath made of 6 to 9 strands arranged around the core are twisted together. It is a steel cord, and the wavelength L and the wave height H related to at least one of the strands constituting the sheath are the strand diameter d ₁ and the twist pitch p ₁ of the sheath,

## EQU00003 ## A steel cord for reinforcing a rubber article formed by shaping a corrugation satisfying the ranges of L ≦ p ₁ and 5d ₁ ≦ L ≦ 30d ₁ and 1.05d ₁ ≦ H ≦ 2.0d ₁ and the sheath is arranged around the sheath. Done 11
A steel cord obtained by further twisting an outer sheath made up of ~ 15 strands, wherein at least one of the strands constituting the outer sheath has a strand diameter d ₂ and a twist of the outer sheath. Wavelength L for pitch p ₂
And the wave height H is

Equation 4 is a L ≦ p ₂ and 5d ₂ ≦ L ≦ 30d ₂ and 1.05d ₂ ≦ H ≦ 2.0d steel cord for reinforcement of rubber articles formed by embossing a satisfactory waveform range of _2.

Further, according to the present invention, in manufacturing the steel cord having the two-layer twisted structure, at least one of the sheath strands is corrugated between the twisting machine and the device for supplying the strands to be used for the sheath. In the method for producing a steel cord for reinforcing a rubber article, which comprises placing the strands of a sheath on the outer periphery of the core and twisting the strands, and the steel cord having the three-layer twist structure, At least one of the outer sheath wires is provided between the twisting machine and the wire feeder for the core.
A method for manufacturing a steel cord for reinforcing a rubber article, which comprises subjecting a book to a corrugated pattern, and then arranging the strands of an outer sheath on the outer periphery of an inner sheath that is twisted with a core and twisting the strands.

In addition to a planar waveform, a three-dimensional waveform, that is, a spiral shape is advantageously suitable for the above-mentioned waveform, and in this spiral shape, the pitch of the spiral corresponds to the wavelength L and the diameter corresponds to the wave height H.

In the present invention, the wire constituting the steel cord has a chemical composition equivalent to that of a piano wire or a hard steel wire having a carbon content of 0.70 to 0.85 wt% and is a wire rod containing few non-metallic inclusions. It is preferable to use a steel wire having a diameter of 0.12 to 0.35 mm by wire processing. Where the carbon content is 0.70 wt
% Or more is for increasing the tensile strength per unit weight of the steel cord in order to reduce the weight of the tire, for example, and if it exceeds 0.85 wt%, the fatigue resistance decreases. Also, the diameter of the strands constituting the cord is set to 0.35 mm or less because the fatigue resistance of the cord is reduced when it exceeds 0.35 mm, while 0.12 mm or more is reinforced, for example, for heavy-duty tires. This is to impart sufficient tensile strength to the cord.

FIG. 1 shows a sectional shape of the steel cord according to the present invention. In the figure, reference numeral 1 denotes a core made of one element wire, and a sheath 3 made of six element wires 2a and 2b is arranged around the core 1. Of the wires forming the sheath 3, the wire 2a has a corrugated shape as shown in FIG. 2 (a) or (b). This waveform shows that the wavelength L and the wave height H are L ≦ p ₁ and 5d ₁ ≦ L ≦ 30d ₁ and 1.05d ₁ ≦ for the diameter d ₁ and the twist pitch p ₁ of the strand 2a of the sheath 3, respectively.
It is important to satisfy the range of H ≦ 2.0d ₁ , and the shape may be linear or curved. Furthermore, the wire 2a having a corrugated shape is used as the sheath 3 together with the wire 2b,
The strand 2a is twisted around the core 1 and has a shape as shown in FIG.

Although FIG. 1 shows an example in which a single wire 2a of the sheath 3 is corrugated, as shown in FIGS. 3 (a) and 3 (b), the wire forming the sheath 3 is formed. It is also possible to pattern the waveform on a plurality of the. Further, in the example shown in FIG. 3C, a sheath 3 made up of eight strands is arranged around a core 1 made up of three strands, and one strand 2a of the sheath 3 is shaped into a waveform. It was done.

4 (a) and 4 (b) show the sectional shape of a steel cord having a three-layer structure. In the steel cord shown in FIG. 4 (a), an outer sheath 5 composed of eleven strands 4a and 4b is arranged on the outer side of the steel cord having a two-layer structure similar to that of FIG. 1, and the outer sheath 5 is configured. Of the strands to be formed, six strands 4a are formed by corrugation. Next, in the steel cord shown in FIG. 3 (b), the outer sheath 5 composed of 13 strands 4a and 4b is arranged outside the cord shown in FIG. 3 (c), and the outer sheath 5 is constructed. Of the strands to be formed, six strands 4a are formed by corrugation.

In the steel cord having the two-layer structure, for example, using the manufacturing equipment shown in FIG. 5 (a), first, the wire to be the core 1 is sent out from the bobbin 6, while the number of wires constituting the sheath 3 and The wires of the sheath 3 are sent from the storage wire portion 7 having the same number of bobbins to the side of the twisting and shaping device 10. At this time, the wire pulled out from the bobbin in the storage wire portion 7 is
As shown in FIG. 5, the wire 2a is passed through a corrugating device 8 consisting of a pair of wheels 8a, 8b having teeth of a predetermined pitch, and a waveform according to the above-mentioned wavelength and wave height is imparted to the wire 2a. A predetermined number of strands drawn from the wire portion 7
Spiral shaping is performed by passing through the twisting and shaping device 9, and then these strands are introduced into the twisting machine 10 together with the strands sent from the bobbin 6, and twisted according to the tubular system to form the two-layer twisted cord 11. obtain.

Further, the manufacturing equipment shown in FIG.
In (a), the step of applying the corrugation by passing the wire drawn from the bobbin in the storage wire portion 7 through the corrugating device 8 is performed in advance outside the storage wire portion 7 to form the corrugated wire 2a. The wound bobbin 12 is arranged in the storage line portion 7.

Next, in the manufacturing equipment shown in FIG. 7 (a), the cores and the wires for the sheaths drawn from the bobbins 13a, 13b, 13c ----- corresponding to the number of the sheaths are replaced with the wires for the sheaths. The wire can be introduced into a wire twisting machine 10 through a twisting type forming device 9 and twisted according to a buncher method to obtain a two-layer twisted cord 11. And the equipment shown in FIG. 7 (b) is also shown in FIG.
Similar to (b), in FIG. 7 (a), the wire drawn from the bobbin 13a is passed through the corrugating device 8 to give a waveform, and the corrugated wire 2a is wound around the bobbin 13a. It is set aside and the same twisting is performed thereafter.

In order to obtain the three-layer steel cord by further disposing the outer sheath 5 around the sheath 3, the sheath 3 is arranged around the core 1, so that the illustration is omitted. However, after applying a corrugated pattern to the desired number of 11 to 15 strands, all strands are passed through a twisting and shaping device to form a spiral shape, and then the two-layer twisted cord and each strand are It may be introduced into a twisting machine and twisted.

[0017]

The reason why the structure of the steel cord according to the present invention is twisted in two or three layers is to ensure fatigue resistance, and the sheath or inner sheath and outer sheath are made of strands rather than strands. The reason is that, in addition to improving productivity, it is difficult to intrude rubber into the inside of the twisted wire, which reduces the corrosion resistance of the cord.

Next, the wavelength L of the waveform to be molded on at least one of the strands constituting the sheath or outer sheath is L≤p and 5d with respect to the strand diameter d and the twist pitch p of the sheath or outer sheath. The definition of ≤L≤30d is that the lateral pressure resistance (the resistance of the cord to the pressure when pressure acts on the cord side) decreases when the wavelength L exceeds 30d or the twist pitch p. This is because the gap between the strands of the cord is reduced during the process and it becomes difficult for rubber to enter the inside of the cord. On the other hand, when the wavelength L is less than 5d, the corrugation-type processing conditions of the core wire become severe, and the tensile strength of the core wire is reduced. Further, a particularly preferable range of the wavelength L is 8.9d≤L≤17.6d.

Similarly, the wave height H of the waveform to be molded is 1.
The reason for limiting the range to 05d ≤ H ≤ 2.0d is that if it is less than 1.05d, the gap between the strands in the core becomes small and the rubber penetration into the core and the sheath deteriorates.
This is because if the diameter exceeds the above range, the arrangement of the strands in the sheath or the inner sheath and the outer sheath is disturbed, the intervals between the strands become non-uniform, and portions where rubber does not enter between the strands occur. Furthermore, the particularly preferable range of the wave height H is 1.11d.
≤H≤1.25d.

The twisting directions of the core and the sheath may be either forward or reverse. However, when the wrapping wire is not wound around the outer circumference of the cord, the twisting of the core is taken into consideration in consideration of buckling fatigue of the cord due to compressive stress. If the direction is S (Z), the twist direction of the sheath is Z (S), and the twist direction of the inner sheath is S (Z).
If it is (Z), it is preferable to set the twist direction of the outer sheath to Z (S).

[0021]

Example A steel cord having a structure shown in Table 1 was manufactured by using a buncher twisting machine to obtain a wire obtained by drawing a wire of a steel cord for tires to a predetermined diameter by a usual manufacturing method. The corrugation pattern of the wires used for the sheath was given a corrugated shape having a predetermined shape shown in the same table as shown in FIG. 7 (a).

The steel cord thus obtained was placed between two unvulcanized rubber sheets and then vulcanized under heat and pressure. Next, take out the steel cord from the vulcanized rubber, and attach the amount of rubber adhered on the inner sheath after removing the wires of the outer sheath and the amount of rubber adhered on the core after removing the wires of the inner sheath. The amount of rubber adhered and the amount of rubber adhered to the core wire inside the core after the core wire was removed were investigated. That is, on the surface of the inner sheath or core, all the elements of the inner sheath or core except for the part where the element wires of the outer sheath and the element wires of the inner sheath or the element wires of the inner sheath and the element wires of the core are in contact with each other. The adhesion rate of the rubber was investigated when the state where the rubber was adhered to the surface of the wire was 100%, and this was evaluated as the rubber penetration.

After vulcanizing the composite of the above-mentioned steel cord and two unvulcanized rubber sheets, a test piece having a cross section in which the steel cord is exposed is prepared by cutting the end of the vulcanized rubber sheet. After the pieces were immersed in 10% saline for a certain period of time, the cord was taken out from the rubber, and the cut separation resistance was evaluated by the length of defective adhesion in the core, inner sheath and outer sheath. The results of these evaluations and investigations are also shown in Table 1 together with the code structure.

[0024]

[Table 1]

[0025]

According to the present invention, the rubber penetration into the inside of the cord can be remarkably improved without lowering the cord strength of the two- or three-layer twisted cord, and the fatigue resistance and durability are excellent. A steel cord for reinforcing a rubber article and a method for manufacturing the same can be provided.

[Brief description of drawings]

1 is a cross-sectional view of a steel cord according to the present invention.

FIG. 2 is an explanatory diagram showing a waveform applied to a core.

FIG. 3 is a sectional view of a steel cord according to the present invention.

FIG. 4 is a schematic diagram showing a steel cord manufacturing facility.

FIG. 5 is a schematic diagram showing a steel cord manufacturing facility.

FIG. 6 is a schematic view showing another patterning device.

FIG. 7 is a schematic view showing another patterning device.

FIG. 8 is a sectional view of a steel cord.

[Explanation of symbols]

 1 core 2a strand 2b strand 3 sheath 4a strand 4b strand 5 outer sheath 6 bobbin 7 storage part 8 corrugating device 8a wheel 8b wheel 9 twisting and shaping device 10 twisting machine 11 cord 13a, 13b, 13c bobbin

Claims (4)

[Claims] 1. A core formed by twisting one to four strands of wire together,
A steel cord formed by twisting together a sheath composed of 6 to 9 strands arranged around this core, wherein at least one strand constituting the sheath has a strand diameter d Waveform L and wave height H with respect to ₁ and the twist pitch p ₁ of the sheath are shaped such that L ≦ p ₁ and 5d ₁ ≦ L ≦ 30d ₁ and 1.05d ₁ ≦ H ≦ 2.0d ₁ Steel cord for reinforcing rubber articles. 2. A core in which 1 to 4 strands are twisted together,
A steel cord formed by twisting an inner sheath made of 6 to 9 strands arranged around the core and an outer sheath made of 11 to 15 strands arranged around the inner sheath. , At least one of the strands constituting the outer sheath has a wavelength L related to the strand diameter d ₂ and the twist pitch p ₂ of the outer sheath.
A steel cord for reinforcing a rubber article, which is obtained by shaping a corrugated product having a wave height H satisfying the following expressions: L ≦ p ₂ and 5d ₂ ≦ L ≦ 30d ₂ and 1.05d ₂ ≦ H ≦ 2.0d ₂ . 3. In manufacturing the steel cord according to claim 1, at least one of the sheath strands is provided between a twisting machine and a device for supplying strands for a sheath.
A method for manufacturing a steel cord for reinforcing a rubber article, which comprises applying a corrugated pattern to a book, and then arranging the strands of the sheath around the outer periphery of the core and twisting them together. 4. In manufacturing the steel cord according to claim 2, at least one of the outer sheath wires is corrugated between the twisting machine and the device for supplying the wire to be used for the core. The method for producing a steel cord for reinforcing a rubber article, comprising the steps of: