JPH05156580A - Rubber good-reinforcing steel cord and its production - Google Patents

Abstract

PURPOSE:To produce the subject steel cord improved in fatigue resistance, corrosion resistance, etc., and suitable, e.g. for a tire of a heavy car by giving a wave pattern to strands between a twister and a unit for feeding the strand to a core and subsequently intertwisting the above-mentioned strands with strands of an inner sheath. CONSTITUTION:After a wave pattern is given to strands 2a and 2b by a wave- patterning unit 8 between a twister 11 and a unit for feeding the strands 2a and 2b to a core 1, strands 3 of an inner sheath 4 are intertwisted therewith by a twister 10. Thereby, the core 1 composed of 2 to 4 intertwisted strands 2a and 2b is intertwisted with the inner sheath 4 composed of 6 to 9 strands 3 around the core 1 to prepare the core. To one or more strands amoung the above-mentioned strands, a wave pattern having a wave length (L) and a wave height (H) respectively satisfying L<=P1, 5d<=L<=30d and 1.05d<=H<=2.0d in relation to the diameter (d) of the strand and the twist pitch (P1) of the core is given, thus obtaining the objective steel cord having 1.2 to 2.5 ratio (P2/P1) provided that (P1) and (P2) are respectively the twist pitch of the core and the twist pitch of the inner sheath.

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, steel cords used for heavy duty tires are required to have many characteristics, and rubber adhesion is an important characteristic because it has a great influence on 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 contacting 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.

A three-layer twisted steel cord having a 3 + 9 + 15 structure has been widely used as a reinforcing material for heavy-duty tires because it has excellent fatigue resistance. However, in this three-layer twisted steel cord, when the wire diameters of the respective strands are made substantially the same, the strands of each layer are in contact with each other, and it becomes difficult for rubber to enter the inside of the cord, resulting in a problem of poor corrosion resistance of the cord. ..

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 leave a gap between the wires. ing. However, with a cord in which the core wire is formed in a helical shape and multiple side wires are twisted around it, the wire in the middle layer may fall into the circle formed in the helical shape, and as a result, Rubber penetration is impaired, the alignment of the wires in the middle and outer layers deteriorates, and the cord strength and fatigue resistance deteriorate. When the number of strands reduced in the middle and outer layers is small, rubber penetration into the inside of the cord is inferior, but if the number of strands is reduced to improve this, the cord strength decreases and the tire reinforcement material Would be unsuitable as

[0005]

SUMMARY OF THE INVENTION The present invention provides a three-layer twisted cord and a two-layer twisted cord excellent in fatigue resistance as described above,
An object of the present invention is to propose a steel cord for reinforcing a rubber article, which has a significantly improved rubber penetration into the inside of the cord and has improved durability, and a method for manufacturing the same, without lowering the cord strength.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a core formed by twisting two to four strands and an inner sheath made of six to nine strands arranged around the core are twisted together. And a wavelength L and a wave height H relating to the wire diameter d and the twist pitch p ₁ of at least one of the wires constituting the core, L ≦ p ₁ and 5d ≦ L ≦ Waveforms that satisfy the range of 30d and 1.05d ≤ H ≤ 2.0d, and the twist pitch of the core
The ratio of p ₁ to the twisting pitch p ₂ of the inner sheath, p ₂ / p ₁ is 1.2 to
The steel cord for reinforcing rubber articles characterized by the value of 2.5 and 11 to 15 arranged around the inner sheath.
A steel cord obtained by further twisting an outer sheath made of two strands of wire, which comprises at least one strand constituting the core, and a wavelength L relating to the strand diameter d and the twist pitch p ₁ and Waveform H with L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.05d ≦ H ≦ 2.0d is used.
The ratio of p ₁ to the twisting pitch p ₂ of the inner sheath, p ₂ / p ₁ is 1.2 to
2.5 and the ratio p ₃ / p ₂ between the pitch p ₂ and twisting pitch p ₃ of the outer sheath twisted inner sheath is steel cord for reinforcement of rubber articles, which is a 1.2 to 2.3.

Further, according to the present invention, in manufacturing the above-mentioned steel cord, at least one of the strands forming the core is flush with the twisting machine and the device for supplying the strand to be supplied to the core. A method for manufacturing a steel cord for reinforcing a rubber article, which is characterized by applying a corrugated pattern extending upward and then twisting the strands of the inner sheath or further twisting the strands of the outer sheath.

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 to increase 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 will decrease. The diameter of the wires forming the cord is 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 (a) shows the sectional shape of the steel cord according to the present invention. In the figure, 1 is three strands 2a and 2b
The core 1 is composed of the core 1, and the inner sheath 4 composed of the eight strands 3 is arranged around the core 1. Core 1
2a of the wires forming the
Alternatively, the waveform is modeled as shown in (b). This waveform shows that the wavelength L and the wave height H are L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.d with respect to the diameter d and the twist pitch p ₁ of the core wire 2a.
It is essential that the range of 05d ≤ H ≤ 2.0d is satisfied, and the shape may be linear or curved. Further, the wavy shaped strands 2a are twisted together as the core 1 together with the strands 2b, and the strands 2a have a shape as shown in FIG. An example in which the core wire 2a is made smaller in diameter than the wire 2b is shown in FIG. 1 (b).
It is also possible to configure the core 1 from the strands 2 having the same diameter, as shown in FIG.

3 (a) and 3 (b) show the sectional shape of a steel cord having a three-layer structure. The illustrated steel cord is the two-layer steel cord shown in FIGS. 1 (a) and 1 (b).
An outer sheath 6 composed of 13 strands 5 is arranged. The structure of the core 1 is similar to that shown in FIGS. 1 (a) and 1 (b).

In the steel cord having the two-layer structure, for example, by using the manufacturing equipment shown in FIG. 4, first, the wire to be the wire 2a of the core 1 is sent out from the unwinding reel 7, and the wire is set at a predetermined pitch. Through a corrugating device 8 consisting of a pair of wheels 8a, 8b, which is provided with a waveform according to the above wavelength and wave height to form a wire 2a, and the wire 2a and the two wires drawn from the storage wire portion 9 The strands 2b and 2 are passed through a twisting and shaping device 10 to form a spiral shape, and then the strands 2a and 2b are twisted by a stranding machine 11
The core 1 is introduced into and twisted together. Further, as shown in FIG. 5, the core 1 is introduced into the twisting machine 14 through the storage wire portion 12 and the twisting type forming device 13 arranged in the downstream process of the twisting wire machine 11 while being pulled out from the storage wire portion 12. The eight strands 3 are passed through a twisting and shaping device 13 to form a spiral shape, and then the strands 3 are introduced into a twisting machine 14 and twisted together with the core 1 to form a core 1
A two-layer twisted cord in which an inner sheath 4 composed of eight strands 3 is arranged on the outer side of is obtained.

Further, the outer sheath 6 is further arranged around the inner sheath 4 to obtain a steel cord having a three-layer structure, which is similar to the case where the inner sheath 4 is arranged around the core 1, so that the illustration is omitted. But 13 strands 5
Is passed through a shaping device to form a spiral shape, and then the two-layer twisted cord and each strand 5 are introduced into a twisting machine and twisted.

[0013] Here Upon combining twisting the second layer, the ratio p ₂ / p of the pitch p ₁ and the twisting pitch p ₂ of the inner sheath twisted core
_1, in the range of 1.2 to 2.5, when combining further twisting the third layer, the ratio p ₃ / p ₂ between the pitch p ₂ and twisting pitch p ₃ of the outer sheath twisted inner sheath, the 1.2 to 2.3 It is important to set the range.

The corrugating device 8 used for the core wire
As shown in FIG. 6, the twist type attaching device 10 shown in FIG.
7 may be provided on the outlet side of the corrugating device, and as shown in FIG. 7, the wheels 8a and 8b of the corrugating device may be configured to rotate around the wires passing between the wheels. An extending corrugation can be applied.

[0015]

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 inner sheath and the 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 forming the core is L≤p ₁ and 5d≤L≤30d with respect to the strand diameter d and the core twist pitch p _1. When the wavelength L exceeds 30d or the twist pitch p ₁ , the lateral pressure resistance (the resistance of the cord to the pressure when the pressure acts on the cord side surface) decreases, and, for example, during the tire manufacturing process. This is because the gap between the cord wires is reduced and it becomes difficult for rubber to enter the inside of the cord. On the other hand, the wavelength L is
If it is less than 5d, the corrugating process conditions for the core wire become severe, and the tensile strength of the core wire decreases.

Similarly, the wave height H of the waveform to be modeled 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 rubber penetration into the core deteriorates. This is because the disposition of the strands in the sheath and the outer sheath is disturbed and the intervals between the strands become non-uniform, resulting in portions where rubber does not enter between the strands.

[0018] In order to penetrate rubber between the further core and the inner sheath, the ratio p ₂ / p ₁ between the pitch p ₁ and the twisting pitch p ₂ of the inner sheath twisted cores in the range of 1.2 to 2.5,
For the rubber to penetrate to also between the inner sheath and the outer sheath in the case of three layers, the ratio p ₃ / p ₂ between the pitch p ₂ and twisting pitch p ₃ of the outer sheath twisted inner sheath 1.2
Within the range of ~ 2.3, the inner sheath strands shall not enter between the core strands, and the outer sheath strand shall not enter between the inner sheath strands.

As a method for twisting the cord, a twisting method in which the strand of the cord does not twist, that is, a tubular twisted wire is preferable from the viewpoint of fatigue resistance. The twisting direction of the core, inner sheath, and outer sheath may be either forward or reverse.If the wrapping wire is not wound around the outer circumference of the cord, consider the buckling fatigue of the cord due to compressive stress, and twist the core. If the direction is S (Z), the twisting direction of the inner sheath is Z (S), and the twisting direction of the inner sheath is S
If it is (Z), it is preferable that the twisting direction of the outer sheath is Z (S). Further, the corrugations applied to the strands of the core 1 may be those extending on the same plane or spirals.

[0020]

Example A wire obtained by drawing a steel cord wire for a tire to a predetermined diameter by an ordinary manufacturing method was used to form a wire having a structure shown in Table 1 by using a tubular twisting machine or a buncher twisting machine. Steel cord was manufactured. Here, the corrugated patterning of the wires used for the core is as shown in FIG.
A waveform having a predetermined shape shown in the table was applied.

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 portion where the element wires of the outer sheath contact the element wires of the inner sheath or the element wires of the inner sheath and the element wires of the core. 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 rubber penetration.

Further, 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 thereof, and then this test is conducted. After immersing the piece in 10% saline for a certain period of time, take out the cord from the rubber, evaluate the cut separation resistance by the length of defective adhesion in the core, inner sheath and outer sheath, and take the cord out of the rubber in the same way, and The generation of rust was observed in the inner sheath and outer sheath.

Further, only the rubber portion at a predetermined position of the above composite was cut and then immersed in a 10% saline solution for 1 hour, and then the temperature was adjusted.
While applying a predetermined tensile force in an environment of 50 ° C and humidity of 90%, repeated bending with a curvature of 120 mm was applied, and the fracture rate of the wire after a predetermined time was examined to evaluate the corrosion fatigue resistance. .. The results of these evaluations and surveys 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.

FIG. 9 is a sectional view of a steel cord.

[Explanation of symbols]

 1 core 2a element wire 2b element wire 3 element wire 4 inner sheath 5 element wire 6 outer sheath 7 unwind reel 8 corrugating device 8a wheel 8b wheel 9 storage part 10 twist forming device 11 twisting machine 12 storage part 13 twist Modeling device 14 Stranding machine

Claims (4)

[Claims] 1. A core formed by twisting two to four strands together,
A steel cord formed by twisting an inner sheath composed of 6 to 9 strands arranged around this core, wherein at least one strand constituting the core is provided with a diameter of the strand. Waveform L and wave height H with respect to d and the twist pitch p ₁ of the core are typed with a waveform satisfying the ranges of L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.05d ≦ H ≦ 2.0d, and the twist pitch of the core
The ratio of p ₁ to the twisting pitch p ₂ of the inner sheath, p ₂ / p ₁ is 1.2 to
A steel cord for reinforcing rubber articles, characterized by being 2.5. 2. A core in which 2 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. , The wavelength L and the wave height H relating to the wire diameter d and the twist pitch p ₁ of at least one of the wires constituting the core are: L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.05d ≦ H Shape a waveform that satisfies the range of ≤ 2.0d, and twist the core
The ratio of p ₁ to the twisting pitch p ₂ of the inner sheath, p ₂ / p ₁ is 1.2 to
2.5 and steel cord for reinforcement of rubber articles that the ratio p ₃ / p ₂ between the pitch p ₂ and twisting pitch p ₃ of the outer sheath twisted inner sheath is characterized by a 1.2 to 2.3. 3. In manufacturing the steel cord according to claim 1, between the twisting machine and a device for supplying the strand to be used for the core, the strand is corrugated, and then the strand of the inner sheath is formed. A method for manufacturing a steel cord for reinforcing a rubber article, which comprises twisting wires together. 4. In manufacturing the steel cord according to claim 2, between the twisting machine and a device for supplying the strand to be used for the core, the strand is corrugated, and then the inner sheath is stranded. A method for manufacturing a steel cord for reinforcing rubber articles, which comprises twisting wires together and then twisting wires of an outer sheath.