JP3213114B2 - Steel cord for reinforcing rubber articles and method for producing the same - 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 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 more particularly to steel cords for heavy-duty tires. It is intended to improve the fatigue resistance, corrosion resistance, and the like 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 properties. Among them, rubber adhesion is an important property because it greatly affects fatigue resistance and corrosion resistance. Kimiaki Jitsumi concerning the improvement of rubber adhesion
No. 56-14396 discloses that a core wire is formed in a helical shape, and a plurality of side wires are twisted around the core wire in a state where they are not in contact with each other, so that rubber can penetrate into the inside of the cord to improve rubber adhesiveness. The improvement is described together with the improvement of the rust prevention of the steel cord itself due to rubber penetration into the inside of the cord.

[0003] Further, a multi-layer twisted steel cord such as a 3 + 9 + 15 structure has been widely used as a reinforcing material for a heavy duty tire because of its excellent fatigue resistance. However, in these layered steel cords, when the wire diameters of the respective wires are substantially the same, the wires of the respective layers come into contact with each other, so that rubber hardly enters the inside of the cord, and there is a problem that the corrosion resistance of the cord is deteriorated.

To cope with this problem, Japanese Patent Application Laid-Open No. Sho 59-223503 proposes a 4 + 9 + 14 structure in which the number of strands in the intermediate layer and the outer layer is made smaller than that of the closest-packed structure and a gap is provided between the strands. ing. However, in a cord in which a core strand is formed in a helical shape and multiple side wires are twisted around it, the strand of the intermediate layer may fall into a helically formed circle, and as a result, The rubber penetration of the intermediate layer and the alignment of the wires of the intermediate layer and the outer layer are deteriorated, and the cord strength and fatigue resistance are deteriorated. When the number of wires in the intermediate layer and the outer layer is small, the rubber permeability into the cord is poor when the number of wires is small. Will be inappropriate.

[0005]

SUMMARY OF THE INVENTION The present invention provides a three-layer twisted cord excellent in fatigue resistance as described above. It is an object of the present invention to propose an improved steel cord for reinforcing rubber articles and a method for producing the same.

[0006]

According to the present invention, there is provided an inner sheath comprising a core in which 1 to 4 strands are twisted, 6 to 9 strands arranged around the core, and the inner sheath. A steel cord obtained by twisting an outer sheath consisting of 11 to 15 strands arranged around the wire, wherein at least one strand constituting the outer sheath has a strand diameter d And the wavelength L and the wave height H of the twist pitch p of the outer sheath are

## EQU2 ## A steel cord for reinforcing a rubber article formed by shaping a waveform satisfying a range of L ≦ p and 5d ≦ L ≦ 30d and 1.05d ≦ H ≦ 2.0 d.

According to the present invention, in manufacturing the steel cord having a three-layer twist structure, at least one of the outer sheath wires is provided between a twisting machine and a device for supplying a wire to be provided to a core. A method for producing a rubber cord for reinforcing a rubber article, characterized in that a corrugated pattern is formed on the outer sheath, and the strands of the outer sheath are arranged on the outer periphery of the inner sheath twisted with the core and then twisted.

[0008] In addition to a planar waveform, the above-mentioned waveform is also advantageously adapted to a three-dimensional waveform, that is, a spiral, in which 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% by weight, and is formed by drawing a wire having few nonmetallic inclusions. It is preferable to use a steel wire having a diameter of 0.12 to 0.35 mm by wire working. Where the carbon content is 0.70wt
% 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 when it exceeds 0.85 wt%, the fatigue resistance is reduced. The reason why the diameter of the wire constituting the cord is set to 0.35 mm or less is that if it exceeds 0.35 mm, the fatigue resistance of the cord is reduced, while the diameter is set to 0.12 mm or more, for example, for reinforcing heavy duty tires. This is for imparting sufficient tensile strength to the cord.

FIG. 1 shows a sectional shape of a steel cord according to the present invention. In the figure, reference numeral 1 denotes a core composed of one strand, and an inner sheath 3 composed of six strands 2 is arranged around the core 1, and eleven strands are further disposed outside the inner sheath 3. An outer sheath 5 composed of 4a and 4b is arranged, and among the strands forming the outer sheath 5, six strands 4a are corrugated. Here, among the wires constituting the outer sheath 5, the wire 4a is formed by shaping a waveform as shown in FIG. 2 (a) or (b). In this waveform, the wavelength L and the wave height H are L ≦ p and 5d ≦ L ≦ 30d and 1.05d ≦ with respect to the diameter d and the twist pitch p of the strand 4a of the outer sheath 5, respectively.
It is important to satisfy the range of H ≦ 2.0 d, and the shape may be any of a linear shape and a curved shape. Further, the wire 4a having the corrugated shape is connected to the outer sheath 5 together with the wire 4b.
And twisted around the inner sheath 3
4a has a shape obtained by twisting and forming after corrugating as shown in FIG. 2 (c).

In the cord shown in FIG. 3, an inner sheath 3 consisting of eight wires is disposed around a core 1 consisting of three wires, and 13 wires 4a and 13
An outer sheath 5 made of 4b is arranged, and among the wires constituting the outer sheath 5, six wires 4a are subjected to waveform shaping.

The above steel cord is, for example, shown in FIG.
First, while the element wire serving as the core 1 is sent out from the bobbin 6, the same number of bobbins as the number of element wires constituting the inner sheath 3 (in FIG. 4, two bobbins are shown as representatives) are used. The wires of the inner sheath 3 are sent out from the storage wire section 7 provided to the twisting device 9 side, and these wires are introduced into the twisting machine 10 together with the wires sent out from the bobbin 6, and twisted according to the tubular method. Then, the inner sheath 3 is twisted to the core 1.

Next, the thus obtained product is again sent out from the bobbin 6 in the manufacturing facility having the same structure as that shown in FIG.
, The outer sheath 5 is formed from a storage wire portion 7 further including bobbins (in FIG. 4, two bobbins are representatively shown) in the same number as the number of the wires constituting the outer sheath 5.
11 to 15 strands are sent out to the twisting and forming apparatus 9 side. At this time, a desired number of the wires drawn out of the bobbin in the wire storage unit 7 is transferred to a corrugating device 8 comprising a pair of wheels 8a and 8b having teeth of a predetermined pitch as shown in FIG. A wire according to the above-mentioned wavelength and wave height is given to form a wire 4a, and a predetermined number of wires drawn from the storage section 7 including the wire 4a are passed through a twisting and forming device 9 to form a spiral. Then, these strands are introduced into a twisting machine 10 together with a core 1 sent out from a bobbin 6 and an inner sheath 3 twisted, and twisted according to a tubular method to obtain a three-layer twisted cord 11.

Further, the manufacturing equipment shown in FIG.
In (a), the step of applying a waveform by passing the wire drawn out of the bobbin in the wire storage unit 7 through the corrugating device 8 is performed outside the wire storage unit 7 in advance, and the corrugated wire 4a is formed. The wound bobbin 12 is arranged in the wire storing section 7.

Next, in the manufacturing equipment shown in FIG. 6 (a), the cores drawn out from the bobbins 13a, 13b, 13c ----- corresponding to the number of the sheaths are twisted with the inner sheath and the outer sheath is used. The predetermined number of the wires for the outer sheath is introduced into the twisting machine 10 through the corrugating device 8, and then twisted according to the buncher method to form a three-layer twisted cord.
You can get 11. 6 (a), the equipment shown in FIG. 6 (b) is preliminarily subjected to a step of applying a waveform by passing the wire drawn from the bobbin 13a through the corrugating device 8 in FIG. 6 (a). Then, the corrugated wire 2a is wound around the bobbin 13a, and thereafter the same twisting is performed.

[0016]

The reason why the structure of the steel cord according to the present invention is three-layer twisted is to ensure fatigue resistance, and the inner sheath and the outer sheath are made of strands instead of strands. This is because, in addition to the improvement in productivity, when the stranded wire is used, it is difficult for rubber to penetrate into the inside, and the corrosion resistance of the cord is reduced.

Next, the wavelength L of the waveform to be molded on at least one of the wires constituting the outer sheath is expressed as L with respect to the wire diameter d and the twist pitch p of the outer sheath.
≦ p and 5d ≦ L ≦ 30d, because the wavelength L is 30d
Or, when the twist pitch p is exceeded, the lateral pressure resistance (the resistance of the cord to the pressure when pressure acts on the cord side) decreases, and for example, the gap between the strands of the cord decreases during the tire manufacturing process, and This is because it is difficult for rubber to enter the inside. On the other hand, when the wavelength L is less than 5d, the waveform shaping processing conditions of the outer sheath wire become severe, and the tensile strength of the outer sheath wire is reduced. Further, a particularly preferable range of the wavelength L is 8.9 d ≦ L ≦ 17.6 d.

Similarly, the wave height H of the waveform to be shaped is set to 1.
The reason for limiting to the range of 05d ≦ H ≦ 2.0d is that if it is less than 1.05d, the gap between the wires in the core becomes small, and the penetration of rubber into the core and the inside of the sheath deteriorates, while 2.
If the distance exceeds 0 d, the arrangement of the wires in the outer sheath is disturbed, the interval between the wires becomes uneven, and a portion where rubber does not enter between the wires is generated. Further, a particularly preferable range of the wave height H is 1.11d ≦ H ≦ 1.25d.

The twisting direction 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 buckling fatigue of the cord due to compressive stress is taken into consideration, and the twisting of the core is performed. If the direction is S (Z), the twisting direction of the inner sheath is Z (S). If the twisting direction of the inner sheath is Z (S), the twisting direction of the outer sheath is S.
(Z) is preferable.

[0020]

EXAMPLE A steel cord having the structure shown in Table 1 was produced from a strand obtained by drawing a wire rod of a steel cord for a tire to a predetermined diameter by a usual production method, using a buncher twisting machine. Here, for the waveform shaping of the wires used for the sheath, a waveform having a predetermined shape shown in the table was given according to the place shown in FIG. 6 (a). FIG. 7 shows the structure of the comparative example.

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

After vulcanizing a composite of the above-described steel cord and the two-ply unvulcanized rubber sheet, the end is cut to prepare a test piece having a cross section in which the steel cord is exposed. After the pieces were immersed in 10% saline for a certain period of time, the cord was taken out of the rubber, and cut separation resistance was evaluated based on the length of poor adhesion between the core, inner sheath and outer sheath. The results of these evaluations and surveys are shown in Table 1 together with the code structure.

[0023]

[Table 1]

[0024]

According to the present invention, it is possible to significantly improve rubber penetration into the inside of a three-layer twisted cord without lowering the cord strength, and to provide a rubber article having excellent fatigue resistance and durability. A reinforcing steel cord and a method of manufacturing the same can be provided.

[Brief description of the drawings]

FIG. 1 is a 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 view showing a strand forming device.

FIG. 6 is a schematic diagram showing another manufacturing facility.

FIG. 7 is a sectional view of a steel cord.

[Explanation of symbols]

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

Claims (2)

(57) [Claims] 1. A core formed by twisting 1 to 4 strands,
A steel cord obtained by twisting an inner sheath composed of 6 to 9 strands arranged around the core and an outer sheath composed of 11 to 15 strands arranged around the inner sheath. And at least one of the wires constituting the outer sheath has a wavelength L relating to the wire diameter d and the twist pitch p of the outer sheath.
And a wave height H that satisfies the following conditions: L ≦ p and 5d ≦ L ≦ 30d and 1.05d ≦ H ≦ 2.0 d. 2. A method of manufacturing a steel cord according to claim 1, wherein at least one of the outer sheath wires is corrugated between a twisting machine and a wire supplying device for supplying a core. And then twisting by arranging the strands of the outer sheath around the outer circumference of the inner sheath twisted with the core.