JP3093390B2 - 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, thereby allowing the rubber to penetrate into the inside of the cord to improve rubber adhesion. 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] In addition, 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 of its excellent fatigue resistance. However, in this three-layer stranded steel cord, when the wire diameter of each strand is substantially the same, the strands of each layer come into contact with each other, rubber hardly enters the inside of the cord, and the corrosion resistance of the cord is poor. .

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 of the intermediate layer and the outer layer is reduced from the number 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. In addition, 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, but when the number of wires is reduced to improve this, the cord strength is reduced and the tire reinforcement Will be inappropriate.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a three-layer twisted cord and a two-layer twisted cord having excellent fatigue resistance.
An object of the present invention is to propose a steel cord for reinforcing a rubber article which has improved durability by significantly improving the penetration of rubber into the cord without reducing the cord strength, and a method of manufacturing the same.

[0006]

According to the present invention, a core formed by twisting two to four strands and an inner sheath consisting of six to nine strands disposed around the core are twisted. a steel cord, constituting the core, any at least one strand, the wavelength L and the wave height H related to the wire diameter d and twist pitch p ₁ is, L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.05d ≤ H ≤ 2.0d
p ₁ and the ratio p ₂ / p ₁ between the pitch p ₂ twist of the inner sheath 1.2
The steel cord for reinforcing a rubber article, characterized by being 2.5, and 11 to 15 disposed around the inner sheath.
Outer sheath consisting of two strands, a steel cord further twisted, constituting the core, at least one of the strands, the wire diameter d and the twist pitch p ₁ wavelength L and wave height H is, by typing a waveform that satisfies the range of L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.05d ≦ H ≦ 2.0d, also twisting the core pitch
p ₁ and the ratio p ₂ / p ₁ between the pitch p ₂ twist of the inner sheath 1.2
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.

According to the present invention, at the time of manufacturing the steel cord, at least one of the strands constituting the core is co-planar between the twisting machine and a feeder for the strand to be supplied to the core. A method of manufacturing a steel cord for reinforcing rubber articles, characterized by applying a corrugated pattern extending upward and then twisting the wires of an inner sheath or further twisting the wires of an 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% 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. 1A shows a sectional shape of a steel cord according to the present invention. In the figure, 1 denotes three strands 2a and 2b
And an inner sheath 4 composed of eight strands 3 is arranged around the core 1. Core 1
Of the wires constituting the wire 2a, the wire 2a having a small diameter is shown in FIG.
Alternatively, the waveform is typed as shown in (b). This waveform, wavelength L and the wave height H is relates diameter d and twist pitch p ₁ of the core of the wire 2a, respectively L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.
It is important to satisfy the range of 05d ≦ H ≦ 2.0d, and the shape may be any of a straight line and a curved line. The corrugated strand 2a is twisted together with the strand 2b as the core 1, and the strand 2a has a shape obtained by twisting after corrugation as shown in FIG. 2 (c). An example in which the diameter of the core wire 2a is smaller than that of the wire 2b is shown in FIG. 1 (b).
As shown in (1), the core 1 can be composed of the wires 2 having the same diameter.

FIGS. 3A and 3B show cross sections of a steel cord having a three-layer structure. The illustrated steel cord is the same as the steel cord of the two-layer structure shown in FIGS.
An outer sheath 6 composed of 13 strands 5 is arranged. The structure of the core 1 is the same as that shown in FIGS. 1 (a) and 1 (b).

In the above-described steel cord having a two-layer structure, a wire serving as a wire 2a of the core 1 is first sent out from an unwinding reel 7 using, for example, a manufacturing facility shown in FIG. Through a corrugating device 8 composed of a pair of wheels 8a and 8b having a waveform and a waveform according to the above-mentioned wavelength and wave height to give a strand 2a. The strand 2a and two strands drawn from the storage section 9 The strand 2b and the strand 2b are passed through a twist molding apparatus 10 to perform spiral molding, and then the strands 2a and 2b are
And twisted to form a core 1. Further, as shown in FIG. 5, the core 1 is introduced into the stranded wire machine 14 via the wire storage unit 12 and the twist forming device 13 arranged in the downstream process of the stranded wire machine 11, and is pulled out from the wire storage unit 12. The eight strands 3 are spirally shaped by passing them through a twisting and shaping device 13, and then the strands 3 are introduced into a twisting machine 14 and twisted together with the core 1 to form a core 1.
To obtain a two-layer stranded cord in which an inner sheath 4 composed of eight strands 3 is arranged outside.

In order to obtain a three-layer steel cord by further arranging the outer sheath 6 around the inner sheath 4, it is the same as the case of arranging the inner sheath 4 around the core 1, so that illustration is omitted. Yes, but 13 strands 5
Is passed through a shaping device to perform spiral shaping, and then the two-layer twisted cord and each of the strands 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.

A corrugating device 8 for the core element wire
As shown in FIG. 6, the twisting device 10 shown in FIG.
7, and as shown in FIG. 7, the wheels 8a and 8b of the corrugating device may be configured to rotate around a wire passing between the wheels. An elongated waveform can be provided.

[0015]

The structure of the steel cord according to the present invention is twisted in two or three layers in order to ensure fatigue resistance, and the inner sheath and the outer sheath are constituted by 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 stranded wire, and the corrosion resistance of the cord is reduced.

Next, the wavelength L of the waveform to be molded into at least one of the strands constituting the core is represented by L ≦ p ₁ and 5d ≦ L ≦ 30d with respect to the strand diameter d and the twist pitch p ₁ of the core. as defined is to decrease lateral pressure resistance exceeds the pitch p ₁ wavelength L is 30d or twist (resistance of the code for the pressure when pressure is exerted on the code side), then for example in a tire manufacturing process This is because the gap between the wires of the cord is reduced, so that rubber hardly enters the cord. On the other hand, if the wavelength L is
If it is less than 5d, the corrugation shaping condition of the core strand becomes severe, and the tensile strength of the core strand is reduced.

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 is deteriorated. This is because the arrangement of the wires in the sheath and the outer sheath is disturbed, the intervals between the wires are not uniform, and a portion where rubber does not enter between the wires is generated.

[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
To 2.3, so that the wires of the inner sheath do not enter between the wires of the core, and the wires of the outer sheath do not enter between the wires of the inner sheath.

As a method for twisting the cord, a twisting method in which the strands of the cord are not twisted, that is, a tubular twisted wire is desirable from the viewpoint of fatigue resistance. The twist direction of the core, inner sheath and outer sheath may be either forward or reverse.However, if the wrapping wire is not wound around the cord, take into account 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 (Z).
In the case of (Z), the twist direction of the outer sheath is preferably set to Z (S). Further, the waveform applied to the strands of the core 1 may be one extending on the same plane or one extending spirally.

[0020]

EXAMPLE A wire obtained by drawing a wire rod of a steel cord for a tire to a predetermined diameter by a normal manufacturing method was used to form a wire having a structure shown in Table 1 using a tubular twisting machine or a buncher twisting machine. Steel cord was manufactured. Here, the waveform shaping of the wires used for the core is performed according to the place shown in FIG.
A waveform having a predetermined shape shown in the same table was given.

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 the elements 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 or the strand of the inner sheath and the strand of the core are in contact. The adhesion rate of the rubber when the state where the rubber adhered to the wire surface was defined as 100% was examined, 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 soaking the piece in 10% saline for a certain period of time, take out the cord from the rubber, evaluate the cut separation resistance based on the length of poor adhesion in the core, inner sheath and outer sheath. The occurrence of rust on the inner sheath and the outer sheath was observed.

Further, only the rubber portion at a predetermined portion of the above-mentioned composite was cut, and then immersed in 10% saline for 1 hour.
While applying a predetermined tensile force in an environment of 50 ° C and a humidity of 90%, the steel sheet was repeatedly bent with a curvature of 120 mm, and the breaking rate of the wire after a predetermined time was examined to evaluate the corrosion fatigue resistance. . The results of these evaluations and surveys are shown in Table 1 together with the code structure.

[0024]

[Table 1]

[0025]

According to the present invention, the rubber penetration into the cord can be significantly 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 rubber articles and a method for 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 steel cord manufacturing facility.

FIG. 6 is a schematic diagram showing another molding device.

FIG. 7 is a schematic diagram showing another molding device.

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

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 core 2a strand 2b strand 3 strand 4 inner sheath 5 strand 6 outer sheath 7 unwinding reel 8 corrugating device 8a wheel 8b wheel 9 storage unit 10 twisting unit 11 twisting machine 12 storage unit 13 twist Molding device 14 Stranding machine

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) D07B 1/00-9/00

Claims (4)

(57) [Claims] 1. A core in which two to four strands are twisted,
A steel cord obtained by twisting an inner sheath consisting of 6 to 9 strands arranged around the core, wherein at least one strand constituting the core has a strand diameter of at least one strand. Waveform L and wave height H relating to d and the core twist pitch p ₁ are shaped to satisfy the following ranges: L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.05d ≦ H ≦ 2.0d, and the core twist pitch
p ₁ and the ratio p ₂ / p ₁ between the pitch p ₂ twist of the inner sheath 1.2
A steel cord for reinforcing rubber articles, characterized in that it is 2.5. 2. A core in which two to four strands are twisted,
A steel cord obtained by twisting an inner sheath consisting of 6 to 9 strands arranged around the core and an outer sheath consisting of 11 to 15 strands arranged around the inner sheath. , constituting the core, either in at least one strand, the wavelength L and the wave height H related to the wire diameter d and twist pitch p ₁ is, L ≦ p ₁ and 5d ≦ L ≦ 30d and 1.05D ≦ H ≤2.0d, and the core twist pitch
p ₁ and the ratio p ₂ / p ₁ between the pitch p ₂ twist of the inner sheath 1.2
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. A steel cord according to claim 1, wherein the wire is corrugated between a twisting machine and a device for supplying a wire to be provided to a core. A method for producing a steel cord for reinforcing rubber articles, comprising twisting wires. 4. The method of manufacturing a steel cord according to claim 2, wherein the strand is corrugated between a twisting machine and a feeder of a strand to be provided to a core, and then the inner sheath element is formed. A method for producing a steel cord for reinforcing rubber articles, comprising twisting wires and subsequently twisting wires of an outer sheath.