JPH1181168A - Steel code for rubber article and pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To economically produce steel codes having superior corrosion resistance to that of the conventional steel codes and lighten the weight of tires by using the steel codes as a reinforcing material for pneumatic tires. SOLUTION: In the steel codes 1 having a 2+6 structure, the core 4 comprises two straight steel filaments 2, and six steel filaments 3 are spirally wound around the core as the sheath 5. The diameter of the core steel filament (dc) ranges from 0.25-0.40 mm, the diameters of the core filament 2 and the sheath filament 3 (dc)and(ds)} satisfy the following relation 0.05<=0.75 dc-0.50ds <=0.10 and the flatness of the cross section of the code 1 exceeds 1.0.

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 rubber articles and a pneumatic radial tire using the steel cord as a reinforcing material.

[0002]

2. Description of the Related Art As a conventional steel cord structure used for a belt layer of a pneumatic radial tire, three small diameter filaments are twisted to form a core, and six large diameter filaments are formed around the core. The closest-twisted structure wound in the opposite direction to the mainstream was the mainstream.

However, since the rubber does not penetrate into the cord in the most-twisted structure, Japanese Unexamined Patent Publication No. Hei 6-33383 discloses a (1 × 2) + n structure where n is a plurality of strands and the core is located between the strands. It has been proposed to attempt to improve the durability by a steel cord having a gap, a flat section in a flatness ratio of 1.3 to 2.0 in one direction, and a long twisted pitch in the same direction as the core. However, since the core is twisted so that there is a gap, the cord is easily stretched by a small force, causing problems in the accuracy of tire molding, and when the cord cross section is extremely flat, the wire surface will There is a drawback that scratches occur and fatigue resistance is reduced.

In Japanese Patent Application Laid-Open No. 7-1911, in a radial tire using the same twisted 2 + 6 structure code as a breaker, the diameter of the sheet filament is increased by 130 to 200% with respect to the core filament. The twisting pitch of the core is 65% or less of the twisting pitch of the sheet, the molding rate of the sheet filament is 90 to 110%, and the diameter of the sheet filament is 0.30 to 0.40 mm. Proposals have been made to improve the durability of tires by code. However, when the diameter of the sheet filament is large, the sheet filaments come into contact with each other, making it difficult for the rubber to penetrate into the core, resulting in a reduction in corrosion resistance. Further, the number of steps for twisting the core increases. I will. However, there is a method in which the core and the sheath are twisted at a time by using a double twisting wire machine.
And two locations are required, resulting in a problem that equipment costs and installation locations are increased.

Further, in Japanese Patent Application Laid-Open No. 9-158066, in a steel cord having a 2 + 6 structure, the twist pitch of the core is 30 mm or more, and the diameter d of the core filament is d.
c and the sheath filament diameter ds are 0.58 <ds /
It has been proposed that by setting dc <1.615, the rubber penetration into the cord can be improved. However, in the code according to this proposal, if the gap between the sheath filaments is narrow, the penetration of rubber into the cord is reduced, and the corrosion resistance is deteriorated. If the gap between the sheaths is too wide, However, the arrangement of the sheet filaments is disturbed, so that the intrusion of the rubber becomes non-uniform, and it is impossible to prevent the core from protruding from the code terminal.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a steel code having excellent corrosion fatigue resistance as compared with the conventional steel code as described above can be economically manufactured, and this steel pneumatic tire can be manufactured. It is an object of the present invention to reduce the weight of a tire by using the reinforcing material.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the first aspect of the present invention is a steel cord for reinforcing rubber articles, which is a core. In a steel cord having a 2 + 6 structure composed of a single-layer sheet in which two steel filaments and a core thereof are twisted with six steel filaments around the core, two cores are not twisted. The core steel filament has a diameter dc in the range of 0.25 mm to 0.40 mm. The straight steel filament is formed by winding six steel filaments around the core to form a sheet. ,
The diameters dc and ds of the core filament and the steel filament are respectively 0.05 ≦ 0.75 dc−0.5.
ds.ltoreq.0.10 and the flatness of the cross section of the cord exceeds 1.0. Preferably, the diameter dc of the core steel filament and the sheath
The relationship with the diameter ds of the sfilament is 0.05 ≦ 0.7
5dc−0.5ds ≦ 0.07 is satisfied.

On the other hand, a second aspect of the present invention is a pneumatic radial tire, in which a carcass extends in a toroidal shape between a pair of beads, and an air in which the crown of the carcass is reinforced by a belt layer. In the radial tire, the steel cord for forming the carcass and / or belt layer uses the steel article reinforcing steel cord of the first aspect of the present invention, and the long axis of the cord section is reinforced. It is a carcass and / or belt layer embedded in a certain direction in the width direction of the layer.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a first embodiment of a steel cord 1 according to the present invention. In the figure, reference numeral 2 denotes two parallel core filaments, 3 denotes a sheath filament, 4 denotes a core, and 5 denotes a sheath portion. s indicates a gap between the sheet filaments 3 and 3 and is a portion where rubber enters. Further, a / b in the figure represents the flatness of the code section.

In the first aspect of the present invention, the core is composed of two steel filaments which are not twisted but are aligned in parallel on the same plane. It is to give.

The reason why the cord is made to have anisotropy in bending rigidity is that the cord of the pneumatic radial tire of the second invention has
When used as a bead, a carcass ply rubber-coated on both sides with low bending stiffness improves bendability of the bead portion, and further reduces the bending stiffness of the side wall portion, thereby improving ride comfort. is there. Also, when used as a belt code, arranging the side having a low bending rigidity in the thickness direction of the belt layer improves the riding comfort, increases the rigidity in the belt width direction, and improves the maneuverability of the tire. It is because it is improved.

FIG. 2 is a sectional view of a pneumatic radial tire, in which 6 is a carcass, 7 is a bead portion, 8 is a belt layer, and 9 is a belt layer.
Is a tread part. First steel code 1 of the present invention
Is used for the carcass 6 or the belt layer 8.

Further, by making the cord section flat, rubber can easily penetrate into the core, and the core can be prevented from protruding from the cord end due to repeated bending deformation.
Further, since the cores are not twisted, the step of twisting the cores can be omitted, thereby improving the twisting productivity and eliminating the need for a facility for twisting the cores.

The reason why the core is made of two steel filaments is that it is difficult to obtain anisotropy in bending stiffness with one steel filament, and triangular, square or triangular with three or more steel filaments. When a core having a polygonal cross section is formed, moisture is propagated by a cavity formed at the center of the core, and the corrosion resistance is reduced. If a core having three or more steel filaments arranged on one plane is compressed, the core is compressed. This is because the characteristics deteriorate.

Furthermore, the structure in which the sheet is wound around the core with six steel filaments is to provide a gap between adjacent filaments in the sheet. Penetrates and adheres to the core filament, thereby preventing the core filament from jumping out of the code terminal due to the repeated deformation of the code during running of the tire, thereby reducing tire damage.

The relationship between the core filament diameter dc and the sheath filament diameter ds is 0.05 ≦ 0.7.
By satisfying the relationship of 5dc-0.5ds ≦ 0.10, a gap between adjacent steel filaments in the sheet is secured, and rubber invades around the outer periphery of the core and the code. The corrosion resistance of the core can be improved, the protrusion of the core from the code terminal can be reduced, and the fretting between the core and the sheath can be reduced. In order to make the penetration of rubber uniform by making the gap between the sheet filaments uniform and to improve the fatigue resistance,
Preferably, 0.05 ≦ 0.75dc−0.5ds ≦
By setting the value to 0.07, the feature of the steel code of the present invention becomes remarkable.

The diameter of the filament is preferably at least 0.25 mm in order to increase the cord strength, and less than 0.40 mm in order not to significantly deteriorate the bending fatigue resistance of the cord.

From the viewpoint of reducing the weight of the tire, it is desirable that the tensile strength of the steel filament is 3000 N / mm ² or more. In order to increase the tensile strength of the steel filament to 3000 N / mm ² or more, a steel cord wire having a carbon content of 0.80% by weight or more should have a total area reduction rate of 95.5% or more from the final patenting. Obtained by drawing. In order to maintain the ductility of the steel filament, the wire temperature at the time of final wet drawing is set to 150 ° C. or less. To reduce the temperature to 150 ° C. or lower, means such as slowing down the drawing speed, controlling the temperature of the aqueous lubricant at a low temperature, selecting the shape of the drawing die, and optimizing the drawing pass schedule alone or in combination. Can be achieved by:

Before the sheath filament is wound around the core, a twist spiral is formed. The radius R of the spiral is R = (3dc / D) of the diameter dc of the core filament and the diameter ds of the sheath filament. 2) Set to + 2ds. The pitch of the helix is the same as the twist pitch. FIG. 3 is a diagram for explaining the twisting rate of the sheet filament constituting the steel code of the present invention.

By performing the spiral molding in this way,
The sheath filament is wound around the core while maintaining a substantially equally spaced gap. After winding the sheet,
The steel cord is passed through a straightening jig in order to improve the twist properties of the steel cord. The interval between the rolls on the code entrance side of this correction jig is Pb, and the interval between the rolls on the exit side is Pc.
By setting the roll spacing so as to satisfy the relationship of 1.2P ≦ Pb ≦ 2.2P and 2.4P ≦ Pc ≦ 4.0P with respect to the twist pitch P of the core, a sheet is formed around the core. The filaments will be arranged regularly. FIG. 4 is a view for explaining the roll interval of the correction jig. In the figure, reference numeral 10 denotes a correction jig, 11 denotes a roll on the code entrance side, and 12 denotes a roll on the exit side.

That is, by setting the roll interval Pb at the cord entrance side of the correction jig to 1.2P ≦ Pb ≦ 2.2P,
In order to perform the straightening process by restraining the movement of the sheath filament in the axial direction, a change in the twist pitch of the sheath filament is suppressed, and the exit side roll interval Pc is set to 2.4P ≦ Pc ≦
By setting it to 4.0P, in order to perform straightening without restraining the axial movement of the sheet filament,
The spacing between the sheet filaments can be made uniform.

At this time, a code having a flat cross section can be obtained by passing the long axis of the core parallel to the roll rotation axis. If the degree of flattening is too flat, the arrangement of the sheet filaments will be disturbed, making it difficult for the rubber to uniformly infiltrate around the core. Decreases the rubber penetration.

In a tire reinforcing sheet in which a large number of cords are arranged in parallel at equal intervals and covered with rubber, when the cords are arranged so that the long axis of the core is positioned in the direction in which the cords are adjacent to each other, the reinforcing sheet is provided. -The thickness of the tire is reduced, and the weight of the tire can be reduced.
The spiral pitch is 95% of the cord twist pitch.
From about 99%, the contact pressure between the core and the sheath is increased, and the occurrence of cord torsion and curl can be prevented.

[0024]

【Example】

(A) Production of steel code of the first invention 0.8% carbon, 0.50 manganese, 0.20 silicon, 0.009 sulfur, 0.009 phosphorus, and the balance iron After a steel wire having a diameter of 5.5 mm consisting of unavoidable impurities is reduced to a desired diameter by dry drawing, a patenting process and a plating process for securing adhesion to rubber are performed. After application, the filament was finished by wet drawing. In a patenting process using a fluidized bed prior to wet drawing, the material is rapidly heated to a solution temperature to form a solution, and then to a pearlite transformation temperature so that high surface area reduction processing can be performed with high productivity in wet drawing. After rapid cooling in a very short time as described below, the transformation was completed at the pearlite transformation temperature to reduce the pearlite block size on the surface of the wire.

Further, the steel filament after the wet drawing can be repeatedly bent while applying tension to apply a residual stress on the compression side to the surface of the steel filament to improve the fatigue resistance. . In particular, by performing the above-described treatment on a core filament having insufficient rubber permeability, the corrosion resistance is improved.

The stranded wire may be either a tuber stranded wire machine or a buncher stranded wire machine. The core filament is supplied from one end of the twisting machine, the sheath filament is supplied from the inside of the twisting machine, and the pins are twist-molded by another molding jig, and the molding pitch is 95 to less than 100%. Within this range, the contact pressure with the core is increased, the movement of the sheet filaments in the longitudinal direction is suppressed, and the gap between adjacent sheet filaments becomes uniform. If the contact pressure between the core and the sheath is too high, fretting will occur and the fatigue resistance will be reduced, and the gap between the core and the sheath will be small, making it difficult for rubber to penetrate. If the distance is too large, the gap between adjacent sheet filaments becomes uneven because the sheet filament moves in the longitudinal direction. The core is wound with a collective die to form a cord. The twisting property of the cord is adjusted by a straightening jig, and the core is wound around a reel.

(B) Pneumatic radial tire of the second invention The code manufactured in the above embodiment was replaced with a tire having a tire size of 10.0.
The evaluation was performed using a belt layer of a pneumatic radial tire of 0R20.

(C) Various tests a: Penetration of rubber
The cord was taken out and the amount of rubber adhered to the core was measured by untwisting the sheet filament. FIG. 5 is a diagram for explaining the rubber penetration property surrounding the core. The measurement was performed by observing the amount of rubber at both ends a and b of the long axis of the core.

B: Rotational bending fatigue resistance A fatigue life curve for bending strain is determined with the number of rotations until the cord breaks at a certain bending strain as fatigue life, and the strain at the inflection point of the fatigue life curve is limited to the fatigue limit. And The results are shown as an index with the fatigue limit of the cord of the conventional example being 100. The larger the index, the greater the fatigue limit and the better the bending fatigue life.

C: Corrosion propagation length After immersing one end of the steel cord taken out of the belt layer into salt water for a certain length of time for a certain length of time, untwist the cord until the rubber does not peel off. Was measured for length. The shorter the length, the better the corrosion resistance.

D: Presence or absence of separation The test tire was mounted on a 10-ton truck, and the tire which had been completely worn by running on a rough road was dissected, and the code and rubber due to moisture propagation inside the steel code were dissected. The presence / absence of a large separation caused by the deterioration of the adhesion was examined. The results are summarized in Table 1.

[0032]

[Table 1]

[0033]

The steel cord having excellent corrosion fatigue resistance can be economically manufactured, and when used as a reinforcing material for a pneumatic tire, the weight of the tire can be reduced and the durability of the tire can be improved. .

[Brief description of the drawings]

FIG. 1 is a steel cord sectional view of the present invention.

FIG. 2 is a sectional view of a pneumatic radial tire.

FIG. 3 is a sheet constituting a steel code according to the present invention.
It is a figure explaining the twist type attachment rate of a sfilament.

FIG. 4 is a view for explaining a roll interval of the correction jig.

FIG. 5 is a diagram for explaining rubber penetration around a core. Measurements were made at both ends of a long axis of the core and at both ends of a short axis of the core.
The amount of rubber on the side was observed.

[Explanation of symbols]

 1 ‥‥ steel cord, 2 ‥‥ core filament, 3 ‥‥ sheath filament, 4 ‥‥ core, 5 ‥‥ sheath, 6 ‥‥ carcass, 7 ‥‥ bead part, 8 ‥‥ belt layer, 9 ‥‥ tread, 10 ‥‥ straightening jig, 11 ‥‥ cord entrance side roll, 12 ‥‥ cord exit side roll, dc ‥‥ core filament diameter Ds: diameter of the sheath filament, s: gap between the sheath filaments, Pb: the distance between the rolls on the code entry side of the correction jig, Pc: the code of the correction jig Roll spacing on exit, R ‥‥ radius of helix.

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[Procedure amendment]

[Submission date] December 25, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Added

[Correction contents]

FIG. 5

Claims (3)

[Claims] 1. A steel cord having a 2 + 6 structure comprising a single-layered sheet in which two steel filaments serving as a core and six core filaments are twisted around the core, The core is composed of two straight steel filaments that are not twisted, and six steel filaments are wound around the core to form a sheet. The diameter dc of the core steel filament is 0.25 mm. ~
The diameters dc and ds of the core filament and the sheath steel filament are in the range of 0.40 mm.
A steel cord for reinforcing rubber articles, characterized by satisfying the relationship of 0.05 ≦ 0.75dc−0.5ds ≦ 0.10, and having a flatness of the cross section of the cord exceeding 1.0. 2. The relationship between the diameter dc of the core steel filament and the diameter ds of the sheath filament is 0.05 ≦.
2. The steel cord for reinforcing a pneumatic rubber article according to claim 1, wherein a relation of 0.75 dc-0.5 ds.ltoreq.0.07 is satisfied. 3. A pneumatic radial tire in which a carcass extending in a toroidal shape between a pair of beads and a crown portion of the carcass is reinforced with a belt layer, wherein the carcass and / or the belt are provided. The steel cord constituting the layer is the steel cord for reinforcing the tire according to claim 1, and the major axis of the cord section is embedded in a fixed direction in the width direction of the reinforcing layer. A pneumatic radial tire comprising a carcass and / or belt layer.