JPH08109585A - Steel cord for reinforcing rubber product and pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE: To obtain a tire improved in durability especially on the run of the tire on a wasteland by applying cords enhanced in durability against breakage caused by large curve deformation without enlarging the diameters of the cords. CONSTITUTION: A core strand 3 is twisted with six sheath strands 4 to obtain a steel cord for reinforcing a rubber product. The core strand 3 is produced by twisting a core 1 comprising 1-3 steel filaments with at least one layer sheath 2 comprising many steel filaments 3 disposed around the core 1. Each of the six sheath strands 4 is produced by twisting a core 1a comprising one to three steel filaments with at least one layer sheath 2a comprising many steel filaments disposed around the core 1a. In the cord, the sheath filaments forming the outermost layer of the core strand 3 and the sheath filaments forming the outermost layer of the sheath strand 4 are twisted in the reverse directions, respectively. The cords are applied to the belt of a tire.

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, and a pneumatic tire having a carcass reinforced with a belt made of the steel cord. It is intended to improve the durability against breakage of the cord.

Tires well known as rubber products reinforced with steel cords, especially heavy-duty tires for supporting heavy loads such as those for trucks / buses and construction vehicles, have many opportunities to run on rough terrain and wastelands. , When the tire rides on a large protrusion or rock during this running, the portion that hits the protrusion or rock locally deforms significantly, so the belt cord should have compressive force on the tire radial outside and inside. In many cases, the tensile force acts on each of the cords, and as a result, the cord is broken due to a crack from the tensile side, and as a result, the belt is cut and the tire is broken.

[0003]

2. Description of the Related Art Conventionally, as a method of avoiding the breakage of a belt, the belt diameter is increased by enlarging the cord diameter in order to increase the belt rigidity to reduce local deformation and to withstand a large tension generated at the time of deformation. It is customary to increase the total strength of the.

[0004]

However, when the cord diameter is increased, the area of the cord end face where strain is concentrated during load rolling of the tire, that is, the non-adhesive face with rubber, is increased. The separation easily occurs, and as the cord diameter increases, the belt, and thus the tread, becomes thicker, and the tire heat is increased during running, so deterioration of the belt durability cannot be avoided. In addition, the increase in belt weight naturally goes against the reduction of tire manufacturing costs and the reduction of fuel consumption of automobiles.

Therefore, an object of the present invention is to provide a cord having increased durability against breakage caused by a large bending deformation without increasing the cord diameter, and by applying this cord, particularly in wasteland traveling. It is to provide a tire having improved durability.

[0006]

According to the present invention, a core composed of one to three steel filaments and a sheath of at least one layer composed of a large number of steel filaments arranged around the core are twisted together. Around the core strand, a core made of 1 to 3 steel filaments and at least one layer of a sheath made of a large number of steel filaments arranged around the core are twisted together, and 6 sheath strands are arranged. A cord for reinforcing rubber articles, wherein the cords are twisted together and the sheath filaments forming the outermost layers of the core strand and the sheath strand are twisted in opposite directions.

Further, the present invention is a pneumatic radial tire in which a carcass extending in a toroidal shape between a pair of bead portions is used as a skeleton, and the crown portion of the carcass is further reinforced by a belt having at least two layers. A pneumatic tire comprising a plurality of cords extending in a direction inclined with respect to the equatorial plane of the tire and arranged in parallel with each other, and applying the above cords to the cords.

Now, FIG. 1 shows a cross section of a steel cord applied to a belt of a tire or the like according to the present invention for a twist structure 1 × (1 + 6) + 6 × (1 + 6) +1. The cord is composed of a core 1 made of one steel filament and a sheath 2 made of six steel filaments twisted around the core strand 3, and a core strand 3 having the same structure as that of the core strand 3, that is, 1 Six sheath strands 4 in which six sheaths 2a made of steel filaments are twisted around a core 1a are twisted together. Where the core strand 3
It is important to reverse the twisting directions of the sheath 2 and the sheath 2a of the sheath strand 4. Furthermore, in the illustrated example,
Although the wrap filament 5 is spirally wound around the six sheath strands 4 to strengthen the bundling of the cords, the wrap filament 5 may be omitted.

The cord shown in FIG. 2 has a twisted structure of 1 ×.
(3 + 9) + 6 × (3 + 9) +1, that is, the core strand 3 or the sheath strand 4 is 9 around the core 1 or 1a made of three steel filaments.
It has a structure in which the sheath 2 or 2a made of a steel filament is twisted together. In this case as well, the twisting directions of the sheath 2 of the core strand 3 and the sheath 2a of the sheath strand 4 are reversed. Note that the wrap filament 5 is spirally wound around the sheath strand 4 to strengthen the bundling of cords, as in the cord of FIG. 1.

Further, the cord shown in FIG. 3 has a twisted structure 1
× (3 + 9 + 15) + 6 × (3 + 9 + 15) +1, that is, the core strand 3 or sheath strand 4 twists the sheath 2 or 2a made of 9 steel filaments around the core 1 or 1a made of 3 steel filaments. The second sheath 6 or 6a made of 15 steel filaments is twisted around the sheath 2, and in this case, the second sheath 6 of the core strand 3 and the second sheath 6 of the sheath strand 4 are twisted together.
It is necessary to reverse the twisting direction with the sheath 6a. Note that the wrap filament 5 is spirally wound around the sheath strand 4 to strengthen the bundling of cords, as in the cord of FIG. 1.

The cords shown in FIGS. 1 to 3 are used to reinforce a carcass by applying a ply obtained by aligning a plurality of the cords in parallel with each other and burying them in a rubber sheet to a belt of a tire. The tire structure may be in accordance with a conventional pneumatic tire for trucks, buses, or construction vehicles. For example, the belt arrangement shown in FIG. 4 is advantageously suitable. In this figure, reference numeral 7 is a bead core, 8 is a carcass wound around the bead core 7 from the inside to the outside of the tire, and 9 is arranged on the carcass 6.
The layered belt and 10 are treads placed on this belt.

[0012]

For example, the durability of the cord constituting the tire belt against breakage can be evaluated by a plunger test. That is, as shown in FIG.
By pressing the tread of the tread against the plunger, the tire belt is locally bent and deformed as shown in FIG. 6, and as a result, the cord on the tension side is cracked and the cord is broken. To do.

Then, in a plunger test for a cord made by twisting a plurality of strands having a ply twist structure, which is particularly used for heavy-duty tires, the fracture form of the cord was investigated in a plunger test. In most of the cases, cracks and fractures occurred in the contact area between the sheath filaments of the core strands arranged in the center of the cord and the sheath filaments of the sheath strands arranged around the core strand, and in particular, FIG.
It was found that the intersection P of both sheath filaments was the starting point of fracture, as shown in FIG.

This is because, when subjected to a large deformation by the plunger, a large tension F due to bending acts on the cord as shown in FIG. 6, and as a result, stress is applied to the intersection P where both filaments make point contact. This is to concentrate.

Therefore, it is important to reduce stress concentration by not contacting both filaments at a point, that is, by making both filaments in a line contact relationship.
Specifically, by making the twist directions of the sheath filaments forming the outermost layer of the core strand and the sheath strand mutually opposite, wire contact between the two sheath filaments is realized, and the breaking resistance of the cord is significantly improved. Of.

As described above, heavy-duty tires have many opportunities to ride on large protrusions, rocks, and the like while running on rough terrain and in rough terrain, and the cuts received on the tread tread at this time. A fatal failure called so-called cut-through failure may occur in which the belt is cut without being limited to the section. Therefore, it is preferable that the heavy duty tire also has excellent cut penetration resistance. Since it has been confirmed that the cut penetration resistance and the result of the plunger test correspond very well, the adoption of the cord according to the present invention improves the result of the plunger test, so that the cut penetration resistance is improved. Is also achieved.

[0017]

【Example】

Example 1 A cord having the structure shown in FIG. 1 was manufactured under the specifications shown in Table 1, and the cord was used in 6 tire belts shown in FIG.
Driving number: 14.0 on 1 to 4 layer belt near the carcass side
It was applied at / 5 cm and prototyped a radial tire for construction vehicles of size 36.00R51. In addition, 0.32 mmφ was used for the steel filament forming each strand of the cord. The tire energy thus obtained was measured or evaluated for plunger energy, exothermic temperature, belt weight and durability. The results are shown in Table 2.

Plunger energy is measured from the time when each tire is filled with an internal pressure of 700 kPa until the belt is broken by pressing each tire against a plunger having a head of 90 mmφ as shown in FIG. The energy is represented by the hatched area in FIG. 8, and is an index when the calculated area of each tire is 100 for the conventional tire.
The results are shown in Table 2. As for the heat generation temperature, the tire was placed on the drum under the condition that the tire was filled with the internal pressure of 700 kPa and the specified load was applied.
After running for 24 hours under the condition of h, the surface temperature of the tread was measured. Then, the belt weight was compared by the total amount of each material of the belt. Furthermore, the durability is 24 at a speed of 8 km / h when a tire filled with a specified internal pressure is placed on a drum under the conditions of specified load and slip angle of 1 °.
Run for an hour, then increase the load by 10% of the specified load, then run at the same speed for 24 hours, then increase the load by 10% of the specified load, and then run at the same speed until a tire failure occurs. Evaluation was made based on the running distance. This evaluation is also based on the index when the conventional tire is 100, and is shown in Table 2.
It was shown to.

[0019]

[Table 1]

[0020]

[Table 2]

Example 2 A cord having the structure shown in FIG. 2 was manufactured under the specifications shown in Table 3, and the cord was applied to the belt of the tire shown in FIG. 4 with a driving number of 14.0 lines / 5 cm. A prototype radial tire for construction vehicles of size 36.00R51 was produced. In addition, 0.23 mmφ was used for the steel filament forming each strand of the cord. For the tire thus obtained, the plunger energy, heat generation temperature, belt weight and durability
It was measured or evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0022]

[Table 3]

[0023]

[Table 4]

Example 3 A cord having the structure shown in FIG. 3 was manufactured under the specifications shown in Table 5, and the cord was applied to the belt of the tire shown in FIG. A prototype radial tire for construction vehicles of size 36.00R51 was produced. In addition, 0.175 mmφ was used for the steel filament forming each strand of the cord. For the tire thus obtained, the plunger energy, heat generation temperature, belt weight and durability
It was measured or evaluated in the same manner as in Example 1. The results are shown in Table 6.

[0025]

[Table 5]

[0026]

[Table 6]

[0027]

According to the present invention, the breaking resistance of the cord can be improved without enlarging the cord diameter. Therefore, by applying the cord to the belt of the tire, the durability thereof is improved especially in the wasteland. It is possible to provide a tire suitable for a heavy-duty tire having improved tire.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing a cord of the present invention.

FIG. 3 is a sectional view showing a cord of the present invention.

FIG. 4 is a cross-sectional view showing a tire structure suitable for the present invention.

FIG. 5 is a schematic diagram showing a procedure of a plunger test.

FIG. 6 is a schematic view showing a state of a belt during a plunger test.

FIG. 7 is a schematic diagram showing a filament contact state between strands forming a cord.

FIG. 8 is a diagram illustrating a procedure for measuring plunger energy.

[Explanation of symbols]

 1,1a core 2,2a sheath 3 core strand 4 sheath strand 5 wrap filament 6,6a sheath 7 bead core 8 carcass 9 belt 10 tread

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[Procedure amendment]

[Submission date] November 7, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Plunger energy is measured from the time when each tire is filled with an internal pressure of 700 kPa until the belt is broken by pressing each tire against a plunger having a head of 90 mmφ as shown in FIG. The energy is represented by the hatched area in FIG. 8, and is an index when the calculated area of each tire is 100 for the conventional tire.
The results are shown in Table 2. As for the heat generation temperature, the tire was placed on the drum under the condition that the tire was filled with the internal pressure of 700 kPa and the specified load was applied.
After running for 24 hours under the condition of h, the internal temperature of the tread was measured. Then, the belt weight was compared by the total amount of each material of the belt. Furthermore, the durability is 24 at a speed of 8 km / h when a tire filled with a specified internal pressure is placed on a drum under the conditions of specified load and slip angle of 1 °.
Run for an hour, then increase the load by 10% of the specified load, then run at the same speed for 24 hours, then increase the load by 10% of the specified load, and then run at the same speed until a tire failure occurs. Evaluation was made based on the running distance. This evaluation is also based on the index when the conventional tire is 100, and is shown in Table 2.
It was shown to.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022]

[Table 3]

Claims (2)

[Claims] 1. A core strand composed of 1 to 3 steel filaments and a sheath of at least one layer composed of a large number of steel filaments arranged around the core, which are twisted together to form 1 to 3 around a core strand. A cord formed by twisting a core made of two steel filaments and at least one layer of a sheath made of a large number of steel filaments arranged around the core, wherein six sheath strands are arranged and twisted together. A cord for reinforcing a rubber article, characterized in that the sheath filaments forming the outermost layers of the core strand and the sheath strand are twisted in opposite directions. 2. A pneumatic radial tire in which a carcass extending in a toroidal shape between a pair of bead portions has a skeleton, and the crown portion of the carcass is reinforced by at least two layers of belts, the belts being on the tire equatorial plane. A pneumatic tire comprising a plurality of cords extending in an inclined direction with respect to each other and arranged in parallel with each other, wherein the cord according to claim 1 is applied to the cords.