JP3506279B2 - Steel cord and pneumatic tire for reinforcing rubber articles - 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 for reinforcing a rubber article, and more particularly, to improving the strength of a steel cord for reinforcing a rubber article having a double twist structure in which strands obtained by twisting a plurality of steel filaments are further twisted. Further, the present invention relates to a pneumatic tire that achieves weight reduction, fuel consumption reduction, and transportation cost reduction by using the steel cord as a reinforcing material.

[0002]

2. Description of the Related Art Steel cords used for reinforcing tires for construction vehicles and reinforcing conveyor belts are required to have high strength, and a steel having a double twist structure in which a plurality of steel filaments are twisted and strands are further twisted. The code is widely used.

[0003]

However, in a steel cord having a multi-twisted structure, which has been heretofore known as a reinforcing material for tires, when a tensile input is applied to the cord, the contact portion between the outermost filaments of the strands is increased. However, there was a problem that the cord strength was significantly reduced as compared with the total strength of the strand due to the preceding breakage.

Therefore, an object of the present invention is to solve the above-mentioned problems and to improve the strength of the steel cord having a double twist structure, and by using the steel cord as a reinforcing material, the weight is reduced, the fuel consumption is reduced, and the transportation cost is suppressed. To provide a pneumatic tire having the above-mentioned structure.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that in the steel cord having a multi-twisted structure which has been used as a reinforcing material for tires, a core strand is used. Since the area of the contact portion between the outer layer filament that constitutes the outer layer filament and the outer layer filament that constitutes the sheath strand is small, so-called point contact, when a tensile input is applied to the cord, this contact portion breaks first and the cord strength is increased. It turns out that it doesn't come out enough.

On the other hand, even if the outermost layer filaments forming the strand and the sheath strand have the same twist direction in order to increase the contact area of the contact portion, it is disclosed in, for example, Japanese Patent Application No. 3-51359. When such a strand has a compact structure, the circularity (circularity) of the strand is poor, so that it becomes easy for only some of the outermost filaments of the core strand and the sheath strand to come into contact with each other. Therefore, it turns out that the code is not strong enough.

As a result of further studies based on the above findings, the present inventor selects a strand having a specific structure with good roundness, and twists seven strands in the same direction as the outermost layer filament, The present invention has been completed by finding that the outer layer filaments of the core strand and the outer layer filaments of the sheath strand are in contact with each other on many surfaces and the tensile strength is sufficiently increased.

That is, the steel cord for reinforcing a rubber article of the present invention is a steel cord for reinforcing a rubber article having a double-twisted structure in which seven strands having a 3 + 9 or 3 + 9 + 15 layer twist structure made of filaments having the same diameter are twisted together. And the twisting direction of the outermost layer of the sheath filament and the twisting direction of the sheath strand are the same.

Examples of preferred embodiments of the steel cord for reinforcing rubber articles of the present invention are listed below. (1) Of the above strands, the structure of six sheath strands is the same.

(2) The diameter of the filament is 0.15
It is 0.40 mm.

The present invention also relates to a pneumatic tire using the steel cord for reinforcing a rubber article as a reinforcing material.

[0012]

In the steel cord for reinforcing a rubber article of the present invention, a strand having a good roundness and having a layer twist structure of two or more layers is used, and the strand has seven strands in the same direction as the outermost layer filament. By twisting,
The area of the contact portion between the outer layer filament of the core strand and the outer layer filament of the sheath strand is significantly increased. As a result, the preceding breakage of the contact portion between the outermost filaments of the strand is suppressed, and the cord strength is significantly improved as compared with the conventional steel cord for reinforcing rubber articles.

As a layer twist structure of two or more layers of strands having good roundness, 3 + 9, 3 + 9 + 15 and the like can be mentioned.

In the present invention, it is not necessary that the structures of all the strands are the same, but from the viewpoints of the uniformity of the cord, the contact area between the filaments, the manufacturing cost, etc., the structure of the six sheath strands among the above strands is used. Are preferably the same.

The length of the contact portion between the outer layer filaments of the strand is affected by the rigidity of the filament, but within the filament diameter range of 0.15 to 0.40 mm, the length is almost the same regardless of the filament diameter. Indicates twist loss (cord strength / strand strength before twisting).

Since the steel cord for reinforcing rubber articles of the present invention has improved cord strength as compared with the conventional steel cord having the double twist structure as described above, for example, instead of the steel cord having the conventional double twist structure. A conventional pneumatic radial tire for trucks / buses or construction vehicles, in which this cord is used, and a ply obtained by aligning a plurality of the cords in parallel with each other and embedding in a rubber sheet is applied to a belt layer, It is possible to reduce weight, reduce fuel consumption, and control transportation costs.

[0017]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. Various steel cords according to the cord structure, the twist pitch, and the twist direction shown in Table 1 below were prototyped. In addition, among the steel cords shown in Table 1, 7 × (3 + 9) +1 structure steel cords obtained by twisting 7 strands consisting of 3 core filaments and 9 sheath filaments and further winding 1 spiral filament are shown in FIG. 2 strands of 3 core filaments, 9 inner layer sheath filaments, and 15 outer layer sheath filaments are twisted together and 1 spiral filament is wound around, and 7 × (3 + 9 + 15) +1 is shown in FIG.
In addition, 7 × (1 × 12) +1 in which 7 strands of a compact structure composed of 12 filaments are twisted together and 1 spiral filament is further wound is shown in FIG.
, Respectively. In the figure, reference numeral 1 indicates a core strand, and 2
Indicates a sheath strand, 3 indicates an outermost layer filament of the core strand, 4 indicates an outermost layer filament of the sheath strand, and 5 indicates a spiral filament.

Regarding these prototype steel cords, JI
The strength was measured based on the measuring method for "cutting load" in Section 6.4 defined in "Steel Tire Cord Test Method" of SG3510. The obtained results are also shown in Table 1.

[0019]

[Table 1]

When the steel cord of the present invention (Example 1) was applied to the ply cord of a radial tire for construction vehicles of size 36.00R51 and the strength after running for 4000 hours was examined, as shown in Table 2 below. It was found that the retention of strength was higher than that of Comparative Example 1.

[0021]

[Table 2]

[0022]

As described above, in the steel cord for reinforcing a rubber article of the present invention, a strand having a specific structure having good roundness is selected, and the strand has seven strands in the same direction as the outermost layer filament. By twisting, the area of the contact portion between the outer layer filaments of the strand is significantly increased, which suppresses the preceding breakage of the contact portion, and the cord strength is significantly larger than the conventional steel cord for reinforcing rubber articles. Improve to. Therefore, by using the steel cord as a reinforcing material for a pneumatic tire, it is possible to reduce weight, reduce fuel consumption, and suppress transportation costs.

[Brief description of drawings]

FIG. 1 is a sectional view of a steel cord having a 7 × (3 + 9) +1 structure.

FIG. 2 is a sectional view of a steel cord having a 7 × (3 + 9 + 15) +1 structure.

FIG. 3 is a sectional view of a steel cord having a 7 × (1 × 12) +1 structure.

[Explanation of symbols]

1 core strand 2 sheath strand Outermost layer filament of 3 core strands 4 Outermost layer filament of sheath strand 5 spiral filament

Claims (3)

(57) [Claims] 1. A 3 + 9 or 3 + 9 filament consisting of filaments of the same diameter.
Is a steel cord for reinforcing rubber articles having a double twist structure in which seven strands having a 3 + 9 + 15 layer twist structure are twisted, and the twist direction of the sheath filament of the outermost layer constituting the strand and the twist direction of the sheath strand are Steel cords for reinforcing rubber articles, characterized in that they are the same. 2. The filament has a diameter of 0.15 to 0.4.
The steel cord for reinforcing rubber articles according to claim 1, which has a length of 0 mm. 3. A pneumatic tire using the steel cord for reinforcing a rubber article according to claim 1 or 2 as a reinforcing material.