JP3497935B2 - Steel cord for reinforcing rubber articles and pneumatic radial tire - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber article reinforcing steel cord used as a reinforcing material for rubber articles such as pneumatic radial tires and conveyor belts, and a pneumatic radial tire using the cord as a reinforcing material.

[0002]

2. Description of the Related Art Steel cords have been used as a reinforcing material for rubber articles such as pneumatic tires. For example, as a steel cord used for tires for heavy-duty vehicles, strands of the same diameter are layer-by-layer. 3 twisted with different twist pitch
Those having a + 9 + 15 structure are widely used. However, in the case of such a structure, since there is no gap where the rubber penetrates inside the cord, when the cord comes into contact with moisture, the rubber does not penetrate, and moisture enters the cavity inside the cord, causing corrosion of the cord. In addition, moisture propagates through the cavity and the corroded area expands.

On the other hand, in order to solve the corrosion problem, Japanese Utility Model Laid-Open Publication No. Sho 64-30398 discloses that
2 having a core formed by drawing 3 strands in parallel
A layer-twisted or three-layer twisted steel cord is disclosed.

[0004]

However, in the embodiment of Japanese Utility Model Laid-Open No. 64-30398, the core has three or more strands, and a space where no rubber penetrates is formed at the center of the core. There is. When such a steel cord is used for the belt layer of a tire, moisture penetrates into the cord from a portion cut by running on a bad road to corrode the cord, and further moisture propagates inside the cord to expand a corroded area. It is predicted that such a problem will occur.

Therefore, an object of the present invention is to solve the above problems and to improve the corrosion resistance and the productivity by reinforcing steel cords for reinforcing rubber articles, and by using the cords as a reinforcing material. It is to provide a pneumatic radial tire having improved durability.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a two-layer twisted steel cord, a sheath consisting of a core consisting of two strands of wire and seven strands of wire wound around the core. In a steel cord for reinforcing rubber articles consisting of
The average twist pitch of the core is 30 mm or more, and the ratio of the diameter ds of the strand of the sheath to the diameter dc of the strand of the core ((ds / dc) × 1)
00) is in the range of 47.3% <ds / dc <121.1%, and the ratio of the minor axis a to the major axis b of the cord diameter ((a / b) × 100) in any cross section.
Is in the range of 100.0% ≧ a / b ≧ 75.0%.

[0007]

Further, in the above steel cord, the diameter dc of the wire constituting the core is 0.10 mm≤dc≤
It is also particularly advantageous in practice that the diameter ds of the wire constituting the sheath is within the range of 0.40 mm and the range of 0.10 mm ≦ ds ≦ 0.37 mm.

Further, in the above steel cord, the case where the strands constituting the core are non-twisted are also included in the present invention.

The present invention also relates to a pneumatic radial tire obtained by applying the above steel cord for reinforcing rubber articles to a cord constituting a carcass or a belt layer.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the steel cord of the present invention, the number of wires constituting the core is limited to two,
In the case of a cord having a core consisting of one strand, even if the rubber penetrates into the core, the strands of the sheath are eccentrically arranged, so there is an unpenetrated part of the rubber in a spiral shape, and the core has corrosion resistance. This is because it is significantly inferior to the case of two strands, while a core formed of three or more strands has a cavity into which rubber does not penetrate, which also reduces the corrosion propagation resistance of the cord.

The reason why the average twist pitch of the core is set to 30 mm or more is that if it is less than 30 mm, it becomes difficult for rubber to penetrate between the strands of the core, and the productivity of the twisted wire decreases. Here, "the average pitch is 30 mm or more" means that the two strands of the core are rotated by 360 ° at 30 mm or more. Therefore, for example, the first 10 mm rotates 180 °, and the next 10 mm is straight, 18 again at the last 10 mm
One pitch may be formed by rotating 0 °, or the first 20 mm may be straight and the remaining 10 mm may be rotated by 360 ° to form one pitch. In addition, the non-twisted structure can further improve the permeability of rubber and can significantly improve the productivity. Furthermore, even if one or both strands of the core are corrugated or spiraled, or a combination of these is used, the effect of the present invention is not impaired.

Ratio ((ds / dc) × 1) of the diameter ds of the wire of the sheath to the diameter dc of the wire of the core
00) was set to the range of 47.3% <ds / dc <121.1% in order to secure a sufficient gap between the adjacent strands of the sheath so that the rubber can uniformly penetrate into the cord. This is to secure a sufficient gap between the adjacent strands of the sheath even when the strands of the sheath fall into the core.
If it exceeds this range, the gap between the adjacent strands of the sheath becomes small and it becomes difficult for the rubber to penetrate into the core.

The ratio of the minor diameter a of the cord diameter to the major diameter b ((a /
It is preferable that b) × 100) is in the range of 100.0% ≧ a / b> 66.1%, because when applied to a cord constituting a belt layer of a pneumatic radial tire, a cut caused by running on a rough road This is because it becomes difficult to receive the cut, and if it exceeds this range, it becomes easy to receive a cut due to traveling on a bad road.

Further, the diameter dc of the wire constituting the core is
0.10 mm ≦ dc ≦ 0.40 mm, and the diameter ds of the wire forming the sheath is 0.10 mm ≦ ds ≦
The range of 0.37 mm is preferable because if the lower limit is exceeded, it becomes extremely difficult to manufacture the wire, and if the upper limit is exceeded, the cord is coated with a rubber sheet to form a tire member. This is because the strands are plastically deformed in the manufacturing process and warp occurs in the member, resulting in poor productivity.

[0016]

EXAMPLES The present invention will be specifically described below based on examples. The cords having the structures shown in Tables 1 and 2 below and FIGS. 1 and 2 (Examples), and the cords having the structures shown in Tables 1 and 3 below as a conventional example are used for the belt layer, and the size is 10.00
R20 pneumatic radial tires were manufactured as prototypes, and the following evaluations were performed on these tires. In the figure, 1 is a core, 2 is an (intermediate) sheath, 3 is an outer layer sheath, and 4 is a spiral wire.

Permeability of rubber inside the cord Take out the steel cord from the belt layer of the tire under test,
And through the outer layer sheath wires of the steel cord to determine the amount of rubber adhering onto the intermediate sheath, then through the intermediate sheath wires to determine the amount of rubber adhering onto the core, respectively Is 0 when the rubber is not adhered to the surface at all.
The evaluation was made in terms of%.

Separation resistance A test tire was mounted on a 10-ton truck, run on a bad road, and a completely worn tire was dissected. This was caused by corrosion of the steel cord due to moisture transmission inside the steel cord.
The presence or absence of large separation of cm ² or more was examined.

Number of Tread Penetration Cuts The test tire was mounted on a 10-ton truck, run on a bad road to dissect a completely worn tire, and the number of cuts penetrating the tread per unit area was measured. The obtained results are shown in Tables 1 and 2 below.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

According to the present invention, it is possible to obtain a steel cord for reinforcing a rubber article, which has significantly improved corrosion propagation resistance and productivity, and a pneumatic radial tire in which the steel cord is applied to a belt layer is provided. Since the permeability of rubber to the inside of the cord is good, it exhibits excellent durability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a steel cord for reinforcing a rubber article according to an example of the present invention.

FIG. 2 is a sectional view of another example of a steel cord for reinforcing a rubber article according to the present invention.

FIG. 3 is a sectional view of a conventional steel cord for reinforcing a rubber article.

[Explanation of symbols]

1 core 2 (middle) sheath 3 Outer layer sheath 4 spiral wire

Claims (4)

(57) [Claims] 1. A steel cord having a two-layer twist, comprising:
In a core consisting wire of the present, the steel cord for reinforcing a rubber article comprising a sheath consisting of 7 strands that are attached-out around the periphery of the core, the average pitch twisting of the core is 30mm or more And the ratio of the diameter ds of the strand of the sheath to the diameter dc of the strand of the core ((ds / dc) × 1
00) is state, and are a range of 47.3% <ds / dc <121.1 %, further in any section, the call
Ratio of minor diameter a of major diameter to major diameter b ((a / b) × 100)
Is in the range of 100.0% ≧ a / b ≧ 75.0%, a steel cord for reinforcing rubber articles. 2. The diameter dc of the wire constituting the core is
0.10 mm ≦ dc ≦ 0.40 mm, and the diameter ds of the wire forming the sheath is 0.10 mm
The steel cord for reinforcing a rubber article according to claim 1, wherein the range is ≤ds≤0.37 mm. 3. The steel cord for reinforcing a rubber article according to claim 1, wherein the strands constituting the core are untwisted. 4. A pneumatic radial tire, wherein the steel cord according to any one of claims 1 to 3 is used as a cord constituting a carcass or a belt layer.