KR100483499B1 - Tire steel cord - Google Patents

Abstract

The present invention aims to provide a tire steel cord by reducing the number of filaments of the sheath layer to improve rubber permeability and at the same time, by arranging the filaments of the two cores in a straight line in parallel and not stranded.

The steel cord of the present invention comprises a core layer in which two filaments are arranged in parallel in a straight line, a first sheath layer composed of eight filaments surrounding the core layer, and 13 to 14 filaments adjacent to the first sheath layer. 2 + 8 + n (n = 13-14) structure which consists of a 2nd sheath layer comprised, or 2 + 8 + n + w structure which has a lapping wire as outermost layer of 2 + 8 + n structure.

Description

Tire steel cord {Tire steel cord}

The present invention relates to a tire steel cord. The present invention relates to a tire steel cord obtained by reducing the number of filaments of the sheath layer to improve rubber permeability and simultaneously twisting the filaments of the sheath layer without arranging the filaments of the two cores in parallel in a straight line.

A steel cord used for a carcass layer of a pneumatic radial tire for a truck or bus, which is conventionally shown in FIG. 1 of the accompanying drawings, having the same diameter as the filament of the core around the core in which the three filaments are associated. A first sheath layer consisting of three filaments, and a 3 + 9 + w structure having a spiral wrapping layer at the outermost layer, or 15 filaments around the core, the first sheath layer and the first sheath layer A 3 + 9 + 15 + w structure having a second sheath layer and a spiral wrapping layer at its outermost layer is generally used.

However, in the general 3 + 9 + w structure or 3 + 9 + 15 + w structure, each of the filaments constituting the inner sheath layer adjacent to the wrapping wire is in compact contact with each other, which makes rubber penetration into the interior difficult and thus creates a closed space. It cannot be formed and it is impossible for carcass rubber to fully penetrate to the center of the core on the finished tire.

Therefore, the moisture contained in the tire during the tire manufacturing process, or the moisture penetrating from the cracks caused by the trauma received during driving, etc., causes corrosion on the metal surface of the steel cord, which is caused by the deterioration of the physical properties of the steel cord itself due to such corrosion. The breakdown of the carcass layer occurs due to the deterioration of the adhesion of the rubber and steel cord in the belt layer due to the breakdown and corrosion of one carcass layer.

In addition, the repetitive deformation of the carcass that occurs during the running of the tire causes fritting between the filaments constituting the steel cord, and this fret can be accelerated by the wrapping wire.

In addition, the wrapping wire increases the diameter of the steel cord to increase the topping gauge, thereby increasing the weight of the tire and increasing the RR, thereby lowering fuel efficiency.

Recently, in order to compensate for the shortcomings of the 3 + 9 + w structure and the 3 + 9 + 15 + w structure, a compact structure having a 1 × 12 structure as shown in FIG. 2A or a 1 × 27 structure as shown in FIG. 2B has been developed. This compact structure has the same twisting length of all the filaments constituting the same, so that the contact pressure between the filaments is changed from the contact form to the line contact form, thereby reducing the contact pressure, thereby suppressing the occurrence of fritting.

In addition, the twist lengths of all the filaments are the same to simplify the manufacturing process of the steel cord through the simplification of the twisted pair process, thereby improving the productivity of the steel cord and reduce the manufacturing cost.

However, due to the compact structure, it shows poor performance in terms of rubber penetration into the interior. As a result, corrosion of the steel cord and weak binding force of the sheath filament to the core result in repeated compression or bending of the tire while the tire is running. The so-called core migration phenomenon, in which the filament exits the cut portion of the cord, is likely to occur.

In order to improve rubber permeability and to prevent core movement, a technique of forming a space to facilitate rubber penetration between filaments by adding a wave-like or spiral shape to at least one of the filaments of the core or the sheath is proposed.

However, such a technique is disadvantageous in terms of weight reduction of the tire because it requires a step of applying a wave-shaped or spiral-shaped mold in advance and increases the thickness of the rubber during rolling with an increase in the cord diameter.

In addition, in the case of a cord having a wavy or spiral shape, the elongation during deterioration is large, so that it is easily deformed by the cord tension at the time of rolling, resulting in poor flatness of the rolled product, and thus precise cord tension to ensure flatness. There is a disadvantage that management must be done.

The present invention relates to reducing the number of filaments of the sheath layer to improve rubber permeability, while simultaneously stranding the filaments of the sheath layer without arranging the two filaments in a straight line in parallel.

In the case of the steel cord manufactured by this method, the arrangement of the side lines is not compact, sufficient rubber permeability to the core can be ensured in the space between the filaments, so that the durability of the steel cord can be improved, and there is no twisting of the core. The cross section of the steel cord completed by the two filaments of the cores arranged in parallel in a straight line has a constant elliptical shape in the axial direction, and thus has anisotropic properties.

Using this anisotropic property, it is possible to manufacture steel cords with equal bending resistance while lowering the topping gauge.

In the present invention, two filaments are wrapped in a straight line parallel to the core layer and the core layer for the purpose of preventing the frit between the filaments through the rubber permeability improvement and the manufacturing cost through the improvement of the manufacturing productivity of the cord, 2 + 8 + n (n = 13-14) structure or 2 + 8 + consisting of a first sheath layer of eight filaments and a second sheath layer of thirteen to fourteen filaments adjacent to the first sheath layer The steel cord of the 2 + 8 + n + w structure which has a lapping wire as an outermost layer of n structure.

The diameter (Dc) of the core filaments arranged in a straight line in parallel without kinks is equal to or equal to the diameters (Ds1 & Ds2) of the sheath filaments constituting the sheath layer, so that the spacing between the filaments can be maintained. The relationship of Ds2, 1? Dc / Ds1? 1.3, 0.20 mm? Dc? 0.35 mm is satisfied.

The relationship between the twist length Ls1 of the first sheath layer and the twist length Ls2 of the second sheath layer has a relationship of Ls1 / Ls2 ≦ 1.0 and 7.0 mm ≦ Ls1 ≦ 20.0 mm.

In addition, since the filaments of two cores are arranged in parallel, the manufacturing process of the cord can be reduced (in the case of a 2 + 8 + n structure in which Ls1 = Ls2, one step can be manufactured), thereby reducing the manufacturing cost of the cord. In addition, the cross-sectional shape of the manufactured steel cord has an elliptical shape, so that the characteristics of the steel cord have anisotropy, thereby increasing the bending rigidity of the carcass cord in the driving direction, thereby improving steering stability.

According to the present invention, a first sheath layer consisting of two core filaments arranged in parallel without twist and eight filaments surrounding the core filaments, and a thirteen to fourteen filaments twisted adjacent to the first sheath layer 2 + 8 + n (n = 13-14) structure composed of 2 sheath layers or 2 + 8 + n + w (n = 13-14) structure having lapping wire as outermost layer of 2 + 8 + n structure As a steel cord, it is possible to provide a tire having good durability by having good rubber permeability to the inside of the core and excellent resistance to fretting phenomenon due to corrosion and core movement due to moisture infiltration.

In addition, since the cord section is elliptical, the thinning of the carcass layer can be realized, and the weight of the tire can be reduced, and the bending rigidity in the running direction of the carcass layer on the tire is improved, which is excellent in cornering characteristics and steering stability. It is possible to provide a tire.

Examples according to the present invention are shown in Figure 3 and Table 1.

As shown in FIG. 3, 2 (0.24) + 8 + 13 (0.22) +0.15, a space is stably formed between the sheath filaments of the steel cord manufactured according to the present invention, so that the rubber can sufficiently penetrate the core filament. Do. As shown in Table 1, due to the increased rubber permeability, the adhesiveness retention in water and saline is excellent, which is suitable for preventing carcass cord breakage caused by corrosion, thereby providing a tire having excellent durability. .

In addition, as shown in Table 1, the cord diameter (short diameter) is small, so that the thickness of the carcass layer can be reduced, thereby making it possible to reduce the weight and thereby realize a low fuel consumption tire.

The test method described in Table 1 is as follows.

※ Stiffness ratio (longer diameter / shorter diameter): The stiffness for 15 degree bending is measured in the long and short diameter direction by using Taber stiffness tester.

※ Rubber Penetration: Measures the rubber adhesion rate to the filament inside the core for the entire length of the cord.

※ Moisture and brine adhesion retention rate: The ratio of adhesion strength after aging under the conditions of moisture (70 ℃ 3 weeks) and brine (20% NaCl × 3 weeks) compared to the adhesion before the aging test.

characteristic unit Example Comparative Example 1 Comparative Example 2 Steel Cord Properties rescue - 2 (0.24) + 8 + 13 (0.22) + w 3 + 9 + 15 (0.22) + w 1 × 27 (0.22) + w Twist Length (Core / First Sheath / Second Sheath / Lapping) mm -/ 10.0 / 15.0 / 5.0 6.0 / 12.0 / 18.0 / 3.5 16.0 / 5.0 Twisting direction (core / first sheath / second sheath / lapping) - -/ S / S / Z S / S / Z / S S / Z Stiffness Ratio (Long Diameter / Short Diameter) % 11.5 100 100 Rubber adhesion rate of core % 50 20 10 Rubber Adhesion Retention Rate Domestic aging % 95 80 70 Salt water aging % 95 75 40

The present invention has the effect of reducing the manufacturing cost through the prevention of fritting between the filament through the rubber permeability improvement and the improvement of the manufacturing productivity of the steel cord.

1 is a schematic diagram of a steel cord having a structure of conventional 3 + 9 + 15 (0.22) + w.

2A is a schematic diagram of a steel cord having a conventional structure of 1 × 12 (0.22).

2B is a schematic diagram of a steel cord having a conventional structure of 1 × 27 (0.22).

3 is a schematic diagram of a steel cord having a structure of 2 (0.24) + 8 + 13 (0.22) + w according to the present invention.

Claims (2)

delete A core layer composed of two filaments arranged in a straight line without twisting each other, a first sheath layer composed of eight filaments surrounding the core filament, and thirteen to fourteen twisted adjacent to the first sheath layer Air having a 2 + 8 + n (n = 13 to 14) structure or a 2 + 8 + n + w structure having lapping filaments as an outermost layer having a second sheath layer composed of filaments or a 2 + 8 + n structure In the steel cord applied to the carcass constituting the mouth radial tire, The diameter (Dc) of the filament of the core layer is equal to or larger than the diameter (Ds1, Ds2) of the filament of the sheath layer, the diameter (Ds1) of the filament of the first sheath layer and the diameter of the filament of the second sheath layer ( Ds2) satisfies the relationship of 1? The steel cord of the pneumatic radial tire, wherein the relationship of (Ls2) satisfies Ls1 / Ls2≤1.0 and 7.0mm≤Ls1≤20.0mm, but the same twist direction is manufactured.