JPH0519394U - Steel cord - Google Patents

Abstract

(57) [Abstract] [Purpose] In the 3 + 8 structure, the diameter of the core wire is appropriately reduced to make the gap between the wires proper, and the rubber characteristics as well as the cord characteristics and reliability are improved to improve the service life. It is in providing the steel cord. [Structure] A steel cord comprising a core portion formed by twisting three strands 1 and an outer layer formed by twisting eight strands 2 around the core portion The wire diameter ratio d / D with the wire 2 of the outer layer is 0.88 to 0.95.
It is characterized by being configured into.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 TECHNICAL FIELD The present invention relates to a reinforcing material for a radial tire, and particularly to a steel cord suitable for reinforcing the belt layer thereof.

[0002]

[Prior Art]

 The above-mentioned conventional steel cord is formed by twisting three core wires a and nine core wires b around the core portion formed by twisting three core wires a as shown in FIG. 2 (A). A steel cord with a 3 + 9 structure consisting of outer layers is commonly used. However, as shown in the figure, this steel cord has a structure in which the outer layer strands b are wound in an orderly and parallel manner around the core, so that almost no gap is formed between the strands, and the rubber penetrates inside the cord. A void space is formed, which may cause water infiltration, cord corrosion due to propagation, and shortened tire life. Recently, as shown in FIG. 2B, nine strands b1 having a smaller diameter than the strand a are twisted around the core part formed by twisting three strands a to form an outer layer. The number of strands is reduced around the steel cord formed by forming gaps s1 between the strands to improve rubber permeability, and around the core part consisting of three strands a as shown in FIG. A steel cord having a 3 + 8 structure has been developed in which eight strands b are twisted together to form an outer layer, and a gap s2 is formed between the strands to enhance rubber permeability.

[0003]

[Problems to be solved by the device]

 In the conventional steel cord shown in FIG. 2B, the strand of the outer layer has a small diameter, so that the bending rigidity and the shearing impact property of the cord are significantly deteriorated, which causes a decrease in safety. There are problems with code characteristics and reliability. In the steel cord shown in Fig. 3, the number of strands in the outer layer is reduced, and the strands are too wide, and the core of three strands pops out from the strands in the outer layer during cord manufacturing (stranding). There are problems such as a high incidence of defects in the cord twist shape, and a large difference in the effective area, which leads to deterioration of the cord characteristics and reliability.

The present invention was developed in order to address the above-mentioned problems, and the object of the present invention is to provide a 3 + 8 structure by appropriately reducing the diameter of the core wire. The purpose is to provide a steel cord that has an appropriate gap between the wires and has improved rubber penetration as well as cord characteristics and reliability, thus improving the service life.

[0005]

[Means for Solving the Problems]

 The present invention relates to a steel cord comprising a core portion formed by twisting three strands and an outer layer formed by twisting eight strands around the core portion. The wire diameter ratio with each wire is set to 0.88 to 0.95 to optimize the gap between the wires to improve the rubber penetration and the accuracy of the cord twist shape, as well as the bending rigidity and shear strength. The impact characteristics are improved.

[0006]

[Action]

 In a steel cord composed of a core portion formed by twisting three strands and an outer layer formed by twisting eight strands around the core portion, a strand of the core portion and a strand of the outer layer By configuring the wire diameter ratio of the wires to be 0.88 to 0.95, the gap between the wires is properly adjusted, the rubber penetration and the shape accuracy of the cord twist are improved, and the bending rigidity and shearing of the cord are improved. Impact properties are effectively improved.

[0007]

【Example】

 FIG. 1 shows an embodiment of the present invention. In the figure, 1 is an element wire that constitutes a core portion, 2 is an element wire that constitutes an outer layer, and a core portion formed by twisting three strands 1 and eight core wires around the core portion. In a steel cord having a 3 + 8 structure composed of an outer layer formed by twisting the strands 2, a strand diameter ratio d / D between each strand 1 of the core and each strand 2 of the outer layer is 0.88-0. It is a steel cord configured in 95.

In the steel cord, as described above, in the 3 + 8 structure, the strands 1 of the core portion are made smaller in diameter to the strands 2 of the outer layer, and the gap S between the strands 2 of the outer layer is appropriately adjusted. It is characterized by the composition. For example, in a steel cord having a 3 + 8 structure as shown in Table 1, the strand diameter of each strand 2 of the outer layer is 0.35 mm, whereas the strand diameter of each strand 1 of the core is 0.33 mm. Steel cord having the structure (Example 1), steel wire having a structure in which the wire diameter of each wire 1 of the core is 0.32 mm (Example 2), wire diameter of each wire of the core 0.31 mm The steel cord (Example 3) having the above-described structure is used, and the wire diameter ratio d / D between the wire 1 of the core and the wire 2 of the outer layer is 0.94 in Example 1 and 0 in Example 2. .91, and Example 3 is 0.89, and the steel cord of the present invention is implemented with the wire diameter ratio d / D within the range of 0.88 to 0.95. In the above embodiment, preferably, the twisting directions of the core portion and the outer layer are the same, and the cord pitch is enhanced by setting the twist pitch of the core portion to 1/4 to 3/4 of the twist pitch of the outer layer.

Further, in addition to Examples 1 to 3 above, Conventional Example 1 having a 3 × 0.35 + 8 × 0.35 structure (see FIG. 3), Conventional Example 2 having a 3 × 0.35 + 9 × 0.35 structure (see FIG. 2A), and 3 Steel of Conventional Example 3 with a structure of × 0.35 + 9 × 0.32 (see FIG. 2B), Conventional Example 4 with a structure of 3 × 0.35 + 9 × 0.31 (see FIG. 2B), and Comparative Example 1 of a structure of 3 × 0.30 + 8 × 0.35 A code was prototyped, and the physical properties were compared by the following means, and the results shown in Tables 1 and 2 were obtained. For rubber penetration, a rubber vulcanization with a cord length of 100 mm was performed, and the rubber penetration between the outer layer wire and the core wire was compared. Corrosion fatigue resistance was measured by a de-matcher fatigue tester. A cord coated with belt-shaped rubber was set, and a fatigue test was conducted while immersing the cord end in a 5% NaCl solution. After a certain period of time, the residual strength was compared and the bending rigidity was 15 degrees. The comparative value of the torque required to bend at an angle, the shear impact characteristic, is the comparative value of the energy required to cut by dropping a weight with an edge at the center of the cord with a fulcrum of 100 mm.

[0010]

[Table 1]

[Table 2]

As is clear from Tables 1 and 2, the conventional example 2 (3 × 0.35 + 9 × 0.35 structure-see FIG. 2A) has problems in rubber permeability and corrosion fatigue, whereas in the conventional example. Nos. 3 and 4 (3 x 0.35 + 9 x 0.32 (0.31) structure-see Fig. 2B) have improved rubber permeability and corrosion fatigue resistance, but deterioration of cord characteristics such as bending rigidity and shear impact characteristics becomes a problem. In addition, in Conventional Example 1 (3 × 0.35 + 8 × 0.35 structure—see FIG. 3), it has excellent rubber permeability and corrosion fatigue resistance, but has a high rate of occurrence of defective cord twist shape, This is the cause of the decrease in reliability.

In Examples 1 to 3 of the present invention, as is clear from Tables 1 and 2, good results similar to those of Conventional Example 1 were obtained in rubber permeability and corrosion fatigue resistance. The shape is remarkably improved as compared with Conventional Example 1, and the deterioration of the cord bending rigidity and the shearing impact characteristics is also lighter than that of Conventional Example 1, and overall excellent cord characteristics and reliability are obtained (Conventional Example 2 The rubber penetration and corrosion fatigue resistance are extremely poor, and the conventional products 3 and 4 have poor bending rigidity and shear impact properties. Further, as is clear from the comparison between the conventional example 1 and the comparative example 1, the strand diameter ratio d / D between the core strand 1 and the outer strand 2 is 0.88 of Examples 1-3. It is preferable to configure it within the range of 0.95, the gap S between the outer layer wires 2 is properly adjusted, the rubber permeability is improved, the voids are eliminated, corrosion is prevented, and at the same time fatigue is improved. At the same time, the twisting accuracy of the core portion is improved by reducing the gap S and reducing the diameter of the wire 1. Further, the reduction in diameter of the strand 1 causes less reduction in the effective cross-sectional area of the cord as compared with the case of the strand 2, and the influence on the bending rigidity of the cord, the shearing impact characteristics, etc. is reduced. In addition, if necessary, the wire diameter D of each wire 2 of the outer layer can be increased relatively appropriately, and the deterioration of the cord characteristics and reliability is almost eliminated, and the good results as described above are obtained. Is obtained.

[0013]

[Effect of the device]

 The present invention relates to a steel cord having a 3 + 8 structure including a core portion formed by twisting three strands and an outer layer formed by twisting eight strands around the core portion. By configuring the wire diameter ratio between the wires of the outer layer and the wires of the outer layer to be 0.88 to 0.95, the gap between the wires is appropriately adjusted to enhance the rubber permeability, and further, the core wire By reducing the diameter of the wire, the accuracy of the shape of the cord twist is improved, and its bending rigidity and shear impact characteristics are more effective than the conventional example in which the outer layer wire diameter is smaller than the core wire. As a result, the overall code characteristics and reliability have been improved, and the service life has been significantly improved.

[Brief description of drawings]

FIG. 1 is a diagram of a cord traversing mechanism showing an embodiment of the present invention.

FIG. 2 is a diagram of each cord crossing mechanism showing a conventional example (A),
(B)

FIG. 3 is a code crossing mechanism diagram showing another conventional example.

[Explanation of symbols]

 1 core wire 2 outer layer wire d core wire diameter D outer wire diameter S gap

Claims (1)

[Scope of utility model registration request] 1. A steel cord comprising a core portion formed by twisting three strands and an outer layer formed by twisting eight strands around the core portion. A steel cord characterized in that a wire diameter ratio with the wire of the outer layer is set to 0.88 to 0.95.