JP5126979B2 - Steel cords for reinforcing rubber articles and pneumatic tires - Google Patents

Description

  The present invention relates to a steel cord for reinforcing rubber articles (hereinafter also simply referred to as “steel cord”) and a pneumatic tire (hereinafter also simply referred to as “tire”), and more specifically has a breaking elongation of 4% or more. Steel cord for reinforcing rubber articles having a high twist strength and suitable for reinforcing a circumferential belt of a pneumatic tire, and a pneumatic cord using the steel cord for reinforcing rubber articles as a reinforcing material for a circumferential belt Related to tires.

  In general, a pneumatic tire has a carcass layer extending in a toroidal shape between a pair of bead portions as a skeleton, and a belt layer formed by rubberizing various reinforcing elements or a belt reinforcing layer on the outer periphery thereof. The surface portion has a reinforced structure.

In a steel cord having a double twist structure used as a reinforcing material for a circumferential belt of a pneumatic tire, it is common to twist three strands at a large twist angle. For example, Patent Document 1 proposes to apply a steel cord having a structure of 3 × (1 × 0.34 + 6 × 0.30) to a circumferential reinforcing layer of a pneumatic tire. Further, in Patent Document 2, in a steel cord in which four or five strands of strands of four or five sheath filaments are twisted around the core filament, the core filament has a smaller diameter than the sheath filament. A steel cord having a twisted structure is disclosed.
Japanese Patent No. 3983270 JP 2000-154483 A

  Steel cords having a double twist structure for reinforcing circumferential belts disclosed in Patent Documents 1 and 2 give consideration to design in a direction in which elongation is increased with an emphasis on elongation at break. Therefore, the strand twist angle is large, and there is a tendency that a large breaking strength is difficult to obtain. If the strength of the circumferential belt member serving as a tag in the tire is not sufficient, there is a problem that the strength against impact input from the outside as the tire is reduced.

  Accordingly, an object of the present invention is to provide a steel cord for reinforcing rubber articles having a double twist structure that has a breaking elongation of 4% or more and has a high breaking strength and is suitably used as a reinforcing material for a circumferential belt of a pneumatic tire. An object of the present invention is to provide a pneumatic tire using the steel cord for reinforcing rubber articles as a reinforcing material for a circumferential belt.

  As a result of diligent studies to solve the above problems, the present inventor has found that the above object can be achieved by adopting the following configuration, and has completed the present invention.

  That is, the steel cord for reinforcing rubber articles according to the present invention is a steel cord for reinforcing rubber articles having a twisted strand angle of 13 ° to 25 °, a strand number of 4 or 5, and no core strand, and having no core strand. The strand has a twisted structure composed of a core and a single-layer sheath, and the diameter of the filament of the core is larger than the diameter of the filament of the sheath.

  In the present invention, the material of the core filament and the sheath filament is preferably high carbon steel containing a carbon component of 0.80% by mass or more.

  The pneumatic tire according to the present invention is characterized in that the steel cord for reinforcing rubber articles according to the present invention is used as a reinforcing material for a circumferential belt.

  According to the present invention, a rubber article having a double twist structure that has a breaking elongation of 4% or more and a high breaking strength and is suitably used as a reinforcing material for a circumferential belt of a pneumatic tire. It is possible to provide a steel tire for reinforcement and a pneumatic tire using the steel cord for reinforcing rubber articles as a reinforcing material for a circumferential belt.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of an example of a steel cord for reinforcing rubber articles according to the present invention. The steel cord 1 is composed of four or five (four in the illustrated example) strands 2 and has no core strand. The strand 2 is composed of a single-layer sheath composed of one core filament 3 and a plurality of sheath filaments 4 (six in the illustrated example). The four strands 2 are twisted at a strand twist angle of 13 to 25 °.

  In the present invention, the diameter of the core filament 3 is larger than the diameter of the sheath filament 4. The core filament 3 in the strand 2 is affected only by the spiral processing of the strand, but the sheath filament 4 is further affected by the spiral processing inside the strand. Therefore, the core filament 3 that is less affected by the strength reduction due to the spiral processing is made larger in diameter than the sheath filament 4 and the area ratio of the core filament 3 occupying the cross-sectional area of the steel cord 1 is increased. Can be improved.

  Moreover, the space is provided in the center part of the steel cord 1 of a double twist structure by twisting 4 or 5 strands 2 without providing a core strand. With such a structure, when embedding the steel cord 1 in rubber, the central space of the steel cord 1 having a double twist structure can be filled with rubber, and the tightening stress between the strands 2 is dispersed. Prior breakage of the sheath filament 4 serving as the contact portion is suppressed. As a result, good steel cord strength can be obtained.

  In the present invention, the number of strands is set to 4 or 5 when the steel cord diameter and the strand cross-sectional structure are the same, and the number of strands is 3 or less as shown in FIG. This is because the ratio of the area of the circumscribing circle of the strand cross section in the area becomes small. That is, when the amount of steel in the cross-sectional area of the steel cord decreases, the strength of the steel cord decreases. On the other hand, when the number of strands is 6 or more as shown in FIG. 4, the size of the space formed in the center portion of the steel cord becomes equal to or larger than the strand diameter, the strands are likely to fall, and the twisting property becomes unstable. This is because it is easy.

  Furthermore, the desired breaking elongation of the steel cord can be ensured by setting the strand twist angle to 13 to 25 °. When the twist angle of the strand is less than 13 °, the breaking elongation becomes small, and it becomes impossible to obtain a breaking elongation of 4% or more. On the other hand, if it exceeds 25 °, the utilization efficiency of the breaking strength of the entire steel cord compared to the breaking strength of the steel filament itself is deteriorated. Preferably it is 16-23 degrees. Here, the strand twist angle is an angle formed by the strand helical axis with respect to the longitudinal direction of the steel cord.

  As described above, in the steel cord of the present invention, the breaking elongation can be secured at 4% or more, and both the breaking elongation and the breaking strength can be achieved.

  The filament material used in the present invention is not particularly limited, and any conventionally used material can be used. However, the filament material is a high carbon steel having a carbon component of 0.80% by mass or more. preferable. The effect of the present invention can be obtained satisfactorily by making the filament material a high carbon steel having a high hardness carbon component of 0.80% by mass or more. On the other hand, if the carbon component exceeds 1.5%, the ductility is lowered and the fatigue resistance is deteriorated, which is not preferable.

  The pneumatic tire of the present invention is a pneumatic tire using the steel cord for reinforcing rubber articles of the present invention as a reinforcing material for a circumferential belt. When the steel cord of the present invention is embedded in rubber, the center portion of the steel cord having a double twist structure is preferably filled with rubber. As described above, the space at the center of the steel cord having a double twist structure is filled with rubber, so that the fastening stress between the strands is dispersed, and the preceding breakage of the sheath filament serving as the contact portion is suppressed. As a result, a high steel cord strength can be obtained, and a tire with improved strength against input from the outside of the tire can be provided.

  The pneumatic tire of the present invention relates to an improvement in the structure of a steel cord used as a reinforcing material for a circumferential belt, and other structures and materials are not particularly limited, and are known structures and Materials can be adopted as appropriate.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Examples 1-3, Comparative Examples 1-6)
Steel cords having the same twist diameter and twist angle shown in Tables 1 to 3 below and the twist direction are prepared using steel materials having the carbon amount shown in the same table, and these are reinforced in the circumferential belt. Tires of tire size 495 / 45R225 were produced as materials. For each of the obtained tires, the steel cord center rubber penetration, the breaking elongation index, and the breaking strength comparison index were evaluated as follows. The obtained results are also shown in Tables 1-3. In addition, the corresponding figure of the used steel cord cross section is shown in FIGS.

(Steel cord center rubber penetration)
Steel cords were taken out from the tires of Examples 1 to 3 and Comparative Examples 1 to 6, respectively, and the taken out steel cords were loosened in units of strands, and it was visually confirmed whether rubber was contained in the center portion of the steel cords. The case where it was entered was “present”, and the case where it was not entered was “none”.

(Breaking strength comparison index)
Steel cords were taken out from the tires of Examples 1 to 3 and Comparative Examples 1 to 6, respectively, and the breaking strength was measured. The method for calculating the breaking strength comparison index is as follows.
1) In the case of Example 1 and Comparative Examples 1 to 4 (Each steel cord breaking strength (N) of Example 1 and Comparative Examples 1 to 4 / Steel cord breaking strength (N) of Comparative Example 2) × 100
2) In the case of Example 2 and Comparative Example 5 (Each steel cord breaking strength (N) of Example 2 and Comparative Example 5 / Steel cord breaking strength (N) of Comparative Example 5) × 100
3) In the case of Example 3 and Comparative Example 6 (Each steel cord breaking strength (N) of Example 3 and Comparative Example 6 / Steel cord breaking strength (N) of Comparative Example 6) × 100
The break strength was measured by a tensile test based on JIS G 3510 and JIS Z 2241, and the maximum tensile load until the steel cord was broken was defined as the break strength of the steel cord.

(Elongation at break)
Steel cords were taken out from the tires of Examples 1 to 3 and Comparative Examples 1 to 6, respectively, and the elongation at break was measured. The breaking elongation index 4 was evaluated when the breaking elongation was 4% or more and less than 5%, and the breaking elongation index 5 was evaluated when the breaking elongation was 5% or more and less than 6%.
The elongation at break was measured by a tensile test based on JIS G 3510 and JIS Z 2241, and the elongation until the steel cord broke was defined as the elongation at break of the steel cord.

※１：スチールコード中心部ゴムペネトレーション

* 1: Steel cord center rubber penetration

  From Tables 1 to 3, it can be seen that the steel cord for reinforcing rubber articles of the present invention has improved breaking strength.

It is sectional drawing of the steel cord for rubber article reinforcement of 4 * (0.28 + 6 * 0.25) structure of one embodiment of this invention. It is sectional drawing of the steel cord for rubber article reinforcement of the 5 * (0.25 + 6 * 0.225) structure of other embodiment of this invention. 3 is a cross-sectional view of a steel cord for reinforcing rubber articles having a 3 × (0.32 + 6 × 0.28) structure according to Comparative Example 1. FIG. 6 is a cross-sectional view of a steel cord for reinforcing rubber articles having a 6 × (0.225 + 6 × 0.20) structure according to Comparative Examples 2 and 4. FIG. 4 is a cross-sectional view of a steel cord for reinforcing rubber articles having a 3 × (0.26 + 5 × 0.31) structure according to Comparative Example 3. FIG. 6 is a cross-sectional view of a steel cord for reinforcing rubber articles having a 4 × (0.22 + 5 × 0.28) structure according to Comparative Example 5. FIG. 6 is a cross-sectional view of a steel cord for reinforcing rubber articles having a 5 × (0.20 + 5 × 0.25) structure according to Comparative Example 6. FIG.

Explanation of symbols

1 Steel cord 2 Strand 3 Core filament 4 Sheath filament

Claims (3)

  A steel cord for reinforcing a rubber article having a strand twist angle of 13 ° to 25 °, the number of strands of 4 or 5, and no core strand, and having no core strand, the strand comprising a core, a single layer sheath, A steel cord for reinforcing rubber articles, wherein the core cord has a twisted structure, and the diameter of the filament of the core is larger than the diameter of the filament of the sheath.   The steel cord for reinforcing rubber articles according to claim 1, wherein the material of the filament of the core and the filament of the sheath is a high carbon steel containing 0.80 mass% or more of a carbon component.   A pneumatic tire comprising the steel cord for reinforcing rubber articles according to claim 1 or 2 as a reinforcing material for a circumferential belt.

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