JP2006291419A - Steel cord for rubber reinforcement and pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide steel cord for rubber reinforcement enabling the unconventional durability of tire to be attained through improving fatigue resistance of the tire, and to provide a pneumatic radial tire using the cord as reinforcing material. <P>SOLUTION: The steel cord for rubber reinforcement has such a structure as to intertwist 3 or more core strands and intertwist 6 or more sheath strands therearound, wherein the core strands and the sheath strands are mutually intertwisted in the same direction. The pneumatic radial tire has such a structure that a carcass extending toroidally between a pair of beads serves as skeleton and the crown of the carcass is reinforced with belt plies, wherein the above steel cords are applied as the cords constituting the carcass and/or the belt plies. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber-reinforced steel cord and a pneumatic radial tire, and more particularly, to a rubber-reinforced steel cord and a pneumatic radial tire that are more durable than ever, and more particularly to a pneumatic radial tire for construction vehicles. (ORR).

  Today, with the development of vehicles, the demand for tires is also demanded for durability at higher speeds and higher loads. In particular, pneumatic radial tires for construction vehicles such as mining vehicles run on rough roads with high loads, so that even tire reinforcing steel cords have fatigue resistance to inputs such as bending and compression, and resistance to trauma. There is a need to further improve the cut performance.

  Conventionally, steel cords for reinforcing such tires for vehicles require high strength, and therefore, steel cords having a multi-twist structure in which strands obtained by twisting a plurality of steel filaments are further twisted are widely used. For example, a steel cord having a structure of 1 × (3 + 9 + 15) + 6 × (3 + 9 + 15) +1 as shown in FIG. 7 is known.

  In addition, in Patent Documents 1 and 2, as a steel cord for reinforcing a rubber article having a multi-twist structure, which can efficiently obtain a cord strength and is excellent in corrosion resistance propagation property, a core and a sheath are formed by a cord having two or three layers. At least one of the filaments constituting the core and the sheath with a steel cord in which at least a part of the filaments further comprises a strand composed of one core filament and four sheath filaments, and a cord with two or three layers twisted Steel cords each having a strand composed of one core filament and three sheath filaments have been proposed.

Further, in Patent Document 3, on the premise that the cord diameter is substantially the same as that of the steel cord so far, it is possible to reduce the cord rigidity while making the cord breaking strength at least equal to or higher, or Conversely, a steel cord having a predetermined cord diameter and filament diameter as a steel cord capable of increasing the cord breaking strength while keeping the cord rigidity at least equal to or less, and twisting three core strands around A steel cord is proposed in which eight or more side strands are twisted and one of the core strand and the side strand has a layer twist structure of two or more layers, and the other has a layer twist structure of three or more layers. ing.
Japanese Patent Laid-Open No. 10-298878 (claims, etc.) JP-A-10-298879 (Claims etc.) Japanese Patent Laid-Open No. 2002-30588 (Claims etc.)

  As described above, steel cords applied to pneumatic radial tires for construction vehicles are strongly required to have improved fatigue resistance against inputs such as bending and compression. Today, steel cords having a conventional double twist structure are required. Then, it must be said that the performance improvement has reached the limit.

  Accordingly, an object of the present invention is to provide a steel cord for reinforcing rubber that has improved fatigue resistance more than ever and can realize unprecedented durability, and a pneumatic radial tire using the steel cord as a reinforcing material. It is in.

  As a result of intensive studies to solve the above problems, the present inventors have obtained the following knowledge. That is, the increase in the input of bending and compression due to the high speed and high load of the tire sometimes causes the steel cord for reinforcement to be locally greatly compressed and deformed, resulting in fatigue breakage of the cord. Deformation due to compression is deformed to approximate a sine wave of half wavelength or one wavelength. When this deformation is an ideal sine wave deformation, the strain due to compression is dispersed and the life until breakage is improved. However, when the deformation is close to the triangular wave deformation, the strain concentrates in the vicinity of the apex, and the life until breakage is greatly reduced.

  As a result of further intensive studies based on the above knowledge that the life to fatigue fracture can be improved if the compression deformation can be controlled by the cord structure, the present inventor has completed the present invention.

  That is, the steel cord for rubber reinforcement of the present invention is formed by twisting three or more core strands and twisting six or more sheath strands around the core strand, and the core strand and the sheath strand are in the same direction. It is characterized by being twisted together.

In the steel cord for reinforcing rubber of the present invention, the strand preferably has a twisted structure of two or more layers, and a suitable cord structure is 3 × (3 + 9 + 15) + 9 × (3 + 9 + 15), 3 × (3 + 9). Mention may be made of twisted structures of + 9 × (3 + 9), 3 × (3 + 9) + 8 × (3 + 9 + 15) and 3 × (3 + 9) + 6 × (3 + 9 + 15). The strand diameter of the filament constituting the strand is preferably 0.14 mm or more and 0.36 mm or less. Furthermore, the spiral radius of the core strand is r, the spiral pitch is p, and the spiral radius of the sheath strand. Is R and the helical pitch is P,
It is preferable that the relationship represented by 86 ° ≧ tan ⁻¹ (p / 2πr) ≧ tan ⁻¹ (P / 2πR) ≧ 74 ° is satisfied.

  The pneumatic radial tire of the present invention is a pneumatic radial tire in which a carcass extending in a toroidal shape between a pair of bead portions is used as a skeleton, and a crown portion of the carcass is reinforced with a belt layer, and the carcass and / or The rubber reinforcing steel cord is applied to a cord constituting the belt layer.

  According to the steel cord for reinforcing rubber of the present invention, fatigue resistance can be improved more than ever, and unprecedented durability can be improved. Therefore, a pneumatic radial tire using the rubber-reinforced steel cord as a reinforcing material exhibits excellent durability, and can be particularly preferably applied to a pneumatic radial tire (ORR) for construction vehicles.

Hereinafter, embodiments of the present invention will be specifically described.
In the steel cord for rubber reinforcement of the present invention, 3 or more, preferably 3 or 4 core strands are twisted, and 6 or more, preferably 6 or more, 12 or less sheath strands are wound around them. More preferably, it is important that the core strand and the sheath strand are twisted together in the same direction.

  When a compression cord is given compression force, the twisted cord tends to deform sine waves in the direction of untwisting, that is, in the direction opposite to the direction of twisting, due to its rotation. At this time, for example, a cord having a twisted structure (1 + 6) having no twist at the center of the cord, the behavior of the core strand and the behavior of the sheath strand are greatly different at the time of compression. We found out that the behavior during compression is not ideal sine wave deformation. Furthermore, in order to obtain an ideal sine wave deformation, three or more core strands are double twisted to form a (n × m) double twist structure, and the twist direction of the core strand and the sheath strand is the same direction. As a result, we came to find that the compression deformation approaches the ideal sine wave deformation.

  Here, when the twist direction of the core strand and the twist direction of the sheath strand are reversed, the deformation at the time of compression becomes the opposite movement of the core strand and the sheath strand, and ideal sine wave deformation is performed. As a result, the compression fatigue property cannot be improved. Therefore, in the present invention, it is important that the core strand and the sheath strand are twisted in the same direction.

  In the steel cord for reinforcing rubber of the present invention, it is preferable that the sheath strand is composed of two or more layer twist structures. This is because a single layer cannot sufficiently secure the strength required for construction vehicle tires, and the applicable range is limited. More preferably, from the productivity and the cord diameter after double twisting, a three-layered layer structure is adopted. Also, the core strand is preferably a two-layer or three-layer twist structure from the viewpoint of productivity and the cord diameter after double twisting.

  From the above viewpoint, as a preferred embodiment of the steel cord of the present invention, 3 × (3 + 9 + 15) + 9 × (3 + 9 + 15) (see FIG. 1), 3 × (3 + 9) + 9 × (3 + 9) (see FIG. 2), 3 × (3 + 9) + 8 × (3 + 9 + 15) (see FIG. 3), 3 × (3 + 9) + 6 × (3 + 9 + 15) (see FIG. 4), 3 × (3 + 9 + 15) + 8 × (3 + 9) (see FIG. 5) and 4 × 5 + 6 × A twisted structure of (3 + 9 + 15) (see FIG. 6) can be given.

  Moreover, the strand diameter of the filament which comprises a strand becomes like this. Preferably it is 0.14 mm or more and 0.36 mm or less. If the wire diameter is less than 0.14 mm, the air pressure necessary for the pneumatic radial tire for construction vehicles cannot be maintained, and the applicable range is limited. The fatigue properties of the steel will be reduced. From productivity and the cord diameter after double twisting, it is more preferably 0.17 mm or more and 0.25 mm or less. Furthermore, the diameter of the strand constituting the central structure can be made larger than that of the strand constituting the outer layer, so that the rubber can penetrate into the cord and the corrosion resistance can be enhanced.

Furthermore, when the spiral radius formed by the core strand is r, the spiral pitch is p, the spiral radius of the sheath strand is R, and the spiral pitch is P,
It is preferable that the relationship represented by 86 ° ≧ tan ⁻¹ (p / 2πr) ≧ tan ⁻¹ (P / 2πR) ≧ 74 ° is satisfied. When the value of tan ⁻¹ (p / 2πr) is larger than 86 °, for example, the workability is greatly deteriorated due to the high rigidity in the tire molding operation. In addition, when the value of tan ⁻¹ (P / 2πR) is smaller than 74 °, the cord breaking strength becomes small, and the applicable range is limited. Further, in the case of tan ⁻¹ (P / 2πR)> tan ⁻¹ (p / 2πr), an improvement effect cannot be expected in terms of breaking strength, which is not preferable.

  As described above, the steel cord for rubber reinforcement of the present invention has significantly improved durability as compared with a steel cord having a conventional double twist structure. For example, instead of a steel cord having a conventional double twist structure, A pneumatic radial tire in which a ply formed by arranging a plurality of cords in parallel with each other and embedded in a rubber sheet is applied to a carcass and / or a belt layer has a greatly improved durability. Therefore, although not shown, the pneumatic radial tire of the present invention has a carcass extending in a toroidal shape between a pair of bead portions as a skeleton, and a pneumatic radial tire in which a crown portion of the carcass is reinforced with a belt layer. The above-described rubber cord for reinforcing steel according to the present invention is applied to the belt layer.

Next, the present invention will be specifically described with reference to examples and comparative examples.
Example 1
A steel cord according to the cord structure shown in Example 1 in Table 1 below was made as a prototype. This steel cord is a strand of the same layer twist structure around three core strands of a 3 + 9 + 15 layer twist structure composed of three core filaments 1, nine inner sheath filaments 2 and fifteen outer sheath filaments 3. Nine strands are twisted in the same direction as the core strand, and one spiral filament 4 is further wound. The cross-sectional structure of this steel cord is shown in FIG.

Example 2
A steel cord according to the cord structure shown in Example 2 in Table 1 below was made as a prototype. This steel cord is composed of three core strands of 3 + 9 layer twist structure composed of three core filaments 11 and nine sheath filaments 12, and nine strands of the same layer twist structure in the same direction as the core strand. Are twisted together and further wound with one spiral filament 13. A cross-sectional structure of this steel cord is shown in FIG.

Example 3
A steel cord according to the cord structure shown in Example 3 in Table 1 below was made as a prototype. This steel cord has three core filaments 31 and nine inner sheath filaments 32 around three core strands having a 3 + 9 layer twist structure composed of three core filaments 21 and nine sheath filaments 22. 8 strands of a 3 + 9 + 15 layer twist structure composed of 15 outer sheath filaments 33 are twisted in the same direction as the core strand, and one spiral filament 23 is wound, and the central structure is twisted together. It consists of 3 strands combined. The cross-sectional structure of this steel cord is shown in FIG.

Example 4
A steel cord according to the cord structure shown in Example 4 in Table 1 below was prototyped. This steel cord has three core filaments 51 and nine inner sheath filaments 52 around three core strands of a 3 + 9 layer twist structure composed of three core filaments 41 and nine sheath filaments 42. Six strands having a layer twist structure of 3 + 9 + 15 composed of 15 outer sheath filaments 53 are twisted in the same direction as the core strand, and further, one spiral filament 43 is wound, and the central structure is twisted to each other. It consists of 3 strands combined. The cross-sectional structure of this steel cord is shown in FIG.

Comparative Example 1
A steel cord according to the cord structure shown in Comparative Example 1 in Table 1 below was made as an experiment. In this steel cord, six strands are twisted around one strand of a 3 + 9 + 15 layer twist structure composed of three core filaments 101, nine inner sheath filaments 102 and fifteen outer sheath filaments 103. Further, one spiral filament 104 is wound, and the central structure is composed of one strand. A cross-sectional structure of this steel cord is shown in FIG.

Comparative Example 2
A steel cord according to the cord structure shown in Comparative Example 2 in Table 1 below was prototyped. In this steel cord, six strands are twisted around one strand of a 3 + 9 layer twist structure composed of three core filaments 201 and nine sheath filaments 202, and one spiral filament 203 is further formed. It is wound and the central structure consists of one strand. A cross-sectional structure of this steel cord is shown in FIG.

Comparative Example 3
A steel cord according to the cord structure shown in Comparative Example 3 in Table 1 below was made as an experiment. This steel cord has nine strands having the same layer twist structure around three core strands having a 3 + 9 + 15 layer twist structure composed of three core filaments, nine inner sheath filaments and fifteen outer sheath filaments. The core strand is twisted in the opposite direction and further wound with one spiral filament. The cross-sectional structure of this steel cord is the same as that shown in FIG.

  We prepared tires 53 / 80R63 for construction vehicles in which these prototype steel cords were applied to the belt, applied 150% of the normal load with the normal internal pressure specified by JATMA, and a drum diameter of 5 m and a speed of 8 km / h. An endurance test was carried out to go straight at high speed. In this endurance test, traveling was continued until failure, and the failure time was displayed as an index with Comparative Example 1 as 100. The larger the number, the longer the run and the higher the durability. In addition, the presence or absence of breakage of the steel cord was examined. The obtained results are shown in Table 1 below.

  As is clear from Table 1 above, it was confirmed that all the tires of the examples exhibited high tire durability without breaking the steel cord.

1 is a cross-sectional view of a steel cord of Example 1. FIG. It is sectional drawing of the steel cord of Example 2. 6 is a sectional view of a steel cord of Example 3. FIG. 6 is a cross-sectional view of a steel cord of Example 4. FIG. It is sectional drawing of the steel cord of the other suitable example of this invention. It is sectional drawing of the steel cord of the further another suitable example of this invention. 3 is a cross-sectional view of a steel cord of Comparative Example 1. FIG. 6 is a cross-sectional view of a steel cord of Comparative Example 2. FIG.

Explanation of symbols

1, 11, 21, 31, 41, 51 Core filament 2, 32, 52 Inner sheath filament 3, 33, 53 Outer sheath filament 4, 13, 23, 43 Spiral filament 12, 22, 42 Sheath filament

Claims (10)

  A rubber reinforcement characterized in that three or more core strands are twisted, and six or more sheath strands are twisted around the core strands, and the core strands and the sheath strands are twisted in the same direction. Steel cord.   The steel cord for rubber reinforcement according to claim 1, wherein the sheath strand has a layer twist structure of two or more layers.   The steel cord for rubber reinforcement according to claim 2, wherein the cord structure is a twisted structure of 3x (3 + 9 + 15) + 9x (3 + 9 + 15).   The steel cord for rubber reinforcement according to claim 2, wherein the cord structure is a twisted structure of 3x (3 + 9) + 9x (3 + 9).   The steel cord for rubber reinforcement according to claim 2, wherein the cord structure is a twisted structure of 3x (3 + 9) + 8x (3 + 9 + 15).   The steel cord for rubber reinforcement according to claim 2, wherein the cord structure is a twisted structure of 3x (3 + 9) + 6x (3 + 9 + 15).   The steel cord for rubber reinforcement according to claim 2, wherein the cord structure is a twisted structure of 3x (3 + 9) + 9x (3 + 9 + 15).   The steel cord for rubber reinforcement according to any one of claims 1 to 7, wherein a strand diameter of a filament constituting the strand is 0.14 mm or more and 0.36 mm or less. When the spiral radius formed by the core strand is r, the spiral pitch is p, the spiral radius of the sheath strand is R, and the spiral pitch is P,
The steel cord for rubber reinforcement according to any one of claims 1 to 8, which satisfies a relationship represented by 86 ° ≧ tan ⁻¹ (p / 2πr) ≧ tan ⁻¹ (P / 2πR) ≧ 74 °.   A pneumatic radial tire in which a carcass extending in a toroidal shape between a pair of bead portions is used as a skeleton, and a crown portion of the carcass is reinforced with a belt layer, and the cord constituting the carcass and / or the belt layer is defined in claim 1. A pneumatic radial tire, wherein the steel cord for rubber reinforcement according to any one of 9 is applied.

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