JP2008138311A - Rubber reinforcing steel cord and pneumatic radial tire using the steel cord - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber reinforcing steel cord capable of minimizing the cord diameter and suppressing a dimensional change while ensuring sufficient adhesiveness between the cord and the rubber and to provide a pneumatic radial tire using the steel cord. <P>SOLUTION: The steel cord 10 used in a belt layer 6 has a flat structure in which four side strands 12 having the same wire diameter as the core strand 11 are stranded and arranged on the outside of the one core wire 11 subjected to helical preforming and the circumscribed circle C11 of the core strand 11, and the circumscribed circle C12 of the side strands 12 form an elliptical shape, respectively. The twisting direction of the core strand 11 is the same as the strand direction of the side strands 12 and the preforming pitch of the core strand 11 is the same as the strand pitch of the side strands 12. The relationship between a minor axis ds of the circumscribed circle C11 of the core strand 11 and the wire diameter d satisfies ds>d. The minor axis Ds of the circumscribed circle C12 of the side strands 12 satisfies 2d<Ds<3d and the major axis Dl of the circumscribed circle C12 of the side strands 12 satisfies 2.9d<D1<3.7d. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a 1 + 4 rubber reinforcing steel cord and a pneumatic radial tire using the same. More specifically, the cord diameter is made as small as possible while ensuring sufficient adhesion between the cord and rubber. The present invention relates to a steel cord for reinforcing rubber that is made small and capable of suppressing dimensional changes, and a pneumatic radial tire using the same.

  In order to improve the rubber permeability of a steel cord having a 1 + N configuration in which N (for example, 3 to 8) side strands are twisted outside one core strand, the core strand is corrugated or It has been proposed to apply a spiral brazing or to flatten the cord in addition to the brazing of the core wire (see, for example, Patent Document 1). Further, from the viewpoint of ensuring rubber permeability, an open structure having a 1 × N configuration in which N strands are simultaneously twisted is also being studied.

  However, in the steel cord of the conventional 1 + N configuration, the core strand brazed inside the inscribed circle of the N side strands has an amplitude, so that the cord diameter tends to increase. As a result, When a sheet made of a composite of rubber and cord is formed, the sheet becomes thick, which is disadvantageous in terms of weight reduction.

On the other hand, the steel cord having an open structure of 1 × N configuration has good rubber permeability and can reduce the thickness of the composite of rubber and cord, but the elongation is large because of the open structure. Tend to be. Therefore, for example, when a steel cord having an open structure with a 1 × N configuration is used for the belt layer of a pneumatic radial tire, there is a drawback that the tire is likely to change in dimensions after traveling.
JP-A-8-325962

  SUMMARY OF THE INVENTION An object of the present invention is to provide a steel cord for rubber reinforcement capable of reducing a cord diameter as much as possible and suppressing a dimensional change while ensuring sufficient adhesion between the cord and rubber. It is to provide a pneumatic radial tire using the tire.

  In order to achieve the above object, the steel cord for reinforcing rubber according to the present invention comprises four side elements having the same wire diameter as that of the core element wire on the outer side of one core element wire that is spirally brazed. A steel cord having a flat structure in which wires are twisted and a circumscribed circle of the core strand and a circumscribed circle of the side strand are each elliptical, and the twist direction of the core strand is the side strand The brazing pitch of the core strand is the same as the twist pitch of the side strand, and the minor diameter ds of the circumscribed circle of the core strand is ds> d, the minor diameter Ds of the circumscribed circle of the side strand is 2d <Ds <3d with respect to the strand diameter d, and the major axis Dl of the circumscribed circle of the side strand is 2 with respect to the strand diameter d. .9d <Dl <3.7d.

  In order to achieve the above object, a pneumatic radial tire according to the present invention is a pneumatic radial tire using a steel cord as a belt layer, wherein the steel cord is a single core element with a helical brazing. Four side strands having the same strand diameter as the core strand are twisted and arranged outside the wire, and the circumcircle of the core strand and the circumcircle of the side strand each form an elliptical shape. Having a flat structure, the twisting direction of the core strand is the same as the twisting direction of the side strand, the brazing pitch of the core strand is the same as the twisting pitch of the side strand, The minor diameter ds of the circumscribed circle of the wire is ds> d with respect to the strand diameter d, the minor diameter Ds of the circumscribed circle of the side strand is 2d <Ds <3d with respect to the strand diameter d, and The major axis Dl of the circumscribed circle of the side strand is 2.9d <Dl <3.7d with respect to the strand diameter d. And it is characterized in and.

  In the present invention, in the steel cord having a flat structure of 1 + 4 configuration, the twisting direction of the core element wire is the same as the twisting direction of the side element wire, and the brazing pitch of the core element wire is the same as the twisting pitch of the side element wire, By defining the minor axis ds of the circumscribed circle of the core element wire, the minor axis Ds of the circumscribed circle of the side element line, and the major axis Dl of the circumscribed circle of the side element line, the core element wire and the side when flattened In order to reduce the contact with the strands and cause interruption of the core strands between the side strands, the rubber permeability similar to that of the 1 × 5 configuration steel cord is secured and the conventional 1 + 4 configuration steel is used. An increase in the cord diameter can be suppressed compared to the cord. Therefore, the cord diameter can be made as small as possible while sufficiently securing the adhesion of the steel cord to the rubber.

  Moreover, since the core strand is arrange | positioned inside a side strand, generation | occurrence | production of the elongation at the time of the low load which is a fault of the steel cord of 1x5 structure can be suppressed. Therefore, when the steel cord is used as a reinforcing material for rubber products, it is possible to suppress dimensional changes associated with the use of rubber products. In particular, when the steel cord is used for a belt layer of a pneumatic radial tire, a dimensional change (outer diameter growth) associated with running of the tire can be suppressed.

  In the present invention, the strand diameter of the core strand is preferably 0.20 mm to 0.45 mm. Such dimensions are suitable for the belt layer of a pneumatic radial tire. However, the steel cord for reinforcing rubber of the present invention can also be used as a reinforcing member for rubber products such as tire constituent members other than belt layers and conveyor belts.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention, where 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3, 3, and an end portion of the carcass layer 4 is folded around the bead core 5 from the inside of the tire to the outside. A plurality of belt layers 6 and 6 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6 and 6 are disposed such that the reinforcing cords are inclined with respect to the tire circumferential direction and the reinforcing cords cross each other between the layers. As the reinforcing cord of the belt layer 6, a steel cord having a 1 + 4 configuration is used. Furthermore, if necessary, a belt cover layer formed by winding a reinforcing cord in the tire circumferential direction may be disposed on the outer peripheral side of the belt layers 6 and 6.

  FIG. 1 illustrates a pneumatic radial tire for passenger cars or light trucks, but the present invention can also be applied to a pneumatic radial tire for trucks and buses as shown in FIG.

  FIG. 3 is a cross-sectional view showing a steel cord having a 1 + 4 configuration used for the belt layer of the pneumatic radial tire of the present invention. As shown in FIG. 3, the steel cord 10 includes four side strands 12 having the same strand diameter as the core strand 11 on the outside of one core strand 11 subjected to spiral brazing. The circumscribed circle C11 of the core element wire 11 and the circumscribed circle C12 of the side element wire 11 have a flat structure in which the core element wire 11 and the circumscribed circle C12 of the side element wire have an elliptical shape. The circumscribed circles C11 and C12 have the same major axis direction. As the belt cord, the strand diameters d of the core strand 11 and the side strand 12 are preferably in the range of 0.20 mm to 0.45 mm.

  In the steel cord 10, both the core strand 11 and the side strand 12 are spirally extended, but the twist direction of the core strand 11 is the same as the twist direction of the side strand 12. The brazing pitch of 11 is the same as the twist pitch of the side wires 12. Therefore, the contact between the core strand 11 and the side strand 12 when flattening is performed after twisting is reduced, and the interruption of the core strand 11 between the side strands 12 and 12 is likely to occur. That is, when the twisting direction of the core strand 11 is opposite to the twisting direction of the side strand 12, or when the brazing pitch of the core strand 11 is different from the twisting pitch of the side strand 12, The core strand 11 and the side strand 12 are in contact with each other to prevent interruption of the core strand 11 between the side strands 12 and 12.

  As described above, the contact between the core strand 11 and the side strand 12 is reduced, and the interruption of the core strand 11 between the side strands 12 and 12 is facilitated. While ensuring the same rubber permeability, an increase in the cord diameter can be suppressed as compared with a conventional steel cord having a 1 + 4 configuration. Therefore, the cord diameter can be made as small as possible while sufficiently securing the adhesion of the steel cord 10 to the rubber. Reducing the cord diameter is advantageous in reducing the weight of the tire by making the belt layer 6 thinner.

  Here, the short diameter ds of the circumscribed circle C11 of the core strand 11 is preferably in a relationship of ds> d with respect to the strand diameter d. That is, it is set as a three-dimensional brazing by setting ds> d. However, it is desirable to satisfy 2d> ds in order to reduce the weight of the composite of the cord and rubber.

  The minor diameter Ds of the circumscribed circle C12 of the side strand 12 is preferably in a relationship of 2d <Ds <3d with respect to the strand diameter d. That is, by setting Ds <3d, the core element wire 11 is in a state of being bitten between the adjacent side element wires 12 and 12. However, since it is necessary to arrange the core strand 11 inside the side strand 12, it is desirable to satisfy Ds> 2d.

  The major axis Dl of the circumscribed circle C12 of the side strand 12 is preferably in a relationship of 2.9d <Dl <3.7d with respect to the strand diameter d. That is, by setting Dl> 2.9d, it is possible to secure the space between the core strand 11 and the side strand 12 and improve the rubber permeability. However, it is desirable to satisfy Dl <3.7d in order to prevent the code from being broken.

  The ratio of the minor axis Ds to the major axis Dl of the circumscribed circle C12 of the side strand 12 is preferably in a relationship of Dl / Ds> 1.2. That is, a flat structure excellent in rubber permeability is defined by Dl / Ds> 1.2. However, it is desirable to satisfy Dl / Ds <1.7 in order to prevent the code from being broken.

  The steel cord 10 described above is embedded in the coated rubber so that the major axis direction of the belt layer 6 of the pneumatic radial tire coincides with the surface direction of the belt layer 6. In a pneumatic radial tire using such a steel cord 10 as the belt layer 6, the steel cord 10 has good adhesion to rubber, and the cord diameter (the short diameter Ds of the circumscribed circle C12 of the side strand 12) ) Is small, the belt layer 6 can be made thin to reduce the weight. Moreover, since the core strand 11 exists inside the side strand 12 of the steel cord 10, the dimensional change (outer diameter growth) accompanying a running | running | working of a tire can be suppressed.

  Four side strands having the same strand diameter as that of the core strand are twisted and arranged on the outside of one core strand (d = 0.25 mm) subjected to spiral brazing, and the core In the steel cord of 1 + 4 configuration in which the circumscribed circle of the element wire and the circumscribed circle of the side element wire are respectively elliptical, the twist direction of the core element wire is the same as the twist direction of the side element wire, and the brazing pitch of the core element wire is set Table 1 shows the strand diameter d, the major diameter dl and minor diameter ds of the circumscribed circle of the core strand, and the major axis Dl and minor diameter Ds of the circumscribed circle of the side strand as shown in Table 1. Various steel cords of Examples 1 to 3 and Comparative Examples 1 to 4 were prepared. For comparison, a steel cord having a 1 × 5 structure in which five strands (d = 0.25 mm) were twisted was prepared as Comparative Example 5.

  For the steel cords of Examples 1 to 3 and Comparative Examples 1 to 5, the rubber penetration rate and the initial elongation rate were evaluated by the following methods, and the results are also shown in Table 1.

Rubber penetration rate:
Each steel cord was covered with rubber and vulcanized in a state where a tensile load of 10 N per cord was applied, and then the steel cord was disassembled to obtain the rubber penetration rate (the degree of rubber penetration into the core). Here, “100%” means a state in which the rubber has completely penetrated to the core.

Initial elongation:
The initial elongation (%) of each steel cord was determined in accordance with JIS G3510. That is, the tensile load with respect to each steel cord was gradually increased, the elongation at that time was measured, the difference between the elongation at the time of 100 N and the elongation at the time of 5 N was obtained, and this was used as the initial elongation.

  As is apparent from Table 1, the steel cords of Examples 1 to 3 had a high rubber penetration rate, and the initial elongation was smaller than that of a steel cord having a 1 × 5 configuration (Comparative Example 5). .

  On the other hand, although the steel cord of Comparative Example 1 has no problem in physical properties, since Ds / d is too large, the gauge thickness becomes excessive when a composite of the cord and rubber is formed. The steel cord of Comparative Example 2 had ds / d of 1.0, and the core wire was two-dimensionally brazed, so that the rubber penetration rate was insufficient. The steel cord of Comparative Example 3 had an insufficient rubber penetration rate because Ds / d was too small. The steel cord of Comparative Example 4 had insufficient rubber penetration because Dl / d was too small.

  Next, four side strands having the same strand diameter as the core strand are twisted and arranged on the outside of one core strand (d = 0.37 mm) subjected to spiral brazing. In the steel cord of 1 + 4 configuration in which the circumscribed circle of the core element wire and the circumscribed circle of the side element wire each have an elliptical shape, the twist direction of the core element wire is made the same as the twist direction of the side element wire. The attached pitch is the same as the twisting pitch of the side strands, and the strand diameter d, the major axis dl and minor axis ds of the circumscribed circle of the core filament, and the major axis Dl and minor axis Ds of the circumscribed circle of the side strand are shown in Table 2. A steel cord of Example 4 set as described above was prepared. For comparison, a steel cord having a 1 × 5 configuration in which five strands (d = 0.37 mm) were twisted together was prepared as Comparative Example 6.

  With respect to the steel cords of Example 4 and Comparative Example 6, the rubber penetration rate and the initial elongation rate were evaluated by the method described above, and the results are also shown in Table 2.

  Further, pneumatic radial tires (tire size: 11R22.5) using the steel cords of Example 4 and Comparative Example 6 as belt layers were manufactured, and the outer diameter growth was evaluated. That is, after running an actual vehicle of 50,000 km, the outer diameter of the tire at the groove bottom was measured, and the amount of growth from the new article was obtained. The evaluation results are shown as an index with Comparative Example 6 as 100. A smaller index value means less outer diameter growth.

  As is apparent from Table 2, the steel cord of Example 4 had a high rubber penetration rate and a small initial elongation as compared with a steel cord having a 1 × 5 configuration (Comparative Example 6). Further, the pneumatic radial tire using the steel cord of Example 4 as the belt layer had little outer diameter growth accompanying traveling.

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention. It is a meridian half sectional view showing a pneumatic radial tire according to another embodiment of the present invention. It is sectional drawing which shows the steel cord of 1 + 4 structure used for the belt layer of the pneumatic radial tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 10 Steel cord 11 Core element wire 12 Side element line C11 Core element line circumscribed circle C12 Side element circumscribed circle

Claims (4)

  Four side strands having the same strand diameter as the core strand are twisted and arranged on the outside of one core strand subjected to spiral brazing, and a circumscribed circle of the core strand and In the steel cord having a flat structure in which the circumscribed circles of the side strands each have an elliptical shape, the twisting direction of the core strands is the same as the twisting direction of the side strands, and the brazing pitch of the core strands is It is the same as the twisting pitch of the side strands, the minor diameter ds of the circumscribed circle of the core strand is ds> d with respect to the strand diameter d, and the minor diameter Ds of the circumscribed circle of the side strand is a prime Rubber reinforcement, wherein 2d <Ds <3d with respect to the wire diameter d, and the long diameter Dl of the circumscribed circle of the side wire is 2.9d <Dl <3.7d with respect to the wire diameter d Steel cord.   The steel cord for rubber reinforcement according to claim 1, wherein a wire diameter of the core wire is 0.20 mm to 0.45 mm.   In a pneumatic radial tire using a steel cord as a belt layer, the steel cord has four strands having the same strand diameter as the core strand on the outer side of one core strand subjected to spiral brazing. Side strands are twisted and arranged, and a circumscribed circle of the core strand and a circumscribed circle of the side strand have an elliptical shape, and the twist direction of the core strand is the side strand The brazing pitch of the core strand is the same as the twist pitch of the side strand, and the minor diameter ds of the circumscribed circle of the core strand is ds> d, the minor diameter Ds of the circumscribed circle of the side strand is 2d <Ds <3d with respect to the strand diameter d, and the major axis Dl of the circumscribed circle of the side strand is 2 with respect to the strand diameter d. A pneumatic radial tire characterized in that .9d <Dl <3.7d.   The pneumatic radial tire according to claim 3, wherein a wire diameter of the core wire is 0.20 mm to 0.45 mm.

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