JP4904912B2 - Steel cord for rubber reinforcement and pneumatic radial tire using the same - Google Patents

Description

  The present invention relates to a steel cord for rubber reinforcement having a 1 + N structure and a pneumatic radial tire using the same. More specifically, the present invention secures sufficient adhesion between the cord and rubber and reduces contact between strands. In addition, the present invention relates to a rubber-reinforcing steel cord 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 conventional steel cord of 1 + N configuration, the contact between the core strand and the side strand is liable to occur when the flattening process is performed, so that the cord is likely to be damaged due to the contact between the strands. There's a problem. Further, when the strands are in contact with each other, the cord diameter increases, and 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, a steel cord having an open structure with a 1 × N configuration has good rubber permeability and is unlikely to cause contact between strands, but tends to increase in elongation due to the open structure. 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

  An object of the present invention is to secure a sufficient adhesion between a cord and rubber, reduce the contact between the strands, and suppress a dimensional change, and a rubber cord for reinforcing the same The object is to provide a used pneumatic radial tire.

  In order to achieve the above object, the steel cord for reinforcing rubber according to the present invention is formed by twisting N (N = 3 to 8) side strands on the outside of one core strand which is spirally brazed. And a steel cord having a flat structure in which a circumscribed circle of the core element wire and a circumscribed circle of the side element wire each have an elliptical shape, the twist direction of the core element wire is the twist direction of the side element wire It is the same, The brazing pitch Pc of the said core strand is larger than the twist pitch Ps of the said side strand, It is characterized by the above-mentioned.

  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. N side strands (N = 3 to 8) are twisted and arranged outside the wire, and the circumscribed circle of the core strand and the circumscribed circle of the side strand have an oblate shape, respectively. The twist direction of the core strand is the same as the twist direction of the side strand, and the brazing pitch Pc of the core strand is larger than the twist pitch Ps of the side strand. is there.

  In the present invention, in the steel cord having a flat structure of 1 + N configuration, the twisting direction of the core element wire is made the same as the twisting direction of the side element wire, and the brazing pitch Pc of the core element wire is larger than the twist pitch Ps of the side element wire. By enlarging, while ensuring the same rubber permeability as that of the steel cord having the 1 × N configuration, it is possible to reduce the contact between the core strand and the side strand when the flattening process is performed. Accordingly, it is possible to prevent the cord from being damaged due to the contact between the strands while sufficiently securing the adhesiveness of the steel cord to the rubber, and to make the cord diameter as small as possible.

  Moreover, since the core strand is arrange | positioned inside the side strand, generation | occurrence | production of the elongation at the time of the low load which is a fault of the steel cord of a 1xN 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, it is preferable that the brazing pitch Pc of the core strand satisfies the relationship of Pc = n × Ps (n: an integer of 2 or more) with respect to the twist pitch Ps of the side strand. When the brazing pitch Pc of the core strands and the twist pitch Ps of the side strands satisfy the above relationship, the frequency with which the core strands and the side strands overlap when flattening processing is reduced, and the flapping between the strands is reduced. Can be effectively prevented.

  The strand diameter of the core strand is preferably 0.20 mm to 0.45 mm. Moreover, it is preferable that a core strand and a side strand have the same strand diameter. 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 + 5 configuration is used. Further, 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 1 + 5 steel cord used for the belt layer of the pneumatic radial tire of the present invention, and FIG. 4 shows a core wire and side strands included in the steel cord of FIG. FIG. As shown in FIG. 3, the steel cord 10 has five 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, as shown in FIG. 4, the core strand 11 and the side strand 12 both extend spirally, but the twist direction of the core strand 11 is the twist direction of the side strand 12. It is the same, and the brazing pitch Pc of the core strand 11 is larger than the twist pitch Ps of the side strand 12. Therefore, the contact between the core strand 11 and the side strand 12 is reduced when flattening is performed after twisting. That is, when the twist direction of the core strand 11 is opposite to the twist direction of the side strand 12, or when the brazing pitch Pc of the core strand 11 is smaller than the twist pitch Ps of the side strand 12, flattening is performed. When processed, the core strand 11 and the side strand 12 are likely to contact each other.

  In particular, it is preferable that the brazing pitch Pc of the core strand 11 satisfies the relationship of Pc = n × Ps (n: an integer of 2 or more) with respect to the twist pitch Ps of the side strand 12. In this case, when the steel cord 10 is flattened, the frequency with which the core strand 11 and the side strand 12 overlap is reduced, and fretting of the strands can be effectively prevented.

  According to the steel cord 10 described above, the rubber permeability similar to that of the steel cord having the 1 × 6 configuration can be secured, and at the same time, the contact between the core strand 11 and the side strand 12 can be reduced. Therefore, while ensuring sufficient adhesion to rubber, it is possible to prevent cord damage due to contact between the strands and to make the cord diameter as small as possible compared to the conventional steel cord of 1 + 5 configuration. Become. 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 2.0d> 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 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 wire 11 inside the side wire 12, it is desirable to satisfy 2.5d <Ds.

  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 1.6> Dl / Ds 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.

  In the above-described embodiment, the case of a steel cord having a 1 + 5 configuration has been described. However, the number of side strands can be arbitrarily selected from a range of 3 to 8. In either case, it is possible to obtain an effect of ensuring sufficient adhesion between the cord and the rubber, reducing contact between the strands, and suppressing dimensional change.

  Five side strands are twisted and arranged on the outside of one core strand that has been spirally brazed, and the circumscribed circle of the core strand and the circumscribed circle of the side strand are each elliptical. In the steel cord of 1 + 5 configuration, the twisting direction of the core strand is made the same as the twisting direction of the side strand, the brazing pitch Pc of the core strand is made larger than the twist pitch Ps of the side strand, Steel cords of Examples 1 to 4 in which the ratio (Pc / Ps) of the attaching pitch Pc and the twisted pitch Ps of the side strands was varied as shown in Table 1 were prepared. For comparison, as Comparative Example 1, a steel cord having a 1 + 5 configuration in which the twisting direction of the core strand was reversed from the twisting direction of the side strand was prepared.

  About the steel cords of Examples 1 to 4 and Comparative Example 1, 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 was applied per cord, and then the steel 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 load 100N and the elongation at the time of load 5N was determined, and this was used as the initial elongation.

In addition, pneumatic radial tires (tire size: 11R22.5) using the steel cords of Examples 1 to 4 and Comparative Example 1 as the belt layer were manufactured, and after the drum test of 20,000 km, the steel of the belt layer was formed from the tire. The cord was taken out, the core strand and the side strand were separated, and the amount of scratches generated on the surface of these strands was examined. The evaluation results are shown as “None” when there is no scratch, “Fine” when a small amount of scratch is observed, and “Low” when a small amount of scratch is observed, and a large amount of scratch is observed. Cases are indicated by "many".

  As is apparent from Table 1, all of the steel cords of Examples 1 to 4 had a high rubber penetration rate. Further, in the pneumatic radial tire using the steel cord of Examples 1 to 4 as the belt layer, the steel cord in which the twisting direction of the core strand is reversed from the twisting direction of the side strand (Comparative Example 1). ), The cord surface scratches after the drum test were small.

  Next, 5 side strands are twisted and arranged on the outside of one core strand that has been spirally brazed, and the circumscribed circle of the core strand and the circumscribed circle of the side strand are each elliptical. In the steel cord of 1 + 5 configuration having a shape, the twist direction of the core strand is made the same as the twist direction of the side strand, and the brazing pitch Pc of the core strand is made larger than the twist pitch Ps of the side strand, A steel cord of Example 5 was prepared in which the ratio (Pc / Ps) between the wire brazing pitch Pc and the twisted pitch Ps of the side strands was set as shown in Table 2. For comparison, the steel cord of Comparative Example 2 in which the brazing pitch Pc of the core strands is smaller than the twist pitch Ps of the side strands, and the steel cord of Comparative Example 3 in which the core strands are brazed with plane waves A steel cord of Comparative Example 4 having a 1 × 6 configuration obtained by twisting six strands was prepared.

  With respect to the steel cords of Example 5 and Comparative Examples 2 to 4, 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.

  In addition, a pneumatic radial tire (tire size: 11R22.5) using the steel cord of Example 5 and Comparative Examples 2 to 4 as a belt layer was manufactured, and after running an actual vehicle of 50,000 km, the steel of the belt layer was formed from the tire. The cord was taken out, the core strand and the side strand were separated, and the amount of scratches generated on the surface of these strands was examined. The evaluation results are shown as “None” when there is no scratch, “Fine” when a small amount of scratch is observed, and “Low” when a small amount of scratch is observed, and a large amount of scratch is observed. Cases are indicated by "many".

Further, pneumatic radial tires (tire size: 11R22.5) using the steel cords of Example 5 and Comparative Examples 2 to 4 as belt layers were manufactured, and the outer diameter growth was evaluated. That is, after running an actual vehicle of 50,000 km, the tire outer diameter 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 4 as 100. A smaller index value means less outer diameter growth.

  As is apparent from Table 2, the steel cord of Example 5 had a high rubber penetration rate, and the initial elongation was smaller than that of a steel cord having a 1 × 6 configuration (Comparative Example 4). In addition, the pneumatic radial tire using the steel cord of Example 5 as the belt layer has little outer diameter growth during running, and less cord surface scratches after running the actual vehicle.

  On the other hand, in the steel cord of Comparative Example 2, the brazing pitch Pc of the core strands was made smaller than the twisting pitch Ps of the side strands, but the outer diameter increased with running. Although the steel cord of Comparative Example 3 was obtained by applying a plane wave brazing to the core strand, there were many cord surface scratches after running the actual vehicle.

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 + 5 structure used for the belt layer of the pneumatic radial tire of this invention. It is a top view which extracts and shows the core strand and the side strand contained in the steel cord of FIG.

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 (8)

  N side strands (N = 3 to 8) are twisted and arranged on the outside of one core strand subjected to spiral brazing, and a circumscribed circle of the core strand and the side strand In the steel cord having a flat structure in which each circumscribed circle has an elliptical shape, the twist direction of the core strand is the same as the twist direction of the side strand, and the brazing pitch Pc of the core strand is the side strand A steel cord for reinforcing rubber characterized by being larger than the twisted pitch Ps of the wire.   The brazing pitch Pc of the core strand satisfies the relationship of Pc = n × Ps (n: an integer of 2 or more) with respect to the twist pitch Ps of the side strands. Steel cord for rubber reinforcement.   The steel cord for rubber reinforcement according to claim 1 or 2, wherein a strand diameter of the core strand is 0.20 mm to 0.45 mm.   The steel cord for rubber reinforcement according to any one of claims 1 to 3, wherein the core strand and the side strand have the same strand diameter.   In a pneumatic radial tire using a steel cord for a belt layer, the steel cord has N (N = 3 to 8) side strands on the outside of one core strand that has been spirally brazed. The core element wire has a flat structure in which a circumscribed circle of the core element wire and a circumscribed circle of the side element wire each have an elliptical shape, and the twist direction of the core element wire is the twist direction of the side element wire The pneumatic radial tire is the same, and the brazing pitch Pc of the core strand is larger than the twist pitch Ps of the side strand.   The brazing pitch Pc of the core strand satisfies the relationship of Pc = n × Ps (n: an integer of 2 or more) with respect to the twist pitch Ps of the side strands. Pneumatic radial tire. The pneumatic radial tire according to claim 5 or 6 , wherein a strand diameter of the core strand is 0.20 mm to 0.45 mm. The pneumatic radial tire according to any one of claims 5 to 7, wherein the core strand and the side strand have the same strand diameter.

Images