JP4802943B2 - Steel cord for rubber reinforcement and pneumatic radial tire using the same - Google Patents

Description

  The present invention relates to a 1 + 5 rubber reinforcing steel cord and a pneumatic radial tire using the same, and more particularly, a core wire and a side wire while ensuring sufficient adhesion between the cord and rubber. The present invention relates to a rubber cord for reinforcing steel capable of preventing contact with the tire and suppressing dimensional change, 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 unavoidable at the time of flattening, so the cord diameter tends to increase, and as a result, the composite of rubber and cord When a sheet made of a body is formed, the sheet becomes thick, which is disadvantageous in terms of weight reduction. Also, when the core strand and the side strand are in contact, when the steel cord is used as a rubber reinforcing material, scratches are formed on the surface of the strand due to rubbing between the strands, which is preferable from the viewpoint of durability. Absent.

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

  An object of the present invention is for rubber reinforcement capable of avoiding contact between a core element wire and a side element wire and suppressing a dimensional change while ensuring sufficient adhesion between a cord and rubber. The object is to provide a steel cord and a pneumatic radial tire using the same.

  In order to achieve the above object, the steel cord for reinforcing rubber according to the present invention has five side elements having the same wire diameter as the core wire on the outer side of one core wire subjected to spiral brazing. And a circumscribed circle of the core strand and a circumscribed circle of the side strand have an oblate shape, and the major axis Dl and minor axis Ds of the circumscribed circle of the side strand In the steel cord having a ratio of 1.1 ≦ Dl / Ds ≦ 2.0, the twist direction of the core strand is the same as the twist direction of the side strand, and the twist pitch of the side strand Is substantially 5 times the brazing pitch of the core strand, and the center point of the core strand is substantially 1/5 times the diameter of the circumscribed circle of the side strand It is characterized by being on an elliptical orbit having dimensions.

  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. Five side strands having the same strand diameter as that of the core strand are twisted and arranged on the outside of the strand, and the circumcircle of the core strand and the circumcircle of the side strand each form an elliptical shape. A steel cord having a flat structure, wherein a ratio of a major axis Dl and a minor axis Ds of a circumscribed circle of the side strands is in a range of 1.1 ≦ Dl / Ds ≦ 2.0, The twisting direction is the same as the twisting direction of the side strands, the twisting pitch of the side strands is substantially five times the brazing pitch of the core strands, and the center point of the core strands is An ellipse having a diameter that is substantially 1/5 times the diameter of the circumscribed circle of the side element wire. It is characterized in that in orbit.

  In the present invention, in the steel cord having a flat structure of 1 + 5 configuration, the twisting direction of the core strand is made the same as the twisting direction of the side strand, and the twisting pitch of the side strand is substantially equal to the brazing pitch of the core strand. The center point of the core wire is arranged on an elliptical orbit having a diameter dimension substantially 1/5 times the diameter dimension of the circumscribed circle of the side element wire, thereby flattening processing. When performing, the interruption of the core strand between the side strands can be generated, and the contact between the core strand and the side strand can be reduced. As a result, the same rubber penetration as the steel cord of 1 × 6 configuration is secured, and the diameter of the cord is increased compared with the conventional steel cord of 1 + 5 configuration while ensuring sufficient adhesion between the cord and rubber. In addition, it is possible to prevent rubbing between the strands.

  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 1x6 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 above-described twisted structure, the twisting pitch of the side strands is ideally 5 times the brazing pitch of the core strands, but manufacturing errors are allowed. The allowable error range of the twisting pitch of the side strands is 95% to 105%, which is five times the brazing pitch of the core strands. On the other hand, it is ideal that the center point of the core wire is on an elliptical orbit having a diameter of 1/5 times the diameter of the circumscribed circle of the side wire, but manufacturing errors are allowed. . The allowable error range of the diameter of the elliptical orbit is 95% to 105% of the value of 1/5 times the diameter of the circumscribed circle of the side strand.

  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 + 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 plan view showing a steel cord having a 1 + 5 configuration used for the belt layer of the pneumatic radial tire of the present invention, and FIG. 4 is a sectional view thereof. FIG. 3 shows a state in which the strands are drawn thinly to facilitate understanding of the strand arrangement. As shown in FIGS. 3 and 4, the steel cord 10 includes five side elements having the same wire diameter as the core wire 11 on the outside of one core wire 11 subjected to spiral brazing. The wires 12 are twisted and arranged, and the circumscribed circle C11 of the core element wire 11 and the circumscribed circle C12 of the side element wires each have a flat structure in which each has 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, the core strand 11 and the side strand 12 both extend spirally, but the twist direction of the core strand 11 is the same as the twist direction of the side strand 12, and the side strand The twisting pitch P12 of 12 is about 5 times the brazing pitch P11 of the core strand 11, and the center point O of the core strand 11 is about 1 / diameter of the diameter of the circumscribed circle C12 of the side strand 12. It exists on an elliptical orbit CO having a diameter of 5 times. That is, the elliptical trajectory CO is similar to the circumscribed circle C12 of the side element wire 12, and the minor axis ds and the major axis dl thereof are about 1/5 times the minor axis Ds and the major axis Dl of the circumscribed circle C12 of the side element line 12, respectively. It is.

  In the steel cord 10, the contact between the core strand 11 and the side strand 12 when flattening is performed after twisting is reduced, and an interruption of the core strand 11 between the side strands 12 and 12 occurs. It becomes easy. This is based on the ratio between the twisting pitch P12 of the side strands 12 and the brazing pitch P11 of the core strands 11 and the amplitude of the core strands 11 defined by the elliptical orbit CO, as shown in FIG. This is because the core strand 11 is arranged in parallel to the side strand 12. In such an interrupt structure, when the twist direction of the core strand 11 is opposite to the twist direction of the side strand 12, or the brazing pitch P11 of the core strand 11 and the twist pitch P12 of the side strand 12 are It does not occur when the above relationship is not satisfied.

  The above configuration ensures the same rubber permeability as the steel cord of 1 × 6 configuration and increases the diameter of the cord compared to the conventional 1 + 5 configuration steel cord while ensuring sufficient adhesion of the steel cord 10 to rubber. In addition, it is possible to prevent rubbing between the strands.

  Here, the ratio between the minor axis Ds and the major axis Dl of the circumscribed circle C12 of the side strand 12 is set to a relationship of 1.1 ≦ Dl / Ds ≦ 2.0. That is, a flat structure excellent in rubber permeability is defined by Dl / Ds ≧ 1.1. However, it is assumed that the relationship of Dl / Ds ≦ 2.0 is satisfied in order to prevent the code from being broken.

  The minor diameter Ds of the circumscribed circle C12 of the side strand 12 is preferably in a relationship of 2.5d <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 major axis Dl of the circumscribed circle C12 of the side strand 12 is preferably in a relationship of 3.6d <Dl <3.9d with respect to the strand diameter d. That is, by setting Dl> 3.6d, the space between the core strand 11 and the side strand 12 can be secured and the rubber permeability can be improved. However, it is desirable to satisfy 3.9d> Dl in order to prevent the code from breaking.

  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 thinned to reduce the weight, and since the rubbing of the strands hardly occurs, the durability is good. 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.

  Five side strands having the same strand diameter as 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 + 5 configuration in which the circumscribed circle of the element wire and the circumscribed circle of the side element wire each form an ellipse shape, the brazing structure of the core element wire, the brazing pitch P11 of the core element wire, the twist pitch P12 of the side element wire, The ratio between the brazing pitch P11 of the core strand and the twist pitch P12 of the side strand, the ratio of the major axis dl of the elliptical orbit passing through the center point of the core strand to the major axis Dl of the circumscribed circle of the side strand, side strand Steel cords of Examples 1 to 3 and Comparative Examples 1 to 3 in which the ratio between the major axis Dl and the minor axis Ds of the circumscribed circle was varied as shown in Table 1 were prepared. For comparison, as Comparative Example 4, a steel cord having a 1 × 6 configuration in which six strands (d = 0.25 mm) were twisted was prepared. Regarding the brazing structure of the core wire in Table 1, “same spiral” means that the twist direction of the core wire subjected to the spiral brazing is the same as the twist direction of the side strand, "Means that the twisted direction of the core wire subjected to the helical brazing is opposite to the twist direction of the side strand.

  About the steel cords of Examples 1 to 3 and Comparative Examples 1 to 4, 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 load 100N and the elongation at the time of load 5N was determined, and this was used as the initial elongation.

  Also, pneumatic radial tires (tire size: 265 / 70R15) using the steel cords of Examples 1 to 3 and Comparative Examples 1 to 4 as the belt layer were manufactured, and the wire surface scratches on the steel cord after running the drum were made. evaluated. That is, after running indoor durability of 20,000 km, the steel cord was taken out from the belt layer of the tire, the wire was disassembled, and the number of surface scratches was measured. The evaluation results indicate “no” when there is no surface damage on the core wire, and “fine” when the number of core surface scratches per cord length for 20 pitches of the side wires is less than 250. The case of 250 to 300 was indicated by “small”, and the case of more than 300 was indicated by “many”.

  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 × 6 configuration (Comparative Example 4). . Further, the pneumatic radial tire using the steel cords of Examples 1 to 3 as the belt layer had few surface scratches on the steel cord after running the drum.

  On the other hand, in the pneumatic radial tire using the steel cords of Comparative Examples 1 to 3 as the belt layer, the wire surface scratches of the steel cord after running the drum were larger than those of Examples 1 to 3. Further, the steel cord of Comparative Example 3 also had an insufficient rubber penetration rate.

  Next, five 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 = 0.37 mm) subjected to spiral brazing. In addition, in the steel cord of 1 + 5 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 core element brazing structure, the core element brazing pitch P11, and the side element strand twisting The pitch P12, the ratio of the brazing pitch P11 of the core wire to the twisted pitch P12 of the side strand, the ratio of the major axis dl of the elliptical orbit passing through the center point of the core strand to the major axis Dl of the circumscribed circle of the side strand, Steel cords of Example 4 and Comparative Examples 5 to 6 in which the ratio between the major axis Dl and the minor axis Ds of the circumscribed circle of the side strands was set as shown in Table 2 were prepared. For comparison, as Comparative Example 7, a steel cord having a 1 × 6 configuration in which six strands (d = 0.37 mm) were twisted was prepared. With respect to the brazing structure of the core wire in Table 2, “same spiral” means that the twist direction of the core wire subjected to the spiral brazing is the same as the twist direction of the side strand, and “plane wave” Means that the core wire is brazed with a plane wave.

  With respect to the steel cords of Example 4 and Comparative Examples 5 to 7, 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.

  Also, a pneumatic radial tire (tire size: 11R22.5) using the steel cord of Example 4 and Comparative Examples 5 to 7 as the belt layer was manufactured, and the outer diameter growth after running the actual vehicle and the surface of the strand of the steel cord The wound was evaluated. That is, after running on a field of 50,000 km, the tire outer diameter at the bottom of the groove was measured, and the amount of growth from when it was new was determined. The evaluation results are shown as an index with Comparative Example 7 as 100. A smaller index value means less outer diameter growth. Further, the steel cord was taken out from the belt layer of the tire after running, the strands were disassembled, and the number of surface scratches was measured. The evaluation results indicate “no” when there is no surface damage on the core wire, and “fine” when the number of core surface scratches per cord length for 20 pitches of the side wires is less than 250. The case of 250 to 300 was indicated by “small”, and the case of more than 300 was indicated by “many”.

  As can be seen from Table 2, the steel cord of Example 4 had a high rubber penetration rate and a smaller initial elongation than the 1 × 6 steel cord (Comparative Example 7). In addition, the pneumatic radial tire using the steel cord of Example 4 as the belt layer had little growth of the outer diameter during running, and there was little surface damage on the steel cord after running the actual vehicle.

  On the other hand, in the pneumatic radial tire using the steel cords of Comparative Examples 5 to 6 as the belt layer, the wire surface scratches on the steel cord after running on the actual vehicle were larger than those in Example 4. Further, the steel cord of Comparative Example 6 also had an insufficient rubber penetration rate.

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 a top view which shows the steel cord of 1 + 5 structure used for the belt layer of the pneumatic radial tire of this invention. It is sectional drawing of the steel cord shown in 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 strand C11 Core element circumscribed circle C12 Side element circumscribed circle CO Elliptical track

Claims (4)

  Five 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 The circumscribed circle of the side element wire has an oblate structure, and the ratio of the major axis Dl to the minor axis Ds of the circumscribed circle of the side element line is 1.1 ≦ Dl / Ds ≦ 2.0. The twisted direction of the core strand is the same as the twist direction of the side strand, and the twist pitch of the side strand is substantially five times the brazing pitch of the core strand. And the center point of the core wire is on an elliptical orbit having a diameter dimension substantially 1/5 times the diameter dimension of the circumscribed circle of the side element wire. code.   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 for a belt layer, the steel cord has five 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 the circumscribed circle of the core strands and the circumscribed circle of the side strands have an elliptical structure, respectively. A steel cord having a ratio with the diameter Ds in a range of 1.1 ≦ Dl / Ds ≦ 2.0, wherein the twist direction of the core strand is the same as the twist direction of the side strand, The twisting pitch of the wire is substantially 5 times the brazing pitch of the core strand, and the center point of the core strand is substantially 1 / diameter of the diameter of the circumscribed circle of the side strand. A pneumatic radial tire characterized by being on an elliptical track having a diameter five times as large.   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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