JP2009114592A - Steel cord for rubber reinforcement and pneumatic radial tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel cord capable of avoiding contact of a core wire with side wires and suppressing dimensional change, and to provide a pneumatic radial tire using the steel cord. <P>SOLUTION: The steel cord 10 for belt layers is obtained by twisting six side wires 12 on the outside of one core wire 11 subjected to helical preformation, and the circumscribed circle C11 of the core wire 11 and the circumscribed circle C12 of the side wires 12 form elliptical shapes. The ratio of the major axis Dl to the minor axis Ds of the circumscribed circle C12 of the side wires 12 is 1.1≤Dl/Ds≤2.0. The core wire 11 is thinner than the side wires 12 and the torsional direction of the core wire 11 is the same as the twist direction of the side wires 12. The twist pitch P12 of the side wires 12 is three times the preformed pitch 11 of the core wire 11. When a first elliptical track C1 having a diameter dimension of 1/3 of the diameter dimension of the circumscribed circle C12 of the side wires 12 and a second elliptical track C2 circumscribed with an imaginary circle in moving the center O of the imaginary circle having the same diameter as the side wires 12 on the first elliptical track C1 are assumed, the core wire 11 is within the second elliptical track C2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a 1 + 6 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, a steel cord for reinforcing rubber according to the present invention has six side strands twisted and arranged on the outside of one core strand subjected to helical brazing, and the core The circumscribed circle of the element wire and the circumscribed circle of the side element wire each have an elliptical 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 In the steel cord in the range of ≦ 2.0, the core strand is thinner than the side strand, the twist direction of the core strand is the same as the twist direction of the side strand, and the side The strand pitch of the strand is substantially 3 times the brazing pitch of the core strand, and has a diameter dimension substantially 1/3 times the diameter of the circumscribed circle of the side strand. Outside the virtual circle when the center of the virtual circle having the same diameter as the side strand is moved on the first elliptical track and the first elliptical track When assuming the second elliptical orbits, in which the core wire is characterized in that positioned in the second elliptical orbits.

  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. 6 side strands are twisted and arranged on the outside of the wire, and the circumscribed circle of the core strand and the circumscribed circle of the side strand have an elliptical shape, respectively, A steel cord having a ratio of a major axis Dl to a minor axis Ds of a circumscribed circle in a range of 1.1 ≦ Dl / Ds ≦ 2.0, wherein the core strand is thinner than the side strand, The twist direction of the core strand is the same as the twist direction of the side strand, the twist pitch of the side strand is substantially three times the brazing pitch of the core strand, The first ellipse having a diameter that is substantially 1/3 times the diameter of the circumscribed circle of the line. Assuming a second elliptical orbit circumscribing the virtual circle when the center of the virtual circle having the same diameter as the side elemental wire is moved on the orbit and the first elliptical orbit, the core element wire is the second elliptical orbit. It is located in an elliptical orbit.

  In the present invention, in the steel cord having a flat structure of 1 + 6 configuration, the core element wire is thinner than the side element wire, the twist direction of the core element wire is the same as the twist direction of the side element wire, and the twist of the side element wire A first elliptical orbit having a pitch substantially three times as large as the brazing pitch of the core wire and having a diameter of substantially 1/3 times the diameter of the circumscribed circle of the side strand; When the second elliptical orbit circumscribing the virtual circle when the center of the virtual circle having the same diameter as the side element is moved on one elliptical orbit is assumed, the core elemental wire is positioned in the second elliptical orbit. By doing so, when performing the flattening process, 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. This ensures the same rubber permeability as the 1x6 steel cord and increases the cord diameter compared to the conventional 1 + 6 steel cord 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, it is ideal that the twisting pitch of the side strands is three 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 three times the brazing pitch of the core strands.

  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 + 6 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 1 + 6 steel cord used for the belt layer of the pneumatic radial tire of the present invention, and FIG. 4 is a sectional view thereof. Note that FIG. 3 shows a state in which all the strands are thinly drawn with the same thickness in order to facilitate understanding of the strand arrangement. As shown in FIG. 3 and FIG. 4, the steel cord 10 is formed by twisting six side strands 12 on the outside of one core strand 11 subjected to spiral brazing, The circumscribed circle C11 of the line 11 and the circumscribed circle C12 of the side strands each have a flat structure that is elliptical. The circumscribed circles C11 and C12 have the same major axis direction. The core strand 11 is thinner than the side strand 12. As the belt cord, the strand diameter dc of the core strand 11 is preferably in the range of 0.10 mm to 0.45 mm, and the strand diameter ds of the side strand 12 is 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 3 times the brazing pitch P11 of the core strand 11. Here, a virtual circle having the same diameter as that of the side strand 12 on the first elliptical orbit C1 and the first elliptical orbit C1 having a diameter of about １ ／ times the diameter of the circumscribed circle C12 of the side strand 12. Assuming a second elliptical orbit C2 circumscribing the virtual circle 13 when the center O of 13 is moved, the core wire 11 is located inside the second elliptical orbit C2. The first elliptical orbit C1 is similar to the circumscribed circle C12 of the side element wire 12, and the minor axis and major axis thereof are about 1/3 times the minor axis Ds and major axis Dl of the circumscribed circle C12 of the side element wire 12, respectively. . FIG. 4 shows a case where the circumscribed circle C11 of the core element wire 11 and the second elliptical orbit C2 coincide with each other, but the circumscribed circle C11 of the core element wire 11 has a diameter smaller than that of the second elliptical orbit C2. It may be a thing.

  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 second elliptical orbit C2. This is because the core strands 11 are arranged so as to be nearly parallel to the side strands 12 as shown. 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 cord diameter compared to the conventional 1 + 6 configuration steel cord while ensuring sufficient adhesion of the steel cord 10 to the 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 element wire 12 is preferably in a relationship of 2.5ds <Ds <3ds with respect to the element wire diameter ds of the side element wire 12. That is, by setting Ds <3ds, 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 2.5ds <Ds.

  The major axis Dl of the circumscribed circle C12 of the side strand 12 is preferably in a relationship of 3.6ds <Dl <3.9ds with respect to the strand diameter ds of the side strand 12. That is, by setting Dl> 3.6 ds, 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 3.9 ds> Dl in order to prevent the code from being broken.

  The short diameter Dis of the circumscribed circle C11 of the core element wire 11 is preferably 1.0 ds <Dis with respect to the element wire diameter ds of the side element wire 12. On the other hand, the long diameter Dil of the circumscribed circle C11 of the core strand 11 is preferably in a relationship of Dil> 1.1ds with respect to the strand diameter ds of the side strand 12. That is, by satisfying 1.0 ds <Dis and Dil> 1.1 ds, rubber permeability into the cord can be improved.

  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.

  Six side strands (ds = 0.25 mm) are twisted and arranged on the outside of one core strand subjected to spiral brazing, and the circumscribed circle of the core strand and the circumscribing of the side strand In a steel cord having a 1 + 6 configuration in which each circle has an elliptical shape, a side wire strand diameter ds, a side strand twist pitch P12, a core strand strand diameter dc, a core strand brazing pitch P11, a core The ratio of the major axis Dil of the circumscribed circle of the core element wire to the major axis of the second elliptical orbit (C2) obtained from the brazing structure of the element wire, the diameter of the circumscribed circle of the side element wire, and the element wire diameter of the side element wire, The ratio of the minor axis Dis of the circumscribed circle of the core element wire to the minor axis of the two elliptical orbit (C2), the ratio of the major axis Dl and the minor axis Ds of the circumscribed circle of the side element wire, the brazing pitch P11 and the side of the core element wire Steel cords of Examples 1 to 4 and Comparative Examples 1 to 6 in which the ratios of the strands to the strand pitch P12 are varied as shown in Table 1 It was prepared. For comparison, a steel cord having a 1 × 6 configuration formed by twisting six strands (ds = 0.25 mm) was prepared as Comparative Example 7. 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 4 and Comparative Examples 1 to 7, 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.

  In addition, pneumatic radial tires (tire size: 265 / 70R15) using the steel cords of Examples 1 to 4 and Comparative Examples 1 to 7 as the belt layer were manufactured, and the wire surface scratches on the steel cord after running the drum 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 clear from Table 1, the steel cords of Examples 1 to 4 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 7). . Moreover, the pneumatic radial tire using the steel cords of Examples 1 to 4 as the belt layer had slight surface damage 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 6 as the belt layer, the wire surface scratches of the steel cord after running the drum were larger than those of Examples 1 to 4. Further, the steel cords of Comparative Examples 3 and 6 also had insufficient rubber penetration.

  Next, six side strands (ds = 0.37 mm) are twisted and arranged on the outside of one core strand subjected to spiral brazing, and the circumscribed circle and side segments of the core strand are arranged. In a steel cord having a 1 + 6 configuration in which the circumscribed circles of the wires each have an elliptical shape, the strand diameter ds of the side strands, the strand pitch P12 of the side strands, the strand diameter dc of the core strands, and the brazing pitch of the core strands P11, the core element brazing structure, the diameter of the circumscribed circle of the side element wire and the major axis of the circumscribed circle of the core element wire with respect to the major axis of the second elliptical orbit (C2) obtained from the element diameter of the side element wire Ratio, ratio of minor axis Dis of the circumscribed circle of the core wire to minor axis of the second elliptical orbit (C2), ratio of major axis Dl and minor axis Ds of the circumscribed circle of the side element wire, brazing pitch of the core element wire The steel cords of Example 5 and Comparative Examples 8 to 9 in which the ratio of P11 to the twisted pitch P12 of the side strands was set as shown in Table 2 were used. It was. For comparison, a steel cord having a 1 × 6 configuration in which six strands (ds = 0.37 mm) were twisted was prepared as Comparative Example 10. 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.

  About the steel cord of these Example 5 and Comparative Examples 8-10, the rubber penetration rate and initial stage elongation rate were evaluated by the above-mentioned method, and the result was combined with Table 2 and shown.

  In addition, pneumatic radial tires (tire size: 11R22.5) using the steel cords of Example 5 and Comparative Examples 8 to 10 as the belt layer were manufactured, and the outer diameter growth after running the actual vehicle and the surface of the steel cord strands. 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 10 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 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 10). In addition, the pneumatic radial tire using the steel cord of Example 5 as the belt layer had little outer diameter growth 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 8 to 9 as the belt layer, the wire surface scratches on the steel cord after running on the actual vehicle were larger than those in Example 5. Further, the steel cord of Comparative Example 9 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 + 6 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 strand 12 Side strand C1 1st elliptical track C2 2nd elliptical track C11 Circumferential circle of core strand C12 Side strand Circumscribed circle

Claims (4)

  6 side strands are twisted and arranged on the outside of one core strand with spiral brazing, and the circumcircle of the core strand and the circumcircle of the side strand are each elliptical A steel cord in which the ratio of the major axis Dl to the minor axis Ds of the circumscribed circle of the side element wire is in the range of 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 relative to the brazing pitch of the core strand. A first elliptical orbit having a diameter that is substantially three times the diameter of a circumscribed circle of the side element wire, and the side element wire on the first ellipse orbit. Assuming a second elliptical trajectory circumscribing the virtual circle when the center of the virtual circle of the same diameter is moved, the core wire is the second elliptical trajectory. Rubber reinforcing steel cord, characterized in that located within.   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 is arranged by twisting six side strands on the outside of one core strand subjected to spiral brazing, and The circumscribed circle of the core element wire and the circumscribed circle of the side element wire each have a flat 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 Steel cord, wherein the core strand is thinner than the side strand, and the twist direction of the core strand is the same as the twist direction of the side strand Yes, the twisting pitch of the side strands is substantially 3 times the brazing pitch of the core strands, and is substantially 1/3 times the diameter of the circumscribed circle of the side strands A first elliptical orbit having a radial dimension and a center of a virtual circle having the same diameter as the side strand on the first elliptical orbit are moved. When assuming the second elliptical orbit circumscribing the said imaginary circle when allowed to pneumatic radial tire, wherein the core wire is positioned in the second elliptical orbits.   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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