JP4915286B2 - Steel cord for rubber reinforcement and pneumatic radial tire using the same - Google Patents

Description

  The present invention relates to a 1 + 6 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, 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 In the steel cord having a flat structure in which the circumscribed circle of the element wire and the circumscribed circle of the side element wire each have an elliptical shape, the core element wire is thinner than the side element wire, and the twist direction of the core element wire Is the same as the twist direction of the side strands, the brazing pitch of the core strands is the same as the twist pitch of the side strands, and the short diameter dis of the circumscribed circle of the core strands is the core strand Dis> dc with respect to the element wire diameter dc, the short diameter Dos of the circumscribed circle of the side element wire is 2ds <Dos <3ds with respect to the element wire diameter ds of the side element wire, and the side element wire The long diameter Dol of the circumscribed circle is 2.73 ds <Dol <4.5 with respect to the strand diameter ds of the side strand. S, and and wherein the ratio of the minor Dos and the major axis Dol is characterized in that a Dol / Dos> 1.2.

  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 a circumscribed circle of the core strand and a circumscribed circle of the side strand have an elliptical shape, respectively, The twisted direction of the core strand is the same as the twist direction of the side strand, and the brazing pitch of the core strand is the same as the twist pitch of the side strand. The short diameter dis of the circumscribed circle of the core element wire is dis> dc relative to the element wire diameter dc of the core element wire, and the short diameter Dos of the circumcircle of the side element wire is the element of the side element wire The length of the circumscribed circle of the side strand is 2ds <Dos <3ds with respect to the wire diameter ds Dol is 2.73 ds <Dol <4.5 ds with respect to the strand diameter ds of the side strand, and the ratio of the short diameter Dos to the long diameter Dol is Dol / Dos> 1.2. It is a feature.

  In the present invention, in a steel cord having a flat structure of 1 + 6 configuration, the core strand is made 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 core strand is brazed The pitch is the same as the twisting pitch of the side strands, the short diameter dis of the circumcircle of the core strand, the short diameter Dos of the circumcircle of the side strand, the long diameter Dol of the circumcircle of the side strand, and the short diameter Dos By defining the ratio with the long diameter Dol, the contact between the core element wire and the side element wire when flattened is reduced, and an interruption of the core element wire between the side element wires is generated. The rubber permeability similar to that of the steel cord having the 6 configuration can be secured, and an increase in the cord diameter can be suppressed as compared with the steel cord having the conventional 1 + 6 configuration. 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 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 this invention, it is preferable that the strand diameter of a side strand is 0.20 mm-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 cross-sectional view showing a 1 + 6 steel cord used for the belt layer of the pneumatic radial tire of the present invention. As shown in FIG. 3, the steel cord 10 is formed by twisting and arranging six side strands 12 on the outside of one core strand 11 subjected to spiral brazing. The circumscribed circle C11 and the circumscribed circle C12 of the side strands each have a flat structure having an elliptical shape. The circumscribed circles C11 and C12 have the same major axis direction. As the core wire 11, a wire thinner than the side wire 12 is used. As the belt cord, the strand diameter dc of the core strand 11 is preferably in the range of 0.10 mm to 0.38 mm, and the strand diameter ds of the side strand 12 is preferably in the range of 0.20 mm to 0.45 mm. Further, the ratio of the strand diameter dc of the core strand 11 and the strand diameter ds of the side strand 12 is preferably in a relationship of 1.18 ≦ ds / dc ≦ 4.50.

  In the steel cord 10, the core element wire 11 and the side element wire 12 are both brazed in a spiral shape, but the twist direction of the core element wire 11 is the same as the twist direction of the side element wire 12. The brazing pitch of the wires 11 is the same as the twisting 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 element 11 and the side element 12 is reduced, and the interruption of the core element 11 between the side elements 12 and 12 can be easily generated. 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 + 6 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 dis of the circumscribed circle C <b> 11 of the core element wire 11 is preferably in a relationship of dis> dc with respect to the element wire diameter dc of the core element wire 11. That is, it is set as a three-dimensional brazing by setting dis> dc. However, in order to reduce the weight of the composite of the cord and the rubber, it is desirable to satisfy 3dc> dis, more desirably 2.5dc> dis, and further desirably 2dc> dis.

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

  The major axis Dol of the circumscribed circle C12 of the side element wire 12 is preferably in a relationship of 2.73 ds <Dol <4.5 ds with respect to the element wire diameter ds of the side element wire 12. That is, by setting 2.73 ds <Dol, 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 4.5 ds> Dol in order to prevent the code from being broken.

  The ratio of the short diameter Dos to the long diameter Dol of the circumscribed circle C12 of the side element wire 12 is preferably in a relationship of Dol / Dos> 1.2. That is, a flat structure excellent in rubber permeability is defined by Dol / Dos> 1.2. However, it is desirable to satisfy 2.0> Dol / Dos 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 for the belt layer 6, the steel cord 10 has good adhesion to rubber, and the cord diameter (the short diameter Dos of the circumscribed circle C12 of the side element wire 12) is good. ) 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.

  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 with a 1 + 6 configuration in which each circle has an elliptical shape, the core strand is made 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 brazing pitch of the core strand Is equal to the twisting pitch of the side strands, and the strand diameter dc of the core strand, the major axis dir and minor axis dis of the circumcircle of the core strand, and the major axis Dol and minor axis Dos of the circumcircle of the side strand As shown in Table 1, steel cords of Examples 1 to 3 and Comparative Examples 1 to 4 differently prepared were prepared. For comparison, as Comparative Example 5, a steel cord having a 1 × 6 configuration formed by twisting six strands (ds = 0.25 mm) was prepared.

  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 load 100N and the elongation at the time of load 5N was determined, 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 × 6 configuration (Comparative Example 5). .

  On the other hand, the steel cord of Comparative Example 1 has no problem in terms of physical properties, but has a disadvantage that the gauge thickness becomes excessive when a composite of cord and rubber is formed because Dos / ds is too large. The steel cord of Comparative Example 2 had a dis / dc of 1.00, 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 Dos / ds was too small and Dol / ds was too large. The steel cord of Comparative Example 4 had insufficient rubber penetration because Dol / Dos was too small.

  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 the steel cord of 1 + 6 configuration in which the circumscribed circles of the wires are each elliptical, the core strand is made thinner than the side strand, the twist direction of the core strand is the same as the twist direction of the side strand, The brazing pitch is the same as the twisting pitch of the side strands, the core wire diameter dc, the core circle circumscribed circle long diameter dir and short diameter dis, and the side strand circumscribed circle major diameter Dol and short A steel cord of Example 4 in which the diameter Dos was set as shown in Table 2 was prepared. 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 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 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 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 × 6 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 + 6 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)

  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 In the steel cord having a flat structure, 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 core strand The brazing pitch of the side strands is the same as the twist pitch of the side strands, the short diameter dis of the circumscribed circle of the core strands is dis> dc with respect to the strand diameter dc of the core strands, The short diameter Dos of the circumscribed circle of the wire is 2ds <Dos <3ds with respect to the strand diameter ds of the side strand, and the long diameter Dol of the circumscribed circle of the side strand is the strand diameter ds of the side strand. In contrast, 2.73 ds <Dol <4.5 ds, and the ratio of the short diameter Dos to the long diameter Dol is Dol Rubber reinforcing steel cord, which is a dos> 1.2.   The steel cord for rubber reinforcement according to claim 1, wherein a strand diameter of the side strand 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 A circumscribed circle of the core element wire and a circumscribed circle of the side element wire each have an elliptical structure, the core element wire is thinner than the side element wire, and the twist direction of the core element wire Is the same as the twist direction of the side strands, the brazing pitch of the core strands is the same as the twist pitch of the side strands, and the short diameter dis of the circumscribed circle of the core strands is the core strand Dis> dc with respect to the element wire diameter dc, the short diameter Dos of the circumscribed circle of the side element wire is 2ds <Dos <3ds with respect to the element wire diameter ds of the side element wire, and the side element wire The major diameter Dol of the circumscribed circle is 2.73 ds <Dol <4. A ds, and the pneumatic radial tire and a ratio of minor Dos and the major axis Dol is Dol / Dos> 1.2.   The pneumatic radial tire according to claim 3, wherein a strand diameter of the side strand is 0.20 mm to 0.45 mm.

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