JP2019137932A - Steel cord and pneumatic radial tire using the same - Google Patents

Abstract

To provide a steel cord having improved rubber penetrability and capable of improving durability and to provide a pneumatic radial tire using the same.SOLUTION: In the pneumatic radial tire, used as a reinforcement cord is a steel cord 20 having a 7×(N+M+L) structure that comprises seven strands 10 comprising a core 12 comprising N (N=1-3) filaments 11, an intermediate layer 14 comprising M (M=6-9) filaments 13 twisted around the core 12 and an outermost layer 16 comprising L (L=12-15) filaments 15 twisted around the intermediate layer 14 and in which, around one strand 10, remaining 6 strands 10 are twisted. Among the filaments 15 in the outermost layer 16 of each strand 10, 2 to (L-2) filaments 15A are reformed and all the reformed filaments 15A are arranged so as to be continuously aligned around the intermediate layer 14.SELECTED DRAWING: Figure 2

Description

  The present invention includes a core composed of N (N = 1 to 3) filaments, an intermediate layer composed of M (M = 6 to 9) filaments twisted around the core, and a periphery of the intermediate layer 7 strands having an outermost layer of L (L = 12-15) filaments twisted together, and the remaining 6 strands around one of the 7 strands The present invention relates to a steel cord having a 7 × (N + M + L) structure twisted together and a pneumatic radial tire using the steel cord as a reinforcing cord for a reinforcing layer, and more specifically, improving rubber permeability and improving durability. The present invention relates to a steel cord that can be used and a pneumatic radial tire using the same.

  In a pneumatic radial tire for construction vehicles, a steel cord having a double twist structure is used as a reinforcement cord for a belt layer (for example, see Patent Documents 1 to 3). More specifically, for example, a core composed of three filaments, an intermediate layer composed of nine filaments twisted around the core, and 15 filaments twisted around the intermediate layer. Examples include a 7 × (3 + 9 + 15) structure steel cord including seven strands having an outermost layer, and the remaining six strands are twisted around one of the seven strands.

  Steel cords having such a double twist structure are generally tight cords, but brazing may be applied to the filaments constituting each strand in order to improve rubber permeability. However, when brazing is applied to the filament, the elongation characteristics of the steel cord change, and the initial elongation (elongation rate in the low load region) tends to be excessive. And if the initial elongation of the steel cord is excessive, there is a concern that the durability of the pneumatic radial tire is lowered due to this.

JP 2013-227698 A JP 2013-234212 A Japanese Patent Laid-Open No. 2006-56457

  An object of the present invention is to provide a steel cord and a pneumatic radial tire using the same, which can improve rubber permeability and durability.

  To achieve the above object, the steel cord of the present invention comprises a core composed of N (N = 1 to 3) filaments and M (M = 6 to 9) filaments twisted around the core. And seven strands having an outermost layer composed of L (L = 12 to 15) filaments twisted around the intermediate layer, and one of the seven strands. In a steel cord having a 7 × (N + M + L) structure in which the remaining six strands are twisted around the strand, 2 to (L−2) filaments of the outermost layer filaments of each strand are brazed And all the braided filaments are arranged so as to be continuously arranged around the intermediate layer.

  In order to achieve the above object, a pneumatic radial tire according to the present invention is a pneumatic radial tire including a reinforcing layer including a plurality of reinforcing cords. N (N = 1 to 3) filaments are used as the reinforcing cords. An intermediate layer composed of M (M = 6 to 9) filaments twisted around the core, and L (L = 12 to 15) filaments twisted around the intermediate layer 7 × (N + M + L) steel cord is used, which includes seven strands having an outermost layer made of and the remaining six strands are twisted around one of the seven strands 2 to (L-2) filaments of the outermost filaments of each strand are brazed, and all of the braided filaments are braided There is characterized in that it is arranged side by side in succession around said intermediate layer.

  The present inventor has conducted intensive research on a steel cord having a 7 × (N + M + L) structure. In order to improve rubber permeability by brazing the outermost filament of each strand, the number of braided outermost filaments is improved. And by prescribing the arrangement thereof, it was found that the initial elongation of the steel cord can be suppressed and the durability can be effectively improved, and the present invention has been achieved.

  That is, in the present invention, as a reinforcing cord of the reinforcing layer of the pneumatic radial tire, a core composed of N (N = 1 to 3) filaments and M (M = 6 to 9) twisted around the core. ) And an outermost layer consisting of L (L = 12 to 15) filaments twisted around the intermediate layer, the seven strands being When using a steel cord having a structure of 7 × (N + M + L) in which the remaining six strands are twisted around one strand of each of the two strands, 2 to (L-2) of the outermost filaments of each strand By brazing the filaments, rubber penetration into the inside of the steel cord can be improved, and all of the braided filaments are placed around the middle layer. By arranging so as to be aligned continue, and it is possible to suppress the initial elongation of the steel cord, it is possible to effectively improve the durability of the pneumatic radial tire.

  In the present invention, the core filament diameter Dc, the filament filament diameter Dm of the intermediate layer, and the filament diameter Ds of the outermost filament are 0.8 ≦ Dm / Dc <1.0 and Dm = Ds. It is preferable to satisfy. Thus, by making the filament of the core thicker than the filament of the intermediate layer, the rubber permeability into the steel cord can be improved. Further, when the filament of the core is made thicker than the filament of the intermediate layer, the steel cord becomes difficult to buckle, which is preferable from the viewpoint of durability.

  In the present invention, the reinforcing layer of the pneumatic radial tire in which the steel cord is used is not particularly limited, and examples thereof include a carcass layer, a belt layer, and a side reinforcing layer. However, in consideration of the characteristics of the steel cord, the reinforcing layer in which the steel cord is used is preferably a belt layer. In this case, the rubber permeability of the steel cord contained in the belt layer can be improved, and the durability of the pneumatic radial tire can be effectively improved. The steel cord can also be used as a reinforcing cord for reinforcing rubber products other than tires.

  The present invention is preferably applied to pneumatic radial tires for construction vehicles. However, as long as the steel cord as described above is used as a reinforcing cord for the reinforcing layer, the pneumatic radial tire is used for purposes other than the above. It can also be applied to tires.

It is a meridian half section view showing a pneumatic radial tire for construction vehicles which constitutes an embodiment of the present invention. It is sectional drawing which shows an example of the steel cord which has a 7 * (N + M + L) structure used by this invention. It is sectional drawing which shows the strand of the steel cord of FIG. It is sectional drawing which shows the other example of the steel cord which has a 7 * (N + M + L) structure used by this invention. It is sectional drawing which shows the strand of the steel cord of FIG. It is sectional drawing which shows an example of the steel cord which has a 7 * (N + M + L) structure which does not satisfy the requirements of this invention. It is sectional drawing which shows the strand of the steel cord of FIG. It is a graph which shows the elongation characteristic of the steel cord of FIG.2 and FIG.6. It is a side view which extracts and shows the filament of the outermost layer brazed in the strand of FIG.3 and FIG.5. It is a side view which extracts and shows the filament of the outermost layer, intermediate | middle layer, and core which are not brazed in the strand of FIG.3 and FIG.5. (A)-(g) is sectional drawing which shows the various steel cords used for the test.

  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 for a construction vehicle according to an embodiment of the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 including a plurality of reinforcing cords extending in the tire radial direction 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 to the outside of the tire. It is.

  A plurality of belt layers 6 a, 6 b, 6 c, 6 d are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6a to 6d include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layers 6a to 6d, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 15 ° to 40 °, and the cord driving density is set in a range of, for example, 10 pieces / 50 mm to 25 pieces / 50 mm. Yes.

  A plurality of belt protective layers 7a and 7b are embedded on the outer peripheral side of the belt layers 6a to 6d. The belt layers 6a to 6d carry the reinforcement of the tread portion 1, whereas the belt protective layers 7a and 7b are provided for the purpose of protecting the belt layers 6a to 6d. These belt protective layers 7a and 7b include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords intersect each other between the layers. In the belt protective layers 7a and 7b, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 20 ° to 40 °, and the cord driving density is set in a range of, for example, 10 pieces / 50 mm to 30 pieces / 50 mm. ing. As the reinforcing cords for the belt protective layers 7a and 7b, for example, steel cords having a breaking elongation of 4% or more are used.

  In the pneumatic radial tire, a steel cord having a 7 × (N + M + L) structure described later is used as a reinforcement cord for the belt layers 6a to 6d.

  FIG. 2 shows an example of a steel cord having a 7 × (N + M + L) structure used in the present invention, and FIG. 3 shows its strand. As shown in FIG. 2 and FIG. 3, the steel cord 20 includes a core 12 composed of N (N = 1 to 3) filaments 11 and M (M = 6 to 9) twisted around the core 12. ) Including seven strands 10 having an intermediate layer 14 composed of filaments 13 and outermost layer 16 composed of L (L = 12 to 15) filaments 15 twisted around the intermediate layer 14. The strand 6 has a 7 × (N + M + L) structure in which the remaining six strands 10 are twisted around each other. In the present embodiment, each strand 10 is composed of a core 12 composed of three filaments 11, an intermediate layer 14 composed of nine filaments 13, and an outermost layer 16 composed of 15 filaments 15. That is, it is a 7 × (3 + 9 + 15) structure. Other examples include a 7 × (1 + 6 + 12) structure as shown in FIGS. 4 and 5. In addition, when the core 12 of each strand 10 has the several filament 11, it is desirable that these filaments 11 are mutually twisted.

  In the steel cord 20 described above, among the L filaments 15 constituting the outermost layer 16 of each strand 10, 2 to (L-2) filaments 15A (with diagonal lines) are brazed. The remaining sheath filament 15B (not shaded) is not brazed. 2 to 5, each of the five filaments 15A is brazed. The braided filaments 15A are all arranged continuously around the intermediate layer 14, while the unbraided filaments 15B are arranged continuously around the intermediate layer 14. Is arranged. That is, as shown in FIGS. 2 to 5, the L filaments 15 constituting the outermost layer 16 of each strand 10 are arranged so as to surround the intermediate layer 14, but all the braided filaments 15 </ b> A are arranged. All the filaments 15B that are arranged adjacent to each other and are not brazed are arranged adjacent to each other. In addition, like the filament 15B of the outermost layer 16, the filament 11 of the core 12 and the filament 13 of the intermediate layer 14 are not brazed.

  In the pneumatic radial tire described above, as a reinforcing cord of the belt layer 7, a core 12 composed of N (N = 1 to 3) filaments 11 and M (M = 6 to M) twisted around the core 12 are twisted. 9) including seven strands 10 having an intermediate layer 14 made of filaments 13 and an outermost layer 16 made of L (L = 12 to 15) filaments 15 twisted around the intermediate layer 14; When using a steel cord 20 having a 7 × (N + M + L) structure in which the remaining six strands 10 are twisted around one strand 10, 2 to (L of filaments 15 of the outermost layer 16 of each strand 10 (L -2) By brazing the filament 15A, the rubber penetration into the inside of the steel cord 20, especially the rubber immersion into the inside of each strand 10 It is possible to improve the sex. Moreover, by arranging all of the braided filaments 15A so as to be continuously arranged around the intermediate layer 14, the filaments 15A are arranged at predetermined positions in a state where the brazing phases are aligned. The initial elongation of the steel cord 20 can be suppressed, and the durability of the pneumatic radial tire can be effectively improved.

  Here, the difference between the physical properties of the steel cord 20 (FIG. 2) included in the present invention and the physical properties of the steel cord 20 ′ (FIG. 6) not included in the present invention will be described. In the steel cord 20 ′ shown in FIG. 6, among the filaments 15 constituting the outermost layer 16 of each strand 10 ′ (FIG. 7), the filament 15A is brazed, and the filament 15B is brazed. 2 is the same as the example of FIG. 2, but unlike the example of FIG. 2, all the braided filaments 15 </ b> A are not arranged so as to be continuously arranged around the intermediate layer 14. When the elongation percentage (%) was measured while changing the tensile load (N) for the steel cord 20 shown in FIG. 2 and the steel cord 20 ′ shown in FIG. 6, the results shown in FIG. 8 were obtained. As shown in FIG. 8, the steel cord 20 'of FIG. 6 in which not all of the braided filaments 15A are arranged continuously around the intermediate layer 14 is obtained when all of the braided filaments 15A are The initial elongation is larger than that of the steel cord 20 of FIG. 2 arranged so as to be continuously arranged around the intermediate layer 14. Such an increase in initial elongation is attributed to the arrangement of brazed filaments 15A.

  In each strand 10 of the steel cord 20 described above, the number of filaments 11 constituting the core 12 is N (N = 1 to 3), and the number of filaments 13 constituting the intermediate layer 14 is M (M = 6 to 9), and the number of filaments 15 constituting the outermost layer 16 is L (L = 12 to 15), which is to ensure rubber permeability and shape stability. If the number of the filaments 11 of the core 12, the filaments 13 of the intermediate layer 14, and the filaments 15 of the outermost layer 16 is too large, the rubber permeability decreases, and the number of the filaments 13 of the intermediate layer 14 and the filaments 15 of the outermost layer 16 is too small. It becomes difficult to obtain a stable twisted structure. Further, although 2 to (L-2) filaments 15A are brazed, this is for suppressing initial elongation while ensuring rubber permeability. If the number of braided filaments 15A is too small, the rubber permeability decreases, and conversely if too large, the initial elongation becomes excessive. In particular, it is preferable that 4 to (L-4) filaments 15A among the filaments 15 of the outermost layer 16 are brazed.

  As shown in FIG. 9, the filament 15A constituting the outermost layer 16 of each strand 10 is brazed so as to meander along the longitudinal direction thereof. The form of brazing may be wavy or helical. The wave height H of the filament 15A is preferably in the range of 1.3 ≦ H / Ds ≦ 2.0 with respect to the filament diameter Ds of the filament 15A. If this ratio H / Ds is too small, the effect of improving rubber permeability is reduced. Conversely, if the ratio H / Ds is too large, the effect of suppressing initial elongation is reduced. The brazing pitch W of the filament 15A is preferably in the range of 10 ≦ W / H ≦ 30 with respect to the wave height H of the filament 15A. If this ratio W / H is too small, the effect of suppressing the initial elongation is lowered, while if too large, the effect of improving rubber permeability is lowered.

  In each strand 10, the twist direction and the twist pitch of the core 12, the intermediate layer 14, and the outermost layer 16 are not particularly limited. For example, in FIG. 10, in each strand 10, the filament 11 of the core 12 has a pitch Pc. Are twisted together in one direction (for example, S twist), the filament 13 of the intermediate layer 14 is twisted in one direction (for example, S twist) by the pitch Pm, and the filament 15 of the outermost layer 16 is twisted in one direction (for example, by the pitch Ps) S twist). The pitch Pc, the pitch Pm, and the pitch Ps are set to the same value. Thus, it is preferable that the core 12, the intermediate | middle layer 14, and the outermost layer 16 are twisted together by the same direction and the same pitch. Thereby, the filament 11 of the core 12, the filament 13 of the intermediate layer 14, and the filament 15 of the outermost layer 16 can be twisted together, so that the productivity of the steel cord 20 can be increased. Moreover, even when such a twisted structure is employed, sufficient rubber permeability can be ensured. Further, in the steel cord 20, the twist direction of the strand 10 is preferably opposite to the twist direction of the outermost layer 16. Thereby, stability of steel cord 20 can be improved.

  In each strand 10, the strand diameter Dc of the filament 11 constituting the core 12, the strand diameter Dm of the filament 13 constituting the intermediate layer 14, and the strand diameter Ds of the filament 15 constituting the outermost layer 16 are 0.8 ≦. It is preferable that the relationship of Dm / Dc <1.0 and Dm = Ds is satisfied. Thus, by making the filament 11 of the core 12 thicker than the filament 13 of the intermediate layer 14 and the filament 15 of the outermost layer 16, rubber permeability into the steel cord 20, particularly rubber penetration into each strand 10. Can improve sex. In addition, when the filament 11 of the core 12 is thicker than the filaments 13 and 15, the steel cord 20 becomes difficult to buckle, which is preferable from the viewpoint of durability. However, if the ratio Dm / Dc is too small, the balance of strength between the filament 11 of the core 12 and the filaments 13 and 15 is deteriorated, and inconvenience such as disconnection is likely to occur.

  In each strand 10, the strand diameter Dc of the filament 11 constituting the core 12, the strand diameter Dm of the filament 13 constituting the intermediate layer 14, and the strand diameter Ds of the filament 15 constituting the outermost layer 16 are 0.15 mm to It is preferable to set in the range of 0.40 mm. Thus, by optimizing the wire diameters Dc, Dm, and Ds, it is possible to ensure good fatigue resistance while sufficiently securing the cord strength. If the wire diameters Dc, Dm, and Ds are smaller than 0.15 mm, the cord strength is insufficient, and conversely if it is larger than 0.40 mm, the fatigue resistance is lowered.

  In the embodiment described above, the case where the steel cord 20 having the 7 × (N + M + L) structure is used for the belt layer 6 has been described, but in the present invention, the steel cord 20 as described above is applied to another reinforcing layer. Is possible.

  In the pneumatic radial tire of tire size 2700R49, tires of conventional examples, comparative examples 1 to 4 and examples 1 to 5 in which only the reinforcement cords of the belt layer were changed were manufactured.

  That is, in the conventional example, the comparative examples 1 to 4, and the examples 1 to 5, as the reinforcing cords for the belt layer, seven core filaments, nine intermediate layer filaments, and 15 outermost layer filaments are used. A 7 × (3 + 9 + 15) structure steel cord in which the remaining six strands are twisted around one strand, or one core filament, six intermediate layer filaments and twelve outermost strands. 7 × (1 + 6 + 12) structure steel cord including 7 strands having outer layer filaments and the remaining 6 strands twisted around one strand, cord driving density, core filament Wire diameter Dc, strand diameter Dm of intermediate layer filament, strand diameter Ds of outermost layer filament, ratio Dm / Dc, brazed outermost layer The number of filaments and the arrangement of braided outermost layer filaments were set as shown in Table 1. In addition, arrangement | positioning of the braided outermost layer filament is as FIG. 11 (a)-(g). In FIGS. 11A to 11G, the outermost filaments brazed are hatched. In the conventional example, Comparative Examples 1 to 4 and Examples 1 to 5, steel cords having the same structure were applied to the six belt layers (all belt layers).

  These test tires were evaluated for rubber penetration and tire durability by the following evaluation methods, and the results are also shown in Table 1.

Rubber penetration rate:
The steel cord of the belt layer (the third belt layer counted from the inside of the tire) is taken out from each test tire, the strand at the center position is taken out from the steel cord, and the rubber adhered to the outside of the strand is removed with a cutter knife. After removing one filament from the outer layer, the rubber penetration rate inside the filament was visually measured. Further, all the filaments in the outermost layer were removed, and the rubber adhered to the outside of the intermediate layer was removed. Then, one filament was removed from the intermediate layer, and the rubber penetration rate inside thereof was measured visually. Further, all the filaments in the intermediate layer were removed, and the rubber adhered to the outside of the core was removed. Then, one filament was removed from the core, and the rubber penetration rate inside the core was visually measured. And the rubber penetration rate as the whole strand of a center position was calculated | required based on these measured values. Such measurement was performed on steel cords arranged at eight locations on the tire circumference, and an average value of rubber penetration rates of these eight steel cords was obtained, and this was used as the rubber penetration rate.

Tire durability:
An indoor drum equipped with a cleat drum having a height of 200 mm under the conditions of an air pressure of 700 kPa, a speed of 10 km / h, and an initial load of 183 kN, with each test tire mounted on a test rim having a rim size of 49 × 19.50-4.0 A running test was performed using a test machine, and the load was increased by 52 kN every 10 hours, and the running time until the tire broke down was measured. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the durability. In addition, all the destruction modes of the tire were belt edge separation.

  As is clear from Table 1, in Examples 1 to 5, the rubber penetration rate of the steel cord was high and the tire durability was excellent in comparison with the conventional example. In particular, as can be seen from Examples 3 to 5, when the strand diameter Dc of the core filament is appropriately thicker than the strand diameter Dm of the intermediate filament and the strand diameter Ds of the outermost filament, the tire durability is improved. The effect was remarkable. On the other hand, in Comparative Examples 1 and 2, since all of the braided outermost layer filaments are not arranged so as to be continuously arranged around the intermediate layer, tire durability is attributed to an increase in initial elongation. The improvement effect was not obtained. Further, in Comparative Example 3, since the number of braided outermost layer filaments was too small, the rubber permeability was insufficient, and the effect of improving tire durability could not be obtained. On the other hand, in Comparative Example 4, since the number of braided outermost layer filaments was too large, an effect of improving tire durability was not obtained due to an increase in initial elongation.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6a, 6b, 6c, 6d Belt layer 7a, 7b Belt protective layer 10 Strand 11 Filament (core)
12 core 13 filament (intermediate layer)
14 Intermediate layer 15 Filament (outermost layer)
15A Brazed filament 15B Unbraided filament 16 Outermost layer 20 Steel cord

Claims (5)

  A core composed of N (N = 1 to 3) filaments, an intermediate layer composed of M (M = 6 to 9) filaments twisted around the core, and twisted around the intermediate layer 7 strands having an outermost layer composed of L (L = 12 to 15) filaments, and the remaining 6 strands were twisted around one of the 7 strands In a steel cord having a 7 × (N + M + L) structure, 2 to (L−2) filaments of the outermost filaments of each strand are brazed, and all of the braided filaments are A steel cord characterized by being arranged in a line around the middle layer.   The core filament diameter Dc, the intermediate filament filament diameter Dm, and the outermost filament filament diameter Ds are 0.8 ≦ Dm / Dc <1.0 and Dm = Ds. The steel cord according to claim 1, wherein the steel cord is satisfied.   In a pneumatic radial tire including a reinforcing layer including a plurality of reinforcing cords, as the reinforcing cord, a core composed of N (N = 1 to 3) filaments and M pieces (twisted around the core) ( 7 strands having an intermediate layer composed of M = 6-9) filaments and an outermost layer composed of L (L = 12-15) filaments twisted around the intermediate layer, A steel cord having a structure of 7 × (N + M + L) in which the remaining six strands are twisted around one of the strands is used, and the filament of the outermost layer of each strand is used. 2 to (L-2) filaments are brazed, and all of the braided filaments are arranged continuously around the intermediate layer. A pneumatic radial tire which is characterized. The core filament diameter Dc, the intermediate filament filament diameter Dm, and the outermost filament filament diameter Ds are 0.8 ≦ Dm / Dc <1.0 and Dm = Ds. The pneumatic radial tire according to claim 3, wherein the pneumatic radial tire is satisfied.   The pneumatic radial tire according to claim 3 or 4, wherein the reinforcing layer is a belt layer.

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