JP2015203167A - Steel cord and pneumatic tire for construction vehicle using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a steel cord allowing improvement of durability by improving rubber permeability into a strand; and a pneumatic tire for a construction vehicle using the steel cord.SOLUTION: A pneumatic tire for a construction vehicle in which a belt layer is disposed on the outer peripheral side of a carcass layer in a tread part and a belt protecting layer is disposed on the outer peripheral side of the belt layer uses a steel cord 10, as a reinforcing cord constituting the belt protecting layer, having an N×(1+N) structure made by twisting N (N=3 to 5) strands 11 consisting of one core filament 11c and M (M=4 to 6) sheath filaments 11 s. In the steel cord 10, the core filament 11c has a flat shape and is twisted around its axis; the long diameter Da and the short diameter Db of the core filament 11c satisfy a relation of 1<Da/Db≤3; and the long diameter Da of the core filament 11c and the diameter Ds of the sheath filament 11 s satisfy a relation of 1≤Da/Ds.

Description

  The present invention is a steel cord having an N × (1 + M) structure in which N (N = 3 to 5) strands composed of one core filament and M (M = 4 to 6) sheath filaments are twisted together. And, more specifically, a pneumatic tire for construction vehicles using the steel cord as a reinforcement cord for a belt protective layer, and more particularly, a steel cord that has improved durability of rubber by improving rubber permeability into the strand, and The present invention relates to a used pneumatic tire for construction vehicles.

  Steel cords having a double twist structure in which a plurality of filaments are twisted together to form a strand and a plurality of strands are twisted together are widely used as steel cords for rubber reinforcement (for example, Patent Document 1). To 4).

  For example, in a pneumatic tire for construction vehicles, a belt layer is disposed on the outer circumferential side of the carcass layer in the tread portion, and a belt protective layer for the purpose of protecting the belt layer is disposed on the outer circumferential side of the belt layer. However, a steel cord having a double twist structure represented by 4 × (1 + 5) × 0.25HE is also used as a reinforcing cord for such a belt protective layer.

  However, a steel cord having a double twist structure has a drawback that rubber penetration into the strand is poor because a plurality of strands are twisted together. Therefore, when moisture penetrates into the steel cord with a double twist structure embedded in the rubber product, the moisture propagates along the longitudinal direction of the steel cord, and as a result, rust grows in a wide range and the rubber product It will reduce the durability.

  In view of such inconveniences, it is required to improve rubber permeability into strands in a steel cord having a double twist structure. In particular, pneumatic tires for construction vehicles are used on a rough surface such as a mine under high load conditions, and the tread portion is easily damaged. Therefore, in order to prevent moisture from being transmitted from the damaged portion, a belt protective layer is used. The steel cord used for the rubber is required to have good rubber permeability.

JP-A-8-284080 JP 2010-90509 A Japanese Patent No. 3759292 Japanese Patent No. 4582672

  An object of the present invention is to provide a steel cord in which rubber penetration into a strand is improved and durability can be improved, and a pneumatic tire for a construction vehicle using the steel cord.

  In order to achieve the above object, the steel cord of the present invention is formed by twisting N (N = 3-5) strands composed of one core filament and M (M = 4-6) sheath filaments. In the steel cord having an N × (1 + M) structure, the core filament has a flat shape and is twisted around its axis, and the major diameter Da and the minor diameter Db of the core filament satisfy 1 <Da / Db ≦ 3. The long diameter Da of the core filament and the diameter Ds of the sheath filament satisfy the relationship 1 ≦ Da / Ds.

  In order to achieve the above object, a pneumatic tire for a construction vehicle according to the present invention includes a belt layer disposed on an outer peripheral side of a carcass layer in a tread portion, and an air for a construction vehicle including a belt protective layer disposed on the outer peripheral side of the belt layer. In a contained tire, N (N = 3 to 5) strands made of one core filament and M (M = 4 to 6) sheath filaments are twisted together as a reinforcing cord constituting the belt protective layer. In addition, a steel cord having an N × (1 + M) structure is used, the core filament has a flat shape and is twisted about its axis, and the major axis Da and minor axis Db of the core filament are 1 <Da / Db ≦ 3 in which the long diameter Da of the core filament and the diameter Ds of the sheath filament satisfy the relationship 1 ≦ Da / Ds. That.

  In the present invention, when forming a steel cord having an N × (1 + M) structure, the core filament of each strand is formed into a flat shape, torsion is imparted to the core filament, and the major axis Da and minor axis of the core filament are provided. Db satisfies the relationship 1 <Da / Db ≦ 3, and the core filament long diameter Da and the sheath filament diameter Ds satisfy the relationship 1 ≦ Da / Ds, thereby improving rubber permeability into the strand. The durability of rubber products using the steel cord can be improved.

  In the present invention, the long diameter Da of the core filament and the diameter Ds of the sheath filament preferably satisfy a relationship of 1.05 ≦ Da / Ds ≦ 1.20. Thereby, the rubber permeability into the strand can be improved, and the durability of the rubber product using the steel cord can be improved.

  Moreover, when the above-mentioned steel cord is used as the steel cord constituting the belt protective layer of the pneumatic radial tire for construction vehicles, the rubber penetration into the strand can be improved and the tire durability can be improved.

It is a meridian half sectional view showing a pneumatic tire for construction vehicles according to an embodiment of the present invention. It is sectional drawing which shows an example of the steel cord which has a Nx (1 + M) structure used by this invention. It is sectional drawing which shows an example of the steel cord which has the conventional Nx (1 + M) structure.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire for construction vehicles 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. Steel cords are used as reinforcing cords for the belt layers 6a to 6d.

  Further, 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. And the steel cord which has the following Nx (1 + M) structure is used as a reinforcement cord of the belt protective layers 7a and 7b.

  FIG. 2 shows an example of a steel cord having an N × (1 + M) structure used in the present invention. As shown in FIG. 2, the steel cord 10 twists N (N = 3 to 5) strands 11 composed of one core filament 11c and M (M = 4 to 6) sheath filaments 11s. N × (1 + M) structure. In this embodiment, the steel cord 10 has four strands 11, and each strand 11 is composed of one core filament 11c and five sheath filaments 11s. That is, it is a 4 × (1 + 5) structure. Other examples include a 3 × (1 + 4) structure, a 3 × (1 + 5) structure, a 4 × (1 + 4) structure, a 5 × (1 + 4) structure, and a 5 × (1 + 5) structure.

  The steel cord 10 has a breaking elongation of 4% or more. By giving such a breaking elongation to the steel cord 10, the belt protective layers 7a and 7b can sufficiently exhibit a protective function for the belt layers 6a to 6d.

  In the steel cord 10, the core filament 11c of each strand 11 has a flat shape and is twisted about its axis. The cross-sectional shape of the core filament 11c is not particularly limited as long as it is a flat shape having a major axis Da and a minor axis Db. For example, an elliptical shape as illustrated can be adopted. The major axis Da and the minor axis Db of the core filament 11c satisfy the relationship 1 <Da / Db ≦ 3, and the major axis Da of the core filament 11c and the diameter Ds of the sheath filament 11s satisfy the relationship 1 ≦ Da / Ds. ing.

  In the pneumatic tire described above, N (N = 3-5) comprising one core filament 11c and M (M = 4-6) sheath filaments 11s as reinforcing cords for the belt protective layers 7a, 7b. When the steel cord 10 having an N × (1 + M) structure in which the strands 11 are twisted is used, the core filament 11c of each strand 11 is formed into a flat shape, torsion is applied to the core filament 11c, and the core filament When the major axis Da and the minor axis Db of 11c satisfy the relationship 1 <Da / Db ≦ 3, and the major axis Da of the core filament 11c and the diameter Ds of the sheath filament 11s satisfy the relationship 1 ≦ Da / Ds, The rubber permeability into 11 can be improved.

  More specifically, as shown in FIG. 2, a sufficient space is formed between the core filament 11c having a flat shape and torsion, and the sheath filament 11s having a circular cross-sectional shape, and the strand Rubber easily penetrates into 11. On the other hand, in the conventional steel cord 20 as shown in FIG. 3, a sufficient space is not formed between the core filament 21c having a circular cross-sectional shape and the sheath filament 21s having a circular cross-sectional shape. It is difficult for rubber to penetrate.

  Since the steel cord 10 described above is used as a reinforcement cord for the belt protective layers 7a and 7b, pneumatic tires for construction vehicles are used on a rough surface such as a mine under high load conditions, and the tread portion 1 is damaged. Even if it is received, moisture propagation from the wounded portion can be suppressed. Thereby, corrosion of the belt protective layers 7a and 7b can be suppressed, and tire durability can be improved.

  In each strand 11, M (M = 4 to 6) sheath filaments 11s are twisted around one core filament 11c. When the number of sheath filaments 11s is out of the above range, the sheath filaments 11s are removed. It becomes difficult to arrange at a predetermined position, it becomes difficult to obtain a stable twisted structure, and the effect of improving rubber permeability becomes insufficient.

  Further, in the steel cord 10, N (N = 3 to 5) strands 11 are twisted together, but if the number of the strands 11 is out of the above range, the strands 11 may be arranged at predetermined positions. It becomes difficult and it becomes difficult to obtain a stable twisted structure, and the effect of improving rubber permeability becomes insufficient.

  The major diameter Da and the minor diameter Db of the core filament must satisfy the relationship 1 <Da / Db ≦ 3. A continuous space in which the core filament 11c has a flat shape with a Da / Db greater than 1 and is twisted between the core filament 11c and the sheath filament 11s by applying a twist. Is formed, and the rubber permeability into the strand 11 is improved. However, when Da / Db is greater than 3, the continuous space as described above increases, but the strength of the core filament 11c becomes insufficient. In particular, it is preferable that the major axis Da and the minor axis Db of the core filament satisfy the relationship of 1.5 ≦ Da / Db ≦ 2.3.

  The major axis Da of the core filament 11c and the diameter Ds of the sheath filament 11s must satisfy the relationship 1 ≦ Da / Ds. When Da / Ds is smaller than 1, the effect of improving rubber permeability into the strand 11 becomes insufficient. In particular, it is preferable that the major axis Da of the core filament 11c and the diameter Ds of the sheath filament 11s satisfy the relationship of 1.05 ≦ Da / Ds ≦ 1.20. Thus, when the major axis Da of the core filament 11c is larger than the diameter Ds of the sheath filament 11s, the rubber permeability into the strand 11 is further improved.

The major axis Da of the core filament 11c is preferably set in the range of 0.15 mm to 0.45 mm, and the diameter Ds of the sheath filament 11s is preferably set in the range of 0.15 mm to 0.35 mm. Thereby, the steel cord 10 suitable as a reinforcement cord for the belt protective layers 7a and 7b of the pneumatic tire for construction vehicles can be configured.

  Further, the twist pitch in the longitudinal direction of the core filament 11c is preferably set in the range of 8.0 mm to 20.0 mm. When the twisting pitch in the longitudinal direction of the core filament 11c is smaller than 8.0 mm, the effect of improving the rubber permeability into the strand 11 is lowered, and conversely when it is larger than 20.0 mm, the core filament 11c and the sheath filament 11s. It becomes difficult to form a space between the two.

  In the above-described embodiment, the case where the steel cord 10 having a predetermined double twist structure is used for the belt protective layers 7a and 7b of the pneumatic tire for construction vehicles has been described. However, in the present invention, the steel cord 10 as described above is used. It can be used as a reinforcing material for various rubber products.

  In a pneumatic tire having a tire size of 2700R49 and four belt layers arranged on the outer peripheral side of the carcass layer in the tread portion, and two belt protective layers arranged on the outer peripheral side of the belt layer, the reinforcing cord of the belt protective layer The tires of the conventional example, the comparative examples 1 and 2, and the examples 1 to 4 were made different from each other.

  That is, in the conventional example, the comparative examples 1 and 2, and the examples 1 to 4, as a reinforcing cord of the belt protective layer, 4 × strands of four strands made of one core filament and five sheath filaments are twisted together. Using a steel cord having a (1 + 5) structure, the ratio Da / Db of the major axis Da to the minor axis Db of the core filament, the ratio Da / Ds of the major axis Da of the core filament to the diameter Ds of the sheath filament, and the twist of the core filament The presence or absence of kinks was set as shown in Table 1. The twisting pitch of the core filament was 10.0 mm.

  In the above pneumatic tire for construction vehicles, the width of the inner belt protective layer is 590 mm, the width of the outer belt protective layer is 500 mm, and the cord angles of both belt protective layers with respect to the tire circumferential direction are 30 °, respectively. The cord driving density of both belt protective layers was 15/50 mm, respectively. Moreover, in the belt protective layers of all tires, the steel cord was S-twisted, the strand was S-twisted, the steel cord twist pitch was 9 mm, and the strand twist pitch was 6 mm.

  About these test tires, the rubber penetration rate, the rust growth distance, and the tire durability were evaluated by the following evaluation methods, and the results are also shown in Table 1.

Rubber penetration rate:
The steel cord is taken out from the belt protective layer of the test tire, the rubber adhering to the outside of the cord is removed with a cutter knife, one strand is removed from the steel cord, and the rubber penetration rate (% in the cord surrounded by the strand) ) Was measured based on the image data. Further, one filament was removed from the strand, and the rubber penetration rate (%) in the strand surrounded by the filament was measured based on the image data. Such measurement was performed at 8 locations on the tire circumference, and the average value of the rubber penetration rates measured at these 8 locations was taken as the rubber penetration rate in the cord and in the strand.

Rust growth distance:
A hole that reaches the belt protection layer is formed by drilling at one location on the tread portion of the test tire, the test tire is mounted on a construction vehicle, and after running for 300 hours, the tread rubber is peeled off to remove the belt protection layer. The rust growth distance from the drill hole was measured. The evaluation results are indicated by an index with the conventional example being 100. A smaller index value means a shorter rust growth distance.

Tire durability:
A hole that reaches the belt protective layer is formed by drilling in one place on the tread portion of the test tire, the test tire is mounted on a construction vehicle, and after running for 300 hours, the test tire has a rim size of 19.50. Using a drum tester mounted on the OR test rim and provided with a cleat having a height of 200 mm on the outer peripheral surface of the drum, a running test was started under the conditions of an internal pressure of 700 kPa, a speed of 10 km / h, and an initial load of 183 kN. The load was increased by 52 kN, and the distance traveled until the tire failed was measured. The measurement of such travel distance was performed ten times for each test tire, and the average value was obtained. The evaluation results are indicated by an index with the conventional example being 100. A larger index value means better tire durability.

  As apparent from Table 1, in Examples 1 to 4, the rubber penetration rate in the strands of the steel cord constituting the belt protective layer was high, and accordingly, the rust growth distance was shortened accordingly. As a result, the tires of Examples 1 to 4 were excellent in durability in comparison with the conventional example.

  On the other hand, in the tire of Comparative Example 1, since the ratio Da / Ds between the long diameter Da of the core filament and the diameter Ds of the sheath filament is too small, the rubber penetration rate in the strand of the steel cord constituting the belt protective layer The rust growth distance was long and the durability was poor. Further, in the tire of Comparative Example 2, since the flat core filament is not twisted, the rubber penetration rate in the steel cord strand constituting the belt protective layer is low, the rust growth distance is long, and the durability is high. It was inferior in nature.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6a-6d Belt layer 7a, 7b Belt protective layer 10 Steel cord 11 Strand 11c Core filament 11s Sheath filament

Claims (4)

  A steel cord having an N × (1 + M) structure in which N (N = 3 to 5) strands composed of one core filament and M (M = 4 to 6) sheath filaments are twisted together. The filament has a flat shape and is twisted around its axis, the major axis Da and the minor axis Db of the core filament satisfy the relationship 1 <Da / Db ≦ 3, and the major axis Da of the core filament and the sheath filament The steel cord is characterized in that the diameter Ds of the steel satisfies a relationship of 1 ≦ Da / Ds.   2. The steel cord according to claim 1, wherein a long diameter Da of the core filament and a diameter Ds of the sheath filament satisfy a relationship of 1.05 ≦ Da / Ds ≦ 1.20.   In a pneumatic tire for a construction vehicle in which a belt layer is disposed on the outer peripheral side of the carcass layer in the tread portion, and the belt protective layer is disposed on the outer peripheral side of the belt layer, one reinforcing cord constituting the belt protective layer is provided. A steel cord having an N × (1 + M) structure obtained by twisting N (N = 3 to 5) strands composed of a core filament and M (M = 4 to 6) sheath filaments is used. The core filament has a flat shape and is twisted about its axis, and the major axis Da and the minor axis Db of the core filament satisfy the relationship 1 <Da / Db ≦ 3, and the major axis Da of the core filament and the diameter of the sheath filament A pneumatic tire for construction vehicles, wherein Ds satisfies a relationship of 1 ≦ Da / Ds.   The pneumatic tire for a construction vehicle according to claim 3, wherein a long diameter Da of the core filament and a diameter Ds of the sheath filament satisfy a relationship of 1.05 ≦ Da / Ds ≦ 1.20.

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