Steel cord and pneumatic radial tire using the same

Abstract

To provide a steel cord capable of improving rubber permeability, and a pneumatic radial tire using the same.SOLUTION: In a pneumatic radial tire having a carcass layer 4 as a reinforcing layer including a plurality of reinforcing cords, there is used a steel cord 10 having a 1+5+10 structure including a first layer L1 composed of one filament 11, a second layer L2 composed of five filaments 12, and a third layer L3 composed of 10 filaments 13 as a reinforcing cord of the carcass layer 4, the first layer L1, the second layer L2, and the third layer L3 are formed by a process of twisting one time, and two-dimensional waving processing is applied to a filament 13B at at least one non-apex position P2 of five non-apex positions P2 defined between mutual five apex positions P1 of the third layer L3.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a steel cord having a 1 + 5 + 10 structure and a pneumatic radial tire using the steel cord as a reinforcing cord of a reinforcing layer typified by a carcass layer. More specifically, the present invention relates to a steel cord capable of improving rubber permeability and a pneumatic radial tire using the same.

Background Art

[0002] In a pneumatic radial tire for trucks and buses, as a reinforcing cord of a carcass layer, a steel cord having a 1 + 5 + 10 structure including a first layer composed of one filament, a second layer composed of five filaments, and a third layer composed of ten filaments is generally used (see, for example, Patent Document 1).

[0003] The steel cord having the 1 + 5 + 10 structure as described above has an advantage that the production cost can be suppressed because the three layers can be twisted at once, but has a disadvantage that the rubber permeability into the cord is poor because the filament intervals are clogged. Therefore, when moisture penetrates into the cord, the moisture propagates along the longitudinal direction of the steel cord, and rust grows in a wide range. As a result, there is a problem that the durability of the pneumatic radial tire is reduced.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a steel cord capable of improving rubber permeability and a pneumatic radial tire using the same.

Means for Solving the Problems

[0006] The steel cord of the present invention for achieving the above object is a steel cord having a 1+5+10 structure including a first layer composed of one filament, a second layer composed of five filaments, and a third layer composed of ten filaments. The first layer, the second layer, and the third layer are formed by twisting together in a single twisting process, and two-dimensional corrugation is applied to the filaments at at least one of the five non-vertex positions defined between the five vertex positions of the third layer. , the filament with the wave applied is arranged such that its amplitude direction coincides with the cord diameter direction It is characterized by this.

[0007] The pneumatic radial tire of the present invention for achieving the above object is a pneumatic radial tire provided with a reinforcing layer including a plurality of reinforcing cords. As the reinforcing cord, a steel cord having a 1+5+10 structure including a first layer composed of one filament, a second layer composed of five filaments, and a third layer composed of ten filaments is used. The first layer, the second layer, and the third layer are formed by twisting together in a single twisting process, and two-dimensional corrugation is applied to the filaments at at least one of the five non-vertex positions defined between the five vertex positions of the third layer. , the filament with the wave applied is arranged such that its amplitude direction coincides with the cord diameter direction It is characterized by this.

Effect of the Invention

[0008] As a result of intensive research on a steel cord having a 1+5+10 structure with low production costs, the present inventor has found that by applying two-dimensional corrugation to the filaments at the non-vertex positions of the third layer, the rubber permeability is effectively improved, and thus the present invention has been achieved.

[0009] That is, in the present invention, when adopting a steel cord having a 1+5+10 structure including a first layer composed of one filament, a second layer composed of five filaments, and a third layer composed of ten filaments as the reinforcing cord of a pneumatic radial tire, the first layer, the second layer, and the third layer are formed by twisting together in a single twisting process. By applying two-dimensional corrugation to the filaments at at least one of the five non-vertex positions defined between the five vertex positions of the third layer, sufficient gaps are formed between the filaments, so that the rubber permeability into the cord can be improved, and the durability of the pneumatic radial tire can be improved.

[0010] In the above steel cord, it is preferable that the wire diameter Ds of the filaments of the third layer and the corrugation height Dh satisfy the relationship of 1.07 ≦ Dh / Ds ≦ 2.0. By defining the corrugation height Dh in this way, while improving the rubber permeability into the cord, the breakage of the cord terminals can be effectively prevented.

[0011] In the above steel cord, it is preferable that two-dimensional corrugation is applied to all the filaments at the five non-vertex positions. Thereby, the rubber permeability into the cord can be effectively improved.

[0012] In the above steel cord, it is preferable that the filaments with corrugation are arranged such that the amplitude direction thereof coincides with the cord diameter direction. Thereby, the shape of the steel cord is stabilized, and the breakage of the cord terminals can be effectively suppressed.

[0013] In the present invention, the reinforcing layer of the pneumatic radial tire in which the above steel cord is used is not particularly limited, and examples thereof include a carcass layer, a belt layer, and a side reinforcing layer. However, considering the characteristics of the above steel cord, the reinforcing layer in which the steel cord is used is preferably a carcass layer.

[0014] The present invention is preferably applicable to pneumatic radial tires for trucks and buses, but is also applicable to pneumatic radial tires for other uses as long as the steel cord as described above is used as the reinforcing cord of the reinforcing layer.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0016] 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 the tread portion, 2 is the sidewall portion, and 3 is the bead portion. A carcass layer 4 including a plurality of reinforcing cords extending in the tire radial direction is mounted between a pair of left and right bead portions 3, 3, and the ends of the carcass layer 4 are folded back from the inside to the outside of the tire around the bead core 5.

[0017] Further, a plurality of belt layers 6 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged such that the reinforcing cords cross each other between the layers. In the belt layer 6, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 20° to 60°.

[0018] In the pneumatic radial tire, a steel cord having a 1+5+10 structure described later is used as the reinforcing cord of the carcass layer 4.

[0019] FIG. 2 shows a steel cord having a 1+5+10 structure used in the present invention, and FIGS. 3 and 4 show an extraction of filaments of a third layer subjected to two-dimensional corrugation in the steel cord.

[0020] As shown in FIG. 2, the steel cord 10 has a 1+5+10 structure including a first layer L1 composed of one filament 11, a second layer L2 composed of five filaments 12, and a third layer L3 composed of ten filaments 13. The steel cord 10 having this 1+5+10 structure is formed by twisting these three layers L1 to L3 together at once in a state where the first layer L1 composed of one filament 11, the second layer L2 composed of five filaments 12, and the third layer L3 composed of ten filaments 13 are bundled. Therefore, there is an advantage that the production cost of the steel cord 10 can be suppressed.

[0021] In the steel cord 10, there are five vertex positions P1 in the third layer L3. The vertex position P1 is a position where the filament 11 of the first layer L1, the filament 12 of the second layer L2, and the filament 13 of the third layer L3 are arranged in series along the cord diameter direction. And between the five vertex positions P1, five non-vertex positions P2 are defined. In the third layer L3, the filament 13 at the vertex position P1 is designated as filament 13A, and the filament 13 at the non-vertex position P2 is designated as filament 13B. The filament 13B at at least one of these five non-vertex positions P2, more preferably, all the filaments 13B at the five non-vertex positions P2 are provided with a two-dimensional corrugation as shown in FIGS. 2 to 4. In contrast, the filament 13A at the five vertex positions P1 is not provided with a two-dimensional corrugation.

[0022] In the above-described pneumatic radial tire, when adopting the steel cord 10 having a 1 + 5 + 10 structure including the first layer L1 composed of one filament 11, the second layer L2 composed of five filaments 12, and the third layer L3 composed of ten filaments 13 as the reinforcing cord of the carcass layer 4, since the filament 13B at at least one of the five non-vertex positions P2 defined between the five vertex positions P1 of the third layer L3 is provided with a two-dimensional corrugation, a sufficient gap is formed between the filaments 12 and 13. Thereby, the rubber permeability into the steel cord 10 can be improved, and the durability of the pneumatic radial tire can be improved.

[0023] Fig. 5 shows a steel cord having a conventional 1 + 5 + 10 structure. In Fig. 5, the steel cord 20 has a 1 + 5 + 10 structure including a first layer L1 composed of one filament 21, a second layer L2 composed of five filaments 22, and a third layer L3 composed of ten filaments 23. In the steel cord 20, the filaments 23A at five vertex positions P1 and the filaments 23B at five non-vertex positions P2 are not provided with two-dimensional corrugation. Therefore, the filaments 23B at the non-vertex positions P2 and the filaments 23A, 23A located on both sides thereof are arranged linearly, and the cross-sectional shape of the steel cord 20 is generally pentagonal. In this case, since the filaments 23B at the non-vertex positions P2 in the third layer L3 are arranged so as to close the gaps between the filaments 22, 22 in the second layer L2, the rubber permeability is poor.

[0024] On the other hand, in the above-described steel cord 10, since the filaments 13B at the non-vertex positions P2 in the third layer L3 are provided with two-dimensional corrugation, the effect of improving the rubber permeability is extremely high. Thus, while taking advantage of the steel cord 10 having a 1 + 5 + 10 structure with low production costs, it becomes possible to improve its rubber permeability. In the steel cord 10 having a 1 + 5 + 10 structure, even if the filaments 13A at the vertex positions P1 in the third layer L3 are provided with two-dimensional corrugation, almost no effect of improving the rubber permeability can be obtained.

[0025] In the above steel cord 10, it is preferable that the wire diameter Ds of the filaments 13 (13B) in the third layer L3 and the corrugation height Dh satisfy the relationship of 1.07 ≦ Dh / Ds ≦ 2.0. By defining the corrugation height Dh in this way, it is possible to improve the rubber permeability into the steel cord 10 while preventing the steel cord 10 from coming apart. Here, if Dh / Ds < 1.07, the effect of improving the rubber permeability decreases, and if Dh / Ds > 2.0, the cord shape becomes unstable and the cord ends are likely to come apart.

[0026] In the above steel cord 10, the wire diameter Dc of the filaments 11 constituting the first layer L1, the wire diameter Dm of the filaments 12 constituting the second layer L2, and the wire diameter Ds of the filaments 13 constituting the third layer L3 may be the same, or may be different from each other. However, it is preferable that the wire diameters Dc, Dm, and Ds are set in the range of, for example, 0.15 mm to 0.25 mm.

[0027] In particular, it is preferable that the wire diameter Dc of the filaments 11 in the first layer L1, the wire diameter Dm of the filaments 12 in the second layer L2, and the wire diameter Ds of the filaments 13 in the third layer L3 satisfy the relationship Dc < Dm < Ds. In this way, rather than sequentially increasing the wire diameter Dc of the filaments 11 in the first layer L1, the wire diameter Dm of the filaments 12 in the second layer L2, and the wire diameter Ds of the filaments 13 in the third layer L3 toward the outside in the cord diameter direction, the shape of the steel cord 10 having a 1 + 5 + 10 structure is stabilized, and the loosening of the cord end can be effectively suppressed.

[0028] In the above-described steel cord 10, as shown in FIG. 2, it is preferable that the corrugated filaments 13B are arranged such that the amplitude direction thereof coincides with the cord diameter direction. Thereby, the shape of the steel cord 10 is stabilized, and the loosening of the cord end can be effectively suppressed. That is, by making the amplitude direction of the corrugated filaments 13B coincide with the cord diameter direction, a stable arrangement structure as shown in the figure can be realized without the filaments 13B at the non-apex position P2 displacing the filaments 13A at the apex position P1.

Example

[0029] As a reinforcing cord constituting the carcass layer of a pneumatic radial tire of tire size 11R22.5, steel cords of a conventional example, Comparative Example 1, and Examples 1 to 6 were manufactured.

[0030] That is, in the conventional example, Comparative Example 1, and Examples 1 to 6, a steel cord having a 1+5+10 structure including a first layer composed of one filament, a second layer composed of five filaments, and a third layer composed of ten filaments was used as the reinforcing cord for the carcass layer. Then, the number of filaments with corrugations (corrugation number) in the third layer and the ratio Dh / Ds of the wire diameter of the filaments in the third layer to the corrugation height were set as shown in Table 1. The wire diameter Dc of the filaments in the first layer was 0.15 mm, the wire diameter Dm of the filaments in the second layer was 0.20 mm, and the wire diameter Ds of the filaments in the third layer was 0.22 mm.

[0031] Then, by the following evaluation method, the rubber adhesion rate, end breakage, and fatigue resistance of the steel cord were evaluated, and the results are shown together in Table 1.

[0032] Rubber adhesion rate of the steel cord: After preparing a test piece by embedding the steel cord used for the carcass layer in rubber and vulcanizing it, the test piece was cut so that the cut end of the steel cord was exposed, and the cut end of the steel cord of the test piece was immersed in salt water with a concentration of 25% and a temperature of 25°C and left for 14 days. Then, the steel cord was pulled out from the test piece, and the rubber adhesion rate (%) on the cord surface was measured. A higher rubber adhesion rate means better rubber permeability into the cord interior.

[0033] End breakage of the steel cord: The steel cord used for the carcass layer was cut with pliers while being held at a position 70 cm away from the cut end, and the breakage of the filaments at the cut end was observed. The evaluation results were indicated as "A" when no breakage occurred after cutting, "B" when the breakage length was 50 mm or less, and "C" when the breakage length exceeded 50 mm.

[0034] Fatigue resistance of the steel cord: A test piece was prepared by embedding a steel cord used in a carcass layer in rubber and vulcanizing it. After that, the test piece was mounted on a three-point roller type rotational bending fatigue testing machine with a roller diameter of 35 mm, and the logarithmic value of the number of bending cycles was recorded until the steel cord in the test piece broke under the condition of a cord tension of 180 N. The evaluation results were shown by an index with the conventional example taken as 100. The larger this index value is, the more excellent the fatigue resistance of the steel cord is.

[0035]

Table 1

[0036] As is clear from Table 1, in Examples 1 to 6, in comparison with the conventional example, the rubber attachment rate of the steel cord constituting the carcass layer was high, that is, the rubber permeability into the cord interior was good. However, in Example 3, since the ratio Dh / Ds of the wire diameter of the filaments in the third layer to the corrugation height was small, the effect of improving rubber permeability was small. In Example 6, since the ratio Dh / Ds of the wire diameter of the filaments in the third layer to the corrugation height was large, although the effect of improving rubber permeability was large, terminal breakage of the steel cord was likely to occur.

[0037] On the other hand, in Comparative Example 1, although the filaments at the apex positions of the third layer were corrugated, the filaments at the non-apex positions of the third layer were not corrugated, so the rubber permeability into the cord interior was insufficient.

Explanation of Signs

[0038] 1 Tread portion 2 Sidewall portion 3 Bead portion 4 Carcass layer 5 Bead core 6 Belt layer 10 Steel cord 11 Filaments of the first layer 12 Filaments of the second layer 13 Filaments of the third layer 13A Filaments at the apex positions Filament at non-vertex position 13B

Claims

1. In a steel cord having a 1 + 5 + 10 structure including a first layer composed of one filament, a second layer composed of five filaments, and a third layer composed of ten filaments, the first layer, the second layer, and the third layer are formed by twisting together in a single twisting process, and two-dimensional corrugation is applied to at least one filament at a non-apex position among five non-apex positions defined between the five apex positions of the third layer, and the filament to which the corrugation is applied is arranged such that the amplitude direction thereof coincides with the cord diameter direction. A steel cord characterized by the above.

2. The steel cord according to claim 1, characterized in that the relationship between the wire diameter Ds of the filaments of the third layer and the corrugation height Dh satisfies 1.07 ≤ Dh / Ds ≤ 2.

0.

3. The steel cord according to claim 1 or 2, characterized in that two-dimensional corrugation is applied to all filaments at the five non-apex positions.

4. In a pneumatic radial tire provided with a reinforcing layer including a plurality of reinforcing cords, as the reinforcing cord, a steel cord having a 1 + 5 + 10 structure including a first layer composed of one filament, a second layer composed of five filaments, and a third layer composed of ten filaments is used, the first layer, the second layer, and the third layer are formed by twisting together in a single twisting process, and two-dimensional corrugation is applied to at least one filament at a non-apex position among five non-apex positions defined between the five apex positions of the third layer, and the filament to which the corrugation is applied is arranged such that the amplitude direction thereof coincides with the cord diameter direction. A pneumatic radial tire characterized by the above.

5. The pneumatic radial tire according to claim 4, characterized in that the relationship between the wire diameter Ds of the filaments of the third layer and the corrugation height Dh satisfies 1.07 ≤ Dh / Ds ≤ 2.

0.

6. The pneumatic radial tire according to claim 4 or 5, characterized in that two-dimensional corrugation is applied to all filaments at the five non-apex positions.

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