CABLE BEAD FOR PNEUMATIC TIRE AND PNEUMATIC TIRE HAVING THE SAME

Abstract

The present disclosure relates to a cable bead for a pneumatic tire which constitutes a bead part of a pneumatic tire, improves rubber permeability by restricting a ratio between a diameter of a cable and a pitch of an outer wire, and improves durability of a pneumatic tire by improving rubber adhesive properties through cobalt coating on a surface of the outer wire, and a pneumatic tire having the same, and the cable bead for a pneumatic tire is characterized in that the diameter D of the cable and a pitch P of the outer wire 20 satisfy a relationship formula, P/D=25 to 45, and further characterized in that the surface of the outer wire 20 is coated with cobalt after wire drawing.

Claims

1. A cable bead for a pneumatic tire, which is applied to a bead part of the pneumatic tire, formed by twisting and winding one or more outer wires 20 around a core wire 10 and has a cable including the outer wires 20 and the core wire 10, wherein a diameter D of the cable and a pitch P of the outer wire 20 satisfy a relationship formula, P/D=25 to 45.

2. The cable bead according to claim 1, wherein a diameter d.sub.o of the outer wire 20 is 25 to 75% of a diameter d of the core wire 10, and six to fifteen outer wires 20 are wound around the core wire 10.

3. The cable bead according to claim 1, wherein the outer wires 20 are wound around the core wire 10 in any one of a right-winding manner or a left-winding manner.

4. The cable bead according to claim 1, wherein a surface of the outer wires 20 are coated with cobalt after wire drawing.

5. The cable bead according to claim 4, wherein the cobalt coating is performed on the outer wires 20 at a ratio of 0.4 to 1.2 mg/kg.

6. A pneumatic tire to which the cable bead according to claim 1 is applied.

7. A pneumatic tire to which the cable bead according to claim 2 is applied.

8. A pneumatic tire to which the cable bead according to claim 3 is applied.

9. A pneumatic tire to which the cable bead according to claim 4 is applied.

10. A pneumatic tire to which the cable bead according to claim 5 is applied.

Description

DRAWINGS

[0028] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

[0029] FIG. 1 is a configuration view illustrating a cable bead for a pneumatic tire according to the present disclosure;

[0030] FIG. 2 is a cross-sectional view of the cable bead for a pneumatic tire of the present disclosure;

[0031] FIG. 3 is a cross-sectional view illustrating a pitch of an outer wire of the cable bead for a pneumatic tire of the present disclosure; and

[0032] FIG. 4 is a reference view illustrating twisted shapes of the cable bead for a pneumatic tire of the present disclosure.

[0033] Corresponding reference numerals indicate corresponding parts or features throughout the several views of the drawings.

DETAILED DESCRIPTION

[0034] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0035] Hereinafter, a cable bead for a pneumatic tire of the present disclosure will be described below with reference to the accompanying drawings.

[0036] The cable bead for a pneumatic tire according to the present disclosure is applied to a bead part for a pneumatic tire, and as illustrated in FIG. 1, the cable bead is formed by twisting and winding one or more outer wires 20 around a core wire 10.

[0037] In this case, preferably, a diameter D of the cable and a pitch P of the outer wire 20 may satisfy a relationship formula, P/D=25 to 45. The reason is that in a case in which P/D is below 25, the outer wire 20 is excessively bent such that an air gap between the core wire 10 and the outer wire 20 is irregular and thus the outer wire 20 is unstably twisted, and in a case in which P/D is above 45, a line contact surface of the outer wire is increased such that rubber does not easily permeate.

[0038] Further, a diameter d.sub.o of the outer wire 20 is 25 to 75% of a diameter d of the core wire 10, and preferably, 40 to 60% of the diameter d of the core wire 10. Six to fifteen outer wires 20 may be wound around the single core wire 10. The reason is that in a case in which the diameter d.sub.o is below 25% of the diameter d, the number of outer wires 20 needs to be increased to implement a reinforcement effect by the outer wires 20 and the outer wire 20 is likely to be broken by impact, and in a case in which the diameter d.sub.o is above 75% of the diameter d, a diameter D of the cable including the core wire 10 and the outer wires 20 may be excessively increased.

[0039] In a case in which the pitch P of the outer wire 20 is determined depending on the diameter D of the cable as described above, a clearance is formed between the outer wires 20, and as a result, the rubber easily permeates.

[0040] To verify an effect of the relationship formula, P/D=25 to 45, a breathability test capable of checking rubber permeability was carried out. Typically, the breathability test is a test method which compares rubber permeability of steel cords, and measures time elapsed until air passes through a test material when covering the test material with rubber, vulcanizing the rubber, and then applying air pressure to one end of the test material.

[0041] In the present test, a plurality of samples was manufactured while changing a value of P/D, and rubber permeability was checked through the breathability test and evaluation for each specimen, and as a result, a result as shown in Table 1 was obtained.

TABLE-US-00001 TABLE 1 Com- Com- parative Ex- Ex- Ex- Ex- parative Classifi- Example ample ample ample ample Example cation 1 1 2 3 4 2 P/D 22 32 35 40 45 47 Sample 1 1.97 9.53 13.22 10.35 9.49 3.56 Sample 2 1.27 10.94 10.85 11.92 9.21 4.21 Sample 3 1.30 10.23 11.32 12.21 8.99 3.32 Average 1.51 10.23 11.79 11.49 9.23 3.70 (second/ 100 ml)

[0042] Referring to Table 1, in Example 1 and Example 2 which belong to the scope of the present disclosure and have P/D values of 32 and 35, respectively, the average values were 10.23 seconds and 11.79 seconds, and as a result, a satisfactory breathability test result was confirmed. In Comparative Example 1 in which the P/D value was 22 which is below a lower limit value, the time elapsed until air passes was 1.51 seconds in average which is extremely small, and in Comparative Example 2 in which the P/D value was 47 which is above an upper limit value, the time was 3.7 seconds in average, such that the time elapsed until air passes is increased in comparison with Comparative Example 1, but it was confirmed that the time was incomparably smaller than those in Examples.

[0043] Meanwhile, a surface of the outer wire 20 may be coated with cobalt after wire drawing. In this case, the cobalt coating is performed on the outer wire 20 at a ratio of 0.4 to 1.2 mg/kg, more particularly, 0.8 to 0.9 mg/kg. The reason is that in a case in which the cobalt coating was performed on the outer wire 20 at a ratio of below 0.4 mg/kg, an effect was inadequate, and in a case in which the cobalt coating was performed on the outer wire 20 at a ratio of 1.2 mg/kg or more, an effect was not increased any further. Further, the cobalt coating on the outer wire 20 serves to improve wet aging adhesive properties of the rubber.

[0044] To verify an effect of the cobalt coating, a wet heat adhesive force evaluation test, which is a test for checking a change in adhesive force after the outer wire has aged due to an environment, was carried out. In the wet heat adhesive force evaluation test, after the cord and the rubber were vulcanized together, and then left unattended under a condition of 80 C. and R.H 85% for three or more weeks, an attachment ratio between the cord and the rubber was investigated, and a result thereof is as shown in the following Table 2. In Table 2, the attachment ratios between the cord and the rubber in the multiple examples, in which the amount of cobalt coating is changed based on Comparative Example 1 (100%), are indicated by comparison indexes %.

[0045] Referring to Table 2, it was confirmed that an effect was realized when the amount of cobalt coating is 0.4 mg/kg, and the effect was consistently maintained even though the amount of cobalt coating exceeds 1.2 mg/kg.

TABLE-US-00002 TABLE 2 Comparative Comparative Example Example Example Example Example Example Classification Example 1 Example 2 1 2 3 4 5 6 Amount of Cobalt 0 0.3 0.4 0.5 0.59 0.87 1.2 1.5 (mg/kg) Wet Heat 3-Week 100% 100% 105% 110% 117% 128% 129% 129% Attachment Index (%)

[0046] In the related art, a plating layer is formed on the surface of the outer wire by copper plating or zinc plating, but the copper plating layer or the zinc plating layer is easily corroded due to moisture, and acts as a factor that decreases adhesive force between the rubber and the outer wire due to excessive growth of an adhesive layer caused by moisture. Therefore, the cobalt coating layer, which is capable of preventing the deterioration of the adhesive layer caused by moisture, is formed to improve age-adhesive force due to wetting of the outer wire, and to improve corrosion resistance of the wire.

[0047] Further, in order to verify an effect of the cobalt coating layer, the cable beads were manufactured as follows in accordance with Example and Comparative Example, adhesive force indexes and rubber attachment ratios were checked over time, and the results are as shown in Tables 3 and 4.

EXAMPLE

[0048] The cable bead has a structure of 1*3.0+10*1.30, the diameter D is 5.6 mm, the pitch P of the outer wire is 163 mm, and the outer wire is coated with cobalt so as to have a cobalt content of 0.87 mg/kg.

COMPARATIVE EXAMPLE

[0049] The cable bead, which is identical to that of Example, is manufactured, but the cobalt coating process is omitted, such that the outer wire does not have a cobalt content.

[0050] Referring to Tables 3 and 4, it can be seen that in Comparative Example, the adhesive force index and the rubber attachment ratio are continuously decreased as time passed. However, it can be seen that in Example, the adhesive force index and the rubber attachment ratio are significantly decreased at the initial time, but a decrease rate is gradually decreased after predetermined time has elapsed, and as a result, the adhesive force index and the rubber attachment ratio are excellent in comparison with Comparative Example.

[0051] Further, 205/60R 16 tires were manufactured by using the cable beads according to Example and Comparative Example, and the finished product tires were piled up in open air in a state of being left unattended for one month, and stored in a wet heat chamber (85 C., 85% RH) condition for one month, and then a tire durability experiment was carried out, and durability indexes according to the experimental result are as shown in the following Table 5.

TABLE-US-00003 TABLE 5 Classification Comparative Example Example Normal Condition 100% 100% One-month Piled Up 100% 110% One-month Wet Heat 100% 126% Chamber

[0052] The durability (%) shown in Table 5 shows, as a percentage (%), time elapsed until the bead part of the tire is broken, which is increased in comparison with Comparative Example, in accordance with evaluation of load durability of the bead part, and it can be seen that durability in Example is excellent by about 10 to 26% in an environment aging condition in comparison with Comparative Example.

[0053] While several exemplary embodiments for explaining the technical spirit of the present disclosure have been described and illustrated as described above, it will be well understood by those skilled in the art that the present disclosure is not limited to the configurations and the operations as described above, but the present disclosure may be variously changed and modified without departing from the scope of the technical spirit disclosed in the specification. Therefore, all of the appropriate changes, modifications, and equivalents thereto should be considered as being included in the scope of the present disclosure.

[0054] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.