KR101106367B1 - Steel Cord for Reinforcement of a Tire with Increased Rubber Penetration and Air Injection Radial Tire Comprising The Same - Google Patents

Abstract

The present invention relates to a steel cord for tire reinforcement and a pneumatic radial tire including the same, in particular, a first layer core composed of three filaments, and a second layer composed of seven or eight filaments and surrounding the first layer core. In the steel cord consisting of a layer core, the tire reinforcing steel which improves tire permeability and improves tire durability by providing a mold to at least one or all of the seven to eight filaments constituting the second layer core. A cord and a pneumatic radial tire comprising the same.

Steel cord for tire reinforcement, rubber permeability, fretting fatigue, first layer core, second layer core, two-dimensional corrugation, pneumatic radial tire.

Description

Steel Cord for Reinforcement of Tires with High Rubber Penetration and Pneumatic Radial Tires Comprising the Same

The present invention relates to a steel cord for tire reinforcement and a pneumatic radial tire including the same, in particular, a first layer core composed of three filaments, and a second layer composed of seven or eight filaments and surrounding the first layer core. In the steel cord consisting of a layer core, the tire reinforcing steel which improves tire permeability and improves tire durability by providing a mold to at least one or all of the seven to eight filaments constituting the second layer core. A cord and a pneumatic radial tire comprising the same.

Steel cords for tires typically used in trucks or buses are made by twisting a plurality of filaments into two or three layers. In general, a method of manufacturing a two-layered steel cord is formed by first twisting three filaments in one of the left and right directions to form a first layer core, and then twisting seven or eight filaments in a direction opposite to the first layer core. The second layer core is formed by different twisting cycles from the first layer core, and the second layer core wraps around the first layer core to be integrated to complete the two-layer steel cord.

However, such two-layer steel cords have different twisting directions and twisting periods of the first layer core and the second layer core, so that the contact portion between the first layer core and the second layer core becomes small, and thus the filament of the first layer core and the second layer core are reduced. The filaments of the layer core are in point contact. Therefore, when the tire is repeatedly bent by external force, Fretting fatigue (mechanical friction between the filaments and chemical corrosion caused by moisture or salt penetrating from the outside) is greatly generated. There is a problem that durability is lowered. In addition, the twist direction and / or twist period of the first layer core and the second layer core are different, and thus, the first layer core and the second layer core must be separately twisted in a separate process during manufacturing, thereby lowering productivity and increasing manufacturing costs. There is.

Meanwhile, a three-layer lead structure which is generally used is a 3 + 9 + 15 + w (wrapping) structure. When the manufacturing method thereof is outlined, first, the first layer core is twisted by twisting three filaments in one of the leftlets. Forming a second layer core by twisting nine filaments in the same direction as the first layer core and varying the twisting cycle with the first layer core, and allowing the second layer core to be integrally wrapped around the first layer core. .

Subsequently, the 15 filaments are twisted in a direction opposite to the first and second layer cores to form a third layer core with a different twisting period from the second layer core, and then the third layer core surrounds the second layer core and is integrally formed. And by wrapping the filament in the opposite direction to the third layer core to form a wrapping core with a predetermined twisting period, the wrapping core wraps around the third layer core and integrates the wrapped three-layer steel cord. Complete

The wrapped three-layered steel cord is used as a steel cord for reinforcing the carcass or belt part of a large tire such as a truck or a bus because the three-layer steel cord has a high strength by a large number of filaments and a large binding force between the filaments due to the lapping treatment. However, the wrapped three-layered steel cord also has a different twisting direction and / or twisting period of the first and second layer cores, as in the case of the two-layered steel cord, so that fritting fatigue and productivity decrease, There is a problem of an increase in manufacturing cost.

In order to solve this problem, the Korean registered patent KR 0305503 consists of a first layer core composed of three filaments, and a second layer core composed of seven or eight filaments to surround the first layer core. And two-layer steel cords for tire reinforcement having the same twisting direction and twisting cycle of the second layer core have been disclosed. However, in the case of this two-layered steel cord, the manufacturing process of the steel cord is simplified, but the contact area due to the same twisting length and twisting cycle is maximized, so that the complete rubber penetration to the first layer core part consisting of three filaments cannot be completely achieved. . In addition, the 3 + 8 or 3/8 structure is unstable structure in which the second layer core filament is subtracted from one strand in the 3 + 9 structure, so that the second layer core filament is biased to one side when manufactured by a simple twisting process. Therefore, when the tire is repeatedly bent by external force due to the inability to penetrate the rubber into the first layer core, there is a possibility of fretting fatigue, there is a fear that the durability of the tire applied thereto.

The present invention is to solve the problems of the prior art as described above, one object of the present invention is a first layer core consisting of three filaments, and a second layer consisting of seven or eight filaments surrounding the first layer core In a steel cord consisting of a layer core, the 7 to 8 filaments constituting the second layer core have the same twisting direction and twisting period as the first layer core, and have rubber permeability by imparting a mold to at least one or all of them. This is to provide a steel cord for reinforcing tires that can improve tire durability.

Another object of the present invention is to provide a pneumatic radial tire applied to the steel cord according to the present invention as described above to at least one of the carcass, the soaking portion and the belt portion of the tire.

One aspect of the present invention for achieving the above object is three

A first layer core composed of a filament, and a second layer core composed of seven to eight filaments and surrounding the first layer core, wherein the first layer core and the second layer core have a twisting direction and a twisting period Is the same, and the filament constituting the second layer core relates to a steel cord for tire reinforcement, characterized in that at least one of the filaments has a two-dimensional waveform shape.

The steel cord of the present invention may further include a wrapping core composed of one filament surrounding the outer circumferential surface of the second layer core.

The steel cord of the present invention is characterized in that the filaments of the two-dimensional waveform shape constituting the second layer core satisfy the conditions of L = (0 to 100) d ₂ and A = (0.02 to 30) d ₂ . . (Where d ₂ is the diameter of the second layer core filament (mm), L is the wavelength of the two-dimensional waveform (mm), and A is the amplitude of the two-dimensional waveform (mm))

In the steel cord of the present invention, the diameter of the filaments constituting the second layer core is 0.10 mm ≤ d ₂ ≤ 0.40 mm, the diameter of the filaments constituting the first layer core is 0.08 mm ≤ d ₁ ≤ 0.42 mm, The twisting period of the first and second layer cores is characterized by being 20 to 100 times the diameter of the filaments constituting the second layer core.

In the steel cord of the present invention, after the filaments constituting the first and second layer cores and the wrapping cores are drawn out of carbon steel containing 0.70 to 1.20 wt% of carbon, the surface thereof is brass, bronze, copper, zinc In addition, nickel or brass in brass, or cobalt-containing alloy is characterized in that the plating with a thickness of 0.01 ~ 5.0㎛.

Another aspect of the present invention for achieving the above object is directed to a pneumatic radial tire to which the steel cord of the present invention as described above is applied to at least one of the carcass portion, the soaking portion and the belt portion.

Tire reinforcing steel cord according to the present invention and the pneumatic radial tire using the same is easy to penetrate the rubber to the first layer core portion, even if the tire is bent repeatedly by the external force does not cause the fretting fatigue tire durability It is effective to increase.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, examples, and the like.

1 is a cross-sectional view of a steel cord according to an embodiment of the present invention. Referring to Figure 1, the steel cord according to the invention comprises a first layer core 1 consisting of three filaments 1a and a second layer core 2 consisting of seven or eight filaments 2a. Is done. On the other hand, the twisting directions and twisting periods of the first layer core 1 and the second layer core 2 are the same.

Fig. 2 is an enlarged view of the filament 2a of the two-dimensional waveform shape constituting the second layer core 2 in the steel cord according to the embodiment of the present invention. Referring to FIG. 2, in the steel cord according to the embodiment of the present invention, at least one or more of the filaments 2a constituting the second layer core 2 have a two-dimensional waveform shape as shown in FIG. The filament 2a having the two-dimensional waveform satisfies the condition that the wavelength L is L = (0 to 100) d ₂ (mm) and the amplitude A is A = (0.02 to 30) d ₂ (mm). (Where d ₂ is the diameter of the second layer core filament in mm)

In addition, the diameter (d ₂₎ is 0.10mm≤d ₂ ≤0.40mm of filaments (2a) constituting the second core layer (2) from the steel cord in accordance with one embodiment of the invention, the first layer a core ( 1) constituting filaments (1a a) has a diameter (d ₁₎ is preferably 0.08mm≤d ₁ ≤0.42mm. If the diameters (d ₁ , d ₂ ) of the filaments (1a, 2a) constituting the cord is smaller than 0.08mm, it is difficult to manufacture the filament and the manufacturing cost is increased, and if larger than 0.42mm, tire durability is deteriorated. .

In addition, the twisting period of the first layer core 1 and the second layer core 2 having the same twisting direction and twisting period is 20 to 100 times the filament diameter d ₁ constituting the first layer core 1. It is preferable. If the twisting cycle is too small for the diameter, the structural elongation is increased to reduce workability. On the contrary, if the twisting period is too large, the structural elongation is too small to reduce tire durability.

3 is a cross-sectional view of a steel cord according to another embodiment of the present invention. Referring to FIG. 3, the steel cord according to the present invention further includes a wrapping core 3 composed of one filament 3a surrounding the outer circumferential surface of the second layer core 2. Here, the diameters of the filaments 1a and 2a constituting the first layer core 1 and the second layer core 2 and their relations are the same as in Fig. 1, that is, in the case of unwrapped steel cords. The twisting direction of the filament 3a of the wrapping core 3 is opposite to that of the first and second layer cores, and the twisting period is 2 to 10 mm.

 In addition, the filaments (1a, 2a) constituting the first and second layer cores (1, 2), after drawing the carbon steel containing 0.70 to 1.20% by weight of carbon, the brass on the surface It is preferable to use those obtained by plating with a thickness of 0.01 to 5.00 μm of a bronze, copper, zinc or an alloy containing nickel in brass or cobalt in brass. As described above, when the surface of the filaments 1a and 2a of the first and second layer cores 1 and 2 are plated, the mutual adhesion between the filaments 1a and 2a and rubber is greatly increased.

As described above, the steel cord according to the present invention has the same twisting period and twisting direction of the first layer core 1 and the second layer core 2, and thus has a three-layer lead structure such as 3 + 9 + 15 + w. As it is manufactured through three steps as in the productivity is lowered, there is no problem that the product cost is increased.

Also, in the conventional 3 + 7, 3 + 8 or 3/7, 3/8 structure (/ means the twist direction and the twist period is the same), the two-layer steel cord, the structure is When the second layer core filament is manufactured by a simple twisting process in which an unstable structure is subtracted from one strand to two strands, the second layer core filament may be biased to one side. Therefore, when the tire is repeatedly bent by external force due to the inability to penetrate the rubber into the first layer core, fretting fatigue may occur, and durability of the tire to which the tire is applied may be reduced.

However, the steel cord according to the present invention has a filament in which at least one up to eight two-dimensional dies are provided to a second layer core composed of eight filaments, thereby securing space between the second layer core filaments, By making it easy to penetrate to the first layer core, there is an effect of improving the durability of the tire to which it is applied.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples. However, this is for the purpose of explanation and the present invention is not limited thereto.

Example 1

   The steel cord of the 3/8 structure according to the present invention was manufactured by applying a mold to four strands of the core filament of the second layer, and the physical properties were evaluated and shown in Table 1.

Comparative Example 1

 Table 1 shows the physical properties of the steel cord having a conventional 3 + 9 structure.

  Comparative Example 2

   In the conventional 3/8 structure, a filament was not provided to the second layer core, and the results of evaluation of the physical properties are shown in Table 1.

[Table 1]

division Comparative Example 1 Comparative Example 2 Example 1 standard 3 + 9 (0.20) 3/8 (0.20) 3/8 (0.20) Wire Rod C wt% 0.82 0.92 0.92 Core wire (the second floor)
Brother-in-law x x 0 Fatigue limit stress
(kgf / mm2) over 90 over 90 over 90 Initial adhesion
(150 ℃ x30min) 106 105 106 Heat aging
(100 ℃ oven) 7 days
14 days
21st 95
85
70 97
89
74 106
98
85 inroad
(70 ℃, 96% RH) 7 days
14 days
21st 94
69
62 99
84
74 104
100
85 Hot water
(70 ℃) 7 days
14 days
21st 84
66
53 95
78
69 100
89
84 Saline
(NaCl 20%) 7 days
14 days
21st 85
65
51 96
85
69 103
91
82

[Property evaluation method]

* Fatigue limit stress was measured by RBT (Rotating Beam Tester, made in Bekaert)

(1 million revolutions at fatigue limit stress)

* Initial rubber adhesion was measured by ASTM D2229-99 of Instron at 150 ℃ 30min conditions.

* Thermal aging was set in the oven (oven) conditions of 100 ℃, moisture resistance was determined as the ratio of the adhesive strength after aging at 70 ℃, 96% RH conditions, respectively, the adhesive strength was measured by ASTM D2229-99 of Instron.

* The hot water resistance was determined at 70 ° C., and the salt water resistance was determined by the ratio of adhesion after aging at 20% NaCl. The adhesion was measured by Instron's ASTM D2229-99.

As can be seen in Table 1 above, the 3/8 structure in which the two-dimensional waveform is given to the second layer core as in Example 1 according to the present invention has the 3 + 9 structure of Comparative Example 1 throughout the durability including the initial adhesive force. And it can be seen that the effect is superior to the 3/8 structure that does not impart a mold to the second layer core of Comparative Example 2.

Although the present invention has been described in detail with reference to preferred embodiments of the present invention, the present invention is not limited to the above-described embodiments, and many modifications are made by those skilled in the art to which the present invention pertains within the scope of the technical idea of the present invention. This possibility will be self-evident.

1 is a cross-sectional view of a steel cord according to an embodiment of the present invention.

2 is an enlarged view of a two-dimensional corrugated filament constituting the second layer core in the steel cord according to the embodiment of the present invention.

3 is a cross-sectional view of a steel cord according to another embodiment of the present invention.

Claims (8)

A first layer core consisting of three filaments and seven to eight filaments And a second layer core configured to surround the first layer core, wherein the first layer core and the second layer core have the same twist direction and the twist period, and at least one filament constituting the second layer core. This is a two-dimensional waveform shape, The two-dimensional corrugated filaments constituting the second layer core satisfies the conditions of L = (0 ~ 100) d ₂ , A = (0.02 ~ 30) d ₂ . (Where d ₂ is the diameter of the second layer core filament (mm), L is the wavelength of the two-dimensional waveform (mm), and A is the amplitude of the two-dimensional waveform (mm)) The method of claim 1, further comprising a wrapping core composed of one filament surrounding the outer peripheral surface of the second layer core, the twisting direction of the wrapping core is opposite to the twisting direction of the first layer and the second layer core Steel cord for reinforcing tires, characterized in that. delete The diameter of the filament constituting the second layer core is 0.10 mm ≤ d ₂ ≤ 0.40 mm, and the diameter of the filament constituting the first layer core is 0.08 mm ≤ d ₁ ≤ 0.42 mm, the twisting period of the first layer and the second layer core is 20 to 100 times the diameter of the filaments constituting the second layer core, steel cord for tire reinforcement. The steel cord for tire reinforcement according to claim 2, wherein a twisting period of the wrapping core is 2 to 10 mm. According to claim 1 or 2, wherein the filaments constituting the first and second layer cores and lapping cores after drawing carbon steel containing 0.70 to 1.20% by weight of carbon content, the surface of brass, bronze, Steel cord for reinforcing tires, characterized in that the copper, zinc, or nickel in brass, or an alloy containing cobalt in brass plated to a thickness of 0.01 ~ 5.0㎛. The pneumatic radial tire according to claim 1 or 2, wherein the steel cord according to claim 1 is applied to the reinforcing steel cord of at least one of the carcass portion, the sieving portion, and the belt portion. 8. The pneumatic radial tire according to claim 7, wherein rubber topping is applied to the steel cord in order to apply the steel cord to at least one of the carcass portion, the soaking portion and the belt portion. . n = 0.6 / (0.27 d ₁ ² + 0.73 d ₂ ² ), D + 0.1 ≤ t ≤ D + 2.4 Where n is the number of strands of steel cord per inch of width when rubber topping, t is the thickness of the sheet including the steel cord, d ₁ , d ₂ are the diameters of the first and second layer core filaments, respectively, and D is the diameter of the steel cord. being)

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