KR20130073144A - Tire reinforcing steel cord and an air injection radial tire using the same - Google Patents

Abstract

PURPOSE: A tire reinforcing steel cord and an air injection radial tire using the same are provided to improve the durability of a tire by improving initial adhesion, aging adhesion, fatigue resistance, a rubber penetration rate, and strain degradation properties. CONSTITUTION: A tire reinforcing steel cord comprises one or more strands (2a) to combine each other. One or more strands are topped by rubber. One or more strands are formed with a two-dimensional spiral or waved curvature part along the longitudinal direction of the strands.

Description

Steel cord for tire reinforcement and pneumatic radial tire using it {TIRE REINFORCING STEEL CORD AND AN AIR INJECTION RADIAL TIRE USING THE SAME}

The present invention relates to a steel cord for reinforcing tires and a pneumatic radial tire using the same. More particularly, at least one strand of the steel cord formed by twisting and joining several strands of steel strands is twisted and stranded with rubber. The present invention relates to a steel reinforcing steel cord having excellent adhesiveness, fatigue resistance, and handling workability, and a pneumatic radial tire using the same.

In recent years, tires are required to be lightweight for saving resources, long-lasting durability, and high functionality with excellent cornering comfort, and steel cords for tire reinforcement used as reinforcing materials are also required to improve characteristics that meet the above functions. .

In order to reinforce, the belt cord and the carcass layer of the tire are buried with steel cords formed by twisting two to 40 pairs of ultrafine steel wires having a circular cross section of 0.12 to 0.38 mm in diameter. These steel cords have been required to have excellent strength, modulus, heat resistance, heat transfer rate, fatigue resistance, adhesiveness, and the like, and their usage is rapidly increasing.

Some typical structures of steel cords embedded in rubber products and serving as reinforcing materials will be described with reference to FIGS. 1 to 3.

1 is a cross-sectional view of a conventional hermetic steel cord. As shown in FIG. 1, a steel cord 1 having a 1 × 3 structure in which three strands of steel wires 1a are strandedly bonded to each other, which is enclosed by the steel wires 1a when embedded in a rubber to be reinforced and vulcanized and bonded to the rubber to be reinforced The air remains without filling the rubber in the central space portion H inside.

When the steel cord 1 having such a structure is used as a belt reinforcing material of a tire, deterioration of rubber is promoted by heat generation of the tire and air remaining in the center space portion H while the vehicle is running, and the steel cord and the rubber The phenomenon of separation of the adhesive interface layer is caused. When the tire tread portion is damaged by repeated impacts applied during driving of the vehicle or stones or nails on the road surface, water enters the damaged portion by capillary action and enters the central space portion H of the steel cord 1. The water penetrated into the central space portion is diffused in the longitudinal direction of the steel cord along the central space portion that serves as a passage to induce rapid rusting of the steel cord. Furthermore, the moisture penetrated into the central space portion H of the steel cord not only causes the cord itself to come out, but also fatally destroys the adhesive interfacial layer between the rubber and the cord, resulting in separation between the two members, thereby lowering the durability of the tire.

Further, in the steel cord 1 of the hermetic structure, since the line contact is made between the steel wires 1a that are twisted and coupled with each other, the tire belt 1 which is in contact with the ground plane is repeatedly stretched and compressed every time the tire is rotated. As severe external pressure is transmitted, internal friction progresses gradually in the contact area between the wires, and as a result, the contact surface of the wires wears out, causing the air supply to cut off a part of the cord inside the belt due to abrasion fatigue. In addition, in the hermetic steel cord 1, when water intrudes into the central space portion H in a state in which the brass plating layer on the surface is damaged by abrasion as described above, erosion is easily performed and corrosion progresses. This will occur.

A so-called open steel cord as shown in FIG. 2 is known as JP-A-57-43866 as one of structures developed to solve the problems posed by such a hermetic steel cord. The open steel cord 2 has a structure in which a certain clearance S is maintained between adjacent steel wires 2a in forming a steel cord by twisting a plurality of steel wires 2a. In such an open steel cord (2) structure, the rubber penetration through the gap (S) formed between the steel wires (2a) has the advantage that the rubber permeability is improved, but all steel wires are similar in the longitudinal direction more than 100% high Since it has a mold part ratio, a large gap is created between steel wires, so it exhibits a very high elongation at low load. Therefore, it is very unstable in terms of structural stability of stranded wire. There is a problem falling. In addition, the structure of the open steel cord 2 has a problem in that the shape of the shape (maintenance to maintain the shape) of the open steel cord 2 is easily closed when the external pressure is applied during vulcanization bonding, thereby deforming into a closed steel cord.

In view of the disadvantages pointed out in the conventional open code, Japanese Unexamined Patent Application Publication No. Hei 5-163687 discloses some strands 3a 'in forming a cord by stranding various strands of steel wires 3a as shown in FIG. A strand stranded (or partially open) steel cord 3 is disclosed, which is provided with a die.

In the one-strand shaped steel cord 3, rubber penetration and improved moderate elongation can be achieved to some extent, but instantaneous severe impact due to external tension and compressive stress is transmitted during driving of the steel cord 3 ), When the load is applied, the tensile and compressive stresses are intensively biased to the steel wire with a relatively low mold rate, that is, the small wire supply length per unit length. There is a disadvantage in that the structural stability is poor due to fracture.

The structure of the open steel cord 2 of FIG. 2 and the single-stranded shaped steel cord 3 of FIG. 3 are mechanically processed by using a mold-making machine to give a constant mold to the steel wire within a predetermined range. Deformation is applied, and at this time, the friction between the mold and the steel wire causes the chipping or damage of the brass layer on the surface of the steel wire, thereby degrading the adhesive property with the rubber. In addition, in the steel cords of these structures, the variation of the mechanical properties in the longitudinal direction of the steel wire increases, particularly in the case of local uneven parts, i.e., a relatively small radius of curvature, which causes severe plastic damage.

The present invention is to overcome the above-mentioned problems of the prior art, one object of the present invention is to provide a steel wire with adjacent steel wire of the stranded structure without significantly deteriorating other quality characteristics such as reduced elongation required for the material for reinforcing tires It is to provide a steel reinforcing steel cord and a pneumatic radial tire using the same to provide a gap therebetween to improve fatigue resistance, rubber adhesiveness and handling workability and ultimately improve tire durability.

One aspect of the present invention for achieving the above object is configured by twisting one or more strands of stranded wire, one or more strands are topping with rubber, one or more strands are two-dimensional spiral or along the longitudinal direction of the strands It relates to a steel cord for reinforcing tires, characterized in that the curved portion formed.

Another aspect of the present invention for achieving the above object relates to a pneumatic radial tire, characterized in that the steel cord of the present invention is applied to the reinforcing steel cord of at least one of the carcass portion, the soaking portion and the belt portion. will be.

The steel cord of the present invention has sufficient filling of the rubber in the center to improve rubber penetration rate, thereby improving corrosion resistance and suppressing adhesion interface breakage with the rubber, thereby contributing to improving tire durability, and aging characteristics It has excellent performance. In addition, in the fatigue resistance aspect, the gap between the open central space and the adjacent steel wire is filled with rubber, so that friction due to direct contact between the steel wires is suppressed. Since wear is minimized, fatigue resistance is increased.

In addition, in the steel cord of the present invention, there is no fear of damaging the brass plating layer caused in the process of inducing the opening of the central space through the provision of a mold by mechanical plastic working to a conventional steel wire, and in the rubber topping process of the wire Many adhesive interface layers can be ensured.

In addition, the steel wire constituting the steel cord of the present invention has a low elongation during deterioration because the moldability of the steel cord is approximately 70 to 95%. .

1A is a schematic cross-sectional view of a conventional hermetic steel cord.
1B is a schematic cross-sectional view of a conventional open steel cord.
1C is a schematic cross-sectional view of a conventional partially shaped steel cord.
Figure 2 is a perspective view of a rubber topping filament of the steel cord for tire reinforcement according to an embodiment of the present invention.

Hereinafter, the configuration of the present invention will be described in more detail with reference to the accompanying drawings.

In order to clearly describe the present invention, a detailed description of related general functions or configurations is omitted. In addition, all terms including technical terms and scientific terms used below have the same meaning as commonly understood by one of ordinary skill in the art.

The present invention is to improve the rubber penetration rate when manufacturing a steel cord for the reinforcement belt of the existing high-performance radial tire, at least one strand is to be achieved by a steel cord to be stranded by a rubber topping. The present invention has a technical feature to allow the penetration of the rubber to the inside of the steel cord by the twisted pair of topping element wire.

The present invention eliminates the fear of plating layer damage by providing rubber toppings in advance to strands that are stranded together without imparting excessive molds resulting in chipping or damage of the brass plating layer in the conventional steel cord structure. Since the rubber is filled up to the center of the cord, even when moisture is infiltrated by damage to the tread when applied as a tire reinforcement, the adhesive interface layer with the rubber is protected as the propagation and diffusion path of the water is blocked.

In addition, in the present invention, the contact between the steel wires is minimized to improve fatigue resistance, and there is no increase in elongation during deterioration, thereby improving the handling workability. Steel cords can be provided.

Steel cord of an embodiment of the present invention is configured by combining one or more strands of stranded wire, one or more strands are topping with rubber, one or more strands are formed in a two-dimensional spiral or corrugated bend along the longitudinal direction of the strands do.

Further details of the steel cord for reinforcing tires excellent in rubber permeability of the present invention will be clearly understood by referring to the following drawings showing preferred embodiments of the present invention.

Figure 4 shows one element wire topping with rubber of one embodiment of the present invention. Referring to Figure 4, in the steel cord of the present invention it can be seen that one wire is topping with rubber, the thickness of the topping is 10 ± 5% of the wire diameter, the elongation at low is 0.28 ± 0.03%.

The reason for limiting the topping thickness of the present invention as described above is as follows. First, when the topping thickness of the element wire exceeds 15%, the space between the steel cords is increased during twisting of stranded strands, thereby increasing the elongation during deterioration. This is very unstable in terms of structural stability of the stranded wire, it is easy to stretch when subjected to tension in the longitudinal direction of the cord has a problem that the handling of the cord in the molding process of the tire is inferior

On the contrary, when the topping thickness of the wire is less than 5%, the effect of infiltrating the rubber into the steel cord by the topping becomes less. As the internal friction progresses gradually in the contact area between the wires, the air contact surface wears out as abrasion fatigue. This causes damage to the brass plating layer on the surface.

The process of stranding rubber toppings requires a very high technical level. Increasing the tension applied to the strands in the twisted pair process of the topping element wires, the pressure is applied to the topping rubber by the pressure between the element wires instead of the strands are well connected, and the wires are in contact with each other, which in turn hinders rubber permeability. On the contrary, when the tension on the wire is small, the elongation during deterioration increases, which is unstable in terms of structural stability, and adversely affects workability during rolling work in a tire factory.

On the other hand, the reason for setting the range of lowering elongation as described above is as follows. The lowering elongation is a property directly related to workability during the tire rolling process. If the lowered elongation rate is less than 0.25%, rubber penetration does not occur perfectly. This is a phenomenon caused by the wires pushing the rubber due to the large pressure acting between the wires. In addition, when the lowered elongation value exceeds 0.31%, it is unstable in terms of structural stability, resulting in flatness of the rolled sheet and end-per-inch defects.

In the steel cord of the present invention, the mold portion ratio (wave height (h) / d (line diameter) × 100) of the bent portion of the two-dimensional waveform is 70% to 95%, and the ratio of the lengths of the bent portion and the non-bended portion of the steel cord is May be repeated in a length ratio of 1: 9 to 9: 1. If the bent portion and the non-bended portion of the steel cord is in the range of 1: 9 to 9: 1, the linearity and elongation can be adjusted more easily.

In the present invention, the single-wire steel cord preferably has a mold part ratio of 70 to 95%, and if it satisfies this range, linearity can be easily adjusted and adhesiveness can be improved.

※ Mold rate = h (wave height) / d (wire diameter) x 100

Another aspect of the present invention relates to a pneumatic radial tire, characterized in that the tire reinforcing steel cord described above is applied to the reinforcing steel cord of at least one of the carcass, the sowing portion and the belt portion of the tire.

The steel cord of the present invention can be used for the reinforcement of the carcass portion in which the carcass portion reinforcement cords are arranged, and the belt portion in which the belt portion reinforcement cords are arranged like a "tele" of a barrel in the tire circumferential direction. In the tires for passenger cars, steel cords are used for the belt part, and industrial fiber cords are used for the carcass part, and steel cords can be used for both the carcass part and the belt part for heavy load tires for trucks and buses.

Hereinafter, the present invention will be described in more detail with reference to specific examples, which are merely for the purpose of description and the present invention is not limited thereto.

[Example 1]

As a steel cord having a 1 x 3 structure according to the present invention, a steel cord having a dimensional waveform is given to one strand and a rubber topping on one strand was prepared, and its physical properties were evaluated.

Comparative Example 1

The physical property evaluation of the conventional closed type steel cord of 1x3 structure was performed.

Comparative Example 2

The property evaluation was carried out as an open steel cord having a conventional 1 x 3 structure.

[Comparative Example 3]

The property evaluation was carried out as a shaped steel cord in which a two-dimensional waveform was given to one strand of a conventional 1 × 3 structure.

Experimental Example  One

For the tires for evaluation obtained in Example 1 and Comparative Examples 1 to 3, the rubber penetrability, lowered elongation rate, fatigue resistance, initial adhesive strength, and aging adhesive strength were evaluated by the following measuring method, and the results are shown in Table 3 below. Together.

[Property evaluation method]

* Rubber permeability was measured by embedding steel cord in rubber for tires and vulcanizing, and then evaluating the rubber permeability (%) by the ratio of the area filled with rubber with respect to the total area of the central space of the steel cord cross section.

Low load elongation is expressed as a percentage of elongation of each specimen under a low load of 0.25 to 5.1 kgf.

* Fatigue resistance was measured by RBT (Rotating Beam Tester, manufactured by Bekaert) (rotation of 1 million times or more at fatigue limit stress).

* Initial Adhesion Force The initial rubber adhesion force was measured by ASTM D2229-99 of Instron at 150 ° C. × 30 min vulcanization conditions.

* Aging adhesive strength was measured by Instron's ASTM D2229-99 after immersing the rubber composition containing the steel cord of the example in saline for 3 weeks.

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 rescue 1 x 3 1 x 3 1 x 3 1 x 3 Characteristic Hermetic Open Grant of brotherhood Rubber topping Rubber penetration (%) 50 90 90 100 Fatigue Resistance (kgf / mm ² ) 90 100 100 120 Low Elongation (%) (0.2 ~ 1.6kgf) 0.019 0.031 0.29 0.28 Early
Adhesion Micheal 44 47 48 50 Regular price 45 47 47 49 And 40 40 38 40 Aging
Adhesion HA 1 week 43 43 42 44 2 weeks 40 44 43 44 3 weeks 39 42 42 42 HWR 1 week 44 46 45 47 2 weeks 42 44 43 46 3 weeks 41 45 43 44 MPA 1 week 40 46 46 50 2 weeks 39 41 42 47 3 weeks 37 41 40 45 SCR 1 week 40 47 46 49 2 weeks 37 45 40 45 3 weeks 32 39 38 45

Experimental Example  2

After the steel cord was manufactured by varying the thickness of the rubber topping on the 0.30 mm thick wire as shown in Table 1 below, the physical properties thereof were compared and shown in Table 2 below.

Comparative Example 4 Example 2 Comparative Example 5 Comparative Example 6 Rubber topping thickness (mm) 0.02 0.03 0.04 0.05 Lowered Elongation Rate (%)
(0.2 ~ 1.6kgf) 0.10 0.27 0.50 0.90 Rubber penetration (%) 60 100 100 100 Bad when rolling Yu / Mu radish radish U U

Experimental Example  3

In order to confirm the effect according to the range of the lowered elongation, the tension of the stranded wire was prepared as shown in Table 3, and then the steel cords were prepared, and the physical properties thereof were compared and shown in Table 3 below.

Comparative Example 7 Comparative Example 8 Example 3 Comparative Example 9 Comparative Example 10 Twisted Pair Tension 3.0 kg 2.5 kg 2.0 kg 1.5 kg 1.0 kg Lowered Elongation Rate (%)
(0.2 ~ 1.6kgf) 0.18 0.23 0.28 0.34 0.40 Rubber penetration (%) 70 90 100 100 100 Rolling
Bad none none none has exist has exist

As confirmed through Table 1-3, in Comparative Example 1 it can be seen that the rubber penetration, fatigue resistance, elongation during deterioration, adhesion level is very low. This may cause a decrease in tire performance and durability. In Comparative Example 2 and Comparative Example 3, the rubber penetrability, fatigue resistance, lowered elongation rate, adhesive strength is superior to Comparative Example 1, but is less than the present invention. Cord of the present invention is excellent in the initial adhesive strength, aging adhesive strength, fatigue resistance, rubber penetration rate, low elongation rate characteristics can contribute to improving the durability of the tire.

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. It will be apparent that this is possible. Therefore, the scope of protection of the present invention should be defined by the scope of the claims and their equivalents.

1, 2, 3: core
1a, 2a 3a: Element wire
10: strand strand
20: topping rubber

Claims (6)

Steel cord for reinforcing tires, characterized in that one or more strands are connected by stranded wires, one or more element wires are topping with rubber, and one or more element wires are formed with two-dimensional spiral or corrugated bends along the length direction of the element wires. .
The steel cord for reinforcing tires according to claim 1, wherein the steel cord is a steel cord having a short or double structure.
The steel cord of claim 1, wherein the rubber topping is rubber topping having a thickness of 10 ± 5% of the wire diameter.
2. The steel cord for reinforcing tires according to claim 1, wherein the steel cord has a value of lowered elongation of 0.28 ± 0.03%.
The bending ratio (wave height (h) / d (line diameter) × 100) of the bent portion is 70% to 95%, and the ratio of the length of the bent portion and the non-bended portion of the steel cord is 1: 9 to. A steel cord for reinforcing tires, characterized in that it is repeated at a length ratio of 9: 1.
A pneumatic radial tire, wherein the steel cord according to any one of claims 1 to 5 is applied to the reinforcing steel cord of at least one of a carcass portion, a sieving portion, and a belt portion.

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