KR102285067B1 - Steel cord for radial tire - Google Patents

Abstract

The present invention discloses a steel cord for a radial tire.
In the steel cord for a radial tire according to the present invention, in the steel cord for a radial tire, the number of inner core lines is 2, the number of side strands provided outside the core line is 4 to 7, and the virtual inner diameter ( Di), it is characterized in that the virtual outer diameter (D ₀ ) formed by the side strands is defined by the above-described Equations 1 and 2, respectively, by increasing the elongation and improving the rubber penetration through a sufficient gap secured between the wires. It has high fatigue resistance against load and can exhibit improved resistance to the impact of the tire.

Description

Steel cord for radial tire

The present invention relates to a steel cord for a radial tire, and more particularly, it has high fatigue resistance against dynamic loads by increasing elongation and improving rubber penetration through a sufficient gap secured between wire wires, and has improved resistance to impact of the tire. It is about a steel cord for a radial tire that can be demonstrated.

In general, among various types of reinforcing materials used for reinforcing elastomer products such as vehicle tires and conveyor belts, steel cord is required for tire reinforcement compared to other types of reinforcing materials such as strength, modulus, heat transfer rate, fatigue resistance, and adhesion. Because it satisfies the quality characteristics that are required, it has been widely used especially for tire reinforcement, and its use is rapidly increasing day by day.

A conventional steel cord is manufactured by twisting several strands of steel wire in the same direction or in the opposite direction to form a stranded wire connection. It is in a sealed state surrounded by the outer steel wires after making point contact.

In this way, in the sealed steel cord surrounded by steel wires, vulcanization proceeds without filling the inner central space surrounded by the steel wires in the process of vulcanizing and vulcanizing it by burying it in rubber.

When the tread of a tire is damaged by repeated impacts applied while driving or by stones or nails on the road surface, moisture enters the damaged area by capillary action and reaches the central space of the steel cord. Moisture penetrated into the unit is diffused along the central space serving as a passage in the longitudinal direction of the steel cord to induce rusting of the steel cord.

As described above, as a technique for improving rubber permeability in the related art, there are Korean Patent Publication Nos. 10-1742938, 10-1522467, and 10-075855241. Republic of Korea Patent Publication No. 10-1742938 is a steel cord, and by differentiating the diameters of the two core filaments, the inner space between the sheath layer filaments is opened to improve rubber permeability. It is characterized in that the core layer and the upper first sheath layer composed of three lower stranded filaments are in a direction opposite to the lower one, and the upper second sheath layer is anisotropic to the first sheath layer.

In addition, in the case of Korean Patent Publication No. 10-07855241, openness between the lower and lateral lines is given to improve the rubber penetration, but due to the same length and direction of the upper and lower strands, maintaining the shape between the lower and upper edges is unstable, so that the tire runs. There is a disadvantage that the core wire may slide out in the middle.

Moreover, in the radial tire for trucks and buses, the belt layer meeting the tread absorbs stones and shocks from the road surface well to prevent damage to the belt layer. Due to the high and expensive disadvantage, it is used only for tires used exclusively for unpaved roads. A high elongation cord of 3*n, 4*n structure is used as a belt.

Therefore, the present invention suppresses damage to the tread portion of the tire by stones or nails on the road surface in a radial tire for truck bus having a steel belt layer, and moisture after damage rides the damaged area due to capillary action to suppress corrosion of the steel cord. In order to provide a steel cord for a pneumatic radial tire that has high fatigue resistance against dynamic loads by increasing elongation and improving rubber penetration through a sufficient gap secured between the wires, and exhibiting improved resistance to the impact of the tire. will be.

In order to solve the above technical problem, in the steel cord for a radial tire, the number of inner core lines is 2, and the number of side strands provided outside the core line is 4 to 7, and the virtual inner Provided is a steel cord for a radial tire, characterized in that the radius Di and the virtual outer radius D _{0 formed by the side edge are defined by Equations 1 and 2, respectively.}

<Equation 1>

2*d _lower ＜ Di ≤ 2*(d _lower + h _{lower max} )

( _{Waveform under} h: |-3.6779*10 ^-5 *X ⁵ + 8.26*10 ^-4 *X ⁴ - 5.6074*10 ^-3 *X ³ + 8.8943*10 ^-3 *X ² + 1.33822*10 ^-2 * X - 3.1338*10 ^-4 |)

( _lower h max : _{the maximum value under} h, X: the advanced length of the lower edge Laylength in the axial direction)

<Equation 2>

Di + 2*d _phase ＜ Do ≤ Di + 2*(d _phase + h _{phase max} )

(waveform of _the ^{h: | -2.7919 * 10 -6 *} Y 5 + 1.2547 * 10 -4 * Y 4 - 1.76768 * 10 -3 * Y 3 + 7.11569 * 10 -3 * Y 2 + 6.11691 * 10 -3 * Y - 1.33997*10 ^-3 |)

(h _{phase max} : _{maximum value of h phase} , Y: advanced length in the axial direction of phase layer length)

According to an embodiment of the present invention, the virtual inner diameter may be the diameter of the abyss formed by the cross-sectional area of two lower edge cords having a shape portion having a predetermined height and spacing extended with a twist.

According to another embodiment of the present invention, the virtual outer diameter may be the diameter of the outer periphery formed in cross-section by combining 4 to 7 upper edge cords having a twist in the S direction with a preform at regular intervals in the abyss. .

The present invention relates to a pneumatic layered tire, and more particularly, it has high fatigue resistance against dynamic loads by increasing elongation and improving rubber penetration through a sufficient gap secured between wire wires, and has improved resistance to impact of the tire. It is about a pneumatic radial tire that can show off.

1 is a cross-sectional view showing the diameter of an abyss formed in cross-section by extending with twisting two lower lead cords provided in a steel cord for a radial tire of the present invention;
2 is a cross-sectional view showing the diameter of the outer periphery formed in cross-section by associating the abyss provided in the steel cord for a radial tire according to the present invention by 4 to 7 upper cords having a twist in the S direction with preforms at regular intervals. .

Hereinafter, the present invention will be described in detail.

It should be noted that the technical terms used in the present invention are used only to describe specific embodiments, and are not intended to limit the present invention, and the technical terms used in the present invention are not specifically defined in other meanings in the present invention. Unless, it should be interpreted in a meaning generally understood by those of ordinary skill in the art to which the present invention pertains, and should not be interpreted in an excessively comprehensive meaning or in an excessively reduced meaning.

In addition, when the technical term used in the present invention is an erroneous technical term that does not accurately express the spirit of the present invention, it should be understood by being replaced with a technical term that can be correctly understood by those skilled in the art, and the general Terms should be interpreted as defined in the dictionary or according to the context before and after, and should not be construed in an excessively reduced sense.

In addition, the singular expression used in the present invention includes a plural expression unless the context clearly indicates otherwise. It should not be construed as necessarily including all of the various steps, and it should be construed that some components or some steps may not be included or may further include additional components or steps.

1 is a cross-sectional view showing the diameter of an abyss formed in cross-section by extending with twisting two lower lead cords provided in the steel cord for a radial tire of the present invention, and FIG. It is a figure showing the diameter of the outer edge formed in cross-section by associating the prepared abyss with preforms at regular intervals and 4 to 7 lead cords having twist in the S direction, refer to this.

In the steel cord for a radial tire according to the present invention, the number of inner core lines is two, and the number of side strands provided outside the core line is 4 to 7, and the virtual inner diameter formed by the core line, and the virtual outer diameter formed by the side edge line It is characterized in that it is defined by Equation 1 and Equation 2, respectively.

<Equation 1>
2*d _lower ＜ Di ≤ 2*(d _lower + h _{lower max} )

( _{Waveform under} h: |-3.6779*10 ^-5 *X ⁵ + 8.26*10 ^-4 *X ⁴ - 5.6074*10 ^-3 *X ³ + 8.8943*10 ^-3 *X ² + 1.33822*10 ^-2 * X - 3.1338*10 ^-4 |)

( _lower h max : _{the maximum value under} h, X: the advanced length of the lower edge Laylength in the axial direction)

<Equation 2>

Di + 2*d _phase ＜ Do ≤ Di + 2*(d _phase + h _{phase max} )

(waveform of _the ^{h: | -2.7919 * 10 -6 *} Y 5 + 1.2547 * 10 -4 * Y 4 - 1.76768 * 10 -3 * Y 3 + 7.11569 * 10 -3 * Y 2 + 6.11691 * 10 -3 * Y - 1.33997*10 ^-3 |)

(h _{phase max} : _{maximum value of h phase} , Y: advanced length in the axial direction of phase layer length)

Here, h is the height of the _{lower edge preform, h is the maximum height of the lower} edge preform, X is the length of the lower edge laylength (mm), D _i is the diameter of the preformed lower edge strand (Diameter), and d is the _lower edge of the preform. Diameter, h _phase is the height of the preform of the _{upper edge, h phase max} is the maximum height of the upper edge preform, Y is the length of the upper layer length (mm), D _o is the diameter of the preformed upper strand strand, d is the _{upper edge} is defined as the diameter of

In addition, the laylength may be defined as the distance (mm) progressed in the axial direction until the filament rotates 360 degrees along the rotation axis.

This can be generalized to the 2+n (n=4~7) structure of the steel cord, and a preform that is given before twisting a certain shape to the wire for the purpose of improving air permeability by stabilizing the shape of the cord or widening the gap between the wires (preform) can be implemented.

That is, the cord filament passes through a molding machine of a hexagonal roller (Roller type), and the preformed cords undergo a twisting process to become a strand.

It is desirable to maintain the tensile strength applied to the cord at 1000 ~ 1200 cN during twisting so that the preform shape can be maintained after the twisting process during preforming in the molding machine. If it exceeds 1200 cN, not only it is impossible to maintain the shape of the preform described by the above formula, but also a decrease in manufacturing yield may occur due to an increase in disconnection defects (1cN=1.0197gf=0.01N).

Here, based on Equation 1 above, the maximum height of the preform at the lower edge is Max. Lower edge 2 with a height of 0.03 mm, +0.03mm upward when variable X=2.25mm, -0.03mm space below when X=6.75mm, and a mold part with an interval of 2/La (La: stranded length of lower edge) Based on the dog (strand) and Equation 2 above, the maximum height of the stage cord having an S-shaped twist Max. It has a preform height of 0.056 mm, and when the variable Y=4.5mm, it is +0.056mm upward, and when Y=13.5mm, there is a -0.056mm space below, and a mold part with an interval of 2 pieces/Lb (Lb: stranded length of the upper edge) can be given, the elongation is improved by about 10 to 15%, and the distance between the cords can be increased by two or more times, so that the penetration of rubber is naturally improved, thereby improving the impact strength of the belt.

To paraphrase, the lower two strands are Max. It has a preform height of 0.03 mm and two preforms per pitch, and the mold length is preferably 8 to 11 mm. If it is less than 8 mm, the shape may become unstable and it may be difficult to secure a stable elongation. , code flare quality problems may occur.

In addition, the wire diameter of the lower edge is preferably 0.14 to 0.22 mm. If it is less than 0.14 mm, the elongation increases and BF (Break Force or Break Strength: generally means strong strength, in other words it is interpreted as peak strength of the cord. ) is lowered, and there may be a problem in that the unit weight and manufacturing cost increase, and conversely, if it exceeds 0.22mm, there may be a problem in that a flare (filament loosens when cutting the cord) occurs.

These steel cords are made of carbon steel with a carbon content (wt%) of 0.60% to 1.02%, with a final wire diameter of 0.1 to 0.5 mm, and a brass plating layer formed on the surface of the steel wire. Manufactured by twisting, in the conventional method of manufacturing a steel cord having a 2+n structure, the carbon content (wt%) of carbon steel is 0.60% to 1.02%, and the surface is plated with brass to maintain adhesion to rubber. Form a shim with 2 strands and twist so that n strands of the lateral wire are twisted around it. At the same time, the twist length and twist direction are the same, and at the same time, a steel cord is manufactured so that the lateral wire is in contact with the shim to arrange the n strands of the lateral wire. Because the lateral wire is in contact, it is not easy for rubber to penetrate, and due to friction against the contact, the lateral wire is not evenly arranged around the seam, so the lateral wire is pushed to one side, resulting in softness (pitch non-uniformity) in many cases. The invention is a steel cord with a structure of 2+n, by giving a shape to the lower two strands and to the upper n strands to maintain an open state between the filaments, so that the enclosed space surrounded by the wires is excluded and the inside of the steel cord By improving the rubber permeability of the furnace, corrosion propagation speed is suppressed, fatigue resistance is improved, and the lifespan of the tire itself and the possibility of using the casing regeneration can be promoted. is preferably 1.5 to 2 times that of the lower edge, and the reason is to secure the structural stability between the two layers by securing a gap between the upper and lower edges in the preform before twisting.

According to the present invention, the diameter of the lower strand is preferably 0.45 to 0.55 mm by the shape, and the preform section has two per length, and in order to increase the rubber penetration, the upper cord has twice the length of the lower edge. , the internal space between the filaments is opened so that the rubber can sufficiently penetrate during vulcanization.

In addition, in order to increase the retretting reuse casing rate after tire wear is completed, and to improve the long-term adhesion between the steel cord and rubber, the present invention provides a cobalt coating treatment on the surface of the cord during the stranding process of the steel cord to protect against moisture during tire use. This reduces the acceleration of growth of the adhesive layer between the steel cord and rubber, thereby improving the casing durability.

Examples and Comparative Examples

In the form shown in FIGS. 1 and 2, a steel cord was manufactured according to the embodiment according to the present invention according to the configuration in Table 1, and the existing cord structure 1+n(1+6) structure was used as Comparative Example 1 and Conventional 2 The results of evaluation of the +n(2+5) structure as Comparative Example 2 are shown in Table 1 below.

Laylength of steel cord indicates the distance (mm) in the axial direction until the filament rotates 360 degrees along the axis of rotation, where X indicates the distance traveled in the axial direction. In the above equations 1 and 2, the filament rotates 360 and h is the Max. This is to stabilize the rubber penetration and the cross-sectional shape of the steel cord without exceeding 15%, and the list of variables is as follows.

<list>

h is the height of the _{lower edge preform, h is the maximum height of the lower} edge preform, X is the length of the lower edge laylength (mm), D _i is the diameter of the preformed lower edge strand (Diameter), d is the diameter of the _{lower edge (} Diameter), h _phase is the height of the preform of the _{upper edge, h phase max} is the maximum height of the upper edge preform, Y is the length of the upper layer length (mm), D _o is the diameter of the preformed upper strand strand, and d is the diameter of the _{upper edge} .

In addition, in Comparative Example 3, it has a 2+5 structure and gives openness between the lower and upper edges, so that the rubber penetration is excellent. Table 1 and Table 2 show the evaluation results confirming that the adhesive strength is significantly lowered.

In addition, Comparative Example 4 had a 2+5 structure, and structurally openness was imparted to the cord by reversing the twist directions of the upper and lower edges. will cause serious problems.

division Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 rescue 2*0.20+5*0.37 1*0.37+6*0.33 2*0.25+5*0.35 2*0.20+5*0.37 2*0.20+5*0.37 strand direction S/S - S/Z S/S S/Z twist length 9mm/18mm -/18mm 16mm/16mm 5mm/5mm 16mm/32mm cutting strength
(kgf) 205 191 157 187 189 cut elongation
(%) 2.9 2.5 2.7 4.5 2.6 rubber penetration 100% 90% 95% 89% 82%

It can be seen that the Example of the present invention is improved by 7% with a cut elongation of 2.7-> 2.9 when compared with the Comparative Example, and the rubber penetration is also excellent in the Example according to the present invention.

division Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 shape stability stability
(circle) stability
(circle) Instability
(oval) stability
(circle) Unstable (circular)
Flare occurrence rubber adhesion rate
(Early) 100% 100% 100% 100% 100% sticking rate
(wet heat/3 weeks) 100% 88% 82% 100% 80% deep adhesion 100% 98% 95% 70% 100%

In addition, it was confirmed that the Example was superior to the Comparative Example in the seam adhesive strength that can confirm the stability of the stranded wire as well as the shape stability of the cross section of the steel cord.

Table 3 also shows the results of checking the degree of damage to the tread part due to external protrusions through the comparison of the impact resistance of the belt part and the evaluation of the actual vehicle for manufacturing truck bus tires using the steel cords of the Examples and Comparative Examples.

division Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 impact resistance 121% 100% 106% 125% 107% Tread damage rate (%) 130% 100% 103% 132% 115% weight saving 103% 100% 102% 89% 105%

Referring to Table 3, it can be seen that the resistance to damage to the belt by external impact is improved through the improvement of the rubber penetration into the belt cord and the improvement of the cutting elongation, and Comparative Example 3 is superior to the Example in terms of performance, but the cut elongation is lower. high and inferior in weight by 89%.

In addition, the evaluation results of the cord tension optimization for stably producing the steel cord of the present invention are shown in Tables 4 and 5. Table 4 below is a test to check whether the occurrence of quality problems such as poor softness/disconnection of steel cords is prevented by managing the n Filament (Diameter: 0.37mm), which is the upper edge of the 2+n cord.

division cord tension 800 cN 1000 cN 1200cN 1400 cN poor performance Occur non-occurring non-occurring non-occurring monorail non-occurring non-occurring non-occurring Occur

division Example Comparative Example 1 note Legislative Durability 100 100 equal Wet Durability 100 112 Great Impact resistance characteristics after actual vehicle 100 125 Great Wear 100 101 equal

Referring to Tables 4 and 5 above, after drilling the finished tire to which the embodiment according to the present invention is applied and the product of Comparative Example 1 of the existing product by simulating the stone drill of the tread, 80 degrees, 85% R.H. After standing for one month under the condition, the tire evaluation showed excellent results, and as a result of comparing the damage to the trebu peeled external impact on the finished product, the Example was confirmed to be better, as a result, the elongation of the steel cord was increased and the rubber penetration was improved. It was confirmed that it has high fatigue resistance against dynamic loads and can exhibit improved resistance to impact of tires.

Claims (3)

In the steel cord for a radial tire,
The number of inner abyssal lines is 2, and 4 to 7 side edges provided outside the abyssal line are, respectively, the virtual inner diameter (Di) formed by the abyssal line, and the virtual outer diameter (D ₀ ) formed by the side edge line, respectively. A steel cord for a radial tire, characterized in that it is defined by Equation 1 and Equation 2.
<Equation 1>
2*d _lower ＜ Di ≤ 2*(d _lower + h _{lower max} )
( _{Waveform under} h: |-3.6779*10 ^-5 *X ⁵ + 8.26*10 ^-4 *X ⁴ - 5.6074*10 ^-3 *X ³ + 8.8943*10 ^-3 *X ² + 1.33822*10 ^-2 * X - 3.1338*10 ^-4 |)
(h _{lower max} : _{maximum value under} h, X: the advanced length of the lower edge laylength in the axial direction (mm))
<Equation 2>
Di + 2*d _phase ＜ Do ≤ Di + 2*(d _phase + h _{phase max} )
(waveform of _the ^{h: | -2.7919 * 10 -6 *} Y 5 + 1.2547 * 10 -4 * Y 4 - 1.76768 * 10 -3 * Y 3 + 7.11569 * 10 -3 * Y 2 + 6.11691 * 10 -3 * Y - 1.33997*10 ^-3 |)
(h _{phase max} : h _phase maximum value, Y: axial length of the upper edge layer length (mm))
( _upper d = diameter of upper edge (mm), _lower d = diameter of lower edge (mm))
(Here, h is the height of the _{lower edge preform, h is the maximum height of the lower} edge preform, X is the length of the lower edge laylength (mm), D _i is the diameter of the preformed lower edge strand (Diameter), d is the _lower edge the diameter (diameter), h _the height of the upper edge preform, h _{a max} is the maximum height of the upper edge preform, Y is _the length of the upper edge Laylength (㎜), D _o is the Strand of the preform stage diameter, d is Defined as the diameter of the upper edge, and the laylength is defined as the distance (mm) progressed in the axial direction until the filament rotates 360 degrees along the axis of rotation)
(In Equations 1 and 2, the maximum height of the preform at the lower edge is Max. La: the length of the lower strand (stranded wire length of the lower edge) with two lower edges (strands) having an interval, and the maximum height of the upper strand having an S twist. Max. With a preform height of 0.056 mm, it is +0.056 mm upwards when the variable Y=4.5 mm. and, when Y=13.5mm, -0.056mm space is created downward, and a shape part with an interval of 2/Lb (Lb: stranded strand length of the upper edge) can be given, improving elongation and increasing the spacing between cords more than twice. can)
The method of claim 1,
The virtual inner diameter is a steel cord for a radial tire, characterized in that it is the diameter of the abyss formed by the cross-sectional area of two lower edge cords having a shape portion having a predetermined height and spacing extending with a twist.
3. The method of claim 2,
The virtual outer diameter is a steel cord for a radial tire, characterized in that it is the diameter of the outer edge formed by combining 4 to 7 upper edge cords having a twist in the S direction with preforms at regular intervals in the abyss.

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