Steel cord, cord-rubber composite, tire

Abstract

A single-wire steel cord, It has a brass plating film on the surface, Cord diameter is 0.25mm or more and 0.42mm or less, The average value of the coil diameter measured at three locations is 500 mm or more and 600 mm or less, and the variation width of the coil diameter measured at the three locations is 50 mm or less, A steel cord with a torsion of within ±1 turn per 6m.

Description

Technical Field

[0001] The present disclosure relates to steel cords, cord-rubber composites, and tires.

Background Art

[0002] Patent Document 1 discloses a pneumatic tire in which a belt layer including a plurality of aligned single-wire steel wires is embedded on the outer peripheral side of a carcass layer in a tread portion, wherein the single-wire steel wire has a flat cross-sectional shape and the thickness of the under-groove rubber in the tread portion is 1.0 mm to 2.0 mm.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The steel cord of the present disclosure is a single-wire steel cord, having a brass plating film on the surface, with a cord diameter of 0.25 mm or more and 0.42 mm or less, the average value of the coil diameters measured at three locations is 500 mm or more and 600 mm or less, and the variation width of the coil diameters measured at the three locations is 50 mm or less, the torsion per 6 m is within ±1 turn.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a perspective view of a steel cord according to one aspect of the present disclosure. [Figure 2] FIG. 2 is an explanatory diagram of the coil diameter of a steel cord according to one aspect of the present disclosure. [Figure 3] FIG. 3 is an explanatory diagram of a manufacturing method of a steel cord according to one aspect of the present disclosure. [Figure 4] Figure 4 is a perspective view of a cord-rubber composite according to one aspect of the present disclosure. [Figure 5] Figure 5 is a cross-sectional view of a tire according to one aspect of the present disclosure. [Figure 6] Figure 6 is an explanatory diagram of the method for evaluating bending stiffness. [Figure 7] Figure 7 is an explanatory diagram of the method for evaluating package bending stiffness. [Figure 8] Figure 8 is an explanatory diagram of the arrangement of steel cords within a cord-rubber composite used for evaluating package bending stiffness. [Figure 9] Figure 9 is an explanatory diagram of the evaluation method for assessing curvature. [Figure 10] Figure 10 is an explanatory diagram of the method for evaluating positional accuracy. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] To improve fuel efficiency in automobiles, there is a growing demand for lighter tires and reduced rolling resistance. One way to lighten tires is to reduce the thickness of the tire's belt layer. For this reason, the diameter of the steel cords used in the tire's belt layer is being considered.

[0007] However, reducing the diameter of the steel cord sometimes caused the sheet-shaped cord-rubber composite used in the belt layer to bend. This resulted in a decrease in productivity when manufacturing products such as tires.

[0008] Furthermore, reducing the diameter of the steel cords can cause the position of the steel cords to vary within the cord-rubber composite. This can necessitate increasing the thickness of the rubber in the cord-rubber composite to embed the steel cords, sometimes preventing the belt layer from being made thinner.

[0009] Therefore, an object of the present disclosure is to provide a steel cord that suppresses bending when formed into a cord-rubber composite and has excellent positional accuracy within the cord-rubber composite. [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a steel cord that suppresses bending when formed into a cord-rubber composite and has excellent positional accuracy within the cord-rubber composite.

[0010] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0011] (1) The steel cord according to one aspect of the present disclosure is a single-wire steel cord, having a brass plating film on its surface, with a cord diameter of 0.25 mm or more and 0.42 mm or less, the average value of the coil diameters measured at three locations being 500 mm or more and 600 mm or less, and the variation width of the coil diameters measured at the three locations being 50 mm or less, and the torsion per 6 m being within ±1 turn.

[0012] The copper contained in the brass plating film reacts with sulfur (S) contained in the rubber when the steel cord is embedded in the rubber to form a cord-rubber composite or the like. Then, an adhesive layer containing copper sulfide (Cu2S), which is a reaction product, is formed near the interface between the steel cord and the rubber in the rubber.

[0013] The formed adhesive layer can enhance the initial adhesion performance between the steel cord and the rubber.

[0014] Also, it is considered that the zinc contained in the brass plating film promotes and controls the reaction for forming the adhesive layer.

[0015] By setting the cord diameter of the steel cord to 0.42 mm or less, when applied to a cord-rubber composite, the thickness of the cord-rubber composite can be reduced. Therefore, the tire including the cord-rubber composite can be lightened. By setting the cord diameter to 0.25 mm or more, the tensile strength of the steel cord can be increased. Therefore, when manufacturing a cord-rubber composite or a tire, the number of steel cords required to satisfy characteristics such as bending rigidity can be suppressed, and the productivity of the cord-rubber composite or the like can be increased. Further, by setting the cord diameter to 0.25 mm or more, the number of steel cords required when manufacturing a cord-rubber composite or the like can be suppressed, so that a sufficient interval can be taken between the steel cords, and a sufficient amount of rubber can be arranged between the steel cords. Therefore, the adhesion between the steel cord and the rubber is enhanced, and the durability of the cord-rubber composite and the tire can be increased.

[0016] By setting the average value of the coil diameter to 500 mm or more, when the steel cord is applied to a cord-rubber composite, bending of the cord-rubber composite can be suppressed. Therefore, the productivity when manufacturing products such as tires using the cord-rubber composite can be increased.

[0017] By setting the average value of the coil diameter to 600 mm or less, the steel cord is less likely to be twisted, and when applied to a cord-rubber composite, the positional accuracy of the steel cord within the cord-rubber composite can be increased. Therefore, the thickness of the rubber disposed around the steel cord for embedding the steel cord can be suppressed, and the cord-rubber composite and the tire can be lightened.

[0018] By setting the variation width of the coil diameter to 50 mm or less, it means that the coil diameter is uniform for the steel cord. Therefore, the characteristics of the cord-rubber composite and the tire manufactured using the steel cord according to one aspect of the present disclosure can be made uniform and stable.

[0019] By keeping the torsion per 6m within ±1 turn, i.e., between -1 and +1 turn, it means that twisting along the longitudinal direction of the steel cord 10 is suppressed. Therefore, when the steel cord of this embodiment is used in a cord-rubber composite, it is possible to prevent a force from being applied to the rubber arranged around the steel cord, causing it to rotate around the steel cord as the axis of rotation. As a result, bending of the cord-rubber composite is prevented, and the positional accuracy of the steel cord is also improved.

[0020] (2) In (1), the brass plating film may contain one or more elements selected from cobalt, nickel, tin, iron, and manganese.

[0021] The additive elements cobalt, nickel, tin, iron, and manganese have a greater ionization tendency than copper. Therefore, by including these additive elements in addition to copper and zinc, the brass plating film can function as a sacrificial corrosion protectant, or it can increase the synthesis potential of copper and zinc. Consequently, the inclusion of these additive elements in the brass plating film can improve the corrosion resistance of steel cords.

[0022] (3) In (1) or (2), the tensile strength may be 2500 MPa or more and 4500 MPa or less.

[0023] Tensile strength refers to the resistance to deformation when a steel cord is pulled. By setting the tensile strength of the steel cord to 2500 MPa or higher, the number of steel cords required to satisfy the bending rigidity and other properties of the cord-rubber composite can be reduced when applying it to the composite. This allows for weight reduction in products such as cord-rubber composites and tires.

[0024] Furthermore, by limiting the tensile strength of the steel cord to 4500 MPa or less, productivity in manufacturing the steel cord 10 can be increased.

[0025] (4) A code-rubber composite according to one aspect of the present disclosure comprises rubber and The rubber has one of the steel cords (1) to (3) embedded in it.

[0026] The steel cord contained in the cord-rubber composite according to one aspect of this disclosure is small in diameter, and when formed into a cord-rubber composite, it suppresses bending of the cord-rubber composite and provides excellent positional accuracy within the cord-rubber composite.

[0027] Therefore, the cord-rubber composite according to one aspect of this disclosure offers excellent handling properties when manufacturing products such as tires, thereby increasing productivity.

[0028] Furthermore, in a cord-rubber composite according to one aspect of this disclosure, the positional accuracy of the steel cord is high, which allows for a reduction in the thickness of the rubber placed above and below the steel cord, which is necessary for embedding the steel cord. As a result, the thickness of the cord-rubber composite can be reduced, and its weight can be reduced.

[0029] (5) In (4), the bending stiffness is 0.01N or more and 0.05N or less, In the case of a laminate formed by laminating two layers of the aforementioned cord-rubber composite, the short sides located at both ends along the long side of the laminate are fixed with fixing jigs, and when the center of the long side of the laminate is displaced by 0.03 mm along the short side, the reaction force when this displacement is defined as the package bending stiffness may be 2N or more and 10N or less.

[0030] Bending stiffness is an indicator of how resistant a material is to bending deformation; high bending stiffness means that the material is resistant to bending deformation. Therefore, by setting the bending stiffness of the cord-rubber composite to 0.01N or higher, the cord-rubber composite and products such as tires containing the cord-rubber composite will be resistant to bending deformation, thus increasing their durability.

[0031] Furthermore, by setting the bending rigidity of the cord-rubber composite to 0.05N or less, the number of steel cords placed within the cord-rubber composite can be reduced, thereby reducing the weight of the cord-rubber composite and products such as tires that contain the cord-rubber composite, resulting in a lighter product.

[0032] By setting the package bending rigidity to 2N or higher, the handling stability when using the cord-rubber composite in a tire can be improved. Furthermore, by setting the package bending rigidity of the cord-rubber composite to 10N or lower, the durability when using the cord-rubber composite of this embodiment in a tire can be improved.

[0033] (6) In (4) or (5), the steel cord may be included such that the end is 30 strands / 50 mm or more and 60 strands / 50 mm or less.

[0034] By setting the end spacing of the cord-rubber composite to 30 cords / 50 mm or more, the gaps between the steel cords contained in the cord-rubber composite are suppressed, allowing for a high-density arrangement of steel cords. This enhances the puncture resistance, a property that prevents foreign objects from penetrating the cord-rubber composite if they pierce it. Furthermore, it significantly improves the durability of products such as tires that contain cord-rubber composites.

[0035] By limiting the number of ends in the cord-rubber composite to 60 strands / 50 mm or less, the number of supply devices that provide steel cord during the manufacturing of the cord-rubber composite can be reduced, thereby increasing productivity.

[0036] (7) A tire containing a steel cord as described in any of (1) through (3).

[0037] The steel cords contained in the tire according to one aspect of this disclosure are small in diameter and, when formed into a cord-rubber composite, suppress the bending of the cord-rubber composite and have excellent positional accuracy within the cord-rubber composite. For this reason, the cord-rubber composite contained in the tire according to one aspect of this disclosure can also be made thinner and lighter, and the tire according to one aspect of this disclosure can also be made lighter.

[0038] [Details of the embodiments of this disclosure] Specific examples of steel cords, cord-rubber composites, and tires according to one embodiment of this disclosure (hereinafter referred to as "this embodiment") will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to be shown by the claims, with all modifications within the meaning and scope of the equivalents of the claims being included.

[0039] [Steel cord] The steel cord according to this embodiment will be described below with reference to Figures 1, 2, and 3. (1) Structure of steel cord Figure 1 shows a perspective view of the steel cord of this embodiment. In Figure 1, the Y-axis is the axis along the longitudinal side of the steel cord 10. The XZ plane is the plane perpendicular to the longitudinal side of the steel cord 10.

[0040] As shown in Figure 1, the steel cord 10 in this embodiment is a single-strand steel cord. A single-strand steel cord means that it is made up of a single strand, not a stranded cord made by twisting multiple strands together. It is preferable that the steel cord 10 in this embodiment is not twisted along its length. In other words, it is preferable that the steel cord 10 in this embodiment is a straight steel cord.

[0041] Furthermore, it is preferable that the steel cord 10 of this embodiment has a circular shape on the surface perpendicular to its longitudinal side. The circular shape is not limited to a perfect circle, but also includes shapes other than a perfect circle, such as an ellipse.

[0042] The steel cord 10 of this embodiment may have a brass plating film 12 on its surface. Specifically, the steel cord 10 may have a wire 11 and a brass plating film 12 covering the wire 11. (wire rod) The wire 11 can be, for example, a steel wire, and a high-carbon steel wire can be used more preferably. (Brass plating film) The brass plating film 12 may contain copper (Cu) and zinc (Zn). As shown in Figure 1, the brass plating film 12 can be positioned to cover the side surface 11A of the wire 11.

[0043] The copper contained in the brass plating film 12 reacts with the sulfur (S) contained in the rubber when the steel cord 10 is embedded in the rubber to form a cord-rubber composite, etc. This creates an adhesive layer containing the reaction product, copper sulfide (Cu2S), near the interface between the steel cord 10 and the rubber.

[0044] The resulting adhesive layer can enhance the initial bonding performance between the steel cord 10 and the rubber. Initial bonding performance refers to the bonding performance between the steel cord 10 and the rubber immediately after vulcanization during the manufacturing of the cord-rubber composite or a tire containing a cord-rubber composite.

[0045] The zinc contained in the brass plating film 12 is thought to promote and control the reaction that forms the adhesive layer.

[0046] The brass plating film 12 may also contain elements other than copper and zinc. The brass plating film 12 may further contain one or more elements selected from cobalt (Co), nickel (Ni), tin (Sn), iron (Fe), and manganese (Mn).

[0047] The additive elements, cobalt, nickel, tin, iron, and manganese, have a greater ionization tendency than copper. Therefore, by including these additive elements in addition to copper and zinc, the brass plating film 12 can function as a sacrificial corrosion protectant, or it can increase the synthesis potential of copper and zinc. Consequently, the inclusion of these additive elements in the brass plating film 12 can improve the corrosion resistance of the steel cord 10. (2) Characteristics of steel cord (2-1) Regarding cord diameter The steel cord 10 preferably has a cord diameter D10 of 0.25 mm or more and 0.42 mm or less. More preferably, the cord diameter D10 is 0.30 mm or more and 0.42 mm or less, even more preferably 0.34 mm or more and 0.38 mm or less, and particularly preferably 0.35 mm or more and 0.37 mm or less.

[0048] By setting the cord diameter D10 to 0.42 mm or less, the thickness of the cord-rubber composite can be reduced when applied to it. This allows for weight reduction of tires containing the cord-rubber composite. By setting the cord diameter D10 to 0.25 mm or more, the tensile strength of the steel cord 10 can be increased. This reduces the number of steel cords required to satisfy the required bending rigidity and other properties when manufacturing the cord-rubber composite or tire, thereby increasing productivity. Furthermore, by setting the cord diameter D10 to 0.25 mm or more, the number of steel cords required when manufacturing the cord-rubber composite can be reduced, allowing for sufficient spacing between the steel cords and enabling a sufficient amount of rubber to be placed between the steel cords. This improves the adhesion between the steel cord and rubber, increasing the durability of the cord-rubber composite and tire.

[0049] The cord diameter D10 can be determined by measuring it at any cross-section perpendicular to the longitudinal side of the steel cord 10. To measure the cord diameter D10, first, two orthogonal diameters D101 and D102 can be measured at a cross-section perpendicular to the longitudinal side of the steel cord 10. Then, the average of these two diameters D101 and D102 can be used as the cord diameter D10 of the steel cord 10. (2-2) Regarding coil diameter The steel cord 10 in this embodiment is thin, with a cord diameter D10 of 0.42 mm or less. When forming a sheet-shaped cord-rubber composite using such a thin steel cord, the cord-rubber composite sometimes curved. Also, when forming a sheet-shaped cord-rubber composite, multiple steel cords are aligned under a certain tension and embedded in rubber. However, the position of the steel cords may shift before the rubber has fully hardened, resulting in variations in the position of the steel cords within the cord-rubber composite. Therefore, even though the steel cord is thin, when forming the cord-rubber composite, it is necessary to ensure sufficient thickness of rubber above and below the steel cord in order to embed the steel cord in the rubber, which may prevent the cord-rubber composite from being made thin.

[0050] Therefore, the inventors of the present invention conducted an investigation. As a result, they found that the coil diameter, which had previously received little attention, is influencing the curvature of the cord-rubber composite and the decrease in the positional accuracy of the steel cord within the cord-rubber composite that occurs when the diameter of the steel cord is reduced.

[0051] Therefore, it is preferable that the steel cord 10 of this embodiment has an average coil diameter of 500 mm or more and 600 mm or less, measured at three locations.

[0052] By setting the average coil diameter to 500 mm or more, when steel cord 10 is applied to the cord-rubber composite, bending of the cord-rubber composite can be suppressed. Therefore, productivity can be increased when manufacturing products such as tires using the cord-rubber composite.

[0053] By keeping the average coil diameter below 600mm, the steel cord 10 becomes less prone to twisting, improving the positional accuracy of the steel cord 10 within the cord-rubber composite when applied to it. As a result, the thickness of the rubber surrounding the steel cord 10 can be reduced to embed it, making the cord-rubber composite and the tire lighter.

[0054] When measuring the coil diameter of the steel cord 10, the steel cord 10 can be repeatedly cut along its length until three pieces of the steel cord 10 are formed, each having an annular portion 21 that contacts a horizontal test stand 20.

[0055] As shown in Figure 2, the coil diameter D20 of each cut piece refers to the diameter of the annular portion 21 that is naturally formed on each cut piece of steel cord 10 without any force being applied. Therefore, when measuring the coil diameter D20 of each cut piece, the cut piece of steel cord 10 is placed on a horizontal test stand 20. Then, when the annular portion 21 is formed on the test stand 20, the two orthogonal diameters D211 and D212 of the annular portion 21 are measured. Next, the average value of the two measured diameters D211 and D212 can be calculated and used as the coil diameter D20 of each cut piece.

[0056] Then, the coil diameter D20 is measured for three cut pieces, each having an annular portion 21 in contact with a horizontal test stand 20. The average value of the coil diameters of the three cut pieces can then be used as the average value of the coil diameters measured at three locations for the steel cord 10 used for measurement.

[0057] Furthermore, the difference between the maximum and minimum values ​​of the coil diameter D20 of the three measured cut pieces can be determined as the variation range of the coil diameter measured at three locations for the steel cord 10 used for measurement.

[0058] In this embodiment, the steel cord 10 preferably has a variation in coil diameter of 50 mm or less, measured at three locations, and more preferably 40 mm or less.

[0059] By limiting the variation in coil diameter to 50 mm or less, the steel cord 10 of this embodiment has a uniform coil diameter. Therefore, the characteristics of the cord-rubber composite and tires manufactured using the steel cord of this embodiment can be made uniform and stable.

[0060] While there is no particular lower limit to the variation in coil diameter, it is preferable to set it to 0 mm or more, and more preferable to set it to 10 mm or more from the viewpoint of increasing productivity.

[0061] The variation in coil diameter is preferably between 0 mm and 50 mm, and more preferably between 10 mm and 40 mm. (2-3) Torsion In this embodiment, the steel cord 10 preferably has a torsion of ±1 turn or less per 6m, and more preferably ±0.5 turns or less.

[0062] Torsion refers to the number of rotations of the steel cord 10 when one end of the steel cord 10 is free.

[0063] By keeping the torsion per 6m within ±1 turn, i.e., between -1 and +1 turn, it means that twisting along the longitudinal direction of the steel cord 10 is suppressed. Therefore, when the steel cord of this embodiment is made into a cord-rubber composite, it is possible to prevent a force from being applied to the rubber arranged around the steel cord in a way that causes it to rotate around the steel cord as the axis of rotation. As a result, bending of the cord-rubber composite is prevented, and the positional accuracy of the steel cord is also improved.

[0064] Torsion can be evaluated using the same procedure as for residual torsion in JIS G 3510 (1992). During measurement, the reference steel cord was observed from the end bent at a right angle, and a clockwise (rightward) rotation of the steel cord was recorded as + (positive), while a counterclockwise (leftward) rotation of the steel cord was recorded as - (negative). (2-4) Regarding tensile strength The steel cord 10 preferably has a tensile strength of 2500 MPa or more and 4500 MPa or less, more preferably 3000 MPa or more and 4200 MPa or less, and even more preferably 3150 MPa or more and 3500 MPa or less.

[0065] Tensile strength refers to the resistance to deformation when the steel cord 10 is pulled. By setting the tensile strength of the steel cord 10 to 2500 MPa or higher, the number of steel cords required to satisfy the bending rigidity and other properties of the cord-rubber composite can be reduced when applied to the cord-rubber composite. As a result, the weight of the cord-rubber composite and products such as tires can be reduced.

[0066] Furthermore, by setting the tensile strength of the steel cord 10 to 4500 MPa or less, productivity in manufacturing the steel cord 10 can be increased. (3) Regarding the manufacturing method of steel cord, The method for manufacturing the steel cord in this embodiment is not particularly limited. For example, it can be manufactured by drawing a cord base material, which has a brass plating film on its surface, using a die or a roll.

[0067] Specifically, as shown in Figure 3, for example, the cord base material 30 is drawn by passing it through dies 311 and 312. Then, the cord base material 30 that has been drawn by the dies is pressed by a roll 32 to further draw it to the desired cord diameter.

[0068] As shown in Figure 3, the roll 32 can be configured with upper rolls 321A, 321B, and 321C positioned above the cord base material 30 to be drawn, and lower rolls 322A and 322B positioned below it. The cord base material 30 can then be pressed from above and below by the upper rolls 321A, 321B, and 321C and the lower rolls 322A and 322B.

[0069] Note that the number and arrangement of dies, and the shape, number, and arrangement of the rolls constituting the roll 32 are not limited to the example in Figure 3. For example, it is preferable to conduct preliminary tests and select the shape, arrangement, and number of dies and rolls, as well as the pressure applied to the cord base material, according to the average value and variation range of the coil diameter of the steel cord manufactured in the preliminary tests.

[0070] For example, regarding the shape of the roll, the shape of the groove provided on the roll can be selected. The shape of the groove provided on the roll can be such that the curvature is constant in a cross section perpendicular to the longitudinal side of the groove. Furthermore, the grooves provided on the upper roll and the lower roll, which are arranged adjacent to each other along the conveying path of the cord base material 30, can have a shape with a constant curvature in a cross section perpendicular to the longitudinal side of the groove, and can also differ from the cord diameter of the steel cord to be manufactured, up to a maximum of 30%. By selecting the shape of the grooves provided on the upper roll and the lower roll, the controllability of parameters such as the coil diameter of the steel cord to be manufactured can be increased.

[0071] Furthermore, when drawing the cord base material 30, the torsion of the resulting steel cord can be adjusted by adjusting the arrangement of rolls placed on the transport line (pass line) for transporting the cord base material 30, and by adjusting the pressure applied to the cord base material 30 by the rolls. Specifically, for example, it is preferable from the viewpoint of reducing torsion to adjust the position of the rolls, etc., so that the pressure applied to the outer surface of the cord base material 30 is uniform regardless of the location on the outer surface of the cord base material 30. [Cord-rubber composite] Figure 4 shows a perspective view of the cord-rubber composite 40 of this embodiment. In Figure 4, the Y-axis is the axis along the longitudinal side of the steel cord 10. The XZ plane is the plane perpendicular to the longitudinal side of the steel cord 10.

[0072] As shown in Figure 4, the cord-rubber composite 40 of this embodiment includes rubber 41 and the steel cord 10 of this embodiment embedded in the rubber 41. (1) Regarding the components contained in the cord-rubber composite (1-1) Steel cord The cord-rubber composite 40 may contain a plurality of steel cords 10 according to this disclosure. The steel cords 10 contained in the cord-rubber composite 40 can be arranged such that the longitudinal length of each steel cord 10 is aligned with the Y-axis in Figure 4. The plurality of steel cords 10 can then be arranged along the width of the cord-rubber composite 40, i.e., along the X-axis in Figure 4.

[0073] It is preferable that the multiple steel cords 10 are arranged parallel to each other. "Parallel" here does not mean parallel in a strict sense, but rather that the steel cords 10 are arranged in parallel.

[0074] Since details about Steel Code 10 have already been explained, I will omit further explanation here. (1-2) Rubber The rubber 41 of the cord-rubber composite 40 can be manufactured by molding a rubber composition and vulcanizing it as needed.

[0075] The specific composition of the rubber can be selected according to the application of the various products, such as tires, to which the code-rubber composite 40 is applied, as well as the required properties, and is not particularly limited. The rubber may include, for example, rubber components, sulfur, and a vulcanization accelerator.

[0076] The rubber component preferably contains 60% by mass or more of one or more selected from, for example, natural rubber (NR) and isoprene rubber (IR), and is more preferably 70% by mass or more, and even more preferably 100% by mass.

[0077] This is preferable because setting the proportion of one or more types of rubber selected from natural rubber and isoprene rubber in the rubber component to 60% by mass or more can increase the tensile strength of the cord-rubber composite 40 and the tire.

[0078] Examples of rubber components used in combination with natural rubber or isoprene rubber include one or more selected from styrene-butadiene rubber (SBR), butadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), butyl rubber (IIR), and acrylonitrile-butadiene rubber (NBR).

[0079] While the type of sulfur is not particularly limited, sulfur commonly used as a vulcanizing agent in the rubber industry can be used.

[0080] The sulfur content of the rubber is not particularly limited, but it is preferably, for example, 5 to 8 parts by mass per 100 parts by mass of the rubber component.

[0081] This is because setting the ratio of sulfur to 5 parts by mass or more per 100 parts by mass of rubber component increases the crosslinking density of the resulting rubber, and in particular enhances the adhesion between the steel cord and the rubber. Furthermore, setting the ratio of sulfur to 8 parts by mass or less per 100 parts by mass of rubber component is preferable because it allows for particularly uniform dispersion of sulfur within the rubber and suppresses blooming.

[0082] The vulcanization accelerator is not particularly limited, but sulfenamide-based accelerators such as N,N′-dicyclohexyl-2-benzothiazolyl sulfenamide, N-cyclohexyl-2-benzothiazolyl sulfenamide, N-tert-butyl-2-benzothiazolyl sulfenamide, and N-oxydiethylene-2-benzothiazolyl sulfenamide are preferably used. Additionally, thiazole-based accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide, or thiuram-based accelerators such as tetrabenzyl thiuram disulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrakis(2-ethylhexyl) thiuram disulfide, and tetramethyl thiuram monosulfide may be used if desired.

[0083] The rubber composition used in the cord-rubber composite 40 of this embodiment can be manufactured by kneading raw materials such as rubber components, heating them, and extruding them.

[0084] The rubber of the cord-rubber composite 40 in this embodiment preferably contains one or more selected from elemental cobalt and cobalt-containing compounds.

[0085] Examples of compounds containing cobalt include organic cobalt acids and inorganic cobalt acids.

[0086] As the organic cobalt acid, one or more selected from, for example, cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tall oilate, etc., can preferably be used. Note that the organic cobalt acid may also be a composite salt in which some of the organic acids are replaced with boric acid.

[0087] As the inorganic cobalt acid, one or more selected from, for example, cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, and cobalt chromate can preferably be used.

[0088] In particular, the rubber of the cord-rubber composite 40 in this embodiment is more preferably made to contain organic cobalt. This is because the inclusion of organic cobalt can particularly improve the initial adhesion performance between the steel cord and the rubber.

[0089] Furthermore, according to the inventors' research, adding cobalt to rubber can increase the proportion of copper sulfide (Cu2S) in the adhesive layer, thereby improving the adhesion between the steel cord and the rubber. This tendency is particularly pronounced when organic cobalt is used as the added cobalt. For this reason, the rubber of the cord-rubber composite 40 in this embodiment preferably contains cobalt, especially organic cobalt, which makes it possible to produce a cord-rubber composite 40 or tire with particularly excellent durability.

[0090] Furthermore, rubber may contain any components other than the above-mentioned rubber components, sulfur, vulcanization accelerators, cobalt, etc. Rubber may also contain well-known rubber additives such as reinforcing agents (carbon black, silica, etc.), waxes, and anti-aging agents. (2) Characteristics of the cord-rubber composite (2-1) Ends The number of steel cords 10 in the cord-rubber composite 40 of this embodiment is not particularly limited and can be selected according to the characteristics required of the cord-rubber composite 40 and the tire containing the cord-rubber composite 40. Here, the number of steel cords present per 50 mm width of the cord-rubber composite 40 in a cross section perpendicular to the longitudinal side of the steel cords of the cord-rubber composite 40 of this embodiment is defined as the ends. For this reason, in this specification, the unit of ends is "ends / 50 mm". In this case, the ends are preferably, for example, 30 ends / 50 mm or more and 60 ends / 50 mm or less, more preferably 36 ends / 50 mm or more and 60 ends / 50 mm or less, and even more preferably 40 ends / 50 mm or more and 60 ends / 50 mm or less.

[0091] By setting the end length of the cord-rubber composite 40 in this embodiment to 30 cords / 50 mm or more, the gaps between the steel cords 10 contained in the cord-rubber composite 40 are suppressed, and the steel cords can be arranged at high density. As a result, the puncture resistance, which is the property that prevents foreign objects from penetrating the cord-rubber composite when they pierce it, can be improved. In addition, the durability of products such as tires that include the cord-rubber composite 40 can be particularly improved.

[0092] By setting the number of ends of the cord-rubber composite 40 in this embodiment to 60 strands / 50 mm or less, and by reducing the number of supply devices that supply steel cord when manufacturing the cord-rubber composite, productivity can be increased. (2-2) Bending stiffness The cord-rubber composite 40 of this embodiment preferably has a bending stiffness of 0.01 N or more and 0.05 N or less, and more preferably 0.01 N or more and 0.03 N or less.

[0093] Bending stiffness is an indicator of how resistant a material is to bending deformation; high bending stiffness means that it is difficult to bend. Therefore, by setting the bending stiffness of the cord-rubber composite 40 to 0.01N or higher, the cord-rubber composite and products such as tires containing the cord-rubber composite will be resistant to bending deformation, thus increasing their durability.

[0094] Furthermore, by setting the bending rigidity of the cord-rubber composite 40 to 0.05N or less, the number of steel cords placed within the cord-rubber composite 40 can be reduced, thereby reducing the weight of the cord-rubber composite and products such as tires that include the cord-rubber composite, resulting in a lighter product. (2-3) Package curvature rigidity In this embodiment, for a laminate formed by laminating two layers of the cord-rubber composite, the short sides located at both ends along the long side of the laminate are fixed with fixing jigs, and the reaction force when the center of the long side of the laminate is displaced by 0.03 mm along the short side is defined as the package bending stiffness.

[0095] The package bending rigidity of the cord-rubber composite in this embodiment is preferably 2N or more and 10N or less, and more preferably 2.5N or more and 5N or less.

[0096] Package curvature rigidity is a characteristic that corresponds to the cornering power when a cord-rubber composite is used in a tire. Specifically, it is a characteristic that corresponds to the handling stability when a cord-rubber composite is used in a tire.

[0097] By setting the package bending rigidity of the cord-rubber composite of this embodiment to 2N or more, the handling stability when the cord-rubber composite of this embodiment is used in a tire can be improved. Furthermore, by setting the package bending rigidity of the cord-rubber composite of this embodiment to 10N or less, the durability when the cord-rubber composite of this embodiment is used in a tire can be improved.

[0098] The steel cord 10 contained in the cord-rubber composite 40 of this embodiment is small in diameter, and when formed into the cord-rubber composite 40, it suppresses bending of the cord-rubber composite 40 and provides excellent positional accuracy within the cord-rubber composite 40.

[0099] Therefore, the cord-rubber composite 40 according to this embodiment offers excellent handling properties when manufacturing products such as tires, thereby increasing productivity.

[0100] Furthermore, in the cord-rubber composite 40 of this embodiment, the positional accuracy of the steel cord 10 is high. Therefore, the thickness of the rubber 41 placed above and below the steel cord 10, which is necessary for burying the steel cord 10, i.e., thicknesses T411 and T412 in Figure 4, can be reduced. As a result, the thickness T40 of the cord-rubber composite 40 can also be reduced, making it lighter. (3) Method for manufacturing cord-rubber composite The method for manufacturing the cord-rubber composite of this embodiment is not particularly limited, and can be manufactured, for example, by embedding multiple steel cords arranged in parallel in rubber to form a desired end.

[0101] The cord-rubber composite of this embodiment may include, for example, a reel installation process, a drawing process, an arrangement process, and an burying process. The outline of each process will be described below. (Reel installation process) In the reel installation process, multiple reels corresponding to the number of cords to be embedded in the rubber can be installed in the steel cord supply device within the belt layer of the cord-rubber composite. Each reel is wound with steel cord according to one aspect of this disclosure. The steel cord supply device controls the rotation of the reels and supplies the steel cord wound on each reel. The steel cord supply device is sometimes also called a reel supply. (Extraction process) In the drawing process, a steel cord supply device can draw steel cords from each prepared reel and transport and supply them to the arrangement process.

[0102] Since the reel is wound with a steel cord according to one aspect of this disclosure, the average coil diameter of the pulled-out steel cord is within a predetermined range. Therefore, by applying tension to the steel cord that matches the average coil diameter during the arrangement and burial processes, variations in the position of the steel cord can be suppressed.

[0103] Furthermore, after the steel cord is drawn out from each reel during the drawing process, a roll with a groove having a constant curvature in a cross-section perpendicular to the longitudinal side of the groove can be placed on the steel cord's transport path to apply tension to the steel cord. By placing a roll with a groove of a predetermined shape on the steel cord's transport path and applying tension to the steel cord, the coiling of the steel cord can be reduced and eliminated. This particularly suppresses variations in the position of the steel cord, allowing the cord-rubber composite to be made thinner. (Arrangement process) In the arrangement process, multiple steel cords pulled from the reel can be arranged in a single line in a cross-section perpendicular to the length of the steel cord.

[0104] In the arrangement process, for example, an arrangement device can be used to arrange multiple steel cords in a single line.

[0105] The configuration of the arraying device is not particularly limited, but for example, in order to arrange steel cords in a single row, it may have a guide plate with grooves through which the steel cords pass.

[0106] During the alignment process, the position of the steel cords can be further corrected and aligned using grooved rolls as needed. (burying process) In the burial process, multiple steel cords can be embedded in rubber to produce a cord-rubber composite.

[0107] Specifically, for example, a cord-rubber composite can be manufactured by using a calender roll to place multiple steel cords between rubber fibers and then performing a calendering process. If the cord-rubber composite has multiple belt layers, the process from reel installation to burial can be carried out for each belt layer.

[0108] 〔tire〕 The tire in this embodiment will be described with reference to Figure 5.

[0109] The tire of this embodiment may include the steel cord of this embodiment.

[0110] Figure 5 shows a cross-sectional view of the tire 50 according to this embodiment, taken from a plane perpendicular to the outer circumference. Although Figure 5 only shows the portion to the left of the CL (center line), the same structure is continuously present to the right of the CL, with the CL as the axis of symmetry.

[0111] As shown in Figure 5, the tire 50 comprises a tread portion 51, a sidewall portion 52, and a bead portion 53.

[0112] The tread portion 51 is the part that contacts the road surface. The bead portion 53 is located closer to the inner diameter of the tire 50 than the tread portion 51. The bead portion 53 is the part that contacts the rim of the vehicle's wheel. The sidewall portion 52 connects the tread portion 51 and the bead portion 53. When the tread portion 51 receives an impact from the road surface, the sidewall portion 52 elastically deforms and absorbs the impact.

[0113] The tire 50 comprises an inner liner 54, a carcass 55, a belt layer 56, and a bead wire 57.

[0114] The inner liner 54 is made of rubber and seals the space between the tire 50 and the wheel.

[0115] The carcass 55 forms the framework of the tire 50. The carcass 55 is composed of organic fibers such as polyester, nylon, and rayon, or steel cords, and rubber.

[0116] The bead wire 57 is provided in the bead portion 53. The bead wire 57 withstands the tensile force acting on the carcass.

[0117] The belt layer 56 tightens the carcass 55, increasing the rigidity of the tread portion 51. In the example shown in Figure 5, the tire 50 has two belt layers 56.

[0118] The belt layer 56 has a plurality of steel cords and rubber. The plurality of steel cords are arranged in parallel in a row. That is, the belt layer 56 may include the cord-rubber composite according to the present disclosure.

[0119] The steel cords included in the tire of this embodiment are small in diameter, and when combined with the cord-rubber composite, they suppress bending of the cord-rubber composite, resulting in excellent positional accuracy within the cord-rubber composite. Therefore, the cord-rubber composite contained in the tire of this embodiment can also be made thinner and lighter, and the tire of this embodiment can also be made lighter.

[0120] Although embodiments have been described in detail above, the invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope described in the claims. [Examples]

[0121] The present invention will be described with specific examples below, but it is not limited to these examples. (Evaluation method) (1) Evaluation method for steel cord The evaluation method for the steel cords fabricated in the following experimental example is described below. (1-1) Cord diameter The steel cord to be evaluated was embedded in transparent resin, and the sample was cut out so that the longitudinal side and the surface (cross-section) perpendicular to the steel cord were exposed.

[0122] The diameters D101 and D102 of two perpendicular lines were measured in a cross section perpendicular to the longitudinal side of the cut steel cord 10 (see Figure 1). The average of the two diameters D101 and D102 was then defined as the cord diameter D10 of the steel cord 10. (1-2) Average value of coil diameter, variation range of coil diameter When measuring the coil diameter, the steel cord 10 was repeatedly cut along its length until three pieces of the steel cord 10, each having an annular portion 21 in contact with a horizontal test stand 20, were formed.

[0123] Next, as shown in Figure 2, the cut pieces of steel cord 10 were left on a horizontal test stand 20. For the cut pieces in which the annular portion 21 was formed on the test stand 20, the two orthogonal diameters D211 and D212 of the annular portion 21 were measured. Then, the average value of the two measured diameters D211 and D212 was calculated and taken as the coil diameter D20 of the measured cut piece.

[0124] The average of the coil diameters D20 of the three measured cut pieces was taken as the average of the coil diameters measured at three locations for the steel cord 10 used for measurement.

[0125] Furthermore, the difference between the maximum and minimum coil diameters D20 of the three measured cut pieces was determined and used as the variation range of coil diameters measured at three locations for the steel cord 10 used for measurement. (1-3) Torsion Torsion was evaluated using the same procedure as for residual torsion in JIS G 3510 (1992).

[0126] During measurement, the reference point was the end of a steel cord bent at a right angle. A clockwise (rightward) rotation of the steel cord was considered positive (+), and a counterclockwise (leftward) rotation was considered negative (-). (1-4) Tensile strength The tensile strength was measured in accordance with JIS Z 2241 (2022). (2-1) Bending stiffness As shown in Figure 6, the bending stiffness of the cord-rubber composite 40 was evaluated by a three-point bending test.

[0127] Specifically, the first end 601 and the second end 602, which are the width ends of the cord-rubber composite 40, were supported from below by support jigs 611 and 612. Next, the midpoint between support jig 611 and support jig 612 was pressed downward by a pressing jig 613, as shown by block arrow 62.

[0128] Therefore, distance L401 and distance L402 in Figure 4 are equal. Distance L401 represents the distance between the point where the cord-rubber composite 40 contacts the support jig 611 and the point where the cord-rubber composite 40 contacts the pressing jig 613. Distance L402 represents the distance between the point where the cord-rubber composite 40 contacts the support jig 612 and the point where the cord-rubber composite 40 contacts the pressing jig 613.

[0129] Then, the reaction force was measured when the area pressed by the pressing jig 613 was displaced by 0.1 mm along the block arrow 62.

[0130] For the bending stiffness tests, the cord-rubber composites prepared in each experimental example were cut to create 30 mm × 1.2 mm test specimens. The distance between support fixtures 611 and 612 was set to 30 mm. (2-2) Package bending rigidity As shown in Figure 7, a laminate 70 was prepared by laminating the first cord-rubber composite 401 and the second cord-rubber composite 402, which were fabricated in each experimental example. The laminate 70 had a width W70 of 30 mm and a depth D70 of 10 mm.

[0131] Next, the short sides 701 and 702 located at both ends along the long side 703 of the laminate 70 were fixed using fixing jigs 711 and 712. Fixing jigs 711 and 712 fixed the entire short sides 701 and 702 of the laminate 70 along their respective edges.

[0132] Then, the center of the long side of the laminate 70, that is, the center between the two ends fixed by the fixing jigs 711 and 712, was pulled by 0.03 mm along the short sides 701 and 702, that is, along the block arrow 73, using the pulling jig 72, and the reaction force was defined as the package curvature stiffness.

[0133] Therefore, distance L701 and distance L702 in Figure 7 are equal.

[0134] Furthermore, the steel cords 10 are arranged in the first cord-rubber composite 401 and the second cord-rubber composite 402, which constitute the laminate 70, so as to be inclined with respect to the short sides 701 and 702.

[0135] As shown in Figure 8, the steel cord 10 is arranged in the first cord-rubber composite 401 such that the angle θ1 with respect to the short side 702 is 30 degrees. In the second cord-rubber composite 402, the steel cord 10 is arranged such that the angle θ2 with respect to the short side 702 is -30 degrees. Note that in Figure 8, for the sake of drawing convenience, angles θ1 and θ2 are shown as angles with respect to a straight line parallel to the short side 702 shown in the center of Figure 8.

[0136] Figure 8 is a top view of the laminate 70, which is an enlarged view of the vicinity of the fixing jig 712. It is shown with a portion of the first cord-rubber composite removed so that the arrangement of the steel cords 10 in the second cord-rubber composite 402 can be seen. (2-3) Curvature evaluation The cord-rubber composites prepared in the following experimental examples were cut to a size of 1m x 1m and used for evaluation.

[0137] As shown in Figure 9, the evaluation was performed by placing the cord-rubber composite 40, cut to the above size, on the upper surface 90A of the test stand 90, and measuring the maximum height H40 without applying any external force.

[0138] A maximum height of H40 was rated A if it was less than 5mm, B if it was 5mm or more but less than 20mm, and C if it was 20mm or more.

[0139] A rating of A indicates the highest degree of suppression of bending in the cord-rubber composite, with the rating decreasing in the order of B and C. A rating of A or B indicates that the degree of bending in the cord-rubber composite is sufficiently suppressed. (2-4)Position accuracy As shown in Figure 10, the cord-rubber composite 40 prepared in each experimental example was placed on a flat test stand 100. At this time, the test stand was positioned so that a measurement area was exposed where five steel cords 101, 102, 103, 104, and 105 were arranged in a continuous line in a cross section perpendicular to the longitudinal side of the steel cord 10.

[0140] Next, 0.05 kg / mm² per unit area is applied to the surface 110 of the cord-rubber composite 40 opposite to the surface in contact with the test stand 100. 2 A weight (not shown) was placed to apply a load, and the cord-rubber composite 40 was pressed against the test stand 100. As the weight, a plate-shaped weight was used in which the surface facing the cord-rubber composite 40 being evaluated had the same area as the surface 110 of the cord-rubber composite 40.

[0141] The cord-rubber composite 40 was cut so that both the surface in contact with the test stand 100 and the surface 110 in contact with the weight were square, and then used for the test.

[0142] A reference line L parallel to the top surface of the test stand 100 was set so as to pass through the center of the steel cord 101 located at the end of the cord-rubber composite 40, which is part of the steel cord 10 contained in the cord-rubber composite 40.

[0143] Next, for each of the steel cords 102, 103, 104, and 105, other than the standard steel cord 101, the variation width along the thickness of the cord-rubber composite 40 was measured.

[0144] The variation width of each steel cord 10 was determined by measuring the distance between a reference line L, which is aligned with the thickness of the cord-rubber composite 40, and the center of each steel cord 10. In Figure 10, the center is indicated by a black dot. The variation width of steel cord 102 is L102, the variation width of steel cord 103 is L103, the variation width of steel cord 104 is L104, and the variation width of steel cord 105 is L105.

[0145] The average of the variation widths L102, L103, L104, and L105 was taken as the variation width of the position of the steel cords 10 in the cord-rubber composite 40.

[0146] The variation in the position of the steel cord 10 was evaluated as A if it was less than 0.3 mm, B if it was 0.3 mm or more but less than 0.5 mm, and C if it was 0.5 mm or more.

[0147] A rating of A indicates that the positional variation of the steel cords 10 in the cord-rubber composite is suppressed, resulting in the highest positional accuracy. The ratings decrease in the order of B and C. A rating of A or B indicates that the positional accuracy of the steel cords in the cord-rubber composite is sufficiently high.

[0148] The manufacturing conditions for steel cord in each experimental example are described below. Experimental Examples 1 to 3, Experimental Examples 6 to 9, Experimental Examples 12 to 16, and Experimental Examples 19 to 23 are examples. Experimental Examples 4, 5, 10, 11, 17, and 18 are comparative examples. [Experimental Example 1] (Manufacturing of steel cords) Steel cord was manufactured using the apparatus shown in Figure 3.

[0149] A cord base material 30 was prepared by forming a copper layer and a zinc layer on the surface of a steel base material by plating, and a steel cord was manufactured by drawing the cord.

[0150] As shown in Figure 3, the wire drawing process involved gradually reducing the cord diameter by first passing the cord base material through dies 311 and 312. Next, the cord base material 30 was passed between rolls 32, each having grooves on its contact surface with the steel cord, to process it to the desired values ​​for cord diameter, coil diameter, and torsion, thereby producing steel cord. The number of rolls 32, the pressure applied, and the groove shape were selected according to the desired cord diameter, average coil diameter, and variation range of the coil diameter. The grooves on the rolls 32 had a constant curvature in a cross-section perpendicular to the longitudinal side of the groove. Furthermore, the arrangement of the rolls used to transport the cord base material 30, and the pressure applied to the cord base material 30, were selected according to the desired torsion. In the following other experimental examples, the conditions described here were selected and adjusted based on the results of preliminary tests conducted in advance to achieve the desired values ​​for cord diameter, average coil diameter, variation range of coil diameter, and torsion.

[0151] The obtained steel cords were evaluated. The evaluation results are shown in Table 1. (Manufacturing of cord-rubber composites) Multiple steel cords were embedded in rubber to create the ends shown in Table 1, thereby producing a cord-rubber composite.

[0152] Specifically, a cord-rubber composite was manufactured by using a calender roll to place multiple steel cords between rubber fibers and then performing a calendering process.

[0153] The above rubber was manufactured using a rubber composition comprising a rubber component and additives. The rubber composition contains 100 parts by mass of natural rubber as the rubber component. The rubber composition also contains, as additives, 60 parts by mass of carbon black, 7 parts by mass of sulfur, 0.5 parts by mass of vulcanization accelerator, 8 parts by mass of zinc oxide, and 2 parts by mass of cobalt stearate as an organic cobalt, per 100 parts by mass of the rubber component.

[0154] The cord-rubber composite was first prototyped using the steel cord from this experimental example, and the variation in the position of the steel cord 10 in the cord-rubber composite 40 was measured in order to evaluate the positional accuracy. In addition, the rubber thickness was determined by adding a constant for the thickness that was set in advance to the measured variation in the position of the steel cord 10 in the cord-rubber composite 40 so that the steel cord 10 could be embedded.

[0155] In this experimental example, when manufacturing the cord-rubber composite, the manufacturing conditions were selected so that the thickness of the rubber placed above and below the steel cord 10 was the predetermined rubber thickness. In the other experimental examples below, the rubber thickness was determined in advance using the steel cords produced in each experiment and used when manufacturing the cord-rubber composite.

[0156] The thickness of the rubber placed above and below the steel cord 10 corresponds to thicknesses T411 and T412 in Figure 4.

[0157] The obtained cord-rubber composite was evaluated. The evaluation results are shown in Table 1. [Experimental Examples 2 to 18] When manufacturing the steel cord, the cord diameter, average coil diameter, variation range of coil diameter, and torsion were processed to achieve the desired values ​​in each experimental example.

[0158] Except for the points mentioned above, steel cords and cord-rubber composites were manufactured and evaluated under the same conditions as in Experimental Example 1. The evaluation results are shown in Tables 1 and 2. [Experimental Examples 19 to 22] When manufacturing the steel cord, the cord diameter, average coil diameter, variation range of coil diameter, and torsion were processed to achieve the desired values ​​in each experimental example.

[0159] Furthermore, when manufacturing the cord-rubber composite, the end value was modified to match the values ​​shown in Table 2. Aside from these points, steel cords and cord-rubber composites were manufactured and evaluated under the same conditions as in Experimental Example 2. The evaluation results are shown in Table 1.

[0160] Except for the points mentioned above, steel cords and cord-rubber composites were manufactured and evaluated under the same conditions as in Experimental Example 1. The evaluation results are shown in Table 2. [Experimental Example 23] A cord base material 30 was used, in which copper, cobalt, and zinc layers were plated onto the surface of a steel base material. When manufacturing the steel cord, it was processed so that the average value of the cord diameter and coil diameter, the variation range of the coil diameter, and the torsion were to meet the desired values.

[0161] Except for the points mentioned above, steel cords and cord-rubber composites were manufactured and evaluated under the same conditions as in Experimental Example 1. The evaluation results are shown in Table 2.

[0162] [Table 1]

[0163] [Table 2] According to Tables 1 and 2, the cord-rubber composites using steel cords in Experimental Examples 1 to 3, 6 to 9, 12 to 16, and 19 to 23, where the average cord diameter, coil diameter, coil diameter variation range, and torsion were within the specified range, were confirmed to achieve a bending performance evaluation and a positional accuracy evaluation of A or B. In other words, it was confirmed that the steel cords in these experimental examples, when combined into a cord-rubber composite, could prevent bending and exhibited excellent positional accuracy within the cord-rubber composite. [Explanation of symbols]

[0164] 10 Steel cord 11 Wire rod 11A side 12 Brass plating film D10 cord diameter D101, D102 diameter 20 test benches 21 Ring section D20 coil diameter D211, D212 diameter 30 Cord base material 311, 312 dice 32 rolls 321A, 321B, 321C Upper Roll 322A, 322B Lower Roll 40 Cord-Rubber Composite 41 Rubber T411, T412 thickness T40 Thickness CL Centerline 50 tires 51 Tread section 52 Sidewall section 53 Bead section 54 Inner Liner 55 Carcass 56 Belt Layer 57 Bead wire 601 First end 602 Second end 611, 612 Support fixtures 613 Pressing jig 62 Block Arrows L401, L402 distance 401 Code 1 - Rubber Composite 402 Second Code - Rubber Composite 70-layer structure W70 width D70 Depth 701, 702 Short side 703 Long side L701, L702 distance 711, 712 Fixing fixtures 72. Traction jig 73 Block Arrows θ1, θ2 angle 90 Test benches 90A top H40 Maximum Height 100 test benches 101, 102, 103, 104, 105 Steel Code 110 sides L reference line L102, L103, L104, L105 Variation range

Claims

1. A single-wire steel cord, It has a brass plating film on the surface, The cord diameter is 0.25 mm or more and 0.42 mm or less. The average value of the coil diameter measured at three points is 500 mm or more and 600 mm or less, and the variation width of the coil diameter measured at the three points is 50 mm or less, A steel cord with a torsion of within ±1 turn per 6 m.

2. 2. The steel cord according to claim 1, wherein the brass plating film contains at least one selected from the group consisting of cobalt, nickel, tin, iron, and manganese.

3. 3. The steel cord according to claim 1 or 2, having a tensile strength of 2500 MPa or more and 4500 MPa or less.

4. Rubber and A cord-rubber composite comprising: the steel cord according to claim 1 or 2 embedded in the rubber.

5. The bending stiffness is 0.01 N or more and 0.05 N or less, 5. The cord-rubber composite according to claim 4, wherein a laminate having two layers of the cord-rubber composite is fixed with a fixing jig at short sides located at both ends along a long side of the laminate, and the package bending rigidity is defined as a reaction force generated when a center of the long side of the laminate is displaced 0.03 mm along the short side. The package bending rigidity is 2 N or more and 10 N or less.

6. The cord-rubber composite according to claim 4, comprising the steel cords so that the ends are 30 cords / 50 mm or more and 60 cords / 50 mm or less.

7. A tire comprising the steel cord according to claim 1 or 2.

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