Cord-rubber composite and tire

Abstract

This cord-rubber composite includes: a plurality of steel cords, and rubber in which the plurality of steel cords aligned in parallel are embedded. Each of the steel cords has a single twisted structure. When the diameter of an element wire included in each of the steel cords is d (unit: mm), the strength of the element wire is 4350-2000 × dMPa or greater. In a cross section of the cord-rubber composite, the cross section being taken perpendicular to the longitudinal direction of the steel cords, the ratio of an inter-cord distance, which is the distance between adjacent steel cords, to a rubber thickness, which is the thickness of the rubber disposed on the steel cords, is 1.8 or greater, and the rubber thickness is 0.175 mm to 0.225 mm.

Description

Cord-rubber composite, tire

[0001] This disclosure relates to a cord-rubber composite tire. This application claims priority to Japanese Application No. 2024-108440, filed July 4, 2024, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Document 1 discloses a steel cord-rubber composite comprising a steel cord and a coating rubber that coats the steel cord, wherein a predetermined rubber composition for coating a steel cord is used for the coating rubber.

[0003] Japanese Patent Application Laid-Open No. 2017-002152

[0004] The cord-rubber composite of the present disclosure is a cord-rubber composite comprising a plurality of steel cords and rubber in which the plurality of steel cords, which are arranged in parallel, are embedded, wherein the steel cords have a single twist structure, and where d is the wire diameter of the wires contained in the steel cords, the strength of the wires is 4350-2000×d MPa or more, and in a cross section of the cord-rubber composite perpendicular to the longitudinal direction of the steel cords, the ratio of the inter-cord distance, which is the distance between adjacent steel cords, to the rubber thickness, which is the thickness of the rubber arranged on the steel cords, is 1.8 or more, and the rubber thickness is 0.175 mm or more and 0.225 mm or less.

[0005] FIG. 1 is a cross-sectional view of a cord-rubber composite according to one embodiment of the present disclosure. FIG. 2 is a perspective view of a steel cord having a 1x4 structure. FIG. 3 is a cross-sectional view of a tire according to one embodiment of the present disclosure. FIG. 4 is an explanatory diagram of the relationship between the cord distance / rubber thickness and the component weight in an experimental example. FIG. 5 is an explanatory diagram of the relationship between the cord distance / rubber thickness and the adhesive strength in an experimental example.

[0006] Conventionally, a sheet-like cord-rubber composite, in which a plurality of steel cords are aligned and embedded in rubber, has been used as a tire component.

[0007] In order to increase the rigidity of tires, it is necessary to increase the strength of the cord-rubber composite member, and in order to reduce the rolling resistance of tires, it is also necessary to reduce the weight of the cord-rubber composite member.

[0008] However, in order to increase the strength of the cord-rubber composite member, it is necessary to increase the number of steel cords, which increases the weight of the cord-rubber composite, making it difficult to achieve weight reduction.

[0009] An object of the present disclosure is to provide a cord-rubber composite having high component strength and reduced component weight.

[0010] According to the present disclosure, a cord-rubber composite body having high component strength and reduced component weight can be provided.

[0011] First, embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements will be denoted by the same reference numerals, and the same description will not be repeated.

[0012] (1) A cord-rubber composite according to one aspect of the present disclosure is a cord-rubber composite comprising a plurality of steel cords and rubber in which the plurality of steel cords, which are aligned in parallel, are embedded, wherein the steel cords have a single twist structure, and when the wire diameter of the wires included in the steel cords is d (unit: mm), the strength of the wires is 4350-2000×dMPa or more, and in a cross section of the cord-rubber composite perpendicular to the longitudinal direction of the steel cords, the ratio of the inter-cord distance, which is the distance between adjacent steel cords, to the rubber thickness, which is the thickness of the rubber arranged on the steel cords, is 1.8 or more, and the rubber thickness is 0.175 mm or more and 0.225 mm or less.

[0013] By setting the strength of the wires of the steel cord to 4350-2000×dMPa or more, the strength of the steel cord is increased, and the strength of the cord-rubber composite member can be increased without excessively increasing the number of steel cords in the cord-rubber composite.

[0014] By setting the ratio of the cord distance to the rubber thickness to 1.8 or more, the adhesive strength between the steel cord and the rubber can be increased, and the durability of the cord-rubber composite and the tire including the cord-rubber composite can be improved.

[0015] By setting the rubber thickness to 0.175 mm or more, the rubber surrounding the steel cord can be made sufficiently thick, thereby particularly enhancing the adhesive strength between the steel cord and the rubber. By setting the rubber thickness to 0.225 mm or less, the thickness of the cord-rubber composite can be made thin, thereby reducing the weight of the cord-rubber composite member.

[0016] (2) In (1), the ratio of the distance between the cords to the rubber thickness may be 2.2 or more.

[0017] By setting the ratio of the cord distance to the rubber thickness to 2.2 or more, the adhesive strength between the steel cord and the rubber in particular can be increased, and the durability of the cord-rubber composite and the tire including the cord-rubber composite can be improved.

[0018] (3) In (1) or (2), the steel cord may have a 1×n structure, where n is 3 or more and 5 or less.

[0019] By setting n to 3 or more, the strength of the steel cord can be particularly increased. Furthermore, by setting n to 5 or less, the cord diameter of the steel cord can be reduced. Therefore, the member thickness, which is the thickness of the cord-rubber composite, selected so that the steel cord can be embedded, can be reduced, and the weight of the cord-rubber composite member can also be reduced.

[0020] (4) In any one of (1) to (3), the inter-cord distance may be 80% or more and 150% or less of the cord diameter of the steel cord.

[0021] By making the inter-cord distance 80% or more of the cord diameter, the inter-cord distance can be made sufficiently long, and a sufficient amount of rubber can be placed between the steel cords, thereby particularly enhancing the adhesive strength between the steel cords and the rubber.

[0022] Furthermore, by setting the inter-cord distance to 150% or less of the cord diameter, the distance between the steel cords in the cord-rubber composite can be prevented from becoming excessively large, and the punching resistance of the cord-rubber composite can be improved.

[0023] (5) In any one of (1) to (4), the wire diameter may be 0.15 mm or more and 0.30 mm or less.

[0024] By setting the wire diameter to 0.30 mm or less, the cord diameter of the steel cord can be made particularly small. The thickness of the cord-rubber composite is selected so that the steel cord contained therein can be embedded. Therefore, by reducing the cord diameter of the steel cord, the thickness of the cord-rubber composite member using the steel cord can also be reduced, thereby enabling weight reduction of the cord-rubber composite and a tire including the cord-rubber composite.

[0025] By setting the wire diameter to 0.15 mm or more, the strength of the steel cord can be increased, and the number of steel cords required to achieve a desired component strength for the cord-rubber composite can be reduced, thereby enabling weight reduction of the cord-rubber composite and a tire including the cord-rubber composite.

[0026] (6) A tire according to one embodiment of the present disclosure includes the cord-rubber composite according to any one of (1) to (5).

[0027] According to a tire according to one aspect of the present disclosure, the component strength of the belt layer is high, and the component weight can be reduced. Therefore, according to a tire according to one aspect of the present disclosure, the rigidity of the tire can be increased and the rolling resistance can be reduced. In other words, the tire according to one aspect of the present disclosure can be a tire with excellent running stability, low fuel consumption, and excellent durability.

[0028] [Details of the embodiment of the present disclosure] Specific examples of a cord-rubber composite and a tire according to one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described below with reference to the drawings. The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. [Cord-Rubber Composite] The cord-rubber composite according to this embodiment will be described below.

[0029] Fig. 1 is a cross-sectional view of a cord-rubber composite body of this embodiment. Fig. 1 is a cross-section perpendicular to the longitudinal direction of a steel cord included in the cord-rubber composite body 10. Fig. 2 is a perspective view of a 1 x 4 steel cord having a single twist structure.

[0030] 1 and 2, the Y axis is an axis along the longitudinal direction of the steel cord 11. The XZ plane in FIGS.

[0031] Figure 1 is a cross-sectional view of a cord-rubber composite 10 of this embodiment, in which a cord-rubber composite 10A and a cord-rubber composite 10B are laminated together. In Figure 1, the cord-rubber composite 10A and the cord-rubber composite 10B have the same configuration, so unless there is a need to distinguish between them, they will simply be referred to as the cord-rubber composite 10. The following description will mainly focus on the cord-rubber composite 10A.

[0032] As shown in FIG. 1, the cord-rubber composite 10 of this embodiment includes a plurality of steel cords 11 and rubber 12 in which the plurality of steel cords 11 are embedded. The steel cords 11 contained in the cord-rubber composite 10 can be arranged parallel to one another with the longitudinal direction of each steel cord 11 aligned along the Y axis in FIG. 1. The plurality of steel cords 11 are embedded in the rubber 12 in a parallel, aligned state. The plurality of steel cords 11 can be arranged along the width of the cord-rubber composite 10 (along the X axis in FIG. 1). (1) Steel Cord (1-1) Regarding Structure As shown in FIGS. 1 and 2, the steel cord 11 can be a twisted wire formed by twisting together a plurality of wires 111. Specifically, as shown in FIG. 2, the steel cord 11 can be formed by twisting together the wires 111 in a spiral shape along the longitudinal direction of the steel cord 11. The steel cord 11 can have a single-twist structure.

[0033] The single-twist structure means a structure in which a plurality of wires 111 are twisted together to form a single layer (one layer). The single layer means a structure in which the wires 111 are arranged in a single row along the circumference of a circle in a cross section perpendicular to the longitudinal direction of the steel cord 11.

[0034] The steel cord 11 having a single twist structure can be expressed as a 1×n structure, where "n" means the number of wires contained in the steel cord 11, and "1" means the number of layers formed by a plurality of wires, as described above. Although Figures 1 and 2 show an example of a steel cord 11 having a 1×4 structure with four wires, the number of wires contained in the steel cord 11 is not particularly limited and can be selected as desired.

[0035] For example, the steel cord 11 used in the cord-rubber composite 10 of this embodiment may have a 1×n structure, where n is 3 or more and 5 or less. By setting n to 3 or more, the strength of the steel cord can be particularly increased. Furthermore, by setting n to 5 or less, the cord diameter (outer diameter) of the steel cord 11 can be reduced. As a result, the member thickness T10, which is the thickness of the cord-rubber composite 10 in which the steel cord 11 can be embedded, can also be reduced, and the member weight of the cord-rubber composite 10 can also be reduced. (1-2) Regarding the Wire (Wire Diameter) The wire diameter d of the wire 111 included in the steel cord 11 of this embodiment is not particularly limited, and may be, for example, less than 2.175 mm, 0.50 mm or less, or 0.30 mm or less.

[0036] The wire diameter d of the wire 111 may be 0.12 mm or more, or 0.15 mm or more.

[0037] Therefore, the wire diameter d of the wire 111 may be 0.12 mm or more and less than 2.175 mm, 0.12 mm or more and 0.50 mm or less, or 0.15 mm or more and 0.30 mm or less.

[0038] By setting the wire diameter d to less than 2.175 mm, the cord diameter D11 of the steel cord 11 can be reduced. By setting the wire diameter d to 0.50 mm or less, the cord diameter D11 of the steel cord 11 can be further reduced. By setting the wire diameter d to 0.30 mm or less, the cord diameter D11 of the steel cord 11 can be made particularly small. The thickness of the cord-rubber composite is selected so that the steel cord 11 contained therein can be embedded. Therefore, by reducing the cord diameter D11 of the steel cord 11, the thickness of the cord-rubber composite member using the steel cord 11 can also be reduced, thereby enabling weight reduction of the cord-rubber composite and a tire including the cord-rubber composite.

[0039] By setting the wire diameter d to 0.12 mm or more, the strength of the steel cord 11 can be increased, and the number of steel cords 11 required to achieve the desired component strength for the cord-rubber composite can be reduced. By setting the wire diameter d to 0.15 mm or more, the strength of the steel cord 11 can be particularly increased, and the number of steel cords 11 required to achieve the desired component strength for the cord-rubber composite can be reduced. This allows for weight reduction of the cord-rubber composite and tires including the cord-rubber composite. (Material of the Wire) The wires 111 of the steel cord 11 of this embodiment can be composed of wire material only, or the wire material can have a brass plating film on the surface.

[0040] The wire may be, for example, a steel wire or a high carbon steel wire.

[0041] The brass plating film contains copper (Cu) and zinc (Zn) and can be disposed so as to cover the side surface (outer periphery) of the wire.

[0042] When the steel cord is embedded in rubber to form a cord-rubber composite, the copper contained in the brass plating film reacts with the sulfur (S) contained in the rubber. Then, copper sulfide (Cu), a reaction product, is formed in the rubber near the interface between the wire and the rubber. ２ S).

[0043] The adhesive layer thus formed can improve the initial adhesive performance between the steel cord and rubber. The initial adhesive performance refers to the adhesive performance between the steel cord and rubber immediately after vulcanization during the production of a cord-rubber composite or a tire including the cord-rubber composite.

[0044] It is believed that the zinc contained in the brass plating film promotes and controls the reaction that forms the adhesive layer.

[0045] The brass plating film may contain elements other than copper and zinc, such as one or more selected from the group consisting of cobalt (Co), nickel (Ni), tin (Sn), iron (Fe), and manganese (Mn).

[0046] The additive elements cobalt, nickel, tin, iron, and manganese have a greater tendency to ionize than copper. Therefore, when the brass plating film contains additive elements in addition to copper and zinc, the brass plating film functions as a sacrificial corrosion protection film or makes the combined potential of copper and zinc more noble. Therefore, when the brass plating film contains additive elements, the corrosion resistance of the steel cord 11 can be improved.

[0047] The wires 111 of the steel cord 11 may be corrugated wires or the like having bent portions and non-bent portions alternately along the length. (Strength of Wire) The inventors of the present disclosure have conducted research into cord-rubber composites that have high component strength and reduced component weight.

[0048] In this specification, a cord-rubber composite having high component strength and reduced component weight means a cord-rubber composite having a component strength equal to or greater than that of the cord-rubber composite of Experimental Example 15 (see Table 2), but a component weight lighter than that of the cord-rubber composite of Experimental Example 15. The cord-rubber composite shown in Experimental Example 15 uses a steel cord made by twisting together commonly used wires having a wire strength of 3110 MPa to form a 1 x 4 structure, and embeds a number of steel cords in the rubber that will give the cord-rubber composite a sufficiently high component strength.

[0049] As a result of studies by the inventors of the present disclosure, they have found that by using a steel cord having wires with a predetermined strength, it is possible to increase the strength of the cord-rubber composite member without excessively increasing the number of steel cords used in the cord-rubber composite.

[0050] When the wire diameter (diameter) of the wire 111 of the steel cord 11 is d, the strength of the wire 111 can be set to 4350-2000×d MPa or more.

[0051] By setting the strength of the wires 111 of the steel cord 11 to 4350-2000×dMPa or more, it is possible to ensure sufficient strength of the wires 111 according to the wire diameter, thereby increasing the strength of the steel cord 11. As a result, the strength of the cord-rubber composite 10 can be increased without excessively increasing the number of steel cords 11 in the cord-rubber composite 10. Note that the unit of "4350" in the above formula is "MPa", the unit of "2000" is "MPa / mm", and the unit of "d" is "mm".

[0052] The −2000×d in the formula 4350−2000×d relating to the strength of the wires 111 of the steel cord 11 is a correction term for canceling out the wire diameter dependency of the strength. For example, when the wire diameter is 0.25 mm, the value of the correction term is −500, and the strength can be set to 3850 MPa or more.

[0053] The upper limit of the strength of the wires 111 of the steel cord 11 is not particularly limited, but may be, for example, 5350-2000×dMPa or less.

[0054] The strength of the wire 111 can be kept within a predetermined range by, for example, selecting the material of the wire. For example, the strength of the wire 111 can be kept within a predetermined range by selecting the amount of carbon contained in the steel used for the wire. (2) Rubber The rubber 12 of the cord-rubber composite 10 can be produced by molding a rubber composition and vulcanizing it as necessary.

[0055] The specific composition of the rubber is not particularly limited and can be selected depending on the application of various products such as tires to which the cord-rubber composite 10 is applied, the required properties, etc. The rubber can contain, for example, a rubber component, sulfur, and a vulcanization accelerator.

[0056] The rubber component may contain, for example, 60% by mass or more, 70% by mass or more, or 100% by mass of one or more types selected from natural rubber (NR) and isoprene rubber (IR).

[0057] By making the proportion of one or more types of rubber selected from natural rubber and isoprene rubber in the rubber component 60% by mass or more, the breaking strength of the cord-rubber composite 10 and the tire can be increased.

[0058] 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).

[0059] The sulfur is not particularly limited, but for example, sulfur generally used as a vulcanizing agent in the rubber industry can be used.

[0060] The sulfur content of the rubber is not particularly limited, but may be, for example, 5 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the rubber component.

[0061] By setting the ratio of sulfur to 100 parts by mass of the rubber component to 5 parts by mass or more, the crosslink density of the resulting rubber can be increased, and the adhesive strength between the steel cord and the rubber can be particularly increased. Also, by setting the ratio of sulfur to 8 parts by mass or less, the sulfur can be dispersed particularly uniformly in the rubber, and blooming can be prevented.

[0062] The vulcanization accelerator is not particularly limited, and examples thereof include sulfenamide accelerators such as N,N'-dicyclohexyl-2-benzothiazolylsulfenamide, N-cyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, and N-oxydiethylene-2-benzothiazolylsulfenamide. If desired, thiazole accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide, and thiuram accelerators such as tetrabenzylthiuram disulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, and tetramethylthiuram monosulfide may also be used.

[0063] The rubber composition used in the cord-rubber composite 10 of this embodiment can be produced by kneading raw materials such as rubber components, heating the mixture, and extruding it.

[0064] The rubber of the cord-rubber composite 10 of this embodiment may also contain a cobalt component, which is one or more types selected from simple cobalt and compounds containing cobalt.

[0065] Examples of the cobalt-containing compound include organic acid cobalt and inorganic acid cobalt.

[0066] The organic cobalt salt may be, for example, one or more selected from cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tallate, etc. The organic cobalt salt may be a composite salt in which part of the organic acid is replaced with boric acid.

[0067] As the inorganic acid cobalt, for example, one or more selected from cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate, and cobalt chromate may be used.

[0068] The rubber may also contain optional components other than the above rubber components, sulfur, vulcanization accelerator, cobalt, etc. The rubber may also contain well-known rubber additives, such as reinforcing agents (carbon black, silica, etc.), wax, and antioxidants. (3) Regarding the Arrangement of Steel Cords in the Cord-Rubber Composite Increasing the number of steel cords 11 in the cord-rubber composite 10 can increase the component strength of the cord-rubber composite 10. However, increasing the number of steel cords 11 in the cord-rubber composite 10 also increases the component weight of the cord-rubber composite 10. Furthermore, increasing the number of steel cords 11 in the cord-rubber composite 10 shortens the distance between the steel cords 11, thereby reducing the adhesive strength between the steel cords 11 and the rubber 12 and reducing the durability of the cord-rubber composite 10. (Ratio of Inter-Cord Distance to Rubber Thickness) Here, the thickness of the rubber 12 arranged on the steel cords 11 in the cross section of the cord-rubber composite 10 of this embodiment perpendicular to the longitudinal direction of the steel cords 11 is defined as rubber thickness T12. The distance between adjacent steel cords 11 is defined as an inter-cord distance L11.

[0069] In this case, in the cord-rubber composite 10 of this embodiment, the ratio (L11 / T12) of the cord-to-cord distance L11 to the rubber thickness T12 can be set to 1.8 or more.

[0070] By setting the ratio of the inter-cord distance L11 to the rubber thickness T12 to be 1.8 or more, the adhesive strength between the steel cords 11 and the rubber 12 is increased, and the durability of the cord-rubber composite 10 and a tire including the cord-rubber composite 10 can be improved.

[0071] The ratio (L11 / T12) of the inter-cord distance L11 to the rubber thickness T12 may be 2.2 or more.

[0072] According to studies by the inventors of the present disclosure, by setting the ratio of the inter-cord distance L11 to the rubber thickness T12 to be 2.2 or more, it is possible to increase the adhesive strength particularly between the steel cords 11 and the rubber 12, and to improve the durability of the cord-rubber composite 10 and a tire including the cord-rubber composite 10. (Rubber Thickness) The rubber thickness T12 of the cord-rubber composite 10 of the present embodiment can be set to be 0.175 mm or more and 0.225 mm or less.

[0073] By setting the rubber thickness to 0.175 mm or more, the rubber 12 surrounding the steel cord 11 can be made sufficiently thick, thereby particularly enhancing the adhesive strength between the steel cord 11 and the rubber 12. By setting the rubber thickness T12 to 0.225 mm or less, the member thickness T10 of the cord-rubber composite 10 can be made thin, thereby reducing the member weight of the cord-rubber composite 10. (Inter-cord distance) The inter-cord distance L11 may be, for example, 80% or more and 150% or less of the cord diameter D11 of the steel cord 11.

[0074] By making the inter-cord distance L11 80% or more of the cord diameter D11, the inter-cord distance L11 can be made sufficiently long, and a sufficient amount of rubber 12 can be placed between the steel cords 11. As a result, the adhesive strength between the steel cords 11 and the rubber 12 can be particularly enhanced.

[0075] Furthermore, by setting the inter-cord distance L11 to 150% or less of the cord diameter D11, the distance between the steel cords 11 in the cord-rubber composite 10 can be prevented from becoming excessively large, and the punching resistance of the cord-rubber composite 10 can be improved.

[0076] The punching resistance property of the cord-rubber composite 10A means a property that can prevent the formation of a hole penetrating the cord-rubber composite 10 when a foreign object comes into contact with the upper surface 100 of the cord-rubber composite 10A and presses against it.

[0077] The method for measuring and calculating the rubber thickness of the cord-rubber composite and the distance between cords will be described in the explanation of the evaluation method in the Examples, and therefore the explanation will be omitted.

[0078] 1, the cord-rubber composite 10 is often formed by laminating a cord-rubber composite 10A and a cord-rubber composite 10B, which are multiple cord-rubber composites 10. When multiple cord-rubber composites 10 are laminated in this manner, it may be impossible to confirm the boundary line 13 between the cord-rubber composite 10A and the cord-rubber composite 10B, which is the upper surface 100 of the cord-rubber composite 10A.

[0079] 1, when a plurality of cord-rubber composites 10 are laminated, the rubber thickness T12 can be measured by first measuring the thickness T11, which is the minimum thickness of the rubber 12 between the steel cords 11 arranged along the thickness of the laminated cord-rubber composites 10. Then, half the value of the thickness T11 may be taken as the rubber thickness T12 of the measured steel cord 11.

[0080] FIG. 1 shows only the thickness T11A of the rubber 12 between the steel cords 11 arranged along the thickness of the laminated cord-rubber composite 10 at the position of the steel cord 11A, but the rubber thickness can also be measured and calculated at the positions of other steel cords 11B, etc., using the same procedure.

[0081] [Tire] Next, the tire according to this embodiment will be described with reference to FIG.

[0082] The tire of this embodiment may include a cord-rubber composite 10 according to one aspect of the present disclosure.

[0083] Fig. 3 shows a cross-sectional view of a tire 30 according to this embodiment taken along a plane perpendicular to the outer periphery. Although Fig. 3 shows only the portion to the left of the center line (CL), the same structure continues to the right of the center line (CL), with the center line (CL) as the axis of symmetry.

[0084] As shown in FIG. 3 , the tire 30 includes a tread portion 31 , a sidewall portion 32 , and a bead portion 33 .

[0085] The tread portion 31 is the portion that comes into contact with the road surface. The bead portions 33 are provided at positions closer to the inner diameter of the tire 30 than the tread portion 31. The bead portions 33 are the portions that come into contact with the rim of a vehicle wheel. The sidewall portions 32 connect the tread portion 31 and the bead portions 33. When the tread portion 31 receives an impact from the road surface, the sidewall portions 32 elastically deform to absorb the impact.

[0086] The tire 30 includes an inner liner 34 , a carcass 35 , a belt layer 36 , and a bead wire 37 .

[0087] The inner liner 34 comprises rubber and seals the space between the tire 30 and the wheel.

[0088] The carcass 35 forms the framework of the tire 30. The carcass 35 includes organic fibers such as polyester, nylon, or rayon, or steel cords, and rubber.

[0089] The bead wire 37 is provided in the bead portion 33. The bead wire 37 receives a tensile force acting on the carcass 35.

[0090] The belt layer 36 tightens the carcass 35 to increase the rigidity of the tread portion 31. In the example shown in Fig. 3, the tire 30 has two belt layers 36. The cord-rubber composite 10 according to one embodiment of the present disclosure can be used as the belt layer 36. The cord-rubber composite 10 has already been described, so a description thereof will be omitted.

[0091] As described above, in the tire of the present embodiment, the cord-rubber composite 10 according to one aspect of the present disclosure is used for the belt layer 36 .

[0092] Therefore, according to the tire 30 of this embodiment, the member strength of the belt layer 36 is high and the member weight can be reduced. Therefore, according to the tire 30 of this embodiment, the rigidity of the tire can be increased and the rolling resistance can be reduced. In other words, the tire 30 of this embodiment can be a tire with excellent running stability, low fuel consumption, and excellent durability.

[0093] Although the embodiments have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and changes are possible within the scope of the claims.

[0094] Specific examples will be given below for explanation, but the present invention is not limited to these examples. (Evaluation Method) First, the evaluation method for the steel cords and cord-rubber composites produced in the following experimental examples will be explained. (1) Wire diameter, cord diameter, cord spacing, rubber thickness, member thickness The wire diameter, cord diameter, cord spacing, and rubber thickness were measured from the cross section of the cord-rubber composite.

[0095] For the evaluation, one cross section perpendicular to the longitudinal direction of one steel cord (hereinafter referred to as the "reference steel cord") included in the cord-rubber composite was exposed. Specifically, the same cross section as the cord-rubber composite 10A shown in FIG. 1 was exposed. In addition, two more cross sections spaced 100 mm apart along the longitudinal direction of the reference steel cord were exposed. The following description will be given using the cord-rubber composite 10A in FIG. 1. In this case, steel cord 11A is taken as the reference steel cord.

[0096] In the three exposed cross sections, the wire diameter d, cord diameter D11, inter-cord distance L11, and rubber thickness T12 were measured and calculated for five steel cords 11, including the reference steel cord. In the case of Figure 1, the five steel cords 11, including the reference steel cord, are steel cord 11A, steel cord 11B, steel cord 11C, steel cord 11D, and steel cord 11E. Specific measurement and calculation methods for each part are described below. (Wire Diameter) In one cross section, the diameters of all the wires 111 included in steel cord 11A, the reference steel cord, were measured and the average value was calculated. The calculated average value was used as the wire diameter in the measured cross section. The wire diameters were measured in the remaining two cross sections using the same procedure, and the average value of the wire diameters in the three cross sections was used as the wire diameter d of the wires 111 of the steel cord 11 included in the cord-rubber composite 10A.

[0097] The formula 4350 - 2000 x d was calculated from the wire diameter d, and the calculated value is shown in the column "4350 - 2000 x d". (Cord Diameter) In one cross section, the diameters of the smallest inclusive circles were measured for steel cords 11A to 11E, which were the five steel cords 11 to be evaluated, and the average value was calculated. The smallest inclusive circles of steel cords 11A to 11E were smallest inclusive circle C11A, smallest inclusive circle C11B, smallest inclusive circle C11C, smallest inclusive circle C11D, and smallest inclusive circle C11E, respectively. The calculated average value was used as the cord diameter of the steel cord 11 in the measured cross section. The cord diameter of the steel cord 11 was measured in the remaining two cross sections using the same procedure, and the average value of the cord diameters in the three cross sections was used as the cord diameter D11 of the steel cord 11 included in the cord-rubber composite 10A. (Inter-cord distance) In one cross section, the inter-cord distances L11A, L11B, L11C, and L11D between adjacent steel cords 11 were measured for steel cords 11A to 11E, and average values ​​were calculated. The calculated average values ​​were used as the inter-cord distances in the measured cross section. The inter-cord distances were calculated for the remaining two cross sections using the same procedure, and the average value of the inter-cord distances in the three cross sections was used as the inter-cord distance L11 of the steel cords 11 included in the cord-rubber composite 10A. (Rubber thickness) In one cross section, the rubber thicknesses T12A, T12B, T12C, T12D, and T12E, which are the minimum thicknesses of the rubber 12 arranged on the steel cords 11, were measured for steel cords 11A to 11E, and average values ​​were calculated. In this case, the minimum thickness refers to the minimum distance between the surface of the rubber 12 and the steel cord 11. The calculated average values ​​were used as the rubber thickness in the measured cross section. The rubber thickness was calculated using the same procedure for the remaining two cross sections, and the average value of the rubber thicknesses for the three cross sections was taken as the rubber thickness T12 for the cord-rubber composite 10A. (Component Thickness) The thickness of the cord-rubber composite 10A was measured at one location in one cross section. The thickness of the cord-rubber composite was measured using the same procedure for the remaining two cross sections, and the average value of the thicknesses of the cord-rubber composite for the three cross sections was taken as the rubber thickness T10 for the cord-rubber composite 10A.(Ratio of Inter-Cord Distance to Cord Diameter, and Ratio of Inter-Cord Distance to Rubber Thickness) The ratio of inter-cord distance to cord diameter and the ratio of inter-cord distance to rubber thickness were calculated using the cord diameter, inter-cord distance, and rubber thickness. The ratio of inter-cord distance to rubber thickness is expressed as inter-cord distance / rubber thickness in the following explanation, Tables 1 and 2, and Figures 4 and 5. (2) Wire Strength and Member Strength The strength and elongation properties of the wire and the cord-rubber composite were measured using a tensile tester in accordance with the measurement method described in "6.4 Breaking Load and Total Elongation at Break" of JIS G 3510 (1992), and were taken as the wire strength and member strength, respectively.

[0098] The member strength was measured in each experimental example and normalized to the evaluation result of the cord-rubber composite in Experimental Example 15, which was set as the standard, i.e., 100, and used as an index value. (3) Adhesion Strength The test specimens for evaluating adhesion strength produced in each of the following experimental examples were pulled between the upper and lower cord-rubber composites at a speed of 50 mm / min, and a peel test was carried out to measure the peel resistance.

[0099] The test specimen for evaluating adhesive strength had a structure in which a cord-rubber composite 10A and a cord-rubber composite 10B were laminated together as shown in Fig. 1, and after vulcanization, the test specimen was cut out so that the width, i.e., the length along the X axis in Fig. 1, was 25 mm. The adhesive strength was evaluated by conducting a peel test between the cord-rubber composite 10A and the cord-rubber composite 10B in Fig. 1, for example.

[0100] The adhesive strength was normalized by setting the evaluation result of the adhesive strength evaluation specimen of Experimental Example 15 as the standard, i.e., 100, and the adhesive strength measured in each Experimental Example was used as an index value.

[0101] When the adhesive strength index value is greater than 100, it can be said that the adhesive strength between the steel cord and the rubber is excellent, and the larger the value, the greater the adhesive strength. (4) Weight of Component The cord-rubber composite produced in each experimental example was cut into a 100 mm square piece and the weight was measured. The size here is the size as seen from the top surface 100 of the cord-rubber composite 10A shown in FIG. 1.

[0102] The weight of the member was standardized by taking the evaluation result of the cord-rubber composite of Experimental Example 15 as the standard, that is, 100, and the weight measured in each Experimental Example was used as an index value.

[0103] When the index value for the component weight is less than 100, it can be said that the component weight of the cord-rubber composite has been reduced, and the smaller the value, the lighter the weight. (Experimental Examples) The experimental conditions will be explained below. Experimental Examples 1 to 14 are working examples, and Experimental Examples 15 to 20 are comparative examples. [Experimental Example 1] In this experimental example, a cord-rubber composite 10A shown in Figure 1 was manufactured.

[0104] As shown in Table 1, a steel cord 11 was prepared by twisting together four wires having the wire strength and wire diameter d shown in Table 1 to form a 1 x 4 structure, which is a single twist structure.

[0105] Then, the steel cords 11 were aligned in parallel and embedded in rubber to produce a cord-rubber composite 10 having the structure shown in FIG.

[0106] The rubber was manufactured using a rubber composition containing a rubber component and additives. The rubber composition contained 100 parts by mass of natural rubber as the rubber component. The rubber composition also contained, as additives, 60 parts by mass of carbon black, 7 parts by mass of sulfur, 0.5 parts by mass of a vulcanization accelerator, 8 parts by mass of zinc oxide, and 2 parts by mass of cobalt stearate as an organic cobalt acid salt, relative to 100 parts by mass of the rubber component.

[0107] The cord-rubber composite 10A was manufactured so that the inter-cord distance and rubber thickness were predetermined values. In addition, a test specimen for evaluating adhesive strength was manufactured under the same conditions as the cord-rubber composite, except that two cord-rubber composites were laminated together and further vulcanized at 160°C for 20 minutes.

[0108] The evaluation results are shown in Table 1. The relationship between the cord-to-cord distance / rubber thickness and the weight of the member is shown in FIG. 4, and the relationship between the cord-to-cord distance / rubber thickness and the adhesive strength is shown in FIG. 5. [Experimental Examples 2 to 14] Steel cords 11 were prepared by twisting together wires having the wire strength and wire diameter d shown in Table 1 to form a 1×n structure, which is a single twist structure shown in Table 1. The cord-rubber composites and test specimens for adhesive strength evaluation were then manufactured so that the cord-to-cord distance and rubber thickness were predetermined values. Except for the above points, the cord-rubber composites and test specimens for adhesive strength evaluation were manufactured and evaluated using the same procedures as in Experimental Example 1.

[0109] The evaluation results are shown in Table 1. The relationship between the cord-to-cord distance / rubber thickness and the weight of the member is shown in FIG. 4, and the relationship between the cord-to-cord distance / rubber thickness and the adhesive strength is shown in FIG. 5. [Experimental Examples 15 to 20] Steel cords 11 were prepared by twisting together wires having the wire strength and wire diameter d shown in Table 2 to form a 1×n structure, which is a single twist structure, shown in Table 2. The cord-rubber composites and test specimens for adhesive strength evaluation were then manufactured so that the cord-to-cord distance and rubber thickness were predetermined values. Except for the above points, the cord-rubber composites and test specimens for adhesive strength evaluation were manufactured and evaluated using the same procedures as in Experimental Example 1.

[0110] The evaluation results are shown in Table 2. For Experimental Examples 16 to 20, the relationship between the cord distance / rubber thickness and the member weight is shown in FIG. 4, and the relationship between the cord distance / rubber thickness and the adhesive strength is shown in FIG. 5.

[0111]

[0112] According to the results shown in Table 1, it was confirmed that the steel cords contained in the cord-rubber composites of Experimental Examples 1 to 14 had a 1×n structure in which the wires were single-twisted, and that the strength of the wires was equal to or greater than the value shown in the "4350-2000×d" column in Table 1. Furthermore, in the cord-rubber composites of Experimental Examples 1 to 14, the ratio of inter-cord distance / rubber thickness was 1.8 or greater, and the rubber thickness was 0.175 mm or greater and 0.225 mm or less.

[0113] The cord-rubber composites of Experimental Examples 1 to 14 had a member weight value of less than 100, confirming that the member weight was reduced. Furthermore, the cord-rubber composites of Experimental Examples 1 to 14 also had a member strength of 100 or more, indicating that the cord-rubber composites have high member strength.

[0114] 4, which is a diagram showing the relationship between inter-cord distance / rubber thickness and component weight, it was confirmed that the component weight tends to decrease as the inter-cord distance / rubber thickness increases in the results of Experimental Examples 1 to 14 and Experimental Examples 16 to 20. In particular, it was confirmed that for approximation line 40, which was drawn to show the distribution trend of each measurement point shown in Figure 4, changes in the component weight decrease trend could be seen before and after dotted line A, where the inter-cord distance / rubber thickness is 1.8, and dotted line B, where the inter-cord distance / rubber thickness is 2.2.

[0115] Furthermore, in Experimental Examples 1 to 11, the adhesive strength exceeded 100, confirming that the adhesive strength between the steel cord and the rubber was also high.

[0116] 5, which is a diagram showing the relationship between inter-cord distance / rubber thickness and adhesive strength, the results of Experimental Examples 1 to 14 and Experimental Examples 16 to 20 confirmed a tendency for adhesive strength to increase as the inter-cord distance / rubber thickness increased. Since the rubber thickness was approximately the same in Experimental Examples 1 to 18, this means that the inter-cord distance / rubber thickness increases as the inter-cord distance increases. For this reason, it is thought that the amount of rubber placed between the steel cords increases as the inter-cord distance / rubber thickness increases, resulting in an increase in adhesive strength.

[0117] In particular, it was confirmed that for approximation lines 50 and 51 drawn to show the distribution tendency of each measurement point shown in Figure 5, a large change in tendency can be seen before and after dotted line A, where the inter-cord distance / rubber thickness is 1.8, and dotted line B, where the inter-cord distance / rubber thickness is 2.2. In particular, it was confirmed that when the inter-cord distance / rubber thickness increases beyond dotted line B, where the inter-cord distance / rubber thickness is 2.2, the adhesive strength increases significantly compared to when the inter-cord distance / rubber thickness is less than 2.2, and that the increasing tendency also changes.

[0118] 10 Cord-rubber composite 10A Cord-rubber composite 10B Cord-rubber composite T10 Component thickness 100 Upper surface 11 Steel cord D11 Cord diameter 11A Steel cord 11B Steel cord 11C Steel cord 11D Steel cord 11E Steel cord C11A Minimum inclusive circle C11B Minimum inclusive circle C11C Minimum inclusive circle C11D Minimum inclusive circle C11E Minimum inclusive circle L11 Distance between cords L11A Distance between cords L11B Distance between cords L11C Distance between cords L11D Distance between cords 111 Wire d Wire diameter 12 Rubber T11 Thickness T11A Thickness T12 Rubber thickness T12A Rubber thickness T12B Rubber thickness T12C Rubber thickness T12D Rubber thickness T12E Rubber thickness 13 Boundary line 30 Tire 31 Tread portion 32 Sidewall portion 33 Bead portion 34 Inner liner 35 Carcass 36 Belt layer 37 Bead wire CL Center line 40 Approximate line 50 Approximate line 51 Approximate line A Dotted line B Dotted line

Claims

1. A cord-rubber composite comprising: a plurality of steel cords; and rubber in which the steel cords, arranged in parallel, are embedded; the steel cords have a single twist structure; when the wire diameter of the wires contained in the steel cords is d (unit: mm), the strength of the wires is 4350-2000 x dMPa or more; in a cross section of the cord-rubber composite perpendicular to the longitudinal direction of the steel cords, the ratio of the inter-cord distance, which is the distance between adjacent steel cords, to the rubber thickness, which is the thickness of the rubber arranged on the steel cords, is 1.8 or more; and the rubber thickness is 0.175 mm or more and 0.225 mm or less.

2. The cord-rubber composite according to claim 1, wherein the ratio of the distance between the cords to the thickness of the rubber is 2.2 or more.

3. A cord-rubber composite according to claim 1 or 2, wherein the steel cord has a 1×n structure, where n is 3 or more and 5 or less.

4. A cord-rubber composite according to any one of claims 1 to 3, wherein the inter-cord distance is 80% or more and 150% or less of the cord diameter of the steel cord.

5. A cord-rubber composite according to any one of claims 1 to 4, wherein the wire diameter is 0.15 mm or more and 0.30 mm or less.

6. A tire comprising the cord-rubber composite of any one of claims 1 to 5.

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