tire

Abstract

To provide a tire which can be made lightweight, and yet can maintain plunger durability, furthermore is improved in steering stability.SOLUTION: A tire 100 is provided, comprising: a belt 60 constituted of at least two belt layers 60A, 60B arranged in a tread portion 30; and belt reinforcing layers 70A, 70B arranged in an outside in a tire diameter direction, of the belt 60. In the tire 100, the belt layers 60A, 60B and the belt reinforcing layers 70A, 70B are formed by coating reinforcing material by elastomer, the reinforcing material of the belt layers 60A, 60B are metal monofilaments each having a filament diameter d of less than 0.30 mm, and each of the reinforcing material of the belt reinforcing layers 70A, 70B is an organic fiber cord having a cutting strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex %) or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Generally, a carcass including reinforcing cords embedded along the meridian direction of a ring-shaped tire body is disposed inside a tire where strength is required, and a belt layer is disposed radially outward of the carcass. The belt layer is usually formed using a metal cord-elastomer composite in which metal cords such as steel cords are coated with an elastomer, and provides the tire with load-bearing capacity, traction resistance, etc.

[0003] In recent years, there has been an increasing demand for lighter tires in order to improve the fuel efficiency of automobiles. Metal cords for the belt layer have attracted attention as a means of reducing the weight of tires, and many technologies have been published that use metal filaments as cords for the belt layer without twisting them. For example, Patent Document 1 listed below discloses a steel cord for reinforcing a tire, in which a thermoplastic elastomer composition in which an elastomer is dispersed in a thermoplastic resin is coated around a steel cord body made of a single monofilament, and a tire using the same. Furthermore, Patent Document 2 listed below discloses a pneumatic radial tire in which a steel cord is used in the belt layer of the tire, the steel cord being formed by arranging two to six main filaments of the same diameter in parallel to form a single layer without twisting them together to form a main filament bundle, and winding one straight steel filament with a smaller diameter than the main filaments as a wrapping filament around the main filament bundle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-053495 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-106570 Summary of the Invention [Problem to be solved by the invention]

[0005] As proposed in the above Patent Documents 1 and 2, by forming a belt layer by coating a metal monofilament with an elastomer, it is possible to reduce the gauge of the belt layer and thereby reduce the weight of the tire. However, after studies by the present inventors, it was found that tires using belt layers formed by coating a metal monofilament with an elastomer have reduced plunger durability (durability against protrusion input) and also have insufficient handling stability, leaving room for improvement.

[0006] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology, and to provide a tire that can maintain plunger durability while being lightweight, and further has improved steering stability. [Means for solving the problem]

[0007] The gist of the tire of the present invention that solves the above problems is as follows.

[0008] [1] A tire having a belt consisting of at least two belt layers arranged in a tread portion and a belt reinforcing layer arranged radially outward of the belt, The belt layer and the belt reinforcing layer are formed by coating a reinforcing material with an elastomer, The reinforcing material of the belt layer is a metal monofilament having a filament diameter d of less than 0.30 mm, A tire characterized in that the reinforcing material of the belt reinforcing layer is an organic fiber cord having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more. The tire of the present invention is lightweight while maintaining plunger durability and also has improved handling stability.

[0009] [2] The tire according to [1], wherein the metal monofilament used as a reinforcing material for the belt layer has a filament diameter d of 0.15 mm or more. In this case, the plunger durability and driving stability of the tire are further improved.

[0010] [3] The tire according to [1] or [2], wherein the belt layer is formed by coating a metal cord consisting of a bundle of multiple metal monofilaments arranged in a row without being twisted together with an elastomer. In this case, the tire can be made even lighter.

[0011] [4] The tire according to [3], wherein the interval w1 between adjacent metal monofilaments constituting the metal cord is 0.01 mm or more and less than 0.24 mm. In this case, the elastomer sufficiently penetrates between the metal monofilaments in the metal cord, and separation between the metal monofilaments in the metal cord can be suppressed.

[0012] [5] The filament diameter d (mm) of the metal monofilament, the interval w1 (mm) between adjacent metal monofilaments constituting the metal cord, and the number n (pieces) of metal monofilaments constituting the metal cord are expressed by the following formula (1): 0.45≦[(d / 2) 2 ×π×n] / {d×[d×n+w1×(n-1)]}≦0.77 ··· (1) The tire according to [3] or [4], which satisfies the relationship: [wherein d is the filament diameter (mm) of the metal monofilament, w1 is the distance (mm) between adjacent metal monofilaments that constitute the metal cord, and n is the number (pieces) of metal monofilaments that constitute the metal cord, with the proviso that d > 0, w1 > 0, and n is an integer]. In this case, it is possible to improve in a balanced manner the light weight of the tire, plunger durability, steering stability, corrosion progress resistance, and belt layer separation resistance.

[0013] [6] The ratio G / w2 of the distance G between the surfaces of the metal monofilaments embedded in two adjacent belt layers in the belt to the interval w2 between the metal cords is 1.6 or less, a ratio w1 / W of a distance w1 between adjacent metal monofilaments constituting the metal cord to a width W of the metal cord is 0.07 or more; The tire according to any one of [3] to [5], wherein a ratio d / w1 of a filament diameter d of the metal monofilament to a spacing w1 between adjacent metal monofilaments constituting the metal cord is 1.2 or more and less than 2. In this case, it is possible to further reduce the weight of the tire and reduce the rolling resistance.

[0014] [7] The tire according to any one of [1] to [6], wherein the belt layer has a thickness t of 0.8 mm or less. In this case, the tire can be made even lighter.

[0015] [8] The tire according to any one of [1] to [7], wherein the organic fiber cord serving as a reinforcing material for the belt reinforcing layer is a cord made of polyethylene terephthalate. In this case, the plunger durability and driving stability of the tire are further improved.

[0016] [9] The belt includes a first belt layer and a second belt layer laminated on the outer side of the first belt layer in the tire radial direction, The shortest distance a between the metal monofilaments of the second belt layer and the metal monofilaments of the first belt layer in the tire center portion and the shortest distance b between the metal monofilaments of the end portion of the second belt layer and the metal monofilaments of the first belt layer satisfy the following formula (2): 1.8≦b / a≦4.0 (2) The tire according to any one of [1] to [8], which satisfies the relationship: [wherein a is the shortest distance between the metal monofilaments of the second belt layer in the tire center portion and the metal monofilaments of the first belt layer, and b is the shortest distance between the metal monofilaments at the end portion of the second belt layer and the metal monofilaments of the first belt layer]. In this case, the durability of the belt end portion of the tire can be sufficiently improved. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a tire that is lightweight, yet maintains plunger durability, and further has improved steering stability. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of one embodiment of a tire of the present invention. [Figure 2] FIG. 1 is a diagram showing a load-elongation curve of a cord. [Figure 3] 1 is a partial cross-sectional view in the width direction of a belt layer according to one embodiment of a tire of the present invention. [Figure 4] FIG. 2 is a schematic plan view of a metal cord of a belt layer according to one embodiment of a tire of the present invention. [Figure 5] FIG. 2 is an explanatory diagram relating to the definition of the ratio of the cross-sectional area of ​​the metal monofilament included in the cross section of the metal cord. [Figure 6] 2 is an enlarged partial cross-sectional view of a belt according to one embodiment of the tire of the present invention. FIG. [Figure 7] FIG. 4 is a schematic plan view of a metal cord in a belt layer according to another embodiment of the tire of the present invention. [Figure 8] FIG. 4 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer according to another embodiment of a tire of the present invention. [Figure 9] FIG. 2 is an explanatory diagram of a metal monofilament showing the definitions of the shaping amount and shaping pitch of the metal monofilament. [Figure 10] FIG. 4 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer according to another embodiment of a tire of the present invention. [Figure 11] FIG. 4 is a schematic plan view of a metal cord in a belt layer according to another embodiment of the tire of the present invention. [Figure 12] FIG. 4 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer according to another embodiment of a tire of the present invention. [Figure 13] FIG. 2 is an explanatory diagram of a metal monofilament showing the definitions of the shaping amount and shaping pitch of the metal monofilament. [Figure 14] FIG. 4 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer according to another embodiment of a tire of the present invention. [Figure 15] FIG. 4 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer according to another embodiment of a tire of the present invention. [Figure 16] FIG. 4 is a schematic plan view of a metal cord in a belt layer according to another embodiment of the tire of the present invention. [Figure 17] FIG. 4 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer according to another embodiment of a tire of the present invention. [Figure 18] FIG. 4 is a schematic cross-sectional view of an end portion of a belt according to another embodiment of the tire of the present invention. [Figure 19] FIG. 4 is a schematic cross-sectional view of a center portion of a belt according to another embodiment of the tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The tire of the present invention will be described in detail below by way of example based on an embodiment thereof.

[0020] The tire of this embodiment includes a belt consisting of at least two belt layers disposed in a tread portion, and a belt reinforcing layer disposed radially outward of the belt. The tire of this embodiment is characterized in that the belt layer and the belt reinforcing layer are formed by coating a reinforcing material with an elastomer, the reinforcing material of the belt layer is a metal monofilament having a filament diameter d of less than 0.30 mm, and the reinforcing material of the belt reinforcing layer is an organic fiber cord having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more.

[0021] The tire of this embodiment comprises a belt layer formed by covering metal monofilaments having a filament diameter d of less than 0.30 mm with an elastomer, and since the thickness of the belt layer is thin, the tire is lightweight. If a tire simply comprises a belt layer containing metal monofilaments, the in-plane rigidity of the belt layer will be lower than that of a normal belt layer, resulting in lower plunger durability (durability against projection input) and insufficient steering stability. However, the tire of this embodiment comprises a belt reinforcing layer formed by coating organic fiber cords with an elastomer, the elongation at break being 6.5 cN / dtex or more, a breaking strength being 10% or more, and a modulus of elasticity at 7% elongation being 6.0 mN / (dtex·%) or more. The belt reinforcing layer compensates for the rigidity of the belt layer, thereby suppressing the decrease in plunger durability and further improving steering stability. Therefore, the tire of this embodiment is lightweight while maintaining plunger durability, and also has improved steering stability.

[0022] Next, an embodiment of the tire of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view of one embodiment of a tire of the present invention. The tire 100 shown in Fig. 1 includes a pair of bead portions 10, a pair of sidewall portions 20, a tread portion 30, a carcass 50 extending in a toroidal shape between bead cores 40 embedded in the bead portions 10, a belt 60 consisting of two belt layers 60A and 60B arranged in the tread portion 30 (more specifically, arranged radially outward of the crown portion of the carcass 50), a belt reinforcing layer (also referred to as a "cap layer") 70A arranged radially outward of the belt 60 so as to cover the entire belt 60, and a pair of belt reinforcing layers (also referred to as "layer layers") 70B arranged so as to cover only both end portions of the belt reinforcing layer 70A.

[0023] In the tire 100 shown in Fig. 1, the carcass 50 is composed of one carcass ply and includes a main body portion extending in a toroidal shape between a pair of bead cores 40 embedded in the bead portions 10, and a folded-up portion wound up radially outward from the inner side to the outer side in the tire width direction around each bead core 40. However, in the tire of the present invention, the number and structure of the plies of the carcass 50 are not limited to this. Here, the carcass ply constituting the carcass 50 is preferably formed by coating a plurality of reinforcing cords with an elastomer and extending in a direction substantially perpendicular to the tire circumferential direction (for example, extending at an angle of 70 to 90°). In other words, the carcass 50 is preferably a radial carcass. The reinforcing cords of the carcass 50 may be organic fiber cords such as polyethylene terephthalate cords, nylon cords, or rayon cords, or steel cords.

[0024] The belt 60 of the tire 100 shown in FIG. 1 is made up of two belt layers 60A and 60B. Each of the belt layers 60A and 60B is usually made of a metal monofilament (reinforcement material) extending at an angle (for example, at an angle of 15 to 40 degrees) to the tire equatorial plane. Preferably, a steel monofilament is coated with an elastomer, and further, two belt layers 60A, 60B are laminated such that the metal monofilaments constituting the belt layers 60A, 60B cross each other with the tire equatorial plane in between to form the belt 60. The belt 60 in the figure is made up of two belt layers 60A and 60B (hereinafter, the belt layer 60A may be referred to as the "first belt layer" and the belt layer 60B may be referred to as the "second belt layer"). However, in the tire of the present invention, the number of belt layers constituting the belt is not limited to two as long as it is two or more. The metal monofilaments serving as reinforcing materials for the belt layers 60A, 60B have a filament diameter d of less than 0.30 mm, which allows the thickness of the belt layers 60A, 60B to be reduced, thereby contributing to a lighter tire. Here, the filament diameter d of the metal monofilaments serving as reinforcing materials for the belt layers is preferably 0.15 mm or more and 0.28 mm or less. When the filament diameter d of the metal monofilaments is 0.15 mm or more, the plunger durability and handling stability of the tire are further improved, and when it is 0.28 mm or less, the tire becomes even lighter.

[0025] The metal monofilament (also called "single wire") is not particularly limited in its specific structure as long as it satisfies the above-mentioned filament diameter d. For example, the metal monofilament may be a straight metal monofilament, a metal monofilament twisted around its axis, a metal monofilament with a flat cross section, a metal monofilament shaped into a spiral, or a metal monofilament shaped into a planar wave shape.

[0026] In the tire 100 shown in Fig. 1, the belt reinforcing layers 70A, 70B are formed by coating organic fiber cords (reinforcing material) that are aligned substantially parallel to the tire circumferential direction (for example, at an angle of 0 to 5 degrees relative to the tire circumferential direction) with an elastomer. The belt reinforcing layers 70A, 70B are formed by continuously spirally winding narrow strips prepared by coating organic fiber cords with an elastomer in the tire circumferential direction. In this case, the absence of joints in the tire circumferential direction improves tire uniformity, and the absence of joints also prevents strain concentration at the joints. 1 includes a belt reinforcing layer 70A and a belt reinforcing layer 70B, but a tire in which either one of the belt reinforcing layer 70A or the belt reinforcing layer 70B is omitted is also an embodiment of the tire of the present invention. In addition, in the tire 100 shown in FIG. 1, each of the belt reinforcing layers 70A and 70B is one layer, but they may be two or more layers. The organic fiber cords that are the reinforcing material of the belt reinforcing layers 70A and 70B have a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more, and therefore have high rigidity and are highly effective in reinforcing the belt 60 (belt layers 60A and 60B), contributing to improved plunger durability and handling stability of the tire.

[0027] In the carcass 50, the belt 60 (belt layers 60A, 60B), and the belt reinforcing layers 70A, 70B, the elastomer that coats the reinforcing material (reinforcing cord) is not particularly limited, and various elastomers can be applied. The elastomer preferably has a 50% modulus value of 1.5 MPa or more, more preferably 1.8 MPa or more, and even more preferably 2.0 MPa or more, measured in accordance with JIS K 6251 (2010). When such an elastomer is used to cover the reinforcing material (reinforcing cord), even if the reinforcing material (reinforcing cord) stretches in the longitudinal direction, the high rigidity of the elastomer inside the carcass 50, belt 60, and belt reinforcing layers 70A, 70B inhibits the reinforcing material (reinforcing cord) from stretching in the longitudinal direction, thereby further improving the handling stability of the tire.

[0028] The main components of the elastomer are natural rubber (NR), isoprene rubber (IR), and elastomer. Diene rubbers and their hydrogenated derivatives, such as epoxidized natural rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR, high cis BR and low cis BR), nitrile rubber (NBR), hydrogenated NBR, and hydrogenated SBR, ethylene-propylene rubber (EPDM, EPM), maleic acid-modified ethylene-propylene rubber (M-EPM), butyl rubber (IIR), copolymers of isobutylene with aromatic vinyl or diene monomers, acrylic rubber (ACM), olefin rubbers, such as ionomers, Br-IIR, Cl-IIR, brominated isobutylene-paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHR), and chlorosulfonated polyethylene. Examples of suitable elastomers include halogen-containing rubbers such as methyl methylsilicone rubber (CSM), chlorinated polyethylene rubber (CM), and maleic acid-modified chlorinated polyethylene rubber (M-CM); silicone rubbers such as methyl vinyl silicone rubber, dimethyl silicone rubber, and methyl phenyl vinyl silicone rubber; sulfur-containing rubbers such as polysulfide rubber; fluororubbers such as vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicone rubber, and fluorine-containing phosphazene rubber; and thermoplastic elastomers such as styrene elastomers, olefin elastomers, ester elastomers, urethane elastomers, and polyamide elastomers. The 50% modulus value of the elastomer (coating rubber) was measured in accordance with JIS K 6251 (2010) after vulcanizing the rubber composition of each sample at 145°C for 40 minutes to produce a vulcanized rubber.

[0029] In addition to sulfur, a vulcanization accelerator, and carbon black, the elastomer may also contain antioxidants, zinc oxide (zinc white), stearic acid, and the like that are commonly used in rubber products such as tires.

[0030] The organic fiber cords used in the belt reinforcing layers 70A and 70B have a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and a modulus of elasticity at 7% elongation of 6.0 mN / (dtex·%) or more. Here, the breaking strength, breaking elongation, and modulus of elasticity at 7% elongation of the organic fiber cords are values ​​measured at room temperature (23°C). The physical properties of the organic fiber cords are measured in accordance with JIS It can be measured in accordance with L 1013 "Testing methods for chemical fiber filament yarns." The elastic modulus at 7% elongation is calculated by converting the slope (N / %) of the tangent at a point on the load-elongation curve of the cord that corresponds to 7% elongation into a value per dtex. The slope of the tangent at a point on the load-elongation curve that corresponds to 7% elongation means the slope of the tangent S at a point on the load-elongation curve C of the cord that corresponds to 7% elongation, as shown in Figure 2. An organic fiber cord having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and a modulus of elasticity at 7% elongation of 6.0 mN / (dtex·%) or more has high strength at break, large elongation at break, and a high modulus of elasticity at 7% elongation. Therefore, by applying an organic fiber cord with such physical properties to the belt reinforcing layer to supplement the rigidity of the belt layer, it is possible to improve the handling stability of the tire while suppressing the decrease in plunger durability that occurs when a belt layer containing a metal monofilament is applied.

[0031] The material of the organic fiber cords is not particularly limited, but examples thereof include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), nylons such as 6-nylon, 6,6-nylon, and 4,6-nylon, and celluloses such as rayon and lyocell. Among these, polyethylene terephthalate is preferred, that is, the organic fiber cords used as reinforcing materials for the belt reinforcing layers 70A and 70B are preferably cords made of polyethylene terephthalate (hereinafter sometimes simply referred to as "polyethylene terephthalate cords"). Polyethylene terephthalate cords have higher rigidity than commonly used nylon cords and are excellent in improving the plunger durability and steering stability of tires.

[0032] The organic fiber cord has an elastic modulus of 2.5 mN / s when loaded with 29.4 N at 160°C. Here, the modulus of elasticity at a load of 29.4 N measured at 160°C is calculated by converting the slope (N / %) of the tangent at the point corresponding to a load of 29.4 N on the load-elongation curve of the cord measured at 160°C into a value per dtex. The modulus of elasticity is measured at 160°C because the temperature inside a tire rises as the tire travels at high speeds. By the time tire failure occurs during high-speed travel, the temperature of the belt reinforcement layer has already reached 160°C. Polyethylene terephthalate cords, in particular, exhibit a significant decrease in modulus of elasticity at high temperatures compared to room temperature. Therefore, even cords with high elasticity at room temperature cannot fully demonstrate their belt reinforcing effect (improving durability against protruding inputs and suppressing belt extrusion) unless they maintain a high modulus at high temperatures. Therefore, the modulus of elasticity at high temperatures is crucial. A cord modulus of elasticity of 2.5 mN / (dtex·%) or higher under a load of 29.4 N measured at 160°C can improve tire plunger durability and suppress belt extrusion during high-speed travel. This reduces stress during tire indentation and extrusion, improving tire handling stability during high-speed travel.

[0033] In order to improve the elastic modulus of the organic fiber cord at 160°C, it is preferable to perform the dip treatment under high tension. The inventors adjusted the tension applied to the cord during the dip treatment to prepare organic fiber cords with various elastic moduli, coated the obtained dipped cords with an elastomer, applied them to a belt reinforcing layer, and investigated the plunger durability and handling stability of a tire. As a result, they found that the plunger durability and handling stability of a tire were significantly improved when the elastic modulus of the cord under a load of 29.4 N, measured at 160°C, was in the range of 2.5 mN / (dtex·%) or more.

[0034] In order to make the cord sufficiently elastic, the tension during adhesive treatment must be 6.9 x 10 -2It is preferable to set the elasticity to N / tex or more. However, the method for increasing the elasticity of the cord is not limited to this, and other methods such as reducing the twist of the cord may also be used. The adhesive treatment comprises dry treatment, hot treatment, normalizing treatment, etc., and is carried out by appropriately adjusting the temperature and time in addition to the tension. In the present invention, the adhesive treatment may be carried out by either one-bath treatment or two-bath treatment, but two-bath treatment is preferred, with a maximum elasticity of 6.9 × 10 -2 It is preferable to apply a tension of N / tex or more to the cord during the hot treatment in the second bath.

[0035] The organic fiber cord is a fiber having the following formula (3): α=T×D 1 / 2 (3) The twist coefficient α, expressed by the formula [where α is the twist coefficient, T is the number of twists (turns / 100 mm), and D is the total cord fineness (dtex)], is preferably 500 to 2500. When the twist coefficient α of the cord is 500 or more, the binding force of the filaments becomes strong and adhesion becomes sufficient, and when it is 2500 or less, a sufficient elastic modulus can be exhibited to obtain the effect of improving durability against projection input and the effect of suppressing the belt from squeezing out.

[0036] The organic fiber cords preferably have a total fineness of 1000 to 3500 dtex. If the total fineness of the cords is 1000 dtex or more, a sufficient elastic modulus can be exhibited to improve durability against protrusion input and to suppress the belt from squeezing out, while if the total fineness is 3500 dtex or less, the cords can be densely packed and sufficient rigidity per unit width can be ensured.

[0037] Since raw tires expand by several percent in the tire radial direction during vulcanization, if the elastic modulus of the cords used in the belt reinforcing layer is high, they will not be able to keep up with the tire expansion during vulcanization molding, and there is a possibility that the organic fiber cords in the belt reinforcing layer and the metal monofilaments in the belt layer will come into direct contact without the elastomer (coated rubber) in between. Therefore, it is necessary to design the diameter of the raw tire to a certain size in advance, and to appropriately adjust the tension when winding the elastomer-coated cords to form the belt reinforcing layer, thereby ensuring a sufficient gauge between the belt and the cords in the belt reinforcing layer. Therefore, it is preferable that the organic fiber cord has an elongation rate of 2% or less in the tire after vulcanization relative to the original cord length before vulcanization. When a tire is molded with a cord elongation rate of 2% or less, contact between the organic fiber cord and the belt can be suppressed, and separation at the belt ends during running can be suppressed.

[0038] The raw material of the organic fiber cord is not particularly limited, and may be derived from a synthetic product, a biological product, a mechanically recycled product obtained by crushing, melting, and re-spinning PET products such as PET bottles, or a chemically recycled product obtained by depolymerizing and repolymerizing PET products such as PET bottles.

[0039] The form of the organic fiber cord is not particularly limited, and may be a single twist structure or a twisted structure (such as a double twist structure). In the case of a single twist structure, for example, raw yarns are aligned and twisted in one direction to obtain a twisted yarn cord. In the case of a double twist structure, for example, raw yarns are first twisted, and then multiple such yarns are combined and twisted in the opposite direction to obtain a twisted yarn cord.

[0040] The organic fiber cord (particularly a polyethylene terephthalate cord) is preferably treated with an adhesive composition containing a thermoplastic polymer (A), a thermally reactive aqueous urethane resin (B), and an epoxy compound (C), or an adhesive composition containing these (A) to (C) plus a rubber latex (D), wherein the main chain of the thermoplastic polymer (A) is substantially free of addition-reactive carbon-carbon double bonds and has at least one pendant functional group with crosslinkability. Treating the cord with this adhesive composition can improve the adhesion of the cord to the elastomer (coating rubber) at high temperatures.

[0041] Conventionally, adhesive treatment of organic fiber cords (especially polyethylene terephthalate cords) has been performed using a two-bath process, in which an epoxy or isocyanate coating is applied to the cord surface, followed by a treatment with a resin (hereinafter referred to as RFL resin) composed of a mixture of resorcinol, formaldehyde, and latex. However, this method can result in the resin used in the first bath becoming very hard, which can increase strain input to the cord and reduce cord fatigue resistance. Furthermore, while such resins can exhibit sufficient cord-to-elastomer adhesion at room temperature, they can experience a significant decrease in adhesion at temperatures above 130°C. In contrast, a one-bath mixture containing a thermoplastic polymer (A) having at least one crosslinkable functional group as a pendant group and substantially free of addition-reactive carbon-carbon double bonds in its main chain structure, a thermally reactive aqueous urethane resin (B), and an epoxy compound (C) can be used to ensure sufficient adhesion to the elastomer (coating rubber) even at temperatures above 180°C without curing the cord.

[0042] The main chain of the thermoplastic polymer (A) is mainly a linear structure, and the main chain is preferably, for example, an ethylenic addition polymer such as an acrylic polymer, a vinyl acetate polymer, or a vinyl acetate-ethylene polymer, or a urethane high molecular weight polymer. However, the thermoplastic polymer (A) is not limited to an ethylenic addition polymer or a urethane high molecular weight polymer, as long as it has the function of suppressing resin fluidity at high temperatures and ensuring the breaking strength of the resin by crosslinking functional groups of the pendant groups.

[0043] The functional group of the pendant group of the thermoplastic polymer (A) is preferably an oxazolidine group, a bismaleimide group, a (blocked) isocyanate group, an aziridine group, a carbodiimide group, a hydrazino group, an epoxy group, an epithio group, or the like.

[0044] The monomer constituting the ethylenic addition polymer is a monomer having one carbon-carbon double bond. Examples of the monomer include an ethylenically unsaturated monomer having two or more carbon-carbon double bonds, and a monomer having two or more carbon-carbon double bonds.Here, examples of the ethylenically unsaturated monomer having one carbon-carbon double bond include α-olefins such as ethylene, propylene, butylene, and isobutylene; α,β-unsaturated aromatic monomers such as styrene, α-methylstyrene, monochlorostyrene, vinyltoluene, vinylnaphthalene, and sodium styrenesulfonate; ethylenically unsaturated carboxylic acids and salts thereof such as itaconic acid, fumaric acid, maleic acid, acrylic acid, methacrylic acid, and butenetricarboxylic acid; acid anhydrides such as maleic anhydride and itaconic anhydride; methyl (meth)acrylate, and (meth)acrylic acid. Esters of unsaturated carboxylic acids such as ethyl, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-aminoethyl (meth)acrylate; monoesters of ethylenic dicarboxylic acids such as monoethyl itaconic acid, monobutyl fumaric acid, monobutyl maleic acid; diesters of ethylenic dicarboxylic acids such as diethyl itaconic acid, dibutyl fumaric acid; acrylamide, maleic acid amide, Amides of α,β-ethylenically unsaturated acids such as N-methylolacrylamide, N-(2-hydroxyethyl)acrylamide, methacrylamide, N-methylolmethacrylamide, N-(2-hydroxyethyl)methacrylamide, and maleic acid amide; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate and polyethylene glycol mono(meth)acrylate; unsaturated nitriles such as acrylonitrile, methacrylonitrile, fumaronitrile, and α-chloroacrylonitrile; methyl vinyl ether, ethyl vinyl ether, etc. vinyl ethers such as vinyl ethers of ...In the present invention, it is preferable to obtain polymer (A) by radical addition polymerization of these monomers. Furthermore, among the monomers constituting the main chain skeleton, examples of the monomer containing two or more carbon-carbon double bonds include conjugated diene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and halogen-substituted butadienes such as chloroprene. Furthermore, examples of the non-conjugated diene monomers include non-conjugated diene monomers such as vinylnorbornene, dicyclopentadiene, and 1,4-hexadiene. These may be used alone or in combination of two or more.

[0045] The ethylenic addition polymer comprises units derived from an ethylenically unsaturated monomer having one carbon-carbon double bond and a monomer having two or more carbon-carbon double bonds, and the sulfur-reactive carbon-carbon double bond is preferably contained in an amount of 10 mol % or less, more preferably 0 mol %, of the monomer composition based on the amount of all the monomers charged.

[0046] The method for introducing a crosslinkable functional group into the ethylenic addition polymer to form the thermoplastic polymer (A) is not particularly limited. For example, a method can be employed in which an addition polymerizable monomer having an oxazoline group, an addition polymerizable monomer having an epoxy group, an addition polymerizable monomer having a maleimide group, an addition polymerizable monomer having a blocked isocyanate group, an addition polymerizable monomer having an epithio group, or the like is copolymerized during polymerization of the ethylenic addition polymer.

[0047] The urethane-based polymer is a polymer having a large number of bonds resulting from the reaction of an isocyanate group with active hydrogen, such as urethane bonds obtained by polyaddition reaction of polyisocyanate with a compound having two or more active hydrogens, or urea bonds, in the molecule. The polymer may also be a polymer containing an ester bond, an ether bond, an amide bond, or a uretdione or carbodiimide formed by a reaction between isocyanate groups in the molecule.

[0048] The thermally reactive aqueous urethane resin (B) is preferably a resin having two or more thermally dissociable blocked isocyanate groups in one molecule, for example, a resin represented by the following general formula (4): [ka] [wherein A represents an isocyanate residue of an organic polyisocyanate compound having 3 to 5 functional groups, Y represents an active hydrogen residue of a blocking agent compound that liberates an isocyanate group upon heat treatment, Z represents an active hydrogen residue of a compound having at least one active hydrogen atom and at least one anion-forming group in the molecule, X represents an active hydrogen residue of a polyol compound having 2 to 4 hydroxyl groups and an average molecular weight of 5,000 or less, n is an integer of 2 to 4, and p+m is an integer of 2 to 4 (m≧0.25)] are particularly preferred.

[0049] The epoxy compound (C) may be any compound containing two or more, preferably four or more, epoxy groups per molecule, and is preferably a compound containing an epoxy group or a reaction product of a polyhydric alcohol with epichlorohydrin. Specific examples of the epoxy compound include reaction products of epichlorohydrin with polyhydric alcohols such as diethylene glycol diglycidyl ether, polyethylene diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, and sorbitol polyglycidyl ether; novolac epoxy resins such as phenol novolac epoxy resins and cresol novolac epoxy resins; and bisphenol A epoxy resins.

[0050] The rubber latex (D) is preferably a vinylpyridine-styrene-butadiene copolymer latex, a styrene-butadiene copolymer latex, or the like, but is not particularly limited.

[0051] For the organic fiber cord (especially polyethylene terephthalate cord), it is preferable to use the three components (A), (B), and (C) as a single-bath treatment solution, and a conventional RFL solution as a double-bath treatment solution. It is also possible to treat the organic fiber cord (especially polyethylene terephthalate cord) with a single-bath treatment solution consisting of a mixture of components (A), (B), (C), and (D). The dry weight ratios of these components are preferably such that (A) is 2 to 75% of the dry weight of the adhesive composition, (B) is 15 to 87%, (C) is 11 to 70%, and (D) is 20% or less.

[0052] The belt reinforcing layer is preferably formed by treating the organic fiber cord with an adhesive, coating it with an elastomer to form a narrow strip, and then winding the strip spirally in the tire circumferential direction.

[0053] Next, an embodiment of the belt layer of the tire of the present invention will be described by way of example. Fig. 3 is a partial cross-sectional view in the width direction of the belt layer according to one embodiment of the tire of the present invention, and Fig. 4 is a schematic plan view of the metal cord of the belt layer according to one embodiment of the tire of the present invention.

[0054] The belt layer 60A (60B) shown in Fig. 3 is formed by covering a metal cord 2 made of a bundle of multiple metal monofilaments 1 that are aligned in a row without being twisted together with an elastomer 3. By covering the metal cord 2 made of a bundle of multiple metal monofilaments 1 that are aligned in a row without being twisted together with the elastomer 3 and applying it to the belt layer 60A (60B), the thickness of the belt layer 60A (60B) can be reduced, thereby enabling the tire to be further lightened.

[0055] Here, the metal monofilaments 1 preferably comprise two or more, more preferably five or more, and preferably comprise 20 or less, more preferably 12 or less, even more preferably 10 or less, and particularly preferably 9 or less, bundled to form the metal cord 2. In the belt layer 60A (60B) shown in Fig. 3, five metal monofilaments 1 are pulled together without being twisted together to form the metal cord 2. With this configuration, the thickness of the belt layer 60A (60B) can be reduced, thereby enabling the tire to be made lighter.

[0056] The distance w1 between adjacent metal monofilaments 1 constituting the metal cord 2 is preferably 0.01 mm or more and less than 0.24 mm. Providing a distance w1 within the above range between adjacent metal monofilaments 1 allows the elastomer 3 to sufficiently penetrate, thereby enabling the metal cord 2 to undergo out-of-plane deformation during compression and preventing breakage of the metal cord. Furthermore, setting the distance w1 between the metal monofilaments 1 to less than 0.24 mm prevents separation between the metal monofilaments 1 within the metal cord 2. On the other hand, setting the distance w1 between the metal monofilaments 1 to 0.01 mm or more allows the elastomer 3 to sufficiently penetrate between the metal monofilaments 1 within the metal cord 2. The distance w1 between the metal monofilaments 1 is more preferably 0.03 mm or more and 0.20 mm or less, and even more preferably 0.03 mm or more and 0.18 mm or less.

[0057] In a bundle of metal monofilaments 1, the elastomer does not easily penetrate between closely adjacent monofilaments, resulting in non-elastomer-coated regions that are not covered with elastomer, and in these non-elastomer-coated regions, the metal monofilaments may shift relative to each other when the tire rolls, reducing the in-plane rigidity of the belt. However, in the belt layer 60A (60B) shown in Figure 3, the elastomer 3 sufficiently penetrates between adjacent metal monofilaments 1, making it difficult for non-elastomer-coated regions to form, thereby sufficiently improving the in-plane rigidity of the belt and further improving the plunger durability and handling stability of the tire.

[0058] In the belt layer 60A (60B), in order to eliminate the presence of continuous non-elastomer-coated regions between adjacent metal monofilaments, ensure corrosion progress resistance, improve the in-plane rigidity of the belt, and effectively obtain the effects of improving the plunger durability and steering stability of the tire, the elastomer coverage rate of adjacent metal monofilaments 1 on the widthwise side of the metal cord 2 per unit length is preferably 10% or more, more preferably 20% or more, even more preferably 50% or more, still more preferably 80% or more, and particularly preferably 90% or more. Here, the elastomer coverage is, for example, a method in which rubber is used as the elastomer, a metal monofilament is coated with the rubber, and the metal monofilament is vulcanized. After that, the metal monofilament is pulled out from the obtained rubber-metal monofilament composite, and the length of the side surface of the metal monofilament in the width direction that is coated with the rubber that has penetrated into the gaps between the metal monofilaments is measured, and the elastomer coverage is calculated by the following formula: Elastomer coverage rate = (rubber coverage length / sample length) x 100 (%) The average of the values ​​calculated based on the above. The same calculation can be performed when an elastomer other than rubber is used as the elastomer.

[0059] In the belt layer 60A (60B), the filament diameter of the metal monofilament 1 (" The filament diameter d of the metal monofilament 1 is less than 0.30 mm, and is preferably 0.15 mm or more, more preferably 0.18 mm or more, and even more preferably 0.20 mm or more. By making the filament diameter d of the metal monofilament 1 less than 0.30 mm, the lightweight effect of the tire can be sufficiently obtained. Furthermore, by making the filament diameter d of the metal monofilament 1 0.15 mm or more, the strength of the belt layer is improved, and the plunger durability and handling stability of the tire are further improved.

[0060] In the belt layer 60A (60B) shown in FIG. 3, the spacing w2 between the metal cords 2, measured in a direction perpendicular to the direction in which the metal cords 2 extend, is preferably 0.25 mm or more and 2.0 mm or less. By setting the spacing w2 between the metal cords 2 to 0.25 mm or more, it is possible to suppress belt edge separation, in which elastomer peeling originating from the cord end at the belt width direction end spreads between adjacent metal cords. Furthermore, by setting the spacing w2 between the metal cords 2 to 2.0 mm or less, it is possible to maintain the rigidity of the belt. The spacing w2 between the metal cords 2 is more preferably 0.3 mm or more and 1.8 mm or less, and even more preferably 0.35 mm or more and 1.5 mm or less.

[0061] The thickness t of the belt layer 60A (60B) is preferably 0.8 mm or less, and more preferably more than 0.30 mm. By setting the thickness t of the belt layer to 0.8 mm or less, the tire can be further lightened. Furthermore, by setting the thickness t of the belt layer to more than 0.30 mm, the strength of the belt can be improved, and the plunger durability and handling stability of the tire can be further improved.

[0062] In the belt layer 60A (60B), the metal monofilament 1 is preferably steel, i.e., a linear metal whose main component is iron (the mass of iron relative to the total mass of the metal monofilament exceeds 50 mass %), and may be composed of only iron, or may contain metals other than iron, such as zinc, copper, aluminum, and tin.

[0063] In the belt layer 60A (60B), the surface state of the metal monofilament 1 is not particularly limited, but can take the following form, for example. That is, it is preferable that the metal monofilament 1 has a surface N atom content of 2 atomic % or more and 60 atomic % or less, and a surface Cu / Zn ratio of 1 or more and 4 or less. It is also preferable that the metal monofilament 1 has an amount of phosphorus contained as an oxide in the outermost layer of the metal monofilament up to 5 nm inward in the radial direction of the filament from the surface of the metal monofilament, in terms of the proportion of the total amount excluding the amount of C, of ​​7.0 atomic % or less.

[0064] In the belt layer 60A (60B), the surface of the metal monofilament 1 may be plated. The type of plating is not particularly limited, and examples thereof include zinc (Zn) plating, copper (Cu) plating, tin (Sn) plating, brass (copper-zinc (Cu-Zn)) plating, bronze (copper-tin (Cu-Sn)) plating, and ternary plating such as copper-zinc-tin (Cu-Zn-Sn) plating and copper-zinc-cobalt (Cu-Zn-Co) plating. Among these, brass plating and copper-zinc-cobalt plating are preferred. This is because brass-plated metal monofilaments have excellent adhesion to elastomers (coating rubbers). Brass plating typically has a copper to zinc ratio (copper:zinc) of 60 to 70:30 to 40 by mass, while copper-zinc-cobalt plating typically has a copper content of 60 to 75% by mass and a cobalt content of 0.5 to 10% by mass. The thickness of the plating layer is preferably 100 nm or more and 300 nm or less.

[0065] In the belt layer 60A (60B), there is no particular limitation on the tensile strength or cross-sectional shape of the metal monofilament 1. For example, the metal monofilament 1 may have a tensile strength of 2500 MPa (250 kg / mm 2 ) or more can be used. The cross-sectional shape of the filament 1 in the width direction is not particularly limited, and may be circular, elliptical, rectangular, triangular, polygonal, or the like. The metal monofilament 1 is preferably a substantially straight metal monofilament, as shown in FIG. 4. Here, a straight metal monofilament refers to a metal monofilament that has not been intentionally shaped and is essentially unshaped. In the belt layer 60A (60B) shown in FIG. 3, a wrapping filament (spiral filament) may be used when it is necessary to constrain the bundle of metal monofilaments 1 that constitute the metal cord 2.

[0066] The belt layer 60A (60B) can be manufactured by a known method. For example, it can be manufactured by arranging steel cords as metal cords, which are bundles of metal monofilaments that are not twisted together, in parallel at a predetermined interval and covering them with elastomer (coating rubber). Evaluation samples can then be manufactured by vulcanizing them under general conditions. In addition, shaping of the metal monofilaments can be performed using a normal shaping machine according to conventional methods.

[0067] The filament diameter d (mm) of the metal monofilament 1, the interval w1 (mm) between adjacent metal monofilaments 1 constituting the metal cord 2, and the number n (pieces) of metal monofilaments 1 constituting the metal cord 2 are expressed by the following formula (1): 0.45≦[(d / 2) 2 ×π×n] / {d×[d×n+w1×(n-1)]}≦0.77 (1) It is preferable that the following relationship is satisfied. In formula (1), d is the filament diameter (mm) of the metal monofilament 1, w1 is the distance (mm) between adjacent metal monofilaments 1 measured in a direction perpendicular to the extension direction of the metal cord 2 (also called the "distance between surfaces" or "gap amount"), and n is the number (pieces) of metal monofilaments 1 that make up the metal cord 2, provided that d>0, w1>0, and n are an integer.

[0068] Since w1 > 0, i.e., a gap is provided between adjacent metal monofilaments 1, the elastomer 3 enters the gap, eliminating continuous non-elastomer-coated regions between the metal monofilaments 1, allowing the elastomer to sufficiently penetrate between adjacent metal monofilaments 1. As a result, the metal cord can deform out-of-plane when a compressive load is applied, preventing the metal cord from breaking. Furthermore, since there is no water passage path when water is introduced into the tire due to damage, corrosion progression resistance is significantly improved. Furthermore, since adjacent metal monofilaments 1 are restrained by the elastomer 3, adjacent metal monofilaments do not shift relative to each other even when the tire is rolling. As a result, the in-plane rigidity of the belt can be improved, and the plunger durability and handling stability of the tire can be further improved.

[0069] Figure 5 shows an explanatory diagram relating to the regulation of the ratio of the cross-sectional areas of metal monofilaments contained within the cross section of a metal cord. In Figure 5, seven metal monofilaments 1 are pulled together without being twisted together to form a metal cord 2. Specifically, the seven straight, unshaped metal monofilaments 1 are arranged in parallel with equally spaced intervals and are covered with an elastomer 3. Here, the equally spaced intervals refer to a range that includes manufacturing tolerances. The above formula (1) defines the ratio of the cross-sectional area of ​​the metal monofilament 1 to the cross-sectional area of ​​each metal cord 2, with the cross-sectional area of ​​the dotted line portion in the figure being the cross-sectional area of ​​the metal cord 2. That is, the cross-sectional area of ​​the dotted line portion in the figure (cross-sectional area of ​​the metal monofilament 1 + cross-sectional area of ​​the elastomer 3) is expressed by the denominator {d × [d × n + w1 × (n-1)]} in the above formula (1), and the cross-sectional area of ​​the metal monofilament 1 included in the dotted line portion in the figure is expressed by the numerator [(d / 2) 2 ×π×n].

[0070] By using the metal cord 2 made of a bundle of metal monofilaments 1 drawn together with a predetermined gap therebetween and by specifying the ratio of the cross-sectional area of ​​the metal monofilaments 1 contained in the cross section of the metal cord 2 within a predetermined range, it is possible to achieve a balanced improvement in light weight, plunger durability, handling stability, corrosion progression resistance, and separation resistance of the belt layers.

[0071] From the viewpoint of obtaining a good balance of each performance, the following formula (1'): 0.48≦[(d / 2) 2 ×π×n] / {d×[d×n+w1×(n-1)]}≦0.77 (1') It is more preferable that the relationship of the following formula (1") is satisfied: 0.50≦[(d / 2) 2 ×π×n] / {d×[d×n+w1×(n-1)]}≦0.77 (1”) It is even more preferable that the following relationship is satisfied.

[0072] Fig. 6 shows an enlarged partial cross-sectional view of a belt according to one embodiment of the tire of the present invention. In Fig. 6, the ratio G / w2 of the distance G between the surfaces of metal monofilaments 1 embedded in two adjacent belt layers 60A, 60B in a belt 60 (also referred to as "interlayer gauge") to the spacing w2 between the metal cords 2 is preferably 1.6 or less. Also in Fig. 6, the ratio w1 / W of the spacing w1 between adjacent metal monofilaments 1 constituting the metal cord 2 to the width W of the metal cord 2 is preferably 0.07 or more. Furthermore, in Fig. 6, the ratio d / w1 of the filament diameter d of the metal monofilament 1 to the spacing w1 between adjacent metal monofilaments 1 constituting the metal cord 2 is preferably 1.2 or more and less than 2.

[0073] By ensuring that the ratio G / w2 (G = distance between the surfaces of the metal monofilaments 1 between adjacent belt layers 60A, 60B) to the spacing w2 between the metal cords 2, the ratio w1 / W (W = spacing w1 between the metal monofilaments 1 constituting the metal cord 2 to the width W of the metal cord), and the ratio d / w1 (D = filament diameter d of the metal monofilaments 1 to the spacing w1 between adjacent metal monofilaments 1 constituting the metal cord 2) fall within the above ranges, it is possible to achieve weight reduction and low rolling resistance without deteriorating the strain between the belt layers and the plunger durability and handling stability of the tire. The ratio G / w2 is more preferably 0.2 to 1.6, and even more preferably 0.4 to 1.4. The ratio w1 / W is more preferably 0.07 to 0.18, and even more preferably 0.07 to 0.15. The ratio d / w1 is more preferably 1.3 to less than 2, and even more preferably 1.4 to less than 2.

[0074] The distance G between the surfaces of the metal monofilaments 1 embedded in two adjacent belt layers within the belt (also referred to as the "interlayer gauge") is preferably 0.10 mm or more and 0.60 mm or less, and more preferably 0.35 mm or more and 0.45 mm or less. By setting the interlayer gauge G to 0.10 mm or more and 0.60 mm or less, it is possible to achieve a good balance between suppressing distortion between the belt layers and the effects of lightweight construction and low rolling resistance. When the interlayer gauge G becomes smaller, the belt layers become thinner, which is advantageous in terms of lightweight construction and low rolling resistance, but it also worsens interlayer distortion.

[0075] In the above-mentioned FIGS. 3 and 4, the metal monofilament 1 is a substantially straight metal monofilament, but in the tire of the present invention, the shape of the metal monofilament may be other than straight.

[0076] FIG. 7 is a schematic plan view of a metal cord in a belt layer according to another embodiment of the tire of the present invention. FIG. 8 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer according to another embodiment of the tire of the present invention.

[0077] 7 and 8, there is at least one pair of adjacent metal monofilaments 1 in which at least one of the shaping amount and shaping pitch in the direction perpendicular to the extension direction of the metal monofilaments 1 is different. Preferably, in 50% or more of the pairs, at least one of the shaping amount and shaping pitch in the direction perpendicular to the extension direction of the metal monofilaments 1 is different between adjacent metal monofilaments 1. 9 is an explanatory diagram of a metal monofilament showing the definitions of the shaping amount h and shaping pitch p of the metal monofilament, where the shaping amount h refers to the range of variation excluding the filament diameter of the metal monofilament 1. The shaping amount h of the metal monofilament 1 is measured by projecting the shaped metal monofilament 1 using a projector and projecting the projected image of the metal monofilament onto a screen or the like.

[0078] In Figures 7 and 8, shaped metal monofilaments 1a and unshaped metal monofilaments 1b (shaping amount 0 mm, shaping pitch ∞ mm) are arranged alternately, but metal monofilaments with different shaping amounts or different shaping pitches may also be arranged alternately. Preferably, the metal monofilaments constituting the bundle are arranged so that both sides are straight metal monofilaments that are not shaped. In this way, by arranging metal monofilaments 1 with different shaping amounts or shaping pitches adjacent to each other, it is possible to prevent the phases of the two monofilaments from matching. This configuration allows the elastomer to sufficiently penetrate between adjacent metal monofilaments 1, which results in out-of-plane deformation of the metal cord when a compression input is applied, and prevents the metal coat from breaking.

[0079] In the belt layer, if the shaping amount h of the metal monofilament 1 is too large, the distance w2 between the metal cords 2 in the belt layer becomes short, causing a decrease in the strength of the belt. Therefore, the shaping amount h of the metal monofilament 1 is preferably about 0.03 to 0.30 mm. If the shaping amount h is 0.30 mm or less, a decrease in the strength of the belt layer can be sufficiently suppressed. In particular, from the viewpoint of the distance w2 between the metal cords 2 and the strength of the metal monofilament 1, when shaping the metal monofilament 1, the shaping amount h is preferably 0.03 to 0.30 mm, more preferably 0.03 to 0.25 mm, and even more preferably 0.03 to 0.20 mm. Furthermore, the shaping pitch p of the metal monofilament 1 is preferably 2 to 30 mm, more preferably 2 to 20 mm, and even more preferably 3 to 15 mm.

[0080] In the metal cord 2 shown in Figs. 7 and 8, the shaped metal monofilaments 1a are shaped in the width direction of the metal cord 2, but the shaping direction of the metal monofilaments 1 in the belt layer may be inclined with respect to the width direction of the metal cord 2. Fig. 10 is a schematic cross-sectional view in the width direction of a metal cord in the belt layer of another embodiment of the tire of the present invention. Even with this structure, it is possible to sufficiently infiltrate the elastomer between adjacent metal monofilaments 1. However, from the viewpoint of lightweight properties, it is preferable that the shaping direction between adjacent metal monofilaments 1 is the width direction of the metal cord 2, since this allows the belt layer to be made thinner.

[0081] In the belt layer, it is preferable that at least one of the metal monofilaments 1 in the metal cord 2 is a substantially straight metal monofilament. As shown in Figs. 7 and 8, when an unshaped straight metal monofilament 1b and a shaped metal monofilament 1a are adjacent to each other, elastic fibers penetrating between the two metal monofilaments 1 can penetrate the straight metal monofilament 1b and the shaped metal monofilament 1a. Since the amount of elastomer increases, the coverage of the elastomer between adjacent metal monofilaments 1 on the width-direction side surfaces of the metal cord 2 increases. Furthermore, by using straight metal filaments for the metal monofilaments 1 arranged at both ends of the metal cord 2, the distance w2 between adjacent metal cords 2 in the elastomer can be increased, thereby improving durability. Furthermore, as shown in Figure 7, it is more preferable that unshaped straight metal monofilaments 1b and shaped metal monofilaments 1a are arranged alternately.

[0082] FIG. 11 is a schematic plan view of a metal cord in a belt layer according to another embodiment of a tire of the present invention, and FIG. 12 is a schematic widthwise cross-sectional view of a metal cord in a belt layer according to another embodiment of a tire of the present invention.

[0083] In the metal cord 2 shown in Figures 11 and 12, all of the metal monofilaments 1 are shaped with the same shaping amount and the same pitch, and there is at least one pair of metal monofilaments in the metal cord 2 in which the phases of adjacent metal monofilaments are different. 13 is an explanatory diagram of a metal monofilament showing the definitions of the shaping amount h and shaping pitch p of the metal monofilament, where the shaping amount h refers to the range of variation excluding the filament diameter of the metal monofilament 1. The shaping amount h of the metal monofilament 1 is measured by projecting the shaped metal monofilament 1 using a projector and projecting the projected image of the metal monofilament onto a screen or the like.

[0084] As in the metal cord 2 shown in Figures 11 and 12, by making the phases of metal monofilaments 1 that have the same shaping amount h and shaping pitch p different, it is possible to prevent the phases of the two from matching. This configuration allows the elastomer to sufficiently penetrate between adjacent metal monofilaments 1, which allows the metal cord to deform in-plane when a compressive input is applied, preventing the fatigue resistance of the metal cord from worsening.

[0085] 11 and 12, the phases of adjacent metal monofilaments differ at least at one location in the metal cord 2, and the phase difference is preferably π / 4 to 7π / 4. By setting the phase difference in this range, it becomes possible to more fully penetrate the elastomer between adjacent metal monofilaments 1. More preferably, the phase difference is π / 2 to 3π / 2, and particularly preferably, the phase difference is π.

[0086] In the belt layer, if the shaping amount h of the metal monofilament 1 is too large, the distance w2 between the metal cords 2 becomes short, causing a decrease in the strength of the belt. Therefore, the shaping amount h of the metal monofilament 1 is preferably about 0.03 to 0.30 mm. If the shaping amount h is 0.30 mm or less, a decrease in the strength of the belt layer can be sufficiently suppressed. In particular, from the viewpoint of the distance w2 between the metal cords 2 and the strength of the metal monofilament 1, when shaping the metal monofilament 1, the shaping amount h is preferably 0.03 to 0.30 mm, more preferably 0.03 to 0.25 mm, and even more preferably 0.03 to 0.20 mm. Furthermore, the shaping pitch p of the metal monofilament 1 is preferably 2 to 30 mm, more preferably 2 to 20 mm, and even more preferably 3 to 15 mm.

[0087] 11 and 12, the shaped metal monofilaments 1 are shaped in the width direction of the metal cord 2, but the shaping direction of the metal monofilaments 1 may be inclined with respect to the width direction of the metal cord 2. FIG. 14 is a schematic cross-sectional view in the width direction of a metal cord of a belt layer of another embodiment of the tire of the present invention. Even with this structure, it is possible to allow rubber to sufficiently penetrate between adjacent metal monofilaments 1. However, from the viewpoint of lightweight properties, it is preferable that the shaping direction between adjacent metal monofilaments 1 is the width direction of the metal cord 2, since this allows the belt layer to be made thinner.

[0088] Furthermore, in the belt layer, shaping is not limited to two-dimensional shaping, but may be three-dimensional shaping. Fig. 15 is a schematic cross-sectional view in the width direction of a metal cord in a belt layer of yet another embodiment of a tire of the present invention. In the illustrated example, the metal monofilament 1 is spirally shaped, and five spirally shaped metal monofilaments 1 are drawn in a row without being twisted together to form the metal cord 2.

[0089] FIG. 16 is a schematic plan view of a metal cord in a belt layer according to another embodiment of a tire of the present invention, and FIG. 17 is a schematic widthwise cross-sectional view of a metal cord in a belt layer according to another embodiment of a tire of the present invention.

[0090] 16 and 17, there is at least one pair of adjacent metal monofilaments 1 in which at least one of the amount of three-dimensional shaping and the shaping pitch is different in the metal cord 2. Preferably, at least one of the amount of three-dimensional shaping and the shaping pitch of the adjacent metal monofilaments 1 is different in 50% or more of the pairs. Here, the shaping amount h and shaping pitch p of the metal monofilament are as shown in Fig. 13, and the shaping amount h refers to the range of variation excluding the filament diameter of the metal monofilament 1. The shaping amount h of the metal monofilament 1 is measured by projecting the shaped metal monofilament 1 with a projector and projecting the projected image of the metal monofilament onto a screen or the like.

[0091] 16 and 17, spirally shaped metal monofilaments 1a and unshaped metal monofilaments 1b (shaping amount 0 mm, shaping pitch ∞ mm) are arranged alternately. In this way, by arranging metal monofilaments 1 with different shaping amounts or shaping pitches adjacent to each other, it is possible to prevent the phases of the two from matching. This configuration makes it possible for elastomer to sufficiently penetrate between adjacent metal monofilaments 1, which results in the metal cord being able to deform out-of-plane when a compressive load is applied, thereby preventing the metal cord from breaking.

[0092] In the belt layer, if the shaping amount h of the metal monofilaments 1 is too large, the distance w2 between the metal cords 2 will be shortened, causing a decrease in the strength of the belt. Therefore, the shaping amount h of the metal monofilaments 1 is preferably about 0.10 to 0.50 mm. In particular, from the viewpoint of the distance w2 between the metal cords 2 and the strength of the metal monofilaments, a shaping amount h of 0.2 to 0.3 mm is suitable. Furthermore, the shaping pitch p of the metal monofilaments 1 is preferably 5 mm or more, more preferably 8 to 20 mm.

[0093] In the belt layer, it is preferable that at least one of the metal monofilaments 1 in the metal cord 2 is a substantially straight metal monofilament. As shown in FIGS. 16 and 17, when an unshaped straight metal monofilament 1b and a shaped metal monofilament 1a are adjacent to each other, a large amount of elastomer penetrates between the two metal monofilaments 1, resulting in a high elastomer coverage on the widthwise side of the metal cord 2 between the adjacent metal monofilaments 1. Furthermore, by using straight metal monofilaments 1 at both ends of the metal cord 2, the distance w2 between adjacent metal cords 2 in the elastomer can be increased, thereby improving the durability of the belt. It is more preferable that the unshaped straight metal monofilaments 1b and the shaped metal monofilaments 1a are arranged alternately, as shown in FIGS. 16 and 17.

[0094] Next, other embodiments of the belt according to the tire of the present invention will be described by way of example. Fig. 18 is a schematic cross-sectional view of an end portion of a belt according to another embodiment of the tire of the present invention. The belt 60 shown in Fig. 18 includes a first belt layer 60A and a second belt layer 60B laminated on the tire radial direction outer side of the first belt layer 60A. In the illustrated example, the belt consists of two belt layers, but the belt may consist of three or more belt layers.

[0095] In the belt 60 shown in FIG. 18, the shortest distance a between the metal monofilament 1B of the second belt layer 60B in the tire center portion and the metal monofilament 1A of the first belt layer 60A, and the shortest distance b between the metal monofilament 1B at the end of the second belt layer 60B and the metal monofilament 1A of the first belt layer 60A are set to satisfy the following formula (2): 1.8≦b / a≦4.0 It is preferable that the following relationship is satisfied. In formula (2), a is the shortest distance between the metal monofilaments of the second belt layer and the metal monofilaments of the first belt layer in the tire center portion, and b is the shortest distance between the metal monofilaments at the end of the second belt layer and the metal monofilaments of the first belt layer.

[0096] In this way, by widening the gap between the metal monofilaments of the first belt layer 60A and the second belt layer 60B at the belt end where belt edge separation starts, distortion at the belt end can be suppressed and belt edge separation resistance can be improved. Furthermore, by making the b / a ratio 1.8 or more, the durability of the belt end (particularly, belt edge separation durability) can be sufficiently improved. Furthermore, by making the b / a ratio 4.0 or less, sufficiently low rolling resistance can be ensured. More preferably, the following formula (2') is satisfied: 1.8≦b / a≦3.8 Satisfy the relationship.

[0097] In order to widen the gap between the metal monofilaments of the first belt layer 60A and the second belt layer 60B at the belt ends, in the illustrated example, the inter-belt layer rubber 4 is disposed between the first belt layer 60A and the second belt layer 60B, but the thickness of the elastomer (coating rubber) 3 at the ends of the belt layers 60A, 60B may be increased, or the ends of the belt layers 60A, 60B may be wrapped with another rubber sheet. The inter-belt layer rubber 4 and the rubber sheet wrapping the ends of the belt layers 60A, 60B may be made of the same material as the elastomer (coating rubber) 3 of the first belt layer 60A and the second belt layer 60B.

[0098] Fig. 19 is a schematic cross-sectional view of a center portion of a belt according to another embodiment of the tire of the present invention, which corresponds to the portion surrounded by the dashed line in Fig. 18. In Fig. 19, it is preferable that the distances c1 and c2 from both the upper and lower surfaces of the first belt layer 60A in the tire center portion to the metal monofilament 1A are both 0.14 mm or less, and that the distances c3 and c4 from both the upper and lower surfaces of the second belt layer 60B in the tire center portion to the metal monofilament 1B are both 0.14 mm or less. With this configuration, it is possible to sufficiently improve the low rolling resistance of the tire.

[0099] Depending on the type of tire to be applied, the tire of the present invention may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization step or the like and then further vulcanizing it. Note that the components of the tire of the present invention other than the belt (belt layer) and belt reinforcing layer are not particularly limited, and known components can be used. Furthermore, the tire of the present invention is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. [Example]

[0100] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0101] (Preparation of rubber-steel cord composite) A steel cord (steel monofilament) having the specifications shown in Comparative Examples 1 to 4 and Reference Example 1 in Table 1 was covered from both the top and bottom with a sheet of a rubber composition (elastomer) having a thickness of approximately 0.5 mm to produce a steel cord-rubber composite. The rubber composition for coating was prepared according to a conventional method by adding carbon black (N326, DPB oil absorption = 72 mL / 100 g, NSA = 78 m 2The rubber composition was prepared by blending and kneading 61 parts by mass of zinc oxide (1 / g), 5 parts by mass of zinc oxide, 1 part by mass of an antioxidant (N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C"), 1 part by mass of a vulcanization accelerator (N,N'-dicyclohexyl-2-benzothiazylsulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccela DZ"), and 5 parts by mass of sulfur (insoluble sulfur, manufactured by Flexis Co., Ltd., trade name "Crystex HS OT-20"). The obtained steel cord-rubber composite was vulcanized at 160°C for 20 minutes and subjected to the following evaluations.

[0102] Here, the metal cord of Comparative Example 3 is a cord made of evenly arranged steel monofilaments with a filament diameter of 0.35 mm that are laid out in a row without being twisted together. The metal cord of Reference Example 1 is a cord made of a bundle of five steel monofilaments with a filament diameter of 0.26 mm that are laid out in a row without being twisted together. The metal cord of Comparative Example 4 is a cord made of a bundle of three steel monofilaments with a filament diameter of 0.3 mm that are laid out in a row without being twisted together.

[0103] <Belt weight> A belt layer sample was prepared using the obtained steel cord-rubber composite, and its weight was measured and expressed as an index with the belt weight of Comparative Example 1 set to 100. The smaller the value, the lighter the weight, and the more preferable it is.

[0104] (Evaluation by tire) A passenger tire with a tire size of 195 / 65R15 was fabricated using each steel cord-rubber composite in two belt layers, with the structure shown in Figure 1 except for the absence of a belt reinforcing layer. The belt angle was ±28° relative to the tire circumferential direction.

[0105] <Rolling resistance> The rolling resistance of each test tire was measured using a rolling resistance tester in accordance with SAE J 1269. The results were expressed as an index, with Comparative Example 1 being set at 100. The smaller the value, the better the results.

[0106] <Interlayer distortion> For each sample tire, the magnitude of strain between the two belt layers was calculated using the finite element method (FEM). The results were expressed as an index with Comparative Example 1 being 100. The smaller the index, the better the results. However, if the index was within the range of 95 to 105, it was evaluated as being at the same level.

[0107] <Handling stability> Using samples of the cross belt layers prepared using the steel cord-rubber composites of Comparative Examples 1 to 4 and Reference Example 1, the in-plane rigidity was evaluated by a conventional method and used as an index of steering stability. The results were indexed, with the in-plane rigidity value of Comparative Example 1 set to 100, and based on this index value, a value of less than 90 was evaluated as ×, a value of 90 or more but less than 100 was evaluated as △, and a value of 100 or more but less than 110 was evaluated as △. A score of 0 was given if the value was 110 or higher, and a score of ⊚ was given if the value was 110 or higher.

[0108] Next, the belt weight, rolling resistance, and steering stability were evaluated under the same conditions as above for Reference Examples 2 to 7 in Table 1, and the evaluation results were obtained as predicted values. Also, for Reference Examples 2 to 7 shown in Table 1, the interlayer strain was evaluated using the finite element method (FEM) in the same manner as above. The results are shown in Table 1 below.

[0109] [Table 1]

[0110] *1 The cords of Comparative Examples 1 and 2 have an oval cross section, and the filament diameter of the metal filaments in Comparative Examples 1 and 2 means the average cord diameter [(major diameter 0.64 mm + minor diameter 0.53 mm) / 2]. *2 The cords of Comparative Examples 1 and 2 have an oval cross section, and the spacing between the metal monofilaments (intercord spacing) varies depending on the direction in which the cords are inserted.

[0111] The results in Table 1 show that the weight of a tire can be reduced by applying to the tire a belt layer formed by covering a metal monofilament having a filament diameter d of less than 0.30 mm with an elastomer.

[0112] <Effect of the belt reinforcement layer> In the tires shown in Reference Examples 1 to 7 in Table 1, by disposing a belt reinforcing layer on the radially outer side of the belt, the belt reinforcing layer is made of polyethylene terephthalate cords coated with an elastomer, the cords having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more. It can be confirmed that the belt reinforcing layer compensates for the rigidity of the belt, improving the plunger durability and handling stability of the tire.

[0113] <Effect of interlayer rubber in the belt> In the tires shown in Reference Examples 1 to 7 in Table 1, a belt reinforcing layer is disposed on the radially outer side of the belt, the belt being formed by coating cords made of polyethylene terephthalate with an elastomer, the cords having a breaking strength of 6.5 cN / dtex or more, an elongation at break of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more, and further by disposing belt interlayer rubber at the end of the belt (between the end of the first belt layer and the end of the second belt layer) and setting b / a in the above formula (2) to 1.8 to 4.0, it can be confirmed that distortion at the belt end is suppressed and durability of the tire belt end is improved. [Explanation of symbols]

[0114] 100: tire, 10: bead portion, 20: sidewall portion, 30: tread portion, 40: bead core, 50: carcass, 60: belt, 60A: belt layer (first belt layer), 60B: belt layer (second belt layer), 70A: belt reinforcing layer (cap layer), 70B: belt reinforcing layer (layer layer), C: load-elongation curve of cord, S: tangent at a point corresponding to 7% elongation on the load-elongation curve of cord, 1, 1A, 1B: metal monofilament, 2: metal cord, 3: elastomer (coated rubber), w1: spacing between adjacent metal monofilaments constituting the metal cord, w2: spacing between metal cords, t: thickness of belt layer, d: filament diameter of metal monofilament (wire diameter, wire diameter, diameter), G: distance between surfaces of metal monofilaments embedded in two adjacent belt layers in the belt (interlayer gauge), h: amount of shaping of metal monofilament, p: shaping pitch of metal monofilament, 1a: shaped metal monofilament, 1b: unshaped metal monofilament, 4: interlayer rubber of belt

Claims

1. A tire comprising a belt consisting of at least two belt layers disposed in a tread portion, and a belt reinforcing layer disposed radially outward of the belt, The belt layer and the belt reinforcing layer are formed by coating a reinforcing material with an elastomer, The reinforcing material of the belt layer is a metal monofilament having a filament diameter d of less than 0.30 mm, A tire characterized in that the reinforcing material of the belt reinforcing layer is an organic fiber cord having a breaking strength of 6.5 cN / dtex or more, a breaking elongation of 10% or more, and an elastic modulus at 7% elongation of 6.0 mN / (dtex·%) or more.

2. The tire according to claim 1, wherein the metal monofilament used as the reinforcing material of the belt layer has a filament diameter d of 0.15 mm or more.

3. 2. The tire according to claim 1, wherein the belt layer is formed by covering, with an elastomer, metal cords each consisting of a bundle of a plurality of metal monofilaments arranged in a single row without being twisted together.

4. The interval w between adjacent metal monofilaments constituting the metal cord １ The tire according to claim 3, wherein the thickness of the groove is equal to or greater than 0.01 mm and less than 0.24 mm.

5. The filament diameter d (mm) of the metal monofilament and the interval w between adjacent metal monofilaments constituting the metal cord １ (mm) and the number n (pieces) of metal monofilaments constituting the metal cord satisfy the following formula (1): 0.45≦[(d / 2) ２ ×π×n] / {d×[d×n+w １ ×(n-1)]}≦0.77 ・・・ (1) [wherein d is the filament diameter (mm) of the metal monofilament, and w １ is the distance (mm) between adjacent metal monofilaments constituting the metal cord, n is the number (number) of metal monofilaments constituting the metal cord, provided that d>0, and w １ 4. The tire according to claim 3, wherein n satisfies the relationship: n > 0, and n is an integer.

6. The distance G between the surfaces of the metal monofilaments embedded in two adjacent belt layers in the belt, and the interval w between the metal cords ２ The ratio G / w ２ is 1.6 or less, The interval w between adjacent metal monofilaments constituting the metal cord １ and the width W of the metal cord, １ / W is 0.07 or more, The filament diameter d of the metal monofilament and the interval w between adjacent metal monofilaments constituting the metal cord １ The ratio d / w １ The tire according to claim 3, wherein is equal to or greater than 1.2 and less than 2.

7. The tire according to claim 1, wherein the belt layer has a thickness t of 0.8 mm or less.

8. 2. The tire according to claim 1, wherein the organic fiber cords serving as reinforcing materials for the belt reinforcing layer are cords made of polyethylene terephthalate.

9. the belt includes a first belt layer and a second belt layer laminated on the outer side of the first belt layer in the tire radial direction, The shortest distance a between the metal monofilaments of the second belt layer and the metal monofilaments of the first belt layer in the tire center portion and the shortest distance b between the metal monofilaments of the end portion of the second belt layer and the metal monofilaments of the first belt layer are expressed by the following formula (2): 1.8≦b / a≦4.0 (2) 2. The tire according to claim 1, wherein the relationship is satisfied: [wherein a is the shortest distance between the metal monofilaments of the second belt layer and the metal monofilaments of the first belt layer in the tire center portion, and b is the shortest distance between the metal monofilaments of the end portion of the second belt layer and the metal monofilaments of the first belt layer].

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