JP2008189048A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire obtaining low fuel consumption property in a tread rubber adopting high-grip composition. <P>SOLUTION: The pneumatic tire is equipped with a carcass 2, a tread part 11, and a belt 3 which is disposed between them and composed of at least two belt layer forming a reinforcing part. A first belt layer 3a of the first layer of the belt 3 and a second layer 3b of the second belt layer are arranged in a belt width direction in parallel and are buried in a coating rubber 5 making a bundle that 5-7 mono-filament cords having a filament diameter of 0.18-0.26 mm are aligned as a unit. A gauge of the rubber layer between the first belt layer 3a at the end part of the second belt layer 3b and the mono-filament cord 4 of the second belt layer 3b is 1.3-3.0 times the gauge at a central part of the tire, and the value of tanδ at 30°C of the tread rubber composing the tread part is 0.080 or more and 0.60 or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly, a pneumatic tire according to improvement in wear resistance when using a tread rubber compounded with high Tg, particularly suitable for a passenger car. Related to pneumatic tires.

  Generally, a pneumatic tire has a carcass extending in a toroidal shape between a pair of bead portions as a skeleton, and a belt layer made of rubberized steel cord is disposed as a reinforcing layer on the outer side in the tire radial direction. . Further, tread rubber is disposed outside the belt layer in the tire radial direction to form a tread surface portion.

  In recent years, with the improvement in performance of automobiles, higher performance is also required for tires. On the other hand, a target grip performance has been conventionally obtained by so-called high loss performance in which a loss tangent (tan δ) is increased using a polymer having a high glass transition temperature (Tg) for tread rubber ( Patent Document 1).

  Moreover, the request | requirement with respect to the fuel-consumption improvement of a motor vehicle has also increased, and the weight reduction of the tire has been achieved for this reason. When considering weight reduction in a belt portion using a conventional twisted steel cord, assuming that a certain level of tensile strength is ensured, the steel belt layer can only be thinned. From such a viewpoint, a technique for using a metal monofilament as a cord for a belt without twisting has been developed, and various proposals have been made so far. For example, in Patent Document 2, for the purpose of improving fuel consumption and riding comfort, a bundle of three or four metal wires (monofilaments) arranged side by side in the width direction of the belt without being twisted is embedded in rubber as a unit. A pneumatic radial tire having a belt formed as described above has been proposed.

Further, in Patent Document 3, in order to respond to the need for weight reduction of tires and to solve problems such as a decrease in durability due to breakage of metal wires, the belt layer is made of a metal monofilament having a predetermined width in the belt ply width direction. A pneumatic radial tire composed of three belt plies arranged under conditions and embedded in a covered rubber has been proposed. Furthermore, Patent Document 4 discloses that a second belt layer of the second layer is used in order to obtain a pneumatic radial tire that suppresses belt end separation and achieves both improved belt durability and reduced tire weight. A technique is disclosed in which the gauge between the monofilament cords of the first belt and the second belt at the end is 1.3 to 3.0 times the gauge at the center of the tire.
JP-A-10-60176 ([0002] etc.) JP-A-11-208210 (Claims etc.) JP 2001-334810 A (Claims etc.) JP 2005-349999 A (Claims etc.)

  As described above, as a tread rubber, a compounding system having a high tan δ and a storage elastic modulus E ′ has been conventionally used in order to improve grip performance and handling stability. However, since such a blend cannot satisfy the low fuel consumption demanded in recent years, establishment of a technique capable of satisfying both has been desired.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire that solves the problems in the prior art and realizes low fuel consumption in a tread rubber to which a high grip formulation is applied.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by combining a tread rubber to which a high grip formulation is applied and a predetermined belt structure, and has completed the present invention.

That is, the pneumatic tire of the present invention is disposed on the outer side in the tire radial direction of a carcass layer including at least one carcass layer straddling a toroidal shape between a pair of left and right bead cores, and a crown region of the carcass. In a pneumatic tire comprising: a tread portion that forms a belt, and a belt that is disposed between the tread portion and the crown region of the carcass and that forms a reinforcing portion, and is formed of at least two belt layers.
The first belt layer of the first layer and the second belt layer of the second layer of the belt are each a bundle of 5-7 monofilament cords having a filament diameter of 0.18 to 0.26 mm. The gauge of the rubber layer between the monofilament cords of the first belt layer and the second belt layer at the end of the second belt layer is arranged in parallel in the belt width direction and embedded in the coating rubber. 1.3 to 3.0 times, and
The tread rubber constituting the tread portion has a tan δ value at 30 ° C. of 0.080 or more and 0.60 or less.

In the present invention, the tread rubber preferably has a tan δ value at 60 ° C. of 0.150 or more and 0.550 or less. In the present invention, the tread rubber preferably contains 20 to 100 parts by weight of a white filler with respect to 100 parts by weight of the rubber component, and the tread rubber has the following formula (I),
HOOC—CH═CH—COO—R ¹ —CO—CH═CH—COOH (I)
Wherein R ¹ is a group represented by the formula —R ² O—, a group represented by the formula — (R ³ O) _S —, a group represented by the formula —CH ₂ CH (OH) CH ₂ O—, or A group represented by the formula — (R ⁴ O—COR ⁵ —COO—) _t R ⁴ O—, wherein R ² is an alkylene group having ² to 36 carbon atoms, an alkenylene group or a divalent aromatic hydrocarbon group; ³ is an alkylene group having 2 to 4 carbon atoms, s is a number from 1 to 60 indicating the average number of moles added of the oxyalkylene group, R ⁴ is an alkylene group having 2 to 18 carbon atoms, an alkenylene group, a divalent aromatic carbonization A hydrogen group or — (R ⁶ O) _u R ⁶ — (R ⁶ is an alkylene group having 2 to 4 carbon atoms, u is a 1 to 30 number indicating the average number of moles added of the oxyalkylene group), and R ⁵ is a carbon number 2-18 alkylene group, alkenylene group or divalent aromatic hydrocarbon group, t is an average value of 1-3 It is also preferred to include a number.) A compound having a structure represented by.

  Further, the distance in the belt width direction between the monofilament cord bundles is preferably more than 0.4 mm and less than 1.2 mm, and preferably the number of driven monofilament cord bundles is 18 to 32 bundles / 50 mm. .

  Furthermore, in the tire of the present invention, an inter-belt rubber is disposed between the first belt layer and the second belt layer at the end of the second belt, and the elastic modulus of the inter-belt rubber is the elasticity of the coating rubber. It is preferably 1.02 to 2.0 times the rate. Furthermore, the tan δ (25 ° C.) of the inter-belt rubber is preferably 0.20 or less, and the tan δ (25 ° C.) of the inter-belt rubber is 0.85 of the tan δ (25 ° C.) of the belt coating rubber. It is also preferable that it is -0.98 times. Furthermore, in the present invention, it is preferable that bismaleimide is blended in the inter-belt rubber in an amount of 0.5 to 3.0 parts by weight with respect to 100 parts by weight of the rubber component.

  According to the present invention, with the above-described configuration, it is possible to realize a pneumatic tire with improved fuel efficiency in the tread rubber to which the high grip formulation is applied.

Hereinafter, preferred embodiments of the present invention will be described in detail.
FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. The illustrated tire includes a tread portion 11 that is disposed on the outer side in the tire radial direction of the crown region of the carcass and forms a ground contact portion, and a pair of sides that extend inward in the tire radial direction continuously on both sides of the tread portion 1. A wall portion 12 and a bead portion 13 continuous on the inner peripheral side of each sidewall portion 12 are provided.

  The tread portion 11, the sidewall portion 12, and the bead portion 13 are reinforced by a carcass 2 made of a single carcass layer extending in a toroid shape between the bead cores 1 embedded in the bead portions 13. Further, the tread portion 11 includes at least two first belt layers 3a and second belt layers 3b arranged in the tire radial direction outer side of the crown region of the carcass 2, which will be described in detail below, in the illustrated example. It is reinforced by a belt 3 consisting of Here, a plurality of carcass layers of the carcass 2 may be used, and an organic fiber cord extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 ° can be preferably used.

  In the tire 10 of the present invention, the value of tan δ at 30 ° C. of the tread rubber constituting the tread portion 11 is 0.080 or more and 0.60 or less. If the value of tan δ at 30 ° C. is smaller than 0.080, steering stability is insufficient, while if it exceeds 0.60, high speed performance is insufficient. Preferably, the tread rubber has a tan δ value at 60 ° C. of 0.150 or more and 0.550 or less.

  On the other hand, as described above, such a high-grip blended tread rubber has a drawback that fuel efficiency is poor. In the present invention, this tread rubber and a belt having a specific structure described in detail below are used in combination. Can make up for this shortcoming. That is, since the belt used in the present invention can achieve low fuel consumption by thinning the gauge, even if a tread rubber blended with a high grip is applied, the entire tire can be combined with such a belt, It is possible to satisfy low fuel consumption.

  In FIG. 2, the cross section of the width direction of the belt edge part in the tire 10 of this invention is expanded and shown. As shown in the figure, in the present invention, the first belt layer 3a of the first layer and the second belt layer 3b of the second layer of the belt 3 are both 5-7 monofilament cords 4, 6 in the illustrated example. A bundle bundled in a book is used as a unit, and is juxtaposed in the belt width direction and embedded in the coating rubber 5.

  In this case, by increasing the rubber gauge between the cords, it is possible to improve the BES resistance by suppressing the distortion of the belt end that is the starting point of belt edge separation (BES). When the distance in the width direction, that is, the cord interval w is as dense as 0.4 mm or less, cracks are easily connected between adjacent cords, and the effect of rubber between the belts is not sufficient, and the BES resistance is inferior in comparison with conventional cords. Result. Further, even when the cord interval w is extremely sparse as 1.2 mm or more, the crack progresses rapidly along the cord, which also results in poor BES resistance. Therefore, in the present invention, a bundle of 5 to 7 monofilament cords is applied to the belt, and while maintaining the total strength, the cord interval w is secured in an appropriate range, and good BES resistance is obtained. Is. Therefore, for the reasons described above, in the present invention, the belt width direction distance w between the monofilament cord bundles is preferably more than 0.4 mm and less than 1.2 mm.

  In consideration of belt folding, the filament diameter of the monofilament cord needs to be 0.18 to 0.26 mm, particularly 0.20 to 0.24 mm. When the filament diameter is thinner than 0.18 mm, the buckling wavelength during the turning of the figure 8 is shortened, the surface distortion generated at that time is increased, and the belt folding property is inferior. On the other hand, when it becomes larger than 0.26 mm, the surface distortion becomes large, which also results in poor belt folding.

Furthermore, the tensile strength of the monofilament cord 4 is preferably 2700 N / mm ² or more. As the monofilament cord having a high tensile strength, one containing at least 0.7% by mass, particularly at least 0.8% by mass of carbon can be suitably used.

Further, in the present invention, the gauge H _E of the rubber layer between the monofilament cord 4 between the first belt layer 3a and a second belt layer 3b in the second belt layer 3b end, of the gauge H _C in the tire center portion 1 .3 to 3.0 times, preferably 1.8 to 2.6 times. By applying a thick gauge inter-belt rubber to the monofilament cord coated with a thin gauge at the belt end, both weight reduction of the tire and belt durability can be achieved. If this value is less than 1.3 times, the belt end separation is not sufficiently suppressed. On the other hand, if it exceeds 3.0 times, the weight of the tire cannot be sufficiently reduced.

  Therefore, in the present invention, the monofilament cords satisfying the above-mentioned predetermined filament diameter are bundled at a predetermined number of cords and applied to the belt, and the rubber gauge at the end of the belt is compared with the center 1.3--3 while ensuring the cord interval. By increasing to 3.0 times, good BES resistance can be ensured without deteriorating the belt foldability, and as a result, a pneumatic tire having both excellent durability and light weight can be obtained. Can do.

  In the present invention, the number of monofilament cord bundles to be driven is preferably 18 to 32 bundles / 50 mm. If the number of driving is too small, it will be difficult to ensure the tensile strength, and if it is too large, it will be difficult to ensure the cord interval, which is not preferable.

In the present invention, as described above, the thicker than the gauge H _E of the first belt layer 3a and a rubber layer between the monofilament cord 4 of the second belt layer 3b in the belt end to gauge H _C of the tire center portion The inter-belt rubber 6 may be disposed between the first belt layer 3a and the second belt layer 3b at the end of the second belt layer 3b. The elastic modulus of the inter-belt rubber 6 is preferably 1.02 to 2.0 times, particularly 1.1 to 1.8 times the elastic modulus of the belt coating rubber 5. When the elastic modulus is within the range of the elastic modulus, the distortion of the belt end is satisfactorily suppressed, and both the weight reduction of the tire weight and the belt durability can be achieved at a high level.

  Further, the tangent loss tan δ (25 ° C.) of the inter-belt rubber 6 is preferably 0.20 or less, and in particular, 0.85 to 0.98 times the tan δ (25 ° C.) of the belt coating rubber 5. By using such a low-loss rubber as the belt-to-belt rubber 6, distortion at the belt end is suppressed and an increase in tire temperature is suppressed.

（式中、Ｒは炭素数６〜１８の芳香族基、または炭素数７〜２４のアルキル芳香族基を表し、ｘおよびｙは０〜３のいずれかの整数をそれぞれ独立に表す）で表されるビスマレイミドを好適に用いることができる。具体的には例えば、Ｎ，Ｎ’−１，２−フェニレンビスマレイミド、Ｎ，Ｎ’−１，３−フェニレンビスマレイミド、Ｎ，Ｎ’−１，４−フェニレンビスマレイミド、Ｎ，Ｎ’−（４，４’−ジフェニルメタン）ビスマレイミド、２，２−ビス［４−（４−マレイミドフェノキシ）フェニル］プロパン、ビス（３−エチル−５−メチル−４−マレイミドフェニル］メタン等を例示することができ、特に好ましくは、Ｎ，Ｎ’−（４，４’−ジフェニルメタン）ビスマレイミドであり、ゴム配合中に、これらを１種以上含むことができる。また、ベルト間ゴム６のゴム成分としては、具体的には例えば、スチレン・ブタジエン共重合体ゴム（ＳＢＲ）、天然ゴム（ＮＲ）や、スチレン・イソプレン共重合体ゴム（ＳＩＲ）、ポリイソプレンゴム（ＩＲ）、ポリブタジエンゴム（ＢＲ）、ブチルゴム（ＩＩＲ）およびエチレン・プロピレン共重合体等の合成ゴムが挙げられる。 Furthermore, in this invention, it is preferable to mix | blend bismaleimide with the rubber | gum 6 between belts at 0.5-3.0 weight part with respect to 100 weight part of rubber components. As a result, the tangent loss tan δ (25 ° C.) can be kept low while improving the elastic modulus. As bismaleimide, the following general formula (II),

(Wherein R represents an aromatic group having 6 to 18 carbon atoms or an alkyl aromatic group having 7 to 24 carbon atoms, and x and y each independently represents an integer of 0 to 3) The bismaleimide prepared can be preferably used. Specifically, for example, N, N′-1,2-phenylenebismaleimide, N, N′-1,3-phenylenebismaleimide, N, N′-1,4-phenylenebismaleimide, N, N′- Illustrate (4,4′-diphenylmethane) bismaleimide, 2,2-bis [4- (4-maleimidophenoxy) phenyl] propane, bis (3-ethyl-5-methyl-4-maleimidophenyl] methane, etc. Particularly preferred is N, N ′-(4,4′-diphenylmethane) bismaleimide, which can contain one or more of these in the rubber compounding, and as a rubber component of the inter-belt rubber 6. Specifically, for example, styrene / butadiene copolymer rubber (SBR), natural rubber (NR), styrene / isoprene copolymer rubber (SIR), polyisoprene rubber (IR), Examples include synthetic rubbers such as polybutadiene rubber (BR), butyl rubber (IIR), and ethylene / propylene copolymer.

  The first belt layer 3a and the second belt layer 3b that are the belt layers on the carcass 2 side preferably have a cord driving angle of 10 ° to 30 ° with respect to the tire circumferential direction, and the first belt layer 3a and The second belt layers 3b are crossed with each other.

  Moreover, as tread rubber used for this invention, specifically, what contains 20-100 mass parts of white fillers with respect to 100 mass parts of rubber components can be used suitably. When the number of parts of the white filler is less than 20 parts by mass, the handling stability on the wet road surface is insufficient. On the other hand, when it exceeds 100 parts by mass, the workability of the rubber sheet becomes poor and the workability is poor.

  As the rubber component of the tread rubber, the same rubber component as that of the inter-belt rubber 6 can be used. Examples of the white filler include silica and aluminum hydroxide, and among these, silica is preferable. Examples of the silica include, but are not limited to, wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Wet silica is preferred because it is excellent in the effect of achieving both grip properties and low rolling resistance. In addition, when using a silica as a white filler, it is preferable to add a silane coupling agent at the time of a mixing | blending from a viewpoint of further improving the reinforcement. Such silane coupling agents include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilyl). Ethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltri Methoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarba Yl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate Monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, dimethoxy Methylsilylpropylbenzothiazole tetrasulfide, and the like. Among these, bis (3 Triethoxysilylpropyl) tetrasulfide and 3-trimethoxysilylpropyl benzothiazole tetrasulfide are preferable. These silane coupling agents may be used alone or in combination of two or more.

The tread rubber is preferably the following formula (I),
HOOC—CH═CH—COO—R ¹ —CO—CH═CH—COOH (I)
Wherein R ¹ is a group represented by the formula —R ² O—, a group represented by the formula — (R ³ O) _S —, a group represented by the formula —CH ₂ CH (OH) CH ₂ O—, or A group represented by the formula — (R ⁴ O—COR ⁵ —COO—) _t R ⁴ O—, wherein R ² is an alkylene group, an alkenylene group or a divalent aromatic hydrocarbon group having ² to 36 carbon atoms. Preferably, it is an alkylene group having 2 to 18 carbon atoms or a phenylene group, more preferably an alkylene group having 4 to 12 carbon atoms, and R ³ is an alkylene group having 2 to 4 carbon atoms, preferably an ethylene group or It is a propylene group, and s is a number of 1 to 60 indicating the average number of added moles of the oxyalkylene group, preferably 2 to 40, more preferably 4 to 30. R ⁴ has 2 to 18 carbon atoms. Alkylene group, alkenylene group, divalent aromatic A hydrocarbon group or — (R ⁶ O) _u R ⁶ — (R ⁶ is an alkylene group having 2 to 4 carbon atoms, u is a number of 1 to 30 indicating the average number of added moles of an oxyalkylene group, preferably And R ⁵ is an alkylene group, alkenylene group or divalent aromatic hydrocarbon group having 2 to 18 carbon atoms, preferably 2 to 2 carbon atoms. 12 is an alkylene group or phenylene group, more preferably an alkylene group having 2 to 8 carbon atoms, and t is an average value of 1 to 30, preferably 1 to 20, and more preferably 1 to 15. The compound of the above formula (I) can be added to the tread rubber to improve the steering stability merit on the dry road surface of the compound represented by the formula (I). As a specific example Glycerin dimaleate, 1,4-butanediol dimaleate, alkylene diol dimaleate such as 1,6-hexanediol dimaleate, alkylene diol difumarate such as 1,6-hexanediol dimaleate, PEG 200 dimaleate , PEG600 dimaleate polyoxyalkylene glycol dimaleate (here, PEG200 and PEG600 are polyethylene glycols having an average molecular weight of 200 or 600, respectively), polybutylene maleate having carboxyl groups at both ends, carboxyl groups at both ends A poly (PEG200) maleate having both ends carboxylic acid type polyalkylene glycol / maleic polyester, polybutylene adipate maleate having carboxyl groups at both ends, Polyoxyalkylene glycol difumarate such as PEG600 difumarate, polybutylene fumarate having carboxyl groups at both ends, poly (PEG200) fumarate having carboxyl groups at both ends, etc. Is mentioned. This compound preferably has a molecular weight of 250 or more, more preferably in the range of 250 to 5000, and particularly preferably in the range of 250 to 3000. Within this range, the flash point is high, which is desirable not only from the viewpoint of safety, but also from the viewpoint of the working environment because it produces less smoke. In the present invention, such compounds may be used alone or in combination of two or more. The blending amount is preferably in the range of 1.0 to 4.0 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount is less than 1.0 part by mass, the effect of improving the dynamic storage elastic modulus E ′ and the effect of suppressing the sagging are insufficient, whereas when it exceeds 4.0 parts by mass, there is a concern of a decrease in wear resistance. Neither is preferred.

  In addition to the above, carbon black can be added to the tread rubber as a filler. Such carbon black is not particularly limited, and those of FEF, SRF, HAF, ISAF, SAF grade, etc. can be used. Particularly, the iodine adsorption amount (IA) is 60 mg / g or more and A dibutyl phthalate (DBP) oil absorption of 80 mL / 100 g or more is preferred. By compounding carbon black, various physical properties of the rubber composition can be improved, but from the viewpoint of improving the wear resistance, those of HAF, ISAF, and SAF grades are more preferable. As a compounding quantity of carbon black, it is the range of 30-90 mass parts suitably with respect to 100 mass parts of rubber components. If the blending amount of the carbon black is less than 30 parts by mass, the processability is inferior in heat transfer properties and the like, whereas if it exceeds 90 parts by mass, the merit of steering stability on a wet road surface decreases.

  Further, the tread rubber may contain a softening agent, and the blending amount thereof is in the range of 0 to 30 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount of the softening agent exceeds 30 parts by mass, the tensile strength and low heat build-up property of the vulcanized rubber tend to deteriorate. As the softener, process oil or the like can be used, and specific examples of the process oil include paraffin oil, naphthenic oil, aroma oil, and the like. Among these, an aroma oil is preferable from the viewpoint of tensile strength and wear resistance, and naphthenic oil and paraffin oil are preferable from the viewpoint of hysteresis loss and low-temperature characteristics.

  As the tread rubber, a general rubber crosslinking system can be used, and it is preferable to use a combination of a crosslinking agent and a vulcanization accelerator. As the cross-linking agent, sulfur or the like can be used, and the amount used thereof is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass as the sulfur content with respect to 100 parts by mass of the rubber component. preferable. When the compounding amount of the crosslinking agent is less than 0.1 parts by mass as the sulfur content with respect to 100 parts by mass of the rubber component, the fracture strength, wear resistance and low heat build-up of the vulcanized rubber are lowered, while exceeding 10 parts by mass. And rubber elasticity is lost. The vulcanization accelerator is not particularly limited, but 2-mercaptobenzothiazole (M), dibenzothiazyl disulfide (DM), N-cyclohexyl-2-benzothiazylsulfenamide (CZ). And thiazole vulcanization accelerators such as Nt-butyl-2-benzothiazolylsulfenamide (NS), and guanidine vulcanization accelerators such as diphenylguanidine (DPG). As a usage-amount of a vulcanization accelerator, the range of 0.1-5 mass parts is preferable with respect to 100 mass parts of rubber components, and the range of 0.2-3 mass parts is more preferable. These vulcanization accelerators may be used alone or in combination of two or more.

  In addition to the above, for tread rubber, additives commonly used in the rubber industry such as anti-aging agent, zinc oxide, stearic acid, antioxidant, ozone degradation inhibitor, and the like are within the range not impairing the object of the present invention. Can be appropriately selected and blended.

  In the present invention, the desired effect can be obtained by satisfying the conditions relating to the tread rubber and the belt, and the structure and material of the other members other than the above are not particularly limited. It can be selected appropriately according to a conventional method. For example, a tread pattern is appropriately formed on the surface of the tread portion 11 of the tire 10 of the present invention, and an inner liner is formed on the innermost layer (not shown). Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than normal air or the air which adjusted oxygen partial pressure, can be used.

Hereinafter, the present invention will be described more specifically with reference to examples.
A pneumatic tire having a structure including the two-layer steel belt shown in FIG. 1 was manufactured under the conditions shown in Tables 1 to 4 below. The tire size was 195 / 65R15, and the driving angles of the monofilament cords 4 of the first belt layer 3a and the second belt layer 3b were + 22 ° and −22 °, respectively, with respect to the tire circumferential direction.

The composition of the tread rubber used is shown in Table 1 below.
The compound rubber of the inter-belt rubber 6 includes 100 parts by weight of natural rubber, 50 parts by weight of carbon black (N330), 1.0 part by weight of cobalt salt (cobalt naphthenate), 10 parts by weight of zinc oxide, and a vulcanization accelerator. (N, N′-dicyclohexyl-2-benzothiazolylsulfenamide, Noxeller DZ manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1.0 part by weight, sulfur 6.0 part by weight, bismaleimide (N, N′- (4,4′-diphenylmethane bismaleimide)) A composition comprising 2.0 parts by weight was used.

  Each of the obtained test tires was evaluated according to the following. The results are shown in Tables 3 and 4 below together with the measured value of tan δ at 30 ° C. of the tread rubber.

(Measurement of tan δ)
The loss tangent (tan δ) at 30 ° C. of the tread rubber was measured under the conditions of a frequency of 15 Hz and a strain of 5% using a rheometrics viscoelasticity measuring device, and the main dispersion peak temperature was determined.

(RRC evaluation)
Evaluation with an RRC drum was performed, and the result was shown as an index with Comparative Example 1 being 100. The higher the number, the better the result.

(Evaluation of steering stability)
Each test tire was mounted on an actual vehicle, and the driving stability was evaluated by scoring the actual vehicle. The evaluation criteria are as follows: grade 5: standard, grade 6: good, grade 7: good for anyone to discriminate. The larger the value, the better the steering stability and the better.

(Evaluation of high speed)
In the tire size 195 / 65R15, a tire satisfying the JATMA standard (91V) was rated as ◯, and a tire tire not satisfying it was rated as ×.

(Evaluation of wet performance)
Each test tire was mounted on an actual vehicle, and the vehicle was run to evaluate the braking performance on a wet road surface. The results are shown as an index with Comparative Example 1 as 100. The higher the number, the better the result.

(Evaluation of steering stability at the limit)
The side force value at a slip angle of 2 ° was evaluated. The results are shown as an index with Comparative Example 1 as 100. The higher the number, the better the result.

(Processability evaluation)
Evaluation was made based on workability (viscosity, etc.) during kneading. The case where the workability was good was marked as ◎, the case where the work could be performed without any problem was marked as ◯, and the case where the workability was slightly problematic was marked as △.

＊１）シリカおよびポリ（ＰＥＧ２００）マレエートの、ゴム成分１００質量部に対する部数（質量部）を示す。
＊２）式（Ｉ）において、Ｒ^１が−（Ｒ^４Ｏ−ＣＯＲ^５−ＣＯＯ−）_ｔＲ^４Ｏ−で示される基であり、Ｒ^４が−（Ｒ^６Ｏ）ｕＲ^６−（Ｒ^６がエチレン基、ｕ＝３．５）であり、Ｒ^５が−ＣＨ＝ＣＨ−、ｔ＝４の化合物である。

* 1) Number of parts (parts by mass) of silica and poly (PEG200) maleate with respect to 100 parts by mass of the rubber component.
* 2) In the formula (I), R ¹ is a group represented by — (R ⁴ O—COR ⁵ —COO—) _t R ⁴ O—, and R ⁴ is — (R ⁶ O) uR ⁶ — (R ⁶ is an ethylene group, u = 3.5), R ⁵ is —CH═CH—, t = 4.

  As shown in Tables 3 and 4 above, the pneumatic tires of the examples using belts and tread rubbers that satisfy the predetermined conditions according to the present invention achieve high fuel efficiency while ensuring high grip performance. It was confirmed that it could be done.

1 is a schematic cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. It is an expanded partial sectional view showing the edge part neighborhood of a belt layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 3 Belt 3a 1st belt layer 3b 2nd belt layer 4 Monofilament cord 5 Belt coating rubber 6 Rubber between belts 11 Tread part 12 Side wall part 13 Bead part

Claims (10)

A carcass formed of at least one carcass layer straddling a pair of left and right bead cores in a toroidal shape, a tread portion disposed on the outer side in the tire radial direction of the crown region of the carcass to form a ground contact portion, and the tread portion A pneumatic tire comprising: a belt composed of at least two belt layers disposed between a crown region of the carcass and forming a reinforcing portion;
The first belt layer of the first layer and the second belt layer of the second layer of the belt are each a bundle of 5-7 monofilament cords having a filament diameter of 0.18 to 0.26 mm. The gauge of the rubber layer between the monofilament cords of the first belt layer and the second belt layer at the end of the second belt layer is arranged in parallel in the belt width direction and embedded in the coating rubber. 1.3 to 3.0 times, and
The pneumatic tire according to claim 1, wherein a value of tan δ at 30 ° C. of the tread rubber constituting the tread portion is 0.080 or more and 0.60 or less.   The pneumatic tire according to claim 1, wherein a value of tan δ at 60 ° C of the tread rubber is 0.150 or more and 0.550 or less.   The pneumatic tire according to claim 1 or 2, wherein in the tread rubber, 20 to 100 parts by mass of a white filler is blended with respect to 100 parts by mass of the rubber component. The tread rubber has the following formula (I),
HOOC—CH═CH—COO—R ¹ —CO—CH═CH—COOH (I)
Wherein R ¹ is a group represented by the formula —R ² O—, a group represented by the formula — (R ³ O) _S —, a group represented by the formula —CH ₂ CH (OH) CH ₂ O—, or A group represented by the formula — (R ⁴ O—COR ⁵ —COO—) _t R ⁴ O—, wherein R ² is an alkylene group having ² to 36 carbon atoms, an alkenylene group or a divalent aromatic hydrocarbon group; ³ is an alkylene group having 2 to 4 carbon atoms, s is a number from 1 to 60 indicating the average number of moles added of the oxyalkylene group, R ⁴ is an alkylene group having 2 to 18 carbon atoms, an alkenylene group, a divalent aromatic carbonization A hydrogen group or — (R ⁶ O) _u R ⁶ — (R ⁶ is an alkylene group having 2 to 4 carbon atoms, u is a 1 to 30 number indicating the average number of moles added of the oxyalkylene group), and R ⁵ is a carbon number 2-18 alkylene group, alkenylene group or divalent aromatic hydrocarbon group, t is an average value of 1-3 A pneumatic tire as claimed in any one of claims 1 to 3, containing a compound having a structure represented by a number.) Of.   The pneumatic tire according to any one of claims 1 to 4, wherein a distance in the belt width direction between the monofilament cord bundles is more than 0.4 mm and less than 1.2 mm.   The pneumatic tire according to any one of claims 1 to 5, wherein the number of driven monofilament cord bundles is 18 to 32 bundles / 50 mm.   An inter-belt rubber is disposed between the first belt layer and the second belt layer at the end of the second belt, and the elastic modulus of the inter-belt rubber is 1.02 to 2.0 times the elastic modulus of the coating rubber. The pneumatic tire according to any one of claims 1 to 6.   The pneumatic tire according to claim 7, wherein tan δ (25 ° C.) of the inter-belt rubber is 0.20 or less.   The pneumatic tire according to claim 7 or 8, wherein the tan δ (25 ° C) of the inter-belt rubber is 0.85 to 0.98 times the tan δ (25 ° C) of the belt coating rubber.   The pneumatic tire according to any one of claims 7 to 9, wherein bismaleimide is blended in the inter-belt rubber in an amount of 0.5 to 3.0 parts by weight with respect to 100 parts by weight of a rubber component.

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