JP2008143485A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire superior in controllability and stability on a dry road surface and a wet road surface, while making low fuel consumption and abrasion resistance compatible. <P>SOLUTION: This pneumatic tire is provided by successively arranging a crossing belt layer 2 and tread rubber 3 of at least two layers of coating a steel cord with rubber, on the outside in the radial direction of its crown part, with a carcass 1 extending in a toroidal shape between a pair of bead parts 11 as a skeleton. The steel cord has a single stranded structure or a core-single layer sheath structure composed of steel stranded wires of 6 to 10 pieces having a stranded wire diameter of 0.1 to 0.20 mm. The driving number of the steel cord is set to 40 pieces/50 mm or more, and a distance between the steel cords adjacent in the belt layer 2 is set to 0.3 mm or more, and a dynamic storage elastic modulus E'(MPa) at 30 °C of the tread rubber and loss tangent tanδ at 60 °C, satisfy the relationship expressed by 5.0 ≤ E' and 0.050 ≤ tanδ ≤ 0.240. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more specifically, for passenger cars having excellent steering stability and improved dry performance, wet performance, uneven wear resistance, and low fuel consumption. 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, in order to improve the safety of vehicles, it has been required to increase the friction coefficient (μ) on both the dry road surface and the wet road surface of the tire to simultaneously improve the dry performance and wet performance of the tire. Various techniques have been developed to meet the demand for improvement in dry performance and wet performance. For example, in the development of a tire tread rubber composition that directly contributes to the dry performance and wet performance of a tire, the loss tangent (tan δ) near 0 ° C. and the loss tangent (tan δ) near 30 ° C. are used as indices. It is generally effective, and specifically, by using a rubber composition having a high tan δ at around 0 ° C. for the tread, the coefficient of friction (μ) on the wet road surface of the tire is increased to improve the wet performance. On the other hand, by using a rubber composition having a high tan δ at around 30 ° C. for the tread, the friction coefficient (μ) on the dry road surface of the tire can be increased and the dry performance can be improved. .

  In addition, demands for reducing fuel consumption of automobiles are also increasing in connection with the movement of global carbon dioxide emission regulations accompanying the recent increase in interest in environmental problems. In order to meet such demands, reduction of rolling resistance is also demanded for tire performance. Here, in developing a rubber composition for a tire tread that contributes to the rolling resistance of the tire, it is generally effective to use a loss tangent (tan δ) around 60 ° C. as an index. By using a rubber composition having a low tan δ in the vicinity for the tread, heat generation of the tire is suppressed and rolling resistance is reduced, and as a result, low fuel consumption of the tire can be improved.

As a technique for realizing a tire having both dry performance, wet performance, and low fuel consumption, for example, Patent Document 1 describes a rubber component (A) containing 100 parts by mass of a styrene / butadiene copolymer rubber. 20 to 70 parts by mass of at least one filler (B) selected from the group consisting of carbon black and white filler, 0 to 30 parts by mass of the softener (C), and a polystyrene equivalent weight average molecular weight of 2 × 10 ^A rubber composition obtained by blending 3 to 30 parts by mass of a (meth) acrylate-based (co) polymer (D) that is ³ to 50 × 10 ³ is disclosed.

  On the other hand, with respect to the steel cord used for the belt layer, various studies have been made from the viewpoint of improving the handling stability and the riding comfort. For example, Patent Document 2 discloses a thin wire diameter. (Element diameter 0.06 to 0.10 mm) A technique for improving maneuverability and stability during cornering by using a specific steel cord is described. Patent Document 3 discloses a tire in which a steel cord is defined by bending resistance and tensile elongation. Patent Documents 4 to 6 disclose a belt layer, a cord diameter, the number of filaments in one cord, and driving of the belt layer. Tires defined by a relational expression with the number of cords are disclosed respectively.

Further, Patent Document 7 discloses a tire that is a steel cord made of a predetermined steel filament and that prescribes a predetermined range of values defined by belt bending rigidity, cord strength, and gap amount of the belt cord. Documents 8 to 10 disclose a steel cord for reinforcing tires having a predetermined twist structure and predetermining a range of values defined by cord strength, cord break elongation and cord bending rigidity. Further, Patent Document 11 discloses a tire in which a belt is defined by a belt cord twisted structure and wire diameter and the number of belt cords driven, and Patent Document 12 discloses a twisted structure, a bending rigidity / cord strength ratio, a cord strength. Patent Document 13 discloses a tire in which a belt cord structure and a belt ply with a predetermined number of drivings are arranged via a buffer rubber, respectively. .
JP 2006-274049 A (Claims etc.) JP 59-38102 A (Claims etc.) JP-A-60-185602 (Claims) JP 63-2702 (Claims etc.) JP 63-2703 (Claims etc.) JP 63-2704 A (Claims etc.) JP-A 64-855381 (Claims etc.) JP-A 64-85382 (Claims etc.) JP-A 64-85383 (Claims etc.) JP-A 64-85384 (Claims etc.) JP-A-1-141103 (Claims etc.) JP-A-3-74206 (Claims etc.) JP-A-3-143703 (Claims etc.)

  However, it is generally known that the tread rubber having excellent fuel efficiency as described above has a problem that it is inferior in uneven wear. Accordingly, it has been desired to establish a technology that can achieve a tire having both required performance and various performance requirements.

  Accordingly, an object of the present invention is a pneumatic tire that solves the above-described problems, achieves both low fuel consumption and uneven wear resistance, and is excellent in handling stability on a dry road surface (dry) and a wet road surface (wet). Is to provide.

  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 low fuel consumption composition is applied and a predetermined belt structure, and has completed the present invention.

That is, the pneumatic tire of the present invention has a carcass extending in a toroidal shape between a pair of bead portions as a skeleton, and at least two crossing belt layers formed by rubberizing steel cords on the outer side in the radial direction of the crown portion of the carcass. And the tread rubber are sequentially arranged, the steel cord has a single twist structure or a core-single layer sheath structure composed of 6 to 10 steel strands having a strand diameter of 0.10 to 0.20 mm. And the number of driven steel cords is 40/50 mm or more, the distance between the steel cords adjacent in the belt layer is 0.3 mm or more, and the tread rubber is dynamically stored at 30 ° C. The elastic modulus E ′ (MPa) and the loss tangent tan δ at 60 ° C. are respectively expressed by the following equations:
5.0 ≦ E '
0.050 ≦ tan δ ≦ 0.240
It is characterized by satisfying the relationship represented by

In the present invention, in the tread rubber, 20 to 80 parts by mass of white filler and 10 to 30 parts by mass of carbon black are blended with 100 parts by mass of the rubber component, and the number A of the white filler and the carbon are mixed. The number of black copies B is
20 ≦ (A / (A + B)) × 100 ≦ 95
It is preferable to satisfy the relationship represented by these.

  Further, in the present invention, the steel cord preferably has a structure formed by twisting so as to have a gap into which rubber can enter between at least one pair of adjacent steel strands located in the outermost layer of the cord, It is also preferable that the cross-sectional shape of the steel cord is flat and the major axis direction of the flat cross-section is arranged along the width direction of the belt layer. In particular, the steel cord has two steel strands arranged in parallel without being twisted together as a core, and the remaining steel strands around at least one pair of adjacent steel strands around the core. It has a core-single layer sheath structure that is twisted so as to have a gap that allows rubber to enter between the wires. Still preferably, the number of steel cords to be driven is 40 to 60/50 mm, and the distance between adjacent steel cords in the belt layer is 0.4 to 1.0 mm.

  According to the present invention, it is possible to realize a pneumatic tire that achieves both low fuel consumption and uneven wear resistance and is excellent in handling stability on a dry road surface and a wet road surface. became.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In FIG. 1, the schematic sectional drawing of an example of the pneumatic radial tire of this invention is shown. As shown in the figure, the tire of the present invention has a carcass 1 extending in a toroidal shape between a pair of bead portions 11 as a skeleton, and at least two layers of cross belts formed by rubberizing a steel cord on the outer side in the radial direction of the crown portion. The layer 2 (2a, 2b) and the tread rubber 3 are sequentially arranged.

In the present invention, as the tread rubber 3, the dynamic storage elastic modulus E ′ (MPa) at 30 ° C. and the loss tangent tan δ at 60 ° C. are respectively expressed by the following equations:
5.0 ≦ E '
0.050 ≦ tan δ ≦ 0.240
The one satisfying the relationship represented by is used. Thereby, while ensuring low fuel consumption, the steering stability on a dry road surface can be improved.

If the dynamic storage elastic modulus E ′ at 30 ° C. is less than 5.0 MPa, the effect of improving the steering stability on the dry road surface cannot be obtained. This dynamic storage modulus E ′ is preferably further represented by the following formula:
8.0 ≦ E ′
Shall be satisfied. On the other hand, when the loss tangent tan δ at 60 ° C. is less than 0.050, there is a concern about steering stability due to grip reduction, while when it exceeds 0.240, the superiority in rolling resistance is lost.

  Further, in the tire of the present invention, the cross belt layer 2 has a predetermined belt structure to be described later, so that it exhibits high circumferential tensile rigidity and in-plane bending rigidity, and has low out-of-plane bending rigidity. Have.

  Since the belt layer has a high tensile rigidity in the circumferential direction, the belt member bears the tension due to the internal pressure and can exert its effect, and since it has a high in-plane bending rigidity, it can be used during cornering. Since the in-plane bending deformation is reduced, a large cornering force can be generated and good steering stability can be exhibited.

  Further, the belt layer is subjected to a large in-plane bending deformation in the vicinity of the cornering limit point, and due to this deformation, the belt layer is subjected to a large compressive deformation inside the bending deformation, and buckling occurs. However, in the present invention, by reducing the out-of-plane bending rigidity of the two-layer belt layer, the out-of-plane deformation pressure accompanying compression is reduced, and buckling deformation can be suppressed by the tire internal pressure, resulting in ground contact. It is possible to improve the ground contact by suppressing the pressure drop and to make the ground pressure distribution uniform in the tread. As a result, the input applied to the tread rubber can be made uniform, and uneven wear resistance and wear resistance can be improved. As described above, the low-fuel-consumption-type tread rubber used in the present invention is inferior in uneven wear resistance, but when used in combination with such a belt layer, the low-fuel-consumption type tread rubber generates uneven wear. It becomes possible to apply without.

  In the present invention, the steel cord of the belt layer 2 has a single-stranded structure or core comprising 6 to 10 steel strands having a strand diameter of 0.10 to 0.20 mm, preferably 0.15 to 0.20 mm. It has a single layer sheath structure.

  The reason why the strand diameter is set to 0.10 to 0.20 mm is that when the strand diameter exceeds 0.20 mm, the bending rigidity of the cord increases and it becomes difficult to reduce the out-of-plane bending rigidity of the belt layer. It is. On the other hand, when the strand diameter is less than 0.10 mm, it becomes difficult to obtain high circumferential tensile rigidity under the conditions of the number of strands and the distance between adjacent cords suitable for the present invention, and the cost is high. Become.

  Also, if the number of strands is large, the bending rigidity increases due to interference between strands when the cord is bent. However, in the present invention, the number of strands is as small as 10 or less, so bending of interference between strands is difficult. The effect on rigidity is small. On the other hand, when the number of strands is less than 6, it is difficult to obtain a high circumferential tensile rigidity under the conditions of the number of strands and the distance between adjacent cords suitable for the present invention.

  Furthermore, in the present invention, the steel cord has a single twist structure or a core-single-layer sheath structure composed of 6 to 10 steel strands, and has a simple twist structure that limits the maximum number of strands. Is easy to secure. In particular, it is preferable that the steel cord has an open structure in which rubber is twisted so as to have a gap into which rubber can enter between at least one pair of adjacent steel strands located in the outermost layer of the cord. Thereby, the merit that productivity is high compared with a double twisted cord, and cost reduction is possible is also acquired.

  In the present invention, the number of steel cords to be driven is 40/50 mm or more, preferably 40 to 60/50 mm. The reason why the number of driving is set to 40/50 mm or more is that (1) it is necessary to secure the minimum necessary steel occupation ratio in order to obtain the necessary circumferential tensile rigidity and circumferential tensile rigidity. ) Due to the fact that the circumferential tensile stiffness and circumferential tensile stiffness of the crossing belt layer are the same steel occupancy ratio, the steel cord formed by the upper and lower belt layers has a smaller mesh and a higher number. Is.

  Here, it is preferable that the smaller the strand diameter and the smaller the number of strands, the greater the number of driven wires, and particularly effective use of the effect (2) above. It is important that the distance between the cords is 0.3 mm or more. If the distance between adjacent steel cords in the belt layer is less than 0.3 mm, fine cracks generated at the ends of the steel cords grow between adjacent steel cords, and then between the belt laminations. This leads to rapid expansion and the crack growth rate leading to belt separation becomes much faster. The distance between the adjacent steel cords is preferably about 0.4 to 1.0 mm.

  Preferably, the cross-sectional shape of the steel cord is flat, and the major axis direction of the flat cross-section is arranged along the width direction of the belt layer, so that higher in-plane bending rigidity and lower out-of-plane bending rigidity are obtained. Obtainable. It is also effective for ensuring rubber penetrability.

  The steel cord structure with a flat cross-sectional shape has a single twist structure in which the spiral shape of the strands is crushed in one direction, or two steel strands arranged in parallel without being twisted together, and the core A structure in which a sheath is formed by twisting steel strands around the periphery can be applied. In particular, two steel strands such as 2 parallels +4 to 7 are arranged in parallel without being twisted with each other as a core, and the remaining steel strands around at least one pair of adjacent steel strands. Applying a steel cord with a core-single-layer sheath structure that is twisted so that there is a gap through which rubber can enter, results in higher in-plane bending stiffness, lower out-of-plane bending stiffness, and good rubber penetrability Is particularly preferable.

Specifically, as the tread rubber 3 used in the present invention, 20 to 80 parts by weight of white filler and 10 to 30 parts by weight of carbon black are blended with 100 parts by weight of the rubber component, and these white fillers are filled. The number of parts A of the agent and the number B of the carbon black is
20 ≦ (A / (A + B)) × 100 ≦ 95
Those satisfying the relationship represented by can be suitably used.

  If the number A of the white filler is less than 20 parts by mass, no merit of steering stability on a wet road surface can be obtained. On the other hand, if it exceeds 80 parts by mass, the processability of the rubber sheet is deteriorated. It will be. Further, if the carbon black is less than 10 parts by mass, the heatability and the like are inferior in workability, and if it exceeds 30 parts by mass, the merit of steering stability on a wet road surface decreases. Further, if (A / (A + B)) × 100 <20, the merit of steering stability on a wet road surface cannot be obtained, whereas if (A / (A + B)) × 100> 95, a rubber sheet It will be inferior in workability, such as poor unity.

  Specific examples of the rubber component of the tread rubber 3 include styrene / butadiene copolymer rubber (SBR), natural rubber (NR), styrene / isoprene copolymer rubber (SIR), and polyisoprene rubber (IR). And synthetic rubbers such as polybutadiene rubber (BR), butyl rubber (IIR), and ethylene / propylene copolymer.

  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.

  Furthermore, the carbon black is not particularly limited, but those of FEF, SRF, HAF, ISAF, SAF grade, etc. can be used. Especially, the iodine adsorption amount (IA) is 60 mg / g or more. And the thing whose dibutyl phthalate (DBP) oil absorption is 80 mL / 100g or more is suitable. 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.

  The tread rubber 3 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 3, 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 the tread rubber 3, for example, additives commonly used in the rubber industry such as anti-aging agent, zinc oxide, stearic acid, antioxidant, ozone deterioration preventing agent, and the like do not impair the purpose of the present invention. It can select suitably and mix | blend it.

  In the present invention, a desired effect can be obtained by satisfying the conditions relating to the tread rubber 3 and the belt layer 2, and the structure and material of the other members other than the above are particularly limited. It is not something. For example, as shown in the figure, a bead core 4 is embedded in each of the pair of bead portions 11 of the tire of the present invention, and the carcass 1 is folded around the bead core 4 from the inside of the tire to the outside and locked. A tread portion 12 made of a tread rubber 3 is disposed on the outer periphery of the crown portion of the belt layer 2, and a sidewall portion 13 is disposed on the side portion of the carcass 1. Furthermore, as a gas filled in the tire, an inert gas such as nitrogen, argon, helium, or the like can be used in addition to normal air or air whose oxygen partial pressure is adjusted.

Hereinafter, the present invention will be described in more detail with reference to examples.
As shown in FIG. 1, a pneumatic radial tire including two cross belt layers 2 a and 2 b formed by rubber-drawing steel cords and a tread rubber 3 in the radial direction of the crown portion of the carcass 1 was manufactured. As the belt layer of each example and comparative example, those satisfying the conditions according to the following Tables 2 and 3 were used. The tire size was 225 / 45R17, and the angles of the intersecting belt layers 2a and 2b were ± 63 ° with respect to the tire width direction. The composition of the tread rubber used is shown in Table 1 below.

  Each of the obtained test tires was evaluated according to the following. The results are shown together in Table 3 below together with the measured values of the dynamic storage elastic modulus E ′ at 30 ° C. and the loss tangent tan δ at 60 ° C. of the tread rubber.

(Measurement of E ′ and tan δ)
The dynamic storage elastic modulus (E ′) at 30 ° C. and the loss tangent (tan δ) at 60 ° C. of the tread rubber were measured under the conditions of a frequency of 15 Hz and a strain of 5% using a rheometrics viscoelasticity measuring device. .

(Maneuvering stability)
Each test tire was mounted on an actual vehicle, and the steering stability was evaluated by the driver's feeling running on a dry (dry) and wet (wet) circuit. The results are shown on a 10-point scale. The larger the value, the better the steering stability and the better. Regarding dry steering stability, the difference of 0.5 points is large in performance, and is a level at which a general driver can recognize the performance difference.

(Uneven wear)
Evaluation of uneven wear resistance was performed according to the following.
A sample having the shape shown in FIG. 2 is prepared, a wear test is performed using a lambone tester, the value of (b−a) is measured after the test, and the change from the original difference (= 4 mm) is small. Was judged to be superior in uneven wear resistance. The test conditions were slip ratio: 45%, test time: 30 minutes / sample, and the original values were a: 46 mm and b: 50 mm.

(Processability)
The workability was evaluated according to the following.
After unvulcanized rubber was seated on a sheeting roll, it was punched into a 10 cm × 2 cm × 2 mm mold, and after 24 hours of standing, the shrinkage change after punching was measured. The case where the amount of shrinkage was 40% or less was evaluated as ◯ (good), the case where it exceeded 40% and 60% or less was evaluated as Δ, and the case where it exceeded 60% was evaluated as ×.

＊１）Ａ：シリカ（白色充填剤）およびＢ：カーボンブラックの、ゴム成分１００質量部に対する部数（質量部）を示す。

* 1) A: The number of parts (parts by mass) of silica (white filler) and B: carbon black with respect to 100 parts by mass of the rubber component.

  As shown in Table 3 above, in the pneumatic tire of the example using the steel cord and the tread rubber of the belt layer satisfying the predetermined condition according to the present invention, both low fuel consumption and uneven wear resistance are achieved. In addition, it was confirmed that excellent performance can be obtained with respect to steering stability on a dry road surface and a wet road surface.

1 is a schematic cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. It is the schematic which shows the sample shape used for the evaluation test of the uneven wear resistance in an Example.

Explanation of symbols

1 Carcass 2 (2a, 2b) Crossing belt layer 3 Tread rubber 4 Bead core 11 Bead portion 12 Tread portion 13 Side wall portion

Claims (7)

A pneumatic structure in which a carcass extending in a toroidal shape between a pair of bead portions is used as a skeleton, and at least two crossing belt layers formed by rubber-drawing steel cords and a tread rubber are sequentially arranged outside the crown portion of the carcass in the radial direction. In the tire,
The steel cord has a single twist structure or a core-single layer sheath structure composed of 6 to 10 steel strands having a strand diameter of 0.10 to 0.20 mm, and the number of driven steel cords is 40/50 mm. The distance between the steel cords adjacent in the belt layer is 0.3 mm or more, and
The dynamic storage elastic modulus E ′ (MPa) at 30 ° C. and the loss tangent tan δ at 60 ° C. of the tread rubber are respectively expressed by the following equations:
5.0 ≦ E '
0.050 ≦ tan δ ≦ 0.240
A pneumatic tire characterized by satisfying the relationship expressed by: In the tread rubber, 20 to 80 parts by weight of white filler and 10 to 30 parts by weight of carbon black are blended with respect to 100 parts by weight of the rubber component, and the number A of the white filler and the number B of the carbon black Is the following formula:
20 ≦ (A / (A + B)) × 100 ≦ 95
The pneumatic tire according to claim 1, satisfying a relationship represented by:   The pneumatic tire according to claim 1 or 2, wherein the steel cord has a structure in which rubber is twisted between at least one pair of adjacent steel wires located in the outermost layer of the cord so as to have a gap into which rubber can enter.   The pneumatic tire according to any one of claims 1 to 3, wherein a cross-sectional shape of the steel cord is flat, and a major axis direction of the flat cross-section is arranged along a width direction of the belt layer. .   The steel cord has two steel strands arranged in parallel without being twisted with each other as a core, and the remaining steel strands are disposed between at least one pair of adjacent steel strands around the core. The pneumatic tire according to claim 4, which has a core-single layer sheath structure in which rubber is twisted so as to have a gap into which rubber can enter.   The pneumatic tire according to any one of claims 1 to 5, wherein the number of driven steel cords is 40 to 60/50 mm.   The pneumatic tire according to any one of claims 1 to 6, wherein a distance between adjacent steel cords in the belt layer is 0.4 to 1.0 mm.

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