Pneumatic tire

Abstract

The invention provides a pneumatic tire capable of improving rolling resistance performance without compromising riding comfort performance. The present invention is a pneumatic tire having a tread portion (2). The tread portion (2) includes a cord reinforcement layer (10) including a belt ply (7A), and a tread rubber (2G). The product of the thickness (T1: mm) of the tread rubber (2G) at the tire equator (C), the average thickness (T2: mm) of one belt ply (7A), the land ratio (La) of the ground contact surface (2s), and the loss tangent (tan [delta] 1) of the tread rubber (2G) at 30 DEG C (T1 * T2 * La * tan [delta] 1) is 0.33-1.10.

Description

Technical Field

[0001] The present invention relates to pneumatic tires. Background Art

[0002] Patent Document 1 listed below proposes a tire in which the loss tangent of the cap rubber layer of the tread portion and the thickness of the tread portion are determined to improve the rolling resistance when the vehicle starts moving.

[0003] Patent Document 1: Japanese Patent No. 7337333

[0004] In recent years, there has been a desire to improve vehicle fuel economy and further reduce the rolling resistance of tires installed on these vehicles. Known methods for reducing tire rolling resistance (hereinafter referred to as "improving rolling resistance performance") include reducing the volume of the tread rubber and belt layers, and reducing the tread rubber loss tangent.

[0005] However, the above methods all have the problem that minute vibrations of the tires are easily transmitted to the vehicle side when the vehicle is running, thereby impairing the ride comfort performance. Summary of the Invention

[0006] The present invention has been made in view of the above-mentioned actual situation, and a main object of the present invention is to provide a pneumatic tire having improved rolling resistance performance without impairing ride comfort performance.

[0007] The pneumatic tire of the present invention has a tread portion, which includes: a cord reinforcement layer, which includes at least one belt cord formed by covering a plurality of steel cords with a rubber coating; and a tread rubber, which is formed from the radial outer surface of the tire of the cord reinforcement layer to the ground contact surface of the tread portion, the thickness T1 of the tread rubber at the position of the tire equator, the average thickness T2 of the belt cord, the land ratio La of the ground contact surface and the product T1·T2·La·tanδ1 of the loss tangent tanδ1 of the tread rubber at 30°C are 0.33 to 1.10, and the units of the thickness T1 and the thickness T2 are mm.

[0008] The pneumatic tire of the present invention, by adopting the above-described structure, can improve rolling resistance performance without sacrificing ride comfort performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a transverse cross-sectional view of a tire according to one embodiment of the present invention.

[0010] Figure 2 yes Figure 1 An enlarged cross-sectional view of the tread portion.

[0011] Figure 3 Yes Figure 1Expanded view of the cord arrangement of the cord reinforcement layer.

[0012] Figure 4 It is a cross-sectional view of a steel cord according to another embodiment.

[0013] Explanation of reference numerals: 2...tread portion; 2s...contact patch; 2G...tread rubber; 12...steel cord; 13...top coat; 7A...belt; 10...cord reinforcement layer; T1...thickness of the tread rubber at the tire equator; T2...average thickness of a piece of belt; La...land ratio of the contact patch of the tread portion; tanδ1...loss tangent of the tread rubber at 30°C. DETAILED DESCRIPTION

[0014] The following describes one embodiment of the present invention based on the accompanying drawings. The drawings include and describe the features of the present invention; however, to aid understanding of the present invention, they may sometimes include exaggerated representations or representations that differ in dimensional ratio from the actual structure. Furthermore, throughout the various embodiments, identical or shared elements are denoted by the same reference numerals, and duplicate descriptions are omitted. Furthermore, structures not described in this specification may be appropriately adapted to known structures.

[0015] exist Figure 1 1 is a transverse cross-sectional view of a pneumatic tire 1 (hereinafter, sometimes simply referred to as “tire 1 ”) showing one embodiment of the present invention. Figure 1 : is a tire meridian cross-sectional view of a tire 1 in a normal state, including the tire rotation axis. Figure 1 As shown, the tire 1 of this embodiment is suitable for use as a pneumatic tire for passenger cars, for example. However, the present invention is not limited to this embodiment, and can also be used as a pneumatic tire for heavy loads, for example.

[0016] In the case of pneumatic tires with various specifications specified, the "normal state" refers to a state in which the tire rim is assembled to a normal rim, filled with a normal internal pressure, and is unloaded. In the case of tires with various specifications not specified, the normal state refers to a standard usage state corresponding to the intended use of the tire, a state in which the tire is not installed on a vehicle, and is unloaded. In this specification, unless otherwise specified, the dimensions of various parts of the tire are values measured in the normal state. In addition, the dimensions of structures that cannot be measured in the normal state (for example, internal components of the tire 1) are values measured by making the tire 1 as close to the normal state as possible.

[0017] "Regular rims" are rims whose specifications are specified for each tire within the standard system that includes the tire's specifications. For example, JATMA has "standard rims," TRA has "design rims," and ETRTO has "measuring rims."

[0018] "Normal internal pressure" refers to the air pressure specified for each tire in the specification system that includes the specifications to which the tire is based. If it is JATMA, it is the "maximum air pressure". If it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES". If it is ETRTO, it is "INFLATION PRESSURE".

[0019] The tire 1 includes: a tread portion 2, a first sidewall portion 3A and a second sidewall portion 3B, a first bead portion 4A and a second bead portion 4B. The first sidewall portion 3A is connected to the first end portion 2a of the tread portion 2 in the tire axial direction (the right end in the various figures of this specification) and extends radially inwardly of the tire. The second sidewall portion 3B is connected to the second end portion 2b of the tread portion 2 in the tire axial direction (the left end in the various figures of this specification) and extends radially inwardly of the tire. The first sidewall portion 3A and the second sidewall portion 3B each include a tire maximum width position 1M. The first bead portion 4A is connected to the radially inner side of the first sidewall portion 3A. The second bead portion 4B is connected to the radially inner side of the second sidewall portion 3B.

[0020] The tire 1 includes a carcass 6. The carcass 6 extends from the first bead portion 4A to the second bead portion 4B via the first sidewall portion 3A, the tread portion 2, and the second sidewall portion 3B.

[0021] The carcass 6 is formed, for example, from a single carcass ply 6A. The carcass ply 6A includes, for example, a main body portion 6a and a turnback portion 6b. The main body portion 6a extends, for example, between the first bead portion 4A and the second bead portion 4B. The turnback portion 6b is, for example, connected to the main body portion 6a and folded around the bead core 5 from the axially inner side to the outer side of the tire.

[0022] The carcass ply 6A comprises a plurality of carcass cords and a topping rubber (not shown) covering the carcass cords. The carcass cords are made of organic fiber cords such as aramid or rayon. The carcass cords are preferably arranged at an angle of 70° to 90° relative to the tire equator C. In other words, the tire 1 of this embodiment has a radial carcass.

[0023] In addition, when numerical ranges for various parameters are described in this specification, unless otherwise specified, the numerical ranges refer to the numerical ranges of the average values for the parameters. Therefore, the numerical ranges for the carcass cord angles described above refer to the numerical ranges of the average values measured at various positions on multiple carcass cords. The same applies to the other parameters described below.

[0024] exist Figure 2 Shown in Figure 1 An enlarged cross-sectional view of the tread portion 2. Figure 2 As shown, the tread portion 2 of this embodiment includes a cord reinforcement layer 10. The cord reinforcement layer 10 is arranged on the carcass 6 (as shown in FIG. Figure 1 (shown) on the radially outer side of the tire.

[0025] exist Figure 3 FIG. 1 is a diagram showing a conceptual arrangement of the cords of the cord reinforcement layer 10. Figure 3 As shown, the cord reinforcement layer 10 of this embodiment includes at least one belt fabric 7A formed by covering a plurality of steel cords 12 with a topping 13. The cord reinforcement layer 10 of this embodiment includes a belt layer 7 including the belt fabric 7A and a band layer 8.

[0026] The belt layer 7 of this embodiment comprises two belt plies 7A stacked in the tire radial direction. The steel cords 12 in each belt ply 7A are arranged at an angle θ1 of 15° to 45° relative to the tire circumferential direction. Furthermore, the steel cords 12 in one belt ply 7A and the steel cords 12 in the other belt ply 7A are inclined in opposite directions relative to the tire circumferential direction. This effectively reinforces the tread portion 2.

[0027] The band layer 8 is composed of, for example, a single belt ply 8A. The belt ply 8A includes, for example, belt cords 8c arranged at an angle θ2 of 5° or less relative to the tire circumferential direction, and a topping rubber 8g covering the belt cords. The band layer 8 of this embodiment is arranged to cover the entire belt layer 7.

[0028] like Figure 2 As shown, the tread portion 2 includes a tread rubber 2G formed from the tire radial direction outer surface of the cord reinforcement layer 10 to the ground contact surface 2s of the tread portion 2. Figure 2 In the figure, hatching is applied to indicate that the tread rubber 2G is composed of a single layer of rubber, but the present invention is not limited to such a method. That is, the tread rubber 2G may also be composed of a plurality of rubber layers stacked together.

[0029] The tread rubber 2G has a thickness T1 at the tire equator C. When the circumferential groove 9 is provided at the tire equator C of the tread portion 2 , the thickness T1 refers to the thickness in a virtual state where the circumferential groove 9 is filled.

[0030] The tread rubber 2G has a loss tangent tanδ1 at 30°C. This loss tangent tanδ1 is measured using a viscoelasticity spectrometer under the following conditions in accordance with JIS-K6394. The loss tangent tanδ1 is the average loss tangent of the tread rubber 2G at 30°C. Therefore, if the tread rubber 2G has multiple rubber layers, the volume-weighted average loss tangent of the loss tangents of each rubber layer at 30°C corresponds to the loss tangent tanδ1 of the tread rubber 2G.

[0031] Initial strain: 10%

[0032] Amplitude: ±2%

[0033] Frequency: 10Hz

[0034] Deformation Mode: Stretch

[0035] Measurement temperature: 30°C

[0036] The contact surface 2s of the tread portion 2 is the surface of the outer surface of the tread portion 2 that contacts the road surface during normal driving. The first tread end Te1 and the second tread end Te2 correspond to the boundary between the contact surface 2s and the non-contact surface during normal driving.

[0037] For pneumatic tires with various specifications, the "normal load" refers to the load specified for each tire within the standard system that includes the tire's specifications. For JATMA, this refers to the "maximum load capacity," for TRA, it refers to the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table, and for ETRTO, it refers to "LOAD CAPACITY." For tires without various specifications, the "normal load" refers to the maximum load applicable when the tire is used, based on the aforementioned specifications.

[0038] The contact surface 2s of the tread portion 2 has a land ratio La. The land ratio La corresponds to the ratio of the actual contact area to the virtual contact area in a state where all the grooves, sipes, and recesses provided in the contact surface 2s are filled. Figure 2 In the figure, only a plurality of circumferential grooves 9 extending continuously in the tire circumferential direction are shown as grooves provided on the contact surface 2s of the tread portion 2. However, lateral grooves (not shown) extending in the tire axial direction may also be provided on the contact surface 2s of the tread portion 2. The specific arrangement of these grooves is not particularly limited in the present invention.

[0039] In the present invention, the product (T1·T2·La·tanδ1) of the thickness T1 (mm) of the tread rubber 2G at the tire equator C, the average thickness T2 (mm) of a single belt cord 7A, the land ratio La of the contact patch 2s, and the loss tangent tanδ1 of the tread rubber 2G at 30°C is 0.33 to 1.10. As a result, the tire 1 of the present invention can improve rolling resistance without sacrificing ride comfort. The reasons for this are as follows.

[0040] The above parameters can be determined independently. On the other hand, the smaller the values of thickness T1, thickness T2 and land area ratio La among the above parameters, the more lightweight the tire can be achieved, and the more rolling resistance performance can be improved. In addition, the smaller the value of loss tangent tanδ1, the more energy loss during tire rotation can be reduced, and the more rolling resistance performance can be improved. That is, the above parameters are all based on the above mechanism, and the smaller the values, the more we can expect the improvement of rolling resistance performance. However, the smaller the values of the above parameters, the easier it is for the tire's tiny vibration to be transmitted to the vehicle side when the vehicle is traveling, and there is a situation where the ride comfort performance is damaged.

[0041] On the contrary, if the values of the above parameters (ie, thickness T1, thickness T2, land ratio La, and loss tangent tan δ1) increase, although improvement in ride comfort can be expected, rolling resistance performance may be impaired.

[0042] The inventors investigated the degree of variation between the aforementioned parameters and rolling resistance and ride comfort performance. They found that, at least within the numerical ranges typically adopted by tires for the aforementioned parameters (hereinafter referred to as the "adoptable range"), the transition characteristics of rolling resistance and ride comfort performance are similar between the parameters. Furthermore, a more detailed investigation revealed that the degree of similarity is sufficiently high that even multiplying the parameters together and treating them as a single parameter to define rolling resistance and ride comfort performance is sufficient.

[0043] Based on these findings, the present invention specifies the product T1·T2·La·tanδ1 within a range of 0.33 to 1.10, thereby improving rolling resistance without compromising ride comfort. However, if the product T1·T2·La·tanδ1 is less than 0.33, tire vibrations are easily perceived by the driver, degrading ride comfort. Furthermore, if the product T1·T2·La·tanδ1 exceeds 1.10, while ride comfort is maintained, no improvement in rolling resistance can be expected.

[0044] In the present invention, the applicable range of thickness T1 is 7 to 15.5 mm. Furthermore, the applicable range of thickness T2 is 0.5 to 2.0 mm. The applicable range of land ratio La is 0.40 to 0.95. The applicable range of loss tangent tanδ1 is 0.10 to 0.30. In the present invention, the aforementioned effects can be expected at least when the parameters are within the aforementioned applicable ranges.

[0045] The following describes the structure of this embodiment in more detail. Furthermore, each of the structures described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the aforementioned effects even without the structures described below. Furthermore, by applying any of the structures described below individually to the tire 1 of the present invention having the aforementioned features, it is expected that the performance corresponding to each structure will be improved. Furthermore, by applying a combination of several of the structures described below, it is expected that the performance corresponding to the combination of the aforementioned structures will be improved.

[0046] In a further preferred embodiment, various parameters are preferably defined so that the product of T1·T2·La·tanδ1 falls within the range of 0.50 to 1.00. This ensures the above-mentioned effects.

[0047] Even if the numerical range of the product T1·T2·La·tanδ1 is specified except for the thickness T2, the same effect can be expected. From this point of view, the product T1·La·tanδ1 of the thickness T1 (mm), the land ratio La, and the loss tangent tanδ1 is preferably 0.51 to 1.12.

[0048] The loss tangent tanδ1 is preferably 0.12 or greater, more preferably 0.14 or greater, and preferably 0.22 or less, more preferably 0.20 or less. This optimizes the heat generation of the tread portion 2, reliably maintaining ride comfort and also reducing road noise.

[0049] The land ratio La is preferably 0.60 or greater, more preferably 0.64 or greater, and is preferably 0.78 or less, more preferably 0.68 or less. This improves ride comfort and rolling resistance in a balanced manner.

[0050] From the same viewpoint, the thickness T1 is preferably 9.0 mm or more, more preferably 9.5 mm or more, and preferably 12.0 mm or less, more preferably 11.6 mm or less. However, the present invention is not limited to this embodiment.

[0051] The thickness T2 is preferably, for example, 1.20 mm or less, and more preferably 1.00 mm or less. In this embodiment, the thickness T2 is preferably 0.66 to 0.98 mm. Furthermore, in this embodiment, the thickness T2 for each of the two belt plies 7A falls within the aforementioned range. The belt layer 7 composed of these belt plies 7A can enhance the tread portion 2's reinforcement while achieving lightweighting, thereby reliably improving rolling resistance performance.

[0052] From the same viewpoint, the weight per unit area of one belt fabric 7A is preferably 1350 to 1980 g / m 2 In addition, the weight of the rubber per unit area of the belt fabric 7A is preferably 600 to 1300 g / m 2 .

[0053] like Figure 3 As shown, one belt fabric preferably includes 40 to 60 steel cords 12 per 5 cm width (width of the steel cords 12 in a direction perpendicular to the longitudinal direction).

[0054] The steel cord 12 can be made of, for example, a so-called ST material (super tensile material) that can be expected to have a tensile strength of 3600 MPa or more, a so-called UT material (ultra tensile material) that can be expected to have a tensile strength of 4000 MPa or more, or a so-called MT material (super tensile material) that can be expected to have a tensile strength of 4500 MPa or more. Therefore, the carbon content of the steel cord 12 is preferably 0.79% to 1.00%. However, the steel cord 12 of the present invention is not limited to this embodiment. The tensile strength is measured using a known method.

[0055] The strength of a single steel cord 12 is preferably 350 to 540 N. Furthermore, the outer diameter of the steel cord 12 is preferably 0.22 to 0.55 mm. This ensures the reinforcement effect of the tread portion 2 by the belt layer 7, while also achieving a lighter tire and improving rolling resistance. The strength is measured using known methods, but methods according to JIS G3510 may also be used as needed.

[0056] The steel cord 12 of the present embodiment has a 1×1 structure (not shown) composed of, for example, a single filament. The outer diameter of the single filament is, for example, 0.30 to 0.50 mm. However, the present invention is not limited to this embodiment.

[0057] exist Figure 4 , a cross-sectional view of a steel cord 12 according to another embodiment is shown. Figure 4 As shown, the steel cord 12 may also be a 1×n structure consisting of a plurality (n) of wires 15. Figure 41×4 steel cord 12 is shown in FIG. The outer diameter D1 of each of the plurality of wires 15 is, for example, 0.15 to 0.30 mm. This improves the ride comfort and rolling resistance in a balanced manner.

[0058] As mentioned above, the tire according to one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above-described specific embodiment, but can be implemented in various modified forms.

[0059] Example

[0060] Based on the specifications in Table 1 and 2, we have produced Figure 1 A pneumatic tire with a size of 205 / 55R16, based on the basic structure shown, was produced as Comparative Examples 1-4. Tires were produced in which the product of T1·T2·La·tanδ1 fell outside the numerical range specified by the present invention. The tires of Comparative Examples 1-4 were essentially the same as the tires of the examples, except for the above-mentioned items. The rolling resistance and ride comfort performance of each test tire were tested. The common specifications and testing methods for each test tire are described below.

[0061] Mounting rim: 16×6.5

[0062] Tire internal pressure: 250kPa

[0063] Test vehicle: 2000cc displacement, FF vehicle

[0064] Rolling resistance performance

[0065] The rolling resistance of each test tire was measured using a rolling resistance tester. The results were indexed, with smaller values indicating lower rolling resistance.

[0066] Ride Comfort

[0067] The test tires were installed on all wheels of the test vehicle, and the driver's sensory evaluation of ride comfort was conducted while driving on the test track. The results were expressed as a score, with higher values indicating better ride comfort.

[0068] The test results are shown in Tables 1 and 2.

[0069] Table 1

[0070]

[0071] Table 2

[0072]

[0073] As shown in Tables 1 and 2, Comparative Examples 1 and 2 have a large rolling resistance performance of 8.1 to 8.6 points due to the large product of T1·T2·La·tanδ1. On the other hand, Comparative Examples 3 and 4 have a small product of T1·T2·La·tanδ1, so the rolling resistance performance is improved, but the ride comfort performance is 45 points. In contrast, it can be understood that Examples 1 to 20 can maintain a high ride comfort performance of 55 to 70 points and improve the rolling resistance performance to 6.2 to 7.3 points by setting the above-mentioned product T1·T2·La·tanδ1 to a specific range. In other words, it can be confirmed that the tire of the present invention improves the rolling resistance performance without compromising the ride comfort performance.

[0074] [Note]

[0075] The present invention includes the following aspects.

[0076] [Present invention 1]

[0077] A pneumatic tire having a tread portion, wherein the tread portion includes: a cord reinforcement layer comprising at least one belt cord formed by covering a plurality of steel cords with a rubber coating; and a tread rubber extending from the radially outer surface of the cord reinforcement layer to a contact patch of the tread portion, wherein the thickness T1 of the tread rubber at the tire equator, the average thickness T2 of the belt cord, the land ratio La of the contact patch, and the product T1·T2·La·tanδ1 of the loss tangent tanδ1 of the tread rubber at 30°C are 0.33 to 1.10, and the units of the thickness T1 and the thickness T2 are mm.

[0078] [Present invention 2]

[0079] In the pneumatic tire according to Invention 1, the thickness T2 is 0.66 to 0.98 mm.

[0080] [Present invention 3]

[0081] In the pneumatic tire according to Invention 1 or 2, a product T1·La·tanδ1 of the thickness T1, the land ratio La, and the loss tangent tanδ1 is in the range of 0.51 to 1.12.

[0082] [Present invention 4]

[0083] The pneumatic tire according to any one of Inventions 1 to 3 includes a radial carcass including a plurality of carcass cords arranged at an angle of 70° to 90° with respect to the tire equator, and is a pneumatic tire for a passenger car.

[0084] [Present invention 5]

[0085] In the pneumatic tire described in any one of the present inventions 1 to 4, the cord reinforcement layer includes: a belt layer on which two belt plies are stacked, and a band layer arranged on the radially outer side of the belt layer, and the band layer includes band cords oriented at an angle of less than 5° relative to the tire circumferential direction.

[0086] [Present invention 6]

[0087] In the pneumatic tire according to any one of Inventions 1 to 5, the outer diameter of the steel cord is 0.22 to 0.55 mm.

[0088] [Present invention 7]

[0089] In the pneumatic tire according to any one of Inventions 1 to 6, the steel cord has a 1×1 structure composed of a monofilament, and the outer diameter of the monofilament is 0.30 to 0.50 mm.

[0090] [Present invention 8]

[0091] In the pneumatic tire according to any one of Inventions 1 to 7, the steel cord has a 1×n structure composed of a plurality of n filaments, and the outer diameter of each of the plurality of filaments is 0.15 to 0.30 mm.

[0092] [Present invention 9]

[0093] In the pneumatic tire according to any one of Inventions 1 to 8, the strength of one steel cord is 350 to 540N.

[0094] [Present invention 10]

[0095] In the pneumatic tire according to any one of Inventions 1 to 9, the carbon content of the steel cord is 0.79% to 1.00%.

[0096] [Present invention 11]

[0097] In the pneumatic tire according to any one of Inventions 1 to 10, the belt fabric includes 40 to 60 steel cords per 5 cm width.

Claims

1. A pneumatic tire having a tread portion, characterized in that: The tread portion includes: a cord reinforcement layer comprising at least one belt fabric formed by covering a plurality of steel cords with a topping rubber; and a tread rubber formed from the tire radial direction outer surface of the cord reinforcement layer to the ground contact surface of the tread portion. The product of the thickness T1 of the tread rubber at the tire equator, the average thickness T2 of the belt cord, the land ratio La of the contact patch, and the loss tangent tanδ1 of the tread rubber at 30°C (T1·T2·La·tanδ1) is 0.33 to 1.

10. The units of the thickness T1 and the thickness T2 are mm.

2. The pneumatic tire according to claim 1, wherein: The thickness T2 is 0.66-0.98 mm.

3. The pneumatic tire according to claim 2, wherein: The product T1·La·tanδ1 of the thickness T1, the land ratio La, and the loss tangent tanδ1 is 0.51 to 1.

12.

4. The pneumatic tire according to claim 3, wherein: A radial carcass comprising a plurality of carcass cords arranged at an angle of 70° to 90° relative to the tire equator. The pneumatic tire is a pneumatic tire for passenger vehicles.

5. The pneumatic tire according to claim 4, wherein: The cord reinforcement layer includes a belt layer on which two belt cords are stacked, and a band layer arranged on the outer side of the belt layer in the tire radial direction. The belt layer includes belt cords oriented at an angle of 5° or less with respect to the tire circumferential direction.

6. The pneumatic tire according to any one of claims 1 to 5, characterized in that: The outer diameter of the steel cord is 0.22-0.55 mm.

7. The pneumatic tire according to any one of claims 1 to 5, characterized in that: The steel cord is a 1×1 structure consisting of monofilaments. The outer diameter of the monofilament is 0.30 to 0.50 mm.

8. The pneumatic tire according to any one of claims 1 to 5, characterized in that: The steel cord is a 1×n structure consisting of a plurality of n wires. The outer diameter of each of the plurality of wires is 0.15 to 0.30 mm.

9. The pneumatic tire according to any one of claims 1 to 5, characterized in that: The strength of one of the steel cords is 350-540N.

10. The pneumatic tire according to any one of claims 1 to 5, characterized in that The carbon content of the steel cord is 0.79% to 1.00%.

11. The pneumatic tire according to any one of claims 1 to 5, characterized in that: The belt fabric comprises 40 to 60 steel cords per 5 cm width.

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