pneumatic tires

Abstract

To provide a pneumatic tire enhanced in noise absorbing effect.SOLUTION: A pneumatic tire 1 includes a bead core 5, a carcass layer 6, a belt layer 7, a tread rubber 2G, an inner liner rubber layer 10, and a porous noise absorbing body 20 disposed on the tire inner cavity side of the inner liner rubber layer 10. In a normal condition, the tire axial length of the noise absorbing body 20 is smaller than a tire-radial distance H from a bead base line to the maximum width position on the inner cavity surface of a side wall portion 3; and, in a region in a tire axial direction in which the noise absorbing body 20 is provided, a tread portion 2 includes a plurality of rubber layers 30 layered in a tire radial direction with a thickness larger than the inner liner rubber layers 10 without including a cord. The further inside in the tire radial direction each rubber layer 30 is located, the smaller its thickness is.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, pneumatic tires in which a porous noise-damping body is disposed on the tire cavity surface have been known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-262920 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to improve the durability of the tire and the noise damper, it is effective to set the length of the noise damper in the axial direction of the tire to be short. However, if the length of the noise damper in the axial direction of the tire is reduced, the noise damping effect decreases.

[0005] The present invention was devised in consideration of the above-described circumstances, and its main object is to provide a pneumatic tire that can improve the durability of the tire and noise damper while maintaining sufficient noise damping effect. [Means for solving the problem]

[0006] The present invention is a pneumatic tire comprising: a pair of bead cores; a carcass layer having a carcass ply that straddles the pair of bead cores via a tread portion and a pair of sidewall portions; a belt layer disposed radially outward of the carcass layer; tread rubber disposed radially outward of the belt layer; an inner liner rubber disposed on the tire cavity side of the carcass layer; and a porous noise-damping body disposed in the tread portion on the tire cavity side of the inner liner rubber, wherein, when the tire is mounted on a normal rim and in a normal unloaded state in which the normal internal pressure is filled, the axial length of the noise-damping body is smaller than the radial distance from the bead base line to the maximum width position on the inner cavity surface of the sidewall portions, and the tread portion includes, in the axial region of the tire where the noise-damping body is provided, a plurality of rubber layers that do not include cords and are laminated in the radial direction of the tire to a thickness equal to or greater than the inner liner rubber, and the hardness of each rubber layer is smaller toward the radially inner side of the tire.

[0007] In the pneumatic tire according to the present invention, it is desirable that the axial length W1 of the noise damper is 50% or less of the tread ground contact width TW.

[0008] In the pneumatic tire according to the present invention, it is desirable that the length W1 of the noise damper in the tire axial direction is 40% or less of the tread ground contact width TW.

[0009] In the pneumatic tire according to the present invention, it is desirable that the hardness Ho of the rubber layer that is arranged radially outermost among the rubber layers is 105% or more of the hardness Hi of the rubber layer that is arranged radially innermost among the rubber layers.

[0010] In the pneumatic tire according to the present invention, the length W1 of the noise damper in the tire axial direction, the tread contact width TW, the hardness Ho of the rubber layer disposed on the outermost side in the tire radial direction among the rubber layers, and the hardness Hi of the rubber layer disposed on the innermost side in the tire radial direction among the rubber layers are (W1 / TW) / (Ho / Hi)≦0.5 It is desirable to satisfy the relationship:

[0011] In the pneumatic tire according to the present invention, the length W1, the tread contact width TW, the hardness Ho, and the hardness Hi are: (W1 / TW) / (Ho / Hi)≦0.4 It is desirable to satisfy the relationship:

[0012] In the pneumatic tire according to the present invention, the length W1, the tread contact width TW, the hardness Ho, and the hardness Hi are: (W1 / TW) / (Ho / Hi)≦0.3 It is desirable to satisfy the relationship:

[0013] In the pneumatic tire according to the present invention, it is desirable that the length W1 of the noise damper in the tire axial direction is 150 mm or less.

[0014] In the pneumatic tire according to the present invention, it is desirable that the length W1 be 100 mm or less.

[0015] In the pneumatic tire according to the present invention, it is desirable that the length H1 of the noise damper in the tire radial direction is 50 mm or less.

[0016] In the pneumatic tire according to the present invention, it is desirable that the length H1 be 30 mm or less.

[0017] In the pneumatic tire according to the present invention, the loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C of the rubber layer disposed outermost in the tire radial direction among the rubber layers are 0℃ tanδ / 30℃ tanδ≦3 It is desirable to satisfy the relationship:

[0018] In the pneumatic tire according to the present invention, the loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C are 0℃ tanδ / 30℃ tanδ≦2 It is desirable to satisfy the relationship:

[0019] In the pneumatic tire according to the present invention, it is desirable that each of the rubber layers contains a filler component and a plasticizer component, and that the ratio of the total amount of the filler component to the total amount of the plasticizer component in each of the rubber layers is smaller toward the inner side in the tire radial direction.

[0020] The pneumatic tire according to the present invention preferably further includes a sealant layer for preventing punctures on the tire cavity surface, and the hardness of the sealant layer is lower than the hardness of the inner liner rubber layer. [Effects of the Invention]

[0021] In the pneumatic tire of the present invention, the hardness of each rubber layer is smaller toward the inner side in the tire radial direction, so vibrations attenuate toward the inner side in the tire radial direction. Therefore, even if the noise damper has a small axial length, sufficient noise damping effect can be obtained. As a result, the axial length of the noise damper can be reduced while maintaining the noise damping effect, thereby improving the durability of the tire and the noise damper. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a meridional cross-sectional view showing an embodiment of a pneumatic tire of the present invention. [Figure 2] FIG. 2 is a meridian cross-sectional view showing a modified example of the pneumatic tire of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a meridian cross-sectional view including a tire rotation axis (not shown) of a pneumatic tire 1 of this embodiment in a normal state.

[0024] The "normal state" refers to a state in which the pneumatic tire 1 is mounted on a normal rim (see FIG. 2), inflated to a normal internal pressure, and no load is applied. Unless otherwise specified below, the dimensions of each part of the pneumatic tire 1 are values ​​measured in this normal state.

[0025] A "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which the pneumatic tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0026] The "normal internal pressure" is the air pressure determined for each tire by each standard in a standard system including the standard on which the pneumatic tire 1 is based, and is the "maximum air pressure" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS SAT VARIOUSCOLD INFLATION PRESSURE" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO. When the pneumatic tire 1 is for a passenger car, the normal internal pressure may be, for example, 180 kPa.

[0027] The pneumatic tire 1 of this embodiment is suitable for use as a radial tire for a small truck having a normal internal pressure of 350 to 600 kPa. The pneumatic tire 1 includes a pair of bead cores 5, a carcass layer 6, a belt layer 7, and a pair of bead apex rubbers 8.

[0028] The bead core 5 is disposed in a pair of bead portions 4. The bead core 5 is formed, for example, into a polygonal cross section by winding a steel bead wire (not shown) in multiple rows and multiple stages.

[0029] The carcass layer 6 has at least one carcass ply. The carcass ply is formed, for example, by covering an array of carcass cords with a topping rubber. The carcass cords are made of, for example, organic fibers such as polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber, or steel.

[0030] The carcass layer 6 of this embodiment has a carcass ply 6A and a carcass ply 6B. The carcass layer 6 includes topping rubber for the carcass plies 6A and 6B, and a sheet-like rubber in an embodiment in which a sheet-like rubber is provided between the carcass plies 6A and 6B. The carcass ply 6A is disposed across a pair of bead cores 5 via the tread portion 2 and a pair of sidewall portions 3. The carcass ply 6B is disposed on the outer side of the carcass ply 6A.

[0031] The belt layer 7 is disposed radially outward of the carcass layer 6. The belt layer 7 is composed of at least one belt ply, and in this embodiment, two belt plies 7A and 7B, one on the inner side and one on the outer side in the radial direction of the tire. The belt plies 7A and 7B are formed, for example, by covering an arrangement of belt cords with a topping rubber. The belt cords are disposed in the circumferential direction of the tire. That is, it is desirable that the belt cords are disposed at an angle of, for example, 15 to 45 degrees with respect to the tire equator C. It is desirable that the belt cords be made of highly elastic material such as steel cords.

[0032] The bead apex rubber 8 is disposed on the outer side in the tire radial direction of the bead core 5. The bead apex rubber 8 is formed in a substantially triangular cross section that tapers toward the outer side in the tire radial direction.

[0033] A band layer 9 may be disposed radially outward of the belt layer 7. The band layer 9 is composed of at least one band ply in which organic fiber cords are arranged at a small angle, for example, 10 degrees or less, with respect to the circumferential direction of the tire. The band ply may be either a jointless band formed by spirally winding a band cord or a ribbon-shaped strip ply, or a ply formed by splicing plies.

[0034] An inner liner rubber layer 10 is formed inside the carcass layer 6, that is, on the tire cavity surface. The inner liner rubber layer 10 is made of air-impermeable rubber and maintains internal pressure.

[0035] A tread rubber 2G is disposed radially outward of the belt layer 7 and the band layer 9. The tread rubber 2G of this embodiment includes a cap rubber layer 2GA disposed radially outward and a base rubber layer 2GB disposed radially inward of the cap rubber layer 2GA. The tread rubber 2G may be formed of a single rubber layer.

[0036] The pneumatic tire 1 of this embodiment includes a noise damper 20 on the radially inner side of the tread portion 2. The noise damper 20 is disposed on the tire cavity side of the inner liner rubber layer 10.

[0037] The sound damper 20 is made of, for example, a porous sponge material. The sponge material is a spongy porous structure, and includes, for example, a sponge itself with open cells formed by foaming rubber or synthetic resin, as well as a web-like structure made by intertwining animal fibers, plant fibers, synthetic fibers, etc. Furthermore, the term "porous structure" includes not only those with open cells but also those with closed cells. The sound damper 20 in this example uses an open-cell sponge material made of polyurethane. This sound damper 20 has a lower hardness than the rubber layer 30 and the sealant layer 40, which will be described later.

[0038] The sponge material described above converts the vibration energy of the vibrating air in the porous portions on the surface or inside into heat energy and consumes it, thereby reducing sound (cavity resonance energy) and reducing the running noise of the pneumatic tire 1. In addition, since the sponge material is easily deformed, such as by shrinking and bending, it does not substantially affect the deformation of the tire during running. This prevents a deterioration in steering stability. Moreover, since the sponge material has an extremely low specific gravity, it prevents a deterioration in the weight balance of the tire.

[0039] As the sponge material, synthetic resin sponges such as ether-based polyurethane sponge, ester-based polyurethane sponge, and polyethylene sponge, and rubber sponges such as chloroprene rubber sponge (CR sponge), ethylene propylene rubber sponge (EDPM sponge), and nitrile rubber sponge (NBR sponge) can be suitably used, and polyurethane-based or polyethylene-based sponges including ether-based polyurethane sponge are particularly preferred from the viewpoints of sound-damping properties, light weight, foam adjustability, durability, etc.

[0040] The noise damper 20 is in the form of a long strip having a bottom surface fixed to the inner cavity surface of the tread portion 2, and extends in the circumferential direction of the tire. In this case, the outer ends in the circumferential direction may be butted against each other to form a substantially annular shape, or the outer ends may be spaced apart in the circumferential direction.

[0041] The noise damper 20 has substantially the same cross-sectional shape at each circumferential position except for the outer end portion. This cross-sectional shape is preferably flat and oblong, with its height being small relative to its width in the axial direction of the tire, in order to prevent collapse or deformation during running.

[0042] In a normal pneumatic tire 1, the axial length W1 of the noise damper 20 (ie, the width of the noise damper 20) is smaller than the radial distance H from the bead base line to the maximum width position on the cavity surface of the sidewall portion.

[0043] The tread portion 2 includes a plurality of rubber layers 30 laminated in the tire radial direction in an axial region where the noise damper 20 is provided. Here, the term "rubber layer" refers to a rubber layer that does not include cords and is at least as thick as the inner liner rubber layer 10. The tread rubber 2G (cap rubber layer 2GA and base rubber layer 2GB) and the inner liner rubber layer 10 are included in the rubber layer 30. The rubber layer 30 may also include an intermediate rubber layer between the carcass plies 6A and 6B, an intermediate rubber layer between the belt plies 7A and 7B, an intermediate rubber layer between the carcass layer 6 and the belt layer 7, an intermediate rubber layer between the belt layer 7 and the band layer 9, and an intermediate rubber layer between the carcass layer 6 and the inner liner rubber layer 10.

[0044] In the pneumatic tire 1, the hardness of each rubber layer 30 decreases toward the inner side in the tire radial direction. For example, the hardness of the base rubber layer 2GB is lower than that of the cap rubber layer 2GA. The hardness of the inner liner rubber layer 10 is also lower than that of the base rubber layer 2GB. With this configuration, vibrations input from the tread surface of the tread portion 2 are attenuated toward the inner side in the tire radial direction. Therefore, even if the noise damper 20 has a small length in the tire axial direction, a sufficient noise damping effect can be obtained.

[0045] The noise damper 20 is attached to the inner liner rubber layer 10 using, for example, an adhesive. However, if there is a large difference in hardness between the porous noise damper 20 and the inner liner rubber layer 10, stress may concentrate at the interface between them during long-term use of the pneumatic tire 1, which could cause separation of the noise damper 20. In this embodiment, the hardness of each rubber layer 30 is smaller the closer to the inside in the tire radial direction, so the difference in hardness between the noise damper 20 and the inner liner rubber layer 10 is small, and the peeling resistance of the noise damper 20 can be improved.

[0046] The tire axial length W1 of the noise damper 20 is preferably 50% or less of the tread contact width TW. The tread contact width TW is the distance in the tire axial direction between the tread contact edges TE1, TE2 when a tire in a normal state is placed on the ground flat with a normal load and a camber angle of 0°. Such a noise damper 20 prevents the noise damper 20 from peeling off from the inner surface of the tread portion 2, making it easy to improve the durability of the pneumatic tire 1 and the noise damper 20. From the above perspective, the tire axial length W1 of the noise damper 20 is more preferably 40% or less of the tread contact width TW.

[0047] The hardness Ho of the rubber layer 30 (in this embodiment, the cap rubber layer 2GA) disposed on the outermost side in the tire radial direction among the rubber layers 30 is desirably 105% or more of the hardness Hi of the rubber layer 30 (in this embodiment, the inner liner rubber layer 10) disposed on the innermost side in the tire radial direction among the rubber layers 30. A rubber layer 30 with such hardness suppresses separation of the noise damper 20 from the inner cavity surface of the tread portion 2.

[0048] The hardness Ho of the rubber layer 30 disposed on the outermost side in the tire radial direction among the rubber layers 30 is preferably less than 200% of the hardness Hi of the rubber layer 30 disposed on the innermost side in the tire radial direction among the rubber layers 30. A rubber layer 30 with such hardness can provide an even greater noise-damping effect.

[0049] The hardness of the rubber layer 30 can be measured, for example, using a durometer with a needle diameter of 0.5 mm or less. Using such a durometer makes it possible to evaluate the flexibility that can follow road surface irregularities at a microscopic level, and obtain noise-damping effects during actual driving.

[0050] The tire axial length W1 of the noise damper 20, the tread contact width TW, and the hardness Ho and Hi of the rubber layer are (W1 / TW) / (Ho / Hi)≦0.5 In such a pneumatic tire 1, the durability of the pneumatic tire 1 and the noise damper 20 can be improved while maintaining a sufficient noise damping effect.

[0051] Furthermore, a more desirable relationship between the tire axial length W1 of the noise damper 20, the tread contact width TW, and the hardness Ho and Hi of the rubber layer is as follows: (W1 / TW) / (Ho / Hi)≦0.4 is.

[0052] A more desirable relationship between the tire axial length W1 of the noise damper 20, the tread contact width TW, and the hardness Ho and Hi of the rubber layer is as follows: (W1 / TW) / (Ho / Hi)≦0.3 is.

[0053] The length W1 of the noise damper 20 in the tire axial direction is desirably 70% or less of the length W2 of the belt layer 7 in the tire axial direction. Such a noise damper 20 suppresses separation of the noise damper 20 from the inner cavity surface of the tread portion 2, and the durability of the pneumatic tire 1 and the noise damper 20 can be easily improved.

[0054] The axial length W1 of the noise damper 20 is desirably 150 mm or less. Such a noise damper 20 prevents the noise damper 20 from peeling off from the inner cavity surface of the tread portion 2, and the durability of the pneumatic tire 1 and the noise damper 20 can be easily improved.

[0055] From the above viewpoint, the length W1 of the noise damper 20 in the tire axial direction is more preferably 120 mm or less, and even more preferably 100 mm or less.

[0056] The tire radial direction length H1 of the noise damper 20 is desirably 50 mm or less. Such a noise damper 20 prevents the noise damper 20 from peeling off from the inner cavity surface of the tread portion 2, and the durability of the pneumatic tire 1 and the noise damper 20 can be easily improved.

[0057] From the above viewpoint, the tire radial direction length H1 of the noise damper 20 is more preferably 30 mm or less.

[0058] The loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C of the rubber layer 30 arranged on the outermost side in the tire radial direction are 0℃ tanδ / 30℃ tanδ≦3 It is desirable to satisfy the following relationship: In such a pneumatic tire 1, the temperature dependency of the noise damping effect is small, and a good noise damping effect can be obtained over a wide temperature range.

[0059] From the above viewpoint, the more desirable loss tangent tanδ at 0° C. and the more desirable loss tangent tanδ at 30° C. 0℃ tanδ / 30℃ tanδ≦2 is.

[0060] The loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C are values ​​measured in accordance with the provisions of JIS-K6394 using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions of each measurement temperature (0°C or 30°C), a frequency of 10 Hz, an initial elongation strain of 10%, and a dynamic strain amplitude of ±2%.

[0061] Each rubber layer 30 contains a filler component. Examples of the filler component include carbon black and silica. The filler component is measured as an ash content by subjecting the vulcanized rubber to thermogravimetric analysis (TGA) in accordance with JIS K 6226-1:2003, for example.

[0062] In the pneumatic tire 1, it is desirable that the total amount of filler components in each rubber layer 30 be smaller as it approaches the inner side in the tire radial direction. This allows vibration to be attenuated toward the inner side in the tire radial direction. Therefore, even if the noise damper 20 has a small length in the tire axial direction, a sufficient noise damping effect can be obtained.

[0063] Each rubber layer 30 contains a plasticizer component. Examples of the plasticizer component include oil. The plasticizer component is measured, for example, as an acetone extractable component in accordance with JIS K 6229:2015.

[0064] In the pneumatic tire 1, it is desirable that the total amount of plasticizer components in each rubber layer 30 be greater toward the inner side in the tire radial direction. This allows vibration to be attenuated toward the inner side in the tire radial direction. Therefore, even if the noise damper 20 has a small length in the tire axial direction, a sufficient noise damping effect can be obtained.

[0065] It is desirable that the ratio of the total amount of filler components to the total amount of plasticizer components in each rubber layer be smaller as it gets closer to the inside in the tire radial direction. This allows vibration to be attenuated toward the inside in the tire radial direction. Therefore, even if the noise damper 20 has a short length in the tire axial direction, a sufficient noise damping effect can be obtained.

[0066] Fig. 2 shows a pneumatic tire 1A that is a modified example of the pneumatic tire 1 in Fig. 1. The configuration of the pneumatic tire 1 described above can be adopted for parts of the pneumatic tire 1A that are not described below.

[0067] The pneumatic tire 1A further includes a sealant layer 40 for preventing punctures on the tire cavity surface. The sealant layer 40 is formed on the cavity side of the inner liner rubber layer 10. The noise damper 20 is formed on the cavity side of the sealant layer 40.

[0068] Although there are no particular restrictions on the sealant used to form the sealant layer 40, the sealant in this example contains a rubber component, a liquid polymer, and a crosslinking agent.

[0069] As the rubber component, butyl-based rubbers such as butyl rubber and halogenated butyl rubber are used, and as the rubber component, butyl-based rubbers and diene-based rubbers can be used in combination.

[0070] Examples of liquid polymers include liquid polybutene, liquid polyisobutene, liquid polyisoprene, liquid polybutadiene, liquid poly-α-olefin, liquid isobutylene, liquid ethylene-α-olefin copolymer, liquid ethylene-propylene copolymer, and liquid ethylene-butylene copolymer.

[0071] Although well-known compounds can be used as crosslinking agents, organic peroxides are preferred. In organic peroxide crosslinking systems, the use of butyl rubber or liquid polymers improves adhesion, sealing properties, fluidity, and processability.

[0072] Examples of organic peroxides (crosslinking agents) include acyl peroxides such as benzoyl peroxide, dibenzoyl peroxide, and p-chlorobenzoyl peroxide, peroxyesters such as 1-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butyl peroxyphthalate, ketone peroxides such as methyl ethyl ketone peroxide, alkyl peroxides such as di-t-butyl peroxybenzoate and 1,3-bis(1-butylperoxyisopropyl)benzene, hydroperoxides such as t-butyl hydroperoxide, dicumyl peroxide, and t-butylcumyl peroxide. Among these, from the viewpoints of adhesion and fluidity, acyl peroxides are preferred, and dibenzoyl peroxide is particularly preferred.

[0073] A cross-linking aid (vulcanization accelerator), an inorganic filler, a plasticizer, etc. may be added to the sealant material as appropriate.

[0074] The crosslinking aid (vulcanization accelerator) can be selected from the group consisting of sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamine-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, xanthogenic acid-based, quinonedioxime compounds (quinoid compounds), and the like.

[0075] The inorganic filler can be selected from the group consisting of carbon black, silica, calcium carbonate, calcium silicate, magnesium oxide, aluminum oxide, barium sulfate, talc, mica, and the like.

[0076] The plasticizer can be selected from the group consisting of aromatic process oil, naphthenic process oil, paraffinic process oil, and the like.

[0077] It is desirable that the hardness of the sealant layer 40 be lower than that of the inner liner rubber layer 10. This allows vibration to be attenuated radially inward of the tire. Therefore, even if the noise damper 20 has a small axial length, a sufficient noise damping effect can be obtained.

[0078] The pneumatic tires 1, 1A of the present invention are suitable for passenger cars, and are particularly suitable for sizes having a tire width of 155 or more. Among these, a tire width of 205 or more is preferred, a tire width of 225 or more is more preferred, and a tire width of 265 or more is even more preferred.

[0079] Although the pneumatic tire 1 of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects.

[0080] A 195 / 65R15 size pneumatic tire with the basic structure shown in Figure 1 was prototyped based on the specifications in Table 1, and its noise performance and durability were evaluated. The hardness of the rubber layer was measured using a durometer with a needle diameter of 0.5 mm or less, by pressing the needle in a direction perpendicular to the meridian cross section of the tire (the same applies below). Specifications of each sample tire that are not listed in Table 1 are common to all samples. The test method is as follows:

[0081] <Noise performance> Noise was measured when a test vehicle equipped with the sample tires was traveling at a speed of 60 km / h. The results are expressed as an index, with Comparative Example 1 being set at 100, with a higher index indicating better noise performance.

[0082] <Durability> Each test tire was run 30,000 km using a drum testing machine under conditions of an internal pressure of 230 kPa, a load of 4.24 kN, and a speed of 80 km / h, and the degree of damage to the noise damper after the run was confirmed. The results are expressed as an index with Comparative Example 1 being 100, and a higher value indicates better durability.

[0083] [Table 1]

[0084] The compounding ratios (PHR) of the cap rubber, base rubber, and inner liner rubber used in this Example 1 and the like, and their hardnesses are as shown in Table 2. [Table 2]

[0085] The details of each formulation are as follows: Natural rubber (NR): RSS#1 Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd. Styrene-butadiene rubber (SBR): HPR850 manufactured by JSR Corporation Butyl rubber: Regular butyl rubber 268 manufactured by Exxon Chemical Co., Ltd. Carbon: Show Black N550 manufactured by Cabot Japan Co., Ltd. Wax: Sunnock Wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 6C: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Antioxidant RD: Nocrac 224 manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Process oil: Mineral oil PW-380 manufactured by Idemitsu Kosan Co., Ltd. Stearic acid: Tsubaki (made by Nippon Oil & Fats Co., Ltd.) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. 5% sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator: Noccela NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0086] As is clear from Table 1, it was confirmed that the pneumatic tires of the examples had a well-balanced improvement in noise performance and durability performance compared to the comparative examples.

[0087] Pneumatic tires of the above sizes having the basic structure shown in Figure 1 were prototyped based on the specifications in Table 3, and their noise performance and durability were evaluated. Specifications of each test tire that are not listed in Table 3 are common to all tires. The test method is as follows.

[0088] <Noise performance> Noise was measured in the same manner as above on a test vehicle equipped with the test tire. The results are expressed as an index with Example 3 being 100, with a larger index indicating better noise performance.

[0089] <Durability> Damage to the noise damper after driving was confirmed in the same manner as above. The results are expressed as an index with Example 3 being 100, with a larger index indicating better durability.

[0090] [Table 3]

[0091] Pneumatic tires of the above sizes having the basic structure shown in Figure 1 were prototyped based on the specifications in Table 4, and their noise performance was evaluated. Specifications of each test tire that are not listed in Table 4 are common to all tires. The test method is as follows.

[0092] <Noise performance> Noise was measured in the same manner as above on a test vehicle equipped with the test tire. The results are expressed as an index with Example 8 being 100, with a larger index indicating better noise performance.

[0093] <Durability> Damage to the noise damper after driving was confirmed in the same manner as above. The results are expressed as an index with Example 8 being 100, with a larger index indicating better durability.

[0094] [Table 4]

[0095] Pneumatic tires of the above sizes having the basic structure shown in Figure 1 were prototyped based on the specifications in Table 5, and their noise performance was evaluated. Specifications of each test tire that are not listed in Table 5 are common to all tires. The test method is as follows.

[0096] <Noise performance> Noise was measured in the same manner as above on a test vehicle equipped with the test tire. The results are expressed as an index with Example 13 being 100, with a larger index indicating better noise performance.

[0097] <Durability> Damage to the noise damper after driving was confirmed in the same manner as above. The results are expressed as an index with Example 13 being 100, with a larger index indicating better durability.

[0098] [Table 5]

[0099] Pneumatic tires of the above sizes having the basic structure shown in Figure 1 were prototyped based on the specifications in Table 6, and their noise performance was evaluated. Specifications of each test tire that are not listed in Table 6 are common to all tires. The test method is as follows.

[0100] <Noise performance> Noise was measured in the same manner as above on a test vehicle equipped with the test tire. The results are expressed as an index with Example 18 being 100, with a larger index indicating better noise performance.

[0101] <Durability> Damage to the noise damper after driving was confirmed in the same manner as above. The results are expressed as an index with Example 18 being 100, with a larger index indicating better durability.

[0102] [Table 6]

[0103] Pneumatic tires of the above sizes having the basic structure shown in Figure 1 were prototyped based on the specifications in Table 7, and their noise performance was evaluated. Specifications of each test tire that are not listed in Table 7 are common to all tires. The test method is as follows.

[0104] <Noise performance> Noise was measured in the same manner as above on a test vehicle equipped with the test tire. The results are expressed as an index with Example 22 being 100, with a larger index indicating better noise performance.

[0105] <Durability> Damage to the noise damper after driving was confirmed in the same manner as above. The results are expressed as an index with Example 22 being 100, with a larger index indicating better durability.

[0106] [Table 7]

[0107] Pneumatic tires of the above sizes having the basic structure shown in Figure 1 were prototyped based on the specifications in Table 8, and their noise performance was evaluated. Specifications of each test tire that are not listed in Table 8 are common to all tires. The test method is as follows.

[0108] <Noise performance> Noise was measured on a test vehicle fitted with the test tires at outside temperatures of 0°C and 30°C in the same manner as above. The results were expressed as an index, with noise performance at 30°C being set at 100, with a smaller index indicating better temperature dependency of noise performance.

[0109] [Table 8] [Explanation of symbols]

[0110] 1 pneumatic tire 1A Pneumatic tire 2 Tread section 2G tread rubber 2GA Cap Rubber Layer 2GB base rubber layer 3 Sidewall 5 bead core 6 carcass layers 6A carcass ply 6B carcass ply 7 Belt Layer 10 Inner liner rubber layer 20 Sound damping body 30 rubber layer 40 Sealant Layer H Radial distance of tire TW tread width W Maximum width

Claims

1. A pneumatic tire, a pair of bead cores; a carcass layer having a carcass ply extending across the pair of bead cores via a tread portion and a pair of sidewall portions; a belt layer disposed radially outward of the carcass layer; a tread rubber disposed on the outer side of the belt layer in the tire radial direction; an inner liner rubber layer disposed on the tire cavity side of the carcass layer; a porous noise-damping body disposed in the tread portion on the tire cavity side of the inner liner rubber layer, When the tire is mounted on a regular rim and inflated to a regular internal pressure under no load, the axial length of the noise damper is shorter than the radial distance from the bead base line to the maximum width position on the inner cavity surface of the sidewall portion, the tread portion includes, in an axial region of the tire where the noise damper is provided, a plurality of rubber layers that are laminated in the radial direction of the tire to a thickness equal to or greater than that of the inner liner rubber layer, without including cords; The rubber layers include a cap rubber layer disposed on the outermost side in the tire radial direction among the tread rubber layers, a base rubber layer disposed on the inner side in the tire radial direction of the cap rubber layer, and the inner liner rubber layer, the hardness of the base rubber layer is lower than the hardness of the cap rubber layer, and the hardness of the inner liner rubber layer is lower than the hardness of the base rubber layer; Pneumatic tires.

2. The pneumatic tire according to claim 1 , wherein the axial length W1 of the noise damper is equal to or less than 50% of the tread contact width TW.

3. The pneumatic tire according to claim 2 , wherein the axial length W1 of the noise damper is equal to or less than 40% of the tread contact width TW.

4. 4. The pneumatic tire according to claim 1, wherein a hardness Ho of the rubber layer disposed at an outermost position in the tire radial direction among the rubber layers is 105% or more of a hardness Hi of the rubber layer disposed at an innermost position in the tire radial direction among the rubber layers.

5. The length W1 of the noise damper in the tire axial direction, the tread contact width TW, the hardness Ho of the rubber layer disposed on the outermost side in the tire radial direction among the rubber layers, and the hardness Hi of the rubber layer disposed on the innermost side in the tire radial direction among the rubber layers are (W1 / TW) / (Ho / Hi)≦0.5 The pneumatic tire according to claim 1 , wherein the following relationship is satisfied:

6. The length W1, the tread width TW, the hardness Ho, and the hardness Hi are (W1 / TW) / (Ho / Hi)≦0.4 The pneumatic tire according to claim 5 , which satisfies the relationship:

7. The length W1, the tread width TW, the hardness Ho, and the hardness Hi are (W1 / TW) / (Ho / Hi)≦0.3 The pneumatic tire according to claim 6 , which satisfies the relationship:

8. 8. The pneumatic tire according to claim 1, wherein the axial length W1 of the noise damper is 150 mm or less.

9. The pneumatic tire according to claim 8, wherein the length W1 is 100 mm or less.

10. 10. The pneumatic tire according to claim 1, wherein a length H1 of the noise damper in the tire radial direction is 50 mm or less.

11. The pneumatic tire according to claim 10, wherein the length H1 is 30 mm or less.

12. The loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C of the rubber layer disposed outermost in the tire radial direction among the rubber layers are 0℃ tanδ / 30℃ tanδ≦3 The pneumatic tire according to claim 1 , wherein the following relationship is satisfied:

13. The loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C are 0℃ tanδ / 30℃ tanδ≦2 The pneumatic tire according to claim 12 , which satisfies the relationship:

14. Each of the rubber layers contains a filler component and a plasticizer component, The pneumatic tire according to claim 1 , wherein a ratio of the total amount of the filler components to the total amount of the plasticizer components in each of the rubber layers decreases toward the inner side in the tire radial direction.

15. 15. The pneumatic tire according to claim 1, further comprising a sealant layer for preventing punctures on the tire cavity surface, wherein the hardness of the sealant layer is lower than the hardness of the inner liner rubber layer.

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