pneumatic tires

Abstract

The pneumatic tire (1) has a noise damper (20) made of a porous material fixed to the tire cavity surface (17) of the tread portion (2). The noise damper (20) has a ratio H1 / H2 of 2.0 or less, where H1 is a first hardness at 25% compression load measured in accordance with JIS K6400-2 at an atmosphere of 23°C and H2 is a second hardness at 25% compression load measured in accordance with JIS K6400-2 at an atmosphere of 50°C.

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire having a noise damper disposed on the tire cavity surface. [Background technology]

[0002] Patent Document 1 below proposes a pneumatic tire in which a noise damper made of a porous material is fixed to the tire cavity surface. The noise damper absorbs cavity resonance noise in the tire cavity and reduces the running noise of the pneumatic tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4960626 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the sound-damping body has a problem in that its hardness decreases at high temperatures, and repeated deformation caused by the running of the tire can cause internal destruction, reducing its sound-absorbing effect.

[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 maintain the sound absorption performance of a noise damper by improving the durability of the noise damper in high-temperature environments. [Means for solving the problem]

[0006] The pneumatic tire of the present invention has a noise damper made of a porous material fixed to the tire cavity surface of the tread portion, and the noise damper has a ratio H1 / H2 of 2.0 or less between a first hardness H1 measured in an atmosphere at 23°C in accordance with JIS K6400-2 Method D and a second hardness H2 measured in an atmosphere at 50°C in accordance with JIS K6400-2 Method D.

[0007] In the pneumatic tire according to the present invention, it is desirable that the ratio H1 / H2 is 1.7 or less.

[0008] In the pneumatic tire according to the present invention, it is desirable that the ratio H1 / H2 is 1.4 or less.

[0009] In the pneumatic tire according to the present invention, it is desirable that the first hardness H1 is 100N or less.

[0010] In the pneumatic tire according to the present invention, it is desirable that the first hardness H1 is 60N or less.

[0011] In the pneumatic tire according to the present invention, it is desirable that the second hardness H2 is 35N or more.

[0012] In the pneumatic tire according to the present invention, the noise damper has an air permeability of 60 cm as measured in accordance with JIS K6400-7. 3 / cm 2 It is desirable that the frequency be less than / s.

[0013] In the pneumatic tire according to the present invention, the noise damper has an air permeability of 30 cm 3 / cm 2 It is desirable that the frequency be less than / s.

[0014] In the pneumatic tire according to the present invention, the noise damper has an air permeability of 10 cm 3 / cm 2 It is desirable that the frequency be less than / s.

[0015] In the pneumatic tire according to the present invention, it is preferable that the noise damper has closed-cell cells, and the number of the cells is 55 cells / 25 mm or less.

[0016] In the pneumatic tire according to the present invention, it is desirable that the noise damper have a tensile strength of 160 kPa or less when measured in an atmosphere of 23° C. in accordance with JIS K6400-5.

[0017] In the pneumatic tire according to the present invention, it is desirable that the noise damper has a tensile strength of 130 kPa or less.

[0018] In the pneumatic tire according to the present invention, it is desirable that the noise damper has an elongation of 140% or more when measured in an atmosphere of 23° C. in accordance with JIS K6400-5.

[0019] In the pneumatic tire according to the present invention, it is desirable that the elongation of the noise damper is 170% or more.

[0020] In the pneumatic tire according to the present invention, it is preferable that the tread portion is made of a rubber composition containing natural rubber, butadiene rubber, and styrene-butadiene rubber. [Effects of the Invention]

[0021] The pneumatic tire of the present invention has a noise damper fixed to the tire cavity surface of the tread portion. The noise damper is made of a porous material and absorbs cavity resonance noise in the tire cavity, thereby reducing the running noise of the pneumatic tire.

[0022] Furthermore, the noise damper has a ratio H1 / H2 of 2.0 or less, where H1 is the first hardness in a 23°C atmosphere and H2 is the second hardness in a 50°C atmosphere. This noise damper maintains sufficient hardness even in high-temperature environments, thereby suppressing internal damage caused by repeated deformation as the tire travels. This increases the durability of the noise damper, making it easier to maintain the sound-absorbing performance of the noise damper. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view showing an embodiment of a pneumatic tire of the present invention. [Figure 2] FIG. 1 is a cross-sectional view illustrating a state in which a tire with a puncture has been repaired. [Figure 3]FIG. 3 is a cross-sectional view showing another embodiment of the pneumatic tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of the present invention will now be described with reference to the drawings. 1 is a tire meridian cross-sectional view including the tire rotation axis of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of this embodiment in a normal state. Here, the normal state refers to a state in which the tire is mounted on a normal rim RM, inflated to a normal internal pressure, and no load is applied. Unless otherwise specified below, the dimensions of each part of tire 1 are values ​​measured in this normal state.

[0025] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0026] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system including the standard on which the tire is based. In the case of JATMA, it is "maximum air pressure", and in the case of TRA, it is "standard pressure". The maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" or "INFLATION PRESSURE" for ETRTO. If the tire is for passenger cars, it is set at a uniform 200kPa, taking into account the actual frequency of use, etc.

[0027] 1, a tire 1 of this embodiment is suitably used as, for example, a radial tire for a passenger car. The tire 1 has a carcass 6, a belt layer 7, a band layer 9, an inner liner 10, and a noise damper 20.

[0028] The carcass 6 extends across a pair of bead portions 4, 4. The carcass 6 is composed of at least one carcass ply 6A, one carcass ply in this embodiment. The carcass ply 6A includes a main portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a turned-up portion 6b that is continuous with the main portion 6a and is turned back around the bead core 5 from the axially inner side to the outer side. A bead apex rubber 8 that extends tapered from the bead core 5 toward the radially outer side of the tire is disposed between the main portion 6a and the turned-up portion 6b of the carcass ply 6A.

[0029] The carcass ply 6A is provided with carcass cords (not shown) arranged at an angle of, for example, 80 to 90 degrees with respect to the tire equator C. As the carcass cords, for example, organic fiber cords such as aromatic polyamide and rayon are used.

[0030] On the outside of the carcass 6, there are arranged tread rubber 11 arranged in the tread portion 2, sidewall rubber 12 forming the outer surface of the sidewall portion 3, and bead rubber 13 forming the outer surface of the bead portion 4. On the outer surface of the tread rubber 11, there are provided grooves 14 recessed radially inward from the contact surface.

[0031] The belt layer 7 is disposed radially outward of the carcass 6 and within the tread portion 2. The belt layer 7 of this embodiment is composed of two belt plies 7A and 7B, one inner and one outer in the radial direction of the tire. The belt plies 7A and 7B have belt cords (not shown) arranged at an angle of, for example, 10 to 35 degrees relative to the circumferential direction of the tire. These belt plies 7A and 7B are overlapped with the belt cords crossing each other. For example, steel, aramid, rayon, or the like can be suitably used as the belt cords.

[0032] The band layer 9 is disposed radially outward of the belt layer 7. The band layer 9 of this embodiment includes a band ply 9A in which a band cord (not shown) is spirally wound at an angle of 10 degrees or less, preferably 5 degrees or less, relative to the tire circumferential direction. As the band cord, for example, an organic fiber cord such as a nylon cord can be used. The band layer 9 is provided as needed, and may be omitted depending on the application of the tire 1, etc.

[0033] The inner liner 10 is disposed radially inward of the carcass 6. The inner liner 10 forms a tire cavity surface 16. The inner liner 10 is made of, for example, air-impermeable butyl rubber.

[0034] The noise damper 20 is made of a porous material having a large number of pores (cells) on its surface. This noise damper 20 is fixed to the tire cavity surface 16 of the tread portion 2. The noise damper 20 of this embodiment is formed in the shape of a long strip having a bottom surface that is fixed to the tire cavity surface 16, and extends in the tire circumferential direction. The noise damper 20 is formed in a substantially annular shape by a pair of outer end portions (not shown) arranged on both sides in the tire circumferential direction butting against each other. The pair of outer end portions may be spaced apart in the tire circumferential direction.

[0035] An example of a porous material is a porous sponge material. The sponge material has a spongy porous structure. The sponge material includes not only a so-called sponge made from foamed rubber or synthetic resin, but also materials made by intertwining and connecting animal fibers, plant fibers, synthetic fibers, etc.

[0036] 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.

[0037] The noise damper 20 absorbs the air in the tire cavity 17 through its surface and internal pores (cells), converting the vibrational energy of the vibrating air into thermal energy for consumption. This allows the noise damper 20 to reduce sound (cavity resonance energy) and absorb cavity resonance noise in the tire cavity (for example, running noise around 250 Hz). Furthermore, the porous material (for example, sponge material) that makes up the noise damper 20 is easily deformed, such as contracted or bent. Therefore, the noise damper 20 can flexibly deform in accordance with the deformation of the inner liner 10 during driving.

[0038] The noise damper 20 of this embodiment has substantially the same cross-sectional shape at each position around the tire circumferential direction except for the outer end (not shown). Furthermore, the cross-sectional shape is formed into a flat, horizontally elongated shape in which the height in the tire radial direction is smaller than the width in the tire axial direction in order to prevent collapse or deformation during running. Furthermore, a recessed groove 21 extending continuously in the circumferential direction is provided on the inner side of the noise damper 20 in the tire radial direction. This recessed groove 21 increases the surface area of ​​the noise damper 20, enabling it to absorb more resonance energy and improving heat dissipation to suppress temperature rise of the sponge material.

[0039] The hardness of the porous material used in the noise damper 20 is temperature dependent, and typically decreases as the temperature rises. In this embodiment, a porous material with low temperature dependency of hardness is used so that sufficient hardness can be maintained even when the tire 1 is in a heated state.

[0040] That is, in the sound damper 20 of this embodiment, the ratio H1 / H2 of the first hardness H1 in an atmosphere at 23° C. to the second hardness H2 in an atmosphere at 50° C. is 2.0 or less. Here, the first hardness H1 and the second hardness H2 are measured after leaving a test piece of the porous material in an atmosphere at each temperature for 10 minutes and then compressing the test piece by a constant 25% for 20 seconds using a testing machine (for example, a UFT urethane testing machine (UFT-5KN) manufactured by Japan Measurement Systems Co., Ltd.) in accordance with Method D of Section 6 "Hardness test" of JIS K6400-2:2012.

[0041] Such noise damper 20 maintains sufficient hardness even when the tire heats up due to running, thereby suppressing internal damage caused by repeated deformation associated with running of tire 1. Therefore, the durability of noise damper 20 in high-temperature environments is improved, and the sound absorption performance of noise damper 20 can be easily maintained.

[0042] As described above, the present invention is characterized in that a noise damper is provided in the tire cavity, in which the ratio H1 / H2 of the first hardness H1 in an atmosphere at 23°C to the second hardness H2 in an atmosphere at 50°C is 2.0 or less. Here, the ratio H1 / H2 indicates that the hardness of the noise damper is less dependent on temperature. Techniques for reducing the temperature dependency of the hardness of a noise damper are themselves publicly known, and by referring to these, the noise damper according to the present invention can be easily realized.

[0043] For example, Patent No. 5833155 indicates that in a polyol composition containing polyester triol, a sound damper with low temperature dependency of hardness can be realized by setting the polyester triol content based on the weight of the polyol composition to 15 to 30 wt % and the ester group concentration of the polyol composition to 0.1 to 5.0 mmol / g.

[0044] Also, for example, JP 2013-119620 A discloses a polyol having a hydroxyl value of 20 to 28 mg KOH / g, a molecular weight of 6000 to 8500, a functionality of 3, and an ethylene oxide content of 10 to 25% by weight, a polyol having a hydroxyl value of 200 to 280 mg KOH / g, a molecular weight of 600 to 850, a functionality of 2, and an ethylene oxide content of 0% by weight, and a polyol having a hydroxyl value of 50 to 140 mg KOH / g, a molecular weight of 800 to 2200, a functionality of 2, and an ethylene oxide content of 0% by weight. This shows that by blending a polyol with an oxide content of 0% by weight, a polyol with a hydroxyl value of 40-80 mg KOH / g, a molecular weight of 2000-4000, a functionality of 3, and an ethylene oxide content of 50-90% by weight, and a polyol with a hydroxyl value of 40-80 mg KOH / g, a molecular weight of 2000-4000, a functionality of 3, and 100 mol% terminal primary OH in specified blending amounts, it is possible to create a sound damper with low temperature dependency of hardness.

[0045] Furthermore, for example, Japanese Patent No. 5258215 discloses that a sound damper having low temperature dependency of hardness can be realized by reacting A) an isocyanate prepolymer consisting of a reaction product of a high-melting point polyisocyanate with a polyol component consisting of α-hydro-ω-hydroxypoly(oxytetramethylene), and α-hydro-ω-hydroxypoly(oxypropylene-1,2) and / or α-hydro-ω-hydroxypoly(oxypropylene-1,2-co-oxyethylene), with B) at least one chain extender selected from the group consisting of an aliphatic diol, a trifunctional polyol, a polyol, a mixture of polyol or water, and an aromatic diamine.

[0046] Furthermore, for example, Japanese Patent Application Laid-Open No. 2004-300352 discloses that a sound damper with low temperature dependency of hardness can be realized by reacting a polyol component containing a monool with an OH equivalent of 5000 or less with an organic polyisocyanate in the presence of a catalyst and a blowing agent.

[0047] Furthermore, for example, Japanese Patent Application Laid-Open No. 2004-231899 discloses that a sound damper with low temperature dependency of hardness can be realized by reacting a polyol component containing a polyoxypropylene (polyoxyethylene) polyol having an average functionality of 2 to 4, a hydroxyl value of 47 to 160 mgKOH / g, and a terminal oxyethylene unit content of 0 to 20% by mass, and a polyoxypropylene polyoxyethylene polyol having an average functionality of 2 to 4, a hydroxyl value of 20 to 40 mgKOH / g, and a terminal oxyethylene unit content of 10 to 30% by mass, with a polyisocyanate containing an MDI-based urethane prepolymer.

[0048] Furthermore, for example, Japanese Patent Application Laid-Open No. 2004-35784 discloses that a sound damper with low temperature dependency of hardness can be realized by making the difference in solubility parameters (δ) between two polyols with different molecular weights 1 or more, and by mixing one polyol and an isocyanate to obtain an isocyanate-terminated prepolymer, and then mixing the other polyol.

[0049] Furthermore, for example, Japanese Patent Publication No. 6-74046 discloses that the polyol component of semi-rigid polyurethane is a polyether polyol, the polyisocyanate component is a mixed system of partially modified MDI / polymeric MDI = 9 / 1 to 6 / 4 (weight ratio), the partially modified MDI contains both a carbodiimide modified product and a urethane modified product, and the urethane modified product is modified with a glycol having an average molecular weight of 1000 to 6000, thereby realizing a sound damper with low temperature dependency of hardness.

[0050] From the viewpoint of improving the durability of the noise damper 20 in the above-mentioned high-temperature environment and easily maintaining the sound absorption performance of the noise damper 20, the ratio H1 / H2 is preferably 1.7 or less, and more preferably 1.4 or less.

[0051] The first hardness H1 of the noise damper 20 is desirably 100 N or less. Such a noise damper 20 is easily deformable in a temperature range around 23°C, and is therefore suitable for efficiently absorbing the resonance energy of vibrating air and converting it into heat energy for consumption.

[0052] From the viewpoint of efficiently absorbing the above-mentioned air resonance energy, the first hardness H1 of the noise damper 20 is preferably 60 N or less.

[0053] The second hardness H2 of the noise damper 20 is desirably 35 N or greater. Such a noise damper 20 can maintain an even higher hardness even when the tire is heated during driving, which further improves the durability of the noise damper 20 in high-temperature environments and makes it even easier to maintain the sound-absorbing performance of the noise damper 20.

[0054] 2 is a cross-sectional view illustrating a state in which tire 1 with a puncture hole 26 has been repaired. To repair a puncture in tire 1 having noise damper 20, for example, tire sealant 27 is used to fill puncture hole 26. When tire cavity 17 is filled with tire sealant 27, puncture hole 26 is filled with tire sealant 27 and the puncture hole 26 is sealed.

[0055] The noise damper 20 of this embodiment preferably has closed-cell cells (not shown). Such a noise damper 20 suppresses the penetration of the tire repair fluid 27 during tire repair, making it possible to repair a tire with a small amount of tire repair fluid 27.

[0056] To effectively suppress the penetration of the tire repair fluid 27, the number of closed-cell cells is preferably 55 cells / 25 mm or less. The number of cells is measured in accordance with Appendix A of JIS K6401-1:2012. In this embodiment, the number of cells per 25 mm of the test piece (50 x 50 x 3 mm) is measured visually using a graduated magnifying device with a magnification sufficient to recognize the cells (for example, a Leica digital microscope).

[0057] The ventilation volume of the sound damper 20 is 60 cm 3 / cm 2 / s or less is desirable. Here, the air permeability is measured in accordance with Section 6 "Method B" of JIS K6400-7:2012 after leaving the test piece in an atmosphere at 23°C for 10 minutes. Such a noise damper 20 effectively suppresses the penetration of the tire repair fluid 27.

[0058] From the viewpoint of suppressing the penetration of the tire repair fluid 27, the desirable ventilation amount of the noise damper 20 is 30 cm 3 / cm 2 / s or less, and the more desirable ventilation rate is 10 cm 3 / cm 2 The air permeability of the noise damper 20 can be adjusted appropriately by, for example, changing the blending of the raw materials of the porous material, the reaction temperature, and the reaction time.

[0059] The sound damper 20 desirably has a tensile strength of 160 kPa or less in an atmosphere at 23°C. Here, the tensile strength is measured in accordance with Section 5 "Tensile strength and elongation" of JIS K6400-5:2012 after leaving a test piece in an atmosphere at 23°C for 10 minutes.

[0060] If the tensile strength of the noise damper 20 exceeds 160 kPa, when a foreign object such as a nail penetrates the area of ​​the tread portion 2 including the noise damper 20, the noise damper 20 may be pulled by the foreign object and peeled off from the inner surface of the tread portion 2.

[0061] A more desirable tensile strength of the noise damper 20 is 130 kPa or less from the viewpoint of preventing peeling of the noise damper 20. The tensile strength of the noise damper 20 can be adjusted as appropriate by, for example, changing the blending of the raw materials of the porous material, the reaction temperature, and the reaction time.

[0062] The sound damper 20 desirably has an elongation of 140% or more in an atmosphere at 23°C. Here, the elongation is measured in accordance with Section 5 "Tensile strength and elongation" of JIS K6400-5:2012 after leaving a test piece in an atmosphere at 23°C for 10 minutes.

[0063] If the tensile strength of the noise damper 20 is less than 140%, when a foreign object such as a nail penetrates the area of ​​the tread portion 2 including the noise damper 20, the noise damper 20 may be pulled by the foreign object and peeled off from the inner surface of the tread portion 2.

[0064] From the viewpoint of preventing the separation of the noise damper 20, the tensile strength of the noise damper 20 is more preferably 170% or more.

[0065] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the illustrated embodiment and can be modified and implemented in various ways.

[0066] For example, Fig. 3 shows a tire 1A which is an embodiment different from the tire 1 shown in Fig. 1. In the tire 1A, a vibration-damping rubber body 30 for suppressing vibration is provided inside the tread portion 2 between the carcass 6 and the belt layer 7. The vibration-damping rubber body 30 may be disposed, for example, between the belt layer 7 and the band layer 9, or may be disposed outside the band layer 9 in the tire radial direction. The configuration of the tire 1 described above may be adopted for portions of the tire 1A not described below.

[0067] The vibration-damping rubber body 30 is made of rubber that is different from the topping rubber (not shown) included in the carcass ply 6A and the belt ply 7A.

[0068] In this embodiment, the hardness H3 of the vibration-damping rubber body 30 is set to be smaller than the hardness H4 of the tread rubber 11 arranged in the tread portion 2. Here, "rubber hardness" refers to rubber hardness measured by a durometer type A in accordance with JIS K6253 under an environment of 23°C.

[0069] Such a vibration-damping rubber body 30 can suppress vibrations in the tread portion 2, and therefore can effectively reduce running noise (for example, around 160 Hz). Moreover, the tire 1A of this embodiment can also reduce running noise around 250 Hz using the sound-damping body 20, and therefore can effectively improve the noise performance of the tire 1A. Furthermore, since the vibration-damping rubber body 30 of this embodiment is disposed between the carcass 6 and the belt layer 7, it can suppress vibrations of the carcass 6 and the belt layer 7 and reduce road noise.

[0070] To effectively exert the above-mentioned effects, it is desirable to set the ratio (H3 / H4) of the hardness H3 of the vibration-damping rubber body 30 to the hardness H4 of the tread rubber 11 at 0.5 or more and less than 1.0. If the ratio (H3 / H4) is 1.0 or more, vibrations of the tread portion 2 may not be sufficiently suppressed. Conversely, if the ratio (H3 / H4) is less than 0.5, the rigidity of the vibration-damping rubber body 30 may be reduced, making it difficult to maintain steering stability. From this perspective, the ratio (H3 / H4) is more preferably 0.8 or less, and more preferably 0.6 or more. [Example]

[0071] A pneumatic tire of size 165 / 65R18 having the basic structure shown in Figure 1 was prototyped based on the specifications in Table 1, and the noise performance and durability of the sound damper were tested. The specifications common to each example and comparative example are as follows. Tread rubber composition: Natural rubber (TSR20): 15 phr SBR1 (terminally modified): 45 phr (bound styrene content: 28%, vinyl group content: 60%, glass transition temperature: -25°C) SBR2 (terminally modified): 25 phr (bound styrene content: 35%, vinyl group content: 45%, glass transition temperature: -25°C) BR(BR150B):15phr Silane coupling agent (Si266): 4 phr Resin (Arizona Chemical Company SYLVARES SA85): 8 phr Oil: 4 phr Wax: 1.5 phr Antioxidant (6C): 3 phr Stearic acid: 3 phr Zinc oxide: 2 phr Vulcanization accelerator (NS): 2 phr Vulcanization accelerator (DPG): 2 phr Carbon black (N220): 5 phr Silica (VN3, 1115MP): 70 phr Sulfur: 2 phr Hardness of tread rubber in vulcanized tires: 64 degrees Maximum tread rubber thickness: 10mm The test method is as follows.

[0072] <Noise performance> Each test tire was mounted on an 18x7JJ rim and installed on all wheels of a vehicle (a domestically produced 2500cc FR vehicle) under an internal pressure of 320 kPa. The vehicle was driven at a speed of 60 km / h on a road noise measurement road (a rough asphalt road), and the total sound pressure (decibels) at frequencies of 100-200 Hz and 200-300 Hz was measured using a sound-collecting microphone attached to the center of the backrest of the driver's seat. The results are expressed as an index, with Comparative Example 1 being 100, and the higher the index, the lower the running noise and the better the result.

[0073] <Durability> Each sample tire of Comparative Examples 2 to 4 and the Example was mounted on an 18x7JJ rim, and using a drum testing machine, the condition of the noise damper after 250 hours of driving was visually inspected by an operator under conditions of an internal pressure of 320 kPa, a load of 4.8 kN, and a speed of 80 km / h. The results are expressed as a score with Comparative Example 3 being 100, and the higher the score, the less progress there was in the internal destruction of the noise damper and the better the durability performance in high-temperature environments.

[0074] [Table 1]

[0075] As a result of the test, it was confirmed that the tire of the example had improved noise performance compared to the tire of comparative example 1. It was also confirmed that the tire of the example had superior durability performance of the noise damper in a high temperature environment compared to the tires of comparative examples 2 to 4.

[0076] Furthermore, as shown in Table 2, pneumatic tires of Examples 8 to 12 were produced as prototypes and tested for noise performance, durability of the noise damper, and ease of puncture repair. The test methods for noise performance and durability of the noise damper were the same as those described above, and the test method for ease of puncture repair was as follows.

[0077] <Ease of puncture repair> Each test tire mounted on an 18x7JJ rim with an internal pressure of 320 kPa was punctured by hitting a nail, repaired using tire repair fluid (for the Instant Mobility System (IMS) manufactured by Sumitomo Rubber Industries, Ltd.), and the amount of tire repair fluid used was measured. The results were expressed as an index, with Example 9 being set at 100, and the larger the index, the less tire repair fluid was used and the easier the tire was to repair.

[0078] [Table 2]

[0079] Furthermore, as shown in Table 3, pneumatic tires of Examples 13 to 20 were prototyped and tested for noise performance, durability of the noise damper, and peeling resistance of the noise damper when hitting a nail. The test methods for noise performance and durability of the noise damper were the same as those described above, and the test method for peeling resistance was as follows.

[0080] <Sound damping body peeling resistance when stepping on a nail> Each test tire mounted on an 18x7JJ rim was punctured by hitting a nail, and the damaged area was dismantled to measure the area of ​​the noise damper that had been pulled by the nail and peeled off from the inner surface of the tread. The results were expressed as a score, with the value for Example 15 being 100, and the higher the score, the better the peeling resistance.

[0081] [Table 3]

[0082] Furthermore, as shown in Table 4, pneumatic tires of Comparative Example 5 and Examples 21 to 23 were produced as prototypes, and the noise performance and durability performance of the noise damper were tested. The test methods for the noise performance and durability performance of the noise damper were the same as those described above.

[0083] [Table 4] [Explanation of symbols]

[0084] 1 pneumatic tire 2 Tread section 17 Tire cavity surface 20 Sound damping body

Claims

1. A pneumatic tire, A noise-damping body made of porous material is fixed to the tire cavity surface of the tread portion, the noise damper has a ratio H1 / H2 of a first hardness H1 measured in accordance with JIS K6400-2 D method in an atmosphere at 23°C to a second hardness H2 measured in accordance with JIS K6400-2 D method in an atmosphere at 50°C, which is 2.0 or less; the tread portion is made of a rubber composition containing natural rubber, butadiene rubber, and styrene-butadiene rubber; Pneumatic tires.

2. The pneumatic tire according to claim 1 , wherein the ratio H1 / H2 is 1.7 or less.

3. The pneumatic tire according to claim 2, wherein the ratio H1 / H2 is 1.4 or less.

4. The pneumatic tire according to claim 1 , wherein the first hardness H1 is equal to or less than 100 N.

5. The pneumatic tire according to claim 4 , wherein the first hardness H1 is 60 N or less.

6. The pneumatic tire according to claim 1 , wherein the second hardness H2 is 35 N or more.

7. The sound damper has an air permeability of 60 cm as measured in accordance with JIS K6400-7. 3 / cm 2 The pneumatic tire according to any one of claims 1 to 6, wherein the flexural modulus is 1 / s or less.

8. The noise damper has an airflow rate of 30 cm 3 / cm 2 The pneumatic tire according to claim 7, wherein the flexural modulus is 1 / s or less.

9. The noise damper has an airflow rate of 10 cm 3 / cm 2 The pneumatic tire according to claim 8, wherein the flexural modulus is 1 / s or less.

10. The noise damper has closed-cell cells, The pneumatic tire according to any one of claims 1 to 9, wherein the number of the cells is 55 cells / 25 mm or less.

11. The pneumatic tire according to any one of claims 1 to 10, wherein the noise damper has a tensile strength of 160 kPa or less when measured in an atmosphere of 23°C in accordance with JIS K6400-5.

12. The pneumatic tire according to claim 11, wherein the tensile strength of the noise damper is 130 kPa or less.

13. The pneumatic tire according to any one of claims 1 to 12, wherein the noise damper has an elongation of 140% or more when measured in an atmosphere of 23°C in accordance with JIS K6400-5.

14. The pneumatic tire according to claim 13, wherein the elongation of the noise damper is 170% or more.

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