Pneumatic tire

Abstract

The present invention provides a pneumatic tire with improved sound deadening effect. The invention is a pneumatic tire (1) comprising a bead core (5), a carcass layer (6), a belt layer (7), a tread rubber (2G), an inner liner rubber layer (10), a porous sound deadener (20) disposed on the inner liner rubber layer (10) on the tire cavity side. In the normal state, the tire axial length (W1) of the sound deadener (20) is less than the tire radial distance (H) from the bead base line to the position of the maximum width in the inner cavity surface of the sidewall portion 3, and the tread portion (2) in the region of the tire axis where the sound deadener (20) is provided comprises: a plurality of rubber layers (30) stacked in the tire radial direction with a thickness of the inner liner rubber layer (10) or more without including cords. The hardness of each rubber layer (30) is smaller the closer it is to the inner side of the tire radial direction.

Description

Technical Field

[0001] This invention relates to pneumatic tires. Background Technology

[0002] Previously, pneumatic tires with porous sound-absorbing materials disposed on the inner surface of the tire cavity are known (for example, see Patent Document 1).

[0003] [Existing Technical Documents]

[0004] [Patent Literature]

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-262920 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] Reducing the tire axial length of the muffler is an effective way to improve the durability of tires and mufflers. However, if the tire axial length of the muffler is reduced, its noise reduction effect will decrease.

[0008] The present invention was proposed in view of the above actual situation, and its main purpose is to provide a pneumatic tire that can maintain sufficient noise reduction effect and improve the durability of the tire and the noise reduction body.

[0009] [Methods used to solve problems]

[0010] This invention relates to a pneumatic tire, comprising: a pair of bead cores; a carcass layer having carcass cords extending through the tread portion and a pair of sidewall portions and crossing the pair of bead cores; a belt layer disposed radially outward of the carcass layer; a tread rubber disposed radially outward of the belt layer; an inner liner rubber layer disposed on the inner cavity side of the carcass layer; and a porous silencing element disposed on the inner cavity side of the inner liner rubber layer in the tread portion. Under normal, unloaded conditions when mounted on a standard rim and filled with a standard internal pressure, the axial length W1 of the silencing element is less than the radial distance H between the bead baseline and the position of maximum width in the inner cavity surface of the sidewall portion. The tread portion, in the region radially in which the silencing element is disposed, comprises: a plurality of rubber layers stacked radially in the tire direction with a thickness greater than or equal to that of the inner liner rubber layer, excluding the cords; the hardness of each rubber layer decreases towards the inner radial direction of the tire.

[0011] In the pneumatic tire of the present invention, it is preferable that the tire axial length W1 of the silencing body is less than 50% of the tread ground contact width TW.

[0012] In the pneumatic tire of the present invention, it is preferable that the tire axial length W1 of the silencing body is 40% or less of the tread ground contact width TW.

[0013] In the pneumatic tire of the present invention, it is preferable that the hardness Ho of the outermost rubber layer disposed in the radial direction of the tire is 105% or more of the hardness Hi of the innermost rubber layer disposed in the radial direction of the tire.

[0014] In the pneumatic tire of the present invention, preferably the tire axial length W1 of the silencing body, the tread contact width TW, the hardness Ho of the outermost rubber layer disposed in the tire radial direction, and the hardness Hi of the innermost rubber layer disposed in the tire radial direction satisfy the following:

[0015] The relationship is (W1 / TW) / (Ho / Hi)≤0.5.

[0016] In the pneumatic tire of the present invention, preferably the length W1, the tread contact width TW, the hardness Ho, and the hardness Hi satisfy the following:

[0017] The relationship is (W1 / TW) / (Ho / Hi)≤0.4.

[0018] In the pneumatic tire of the present invention, preferably the length W1, the tread contact width TW, the hardness Ho, and the hardness Hi satisfy the following:

[0019] The relationship is (W1 / TW) / (Ho / Hi)≤0.3.

[0020] In the pneumatic tire of the present invention, it is preferable that the axial length W1 of the silencing body is 150 mm or less.

[0021] In the pneumatic tire of the present invention, the length W1 is preferably 100 mm or less.

[0022] In the pneumatic tire of the present invention, it is preferable that the radial length H1 of the silencing body is 50 mm or less.

[0023] In the pneumatic tire of the present invention, the length H1 is preferably 30 mm or less.

[0024] In the pneumatic tire of the present invention, preferably, the loss tangent tanδ of the outermost rubber layer disposed in the radial direction of the tire satisfies the following:

[0025] The relationship between 0℃tanδ / 30℃tanδ≤3.

[0026] In the pneumatic tire of the present invention, the loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C preferably satisfy the following:

[0027] The relationship between 0℃tanδ / 30℃tanδ≤2.

[0028] In the pneumatic tire of the present invention, preferably each of the rubber layers contains a filler component and a plasticizer component, and 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 towards the inner radial side of the tire.

[0029] In the pneumatic tire of the present invention, the pneumatic tire further includes a sealant layer for puncture prevention on the inner surface of the tire cavity, and the hardness of the sealant layer is less than the hardness of the inner liner rubber layer.

[0030] [The effects of the invention]

[0031] Regarding the pneumatic tire of the present invention, the hardness of each rubber layer decreases towards the inner radial direction of the tire, thus vibrations are attenuated towards the inner radial direction of the tire. Therefore, even a noise muffler with a small tire axial length can achieve sufficient noise reduction. Thus, while maintaining the noise reduction effect, the tire axial length of the noise muffler can be reduced, improving the durability of both the tire and the noise muffler. Attached Figure Description

[0032] Figure 1 This is a meridional cross-sectional view showing one embodiment of the pneumatic tire of the present invention.

[0033] Figure 2 It means Figure 1 Meridional cross-section diagram of a deformed pneumatic tire.

[0034] [Figure Labels]

[0035] 1: Pneumatic tires

[0036] 1A: Pneumatic tire

[0037] 2: Fetal face

[0038] 2G: Tread rubber

[0039] 2GA: Cap rubber layer (driving surface rubber layer)

[0040] 2GB: Base rubber layer

[0041] 3: Sidewall

[0042] 5: Tire bead core

[0043] 6: Fetal body layer

[0044] 6A: Carcass ply

[0045] 6B: Carcass cord fabric

[0046] 7: Belt layer

[0047] 10: Inner lining rubber layer

[0048] 20: Silencer

[0049] 30: Rubber layer

[0050] 40: Sealant layer

[0051] H: Tire radial distance

[0052] TW: Tread contact width

[0053] W: Maximum width Detailed Implementation

[0054] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a meridional cross-sectional view of the pneumatic tire 1 in its normal state, including the tire rotation axis (not shown).

[0055] The term "proper condition" refers to the pneumatic tire being mounted on a properly fitted rim (see [link to relevant documentation]). Figure 2 The pneumatic tire 1 is in a state where it is filled with normal internal pressure and is unloaded. Unless otherwise specified, the dimensions of each part of the pneumatic tire 1 are values ​​measured under this normal condition.

[0056] The term "standard rim" refers to the rim specified for each type of tire within a specification system, including the specifications on which the pneumatic tire 1 is based. For example, if it is JATMA, it is a "standard rim"; if it is TRA, it is a "design rim"; and if it is ETRTO, it is a "measuring rim".

[0057] The term "standard tire pressure" refers to the air pressure specified for each type of tire within the specification system, including the specification on which pneumatic tire 1 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 at Various Cold Inflation Pressures"; if it is ETRTO, it is the "inflation pressure". When pneumatic tire 1 is used for passenger vehicles, the standard tire pressure can be, for example, 180 kPa.

[0058] The pneumatic tire 1 of this embodiment is suitable for use as a radial tire for light trucks with a standard internal pressure of 350-600 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 triangle rubbers 8.

[0059] The bead core 5 is disposed on a pair of bead portions 4. The bead core 5 is formed, for example, by winding steel bead wire (not shown) into a multi-row, multi-segment polygonal cross-section.

[0060] Carcass layer 6 has at least one carcass cord. The carcass cord is formed, for example, by covering the arrangement of carcass cords with topping rubber. Organic fibers such as polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber, or steel can be used in the carcass cords.

[0061] The carcass layer 6 of this embodiment includes: carcass ply 6A and carcass ply 6B. The carcass layer 6 comprises: adhesive rubber for the carcass ply 6A and 6B, and sheet rubber (in the form of sheet rubber disposed between the carcass ply 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 outside the carcass ply 6A.

[0062] The belt layer 7 is disposed on the radially outer side of the carcass layer 6. The belt layer 7 has at least one belt cord; in this embodiment, the belt layer 7 is composed of two belt cords 7A and 7B, located radially inside and outside the tire. The belt cords 7A and 7B are formed, for example, by an arrangement of belt cords covered with adhesive rubber. The belt cords are disposed circumferentially around the tire. That is, preferably, the belt cords are arranged at an angle of 15 to 45° relative to the tire equator C. The belt cords are preferably highly elastic, such as steel cords.

[0063] The bead triangular rubber 8 is disposed on the radial outer side of the tire bead core 5. The bead triangular rubber 8 is formed into a roughly triangular cross-section that gradually tapers towards the radial outer side of the tire.

[0064] A band layer 9 may be disposed on the outer radial side of the band layer 7. This band layer 9 consists of at least one band ply, which is obtained by arranging organic fiber cords at a small angle, such that the organic fiber cords are at, for example, less than 10 degrees relative to the tire circumference. The band ply can be either a seamless band formed by spirally winding band ply or ribbon-like cords, or a band formed by splicing together fabrics.

[0065] An inner liner rubber layer 10 is formed on the inner side of the carcass layer 6, i.e., the inner cavity surface of the tire. The inner liner rubber layer 10 is formed of air-impermeable rubber and can maintain internal pressure.

[0066] A tread rubber 2G is disposed on the outermost side of the belt layer 7 and belt layer 9 in the tire radial direction. In this embodiment, the tread rubber 2G comprises: a tread rubber layer 2GA disposed on the outermost side of the tire radial direction and a base rubber layer 2GB disposed on the inner side of the tread rubber layer 2GA in the tire radial direction. The tread rubber 2G may be composed of a single rubber layer.

[0067] In this embodiment, the pneumatic tire 1 includes a noise-absorbing body 20 on the inner side of the tire tread 2 in the tire radial direction. The noise-absorbing body 20 is disposed on the inner cavity side of the inner liner rubber layer 10.

[0068] The sound-absorbing body 20 is, for example, made of a porous sponge material. The sponge material is a sponge-like porous structure; for example, in addition to the so-called sponge itself, which has continuous air bubbles formed by foaming rubber or synthetic resin, it also includes a mesh of intertwined animal fibers, plant fibers, or synthetic fibers. Furthermore, the "porous structure" contains not only continuous air bubbles but also individual air bubbles. In this example, the sound-absorbing body 20 uses a sponge material with continuous air bubbles formed of polyurethane. The hardness of such a sound-absorbing body 20 is less than that of the rubber layer 30 and the sealing layer 40 described later.

[0069] This type of sponge material reduces sound (cavity resonance energy) and lowers the driving noise of the pneumatic tire 1 by converting the vibrational energy of the air vibrating through its porous surface and interior into heat energy. Furthermore, the sponge material is easily deformed by shrinking and bending, thus having no substantial impact on tire deformation during driving. Therefore, it prevents a deterioration in handling stability. Moreover, the sponge material has a very low specific gravity, thus preventing a deterioration in the tire's weight balance.

[0070] As a sponge material, preferably, synthetic resin sponges such as ether-based polyurethane sponge, ester-based polyurethane sponge, and polyethylene sponge, as well as rubber sponges such as chloroprene rubber sponge (CR sponge), ethylene propylene rubber sponge (EDPM sponge), and nitrile rubber sponge (NBR sponge) can be used. From the viewpoints of sound absorption, lightweight, adjustable foaming, and durability, polyurethane-based or polyethylene-based sponges, including ether-based polyurethane sponge, are particularly preferred.

[0071] The muffler 20 is formed as a long strip with a bottom surface fixed to the inner cavity surface of the tread 2, extending along the circumference of the tire. At this time, the outer ends in the circumferential direction can be joined together to form a roughly circular shape, or the outer ends can be separated in the circumferential direction.

[0072] The muffler 20 has substantially the same cross-sectional shape at all circumferential locations except for the ends. As for this cross-sectional shape, in order to prevent tipping or deformation during driving, a flat, transversely elongated cross-sectional shape with a height that is smaller relative to the width (width) of the tire axial direction is preferred.

[0073] In a properly inflated pneumatic tire 1, the axial length W1 of the muffler 20 (i.e., the width of the muffler 20) is less than the radial distance H between the tire bead baseline and the position of the maximum width in the inner cavity surface of the sidewall portion.

[0074] The tread 2, in the region along the tire axial direction where the muffler 20 is provided, includes a plurality of rubber layers 30 stacked radially in the tire. Here, "rubber layer" refers to a rubber layer with a thickness of more than the inner liner rubber layer 10, excluding cords. The tread rubber 2G (driving tread rubber layer 2GA and base rubber layer 2GB) and the inner liner rubber layer 10 are included in the rubber layers 30. In addition, intermediate rubber layers between carcass plies 6A and 6B, intermediate rubber layers between belt plies 7A and 7B, intermediate rubber layers between carcass layer 6 and belt layer 7, intermediate rubber layers between belt layer 7 and belt layer 9, and intermediate rubber layers between carcass layer 6 and inner liner rubber layer 10 may also be included in the rubber layers 30.

[0075] In the pneumatic tire 1, the hardness of each rubber layer 30 decreases towards the inner radial direction of the tire. For example, the hardness of the base rubber layer 2GB is less than that of the tread rubber layer 2GA. Furthermore, the hardness of the inner liner rubber layer 10 is less than that of the base rubber layer 2GB. With this configuration, vibrations input from the tread surface 2 are attenuated towards the inner radial direction of the tire. Therefore, even the muffler 20, which has a small axial length, can achieve sufficient noise reduction.

[0076] The muffler 20 is attached to the inner liner rubber layer 10, for example, using an adhesive. However, if the hardness difference between the porous muffler 20 and the inner liner rubber layer 10 is large, stress concentration at the interface between the two may occur due to long-term use of the pneumatic tire 1, raising concerns about the muffler 20 separating. In this embodiment, the harder each rubber layer 30 is, the closer it is to the radial inner side of the tire. Therefore, the hardness difference between the muffler 20 and the inner liner rubber layer 10 is small, which improves the peel resistance of the muffler 20.

[0077] The tire axial length W1 of the muffler 20 is preferably 50% or less of the tread contact width TW. The tread contact width TW refers to the axial distance between the tread contact ends TE1 and TE2 when a normal load is applied to the tire in its normal state, and the tire's camber angle is 0° and it contacts the ground plane. With such a muffler 20, peeling of the muffler 20 from the inner surface of the tread portion 2 can be suppressed, and the durability of both the pneumatic tire 1 and the muffler 20 can be easily improved. Furthermore, from the above perspective, a more preferable tire axial length W1 for the muffler 20 is 40% or less of the tread contact width TW.

[0078] Preferably, the hardness Ho of the outermost rubber layer 30 disposed in the radial direction of the tire (in this embodiment, the tread rubber layer 2GA) is 105% or more of the hardness Hi of the innermost rubber layer 30 disposed in the radial direction of the tire (in this embodiment, the inner liner rubber layer 10). With a rubber layer 30 of such hardness, the peeling of the muffler 20 from the inner surface of the tread 2 can be suppressed.

[0079] Preferably, the hardness Ho of the outermost rubber layer 30 disposed in the radial direction of the tire is less than 200% of the hardness Hi of the innermost rubber layer 30 disposed in the radial direction of the tire. With a rubber layer 30 of such hardness, a further noise reduction effect can be obtained.

[0080] The hardness of the rubber layer 30 can be measured using a hardness tester with a diameter of 0.5 mm or less, for example, using an indenter. By using such a hardness tester, the flexibility to follow road surface irregularities can be evaluated at a microscopic level, resulting in noise reduction during actual driving.

[0081] The tire axial length W1, tread contact width TW, and rubber layer hardness Ho and Hi of the muffler 20 preferably satisfy the following:

[0082] The relationship (W1 / TW) / (Ho / Hi) ≤ 0.5. Such a pneumatic tire 1 can maintain sufficient noise reduction effect and improve the durability of the pneumatic tire 1 and the noise muffler 20.

[0083] Furthermore, the relationship between the tire axial length W1, tread contact width TW, and rubber layer hardness Ho and Hi of the more preferred muffler 20 is as follows:

[0084] (W1 / TW) / (Ho / Hi)≤0.4.

[0085] The relationship between the tire axial length W1, tread contact width TW, and rubber layer hardness Ho and Hi of the further optimized muffler 20 is as follows:

[0086] (W1 / TW) / (Ho / Hi)≤0.3.

[0087] The tire axial length W1 of the muffler 20 is preferably less than 70% of the tire axial length W2 of the belt layer 7. With such a muffler 20, peeling of the muffler 20 from the inner surface of the tread 2 can be suppressed, and the durability of the pneumatic tire 1 and the muffler 20 can be easily improved.

[0088] The tire axial length W1 of the muffler 20 is preferably 150 mm or less. With such a muffler 20, peeling of the muffler 20 from the inner surface of the tread 2 can be suppressed, and the durability of the pneumatic tire 1 and the muffler 20 can be easily improved.

[0089] Furthermore, from the above perspective, a more preferred tire axial length W1 of the muffler 20 is 120 mm or less, and a more preferred tire axial length W1 of the muffler 20 is 100 mm or less.

[0090] The radial length H1 of the silencing body 20 is preferably 50 mm or less. With such a silencing body 20, peeling of the silencing body 20 from the inner surface of the tread 2 can be suppressed, and the durability of the pneumatic tire 1 and the silencing body 20 can be easily improved.

[0091] Furthermore, from the above perspective, a more preferable tire radial length H1 for the muffler 20 is 30 mm or less.

[0092] The outermost rubber layer 30 located in the radial direction of the tire preferably satisfies the following relationship: 0℃ tanδ / 30℃ tanδ ≤ 3. In such a pneumatic tire 1, the noise reduction effect has low temperature dependence and can achieve good noise reduction effect over a wide temperature range.

[0093] Furthermore, considering the above viewpoint, the more preferred loss tangent tanδ of the rubber layer 30 at 0°C and at 30°C are:

[0094] 0℃tanδ / 30℃tanδ≤2.

[0095] In addition, the loss tangent tanδ at 0°C and the loss tangent tanδ at 30°C were measured as follows: in accordance with JIS-K6394, the measurements were performed using a viscoelastic spectrometer manufactured by Iwamoto Manufacturing Co., Ltd., under the conditions of each measurement temperature (0°C or 30°C), frequency 10 Hz, initial tensile strain 10%, and dynamic strain amplitude ±2%.

[0096] Each rubber layer 30 contains a filler component. Examples of filler components include, for example, carbon black and silica. Regarding the filler component, for example, the ash content is determined by thermogravimetric analysis (TGA) of the vulcanized rubber according to JIS K 6226-1:2003.

[0097] In the pneumatic tire 1, preferably, the total amount of filler component in each rubber layer 30 decreases towards the inner radial direction of the tire. This causes vibrations to attenuate towards the inner radial direction of the tire. Therefore, even a sound-absorbing body 20 with a small axial length can achieve sufficient noise reduction.

[0098] Each rubber layer 30 contains a plasticizer component. Examples of plasticizer components include, for example, oils. The plasticizer component is determined, for example, as an acetone extract according to JIS K 6229:2015.

[0099] In the pneumatic tire 1, preferably, the total amount of plasticizer component in each rubber layer 30 is greater towards the inner radial direction of the tire. As a result, vibrations are attenuated towards the inner radial direction of the tire. Therefore, even the muffler 20 with a small axial length can achieve sufficient noise reduction.

[0100] Preferably, the ratio of the total filler content to the total plasticizer content in each rubber layer decreases towards the inner radial direction of the tire. This causes vibrations to attenuate towards the inner radial direction of the tire. Therefore, even with a small tire axial length, the muffler 20 can achieve sufficient noise reduction.

[0101] Figure 2 Indicates as Figure 1 A modified example of the pneumatic tire 1 is a pneumatic tire 1A. In the pneumatic tire 1A, the configuration of the pneumatic tire 1 described above can be used in the parts not described below.

[0102] The pneumatic tire 1A also includes a sealing layer 40 on the inner surface of the tire cavity for puncture prevention. The sealing layer 40 is formed on the inner cavity side of the inner liner rubber layer 10. A sound damper 20 may be formed on the inner cavity side of the sealing layer 40.

[0103] There are no specific provisions for the sealing material used to form the sealing layer 40, but in this example, the sealing material contains rubber components, liquid polymers, and crosslinking agents.

[0104] Butyl rubber and halogenated butyl rubber, among other butyl-based rubbers, can be used as rubber components. Butyl-based rubbers and diene-based rubbers can also be mixed as rubber components.

[0105] Examples of liquid polymers include liquid polybutene, liquid polyisobutylene, liquid polyisoprene, liquid polybutadiene, liquid polyalphaolefin, liquid isobutylene, liquid ethylene alpha olefin copolymer, liquid ethylene propylene copolymer, and liquid ethylene butene copolymer.

[0106] Known compounds can be used as crosslinking agents, but organic peroxides are preferred. In organic peroxide crosslinking systems, adhesion, sealing properties, flowability, and processability are improved by using butyl rubber or liquid polymers.

[0107] Examples of organic peroxides (crosslinking agents) include acyl peroxides such as benzoyl peroxide, dibenzoyl peroxide, and p-chlorobenzoyl peroxide; peroxide esters such as 1-butyl peracetate, tert-butyl peroxide, and tert-butyl peroxide; ketone peroxides such as methyl ethyl ketone peroxide; alkyl peroxides such as di-tert-butyl peroxide and 1,3-bis(1-butylperoxyisopropyl)benzene; hydroperoxides such as tert-butyl hydroperoxide; and dicumyl peroxide and tert-butyl cumyl peroxide. From the viewpoint of adhesion and flowability, acyl peroxides are preferred, and dibenzoyl peroxide is particularly preferred.

[0108] In sealing materials, crosslinking aids (vulcanization accelerators), inorganic fillers, plasticizers, etc. can be added appropriately.

[0109] As a crosslinking aid (vulcanization accelerator), it can be selected from sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine, aldehyde-amine, imidazoline, xanthic acid and quinoid dioxime compounds (quinoid compounds), etc.

[0110] As an inorganic filler, it can be selected from carbon black, silicon dioxide, calcium carbonate, calcium silicate, magnesium oxide, aluminum oxide, barium sulfate, talc and mica, etc.

[0111] As a plasticizer, it can be selected from aromatic processing oils, naphthenic processing oils, paraffinic processing oils, etc.

[0112] Preferably, the hardness of the sealing layer 40 is less than that of the inner liner rubber layer 10. This causes vibrations to attenuate radially inwards towards the tire. Therefore, even the muffler 20, with its small axial length, can achieve sufficient noise reduction.

[0113] The pneumatic tires 1 and 1A of the present invention are suitable for passenger vehicles, and are particularly suitable for tires with a width of 155 mm or more. Preferably, the tire width is 205 mm or more, more preferably 225 mm or more, and even more preferably 265 mm or more.

[0114] The pneumatic tire 1 of the present invention has been described in detail above, but the present invention is not limited to the specific embodiments described above, and can be implemented in various ways.

[0115] have Figure 1 The basic structural dimensions: 195 / 65R15 pneumatic tires were tested based on the specifications in Table 1 to evaluate noise performance and durability. Regarding the hardness of the rubber layer, a durometer with an indenter diameter of 0.5 mm or less was used, pressing the indenter perpendicular to the tire's meridional section for measurement (the same applies below). Specifications of all tested tires not listed in Table 1 are common. The testing methods are as follows.

[0116] <Noise Performance>

[0117] The noise level of the test vehicle, equipped with the test tires, was measured when it was driven at 60 km / h. The results are expressed as an index of 100 for Comparative Example 1, with a higher value indicating better noise performance.

[0118] <Durability>

[0119] Using a roller testing machine, each test tire was driven for 30,000 km under conditions of internal pressure 230 kPa, load 4.24 kN, and speed 80 km / h to confirm the degree of damage to the muffler after driving. The results are expressed as an index of 100 for Comparative Example 1, with a higher value indicating better durability.

[0120] Table 1

[0121] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Example 1 Silencer have have have have have The length W1 of the silencer W1 < H W1 < H W1 < H W1>H W1 < H Hardness (°) of the rubber layer on the driving surface 50 70 70 70 70 Hardness (°) of the base rubber layer 60 70 60 60 60 Hardness (°) of the inner lining rubber layer 70 70 60 50 50 Noise performance (index) 100 90 110 120 120 Durability (index) 100 100 100 90 100

[0122] In addition, the formulations (PHR) and hardness of the surface rubber, base rubber, and inner liner rubber used in this embodiment 1 are shown in Table 2.

[0123] Table 2

[0124] Rubber layer of driving surface Base rubber layer Inner lining rubber layer natural rubber 40 50 50 Butadiene rubber 20 50 Styrene-butadiene rubber 40 Butyl rubber 50 carbon black 70 60 50 wax 3 3 Anti-aging agent 6C 3 3 Anti-aging agent RD 3 3 3 Operating oil 10 10 10 stearic acid 3 3 3 Zinc oxide 3 3 3 Sulfur containing 5% oil 2 2 2 NS vulcanization accelerator 1 1 1 DPG vulcanization accelerator 1 1 1 Hardness (°) 70 60 50

[0125] Detailed information for each formula is as follows.

[0126] Natural Rubber (NR): RSS#1

[0127] Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd.

[0128] Styrene-butadiene rubber (SBR): HPR850 manufactured by JSR Corporation

[0129] Butyl rubber: Regular butyl rubber 268 manufactured by Exxon Chemical Co., Ltd.

[0130] Carbon black: Showblack N550 manufactured by Cabot Corporation, Japan

[0131] Wax: Sunnoc Wax manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0132] Anti-aging agent 6C: Antigene 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Industries, Ltd.

[0133] Antioxidant RD: NOCRAC 224 manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0134] Operating oil: Mineral oil PW-380 manufactured by Idemitsu Kosan Co., Ltd.

[0135] Stearic acid: Tsubaki, manufactured by Nippon Oils & Fats Co., Ltd.

[0136] Zinc oxide: Zinc White No. 1 manufactured by Mitsui Metals Mining Co., Ltd.

[0137] Sulfur containing 5% oil: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd.

[0138] Vulcanization accelerator: Nocceler NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0139] As can be clearly seen from Table 1, compared to the comparative example, the pneumatic tires of the embodiment have a balanced and good improvement in noise performance and durability.

[0140] have Figure 1 Pneumatic tires of the above dimensions with the basic structure were tested based on the specifications in Table 3 to evaluate their noise performance and durability. Specifications of all tested tires not listed in Table 3 are common. The testing methods are as follows.

[0141] <Noise Performance>

[0142] The noise level of the test vehicle equipped with the test tires was measured in the same manner as described above. The results are expressed as an index of 100 (as in Example 3), with higher values ​​indicating better noise performance.

[0143] <Durability>

[0144] Damage to the muffler after driving was confirmed in the same manner as described above. The results, expressed as an index of 100 (with Example 3 as 100), show that a higher value indicates better durability.

[0145] Table 3

[0146] Example 2 Example 3 Example 4 Example 5 Silencer have have have have The length W1 of the silencer W1 < H W1 < H W1 < H W1 < H W1 / TW (%) 60 50 40 30 Hardness (°) of the rubber layer on the driving surface 70 70 70 70 Hardness (°) of the base rubber layer 60 60 60 60 Hardness (°) of the inner rubber lining layer 50 50 50 50 Noise performance (index) 110 100 90 85 Durability (index) 90 100 110 120

[0147] have Figure 1Pneumatic tires of the above dimensions with the basic structure were prototyped based on the specifications in Table 4 to evaluate their noise performance and durability. Specifications of all tested tires not listed in Table 4 are common. The testing methods are as follows.

[0148] <Noise Performance>

[0149] The noise level of the test vehicle equipped with the test tires was measured in the same manner as described above. The results are expressed as an index of 100 (as in Example 8), with higher values ​​indicating better noise performance.

[0150] <Durability>

[0151] Damage to the muffler after driving was confirmed in the same manner as described above. The results, expressed as an index of 100 (with Example 8 as the index), show that a higher value indicates better durability.

[0152] Table 4

[0153] Example 6 Example 7 Example 8 Example 9 Example 10 Silencer have have have have have The length W1 of the silencer W1 < H W1 < H W1 < H W1 < H W1 < H Hardness (°) of the rubber layer on the driving surface 61 62 70 80 90 Hardness (°) of the base rubber layer 60 60 60 60 60 Hardness (°) of the inner rubber lining layer 59 59 50 40 30 Ho / Hi (%) 103 105 140 200 300 Noise performance (index) 100 100 100 100 100 Durability (index) 80 90 100 110 120

[0154] have Figure 1 Pneumatic tires of the above dimensions with the basic structure were tested based on the specifications in Table 5 to evaluate noise performance and durability. Specifications of all tested tires not listed in Table 5 are common. The testing methods are as follows.

[0155] <Noise Performance>

[0156] The noise level of the test vehicle equipped with the test tires was measured in the same manner as described above. The results are expressed as an index of 100 in Example 13, with a higher value indicating better noise performance.

[0157] <Durability>

[0158] Damage to the muffler after driving was confirmed in the same manner as described above. The results, expressed as an index of 100 (for Example 13), show that a higher value indicates better durability.

[0159] Table 5

[0160] Example 11 Example 12 Example 13 Example 14 Example 15 Silencer have have have have have The length W1 of the silencer W1 < H W1 < H W1 < H W1 < H W1 < H Hardness (°) of the rubber layer on the driving surface 70 70 70 70 70 Hardness (°) of the base rubber layer 60 60 60 60 60 Hardness (°) of the inner rubber lining layer 50 50 50 50 50 (W1 / TW) / (Ho / Hi) 0.8 0.5 0.4 0.3 0.2 Noise performance (index) 70 90 100 100 100 Durability (index) 70 90 100 110 120

[0161] have Figure 1 Pneumatic tires of the above dimensions with the basic structure were tested based on the specifications in Table 6 to evaluate noise performance and durability. Specifications of all tested tires not listed in Table 6 are common. The testing methods are as follows.

[0162] <Noise Performance>

[0163] The noise level of the test vehicle equipped with the test tires was measured in the same manner as described above. The results are expressed as an index of 100 (as in Example 18), with higher values ​​indicating better noise performance.

[0164] <Durability>

[0165] Damage to the muffler after driving was confirmed in the same manner as described above. The results, expressed as an index of 100 (with Example 18 as 100), show that a higher value indicates better durability.

[0166] Table 6

[0167] Example 16 Example 17 Example 18 Example 19 Silencer have have have have The length W1 of the silencer W1 < H W1 < H W1 < H W1 < H The length W1 (mm) of the silencer 200 150 100 70 Hardness (°) of the rubber layer on the driving surface 65 65 65 65 Hardness (°) of the base rubber layer 60 60 60 60 Hardness (°) of the inner rubber lining layer 50 50 50 50 Noise performance (index) 150 130 100 80 Durability (index) 70 90 100 120

[0168] have Figure 1 Pneumatic tires of the above dimensions with the basic structure were prototyped based on the specifications in Table 7 to evaluate noise performance and durability. Specifications of all tested tires not listed in Table 7 are common. The testing methods are as follows.

[0169] <Noise Performance>

[0170] The noise level of the test vehicle equipped with the test tires was measured in the same manner as described above. The results are expressed as an index of 100 (as in Example 22), with a higher value indicating better noise performance.

[0171] <Durability>

[0172] Damage to the muffler after driving was confirmed in the same manner as described above. The results, expressed as an index of 100 (for Example 22), show that a higher value indicates better durability.

[0173] Table 7

[0174] Example 20 Example 21 Example 22 Example 23 Silencer have have have have The length W1 of the silencer W1 < H W1 < H W1 < H W1 < H The length H1 (mm) of the silencer 80 50 30 20 Hardness (°) of the rubber layer on the driving surface 65 65 65 65 Hardness (°) of the base rubber layer 60 60 60 60 Hardness (°) of the inner rubber lining layer 50 50 50 50 Noise performance (index) 120 110 100 90 Durability (index) 80 90 100 120

[0175] have Figure 1 The above-mentioned pneumatic tires with the basic structure and dimensions were tested based on the specifications in Table 8 to evaluate noise performance. Specifications of all tested tires not listed in Table 8 are common. The testing methods are as follows.

[0176] <Noise Performance>

[0177] The noise levels of the test vehicle equipped with the test tires were measured at outside temperatures of 0°C and 30°C in the same manner as described above. The results are expressed as an index with noise performance at 30°C set at 100; the smaller the value, the better the temperature dependence of the noise performance.

[0178] Table 8

[0179] Example 24 Example 25 Example 26 Example 27 Example 28 Silencer have have have have have The length W1 of the silencer W1 < H W1 < H W1 < H W1 < H W1 < H Hardness (°) of the rubber layer on the driving surface 65 65 65 65 65 Hardness (°) of the base rubber layer 60 60 60 60 60 Hardness (°) of the inner rubber lining layer 50 50 50 50 50 0℃tanδ / 30℃tanδ 4.0 3.0 2.0 1.5 1.2 Noise performance at 0°C (index) 90 100 110 115 120 Noise performance at 30℃ (index) 100 100 100 100 100

Claims

1. A pneumatic tire, characterized in that, Include: A pair of tire bead cores; The carcass layer has: a carcass cord that extends across the pair of bead cores via the tread portion and a pair of sidewall portions; A belt layer disposed on the outer side of the tire carcass ply in the tire radial direction; Tread rubber, the tread rubber being disposed on the radially outer side of the belt layer of the tire; An inner liner rubber layer, the inner liner rubber layer being disposed on the tire cavity side of the carcass layer; as well as The tread portion includes a porous sound-absorbing material, which is disposed on the inner cavity side of the inner liner rubber layer. Under normal conditions of no load and installation on a standard rim with standard internal pressure, the tire axial length W1 of the muffler is less than the tire radial distance H between the tire bead baseline and the position of maximum width in the inner cavity surface of the tire sidewall. The tread portion, in the axial region of the tire where the muffler is located, comprises: a plurality of rubber layers stacked radially in the tire direction with a thickness greater than that of the inner liner rubber layer, excluding the cords. The plurality of rubber layers include a tread rubber layer, a base rubber layer, and an inner liner rubber layer, and the hardness of each rubber layer decreases as it moves towards the radial direction inwards from the tire. The tire axial length W1 of the muffler, the tread contact width TW, the hardness Ho of the outermost rubber layer in the tire radial direction, and the hardness Hi of the innermost rubber layer in the tire radial direction satisfy the following: The relationship is (W1 / TW) / (Ho / Hi)≤0.

5.

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

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

4. The pneumatic tire according to any one of claims 1 to 3, wherein, The hardness Ho of the outermost rubber layer in the radial direction of the tire is 105% or more of the hardness Hi of the innermost rubber layer in the radial direction of the tire.

5. The pneumatic tire according to claim 1, wherein, The length W1, the tread ground contact width TW, the hardness Ho, and the hardness Hi satisfy the following: The relationship is (W1 / TW) / (Ho / Hi)≤0.

4.

6. The pneumatic tire according to claim 5, wherein, The length W1, the tread ground contact width TW, the hardness Ho, and the hardness Hi satisfy the following: The relationship is (W1 / TW) / (Ho / Hi)≤0.

3.

7. The pneumatic tire according to any one of claims 1 to 6, wherein, The tire axial length W1 of the muffler is less than 150mm.

8. The pneumatic tire according to claim 7, wherein, The length W1 is less than 100mm.

9. The pneumatic tire according to any one of claims 1 to 8, wherein, The radial length H1 of the tire of the muffler is less than 50 mm.

10. The pneumatic tire according to claim 9, wherein, The length H1 is less than 30 mm.

11. The pneumatic tire according to any one of claims 1 to 10, wherein, The loss tangent tanδ of the outermost rubber layer located in the radial direction of the tire satisfies the following conditions: at 0°C, the loss tangent tanδ is equal to the following condition: The relationship between 0℃tanδ / 30℃tanδ≤3.

12. The pneumatic tire according to claim 11, wherein, The loss tangent tanδ at 0℃ and the loss tangent tanδ at 30℃ satisfy: The relationship between 0℃tanδ / 30℃tanδ≤2.

13. The pneumatic tire according to any one of claims 1 to 12, wherein, Each rubber layer contains filler and plasticizer components. The ratio of the total amount of filler components to the total amount of plasticizer components in each rubber layer decreases as it moves towards the inner radial direction of the tire.

14. The pneumatic tire according to any one of claims 1 to 13, wherein, The pneumatic tire also includes a puncture-proof sealing layer on the inner surface of the tire, the hardness of which is less than the hardness of the inner liner rubber layer.

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