pneumatic tires

Abstract

To provide a pneumatic tire capable of improving noise performance and durability.SOLUTION: A pneumatic tire 1 as the pneumatic tire 1 which has a tread part 2 includes tread rubber 13 arranged on the tread part 2 and a sound controlling body 14 which is adhered onto a tire inner cavity surface 9 of the tread part 2 and comprises porous material. The tread rubber 13 includes an outer side tread rubber 13A constituting a tread grounding surface 2S and an inner side tread rubber 13B arranged on the tire radial direction inner side of the outer side tread rubber 13A and the tire radial direction outer side of the sound controlling body 14. A loss tangent tanδ at 30°C of the inner side tread rubber 13B is less than the loss tangent tanδ at 30°C of the outer side tread rubber 13A.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to pneumatic tires. [Background technology]

[0002] Patent Document 1 below describes a pneumatic tire. This pneumatic tire is provided with a strip-shaped noise-damping body made of a sponge material that is attached to the radially inner surface of the tread portion and extends in the tire circumferential direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-86600 Summary of the Invention [Problem to be solved by the invention]

[0004] The noise damper converts the vibration energy of the air in the tire cavity into thermal energy to achieve noise damping. Therefore, the tread rubber to which the noise damper is attached is prone to accumulating heat while the tire is running. If the heat accumulation capacity of the tread rubber increases, the durability of the tread portion deteriorates, which is a problem.

[0005] The present disclosure has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire that can improve noise performance and durability. [Means for solving the problem]

[0006] The present disclosure relates to a pneumatic tire having a tread portion, the pneumatic tire including: tread rubber arranged in the tread portion; and a noise damper made of a porous material and fixed to the tire cavity surface of the tread portion, the tread rubber including an outer tread rubber that forms the tread contact surface, and an inner tread rubber arranged radially inward of the outer tread rubber and radially outward of the noise damper, the inner tread rubber having a loss tangent tanδ at 30°C that is smaller than the loss tangent tanδ at 30°C of the outer tread rubber. [Effects of the Invention]

[0007] By employing the above-described configuration, the pneumatic tire of the present disclosure can improve noise performance and durability. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a tire meridian cross-sectional view showing a pneumatic tire of the present embodiment. [Figure 2] 2 is an enlarged meridian cross section of the tire showing the tread portion of FIG. 1 together with the noise damper. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be understood that the drawings include exaggerated representations and representations that differ from the dimensional ratios of actual structures in order to facilitate understanding of the contents of the disclosure. Furthermore, identical or common elements are designated by the same reference numerals throughout the embodiments, and redundant explanations will be omitted. Furthermore, the specific configurations shown in the embodiments and drawings are intended to facilitate understanding of the contents of the present disclosure, and the present disclosure is not limited to the specific configurations shown in the drawings.

[0010] [Pneumatic tire (first embodiment)] FIG. 1 is a tire meridian cross-sectional view showing a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of this embodiment. The tire 1 of this embodiment is exemplified as a pneumatic tire for passenger cars, for example. However, the tire 1 is not limited to this form and may be, for example, a pneumatic tire for heavy loads, etc.

[0011] 1, a tire 1 has a tread portion 2. Furthermore, the tire 1 of this embodiment is provided with a carcass 6 and a belt layer 7.

[0012] [Carcass] The carcass 6 of this embodiment extends across a pair of bead portions 4, 4. The carcass 6 of this embodiment is made up of at least one carcass ply 6A, one carcass ply in this embodiment.

[0013] The carcass ply 6A of this embodiment includes a main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead cores 5 of the bead portions 4, and a turned-up portion 6b that is continuous with the main body portion 6a and is turned back from the axially inner side to the axially outer side around the bead cores 5. A bead apex rubber 8 that extends tapered from the bead cores 5 toward the radially outer side of the tire is disposed between the main body portion 6a and the turned-up portion 6b of the carcass ply 6A.

[0014] The carcass ply 6A of this embodiment 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.

[0015] In this embodiment, an inner liner rubber 10 that forms the tire cavity surface 9 is arranged inside the carcass 6. The inner liner rubber 10 is made of air-impermeable rubber such as butyl rubber, and keeps the air filled in the tire 1 airtight.

[0016] [Belt layer] The belt layer 7 of this embodiment is disposed on the outer side of the carcass 6 in the tire radial direction and inside the tread portion 2. The belt layer 7 of this embodiment is composed of two belt plies 7A and 7B on the inner and outer sides in the tire radial direction.

[0017] In the belt plies 7A and 7B of this embodiment, belt cords (not shown) are arranged at an angle of, for example, 10 to 35 degrees with respect to the tire circumferential direction. These belt plies 7A and 7B are overlapped with the belt cords in a direction crossing each other. For example, steel, aramid, rayon, or the like can be suitably used as the belt cords.

[0018] [Tread] The tread portion 2 of this embodiment is provided with a pair of tread ground contact edges 2t, 2t. The pair of tread ground contact edges 2t, 2t are identified as the axially outermost edges of the tread ground contact surface 2S when the tire 1 in a normal state is loaded with a normal load and brought into contact with a flat surface with a camber angle of 0°. In addition, in the normal state, the axial distance between the tread ground contact edges 2t, 2t is defined as the tread ground contact width TW.

[0019] The normal state refers to a state in which the tire 1 is mounted on a normal rim (not shown), inflated to the normal internal pressure, and no load is applied. Unless otherwise specified, the dimensions of each part of the tire are shown as values ​​measured in the normal state. Note that the dimensions of each part of the tire are allowed for normal errors that are inherent in rubber molded products.

[0020] A "genuine rim" is a rim that is defined for each tire by a standard system that includes the standard on which tire 1 is based. Therefore, a genuine rim is, for example, a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO.

[0021] 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 tire 1 is based. Therefore, the normal internal pressure is, for example, the "maximum air pressure" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO.

[0022] The "normal load" is the load determined for each tire by each standard in the standard system including the standard on which the tire 1 is based. Therefore, the normal load is, for example, "maximum load capacity" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "LOAD CAPACITY" in the case of ETRTO.

[0023] The tire 1 of this embodiment includes a tread rubber 13 and a noise damper 14.

[0024] [Sound control body] The noise damper 14 of this embodiment is fixed to the tire cavity surface 9 of the tread portion 2. The noise damper 14 of this embodiment is formed in a long strip shape having a bottom surface fixed to the tire cavity surface 9, and extends in the tire circumferential direction. The noise damper 14 is formed in a substantially annular shape by a pair of outer end portions (not shown) 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.

[0025] The noise damper 14 of this embodiment has substantially the same cross-sectional shape at each position in the tire circumferential direction except for a pair of outer end portions (not shown) in the tire circumferential direction, but is not particularly limited to this. The cross-sectional shape of the noise damper 14 can be set as appropriate. The noise damper 14 of this embodiment is formed in a flat, horizontally elongated shape (in this embodiment, a horizontally elongated rectangular shape) in which the thickness in the tire radial direction (maximum thickness T1) is smaller than the width in the tire axial direction (maximum width W1). This can prevent the noise damper 14 from collapsing or deforming during running.

[0026] The noise damper 14 of this embodiment is made of a porous material. An example of a porous material is a porous sponge material. The sponge material has a spongy porous structure. The sponge material may be a so-called sponge made by foaming rubber or synthetic resin, or may be a material made by intertwining and connecting animal fibers, plant fibers, synthetic fibers, or the like.

[0027] Examples of sponge materials include synthetic resin sponges such as ether-based polyurethane sponge, ester-based polyurethane sponge, and polyethylene sponge, as well as chloroprene rubber sponge (CR sponge). Other examples of sponge materials include ethylene propylene rubber sponge (EDPM sponge) and nitrile rubber sponge (NBR sponge). In particular, polyurethane-based or polyethylene-based sponges, including ether-based polyurethane sponges, are preferred from the standpoints of sound-damping properties (noise performance), light weight, foam controllability, and durability.

[0028] The porous material (in this example, a sponge material) is easily deformed by shrinking or bending, etc. Therefore, the noise damper 14 can flexibly deform in accordance with the deformation of the inner liner rubber 10 during driving.

[0029] The noise damper 14 made of such a porous material can absorb air vibrations in the tire cavity 12 through its surface and internal pores (cells), converting them into thermal energy and consuming it. This reduces interior noise caused by air resonance. Furthermore, the noise damper 14 can absorb impacts received from the tread portion 2 during driving from the inside in the tire radial direction, thereby reducing road noise. Therefore, the tire 1 of this embodiment has improved noise performance.

[0030] Furthermore, the noise damper 14 generates heat while running because it converts air vibrations in the tire cavity 12 into thermal energy to achieve noise damping. If this heat from the noise damper 14 is transmitted to the tread edge 2t side of the tread rubber 13, which tends to generate more heat while running, the amount of heat stored in the tread rubber 13 on the tread edge 2t side increases, which may make it difficult to improve durability. For this reason, it is preferable that the axially outer end 14t of the noise damper 14 be positioned axially more inward than the tread edge 2t. This prevents the amount of heat stored on the tread rubber 13 on the tread edge 2t side of the tire 1 of this embodiment from increasing, improving durability.

[0031] The maximum width W1 of the noise damper 14 in the tire axial direction is preferably set to 70% to 95% of the tread contact width TW. By setting the maximum width W1 of the noise damper 14 to 95% or less of the tread contact width TW, it is possible to suppress the transmission of heat from the noise damper 14 to the tread contact edge 2t side of the tread rubber 13, thereby improving durability. On the other hand, by setting the maximum width W1 of the noise damper 14 to 70% or more of the tread contact width TW, air vibrations within the tire cavity 12 are effectively absorbed, improving noise performance. From this perspective, the maximum width W1 of the noise damper 14 is preferably 90% or less of the tread contact width TW, and preferably 75% or more.

[0032] The maximum thickness T1 of the noise damper 14 (maximum thickness in the tire radial direction) is preferably set to 70 mm or less. This makes it possible to suppress excessive heat generation in the noise damper 14, improving durability. Furthermore, the maximum thickness T1 is preferably set to 40 mm or more. This enables the noise damper 14 to efficiently absorb air vibrations within the tire cavity 12, improving noise performance. From this perspective, the maximum thickness T1 is preferably set to 60 mm or less, and more preferably 50 mm or more.

[0033] [Tread rubber] The tread rubber 13 of this embodiment is disposed in the tread portion 2. The tread rubber 13 of this embodiment is disposed outside the carcass 6 and the belt layer 7 in the tire radial direction.

[0034] The tread rubber 13 of this embodiment is configured to include an outer tread rubber 13A and an inner tread rubber 13B. Furthermore, the tread rubber 13 of this embodiment includes an intermediate tread rubber 13C. Fig. 2 is an enlarged meridian cross section of the tire showing the tread portion 2 of Fig. 1 together with the noise damper 14.

[0035] The outer tread rubber 13A of this embodiment forms the tread ground contact surface 2S. The outer tread rubber 13A of this embodiment extends axially outward beyond the axial outer end 7t of the belt layer 7.

[0036] The inner tread rubber 13B is disposed radially inward of the outer tread rubber 13A and radially outward of the noise damper 14. The inner tread rubber 13B of this embodiment is disposed adjacent to the belt layer 7.

[0037] The intermediate tread rubber 13C is disposed between the outer tread rubber 13A and the inner tread rubber 13B. In this embodiment, the intermediate tread rubber 13C extends axially outward beyond the axial outer end 13Bt of the inner tread rubber 13B and the axial outer end 7t of the belt layer 7.

[0038] The rubber compounding of the outer tread rubber 13A, the inner tread rubber 13B, and the intermediate tread rubber 13C is not particularly limited. The rubber compounding includes a rubber base material, a reinforcing agent (filler), a cross-linking agent, and a vulcanization accelerator. The rubber base material may be, for example, a diene rubber such as natural rubber, butadiene rubber, isoprene rubber, or styrene-butadiene rubber, or a mixture of these. The reinforcing agent (filler) may be, for example, carbon or silica. The cross-linking agent may be, for example, sulfur. The vulcanization accelerator may be, for example, a thiazole-based, guanidine-based, sulfenamide-based, or thiuram-based compound.

[0039] As described above, the noise damper 14 generates heat while the vehicle is running. Therefore, the tread rubber 13 to which the noise damper 14 is fixed is prone to accumulating heat as heat is transmitted from the noise damper 14. If the heat accumulation capacity of the tread rubber 13 increases, the durability of the tread portion 2 is likely to deteriorate.

[0040] In the tire 1 of the present embodiment, the loss tangent tanδ of the inner tread rubber 13B at 30° C. is set to be smaller than the loss tangent tanδ of the outer tread rubber 13A at 30° C. Note that the loss tangent tanδ at 30° C. can be set by, for example, adjusting the amounts of the reinforcing agent and cross-linking agent added, or the type and amount of vulcanization accelerator added.

[0041] In this specification, the loss tangent tan δ at 30° C. is a value measured in accordance with the provisions of JIS-K6394 using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions. Initial strain: 10% Amplitude: ±2% Frequency: 10Hz Deformation mode: tension Measurement temperature: 30°C

[0042] The inner tread rubber 13B of this embodiment has a loss tangent tanδ at 30°C set to be smaller than the loss tangent tanδ of the outer tread rubber 13A at 30°C, and thereby generates less heat from the start of running than the outer tread rubber 13A. Since the inner tread rubber 13B configured as such a low heat generation rubber is disposed radially outward of the noise damper 14, it is possible to suppress heat accumulation due to heat generated by the noise damper 14 during running. As a result, the tire 1 of this embodiment can suppress an increase in the heat accumulation capacity of the tread rubber 13, and the durability of the tread portion 2 is improved. Therefore, the tire 1 of this embodiment can improve noise performance and durability.

[0043] In order to effectively exert the above-mentioned effects, the loss tangent tanδ of the inner tread rubber 13B at 30°C is preferably set to 0.15 or less. By setting the loss tangent tanδ of the inner tread rubber 13B at 30°C to 0.15 or less, heat generation in the inner tread rubber 13B during running is further suppressed. This reduces the heat storage capacity of the tread rubber 13, improving the durability of the tread portion 2. From this perspective, the loss tangent tanδ of the inner tread rubber 13B at 30°C is preferably 0.13 or less.

[0044] Furthermore, the loss tangent tanδ of the inner tread rubber 13B at 30° C. is preferably set to, for example, 0.10 or more, which prevents deformation of the inner tread rubber 13B during running from becoming smaller than necessary, thereby maintaining steering stability.

[0045] On the other hand, the loss tangent tanδ of the outer tread rubber 13A at 30° C. can be set appropriately as long as it is larger than the loss tangent tanδ of the inner tread rubber at 30° C. In order to improve steering stability, the loss tangent tanδ of the outer tread rubber 13A of the present embodiment at 30° C. can be set to, for example, 0.13 to 0.30.

[0046] An axially outer end 13Bt of the inner tread rubber 13B is preferably arranged axially more inward than a tread ground-contact edge 2t of the tread portion 2. This prevents the inner tread rubber 13B, which has a relatively small deformation (loss tangent tanδ), from being arranged on the tread ground-contact edge 2t side where ground pressure becomes relatively large during cornering, thereby increasing grip during cornering and maintaining steering stability.

[0047] Furthermore, it is preferable that the axially outer end 13Bt of the inner tread rubber 13B is arranged axially more inward than the axially outer end 14t of the noise damper 14. This prevents the axially occupying area of ​​the inner tread rubber 13B relative to the noise damper 14 from becoming larger than necessary, and steering stability can be maintained.

[0048] The maximum axial width W2 of the inner tread rubber 13B is preferably set to 70% to 90% of the maximum axial width W1 of the noise damper 14. By setting the maximum width W2 of the inner tread rubber 13B to 90% or less of the maximum width W1 of the noise damper 14, the area occupied by the inner tread rubber 13B is prevented from becoming larger than necessary, and steering stability is maintained. On the other hand, by setting the maximum width W2 of the inner tread rubber 13B to 70% or more of the maximum width W1 of the noise damper 14, the heat storage capacity of the tread rubber 13 is prevented from increasing, and the durability of the tread portion 2 is improved. From this perspective, the maximum width W2 of the inner tread rubber 13B is preferably 85% or less of the maximum width W1 of the noise damper 14, and more preferably 75% or more.

[0049] The maximum thickness T2 of the inner tread rubber 13B (maximum thickness in the tire radial direction) is preferably set to 20% or less of the maximum thickness T3 of the tread rubber 13 (maximum thickness in the tire radial direction). This prevents the proportion of the inner tread rubber 13B in the entire tread rubber 13 from becoming larger than necessary, thereby maintaining steering stability. On the other hand, the maximum thickness T2 of the inner tread rubber 13B is preferably set to 8% or more of the maximum thickness T3 of the tread rubber 13. This prevents the heat storage capacity of the tread rubber 13 from increasing, improving the durability of the tread portion 2. From this perspective, the maximum thickness T2 of the inner tread rubber 13B is preferably 15% or less, and more preferably 10% or more, of the maximum thickness T3 of the tread rubber 13.

[0050] In this embodiment, the loss tangent tanδ of the inner tread rubber 13B at 30°C is set to be smaller than the loss tangent tanδ of the intermediate tread rubber 13C at 30°C. As a result, the inner tread rubber 13B is less likely to generate heat from the start of running compared to the intermediate tread rubber 13C. Therefore, the inner tread rubber 13B is subjected to heat from the sound damper 14 that generates heat while running, and heat accumulation in the tread rubber 13 is suppressed, improving durability.

[0051] The loss tangent tanδ of the intermediate tread rubber 13C at 30°C is preferably set to be larger than the loss tangent tanδ of the outer tread rubber 13A at 30°C. As a result, of the outer tread rubber 13A, inner tread rubber 13B, and intermediate tread rubber 13C that constitute the tread rubber 13, the loss tangent tanδ of the intermediate tread rubber 13C at 30°C is set to be the largest, and the amount of heat generated in the outer tread rubber 13A is suppressed. This suppresses the transfer of heat from the sound damper 14 to the tread rubber 13, improving the durability of the tread portion 2. In order to effectively exert this effect, the loss tangent tanδ of the intermediate tread rubber 13C at 30°C is set to be 0.20 to 0.40, for example.

[0052] [Pneumatic tire (second embodiment)] In the tread rubber 13 of the embodiments described above, an embodiment has been described in which the intermediate tread rubber 13C is included between the outer tread rubber 13A and the inner tread rubber 13B, but the present invention is not limited to such an embodiment. For example, the intermediate tread rubber 13C may be omitted. In such a tire 1, similar to the tire 1 of the embodiments described above, the loss tangent tanδ of the inner tread rubber 13B at 30°C is set to be smaller than the loss tangent tanδ of the outer tread rubber 13A at 30°C. This prevents the heat storage capacity of the tread rubber 13 from increasing, and improves the durability of the tread portion 2.

[0053] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the illustrated embodiments and can be modified and implemented in various forms. [Example]

[0054] The pneumatic tires shown in Fig. 1 were prototyped (Examples 1 to 8) based on the specifications in Table 1. For comparison, a tire was prototyped in which the loss tangent tanδ of the inner tread rubber at 30°C was the same as the loss tangent tanδ of the outer tread rubber at 30°C (Comparative Example).

[0055] Each prototype tire was evaluated for durability, noise performance, and handling stability. The specifications of each tire were the same except for the configuration shown in Table 1, and the tire sizes, etc. were as follows. The test methods were also as follows. The test results are shown in Table 1. Tire size: 225 / 65R17 102H Rim size: 17 x 5.5J Internal pressure: 230kPa Vehicle: Passenger car (engine displacement 2000cc) Tread width TW: 180mm Maximum tread rubber thickness T3: 11.5mm Inner tread rubber: Maximum width W2 / Maximum width W1 of sound damper: 90% Maximum thickness T2 / Maximum thickness of tread rubber T3: 10% Position of the outer edge of the tire in the axial direction: Axially inside the tread edge Outer tread rubber: Loss tangent tanδ at 30°C: 0.20 Intermediate tread rubber: Loss tangent tanδ at 30°C: 0.30

[0056] <Durability (high speed durability)> Each prototype tire filled to the above internal pressure was run under a load of 6.67 kN in a drum running tester, and the speed was increased by 10 km / h every 10 minutes from 80 km / h, and the running time until damage to the tire occurred was measured. The evaluation is expressed as an index, with the running time of Example 1 set to 100. The larger the value, the better the durability (high-speed durability). A rating of 80 or higher indicates good durability.

[0057] <Noise performance> A vehicle fitted with each prototype tire under the above conditions was driven on a dry test course (travel speed: 30 km / h), and the noise (external noise) generated by the prototype tire was evaluated by sensory evaluation. The evaluation was based on a score of 100 for Example 1. The higher the score, the better the performance. A score of 80 or higher indicates good noise performance.

[0058] <Handling stability> A vehicle fitted with each prototype tire under the above conditions was driven on a dry test course (driving speed: 40-80 km / h), and the handling stability (responsiveness, stiffness, grip, stability, and transient characteristics) was evaluated by the test driver's senses. The evaluation was expressed as a score based on Example 1 being 100, with the higher the score, the better the performance. A score of 80 or higher satisfied the performance required of the vehicle.

[0059] [Table 1]

[0060] The test results showed that Examples 1 to 8 had improved noise performance and durability (good overall evaluation) compared to the comparative examples. Furthermore, Examples with good loss tangent tanδ of the inner tread rubber, ratio of the maximum width W1 of the noise damper to the tread ground contact width TW, and maximum thickness T1 of the noise damper had a well-balanced improvement in noise performance and durability, and also improved handling stability compared to the other Examples.

[0061] [Example B] The pneumatic tires shown in FIG. 1 were prototyped based on the specifications in Table 2 (Examples 9 to 14). Each prototype tire was evaluated for durability, noise performance, and steering stability. The specifications of each tire were the same except for the configurations listed in Table 2, and the tire size and other factors were the same as those of Example A, except as noted below. The test method was also the same as that of Example A. The test results are shown in Table 2. Sound damping body: Maximum width W1 / tread width TW: 80% Maximum thickness T1: 50mm Inner tread rubber: Loss tangent tanδ at 30°C: 0.15 Outer tread rubber: Loss tangent tanδ at 30°C: 0.20 Intermediate tread rubber: Loss tangent tanδ at 30°C: 0.30

[0062] [Table 2]

[0063] The test results showed that Examples 9 to 14 were able to improve noise performance and durability (achieve a good overall evaluation) compared to the comparative examples in Table 1. Furthermore, for the inner tread rubber, Examples with good ratios of the maximum width W2 to the maximum width W1 of the sound damper, the position of the outer edge, and the ratio of the maximum thickness T2 to the maximum thickness T3 of the tread rubber showed well-balanced improvements in noise performance and durability, and also improved handling stability, compared to the other Examples.

[0064] [Note] The present disclosure includes the following aspects.

[0065] [Disclosure 1] A pneumatic tire having a tread portion, a tread rubber disposed in the tread portion; a noise damper fixed to the tire cavity surface of the tread portion and made of a porous material, The tread rubber is An outer tread rubber that forms the tread contact surface; an inner tread rubber disposed radially inward of the outer tread rubber and radially outward of the noise damper, a loss tangent tanδ of the inner tread rubber at 30°C is smaller than a loss tangent tanδ of the outer tread rubber at 30°C; Pneumatic tires. [Disclosure 2] The pneumatic tire according to Disclosure 1, wherein an axially outer end of the inner tread rubber is disposed axially more inward than an axially outer end of the noise damper. [Disclosure 3] The pneumatic tire according to Disclosure 2, wherein the maximum axial width of the inner tread rubber is 70% to 90% of the maximum axial width of the noise damper. [Disclosure 4] The pneumatic tire according to any one of Disclosures 1 to 3, wherein an outer end of the inner tread rubber in the tire axial direction is disposed axially more inward than a ground-contact edge of the tread portion. [Disclosure 5] The pneumatic tire according to any one of Disclosures 1 to 4, wherein the maximum thickness of the inner tread rubber is 20% or less of the maximum thickness of the tread rubber. [Disclosure 6] The pneumatic tire according to any one of Disclosures 1 to 5, wherein the inner tread rubber has a loss tangent tanδ at 30° C. of 0.15 or less. [Disclosure 7] The tread rubber includes an intermediate tread rubber between the outer tread rubber and the inner tread rubber, The pneumatic tire according to any one of Disclosures 1 to 6, wherein the loss tangent tanδ at 30°C of the intermediate tread rubber is greater than the loss tangent tanδ at 30°C of the outer tread rubber. [Disclosure 8] The pneumatic tire according to any one of Disclosures 1 to 7, wherein the maximum width of the noise damper in the tire axial direction is 70% to 95% of the tread ground contact width. [Disclosure 9] The pneumatic tire according to any one of Disclosures 1 to 8, wherein the maximum thickness of the noise damper is 70 mm or less. [Explanation of symbols]

[0066] 1 pneumatic tire 2 Tread section 2S tread contact surface 9 Tire cavity surface 13 Tread rubber 13A Outer tread rubber 13B inner tread rubber 14 Sound damping body

Claims

1. A pneumatic tire having a tread portion, a tread rubber disposed in the tread portion; a noise damper fixed to the tire cavity surface of the tread portion and made of a porous material, The tread rubber is An outer tread rubber that forms the tread contact surface; an inner tread rubber disposed radially inward of the outer tread rubber and radially outward of the noise damper, a loss tangent tanδ of the inner tread rubber at 30°C is smaller than a loss tangent tanδ of the outer tread rubber at 30°C, an outer end of the inner tread rubber in the tire axial direction is disposed axially more inward than a tread ground-contact edge of the tread portion, The maximum thickness of the inner tread rubber is 20% or less of the maximum thickness of the tread rubber. Pneumatic tires.

2. A pneumatic tire having a tread portion, a tread rubber disposed in the tread portion; a noise damper fixed to the tire cavity surface of the tread portion and made of a porous material, The tread rubber is An outer tread rubber that forms the tread contact surface; an inner tread rubber disposed radially inward of the outer tread rubber and radially outward of the noise damper; an intermediate tread rubber between the outer tread rubber and the inner tread rubber; a loss tangent tanδ of the inner tread rubber at 30°C is smaller than a loss tangent tanδ of the outer tread rubber at 30°C, an outer end of the inner tread rubber in the tire axial direction is disposed axially more inward than a tread ground-contact edge of the tread portion, The loss tangent tanδ of the intermediate tread rubber at 30°C is greater than the loss tangent tanδ of the outer tread rubber at 30°C. Pneumatic tires.

3. A pneumatic tire as described in claim 1 or 2, wherein the axially outer end of the inner tread rubber is positioned axially more inward than the axially outer end of the sound-damping body.

4. A pneumatic tire as described in claim 3, wherein the maximum axial width of the inner tread rubber is 70% to 90% of the maximum axial width of the sound-damping body.

5. A pneumatic tire as described in any one of claims 1 to 4, wherein the loss tangent tanδ of the inner tread rubber at 30°C is 0.15 or less.

6. A pneumatic tire as described in any one of claims 1 to 5, wherein the maximum width of the sound-damping body in the tire axial direction is 70% to 95% of the tread contact width.

7. A pneumatic tire described in any one of claims 1 to 6, wherein the maximum thickness of the sound-damping body is 70 mm or less.

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