pneumatic tires

Abstract

To provide a pneumatic tire that can suppress a sound control body from coming off from a tire inner cavity face over a long term.SOLUTION: The pneumatic tire includes a tire inner cavity face 1i. A sound control body 10 in a porous shape is tightly fastened to the tire inner cavity face 1i through an immobilizing layer 11. Hardness Ga of the sound control body 10 and hardness Gb of the immobilizing layer 11 satisfy the following formula (1): |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≤10 (1).SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Patent Document 1 below proposes a pneumatic tire in which a porous noise-damping body is fixed to the inner surface of the tread portion. This pneumatic tire is expected to suppress running noise by the noise-damping body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-142503 Summary of the Invention [Problem to be solved by the invention]

[0004] In the pneumatic tire as described above, the noise damper tends to peel off from the tire cavity surface as the tire is driven, and an improvement has been desired.

[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 prevent noise-damping material from peeling off from the tire inner cavity surface over a long period of time. [Means for solving the problem]

[0006] The present invention is a pneumatic tire including a tire cavity surface, wherein a porous noise damper is fixed to the tire cavity surface via a fixing layer, and a hardness Ga of the noise damper and a hardness Gb of the fixing layer satisfy the following formula (1): |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦10 …(1)

[0007] The pneumatic tire of the present invention preferably satisfies the following formula (2). |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦5 …(2)

[0008] The pneumatic tire of the present invention preferably satisfies the following formula (3). |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦1 …(3)

[0009] The noise damper of the pneumatic tire of the present invention has a width W1 in the tire axial direction, and the width W1 / the hardness Gb is 1.1×10 -4 It is desirable that this is the case.

[0010] In the pneumatic tire of the present invention, the width W1 / the hardness Gb is 1.5×10 -4 It is desirable that this is the case.

[0011] In the pneumatic tire of the present invention, the fixing layer has a width W2 in the tire axial direction, and the width W2 / the hardness Ga is 1.1×10 -4 It is desirable that this is the case.

[0012] In the pneumatic tire of the present invention, the width W2 / the hardness Ga is 1.5×10 -4 It is desirable that this is the case.

[0013] In the pneumatic tire of the present invention, the hardness Ga is preferably greater than the hardness Gb.

[0014] In the pneumatic tire of the present invention, the difference between the hardness Ga and the hardness Gb is 1.0 × 10 4 It is desirable that it is smaller than (Pa).

[0015] In the pneumatic tire of the present invention, it is desirable that the outer peripheral surface of the noise damper in the tire radial direction includes a first portion fixed to the tire cavity surface via the fixation layer, and a second portion not fixed to the tire cavity surface.

[0016] In the pneumatic tire of the present invention, it is desirable that the total area S1 of the first portions be smaller than the total area S2 of the second portions.

[0017] In the pneumatic tire of the present invention, it is desirable that the total area S1 of the first portion / the hardness Gb is 0.3 or more.

[0018] In the pneumatic tire of the present invention, it is preferable that the fixing layer includes a central portion in the tire axial direction and end portions in the tire axial direction that are thicker than the central portion.

[0019] The pneumatic tire of the present invention preferably has a belt layer disposed in the tread portion, and the axially outer end of the fixing layer is disposed axially more inward than the axially outer end of the belt layer.

[0020] In the pneumatic tire of the present invention, it is desirable that the fixation layer has a width W2 in the tire axial direction, the belt layer has a width W3 in the tire axial direction, and the width W2, the width W3 and the hardness Ga satisfy the following formula (4). (W3-W2) / Ga<1.0×10 -4 …(4)

[0021] In the pneumatic tire of the present invention, the noise damper is fixed to the tread portion, and when assembled into a normal rim and in a normal unloaded state with the normal internal pressure filled, the axial width W1 of the noise damper is preferably smaller than the radial distance from the bead base line to the maximum width position on the inner surface of the sidewall portion. [Effects of the Invention]

[0022] By adopting the above-described configuration, the pneumatic tire of the present invention can suppress separation of the noise damper from the tire cavity surface for a long period of time. [Brief explanation of the drawings]

[0023] [Figure 1]1 is a tire meridian cross-sectional view showing one embodiment of a pneumatic tire of the present invention. [Figure 2] FIG. 2 is an enlarged view of the tread portion of FIG. [Figure 3] FIG. 4 is an enlarged view of a tread portion of another embodiment 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. Fig. 1 is a tire meridian cross-sectional view of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 in a normal state, showing one embodiment of the present invention. In this embodiment, a pneumatic tire 1 for passenger cars is shown as a preferred aspect. However, the present invention may also be adopted as a pneumatic tire 1 for motorcycles or heavy loads, for example.

[0025] The "normal condition" refers to a state in which, in the case of a pneumatic tire for which various standards are established, the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal condition refers to a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0026] 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."

[0027] "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. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0028] As shown in Fig. 1, conventional tire components such as a carcass 6 and a belt layer 7 are arranged inside a tire 1 of this embodiment. Known embodiments can be appropriately adopted for these tire components.

[0029] The carcass 6 extends from the bead portion 4 on one side through the sidewall portion 3 on one side, the tread portion 2, and the sidewall portion 3 on the other side to the bead portion 4 on the other side. The carcass 6 also has at least one carcass ply 6A, two in this embodiment. The carcass ply 6A is formed, for example, by covering an array of carcass cords with a topping rubber. The carcass cords are arranged, for example, at an angle of 75 to 90° relative to the tire circumferential direction. The carcass cords are made of organic fibers such as polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

[0030] The carcass ply 6A includes, for example, a main body portion 6a and a turned-up portion 6b. The main body portion extends from the tread portion 2 through the sidewall portion 3 to the bead cores 5. The turned-up portion 6b is continuous with the main body portion 6a and is turned around the bead cores 5 from the axially inner side to the outer side, extending radially outward in the tire direction.

[0031] The belt layer 7 is disposed radially outward of the carcass 6 in the tread portion 2. The belt layer 7 includes at least one belt ply, and the belt layer 7 in this embodiment is composed of two belt plies 7A and 7B. The belt plies 7A and 7B are formed, for example, by covering an arrangement of belt cords with a topping rubber.

[0032] Fig. 2 shows an enlarged view of the tread portion 2. As shown in Fig. 2, a porous noise-damping body 10 is fixed to the tire cavity surface 1i of the tread portion 2 via a fixing layer 11. This noise-damping body 10 can absorb air vibrations inside the tire while it is running, and helps to reduce noise generated by the tire. Note that in Fig. 2, the fixing layer 11 is drawn thicker than it actually is to make the invention easier to understand.

[0033] The noise damper 10 has a hardness Ga. The immobilizing layer 11 has a hardness Gb. In this specification, the hardnesses Ga and Gb respectively refer to the storage modulus of each member, and can be measured, for example, by a method specified in the JIS K7244 standard.

[0034] In this embodiment, the hardness Ga and Gb are measured using a 1 mm thick sample of each member. The measurement method involves placing the sample between parallel plates of an ARES (manufactured by TA Instruments) equipped with 7.9 mm diameter parallel plates, heating the sample to 50°C, and then confirming that the normal force has stabilized. The storage modulus is then measured under conditions of a temperature of 30°C, an angular frequency of 10 Hz, and a dynamic strain of ±2%.

[0035] If it is difficult to collect a sample of 1 mm thickness from the immobilization layer 11, the sample may be prepared by collecting and stacking small pieces of the immobilization layer 11 that can be collected.

[0036] In the present invention, the hardness Ga of the noise damper 10 and the hardness Gb of the fixing layer 11 satisfy the following formula (1). As a result, in the present invention, peeling of the noise damper 10 from the tire cavity surface 1i can be suppressed for a long period of time. The following mechanism is presumed to be the reason for this. |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦10 …(1)

[0037] In conventional pneumatic tires with noise dampers, the noise dampers, which are made of a relatively soft material such as urethane foam, are often fixed to the tire cavity surface via a fixing layer made of a curing adhesive. This type of configuration has the problem of the noise dampers being prone to peeling. This is thought to be because the large difference in hardness between the noise dampers and the fixing layer causes stress concentration between the noise dampers and the fixing layer.

[0038] For this reason, in order to suppress the above-mentioned problems, it is considered desirable to reduce the difference in hardness between the sound damper and the fixing layer. Meanwhile, various materials can be used for the sound damper and the fixing layer. The fixing layer may be a cured adhesive or an adhesive tape. Furthermore, the sound damper 10 is porous, absorbing air vibrations. For this reason, there has been a problem in that it is difficult to uniquely define the difference in hardness between the sound damper and the fixing layer.

[0039] As a result of extensive research, the inventors discovered that the difference in hardness between noise damper 10 and fixing layer 11 can be uniquely defined by the above formula (1), and have thus completed the present invention. In the present invention, when the difference between the hardness Ga of noise damper 10 and the hardness Gb of fixing layer 11 satisfies the above formula (1), stress concentration is less likely to occur between noise damper 10 and fixing layer 11, and it is thought that peeling of noise damper 10 can be suppressed.

[0040] The following describes the configuration of this embodiment in more detail. Each of the configurations described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even if it does not include the configurations described below. Even if any one of the configurations described below is applied alone to a tire of the present invention having the above-described characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, an improvement in combined performance corresponding to each configuration can be expected. The dimensions of each part described below refer to the dimensions when the tire is not mounted on a rim, the distance between two bead cores 5 (shown in FIG. 1) is the same as in the normal state, and there is no load.

[0041] To further enhance the above-mentioned effect, the hardness Ga of the noise damper 10 and the hardness Gb of the immobilization layer 11 preferably satisfy the following formula (2), and more preferably satisfy the following formula (3). |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦5 …(2) |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦1 …(3)

[0042] 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 (EPDM sponge), and nitrile rubber sponge (NBR sponge) can be suitably used as the sound damper 10. Among these, polyurethane sponges including ether-based polyurethane sponges are preferred from the viewpoints of sound damping properties, light weight, foam adjustability, durability, etc.

[0043] The width W1 of the noise damper 10 in the tire axial direction is, for example, 60 to 100 mm, and preferably 70 to 90 mm. The thickness of the noise damper 10 is, for example, 25 to 50 mm, and preferably 30 to 40 mm. However, the noise damper 10 is not limited to these dimensions.

[0044] In this embodiment, in the normal state, the width W1 of the noise damper 10 in the tire axial direction is smaller than the distance h1 in the tire radial direction from the bead base line to the maximum width position on the inner surface of the sidewall portion 3. The bead base line is a line in the tire axial direction that passes through the rim diameter position determined by the tire standard.

[0045] As a result of various experiments, the inventors have found that the noise reduction effect of the noise damper 10 can be sufficiently exhibited even when the width W1 of the noise damper 10 is smaller than the distance h1 in the tire radial direction. In this embodiment, by specifying the width W1 of the noise damper 10 to be smaller than the distance h1 in the tire radial direction, it is possible to sufficiently reduce noise while minimizing the increase in tire weight due to the noise damper 10.

[0046] From the viewpoint of improving noise performance while suppressing an increase in tire weight, the width W1 of the noise damper 10 is preferably 70% or more of the tire radial distance h1, more preferably 75% or more, and even more preferably 80% or more, and is preferably 95% or less, and more preferably 90% or less.

[0047] The hardness Ga of the sound damper 10 is, for example, 3.0 × 10 3 (Pa) ~ 5.0 × 10 7 (Pa). Such a noise damper 10 can be manufactured by a known method. However, the hardness Ga of the noise damper 10 is not limited to this range.

[0048] The immobilizing layer 11 in this embodiment is made of a cured adhesive. However, the present invention is not limited to this, and the immobilizing layer 11 may be made of a pressure-sensitive adhesive having adhesive properties. The immobilizing layer 11 may also be made of double-sided tape.

[0049] Examples of adhesives and adhesives that can be used for the immobilization layer 11 include inorganic adhesives (adhesives) and organic adhesives (adhesives). Examples of inorganic adhesives (adhesives) include sodium silicate, cement, ceramics, etc. Examples of organic adhesives (adhesives) include natural and synthetic adhesives (adhesives) (thermoplastic resins, thermosetting resins, elastomers, etc.). Examples of natural pressure-sensitive adhesives (adhesives) include starch-based, protein-based, natural rubber-based, and asphalt-based. Examples of thermoplastic resins include vinyl acetate resins, polyvinyl acetal-based, ethylene vinyl acetate resins, vinyl chloride resins, acrylic resins (acrylic acid esters such as butyl acrylate), polyamides, cellulose-based, and α-olefin-based. Examples of thermosetting resins include urea resins, melamine resins, phenolic resins, resorcinol resins, epoxy resins, structural acrylic resins, polyesters, and polyaromatic resins. Examples of elastomers include chloroprene-based, nitrile rubber-based, styrene butadiene rubber-based, polysulfide-based, butyl rubber-based, silicone rubber-based, acrylic rubber-based, modified silicone rubber-based, urethane rubber-based, silylated urethane resin-based, telechelic polyacrylate-based, and cyanoacrylate-based.

[0050] The double-sided tape that can be used for the immobilization layer 11 includes a sheet-like substrate and an adhesive attached to both sides of the substrate. Suitable substrates include, for example, plastic films such as polyethylene, polypropylene, polyvinyl chloride, and polyester (e.g., polyethylene terephthalate), rayon, pulp, synthetic fibers, woven fabrics, nonwoven fabrics, cotton fabrics, acrylates, plastic foam sheets (e.g., acrylic foam using a foaming agent), and metals (e.g., aluminum and copper). The adhesives described above can be used.

[0051] The hardness Gb of the immobilization layer 11 is, for example, 3.0×10 3 (Pa) ~ 2.0 × 10 7 (Pa). Such immobilization layer 11 can be manufactured by a known method. However, the hardness Gb of immobilization layer 11 is not limited to this range.

[0052] In the present invention, as long as the above formula (1) is satisfied, it does not matter which of the hardness Ga and the hardness Gb is larger. That is, the hardness Ga may be larger than the hardness Gb, or the hardness Ga may be smaller than the hardness Gb.

[0053] The difference between the hardness Ga and the hardness Gb is 1.0 × 10 4 (Pa) or less is desirable, and 0.5×10 4 (Pa)The following are available.

[0054] In this embodiment, the axially outer end of the fixing layer 11 is preferably arranged axially more inward than the axially outer end of the belt layer 7. This allows the noise damper 10 to be included in a region obtained by virtually extending the belt layer 7 radially inward, making the noise damper 10 less likely to peel off.

[0055] In this embodiment, the width W2 of the fixing layer 11 in the tire axial direction is the same as the width W1 of the outer peripheral surface 10o of the noise damper 10 in the tire axial direction. This prevents the fixing layer 11 from being exposed to the tire cavity surface 1i, preventing dust and the like from adhering to it. However, the width W2 of the fixing layer 11 in the tire axial direction may be larger than the width W1 of the outer peripheral surface 10o of the noise damper 10 in the tire axial direction, for example. This embodiment makes it easier to fix the noise damper 10 to the tire cavity surface 1i during tire manufacturing.

[0056] In this embodiment, the entire outer peripheral surface 10o of the noise damper 10 in the tire radial direction is fixed to the tire cavity surface 1i via the fixing layer 11. This ensures that the noise damper 10 is fixed securely.

[0057] In this embodiment, regarding the width W1 (mm) of the sound damper 10 and the hardness Gb (Pa) of the fixing layer 11, the width W1 / hardness Gb (mm / Pa) is preferably 1.1×10 -4 More preferably, 1.5 x 10 -4 or more, and preferably 3.0 × 10 -2 Less than or equal to 5.0×10-3 This allows the width of the noise damper 10 to be secured appropriately, suppressing the above-mentioned peeling and exhibiting excellent noise performance.

[0058] From the same viewpoint, regarding the width W2 (mm) of the immobilization layer 11 and the hardness Ga (Pa) of the sound damper 10, the ratio of the width W2 / the hardness Ga (mm / Pa) is preferably 1.1×10 -4 More preferably, 1.5 x 10 -4 or more, and preferably 3.0 × 10 -2 Less than or equal to 5.0×10 -3 The following is the result.

[0059] As a more desirable aspect, in this embodiment, the width W2 (mm) of the fixation layer 11, the width W3 (mm) of the belt layer 7 in the tire axial direction, and the hardness Ga (Pa) of the noise damper 10 satisfy the following formula (4). This ensures a sufficient width for the fixation layer 11, and reliably suppresses peeling of the noise damper 10. (W3-W2) / Ga<1.0×10 -4 …(4)

[0060] The fixation layer 11 in this embodiment has, for example, a constant thickness over the entire surface. This makes it difficult for stress concentration to occur, further suppressing peeling of the noise damper 10. In other embodiments, the fixation layer 11 may have a thickness that varies in the axial direction of the tire. In this case, it is desirable that the fixation layer 11 include a central portion in the axial direction of the tire and end portions in the axial direction that are thicker than the central portion. Since the tread portion 2 is more deformed in portions that are farther from the tire equator C, peeling of the noise damper 10 can be further suppressed by increasing the thickness of the end portions of the fixation layer 11.

[0061] 3 shows an enlarged cross-sectional view of a tread portion 2 of another embodiment of the present invention. In this embodiment, the outer peripheral surface 10o in the tire radial direction of the noise damper 10 includes a first portion 16 that is fixed to the tire cavity surface 1i via the fixing layer 11, and a second portion 17 that is not fixed to the tire cavity surface 1i. This embodiment can reduce the volume of the fixing layer 11 to suppress an increase in tire weight, and can maintain heat dissipation properties on the tire cavity surface 1i side of the tread portion 2.

[0062] The first portions 16 are located at least at both axial end portions of the noise damper 10. In a more desirable embodiment, the first portions 16 are also located at the axial center portion of the noise damper 10. This allows the noise damper 10 to be reliably fixed while still achieving the above-described effects.

[0063] To make the noise damper 10 less likely to peel off, the first portion 16 extends continuously around the entire circumference of the tire. However, the present invention is not limited to this configuration, and the first portions 16 may be spaced apart in the tire circumferential direction. This can further suppress an increase in tire weight.

[0064] The total area S1 of the first portions 16 is 10% to 40% of the total area of ​​the outer peripheral surface 10o of the noise damper 10 in the tire radial direction. The total area S1 of the first portions 16 is desirably smaller than the total area S2 of the second portions 17. The ratio S1 / S2 of the total areas S1 and S2 is, for example, 0.2 to 0.6. This makes it possible to suppress peeling of the noise damper 10 while maintaining the tire weight.

[0065] In this embodiment, the total area S1 (mm 2 ) and the hardness Gb (Pa), the total area S1 / the hardness Gb (mm 2 / Pa) is preferably 0.3 or more, more preferably 3.0 or more, and is preferably 40.0 or less, more preferably 30.0 or less. This makes the total area S1 of the first portions 16 appropriate, suppressing an increase in tire weight and further reliably suppressing peeling of the noise damper 10.

[0066] The fixing layer 11 of this embodiment includes a central portion 21 in the tire axial direction and end portions 22 in the tire axial direction. In this embodiment, these portions have a constant thickness. However, this is not limited to this, and for example, the thickness of the end portions 22 may be greater than the thickness of the central portion 21. In this case, the thickness of the end portions 22 is, for example, 105% to 120% of the thickness of the central portion 21. This further suppresses peeling of the noise damper 10 from the end portions in the tire axial direction.

[0067] Although the pneumatic tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and implemented in various aspects. [Example]

[0068] Pneumatic tires having the basic structure of FIG. 1 and a size of 215 / 55R17 were manufactured based on the specifications of Tables 1 and 2. In addition, pneumatic tires not satisfying formula (1) were manufactured as comparative examples 1 to 5. The comparative example tires were substantially the same as the example tires except for the above-mentioned points. In addition, in comparative examples 1 to 5 and each example, the width W1 of the noise damper in the tire axial direction was approximately 90% of the distance h1 in the tire radial direction from the bead base line to the maximum width position on the inner cavity surface of the sidewall portion. These test tires were tested for the peeling resistance of the noise damper. The common specifications and test methods for each test tire are as follows: Rim: 17 x 7.5J Tire pressure: 250kPa The radial distance h1 from the bead base line to the maximum width position is 62.7 mm Width of sound damper in tire axial direction W1 = 56.4 mm Width of the fixing layer in the tire axial direction W2 = 56.4 mm Width of belt layer in tire axial direction W3 = 164.7 mm Outer surface area of ​​the sound damper = 109810.8 mm 2

[0069] <Sound-damping body peeling resistance> The test tire was run at a constant speed under a constant vertical load on a drum testing machine with multiple protrusions on the running surface, and the running distance until the noise damper peeled off was measured. The results are shown as an index, with the running distance of Comparative Example 1 set to 100, and the larger the index value, the better the durability of the noise damper. The test results are shown in Tables 1-2.

[0070] [Table 1]

[0071] [Table 2]

[0072] As shown in Tables 1 and 2, it was confirmed that the tires of the examples prevented the noise damper from peeling off from the tire cavity surface for a long period of time. [Explanation of symbols]

[0073] 1i Tire cavity surface 10 Sound damping body 11 Immobilization layer Ga Hardness of sound damper Gb Hardness of the immobilized layer

Claims

1. A pneumatic tire including a tire cavity surface, a porous noise-damping body is fixed to the tire cavity surface via a fixing layer, The hardness Ga of the noise damper and the hardness Gb of the immobilization layer satisfy the following formula (1): Pneumatic tires. |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦10...(1)

2. The pneumatic tire according to claim 1, which satisfies the following formula (2): |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦5...(2)

3. The pneumatic tire according to claim 1, which satisfies the following formula (3): |(Ga-Gb) / Ga+(Gb-Ga) / Gb|≦1...(3)

4. The noise damper has a width W1 in the tire axial direction, The width W1 / hardness Gb is 1.1×10 －４ The pneumatic tire according to any one of claims 1 to 3, wherein:

5. The width W1 / the hardness Gb is 1.5×10 －４ The pneumatic tire according to claim 4 .

6. The fixing layer has a width W2 in the tire axial direction, The width W2 / hardness Ga is 1.1×10 －４ The pneumatic tire according to any one of claims 1 to 5, wherein

7. The width W2 / hardness Ga is 1.5×10 －４ The pneumatic tire according to claim 6 .

8. The pneumatic tire according to claim 1 , wherein the hardness Ga is greater than the hardness Gb.

9. The difference between the hardness Ga and the hardness Gb is 1.0 × 10 ４ The pneumatic tire according to any one of claims 1 to 7, wherein the axial load is smaller than 100 Pa.

10. 10. The pneumatic tire according to claim 1, wherein an outer peripheral surface of the noise damper in the tire radial direction includes a first portion fixed to the tire cavity surface via the fixing layer, and a second portion not fixed to the tire cavity surface.

11. The pneumatic tire according to claim 10 , wherein a total area S1 of the first portions is smaller than a total area S2 of the second portions.

12. The pneumatic tire according to claim 10 or 11, wherein a ratio of the total area S1 of the first portion to the hardness Gb is 0.3 or more.

13. The pneumatic tire according to claim 1 , wherein the fixing layer includes a central portion in an axial direction of the tire and end portions in the axial direction of the tire that are thicker than the central portion.

14. A belt layer is arranged in the tread part, The pneumatic tire according to claim 1 , wherein an outer end of the fixing layer in the tire axial direction is disposed axially more inward than an outer end of the belt layer in the tire axial direction.

15. The fixing layer has a width W2 in the tire axial direction, The belt layer has a width W3 in the tire axial direction, The pneumatic tire according to claim 14, wherein the width W2, the width W3, and the hardness Ga satisfy the following formula (4): (W3W2) / Ga<1.0×10 －４ …(4)

16. The noise damper is fixed to the tread portion, 16. The pneumatic tire according to claim 1, wherein, when the tire is mounted on a standard rim, inflated to a standard internal pressure, and in a normal, unloaded state, a width W1 of the noise damper in the tire axial direction is smaller than a distance in the tire radial direction from a bead baseline to a maximum width position on an inner cavity surface of a sidewall portion.

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