Pneumatic tire and sound deadening body

Abstract

The present invention provides a pneumatic tire capable of suppressing deterioration of puncture maintainability of a puncture service kit while suppressing road noise and the like. The present invention provides a pneumatic tire capable of performing tire burst maintenance by injecting a tire burst sealant. The pneumatic tire has a pneumatic tire main body 1A defining a tire inner tube 1B, and a silencer 10 disposed in the tire inner tube 1B. The silencing body (10) has a first porous layer (11) disposed on the inner tread side of the tread portion (2) of the pneumatic tire main body (1A), and a second porous layer (12) disposed on the inner side of the first porous layer (11) in the tire radial direction. The air permeability of the first porous layer (11) is greater than the air permeability of the second porous layer (12).

Description

Technical Field

[0001] The present invention relates to a pneumatic tire and a sound absorber. Background Art

[0002] In Patent Document 1 below, a pneumatic tire is proposed in which a porous sound absorber is fixed to the inner surface of the tread portion. The pneumatic tire can suppress road noise and the like by the sound absorber. Prior Art Documents Patent Documents

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2022-069984 Summary of the Invention Problems to be Solved by the Invention

[0004] In recent years, a puncture repair kit that can inject a puncture sealant into the inner tube of a pneumatic tire to plug a puncture hole when the pneumatic tire is punctured has become popular. In addition, in vehicles, the case of replacing a spare tire with the puncture repair kit is also increasing.

[0005] However, when repairing a pneumatic tire equipped with the sound absorber using a puncture repair kit, there is a case where the sound absorber hinders the inflow of the puncture sealant into the puncture hole in the tread portion, resulting in deterioration of puncture repairability such as an increase in the time required to plug the puncture hole.

[0006] In view of the above actual situation, the present invention is proposed, and the main object is to provide a pneumatic tire that can suppress deterioration of puncture repairability of a puncture repair kit while suppressing road noise and the like. Means for Solving the Problems

[0007] The present invention is a tire that can be repaired by injecting a puncture sealant, which has a pneumatic tire body that defines an inner tube of the tire and a sound absorber disposed in the inner tube of the tire. The sound absorber has a first porous layer disposed on the inner tube surface side of the tread portion of the pneumatic tire body and a second porous layer disposed radially inside the tire of the first porous layer, and the air permeability of the first porous layer is greater than the air permeability of the second porous layer. Effects of the Invention

[0008] By adopting the above structure, the pneumatic tire of the present invention can suppress deterioration of puncture repairability of a puncture repair kit while suppressing road noise and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A tire meridian sectional view of an embodiment of the pneumatic tire of the present invention. Figure 2 A schematic diagram of a puncture repair kit. Figure 3 ​​​​Figure 1 Enlarged cross-sectional view of the sound deadening body.

Figure 4

Figure 5

[0010] Hereinafter, an embodiment of the present invention will be described based on the drawings. Although the features of the present invention are described in the drawings, for the purpose of facilitating the understanding of the present invention, the drawings sometimes include exaggerated expressions or expressions different from the actual structural size ratio. In addition, in each embodiment, the same or common elements are denoted by the same reference numerals, and repeated descriptions are omitted.

[0011] Figure 1 It is a cross-sectional view of the tire meridian in the normal state of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 showing an embodiment of the present invention. In addition, Figure 1 It shows a cross-sectional view of the tire 1 when the annularly extending tire 1 passes through the tire rotation axis and is cut by a virtual plane orthogonal to the tire circumferential direction. As Figure 1 shown, this embodiment is a pneumatic tire 1 for a passenger car. However, the present invention can also be applied to, for example, a pneumatic tire 1 for heavy loads.

[0012] The so-called "normal state", in the case of a pneumatic tire with various specified specifications, refers to the state where the tire is mounted on a normal rim, filled with a normal internal pressure, and has no load. In the case of a tire without various specified specifications, the normal state refers to the standard use state corresponding to the use purpose of the tire, not mounted on a vehicle and having no load. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the above-mentioned normal state.

[0013] For the "normal rim", in the specification system including the specifications on which the tire is based, it refers to the rim specified for each tire by the specification. For example, in JATMA, it refers to the "standard rim", in TRA, it refers to the "Design Rim", and in ETRTO, it refers to the "Measuring Rim".

[0014] For "normal internal pressure", in the specification system including the specifications on which the tire is based, it refers to the air pressure specified for each tire by this specification, "maximum air pressure" in JATMA, the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and "INFLATION PRESSURE" in ETRTO.

[0015] The tire 1 of the present embodiment is a pneumatic tire that can be repaired for a flat tire by injecting a flat tire sealant. Therefore, the tire 1 of the present embodiment can be mounted on a vehicle equipped with a flat tire repair kit containing a flat tire sealant. In Figure 2 a schematic view of the flat tire repair kit 20 is shown. Additionally, in Figure 2 the flat tire repair kit 20 is depicted as being larger than its actual size compared to the tire 1. The flat tire repair kit 20 has a container unit 21 containing a flat tire sealant and a compressor 22 capable of supplying high-pressure air. The container unit 21 is preferably used by being mounted on the compressor 22. The flat tire repair kit 20 repairs a flat tire by injecting the flat tire sealant through the valve of the flat tire. The flat tire sealant injected into the tire interior solidifies when passing through the flat tire hole and blocks it.

[0016] Therefore, as Figure 1 shown, the tread surface portion 2 of the tire 1 of the present embodiment has a corresponding degree of rigidity such that even when driving after flat tire repair, the blocked flat tire hole does not open again. Specifically, it at least includes a carcass 6 and a belt layer 7 described below.

[0017] The carcass 6 extends from a bead portion 4 on one side through a sidewall portion 3 on one side, the tread surface portion 2, the sidewall portion 3 on the other side to the bead portion 4 on the other side. Additionally, the carcass 6 has at least 1 layer of carcass ply, which is 2 layers of carcass ply 6A in the present embodiment. The carcass ply 6A is formed, for example, by covering an arrangement of carcass cords with skim coat. The carcass cords are arranged, for example, at an angle of 75 to 90° with respect to the tire circumferential direction. The carcass cords can be applicable to, for example, organic fibers such as polyester fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber.

[0018] The carcass ply 6A includes, for example, a main body portion 6a and a folded-back portion 6b. The main body portion passes from the tread surface portion 2 through the sidewall portion 3 to the bead core 5. The folded-back portion 6b is connected to the main body portion 6a and extends radially outward of the tire by folding back from the inner side to the outer side of the tire axial direction around the bead core 5.

[0019] The belt layer 7 is disposed on the tread portion 2 on the radially outer side of the carcass 6 of the tire. The belt layer 7 includes at least one belt ply, and the belt layer 7 of the present 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 skim coat.

[0020] The tire 1 of the present invention has a pneumatic tire body 1A that defines an inner tube 1B of the tire, and a sound absorber 10 disposed in the inner tube 1B of the tire. The sound absorber 10 can absorb the air vibration inside the tire 1 during driving, thereby suppressing road noise generated by the tire and the like.

[0021] On the other hand, in the prior art, when repairing a pneumatic tire equipped with a sound absorber using a flat tire repair kit, there is a case where the sound absorber hinders the flat tire sealant from flowing into the flat tire hole in the tread portion, resulting in deterioration of flat tire repairability such as an increase in the time required to block the flat tire hole.

[0022] Figure 3 It is an enlarged cross-sectional view of the sound absorber 10. Figure 4 It is a partially enlarged perspective view schematically showing the outer surface state of the sound absorber 10. As Figure 3 and Figure 4 shown, in the present invention, the sound absorber 10 has a first porous layer 11 disposed on the inner tread side of the tread portion 2 ( Figure 1 shown) of the pneumatic tire body 1A, and a second porous layer 12 disposed on the radially inner side of the first porous layer 11. In addition, the air permeability of the first porous layer 11 is greater than the air permeability of the second porous layer 12.

[0023] Therefore, in the tire 1 of the present invention, when repairing a flat tire with the flat tire repair kit, the flat tire sealant can easily reach the flat tire hole through the first porous layer 11, and defects such as an increase in the time required for the flat tire sealant to block the flat tire hole can be prevented. Therefore, the tire 1 of the present invention can suppress deterioration of flat tire repairability of the flat tire repair kit while suppressing road noise and the like through the sound absorber 10.

[0024] The more detailed structure of the present embodiment will be described below. In addition, each structure described below shows a specific mode of the present embodiment. Therefore, the present invention can exhibit the above-described effects even without the structures described below. In addition, for the tire of the present invention having the above-described features, even if only any one of the structures described below is applied alone, an improvement in performance corresponding to each structure can be expected. In addition, when several of the structures described below are applied in combination, an improvement in composite performance corresponding to each structure can be expected.

[0025] In addition, unless otherwise specified, the dimensions of the sound deadening body 10 described below are measured in a state where the tire 1 is not mounted on the rim, the distance between a pair of bead cores 5 is in the normal state, and the sound deadening body 10 is disposed in the tire inner tube 1B.

[0026] As Figure 1 shown, the sound deadening body 10 has, for example, a horizontally long rectangular cross-section in the tire axial direction and continuously extends in the tire circumferential direction. In addition, the entire sound deadening body 10 is made of a porous sponge material and, in the present embodiment, is composed only of the first porous layer 11 and the second porous layer 12. However, the sound deadening body 10 may also have layers other than the first porous layer 11 and the second porous layer 12. The sponge material is, for example, a material having continuous air bubbles formed by foaming rubber or synthetic resin.

[0027] The average density of the sound deadening body 10 is, for example, 5 to 60 kg / m 3 , preferably 20 to 40 kg / m 3 . In addition, the first porous layer 11 and the second porous layer 12 each have a continuous air bubble structure in which ether structures and ester bonds are mixed. Such a sound deadening body 10 has excellent durability and can exhibit high sound absorption performance.

[0028] The cross-sectional area of the sound deadening body 10 is preferably 3% to 20% of the total cross-sectional area of the pneumatic tire body 1A and the tire inner tube 1B. Thereby, while suppressing an excessive increase in the tire weight, excellent noise performance can be exhibited. In addition, the total cross-sectional area represents the area of a region surrounded by a virtual line 15 connecting the radially inner ends of the two bead portions 4 and the inner tube surface 1Bs defining the tire inner tube 1B.

[0029] As Figure 3 shown, the average thickness ta of the sound deadening body 10 is, for example, 25 to 35 mm. The length L1 of the sound deadening body 10 in the tire axial direction is, for example, 50 to 150 mm. In addition, the average thickness ta is measured in a hypothetical state where all the fine units (air holes) contained in the porous sound deadening body 10 are filled, and corresponds to the result obtained by dividing the cross-sectional area of the sound deadening body 10 by its length L1 in the tire axial direction. The thicknesses of the first porous layer 11 and the second porous layer 12 described later are also the same.

[0030] The air permeability of the first porous layer 11 and the second porous layer 12 is determined by the magnitude of the air permeability measured in accordance with JIS K6400-7. That is, in the present invention, the air permeability of the first porous layer 11 is greater than the air permeability of the second porous layer 12.

[0031] The air permeability V1 of the first porous layer 11 measured in accordance with JIS K6400-7 is preferably, for example, 62 ml / cm 2 / s or more. From the perspective of more effectively suppressing the deterioration of puncture repairability, the air permeability V1 is more preferably 100 ml / cm 2 / s or more, and further preferably 200 ml / cm 2 / s or more. However, if the air permeability V1 is excessively increased, the permeability of the puncture sealant will saturate. On the other hand, the durability of the first porous layer 11 may be damaged. From this perspective, the air permeability V1 is, for example, 300 ml / cm 2 / s or less, preferably 250 ml / cm 2 / s or less, and further preferably 220 ml / cm 2 / s or less.

[0032] When the tire 1 is in use, the first porous layer 11 has a tendency to be compressed radially outward of the tire. At this time, from the perspective of fully exerting the above-mentioned effects, the hardness H1 at 25% compression load of the first porous layer 11 measured according to JIS K6400-2 D method is, for example, 1.1 kPa or more, preferably 1.9 kPa or more, and more preferably 2.9 kPa or more. However, if the hardness H1 is too large, other problems such as an increase in tire weight may occur. From this perspective, the hardness H1 is preferably 3.5 kPa or less.

[0033] The number of pores N1 (pieces / 25 mm) of the first porous layer 11 is, for example, 30 ± 4 or less, preferably 20 ± 4 or less, and more preferably 8 ± 2 or less. The number of pores is measured according to JIS-K6400. In addition, the average thickness t1 of the first porous layer 11 is, for example, 2 to 10 mm. By having the above-mentioned number of pores N1 and thickness t1, the first porous layer 11 alone can be composed of a sponge material with a roughness that can transmit visible light (that is, the degree that the other side can be seen).

[0034] As Figure 1 shown, the sound absorber 10 has a contact surface 10s that contacts the pneumatic tire body 1A. At least 30% or more, preferably 60% or more, and more preferably 80% or more of the contact surface 10s is formed by the first porous layer 11. As a more preferred mode, in this embodiment, the entire contact surface 10s is formed by the first porous layer 11. Thereby, the deterioration of puncture repairability can be more effectively suppressed.

[0035] As Figure 3 shown, the first porous layer 11 is fixed to the second porous layer 12. The first porous layer 11 and the second porous layer 12 can be bonded by an adhesive, or can be bonded by heat fusion (bonding by melting the sponge material with heat) without using an adhesive.

[0036] From the perspective of enabling the second porous layer 12 to exhibit sound absorption performance, the air permeability V2 of the second porous layer 12 measured in accordance with JIS K6400-7 is, for example, less than 100 ml / cm 2 / s, preferably less than 80 ml / cm 2 / s, more preferably less than 70 ml / cm 2 / s, still more preferably less than 62 ml / cm 2 / s. Additionally, if the above-mentioned air permeability V2 is too small, the second porous layer 12 may reflect sound waves and impair the sound absorption performance. From this perspective, the air permeability V2 is, for example, 2 ml / cm 2 / s or more, preferably 5 ml / cm 2 / s or more, more preferably 10 ml / cm 2 / s or more, still more preferably 20 ml / cm 2 / s or more.

[0037] The number of pores N2 (per 25 mm) of the second porous layer 12 is, for example, 50 ± 5 or more, preferably 55 ± 10 or more. Additionally, the average thickness t2 of the second porous layer 12 is, for example, 5 mm or more, preferably 15 to 30 mm. By having the above-mentioned number of pores N2 and thickness t2, the single second porous layer 12 can be composed of a sponge material with a roughness such that at least visible light cannot pass through (i.e., the other side cannot be seen).

[0038] Figure 5 is a schematic view of the side of the tire 1. In Figure 5 the outer surface of the sound absorber 10 and the boundary between the first porous layer 11 and the second porous layer 12 are shown by dashed lines. As Figure 5 shown, the sound absorber 10 of the present embodiment is a ring structure, and this ring structure includes a first end 10a in the tire circumferential direction, a second end 10b in the tire circumferential direction, and a fixing portion 13 that fixes the first end 10a and the second end 10b. Additionally, in Figure 5 the fixing portion 13 is marked with small dots. Such a sound absorber 10 can suppress wear of the ends of the sound absorber 10 due to contact with the rim or the like, and excellent durability can be obtained.

[0039] The first end 10a and the second end 10b are fixed, for example, by an adhesive. In another embodiment, the first end 10a and the second end 10b can be welded.

[0040] In this embodiment, preferably, by slightly compressing the ring-shaped sound absorber 10 and disposing it in the tire inner tube 1B ( Figure 1 shown), the sound absorber 10 will not locally lift from the pneumatic tire main body 1A. Thereby, contact between the sound absorber 10 and the rim or the like can be prevented, and the durability of the sound absorber 10 can be improved. Additionally, the first porous layer 11 of the sound absorber 10 (Figure 3 Preferably, it is not fixed to the pneumatic tire body 1A. Thus, for example, in the formal vehicle repair after an emergency flat tire repair, it is possible to easily replace the sound absorber 10 that has penetrated the flat tire sealant.

[0041] From the viewpoint of realizing the above-described manner, in the natural state where the fixing between the first end 10a and the second end 10b of the sound absorber 10 is released and it extends linearly on a plane, the maximum length of the sound absorber 10 from the first end 10a to the second end 10b is preferably 94% to 107% of the maximum circumference of the tire inner tube 1B ( Figure 1 shown). In addition, the maximum circumference of the tire inner tube 1B means the maximum length in the tire circumferential direction on the inner surface of the pneumatic tire body 1A. In the present embodiment where the tread surface 2 bulges and bends outward in the tire direction, the circumferential length of the circle formed by the intersection of the inner surface of the pneumatic tire body 1A and the tire equatorial plane corresponds to the above-described maximum circumference.

[0042] The pneumatic tire and the like of one embodiment of the present invention have been described in detail above, but the present invention is not limited to the above-described specific embodiments, and various modifications can be made. Examples

[0043] Manufacture a pneumatic tire having a Figure 1 basic structure and having a size of 215 / 55R17 based on the specifications in Table 1. In addition, as a comparative example, a pneumatic tire having a porous layer with an air permeability of 42 ml / cm 2 / s for the entire sound absorber was trial-produced. Except for the above matters, the tires of the comparative example are substantially the same as those of the example. The flat tire reparability and sound absorption performance of these test tires were evaluated. The general specifications and test methods of each test tire are as follows. Mounting rim: 17×7.5J Tire internal pressure: 250 kPa Material of the sound absorber: Polyurethane Axial length L1 of the sound absorber in the tire: 100 mm Thickness ta of the sound absorber = 30 mm

[0044] <Flat tire reparability> After forming a flat tire hole with a diameter of 4 mm in the circumferential groove at the center of the tread of the test tire, 400 ml of flat tire sealant was immediately injected into the tire inner tube. Then, the tire internal pressure was adjusted to 200 kPa, and the tire was run on a drum test machine under the conditions of a load of 4.6 kN and a running speed of 30 km / h. In addition, every 1 minute, it was confirmed whether the flat tire hole was blocked, and the time until the flat tire hole was completely blocked was measured. The results are expressed as an index with Example 1 being 100, and the smaller the value, the shorter the time from the injection of the flat tire sealant to the blocking of the flat tire hole, and the better the flat tire reparability.

[0045] <Sound absorption performance> The test tire is installed on all the wheels of a vehicle (2000 cc displacement, FF vehicle). The in-vehicle noise when driving on an asphalt road at a speed of 60 km / h is collected by a microphone set at the ear position on the driver's seat window side. In addition, the sound pressure level of the peak value of the cavity resonance sound in the narrowband region near 220 Hz in the in-vehicle noise is measured. The result is expressed as the reduction value of the sound pressure level relative to the tire without the sound absorber, and a value of 70 or more is the qualified level. The test results are shown in Table 1.

[0046]

Table 1

[0047] As shown in Table 1, the sound absorption performance of the comparative example and each example is 90 - 100 points, and it can be understood that road noise and the like are sufficiently suppressed. On the other hand, the puncture repairability of the comparative example is 400 points, and the time required to block the puncture hole becomes longer, but the puncture repairability of each example is 67 - 233 points, and it is confirmed that the puncture repairability is significantly improved.

[0048] [Note] The present invention includes the following embodiments.

[0049] [Invention 1] A tire that can be repaired for a puncture by injecting a puncture sealant, which has a pneumatic tire body defining an inner tube of the tire and a sound absorber disposed in the inner tube of the tire, the sound absorber has a first porous layer disposed on the inner tube surface side of the tread surface of the pneumatic tire body and a second porous layer disposed radially inside the tire of the first porous layer, the air permeability of the first porous layer is greater than the air permeability of the second porous layer. [Invention 2] The pneumatic tire according to Invention 1, wherein the air permeability of the first porous layer measured according to JIS K6400 - 7 is 62 ml / cm 2 / s or more. [Invention 3] The pneumatic tire according to Invention 1 or 2, wherein the hardness at 25% compressive load of the first porous layer measured according to JIS K6400 - 2 D method is 1.1 kPa or more. [Invention 4] The pneumatic tire according to any one of Inventions 1 to 3, wherein the sound absorber has a contact surface with the pneumatic tire body, the entire contact surface is formed of the first porous layer. [Inflatable tire according to the present invention 5] The pneumatic tire according to any one of claims 1 to 4 of the present invention, wherein the average thickness of the first porous layer is 2 to 10 mm. [Inflatable tire according to the present invention 6] The pneumatic tire according to any one of claims 1 to 5 of the present invention, wherein the first porous layer is fixed to the second porous layer. [Inflatable tire according to the present invention 7] The pneumatic tire according to any one of claims 1 to 6 of the present invention, wherein the sound absorber is composed only of the first porous layer and the second porous layer. [Inflatable tire according to the present invention 8] The pneumatic tire according to any one of claims 1 to 7 of the present invention, wherein the average thickness of the second porous layer is 5 mm or more. [Inflatable tire according to the present invention 9] The pneumatic tire according to any one of claims 1 to 8 of the present invention, wherein the sound absorber is a ring structure, and the ring structure includes a first end in the tire circumferential direction, a second end in the tire circumferential direction, and a fixing portion for fixing the first end and the second end. [Inflatable tire according to the present invention 10] The pneumatic tire according to any one of claims 1 to 9 of the present invention, wherein the first porous layer is not fixed to the pneumatic tire main body. [Inflatable tire according to the present invention 11] The pneumatic tire according to any one of claims 1 to 10 of the present invention, wherein the average density of the sound absorber is 5 to 60 kg / m 3 . [Inflatable tire according to the present invention 12] The pneumatic tire according to any one of claims 1 to 11 of the present invention, wherein the first porous layer and the second porous layer are each a continuous bubble structure in which an ether structure and an ester bond are mixed. [Inflatable tire according to the present invention 13] The pneumatic tire according to any one of claims 1 to 12 of the present invention, wherein the cross-sectional area of the sound absorber is 3% to 20% of the total cross-sectional area of the pneumatic tire main body and the tire inner tube. [Inflatable tire according to the present invention 14] A sound absorber for being disposed in a tire inner tube of a pneumatic tire, The sound absorber has a first porous layer disposed on the inner tube surface side of the tread portion of the pneumatic tire and a second porous layer disposed more radially inward of the tire than the first porous layer, The air permeability of the first porous layer is greater than the air permeability of the second porous layer.

Claims

1. A pneumatic tire that can be repaired from a flat tire by injecting a flat tire sealant. It has a pneumatic tire body that defines the inner tube of the tire and a sound-absorbing body disposed in the inner tube of the tire. The sound-absorbing body has a first porous layer disposed on the inner tube surface side of the tread surface of the pneumatic tire body and a second porous layer disposed on the radially inner side of the tire of the first porous layer. The air permeability of the first porous layer is greater than the air permeability of the second porous layer.

2. The pneumatic tire according to claim 1, wherein, The air permeability of the first porous layer measured according to JIS K6400-7 is 62 ml / cm 2 / s or more.

3. The pneumatic tire according to claim 1, wherein, The air permeability of the first porous layer measured according to JIS K6400-7 is 300 ml / cm 2 / s or less.

4. The pneumatic tire according to claim 1, wherein, The air permeability of the first porous layer measured according to JIS K6400-7 is 100 ml / cm 2 / s to 220 ml / cm 2 / s.

5. The pneumatic tire according to claim 1, wherein, The air permeability of the second porous layer measured according to JIS K6400-7 is less than 100 ml / cm 2 / s.

6. The pneumatic tire according to claim 1, wherein, The air permeability of the second porous layer measured according to JIS K6400-7 is 2 ml / cm 2 / s or more.

7. The pneumatic tire according to claim 1, wherein, The air permeability of the second porous layer measured according to JIS K6400-7 is 20 ml / cm 2 / s to 62 ml / cm 2 / s.

8. The pneumatic tire according to claim 1 or 2, wherein, The hardness of the first porous layer at a 25% compression load measured according to JIS K6400-2 D method is 1.1 kPa or more.

9. The pneumatic tire according to claim 1 or 2, wherein, The hardness of the first porous layer at a 25% compression load measured according to JIS K6400-2 D method is 3.5 kPa or less.

10. The pneumatic tire according to claim 1 or 2, wherein, The sound-absorbing body has a contact surface with the pneumatic tire body. The entire contact surface is formed by the first porous layer.

11. The pneumatic tire according to claim 1 or 2, wherein, The average thickness of the first porous layer is 2 to 10 mm.

12. The pneumatic tire according to claim 1 or 2, wherein, The first porous layer is fixed to the second porous layer.

13. The pneumatic tire according to claim 1 or 2, wherein, The sound-absorbing body is composed only of the first porous layer and the second porous layer.

14. The pneumatic tire according to claim 1 or 2, wherein, The average thickness of the second porous layer is 5 mm or more.

15. The pneumatic tire according to claim 1 or 2, wherein, The average thickness of the second porous layer is 15 to 30 mm.

16. The pneumatic tire according to claim 1 or 2, wherein, The sound-absorbing body is a ring structure that includes a first end in the tire circumferential direction, a second end in the tire circumferential direction, and a fixing portion that fixes the first end and the second end.

17. The pneumatic tire according to claim 1 or 2, wherein, The first porous layer is not fixed to the pneumatic tire body.

18. The pneumatic tire according to claim 1 or 2, wherein, The average density of the sound-absorbing body is 5 to 60 kg / m 3 .

19. The pneumatic tire according to claim 1 or 2, wherein, The first porous layer and the second porous layer are each a continuous bubble structure mixed with an ether structure and an ester bond.

20. The pneumatic tire according to claim 1 or 2, wherein, The cross-sectional area of the sound-absorbing body is 3% to 20% of the total cross-sectional area of the pneumatic tire body and the inner tube of the tire.

21. A sound-absorbing body for being disposed in the inner tube of a pneumatic tire. The sound-absorbing body has a first porous layer disposed on the inner tube surface side of the tread surface of the pneumatic tire and a second porous layer disposed on the radially inner side of the tire than the first porous layer. The air permeability of the first porous layer is greater than the air permeability of the second porous layer.

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