Pneumatic tire

Abstract

To provide a pneumatic tire which can reduce cavernous resonance with a simple configuration.SOLUTION: A pneumatic tire 1 includes a tread part 2, a pair of side wall parts 3 extending from both sides in a tire axial direction of the tread part 2 to inside in a tire radial direction, a pair of bead parts 4 positioned inside in the tire radial direction of the pair of side wall parts 3, and a plurality of Helmholts sound absorbers 9 arranged on a tire inner cavity surface 1i. The plurality of Helmholts sound absorbers 9 includes a first sound absorber 9A having a first resonance frequency f1, and a second sound absorber 9B having a second resonance frequency f2 different from the first resonance frequency f1. Each of the first sound absorber 9A and the second sound absorber 9B is arranged inside in the tire axial direction of at least one of the pair of side wall parts 3 and the pair of bead parts 4.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire capable of reducing cavity resonance noise. [Background technology]

[0002] Conventionally, there are known pneumatic tires equipped with a means for reducing cavity resonance noise generated inside the tire during running. For example, the following Patent Document 1 proposes a pneumatic tire in which a large number of resonators, which are Helmholtz type sound absorbers, are attached to the inner circumferential surface of the tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6289506 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the pneumatic tire of Patent Document 1 requires a large number of Helmholtz sound absorbers with different resonance frequencies to accommodate cavity resonance noise within the tire, which varies depending on the running speed, and there was a demand for further improvement in terms of manufacturing and weight.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire capable of reducing cavity resonance noise with a simple configuration. [Means for solving the problem]

[0006] The present invention is a pneumatic tire including a tread portion, a pair of sidewall portions extending radially inward from both axial sides of the tread portion, a pair of bead portions located radially inward of the pair of sidewall portions, and a plurality of Helmholtz-type sound absorbers arranged on the tire cavity surface, wherein the plurality of Helmholtz-type sound absorbers include a first sound absorber having a first resonant frequency and a second sound absorber having a second resonant frequency different from the first resonant frequency, and the first sound absorber and the second sound absorber are each arranged axially inward of at least one of the pair of sidewall portions and the pair of bead portions. Effect of the Invention

[0007] The pneumatic tire of the present invention has the above-mentioned configuration, and thus can reduce cavity resonance noise with a simple configuration. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing one embodiment of a pneumatic tire of the present invention. [Diagram 2] 1 is a schematic cross-sectional view of a pneumatic tire as viewed from the tire axial direction. [Diagram 3] FIG. 1 is a perspective view of a Helmholtz sound absorber according to an embodiment of the present invention. [Figure 4] FIG. 11 is a perspective view of a Helmholtz sound absorber according to a second embodiment. [Diagram 5] FIG. 11 is a perspective view of a Helmholtz sound absorber according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 is a tire meridian cross-sectional view showing a pneumatic tire 1 of this embodiment in a normal state. Here, the "normal state" refers to a state in which the pneumatic tire 1 is mounted on a normal rim, and is adjusted to a normal internal pressure and unloaded. Hereinafter, unless otherwise specified, the dimensions of each part of the pneumatic tire 1 are values ​​measured in this normal state.

[0010] A "genuine rim" is a rim that is determined for each tire by a standard system that includes the standard on which the pneumatic tire 1 is based, for example, a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. If there is no standard system that includes the standard on which the pneumatic tire 1 is based, a "genuine rim" is a rim that can be assembled and does not leak air, and that has the smallest rim diameter and the smallest rim width among the rims that can be assembled and do not leak air.

[0011] "Normal internal pressure" is the air pressure set for each tire by a standard system that includes the standard on which the pneumatic tire 1 is based, such as "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. "Normal internal pressure" is the air pressure set for each tire by the manufacturer, etc., when there is no standard system that includes the standard on which the pneumatic tire 1 is based.

[0012] 1, the pneumatic tire 1 of the present embodiment is suitable for use as a passenger vehicle tire. The pneumatic tire 1 is not limited to passenger vehicle tires, and may be used as various tires, such as heavy load tires, motorcycle tires, racing vehicle tires, and industrial vehicle tires.

[0013] The pneumatic tire 1 of this embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portions 3 are, for example, portions extending radially inward from both axial sides of the tread portion 2. The bead portions 4 are, for example, portions located radially inward of the sidewall portions 3. The bead portions 4 of this embodiment are portions that come into contact with a regular rim.

[0014] Each of the pair of bead portions 4 has, for example, an annular bead core 5 extending in the tire circumferential direction, and a bead apex 8 extending from the bead core 5 outward in the tire radial direction. The bead core 5 is formed, for example, from a steel wire. The bead apex 8 is formed, for example, from a hard rubber. Since such a bead portion 4 has high rigidity, deformation during running is suppressed, which helps to reduce cavity resonance noise of the pneumatic tire 1.

[0015] The pneumatic tire 1 of this embodiment includes a carcass 6 extending between a pair of bead portions 4, and a belt layer 7 arranged in the tread portion 2. The belt layer 7 is arranged, for example, on the outer side in the tire radial direction of the carcass 6. The pneumatic tire 1 desirably includes a tire cavity surface 1i on the inner side of the carcass 6 that defines the tire cavity.

[0016] Fig. 2 is a schematic cross-sectional view of a pneumatic tire 1 as viewed from the tire axial direction. As shown in Figs. 1 and 2, the pneumatic tire 1 of this embodiment includes a plurality of Helmholtz sound absorbers 9 arranged on the tire cavity surface 1i. The plurality of Helmholtz sound absorbers 9 of this embodiment include a first sound absorber 9A having a first resonance frequency f1 and a second sound absorber 9B having a second resonance frequency f2 different from the first resonance frequency f1. By resonating with a plurality of frequencies, such a pneumatic tire 1 can reduce cavity resonance noise within the tire that varies depending on the running speed.

[0017] The first sound absorber 9A and the second sound absorber 9B of this embodiment are each disposed on the axially inner side of at least one of the sidewall portion 3 and the bead portion 4. Such a Helmholtz sound absorber 9 suppresses the fluctuation of the Helmholtz sound absorber 9 itself even when the tread portion 2 deforms when the tire touches the ground, and can suppress the resonance sound generated from the Helmholtz sound absorber 9 due to the impact when the tire touches the ground. Therefore, the pneumatic tire 1 of this embodiment can reduce cavity resonance sound with a simple configuration.

[0018] In a more preferred embodiment, the first resonance frequency f1 is a maximum resonance frequency fmax in a frequency band including the resonance frequencies f of the multiple Helmholtz sound absorbers 9. The second resonance frequency f2 in this embodiment is a minimum resonance frequency fmin in a frequency band including the resonance frequencies f of the multiple Helmholtz sound absorbers 9.

[0019] The difference (f1-f2) between the first resonance frequency f1 and the second resonance frequency f2 is preferably 10 to 90 Hz. Such a pneumatic tire 1 can efficiently reduce cavity resonance noise generated at a running speed of 10 to 200 km per hour, and the number of Helmholtz sound absorbers 9 can be reduced. Therefore, the pneumatic tire 1 of the present embodiment can reduce cavity resonance noise with a simple configuration. From this perspective, the difference (f1-f2) between the first resonance frequency f1 and the second resonance frequency f2 is more preferably 10 to 60 Hz.

[0020] The first resonance frequency f1 of the Helmholtz sound absorber 9 is preferably 130 to 350 Hz. The second resonance frequency f2 of the Helmholtz sound absorber 9 is preferably 120 to 340 Hz. Such a Helmholtz sound absorber 9 can accommodate the frequency band of cavity resonance noise generated in passenger vehicle tires, and can efficiently reduce cavity resonance noise in passenger vehicle tires.

[0021] The multiple Helmholtz sound absorbers 9 may have at least one resonance frequency f different from the first resonance frequency f1 and the second resonance frequency f2, for example. Such a Helmholtz sound absorber 9 can resonate over a wide frequency band of cavity resonance sounds, and can more reliably reduce cavity resonance sounds.

[0022] It is desirable that the unit width df, which is the difference between a pair of adjacent resonant frequencies f in a frequency band, of the multiple Helmholtz sound absorbers 9 is substantially equal. Here, "substantially equal unit widths df" means that the difference between the respective unit widths df is 10% or less of the unit width df. Such a Helmholtz sound absorber 9 can absorb sound evenly across the entire frequency band.

[0023] The multiple Helmholtz sound absorbers 9 preferably have a unit width df of 3 to 10 Hz. Such Helmholtz sound absorbers 9 can absorb sound evenly across the entire frequency band without excessively increasing the number of types.

[0024] The first sound absorber 9A and the second sound absorber 9B are desirably disposed on the axially inner side of the bead portion 4. Such a Helmholtz sound absorber 9 can more reliably reduce cavity resonance noise without causing resonance noise due to impact when the tire touches the ground.

[0025] The first sound absorber 9A and the second sound absorber 9B are arranged, for example, on the inside in the tire axial direction from the inner end 5e of the bead core 5 in the tire radial direction to the outer end 8e of the bead apex 8 in the tire radial direction. That is, each of the multiple Helmholtz sound absorbers 9 is desirably arranged within a range of height H from the inner end 5e of the bead core 5 to the outer end 8e of the bead apex 8. Since such a Helmholtz sound absorber 9 is arranged within a range having high rigidity, it is possible to more reliably reduce cavity resonance noise.

[0026] The first sound absorber 9A and the second sound absorber 9B are preferably arranged radially inward of the outer ends 6e of the carcass plies 6A, 6B even when they are arranged axially inward of the sidewall portion 3. Such a Helmholtz sound absorber 9 is useful for suppressing resonant noise generated from the Helmholtz sound absorber 9 due to impact when the tire touches the ground.

[0027] 1, the carcass 6 includes at least one, and in this embodiment, two carcass plies 6A and 6B. The two carcass plies 6A and 6B include, for example, a first carcass ply 6A located on the inner side in the tire radial direction in the tread portion 2, and a second carcass ply 6B located on the outer side in the tire radial direction of the first carcass ply 6A.

[0028] At least one of the carcass plies 6A, 6B desirably includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a turned-up portion 6b continuing to the main body portion 6a and folded back around the bead core 5 from the inner side to the outer side in the tire axial direction. The first carcass ply 6A and the second carcass ply 6B of this embodiment each include a main body portion 6a and a turned-up portion 6b. Such a carcass 6 improves the rigidity of the bead portion 4 and helps to reduce cavity resonance noise of the pneumatic tire 1.

[0029] It is desirable that at least one of the carcass plies 6A, 6B has a radially outer end 6e of the turned-up portion 6b located radially outward of the tire maximum width position P where the tire cross-sectional width W is maximum. In the carcass 6, for example, the outer end 6e of the turned-up portion 6b of the first carcass ply 6A is located radially outward of the tire maximum width position P, and the outer end 6e of the turned-up portion 6b of the second carcass ply 6B is located radially inward of the tire maximum width position P. Such a carcass 6 can achieve both rigidity and weight reduction of the sidewall portion 3, and can reduce cavity resonance noise and rolling resistance of the pneumatic tire 1.

[0030] The carcass plies 6A and 6B include carcass cords (not shown) made of, for example, organic fiber cords. Examples of the organic fiber cords include cords made of one type of fiber alone or two or more types of hybrid fibers selected from the group consisting of polyethylene terephthalate fiber, polyethylene naphthalate fiber, nylon fiber, aramid fiber, and rayon fiber.

[0031] The carcass cords are preferably arranged at an angle of 25 to 90° with respect to the tire circumferential direction. When the carcass cords are inclined at an angle of less than 90° with respect to the tire circumferential direction, it is desirable that the carcass cords of the first carcass ply 6A and the carcass cords of the second carcass ply 6B are inclined in opposite directions with respect to the tire circumferential direction. For example, a bias structure may be adopted for the carcass 6. Here, the angle of the carcass cords is the angle in the pneumatic tire 1 in a normal state, and can be confirmed, for example, by partially peeling off the tread portion 2.

[0032] The belt layer 7 includes at least one, preferably two or more, and in this embodiment, two belt plies 7A and 7B. The two belt plies 7A and 7B include, for example, a first belt ply 7A located on the inner side in the tire radial direction and a second belt ply 7B located on the outer side of the first belt ply 7A. The outer end 7e of the belt layer 7 in this embodiment is the outer end 7e of the first belt ply 7A in the tire axial direction. Such a belt layer 7 can improve the rigidity of the tread portion 2 and reduce cavity resonance noise of the pneumatic tire 1.

[0033] The belt plies 7A and 7B each include a belt cord (not shown) made of, for example, a steel cord. The belt cord may be, for example, a steel solid wire or a twisted wire made by twisting together a plurality of steel filaments.

[0034] The belt cords are arranged at an angle of, for example, 10 to 30° with respect to the tire circumferential direction. The belt cords of the first belt ply 7A and the belt cords of the second belt ply 7B are desirably inclined in opposite directions with respect to the tire circumferential direction. Such a belt layer 7 can increase the rigidity of the tread portion 2 in a well-balanced manner and reduce cavity resonance noise of the pneumatic tire 1. Here, the angle of the belt cords is the angle in the pneumatic tire 1 in a normal state, and can be confirmed, for example, by partially peeling off the tread portion 2.

[0035] The tread portion 2 of this embodiment has a ground contact surface 2s extending between a pair of tread ends Te. Here, the tread end Te is the axially outermost ground contact position when the pneumatic tire 1 in a normal state is subjected to a load of 70% of the normal load and contacts a flat surface with a camber angle of 0°. The ground contact surface 2s has a tire tread width TW, which is the distance in the tire axial direction between the pair of tread ends Te. The central position in the tire axial direction between the pair of tread ends Te is the tire equator C.

[0036] The "normal load" is the load determined for each tire by a standard system that includes the standard on which the pneumatic tire 1 is based, such as the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "LOAD CAPACITY" for ETRTO. If there is no standard system that includes the standard on which the pneumatic tire 1 is based, the "normal load" is the load determined for each tire by the manufacturer, etc. as the maximum load that can be applied when using the pneumatic tire 1.

[0037] In this embodiment, the outer end 7e of the belt layer 7 is located axially outward of the tread end Te. Such a belt layer 7 can improve the rigidity of the entire ground contact surface 2s of the tread portion 2, and is useful for reducing cavity resonance noise of the pneumatic tire 1.

[0038] As shown in Figures 1 and 2, it is preferable that the multiple Helmholtz sound absorbers 9 are arranged spaced apart from each other. The first sound absorber 9A and the second sound absorber 9B are arranged, for example, spaced apart in the tire circumferential direction. It is preferable that the multiple Helmholtz sound absorbers 9 are provided such that the same first sound absorber 9A or second sound absorber 9B are provided at positions opposing each other in the tire axial direction. Such a pneumatic Helmholtz sound absorber 9 of this embodiment can reduce cavity resonance noise over the entire area of ​​the pneumatic tire 1.

[0039] The multiple Helmholtz sound absorbers 9 of this embodiment include multiple first sound absorbers 9A and multiple second sound absorbers 9B. It is preferable that the first sound absorbers 9A and the second sound absorbers 9B are provided in even numbers in each row arranged in the tire circumferential direction. Such Helmholtz sound absorbers 9 facilitate adjustment of balance during tire rotation. Note that, although the multiple Helmholtz sound absorbers 9 of this embodiment are illustrated as being arranged in two rows, the multiple Helmholtz sound absorbers 9 may be arranged in only one row on one side in the tire axial direction, or in multiple rows in the tire radial direction.

[0040] A pair of first sound absorbers 9A provided in each row are disposed, for example, at positions facing each other across the tire rotation axis. A pair of second sound absorbers 9B provided in each row are disposed, for example, at positions facing each other across the tire rotation axis. Such a Helmholtz sound absorber 9 has excellent balance during tire rotation and can suppress the generation of vibrations and noise when the pneumatic tire 1 is running.

[0041] Fig. 3 is a perspective view of a Helmholtz sound absorber 9 of this embodiment. As shown in Fig. 3, the Helmholtz sound absorber 9 includes a sound absorbing chamber 9a having a space therein, and a tube portion 9b connecting the sound absorbing chamber 9a to the tire cavity. Such a Helmholtz sound absorber 9 can have different resonance frequencies f by adjusting the volume of the sound absorbing chamber 9a and the length of the tube portion 9b.

[0042] The first sound absorber 9A of this embodiment includes a first sound absorbing chamber 9a having a first resonant frequency f1. Although not shown, the second sound absorber 9B includes, for example, a second sound absorbing chamber 9c having a second resonant frequency f2.

[0043] The first sound absorber 9A and the second sound absorber 9B are desirably made of a resin that does not change shape at temperatures below 120° C. Such a Helmholtz sound absorber 9 is capable of maintaining its sound absorbing performance without changing shape even when the pneumatic tire 1 becomes hot during high-speed driving.

[0044] Examples of materials for the Helmholtz sound absorber 9 include polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polyamide (PA), polycarbonate (PC), polyphenylene sulfide (PPS), polyimide (PI), polyetherimide (PEI), polysulfone (PSF), polysulfone (PSU), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyamideimide (PAI), phenolic resin (PF), melamine resin (MF), unsaturated polyester (UP), polyurethane (PU), polydiallyl phthalate (PDAP), silicone resin (SI), epoxy resin (EP), furan-formaldehyde resin (FF), cellulose acetate (CA), cellulose nitrate (CN), cellulose propionate (CP), and ethyl cellulose (EC).

[0045] Fig. 4 is a perspective view of a Helmholtz sound absorber 10 of a second embodiment. As shown in Fig. 4, each of the multiple Helmholtz sound absorbers 10 may include, for example, a hemispherical sound absorbing chamber 10a and a tubular portion 10b extending along the sound absorbing chamber 10a. Such a Helmholtz sound absorber 10 can absorb cavity resonance sounds in a tire cavity in a well-balanced manner by adjusting the orientation of the tubular portion 10b.

[0046] Fig. 5 is a perspective view of a Helmholtz sound absorber 11 according to a third embodiment. As shown in Fig. 5, each of the multiple Helmholtz sound absorbers 11 may include, for example, at least one first sound absorbing chamber 11a having a first resonance frequency f1 and at least one second sound absorbing chamber 11c having a second resonance frequency f2. Such a Helmholtz sound absorber 11 can have multiple resonance frequencies f per Helmholtz sound absorber 11. Therefore, the Helmholtz sound absorber 11 according to the third embodiment can reduce cavity resonance sound with a simple configuration.

[0047] It is desirable that the first sound absorber 11A having the first sound absorbing chamber 11a and the second sound absorber 11B having the second sound absorbing chamber 11b are integrally formed with each other. Such a Helmholtz sound absorber 11 can reduce cavity resonance sounds over a wide frequency range while reducing the number of parts.

[0048] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment and can be modified in various ways. EXAMPLES

[0049] 1 to 3, a pneumatic tire of the embodiment having a tire size of 215 / 55R17 was prototyped based on the specifications in Table 1. As Comparative Example 1, a pneumatic tire of the same size without a Helmholtz type sound absorber was prototyped, and as Comparative Example 2, a pneumatic tire in which a Helmholtz type sound absorber was disposed on the radially inner side of the contact surface was prototyped. Noise performance at different running speeds was tested using the prototype pneumatic tires.

[0050] <Noise performance> The prototype pneumatic tire was mounted on a bench test machine, and the axial force was measured when the tire was run at speeds of 20 km / h, 60 km / h, and 150 km / h, and the sound pressures of the low and high frequency sides of the cavity resonance sound were determined. The results are shown as an index with Comparative Example 1 set at 100, and the smaller the value, the smaller the sound pressure and the more excellent the noise performance.

[0051] The results of the tests are shown in Table 1. [Table 1]

[0052] As a result of the test, it was confirmed that the pneumatic tire of the embodiment had superior noise performance at all running speeds compared to the comparative example, and that the cavity resonance noise can be reduced with a simple configuration.

[0053] [Note] The present invention is as follows.

[0054] [Invention 1] A pneumatic tire, The tire includes a tread portion, a pair of sidewall portions extending radially inward from both axial sides of the tread portion, a pair of bead portions positioned radially inward of the pair of sidewall portions, and a plurality of Helmholtz sound absorbers disposed on a tire cavity surface, the plurality of Helmholtz sound absorbers include a first sound absorber having a first resonant frequency and a second sound absorber having a second resonant frequency different from the first resonant frequency; the first sound absorber and the second sound absorber are each disposed on an inner side in the tire axial direction of at least one of the pair of sidewall portions and the pair of bead portions; Pneumatic tires.

[0055] [Invention 2] The pneumatic tire according to claim 1, wherein the first sound absorber and the second sound absorber are disposed on inner sides of the pair of bead portions in the tire axial direction.

[0056] [Invention 3] Each of the pair of bead portions has an annular bead core extending in a tire circumferential direction and a bead apex extending from the bead core outward in a tire radial direction, The pneumatic tire according to claim 1 or 2, wherein the first sound absorber and the second sound absorber are arranged on the inside in the tire axial direction from the radially inner end of the bead core to the radially outer end of the bead apex.

[0057] [Invention 4] The pneumatic tire according to any one of claims 1 to 3, wherein the first sound absorber and the second sound absorber are made of a resin that does not change shape at 120°C or lower.

[0058] [Invention 5] the first resonant frequency is a maximum resonant frequency in a frequency band; 5. The pneumatic tire according to any one of claims 1 to 4, wherein the second resonant frequency is a minimum resonant frequency in a frequency band.

[0059] [Invention 6] The first resonant frequency is 130 to 350 Hz, 6. The pneumatic tire according to claim 5, wherein the second resonance frequency is 120 to 340 Hz.

[0060] [Invention 7] The pneumatic tire according to any one of claims 1 to 6, wherein the plurality of Helmholtz sound absorbers have at least one resonant frequency different from the first resonant frequency and the second resonant frequency.

[0061] [Invention 8] The pneumatic tire according to invention 7, wherein the plurality of Helmholtz sound absorbers have a substantially equal unit width, which is the difference between the resonant frequencies of a pair of adjacent ones of the Helmholtz sound absorbers in a frequency band.

[0062] [The present invention 9] 9. The pneumatic tire according to invention 8, wherein the unit width is 3 to 10 Hz. [Explanation of symbols]

[0063] 1. Pneumatic tires 1i Tire inner cavity surface 2 Tread section 3 Sidewall 4 Bead section 9. Helmholtz Sound Absorber 9A 1st sound absorber 9B 2nd sound absorber

Claims

1. A pneumatic tire, The tire includes a tread portion, a pair of sidewall portions extending radially inward from both axial sides of the tread portion, a pair of bead portions positioned radially inward of the pair of sidewall portions, and a plurality of Helmholtz sound absorbers disposed on a tire cavity surface, the plurality of Helmholtz sound absorbers include a first sound absorber having a first resonant frequency and a second sound absorber having a second resonant frequency different from the first resonant frequency; the first sound absorber and the second sound absorber are each disposed on an inner side in the tire axial direction of at least one of the pair of sidewall portions and the pair of bead portions; Pneumatic tires.

2. The pneumatic tire according to claim 1 , wherein the first sound absorber and the second sound absorber are disposed on inner sides of the pair of bead portions in the tire axial direction.

3. Each of the pair of bead portions has an annular bead core extending in a tire circumferential direction and a bead apex extending from the bead core outward in a tire radial direction, The pneumatic tire according to claim 1 , wherein the first sound absorber and the second sound absorber are arranged on the inside in the tire axial direction from an inner end of the bead core in the tire radial direction to an outer end of the bead apex in the tire radial direction.

4. The pneumatic tire according to claim 1 , wherein the first sound absorber and the second sound absorber are made of a resin that does not change shape at 120° C. or lower.

5. the first resonant frequency is a maximum resonant frequency in a frequency band; The pneumatic tire of claim 1 , wherein the second resonant frequency is a minimum resonant frequency in a frequency band.

6. the first resonant frequency is 130 to 350 Hz; The pneumatic tire according to claim 5, wherein the second resonant frequency is 120 to 340 Hz.

7. The pneumatic tire according to claim 1 , wherein the plurality of Helmholtz sound absorbers have at least one resonant frequency different from the first resonant frequency and the second resonant frequency.

8. The pneumatic tire according to claim 7 , wherein the plurality of Helmholtz sound absorbers have a unit width, which is a difference between a pair of the resonant frequencies adjacent to each other in a frequency band, that is substantially equal to each other.

9. The pneumatic tire according to claim 8, wherein the unit width is 3 to 10 Hz.

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