Sound-absorbing structures and tires

Abstract

The present invention provides a sound-absorbing structure and a tire that can reduce resonance noise within the tire cavity. [Solution] The sound-absorbing structure 1 attached to the inner cavity 102 of the tire 101 comprises a skin 10 having through holes 11, a porous sound-absorbing body 20 housed in the skin 10, and a hollow neck portion 30 that communicates with the through holes 11 and is embedded in the porous sound-absorbing body 20. The skin 10 has a top portion 12 having through holes 11, and a side portion 13 extending from the peripheral edge of the top portion 12 to the mounting surface 2 attached to the inner cavity 102 of the tire 101.

Description

Technical Field

[0001] The present disclosure relates to a sound-absorbing structure for a tire and a tire.

Background Art

[0002] In recent years, techniques have been developed to reduce the tire cavity resonance sound generated during the running of a vehicle such as an automobile by arranging a sound-absorbing structure in the tire of the vehicle. The tire cavity resonance sound generated during the running of the vehicle as described above is in a low frequency band of, for example, about 200 Hz to 300 Hz. Patent Document 1 describes a sound-absorbing structure (sound damping body) extending in the tire circumferential direction over the entire circumference of the inner peripheral surface of the tire. This sound-absorbing structure includes a porous portion attached to the inner peripheral surface of the tire and a thin film portion laminated on the porous portion and having a plurality of holes formed therein, and the natural vibration frequency of the thin film portion is 200 Hz or more and 300 Hz or less.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the description of Patent Document 1, in the sound-absorbing structure described in Patent Document 1, the film vibration of the thin film portion is excited by the tire cavity resonance sound propagated through the tire cavity, and the film vibration of the thin film portion is converted into thermal energy, whereby the tire cavity resonance sound is reduced. Further, the tire cavity resonance sound is reduced by the friction between the hole wall surface when passing through the through holes of the thin film portion and the turbulent flow generated after passing through the through holes, and is further absorbed by being transmitted to the porous portion through the through holes. However, the effect of reducing the tire cavity resonance sound by the sound-absorbing structure described in Patent Document 1 is not always sufficient.

[0005] This disclosure aims to provide a sound-absorbing structure and a tire that can reduce resonance noise within the tire cavity. [Means for solving the problem]

[0006] The sound-absorbing structure according to this disclosure is a sound-absorbing structure attached to the inner cavity of a tire, comprising: a skin having through holes; a porous sound-absorbing body housed in the skin; and a hollow neck portion communicating with the through holes and embedded in the porous sound-absorbing body, wherein the skin has a top portion having through holes and a side portion extending from the peripheral edge of the top portion to a mounting surface attached to the inner cavity.

[0007] In this sound-absorbing structure, a hollow neck portion, which communicates with through-holes in the outer layer, is embedded in a porous sound-absorbing material housed within the outer layer. The outer layer has a top portion with through-holes and a circumferential portion extending from the periphery of the top portion to the mounting surface. As a result, the sound-absorbing structure attached to the inner cavity of the tire can function as a Helmholtz resonator. This allows the resonance sound within the tire cavity to be reduced by the resonance generated in the hollow portion of the neck, and the resonance sound within the tire cavity that has passed through the neck can be absorbed by the porous sound-absorbing material.

[0008] Other sound-absorbing structures relating to this disclosure are sound-absorbing structures attached to the inner cavity of a tire, and include a Helmholtz resonance structure that generates Helmholtz resonance at a resonance frequency within ±100 Hz of the tire cavity resonance frequency calculated from F = c / ((R+r)×π), where F is the frequency of the tire cavity resonance sound, c is high speed, R is the radius of the inner cavity of the tire, r is the radius of the rim of the wheel assembled to the tire, and π is pi.

[0009] This sound-absorbing structure incorporates a Helmholtz resonance structure that generates Helmholtz resonances at resonant frequencies within ±100 Hz of the tire cavity resonance frequency, thereby reducing tire cavity resonance noise.

[0010] In the other sound-absorbing structures described above, the Helmholtz resonance structure may include a skin having a top portion with through holes and a circumferential portion extending from the peripheral edge of the top portion, a porous sound-absorbing material covered by the skin, and a hollow neck portion communicating with the through holes in the skin and embedded in the porous sound-absorbing material. In this sound-absorbing structure, the hollow neck portion communicating with the through holes in the skin is embedded in the porous sound-absorbing material housed in the skin, and the skin has a top portion with through holes and a circumferential portion extending from the peripheral edge of the top portion to the mounting surface. Therefore, the sound-absorbing structure attached to the inner cavity of a tire can function as a Helmholtz resonator. This allows the resonance sound inside the tire cavity to be reduced by the resonance generated in the hollow portion of the neck, and the resonance sound inside the tire cavity that has passed through the neck portion can be absorbed by the porous sound-absorbing material.

[0011] At least a portion of the neck may have a section that intersects with the thickness direction of the sound-absorbing structure. In this sound-absorbing structure, having a section of the neck that intersects with the thickness direction of the sound-absorbing structure allows the neck to be made longer than the thickness of the sound-absorbing structure. This also reduces low-frequency resonance noise within the tire cavity.

[0012] The top section has a first through-hole and a second through-hole, and the neck section has a first neck section communicating with the first through-hole and a second neck section communicating with the second through-hole, and the frequencies of the Helmholtz resonance generated in the first neck section and the second neck section may be different from each other. In this sound-absorbing structure, there is a first neck section communicating with the first through-hole and a second neck section communicating with the second through-hole, and the frequencies of the Helmholtz resonance generated in the first neck section and the second neck section are different from each other. Therefore, tire cavity resonance noise can be reduced over a wide frequency range.

[0013] The periphery may have a tapered shape that narrows towards the top. In this sound-absorbing structure, the periphery has a tapered shape that narrows towards the top, which improves the ease of manufacturing the outer layer.

[0014] The outer layer may further have a bottom portion that extends from the circumferential side and covers the opposite side of the top portion of the porous sound-absorbing material. In this sound-absorbing structure, because the outer layer further has a bottom portion that extends from the circumferential side and covers the opposite side of the top portion of the porous sound-absorbing material, the sound-absorbing structure alone can generate Helmholtz resonance. For this reason, even if a gap is created between the sound-absorbing structure and the inner cavity of the tire when the sound-absorbing structure is attached to the inner cavity of the tire, the tire cavity resonance noise can be reduced.

[0015] The outer layer may further include a flange portion extending outward from the tip opposite the top of the side circumference. In this sound-absorbing structure, because the outer layer further includes a flange portion extending outward from the tip opposite the top of the side circumference, the sound-absorbing structure can be easily attached to the inner cavity of the tire. In addition, the sealing performance between the outer layer and the inner cavity of the tire can be improved, thereby suppressing water absorption by the porous sound-absorbing material.

[0016] The sound-absorbing structure may be formed in a rectangular strip shape, which is long in the length direction perpendicular to the thickness direction and short in the width direction perpendicular to both the thickness and length directions. In this sound-absorbing structure, the ease of installation into the inner cavity of the tire is improved because it is formed in a rectangular strip shape.

[0017] The width in the width direction may be between 30 mm and 40 mm. Because this sound-absorbing structure has a width of 30 mm to 40 mm, it can be attached to only a portion of the tire's internal cavity. This allows heat generated by the tire tread to dissipate more easily from the tire's internal cavity. This contributes to extending the tire's lifespan and reduces material usage.

[0018] The thickness may be 20 mm or less. Because this sound-absorbing structure is small with a thickness of 20 mm or less, it is easier to install into the inner cavity of the tire and the amount of material used can be reduced.

[0019] It may be curved in an arc shape. Because this sound-absorbing structure is curved in an arc shape, it is easier to attach to the inner cavity of the tire.

[0020] The tire according to the present disclosure includes the above-described sound absorption structure attached to the inner cavity portion. In this tire, by including the above-described sound absorption structure, the resonance sound in the tire inner cavity can be reduced.

Effects of the Invention

[0021] According to the present disclosure, the resonance sound in the tire inner cavity can be reduced.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view of a tire to which a sound absorption structure according to an embodiment is attached. [Figure 2] FIG. 2 is a schematic perspective view of the sound absorption structure shown in FIG. 1. [Figure 3] FIG. 3 is a schematic cross-sectional view of the sound absorption structure shown in FIG. 1. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of a method for manufacturing a sound absorption structure by a salt aggregation method. [Figure 5] FIG. 5 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 8] FIG. 8 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 9] FIG. 9 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 10] FIG. 10 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 11] FIG. 11 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 12] FIG. 12 is a schematic cross-sectional view showing a sound absorption structure of a modification example. [Figure 13] FIG. 13 is a diagram showing a method for calculating the resonance frequency of a Helmholtz resonance structure. [Modes for carrying out the invention]

[0023] The embodiments of the sound-absorbing structure according to this disclosure will be described in detail below with reference to the drawings.

[0024] Figure 1 is a schematic cross-sectional view of a tire to which a sound-absorbing structure according to this embodiment is attached. In the tire 101, cavity resonance can occur when the air inside resonates in response to vibrations as the vehicle passes over uneven surfaces on the road. The frequency of the sound due to cavity resonance is approximately 200 Hz to 300 Hz, typically around 250 Hz. The sound-absorbing structure 1 according to this embodiment is attached to the inner cavity 102 of the tire 101 in order to efficiently absorb low-frequency sounds due to cavity resonance. The inner cavity 102 is the inner circumferential surface of the tread 103.

[0025] Figure 2 is a schematic perspective view of the sound-absorbing structure shown in Figure 1. Figure 3 is a schematic cross-sectional view of the sound-absorbing structure shown in Figure 1. As shown in Figures 1 to 3, the sound-absorbing structure 1 according to this embodiment is a thin sound-absorbing structure equipped with a Helmholtz resonance structure. The sound-absorbing structure 1 being equipped with a Helmholtz resonance structure means that the sound-absorbing structure 1 alone generates Helmholtz resonance, or that Helmholtz resonance is generated when the sound-absorbing structure 1 is attached to the inner cavity 102 of the tire 101. The sound-absorbing structure 1 includes a mounting surface 2 that is attached to the inner cavity 102 of the tire 101, and a top surface 3 that is positioned opposite the mounting surface 2. For example, an adhesive sheet 4 for attaching the sound-absorbing structure 1 to the inner cavity 102 of the tire 101 is attached to the mounting surface 2.

[0026] The sound-absorbing structure 1 is formed in the shape of a rectangular strip. The direction in which the mounting surface 2 and the top surface 3 face each other is called the thickness direction D1 of the sound-absorbing structure 1. In a plan view from the thickness direction D1, the sound-absorbing structure 1 is formed in a rectangular shape. Of the directions perpendicular to the thickness direction D1, the direction that is the longitudinal direction of the sound-absorbing structure 1 is called the length direction D2, and the direction that is the short side of the sound-absorbing structure 1 is called the width direction D3. The thickness T2 of the sound-absorbing structure 1 is, for example, 20 mm or less. Thickness T2 is the dimension in the thickness direction D1. The width W1 of the sound-absorbing structure 1 is, for example, approximately 30 mm to 40 mm. Width W1 is the dimension in the width direction D3. The length of the sound-absorbing structure 1 is, for example, approximately 30 mm to 2000 mm. The length of the sound-absorbing structure 1 is the dimension in the length direction D2.

[0027] The sound-absorbing structure 1 comprises an outer layer 10, a porous sound-absorbing body 20 housed within the outer layer 10, and a neck portion 30 embedded within the porous sound-absorbing body 20.

[0028] The outer layer 10 has through holes 11 that serve as entry points for the resonant sound inside the tire cavity. The number of through holes 11 in the outer layer 10 is not particularly limited and may be one or multiple. The outer layer 10 is non-permeable and is formed of a resin material such as plastic or rubber.

[0029] Examples of plastic materials include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), polyurethane (PU), epoxy resin, phenolic resin, and melamine resin.

[0030] Examples of rubber materials include natural rubber (NR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), silicone rubber, and urethane rubber.

[0031] The outer skin 10 comprises a top portion 12, a side circumference portion 13, and a flange portion 14. The thickness T1 of the outer skin 10 is, for example, about 0.1 mm to 2 mm. In other words, the thickness T1 of the top portion 12, the side circumference portion 13, and the flange portion 14 is, for example, about 0.1 mm to 2 mm.

[0032] The top portion 12 forms the top surface 3 and has through holes 11. The top portion 12 is formed in a roughly rectangular shape when viewed from the thickness direction D1 in a plan view. The through holes 11 are holes that penetrate the top portion 12. The cross-sectional shape of the through holes 11 is, for example, circular. The cross-sectional shape of the through holes 11 is not limited to circular, but may be triangular, rectangular, polygonal, elliptical, or other shapes. The inner diameter of the through holes 11 is, for example, about 1 mm to 5 mm. The opening ratio of the top portion 12 due to the through holes 11 (the ratio of the total area of ​​the through holes 11 to the area of ​​the top portion 12 on the surface of the top portion 12) is, for example, about 0.1% to 10%.

[0033] The side circumference portion 13 is the part that extends from the peripheral edge of the top portion 12 to the mounting surface 2. The side circumference portion 13 extends from the peripheral edge of the top portion 12 to the mounting surface 2 around the entire circumference of the top portion 12. The cross-section of the side circumference portion 13 perpendicular to the thickness direction D1 is formed in an endless rectangular ring shape. The side circumference portion 13 has a tapered shape that narrows towards the top portion 12. In other words, the side circumference portion 13 is inclined with respect to the thickness direction D1 so that it widens from the top portion 12 towards the mounting surface 2. The inclination angle θ of the side circumference portion 13 with respect to the thickness direction D1 is, for example, about 0° to 50°.

[0034] The flange portion 14 is a part that extends outward from the peripheral edge of the side circumference portion 13 on the mounting surface 2 side, in order to be attached to the inner cavity portion 102 of the tire 101. The flange portion 14 forms a part of the mounting surface 2. The width W2 of the flange portion 14 is, for example, about 1 mm to 20 mm. The width W2 is the dimension in the direction away from the side circumference portion 13.

[0035] The porous sound-absorbing material 20 is positioned in the region surrounded by the top portion 12 and the side periphery portion 13 of the skin 10. The porous sound-absorbing material 20 forms a part of the mounting surface 2. The mounting surface 2 is formed by the flange portion 14 and the porous sound-absorbing material 20.

[0036] The porous sound-absorbing body 20 is formed by foam molding of a resin material such as plastic or rubber. Examples of plastic materials include foamed polyurethane. Either rigid foamed polyurethane or flexible foamed polyurethane may be used. A general method for producing foamed polyurethane can be used. For example, a porous sound-absorbing body 20 can be obtained by mixing a polyol and a polyisocyanate with a foaming agent, antifoaming agent, catalyst, etc., filling the mixture into a mold, and foaming and curing it.

[0037] Examples of rubber materials include natural rubber (NR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and chloroprene rubber (CR), which are rubber materials obtained from latex. By foaming and solidifying these rubber materials, a porous sound-absorbing body 20 can be obtained.

[0038] The pore diameter of the porous sound-absorbing material 20 is, for example, 1 μm or less, preferably 500 μm or less. The open porosity of the porous sound-absorbing material 20 (the ratio of the total area of ​​pores to the total area of ​​the porous sound-absorbing material 20 on its surface) is, for example, about 65% to 99%, preferably about 80% to 95%. The pore diameter and open porosity can be measured, for example, using an X-ray computed tomography (CT scan) device. For calculating the open pore diameter, the average value of the diameters of multiple (e.g., 100) pores extracted based on the observation image can be used. For calculating the open porosity, the division value obtained by dividing the total area of ​​all pores extracted based on the observation image by the area of ​​the porous sound-absorbing material can be used.

[0039] The neck portion 30 is a hollow member that communicates with the through hole 11. The neck portion 30 is embedded in the porous sound-absorbing material 20. The base end of the neck portion 30 is connected to the through hole 11. The tip of the neck portion 30 is an open end where the hollow portion S of the neck portion 30 is exposed and is located inside the porous sound-absorbing material 20. The neck portion 30 is formed integrally with the outer skin 10, for example. If the outer skin 10 has a plurality of through holes 11, for example, the same number of neck portions 30 as the number of through holes 11 are provided, and each of the neck portions 30 is connected to each of the through holes 11.

[0040] The neck portion 30 is non-breathable, similar to the outer skin 10. Because the neck portion 30 is non-breathable, it is formed from a resin material such as plastic or rubber. The plastic and rubber materials can be the same as those used for the outer skin 10.

[0041] The hollow portion S of the neck portion 30 has a cross-section that is the same as or larger than the cross-section of the through hole 11. By increasing the extended length of the neck portion 30, the resonance frequency of the sound-absorbing structure 1, which functions as a Helmholtz resonator, can be reduced. In other words, by increasing the extended length of the neck portion 30, low-frequency resonance can be reduced. The tip of the neck portion 30 on the through hole 11 side is considered the base end, and the tip of the neck portion 30 opposite the through hole 11 is considered the tip. The extended length of the neck portion 30 is the length of the extended axis of the neck portion 30 from the base end on the through hole 11 side to the tip opposite the through hole 11.

[0042] The sound-absorbing structure 1 configured in this way can be manufactured, for example, by a salt flocculation method.

[0043] Figure 4 is a schematic cross-sectional view showing an example of a method for manufacturing a sound-absorbing structure using the salt flocculation method.

[0044] As shown in Figure 4, in the method for manufacturing a sound-absorbing structure using the salt flocculation method, first, a mold 110 corresponding to the skin 10 and the neck portion 30 is prepared. The mold 110 has a skin molding surface 111 corresponding to the surface shape of the skin 10 and a neck forming surface 112 corresponding to the hollow portion S of the neck portion 30.

[0045] Next, calcium chloride is applied to the parts of the mold 110 corresponding to the skin 10 and neck portion 30, and the mold 110 is immersed in a liquid that will serve as a precursor for the skin 10 and neck portion 30. The precursor liquid is, for example, latex or uncured resin. The precursor then aggregates in the calcium chloride-coated parts of the mold 110, and the skin 10 and neck portion 30 are formed integrally. Once the skin 10 and neck portion 30 are formed, they are peeled off the mold 110.

[0046] Next, a resin material such as plastic or rubber is foam-molded in the region surrounded by the top portion 12, the side periphery portion 13, and the neck portion 30 of the outer skin 10. At this time, it is preferable to close the hollow portion S of the neck portion 30. This gives rise to a sound-absorbing structure 1 comprising the outer skin 10, the porous sound-absorbing body 20, and the neck portion 30.

[0047] As described above, in the sound-absorbing structure 1, a hollow neck portion 30 that communicates with the through-hole 11 of the skin 10 is embedded in a porous sound-absorbing material 20 housed in the skin 10, and the skin 10 has a top portion 12 having the through-hole 11 and a side portion 13 that extends from the peripheral edge of the top portion 12 to the mounting surface 2. Therefore, the sound-absorbing structure 1 attached to the inner cavity 102 of the tire 101 can function as a Helmholtz resonator. This makes it possible to reduce the tire cavity resonance sound by resonance generated in the hollow portion S of the neck portion 30, and to absorb the tire cavity resonance sound that has passed through the neck portion 30 with the porous sound-absorbing material 20.

[0048] Furthermore, since the sound-absorbing structure 1 has a tapered shape in which the side circumference 13 narrows towards the top 12, it becomes easier to remove the sound-absorbing structure 1 from the mold when manufacturing it by methods such as salt agglutination. This improves the ease of manufacturing the surface 10.

[0049] Furthermore, in this sound-absorbing structure 1, the outer layer 10 is provided with a flange portion 14 that extends outward from the tip of the side circumference 13 opposite to the top portion 12, allowing the sound-absorbing structure 1 to be easily attached to the inner cavity 102 of the tire 101. In addition, the sealing performance between the outer layer 10 and the inner cavity 102 of the tire 101 can be improved, thereby suppressing water absorption by the porous sound-absorbing material 20.

[0050] Furthermore, since this sound-absorbing structure 1 is formed in a rectangular strip shape, it is easier to attach it to the inner cavity of the tire.

[0051] Furthermore, in this sound-absorbing structure 1, since the width W1 in the width direction D3 is 30 mm or more and 40 mm or less, the sound-absorbing structure 1 can be attached only to a part of the inner cavity 102 of the tire 101. As a result, the heat generated in the tread 103 of the tire 101 is more easily dissipated from the inner cavity 102 of the tire 101. This contributes to extending the lifespan of the tire 101. In addition, the amount of material used can be reduced.

[0052] Furthermore, since this sound-absorbing structure 1 is small, with a thickness T2 of 20 mm or less in the thickness direction D1, it is easier to install into the inner cavity of the tire and the amount of material used can be reduced.

[0053] Here, as shown in Figure 1, let F be the frequency of the tire cavity resonance sound, c be high speed, R be the radius of the cavity 102 of the tire 101, r be the radius of the rim 105 of the wheel 104 assembled to the tire 101, and π be pi. In this case, the frequency of the tire cavity resonance sound is calculated by F = c / ((R + r) × π). It is preferable that the sound-absorbing structure 1 is equipped with a Helmholtz resonance structure that generates a Helmholtz resonance at a resonance frequency within ±100 Hz of the tire cavity resonance sound frequency calculated from F = c / ((R + r) × π).

[0054] A Helmholtz resonance structure is a structure that comprises components of a Helmholtz resonator that resonate with sound incident through a hole. In the sound-absorbing structure 1, the Helmholtz resonance structure is composed of a skin 10, a porous sound-absorbing material 20, and a neck portion 30. That is, in the sound-absorbing structure 1, the non-permeable skin 10 extends to the mounting surface 2, and the hollow neck portion 30 is connected to the through-hole 11 of the skin 10, so that Helmholtz resonance of the sound resonating inside the tire cavity can be generated in the hollow portion S of the neck portion 30. The resonance frequency of the sound-absorbing structure 1, which functions as a Helmholtz resonator, changes depending on the extension length of the neck portion 30, the inner diameter of the through-hole 11, etc. For example, the longer the extension length of the neck portion 30, the lower the resonance frequency. Also, the smaller the inner diameter of the through-hole 11, the lower the resonance frequency. Furthermore, the wider the distance and width W1 between adjacent through-holes 11, the larger the body volume of the Helmholtz resonator and the lower the resonance frequency. Therefore, it is preferable that the sound-absorbing structure 1 is configured such that these conditions are adjusted so that Helmholtz resonance occurs at a resonant frequency within ±100 Hz of the frequency of the tire cavity resonance sound calculated from F = c / ((R+r)×π).

[0055] Thus, by incorporating a Helmholtz resonance structure that generates Helmholtz resonances at resonant frequencies within ±100 Hz of the tire cavity resonance frequency, the tire cavity resonance noise can be reduced.

[0056] Figure 13 shows a method for calculating the resonance frequency of a Helmholtz resonance structure. In the figure, the areas enclosed by dashed lines represent Helmholtz resonance structure units. The resonance frequency of the Helmholtz resonance structure that resonates with sound incident from each through-hole 11 can be adjusted from various dimensions of the porous sound absorber 20 according to this calculation method.

[0057] In Figure 13, V is the volume of the porous sound absorber 20 when it is divided into Helmholtz resonance structure units. When the through-holes 11 are arranged in a grid with a constant period, that is, when the pitch P between the through-holes 11 is constant, V is calculated as the volume of a rectangular prism or cube obtained by multiplying the thickness T of the porous sound absorber 20 by a square or rectangle that starts from the center of adjacent through-holes 11 and passes through the midpoints of the through-holes 11. If there are multiple drawing methods when drawing the rectangle that passes through the midpoints of the through-holes 11, the rectangle is drawn so that adjacent rectangles do not overlap and the area is maximized. Furthermore, when the through-holes 11 are not arranged with a constant period and are randomly arranged at an unspecified pitch interval, that is, when the pitch P between the through-holes 11 is unspecified, V is calculated as the volume of a polygonal prism obtained by multiplying the thickness T of the porous sound absorber 20 by a polygon that starts from the center of adjacent through-holes 11 and has the midpoints of the through-holes 11 as its vertices. In either case, if the neck portion 30 extends within the porous sound-absorbing material 20, V is the volume obtained by subtracting the volume of the neck portion 30. α is the area of ​​the through-hole 11 when the porous sound-absorbing material 20 is viewed from the thickness direction. δ is the opening end correction; for example, if the shape of the through-hole 11 is circular, δ can be calculated as 0.8 times the diameter of the through-hole 11. If the shape of the through-hole 11 is not circular, δ can be calculated as 0.8 times the diameter of a perfect circle having the same area as the through-hole 11. L is the depth of the through-hole 11, that is, the extending length of the neck portion 30 (hollow portion).

[0058] This disclosure is not limited to the embodiments described above and may be modified as appropriate without departing from the spirit of this disclosure.

[0059] For example, the shape of the neck portion 30 is not particularly limited. For example, as shown in Figure 3, the neck portion 30 may extend linearly from the through hole 11 in the thickness direction D1. Also, as shown in Figures 5 to 7, at least a part of the neck portion 30 may have a portion that intersects with the thickness direction D1 of the sound-absorbing structure 1. The portion that intersects with the thickness direction D1 of the sound-absorbing structure 1 means that the extending direction of the neck portion 30 does not coincide with the thickness direction D1 of the sound-absorbing structure 1, and is inclined at an angle greater than 0° with respect to the thickness direction D1. Figures 5 to 7 are schematic cross-sectional views showing modified sound-absorbing structures. The neck portion 30 of the sound-absorbing structure 1 shown in Figure 5 has a linear shape. That is, the neck portion 30 shown in Figure 5 extends linearly from the base to the tip in a direction inclined with respect to the thickness direction D1. The neck portion 30 of the sound-absorbing structure 1 shown in Figure 6 has a curved shape. In other words, the neck portion 30 shown in Figure 6 extends from the base to the tip in a gently curving direction that is inclined with respect to the thickness direction D1. The neck portion 30 of the sound-absorbing structure 1 shown in Figure 7 has a helical shape. In other words, the neck portion 30 shown in Figure 7 extends spirally from the base to the tip. In this way, by having a portion of the neck portion 30 that intersects with the thickness direction D1 of the sound-absorbing structure 1, the neck portion 30 can be made longer than the thickness T2 of the sound-absorbing structure 1. This also reduces low-frequency resonance noise inside the tire cavity.

[0060] Furthermore, for example, if the structure includes multiple through-holes and neck sections, the frequencies of the Helmholtz resonances generated in at least two of the neck sections may be different from each other. Figure 8 is a schematic cross-sectional view showing a modified sound-absorbing structure. In the sound-absorbing structure 1 shown in Figure 8, the skin 10 has a first through-hole 11a and a second through-hole 11b formed in the top section 12, a first neck section 30a communicating with the first through-hole 11a is connected to the first through-hole 11a, and a second neck section 30b communicating with the second through-hole 11b is connected to the second through-hole 11b. The first neck section 30a and the second neck section 30b have different extending lengths, resulting in different frequencies of the Helmholtz resonances they generate. In this way, by having different frequencies of Helmholtz resonances generated in the first neck section 30a and the second neck section 30b, tire cavity resonance noise can be reduced over a wide frequency range.

[0061] Furthermore, for example, the skin may include parts other than the top, side circumferential, and flange portions. Figure 9 is a schematic cross-sectional view showing a modified sound-absorbing structure. The skin 10 of the sound-absorbing structure 1 shown in Figure 9 includes a bottom portion 15 in addition to the top portion 12, side circumferential portion 13, and flange portion 14. The bottom portion 15 extends from the side circumferential portion 13 and covers the side of the porous sound-absorbing body 20 opposite to the top portion 12. In other words, the bottom portion 15 closes the space surrounded by the top portion 12 and side circumferential portion 13 at the mounting surface 2. In this way, by further including the bottom portion 15 that extends from the side circumferential portion 13 and covers the side of the porous sound-absorbing body 20 opposite to the top portion 12, the sound-absorbing structure 1 alone can generate Helmholtz resonance. Therefore, even if a gap is created between the sound-absorbing structure 1 and the inner cavity 102 of the tire 101 when the sound-absorbing structure 1 is attached to the inner cavity 102 of the tire 101, the resonance noise inside the tire cavity can be reduced.

[0062] Furthermore, for example, the periphery of the skin does not necessarily have to have a tapered shape. Figure 10 is a schematic cross-sectional view showing a modified sound-absorbing structure. The periphery 13 of the sound-absorbing structure 1 shown in Figure 10 is not inclined with respect to the thickness direction D1, and extends in the thickness direction D1 from the peripheral edge of the top portion 12 to the mounting surface 2.

[0063] Furthermore, for example, the outer skin does not necessarily need to have a flange. Figure 11 is a schematic cross-sectional view showing a modified sound-absorbing structure. In the sound-absorbing structure 1 shown in Figure 11, the outer skin 10 has a top portion 12 and a side circumferential portion 13, but does not have a flange portion 14. In this way, even without a flange portion 14, the side circumferential portion 13 can be attached to the inner cavity 102 of the tire 101, allowing the sound-absorbing structure 1 to function as a Helmholtz resonator.

[0064] Furthermore, for example, the sound-absorbing structure 1 may be formed in a flat plate shape or a curved shape. Figure 12 is a schematic cross-sectional view showing a modified sound-absorbing structure. The sound-absorbing structure 1 shown in Figure 12 may be curved in an arc shape along the inner cavity 102 of the tire 101. By curving the sound-absorbing structure 1 in an arc shape in this way, the ease of attachment to the inner cavity 102 of the tire 101 is improved. For example, the sound-absorbing structure 1 can be curved in an arc shape by curving the surface molding surface 111 of the mold 110 shown in Figure 4 in an arc shape.

[0065] Furthermore, for example, when attaching multiple sound-absorbing structures to a tire, two or more sound-absorbing structures that generate Helmholtz resonances at different resonant frequencies may be attached to the tire.

[0066] The gist of this disclosure is as follows: [1] to

[13] . [1] A sound-absorbing structure to be attached to the inner cavity of a tire, comprising: a skin having through holes; a porous sound-absorbing body housed in the skin; and a hollow neck portion communicating with the through holes and embedded in the porous sound-absorbing body, wherein the skin has a top portion having the through holes and a side portion extending from the peripheral edge of the top portion to a mounting surface attached to the inner cavity. [2] A sound-absorbing structure to be attached to the inner cavity of a tire, comprising a Helmholtz resonance structure that generates a Helmholtz resonance at a resonance frequency within ±100 Hz of the tire cavity resonance frequency calculated from F = c / ((R+r)×π), where F is the frequency of the tire cavity resonance sound, c is high speed, R is the radius of the inner cavity of the tire, r is the radius of the rim of the wheel assembled to the tire, and π is pi. [3] The Helmholtz resonance structure is the sound-absorbing structure according to [2], comprising: a skin having a top portion with through holes and a side portion extending from the peripheral edge of the top portion; a porous sound-absorbing body covered by the skin; and a hollow neck portion communicating with the through holes of the skin and embedded in the porous sound-absorbing body. [4] The sound-absorbing structure according to [1] or [3], wherein at least a portion of the neck portion has a portion that intersects with the thickness direction of the sound-absorbing structure. [5] The top portion has a first through hole and a second through hole as the holes, and the neck portion has a first neck portion communicating with the first through hole and a second neck portion communicating with the second through hole, wherein the frequencies of the Helmholtz resonances generated in the first neck portion and the second neck portion are different from each other, the sound-absorbing structure according to any one of [1], [3] and [4]. [6] The sound-absorbing structure according to any one of [1], [3] to [5], wherein the side circumference has a tapered shape that narrows towards the top. [7] The sound-absorbing structure according to any one of [1], [3] to [6], wherein the surface further has a bottom portion that extends from the side periphery and covers the opposite side from the top portion of the porous sound-absorbing body. [8] The sound-absorbing structure according to any one of [1], [3] to [7], further comprising a flange portion extending in a direction that widens from the tip of the side circumference opposite to the top portion of the surface. [9] The sound-absorbing structure according to any one of [1] to [8], wherein the sound-absorbing structure is formed in the shape of a rectangular strip that is long in the length direction perpendicular to the thickness direction and short in the width direction perpendicular to the thickness direction and the length direction.

[10] The sound-absorbing structure according to any one of [1] to [9], wherein the width in the width direction is 30 mm or more and 40 mm or less.

[11] A sound-absorbing structure described in any one of [1] to

[10] , having a thickness of 20 mm or less.

[12] An arc-shaped sound-absorbing structure as described in any one of [1] to

[11] .

[13] A tire having a sound-absorbing structure attached to the lumen, as described in any one of [1] to

[12] . [Explanation of Symbols]

[0067] 1...Sound-absorbing structure, 2...Mounting surface, 3...Top surface, 4...Adhesive sheet, 10...Skin, 11...Through hole, 11a...First through hole, 11b...Second through hole, 12...Top part, 13...Side circumference part, 14...Flange part, 15...Bottom part, 20...Porous sound-absorbing material, 30...Neck part, 30a...First neck part, 30b...Second neck part, 101...Tire, 102...Inner cavity part, 103...Tread, 104...Wheel, 105...Rim, 110...Molding mold, 111...Skin molding surface, 112...Neck forming surface, D1...Thickness direction, D2...Length direction, D3...Width direction, S...Hollow part.

Claims

1. A sound-absorbing structure that is attached to the inner cavity of a tire, The epidermis having through holes, A porous sound-absorbing material housed in the aforementioned surface, It comprises a hollow neck portion that communicates with the through-hole and is embedded in the porous sound-absorbing material, The aforementioned epidermis is The top part having the aforementioned through hole, It has a side circumferential portion that extends from the peripheral edge of the top portion to the mounting surface that is attached to the inner cavity portion, Sound-absorbing structure.

2. A sound-absorbing structure that is attached to the inner cavity of a tire, The Helmholtz resonance structure generates a Helmholtz resonance at a resonance frequency within ±100 Hz of the tire cavity resonance frequency calculated from F = c / ((R + r) × π), where F is the frequency of the tire cavity resonance sound, c is high speed, R is the radius of the tire cavity, r is the radius of the wheel rim mounted on the tire, and π is pi. Sound-absorbing structure.

3. The aforementioned Helmholtz resonance structure is A skin having a top portion with a through hole, and a side portion extending from the peripheral edge of the top portion, A porous sound-absorbing material covered with the aforementioned surface, It comprises a hollow neck portion that communicates with the through-holes in the skin and is embedded in the porous sound-absorbing material, The sound-absorbing structure according to claim 2.

4. At least a portion of the neck portion has a part that intersects with the thickness direction of the sound-absorbing structure. The sound-absorbing structure according to claim 1 or 3.

5. The top part has a first through hole and a second through hole as the through holes, The neck portion has a first neck portion that communicates with the first through hole and a second neck portion that communicates with the second through hole. The frequencies of the Helmholtz resonances generated in the first neck portion and the second neck portion are different from each other. The sound-absorbing structure according to claim 1 or 3.

6. The side circumference has a tapered shape that narrows towards the top. The sound-absorbing structure according to claim 1 or 3.

7. The surface further has a bottom portion that extends from the side periphery and covers the opposite side from the top portion of the porous sound-absorbing body. The sound-absorbing structure according to claim 1 or 3.

8. The skin further comprises a flange portion extending in a direction that widens from the tip of the side circumference opposite to the top portion. The sound-absorbing structure according to claim 1 or 3.

9. The sound-absorbing structure is formed in a rectangular strip shape that is long in the length direction perpendicular to the thickness direction and short in the width direction perpendicular to both the thickness direction and the length direction. The sound-absorbing structure according to claim 1 or 2.

10. The width in the aforementioned width direction is 30 mm or more and 40 mm or less. The sound-absorbing structure according to claim 9.

11. The thickness is 20 mm or less. The sound-absorbing structure according to claim 1 or 2.

12. It is curved in an arc shape. The sound-absorbing structure according to claim 1 or 2.

13. A sound-absorbing structure according to claim 1 or 2 is attached to the internal cavity, tire.

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