Sound absorbing structure and tires

Abstract

To correspond to a shape change of a member forming a cavity and to exhibit sound absorption effect with a wide frequency area.SOLUTION: A sound absorption structure attached to a cavity forming member forming a cavity comprises: a sub-chamber forming part for forming a sub-chamber being a space smaller than the cavity in the cavity; and a flange part extending along the cavity forming member from an edge of the sub-chamber forming part. The sub-chamber forming part has an opening where the sub-chamber and the cavity are communicated, is formed of a material with Young's modulus of 1 MPa to 1 GPa, and reduces vibration in the cavity by Helmholtz resonance generated by the sub-chamber and the opening.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a sound absorbing structure and a tire. [Background technology]

[0002] Conventionally, there are known means for reducing noise and vibration generated in vehicles and the like (see, for example, Patent Document 1). Patent Document 1 discloses a technology in which a sponge is arranged as a sound absorbing material inside the tire rubber of a vehicle. Patent Document 2 discloses a structure regarding an auxiliary chamber arranged as a Helmholtz resonator on the surface of the tire rubber of a vehicle opposite to the installation surface. The auxiliary chambers are formed at equal intervals along the circumferential direction centered on the rotation axis of the tire. Patent Document 3 discloses a technology in which an auxiliary chamber is formed in the wheel of a vehicle tire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-1285 A [Patent Document 2] JP 2018-75839 A [Patent Document 3] JP 2015-160564 A Summary of the Invention [Problem to be solved by the invention]

[0004] In vehicle tires, tire-specific cavity resonance noise (200 to 300 Hz) occurs when the vehicle is in motion, and this cavity resonance noise is one of the factors that worsen noise levels both inside and outside the vehicle. In particular, as more and more vehicles are converted to EVs, engine noise will disappear, making it important to take measures against noise sources other than the engine.

[0005] The porous sound-absorbing material such as urethane described in Patent Document 1 has a small sound-absorbing effect in the range below 1000 Hz, and is small in effect against cavity resonance. The technology described in Patent Document 2 does not take into consideration the deformation of the tire during running. In addition, a sufficient sound-absorbing effect cannot be obtained by forming a single auxiliary chamber every 90° along the circumferential direction of the tire. In the technology described in Patent Document 3, a countermeasure must be incorporated into the structure to prevent the auxiliary chamber from moving due to the centrifugal force generated during running. This structure increases the unsprung weight. In addition, since the auxiliary chamber is formed radially inward with the rotation axis as the center, the space for forming the auxiliary chamber is limited. In addition, since the wheel is made of metal, it is difficult to adjust the sound-absorbing structure (for example, the opening area) after the auxiliary chamber is formed.

[0006] Therefore, there was a need to reduce vibrations over a wide frequency range while responding to changes in the shape of the component to which the sound-absorbing structure is attached and to forces such as centrifugal force, etc. Furthermore, this problem was common to all components that form cavities in which sound absorption is desired, regardless of the field of vehicle tires that form cavities inside.

[0007] The present invention has been made to solve the above-mentioned problems, and provides a sound-absorbing structure that reduces vibrations over a wide frequency range while adapting to changes in the shape of the members that form the cavity. [Means for solving the problem]

[0008] The present invention has been made to solve the above-mentioned problems, and can be realized in the following form: A sound absorbing structure attached to a cavity forming member that forms a cavity, the sound absorbing structure comprising: an auxiliary chamber forming part that forms an auxiliary chamber, which is a space smaller than the cavity, within the cavity, and a flange part extending from an edge of the auxiliary chamber forming part along the cavity forming member, the auxiliary chamber forming part has an opening that connects the auxiliary chamber and the cavity, and is formed of a material with a Young's modulus of 1 MPa to 1 GPa, vibrations within the cavity are reduced by Helmholtz resonance generated by the auxiliary chamber and the opening, and the Young's modulus of the material forming the flange part is smaller than the Young's modulus of the material forming the cavity forming member.Ku , The auxiliary chamber forming portion is provided with a plurality of the auxiliary chamber forming portions, and the flange portion extends from an edge of each of the auxiliary chamber forming portions along the cavity forming member, and at least a part of the flange portion located between one of the auxiliary chamber forming portions and the other of the auxiliary chamber forming portions is formed with a thin-walled portion that is thinner than the remaining part. , a sound absorbing structure. In addition, the present invention can be realized in the following forms.

[0009] (1) According to one aspect of the present invention, there is provided a sound absorbing structure attached to a cavity forming member that forms a cavity. The sound absorbing structure includes an auxiliary chamber forming part that forms an auxiliary chamber that is a space smaller than the cavity within the cavity, and a flange part that extends from an edge of the auxiliary chamber forming part along the cavity forming member, the auxiliary chamber forming part has an opening that connects the auxiliary chamber and the cavity, and is formed of a material with a Young's modulus of 1 MPa to 1 GPa, and reduces vibrations within the cavity by Helmholtz resonance generated by the auxiliary chamber and the opening.

[0010] According to this configuration, the flange portion extending from the edge of the auxiliary chamber forming portion along the cavity forming member is fixed to the cavity forming member, thereby fixing the sound absorbing structure to the cavity forming member. Since the auxiliary chamber forming portion is formed of a relatively soft material with a Young's modulus of 1 MPa to 1 GPa, the sound absorbing structure can deform in response to the deformation of the cavity forming member. Furthermore, the damping properties of the material itself of the auxiliary chamber forming portion reduce vibrations in the high frequency range. Furthermore, in this configuration, Helmholtz resonance reduces vibrations in the low frequency range. That is, this configuration can reduce vibrations in a wide frequency range while responding to changes in the shape of the cavity forming member.

[0011] (2) In the sound absorbing structure of the above aspect, the flange portion may be made of a material having a Young's modulus of 1 MPa to 1 GPa. According to this configuration, in addition to the sub-chamber forming portion, the flange portion fixed to the cavity forming member also has a Young's modulus of 1 MPa to 1 GPa. Therefore, this configuration can further accommodate deformation of the cavity forming member and also reduce vibrations in the flange portion.

[0012] (3) In the sound absorbing structure of the above form, a plurality of the sub-chamber forming portions may be provided, and the flange portion may extend from the edge of each of the sub-chamber forming portions along the cavity forming member, and at least a portion of the flange portion located between one of the sub-chamber forming portions and the other of the sub-chamber forming portions may be formed with a thin-walled portion that is thinner than the remaining portion. According to this configuration, a thin-walled portion is formed in a part of the flange portion connecting one pre-chamber forming portion with the other pre-chamber forming portion. When the cavity-forming member deforms, the sound absorbing structure deforms first in the vicinity of the thin-walled portion. Therefore, with this configuration, it is possible to accommodate deformation of the cavity-forming member while maintaining as much as possible the shapes of the pre-chamber and the opening related to Helmholtz resonance.

[0013] (4) In the sound absorbing structure of the above aspect, at least some of the plurality of sub-chamber forming portions may have openings with sizes different from the openings of the other sub-chamber forming portions. According to this configuration, since at least some of the openings have different sizes, each of the plurality of sub-chambers functions as a Helmholtz resonator that resonates at a different frequency, and therefore, with this configuration, it is possible to reduce vibrations over a wider frequency range.

[0014] (5) According to another aspect of the present invention, there is provided a tire comprising a sound absorbing structure of the above aspect attached to the tire within a cavity of the tire. According to this configuration, the tire is used as a cavity-forming member and the sound absorbing structure is disposed inside the tire cavity. Therefore, the sound absorbing structure can reduce vibrations caused by tire cavity resonance that is specific to the tire by the auxiliary chamber forming portion and the opening that function as a Helmholtz resonator. The sound absorbing structure can also reduce vibrations in the high frequency range by the soft material that forms the auxiliary chamber forming portion.

[0015] (6) In the tire of the above aspect, within the cavity of the tire, the sound absorbing structure may be disposed on a surface of the tire opposite to a contact surface thereof. According to this configuration, when a vehicle equipped with the tire runs, the sound absorbing structure receives a force directed radially outward from the tire's axis of rotation due to the centrifugal force of the rotating tire. This force presses the sound absorbing structure against the opposite surface of the tire, so that the sound absorbing structure is firmly fixed to the tire. This reduces the number of materials (e.g., adhesive or double-sided tape) required to attach the sound absorbing structure to the cavity-forming member. Also, with this configuration, it is only necessary to attach the sound absorbing structure to the cavity-forming member, so that additional processing of the wheel, for example, is not required, and vibration can be reduced at low cost. Furthermore, by attaching the sound absorbing structure to the opposite surface of the ground contact surface, vibration of the tire tread can also be reduced, and in addition to cavity resonance, air-borne and solid-borne road noise caused by vibration of the tire tread can also be reduced.

[0016] The present invention can be realized in various forms, for example, in the form of a sound absorbing structure, a vibration damping structure, a sound absorbing material, a sound insulating material, structures using these, manufacturing methods thereof, a sound absorbing method, a vibration damping method, and a sound insulating method. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic perspective view of a tire according to one embodiment of the present invention; [Diagram 2] 2 is a schematic diagram of a cross section taken along line AA in FIG. 1, which is parallel to the YZ plane. [Diagram 3] FIG. 3 is an enlarged view of the X1 portion in FIG. [Figure 4] 2 is a schematic diagram of a cross section taken along a line BB parallel to the XY plane in FIG. 1. [Diagram 5] FIG. 1 is an explanatory diagram of the effect of a Helmholtz resonator. [Figure 6] FIG. 4 is an explanatory diagram of the effect of tire cavity resonance of the sound absorbing structure. [Figure 7] FIG. 13 is an explanatory diagram of samples for evaluating the damping properties of the example and comparative examples 3 and 4. [Figure 8] FIG. 13 is an explanatory diagram of samples for evaluating the damping properties of the example and comparative examples 3 and 4. [Figure 9]FIG. 13 is an explanatory diagram of samples for evaluating the damping properties of the example and comparative examples 3 and 4. [Figure 10] 10 is an explanatory diagram of the vibration amplitude reduction effect of the sample of the embodiment and the samples of Comparative Examples 3 and 4. FIG. [Figure 11] FIG. 4 is a schematic cross-sectional view of a tire according to a second embodiment. [Figure 12] FIG. 4 is a schematic cross-sectional view of a tire according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] First Embodiment FIG. 1 is a schematic perspective view of a tire 100 according to an embodiment of the present invention. The tire 100 according to the first embodiment is mounted on a vehicle and rotates about a rotation axis OL when the vehicle is traveling. FIG. 1 shows only the tire 100, and does not show a wheel. In this embodiment, an orthogonal coordinate system shown in FIG. 1 is defined, which is composed of a Z axis parallel to the rotation axis OL, and an X axis and a Y axis each perpendicular to the Z axis. This orthogonal coordinate system corresponds to the orthogonal coordinate systems shown in FIGS. 2 to 4, 11, and 12.

[0019] Fig. 2 is a schematic diagram of an AA cross section parallel to the YZ plane in Fig. 1. As shown in Fig. 2, a tire 100 includes a cavity-forming member 10 that forms a cavity HL, and a sound-absorbing structure (sound-absorbing structure) 20 attached to a first surface (opposite surface) FC1 on the opposite side to the contact surface 12 of the cavity-forming member 10. The material of the cavity-forming member 10 is rubber.

[0020] The sound absorbing structure 20 includes a plurality of sub-chamber forming portions 21-23 and flange portions 28, 29. Each of the plurality of sub-chamber forming portions 21-23 forms a sub-chamber CH21-CH23, which is a space smaller than the cavity HL. As shown in FIG. 2, the cross-sectional shape of the sub-chambers CH21-CH23 in the YZ plane is substantially trapezoidal. In this embodiment, each of the sub-chambers CH21-CH23 is formed to have the same volume. In this embodiment, the material of the sub-chamber forming portions 21-23 and the flange portions 28, 29 is pulp mold. The Young's modulus of the pulp mold is approximately 300 MPa (1 MPa or more and 1 GPa or less), which is smaller than the Young's modulus of the cavity forming member 10. Therefore, the shape of the sound absorbing structure 20 changes in accordance with the change in shape of the cavity forming member 10.

[0021] Openings AP21 to AP23 are formed in each of the sub-chamber forming portions 21 to 23. The openings AP21 to AP23 have a circular cross section penetrating the sub-chamber forming portions 21 to 23 in the thickness direction. In this embodiment, the areas of the openings AP21 to AP23 are different. Specifically, of the openings AP21 to AP23, the area of ​​opening AP22 is the smallest, and the area of ​​opening AP23 is the largest.

[0022] The flange portions 28, 29 extend from the edges of the sub-chamber forming portions 21-23 along the cavity forming member 10 and are bonded to a first surface FC1 of the cavity forming member 10 with an adhesive. The flange portion 28 is located between two sub-chamber forming portions (e.g., the sub-chamber forming portions 21, 22 or the sub-chamber forming portions 21, 23). The flange portion 29 is located on the end face sides (the Z-axis positive and negative direction sides) of the sound absorbing structure 20.

[0023] FIG. 3 is an enlarged view of the X1 portion in FIG. 2. As shown in FIG. 3, the flange portion 28 is formed with a thin wall portion 281 that is thinner than the remaining portion. Since the thin wall portion 281 is thinner than the remaining portion, it is more likely to deform in response to the shape change of the cavity forming member 10 compared to the remaining portion of the flange portion 28. In this embodiment, the thickness of the thin wall portion 281 is 1 mm, and the thickness of the remaining portion of the flange portion 28, the flange portion 29, and the auxiliary chamber forming portions 21 to 23 is 2 mm. In other embodiments, the thicknesses of the auxiliary chamber forming portions 21 to 23 and the flange portions 28 and 29 may be different values. As shown in FIG. 2 and FIG. 3, the thin wall portion 281 is not formed in the flange portion 29 that is not located between the two auxiliary chamber forming portions.

[0024] FIG. 4 is a schematic diagram of a BB cross section parallel to the XY plane in FIG. 1. As shown in FIG. 4, a plurality of sub-chamber forming portions 21 are formed in a row over the entire circumference of a first surface FC1 along the circumferential direction centered on the rotation axis OL. The cross-sectional shape of the sub-chamber CH21 in the XY plane is a substantially trapezoid. The cross-sectional shape of the sub-chamber CH21 shown in FIG. 4 is a substantially trapezoid with smaller upper and lower sides than the cross section in the YZ plane shown in FIGS. 2 and 3. As shown in FIG. 2, in this embodiment, the sub-chamber forming portions 21 to 23 are formed side by side along the axial direction (Z-axis direction) of the rotation axis OL, and like the sub-chamber forming portion 21 shown in FIG. 4, each of the multiple sub-chamber forming portions 22 and each of the multiple sub-chamber forming portions 23 are arranged side by side along the circumferential direction of the rotation axis OL.

[0025] When the sub-chambers CH21-CH23 and the openings AP21-AP23 are formed by the sub-chamber forming portions 21-23, the sub-chambers CH21-CH23 resonate due to Helmholtz resonance at a natural frequency f determined by the following formula (1). When this resonance occurs, the sound pressure during resonance in the cavity HL is reduced.

number

[0026] Fig. 5 is an explanatory diagram of the effect of the Helmholtz resonator. In Fig. 5, a sound absorption curve C1 that indicates the sound absorption coefficient that changes according to frequency (Hz) when the sound absorbing structure 20 of this embodiment is fixed to the first surface FC1 is shown by a solid line. Also, in Fig. 5, a sound absorption curve C2 is shown by a dashed line when a nonwoven fabric sound absorbing material without an auxiliary chamber forming portion is fixed to the first surface FC1 as Comparative Example 1. The sound absorption coefficient shown in Fig. 5 is a value converted on an energy (J) basis.

[0027] As shown by the sound absorption curves C1 and C2 in Fig. 5, the higher the frequency range, the greater the sound absorption effect of the pulp mold and the fibers of the nonwoven fabric, and the higher the sound absorption coefficient. Furthermore, the sound absorbing structure 20 formed of the pulp mold has a higher sound absorption coefficient. On the other hand, in the low frequency range (approximately 1000 Hz), the sound absorbing structure 20 of this embodiment exhibits a sound absorbing effect as a Helmholtz resonator, and has a high sound absorption coefficient.

[0028] FIG. 6 is an explanatory diagram of the effect of tire cavity resonance of the sound absorbing structure 20. FIG. 6 shows the change in sound pressure (Acoustic Pressure (dB)) that changes according to frequency in the low frequency range. In FIG. 6, a sound pressure curve C11 of a tire 100 equipped with the sound absorbing structure 20 is shown by a solid line, and a sound pressure curve C12 of a tire of Comparative Example 2 that does not have the sound absorbing structure 20 is shown by a dashed line. As shown in FIG. 6, the peak of the sound pressure curve C11 of the tire 100 of this embodiment is smaller than the peak of the sound pressure curve C12 of Comparative Example 2. In this embodiment, the difference ΔP between the peak of the sound pressure curve C11 and the peak of the sound pressure curve C12 is about 4 dB.

[0029] Since the sound absorbing structure 20 is made of pulp mold, it has a vibration damping property due to the material in addition to the sound absorbing effect as a Helmholtz resonator. Figs. 7 to 9 are explanatory diagrams of samples for evaluating the damping property of the embodiment and comparative examples 3 and 4. Fig. 7 shows a schematic perspective view of sample SA as an embodiment. Sample SA is a member in which four sub-chamber forming parts 21 and flange parts 28, 29, which are part of the sound absorbing structure 20, are bonded to one surface FC1 of a flat steel material ST. The Cartesian coordinate system shown in Fig. 7 is a coordinate system when the sound absorbing structure 20, which was bonded to the first surface FC1 on the circumference with the rotation axis OL as the center, is removed.

[0030] FIG. 8 shows a schematic perspective view of sample SAx as comparative example 3. Sample SAx is composed of only steel material ST included in sample SA of the embodiment. FIG. 9 shows a schematic perspective view of sample SAy as comparative example 4. In sample SAy, a flat sound-absorbing board material PM made of pulp mold is bonded to the second surface FC2 of steel material ST. The sound-absorbing board material PM of comparative example 4 does not have an auxiliary chamber. The area of ​​the surface parallel to the second surface FC2 of the sound-absorbing board material PM is the same as the area of ​​the surface connecting the end surfaces of the flange portions 29 at both ends in sample SA of the embodiment. In addition, the thickness of the sound-absorbing board material PM is the same as the thickness of the auxiliary chamber forming portions 21 to 23 and the flange portion 29.

[0031] FIG. 10 is an explanatory diagram of the vibration amplitude reduction effect of sample SA of the embodiment and samples SAx and SAy of comparative examples 3 and 4. FIG. 10 shows the change in amplitude (dB) according to the frequency of each sample. In FIG. 10, the amplitude curve C21 of sample SA is shown by a solid line, the amplitude curve C22 of sample SAx is shown by a dashed line, and the amplitude curve C23 of sample SAy is shown by a dashed line. As shown in FIG. 10, the amplitude of the peak of each resonance frequency is the smallest for sample SA of the embodiment. That is, in the three samples SA, SAx, and SAy of the embodiment and comparative examples 3 and 4, the vibration amplitude reduction effect of the embodiment is the largest in the low frequency range.

[0032] As described above, the sound absorbing structure 20 of this embodiment is attached to the cavity forming member 10. The sound absorbing structure 20 includes the sub-chamber forming parts 21-23 that form the sub-chambers CH21-CH23 smaller than the cavity HL, and flange parts 28, 29. The sub-chamber forming parts 21-23 have openings AP21-AP23. The material of the sub-chamber forming parts 21-23 is made of a relatively soft material with a Young's modulus of 300 MPa (1 MPa or more and 1 GPa or less). Therefore, the sub-chamber forming parts 21-23 can deform according to the deformation of the cavity forming member 10. Furthermore, as shown in FIG. 5, vibrations in the high frequency range are reduced due to the damping property of the material constituting the sub-chamber forming parts 21-23. Furthermore, vibrations in the low frequency range are reduced due to the Helmholtz resonance generated by the sub-chambers CH21-CH23 and the openings AP21-AP23, as shown in FIG. 10. That is, the sound absorbing structure 20 of this embodiment can accommodate changes in the shape of the cavity forming member 10 and reduce vibrations over a wide frequency range.

[0033] In this embodiment, the flange portions 28, 29 are made of a material with a Young's modulus of 300 MPa (1 MPa or more and 1 GPa or less). In addition to the sub-chamber forming portions 21-23, the flange portions 28, 29 fixed to the cavity forming member 10 are also made of a relatively soft material. Therefore, the sound absorbing structure 20 can further accommodate deformation of the cavity forming member 10 and also reduce vibrations at the flange portions 28, 29.

[0034] Moreover, the sound absorbing structure 20 of this embodiment includes a plurality of sub-chamber forming portions 21-23. A thin portion 281 that is thinner than other portions is formed in at least a part of the flange portion 28 that connects the sub-chamber forming portions. Therefore, when the cavity forming member 10 deforms, the sound absorbing structure 20 near the thin portion 281 deforms first in accordance with the deformation. This allows the sound absorbing structure 20 to accommodate deformation of the cavity forming member 10 while maintaining as much as possible the shapes of the sub-chamber forming portions 21-23 and the openings AP21-AP23 that are related to Helmholtz resonance.

[0035] In addition, the auxiliary chamber forming portions 21-23 of this embodiment each have openings AP21-AP23 of different sizes. Since the openings AP21-AP23 related to Helmholtz resonance have different sizes (the above formula (1)), the auxiliary chamber forming portions 21-23 function as Helmholtz resonators with different resonance frequencies. Therefore, the sound absorbing structure 20 can reduce vibrations over a wider frequency range.

[0036] The tire 100 of this embodiment also includes a sound absorbing structure 20 attached within the cavity HL. Therefore, the sound absorbing structure 20 can reduce road noise generated by tire cavity resonance specific to the tire during vehicle running, by using the sub-chambers CH21-CH23 and the openings AP21-AP23. The sound absorbing structure 20 can also reduce vibrations in the high frequency range by using the soft material that forms the sub-chamber forming portions 21-23.

[0037] The sound absorbing structure 20 of this embodiment is disposed on a first surface FC1 of the tire 100 opposite to the ground contact surface 12 in the cavity HL of the tire 100. When a vehicle equipped with the tire 100 runs, the sound absorbing structure 20 receives a force directed radially outward around the rotation axis OL due to the centrifugal force of the tire 100 rotating around the rotation axis OL. This force presses the sound absorbing structure 20 against the first surface FC1, so that the sound absorbing structure 20 is firmly fixed to the tire 100. For example, when a vehicle runs at a speed of 60 km / h, the rotational angular velocity ω of a 16-inch tire is 52.1 rad / s. In this case, if the mass m of one auxiliary chamber forming portion 21 is set to 20 grams (g) and the radial distance r along the radial direction where the auxiliary chamber forming portion 21 is formed is set to 150 mm, the centrifugal force F acting on the auxiliary chamber forming portion 21 expressed by the following formula (2) is approximately 8.1 N (0.8 kgf). F=mrω 2 (2) The centrifugal force F is about 57.9 N (5.9 kgf) when the vehicle speed is 160 km / h. Thus, the centrifugal force F is a sufficient pressure-bonding force to fix the sub-chamber forming parts 21-23 to the first surface FC1. This reduces the amount of adhesive or double-sided tape required to attach the sound-absorbing structure 20 to the first surface FC1. In addition, in this embodiment, since it is only necessary to attach the sound-absorbing structure 20 to the cavity forming member 10, additional processing of the wheel of the tire 100, for example, is not required, and vibration can be reduced at low cost. In addition, by attaching the sub-chambers CH21-CH23 to the first surface FC1 on the opposite side of the ground contact surface 12, vibration of the tire tread portion can also be reduced, and in addition to cavity resonance, air-transmitted and solid-transmitted road noise caused by vibration of the tire tread portion can also be reduced.

[0038] <Second embodiment> 11 and 12 are schematic cross-sectional views of a tire 100a of the second embodiment. FIG. 11 shows a schematic view of the tire 100a of the second embodiment in an AA cross section parallel to the YZ plane in FIG. 1. FIG. 12 shows a schematic view of the tire 100a of the second embodiment in a BB cross section parallel to the XY plane in FIG. 1. The tire 100a of the second embodiment includes the same cavity forming member 10 as the first embodiment and a sound absorbing structure 20a different from the first embodiment. Therefore, in the second embodiment, the configuration and shape different from the first embodiment will be described, and the description of the configuration and shape the same as the first embodiment will be omitted.

[0039] The sound absorbing structure 20a of the second embodiment is a structure in which the arrangement of the sound absorbing structure 20 of the first embodiment is interchanged between the circumferential direction and the axial direction of the rotation axis OL. In the cross section parallel to the YZ plane shown in FIG. 11, five auxiliary chamber forming parts 21, four flange parts 28 connecting the auxiliary chamber forming parts 21, and flange parts 29 at both ends are formed. As shown in FIG. 12, in the cross section parallel to the XY plane, the auxiliary chamber forming parts 21 to 23 are formed in order in the clockwise direction in FIG. 12, such as the auxiliary chamber forming parts 22, 23, 21, 22, and 23. Therefore, in the tire 100a different from the cross section shown in FIG. 11, for example, there are cross sections in which five auxiliary chamber forming parts 22 are arranged side by side and cross sections in which five auxiliary chamber forming parts 23 are arranged side by side. The sound absorbing structure 20a and the tire 100a of the second embodiment can exhibit a sound absorbing effect in a wide frequency range while responding to the shape change of the cavity forming member 10, as in the first embodiment.

[0040] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit and scope of the invention. For example, the following modifications are also possible.

[0041] In the above first and second embodiments, one example of the sound absorbing structure 20, 20a and the tire 100, 100a has been described, but the configuration and shape of the sound absorbing structure 20, 20a and the tire 100, 100a can be modified in various ways. The cavity forming member 10 to which the sound absorbing structure 20, 20a is attached may be a member other than the tire 100, 100a.

[0042] The sound absorbing structure 20, 20a does not necessarily have to include a plurality of sub-chamber forming portions 21-23, and may have only one sub-chamber forming portion. Also, one sub-chamber forming portion may form two or more sub-chambers. The method of attaching the plurality of sub-chamber forming portions 21-23 to the cavity forming member 10 can be modified in various ways, and the sound absorbing structure 20, 20a does not necessarily have to include a flange portion 28 connecting the two sub-chamber forming portions, and may have only a flange portion 29. The flange portion 28 does not necessarily have to have a thin wall portion 281, and the thin wall portion 281 may be formed in a part of the flange portion 28 (for example, the flange only between the sub-chamber forming portions 21), or none of the thin wall portion 281 may be formed. On the other hand, the thin wall portion 281 may be formed in a part of the sub-chamber forming portions 21-23, or may be formed in the flange portion 29. The auxiliary chamber forming portions 21-23 do not necessarily have to be formed on the first surface FC1 on the opposite side of the ground contact surface 12 of the tires 100, 100a. For example, they may be formed on a surface approximately parallel to the XY plane perpendicular to the rotation axis OL of the tires 100, 100a.

[0043] The sound absorbing structure 20, 20a may include one type of sub-chamber forming portion 21 as the multiple sub-chamber forming portions. The shapes and dimensional relationship of the multiple sub-chamber forming portions 21-23 may be variously modified. The volumes of the sub-chambers CH21-CH23 formed by each of the multiple sub-chamber forming portions 21-23 may be different. The cross-sectional shape of the openings AP21-AP23 formed in the sub-chamber forming portions 21-23 is not limited to a circle, and may be a rectangle or a polygon. In this case, the cross-sectional area S of the openings AP21-AP23 in the above formula (1) may be treated in the above formula (1) as an appropriately modified parameter. The length L (FIG. 3) of the openings AP21-AP23 may be adjusted to be longer by forming a cylindrical member extending from the outside of the sub-chamber forming portions 21-23. Conversely, the length L may be shorter by reducing the thickness of the sub-chamber forming portions 21-23.

[0044] The pre-chamber forming portions 21-23 may be formed of a material having a Young's modulus of 1 MPa or more and 1 GPa or less other than pulp mold. For example, the pre-chamber forming portions 21-23 may be formed of rubber, Teflon (registered trademark), resin, nylon, or the like, and the materials of the pre-chamber forming portions 21-23 may be different. The flange portions 28, 29 do not need to be formed of the same material as the pre-chamber forming portions 21-23, and may be formed of a material having a Young's modulus less than 1 MPa or more than 1 GPa. For example, the flange portions 28, 29 may be made of metal, and the pre-chamber forming portions 21-23 may be fixed to the cavity forming member 10 by bolt fastening.

[0045] Although the present aspect has been described above based on the embodiment and modified examples, the above-mentioned embodiment of the aspect is intended to facilitate understanding of the present aspect and does not limit the present aspect. The present aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents are included in the present aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate. [Explanation of symbols]

[0046] 10...Cavity forming member 12…Ground surface 20, 20a...Sound absorbing structure (sound absorbing structure) 21~23…Subchamber forming part 28, 29…Flange section 100,100a…Tires 281…Thin section AP21~AP23…Aperture C1,C2…sound absorption curve C11, C12…Sound pressure curve C21~C23…Amplitude curve CH21~CH23…Antechamber FC1: 1st side (opposite side) FC2…the second side HL…Cavity OL…Rotation axis PM…Sound absorbing board material SA…Example sample SAx, SAy...Samples for comparison ST... steel materials

Claims

1. A sound absorbing structure attached to a cavity forming member that forms a cavity, a sub-chamber forming portion that forms a sub-chamber that is a space smaller than the cavity within the cavity; a flange portion extending from an edge of the sub-chamber forming portion along the cavity forming member; Equipped with The auxiliary chamber forming portion is an opening communicating between the auxiliary chamber and the cavity; It is made of a material having a Young's modulus of 1 MPa to 1 GPa, Vibrations within the cavity are reduced by Helmholtz resonance generated by the sub-chamber and the opening, the Young's modulus of a material forming the flange portion is smaller than the Young's modulus of a material forming the cavity forming member, A plurality of the sub-chamber forming portions are provided, The flange portion extends from an edge of each of the sub-chamber forming portions along the cavity forming member, a sound absorbing structure, wherein at least a portion of the flange portion located between one of the sub-chamber forming portions and the other of the sub-chamber forming portions has a thin-walled portion that is thinner than the remaining portion.

2. 2. The sound absorbing structure according to claim 1, The flange portion is made of a material having a Young's modulus of 1 MPa to 1 GPa.

3. The sound absorbing structure according to claim 1 or 2, A sound absorbing structure in which at least some of the plurality of sub-chamber forming portions have openings that are different in size from the other sub-chamber forming portions.

4. A tire, A tire comprising, within the tire cavity, a sound absorbing structure according to any one of claims 1 to 3 attached to the tire.

5. 5. A tire according to claim 4, A tire, wherein within the tire cavity, the sound absorbing structure is disposed on a surface of the tire opposite to a contact surface.

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