Sound absorption unit

Abstract

This sound absorption unit attached to an attachment surface of a tire is provided with a resonance sound absorption body and a support body. The support body has: a placement part on which the resonance sound absorption body is placed; and a first holding wall and a second holding wall between which the resonance sound absorption body is disposed. The resonance sound absorption body has: a resonance box; and a neck part extending into a hollow part inside the resonance box. At least a portion of the neck part is disposed between a first groove inner wall surface and a second groove inner wall surface of a groove part provided in the bottom wall of the resonance box.

Description

Sound absorbing unit

[0001] The present disclosure relates to a sound absorbing unit that is attached to a mounting surface of a tire cavity.

[0002] For example, as described in Japanese Patent Application Laid-Open No. 2021-067767, a resonant sound absorber that absorbs sound using the principle of Helmholtz resonance is known. This resonant sound absorber absorbs resonant sound generated in the tire cavity. This resonant sound absorber has a hollow portion formed inside and a resonance box with an opening that connects the hollow portion to the outside.

[0003] In the above-mentioned resonance sound absorber, in order to adjust the frequency of sound absorption, it is conceivable to connect the hollow part of the resonance box to the outside via a hollow neck part. Another conceivable solution is to have this neck part extend into the resonance box. However, when vibrations and centrifugal forces are applied to the resonance sound absorber as the tire rotates, the position of the neck part extending into the resonance box may shift.

[0004] Therefore, the present disclosure describes a sound absorbing unit that can hold a neck portion extending into a resonance box within a hollow portion.

[0005] One aspect of the present disclosure is a sound absorbing unit that is attached to a mounting surface of a tire cavity, the sound absorbing unit comprising: a resonance sound absorber; and a support that supports the resonance sound absorber against the mounting surface while being spaced apart from the mounting surface; the support has: a mounting portion having a mounting surface on which the resonance sound absorber is placed; first and second retaining walls that each rise from the mounting surface and face each other at a predetermined distance in a first direction, with the resonance sound absorber disposed between them; and legs that support the mounting portion while being spaced apart from the mounting surface; the resonance sound absorber has a resonance box with an opening, and a hollow neck that communicates with the opening and extends into a hollow portion inside the resonance box; the resonance box has a bottom wall that faces the mounting surface, and a groove that is provided on the surface of the bottom wall that faces the hollow portion; the groove has a first groove inner wall surface and a second groove inner wall surface that face each other in the first direction, and at least a portion of the neck is located between the first groove inner wall surface and the second groove inner wall surface.

[0006] In this sound absorbing unit, the opposing direction of the first retaining wall and the second retaining wall between which the resonant sound absorber is arranged is the same as the opposing direction of the inner wall surface of the first groove and the inner wall surface of the second groove between which the neck portion is arranged inside the resonance box.

[0007] For example, when centrifugal force acts on the sound absorbing unit as the tire rotates, the centrifugal force causes the resonant sound absorber to press against the mounting portion of the support, causing the mounting portion to bend convexly toward the mounting surface of the tire cavity. This deformation of the mounting portion causes the first and second retaining walls to collapse inward (toward each other). In other words, the resonance box of the resonant sound absorber is sandwiched between the first and second retaining walls in the first direction. This applies a compressive force to the resonance box in the first direction. Furthermore, a groove is provided in the bottom wall of the resonance box, and the first and second groove inner wall surfaces of the groove face each other in the first direction. Therefore, the compressive force applied to the resonance box by the first and second retaining walls applies a force to the first and second groove inner wall surfaces in a direction that brings them closer to each other. As a result, the neck portion disposed between the first and second inner wall surfaces of the groove is sandwiched and held between the first and second inner wall surfaces. In other words, the neck portion is gripped by the first and second inner wall surfaces. In this way, the sound-absorbing unit can hold the neck portion extending into the resonance box within the hollow portion.

[0008] Furthermore, the neck portion is sandwiched and held between the inner wall surfaces of the first groove and the second groove, so that the neck portion and the bottom wall portion become one body. In this case, the thickness of the bottom wall portion is increased by the thickness of the neck portion. This allows the sound absorbing unit to hold the neck portion and improve the strength of the bottom wall portion.

[0009] In the above sound absorbing unit, the bottom wall may be provided with a first protrusion and a second protrusion, each protruding toward the hollow portion, the first protrusion and the second protrusion being spaced apart from each other at a predetermined distance in the first direction, and the groove may be formed by a portion of the bottom wall between the first protrusion and the second protrusion. In this case, the groove does not protrude outward from the bottom of the resonance box. This prevents the resonant sound absorber from becoming too large.

[0010] In the sound absorbing unit, the mounting surface may have, in a portion between the first retaining wall and the second retaining wall, a first separation region adjacent to the first retaining wall and separated from the resonant sound absorber by a predetermined gap, a second separation region adjacent to the second retaining wall and separated from the resonant sound absorber by a predetermined gap, and a mounting region between the first separation region and the second separation region and abutting the bottom wall. In this case, centrifugal force generated in the resonant sound absorber as the tire rotates is input to the mounting region, which is the central portion of the mounting surface. This makes it easier for the mounting region to curve convexly toward the mounting surface of the tire cavity, and makes it easier for the first retaining wall and the second retaining wall to collapse inward toward each other.

[0011] In the sound absorbing unit, the neck portion may be recessed into the groove by at least half of its radial extent in the depth direction of the groove, in which case the neck portion can be more reliably sandwiched and held between the first groove inner wall surface and the second groove inner wall surface, thereby preventing the neck portion from jumping out of the groove.

[0012] In the sound absorbing unit, the legs may include a first leg and a second leg, the first leg extending from one end of the mounting portion in the first direction toward the mounting surface, and the second leg extending from the other end of the mounting portion in the first direction toward the mounting surface. In this case, the support can support the mounting portion against the mounting surface while easily curving the mounting portion convexly toward the mounting surface.

[0013] In the above-described sound-absorbing unit, the neck portion may be inserted into the opening and fixed to the resonance box. In this case, the resonance box and the neck portion may be formed as separate parts depending on the performance required for each. Furthermore, even if the resonance box and the neck portion are separate parts in the sound-absorbing unit, the neck portion extending into the resonance box can be held within the hollow portion.

[0014] In the above sound absorbing unit, when the direction in which the mounting portion and the resonant sound absorber placed on the mounting surface are aligned and perpendicular to the first direction is defined as a second direction, and the direction perpendicular to the first and second directions is defined as a third direction, the resonance box may be configured to be long in the third direction, and the neck portion may extend in the third direction. This makes it possible to increase the length of the neck portion within the resonance box even when the length of the neck portion needs to be increased depending on the frequency of sound to be absorbed.

[0015] In the sound-absorbing unit described above, the resonance box may have a bottom wall and a top wall that defines a hollow between the bottom wall and the top wall. Both ends of the top wall in the first direction are connected to both ends of the mounting portion in the first direction, respectively. The top wall may be formed in an arc shape greater than half the circumference of a circle in a cross section perpendicular to the third direction. In this case, when viewed along the third direction, the outer shape of the top wall gradually decreases in the first direction around the connection between the top wall and the bottom wall, while both ends of the top wall are connected to both ends of the bottom wall. For example, centrifugal force generated by tire rotation may cause the top wall to deform and be pressed toward the mounting portion (bottom wall). In this case, forces are applied to the bottom wall from both ends of the top wall that compress the bottom wall in the first direction. In other words, a force is applied to the bottom wall from the top wall in a direction that brings the first groove inner wall surface and the second groove inner wall surface closer to each other. This allows the sound absorbing unit to more firmly hold the neck portion extending into the resonance box within the hollow portion.

[0016] In the above sound absorbing unit, the resonance box may have a first side wall portion having an opening and a second side wall portion, the first side wall portion covering the opening formed by the top wall portion and the bottom wall portion at one end of the top wall portion and the bottom wall portion in the third direction, and the second side wall portion covering the opening formed by the top wall portion and the bottom wall portion at the other end of the top wall portion and the bottom wall portion in the third direction. In this case, the resonance box can have a hollow portion formed by the bottom wall portion, the top wall portion, the first side wall portion, and the second side wall portion.

[0017] In the above sound absorbing unit, the resonance sound absorber includes a piezoelectric film, and the resonance box has a first side wall portion with an opening, the first side wall portion covering the opening formed by the top wall portion and the bottom wall portion at one end of the top wall portion and the bottom wall portion in the third direction, and the piezoelectric film covering the opening formed by the top wall portion and the bottom wall portion at the other end of the top wall portion and the bottom wall portion in the third direction. In this case, the resonance sound absorber can form a hollow portion with the bottom wall portion, the top wall portion, the first side wall portion, and the piezoelectric film. Furthermore, the piezoelectric film can be vibrated by air vibrations within the cavity caused by rotating the tire. Here, sound pressure is high within the tire cavity. Furthermore, because the tire cavity is sealed, acoustic energy is not diffracted or diffused. Therefore, the sound absorbing unit can efficiently vibrate the piezoelectric film by air vibrations within the tire cavity to generate electricity.

[0018] In the above sound absorbing unit, the resonant sound absorber may include a piezoelectric film, and the piezoelectric film may define a part of the hollow portion with the resonance box. Even in this case, the sound absorbing unit can generate electricity by efficiently vibrating the piezoelectric film with air vibrations within the tire cavity.

[0019] In the sound absorbing unit, the support body may have a connecting wall connecting a tip end of the first retaining wall in a direction rising from the mounting surface to a tip end of the second retaining wall in a direction rising from the mounting surface, and the mounting portion, the first retaining wall, the second retaining wall, and the connecting wall may surround the resonance box. In this case, the support body can hold the resonance sound absorber so that it does not fall off.

[0020] According to the present disclosure, the neck portion extending into the resonance box can be held within the hollow portion.

[0021] FIG. 1 is a schematic cross-sectional view of a tire to which a sound absorbing unit according to a first embodiment is attached. FIG. 2 is a schematic perspective view of the sound absorbing unit according to the first embodiment, viewed from the opening side. FIG. 3 is a schematic front view of the sound absorbing unit of FIG. 2, viewed from the opening side. FIG. 4 is a schematic perspective view of the resonant sound absorber of FIG. 2, viewed from the opening side. FIG. 5 is a schematic perspective view of the resonant sound absorber of FIG. 2, viewed from the bottom wall side. FIG. 6 is a schematic front view of the resonant sound absorber of FIG. 2, viewed from the opening side. FIG. 7 is a schematic cross-sectional view of the resonant sound absorber of FIG. 2, cut along the axis. FIG. 8 is a schematic cross-sectional view of the resonant sound absorber of FIG. 2, cut in a direction perpendicular to the axis. FIG. 9 is a schematic perspective view of a sound absorbing unit according to a second embodiment, viewed from the opening side. FIG. 10 is a side view of the sound absorbing unit of FIG. 9. FIG. 11 is a schematic front view of the sound absorbing unit of FIG. 9, viewed from the opening side. Fig. 12 is a schematic rear view of the sound absorbing unit of Fig. 9, as seen from the piezoelectric film side. Fig. 13 is a cross-sectional view of the sound absorbing unit of Fig. 9, taken along the axis of the resonant sound absorber. Fig. 14 is a cross-sectional view taken along line XIV-XIV in Fig. 13. Fig. 15 is a cross-sectional view taken along line XV-XV in Fig. 13. Fig. 16 is a cross-sectional view taken along line XVI-XVI in Fig. 13. Fig. 17 is a cross-sectional view taken along line XVII-XVII in Fig. 13. Fig. 18 is a schematic front view of a sound absorbing unit according to a modified example of the second embodiment, as seen from the opening side.

[0022] Hereinafter, with reference to the drawings, an embodiment of a sound-absorbing unit according to the present disclosure will be described in detail. Note that in the drawings, identical or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, numerical ranges indicated using "to" indicate ranges that include the numerical values ​​before and after "to" as the minimum and maximum values, respectively.

[0023] First Embodiment First, a first embodiment of the sound absorbing unit will be described. FIG. 1 is a schematic cross-sectional view of a tire to which a sound absorbing unit according to the first embodiment is attached. In a tire T, cavity resonance can occur, in which the air in the cavity S resonates due to vibrations caused by passing over uneven road surfaces while the vehicle is traveling. The cavity resonance frequency is, for example, approximately 180 Hz to 250 Hz. The cavity resonance frequency varies depending on factors such as the size of the tire T. The sound absorbing unit 100 according to this embodiment is attached to the mounting surface Ta of the cavity S of the tire T in order to efficiently absorb cavity resonance in such a low frequency band (for example, approximately 180 Hz to 250 Hz). The mounting surface Ta is the inner circumferential surface of the tread Tb of the tire T. The cavity S of the tire T is an annular space defined by the outer circumferential surface of a wheel on which the tire T is mounted and the inner surface of the tire T.

[0024] In this embodiment, four sound absorbing units 100 are provided in the cavity S of the tire T. In this embodiment, the four sound absorbing units 100 are attached to the attachment surface Ta at positions that are offset by 90° from one another in the rotational direction of the tire T. However, the number and attachment positions of the sound absorbing units 100 are not limited to the configuration shown in FIG. 1 . Furthermore, the sound absorbing units 100 may be attached to the cavity S of the tire T in combination with other functional components such as a power generation device, a sensor device, a secondary battery, a capacitor, an antenna device, a transmitter, a processor, a memory, and a circuit, as needed. In this case, it is preferable to attach the sound absorbing units 100 in an appropriate position so that the weight within the tire T is uniform, taking into consideration the weight and number of the attached functional components and sound absorbing units 100.

[0025] The sound absorbing unit 100 according to the first embodiment will be described with reference to FIGS. 2 and 3 . FIG. 2 is a schematic perspective view of the sound absorbing unit according to the first embodiment, as viewed from the open side. FIG. 3 is a schematic front view of the sound absorbing unit of FIG. 2, as viewed from the open side. As shown in FIGS. 2 and 3 , the sound absorbing unit 100 includes a resonance sound absorber 1 and a support body 5. The resonance sound absorber 1 has a Helmholtz resonance structure. The resonance sound absorber 1 absorbs cavity resonance within the inner cavity S of the tire T. The resonance sound absorber 1 has a shape that extends along the axis L1. In other words, the resonance sound absorber 1 has a substantially cylindrical shape with its longitudinal direction along the axis L1. In this embodiment, the sound absorbing unit 100 is attached to the mounting surface Ta of the tire T, for example, so that the axis L1 is parallel (substantially parallel) to the rotational axis of the tire T.

[0026] The support body 5 is attached to the mounting surface Ta of the tire T. The support body 5 supports the resonance sound absorber 1 against the mounting surface Ta while being spaced apart from the mounting surface Ta. In the present embodiment, three support bodies 5 are provided, as an example. The three support bodies 5 are arranged side by side along the axis L1. The three support bodies 5 have the same shape. The resonance sound absorber 1 is supported against the mounting surface Ta by the three support bodies 5. However, the number of support bodies 5 supporting the resonance sound absorber 1 is not limited to three.

[0027] The support body 5 includes a mounting portion 50, a first retaining wall 51, a second retaining wall 52, a connecting wall 53, a first leg (leg) 54, and a second leg (leg) 55. The resonance sound absorber 1 is mounted on the mounting portion 50. The mounting portion 50 has a mounting surface 50a on which the resonance sound absorber 1 is mounted. The mounting portion 50 has an opposing surface 50b that faces the mounting surface Ta when the support body 5 is mounted on the mounting surface Ta of the tire T. The mounting surface 50a is the surface opposite to the opposing surface 50b.

[0028] The first retaining wall 51 and the second retaining wall 52 each rise from the mounting surface 50a of the mounting portion 50 and face each other at a predetermined distance. That is, the first retaining wall 51 and the second retaining wall 52 rise from the mounting portion 50 toward the opposite side of the mounting surface Ta of the tire T. The resonance sound absorber 1 placed on the mounting surface 50a of the mounting portion 50 is disposed between the first retaining wall 51 and the second retaining wall 52. Here, the direction in which the first retaining wall 51 and the second retaining wall 52 face each other is defined as a first direction D1. The first direction D1 is a direction perpendicular to the direction along the axis L1. The alignment direction of the mounting portion 50 and the resonance sound absorber 1 placed on the mounting surface 50a of the mounting portion 50 is defined as a second direction D2. The second direction D2 is a direction perpendicular to the first direction D1. The second direction D2 is also the opposing direction between the mounting portion 50 and the mounting surface Ta of the tire T. The second direction D2 is also the height direction of the sound absorbing unit 100 relative to the mounting surface Ta of the tire T. A direction perpendicular to the first direction D1 and the second direction D2 is defined as a third direction D3. The third direction D3 is also a direction along the axis L1. The resonant sound absorber 1 is sandwiched between the first retaining wall 51 and the second retaining wall 52 in the first direction D1.

[0029] The connecting wall 53 connects the tip of the first retaining wall 51 in the direction rising from the mounting surface 50a to the tip of the second retaining wall 52 in the direction rising from the mounting surface 50a. As a result, the mounting portion 50, the first retaining wall 51, the connecting wall 53, and the second retaining wall 52 form an annular retaining portion 56. In this manner, the first retaining wall 51 and the second retaining wall 52 may not be independent but may be integrated with each other, or may be integrated via another member. The retaining portion 56 surrounds the resonance sound absorber 1 (resonance box 10). The retaining portion 56 surrounds and holds the resonance sound absorber 1. The retaining portion 56 is elastically deformable. The retaining portion 56 can detachably hold the resonance sound absorber 1 by its elastic force.

[0030] 3, the mounting surface 50a of the mounting part 50 has a first separation region 50c, a second separation region 50d, and a mounting region 50e in a portion between the first retaining wall 51 and the second retaining wall 52 in the first direction D1. The first separation region 50c is a region on the mounting surface 50a that is adjacent to the first retaining wall 51 and is separated from the resonant sound absorber 1 at a predetermined gap. The second separation region 50d is a region on the mounting surface 50a that is adjacent to the second retaining wall 52 and is separated from the resonant sound absorber 1 at a predetermined gap. The mounting region 50e is a region between the first separation region 50c and the second separation region 50d, and is a region that abuts against the resonant sound absorber 1 (bottom wall portion 11).

[0031] The first leg 54 and the second leg 55 support the mounting portion 50 in a state spaced apart from the mounting surface Ta of the tire T. The first leg 54 and the second leg 55 are each attached to the mounting surface Ta of the tire T. A space is formed between the mounting portion 50 and the mounting surface Ta. The first leg 54 and the second leg 55 are provided on the mounting portion 50 at a predetermined distance from each other in the first direction D1. The first leg 54 extends from one end of the mounting portion 50 in the first direction D1 toward the mounting surface Ta of the tire T. The second leg 55 extends from the other end of the mounting portion 50 opposite the one end in the first direction D1 toward the mounting surface Ta of the tire T.

[0032] The first leg portion 54 includes a first main body portion 54a and a first mounting portion 54b. The first mounting portion 54b is attached to the mounting surface Ta of the tire T. The first main body portion 54a connects the first mounting portion 54b to the mounting portion 50. The first mounting portion 54b protrudes outward from the first main body portion 54a (toward the opposite side from the second leg portion 55).

[0033] The second leg portion 55 includes a second main body portion 55a and a second mounting portion 55b. The second mounting portion 55b is attached to the mounting surface Ta of the tire T. The second main body portion 55a connects the second mounting portion 55b to the mounting portion 50. The second mounting portion 55b protrudes outward from the second main body portion 55a (toward the opposite side from the first leg portion 54).

[0034] The first mounting portion 54b of the first leg portion 54 and the second mounting portion 55b of the second leg portion 55 are attached to the mounting surface Ta of the tire T by, for example, double-sided tape with adhesive surfaces on both sides, adhesive, welding, etc.

[0035] 3 , a sealant layer F may be provided on the mounting surface Ta of the tire T. This sealant layer F may have the function of sealing holes in the tire T, for example, to prevent punctures of the tire T. In this case, the first mounting portion 54b and the second mounting portion 55b are attached to the sealant layer F provided on the mounting surface Ta. That is, the first mounting portion 54b, etc. are attached to the mounting surface Ta via the sealant layer F. The first mounting portion 54b, etc. are attached to the sealant layer F, for example, with an adhesive or the like. Furthermore, the first mounting portion 54b, etc. may be disposed on the sealant layer F when the sealant layer F is cured, and may be adhered to the sealant layer F as the sealant layer F cures.

[0036] Thus, in this specification, attaching an attachment portion such as the first attachment portion 54b to the attachment surface Ta includes attaching the first attachment portion 54b etc. directly to the attachment surface Ta, and attaching the first attachment portion 54b etc. to the attachment surface Ta via a member such as a sealant layer F.

[0037] The material of the support body 5 may be, for example, a dynamically crosslinked thermoplastic elastomer (TPV) or vulcanized rubber such as styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), butadiene rubber (BR), chloroprene rubber (CR), and isoprene rubber (IR). By using these materials, a support body 5 having excellent elasticity, heat resistance, and flexibility and suitable as a supporting member within the cavity S of the tire T can be obtained.

[0038] However, the material of the support body 5 is not limited to these. In addition to these, the material of the support body 5 may be a thermoplastic elastomer other than the dynamically crosslinked thermoplastic elastomer (TPV) (for example, a styrene-based elastomer (TPS), a polyolefin-based elastomer (TPO), a polyurethane-based elastomer (TPU), a polyester-based elastomer (TPEE), a polyester-based elastomer (TPC), etc.). Furthermore, the material of the support body 5 may be various foam materials (for example, foamed rubber, foamed urethane, etc.).

[0039] The support body 5 is configured to be elastically deformable by centrifugal force generated by rotation of the tire T. This rotation of the tire T refers to the rotation when a vehicle equipped with the tire T is running. The support body 5 may be configured so that only a portion thereof is elastically deformable by centrifugal force. The support body 5 may be configured so that at least the mounting portion 50 is elastically deformable by centrifugal force.

[0040] As shown in Figures 2 and 3, the resonance sound absorber 1 includes a resonance box 10 and a neck portion 20. The resonance sound absorber 1 will be described in detail below. Figure 4 is a schematic perspective view of the resonance sound absorber of Figure 2, viewed from the opening side. Figure 5 is a schematic perspective view of the resonance sound absorber of Figure 2, viewed from the bottom wall side. Figure 6 is a schematic front view of the resonance sound absorber of Figure 2, viewed from the opening side. Figure 7 is a schematic cross-sectional view of the resonance sound absorber of Figure 2, taken along the axis. Figure 8 is a schematic cross-sectional view of the resonance sound absorber of Figure 2, taken along a direction perpendicular to the axis. Figure 8 is also a cross-sectional view taken along line VIII-VIII in Figure 7.

[0041] As shown in FIGS. 4 to 8 , a hollow portion R is formed inside the resonance box 10 (see FIG. 7 ). The resonance box 10 has an opening 10b (see FIG. 7 ) that connects the hollow portion R with the external space (the space outside the resonance box 10). The resonance box 10 is configured to be long in the third direction D3. The length of the resonance box 10 in the third direction D3 is, for example, approximately 30 mm to 80 mm. The length of the resonance box 10 in the first direction D1 is, for example, approximately 20 mm to 50 mm. The length of the resonance box 10 in the second direction D2 (i.e., the height of the resonance box 10) is, for example, approximately 20 mm to 50 mm. The length of the entire sound absorbing unit 100, including the resonance absorber 1 and the support body 5, in the second direction D2 (i.e., the height of the sound absorbing unit 100) is, for example, approximately 25 mm to 60 mm.

[0042] The resonance box 10 includes a bottom wall 11, a top wall 12, a first side wall 13, a second side wall 14, and a fixed cylinder 15 (see FIG. 7 ). The bottom wall 11 is formed in a generally rectangular plate shape that is long in the third direction D3 and short in the first direction D1. The bottom wall 11 faces a mounting surface 50a of a mounting portion 50 of the support body 5. That is, the resonance sound absorber 1 is placed on the mounting surface 50a so that the bottom wall 11 of the resonance box 10 faces the mounting surface 50a of the mounting portion 50. When the resonance sound absorber 1 is placed on the mounting portion 50, the bottom wall 11 abuts against the mounting surface 50a.

[0043] The top wall portion 12 forms a hollow portion R between itself and the bottom wall portion 11. The top wall portion 12 covers the hollow portion R from the side opposite to the bottom wall portion 11. As shown in Figure 8, both ends (ends 12a and 12b) of the top wall portion 12 in the first direction D1 are connected to both ends (ends 11a and 11b) of the bottom wall portion 11 in the first direction D1, respectively.

[0044] The top wall 12 is curved in an arc shape when viewed in the third direction D3. In a cross section perpendicular to the third direction D3 (a cross section along the first direction D1 and the second direction D2), the top wall 12 is formed in an arc shape that follows an arc larger than half the circumference of a circle.

[0045] In other words, as shown in FIG. 8 , when viewed along the axis L1 (third direction D3), the top wall portion 12 has a shape that follows a cylindrical surface M whose axis is a central axis L2 that is aligned with the axis L1. The cylindrical surface M whose axis is the central axis L2 is a cylindrical surface that surrounds the central axis L2 and is centered on the central axis L2. However, the shape of the top wall portion 12 is not limited to being completely aligned with the cylindrical surface M. The top wall portion 12 may have any shape that is close to being aligned with the cylindrical surface M. For example, the angle α from the end 12a to the end 12b of the top wall portion 12 in the circumferential direction about the central axis L2 is an angle that is greater than half the circumference (180°) of the circular shape.

[0046] The first side wall 13 has a plate shape and covers a tube opening (opening) H1 (see FIG. 7 ) formed by the top wall 12 and the bottom wall 11 at one end of the top wall 12 and the bottom wall 11 in the third direction. The first side wall 13 has an opening 10b.

[0047] The second side wall 14 has a plate-like shape. The second side wall 14 covers a cylindrical opening (opening) H2 (see FIG. 7 ) formed by the top wall 12 and the bottom wall 11 at the other end opposite to one end of the top wall 12 and the bottom wall 11 in the third direction. In this way, the resonance box 10 has a hollow portion R formed therein, and the rest of the resonance box 10 is closed except for the opening 10b. The opening 10b introduces air vibrations from outside the resonance box 10 into the hollow portion R.

[0048] 6 and 7 , opening 10b provided in first side wall portion 13 is located closer to bottom wall portion 11 than the central axis L2 of cylindrical surface M along which top wall portion 12 extends, when viewed along axis L1 (third direction D3). In other words, opening 10b is located between central axis L2 and bottom wall portion 11. That is, opening 10b is located near the edge of first side wall portion 13 that is connected to bottom wall portion 11. Opening 10b is located closer to the edge of first side wall portion 13 that is connected to bottom wall portion 11 than the edge that is connected to top wall portion 12.

[0049] The portion of the top wall 12 facing the bottom wall 11 in the second direction D2 is referred to as the upper wall 12c. The upper wall 12c is the portion of the top wall 12 facing the bottom wall 11 across the central axis L2. The thickness of the bottom wall 11 is thicker than the thickness of the upper wall 12c of the top wall 12. For example, the thickness of the bottom wall 11 may be 1.1 times or more the thickness of the upper wall 12c of the top wall 12. For example, the thickness of the upper wall 12c of the top wall 12 may be approximately 0.4 mm or less. Furthermore, the thickness of the second side wall 14 is thicker than the thickness of the upper wall 12c of the top wall 12. For example, the thickness of the second side wall 14 may be 1.1 times or more the thickness of the upper wall 12c of the top wall 12.

[0050] The bottom wall 11 is provided with a first bead (first protrusion) 11c and a second bead (second protrusion) 11d extending along the third direction D3 (axis L1). The first bead 11c and the second bead 11d extend parallel to each other along the third direction D3. The first bead 11c and the second bead 11d provided on the bottom wall 11 each protrude toward the hollow portion R (inside the resonance box 10).

[0051] As shown in Fig. 8, the first bead 11c protrudes toward the hollow portion R so that a cross section cut along a direction perpendicular to the third direction D3 has a generally arc-shaped cross section. Similar to the first bead 11c, the second bead 11d also protrudes toward the hollow portion R so that the cross section has a generally arc-shaped cross section. However, the shapes of the first bead 11c and the second bead 11d are not limited to a generally arc-shaped cross section, and may be other shapes. The first bead 11c and the second bead 11d may have any shape that protrudes toward the hollow portion R.

[0052] A groove 16 is provided on the surface of the bottom wall 11 facing the hollow portion R. That is, the groove 16 is provided on the inner surface of the resonance box 10, in the bottom wall 11 portion. The groove 16 is recessed from the hollow portion R toward the mounting surface 50a of the mounting portion 50. The groove 16 extends along the third direction D3. In this embodiment, the first bead 11c and the second bead 11d are spaced apart from each other at a predetermined interval in the first direction D1. In this embodiment, the groove 16 is defined by the portion of the bottom wall 11 between the first bead 11c and the second bead 11d.

[0053] The groove 16 has a first groove inner wall surface 16a and a second groove inner wall surface 16b that face each other in the first direction D1. The first groove inner wall surface 16a is formed by the surface of the first bead 11c that faces the hollow portion R and faces the second bead 11d. The second groove inner wall surface 16b is formed by the surface of the second bead 11d that faces the hollow portion R and faces the first bead 11c.

[0054] As shown in Figure 7, the fixed cylinder portion 15 is provided on the outer surface of the first side wall portion 13. The outer surface of the first side wall portion 13 is the surface facing outward in the resonance box 10. The fixed cylinder portion 15 has a cylindrical shape. In the present embodiment, the fixed cylinder portion 15 has a cylindrical shape, for example. The fixed cylinder portion 15 communicates with an opening 10b provided in the first side wall portion 13. As a result, the hollow portion R within the resonance box 10 and the external space communicate with each other via the opening 10b provided in the first side wall portion 13 and the fixed cylinder portion 15.

[0055] The neck portion 20 communicates with the opening 10b provided in the first side wall portion 13 and extends into the hollow portion R inside the resonance box 10. The base end 20a of the neck portion 20 may extend outward from the resonance box 10 (here, the fixed cylinder portion 15). The neck portion 20 has a hollow portion 20c formed therein. The base end 20a and the tip end 20b of the neck portion 20 are open ends that expose the hollow portion 20c. The length of the neck portion 20 in the third direction D3 is, for example, approximately 10 mm to 50 mm.

[0056] The neck portion 20 has a tube main body portion 21 and a folded portion 22. The tube main body portion 21 has a tubular shape that forms a hollow portion 20c inside. In this embodiment, the tube main body portion 21 has a cylindrical shape, as an example. The folded portion 22 has a cylindrical shape. The folded portion 22 is arranged at the base end 20a of the neck portion 20 so as to surround the tube main body portion 21. In this embodiment, the folded portion 22 has a cylindrical shape, as an example. A predetermined gap is provided between the outer peripheral surface of the tube main body portion 21 and the inner peripheral surface of the folded portion 22. The tube main body portion 21 and the folded portion 22 are connected to each other at the base end 20a of the neck portion 20. The fixed tube portion 15 of the resonance box 10 can be inserted into the gap between the outer peripheral surface of the tube main body portion 21 and the inner peripheral surface of the folded portion 22.

[0057] The neck portion 20 is inserted into the fixed cylinder portion 15 and the opening 10b of the resonance box 10 and fixed to the resonance box 10, and extends into the hollow portion R of the resonance box 10. In other words, the tip 20b of the neck portion 20 is located within the hollow portion R. The neck portion 20 is inserted into the resonance box 10 so as to extend in the third direction D3. As a result, the hollow portion R of the resonance box 10 and the external space communicate with each other via the hollow portion 20c of the neck portion 20.

[0058] The neck portion 20 is inserted into the fixed cylinder portion 15 of the resonance box 10 and the opening 10b so that the fixed cylinder portion 15 of the resonance box 10 fits into the gap between the outer peripheral surface of the cylinder main body portion 21 and the inner peripheral surface of the folded portion 22. In other words, the cylinder main body portion 21 of the neck portion 20 is inserted into the fixed cylinder portion 15 of the resonance box 10 and the opening 10b. The neck portion 20 is fixed to the fixed cylinder portion 15 of the resonance box 10. The neck portion 20 and the fixed cylinder portion 15 of the resonance box 10 are fixed to each other by, for example, engaging a recess with a protrusion, engaging a thread with a screw groove, or by adhesive bonding. There are no particular limitations on the method for fixing the neck portion 20 to the fixed cylinder portion 15 of the resonance box 10.

[0059] 7 and 8 , the tube main body 21 of the neck portion 20 inserted into the opening 10b of the first side wall 13 is disposed between the first groove inner wall surface 16a and the second groove inner wall surface 16b of the groove 16 and is supported by the first groove inner wall surface 16a and the second groove inner wall surface 16b. At least a portion of the tube main body 21 of the neck portion 20 is inserted into the groove 16 in the depth direction of the groove 16 (second direction D2). Note that the neck portion 20 may abut against the bottom of the groove 16 or may be spaced apart from the bottom of the groove 16 as shown in FIG. 8 . It is sufficient that at least a portion of the neck portion 20 is disposed between the first groove inner wall surface 16a and the second groove inner wall surface 16b in the third direction D3.

[0060] As described above, the resonance box 10 and the neck portion 20 are separate components in the resonance sound absorber 1. The neck portion 20 is inserted into the fixed cylindrical portion 15 and the opening 10b of the resonance box 10, and is fixed to the fixed cylindrical portion 15 of the resonance box 10. In this way, the resonance box 10 and the neck portion 20 are integrated together.

[0061] For example, the resonance box 10 is required to have higher rigidity than the neck portion 20 so that the hollow portion R is not crushed by centrifugal force when the tire T rotates. Furthermore, the resonance sound absorber 1 is also required to be lightweight overall. Thus, the resonance sound absorber 1 is required to be able to respond to various conditions. In this embodiment, the resonance box 10 and the neck portion 20 of the resonance sound absorber 1 are separate components. Therefore, different materials can be used for the resonance box 10 and the neck portion 20 so that the respective requirements are met. Furthermore, different manufacturing methods can be used for the resonance box 10 and the neck portion 20 so that the respective requirements are met.

[0062] For example, the material constituting the resonance box 10 may have a higher elastic modulus than the material constituting the neck portion 20. This allows the resonance box 10 to be tightly supported by the neck portion 20 when the neck portion 20 is sandwiched between the first groove inner wall surface 16a and the second groove inner wall surface 16b, as described in detail below. The material constituting the resonance box 10 may have a higher rigidity than the material constituting the neck portion 20. This can suppress deformation of the resonance box 10 or allow the resonance box 10 to stably support the neck portion 20. The material constituting the resonance box 10 may have a higher specific gravity than the material constituting the neck portion 20. This can reduce the weight of the neck portion 20.

[0063] For example, the materials of the resonance box 10 and the neck portion 20 may be thermoplastics such as polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), polycarbonate (PC), polyacetal (POM), polyphenylene sulfide (PPS), etc.; thermoplastic elastomers such as olefin-based (TPO), dynamically crosslinked (TPV), styrene-based (TPS), polyurethane-based (TPU), and polyester-based (TPEE); or vulcanized rubbers such as natural rubber (NR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), butadiene rubber (BR), and chloroprene rubber (CR).

[0064] The resonance box 10 can be manufactured by blow molding, as an example. In this case, the manufacturing method of the resonance box 10 of the resonance sound absorber 1 includes the steps of placing the material (parison) of the resonance box 10 in a mold in which a cavity corresponding to the outer shape of the resonance box 10 is formed, injecting gas into the material to form the resonance box 10 by blow molding, and removing the molded resonance box 10 from the mold. Note that the air blowing port that injects gas into the material in the step of molding the resonance box 10 by blow molding serves as the opening 10b of the resonance box 10. By molding the resonance box 10 by blow molding, the resonance box 10 having the hollow portion R can be easily manufactured.

[0065] As described above, the resonance box 10 is formed by blow molding so as to satisfy various conditions, such as the condition for the position of the opening 10b provided in the first side wall 13, the condition for the difference in thickness between the bottom wall 11 and the upper wall 12c, and the condition for the difference in thickness between the bottom wall 11 and the upper wall 12c of the top wall 12. Specifically, the resonance box 10 having the above-described configuration is obtained by adjusting, for example, the temperature and temperature distribution of the mold, the temperature and temperature distribution of the material of the resonance box 10, the position at which air is supplied into the material placed in the mold (the position that becomes the opening 10b), the pressure of the gas supplied into the material placed in the mold, the temperature difference between the mold and the material, the dimensional difference between the mold and the material, the material of the resonance box 10, etc.

[0066] The neck portion 20 may be manufactured by, for example, injection molding, extrusion molding, modeling using a 3D printer, salt coagulation, or the like. However, there are no particular limitations on the manufacturing method for the neck portion 20. As such, since the resonance box 10 and the neck portion 20 are separate components, they can be manufactured by different manufacturing methods.

[0067] Next, a method for manufacturing the resonance absorber 1 will be described. The method for manufacturing the resonance absorber 1 includes the steps of manufacturing the resonance box 10 having the opening 10b and the hollow portion R formed therein, manufacturing the hollow neck portion 20, and inserting the neck portion 20 into the opening 10b of the resonance box 10 and fixing the neck portion 20 to the resonance box 10. In this way, the resonance box 10 and the neck portion 20, which are separate components, are assembled to obtain the resonance absorber 1. Note that the order of the steps for manufacturing the resonance box 10 and the neck portion 20 does not matter.

[0068] As described above, in the sound absorbing unit 100, the opposing direction between the first retaining wall 51 and the second retaining wall 52 of the support body 5 between which the resonant sound absorber 1 is arranged, and the opposing direction between the first groove inner wall surface 16a and the second groove inner wall surface 16b of the groove portion 16 between which the neck portion 20 (tube main body portion 21) is arranged within the resonance box 10, are the same direction (first direction D1).

[0069] For example, when centrifugal force acts on the resonance sound absorber 1 as the tire T rotates, the centrifugal force causes the resonance sound absorber 1 to press against the mounting portion 50 of the support body 5, causing the mounting portion 50 to bend convexly toward the mounting surface Ta of the tire T. This deformation of the mounting portion 50 causes the first retaining wall 51 and the second retaining wall 52 to collapse inward (toward each other). That is, as shown in FIG. 3 , the mounting portion 50 is pressed in the direction indicated by arrow A1 by the resonance sound absorber 1, causing the mounting portion 50 to bend convexly in the direction indicated by arrow A1. As the mounting portion 50 bends (deforms), the resonance box 10 of the resonance sound absorber 1 is sandwiched between the first retaining wall 51 and the second retaining wall 52 in the first direction D1, as indicated by arrow A2.

[0070] As a result, a compressive force is applied to the resonance box 10 in the first direction D1, as indicated by arrow A2. The bottom wall 11 of the resonance box 10 also includes a groove 16. The first and second groove inner wall surfaces 16a and 16b of the groove 16 face each other in the first direction D1. Therefore, the compressive force applied to the resonance box 10 by the first and second retaining walls 51 and 52 applies a force to the first and second groove inner wall surfaces 16a and 16b in a direction that moves them closer to each other. As a result, the neck portion 20, which is disposed between the first and second groove inner wall surfaces 16a and 16b of the groove 16, is sandwiched and held between the first and second groove inner wall surfaces 16a and 16b. In other words, the neck portion 20 is gripped by the first and second groove inner wall surfaces 16a and 16b. In this way, the resonance sound absorber 1 can hold the neck portion 20 extending into the resonance box 10 within the hollow portion R by the centrifugal force generated by the rotation of the tire T.

[0071] Furthermore, the neck portion 20 is sandwiched and held between the first groove inner wall surface 16a and the second groove inner wall surface 16b, thereby integrating the neck portion 20 with the bottom wall portion 11. In this case, it can be said that the thickness of the bottom wall portion 11 is increased by the amount of the neck portion 20. This allows the resonant sound absorber 1 to hold the neck portion 20 and improve the strength of the bottom wall portion 11.

[0072] Here, if the size (radius) of the tire T to which the sound absorbing unit 100 is attached changes, the degree of curvature of the mounting surface Ta of the tire T also changes. Therefore, in general, in order to press the first groove inner wall surface 16a and the second groove inner wall surface 16b against the neck portion 20 so as to hold the neck portion 20, it is necessary to make detailed adjustments to the shape of each part, taking into account the degree of curvature of the mounting surface Ta of the tire T. In contrast, with the sound absorbing unit 100 according to this embodiment, the centrifugal force generated by the rotation of the tire T can bring the first groove inner wall surface 16a and the second groove inner wall surface 16b closer to each other. Therefore, with the sound absorbing unit 100 according to this embodiment, even if the size of the tire T to be attached changes, the centrifugal force can press the first groove inner wall surface 16a and the second groove inner wall surface 16b against the neck portion 20, thereby more reliably holding the neck portion 20. In this way, the sound absorbing unit 100, by using a configuration that utilizes centrifugal force, can more reliably hold the neck portion 20 while avoiding complex design. Furthermore, the sound absorbing unit 100 does not require any member for fixing the neck portion 20 to the bottom wall portion 11, which allows for a reduction in weight.

[0073] In the sound absorbing unit 100, the state of the centrifugal force applied also changes depending on the rotation state of the tire T. Therefore, in the sound absorbing unit 100, when the tire T stops rotating, the compression of the resonance box 10 by the first retaining wall 51 and the second retaining wall 52 is released, and the clamping of the neck portion 20 is also released. In other words, in the sound absorbing unit 100, the resonance box 10 returns to its original shape when the rotation of the tire T stops. In this way, because the sound absorbing unit 100 can restore the shape of the resonance box 10 to its original state, permanent deformation of the resonance box 10 can be suppressed.

[0074] The groove 16 is formed by a first bead 11c and a second bead 11d provided on the bottom wall 11. The first bead 11c and the second bead 11d protrude toward the hollow portion R inside the resonance box 10. In this case, the groove 16 does not protrude outward from the bottom surface of the resonance box 10 (the surface that abuts against the mounting surface 50a of the mounting portion 50). This prevents the resonant sound absorber 1 from becoming too large.

[0075] The mounting surface 50a of the mounting portion 50 has a mounting region 50e with which the resonance sound absorber 1 abuts, and a first separated region 50c and a second separated region 50d with which the resonance sound absorber 1 does not abut. The mounting region 50e is located between the first separated region 50c and the second separated region 50d. In this case, centrifugal force generated in the resonance sound absorber 1 as the tire T rotates is input to the mounting region 50e, which is the central part of the mounting surface 50a of the mounting portion 50. This makes it easier for the mounting portion 50 to curve convexly toward the mounting surface Ta of the tire T, and makes it easier for the first retaining wall 51 and the second retaining wall 52 to collapse inward toward each other.

[0076] The first leg 54 is connected to one end of the mounting portion 50 in the first direction D1, and the second leg 55 is connected to the other end of the mounting portion 50 in the first direction D1. In this case, the support body 5 can easily curve the mounting portion 50 in a convex shape toward the mounting surface Ta of the tire T, while supporting the mounting portion 50 against the mounting surface Ta.

[0077] The neck portion 20 is inserted into the opening 10b of the resonance box 10 and fixed to the resonance box 10. In this case, the resonance box 10 and the neck portion 20 can be formed as separate parts depending on the performance required of each. Furthermore, even if the resonance box 10 and the neck portion 20 are separate parts, the sound absorbing unit 100 can hold the neck portion 20 extending inside the resonance box 10.

[0078] The resonance box 10 is configured to be long in the third direction D3. The neck portion 20 extends in the third direction D3 within the hollow portion R inside the resonance box 10. This makes it possible to increase the length of the neck portion 20 within the resonance box 10 even when the length of the neck portion 20 needs to be increased depending on the frequency of sound to be absorbed.

[0079] As shown in FIG. 8 , the top wall portion 12 is formed in an arc shape along an arc larger than half the circumference of a circle in a cross section perpendicular to the third direction D3. In this case, when viewed along the third direction D3, the outer shape of the top wall portion 12 gradually decreases in size in the first direction D1 around the connection between the top wall portion 12 and the bottom wall portion 11, while both ends (ends 12a and 12b) of the top wall portion 12 are connected to both ends (ends 11a and 11b) of the bottom wall portion 11. For example, centrifugal force accompanying the rotation of the tire T tends to deform the top wall portion 12 so as to be pressed toward the mounting portion 50 (bottom wall portion 11). In this case, forces are applied to the bottom wall portion 11 from both ends (ends 12a and 12b) of the top wall portion 12, compressing the bottom wall portion 11 in the first direction D1. In other words, a force is applied from the top wall 12 to the bottom wall 11 in a direction that moves the first groove inner wall surface 16 a and the second groove inner wall surface 16 b closer to each other. This allows the sound-absorbing unit 100 to more firmly hold the neck portion 20 extending into the resonance box 10 within the hollow portion R.

[0080] The resonance box 10 includes a bottom wall portion 11, a top wall portion 12, a first side wall portion 13, and a second side wall portion 14. In this case, the resonance box 10 can form a hollow portion R defined by these portions.

[0081] The support body 5 includes a holding portion 56 formed by a mounting portion 50, a first holding wall 51, a second holding wall 52, and a connecting wall 53. The holding portion 56 has an annular shape and surrounds the resonance box 10. In this case, the support body 5 can hold the resonance sound absorber 1 so that it does not fall off.

[0082] Second Embodiment Next, a second embodiment of the sound absorbing unit will be described. The sound absorbing unit according to the second embodiment is attached to the mounting surface Ta of the tire T shown in FIG. 1, similar to the sound absorbing unit 100 according to the first embodiment. A sound absorbing unit 100A according to the second embodiment will be described with reference to FIGS. 9 to 13. FIG. 9 is a schematic perspective view of the sound absorbing unit according to the second embodiment, as seen from the opening side. FIG. 10 is a side view of the sound absorbing unit of FIG. 9. FIG. 11 is a schematic front view of the sound absorbing unit of FIG. 9, as seen from the opening side. FIG. 12 is a schematic rear view of the sound absorbing unit of FIG. 9, as seen from the piezoelectric film side. FIG. 13 is a cross-sectional view of the sound absorbing unit of FIG. 9, taken along the axis of the resonant sound absorber.

[0083] The sound absorbing unit 100A includes a resonance absorber 1A and a support body 5A. The resonance absorber 1A has a Helmholtz resonance structure. The resonance absorber 1A absorbs cavity resonance within the inner cavity S of the tire T. The resonance absorber 1A has a shape that extends along an axis L1A. In other words, the resonance absorber 1A has a substantially cylindrical shape with the direction along the axis L1A as the longitudinal direction.

[0084] The support body 5A is attached to the mounting surface Ta of the tire T. The support body 5A supports the resonance sound absorber 1A with respect to the mounting surface Ta while being spaced apart from the mounting surface Ta. The support body 5A includes a first support portion 510, a second support portion 520, and a third support portion 530. The first support portion 510 includes a mounting portion 150, a first retaining wall 151, a second retaining wall 152, a connecting wall 153, a first leg portion (leg portion) 154, and a second leg portion (leg portion) 155. The resonance sound absorber 1A is placed on the mounting portion 150. The mounting portion 150 has a mounting surface 150a on which the resonance sound absorber 1A is placed. The mounting portion 150 has an opposing surface 150b that faces the mounting surface Ta when the support body 5A is attached to the mounting surface Ta of the tire T. The placement surface 150a is the surface opposite to the facing surface 150b.

[0085] The first retaining wall 151 and the second retaining wall 152 each rise from the mounting surface 150a of the mounting portion 150 and face each other at a predetermined distance. That is, the first retaining wall 151 and the second retaining wall 152 rise from the mounting portion 150 toward the opposite side of the mounting surface Ta of the tire T. The resonance sound absorber 1A mounted on the mounting surface 150a of the mounting portion 150 is disposed between the first retaining wall 151 and the second retaining wall 152. Here, the direction in which the first retaining wall 151 and the second retaining wall 152 face each other is defined as a first direction D1A. The first direction D1A is a direction perpendicular to the direction along the axis L1A. The alignment direction of the mounting portion 150 and the resonance sound absorber 1A mounted on the mounting surface 150a of the mounting portion 150 is defined as a second direction D2A. The second direction D2A is a direction perpendicular to the first direction D1A. The second direction D2A is also the opposing direction between the mounting portion 150 and the mounting surface Ta of the tire T. The second direction D2A is also the height direction of the sound absorbing unit 100A relative to the mounting surface Ta of the tire T. The direction perpendicular to the first direction D1A and the second direction D2A is a third direction D3A. The third direction D3A is also a direction along the axis L1A. The resonant sound absorber 1A is sandwiched between the first retaining wall 151 and the second retaining wall 152 in the first direction D1A.

[0086] The connecting wall 153 connects the leading end of the first retaining wall 151 in the direction rising from the mounting surface 150a to the leading end of the second retaining wall 152 in the direction rising from the mounting surface 150a. Thus, the mounting portion 150, the first retaining wall 151, the connecting wall 153, and the second retaining wall 152 form an annular retaining portion 156. In this manner, the first retaining wall 151 and the second retaining wall 152 may not be independent but may be integrated with each other, or may be integrated via another member. The retaining portion 156 surrounds the resonant sound absorber 1A (resonance box 10A). The retaining portion 156 surrounds and holds the resonant sound absorber 1A. The retaining portion 156 is elastically deformable. The retaining portion 156 can detachably hold the resonant sound absorber 1A by its elastic force. The retaining portion 156 holds the vicinity of the end of the resonant sound absorber 1A on the side where the neck portion 20 is inserted.

[0087] 11 , the mounting surface 150a of the mounting portion 150 has a first separation region 150c, a second separation region 150d, and a mounting region 150e in the portion between the first retaining wall 151 and the second retaining wall 152 in the first direction D1A. The first separation region 150c is a region on the mounting surface 150a that is adjacent to the first retaining wall 151 and is separated from the resonant sound absorber 1A by a predetermined gap. The second separation region 150d is a region on the mounting surface 150a that is adjacent to the second retaining wall 152 and is separated from the resonant sound absorber 1A by a predetermined gap. The mounting region 150e is a region between the first separation region 150c and the second separation region 150d that abuts against the resonant sound absorber 1A (bottom wall portion 11A).

[0088] The first leg 154 and the second leg 155 support the mounting portion 150 in a state spaced apart from the mounting surface Ta of the tire T. The first leg 154 and the second leg 155 are each attached to the mounting surface Ta of the tire T. A space is formed between the mounting portion 150 and the mounting surface Ta. The first leg 154 and the second leg 155 are provided on the mounting portion 150 at a predetermined distance from each other in the first direction D1A. The first leg 154 extends from one end of the mounting portion 150 in the first direction D1A toward the mounting surface Ta of the tire T. The second leg 155 extends from the other end of the mounting portion 150 opposite to the one end in the first direction D1A toward the mounting surface Ta of the tire T.

[0089] The first leg portion 154 includes a first main body portion 154a and a first mounting portion 540. The first mounting portion 540 is a portion that is attached to the mounting surface Ta of the tire T. The first main body portion 154a connects the first mounting portion 540 to the mounting portion 150. The first mounting portion 540 protrudes outward from the first main body portion 154a (toward the opposite side from the second leg portion 155).

[0090] The second leg portion 155 includes a second main body portion 155a and a second mounting portion 550. The second mounting portion 550 is a portion that is attached to the mounting surface Ta of the tire T. The second main body portion 155a connects the second mounting portion 550 to the mounting portion 150. The second mounting portion 550 protrudes outward from the second main body portion 155a (toward the opposite side from the first leg portion 154).

[0091] The first mounting portion 540 and the second mounting portion 550 are attached to the mounting surface Ta of the tire T in the same manner as the first mounting portion 54b etc. according to the first embodiment.

[0092] 12 , the second support part 520 includes a mounting part 250, a first retaining wall 251, a second retaining wall 252, a connecting wall 253, a first leg (leg) 254, and a second leg (leg) 255. The mounting part 250 has a mounting surface 250a on which the resonant sound absorber 1A is placed. The mounting part 250, the first retaining wall 251, the second retaining wall 252, the connecting wall 253, the first leg 254, and the second leg 255 of the second support part 520 have the same configuration as the mounting part 150, the first retaining wall 151, the second retaining wall 152, the connecting wall 153, the first leg 154, and the second leg 155 of the first support part 510.

[0093] The mounting portion 250, the first retaining wall 251, the connecting wall 253, and the second retaining wall 252 form an annular retaining portion 256. The retaining portion 256 has a configuration similar to that of the retaining portion 156 of the first support portion 510. The retaining portion 156 holds the vicinity of the end portion of the resonance sound absorber 1A opposite to the end portion into which the neck portion 20 is inserted. In other words, the first support portion 510 and the second support portion 520 respectively hold the vicinity of both end portions of the resonance sound absorber 1A in the direction along the axis L1A.

[0094] The first leg portion 254 includes a first main body portion 254a and a first mounting portion 540. The first main body portion 254a connects the first mounting portion 540 to the mounting portion 250. The first mounting portion 540 is a common member with the first mounting portion 540 of the first support portion 510. The first mounting portion 540 extends in the third direction D3A.

[0095] The second leg portion 255 includes a second main body portion 255a and a second mounting portion 550. The second main body portion 255a connects the second mounting portion 550 to the mounting portion 250. The second mounting portion 550 is a common member with the second mounting portion 550 of the first support portion 510. The second mounting portion 550 extends in the third direction D3A.

[0096] The third support portion 530 supports the vicinity of the center of the resonant sound absorber 1A in the third direction D3A. The third support portion 530 is provided between the first support portion 510 and the second support portion 520 in the third direction D3A. The third support portion 530 includes a mounting portion 350, a first leg portion 354, and a second leg portion 355. The first leg portion 354 and the second leg portion 355 of the third support portion 530 have the same configuration as the first leg portion 154 and the second leg portion 155 of the first support portion 510.

[0097] The mounting portion 350 has a mounting surface 350a on which the resonance sound absorber 1A is placed. The mounting portion 350 has an opposing surface 350b that faces the mounting surface Ta when the support body 5A is attached to the mounting surface Ta of the tire T. The mounting surface 350a is the surface opposite to the opposing surface 350b. The mounting surface 350a of the mounting portion 350 is provided with a recess 350c (see FIG. 13 ). The recess 350c extends in the first direction D1A.

[0098] The first leg portion 354 includes a first main body portion 354a and a first attachment portion 540. The first main body portion 354a connects the first attachment portion 540 to the mounting portion 350. The first attachment portion 540 is a common member with the first attachment portions 540 of the first support portion 510 and the second support portion 520.

[0099] The second leg portion 355 includes a second main body portion 355a and a second attachment portion 550. The second main body portion 355a connects the second attachment portion 550 to the mounting portion 350. The second attachment portion 550 is a common member with the second attachment portions 550 of the first support portion 510 and the second support portion 520.

[0100] The support body 5A may be made of the same material as the support body 5 according to the first embodiment. The support body 5A is configured to be elastically deformable by centrifugal force generated by the rotation of the tire T. This rotation of the tire T refers to the rotation when a vehicle equipped with the tire T is running. The support body 5A may be configured so that only a portion of it is elastically deformable by centrifugal force. The support body 5A may be configured so that at least the mounting portions 150, 250, and 350 are elastically deformable by centrifugal force.

[0101] 9 and 13, the resonance sound absorber 1A includes a resonance box 10A, a neck portion 20, and a piezoelectric film 30. The resonance sound absorber 1A will be described in detail below. Note that in the following description of the resonance sound absorber 1A, differences from the resonance sound absorber 1 according to the first embodiment will be described, and components similar to those of the resonance sound absorber 1 according to the first embodiment will be assigned the same reference numerals and detailed description thereof will be omitted.

[0102] Fig. 14 is a cross-sectional view taken along line XIV-XIV in Fig. 13. Fig. 15 is a cross-sectional view taken along line XV-XV in Fig. 13. Fig. 16 is a cross-sectional view taken along line XVI-XVI in Fig. 13.

[0103] As shown in Figures 13 to 16, a hollow space R is formed inside the resonance box 10A (see Figure 13). The resonance box 10A has an opening 10b (see Figure 13) that connects the hollow space R with the external space (the space outside the resonance box 10A). The resonance box 10A is configured to be elongated in the third direction D3A. The size of the resonance box 10A is approximately the same as that of the resonance box 10 according to the first embodiment.

[0104] The resonance box 10A includes a bottom wall 11A, a top wall 12A, a first side wall 13, and a fixed cylinder 15 (see FIG. 13 ). The bottom wall 11A is formed in a generally rectangular plate shape that is long in the third direction D3A and short in the first direction D1A. The bottom wall 11A faces the mounting portion 150 of the first support portion 510, the mounting portion 250 of the second support portion 520, and the mounting portion 350 of the third support portion 530 of the support body 5A. In other words, the resonance sound absorber 1A is placed on the mounting surfaces 150a, 250a, and 350a so that the bottom wall 11A of the resonance box 10A faces the mounting portions 150, 250, and 350 of the support body 5A. When the sound absorber 1A is placed on the mounting portions 150, 250, and 350, the bottom wall portion 11A abuts against the mounting surfaces 150a, 250a, and 350a, respectively.

[0105] 13 , a convex portion 11k is provided on an opposing surface 11j of the bottom wall 11A of the third support 530, the opposing surface 11j facing the mounting surface 350a of the mounting portion 350. The convex portion 11k may extend along the first direction D1A. The convex portion 11k is fitted into and engages with a concave portion 350c provided in the mounting portion 350 of the third support 530. The engagement of the convex portion 11k with the concave portion 350c restricts movement of the resonance sound absorber 1A in the third direction D3A relative to the third support 530. In other words, the convex portion 11k and the concave portion 350c function to prevent the resonance sound absorber 1A from coming off the support 5A in the third direction D3A.

[0106] The top wall portion 12A forms a hollow portion R between itself and the bottom wall portion 11A. The top wall portion 12A covers the hollow portion R from the side opposite to the bottom wall portion 11A. As shown in Figure 14, both end portions (end portion 12e and end portion 12f) of the top wall portion 12A in the first direction D1A are connected to both end portions (end portion 11e and end portion 11f) of the bottom wall portion 11A in the first direction D1A, respectively.

[0107] The top wall portion 12A is curved in an arc shape when viewed in the third direction D3A. In a cross section perpendicular to the third direction D3A (a cross section along the first direction D1A and the second direction D2A), the top wall portion 12A is formed in an arc shape that follows an arc that is larger than half the circumference of a circle.

[0108] In other words, as shown in FIG. 14 , when viewed along the axis L1A (third direction D3A), the top wall portion 12A has a shape that generally follows a cylindrical surface MA whose axis is a central axis L2A that is aligned with the axis L1A. The cylindrical surface MA whose axis is the central axis L2A is a cylindrical surface that surrounds the central axis L2A and is centered on the central axis L2A. However, the shape of the top wall portion 12A is not limited to being completely aligned with the cylindrical surface MA. The top wall portion 12A may have any shape that is close to a shape that follows the cylindrical surface MA. For example, the angle β from the end 12e to the end 12f in the circumferential direction about the central axis L2A is greater than half the circumference (180°) of the circular shape.

[0109] The first side wall portion 13 has the same configuration as the first side wall portion 13 according to the first embodiment. An opening 10b is provided in the first side wall portion 13. The first side wall portion 13 covers a tube opening (opening) H1 (see FIG. 13 ) formed by the top wall portion 12A and the bottom wall portion 11A at one end of the top wall portion 12A and the bottom wall portion 11A in the third direction D3A.

[0110] Unlike the resonance box 10 according to the first embodiment, the resonance box 10A according to the present embodiment does not include a wall portion (the second side wall portion 14 according to the first embodiment) that faces the first side wall portion 13 in the third direction D3A. Therefore, the resonance box 10A has a tubular portion opening (opening) H2 formed by the top wall portion 12A and the bottom wall portion 11A at the other end opposite to one end (the end on the side where the first side wall portion 13 is provided) of the top wall portion 12A and the bottom wall portion 11A in the third direction D3A.

[0111] 11 , when viewed along the axis L1A (third direction D3A), the opening 10b provided in the first side wall portion 13 is located closer to the bottom wall portion 11A than the central axis L2A of the cylindrical surface MA along which the top wall portion 12A extends. In other words, the opening 10b is located between the central axis L2A and the bottom wall portion 11A. In other words, the opening 10b is located near the edge of the first side wall portion 13 that is connected to the bottom wall portion 11A. The opening 10b is located closer to the edge of the first side wall portion 13 that is connected to the bottom wall portion 11A than the edge that is connected to the top wall portion 12A.

[0112] The portion of the top wall 12A facing the bottom wall 11A in the second direction D2A is referred to as the upper wall 12c. The upper wall 12c is the portion of the top wall 12A facing the bottom wall 11A across the central axis L2A. The thickness of the bottom wall 11A is thicker than the thickness of the upper wall 12c of the top wall 12A. For example, the thickness of the bottom wall 11A may be 1.1 times or more the thickness of the upper wall 12c of the top wall 12A. For example, the thickness of the upper wall 12c of the top wall 12A may be approximately 0.4 mm or less.

[0113] 13, the fixed cylinder portion 15 is provided on the outer surface of the first side wall portion 13. The configuration of the fixed cylinder portion 15 according to this embodiment is the same as the configuration of the fixed cylinder portion 15 according to the first embodiment, and detailed description thereof will be omitted.

[0114] The neck portion 20 communicates with an opening 10b provided in the first side wall portion 13 of the resonance box 10A and extends into the hollow portion R inside the resonance box 10A. The configuration of the neck portion 20 according to this embodiment is the same as that of the neck portion 20 according to the first embodiment, and therefore a detailed description thereof will be omitted. Furthermore, the attachment configuration for attaching the neck portion 20 to the resonance box 10A using the fixing cylinder portion 15 is the same as that of the neck portion 20 according to the first embodiment, and therefore a detailed description thereof will be omitted.

[0115] The piezoelectric film 30 covers a cylindrical opening (opening) H2 formed by the top wall portion 12A and the bottom wall portion 11A at the other end opposite to one end (the end on the side where the first side wall portion 13 is provided) of the top wall portion 12A and the bottom wall portion 11A in the third direction D3A. The piezoelectric film 30 is attached to the resonance box 10A so as to tightly cover the cylindrical opening H2. The piezoelectric film 30 and the resonance box 10A define a hollow portion R. The piezoelectric film 30 generates an electromotive force when stress is applied. The piezoelectric film 30 has a conductive layer such as copper foil and can output power to the outside. The piezoelectric film 30 generates power when vibrated by vibrations of air within the cavity S of the tire T.

[0116] The piezoelectric film 30 contains a piezoelectric material. The piezoelectric material may be, for example, in the form of particles. Examples of the piezoelectric material include ceramic-based piezoelectric materials and polymer-based piezoelectric materials. From the viewpoint of obtaining good piezoelectric performance, the piezoelectric material is preferably a ceramic-based piezoelectric material.

[0117] Examples of ceramic piezoelectric materials include barium titanate (BT) piezoelectric materials, lead zirconate titanate (PZT) piezoelectric materials, lead lanthanum zirconate titanate (PLZT) piezoelectric materials, and lead titanate (PT)-lead zirconate (PZ) piezoelectric materials. Specific examples of ceramic piezoelectric materials include barium titanate (BaTiO ３ ), strontium titanate (SrTiO ３ ), lithium niobate (Li ２ NbO ３ ), lithium titanate (LiTiO ３ ), lead titanate (PbTiO ３ ), barium lead titanate ((Ba,Pb)TiO ３ ), barium calcium titanate ((Ba,Ca)TiO ３ ), potassium sodium niobate ((K,Na)NbO ３ ), potassium lithium niobate ((K,Li)NbO ３ ), and lead zirconate titanate (Pb(Zr,Ti)O ３ ) are listed.

[0118] Examples of polymer-based piezoelectric materials include polyvinylidene fluoride, polytetrafluoroethylene, iodinated polyvinyl acetate, polyurea, and polylactic acid.

[0119] The piezoelectric film 30 may further contain a matrix in addition to the piezoelectric material. In this case, the piezoelectric material, for example, particulate piezoelectric material, may be dispersed in the matrix.

[0120] The matrix may be, for example, a resin such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polytetrafluoroethylene (PTFE), ABS resin (acrylonitrile butadiene styrene resin), acrylic resin, polyamide, polycarbonate, polyethylene terephthalate (PET), thermoplastic polyimide, phenolic resin, epoxy resin, melamine resin, or polyimide (excluding the above-mentioned polymeric piezoelectric materials).

[0121] From the viewpoint of providing the piezoelectric film 30 with excellent flexibility, heat resistance, elongation, etc., the matrix may preferably be an acrylic resin containing, as monomer units, a compound represented by the following formula (1), a compound represented by the following formula (2), a compound represented by the following formula (3), and other polymerizable compounds. In formula (1), R １１ and R １２ each independently represents a hydrogen atom or a methyl group, R １３ represents a divalent group having a polyoxyalkylene chain. In formula (2), R ２１ and R ２２ each independently represents a hydrogen atom or a methyl group, R ２３ represents a divalent group having a poly(meth)acrylate chain. In formula (3), R ３１ and R ３２ R each independently represents a hydrogen atom or a monovalent organic group, and may be bonded to each other to form a ring. ３３ represents a hydrogen atom or a methyl group.

[0122] R １３ The polyoxyalkylene chain in may be a divalent group having a polyoxyethylene chain, a divalent group having a polyoxypropylene chain, or a divalent group having a copolymer chain of a polyoxyethylene chain and a polyoxypropylene chain. The copolymer chain may be any of an alternating copolymer chain, a block copolymer chain, and a random copolymer chain.

[0123] R ２３ The poly(meth)acrylate chain in may contain a structural unit represented by the following formula (2a): In formula (2a), R ２４ represents a hydrogen atom or a monovalent organic group, R ２５ represents a hydrogen atom or a methyl group.

[0124] R ２４ The monovalent organic group represented by the formula (I) may be, for example, a hydrocarbon group, an alkyl group, or an organic group having an oxygen atom, a nitrogen atom, or the like.

[0125] R ３１ and R ３２ When R are not bonded to each other to form a ring, the monovalent organic group may be, for example, a monovalent hydrocarbon group or an alkyl group. ３１ and R ３２ are preferably bonded to each other to form a ring. In this case, the ring may be, for example, a six-membered ring. The ring is formed by bonding a nitrogen atom and R ３１ and R ３２ and a group represented by the following formula (1): and may contain, in addition to the nitrogen atom, a carbon atom, a hydrogen atom, an oxygen atom, a sulfur atom, etc.

[0126] The other polymerizable compound may be, for example, an alkyl(meth)acrylate, or a (meth)acrylate having a hydroxyl group, a carboxyl group, an amino group, or an epoxy group in addition to a (meth)acryloyl group.

[0127] The matrix may be, for example, a rubber such as acrylic rubber, acrylonitrile butadiene rubber, isoprene rubber, urethane rubber, silicone rubber, natural rubber, styrene butadiene rubber, styrene isoprene butadiene rubber, ethylene propylene diene rubber, chloroprene rubber, epoxidized natural rubber, or epoxidized butadiene rubber.

[0128] Furthermore, the bottom wall 11A of the resonance box 10A is provided with a first protrusion 11g and a second protrusion 11h, each of which protrudes toward the hollow portion R. The first protrusion 11g and the second protrusion 11h are portions that protrude toward the hollow portion R (toward the upper wall portion 12c of the top wall 12A) relative to portions of the bottom wall 11A where the first protrusion 11g and the second protrusion 11h are not provided. The first protrusion 11g and the second protrusion 11h are spaced apart from each other at a predetermined interval in the first direction D1A.

[0129] A groove 16A is provided on the surface of the bottom wall 11A facing the hollow portion R. That is, the groove 16A is provided on the inner surface of the resonance box 10A in the bottom wall 11A. The groove 16A is recessed from the hollow portion R toward the mounting surface 150a of the mounting portion 150 of the first support portion 510 (the mounting surface 250a of the mounting portion 250 of the second support portion 520 and the mounting surface 350a of the mounting portion 350 of the third support portion 530). The groove 16A extends along the third direction D3A. In this embodiment, the groove 16A is defined by a portion of the bottom wall 11A between the first raised portion 11g and the second raised portion 11h.

[0130] The groove 16A has a first groove inner wall surface 16c and a second groove inner wall surface 16d that face each other in the first direction D1A. The first groove inner wall surface 16c is formed by the surface of the first protrusion 11g that faces the hollow portion R and faces the second protrusion 11h. The second groove inner wall surface 16d is formed by the surface of the second protrusion 11h that faces the hollow portion R and faces the first protrusion 11g.

[0131] As shown in Figures 13 to 15, the tube main body 21 of the neck portion 20 inserted into the opening 10b of the first side wall 13 is disposed between the first groove inner wall surface 16c and the second groove inner wall surface 16d of the groove 16A and is supported by the first groove inner wall surface 16c and the second groove inner wall surface 16d. At least a portion of the tube main body 21 of the neck portion 20 is recessed within the groove 16A in the depth direction of the groove 16A (second direction D2A). In this embodiment, more than half of the radial extent of the neck portion 20 (tube main body 21) is recessed within the groove 16A in the depth direction of the groove 16A. The neck portion 20 may be in contact with the bottom of the groove 16A or may be spaced apart from the bottom of the groove 16A as shown in Figure 15.

[0132] The first raised portion 11g and the second raised portion 11h provided on the bottom wall portion 11A may be provided at a position where the neck portion 20 can be supported within the hollow portion R by at least the groove portion 16A formed by the first raised portion 11g and the second raised portion 11h. For example, the first raised portion 11g and the second raised portion 11h may be provided so that the entire neck portion 20 (tube main body portion 21) can be supported by the groove portion 16A in the third direction D3A. It is only necessary that at least a portion of the neck portion 20 be disposed between the first groove inner wall surface 16c and the second groove inner wall surface 16d in the third direction D3A.

[0133] The resonance box 10A and the neck portion 20 can be made of the same materials as those of the resonance box 10 and the neck portion 20 according to the first embodiment. The resonance box 10A and the neck portion 20 can be manufactured by the same manufacturing method as those of the resonance box 10 and the neck portion 20 according to the first embodiment.

[0134] As described above, in the sound absorbing unit 100A, the opposing direction between the first retaining wall 151 and the second retaining wall 152 of the first support part 510, between which the resonant sound absorber 1A is disposed, and the opposing direction between the first groove inner wall surface 16 c and the second groove inner wall surface 16 d of the groove part 16A, between which the neck part 20 (the cylindrical main body part 21) is disposed, in the resonance box 10A, are the same direction (first direction D1A). Similarly, the opposing direction between the first retaining wall 251 and the second retaining wall 252 of the second support part 520, between which the resonant sound absorber 1A is disposed, and the opposing direction between the first groove inner wall surface 16 c and the second groove inner wall surface 16 d of the groove part 16A, between which the neck part 20 (the cylindrical main body part 21) is disposed, in the resonance box 10A, are the same direction (first direction D1A).

[0135] For example, when centrifugal force acts on the resonance sound absorber 1A as the tire T rotates, the centrifugal force causes the resonance sound absorber 1A to press against the support body 5A, causing the mounting portion 150 of the first support portion 510 and the mounting portion 250 of the second support portion 520 to curve convexly toward the mounting surface Ta of the tire T. This deformation of the mounting portion 150 of the first support portion 510 causes the first retaining wall 151 and the second retaining wall 152 to collapse inward (toward each other). Similarly, deformation of the mounting portion 250 of the second support portion 520 causes the first retaining wall 251 and the second retaining wall 252 to collapse inward (toward each other). That is, as shown in FIG. 17 , the mounting portion 150 of the first support portion 510 is pressed by the resonance sound absorber 1A in the direction indicated by arrow A3, causing the mounting portion 150 to curve convexly in the direction indicated by arrow A3. As the mounting portion 150 of the first support portion 510 curves (deforms), the resonance box 10A of the resonance sound absorber 1A is sandwiched in the first direction D1A by the first retaining wall 151 and the second retaining wall 152, as shown by arrow A4. The second support portion 520 also deforms in the same manner as the first support portion 510. As the mounting portion 250 of the second support portion 520 curves (deforms), the resonance box 10A of the resonance sound absorber 1A is sandwiched in the first direction D1A by the first retaining wall 251 and the second retaining wall 252.

[0136] As a result, a compressive force is applied to the resonance box 10A in the first direction D1A, as indicated by arrow A4. The bottom wall 11A of the resonance box 10A is provided with a groove 16A. The first groove inner wall surface 16c and the second groove inner wall surface 16d of the groove 16A face each other in the first direction D1A. Therefore, the compressive force applied to the resonance box 10A by the first retaining wall 151, the second retaining wall 152, and the first retaining wall 251, the second retaining wall 252 applies a force to the first groove inner wall surface 16c and the second groove inner wall surface 16d in a direction that moves them closer to each other. As a result, the neck portion 20, which is disposed between the first groove inner wall surface 16c and the second groove inner wall surface 16d of the groove 16A, is sandwiched and held between the first groove inner wall surface 16c and the second groove inner wall surface 16d. That is, the neck portion 20 is gripped by the first groove inner wall surface 16 c and the second groove inner wall surface 16 d. In this way, the resonance sound absorber 1A can hold the neck portion 20 extending inside the resonance box 10A by the centrifugal force generated by the rotation of the tire T.

[0137] Furthermore, the neck portion 20 is sandwiched and held between the first groove inner wall surface 16c and the second groove inner wall surface 16d, thereby integrating the neck portion 20 with the bottom wall portion 11A. In this case, it can be said that the thickness of the bottom wall portion 11A is increased by the amount of the neck portion 20. This allows the resonant sound absorber 1A to hold the neck portion 20 and improve the strength of the bottom wall portion 11A.

[0138] Furthermore, in the sound absorbing unit 100A according to this embodiment, as with the sound absorbing unit 100 according to the first embodiment, even if the size of the tire T to be mounted changes, centrifugal force can be used to press the first groove inner wall surface 16c and the second groove inner wall surface 16d against the neck portion 20, thereby more reliably holding the neck portion 20. In this way, by using centrifugal force, the sound absorbing unit 100A can more reliably hold the neck portion 20 while avoiding a complex design. Furthermore, the sound absorbing unit 100A does not require a component for fixing the neck portion 20 to the bottom wall portion 11A, thereby achieving a lighter weight. In the sound absorbing unit 100A according to this embodiment, as with the sound absorbing unit 100 according to the first embodiment, the shape of the resonance box 10A can be restored to its original state, thereby preventing permanent deformation of the resonance box 10A.

[0139] The groove 16A is formed by a first protrusion 11g and a second protrusion 11h provided on the bottom wall 11A. The second protrusion 11h and the first protrusion 11g protrude toward the hollow portion R inside the resonance box 10A. In this case, the groove 16A does not protrude outward from the bottom surface of the resonance box 10A (the opposing surface 11j of the bottom wall 11A). This prevents the resonant sound absorber 1A from becoming too large.

[0140] The mounting surface 150a of the mounting portion 150 provided on the first support portion 510 has a mounting region 150e with which the resonant sound absorber 1A abuts, and a first separated region 150c and a second separated region 150d with which the resonant sound absorber 1A does not abut. The mounting region 150e is located between the first separated region 150c and the second separated region 150d. In this case, centrifugal force generated in the resonant sound absorber 1A as the tire T rotates is input to the mounting region 150e, which is the central portion of the mounting surface 150a of the mounting portion 150. This makes it easier for the mounting portion 150 to curve convexly toward the mounting surface Ta of the tire T, and makes it easier for the first retaining wall 151 and the second retaining wall 152 to collapse inward toward each other. The second support portion 520 has a configuration similar to that of the first support portion 510. Therefore, in the second support portion 520 as well, the first holding wall 251 and the second holding wall 252 can be made to easily collapse inward toward each other.

[0141] More than half of the radial length of neck portion 20 in the depth direction of groove portion 16A is recessed within groove portion 16A. In this case, neck portion 20 can be more reliably sandwiched and held between first groove inner wall surface 16c and second groove inner wall surface 16d of groove portion 16A, and neck portion 20 can be prevented from jumping out of groove portion 16A.

[0142] In the first support portion 510 of the support body 5A, the first leg portion 154 is connected to one end of the mounting portion 150 in the first direction D1A, and the second leg portion 155 is connected to the other end of the mounting portion 150 in the first direction D1A. In this case, the first support portion 510 can support the mounting portion 150 relative to the mounting surface Ta while easily curving the mounting portion 150 in a convex shape toward the mounting surface Ta of the tire T. The first leg portion 254 and the second leg portion 255 of the second support portion 520 have the same configuration as the first leg portion 154 and the second leg portion 155 of the first support portion 510. Therefore, the second support portion 520 can also support the mounting portion 250 relative to the mounting surface Ta while easily curving the mounting portion 250 in a convex shape toward the mounting surface Ta of the tire T.

[0143] The neck portion 20 is inserted into the opening 10b of the resonance box 10A and fixed to the resonance box 10A. In this case, the resonance box 10A and the neck portion 20 can be formed as separate parts depending on the performance required of each. Furthermore, even if the resonance box 10A and the neck portion 20 are separate parts, the sound absorbing unit 100A can hold the neck portion 20 extending inside the resonance box 10A.

[0144] The resonance box 10A is configured to be long in the third direction D3A. The neck portion 20 extends in the third direction D3A within the hollow portion R inside the resonance box 10A. This makes it possible to increase the length of the neck portion 20 within the resonance box 10A even when the length of the neck portion 20 needs to be increased depending on the frequency of sound to be absorbed.

[0145] As shown in FIG. 14 , the top wall portion 12A is formed in an arc shape along an arc larger than half the circumference of a circle in a cross section perpendicular to the third direction D3A. In this case, when viewed along the third direction D3A, around the connection between the top wall portion 12A and the bottom wall portion 11A, the outer shape of the top wall portion 12A gradually decreases in the first direction D1A, while both ends (ends 12e and 12f) of the top wall portion 12A are connected to both ends (ends 11e and 11f) of the bottom wall portion 11A. For example, centrifugal force accompanying the rotation of the tire T tends to deform the top wall portion 12A so as to be pressed toward the mounting portion 150 (bottom wall portion 11A) of the first support portion 510. In this case, forces are applied to the bottom wall portion 11A from both ends (ends 12e and 12f) of the top wall portion 12A, compressing the bottom wall portion 11A in the first direction D1A. In other words, a force is applied from the top wall 12A to the bottom wall 11A in a direction that moves the first groove inner wall surface 16c and the second groove inner wall surface 16d closer to each other, thereby enabling the sound absorbing unit 100A to more firmly hold the neck portion 20 extending inside the resonance box 10A.

[0146] The resonance box 10A includes a bottom wall 11A, a top wall 12A, and a first side wall 13. The first side wall 13 covers a tubular opening H1 formed by the top wall 12A and the bottom wall 11A at one end of the top wall 12A and the bottom wall 11A in the third direction D3A. A tubular opening H2 formed by the top wall 12A and the bottom wall 11A at the other end of the top wall 12A and the bottom wall 11A in the third direction D3A is covered by a piezoelectric film 30. In this case, the bottom wall 11A, the top wall 12A, the first side wall 13, and the piezoelectric film 30 can form a hollow portion R in the resonance sound absorber 1A.

[0147] Furthermore, the piezoelectric film 30 can be vibrated by air vibrations within the cavity S that occur when the tire T is rotated. Here, sound pressure is high within the cavity S of the tire T. Furthermore, because the cavity S of the tire T is sealed, acoustic energy is not diffracted or diffused. Therefore, the resonance sound absorber 1A can generate electricity by efficiently vibrating the piezoelectric film 30 with air vibrations within the cavity S of the tire T.

[0148] There are no particular limitations on the use of the power generated by the piezoelectric film 30. For example, the power generated by the piezoelectric film 30 may be used as power for operating a transmitting device (e.g., a wireless communication device) that transmits information about the inside of the lumen S of the tire T to the outside of the lumen S. This information about the inside of the lumen S of the tire T may be, for example, electromotive force information including the magnitude of the electromotive force generated by the piezoelectric film 30, temperature information about the inside of the lumen S measured by a temperature sensor, or other information.

[0149] The first support part 510 includes a holding part 156 formed by a mounting part 150, a first holding wall 151, a second holding wall 152, and a connecting wall 153. The holding part 156 is annular and surrounds the resonance box 10A. The second support part 520 also includes a holding part 256 having a similar configuration to the holding part 156 of the first support part 510. Therefore, the support body 5A can hold the resonance sound absorber 1A so that it does not fall off.

[0150] However, as shown in FIG. 18 , the first support portion 510 does not necessarily have to have the connecting wall 153. That is, the leading end of the first retaining wall 151 of the first support portion 510 in the rising direction and the leading end of the second retaining wall 152 of the first support portion 510 in the rising direction do not necessarily have to be connected to each other. The rising height of the first retaining wall 151 and the second retaining wall 152 from the mounting surface 150a of the mounting portion 150 need only be sufficient to sandwich the resonance box 10A in the first direction D1A. As shown in FIG. 18 , the leading end of the first retaining wall 151 in the rising direction and the leading end of the second retaining wall 152 in the rising direction may each be curved inward to fit along the upper wall portion 12c of the top wall portion 12A. Even in this case, the first support portion 510 can hold the resonant sound absorber 1A so that it does not separate from the mounting portion 150. Similar to the first support portion 510 , the second support portion 520 does not necessarily have to have the connecting wall 253 .

[0151] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the sound absorbing unit 100A according to the second embodiment, the position at which the piezoelectric film 30 is provided is not limited to the position on the opposite side of the opening 10b in the third direction D3A. The piezoelectric film may be provided at any appropriate position on the resonance box. It is sufficient that the piezoelectric film and the resonance box define a hollow space. For example, the piezoelectric film may be provided on the top wall of the exterior wall. Furthermore, the sound absorbing unit 100A according to the second embodiment does not necessarily have to include the piezoelectric film 30. In this case, the sound absorbing unit 100A may be provided with the second side wall portion 14 according to the first embodiment instead of the piezoelectric film 30.

[0152] The gist of the present disclosure is as follows: [1] A sound absorbing unit to be attached to a mounting surface of a tire cavity, comprising: a resonance sound absorber; and a support body that supports the resonance sound absorber against the mounting surface in a state spaced apart from the mounting surface, wherein the support body has: a mounting portion having a mounting surface on which the resonance sound absorber is to be placed, first and second retaining walls that each rise from the mounting surface, face each other at a predetermined interval in a first direction, and have the resonance sound absorber disposed between them, and legs that support the mounting portion in a state spaced apart from the mounting surface, wherein the resonance sound absorber has: a resonance box having an opening, and a hollow neck portion that communicates with the opening and extends into a hollow portion inside the resonance box, wherein the resonance box has a bottom wall portion facing the mounting surface, and a groove portion is provided on a surface of the bottom wall portion facing the hollow portion, and the groove portion has first and second groove inner wall surfaces that face each other in the first direction, a sound absorbing unit according to any one of the preceding items [1] to [2], wherein the bottom wall portion is provided with a first raised portion and a second raised portion each protruding toward the hollow portion, the first raised portion and the second raised portion being spaced apart from each other at a predetermined interval in the first direction, and the groove portion is defined by a portion of the bottom wall portion between the first raised portion and the second raised portion; [3] The sound absorbing unit according to any one of the preceding items [1] to [2], wherein the mounting surface has, in a portion between the first retaining wall and the second retaining wall, a first separation region adjacent to the first retaining wall and spaced apart from the resonant sound absorber at a predetermined gap, a second separation region adjacent to the second retaining wall and spaced apart from the resonant sound absorber at a predetermined gap, and a mounting region between the first separation region and the second separation region, the mounting region abutting the bottom wall portion. [4] A sound absorbing unit described in any one of [1] to [3] above, wherein more than half of the neck portion in the radial direction is inserted into the groove portion in the depth direction of the groove portion.[5] The sound absorbing unit according to any one of [1] to [4] above, wherein the legs include a first leg and a second leg, the first leg extending from one end of the mounting portion in the first direction toward the mounting surface, and the second leg extending from the other end of the mounting portion in the first direction toward the mounting surface. [6] The sound absorbing unit according to any one of [1] to [5] above, wherein the neck is inserted into the opening and fixed to the resonance box. [7] The sound absorbing unit according to any one of [1] to [6] above, wherein a direction in which the mounting portion and the resonance sound absorber placed on the mounting surface are aligned and which is orthogonal to the first direction is defined as a second direction, and a direction orthogonal to the first direction and the second direction is defined as a third direction, the resonance box is configured to be long in the third direction, and the neck extends in the third direction. [8] The sound absorbing unit according to [7] above, wherein the resonance box has the bottom wall and a top wall that forms the hollow between the bottom wall and the resonance box, both ends of the top wall in the first direction are connected to both ends of the mounting part in the first direction, and the top wall is formed in an arc shape that is larger than half the circumference of a circle in a cross section perpendicular to the third direction. [9] The sound absorbing unit according to [8] above, wherein the resonance box has a first side wall having the opening and a second side wall, and the first side wall covers the opening formed by the top wall and the bottom wall at one end of the top wall and the bottom wall in the third direction, and the second side wall covers the opening formed by the top wall and the bottom wall at the other end of the top wall and the bottom wall in the third direction.

[10] The sound absorbing unit described in [8] above, wherein the resonant sound absorber comprises a piezoelectric film, the resonance box has a first side wall portion having the opening, the first side wall portion covers the opening formed by the top wall portion and the bottom wall portion at one end of the top wall portion and the bottom wall portion in the third direction, and the piezoelectric film covers the opening formed by the top wall portion and the bottom wall portion at the other end of the top wall portion and the bottom wall portion in the third direction.

[11] The sound absorbing unit according to any one of [1] to [9] above, wherein the resonant sound absorber includes a piezoelectric film, and the piezoelectric film defines a part of the hollow portion together with the resonance box.

[12] The sound absorbing unit according to any one of [1] to

[11] above, wherein the support body has a connecting wall that connects a tip end of the first retaining wall in a direction rising from the mounting surface to a tip end of the second retaining wall in a direction rising from the mounting surface, and the mounting portion, the first retaining wall, the second retaining wall, and the connecting wall surround the resonance box.

[0153] REFERENCE SIGNS LIST 1, 1A... resonance sound absorber, 5, 5A... support, 10, 10A... resonance box, 10b... opening, 11, 11A... bottom wall portion, 11c... first bead (first raised portion), 11d... second bead (second raised portion), 11g... first raised portion, 11h... second raised portion, 12, 12A... top wall portion, 13... first side wall portion, 14... second side wall portion, 15... fixed cylinder portion, 16, 16A... groove portion, 16a, 16c... first groove inner wall surface, 16b, 16d... second groove inner wall surface, 50, 150, 250... placement portion, 50a, 150a, 250a... placement surface, 50c, 150c... first Separation area, 50d, 150d...second separation area, 50e, 150e...mounting area, 51, 151, 251...first retaining wall, 52, 152, 252...second retaining wall, 53, 153, 253...connecting wall, 54, 154, 254...first leg portion, 55, 155, 255...second leg portion, 20...neck portion, 30...piezoelectric film, 100, 100A...sound absorbing unit, D1, D1A...first direction, D2, D2A...second direction, D3, D3A...third direction, H1, H2...tubular portion opening (opening), R...hollow portion, S...inner cavity, T...tire, Ta...mounting surface.

Claims

1. A sound absorbing unit to be attached to a mounting surface of a cavity of a tire, comprising: a resonance sound absorber; and a support which supports the resonance sound absorber against the mounting surface in a state spaced apart from the mounting surface, wherein the support has: a mounting portion having a mounting surface on which the resonance sound absorber is placed; first and second retaining walls which each rise from the mounting surface, face each other at a predetermined interval in a first direction, and between which the resonance sound absorber is placed; and legs which support the mounting portion in a state spaced apart from the mounting surface, wherein the resonance sound absorber comprises: a resonance box having an opening; and a hollow neck portion which is connected to the opening and extends into a hollow portion inside the resonance box, wherein the resonance box has a bottom wall portion facing the mounting surface, and a groove portion is provided on a surface of the bottom wall portion facing the hollow portion, and the groove portion has a first groove inner wall surface and a second groove inner wall surface which face each other in the first direction, A sound absorbing unit, wherein at least a portion of the neck portion is disposed between the first groove inner wall surface and the second groove inner wall surface.

2. A sound absorbing unit as described in claim 1, wherein the bottom wall portion is provided with a first raised portion and a second raised portion each protruding toward the hollow portion, the first raised portion and the second raised portion are spaced apart from each other at a predetermined interval in the first direction, and the groove portion is formed by the area of ​​the bottom wall portion between the first raised portion and the second raised portion.

3. The sound absorbing unit of claim 1, wherein the mounting surface has, in a portion between the first retaining wall and the second retaining wall, a first separation region adjacent to the first retaining wall and separated from the resonant sound absorber by a predetermined gap, a second separation region adjacent to the second retaining wall and separated from the resonant sound absorber by a predetermined gap, and a mounting region between the first separation region and the second separation region, which abuts the bottom wall portion.

4. The sound absorbing unit according to claim 1, wherein more than half of the radial direction of said neck portion in the depth direction of said groove portion is recessed into said groove portion.

5. The sound absorbing unit as described in claim 1, wherein the leg includes a first leg and a second leg, the first leg extending from one end of the mounting portion in the first direction toward the mounting surface, and the second leg extending from the other end of the mounting portion in the first direction toward the mounting surface.

6. The sound absorbing unit according to claim 1, wherein the neck portion is inserted into the opening and fixed to the resonance box.

7. The sound absorbing unit as described in claim 1, wherein when a direction in which the mounting portion and the resonant sound absorber placed on the mounting surface are aligned and perpendicular to the first direction is defined as a second direction, and a direction perpendicular to the first direction and the second direction is defined as a third direction, the resonance box is configured to be long in the third direction, and the neck portion extends in the third direction.

8. The sound absorbing unit as described in claim 7, wherein the resonance box has a bottom wall portion and a top wall portion which forms the hollow portion between the bottom wall portion and the top wall portion, both ends of the top wall portion in the first direction are connected to both ends of the placement portion in the first direction, and the top wall portion is formed in an arc shape along an arc larger than half the circumference of a circle in a cross section perpendicular to the third direction.

9. The sound absorbing unit described in claim 8, wherein the resonance box has a first side wall portion having the opening and a second side wall portion, the first side wall portion covers the opening formed by the top wall portion and the bottom wall portion at one end of the top wall portion and the bottom wall portion in the third direction, and the second side wall portion covers the opening formed by the top wall portion and the bottom wall portion at the other end of the top wall portion and the bottom wall portion in the third direction.

10. A sound absorbing unit as described in claim 8, wherein the resonating sound absorber comprises a piezoelectric film, the resonance box has a first side wall portion having the opening, the first side wall portion covers the opening formed by the top wall portion and the bottom wall portion at one end of the top wall portion and the bottom wall portion in the third direction, and the piezoelectric film covers the opening formed by the top wall portion and the bottom wall portion at the other end of the top wall portion and the bottom wall portion in the third direction.

11. The sound absorbing unit according to claim 1, wherein the resonant sound absorber comprises a piezoelectric film, and the piezoelectric film defines a part of the hollow portion together with the resonance box.

12. The sound absorbing unit of claim 1, wherein the support body has a connecting wall that connects the tip of the first retaining wall in the direction rising from the mounting surface and the tip of the second retaining wall in the direction rising from the mounting surface, and the mounting portion, the first retaining wall, the second retaining wall, and the connecting wall surround the resonance box.

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