Resonant absorber and tire

Abstract

The resonance absorber includes a resonance box having a hollow portion and a hollow neck portion connected to the resonance box. The neck portion forms an opening that communicates with the hollow portion of the resonance box and the external space of the resonance box. The opening has an inner outlet that opens into the hollow portion and an outer outlet that opens into the external space, and the opening area of the inner outlet is different from the opening area of the outer outlet. The tire includes the above-described resonance absorber, and the resonance absorber is attached to the inner cavity portion.

Description

Technical Field

[0001] The present disclosure relates to a resonance sound absorber and a tire.

Background Art

[0002] In recent years, technologies have been developed to reduce the tire cavity resonance sound generated during vehicle travel by arranging a sound absorption structure in the tires of vehicles such as automobiles. The tire cavity resonance sound is in a low frequency range of, for example, about 200 Hz to 300 Hz. Patent Document 1 describes a sound absorption structure in which an opening is formed in a sub-chamber forming portion that forms a sub-chamber to reduce the tire cavity resonance sound by Helmholtz resonance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the sound absorption structure described in Patent Document 1, the sound absorption characteristics are enhanced by providing a plurality of sub-chamber forming portions that are Helmholtz resonators. However, in terms of each Helmholtz resonator unit, the sound absorption characteristics are not necessarily sufficient. Therefore, improvement of the sound absorption characteristics is desired.

[0005] An object of the present disclosure is to provide a resonance sound absorber and a tire capable of improving sound absorption characteristics.

Means for Solving the Problems

[0006] As a result of intensive research on the above problems, the present inventor has obtained the following findings. In a Helmholtz resonator, sound waves enter the resonator through an opening, and resonant vibrations at the characteristic frequency occur inside the resonator. At this time, intense inflow and outflow of air occur at the opening, and acoustic energy is lost due to the viscous loss of air associated with this intense inflow and outflow of air at the opening, thereby exhibiting a sound absorption phenomenon. In view of the principle of such a Helmholtz resonator, it has been found that the sound absorption characteristics can be improved by configuring the opening to have a large air viscous loss. One aspect of the present disclosure is based on the above findings.

[0007] That is, the resonance sound absorber according to the present disclosure includes a resonance box having a hollow portion, and an opening that communicates with the hollow portion of the resonance box and the external space of the resonance box. The opening has an inner outlet that opens into the hollow portion and an outer outlet that opens into the external space, and the opening area of the inner outlet and the opening area of the outer outlet are different.

[0008] In this resonance sound absorber, since the opening area of the inner outlet of the opening and the opening area of the outer outlet are different, the viscous loss of air at the opening is increased and the loss of acoustic energy is increased compared to the case where the opening has the same shape from the inner outlet to the outer outlet. Therefore, the sound absorption characteristics can be improved.

[0009] In the above-described resonance sound absorber, a hollow neck portion connected to the resonance box and forming an opening may be further provided. In this resonance sound absorber, since a hollow neck portion connected to the resonance box and forming an opening is provided, the length of the opening can be increased to lower the sound absorption characteristics to a lower frequency range.

[0010] In the above-described resonance sound absorber, the length of the opening may be 1 mm or more and 100 mm or less. In this resonance sound absorber, since the length of the opening is 1 mm or more and 100 mm or less, the sound absorption characteristics in the low frequency range such as the resonance sound of the tire inner cavity can be enhanced.

[0011] In the resonance absorber described above, the opening is a circular hole, and the opening diameter of the inner outlet and the opening diameter of the outer outlet may be different. In this resonance absorber, since the opening is a circular hole and the opening diameter of the inner outlet and the opening diameter of the outer outlet are different, it is possible to increase the viscous loss of air at the opening and increase the loss of acoustic energy.

[0012] In the resonance absorber described above, the gradient of the opening diameter of the opening may be 0.5° or more and 5.0° or less. In this resonance absorber, since the gradient of the opening diameter of the opening is 0.5° or more and 5.0° or less, it is possible to increase the viscous loss of air at the opening while smoothly allowing the air to enter and exit the opening.

[0013] In the resonance absorber described above, the value obtained by dividing the difference between the opening diameter of the inner outlet and the opening diameter of the outer outlet by the length of the opening may be 0.01 or more and 0.1 or less. In this resonance absorber, since the value obtained by dividing the difference between the opening diameter of the inner outlet and the opening diameter of the outer outlet by the length of the opening is 0.01 or more and 0.1 or less, it is possible to increase the viscous loss of air at the opening while smoothly allowing the air to enter and exit the opening.

[0014] In the resonance absorber described above, the opening area of the outer outlet may be larger than the opening area of the inner outlet. In this resonance absorber, since the opening area of the outer outlet is larger than the opening area of the inner outlet, sound waves are more likely to enter the opening.

[0015] In the resonance absorber described above, the opening area of the opening may gradually increase from the inner outlet to the outer outlet. In this resonance absorber, since the opening area of the opening gradually increases from the inner outlet to the outer outlet, when manufacturing the resonance absorber by a manufacturing method using a mold such as injection molding, it becomes easier to remove the mold disposed in the opening to the outer outlet side.

[0016] In the resonance absorber described above, the opening is a circular hole, and the opening diameter of the opening may gradually increase from the inner outlet to the outer outlet. In this resonance absorber, since the opening is a circular hole and the opening diameter of the opening gradually increases from the inner outlet to the outer outlet, when manufacturing the resonance absorber by a manufacturing method using a mold such as injection molding, the mold disposed in the opening can be easily removed to the outer outlet side.

[0017] In the resonance absorber described above, the ratio of the opening area of the inner outlet to the opening area of the outer outlet may be 20% or more and 90% or less. In this resonance absorber, since the ratio of the opening area of the inner outlet to the opening area of the outer outlet is 20% or more and 90% or less, it is possible to increase the viscous loss of air at the opening while smoothly allowing the air to flow in and out of the opening.

[0018] In the resonance absorber described above, the opening area of the outer outlet may be smaller than the opening area of the inner outlet. In this resonance absorber, since the opening area of the outer outlet is smaller than the opening area of the inner outlet, foreign matters such as dust are less likely to enter the opening.

[0019] In the resonance absorber described above, the opening area of the opening may gradually decrease from the inner outlet to the outer outlet. In this resonance absorber, since the opening area of the opening gradually decreases from the inner outlet to the outer outlet, when manufacturing the resonance absorber by a manufacturing method using a mold such as injection molding, the mold disposed in the opening can be easily removed to the inner outlet side.

[0020] In the resonance absorber described above, the opening is a circular hole, and the opening diameter of the opening may gradually decrease from the inner outlet to the outer outlet. In this resonance absorber, since the opening diameter of the circular hole gradually decreases from the inner outlet to the outer outlet, when manufacturing the resonance absorber by a manufacturing method using a mold such as injection molding, the mold disposed in the opening can be easily removed to the inner outlet side.

[0021] In the resonance absorber described above, the ratio of the opening area of the outer outlet to the opening area of the inner outlet may be 20% or more and 90% or less. In this resonance absorber, since the ratio of the opening area of the outer outlet to the opening area of the inner outlet is 20% or more and 90% or less, it is possible to smoothly allow air to flow in and out of the opening while increasing the viscous loss of air at the opening.

[0022] The tire according to the present disclosure includes any one of the above resonance absorbers, and the resonance absorber is attached to the inner cavity portion. In this tire, since the above-described resonance absorber is attached to the inner cavity portion, the sound absorption characteristics in the inner cavity portion can be improved.

[0023] In the tire described above, when the frequency of the tire inner cavity resonance sound is F, the speed of light is c, the radius of the inner cavity portion of the tire is R, the radius of the rim of the wheel assembled to the tire is r, and the pi is π, the resonance absorber may have a Helmholtz resonance structure in which Helmholtz resonance occurs at a resonance frequency within the range of ±100 Hz of the frequency of the tire inner cavity resonance sound calculated from F = c / ((R + r) × π). In this tire, since it has a Helmholtz resonance structure in which Helmholtz resonance occurs at a resonance frequency within the range of ±100 Hz of the frequency of the tire inner cavity resonance sound, the tire inner cavity resonance sound can be reduced.

Effect of the Invention

[0024] According to the present disclosure, the sound absorption characteristics can be improved.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0026] Hereinafter, embodiments of the resonance absorber according to the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. In addition, the numerical range indicated by "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

[0027] [First Embodiment] <Tire> FIG. 1 is a schematic cross-sectional view of a tire to which a resonance absorber according to the first embodiment is attached. In tire 101, cavity resonance may occur in which the internal air resonates upon receiving vibrations when passing over road surface irregularities during vehicle travel. The frequency of the cavity resonance is about 200 Hz to 300 Hz, typically about 250 Hz. The resonance absorber 1 according to the present embodiment is attached to the inner cavity 102 of the tire 101 in order to efficiently absorb the cavity resonance in the low frequency band. The inner cavity 102 is the inner peripheral surface of the tread 103. The resonance absorber 1 is attached to the inner cavity 102 of the tire 101, for example, by a double-sided adhesive tape 12 attached to the attachment surface 11. The attachment surface 11 is the surface (back surface) of the resonance absorber 1 that is attached to the inner cavity 102 of the tire 101.

[0028] The double-sided adhesive tape 12 is a tape having adhesiveness on both sides. The double-sided adhesive tape 12 may be configured, for example, such that adhesives (not shown) are disposed on both sides of a base material (not shown), or may be configured such that the base material is impregnated with an adhesive. The double-sided adhesive tape 12 may further include a release sheet disposed on the adhesive. As the double-sided adhesive tape 12, for example, EBISU TAPE #700 manufactured by Ebisu Kasei Co., Ltd. can be used. As the base material, for example, thin paper such as non-woven fabric can be used. As the adhesive, for example, an adhesive such as an acrylic adhesive can be used. The thickness of the double-sided adhesive tape 12 is, for example, 0.05 mm to 1 mm. The double-sided adhesive tape 12 may include a separator disposed on one or both of the adhesives. When the double-sided adhesive tape 12 includes a separator, the separator is peeled off from the adhesive, and the adhesive is attached to the attachment surface 11 of the resonance absorber 1 or the inner cavity 102 of the tire 101. Note that the thickness of the double-sided adhesive tape 12 described above is the thickness excluding the separator, that is, the thickness of the base material and the adhesive.

[0029] Here, a method for attaching the resonance absorber 1 will be described. The method for attaching the resonance absorber 1 includes a pretreatment step of polishing the attachment region R of the inner cavity 102, and an attachment step of attaching the resonance absorber to the attachment region R after the pretreatment step. The attachment region R is a region to which the resonance absorber 1 is attached.

[0030] In the inner cavity 102 of the tire 101, a release agent such as silicone oil is applied. Therefore, by polishing the attachment region R in the pretreatment process, the release agent is removed from the attachment region R. In the pretreatment process, at least the attachment region R may be polished, and regions other than the attachment region R may also be polished. In the present embodiment, the entire circumference of the inner cavity 102 including the attachment region R is polished. The polishing of the attachment region R can be performed, for example, by buffing. In buffing, first, a disk-shaped buff is inserted into the inner cavity of the tire 101. As the buff, for example, a buff brush in which filament materials are planted in the radial direction of the core around a cylindrical core can be used. The filament materials can be made of, for example, metal or synthetic resin. The synthetic resin filament materials may contain abrasive grains such as alumina oxide and silicon carbide. Then, the buff is rotated in a first direction, and the tire is rotated in a second direction opposite to the first direction, and the buff is brought into contact with the inner cavity 102. Thereby, the entire circumference of the inner cavity 102 including the attachment region R is polished (buffed). In the polishing of the attachment region R, for example, the depth of polishing is set to be 3% or more and 30% or less of the thickness of the inner liner layer (not shown) of the tire 101. The inner liner layer is a rubber layer that forms the inner cavity 102.

[0031] In the pasting process, the resonance sound absorber 1 is pasted on the attachment region R using the double-sided adhesive tape 12. In the pasting process, after the double-sided adhesive tape 12 is pasted on the attachment surface 11 of the resonance sound absorber 1, the double-sided adhesive tape 12 may be pasted on the attachment region R of the inner cavity 102, or after the double-sided adhesive tape 12 is pasted on the attachment region R of the inner cavity 102, the double-sided adhesive tape 12 may be pasted on the attachment surface 11 of the resonance sound absorber 1. Thereby, the resonance sound absorber 1 is attached to the inner cavity 102 of the tire 101.

[0032] By laying at least one single resonance absorber 1 or a connected absorber formed by connecting a plurality of resonance absorbers 1 in the inner cavity 102 of the tire 101, the resonance sound in the tire cavity can be reduced. When laying two or more resonance absorbers 1 or connected absorbers, the plurality of resonance absorbers 1 or connected absorbers may be laid adjacent to each other, or may be laid in an intermittent arrangement with a space between them. From the viewpoint of the weight balance in the circumferential direction of the tire 101, it is preferable to arrange the plurality of resonance absorbers 1 or connected absorbers intermittently.

[0033] Also, it is known that the resonance sound in the tire cavity becomes high in sound pressure at the ground contact portion of the tire 101 and on the opposite side. Even if the position of the resonance absorber 1 with respect to the ground contact portion changes due to the rotation of the tire 101, it is preferable that as many resonance absorbers 1 as possible are located in the high sound pressure portion. From this viewpoint, for example, it is preferable to lay a plurality of resonance absorbers 1 or connected absorbers in the tire 101 in an intermittent arrangement as shown in FIG. 9 or FIG. 10.

[0034] FIGS. 9(a), 9(b), 9(c), and 9(d) are schematic cross-sectional views showing examples of the intermittent arrangement of the resonance absorbers. In the example shown in FIG. 9(a), two resonance absorbers 1 are intermittently arranged at positions that are 90° with respect to the center of the tire 101. In the example shown in FIG. 9(b), three resonance absorbers 1 are intermittently arranged at equally spaced positions. That is, in this example, the three resonance absorbers 1 are intermittently arranged at positions that are 120° with respect to the center of the tire 101. In the example shown in FIG. 9(c), four resonance absorbers 1 are intermittently arranged at equally spaced positions. That is, in this example, the four resonance absorbers 1 are intermittently arranged at positions that are 90° with respect to the center of the tire 101. In the example shown in FIG. 9(d), eight resonance absorbers 1 are intermittently arranged at equally spaced positions. That is, in this example, the eight resonance absorbers 1 are intermittently arranged at positions that are 45° with respect to the center of the tire 101.

[0035] Figs. 10(a), 10(b), 10(c), and 10(d) are schematic cross-sectional views showing examples of the intermittent arrangement of the connected sound absorbers. In Figs. 10(a), 10(b), 10(c), and 10(d), as an example of the connected sound absorbers in which a plurality of resonance sound absorbers 1 are connected, a connected sound absorber 1Z in which two resonance sound absorbers 1 are connected is shown. In the example shown in Fig. 10(a), two connected sound absorbers 1Z are intermittently arranged at positions that are 90° with respect to the center of the tire 101. In the example shown in Fig. 10(b), three connected sound absorbers 1Z are intermittently arranged at positions that are equally spaced from each other. That is, in this example, the three connected sound absorbers 1Z are intermittently arranged at positions that are 120° from each other with respect to the center of the tire 101. In the example shown in Fig. 10(c), four connected sound absorbers 1Z are intermittently arranged at positions that are equally spaced from each other. That is, in this example, the four connected sound absorbers 1Z are intermittently arranged at positions that are 90° from each other with respect to the center of the tire 101. In the example shown in Fig. 10(d), eight connected sound absorbers 1Z are intermittently arranged at positions that are equally spaced from each other. That is, in this example, the eight connected sound absorbers 1Z are intermittently arranged at positions that are 45° from each other with respect to the center of the tire 101.

[0036] <resonance sound absorber> Referring to Figs. 2 and 3, the resonance sound absorber 1 according to the first embodiment will be described. Fig. 2 is a schematic perspective view of the resonance sound absorber according to the first embodiment. Fig. 3 is a schematic cross-sectional view taken along line III-III shown in Fig. 2. As shown in Figs. 1 to 3, the resonance sound absorber 1 according to the present embodiment has a Helmholtz resonance structure. That is, the resonance sound absorber 1 absorbs sound by generating Helmholtz resonance. The resonance sound absorber 1 has a resonance box 2 and a hollow neck portion 3.

[0037] The resonance box 2 is a box-shaped member having a hollow portion 5 inside. The resonance box 2 forms the outer shape of the resonance sound absorber 1. The resonance box 2 is composed of a bottom wall portion 2a forming a mounting surface 11 and an upper wall portion 2b forming a hollow portion 5 between the bottom wall portion 2a. That is, the space surrounded by the bottom wall portion 2a and the upper wall portion 2b becomes the hollow portion 5 of the resonance box 2. The shape of the resonance box 2 is not particularly limited, and for example, it can be a rectangular parallelepiped, a semi-cylindrical shape, etc. In the drawings, as an example, the case where the resonance box 2 is a rectangular parallelepiped is shown. Note that the dimensions of the width X, depth Y, and height Z of the resonance box 2 can be set as appropriate.

[0038] The resonance box 2 has self-supportability to the extent that it can maintain its shape in a stationary state. The resonance box 2 has airtightness. The resonance box 2 has at least one of a Shore A hardness of 40 to 100 and a Shore D hardness of 10 to 70. In this case, the Shore A hardness of the resonance box 2 may be 50 to 80, or may be 60 to 70. Also, the Shore D hardness of the resonance box 2 may be 10 to 50, or may be 10 to 40.

[0039] The Shore A hardness of the resonance box 2 can be measured using a durometer in accordance with JIS K6253-3. For example, GS-709N TYPE A manufactured by Techlock Co., Ltd. can be used. The Shore D hardness of the resonance box 2 can be measured using a durometer in accordance with JIS K6253-3. For example, GS-720N TYPE D manufactured by Techlock Co., Ltd. can be used. When the allowable number of laminated test pieces (3 or less) defined in JIS K6253-3 does not satisfy the specified measurement thickness (6 mm or more), they can be stacked more than 3 pieces and measured at the regulated thickness.

[0040] The material of the resonance box 2 includes, for example, resins such as elastomers such as thermoplastic elastomers, plastics, rubbers, and rubber-like materials.

[0041] Examples of the elastomer material include thermoplastic elastomers such as styrene block copolymer (SBC), polyolefin (TPO), polyurethane (TPU), polyester (TPC), polyamide (TPA), dynamically crosslinked type (TPV), soft polyvinyl chloride (PVC), and acrylic.

[0042] Examples of the plastic material include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polyphenylene sulfide (PPS), polyurethane (PU), epoxy resin, phenol resin, and melamine resin.

[0043] Examples of the rubber material include natural rubber (NR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), silicone rubber, and urethane rubber.

[0044] Examples of the rubber-like material include an acrylic rubber-like material having UV curability.

[0045] The neck portion 3 is connected to the upper wall portion 2b constituting the resonance box 2 and extends into the hollow portion 5 of the resonance box 2. The neck portion 3 forms an opening 4 that communicates the hollow portion 5 with the external space 6 of the resonance box 2. The external space 6 is the space outside the resonance box 2 and is the space separated from the hollow portion 5 by the bottom wall portion 2a and the upper wall portion 2b constituting the resonance box 2. The opening 4 is formed by the hollow portion of the neck portion 3. The opening 4 penetrates the upper wall portion 2b constituting the resonance box 2, and the hollow portion 5 communicates with the external space 6 only at the opening 4.

[0046] The neck portion 3 is disposed on the bottom wall portion 2a so as to extend along the bottom wall portion 2a. The neck portion 3 is, for example, integrated (formed integrally) with the bottom wall portion 2a and connected to the bottom wall portion 2a. The neck portion 3 has airtightness similar to that of the resonance box 2. The neck portion 3 has at least one of the same Shore A hardness and Shore D hardness as the resonance box 2. The material of the neck portion 3 can be the same as the material of the resonance box 2.

[0047] The opening 4 has an inner outlet 41 that opens into the hollow portion 5 and an outer outlet 42 that opens into the external space 6. The opening 4 is a space extending from the inner outlet 41 to the outer outlet 42. The inner outlet 41 is the tip of the opening 4 on the side of the hollow portion 5. The outer outlet 42 is the tip of the opening 4 on the side of the external space 6. When the neck portion 3 does not protrude from the resonance box 2 to the external space 6 as in this embodiment, the outer outlet 42 is formed on the outer surface of the resonance box 2. On the other hand, when the neck portion 3 protrudes from the resonance box 2 to the external space 6, the outer outlet 42 is not formed on the outer surface of the resonance box 2 and is formed only at the protruding tip of the neck portion 3. The shape of the opening 4 is not particularly limited. The opening 4 can be a circular hole, a triangular, rectangular, polygonal, elliptical or other hole, etc., but from the viewpoint of ease of manufacture, etc., it is preferably a circular hole. That the opening 4 is a circular hole means that the shape of the opening 4 in a cross section orthogonal to the extending axis of the opening 4 is circular. In this case, the neck portion 3 can be formed in a circular tube shape.

[0048] The length L of the opening 4 is, for example, 1 mm or more and 100 mm or less, 5 mm or more and 50 mm or less, or 10 mm or more and 40 mm or less. The length L of the opening 4 is the length of the extending axis of the opening 4 from the inner outlet 41 to the outer outlet 42.

[0049] In the opening 4, the opening area of the inner outlet 41 is different from the opening area of the outer outlet 42. The opening area of the inner outlet 41 is the area (cross-sectional area) of the inner outlet 41 in a cross-section orthogonal to the extension axis of the opening 4, and the opening area of the outer outlet 42 is the area (cross-sectional area) of the outer outlet 42 in a cross-section orthogonal to the extension axis of the opening 4. When the opening 4 is a circular hole, the opening diameter D1 of the inner outlet 41 is different from the opening diameter D2 of the outer outlet 42. The opening diameter D1 of the inner outlet 41 is the diameter of the inner outlet 41 in a cross-section orthogonal to the extension axis of the opening 4, and the opening diameter D2 of the outer outlet 42 is the diameter of the outer outlet 42 in a cross-section orthogonal to the extension axis of the opening 4.

[0050] Specifically, in the opening 4, since the opening area of the opening 4 gradually increases from the inner outlet 41 to the outer outlet 42, the opening area of the outer outlet 42 is larger than the opening area of the inner outlet 41. When the opening 4 is a circular hole, since the opening diameter of the opening 4 gradually increases from the inner outlet 41 to the outer outlet 42, the opening diameter D2 of the outer outlet 42 is larger than the opening diameter D1 of the inner outlet 41. The opening 4 is formed, for example, in a tapered shape that becomes narrower from the outer outlet 42 toward the inner outlet 41.

[0051] The ratio of the opening area of the inner outlet 41 to the opening area of the outer outlet 42 is, for example, 20% or more and 90% or less, 30% or more and 80% or less, or 40% or more and 70% or less. When the opening 4 is a circular hole, the ratio of the opening diameter D1 of the inner outlet 41 to the opening diameter D2 of the outer outlet 42 is, for example, 40% or more and 95% or less, 50% or more and 90% or less, or 60% or more and 80% or less.

[0052] When the opening 4 is a circular hole, the gradient of the opening diameter of the opening 4 is, for example, 0.5° or more and 5.0° or less, 0.8° or more and 3.0° or less, or 1.0° or more and 2.0° or less. This gradient refers to the inclination angle of one contour line of the opening 4 with respect to the other contour line in a cross-section (the cross-section shown in FIG. 3) along the extension axis of the opening 4.

[0053] Also, when the opening 4 is a circular hole, the value obtained by dividing the difference between the opening diameter D1 of the inner outlet 41 and the opening diameter D2 of the outer outlet 42 by the length L of the opening 4 is, for example, 0.01 or more and 0.1 or less, 0.015 or more and 0.07 or less, or 0.02 or more and 0.05 or less. This value can be obtained by (D2 - D1) / L.

[0054] The resonance sound absorber 1 configured in this way can be manufactured, for example, by injection molding, extrusion molding, shaping by a 3D printer, the salt aggregation method, or the like.

[0055] As described above, in the resonance sound absorber 1 according to the present embodiment, since the opening areas of the inner outlet 41 and the outer outlet 42 of the opening 4 are different, compared with the case where the opening 4 has the same shape from the inner outlet 41 to the outer outlet 42, the viscous loss of air in the opening 4 increases and the acoustic energy loss increases. Therefore, the sound absorption characteristics can be improved.

[0056] By the way, the longer the opening 4 is, the lower the frequency of the sound absorption characteristics becomes. This is presumably because the longer the opening 4 is, the greater the viscous loss of air in the opening 4 becomes, so the sound absorption characteristics shift to lower frequencies. And in this resonance sound absorber 1, since the opening areas of the inner outlet 41 and the outer outlet 42 are different, the viscous loss of air in the opening 4 increases, so the sound absorption characteristics can also be shifted to lower frequencies.

[0057] Also, in this resonance sound absorber 1, since it is provided with a hollow neck portion 3 that is connected to the resonance box 2 and forms the opening 4, the length L of the opening 4 can be increased to shift the sound absorption characteristics to lower frequencies.

[0058] Also, in this resonance sound absorber 1, since the length L of the opening 4 is 1 mm or more and 100 mm or less, 5 mm or more and 50 mm or less, or 10 mm or more and 40 mm or less, the sound absorption characteristics in the low frequency range such as the resonance sound of the tire inner cavity can be enhanced.

[0059] In addition, in this resonance absorber 1, when the opening 4 is a circular hole, since the opening diameter D1 of the inner outlet 41 and the opening diameter D2 of the outer outlet 42 are different, the viscous loss of air at the opening 4 can be increased to increase the loss of acoustic energy.

[0060] In addition, in this resonance absorber 1, when the opening 4 is a circular hole, since the gradient of the opening diameter of the opening 4 is 0.5° or more and 5.0° or less, 0.8° or more and 3.0° or less, or 1.0° or more and 2.0° or less, while smoothly allowing the air to flow in and out at the opening 4, the viscous loss of air at the opening 4 can be increased.

[0061] In addition, in this resonance absorber 1, when the opening 4 is a circular hole, since the value obtained by dividing the difference between the opening diameter D1 of the inner outlet 41 and the opening diameter D2 of the outer outlet 42 by the length L of the opening 4 is 0.01 or more and 0.1 or less, 0.015 or more and 0.07 or less, or 0.02 or more and 0.05 or less, while smoothly allowing the air to flow in and out at the opening 4, the viscous loss of air at the opening 4 can be increased.

[0062] In addition, in this resonance absorber 1, since the opening area of the outer outlet 42 is larger than the opening area of the inner outlet 41, sound waves are more likely to enter the opening.

[0063] In addition, in this resonance absorber 1, since the opening area of the opening 4 gradually increases from the inner outlet 41 to the outer outlet 42, when manufacturing the resonance absorber 1 by a manufacturing method using a mold such as injection molding, the mold disposed in the opening 4 is more easily removed to the outer outlet 42 side.

[0064] In addition, in this resonance absorber 1, when the opening 4 is a circular hole, since the opening diameter of the opening 4 gradually increases from the inner outlet 41 to the outer outlet 42, when manufacturing the resonance absorber 1 by a manufacturing method using a mold such as injection molding, the mold disposed in the opening 4 is more easily removed to the outer outlet 42 side.

[0065] In addition, in this resonance sound absorber 1, since the ratio of the opening area of the inner outlet 41 to the opening area of the outer outlet 42 is 20% or more and 90% or less, 30% or more and 80% or less, or 40% or more and 70% or less, it is possible to smoothly let air in and out of the opening 4 while increasing the viscous loss of air at the opening 4. Similarly, when the opening 4 is a circular hole, since the ratio of the opening diameter D1 of the inner outlet 41 to the opening diameter D2 of the outer outlet 42 is 40% or more and 95% or less, 50% or more and 90% or less, or 60% or more and 85% or less, it is possible to smoothly let air in and out of the opening 4 while increasing the viscous loss of air at the opening 4.

[0066] In the tire 101 according to the present embodiment, since the above-described resonance sound absorber 1 is attached to the inner cavity portion 102, the sound absorption characteristics in the inner cavity portion 102 can be improved.

[0067] Here, as shown in FIG. 1, let the frequency of the tire inner cavity resonance sound be F, the speed of light be c, the radius of the inner cavity portion 102 of the tire 101 be R, the radius of the rim 105 of the wheel 104 assembled to the tire 101 be r, and the pi be π. In this case, the frequency of the tire inner cavity resonance sound is calculated by F = c / ((R + r) × π). The resonance sound absorber 1 preferably has a Helmholtz resonance structure in which Helmholtz resonance occurs at a resonance frequency within a range of ±100 Hz of the frequency of the tire inner cavity resonance sound calculated from F = c / ((R + r) × π).

[0068] The Helmholtz resonance structure is a structure provided with components of a Helmholtz resonator that resonates with sound incident from an opening. In the resonance absorber 1, the Helmholtz resonance structure is constituted by a resonance box 2 and a neck portion 3. That is, since the non-ventilated resonance box 2 and the neck portion 3 form an opening 4 that communicates the hollow portion 5 and the external space 6, the resonance frequency of the resonance absorber 1 that functions as a Helmholtz resonator changes depending on the extension length of the opening 4, the cross-sectional area of the opening 4, and the like. For example, the resonance frequency becomes lower as the extension length of the opening 4 increases. Also, the resonance frequency becomes lower as the cross-sectional area of the opening 4 decreases. Therefore, it is preferable that the resonance absorber 1 is adjusted such that Helmholtz resonance occurs at a resonance frequency within the range of ±100 Hz of the frequency of the tire inner cavity resonance sound calculated from F = c / ((R + r) × π).

[0069] Thus, since it is provided with a Helmholtz resonance structure in which Helmholtz resonance occurs at a resonance frequency within the range of ±100 Hz of the frequency of the tire inner cavity resonance sound, the tire inner cavity resonance sound can be reduced.

[0070] FIG. 4 is a diagram for explaining a method of calculating the resonance frequency of the Helmholtz resonance structure. The resonance frequency of the Helmholtz resonance structure that resonates with the sound incident from the opening 4 can be adjusted from the various dimensions of the opening 4 and the hollow portion 5 according to this calculation method.

[0071] In FIG. 4, V is the volume of the hollow portion 5. When the neck portion 3 extends into the hollow portion 5, V is the volume obtained by subtracting the volume of the neck portion 3. As shown in the third embodiment and the like described later, when a porous sound absorber is disposed in the hollow portion 5, V is the volume of the hollow portion 5 including the porous sound absorber. α is the area of the opening 4 when viewed in the thickness direction of the outer wall. When, as in the present embodiment, the opening area of the inner outlet 41 of the opening 4 is different from the opening area of the outer outlet 42, α is the area of the opening 4 when viewed in the thickness direction of the outer wall. Further, when the area (diameter) of the opening 4 gradually increases or decreases from the inner outlet 41 to the outer outlet 42, α is the area (diameter) of the opening 4 at the center between the inner outlet 41 and the outer outlet 42. δ is the opening end correction. For example, when the shape of the opening 4 is circular, δ can be calculated as 0.8 times the diameter of the opening 4. When the shape of the opening 4 is not circular, δ can be calculated as 0.8 times the diameter of a perfect circle having the same area as the area of the opening 4. L is the depth of the opening 4, that is, the extending length of the neck portion 3 (hollow portion).

[0072] (Second Embodiment) Referring to FIG. 5, the resonance sound absorber 1A according to the second embodiment will be described. The second embodiment is basically the same as the first embodiment (see FIGS. 2 and 3), and is different from the first embodiment only in that the magnitude relationship between the opening area of the inner outlet and the opening area of the outer outlet is reversed. Therefore, only matters different from the first embodiment will be described below, and description of matters the same as those in the first embodiment will be omitted.

[0073] FIG. 5 is a schematic cross-sectional view of the resonance sound absorber according to the second embodiment. As shown in FIG. 5, the resonance sound absorber 1A according to the present embodiment includes a resonance box 2 and a hollow neck portion 3A corresponding to the neck portion 3 of the first embodiment.

[0074] The neck portion 3A forms an opening 4A that communicates the hollow portion 5 and the external space 6. The opening 4A is a hole formed by the hollow portion of the neck portion 3A. The opening 4A penetrates the upper wall portion 2b constituting the resonance box 2, and the hollow portion 5 communicates with the external space 6 only at the opening 4A.

[0075] The opening 4A has an inner outlet 41A that opens into the hollow portion 5 and an outer outlet 42A that opens into the external space 6. The length L of the opening 4A can be the same as that in the first embodiment.

[0076] In the opening 4A, the opening area of the opening 4A gradually decreases from the inner outlet 41A to the outer outlet 42A, so that the opening area of the outer outlet 42A is smaller than the opening area of the inner outlet 41A. When the opening 4A is a circular hole, the opening diameter of the opening 4A gradually decreases from the inner outlet 41A to the outer outlet 42A, so that the opening diameter D2 of the outer outlet 42 is smaller than the opening diameter D1 of the inner outlet 41. The opening 4A is formed, for example, in a tapered shape that becomes narrower from the inner outlet 41A toward the outer outlet 42A.

[0077] The ratio of the opening area of the outer outlet 42A to the opening area of the inner outlet 41A is, for example, 20% or more and 90% or less, 30% or more and 80% or less, or 40% or more and 70% or less. When the opening 4A is a circular hole, the ratio of the opening diameter D2 of the outer outlet 42A to the opening diameter D1 of the inner outlet 41A is, for example, 40% or more and 95% or less, 50% or more and 90% or less, or 60% or more and 85% or less.

[0078] When the opening 4A is a circular hole, the gradient of the opening diameter of the opening 4A and the value obtained by dividing the difference between the opening diameter D1 of the inner outlet 41A and the opening diameter D2 of the outer outlet 42A by the length L of the opening 4A can be the same as those in the first embodiment. In the second embodiment, since the opening diameter D2 of the outer outlet 42 is smaller than the opening diameter D1 of the inner outlet 41, the value obtained by dividing the difference between the opening diameter D1 of the inner outlet 41A and the opening diameter D2 of the outer outlet 42A by the length L of the opening 4A can be obtained by (D1 - D2) / L.

[0079] As described above, in the resonance sound absorber 1A according to this embodiment, since the opening area of the outer outlet 42A is smaller than the opening area of the inner outlet 41A, foreign matters such as dust are less likely to enter the opening 4A.

[0080] Further, in this resonance absorber 1A, since the opening area of the opening 4A gradually decreases from the inner outlet 41A to the outer outlet 42A, when manufacturing the resonance absorber 1 by a manufacturing method using a mold such as injection molding, the mold disposed in the opening 4A can be easily removed to the outer outlet 42A side.

[0081] Further, in this resonance absorber 1A, when the opening 4A is a circular hole and the opening diameter of the opening 4A gradually decreases from the inner outlet 41A to the outer outlet 42A, when manufacturing the resonance absorber by a manufacturing method using a mold such as injection molding, the mold disposed in the opening 4A can be easily removed to the outer outlet 42A side.

[0082] Further, in this resonance absorber 1A, since the ratio of the opening area of the outer outlet 42A to the opening area of the inner outlet 41A is 20% or more and 90% or less, 30% or more and 80% or less, or 40% or more and 70% or less, while smoothly allowing the air to flow in and out of the opening 4A, the viscous loss of the air in the opening 4A can be increased.

[0083] (Third Embodiment) Referring to FIG. 6, the resonance absorber 1B according to the third embodiment will be described. The third embodiment is basically the same as the first embodiment (see FIGS. 2 and 3), and is different from the first embodiment only in that it further includes a porous sound absorber. Therefore, hereinafter, only the matters different from the first embodiment will be described, and the description of the matters the same as the first embodiment will be omitted.

[0084] FIG. 6 is a schematic cross-sectional view of the resonance absorber according to the third embodiment. As shown in FIG. 6, the resonance absorber 1B according to the present embodiment includes a resonance box 2, a hollow neck portion 3, and a porous sound absorber 8 disposed in the hollow portion 5 of the resonance box 2.

[0085] The porous sound absorber 8 is disposed around the neck portion 3 in the hollow portion 5 and is not disposed in the hollow portion of the neck portion 3.

[0086] The porous sound absorber 8 is formed by, for example, foam molding of a resin material such as plastic or rubber. Examples of the plastic material include foamed polyurethane. Either rigid foamed polyurethane or soft foamed polyurethane may be used. As the manufacturing method of the foamed polyurethane, a general method can be used. For example, by mixing a polyol and a polyisocyanate with a foaming agent, a foam stabilizer, a catalyst, etc., filling the mixture into a mold, and foaming and curing it, the porous sound absorber 8 can be obtained.

[0087] Examples of the rubber material include rubber materials obtained from latex such as natural rubber (NR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and chloroprene rubber (CR). By foaming and solidifying these rubber materials, the porous sound absorber 8 can be obtained.

[0088] The pore diameter of the porous sound absorber 8 is, for example, 1 μm or less, preferably 500 μm or less. The open porosity of the porous sound absorber 8 (the ratio of the total area of the pores to the area of the porous sound absorber on the surface of the porous sound absorber 8) is, for example, about 65% to 99%, preferably about 80% to 95%. The pore diameter and the open porosity can be measured, for example, using a computed tomography (CT scan) device using X-rays. For calculating the pore diameter, the average value of the diameters of a plurality (for example, 100) of pores extracted based on the observation image can be used. For calculating the open porosity, the division value obtained by dividing the total area of all the pores extracted based on the observation image by the area of the porous sound absorber can be used.

[0089] As described above, in the resonance sound absorber 1B according to the present embodiment, since the porous sound absorber 8 is disposed in the hollow portion 5, the sound in the high frequency range can be reduced.

[0090] The present disclosure is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present disclosure.

[0091] For example, in the above-described embodiment, it has been described that the opening area and the opening diameter of the opening gradually increase or decrease from the inner outlet to the outer outlet. However, if the opening area of the inner outlet is different from the opening area of the outer outlet, the shape, opening area, opening diameter, etc. of the opening between the inner outlet and the outer outlet can be arbitrarily set.

[0092] Also, in the above-described embodiment, as an example of the shape of the resonance box, a rectangular parallelepiped and a semi-cylindrical shape have been shown. However, the resonance box 2 may be formed, for example, in a tapered shape that becomes thinner on one side. When the resonance box is formed in a tapered shape, the resonance box may be formed, for example, in a tapered shape that becomes thinner in the direction in which the opening extends (the depth direction Y) as illustrated in FIGS. 11 and 12. FIG. 11 is a schematic cross-sectional view of a resonance sound absorber according to a modified example of the first embodiment. FIG. 12 is a schematic cross-sectional view of a resonance sound absorber according to a modified example of the second embodiment. In the resonance sound absorber 1C according to the modified example of the first embodiment shown in FIG. 11, the resonance box 2C is formed in a tapered shape that becomes thinner from the outer outlet 42 side toward the inner outlet 41 side like the opening 4. In the resonance sound absorber 1D according to the modified example of the second embodiment shown in FIG. 12, the resonance box 2D may be formed in a tapered shape that becomes thinner from the inner outlet 41A side toward the outer outlet 42A side like the opening 4A. Further, when the resonance box is formed in a tapered shape, the entire resonance box may be formed in a tapered shape, or a part of the resonance box may be formed in a tapered shape. When a part of the resonance box is formed in a tapered shape, for example, in a cross-section orthogonal to the bottom wall portion along the opening, it may be formed in a tapered shape. That is, the resonance box may be formed in a tapered shape by the bottom wall portion and the upper wall portion approaching each other.

Example

[0093] Next, examples of the present disclosure will be described. However, the present disclosure is not limited to the following examples.

[0094] (Example 1) As Example 1, a resonance absorber similar to the resonance absorber 1 shown in FIGS. 2 and 3 was fabricated using a 3D printer. In the following description, for convenience, the resonance absorbers of Examples 1 to 2 and Comparative Example 1 are given the same reference numerals as the resonance absorber 1 shown in FIGS. 2 and 3. In the resonance absorber 1 of Example 1, the resonance box 2 was formed in the shape of a rectangular parallelepiped box with a wall thickness of 1.0 mm, a width X of 20 mm, a depth Y of 40 mm, and a height Z of 20 mm. The opening 4 formed by the internal space of the neck portion 3 was a circular hole. The opening 4 was tapered with a gradient of 1° in the opening diameter. The opening diameter (diameter) of the inner outlet 41 opening into the hollow portion 5 was set to 4.0 mm, and the opening diameter of the outer outlet 42 opening into the external space 6 was set to 5.0. The length of the opening 4 (the length of the neck portion 3) was set to 30 mm.

[0095] The normal incidence sound absorption rate of the fabricated resonance absorber 1 was measured as follows. In the measurement of the normal incidence sound absorption rate, as shown in FIG. 7, six resonance absorbers 1 were arranged on the test body holder 202 in the acoustic tube 201 so that the opening 4 was not blocked by other resonance absorbers 1. The results are shown in FIG. 8 and Table 1. Device name: Type 4206 impedance tube (Brüel & Kjær) Measurement method: Normal incidence sound absorption rate (conforming to JIS A 1405-1) Measurement range: 50 - 3500 Hz Measurement sample size: Φ98 mm (for low-frequency side measurement: measurement range 125 - 1600 Hz)

[0096]

Table 1

[0097] (Example 2) A resonance absorber was fabricated under the same conditions as in Example 1 except that the opening diameter of the inner outlet 41 opening into the hollow portion 5 was set to 5.0 mm and the opening diameter of the outer outlet 42 opening into the external space 6 was set to 4.0, and the normal incidence sound absorption rate was measured. The results are shown in FIG. 8.

[0098] (Comparative Example 1) With the opening diameters of the inner outlet 41 opening into the hollow portion 5 and the outer outlet 42 opening into the external space 6 being set to 5.0 mm, and the opening 4 having the same shape from the inner outlet 41 to the outer outlet 42, a resonance sound absorber was fabricated under the same conditions as in Example 1, and the normal incidence sound absorption rate was measured. The results are shown in Fig. 8.

[0099] (Results) As shown in Fig. 8 and Table 1, in both Example 1 and Example 2, compared with Comparative Example 1, the sound absorption rate improved, the peak of the sound absorption rate shifted to the low-frequency side, and the sound absorption rate improved. From these results, it is presumed that the difference between the opening area of the inner outlet and the opening area of the outer outlet increases the viscous loss of air at the opening 4, so that the sound absorption characteristics can be improved and the sound absorption characteristics can also be shifted to lower frequencies.

Industrial Applicability

[0100] The present disclosure can be used as a resonance sound absorber and a tire.

Explanation of Signs

[0101] 1... Resonance sound absorber, 1A... Resonance sound absorber, 1B... Resonance sound absorber, 1C... Resonance sound absorber, 1D... Resonance sound absorber, 1Z... Connecting sound absorber, 2... Resonance box, 2a... Bottom wall portion, 2b... Upper wall portion, 2C... Resonance box, 2D... Resonance box, 3... Neck portion, 3A... Neck portion, 4... Opening, 41... Inner outlet, 42... Outer outlet, 4A... Opening, 41A... Inner outlet, 42A... Outer outlet, 5... Hollow portion, 6... External space, 8... Porous sound absorber, 11... Mounting surface, 12... Double-sided adhesive tape, 101... Tire, 102... Inner cavity portion, 103... Tread, 104... Wheel, 105... Rim, 201... Acoustic tube, 202... Specimen holder, D1... Opening diameter, D2... Opening diameter, R... Mounting area.

Claims

1. A resonance box having a hollow portion, An opening that communicates between the hollow portion of the resonance box and the external space of the resonance box, A hollow neck portion that is connected to the resonance box and forms the opening, The opening has an inner outlet that opens into the hollow portion and an outer outlet that opens into the external space, The opening area of the inner outlet is different from the opening area of the outer outlet, The neck portion extends along the wall of the resonance box, The opening is a circular hole, The opening diameter of the inner outlet is different from the opening diameter of the outer outlet, The value obtained by dividing the difference between the opening diameter of the inner outlet and the opening diameter of the outer outlet by the length of the opening is 0.01 or more and 0.1 or less, Resonance sound absorber.

2. The resonance box has a bottom wall portion disposed on the mounting target side for mounting the resonance sound absorber, The neck portion extends along the bottom wall portion, The resonance sound absorber according to claim 1.

3. The neck portion is disposed on the bottom wall portion, The resonance sound absorber according to claim 2.

4. The length of the opening is 1 mm or more and 100 mm or less, The resonance sound absorber according to claim 1.

5. The gradient of the opening diameter of the opening is 0.5° or more and 5.0° or less, The resonance sound absorber according to claim 1.

6. The opening area of the outer outlet is larger than the opening area of the inner outlet, The resonance sound absorber according to claim 1.

7. The opening area of the opening gradually increases from the inner outlet to the outer outlet, The resonance sound absorber according to claim 6.

8. The opening is a circular hole, and the opening diameter of the opening gradually increases from the inner outlet to the outer outlet. The resonance sound absorber according to claim 6.

9. The ratio of the opening area of the inner outlet to the opening area of the outer outlet is 20% or more and 90% or less. The resonance sound absorber according to claim 6.

10. The opening area of the outer outlet is smaller than the opening area of the inner outlet. The resonance sound absorber according to claim 1.

11. The opening area of the opening gradually decreases from the inner outlet to the outer outlet. The resonance sound absorber according to claim 10.

12. The opening is a circular hole, and the opening diameter of the opening gradually decreases from the inner outlet to the outer outlet. The resonance sound absorber according to claim 10.

13. The ratio of the opening area of the outer outlet to the opening area of the inner outlet is 20% or more and 90% or less. The resonance sound absorber according to claim 10.

14. The resonance box is semi-cylindrical. The resonance sound absorber according to claim 1.

15. A tire comprising the resonance sound absorber according to any one of claims 1 to 14, wherein the resonance sound absorber is attached to the inner cavity. Tire.

Images