JP2010095235A - Vehicular sound absorbing body and vehicular sound absorbing structure using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular sound absorbing body and a vehicular sound absorbing structure having the high-degree sound absorbing effect in a low frequency area, being small and lightweight, and capable of imparting the sound absorbing effect even to a surface being not a flat surface. <P>SOLUTION: This vehicular sound absorbing body 1 has a frame body 2 having a through-hole 2a and a sound absorbing material 3 for covering one opening part of the through-hole 2a. The vehicular sound absorbing structure is provided by covering the other opening part of the through-hole 2a with a construction surface 4 (a constituent member of a vehicle). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sound absorber for a vehicle and a sound absorbing structure for a vehicle using the same.

Vehicles for transportation such as trains and automobiles are usually provided with sound absorbers in order to increase the quietness in the passenger compartment.
As conventional sound-absorbing materials, for example, porous materials such as glass wool and rock wool-like fibers formed into a cotton-like or board-like shape, and polymer foam-like materials such as polyurethane foam are known. Yes. When sound waves are incident on these porous materials, the sound waves vibrate the air in the gaps in the materials, so some of the vibration energy is converted into heat energy and dissipated by the viscosity of the air itself and the friction with the surroundings. An effect is obtained.

However, a conventional sound absorber using a porous material has a problem that a sufficient sound absorbing effect cannot be obtained in a low frequency region of 500 Hz or less.
For example, FIG. 9 shows the frequency of sound absorption for foamed urethane (thickness 10, 20, 50 mm), felt (thickness 10, 50 mm), and ethylene-vinyl acetate copolymer foam (foamed EVA, thickness 10 mm). It is a graph which shows the result of having measured the characteristic. The horizontal axis represents frequency (unit: Hz), and the vertical axis represents sound absorption rate.
As shown in this figure, when the thickness of the porous material is increased, the sound absorption coefficient in the low frequency region is improved. For example, if the thickness of the urethane foam is 50 mm, the porous material is 0 in the frequency region of 450 to 500 Hz. It is possible to achieve a sound absorption coefficient of about .5 to 0.6. However, when the thickness of the porous material is increased, the sound absorber is increased in size. In particular, it is important that a sound absorber for a vehicle provided in a limited space called a vehicle is thin and light.

  The following Patent Document 1 describes a vehicle soundproofing member using a perforated plate and utilizing the Helmholtz principle, but the frequency range in which sound can be effectively absorbed is about 1 to 3 kHz, and sound absorption in a low frequency range is performed. Is insufficient.

As a sound absorber capable of obtaining a good sound absorption effect in a low frequency region of 500 Hz or less, the present inventors have previously configured a configuration in which an opening provided in a frame is covered with a sound absorbing material having a specific storage elastic modulus. A membrane vibration type sound absorber having the above has been proposed (Patent Document 2).
JP-A-6-298014 JP 2008-96826 A

However, in the case of a sound absorber for a vehicle, there are special demands such as that the sound absorber itself is thin and light, and that a sound absorbing effect can be imparted to a non-flat surface. The example used for is not known.
The present invention has been made in view of the above circumstances, and has a high sound absorption effect in a low frequency region, is small and lightweight, and can provide a sound absorption effect even on a non-flat surface. An object is to provide a sound absorbing structure.

  In order to solve the above-described problems, a sound absorber for a vehicle according to the present invention (hereinafter sometimes simply referred to as a sound absorber) includes a frame body having a through hole and a sound absorbing material that covers one opening of the through hole. It is characterized by providing.

  The sound absorbing structure for a vehicle according to the present invention includes a frame having a through hole and a sound absorbing material that covers one opening of the through hole, and the other opening of the through hole is covered with a vehicle component. It is characterized by that.

The vehicle sound absorber of the present invention has a high sound absorption effect in a low frequency region, is small and lightweight, and can impart a sound absorption effect even to a non-flat surface.
The sound absorbing structure for a vehicle according to the present invention is a structure in which the sound absorbing body for a vehicle according to the present invention is directly mounted on a structural member of the vehicle, and an advanced sound absorbing effect is obtained in a low frequency region.

The value of the storage elastic modulus (E ′) in the present invention is a measurement method according to JIS K7244-4 (tensile vibration). The sample size is 40 mm in length, 10 mm in width, and 1 mm in thickness. , A value (unit: Pa) obtained as a distortion amplitude of 6 μm, 25 ° C., and 20 Hz.
Tan δ (loss tangent) is a value represented by the absolute value of the ratio (E ″ / E ′) of the loss elastic modulus (E ″) to the storage elastic modulus (E ′). The storage elastic modulus (E ′) and the measurement frequency of tan δ are generally 20 Hz because they are closer to the actual sound absorption frequency within a measurable range (0.2 to 50 Hz) (note that 50 Hz) However, since there are many variations in data, it was set to 20 Hz.)
In addition, the viscoelastic property at normal temperature (25 ° C.) in the low frequency region (about 250 to 400 Hz) is similar to the viscoelastic property at 15 ° C. at 20 Hz when estimated based on the master curve. 15 ° C. was adopted.
The storage elastic modulus (E ′) and tan δ (loss tangent) are values determined by the material.
The storage elastic modulus (E ′) and tan δ (loss tangent) were measured using a viscoelastic spectrometer EXSTAR6000 DMS, model name DMS6100, manufactured by SII Nanotechnology.

The sound absorption coefficient in this specification means “normal incidence sound absorption coefficient”, and is a value measured by a method according to JIS A 1405-2. The sound absorption rate is measured while changing the incident frequency, and the frequency at which the sound absorption rate becomes the highest is called the peak frequency.
Further, since the sound absorption by the sound absorber of the present invention is a membrane vibration type sound absorption, the sound absorption is performed at a resonating frequency. Therefore, an average of the sound absorption rate in the range of the peak frequency ± 50 Hz is defined as a value that serves as an index of the range of the frequency range where good sound absorption occurs, and is defined as the average sound absorption rate.

1A and 1B show an embodiment of a sound absorber according to the present invention. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line BB in FIG. In the figure, reference numeral 1 denotes a sound absorbing body, 2 denotes a frame body, 3 denotes a sound absorbing material, and 4 denotes a construction surface of the sound absorbing body. The sound absorber of the present invention is used by being directly fixed to the surface of a vehicle component. That is, the construction surface 4 is the surface of the vehicle component. In this embodiment, the construction surface 4 is a flat surface. In the present invention, a structure in which the sound absorber 1 is fixed on a vehicle component is referred to as a vehicle sound absorbing structure.
The frame 2 has a through-hole 2a that communicates the front surface and the back surface, and an opening is formed on each of the front and back surfaces. The end surface 2b on the surface side of the frame 2 is a flat surface. The sound absorbing material 3 is laminated and fixed on the end surface 2b on the surface side so as to cover the opening of the through hole 2a.
The end surface 2c on the back surface side of the frame 2 is also a flat surface. The end surface 2 c on the back surface side is bonded and fixed to the construction surface 4. That is, the opening on the back side is covered with the construction surface 4, and the space surrounded by the sound absorbing material 3, the construction surface 4, and the frame body 2 is the back air layer 5. That is, the back air layer 5 is formed adjacent to the sound absorbing material 3.

The frame body 2 of the present embodiment has a circular outer shape and has concentric through holes. The frame body 2 may have any shape as long as it has an opening on the surface side and can form a space that becomes the back air layer 5 adjacent to the opening. The outer shape can be arbitrary. The frame 2 itself may or may not have sound absorbing performance. The material of the frame 2 is not particularly limited, but a material having a low specific gravity such as a resin is preferable from the viewpoint of weight reduction.
In this invention, thickness T2 of the frame ₂ is 3-50 mm, Preferably it is 5-20 mm. When the thickness is 3 mm or more, good primary vibration of the sound absorbing material is easily obtained. When it is 50 mm or less, it is easy to realize a reduction in size and weight.
When the thickness of the frame 2 is not uniform in the opening 2a uses the average value as T _2.

The shape of the opening on the surface side of the frame body 2 (the shape of the opening of the through hole 2a in the end surface 2b on the surface side) is not limited to a circle but may be an arbitrary shape such as a polygon.
In the present invention, the area of one opening on the surface side of the frame body 2 is preferably 3800 to 20000 mm ² , more preferably 5000 to 13200 mm ² .
When the opening has a circular diameter, the inner diameter D is preferably 70 to 160 mm, more preferably 80 to 130 mm. When it is 70 mm or more, the peak frequency tends to be low, and when it is 160 mm or less, it is preferable in terms of miniaturization. When the opening 2a is smaller, the number of openings 2a that can be provided in a certain area is increased, and the sound absorption performance in the certain area is improved.
In the present invention, when the opening 2a is not circular, the value of the inner diameter D of the opening 2a is the diameter of a circle having the same area as the area of the opening 2a.
When the opening 2a is a square, the length of one side is preferably 62 to 142 mm, and more preferably 71 to 120 mm.

The thickness T 2 of the frame body ₂ and the area of one opening on the surface side change the sound absorption characteristics (such as peak frequency and sound absorption coefficient) of the sound absorber 1 due to these, so that a high sound absorption effect can be obtained in a desired frequency region. These dimensions are preferably set so that
The sound absorption characteristics vary depending on the material and thickness of the sound absorbing material 3 if the shape of the frame 2 is constant and the average thickness of the frame 2 is constant. The average thickness of the frame 2 is the average value of the distance from the sound absorbing material 3 to the construction surface 4 inside the frame 2. The average value is obtained as an average value of the distances from the sound absorbing material 3 to the construction surface 4 at all points, regarding the construction surface as a set of points. For example, as shown in Example 1 (FIG. 4) to be described later, in the frame 2, when the distance from the sound absorbing material 3 to the construction surface 4 is 27.5 mm and 32.5 mm, If the areas of the two regions on the surface 4 are the same, the average thickness of the frame body 2 is 30 mm.

In addition, when a plurality of openings are provided in the sound absorbing surface, if the sound absorbing material 3 has the same configuration and the average thicknesses of the respective frames 2 are the same, the sound absorbing characteristics of the sound absorbing surface are narrow in the width of the sound absorbing frequency. Thus, the peak value of the sound absorption rate is improved. On the other hand, although the sound absorbing material 3 has the same configuration, if the average thicknesses of the respective frames 2 are different from each other, the peak value of the sound absorption coefficient is slightly lowered, but the width of the sound absorbing frequency is widened.
That is, the sound absorption characteristics of the sound absorbing surface can be controlled by controlling the variation in the average thickness of the frame 2 in the plurality of openings provided in the sound absorbing surface.

When trying to obtain a high sound absorption coefficient peak value by making the average thicknesses of the plurality of frames 2 the same, the average thickness of the frames 2 having the largest variation in the average thickness of the plurality of frames 2 is 100%. When it does, it is preferable that the average thickness of the smallest frame 2 is 95 to 99%. Within this range, the desired effect can be obtained satisfactorily.
On the other hand, when it is intended to increase the width of the sound absorption frequency by giving the average thickness of the plurality of frames 2 wide, the average thickness of the frames 2 having the largest variation in the average thickness of the plurality of frames 2 is 100. %, It is preferable that the average thickness of the smallest frame 2 is 80 to 94%. Within this range, the desired effect can be obtained satisfactorily. If it is less than 80%, the sound absorption coefficient peak in each opening becomes independent, and the sound absorption coefficient peak value as a whole becomes low.

The sound absorbing material 3 is made of a material that can generate a sound absorbing action by membrane vibration. Specifically, in order for the sound absorbing material 3 to generate a sound absorbing action by membrane vibration, the flow resistance in the sound absorbing material 3 is preferably 1 × 10 ⁶ N · s / m ⁴ or more. The value of the flow resistance in this specification is the pressure difference between the two surfaces of the sound absorbing material (the pressure on the front surface side and the pressure on the back surface side) when a constant air flow is passed through the surface of the sound absorbing material 3 in the vertical direction. (Difference) divided by air flow velocity. Since sound corresponds to a state where the flow velocity is very small, it is defined as a limit value when the flow velocity approaches zero. The measurement method conforms to the DC method of ISO 9053.

The sound absorbing material 3 may be a laminate in which a plurality of membrane vibration type sound absorbing materials are laminated and integrated. In the case of a laminated body, in addition to the sound absorbing material, it may have other layers that do not affect the sound absorbing characteristics of the sound absorbing material. For example, if the thickness of the adhesive layer is 0.5 mm or less, it does not affect the sound absorption characteristics of the sound absorbing material.
When the sound absorbing material 3 is composed of a laminated body in which a plurality of sound absorbing materials are integrated, the sound absorbing material layer having the highest storage elastic modulus among the plurality of sound absorbing materials is designated as the first sound absorbing layer, and the sound absorbing material having the lowest storage elastic modulus is provided. When the material layer is the second sound absorbing layer, the storage elastic modulus of the first sound absorbing layer is E′1, and the storage elastic modulus of the second sound absorbing layer is E′2, (E′1 / E′2) It is preferable that ≧ 3 and that the storage elastic modulus of each sound absorbing layer gradually decreases from the first sound absorbing layer toward the outside in the laminate. By laminating a plurality of sound absorbing materials in this way, the frequency region can be shifted to a lower frequency side than the case of a single layer of the sound absorbing material.

The value of E′1 / E′2 is preferably 4 or more, more preferably 17 or more. When the ratio of E′1 and E′2 is within the above range, an effect of shifting the frequency region to the low frequency side by stacking the sound absorbing layer is easily obtained.
The upper limit of E′1 / E′2 is not particularly limited, but is preferably 1600 or less. If it is larger than this, the heat resistance and strength of the membrane vibration type sound absorbing material 3 may be insufficient.
The range of the storage elastic modulus E′1 of the first sound absorbing layer constituting the membrane vibration type sound absorbing material 3 is not particularly limited, but is preferably 5 × 10 ^{7 to} 5 × 10 ⁹ Pa, for example, 1 × 10 ⁸ to 1 × 10 ⁹ Pa is more preferable.

  When there are two sound absorbing material layers constituting the membrane vibration type sound absorbing material 3, the second sound absorbing layer may be laminated on either the front side or the back side (the frame 2 side) with respect to the first sound absorbing layer. Good. From the viewpoint of durability against temperature changes, it is preferable that the storage elastic modulus of the sound absorbing layer closest to the frame 2 is larger.

The specific gravity G of the sound absorbing material 3 is preferably 0.86 to 1.65, more preferably 0.9 to 1.6. When the specific gravity G is 0.86 or more, a good sound absorption effect in the low frequency region is easily obtained. It is preferable from the point of weight reduction that it is 1.65 or less.
In the present invention, the storage elastic modulus E ′ of the sound absorbing material 3 is preferably 1 × 10 ⁸ to 1 × 10 ⁹ Pa, and more preferably 1 × 10 ^{8 to} 5 × 10 ⁸ Pa.
When the storage elastic modulus E ′ is 1 × 10 ⁸ Pa or more, it is easy to obtain a good primary vibration of the sound absorbing material, and a good sound absorbing effect in a low frequency region is easily obtained. If it is 1 × 10 ⁹ Pa or less, the peak frequency tends to be low.
The tan δ of the sound absorbing material 3 is preferably 0.01 to 0.3, and more preferably 0.03 to 0.2. When it is 0.01 or more, a high sound absorption coefficient is easily obtained, and when it is 0.2 or less, the peak frequency tends to be low.

The sound absorbing material 3 may be made of a single material or a mixture of two or more materials.
As a constituent material of the sound absorbing material 3, for example, a thermoplastic resin can be used. Specifically, EEA (ethylene ethyl acrylate), EVA (vinyl acetate copolymer), PE (polyethylene), CPE (chlorinated polyethylene). ), PVC (polyvinyl chloride), PP (polypropylene), EBR (ethylene butadiene rubber), SEBS (styrene ethylene butylene styrene block copolymer), styrene isoprene styrene block copolymer or a hydrogenated product thereof (hereinafter collectively referred to as generic name). SIS), SEPS (styrene ethylene propylene styrene block copolymer), PET (polyethylene terephthalate), acrylic resin, polymethylpentene, polybutene, PEEK (polyether ether ketone), cyclic olefin, polylactic acid, etc. 1 Seed The two or more resins, or these resins as a base resin, which inorganic fillers and or mixtures of the organic filler appropriately added can be mentioned in the.
Among the resins listed above, PE (particularly HDPE (high density polyethylene), LLDPE (linear low density polyethylene)), PP (polypropylene), CPE (chlorinated polyethylene), EBR, ethylene-α olefin copolymer , SIS or a mixed resin thereof is preferable.

Examples of the inorganic filler include mica, talc, calcium carbonate, magnesium hydroxide, barium sulfate and the like.
When the inorganic filler is blended, the blending amount is not particularly limited as long as a favorable range of the specific gravity G and storage elastic modulus E ′ of the sound absorbing material can be obtained. From the point of mechanical strength, 80 mass% or less is preferable in the constituent material of the sound-absorbing material 3, and 60 mass% or less is more preferable.
Examples of organic fillers include 3,3 ′, 3 ″, 5,5 ′, 5 ″ -hexa-tert-butyl-a, a ′, a ″-(mesitylene-2,4,6-triyl ) Tri-p-cresol (for example, product name: ADK STAB AO-330, manufactured by ADEKA), tris (2,4 di-tert-butylphenyl) phosphite (for example, product name: Irg168, Ciba Specialty Chemicals) Product).
When the organic filler is blended, the blending amount is not particularly limited as long as a favorable range of the specific gravity G and storage elastic modulus E ′ of the sound absorbing material can be obtained. From the viewpoint of mechanical strength, 50% by mass or less is preferable in the constituent material of the sound absorbing material 3, and 30% by mass or less is more preferable.

In the present invention, the thickness T ₁ of the sound absorbing material 3 is 0.5 to 3 mm, and preferably 0.6 to 2 mm. When the thickness is 0.5 mm or more, good primary vibration of the sound absorbing material is easily obtained. It is preferable from the point of weight reduction that it is 3 mm or less.
If the thickness of the sound absorbing material 3 is not uniform, using an average value as T _1.

  As a means for fixing the sound absorbing material 3 to the frame body 2, an adhesive means such as an adhesive or a double-sided tape may be used, and it may be fixed by pressure bonding or melt pressure bonding.

Further, another sound absorbing layer (not shown) may be laminated on the surface of the sound absorbing material 3 (on the side opposite to the frame 2 side). Specifically, the other sound absorbing layer is formed of a layer having a flow resistance smaller than 1 × 10 ⁶ N · s / m ⁴ . As the other sound absorbing layer, a known sound absorbing material satisfying the above flow resistance range can be appropriately used. Specific examples include foamed resin, felt, fiber material, glass wool, rock wool, wood powder cement, and the like. Particularly preferred are foamed resin, felt, fiber material, and glass wool.
By laminating such other sound absorbing layers, the frequency range in which the sound absorbing effect can be obtained can be broadened as the sound absorber 1 as a whole. For example, when the sound absorbing material 3 is provided with another sound absorbing layer having a sound absorbing effect in a higher frequency region than the frequency region in which the sound absorbing effect is obtained, the sound absorbing effect is obtained in both frequency regions. .

<Vehicle sound absorption structure>
The construction surface 4 of the sound absorber 1 is a surface of a member constituting the vehicle. For example, instrument panel (instrument panel) back surface, door trim back surface, pillar trim back surface, cabin side surface of the partition between the engine room and cabin, ceiling back surface, seat bottom surface, carpet back under seat, rear shelf board back surface, side sill cover back surface, Examples include the back of the trunk room trim and the back of the rear seat trim (quarter trim).
The material of the construction surface 4 is not particularly limited as long as the sound absorbing material 3 can vibrate in the sound absorbing body 1. Examples of the material of the construction surface 4 include metals, synthetic resins, ceramics, and the like.
As a means for fixing the sound absorber 1 to the construction surface 4, an adhesive, or an adhesive means such as a double-sided adhesive tape or an adhesive can be used as appropriate.

  If the construction surface 4 is a flat surface, the sound absorber 1 can be easily attached. However, the construction surface 4 may be curved and undulate as long as the sound absorbing material 3 is capable of membrane vibration. It may be a surface. For example, as shown in FIG. 2, when the construction surface 14 is a curved surface, the shape of the frame body 12 is adjusted so that the sound absorbing material 13 does not sag in a state where the sound absorber 11 is fixed to the construction surface 14. . Reference numeral 15 in the figure denotes a back air layer.

It is preferable to provide a plurality of sound absorbers 1 on a surface (construction surface 4) where a sound absorbing effect is to be obtained. When a plurality of sound absorbers 1 are provided, it is preferable to arrange them side by side so that the opening on the surface side of the frame 2, that is, the space other than the region where the sound absorbing material 3 vibrates is minimized. The plurality of sound absorbers 1 may be separate from each other. For example, the frames may be integrated as shown in FIG.
The sound absorber 21 shown in FIG. 3 has a plurality of through holes 22 a provided in a plate-like frame body 22, and collectively covers the openings of the plurality of through holes 22 a on one surface of the frame body 22. In this way, the sound absorbing material 23 is laminated and fixed. This figure is a perspective view of the sound absorber 21 as viewed from the frame body 22 side. Although the arrangement of the plurality of through holes 22a is arbitrary, the efficiency of sound absorption in the sound absorber 21 increases as the distance P between the adjacent through holes 22a decreases.

When a plurality of sound absorbers 1 are provided on the construction surface 4 to obtain a sound absorption effect in a predetermined frequency region, the sound absorption characteristics of the plurality of sound absorbers 1 are preferably the same. As shown in the examples described later, in the plurality of sound absorbers 1, when the shape and area of the opening on the surface side of the frame body 2, the material of the sound absorber 3 and the thickness T ₁ are the same, the frame body If the average thickness of 2 is substantially the same, substantially the same sound absorption characteristics can be obtained.
Therefore, when providing the several sound absorber 1 in the construction surface 4 with a curved surface and undulations, what is necessary is just to adjust the shape of the frame 2 so that the average thickness of each frame 2 may become substantially the same. The shape and size of the through hole of the frame body 2 may not be constant in the thickness direction of the frame body 2. For example, as shown in FIG. 4, the through hole 32 a of the frame body 32 has a thickness of the frame body 32. The diameter may be gradually increased in the vertical direction. Alternatively, although not shown, the through hole 32 a of the frame body 32 may gradually increase in diameter in the thickness direction of the frame body 32.

According to the sound absorber of the present invention, since a sound absorbing action by membrane vibration can be obtained, a good sound absorbing effect can be obtained in a low frequency region of 500 Hz or less while being small and light, as shown in Examples described later. . Therefore, it can be suitably used to absorb 250-400 Hz noise peculiar to vehicles, which is called road noise.
Further, the sound absorber of the present invention can be attached even if the construction surface is not a flat surface, and the sound absorption characteristics can be made uniform by aligning the average thickness of the frames 2 of the plurality of sound absorbers. Therefore, the degree of freedom with respect to the shape of the construction surface is high, and it is suitable as a sound absorber for vehicles.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
(Examples 1 and 2)
The sound absorption characteristics of the sound absorbers having different frame shapes and the same average thickness of the frame 2 were examined.
4 shows the sound absorber 31 of the first embodiment, and FIG. 5 shows the sound absorber 41 of the second embodiment, where (a) is a top view and (b) is taken along line AA in (a). It is sectional drawing. The shape of the through holes 32a and 42a of the frames 32 and 42 when viewed from above is a square. In the figure, reference numerals 33 and 43 denote sound absorbing materials, 34 and 44 denote construction surfaces, and 35 and 45 denote back air layers. Each dimension is as follows.
Length of one side of the opening on the surface side: a = 107.5 mm.
Frame thickness: b = 32.5 mm, c = 27.5 mm, d = 30 mm.
The step on the construction surface is equidistant from the both ends of the opening (that is, a1 = 53.75 mm).
From these dimensions, when the average thickness in the through holes 32a and 42a is determined, both of the first and second embodiments are 30 mm.

As the sound absorbing materials 33 and 43, a 0.2 mm thick SIS made of SIS is formed on a first film of 0.6 mm thick made of a mixture of HDPE and LLDPE (HDPE: LLDPE mass ratio = 7: 3). Using a laminated sheet in which the two films were laminated, this was fixed to the frames 32 and 42 with double-sided adhesive tape so that the first film (film made of a mixture of HDPE and LLDPE) was on the side in contact with the frame . For the integration of the first film and the second film, an adhesive was not used, and a laminated sheet was produced by 140 ° C. hot pressing.
The materials used are as follows.
HDPE: HY540 (product name), manufactured by Japan Polyethylene Corporation.
LLDPE: UF240 (product name), manufactured by Japan Polyethylene Corporation.
SIS: Hibler 5127 (product name), manufactured by Kuraray Co., Ltd.
Double-sided adhesive tape: manufactured by Hose Care Products, product number: NoH100.
Material of the frames 32, 42: aluminum.
Material of construction surfaces 34 and 44: Aluminum.
First film: storage elastic modulus E ′ = 6.3 × 10 ⁸ , tan δ = 0.03, specific gravity G = 0.95.
Second membrane: storage elastic modulus E ′ = 6.6 × 10 ⁷ , tan δ = 0.36, specific gravity G = 0.94.
It was confirmed that the flow resistance of the laminated sheet composed of the first film and the second film was 1 × 10 ⁶ N · s / m ⁴ or more.

For the sound absorbers of Examples 1 and 2, the sound absorption rate was measured by the following method. The results are shown in FIG. In the graph of FIG. 6, the horizontal axis represents frequency (unit: Hz), and the vertical axis represents sound absorption rate.
[Measurement method of sound absorption coefficient]
The “normal incidence sound absorption coefficient” was measured by a method according to JIS A 1405-2. Specifically, a square impedance tube (made of aluminum, thickness 15 mm) having an inner size of 240 mm × 240 mm was used. The sample installation surface was an aluminum plate, and the sound absorbers of Examples 1 and 2 were fixed to the center of the plate with a double-sided adhesive tape, and measurement was performed.

Examples 1 and 2, the shape and area of the opening of the frame 32, 42, the material and thickness T ₁ of the sound absorbing material 33 are the same as each other. While Example 1 is the distance from the construction surface 34 to the sound absorbing material 33 not constant, the average thickness T ₂ of the frame body 32 and 42 is designed to be the same in Examples 1 and 2.
In the first and second embodiments, substantially the same sound absorption characteristics can be obtained as shown in FIG.

(Example 3)
The sound absorption characteristics on the surface where a plurality of sound absorbers are arranged side by side were examined.
7A and 7B show the sound absorber 51 of this example, where FIG. 7A is a top view and FIG. 7B is a cross-sectional view taken along line AA in FIG. In this example, the frame body 52 is provided with four square through holes 52a arranged in a lattice pattern. The shape and size of the through hole 52 a are constant in the thickness direction of the frame body 52. In the figure, reference numeral 53 denotes a sound absorbing material, 54 denotes a construction surface, and 55 denotes a back air layer. Each dimension is as follows.
Length of one side of the opening: a = 100 mm.
Frame thickness: b = 10 mm.

As the sound absorbing material 53, a film having a thickness of 1.13 mm made of a mixture of 50% by mass of LLDPE, 20% by mass of EBR and 30% by mass of barium sulfate was used, and this was fixed to the frame body 52 with an adhesive. .
The materials used are as follows.
LLDPE: UF240 (product name), manufactured by Japan Polyethylene Corporation.
EBR: ENR7270 (product name), manufactured by Dow Chemical Japan.
Barium sulfate: Barium sulfate BA, manufactured by Sakai Chemical Industry Co., Ltd.
Double-sided adhesive tape: manufactured by Hose Care Products, product number: NoH100.
Material of frame 52: ABS resin.
Material of construction surface 54: aluminum.
Sound absorbing material: storage elastic modulus E ′ = 3 × 10 ⁸ , tan δ = 0.06, specific gravity G = 1.19.
It was confirmed that the flow resistance of the sound absorbing material was 1 × 10 ⁶ N · s / m ⁴ or more.

The sound absorption rate of the sound absorber of this example was measured by the following method. The results are shown in FIG. In the graph of FIG. 8, the horizontal axis represents frequency (unit: Hz), and the vertical axis represents sound absorption coefficient.
The same method as in Example 1 was used for measuring the sound absorption rate.

  As shown in the results of FIG. 8, the peak frequency was 304 Hz, the sound absorption rate was 0.67, and the average sound absorption rate was 0.29.

BRIEF DESCRIPTION OF THE DRAWINGS One Embodiment of the sound-absorbing body and vehicle sound-absorbing structure of this invention is shown, (a) is a top view, (b) is sectional drawing which follows the BB line in (a). It is sectional drawing which shows other embodiment of the sound-absorbing body of this invention, and the sound-absorbing structure for vehicles. It is a perspective view which shows other embodiment of the sound-absorbing body and vehicle sound-absorbing structure of this invention. The other embodiment of the sound-absorbing body and vehicle sound-absorbing structure of this invention is shown, (a) is a top view, (b) is sectional drawing which follows the AA line in (a). The other embodiment of the sound-absorbing body and vehicle sound-absorbing structure of this invention is shown, (a) is a top view, (b) is sectional drawing which follows the AA line in (a). It is a graph which shows the example of the sound absorption coefficient measurement result concerning an Example. The other embodiment of the sound-absorbing body and vehicle sound-absorbing structure of this invention is shown, (a) is a top view, (b) is sectional drawing which follows the AA line in (a). It is a graph which shows the example of the sound absorption coefficient measurement result concerning an Example. It is a graph which shows the sound absorption characteristic in the conventional sound-absorbing material.

Explanation of symbols

1, 11, 21, 31, 41, 51 ... sound absorber,
2, 12, 22, 32, 42, 52 ... frame,
2a, 22a, 32a, 42a, 52a ... opening,
3, 13, 23, 33, 43, 53 ... sound absorbing material,
5, 15, 35, 45, 55 ... Air layer behind.

Claims (2)

  A vehicle sound absorber, comprising: a frame having a through hole; and a sound absorbing material that covers one opening of the through hole.   A vehicle sound absorbing structure comprising: a frame having a through hole; and a sound absorbing material that covers one opening of the through hole, wherein the other opening of the through hole is covered with a vehicle component. .

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