JP3332883B2 - Sound absorbing structure - Google Patents
Sound absorbing structureInfo
- Publication number
- JP3332883B2 JP3332883B2 JP07615299A JP7615299A JP3332883B2 JP 3332883 B2 JP3332883 B2 JP 3332883B2 JP 07615299 A JP07615299 A JP 07615299A JP 7615299 A JP7615299 A JP 7615299A JP 3332883 B2 JP3332883 B2 JP 3332883B2
- Authority
- JP
- Japan
- Prior art keywords
- sound absorbing
- sound
- foam material
- holes
- absorbing structure
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Landscapes
- Vehicle Interior And Exterior Ornaments, Soundproofing, And Insulation (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明はフォーム材からなる
吸音構造体に関し、特に自動車用エンジンカバーに好適
に用いられる吸音構造体に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing structure made of a foam material, and more particularly to a sound absorbing structure suitably used for an automobile engine cover.
【０００２】[0002]
【従来の技術】連続気泡のフォーム材およびグラスウー
ルなどの連続気泡のみからなる多孔質体は、良好な吸音
特性を有することが一般的に知られている。そのため、
例えば自動車から放射される騒音低減を目的として、自
動車のエンジンカバーの内部やボンネットの内部などの
吸音処理に用いられている。しかし、これらの連続気泡
構造の多孔質体は中低音域の吸音率を高くするためには
吸音材を厚くする必要があるが、エンジンカバーやボン
ネットの内側はスペースが限られているために厚い吸音
材を設置できない場合が多く、従来の連続気泡構造の吸
音材では十分な吸音効果が得られないといった欠点があ
る。2. Description of the Related Art It is generally known that a porous body composed of only open cells such as an open-cell foam material and glass wool has good sound absorbing properties. for that reason,
For example, for the purpose of reducing noise radiated from an automobile, it is used for sound absorption processing inside an engine cover or inside a hood of an automobile. However, these porous bodies with an open-cell structure require a thicker sound-absorbing material in order to increase the sound absorption coefficient in the mid-low range, but are thicker due to limited space inside the engine cover and hood. In many cases, a sound absorbing material cannot be installed, and there is a disadvantage that a sufficient sound absorbing effect cannot be obtained with a conventional sound absorbing material having an open-cell structure.
【０００３】また、連続気泡と独立気泡との混成の気泡
構造を有するフォーム材も吸音材として使用されてい
る。この混成気泡構造を有するフォーム材は比較的低周
波側に吸音のピークを有するが、そのピーク値自体は十
分に高いとはいえない。また、厚いものほど低周波側に
ピークがシフトするが、そのピーク自体の周波数の幅が
狭いため、特定の単一周波数もしくはその極く近傍の周
波数の音源に対してのみそれらの周波数に対応した厚さ
の材料を用いることである程度の吸音効果が得られる場
合がある。しかし、例えば、エンジンカバーの内部やボ
ンネットの内部などの使用部位の構造の制約上、フォー
ム材の厚さを自由に変更することができない場合が多
い。また、自動車のエンジンルームの騒音は、通常ある
程度の周波数の幅を持つため、吸音率ピークの周波数幅
が狭く、しかもこのピークを示す周波数が厚さに依存す
る混成気泡構造を有するフォーム材では、十分な吸音効
果が得られない。Further, a foam material having a mixed cell structure of open cells and closed cells is also used as a sound absorbing material. The foam material having the hybrid cell structure has a sound absorption peak on a relatively low frequency side, but the peak value itself is not sufficiently high. In addition, the peak shifts to the lower frequency side as the thickness increases, but the frequency width of the peak itself is narrow, so that only the sound source of a specific single frequency or a frequency very close to it corresponds to those frequencies. The use of a thick material may provide a certain level of sound absorbing effect. However, for example, in many cases, the thickness of the foam material cannot be freely changed due to the restriction of the structure of a used portion such as the inside of an engine cover or the inside of a hood. In addition, since the noise in the engine room of an automobile usually has a certain range of frequency, the frequency width of the sound absorption coefficient peak is narrow, and the foam material having a hybrid cell structure in which the frequency showing this peak depends on the thickness, A sufficient sound absorbing effect cannot be obtained.
【０００４】また、独立気泡のみからなる気泡構造を有
するフォーム材も使用されているが、全周波数域におい
て吸音率が低く、それ自体ほとんど吸音効果を示さな
い。Further, a foam material having a cell structure consisting of closed cells alone is also used, but has a low sound absorption coefficient over the entire frequency range and exhibits almost no sound absorption effect itself.
【０００５】[0005]
【発明が解決しようとする課題】本発明は上記の状況を
鑑みてなされたものであり、広い周波数域において良好
な吸音特性を有し、さらに目的等に応じて所望の周波数
域の吸音特性を高くしたりあるいは、特に広い周波数域
においての吸音率を全体的に向上させることが可能な吸
音構造体、並びに前記吸音構造体を用いた自動車用エン
ジンカバーを提供することを目的とするものである。SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, has good sound absorption characteristics in a wide frequency range, and further has a desired sound absorption characteristic in a desired frequency range according to the purpose. It is an object of the present invention to provide a sound-absorbing structure capable of increasing the overall sound-absorbing coefficient or improving the sound-absorbing coefficient in a particularly wide frequency range, and an automobile engine cover using the sound-absorbing structure. .
【０００６】[0006]
【課題を解決するための手段】本発明者らは鋭意検討し
た結果、特定の気泡構造を有するフォーム材に特定の孔
加工を施すことによって、広い周波数域において良好な
吸音効果を有し、また、容易に所望の周波数を含むある
程度の幅を持った周波数域における吸音特性を高くした
り、あるいは、特に広い周波数域においての吸音率を全
体的に向上させることが可能となり、その吸音特性を任
意に制御することが可能であることを見出した。さら
に、従来のフォーム材からなる吸音材と比較して、その
厚さが半分以下であっても同等以上の吸音特性を示すこ
とを見出した。本発明はこのような知見に基づくもので
ある。すなわち、本発明は、連続気泡と独立気泡との混
成の気泡構造を有するフォーム材に、音源と対向する側
の面の開口面積が最大で、厚み方向に沿って開口面積が
小さくなる径違い穴を複数形成してなることを特徴とす
る吸音構造体、並びに前記吸音構造体を用いた自動車用
エンジンカバーである。Means for Solving the Problems As a result of intensive studies, the present inventors have found that a foam material having a specific cell structure is subjected to a specific hole processing so that a good sound absorbing effect can be obtained in a wide frequency range. It is possible to easily improve the sound absorption characteristics in a frequency range having a certain width including a desired frequency, or to improve the sound absorption coefficient in a particularly wide frequency range as a whole. It was found that it was possible to control Furthermore, it has been found that as compared with a conventional sound absorbing material made of a foam material, even if the thickness is less than half, the same sound absorbing characteristics are exhibited. The present invention is based on such findings. That is, the present invention relates to a foam material having a mixed cell structure of open cells and closed cells, wherein the opening area of the surface on the side facing the sound source is the largest, and the diameter of the reduced hole becomes smaller along the thickness direction. And a vehicle engine cover using the sound absorbing structure.
【０００７】[0007]
【発明の実施の形態】以下、本発明に関して詳細に説明
する。一般的にフォーム材の気泡構造は連続気泡、連続
気泡と独立気泡との混成、独立気泡単独に大別される。
連続気泡のみからなるフォーム材は、低周波側の垂直入
射吸音率が低いため、材料を厚くする必要がある。ま
た、連続気泡のみからなるフォーム材に径違い孔を設け
ても吸音効果は向上しないばかりか、むしろ低下する場
合すらある。一方、独立気泡構造のフォーム材に前記加
工を施すことで吸音効果を向上させることができるが、
得られた構造体は吸音率のピーク値が低く、また、ピー
クの周波数の幅も狭いため、上記の課題を解決し得な
い。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Generally, the foam structure of a foam material is roughly classified into open cells, a mixture of open cells and closed cells, and closed cells alone.
A foam material consisting of open cells alone has a low normal incidence sound absorption coefficient on the low frequency side, and therefore needs to be thicker. Further, even if a hole having a reduced diameter is provided in a foam material comprising only open cells, the sound absorbing effect is not only improved, but may even be reduced. On the other hand, the sound absorbing effect can be improved by performing the above processing on the foam material having the closed cell structure.
Since the obtained structure has a low peak value of the sound absorption coefficient and a narrow frequency range of the peak, the above problem cannot be solved.
【０００８】これに対し、本発明の吸音構造体は、連続
気泡と独立気泡との混成の気泡構造を有したフォーム材
に、後述されるように、音源と対向する側の面の開口面
積が最大で、厚み方向に沿って開口面積が小さくなる径
違い穴を複数形成してなることを特徴とする。このよう
な孔加工を施すことで、広い周波数域において良好な吸
音効果を有するものとなる。On the other hand, the sound-absorbing structure of the present invention has a foam material having a mixed cell structure of open cells and closed cells, as described later, having an opening area on the surface facing the sound source. It is characterized in that a plurality of reduced-diameter holes whose opening area decreases along the thickness direction are formed at the maximum. By performing such a hole processing, a good sound absorbing effect can be obtained in a wide frequency range.
【０００９】本発明で使用するフォーム材料は、その主
成分がゴムまたはエラストマーであることが好ましい。
これらは柔軟なフォームとなり、フォームを構成するセ
ル壁の膜振動による吸音機構が発現するため、吸音特性
の良好な吸音構造体が得られる。ゴムまたはエラストマ
ーとしては天然ゴム、ＣＲ（クロロプレンゴム）、ＳＢ
Ｒ（スチレン・ブタジエンゴム）、ＮＢＲ（ニトリル・
ブタジエンゴム）、ＥＰＤＭ（エチレン・プロピレン・
ジエン三元共重合体）、シリコーンゴム、フッ素ゴム、
アクリルゴムなどの各種ゴム、熱可塑性エラストマー、
軟質ウレタン等の各種エラストマーが挙げられるが、こ
れらに限定されない。特にＥＰＤＭを主成分とするフォ
ーム材は耐熱性、耐オゾン性、価格のバランスが良いた
め、自動車のエンジンカバー用としては好ましい。ま
た、このようなフォーム材として、例えば建築用や弱電
用の止水シール材として市販されているＥＰＤＭやＮＢ
Ｒのフォーム材シートを使用してもよい。[0009] The foam material used in the present invention is preferably composed mainly of rubber or elastomer.
These are flexible foams, and a sound absorbing mechanism is exhibited by the membrane vibration of the cell walls constituting the foam, so that a sound absorbing structure having good sound absorbing characteristics can be obtained. Natural rubber, CR (chloroprene rubber), SB as rubber or elastomer
R (styrene / butadiene rubber), NBR (nitrile /
Butadiene rubber), EPDM (ethylene / propylene /
Diene terpolymer), silicone rubber, fluoro rubber,
Various rubbers such as acrylic rubber, thermoplastic elastomers,
Examples include, but are not limited to, various elastomers such as soft urethane. In particular, a foam material containing EPDM as a main component has a good balance of heat resistance, ozone resistance, and price, and is therefore preferably used as an automobile engine cover. Further, as such a foam material, for example, EPDM or NB which is commercially available as a waterproof sealing material for construction or for weak electricity use
An R foam material sheet may be used.
【００１０】本発明で使用されるフォーム材は連続気泡
と独立気泡との混成気泡構造であるから、連続気泡の割
合が多くなると連続気泡単独のフォーム材の欠点が現れ
るようになり、独立気泡の割合が多くなると、独立気泡
単独のフォーム材の欠点が現れるようになる。一般的
に、連続気泡構造のフォーム材は吸水率が大きく、独立
気泡構造のフォーム材は吸水率が小さく、連続気泡と独
立気泡との混成気泡構造のフォーム材はその中間であ
る。したがって、この吸水率を特定することにより、連
続気泡と独立気泡の割合を規定することができるように
なる。吸水率はJIS K6767のB法によって測定され、本発
明で使用するのフォーム材の吸水率は好ましくは0.01 g
/cm3以上で0.2g/cm3以下、より好ましくは0.02g/cm3 以
上で0.15g/cm3 以下、さらに好ましくは0.04g/cm3 以上
で0.1g/cm3以下とするのが良い。この範囲の連続気泡と
独立気泡の混成気泡構造を有するフォーム材は特に径違
い穴を設けた場合の吸音特性の向上効果が大きい。[0010] Since the foam material used in the present invention has a mixed cell structure of open cells and closed cells, when the proportion of open cells increases, the disadvantage of the open cell alone foam material appears, As the proportion increases, the disadvantage of the foam material consisting of closed cells alone appears. Generally, a foam material having an open-cell structure has a large water absorption rate, a foam material having a closed-cell structure has a low water absorption rate, and a foam material having a mixed-cell structure of open cells and closed cells is intermediate. Therefore, by specifying the water absorption, the ratio between the open cells and the closed cells can be defined. The water absorption is measured by the method B of JIS K6767, and the water absorption of the foam material used in the present invention is preferably 0.01 g.
/ cm 3 or more at 0.2 g / cm 3 or less, more preferably 0.15 g / cm 3 or less at 0.02 g / cm 3 or more, more preferably from to the 0.1 g / cm 3 or less at 0.04 g / cm 3 or more . A foam material having a mixed cell structure of open cells and closed cells in this range has a great effect of improving the sound absorbing characteristics particularly when a hole having a reduced diameter is provided.
【００１１】密度の低いフォーム材は低周波側の垂直入
射吸音率が低いため、材料を厚くする必要がある。ま
た、密度の低いフォーム材のみに径違い穴を設けても吸
音効果ほとんど向上しない。密度の高いフォーム材は全
周波数域において低い垂直入射吸音率しか示さない。ま
た、密度の高いフォーム材のみに径違い穴を設けても吸
音効果はほとんど向上しない。したがって、本発明で使
用するフォーム材はある特定の範囲の密度を持つことが
好ましい。本発明で使用するフォーム材の密度は好まし
くは20kg/m3 以上で400kg/m3以下、より好ましくは30kg
/m3 以上で300kg/m3以下、さらに好ましくは50kg/m3 以
上で200kg/m3以下とするのが良い。A low-density foam material has a low normal incidence sound absorption coefficient on the low frequency side, and therefore requires a thicker material. Further, even if a hole having a reduced diameter is provided only in a foam material having a low density, the sound absorbing effect is hardly improved. Dense foam materials show low normal incidence sound absorption over the entire frequency range. Further, even if a hole having a reduced diameter is provided only in a foam material having a high density, the sound absorbing effect is hardly improved. Therefore, it is preferable that the foam material used in the present invention has a specific range of density. Density of the foam material used in the present invention is 400 kg / m 3 or less preferably 20 kg / m 3 or higher, more preferably 30kg
It is good to be 300 kg / m 3 or less at / m 3 or more, and more preferably 200 kg / m 3 or less at 50 kg / m 3 or more.
【００１２】一般的に、柔軟なフォーム材ほどセル壁の
膜振動による吸音機構が発現するため、吸音特性の良好
な構造体が得られる。逆に硬いフォーム材はセル壁の膜
振動による吸音機構が発現しないため、全周波数域にお
いて低い垂直入射吸音率しか示さない。このような、硬
いフォーム材に径違い穴を設けても吸音効果はほとんど
向上しない。従って、本発明で使用するフォーム材はあ
る特定の範囲の圧縮硬さを持つことが好ましい。具体的
には、25％圧縮硬さにおいて、好ましくは0.5N/cm2以
下、より好ましくは0.3N/cm2以下、さらに好ましくは0.
1N/cm2以下とするのが良い。この範囲の25％圧縮硬さを
有する連続気泡と独立気泡との混成の気泡構造を有する
フォーム材は、特に径違い穴を設けたときの吸音特性の
向上効果が大きい。尚、この25％圧縮硬さはJIS K6767
によって測定される。In general, the more flexible the foam material, the more the sound absorbing mechanism is exhibited by the membrane vibration of the cell wall, so that a structure having good sound absorbing characteristics can be obtained. Conversely, a rigid foam material does not exhibit a sound absorbing mechanism due to the membrane vibration of the cell wall, and thus exhibits only a low normal incidence sound absorbing coefficient over the entire frequency range. Even if such a rigid foam material is provided with a reduced diameter hole, the sound absorbing effect is hardly improved. Therefore, the foam material used in the present invention preferably has a specific range of compression hardness. Specifically, at a 25% compression hardness, preferably 0.5 N / cm 2 or less, more preferably 0.3 N / cm 2 or less, and still more preferably 0.1 N / cm 2 or less.
It is better to be 1 N / cm 2 or less. A foam material having a mixed cell structure of open cells and closed cells having a compression hardness of 25% in this range has a large effect of improving the sound absorption characteristics particularly when a hole having a reduced diameter is provided. This 25% compression hardness is JIS K6767
Is measured by
【００１３】本発明の吸音構造体は、上記したフォーム
材に複数の径違い穴が設けられており、各径違い穴は音
源に近い側の開口面積がより大きくなる構造となってい
る。径違い穴の構造としては、例えば一方の面（音源と
対向する面：以下、音源面と呼ぶ）から他方の面に向か
って段階的に開口面積が小さくなるように変化する多重
穴構造や、音源面から他方の面に向かって徐々に開口面
積が小さくなるように変化する構造の穴（以下、テーパ
ー穴と呼ぶ）にすることができるが、これらに限定され
ない。また、各々の径違い穴はフォーム材を貫通する貫
通構造としても良いし、音源面のみを開口端とする未貫
通構造としてもよい。The sound absorbing structure of the present invention has a structure in which a plurality of reduced diameter holes are provided in the above-described foam material, and each reduced diameter hole has a larger opening area on the side closer to the sound source. Examples of the structure of the reduced-diameter hole include a multi-hole structure in which the opening area gradually changes from one surface (a surface facing the sound source: hereinafter, referred to as a sound source surface) toward the other surface, A hole having a structure that changes so that the opening area gradually decreases from the sound source surface to the other surface (hereinafter, referred to as a tapered hole) can be used, but is not limited thereto. Further, each of the reduced diameter holes may have a penetrating structure penetrating the foam material, or may have a non-penetrating structure in which only the sound source surface is an open end.
【００１４】この径違い穴は、テーパ穴とする場合は、
例えば円錐状のドリルを用いてフォーム材に円錐状の凹
部を形成することができる。多重穴構造とする場合は、
大径の円筒状のドリルを用いてフォーム材の厚み方向に
所定深さの第１の凹部を形成し、次いで小径のドリルを
用いて第１の凹部の底面にさらに所定深さの第２の凹部
や貫通穴を形成する。また、貫通穴の開口面積が相違す
る複数種のフォーム材を用い、開口面積の大きなフォー
ム材から順次開口面積の小さなフォーム材となるよう
に、貫通穴同士を同軸状に配置して積層してもよい。When the reduced diameter hole is a tapered hole,
For example, a conical recess can be formed in the foam material using a conical drill. When using a multi-hole structure,
A first concave portion having a predetermined depth is formed in the thickness direction of the foam material using a large-diameter cylindrical drill, and then a second concave portion having a predetermined depth is formed on the bottom surface of the first concave portion using a small-diameter drill. Form recesses and through holes. Further, by using a plurality of types of foam materials having different opening areas of the through holes, the through holes are coaxially arranged and laminated so that the foam materials having a larger opening area are sequentially reduced to a foam material having a smaller opening area. Is also good.
【００１５】また、径違い穴の音源面における開口面積
の合計（以下、全開口面積と呼ぶ）が音源面の面積に対
して小さすぎる場合は、十分に高い吸音特性を示さな
い。他方、径違い穴の全開口面積の割合が大きすぎる場
合は逆に吸音特性が低下する場合もある。従って、本発
明においては径違い穴の全開口面積の割合がある特定の
値を持つことが好ましく、好ましくは１％以上70％以
下、より好ましくは３％以上50％以下、さらに好ましく
は５％以上40％以下とするのがよい。径違い穴の全開口
面積の割合がこの範囲にある吸音構造体は吸音特性の向
上効果が大きい。On the other hand, if the sum of the opening areas of the reduced diameter holes on the sound source surface (hereinafter, referred to as the total opening area) is too small with respect to the area of the sound source surface, a sufficiently high sound absorption characteristic is not exhibited. On the other hand, if the ratio of the total opening area of the reduced-diameter hole is too large, the sound absorption characteristics may be deteriorated. Therefore, in the present invention, it is preferable that the ratio of the total opening area of the reduced diameter hole has a certain value, preferably 1% or more and 70% or less, more preferably 3% or more and 50% or less, further more preferably 5% or less. It is better to be at least 40%. The sound absorbing structure in which the ratio of the total opening area of the reduced diameter hole is within this range has a large effect of improving the sound absorbing characteristics.
【００１６】更に、径違い穴の最小の開口面積が最大の
開口面積に対して大きすぎる場合は、特定の周波数とそ
の近傍の限られた周波数域では高い吸音特性を示すもの
の、全周波数域の吸音特性は十分に高い値を示さない。
従って、本発明においては、少なくとも一部の径違い穴
は、その最小の開口面積が最大の開口面積に対してある
特定の値を持つことが好ましく、好ましくは90％以下、
より好ましくは70％以下、さらに好ましくは50％以下と
するのがよい。このような開口面積比を有する吸音構造
体は、吸音特性の向上効果が大きい。Further, when the minimum opening area of the reduced diameter hole is too large with respect to the maximum opening area, high sound absorption characteristics are exhibited at a specific frequency and a limited frequency range in the vicinity of the specific frequency. The sound absorption characteristics do not show sufficiently high values.
Therefore, in the present invention, it is preferable that at least a part of the reduced diameter hole has a minimum opening area having a specific value with respect to a maximum opening area, preferably 90% or less,
It is more preferably at most 70%, further preferably at most 50%. A sound absorbing structure having such an opening area ratio has a large effect of improving sound absorbing characteristics.
【００１７】以下に、本発明の吸音構造体の好ましい実
施形態を図面を参照して説明する。尚、各平面図におい
て、紙面手前側を音源側とする。例えば、図１に示すよ
うにフォーム材(a)の全面に、大径で円筒状の第１の凹
部(b)を等間隔の格子の各交点に設け、第１の凹部(b)の
底部の中央に、この第１の凹部(b)よりも径の小さい円
筒状の第２の凹部(c)を設けることによって、二重構造
の径違い穴を有する吸音構造体とすることができる。A preferred embodiment of the sound absorbing structure of the present invention will be described below with reference to the drawings. In each plan view, the front side of the drawing is the sound source side. For example, as shown in FIG. 1, a large-diameter cylindrical first concave portion (b) is provided at each intersection of a grid at equal intervals on the entire surface of the foam material (a), and the bottom portion of the first concave portion (b) is provided. By providing a cylindrical second concave portion (c) having a diameter smaller than that of the first concave portion (b) at the center, a sound-absorbing structure having a double-diameter difference hole can be obtained.
【００１８】また、例えば、図２に示すようにフォーム
材(a)の全面に、大径で円筒状の第１の凹部(d)を等間隔
の格子の各交点に設け、第１の凹部(d)の底部の中央
に、この第１の凹部(d)よりも径の小さい円筒状の第２
の凹部(e)を設け、さらに第２の凹部(e)の底部の中央
に、第２の凹部(e)よりも径の小さい円筒状の第３の凹
部(f)を設けることによって、三重構造の径違い穴を有
する吸音構造体とすることができる。For example, as shown in FIG. 2, on the entire surface of the foam material (a), large-diameter cylindrical first concave portions (d) are provided at respective intersections of a grid at equal intervals, and the first concave portions are formed. At the center of the bottom of (d), a second cylindrical member having a smaller diameter than the first concave portion (d) is provided.
By providing a third concave portion (f) having a smaller diameter than the second concave portion (e) in the center of the bottom of the second concave portion (e), A sound absorbing structure having a hole having a reduced diameter can be provided.
【００１９】また、例えば、図３に示すようにフォーム
材(a)の全面に、大径で円筒状の第１の凹部(g)を等間隔
の格子の各交点に設け、第１の凹部(g)の底部の中央
に、この第１の凹部(g)よりも径の小さい円筒状の貫通
穴(h)を設けることによって、二重構造で貫通する径違
い穴を有する吸音構造体とすることができる。For example, as shown in FIG. 3, a large-diameter cylindrical first concave portion (g) is provided at each intersection of a grid at equal intervals on the entire surface of the foam material (a). By providing a cylindrical through hole (h) having a diameter smaller than that of the first concave portion (g) at the center of the bottom of (g), a sound absorbing structure having a reduced diameter hole penetrating in a double structure is provided. can do.
【００２０】また、例えば、図４に示すようにフォーム
材(a)の全面に、音源面の表面から徐々に開口面積が小
さくなるように変化させた円錐状のテーパー穴(i)を等
間隔の格子の各交点に設け、径違い穴を有する吸音構造
体とすることができる。Further, for example, as shown in FIG. 4, conical tapered holes (i) which are gradually changed from the surface of the sound source surface so as to gradually reduce the opening area are formed at equal intervals on the entire surface of the foam material (a). Provided at each intersection of the lattice, and can be a sound absorbing structure having holes of reduced diameter.
【００２１】また、例えば、図５に示すようにフォーム
材(a)の全面に、音源面の表面から徐々に開口面積が小
さくなるように変化し、かつそれに連続する底面を有す
る、断面が台形状のテーパー穴(j)を等間隔の格子の各
交点に設け、径違い穴を有する吸音構造体とすることが
できる。Further, for example, as shown in FIG. 5, the entire surface of the foam material (a) has a bottom surface which changes from the surface of the sound source surface so that the opening area gradually decreases and has a continuous bottom surface. A tapered hole (j) having a shape may be provided at each intersection of the grid at equal intervals to provide a sound absorbing structure having holes of different diameters.
【００２２】また、例えば、図６に示すようにフォーム
材(a)の全面に、大径で円筒状の第１の凹部(k)を等間隔
の正三角形の各セルの頂点に設け、この第１の凹部(k)
の底部の中央に、第１の凹部(k)よりも径の小さい円筒
状の第２の凹部(l)を設けることによって、二重構造の
径違い穴が千鳥格子状に配置された吸音構造体とするこ
とができる。Further, for example, as shown in FIG. 6, a large-diameter cylindrical first concave portion (k) is provided at the apex of each equiangular triangular cell on the entire surface of the foam material (a). First recess (k)
By providing a cylindrical second concave portion (l) having a smaller diameter than the first concave portion (k) at the center of the bottom of the sound absorbing member, the double-diameter reduced holes are arranged in a staggered lattice pattern. It can be a structure.
【００２３】また、例えば、図７に示すように互いに開
口径の異なる２枚のフォーム材(a)からなるシートを用
い、大きい穴(m)を設けたシートを音源側、小さい穴(n)
を設けたシートを音源と反対側とし、また穴同士が同軸
上に位置するように両者を積層することによって、二重
構造で貫通する径違い穴を有する吸音構造体とすること
ができる。For example, as shown in FIG. 7, two sheets of foam material (a) having different opening diameters are used, and a sheet provided with a large hole (m) is placed on the sound source side and a small hole (n) is provided.
The sound absorbing structure having a reduced diameter hole that penetrates in a double structure can be obtained by making the sheet provided with 音源 on the opposite side to the sound source and laminating the two so that the holes are positioned coaxially.
【００２４】本発明においては、径違い穴の音源面側の
開口面積および/または底部の開口面積を大きくする
か、または音源面の単位面積当たりの径違い穴の数を多
くすると高周波側の吸音率が向上する。また、逆に径違
い穴の音源面側の開口面積部および/または底面の開口
面積を小さくするか、または音源面の単位面積当たりの
径違い穴の数を少なくすると低周波側の吸音率が向上す
る。また、音源側と底部との開口面積の差が大きいほ
ど、特に広い周波数域にわたり吸音率が高くなる。逆に
上層部と下層部の開口面積の差が小さいほど、特定の周
波数とその近辺の吸音率のみが特に高くなる。以上のよ
うに、特に広い特定の周波数域の吸音率を高くしたり、
あるいは所望の周波数を含むある程度の幅を持った周波
数域の吸音率を特に高くする場合は、目的に応じて径違
い穴を設ける格子の間隔や、音源側と底部との比率を含
めて径違い穴の径を適当な値に設定すれば良い。In the present invention, if the opening area of the reduced diameter hole on the sound source surface side and / or the opening area of the bottom portion is increased, or if the number of reduced diameter holes per unit area of the sound source surface is increased, the sound absorption on the high frequency side is increased. The rate is improved. Conversely, if the opening area on the sound source side and / or the bottom opening area of the reduced hole is reduced, or the number of reduced holes per unit area of the sound source surface is reduced, the sound absorption coefficient on the low frequency side is reduced. improves. In addition, as the difference in the opening area between the sound source side and the bottom increases, the sound absorption coefficient increases over a particularly wide frequency range. Conversely, as the difference between the opening areas of the upper layer portion and the lower layer portion is smaller, only the specific frequency and the sound absorption coefficient near the specific frequency are particularly high. As described above, it is possible to increase the sound absorption coefficient especially in a wide specific frequency range,
Alternatively, if the sound absorption coefficient in a frequency range having a certain width including a desired frequency is particularly increased, the diameter of the grid including the gap between the grids and the ratio between the sound source side and the bottom part may be reduced according to the purpose. The diameter of the hole may be set to an appropriate value.
【００２５】上記において、径違い穴の開口形状（穴の
平面形状）も制限されるものではなく、円や三角形、矩
形、多角形、楕円等の他、場合によっては無定形であっ
てもよい。また、その深さも制限されない。また、径違
い穴の平面配列は、碁盤目状の格子状配置の他、ランダ
ム配置とすることもできる。更に、孔径や開口形状、深
さの異なる２種類以上の径違い穴を混在して配置しても
良い。In the above description, the opening shape of the reduced diameter hole (planar shape of the hole) is not limited, and may be a circle, a triangle, a rectangle, a polygon, an ellipse, or an amorphous shape depending on the case. . Also, the depth is not limited. In addition, the planar arrangement of the reduced diameter holes may be a random arrangement other than a grid-like lattice arrangement. Further, two or more kinds of reduced diameter holes having different hole diameters, opening shapes, and depths may be mixedly arranged.
【００２６】本発明による吸音構造体は、径違い穴の形
状や配置が同じ場合は従来のフォーム材からなる吸音材
と同様に、厚いものほど低周波側の吸音率が良好とな
り、逆に薄いものは高周波側の吸音率が良好となり、そ
の厚みにより吸音効果の大きい周波数域が異なる。しか
し、径違い穴の形状や配置を変化させることにより、吸
音特性を任意に変えることができるため、例えばエンジ
ンカバーの内部やボンネットの内部など使用部位により
フォーム材の厚さを変更する必要がある場合、従来では
吸音効果が部位により異なるという不具合が生じていた
が、本発明によれば、厚さの変化に対応して径違い穴の
音源側および／または底部の形状や径、深さ、あるは径
違い穴の配置（粗密）を適宜変更することにより部位
（厚み）にかかわらず所望の周波数の吸音率を高めるた
り、また特に広い特定の周波数域の吸音率を高くするな
ど、目的に応じた吸音効果を発現させることができる。When the shape and arrangement of the reduced diameter holes are the same, the thicker the sound absorbing structure according to the present invention, the better the sound absorbing coefficient on the low frequency side, and conversely, the thinner the sound absorbing material, which is made of a foam material. The sound absorbing coefficient on the high frequency side becomes good, and the frequency range in which the sound absorbing effect is large differs depending on the thickness. However, since the sound absorption characteristics can be arbitrarily changed by changing the shape and arrangement of the reduced diameter holes, it is necessary to change the thickness of the foam material depending on a used portion, for example, inside the engine cover or inside the hood. In the past, there was a problem that the sound absorbing effect was different depending on the region. However, according to the present invention, the shape, diameter, depth, and the like of the sound source side and / or the bottom of the reduced diameter hole corresponding to the change in the thickness. Alternatively, by appropriately changing the arrangement (roughness / density) of the reduced-diameter holes, the sound absorption at a desired frequency can be increased irrespective of the region (thickness), or the sound absorption at a particularly wide specific frequency range can be increased. A suitable sound absorbing effect can be exhibited.
【００２７】[0027]
【実施例】以下、本発明を実施例にてさらに詳しく説明
するが、本発明は以下の実施例に限定されるものではな
い。尚、実施例においては、切削加工によりフォーム材
に径違い穴を形成するか、あるいは、複数のフォーム材
シートを打ち抜いて積層することで多重穴を形成して吸
音構造体とした。また、比較例７以外は、音源面におけ
る径違い穴の全開口面積は７０％以下である。EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. In the examples, a sound-absorbing structure was formed by forming a reduced-diameter hole in the foam material by cutting, or by punching and laminating a plurality of foam material sheets to form multiple holes. Except for Comparative Example 7, the total opening area of the reduced diameter holes on the sound source surface is 70% or less.
【００２８】（実施例１）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、φ5の貫通孔を20mmピッチの格子の各
交点上に設けたシートと、φ15の貫通孔を20mmピッチの
格子の各交点上に設けたシートとを積層して二重穴を有
する合計厚さ20mmの吸音構造体を作製し、φ５の貫通孔
を設けたシートを剛壁側として垂直入射吸音率を測定し
た。(Example 1) EPDM, thickness 10 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , using a foam material having a 25% compression hardness of 0.040 N / cm 2 , a sheet provided with φ5 through-holes at each intersection of a grid of 20 mm pitch, and a sheet of φ15 A sound absorbing structure having a total thickness of 20 mm having double holes is manufactured by laminating sheets having through holes on each intersection of a grid with a pitch of 20 mm, and the sheet having through holes of φ5 is defined as a rigid wall side. The normal incidence sound absorption coefficient was measured.
【００２９】（実施例２）EPDM製で厚さ20mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、切削加工によりφ15、深さ10mmの穴を
20mmピッチの格子の各交点上に設け、さらにそれら各穴
の底の中心にφ５の貫通孔を設けて二重穴を有する厚さ
20mmの吸音構造体を作製し、φ５の貫通孔側を剛壁側と
して垂直入射吸音率を測定した。(Embodiment 2) EPDM, thickness 20 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2
Thickness with double holes provided at each intersection of a grid of 20 mm pitch, and a through hole of φ5 provided at the center of the bottom of each hole
A 20-mm sound-absorbing structure was prepared, and the normal incidence sound absorption coefficient was measured with the φ5 through-hole side as the hard wall side.
【００３０】（実施例３）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、φ５の貫通孔を20mmピッチの格子の各
交点上に設けたシートと、φ10の貫通孔を20mmピッチの
格子の各交点上に設けたシートとを積層して二重穴を有
する合計厚さ20mmの吸音構造体を作製し、φ５の貫通孔
を設けたシートを剛壁側として垂直入射吸音率を測定し
た。(Embodiment 3) EPDM, thickness 10 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2 using a foam material, a sheet provided with φ5 through-holes at each intersection of a grid of 20 mm pitch, and a sheet of φ10 A sound absorbing structure having a total thickness of 20 mm having double holes is manufactured by laminating sheets having through holes on each intersection of a grid with a pitch of 20 mm, and the sheet having through holes of φ5 is defined as a rigid wall side. The normal incidence sound absorption coefficient was measured.
【００３１】（実施例４）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、φ10の貫通孔を20mmピッチの格子の各
交点上に設けたシートと、φ15の貫通孔を20mmピッチの
格子の各交点上に設けたシートとを積層して二重穴を有
する合計厚さ20mmの吸音構造体を作製し、φ10の貫通孔
を設けたシートを剛壁側として垂直入射吸音率を測定し
た。(Embodiment 4) EPDM, thickness 10 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , using a foam material having a 25% compression hardness of 0.040 N / cm 2 , a sheet provided with φ10 through-holes at each intersection of a 20 mm pitch lattice, and a sheet of φ15 A 20 mm pitch sound-absorbing structure having a total thickness of 20 mm with double holes was prepared by laminating a sheet with through holes on each intersection of a 20 mm pitch grid, and the sheet with through holes of φ 10 as the rigid wall side. The normal incidence sound absorption coefficient was measured.
【００３２】（実施例５）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、φ５の貫通孔を15mmピッチの格子の各
交点上に設けたシートと、φ10の貫通孔を15mmピッチの
格子の各交点上に設けたシートとを積層して二重穴を有
する合計厚さ20mmの吸音構造体を作製し、φ５の貫通孔
を設けたシートを剛壁側として垂直入射吸音率を測定し
た。(Embodiment 5) EPDM, thickness 10 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2 using a foam material, φ5 through holes provided on each intersection of a 15 mm pitch grid, A sound absorbing structure having a total thickness of 20 mm having a double hole is produced by laminating a sheet provided with through holes at respective intersections of a grid of 15 mm pitch, and a sheet provided with a through hole of φ5 is used as a rigid wall side. The normal incidence sound absorption coefficient was measured.
【００３３】（実施例６）NBR製で厚さ10mm、密度120kg
/m3、吸水率0.058 g/cm3、25%圧縮硬さ0.070N/cm 2のフ
ォーム材を用い、φ５の貫通孔を20mmピッチの格子の各
交点上に設けたシートと、φ15の貫通孔を20mmピッチの
格子の各交点上に設けたシートとを積層して二重穴を有
する合計厚さ20mmの吸音構造体を作製し、φ５の貫通孔
を設けたシートを剛壁側として垂直入射吸音率を測定し
た。(Example 6) Made of NBR, thickness 10 mm, density 120 kg
/ mThree, Water absorption 0.058 g / cmThree, 25% compression hardness 0.070N / cm TwoNo
5 through holes with a pitch of 20mm
The sheet provided on the intersection and the through hole of φ15
The sheet provided on each intersection of the grid is laminated to have a double hole.
To produce a sound absorbing structure with a total thickness of 20mm
Measure the normal incidence sound absorption coefficient with the sheet provided with
Was.
【００３４】（実施例７）EPDM製で厚さ15mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、φ５の貫通孔を20mmピッチの格子の各
交点上に設けたシートと、φ15の貫通孔を20mmピッチの
格子の各交点上に設けたシートとを積層して二重穴を有
する合計厚さ30mmの吸音構造体を作製し、φ５の貫通孔
を設けたシートを剛壁側として垂直入射吸音率を測定し
た。(Example 7) EPDM, thickness 15 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2 using a foam material, a sheet provided with φ5 through holes at each intersection of a 20 mm pitch lattice, and a sheet of φ15 A sound absorbing structure having a total thickness of 30 mm having double holes is manufactured by laminating a sheet provided with through holes at respective intersections of a 20 mm pitch grid, and the sheet provided with φ5 through holes is defined as a rigid wall side. The normal incidence sound absorption coefficient was measured.
【００３５】（実施例８）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、貫通孔を設けていないシートと、φ５
の貫通孔を20mmピッチの格子の各交点上に設けたシート
と、φ15の貫通孔を20mmピッチの格子の各交点上に設け
たシートとを、下層側より順に貫通孔を設けていないシ
ート、φ５の貫通孔を設けたシート、φ15の貫通孔を設
けたシートを積層して二重穴を有する合計厚さ20mmの吸
音構造体を作製し、貫通孔を設けていないシートを剛壁
側として垂直入射吸音率を測定した。(Embodiment 8) EPDM, thickness 10 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2, a sheet without through holes,
A sheet in which through-holes are provided on each intersection of a 20 mm pitch lattice, and a sheet in which φ15 through-holes are provided on each intersection of a 20 mm pitch lattice, a sheet in which no through-hole is provided in order from the lower layer side, A sheet with a through-hole of φ5 and a sheet with a through-hole of φ15 are laminated to produce a sound absorbing structure with a total thickness of 20 mm with double holes, and the sheet without the through-hole as the rigid wall side. The normal incidence sound absorption coefficient was measured.
【００３６】（実施例９）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、φ５の貫通孔を20mmピッチの格子の各
交点上に設けたシートと、φ10の貫通孔を20mmピッチの
格子の各交点上に設けたシートと、φ15の貫通孔を20mm
ピッチの格子の各交点上に設けたシートとを、下層側よ
り順位にφ５の貫通孔を設けたシート、φ10の貫通孔を
設けたシート、φ15の貫通孔を設けたシートを積層して
三重穴を有する合計厚さ20mmの吸音構造体を作製し、φ
５の貫通孔を設けたシートを剛壁側として垂直入射吸音
率を測定した。(Embodiment 9) EPDM, thickness 10 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2 using a foam material, a sheet provided with φ5 through-holes at each intersection of a grid of 20 mm pitch, and a sheet of φ10 Sheets with through holes on each intersection of a 20 mm pitch grid and φ15 through holes of 20 mm
A sheet provided on each intersection of the pitch grid is laminated with a sheet provided with a through-hole of φ5, a sheet provided with a through-hole of φ10, and a sheet provided with a through-hole of φ15 in order from the lower layer to form a triple. A sound absorbing structure having a total thickness of 20 mm with holes was prepared, and φ
The normal incidence sound absorption coefficient was measured using the sheet provided with the through holes of No. 5 as the rigid wall side.
【００３７】（実施例10）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、一辺10mmの正方形の貫通孔を20mmピッ
チの格子の各交点上に設けたシートと、一辺５mmの貫通
孔を20mmピッチの格子の各交点上に設けたシートとを積
層して二重穴を有する合計厚さ20mmの吸音構造体を作製
し、一辺５mmの貫通孔を設けたシートを剛壁側として垂
直入射吸音率を測定した。(Example 10) 10 mm thick made of EPDM, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , using a foam material having a 25% compression hardness of 0.040 N / cm 2 , a sheet having a square through hole of 10 mm on each side provided at each intersection of a 20 mm pitch lattice. A sheet in which a through-hole of 5 mm on each side is provided on each intersection of a grid with a pitch of 20 mm to form a sound absorbing structure having a total thickness of 20 mm having double holes and a through-hole of 5 mm on a side is provided. Was used as the rigid wall side, and the normal incidence sound absorption coefficient was measured.
【００３８】（実施例11）EPDM製で厚さ20mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を用い、切削加工によりφ15、深さ10mmの円錐
状の穴を20mmピッチの格子の各交点上に設けて吸音構造
体を作製し、穴を設けていない方の面を剛壁側として垂
直入射吸音率を測定した。(Example 11) Made of EPDM, thickness 20 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2 Foam material, cutting φ15, conical hole with depth 10mm, each intersection of 20mm pitch grid A sound absorbing structure was prepared by providing the sound absorbing structure on the upper side, and the surface on which the hole was not provided was taken as the rigid wall side, and the normal incidence sound absorbing coefficient was measured.
【００３９】（比較例１）EPDM製で厚さ20mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材を貫通孔や半貫通孔や二重穴を設けることなく
吸音構造体とし、垂直入射吸音率を測定した。(Comparative Example 1) Made of EPDM, thickness 20 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2 Foam material is used as a sound absorbing structure without through holes, semi-through holes or double holes, and normal incidence sound absorption coefficient Was measured.
【００４０】（比較例２）EPDM製で厚さ20mm、密度100k
g/m3、吸水率0.106 g/cm3、25%圧縮硬さ0.470N/cm2のフ
ォーム材を貫通孔や半貫通孔や二重穴を設けることなく
吸音構造体とし、垂直入射吸音率を測定した。(Comparative Example 2) Made of EPDM, thickness 20 mm, density 100 k
g / m 3 , water absorption 0.106 g / cm 3 , 25% compression hardness 0.470 N / cm 2 Foam material is used as a sound absorbing structure without through holes, semi-through holes or double holes, and normal incidence sound absorption coefficient Was measured.
【００４１】（比較例３）EPDM製で厚さ20mm、密度460k
g/m3、吸水率0.0028 g/cm3、25%圧縮硬さ1.05N/cm2のフ
ォーム材を貫通孔や半貫通孔や二重穴を設けることなく
吸音構造体とし、垂直入射吸音率を測定した。(Comparative Example 3) EPDM made with a thickness of 20 mm and a density of 460 k
g / m 3 , water absorption 0.0028 g / cm 3 , 25% compression hardness 1.05 N / cm 2 Foam material with no through hole, semi-through hole or double hole as sound absorbing structure, normal incidence sound absorption Was measured.
【００４２】（比較例４）軟質ウレタン製で厚さ20mm、
密度25kg/m3、吸水率0.76 g/cm3、25%圧縮硬さ0.065N/c
m2のフォーム材を貫通孔や半貫通孔や二重穴を設けるこ
となく吸音構造体とし、垂直入射吸音率を測定した。(Comparative Example 4) Made of soft urethane and having a thickness of 20 mm
Density 25 kg / m 3 , water absorption 0.76 g / cm 3 , 25% compression hardness 0.065 N / c
The m 2 foam material was used as a sound absorbing structure without providing through holes, semi-through holes, or double holes, and the normal incidence sound absorption coefficient was measured.
【００４３】（比較例５）EPDM製で厚さ10mm、密度460k
g/m3、吸水率0.0028 g/cm3、25%圧縮硬さ1.05N/cm2のフ
ォーム材に関し、φ５の貫通孔を20mmピッチの格子の各
交点上に設けたシートと、φ15の貫通孔を20mmピッチの
格子の各交点上に設けたシートを積層して二重穴を有す
る合計厚さ20mmの吸音構造体を作製し、φ５の貫通孔を
設けたシートを剛壁側として垂直入射吸音率を測定し
た。(Comparative Example 5) Made of EPDM, thickness 10 mm, density 460 k
g / m 3 , water absorption 0.0028 g / cm 3 , 25% compression hardness 1.05 N / cm 2 For a foam material, a sheet with φ5 through-holes provided at each intersection of a 20 mm pitch lattice, and a φ15 through hole Sheets with holes provided on each intersection of a grid with a pitch of 20 mm are stacked to produce a sound absorbing structure with a total thickness of 20 mm having double holes, and a sheet with a through hole of φ5 as a rigid wall side and vertically incident The sound absorption was measured.
【００４４】（比較例６）軟質ウレタン製で厚さ10mm、
密度25kg/m3、吸水率0.76 g/cm3、25%圧縮硬さ0.065N/c
m2のフォーム材に関し、φ５の貫通孔を20mmピッチの格
子の各交点上に設けたシートと、φ15の貫通孔を20mmピ
ッチの格子の各交点上に設けたシートを積層して二重穴
を有する吸音構造体を作製し、φ５の貫通孔を設けたシ
ートを剛壁側として垂直入射吸音率を測定した。(Comparative Example 6) Made of soft urethane and having a thickness of 10 mm
Density 25 kg / m 3 , water absorption 0.76 g / cm 3 , 25% compression hardness 0.065 N / c
respect foam material m 2, a sheet having a through-hole of φ5 on each intersection of the lattice of 20mm pitch, double holes by laminating sheets having a through hole of φ15 on each intersection of the lattice of 20mm pitch Was prepared, and the sheet provided with a through-hole of φ5 was used as a rigid wall side to measure the normal incidence sound absorption coefficient.
【００４５】（比較例７）EPDM製で厚さ10mm、密度100k
g/m3、吸水率0.071 g/cm3、25%圧縮硬さ0.040N/cm2のフ
ォーム材に関し、一辺17mmの正方形の貫通孔を20mmピッ
チの格子の各交点上に設けたシートと、一辺５mmの貫通
孔を20mmピッチの格子の各交点上に設けたシートとを積
層して二重穴を有する合計厚さ20mmの吸音構造体を作製
し、一辺５mmの貫通孔を設けたシートを剛壁側として垂
直入射吸音率を測定した。この吸音構造体の二重穴の音
源面における全開口面積は72％であった。(Comparative Example 7) EPDM, thickness 10 mm, density 100 k
g / m 3 , water absorption 0.071 g / cm 3 , 25% compression hardness 0.040 N / cm 2 For a foam material, a sheet having a square through hole of 17 mm on each side provided at each intersection of a 20 mm pitch lattice, A sheet provided with through holes of 5 mm on each side on each intersection of a grid with a pitch of 20 mm was laminated to produce a sound absorbing structure having a total thickness of 20 mm having double holes, and a sheet provided with through holes of 5 mm on a side was prepared. The normal incidence sound absorption coefficient was measured as the rigid wall side. The total opening area on the sound source surface of the double hole of this sound absorbing structure was 72%.
【００４６】上記の各吸音構造体に関して、所定の周波
数毎に垂直入射吸音率を測定した。測定はJIS A1405に
準じて剛壁密着の条件で測定した。測定結果を図８〜図
16に示す。実施例の結果から、本発明による構造体が優
れた吸音特性を示すことは明らかである。また、二重穴
の配置（粗密）を適宜変更することにより部位（厚み）
にかかわらず所望の周波数の吸音率を高めることが可能
となったり、または特に広い特定の周波数域の吸音率を
高くするなど、目的に応じた吸音効果を発現させること
ができる。For each of the above sound absorbing structures, the normal incidence sound absorption coefficient was measured at each predetermined frequency. The measurement was carried out in accordance with JIS A1405 under the condition of rigid wall contact. Fig. 8 to Fig.
See Figure 16. It is clear from the results of the examples that the structure according to the invention exhibits excellent sound absorption properties. Also, by appropriately changing the arrangement (coarse and dense) of the double holes,
Irrespective of this, it is possible to achieve a sound absorbing effect according to the purpose, such as to increase the sound absorbing coefficient of a desired frequency or to increase the sound absorbing coefficient of a particularly wide specific frequency range.
【００４７】[0047]
【発明の効果】以上説明したように、本発明によれば、
広い周波数域において良好な吸音特性を有し、さらに目
的等に応じて所望の周波数域の吸音特性を高くしたりあ
るいは、特に広い周波数域においての吸音率を全体的に
向上させることが可能な吸音構造体、並びに前記吸音構
造体を用いた自動車用エンジンカバーを提供することが
できる。As described above, according to the present invention,
Sound absorption that has good sound absorption characteristics in a wide frequency range and can further enhance the sound absorption characteristics in a desired frequency range or improve the overall sound absorption coefficient particularly in a wide frequency range according to the purpose and the like. A structure and an automobile engine cover using the sound absorbing structure can be provided.
【図１】本発明の吸音構造体の一例を示す図である。FIG. 1 is a diagram showing an example of a sound absorbing structure of the present invention.
【図２】本発明の吸音構造体の他の例を示す図である。FIG. 2 is a diagram showing another example of the sound absorbing structure of the present invention.
【図３】本発明の吸音構造体の更に他の例を示す図であ
る。FIG. 3 is a view showing still another example of the sound absorbing structure of the present invention.
【図４】本発明の吸音構造体の更に他の例を示す図であ
る。FIG. 4 is a view showing still another example of the sound absorbing structure of the present invention.
【図５】本発明の吸音構造体の更に他の例を示す図であ
る。FIG. 5 is a view showing still another example of the sound absorbing structure of the present invention.
【図６】本発明の吸音構造体の更に他の例を示す図であ
る。FIG. 6 is a view showing still another example of the sound absorbing structure of the present invention.
【図７】本発明の吸音構造体の更に他の例を示す図であ
る。FIG. 7 is a view showing still another example of the sound absorbing structure of the present invention.
【図８】実施例１及び実施例２の吸音構造体の吸音率を
測定した結果を示すグラフである。FIG. 8 is a graph showing the results of measuring the sound absorption coefficients of the sound absorbing structures of Examples 1 and 2.
【図９】実施例１、実施例３及び実施例４の吸音構造体
の吸音率を測定した結果を示すグラフである。FIG. 9 is a graph showing the results of measuring the sound absorption coefficients of the sound absorbing structures of Examples 1, 3 and 4.
【図１０】実施例１及び実施例５の吸音構造体の吸音率
を測定した結果を示すグラフである。FIG. 10 is a graph showing the results of measuring the sound absorption coefficient of the sound absorbing structures of Examples 1 and 5.
【図１１】実施例１及び実施例６の吸音構造体の吸音率
を測定した結果を示すグラフである。FIG. 11 is a graph showing the results of measuring the sound absorption coefficients of the sound absorbing structures of Examples 1 and 6.
【図１２】実施例１及び実施例７の吸音構造体の吸音率
を測定した結果を示すグラフである。FIG. 12 is a graph showing the results of measuring the sound absorption coefficients of the sound absorbing structures of Examples 1 and 7.
【図１３】実施例８及び実施例９の吸音構造体の吸音率
を測定した結果を示すグラフである。FIG. 13 is a graph showing the results of measuring the sound absorption coefficients of the sound absorbing structures of Examples 8 and 9.
【図１４】実施例10及び実施例11の吸音構造体の吸音率
を測定した結果を示すグラフである。FIG. 14 is a graph showing the results of measuring the sound absorption coefficients of the sound absorbing structures of Examples 10 and 11.
【図１５】比較例１、比較例２及び比較例３の吸音構造
体の吸音率を測定した結果を示すグラフである。FIG. 15 is a graph showing the results of measuring the sound absorption coefficients of the sound absorbing structures of Comparative Example 1, Comparative Example 2, and Comparative Example 3.
【図１６】比較例４、比較例５、比較例６及び比較例７
の吸音構造体の吸音率を測定した結果を示すグラフであ
る。FIG. 16 shows Comparative Examples 4, 5, 6, and 7;
6 is a graph showing the results of measuring the sound absorption coefficient of the sound absorbing structure of FIG.
(a) フォーム材 (b)〜(g) 凹部 (i) , (j) テーパー穴 (k)〜(l) 凹部 (h),(m),(n) 貫通穴 (a) Foam material (b) to (g) Recess (i), (j) Taper hole (k) to (l) Recess (h), (m), (n) Through hole
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平５−2397（ＪＰ，Ａ) 実開 昭50−126831（ＪＰ，Ｕ) (58)調査した分野(Int.Cl.7，ＤＢ名) F02B 77/13 B60R 13/08 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-2397 (JP, A) Japanese Utility Model 50-126831 (JP, U) (58) Fields investigated (Int. Cl. 7 , DB name) F02B 77/13 B60R 13/08
Claims (7)
を有するフォーム材に、音源と対向する側の面の開口面
積が最大で、厚み方向に沿って開口面積が小さくなる径
違い穴を複数形成してなることを特徴とする吸音構造
体。1. A foam material having a mixed cell structure of open cells and closed cells is provided with a reduced-diameter hole having the largest opening area on the surface facing the sound source and having a smaller opening area along the thickness direction. A sound absorbing structure formed by forming a plurality of sound absorbing structures.
ォーム材を、貫通穴同士が同軸上に配置されるように積
層してなることを特徴とする吸音構造体。2. A sound absorbing structure comprising a plurality of types of foam materials having different opening areas of through-holes laminated so that the through-holes are arranged coaxially.
の開口面積の合計が１％以上で70％以下であることを特
徴とする請求項１または２に記載の吸音構造体。3. The sound-absorbing structure according to claim 1, wherein the total opening area of the reduced-diameter holes on the surface facing the sound source is 1% or more and 70% or less.
0.2g/cm3以下であり、かつ密度が20kg/ m3以上で400kg/
m3以下であることを特徴とする請求項１〜３の何れか一
項に記載の吸音構造体。4. When the water absorption of the foam material is 0.01 g / cm 3 or more.
0.2 g / cm 3 or less and a density of 20 kg / m 3 or more 400 kg /
The sound absorbing structure according to claim 1, wherein m is 3 or less.
下であることを特徴とする請求項１〜４の何れか一項に
記載の吸音構造体。5. The sound absorbing structure according to claim 1, wherein a 25% compression hardness of the foam material is 0.5 N / m 3 or less.
かつ厚さによって径違い穴の開口形状、深さ及び配置の
少なくとも１つが異なることを特徴とする請求項１〜５
の何れか一項に記載の吸音構造体。6. The thickness of the foam material varies depending on the part,
6. The method according to claim 1, wherein at least one of an opening shape, a depth, and an arrangement of the reduced diameter hole differs depending on the thickness.
The sound absorbing structure according to any one of the above.
構造体を用いたことを特徴とする自動車用エンジンカバ
ー。7. An automobile engine cover using the sound absorbing structure according to any one of claims 1 to 6.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07615299A JP3332883B2 (en) | 1999-03-19 | 1999-03-19 | Sound absorbing structure |
| EP00100679.0A EP1020846B1 (en) | 1999-01-14 | 2000-01-13 | Sound absorbing structure |
| US09/482,731 US6720069B1 (en) | 1999-01-14 | 2000-01-14 | Sound absorbing structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07615299A JP3332883B2 (en) | 1999-03-19 | 1999-03-19 | Sound absorbing structure |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000274257A JP2000274257A (en) | 2000-10-03 |
| JP3332883B2 true JP3332883B2 (en) | 2002-10-07 |
Family
ID=13597063
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP07615299A Expired - Lifetime JP3332883B2 (en) | 1999-01-14 | 1999-03-19 | Sound absorbing structure |
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| Country | Link |
|---|---|
| JP (1) | JP3332883B2 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4239705B2 (en) * | 2003-06-25 | 2009-03-18 | トヨタ自動車株式会社 | Sound absorbing structure |
| JP5257203B2 (en) * | 2009-03-31 | 2013-08-07 | アイシン精機株式会社 | Engine cover structure |
| CN108281132A (en) * | 2018-03-13 | 2018-07-13 | 吉林大学 | With Cylindrical Pit bionic non-smooth surface polyurethane foam board and preparation method |
| CN108281133A (en) * | 2018-03-13 | 2018-07-13 | 吉林大学 | With spherical pit bionic non-smooth surface polyurethane foam board and preparation method |
| CN108731058B (en) * | 2018-05-31 | 2024-04-30 | 广东美的厨房电器制造有限公司 | Fume exhaust fan |
| CN108417195B (en) * | 2018-06-13 | 2023-11-10 | 山东理工大学 | Medium-low frequency sound absorption metamaterial structure based on resonant cavity |
| JP7168364B2 (en) * | 2018-07-20 | 2022-11-09 | 西川ゴム工業株式会社 | Automotive soundproofing material |
| KR20210073642A (en) * | 2019-12-10 | 2021-06-21 | 현대자동차주식회사 | Holey plate and composite panel for sound absoption and sound insulation using the same |
-
1999
- 1999-03-19 JP JP07615299A patent/JP3332883B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| JP2000274257A (en) | 2000-10-03 |
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