JP2005009322A

JP2005009322A - Intake duct

Info

Publication number: JP2005009322A
Application number: JP2003171190A
Authority: JP
Inventors: Teruo Shiraishi; 輝男白石
Original assignee: Inoue MTP KK; Inoac Corp
Current assignee: Inoac Corp
Priority date: 2003-06-16
Filing date: 2003-06-16
Publication date: 2005-01-13

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently reduce intake noise, while reducing the number of components, rationalizing molding work, and reducing a manufacturing cost. <P>SOLUTION: An intake duct 10 comprises a first duct component 20 and a second duct component 22 blow-molded in a shape where they are joined to face each other along a longitudinal direction and an air flow passage 12 is formed therein when they are joined. Each of the duct components 20, 22 has: an outer wall part 28 of a predetermined shape; an inner wall part 30 forming the air flow passage 12 when the components are joined; and partition wall parts 32 positioned between the outer wall part 28 and the inner wall part 30 at appropriate intervals in the longitudinal direction and extending in a cross direction to form a plurality of spaces 34 by partitioning. Communicating ports 36 are formed in the inner wall part 30 responding to each space 34 to spatially making the spaces 34 communicate with the air flow passage 12, so that the spaces 34 function as resonance chambers S having different resonant frequency to reduce the intake noise in the air flow passage 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、吸気ダクトに関し、更に詳細には、自動車等に搭載されるエンジンの吸気側等に連結され、該エンジンに必要な外部空気を吸引する際に発生する吸気音を低減する機能を具備した吸気ダクトに関するものである。
【０００２】
【従来の技術】
自動車等に搭載されるエンジンは、その吸気側に連結された吸気ダクトおよびエアクリーナー等を介して、回転駆動時に必要な外部空気を吸引するようになっている。ここで、前記吸気ダクトから外部空気を吸引する際には、▲１▼吸気ダクトの形状およびサイズ（全長、内径等）、▲２▼空気の吸引量および吸引速度、等の諸条件に基づき、様々な周波数の吸気音が発生するようになり、殊に気柱共鳴に伴って特定かつ複数の周波数の音域が増幅する傾向がある。そこで、このような吸気音を低減するための対策として、共鳴効果を利用して吸気音の低減を図るレゾネータ（共鳴器）を、前記吸気ダクトの所要位置に装着するようにした技術が多く提案されている。このような吸気音の低減対策に関する技術は、例えば特許文献１および特許文献２等に開示されている。
【０００３】
特許文献１に開示されたエンジンの吸気装置は、車体に固定された吸気ダクトとエアクリーナーとの間に配設されるインレットパイプに、箱体状に形成されたレゾネータを外付け状態で配設した構成となっている。すなわち前記レゾネータは、吸気ダクトの一部と見なされる前記インレットパイプに接合されると共に、トランスミッション、ウォータパイプおよびエアクリーナー等に取付けて、複数箇所で固定されている。
【０００４】
また特許文献２に開示のレゾネータは、吸気管（吸気ダクト）の外周に、該吸気管の外面と所定の間隔をもって周方向および長手方向に延在するアウターパネルを組付け、これら吸気管とアウターパネルとの間に画成される空間を共鳴室として機能させると共に、当該吸気管の外周面に該共鳴室内と吸気管内部とを連通する共鳴管を開設した構成となっている。すなわち前記レゾネータは、吸気管の外側に沿うように設けた構成となっている。
【０００５】
【特許文献１】
特開２００１−０９９０２６号公報
【特許文献２】
特開平６−１５９１７４号公報
【０００６】
【発明が解決しようとする課題】
ところで、前記特許文献１に開示された構成では、前述したように、箱体状に形成された前記レゾネータが外付け状態で取付けられる構成となっているため、当該レゾネータのための設置スペースをエンジンルーム内に確保する必要がある。しかしながらエンジンルーム内には、エンジンをはじめとする種々の車載機器類が所狭しと設置されるようになっているため、前記レゾネータの設置スペースを確保するためにエンジンルーム全体の設計変更が必要となったり、エンジンルームが狭い車両では設置スペースの確保が困難となる不都合等が発生していた。また前述したように、複数の取付箇所を設定して強固に取付けるようにしなければ、走行時の振動等で取付不備が発生する問題もあった。
【０００７】
一方、特許文献２に開示された構成では、吸気管の外周に共鳴室を形成するようになっているため、設置スペースの確保に支障を来たすことがなくなる利点がある。しかしながら、前記吸気管およびアウターパネルが別部材として構成されると共に、後工程において該吸気管に対してアウターパネルを組付けるようになっており、構成部品点数の増加に伴って成形作業工数および組付作業工数等が増えるため、これにより製造コストが嵩む問題等を内在していた。
【０００８】
【発明の目的】
本発明は、前述した課題を好適に解決するべく提案されたもので、構成部品点数の低減、成形作業の合理化、そしてこれに基づく製造コストの削減等を可能としたもとで、吸気音の効率的な低減を図り得るよう構成した吸気ダクトを提供することを目的とする。
【０００９】
【課題を解決するための手段】
前記課題を解決して、所期の目的を達成するため本発明は、長手方向に沿って対向的に接合可能な形状に形成され、相互に接合した際に空気流通路が内部に画成される一対のダクト構成体からなり、
前記夫々のダクト構成体は、所要形状の外壁部と、この外壁部に対し適宜間隔をおいて内側に位置し、前記接合時に前記空気流通路となる内壁部と、前記外壁部および内壁部の間で長手方向へ適宜間隔に位置して短手方向へ延在し、前記外壁部および内壁部の間に複数の空間を内部画成する隔壁部とを有し、
前記内壁部に、前記各空間と前記空気流通路とを空間的に連通する連通口を対応的に開設し、
前記連通口を介して空気流通路に連通する各空間を、相互に異なる共鳴周波数を有する共鳴室として機能させ、前記空気流通路内における吸気音を低減させ得るよう構成したことを特徴とする。
【００１０】
【発明の実施の形態】
次に、本発明に係る吸気ダクトにつき、好適な実施例を挙げて、添付図面を参照しながら以下説明する。実施例の吸気ダクトは、例えば自動車等に搭載されるエンジンの吸気側に配設されて、該エンジンの駆動時に必要な空気を吸引するために供され、この空気吸引時に発生する吸気音を、共鳴現象
（効果）を利用して低減（減音）する機能を具備した構成とされている。なお実施例では、理解の容易化を図るため、単純な真直円筒形状で図示表示する。
【００１１】
図１は、本発明の好適実施例に係る吸気ダクトの概略斜視図、図２は図１のＩＩ−ＩＩ線断面図、図３は図１のＩＩＩ−ＩＩＩ線断面図、図４は図１のＩＶ−ＩＶ線断面図、図５は図１のＶ−Ｖ線断面図、図６は図１のＶＩ−ＶＩ線断面図である。また図７は、図１に例示した実施例の吸気ダクトを構成する一対のダクト構成体を、接合前の展開状態で例示した概略斜視図である。
【００１２】
実施例の吸気ダクト１０は、長手方向に沿って対向的に接合可能な形状に形成されて、相互に接合した際に空気流通路１２が内部に画成される一対のダクト構成体２０，２２から構成されている。そして、一方端縁（図１の手前側）に空気吸引口１４が形成され、また他方端縁（図１の奥側）に空気送出口１６が形成されている。なお説明の便宜上、図１において下側に位置するダクト構成体２０を「第１ダクト構成体」と称し、上側に位置するダクト構成体２２を「第２ダクト構成体」とする。
【００１３】
（ダクト構成体）
前記第１ダクト構成体２０および第２ダクト構成体２２は、例えばポリプロピレン（ＰＰ）等の合成樹脂を材質とし、後述するように公知技術であるブロー成形技術に基づいて成形された中空体である。具体的には、図７に例示するように、何れも端面形状が半円状とされた樋形状を呈しており、短手方向に離間した両端縁に長手方向へ延在する当接接合面２４，２４が形成されている。なお実施例では、後述するように、前記第１ダクト構成体２０および第２ダクト構成体２２を、相互に端部接合した連結状態で一体的にブロー成形した後、これら第１ダクト構成体２０および第２ダクト構成体２２の境界ラインに沿って延在する折曲ライン２６で折り曲げることで対向的に接合する態様となっており、これにより円筒状の前記吸気ダクト１０を形成するようになっている。
【００１４】
ブロー成形により形成される前記第１ダクト構成体２０および第２ダクト構成体２２は、所要形状の外壁部２８と、この外壁部２８に対し適宜間隔をおいて内側に位置し、前記接合時に前記空気流通路１２となる内壁部３０と、前記外壁部２８および内壁部３０の間で長手方向へ適宜間隔に位置すると共に短手方向へ延在する隔壁部３２とを有している。前記隔壁部３２は、前記外壁部２８の裏面に接触するように前記内壁部３０に突設されており、第１ダクト構成体２０および第２ダクト構成体２２には夫々所要間隔に合計３個ずつが突設されている。従って、第１ダクト構成体２０および第２ダクト構成体２２には、前記内壁部３０および外壁部２８の間に前記各隔壁部３２で仕切られた合計４個ずつの空間３４，３４，３４，３４が、その長手方向へ直列状に画成されている。但し実施例では、全各隔壁部３２を同一間隔に突設して、各空間３４の内部容積を同一とした状態で例示してある。
【００１５】
（連通口）
また、前記第１ダクト構成体２０および第２ダクト構成体２２における各々の内壁部３０には、前記各々の空間３４，３４，３４，３４に臨む位置に、該空間３４，３４，３４，３４と前記空気流通路１２とを空間的に連通する複数の連通口３６を対応的に開設してある。ここで、内壁部３０に開設された全ての連通口３６は、その開口形状および開口サイズが何れも同一となっており、個々の開口面積は等しくなっている。従って、前記各空間３４，３４，３４，３４と空気流通路１２との連通面積Ａ１，Ａ２，Ａ３，Ａ４は、後述するように、前記連通口３６の開設個数に基づいて設定されている。
【００１６】
このような第１ダクト構成体２０および第２ダクト構成体２２からなる実施例の吸気ダクト１０では、前記各空間３４，３４，３４，３４が１個または複数個の前記連通口３６を介して前記空気流通路１２と空間的に連通して構造となっているため、これら空間３４，３４，３４，３４を共鳴室Ｓとして機能させ、該空気流通路１２内における吸気音を低減させ得るようになっている。なお、説明の便宜上、前記空気吸引口１４に隣接した側（図１の手前側）から、第１共鳴室Ｓ１、第２共鳴室Ｓ２、第３共鳴室Ｓ３、第４共鳴室Ｓ４とする。但し、実施例の吸気ダクト１０は、前記第１ダクト構成体２０および第２ダクト構成体２２が、対称形状とされた独立中空体として形成されているため、２つずつの前記第１共鳴室Ｓ１、第２共鳴室Ｓ２、第３共鳴室Ｓ３および第４共鳴室Ｓ４が設けられていることになる。
【００１７】
（共鳴周波数）
ここで、ダクトにおける共鳴器（レゾネータ）の共鳴周波数は、周知のように、下記の計算式に基づいて算出することができる。
【００１８】
【数１】

【００１９】
前記計算式における各符号は、次のようになっている。
ｆｒ：共鳴周波数（Ｈｚ）
Ｃ：音速３４０×１０^３（ｍｍ／ｓ）
Ｖ：共鳴室Ｓの内部容積（ｍｍ^３）
Ｇ：コンダクティビティ
Ｌｅ＝ｔ＋（π／２）ａ
Ａ：連通面積（ｍｍ^２）、
（連通口３６の半径ａ（ｍｍ）、個数ｎの場合：ｎπａ^２）
ｔ：内壁部３０の肉厚（連通口３６の長さ）（ｍｍ）
【００２０】
前記計算式によれば、前記連通面積Ａの広狭設定条件や、前記内部容積Ｖの大小設定条件が、共鳴周波数ｆｒに大きく関与することが理解できる。すなわち、前記第１共鳴室Ｓ１、第２共鳴室Ｓ２、第３共鳴室Ｓ３および第４共鳴室Ｓ４の共鳴周波数ｆｒ１，ｆｒ２，ｆｒ３，ｆｒ４は、各々の内部容積Ｖ１，Ｖ２，Ｖ３，Ｖ４や、前記連通口３６の開設個数により設定される各々の連通面積Ａ１，Ａ２，Ａ３，Ａ４等の設定条件によって決定されるようになる。
【００２１】
なお、前記第１共鳴室Ｓ１、第２共鳴室Ｓ２、第３共鳴室Ｓ３および第４共鳴室Ｓ４の内部容積Ｖ１，Ｖ２，Ｖ３，Ｖ４は、ブロー成形に供されるブロー成形型４０における成形面の形状設定により設定可能である。例えば、前記外壁部２８と内壁部３０との間隔を一定とした場合では、前記各隔壁部３２の形成位置を調整することで、第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４の内部容積Ｖ１，Ｖ２，Ｖ３，Ｖ４の設定変更が可能である。また、前記各隔壁部３２の形成間隔を一定とした場合では、前記外壁部２８と内壁部３０との形成間隔を調整することで、各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４の内部容積Ｖ１，Ｖ２，Ｖ３，Ｖ４の設定変更が可能である。
【００２２】
一方、前記第１共鳴室Ｓ１、第２共鳴室Ｓ２、第３共鳴室Ｓ３および第４共鳴室Ｓ４の連通面積Ａ１，Ａ２，Ａ３，Ａ４は、前述したように、図１０に例示した穿孔装置（穿孔手段）５０により開設される前記連通口３６の開設個数により設定可能である。すなわち、連通面積Ａ１，Ａ２，Ａ３，Ａ４を大きく設定する必要がある場合は、前記連通口３６の開設個数を多くすればよく、逆に連通面積Ａ１，Ａ２，Ａ３，Ａ４を小さく設定する必要がある場合は、該連通口３６の開設個数を少なくすればよい。
【００２３】
次に、前述のように構成された実施例の吸気ダクト１０の成形方法について説明する。
【００２４】
（ダクト構造体の成形工程）
実施例の吸気ダクト１０は、図９に略示したブロー成形型４０を使用したブロー成形技術に基づき、先ず前記第１ダクト構成体２０および第２ダクト構成体２２を相互横並び状に端部接合した連結状態に一体成形する（図７、図８）。すなわちブロー成形型４０は、凹部４２Ｂ，４２Ｂを陥設して前記外壁部２８の成形に供される第１成形面４２Ａを有する第１成形型４２と、凸部４４Ｂ，４４Ｂを突設して前記内壁部３０および前記隔壁部３２の成形に供される第２成形面４４Ａを有する第２成形型４４から構成されている。従って、前記第１成形型４２および第２成形型４４を型開きしたもとでパリソンＰをセットした後（図９（ａ））、これら第１成形型４２および第２成形型４４を型閉めすると共に、該パリソンＰ内へ成形空気を吹き込むことで、前記第１ダクト構成体２０および第２ダクト構成体２２が、相互横並び状に端部接合した開放連結状態で一体的に予備成形される（図９（ｂ））。
【００２５】
（連通口の開設工程）
前記第１ダクト構成体２０および第２ダクト構成体２２の予備成形が完了したら、各々のダクト構成体２０，２２の内壁部３０の所要位置に前記連通口３６を開設する。前記各連通口３６は、例えば図１０に例示するような穿孔装置（穿孔手段）５０を使用することで、前記第１ダクト構成体２０および第２ダクト構成体２２の内壁部３０に対し、同一の開口形状および開口サイズに開設される。ここで前記穿孔装置５０は、旋回可能な本体５２と、該本体５２にスライド可能に配設され、加熱昇温される穿孔部材５６を先端に配設した穿孔ロッド５４と、該穿孔部材５６を図示しない加熱手段等から構成されている。このような穿孔装置５０による連通口３６の開設作業では、第１ダクト構成体２０および第２ダクト構成体２２の円弧中心に前記本体５２を位置させ、前記加熱手段で加熱させた前記穿孔部材５６を、前記穿孔ロッド５４の前進移動のもとに内壁部３０へ押付ければ、前記連通口３６の開設が可能となる。従って、前記本体５２を所要の旋回角度に旋回・停止させる毎に前記穿孔ロッド５４を前進させることで、前記内壁部３０に対して所定数の連通口３６を短手方向へ直列状に開設し得る。
【００２６】
そして、前記本体５２を、第１ダクト構成体２０および第２ダクト構成体２２の長手方向へ所要量ずつスライド移動させ、前述した作業を繰り返せば、前記第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４に対応した位置で、前記内壁部３０に対して連通口３６を開設し得る。すなわち、本体５２の旋回制御およびスライド制御を適切に行なうようにすれば、内壁部３０の何れの部位であっても前記連通口３６を自在に開設することが可能である。
【００２７】
（各ダクト構成体の接合工程）
前記第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４に対応して、前記内壁部３０の所要位置に所要数の連通口３６の穿設作業が完了したら、前記第１ダクト構成体２０および第２ダクト構成体２２を、これらの境界ラインに沿って延在する折曲ライン２６で合掌状に折り曲げることで、両ダクト構成体２０，２２の各当接接合面２４，２４同士が対応的に密着するようになり、両ダクト構成体２０，２２の接合がなされる。なお、前記第１ダクト構成体２０および第２ダクト構成体２２の接合は、図示しない適宜の係合手段や接着剤等の公知手段により、容易に分離開放しないように接合される。
【００２８】
このように実施例の吸気ダクト１０では、第１ダクト構成体２０および第２ダクト構成体２２により、空気流通路１２および該空気流通路１２の外周に複数の共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４を画成した構造となっているため、エンジンルーム内に設置スペースを大きく確保する必要がなく、また該共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４の取付形態を検討する必要もないので、前記特許文献１に内在した問題を好適に回避できる。
【００２９】
また、吸気ダクト１０を構成する前記第１ダクト構成体２０および第２ダクト構成体２２は、ブロー成形技術に基づいて一体的に形成されるため、特許文献２に開示の構成に比べて構成部品点数が大幅に削減されている。しかも、前記第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４と空気流通路１２との連通面積Ａ１，Ａ２，Ａ３，Ａ４は、単一サイズの前記連通口３６の開設個数に基づいて設定するようになっており、前記穿孔装置５０によって連通口３６の開設作業を効率的に実施し得る。従って、実施例の吸気ダクト１０の成形に際しては、部品点数削減および成形工程削減に伴う成形作業の合理化および効率化が図られるようになり、大幅な製造コストの低減が可能となっている。更に、第１ダクト構成体２０と第２ダクト構成体２２とは、折曲ライン２６で合掌的に接合するだけで組立てが完了するため組立作業工数の削減も図られ、これによる製造コストの低減も期待できる。
【００３０】
また、前記ブロー成形型４０の第１成形面４２Ａおよび第２成形面４４Ａの形状変更により、種々形状の吸気ダクト１０の成形が可能である。これに伴い、共鳴室Ｓの形成個数および内部容積Ｖ等を自由に設定することができることは勿論、前記穿孔装置５０の動作制御により該共鳴室Ｓと空気流通路１２との連通面積Ａも自由に設定することができる。従って、異なる共鳴周波数ｆｒを有する複数の共鳴室Ｓを設けることが可能であり、空気流通路１２で発生する吸気音における複数の周波数の音域を好適に減音することが可能である。
【００３１】
一方、吸気ダクト１０の成形方法は、前述したものに限定されるものではなく、例えば前記第１ダクト構成体２０および第２ダクト構成体２２を、図９に例示したブロー成形型４０とは異なるブロー成形型を使用したもとで、完全に分離した別体として個別にブロー成形し、前記穿孔装置５０による前記連通口３６の開設作業の完了後に、相互対向的に接合するようにしてもよい。
【００３２】
なお前記実施例では、前記第１ダクト構成体２０および第２ダクト構成体２２を対称形状に形成した吸気ダクト１０を場合を例示したが、これら第１ダクト構成体２０および第２ダクト構成体２２を非対称形状に形成するようにしてもよい。そして、第１ダクト構成体２０および第２ダクト構成体２２は、外形形状を変更したり、前記外壁部２８の形状および／または隔壁部３２の形成位置を変更することで、各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４の内部容積Ｖ１，Ｖ２，Ｖ３，Ｖ４を不均一に設定したり、前記隔壁部３２の形成数の増減により共鳴室Ｓの画成数を変更するようにしてもよい。更には、第１ダクト構成体２０または第２ダクト構成体２２の何れか一方のみに、前記共鳴室Ｓを内部画成するようにしてもよい。
【００３３】
また前記実施例では、前記内壁部３０に前記各々の隔壁部３２を一体的に形成した場合を例示したが、図１２および図１３に示するように、該隔壁部３２を前記外壁部２８に形成するようにしてもよい。このように隔壁部３２を外壁部２８に形成しても、該隔壁部３２が内壁部３０の内側に適切に接触していれば、前記各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４を好適に画成することができる。しかも、空気流通路１２の全域に亘って内壁部３０が平滑面となるため、吸引空気のスムーズな流通が期待できる。
【００３４】
更に前記実施例では、前記第１ダクト構成体２０および第２ダクト構成体２２の夫々を独立した中空体とした場合を例示したが、例えば図１４に例示するように、前記当接接合面２４，２４を形成する壁部分を後加工により切除した後、これら第１ダクト構成体２０および第２ダクト構成体２２を合掌状に接合するようにしてもよい。この場合では、前記第１ダクト構成体２０から第２ダクト構成体２２に亘って円筒状の空間が画成されるため、内部容積Ｖを大きく設定した共鳴室Ｓを内部画成することが可能となる。
【００３５】
一方、前記実施例では、穿孔部材５６を所定温度まで加熱するようにした構成の穿孔装置５０により、該穿孔部材５６で前記内壁部３０を溶融させながら連通口３６を開設する場合を例示したが、該連通口３６の開設方法はこれに限定されるものではない。例えば、前記穿孔部材５６をドリル形態の回転刃として、前記内壁部３０を切削しながら連通口３６を開設するようにしてもよい。
【００３６】
（設定例）
次に、前述のように構成された実施例の吸気ダクト１０につき、具体的に１つの設定例を例示する。ここでは、図１４に例示した形態の吸気ダクト、すなわち、第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４を、前記第１ダクト構成体２０から第２ダクト構成体２２に亘って円筒状に画成したタイプの吸気ダクトを前提として説明する。なお、前記第１ダクト構成体２０および第２ダクト構成体２２における各内壁部３０，３０により形成された前記空気流通路１２の寸法は、
・空気流通路１２の全長Ｌ＝４００ｍｍ、
・空気流通路１２の内径Ｄ＝５４ｍｍ
とする。
【００３７】
前述した寸法の空気流通路１２を有する吸気ダクト１０は、共鳴室が設けられていない場合、スピーカー加振に基づく気柱共鳴試験によって得られる気柱共鳴周波数ｆが、図１５に例示するように、１次気柱共鳴周波数ｆ１＝３３８Ｈｚ、２次気柱共鳴周波数ｆ２＝６７４Ｈｚ、３次気柱共鳴周波数ｆ３＝１，０２０Ｈｚ、４次気柱共鳴周波数ｆ４＝１，３５０Ｈｚとなる。すなわち、前記吸気ダクト１０で空気を吸引する際の吸気音は、前記複数の周波数における音域が増幅されることが確認できる。
【００３８】
従って実施例の吸気ダクト１０では、前記１次気柱共鳴周波数ｆ１の音域を前記第１共鳴室Ｓ１で減音し、前記２次気柱共鳴周波数ｆ２の音域を前記第２共鳴室Ｓ２で減音し、前記３次気柱共鳴周波数ｆ３の音域を前記第３共鳴室Ｓ３で減音し、前記４次気柱共鳴周波数ｆ４の音域を前記第４共鳴室Ｓ４で減音し得るように設定する。ここで図１６に例示するように、１次気柱共鳴のピークはＬ／２の部分となり（図１６（ａ））、２次気柱共鳴のピークはＬ／４および３Ｌ／４の各部分となり（図１６（ｂ））、３次気柱共鳴のピークはＬ／６、３Ｌ／６および５Ｌ／６の各部分となり（図１６（ｃ））、４次気柱共鳴のピークはＬ／８、３Ｌ／８、５Ｌ／８、７Ｌ／８の各部分となる（図１６（ｄ））。従って、１次〜４次の各気柱共鳴周波数ｆ１〜ｆ４の音域を減音するには、夫々のピーク部分またはその近傍において行なうようにするのが効果的であるため、本設定例の吸気ダクト１０では、図１７に例示するように、空気吸引口１４の側から、第３共鳴室Ｓ３、第１共鳴室Ｓ１、第４共鳴室Ｓ４、第２共鳴室Ｓ２の順に配置するようにした。
【００３９】
そして、前記空気流通路１２の内径Ｄ＝５４ｍｍに設定されていることにより、前記内壁部３０の肉厚ｔ＝３ｍｍであるから、前記第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４の内径（内壁部３０の外径）Ｐ１＝６０ｍｍに設定される。これにより、第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４の外径（外壁部２８の内径）Ｐ２を、７１ｍｍに設定した。そして、前記各隔壁部３２の厚みを各々４ｍｍ、空気吸引口１４側の壁部および空気送出口１６側の壁部の厚みを各々２ｍｍとしたもとで、前記第１共鳴室Ｓ１の室内長Ｑ１＝９９．５ｍｍ、第２共鳴室Ｓ２の室内長Ｑ２＝１００．０ｍｍ、第３共鳴室Ｓ３の室内長Ｑ３＝９７．５ｍｍ、第４共鳴室Ｓ４の室内長Ｑ４＝８７．０ｍｍとなるように、各々の隔壁部３２の形成位置を決定した。これにより表１に示したように、第１共鳴室Ｓ１の内部容積Ｖ１＝１１２，６１４．１ｍｍ^３、第２共鳴室Ｓ２の内部容積Ｖ２＝１１３，１８０．０ｍｍ^３、第３共鳴室Ｓ３の内部容積Ｖ３＝１１０，３５０．５ｍｍ^３、第４共鳴室Ｓ４の内部容積Ｖ４＝９８，４６６．６ｍｍ^３となっている。
【００４０】
【表１】

【００４１】
そして、前記計算式に基づき、前記第１共鳴室Ｓ１、第２共鳴室Ｓ２、第３共鳴室Ｓ３および第４共鳴室Ｓ４が、対応の前記１次〜４次の気柱共鳴周波数ｆ１，ｆ２，ｆ３，ｆ４に対応した共鳴周波数ｆｒ１，ｆｒ２，ｆｒ３，ｆｒ４を有するように、各々の内部容積Ｖ１，Ｖ２，Ｖ３，Ｖ４を基にして各々の連通面積Ａ１，Ａ２，Ａ３，Ａ４を算出すると共に、これら連通面積Ａ１，Ａ２，Ａ３，Ａ４を基に前記連通口３６の開口寸法および開設個数等を決定した。すなわち、表２に例示するように、第１共鳴室Ｓ１の連通面積Ａ１＝３６．３２ｍｍ^２、第２共鳴室Ｓ２の連通面積Ａ２＝１４５．２８ｍｍ^２、第３共鳴室Ｓ３の連通面積Ａ３＝３２６．８８ｍｍ^２、第４共鳴室Ｓ４の連通面積Ａ４＝５０８．４８ｍｍ^２とした。更に、前記連通口３６を直径６．８ｍｍの円形状とすると共に、該連通口３６の開設個数により前述した各連通面積Ａ１〜Ａ４を確保するようにした。
【００４２】
従って表２に例示したように、第１共鳴室Ｓ１では、１個の連通口３６を内壁部３０の所要位置に開設することで連通面積Ａ１（＝３６．３２ｍｍ^２）とし、第２共鳴室Ｓ２では、４個の連通口３６を内壁部３０の所要位置に開設することで連通面積Ａ２（＝１４５．２８ｍｍ^２）とし、第３共鳴室Ｓ３では、９個の連通口３６を内壁部３０の所要位置に開設することで連通面積Ａ３（＝３２６．８８ｍｍ^２）とし、第４共鳴室Ｓ４では、１４個の連通口３６を内壁部３０の所要位置に開設することで連通面積Ａ４（＝５０８．４８ｍｍ^２）とした。
【００４３】
【表２】

【００４４】
このように設定したことにより、第１共鳴室Ｓ１の共鳴周波数ｆｒ１＝３３７Ｈｚ、第２共鳴室Ｓ２の共鳴周波数ｆｒ２＝６７１Ｈｚ、第３共鳴室Ｓ３の共鳴周波数ｆｒ３＝１０２０Ｈｚ、第４共鳴室Ｓ４の共鳴周波数ｆｒ４＝１３４７Ｈｚに夫々設定され、前記１次〜４次の各気柱共鳴周波数ｆ１（３３８Ｈｚ）、ｆ２（６７４Ｈｚ）、ｆ３（１，０２０Ｈｚ）、ｆ４（１，３５０Ｈｚ）に一致または近似するようになった。従って、前述した共鳴周波数ｆｒ１，ｆｒ２，ｆｒ３，ｆｒ４に設定された第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４を具備した実施例の吸気ダクト１０では、図１５に例示したように、吸気音における前記１次気柱共鳴周波数ｆ１（３３８Ｈｚ）の音域を、前記共鳴周波数ｆｒ１（３３７Ｈｚ）に設定した第１共鳴室Ｓ１で好適に減音することができ、吸気音における前記２次気柱共鳴周波数ｆ２（６７４Ｈｚ）の音域を、前記共鳴周波数ｆｒ２（６７１Ｈｚ）に設定した第２共鳴室Ｓ２で好適に減音することができる。同様に、吸気音における前記３次気柱共鳴周波数ｆ３（１０２０Ｈｚ）の音域を、前記共鳴周波数ｆｒ３（１０２０Ｈｚ）に設定した第３共鳴室Ｓ３で好適に減音することができ、吸気音における前記４次気柱共鳴周波数ｆ４（１３５０Ｈｚ）の音域を、前記共鳴周波数ｆｒ４（１３４７Ｈｚ）に設定した第４共鳴室Ｓ４で好適に減音することができる。よって、設定例の吸気ダクト１０によれば、前記空気吸引口１４を介して外部空気を吸引する際に空気流通路１２内で発生する吸気音に対し、複数の周波数の音域を効果的に減音することが可能となる。
【００４５】
なお図１７では、前記連通口３６の開設位置を、前記第１〜第４の各共鳴室Ｓ１，Ｓ２，Ｓ３，Ｓ４における長手方向の略中央とした場合を例示しているが、該連通口３６の開設位置は、１次〜４次の各気柱共鳴のピーク位置に近い部位に開設するようにした方が効果的な減音が期待できる。
【００４６】
また前記設定例では、空気吸引口１４の側から第３共鳴室Ｓ３、第１共鳴室Ｓ１、第４共鳴室Ｓ４、第２共鳴室Ｓ２の順に配置するようにしたが、図１等に例示した実施例のように、空気吸引口１４の側から第１共鳴室Ｓ１、第２共鳴室Ｓ２、第３共鳴室Ｓ３、第４共鳴室Ｓ４の順に配置するようにしてもよい。
【００４７】
【発明の効果】
以上説明した如く、本発明に係る吸気ダクトによれば、一対のダクト構成体により、空気流通路および該空気流通路の外周に複数の共鳴室を画成した構造となっているため、エンジンルーム内に設置スペースを大きく確保する必要がない利点がある。また、前記一対のダクト構成体は、ブロー成形技術に基づいて一体的に形成されるために構成部品点数が大幅に削減される一方、単一サイズの連通口の開設個数に基づいて共鳴室と空気流通路との連通面積を設定するようにしため、部品点数削減および成形工程削減に伴う成形作業の合理化および効率化が図られて大幅な製造コストの低減が可能となる有益な効果を奏する。
更に、一対のダクト構成体を、相互に端部接合された連結状態に一体成形すれば、折曲ラインで折曲げて合掌的に接合するだけで両ダクト構成体の組立てが完了するため、組立作業工数の削減も図られてこれによる製造コストの低減も期待できる等の利点もある。
【図面の簡単な説明】
【図１】本発明の好適実施例に係る吸気ダクトの概略斜視図である。
【図２】図１のＩＩ−ＩＩ線断面図である。
【図３】図１のＩＩＩ−ＩＩＩ線断面図である。
【図４】図１のＩＶ−ＩＶ線断面図である。
【図５】図１のＶ−Ｖ線断面図である。
【図６】図１のＶＩ−ＶＩ線断面図である。
【図７】図１に例示した実施例の吸気ダクトを構成する一対のダクト構成体を、折曲して接合する前の展開状態で例示した概略斜視図である。
【図８】図１に例示した実施例の吸気ダクトを構成する一対のダクト構成体を、折曲して接合する前の展開状態で例示した平面図である。
【図９】一対のダクト構成体を展開状態でブロー成形する状態を示した説明断面図であって、（ａ）は、型開きしたブロー成形型にパリソンをセットした状態を示し、（ｂ）は、ブロー成形型を型閉めすることで一対のダクト構成体を成形した状態を示している。
【図１０】予備成形された一対のダクト構成体における内壁部に、穿孔装置により連通口を開設している状態を示した説明断面図である。
【図１１】連通口の開設が完了した後、両ダクト構成体を合掌状に接合することで、吸気ダクトの組立てが完了することを示した説明断面図である。
【図１２】別実施例に係る吸気ダクトの概略斜視図である。
【図１３】図１２のＸ−Ｘ線断面図である。
【図１４】更に別実施例に係る吸気ダクトの概略斜視図である。
【図１５】同一サイズの空気流通路を有する吸気ダクトにおいて、共鳴室を設けた場合と設けない場合の吸気音の減音量を示したグラフである。
【図１６】吸気ダクトにおける気柱共鳴のピーク部分を示した説明図であって、（ａ）は１次気柱共鳴を示し、（ｂ）は２次気柱共鳴を示し、（ｃ）は３次気柱共鳴を示し、（ｄ）は４次気柱共鳴を示している。
【図１７】設定例における吸気ダクトの構成および各部寸法を示した説明断面図である。
【符号の説明】
１２空気流通路
２０第１ダクト構成体（ダクト構成体）
２２第２ダクト構成体（ダクト構成体）
２８外壁部
３０内壁部
３２隔壁部
３４空間
３６連通口
５０穿孔装置（穿孔手段）
Ａ／Ａ１，Ａ２，Ａ３，Ａ４連通面積
ｆｒ／ｆｒ１，ｆｒ２，ｆｒ３，ｆｒ４共鳴周波数
Ｓ／Ｓ１，Ｓ２，Ｓ３，Ｓ４共鳴室
Ｖ／Ｖ１，Ｖ２，Ｖ３，Ｖ４内部容積[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an intake duct, and more particularly, is connected to an intake side of an engine mounted on an automobile or the like, and has a function of reducing intake noise generated when sucking external air necessary for the engine. It relates to the intake duct.
[0002]
[Prior art]
An engine mounted on an automobile or the like sucks external air necessary for rotational driving through an intake duct and an air cleaner connected to the intake side of the engine. Here, when the outside air is sucked from the intake duct, (1) the shape and size of the intake duct (full length, inner diameter, etc.), (2) the air suction amount and the suction speed, etc. Inspiratory sounds with various frequencies are generated, and there is a tendency that sound ranges of specific and plural frequencies are amplified especially with air column resonance. Therefore, as a measure to reduce such intake noise, many technologies have been proposed in which a resonator (resonator) that uses the resonance effect to reduce intake noise is installed at the required position of the intake duct. Has been. Techniques relating to such measures for reducing intake noise are disclosed in, for example, Patent Document 1 and Patent Document 2.
[0003]
An engine air intake device disclosed in Patent Document 1 is provided with a box-shaped resonator attached to an inlet pipe disposed between an air intake duct fixed to a vehicle body and an air cleaner in an externally attached state. It has become the composition. That is, the resonator is joined to the inlet pipe, which is regarded as a part of the intake duct, and is attached to a transmission, a water pipe, an air cleaner, and the like and fixed at a plurality of locations.
[0004]
In the resonator disclosed in Patent Document 2, an outer panel extending in the circumferential direction and the longitudinal direction with a predetermined distance from the outer surface of the intake pipe is assembled to the outer periphery of the intake pipe (intake duct). A space defined between the panel and the panel is made to function as a resonance chamber, and a resonance pipe is provided on the outer peripheral surface of the intake pipe to communicate the resonance chamber with the inside of the intake pipe. That is, the resonator is configured to be provided along the outside of the intake pipe.
[0005]
[Patent Document 1]
JP 2001-099026 A
[Patent Document 2]
JP-A-6-159174
[0006]
[Problems to be solved by the invention]
Incidentally, in the configuration disclosed in Patent Document 1, as described above, the resonator formed in a box shape is configured to be attached in an externally attached state. Must be secured in the room. However, because various in-vehicle devices such as engines are installed in the engine room, it is necessary to change the design of the entire engine room in order to secure the installation space for the resonator. Or inconvenient that it is difficult to secure the installation space in a vehicle having a small engine room. In addition, as described above, if a plurality of attachment locations are not set and firmly attached, there is a problem that an attachment failure occurs due to vibration during traveling.
[0007]
On the other hand, the configuration disclosed in Patent Document 2 has an advantage that a resonance chamber is formed on the outer periphery of the intake pipe, which does not hinder the securing of the installation space. However, the intake pipe and the outer panel are configured as separate members, and the outer panel is assembled to the intake pipe in a later process, and as the number of components increases, Since the number of attaching work man-hours and the like is increased, there is a problem that the manufacturing cost increases due to this.
[0008]
OBJECT OF THE INVENTION
The present invention has been proposed to suitably solve the above-mentioned problems, and it is possible to reduce the number of component parts, rationalize the molding operation, reduce the manufacturing cost based on this, and the like. It is an object of the present invention to provide an air intake duct configured to achieve efficient reduction.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and to achieve the intended purpose, the present invention is formed in a shape that can be opposed to each other along the longitudinal direction, and an air flow passage is defined inside when bonded together. A pair of duct components,
Each of the duct structures includes an outer wall portion having a required shape, an inner wall portion that is positioned inside the outer wall portion at an appropriate interval and that serves as the air flow passage at the time of joining, and the outer wall portion and the inner wall portion. A partition wall portion that is positioned at an appropriate interval in the longitudinal direction and extends in the short-side direction and internally defines a plurality of spaces between the outer wall portion and the inner wall portion,
In the inner wall portion, a communication port that spatially communicates each space and the air flow passage is opened correspondingly,
Each space communicating with the air flow passage via the communication port functions as a resonance chamber having mutually different resonance frequencies so that intake noise in the air flow passage can be reduced.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, an intake duct according to the present invention will be described below with reference to the accompanying drawings by way of preferred embodiments. The intake duct of the embodiment is disposed on the intake side of an engine mounted on an automobile or the like, for example, and is used to suck in air necessary for driving the engine. Resonance phenomenon
(Effect) is used for reduction (sound reduction). In the embodiment, in order to facilitate understanding, a simple straight cylindrical shape is illustrated and displayed.
[0011]
1 is a schematic perspective view of an intake duct according to a preferred embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is a sectional view taken along line III-III in FIG. 4 is a cross-sectional view taken along line IV-IV, FIG. 5 is a cross-sectional view taken along line V-V in FIG. 1, and FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. FIG. 7 is a schematic perspective view illustrating a pair of duct structures constituting the intake duct of the embodiment illustrated in FIG. 1 in an unfolded state before joining.
[0012]
The intake duct 10 of the embodiment is formed in a shape that can be joined oppositely along the longitudinal direction, and a pair of

duct structures

20, 22 in which the air flow passage 12 is defined inside when joined together. It is composed of An air suction port 14 is formed at one end edge (front side in FIG. 1), and an air outlet 16 is formed at the other end edge (back side in FIG. 1). For convenience of explanation, the duct structure 20 located on the lower side in FIG. 1 is referred to as a “first duct structure”, and the duct structure 22 located on the upper side is referred to as a “second duct structure”.
[0013]
(Duct structure)
The first duct structure 20 and the second duct structure 22 are made of a synthetic resin such as polypropylene (PP), for example, and are hollow bodies formed on the basis of a known blow molding technique as will be described later. . Specifically, as illustrated in FIG. 7, all of them have a bowl shape with a semicircular end surface shape, and a contact joint surface extending in the longitudinal direction at both end edges spaced apart in the lateral direction. 24, 24 are formed. In the embodiment, as will be described later, after the first duct structure 20 and the second duct structure 22 are integrally blow-molded in a connected state in which end portions thereof are joined to each other, the first duct structure 20 And it becomes the mode which joins oppositely by bending with the bending line 26 extended along the boundary line of the 2nd duct structure 22, Thereby, the cylindrical said intake duct 10 is formed. ing.
[0014]
The first duct structure body 20 and the second duct structure body 22 formed by blow molding are positioned on the inner side of the outer wall portion 28 having a required shape and at an appropriate interval with respect to the outer wall portion 28. It has the inner wall part 30 used as the air flow path 12, and the partition part 32 which is located in the longitudinal direction at appropriate intervals between the outer wall part 28 and the inner wall part 30, and extends in the short direction. The partition wall 32 protrudes from the inner wall 30 so as to be in contact with the back surface of the outer wall 28, and a total of three partition walls 32 are provided in the first duct structure 20 and the second duct structure 22, respectively, at required intervals. Each one is protruding. Accordingly, the first duct structure 20 and the second duct structure 22 include a total of four

spaces

34, 34, 34, partitioned by the partition walls 32 between the inner wall 30 and the outer wall 28. 34 are defined in series in the longitudinal direction. However, in the embodiment, all the partition walls 32 are projected at the same interval, and the internal volume of each space 34 is illustrated in the same state.
[0015]
(Communication entrance)
Further, each of the inner wall portions 30 in the first duct structure 20 and the second duct structure 22 has

spaces

34, 34, 34, 34 at positions facing the

spaces

34, 34, 34, 34. And a plurality of communication ports 36 that spatially communicate with the air flow passage 12 are opened correspondingly. Here, all the communication ports 36 opened in the inner wall portion 30 have the same opening shape and opening size, and the respective opening areas are equal. Therefore, the communication areas A1, A2, A3, A4 between the

spaces

34, 34, 34, 34 and the air flow passage 12 are set based on the number of the communication ports 36, as will be described later.
[0016]
In the intake duct 10 according to the embodiment including the first duct structure 20 and the second duct structure 22, each of the

spaces

34, 34, 34, 34 is provided via one or a plurality of communication ports 36. Since the air flow passage 12 is spatially communicated with each other, the

spaces

34, 34, 34, 34 can function as the resonance chamber S so that the intake noise in the air flow passage 12 can be reduced. It has become. For convenience of explanation, the first resonance chamber S1, the second resonance chamber S2, the third resonance chamber S3, and the fourth resonance chamber S4 are defined from the side adjacent to the air suction port 14 (the front side in FIG. 1). However, in the intake duct 10 of the embodiment, since the first duct structure 20 and the second duct structure 22 are formed as independent hollow bodies having a symmetrical shape, two first resonance chambers are provided. S1, the second resonance chamber S2, the third resonance chamber S3, and the fourth resonance chamber S4 are provided.
[0017]
(Resonance frequency)
Here, as is well known, the resonance frequency of the resonator (resonator) in the duct can be calculated based on the following calculation formula.
[0018]
[Expression 1]

[0019]
Each code in the calculation formula is as follows.
fr: resonance frequency (Hz)
C: Sound speed 340 × 10 ³ (Mm / s)
V: Internal volume of the resonance chamber S (mm ³ )
G: Conductivity
Le = t + (π / 2) a
A: Communication area (mm ² ),
(In the case of the radius a (mm) of the communication port 36 and the number n: nπa ² )
t: Wall thickness of the inner wall 30 (length of the communication port 36) (mm)
[0020]
According to the calculation formula, it can be understood that the wide and narrow setting conditions of the communication area A and the large and small setting conditions of the internal volume V are greatly related to the resonance frequency fr. That is, the resonance frequencies fr1, fr2, fr3, and fr4 of the first resonance chamber S1, the second resonance chamber S2, the third resonance chamber S3, and the fourth resonance chamber S4 are the internal volumes V1, V2, V3, and V4, respectively. These are determined according to the setting conditions such as the communication areas A1, A2, A3, A4 and the like set according to the number of the communication ports 36 opened.
[0021]
The internal volumes V1, V2, V3, V4 of the first resonance chamber S1, the second resonance chamber S2, the third resonance chamber S3, and the fourth resonance chamber S4 are formed in a blow mold 40 that is used for blow molding. It can be set by setting the shape of the surface. For example, when the distance between the outer wall portion 28 and the inner wall portion 30 is constant, the first to fourth resonance chambers S1, S2, S3, S4 are adjusted by adjusting the formation positions of the partition walls 32. The internal volume V1, V2, V3, V4 can be changed. Further, when the formation interval of each partition wall 32 is constant, the internal volume V1, of each resonance chamber S1, S2, S3, S4 is adjusted by adjusting the formation interval between the outer wall 28 and the inner wall 30. The setting of V2, V3, and V4 can be changed.
[0022]
On the other hand, the communication areas A1, A2, A3, and A4 of the first resonance chamber S1, the second resonance chamber S2, the third resonance chamber S3, and the fourth resonance chamber S4 are the perforating apparatus illustrated in FIG. It can be set by the number of the communication ports 36 opened by the (perforating means) 50. That is, when it is necessary to set the communication areas A1, A2, A3, and A4 to be large, it is only necessary to increase the number of the communication ports 36, and conversely, it is necessary to set the communication areas A1, A2, A3, and A4 to be small. If there is, the number of the communication openings 36 may be reduced.
[0023]
Next, a method for forming the intake duct 10 of the embodiment configured as described above will be described.
[0024]
(Duct structure forming process)
The air intake duct 10 of the embodiment is based on the blow molding technique using the blow molding die 40 schematically shown in FIG. 9, and the first duct component 20 and the second duct component 22 are first joined to each other in an end-to-side manner. It integrally molds to the connected state (FIGS. 7 and 8). That is, the blow mold 40 is provided with a first mold 42 having a first molding surface 42A provided in the

depressions

42B and 42B and used for molding the outer wall 28, and

projections

44B and 44B. It is comprised from the 2nd shaping | molding die 44 which has the 2nd shaping | molding surface 44A with which the said inner wall part 30 and the said partition part 32 are shape | molded. Therefore, after the parison P is set with the first mold 42 and the second mold 44 opened (FIG. 9A), the first mold 42 and the second mold 44 are closed. At the same time, by blowing molding air into the parison P, the first duct structure 20 and the second duct structure 22 are integrally preformed in an open connection state in which end portions are joined side by side to each other. (FIG. 9B).
[0025]
(Opening process of communication port)
When the preforming of the first duct structure 20 and the second duct structure 22 is completed, the communication port 36 is opened at a required position of the inner wall portion 30 of each

duct structure

20, 22. Each communication port 36 is the same as the inner wall portion 30 of the first duct structure 20 and the second duct structure 22 by using, for example, a perforating apparatus (perforating means) 50 illustrated in FIG. Opening shape and opening size. Here, the perforating apparatus 50 includes a pivotable main body 52, a perforating rod 54 which is slidably disposed on the main body 52 and is provided with a perforating member 56 which is heated and heated at the tip, and the perforating member 56. It is comprised from the heating means etc. which are not shown in figure. In the opening operation of the communication port 36 by such a drilling device 50, the main body 52 is positioned at the arc center of the first duct structure 20 and the second duct structure 22, and the punching member 56 heated by the heating means is used. Is pressed against the inner wall 30 under the forward movement of the perforating rod 54, the communication port 36 can be opened. Therefore, each time the main body 52 is swung and stopped at a required swivel angle, the perforating rod 54 is advanced to open a predetermined number of communication ports 36 in series in the short direction with respect to the inner wall portion 30. obtain.
[0026]
Then, the main body 52 is slid by a predetermined amount in the longitudinal direction of the first duct structure 20 and the second duct structure 22, and the above-described operations are repeated, so that the first to fourth resonance chambers S1, A communication port 36 can be opened for the inner wall 30 at a position corresponding to S2, S3, and S4. That is, if the turning control and the sliding control of the main body 52 are appropriately performed, the communication port 36 can be freely opened at any part of the inner wall portion 30.
[0027]
(Joint process for each duct component)
When the required number of communication ports 36 have been drilled in the required positions of the inner wall 30 corresponding to the first to fourth resonance chambers S1, S2, S3, S4, the first duct structure 20 and the second duct constituent body 22 are bent in a palm-like manner along a folding line 26 extending along these boundary lines, so that the abutting

joint surfaces

24, 24 of both duct

constituent bodies

20, 22 are joined together. Correspondingly, the two

duct components

20 and 22 are joined together. The first duct structure 20 and the second duct structure 22 are joined so as not to be easily separated and opened by a known means such as an appropriate engagement means or an adhesive (not shown).
[0028]
As described above, in the intake duct 10 according to the embodiment, the first duct structure 20 and the second duct structure 22 provide the air flow passage 12 and a plurality of resonance chambers S1, S2, S3, S4 on the outer periphery of the air flow passage 12. Therefore, it is not necessary to secure a large installation space in the engine room, and it is not necessary to examine the mounting form of the resonance chambers S1, S2, S3, and S4. The problem inherent in 1 can be preferably avoided.
[0029]
Moreover, since the said 1st duct structure 20 and the 2nd duct structure 22 which comprise the air intake duct 10 are integrally formed based on blow molding technique, it is a component compared with the structure currently disclosed by patent document 2 The score has been greatly reduced. In addition, the communication areas A1, A2, A3, and A4 between the first to fourth resonance chambers S1, S2, S3, and S4 and the air flow passage 12 are based on the number of the communication ports 36 having a single size. The opening operation of the communication port 36 can be efficiently performed by the punching device 50. Accordingly, when the intake duct 10 of the embodiment is formed, the number of parts and the forming operation associated with the reduction of the forming process can be rationalized and improved, and the manufacturing cost can be greatly reduced. Furthermore, since the assembly of the first duct structure 20 and the second duct structure 22 is completed simply by joining them together at the folding line 26, the number of assembling operations can be reduced, thereby reducing the manufacturing cost. Can also be expected.
[0030]
Further, the intake duct 10 having various shapes can be formed by changing the shapes of the first molding surface 42A and the second molding surface 44A of the blow molding die 40. Accordingly, the number of resonance chambers S to be formed, the internal volume V, and the like can be freely set, and the communication area A between the resonance chamber S and the air flow passage 12 is also freely controlled by the operation control of the perforating apparatus 50. Can be set to Therefore, it is possible to provide a plurality of resonance chambers S having different resonance frequencies fr, and it is possible to suitably reduce the sound range of a plurality of frequencies in the intake sound generated in the air flow passage 12.
[0031]
On the other hand, the method for forming the intake duct 10 is not limited to the one described above. For example, the first duct structure 20 and the second duct structure 22 are different from the blow mold 40 illustrated in FIG. Under the use of a blow molding die, blow molding may be performed individually as a completely separated separate body, and after the opening operation of the communication port 36 by the punching device 50 is completed, they may be joined to each other. .
[0032]
In the above embodiment, the intake duct 10 in which the first duct structure 20 and the second duct structure 22 are formed in a symmetrical shape is exemplified. However, the first duct structure 20 and the second duct structure 22 are illustrated. May be formed in an asymmetric shape. And the 1st duct structure 20 and the 2nd duct structure 22 change each resonance chamber S1, by changing the external shape, or changing the shape of the said outer wall part 28, and / or the formation position of the partition part 32. The internal volumes V1, V2, V3, and V4 of S2, S3, and S4 may be set non-uniformly, or the number of defined resonance chambers S may be changed by increasing or decreasing the number of partition walls 32 formed. Furthermore, the resonance chamber S may be defined inside only one of the first duct structure 20 and the second duct structure 22.
[0033]
Further, in the embodiment, the case where the respective partition walls 32 are integrally formed on the inner wall portion 30 is exemplified, but as shown in FIGS. 12 and 13, the partition walls 32 are formed on the outer wall portion 28. You may make it form. Even if the partition wall portion 32 is formed on the outer wall portion 28 as described above, the resonance chambers S1, S2, S3, and S4 are preferably defined as long as the partition wall portion 32 is in proper contact with the inner side of the inner wall portion 30. Can be made. And since the inner wall part 30 becomes a smooth surface over the whole region of the airflow path 12, the smooth circulation of suction air can be expected.
[0034]
Furthermore, in the said Example, although the case where each of the said 1st duct structure 20 and the 2nd duct structure 22 was made into the independent hollow body was illustrated, for example, as illustrated in FIG. , 24 may be cut by post-processing, and the first duct structure 20 and the second duct structure 22 may be joined in a palm-like shape. In this case, since a cylindrical space is defined from the first duct structure 20 to the second duct structure 22, it is possible to internally define the resonance chamber S having a large internal volume V. It becomes.
[0035]
On the other hand, in the above embodiment, the case where the communication port 36 is opened while the inner wall portion 30 is melted by the punching member 56 by the punching device 50 configured to heat the punching member 56 to a predetermined temperature is illustrated. The opening method of the communication port 36 is not limited to this. For example, the piercing member 56 may be a drill-type rotary blade, and the communication port 36 may be opened while cutting the inner wall portion 30.
[0036]
(Setting Example)
Next, one specific setting example is illustrated for the intake duct 10 of the embodiment configured as described above. Here, the intake duct of the form illustrated in FIG. 14, that is, the first to fourth resonance chambers S 1, S 2, S 3, S 4, extends from the first duct structure 20 to the second duct structure 22. The description will be made on the assumption that the intake duct is of a cylindrical type. In addition, the dimension of the said air flow path 12 formed by each

inner wall part

30 and 30 in the said 1st duct structure 20 and the 2nd duct structure 22 is as follows.
-The total length L of the air flow passage 12 is 400 mm,
・ Inner diameter D of air flow passage 12 = 54 mm
And
[0037]
In the intake duct 10 having the air flow passage 12 having the above-described dimensions, when the resonance chamber is not provided, the air column resonance frequency f obtained by the air column resonance test based on speaker excitation is as illustrated in FIG. The primary air column resonance frequency f1 = 338 Hz, the secondary air column resonance frequency f2 = 674 Hz, the third air column resonance frequency f3 = 1,020 Hz, and the fourth air column resonance frequency f4 = 1,350 Hz. That is, it can be confirmed that the intake sound when the air is sucked through the intake duct 10 is amplified in the sound range at the plurality of frequencies.
[0038]
Therefore, in the intake duct 10 of the embodiment, the sound range of the primary air column resonance frequency f1 is reduced in the first resonance chamber S1, and the sound range of the secondary air column resonance frequency f2 is reduced in the second resonance chamber S2. The sound range of the third air column resonance frequency f3 is reduced in the third resonance chamber S3, and the sound region of the fourth air column resonance frequency f4 is set to be reduced in the fourth resonance chamber S4. To do. Here, as exemplified in FIG. 16, the peak of the primary air column resonance is a portion of L / 2 (FIG. 16 (a)), and the peak of the secondary air column resonance is a portion of L / 4 and 3L / 4. (FIG. 16 (b)), the third-order column resonance peaks are L / 6, 3L / 6, and 5L / 6 portions (FIG. 16 (c)), and the fourth-order column resonance peak is L /. 8, 3L / 8, 5L / 8, and 7L / 8 (FIG. 16D). Therefore, in order to reduce the sound range of the first to fourth air column resonance frequencies f1 to f4, it is effective to perform at or near each peak portion. In the duct 10, as illustrated in FIG. 17, the third resonance chamber S3, the first resonance chamber S1, the fourth resonance chamber S4, and the second resonance chamber S2 are arranged in this order from the air suction port 14 side. .
[0039]
Since the inner diameter D of the air flow passage 12 is set to 54 mm, and the wall thickness t of the inner wall portion 30 is 3 mm, the first to fourth resonance chambers S1, S2, S3, The inner diameter of S4 (the outer diameter of the inner wall portion 30) P1 = 60 mm. Thereby, the outer diameter (inner diameter of the outer wall portion 28) P2 of each of the first to fourth resonance chambers S1, S2, S3, S4 was set to 71 mm. The length of each partition wall 32 is 4 mm, the thickness of the wall on the air suction port 14 side and the thickness of the wall on the air delivery port 16 side is 2 mm, respectively. Q1 = 99.5 mm, the indoor length Q2 of the second resonance chamber S2 = 100.0 mm, the indoor length Q3 of the third resonance chamber S3 = 97.5 mm, and the indoor length Q4 of the fourth resonance chamber S4 = 87.0 mm. Then, the formation position of each partition wall 32 was determined. As a result, as shown in Table 1, the internal volume V1 of the first resonance chamber S1 is 112, 614.1 mm. ³ The internal volume V2 of the second resonance chamber S2 = 113, 180.0 mm ³ The internal volume V3 of the third resonance chamber S3 = 110, 350.5 mm ³ The internal volume V4 of the fourth resonance chamber S4 is 98, 466.6 mm. ³ It has become.
[0040]
[Table 1]

[0041]
Then, based on the calculation formula, the first resonance chamber S1, the second resonance chamber S2, the third resonance chamber S3, and the fourth resonance chamber S4 have the corresponding first to fourth order air column resonance frequencies f1, f2. , F3, and f4, the respective communication areas A1, A2, A3, and A4 are calculated based on the internal volumes V1, V2, V3, and V4 so as to have the resonance frequencies fr1, fr2, fr3, and fr4. At the same time, based on these communication areas A1, A2, A3, and A4, the opening size and the number of openings of the communication port 36 were determined. That is, as illustrated in Table 2, the communication area A1 of the first resonance chamber S1 = 36.32 mm. ² The communication area A2 of the second resonance chamber S2 = 145.28 mm ² The communication area A3 of the third resonance chamber S3 = 326.88 mm ² The communication area A4 of the fourth resonance chamber S4 = 508.48 mm ² It was. Further, the communication port 36 has a circular shape with a diameter of 6.8 mm, and the communication areas A1 to A4 described above are ensured by the number of the communication ports 36 opened.
[0042]
Therefore, as illustrated in Table 2, in the first resonance chamber S1, the communication area A1 (= 36.32 mm) is established by opening one communication port 36 at a required position of the inner wall 30. ² In the second resonance chamber S2, the communication area A2 (= 145.28 mm) is established by opening the four communication ports 36 at the required positions on the inner wall 30. ² In the third resonance chamber S3, the communication area A3 (= 326.88 mm) is established by opening nine communication ports 36 at required positions on the inner wall 30. ² In the fourth resonance chamber S4, the communication area A4 (= 508.48 mm) is established by opening the 14 communication ports 36 at the required positions of the inner wall portion 30. ² ).
[0043]
[Table 2]

[0044]
With this setting, the resonance frequency fr1 of the first resonance chamber S1 is 337 Hz, the resonance frequency fr2 of the second resonance chamber S2 is 671 Hz, the resonance frequency fr3 of the third resonance chamber S3 is 1020 Hz, the resonance frequency of the fourth resonance chamber S4 is Resonance frequency fr4 is set to 1347 Hz, respectively, and matches or approximates the first to fourth-order air column resonance frequencies f1 (338 Hz), f2 (674 Hz), f3 (1,020 Hz), and f4 (1,350 Hz). It became so. Therefore, in the intake duct 10 of the embodiment provided with the first to fourth resonance chambers S1, S2, S3, S4 set to the above-described resonance frequencies fr1, fr2, fr3, fr4, as illustrated in FIG. Furthermore, the sound range of the primary air column resonance frequency f1 (338 Hz) in the intake sound can be suitably reduced in the first resonance chamber S1 set to the resonance frequency fr1 (337 Hz). The sound range of the secondary air column resonance frequency f2 (674 Hz) can be suitably reduced in the second resonance chamber S2 set to the resonance frequency fr2 (671 Hz). Similarly, the sound range of the tertiary air column resonance frequency f3 (1020 Hz) in the intake sound can be suitably reduced in the third resonance chamber S3 set to the resonance frequency fr3 (1020 Hz). The sound range of the fourth column resonance frequency f4 (1350 Hz) can be suitably reduced in the fourth resonance chamber S4 set to the resonance frequency fr4 (1347 Hz). Therefore, according to the intake duct 10 of the setting example, the sound range of a plurality of frequencies is effectively reduced with respect to the intake sound generated in the air flow passage 12 when the external air is sucked through the air suction port 14. It is possible to make a sound.
[0045]
FIG. 17 illustrates the case where the opening position of the communication port 36 is set to the approximate center in the longitudinal direction in each of the first to fourth resonance chambers S1, S2, S3, S4. It is possible to expect an effective sound reduction when the opening position 36 is set at a position close to the peak position of each of the first to fourth air column resonances.
[0046]
In the setting example, the third resonance chamber S3, the first resonance chamber S1, the fourth resonance chamber S4, and the second resonance chamber S2 are arranged in this order from the air suction port 14 side. As in the embodiment, the first resonance chamber S1, the second resonance chamber S2, the third resonance chamber S3, and the fourth resonance chamber S4 may be arranged in this order from the air suction port 14 side.
[0047]
【The invention's effect】
As described above, the intake duct according to the present invention has a structure in which a plurality of resonance chambers are defined on the outer periphery of the air flow passage and the air flow passage by the pair of duct structures. There is an advantage that it is not necessary to secure a large installation space inside. In addition, since the pair of duct structures are integrally formed based on the blow molding technique, the number of components is greatly reduced, while the resonance chamber and the resonance chamber are formed based on the number of open single-size communication ports. Since the communication area with the air flow passage is set, the number of parts and the molding operation associated with the reduction of the molding process can be rationalized and improved, and the manufacturing cost can be greatly reduced.
Furthermore, if the pair of duct components are integrally formed in a connected state in which the ends are joined to each other, the assembly of both duct components is completed simply by bending them at the folding line and joining them jointly. There is also an advantage that the number of work steps can be reduced and the manufacturing cost can be expected to be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of an intake duct according to a preferred embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
3 is a cross-sectional view taken along line III-III in FIG.
4 is a cross-sectional view taken along line IV-IV in FIG.
FIG. 5 is a cross-sectional view taken along line VV in FIG.
6 is a cross-sectional view taken along line VI-VI in FIG.
7 is a schematic perspective view illustrating a pair of duct structures constituting the intake duct of the embodiment illustrated in FIG. 1 in an unfolded state before being bent and joined. FIG.
FIG. 8 is a plan view illustrating a pair of duct structures constituting the intake duct of the embodiment illustrated in FIG. 1 in an unfolded state before being bent and joined.
FIG. 9 is an explanatory cross-sectional view showing a state in which a pair of duct components are blow-molded in an unfolded state, where (a) shows a state in which a parison is set in a blow-molded mold that has been opened; These show the state which shape | molded a pair of duct structure by closing a blow molding die.
FIG. 10 is an explanatory cross-sectional view showing a state in which a communication port is opened by a punching device in the inner wall portion of a pair of preformed duct structures.
FIG. 11 is an explanatory cross-sectional view showing that the assembly of the intake duct is completed by joining both duct components together in a palm shape after the opening of the communication port is completed.
FIG. 12 is a schematic perspective view of an intake duct according to another embodiment.
13 is a cross-sectional view taken along line XX in FIG.
FIG. 14 is a schematic perspective view of an intake duct according to another embodiment.
FIG. 15 is a graph showing the volume reduction of the intake sound with and without a resonance chamber in an intake duct having air flow passages of the same size.
FIGS. 16A and 16B are explanatory diagrams showing peak portions of air column resonance in the intake duct, where FIG. 16A shows primary air column resonance, FIG. 16B shows secondary air column resonance, and FIG. 3rd order air column resonance is shown, and (d) shows 4th order air column resonance.
FIG. 17 is an explanatory cross-sectional view showing the configuration and dimensions of each part of the intake duct in the setting example.
[Explanation of symbols]
12 Air flow passage
20 First duct structure (duct structure)
22 Second duct structure (duct structure)
28 Exterior wall
30 Inner wall
32 Bulkhead
34 space
36 Communication port
50 Punching device (Punching means)
A / A1, A2, A3, A4 communication area
fr / fr1, fr2, fr3, fr4 resonance frequency
S / S1, S2, S3, S4 resonance chamber
V / V1, V2, V3, V4 Internal volume

Claims

Formed of a pair of duct structures (20, 22) that are formed in shapes that can be opposed to each other along the longitudinal direction and in which the air flow passages (12) are defined when joined together,
Each of the duct structures (20, 22) is located on the inner side of the outer wall portion (28) having a required shape and an appropriate distance from the outer wall portion (28), and the air flow passage (12 Between the inner wall portion (30) and the outer wall portion (28) and the inner wall portion (30), which are positioned at appropriate intervals in the longitudinal direction and extend in the short direction, and the outer wall portion (28) and the inner wall A partition wall (32) that internally defines a plurality of spaces (34, 34, 34, 34) between the sections (30),
In the inner wall (30), a communication port (36) for spatially communicating the spaces (34, 34, 34, 34) and the air flow passage (12) is opened correspondingly.
Resonances having different resonance frequencies (fr / fr1, fr2, fr3, fr4) in the spaces (34, 34, 34, 34) communicating with the air flow passage (12) via the communication port (36). An intake duct that functions as a chamber (S / S1, S2, S3, S4) and is configured to reduce intake noise in the air flow passage (12).

The resonance frequency (fr1, fr2, fr3, fr4) of each resonance chamber (S / S1, S2, S3, S4) is the internal volume (V / V1) of the resonance chamber (S / S1, S2, S3, S4). , V2, V3, V4), the communication area (A / A1, A2, A3, A4) set by the communication port (36), and the like.

The communication ports (36) opened to correspond to the resonance chambers (S / S1, S2, S3, S4) have the same opening shape and opening size, and the communication ports (36) are opened. The intake air according to claim 2, wherein the communication area (A / A1, A2, A3, A4) of each resonance chamber (S / S1, S2, S3, S4) with respect to the air flow passage (12) is set according to the number. duct.

Each said communicating port (36) is opened in any one of Claims 1-3 using the perforation means (50) with respect to the inner wall part (30) of each said duct structure (20,22). Intake duct.

Each said duct structure (20, 22) is formed as a hollow body which internally defined each said resonance chamber (S / S1, S2, S3, S4) based on the blow molding technique. The intake duct according to any one of the above.

The intake duct according to claim 5, wherein each of the duct structures (20, 22) is joined to each other after being individually molded.

6. The air intake duct according to claim 5, wherein each of the duct structural bodies (20, 22) is integrally formed in a connected state in which end portions thereof are joined to each other, and then joined in an opposing manner by bending along the longitudinal direction.