JP3782596B2

JP3782596B2 - Insulated metal carrier for exhaust gas purification

Info

Publication number: JP3782596B2
Application number: JP35324898A
Authority: JP
Inventors: 雅幸糟谷; 裕一岡崎; 卓三加古; 篤比古今井; 史雄三治; 洋平山
Original assignee: Nippon Steel Corp; Toyota Motor Corp
Current assignee: Nippon Steel Corp; Toyota Motor Corp
Priority date: 1998-12-11
Filing date: 1998-12-11
Publication date: 2006-06-07
Anticipated expiration: 2018-12-11
Also published as: JP2000179332A

Description

【０００１】
【発明の属する技術分野】
本発明は、自動車エンジン等の内燃機関から排出される排ガスを浄化する触媒を担持するためのメタル担体に関するものである。
【０００２】
【従来の技術】
近年、自動車排ガス浄化用の触媒装置には排ガスの初期浄化能が優れていて排気抵抗の小さいメタル担体が使用されることが多くなっている。メタル担体は、金属平箔と金属平箔を長さ方向に波形形状の塑性加工した金属波箔とを重ね合せて、これを例えば渦巻状に巻き回して円筒形のハニカム体を構成し、このハニカム体を金属外筒等のケーシングに組み込んだ上で相互に接合したものが知られており、上記ハニカム体に触媒を担持して自動車排ガス浄化装置として使用している。
【０００３】
例えば、メタル担体は、耐熱性ステンレス鋼箔からなるハニカム体を金属製の外筒内に組み込んで製造されている。ハニカム体は、主として厚さ５０μｍ程度の帯状の平箔と、該平箔を波付け加工した帯状の波箔とを重ねて巻き回し、渦巻状にして製造される。渦巻状に巻回された円筒状のメタルハニカム体は、円柱の軸方向に多数の通気孔を有している。そして、この通気孔に触媒を担持させて触媒コンバータとしている。
【０００４】
触媒担体を自動車エンジンの排ガス系に搭載固定して使用するとき、エンジン稼働中は振動を受けるとともに、排ガス及び触媒反応により加熱される。メタル担体が加熱される際、排ガスの流速が大きいメタルハニカム体半径方向中心部が最も大きな入熱を受ける。一方、外筒は外気にさらされているため温度が低く、これに接しているメタルハニカム体外周部は外筒に熱を奪われる。また、ハニカム体の外周部は排ガス流速が小さいために入熱量も少ないので、ハニカム体外周部は中心部に比較して温度が低い。排ガスの触媒反応は触媒温度が高いほど進行するため、温度の低いハニカム体外周部は触媒反応効率がハニカム体中心部より低くなる。
【０００５】
また、ハニカム体の中心部と外周部との温度差、及びハニカム体と外筒との温度差により、メタルハニカム体の内部全体あるいはメタルハニカム体と外筒との接合部に、熱膨張差による応力が集中して、破断や座屈あるいは剥離などが生じるようになる。更にエンジン始動時や加速時には急速に加熱され、ブレーキ時や停車時には急速に冷却され、急加熱−急冷の熱サイクルが走行時に繰り返される。このような熱サイクルに伴って、メタル担体は膨張と収縮を繰り返す。急速加熱・冷却される際には、ハニカム体中心部とハニカム体外周部、外筒との間の温度差により、熱膨張差による応力が集中し、同様に破断、座屈、剥離などが生じるようになる。
【０００６】
ハニカム体から外筒へ流れる熱損失を低減するため、ハニカム体と外筒との間に断熱材を挿入する方法が知られている。また、ハニカム体の最外周部の何層かのセルに断熱物質を充填し、もって熱遮断を行う方法が特開平５−７５４３０号公報に開示されている。
【０００７】
特開平４−２３５７１７号公報においては、ハニカム体外周部と外筒との間に空間部を設け、ハニカム体と外筒との間はリング状弾性保持部材によって弾性変形自在に保持する方法が開示されている。ハニカム体と外筒との間に空間部を設けることでハニカム体から外筒への熱流を遮断し、かつハニカム体と外筒との間の熱膨張差をリング状弾性保持部材の弾性変形によって吸収し、熱応力の発生を防止している。特開平９−２６２４３８号公報では、上記に加え、ハニカム体と外筒との間の空間部を減圧することによって熱遮断を強化している。
【０００８】
特開昭６１−１７９４３６号公報、特開平９−１０８５７６号公報においては、ハニカム体を収容する内側の円筒部と、更にその外側に外側の円筒部を設け、内側の円筒部と外側の円筒部との間に空間部を設けて熱の流出を遮断する方法が開示されている。
【０００９】
特開平８−１９６９１７号公報においては、メタルハニカム体と外筒の双方が両端に縮径部を有し、該縮径部においてハニカム体と外筒とが密着し、縮径部間の拡径部においてはハニカム体と外筒との間に空間を有するメタル担体が開示されている。
【００１０】
実公平６−１０１３２号公報においては、両端に縮径部を有する外筒に２個のハニカム体がガス流れ方向に直列に配置され、各ハニカム体の一端が外筒の縮径部内壁面に固着された排気ガス浄化装置が開示されている。外筒の縮径部に固着された部分以外については、ハニカム体と外筒との間には空間部が存在する。外筒と固着されない側のハニカム体の端部は、外筒と固定せずに自由状態におくか、あるいはスペーサーによって保持される。
【００１１】
【発明が解決しようとする課題】
ハニカム体と外筒との間に断熱材を充填する方法においては、断熱材を使用することによるコストの増加が避けられない。長期間の使用において劣化しない断熱材を選択する必要もある。また、ハニカム体最外周部のセルに断熱材を充填する方法においては、本来排気ガスを浄化するためのセルをつぶすこととなり、また断熱材を充填してもハニカム体の箔を介しての熱伝導は残るので断熱効果も十分とはいえない。
【００１２】
ハニカム体と外筒との間に空間部を設け、両者をリング状弾性保持部材で結合する方法においては、加熱−冷却のサイクルの繰り返しによってリング状弾性保持部材が変形を繰り返しても破損しない保持部材を選択する必要があり、かかるリング状弾性保持部材の製造、及び該保持部材によるハニカム体と外筒との接合に伴うコストの増加が避けられない。
【００１３】
ハニカム体の外側に２重の円筒部を設ける方法においては、内側の円筒はハニカム体と接しているため、エンジン始動時にハニカム体から内側の円筒に熱を奪われ、始動初期のハニカム体の温度上昇を遅らせるという問題を解決することができない。また、２重の円筒部を設けるため、コストアップを避けることもできない。
【００１４】
ハニカム体と外筒の双方の両端に縮径部を設け、縮径部において両者を密接させる方法においては、ハニカム体の最外周部のセルがつぶされるので排ガス浄化に寄与するセルが減少するという問題があり、更に外筒の縮径部によってハニカム体の拡径部両端が拘束されているため、加熱時のハニカム体と外筒の熱膨張差が開放されず、熱応力が発生するという問題もある。
【００１５】
両端に縮径部を有する外筒に２個のハニカム体を直列に接続する方法においては、外筒と接合しない側のハニカム体が外筒に保持されないため、振動によってハニカム体の寿命が短縮するという問題がある。スペーサーによって外筒とハニカム体との間を保持する方法を採用すると、スペーサー設置に伴うコストアップを避けることができない。
【００１６】
本発明は、これらの問題点を解決し、コストアップとならず、ハニカム体のセルを無駄にせず、ハニカム体と外筒との熱膨張差を解消して熱応力の発生を防止しながら、ハニカム体から外筒への熱損失を防止できるメタル担体を提供することを目的とする。
【００１７】
また、熱ロスの低減したハニカム体外周部のセルへの排ガス供給量を増大し、排ガス浄化性能を向上したメタル担体を提供することを他の目的とする。
【００１８】
【課題を解決するための手段】
即ち、本発明の要旨とするところは、
（１）金属製平箔と該平箔にコルゲート加工を施した波箔とを交互に巻き回したハニカム体と、両端に縮径部を有する金属製外筒よりなり、該外筒の排ガス出側端面の縮径部の内面とハニカム体の外面を、ハニカム体軸方向の長さの 1/10 以上の長さで接合し、該外筒の排ガス入り側端面の縮径部の内面とハニカム体の外面を、該ハニカム体軸方向の長さの１／１００以上の長さで摺動可能に接し、両縮径部間における外筒の内面とハニカム体の外面を非接触とし、両縮径部間における外筒の内面とハニカム体の外面との間に空気断熱層を設けることを特徴とする排ガス浄化用メタル担体。
（２）金属製平箔と該平箔にコルゲート加工を施した波箔とを交互に巻き回したハニカム体と、両端に縮径部を有する金属製外筒よりなり、該外筒の排ガス出側端面の縮径部の内面とハニカム体の外面とを接合し、該外筒の排ガス入り側端面の縮径部の内面とハニカム体の外面とを摺動可能に接し、両縮径部間における外筒の内面とハニカム体の外面を非接触とし、両縮径部間における外筒の内面とハニカム体の外面との間に空気断熱層を設けた排ガス浄化用メタル担体において、
前記外筒の内面に面する前記ハニカム体外周部の箔以外を構成する箔の表面に多数の通気孔を有することを特徴とする排ガス浄化用メタル担体。
（３）前記空気断熱層の間隔を１ｍｍ〜５ｍｍとすることを特徴とする上記（１）または（２）に記載の排ガス浄化用メタル担体。
（４）前記ハニカム体の排ガス入り側端面形状を凸形状とし、排ガス出側端面形状を凹形状とすることを特徴とする請求項１乃至３のいずれかに記載の排ガス浄化用メタル担体。
（５）前記ハニカム体の上流部に、整流用ハニカム体を配設することを特徴とする上記（１）乃至（４）のいずれかに記載の排ガス浄化用メタル担体。
である。
【００１９】
本発明においては、図１に示すように、金属製の外筒２は両端に縮径部３、４を有し、縮径部の内径はハニカム体１の外径と略等しくする。金属製外筒の排ガス出側端面の縮径部４の内面とハニカム体１の外面とをろう付け、ないしは拡散接合によって接合する。外筒の排ガス入り側端面の縮径部３の内面とハニカム体１の外面とは摺動可能に接している。ハニカム体はハニカム体の軸に垂直方向の応力に対してはハニカム体両端において外筒の両縮径部に支持される。また、ハニカム体の軸に平行な方向の応力に対しては排ガス出側の接合部７によって外筒２に支持されている。一方、ハニカム体１と外筒２との温度差に伴う熱膨張差が発生しても、ハニカム体１が排ガス入り側端面の縮径部３において摺動可能となっているため、熱応力を発生することがない。
【００２０】
外筒２の両端の縮径部ではさまれた胴部５については、外筒内周部とハニカム体外周部との間には空間部（空気断熱層）６が存在するので、この空間によってハニカム体１から外筒２への熱伝導が妨げられ、ハニカム体からの熱ロスを低減することができる。ハニカム体と外筒との間に空間部６があるため、定常運転中のハニカム体からの熱ロスが低減できるだけでなく、エンジン始動時においても熱容量の大きい外筒２がハニカム体１に接していないためにハニカム体１の温度上昇が速く、エンジン始動後いち早く排ガスの浄化を開始することができる。
【００２１】
本発明においては、リング状弾性保持部材やスペーサーを用いることなくハニカム体を外筒によって支持することができるので、コストを上昇させることなく上記機能を確保することができる。また、ハニカム体外周部に縮径部を設けたりセルに断熱材を充填することがないので、ハニカム体のセルの全体を排ガスの浄化に用いることができる。
【００２２】
本発明においては、更にハニカム体外周部のセル内の排ガス流速を増大し、ハニカム体外周部を有効に排ガス浄化に用いることができる。従来のようにハニカム体の外周部からの熱ロスが大きいメタル担体においては、たとえハニカム体外周部のセル内排ガス流速を増大したとしても、ハニカム体外面からの熱損失が大きいために触媒の温度が十分に上昇せず、結局は効率良くハニカム体外周部セルによって排ガス浄化を行うことができなかった。これに対し、本発明においてはハニカム体１と外筒２との間に空間部６を有するためにハニカム体外周面からの熱ロスが少ないので、ハニカム体外周部のセル内排ガス流速を増大すれば、外周部においても十分に効率の高い排ガス浄化を行うことが可能になった。
【００２３】
図２に示すように、ハニカム体１を構成する箔の表面に多数の通気孔１４を形成することにより、ハニカム体の隣合うセル間での排ガスの流通が可能になる。その結果、ハニカム体排ガス入り側ではハニカム体中心部のセルに流れる排ガスが多くても、ハニカム体内部で排ガスが中央のセルから外周部のセルに移動し、ハニカム体半径方向に排ガス流速を均一化し、ハニカム体外周部のセルを有効に利用することができる。箔の表面の通気孔１４は、ハニカム体外面に面する箔の表面には設けない。これにより、排ガスがハニカム体外面からハニカム体と外筒との間の空間部６に流出することを防止できる。
【００２４】
図３に示すように、ハニカム体１の排ガス入り側端面の形状を凸形状とすると、該端面を平面とした場合と比較してハニカム体半径方向の排ガス流速分布を均一化し、外周部のセル内排ガス流速を増大することができる。これによっても上記と同様ハニカム体外周部セルの排ガス浄化効率を向上することができる。
【００２５】
図４に示すように、排ガス浄化用のハニカム体１の上流側に整流用ハニカム体１１を配設することにより、同じようにハニカム体半径方向の排ガス流速分布を均一化し、排ガス浄化用ハニカム体外周部のセル内排ガス流速を増大することができる。これによって上記と同じ効果を得ることができる。
【００２６】
【発明の実施の形態】
本発明のメタル担体は、図１に示すように、ハニカム体１が金属製の外筒２内に組み込まれている。ハニカム体１は、耐熱性ステンレス鋼からなる帯状の平箔と、この平箔を波付け加工した帯状の波箔とを重ねて巻き回し、渦巻状にして製造される。渦巻状に巻回された円筒状のハニカム体１は、平箔と波箔との接触部の全部又は一部を接合し、円柱の軸方向に多数のセルを有している。
【００２７】
ハニカム体１の材料としては、耐熱性合金元素としてＡｌ３〜１０％、Ｃｒ１５〜２５％を含有するフェライト系ステンレス鋼、例えば２０％Ｃｒ−５％Ａｌ−Ｆｅ鋼が採用される。また外筒２用の材料としては、ハニカム体１ほどの耐熱性は要求されないので、Ａｌ等の耐熱性合金元素を含有しないステンレス鋼を採用してもよい。
【００２８】
外筒２はその両端に縮径部３、４を有する。縮径部の内径はハニカム体１の外径と略等しい。ハニカム体１を外筒２に組み込み、排ガス出側端部においてハニカム体外面と外筒縮径部４の内面の相接している部分を接合する。接合は、ろう付けないしは拡散接合によって行うことができる。排ガス入り側端部においては、ハニカム体外面ともう一方の縮径部３の内面とが相接する。縮径部３の内径をハニカム体１の外径と同等か若干大きくすることにより、ハニカム体１は縮径部３において摺動可能に保持される。外筒の両縮径部にはさまれた胴部５は、その内径がハニカム体外径よりも大きく、ハニカム体と外筒とを組合わせた状態で両者の間に空間部６が形成される。
【００２９】
排ガス出側を接合部７とし、排ガス入り側を摺動部８とするのは以下の理由からである。即ち、排ガス出側を接合部７にする理由は、排ガスに直接さらされる入り側のハニカム体１あるいは外筒２の温度変化に対し、出側のハニカム体あるいは外筒の温度は変化が少なく、熱応力が入り側に比べて発生しにくいため、及び出側を接合部にすればハニカム体の保持寿命が入り側を接合して保持する場合に比べて格段に向上するからである。また、排ガス入り側を摺動部８とする理由は、温度変化が激しく発生する入り側の外筒とハニカム体で発生する熱歪を外筒とハニカム体を非接合にすることで軸方向、径方向ともに開放する必要があるからである。さらに、ハニカム体を摺動可能で外筒内面と接する理由は、ハニカム体の振動を外筒の両端の接触面で抑えて防止し、ハニカム体の保持寿命をさらに延ばすとともに、触媒コート時に空間部６への触媒浸入を防止することができるからである。
【００３０】
ハニカム体１を外筒２によって十分に支持するためには、外筒両端の縮径部におけるハニカム体との接触部を確保する必要がある。排ガス出側端部においては、外筒縮径部４内面とハニカム体１外面とのメタル担体軸方向接触長さを、ハニカム体１長さの１／１０以上とすることにより、ハニカム体１を強固に外筒２によって支持することができる。接合は、ろう付けあるいは固体拡散接合等の手段を用いて行う。
【００３１】
一方、排ガス入り側端部においては、排ガスの流れる方向に垂直な応力に対してハニカム体１を支持できればよいので、常温においてハニカム体１外面と外筒縮径部３の内面とがわずかでも接していれば本発明の機能を発揮することができる。ハニカム体１と外筒２との製作精度、組立精度を考慮すると、外筒の縮径部３内面とハニカム体１外面とのメタル担体軸方向接触長さがハニカム体長さの１／１００以上であれば目的を達成することができる。
【００３２】
上記の両縮径部の長さ条件を満足し、かつ上記ハニカム体１と外筒２とが接しない空間部６の面積をできるかぎり広くとることで、ハニカム体と外筒との間の断熱効果を得ることができる。
【００３３】
両縮径部の間の胴部５におけるハニカム体１と外筒２との間の間隔は、狭すぎると断熱効果が十分ではなく、本発明の効果が十分には発揮できない。一方、該間隔を大きくしようとすると、メタル担体を収容する部位のスペースからメタル担体の外径は制約されるため、結局ハニカム体１の直径を小さくせざるをえず、排ガス浄化性能を十分に発揮できなくなる。胴部５における外筒内面とハニカム体外面との間の間隔を１ｍｍ〜５ｍｍとすることにより、本発明の効果を最も良好に発揮することができる。
【００３４】
メタル担体が接続される排気管の内径はハニカム体外径に比較して小さいので、ハニカム体の上流側には排気管からの径拡大部９、下流側には径縮小部１０を設ける。径拡大部９、径縮小部１０とメタル担体の外筒２とはそれぞれ別個に製造し、外筒２にハニカム体１を組み込んだ後に外筒の縮径部端部と径拡大部９、径縮小部１０とを接合することができる。もちろん、外筒２と径拡大部９、あるいは外筒２と径縮小部１０を一体に製作し、これにハニカム体を組み込むことも可能である。
【００３５】
通常のメタル担体触媒コンバータにおいては、排気管から径拡大部９を経てハニカム体排ガス流入側端面に到達した排ガスの流速分布は、径拡大部９で十分に広がることができず、ハニカム体入り側端部において、ハニカム体中心部の排ガス流速が速く、ハニカム体周辺部の流速は遅い。本発明においてはハニカム体周辺部における外部への熱ロスが減少しているので、ハニカム体周辺部へも十分な流速の排ガスを供給することができれば、周辺部セルでも高い温度が確保されてハニカム体全体が均一な浄化能力を有することとなり、排ガス浄化効率を一層増大することが可能になる。
【００３６】
本発明では、図２に示すように、ハニカム体１を構成する箔の表面に多数の通気孔１４を形成することにより、ハニカム体の隣合うセル間での排ガスの流通が可能になる。その結果、ハニカム体排ガス入り側ではハニカム体中心部のセルに流れる排ガスが多くても、ハニカム体内部で排ガスが中央のセルから外周部のセルに移動し、ハニカム体半径方向に排ガス流速を均一化し、ハニカム体外周部のセルを有効に利用することができる。箔の表面の通気孔１４は、ハニカム体外面に面する箔の表面には設けない。これにより、排ガスがハニカム体外面からハニカム体と外筒との間の空間部６に流出することを防止できる。
【００３７】
従来、ハニカム体の排ガス流入側端面形状として平面が採用されていたが、本発明においては更に、図３に示すように、ハニカム体排ガス流入側端面を凸形状とすることにより、ハニカム体外周部セルにおける排ガス流速を増大することができる。凸形状としては、円錐状、ドーム状等の形状から選択することができる。ハニカム体端面形状を凸形状とすることにより、端面の中心部は径拡大部の空間部１２内に入り込み、これによって径拡大部内における排気ガス流れが影響を受け、ハニカム体の外周部のセルにも排気ガスが十分に供給されるようになったものと考えられる。
【００３８】
以上述べてきたハニカム体は触媒反応を起こさせるためのハニカム体１であり、以後整流用ハニカム体１１と区別するためにメインハニカム体１とよぶ。
【００３９】
本発明においては、図４に示すようにメインハニカム体１の上流に整流用ハニカム体１１を配設することにより、メインハニカム体１の排ガス流速分布を均一化し、ハニカム体外周部セルの排ガス流速を増大することができる。これにより、本発明においてはハニカム体周辺部における外部への熱ロスが減少しているので、周辺部セルでも高い温度が確保されてハニカム体全体が均一な浄化能力を有することとなり、排ガス浄化効率を一層増大することが可能になる。整流用ハニカム体１１は排ガスの整流化が目的なので、熱ロスを防ぐために極力その厚みを薄くする。整流用ハニカム体１１の形状としては、図５（ａ）に示す平面形状、同図（ｂ）に示すドーム形状、同図（ｃ）に示す円錐形状等を採用することができる。
【００４０】
整流用ハニカム体１１の形状毎の整流化効果は、平面形状よりもドーム形状、円錐形状の方が優れた効果を有する。ドーム形状、円錐形状の場合は、整流用ハニカム体の排ガス流入側端面が凸形状となるので、該端面の中央部は径拡大部の空間部１２内に入り込み、これによって径拡大部内における排気ガス流れが影響を受け、整流用ハニカム体の外周部のセルにも排気ガスが十分に供給されるようになったものと考えられる。更に、整流用ハニカム体１１の排ガス出側端面形状が凹形状となるため、整流用ハニカム体１１とメインハニカム体１との間には十分な空間部１３が形成され、この空間部１３において排ガスが混合するためにメインハニカム体入り側における排ガスの流速が均一化されるものと考えられる。また、整流用ハニカム体１１の剛性も、平面形状よりもドーム形状、円錐形状の方が優れている。
【００４１】
本発明の排気ガス流入側の端面が凸形状を有するメインハニカム体１、あるいは整流用ハニカム体１１の端面形状は、ハニカム体の中心部を通る断面の外縁部における表面の接線と、排気ガス流路と直交する線との間の角度θは６０°以下とすることが好ましい。６０°を超えると、第１に整流用ハニカム体の平箔と波箔との軸方向の重なり代（ラップ代）が少なくなり、半径方向の圧縮及び引張力に対抗するハニカム剛性が低下する。そのため、ハニカム体が熱や応力によって容易に変形したり、排ガスの脈動で振動したりして破壊しやすくなり、耐久性が圧下する。また第２に、径拡大部とハニカム体の外周部との空間が狭くなり、排気ガスが外周部へ供給されにくくなるため、整流化効果が低下するからである。
【００４２】
上記角度θは、より好ましくは２０°〜４５°とする。２０°未満では半径方向の熱応力が解放されにくくなるために耐久性の向上効果が低減すると同時に、凸型が偏平に近くなるため、凸型の形状効果が低下し、整流化効果が薄まるからである。またθを４５°以下とすることでハニカム体の耐久性、整流化効果ともに最良の結果を得ることができる。
【００４３】
【実施例】
自動車のエンジンマニホールドのすぐ下流側に配置するメタル担体触媒コンバーターにおいて本発明を実施した。ハニカム体は、いずれも厚み２０μｍのステンレス鋼平箔と該平箔をコルゲート加工した波箔とを巻き回し、該平箔と波箔との接触部をろう付け接合することによって形成した。ハニカム体（メインハニカム体）１は、幅１００ｍｍのステンレス鋼平箔と波箔とを円筒形に巻き回し、直径１００ｍｍ、長さ１００ｍｍの円筒形に成形した。外筒２は、厚み１．５ｍｍのステンレス製円筒を用い、両端に内径１００ｍｍの縮径部、中央に内径１０６ｍｍの胴部を有する。排ガス入り側縮径部長さは１０ｍｍ、排ガス出側縮径部長さは３０ｍｍ、胴部の長さは６０ｍｍである。
【００４４】
整流用ハニカム体１１については、厚み３０μｍのステンレス鋼平箔と波箔とを巻き回して円筒形のハニカム体とし、次いで前記ハニカム体を該ハニカム体の中心線に直交する面で複数に切断し、該切断したハニカム体の外周に厚み１．５ｍｍのステンレス鋼の外筒を配し、次いで該切断したハニカム体を凹治具と凸治具とでプレスすることにより該ハニカム体の一方の面は凸型の形状とし他方の面は凹型の形状とし、その後に該平箔と波箔との接触部をろう付け接合することによって形成した。
【００４５】
本発明例１においては、図１に示すように、排ガス出側縮径部４におけるハニカム体１との接触部長さは２５ｍｍとし、ろう付けによって外筒２とハニカム体１を接合した。排ガス入り側縮径部３においては、ハニカム体１と縮径部３とは長さ５ｍｍにわたって接触している。
【００４６】
本発明例２を図２に示す。ハニカム体１と外筒２との接続は本発明例１と同様である。ハニカム体１を構成する平箔及び波箔には予め直径２ｍｍの通気孔１４を１個／ｃｍ²の密度で配置し、この平箔と波箔とを巻き回してハニカム体とした。ハニカム体の最外周の平箔には通気孔は設けていない。その他の条件は本発明例１と同様である。
【００４７】
本発明例３は、図６に示す形状のハニカム体１に、更に本発明例２と同様の通気孔１４を配設した平箔と波箔とを用いたものである。本発明例３のハニカム体１は、排ガス入り側端面が凸形状、出側端面が凹形状をなし、端面の円錐形の陵線と、排気ガス流路と直交する線との間の角度θは３０度である。その他の条件は本発明例１と同様である。
【００４８】
本発明例４を図７に示す。本発明例３と同様のメインハニカム体１と外筒２との組合わせの排ガス上流側に、厚み１０ｍｍの整流用ハニカム体１１を配置した。整流用ハニカム体１１の排ガス入り側端面、出側端面は円錐形をなし、端面の円錐形の陵線と、排気ガス流路と直交する線との間の角度θは４５度である。本発明例に用いる径拡大部９は、整流用ハニカム体１１を収容するために円筒部の長さが他の発明例に比較して長くなっている。径拡大部９と外筒２との間を溶接接合することにより、整流用ハニカム体１１はメタル担体内に収容される。
【００４９】
比較例として、外筒２に内径１００ｍｍの円筒を用いたメタル担体を採用した。ハニカム体１の外周部全体において外筒と接触している。
【００５０】
本発明例１〜４及び比較例をエンジンの排気ガス系に設置し、メタル担体の昇温特性、降温特性、浄化性能の比較を行った。昇温特性、降温特性は、ハニカム体の外周部から２層内側のハニカム体長さ中央部の温度を測定し、昇温特性についてはコールドスタート後５０秒における当該部の温度により、降温特性については排ガス流入停止１０分後の当該部の温度により評価した。浄化性能については、エンジン始動時のメタル担体の初期浄化性能を調査するために、ＨＣ５０％浄化率到達時間によって評価した。
【００５１】
評価結果を表１に示す。
【００５２】
【表１】

【００５３】
昇温特性評価における外周部のハニカム体温度について、本発明例は比較例に対していずれも昇温速度が速く、本発明例の中では本発明例４、３、２、１の順で昇温特性が良好であった。本発明のハニカム体と外筒との間の断熱効果によって昇温速度が上昇し、更に本発明例２、３、４においてはハニカム体外周部排ガス流速向上対策効果が上乗せされ、一層の昇温速度の上昇が実現した。
【００５４】
降温特性については、本発明例はいずれも比較例に対して良好であった。本発明のハニカム体と外筒との間の断熱効果によるものである。
【００５５】
ＨＣ浄化性能については、本発明例４が最も優れており、以下本発明例３、２、１の順で、比較例が最も悪い成績であった。
【００５６】
【発明の効果】
本発明は、外筒内周面とハニカム体外周面との間に空気断熱層が存在し、この空気断熱層の面積を広くすることができるので、この空気断熱層によってハニカム体から外筒への熱伝導が妨げられ、ハニカム体からの熱ロスを低減することができる。定常運転中のハニカム体からの熱ロスが低減できるだけでなく、エンジン始動時においてもハニカム体の温度上昇が速く、エンジン始動後いち早く排ガスの浄化を開始することができる。
【００５７】
本発明においては、リング状弾性保持部材やスペーサーを用いることなくハニカム体を外筒によって支持することができるので、コストを上昇させることなく上記機能を確保することができる。また、ハニカム体外周部に縮径部を設けたりセルに断熱材を充填することがないので、ハニカム体のセルの全体を排ガスの浄化に用いることができる。
【００５８】
本発明においては、ハニカム体の断熱効果に加え、外筒の内面に面する前記ハニカム体外周部の箔以外を構成する箔の表面に多数の通気孔を有することにより、ハニカム体外周部のセル内の排ガス流速を増大し、ハニカム体外周部を更に有効に排ガス浄化に用いることができる。
さらに、ハニカム体外周部の排ガス流速増大手段として、ハニカム体排ガス入り側端部を凸形状とする方法、ハニカム体排ガス入り側に整流用ハニカム体を配置する方法を採用することができる。これらの相乗効果により、ハニカム体外周部の昇温特性を更に向上し、定常運転時においてもハニカム体外周部の温度を高温に保ち、メタル担体の浄化性能を向上することができた。
【図面の簡単な説明】
【図１】本発明のメタル担体の断面図である。
【図２】本発明のメタル担体の断面図である。
【図３】本発明のメタル担体の断面図である。
【図４】本発明のメタル担体の断面図である。
【図５】本発明の整流用ハニカム体の断面図であり、（ａ）は平面形状、（ｂ）はドーム形状、（ｃ）は円錐形状のものを示す。
【図６】本発明のメタル担体の断面図である。
【図７】本発明のメタル担体の断面図である。
【符号の説明】
１ハニカム体（メインハニカム体）
２外筒
３縮径部（排ガス入り側）
４縮径部（排ガス出側）
５胴部
６空間部
７接合部
８非接合部（摺動部）
９径拡大部
１０径縮小部
１１整流用ハニカム体
１２、１３空間部
１４通気孔
１５外筒[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal carrier for supporting a catalyst for purifying exhaust gas discharged from an internal combustion engine such as an automobile engine.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a catalyst carrier for purifying automobile exhaust gas is often used with a metal carrier that has excellent exhaust gas initial purification ability and low exhaust resistance. The metal carrier is composed of a metal flat foil and a metal corrugated metal foil that is formed by corrugated plastic processing in the length direction and wound into a spiral shape to form a cylindrical honeycomb body. It is known that a honeycomb body is incorporated in a casing such as a metal outer cylinder and joined to each other. A catalyst is supported on the honeycomb body and used as an automobile exhaust gas purification device.
[0003]
For example, the metal carrier is manufactured by incorporating a honeycomb body made of a heat-resistant stainless steel foil into a metal outer cylinder. The honeycomb body is manufactured in a spiral shape by mainly winding a strip-shaped flat foil having a thickness of about 50 μm and a strip-shaped corrugated foil obtained by corrugating the flat foil. A cylindrical metal honeycomb body wound in a spiral shape has a large number of air holes in the axial direction of the column. A catalyst is supported on the vent hole to form a catalytic converter.
[0004]
When the catalyst carrier is mounted and fixed on an exhaust gas system of an automobile engine, the catalyst carrier is subjected to vibration during operation of the engine and is heated by exhaust gas and catalytic reaction. When the metal carrier is heated, the central portion in the radial direction of the metal honeycomb body where the flow rate of the exhaust gas is large receives the largest heat input. On the other hand, since the outer cylinder is exposed to the outside air, the temperature is low, and the outer peripheral portion of the metal honeycomb body in contact with the outer cylinder is deprived of heat by the outer cylinder. Moreover, since the outer peripheral portion of the honeycomb body has a small exhaust gas flow rate, the amount of heat input is also small, so the outer peripheral portion of the honeycomb body has a lower temperature than the central portion. Since the catalytic reaction of exhaust gas proceeds as the catalyst temperature increases, the outer peripheral portion of the honeycomb body having a low temperature has a lower catalytic reaction efficiency than the central portion of the honeycomb body.
[0005]
Further, due to the temperature difference between the central portion and the outer peripheral portion of the honeycomb body and the temperature difference between the honeycomb body and the outer cylinder, the entire inside of the metal honeycomb body or the joint portion between the metal honeycomb body and the outer cylinder is caused by the difference in thermal expansion. Stress concentrates, causing breakage, buckling or peeling. Further, the engine is rapidly heated when the engine is started or accelerated, rapidly cooled when the engine is braked or stopped, and the rapid heating / cooling thermal cycle is repeated during traveling. With such a heat cycle, the metal carrier repeatedly expands and contracts. During rapid heating / cooling, the stress due to the difference in thermal expansion is concentrated due to the temperature difference between the center of the honeycomb body, the outer periphery of the honeycomb body, and the outer cylinder, and similarly breakage, buckling, peeling, etc. occur. It becomes like this.
[0006]
In order to reduce the heat loss flowing from the honeycomb body to the outer cylinder, a method of inserting a heat insulating material between the honeycomb body and the outer cylinder is known. Japanese Laid-Open Patent Publication No. 5-75430 discloses a method in which a plurality of cells in the outermost peripheral portion of a honeycomb body are filled with a heat insulating material to thereby block heat.
[0007]
Japanese Patent Application Laid-Open No. 4-235717 discloses a method in which a space is provided between the outer peripheral portion of the honeycomb body and the outer cylinder, and the honeycomb body and the outer cylinder are held elastically deformable by a ring-shaped elastic holding member. Has been. By providing a space between the honeycomb body and the outer cylinder, the heat flow from the honeycomb body to the outer cylinder is blocked, and the difference in thermal expansion between the honeycomb body and the outer cylinder is caused by the elastic deformation of the ring-shaped elastic holding member. Absorbs and prevents the generation of thermal stress. In Japanese Patent Laid-Open No. 9-262438, in addition to the above, heat insulation is enhanced by reducing the pressure of the space between the honeycomb body and the outer cylinder.
[0008]
In JP-A-61-179436 and JP-A-9-108576, an inner cylindrical part for accommodating a honeycomb body and an outer cylindrical part on the outer side are provided, and an inner cylindrical part and an outer cylindrical part are provided. A method of blocking the outflow of heat by providing a space between the two.
[0009]
In Japanese Patent Application Laid-Open No. 8-196917, both the metal honeycomb body and the outer cylinder have reduced diameter portions at both ends, and the honeycomb body and the outer cylinder are in close contact with each other at the reduced diameter portion, and the diameter between the reduced diameter portions is increased. In the section, a metal carrier having a space between the honeycomb body and the outer cylinder is disclosed.
[0010]
In Japanese Utility Model Publication No. 6-10132, two honeycomb bodies are arranged in series in the gas flow direction in an outer cylinder having a reduced diameter portion at both ends, and one end of each honeycomb body is fixed to the inner wall surface of the reduced diameter portion of the outer cylinder. An exhaust gas purification device is disclosed. Except for the portion fixed to the reduced diameter portion of the outer cylinder, there is a space between the honeycomb body and the outer cylinder. The end of the honeycomb body that is not fixed to the outer cylinder is left in a free state without being fixed to the outer cylinder, or is held by a spacer.
[0011]
[Problems to be solved by the invention]
In the method of filling a heat insulating material between the honeycomb body and the outer cylinder, an increase in cost due to the use of the heat insulating material is inevitable. It is also necessary to select a heat insulating material that does not deteriorate during long-term use. In addition, in the method of filling the cells in the outermost peripheral portion of the honeycomb body with the heat insulating material, the cells for purifying the exhaust gas are basically crushed. Since conduction remains, the heat insulation effect is not sufficient.
[0012]
In a method in which a space is provided between the honeycomb body and the outer cylinder and the both are joined by a ring-shaped elastic holding member, the ring-shaped elastic holding member is held without being damaged even if the ring-shaped elastic holding member is repeatedly deformed by repeated heating and cooling cycles It is necessary to select a member, and an increase in cost associated with the production of such a ring-shaped elastic holding member and the joining of the honeycomb body and the outer cylinder by the holding member is inevitable.
[0013]
In the method of providing the double cylindrical portion on the outside of the honeycomb body, the inner cylinder is in contact with the honeycomb body, and therefore, when the engine is started, heat is taken from the honeycomb body to the inner cylinder, and the temperature of the honeycomb body at the initial stage of startup The problem of delaying the rise cannot be solved. Moreover, since a double cylindrical part is provided, an increase in cost cannot be avoided.
[0014]
In the method in which the diameter-reduced portions are provided at both ends of the honeycomb body and the outer cylinder, and the cells are closely contacted with each other in the diameter-reduced portion, the cells at the outermost peripheral portion of the honeycomb body are crushed, so the number of cells contributing to exhaust gas purification is reduced. There is a problem, and since the both ends of the enlarged diameter portion of the honeycomb body are constrained by the reduced diameter portion of the outer cylinder, the thermal expansion difference between the honeycomb body and the outer cylinder during heating is not released and thermal stress is generated. There is also.
[0015]
In the method in which two honeycomb bodies are connected in series to an outer cylinder having a diameter-reduced portion at both ends, the honeycomb body on the side not joined to the outer cylinder is not held by the outer cylinder, so that the lifetime of the honeycomb body is shortened by vibration. There is a problem. If the method of holding the space between the outer cylinder and the honeycomb body by the spacer is adopted, the cost increase accompanying the spacer installation cannot be avoided.
[0016]
The present invention solves these problems, does not increase the cost, does not waste the cells of the honeycomb body, eliminates the thermal expansion difference between the honeycomb body and the outer cylinder, and prevents the occurrence of thermal stress, An object of the present invention is to provide a metal carrier capable of preventing heat loss from the honeycomb body to the outer cylinder.
[0017]
Another object of the present invention is to provide a metal carrier having an increased exhaust gas supply amount to cells on the outer peripheral portion of the honeycomb body with reduced heat loss and improved exhaust gas purification performance.
[0018]
[Means for Solving the Problems]
That is, the gist of the present invention is that
(1) A honeycomb body in which a metal flat foil and corrugated corrugated foils are alternately wound, and a metal outer cylinder having reduced diameter portions at both ends, The inner surface of the reduced diameter portion of the side end surface and the outer surface of the honeycomb bodyThe length of the honeycomb body in the axial direction 1/10 Over the lengthThe inner surface of the reduced diameter portion of the end surface containing the exhaust gas of the outer cylinder and the outer surface of the honeycomb bodyWith a length of 1/100 or more of the length in the axial direction of the honeycomb bodyIt is slidably in contact, and the inner surface of the outer cylinder and the outer surface of the honeycomb body are not in contact with each other between the reduced diameter portions.In addition, an air heat insulating layer is provided between the inner surface of the outer cylinder and the outer surface of the honeycomb body between both reduced diameter portions.A metal carrier for exhaust gas purification characterized by the above.
(2)A honeycomb body obtained by alternately winding a flat metal foil and a corrugated corrugated foil foil, and a metal outer cylinder having reduced diameter portions at both ends, the exhaust gas exhaust side end face of the outer cylinder The inner surface of the reduced diameter portion and the outer surface of the honeycomb body are joined, and the inner surface of the reduced diameter portion on the exhaust gas containing side end surface of the outer cylinder and the outer surface of the honeycomb body are slidably contacted, and the outer cylinder between the two reduced diameter portions In the metal carrier for exhaust gas purification in which the inner surface of the honeycomb body and the outer surface of the honeycomb body are not in contact with each other, and an air heat insulating layer is provided between the inner surface of the outer cylinder and the outer surface of the honeycomb body between both reduced diameter portions,
An exhaust gas purifying metal carrier having a large number of air holes on the surface of a foil constituting other than the foil on the outer peripheral portion of the honeycomb body facing the inner surface of the outer cylinder.
(3)Of the air insulation layer(1), wherein the interval is 1 mm to 5 mmOr (2)A metal carrier for purifying exhaust gas as described in 1.
(4The exhaust gas-containing side end face shape of the honeycomb body is a convex shape, and the exhaust gas outlet side end face shape is a concave shape.1 to 3The metal carrier for exhaust gas purification as described.
(5) The honeycomb bodyuponFlowPart(1) to (1) above, wherein a rectifying honeycomb body is provided.4The metal carrier for exhaust gas purification according to any one of the above.
It is.
[0019]
In the present invention, as shown in FIG. 1, the metal outer cylinder 2 has reduced

diameter portions

3 and 4 at both ends, and the inner diameter of the reduced diameter portion is substantially equal to the outer diameter of the honeycomb body 1. The inner surface of the reduced diameter portion 4 on the exhaust gas outlet side end surface of the metal outer cylinder and the outer surface of the honeycomb body 1 are joined by brazing or diffusion bonding. The inner surface of the reduced diameter portion 3 on the exhaust gas containing side end surface of the outer cylinder and the outer surface of the honeycomb body 1 are slidably in contact with each other. The honeycomb body is supported by both reduced diameter portions of the outer cylinder at both ends of the honeycomb body against stress in a direction perpendicular to the axis of the honeycomb body. Further, against the stress in the direction parallel to the axis of the honeycomb body, it is supported on the outer cylinder 2 by the joint 7 on the exhaust gas outlet side. On the other hand, even if a thermal expansion difference due to the temperature difference between the honeycomb body 1 and the outer cylinder 2 occurs, the honeycomb body 1 is slidable at the reduced diameter portion 3 on the end surface containing the exhaust gas. It does not occur.
[0020]
About the trunk | drum 5 pinched by the reduced diameter part of the both ends of the outer cylinder 2, it is a space part between an outer cylinder inner peripheral part and a honeycomb body outer peripheral part.(Air insulation layer)6 exists, this space prevents heat conduction from the honeycomb body 1 to the outer cylinder 2, and heat loss from the honeycomb body can be reduced. Since there is a space 6 between the honeycomb body and the outer cylinder, not only the heat loss from the honeycomb body during steady operation can be reduced, but also the outer cylinder 2 having a large heat capacity is in contact with the honeycomb body 1 even when the engine is started. Therefore, the temperature rise of the honeycomb body 1 is fast, and the exhaust gas purification can be started as soon as the engine is started.
[0021]
In the present invention, since the honeycomb body can be supported by the outer cylinder without using a ring-shaped elastic holding member or spacer, the above function can be ensured without increasing the cost. In addition, since the diameter-reduced portion is not provided on the outer periphery of the honeycomb body and the cells are not filled with a heat insulating material, the entire cells of the honeycomb body can be used for exhaust gas purification.
[0022]
In the present invention, the exhaust gas flow rate in the cells on the outer periphery of the honeycomb body can be further increased, and the outer periphery of the honeycomb body can be used effectively for exhaust gas purification. In the conventional metal carrier having a large heat loss from the outer peripheral portion of the honeycomb body, even if the exhaust gas flow rate in the cell at the outer peripheral portion of the honeycomb body is increased, the heat loss from the outer surface of the honeycomb body is large. As a result, the exhaust gas purification could not be performed efficiently by the honeycomb body outer peripheral cell. In contrast, in the present invention, since the space portion 6 is provided between the honeycomb body 1 and the outer cylinder 2, heat loss from the outer peripheral surface of the honeycomb body is small, so that the exhaust gas flow rate in the cell at the outer peripheral portion of the honeycomb body is increased. In this way, it has become possible to perform exhaust gas purification with sufficiently high efficiency even at the outer periphery.
[0023]
As shown in FIG. 2, by forming a large number of air holes 14 on the surface of the foil constituting the honeycomb body 1, the exhaust gas can be circulated between adjacent cells of the honeycomb body. As a result, even if there is a lot of exhaust gas flowing into the cells in the center of the honeycomb body on the honeycomb body exhaust gas entry side, the exhaust gas moves from the center cell to the outer peripheral cell inside the honeycomb body, and the exhaust gas flow rate is uniform in the radial direction of the honeycomb body. Thus, the cells on the outer periphery of the honeycomb body can be used effectively. The air holes 14 on the surface of the foil are not provided on the surface of the foil facing the outer surface of the honeycomb body. Thereby, exhaust gas can be prevented from flowing out from the outer surface of the honeycomb body to the space 6 between the honeycomb body and the outer cylinder.
[0024]
As shown in FIG. 3, when the end face of the honeycomb body 1 on the exhaust gas entering side has a convex shape, the exhaust gas flow velocity distribution in the honeycomb body radial direction is made uniform as compared with the case where the end face is a flat surface. The internal exhaust gas flow rate can be increased. Also by this, the exhaust gas purification efficiency of the honeycomb body outer peripheral cell can be improved as described above.
[0025]
As shown in FIG. 4, by arranging the rectifying honeycomb body 11 on the upstream side of the exhaust gas purification honeycomb body 1, the exhaust gas flow velocity distribution in the radial direction of the honeycomb body is similarly uniformed, and the exhaust gas purification honeycomb body outside The exhaust gas flow velocity in the cell in the periphery can be increased. As a result, the same effect as described above can be obtained.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
In the metal carrier of the present invention, as shown in FIG. 1, a honeycomb body 1 is incorporated in a metal outer cylinder 2. The honeycomb body 1 is manufactured in a spiral shape by laminating a strip-shaped flat foil made of heat-resistant stainless steel and a strip-shaped corrugated foil obtained by corrugating the flat foil. The cylindrical honeycomb body 1 wound in a spiral shape joins all or part of the contact portion between the flat foil and the corrugated foil, and has a large number of cells in the axial direction of the cylinder.
[0027]
As the material of the honeycomb body 1, ferritic stainless steel containing Al 3 to 10% and Cr 15 to 25% as a heat resistant alloy element, for example, 20% Cr-5% Al—Fe steel is adopted. Further, as the material for the outer cylinder 2, since the heat resistance as high as that of the honeycomb body 1 is not required, stainless steel not containing a heat-resistant alloy element such as Al may be adopted.
[0028]
The outer cylinder 2 has reduced

diameter portions

3 and 4 at both ends thereof. The inner diameter of the reduced diameter portion is substantially equal to the outer diameter of the honeycomb body 1. The honeycomb body 1 is incorporated into the outer cylinder 2, and the contact portion between the outer surface of the honeycomb body and the inner surface of the outer cylinder diameter-reduced portion 4 is joined at the exhaust gas outlet side end. Bonding can be performed by brazing or diffusion bonding. At the end portion containing the exhaust gas, the outer surface of the honeycomb body and the inner surface of the other reduced diameter portion 3 are in contact with each other. By making the inner diameter of the reduced diameter portion 3 equal to or slightly larger than the outer diameter of the honeycomb body 1, the honeycomb body 1 is slidably held in the reduced diameter portion 3. The trunk portion 5 sandwiched between the reduced diameter portions of the outer cylinder has an inner diameter larger than the outer diameter of the honeycomb body, and a space 6 is formed between the honeycomb body and the outer cylinder in a combined state. .
[0029]
The exhaust gas outlet side is the joining portion 7 and the exhaust gas inlet side is the sliding portion 8 for the following reason. That is, the reason why the exhaust gas outlet side is the joint 7 is that the temperature of the outlet honeycomb body or outer cylinder 2 is less changed with respect to the temperature change of the inlet honeycomb body 1 or outer cylinder 2 exposed directly to the exhaust gas, This is because thermal stress is less likely to occur compared to the entrance side, and if the exit side is a joined portion, the retention life of the honeycomb body is significantly improved compared to the case where the entrance side is joined and retained. Further, the reason why the exhaust gas containing side is the sliding portion 8 is that the thermal strain generated in the outer cylinder and the honeycomb body on which the temperature change is severely generated is axially removed by non-joining the outer cylinder and the honeycomb body, This is because it is necessary to open both in the radial direction. Furthermore, the reason why the honeycomb body is slidable and in contact with the inner surface of the outer cylinder is to prevent the vibration of the honeycomb body from being suppressed at the contact surfaces at both ends of the outer cylinder, further extending the retention life of the honeycomb body, and This is because it is possible to prevent the catalyst from entering 6.
[0030]
In order to sufficiently support the honeycomb body 1 by the outer cylinder 2, it is necessary to secure contact portions with the honeycomb body at the reduced diameter portions at both ends of the outer cylinder. At the exhaust gas outlet end, the metal carrier axial contact length between the inner surface of the outer cylinder reduced diameter portion 4 and the outer surface of the honeycomb body 1 is 1/10 or more of the length of the honeycomb body 1, thereby It can be firmly supported by the outer cylinder 2. The joining is performed using means such as brazing or solid diffusion joining.
[0031]
On the other hand, at the exhaust gas side end, it is only necessary to support the honeycomb body 1 against stress perpendicular to the flow direction of the exhaust gas, so that the outer surface of the honeycomb body 1 and the inner surface of the outer cylinder reduced diameter portion 3 are in slight contact at room temperature. If so, the functions of the present invention can be exhibited. Considering the manufacturing accuracy and assembly accuracy of the honeycomb body 1 and the outer cylinder 2, the metal carrier axial contact length between the inner surface of the reduced diameter portion 3 of the outer cylinder and the outer surface of the honeycomb body 1 is 1/100 or more of the honeycomb body length. If you can, you can achieve your goals.
[0032]
Heat insulation between the honeycomb body and the outer cylinder is achieved by satisfying the length conditions of the both reduced diameter parts and by taking as large an area as possible the space 6 where the honeycomb body 1 and the outer cylinder 2 do not contact each other. An effect can be obtained.
[0033]
If the space between the honeycomb body 1 and the outer cylinder 2 in the body portion 5 between the two reduced diameter portions is too narrow, the heat insulating effect is not sufficient, and the effect of the present invention cannot be sufficiently exhibited. On the other hand, if the interval is increased, the outer diameter of the metal carrier is restricted due to the space of the part that accommodates the metal carrier, so that the diameter of the honeycomb body 1 must be reduced eventually, and the exhaust gas purification performance is sufficiently improved. Cannot be demonstrated. By setting the distance between the inner surface of the outer cylinder and the outer surface of the honeycomb body in the body portion 5 to 1 mm to 5 mm, the effect of the present invention can be most effectively exhibited.
[0034]
Since the inner diameter of the exhaust pipe to which the metal carrier is connected is smaller than the outer diameter of the honeycomb body, a diameter enlarged portion 9 from the exhaust pipe is provided on the upstream side of the honeycomb body and a diameter reduced section 10 is provided on the downstream side. The diameter-enlarging part 9, the diameter-reducing part 10 and the outer cylinder 2 of the metal carrier are manufactured separately, and after the honeycomb body 1 is incorporated in the outer cylinder 2, the diameter-reduced part end of the outer cylinder, the diameter-enlarging part 9, and the diameter The reduction part 10 can be joined. Of course, it is also possible to manufacture the outer cylinder 2 and the diameter-enlarged portion 9 or the outer cylinder 2 and the diameter-reduced portion 10 integrally, and to incorporate the honeycomb body into this.
[0035]
In an ordinary metal-supported catalytic converter, the flow velocity distribution of the exhaust gas that has reached the honeycomb body exhaust gas inflow side end surface from the exhaust pipe through the diameter enlarged portion 9 cannot be sufficiently widened by the diameter enlarged portion 9, At the end, the exhaust gas flow rate at the center of the honeycomb body is high, and the flow rate at the periphery of the honeycomb body is low. In the present invention, heat loss to the outside in the peripheral portion of the honeycomb body is reduced, so if exhaust gas with a sufficient flow rate can be supplied to the peripheral portion of the honeycomb body, a high temperature is secured even in the peripheral cells. The entire body has a uniform purification capacity, and the exhaust gas purification efficiency can be further increased.
[0036]
In the present invention, as shown in FIG. 2, by forming a large number of vent holes 14 on the surface of the foil constituting the honeycomb body 1, the exhaust gas can be distributed between the adjacent cells of the honeycomb body. As a result, even if there is a lot of exhaust gas flowing into the cells in the center of the honeycomb body on the honeycomb body exhaust gas entry side, the exhaust gas moves from the center cell to the outer peripheral cell inside the honeycomb body, and the exhaust gas flow rate is uniform in the radial direction of the honeycomb body. Thus, the cells on the outer periphery of the honeycomb body can be used effectively. The air holes 14 on the surface of the foil are not provided on the surface of the foil facing the outer surface of the honeycomb body. Thereby, exhaust gas can be prevented from flowing out from the outer surface of the honeycomb body to the space 6 between the honeycomb body and the outer cylinder.
[0037]
Conventionally, a flat surface has been adopted as the exhaust gas inflow side end face shape of the honeycomb body. However, in the present invention, as shown in FIG. The exhaust gas flow rate in the cell can be increased. The convex shape can be selected from shapes such as a conical shape and a dome shape. By making the end face shape of the honeycomb body convex, the center part of the end face enters the space part 12 of the enlarged diameter part, and this affects the exhaust gas flow in the enlarged diameter part, and the cells on the outer peripheral part of the honeycomb body are affected. It is considered that the exhaust gas is sufficiently supplied.
[0038]
The honeycomb body described above is a honeycomb body 1 for causing a catalytic reaction, and is hereinafter referred to as a main honeycomb body 1 to be distinguished from the rectifying honeycomb body 11.
[0039]
In the present invention, as shown in FIG. 4, by arranging a rectifying honeycomb body 11 upstream of the main honeycomb body 1, the exhaust gas flow velocity distribution of the main honeycomb body 1 is made uniform, and the exhaust gas flow velocity of the outer peripheral cells of the honeycomb body is Can be increased. As a result, in the present invention, heat loss to the outside in the peripheral part of the honeycomb body is reduced, so that a high temperature is secured even in the peripheral cells, and the entire honeycomb body has a uniform purification capacity, and exhaust gas purification efficiency Can be further increased. Since the rectifying honeycomb body 11 is intended to rectify exhaust gas, its thickness is made as thin as possible to prevent heat loss. As the shape of the rectifying honeycomb body 11, a planar shape shown in FIG. 5A, a dome shape shown in FIG. 5B, a conical shape shown in FIG.
[0040]
The rectification effect for each shape of the rectifying honeycomb body 11 is more excellent in the dome shape and the conical shape than in the planar shape. In the case of a dome shape or a conical shape, the exhaust gas inflow side end face of the rectifying honeycomb body has a convex shape, so that the central portion of the end face enters the space portion 12 of the enlarged diameter portion, thereby exhaust gas in the enlarged diameter portion. It is considered that the exhaust gas was sufficiently supplied to the cells on the outer periphery of the rectifying honeycomb body due to the influence of the flow. Further, since the exhaust gas outlet side end face shape of the rectifying honeycomb body 11 is concave, a sufficient space portion 13 is formed between the rectifying honeycomb body 11 and the main honeycomb body 1, and the exhaust gas is exhausted in the space portion 13. It is considered that the flow rate of the exhaust gas on the main honeycomb body entrance side is made uniform because of mixing. Further, the rigidity of the rectifying honeycomb body 11 is more excellent in the dome shape and the conical shape than in the planar shape.
[0041]
The end face shape of the main honeycomb body 1 having the convex end face on the exhaust gas inflow side or the rectifying honeycomb body 11 according to the present invention is such that the tangent of the surface at the outer edge portion of the cross section passing through the central part of the honeycomb body and the exhaust gas flow It is preferable that the angle θ between the road and the orthogonal line is 60 ° or less. When the angle exceeds 60 °, firstly, the overlapping allowance (lap allowance) between the flat foil and the corrugated foil of the rectifying honeycomb body is reduced, and the honeycomb rigidity against the compressive and tensile forces in the radial direction is lowered. Therefore, the honeycomb body is easily deformed by heat and stress, or is vibrated by the pulsation of the exhaust gas, so that the honeycomb body is easily broken and the durability is reduced. Second, the space between the enlarged diameter portion and the outer peripheral portion of the honeycomb body is narrowed, and exhaust gas is hardly supplied to the outer peripheral portion, so that the rectification effect is reduced.
[0042]
The angle θ is more preferably 20 ° to 45 °. If the angle is less than 20 °, the thermal stress in the radial direction becomes difficult to be released, so that the effect of improving durability is reduced. At the same time, the convex shape is nearly flat, so the convex shape effect is reduced and the rectification effect is diminished. It is. Further, by setting θ to 45 ° or less, the best results can be obtained for both the durability and the rectifying effect of the honeycomb body.
[0043]
【Example】
The present invention was implemented in a metal-supported catalytic converter located immediately downstream of an automobile engine manifold. The honeycomb bodies were each formed by winding a stainless steel flat foil having a thickness of 20 μm and a corrugated corrugated foil, and brazing and joining the contact portions of the flat foil and corrugated foil. A honeycomb body (main honeycomb body) 1 was formed by winding a stainless steel flat foil having a width of 100 mm and a corrugated foil into a cylindrical shape and having a diameter of 100 mm and a length of 100 mm. The outer cylinder 2 uses a stainless steel cylinder having a thickness of 1.5 mm, and has a reduced diameter portion having an inner diameter of 100 mm at both ends and a barrel portion having an inner diameter of 106 mm at the center. The length of the exhaust gas containing side reduced diameter portion is 10 mm, the length of the exhaust gas outlet side reduced diameter portion is 30 mm, and the length of the body portion is 60 mm.
[0044]
For the rectifying honeycomb body 11, a stainless steel flat foil having a thickness of 30 μm and a corrugated foil are wound to form a cylindrical honeycomb body, and then the honeycomb body is cut into a plurality of planes perpendicular to the center line of the honeycomb body. The outer surface of the cut honeycomb body is provided with a stainless steel outer cylinder having a thickness of 1.5 mm, and then the cut honeycomb body is pressed with a concave jig and a convex jig to thereby provide one surface of the honeycomb body. Is formed in a convex shape and the other surface is formed in a concave shape, and then the contact portion between the flat foil and the corrugated foil is brazed and joined.
[0045]
In Example 1 of the present invention, as shown in FIG. 1, the length of the contact portion with the honeycomb body 1 in the exhaust gas outlet side reduced diameter portion 4 was 25 mm, and the outer cylinder 2 and the honeycomb body 1 were joined by brazing. In the exhaust gas containing side reduced diameter portion 3, the honeycomb body 1 and the reduced diameter portion 3 are in contact with each other over a length of 5 mm.
[0046]
Example 2 of the present invention is shown in FIG. The connection between the honeycomb body 1 and the outer cylinder 2 is the same as that in Example 1 of the present invention. The flat foil and the corrugated foil constituting the honeycomb body 1 are preliminarily provided with one air hole 14 having a diameter of 2 mm / cm.²The flat foil and the corrugated foil were wound to form a honeycomb body. Ventilation holes are not provided in the outermost flat foil of the honeycomb body. Other conditions are the same as those of Example 1 of the present invention.
[0047]
Example 3 of the present invention uses a flat foil and corrugated foil in which the same air holes 14 as those of Example 2 of the present invention are further provided in the honeycomb body 1 having the shape shown in FIG. In the honeycomb body 1 of Example 3 of the present invention, the exhaust gas-containing end surface has a convex shape and the exit side end surface has a concave shape, and the angle θ between the conical line of the end surface and a line orthogonal to the exhaust gas flow path Is 30 degrees. Other conditions are the same as those of Example 1 of the present invention.
[0048]
Example 4 of the present invention is shown in FIG. A rectifying honeycomb body 11 having a thickness of 10 mm was disposed on the exhaust gas upstream side of the combination of the main honeycomb body 1 and the outer cylinder 2 similar to Example 3 of the present invention. The exhaust gas containing side end face and the outlet side end face of the rectifying honeycomb body 11 have a conical shape, and the angle θ between the conical line of the end face and the line orthogonal to the exhaust gas flow path is 45 degrees. In the enlarged diameter portion 9 used in the present invention example, the length of the cylindrical portion is longer than that of the other invention examples in order to accommodate the rectifying honeycomb body 11. The rectifying honeycomb body 11 is accommodated in the metal carrier by welding and joining the enlarged diameter portion 9 and the outer cylinder 2.
[0049]
As a comparative example, a metal carrier using a cylinder with an inner diameter of 100 mm was adopted as the outer cylinder 2. The entire outer periphery of the honeycomb body 1 is in contact with the outer cylinder.
[0050]
Examples 1 to 4 of the present invention and comparative examples were installed in the exhaust gas system of the engine, and the temperature rise characteristics, temperature drop characteristics, and purification performance of the metal carrier were compared. The temperature rise characteristics and temperature fall characteristics are measured by measuring the temperature in the center of the length of the honeycomb body two layers inside from the outer periphery of the honeycomb body, and for the temperature rise characteristics, the temperature drop characteristics depend on the temperature of the part at 50 seconds after cold start. Evaluation was made based on the temperature of the part 10 minutes after the exhaust gas inflow stop. The purification performance was evaluated based on the HC50% purification rate arrival time in order to investigate the initial purification performance of the metal carrier at the start of the engine.
[0051]
The evaluation results are shown in Table 1.
[0052]
[Table 1]

[0053]
Regarding the temperature of the honeycomb body at the outer peripheral portion in the temperature rise characteristic evaluation, each of the examples of the present invention has a higher temperature rise rate than the comparative example. The temperature characteristics were good. The heating rate is increased by the heat insulating effect between the honeycomb body and the outer cylinder of the present invention. Further, in Examples 2, 3, and 4 of the present invention, the effect of improving the exhaust gas flow rate at the outer periphery of the honeycomb body is added, and the temperature is further increased. Increased speed was realized.
[0054]
As for the temperature drop characteristics, all of the inventive examples were better than the comparative examples. This is due to the heat insulation effect between the honeycomb body and the outer cylinder of the present invention.
[0055]
As for HC purification performance, Invention Example 4 was the best, and Comparative Examples were the worst results in the order of Invention Examples 3, 2, and 1 below.
[0056]
【The invention's effect】
  The present invention is the inner circumference of the outer cylindersurfaceAnd honeycomb body peripherysurfaceBetweenThere is an air insulation layer, and the area of this air insulation layer can be widenedSo thisAir insulation layerTherefore, heat conduction from the honeycomb body to the outer cylinder is hindered, and heat loss from the honeycomb body can be reduced. Not only can the heat loss from the honeycomb body during steady operation be reduced, but also the temperature of the honeycomb body rises quickly even when the engine is started, and the purification of exhaust gas can be started as soon as the engine starts.
[0057]
In the present invention, since the honeycomb body can be supported by the outer cylinder without using a ring-shaped elastic holding member or spacer, the above function can be ensured without increasing the cost. In addition, since the diameter-reduced portion is not provided on the outer periphery of the honeycomb body and the cells are not filled with a heat insulating material, the entire cells of the honeycomb body can be used for exhaust gas purification.
[0058]
  In the present invention, in addition to the heat insulating effect of the honeycomb body,By having a large number of ventilation holes on the surface of the foil that constitutes other than the foil of the outer peripheral portion of the honeycomb body facing the inner surface of the outer cylinder,The exhaust gas flow rate in the cells on the outer periphery of the honeycomb body can be increased, and the outer periphery of the honeycomb body can be more effectively used for exhaust gas purification.
  further,As means for increasing the exhaust gas flow velocity at the outer periphery of the honeycomb body, HaIt is possible to employ a method in which the end portion on the side containing the Nicam body exhaust gas is convex, or a method in which the rectifying honeycomb body is disposed on the side containing the honeycomb body exhaust gas. Due to these synergistic effects, the temperature rise characteristic of the outer peripheral portion of the honeycomb body was further improved, and the temperature of the outer peripheral portion of the honeycomb body was kept high even during steady operation, and the purification performance of the metal carrier could be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a metal carrier of the present invention.
FIG. 2 is a cross-sectional view of the metal carrier of the present invention.
FIG. 3 is a cross-sectional view of the metal carrier of the present invention.
FIG. 4 is a cross-sectional view of the metal carrier of the present invention.
FIG. 5 is a cross-sectional view of the rectifying honeycomb body of the present invention, where (a) shows a planar shape, (b) shows a dome shape, and (c) shows a conical shape.
FIG. 6 is a cross-sectional view of the metal carrier of the present invention.
FIG. 7 is a cross-sectional view of the metal carrier of the present invention.
[Explanation of symbols]
1 Honeycomb body (main honeycomb body)
2 outer cylinder
3 Reduced diameter part (exhaust gas side)
4 Reduced diameter part (exhaust gas outlet side)
5 Torso
6 spaces
7 joints
8 Non-joining part (sliding part)
9 Diameter expansion part
10 Diameter reduction part
11 Honeycomb body for rectification
12, 13 Space
14 Vent
15 outer cylinder

Claims

A honeycomb body obtained by alternately winding a flat metal foil and a corrugated corrugated foil foil, and a metal outer cylinder having reduced diameter portions at both ends, the exhaust gas exhaust side end face of the outer cylinder The inner surface of the reduced diameter portion and the outer surface of the honeycomb body are joined by a length of 1/10 or more of the length in the axial direction of the honeycomb body, and the inner surface of the reduced diameter portion on the exhaust gas containing side end surface of the outer cylinder and the outer surface of the honeycomb body Slidably in contact with a length of 1/100 or more of the length of the honeycomb body in the axial direction, and the inner surface of the outer cylinder and the outer surface of the honeycomb body between the two reduced diameter portions are not in contact with each other . A metal carrier for purifying exhaust gas , wherein an air heat insulating layer is provided between the inner surface of the outer cylinder and the outer surface of the honeycomb body .

A honeycomb body obtained by alternately winding a flat metal foil and a corrugated corrugated foil foil, and a metal outer cylinder having reduced diameter portions at both ends, the exhaust gas exhaust side end face of the outer cylinder The inner surface of the reduced diameter portion and the outer surface of the honeycomb body are joined, the inner surface of the reduced diameter portion of the end surface on the exhaust gas entering side of the outer cylinder and the outer surface of the honeycomb body are slidably contacted, and the outer cylinder between both reduced diameter portions In the metal carrier for exhaust gas purification in which the inner surface of the honeycomb body and the outer surface of the honeycomb body are not in contact with each other, and an air heat insulating layer is provided between the inner surface of the outer cylinder and the outer surface of the honeycomb body between both reduced diameter portions,
An exhaust gas purifying metal carrier having a large number of air holes on the surface of a foil other than the outer peripheral foil of the honeycomb body facing the inner surface of the outer cylinder.

The exhaust gas purifying metal carrier according to claim 1 or 2 , wherein an interval between the air insulation layers is set to 1 mm to 5 mm.

The exhaust gas purifying metal carrier according to any one of claims 1 to 3, wherein the honeycomb body has an exhaust gas-containing end face shape having a convex shape and an exhaust gas outlet side end face shape having a concave shape.

Wherein the upper stream portion of the honeycomb body, the exhaust gas purifying metal carrier according to any one of claims 1 to 4, wherein disposing the rectifying honeycomb body.