JP2004197569A

JP2004197569A - Catalyst apparatus for automobile exhaust gas purification

Info

Publication number: JP2004197569A
Application number: JP2002363460A
Authority: JP
Inventors: Kenkichi Hiraki; 謙吉平木; Jun Yagi; 順八木
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2002-12-16
Filing date: 2002-12-16
Publication date: 2004-07-15

Abstract

<P>PROBLEM TO BE SOLVED: To enable the contribution to starting and maintenance of a next stage catalyst reaction using the reaction heat of a catalyst set at a preceding stage; reduction of a great deal of total exhaust amount of components to be reacted, which are exhausted during an operating period from a cold start of an engine, as a whole exhaust system; and protection of the catalyst from an abnormally high exhaust gas temperature such as in an overload operation. <P>SOLUTION: The catalyst apparatus for automobile exhaust gas purification is an automobile exhaust gas purifier consisting of a plurality of the catalyst apparatuses for purifying the automobile exhaust gas. There are arranged a first catalyst apparatus which is formed to come in contact with all or a part of the exhaust gas in an engine exhaust manifold, and a second catalyst apparatus which is directly connected to the manifold; and which is formed to come in contact with the exhaust gas only under a constant running state of the engine. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は自動車等の内燃機関から排出される燃焼排気ガスの浄化技術に係わり、特に、エンジンの冷始動時の排気ガスを効率よく浄化するための排気ガス浄化用触媒装置に関する。
【０００２】
【従来の技術】
自動車等の内燃機関から排出される燃焼排気ガスの浄化には従来から排気系に触媒装置を用いた浄化方法がとられてきた。この触媒装置は化学反応により被浄化物質を接触浄化するため、触媒の良さは反応活性を開始する活性化温度と排気ガスとの接触確率で決まる。一方、触媒を車載するには、エンジン冷始動時を含む全運転状態下の全排気ガスを浄化する必要があり、これには冷始動時の低温度から、高負荷運転時の触媒材破壊に至るほどの高温度まで広範な温度領域で安定した反応と自動車寿命に追従した長時間寿命が求められる。
【０００３】
しかしながら、このような過酷で広範な温度下で長時間使用という条件に完全に適する触媒材は実用化されていないため、従来から、技術的には触媒が安全に機能することを最優先して、排気温度的にマイルドで十分な触媒容量を占めることができる後方床下の排気系域に触媒を配設することで対応してきた。このため、排気系後方域にあっても、排気ガス温度が触媒の活性化温度より十分高く維持できる、定常運転時は当然のこととして、過負荷運転時の異常に高い排気ガスも触媒装置より前方の排気系で放熱され、触媒を高温で破壊することなく安全に浄化処理できるようになった。しかし、エンジンの冷始動時には排気ガスは冷え切った排気系と触媒自体がほとんど大気温度まで下がるために、この運転期間中に排出される排気ガスの浄化は不十分となり、全運転期間を通しては満足な浄化を達成しえない。これに対するこれまでの取り組みは、触媒体の熱容量を小さくすることで、エンジン始動時（触媒の活性開始温度に至らない）から定常運転（触媒が十分に活性する温度）に移行する間に排出される排気ガスの温度上昇速度に触媒全体が可能な限り速く追従することで、エンジン始動から反応開始までに排出される未反応ガスを最少にすることが提案されている。
【０００４】
また、排気系後方に配設した触媒装置を主触媒装置とし、これとは別に排気ガスがより高温にある排気系の前方に副触媒装置を配設することで、冷始動時の浄化改善を行う提案もなされている。（例えば特許文献１）
【０００５】
【特許文献１】
特開平１−２４９９１５号公報（全頁）
【０００６】
【発明が解決しようとする課題】
しかしながら、上記いずれの提案も冷始動時に即反応を開始するに十分な温度を確保できるエンジン近傍域にあって、大量の排気ガスを処理するために必要な触媒容量を配設するに十分な空間を確保するには困難があった。このように冷始動時の排気ガス浄化には、エンジンの近傍に配設可能な小型で効率のよい触媒体が望まれてきた。さらにこの触媒体と触媒装置がエンジンの高負荷運転時の異常な高温にも耐えられるか、さもなくばシステム的に高温ガスを避けられる適切な構造の触媒装置が配設できるかが課題であった。
【０００７】
本発明者等はこのエンジン近傍に配設できる触媒体と触媒装置として最も効率的なクロス触媒を装置に組み込む上でのいくつかの課題について鋭意研究の結果、クロス触媒体の形状と排気ガスとの接触方法ならびに冷始動時のみ触媒と接触可能とした触媒装置構成を見出した。
【０００８】
【課題を解決するための手段】
本発明は、自動車の排気ガスを浄化するために複数の触媒装置を配設した自動車排気浄化装置にあって、シリカクロスを支持体とし、その表面に触媒物質を担持して成るクロス触媒体で構成された触媒装置を前段に配設した自動車排気浄化触媒装置に係わり、エキゾーストマニホルド内に配設したクロス触媒体とマニホルド直下の排気系に配設した冷始動時のみ触媒接触可能な構造でなる触媒装置を組み合わせて成る自動車排気浄化触媒装置を提案する。
【０００９】
本発明は、まずエキゾーストマニホルド内排気管に筒状に形成したクロス触媒体が密着配設され、排気ガスは排気管と同軸上の触媒体に沿面方向で接触する。次に、その後方のマニホルド直下の排気系に、やはり筒状に形成された触媒体で、その内芯筒の終端に開閉可能な弁を具備した構造の触媒装置が配設され、弁のない先端より流入した排気ガスは、弁が閉じているときには、内芯筒から外筒方向に流れを変えることで、触媒体と対面方向に接触する。一方、弁が開いている時は沿面方向に接触する構成でなる。
【００１０】
本発明の作用は、エンジンから排出された排気ガスがまずマニホルド内に配設された筒状触媒体と沿面接触して、排気ガスの一部のみが反応し、浄化低減すると同時に反応熱を排気ガス流に戻し加温することで、マニホルド通過の際の放熱による排気温度の低下を抑える。この結果、続くマニホルド直下の排気系に配設された筒状触媒体に流入する排気ガスはガス温度を高く維持したまま触媒体の内芯筒に流入する。このとき、エンジンが冷始動状態であれば、内芯筒に具備した弁を閉じた状態にすることで、流入した排気ガスは流れ方向を軸方向から径方向に変え、触媒体と対面接触するため、流入した全量の排気ガスが接触反応して浄化する。このときの反応熱は流出する排気ガス全体を加温して、後段に配設した主触媒の反応継続を維持する。一方、エンジンが定常運転に入ると、排気ガス温度、または始動時からの時間等を検出機構で検出し、弁を開放状態にすることで、流入した排気ガスは内芯筒内を軸方向に流れ、触媒体とは沿面で接触し、一部のガスのみが反応して後方排気系に流出する。このときに発生する反応熱は充分に少なく、後段に配設した主触媒が異常に高温加熱するのを防ぐことにもなる。
【００１１】
本発明は、前述したように構成されているので、マニホルド内に配設した触媒体では一部のガスとの反応でしかなく、その反応熱はエンジンからの冷始動時排気ガスをわずか加温することで、ガスの放熱低下を防ぎ、次段触媒の反応開始と維持に寄与するとともに、定常運転時の排気ガスの接触も沿面のわずかな量ですぎず、過負荷運転時などの異常に高い排気ガス温度からも触媒を防ぎ、結果として触媒寿命を永くする。またマニホルド直下の弁付触媒装置では前段のマニホルド内配設触媒で加温保持された全排気ガスが、弁の作用で触媒体と対面接触により接触確率を高めて冷始動時の反応開始を早めるとともに、さらに後方に配設された主触媒の反応開始も早めることになり、排気系全体として、エンジンの冷始動時から運転期間中に排出される被反応成分の総排出量を大幅に低減できることになる。同時に定常運転後に弁を開放状態に作動することで、排気ガスの大半が触媒体を沿面で通過するため、触媒体と接触しないので高温ガスにさらされることが少なく、触媒体の熱的破損や熱的寿命短縮を防ぐことにもなる。
【００１２】
【発明の実施の形態】
以下図面に基づいて本実施の形態を詳細に説明する。
【００１３】
図１〜図５は、本実施の形態の実施例を示すものである。図１は本実施の形態の浄化装置を含む、自動車の排気系全体の構成を示す。図２は４管集結マニホルドの概略図、図３は図２のマニホルドを構成する４本の触媒体配設管の１本あたりの内部構成と触媒体の構成図、図４はマニホルド直下に接続された触媒装置の構成図、そして図５は図４の装置の組立て部品概要図を示す。なお、本実施の形態において図３で示す触媒体の構成図が第１の触媒部に相当し、図４で示す触媒装置が第２の触媒部に相当する。
【００１４】
次に図に基づいて本実施の形態の実施例の詳細を説明する。図１はエンジン１からテールパイプ７に至る排気系全体を示し、特に本実施の形態に関わる構成はエンジンの気筒別排気口につながる触媒を配設したマニホルド配管２とこれに接続するマニホルド直下型触媒装置３である。
【００１５】
図２は図１で示した４気筒型のマニホルド配管２の概要図であり、エンジン１の４箇所の排気口とそれぞれ個別に４本の排気管２ａ〜２ｄが接続されており、これら４本の排気管は１本の集結管２ｅに集結される。本実施の形態では、図２における個別の排気管２ａ〜２ｄの内部に管状の触媒体を配設し、かつ集結管２ｅにあたるものが図１のマニホルド直下型触媒装置３を構成している。
【００１６】
図３はマニホルド内の個別の排気管２ａ〜２ｄの内部構成を示す。ここで個別の排気管２１は個別の排気管２ａ〜２ｄの内の１つであり、排気管２１の内部に、パンチングメタルまたはラスメタル等でなる有孔の内筒部２２の上に触媒金属を担持したクロス触媒を少なくとも１回以上巻き回した触媒体２３を配設した。必要に応じて触媒体２３の外側にもラスメタル等の外筒部２４を構成し巻き締めする。
【００１７】
図４は、図１で示したマニホルド直下型触媒装置３の構成図である。この装置の構成部品図を図５に示しており、ここでは図４と図５の２つの図でマニホルド直下型触媒装置３の説明をする。十字状仕切り３１は前方のマニホルド配管の終端部を個別に接続し一つにするものである。図は４気筒エンジンを想定しているので、十字型仕切りにして４箇所の開口を設けてある。この仕切りは当然のこととして、装置外筒３２の前端開口部の全面に渉る形で取り付けられる。前段のマニホルド個別配管より流入するガスがスムースに流れ込むに必要な距離をおいて、触媒槽流入口となる触媒槽入り口有孔板３３を配し、この開口邪魔板３３に筒状の触媒体３４が取り付けられる。
【００１８】
この筒状の触媒体３４は図５の構成部品図で示すように、有孔の内筒部３４１から開閉可動弁３４５までの５つの構成要素でなり、後述するとおり、エンジンの冷始動時浄化に係わる。筒状の触媒体３４の具体的な構成は、有孔の内筒部３４１にクロス触媒を少なくとも１回以上巻き回して触媒体３４２を形成し、その外側に有孔の外筒部３４３を配して、クロス触媒の巻き締めと共に、ガスの流出孔を形成する。
【００１９】
なお、本実施の形態においては、第１の触媒部および第２の触媒部において、クロス触媒の実施例として、シリカクロスを支持体とし、その表面に触媒物質を担持して成るものを用いている。
【００２０】
一方、有孔の内筒部３４１の終端部は筒状の触媒体３４の終端全面をカバーする邪魔板３４４を配するが、この邪魔板３４４はその中心に有孔内芯筒３４１の終端面と等しい開口部を有し、かつこの開口部を開閉する開閉可動弁３４５が取り付けられている。この開閉可動弁３４５は接触するガスの温度または圧力で自動的に可動する機能を有している。具体的には、可動弁の材料にばね材や記憶合金またバイメタルとばね材の組み合わせ構成などである。またエンジンの運転状態との連携して機械的に開閉する構成も可能である。
次に本実施の形態の作用について詳述する。
【００２１】
まず、自動車の排気系全体の構成を示す図１を用いて、本実施の形態の浄化装置を含む自動車全体の排気系の作用について説明する。
【００２２】
図１において、エンジン１の気筒別排気口から排出したガスは気筒別に配設されたマニホルド配管２から、その直下に設けたマニホルド直下触媒装置３に流入して、通常の排気管５を通り、従来型の主触媒装置４に入り、その後、排気管５でつながる消音器６を経て、テールパイプ７から大気に放出する。
【００２３】
次に、本実施の形態における第１の触媒部の構造を示す図３用いてその作用について説明する。この第１の触媒部は前述したように図１におけるマニホルド配管２の４つの排気管のうちの一つに相当する。
【００２４】
図３で、図２で示すエンジン１の排気口から個別の排気管２１に流入したガスは、その大半が有孔内芯筒２２を通って後方に流出する。このとき、有孔内芯筒２２が有孔材で形成されているので、ガスはこの有孔部分を通じて触媒体２３と沿面接触し、また触媒体外周に有孔の外筒２４が配設されているときには排気管２１と外筒２４の間に空間を形成しているので、極く一部のガスは、有孔の内筒部２２の有孔部分からクロス触媒でなる触媒体２３の織布構成空間と外筒部２４の有孔部分を経て排気管２１との間隙空間を通って後方へ流出する。このときガスはクロス触媒と対面接触をすることになる。この対面接触をより多くするには、有孔の外筒部２４にラスメタルなど薄くかつ開口を大きくとれる材料を選ぶことができる。なお、外筒部２４を設け、内側から内筒部２２、触媒体２３、外筒部２４の順になる構成としたのは、内筒部２２と触媒体２３の間、外筒部２４と触媒体２３の間に排気ガスをため、触媒体２３の内面、外面にできるだけ排気ガス接触するようにするためである。
【００２５】
また図３では排気管２１は直管で図示したが、実際のマニホルド配管は複雑な屈曲管でなっており、実際のガスは屈曲部では触媒体と対面で接触もでき、この構造面からも、この位置に配設する触媒体２３としてクロス触媒は最適である。さらに、本実施の形態における第２の触媒部の構造を示す図４および図５を用いてその作用について説明する。この第２の触媒部は前述したように図１におけるマニホルド直下型触媒装置３に相当するものであり、エンジン１から排出されたガスはマニホルド配管２を経て、この直下型触媒装置３に流入する。
【００２６】
図４において、この直下型触媒装置３の仕切り３１により仕切られた流入口から個別に流入し、触媒槽入り口有孔板３３までの空間で流れを整えて、筒状の触媒体３４に流入する。
【００２７】
この筒状の触媒体３４の作用について、図５を用いて詳細に説明する。図５において、筒状の触媒体３４の軸中心にある有孔の内筒部３４１に流入する。このとき、開閉可動弁３４５が開放状態にあれば、ガスはそのまま有孔の内筒部３４１の軸方向に流れ、開放された開閉可動弁３４５を経て、装置終端板３５を通過して後方排気管３６に排出される。このときガスは排気抵抗が低い軸方向に流れ、終端開口より排出されるため、触媒とはわずかに有孔内芯筒３４１の開口部でのみ沿面で接触する。
【００２８】
一方、開閉可動弁３４５が閉塞状態にあれば、ガスは内筒部３４１から径方向に流れを変え、触媒体３４２を通過して有孔の外筒部３４３から触媒体３４２外に出たあと装置終端板３５の開口から後方排気管３６に排出される。このときガスは筒状触媒層を径方向に流れるため、触媒と対面接触することになる。このマニホルド直下型触媒装置３にあっては、開閉可動弁３４５を操作することで、触媒との接触方向を変え、弁開放時には基本的にガスが触媒層をバイパスすることになり接触反応はせず、また弁閉塞時には触媒層を貫流して全面的に接触反応をする。このように、弁開閉の如何で触媒反応を停止したり、開始したりできる。このような触媒反応可否そのもの以上に、特に高温大量なガスの接触そのこと自体を可否できるため、触媒の耐熱劣化や寿命低下を防ぐことにもなる。
【００２９】
なお、開閉可動弁は、排気ガスの温度もしくは圧力を感知して自動もしくは手動で可動弁を開閉するようにすることでいっそう効率的に浄化し、触媒の耐熱劣化や寿命低下の防止効果が得られる。
【００３０】
次に、本実施の形態による実施例による効果を比較例との比較において詳述する。ここで用いた比較例は、図１に示す排気系において、マニホルドには管内に触媒を配設していない従来のものを用い、また直下型触媒装置は装着せずマニホルドに直接排気管を接続し、排気系の前寄り中ほどの位置に従来型のハニカム触媒装置を装着したものを用いた。
【００３１】
排気試験は４気筒の１６００ｃｃエンジンを用い、エンジンダイナモを負荷とした、冷始動から定負荷運転までの排気ガスを排気系終端パイプより採取してガス成分分析をした。ここで、実施例と比較例の主触媒装置には共に同一の市販自動車に装着された白金系ハニカム触媒装置をそのまま取り付けた。またここでいう冷始動状態には、エンジン運転停止後３時間以上たった状態とし、すくなくともエンジン冷却水温度が室温に下がっていることを確認した。
【００３２】
ガス成分分析は主としてＣＯを測定し、比較例の排気系の排出濃度１．０に対する割合でもって表記した。具体的には、同じ運転モードでエンジン始動０秒から１０秒、２０秒、１分後の比較例排気系のＣＯ濃度を１としたときの実施例排気系の濃度の割合で示した。本実施の形態の効果として、上記試験測定結果について、上記測定方法に基づき表１にまとめた。
【００３３】
【表１】

表１の結果が示すとおり、本実施の形態の構成によらない比較例排気系においては、エンジン運転開始後２０秒後までの間にＣＯ成分の排出があるが、本実施の形態の構成による実施例排気系においては、運転開始後１０秒後に比較例排気系の排出の２割程度のＣＯ排出でしかない。また運転開始から６０秒間の実施例排気系の排出ＣＯは比較例排気系に比べて８７．５％の低減となった。
【００３４】
また表１で示すように、運転開始６０秒後には比較例排気系においてもＣＯ排出濃度は０である。これは比較例排気系ならびに実施例排気系において装着された主触媒装置が適切に反応している結果で、逆にいえば、運転開始後６０秒以内では、主触媒装置が適切に反応しないため、この間にはＣＯガスが反応浄化せずに排気系から大気に排出されることになる。
【００３５】
この主たる要因は、主触媒装置に流入する排気ガスの温度が、反応を開始するに必要な温度以下であることによる。ちなみにこの測定装置での冷始動時の主触媒装置直前の排気ガス温度は、３０〜１５０℃のレベルで、特に冷始動時には排気系のガス放熱冷却と測定前の排気系内残留露結水分の飛来付着で主装置の触媒の開始温度は概略２００℃のレベルにあるため、触媒が反応を開始できないものと考えられる。この排気ガス温度の早期の立ち上げを来たすために、マニホルドの熱容量低減や冷始動時のエンジン回転数の上昇でガス熱容量を増加するなどの改善がエンジン系を含めたシステムでとられてはいるものの効果は不十分で、現実的には、触媒装置の装着位置をマニホルド近辺にまで接近して、ガスの冷却を防ぐ方策しかない。
【００３６】
一方、マニホルド近辺に触媒装置を装着するには、エンジンの高負荷時の極高温大量ガスの接触に耐えると共に、エンジン室内の狭小な空間に納まる小型高能率な触媒が必要で、この点からも現実的に実用されるハニカムなどの触媒材では不適切であった。
【００３７】
本発明の実施の形態の構成は、この相反する条件に適応すべく、形状的に自由度が極めて高く、かつ触媒層の配置如何（沿面接触また対面接触方向の選択）により、少量で効果的な浄化が可能なクロス状触媒の採用と、触媒装置に触媒層をバイパスするガス流路変更機能を有することで、冷始動時と定常また高負荷運転時の接触方向をかえることを可能とし、浄化と耐久の両面で効果をみた。本実施の形態による排気系は従来なしえなかった冷始動から全運転期間にわたる排気浄化が可能となり、エンジンシステムのみでゼロエミッション化を実現する、自動車排気環境対策に極めて効果の大きいシステムである。
【００３８】
本実施の形態の構成では、エンジン直下の触媒の反応開始促進のために、マニホルド内にも筒状の触媒体を配設した構成としているが、エンジンシステムの条件によっては、このマニホルド内触媒の配設をしなくても、本実施の形態の効果を特に損なうものではない。
【００３９】
またマニホルド直下触媒装置で触媒層をバイパスする流路形成を触媒槽流入管の終端に開閉可動弁を設ける構成としたが、流入管先端にこの稼動弁を設けて弁閉塞時に排気ガスが筒状触媒体の外周面より内芯筒に流出し、この内筒を経て装置外の排気管に排出されるように、流れを変えることも、さらには、直下触媒装置の入り口直前に弁を介して装置への導入と装置外の後方排気管につながるバイパス路へ導入する構成をとっても、本実施の形態の効果を妨げるものでない。
【００４０】
【発明の効果】
以上で説明したように、本発明の効果は、前段に設けた触媒の反応熱を利用することで、次段触媒の反応開始と維持に寄与できる。また排気系全体として、エンジンの冷始動時から運転期間中に排出される被反応成分の総排出量を大幅に低減でき、過負荷運転時などの異常に高い排気ガス温度からも触媒を防ぎ触媒寿命を永くできる。
【図面の簡単な説明】
【図１】本実施の形態の構成による自動車排気系概略を示す図
【図２】エンジンマニホルド概要図
【図３】マニホルド内筒状触媒体の構成を示す図
【図４】直下触媒装置の構成を示す図
【図５】直下触媒装置構成部材概要図
【符号の説明】
１エンジン
２マニホルド配管
３マニホルド直下触媒装置
２２、３４１内筒部
２３、３４２触媒体
２４、３４３外筒部
３４触媒部
３４５開閉可動弁[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a technique for purifying combustion exhaust gas discharged from an internal combustion engine of an automobile or the like, and more particularly to an exhaust gas purifying catalyst device for efficiently purifying exhaust gas at the time of a cold start of an engine.
[0002]
[Prior art]
2. Description of the Related Art To purify combustion exhaust gas discharged from an internal combustion engine of an automobile or the like, a purification method using a catalyst device in an exhaust system has conventionally been adopted. This catalytic device catalytically purifies the substance to be purified by a chemical reaction. Therefore, the goodness of the catalyst is determined by the activation temperature at which the reaction activity starts and the contact probability with the exhaust gas. On the other hand, in order to install a catalyst, it is necessary to purify all exhaust gas under all operating conditions including at the time of cold start of the engine, from low temperature at cold start to destruction of catalyst material at high load operation. A stable reaction in a wide temperature range up to an extremely high temperature and a long life following the life of an automobile are required.
[0003]
However, since a catalyst material that is completely suitable for such a condition of being used for a long time under a severe and wide temperature range has not been put into practical use, technically, the highest priority has been given to the technically safe functioning of the catalyst. This has been dealt with by arranging the catalyst in the exhaust system area under the rear floor where the exhaust gas temperature can occupy a mild and sufficient catalyst capacity. For this reason, even in the exhaust system rear region, the exhaust gas temperature can be maintained sufficiently higher than the activation temperature of the catalyst. Naturally during normal operation, abnormally high exhaust gas during overload operation is also higher than that of the catalyst device. The heat is dissipated in the exhaust system ahead, and the catalyst can be safely purified without destroying the catalyst at high temperatures. However, when the engine is started cold, the exhaust gas is completely cooled down because the exhaust system and the catalyst itself have almost cooled down to the atmospheric temperature, and the exhaust gas exhausted during this operation period is not sufficiently purified, and it is satisfactory throughout the entire operation period. Can not achieve a good purification. Up to now, the approach to this problem has been to reduce the heat capacity of the catalyst body, so that it is discharged during the transition from engine startup (not reaching the catalyst activation start temperature) to steady operation (temperature at which the catalyst is sufficiently activated). It has been proposed that the entire catalyst follow the temperature rise rate of the exhaust gas as quickly as possible, thereby minimizing the unreacted gas discharged from the start of the engine to the start of the reaction.
[0004]
In addition, the catalyst device located at the rear of the exhaust system is used as the main catalyst device. Separately, the sub-catalyst device is installed in front of the exhaust system where the exhaust gas has a higher temperature to improve purification during cold start. Some suggestions have been made. (For example, Patent Document 1)
[0005]
[Patent Document 1]
JP-A-1-249915 (all pages)
[0006]
[Problems to be solved by the invention]
However, any of the above proposals is located in the vicinity of the engine where sufficient temperature can be secured to start an immediate reaction at the time of cold start, and has sufficient space for arranging a catalyst capacity necessary for treating a large amount of exhaust gas. There were difficulties to secure. As described above, a small and efficient catalyst that can be disposed near the engine has been desired for purifying exhaust gas during cold start. Another issue is whether the catalyst body and the catalyst device can withstand abnormally high temperatures during high-load operation of the engine, or if a catalyst device with an appropriate structure that can avoid high-temperature gas in a system can be provided. Was.
[0007]
The present inventors have conducted intensive studies on some issues in incorporating the most efficient cross catalyst as a catalyst device and a catalyst device that can be disposed near the engine into the device, and as a result, the shape of the cross catalyst body and the exhaust gas And a catalyst device configuration that allows contact with the catalyst only during cold start.
[0008]
[Means for Solving the Problems]
The present invention relates to a vehicle exhaust purification device in which a plurality of catalyst devices are disposed for purifying exhaust gas of a vehicle, wherein a silica catalyst is used as a support and a catalyst material is supported on the surface thereof. The present invention relates to an automotive exhaust purification catalyst device in which the configured catalyst device is disposed at the front stage, and has a structure in which the catalyst can be brought into contact only at cold start with the cross catalyst body disposed in the exhaust manifold and the exhaust system located immediately below the manifold. The present invention proposes a catalyst device for purifying an automobile exhaust which is composed of a combination of catalyst devices.
[0009]
In the present invention, first, a cross catalyst body formed in a tubular shape is closely attached to an exhaust pipe in an exhaust manifold, and exhaust gas comes into contact with a catalyst body coaxial with the exhaust pipe in a creeping direction. Next, in the exhaust system immediately below the rear manifold, a catalyst device having a structure in which a catalyst body also formed in a cylindrical shape and having an openable / closable valve at the end of the inner core tube is provided, and there is no valve. When the valve is closed, the exhaust gas that has flowed in from the tip changes its flow from the inner core cylinder to the outer cylinder, and thus comes into contact with the catalyst body in the facing direction. On the other hand, when the valve is open, it is configured to make contact in the creeping direction.
[0010]
The effect of the present invention is that the exhaust gas discharged from the engine first comes into surface contact with the cylindrical catalyst body provided in the manifold, and only a part of the exhaust gas reacts, thereby purifying and reducing the reaction heat and simultaneously exhausting the reaction heat. By heating back to the gas flow, a decrease in exhaust gas temperature due to heat radiation when passing through the manifold is suppressed. As a result, the exhaust gas flowing into the cylindrical catalyst body disposed in the exhaust system immediately below the manifold flows into the inner core cylinder of the catalyst body while keeping the gas temperature high. At this time, if the engine is in a cold start state, by closing the valve provided in the inner core tube, the flowing exhaust gas changes the flow direction from the axial direction to the radial direction, and comes into face-to-face contact with the catalyst body. Therefore, the entire amount of exhaust gas that has flowed in is contact-reacted and purified. The reaction heat at this time heats the entire exhaust gas flowing out to maintain the continuation of the reaction of the main catalyst disposed at the subsequent stage. On the other hand, when the engine enters a steady operation, the exhaust gas temperature or the time from the start is detected by a detection mechanism, and by opening the valve, the inflowing exhaust gas flows in the inner cylinder in the axial direction. The flow comes into contact with the catalyst on the surface, and only a part of the gas reacts and flows out to the rear exhaust system. The reaction heat generated at this time is sufficiently small, which also prevents the main catalyst disposed in the subsequent stage from being heated to an abnormally high temperature.
[0011]
Since the present invention is configured as described above, the catalyst disposed in the manifold only reacts with some of the gases, and the reaction heat slightly heats the exhaust gas at the time of cold start from the engine. By doing so, it is possible to prevent a decrease in the heat radiation of the gas and contribute to the initiation and maintenance of the reaction of the next-stage catalyst. Prevents catalysts from high exhaust gas temperatures, resulting in longer catalyst life. In the catalytic converter with a valve directly below the manifold, all exhaust gases heated and held by the catalyst installed in the manifold in the previous stage increase the probability of contact with the catalyst body by face-to-face contact by the action of the valve, so that the reaction start at the cold start is accelerated. At the same time, the start of the reaction of the main catalyst arranged further behind will be accelerated, and the total emission of reactants emitted during the operation period from the cold start of the engine to the exhaust system as a whole can be greatly reduced. become. At the same time, by opening the valve after steady-state operation, most of the exhaust gas passes along the catalyst body along the surface, and does not come into contact with the catalyst body, so it is less exposed to high-temperature gas. This also prevents the thermal life from being shortened.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present embodiment will be described in detail with reference to the drawings.
[0013]
1 to 5 show examples of the present embodiment. FIG. 1 shows the entire configuration of the exhaust system of an automobile including the purification device of the present embodiment. FIG. 2 is a schematic view of a four-pipe consolidating manifold, FIG. 3 is a diagram showing the internal structure of one of the four catalyst-arrangement pipes constituting the manifold of FIG. 2 and the configuration of the catalyst, and FIG. 4 is connected immediately below the manifold. FIG. 5 shows a schematic diagram of the assembled catalyst device, and FIG. In this embodiment, the configuration diagram of the catalyst body shown in FIG. 3 corresponds to the first catalyst unit, and the catalyst device shown in FIG. 4 corresponds to the second catalyst unit.
[0014]
Next, an example of the present embodiment will be described in detail with reference to the drawings. FIG. 1 shows the entire exhaust system from the engine 1 to the tail pipe 7. In particular, the configuration according to the present embodiment is a manifold pipe 2 provided with a catalyst connected to a cylinder-specific exhaust port of the engine, and a manifold directly connected to the manifold pipe 2. The catalyst device 3.
[0015]
FIG. 2 is a schematic view of the four-cylinder type manifold pipe 2 shown in FIG. 1. Four exhaust pipes 2a to 2d are respectively connected to four exhaust ports of the engine 1, and these four Of the exhaust pipes are collected into one collecting pipe 2e. In the present embodiment, a tubular catalyst body is disposed inside the individual exhaust pipes 2a to 2d in FIG. 2, and the one corresponding to the collecting pipe 2e constitutes the manifold direct-type catalyst device 3 in FIG.
[0016]
FIG. 3 shows the internal configuration of the individual exhaust pipes 2a to 2d in the manifold. Here, the individual exhaust pipe 21 is one of the individual exhaust pipes 2a to 2d, and a catalyst metal is provided inside the exhaust pipe 21 on a perforated inner cylindrical portion 22 made of a punching metal, a lath metal, or the like. The catalyst body 23 in which the supported cross catalyst was wound at least once or more was provided. If necessary, an outer cylindrical portion 24 made of lath metal or the like is also formed outside the catalyst body 23 and tightened.
[0017]
FIG. 4 is a configuration diagram of the manifold direct-type catalyst device 3 shown in FIG. FIG. 5 is a diagram showing the components of this apparatus. Here, the catalyst-under-manifold type catalyst apparatus 3 will be described with reference to FIGS. 4 and 5. The cross-shaped partition 31 individually connects the end portions of the front manifold pipes into one. Since the figure assumes a four-cylinder engine, a cross-shaped partition is provided with four openings. As a matter of course, this partition is attached so as to cover the entire front end opening of the device outer cylinder 32. A perforated plate 33 for a catalyst tank inlet serving as a catalyst tank inlet is disposed at a distance necessary for the gas flowing from the manifold individual pipe of the preceding stage to flow smoothly, and a cylindrical catalyst body 34 is provided in the opening baffle plate 33. Is attached.
[0018]
As shown in the component parts diagram of FIG. 5, the tubular catalyst body 34 is composed of five components from a perforated inner cylinder portion 341 to an open / close movable valve 345. As described later, purification at the time of cold start of the engine is performed. Related to A specific configuration of the cylindrical catalyst body 34 is as follows. A cross catalyst is wound at least once around a perforated inner cylinder portion 341 to form a catalyst body 342, and a perforated outer cylinder portion 343 is arranged outside the catalyst body 342. Then, together with the winding of the cross catalyst, a gas outflow hole is formed.
[0019]
In the present embodiment, in the first catalyst section and the second catalyst section, as an example of the cross catalyst, a silica cloth is used as a support, and a catalyst substance is supported on the surface thereof. I have.
[0020]
On the other hand, a baffle plate 344 that covers the entire end of the tubular catalyst body 34 is disposed at the end of the perforated inner cylindrical portion 341, and the baffle plate 344 is provided at the center thereof at the end surface of the perforated inner core tube 341. An opening / closing movable valve 345 that opens and closes this opening is attached. The open / close movable valve 345 has a function of automatically moving at the temperature or pressure of the gas in contact. Specifically, the material of the movable valve is a spring material, a memory alloy, or a combination of a bimetal and a spring material. It is also possible to have a configuration that mechanically opens and closes in cooperation with the operating state of the engine.
Next, the operation of the present embodiment will be described in detail.
[0021]
First, the operation of the exhaust system of the entire vehicle including the purification device of the present embodiment will be described with reference to FIG. 1 showing the configuration of the entire exhaust system of the vehicle.
[0022]
In FIG. 1, gas discharged from an exhaust port for each cylinder of an engine 1 flows from a manifold pipe 2 arranged for each cylinder into a catalyst device 3 directly below a manifold provided therebelow, passes through a normal exhaust pipe 5, and After entering the conventional main catalyst device 4, it is discharged to the atmosphere from a tail pipe 7 through a silencer 6 connected by an exhaust pipe 5.
[0023]
Next, the operation of the first catalyst unit according to the present embodiment will be described with reference to FIG. This first catalyst section corresponds to one of the four exhaust pipes of the manifold pipe 2 in FIG. 1 as described above.
[0024]
In FIG. 3, most of the gas flowing into the individual exhaust pipes 21 from the exhaust port of the engine 1 shown in FIG. At this time, since the perforated inner core tube 22 is formed of a perforated material, the gas comes into surface contact with the catalyst body 23 through the perforated portion, and a perforated outer cylinder 24 is provided on the outer periphery of the catalyst body. In this case, since a space is formed between the exhaust pipe 21 and the outer cylinder 24, a very small portion of the gas flows from the perforated portion of the perforated inner cylindrical portion 22 to the weave of the catalyst body 23 made of the cross catalyst. The air flows backward through the space between the cloth forming space and the exhaust pipe 21 through the perforated portion of the outer cylindrical portion 24. At this time, the gas comes into face-to-face contact with the cross catalyst. In order to increase the face-to-face contact, it is possible to select a thin material such as lath metal and a material having a large opening, such as a lath metal. The outer cylinder 24 is provided, and the inner cylinder 22, the catalyst 23, and the outer cylinder 24 are arranged in this order from the inside. This is because the exhaust gas is accumulated between the media 23 so that the exhaust gas contacts the inner and outer surfaces of the catalyst body 23 as much as possible.
[0025]
Although the exhaust pipe 21 is shown as a straight pipe in FIG. 3, the actual manifold pipe is a complicated bent pipe, and the actual gas can also come into contact with the catalyst body at the bent portion in a face-to-face manner. The cross catalyst is most suitable as the catalyst body 23 disposed at this position. Further, the operation of the second embodiment will be described with reference to FIGS. As described above, the second catalyst portion corresponds to the manifold direct-type catalyst device 3 in FIG. 1, and the gas discharged from the engine 1 flows into the direct-type catalyst device 3 via the manifold pipe 2. .
[0026]
In FIG. 4, the gas flows individually from the inflow port partitioned by the partition 31 of the direct type catalyst device 3, the flow is adjusted in the space up to the perforated plate 33 for the catalyst tank entrance, and then flows into the cylindrical catalyst body 34. .
[0027]
The operation of the cylindrical catalyst body 34 will be described in detail with reference to FIG. In FIG. 5, the fluid flows into a perforated inner cylindrical portion 341 at the center of the axis of the cylindrical catalyst body 34. At this time, if the open / close movable valve 345 is in an open state, the gas flows as it is in the axial direction of the perforated inner cylindrical portion 341, passes through the opened open / close movable valve 345, passes through the device end plate 35, and is exhausted backward. It is discharged to a pipe 36. At this time, the gas flows in the axial direction with low exhaust resistance and is discharged from the terminal opening, so that the gas comes into contact with the catalyst only slightly at the opening of the perforated inner core tube 341.
[0028]
On the other hand, if the open / close movable valve 345 is in a closed state, the gas changes its flow in the radial direction from the inner cylindrical portion 341, passes through the catalyst body 342, and exits the catalyst body 342 from the perforated outer cylindrical portion 343. The air is discharged from the opening of the device end plate 35 to the rear exhaust pipe 36. At this time, the gas flows in the cylindrical catalyst layer in the radial direction, so that the gas comes into face-to-face contact with the catalyst. In the catalyst device 3 directly under the manifold, by operating the open / close movable valve 345, the contact direction with the catalyst is changed. When the valve is opened, the gas basically bypasses the catalyst layer, and the contact reaction is started. In addition, when the valve is closed, it flows through the catalyst layer and makes a contact reaction entirely. In this way, the catalytic reaction can be stopped or started depending on whether the valve is opened or closed. Since contact with a large amount of gas at a high temperature can be permitted or denied more than whether or not such a catalytic reaction is possible, deterioration in heat resistance and life of the catalyst can be prevented.
[0029]
The open / close movable valve detects the temperature or pressure of the exhaust gas and automatically or manually opens and closes the movable valve to purify the catalyst more efficiently, thereby obtaining the effect of preventing heat deterioration of the catalyst and a reduction in life. Can be
[0030]
Next, the effect of the example according to the present embodiment will be described in detail in comparison with a comparative example. In the comparative example used here, in the exhaust system shown in FIG. 1, a conventional one in which no catalyst is provided in the pipe is used for the manifold, and the exhaust pipe is directly connected to the manifold without mounting a direct-type catalyst device. A conventional honeycomb catalyst device was used at a position near the front of the exhaust system.
[0031]
In the exhaust test, a four-cylinder 1600 cc engine was used. Exhaust gas from a cold start to a constant load operation using an engine dynamo as a load was collected from an exhaust system end pipe and analyzed for gas components. Here, the platinum-based honeycomb catalyst devices mounted on the same commercial vehicle were both attached to the main catalyst devices of the example and the comparative example as they were. In this case, the cold start state was at least three hours after the engine operation was stopped, and it was confirmed that at least the temperature of the engine cooling water had dropped to room temperature.
[0032]
In the gas component analysis, CO was mainly measured and expressed as a ratio with respect to the exhaust concentration 1.0 of the exhaust system of the comparative example. Specifically, in the same operation mode, the values are shown by the ratio of the concentration of the exhaust system of the example when the CO concentration of the exhaust system of the comparative example is set to 1 after 0 to 10 seconds, 20 seconds, and 1 minute after the start of the engine. As an effect of the present embodiment, the test measurement results are summarized in Table 1 based on the measurement methods.
[0033]
[Table 1]

As shown in the results of Table 1, in the comparative example exhaust system that does not depend on the configuration of the present embodiment, the CO component is discharged until 20 seconds after the start of the engine operation. In the example exhaust system, only about 20% of the emission of the comparative example exhaust system was emitted 10 seconds after the start of operation. Also, the CO emissions of the exhaust system of the example for 60 seconds from the start of the operation were reduced by 87.5% as compared with the exhaust system of the comparative example.
[0034]
Further, as shown in Table 1, the CO emission concentration is 0 in the exhaust system of the comparative example 60 seconds after the start of operation. This is a result of the main catalyst device installed in the exhaust system of the comparative example and the exhaust system of the example reacting properly. Conversely, within 60 seconds after the start of operation, the main catalyst device does not react properly. During this time, the CO gas is discharged to the atmosphere from the exhaust system without performing reaction purification.
[0035]
The main factor is that the temperature of the exhaust gas flowing into the main catalyst device is lower than the temperature required to start the reaction. By the way, the temperature of the exhaust gas immediately before the main catalytic converter at the time of the cold start in this measurement device is at a level of 30 to 150 ° C., particularly at the time of the cold start, the heat radiation cooling of the exhaust system and the residual moisture in the exhaust system before the measurement. Since the starting temperature of the catalyst of the main unit is approximately 200 ° C. due to the flying adhesion, it is considered that the catalyst cannot start the reaction. In order to raise the temperature of the exhaust gas early, improvements such as reducing the heat capacity of the manifold and increasing the gas heat capacity by increasing the engine speed during cold start have been taken in systems including the engine system. However, the effect is insufficient, and in reality, there is no other way but to prevent the cooling of the gas by bringing the mounting position of the catalyst device close to the vicinity of the manifold.
[0036]
On the other hand, mounting a catalyst device near the manifold requires a small, highly efficient catalyst that can withstand the contact of extremely high-temperature, large-volume gas when the engine is under heavy load and that fits in a small space inside the engine room. It is not suitable for a practically used catalyst material such as a honeycomb.
[0037]
The configuration of the embodiment of the present invention has a very high degree of freedom in terms of shape to adapt to these contradictory conditions, and is effective in a small amount depending on the arrangement of the catalyst layer (selection of the creepage contact or face-to-face contact direction). The adoption of a cross-shaped catalyst that can purify easily, and the catalyst device has a function to change the gas flow path that bypasses the catalyst layer, makes it possible to change the contact direction during cold start and during steady or high load operation, It was effective in both purification and durability. The exhaust system according to the present embodiment is capable of purifying the exhaust gas from the cold start, which has been impossible in the past, to the entire operation period, and achieves zero emission using only the engine system.
[0038]
In the configuration of the present embodiment, a cylindrical catalyst body is provided also in the manifold in order to promote the reaction start of the catalyst immediately below the engine. However, depending on the conditions of the engine system, the catalyst in the manifold may be provided. Even if it is not provided, the effect of the present embodiment is not particularly impaired.
[0039]
In addition, the opening and closing movable valve is provided at the end of the inflow pipe of the catalyst tank to form a flow path that bypasses the catalyst layer in the catalyst device immediately below the manifold. The flow can be changed so that it flows out of the outer peripheral surface of the catalyst body to the inner core tube, and is discharged to an exhaust pipe outside the device via the inner tube, and further, via a valve immediately before the entrance of the immediately below catalyst device. The effect of the present embodiment is not impeded by adopting a configuration in which the device is introduced into the device and the device is introduced into a bypass path leading to a rear exhaust pipe outside the device.
[0040]
【The invention's effect】
As described above, the effect of the present invention can contribute to the initiation and maintenance of the reaction of the next-stage catalyst by utilizing the reaction heat of the catalyst provided in the previous stage. In addition, the exhaust system as a whole can significantly reduce the total amount of reactants emitted during the operation period from the cold start of the engine to the operating period, and prevents the catalyst from abnormally high exhaust gas temperatures such as during overload operation. Life can be extended.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an automobile exhaust system according to a configuration of the present embodiment; FIG. 2 is a schematic diagram of an engine manifold; FIG. 3 is a diagram showing a configuration of a cylindrical catalyst body in a manifold; FIG. [Fig. 5] Schematic diagram of components directly below the catalyst device [Description of reference numerals]
DESCRIPTION OF SYMBOLS 1 Engine 2 Manifold piping 3

Catalyst device

22 and 341 directly under a manifold Inner cylinder part 23, 342 Catalyst body 24, 343 Outer cylinder part 34 Catalyst part 345 Opening / closing movable valve

Claims

An automotive exhaust purification catalyst device disposed in an exhaust system of an automobile, comprising: a first catalyst portion disposed in a cylindrical shape in an engine exhaust manifold directly connected to an engine; and a cylinder in an exhaust pipe directly connected to the engine exhaust manifold. A catalyst device for purifying an exhaust gas of an automobile, comprising a second catalyst portion arranged in a shape.

At least one of the first and second catalyst portions has a cylindrical catalyst body, a cylindrical inner cylinder portion and an outer cylinder portion having a hole, and the inner cylinder portion, the The automotive exhaust purification catalyst device according to claim 1, wherein the catalyst body and the outer cylinder portion are configured.

The second catalyst portion has a cylindrical catalyst body, a cylindrical inner cylinder portion having a hole, and an outer cylinder portion, and comprises the inner cylinder portion, the catalyst body, and the outer cylinder portion in order from the inside. 2. The automotive exhaust purification catalyst device according to claim 1, further comprising an open / close movable valve capable of opening and closing the outflowing gas at the end of the inner cylindrical portion.

By opening and closing the open / close movable valve, the flow of the exhaust gas can be varied in the creepage direction or the facing direction of the catalyst body, and when the movable valve is closed, the exhaust gas flows from the inner cylindrical portion to the outer cylindrical portion, and the exhaust gas flows. 4. The catalyst device for purifying an automobile exhaust gas according to claim 3, wherein the catalyst device comes into contact with the catalyst body in a facing direction.

5. The exhaust gas purifying catalyst device according to claim 4, wherein the open / close movable valve closes the movable valve when the engine is operated at a constant speed, so that the exhaust gas comes into contact with the catalyst body in a facing direction.

6. The catalyst device for purifying automobile exhaust gas according to claim 5, wherein the opening / closing movable valve closes the movable valve for a certain period during cold start of the engine so that the exhaust gas comes into contact with the catalyst body in a facing direction.

The catalyst device for purifying automobile exhaust according to claim 3 or 4, wherein the opening / closing movable valve automatically or manually opens and closes the movable valve by sensing the temperature or pressure of the exhaust gas.

At least one of the catalyst portions of the first catalyst portion and the second catalyst portion has silica cloth as a support, and at least a cross catalyst formed by supporting a catalyst substance on the surface thereof is provided on a winding core having an opening. The catalyst device for purifying an automobile exhaust gas according to any one of claims 1 to 7, wherein the catalyst device is constituted by a cylindrical catalyst body that is wound one or more times.