JP2008255890A - Exhaust emission control device of internal combustion engine - Google Patents

Exhaust emission control device of internal combustion engine Download PDF

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JP2008255890A
JP2008255890A JP2007099123A JP2007099123A JP2008255890A JP 2008255890 A JP2008255890 A JP 2008255890A JP 2007099123 A JP2007099123 A JP 2007099123A JP 2007099123 A JP2007099123 A JP 2007099123A JP 2008255890 A JP2008255890 A JP 2008255890A
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selective reduction
catalyst
main catalyst
cocatalyst
thin partition
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Toshisuke Toshioka
俊祐 利岡
Tomihisa Oda
富久 小田
Kazuhiro Ito
和浩 伊藤
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Toyota Motor Corp
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Toyota Motor Corp
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Priority to PCT/JP2008/057041 priority patent/WO2008126877A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
    • F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
    • F01N13/0097—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series the purifying devices are arranged in a single housing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/2073—Selective catalytic reduction [SCR] with means for generating a reducing substance from the exhaust gases
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2882—Catalytic reactors combined or associated with other devices, e.g. exhaust silencers or other exhaust purification devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2067—Urea
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts
    • B01D53/9477—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on separate bricks, e.g. exhaust systems
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/10—Capture or disposal of greenhouse gases of nitrous oxide (N2O)
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Toxicology (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To prematurely start the selectively reducing action of NOx after the start of an engine. <P>SOLUTION: An NOx selectively reducing main catalyst 15 is disposed in an engine exhaust passage. An NOx selectively reducing auxiliary catalyst 17 having a volume, heat capacity, and pressure loss smaller than those of the NOx selective reducing main catalyst 15 is disposed on the upstream side of the NOx selective reducing main catalyst 15. A urea is supplied from a urea solution supply valve 18 to the NOx selectively reducing auxiliary catalyst 17 to prematurely start the selectively reducing action of NOx after the start of the engine by the NOx selectively reducing auxiliary catalyst 17. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は内燃機関の排気浄化装置に関する。   The present invention relates to an exhaust emission control device for an internal combustion engine.

機関排気通路内にアンモニアによって排気ガス中に含まれるＮＯxを選択的に還元しうるＮＯx選択還元触媒を配置し、このＮＯx選択還元触媒の上流に排気ガス中に含まれるＮＯxを吸蔵しうるＮＯx吸蔵触媒や酸化触媒を配置した内燃機関が公知である（例えば特許文献１を参照）。
特開２００６−５１２５２９号公報 Place the NO x selective reduction catalyst which can selectively reduce NO x contained in the exhaust gas by ammonia in the engine exhaust passage, absorbing the NO x contained in the upstream of the the NO x selective reduction catalyst in the exhaust gas An internal combustion engine in which an NO x storage catalyst and an oxidation catalyst that can be used are arranged is known (see, for example, Patent Document 1).
JP 2006-512529 A

ところでＮＯx選択還元触媒は白金等の貴金属を担持しているＮＯx吸蔵触媒や酸化触媒とは異なって触媒反応による昇温が行われず、従って機関始動後ＮＯx選択還元触媒はＮＯx選択還元触媒に流入する排気ガス温によって温度上昇せしめられる。この場合、ＮＯx吸蔵触媒や酸化触媒において酸化反応が開始されれば排気ガス温は上昇するがＮＯx選択還元触媒は下流に配置されているためＮＯx選択還元触媒が温度上昇してＮＯxの選択還元が開始されるまで時間を要し、斯くして機関始動後にＮＯxの良好な浄化作用を確保することができないという問題がある。 By the way, the NO x selective reduction catalyst is different from the NO x storage catalyst and the oxidation catalyst that carry noble metals such as platinum, so the temperature rise by the catalytic reaction is not performed. Therefore, after the engine is started, the NO x selective reduction catalyst is the NO x selective reduction catalyst. The temperature is raised by the exhaust gas temperature flowing into the catalyst. In this case, if the oxidation reaction is started in the NO x storage catalyst or the oxidation catalyst, the exhaust gas temperature rises, but the NO x selective reduction catalyst is arranged downstream, so the NO x selective reduction catalyst rises in temperature and the NO x Therefore, there is a problem that it takes time until the selective reduction is started, and thus it is impossible to ensure a good NO x purification action after the engine is started.

上記問題を解決するために本発明によれば、機関排気通路内にＮＯx選択還元触媒を配置し、ＮＯx選択還元触媒に尿素を供給してこの尿素から発生するアンモニアにより排気ガス中に含まれるＮＯxを選択的に還元するようにした内燃機関の排気浄化装置において、ＮＯx選択還元触媒がＮＯx選択還元主触媒と、ＮＯx選択還元主触媒の上流に配置されかつＮＯx選択還元主触媒よりも容積、熱容量および圧損の小さいＮＯx選択還元補助触媒とにより構成され、ＮＯx選択還元補助触媒に尿素を供給してＮＯx選択還元補助触媒により機関始動後早期にＮＯxの選択還元作用を開始させるようにしている。 In order to solve the above problem, according to the present invention, a NO x selective reduction catalyst is arranged in the engine exhaust passage, urea is supplied to the NO x selective reduction catalyst, and is contained in the exhaust gas by ammonia generated from this urea. in the exhaust purification system of an internal combustion engine which is adapted to selectively reduce NO x to be, and the NO x selective reduction catalyst the NO x selective reduction main catalyst is disposed upstream of the NO x selective reduction main catalyst and the NO x selective reduction than the main catalyst volume, it is constituted by a small the NO x selective reduction cocatalyst heat capacity and pressure loss, selection of the NO x selective reduction supplemental catalyst by supplying urea the NO x selective reduction cocatalyst by engine startup after early NO x The reduction action is started.

ＮＯx選択還元補助触媒は、ＮＯx選択還元主触媒の上流に配置されかつＮＯx選択還元主触媒に比べて容積および熱容量が小さいので始動後早期に活性化されてＮＯxの選択還元作用が開始される。その結果、ＮＯxの浄化率が向上せしめられる。 The NO x selective reduction supplemental catalyst selective reduction action of the NO x selective disposed upstream of the reduction main catalyst and NO x since selective reduction main catalyst is smaller volume and heat capacity as compared to being activated after starting early NO x is Be started. As a result, the NO x purification rate is improved.

図１に圧縮着火式内燃機関の全体図を示す。
図１を参照すると、１は機関本体、２は各気筒の燃焼室、３は各燃焼室２内に夫々燃料を噴射するための電子制御式燃料噴射弁、４は吸気マニホルド、５は排気マニホルドを夫々示す。吸気マニホルド４は吸気ダクト６を介して排気ターボチャージャ７のコンプレッサ７ａの出口に連結され、コンプレッサ７ａの入口は吸入空気量検出器８を介してエアクリーナ９に連結される。吸気ダクト６内にはステップモータにより駆動されるスロットル弁１０が配置され、更に吸気ダクト６周りには吸気ダクト６内を流れる吸入空気を冷却するための冷却装置１１が配置される。図１に示される実施例では機関冷却水が冷却装置１１内に導かれ、機関冷却水によって吸入空気が冷却される。 FIG. 1 shows an overall view of a compression ignition type internal combustion engine.
Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, 4 is an intake manifold, and 5 is an exhaust manifold. Respectively. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 via the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 9 via the intake air amount detector 8. A throttle valve 10 driven by a step motor is disposed in the intake duct 6, and a cooling device 11 for cooling intake air flowing through the intake duct 6 is disposed around the intake duct 6. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 11, and the intake air is cooled by the engine cooling water.

一方、排気マニホルド５は排気ターボチャージャ７の排気タービン７ｂの入口に連結され、排気タービン７ｂの出口は酸化触媒１２の入口に連結される。この酸化触媒１２の下流には酸化触媒１２に隣接して排気ガス中に含まれる粒子状物質を捕集するためのパティキュレートフィルタ１３が配置され、このパティキュレートフィルタ１３の出口は排気管１４を介してＮＯx選択還元主触媒１５の入口に連結される。このＮＯx選択還元主触媒１５の出口には酸化触媒１６が連結される。本発明によればＮＯx選択還元主触媒１５上流の排気管１４内にＮＯx選択還元主触媒１５よりも容積、熱容量および圧損の小さいＮＯx選択還元補助触媒１７が配置される。 On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the inlet of the oxidation catalyst 12. Downstream of the oxidation catalyst 12, a particulate filter 13 for collecting particulate matter contained in the exhaust gas is disposed adjacent to the oxidation catalyst 12, and the outlet of the particulate filter 13 passes through the exhaust pipe 14. To the inlet of the NO x selective reduction main catalyst 15. An oxidation catalyst 16 is connected to the outlet of the NO x selective reduction main catalyst 15. Volume than the NO x selective reduction main catalyst 15 to the NO x selective reduction main catalyst 15 upstream of the exhaust pipe 14 according to the present invention, less the NO x selective reduction supplemental catalyst 17 heat capacity and pressure loss are disposed.

図１に示されるようにこのＮＯx選択還元補助触媒１７上流の排気管１４内には尿素水溶液供給弁１８が配置され、この尿素水溶液供給弁１８は供給管１９、供給ポンプ２０を介して尿素水溶液タンク２１に連結される。尿素水溶液タンク２１内に貯蔵されている尿素水溶液は供給ポンプ２０によって尿素水溶液供給弁１８から排気管１４内を流れる排気ガス中に噴射され、尿素から発生したアンモニア（（ＮＨ2）2ＣＯ＋Ｈ2Ｏ→２ＮＨ3＋ＣＯ2）によって排気ガス中に含まれるＮＯxがＮＯx選択還元補助触媒１７およびＮＯx選択還元主触媒１５において還元される。 As shown in FIG. 1, a urea aqueous solution supply valve 18 is disposed in the exhaust pipe 14 upstream of the NO x selective reduction auxiliary catalyst 17, and this urea aqueous solution supply valve 18 is urea via a supply pipe 19 and a supply pump 20. Connected to the aqueous solution tank 21. The urea aqueous solution stored in the urea aqueous solution tank 21 is injected from the urea aqueous solution supply valve 18 into the exhaust gas flowing in the exhaust pipe 14 by the supply pump 20, and ammonia generated from urea ((NH 2 ) 2 CO + H 2 O → 2NH 3 + CO 2 ) NO x contained in the exhaust gas is reduced in the NO x selective reduction auxiliary catalyst 17 and the NO x selective reduction main catalyst 15.

排気マニホルド５と吸気マニホルド４とは排気ガス再循環（以下、ＥＧＲと称す）通路２２を介して互いに連結され、ＥＧＲ通路２２内には電子制御式ＥＧＲ制御弁２３が配置される。また、ＥＧＲ通路２２周りにはＥＧＲ通路２２内を流れるＥＧＲガスを冷却するための冷却装置２４が配置される。図１に示される実施例では機関冷却水が冷却装置２４内に導かれ、機関冷却水によってＥＧＲガスが冷却される。一方、各燃料噴射弁３は燃料供給管２５を介してコモンレール２６に連結され、このコモンレール２６は電子制御式の吐出量可変な燃料ポンプ２７を介して燃料タンク２８に連結される。燃料タンク２８内に貯蔵されている燃料は燃料ポンプ２７によってコモンレール２６内に供給され、コモンレール２６内に供給された燃料は各燃料供給管２５を介して燃料噴射弁３に供給される。   The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 22, and an electronically controlled EGR control valve 23 is disposed in the EGR passage 22. A cooling device 24 for cooling the EGR gas flowing in the EGR passage 22 is disposed around the EGR passage 22. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 24, and the EGR gas is cooled by the engine cooling water. On the other hand, each fuel injection valve 3 is connected to a common rail 26 via a fuel supply pipe 25, and this common rail 26 is connected to a fuel tank 28 via an electronically controlled variable discharge amount fuel pump 27. The fuel stored in the fuel tank 28 is supplied into the common rail 26 by the fuel pump 27, and the fuel supplied into the common rail 26 is supplied to the fuel injection valve 3 through each fuel supply pipe 25.

酸化触媒１２は例えば白金のような貴金属触媒を担持しており、この酸化触媒１２は排気ガス中に含まれるＮＯをＮＯ2に転換する作用と排気ガス中に含まれるＨＣを酸化させる作用をなす。一方、パティキュレートフィルタ１３としては触媒を担持していないパティキュレートフィルタを用いることもできるし、例えば白金のような貴金属触媒を担持したパティキュレートフィルタを用いることもできる。 The oxidation catalyst 12 carries a noble metal catalyst such as platinum, for example. The oxidation catalyst 12 functions to convert NO contained in the exhaust gas into NO 2 and oxidize HC contained in the exhaust gas. . On the other hand, the particulate filter 13 may be a particulate filter that does not carry a catalyst, or a particulate filter that carries a noble metal catalyst such as platinum.

また、ＮＯx選択還元補助触媒１７およびＮＯx選択還元主触媒１５は低温で高いＮＯx浄化率を有するアンモニア吸着タイプのＦｅゼオライトから構成されるか、或いはアンモニアの吸着機能がないチタン・バナジウム系の触媒から構成される。酸化触媒１６は例えば白金からなる貴金属触媒を担持しており、この酸化触媒１６はＮＯx選択還元主触媒１５から漏出したアンモニアを酸化する作用をなす。 Further, the NO x selective reduction auxiliary catalyst 17 and the NO x selective reduction main catalyst 15 are composed of an ammonia adsorption type Fe zeolite having a high NO x purification rate at a low temperature, or a titanium / vanadium system having no ammonia adsorption function. It is comprised from the catalyst. The oxidation catalyst 16 carries a noble metal catalyst made of, for example, platinum, and this oxidation catalyst 16 functions to oxidize ammonia leaked from the NO x selective reduction main catalyst 15.

図２に図１に示されるＮＯx選択還元補助触媒１７およびＮＯx選択還元主触媒１５の拡大斜視図を示す。図２からわかるようにＮＯx選択還元主触媒１５は互いに交差する複数の薄肉隔壁３０によって分離された軸線方向に延びる複数のセル３１を有しており、ＮＯx選択還元補助触媒１７も互いに交差する複数の薄肉隔壁３２によって分離された軸線方向に延びる複数のセル３３を有している。 FIG. 2 shows an enlarged perspective view of the NO x selective reduction auxiliary catalyst 17 and the NO x selective reduction main catalyst 15 shown in FIG. As can be seen from FIG. 2, the NO x selective reduction main catalyst 15 has a plurality of cells 31 extending in the axial direction separated by a plurality of thin partition walls 30 intersecting each other, and the NO x selective reduction auxiliary catalyst 17 also intersects each other. A plurality of cells 33 extending in the axial direction are separated by a plurality of thin-walled partition walls 32.

一方、図２に示されるようにＮＯx選択還元補助触媒１７はＮＯx選択還元主触媒１５に比べて軸線方向の長さが短かく、しかもＮＯx選択還元補助触媒１７はＮＯx選択還元主触媒１５に比べて小さな径を有する。従ってＮＯx選択還元補助触媒１７はＮＯx選択還元主触媒１５に比べて容積が小さく、従って熱容量も小さい。 On the other hand, the NO x selective reduction auxiliary catalyst 17 is the length of the axial direction compared to the NO x selective reduction main catalyst 15 is short Moreover the NO x selective reduction supplemental catalyst 17, as shown in FIG. 2 the NO x selective reduction main It has a smaller diameter than the catalyst 15. Therefore, the NO x selective reduction auxiliary catalyst 17 is smaller in volume than the NO x selective reduction main catalyst 15, and therefore has a smaller heat capacity.

また、ＮＯx選択還元補助触媒１７による圧損を小さくすると共にＮＯx選択還元補助触媒１７の熱容量を小さくするために図２に示される如くＮＯx選択還元補助触媒１７のセル３３の流路面積はＮＯx選択還元主触媒１５のセル３１の流路面積よりも大きく形成されており、ＮＯx選択還元補助触媒１７の薄肉隔壁３２の厚みはＮＯx選択還元主触媒１５の薄肉隔壁３０の厚みに比べて薄く形成されている。 Further, the flow passage area of the cell 33 of the NO x selective reduction supplemental catalyst 17 as shown in FIG. 2 in order to reduce the heat capacity of the NO x selective reduction supplemental catalyst 17 together to reduce the pressure loss due to the NO x selective reduction cocatalyst 17 the NO x selective reduction main catalyst and 15 is formed larger than the flow passage area of the cell 31, the thickness of the thin partition wall 32 of the NO x selective reduction auxiliary catalyst 17 is the thickness of the thin partition wall 30 of the NO x selective reduction main catalyst 15 It is formed thinner than that.

また、ＮＯx選択還元主触媒１５の薄肉隔壁３１はセラミックから形成されているがＮＯx選択還元補助触媒１７の熱容量を更に小さくするためにＮＯx選択還元補助触媒１７の薄肉隔壁３２を金属板から形成することもできる。 The metal plate a thin partition wall 32 of the NO x selective reduction supplemental catalyst 17 in order but thin partition wall 31 of the NO x selective reduction main catalyst 15 is formed from a ceramic to further reduce the heat capacity of the NO x selective reduction cocatalyst 17 It can also be formed from.

ところでＮＯx選択還元主触媒１５は白金等の貴金属を担持していないので触媒反応による昇温が行われず、従って機関始動後ＮＯx選択還元主触媒１５はＮＯx選択還元主触媒１５に流入する排気ガス温によって温度上昇せしめられる。この場合、酸化触媒１２において酸化反応が開始されれば排気ガス温は上昇するがＮＯx選択還元主触媒１５は下流に配置されているためＮＯx選択還元主触媒１５が温度上昇してＮＯxの選択還元が開始されるまで時間を要し、斯くして機関始動後にＮＯxの良好な浄化作用を確保することができなくなる。 By the way, since the NO x selective reduction main catalyst 15 does not carry a noble metal such as platinum, the temperature rise by the catalytic reaction is not performed, and therefore the NO x selective reduction main catalyst 15 flows into the NO x selective reduction main catalyst 15 after the engine is started. The temperature is raised by the exhaust gas temperature. In this case, although the exhaust gas temperature if the oxidation reaction is initiated increases the NO x selective reduction main catalyst 15 in the oxidation catalyst 12 is the NO x selective reduction main catalyst 15 because it is arranged downstream is increased temperatures NO x Thus, it takes time until the selective reduction starts, and thus it becomes impossible to ensure a good NO x purification action after the engine is started.

しかしながら本発明ではＮＯx選択還元主触媒１５の上流に、ＮＯx選択還元主触媒１５に比べて容積および熱容量が小さく、従って始動後早期に活性化されるＮＯx選択還元補助触媒１７が配置されているので機関始動後早期にＮＯxの選択還元作用が開始される。その結果、ＮＯxの浄化率を向上することができる。 However upstream of the NO x selective reduction main catalyst 15 in the present invention, a small volume and heat capacity as compared to the NO x selective reduction main catalyst 15, therefore the NO x selective reduction supplemental catalyst 17 to be activated are arranged to start early after selective reduction action of NO x at an early stage after the engine is started since the are is initiated. As a result, the NO x purification rate can be improved.

図３に圧縮着火式内燃機関の別の実施例を示す。この実施例ではパティキュレートフィルタ１３が酸化触媒１６の下流に配置され、従ってこの実施例では酸化触媒１２の出口が排気管１４を介してＮＯx選択還元主触媒１５の入口に連結される。この実施例でもＮＯx選択還元主触媒１５上流の排気管１４内にＮＯx選択還元主触媒１５よりも容積、熱容量および圧損の小さいＮＯx選択還元補助触媒１７が配置される。 FIG. 3 shows another embodiment of the compression ignition type internal combustion engine. In this embodiment, the particulate filter 13 is disposed downstream of the oxidation catalyst 16. Therefore, in this embodiment, the outlet of the oxidation catalyst 12 is connected to the inlet of the NO x selective reduction main catalyst 15 via the exhaust pipe 14. Volume than the NO x selective reduction main catalyst 15 to the NO x selective reduction main catalyst 15 upstream of the exhaust pipe 14 in this embodiment, smaller the NO x selective reduction supplemental catalyst 17 heat capacity and pressure loss are disposed.

圧縮着火式内燃機関の全体図である。1 is an overall view of a compression ignition type internal combustion engine. 図１に示されるＮＯx選択還元主触媒とＮＯx選択還元補助触媒の拡大斜視図である。FIG. 2 is an enlarged perspective view of the NO x selective reduction main catalyst and the NO x selective reduction auxiliary catalyst shown in FIG. 1. 圧縮着火式内燃機関の別の実施例を示す全体図である。It is a general view which shows another Example of a compression ignition type internal combustion engine.

符号の説明Explanation of symbols

４ 吸気マニホルド
５ 排気マニホルド
７ 排気ターボチャージャ
１２，１６ 酸化触媒
１３ パティキュレートフィルタ
１５ ＮＯx選択還元主触媒
１７ ＮＯx選択還元補助触媒
１８ 尿素水溶液供給弁 4 Intake manifold 5 Exhaust manifold 7 Exhaust turbocharger 12, 16 Oxidation catalyst 13 Particulate filter 15 NO x selective reduction main catalyst 17 NO x selective reduction auxiliary catalyst 18 Urea aqueous solution supply valve

Claims (4)

機関排気通路内にＮＯx選択還元触媒を配置し、該ＮＯx選択還元触媒に尿素を供給して該尿素から発生するアンモニアにより排気ガス中に含まれるＮＯxを選択的に還元するようにした内燃機関の排気浄化装置において、上記ＮＯx選択還元触媒がＮＯx選択還元主触媒と、該ＮＯx選択還元主触媒の上流に配置されかつ該ＮＯx選択還元主触媒よりも容積、熱容量および圧損の小さいＮＯx選択還元補助触媒とにより構成され、該ＮＯx選択還元補助触媒に尿素を供給して該ＮＯx選択還元補助触媒により機関始動後早期にＮＯxの選択還元作用を開始させるようにした内燃機関の排気浄化装置。 The the NO x selective reduction catalyst arranged in the engine exhaust passage and adapted to selectively reduce NO x contained in the exhaust gas by the ammonia generated from the urea to supply urea to the the NO x selective reduction catalyst in the exhaust purification system of an internal combustion engine, the the NO x selective reduction catalyst and the NO x selective reduction main catalyst, the NO x is disposed upstream of the selective reduction main catalyst and the the NO x selective reduction main volume than catalysts, heat capacity and pressure loss It is constituted by a small the NO x selective reduction promoter catalyst with, so as to start the selective reduction action of the the NO x selective reduction supplemental catalyst by supplying urea to the the NO x selective reduction cocatalyst by engine startup after early NO x An exhaust purification device for an internal combustion engine. 上記ＮＯx選択還元主触媒およびＮＯx選択還元補助触媒は互いに交差する複数の薄肉隔壁によって分離された軸線方向に延びる複数のセルを有しており、該ＮＯx選択還元補助触媒のセルの流路面積は該ＮＯx選択還元主触媒のセルの流路面積よりも大きく形成されている請求項１に記載の内燃機関の排気浄化装置。 Has the the NO x selective reduction main catalyst and the NO x selective reduction cocatalyst plurality of cells extending to the separated axially by a plurality of thin partition walls which intersect each other, the flow of the the NO x selective reduction cocatalyst cell The exhaust purification device for an internal combustion engine according to claim 1, wherein the passage area is formed larger than the passage area of the cell of the NO x selective reduction main catalyst. 上記ＮＯx選択還元主触媒およびＮＯx選択還元補助触媒は互いに交差する複数の薄肉隔壁によって分離された軸線方向に延びる複数のセルを有しており、該ＮＯx選択還元補助触媒の薄肉隔壁の厚みは該ＮＯx選択還元主触媒の薄肉隔壁の厚みに比べて薄く形成されている請求項１に記載の内燃機関の排気浄化装置。 Has the the NO x selective reduction main catalyst and the NO x selective reduction cocatalyst plurality of cells extending to the separated axially by a plurality of thin partition walls which intersect each other, the thin partition walls of the the NO x selective reduction cocatalyst thickness exhaust gas control apparatus according to claim 1, which is formed thinner than the thickness of the thin partition wall of the the NO x selective reduction main catalyst. 上記ＮＯx選択還元主触媒およびＮＯx選択還元補助触媒は互いに交差する複数の薄肉隔壁によって分離された軸線方向に延びる複数のセルを有しており、該ＮＯx選択還元補助触媒の薄肉隔壁は金属板から形成されており、該ＮＯx選択還元主触媒の薄肉隔壁はセラミックから形成されている請求項１に記載の内燃機関の排気浄化装置。 Has the the NO x selective reduction main catalyst and the NO x selective reduction cocatalyst plurality of cells extending to the separated axially by a plurality of thin partition walls which intersect each other, the thin partition walls of the the NO x selective reduction promoter catalyst It is formed from a metal plate, the NO x thin partition walls of the selective reduction main catalyst exhaust gas control apparatus according to claim 1 which is formed from ceramic.
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JP2013124610A (en) * 2011-12-15 2013-06-24 Mitsubishi Motors Corp Exhaust emission control device of internal combustion engine
KR20150070266A (en) * 2012-10-18 2015-06-24 존슨 맛쎄이 퍼블릭 리미티드 컴파니 Close-coupled scr system
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