JP4698314B2 - Exhaust purification device - Google Patents

Exhaust purification device Download PDF

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JP4698314B2
JP4698314B2 JP2005206319A JP2005206319A JP4698314B2 JP 4698314 B2 JP4698314 B2 JP 4698314B2 JP 2005206319 A JP2005206319 A JP 2005206319A JP 2005206319 A JP2005206319 A JP 2005206319A JP 4698314 B2 JP4698314 B2 JP 4698314B2
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exhaust
flow rate
catalyst
temperature
oxidation
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JP2007023872A (en
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弘樹 上野
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UD Trucks Corp
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UD Trucks Corp
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    • 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
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9431—Processes characterised by a specific device
    • 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
    • B01D53/9495—Controlling the catalytic process
    • 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
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • F01N11/002—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
    • 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
    • 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
    • F01N13/0093—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 of the same type
    • 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
    • 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
    • F01N13/011—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 purifying devices arranged in parallel
    • 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
    • F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
    • F01N3/106—Auxiliary oxidation 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
    • 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
    • F01N3/2053—By-passing catalytic reactors, e.g. to prevent overheating
    • 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
    • F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/06—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a temperature sensor
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/07—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas flow rate or velocity meter or sensor, intake flow meters only when exclusively used to determine exhaust gas parameters
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • 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
    • Y02T10/40—Engine management systems

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

Description

本発明は、還元剤を用いて排気中の窒素酸化物（ＮＯｘ）を還元除去する排気浄化装置において、特に、ＮＯｘ浄化率を向上させる技術に関する。   The present invention relates to an exhaust purification apparatus that reduces and removes nitrogen oxide (NOx) in exhaust gas using a reducing agent, and more particularly to a technique for improving the NOx purification rate.

エンジン排気中のＮＯｘを除去する触媒浄化システムとして、特開２０００−２７６２７号公報（特許文献１）に記載された排気浄化装置が提案されている。
かかる排気浄化装置は、エンジン排気管に配設された還元触媒の排気上流に、エンジン運転状態に応じた還元剤を噴射供給することで、排気中のＮＯｘと還元剤とを触媒還元反応させて、ＮＯｘを無害成分に浄化処理するものである。ここで、還元反応は、ＮＯｘと反応性が良好なアンモニアを用いるもので、還元剤としては、排気熱及び排気中の水蒸気により加水分解してアンモニアを発生する尿素水溶液が用いられる。
特開２０００−２７６２７号公報 As a catalyst purification system for removing NOx in engine exhaust, an exhaust purification device described in Japanese Patent Laid-Open No. 2000-27627 (Patent Document 1) has been proposed.
Such an exhaust purification device causes a catalytic reduction reaction between NOx in the exhaust and the reducing agent by injecting and supplying a reducing agent according to the engine operating state to the upstream side of the exhaust of the reduction catalyst disposed in the engine exhaust pipe. , NOx is purified to harmless components. Here, the reduction reaction uses ammonia having good reactivity with NOx, and as the reducing agent, an aqueous urea solution that generates ammonia by hydrolysis with exhaust heat and water vapor in the exhaust is used.
JP 2000-27627 A

ところで、アンモニアを還元剤として用いる排気浄化装置では、排気中の一酸化窒素（ＮＯ）と二酸化窒素（ＮＯ2）との割合がある所定割合のときに、還元触媒によるＮＯｘ浄化率が最良となることが知られている。このため、還元触媒の排気上流に配設した酸化触媒により排気中のＮＯを酸化し、還元触媒に導入される排気中のＮＯとＮＯ2との割合を改善する技術が開発された。 By the way, in the exhaust purification apparatus using ammonia as a reducing agent, the NOx purification rate by the reduction catalyst is the best when the ratio of nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ) in the exhaust gas is a predetermined ratio. It is known. For this reason, a technique has been developed in which NO in the exhaust is oxidized by an oxidation catalyst disposed upstream of the reduction catalyst and the ratio of NO and NO 2 in the exhaust introduced into the reduction catalyst is improved.

しかしながら、排気中のＮＯとＮＯ2との割合はエンジン運転状態に応じて大きく変化する一方、酸化触媒によるＮＯをＮＯ2へと酸化させる酸化能力は大きく変化しないため、広範な運転領域でＮＯとＮＯ2との割合を所定割合に近づけることは困難であった。そして、排気中のＮＯとＮＯ2との割合が所定割合となっていない運転領域では、還元触媒によるＮＯｘ浄化率が低下し、浄化が不十分な排気が大気中に排出されてしまうおそれがあった。また、燃料である軽油，ガソリン，アルコール類などを還元剤として用いる排気浄化装置もあるが、広範な運転領域でＮＯとＮＯ2との割合を還元反応に適合した所定割合に近づけることが困難であり、同様な問題が発生するおそれがあった。 However, while the ratio of NO and NO 2 in the exhaust gas varies greatly depending on the engine operating state, the oxidation ability to oxidize NO to NO 2 by the oxidation catalyst does not change significantly, so NO and NO in a wide range of operation. It was difficult to bring the ratio of NO 2 close to a predetermined ratio. In the operation region where the ratio of NO to NO 2 in the exhaust gas is not a predetermined ratio, there is a risk that the NOx purification rate by the reduction catalyst is reduced and exhaust gas that is not sufficiently purified is discharged into the atmosphere. It was. There are also exhaust gas purification devices that use light oil, gasoline, alcohol, etc. as fuel as a reducing agent, but it is difficult to bring the ratio of NO and NO 2 close to a predetermined ratio suitable for the reduction reaction in a wide range of operation. There was a risk that similar problems would occur.

そこで、本発明は以上のような従来の問題点に鑑み、酸化触媒を通過させる排気流量を適宜制御することで、還元触媒に導入される排気中のＮＯとＮＯ2との割合を所定割合に近づけ、広範な運転領域でＮＯｘ浄化率を向上させた排気浄化装置を提供することを目的とする。 Therefore, in view of the conventional problems as described above, the present invention appropriately controls the exhaust flow rate through which the oxidation catalyst passes, so that the ratio of NO and NO 2 in the exhaust gas introduced into the reduction catalyst is set to a predetermined ratio. An object of the present invention is to provide an exhaust purification device that is close and has an improved NOx purification rate in a wide range of operation.

このため、請求項１記載の発明では、排気浄化装置は、エンジン排気管に配設され、窒素酸化物を還元剤により還元浄化する還元触媒と、該還元触媒の排気上流に位置する排気管を３つ以上に分岐した各分岐管に夫々配設され、一酸化窒素を二酸化窒素へと酸化させる酸化能力が相互に異なる複数の酸化触媒と、前記各分岐管に分流する排気流量を独立かつ多段階に制御可能な流量制御弁と、排気の体積流量を検出する排気流量検出手段と、前記酸化触媒の触媒温度を検出する温度検出手段と、前記排気流量検出手段により検出された体積流量及び前記温度検出手段により検出された触媒温度に基づいて、前記還元触媒に導入される排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づくように流量制御弁を制御する制御手段と、を含んで構成されたことを特徴とする。 Therefore, according to the first aspect of the present invention, the exhaust purification device includes a reduction catalyst disposed in the engine exhaust pipe for reducing and purifying nitrogen oxides with a reducing agent, and an exhaust pipe located upstream of the reduction catalyst. Each of the branch pipes branched into three or more is provided with a plurality of oxidation catalysts having different oxidation capacities for oxidizing nitric oxide into nitrogen dioxide, and an exhaust flow rate divided into each of the branch pipes independently. A flow control valve that can be controlled in stages, an exhaust flow rate detection means for detecting a volume flow rate of exhaust gas, a temperature detection means for detecting a catalyst temperature of the oxidation catalyst, a volume flow rate detected by the exhaust flow rate detection means, and the Control means for controlling the flow rate control valve based on the catalyst temperature detected by the temperature detection means so that the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst approaches a predetermined ratio; Including Characterized in that it consists in.

請求項２記載の発明では、排気浄化装置は、エンジン排気管に配設され、窒素酸化物を還元剤により還元浄化する還元触媒と、該還元触媒の排気上流に位置する排気管を３つ以上に分岐した各分岐管のうち、少なくとも１つを除いた分岐管に夫々配設され、一酸化窒素を二酸化窒素へと酸化させる酸化能力が相互に異なる複数の酸化触媒と、前記各分岐管に分流する排気流量を独立かつ多段階に制御可能な流量制御弁と、排気の体積流量を検出する排気流量検出手段と、前記酸化触媒の触媒温度を検出する温度検出手段と、前記排気流量検出手段により検出された体積流量及び前記温度検出手段により検出された触媒温度に基づいて、前記還元触媒に導入される排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づくように流量制御弁を制御する制御手段と、を含んで構成されたことを特徴とする。 According to a second aspect of the present invention, the exhaust purification device is provided in the engine exhaust pipe, and includes three or more reduction catalysts for reducing and purifying nitrogen oxides with a reducing agent, and three or more exhaust pipes located upstream of the reduction catalyst. And a plurality of oxidation catalysts that are arranged in the branch pipes except for at least one of the branch pipes branched to each other, and have different oxidation capacities for oxidizing nitric oxide into nitrogen dioxide, and each of the branch pipes. A flow rate control valve capable of controlling the exhaust flow rate to be divided independently and in multiple stages, an exhaust flow rate detection means for detecting the volume flow rate of exhaust gas, a temperature detection means for detecting the catalyst temperature of the oxidation catalyst, and the exhaust flow rate detection means On the basis of the volume flow rate detected by the temperature detector and the catalyst temperature detected by the temperature detection means, the flow rate control valve is set so that the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst approaches a predetermined ratio. And control means for controlling, characterized in that it is configured to include.

請求項３記載の発明では、前記制御手段は、排気の体積流量及び酸化触媒の触媒温度に対応した制御値が設定されたマップを参照して、前記流量制御弁を制御することを特徴とする。
請求項４記載の発明では、前記排気流量検出手段は、吸気の質量流量及びエンジンの燃料消費率から、排気の体積流量を間接的に検出することを特徴とする。 The invention according to claim 3 is characterized in that the control means controls the flow rate control valve with reference to a map in which control values corresponding to the exhaust gas volume flow rate and the catalyst temperature of the oxidation catalyst are set. .
According to a fourth aspect of the present invention, the exhaust flow rate detecting means indirectly detects the volume flow rate of the exhaust gas from the mass flow rate of the intake air and the fuel consumption rate of the engine.

請求項５記載の発明では、前記温度検出手段は、前記酸化触媒の排気上流における排気温度から、該酸化触媒の触媒温度を間接的に検出することを特徴とする。
請求項６記載の発明では、前記所定割合は、前記還元触媒による窒素酸化物の還元反応に適合した割合であることを特徴とする。 The invention according to claim 5 is characterized in that the temperature detecting means indirectly detects the catalyst temperature of the oxidation catalyst from the exhaust temperature upstream of the oxidation catalyst.
The invention according to claim 6 is characterized in that the predetermined ratio is a ratio suitable for a reduction reaction of nitrogen oxides by the reduction catalyst.

請求項１記載の発明によれば、還元触媒の排気上流に位置する排気管を３つ以上に分岐した各分岐管には、一酸化窒素を二酸化窒素へと酸化させる酸化能力が相互に異なる酸化触媒が夫々配設される。そして、還元触媒に導入される排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づくように、酸化触媒の酸化能力と密接な関連がある排気の体積流量及び酸化触媒の触媒温度に基づいて流量制御弁が制御され、各分岐管に分流される排気流量が独立かつ多段階に制御される。このため、一酸化窒素と二酸化窒素との割合が相互に異なる排気を適宜混合することで、排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づき、広範な運転領域において、窒素酸化物の浄化率を向上させることができる。 According to the first aspect of the present invention, each of the branch pipes branched into three or more exhaust pipes located upstream from the exhaust of the reduction catalyst has different oxidation capabilities for oxidizing nitric oxide into nitrogen dioxide. A catalyst is provided for each. The exhaust gas volume flow rate and the oxidation catalyst catalyst temperature are closely related to the oxidation ability of the oxidation catalyst so that the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst approaches a predetermined ratio. Based on this, the flow rate control valve is controlled, and the exhaust flow rate divided into each branch pipe is controlled independently and in multiple stages. For this reason, by appropriately mixing exhaust gases with different ratios of nitrogen monoxide and nitrogen dioxide, the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust approaches a predetermined ratio, and nitrogen oxidation is performed in a wide range of operation. The purification rate of things can be improved.

請求項２記載の発明によれば、還元触媒の排気上流に位置する排気管を３つ以上に分岐した各分岐管のうち、少なくとも１つを除いた分岐管には、一酸化窒素を二酸化窒素へと酸化させる酸化能力が相互に異なる複数の酸化触媒が夫々配設される。そして、還元触媒に導入される排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づくように、酸化触媒の酸化能力と密接な関連がある排気の体積流量及び酸化触媒の触媒温度に基づいて流量制御弁が制御され、各分岐管に分流される排気流量が独立かつ多段階に制御される。このため、一酸化窒素と二酸化窒素との割合が相互に異なる排気と一酸化窒素が酸化されていない排気とを適宜混合することで、排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づき、広範な運転領域において、窒素酸化物の浄化率を向上させることができる。 According to the second aspect of the present invention, nitrogen monoxide is added to the nitrogen dioxide in the branch pipes excluding at least one of the branch pipes branched into three or more exhaust pipes located upstream of the reduction catalyst. A plurality of oxidation catalysts having different oxidation capacities for oxidation to each other are provided. The exhaust gas volume flow rate and the oxidation catalyst catalyst temperature are closely related to the oxidation ability of the oxidation catalyst so that the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst approaches a predetermined ratio. Based on this, the flow rate control valve is controlled, and the exhaust flow rate divided into each branch pipe is controlled independently and in multiple stages. For this reason, the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas is appropriately mixed by appropriately mixing exhaust gas in which the ratios of nitric oxide and nitrogen dioxide are different from each other and exhaust gas in which nitric oxide is not oxidized. Thus, the nitrogen oxide purification rate can be improved in a wide range of operation.

請求項３記載の発明によれば、流量制御弁は、排気の体積流量及び酸化触媒の触媒温度に対応した制御値が設定されたマップを参照して制御されるため、流量制御に係る処理負荷増加を抑制することができる。
請求項４記載の発明によれば、排気の体積流量は、吸気の質量流量及びエンジンの燃料消費率から間接的に検出されるため、例えば、排気により流量センサの検出部が汚れることがなく、長年に亘って排気の体積流量を安定して検出することができる。 According to the third aspect of the present invention, the flow control valve is controlled with reference to a map in which control values corresponding to the exhaust gas volume flow rate and the catalyst temperature of the oxidation catalyst are set. Increase can be suppressed.
According to the invention described in claim 4 , since the volume flow rate of the exhaust gas is indirectly detected from the mass flow rate of the intake air and the fuel consumption rate of the engine, for example, the detection unit of the flow rate sensor is not contaminated by the exhaust gas. It is possible to stably detect the volume flow rate of the exhaust gas for many years.

請求項５記載の発明によれば、酸化触媒の触媒温度は、その排気上流における排気温度から間接的に検出されるため、酸化触媒に温度センサなどを付設する必要がなく、例えば、酸化触媒が部分的に高温になってもその熱影響を受けることを防止できる。
請求項６記載の発明によれば、還元触媒に導入される排気中の一酸化窒素と二酸化窒素との割合は、還元触媒による窒素酸化物の還元反応に適合した所定割合となるので、還元触媒における窒素酸化物の還元反応を効果的に促進することができる。 According to the invention described in claim 5 , since the catalyst temperature of the oxidation catalyst is indirectly detected from the exhaust temperature upstream of the exhaust, there is no need to attach a temperature sensor or the like to the oxidation catalyst. Even if the temperature becomes partially high, it can be prevented from being affected by the heat.
According to the sixth aspect of the present invention, the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst is a predetermined ratio suitable for the reduction reaction of nitrogen oxides by the reduction catalyst. The reduction reaction of nitrogen oxides in can be effectively promoted.

以下、添付された図面を参照して本発明を詳述する。
本発明の第１実施形態を示す図１において、エンジン１０に接続される排気管１２には、排気流通方向に沿って、還元剤としての尿素水溶液を噴射供給する噴射ノズル１４と、尿素水溶液を加水分解して得られるアンモニアによりＮＯｘを還元浄化するＮＯｘ還元触媒１６と、ＮＯｘ還元触媒１６を通過したアンモニアを酸化させるアンモニア酸化触媒１８と、が夫々配設される。噴射ノズル１４には、エンジン運転状態に応じた尿素水溶液が空気と混合した噴霧状態で供給される。また、ＮＯｘ還元触媒１６の排気上流に位置する排気管１２を２つに分岐した各分岐管１２Ａ及び１２Ｂには、排気流通方向に沿って、その排気通路面積（開度）を多段階に制御可能な電磁式の流量制御弁２０Ａ及び２０Ｂと、排気中のＮＯをＮＯ2へと酸化させる酸化触媒２２Ａ及び２２Ｂと、が夫々配設される。各分岐管１２Ａ及び１２Ｂに配設された酸化触媒２２Ａ及び２２Ｂは、相互に異なる酸化能力を有するものであって、例えば、図中上方及び下方に位置する酸化触媒２２Ａ及び２２Ｂとしては、夫々、触媒温度が所定値未満の低温で良好な酸化能力を発揮する低温酸化触媒、触媒温度が所定値以上の高温で良好な酸化能力を発揮する高温酸化触媒を用いることができる。 Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
In FIG. 1 illustrating the first embodiment of the present invention, an exhaust pipe 12 connected to an engine 10 is provided with an injection nozzle 14 for supplying and supplying a urea aqueous solution as a reducing agent along the exhaust circulation direction, and a urea aqueous solution. A NOx reduction catalyst 16 that reduces and purifies NOx with ammonia obtained by hydrolysis and an ammonia oxidation catalyst 18 that oxidizes the ammonia that has passed through the NOx reduction catalyst 16 are provided. The spray nozzle 14 is supplied with an aqueous urea solution corresponding to the engine operating state in a sprayed state mixed with air. In addition, the branch passages 12A and 12B that branch the exhaust pipe 12 located upstream of the NOx reduction catalyst 16 into two are controlled in multiple stages along the exhaust circulation direction. Possible electromagnetic flow control valves 20A and 20B and oxidation catalysts 22A and 22B that oxidize NO in the exhaust to NO 2 are provided, respectively. The oxidation catalysts 22A and 22B disposed in the branch pipes 12A and 12B have different oxidation capabilities. For example, as the oxidation catalysts 22A and 22B positioned at the upper side and the lower side in the figure, respectively, A low temperature oxidation catalyst that exhibits good oxidation ability at a low temperature where the catalyst temperature is less than a predetermined value, and a high temperature oxidation catalyst that exhibits good oxidation ability at a high temperature where the catalyst temperature is equal to or higher than a predetermined value can be used.

一方、排気浄化装置の制御系として、排気温度から酸化触媒２２Ａ及び２２Ｂの触媒温度Ｔを間接的に検出する温度検出手段としての排気温度センサ２４と、吸気の質量流量Ｆiを検出するエアフローセンサ２６と、が夫々設けられる。そして、排気温度センサ２４及びエアフローセンサ２６からの各出力信号は、コンピュータを内蔵したコントロールユニット２８に入力され、そのＲＯＭ（Read Only Memory）に記憶された制御プログラムにより、ＮＯｘ還元触媒１６に導入される排気中のＮＯとＮＯ2との割合が所定割合に近づくように、流量制御弁２０Ａ及び２０Ｂが夫々制御される。また、コントロールユニット２８は、ＣＡＮ（Controller Area Network）などを介して、エンジン１０の燃料噴射制御などを行なうエンジンコントロールユニット３０と相互通信可能に接続され、燃料消費率Ｃを適宜読み込み可能に構成されている。なお、制御プログラムを実行するコントロールユニット２８により制御手段が具現化されると共に、エアフローセンサ２６，コントロールユニット２８及びエンジンコントロールユニット３０の協働により排気流量検出手段が構成される。 On the other hand, as a control system of the exhaust purification device, an exhaust temperature sensor 24 as temperature detecting means for indirectly detecting the catalyst temperature T of the oxidation catalysts 22A and 22B from the exhaust temperature, and an air flow sensor 26 for detecting the mass flow rate Fi of the intake air. Are provided respectively. Each output signal from the exhaust temperature sensor 24 and the air flow sensor 26 is input to a control unit 28 incorporating a computer, and is introduced into the NOx reduction catalyst 16 by a control program stored in a ROM (Read Only Memory). The flow rate control valves 20A and 20B are controlled so that the ratio between NO and NO 2 in the exhaust gas approaches a predetermined ratio. The control unit 28 is connected to an engine control unit 30 that performs fuel injection control of the engine 10 via a CAN (Controller Area Network) or the like so as to be able to communicate with each other, and is configured to be able to read the fuel consumption rate C as appropriate. ing. Note that the control unit is implemented by the control unit 28 that executes the control program, and the exhaust flow rate detection unit is configured by the cooperation of the air flow sensor 26, the control unit 28, and the engine control unit 30.

図２は、コントロールユニット２８において、所定時間ごとに繰り返し実行される制御プログラムの内容を示す。
ステップ１（図では「Ｓ１」と略記する。以下同様）では、排気温度センサ２４から触媒温度Ｔを読み込む。ここで、触媒温度Ｔは、その排気上流における排気温度から間接的に検出されるため、酸化触媒２２Ａ及び２２Ｂに温度センサなどを付設する必要がなく、例えば、酸化触媒２２Ａ及び２２Ｂが部分的に高温となってもその熱影響を受けることを防止できる。 FIG. 2 shows the contents of a control program that is repeatedly executed by the control unit 28 every predetermined time.
In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the catalyst temperature T is read from the exhaust temperature sensor 24. Here, since the catalyst temperature T is indirectly detected from the exhaust temperature upstream of the exhaust, there is no need to attach a temperature sensor or the like to the oxidation catalysts 22A and 22B. For example, the oxidation catalysts 22A and 22B are partially Even if the temperature becomes high, it can be prevented from being affected by the heat.

ステップ２では、エアフローセンサ２６から吸気の質量流量Ｆiを読み込む。
ステップ３では、エンジンコントロールユニット３０から燃料消費率Ｃを読み込む。
ステップ４では、吸気の質量流量Ｆi及び燃料消費率Ｃに基づいて、所定演算式から排気の体積流量Ｆeを演算する。ここで、排気の体積流量Ｆeは、吸気の質量流量Ｆi及び燃料消費率Ｃから間接的に検出されるため、例えば、排気により流量センサの検出部が汚れることがなく、長年に亘って排気の体積流量Ｆeを安定して検出することができる。 In step 2, the mass flow rate Fi of the intake air is read from the air flow sensor 26.
In step 3, the fuel consumption rate C is read from the engine control unit 30.
In step 4, the exhaust volume flow rate Fe is calculated from a predetermined calculation formula based on the intake mass flow rate Fi and the fuel consumption rate C. Here, since the exhaust volume flow rate Fe is indirectly detected from the intake mass flow rate Fi and the fuel consumption rate C, for example, the exhaust gas does not contaminate the detection part of the flow sensor, and the exhaust gas flow rate for many years. The volume flow rate Fe can be detected stably.

ステップ５では、排気の体積流量及び酸化触媒の触媒温度に対応した制御値が設定されたマップを参照し、触媒温度Ｔ及び体積流量Ｆeに応じた制御値を演算する。ここで、制御値としては、流量制御弁２０Ａ及び２０Ｂの開度θ1及びθ2とすることができる。なお、流量制御弁２０Ａ及び２０Ｂの制御値は、マップを参照して演算されるため、流量制御に係る処理負荷増加を抑制することができる。 In step 5, a control value corresponding to the catalyst temperature T and the volume flow rate Fe is calculated with reference to a map in which control values corresponding to the exhaust gas volume flow rate and the catalyst temperature of the oxidation catalyst are set. Here, the control values can be the openings θ 1 and θ 2 of the flow control valves 20A and 20B. In addition, since the control value of the flow control valves 20A and 20B is calculated with reference to the map, an increase in processing load related to the flow control can be suppressed.

ステップ６では、制御値に応じて流量制御弁２０Ａ及び２０Ｂを夫々制御する。
かかる構成によれば、吸気の質量流量Ｆi及び燃料消費率Ｃから排気の体積流量Ｆeが演算された後、排気の体積流量Ｆe並びに酸化触媒２２Ａ及び２２Ｂの触媒温度Ｔをキーとしてマップを参照し、体積流量Ｆe及び触媒温度Ｔに対応した制御値（開度）が演算される。そして、制御値に基づいて流量制御弁２０Ａ及び２０Ｂが夫々制御され、各分岐管１２Ａ及び１２Ｂに分流される排気流量が独立かつ多段階に制御される。このため、実験などを通してマップに適切な制御値を設定しておけば、ＮＯとＮＯ2との割合が相互に異なる排気を適宜混合することで、排気中のＮＯとＮＯ2との割合が所定割合に近づき、広範な運転領域において、ＮＯｘ浄化率を向上させることができる。 In step 6, the flow control valves 20A and 20B are controlled according to the control value.
According to such a configuration, after the exhaust gas volume flow rate Fe is calculated from the intake mass flow rate Fi and the fuel consumption rate C, the map is referred to using the exhaust volume flow rate Fe and the catalyst temperature T of the oxidation catalysts 22A and 22B as keys. The control value (opening degree) corresponding to the volume flow rate Fe and the catalyst temperature T is calculated. Then, the flow rate control valves 20A and 20B are controlled based on the control values, respectively, and the exhaust flow rates divided into the branch pipes 12A and 12B are controlled independently and in multiple stages. Therefore, by setting the appropriate control value to the map through an experiment, the ratio of NO and NO 2 is to mix appropriate different exhaust mutually ratio between NO and NO 2 in the exhaust gas is predetermined As the ratio approaches, the NOx purification rate can be improved in a wide range of operation.

また、ＮＯｘ還元触媒１６の排気上流に空気と共に噴霧状態で噴射供給された尿素水溶液は、排気熱及び排気中の水蒸気により加水分解してアンモニア（ＮＨ3）となり、ＮＯｘ還元触媒１６へと供給される。そして、ＮＯｘ還元触媒１６において、排気中のＮＯｘがアンモニアと還元反応して無害な水（Ｈ2Ｏ）及び窒素（Ｎ2）となって大気中に排出される。このとき、ＮＯｘ還元触媒１６を通過したアンモニアは、その排気下流に配設されたアンモニア酸化触媒１８により酸化されるので、異臭を放つ排気が排出されることがない。 Further, the urea aqueous solution injected and supplied together with air upstream of the exhaust of the NOx reduction catalyst 16 is hydrolyzed by exhaust heat and water vapor in the exhaust to become ammonia (NH 3) and supplied to the NOx reduction catalyst 16. . In the NOx reduction catalyst 16, NOx in the exhaust gas undergoes a reduction reaction with ammonia and becomes harmless water (H 2 O) and nitrogen (N 2 ) and is discharged into the atmosphere. At this time, the ammonia that has passed through the NOx reduction catalyst 16 is oxidized by the ammonia oxidation catalyst 18 disposed downstream of the exhaust gas, so that exhaust that emits a strange odor is not discharged.

次に、本発明に係る排気浄化装置の第２実施形態について説明する。なお、以下の説明では、重複説明を排除する目的から、第１実施形態とは異なる構成についてのみ説明し、共通構成には同一符号を付してその説明を省略又は簡単とする。
本発明の第２実施形態の構成を示す図３において、図中上方に位置する分岐管１２Ａには、排気中のＮＯをＮＯ2へと酸化させる酸化触媒３２が配設される一方、図中下方に位置する分岐管１２Ｂには、その排気通路面積（開度）を多段階に制御可能な電磁式の流量制御弁３４が配設される。ここで、酸化触媒３２としては、例えば、多用されるエンジン運転状態で良好な酸化能力を発揮するものを用いることができる。また、流量制御弁３４を制御する制御プログラムとしては、第１実施形態におけるマップを多少変更するだけで、図２に示すものをそのまま利用することができる。 Next, a second embodiment of the exhaust emission control device according to the present invention will be described. In the following description, for the purpose of eliminating redundant description, only the configuration different from that of the first embodiment will be described, and the common configuration will be denoted by the same reference numeral, and the description thereof will be omitted or simplified.
In FIG. 3 showing the configuration of the second embodiment of the present invention, an oxidation catalyst 32 that oxidizes NO in the exhaust to NO 2 is disposed in the branch pipe 12A located in the upper part of the figure, while in the figure The branch pipe 12B located below is provided with an electromagnetic flow control valve 34 that can control the exhaust passage area (opening) in multiple stages. Here, as the oxidation catalyst 32, for example, a catalyst that exhibits a good oxidation ability in a frequently used engine operating state can be used. Further, as the control program for controlling the flow control valve 34, the one shown in FIG. 2 can be used as it is by only slightly changing the map in the first embodiment.

かかる構成によれば、酸化触媒３２を通過してＮＯがＮＯ2へと酸化された排気とＮＯが酸化されていない排気とを適宜混合することで、排気中のＮＯとＮＯ2との割合が所定割合に近づき、広範な運転領域において、ＮＯｘ浄化率を向上させることができる。
なお、以上説明した実施形態は、２つの分岐管により排気管が２つに分岐される構成であるが、３つ以上の分岐管により排気管を複数に分岐する構成であっても、本発明は適用可能である。このようにすれば、エンジン運転状態にかかわらず、ＮＯｘ還元触媒へと導入される排気中のＮＯとＮＯ2との割合を細かく変化させることが可能となり、ＮＯｘ浄化率を一層向上させることができる。また、各分岐管に分流する排気流量は、排気管の分岐部に配設された１つの流量制御弁で制御するようにしてもよい。 According to such a configuration, by mixing the exhaust and the exhaust and NO to NO through is oxidized to NO 2 oxidation catalyst 32 is not oxidized properly, the ratio of NO and NO 2 in the exhaust gas The NOx purification rate can be improved in a wide range of operation by approaching the predetermined ratio.
The embodiment described above has a configuration in which the exhaust pipe is branched into two by two branch pipes, but the present invention may be applied to a configuration in which the exhaust pipe is branched into a plurality of parts by three or more branch pipes. Is applicable. In this way, the ratio of NO and NO 2 in the exhaust gas introduced into the NOx reduction catalyst can be finely changed regardless of the engine operating state, and the NOx purification rate can be further improved. . Further, the exhaust flow rate to be branched to each branch pipe may be controlled by one flow rate control valve provided at the branch portion of the exhaust pipe.

さらに、還元剤としては、ＮＯｘ還元触媒における還元反応に応じて、炭化水素を主成分とする軽油，ガソリン，アルコール類などの各種燃料を用いるようにしてもよい。この場合、流量制御弁の制御としては、ＮＯｘ還元触媒に導入される排気中のＮＯとＮＯ2との割合が、ＮＯｘ還元触媒によるＮＯｘの還元反応に適合した所定割合に近づくようにすればよい。 Furthermore, as the reducing agent, various fuels such as light oil mainly composed of hydrocarbons, gasoline, and alcohols may be used according to the reduction reaction in the NOx reduction catalyst. In this case, as the control of the flow rate control valve, the ratio of NO and NO 2 in the exhaust gas introduced into the NOx reduction catalyst may be made to approach a predetermined ratio suitable for the NOx reduction reaction by the NOx reduction catalyst. .

本発明に係る排気浄化装置の第１実施形態を示す構成図The block diagram which shows 1st Embodiment of the exhaust gas purification apparatus which concerns on this invention. 排気浄化装置の制御内容を示すフローチャートFlow chart showing control contents of exhaust purification device 本発明に係る排気浄化装置の第２実施形態を示す構成図The block diagram which shows 2nd Embodiment of the exhaust gas purification apparatus which concerns on this invention.

符号の説明Explanation of symbols

１０ エンジン
１２ 排気管
１２Ａ 分岐管
１２Ｂ 分岐管
１６ ＮＯｘ還元触媒
２０Ａ 流量制御弁
２０Ｂ 流量制御弁
２２Ａ 酸化触媒
２２Ｂ 酸化触媒
２４ 排気温度センサ
２６ エアフローセンサ
２８ コントロールユニット
３０ エンジンコントロールユニット
３２ 酸化触媒
３４ 流量制御弁 DESCRIPTION OF SYMBOLS 10 Engine 12 Exhaust pipe 12A Branch pipe 12B Branch pipe 16 NOx reduction catalyst 20A Flow control valve 20B Flow control valve 22A Oxidation catalyst 22B Oxidation catalyst 24 Exhaust temperature sensor 26 Air flow sensor 28 Control unit 30 Engine control unit 32 Oxidation catalyst 34 Flow control valve

Claims (6)

エンジン排気管に配設され、窒素酸化物を還元剤により還元浄化する還元触媒と、
該還元触媒の排気上流に位置する排気管を３つ以上に分岐した各分岐管に夫々配設され、一酸化窒素を二酸化窒素へと酸化させる酸化能力が相互に異なる複数の酸化触媒と、
前記各分岐管に分流する排気流量を独立かつ多段階に制御可能な流量制御弁と、
排気の体積流量を検出する排気流量検出手段と、
前記酸化触媒の触媒温度を検出する温度検出手段と、
前記排気流量検出手段により検出された体積流量及び前記温度検出手段により検出された触媒温度に基づいて、前記還元触媒に導入される排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づくように流量制御弁を制御する制御手段と、
を含んで構成されたことを特徴とする排気浄化装置。 A reduction catalyst disposed in the engine exhaust pipe for reducing and purifying nitrogen oxides with a reducing agent;
A plurality of oxidation catalysts disposed in each branch pipe branched into three or more exhaust pipes located upstream of the reduction catalyst, and having different oxidation capacities for oxidizing nitric oxide into nitrogen dioxide;
A flow rate control valve capable of controlling the exhaust flow rate to be branched into each branch pipe independently and in multiple stages;
An exhaust flow rate detecting means for detecting the volume flow rate of the exhaust;
Temperature detecting means for detecting a catalyst temperature of the oxidation catalyst;
Based on the volume flow rate detected by the exhaust flow rate detection means and the catalyst temperature detected by the temperature detection means, the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst approaches a predetermined ratio. Control means for controlling the flow rate control valve,
An exhaust emission control device comprising: エンジン排気管に配設され、窒素酸化物を還元剤により還元浄化する還元触媒と、
該還元触媒の排気上流に位置する排気管を３つ以上に分岐した各分岐管のうち、少なくとも１つを除いた分岐管に夫々配設され、一酸化窒素を二酸化窒素へと酸化させる酸化能力が相互に異なる複数の酸化触媒と、
前記各分岐管に分流する排気流量を独立かつ多段階に制御可能な流量制御弁と、
排気の体積流量を検出する排気流量検出手段と、
前記酸化触媒の触媒温度を検出する温度検出手段と、
前記排気流量検出手段により検出された体積流量及び前記温度検出手段により検出された触媒温度に基づいて、前記還元触媒に導入される排気中の一酸化窒素と二酸化窒素との割合が所定割合に近づくように流量制御弁を制御する制御手段と、
を含んで構成されたことを特徴とする排気浄化装置。 A reduction catalyst disposed in the engine exhaust pipe for reducing and purifying nitrogen oxides with a reducing agent;
Oxidizing ability to oxidize nitrogen monoxide to nitrogen dioxide , which is provided in each branch pipe except at least one of the branch pipes branched into three or more exhaust pipes located upstream of the reduction catalyst. A plurality of different oxidation catalysts,
A flow rate control valve capable of controlling the exhaust flow rate to be branched into each branch pipe independently and in multiple stages;
An exhaust flow rate detecting means for detecting the volume flow rate of the exhaust;
Temperature detecting means for detecting a catalyst temperature of the oxidation catalyst;
Based on the volume flow rate detected by the exhaust flow rate detection means and the catalyst temperature detected by the temperature detection means, the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst approaches a predetermined ratio. Control means for controlling the flow rate control valve,
An exhaust emission control device comprising: 前記制御手段は、排気の体積流量及び酸化触媒の触媒温度に対応した制御値が設定されたマップを参照して、前記流量制御弁を制御することを特徴とする請求項１又は請求項２に記載の排気浄化装置。 3. The control unit according to claim 1, wherein the control unit controls the flow rate control valve with reference to a map in which control values corresponding to the exhaust gas volume flow rate and the catalyst temperature of the oxidation catalyst are set. The exhaust emission control device described . 前記排気流量検出手段は、吸気の質量流量及びエンジンの燃料消費率から、排気の体積流量を間接的に検出することを特徴とする請求項１〜請求項３のいずれか１つに記載の排気浄化装置。 4. The exhaust according to claim 1, wherein the exhaust flow rate detection unit indirectly detects a volume flow rate of the exhaust gas from a mass flow rate of intake air and a fuel consumption rate of the engine. Purification equipment. 前記温度検出手段は、前記酸化触媒の排気上流における排気温度から、該酸化触媒の触媒温度を間接的に検出することを特徴とする請求項１〜請求項４のいずれか１つに記載の排気浄化装置。 The exhaust according to any one of claims 1 to 4, wherein the temperature detection means indirectly detects the catalyst temperature of the oxidation catalyst from the exhaust temperature upstream of the oxidation catalyst. Purification equipment. 前記所定割合は、前記還元触媒による窒素酸化物の還元反応に適合した割合であることを特徴とする請求項１〜請求項５のいずれか１つに記載の排気浄化装置。 The exhaust gas purification device according to any one of claims 1 to 5, wherein the predetermined ratio is a ratio suitable for a reduction reaction of nitrogen oxides by the reduction catalyst .
JP2005206319A 2005-07-15 2005-07-15 Exhaust purification device Expired - Fee Related JP4698314B2 (en)

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