JP4290032B2 - Exhaust purification equipment - Google Patents
Exhaust purification equipment Download PDFInfo
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- JP4290032B2 JP4290032B2 JP2004041865A JP2004041865A JP4290032B2 JP 4290032 B2 JP4290032 B2 JP 4290032B2 JP 2004041865 A JP2004041865 A JP 2004041865A JP 2004041865 A JP2004041865 A JP 2004041865A JP 4290032 B2 JP4290032 B2 JP 4290032B2
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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
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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
- 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
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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
- 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
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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
- 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
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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
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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
- F01N3/206—Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents
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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
- F01N9/00—Electrical control of exhaust gas treating apparatus
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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
- F01N2390/00—Arrangements for controlling or regulating exhaust apparatus
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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
- F01N2410/00—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device
- F01N2410/02—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device in case of high temperature, e.g. overheating of catalytic reactor
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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
- F01N2410/00—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device
- F01N2410/06—By-passing, at least partially, exhaust from inlet to outlet of apparatus, to atmosphere or to other device at cold starting
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- 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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- 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)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Environmental & Geological Engineering (AREA)
- Toxicology (AREA)
- Exhaust Gas After Treatment (AREA)
- Exhaust Gas Treatment By Means Of Catalyst (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.
エンジンの排気に含まれる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)に開示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必要量の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。
Such an exhaust purification device injects and supplies a required amount of 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, thereby catalytically reducing NOx and the reducing agent in the exhaust. It is reacted to purify NOx into 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.
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制御することで、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 controls the flow rate of exhaust gas that passes through the oxidation catalyst, thereby bringing the ratio of NO and NO 2 in the exhaust gas closer to a predetermined ratio, and in a wide range of operation. An object of the present invention is to provide an exhaust emission control device with an improved NOx purification rate.
このため、請求項1記載の発明では、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制御する流量制御弁と、エンジン運転状態を検出する運転状態検出手段と、該運転状態検出手段により検出されたエンジン運転状態に基づいて、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 reduction catalyst disposed in the engine exhaust pipe and reducing and purifying nitrogen oxides with a reducing agent and the exhaust pipe located upstream of the reduction catalyst are branched into three or more . Each of the branched pipes is provided in a branch pipe except at least one, and is divided into a plurality of oxidation catalysts having different oxidation capacities for oxidizing nitric oxide into nitrogen dioxide, and the branched pipes. A flow rate control valve for controlling the exhaust flow rate, an operating state detecting means for detecting the engine operating state, and monoxide in the exhaust gas introduced into the reduction catalyst based on the engine operating state detected by the operating state detecting means And a control means for controlling the flow rate control valve so that the ratio of nitrogen and nitrogen dioxide approaches a predetermined ratio.
請求項2記載の発明では、前記制御手段は、エンジン運転状態に基づいて、前記各分岐管のうちの1つを排他的に開通させる制御を行うことを特徴とする。
請求項3記載の発明では、前記制御手段は、エンジン運転状態に基づいて、前記各分岐管に分流する排気流量を夫々独立して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
The invention according to claim 3 is characterized in that the control means independently controls the exhaust flow rate to be divided into the branch pipes based on the engine operating state.
The invention according to claim 4 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、エンジン運転状態に基づいて流量制御弁が制御され、各分岐管に分流する排気流量が制御される。このため、エンジン運転状態に適合した酸化触媒により、排気中の一酸化窒素が二酸化窒素へと酸化され、両者の割合を所定割合に近づけることが可能となることから、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, nitrogen monoxide is added to nitrogen dioxide in the branch pipes excluding at least one of the branch pipes obtained by branching the exhaust pipe located upstream of the reduction catalyst into three or more. A plurality of oxidation catalysts having different oxidation capacities for oxidation to each other are provided. Then, the flow rate control valve is controlled based on the engine operating state so that the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst approaches a predetermined rate, and the exhaust flow rate to be branched to each branch pipe is Be controlled. For this reason, the nitric oxide in the exhaust gas is oxidized to nitrogen dioxide by the oxidation catalyst suitable for the engine operating condition, and the ratio of both can be brought close to a predetermined ratio. The purification rate of oxide can be improved.
請求項2記載の発明によれば、エンジン運転状態に基づいて各分岐管のうちの1つを排他的に開通させることで、流量制御弁として、その流路を単に開閉するものを使用することが可能となり、コスト上昇及び制御内容が複雑になることを抑制できる。
請求項3記載の発明によれば、エンジン運転状態に基づいて各分岐管に分流する排気流量を夫々独立して制御することで、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を細かく変化させることができる。このため、エンジン運転状態にかかわらず、窒素酸化物の浄化率を一層向上させることができる。
According to the second aspect of the present invention, a flow control valve that simply opens and closes the flow path is used by exclusively opening one of the branch pipes based on the engine operating state. Therefore, it is possible to suppress an increase in cost and complicated control contents.
According to the third aspect of the present invention, by independently controlling the flow rate of the exhaust gas diverted to each branch pipe based on the engine operating state, the nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst can be reduced. The ratio of can be changed finely. For this reason, the purification rate of nitrogen oxides can be further improved regardless of the engine operating state.
請求項4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、還元触媒により窒素酸化物の還元反応に適合した所定割合となるので、還元触媒によ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 fourth aspect of the present invention, the ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas introduced into the reduction catalyst becomes a predetermined ratio suitable for the reduction reaction of nitrogen oxides by the reduction catalyst. It is possible to effectively promote the reduction reaction of nitrogen oxides due to.
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必要量の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、その排気通路を開閉する流量制御弁としての電磁式開閉弁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、上方及び下方に位置する分岐管12A及び12Bに配設された酸化触媒22A及び22Bとしては、夫々、排気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、排気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。
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
一方、各分岐管12A及び12Bを開閉し、これらに分流する排気流量を制御する電磁式開閉弁20A及び20Bの制御系として、エンジン回転速度Neを検出する回転速度センサ24と、エンジン負荷Qを検出する負荷センサ26と、が夫々設けられる。ここで、負荷Qとしては、アクセル開度,スロットル開度,吸気流量,吸気負圧,燃料噴射量などが利用可能である。そして、回転速度センサ24及び負荷センサ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って、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排気流路を切り替えるべく、電磁式開閉弁20A及び20Bが夫々開閉制御される。なお、コントロールユニット28に記憶された制御プログラムにより、制御手段が実現される一方、回転速度センサ24及び負荷センサ26により、運転状態検出手段が構成される。
On the other hand, as a control system for the electromagnetic on-off
図2は、第1実施形態における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、回転速度センサ24及び負荷センサ26から回転速度Ne及び負荷Qを夫々読み込む。
ステップ2では、エンジン運転状態、即ち、回転速度及び負荷に適合した排気流路が予め設定されたマップを参照し、現在の回転速度Ne及び負荷Qに応じた排気流路を決定する。ここで、「排気流路」とは、排気が流通する分岐管12A又は12Bを特定するものであって、回転速度Ne及び負荷Qにより推定可能な排気性状(特に、排気中のNOとNO2との割合)に応じて、排気を低温酸化触媒22A又は高温酸化触媒22Bのどちらに導入するかを特定するものである。
FIG. 2 shows the contents of a control program that is repeatedly executed at predetermined time intervals in the
In step 1 (abbreviated as “S1” in the figure, the same applies hereinafter), the rotational speed Ne and the load Q are read from the
In
ステップ3では、排気流路を切り替える必要があるか否かを判定する。そして、排気流路を切り替える必要があればステップ4へと進み(Yes)、低温酸化触媒22A又は高温酸化触媒22Bのいずれか一方に排気が排他的に導入されるように、電磁式開閉弁20A及び20Bを夫々開閉制御する。一方、排気流路を切り替える必要がなければ、不要な制御による電力消費量の増大,電磁式開閉弁20A及び20Bからの作動音発生などを防止すべく、電磁式開閉弁20A及び20Bを開閉制御せずに処理を終了する(No)。
In step 3, it is determined whether it is necessary to switch the exhaust passage. If it is necessary to switch the exhaust flow path, the process proceeds to Step 4 (Yes), and the electromagnetic on-off
かかる構成によれば、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べく、エンジンの回転速度Ne及び負荷Qに適合した排気流路が決定され、電磁式開閉弁20A及び20Bが夫々開閉制御される。このため、エンジン10の排気は、低温酸化触媒22A又は高温酸化触媒22Bのいずれか一方に選択的かつ排他的に導入され、その酸化能力に応じてNOがNO2となり、NOとNO2との割合が所定割合に近づくように改善される。酸化触媒22A又は22BによりNOとNO2との割合が改善された排気は、NOx還元触媒16へと導入される。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。
According to such a configuration, the exhaust flow path suitable for the engine speed Ne and the load Q is determined so that the ratio of NO and NO 2 in the exhaust gas introduced into the
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、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30が配設される一方、下方に位置する分岐管12Bには、その排気通路の開口面積を任意に増減制御可能な電磁式流量制御弁32が配設される。ここで、酸化触媒30は、例えば、エンジン定常状態で良好な酸化能力を発揮するものが用いられる。
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, the
図4は、第2実施形態における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11では、回転速度センサ24及び負荷センサ26から回転速度Ne及び負荷Qを夫々読み込む。
ステップ12では、エンジン運転状態、即ち、回転速度及び負荷に適合した弁開度が予め設定されたマップを参照し、現在の回転速度Ne及び負荷Qに応じた電磁式流量制御弁32の弁開度を決定する。ここで、「弁開度」とは、分岐管12B排気通路の開口面積を制御するパラメータであって、その開口面積を増減させることで、各分岐管12A及び12Bを流通する排気流量を任意に制御できる。このため、NOとNO2との割合が未調整の排気と酸化触媒30によりNO2の割合が増加した排気とを混合して、その割合を所定割合に近づけることができる。
FIG. 4 shows the contents of a control program that is repeatedly executed at predetermined time intervals in the
In step 11, the rotational speed Ne and the load Q are read from the
In
ステップ13では、分岐管12Bの開口面積を増減すべく、弁開度に応じて電磁式流量制御弁32を制御する。
かかる構成によれば、酸化触媒30を通過する排気流量とこれを通過しない排気流量とを任意に制御可能であることから、これらを混合して得られる排気中のNOとNO2との割合を連続的に変化させることができる。このため、エンジン運転状態にかかわらず、NOx還元触媒16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ることが可能となり、NOx浄化率を効果的に向上させることができる。
In step 13, the electromagnetic
According to such a configuration, the exhaust gas flow rate that passes through the
なお、以上説明した実施形態では、2つの分岐管により排気管が2つに分岐される構成について説明したが、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、第1実施形態において、各分岐管を流通する排気流量を任意に増減制御したり、第2実施形態において、排気が流通する分岐管を選択的かつ排他的に切り替えるようにしてもよい。 In the above-described embodiment, the configuration in which the exhaust pipe is branched into two by the two branch pipes has been described. However, even in the configuration in which the exhaust pipe is branched into two or more by the three or more branch pipes, The invention 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, in the first embodiment, the exhaust flow rate through each branch pipe may be arbitrarily increased or decreased, or in the second embodiment, the branch pipe through which the exhaust flows may be selectively and exclusively switched.
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. .
10 エンジン
12 排気管
12A 分岐管
12B 分岐管
16 NOx還元触媒
20A 電磁式開閉弁
20B 電磁式開閉弁
22A 酸化触媒
22B 酸化触媒
24 回転速度センサ
26 負荷センサ
28 コントロールユニット
30 酸化触媒
32 電磁式流量制御弁
DESCRIPTION OF
Claims (4)
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制御する流量制御弁と、
エンジン運転状態を検出する運転状態検出手段と、
該運転状態検出手段により検出されたエンジン運転状態に基づいて、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 for controlling an exhaust flow rate to be diverted to each branch pipe;
An operating state detecting means for detecting an engine operating state;
Control means for controlling the flow rate control valve 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 the engine operating condition detected by the operating condition detecting means When,
An exhaust emission control device comprising:
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JP2004041865A JP4290032B2 (en) | 2004-02-18 | 2004-02-18 | Exhaust purification equipment |
PCT/JP2005/001769 WO2005078250A1 (en) | 2004-02-18 | 2005-02-07 | Engine exhaust emission control system |
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US20080295499A1 (en) * | 2007-05-31 | 2008-12-04 | James Joshua Driscoll | Exhaust system utilizing a low-temperature oxidation catalyst |
US8516802B2 (en) * | 2010-10-29 | 2013-08-27 | Tenneco Automotive Operating Company Inc. | High volume exhaust gas treatment system |
CN102003262A (en) * | 2010-11-24 | 2011-04-06 | 奇瑞汽车股份有限公司 | Dual pre-catalysis exhaust device |
KR101474281B1 (en) | 2012-12-13 | 2014-12-18 | 한국에너지기술연구원 | Application and Control Method of Aftertreatment System for Vehicle/Engine to Reduce Ammonia Slip using AOC |
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