JP2008002355A - Exhaust emission control device - Google Patents

Exhaust emission control device Download PDF

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JP2008002355A
JP2008002355A JP2006172414A JP2006172414A JP2008002355A JP 2008002355 A JP2008002355 A JP 2008002355A JP 2006172414 A JP2006172414 A JP 2006172414A JP 2006172414 A JP2006172414 A JP 2006172414A JP 2008002355 A JP2008002355 A JP 2008002355A
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exhaust
reduction catalyst
control device
emission control
exhaust gas
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Hiroshi Funahashi
博 舟橋
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Hino Motors Ltd
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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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  • Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Silencers (AREA)
  • Exhaust-Gas Circulating Devices (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of achieving reduction of NOx immediately after engine starting, which has been difficult in the past. <P>SOLUTION: The exhaust emission control device is equipped with a selective reduction type catalyst 12 in the middle of an exhaust pipe 11, is adapted to reduce NOx by adding urea water 15 (reducing agent) to an upstream side of the selective reduction type catalyst 12 and comprises an exhaust throttle valve 25 (exhaust throttle means) for properly throttling the exhaust pipe 11 (exhaust flow path) and a hot EGR line 23 (EGR line) for recirculating a part of exhaust gas 9 to an intake pipe 5 (intake flow path) on an upstream side from the exhaust throttle valve 25 without cooling the exhaust gas. The exhaust emission control device is enabled to operate the exhaust throttle valve 25 for close and open the hot EGR line 23 at a proper degree of open through an EGR valve 24 in the engine starting. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、ＮＯxを還元剤と反応させて還元浄化する選択還元型触媒を排気管の途中に装備した排気浄化装置に関するものである。   The present invention relates to an exhaust emission control device equipped with a selective reduction catalyst that reduces and purifies NOx by reacting with a reducing agent in the middle of an exhaust pipe.

従来より、ディーゼルエンジンにおいては、排気ガスが流通する排気管の途中に、酸素共存下でも選択的にＮＯxを還元剤と反応させる性質を備えた選択還元型触媒を装備し、該選択還元型触媒の上流側に必要量の還元剤を添加して該還元剤を選択還元型触媒上で排気ガス中のＮＯx（窒素酸化物）と還元反応させ、これによりＮＯxの排出濃度を低減し得るようにしたものがある。   Conventionally, a diesel engine is equipped with a selective reduction catalyst having a property of selectively reacting NOx with a reducing agent even in the presence of oxygen in the middle of an exhaust pipe through which exhaust gas flows, and the selective reduction catalyst A required amount of a reducing agent is added to the upstream side of the catalyst so that the reducing agent undergoes a reduction reaction with NOx (nitrogen oxide) in the exhaust gas on the selective catalytic reduction catalyst, thereby reducing the NOx emission concentration. There is what I did.

他方、プラント等における工業的な排煙脱硝処理の分野では、還元剤にアンモニア（ＮＨ3）を用いてＮＯxを還元浄化する手法の有効性が既に広く知られているところであるが、自動車の場合には、アンモニアそのものを搭載して走行することに関し安全確保が困難であるため、近年においては、毒性のない尿素水を還元剤として使用することが考えられており、既に一部の車両では、尿素水を選択還元型触媒の還元剤としてＮＯxの低減化を図るシステムが実現しているという状況にある。 On the other hand, in the field of industrial flue gas denitration treatment in plants and the like, the effectiveness of a method for reducing and purifying NOx using ammonia (NH 3 ) as a reducing agent is already widely known. Since it is difficult to ensure safety when traveling with ammonia itself, in recent years, it has been considered to use non-toxic urea water as a reducing agent. A system for reducing NOx using urea water as a reducing agent for the selective catalytic reduction catalyst has been realized.

即ち、尿素水を選択還元型触媒の上流側で排気ガス中に添加すれば、約１７０℃以上の温度条件下で前記尿素水がアンモニアと炭酸ガスに分解され、選択還元型触媒上で排気ガス中のＮＯxがアンモニアにより良好に還元浄化されることになる。   That is, if urea water is added to the exhaust gas upstream of the selective catalytic reduction catalyst, the urea water is decomposed into ammonia and carbon dioxide under a temperature condition of about 170 ° C. or higher, and the exhaust gas is exhausted on the selective catalytic reduction catalyst. The NOx contained therein is reduced and purified well by ammonia.

尚、尿素水を還元剤としてＮＯxを還元浄化する選択還元型触媒を用いた排気浄化装置に関連する先行技術文献情報としては、例えば本発明と同じ出願人による下記の特許文献１等がある。
特開２００４−２７０５６５号公報 Prior art document information related to an exhaust purification device using a selective reduction catalyst that reduces and purifies NOx using urea water as a reducing agent includes, for example, the following Patent Document 1 by the same applicant as the present invention.
JP 2004-270565 A

しかしながら、斯かる従来の排気浄化装置においては、始動時にエンジンや管路が冷えきってしまっているので、これらのウォームアップに排気熱の大半が奪われてしまい、選択還元型触媒に導入される排気ガスの温度がなかなか上がってこないという不具合があり、これにより選択還元型触媒の床温度が活性温度域までなかなか上がりきらず、エンジン始動から暫くの間は良好なＮＯx低減効果を得ることができないという問題があった。   However, in such a conventional exhaust purification device, since the engine and the pipe line are completely cooled at the time of starting, most of the exhaust heat is taken away by these warm-ups and introduced into the selective catalytic reduction catalyst. There is a problem that the temperature of the exhaust gas does not rise easily. As a result, the bed temperature of the selective catalytic reduction catalyst does not rise easily to the activation temperature range, and a good NOx reduction effect cannot be obtained for a while from the start of the engine. There was a problem.

特に還元剤として尿素水を使用する場合には、蒸発、加熱、アンモニア化反応、ＮＯx還元浄化反応といった一連の行程を経るのに時間がかかり、しかも、尿素水の蒸発に多くの潜熱が奪われることになるため、エンジン始動直後から選択還元型触媒を良好に働かせることが困難であった。   In particular, when urea water is used as the reducing agent, it takes time to go through a series of steps such as evaporation, heating, ammoniation reaction, NOx reduction purification reaction, and much latent heat is lost to the evaporation of urea water. Therefore, it has been difficult to make the selective catalytic reduction work well immediately after the engine is started.

本発明は上述の実情に鑑みてなしたもので、従来において困難であったエンジン始動直後からのＮＯx低減を実現し得る排気浄化装置を提供することを目的としている。   The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust purification device capable of realizing NOx reduction immediately after engine start, which has been difficult in the prior art.

本発明は、排気管の途中に選択還元型触媒を装備し且つ該選択還元型触媒の上流側に還元剤を添加してＮＯxを還元浄化するようにした排気浄化装置であって、排気流路を適宜に絞り込む排気絞り手段と、該排気絞り手段より上流側で排気ガスの一部を抜き出して吸気流路に再循環するＥＧＲラインとを備え、エンジン始動時に排気絞り手段を閉操作し且つＥＧＲラインを適宜な開度で開通し得るように構成したことを特徴とするものである。   The present invention relates to an exhaust gas purification apparatus equipped with a selective reduction catalyst in the middle of an exhaust pipe and adding a reducing agent to the upstream side of the selective reduction catalyst to reduce and purify NOx. And an EGR line that extracts a part of the exhaust gas upstream of the exhaust throttle means and recirculates it to the intake passage, and closes the exhaust throttle means when the engine is started and EGR It is characterized in that the line can be opened at an appropriate opening degree.

而して、このようにすれば、エンジン始動時に排気絞り手段が閉操作されて排気流路が絞り込まれ、該排気絞り手段より上流側で排気圧力が上昇し且つこの排気圧力の上昇に伴い排気温度も高められる一方、排気抵抗が高まることでエンジンの気筒内に比較的温度の低い吸気が流入し難くなって比較的温度の高い排気ガスの残留量が増加し、この比較的温度の高い排気ガスを多く含む気筒内の空気が圧縮行程で圧縮されて爆発行程を迎えることでも更なる排気温度の上昇が図られる。   Thus, when the engine is started, the exhaust throttle means is closed to narrow the exhaust passage, and the exhaust pressure rises upstream from the exhaust throttle means. While the temperature is increased, the exhaust resistance increases, making it difficult for the intake air having a relatively low temperature to flow into the engine cylinder, and the residual amount of the exhaust gas having a relatively high temperature increases. The exhaust temperature can be further increased by the air in the cylinder containing a large amount of gas being compressed in the compression stroke and reaching the explosion stroke.

この際、ＥＧＲラインが適宜な開度で開通されて排気ガスの一部が吸気流路に再循環されるので、その再循環の度に繰り返し排気温度の上昇が図られて排気絞り手段より上流側の排気温度が相乗的に高まり、これによりエンジンや管路の急速なウォームアップが図られてエンジン始動直後から選択還元型触媒に対して高温の排気ガスが導入されることになる。   At this time, since the EGR line is opened at an appropriate opening degree and a part of the exhaust gas is recirculated to the intake flow path, the exhaust temperature is repeatedly increased every time the recirculation is performed, and the upstream side of the exhaust throttle means. As a result, the exhaust temperature on the side of the engine increases synergistically, so that the engine and pipe line are rapidly warmed up, and high-temperature exhaust gas is introduced into the selective catalytic reduction catalyst immediately after the engine is started.

この結果、エンジン始動から極めて短時間のうちに選択還元型触媒の床温度が活性温度域に到達し、エンジン始動直後から還元剤の添加を開始してＮＯxを選択還元型触媒上で還元浄化することが可能となる。   As a result, the bed temperature of the selective catalytic reduction catalyst reaches the activation temperature within an extremely short time after the engine is started, and the NOx is reduced and purified on the selective catalytic reduction catalyst by starting the addition of the reducing agent immediately after the engine startup. It becomes possible.

また、エンジン始動時からＥＧＲラインを通して排気ガスの一部が再循環されるようになっているので、この排気ガスの再循環により気筒内の燃焼温度が抑制されてＮＯxの発生が低減される作用も併用されることになる。   Further, since a part of the exhaust gas is recirculated through the EGR line from the start of the engine, the exhaust gas recirculation suppresses the combustion temperature in the cylinder and reduces the generation of NOx. Will also be used together.

また、本発明をより具体的に実施するに際しては、ＥＧＲラインが排気ガスを冷却しないまま吸気流路に再循環するホットＥＧＲラインであることが好ましく、更には、還元剤を尿素水として、選択還元型触媒を酸素共存下でも選択的にＮＯxをアンモニアと反応させ得る性質を有するものとすることが好ましい。   Further, when carrying out the present invention more specifically, it is preferable that the EGR line is a hot EGR line that recirculates to the intake passage without cooling the exhaust gas, and further, the reducing agent is selected as urea water. It is preferable that the reducing catalyst has a property capable of selectively reacting NOx with ammonia even in the presence of oxygen.

尚、排気絞り手段は、選択還元型触媒より上流側に配置されていても、選択還元型触媒より下流側に配置されていても良いが、特に選択還元型触媒より下流側に排気絞り手段が配置されている場合には、エンジンから選択還元型触媒まで一緒にウォームアップすることが可能となる。   The exhaust throttle means may be arranged upstream of the selective catalytic reduction catalyst, or may be arranged downstream of the selective catalytic reduction catalyst. In particular, the exhaust throttle means is downstream of the selective catalytic reduction catalyst. When it is arranged, it is possible to warm up together from the engine to the selective catalytic reduction catalyst.

上記した本発明の排気浄化装置によれば、エンジン始動から極めて短時間のうちに選択還元型触媒の床温度を活性温度域に到達させて還元剤の添加を開始することができ、しかも、この際に排気ガスの一部を再循環させてＮＯxの発生を低減する作用を併用することもできるので、従来において困難であったエンジン始動直後からのＮＯx低減を良好に実現することができるという優れた効果を奏し得る。   According to the above-described exhaust purification device of the present invention, it is possible to start the addition of the reducing agent by causing the bed temperature of the selective catalytic reduction catalyst to reach the active temperature range within a very short time from the start of the engine. At the same time, it is also possible to use the effect of reducing the generation of NOx by recirculating a part of the exhaust gas. The effects can be achieved.

以下本発明の実施の形態を図面を参照しつつ説明する。   Embodiments of the present invention will be described below with reference to the drawings.

図１は本発明を実施する形態の一例を示すもので、図１中における１はターボチャージャ２を装備したディーゼルエンジンを示しており、エアクリーナ３から導かれた吸気４が吸気管５を通し前記ターボチャージャ２のコンプレッサ２ａへと送られ、該コンプレッサ２ａで加圧された吸気４がインタークーラ６へと送られて冷却され、該インタークーラ６から更に吸気マニホールド７へと吸気４が導かれてディーゼルエンジン１の各気筒８（図１では直列６気筒の場合を例示している）に分配されるようになっている。   FIG. 1 shows an example of an embodiment for carrying out the present invention. In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a turbocharger 2, and intake air 4 guided from an air cleaner 3 passes through an intake pipe 5. The intake air 4 sent to the compressor 2 a of the turbocharger 2 and pressurized by the compressor 2 a is sent to the intercooler 6 to be cooled, and the intake air 4 is further guided from the intercooler 6 to the intake manifold 7. The diesel engine 1 is distributed to each cylinder 8 (the case of in-line 6 cylinders is illustrated in FIG. 1).

一方、このディーゼルエンジン１の各気筒８から排出された排気ガス９は、排気マニホールド１０を介しターボチャージャ２のタービン２ｂへと送られ、該タービン２ｂを駆動した排気ガス９が排気管１１を介し車外へ排出されるようにしてある。   On the other hand, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 10, and the exhaust gas 9 that has driven the turbine 2b passes through the exhaust pipe 11. It is designed to be discharged outside the vehicle.

また、この排気管１１の途中には、酸素共存下でも選択的にＮＯxをアンモニアと反応させ得る性質を備えた選択還元型触媒１２が触媒ケーシング１３に抱持されて装備されており、この選択還元型触媒１２の後段には、該選択還元型触媒１２を未反応のまま通過した余剰のアンモニアを酸化処理するＮＨ3スリップ防止触媒１４が装備されている。 In the middle of the exhaust pipe 11, a selective reduction catalyst 12 having a property capable of selectively reacting NOx with ammonia even in the presence of oxygen is provided by being held in a catalyst casing 13. An NH 3 anti-slip catalyst 14 that oxidizes surplus ammonia that has passed through the selective reduction catalyst 12 while remaining unreacted is provided downstream of the reduction catalyst 12.

そして、この選択還元型触媒１２の入側と、所要場所に設けられて尿素水１５を貯蔵するタンク１６との間が添加ライン１７により接続されていて、該添加ライン１７の途中に装備したポンプ１８の駆動によりタンク１６内の尿素水１５が抜き出されるようになっている。   The inlet side of the selective catalytic reduction catalyst 12 and a tank 16 that is provided at a required place and stores the urea water 15 are connected by an addition line 17, and a pump equipped in the middle of the addition line 17. The urea water 15 in the tank 16 is extracted by driving 18.

また、添加ライン１７のポンプ１８より下流側に添加バルブ１９が設けられ、該添加バルブ１９に対しエアタンク２０からプロテクションバルブ２１を介して加圧空気を導く添加用エアライン２２が接続されており、前記添加バルブ１９にて添加用エアライン２２からの加圧空気の流れに尿素水１５を随伴させてエア吹きにより前記選択還元型触媒１２の入側に還元剤として噴霧し得るようにしてある。   Further, an addition valve 19 is provided on the downstream side of the pump 18 of the addition line 17, and an addition air line 22 that leads the pressurized air from the air tank 20 via the protection valve 21 is connected to the addition valve 19. The addition valve 19 allows the urea water 15 to accompany the flow of pressurized air from the addition air line 22 and can be sprayed as a reducing agent on the inlet side of the selective catalytic reduction catalyst 12 by air blowing.

ここで、前記エアタンク２０は、従来よりバスやトラック等の車両に搭載されているもので、図示しないエンジン駆動のエアコンプレッサにより昇圧された加圧空気をドライヤを通して湿分を除去した上で貯えるようにしたものである。   Here, the air tank 20 is conventionally mounted on a vehicle such as a bus or a truck, and stores the pressurized air pressurized by an engine-driven air compressor (not shown) after removing moisture through a dryer. It is a thing.

更に、図１に図示している例では、排気マニホールド１０における各気筒８の並び方向の一端部と、吸気マニホールド７に接続されている吸気管５（吸気流路）の一端部との間がホットＥＧＲライン２３（ＥＧＲライン）で接続されており、排気マニホールド１０から抜き出した排気ガス９の一部を冷却しないままＥＧＲバルブ２４を介して吸気管５に再循環するようにしてあると共に、排気管１１におけるタービン２ｂの出口付近には、排気管１１（排気流路）を適宜に絞り込む排気絞りバルブ２５（排気絞り手段）が設けられている。   Further, in the example shown in FIG. 1, there is a gap between one end of the exhaust manifold 10 in the arrangement direction of the cylinders 8 and one end of the intake pipe 5 (intake flow path) connected to the intake manifold 7. It is connected by a hot EGR line 23 (EGR line), and a part of the exhaust gas 9 extracted from the exhaust manifold 10 is recirculated to the intake pipe 5 through the EGR valve 24 without being cooled. In the vicinity of the outlet of the turbine 2b in the pipe 11, an exhaust throttle valve 25 (exhaust throttle means) is provided for appropriately narrowing down the exhaust pipe 11 (exhaust flow path).

そして、これらホットＥＧＲライン２３のＥＧＲバルブ２４及び排気絞りバルブ２５は、エンジン制御コンピュータ（ＥＣＵ：Electronic Control Unit）を成す制御装置２６からの開度指令信号２４ａ，２５ａにより適宜な開度に制御されるようになっており、前記制御装置２６にてディーゼルエンジン１の始動が確認された時に、排気絞りバルブ２５を閉操作し且つＥＧＲバルブ２４を適宜な開度で開操作してホットＥＧＲライン２３を開通し得るようにしてある。   The EGR valve 24 and the exhaust throttle valve 25 of the hot EGR line 23 are controlled to appropriate opening degrees by opening degree command signals 24a and 25a from a control device 26 constituting an engine control computer (ECU: Electronic Control Unit). When the start of the diesel engine 1 is confirmed by the control device 26, the exhaust throttle valve 25 is closed, and the EGR valve 24 is opened at an appropriate opening degree to open the hot EGR line 23. Can be opened.

ここで、排気絞りバルブ２５は、従来より周知の排気ブレーキを機能的に兼用するもので良く、この排気絞りバルブ２５に対し本来の排気ブレーキとしての作動から独立したエンジン始動時専用の特殊な作動を指令し得るようになっていれば良い。   Here, the exhaust throttle valve 25 may be functionally used as a conventionally well-known exhaust brake, and the exhaust throttle valve 25 is specially operated exclusively for engine startup independent of the original exhaust brake operation. As long as it can be commanded.

尚、従来より周知の排気ブレーキがそうであるように、前記排気絞りバルブ２５は、閉操作により排気管１１を全閉としてしまうようなものではなく、ディーゼルエンジン１の始動を阻害しない程度の必要最小開度を残して閉操作されるようになっており、また、ホットＥＧＲライン２３のＥＧＲバルブ２４も、ある程度の制限をもって排気ガス９を再循環させるべく所要の開度に絞られてホットＥＧＲライン２３を開通させるようになっている。   Note that, as is the case with conventionally known exhaust brakes, the exhaust throttle valve 25 is not such that the exhaust pipe 11 is fully closed by a closing operation, and it is necessary not to hinder the starting of the diesel engine 1. The EGR valve 24 of the hot EGR line 23 is also closed to leave the minimum opening, and the EGR valve 24 of the hot EGR line 23 is also throttled to a required opening to recirculate the exhaust gas 9 with a certain limit. The line 23 is opened.

また、前記制御装置２６には、排気管１１における選択還元型触媒１２の入側に設置された温度センサ２７からの検出信号２７ａが入力されるようになっており、この温度センサ２７からの検出信号２７ａに基づいて、選択還元型触媒１２に導入される排気ガス９の温度が所定温度まで到達したことが確認された時に、前記排気絞りバルブ２５を開操作して通常の排気ブレーキとしての作動に復帰せしめ且つＥＧＲバルブ２４を閉止してホットＥＧＲライン２３を閉塞するようにしてある。   Further, a detection signal 27 a from a temperature sensor 27 installed on the inlet side of the selective reduction catalyst 12 in the exhaust pipe 11 is input to the control device 26, and detection from the temperature sensor 27 is performed. Based on the signal 27a, when it is confirmed that the temperature of the exhaust gas 9 introduced into the selective catalytic reduction catalyst 12 has reached a predetermined temperature, the exhaust throttle valve 25 is opened to operate as a normal exhaust brake. The EGR valve 24 is closed and the hot EGR line 23 is closed.

尚、ここに図示している例では、排気管１１における選択還元型触媒１２の入側に温度センサ２７を設置し、この温度センサ２７からの検出信号２７ａに基づいて、選択還元型触媒１２に導入される排気ガス９の温度を確認するようにしているが、エンジン冷却水の温度等を代用値として用いても良い。   In the example shown here, a temperature sensor 27 is installed on the inlet side of the selective catalytic reduction catalyst 12 in the exhaust pipe 11, and the selective catalytic reduction catalyst 12 is applied based on a detection signal 27 a from the temperature sensor 27. Although the temperature of the introduced exhaust gas 9 is confirmed, the temperature of the engine cooling water or the like may be used as a substitute value.

而して、このように排気浄化装置を構成すれば、エンジン始動時に制御装置２６からの開度指令信号２５ａにより排気絞りバルブ２５が閉操作されて排気管１１が絞り込まれ、該排気絞りバルブ２５より上流側で排気圧力が上昇するので、この排気圧力の上昇に伴い排気温度も高められることになる。   Thus, if the exhaust gas purification device is configured in this way, the exhaust throttle valve 25 is closed by the opening command signal 25a from the control device 26 when the engine is started, and the exhaust pipe 11 is throttled. Since the exhaust pressure rises further on the upstream side, the exhaust temperature increases with the increase of the exhaust pressure.

一方、排気抵抗が高まることでディーゼルエンジン１の気筒８内に比較的温度の低い吸気が流入し難くなって比較的温度の高い排気ガス９の残留量が増加し、この比較的温度の高い排気ガス９を多く含む気筒８内の空気が圧縮行程で圧縮されて爆発行程を迎えることでも更なる排気温度の上昇が図られる。   On the other hand, since the exhaust resistance is increased, the intake air having a relatively low temperature is difficult to flow into the cylinder 8 of the diesel engine 1, and the residual amount of the exhaust gas 9 having a relatively high temperature is increased. The exhaust gas temperature can be further increased by the air in the cylinder 8 containing a large amount of the gas 9 being compressed in the compression stroke and reaching the explosion stroke.

この際、ホットＥＧＲライン２３がＥＧＲバルブ２４により適宜な開度で開通されて排気ガス９の一部が冷却されないまま吸気管５に再循環されるので、その再循環の度に繰り返し排気温度の上昇が図られて排気絞りバルブ２５より上流側の排気温度が相乗的に高まり、これによりディーゼルエンジン１や排気管１１等の管路の急速なウォームアップが図られてエンジン始動直後から選択還元型触媒１２に対して高温の排気ガス９が導入されることになる。   At this time, the hot EGR line 23 is opened by the EGR valve 24 at an appropriate opening degree, and a part of the exhaust gas 9 is recirculated to the intake pipe 5 without being cooled. As a result of the increase, the exhaust temperature upstream of the exhaust throttle valve 25 increases synergistically, thereby rapidly warming up the pipelines of the diesel engine 1 and the exhaust pipe 11 and the like. The hot exhaust gas 9 is introduced into the catalyst 12.

この結果、エンジン始動から極めて短時間のうちに選択還元型触媒１２の床温度が活性温度域に到達し、エンジン始動直後から尿素水１５の添加を開始してＮＯxを選択還元型触媒１２上で還元浄化することが可能となる。   As a result, the bed temperature of the selective catalytic reduction catalyst 12 reaches the active temperature range within a very short time after the engine is started, and the addition of the urea water 15 is started immediately after the engine is started, so that NOx is added to the selective catalytic reduction catalyst 12. Reduction and purification can be performed.

また、エンジン始動時からホットＥＧＲライン２３を通して排気ガス９の一部が再循環されるようになっているので、この排気ガス９の再循環により気筒８内の燃焼温度が抑制されてＮＯxの発生が低減される作用も併用されることになる。   Further, since a part of the exhaust gas 9 is recirculated through the hot EGR line 23 from the start of the engine, the recirculation of the exhaust gas 9 suppresses the combustion temperature in the cylinder 8 and generates NOx. The effect of reducing the amount is also used in combination.

尚、選択還元型触媒１２に導入される排気ガス９の温度が所定温度まで到達したことが温度センサ２７により確認されたら、前記排気絞りバルブ２５が開操作されて通常の排気ブレーキとしての作動に復帰し、ＥＧＲバルブ２４は閉止してホットＥＧＲライン２３が閉塞されることになるが、この段階では選択還元型触媒１２の触媒活性が向上して該選択還元型触媒１２によるＮＯxの処理量が十分に増大しているので、もはやホットＥＧＲライン２３を通した排気ガス９の再循環は不要となる。   When the temperature sensor 27 confirms that the temperature of the exhaust gas 9 introduced into the selective catalytic reduction catalyst 12 has reached a predetermined temperature, the exhaust throttle valve 25 is opened to operate as a normal exhaust brake. Then, the EGR valve 24 is closed and the hot EGR line 23 is closed. At this stage, the catalytic activity of the selective catalytic reduction catalyst 12 is improved and the amount of NOx treated by the selective catalytic reduction catalyst 12 is increased. Since it has increased sufficiently, it is no longer necessary to recirculate the exhaust gas 9 through the hot EGR line 23.

従って、上記形態例によれば、エンジン始動から極めて短時間のうちに選択還元型触媒１２の床温度を活性温度域に到達させて尿素水１５の添加を開始することができ、しかも、この際に排気ガス９の一部を再循環させてＮＯxの発生を低減する作用を併用することもできるので、従来において困難であったエンジン始動直後からのＮＯx低減を良好に実現することができる。   Therefore, according to the above embodiment, the addition of the urea water 15 can be started by causing the bed temperature of the selective catalytic reduction catalyst 12 to reach the activation temperature range within a very short time after the engine is started. In addition, since the exhaust gas 9 can be partly recirculated to reduce the generation of NOx, the NOx reduction immediately after starting the engine, which has been difficult in the past, can be satisfactorily realized.

図２は本発明の別の形態例を示すもので、本形態例においては、選択還元型触媒１２を抱持している触媒ケーシング１３の出口側に排気絞りバルブ２５を配置した場合を例示しており、このようにした場合には、エンジン始動時に制御装置２６からの開度指令信号２５ａにより排気絞りバルブ２５が閉操作され、該排気絞りバルブ２５より上流側で排気圧力が上昇して排気温度も高められることになるが、ディーゼルエンジン１から選択還元型触媒１２まで一緒にウォームアップすることが可能となるので、より効果的に選択還元型触媒１２の床温度を上昇させることができる。   FIG. 2 shows another embodiment of the present invention. In this embodiment, the case where the exhaust throttle valve 25 is arranged on the outlet side of the catalyst casing 13 holding the selective catalytic reduction catalyst 12 is illustrated. In this case, when the engine is started, the exhaust throttle valve 25 is closed by the opening command signal 25a from the control device 26, and the exhaust pressure rises on the upstream side of the exhaust throttle valve 25. Although the temperature is also increased, it is possible to warm up the diesel engine 1 to the selective catalytic reduction catalyst 12 together, so that the bed temperature of the selective catalytic reduction catalyst 12 can be increased more effectively.

尚、本発明の排気浄化装置は、上述の形態例にのみ限定されるものではなく、選択還元型触媒に対し軽油等の尿素水以外の還元剤を添加する形式の排気浄化装置にも同様に適用し得ること、また、排気絞り手段は、排気流路を構成する排気管以外の部材に設けられていても良いこと、更に、ＥＧＲラインは、排気管の途中から排気ガスを抜き出したり、吸気マニホールドに排気ガスを再循環させたりする形式のものであっても良いこと、その他、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。   Note that the exhaust purification apparatus of the present invention is not limited to the above-described embodiment, and similarly to an exhaust purification apparatus of a type in which a reducing agent other than urea water such as light oil is added to the selective catalytic reduction catalyst. The exhaust throttle means may be provided in a member other than the exhaust pipe constituting the exhaust flow path. Further, the EGR line may extract exhaust gas from the middle of the exhaust pipe, Of course, the exhaust gas may be recirculated through the manifold, and various changes can be made without departing from the scope of the present invention.

本発明を実施する形態の一例を示す概略図である。It is the schematic which shows an example of the form which implements this invention. 本発明の別の形態例を示す概略図である。It is the schematic which shows another form example of this invention.

符号の説明Explanation of symbols

１ ディーゼルエンジン（エンジン）
５ 吸気管（吸気流路）
９ 排気ガス
１１ 排気管（排気流路）
１２ 選択還元型触媒
１５ 尿素水（還元剤）
２３ ホットＥＧＲライン（ＥＧＲライン）
２４ ＥＧＲバルブ
２４ａ 開度指令信号
２５ 排気絞りバルブ（排気絞り手段）
２５ａ 開度指令信号
２６ 制御装置 1 Diesel engine (engine)
5 Intake pipe (intake flow path)
9 Exhaust gas 11 Exhaust pipe (exhaust flow path)
12 Selective reduction type catalyst 15 Urea water (reducing agent)
23 Hot EGR line (EGR line)
24 EGR valve 24a Opening command signal 25 Exhaust throttle valve (exhaust throttle means)
25a Opening command signal 26 Control device

Claims (5)

排気管の途中に選択還元型触媒を装備し且つ該選択還元型触媒の上流側に還元剤を添加してＮＯxを還元浄化するようにした排気浄化装置であって、排気流路を適宜に絞り込む排気絞り手段と、該排気絞り手段より上流側で排気ガスの一部を抜き出して吸気流路に再循環するＥＧＲラインとを備え、エンジン始動時に排気絞り手段を閉操作し且つＥＧＲラインを適宜な開度で開通し得るように構成したことを特徴とする排気浄化装置。   An exhaust gas purification apparatus equipped with a selective reduction catalyst in the middle of an exhaust pipe and adding a reducing agent to the upstream side of the selective reduction catalyst to reduce and purify NOx. The exhaust throttle means and an EGR line that extracts a part of the exhaust gas upstream from the exhaust throttle means and recirculates it to the intake passage, closes the exhaust throttle means when the engine is started, and sets the EGR line appropriately. An exhaust emission control device configured to be opened at an opening. ＥＧＲラインが排気ガスを冷却しないまま吸気流路に再循環するホットＥＧＲラインであることを特徴とする請求項１に記載の排気浄化装置。   2. The exhaust emission control device according to claim 1, wherein the EGR line is a hot EGR line that recirculates to the intake air flow path without cooling the exhaust gas. 還元剤が尿素水であり、選択還元型触媒が酸素共存下でも選択的にＮＯxをアンモニアと反応させ得る性質を有するものであることを特徴とする請求項１又は２に記載の排気浄化装置。   The exhaust emission control device according to claim 1 or 2, wherein the reducing agent is urea water, and the selective catalytic reduction catalyst has a property capable of selectively reacting NOx with ammonia even in the presence of oxygen. 排気絞り手段が選択還元型触媒より上流側に配置されていることを特徴とする請求項１、２又は３に記載の排気浄化装置。   The exhaust emission control device according to claim 1, 2 or 3, wherein the exhaust throttle means is disposed upstream of the selective catalytic reduction catalyst. 排気絞り手段が選択還元型触媒より下流側に配置されていることを特徴とする請求項１、２又は３に記載の排気浄化装置。   The exhaust purification device according to claim 1, 2 or 3, wherein the exhaust throttle means is disposed downstream of the selective reduction catalyst.
JP2006172414A 2006-06-22 2006-06-22 Exhaust emission control device Pending JP2008002355A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100795249B1 (en) * 2003-05-29 2008-01-15 수미도모 메탈 인더스트리즈, 리미티드 A substrate for a stamper and preparing method for a substrate for a stamper
US9243538B1 (en) * 2014-07-08 2016-01-26 Cummins Inc. Reduced emissions internal combustion engine systems
WO2024134987A1 (en) * 2022-12-20 2024-06-27 株式会社クボタ Diesel engine

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0569317U (en) * 1992-02-24 1993-09-21 日産ディーゼル工業株式会社 Exhaust gas purification device for internal combustion engine
JP2006037769A (en) * 2004-07-23 2006-02-09 Hino Motors Ltd Control method for exhaust emission control device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0569317U (en) * 1992-02-24 1993-09-21 日産ディーゼル工業株式会社 Exhaust gas purification device for internal combustion engine
JP2006037769A (en) * 2004-07-23 2006-02-09 Hino Motors Ltd Control method for exhaust emission control device

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100795249B1 (en) * 2003-05-29 2008-01-15 수미도모 메탈 인더스트리즈, 리미티드 A substrate for a stamper and preparing method for a substrate for a stamper
US9243538B1 (en) * 2014-07-08 2016-01-26 Cummins Inc. Reduced emissions internal combustion engine systems
US20160123203A1 (en) * 2014-07-08 2016-05-05 Cummins Inc. Reduced emissions internal combustion engine systems
US9695729B2 (en) 2014-07-08 2017-07-04 Cummins Inc. Reduced emissions internal combustion engine systems
WO2024134987A1 (en) * 2022-12-20 2024-06-27 株式会社クボタ Diesel engine

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