JP2006132393A - Exhaust emission control device for internal combustion engine - Google Patents

Exhaust emission control device for internal combustion engine Download PDF

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JP2006132393A
JP2006132393A JP2004320848A JP2004320848A JP2006132393A JP 2006132393 A JP2006132393 A JP 2006132393A JP 2004320848 A JP2004320848 A JP 2004320848A JP 2004320848 A JP2004320848 A JP 2004320848A JP 2006132393 A JP2006132393 A JP 2006132393A
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reducing agent
exhaust
exhaust gas
internal combustion
combustion engine
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JP4662334B2 (en
Inventor
Shinichi Saito
真一 斎藤
Yoshihisa Takeda
好央 武田
Satoshi Hiranuma
智 平沼
嘉則 ▲高▼橋
Yoshinori Takahashi
Kenji Kodama
健司 児玉
Ritsuko Shinozaki
律子 篠▲崎▼
Reiko Domeki
礼子 百目木
Hisao Haga
久夫 羽賀
Yasuko Suzuki
康子 鈴木
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Mitsubishi Fuso Truck and Bus Corp
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Mitsubishi Fuso Truck and Bus Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • 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
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/20—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a flow director or deflector
    • 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
    • F01N2470/00—Structure or shape of gas passages, pipes or tubes
    • F01N2470/30—Tubes with restrictions, i.e. venturi or the like, e.g. for sucking air or measuring mass flow
    • 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

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of being constructed in compact and improving NOx conversion rate of an NOx catalyst by sufficiently diffusing reducing agent. <P>SOLUTION: An oxidation catalyst 34 and an SCR catalyst 36 are provided in an exhaust emission upstream side and exhaust emission downstream side in a case 32 respectively. An adding nozzle 48, a restriction part 40, a cylinder part 42, and a diffusion plate 46 are provided in a space 38 between the oxidation catalyst and the SCR catalyst. Urea water is injected in the restriction part to add urea water in exhaust emission. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

近年、内燃機関（以下、エンジンともいう）の排ガス中に含まれる窒素酸化物（ＮＯｘ）を低減する手段の一つとして、排ガス中に尿素水等の還元剤を添加し加水分解により発生するアンモニア（ＮＨ3）により、ＮＯｘを窒素（Ｎ2）と水（Ｈ2Ｏ）に選択還元するＮＯｘ触媒、所謂ＳＣＲ触媒が知られている。
ＳＣＲ触媒によるＮＯｘの浄化を効率的に行うには還元剤を排気中に均一に拡散させアンモニアをＳＣＲ触媒に供給することが必要である。アンモニアがＳＣＲ触媒に十分に供給されなければＮＯｘを浄化しきれなかったり、アンモニアが大気中にそのまま排出される所謂アンモニアスリップ現象が発生するおそれがある。 In recent years, as one means for reducing nitrogen oxide (NOx) contained in exhaust gas of an internal combustion engine (hereinafter also referred to as engine), ammonia generated by hydrolysis by adding a reducing agent such as urea water to the exhaust gas. A so-called SCR catalyst, which is a NOx catalyst that selectively reduces NOx to nitrogen (N 2 ) and water (H 2 O) by (NH 3 ), is known.
In order to efficiently purify NOx by the SCR catalyst, it is necessary to uniformly diffuse the reducing agent in the exhaust gas and supply ammonia to the SCR catalyst. If ammonia is not sufficiently supplied to the SCR catalyst, NOx cannot be completely purified, or a so-called ammonia slip phenomenon may occur in which ammonia is discharged into the atmosphere as it is.

排ガス中への還元剤の添加は一般的にはＳＣＲ触媒より排気上流側の排気管内で行われており、例えばＳＣＲ触媒より排気上流側の排気管内に尿素水等の還元剤を排ガス中に混入する混入部と、当該混入部とＳＣＲ触媒との間に排気流路の断面積を縮小する絞り部や排気を攪拌する攪拌部を設ける技術が開発されている（特許文献１参照）。
また、ＮＯｘ中の一酸化窒素（ＮＯ）と二酸化窒素（ＮＯ2）の割合がおよそ等しいと低温時におけるＳＣＲ触媒のＮＯｘ浄化率が向上することが知られている。
特開２００２−２１３２３３号公報 Addition of the reducing agent to the exhaust gas is generally performed in the exhaust pipe upstream of the SCR catalyst. For example, a reducing agent such as urea water is mixed in the exhaust gas in the exhaust pipe upstream of the SCR catalyst. A technology has been developed in which a mixing section that performs the above-described operation, and a throttle section that reduces the cross-sectional area of the exhaust passage and a stirring section that stirs the exhaust gas are provided between the mixing section and the SCR catalyst (see Patent Document 1).
Further, it is known that when the ratio of nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ) in NOx is approximately equal, the NOx purification rate of the SCR catalyst is improved at low temperatures.
JP 2002-213233 A

しかしながら、上記特許文献１に開示されたような技術では、複数の触媒及びフィルタを別々に設けることになると、排気管を間に介して夫々の触媒及びフィルタを取り付ける必要があるためスペースが必要となり、車両への搭載の際に何らかの制約を受けるおそれがある。
また、上記特許文献１では絞り部の手前で尿素水を添加しているため、尿素水が析出して絞り部に尿素が付着していき排気管を閉塞してしまうおそれもある。 However, in the technique as disclosed in Patent Document 1, when a plurality of catalysts and filters are provided separately, it is necessary to attach the respective catalysts and filters through the exhaust pipe, so that space is required. There is a risk of some restrictions when mounted on a vehicle.
Moreover, since the urea water is added before the throttle part in the above-mentioned Patent Document 1, there is a possibility that the urea water is deposited and urea adheres to the throttle part and closes the exhaust pipe.

本発明はこのような問題を解決するためになされたもので、その目的とするところは、コンパクトな構成とすることができ、且つ還元剤を十分に拡散させＳＣＲ触媒によるＮＯｘの浄化率を向上させることのできる内燃機関の排気浄化装置を提供することにある。   The present invention has been made to solve such problems. The object of the present invention is to make the structure compact and to sufficiently diffuse the reducing agent to improve the NOx purification rate by the SCR catalyst. An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can be made to operate.

上記した目的を達成するために、請求項１の内燃機関の排気浄化装置では、内燃機関の排気系に設けられた酸化触媒と、該酸化触媒の排気下流側に排気流路を縮小するよう形成された絞り部と、該絞り部の近傍で還元剤を排ガス中に添加する還元剤添加手段と、前記絞り部の排気下流側に設けられ前記還元剤により排ガス中のＮＯｘを選択還元するＮＯｘ触媒と、前記酸化触媒と前記絞り部と前記還元剤添加手段と前記ＮＯｘ触媒を内部に有するケースとを備えたことを特徴としている。   In order to achieve the above-described object, in the exhaust gas purification apparatus for an internal combustion engine according to claim 1, an oxidation catalyst provided in an exhaust system of the internal combustion engine, and an exhaust passage is formed to be reduced downstream of the oxidation catalyst. And a reducing agent adding means for adding a reducing agent to the exhaust gas in the vicinity of the throttle portion, and a NOx catalyst that is provided on the exhaust downstream side of the restricting portion and selectively reduces NOx in the exhaust gas by the reducing agent. And a case having the oxidation catalyst, the throttle portion, the reducing agent adding means, and the NOx catalyst therein.

つまり、ひとつのケース内で、酸化触媒により排ガス中のＮＯｘのＮＯとＮＯ2の割合をおよそ等しくして、還元剤を添加し、絞り部により排ガスの速度を増加させることで還元剤を拡散させ、ＮＯｘ触媒（ＳＣＲ触媒）でＮＯｘを選択還元させることとなる。
請求項２の内燃機関の排気浄化装置では、前記絞り部の近傍に、前記還元剤添加手段により排ガス中に添加された還元剤を拡散させる拡散手段を備えたことを特徴としている。 That is, in one case, the ratio of NO and NO 2 in the NOx in the exhaust gas to approximately equal the oxidation catalyst, a reducing agent is added, the reducing agent is diffused by increasing the velocity of the exhaust gas by the throttle portion The NOx is selectively reduced by the NOx catalyst (SCR catalyst).
The exhaust gas purification apparatus for an internal combustion engine according to claim 2 is characterized in that a diffusion means for diffusing the reducing agent added to the exhaust gas by the reducing agent adding means is provided in the vicinity of the throttle portion.

つまり、絞り部の近傍に拡散手段を設け、当該拡散手段により排ガス中に添加された還元剤の拡散を促進させることとなる。
請求項３の内燃機関の排気浄化装置では、前記還元剤添加手段は前記絞り部よりも排気下流側で前記還元剤を排ガス中に供給することを特徴としている。
つまり、排気流路断面積が最小となる絞り部よりも排気下流側で還元剤の添加を行うこととなる。 That is, a diffusing unit is provided in the vicinity of the throttle portion, and the diffusion of the reducing agent added to the exhaust gas is promoted by the diffusing unit.
The exhaust gas purification apparatus for an internal combustion engine according to claim 3 is characterized in that the reducing agent adding means supplies the reducing agent into the exhaust gas downstream of the throttle portion.
That is, the reducing agent is added downstream of the throttle portion where the exhaust passage cross-sectional area is minimum.

請求項４の内燃機関の排気浄化装置では、前記還元剤添加手段は前記還元剤に空気を混合して排ガス中に該還元剤を添加することを特徴としている。
つまり、還元剤に空気を混合することで還元剤を微粒子化して排ガス内に添加させることとなる。
請求項５の内燃機関の排気浄化装置では、前記還元剤添加手段は、前記絞り部の最小となる排気流路断面積に対応した空気量を前記還元剤に混合することを特徴としている。 The exhaust gas purification apparatus for an internal combustion engine according to claim 4 is characterized in that the reducing agent adding means mixes the reducing agent with air and adds the reducing agent to the exhaust gas.
That is, by mixing air with the reducing agent, the reducing agent is atomized and added to the exhaust gas.
The exhaust gas purification apparatus for an internal combustion engine according to claim 5 is characterized in that the reducing agent adding means mixes the reducing agent with an air amount corresponding to an exhaust passage sectional area that minimizes the throttle portion.

つまり、還元剤に混合する空気量を最小限に抑制することとなる。
請求項６の内燃機関の排気浄化装置では、排気流路を縮小するよう形成された絞り部と、該絞り部の排気下流側で還元剤を排ガス中に添加する還元剤添加手段と、前記還元剤添加手段の排気下流側に設けられ前記還元剤により排ガス中のＮＯｘを選択還元するＮＯｘ触媒と、前記絞り部と前記還元剤添加手段と前記ＮＯｘ触媒を内部に有するケースとを備えたことを特徴としている。 That is, the amount of air mixed with the reducing agent is minimized.
The exhaust gas purification apparatus for an internal combustion engine according to claim 6, wherein a throttle part formed so as to reduce the exhaust flow path, a reducing agent addition means for adding a reducing agent into the exhaust gas downstream of the throttle part, and the reduction A NOx catalyst provided on the exhaust downstream side of the agent addition means for selectively reducing NOx in the exhaust gas by the reducing agent, and a case having the throttle portion, the reducing agent addition means, and the NOx catalyst therein. It is a feature.

つまり、ひとつのケース内で、絞り部により排ガスの速度を増加させ絞り部より排気下流側で排ガス中に還元剤を添加することで還元剤を拡散させ、ＮＯｘ触媒（ＳＣＲ触媒）でＮＯｘを選択還元させることとなる。   That is, in one case, the speed of the exhaust gas is increased by the throttle part, and the reducing agent is diffused by adding the reducing agent to the exhaust gas downstream of the throttle part, and NOx is selected by the NOx catalyst (SCR catalyst). It will be reduced.

上記手段を用いる本発明の請求項１の内燃機関の排気浄化装置によれば、ＮＯｘ触媒よりも排気上流側に酸化触媒を設け、排ガス中のＮＯｘのＮＯとＮＯ2の割合をおよそ等しくすることでＮＯｘ触媒（ＳＣＲ触媒）の低温時でのＮＯｘ浄化率を向上させることができる。
また、絞り部を設け排ガスの速度を増加させることで添加した還元剤を拡散させることができ、ＮＯｘ触媒によるＮＯｘの浄化を効率的に行うことができる。 According to the exhaust purification system of an internal combustion engine according to claim 1 of the present invention using the above means, the NOx catalyst an oxidation catalyst provided in the exhaust upstream side, to approximately equal the ratio of NO and NO 2 in the NOx in the exhaust gas Thus, the NOx purification rate at a low temperature of the NOx catalyst (SCR catalyst) can be improved.
Moreover, the reducing agent added can be diffused by providing the throttle part and increasing the speed of the exhaust gas, and the NOx purification by the NOx catalyst can be performed efficiently.

また、酸化触媒、ＮＯｘ触媒、絞り部、還元剤添加手段をひとつのケース内に備えることで排気浄化装置を一体のものとすることができ、車両への搭載性を向上させることができる。
これにより、排気浄化装置をコンパクトな構成とさせることができ、且つ還元剤を十分に拡散させＮＯｘ触媒によるＮＯｘの浄化率を向上させることができる。 Further, by providing the oxidation catalyst, the NOx catalyst, the throttle part, and the reducing agent adding means in one case, the exhaust purification device can be integrated, and the mounting property on the vehicle can be improved.
As a result, the exhaust purification device can be made compact, and the reducing agent can be sufficiently diffused to improve the NOx purification rate by the NOx catalyst.

請求項２の内燃機関の排気浄化装置によれば、拡散手段により還元剤の拡散を促進させることができ、ＮＯｘ触媒によるＮＯｘの浄化を効率的に行うことができる。
請求項３の内燃機関の排気浄化装置によれば、排気流路断面積が最小となる絞り部よりも排気下流側で還元剤の添加を行うことにより、還元剤の付着による絞り部の閉塞を防止することができる。 According to the exhaust gas purification apparatus for an internal combustion engine of claim 2, diffusion of the reducing agent can be promoted by the diffusion means, and NOx purification by the NOx catalyst can be performed efficiently.
According to the exhaust gas purification apparatus for an internal combustion engine according to claim 3, by adding the reducing agent on the downstream side of the exhaust with respect to the throttle portion where the exhaust passage cross-sectional area is minimum, the throttle portion is blocked due to the attachment of the reducing agent. Can be prevented.

請求項４の内燃機関の排気浄化装置によれば、還元剤に空気を混合して排ガス中への添加を行うことにより、還元剤を微粒子化させ、拡散を促進させることができる。
請求項５の内燃機関の排気浄化装置によれば、空気の混合による還元剤の拡散の効果を十分に得ながら、還元剤へ混合する空気量を最小限とすることができ、還元剤への空気混合による無駄なエネルギーを低減させることができる。 According to the exhaust gas purification apparatus for an internal combustion engine of claim 4, the reducing agent can be made fine particles and diffusion can be promoted by mixing the reducing agent with air and adding it to the exhaust gas.
According to the exhaust gas purification apparatus for an internal combustion engine of claim 5, the amount of air mixed into the reducing agent can be minimized while sufficiently obtaining the effect of diffusion of the reducing agent by mixing the air. Wasteful energy due to air mixing can be reduced.

請求項６の内燃機関の排気浄化装置によれば、絞り部を設けることで排ガスの速度を増加させ、添加される還元剤を拡散させることができ、ＮＯｘ触媒によるＮＯｘの浄化を効率的に行うことができる。
排気流路断面積が最小となる絞り部よりも排気下流側で還元剤の添加を行うことにより、還元剤の付着による絞り部の閉塞を防止することができる。 According to the exhaust gas purification apparatus for an internal combustion engine of the sixth aspect, by providing the throttle portion, it is possible to increase the speed of the exhaust gas and to diffuse the reducing agent to be added, and to efficiently purify NOx by the NOx catalyst. be able to.
By adding the reducing agent on the exhaust downstream side of the throttle portion where the exhaust passage cross-sectional area becomes the minimum, it is possible to prevent the throttle portion from being blocked due to the attachment of the reducing agent.

また、ＮＯｘ触媒、絞り部、還元剤添加手段をひとつのケース内に備えることで排気浄化装置を一体のものとすることができ、車両への搭載性を向上させることができる。
これにより、排気浄化装置をコンパクトな構成とさせることができ、且つ還元剤を十分に拡散させＮＯｘ触媒によるＮＯｘの浄化率を向上させることができる。 Further, by providing the NOx catalyst, the throttle part, and the reducing agent adding means in one case, the exhaust purification device can be integrated, and the mounting property to the vehicle can be improved.
As a result, the exhaust purification device can be made compact, and the reducing agent can be sufficiently diffused to improve the NOx purification rate by the NOx catalyst.

以下、本発明の実施の形態を図面に基づき説明する。
まず、実施例１について説明する。
図１を参照すると、本発明に係る内燃機関の排気浄化装置を含むディーゼルエンジンの吸排気系の概略構成図が示されており、図２を参照すると、本発明に係る内燃機関の排気浄化装置の実施例１における排気浄化装置の断面図が示されている。以下、図１、図２に基づき説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, Example 1 will be described.
Referring to FIG. 1, there is shown a schematic configuration diagram of an intake / exhaust system of a diesel engine including an exhaust purification device for an internal combustion engine according to the present invention. Referring to FIG. 2, an exhaust purification device for an internal combustion engine according to the present invention. Sectional drawing of the exhaust gas purification device in Example 1 of this is shown. Hereinafter, a description will be given based on FIGS. 1 and 2.

エンジン１は直列６気筒ディーゼルエンジンであり、コモンレール式燃料噴射装置を備えており、コモンレール２に蓄圧された高圧燃料を各気筒４の燃料噴射弁５に供給し、任意の噴射時期及び噴射量で燃料噴射弁５から各気筒４の筒内に噴射可能に構成されている。
エンジン１の吸気側には吸気マニホールド６が接続されており、吸気マニホールド６からは吸気管８が延びている。吸気管８の吸気上流端にはエアクリーナ１０が設けられており、吸気管８の途中にはターボ過給機１２のコンプレッサ１２ａが設けられ、当該コンプレッサ１２ａの吸気下流側にはインタークーラ１４が設けられている。 The engine 1 is an in-line 6-cylinder diesel engine equipped with a common rail type fuel injection device. The high pressure fuel accumulated in the common rail 2 is supplied to the fuel injection valve 5 of each cylinder 4 at an arbitrary injection timing and injection amount. The fuel injection valve 5 is configured to be able to inject into the cylinder of each cylinder 4.
An intake manifold 6 is connected to the intake side of the engine 1, and an intake pipe 8 extends from the intake manifold 6. An air cleaner 10 is provided at the intake upstream end of the intake pipe 8, a compressor 12a of the turbocharger 12 is provided in the middle of the intake pipe 8, and an intercooler 14 is provided downstream of the compressor 12a. It has been.

一方、エンジン１の排気側には排気マニホールド１６が接続されており、排気マニホールド１６からは排気管１８が延びている。排気マニホールド１６と吸気マニホールド６にはＥＧＲ通路２０が接続されており、ＥＧＲ通路２０にはＥＧＲガスを冷却するＥＧＲクーラ２２やＥＧＲガスの還流量を調節するＥＧＲバルブ２４が設けられている。
また、排気管１８の途中には上記コンプレッサ１２ａと同軸上に連結されているタービン１２ｂが設けられており、排気管１８の排気下流側には、排気温度センサ２６が設けられており、その排気下流側には排気浄化装置３０が接続されている。 On the other hand, an exhaust manifold 16 is connected to the exhaust side of the engine 1, and an exhaust pipe 18 extends from the exhaust manifold 16. An EGR passage 20 is connected to the exhaust manifold 16 and the intake manifold 6, and an EGR cooler 22 that cools the EGR gas and an EGR valve 24 that adjusts the recirculation amount of the EGR gas are provided in the EGR passage 20.
A turbine 12b coaxially connected to the compressor 12a is provided in the middle of the exhaust pipe 18, and an exhaust temperature sensor 26 is provided on the exhaust downstream side of the exhaust pipe 18. An exhaust purification device 30 is connected to the downstream side.

ここで、排気浄化装置３０について詳しく説明する。
図２に示すように、排気浄化装置３０は円筒状のケース３２内部の排気上流側に酸化触媒３４を、排気下流側にＳＣＲ触媒３６（ＮＯｘ触媒）が配設されている。
酸化触媒３４は、例えばハニカム構造のセラミックス製の触媒担体上に白金（Ｐｔ）等の触媒金属を担持して構成されており、排ガス中の炭化水素（ＨＣ）と一酸化炭素（ＣＯ）を二酸化炭素（ＣＯ2）と水（Ｈ2Ｏ）に変えるとともに、ＮＯｘのうち一酸化窒素（ＮＯ）を二酸化窒素（ＮＯ2）に効率よく変化させ、ＮＯｘのＮＯとＮＯ2との割合をおよそ等しくするものである。 Here, the exhaust emission control device 30 will be described in detail.
As shown in FIG. 2, the exhaust purification device 30 is provided with an oxidation catalyst 34 on the exhaust upstream side inside a cylindrical case 32 and an SCR catalyst 36 (NOx catalyst) on the exhaust downstream side.
The oxidation catalyst 34 is configured, for example, by supporting a catalytic metal such as platinum (Pt) on a ceramic catalyst carrier having a honeycomb structure, and is configured to convert hydrocarbon (HC) and carbon monoxide (CO) in exhaust gas into carbon dioxide. While changing to carbon (CO 2 ) and water (H 2 O), nitrogen monoxide (NO) in NOx is efficiently changed to nitrogen dioxide (NO 2 ), and the ratio of NO to NO 2 in NOx is approximately equal. To do.

ＳＣＲ触媒３６は、例えばハニカム構造のセラミックス製の触媒担体上に酸化バナジウム（Ｖ2Ｏ5）等の触媒金属を担持して構成されており、アンモニア（ＮＨ3）により排ガス中のＮＯｘを窒素（Ｎ2）と水（Ｈ2Ｏ）選択還元するものである。
また、ケース３２内の酸化触媒３４とＳＣＲ触媒３６が配設されている間には空間３８が存在し、この空間３８には排気下流側に向かい円錐状に排気流路の断面積を縮小する絞り部４０が形成されており、一定の断面積（例えばケース３２の断面積の１／２程度）まで縮小した絞り部４０の排気下流端からは当該一定の断面積を維持した円筒部４２が形成されている。 The SCR catalyst 36 is configured by, for example, supporting a catalytic metal such as vanadium oxide (V 2 O 5 ) on a ceramic catalyst carrier having a honeycomb structure, and the NOx in the exhaust gas is converted into nitrogen (NH 3 ) by nitrogen ( N 2 ) and water (H 2 O) are selectively reduced.
Further, a space 38 exists between the oxidation catalyst 34 and the SCR catalyst 36 in the case 32, and the space 38 reduces the cross-sectional area of the exhaust passage in a conical shape toward the exhaust downstream side. A throttle portion 40 is formed, and a cylindrical portion 42 that maintains the constant cross-sectional area is provided from the exhaust downstream end of the throttle portion 40 that has been reduced to a constant cross-sectional area (for example, about ½ of the cross-sectional area of the case 32). Is formed.

また、円筒部４２の外周は多数の孔が穿設されており、円筒部４２の下流端はＳＣＲ触媒３６の直上流に設けられている拡散板４６（拡散手段）と当接している。
拡散板４６は外周縁がケース３２の内周壁と当接している円盤状の板部材であり、円筒部４２の径より若干小径な内円部分４６ａを除いて多数の孔が穿設されている。
さらに空間３８内には、ケース３２外部から貫通し先端が絞り部４０の中心軸線上に位置するＬ字状の添加ノズル４８（還元剤添加手段）が設けられている。添加ノズル４８の先端は中心軸を中心に放射状に尿素水が噴射されるよう形成されている。 The outer periphery of the cylindrical portion 42 has a large number of holes, and the downstream end of the cylindrical portion 42 is in contact with a diffusion plate 46 (diffusion means) provided immediately upstream of the SCR catalyst 36.
The diffusing plate 46 is a disk-shaped plate member whose outer peripheral edge is in contact with the inner peripheral wall of the case 32, and has a large number of holes except for an inner circular portion 46 a slightly smaller in diameter than the cylindrical portion 42. .
Further, an L-shaped addition nozzle 48 (reducing agent addition means) that penetrates from the outside of the case 32 and has a tip positioned on the central axis of the throttle portion 40 is provided in the space 38. The tip of the addition nozzle 48 is formed such that urea water is ejected radially about the central axis.

添加ノズル４８は排気浄化装置３０の外部に設けられている尿素水供給装置５０（還元剤添加手段）に連結されており、尿素水供給装置５０は尿素水が貯蔵されている尿素水タンク５２から尿素水が供給されるとともに、エンジン１を動力としたエアコンプレッサ５４から圧縮空気が供給され、当該供給された尿素水と圧縮空気を混合させて添加ノズル４８へ供給する。   The addition nozzle 48 is connected to a urea water supply device 50 (reducing agent addition means) provided outside the exhaust purification device 30. The urea water supply device 50 is connected to a urea water tank 52 in which urea water is stored. Aqueous urea is supplied and compressed air is supplied from an air compressor 54 powered by the engine 1, and the supplied urea water and compressed air are mixed and supplied to the addition nozzle 48.

また、車内にはＥＣＵ（電子コントロールユニット）５６が設けられており、当該ＥＣＵ５６は排気温度センサ２６が検知した排気温度やエンジン回転数、アクセル開度等の各種情報を入力し、当該各種情報に基づき尿素水供給装置４８やＥＧＲバルブ２４、エンジン１等の各種制御を行う。
以下このように構成された本発明に係る内燃機関の排気浄化装置の実施例1における作用について説明する。 Further, an ECU (electronic control unit) 56 is provided in the vehicle, and the ECU 56 inputs various information such as the exhaust temperature detected by the exhaust temperature sensor 26, the engine speed, the accelerator opening, and the like. Based on this, various controls of the urea water supply device 48, the EGR valve 24, the engine 1, and the like are performed.
Hereinafter, the operation of the exhaust gas purification apparatus for an internal combustion engine according to the present invention configured as described above in Embodiment 1 will be described.

エンジン１は、エアクリーナ１０から吸気管８を通りコンプレッサ１２ａにより圧縮された空気を各気筒４に吸気し燃料噴射弁５から燃料を噴射することで燃焼を生起する。燃焼後の排ガスは排気マニホールド１６から途中タービン１２ｂを回転させて排気管１８の下流側へと流れ排気浄化装置３０内へ流入する。
排気浄化装置３０に流入する前の排ガス中には炭化水素（ＨＣ）、一酸化炭素（ＣＯ）、ＮＯｘが含まれており、このときのＮＯｘは一酸化窒素（ＮＯ）の割合が二酸化窒素（ＮＯ2）よりも高い。 The engine 1 causes combustion by inhaling the air compressed by the compressor 12 a from the air cleaner 10 through the intake pipe 8 into each cylinder 4 and injecting fuel from the fuel injection valve 5. The exhaust gas after combustion rotates the turbine 12b from the exhaust manifold 16 to the downstream side of the exhaust pipe 18 and flows into the exhaust purification device 30.
The exhaust gas before flowing into the exhaust purification device 30 contains hydrocarbons (HC), carbon monoxide (CO), and NOx. At this time, the ratio of nitrogen monoxide (NO) is nitrogen dioxide (NO). Higher than NO 2 ).

そして、酸化触媒３４では、排ガス中のほとんどの炭化水素（ＨＣ）と一酸化炭素（ＣＯ）は二酸化炭素（ＣＯ2）と水（Ｈ2Ｏ）に変化し、一酸化窒素（ＮＯ）は二酸化窒素（ＮＯ2）に効率よく変化する。これによりＮＯｘのＮＯとＮＯ2との割合がおよそ等しくなる。
空間３８の絞り部４０では排気流路断面積が縮小しているために当該絞り部４０を通る排ガスは増速する。また、絞り部４０に設けられている添加ノズル４８の先端からは中心軸を中心に放射状に尿素水が噴射され、排ガス中に尿素水が添加される。この噴射される尿素水は圧縮空気が混合されていることにより微粒子化した状態で噴射され、この圧縮空気の量は絞り部４０の排気下流端の断面積、つまり排気流路の最小断面積と同面積程度に尿素水が拡がるようＥＣＵ５６が尿素水供給装置５０を制御している。 In the oxidation catalyst 34, most hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas are changed to carbon dioxide (CO 2 ) and water (H 2 O), and nitrogen monoxide (NO) is carbon dioxide. Efficiently changes to nitrogen (NO 2 ). Thus the ratio between NO and NO 2 in NOx is approximately equal.
In the throttle part 40 of the space 38, the exhaust gas cross-sectional area is reduced, so that the exhaust gas passing through the throttle part 40 increases in speed. Further, urea water is injected radially from the tip of the addition nozzle 48 provided in the throttle unit 40 around the central axis, and urea water is added to the exhaust gas. The injected urea water is injected in a state of being finely divided by mixing the compressed air, and the amount of the compressed air is equal to the cross-sectional area of the exhaust downstream end of the throttle portion 40, that is, the minimum cross-sectional area of the exhaust passage. The ECU 56 controls the urea water supply device 50 so that the urea water spreads to the same area.

そして、増速し尿素水を含む排ガスは円筒部４２を通る際に拡散され、さらに拡散板４６の中央部４６ａへの衝突や多数の孔を通過することによっても尿素水の拡散が促進される。
十分に拡散された尿素水は加水分解及び熱分解されることでアンモニア（ＮＨ3）を生成し、ＳＣＲ触媒３６では当該アンモニアと反応することでＮＯｘの還元が行われ、ＮＯｘは窒素（Ｎ2）と水（Ｈ2Ｏ）に変化する。このとき、酸化触媒３４によってＮＯｘ中のＮＯとＮＯ2はおよそ等しいので低温時でも十分にＮＯｘは浄化される。 The exhaust gas containing the urea water that has been accelerated and diffused is diffused when passing through the cylindrical portion 42, and the diffusion of the urea water is also promoted by colliding with the central portion 46a of the diffusion plate 46 and passing through a large number of holes. .
Sufficiently diffused urea water is hydrolyzed and thermally decomposed to generate ammonia (NH 3 ), and the SCR catalyst 36 reacts with the ammonia to reduce NOx, and NOx is nitrogen (N 2 ) And water (H 2 O). At this time, NO and NO 2 in NOx are approximately equal by the oxidation catalyst 34, so that NOx is sufficiently purified even at low temperatures.

そして、浄化された排ガスは排気浄化装置３０からさらに下流に流れ大気に排出される。
このように、本発明に係る内燃機関の排気浄化装置では、酸化触媒３４、ＳＣＲ触媒３６、添加ノズル４８、絞り部４０等をひとつのケース内に備えることで排気浄化装置３０を一体のものとすることができ、車両への搭載性を向上させることができる。 The purified exhaust gas flows further downstream from the exhaust purification device 30 and is discharged to the atmosphere.
Thus, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the exhaust gas purification apparatus 30 is integrated with the oxidation catalyst 34, the SCR catalyst 36, the addition nozzle 48, the throttle portion 40, etc. in one case. It is possible to improve the mountability to the vehicle.

その上、尿素水に最小限の圧縮空気を混合させ尿素水を微粒子化し、絞り部４０を設け排ガスの流速を増速させ、拡散板４６を設けることで、排ガス中に添加された尿素水を十分に拡散させることができる。これにより、ＳＣＲ触媒３２へ確実にアンモニアを吸着させることができ、ＮＯｘの浄化率を向上させることができる。また、絞り部４０を設けたことで尿素水の添加は絞り部の最小断面積分拡がれば十分に拡散させることができるので、圧縮空気の混合を最小限に抑制することができる。つまりエアコンプレッサが要する仕事量を最小限にすることができ、エンジン１の負荷を抑制することができる。   In addition, the urea water added to the exhaust gas can be reduced by mixing the urea water with a minimum amount of compressed air to make the urea water fine particles, providing the throttle portion 40 to increase the flow rate of the exhaust gas, and providing the diffusion plate 46. Can be sufficiently diffused. Thereby, ammonia can be reliably adsorbed to the SCR catalyst 32, and the NOx purification rate can be improved. In addition, since the throttle section 40 is provided, the addition of urea water can be sufficiently diffused if the minimum cross-sectional integral expansion of the throttle section is expanded, so that mixing of compressed air can be suppressed to a minimum. That is, the amount of work required by the air compressor can be minimized, and the load on the engine 1 can be suppressed.

さらに、ＳＣＲ触媒３６よりも排気上流側に酸化触媒３４を設け、排ガス中のＮＯｘのＮＯとＮＯ2の割合をおよそ等しくすることで低温時でのＳＣＲ触媒３６のＮＯｘ浄化率を向上させることができる。
これらのことより、排気浄化装置３０をコンパクトな構成とすることができる上、尿素水を十分に拡散させＳＣＲ触媒３６によるＮＯｘの浄化率を向上させることができる。 Additionally, than SCR catalyst 36 oxidation catalyst 34 provided in the exhaust upstream side, it is possible to improve the NOx purification efficiency of the SCR catalyst 36 at low temperatures by approximately equal the ratio of NO and NO 2 in the NOx in the exhaust gas it can.
As a result, the exhaust purification device 30 can be made compact, and the urea water can be sufficiently diffused to improve the NOx purification rate by the SCR catalyst 36.

次に、実施例２について説明する。
実施例２は上記実施例１の排気浄化装置３０以外は同様の構成であるため、実施例２の説明は排気浄化装置についてのみするものとし、その他の説明は省略する。
図３を参照すると本発明に係る内燃機関の排気浄化装置の実施例２における排気浄化装置の断面図が示されており、以下実施例２について同図に基づき説明する。 Next, Example 2 will be described.
Since the second embodiment has the same configuration except for the exhaust purification device 30 of the first embodiment, the description of the second embodiment will be made only for the exhaust purification device, and the other description will be omitted.
Referring to FIG. 3, there is shown a cross-sectional view of an exhaust emission control device in Embodiment 2 of the exhaust gas purification device for an internal combustion engine according to the present invention. Embodiment 2 will be described below with reference to FIG.

図３に示すように、排気浄化装置６０は円筒状のケース６２内部の排気上流側に酸化触媒６４を、排気下流側にＳＣＲ触媒６６（ＮＯｘ触媒）が配設されている。
このケース６２、酸化触媒６４、ＳＣＲ触媒６６は上記実施例１のケース３２、酸化触媒３４、ＳＣＲ触媒３６と同様の構成である。
ケース６２内の酸化触媒６４とＳＣＲ触媒６６が配設されている間には空間６８が設けられており、この空間６８には排気下流に向かい円錐状に排気流路の断面積を縮小する絞り部７０が形成されており、一定の断面積（例えばケース６２の断面積の１／２程度）まで縮小した絞り部７０の排気下流端からは円錐状に排気流路の断面積を拡大する拡大部７２が形成されている。拡大部７２はケース６２の内周壁まで断面積を拡大し、排気下流端はＳＣＲ触媒６６の直上流に設けられている拡散板７４（拡散手段）と当接している。 As shown in FIG. 3, the exhaust purification device 60 is provided with an oxidation catalyst 64 on the exhaust upstream side inside a cylindrical case 62 and an SCR catalyst 66 (NOx catalyst) on the exhaust downstream side.
The case 62, the oxidation catalyst 64, and the SCR catalyst 66 have the same configurations as the case 32, the oxidation catalyst 34, and the SCR catalyst 36 of the first embodiment.
A space 68 is provided between the oxidation catalyst 64 and the SCR catalyst 66 in the case 62, and this space 68 is constricted to reduce the cross-sectional area of the exhaust passage in a conical shape toward the exhaust downstream. The portion 70 is formed, and the constriction expands the cross-sectional area of the exhaust passage in a conical shape from the exhaust downstream end of the throttle portion 70 reduced to a constant cross-sectional area (for example, about ½ of the cross-sectional area of the case 62). A portion 72 is formed. The enlarged portion 72 enlarges the cross-sectional area to the inner peripheral wall of the case 62, and the exhaust downstream end is in contact with a diffusion plate 74 (diffusion means) provided immediately upstream of the SCR catalyst 66.

拡散板７４は外周縁がケース６２の内周壁と当接している円盤状の板部材であり、内円部分７４ａを除いて多数の孔が穿設されている。
さらに空間６８内には、ケース６２外部から貫通し先端が拡大部７２の中心軸線上に位置するＬ字状の添加ノズル７６（還元剤添加手段）が設けられている。添加ノズル７６の先端は中心軸を中心に放射状に尿素水が噴射されるよう形成されている。 The diffuser plate 74 is a disk-shaped plate member whose outer peripheral edge is in contact with the inner peripheral wall of the case 62, and has a large number of holes except for the inner circular portion 74a.
Further, an L-shaped addition nozzle 76 (reducing agent addition means) that penetrates from the outside of the case 62 and has a tip located on the central axis of the enlarged portion 72 is provided in the space 68. The tip of the addition nozzle 76 is formed so that urea water is ejected radially about the central axis.

添加ノズル７６は実施例１と同様に排気浄化装置６０の外部に設けられている尿素水供給装置（還元剤添加手段）に連結されており、尿素添加装置はＥＣＵにより制御されている。
以下このように構成された本発明に係る内燃機関の排気浄化装置の実施例２における作用について説明する。 The addition nozzle 76 is connected to a urea water supply device (reducing agent addition means) provided outside the exhaust gas purification device 60 as in the first embodiment, and the urea addition device is controlled by the ECU.
The operation of the exhaust gas purification apparatus for an internal combustion engine according to the present invention configured as described above in Embodiment 2 will be described below.

酸化触媒６４では、排ガス中のほとんどの炭化水素（ＨＣ）と一酸化炭素（ＣＯ）は二酸化炭素（ＣＯ2）と水（Ｈ2Ｏ）に変化し、一酸化窒素（ＮＯ）は二酸化窒素（ＮＯ2）に効率よく変化する。これによりＮＯｘのＮＯとＮＯ2との割合がおよそ等しくなる。
空間６８の絞り部７０では排気流路断面積が縮小しているために当該絞り部を通る排ガスは増速する。また、拡大部７２に設けられている添加ノズル７６の先端からは中心軸を中心に放射状に尿素水が噴射され、排ガス中に尿素水が添加される。この噴射される尿素水は圧縮空気が混合されていることにより微粒子化した状態で噴射され、この圧縮空気の量は絞り部７０の排気下流端の断面積、つまり排気流路の最小断面積と同面積程度に尿素水が拡がるようＥＣＵ５６が尿素水供給装置５０を制御している。 In the oxidation catalyst 64, most hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas are changed to carbon dioxide (CO 2 ) and water (H 2 O), and nitrogen monoxide (NO) is nitrogen dioxide (NO). NO 2) to change efficiently. Thus the ratio between NO and NO 2 in NOx is approximately equal.
Since the exhaust flow passage cross-sectional area is reduced in the throttle portion 70 of the space 68, the exhaust gas passing through the throttle portion is accelerated. Further, urea water is injected radially from the tip of the addition nozzle 76 provided in the enlarged portion 72 around the central axis, and urea water is added to the exhaust gas. The injected urea water is injected in a state of being finely divided by mixing compressed air, and the amount of this compressed air is the cross-sectional area of the exhaust downstream end of the throttle portion 70, that is, the minimum cross-sectional area of the exhaust passage. The ECU 56 controls the urea water supply device 50 so that the urea water spreads to the same area.

そして、排ガスが拡大部７２を通ることにより排ガス中の尿素水は一様に拡散し、さらに拡散板７４の中央部７４ａへの衝突や多数の孔を通過することによっても尿素水の拡散が促進される。
十分に拡散された尿素水は加水分解及び熱分解されることでアンモニア（ＮＨ3）を生成し、ＳＣＲ触媒３６では当該アンモニアと反応することでＮＯｘの還元が行われ、ＮＯｘは窒素（Ｎ2）と水（Ｈ2Ｏ）に変化する。このとき、酸化触媒３４によってＮＯｘ中のＮＯとＮＯ2はおよそ等しいので低温時でも十分にＮＯｘは浄化される。 The urea water in the exhaust gas is uniformly diffused by passing through the enlarged portion 72, and the diffusion of the urea water is also promoted by collision with the central portion 74a of the diffusion plate 74 and passing through a large number of holes. Is done.
Sufficiently diffused urea water is hydrolyzed and thermally decomposed to generate ammonia (NH 3 ), and the SCR catalyst 36 reacts with the ammonia to reduce NOx, and NOx is nitrogen (N 2 ) And water (H 2 O). At this time, NO and NO 2 in NOx are approximately equal by the oxidation catalyst 34, so that NOx is sufficiently purified even at low temperatures.

そして、浄化された排ガスは排気浄化装置３０からさらに下流に流れ大気に排出される。
これにより、当該実施例２においても、コンパクトな構成とすることができる上、尿素水を十分に拡散させＳＣＲ触媒６６によるＮＯｘの浄化率を向上させることのできる内燃機関の排気浄化装置を提供することができるという上記実施例１と同様の効果を得ることができる。 The purified exhaust gas flows further downstream from the exhaust purification device 30 and is discharged to the atmosphere.
Thereby, also in the second embodiment, there is provided an exhaust gas purification apparatus for an internal combustion engine that can be made compact and that can sufficiently diffuse urea water and improve the NOx purification rate by the SCR catalyst 66. The same effect as in the first embodiment can be obtained.

さらに実施例２においては、尿素水の噴射が絞り部７０の最小断面積部分よりも排気下流側である拡大部７２で行われるために、尿素水の析出による絞り部７０の閉塞を防止することができるという効果も奏する。
以上で本発明に係る内燃機関の排気浄化装置の実施形態についての説明を終えるが、実施形態は上記実施形態に限られるものではない。 Further, in the second embodiment, since the urea water injection is performed in the enlarged portion 72 that is downstream of the exhaust gas with respect to the minimum cross-sectional area portion of the throttle portion 70, the blockage of the throttle portion 70 due to precipitation of urea water is prevented. There is also an effect that can be done.
Although the description of the embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention is finished above, the embodiment is not limited to the above embodiment.

例えば、上記実施形態では、尿素水供給装置により尿素水に圧縮空気を混合しているが、圧縮空気を混合せずに尿素水のみで噴射を行うようにしてもよい。そうすることで圧縮空気を生成するためのエアコンプレッサ等の装置を設ける必要がなくなり、さらなるコンパクト化を図ることができ、例えばエアコンプレッサ等を備えていない小型車等にも本願の内燃機関の排気浄化装置を搭載することが可能となる。   For example, in the above embodiment, the compressed water is mixed with the urea water by the urea water supply device, but the injection may be performed only with the urea water without mixing the compressed air. By doing so, it is not necessary to provide a device such as an air compressor for generating compressed air, and further downsizing can be achieved. For example, the exhaust gas purification of the internal combustion engine of the present application can be applied to a small vehicle that does not include an air compressor or the like. It becomes possible to mount the device.

また、上記実施例1では添加ノズル４８の先端が絞り部４０内に位置していたが、実施例２のように絞り部４０よりも排気下流側の円筒部４２内に添加ノズル４８の先端を位置するよう設けてもよい。そうすることで実施例２のように尿素水の析出による絞り部４０の閉塞を防止することができる。
また、上記実施形態では拡散板の形状は内円部分を除いて多数の孔を穿設しているが、これに限られるものではなく、拡散板全体に多数の孔を穿設してもよい。 In the first embodiment, the tip of the addition nozzle 48 is located in the throttle portion 40. However, as in the second embodiment, the tip of the addition nozzle 48 is placed in the cylindrical portion 42 on the exhaust downstream side of the throttle portion 40. You may provide so that it may be located. By doing so, it is possible to prevent clogging of the throttle portion 40 due to precipitation of urea water as in the second embodiment.
In the above embodiment, the diffuser plate has a large number of holes except for the inner circle portion. However, the present invention is not limited to this, and the diffuser plate may have a large number of holes. .

本発明に係る内燃機関の排気浄化装置を含むディーゼルエンジンの吸排気系の概略構成図である。1 is a schematic configuration diagram of an intake / exhaust system of a diesel engine including an exhaust purification device for an internal combustion engine according to the present invention. 本発明に係る内燃機関の排気浄化装置の実施例１における排気浄化装置の断面図である。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an exhaust purification device in Embodiment 1 of an exhaust purification device for an internal combustion engine according to the present invention. 本発明に係る内燃機関の排気浄化装置の実施例２における排気浄化装置の断面図である。It is sectional drawing of the exhaust gas purification apparatus in Example 2 of the exhaust gas purification apparatus of the internal combustion engine which concerns on this invention.

符号の説明Explanation of symbols

１ エンジン（内燃機関）
１８ 排気管
３０ 排気浄化装置
３２、６２ ケース
３４、６４ 酸化触媒
３６、６６ ＳＣＲ触媒（ＮＯｘ触媒）
３８、６８ 空間
４０、７０ 絞り部
４６、７４ 拡散板（拡散手段）
４８、７６ 添加ノズル（還元剤添加手段）
５０ 尿素水供給装置（還元剤添加手段）
５２ 尿素水タンク
５４ エアコンプレッサ
５６ ＥＣＵ（電子コントロールユニット） 1 engine (internal combustion engine)
18 Exhaust pipe 30 Exhaust gas purification device 32, 62 Case 34, 64 Oxidation catalyst 36, 66 SCR catalyst (NOx catalyst)
38, 68 Space 40, 70 Diaphragm 46, 74 Diffusion plate (Diffusion means)
48, 76 Addition nozzle (reducing agent addition means)
50 Urea water supply device (reducing agent addition means)
52 Urea water tank 54 Air compressor 56 ECU (electronic control unit)

Claims (6)

内燃機関の排気系に設けられた酸化触媒と、
該酸化触媒の排気下流側に排気流路を縮小するよう形成された絞り部と、
該絞り部の近傍で還元剤を排ガス中に添加する還元剤添加手段と、
前記絞り部の排気下流側に設けられ前記還元剤により排ガス中のＮＯｘを選択還元するＮＯｘ触媒と、
前記酸化触媒と前記絞り部と前記還元剤添加手段と前記ＮＯｘ触媒を内部に有するケースとを備えたことを特徴とする内燃機関の排気浄化装置。 An oxidation catalyst provided in the exhaust system of the internal combustion engine;
A throttle portion formed to reduce the exhaust flow path on the exhaust downstream side of the oxidation catalyst;
Reducing agent addition means for adding a reducing agent to the exhaust gas in the vicinity of the throttle part;
A NOx catalyst that is provided on the exhaust downstream side of the throttle portion and selectively reduces NOx in the exhaust gas by the reducing agent;
An exhaust purification device for an internal combustion engine, comprising: the oxidation catalyst, the throttle portion, the reducing agent adding means, and a case having the NOx catalyst therein. 前記絞り部の近傍に、前記還元剤添加手段により排ガス中に添加された前記還元剤を拡散させる拡散手段を備えたことを特徴とする請求項１記載の内燃機関の排気浄化装置。   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising a diffusing unit that diffuses the reducing agent added to the exhaust gas by the reducing agent adding unit in the vicinity of the throttle portion. 前記還元剤添加手段は前記絞り部よりも排気下流側で前記還元剤を排ガス中に供給することを特徴とする請求項１または２記載の内燃機関の排気浄化装置。   The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2, wherein the reducing agent adding means supplies the reducing agent into the exhaust gas downstream of the throttle portion. 前記還元剤添加手段は前記還元剤に空気を混合して排ガス中に該還元剤を添加することを特徴とする請求項１乃至３いずれか記載の内燃機関の排気浄化装置。   The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the reducing agent adding means adds air to the reducing agent and adds the reducing agent to exhaust gas. 前記還元剤添加手段は、前記絞り部の最小となる排気流路断面積に対応した空気量を前記還元剤に混合することを特徴とする請求項４記載の内燃機関の排気浄化装置。   5. The exhaust gas purification apparatus for an internal combustion engine according to claim 4, wherein the reducing agent adding means mixes the reducing agent with an air amount corresponding to a cross-sectional area of the exhaust passage that minimizes the throttle portion. 排気流路を縮小するよう形成された絞り部と、
該絞り部の排気下流側で還元剤を排ガス中に添加する還元剤添加手段と、
前記還元剤添加手段の排気下流側に設けられ前記還元剤により排ガス中のＮＯｘを選択還元するＮＯｘ触媒と、
前記絞り部と前記還元剤添加手段と前記ＮＯｘ触媒を内部に有するケースとを備えたことを特徴とする内燃機関の排気浄化装置。 A throttle formed to reduce the exhaust flow path;
Reducing agent addition means for adding a reducing agent to the exhaust gas downstream of the throttle portion;
A NOx catalyst that is provided on the exhaust downstream side of the reducing agent addition means and selectively reduces NOx in exhaust gas by the reducing agent;
An exhaust emission control device for an internal combustion engine, comprising: the throttle portion, the reducing agent addition means, and a case having the NOx catalyst therein.
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