JP2019157737A - Exhaust purifying device for internal combustion engine - Google Patents

Exhaust purifying device for internal combustion engine Download PDF

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JP2019157737A
JP2019157737A JP2018044329A JP2018044329A JP2019157737A JP 2019157737 A JP2019157737 A JP 2019157737A JP 2018044329 A JP2018044329 A JP 2018044329A JP 2018044329 A JP2018044329 A JP 2018044329A JP 2019157737 A JP2019157737 A JP 2019157737A
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朝幸 伊藤
Tomoyuki Ito
朝幸 伊藤
和貴 大石
Kazuki Oishi
和貴 大石
遊大 景山
Yudai Kageyama
遊大 景山
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Isuzu Motors Ltd
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Abstract

To execute purification of harmful material as much as possible under unfavorable conditions for catalyst activation.SOLUTION: An exhaust purifying device for an internal combustion engine 3A has a selective-reduction type first NOx catalyst 11, and an NOx adsorbent 12 disposed downstream from the first NOx catalyst in exhaust flow direction.SELECTED DRAWING: Figure 2

Description

本開示は、内燃機関の排気ガスを浄化するための排気浄化装置に関する。   The present disclosure relates to an exhaust emission control device for purifying exhaust gas of an internal combustion engine.

この種の排気浄化装置としては、排気中の有害物質を除去もしくは低減する複数の触媒等を直列に配置して構成したものが一般的である（例えば特許文献１〜３参照）。   As this type of exhaust emission control device, a configuration in which a plurality of catalysts or the like for removing or reducing harmful substances in exhaust gas are arranged in series is generally used (see, for example, Patent Documents 1 to 3).

特開２０１１−９４４８２号公報JP 2011-94482 A 特開２０１０−１２１５３０号公報JP 2010-121530 A 特開平８−２７０４４０号公報JP-A-8-270440

ところで車両用内燃機関の排気浄化装置には、年々厳しくなる各国の排ガス規制に対処するという一般的課題がある。特に最近では、内燃機関の冷間始動後や排気ガス温度の低温時等、触媒活性化に不利な条件下において、有害物質の浄化を可能な限り実行できる排気浄化装置が望まれている。   By the way, an exhaust emission control device for a vehicle internal combustion engine has a general problem of dealing with exhaust gas regulations in each country that are becoming stricter year by year. In particular, recently, there has been a demand for an exhaust emission control device capable of purifying harmful substances as much as possible under conditions unfavorable for catalyst activation, such as after a cold start of an internal combustion engine or when the exhaust gas temperature is low.

そこで本開示は、かかる事情に鑑みて創案され、その目的は、触媒活性化に不利な条件下において有害物質の浄化を可能な限り実行できる排気浄化装置を提供することにある。   Accordingly, the present disclosure has been created in view of such circumstances, and an object thereof is to provide an exhaust purification device capable of performing as much of the purification of harmful substances as possible under conditions unfavorable for catalyst activation.

本開示の一の態様によれば、
選択還元型第１ＮＯｘ触媒と、
排気流れ方向における前記第１ＮＯｘ触媒の下流側に配置されたＮＯｘ吸着材と、
を備えることを特徴とする内燃機関の排気浄化装置が提供される。 According to one aspect of the present disclosure,
A selective reduction type first NOx catalyst;
A NOx adsorbent disposed downstream of the first NOx catalyst in the exhaust flow direction;
An exhaust emission control device for an internal combustion engine is provided.

好ましくは、前記排気浄化装置は、前記第１ＮＯｘ触媒の下流側かつ前記ＮＯｘ吸着材の上流側に配置された第１アンモニアスリップ触媒をさらに備える。   Preferably, the exhaust emission control device further includes a first ammonia slip catalyst disposed downstream of the first NOx catalyst and upstream of the NOx adsorbent.

好ましくは、前記排気浄化装置は、前記ＮＯｘ吸着材の下流側に配置されたフィルタおよび選択還元型第２ＮＯｘ触媒をさらに備える。   Preferably, the exhaust emission control device further includes a filter and a selective reduction type second NOx catalyst disposed on the downstream side of the NOx adsorbent.

好ましくは、前記排気浄化装置は、前記第２ＮＯｘ触媒の下流側に配置された第２アンモニアスリップ触媒をさらに備える。   Preferably, the exhaust purification device further includes a second ammonia slip catalyst disposed on the downstream side of the second NOx catalyst.

好ましくは、前記排気浄化装置は、前記第１ＮＯｘ触媒の上流側に配置された酸化触媒をさらに備える。   Preferably, the exhaust emission control device further includes an oxidation catalyst disposed on the upstream side of the first NOx catalyst.

好ましくは、前記酸化触媒が電気ヒータを有する。   Preferably, the oxidation catalyst has an electric heater.

本開示によれば、触媒活性化に不利な条件下において有害物質の浄化を可能な限り実行できる。   According to the present disclosure, purification of harmful substances can be performed as much as possible under conditions unfavorable for catalyst activation.

内燃機関の概略図である。1 is a schematic view of an internal combustion engine. 第１実施形態の排気浄化装置を示す図である。It is a figure which shows the exhaust gas purification apparatus of 1st Embodiment. 第２実施形態の排気浄化装置を示す図である。It is a figure which shows the exhaust gas purification apparatus of 2nd Embodiment. 第３実施形態の排気浄化装置を示す図である。It is a figure which shows the exhaust gas purification apparatus of 3rd Embodiment. 第４実施形態の排気浄化装置を示す図である。It is a figure which shows the exhaust gas purification apparatus of 4th Embodiment. 第５実施形態の排気浄化装置を示す図である。It is a figure which shows the exhaust gas purification apparatus of 5th Embodiment. 第６実施形態の排気浄化装置を示す図である。It is a figure which shows the exhaust gas purification apparatus of 6th Embodiment.

以下、添付図面を参照して本開示の実施形態を説明する。   Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

［第１実施形態］
図１に、本実施形態に係る内燃機関を概略的に示す。内燃機関（エンジン）１は車両用であり、多気筒の圧縮着火式内燃機関すなわちディーゼルエンジンである。但し本実施形態は、燃料と空気の混合比率である空気過剰率λが１より大きい、酸素過多の状態で運転されるエンジンを対象としている。よってエンジンは、所謂リーンバーン方式の火花点火式内燃機関すなわちガソリンエンジンであってもよい。エンジンの用途、シリンダ配置形式、気筒数等は任意である。 [First Embodiment]
FIG. 1 schematically shows an internal combustion engine according to this embodiment. The internal combustion engine (engine) 1 is for a vehicle and is a multi-cylinder compression ignition internal combustion engine, that is, a diesel engine. However, this embodiment is intended for an engine that is operated in an excessive oxygen state in which the excess air ratio λ, which is the mixing ratio of fuel and air, is greater than 1. Therefore, the engine may be a so-called lean burn type spark ignition internal combustion engine, that is, a gasoline engine. The use of the engine, the cylinder arrangement type, the number of cylinders, etc. are arbitrary.

エンジン１は、排気管等により画成されて排気ガスＧが流される排気通路２を有する。図示例の排気通路２は単純化のため単なる直線状とされているが、適宜屈曲状あるいは蛇行状等とされてもよい。この排気通路２の途中に、排気ガスを浄化するための排気浄化装置３が設けられる。図１では単純化のため排気浄化装置３を単に破線四角で示す。   The engine 1 has an exhaust passage 2 that is defined by an exhaust pipe or the like and through which exhaust gas G flows. The exhaust passage 2 in the illustrated example is simply a straight line for simplification, but may be appropriately bent or meandered. An exhaust gas purification device 3 for purifying exhaust gas is provided in the middle of the exhaust passage 2. In FIG. 1, the exhaust purification device 3 is simply indicated by a broken-line square for simplification.

詳しくは後述するが、排気浄化装置３は、排気中の種々の有害物質を除去もしくは低減する、複数かつ種々の触媒およびフィルタを含む。これら触媒およびフィルタを総称して後処理部材という。本開示の実施形態で使用される後処理部材には主に次のものがある。   As will be described in detail later, the exhaust purification device 3 includes a plurality of various catalysts and filters that remove or reduce various harmful substances in the exhaust. These catalysts and filters are collectively referred to as post-processing members. The post-processing members used in the embodiments of the present disclosure mainly include the following.

（１）選択還元型ＮＯｘ触媒
選択還元型ＮＯｘ触媒（以下、ＳＣＲ（Selective Catalytic Reduction）という）は、排気ガス中の窒素酸化物ＮＯｘを化学反応により還元除去するための触媒である。ＳＣＲは、還元剤が添加されているときにＮＯｘを連続的に還元し得る。そのため排気流れ方向におけるＳＣＲの上流側には、還元剤としての尿素水を排気通路２内に添加する添加弁が設けられる。 (1) Selective reduction type NOx catalyst A selective reduction type NOx catalyst (hereinafter referred to as SCR (Selective Catalytic Reduction)) is a catalyst for reducing and removing nitrogen oxides NOx in exhaust gas by a chemical reaction. The SCR can continuously reduce NOx when a reducing agent is added. Therefore, an addition valve for adding urea water as a reducing agent into the exhaust passage 2 is provided upstream of the SCR in the exhaust flow direction.

ＳＣＲは、ゼオライト又はアルミナなどの基材表面にＰｔなどの貴金属を担持したものや、その基材表面にＣｕ等の遷移金属をイオン交換して担持させたもの、その基材表面にチタニヤ／バナジウム触媒（Ｖ2Ｏ5／ＷＯ3／ＴｉＯ2）を担持させたもの等が例示できる。ＳＣＲは、その触媒温度（触媒床温）が活性開始温度以上となって活性化しており、且つ、尿素水が添加されているときにＮＯｘを還元浄化する。尿素水が添加されると、尿素水が加水分解され、アンモニアが生成される。ＳＣＲ上で、アンモニアがＮＯｘと反応してＮＯｘが還元される。 SCR is a material in which a noble metal such as Pt is supported on the surface of a substrate such as zeolite or alumina, a material in which a transition metal such as Cu is ion-exchanged on the surface of the substrate, and titania / vanadium on the surface of the substrate. Examples include those carrying a catalyst (V 2 O 5 / WO 3 / TiO 2 ). The SCR is activated when the catalyst temperature (catalyst bed temperature) is equal to or higher than the activation start temperature, and NOx is reduced and purified when urea water is added. When urea water is added, urea water is hydrolyzed and ammonia is generated. On the SCR, ammonia reacts with NOx to reduce NOx.

（２）ＮＯｘ吸着材
ＮＯｘ吸着材（以下、ＰＮＡ（Passive NOx Adsorbers）という）は、排気ガス中の窒素酸化物ＮＯｘを物理的に吸着することにより除去するためのものである。ＰＮＡは、遷移元素と希土類元素の複合酸化物、または遷移元素の酸化物と希土類元素の酸化物との混合物をコージェライト製ハニカムにコーティングしたもの、あるいは多孔質のゼオライトにより形成されたフロースルー型担体等が例示できる。 (2) NOx adsorbent NOx adsorbent (hereinafter referred to as PNA (Passive NOx Adsorbers)) is for removing nitrogen oxide NOx in the exhaust gas by physically adsorbing it. PNA is a composite oxide of transition element and rare earth element, or a mixture of transition element oxide and rare earth element coated on a cordierite honeycomb, or a flow-through type formed of porous zeolite Examples include carriers.

ＰＮＡの活性開始温度、すなわちＰＮＡが活性状態となる温度の最小値は、ＳＣＲの活性開始温度より低い。よってエンジンの冷間始動後、ＳＣＲの活性開始前に、ＰＮＡは活性を開始してＮＯｘを吸着除去可能である。またＰＮＡの温度が活性終了温度、すなわちＰＮＡが活性状態となる温度の最大値よりも上昇すると、ＰＮＡはＮＯｘの吸着を停止し、それまで吸着していたＮＯｘを脱離放出する。このＰＮＡの活性終了温度は一般的にはＳＣＲの活性開始温度付近である。   The minimum value of the PNA activation start temperature, that is, the temperature at which the PNA becomes active is lower than the SCR activation start temperature. Therefore, after the cold start of the engine and before the activation of the SCR, the PNA starts to activate and can adsorb and remove NOx. When the temperature of the PNA rises above the activation end temperature, that is, the maximum value of the temperature at which the PNA enters the active state, the PNA stops the NOx adsorption and desorbs and releases the NOx that has been adsorbed until then. The activation end temperature of this PNA is generally near the activation start temperature of the SCR.

なおＰＮＡは、その名の通り、あくまで自身の温度に依存してＮＯｘの吸着および脱離を行うパッシブ型のＮＯｘ吸着材である。この点で、ＰＮＡは、排気ガスを強制的にリッチ雰囲気にして吸着ＮＯｘの脱離放出を行うアクティブ型のＮＯｘ吸着材、すなわち吸蔵還元型ＮＯｘ触媒（LNT: Lean NOx TrapまたはNSR: NOx Storage Reduction）と異なる。   As its name suggests, PNA is a passive NOx adsorbent that adsorbs and desorbs NOx depending on its own temperature. In this respect, PNA is an active NOx adsorbent that desorbs and releases adsorbed NOx by forcing exhaust gas into a rich atmosphere, that is, an NOx storage reduction catalyst (LNT: Lean NOx Trap or NSR: NOx Storage Reduction). ) Is different.

（３）フィルタ
フィルタ（以下、ＤＰＦ（Diesel Particulate Filter）という）は、排気中に含まれる粒子状物質（PM: Particulate Matter）を捕集して除去するためのものである。ＤＰＦは、ハニカム形状の耐熱性基材の両端開口を互い違いに市松状に閉塞した所謂ウォールフロータイプのもの、あるいは網の目構造のフォーム形状のものなど、ＰＭを物理的に捕集するあらゆるタイプのフィルタを用いることができる。本実施形態ではウォールフロータイプのものを用いる。 (3) The filter filter (hereinafter referred to as DPF (Diesel Particulate Filter)) is for collecting and removing particulate matter (PM) contained in the exhaust gas. DPF is any type that physically collects PM, such as a so-called wall flow type in which both ends of a honeycomb-shaped heat-resistant substrate are alternately closed in a checkered pattern, or a mesh-shaped foam shape. These filters can be used. In this embodiment, a wall flow type is used.

またＤＰＦは、その基材内壁にＰｔ等の貴金属を担持した所謂連続再生式の触媒付きＤＰＦである。この場合、ＤＰＦに供給された排気中のＨＣが触媒作用で酸化、燃焼し、このとき同時にＤＰＦ内部に堆積しているＰＭが燃焼除去される。   The DPF is a so-called continuous regeneration type DPF with a catalyst in which a noble metal such as Pt is supported on the inner wall of the base material. In this case, HC in the exhaust gas supplied to the DPF is oxidized and burned by the catalytic action, and at this time, PM accumulated in the DPF is burned and removed.

（４）酸化触媒
酸化触媒（以下、ＤＯＣ（Diesel Oxidation Catalyst）という）は、排気ガス中の未燃成分（炭化水素ＨＣおよび一酸化炭素ＣＯ）を酸化して浄化するためのものである。ＤＯＣは、基材表面上のコート材にＰｔ等の貴金属を多数分散配置させてなる。ＤＯＣは、排気ガス中のＨＣ，ＣＯの酸化反応時に生じた熱で排気ガスを加熱、昇温する機能を有する。またＤＯＣは、排気中のＮＯをＮＯ2に酸化する機能をも有する。ＤＯＣの下流側にＤＰＦがある場合、ＮＯ2が持つ高い酸化能により、ＤＰＦに捕集されたＰＭを効率よく酸化除去できる。 (4) Oxidation catalyst An oxidation catalyst (hereinafter referred to as DOC (Diesel Oxidation Catalyst)) is for oxidizing and purifying unburned components (hydrocarbon HC and carbon monoxide CO) in exhaust gas. The DOC is formed by dispersing a large number of noble metals such as Pt in a coating material on a substrate surface. The DOC has a function of heating and raising the temperature of the exhaust gas with heat generated during the oxidation reaction of HC and CO in the exhaust gas. The DOC also has a function of oxidizing NO in the exhaust to NO 2. When DPF exists on the downstream side of the DOC, PM collected in the DPF can be efficiently oxidized and removed by the high oxidation ability of NO 2 .

（５）アンモニアスリップ触媒
アンモニアスリップ触媒（以下、ＡＳＣ（Ammonia Slip Catalyst）という）は、ＳＣＲ内でＮＯｘの還元に使用されずＳＣＲの下流側に排出された余剰のアンモニアを酸化して浄化するための触媒である。アンモニアが大気中に放出されると異臭等の原因になるので、これを防止すべく、余剰アンモニアをＡＳＣにより処理する。 (5) Ammonia slip catalyst An ammonia slip catalyst (hereinafter referred to as ASC (Ammonia Slip Catalyst)) is used to oxidize and purify excess ammonia that is not used for NOx reduction in the SCR but discharged downstream of the SCR. It is a catalyst. When ammonia is released into the atmosphere, it causes a strange odor and the like, so that excess ammonia is treated by ASC to prevent this.

図２には、第１実施形態の排気浄化装置３を示す。便宜上、第１実施形態の排気浄化装置３を符号３Ａで表す。   FIG. 2 shows the exhaust purification device 3 of the first embodiment. For convenience, the exhaust purification device 3 of the first embodiment is denoted by reference numeral 3A.

排気浄化装置３Ａは、選択還元型第１ＮＯｘ触媒すなわち第１ＳＣＲ１１と、排気流れ方向における第１ＳＣＲ１１の下流側に配置されたＰＮＡ１２とを備える。また排気浄化装置３Ａは、ＰＮＡ１２の下流側に配置されたＤＰＦ１３と、選択還元型第２ＮＯｘ触媒すなわち第２ＳＣＲ１４とをさらに備える。第２ＳＣＲ１４はＤＰＦ１３の下流側に配置されている。   The exhaust purification device 3A includes a selective reduction type first NOx catalyst, that is, the first SCR 11, and a PNA 12 disposed on the downstream side of the first SCR 11 in the exhaust flow direction. The exhaust purification device 3A further includes a DPF 13 disposed on the downstream side of the PNA 12, and a selective reduction type second NOx catalyst, that is, a second SCR 14. The second SCR 14 is disposed on the downstream side of the DPF 13.

これにより排気通路２には、第１ＳＣＲ１１、ＰＮＡ１２、ＤＰＦ１３および第２ＳＣＲ１４が、上流側から順に直列に配置されている。   Thereby, in the exhaust passage 2, the first SCR 11, the PNA 12, the DPF 13 and the second SCR 14 are arranged in series in order from the upstream side.

第１ＳＣＲ１１の上流側には、排気通路２内に尿素水を添加する第１添加弁１５が配置される。第１添加弁１５は、第１ＳＣＲ１１においてＮＯｘの還元反応に使用される尿素水を添加する。従って第１添加弁１５と第１ＳＣＲ１１は対をなし、これらの間には、如何なる後処理部材や排気ガス成分を変化させる部材も配置されない。こうした関係にある両者の配置を特に対配置という。例えば第１添加弁１５は、第１ＳＣＲ１１に対し対配置される。   A first addition valve 15 that adds urea water into the exhaust passage 2 is disposed upstream of the first SCR 11. The first addition valve 15 adds urea water used for the NOx reduction reaction in the first SCR 11. Therefore, the first addition valve 15 and the first SCR 11 are paired, and no post-processing member or member for changing the exhaust gas component is disposed between them. The arrangement of both in such a relationship is called a pair arrangement. For example, the first addition valve 15 is disposed as a pair with respect to the first SCR 11.

第２ＳＣＲ１４の上流側にも、排気通路２内に尿素水を添加する第２添加弁１６が対配置される。   A pair of second addition valves 16 for adding urea water into the exhaust passage 2 are also arranged upstream of the second SCR 14.

この排気浄化装置３Ａの特徴は次の通りである。まず、ＮＯｘを浄化する第１ＳＣＲ１１、ＰＮＡ１２および第２ＳＣＲ１４と、ＰＭを捕集するＤＰＦ１３とを備えるので、ディーゼルエンジンの主な有害物質であるＮＯｘとＰＭを除去できる。   The features of this exhaust purification device 3A are as follows. First, since the first SCR 11, the PNA 12 and the second SCR 14 for purifying NOx and the DPF 13 for collecting PM are provided, NOx and PM which are main harmful substances of the diesel engine can be removed.

また、第１ＳＣＲ１１の下流側にＰＮＡ１２を配置したので、次の利点がもたらされる。本実施形態の第１ＳＣＲ１１は、一般的に使用される通常のＳＣＲよりも低温で作動可能であり、言い換えれば、第１ＳＣＲ１１の活性開始温度Ｔｓ１は通常のＳＣＲの活性開始温度Ｔｓｎより低い。例えば、通常のＳＣＲの活性開始温度Ｔｓｎが約２００℃であるのに対し、第１ＳＣＲ１１の活性開始温度Ｔｓ１は約１５０℃である。従って、エンジン１の冷間始動後に通常のＳＣＲより早く第１ＳＣＲ１１を活性化させ、より早いタイミングからＮＯｘを除去可能である。また、エンジン１の運転状態がアイドルまたは低負荷運転状態となり、排気ガス温度が低温になっても、通常のＳＣＲより長い時間、第１ＳＣＲ１１の活性状態を維持でき、言い換えれば、第１ＳＣＲ１１が活性状態から失活状態になるタイミングを通常のＳＣＲより遅らせることができる。   Further, since the PNA 12 is arranged on the downstream side of the first SCR 11, the following advantages are brought about. The first SCR 11 of the present embodiment can operate at a lower temperature than a commonly used normal SCR. In other words, the activation start temperature Ts1 of the first SCR 11 is lower than the activation start temperature Tsn of the normal SCR. For example, the activation start temperature Tsn of the normal SCR is about 200 ° C., whereas the activation start temperature Ts 1 of the first SCR 11 is about 150 ° C. Therefore, the first SCR 11 can be activated earlier than the normal SCR after the cold start of the engine 1, and NOx can be removed at an earlier timing. Further, even when the operating state of the engine 1 becomes an idle or low load operating state and the exhaust gas temperature becomes low, the active state of the first SCR 11 can be maintained for a longer time than the normal SCR, in other words, the first SCR 11 is in the active state. Can be delayed from the normal SCR.

こうした低温作動型の第１ＳＣＲ１１を設けた場合、通常のＳＣＲよりも低温側で且つ早いタイミングからＮＯｘを除去可能である。しかしながら、その活性開始温度Ｔｓ１未満では、第１ＳＣＲ１１によっても依然としてＮＯｘを除去できない。そこで、活性開始温度Ｔｓ１未満の低温側の温度領域をカバーするため、補助的にＰＮＡ１２を設けている。   When such a low temperature operation type first SCR 11 is provided, it is possible to remove NOx at a lower temperature side and earlier than a normal SCR. However, below the activation start temperature Ts1, the first SCR 11 still cannot remove NOx. Therefore, in order to cover a low temperature side temperature range lower than the activation start temperature Ts1, a PNA 12 is provided as an auxiliary.

ＰＮＡ１２は、第１ＳＣＲ１１の活性開始温度Ｔｓ１より低い活性開始温度Ｔｐｓを有し、例えばＴｐｓ＝約１２０〜１３０℃で活性（すなわちＮＯｘ吸着）を開始する。またＰＮＡ１２は、通常のＳＣＲの活性開始温度Ｔｓｎとほぼ等しく第１ＳＣＲ１１の活性開始温度Ｔｓ１より高い活性終了温度Ｔｐｅを有し、例えばＴｐｅ＝約２００℃で活性を終了する。そしてＰＮＡ１２は、活性終了温度Ｔｐｅより高温のとき、吸着ＮＯｘの脱離放出を行う。   The PNA 12 has an activation start temperature Tps that is lower than the activation start temperature Ts1 of the first SCR 11, and starts activity (ie, NOx adsorption) at Tps = about 120 to 130 ° C., for example. The PNA 12 has an activation end temperature Tpe that is substantially equal to the activation start temperature Tsn of the normal SCR and higher than the activation start temperature Ts1 of the first SCR 11, and ends the activity at, for example, Tpe = about 200 ° C. The PNA 12 desorbs and releases adsorbed NOx when the temperature is higher than the activation end temperature Tpe.

このＰＮＡ１２を設けることにより、第１ＳＣＲ１１の活性開始温度Ｔｓ１より低い活性開始温度ＴｐｓからＮＯｘを除去可能である。従って、ＰＮＡ１２を設けない場合に比べ、エンジン１の冷間始動後にはより早いタイミングからＮＯｘを除去可能である。またエンジン１の運転状態がアイドルまたは低負荷運転状態となって排気ガス温度が低温になった場合には、排気ガス温度が活性開始温度Ｔｐｓ未満になるまでＮＯｘを除去し続けることができ、ＮＯｘ除去可能な時間をできるだけ長く持続し、ＮＯｘ除去不能となるタイミングを遅らせることができる。   By providing the PNA 12, NOx can be removed from the activation start temperature Tps lower than the activation start temperature Ts1 of the first SCR 11. Therefore, compared to the case where the PNA 12 is not provided, NOx can be removed from an earlier timing after the engine 1 is cold started. Further, when the engine 1 is in an idling or low-load operation state and the exhaust gas temperature becomes low, NOx can be continuously removed until the exhaust gas temperature becomes lower than the activation start temperature Tps. The removable time can be maintained as long as possible, and the timing at which NOx removal cannot be performed can be delayed.

それ故、触媒活性化に不利な条件下においても、有害物質であるＮＯｘの浄化を可能な限り実行することができる。   Therefore, purification of NOx, which is a harmful substance, can be performed as much as possible even under conditions unfavorable for catalyst activation.

また、ＰＮＡ１２の活性温度範囲、すなわちＴｐｓ以上Ｔｐｅ以下の温度範囲のうち、Ｔｓ１以上Ｔｐｅ以下の温度範囲が、第１ＳＣＲ１１の活性温度範囲（Ｔｓ１以上）と重複する。このため、重複温度範囲では、第１ＳＣＲ１１とＰＮＡ１２の二者を使って、より確実にＮＯｘを除去できる。   Further, among the active temperature range of the PNA 12, that is, the temperature range of Ts1 or more and Tpe or less among the temperature range of Tps or more and Tpe or less, the activation temperature range (Ts1 or more) of the first SCR 11 overlaps. For this reason, in the overlapping temperature range, NOx can be more reliably removed using the first SCR 11 and the PNA 12.

また本実施形態では、排気浄化装置３Ａに含まれる４つの後処理部材のうち、第１ＳＣＲ１１を排気浄化装置３Ａの最も上流側に配置したので、第１ＳＣＲ１１が最も高温の排気ガスを受け取ることができ、第１ＳＣＲ１１の活性開始タイミングを早めたり活性状態を維持するのに非常に有利である。   In the present embodiment, among the four post-processing members included in the exhaust purification device 3A, the first SCR 11 is arranged on the most upstream side of the exhaust purification device 3A, so that the first SCR 11 can receive the hottest exhaust gas. This is very advantageous for advancing the activation start timing of the first SCR 11 or maintaining the active state.

また、ＰＮＡ１２の下流側に第２ＳＣＲ１４を配置したので、ＰＮＡ１２から脱離放出されたＮＯｘを第２ＳＣＲ１４で還元処理でき、そのＮＯｘを大気に放出するのを抑制できる。   Further, since the second SCR 14 is arranged on the downstream side of the PNA 12, NOx desorbed and released from the PNA 12 can be reduced by the second SCR 14, and the release of the NOx into the atmosphere can be suppressed.

ここで好ましくは、第１ＳＣＲ１１の容量は第２ＳＣＲ１４の容量よりも小さい。例えば、第１ＳＣＲ１１の容量はエンジン１の排気量と同等程度であるのに対し、第２ＳＣＲ１４の容量はエンジン１の排気量の２倍程度である。このように上流側の第１ＳＣＲ１１を小容量化すると、その熱容量が小さくなって加熱され易くなり、特にエンジン冷間始動後の第１ＳＣＲ１１の早期活性化に非常に有利である。他方、第２ＳＣＲ１４の容量が大きいため、例えばエンジン１の高負荷運転時のように、第１ＳＣＲ１１だけでは処理しきれない比較的多量のＮＯｘが発生した場合であっても、そのＮＯｘを第２ＳＣＲ１４で確実に浄化できる。   Here, preferably, the capacity of the first SCR 11 is smaller than the capacity of the second SCR 14. For example, the capacity of the first SCR 11 is about the same as the displacement of the engine 1, whereas the capacity of the second SCR 14 is about twice the displacement of the engine 1. If the capacity of the first SCR 11 on the upstream side is reduced in this way, the heat capacity is reduced and the first SCR 11 is easily heated, which is particularly advantageous for early activation of the first SCR 11 after engine cold start. On the other hand, since the capacity of the second SCR 14 is large, even when a relatively large amount of NOx is generated that cannot be processed by the first SCR 11 alone, such as during high-load operation of the engine 1, the NOx is transferred to the second SCR 14. It can be purified reliably.

なお、ＤＰＦ１３と第２ＳＣＲ１４の配置は逆であってもよく、すなわち上流側に第２ＳＣＲ１４を、下流側にＤＰＦ１３を配置してもよい。   The arrangement of the DPF 13 and the second SCR 14 may be reversed, that is, the second SCR 14 may be arranged on the upstream side and the DPF 13 may be arranged on the downstream side.

この第１実施形態の構成を便宜上、図中に枠で囲って符号１００で表示する。   For the sake of convenience, the configuration of the first embodiment is surrounded by a frame in the figure and denoted by reference numeral 100.

以下、この第１実施形態を基本として他の実施形態を説明する。但し第１実施形態と同様の部分は説明を割愛し、第１実施形態との相違点を主に説明する。   Hereinafter, other embodiments will be described based on the first embodiment. However, the description of the same parts as in the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

［第２実施形態］
図３に、第２実施形態の排気浄化装置３を示す。便宜上、第２実施形態の排気浄化装置３を符号３Ｂで表す。 [Second Embodiment]
FIG. 3 shows an exhaust emission control device 3 according to the second embodiment. For convenience, the exhaust purification device 3 of the second embodiment is denoted by reference numeral 3B.

第２実施形態は、第１ＳＣＲ１１の下流側かつＰＮＡ１２の上流側に第１ＡＳＣ（第１アンモニアスリップ触媒）１７Ａを配置した点が、第１実施形態と異なる。このように第１ＡＳＣ１７Ａを設けると、第１ＳＣＲ１１で使用されずこれをすり抜けた余剰アンモニアを第１ＡＳＣ１７Ａで除去することができ、アンモニアが大気中に放出されるのを抑制できる。   The second embodiment is different from the first embodiment in that a first ASC (first ammonia slip catalyst) 17A is arranged on the downstream side of the first SCR 11 and the upstream side of the PNA 12. When the first ASC 17A is provided in this way, surplus ammonia that is not used in the first SCR 11 and has passed through the first ASC 17A can be removed by the first ASC 17A, and the release of ammonia into the atmosphere can be suppressed.

第１ＳＣＲ１１と第１ＡＳＣ１７Ａは一体化されていてもよい。例えばゾーンコートにより、共通の担体の上流側（前側）部分に第１ＳＣＲ１１を形成し、下流側（後側）部分に第１ＡＳＣ１７Ａを形成してもよい。   The first SCR 11 and the first ASC 17A may be integrated. For example, the first SCR 11 may be formed in the upstream (front) portion of the common carrier and the first ASC 17A may be formed in the downstream (rear) portion by zone coating.

［第３実施形態］
図４に、第３実施形態の排気浄化装置３を示す。便宜上、第３実施形態の排気浄化装置３を符号３Ｃで表す。 [Third Embodiment]
FIG. 4 shows an exhaust emission control device 3 according to the third embodiment. For convenience, the exhaust purification device 3 of the third embodiment is denoted by reference numeral 3C.

第３実施形態は、第２ＳＣＲ１４の下流側に第２ＡＳＣ（第２アンモニアスリップ触媒）１７Ｂを配置した点が、第１実施形態と異なる。このように第２ＡＳＣ１７Ｂを設けると、第２ＳＣＲ１４をすり抜けた余剰アンモニア、場合によっては第１ＳＣＲ１１をすり抜けた余剰アンモニアも、第２ＡＳＣ１７Ｂで除去することができ、アンモニアが大気中に放出されるのを抑制できる。   The third embodiment is different from the first embodiment in that a second ASC (second ammonia slip catalyst) 17B is disposed on the downstream side of the second SCR. When the second ASC 17B is provided in this way, surplus ammonia that has passed through the second SCR 14 and possibly surplus ammonia that has passed through the first SCR 11 can be removed by the second ASC 17B, and the release of ammonia into the atmosphere can be suppressed. .

なお、第２実施形態（図３）と同様、追加の第１ＡＳＣ１７Ａを、第１ＳＣＲ１１の下流側かつＰＮＡ１２の上流側に配置してもよい。   As in the second embodiment (FIG. 3), the additional first ASC 17A may be arranged on the downstream side of the first SCR 11 and the upstream side of the PNA 12.

［第４実施形態］
図５に、第４実施形態の排気浄化装置３を示す。便宜上、第４実施形態の排気浄化装置３を符号３Ｄで表す。 [Fourth Embodiment]
FIG. 5 shows an exhaust purification device 3 of the fourth embodiment. For convenience, the exhaust purification device 3 of the fourth embodiment is denoted by reference numeral 3D.

第４実施形態は、第１実施形態のＤＰＦ１３および第２ＳＣＲ１４の組を、ＤＰＦおよびＳＣＲを一体化させたフィルタ付き選択還元型ＮＯｘ触媒すなわちＳＣＲＦ（SCR-Filter）１８に置換した点が、第１実施形態と異なる。   In the fourth embodiment, the combination of the DPF 13 and the second SCR 14 of the first embodiment is replaced with a selective reduction-type NOx catalyst with a filter in which the DPF and the SCR are integrated, that is, an SCRF (SCR-Filter) 18. Different from the embodiment.

ＳＣＲＦ１８は、例えばウォールフロータイプのＤＰＦの基材表面にＳＣＲ層をウォッシュコート等により形成したものである。ＳＣＲＦ１８は実質的には、別体のＤＰＦおよびＳＣＲを直列に配置したものと同じである。従って第４実施形態は、実質的には第１実施形態と同じである。ＳＣＲＦ１８の上流側には第２添加弁１６が対配置される。   The SCRF 18 is formed by forming a SCR layer on the surface of a base material of a wall flow type DPF by a wash coat or the like. SCRF 18 is substantially the same as a separate DPF and SCR arranged in series. Therefore, the fourth embodiment is substantially the same as the first embodiment. A pair of second addition valves 16 are arranged upstream of the SCRF 18.

なお、第２実施形態（図３）および第３実施形態（図４）と、後述する第５実施形態（図６）および第６実施形態（図７）とにおいても、ＤＰＦ１３および第２ＳＣＲ１４の組をＳＣＲＦ１８に置換することが可能である。   In the second embodiment (FIG. 3) and the third embodiment (FIG. 4) and the fifth embodiment (FIG. 6) and the sixth embodiment (FIG. 7) described later, a set of the DPF 13 and the second SCR 14 is used. Can be replaced with SCRF18.

［第５実施形態］
図６に、第５実施形態の排気浄化装置３を示す。便宜上、第５実施形態の排気浄化装置３を符号３Ｅで表す。 [Fifth Embodiment]
FIG. 6 shows an exhaust emission control device 3 according to the fifth embodiment. For convenience, the exhaust emission control device 3 of the fifth embodiment is denoted by reference numeral 3E.

第５実施形態は、第１ＳＣＲ１１の上流側にＤＯＣ１９を配置した点が、第１実施形態と異なる。このようにＤＯＣ１９を設けると、ＤＯＣ１９で昇温した排気ガスを第１ＳＣＲ１１に供給し、第１ＳＣＲ１１を昇温して、第１ＳＣＲ１１に吸着した硫黄（Ｓ）を脱離（パージ）させることができる。すなわち、第１ＳＣＲ１１のＳパージを実行してそのＳ被毒を解消し、第１ＳＣＲ１１を回復ないし再生することができる。   The fifth embodiment is different from the first embodiment in that the DOC 19 is arranged on the upstream side of the first SCR 11. When the DOC 19 is provided in this way, the exhaust gas heated by the DOC 19 can be supplied to the first SCR 11, the first SCR 11 can be heated, and sulfur (S) adsorbed on the first SCR 11 can be desorbed (purged). That is, the S purge of the first SCR 11 is executed to eliminate the S poison, and the first SCR 11 can be recovered or regenerated.

このＳパージに際しては、周知のように、筒内でポスト噴射が実行され、あるいは排気管噴射が実行され、未燃燃料たるＨＣがＤＯＣ１９に供給され、ＨＣが燃焼される。これにより排気ガスが昇温され、高温の排気ガスが第１ＳＣＲ１１に供給されて第１ＳＣＲ１１が昇温される。   At the time of this S purge, as is well known, post injection is performed in the cylinder or exhaust pipe injection is performed, HC as unburned fuel is supplied to the DOC 19, and HC is combusted. As a result, the temperature of the exhaust gas is raised, the hot exhaust gas is supplied to the first SCR 11, and the temperature of the first SCR 11 is raised.

また周知のように、ＤＯＣ１９により昇温された排気ガスをＤＰＦ１３に供給し、ＤＰＦ１３に堆積したＰＭを強制的に燃焼除去するＤＰＦ再生を行うこともできる。   Further, as is well known, DPF regeneration in which exhaust gas heated by the DOC 19 is supplied to the DPF 13 and the PM deposited on the DPF 13 is forcibly burned off can be performed.

ところで、第５実施形態では第１ＳＣＲ１１のＳ被毒への対策を積極的に行うため、ＤＯＣ１９を設けているが、第１〜第４実施形態ではＤＯＣ１９を設けていない。従って、第１ＳＣＲ１１がＳ被毒に比較的強い構造の場合（例えばバナジウムを含む場合）には、第１〜第４実施形態のようにＤＯＣ１９を設けず、第１ＳＣＲ１１がＳ被毒に比較的弱い構造の場合（例えば鉄や銅を含む場合）には、第５実施形態のようにＤＯＣ１９を設けるといった棲み分けが可能である。これにより、第１ＳＣＲ１１のＳ被毒への耐性に応じた適切な排気浄化装置３とすることができる。   Incidentally, in the fifth embodiment, the DOC 19 is provided in order to positively take measures against S poisoning of the first SCR 11, but the DOC 19 is not provided in the first to fourth embodiments. Accordingly, when the first SCR 11 has a structure that is relatively resistant to S poisoning (for example, when vanadium is included), the DOC 19 is not provided as in the first to fourth embodiments, and the first SCR 11 is relatively vulnerable to S poisoning. In the case of a structure (for example, when iron or copper is included), it is possible to sort the DOC 19 as in the fifth embodiment. Thereby, it can be set as the suitable exhaust gas purification apparatus 3 according to the tolerance with respect to S poisoning of 1st SCR11.

なお、この第５実施形態の構成のうち、第１実施形態の構成部分１００を、第２実施形態（図３）、第３実施形態（図４）または第４実施形態（図５）のように改変してもよい。   Of the configuration of the fifth embodiment, the component 100 of the first embodiment is the same as the second embodiment (FIG. 3), the third embodiment (FIG. 4), or the fourth embodiment (FIG. 5). May be modified.

［第６実施形態］
図７に、第６実施形態の排気浄化装置３を示す。便宜上、第６実施形態の排気浄化装置３を符号３Ｆで表す。 [Sixth Embodiment]
FIG. 7 shows an exhaust emission control device 3 according to the sixth embodiment. For convenience, the exhaust emission control device 3 of the sixth embodiment is denoted by reference numeral 3F.

第６実施形態は、第１ＳＣＲ１１の上流側にヒータ付き酸化触媒、すなわち電気ヒータ（ＥＨ:Electric Heater）を有するＤＯＣ（ＤＯＣ＋ＥＨ）２０を配置した点が、第１実施形態と異なる。このＤＯＣ２０を設けると、第５実施形態のようにＳパージを実行できるほか、次の利点がもたらされる。   The sixth embodiment is different from the first embodiment in that an oxidation catalyst with a heater, that is, a DOC (DOC + EH) 20 having an electric heater (EH: Electric Heater) is arranged on the upstream side of the first SCR 11. When this DOC 20 is provided, S purge can be executed as in the fifth embodiment, and the following advantages are brought about.

すなわち、ＤＯＣ２０の電気ヒータをオンし、電気ヒータを加熱するだけで排気ガスを昇温し、第１ＳＣＲ１１を昇温できる。またこうした昇温は、任意のタイミングで行うことができ、ＤＯＣ２０が未活性状態のとき、すなわちＤＯＣ２０の温度が活性開始温度Ｔｓｄ未満のときでも行うことができる。従って、エンジンの冷間始動後にＤＯＣ２０の電気ヒータをオンすることにより、ＤＯＣ２０が未活性であっても第１ＳＣＲ１１を昇温でき、第１ＳＣＲ１１の活性化を早めることができる。またエンジン１の運転状態がアイドルまたは低負荷運転状態となって、第１ＳＣＲ１１に供給される排気ガスの温度が活性開始温度Ｔｓ１より低くなった場合でも、ＤＯＣ２０の電気ヒータをオンすることにより、排気ガスの温度を活性開始温度Ｔｓ１以上に高めることができる。よって第１ＳＣＲ１１の活性維持に有利である。   That is, the temperature of the exhaust gas can be raised and the temperature of the first SCR 11 can be raised simply by turning on the electric heater of the DOC 20 and heating the electric heater. Such a temperature increase can be performed at an arbitrary timing, and can be performed even when the DOC 20 is in an inactive state, that is, when the temperature of the DOC 20 is lower than the activation start temperature Tsd. Accordingly, by turning on the electric heater of the DOC 20 after the cold start of the engine, the temperature of the first SCR 11 can be increased even if the DOC 20 is inactive, and the activation of the first SCR 11 can be accelerated. Even when the operating state of the engine 1 is in an idle or low-load operating state and the temperature of the exhaust gas supplied to the first SCR 11 becomes lower than the activation start temperature Ts1, the exhaust gas can be exhausted by turning on the electric heater of the DOC 20. The gas temperature can be increased to the activation start temperature Ts1 or higher. Therefore, it is advantageous for maintaining the activity of the first SCR11.

また、ＤＯＣ２０の電気ヒータをオンした状態で、ポスト噴射等によりＤＯＣ２０に追加のＨＣを供給すれば、ＨＣを電気ヒータで直接的に着火燃焼させ、ＤＯＣ２０をバーナーの如く機能させることができる。これにより極めて高い昇温効果を得ることができる。   Further, if additional HC is supplied to the DOC 20 by post injection or the like with the electric heater of the DOC 20 turned on, the HC can be directly ignited and burned by the electric heater, and the DOC 20 can function as a burner. Thereby, a very high temperature rising effect can be obtained.

なお、この第６実施形態の構成のうち、第１実施形態の構成部分１００を、第２実施形態（図３）、第３実施形態（図４）または第４実施形態（図５）のように改変してもよい。   Of the configuration of the sixth embodiment, the component 100 of the first embodiment is the same as the second embodiment (FIG. 3), the third embodiment (FIG. 4), or the fourth embodiment (FIG. 5). May be modified.

他にも、前述の各実施形態の構成は、特に矛盾が無い限り、部分的にまたは全体的に組み合わせることが可能である。本開示の実施形態は前述の実施形態のみに限らず、特許請求の範囲によって規定される本開示の思想に包含されるあらゆる変形例や応用例、均等物が本開示に含まれる。従って本開示は、限定的に解釈されるべきではなく、本開示の思想の範囲内に帰属する他の任意の技術にも適用することが可能である。   In addition, the configurations of the respective embodiments described above can be combined partially or wholly unless there is a particular contradiction. The embodiment of the present disclosure is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present disclosure defined by the claims. Therefore, the present disclosure should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present disclosure.

１ 内燃機関（エンジン）
２ 排気通路
３，３Ａ，３Ｂ，３Ｃ，３Ｄ，３Ｅ，３Ｆ 排気浄化装置
１１ 選択還元型第１ＮＯｘ触媒（第１ＳＣＲ）
１２ ＮＯｘ吸着材（ＰＮＡ）
１３ フィルタ（ＤＰＦ）
１４ 選択還元型第２ＮＯｘ触媒（第２ＳＣＲ）
１７Ａ 第１アンモニアスリップ触媒（第１ＡＳＣ）
１７Ｂ 第２アンモニアスリップ触媒（第２ＡＳＣ）
１８ フィルタ付き選択還元型ＮＯｘ触媒（ＳＣＲＦ）
１９ 酸化触媒（ＤＯＣ）
２０ ヒータ付き酸化触媒（ＤＯＣ＋ＥＨ） 1 Internal combustion engine
2 Exhaust passages 3, 3A, 3B, 3C, 3D, 3E, 3F Exhaust purification device 11 Selective reduction type first NOx catalyst (first SCR)
12 NOx adsorbent (PNA)
13 Filter (DPF)
14 Selective reduction type second NOx catalyst (second SCR)
17A First ammonia slip catalyst (first ASC)
17B Second ammonia slip catalyst (second ASC)
18 Selective reduction type NOx catalyst with filter (SCRF)
19 Oxidation catalyst (DOC)
20 Oxidation catalyst with heater (DOC + EH)

Claims (6)

選択還元型第１ＮＯｘ触媒と、
排気流れ方向における前記第１ＮＯｘ触媒の下流側に配置されたＮＯｘ吸着材と、
を備えることを特徴とする内燃機関の排気浄化装置。 A selective reduction type first NOx catalyst;
A NOx adsorbent disposed downstream of the first NOx catalyst in the exhaust flow direction;
An exhaust emission control device for an internal combustion engine, comprising: 前記第１ＮＯｘ触媒の下流側かつ前記ＮＯｘ吸着材の上流側に配置された第１アンモニアスリップ触媒をさらに備える
請求項１に記載の内燃機関の排気浄化装置。 The exhaust emission control device for an internal combustion engine according to claim 1, further comprising a first ammonia slip catalyst disposed downstream of the first NOx catalyst and upstream of the NOx adsorbent. 前記ＮＯｘ吸着材の下流側に配置されたフィルタおよび選択還元型第２ＮＯｘ触媒をさらに備える
請求項１または２に記載の内燃機関の排気浄化装置。 The exhaust emission control device for an internal combustion engine according to claim 1 or 2, further comprising a filter and a selective reduction type second NOx catalyst disposed downstream of the NOx adsorbent. 前記第２ＮＯｘ触媒の下流側に配置された第２アンモニアスリップ触媒をさらに備える
請求項３に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 3, further comprising a second ammonia slip catalyst disposed downstream of the second NOx catalyst. 前記第１ＮＯｘ触媒の上流側に配置された酸化触媒をさらに備える
請求項１〜４のいずれか一項に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 4, further comprising an oxidation catalyst disposed upstream of the first NOx catalyst. 前記酸化触媒が電気ヒータを有する
請求項５に記載の内燃機関の排気浄化装置。 The exhaust purification apparatus for an internal combustion engine according to claim 5, wherein the oxidation catalyst has an electric heater.
JP2018044329A 2018-03-12 2018-03-12 Exhaust purifying device for internal combustion engine Pending JP2019157737A (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008291673A (en) * 2007-05-22 2008-12-04 Nissan Diesel Motor Co Ltd Exhaust emission control device for engine
JP2009262098A (en) * 2008-04-28 2009-11-12 Ne Chemcat Corp Exhaust gas clarifying method using selective reduction catalyst
JP2010265862A (en) * 2009-05-18 2010-11-25 Toyota Industries Corp Exhaust emission control device
US20170341026A1 (en) * 2016-05-31 2017-11-30 Johnson Matthey Public Limited Company Vanadium Catalysts for High Engine-Out NO2 Systems

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008291673A (en) * 2007-05-22 2008-12-04 Nissan Diesel Motor Co Ltd Exhaust emission control device for engine
JP2009262098A (en) * 2008-04-28 2009-11-12 Ne Chemcat Corp Exhaust gas clarifying method using selective reduction catalyst
JP2010265862A (en) * 2009-05-18 2010-11-25 Toyota Industries Corp Exhaust emission control device
US20170341026A1 (en) * 2016-05-31 2017-11-30 Johnson Matthey Public Limited Company Vanadium Catalysts for High Engine-Out NO2 Systems

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