JP2012127298A - Device and method for controlling exhaust emission of internal combustion engine - Google Patents
Device and method for controlling exhaust emission of internal combustion engine Download PDFInfo
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本発明は、内燃機関の排気浄化装置及び、排気浄化方法に関する。 The present invention relates to an exhaust gas purification apparatus and an exhaust gas purification method for an internal combustion engine.
ディーゼルエンジン等の内燃機関から排出される排気中に含まれるＮＯｘ（窒素化合物）を浄化する排気浄化触媒として、ＮＯｘをＨＣにより選択的に還元するＨＣ選択還元型ＮＯｘ触媒（ＨＣ−Ｓｅｌｅｃｔｉｖｅ Ｃａｔａｌｙｔｉｃ Ｒｅｄｕｃｔｉｏｎ）が知られている。 As an exhaust purification catalyst for purifying NOx (nitrogen compounds) contained in exhaust gas discharged from an internal combustion engine such as a diesel engine, an HC selective reduction type NOx catalyst (HC-Selective Catalytic Reduction) that selectively reduces NOx by HC It has been known.
このＨＣ選択還元型ＮＯｘ触媒は、尿素ＳＣＲのように余分なタンクを搭載することなく燃料の一部を還元剤として利用するので、装置を小型化できることや、貴金属の量を低減できる等の利点がある。 Since this HC selective reduction type NOx catalyst uses part of the fuel as a reducing agent without mounting an extra tank like the urea SCR, it is possible to reduce the size of the apparatus and reduce the amount of noble metal. There is.
例えば、特許文献１には、この種のＨＣ選択還元型ＮＯｘ触媒を備え、ＨＣ選択還元型ＮＯｘ触媒よりも上流側から順に酸化触媒と、パティキュレートフィルタと、アンモニア選択還元型ＮＯｘ触媒とを設けた排気浄化装置が開示されている。 For example, Patent Document 1 includes this type of HC selective reduction type NOx catalyst, and includes an oxidation catalyst, a particulate filter, and an ammonia selective reduction type NOx catalyst in order from the upstream side of the HC selective reduction type NOx catalyst. An exhaust purification device is disclosed.
ところで、ＨＣ選択還元型ＮＯｘ触媒の触媒活性温度は一般的に２００℃〜３００℃である。そのため、冷間始動時など触媒温度が触媒活性温度に達しない低温域では、ＨＣ選択還元型ＮＯｘ触媒が有効に作用せず、排気中に含まれるＮＯｘの浄化率が低下してしまう可能性がある。 By the way, the catalytic activation temperature of the HC selective reduction type NOx catalyst is generally 200 ° C. to 300 ° C. Therefore, in a low temperature range where the catalyst temperature does not reach the catalyst activation temperature, such as during a cold start, the HC selective reduction type NOx catalyst does not act effectively, and the purification rate of NOx contained in the exhaust gas may decrease. is there.
本発明は、このような点に鑑みてなされたもので、その目的は、冷間始動時等の低温域においても、排気中に含まれるＮＯｘの浄化率を効果的に向上することにある。 The present invention has been made in view of these points, and an object thereof is to effectively improve the purification rate of NOx contained in exhaust gas even in a low temperature range such as during cold start.
上記目的を達成するため、本発明の内燃機関の排気浄化装置は、内燃機関の排気通路に設けられ、前記内燃機関から排出される排気中のＮＯｘを吸着するとともに、前記吸着したＮＯｘを酸化してＮＯ2を生成し、前記生成されたＮＯ2を供給されるＨＣにより還元浄化する排気浄化触媒と、前記排気浄化触媒に還元剤としてのＨＣを供給するＨＣ供給手段と、前記排気中のＣＯにより前記排気浄化触媒の表面を清浄化してＮＯｘの吸着を促進すべく、前記排気中に含まれるＣＯの量がＮＯｘの量よりも多くなるように前記内燃機関の燃焼を制御する制御手段と、を備えることを特徴とする。 In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention is provided in an exhaust passage of the internal combustion engine, adsorbs NOx in the exhaust discharged from the internal combustion engine, and oxidizes the adsorbed NOx. It generates NO 2 Te, and the exhaust gas purifying catalyst to reduce and purify by HC supplied to NO 2 that the generated, the HC supply means for supplying HC as a reducing agent to the exhaust gas purifying catalyst, CO in the exhaust Control means for controlling the combustion of the internal combustion engine so that the amount of CO contained in the exhaust gas is larger than the amount of NOx in order to clean the surface of the exhaust purification catalyst and promote NOx adsorption, It is characterized by providing.
また、前記制御手段は、前記排気中に含まれるＣＯの量がＮＯｘの量に対して５倍以上となるように制御してもよい。 Further, the control means may perform control so that the amount of CO contained in the exhaust gas is five times or more than the amount of NOx.
また、前記排気浄化触媒は、前記排気中のＮＯｘを吸着するとともに、前記吸着したＮＯｘを酸化してＮＯ2を生成する酸化触媒と、前記酸化触媒よりも下流側の排気通路に設けられ、前記酸化触媒で生成されたＮＯ2を供給されるＨＣにより還元浄化するＨＣ選択還元型ＮＯｘ触媒とを含むものであってもよい。 Further, the exhaust gas purifying catalyst, as well as adsorbing the NOx in the exhaust, an oxidation catalyst for generating NO 2 to oxidize the adsorbed NOx, provided in an exhaust passage downstream of the oxidation catalyst, wherein It may include an HC selective reduction type NOx catalyst that reduces and purifies NO 2 produced by the oxidation catalyst by the supplied HC.
また、前記排気浄化触媒もしくは前記酸化触媒は、金属酸化物担体として少なくともＡｌ又はＣｅの酸化物を含むとともに、前記金属酸化物担体に担持される触媒貴金属として少なくともＰｔ又はＰｄを含むものであってもよい。 The exhaust purification catalyst or the oxidation catalyst includes at least Al or Ce oxide as a metal oxide support, and at least Pt or Pd as a catalyst noble metal supported on the metal oxide support. Also good.
また、上記目的を達成するため、本発明の内燃機関の排気浄化方法は、内燃機関の排気通路に設けられた排気浄化触媒に前記内燃機関から排出される排気中のＮＯｘを吸着するとともに、前記吸着したＮＯｘを酸化してＮＯ2を生成し、前記生成されたＮＯ2をＨＣ供給手段から供給されるＨＣにより還元浄化する排気浄化方法において、前記排気中のＣＯにより前記排気浄化触媒の表面を清浄化してＮＯｘの吸着を促進すべく、前記排気中に含まれるＣＯの量がＮＯｘの量よりも多くなるように前記内燃機関の燃焼を制御することを特徴とする。 In order to achieve the above object, an exhaust gas purification method for an internal combustion engine of the present invention adsorbs NOx in exhaust gas exhausted from the internal combustion engine to an exhaust gas purification catalyst provided in an exhaust passage of the internal combustion engine, and In the exhaust purification method in which the adsorbed NOx is oxidized to generate NO 2 and the generated NO 2 is reduced and purified by HC supplied from the HC supply means, the surface of the exhaust purification catalyst is removed by CO in the exhaust. The combustion of the internal combustion engine is controlled so that the amount of CO contained in the exhaust gas is larger than the amount of NOx in order to clean and promote NOx adsorption.
また、前記内燃機関の燃焼を、前記排気中に含まれるＣＯの量がＮＯｘの量に対して５倍以上となるように制御してもよい。 Further, the combustion of the internal combustion engine may be controlled so that the amount of CO contained in the exhaust gas is five times or more than the amount of NOx.
本発明の内燃機関の排気浄化装置及び、排気浄化方法によれば、冷間始動時等の低温域においても、排気中に含まれるＮＯｘの浄化率を効果的に向上することができる。 According to the exhaust gas purification apparatus and the exhaust gas purification method of the present invention, the purification rate of NOx contained in the exhaust gas can be effectively improved even in a low temperature range such as during cold start.
以下、図１〜６に基づいて、本発明の一実施形態に係る内燃機関の排気浄化装置１について説明する。同一の部品には同一の符号を付してあり、それらの名称および機能も同じである。したがって、それらについての詳細な説明は繰返さない。 Hereinafter, based on FIGS. 1-6, the exhaust gas purification apparatus 1 of the internal combustion engine which concerns on one Embodiment of this invention is demonstrated. The same parts are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.
図１に示すように、ディーゼルエンジン（内燃機関）１０には、吸気マニホールド１１と排気マニホールド１２とが設けられている。また、吸気マニホールド１１には、ディーゼルエンジン１０内の吸気弁（不図示）の開弁により新気を導入する吸気通路１３が接続され、排気マニホールド１２には、排気弁（不図示）の開弁により排気を排出する排気通路１４が接続されている。 As shown in FIG. 1, a diesel engine (internal combustion engine) 10 is provided with an intake manifold 11 and an exhaust manifold 12. An intake passage 13 for introducing fresh air by opening an intake valve (not shown) in the diesel engine 10 is connected to the intake manifold 11, and an exhaust valve (not shown) is opened to the exhaust manifold 12. Is connected to an exhaust passage 14 for discharging exhaust gas.
吸気通路１３には、上流側から順にエアフィルタ１５と、ターボ過給機１６のコンプレッサ１６ａと、インタクーラ１７が配設されている。また、排気通路１４には、上流側から順にターボ過給機１６のタービン１６ｂと、排気温度センサ１８と、詳細を後述する排気浄化触媒３０と、ＮＯｘセンサ１９とが配設されている。 In the intake passage 13, an air filter 15, a compressor 16 a of the turbocharger 16, and an intercooler 17 are arranged in order from the upstream side. Further, in the exhaust passage 14, a turbine 16 b of the turbocharger 16, an exhaust temperature sensor 18, an exhaust purification catalyst 30, which will be described in detail later, and a NOx sensor 19 are arranged in order from the upstream side.
さらに、コンプレッサ１６ａよりも上流側の吸気通路１３と、タービン１６ｂよりも下流側の排気通路１４とは、排気の一部を還流するＥＧＲ通路２０で接続され、このＥＧＲ通路２０には、ＥＧＲクーラ２１及びＥＧＲ弁２２が設けられている。 Further, the intake passage 13 upstream of the compressor 16a and the exhaust passage 14 downstream of the turbine 16b are connected by an EGR passage 20 that recirculates part of the exhaust, and the EGR passage 20 includes an EGR cooler. 21 and an EGR valve 22 are provided.
排気浄化触媒３０は、図１に示すように、上流側から順に酸化触媒（以下、ＤＯＣ触媒という）３１と、パティキュレートフィルタ（以下、ＤＰＦという）３２と、ＨＣ選択還元型ＮＯｘ触媒（以下、ＨＣ−ＳＣＲ触媒という）３３とを備え構成されている。また、ＤＯＣ触媒３１とＤＰＦ３２との間には、排気管噴射を行う排気管噴射装置（ＨＣ供給手段）３４が設けられている。なお、本実施形態において、ＤＯＣ触媒３１、ＤＰＦ３２及び、ＨＣ−ＳＣＲ触媒３３は、本発明の排気浄化触媒を構成する。 As shown in FIG. 1, the exhaust purification catalyst 30 includes an oxidation catalyst (hereinafter referred to as a DOC catalyst) 31, a particulate filter (hereinafter referred to as DPF) 32, and an HC selective reduction NOx catalyst (hereinafter referred to as “hereinafter referred to as“ NOx catalyst ”). HC-SCR catalyst) 33). An exhaust pipe injection device (HC supply means) 34 that performs exhaust pipe injection is provided between the DOC catalyst 31 and the DPF 32. In the present embodiment, the DOC catalyst 31, the DPF 32, and the HC-SCR catalyst 33 constitute an exhaust purification catalyst of the present invention.
ＤＯＣ触媒３１は、ハニカム構造を有する金属酸化物担体に触媒貴金属を担持して形成されている。本実施形態において、金属酸化物担体は、Ａｌ（アルミナ）の酸化物（以下、Ａｌ2Ｏ3）又は酸素吸蔵能力を有するＣｅ（セリウム）の酸化物（以下、ＣｅＯ2）を含んで構成されている。また、触媒貴金属は、Ｐｔ（白金）又はＰｄ（パラジウム）を含んで構成されている。 The DOC catalyst 31 is formed by supporting a catalyst noble metal on a metal oxide carrier having a honeycomb structure. In this embodiment, the metal oxide support includes an oxide of Al (alumina) (hereinafter referred to as Al 2 O 3 ) or an oxide of Ce (cerium) having an oxygen storage capacity (hereinafter referred to as CeO 2 ). ing. Further, the catalyst noble metal includes Pt (platinum) or Pd (palladium).
このＤＯＣ触媒３１は、後述するＥＣＵ４０によるディーゼルエンジン１０の燃焼制御により排気中に含まれるＣＯ量が増加されると、このＣＯを利用して触媒表面へのＮＯｘの吸着及びＮＯ2の生成を促進させる。具体的には、図２（ａ）に示すように、排気中のＣＯが触媒貴金属（Ｐｔ又はＰｄ）の表面を清浄化することで、触媒貴金属表面へのＮＯｘの吸着を促進させる。さらに、触媒貴金属表面のＯ2（酸素）と、金属酸化物担体（Ａｌ2Ｏ3，ＣｅＯ2，ＺｒＯ2等）及びこの金属酸化物担体表面から放出されるＯ2とにより、ＮＯｘ＋（２−Ｘ）／２×Ｏ2→ＮＯ2（Ｘ≦２）の反応を促進させる。その後、生成したＮＯ2を、触媒貴金属表面及び金属酸化物担体表面に吸着するとともに、触媒温度が上昇（２００℃〜２５０℃）すると排気中に脱離するように構成されている。 The DOC catalyst 31 is promoted when the amount CO contained in the exhaust gas is increased, the production of adsorption and NO 2 in NOx to the catalyst surface by utilizing the CO by combustion control of the diesel engine 10 by ECU40 described below Let Specifically, as shown in FIG. 2 (a), CO in the exhaust purifies the surface of the catalyst noble metal (Pt or Pd), thereby promoting NOx adsorption on the surface of the catalyst noble metal. Further, NOx + (2−) is obtained by O 2 (oxygen) on the surface of the catalyst noble metal, a metal oxide support (Al 2 O 3 , CeO 2 , ZrO 2, etc.) and O 2 released from the surface of the metal oxide support. X) / 2 × O 2 → NO 2 (X ≦ 2) is promoted. Thereafter, the produced NO 2 is adsorbed on the catalyst noble metal surface and the metal oxide support surface, and desorbed into the exhaust when the catalyst temperature rises (200 ° C. to 250 ° C.).
ＤＰＦ３２は、公知の構造であって、セラミック製のハニカム構造体からなる多数のセル内を排気流路として備え、上流側と下流側とを交互に目封じして形成されている。このＤＰＦ３２は、排気中に含まれるＰＭ（粒子状物質）を捕集するとともに、堆積したＰＭを定期的に燃焼除去する強制再生が行われるように構成されている。 The DPF 32 has a known structure, and is provided with a large number of cells made of a ceramic honeycomb structure as exhaust passages, and the upstream side and the downstream side are alternately sealed. The DPF 32 is configured to collect the PM (particulate matter) contained in the exhaust gas and perform forced regeneration to periodically burn and remove the accumulated PM.
ＨＣ−ＳＣＲ触媒３３は、排気管噴射装置３４から供給されるＨＣを還元剤として排気中のＮＯｘを選択還元するもので、具体的には、ＮＯｘ＋ＨＣ→Ｎ2＋ＣＯ2＋Ｈ2Ｏなる反応式でディーゼルエンジン１０から排出される排気中のＮＯｘを浄化する。このＨＣ−ＳＣＲ触媒３３による還元反応は、排気中のＮＯ2量が他のＮＯｘ量よりも多い場合に効率的に促進される。さらに、ＨＣ−ＳＣＲ触媒３３は、ＤＰＦ３２の強制再生の際に発生するＣＯを酸化してＣＯ2にする機能も有する。 The HC-SCR catalyst 33 selectively reduces NOx in the exhaust gas using HC supplied from the exhaust pipe injector 34 as a reducing agent. Specifically, the HC-SCR catalyst 33 has a reaction formula of NOx + HC → N 2 + CO 2 + H 2 O. The NOx in the exhaust discharged from the diesel engine 10 is purified. This reduction reaction by the HC-SCR catalyst 33 is efficiently promoted when the amount of NO 2 in the exhaust gas is larger than the amount of other NOx. Furthermore, the HC-SCR catalyst 33 also has a function of oxidizing CO generated during forced regeneration of the DPF 32 to CO 2 .
排気管噴射装置３４は、ＨＣ−ＳＣＲ触媒３３に図示しない燃料タンクから還元剤であるＨＣを供給する。また、排気管噴射装置３４は後述するＥＣＵ４０と電気配線を介して接続されている。 The exhaust pipe injection device 34 supplies HC, which is a reducing agent, from a fuel tank (not shown) to the HC-SCR catalyst 33. Further, the exhaust pipe injection device 34 is connected to an ECU 40 described later via electric wiring.
排気温度センサ１８は、排気浄化触媒３０に流入する排気の温度（触媒入口温度）を検出するもので、電気配線を介して後述するＥＣＵ４０に接続されている。 The exhaust temperature sensor 18 detects the temperature of the exhaust gas flowing into the exhaust purification catalyst 30 (catalyst inlet temperature), and is connected to an ECU 40 described later via an electrical wiring.
ＮＯｘセンサ１９は、排気浄化触媒３０を通過した排気中のＮＯｘ濃度を検出するもので、電気配線を介して後述するＥＣＵ４０に接続されている。 The NOx sensor 19 detects the NOx concentration in the exhaust gas that has passed through the exhaust purification catalyst 30, and is connected to an ECU 40 described later via an electrical wiring.
ＥＣＵ（電子制御ユニット）４０は、車両やディーゼルエンジン１０の各種制御を行うもので、公知のＣＰＵやＲＯＭ、ＲＡＭ、入力ポート、出力ポート等を備え構成されている。この各種制御を行うために、ＥＣＵ４０には、エンジン回転センサ（不図示）、アクセル開度センサ（不図示）、排気温度センサ１８、ＮＯｘセンサ１９等の各種センサの出力信号がＡ／Ｄ変換された後に入力される。 The ECU (electronic control unit) 40 performs various controls of the vehicle and the diesel engine 10, and includes a known CPU, ROM, RAM, input port, output port, and the like. In order to perform these various controls, the ECU 40 A / D converts output signals from various sensors such as an engine rotation sensor (not shown), an accelerator opening sensor (not shown), an exhaust temperature sensor 18 and a NOx sensor 19. Will be entered after.
また、ＥＣＵ４０は、燃焼制御部４１と、排気管噴射制御部４２とを一部の機能要素として有する。これら各機能要素は、本実施形態では一体のハードウェアであるＥＣＵ４０に含まれるものとして説明するが、これらのいずれか一部を別体のハードウェアに設けることもできる。 Further, the ECU 40 includes a combustion control unit 41 and an exhaust pipe injection control unit 42 as some functional elements. In the present embodiment, these functional elements are described as being included in the ECU 40, which is an integral piece of hardware. However, any one of these functional elements may be provided in separate hardware.
燃焼制御部４１は、ディーゼルエンジン１０の始動時など、排気温度が低く触媒温度が上昇しない低温域において、排気中に含まれるＣＯ量がＮＯｘ量よりも多くなるようにディーゼルエンジン１０の燃焼を制御する。具体的には、この燃焼制御部４１には、予め実験等で作成した燃料噴射量及び、排気中に含まれるＮＯｘ量に対するＣＯ量の比（ＣＯ／ＮＯｘ）をパラメータとする排気ＣＯ量設定マップが記憶されている。そして、燃焼制御部４１は、この排気ＣＯ量設定マップと燃料噴射量に対応するアクセル開度センサの検出値とに基づいて、排気温度センサ１８の検出値が所定の下限値（例えば、２００℃）よりも低いときは、排気中に含まれるＣＯ量がＮＯｘ量よりも多くなるようにディーゼルエンジン１０の燃焼を制御するように構成されている。 The combustion control unit 41 controls the combustion of the diesel engine 10 so that the amount of CO contained in the exhaust becomes larger than the amount of NOx in a low temperature range where the exhaust temperature is low and the catalyst temperature does not rise, such as when the diesel engine 10 is started. To do. Specifically, the combustion control unit 41 includes an exhaust CO amount setting map that uses, as parameters, a fuel injection amount that has been created in advance through experiments and the like, and a ratio of the CO amount to the NOx amount contained in the exhaust (CO / NOx). Is remembered. Then, the combustion control unit 41 sets the detected value of the exhaust temperature sensor 18 to a predetermined lower limit value (for example, 200 ° C.) based on the exhaust CO amount setting map and the detected value of the accelerator opening sensor corresponding to the fuel injection amount. ), The combustion of the diesel engine 10 is controlled so that the amount of CO contained in the exhaust gas is larger than the amount of NOx.
ここで、排気中に含まれるＮＯｘ量に対するＣＯ量の比（ＣＯ／ＮＯｘ）と、ＤＯＣ触媒３１によるＮＯ2生成率との関係を図３に示す。図３に示すように、ＤＯＣ触媒３１によるＮＯ2の生成率は、ＮＯｘ量に対するＣＯ量の比（ＣＯ／ＮＯｘ）が５〜２０倍の時に高くなることが分かる。したがって、本実施形態において、燃焼制御部４１による燃焼制御は、ＮＯｘ量に対するＣＯ量が５倍以上（又は、５〜２０倍の範囲）となるように設定されている。 Here, the relationship between the ratio of the CO amount to the NOx amount contained in the exhaust gas (CO / NOx) and the NO 2 production rate by the DOC catalyst 31 is shown in FIG. As shown in FIG. 3, it can be seen that the NO 2 production rate by the DOC catalyst 31 increases when the ratio of the CO amount to the NOx amount (CO / NOx) is 5 to 20 times. Therefore, in this embodiment, the combustion control by the combustion control unit 41 is set so that the CO amount with respect to the NOx amount is 5 times or more (or a range of 5 to 20 times).
排気管噴射制御部４２は、排気管噴射装置３４による排気管噴射、すなわち還元剤であるＨＣのＨＣ−ＳＣＲ触媒３３への供給を制御する。具体的には、この排気管噴射制御部４２は、排気温度センサ１８の検出値が所定の下限値（例えば２００℃）を超えると、排気管噴射装置３４に燃料を噴射させる作動信号を出力する。すなわち、ＨＣ−ＳＣＲ触媒３３に還元剤としてのＨＣが供給され、排気中に含まれるＮＯｘの選択還元が促進される。また、排気管噴射制御部４２は、排気温度センサ１８の検出値が所定の下限閾値（例えば、２００℃）以下の場合であっても、ＮＯｘセンサ１９の検出値が所定の上限閾値を超えた時は、排気管噴射装置３４に燃料を噴射させる作動信号を出力するように構成されている。 The exhaust pipe injection control unit 42 controls exhaust pipe injection by the exhaust pipe injection device 34, that is, supply of HC as a reducing agent to the HC-SCR catalyst 33. Specifically, the exhaust pipe injection control unit 42 outputs an operation signal that causes the exhaust pipe injection device 34 to inject fuel when the detection value of the exhaust temperature sensor 18 exceeds a predetermined lower limit value (for example, 200 ° C.). . That is, HC as a reducing agent is supplied to the HC-SCR catalyst 33, and selective reduction of NOx contained in the exhaust is promoted. Further, the exhaust pipe injection control unit 42 has detected the detected value of the NOx sensor 19 exceeding the predetermined upper limit threshold even when the detected value of the exhaust temperature sensor 18 is equal to or lower than a predetermined lower limit threshold (for example, 200 ° C.). At the time, the exhaust pipe injection device 34 is configured to output an operation signal for injecting fuel.
以上のような構成により、本発明の一実施形態に係る内燃機関の排気浄化装置１によれば以下のような作用効果を奏する。 With the configuration as described above, the exhaust gas purification apparatus 1 for an internal combustion engine according to an embodiment of the present invention has the following operational effects.
ディーゼルエンジン１０の始動時など、排気温度センサ１８の検出値が所定の下限閾値（２００℃）よりも低い時、すなわち触媒温度が活性温度まで上昇しない低温域において、ディーゼルエンジン１０の燃焼は、排気中に含まれるＣＯ量がＮＯｘ量よりも多くなるように制御される。そして、排気中に含まれるＣＯがＤＯＣ触媒３１により酸化されることで、貴金属触媒であるＰｔ（又はＰｄ）の貴金属活性点の酸素が消費される。一方、ＮＯを酸化する過程では酸素不足状態となり、貴金属近傍の担体酸化物格子酸素が金属に引きつけられてＮＯ2等の酸化生成物を安定保持するサイトが形成される。さらに、貴金属上でＮＯの酸化により生成されたＮＯ2等の化合物は速やかに安定保持サイトに移動保持されるとともに、排気（触媒）温度が２００℃〜３００℃程度になると脱離される。その後、ＤＯＣ触媒３１から脱離したＮＯ2等の化合物は、ＨＣ−ＳＣＲ触媒３３で排気管噴射装置３４から供給されるＨＣにより選択還元される。 When the detected value of the exhaust temperature sensor 18 is lower than a predetermined lower threshold (200 ° C.), such as when the diesel engine 10 is started, that is, in the low temperature range where the catalyst temperature does not rise to the activation temperature, combustion of the diesel engine 10 The amount of CO contained therein is controlled to be larger than the amount of NOx. Then, the CO contained in the exhaust is oxidized by the DOC catalyst 31, so that oxygen at the noble metal active point of Pt (or Pd) which is a noble metal catalyst is consumed. On the other hand, in the process of oxidizing NO, an oxygen-deficient state occurs, and the carrier oxide lattice oxygen in the vicinity of the noble metal is attracted to the metal to form a site that stably holds an oxidation product such as NO 2 . Further, a compound such as NO 2 generated by oxidation of NO on the noble metal is quickly moved and held at the stable holding site, and is desorbed when the exhaust (catalyst) temperature reaches about 200 ° C. to 300 ° C. Thereafter, compounds such as NO 2 desorbed from the DOC catalyst 31 are selectively reduced by the HC supplied from the exhaust pipe injection device 34 by the HC-SCR catalyst 33.
したがって、ＤＯＣ触媒３１の触媒温度が活性温度に達しない低温域から、ＮＯｘの吸着、ＮＯの酸化及び、ＮＯ2等の化合物の生成が連続的に行われ、その後、ＤＯＣ触媒３１から脱離したＮＯ2をＨＣ−ＳＣＲ触媒３３で効率よく選択還元することが可能となり、排気中に含まれるＮＯｘの浄化率を効果的に向上することができる。 Therefore, NOx adsorption, NO oxidation, and generation of compounds such as NO 2 are continuously performed from a low temperature range where the catalyst temperature of the DOC catalyst 31 does not reach the activation temperature, and then desorbed from the DOC catalyst 31. NO 2 can be selectively reduced efficiently by the HC-SCR catalyst 33, and the purification rate of NOx contained in the exhaust can be effectively improved.
また、本実施形態において、低温域におけるディーゼルエンジン１０の燃焼制御は、ＤＯＣ触媒３１によるＮＯ2の生成効率を高くするために、排気中に含まれるＮＯｘ量に対するＣＯ量が５倍以上（又は、５〜２０倍の範囲）となるように設定されている（図３参照）。 Further, in the present embodiment, the combustion control of the diesel engine 10 in the low temperature region has a CO amount that is five times or more with respect to the NOx amount contained in the exhaust in order to increase the generation efficiency of NO 2 by the DOC catalyst 31 (or The range is set to 5 to 20 times (see FIG. 3).
したがって、排気中のＣＯを利用してＤＯＣ触媒３１の表面が清浄化されることで、低温域からＤＯＣ触媒３１へのＮＯｘの吸着を効果的に促進することができるとともに、ＮＯ2の生成を効率よく行うことが可能となる。 Therefore, by cleaning the surface of the DOC catalyst 31 using CO in the exhaust, it is possible to effectively promote the adsorption of NOx from the low temperature range to the DOC catalyst 31 and to generate NO 2 . It becomes possible to carry out efficiently.
また、本実施形態において、排気浄化触媒３０は、ＤＯＣ触媒３１がＨＣ−ＳＣＲ触媒３３の上流側に配設されている。すなわち、ＨＣ−ＳＣＲ触媒３３に流れ込む排気は、ＮＯ2以外のＮＯｘが多く存在するディーゼルエンジン１０から直接排出された排気ではなく、ＤＯＣ触媒３１の酸化作用によりＮＯ2が多く存在する排気となる。 In the present embodiment, the exhaust purification catalyst 30 has the DOC catalyst 31 disposed upstream of the HC-SCR catalyst 33. That is, the exhaust gas flowing into the HC-SCR catalyst 33 is not exhaust gas directly discharged from the diesel engine 10 in which a large amount of NOx other than NO 2 exists, but is exhaust gas in which a large amount of NO 2 exists due to the oxidizing action of the DOC catalyst 31.
したがって、ＮＯ2が多く存在する排気に対して還元剤であるＨＣを供給することが可能となり、ＨＣ−ＳＣＲ触媒３３によるＮＯｘの選択還元を効率的に行うことができ、ＮＯｘの排出量を効果的に低減することができる。 Therefore, it becomes possible to supply HC as a reducing agent to the exhaust gas in which a large amount of NO 2 exists, and the selective reduction of NOx by the HC-SCR catalyst 33 can be performed efficiently, and the NOx emission amount is effectively reduced. Can be reduced.
ここで、図４〜６に、本実施形態に係る内燃機関の排気浄化装置１において、ＮＯ2生成率及びＮＯｘ浄化率に関し、ＤＯＣ触媒３１の金属酸化物担体にＡｌ2Ｏ3及び触媒貴金属にＰｔを適用した実施品１と、ＤＯＣ触媒３１の金属酸化物担体にＣｅＯ2及び触媒貴金属にＰｔを適用した実施品２と、従来品との比較例を示す。なお、図４は模擬ガス試験の結果であり、５７秒／３秒の間隔でリーン雰囲気とリッチ雰囲気との切替えをして、ＨＣ−ＳＣＲ触媒３３に還元剤であるＨＣの供給を行った。また、図５は、ディーゼルエンジン１０を用いたベンチ試験の結果であり、５７秒／３秒の間隔でリーン雰囲気とリッチ雰囲気との切替えによりＨＣ−ＳＣＲ触媒３３に還元剤であるＨＣを供給した。 4 to 6, in the exhaust gas purification apparatus 1 for an internal combustion engine according to this embodiment, regarding the NO 2 production rate and the NOx purification rate, the metal oxide carrier of the DOC catalyst 31 is Al 2 O 3 and the catalyst noble metal. A comparative example of the product 1 in which Pt is applied, the product 2 in which CeO 2 is applied to the metal oxide support of the DOC catalyst 31 and Pt is used as the catalyst noble metal, and a conventional product will be shown. FIG. 4 shows the result of the simulated gas test. The HC-SCR catalyst 33 was supplied with HC as a reducing agent by switching between a lean atmosphere and a rich atmosphere at intervals of 57 seconds / 3 seconds. FIG. 5 shows the results of a bench test using the diesel engine 10, and HC as a reducing agent was supplied to the HC-SCR catalyst 33 by switching between a lean atmosphere and a rich atmosphere at intervals of 57 seconds / 3 seconds. .
図４では、触媒入口（排気）温度が１８０℃〜３００℃の広い範囲において、本実施形態に係る実施品１，２のＮＯ2生成率が従来品に対して向上されていることを確認できる。また、図５，６では、本実施形態に係る実施品１，２が従来品に対して高いＮＯｘ浄化率を示していることからも、本発明の効果が分かる。 In FIG. 4, it can be confirmed that the NO 2 production rate of the products 1 and 2 according to the present embodiment is improved over the conventional product in a wide range of the catalyst inlet (exhaust) temperature of 180 ° C. to 300 ° C. . 5 and 6 also show that the effects of the present invention can be seen from the fact that the products 1 and 2 according to this embodiment show a higher NOx purification rate than the conventional products.
なお、本発明は、上述の実施形態に限定されるものではなく、本発明の趣旨を逸脱しない範囲で、適宜変形して実施することが可能である。 In addition, this invention is not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably and can implement.
例えば、上述の実施形態において、排気浄化触媒３０はＤＯＣ触媒３１とＨＣ−ＳＣＲ触媒３３とを別体に備えるものとして説明したが、これらＤＯＣ触媒３１とＨＣ−ＳＣＲ触媒３３とを一体に備えることもできる。この場合も上述の実施形態と同様の作用効果を奏することができる。 For example, in the above-described embodiment, the exhaust purification catalyst 30 has been described as including the DOC catalyst 31 and the HC-SCR catalyst 33 separately. However, the exhaust purification catalyst 30 includes the DOC catalyst 31 and the HC-SCR catalyst 33 integrally. You can also. In this case, the same effects as those of the above-described embodiment can be obtained.
また、ＤＯＣ触媒３１の金属酸化物担体に担持される触媒貴金属として、ＰｔやＰｄ以外にＲｈ（ロジウム）を適用してもよい。この場合も上述の実施形態と同様の作用効果を奏することができる。 In addition to Pt and Pd, Rh (rhodium) may be applied as the catalyst noble metal supported on the metal oxide support of the DOC catalyst 31. In this case, the same effects as those of the above-described embodiment can be obtained.
また、排気管噴射装置３４は、ＤＯＣ触媒３１とＤＰＦ３２との間に設けられるものとして説明したが、ＤＯＣ触媒３１よりも上流側の排気通路１４に設けられてもよい。この場合も上述の実施形態と同様の作用効果を奏することができる。 Further, although the exhaust pipe injection device 34 has been described as being provided between the DOC catalyst 31 and the DPF 32, the exhaust pipe injection device 34 may be provided in the exhaust passage 14 upstream of the DOC catalyst 31. In this case, the same effects as those of the above-described embodiment can be obtained.
１ 排気浄化装置
１０ ディーゼルエンジン（内燃機関）
１４ 排気通路
３０ 排気浄化触媒
３１ ＤＯＣ触媒（排気浄化触媒）
３３ ＨＣ−ＳＣＲ触媒（排気浄化触媒）
３４ 排気管噴射装置（ＨＣ供給手段）
４０ ＥＣＵ（制御手段）
４１ 燃焼制御部（制御手段）
４２ 排気管噴射制御部（ＨＣ供給手段）
1 Exhaust purification device 10 Diesel engine (internal combustion engine)
14 Exhaust passage 30 Exhaust purification catalyst 31 DOC catalyst (Exhaust purification catalyst)
33 HC-SCR catalyst (exhaust gas purification catalyst)
34 Exhaust pipe injection device (HC supply means)
40 ECU (control means)
41 Combustion control unit (control means)
42 Exhaust pipe injection control unit (HC supply means)
Claims (6)
前記排気浄化触媒に還元剤としてのＨＣを供給するＨＣ供給手段と、
前記排気中のＣＯにより前記排気浄化触媒の表面を清浄化してＮＯｘの吸着を促進すべく、前記排気中に含まれるＣＯの量がＮＯｘの量よりも多くなるように前記内燃機関の燃焼を制御する制御手段と、を備える
ことを特徴とする内燃機関の排気浄化装置。 It provided in an exhaust passage of an internal combustion engine, as well as adsorbing NOx in exhaust gas discharged from the internal combustion engine, by oxidizing the adsorbed NOx to generate NO 2, is supplied to NO 2 the generated HC An exhaust purification catalyst that reduces and purifies by
HC supply means for supplying HC as a reducing agent to the exhaust purification catalyst;
The combustion of the internal combustion engine is controlled so that the amount of CO contained in the exhaust is larger than the amount of NOx, in order to clean the surface of the exhaust purification catalyst by CO in the exhaust and promote NOx adsorption. And an exhaust gas purifying device for an internal combustion engine.
前記排気中に含まれるＣＯの量がＮＯｘの量に対して５倍以上となるように制御する
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。 The control means includes
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the amount of CO contained in the exhaust gas is controlled to be five times or more than the amount of NOx.
前記排気中のＮＯｘを吸着するとともに、前記吸着したＮＯｘを酸化してＮＯ2を生成する酸化触媒と、
前記酸化触媒よりも下流側の排気通路に設けられ、前記酸化触媒で生成されたＮＯ2を供給されるＨＣにより還元浄化するＨＣ選択還元型ＮＯｘ触媒と、を含む
ことを特徴とする請求項１又は２記載の内燃機関の排気浄化装置。 The exhaust purification catalyst is
An oxidation catalyst that adsorbs NOx in the exhaust and oxidizes the adsorbed NOx to generate NO 2 ;
An HC selective reduction type NOx catalyst that is provided in an exhaust passage downstream of the oxidation catalyst and that reduces and purifies NO 2 generated by the oxidation catalyst by HC supplied thereto. Or the exhaust gas purification apparatus of the internal combustion engine of 2.
金属酸化物担体として少なくともＡｌ又はＣｅの酸化物を含むとともに、前記金属酸化物担体に担持される触媒貴金属として少なくともＰｔ又はＰｄを含む
ことを特徴とする請求項１〜３のいずれかに記載の内燃機関の排気浄化装置。 The exhaust purification catalyst or the oxidation catalyst is
The metal oxide support contains at least an oxide of Al or Ce, and contains at least Pt or Pd as a catalyst noble metal supported on the metal oxide support. An exhaust purification device for an internal combustion engine.
前記排気中のＣＯにより前記排気浄化触媒の表面を清浄化してＮＯｘの吸着を促進すべく、前記排気中に含まれるＣＯの量がＮＯｘの量よりも多くなるように前記内燃機関の燃焼を制御する
ことを特徴とする内燃機関の排気浄化方法。 The exhaust purification catalyst provided in the exhaust passage of the internal combustion engine adsorbs NOx in the exhaust discharged from the internal combustion engine, oxidizes the adsorbed NOx to generate NO 2, and generates the generated NO 2 In the exhaust gas purification method for reducing and purifying by HC supplied from the HC supply means,
The combustion of the internal combustion engine is controlled so that the amount of CO contained in the exhaust is larger than the amount of NOx, in order to clean the surface of the exhaust purification catalyst by CO in the exhaust and promote NOx adsorption. An exhaust gas purification method for an internal combustion engine.
ことを特徴とする請求項５記載の内燃機関の排気浄化方法。 6. The exhaust gas purification method for an internal combustion engine according to claim 5, wherein the combustion of the internal combustion engine is controlled such that the amount of CO contained in the exhaust gas is five times or more than the amount of NOx.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08246849A (en) * | 1995-03-06 | 1996-09-24 | Hino Motors Ltd | Exhaust purifying device of engine |
| JPH1181992A (en) * | 1997-09-16 | 1999-03-26 | Denso Corp | Exhaust gas purifying device in internal combustion engine |
| JP2000345832A (en) * | 1999-06-04 | 2000-12-12 | Toyota Motor Corp | Exhaust emission control device of internal combustion engine |
| JP2010229895A (en) * | 2009-03-27 | 2010-10-14 | Isuzu Motors Ltd | Exhaust emission control system and method for controlling exhaust emission control system |
| JP2010242584A (en) * | 2009-04-03 | 2010-10-28 | Isuzu Motors Ltd | Exhaust gas purifying system and control method of exhaust gas purifying system |
-
2010
- 2010-12-16 JP JP2010280884A patent/JP5782710B2/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH08246849A (en) * | 1995-03-06 | 1996-09-24 | Hino Motors Ltd | Exhaust purifying device of engine |
| JPH1181992A (en) * | 1997-09-16 | 1999-03-26 | Denso Corp | Exhaust gas purifying device in internal combustion engine |
| JP2000345832A (en) * | 1999-06-04 | 2000-12-12 | Toyota Motor Corp | Exhaust emission control device of internal combustion engine |
| JP2010229895A (en) * | 2009-03-27 | 2010-10-14 | Isuzu Motors Ltd | Exhaust emission control system and method for controlling exhaust emission control system |
| JP2010242584A (en) * | 2009-04-03 | 2010-10-28 | Isuzu Motors Ltd | Exhaust gas purifying system and control method of exhaust gas purifying system |
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