JP2010209783A - Exhaust emission control device - Google Patents

Exhaust emission control device Download PDF

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JP2010209783A
JP2010209783A JP2009056378A JP2009056378A JP2010209783A JP 2010209783 A JP2010209783 A JP 2010209783A JP 2009056378 A JP2009056378 A JP 2009056378A JP 2009056378 A JP2009056378 A JP 2009056378A JP 2010209783 A JP2010209783 A JP 2010209783A
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exhaust gas
temperature
oxidation catalyst
catalyst
dpf
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Naotaka Koide
直孝 小出
Yoshifumi Kato
祥文 加藤
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Toyota Industries Corp
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Toyota Industries Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device improving a NOx conversion efficiency and a DPF (Diesel Particulate Filter) regeneration efficiency by an SCR (Selective Catalytic Reduction) catalyst regardless of temperature of an oxidation catalyst including platinum. <P>SOLUTION: The oxidation catalyst 3 including platinum, the DPF 5, the SCR catalyst 6, and an oxidation catalyst 7 are provided in an exhaust pipe 2 for allowing exhaust gas discharged from a diesel engine 1 to circulate. An injection nozzle 8 injecting urea water is provided between the DPF 5 and the SCR catalyst 6. The exhaust pipe 2 is provided with a bypass pipe 20 bypassing the oxidation catalyst 3. A cross valve 21 is provided in the connection of the upstream end of the bypass pipe 20 and the exhaust pipe 2. A first temperature sensor 9 and a second temperature sensor 10 for measuring temperature of exhaust gas circulating through the exhaust pipe 2 are respectively provided upstream of the SCR catalyst 6 and cross valve 21. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

この発明は、排気ガス浄化装置に係り、特に、ディーゼルパティキュレートフィルタ（ＤＰＦ）及び尿素ＳＣＲ（Selective Catalytic Reduction）システムの少なくとも一方を有する排気ガス浄化装置に関する。   The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device having at least one of a diesel particulate filter (DPF) and a urea SCR (Selective Catalytic Reduction) system.

尿素ＳＣＲシステムにおいて、窒素酸化物（ＮＯｘ）中の一酸化窒素（ＮＯ)及び二酸化窒素（ＮＯ２）の割合が１：１のときに、ＳＣＲ触媒によるＮＯｘの浄化効率が最大となることが知られている。一般に、排気ガスには、ＮＯ２よりもＮＯの方が多く含まれている。そこで、特許文献１に記載の排気ガス浄化装置では、尿素ＳＣＲシステムの前に、白金を含む酸化触媒が配置されており、排気ガス中のＮＯの一部をＮＯ２に酸化してＮＯ２の割合を増加することによって、排気ガスに含まれるＮＯｘ中のＮＯ及びＮＯ２の割合を１：１に近くなるように調整している。これにより、ＳＣＲ触媒によるＮＯｘの浄化効率が向上する。 In the urea SCR system, it is known that the NOx purification efficiency by the SCR catalyst is maximized when the ratio of nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ) in the nitrogen oxide (NOx) is 1: 1. It has been. In general, exhaust gas contains more NO than NO 2 . Therefore, in the exhaust gas purifying apparatus described in Patent Document 1, before the urea SCR system is arranged oxidation catalyst containing platinum, the NO 2 by oxidizing a portion of NO in the exhaust gas to NO 2 By increasing the ratio, the ratio of NO and NO 2 in NOx contained in the exhaust gas is adjusted to be close to 1: 1. Thereby, the purification efficiency of NOx by the SCR catalyst is improved.

また、ＮＯに比べてＮＯ２は酸化力が大きいため、ＤＰＦを有する排気ガス浄化装置では、ＤＰＦの再生において、排気ガス中に含まれるＮＯｘ中のＮＯ２の割合が大きくなるほど、ＤＰＦに捕捉されたパティキュレートマター（ＰＭ)が燃焼しやすくなるので、ＤＰＦの再生効率が向上する。そのため、従来の排気ガス浄化装置では、ＤＰＦの前に白金を含む酸化触媒を配置することが公知である。 In addition, since NO 2 has a higher oxidizing power than NO, in an exhaust gas purification apparatus having a DPF, as the proportion of NO 2 in NOx contained in the exhaust gas increases in the regeneration of the DPF, it is captured by the DPF. Since the particulate matter (PM) is easily combusted, the regeneration efficiency of the DPF is improved. For this reason, it is known in the conventional exhaust gas purifying apparatus to arrange an oxidation catalyst containing platinum before the DPF.

特開２００６−７０７７１号公報JP 2006-70771 A

しかしながら、白金を含む酸化触媒は、その温度によって挙動が異なる。すなわち、酸化触媒の温度が２００℃未満の場合には、ＮＯをＮＯ２に酸化する作用よりもＮＯ２をＮＯに還元する作用の方が優勢になるので、酸化触媒を通過した排気ガスは、ＮＯの割合が大きくなる。すると、特許文献１に記載の排気ガス浄化装置では、酸化触媒の温度が２００℃未満の場合には、ＮＯの割合が大きくなった排気ガスがＳＣＲ触媒によって浄化されることになるため、ＳＣＲ触媒におけるＮＯｘの浄化効率が低下してしまうといった問題点があった。また、ＤＰＦを有する従来の排気ガス浄化装置でも、白金を含む酸化触媒の温度が２００℃未満の場合には、ＮＯの割合が大きくなった排気ガスがＤＰＦに流入するため、ＤＰＦの再生効率は低下するといった問題点があった。 However, the oxidation catalyst containing platinum behaves differently depending on its temperature. That is, when the temperature of the oxidation catalyst is less than 200 ° C., the action of reducing NO 2 to NO is more dominant than the action of oxidizing NO to NO 2 . The proportion of NO increases. Then, in the exhaust gas purification apparatus described in Patent Document 1, when the temperature of the oxidation catalyst is less than 200 ° C., the exhaust gas having a large NO ratio is purified by the SCR catalyst. There has been a problem that the purification efficiency of NOx is reduced. Further, even in a conventional exhaust gas purifying apparatus having a DPF, when the temperature of the oxidation catalyst containing platinum is less than 200 ° C., the exhaust gas having a larger NO ratio flows into the DPF. There was a problem that it decreased.

この発明はこのような問題点を解決するためになされたもので、白金を含む酸化触媒の温度にかかわらず、ＳＣＲ触媒によるＮＯｘの浄化効率及びＤＰＦの再生効率を向上できる排気ガス浄化装置を提供することを目的とする。   The present invention has been made to solve such problems, and provides an exhaust gas purification device capable of improving the NOx purification efficiency and the DPF regeneration efficiency by the SCR catalyst regardless of the temperature of the oxidation catalyst containing platinum. The purpose is to do.

この発明に係る排気ガス浄化装置は、内燃機関から排出された排気ガスが流通する排気管と、該排気管に設けられた、白金を含む酸化触媒と、該酸化触媒よりも下流において前記排気管に設けられた、ＳＣＲ触媒及びＤＰＦの少なくとも一方と、前記酸化触媒をバイパスするバイパス管と、前記排気ガスを前記バイパス管及び前記酸化触媒のうちの一方に流通させるように切り替える切替手段とを備え、前記酸化触媒の温度が２００℃よりも高い場合には、前記切替手段は、前記排気ガスを前記酸化触媒に流通させ、前記酸化触媒の温度が２００℃以下の場合には、前記切替手段は、前記排気ガスを前記バイパス管に流通させる。酸化触媒の温度が２００℃より高いとき、すなわち酸化触媒がＮＯをＮＯ２に酸化する作用を発揮するときにのみ、排気ガスが酸化触媒を流通するので、排気ガス中のＮＯの割合を増加することなく、あるいは、排気ガス中のＮＯ２の割合を増加させて、排気ガスがＤＰＦ及びＳＣＲ触媒に流入する。
前記排気管には、前記酸化触媒よりも下流においてＳＣＲ触媒が設けられ、該ＳＣＲ触媒の温度が４５０℃以上の場合には、前記切替手段は、前記排気ガスを前記バイパス管に流通させてもよい。
前記排気管には、前記ＳＣＲ触媒の上流に、排気ガスの温度を測定する第１の温度センサが設けられ、前記ＳＣＲ触媒の温度は、前記第１の温度センサによって測定された温度であってもよい。
前記排気管には、前記切替手段の上流に、排気ガスの温度を測定する第２の温度センサが設けられ、前記酸化触媒の温度は、前記第２の温度センサによって測定された温度であってもよい。
前記内燃機関の運転条件と前記排気ガスの温度との関係を表すマップを備え、前記排気ガスの温度は、前記マップに基づいて前記運転条件から推定され、前記酸化触媒の温度及び前記ＳＣＲ触媒の温度はそれぞれ、前記運転条件から推定された排気ガスの温度からさらに推定してもよい。 An exhaust gas purification apparatus according to the present invention includes an exhaust pipe through which exhaust gas discharged from an internal combustion engine flows, an oxidation catalyst containing platinum provided in the exhaust pipe, and the exhaust pipe downstream of the oxidation catalyst. At least one of the SCR catalyst and the DPF, a bypass pipe for bypassing the oxidation catalyst, and a switching means for switching the exhaust gas to flow to one of the bypass pipe and the oxidation catalyst. When the temperature of the oxidation catalyst is higher than 200 ° C., the switching means causes the exhaust gas to flow through the oxidation catalyst, and when the temperature of the oxidation catalyst is 200 ° C. or less, the switching means The exhaust gas is circulated through the bypass pipe. Since the exhaust gas flows through the oxidation catalyst only when the temperature of the oxidation catalyst is higher than 200 ° C., that is, when the oxidation catalyst exhibits the action of oxidizing NO to NO 2 , the proportion of NO in the exhaust gas is increased. Without increasing the ratio of NO 2 in the exhaust gas, the exhaust gas flows into the DPF and SCR catalyst.
The exhaust pipe is provided with an SCR catalyst downstream from the oxidation catalyst, and when the temperature of the SCR catalyst is 450 ° C. or higher, the switching means may cause the exhaust gas to flow through the bypass pipe. Good.
The exhaust pipe is provided with a first temperature sensor for measuring the temperature of the exhaust gas upstream of the SCR catalyst, and the temperature of the SCR catalyst is a temperature measured by the first temperature sensor. Also good.
The exhaust pipe is provided with a second temperature sensor for measuring the temperature of the exhaust gas upstream of the switching means, and the temperature of the oxidation catalyst is a temperature measured by the second temperature sensor. Also good.
A map representing the relationship between the operating condition of the internal combustion engine and the temperature of the exhaust gas, the temperature of the exhaust gas being estimated from the operating condition based on the map, the temperature of the oxidation catalyst and the temperature of the SCR catalyst Each temperature may be further estimated from the temperature of the exhaust gas estimated from the operating conditions.

この発明によれば、白金を含む酸化触媒がＮＯをＮＯ２に酸化する作用を発揮するときにのみ、排気ガスが酸化触媒を流通し、排気ガス中のＮＯの割合を増加することなく、あるいは、排気ガス中のＮＯ２の割合を増加させて、ＤＰＦ及びＳＣＲ触媒に流入するので、酸化触媒の温度にかかわらず、ＳＣＲ触媒によるＮＯｘの浄化効率及びＤＰＦの再生効率を向上させることができる。 According to the present invention, the exhaust gas flows through the oxidation catalyst only when the oxidation catalyst containing platinum exhibits the action of oxidizing NO to NO 2 , without increasing the proportion of NO in the exhaust gas, or Since the ratio of NO 2 in the exhaust gas is increased and flows into the DPF and the SCR catalyst, the NOx purification efficiency and the DPF regeneration efficiency by the SCR catalyst can be improved regardless of the temperature of the oxidation catalyst.

この発明の実施の形態に係る排気ガス浄化装置の構成を示す模式図である。It is a mimetic diagram showing composition of an exhaust-gas purification device concerning an embodiment of this invention.

以下、この発明の実施の形態を添付図面に基づいて説明する。
この実施の形態に係る排気ガス浄化装置の構成を図１に示す。内燃機関であるディーゼルエンジン１は、ディーゼルエンジン１から排出された排気ガスが流通する排気管２を有している。排気管２には、白金を含む酸化触媒３と、ＤＰＦ５と、ＳＣＲ触媒６と、酸化触媒７とが、この順序で設けられている。ＤＰＦ５とＳＣＲ触媒６との間には、尿素水を噴射する噴射ノズル８が設けられている。また、排気管２には、酸化触媒３をバイパスするように、バイパス管２０が設けられている。バイパス管２０の上流端部と排気管２との接続部分には、切替手段である三方弁２１が設けられている。 Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows the configuration of the exhaust gas purifying apparatus according to this embodiment. A diesel engine 1 that is an internal combustion engine has an exhaust pipe 2 through which exhaust gas discharged from the diesel engine 1 flows. The exhaust pipe 2 is provided with an oxidation catalyst 3 containing platinum, a DPF 5, an SCR catalyst 6, and an oxidation catalyst 7 in this order. An injection nozzle 8 for injecting urea water is provided between the DPF 5 and the SCR catalyst 6. The exhaust pipe 2 is provided with a bypass pipe 20 so as to bypass the oxidation catalyst 3. A three-way valve 21 serving as switching means is provided at a connection portion between the upstream end of the bypass pipe 20 and the exhaust pipe 2.

ＳＣＲ触媒６及び三方弁２１のそれぞれの上流には、排気管２を流通する排気ガスの温度を測定するための第１の温度センサ９及び第２の温度センサ１０が設けられている。第１の温度センサ９及び第２の温度センサ１０はそれぞれ、ＳＣＲ触媒６及び酸化触媒３に流入する排気ガスの温度を測定するためのものであり、これらの測定値は、この実施の形態において、ＳＣＲ触媒６及び酸化触媒３の温度と見なされる。従って、第１の温度センサ９は、ＳＣＲ触媒６の直前に設けることが好ましく、第２の温度センサ１０と、三方弁２１と、酸化触媒３とは、できる限り近接して設けることが好ましい。三方弁２１と、第１の温度センサ９と、第２の温度センサ１０とはそれぞれ、制御装置であるＥＣＵ１１に電気的に接続されている。   A first temperature sensor 9 and a second temperature sensor 10 for measuring the temperature of the exhaust gas flowing through the exhaust pipe 2 are provided upstream of the SCR catalyst 6 and the three-way valve 21. The first temperature sensor 9 and the second temperature sensor 10 are for measuring the temperature of the exhaust gas flowing into the SCR catalyst 6 and the oxidation catalyst 3, respectively, and these measured values are used in this embodiment. , The temperature of the SCR catalyst 6 and the oxidation catalyst 3 is considered. Therefore, the first temperature sensor 9 is preferably provided immediately before the SCR catalyst 6, and the second temperature sensor 10, the three-way valve 21, and the oxidation catalyst 3 are preferably provided as close as possible. The three-way valve 21, the first temperature sensor 9, and the second temperature sensor 10 are each electrically connected to the ECU 11 that is a control device.

次に、この実施の形態に係る排気ガス浄化装置の動作について説明する。
ディーゼルエンジン１の始動後、排出された排気ガスは、排気管２を流通する。第２の温度センサ１０の測定値が２００℃以下の場合には、ＥＣＵ１１は、三方弁２１を作動させて、排気ガスがバイパス管２０を流通するようにする。酸化触媒３の温度が２００℃以下の場合に排気ガスを酸化触媒３に流通させると、排気ガス中のＮＯｘは、酸化触媒３の還元作用によってＮＯ２の一部がＮＯに還元され、排ガスに含まれるＮＯｘ中のＮＯの割合が増加し、ＮＯ及びＮＯ２の割合が１：１から離れるように変化してしまう。しかしながら、この実施の形態では、このような条件の場合に、排気ガスがバイパス管２０を流通して酸化触媒３をバイパスするので、ＮＯｘ中のＮＯの割合が増加してしまうのを防止できる。 Next, the operation of the exhaust gas purification apparatus according to this embodiment will be described.
After the diesel engine 1 is started, the exhaust gas discharged flows through the exhaust pipe 2. When the measured value of the second temperature sensor 10 is 200 ° C. or less, the ECU 11 operates the three-way valve 21 so that the exhaust gas flows through the bypass pipe 20. If the exhaust gas is allowed to flow through the oxidation catalyst 3 when the temperature of the oxidation catalyst 3 is 200 ° C. or lower, a part of NO 2 is reduced to NO by the reduction action of the oxidation catalyst 3 and the exhaust gas is converted into exhaust gas. The ratio of NO in the contained NOx increases, and the ratio of NO and NO 2 changes so as to depart from 1: 1. However, in this embodiment, under such conditions, the exhaust gas flows through the bypass pipe 20 and bypasses the oxidation catalyst 3, so that it is possible to prevent the ratio of NO in NOx from increasing.

ディーゼルエンジン１が始動してからある程度経過すると、排気ガスの温度が上昇し、やがて、第２の温度センサ１０の測定値が２００℃を超える温度になる。すると、ＥＣＵ１１は、三方弁２１を作動させて、排気ガスが酸化触媒３を流通するようにする。酸化触媒３の温度が２００℃よりも高い場合に排気ガスを酸化触媒３に流通させると、排気ガス中のＮＯｘは、酸化触媒３の酸化作用によってＮＯの一部がＮＯ２に酸化される。ディーゼルエンジン１から排出された排気ガス中に含まれるＮＯｘの大部分がＮＯであるため、酸化触媒３の酸化作用により、ＮＯｘ中のＮＯ２の割合が上昇し、ＮＯ及びＮＯ２の割合が１：１に近づくように変化する。 When a certain amount of time has passed since the diesel engine 1 started, the temperature of the exhaust gas rises, and eventually the measured value of the second temperature sensor 10 exceeds 200 ° C. Then, the ECU 11 operates the three-way valve 21 so that the exhaust gas flows through the oxidation catalyst 3. If the exhaust gas is allowed to flow through the oxidation catalyst 3 when the temperature of the oxidation catalyst 3 is higher than 200 ° C., a part of the NOx in the exhaust gas is oxidized to NO 2 by the oxidation action of the oxidation catalyst 3. Since most of the NOx contained in exhaust gas discharged from the diesel engine 1 is NO, the oxidizing action of the oxidation catalyst 3, the proportion of NO 2 in NOx is increased, the ratio of NO and NO 2 is 1 : 1.

バイパス管２０を流通した排気ガス、あるいは、酸化触媒３を流通した排気ガスは、ＤＰＦ５に流入し、排気ガス中のＰＭがＤＰＦ５に捕捉される。続いて、排気ガスはＳＣＲ触媒６に流入するが、適当なタイミングで噴射ノズル８から供給された尿素水がＳＣＲ触媒６において加水分解されてアンモニアと二酸化炭素となり、生成したアンモニアと排ガス中のＮＯｘとが反応して、窒素及び水となる。ＳＣＲ触媒６において消費されずに残ったアンモニアは、酸化触媒７において酸化され、ＮＯｘが浄化された排気ガスが大気中へ排出される。   The exhaust gas flowing through the bypass pipe 20 or the exhaust gas flowing through the oxidation catalyst 3 flows into the DPF 5, and PM in the exhaust gas is captured by the DPF 5. Subsequently, the exhaust gas flows into the SCR catalyst 6, but the urea water supplied from the injection nozzle 8 is hydrolyzed in the SCR catalyst 6 at an appropriate timing to become ammonia and carbon dioxide, and the produced ammonia and NOx in the exhaust gas React with nitrogen and water. Ammonia remaining without being consumed in the SCR catalyst 6 is oxidized in the oxidation catalyst 7, and the exhaust gas from which NOx has been purified is discharged into the atmosphere.

第２の温度センサ１０の測定値が２００℃以下の場合には、排気ガスに含まれるＮＯｘ中のＮＯの割合が上昇しないようにして、すなわち、ＮＯ及びＮＯ２の割合が１：１から離れないようにして、ＳＣＲ触媒６によって排気ガス中のＮＯｘが浄化されるので、ＳＣＲ触媒６によるＮＯｘの浄化効率の低下を防止できる。一方、第２の温度センサ１０の測定値が２００℃より高い場合には、ＮＯｘ中のＮＯ２の割合を上昇させてＮＯ及びＮＯ２の割合が１：１に近づくように調整してから、ＳＣＲ触媒６によって排気ガス中のＮＯｘが浄化されるので、ＳＣＲ触媒６によるＮＯｘの浄化効率を向上させることができる。 When the measured value of the second temperature sensor 10 is 200 ° C. or less, the ratio of NO in NOx contained in the exhaust gas is not increased, that is, the ratio of NO and NO 2 is separated from 1: 1. Since NOx in the exhaust gas is purified by the SCR catalyst 6 in such a manner, it is possible to prevent the NOx purification efficiency from being lowered by the SCR catalyst 6. On the other hand, when the measured value of the second temperature sensor 10 is higher than 200 ° C., the ratio of NO 2 in NOx is increased and adjusted so that the ratio of NO and NO 2 approaches 1: 1. Since NOx in the exhaust gas is purified by the SCR catalyst 6, the NOx purification efficiency by the SCR catalyst 6 can be improved.

さらに、ディーゼルエンジン１の稼働中、第１の温度センサ９の測定値が４５０℃以上になった場合には、たとえ第２の温度センサ１０の測定値が２００℃よりも高い温度であったとしても、ＥＣＵ１１は、三方弁２１を作動させて、排気ガスがバイパス管２０を流通するようにする。すると、排気ガスは酸化触媒３を流通しないので、排気ガス中のＮＯ２の割合が上昇されずに、ＳＣＲ触媒６に排気ガスが流入する。ＳＣＲ触媒６の温度が４５０℃以上であれば、ＮＯ及びＮＯ２の割合にかかわらずに、ＳＣＲ触媒６によるＮＯｘの浄化効率は温度のみに依存するので、ＳＣＲ触媒６によってＮＯｘを浄化する前に、あえて排気ガスを酸化触媒３で処理させる必要はない。これにより、酸化触媒３の作用機会が低減されるので、酸化触媒３の寿命を長くすることができる。 Furthermore, when the measured value of the first temperature sensor 9 is 450 ° C. or higher during operation of the diesel engine 1, it is assumed that the measured value of the second temperature sensor 10 is higher than 200 ° C. In addition, the ECU 11 operates the three-way valve 21 so that the exhaust gas flows through the bypass pipe 20. Then, since the exhaust gas does not flow through the oxidation catalyst 3, the exhaust gas flows into the SCR catalyst 6 without increasing the ratio of NO 2 in the exhaust gas. If the temperature of the SCR catalyst 6 is 450 ° C. or higher, the NOx purification efficiency of the SCR catalyst 6 depends only on the temperature regardless of the ratio of NO and NO 2. It is not necessary to treat the exhaust gas with the oxidation catalyst 3. Thereby, since the opportunity of action of the oxidation catalyst 3 is reduced, the life of the oxidation catalyst 3 can be extended.

また、ＮＯｘ中のＮＯ及びＮＯ２の割合は、ＳＣＲ触媒６によるＮＯｘの浄化効率だけではなく、ＤＰＦ５の再生効率にも影響を与える。ＤＰＦ５にＰＭが補足されていくと、ＤＰＦ５の前後の差圧が上昇する。この差圧を、図示しない差圧計等で検知し、ＤＰＦ５に捕捉されたＰＭを燃焼させることにより、ＤＰＦ５の再生を行う。再生の際、ＤＰＦ５に対して、公知の手段により加熱を行うが、排気ガスに含まれる酸化力の強いＮＯ２を酸化剤として利用すると、燃焼に必用な温度を低下させることができ、その結果、ＤＰＦ５の再生効率が向上される。この実施の形態では、第２の温度センサ１０の測定値が２００℃より高い場合、すなわち、酸化触媒３がＮＯをＮＯ２に酸化する作用を発揮可能なときにのみ、排気ガスは酸化触媒３を流通してＤＰＦ５に流入する。これにより、排気ガス中のＮＯ２の割合が低下せずに、あるいは、酸化触媒３によって排気ガス中のＮＯ２の割合が増加されて、排気ガスがＤＰＦ５に流入し、ＤＰＦ５の再生時に必要な温度を抑えることができるので、ＤＰＦ５の再生効率を向上させることができる。 Further, the ratio of NO and NO 2 in NOx affects not only the NOx purification efficiency by the SCR catalyst 6 but also the regeneration efficiency of the DPF 5. When PM is supplemented to the DPF 5, the differential pressure before and after the DPF 5 increases. This differential pressure is detected by a differential pressure gauge or the like (not shown), and PM captured by the DPF 5 is burned to regenerate the DPF 5. At the time of regeneration, the DPF 5 is heated by a known means, but if NO 2 having a strong oxidizing power contained in the exhaust gas is used as an oxidizing agent, the temperature necessary for combustion can be lowered, and as a result The regeneration efficiency of DPF5 is improved. In this embodiment, when the measured value of the second temperature sensor 10 is higher than 200 ° C., that is, only when the oxidation catalyst 3 can exhibit the action of oxidizing NO to NO 2 , the exhaust gas is emitted from the oxidation catalyst 3. And flows into the DPF 5. As a result, the ratio of NO 2 in the exhaust gas does not decrease, or the ratio of NO 2 in the exhaust gas is increased by the oxidation catalyst 3, so that the exhaust gas flows into the DPF 5 and is necessary for regeneration of the DPF 5. Since the temperature can be suppressed, the regeneration efficiency of the DPF 5 can be improved.

このように、白金を含む酸化触媒３がＮＯをＮＯ２に酸化する作用を発揮するときにのみ、排気ガスが酸化触媒３を流通し、排気ガス中のＮＯの割合を増加することなく、あるいは、排気ガス中のＮＯ２の割合を増加させて、ＤＰＦ５及びＳＣＲ触媒６に流入するので、酸化触媒３の温度にかかわらず、ＳＣＲ触媒６によるＮＯｘの浄化効率及びＤＰＦ５の再生効率を向上させることができる。 Thus, only when the oxidation catalyst 3 containing platinum exhibits the action of oxidizing NO to NO 2 , the exhaust gas flows through the oxidation catalyst 3 without increasing the proportion of NO in the exhaust gas, or Since the ratio of NO 2 in the exhaust gas is increased and flows into the DPF 5 and the SCR catalyst 6, the NOx purification efficiency by the SCR catalyst 6 and the regeneration efficiency of the DPF 5 are improved regardless of the temperature of the oxidation catalyst 3. Can do.

この実施の形態では、ＳＣＲ触媒６及び酸化触媒３の上流に第１の温度センサ９及び第２の温度センサ１０をそれぞれ配置し、ＳＣＲ触媒６及び酸化触媒３に流入する直前の排気ガスの温度を検知して、それらの測定値を酸化触媒３及びＳＣＲ触媒６の温度と見なしていたが、この形態に限定するものではない。酸化触媒３及びＳＣＲ触媒６に温度センサを直接配置して、酸化触媒３及びＳＣＲ触媒６の温度を直接測定するようにしてもよい。また、温度センサを用いる形態に限定するものでもなく、ＥＣＵ１１に、ディーゼルエンジン１の運転条件（回転数や燃料噴射量等）と排気ガス温度とのマップを組み込んでおき、このマップに基づいてディーゼルエンジン１の運転条件から排気ガスの温度を推定し、推定された排気ガスの温度からさらに、ディーゼルエンジン１から酸化触媒３及びＳＣＲ触媒６までの長さ等を考慮して、酸化触媒３及びＳＣＲ触媒６の温度を推定するようにしてもよい。   In this embodiment, a first temperature sensor 9 and a second temperature sensor 10 are disposed upstream of the SCR catalyst 6 and the oxidation catalyst 3, respectively, and the temperature of the exhaust gas immediately before flowing into the SCR catalyst 6 and the oxidation catalyst 3. , And the measured values are regarded as the temperatures of the oxidation catalyst 3 and the SCR catalyst 6, but are not limited to this form. A temperature sensor may be directly disposed on the oxidation catalyst 3 and the SCR catalyst 6 to directly measure the temperatures of the oxidation catalyst 3 and the SCR catalyst 6. Further, the present invention is not limited to the form using the temperature sensor, and a map of the operating conditions (the number of revolutions, the fuel injection amount, etc.) of the diesel engine 1 and the exhaust gas temperature is incorporated in the ECU 11, and the diesel engine is based on this map. The exhaust gas temperature is estimated from the operating conditions of the engine 1, and the length from the estimated exhaust gas temperature to the oxidation catalyst 3 and the SCR catalyst 6 is taken into consideration, and the oxidation catalyst 3 and the SCR. The temperature of the catalyst 6 may be estimated.

この実施の形態では、ＤＰＦ５及びＳＣＲ触媒６が両方とも設けられているが、この構成に限定するものではない。ＤＰＦ５のみが設けられている構成でもよく、ＳＣＲ触媒６のみが設けられている構成でもよい。すなわち、少なくともＤＰＦ５及びＳＣＲ触媒６の一方が設けられていればよい。   In this embodiment, both the DPF 5 and the SCR catalyst 6 are provided, but the present invention is not limited to this configuration. Only the DPF 5 may be provided, or only the SCR catalyst 6 may be provided. That is, it is sufficient that at least one of the DPF 5 and the SCR catalyst 6 is provided.

１ ディーゼルエンジン（内燃機関）、２ 排気管、３ 酸化触媒、５ ＤＰＦ、６ ＳＣＲ触媒、９ 第１の温度センサ、１０ 第２の温度センサ、２０ バイパス管、２１ 三方弁（切替手段）。   1 diesel engine (internal combustion engine), 2 exhaust pipe, 3 oxidation catalyst, 5 DPF, 6 SCR catalyst, 9 first temperature sensor, 10 second temperature sensor, 20 bypass pipe, 21 three-way valve (switching means).

Claims (5)

内燃機関から排出された排気ガスが流通する排気管と、
該排気管に設けられた、白金を含む酸化触媒と、
該酸化触媒よりも下流において前記排気管に設けられた、ＳＣＲ触媒及びＤＰＦの少なくとも一方と、
前記酸化触媒をバイパスするバイパス管と、
前記排気ガスを前記バイパス管及び前記酸化触媒のうちの一方に流通させるように切り替える切替手段と
を備え、
前記酸化触媒の温度が２００℃より高い場合には、前記切替手段は、前記排気ガスを前記酸化触媒に流通させ、前記酸化触媒の温度が２００℃以下の場合には、前記切替手段は、前記排気ガスを前記バイパス管に流通させる排気ガス浄化装置。 An exhaust pipe through which exhaust gas discharged from the internal combustion engine flows;
An oxidation catalyst containing platinum provided in the exhaust pipe;
At least one of an SCR catalyst and a DPF provided in the exhaust pipe downstream of the oxidation catalyst;
A bypass pipe for bypassing the oxidation catalyst;
Switching means for switching the exhaust gas to flow to one of the bypass pipe and the oxidation catalyst,
When the temperature of the oxidation catalyst is higher than 200 ° C., the switching means causes the exhaust gas to flow through the oxidation catalyst, and when the temperature of the oxidation catalyst is 200 ° C. or less, the switching means An exhaust gas purifier for circulating exhaust gas through the bypass pipe. 前記排気管には、前記酸化触媒よりも下流において前記ＳＣＲ触媒が設けられ、
該ＳＣＲ触媒の温度が４５０℃以上の場合には、前記切替手段は、前記排気ガスを前記バイパス管に流通させる、請求項１に記載の排気ガス浄化装置。 The exhaust pipe is provided with the SCR catalyst downstream of the oxidation catalyst,
2. The exhaust gas purification device according to claim 1, wherein when the temperature of the SCR catalyst is 450 ° C. or higher, the switching unit causes the exhaust gas to flow through the bypass pipe. 前記排気管には、前記ＳＣＲ触媒の上流に、排気ガスの温度を測定する第１の温度センサが設けられ、
前記ＳＣＲ触媒の温度は、前記第１の温度センサによって測定された温度である、請求項２に記載の排気ガス浄化装置。 The exhaust pipe is provided with a first temperature sensor for measuring the temperature of the exhaust gas upstream of the SCR catalyst,
The exhaust gas purification device according to claim 2, wherein the temperature of the SCR catalyst is a temperature measured by the first temperature sensor. 前記排気管には、前記切替手段の上流に、排気ガスの温度を測定する第２の温度センサが設けられ、
前記酸化触媒の温度は、前記第２の温度センサによって測定された温度である、請求項１〜３のいずれか一項に記載の排気ガス浄化装置。 The exhaust pipe is provided with a second temperature sensor for measuring the temperature of the exhaust gas upstream of the switching means,
The exhaust gas purification device according to any one of claims 1 to 3, wherein the temperature of the oxidation catalyst is a temperature measured by the second temperature sensor. 前記内燃機関の運転条件と前記排気ガスの温度との関係を表すマップを備え、
前記排気ガスの温度は、前記マップに基づいて前記運転条件から推定され、
前記酸化触媒の温度及び前記ＳＣＲ触媒の温度はそれぞれ、前記運転条件から推定された排気ガスの温度からさらに推定される、請求項１または２に記載の排気ガス浄化装置。 Comprising a map representing the relationship between the operating conditions of the internal combustion engine and the temperature of the exhaust gas;
The temperature of the exhaust gas is estimated from the operating conditions based on the map,
The exhaust gas purification device according to claim 1 or 2, wherein the temperature of the oxidation catalyst and the temperature of the SCR catalyst are each further estimated from the temperature of the exhaust gas estimated from the operating conditions.
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WO2012132095A1 (en) * 2011-03-31 2012-10-04 エヌ・イー ケムキャット株式会社 Ammonia oxidation catalyst, exhaust gas purification device using same, and exhaust gas purification method
CN103104323A (en) * 2011-11-15 2013-05-15 通用汽车环球科技运作有限责任公司 Exhaust system for internal combustion engine
WO2013104633A1 (en) 2012-01-09 2013-07-18 Eminox Limited Exhaust system and method for reducing particulate and no2 emissions
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* Cited by examiner, † Cited by third party
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WO2012132095A1 (en) * 2011-03-31 2012-10-04 エヌ・イー ケムキャット株式会社 Ammonia oxidation catalyst, exhaust gas purification device using same, and exhaust gas purification method
JP2012210570A (en) * 2011-03-31 2012-11-01 Ne Chemcat Corp Ammonia oxidation catalyst, exhaust gas purification device using the same, and exhaust gas purification method
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US8865615B2 (en) 2011-03-31 2014-10-21 N.E. Chemcat Corporation Ammonia oxidation catalyst, exhaust gas purification device using same, and exhaust gas purification method
CN103104323A (en) * 2011-11-15 2013-05-15 通用汽车环球科技运作有限责任公司 Exhaust system for internal combustion engine
WO2013104633A1 (en) 2012-01-09 2013-07-18 Eminox Limited Exhaust system and method for reducing particulate and no2 emissions
CN107178410A (en) * 2017-06-14 2017-09-19 北京福田戴姆勒汽车有限公司 The urea playpipe of exhaust treatment system
CN109424403A (en) * 2017-09-05 2019-03-05 曼能源解决方案公司-德国曼能源解决方案欧洲股份公司之分公司 Combustion engine system
CN109424403B (en) * 2017-09-05 2020-03-24 曼能源解决方案公司-德国曼能源解决方案欧洲股份公司之分公司 Combustion engine system
CN113027577A (en) * 2021-04-25 2021-06-25 潍柴动力股份有限公司 Engine exhaust device and engine exhaust method
CN113027577B (en) * 2021-04-25 2022-07-15 潍柴动力股份有限公司 Engine exhaust device and engine exhaust method

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