JP4640344B2 - Exhaust purification device - Google Patents

Exhaust purification device Download PDF

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JP4640344B2
JP4640344B2 JP2007012820A JP2007012820A JP4640344B2 JP 4640344 B2 JP4640344 B2 JP 4640344B2 JP 2007012820 A JP2007012820 A JP 2007012820A JP 2007012820 A JP2007012820 A JP 2007012820A JP 4640344 B2 JP4640344 B2 JP 4640344B2
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discharge
exhaust gas
catalyst
exhaust
reducing agent
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JP2008180109A (en
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宮男 荒川
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Denso Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/0892—Electric or magnetic treatment, e.g. dissociation of noxious components
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • 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
    • Y02T10/40—Engine management systems

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  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
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  • Chemical Kinetics & Catalysis (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Description

本発明は、エンジンからの排ガスを浄化する排気浄化装置に関する。   The present invention relates to an exhaust purification device that purifies exhaust gas from an engine.

従来から、エンジンの排ガス成分である窒素酸化物（ＮＯｘ）を還元剤により還元して浄化する排気浄化装置が公知である。この還元剤は、例えば、尿素や、尿素の分解により発生するアンモニア（ＮＨ３）等であり、ＮＨ３が触媒によりＮＯｘと還元反応して無害な窒素（Ｎ２）や水（Ｈ２Ｏ）を生成することで、ＮＯｘが浄化される。このため、ＮＯｘの浄化を優先して還元剤の添加量を増やすと、未反応の還元剤が排気される虞がある。 2. Description of the Related Art Conventionally, exhaust emission control devices that reduce and purify nitrogen oxide (NOx), which is an exhaust gas component of an engine, with a reducing agent are known. The reducing agent is, for example, urea or ammonia (NH 3 ) generated by the decomposition of urea, and NH 3 is reduced to NOx by a catalyst to cause harmless nitrogen (N 2 ) or water (H 2 O). By generating NOx, NOx is purified. For this reason, when the amount of addition of the reducing agent is increased by giving priority to the purification of NOx, there is a possibility that unreacted reducing agent may be exhausted.

ところで、未反応の還元剤の処理について、還元剤を酸化して処理するため別途に触媒を具備する排気浄化装置が考えられている（例えば、特許文献１参照）。特許文献１に記載の排気浄化装置は、ＮＯｘを還元するための触媒の下流側に還元剤を酸化するための触媒（第２触媒とする）を備え、第２触媒が活性化温度以上のときに未反応の還元剤を第２触媒に導く。   By the way, regarding the treatment of the unreacted reducing agent, an exhaust emission control device that is separately provided with a catalyst to oxidize and treat the reducing agent has been considered (for example, see Patent Document 1). The exhaust emission control device described in Patent Document 1 includes a catalyst (referred to as a second catalyst) for oxidizing a reducing agent on the downstream side of a catalyst for reducing NOx, and when the second catalyst is at an activation temperature or higher. Then, the unreacted reducing agent is led to the second catalyst.

このため、特許文献１に記載の排気浄化装置によれば、エンジンの始動直後のように、排ガスの温度が低く第２触媒が活性化していないときにＮＯｘの浄化を優先すると、未反応の還元剤が排気される虞が極めて高くなる。
特開２００５−１０５９１４号公報 For this reason, according to the exhaust gas purification apparatus described in Patent Document 1, if the priority is given to the purification of NOx when the temperature of the exhaust gas is low and the second catalyst is not activated, just after starting the engine, the unreacted reduction The risk of the agent being exhausted becomes extremely high.
JP 2005-105914 A

本発明は、上記の問題点を解決するためになされたものであり、その目的は、排ガス成分を還元剤により浄化する排気浄化装置において、排ガスの温度によらず未反応の還元剤の処理を可能とすることにある。   The present invention has been made in order to solve the above-described problems, and an object of the present invention is to treat an unreacted reducing agent regardless of the temperature of exhaust gas in an exhaust gas purification apparatus that purifies exhaust gas components with a reducing agent. It is to make it possible.

〔請求項１の手段〕
請求項１に記載の排気浄化装置は、エンジンからの排ガスを浄化するものであり、還元剤による排ガス成分の還元反応を促進する第１触媒装置と、第１触媒装置よりも下流側に配される放電装置とを備える。
これにより、放電装置が放電するとオゾン等の酸化活性物質が発生し、この酸化活性物質により未反応の還元剤が酸化される。このため、排ガスの温度によらず未反応の還元剤を処理することができる。 [Means of Claim 1]
An exhaust emission control device according to claim 1 purifies exhaust gas from an engine, and is arranged on the downstream side of the first catalyst device and a first catalyst device that promotes a reduction reaction of exhaust gas components by a reducing agent. A discharge device.
As a result, when the discharge device is discharged, an oxidizing active substance such as ozone is generated, and the unreacted reducing agent is oxidized by the oxidizing active substance. For this reason, an unreacted reducing agent can be processed irrespective of the temperature of exhaust gas.

また、排気浄化装置は、第１触媒装置よりも下流側に配され、還元剤の酸化反応を促進する第２触媒装置を備える。In addition, the exhaust purification device includes a second catalyst device that is disposed downstream of the first catalyst device and promotes the oxidation reaction of the reducing agent.
これにより、放電装置と第２触媒装置とを併用して未反応の還元剤を処理することができる。このため、放電電力に要するコストと、第２触媒装置の触媒素材（白金等の貴金属）のコストとの兼ね合いにより、請求項１の効果を有する排気浄化装置の仕様を決定できる。Thereby, an unreacted reducing agent can be processed using a discharge device and a 2nd catalyst device together. For this reason, the specification of the exhaust emission control device having the effect of claim 1 can be determined based on the balance between the cost required for the discharge power and the cost of the catalyst material (noble metal such as platinum) of the second catalyst device.

また、排気浄化装置は、排ガスの温度に応じて放電装置による放電を制御する第２放電制御手段を備える。The exhaust emission control device further includes second discharge control means for controlling discharge by the discharge device in accordance with the temperature of the exhaust gas.
これにより、第２触媒装置を備える排気浄化装置において、第２触媒装置の触媒（第２触媒）の活性化状態に応じて、放電装置による放電を行うことができる。このため、例えば、第２触媒が活性化温度未満のときにのみ放電装置に放電させることにより、放電電力に要するコストを低減することができる。Thereby, in the exhaust emission control device provided with the second catalyst device, discharge by the discharge device can be performed according to the activation state of the catalyst (second catalyst) of the second catalyst device. For this reason, for example, the cost required for the discharge power can be reduced by causing the discharge device to discharge only when the second catalyst is lower than the activation temperature.

〔請求項２の手段〕
請求項２に記載の排気浄化装置は、第１触媒装置から流出した還元剤の濃度を検出する還元剤濃度検出手段と、還元剤濃度検出手段から得られる検出値に応じて放電装置による放電を制御する第１放電制御手段とを備える。
これにより、第１触媒装置を未反応で通過した還元剤の量に応じて、放電装置による放電を行うことができる。このため、例えば、還元剤の未反応通過量に対する閾値を設定し、未反応通過量が閾値以上のときにのみ放電装置に放電させることにより、放電電力に要するコストを低減することができる。 [Means of claim 2]
The exhaust emission control device according to claim 2 includes a reducing agent concentration detecting means for detecting the concentration of the reducing agent flowing out from the first catalyst device, and discharging by the discharging device in accordance with a detection value obtained from the reducing agent concentration detecting means. First discharge control means for controlling.
Thereby, discharge by a discharge device can be performed according to the quantity of the reducing agent which passed the 1st catalyst device unreacted. Thus, for example, set the threshold to unreacted passing amount of the reducing agent, by discharging only the discharge device when the unreacted throughput is not less than the threshold value, Ru can be reduced the cost of discharge power.

〔請求項３の手段〕
請求項３に記載の排気浄化装置は、第２触媒装置に流入する排ガスの温度を検出する排ガス温度検出手段を備え、第２放電制御手段は、排ガス温度検出手段から得られる検出値に応じて放電装置による放電を制御する。
これにより、第２触媒装置に流入する排ガスの温度を直接的に検出することができるので、第２触媒の活性化状態を高精度に把握することができる。 [Means of claim 3 ]
The exhaust emission control device according to claim 3 includes exhaust gas temperature detection means for detecting the temperature of the exhaust gas flowing into the second catalyst device, and the second discharge control means is responsive to a detection value obtained from the exhaust gas temperature detection means. Controls the discharge by the discharge device.
Thereby, since the temperature of the exhaust gas flowing into the second catalyst device can be directly detected, the activation state of the second catalyst can be grasped with high accuracy.

〔請求項４の手段〕
請求項４に記載の排気浄化装置によれば、放電装置は、コロナ放電または沿面放電により放電する。
この手段は、放電の形態を示すものである。 [Means of claim 4 ]
According to the exhaust emission control device of the fourth aspect , the discharge device discharges by corona discharge or creeping discharge.
This means shows the form of discharge.

最良の形態１の排気浄化装置は、エンジンからの排ガスを浄化するものであり、還元剤による排ガス成分の還元反応を促進する第１触媒装置と、第１触媒装置よりも下流側に配される放電装置と、第１触媒装置よりも下流側に配され、還元剤の酸化反応を促進する第２触媒装置と、排ガスの温度に応じて放電装置による放電を制御する第２放電制御手段と、第２触媒装置に流入する排ガスの温度を検出する排ガス温度検出手段を備える。そして、第２放電制御手段は、排ガス温度検出手段から得られる検出値に応じて放電装置による放電を制御する。 The exhaust emission control device of the best mode 1 purifies exhaust gas from an engine, and is arranged on the downstream side of the first catalyst device that promotes the reduction reaction of the exhaust gas component by the reducing agent, and the first catalyst device. A discharge device, a second catalyst device arranged downstream of the first catalyst device and promoting the oxidation reaction of the reducing agent, a second discharge control means for controlling discharge by the discharge device according to the temperature of the exhaust gas, An exhaust gas temperature detecting means for detecting the temperature of the exhaust gas flowing into the second catalyst device is provided. And a 2nd discharge control means controls the discharge by a discharge device according to the detected value obtained from an exhaust gas temperature detection means.

〔参考例１の構成〕
参考例１の排気浄化装置１の構成を、図１を用いて説明する。
排気浄化装置１は、エンジン２からの排ガスを浄化するものであり、排ガス成分である窒素酸化物（ＮＯｘ）を還元して浄化する。還元剤は、例えば、尿素や、尿素の分解により発生するアンモニア（ＮＨ３）等であり、ＮＨ３がＮＯｘと還元反応して無害な窒素（Ｎ２）や水（Ｈ２Ｏ）を生成することで、ＮＯｘが浄化される。 [Configuration of Reference Example 1 ]
The configuration of the exhaust emission control device 1 of Reference Example 1 will be described with reference to FIG.
The exhaust emission control device 1 purifies exhaust gas from the engine 2 and reduces and purifies nitrogen oxide (NOx), which is an exhaust gas component. The reducing agent is, for example, urea or ammonia (NH 3 ) generated by decomposition of urea, and NH 3 undergoes a reduction reaction with NOx to generate harmless nitrogen (N 2 ) or water (H 2 O). Thus, NOx is purified.

排気浄化装置１は、ＮＨ３によるＮＯｘの還元反応を促進する第１触媒装置３と、第１触媒装置３よりも下流側に配される放電装置４と、第１触媒装置３から流出したＮＨ３の濃度を検出する還元剤濃度検出手段としてのＮＨ３濃度センサ５と、放電装置４による放電を制御する電子制御装置（ＥＣＵと呼ぶ）６とを備える。 The exhaust purification device 1 includes a first catalyst device 3 that promotes a reduction reaction of NOx by NH 3 , a discharge device 4 that is disposed downstream of the first catalyst device 3, and NH that has flowed out of the first catalyst device 3. and NH 3 concentration sensor 5 as a reducing agent concentration-detecting means for detecting a third concentration, (referred to as ECU) electronic control device for controlling the discharge by the discharge device 4 and a 6.

なお、還元剤は、添加弁９により排ガスが通る排気管１０の内部に、尿素水として、直接、噴射供給される。また、添加弁９は、第１触媒装置３よりも上流側、かつ、プレ触媒装置１１よりも下流側の排気管１０の内部に突出するように装着される。ここで、プレ触媒装置１１とは、主に、排ガス成分の一酸化窒素（ＮＯ）を酸化させて二酸化窒素（ＮＯ２）にする酸化反応を促進するものであり、白金等の貴金属を触媒素材として設けられている。 The reducing agent is directly injected and supplied as urea water into the exhaust pipe 10 through which the exhaust gas passes through the addition valve 9. The addition valve 9 is mounted so as to protrude into the exhaust pipe 10 upstream of the first catalyst device 3 and downstream of the pre-catalyst device 11. Here, the pre-catalyst device 11 mainly promotes an oxidation reaction that oxidizes nitrogen monoxide (NO) of exhaust gas components to form nitrogen dioxide (NO 2 ), and a precious metal such as platinum is used as a catalyst material. It is provided as.

第１触媒装置３は、酸化バナジウム（Ｖ２Ｏ５）等の金属酸化物を触媒素材として設けられ、ＮＨ３によるＮＯｘの還元反応を促進する。つまり、第１触媒装置３は、ＮＯｘを浄化する機能の中核を担うものである。 The first catalyst device 3 is provided with a metal oxide such as vanadium oxide (V 2 O 5 ) as a catalyst material, and promotes a NOx reduction reaction by NH 3 . That is, the first catalytic device 3 plays a central role in the function of purifying NOx.

放電装置４は、コロナ放電または沿面放電により放電し、酸素（Ｏ２）からオゾン（Ｏ３）を生成する。そして、放電により生成されたＯ３が、第１触媒装置３を未反応で通過したＮＨ３と酸化反応し、無害なＨ２Ｏ、Ｎ２およびＯ２を生成する。なお、Ｏ３の生成量は、図２に示すように、特定の臨界電圧を超えると直線的に増加する。このため、放電電圧を可変することで、Ｏ３の生成量を増減してＮＨ３の酸化反応率を操作することができる。 The discharge device 4 is discharged by corona discharge or creeping discharge, and generates ozone (O 3 ) from oxygen (O 2 ). Then, the O 3 produced by discharging, the first catalytic converter 3 to the oxidation reaction with NH 3 passing through unreacted, to produce a harmless H 2 O, N 2 and O 2. As shown in FIG. 2, the amount of O 3 generated increases linearly when a specific critical voltage is exceeded. For this reason, by varying the discharge voltage, the amount of O 3 produced can be increased or decreased to control the oxidation reaction rate of NH 3 .

ＥＣＵ６は、制御機能および演算機能を発揮するＣＰＵ、ＲＯＭおよびＲＡＭ等の記憶装置、入力装置ならびに出力装置等により構成される周知のマイクロコンピュータであり、エンジン２の運転状態に応じて、各種の機器のアクチュエータに指令して機器の駆動制御を行うものである。   The ECU 6 is a well-known microcomputer that includes a CPU, a ROM, a RAM, and other storage devices, an input device, an output device, and the like that perform a control function and an arithmetic function. Various kinds of equipment are used depending on the operating state of the engine 2. The actuator is commanded to control the drive of the equipment.

そして、ＥＣＵ６は、ＮＨ３濃度センサ５から得られる検出値に応じて放電装置４による放電を制御する第１放電制御手段として機能する。すなわち、ＥＣＵ６は、ＮＨ３の濃度に応じて、放電装置４の作動または作動停止や、放電電圧の可変を行う。なお、ＮＨ３濃度センサ５は、第１触媒装置３よりも下流側、かつ、放電装置４よりも上流側の排気管１０に装着されている。このため、ＮＨ３濃度センサ５は、第１触媒装置３を未反応で通過し放電装置４で酸化される前のＮＨ３の濃度を検出する。したがって、ＥＣＵ６は、第１触媒装置３を未反応で通過したＮＨ３の濃度に応じて放電装置４を制御する。 The ECU 6 functions as first discharge control means for controlling the discharge by the discharge device 4 in accordance with the detection value obtained from the NH 3 concentration sensor 5. That is, the ECU 6 operates or stops the discharge device 4 and varies the discharge voltage according to the concentration of NH 3 . The NH 3 concentration sensor 5 is attached to the exhaust pipe 10 on the downstream side of the first catalyst device 3 and on the upstream side of the discharge device 4. Therefore, the NH 3 concentration sensor 5 detects the concentration of NH 3 before passing through the first catalyst device 3 unreacted and before being oxidized by the discharge device 4. Therefore, the ECU 6 controls the discharge device 4 according to the concentration of NH 3 that has passed through the first catalyst device 3 unreacted.

また、排気浄化装置１は、プレ触媒装置１１よりも下流側、かつ添加弁９よりも上流側の排気管１０にＮＯｘの濃度を検出するＮＯｘ濃度センサ１３を備え、ＥＣＵ６は、ＮＯｘ濃度センサ１３から得られる検出値に応じて還元剤の噴射量を求める。そして、ＥＣＵ６は、求めた噴射量の値に基づき添加弁９の作動を制御する。   Further, the exhaust purification device 1 includes a NOx concentration sensor 13 that detects the concentration of NOx in the exhaust pipe 10 downstream of the pre-catalyst device 11 and upstream of the addition valve 9, and the ECU 6 includes the NOx concentration sensor 13. The injection amount of the reducing agent is obtained according to the detection value obtained from the above. Then, the ECU 6 controls the operation of the addition valve 9 based on the obtained injection amount value.

〔参考例１の制御方法〕
参考例１の排気浄化装置１による制御方法を、図３に示すフローチャートを用いて説明する。
まず、ステップＳ１で、ＮＯｘ濃度センサ１３により排ガスのＮＯｘ濃度を検出し、ステップＳ２で、ＮＯｘ濃度の検出値が所定の閾値以上か否かを判断する。そして、ＮＯｘ濃度の検出値が閾値以上であれば（ＹＥＳ）、ステップＳ３に進み、ＮＯｘ濃度の検出値が閾値未満であれば（ＮＯ）、ステップＳ４に進む。 [Control method of Reference Example 1 ]
A control method by the exhaust emission control device 1 of Reference Example 1 will be described with reference to a flowchart shown in FIG.
First, in step S1, the NOx concentration sensor 13 detects the NOx concentration of the exhaust gas, and in step S2, it is determined whether the detected value of the NOx concentration is equal to or greater than a predetermined threshold value. If the detected value of NOx concentration is equal to or greater than the threshold value (YES), the process proceeds to step S3. If the detected value of NOx concentration is less than the threshold value (NO), the process proceeds to step S4.

ステップＳ３では、添加弁９を作動させ、ＮＯｘ濃度の検出値に応じた量の還元剤を噴射し、ステップＳ５に進む。一方、ステップＳ４では、添加弁９の作動を停止（ＯＦＦ）するとともに、放電装置４の作動を停止（ＯＦＦ）し、ステップＳ１に戻る。   In step S3, the addition valve 9 is operated to inject an amount of reducing agent corresponding to the detected value of the NOx concentration, and the process proceeds to step S5. On the other hand, in step S4, the operation of the addition valve 9 is stopped (OFF), the operation of the discharge device 4 is stopped (OFF), and the process returns to step S1.

次に、ステップＳ５で、ＮＨ３濃度センサ５により第１触媒装置３を未反応で通過したＮＨ３濃度を検出し、ステップＳ６で、ＮＨ３濃度の検出値が所定の閾値以上か否かを判断する。そして、ＮＨ３濃度の検出値が閾値以上であれば（ＹＥＳ）、ステップＳ７に進み、ＮＨ３濃度の検出値が閾値未満であれば（ＮＯ）、ステップＳ５に戻る。 Next, at step S5, the NH 3 concentration sensor 5 detects the NH 3 concentration that has passed through the first catalytic device 3 unreacted, and at step S6, whether or not the detected value of the NH 3 concentration is equal to or greater than a predetermined threshold value. to decide. If the detected value of NH 3 concentration is equal to or greater than the threshold value (YES), the process proceeds to step S7, and if the detected value of NH 3 concentration is less than the threshold value (NO), the process returns to step S5.

ステップＳ７では、放電装置４を作動させ、ＮＨ３濃度の検出値に応じた放電電圧で放電する。次に、ステップＳ８で、再度、ＮＨ３濃度センサ５により第１触媒装置３を未反応で通過したＮＨ３濃度を検出し、ステップＳ９で、ＮＨ３濃度の検出値が所定の閾値未満か否かを判断する。そして、ＮＨ３濃度の検出値が閾値未満であれば（ＹＥＳ）、制御フローを終了し、ＮＨ３濃度の検出値が閾値以上であれば（ＮＯ）、ステップＳ１０に進む。
ステップＳ１０では、ＮＨ３濃度の検出値と閾値との差分に応じて放電電圧を上昇しステップＳ８に戻る。 In step S7, the discharge device 4 is operated and discharged at a discharge voltage corresponding to the detected value of the NH 3 concentration. Next, in step S8, again, detecting the NH 3 concentration having passed through the first catalytic converter 3 in unreacted NH 3 concentration sensor 5, in step S9, the detected value of the NH 3 concentration or less than a predetermined threshold value whether Determine whether. If the detected value of NH 3 concentration is less than the threshold value (YES), the control flow is terminated, and if the detected value of NH 3 concentration is equal to or greater than the threshold value (NO), the process proceeds to step S10.
In step S10, the discharge voltage is increased according to the difference between the detected value of the NH 3 concentration and the threshold value, and the process returns to step S8.

〔参考例１の効果〕
参考例１の排気浄化装置１は、ＮＯｘの還元反応を促進する第１触媒装置３と、第１触媒装置３よりも下流側に配される放電装置４とを備える。
これにより、放電装置４が放電するとＯ３等の酸化活性物質が発生し、この酸化活性物質により未反応のＮＨ３が酸化される。このため、排ガスの温度によらず未反応の還元剤を処理することができる。 [Effect of Reference Example 1 ]
The exhaust purification device 1 of Reference Example 1 includes a first catalyst device 3 that promotes a NOx reduction reaction, and a discharge device 4 that is disposed downstream of the first catalyst device 3.
Thus, when the discharge device 4 is discharged, an oxidation active substance such as O 3 is generated, and unreacted NH 3 is oxidized by the oxidation active substance. For this reason, an unreacted reducing agent can be processed irrespective of the temperature of exhaust gas.

また、排気浄化装置１は、第１触媒装置３から流出したＮＨ３の濃度を検出するＮＨ３濃度センサ５を備え、ＥＣＵ６は、ＮＨ３濃度センサ５から得られる検出値に応じて放電装置４による放電を制御する第１放電制御手段としての機能を具備する。
これにより、第１触媒装置３を未反応で通過したＮＨ３の量に応じて、放電装置４による放電を行うことができる。このため、ＮＨ３の未反応通過量に応じて放電装置４の作動または作動停止や、放電電圧の可変を行うことにより、放電電力に要するコストを低減することができる。 In addition, the exhaust purification device 1 includes an NH 3 concentration sensor 5 that detects the concentration of NH 3 flowing out from the first catalyst device 3, and the ECU 6 determines the discharge device 4 according to the detection value obtained from the NH 3 concentration sensor 5. It has a function as the first discharge control means for controlling the discharge due to.
Thereby, discharge by the discharge device 4 can be performed according to the amount of NH 3 that has passed through the first catalyst device 3 unreacted. For this reason, the cost required for the discharge power can be reduced by operating or stopping the discharge device 4 or varying the discharge voltage according to the unreacted passage amount of NH 3 .

〔実施例１の構成〕
実施例１の排気浄化装置１は、第１触媒装置３よりも下流側に配され、ＮＨ３の酸化反応を促進する第２触媒装置１５と、第２触媒装置１５に流入する排ガスの温度を検出する排ガス温度検出手段としての排気温度センサ１６を備え、放電装置４は、第２触媒装置１５よりも下流側に配される。ここで、第２触媒装置１５は、プレ触媒装置１１と同様に白金等の貴金属を触媒素材として設けられ、ＮＨ３を酸化させて無害なＮ２とＨ２Ｏとにする酸化反応を促進するものである。 [Configuration of Example 1 ]
Exhaust gas purification device 1 of Example 1, than the first catalytic converter 3 is disposed on the downstream side, and the second catalytic converter 15 to promote the oxidation reaction of NH 3, the temperature of the exhaust gas flowing into the second catalytic converter 15 An exhaust gas temperature sensor 16 is provided as an exhaust gas temperature detection means to detect, and the discharge device 4 is disposed downstream of the second catalyst device 15. Here, like the pre-catalyst device 11, the second catalyst device 15 is provided with a noble metal such as platinum as a catalyst material, and promotes an oxidation reaction to oxidize NH 3 to harmless N 2 and H 2 O. Is.

また、ＥＣＵ６は、排気温度センサ１６から得られる検出値に応じて放電装置４による放電を制御する第２放電制御手段として機能する。すなわち、ＥＣＵ６は、排ガスの温度に応じて、放電装置４の作動または作動停止や、放電電圧の可変を行う。なお、排気温度センサ１６は、プレ触媒装置１１よりも下流側、かつ、第１触媒装置３よりも上流側の排気管１０に装着され、第１、第２触媒装置３、１５に流入する直前の排ガスの温度を検出する。したがって、ＥＣＵ６は、第１、第２触媒装置３、１５に流入する直前の排ガスの温度に応じて放電装置４を制御する。   Further, the ECU 6 functions as a second discharge control means for controlling the discharge by the discharge device 4 in accordance with the detection value obtained from the exhaust temperature sensor 16. That is, the ECU 6 operates or stops the discharge device 4 and varies the discharge voltage according to the temperature of the exhaust gas. The exhaust temperature sensor 16 is mounted on the exhaust pipe 10 downstream of the pre-catalyst device 11 and upstream of the first catalyst device 3 and immediately before flowing into the first and second catalyst devices 3 and 15. The temperature of the exhaust gas is detected. Therefore, the ECU 6 controls the discharge device 4 according to the temperature of the exhaust gas immediately before flowing into the first and second catalyst devices 3 and 15.

ここで、ＮＨ３の第２触媒装置１５による酸化反応率は、図５に示すように、排ガスの温度が活性化温度を超えると急激に上昇する。一方、放電装置４による酸化反応率は、排ガスの温度によらずほぼ同水準である。よって、第２触媒装置１５および放電装置４によるＮＨ３の全酸化反応率を下げることなく、排ガスの温度に応じて放電装置４の作動または作動停止や、放電電圧の可変を行うことができる。 Here, the oxidation reaction rate of NH 3 by the second catalyst device 15 rapidly increases when the temperature of the exhaust gas exceeds the activation temperature, as shown in FIG. On the other hand, the oxidation reaction rate by the discharge device 4 is almost the same level regardless of the temperature of the exhaust gas. Therefore, the discharge device 4 can be activated or deactivated and the discharge voltage can be varied according to the temperature of the exhaust gas without lowering the total oxidation reaction rate of NH 3 by the second catalyst device 15 and the discharge device 4.

〔実施例１の効果〕
実施例１の排気浄化装置１は、第１触媒装置３よりも下流側に配され、ＮＨ３の酸化反応を促進する第２触媒装置１５を備え、放電装置４は、第２触媒装置１５よりも下流側に配される。
これにより、放電装置４と第２触媒装置１５とを併用して未反応のＮＨ３を処理することができる。このため、放電電力に要するコストと、第２触媒装置１５の触媒素材のコストとの兼ね合いにより排気浄化装置１の仕様を決定できる。 [Effect of Example 1 ]
Exhaust gas purification device 1 of Example 1, than the first catalytic converter 3 is disposed on the downstream side, a second catalytic converter 15 to promote the oxidation reaction of NH 3, the discharge device 4, from the second catalytic converter 15 Is also arranged downstream.
Thereby, the unreacted NH 3 can be treated by using the discharge device 4 and the second catalyst device 15 in combination. For this reason, the specification of the exhaust emission control device 1 can be determined based on the balance between the cost required for the discharge power and the cost of the catalyst material of the second catalyst device 15.

また、ＥＣＵ６は、排ガスの温度に応じて放電装置４による放電を制御する第２放電制御手段として機能する。
これにより、第２触媒装置１５の触媒（第２触媒）の活性化状態に応じて効率的に放電装置４を作動させ放電電圧を可変することができるので、放電電力に要するコストを低減することができる。 Further, the ECU 6 functions as a second discharge control unit that controls discharge by the discharge device 4 in accordance with the temperature of the exhaust gas.
Thereby, since the discharge device 4 can be operated efficiently and the discharge voltage can be varied according to the activation state of the catalyst (second catalyst) of the second catalyst device 15, the cost required for the discharge power can be reduced. Can do.

また、排気浄化装置１は、第１、第２触媒装置３、１５よりも上流側に排気温度センサ１６を装備し、ＥＣＵ６は、排気温度センサ１６から得られる検出値に応じて放電装置４による放電を制御する。
これにより、第２触媒装置１５に流入する排ガスの温度を直接的に検出することができるので、第２触媒の活性化状態を高精度に把握することができる。 Further, the exhaust purification device 1 is equipped with an exhaust temperature sensor 16 on the upstream side of the first and second catalyst devices 3, 15, and the ECU 6 uses the discharge device 4 according to the detected value obtained from the exhaust temperature sensor 16. Control the discharge.
Thereby, since the temperature of the exhaust gas flowing into the second catalyst device 15 can be directly detected, the activated state of the second catalyst can be grasped with high accuracy .

〔参考例２の構成〕
参考例２の排気浄化装置１は、図６に示すように、第１触媒装置３の下流側にＰＭを捕集するＤＰＦ１８を備え、放電装置４は、ＤＰＦ１８の下流側に配される。
これにより、ナノサイズよりも大きいＰＭはＤＰＦ１８で捕集され、ＤＰＦ１８を通過するナノサイズのＰＭは、放電装置４により静電捕集される。このため、ＰＭの排出量を低減することができる。また、ＤＰＦ１８の再生後の所定期間は、ＤＰＦ１８を通過するＰＭの量が増加するが、放電装置４による静電捕集により、ＤＰＦ１８の再生後のＰＭの排出量の増加を抑制することができる。 [Configuration of Reference Example 2 ]
As shown in FIG. 6, the exhaust purification device 1 of Reference Example 2 includes a DPF 18 that collects PM on the downstream side of the first catalyst device 3, and the discharge device 4 is disposed on the downstream side of the DPF 18.
Thereby, PM larger than nano size is collected by DPF 18, and nano size PM which passes DPF 18 is electrostatically collected by discharge device 4. For this reason, the amount of PM emission can be reduced. Further, during the predetermined period after the regeneration of the DPF 18, the amount of PM passing through the DPF 18 increases, but an increase in the amount of PM discharged after the regeneration of the DPF 18 can be suppressed by electrostatic collection by the discharge device 4. .

〔変形例〕
実施例１、参考例２の排気浄化装置１にＮＨ３濃度センサ５を装備し、実施例１、参考例２のＥＣＵ６に第１放電制御手段の機能を具備させてもよい。 [Modification]
Real Example 1, equipped with a NH 3 concentration sensor 5 to the exhaust gas purification device 1 of Reference Example 2, Example 1, may be a function of the first discharge control means ECU6 of Reference Example 2.

また、参考例１の排気浄化装置１に排気温度センサ１６を装備し、参考例１のＥＣＵ６に第２放電制御手段の機能を具備させてもよい。また、参考例２のＥＣＵ６に第２放電制御手段の機能を具備させてもよい。
また、排気温度センサ１６を装備せず、エンジン回転数やアクセル開度の検出値等から排ガスの温度を推測するようにしてもよい。
さらに、参考例１、実施例１の排気浄化装置１にＤＰＦ１８を装備してもよい。 Moreover, the exhaust gas temperature sensor 16 may be provided in the exhaust gas purification apparatus 1 of Reference Example 1 , and the function of the second discharge control means may be provided in the ECU 6 of Reference Example 1 . Further, the ECU 6 of Reference Example 2 may be provided with the function of the second discharge control means.
Further, the exhaust gas temperature sensor 16 may not be provided, and the exhaust gas temperature may be estimated from the detected value of the engine speed, the accelerator opening, or the like.
Further, the DPF 18 may be provided in the exhaust purification device 1 of Reference Example 1 and Example 1 .

排気浄化装置の構成図である（参考例１）。It is a block diagram of an exhaust emission control device ( Reference Example 1). 放電装置における放電電圧とオゾン生成量との相関を示す相関図である（参考例１）。It is a correlation diagram which shows the correlation with the discharge voltage and ozone production amount in a discharge device ( reference example 1). 排気浄化装置による制御フローを示すフローチャートである（参考例１）。It is a flowchart which shows the control flow by an exhaust gas purification apparatus ( reference example 1). 排気浄化装置の構成図である（実施例１）。 1 is a configuration diagram of an exhaust purification device (Example 1 ). FIG. 排ガスの温度とアンモニアの酸化反応率との相関を示す相関図である（実施例１）。It is a correlation diagram which shows the correlation with the temperature of waste gas, and the oxidation reaction rate of ammonia (Example 1 ). 排気浄化装置の構成図である（参考例２）。It is a block diagram of an exhaust emission control device ( Reference Example 2 ).

１ 排気浄化装置
２ エンジン
３ 第１触媒装置
４ 放電装置
５ ＮＨ３濃度センサ（還元剤濃度検出手段）
６ ＥＣＵ（第１、第２放電制御手段）
１５ 第２触媒装置
１６ 排気温度センサ（排ガス温度検出手段） 1 exhaust gas purification device 2 engine 3 first catalyst device 4 and discharge device 5 NH 3 concentration sensor (reducing agent concentration-detecting means)
6 ECU (first and second discharge control means)
15 Second catalyst device 16 Exhaust temperature sensor (exhaust gas temperature detecting means)

Claims (4)

エンジンからの排ガスを浄化する排気浄化装置において、
還元剤による排ガス成分の還元反応を促進する第１触媒装置と、
この第１触媒装置よりも下流側に配される放電装置と、
前記第１触媒装置よりも下流側に配され、還元剤の酸化反応を促進する第２触媒装置と、
排ガスの温度に応じて前記放電装置による放電を制御する第２放電制御手段とを備える排気浄化装置。 In an exhaust purification device that purifies exhaust gas from an engine,
A first catalyst device for promoting a reduction reaction of exhaust gas components by a reducing agent;
A discharge device disposed downstream of the first catalyst device ;
A second catalyst device disposed downstream of the first catalyst device and promoting an oxidation reaction of the reducing agent;
An exhaust emission control device comprising: second discharge control means for controlling discharge by the discharge device according to the temperature of the exhaust gas . 請求項１に記載の排気浄化装置において、
前記第１触媒装置から流出した還元剤の濃度を検出する還元剤濃度検出手段と、
この還元剤濃度検出手段から得られる検出値に応じて前記放電装置による放電を制御する第１放電制御手段とを備える排気浄化装置。 The exhaust emission control device according to claim 1,
Reducing agent concentration detecting means for detecting the concentration of the reducing agent flowing out of the first catalyst device;
An exhaust emission control device comprising: first discharge control means for controlling discharge by the discharge device in accordance with a detection value obtained from the reducing agent concentration detection means. 請求項１または２に記載の排気浄化装置において、
前記第２触媒装置に流入する排ガスの温度を検出する排ガス温度検出手段を備え、
前記第２放電制御手段は、前記排ガス温度検出手段から得られる検出値に応じて前記放電装置による放電を制御することを特徴とする排気浄化装置。 The exhaust emission control device according to claim 1 or 2,
An exhaust gas temperature detecting means for detecting the temperature of the exhaust gas flowing into the second catalyst device;
The exhaust gas purification apparatus, wherein the second discharge control means controls discharge by the discharge apparatus according to a detection value obtained from the exhaust gas temperature detection means . 請求項１ないし請求項３のいずれか１つに記載の排気浄化装置において、
前記放電装置は、コロナ放電または沿面放電により放電することを特徴とする排気浄化装置。 The exhaust emission control device according to any one of claims 1 to 3 ,
The exhaust gas purifier discharges by corona discharge or creeping discharge .
JP2007012820A 2007-01-23 2007-01-23 Exhaust purification device Expired - Fee Related JP4640344B2 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000126543A (en) * 1998-10-29 2000-05-09 Nissin Electric Co Ltd Discharge gas treatment apparatus
JP2001170441A (en) * 1999-12-15 2001-06-26 Sachiko Okazaki Malodorous component removing method
JP2005105914A (en) * 2003-09-30 2005-04-21 Nissan Diesel Motor Co Ltd Engine exhaust emission control device
JP2006329105A (en) * 2005-05-27 2006-12-07 Toyota Motor Corp Exhaust emission control device of internal combustion engine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000126543A (en) * 1998-10-29 2000-05-09 Nissin Electric Co Ltd Discharge gas treatment apparatus
JP2001170441A (en) * 1999-12-15 2001-06-26 Sachiko Okazaki Malodorous component removing method
JP2005105914A (en) * 2003-09-30 2005-04-21 Nissan Diesel Motor Co Ltd Engine exhaust emission control device
JP2006329105A (en) * 2005-05-27 2006-12-07 Toyota Motor Corp Exhaust emission control device of internal combustion engine

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