JP2006046198A - Exhaust gas purification system - Google Patents

Exhaust gas purification system Download PDF

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JP2006046198A
JP2006046198A JP2004228846A JP2004228846A JP2006046198A JP 2006046198 A JP2006046198 A JP 2006046198A JP 2004228846 A JP2004228846 A JP 2004228846A JP 2004228846 A JP2004228846 A JP 2004228846A JP 2006046198 A JP2006046198 A JP 2006046198A
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exhaust gas
catalyst
gas purification
hydrogen
deterioration
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Shinko Takatani
真弘 高谷
Hitoshi Onodera
仁 小野寺
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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  • Filtering Of Dispersed Particles In Gases (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas purification system capable of suppressing or preventing the degree of NOx conversion from lowering in a catalyst for exhaust gas purification. <P>SOLUTION: A hydrogen catalyst and a catalyst having at least NOx trapping function for exhaust gas purification are arranged in this order from the upstream side in the exhaust gas flow direction in an exhaust gas duct of an internal combustion engine. The hydrogen catalyst and the catalyst for exhaust gas purification are provided with a degree-of-deterioration determing means for determining the degree of a deterioration in the catalysts respectively. The exhaust gas purification system is provided with a restoration processing means for restoring the function provided on the catalyst in the internal combustion engine and/or in the exhaust gas duct upstream of the hydrogen catalyst. When the degree-of-deterioration determing means of the catalyst for exhaust gas purification determines the catalyst for the exhaust gas purificatin deteriorates, and degree-of-deterioration determing mean of the hydrogen catalyst determines the hydrogen catalyst deteriorates, the restoration processing means carries out the restoration processing of the hydrogen catalyst. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、排気ガス浄化システムに係り、更に詳細には、排気ガス流路の上流側に水素触媒を備え、下流側に少なくともＮＯｘトラップ機能を有する排気ガス浄化用触媒を備え、更にこれらの性能回復機能を有する排気ガス浄化システムに関する。   The present invention relates to an exhaust gas purification system. More specifically, the present invention includes a hydrogen catalyst upstream of an exhaust gas flow path, and an exhaust gas purification catalyst having at least a NOx trap function on the downstream side. The present invention relates to an exhaust gas purification system having a recovery function.

近年、燃費向上の社会的要請から内燃機関としてリーンバーンガソリンエンジンやディーゼルエンジンが用いられている。
このような内燃機関の排気ガス浄化システムとして、内燃機関の排気ガス流路の上流側に水素触媒を備え、下流側にＮＯｘ吸着触媒を備えるものが提案されている（例えば、特許文献１参照。）。 In recent years, lean burn gasoline engines and diesel engines have been used as internal combustion engines due to social demands for improving fuel consumption.
As such an exhaust gas purification system for an internal combustion engine, a system having a hydrogen catalyst on the upstream side of the exhaust gas flow path of the internal combustion engine and a NOx adsorption catalyst on the downstream side has been proposed (for example, see Patent Document 1). ).

ＮＯｘ吸着触媒単独では、排気ガスの空燃比がリーン域のときに排気ガス中のＮＯｘをトラップし、トラップしたＮＯｘを排気ガスの空燃比がストイキないしリッチ域のときに脱離浄化する。
しかし、ＮＯｘ機能（吸着・脱離浄化機能）を発揮するには触媒の活性化（例えば触媒温度が３００℃以上）が条件となるが、上流側に水素触媒を備えると、排気ガス中の還元性ガスにおける水素濃度を高めること、特にＨ２／ＣＯ比を高めることができ、これにより触媒が十分に活性化していない、例えば２００〜２５０℃付近においてもＮＯｘトラップ触媒の脱離浄化性能を発揮させることができるなどＮＯｘ転化率をより向上させることが可能となる。
特開平１１−１６９６７０号公報 The NOx adsorption catalyst alone traps NOx in the exhaust gas when the air-fuel ratio of the exhaust gas is in the lean region, and desorbs and purifies the trapped NOx when the air-fuel ratio of the exhaust gas is in the stoichiometric or rich region.
However, to activate the NOx function (adsorption / desorption purification function), activation of the catalyst (for example, the catalyst temperature is 300 ° C. or higher) is a condition. However, if a hydrogen catalyst is provided upstream, reduction in the exhaust gas is possible. The concentration of hydrogen in the reactive gas can be increased, especially the H 2 / CO ratio can be increased. As a result, the catalyst is not fully activated. Thus, the NOx conversion rate can be further improved.
JP-A-11-169670

しかしながら、このような内燃機関の排気ガス浄化システムは、長時間使用するとＣＯ被毒により水素触媒の性能低下（劣化）により、水素触媒通過後のＨ２／ＣＯ比が小さくなり、ＮＯｘ吸着触媒におけるＮＯｘ転化率が低下（劣化）し始めるという技術知見を得た。
ここで「ＣＯ被毒」とは、例えば白金のような貴金属がＣＯを吸着し、貴金属がＣＯにより表面を覆われて触媒活性が失われるという一般的なものだけでなく、水素触媒中の酸素吸蔵材（例えばセリウム酸化物）と酸化されたＣＯ２とが比較的安定な炭酸塩を形成するようにして水素触媒で進行すると推測されているＣＯシフト反応の活性点（酸素吸蔵材）が覆われて触媒活性が失われるというものも含む。 However, when the exhaust gas purification system of such an internal combustion engine is used for a long time, the H 2 / CO ratio after passing through the hydrogen catalyst becomes small due to the deterioration (degradation) of the hydrogen catalyst due to CO poisoning. The technical knowledge that the NOx conversion rate starts to decrease (deteriorate) was obtained.
Here, “CO poisoning” means not only a general thing in which a noble metal such as platinum adsorbs CO and the surface of the noble metal is covered with CO and the catalytic activity is lost, but also oxygen in the hydrogen catalyst. The active point (oxygen storage material) of the CO shift reaction, which is presumed to proceed with a hydrogen catalyst so that the storage material (eg cerium oxide) and oxidized CO 2 form a relatively stable carbonate, is covered. And the catalyst activity is lost.

本発明は、このような技術知見に鑑みてなされたものであり、その目的とするところは、排気ガス浄化用触媒におけるＮＯｘ転化率の低下を抑制ないし防止し得る排気ガス浄化システムを提供することにある。   The present invention has been made in view of such technical knowledge, and an object of the present invention is to provide an exhaust gas purification system capable of suppressing or preventing a decrease in the NOx conversion rate in an exhaust gas purification catalyst. It is in.

本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、水素触媒の劣化を抑制ないし防止することなどにより、上記目的を達成できることを見出し、本発明を完成するに至った。   As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by suppressing or preventing deterioration of the hydrogen catalyst, and the present invention has been completed.

即ち、本発明の排気ガス浄化システムは、内燃機関の排気ガス流路に、排気ガスの流れ方向に対して上流側から排気ガス中の少なくともＣＯを低減しＨ２を生成する及び／又はＣＯを低減しＨ２を透過する機能を有する水素触媒と、少なくともＮＯｘトラップ機能を有する排気ガス浄化用触媒をこの順に配設し、上記水素触媒及び排気ガス浄化用触媒は、該触媒の劣化度合いを判断する劣化度合い判断手段をそれぞれ備え、更に上記内燃機関に及び／又は水素触媒より上流側の排気ガス流路に、少なくとも該水素触媒の有する機能を回復させる回復処理手段を備える。
そして、備える排気ガス浄化用触媒の劣化度合い判断手段が、該排気ガス浄化用触媒が劣化していると判断し、且つ上記水素触媒の劣化度合い判断手段が、該水素触媒が劣化していると判断したときに、上記回復処理手段が水素触媒の回復処理を実行する。 That is, the exhaust gas purification system of the present invention generates at least CO in the exhaust gas from the upstream side in the exhaust gas flow direction of the internal combustion engine to generate H 2 and / or CO in the exhaust gas flow direction. A hydrogen catalyst having a function of reducing and transmitting H 2 and an exhaust gas purification catalyst having at least a NOx trap function are arranged in this order, and the hydrogen catalyst and the exhaust gas purification catalyst determine the degree of deterioration of the catalyst. And a recovery processing means for recovering at least the function of the hydrogen catalyst in the internal combustion engine and / or in the exhaust gas flow path upstream of the hydrogen catalyst.
The deterioration degree judging means for the exhaust gas purification catalyst provided determines that the exhaust gas purification catalyst is deteriorated, and the deterioration degree judgment means for the hydrogen catalyst is deteriorated. When the determination is made, the recovery processing means executes a recovery process for the hydrogen catalyst.

本発明によれば、水素触媒の劣化を抑制ないし防止することなどとしたため、排気ガス浄化用触媒におけるＮＯｘ転化率の低下を抑制ないし防止し得る排気ガス浄化システムを提供することができる。   According to the present invention, since the deterioration of the hydrogen catalyst is suppressed or prevented, it is possible to provide an exhaust gas purification system that can suppress or prevent a decrease in the NOx conversion rate in the exhaust gas purification catalyst.

以下、本発明の排気ガス浄化システムを図面に基いて説明する。
図１は、本発明の排気ガス浄化システムの一実施形態を示す模式的説明図である。同図に示すように、排気ガス浄化システム１は、内燃機関の１種であるリーンバーンガソリンエンジン４０の排気ガス流路に水素触媒１０と排気ガス浄化用触媒２０を備える。
また、水素触媒１０はその入口近傍に排気ガス空燃比を検出する検出器（Ａ／Ｆセンサ）３０ａを備え、出口近傍にＡ／Ｆセンサ３０ａを備える。一方、排気ガス浄化用触媒２０はその入口近傍に排気ガスのＮＯｘ濃度、排気ガス空燃比及び排気ガス温度を検出する検出器（ＮＯｘセンサ、Ａ／Ｆセンサ及び温度センサを組み合わせたセンサ（以下、３種センサと表記する。））３０ｂを備え、出口近傍に３種センサ３０ｂを備える。
Ａ／Ｆセンサ３０ａと３種センサ３０ｂは図示しないコントロールユニット（Ｃ／Ｕ）５０の一部である車載自己診断装置（Ｏｎ−Ｂｏａｒｄ Ｄｉａｇｎｏｓｉｓ：ＯＢＤ）５２とそれぞれ接続されている。本例の場合、２つのＡ／Ｆセンサ３０ａとＯＢＤ５２が協働して、水素触媒劣化度合い判断手段Ａとして機能し、２つの３種センサ３０ｂとＯＢＤ５２が協働して、排気ガス浄化用触媒劣化度合い判断手段Ｂとして機能する。更に、本例の場合、回復処理手段６０はエンジン４０が兼ねる。 Hereinafter, an exhaust gas purification system of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic explanatory view showing an embodiment of the exhaust gas purification system of the present invention. As shown in FIG. 1, the exhaust gas purification system 1 includes a hydrogen catalyst 10 and an exhaust gas purification catalyst 20 in an exhaust gas flow path of a lean burn gasoline engine 40 which is a kind of internal combustion engine.
Further, the hydrogen catalyst 10 includes a detector (A / F sensor) 30a that detects an exhaust gas air-fuel ratio in the vicinity of the inlet, and an A / F sensor 30a in the vicinity of the outlet. On the other hand, the exhaust gas purification catalyst 20 has a detector (a sensor (hereinafter referred to as a combination of a NOx sensor, an A / F sensor, and a temperature sensor) that detects the NOx concentration of exhaust gas, the exhaust gas air-fuel ratio, and the exhaust gas temperature in the vicinity of the inlet. 3) Sensor 30b is provided, and the type 3 sensor 30b is provided in the vicinity of the outlet.
The A / F sensor 30a and the three-type sensor 30b are connected to an on-board diagnosis (OBD) 52 which is a part of a control unit (C / U) 50 (not shown). In this example, the two A / F sensors 30a and the OBD 52 cooperate to function as the hydrogen catalyst deterioration degree determination means A, and the two three-type sensors 30b and the OBD 52 cooperate to form an exhaust gas purification catalyst. It functions as the deterioration degree judgment means B. Further, in the case of this example, the recovery processing means 60 also serves as the engine 40.

本発明において、排気ガス浄化用触媒２０の入口及び出口近傍に配設される検出器３０ｂは、上述したような排気ガスの少なくとも１つ状態を入口側と出口側で検出できれば、特に限定されるものではなく、ＮＯｘセンサ、Ａ／Ｆセンサ又は温度センサの少なくとも１つで足りるが、３つのセンサを組み合わせて用いると劣化判断をより適切にすることができる。一方、水素触媒の入口及び出口近傍に配設される検出器３０ａは、例えば排気ガス空燃比やＯ２ストレージ量などの排気ガスの少なくとも１つの状態を入口側と出口側で検出できれば、特に限定されるものではなく、Ａ／ＦセンサやＯ２センサなどを用いることができ、上述したように組み合わせて用いてもよい。なお、水素触媒１０の出口側の検出器３０ａと排気ガス浄化用触媒２０の入口側の検出器３０ｂは取り付け位置を適宜調整することなどにより、兼用させることも可能となる。 In the present invention, the detector 30b disposed in the vicinity of the inlet and the outlet of the exhaust gas purification catalyst 20 is particularly limited as long as it can detect at least one state of the exhaust gas as described above on the inlet side and the outlet side. However, at least one of a NOx sensor, an A / F sensor, or a temperature sensor is sufficient. However, when three sensors are used in combination, deterioration judgment can be made more appropriate. On the other hand, the detector 30a disposed in the vicinity of the inlet and outlet of the hydrogen catalyst is particularly limited as long as it can detect at least one state of the exhaust gas such as the exhaust gas air-fuel ratio and the O 2 storage amount on the inlet side and the outlet side. Instead, an A / F sensor, an O 2 sensor, or the like can be used, and may be used in combination as described above. Note that the detector 30a on the outlet side of the hydrogen catalyst 10 and the detector 30b on the inlet side of the exhaust gas purification catalyst 20 can also be used together by appropriately adjusting the mounting position.

エンジン４０から排出される排気ガスは排気ガス流路を矢印の方向に流れ、水素触媒１０と排気ガス浄化触媒２０を通って浄化される。
その際に、水素触媒１０はエンジン４０の詳しくは後述するＮＯｘ脱離浄化制御（リッチスパイク制御）により発生した排気ガス中のＨＣやＨ２、ＣＯなどの還元性ガスのうち、少なくともＣＯを低減しＨ２を生成する機能及びＣＯを低減しＨ２を透過する機能の一方又は双方を有し、水素触媒１０を通過前より通過後の排気ガスのＨ２／ＣＯ比を高めるものであり、例えば、ＨＣとＣＯからＨ２を生成する触媒、より具体的にはＰｔ、Ｐｄ又はＲｈ及びこれらの任意の混合物に係る貴金属を含有する貴金属触媒や、ＣＯ・ＨＣ選択酸化触媒、より具体的にはジルコニウム酸化物を含有する触媒、好ましくはＲｈを更に併用した触媒、更には、Ｈ２の消費を抑制する触媒、より具体的には固体酸性ジルコニウム酸化物を含有する触媒、好ましくはＰｔを併用した触媒を用いることができる。 Exhaust gas discharged from the engine 40 flows through the exhaust gas passage in the direction of the arrow, and is purified through the hydrogen catalyst 10 and the exhaust gas purification catalyst 20.
At that time, the hydrogen catalyst 10 reduces at least CO among reducing gases such as HC, H 2 , and CO in exhaust gas generated by NOx desorption purification control (rich spike control), which will be described in detail later on the engine 40. One or both of the function of generating H 2 and the function of reducing CO and permeating H 2 , and increasing the H 2 / CO ratio of the exhaust gas after passing through the hydrogen catalyst 10 before passing through, For example, a catalyst that generates H 2 from HC and CO, more specifically, a noble metal catalyst containing a noble metal related to Pt, Pd or Rh and any mixture thereof, a CO / HC selective oxidation catalyst, and more specifically, catalyst containing zirconium oxide, the catalyst preferably further combined in the catalyst Rh, further, suppresses the consumption of H 2 catalyst, which more specifically contains solid acidic zirconium oxide, Mashiku can be used a catalyst in combination of Pt.

排気ガス浄化用触媒２０は排気ガスのうち少なくともＮＯｘをトラップする機能を有し、上述したようなＨ２／ＣＯ比が高められた還元性ガスなどが到達し、排気ガス浄化触媒２０の周りの雰囲気がストイキないしリッチ域となると、トラップしていたＮＯｘをより効率良く脱離浄化するものであり、例えば、Ｐｔ、Ｐｄ又はＲｈ及びこれらの任意の混合物とアルカリ土類金属の一例であるバリウムとセリアを含む触媒を用いることができる。また、排気ガス浄化用触媒はＨＣトラップ機能を更に有していてもよい。例えば、Ｐｔ−Ｐｄ−Ｒｈを含む触媒で担体にアルミナとβゼオライトとを用い、βゼオライトと貴金属担持アルミナとを積層した触媒を用いることができる。 The exhaust gas purification catalyst 20 has a function of trapping at least NOx in the exhaust gas, and reaches the reducing gas having an increased H 2 / CO ratio as described above, and the surroundings of the exhaust gas purification catalyst 20 When the atmosphere becomes a stoichiometric or rich region, the trapped NOx is more efficiently desorbed and purified. For example, Pt, Pd or Rh and any mixture thereof and barium, which is an example of an alkaline earth metal, A catalyst containing ceria can be used. Further, the exhaust gas purification catalyst may further have an HC trap function. For example, a catalyst containing Pt—Pd—Rh using alumina and β zeolite as a carrier and laminating β zeolite and noble metal-supported alumina can be used.

ここで、ＮＯｘ脱離浄化制御について説明する。
図２は、排気ガス浄化用触媒２０のＮＯｘトラップ量推定を含むＮＯｘ脱離浄化制御のフローチャートである。
Ｓ１では、運転条件（エンジン回転数、負荷、空燃比等）より、エンジン４０からの単位時間当たりのＮＯｘ排出量を（ＤＮＯｘ）を算出（予測）する。
Ｓ２では、次式（１）のように、単位時間当たりのＮＯｘ排出量（ＤＮＯｘ）に所定のトラップ率（ＫＴ）を乗じた値を積算することで、ＮＯｘトラップ量（ＴＮＯｘ）を算出・更新する。
ＴＮＯｘ＝ＴＮＯｘ’＋ＤＮＯｘ×ＫＴ…（１）
このＮＯｘトラップ量（ＴＮＯｘ）は、エンジン停止後もＣ／Ｕ５０に内蔵の記憶内容を保持できるメモリに記憶する。なお、式（１）中のＴＮＯｘ’はメモリに記憶されたＮＯｘトラップ量の初期値（リセットされている場合にはゼロである。）である。また、トラップ率（ＫＴ）は触媒種、更には内燃機関種や搭載される車種などによって、適宜設定されるものである。
ＮＯｘトラップ量の推定は、これに限定されるものではなく、走行距離を積算したり、リーン雰囲気に置かれた時間を積算したりして得られた積算値に基いて行ってもよい。 Here, the NOx desorption purification control will be described.
FIG. 2 is a flowchart of NOx desorption purification control including NOx trap amount estimation of the exhaust gas purification catalyst 20.
In S1, the NOx emission amount per unit time from the engine 40 (DNOx) is calculated (predicted) from the operating conditions (engine speed, load, air-fuel ratio, etc.).
In S2, the NOx trap amount (TNOx) is calculated and updated by integrating a value obtained by multiplying the NOx emission amount (DNOx) per unit time by a predetermined trap rate (KT) as shown in the following equation (1). To do.
TNOx = TNOx ′ + DNOx × KT (1)
This NOx trap amount (TNOx) is stored in a memory that can hold the stored content in the C / U 50 even after the engine is stopped. Note that TNOx ′ in equation (1) is the initial value of the NOx trap amount stored in the memory (it is zero when reset). Further, the trap rate (KT) is appropriately set depending on the catalyst type, the internal combustion engine type, the mounted vehicle type, and the like.
The estimation of the NOx trap amount is not limited to this, and may be performed based on an integrated value obtained by integrating the travel distance or integrating the time spent in a lean atmosphere.

Ｓ３では、ＮＯｘトラップ量（ＴＮＯｘ）が所定値以上となって、脱離浄化時期となったか否かを判定する。判定の結果、脱離浄化時期でない場合は、Ｓ１へ戻る。脱離浄化時期となった場合は、Ｓ４へ進む。
Ｓ４では、脱離浄化可能な運転条件（例えば、暖機後で比較的高回転・高負荷条件）か否かを判定する。判定の結果、脱離浄化可能な運転条件でない場合は、Ｓ１へ戻る。脱離浄化可能な運転条件の場合は、Ｓ５へ進む。 In S3, it is determined whether the NOx trap amount (TNOx) is equal to or greater than a predetermined value and the desorption purification time has come. As a result of the determination, if it is not the desorption purification time, the process returns to S1. If it is time to desorb and purify, the process proceeds to S4.
In S4, it is determined whether or not the operating conditions allow desorption purification (for example, relatively high rotation and high load conditions after warm-up). As a result of the determination, if the operation condition is not desorbable, the process returns to S1. If the operating condition allows desorption and purification, the process proceeds to S5.

Ｓ５では、排気ガス浄化触媒２０のＮＯｘ脱離浄化制御として、例えば吸入空気量を減少させることなどにより、排気ガスの空燃比をストイキないしリッチ域にする（リッチスパイク制御）。これにより、排気ガス浄化用触媒２０にトラップされていたＮＯｘが脱離浄化される。例えば、ディーゼルエンジンの場合にはリッチスパイク制御の際に、更に燃料噴射時期の遅角（又はポスト噴射の実行）により、排気ガス温度を上昇させてもよい。   In S5, as the NOx desorption purification control of the exhaust gas purification catalyst 20, the air-fuel ratio of the exhaust gas is set to a stoichiometric or rich region (rich spike control), for example, by reducing the intake air amount. As a result, the NOx trapped in the exhaust gas purification catalyst 20 is desorbed and purified. For example, in the case of a diesel engine, the exhaust gas temperature may be further increased by retarding the fuel injection timing (or performing post injection) during rich spike control.

Ｓ６では、ＮＯｘの脱離浄化に必要な所定時間が経過したか否かを判定する。経過していない場合には、Ｓ５へ戻って、ＮＯｘ脱離浄化制御を続行する。経過した場合は、Ｓ７へ進む。
Ｓ７では、ＮＯｘの脱離浄化が完了したので、Ｓ２での積算値であるＮＯｘトラップ量（ＴＮＯｘ）をリセットしてＳ１へ戻る。 In S6, it is determined whether or not a predetermined time required for NOx desorption purification has elapsed. If not, the process returns to S5 and the NOx desorption purification control is continued. If it has elapsed, the process proceeds to S7.
In S7, NOx desorption purification is completed, so the NOx trap amount (TNOX), which is the integrated value in S2, is reset, and the process returns to S1.

以上のようなＮＯｘ脱離浄化制御（リッチスパイク制御）により排気ガス浄化用触媒２０から通常運転時にトラップしたＮＯｘを脱離浄化させるわけであるが、排気ガス浄化用触媒２０が劣化するのは好ましくないため、通常運転時（走行中）のリッチスパイク制御中に、図３のフローチャートに従って、排気ガス浄化用触媒と水素触媒の劣化診断を行い、水素触媒の回復処理を実行する。   Although NOx trapped during normal operation is desorbed and purified from the exhaust gas purification catalyst 20 by the above NOx desorption purification control (rich spike control), it is preferable that the exhaust gas purification catalyst 20 deteriorates. Therefore, during the rich spike control during normal operation (running), the exhaust gas purifying catalyst and the hydrogen catalyst are diagnosed for deterioration according to the flowchart of FIG. 3, and the recovery process of the hydrogen catalyst is executed.

図３は、回復処理制御のフローチャートである。
Ｓ１１では、排気ガス浄化用触媒の劣化診断を行う。詳しくは後述するが、排気ガス浄化用触媒２０の入口側３種センサ３０ｂのそれぞれの出力に基づいて入口側のＮＯｘ濃度Ｎ１、空燃比ＡＦ１及び排気ガス温度Ｔ１をそれぞれ検出し、排気ガス浄化用触媒２０の出口側３種センサ３０ｂのそれぞれの出力に基づいて出口側のＮＯｘ濃度Ｎ２、空燃比ＡＦ２及び排気ガス温度Ｔ２をそれぞれ検出し、得られたデータ差に基いて行う。
各センサの少なくとも１つ又は全部のデータ差が所定値に達したときは、排気ガス浄化用触媒２０が劣化していると判断する。
更に、水素触媒の劣化診断を行う。詳しくは後述するが、水素触媒１０の入口側Ａ／Ｆセンサ３０ａの出力に基づいて入口側の空燃比ＡＦ１１を検出し、水素触媒１０の出口側Ａ／Ｆセンサ３０ａの出力に基づいて出口側の空燃比ＡＦ１２を検出し、得られたデータ差に基いて行う。
Ａ／Ｆセンサのデータ差が所定値に達したときに、水素触媒１０が劣化していると判断する。双方が劣化していると判断したときはＳ１２に進む。 FIG. 3 is a flowchart of recovery processing control.
In S11, deterioration diagnosis of the exhaust gas purification catalyst is performed. As will be described in detail later, the NOx concentration N1, the air-fuel ratio AF1, and the exhaust gas temperature T1 on the inlet side are detected based on the respective outputs of the inlet side three-type sensor 30b of the exhaust gas purification catalyst 20, and the exhaust gas purification catalyst is used. The NOx concentration N2, the air-fuel ratio AF2, and the exhaust gas temperature T2 on the outlet side are detected based on the outputs of the three types of the outlet side three-type sensors 30b of the catalyst 20, and the detection is performed based on the obtained data difference.
When the data difference of at least one or all of the sensors reaches a predetermined value, it is determined that the exhaust gas purification catalyst 20 has deteriorated.
Furthermore, the deterioration diagnosis of the hydrogen catalyst is performed. As will be described in detail later, the air-fuel ratio AF11 on the inlet side is detected based on the output of the inlet side A / F sensor 30a of the hydrogen catalyst 10, and the outlet side is detected based on the output of the outlet side A / F sensor 30a of the hydrogen catalyst 10. The air-fuel ratio AF12 is detected, and based on the obtained data difference.
When the data difference of the A / F sensor reaches a predetermined value, it is determined that the hydrogen catalyst 10 has deteriorated. When it is determined that both have deteriorated, the process proceeds to S12.

Ｓ１２では、回復処理手段６０を兼ねるエンジン７０を制御して、回復処理を実行する。水素触媒回復処理は代表的には１８０秒間、温度６８０℃、Ａ／Ｆが２０以下の排気ガスをエンジン７０から排出することにより行えばよく、少なくとも水素触媒１０のＣＯ被毒を解除できれば、これに限定されるものではない。
また、水素触媒１０のＣＯ被毒が解除されると、水素触媒１０の上述したような機能が回復し、排気ガス浄化用触媒２０の機能も回復する。
なお、Ｓ１１で排気ガス浄化用触媒２０のみが劣化していると判断したときは、リッチスパイク制御の間隔を一時的に制御してもよい。また、回復処理を実行した際には、ＮＯｘ浄化制御２０のＮＯｘトラップ量の積算値はリセットされる。 In S12, the engine 70 also serving as the recovery processing means 60 is controlled to execute the recovery process. The hydrogen catalyst recovery treatment is typically performed by discharging exhaust gas having a temperature of 680 ° C. and an A / F of 20 or less from the engine 70 for 180 seconds, and at least if the CO poisoning of the hydrogen catalyst 10 can be eliminated. It is not limited to.
Further, when the CO poisoning of the hydrogen catalyst 10 is released, the above-described function of the hydrogen catalyst 10 is restored, and the function of the exhaust gas purification catalyst 20 is also restored.
When it is determined in S11 that only the exhaust gas purification catalyst 20 has deteriorated, the interval of the rich spike control may be temporarily controlled. When the recovery process is executed, the integrated value of the NOx trap amount of the NOx purification control 20 is reset.

本発明において、回復処理手段は、リーンバーンガソリンエンジンやディゼルエンジンなどの内燃機関を利用することが可能であり、またＥＲＧ装置を適宜利用することもできる。回復処理は、得られたデータ差に基いて、Ｃ／Ｕ５０がエンジン４０への吸入空気量制御、ＥＲＧ装置制御、燃料噴射量制御及び燃料噴射時期制御などを行って実行する。   In the present invention, the recovery processing means can use an internal combustion engine such as a lean burn gasoline engine or a diesel engine, and can appropriately use an ERG device. The recovery processing is executed by the C / U 50 performing intake air amount control, ERG device control, fuel injection amount control, fuel injection timing control, and the like to the engine 40 based on the obtained data difference.

ここで、劣化診断について説明する。
図４は、劣化診断を説明するモデル図である。即ち、同図（ａ）〜（ｃ）は排気ガス浄化用触媒２０におけるＮＯｘ濃度、空燃比及び排気ガス温度の傾向を示すものであり、同図（ｄ）は水素触媒１０における空燃比の傾向を示すものである。
同図（ａ）に示すように、排気ガス浄化触媒２０が正常であれば、ＮＯｘが浄化されるので、リッチスパイク中の排気ガス浄化用触媒２０の入口側ＮＯｘ濃度Ｎ１に比べ、出口側ＮＯｘ濃度Ｎ２が十分に低減される結果、（Ｎ１−Ｎ２）が大きくなる。これに対し、排気ガス浄化用触媒２０が劣化すると、ＮＯｘが浄化されなくなるので、入口側ＮＯｘ濃度Ｎ１に対し、出口側ＮＯｘ濃度Ｎ２がやや低下する程度となり、（Ｎ１−Ｎ２）が小さくなる。従って、（Ｎ１−Ｎ２）が所定値以下であるときは、排気ガス浄化用触媒２０の劣化と判断する。ここでの所定値は用いる内燃機関種類や触媒種、更には搭載される車種などによって適宜設定されるものではあるが、例えばＮＯｘ転化率に換算して、各種排気ガス浄化用触媒の最大ＮＯｘ転化率に対して測定されるＮＯｘ転化率の低下率が１０〜２０％を超えた時などに劣化と判断するように設定してもよい。なお、最大ＮＯｘ転化率は予めＯＢＤにメモリ記憶させておくものとし、更には、使用環境をメモリ記憶させ対応する最大ＮＯｘ転化率に適宜設定してもよい。 Here, the deterioration diagnosis will be described.
FIG. 4 is a model diagram for explaining deterioration diagnosis. That is, FIGS. 4A to 4C show the NOx concentration, the air-fuel ratio, and the exhaust gas temperature in the exhaust gas purification catalyst 20, and FIG. Is shown.
As shown in FIG. 5A, if the exhaust gas purification catalyst 20 is normal, NOx is purified, so that the outlet side NOx concentration is higher than the inlet side NOx concentration N1 of the exhaust gas purification catalyst 20 during the rich spike. As a result of sufficiently reducing the concentration N2, (N1-N2) increases. On the other hand, when the exhaust gas purification catalyst 20 is deteriorated, NOx is not purified, so that the outlet side NOx concentration N2 is slightly reduced with respect to the inlet side NOx concentration N1, and (N1-N2) is reduced. Therefore, when (N1-N2) is less than or equal to the predetermined value, it is determined that the exhaust gas purification catalyst 20 has deteriorated. The predetermined value here is appropriately set depending on the type of internal combustion engine used, the type of catalyst, and the type of vehicle to be used. For example, the maximum NOx conversion of various exhaust gas purification catalysts in terms of NOx conversion rate You may set so that it may judge that it falls when the fall rate of the NOx conversion rate measured with respect to a rate exceeds 10 to 20%. Note that the maximum NOx conversion rate is stored in advance in the OBD in memory, and further, the usage environment may be stored in the memory and set to the corresponding maximum NOx conversion rate as appropriate.

同図（ｂ）に示すように、リッチスパイク中の排気ガス浄化用触媒２０の入口側空燃比ＡＦ１は、還元材として供給されるＨＣやＣＯ、Ｈ２によりリッチ側（小）であり、排気ガス浄化用触媒２０が正常であれば、ＮＯｘ脱離浄化の際に還元材が消費され、出口側空燃比ＡＦ２はリーン側（大）となり、（ＡＦ２−ＡＦ１）が大きくなる。これに対し、排気ガス浄化用触媒２０が劣化すると、還元材が消費されなくなるので、入口側空燃比ＡＦ１に対し出口側空燃比ＡＦ２はほとんど変化せず、（ＡＦ２−ＡＦ１）が小さくなる。従って、（ＡＦ２−ＡＦ１）が所定値以下であるときは、排気ガス浄化触媒の劣化と判断する。ここでの所定値は用いる内燃機関種類や触媒種、更には搭載される車種などによって適宜設定されるものではあるが、例えば各種排気ガス浄化用触媒の最大（ＡＦ２−ＡＦ１）に対して測定される（ＡＦ２−ＡＦ１）の変化率が２０％を超えたときなどに劣化と判断するように設定してもよい。なお、最大（ＡＦ２−ＡＦ１）は予めＯＢＤにメモリ記憶させておくものとし、更には、使用環境をメモリ記憶させ対応する最大（ＡＦ２−ＡＦ１）に適宜設定してもよい。 As shown in FIG. (B), the inlet-side air-fuel ratio AF1 of the exhaust gas purifying catalyst 20 in the rich spike, HC and CO are supplied as a reducing material, with H 2 a rich side (small), the exhaust If the gas purification catalyst 20 is normal, the reducing material is consumed during the NOx desorption purification, the outlet side air-fuel ratio AF2 becomes lean (large), and (AF2-AF1) becomes large. On the other hand, when the exhaust gas purification catalyst 20 deteriorates, the reducing material is not consumed, so that the outlet side air-fuel ratio AF2 hardly changes with respect to the inlet side air-fuel ratio AF1, and (AF2-AF1) becomes small. Therefore, when (AF2-AF1) is less than or equal to the predetermined value, it is determined that the exhaust gas purification catalyst has deteriorated. The predetermined value here is set as appropriate depending on the type of internal combustion engine used, the type of catalyst, the type of vehicle mounted, and the like. For example, the predetermined value is measured with respect to the maximum (AF2-AF1) of various exhaust gas purification catalysts. (AF2-AF1) may be set to be judged to be deteriorated when the rate of change exceeds 20%. Note that the maximum (AF2-AF1) is stored in advance in the OBD in memory, and further, the use environment may be stored in the memory and set appropriately to the corresponding maximum (AF2-AF1).

同図（ｃ）に示すように、排気ガス浄化用触媒２０が正常であれば、反応熱により排気ガス温度が上昇するので、入口側排気ガス温度Ｔ１に比べ、出口側排気ガス温度Ｔ２が上昇する結果、（Ｔ２−Ｔ１）が大きくなる。これに対し、排気ガス浄化用触媒２０が劣化すると、反応が起こらなくなるので、入口側排気ガス温度Ｔ１に対し出口側排気ガス温度Ｔ２がやや上昇する程度か逆に低下することになり、（Ｔ２−Ｔ１）は小さくなる。従って、（Ｔ２−Ｔ１）が所定値以下であるときは、排気ガス浄化触媒の劣化と判断する。ここでの所定値は用いる内燃機関種類や触媒種、更には搭載される車種などによって適宜設定されるものではあるが、例えば各種排気ガス浄化用触媒の最大（Ｔ２−Ｔ１）に対して測定される（Ｔ２−Ｔ１）の上昇率が３０％以下となったときなどに劣化と判断するように設定してもよい。もちろん（Ｔ２−Ｔ１）がマイナスとなる場合に劣化と判断するのは言うまでもない。なお、最大（Ｔ２−Ｔ１）は予めＯＢＤにメモリ記憶させておくものとし、更には、使用環境をメモリ記憶させ対応する最大（Ｔ２−Ｔ１）に適宜設定してもよい。   As shown in FIG. 5C, if the exhaust gas purification catalyst 20 is normal, the exhaust gas temperature rises due to reaction heat, so the outlet side exhaust gas temperature T2 rises compared to the inlet side exhaust gas temperature T1. As a result, (T2-T1) increases. On the other hand, when the exhaust gas purification catalyst 20 deteriorates, the reaction does not occur, and therefore, the outlet side exhaust gas temperature T2 slightly increases or decreases with respect to the inlet side exhaust gas temperature T1 (T2 -T1) becomes smaller. Therefore, when (T2-T1) is less than or equal to the predetermined value, it is determined that the exhaust gas purification catalyst has deteriorated. The predetermined value here is set as appropriate depending on the type of internal combustion engine used, the type of catalyst, the type of vehicle mounted, and the like. (T2-T1) may be set to be judged to be deteriorated when the rate of increase becomes 30% or less. Of course, it is needless to say that the deterioration is determined when (T2−T1) is negative. Note that the maximum (T2-T1) is stored in advance in the OBD in memory, and further, the usage environment may be stored in the memory and set to the corresponding maximum (T2-T1) as appropriate.

同図（ｄ）に示すように、水素触媒１０が正常であれば、リッチスパイク中の水素触媒１０の入口側空燃比ＡＦ１１は、還元材として供給されるＨＣやＣＯ、Ｈ２によりリッチ側（小）であり、水素触媒１０が正常であれば、排気ガスが通過する際に還元材のうちＨＣやＣＯが特に消費され、出口側空燃比ＡＦ１２はリーン側（大）となり、（ＡＦ１２−ＡＦ１１）が大きくなる。これに対し、水素触媒１０が劣化すると、還元材が消費されなくなるので、入口側空燃比ＡＦ１１に対し出口側空燃比ＡＦ１２はほとんど変化せず、（ＡＦ１２−ＡＦ１１）が小さくなる。従って、（ＡＦ１２−ＡＦ１１）が所定値以下であるときは、水素触媒の劣化と判断する。ここでの所定値は用いる内燃機関種類や触媒種、更には搭載される車種などによって適宜設定されるものではあるが、例えば各種水素触媒の最大（ＡＦ１２−ＡＦ１）に対して測定される（ＡＦ１２−ＡＦ１１）の変化率が２０％を超えたときなどに劣化と判断するように設定してもよい。なお、最大（ＡＦ１２−ＡＦ１１）は予めＯＢＤにメモリ記憶させておくものとし、更には、使用環境をメモリ記憶させ対応する最大（ＡＦ１２−ＡＦ１１）に適宜設定してもよい。 As shown in FIG. 4D, when the hydrogen catalyst 10 is normal, the inlet-side air-fuel ratio AF11 of the hydrogen catalyst 10 during the rich spike is rich (by the HC, CO, and H 2 supplied as the reducing material ( If the hydrogen catalyst 10 is normal and the exhaust gas passes, especially the HC and CO of the reducing material are consumed when the exhaust gas passes, and the outlet side air-fuel ratio AF12 becomes lean (large), and (AF12-AF11). ) Becomes larger. On the other hand, when the hydrogen catalyst 10 deteriorates, the reducing material is not consumed, so the outlet side air-fuel ratio AF12 hardly changes with respect to the inlet side air-fuel ratio AF11, and (AF12-AF11) becomes small. Therefore, when (AF12-AF11) is less than or equal to the predetermined value, it is determined that the hydrogen catalyst has deteriorated. The predetermined value here is set as appropriate depending on the type of internal combustion engine used, the type of catalyst, the type of vehicle mounted, and the like. For example, the predetermined value is measured with respect to the maximum (AF12-AF1) of various hydrogen catalysts (AF12). -AF11) may be set so as to be judged to be deteriorated when the rate of change exceeds 20%. Note that the maximum (AF12-AF11) is stored in advance in the OBD in memory, and further, the use environment may be stored in the memory and the corresponding maximum (AF12-AF11) may be set as appropriate.

また、内燃機関がディーゼルエンジンの場合には、通常ディーゼルパティキュレートフィルタ（ＤＰＦ）が排気ガス浄化用触媒の下流側に配設されており、ＤＰＦはススなどのパティキュレートマター（ＰＭ）を一時的に捕集し、ＰＭがあまり溜まらないうちに、エンジンの制御によって燃焼させて再生処理する。ＤＰＦ再生処理は代表的には１８０秒間、温度７００℃、Ａ／Ｆが２０以下の排気ガスをエンジンから排出することにより行えばよい。このように水素触媒の回復処理とＤＰＦの再生処理はほぼ同じような処理方法なので、同期させて実行することにより、燃費や排気ガス浄化性能をより向上させることができる。
ＤＰＦ再生処理や水素触媒回復処理を実行した際には、ＤＰＦの再生処理の捕集量をリセットでき、上述したようにＮＯｘトラップ量もリセットされる。
なお、ＤＰＦとしては、上述したようにＰＭを捕集できればよいが、具体的には燃焼効率を高めたＤＰＦに触媒を担持させた触媒付きＤＰＦなどを使用することが望ましい。 When the internal combustion engine is a diesel engine, a diesel particulate filter (DPF) is usually disposed on the downstream side of the exhaust gas purifying catalyst, and the DPF temporarily stores particulate matter (PM) such as soot. Before PM accumulates much, it is burned by engine control and regenerated. The DPF regeneration process is typically performed by discharging exhaust gas having a temperature of 700 ° C. and an A / F of 20 or less from the engine for 180 seconds. Thus, since the recovery process of the hydrogen catalyst and the regeneration process of the DPF are almost the same processing method, the fuel consumption and the exhaust gas purification performance can be further improved by executing them in synchronization.
When the DPF regeneration process or the hydrogen catalyst recovery process is executed, the trapping amount of the DPF regeneration process can be reset, and the NOx trap amount is also reset as described above.
The DPF may be any PM as long as PM can be collected as described above. Specifically, it is desirable to use a DPF with a catalyst in which a catalyst is supported on a DPF with improved combustion efficiency.

本発明の排気ガス浄化システムの一実施形態を示すシステム図である。1 is a system diagram showing an embodiment of an exhaust gas purification system of the present invention. 排気ガス浄化用触媒のＮＯｘ脱離浄化制御のフローチャートである。It is a flowchart of NOx desorption purification control of the exhaust gas purification catalyst. 回復処理制御のフローチャートである。It is a flowchart of recovery process control. 劣化診断の説明図である。It is explanatory drawing of a deterioration diagnosis.

符号の説明Explanation of symbols

１ 排気ガス浄化システム
１０ 水素触媒
２０ 排気ガス浄化用触媒
３０ａ，３０ｂ 検出器
４０ エンジン DESCRIPTION OF SYMBOLS 1 Exhaust gas purification system 10 Hydrogen catalyst 20 Exhaust gas purification catalyst 30a, 30b Detector 40 Engine

Claims (4)

内燃機関の排気ガス流路に、排気ガスの流れ方向に対して上流側から排気ガス中の少なくともＣＯを低減しＨ２を生成する及び／又はＣＯを低減しＨ２を透過する機能を有する水素触媒と、少なくともＮＯｘトラップ機能を有する排気ガス浄化用触媒をこの順に配設し、
上記水素触媒及び排ガス浄化用触媒は、該触媒の劣化度合いを判断する劣化度合い判断手段をそれぞれ備え、
上記内燃機関に及び／又は水素触媒より上流側の排気ガス流路に、少なくとも該水素触媒の有する機能を回復させる回復処理手段を備える排気ガス浄化システムであって、
上記排気ガス浄化用触媒の劣化度合い判断手段が、該排気ガス浄化用触媒が劣化していると判断し、且つ上記水素触媒の劣化度合い判断手段が、該水素触媒が劣化していると判断したときに、上記回復処理手段が水素触媒の回復処理を実行することを特徴とする排気ガス浄化システム。 Hydrogen having a function of reducing at least CO in the exhaust gas from the upstream side with respect to the flow direction of the exhaust gas to generate H 2 and / or reducing CO and transmitting H 2 to the exhaust gas flow path of the internal combustion engine A catalyst and an exhaust gas purifying catalyst having at least a NOx trap function are arranged in this order,
The hydrogen catalyst and the exhaust gas purifying catalyst are each provided with a deterioration degree judging means for judging the degree of deterioration of the catalyst,
An exhaust gas purification system comprising recovery processing means for recovering at least the function of the hydrogen catalyst in the internal combustion engine and / or the exhaust gas flow path upstream of the hydrogen catalyst,
The exhaust gas purification catalyst deterioration degree determining means determines that the exhaust gas purification catalyst is deteriorated, and the hydrogen catalyst deterioration degree determination means determines that the hydrogen catalyst is deteriorated. The exhaust gas purification system characterized in that the recovery processing means executes a recovery process of the hydrogen catalyst. 請求項１に記載の排気ガス浄化システムが、上記排気ガス浄化用触媒の下流側にディーゼルパティキュレートフィルタを備え、
上記ディーゼルパティキュレートフィルタの再生処理と上記水素触媒の回復処理を同期させて実行することを特徴とする排気ガス浄化システム。 The exhaust gas purification system according to claim 1, further comprising a diesel particulate filter on the downstream side of the exhaust gas purification catalyst,
An exhaust gas purification system, wherein the regeneration process of the diesel particulate filter and the recovery process of the hydrogen catalyst are executed in synchronization. 上記排気ガス浄化用触媒の劣化度合い判断手段が、該排気ガス浄化用触媒の入口側と出口側のＮＯｘ濃度をそれぞれ検出する検出器、該排気ガス浄化用触媒の入口側と出口側の排気ガス空燃比をそれぞれ検出する検出器、及び該排気ガス浄化用触媒の入口側と出口側の排気ガス温度をそれぞれ検出する検出器から成る群より選ばれた少なくとも１種の検出器を有し、入口側と出口側の各検出器が得るデータ差に基いて劣化度合いを判断するものであることを特徴とする請求項１又は２に記載の排気ガス浄化システム。   The exhaust gas purifying catalyst deterioration degree judging means detects a NOx concentration on the inlet side and the outlet side of the exhaust gas purifying catalyst, and the exhaust gas on the inlet side and outlet side of the exhaust gas purifying catalyst. A detector for detecting the air-fuel ratio, and at least one detector selected from the group consisting of detectors for detecting the exhaust gas temperatures on the inlet side and the outlet side of the exhaust gas purifying catalyst. The exhaust gas purification system according to claim 1 or 2, wherein the degree of deterioration is determined based on a data difference obtained by each of the detectors on the side and the outlet side. 上記水素触媒の劣化度合い判断手段が、該水素触媒の入口側と出口側の排気ガス空燃比をそれぞれ検出する検出器及び／又はＦ−Ｒ Ｏ２センサを有し、入口側と出口側の各検出器が得るデータ差に基いて劣化度合いを判断するものであることを特徴とする請求項１〜３のいずれか１つの項に記載の排気ガス浄化システム。 The hydrogen catalyst deterioration degree judging means has a detector and / or an F-R O 2 sensor for detecting the exhaust gas air-fuel ratio on the inlet side and the outlet side of the hydrogen catalyst, respectively. The exhaust gas purification system according to any one of claims 1 to 3, wherein the degree of deterioration is determined based on a data difference obtained by the detector.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010121630A (en) * 2010-02-01 2010-06-03 Hitachi Ltd Engine system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010121630A (en) * 2010-02-01 2010-06-03 Hitachi Ltd Engine system

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