JP5845906B2 - Exhaust gas recirculation device for internal combustion engine - Google Patents

Exhaust gas recirculation device for internal combustion engine Download PDF

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JP5845906B2
JP5845906B2 JP2012003710A JP2012003710A JP5845906B2 JP 5845906 B2 JP5845906 B2 JP 5845906B2 JP 2012003710 A JP2012003710 A JP 2012003710A JP 2012003710 A JP2012003710 A JP 2012003710A JP 5845906 B2 JP5845906 B2 JP 5845906B2
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星野　真樹
真樹 星野
隆夫 和泉
隆夫 和泉
赤間　弘
弘 赤間
岩切　保憲
保憲 岩切
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Nissan Motor Co Ltd
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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
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  • Exhaust-Gas Circulating Devices (AREA)
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  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
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Description

本発明は、排気の一部を吸気通路に還流する内燃機関の排気還流装置に関し、特に吸気通路の還流する排気還流ガスに燃料改質により生成した水素を添加させた内燃機関の排気還流装置に関する。   The present invention relates to an exhaust gas recirculation device for an internal combustion engine that recirculates part of exhaust gas to an intake passage, and more particularly to an exhaust gas recirculation device for an internal combustion engine in which hydrogen generated by fuel reforming is added to exhaust gas recirculation gas that recirculates in an intake passage. .

内燃機関の排気の一部を取り出し、吸気系統に還流させ、吸気に混合させ燃焼時の最高温度を下げ、排気中のＮｏｘを低減するＥＧＲシステムが従来から広く知られている。   2. Description of the Related Art EGR systems that take out part of exhaust gas from an internal combustion engine, recirculate it to an intake system, mix it with intake air, lower the maximum temperature during combustion, and reduce Nox in exhaust gas have been widely known.

また、特許文献１には、このようなＥＧＲシステムに基づき、還流する排気に燃料を供給し、排気の熱を利用して、改質触媒上で改質反応（吸熱反応）を行い、水素と一酸化炭素を含む排気を吸気系に還流することにより、排気熱の回収、燃費向上を図った内燃機関のＥＧＲ改質システムや、上記改質触媒の劣化を検出することにより、燃費悪化やトルク変動を防止する内燃機関のＥＧＲ改質システムが開示されている。   Further, in Patent Document 1, based on such an EGR system, fuel is supplied to the recirculated exhaust gas, and the reforming reaction (endothermic reaction) is performed on the reforming catalyst using the heat of the exhaust gas. The exhaust gas containing carbon monoxide is recirculated to the intake system to recover exhaust heat and improve the fuel efficiency of the internal combustion engine EGR reforming system. An EGR reforming system for an internal combustion engine that prevents fluctuations is disclosed.

改質反応としては、排気中の水蒸気を利用した水蒸気改質反応、および二酸化炭素を利用したドライリフォーミングが想定されるが、いずれも十分な反応を行わせるためには、比較的高い温度（一般的には、例えば６００℃以上の温度）が必要である。一方で、排気温度は、近年のエンジン開発の中で低温化が進んでおり、排気温度が６００℃を超えるような負荷の高い運転領域は、概ね全体の２割程度である。排気温度が４００〜６００℃となるような相対的に負荷の低い運転領域でも改質反応により水素を得ることができれば、吸気通路に水素を導入できる運転領域を拡大でき、内燃機関における燃費をさらに向上することができる。つまり、排気温度が６００℃以下でも改質により水素を得ることができれば、さらに燃費を向上させることができる。   As the reforming reaction, a steam reforming reaction using steam in exhaust gas and dry reforming using carbon dioxide are assumed, but in order to perform a sufficient reaction, a relatively high temperature ( In general, for example, a temperature of 600 ° C. or higher is necessary. On the other hand, exhaust gas temperature has been decreasing in recent engine developments, and the operating range with a high load such that the exhaust temperature exceeds 600 ° C. is about 20% of the whole. If hydrogen can be obtained by the reforming reaction even in an operation region where the exhaust temperature is 400 to 600 ° C., the operation region in which hydrogen can be introduced into the intake passage can be expanded. Can be improved. That is, if hydrogen can be obtained by reforming even at an exhaust temperature of 600 ° C. or lower, fuel efficiency can be further improved.

特許第４０１３７０４号Japanese Patent No. 4013704

しかしながら、特許文献１に開示されるようなＥＧＲ改質システムでは、排気温度が高い場合に改質触媒で水素を生成するものであり、排気温度が高くなる限られた運転領域でしか、吸気に水素を添加することによる燃費の向上効果を得ることができないという問題がある。   However, in the EGR reforming system as disclosed in Patent Document 1, when the exhaust gas temperature is high, hydrogen is generated by the reforming catalyst, and only in a limited operating region where the exhaust gas temperature becomes high, There is a problem that the effect of improving fuel consumption cannot be obtained by adding hydrogen.

そこで、本発明の内燃機関の排気還流装置は、排気通路に設けられた排気浄化触媒上流側から吸気通路に排気を還流可能な排気還流通路と、この排気還流通路に改質用燃料を噴射する改質用燃料噴射手段と、上記排気還流通路に設けられ、改質用燃料から水素を生成する改質触媒と、内燃機関の運転状態に応じて上記吸気通路に還流する排気還流ガス量を調整する排気還流弁と、を有し、上記内燃機関の負荷が低い場合、上記排気浄化触媒上流側の排気を上記吸気通路に還流し、上記内燃機関の負荷が高く、かつ上記排気浄化触媒上流側の排気の酸素濃度が低い場合、上記排気浄化触媒上流側の排気を上記吸気通路に還流することを特徴としている。内燃機関の負荷が低くなるほど、内燃機関から排出される排気の温度は相対的に低くなる。また、内燃機関から排出された排気には酸素が含まれているため、排気浄化触媒上流側の排気を排気還流通路に導入することにより、改質触媒には酸素を含む排気が流入することになる。
Therefore, an exhaust gas recirculation apparatus for an internal combustion engine according to the present invention injects reforming fuel into the exhaust gas recirculation passage, and an exhaust gas recirculation passage capable of recirculating exhaust gas from the upstream side of the exhaust purification catalyst provided in the exhaust passage to the intake air passage. The reforming fuel injection means, the reforming catalyst provided in the exhaust gas recirculation passage and generating hydrogen from the reforming fuel, and the amount of exhaust gas recirculation gas recirculating to the intake passage according to the operating state of the internal combustion engine are adjusted. And when the load on the internal combustion engine is low, the exhaust on the upstream side of the exhaust purification catalyst is recirculated to the intake passage, the load on the internal combustion engine is high, and the upstream side of the exhaust purification catalyst When the oxygen concentration of the exhaust gas is low, the exhaust gas upstream of the exhaust purification catalyst is recirculated to the intake passage . The lower the load on the internal combustion engine, the lower the temperature of the exhaust discharged from the internal combustion engine. Further, since the exhaust gas discharged from the internal combustion engine contains oxygen, the exhaust gas containing oxygen flows into the reforming catalyst by introducing the exhaust gas upstream of the exhaust purification catalyst into the exhaust gas recirculation passage. Become.

本発明によれば、排気温度が低くても、排気中に含まれる酸素の酸化を利用した改質反応により、改質触媒で水素を生成することができるため、排気温度が比較的高いときにのみ改質触媒で水素を生成する場合に比べ、吸気通路に水素の導入が可能となる運転領域を拡大することができる。   According to the present invention, even when the exhaust temperature is low, hydrogen can be generated by the reforming catalyst by the reforming reaction utilizing oxidation of oxygen contained in the exhaust. As compared with the case where only the reforming catalyst generates hydrogen, the operating range in which hydrogen can be introduced into the intake passage can be expanded.

本発明の第１実施例における内燃機関の排気還流装置の全体構成を模式的に示した説明図。BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which showed typically the whole structure of the exhaust gas recirculation apparatus of the internal combustion engine in 1st Example of this invention. 第１実施例におけるＥＧＲ制御弁の制御の流れを示すフローチャート。The flowchart which shows the flow of control of the EGR control valve in 1st Example. 本発明の第２実施例における内燃機関の排気還流装置の全体構成を模式的に示した説明図。Explanatory drawing which showed typically the whole structure of the exhaust gas recirculation apparatus of the internal combustion engine in 2nd Example of this invention. 第２実施例における上流側制御弁及び下流側制御弁の制御の流れを示すフローチャート。The flowchart which shows the flow of control of the upstream control valve and downstream control valve in 2nd Example. 本発明の第３実施例における内燃機関の排気還流装置の全体構成を模式的に示した説明図。Explanatory drawing which showed typically the whole structure of the exhaust gas recirculation apparatus of the internal combustion engine in 3rd Example of this invention. 第３実施例における上流側制御弁及び下流側制御弁の制御の流れを示すフローチャート。The flowchart which shows the flow of control of the upstream control valve and downstream control valve in 3rd Example.

以下、本発明の一実施例を図面に基づいて詳細に説明する。   Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

図１は本発明の第１実施例における内燃機関の排気還流装置の全体構成を模式的に示した説明図である。   FIG. 1 is an explanatory view schematically showing the overall configuration of an exhaust gas recirculation device for an internal combustion engine in a first embodiment of the present invention.

内燃機関１は、例えば自動車等の車両に駆動源として搭載されるものである。この内燃機関１の燃焼室２には、吸気弁３を介して吸気通路４が接続されていると共に、排気弁５を介して排気通路６が接続されている。燃焼室２の中央頂部には、燃焼室２内の混合気を火花点火する点火プラグ７が設けられている。   The internal combustion engine 1 is mounted as a drive source in a vehicle such as an automobile. An intake passage 4 is connected to the combustion chamber 2 of the internal combustion engine 1 via an intake valve 3 and an exhaust passage 6 is connected via an exhaust valve 5. A spark plug 7 for spark-igniting the air-fuel mixture in the combustion chamber 2 is provided at the central top of the combustion chamber 2.

吸気通路４には、吸入空気量を制御するスロットル弁８、このスロットル弁８の下流側に位置して燃料を当該吸気通路４内に噴射する燃料噴射弁９が、配置されている。   A throttle valve 8 that controls the amount of intake air and a fuel injection valve 9 that is located downstream of the throttle valve 8 and injects fuel into the intake passage 4 are disposed in the intake passage 4.

排気通路６には、排気浄化触媒１０が設けられている。この排気浄化触媒１０は、排気通路６の上流側に位置し、内燃機関１が搭載される車両のエンジンルーム内に配置されるものであって、内燃機関１の排気マニホールドの直下流に配置されるいわゆるマニホールド触媒である。排気浄化触媒１０は、排気中の酸素を使って排気の浄化を行うものであって、例えば排気中のＮＯｘ、ＨＣ、ＣＯを同時に浄化する三元触媒である。   An exhaust purification catalyst 10 is provided in the exhaust passage 6. The exhaust purification catalyst 10 is located upstream of the exhaust passage 6 and is disposed in the engine room of a vehicle on which the internal combustion engine 1 is mounted, and is disposed immediately downstream of the exhaust manifold of the internal combustion engine 1. This is a so-called manifold catalyst. The exhaust purification catalyst 10 purifies exhaust using oxygen in the exhaust, and is, for example, a three-way catalyst that simultaneously purifies NOx, HC, and CO in the exhaust.

排気通路６と吸気通路４との間には、排気の一部を吸気通路４に還流する排気還流通路としてのＥＧＲ通路１１が設けられている。ＥＧＲ通路１１は、その一端が排気浄化触媒１０の上流側で排気通路６に接続され、その他端がスロットル弁８と燃料噴射弁９との間に位置する吸気通路４のコレクタ部４ａに接続されている。そして、このＥＧＲ通路１１には、排気通路６側から順に、改質用燃料噴射手段としての改質用燃料噴射弁１２、改質触媒１３、ＥＧＲクーラ１４、排気還流弁としてのＥＧＲ制御弁１５が配置されている。   Between the exhaust passage 6 and the intake passage 4, an EGR passage 11 is provided as an exhaust recirculation passage for returning a part of the exhaust gas to the intake passage 4. One end of the EGR passage 11 is connected to the exhaust passage 6 on the upstream side of the exhaust purification catalyst 10, and the other end is connected to the collector portion 4 a of the intake passage 4 located between the throttle valve 8 and the fuel injection valve 9. ing. The EGR passage 11 includes, in order from the exhaust passage 6 side, a reforming fuel injection valve 12 as a reforming fuel injection means, a reforming catalyst 13, an EGR cooler 14, and an EGR control valve 15 as an exhaust recirculation valve. Is arranged.

改質用燃料噴射弁１２は、燃料噴射弁９で噴射する燃料と同じ燃料を改質用燃料としてＥＧＲ通路１１内に噴射するものである。上記改質用燃料は、ＥＧＲ通路１１に導入された排気とともに改質触媒１３に供給される。   The reforming fuel injection valve 12 injects the same fuel as the fuel injected by the fuel injection valve 9 into the EGR passage 11 as a reforming fuel. The reforming fuel is supplied to the reforming catalyst 13 together with the exhaust gas introduced into the EGR passage 11.

改質触媒１３は、例えばコージェライトからなるハニカム担体に、ロジウムを担持させたものであって、ＥＧＲ通路１１に導入された排気と上記改質用燃料とを用いて水素を生成する。ここで、改質触媒１３における改質反応は、排気中の水蒸気及び二酸化炭素を利用した改質反応と、排気中の酸素の酸化を利用した改質反応に大別される。排気中の水蒸気及び二酸化炭素を利用した改質反応は、温度が比較的高くないと進行しにくい反応であり、例えば６００℃以上の温度雰囲気下で進行して水素を生成する。一方、排気中の酸素の酸化を利用した改質反応は、温度が比較的低くても進行する反応であり、例えば３００℃〜３５０℃程度の温度雰囲気下から進行して水素を生成する。改質触媒１３で生成された水素は、吸気通路４を経て燃焼室２内で燃焼することにより、内燃機関１の燃費向上に寄与することになる。   The reforming catalyst 13 is formed by supporting rhodium on a honeycomb carrier made of, for example, cordierite, and generates hydrogen using the exhaust gas introduced into the EGR passage 11 and the reforming fuel. Here, the reforming reaction in the reforming catalyst 13 is roughly classified into a reforming reaction using steam and carbon dioxide in exhaust gas and a reforming reaction using oxidation of oxygen in exhaust gas. The reforming reaction using water vapor and carbon dioxide in the exhaust gas is a reaction that hardly proceeds unless the temperature is relatively high. For example, the reforming reaction proceeds in a temperature atmosphere of 600 ° C. or higher to generate hydrogen. On the other hand, the reforming reaction using oxidation of oxygen in the exhaust gas proceeds even when the temperature is relatively low. For example, the reforming reaction proceeds from a temperature atmosphere of about 300 ° C. to 350 ° C. to generate hydrogen. The hydrogen produced by the reforming catalyst 13 burns in the combustion chamber 2 through the intake passage 4 and contributes to an improvement in fuel consumption of the internal combustion engine 1.

ＥＧＲクーラ１４は、吸気通路４に還流するＥＧＲガス（排気還流ガス）を冷却するものである。   The EGR cooler 14 cools the EGR gas (exhaust gas recirculation gas) that recirculates to the intake passage 4.

ＥＧＲ制御弁１５は、内燃機関１の運転状態に応じて吸気通路４に還流するＥＧＲガス量（排気還流ガス量）を調整するものである。このＥＧＲ制御弁１５は、ＥＣＵ（エンジンコントロールユニット）１６によってその弁開度が制御されている。   The EGR control valve 15 adjusts the amount of EGR gas (exhaust gas recirculation gas) recirculated to the intake passage 4 according to the operating state of the internal combustion engine 1. The opening degree of the EGR control valve 15 is controlled by an ECU (engine control unit) 16.

ＥＣＵ１６には、排気浄化触媒１０上流側に配置されて燃焼室２から排出された排気の酸素濃度を検知する酸素濃度検知手段としての酸素センサ１７、運転者により操作されるアクセルペダルの開度を検出するアクセル開度センサ１８等の各種センサ類からの信号が入力されている。また、このＥＣＵ１６は、上述したＥＧＲ制御弁１５のほかに、運転状態に応じた燃料噴射弁９からの燃料噴射量、改質用燃料噴射弁１２からの燃料噴射量等の内燃機関１の各種制御を行っている。   The ECU 16 includes an oxygen sensor 17 serving as an oxygen concentration detection unit that is disposed upstream of the exhaust purification catalyst 10 and detects the oxygen concentration of the exhaust discharged from the combustion chamber 2, and the degree of opening of the accelerator pedal operated by the driver. Signals from various sensors such as the accelerator opening sensor 18 to be detected are input. In addition to the EGR control valve 15 described above, the ECU 16 performs various types of internal combustion engine 1 such as the fuel injection amount from the fuel injection valve 9 and the fuel injection amount from the reforming fuel injection valve 12 according to the operating state. Control is in progress.

ここで、この第１実施例では、基本的には、燃焼室２内でストイキ燃焼（理論空燃比での燃焼）したときに排出された排気の一部を排気浄化触媒１０の上流側でＥＧＲ通路１１に導入し、上記改質用燃料を加えて改質触媒１３で水素を生成し、この水素を含んだ排気をＥＧＲガス（排気還流ガス）として吸気通路４に還流している。燃焼室２内でストイキ燃焼（理論空燃比での燃焼）したときの排気には、実際には、未燃の炭化水素や一酸化炭素が含まれており、またこれらのエミッションを排気浄化触媒１０で浄化するために約１％程度の酸素も含まれている。   Here, in the first embodiment, basically, a part of the exhaust discharged when stoichiometric combustion (combustion at the stoichiometric air-fuel ratio) is performed in the combustion chamber 2 on the upstream side of the exhaust purification catalyst 10. The hydrogen is introduced into the passage 11 and the reforming catalyst 13 is added to generate hydrogen by the reforming catalyst 13, and the exhaust gas containing the hydrogen is recirculated to the intake passage 4 as EGR gas (exhaust gas recirculation gas). Exhaust gas when stoichiometric combustion (combustion at the stoichiometric air-fuel ratio) in the combustion chamber 2 actually contains unburned hydrocarbons and carbon monoxide, and these emissions are used as exhaust purification catalyst 10. About 1% oxygen is also included for purification.

また、第１実施例では、基本的には、酸素濃度が１％程度の排気を利用して、改質触媒１３で水素を生成するそのため、改質触媒１３において、排気中の水蒸気及び二酸化炭素を利用した改質反応が進行すると共に、排気中の酸素の酸化を利用した改質反応が進行する。   In the first embodiment, basically, the reforming catalyst 13 generates hydrogen using the exhaust having an oxygen concentration of about 1%. Therefore, in the reforming catalyst 13, the water vapor and carbon dioxide in the exhaust are used. The reforming reaction utilizing oxygen proceeds and the reforming reaction utilizing oxidation of oxygen in the exhaust proceeds.

ここで、内燃機関１の負荷と燃焼室２から排出される排気の温度との間には、相関があり、内燃機関１の負荷が低い場合には、燃焼室２から排出される排気の温度も相対的に低くなる。そのため、内燃機関１の負荷が低いと、改質触媒１３にて排気中の水蒸気及び二酸化炭素を利用した改質反応が進行しない場合がある。内燃機関１の負荷が低くても、燃焼室２から排出される排気の酸素濃度がある程度高ければ（酸素濃度が１％程度）、排気中の酸素の酸化を利用した改質反応が進行するため、改質触媒１３で水素を生成可能である。   Here, there is a correlation between the load of the internal combustion engine 1 and the temperature of the exhaust gas discharged from the combustion chamber 2, and the temperature of the exhaust gas discharged from the combustion chamber 2 when the load of the internal combustion engine 1 is low. Is also relatively low. Therefore, when the load of the internal combustion engine 1 is low, the reforming reaction using the steam and carbon dioxide in the exhaust gas may not proceed at the reforming catalyst 13. Even if the load of the internal combustion engine 1 is low, if the oxygen concentration of the exhaust gas discharged from the combustion chamber 2 is high to some extent (the oxygen concentration is about 1%), the reforming reaction utilizing the oxidation of oxygen in the exhaust gas proceeds. The reforming catalyst 13 can generate hydrogen.

また、内燃機関１の負荷が高いと、燃焼室２から排出される排気の温度も相対的に高くなる。このとき、燃焼室２から排出された排気の酸素濃度が高ければ、排気中の酸素の酸化を利用した改質反応による発熱と、改質触媒１３に導入される高温の排気と、により改質触媒１３が過度に高温となってしまい、改質触媒１３が熱劣化してしまう虞がある。   Further, when the load on the internal combustion engine 1 is high, the temperature of the exhaust gas discharged from the combustion chamber 2 also becomes relatively high. At this time, if the oxygen concentration in the exhaust gas discharged from the combustion chamber 2 is high, reforming is performed by heat generation due to the reforming reaction utilizing oxidation of oxygen in the exhaust gas and high-temperature exhaust gas introduced into the reforming catalyst 13. There is a possibility that the catalyst 13 becomes excessively hot and the reforming catalyst 13 is thermally deteriorated.

そこで、この第１実施例においては、内燃機関１の負荷と、燃焼室２から排出された排気の酸素濃度（排気浄化触媒１０上流側の酸素濃度）と、に応じてＥＧＲ制御弁１５の開閉制御を以下のように実施する。   Therefore, in the first embodiment, the EGR control valve 15 is opened and closed according to the load of the internal combustion engine 1 and the oxygen concentration of the exhaust gas exhausted from the combustion chamber 2 (the oxygen concentration upstream of the exhaust purification catalyst 10). Control is performed as follows.

内燃機関１の負荷が予め設定された所定の負荷よりも低い場合には、ＥＧＲ制御弁１５を開き、ＥＧＲ通路１１に排気浄化触媒１０上流側の排気を導入する。このとき改質用燃料噴射弁１２から改質用燃料を噴射すれば、改質触媒１３において主として酸素の酸化を利用した改質反応から水素が生成される。   When the load of the internal combustion engine 1 is lower than a predetermined load set in advance, the EGR control valve 15 is opened, and the exhaust gas upstream of the exhaust purification catalyst 10 is introduced into the EGR passage 11. If the reforming fuel is injected from the reforming fuel injection valve 12 at this time, hydrogen is generated in the reforming catalyst 13 mainly from the reforming reaction utilizing oxidation of oxygen.

これにより、燃焼室２から排出される排気の温度が低くても、排気中に含まれる酸素の酸化を利用した改質反応により、改質触媒１３で水素を生成することができる。そのため、比較的排気温度が高いときにのみ改質触媒１３で水素を生成する場合に比べ、吸気通路４に水素の導入が可能となる運転領域を拡大することができる。   Thereby, even if the temperature of the exhaust gas discharged from the combustion chamber 2 is low, hydrogen can be generated by the reforming catalyst 13 by the reforming reaction utilizing oxidation of oxygen contained in the exhaust gas. Therefore, compared with the case where hydrogen is generated by the reforming catalyst 13 only when the exhaust temperature is relatively high, the operating range in which hydrogen can be introduced into the intake passage 4 can be expanded.

また、排気中には、燃料や潤滑油（エンジンオイル）に由来する成分が含まれており、これらが改質触媒１３に付着すると触媒毒となり、改質反応が抑制される可能性がある。しかしながら、排気中に含まれる酸素を利用して改質触媒１３に付着した触媒毒を燃焼除去できるので、触媒毒による改質触媒１３の改質反応の悪化を防止することができる。換言すれば、排気中に含まれる酸素を利用して、改質触媒１３で水素を生成すると同時に、改質触媒１３上の触媒毒を除去する再生処理を実施できる。   Further, the exhaust contains components derived from fuel and lubricating oil (engine oil). If these components adhere to the reforming catalyst 13, it becomes a catalyst poison, which may suppress the reforming reaction. However, since the catalyst poison adhering to the reforming catalyst 13 can be burned and removed using oxygen contained in the exhaust gas, it is possible to prevent the reforming reaction of the reforming catalyst 13 from deteriorating due to the catalyst poison. In other words, the regeneration process for removing the catalyst poison on the reforming catalyst 13 can be performed simultaneously with the generation of hydrogen by the reforming catalyst 13 using the oxygen contained in the exhaust gas.

そして、内燃機関１の負荷が予め設定された所定の負荷より高く、排気浄化触媒１０上流側の排気の酸素濃度が予め設定された所定値より低い場合には、ＥＧＲ制御弁１５を開き、ＥＧＲ通路１１に排気浄化触媒１０上流側の排気を導入する。このとき改質用燃料噴射弁１２から改質用燃料を噴射すれば、改質触媒１３において主として排気中の水蒸気及び二酸化炭素を利用した改質反応から水素が生成される。   When the load of the internal combustion engine 1 is higher than the predetermined load set in advance and the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10 is lower than the predetermined value set in advance, the EGR control valve 15 is opened and EGR is set. Exhaust gas upstream of the exhaust purification catalyst 10 is introduced into the passage 11. If the reforming fuel is injected from the reforming fuel injection valve 12 at this time, hydrogen is generated in the reforming catalyst 13 from the reforming reaction mainly using water vapor and carbon dioxide in the exhaust gas.

改質触媒１３に流入する排気の酸素濃度が低ければ、排気に含まれる酸素の酸化を利用した改質触媒１３での改質反応は進行せず、この改質反応による発熱により改質触媒１３の温度が大きく上昇することはない。つまり、改質触媒１３がＥＧＲ通路１１に導入された排気の温度よりも高温とはならない。   If the oxygen concentration in the exhaust gas flowing into the reforming catalyst 13 is low, the reforming reaction in the reforming catalyst 13 utilizing oxidation of oxygen contained in the exhaust does not proceed, and the reforming catalyst 13 is generated by the heat generated by this reforming reaction. The temperature does not increase greatly. That is, the reforming catalyst 13 does not become higher than the temperature of the exhaust gas introduced into the EGR passage 11.

これによって、燃焼室２から排出される排気の温度が高くても、改質触媒１３の温度が過度に高温となることはないので、改質触媒１３の熱劣化を防止することができる。   Thereby, even if the temperature of the exhaust gas discharged from the combustion chamber 2 is high, the temperature of the reforming catalyst 13 does not become excessively high, so that the thermal deterioration of the reforming catalyst 13 can be prevented.

また、内燃機関１の負荷が予め設定された所定の負荷よりも高く、排気浄化触媒１０上流側の排気の酸素濃度が予め設定された所定値より高いときには、ＥＧＲ制御弁１５を閉じ、ＥＧＲ通路１１への排気を導入を中止する。   When the load of the internal combustion engine 1 is higher than a predetermined load set in advance and the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10 is higher than a predetermined value set in advance, the EGR control valve 15 is closed and the EGR passage is closed. The introduction of exhaust to 11 is stopped.

改質触媒１３に流入する排気の酸素濃度が高ければ、排気に含まれる酸素の酸化を利用した改質触媒１３での改質反応が進行するため、この改質反応による発熱により改質触媒１３の温度が大きく上昇する可能性がある。つまり、排気中の酸素の酸化を利用した改質触媒１３での改質反応による発熱と、ＥＧＲ通路１１に導入される排気の元々の温度と、により改質触媒１３が過度に高温となってしまう可能性がある。   If the concentration of oxygen in the exhaust gas flowing into the reforming catalyst 13 is high, the reforming reaction in the reforming catalyst 13 utilizing oxidation of oxygen contained in the exhaust proceeds. Therefore, the reforming catalyst 13 is generated by heat generated by the reforming reaction. The temperature may increase significantly. That is, the reforming catalyst 13 becomes excessively high due to the heat generated by the reforming reaction in the reforming catalyst 13 utilizing the oxidation of oxygen in the exhaust gas and the original temperature of the exhaust gas introduced into the EGR passage 11. There is a possibility.

そこで、内燃機関１の負荷が高く、排気浄化触媒１０上流側の排気の酸素濃度が高い場合には、ＥＧＲ通路１１への排気を導入を中止することで、燃焼室２から排出される高温の排気よりも、改質触媒１３が更に高温となってしまうことを防止することができ、改質触媒１３の熱劣化を確実に防止することができる。   Therefore, when the load on the internal combustion engine 1 is high and the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 10 is high, the introduction of the exhaust gas into the EGR passage 11 is stopped so that the high temperature exhausted from the combustion chamber 2 is increased. It is possible to prevent the reforming catalyst 13 from becoming further hotter than the exhaust, and to reliably prevent thermal degradation of the reforming catalyst 13.

従って、このような第１実施例においては、内燃機関１の負荷と、燃焼室２から排出された排気の酸素濃度（排気浄化触媒１０上流側の酸素濃度）と、に応じてＥＧＲ制御弁１５の開閉制御を行うことで、改質触媒１３の熱劣化を防止しつつ、改質触媒１３で生成された水素が吸気通路４に導入される運転領域を拡大して、内燃機関１の燃費を大幅に向上させることができる。   Accordingly, in such a first embodiment, the EGR control valve 15 depends on the load of the internal combustion engine 1 and the oxygen concentration of the exhaust gas exhausted from the combustion chamber 2 (the oxygen concentration upstream of the exhaust purification catalyst 10). By controlling the opening and closing of the engine, the operating range in which the hydrogen produced by the reforming catalyst 13 is introduced into the intake passage 4 is expanded while preventing the thermal deterioration of the reforming catalyst 13, and the fuel efficiency of the internal combustion engine 1 is improved. It can be greatly improved.

また、排気中に含まれる酸素を利用して改質触媒１３の触媒毒成分を除去する再生処理を実施できるので、触媒毒による改質触媒１３の改質反応の悪化を防止することができる。   In addition, since the regeneration process of removing the catalyst poison component of the reforming catalyst 13 using oxygen contained in the exhaust gas can be performed, it is possible to prevent the reforming reaction of the reforming catalyst 13 from being deteriorated due to the catalyst poison.

図２は、第１実施例におけるＥＧＲ制御弁１５の制御の流れを示すフローチャートである。Ｓ１１では、内燃機関１の負荷が高い状態であるか否かを判定し、高い場合にはＳ１２へ進み、そうでない場合には１３へ進む。Ｓ１２では、排気浄化触媒１０上流側の排気の酸素濃度が高いか否かを判定し、高い場合にはＳ１４へ進み、そうでない場合はＳ１５へ進む。Ｓ１３では、ＥＧＲ制御弁１５を所定の開弁状態に制御する。Ｓ１４では、ＥＧＲ制御弁１５を閉弁状態に制御する。Ｓ１５では、ＥＧＲ制御弁１５を所定の開弁状態に制御する。   FIG. 2 is a flowchart showing a control flow of the EGR control valve 15 in the first embodiment. In S11, it is determined whether or not the load of the internal combustion engine 1 is high. If it is high, the process proceeds to S12, and if not, the process proceeds to 13. In S12, it is determined whether or not the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 10 is high. If so, the process proceeds to S14, and if not, the process proceeds to S15. In S13, the EGR control valve 15 is controlled to a predetermined valve open state. In S14, the EGR control valve 15 is controlled to be closed. In S15, the EGR control valve 15 is controlled to a predetermined valve open state.

なお、上述した第１実施例おいては、内燃機関１の負荷が高く、排気浄化触媒１０上流側の排気の酸素濃度が低い場合に排気還流を実施しているが、内燃機関１の負荷から推定される排気温度が非常に高く、改質触媒１３に流入する直前の排気温度が改質触媒１３の耐熱温度を越えるように予測される場合には、排気浄化触媒１０上流側の排気の酸素濃度が低い場合でも、ＥＧＲ制御弁１５を閉弁状態に制御して、改質触媒１３の熱劣化を確実に防止するようにしてもよい。   In the first embodiment described above, the exhaust gas recirculation is performed when the load on the internal combustion engine 1 is high and the exhaust gas upstream of the exhaust purification catalyst 10 has a low oxygen concentration. If the estimated exhaust temperature is very high and the exhaust temperature immediately before flowing into the reforming catalyst 13 is predicted to exceed the heat resistance temperature of the reforming catalyst 13, the oxygen in the exhaust upstream of the exhaust purification catalyst 10 is predicted. Even when the concentration is low, the EGR control valve 15 may be controlled to be in a closed state to reliably prevent thermal deterioration of the reforming catalyst 13.

また、上述した第１実施例においては、内燃機関１の負荷と排気浄化触媒１０上流側の排気の酸素濃度に応じてＥＧＲ制御弁１５の開閉制御を実施しているが、内燃機関１の負荷のみに応じてＥＧＲ制御弁１５の開閉制御を実施することも可能である。   In the first embodiment described above, the opening / closing control of the EGR control valve 15 is performed according to the load of the internal combustion engine 1 and the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10. It is also possible to carry out the opening / closing control of the EGR control valve 15 only according to the above.

この場合には、内燃機関１の負荷が高い状態であれば、ＥＧＲ制御弁１５を閉弁状態に制御し、内燃機関１の負荷が高い状態でなければ、ＥＧＲ制御弁１５を所定の開弁状態に制御する。   In this case, if the load on the internal combustion engine 1 is high, the EGR control valve 15 is controlled to be closed, and if the load on the internal combustion engine 1 is not high, the EGR control valve 15 is opened to a predetermined value. Control to the state.

排気温度が高い排気をＥＧＲ通路１１に導入した場合、この排気の酸素濃度が高ければ、排気中の酸素の酸化を利用した改質触媒１３での改質反応による発熱と、ＥＧＲ通路１１に導入される排気の元々の温度と、により改質触媒１３が過度に高温となってしまう可能性がある。そこで、内燃機関１の負荷のみに応じてＥＧＲ制御弁１５の開閉制御を行う場合には、内燃機関１の負荷が高い状態であれば、ＥＧＲ制御弁１５を閉弁状態に制御することで、改質触媒１３の熱劣化を確実に防止することができる。   When exhaust gas having a high exhaust temperature is introduced into the EGR passage 11, if the oxygen concentration of the exhaust gas is high, heat is generated by the reforming reaction in the reforming catalyst 13 using oxidation of oxygen in the exhaust gas and introduced into the EGR passage 11. There is a possibility that the reforming catalyst 13 becomes excessively high temperature due to the original temperature of the exhaust gas. Therefore, when performing the opening / closing control of the EGR control valve 15 according to only the load of the internal combustion engine 1, if the load of the internal combustion engine 1 is high, the EGR control valve 15 is controlled to be closed, Thermal deterioration of the reforming catalyst 13 can be reliably prevented.

以下、本発明の他の実施例について説明するが、上述した第１実施例と同一の構成要素については、同一の符号を付し、重複する説明を省略する。   Hereinafter, other embodiments of the present invention will be described, but the same components as those in the first embodiment described above are denoted by the same reference numerals, and redundant description will be omitted.

図３は本発明の第２実施例における内燃機関の排気還流装置の全体構成を模式的に示した説明図である。この第２実施例は、上述した第１実施例と略同一構成となっているが、ＥＧＲ通路２１の一端側は、排気浄化触媒１０上流側で排気通路６に接続される上流側排気導入部２２と、排気浄化触媒１０下流側で排気通路６に接続される下流側排気導入部２３とに分岐する構成となっている。   FIG. 3 is an explanatory view schematically showing the overall configuration of an exhaust gas recirculation device for an internal combustion engine in a second embodiment of the present invention. The second embodiment has substantially the same configuration as the first embodiment described above, but one end side of the EGR passage 21 is connected to the exhaust passage 6 on the upstream side of the exhaust purification catalyst 10. 22 and a downstream side exhaust introduction portion 23 connected to the exhaust passage 6 on the downstream side of the exhaust purification catalyst 10.

そして、上流側排気導入部２２には、上流側排気導入部２２に導入される排気量を調整可能な上流側制御弁２４が配置されている。下流側排気導入部２３には、下流側排気導入部２３に導入される排気量を調整可能な下流側制御弁２５が配置されている。上流側制御弁２４及び下流側制御弁２５は、ＥＣＵ１６によってその弁開度が制御されている。   The upstream side exhaust introduction part 22 is provided with an upstream side control valve 24 that can adjust the amount of exhaust introduced into the upstream side exhaust introduction part 22. The downstream side exhaust introduction part 23 is provided with a downstream side control valve 25 that can adjust the amount of exhaust introduced into the downstream side exhaust introduction part 23. The valve opening degree of the upstream control valve 24 and the downstream control valve 25 is controlled by the ECU 16.

ここで、下流側排気導入部２５から導入される排気は、排気浄化触媒１０を通過する際に酸素が殆ど消費され、酸素を殆ど含まない状態となっている。   Here, the exhaust gas introduced from the downstream side exhaust gas introduction portion 25 is in a state in which almost all oxygen is consumed and hardly contains oxygen when passing through the exhaust purification catalyst 10.

そこで、この第２実施例においては、内燃機関１の負荷と、燃焼室２から排出された排気の酸素濃度（排気浄化触媒１０上流側の酸素濃度）と、に応じて上流側制御弁２４及び下流側制御弁２５の開閉制御を以下のように実施する。   Accordingly, in the second embodiment, the upstream control valve 24 and the oxygen concentration of the exhaust gas exhausted from the combustion chamber 2 (the oxygen concentration upstream of the exhaust purification catalyst 10) and The opening / closing control of the downstream control valve 25 is performed as follows.

内燃機関１の負荷が予め設定された所定の負荷よりも低い場合には、ＥＧＲ制御弁１５及び上流側制御弁２４を開き、かつ下流側制御弁２５を閉じることでＥＧＲ通路２１に排気浄化触媒１０上流側の排気のみを導入する。このとき改質用燃料噴射弁１２から改質用燃料を噴射すれば、改質触媒１３において主として酸素の酸化を利用した改質反応から水素が生成される。   When the load of the internal combustion engine 1 is lower than a predetermined load set in advance, the EGR control valve 15 and the upstream control valve 24 are opened, and the downstream control valve 25 is closed, so that the exhaust gas purification catalyst is provided in the EGR passage 21. 10 Introduce only upstream exhaust. If the reforming fuel is injected from the reforming fuel injection valve 12 at this time, hydrogen is generated in the reforming catalyst 13 mainly from the reforming reaction utilizing oxidation of oxygen.

これにより、燃焼室２から排出される排気の温度が低くても、排気中に含まれる酸素の酸化を利用した改質反応により、改質触媒１３で水素を生成することができる。そのため、比較的排気温度が高いときにのみ改質触媒１３で水素を生成する場合に比べ、吸気通路４に水素の導入が可能となる運転領域を拡大することができる。なお、内燃機関１の負荷が予め設定された所定の負荷よりも低い場合に、排気浄化触媒１０下流側からＥＧＲ通路１１に排気を導入すれば、排気浄化触媒１０を通過することで排気の温度がさらに低下したときに、改質触媒１３に流入する排気の温度が過度に低くなって排気中の水蒸気及び二酸化炭素を利用した改質反応が進行せず、改質触媒１３で水素が生成されない虞がある。   Thereby, even if the temperature of the exhaust gas discharged from the combustion chamber 2 is low, hydrogen can be generated by the reforming catalyst 13 by the reforming reaction utilizing oxidation of oxygen contained in the exhaust gas. Therefore, compared with the case where hydrogen is generated by the reforming catalyst 13 only when the exhaust temperature is relatively high, the operating range in which hydrogen can be introduced into the intake passage 4 can be expanded. If the exhaust gas is introduced into the EGR passage 11 from the downstream side of the exhaust purification catalyst 10 when the load of the internal combustion engine 1 is lower than a predetermined load set in advance, the temperature of the exhaust gas passes through the exhaust purification catalyst 10 and passes through the exhaust purification catalyst 10. When the temperature further decreases, the temperature of the exhaust gas flowing into the reforming catalyst 13 becomes excessively low, and the reforming reaction utilizing water vapor and carbon dioxide in the exhaust gas does not proceed, and hydrogen is not generated by the reforming catalyst 13. There is a fear.

また、改質触媒１３に付着した触媒毒を排気中に含まれる酸素を利用して燃焼除去できるので、触媒毒による改質触媒１３の改質反応の悪化を防止することができる。つまり、排気中に含まれる酸素を利用して、改質触媒１３で水素を生成すると同時に、改質触媒１３上の触媒毒成分を除去する再生処理を実施できる。   Further, since the catalyst poison adhering to the reforming catalyst 13 can be burned and removed using oxygen contained in the exhaust gas, it is possible to prevent the reforming reaction of the reforming catalyst 13 from deteriorating due to the catalyst poison. That is, the regeneration process for removing the catalyst poison component on the reforming catalyst 13 can be performed at the same time that hydrogen is generated by the reforming catalyst 13 using oxygen contained in the exhaust gas.

そして、内燃機関１の負荷が予め設定された所定の負荷より高く、排気浄化触媒１０上流側の排気の酸素濃度が予め設定された所定値より低い場合には、ＥＧＲ制御弁１５及び上流側制御弁２４を開き、かつ下流側制御弁２５を閉じることでＥＧＲ通路２１に排気浄化触媒１０上流側の排気のみを導入する。このとき改質用燃料噴射弁１２から改質用燃料を噴射すれば、改質触媒１３において主として排気中の水蒸気及び二酸化炭素を利用した改質反応から水素が生成される。   When the load of the internal combustion engine 1 is higher than the predetermined load set in advance and the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10 is lower than the predetermined value set in advance, the EGR control valve 15 and the upstream control are performed. By opening the valve 24 and closing the downstream control valve 25, only exhaust gas upstream of the exhaust purification catalyst 10 is introduced into the EGR passage 21. If the reforming fuel is injected from the reforming fuel injection valve 12 at this time, hydrogen is generated in the reforming catalyst 13 from the reforming reaction mainly using water vapor and carbon dioxide in the exhaust gas.

これによって、燃焼室２から排出される排気の温度が高くても、排気に含まれる酸素濃度は低いので、排気浄化触媒１０上流側からＥＧＲ通路１１に排気を導入しても、改質触媒１３の温度が過度に高温となることはないので、改質触媒１３の熱劣化を防止することができる。なお、内燃機関１の負荷が予め設定された所定の負荷より高く、排気浄化触媒１０上流側の排気の酸素濃度が予め設定された所定値より低い場合に、排気浄化触媒１０下流側からＥＧＲ通路１１に排気を導入すれば、排気浄化触媒１０を通過することで排気の温度が低下したときに、改質触媒１３に流入する排気の温度が過度に低くなって排気中の水蒸気及び二酸化炭素を利用した改質反応が進行せず、改質触媒１３で水素が生成されない虞がある。   Accordingly, even if the temperature of the exhaust gas discharged from the combustion chamber 2 is high, the oxygen concentration contained in the exhaust gas is low. Therefore, even if the exhaust gas is introduced from the upstream side of the exhaust purification catalyst 10 into the EGR passage 11, the reforming catalyst 13. Since the temperature does not become excessively high, thermal deterioration of the reforming catalyst 13 can be prevented. Note that when the load of the internal combustion engine 1 is higher than a predetermined load set in advance and the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10 is lower than a predetermined value set in advance, the EGR passage from the downstream side of the exhaust purification catalyst 10 If exhaust gas is introduced into the exhaust gas 11, the temperature of the exhaust gas flowing into the reforming catalyst 13 becomes excessively low when the exhaust gas temperature is lowered by passing through the exhaust gas purification catalyst 10, and water vapor and carbon dioxide in the exhaust gas are reduced. There is a possibility that the used reforming reaction does not proceed and hydrogen is not generated by the reforming catalyst 13.

また、内燃機関１の負荷が予め設定された所定の負荷より高く、排気浄化触媒１０上流側の排気の酸素濃度が予め設定された所定値より高い場合には、ＥＧＲ制御弁１５及び下流側制御弁２５を開き、かつ上流側制御弁２４を閉じることでＥＧＲ通路２１に排気浄化触媒１０下流側の排気のみを導入する。このとき改質用燃料噴射弁１２から改質用燃料を噴射すれば、改質触媒１３において主として排気中の水蒸気及び二酸化炭素を利用した改質反応から水素が生成される。   Further, when the load of the internal combustion engine 1 is higher than a predetermined load set in advance and the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10 is higher than a predetermined value set in advance, the EGR control valve 15 and the downstream control are performed. By opening the valve 25 and closing the upstream control valve 24, only the exhaust on the downstream side of the exhaust purification catalyst 10 is introduced into the EGR passage 21. If the reforming fuel is injected from the reforming fuel injection valve 12 at this time, hydrogen is generated in the reforming catalyst 13 from the reforming reaction mainly using water vapor and carbon dioxide in the exhaust gas.

排気浄化触媒１０下流側から排気をＥＧＲ通路１１に導入することにより、改質触媒１３には、酸素を殆ど含んでいない排気が流入することになり、排気中の酸素の酸化を利用した改質反応は進行しないため、改質触媒１３が過度に高温となることを防止することができ、改質触媒の熱劣化を防止することができる。なお、排気浄化触媒１０下流側から排気をＥＧＲ通路１１に導入する場合、排気浄化触媒１０上流側から排気をＥＧＲ通路１１に導入する場合に比べて、改質触媒１３に排気が到達するまでの経路長が長くなり、その分放熱量も大きくなる。そこで、燃焼室２から排出される排気の温度が高く、酸素濃度が高い場合には、排気浄化触媒１０下流側から排気をＥＧＲ通路１１に導入する方が、改質触媒１３の熱劣化を防止する上で有効である。   By introducing exhaust gas into the EGR passage 11 from the downstream side of the exhaust purification catalyst 10, exhaust gas containing almost no oxygen flows into the reforming catalyst 13, and reforming utilizing oxidation of oxygen in the exhaust gas. Since the reaction does not proceed, it is possible to prevent the reforming catalyst 13 from becoming excessively high in temperature and to prevent thermal degradation of the reforming catalyst. In addition, when exhaust is introduced into the EGR passage 11 from the exhaust purification catalyst 10 downstream side, the exhaust gas reaches the reforming catalyst 13 as compared with when exhaust is introduced into the EGR passage 11 from the exhaust purification catalyst 10 upstream side. The length of the path becomes longer, and the amount of heat radiation increases accordingly. Therefore, when the temperature of the exhaust gas exhausted from the combustion chamber 2 is high and the oxygen concentration is high, it is better to introduce the exhaust gas into the EGR passage 11 from the downstream side of the exhaust purification catalyst 10 to prevent thermal deterioration of the reforming catalyst 13. It is effective in doing.

従って、このような第２実施例においても、上述した第１実施例と同様に、改質触媒１３の熱劣化を防止しつつ、吸気通路４に水素の導入が可能となる運転領域を拡大して内燃機関１の燃費を大幅に向上させることができる。   Therefore, in the second embodiment as well, as in the first embodiment described above, the operating range in which hydrogen can be introduced into the intake passage 4 while the thermal degradation of the reforming catalyst 13 is prevented is expanded. Thus, the fuel consumption of the internal combustion engine 1 can be greatly improved.

図４は、第２実施例における上流側制御弁２４及び下流側制御弁２５の制御の流れを示すフローチャートである。Ｓ２１では、内燃機関１の負荷が高い状態であるか否かを判定し、高い場合にはＳ２２へ進み、そうでない場合には２３へ進む。Ｓ２２では、排気浄化触媒１０上流側の排気の酸素濃度が高いか否かを判定し、高い場合にはＳ２４へ進み、そうでない場合はＳ２５へ進む。Ｓ２３では、ＥＧＲ制御弁１５及び上流側制御弁２４を所定の開弁状態に制御し、下流側制御弁２５を閉弁状態に制御する。Ｓ１４では、ＥＧＲ制御弁１５及び下流側制御弁２５を所定の開弁状態に制御し、上流側制御弁２４を閉弁状態に制御する。Ｓ１５では、ＥＧＲ制御弁１５及び上流側制御弁２４を所定の開弁状態に制御し、下流側制御弁２５を閉弁状態に制御する。   FIG. 4 is a flowchart showing a flow of control of the upstream control valve 24 and the downstream control valve 25 in the second embodiment. In S21, it is determined whether or not the load of the internal combustion engine 1 is high. If it is high, the process proceeds to S22, and if not, the process proceeds to 23. In S22, it is determined whether or not the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 10 is high. If so, the process proceeds to S24, and if not, the process proceeds to S25. In S23, the EGR control valve 15 and the upstream side control valve 24 are controlled to a predetermined valve open state, and the downstream side control valve 25 is controlled to be closed. In S14, the EGR control valve 15 and the downstream control valve 25 are controlled to a predetermined valve open state, and the upstream control valve 24 is controlled to a closed state. In S15, the EGR control valve 15 and the upstream side control valve 24 are controlled to a predetermined valve open state, and the downstream side control valve 25 is controlled to be closed.

なお、上述した第２実施例おいては、内燃機関１の負荷が高く、排気浄化触媒１０上流側の排気の酸素濃度が高い場合に、排気浄化触媒１０下流側の排気をＥＧＲ通路１１に導入しているが、内燃機関１の負荷から推定される排気温度が非常に高く、改質触媒１３に流入する直前の排気温度が改質触媒１３の耐熱温度を越えるように予測される場合には、ＥＧＲ制御弁１５、上流側制御弁２４及び下流側制御弁２５を全て閉弁状態に制御して、改質触媒１３の熱劣化を確実に防止するようにしてもよい。   In the second embodiment described above, the exhaust gas on the downstream side of the exhaust purification catalyst 10 is introduced into the EGR passage 11 when the load on the internal combustion engine 1 is high and the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 10 is high. However, when the exhaust temperature estimated from the load of the internal combustion engine 1 is very high and the exhaust temperature immediately before flowing into the reforming catalyst 13 is predicted to exceed the heat resistance temperature of the reforming catalyst 13, The EGR control valve 15, the upstream side control valve 24, and the downstream side control valve 25 may all be controlled to be closed to reliably prevent thermal deterioration of the reforming catalyst 13.

また、上述した第２実施例においては、内燃機関１の負荷と排気浄化触媒１０上流側の排気の酸素濃度に応じて上流側制御弁２４及び下流側制御弁２５の開閉制御を実施しているが、排気浄化触媒１０上流側の排気の酸素濃度のみに応じて上流側制御弁２４及び下流側制御弁２５の開閉制御を実施することも可能である。   Further, in the second embodiment described above, opening / closing control of the upstream control valve 24 and the downstream control valve 25 is performed according to the load of the internal combustion engine 1 and the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10. However, the opening / closing control of the upstream control valve 24 and the downstream control valve 25 can be performed only in accordance with the oxygen concentration of the exhaust gas upstream of the exhaust purification catalyst 10.

この場合には、排気浄化触媒１０上流側の排気の酸素濃度が低ければ、ＥＧＲ制御弁１５及び上流側制御弁２４を開き、かつ下流側制御弁２５を閉じることでＥＧＲ通路２１に排気浄化触媒１０上流側の排気のみを導入する。また排気浄化触媒１０上流側の排気の酸素濃度が高ければ、ＥＧＲ制御弁１５及び下流側制御弁２５を開き、かつ上流側制御弁２４を閉じることでＥＧＲ通路２１に排気浄化触媒１０下流側の排気のみを導入する。   In this case, if the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 10 is low, the EGR control valve 15 and the upstream control valve 24 are opened, and the downstream control valve 25 is closed, so that the exhaust purification catalyst 21 enters the EGR passage 21. 10 Introduce only upstream exhaust. Also, if the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 10 is high, the EGR control valve 15 and the downstream control valve 25 are opened and the upstream control valve 24 is closed, so that the EGR passage 21 is connected to the downstream side of the exhaust purification catalyst 10. Introduce exhaust only.

酸素濃度が高い排気をＥＧＲ通路２１に導入した場合、この排気の温度が高ければ、排気中に含まれる酸素の酸化を利用した改質反応による発熱と、ＥＧＲ通路２１に導入される排気の元々の温度と、により改質触媒１３が過度に高温となってしまう可能性がある。また、排気浄化触媒１０下流側の排気は、上述したように酸素を殆ど含んでいないので、ＥＧＲ通路２１に導入しても酸素の酸化を利用した改質反応が改質触媒１３で進行せず、ＥＧＲ通路２１に導入される排気の元々の温度以上に改質触媒１３が高温となることはない。   When exhaust gas having a high oxygen concentration is introduced into the EGR passage 21, if the temperature of the exhaust gas is high, the heat generated by the reforming reaction utilizing oxidation of oxygen contained in the exhaust gas and the original exhaust gas introduced into the EGR passage 21. Depending on the temperature, the reforming catalyst 13 may become excessively hot. Further, since the exhaust gas downstream of the exhaust purification catalyst 10 hardly contains oxygen as described above, the reforming reaction utilizing oxidation of oxygen does not proceed in the reforming catalyst 13 even if it is introduced into the EGR passage 21. The reforming catalyst 13 does not become higher than the original temperature of the exhaust gas introduced into the EGR passage 21.

そこで、排気浄化触媒１３上流側の排気の酸素濃度が低い場合には、排気浄化触媒１０上流側から排気を導入することで、仮に排気温度が高かったとしても、排気中に含まれる酸素の酸化を利用した改質反応による発熱の影響で改質触媒１３の温度が過度に上昇してしまうことはなく、改質触媒１３の熱劣化を防止することができる。   Therefore, when the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 13 is low, the exhaust gas is introduced from the upstream side of the exhaust purification catalyst 10 to oxidize oxygen contained in the exhaust gas even if the exhaust temperature is high. The temperature of the reforming catalyst 13 does not rise excessively due to the heat generated by the reforming reaction utilizing the heat, and the thermal deterioration of the reforming catalyst 13 can be prevented.

また、排気浄化触媒１０上流側の排気の酸素濃度が高い場合には、排気浄化触媒１０下流側から排気を導入することで、排気中に含まれる酸素の酸化を利用した改質反応による発熱の影響で改質触媒１３の温度が過度に上昇してしまうことを防止し、改質触媒１３の熱劣化を防止することができる。   In addition, when the oxygen concentration in the exhaust gas upstream of the exhaust purification catalyst 10 is high, the exhaust gas is introduced from the downstream side of the exhaust purification catalyst 10 to generate heat due to the reforming reaction utilizing oxidation of oxygen contained in the exhaust gas. It is possible to prevent the temperature of the reforming catalyst 13 from rising excessively due to the influence, and to prevent thermal degradation of the reforming catalyst 13.

また、上述した第２実施例では、上流側制御弁２４と下流側制御弁２５のうちの一方を開くと他方を閉じるように制御しているが、内燃機関１から排出される排気温度（排気浄化触媒１０上流側の排気温度）に応じて、上流側排気導入部２２から導入される排気量と下流側排気導入部２３から導入される排気量との比率を調整して、改質触媒１３に導入される排気の温度及び酸素濃度がそれぞれ所望の値となるように制御することも可能である。   Further, in the second embodiment described above, control is performed such that when one of the upstream control valve 24 and the downstream control valve 25 is opened, the other is closed, but the exhaust temperature (exhaust gas) discharged from the internal combustion engine 1 is controlled. The ratio of the exhaust amount introduced from the upstream exhaust introduction portion 22 and the exhaust amount introduced from the downstream exhaust introduction portion 23 is adjusted according to the exhaust temperature upstream of the purification catalyst 10), and the reforming catalyst 13 It is also possible to control the temperature and oxygen concentration of the exhaust gas introduced into the gas so as to have desired values.

例えば、内燃機関１が低負荷で、排気浄化触媒１０上流側の排気温度が所定温度以下（例えば６００℃以下）となるような場合には、改質触媒１３において酸素の酸化を利用した改質反応を進行させて水素を生成するべく、上流側排気導入部２２から導入される排気量を下流側排気導入部２３から導入される排気量よりも多くする。また、内燃機関１が高負荷で、排気浄化触媒１０上流側の排気温度が所定温度（例えば６５０℃）よりも高くなるような場合には、酸素の酸化を利用した改質反応により改質触媒１３の温度が過度に高温にならないように、下流側排気導入部２３から導入される排気量を上流側排気導入部２２から導入される排気量よりも多くする。なお、排気浄化触媒１０上流側の排気温度は、例えば内燃機関の負荷と排気温度とを関連付けたマップを用いて算出してもよいし、温度センサで検知するようにしてもよい。   For example, when the internal combustion engine 1 has a low load and the exhaust temperature upstream of the exhaust purification catalyst 10 becomes a predetermined temperature or lower (for example, 600 ° C. or lower), the reforming catalyst 13 uses oxygen oxidation for reforming. In order to generate hydrogen by advancing the reaction, the exhaust amount introduced from the upstream side exhaust introduction unit 22 is made larger than the exhaust amount introduced from the downstream side exhaust introduction unit 23. Further, when the internal combustion engine 1 is heavily loaded and the exhaust temperature upstream of the exhaust purification catalyst 10 becomes higher than a predetermined temperature (for example, 650 ° C.), the reforming catalyst is formed by a reforming reaction utilizing oxygen oxidation. The amount of exhaust introduced from the downstream side exhaust introduction part 23 is made larger than the amount of exhaust introduced from the upstream side exhaust introduction part 22 so that the temperature of 13 does not become excessively high. The exhaust temperature upstream of the exhaust purification catalyst 10 may be calculated using, for example, a map that associates the load of the internal combustion engine and the exhaust temperature, or may be detected by a temperature sensor.

図５は本発明の第３実施例における内燃機関の排気還流装置の全体構成を模式的に示した説明図である。この第３実施例は、上述した第２実施例と略同一構成となっているが、この第３実施例においては、排気浄化触媒１０上流側の排気の酸素濃度を検知する酸素センサが省略された構成となっている。   FIG. 5 is an explanatory view schematically showing the overall configuration of an exhaust gas recirculation device for an internal combustion engine in a third embodiment of the present invention. This third embodiment has substantially the same configuration as the second embodiment described above, but in this third embodiment, an oxygen sensor for detecting the oxygen concentration of the exhaust upstream of the exhaust purification catalyst 10 is omitted. It becomes the composition.

このような第３実施例においては、内燃機関１の負荷に応じて、上流側制御弁２４及び下流側制御弁２５の開閉制御を以下のように実施する。   In the third embodiment, the opening / closing control of the upstream control valve 24 and the downstream control valve 25 is performed as follows according to the load of the internal combustion engine 1.

内燃機関１の負荷が予め設定された所定の負荷よりも低い場合には、ＥＧＲ制御弁１５及び上流側制御弁２４を開き、かつ下流側制御弁２５を閉じることでＥＧＲ通路２１に排気浄化触媒１０上流側の排気のみを導入する。このとき改質用燃料噴射弁１２から改質用燃料を噴射すれば、改質触媒１３において主として酸素の酸化を利用した改質反応から水素が生成される。   When the load of the internal combustion engine 1 is lower than a predetermined load set in advance, the EGR control valve 15 and the upstream control valve 24 are opened, and the downstream control valve 25 is closed, so that the exhaust gas purification catalyst is provided in the EGR passage 21. 10 Introduce only upstream exhaust. If the reforming fuel is injected from the reforming fuel injection valve 12 at this time, hydrogen is generated in the reforming catalyst 13 mainly from the reforming reaction utilizing oxidation of oxygen.

これにより、燃焼室２から排出される排気の温度が低くても、排気中に含まれる酸素の酸化を利用した改質反応により、改質触媒１３で水素を生成することができる。そのため、比較的排気温度が高いときにのみ改質触媒１３で水素を生成する場合に比べ、吸気通路４に水素の導入が可能となる運転領域を拡大することができる。なお、内燃機関１の負荷が予め設定された所定の負荷よりも低い場合に、排気浄化触媒１０下流側からＥＧＲ通路１１に排気を導入すれば、排気浄化触媒１０を通過することで排気の温度がさらに低下したときに、改質触媒１３に流入する排気の温度が過度に低くなって排気中の水蒸気及び二酸化炭素を利用した改質反応が進行せず、改質触媒１３で水素が生成されない虞がある。   Thereby, even if the temperature of the exhaust gas discharged from the combustion chamber 2 is low, hydrogen can be generated by the reforming catalyst 13 by the reforming reaction utilizing oxidation of oxygen contained in the exhaust gas. Therefore, compared with the case where hydrogen is generated by the reforming catalyst 13 only when the exhaust temperature is relatively high, the operating range in which hydrogen can be introduced into the intake passage 4 can be expanded. If the exhaust gas is introduced into the EGR passage 11 from the downstream side of the exhaust purification catalyst 10 when the load of the internal combustion engine 1 is lower than a predetermined load set in advance, the temperature of the exhaust gas passes through the exhaust purification catalyst 10 and passes through the exhaust purification catalyst 10. When the temperature further decreases, the temperature of the exhaust gas flowing into the reforming catalyst 13 becomes excessively low, and the reforming reaction utilizing water vapor and carbon dioxide in the exhaust gas does not proceed, and hydrogen is not generated by the reforming catalyst 13. There is a fear.

また、改質触媒１３に付着した触媒毒を排気中に含まれる酸素を利用して燃焼除去できるので、触媒毒による改質触媒１３の改質反応の悪化を防止することができる。つまり、排気中に含まれる酸素を利用して、改質触媒１３で水素を生成すると同時に、改質触媒１３上の触媒毒成分を除去する再生処理を実施できる。   Further, since the catalyst poison adhering to the reforming catalyst 13 can be burned and removed using oxygen contained in the exhaust gas, it is possible to prevent the reforming reaction of the reforming catalyst 13 from deteriorating due to the catalyst poison. That is, the regeneration process for removing the catalyst poison component on the reforming catalyst 13 can be performed at the same time that hydrogen is generated by the reforming catalyst 13 using oxygen contained in the exhaust gas.

また、内燃機関１の負荷が予め設定された所定の負荷より高い場合には、ＥＧＲ制御弁１５及び下流側制御弁２５を開き、かつ上流側制御弁２４を閉じることでＥＧＲ通路２１に排気浄化触媒１０下流側の排気のみを導入する。このとき改質用燃料噴射弁１２から改質用燃料を噴射すれば、改質触媒１３において主として排気中の水蒸気及び二酸化炭素を利用した改質反応から水素が生成される。   Further, when the load of the internal combustion engine 1 is higher than a predetermined load set in advance, the EGR control valve 15 and the downstream control valve 25 are opened, and the upstream control valve 24 is closed, whereby the exhaust gas purification is performed in the EGR passage 21. Only the exhaust on the downstream side of the catalyst 10 is introduced. If the reforming fuel is injected from the reforming fuel injection valve 12 at this time, hydrogen is generated in the reforming catalyst 13 from the reforming reaction mainly using water vapor and carbon dioxide in the exhaust gas.

排気浄化触媒１０下流側から排気をＥＧＲ通路１１に導入することにより、改質触媒１３には、酸素を殆ど含んでいない排気が流入することになり、排気中の酸素の酸化を利用した改質反応は進行しないため、改質触媒１３が過度に高温となることを防止することができ、改質触媒の熱劣化を防止することができる。なお、排気浄化触媒１０下流側から排気をＥＧＲ通路１１に導入する場合、排気浄化触媒１０上流側から排気をＥＧＲ通路１１に導入する場合に比べて、改質触媒１３に排気が到達するまでの経路長が長くなり、その分放熱量も大きくなる。そこで、燃焼室２から排出される排気の温度が高く、酸素濃度が高い場合には、排気浄化触媒１０下流側から排気をＥＧＲ通路１１に導入する方が、改質触媒１３の熱劣化を防止する上で有効である。   By introducing exhaust gas into the EGR passage 11 from the downstream side of the exhaust purification catalyst 10, exhaust gas containing almost no oxygen flows into the reforming catalyst 13, and reforming utilizing oxidation of oxygen in the exhaust gas. Since the reaction does not proceed, it is possible to prevent the reforming catalyst 13 from becoming excessively high in temperature and to prevent thermal degradation of the reforming catalyst. In addition, when exhaust is introduced into the EGR passage 11 from the exhaust purification catalyst 10 downstream side, the exhaust gas reaches the reforming catalyst 13 as compared with when exhaust is introduced into the EGR passage 11 from the exhaust purification catalyst 10 upstream side. The length of the path becomes longer, and the amount of heat radiation increases accordingly. Therefore, when the temperature of the exhaust gas exhausted from the combustion chamber 2 is high and the oxygen concentration is high, it is better to introduce the exhaust gas into the EGR passage 11 from the downstream side of the exhaust purification catalyst 10 to prevent thermal deterioration of the reforming catalyst 13. It is effective in doing.

このような第３実施例においても、上述した第１実施例と同様に、改質触媒１３の熱劣化を防止しつつ、吸気通路４に水素の導入が可能となる運転領域を拡大して内燃機関１の燃費を大幅に向上させることができる。   In the third embodiment as well, as in the first embodiment described above, the operating range in which hydrogen can be introduced into the intake passage 4 is expanded while preventing the thermal deterioration of the reforming catalyst 13, and the internal combustion engine is expanded. The fuel consumption of the engine 1 can be greatly improved.

図６は、第３実施例における上流側制御弁２４及び下流側制御弁２５の制御の流れを示すフローチャートである。Ｓ３１では、内燃機関１の負荷が高い状態であるか否かを判定し、高い場合にはＳ３２へ進み、そうでない場合には３３へ進む。Ｓ３２では、ＥＧＲ制御弁１５及び下流側制御弁２５を所定の開弁状態に制御し、上流側制御弁２４を閉弁状態に制御する。Ｓ３３では、ＥＧＲ制御弁１５及び上流側制御弁２４を所定の開弁状態に制御し、下流側制御弁２５を閉弁状態に制御する。   FIG. 6 is a flowchart showing the flow of control of the upstream control valve 24 and the downstream control valve 25 in the third embodiment. In S31, it is determined whether or not the load of the internal combustion engine 1 is high. If so, the process proceeds to S32, and if not, the process proceeds to 33. In S32, the EGR control valve 15 and the downstream control valve 25 are controlled to be in a predetermined open state, and the upstream control valve 24 is controlled to be in a closed state. In S33, the EGR control valve 15 and the upstream control valve 24 are controlled to be in a predetermined open state, and the downstream control valve 25 is controlled to be in a closed state.

１…内燃機関
２…燃焼室
３…吸気弁
４…吸気通路
４ａ…コレクタ部
５…排気弁
６…排気通路
７…点火プラグ
８…スロットル弁
９…燃料噴射弁
１０…排気浄化触媒
１１…ＥＧＲ通路
１２…改質用燃料噴射弁
１３…改質触媒
１４…ＥＧＲクーラ
１５…ＥＧＲ制御弁
１６…ＥＣＵ
１７…酸素センサ
１８…アクセル開度センサ
２１…ＥＧＲ通路
２２…上流側排気導入部
２３…下流側排気導入部
２４…上流側制御弁
２５…下流側制御弁 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Combustion chamber 3 ... Intake valve 4 ... Intake passage 4a ... Collector part 5 ... Exhaust valve 6 ... Exhaust passage 7 ... Spark plug 8 ... Throttle valve 9 ... Fuel injection valve 10 ... Exhaust purification catalyst 11 ... EGR passage 12 ... Reforming fuel injection valve 13 ... Reforming catalyst 14 ... EGR cooler 15 ... EGR control valve 16 ... ECU
17 ... oxygen sensor 18 ... accelerator opening sensor 21 ... EGR passage 22 ... upstream exhaust introduction part 23 ... downstream exhaust introduction part 24 ... upstream control valve 25 ... downstream control valve

Claims (6)

内燃機関の排気通路に設けられた排気浄化触媒と、
上記排気浄化触媒上流側から上記内燃機関の吸気通路に排気を還流可能な排気還流通路と、
上記排気還流通路に改質用燃料を噴射する改質用燃料噴射手段と、
上記排気還流通路に設けられ、上記改質用燃料から水素を生成する改質触媒と、
上記内燃機関の運転状態に応じて上記吸気通路に還流する排気還流ガス量を調整する排気還流弁と、を有する内燃機関の排気還流装置において、
上記排気浄化触媒上流側の排気の酸素濃度を検知する酸素濃度検知手段を有し、
上記内燃機関の負荷が低い場合、上記排気浄化触媒上流側の排気を上記吸気通路に還流し、
上記内燃機関の負荷が高く、かつ上記酸素濃度検知手段で検知された酸素濃度が低い場合、上記排気浄化触媒上流側の排気を上記吸気通路に還流することを特徴とする内燃機関の排気還流装置。 An exhaust purification catalyst provided in the exhaust passage of the internal combustion engine;
An exhaust gas recirculation passage capable of recirculating exhaust gas from the upstream side of the exhaust purification catalyst to the intake passage of the internal combustion engine;
Reforming fuel injection means for injecting reforming fuel into the exhaust gas recirculation passage;
A reforming catalyst that is provided in the exhaust gas recirculation passage and generates hydrogen from the reforming fuel;
An exhaust gas recirculation device for an internal combustion engine, comprising: an exhaust gas recirculation valve that adjusts an amount of exhaust gas recirculation gas that recirculates to the intake passage according to an operating state of the internal combustion engine.
Oxygen concentration detection means for detecting the oxygen concentration of the exhaust upstream of the exhaust purification catalyst,
When the load of the internal combustion engine is low, the exhaust gas upstream of the exhaust purification catalyst is recirculated to the intake passage ,
An exhaust gas recirculation device for an internal combustion engine, wherein when the load on the internal combustion engine is high and the oxygen concentration detected by the oxygen concentration detection means is low, the exhaust gas upstream of the exhaust purification catalyst is recirculated to the intake passage. . 上記内燃機関の負荷が高く、かつ上記酸素濃度検知手段で検知された酸素濃度が高い場合、上記排気浄化触媒上流側から上記吸気通路への排気の還流を中止することを特徴とする請求項１に記載の内燃機関の排気還流装置。 The internal combustion engine load is high and when the oxygen concentration of oxygen concentration detected by the detection means is high, according to claim 1, characterized in that to stop the reflux from the exhaust purification catalyst upstream of the exhaust gas into the intake passage 2. An exhaust gas recirculation device for an internal combustion engine according to 1. 上記排気通路に接続される上記排気還流通路の一端側は、上記排気浄化触媒上流側で上記排気通路に接続される上流側排気導入部と、上記排気浄化触媒下流側で上記排気通路に接続される下流側排気導入部とに分岐するよう形成され、
上記内燃機関の負荷が低い場合、上記上流側排気導入部から排気を導入することを特徴とする請求項１に記載の内燃機関の排気還流装置。 One end of the exhaust gas recirculation passage connected to the exhaust passage is connected to the upstream exhaust introduction portion connected to the exhaust passage on the upstream side of the exhaust purification catalyst and to the exhaust passage on the downstream side of the exhaust purification catalyst. Branching to the downstream exhaust introduction part
The exhaust gas recirculation apparatus for an internal combustion engine according to claim 1, wherein when the load on the internal combustion engine is low, exhaust gas is introduced from the upstream side exhaust gas introduction section. 上記内燃機関の負荷が高く、かつ上記酸素濃度検知手段で検知された酸素濃度が低い場合、上記上流側排気導入部から排気を導入することを特徴とする請求項３に記載の内燃機関の排気還流装置。 The exhaust of the internal combustion engine according to claim 3, wherein when the load on the internal combustion engine is high and the oxygen concentration detected by the oxygen concentration detection means is low, exhaust is introduced from the upstream side exhaust introduction section. Reflux apparatus. 上記内燃機関の負荷が高く、かつ上記酸素濃度検知手段で検知された酸素濃度が高い場合、上記下流側排気導入部から排気を導入することを特徴とする請求項３または４に記載の内燃機関の排気還流装置。 High load of the internal combustion engine, and when the oxygen concentration detected oxygen concentration detection means is high, an internal combustion engine according to claim 3 or 4, characterized in that introducing the exhaust from the downstream exhaust inlet portion Exhaust gas recirculation device. 内燃機関の排気通路に設けられた排気浄化触媒と、
上記内燃機関の吸気通路に排気を還流する排気還流通路と、
上記排気還流通路に改質用燃料を噴射する改質用燃料噴射手段と、
上記排気還流通路に設けられ、上記改質用燃料により水素を含有するガスを生成する改質触媒と、
上記内燃機関の運転状態に応じて上記吸気通路に還流する排気還流ガス量を調整する排気還流弁と、
上記排気浄化触媒上流側の排気の酸素濃度を検知する酸素濃度検知手段と、
を有する内燃機関の排気還流装置において、
上記排気還流通路は、上記排気浄化触媒上流側の排気を導入する上流側排気導入部と、上記排気浄化触媒下流側の排気を導入する下流側排気導入部とを有し、
上記酸素濃度検知手段で検知された酸素濃度が低い場合、上記上流側排気導入部から上記排気還流通路への排気の導入を許可し、上記酸素濃度検知手段で検知された酸素濃度が高い場合、上記下流側排気導入部から上記排気還流通路への排気の導入を許可することを特徴とする内燃機関の排気還流装置。 An exhaust purification catalyst provided in the exhaust passage of the internal combustion engine;
An exhaust gas recirculation passage for recirculating exhaust gas to the intake passage of the internal combustion engine;
Reforming fuel injection means for injecting reforming fuel into the exhaust gas recirculation passage;
A reforming catalyst that is provided in the exhaust gas recirculation passage and generates a gas containing hydrogen by the reforming fuel;
An exhaust gas recirculation valve that adjusts an amount of exhaust gas recirculation gas that recirculates to the intake passage according to the operating state of the internal combustion engine;
Oxygen concentration detection means for detecting the oxygen concentration of the exhaust upstream of the exhaust purification catalyst;
In an exhaust gas recirculation device for an internal combustion engine having
The exhaust gas recirculation passage includes an upstream side exhaust introduction part that introduces exhaust gas on the upstream side of the exhaust purification catalyst, and a downstream side exhaust introduction part that introduces exhaust gas on the downstream side of the exhaust purification catalyst,
When the oxygen concentration detected by the oxygen concentration detection means is low, the introduction of the exhaust gas from the upstream exhaust introduction part to the exhaust gas recirculation passage is permitted, and when the oxygen concentration detected by the oxygen concentration detection means is high, An exhaust gas recirculation apparatus for an internal combustion engine, which permits introduction of exhaust gas from the downstream exhaust gas introduction portion into the exhaust gas recirculation passage.
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