JP2009138531A - Control device for internal combustion engine - Google Patents

Control device for internal combustion engine Download PDF

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JP2009138531A
JP2009138531A JP2007312565A JP2007312565A JP2009138531A JP 2009138531 A JP2009138531 A JP 2009138531A JP 2007312565 A JP2007312565 A JP 2007312565A JP 2007312565 A JP2007312565 A JP 2007312565A JP 2009138531 A JP2009138531 A JP 2009138531A
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reforming
fuel
egr
air
internal combustion
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Hideo Yahagi
秀夫 矢作
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Toyota Motor Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of surely preventing oxidation reaction of fuel in a fuel reforming catalyst, and capable of surely suppressing deterioration of the fuel reforming catalyst. <P>SOLUTION: The fuel reforming catalyst 26 is provided in the halfway of EGR passages 32 and 36 of the internal combustion engine 10. Reforming fuel is injected into EGR gas by a reforming fuel injection device 34. The fuel reforming catalyst 26 generates reformed gas including a combustible component by reforming and reacting the EGR gas with the reforming fuel. During execution of reforming operation, an air fuel ratio of cylinders of the internal combustion engine 10 is all controlled to be in a rich air-fuel ratio equal to or less than a stoichiometric air-fuel ratio. Before starting reforming operation, it is preferable to perform EGR operation without reforming in the rich air-fuel ratio. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、内燃機関の制御装置に関する。   The present invention relates to a control device for an internal combustion engine.

ガソリンやバイオ燃料等の燃料と、ＥＧＲガスとを改質反応させる燃料改質触媒を備えた内燃機関が知られている。この内燃機関では、排気ガスの熱等によって加熱した燃料改質触媒において燃料とＥＧＲガスとを反応させることにより、それらを改質ガスに転換させる。改質ガス中には、改質反応により水素ガスおよび一酸化炭素ガスが生成している。この改質ガスは、吸気通路に還流される。そして、改質ガス中の水素および一酸化炭素は、筒内または吸気通路内に噴射された燃料と共に、内燃機関の燃焼室で燃焼する。   There is known an internal combustion engine including a fuel reforming catalyst that performs a reforming reaction between a fuel such as gasoline or biofuel and EGR gas. In this internal combustion engine, fuel and EGR gas are reacted in a fuel reforming catalyst heated by the heat of exhaust gas or the like to convert them into reformed gas. In the reformed gas, hydrogen gas and carbon monoxide gas are generated by the reforming reaction. This reformed gas is returned to the intake passage. The hydrogen and carbon monoxide in the reformed gas are burned in the combustion chamber of the internal combustion engine together with the fuel injected into the cylinder or the intake passage.

上記のような燃料改質を実行する改質運転中に、内燃機関が理論空燃比よりもリーンな空燃比で運転されると、ＥＧＲガス中に酸素が残存するので、燃料改質触媒に酸素が流入することとなる。そうすると、ＥＧＲガス中に添加された燃料が燃料改質触媒において酸化反応（つまり燃焼）し、燃料改質触媒の温度が過上昇して、触媒シンタリング（触媒粒の粗大化）等の触媒劣化や触媒担体の溶損等の触媒故障を生じ易い。   If the internal combustion engine is operated at an air / fuel ratio that is leaner than the stoichiometric air / fuel ratio during the reforming operation that performs the fuel reform as described above, oxygen remains in the EGR gas. Will flow in. Then, the fuel added to the EGR gas undergoes an oxidation reaction (that is, combustion) in the fuel reforming catalyst, the temperature of the fuel reforming catalyst is excessively increased, and catalyst deterioration such as catalyst sintering (coarse particle coarsening) occurs. And catalyst failure such as melting of the catalyst carrier is likely to occur.

特開２００６−３７８１７号公報には、リーン燃焼を行う３つの気筒と、リッチ燃焼を行う１つの気筒とを有する４気筒エンジンにおいて、リッチ燃焼気筒の排気枝管にＥＧＲ通路を接続することにより、酸素を含まないリッチ空燃比のＥＧＲガスを燃料改質触媒に流入させるようにする技術が開示されている。   JP-A-2006-37817 discloses a four-cylinder engine having three cylinders that perform lean combustion and one cylinder that performs rich combustion, by connecting an EGR passage to the exhaust branch pipe of the rich combustion cylinder, A technique for allowing a rich air-fuel ratio EGR gas not containing oxygen to flow into a fuel reforming catalyst is disclosed.

特開２００６−３７８１７号公報JP 2006-37817 A 特開２００６−３７８１６号公報JP 2006-37816 A

しかしながら、排気マニホールド内においては、各気筒の排気脈動の影響により、ある気筒の排気ガスが他の気筒の排気枝管に回り込む場合がある。このため、上記従来のシステムでは、リーン燃焼気筒から排出された酸素を含む排気ガスがＥＧＲ通路を通って燃料改質触媒に流入する可能性を払拭できない。また、上記従来のシステムでは、ＥＧＲ通路が一つの気筒の排気枝管に接続されているので、ＥＧＲガスを大量に取り出すことが困難である。このため、改質ガス流量が制限されるので、燃料改質によるメリットを十分に享受しにくいという問題もある。   However, in the exhaust manifold, the exhaust gas of one cylinder may circulate into the exhaust branch pipe of another cylinder due to the influence of exhaust pulsation of each cylinder. For this reason, in the conventional system, the possibility that exhaust gas containing oxygen discharged from the lean combustion cylinder flows into the fuel reforming catalyst through the EGR passage cannot be eliminated. Further, in the conventional system, since the EGR passage is connected to the exhaust branch pipe of one cylinder, it is difficult to take out a large amount of EGR gas. For this reason, since the reformed gas flow rate is limited, there is also a problem that it is difficult to fully enjoy the merits of fuel reforming.

本発明は、上記の点に鑑みてなされたものであり、燃料改質触媒における燃料の酸化反応を確実に防止し、燃料改質触媒の劣化等を確実に抑制することのできる内燃機関の制御装置を提供することを目的とする。   The present invention has been made in view of the above points, and controls an internal combustion engine that can reliably prevent an oxidation reaction of a fuel in a fuel reforming catalyst and reliably suppress deterioration of the fuel reforming catalyst. An object is to provide an apparatus.

第１の発明は、上記の目的を達成するため、内燃機関の制御装置であって、
多気筒型の内燃機関の排気通路と吸気通路とを接続するＥＧＲ通路と、
前記ＥＧＲ通路を流れるＥＧＲガス中に燃料を噴射する改質用燃料噴射手段と、
前記ＥＧＲ通路の途中であって前記改質用燃料噴射手段の下流側に配置され、前記ＥＧＲガスと前記改質用燃料とを改質反応させることにより、それらを、改質反応生成物である可燃成分を含む改質ガスに転換させる燃料改質触媒と、
前記改質反応に要する熱を前記燃料改質触媒に供給する熱供給手段と、
前記改質用燃料噴射手段により燃料を供給しつつ前記改質ガスを前記吸気通路に還流させる改質運転と、前記改質用燃料噴射手段から燃料を噴射しない非改質運転とを切り換える運転切換手段と、
前記改質運転の実行中に、前記内燃機関の各気筒の空燃比を何れも理論空燃比以下のリッチ空燃比に維持する改質運転時空燃比制御手段と、
を備えることを特徴とする。 In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An EGR passage connecting an exhaust passage and an intake passage of a multi-cylinder internal combustion engine;
Fuel reforming means for injecting fuel into EGR gas flowing through the EGR passage;
It is disposed in the middle of the EGR passage and downstream of the reforming fuel injection means, and reforms the EGR gas and the reforming fuel, so that they are reforming reaction products. A fuel reforming catalyst for converting to a reformed gas containing a combustible component;
Heat supply means for supplying heat required for the reforming reaction to the fuel reforming catalyst;
Operation switching for switching between a reforming operation in which the reformed gas is recirculated to the intake passage while fuel is supplied by the reforming fuel injection means and a non-reforming operation in which no fuel is injected from the reforming fuel injection means. Means,
A reforming operation air-fuel ratio control means for maintaining the air-fuel ratio of each cylinder of the internal combustion engine at a rich air-fuel ratio equal to or lower than the stoichiometric air-fuel ratio during execution of the reforming operation;
It is characterized by providing.

また、第２の発明は、第１の発明において、
前記非改質運転には、ＥＧＲガスを前記吸気通路に還流させるＥＧＲを実行する改質無しＥＧＲ運転と、前記ＥＧＲを実行しない非ＥＧＲ運転とが含まれ、
前記運転切換手段は、前記非改質運転から前記改質運転に切り換える場合に、前記改質無しＥＧＲ運転を実行する期間を経てから前記改質運転を開始することを特徴とする。 The second invention is the first invention, wherein
The non-reforming operation includes a non-reforming EGR operation that executes EGR for returning EGR gas to the intake passage, and a non-EGR operation that does not execute the EGR,
The operation switching means starts the reforming operation after a period of executing the non-reforming EGR operation when switching from the non-reforming operation to the reforming operation.

また、第３の発明は、第２の発明において、
前記改質運転を開始する前の前記改質無しＥＧＲ運転の実行中に、前記燃料改質触媒に流入するＥＧＲガスの空燃比を理論空燃比以下のリッチ空燃比とする改質運転前空燃比制御手段を備えることを特徴とする。 The third invention is the second invention, wherein
During the execution of the non-reforming EGR operation before starting the reforming operation, the air-fuel ratio before the reforming operation is set so that the air-fuel ratio of the EGR gas flowing into the fuel reforming catalyst is a rich air-fuel ratio equal to or lower than the theoretical air-fuel ratio. Control means is provided.

また、第４の発明は、第１乃至第３の発明の何れかにおいて、
前記熱供給手段は、前記内燃機関の排気ガスの熱を前記燃料改質触媒に伝熱させる熱交換器で構成されていることを特徴とする。 According to a fourth invention, in any one of the first to third inventions,
The heat supply means is constituted by a heat exchanger that transfers heat of exhaust gas of the internal combustion engine to the fuel reforming catalyst.

第１の発明によれば、改質運転の実行中に、内燃機関の各気筒の空燃比を何れも理論空燃比以下のリッチ空燃比に維持することができる。これにより、改質運転の実行中、何れの気筒から排出される排気ガスの中にも酸素が残存しなくなるので、排気脈動等の影響にかかわらず、ＥＧＲ通路に酸素が流入することを確実に防止することができる。このため、燃料改質触媒で改質用燃料の酸化反応が生ずることを確実に阻止することができ、燃料改質触媒の過昇温を確実に防止することができるので、燃料改質触媒の劣化や故障を確実に回避することができる。   According to the first invention, during the reforming operation, the air-fuel ratio of each cylinder of the internal combustion engine can be maintained at a rich air-fuel ratio equal to or lower than the stoichiometric air-fuel ratio. As a result, oxygen does not remain in the exhaust gas discharged from any cylinder during the reforming operation, so that oxygen can surely flow into the EGR passage regardless of the influence of exhaust pulsation or the like. Can be prevented. For this reason, it is possible to reliably prevent the oxidation reaction of the reforming fuel from occurring in the fuel reforming catalyst, and it is possible to reliably prevent overheating of the fuel reforming catalyst. Deterioration and failure can be avoided reliably.

第２の発明によれば、非改質運転から改質運転に切り換える場合に、改質無しＥＧＲ運転を実行する期間を経てから改質運転を開始することができる。これにより、改質運転の開始前に、ＥＧＲガスの熱によって燃料改質触媒を十分に予熱することができる。このため、改質運転の開始後、改質反応を安定して生起させることができ、改質効率を十分に高めることができる。また、ＥＧＲ流量の制御を開始し、ＥＧＲ流量が目標値に安定的に制御されるようになった後に、改質反応量の制御を開始することができる。このため、改質運転に切り換えた後、燃焼室への可燃成分流入量の制御誤差を抑制することができ、空燃比やトルクなどを精度良く制御することができる。   According to the second aspect of the invention, when switching from the non-reforming operation to the reforming operation, the reforming operation can be started after a period for executing the non-reforming EGR operation. Thereby, the fuel reforming catalyst can be sufficiently preheated by the heat of the EGR gas before the start of the reforming operation. For this reason, after the start of the reforming operation, the reforming reaction can be stably caused, and the reforming efficiency can be sufficiently increased. Further, the control of the reforming reaction amount can be started after the control of the EGR flow rate is started and the EGR flow rate is stably controlled to the target value. For this reason, after switching to the reforming operation, the control error of the inflow amount of combustible components into the combustion chamber can be suppressed, and the air-fuel ratio, torque, and the like can be controlled with high accuracy.

第３の発明によれば、改質運転を開始する前の改質無しＥＧＲ運転の実行中に、燃料改質触媒に流入するＥＧＲガスの空燃比を理論空燃比以下のリッチ空燃比とすることにより、燃料改質触媒に吸着された酸素を事前に除去することができる。このため、当該酸素による改質効率の低下や改質反応の不安定化を確実に回避することができる。   According to the third aspect of the invention, the air-fuel ratio of the EGR gas flowing into the fuel reforming catalyst is set to a rich air-fuel ratio equal to or lower than the stoichiometric air-fuel ratio during execution of the non-reforming EGR operation before starting the reforming operation. Thus, oxygen adsorbed on the fuel reforming catalyst can be removed in advance. For this reason, the reduction | decrease of the reforming efficiency by the said oxygen and the destabilization of reforming reaction can be avoided reliably.

第４の発明によれば、内燃機関の排気ガスの熱を燃料改質触媒に伝熱させ、燃料改質反応に吸熱させることができる。このため、内燃機関の廃熱を回収することができ、熱効率を十分に向上することができる。   According to the fourth invention, the heat of the exhaust gas of the internal combustion engine can be transferred to the fuel reforming catalyst and absorbed in the fuel reforming reaction. For this reason, the waste heat of an internal combustion engine can be collect | recovered and thermal efficiency can fully be improved.

実施の形態１．
図１は、実施の形態１のシステム構成を説明するための全体構成図を示している。本実施形態のシステムは、多気筒型（図示の構成では４気筒）の内燃機関１０を備えている。本システムで使用される燃料は、特に限定されず、ガソリン等の炭化水素燃料のほかに、アルコール（例えばエタノール）等のバイオマス由来成分を含むバイオ燃料などを用いることもできる。 Embodiment 1 FIG.
FIG. 1 shows an overall configuration diagram for explaining the system configuration of the first embodiment. The system of this embodiment includes a multi-cylinder type (four cylinders in the illustrated configuration) internal combustion engine 10. The fuel used in the present system is not particularly limited, and a biofuel containing a biomass-derived component such as alcohol (for example, ethanol) can be used in addition to a hydrocarbon fuel such as gasoline.

内燃機関１０の吸気通路１２は、吸気マニホールド１４を介して各気筒の吸気ポートに接続されている。吸気通路１２の途中には、吸入空気量を調整する電動式のスロットル弁１６が設置されている。各気筒の吸気ポートには、燃料を噴射するための電磁弁等からなる主燃料噴射装置１８がそれぞれ設けられている。なお、主燃料噴射装置１８は、吸気ポート内でなく、筒内に燃料を直接に噴射するように設けられていてもよい。   An intake passage 12 of the internal combustion engine 10 is connected to an intake port of each cylinder via an intake manifold 14. In the middle of the intake passage 12, an electric throttle valve 16 for adjusting the amount of intake air is installed. A main fuel injection device 18 including an electromagnetic valve or the like for injecting fuel is provided in each intake port of each cylinder. The main fuel injection device 18 may be provided so as to inject fuel directly into the cylinder instead of in the intake port.

内燃機関１０の排気通路２０は、排気マニホールド２２を介して各気筒の排気ポートに接続されている。排気通路２０の途中には、燃料改質器２４が設けられている。燃料改質器２４の内部には、燃料改質触媒２６と排気通路２８とが設けられている。燃料改質触媒２６内には、後述する改質反応を触媒する作用を有する金属（例えばＲｈ、Ｐｔ、Ｃｏ、Ｎｉ等）が担体に担持されて設置されている。   An exhaust passage 20 of the internal combustion engine 10 is connected to an exhaust port of each cylinder via an exhaust manifold 22. A fuel reformer 24 is provided in the middle of the exhaust passage 20. Inside the fuel reformer 24, a fuel reforming catalyst 26 and an exhaust passage 28 are provided. In the fuel reforming catalyst 26, a metal (for example, Rh, Pt, Co, Ni, etc.) having an action of catalyzing a reforming reaction to be described later is installed on a carrier.

燃料改質触媒２６と排気通路２８とは、隔壁で隔てられ、遮断されている。燃料改質触媒２６は、排気通路２８を通る排気ガスの熱を受熱することができる。燃料改質触媒２６は、その受熱した熱を反応熱とすることにより、後述する改質反応を生じさせることができる。すなわち、燃料改質器２４は、排気通路２８を通る排気ガスの熱を燃料改質触媒２６に伝熱させる熱交換器としての機能を有している。図示の構成では、排気通路２８は、並行する複数の通路で構成されている。そして、排気通路２８の入口は排気通路２０に接続され、排気通路２８の出口は排気通路３０に接続されている。   The fuel reforming catalyst 26 and the exhaust passage 28 are separated from each other by a partition wall and blocked. The fuel reforming catalyst 26 can receive the heat of the exhaust gas passing through the exhaust passage 28. The fuel reforming catalyst 26 can cause a reforming reaction to be described later by using the received heat as reaction heat. That is, the fuel reformer 24 has a function as a heat exchanger that transfers the heat of the exhaust gas passing through the exhaust passage 28 to the fuel reforming catalyst 26. In the illustrated configuration, the exhaust passage 28 includes a plurality of parallel passages. The inlet of the exhaust passage 28 is connected to the exhaust passage 20, and the outlet of the exhaust passage 28 is connected to the exhaust passage 30.

排気マニホールド２２の集合部より下流側であって、燃料改質器２４の上流側の排気通路２０からは、ＥＧＲ通路３２が分岐している。このＥＧＲ通路３２によれば、排気通路２０を通る排気ガスの一部をＥＧＲガスとして取り出すことができる。ＥＧＲ通路３２は、燃料改質触媒２６に接続されている。ＥＧＲ通路３２の途中には、改質反応に供するための燃料（以下、改質用燃料とも言う）をＥＧＲガス中に噴射する改質用燃料噴射装置３４が設けられている。改質用燃料噴射装置３４から噴射された燃料は、ＥＧＲガスと共に燃料改質触媒２６に流入し、燃料改質触媒２６の作用によって改質反応を起こす。   An EGR passage 32 is branched from the exhaust passage 20 on the downstream side of the collecting portion of the exhaust manifold 22 and on the upstream side of the fuel reformer 24. According to the EGR passage 32, a part of the exhaust gas passing through the exhaust passage 20 can be taken out as EGR gas. The EGR passage 32 is connected to the fuel reforming catalyst 26. In the middle of the EGR passage 32, a reforming fuel injection device 34 for injecting fuel for use in the reforming reaction (hereinafter also referred to as reforming fuel) into the EGR gas is provided. The fuel injected from the reforming fuel injection device 34 flows into the fuel reforming catalyst 26 together with the EGR gas, and causes a reforming reaction by the action of the fuel reforming catalyst 26.

燃料改質触媒２６には、ＥＧＲ通路３６の一端が更に接続されている。このＥＧＲ通路３６の他端は、吸気通路１２に接続されている。このＥＧＲ通路３６を通して、後述する改質ガス、あるいは単なるＥＧＲガスを、吸気通路１２内に還流させ、吸入空気と混合させることができる。ＥＧＲ通路３６の途中には、ＥＧＲ通路３６を通るガスを冷却するＥＧＲクーラ３８と、ＥＧＲ通路３６を開閉可能な電磁弁等で構成されるＥＧＲ弁４０とが設けられている。   One end of an EGR passage 36 is further connected to the fuel reforming catalyst 26. The other end of the EGR passage 36 is connected to the intake passage 12. Through this EGR passage 36, a reformed gas, which will be described later, or a simple EGR gas can be recirculated into the intake passage 12 and mixed with the intake air. In the middle of the EGR passage 36, an EGR cooler 38 that cools the gas passing through the EGR passage 36, and an EGR valve 40 that includes an electromagnetic valve that can open and close the EGR passage 36 are provided.

排気通路２０を流れる排気ガスのうち、ＥＧＲ通路３２に流入しなかった残りの排気ガスは、排気通路２８，３０を順次通過して、大気中に放出される。燃料改質器２４の下流側の排気通路３０の途中には、有害成分を浄化する三元触媒等を担持した排気浄化触媒４２や、図示しないマフラーが配置されている。また、排気通路２８に、有害成分を浄化する触媒が担持されていてもよい。排気通路２８に排気浄化触媒を担持させることにより、浄化反応の反応熱を排気通路２８で発生させることができるので、燃料改質触媒２６の受熱量（熱回収量）を更に増大させることができ、改質効率を更に向上することができる。   Of the exhaust gas flowing through the exhaust passage 20, the remaining exhaust gas that has not flowed into the EGR passage 32 sequentially passes through the exhaust passages 28 and 30 and is released into the atmosphere. In the middle of the exhaust passage 30 on the downstream side of the fuel reformer 24, an exhaust purification catalyst 42 carrying a three-way catalyst for purifying harmful components and a muffler (not shown) are arranged. The exhaust passage 28 may carry a catalyst for purifying harmful components. By carrying the exhaust purification catalyst in the exhaust passage 28, reaction heat of the purification reaction can be generated in the exhaust passage 28, so that the amount of heat received by the fuel reforming catalyst 26 (heat recovery amount) can be further increased. The reforming efficiency can be further improved.

内燃機関１０が使用する燃料は、燃料タンク４４に貯留されている。燃料タンク４４には、タンク内の燃料を加圧した状態で外部に送出するための燃料ポンプ（図示せず）が付設されている。この燃料ポンプの吐出側には、ポンプから吐出された燃料を主燃料噴射装置１８及び改質用燃料噴射装置３４にそれぞれ供給する燃料配管４６が接続されている。   The fuel used by the internal combustion engine 10 is stored in the fuel tank 44. The fuel tank 44 is provided with a fuel pump (not shown) for sending the fuel in the tank to the outside in a pressurized state. Connected to the discharge side of the fuel pump is a fuel pipe 46 for supplying the fuel discharged from the pump to the main fuel injection device 18 and the reforming fuel injection device 34, respectively.

更に、本実施形態のシステムは、ＥＣＵ（Electronic Control Unit）５０を備えている。ＥＣＵ５０は、ＲＯＭ、ＲＡＭ等の記憶回路を備えたマイクロコンピュータによって構成されている。ＥＣＵ５０の入力側には、触媒温度センサ５４、空燃比センサ５６、水素濃度センサ５８等を含むセンサ系統が接続されている。   Furthermore, the system of the present embodiment includes an ECU (Electronic Control Unit) 50. The ECU 50 is constituted by a microcomputer provided with a storage circuit such as a ROM and a RAM. A sensor system including a catalyst temperature sensor 54, an air-fuel ratio sensor 56, a hydrogen concentration sensor 58, and the like is connected to the input side of the ECU 50.

触媒温度センサ５４は、燃料改質触媒２６に設けられており、燃料改質触媒２６の温度を検出する。空燃比センサ５６は、排気通路２０に設けられており、排気ガスの空燃比に応じた検出信号を出力する。水素濃度センサ５８は、ＥＧＲ通路３６の途中に設けられており、ＥＧＲ通路３６を通る改質ガス中の水素濃度（Ｈ2濃度）に応じた検出信号を出力する。 The catalyst temperature sensor 54 is provided in the fuel reforming catalyst 26 and detects the temperature of the fuel reforming catalyst 26. The air-fuel ratio sensor 56 is provided in the exhaust passage 20 and outputs a detection signal corresponding to the air-fuel ratio of the exhaust gas. The hydrogen concentration sensor 58 is provided in the middle of the EGR passage 36, and outputs a detection signal corresponding to the hydrogen concentration (H 2 concentration) in the reformed gas passing through the EGR passage 36.

また、センサ系統には、例えば機関回転数を検出する回転センサ、吸入空気量を検出するエアフローメータ、冷却水温度を検出する水温センサ、アクセル開度を検出するアクセル開度センサ、スロットル弁１６の開度を検出するスロットル開度センサ等のように、内燃機関１０の運転制御に用いられる一般的なセンサが含まれている。   The sensor system includes, for example, a rotation sensor that detects the engine speed, an air flow meter that detects the intake air amount, a water temperature sensor that detects the cooling water temperature, an accelerator opening sensor that detects the accelerator opening, and a throttle valve 16. A general sensor used for operation control of the internal combustion engine 10 is included, such as a throttle opening sensor for detecting the opening.

一方、ＥＣＵ５０の出力側には、前述したスロットル弁１６、主燃料噴射装置１８、改質用燃料噴射装置３４、ＥＧＲ弁４０、燃料ポンプ等を含む各種のアクチュエータが接続されている。そして、ＥＣＵ５０は、内燃機関１０の運転状態をセンサ系統によって検出しつつ、各アクチュエータを駆動することによって運転制御を行う。   On the other hand, on the output side of the ECU 50, various actuators including the throttle valve 16, the main fuel injection device 18, the reforming fuel injection device 34, the EGR valve 40, the fuel pump and the like are connected. The ECU 50 controls the operation by driving the actuators while detecting the operation state of the internal combustion engine 10 using the sensor system.

（空燃比フィードバック制御）
ＥＣＵ５０は、エアフローメータで検出される吸入空気量等に基づいて、主燃料噴射装置１８から噴射すべき燃料量を算出する。また、ＥＣＵ５０は、空燃比センサ５６の検出信号に基づいて主燃料噴射装置１８の燃料噴射量を補正する空燃比フィードバック制御を行うことにより、内燃機関１０の空燃比（排気通路２０を流れる排気ガスの空燃比）が目標空燃比となるように制御することができる。 (Air-fuel ratio feedback control)
The ECU 50 calculates the amount of fuel to be injected from the main fuel injector 18 based on the intake air amount detected by the air flow meter. Further, the ECU 50 performs air-fuel ratio feedback control for correcting the fuel injection amount of the main fuel injection device 18 based on the detection signal of the air-fuel ratio sensor 56, so that the air-fuel ratio of the internal combustion engine 10 (exhaust gas flowing through the exhaust passage 20). The air / fuel ratio) can be controlled to be the target air / fuel ratio.

（改質運転）
内燃機関１０は、排気ガス（ＥＧＲガス）と改質用燃料との改質反応によって生成された改質ガスを吸気通路１２内に還流させる改質運転を実行可能になっている。改質運転時には、ＥＧＲ通路３２内を流れるＥＧＲガスに対して改質用燃料噴射装置３４から改質用燃料を噴射することにより、改質用燃料を燃料改質触媒２６に供給する。このとき、ＥＣＵ５０は、例えば内燃機関１０の運転状態、ＥＧＲ流量、燃料改質触媒２６の温度等に応じて、改質用燃料の適切な噴射量（供給量）を決定する。 (Reforming operation)
The internal combustion engine 10 is capable of executing a reforming operation in which the reformed gas generated by the reforming reaction between the exhaust gas (EGR gas) and the reforming fuel is recirculated into the intake passage 12. During the reforming operation, the reforming fuel is supplied from the reforming fuel injection device 34 to the EGR gas flowing in the EGR passage 32, thereby supplying the reforming fuel to the fuel reforming catalyst 26. At this time, the ECU 50 determines an appropriate injection amount (supply amount) of the reforming fuel according to, for example, the operating state of the internal combustion engine 10, the EGR flow rate, the temperature of the fuel reforming catalyst 26, and the like.

燃料改質触媒２６内では、触媒作用を有する前述したような種類の金属の作用により、改質用燃料と、ＥＧＲガス中の成分とが改質反応（水蒸気改質反応）を起こす。燃料改質触媒２６で生ずる主な改質反応の化学反応式は、改質用燃料が例えばガソリンである場合には下記式（１）で、改質用燃料が例えばエタノールである場合には下記式（２）で、それぞれ表すことができる。   In the fuel reforming catalyst 26, the reforming fuel and the components in the EGR gas cause a reforming reaction (steam reforming reaction) by the action of the above-described type of metal having catalytic action. The chemical reaction formula of the main reforming reaction occurring in the fuel reforming catalyst 26 is the following formula (1) when the reforming fuel is gasoline, for example, and when the reforming fuel is ethanol, for example, Each can be represented by formula (2).

1.56（7.6CO2＋6.8H2O＋40.8N2）＋3C7.6H13.6＋Q1
→31H2＋34.7CO＋63.6N2 ・・・（１）
C2H5OH＋0.4CO2＋0.6H2O＋2.3N2＋Q2→3.6H2＋2.4CO＋2.3N2 ・・・（２） 1.56 (7.6CO 2 + 6.8H 2 O + 40.8N 2 ) + 3C 7.6 H 13.6 + Q1
→ 31H 2 + 34.7CO + 63.6N 2 (1)
C 2 H 5 OH + 0.4CO 2 + 0.6H 2 O + 2.3N 2 + Q2 → 3.6H 2 + 2.4CO + 2.3N 2 (2)

上記式に示すように、改質反応によれば、ＥＧＲガスおよび改質用燃料を、水素（Ｈ2）および一酸化炭素（ＣＯ）を含む改質ガスに転換させることができる。以下の説明では、水素および一酸化炭素を総称して「可燃成分」とも言う。 As shown in the above formula, according to the reforming reaction, the EGR gas and the reforming fuel can be converted into a reformed gas containing hydrogen (H 2 ) and carbon monoxide (CO). In the following description, hydrogen and carbon monoxide are also collectively referred to as “flammable components”.

上記（１）式中の熱量Q1、及び（２）式中の熱量Q2は、改質反応によって吸収される反応熱である。即ち、これらの改質反応は吸熱反応であるから、上記（１），（２）式中の右辺の可燃成分の有する熱量は、当該各式の左辺に記載された反応前の物質が有する熱量よりも大きくなる。   The amount of heat Q1 in the above equation (1) and the amount of heat Q2 in the equation (2) are reaction heat absorbed by the reforming reaction. That is, since these reforming reactions are endothermic reactions, the calorific value of the combustible component on the right side in the above formulas (1) and (2) is the calorific value of the substance before the reaction described on the left side of each formula. Bigger than.

このため、燃料改質器２４によれば、燃料改質触媒２６が排気通路２８から受熱した熱を、上記改質反応に吸収させることができる。つまり、本実施の形態のシステムでは、排気ガスの熱を回収、利用して、改質用燃料を、より熱量の大きい可燃成分に転換することができる。   Therefore, according to the fuel reformer 24, the heat received by the fuel reforming catalyst 26 from the exhaust passage 28 can be absorbed by the reforming reaction. That is, in the system of the present embodiment, the heat of exhaust gas can be recovered and used to convert the reforming fuel into a combustible component having a larger amount of heat.

上記の改質反応により生成した可燃成分を含む改質ガスは、ＥＧＲ通路３６を通って吸気通路１２内に流入し、吸入空気と混合された上で、内燃機関１０の燃焼室に流入する。そして、改質ガス中の可燃成分は、主燃料噴射装置１８から噴射された燃料と共に燃焼室で燃焼する。ＥＣＵ５０には、改質運転時に内燃機関１０の燃焼室に流入させるべき要求可燃成分量を運転条件等に基づいて決定するためのマップが記憶されている。ＥＣＵ５０は、燃焼室に流入する可燃成分量がその要求可燃成分量となるように、改質ガス流量をＥＧＲ弁４０によって制御するとともに、空燃比を目標空燃比とする上で必要な総燃料量から、流入した可燃成分量を差し引いた残りの分の燃料を、主燃料噴射手段１８に噴射させる。   The reformed gas containing the combustible component generated by the above reforming reaction flows into the intake passage 12 through the EGR passage 36, is mixed with the intake air, and then flows into the combustion chamber of the internal combustion engine 10. The combustible component in the reformed gas is combusted in the combustion chamber together with the fuel injected from the main fuel injection device 18. The ECU 50 stores a map for determining a required combustible component amount to be flown into the combustion chamber of the internal combustion engine 10 during the reforming operation based on the operating conditions and the like. The ECU 50 controls the reformed gas flow rate by the EGR valve 40 so that the amount of combustible components flowing into the combustion chamber becomes the required amount of combustible components, and the total fuel amount necessary for setting the air-fuel ratio to the target air-fuel ratio. Then, the remaining fuel after subtracting the amount of the combustible component that has flowed in is injected into the main fuel injection means 18.

改質ガスは、前述したように、燃料改質器２４によって排気ガスの熱を回収した分だけ、元の燃料よりも熱量が増えている。よって、改質運転時には、改質ガスを吸気系に還流させて燃料の一部として内燃機関１０で燃焼させることにより、システム全体としての熱効率が向上するので、内燃機関１０の燃費性能を改善することができる。   As described above, the amount of heat of the reformed gas is greater than that of the original fuel by the amount of heat recovered from the exhaust gas by the fuel reformer 24. Therefore, during the reforming operation, the reformed gas is recirculated to the intake system and burned in the internal combustion engine 10 as a part of the fuel, so that the thermal efficiency of the entire system is improved, so that the fuel efficiency performance of the internal combustion engine 10 is improved. be able to.

また、改質ガスを吸気系に還流させることは、ＥＧＲ（Exhaust Gas Recirculation）の一種でもある。よって、改質運転によれば、ＥＧＲの一般的な効果、すなわちポンプ損失低減による燃費改善効果や燃焼温度低下によるＮＯｘ生成量低減効果などを得ることもできる。このことに関連して、改質運転には更に次のような利点がある。通常のＥＧＲ運転の場合には、ＥＧＲ率を高くしていくと、燃焼が不安定になるので、ＥＧＲ率には限界がある。これに対し、改質運転の場合には、高い燃焼性を有する（燃焼速度の速い）水素が改質ガスに含まれており、この水素が燃料と共に燃焼室で燃焼する。このため、ＥＧＲ率を高くしても燃焼が不安定になりにくく、ＥＧＲ率の限界を高くすることができる。よって、改質運転時には、大量ＥＧＲが可能となるので、ポンプ損失低減による燃費改善効果や燃焼温度低下によるＮＯｘ生成量低減効果などをより大きく発揮させることができる。   In addition, refluxing the reformed gas to the intake system is also a kind of EGR (Exhaust Gas Recirculation). Therefore, according to the reforming operation, it is possible to obtain a general effect of EGR, that is, a fuel efficiency improvement effect by reducing pump loss, a NOx generation amount reducing effect by reducing combustion temperature, and the like. In this connection, the reforming operation has the following advantages. In the case of normal EGR operation, if the EGR rate is increased, combustion becomes unstable, and therefore there is a limit to the EGR rate. On the other hand, in the reforming operation, hydrogen having high combustibility (high combustion speed) is contained in the reformed gas, and this hydrogen is combusted together with the fuel in the combustion chamber. For this reason, even if the EGR rate is increased, combustion is not likely to become unstable, and the limit of the EGR rate can be increased. Therefore, during the reforming operation, a large amount of EGR is possible, so that the fuel efficiency improvement effect due to the pump loss reduction and the NOx generation amount reduction effect due to the reduction in the combustion temperature can be exhibited more greatly.

前述したように、本実施形態では、排気マニホールド２２の集合部より下流側の排気通路２０からＥＧＲガスを取り出すようにしている。このため、内燃機関１０の全気筒の排気ガスをＥＧＲ通路３２に取り込むことができる。よって、各気筒の排気脈動等の影響にかかわらず、大量のＥＧＲガスを燃料改質触媒２６に流入させることができる。その結果、大量の改質ガスを内燃機関１０に供給することができるので、改質運転による上記効果を十二分に発揮させることができる。   As described above, in the present embodiment, the EGR gas is taken out from the exhaust passage 20 on the downstream side of the collecting portion of the exhaust manifold 22. For this reason, exhaust gases from all cylinders of the internal combustion engine 10 can be taken into the EGR passage 32. Therefore, a large amount of EGR gas can flow into the fuel reforming catalyst 26 regardless of the influence of exhaust pulsation or the like of each cylinder. As a result, a large amount of reformed gas can be supplied to the internal combustion engine 10, so that the above-described effects due to the reforming operation can be fully exhibited.

ところで、改質運転時に、燃料改質触媒２６に酸素が流入したとすると、改質用燃料が燃料改質触媒２６において酸化反応（燃焼）する。このため、その燃焼熱によって燃料改質触媒２６の温度が過度に上昇し、触媒シンタリング（触媒粒の粗大化）等の触媒劣化や、触媒担体の溶損等の触媒故障を生じ易い。   By the way, if oxygen flows into the fuel reforming catalyst 26 during the reforming operation, the reforming fuel undergoes an oxidation reaction (combustion) in the fuel reforming catalyst 26. For this reason, the temperature of the fuel reforming catalyst 26 excessively rises due to the combustion heat, and catalyst failure such as catalyst sintering (catalyst particle coarsening) and catalyst failure such as catalyst carrier erosion are likely to occur.

そこで、本実施形態では、改質運転の実行中は、燃料改質触媒２６への酸素の流入を確実に防止するため、内燃機関１０の各気筒（全気筒）の空燃比が、何れも理論空燃比以下のリッチ空燃比となるように制御することとした。これにより、何れの気筒から排出される排気ガスの中にも酸素が残存しなくなるので、ＥＧＲ通路３２に酸素が流入することを確実に防止することができる。このため、燃料改質触媒２６での改質用燃料の酸化反応を確実に阻止することができ、燃料改質触媒２６の劣化や故障を確実に回避することができる。   Therefore, in the present embodiment, during the reforming operation, in order to reliably prevent the inflow of oxygen into the fuel reforming catalyst 26, the air-fuel ratio of each cylinder (all cylinders) of the internal combustion engine 10 is theoretically all. Control was made so that the rich air-fuel ratio becomes lower than the air-fuel ratio. As a result, oxygen does not remain in the exhaust gas discharged from any cylinder, so that it is possible to reliably prevent oxygen from flowing into the EGR passage 32. For this reason, the oxidation reaction of the reforming fuel in the fuel reforming catalyst 26 can be reliably prevented, and deterioration or failure of the fuel reforming catalyst 26 can be reliably avoided.

なお、改質運転時の内燃機関１０の各気筒の空燃比は、理論空燃比であってもよいが、燃料改質触媒２６への酸素の流入をより確実に防止する観点からは、理論空燃比より僅かに小さい弱リッチ空燃比であることが好ましい。   Note that the air-fuel ratio of each cylinder of the internal combustion engine 10 during the reforming operation may be the stoichiometric air-fuel ratio, but from the viewpoint of more reliably preventing oxygen from flowing into the fuel reforming catalyst 26, the A weakly rich air-fuel ratio that is slightly smaller than the fuel ratio is preferred.

（非改質運転）
本実施形態の内燃機関１０は、上述したような燃料改質を利用せず、主燃料噴射装置１８から噴射する燃料のみを燃焼させて運転することも可能となっている。このような運転を以下「非改質運転」と称する。非改質運転には、ＥＧＲ通路３２，３６を介してＥＧＲガスを吸気通路１２に還流させる通常の外部ＥＧＲを行う運転（以下「改質無しＥＧＲ運転」と称する）と、ＥＧＲ弁４０を閉じることによりＥＧＲ通路３２，３６にＥＧＲガスを流さないようにする運転（以下「非ＥＧＲ運転」と称する）とが含まれる。 (Non-reforming operation)
The internal combustion engine 10 of the present embodiment can be operated by burning only the fuel injected from the main fuel injection device 18 without using the fuel reforming as described above. Such operation is hereinafter referred to as “non-reforming operation”. In the non-reforming operation, an operation in which normal external EGR is performed to recirculate EGR gas to the intake passage 12 via the EGR passages 32 and 36 (hereinafter referred to as “non-reforming EGR operation”) and the EGR valve 40 are closed. Thus, an operation that prevents EGR gas from flowing through the EGR passages 32 and 36 (hereinafter referred to as “non-EGR operation”) is included.

非改質運転時には、内燃機関１０の各気筒の空燃比を理論空燃比より大きいリーン空燃比となるように制御してもよい。   During the non-reforming operation, the air-fuel ratio of each cylinder of the internal combustion engine 10 may be controlled to be a lean air-fuel ratio larger than the stoichiometric air-fuel ratio.

ＥＣＵ５０は、機関回転数や機関負荷等の運転状態に基づいて、非改質運転と改質運転とを切り換える。本実施形態では、非改質運転から改質運転に切り換える際に、改質運転の準備としての改質無しＥＧＲ運転を実行する期間を経てから、改質運転を開始することとした。すなわち、外部ＥＧＲを行わない非ＥＧＲ運転から直接に改質運転に切り換えるのではなく、まず改質用燃料を噴射しない改質無しＥＧＲ運転を行い、その後、改質用燃料の噴射を開始して改質運転に切り換えることとした。このような制御により、次のような利点がある。   The ECU 50 switches between the non-reforming operation and the reforming operation based on the operation state such as the engine speed and the engine load. In the present embodiment, when the non-reforming operation is switched to the reforming operation, the reforming operation is started after a period of executing the non-reforming EGR operation as preparation for the reforming operation. That is, instead of directly switching from non-EGR operation without external EGR to reforming operation, first perform reformed EGR operation without injecting reforming fuel, and then start injection of reforming fuel. Switching to reforming operation was decided. Such control has the following advantages.

（１）改質運転の開始前に燃料改質触媒２６を十分な温度に予熱することができる。燃料改質触媒２６は非ＥＧＲ運転時にも排気通路２８側から排気ガスの熱によって加熱されているが、ＥＧＲ通路３２，３６にＥＧＲガスを流すことにより、排気ガスとＥＧＲガスとの両方の熱で燃料改質触媒２６を加熱することができる。このため、改質運転の準備としての改質無しＥＧＲ運転を実行することにより、燃料改質触媒２６の温度を更に上昇させることができ、改質用燃料の噴射開始直後から改質効率を十分に高めることができる。
（２）改質運転時に燃焼室に流入する可燃成分量は、燃料改質触媒２６における可燃成分生成量（すなわち改質反応量）と、改質ガス流量（すなわちＥＧＲ流量）とに依存して決まる。よって、改質運転時には、ＥＧＲ流量と改質反応量との双方を制御する必要がある。このため、非ＥＧＲ運転から直接に改質運転に切り換える場合には、ＥＧＲ流量の制御と改質反応量の制御との双方を同時に開始することとなる。しかしながら、ＥＧＲ流量や改質反応量は、何れも、それらの値をセンサで直接に検出することは困難であるため、制御開始後、しばらくの間は、制御誤差が大きくなり易い。このため、非ＥＧＲ運転から直接に改質運転に切り換えた場合には、ＥＧＲ流量の制御誤差と改質反応量の制御誤差とが相乗してしまい、燃焼室に流入する可燃成分量の制御誤差が大きくなり易い。これに対し、本実施形態のように、改質運転の準備として改質無しＥＧＲ運転を実行する場合には、まずＥＧＲ流量の制御のみが開始され、ＥＧＲ流量が目標値に安定的に制御されるようになった後に、改質反応量の制御を開始することができる。このため、非改質運転から改質運転に切り換えた後、燃焼室への可燃成分流入量の制御誤差を抑制することができ、空燃比やトルクなどを精度良く制御することができる。 (1) The fuel reforming catalyst 26 can be preheated to a sufficient temperature before the start of the reforming operation. The fuel reforming catalyst 26 is heated by the heat of the exhaust gas from the exhaust passage 28 side even during non-EGR operation. However, by flowing the EGR gas through the EGR passages 32 and 36, the heat of both the exhaust gas and the EGR gas is supplied. Thus, the fuel reforming catalyst 26 can be heated. For this reason, by executing the non-reforming EGR operation as preparation for the reforming operation, the temperature of the fuel reforming catalyst 26 can be further increased, and the reforming efficiency is sufficiently improved immediately after the start of the injection of the reforming fuel. Can be increased.
(2) The amount of combustible components flowing into the combustion chamber during the reforming operation depends on the amount of combustible components generated (ie, the reforming reaction amount) in the fuel reforming catalyst 26 and the reformed gas flow rate (ie, EGR flow rate). Determined. Therefore, it is necessary to control both the EGR flow rate and the reforming reaction amount during the reforming operation. For this reason, when switching directly from the non-EGR operation to the reforming operation, both the control of the EGR flow rate and the control of the reforming reaction amount are started simultaneously. However, since it is difficult to directly detect the values of the EGR flow rate and the reforming reaction amount with a sensor, the control error tends to increase for a while after the start of the control. For this reason, when the non-EGR operation is switched directly to the reforming operation, the control error of the EGR flow rate and the control error of the reforming reaction amount are synergistic, and the control error of the combustible component amount flowing into the combustion chamber. Tends to be large. On the other hand, when the non-reforming EGR operation is executed as preparation for the reforming operation as in this embodiment, only the control of the EGR flow rate is started first, and the EGR flow rate is stably controlled to the target value. Then, control of the reforming reaction amount can be started. For this reason, after switching from the non-reforming operation to the reforming operation, the control error of the inflow of combustible components into the combustion chamber can be suppressed, and the air-fuel ratio, torque, and the like can be accurately controlled.

上述したような改質運転の準備としての改質無しＥＧＲ運転の実行時には、燃料改質触媒２６に流入するＥＧＲガスの空燃比が、好ましくは理論空燃比以下、より好ましくは理論空燃比より小さなリッチ空燃比となるように制御される。通常の改質無しＥＧＲ運転の実行中は、内燃機関１０が理論空燃比より大きなリーン空燃比で運転されることが多い。このため、ＥＧＲガス中に残存する酸素が燃料改質触媒２６に吸着された状態となっている。この状態からいきなり改質運転を開始すると、燃料改質触媒２６に吸着されている酸素が改質反応を阻害し、改質効率が低下したり改質反応が不安定になったりする場合がある。そこで、改質運転開始前の改質無しＥＧＲ運転時に、ＥＧＲガスの空燃比をリッチ空燃比とすることにより、ＥＧＲガス中に残存する未燃燃料と、燃料改質触媒２６に吸着された酸素とを反応させ、当該酸素を除去することができる。よって、改質効率の低下や改質反応の不安定化を確実に回避することができる。   When executing the non-reforming EGR operation as preparation for the reforming operation as described above, the air-fuel ratio of the EGR gas flowing into the fuel reforming catalyst 26 is preferably equal to or lower than the stoichiometric air-fuel ratio, more preferably smaller than the stoichiometric air-fuel ratio. Control is performed to achieve a rich air-fuel ratio. During normal EGR operation without reforming, the internal combustion engine 10 is often operated at a lean air-fuel ratio greater than the stoichiometric air-fuel ratio. For this reason, oxygen remaining in the EGR gas is adsorbed by the fuel reforming catalyst 26. If the reforming operation is suddenly started from this state, oxygen adsorbed on the fuel reforming catalyst 26 may inhibit the reforming reaction, and the reforming efficiency may be lowered or the reforming reaction may become unstable. . Therefore, by setting the air-fuel ratio of the EGR gas to a rich air-fuel ratio during the non-reforming EGR operation before the start of the reforming operation, the unburned fuel remaining in the EGR gas and the oxygen adsorbed by the fuel reforming catalyst 26 And the oxygen can be removed. Therefore, it is possible to reliably avoid a reduction in reforming efficiency and instability of the reforming reaction.

［実施の形態１における具体的処理］
図２は、上記の機能を実現するために本実施形態においてＥＣＵ５０が実行するルーチンのフローチャートである。図２に示すルーチンによれば、まず、ＥＧＲ実行条件の成否が判断される（ステップ１００）。このステップ１００においては、内燃機関１０の動作点が所定のＥＧＲ領域内にあるか否かなどの所定のＥＧＲ実行条件が、各センサの検出信号等に基づいて判断される。その判断の結果、ＥＧＲ実行条件が成立していると判断された場合には、ＥＧＲが実行される（ステップ１０２）。すなわち、ＥＧＲ弁４０を開くことによってＥＧＲガスをＥＧＲ通路３２，３６を介して吸気通路１２に還流させる改質無しＥＧＲ運転が実行される。 [Specific Processing in Embodiment 1]
FIG. 2 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 2, it is first determined whether or not the EGR execution condition is met (step 100). In this step 100, a predetermined EGR execution condition such as whether or not the operating point of the internal combustion engine 10 is within a predetermined EGR region is determined based on detection signals of each sensor. As a result of the determination, when it is determined that the EGR execution condition is satisfied, the EGR is executed (step 102). That is, an unreformed EGR operation is performed in which the EGR gas is recirculated to the intake passage 12 via the EGR passages 32 and 36 by opening the EGR valve 40.

改質無しＥＧＲ運転が実行された場合には、次に、改質運転条件の成否が判断される（ステップ１０４）。このステップ１０４においては、内燃機関１０の動作点が所定の改質領域内にあるか否かや、燃料改質触媒２６の温度が所定温度以上であるか否かなどの所定の改質運転実行条件が、各センサの検出信号等に基づいて判断される。   If the non-reforming EGR operation is executed, it is next determined whether or not the reforming operation conditions are met (step 104). In this step 104, execution of a predetermined reforming operation such as whether or not the operating point of the internal combustion engine 10 is within a predetermined reforming region and whether or not the temperature of the fuel reforming catalyst 26 is equal to or higher than a predetermined temperature. The condition is determined based on the detection signal of each sensor.

上記ステップ１０４で改質運転条件が成立していると判断された場合には、改質運転条件の準備としての改質無しＥＧＲ運転を行うため、各気筒の空燃比がリッチ空燃比となるように制御される（ステップ１０６）。このステップ１０６において空燃比が目標空燃比となるように制御する際には、吸入空気量等に基づいて主燃料噴射装置１８からの燃料噴射量をフィードフォワード的に制御してもよく、あるいは、空燃比センサ５６の検出信号をフィードバックして主燃料噴射装置１８からの燃料噴射量を補正してもよい。   If it is determined in step 104 that the reforming operation condition is satisfied, the non-reforming EGR operation is performed as preparation for the reforming operation condition, so that the air-fuel ratio of each cylinder becomes a rich air-fuel ratio. (Step 106). When the air-fuel ratio is controlled to be the target air-fuel ratio in step 106, the fuel injection amount from the main fuel injection device 18 may be controlled in a feed-forward manner based on the intake air amount or the like, or The fuel injection amount from the main fuel injection device 18 may be corrected by feeding back the detection signal of the air-fuel ratio sensor 56.

上記ステップ１０６の制御によって各気筒の空燃比がリッチ空燃比に制御されたら、所定時間待機する処理が実行される（ステップ１０８）。これにより、リッチ空燃比での改質無しＥＧＲ運転が所定時間継続される。この間に、排気通路２８を流れる排気ガスと、燃料改質触媒２６を流れるＥＧＲガスとの双方によって、燃料改質触媒２６の温度を十分に上昇させることができるとともに、燃料改質触媒２６に吸着された酸素をＥＧＲガス中の未燃燃料と反応させて除去することができる。また、ＥＧＲ流量を目標値に一致させるのに十分な時間を与えることができる。   When the air-fuel ratio of each cylinder is controlled to the rich air-fuel ratio by the control in step 106, a process for waiting for a predetermined time is executed (step 108). Thereby, the non-reforming EGR operation at the rich air-fuel ratio is continued for a predetermined time. During this time, both the exhaust gas flowing through the exhaust passage 28 and the EGR gas flowing through the fuel reforming catalyst 26 can sufficiently raise the temperature of the fuel reforming catalyst 26 and are adsorbed by the fuel reforming catalyst 26. The generated oxygen can be removed by reacting with unburned fuel in the EGR gas. In addition, a sufficient time can be given to make the EGR flow rate coincide with the target value.

上記ステップ１０８による待機時間が経過した後、改質用燃料噴射装置３４からの燃料噴射が実行され、改質運転が開始される（ステップ１１０）。この際、燃料改質触媒２６が十分に予熱されているとともに吸着酸素が事前に除去されているので、改質反応の安定化が図れ、高い改質効率が得られる。   After the standby time in step 108 has elapsed, fuel injection from the reforming fuel injection device 34 is executed, and the reforming operation is started (step 110). At this time, since the fuel reforming catalyst 26 is sufficiently preheated and the adsorbed oxygen is removed in advance, the reforming reaction can be stabilized and high reforming efficiency can be obtained.

改質運転の実行中、各気筒の空燃比は、空燃比センサ５６の検出信号に基づく空燃比フィードバックにより、引き続きリッチ空燃比に維持される（ステップ１１２）。可燃成分を含む改質ガスが燃焼室に流入し始めると、空燃比フィードバック制御の作用により、その分だけ主燃料の噴射量が減少方向に補正されるので、主燃料噴射装置１８からの燃料噴射量が減量される（ステップ１１４）。   During the reforming operation, the air-fuel ratio of each cylinder is continuously maintained at the rich air-fuel ratio by air-fuel ratio feedback based on the detection signal of the air-fuel ratio sensor 56 (step 112). When the reformed gas containing a combustible component starts to flow into the combustion chamber, the fuel injection amount from the main fuel injection device 18 is corrected by the amount of the main fuel injection in the decreasing direction by the air-fuel ratio feedback control. The amount is reduced (step 114).

以上説明した図２に示すルーチンの処理によれば、改質運転の実行中、各気筒の空燃比をリッチ空燃比に維持することができるので、燃料改質触媒２６への酸素の流入を確実に阻止することができる。このため、改質用燃料の酸化反応（燃焼）による燃料改質触媒２６の過昇温を確実に防止することができ、燃料改質触媒２６の劣化や故障を確実に回避することができる。   According to the routine process shown in FIG. 2 described above, the air-fuel ratio of each cylinder can be maintained at a rich air-fuel ratio during the reforming operation, so that the inflow of oxygen to the fuel reforming catalyst 26 is ensured. Can be prevented. For this reason, the excessive temperature rise of the fuel reforming catalyst 26 due to the oxidation reaction (combustion) of the reforming fuel can be reliably prevented, and the deterioration or failure of the fuel reforming catalyst 26 can be reliably avoided.

なお、本実施形態では、燃料改質器２４において、内燃機関１０の排気ガスの熱を燃料改質触媒２６に伝熱させ、改質反応に吸熱させるようにしているが、本発明は、燃料改質触媒２６に加える熱を排気ガスの熱で賄う構成に限定されるものではない。すなわち、本発明では、燃料改質触媒２６をヒータや燃焼器などで加熱する構成としてもよい。   In the present embodiment, in the fuel reformer 24, the heat of the exhaust gas of the internal combustion engine 10 is transferred to the fuel reforming catalyst 26 and absorbed in the reforming reaction. The configuration is not limited to the configuration in which the heat applied to the reforming catalyst 26 is covered by the heat of the exhaust gas. That is, in the present invention, the fuel reforming catalyst 26 may be configured to be heated by a heater, a combustor, or the like.

また、上述した実施の形態１においては、改質用燃料噴射装置３４が前記第１の発明における「改質用燃料噴射手段」に、燃料改質器２４が前記第１の発明における「熱供給手段」に、それぞれ相当している。また、ＥＣＵ５０が、図２に示すルーチンの処理を実行することにより前記第１および第２の発明における「運転切換手段」が、上記ステップ１１２の処理を実行することにより前記第１の発明における「改質運転時空燃比制御手段」が、上記ステップ１０６の処理を実行することにより前記第３の発明における「改質運転前空燃比制御手段」が、それぞれ実現されている。   In the first embodiment described above, the reforming fuel injection device 34 is the “reforming fuel injection means” in the first invention, and the fuel reformer 24 is the “heat supply” in the first invention. It corresponds to “means”. Further, when the ECU 50 executes the processing of the routine shown in FIG. 2, the “operation switching means” in the first and second inventions executes the processing of step 112, and “ The “reformation operation air-fuel ratio control means” executes the processing of step 106, thereby realizing the “pre-reformation air-fuel ratio control means” in the third aspect of the invention.

本発明の実施の形態１のシステム構成を説明するための図である。It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. 本発明の実施の形態１において実行されるルーチンのフローチャートである。It is a flowchart of the routine performed in Embodiment 1 of the present invention.

符号の説明Explanation of symbols

１０ 内燃機関
１２ 吸気通路
１４ 吸気マニホールド
１６ スロットル弁
１８ 主燃料噴射装置
２０，２８，３０ 排気通路
２４ 燃料改質器
２６ 燃料改質触媒
３２，３６ ＥＧＲ通路
３４ 改質用燃料噴射装置
３８ ＥＧＲクーラ
４０ ＥＧＲ弁
４２ 排気浄化触媒
４４ 燃料タンク
４６ 燃料配管
５０ ＥＣＵ
５４ 触媒温度センサ
５６ 空燃比センサ
５８ 水素濃度センサ DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 14 Intake manifold 16 Throttle valve 18 Main fuel injection device 20, 28, 30 Exhaust passage 24 Fuel reformer 26 Fuel reforming catalyst 32, 36 EGR passage 34 Reforming fuel injection device 38 EGR cooler 40 EGR valve 42 Exhaust gas purification catalyst 44 Fuel tank 46 Fuel piping 50 ECU
54 Catalyst temperature sensor 56 Air-fuel ratio sensor 58 Hydrogen concentration sensor

Claims (4)

多気筒型の内燃機関の排気通路と吸気通路とを接続するＥＧＲ通路と、
前記ＥＧＲ通路を流れるＥＧＲガス中に燃料を噴射する改質用燃料噴射手段と、
前記ＥＧＲ通路の途中であって前記改質用燃料噴射手段の下流側に配置され、前記ＥＧＲガスと前記改質用燃料とを改質反応させることにより、それらを、改質反応生成物である可燃成分を含む改質ガスに転換させる燃料改質触媒と、
前記改質反応に要する熱を前記燃料改質触媒に供給する熱供給手段と、
前記改質用燃料噴射手段により燃料を供給しつつ前記改質ガスを前記吸気通路に還流させる改質運転と、前記改質用燃料噴射手段から燃料を噴射しない非改質運転とを切り換える運転切換手段と、
前記改質運転の実行中に、前記内燃機関の各気筒の空燃比を何れも理論空燃比以下のリッチ空燃比に維持する改質運転時空燃比制御手段と、
を備えることを特徴とする内燃機関の制御装置。 An EGR passage connecting an exhaust passage and an intake passage of a multi-cylinder internal combustion engine;
Fuel reforming means for injecting fuel into EGR gas flowing through the EGR passage;
It is disposed in the middle of the EGR passage and downstream of the reforming fuel injection means, and reforms the EGR gas and the reforming fuel, so that they are reforming reaction products. A fuel reforming catalyst for converting to a reformed gas containing a combustible component;
Heat supply means for supplying heat required for the reforming reaction to the fuel reforming catalyst;
Operation switching for switching between a reforming operation in which the reformed gas is recirculated to the intake passage while fuel is supplied by the reforming fuel injection means and a non-reforming operation in which no fuel is injected from the reforming fuel injection means. Means,
A reforming operation air-fuel ratio control means for maintaining the air-fuel ratio of each cylinder of the internal combustion engine at a rich air-fuel ratio equal to or lower than the stoichiometric air-fuel ratio during execution of the reforming operation;
A control device for an internal combustion engine, comprising: 前記非改質運転には、ＥＧＲガスを前記吸気通路に還流させるＥＧＲを実行する改質無しＥＧＲ運転と、前記ＥＧＲを実行しない非ＥＧＲ運転とが含まれ、
前記運転切換手段は、前記非改質運転から前記改質運転に切り換える場合に、前記改質無しＥＧＲ運転を実行する期間を経てから前記改質運転を開始することを特徴とする請求項１記載の内燃機関の制御装置。 The non-reforming operation includes a non-reforming EGR operation that executes EGR for returning EGR gas to the intake passage, and a non-EGR operation that does not execute the EGR,
The operation switching means starts the reforming operation after a period of executing the non-reforming EGR operation when switching from the non-reforming operation to the reforming operation. Control device for internal combustion engine. 前記改質運転を開始する前の前記改質無しＥＧＲ運転の実行中に、前記燃料改質触媒に流入するＥＧＲガスの空燃比を理論空燃比以下のリッチ空燃比とする改質運転前空燃比制御手段を備えることを特徴とする請求項２記載の内燃機関の制御装置。   During the execution of the non-reforming EGR operation before starting the reforming operation, the air-fuel ratio before the reforming operation is set so that the air-fuel ratio of the EGR gas flowing into the fuel reforming catalyst is a rich air-fuel ratio equal to or lower than the theoretical air-fuel ratio. The control apparatus for an internal combustion engine according to claim 2, further comprising a control means. 前記熱供給手段は、前記内燃機関の排気ガスの熱を前記燃料改質触媒に伝熱させる熱交換器で構成されていることを特徴とする請求項１乃至３の何れか１項記載の内燃機関の制御装置。   The internal combustion engine according to any one of claims 1 to 3, wherein the heat supply means includes a heat exchanger that transfers heat of exhaust gas of the internal combustion engine to the fuel reforming catalyst. Engine control device.
JP2007312565A 2007-12-03 2007-12-03 Control device for internal combustion engine Pending JP2009138531A (en)

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Cited By (4)

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JP2011012554A (en) * 2009-06-30 2011-01-20 Toyota Motor Corp Reforming catalyst system
CN102691556A (en) * 2011-03-21 2012-09-26 通用汽车环球科技运作有限责任公司 Method of operating an exhaust gas treatment system to prevent quenching during regeneration
JP2015121151A (en) * 2013-12-24 2015-07-02 日産自動車株式会社 Internal combustion engine system
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JP2005127160A (en) * 2003-10-21 2005-05-19 Toyota Motor Corp Internal combustion engine
JP2006037817A (en) * 2004-07-26 2006-02-09 Toyota Motor Corp Internal combustion engine
JP2006037879A (en) * 2004-07-28 2006-02-09 Toyota Motor Corp Internal combustion engine and operation control device of internal combustion engine
JP2007187111A (en) * 2006-01-13 2007-07-26 Toyota Motor Corp Internal combustion engine by use of hydrogen

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JP2005127160A (en) * 2003-10-21 2005-05-19 Toyota Motor Corp Internal combustion engine
JP2006037817A (en) * 2004-07-26 2006-02-09 Toyota Motor Corp Internal combustion engine
JP2006037879A (en) * 2004-07-28 2006-02-09 Toyota Motor Corp Internal combustion engine and operation control device of internal combustion engine
JP2007187111A (en) * 2006-01-13 2007-07-26 Toyota Motor Corp Internal combustion engine by use of hydrogen

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2011012554A (en) * 2009-06-30 2011-01-20 Toyota Motor Corp Reforming catalyst system
CN102691556A (en) * 2011-03-21 2012-09-26 通用汽车环球科技运作有限责任公司 Method of operating an exhaust gas treatment system to prevent quenching during regeneration
US9371763B2 (en) 2011-03-21 2016-06-21 GM Global Technology Operations LLC Method of operating an exhaust gas treatment system to prevent quenching during regeneration
JP2015121151A (en) * 2013-12-24 2015-07-02 日産自動車株式会社 Internal combustion engine system
WO2015118815A1 (en) * 2014-02-10 2015-08-13 株式会社デンソー Fuel reformulation device for internal combustion engine
JP2015151873A (en) * 2014-02-10 2015-08-24 株式会社デンソー Fuel reformer of internal combustion engine

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