JP2005042569A

JP2005042569A - Combustion control method and combustion control apparatus for internal combustion engine

Info

Publication number: JP2005042569A
Application number: JP2003200878A
Authority: JP
Inventors: Teruhiko Miyake; 照彦三宅
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2003-07-24
Filing date: 2003-07-24
Publication date: 2005-02-17

Abstract

【課題】ＣＯ_２を利用して内燃機関の空燃比を低下させることが可能な内燃機関の燃焼制御方法及び燃焼制御装置を提供する。
【解決手段】第１の状態でＣＯ_２を吸収し、第２の状態で吸収したＣＯ_２を放出するＣＯ_２吸放出手段１０ａ、１０ｂが設けられた内燃機関１に適用され、前記ＣＯ_２吸放出手段は、前記ＣＯ_２吸放出手段から放出されたＣＯ_２を前記内燃機関の吸気系へ供給できるように前記内燃機関の吸気通路３と接続されている。
【選択図】図１An internal combustion engine combustion control method and combustion control apparatus capable of reducing the air-fuel ratio of an internal combustion engine using CO ₂ are provided.
A absorbs CO ₂ in the first state, CO ₂ absorption and release means 10a which releases CO ₂ absorbed in the second state, 10b are applied to an internal combustion engine 1 provided, the CO ₂ absorption release means is connected to the intake passage 3 of the internal combustion engine to the CO ₂ released from the CO ₂ absorbing and releasing means can be supplied to the intake system of the internal combustion engine.
[Selection] Figure 1

Description

【０００１】
【発明の属する技術分野】
本発明は、ＣＯ_２を吸放出するＣＯ_２吸放出材を備えた内燃機関の燃焼制御方法及び燃焼制御装置に関する。
【０００２】
【従来の技術】
２５０℃程度の温度域で、炭酸ガス（ＣＯ_２）吸収能の高い炭酸ガス吸収材が知られている（特許文献１参照）。また、室温から６００℃付近までの温度域でＣＯ_２を吸収し、６８０℃以上の温度域でＣＯ_２を放出するＣＯ_２吸放出材が知られている（非特許文献１参照）。その他、本発明に関連する技術として特許文献２、３が存在する。
【０００３】
【特許文献１】
特開２００１−９６１２２号公報
【特許文献２】
特開２００１−３７７５号公報
【特許文献３】
特開平１１−２６２６３２号公報
【非特許文献１】
東芝レビューＶｏｌ．５６、Ｎｏ．８（２００１）ｐ．１１−１４
【０００４】
【発明が解決しようとする課題】
ディーゼルエンジンの排気浄化装置として、吸蔵還元型ＮＯ_ｘ触媒等の排気浄化触媒を使用した排気浄化システムが実用化されている。この排気浄化システムでは、エンジンが低回転、低負荷で運転されると排気温度が低下し、それに伴って触媒温度が低下して触媒が不活性状態になるおそれがある。そこで、この運転域では、ＥＧＲガス等の不活性ガスを燃焼室へ大量に供給してエンジンの燃焼温度を低下させる処理（低温燃焼）を行い、この低温燃焼により炭化水素（ＨＣ）を発生させて触媒の活性を維持している。
【０００５】
ところで、ディーゼルエンジンから排出される粒子状物質（ＰＭ）とエンジンの空燃比とは相関関係を有しており、特定の空燃比域においてＰＭが大量に発生することが知られている。低温燃焼のために不活性ガスを供給すると空燃比が低下して、この特定の空燃比域に差しかかりＰＭが大量に発生する。そこで、大量の不活性ガスを燃焼室へ短時間で供給して空燃比を低下させることにより、ＰＭが大量に発生する空燃比域を短時間で通過してＰＭの発生量を抑えることが望まれる。不活性ガスにはＣＯ_２が利用できるが、従来、このような目的でＣＯ_２吸放出材を利用することは検討されていない。
【０００６】
そこで、本発明は、ＣＯ_２を利用して内燃機関の空燃比を低下させることが可能な内燃機関の燃焼制御方法及び燃焼制御装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明の内燃機関の燃焼制御方法は、第１の状態でＣＯ_２を吸収し、第２の状態で吸収したＣＯ_２を放出するＣＯ_２吸放出手段が設けられた内燃機関に適用され、不活性ガスの燃焼室内への供給が要求される場合に、前記ＣＯ_２吸放出手段を前記第２の状態にしてＣＯ_２を放出させ、その放出されたＣＯ_２を前記内燃機関の吸気系へ供給することにより、上述した課題を解決する（請求項１）。
【０００８】
本発明の燃焼制御方法によれば、低温燃焼等のために燃焼室内への不活性ガスの供給が要求される場合には、前記ＣＯ_２吸放出手段から内燃機関の吸気系へＣＯ_２を供給することにより、内燃機関の空燃比を低下、すなわち酸素量が相対的に減少する側へ変化させることができる。
【０００９】
本発明の内燃機関の燃焼制御装置は、第１の状態でＣＯ_２を吸収し、第２の状態で吸収したＣＯ_２を放出するＣＯ_２吸放出手段が設けられた内燃機関に適用され、前記ＣＯ_２吸放出手段は、前記ＣＯ_２吸放出手段から放出されたＣＯ_２を前記内燃機関の吸気系へ供給できるように前記内燃機関の吸気通路と接続されることにより、上述した課題を解決する（請求項２）。
【００１０】
本発明の燃焼制御装置によれば、ＣＯ_２吸放出手段から放出されたＣＯ_２を吸気系へ供給することができるので、本発明の燃焼制御方法と同様に、内燃機関の空燃比を低下させることができる。
【００１１】
本発明の内燃機関の燃焼制御装置において、前記ＣＯ_２吸放出手段は、前記内燃機関の排気を前記ＣＯ_２吸放出手段へ導入できるように前記内燃機関の排気通路と接続されてもよい（請求項３）。この場合、内燃機関の排気に含まれるＣＯ_２をＣＯ_２吸放出手段に一時的に蓄え、これを必要に応じて吸気系へ供給することができる。
【００１２】
本発明の内燃機関の燃焼制御装置は、前記排気通路と前記吸気通路とを前記ＣＯ_２吸放出手段を迂回して接続するバイパス通路を備えてもよい（請求項４）。この場合、ＣＯ_２吸放出手段とバイパス通路との両者を介して吸気系へ排気を供給することができる。これにより、吸気系へ供給されるＣＯ_２量の調整の自由度が高まる。例えば、ＣＯ_２吸放出手段がＣＯ_２を吸収している場合、吸気系へ供給されるＣＯ_２量が減少するため、その減少量に応じてバイパス通路から吸気系へ排気を送って排気流量を増加させることによりＣＯ_２の減少を抑制することができる。一方、ＣＯ_２吸放出手段からＣＯ_２が放出されている場合、吸気系へ供給されるＣＯ_２量が過剰になると燃焼に必要な酸素が不足して内燃機関が失火する可能性がある。この場合は、ＣＯ_２放出量の過剰分に応じて排気通路から吸気系へ供給される排気の流量を減少させ、内燃機関が失火しないようなＣＯ_２量に調整する。
【００１３】
本発明の内燃機関の燃焼制御装置は、前記ＣＯ_２吸放出手段と前記バイパス通路の少なくともいずれか一方を通過して前記吸気系へ供給される排気の流量を調整する排気流量調整手段と、前記ＣＯ_２吸放出手段のＣＯ_２吸放出量に基づいて前記排気流量調整手段の動作を制御する動作制御手段とを備えてもよい（請求項５）。この場合、排気流量調整手段の動作を制御することにより上述したようなＣＯ_２の吸収、放出に応じたバイパス流量の調整を行うことができる。
【００１４】
本発明の内燃機関の燃焼制御装置は、前記ＣＯ_２吸放出手段の下流側に配置されて前記ＣＯ_２吸放出手段を通過した排気の空燃比を取得する空燃比取得手段を備え、前記動作制御手段は、前記空燃比取得手段が取得した空燃比に基づいて前記排気流量調整手段の動作を制御してもよい（請求項６）。空燃比取得手段によって、ＣＯ_２吸放出手段からＣＯ_２が吸放出された場合の空燃比の変化を調べることができる。この空燃比の変化より、実際にＣＯ_２吸放出手段から吸放出されたＣＯ_２量をより正確に把握することができる。そのため、吸気系へ供給する排気の流量をより精度よく調整することができる。
【００１５】
本発明の内燃機関の燃焼制御装置は、前記第１の状態と前記第２の状態とが互いに異なる温度範囲に対応付けられており、前記ＣＯ_２吸放出手段の上流側に配置されて前記ＣＯ_２吸放出手段へ導入される排気と熱交換して排気の温度を調整する熱交換器と、前記熱交換器の熱交換量を制御する熱交換量制御手段とを備え、前記熱交換量制御手段は、前記ＣＯ_２吸放出手段に吸収されているＣＯ_２量に基づいて前記熱交換器の熱交換量を制御してもよい（請求項７）。この場合、排気温度を調整することにより、ＣＯ_２吸放出手段を第１の状態又は第２の状態に設定して、ＣＯ_２吸放出手段に吸収されているＣＯ_２量に応じて吸収、放出作用を適切に使い分けることができる。例えば、ＣＯ_２吸放出手段に吸収されているＣＯ_２量が少ない場合は、排気温度を調整してＣＯ_２吸放出手段を第１の状態に設定し、ＣＯ_２吸放出手段にＣＯ_２を吸収させてＣＯ_２吸収量を増加させることができる。
【００１６】
本発明の内燃機関の燃焼制御装置において、前記ＣＯ_２吸放出手段が複数設けられ、前記複数のＣＯ_２吸放出手段のそれぞれは、自己から放出されたＣＯ_２を前記吸気系へ供給できるように前記吸気通路と接続されてもよい（請求項８）。この場合、ＣＯ_２吸放出手段を使い分けることができる。例えば、最も条件の良いもの又は悪いもの（例えば、吸収しているＣＯ_２量の多いもの、又は少ないもの）から順にＣＯ_２を吸収、放出させることができる。また、複数のＣＯ_２吸放出手段を同時に吸収、放出状態にしてＣＯ_２を吸放出させてもよい。
【００１７】
本発明の内燃機関の燃焼制御装置は、前記複数のＣＯ_２吸放出手段のそれぞれの第１の状態及び第２の状態の少なくとも一方が互いに異なっていてもよい（請求項９）。この場合、種々の状態においてＣＯ_２吸放出手段からＣＯ_２を吸放出させることができる。例えば、第２の状態が互いに異なる温度範囲に対応付けられている複数のＣＯ_２吸放出手段を備えた内燃機関の場合、種々の排気温度においてＣＯ_２を吸気系へ供給することができる。また、複数のＣＯ_２吸放出手段の第１の状態が互いに異なる温度範囲に対応付けられていれば、種々の排気温度においてＣＯ_２を吸収させることができる。
【００１８】
【発明の実施の形態】
（第１の実施形態）
図１に本発明の燃焼制御装置が適用される内燃機関の要部を示す。内燃機関１は、燃焼室２に吸気を取り込むための吸気通路３と、燃焼室２からの排気を所定の排気位置まで導くための排気通路４と、これら通路３、４を開閉するための吸気バルブ５及び排気バルブ６とを備えている。吸気通路３には吸気量を調整するための吸気絞り弁７が設けられており、排気通路４にはターボチャージャ８のタービン８ａと、タービン８ａに流入する排気の流速を変化させる可変ノズル８ｂとが設けられている。排気通路４は、排気の一部を吸気通路３へ導入するためＥＧＲ通路９によって吸気通路３と接続されている。
【００１９】
ＥＧＲ通路９には、ＣＯ_２吸放出手段として複数（図１では２個）のＣＯ_２吸放出材１０ａ、１０ｂと、ＣＯ_２吸放出材１０ａ、１０ｂを迂回して排気通路４と吸気通路３とを接続するバイパス通路１１とが設けられている。排気通路４から吸気通路３へ導入される排気の流れは、バイパス弁１２と、ＣＯ_２吸放出材１０ａ、１０ｂから放出されるＣＯ_２量を調整する放出弁１３ａ、１３ｂとによって調整される。
【００２０】
内燃機関１の運転状態はエンジンコントロールユニット（ＥＣＵ）１４により制御される。ＥＣＵ１４は、マイクロプロセッサ及びその動作に必要なＲＯＭ、ＲＡＭ等の周辺装置を組み合わせたコンピュータとして構成されている。ＥＣＵ１４は、例えば内燃機関１がアイドリングや低負荷の状態で運転されている場合にバイパス弁１２の開度を大きくして吸気通路３へ供給される排気の流量を増加させ、内燃機関１の燃焼温度を低下させる低温燃焼を実行する。
【００２１】
ＣＯ_２吸放出材１０ａ、１０ｂは、例えばリチウムジルコネート（Ｌｉ_２ＺｒＯ_３）等のリチウムの複合酸化物を主体として構成され、第１の温度範囲（例えば４００℃〜５８０℃）でＣＯ_２を吸収し、第２の温度範囲（例えば６００℃〜７００℃）でＣＯ_２を放出する特性を備えた公知のものである。なお、ＣＯ_２吸放出材１０ａとＣＯ_２吸放出材１０ｂとは、互いに異なる第１の温度でＣＯ_２の吸収を開始し、且つ互いに異なる第２の温度でＣＯ_２の放出を開始する。図２にＣＯ_２吸放出材１０ａ、１０ｂの第１の温度範囲と第２の温度範囲の一例を示す。図２中の実線はＣＯ_２吸放出材１０ａのＣＯ_２吸放出特性を、図２中の点線はＣＯ_２吸放出材１０ｂのＣＯ_２吸放出特性をそれぞれ示している。図２から明らかなように、ＣＯ_２吸放出材１０ａは図２中の温度Ｔａ未満が第１の温度範囲に、Ｔａよりも高温の範囲が第２の温度範囲にそれぞれ相当し、ＣＯ_２吸放出材１０ｂは図２中の温度Ｔｂ未満が第１の温度範囲に、Ｔｂよりも高温の範囲が第２の温度範囲にそれぞれ相当する。
【００２２】
放出弁１３ａ、１３ｂの動作は、ＥＣＵ１４により制御される。図３は、ＥＣＵ１４が放出弁１３ａ、１３ｂの動作を制御するために実行する放出弁制御ルーチンを示すフローチャートである。図３の制御ルーチンは、内燃機関１の運転中に所定の周期で繰り返し実行される。なお、図３中において、放出弁Ａは放出弁１３ａを、放出弁Ｂは放出弁１３ｂをそれぞれ示している。
【００２３】
図３の制御ルーチンにおいて、ＥＣＵ１４はまずステップＳ１１でＣＯ_２の放出要求が有るか否かを判断する。放出要求は、内燃機関１に低温燃焼を行わせる等、燃焼室２へ不活性ガスを大量に供給して内燃機関１の空燃比を急速に低下させる場合に有ると判断される。ＣＯ_２放出要求が有ると判断した場合はステップＳ１２に進み、ＥＣＵ１４はＣＯ_２吸放出材１０ａ、１０ｂの温度Ｔが図２の温度Ｔａ未満か否かを判断する。ＣＯ_２吸放出材１０ａ、１０ｂの温度ＴがＴａ未満であると判断した場合は、今回の制御ルーチンを終了する。ＣＯ_２吸放出材１０ａ、１０ｂの温度ＴがＴａ未満ではないと判断した場合はステップＳ１３に進み、ＥＣＵ１４はＣＯ_２吸放出材１０ａ、１０ｂの温度Ｔが図２の温度Ｔｂよりも高温か否かを判断する。高温ではないと判断した場合はステップＳ１４に進み、ＥＣＵ１４は放出弁１３ａが開、放出弁１３ｂが閉の状態になるように放出弁１３ａ、１３ｂへ指示を出力し、その後今回の制御ルーチンを終了する。一方、高温であると判断した場合はステップＳ１５に進み、ＥＣＵ１４は放出弁１３ａと放出弁１３ｂとが開の状態になるように放出弁１３ａ、１３ｂへ指示を出力し、その後今回の制御ルーチンを終了する。
【００２４】
ステップＳ１１においてＣＯ_２放出要求が無いと判断した場合は、ステップＳ１６に進み、ＥＣＵ１４はＣＯ_２吸放出材１０ａ、１０ｂの温度Ｔが図２のＴａ未満か否かを判断する。ＣＯ_２吸放出材１０ａ、１０ｂの温度ＴがＴａ未満であると判断した場合はステップＳ１５に進み、放出弁１３ａと放出弁１３ｂとが開の状態になるように放出弁１３ａ、１３ｂへ指示を出力する。その後今回の処理を終了する。ＣＯ_２吸放出材１０ａ、１０ｂの温度ＴがＴａ未満ではないと判断した場合はステップＳ１７に進み、ＥＣＵ１４はＣＯ_２吸放出材１０ａ、１０ｂの温度Ｔが図２のＴｂよりも高温か否かを判断する。高温ではないと判断した場合はステップＳ１８に進み、ＥＣＵ１４は放出弁１３ａが閉、放出弁１３ｂが開の状態になるように放出弁１３ａ、１３ｂへ指示を出力し、その後今回の制御ルーチンを終了する。一方、高温であると判断した場合はステップＳ１９に進み、ＥＣＵ１４は放出弁１３ａと放出弁１３ｂとが閉の状態になるように放出弁１３ａ、１３ｂへ指示を出力し、その後今回の制御ルーチンを終了する。
【００２５】
このように放出弁１３ａ、１３ｂの動作を制御することによって、ＣＯ_２吸放出材１０ａ、１０ｂから吸放出されて内燃機関１の吸気系へ供給されるＣＯ_２量を調整することができる。また、ＣＯ_２の吸収を開始する温度とＣＯ_２の放出を開始する温度とが互いに異なるＣＯ_２吸放出材１０ａ、１０ｂをＥＧＲ通路９に設けることにより、ＣＯ_２の吸収温度範囲と放出温度範囲とを広げることができる。更に、ＣＯ_２吸放出材１０ａ、１０ｂの温度Ｔが図２のＴａ〜Ｔｂの範囲にある場合には、ＣＯ_２の吸収、放出を切り替えることもできる。
【００２６】
図１の実施形態においてＣＯ_２吸放出材１０ａ、１０ｂからＣＯ_２が吸放出される場合、ＥＧＲ通路９を通過して吸気通路３へ供給されるＣＯ_２の量が不足し、又は過剰になることがある。図４及び図５は、このようなＣＯ_２量の不足又は過剰を抑制するためにＥＣＵ１４が実行する制御ルーチンを示している。これらの制御ルーチンを実行することにより、ＥＣＵ１４は動作制御手段として機能する。また、バイパス弁１２と放出弁１３ａ、１３ｂとは排気流量調整手段として機能する。なお、これらの制御ルーチンは、内燃機関１の動作中に所定の周期で繰り返し実行される。以下、各制御ルーチンについて説明する。
【００２７】
図４のバイパス弁補正制御ルーチンは、ＥＣＵ１４が、ＣＯ_２吸放出材１０ａ、１０ｂのＣＯ_２吸収時に、バイパス弁１２の動作を制御するために実行するものである。この制御ルーチンにおいてＥＣＵ１４は、まずステップＳ２１で放出弁１３ａ、１３ｂが開状態で有るか否かを判断する。放出弁１３ａ、１３ｂが開状態ではないと判断した場合は、今回の制御ルーチンを終了する。一方、開状態であると判断した場合はステップＳ２２に進み、ＣＯ_２吸放出材１０ａ、１０ｂの温度がＣＯ_２を吸収する第１の温度範囲内か否かを判断する。吸収温度範囲内ではないと判断した場合は、今回の制御ルーチンを終了する。吸収温度範囲内であると判断した場合はステップＳ２３に進み、ＣＯ_２吸放出材１０ａ、１０ｂのＣＯ_２吸収量を算出する。ＣＯ_２吸収量は、ＣＯ_２吸放出材１０ａ、１０ｂの温度、ＣＯ_２吸放出材１０ａ、１０ｂが設けられている場所の排気圧、ＣＯ_２吸放出材１０ａ、１０ｂに導入される排気のＣＯ_２分圧、ＣＯ_２吸放出材１０ａ、１０ｂが既に吸収しているＣＯ_２の量等に基づいて算出される。
【００２８】
次のステップＳ２４では、ＥＣＵ１４は、ＥＧＲ通路９を通過して吸気通路３へ供給される排気中のＣＯ_２濃度の変化量を算出する。ＣＯ_２濃度の変化量は、算出したＣＯ_２吸収量と排気通路４の排気の空燃比とに基づいて算出される。続くステップＳ２５においてＥＣＵ１４は、算出したＣＯ_２濃度の変化量がバイパス通路１１を通過して吸気通路３へ供給される排気の流量によって相殺されるように、バイパス弁１２の補正操作量を算出する。次のステップＳ２６では、ＥＣＵ１４は、バイパス弁１２の補正操作実行後の内燃機関１の空燃比を算出し、この空燃比が下限値以上か否かを判断する。下限値は、ＰＭが大量に発生する特定の空燃比域に差しかからないような空燃比に設定される。空燃比が下限値以上になると判断した場合はステップＳ２７に進み、算出した補正操作量をバイパス弁１２へ指示し、その後今回の制御ルーチンを終了する。一方、空燃比が下限値以下になると判断した場合はステップＳ２８に進み、内燃機関１の空燃比が下限値以上になるようなバイパス弁１２の補正操作量を再度算出し、その補正操作量をバイパス弁１２へ指示する。その後今回の制御ルーチンを終了する。
【００２９】
このように、ＣＯ_２吸放出材１０ａ、１０ｂのＣＯ_２吸収量に応じてバイパス弁１２の動作を制御することで、吸気通路３へ供給されるＣＯ_２量を適正量に維持することができる。
【００３０】
図４において、「相殺」の概念は、ＣＯ_２濃度の変化量を完全に打ち消す場合に限らず、変化量を部分的に又は不完全に打ち消す等、ＣＯ_２濃度の変化量を減少させる場合も含む。
【００３１】
図５の放出弁補正制御ルーチンは、ＣＯ_２吸放出材１０ａ、１０ｂからＣＯ_２が放出される場合、吸気通路３へＣＯ_２が過剰に供給されることを抑制するためにＥＣＵ１４が実行するものである。なお、図５において、図３及び図４と同一の処理には同一の参照符号を付し、説明を省略する。
【００３２】
図５の制御ルーチンにおいて、ＥＣＵ１４はまずステップＳ１１でＣＯ_２の放出要求が有るか否かを判断する。ＣＯ_２放出要求が無いと判断した場合は、今回の制御ルーチンを終了する。ＣＯ_２放出要求が有ると判断した場合はステップＳ３１に進み、ＥＣＵ１４はＣＯ_２吸放出材１０ａ、１０ｂから放出されるＣＯ_２量を算出する。ＣＯ_２放出量は、ＣＯ_２吸放出材１０ａ、１０ｂの温度、ＣＯ_２吸放出材１０ａ、１０ｂが設けられている場所の排気圧、ＣＯ_２吸放出材１０ａ、１０ｂに導入される排気のＣＯ_２分圧、ＣＯ_２吸放出材１０ａ、１０ｂが既に吸収しているＣＯ_２の量等に基づいて算出される。続くステップＳ２４においてＥＣＵ１４は、ＥＧＲ通路９を通過して吸気通路３へ供給される排気中のＣＯ_２濃度の変化量を算出する。ＣＯ_２濃度の変化量は、算出したＣＯ_２放出量と排気通路４の排気の空燃比とに基づいて算出される。次のステップＳ３２では、ＥＣＵ１４は、放出弁１３ａ、１３ｂの補正操作量を算出する。ＣＯ_２吸放出材１０ａ、１０ｂから吸気通路３へ過剰にＣＯ_２が供給されると、内燃機関１は失火する可能性がある。そこで、過剰に供給されると見込まれるＣＯ_２量を抑制するように放出弁１３ａ、１３ｂの補正操作量が算出される。続くステップＳ３３においてＥＣＵ１４は、放出弁１３ａ、１３ｂへ算出した補正操作量を指示する。その後今回の制御ルーチンを終了する。
【００３３】
このように放出弁１３ａ、１３ｂを制御することによって、吸気通路３へのＣＯ_２の過剰な供給を抑制し、内燃機関１の失火等を防止することができる。
【００３４】
以上の実施形態ではＣＯ_２吸放出材を２つ使用したが、図６に示すようにＣＯ_２吸放出材は１つでもよい。なお、図６において、図１と共通する部分には同一符号を付してある。
【００３５】
図６の例では、ＥＧＲ通路９を通過する排気の流量調整手段として、バイパス弁１２及び放出弁１３ａの他に、ＣＯ_２吸放出材１０ａとバイパス通路１１とを通過する排気流量の比を調整することができる流量比調整弁１３ｃ、１３ｄが設けられている。流量比調整弁１３ｃ、１３ｄもＥＣＵ１４によって動作が制御される。
【００３６】
例えば、ＣＯ_２吸放出材１０ａがＣＯ_２を吸収している場合、吸気通路３へ供給されるＣＯ_２量が減少する。そこで、バイパス通路１１を通過して吸気通路３へ供給される排気の流量が増加するように、流量比調整弁１３ｃ、１３ｄを図６中の矢印Ａの方向に動作させる。また、内燃機関１の空燃比を急速に低下させる場合は、ＣＯ_２吸放出材１０ａから放出されるＣＯ_２が吸気通路３へ供給されるように、流量比調整弁１３ｃ、１３ｄを図６中の矢印Ｂの方向に動作させる。
【００３７】
このように流量比調整弁１３ｃ、１３ｄの動作を制御することでも、吸気通路３へ供給されるＣＯ_２量を調整することができる。なお、排気の流量は、バイパス弁１２、放出弁１３ａ、流量比調整弁１３ｃ、１３ｄの全てを使用して調整する必要はない。ＣＯ_２吸放出材１０ａとバイパス通路１１とを通過する排気の流量は、これらの弁のうちの一つでも調整が可能である。従って、バイパス弁１２、放出弁１３ａ、流量比調整弁１３ｃ、１３ｄのうち少なくとも一つが設けられていればよい。
【００３８】
以上の実施形態ではＣＯ_２吸放出材１０ａ、１０ｂを通過した排気は全て吸気通路３へ導入していたが、図７に示すように、ＣＯ_２吸放出材１０ａ、１０ｂからＣＯ_２を放出させる場合とＣＯ_２を吸収させる場合とで、ＣＯ_２吸放出材１０ａ、１０ｂを通過した排気を導入する位置を変更してもよい。なお、図７において図１と共通する部分には同一符号を付してある。
【００３９】
図７（ａ）はＣＯ_２吸放出材１０ａ、１０ｂからＣＯ_２を放出させる場合、図７（ｂ）はＣＯ_２吸放出材１０ａ、１０ｂへＣＯ_２を吸収させる場合をそれぞれ示している。排気の導入位置を変更するため図７の例には、切り替え弁１５ａ、１５ｂと調量弁１５ｃとが設けられている。切り替え弁１５ａ、１５ｂ及び調量弁１５ｃもＥＣＵ１４によって動作が制御される。
【００４０】
図７（ａ）から明らかなようにＣＯ_２吸放出材１０ａ、１０ｂからＣＯ_２を放出させる場合は、切り替え弁１５ａ、１５ｂの位置と調量弁１５ｃの開度とを変更して図７（ａ）中の矢印の方向へ排気が流れるようにし、排気を吸気通路３へ供給する。図７の実施形態の場合、ＣＯ_２吸放出材１０ａ、１０ｂを通過して吸気通路３へ供給される排気の流量は、放出弁１３ａ、１３ｂの他に調量弁１５ｃの開度を変更することでも調整できる。一方、ＣＯ_２吸放出材１０ａ、１０ｂへＣＯ_２を吸収させる場合は、図７（ｂ）中の矢印の方向へ排気が流れるように切り替え弁１５ａ、１５ｂ及び調量弁１５ｃを動作させ、排気を排気通路４へ導入する。
【００４１】
このように排気の流れを変更することで、ＣＯ_２吸放出材１０ａ、１０ｂのＣＯ_２吸収時に発生していた吸気通路３へ供給する排気中ＣＯ_２濃度の変動をなくすことができる。従って、図１の実施形態で実施していた図４の制御ルーチンを省略することができる。
【００４２】
なお、図７の例において、ＣＯ_２吸放出材の数は２個に限定されず、更に多くのＣＯ_２吸放出材が設けられていてもよい。また、ターボチャージャ８はなくてもよい。
【００４３】
（第２の実施形態）
次に、図８、図９を参照して本発明の第２の実施形態を説明する。但し、各図において図１、図５と共通する部分には同一符号を付し、それらの説明は省略する。
【００４４】
図８に示す第２の実施形態は、ＥＧＲ通路９に排気の空燃比を取得する空燃比取得手段である空燃比センサ１６が設けられている点において第１の実施形態と異なる。空燃比センサ１６の出力はＥＣＵ１４に送られ、ＣＯ_２吸放出材１０ａから吸放出されたＣＯ_２量の推定に使用される。図９は、図８の実施形態においてＣＯ_２吸放出材１０ａからＣＯ_２が放出される場合、内燃機関１へＣＯ_２が過剰に供給されることを抑制するためにＥＣＵ１４が実行する制御ルーチンである。図９の制御ルーチンは、内燃機関１の動作中に所定の周期で繰り返し実行される。
【００４５】
図９の制御ルーチンにおいて、ＥＣＵ１４はまずステップＳ１１でＣＯ_２の放出要求が有るか否かを判断する。ＣＯ_２放出要求が無いと判断した場合は、今回の制御ルーチンを終了する。ＣＯ_２放出要求が有ると判断した場合はステップＳ４１に進み、ＣＯ_２吸放出材１０ａからＣＯ_２が放出される前と放出された後とにおけるＥＧＲ通路９の排気のＣＯ_２濃度変化を取得する。
【００４６】
ＣＯ_２濃度変化は、例えばＥＧＲ通路９に設けられた空燃比センサ用切り替え弁１７の動作を制御し、空燃比センサ１６へ導入される排気を変化させて取得する。空燃比センサ用切り替え弁１７が実線で示した図８のＡの位置にある場合、ＣＯ_２吸放出材１０ａを通過した排気は空燃比センサ１６へ導入されることはない。そのため、放出されたＣＯ_２の影響の無い排気の空燃比を取得することができる。一方、空燃比センサ用切り替え弁１７が点線で示した図８のＢの位置にある場合は、空燃比センサ１６にＣＯ_２吸放出材１０ａから放出されたＣＯ_２が導入される。そのため、放出されたＣＯ_２を含んだ排気の空燃比を取得することができる。このように空燃比センサ用切り替え弁１７の位置を変更して取得した空燃比の変化からＣＯ_２濃度変化を取得する。
【００４７】
次のステップＳ４２では、ＥＣＵ１４は、ＣＯ_２吸放出材１０ａから放出されたＣＯ_２量を算出する。ＣＯ_２放出量は、取得したＣＯ_２濃度変化に基づいて算出される。ＣＯ_２量を算出した後はステップＳ２４以下に進み、図５と同様の処理を行う。
【００４８】
このように、空燃比センサ１６が取得した空燃比の変化に基づいてＣＯ_２放出量を算出するので、より正確にＣＯ_２放出量を推定することができる。従って、放出弁１３ａの制御精度を向上させることができる。また、ＣＯ_２吸放出材１０ａへＣＯ_２を吸収させる場合も、空燃比センサ１６で排気の空燃比の変化を取得することで、ＣＯ_２吸収量をより正確に推定することができる。これにより、バイパス弁１２の補正操作の制御精度を向上させることができる。なお、空燃比センサ１６を配置する位置は図８に示した位置に限定されない。ＣＯ_２吸放出材１０ａからＣＯ_２が吸放出される前と吸放出された後とにおいて吸放出前後の排気の空燃比を取得できる位置であれば、どこに配置してもよい。また、空燃比を取得する手段は空燃比センサに限定されず、酸素濃度センサを使用してもよい。
【００４９】
（第３の実施形態）
次に、図１０を参照して本発明の第３の実施形態を説明する。但し、図１０において図１と共通する部分には同一符号を付し、それらの説明は省略する。
【００５０】
図１０に示す実施形態は、ＥＧＲ通路９に、排気と熱交換して排気を冷却する熱交換器としてのＥＧＲクーラ１８と、ＥＧＲクーラ１８をバイパスさせて排気を下流側へ導くＥＧＲクーラバイパス通路１９と、ＥＧＲクーラ１８へ導入する排気の流量を調整するＥＧＲクーラ用調量弁２０とを備えている点において他の実施形態と異なる。
【００５１】
ＥＧＲクーラ用調量弁２０の動作はＥＣＵ１４によって制御される。図１１は、ＥＣＵ１４がＥＧＲクーラ用調量弁２０の動作を制御するために実行する制御ルーチンを示すフローチャートである。図１１の制御ルーチンを実行することにより、ＥＣＵ１４は熱交換量制御手段として機能する。図１１の制御ルーチンは、内燃機関１の運転中に所定の周期で繰り返し実行される。
【００５２】
図１１の制御ルーチンにおいて、ＥＣＵ１４はまずステップＳ５１で排気の温度を取得する。排気の温度は燃焼室２へ供給された燃料量等に基づいて算出して取得してもよいし、排気通路４に設けた温度センサにより取得してもよい。次のステップＳ５２では、ＥＣＵ１４は、ＣＯ_２吸放出材１０ａ、１０ｂへＣＯ_２を吸収させる要求があるか否かを判断する。ＣＯ_２吸収要求は、例えばＣＯ_２吸放出材１０ａ、１０ｂに内燃機関１の空燃比を急速に低下させるのに必要なＣＯ_２量が吸収されていない場合にあると判断される。ＣＯ_２吸収要求があると判断した場合はステップＳ５３に進み、取得した排気温度が図１２の温度Ｔａよりも高温であるか否か判断する。図１２は、ＣＯ_２吸放出材１０ａのＣＯ_２吸放出特性を示している。図１２から明らかなように、ＣＯ_２吸放出材１０ａはＴａ未満の温度でＣＯ_２を吸収し、Ｔａよりも高温の範囲でＣＯ_２を放出する。排気温度がＴａよりも高温であると判断した場合はステップＳ５４へ進み、ＥＧＲクーラ用調量弁２０を開く。その後、今回の制御ルーチンを終了する。
【００５３】
一方、ステップＳ５２でＣＯ_２吸収要求がないと判断した場合及びステップＳ５３で排気温度がＴａよりも高温ではないと判断した場合は、ステップＳ５５に進み、ＥＧＲクーラ用調量弁２０を閉じる。その後、今回の制御ルーチンを終了する。
【００５４】
このように、ＣＯ_２吸放出材１０ａ、１０ｂへ導入される排気の温度を調整することで、排気通路４の排気温度が高い場合でもＣＯ_２吸放出材１０ａへＣＯ_２を吸収させることができる。また、例えば、排気中のＣＯ_２濃度が高く、排気の圧力が高い方がＣＯ_２を多く吸収するＣＯ_２吸放出材を使用した場合は、排気温度が高温になる状態で内燃機関１が運転されているときの排気中のＣＯ_２濃度は高く、排気の圧力も高くなるので、高温の排気を冷却してＣＯ_２吸放出材へ導入することで、ＣＯ_２吸放出材へＣＯ_２を効率よく吸収させることができる。
【００５５】
なお、ＣＯ_２吸収開始温度の異なる複数のＣＯ_２吸放出材をＥＧＲ通路９へ配置する場合は、例えばこれら複数のＣＯ_２吸放出材のうち最も低いＣＯ_２吸収開始温度を基準としてＥＧＲクーラ用調量弁２０を制御することで、全てのＣＯ_２吸放出材へＣＯ_２を吸収させることができる。
【００５６】
図１３は、図１０の実施形態に使用されるＣＯ_２吸放出材１０ａのＣＯ_２吸放出特性の他の例を示している。図１３から明らかなように、このＣＯ_２吸放出材１０ａは、温度Ｔ−ｍａｘにおいて最も多くＣＯ_２を吸収する。従って、ＥＧＲクーラ用調量弁２０の開度を変更して排気温度をＴ−ｍａｘにすることで、さらにＣＯ_２の吸収効率を向上させることができる。
【００５７】
図１４は、図１３のＣＯ_２吸放出特性を有するＣＯ_２吸放出材が図１０の実施形態に使用された場合に、ＥＣＵ１４がＥＧＲクーラ用調量弁２０の開度を変更するために実行する制御ルーチンを示すフローチャートである。図１４の制御ルーチンは、内燃機関１の運転中に所定の周期で繰り返し実行される。
【００５８】
図１４の制御ルーチンにおいて、ＥＣＵ１４はまずステップＳ５１で排気の温度を取得する。次のステップＳ５２では、ＥＣＵ１４は、ＣＯ_２吸放出材１０ａへＣＯ_２を吸収させる要求があるか否かを判断する。ＣＯ_２吸収要求があると判断した場合はステップＳ６１に進み、取得した排気温度が図１３の温度Ｔ―ｍａｘよりも高温であるか否か判断する。排気温度がＴ−ｍａｘよりも高温であると判断した場合は、ステップＳ６２へ進み、ＥＣＵ１４はＣＯ_２吸放出材１０ａへ導入される排気の温度がＴ−ｍａｘになるようなＥＧＲクーラ用調量弁２０の補正操作量を算出する。補正操作量は例えば、ＥＧＲクーラ用調量弁２０の開度と排気温度との対応関係を予め実験により求めてマップとしてＥＣＵ１４のＲＯＭに記憶しておき、そのマップを参照することで求めることができる。続く、ステップＳ６３において、ＥＣＵ１４は、算出した補正操作量をＥＧＲクーラ用調量弁２０へ指示し、その後今回の制御ルーチンを終了する。
【００５９】
一方、ステップＳ５２でＣＯ_２吸収要求がないと判断した場合、及びステップＳ６１で排気温度がＴ―ｍａｘよりも高温ではないと判断した場合は、ステップＳ５５に進み、ＥＧＲクーラ用調量弁２０を閉じる。その後、今回の制御ルーチンを終了する。
【００６０】
このようにＣＯ_２吸放出材１０ａへＣＯ_２を吸収させる場合は、ＣＯ_２吸放出材１０ａへ導入される排気の温度をＴ−ｍａｘにすることで、ＣＯ_２の吸収効率をさらに向上させることができる。
【００６１】
第３の実施形態において排気温度を調整する方法は、ＥＧＲクーラ用調量弁２０によって排気流量を調整する方法に限定されない。例えば、ＥＧＲクーラ１８が内燃機関１の冷却水を利用して熱交換を行う場合は、その冷却水の流量を変更して排気温度を調整してもよい。また、排気流量の調整と冷却水の流量調整とを併用して排気温度を調整してもよい。熱交換器は、ＥＧＲクーラ等のように排気を冷却するものに限定されず、排気を加熱する加熱器を設けてもよい。
【００６２】
ＥＧＲクーラ１８を配置する位置も図１０に示した位置に限定されない。例えば、図１５に示したように、バイパス通路１１と分岐した後で且つＣＯ_２吸放出材１０ａ、１０ｂの上流側のＥＧＲ通路９に配置してもよい。また、図１５に示したように、ＥＧＲクーラ１８とは別にバイパス通路１１にも、バイパス通路を通過して吸気通路３へ供給される排気を冷却するバイパス通路用ＥＧＲクーラ２１を配置してもよい。
【００６３】
本発明は、上述した実施形態に限定されることなく、種々の形態にて実施してよい。例えばＣＯ_２吸放出材の個数は２個に限定されず、１個でもよいし３個以上のＣＯ_２吸放出材を配置してもよい。また、複数のＣＯ_２吸放出材は、ＣＯ_２を吸収する第１の状態とＣＯ_２を放出する第２の状態とのうち少なくとも一方が互いに異なった温度範囲と対応付けられているものに限定されない。例えば、ＣＯ_２の吸放出速度やＣＯ_２吸収容量等のＣＯ_２吸放出特性が異なる複数のＣＯ_２吸放出材を使用してもよい。さらに、上述した実施形態と同等の効果が得られるのであれば、種々のＣＯ_２吸放出特性を有するＣＯ_２吸放出材を複数組み合わせて使用してよい。
【００６４】
【発明の効果】
以上に説明したように、本発明によれば、ＣＯ_２吸放出材から放出されたＣＯ_２を内燃機関の吸気系へ供給して内燃機関の空燃比を低下させることができる。また、ＣＯ_２を吸収する第１の状態とＣＯ_２を放出する第２の状態とのうち少なくとも一方が互いに異なった複数のＣＯ_２吸放出材を使用することにより、さらに広い範囲でＣＯ_２を吸放出させて内燃機関の燃焼を制御することができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る燃焼制御装置が適用される内燃機関の要部を示す図。
【図２】図１のＣＯ_２吸放出材のＣＯ_２吸放出特性を示す図。
【図３】図１のＥＣＵが放出弁の動作を制御するために実行する制御ルーチンを示す図。
【図４】図１のＥＣＵがバイパス弁の動作を制御するために実行する制御ルーチンを示す図。
【図５】図１のＥＣＵが放出弁の補正操作を行うために実行する制御ルーチンを示す図。
【図６】本発明の第１の実施形態に係る燃焼制御装置の変形例を示す図。
【図７】本発明の第１の実施形態に係る燃焼制御装置の他の変形例を示す図。
【図８】本発明の第２の実施形態に係る燃焼制御装置が適用される内燃機関の要部を示す図。
【図９】図８のＥＣＵが放出弁の補正操作を行うために実行する制御ルーチンを示す図。
【図１０】本発明の第３の実施形態に係る燃焼制御装置が適用される内燃機関の要部を示す図。
【図１１】図１０のＥＣＵがＥＧＲクーラ用調量弁の動作を制御するために実行する制御ルーチンを示す図。
【図１２】図１０のＣＯ_２吸放出材のＣＯ_２吸放出特性を示す図。
【図１３】図１０の燃焼制御装置に使用される他のＣＯ_２吸放出材のＣＯ_２吸放出特性を示す図。
【図１４】図１３のＣＯ_２吸放出特性を有するＣＯ_２吸放出材が燃焼制御装置に使用された場合に、図１０のＥＣＵがＥＧＲクーラ用調量弁の動作を制御するために実行する制御ルーチンを示す図。
【図１５】本発明の第３の実施形態に係る燃焼制御装置の変形例を示す図。
【符号の説明】
１内燃機関
２燃焼室
３吸気通路
４排気通路
１０ａ、１０ｂＣＯ_２吸放出材（ＣＯ_２吸放出手段）
１１バイパス通路
１２バイパス弁（排気流量調整手段）
１３ａ、１３ｂ放出弁（排気流量調整手段）
１３ｃ、１３ｄ流量比調整弁（排気流量調整手段）
１４エンジンコントロールユニット（動作制御手段、熱交換量制御手段）
１６空燃比センサ（空燃比取得手段）
１８ＥＧＲクーラ（熱交換器）
２０ＥＧＲクーラ用調量弁（熱交換量制御手段）[0001]
BACKGROUND OF THE INVENTION
The present invention provides CO ₂ CO to absorb and release ₂ The present invention relates to a combustion control method and a combustion control device for an internal combustion engine provided with an absorption / release material.
[0002]
[Prior art]
In the temperature range of about 250 ° C, carbon dioxide (CO ₂ ) A carbon dioxide absorbent material having a high absorption capacity is known (see Patent Document 1). In the temperature range from room temperature to around 600 ° C, CO ₂ In the temperature range of 680 ° C or higher. ₂ CO that emits ₂ Absorption / release materials are known (see Non-Patent Document 1). In addition, Patent Documents 2 and 3 exist as techniques related to the present invention.
[0003]
[Patent Document 1]
JP 2001-96122 A
[Patent Document 2]
JP 2001-3775 A
[Patent Document 3]
JP 11-262632 A
[Non-Patent Document 1]
Toshiba Review Vol. 56, no. 8 (2001) p. 11-14
[0004]
[Problems to be solved by the invention]
NOx storage reduction as an exhaust gas purification device for diesel engines _x An exhaust purification system using an exhaust purification catalyst such as a catalyst has been put into practical use. In this exhaust purification system, when the engine is operated at a low speed and a low load, the exhaust temperature decreases, and the catalyst temperature decreases accordingly, and the catalyst may become inactive. Therefore, in this operating range, a large amount of inert gas such as EGR gas is supplied to the combustion chamber to reduce the combustion temperature of the engine (low temperature combustion), and hydrocarbons (HC) are generated by this low temperature combustion. The activity of the catalyst is maintained.
[0005]
Incidentally, the particulate matter (PM) discharged from the diesel engine and the air-fuel ratio of the engine have a correlation, and it is known that a large amount of PM is generated in a specific air-fuel ratio region. When an inert gas is supplied for low-temperature combustion, the air-fuel ratio decreases, and a large amount of PM is generated by entering this specific air-fuel ratio region. Therefore, it is desirable to reduce the amount of PM generated by supplying a large amount of inert gas to the combustion chamber in a short time and lowering the air-fuel ratio in a short time through the air-fuel ratio region where a large amount of PM is generated. It is. CO for inert gas ₂ Can be used, but conventionally, for this purpose, CO ₂ The use of absorption / release materials has not been studied.
[0006]
Therefore, the present invention provides CO 2 ₂ An object of the present invention is to provide a combustion control method and a combustion control device for an internal combustion engine that can reduce the air-fuel ratio of the internal combustion engine by using the above-mentioned.
[0007]
[Means for Solving the Problems]
The combustion control method for an internal combustion engine according to the present invention provides a CO 2 in the first state. ₂ CO absorbed in the second state ₂ CO that emits ₂ When applied to an internal combustion engine provided with an intake / discharge means, and when supply of an inert gas into a combustion chamber is required, the CO ₂ The suction / release means is in the second state and the CO ₂ And the released CO ₂ Is supplied to the intake system of the internal combustion engine to solve the above-described problem (claim 1).
[0008]
According to the combustion control method of the present invention, when the supply of inert gas into the combustion chamber is required for low temperature combustion or the like, the CO ₂ CO from the intake / release means to the intake system of the internal combustion engine ₂ By supplying this, the air-fuel ratio of the internal combustion engine can be lowered, that is, the oxygen amount can be changed to a relatively decreasing side.
[0009]
The combustion control apparatus for an internal combustion engine according to the present invention has a CO in the first state. ₂ CO absorbed in the second state ₂ CO that emits ₂ The present invention is applied to an internal combustion engine provided with an intake / discharge means, and the CO ₂ The absorption / release means is the CO ₂ CO released from the absorption / release means ₂ Is connected to the intake passage of the internal combustion engine so as to be supplied to the intake system of the internal combustion engine, thereby solving the above-mentioned problem.
[0010]
According to the combustion control device of the present invention, CO ₂ CO released from the absorption / release means ₂ Can be supplied to the intake system, so that the air-fuel ratio of the internal combustion engine can be lowered as in the combustion control method of the present invention.
[0011]
In the internal combustion engine combustion control apparatus of the present invention, the CO ₂ The intake / discharge means discharges the exhaust gas from the internal combustion engine to the CO. ₂ It may be connected to the exhaust passage of the internal combustion engine so that it can be introduced into the intake / discharge means. In this case, CO contained in the exhaust gas of the internal combustion engine ₂ CO ₂ It can be temporarily stored in the suction / release means and supplied to the intake system as needed.
[0012]
In the combustion control apparatus for an internal combustion engine according to the present invention, the exhaust passage and the intake passage are connected to the CO 2. ₂ A bypass passage that bypasses and connects the suction / release means may be provided. In this case, CO ₂ Exhaust gas can be supplied to the intake system via both the intake / discharge means and the bypass passage. As a result, the CO supplied to the intake system ₂ The degree of freedom in adjusting the amount is increased. For example, CO ₂ The absorption and release means is CO ₂ Is absorbed, CO supplied to the intake system ₂ Since the amount decreases, the exhaust gas is sent from the bypass passage to the intake system according to the decrease amount, and the exhaust gas flow rate is increased. ₂ Can be suppressed. On the other hand, CO ₂ CO from absorption and release means ₂ Is released, CO supplied to the intake system ₂ If the amount is excessive, there is a possibility that the internal combustion engine will misfire due to insufficient oxygen necessary for combustion. In this case, CO ₂ CO that reduces the flow rate of the exhaust gas supplied from the exhaust passage to the intake system in accordance with the excess amount of discharge, so that the internal combustion engine does not misfire. ₂ Adjust to the amount.
[0013]
The combustion control device for an internal combustion engine of the present invention includes the CO ₂ An exhaust flow rate adjusting means for adjusting a flow rate of exhaust gas that passes through at least one of the intake / discharge means and the bypass passage and is supplied to the intake system; and the CO ₂ CO for absorption and release means ₂ Operation control means for controlling the operation of the exhaust flow rate adjustment means based on the amount of intake and discharge may be provided. In this case, the CO 2 as described above is controlled by controlling the operation of the exhaust flow rate adjusting means. ₂ The bypass flow rate can be adjusted according to the absorption and release of water.
[0014]
The combustion control device for an internal combustion engine of the present invention includes the CO ₂ The CO is disposed downstream of the absorption / release means. ₂ Air-fuel ratio acquisition means for acquiring the air-fuel ratio of the exhaust gas that has passed through the intake / discharge means, and the operation control means controls the operation of the exhaust gas flow rate adjustment means based on the air-fuel ratio acquired by the air-fuel ratio acquisition means. (Claim 6). By the air-fuel ratio acquisition means, CO ₂ CO from absorption and release means ₂ It is possible to examine the change in the air-fuel ratio when the gas is absorbed and released. From this change in air-fuel ratio, the actual CO ₂ CO absorbed and released from the absorption and release means ₂ The amount can be grasped more accurately. Therefore, the flow rate of the exhaust gas supplied to the intake system can be adjusted with higher accuracy.
[0015]
In the combustion control apparatus for an internal combustion engine according to the present invention, the first state and the second state are associated with different temperature ranges, and the CO ₂ Disposed on the upstream side of the suction / release means and the CO ₂ A heat exchanger that adjusts the temperature of the exhaust gas by exchanging heat with the exhaust gas that is introduced into the intake / discharge means; and a heat exchange amount control means that controls a heat exchange amount of the heat exchanger, the heat exchange amount control means Is the CO ₂ CO absorbed in the absorption / release means ₂ The amount of heat exchange of the heat exchanger may be controlled based on the amount (Claim 7). In this case, by adjusting the exhaust temperature, CO ₂ CO 2 is set in the first state or the second state, and CO ₂ CO absorbed in the absorption / release means ₂ Depending on the amount, absorption and release can be properly used. For example, CO ₂ CO absorbed in the absorption / release means ₂ If the amount is small, adjust the exhaust gas temperature ₂ The suction / release means is set to the first state, and the CO ₂ CO for absorption and release means ₂ Absorbs CO ₂ Absorption can be increased.
[0016]
In the internal combustion engine combustion control apparatus of the present invention, the CO ₂ A plurality of absorption / release means are provided, and the plurality of CO ₂ Each of the absorption and release means is a CO released from itself. ₂ May be connected to the intake passage so that can be supplied to the intake system. In this case, CO ₂ The absorption / release means can be properly used. For example, the best or bad conditions (for example, absorbed CO ₂ CO in descending order of the quantity) ₂ Can be absorbed and released. Also, multiple CO ₂ Simultaneously absorb and release the absorption / release means and CO ₂ May be absorbed and released.
[0017]
An internal combustion engine combustion control apparatus according to the present invention includes the plurality of COs. ₂ At least one of the first state and the second state of each of the absorption / release means may be different from each other (claim 9). In this case, CO in various states ₂ CO from absorption and release means ₂ Can be absorbed and released. For example, a plurality of COs whose second states are associated with different temperature ranges ₂ In the case of an internal combustion engine provided with intake and discharge means, CO at various exhaust temperatures. ₂ Can be supplied to the intake system. Also, multiple CO ₂ If the first state of the intake / discharge means is associated with different temperature ranges, the CO at various exhaust temperatures. ₂ Can be absorbed.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 shows a main part of an internal combustion engine to which the combustion control device of the present invention is applied. The internal combustion engine 1 includes an intake passage 3 for taking intake air into the combustion chamber 2, an exhaust passage 4 for guiding exhaust from the combustion chamber 2 to a predetermined exhaust position, and intake air for opening and closing these passages 3 and 4. A valve 5 and an exhaust valve 6 are provided. The intake passage 3 is provided with an intake throttle valve 7 for adjusting the intake air amount. The exhaust passage 4 includes a turbine 8a of the turbocharger 8 and a variable nozzle 8b for changing the flow rate of the exhaust gas flowing into the turbine 8a. Is provided. The exhaust passage 4 is connected to the intake passage 3 by an EGR passage 9 in order to introduce part of the exhaust gas into the intake passage 3.
[0019]
The EGR passage 9 has a CO ₂ A plurality (two in FIG. 1) of CO as absorption / release means ₂ Absorption / release materials 10a and 10b and CO ₂ A bypass passage 11 is provided to connect the exhaust passage 4 and the intake passage 3 by bypassing the absorption / release materials 10a and 10b. The flow of exhaust gas introduced from the exhaust passage 4 to the intake passage 3 includes a bypass valve 12, a CO 2 ₂ CO released from the absorption / release materials 10a and 10b ₂ It is adjusted by the discharge valves 13a and 13b for adjusting the amount.
[0020]
The operating state of the internal combustion engine 1 is controlled by an engine control unit (ECU) 14. The ECU 14 is configured as a computer in which a microprocessor and peripheral devices such as ROM and RAM necessary for its operation are combined. The ECU 14 increases the flow rate of the exhaust gas supplied to the intake passage 3 by increasing the opening of the bypass valve 12 when the internal combustion engine 1 is operated under idling or low load conditions, for example. Perform low-temperature combustion to lower the temperature.
[0021]
CO ₂ The absorption / release materials 10a and 10b are, for example, lithium zirconate (Li ₂ ZrO ₃ ) And the like, and is composed of CO in the first temperature range (for example, 400 ° C. to 580 ° C.). ₂ In the second temperature range (eg 600 ° C. to 700 ° C.) ₂ It is a well-known thing with the characteristic to discharge | release. CO ₂ Absorption / release material 10a and CO ₂ The absorption / release material 10b is different from the CO 2 at a first temperature different from each other. ₂ At a second temperature different from each other. ₂ Begins to release. Figure 2 shows CO ₂ An example of the 1st temperature range and 2nd temperature range of the absorption / release material 10a, 10b is shown. The solid line in FIG. ₂ CO of absorption / release material 10a ₂ The dotted line in FIG. ₂ CO of absorption / release material 10b ₂ The absorption / release characteristics are shown respectively. As is apparent from FIG. ₂ The absorbing / releasing material 10a corresponds to the first temperature range below the temperature Ta in FIG. 2 and the second temperature range above the Ta, respectively, ₂ The absorption / release material 10b corresponds to the first temperature range below the temperature Tb in FIG. 2, and the temperature range higher than Tb corresponds to the second temperature range in FIG.
[0022]
The operation of the discharge valves 13a and 13b is controlled by the ECU 14. FIG. 3 is a flowchart showing a release valve control routine executed by the ECU 14 to control the operation of the release valves 13a and 13b. The control routine of FIG. 3 is repeatedly executed at a predetermined cycle during the operation of the internal combustion engine 1. In FIG. 3, the release valve A indicates the release valve 13a, and the release valve B indicates the release valve 13b.
[0023]
In the control routine of FIG. 3, the ECU 14 first performs CO in step S11. ₂ It is determined whether or not there is a release request. It is determined that the release request exists when the air-fuel ratio of the internal combustion engine 1 is rapidly reduced by supplying a large amount of inert gas to the combustion chamber 2 such as causing the internal combustion engine 1 to perform low temperature combustion. CO ₂ If it is determined that there is a release request, the process proceeds to step S12, where the ECU 14 ₂ It is determined whether or not the temperature T of the absorption / release materials 10a and 10b is lower than the temperature Ta in FIG. CO ₂ When it is determined that the temperature T of the absorption / release materials 10a and 10b is lower than Ta, the current control routine is terminated. CO ₂ When it is determined that the temperature T of the absorption / release materials 10a and 10b is not less than Ta, the process proceeds to step S13, where the ECU 14 ₂ It is determined whether or not the temperature T of the materials 10a and 10b is higher than the temperature Tb in FIG. If it is determined that the temperature is not high, the process proceeds to step S14, where the ECU 14 outputs an instruction to the release valves 13a and 13b so that the release valve 13a is open and the release valve 13b is closed, and then ends the current control routine. To do. On the other hand, if it is determined that the temperature is high, the process proceeds to step S15, where the ECU 14 outputs an instruction to the release valves 13a and 13b so that the release valve 13a and the release valve 13b are opened, and then the current control routine is executed. finish.
[0024]
In step S11, CO ₂ If it is determined that there is no release request, the process proceeds to step S16, where the ECU 14 ₂ It is determined whether or not the temperature T of the absorption / release materials 10a and 10b is lower than Ta in FIG. CO ₂ When it is determined that the temperature T of the absorption / release materials 10a and 10b is lower than Ta, the process proceeds to step S15, and an instruction is output to the release valves 13a and 13b so that the release valve 13a and the release valve 13b are opened. . Thereafter, the current process is terminated. CO ₂ When it is determined that the temperature T of the absorption / release materials 10a and 10b is not less than Ta, the process proceeds to step S17, and the ECU 14 ₂ It is determined whether or not the temperature T of the absorption / release materials 10a and 10b is higher than Tb in FIG. If it is determined that the temperature is not high, the process proceeds to step S18, where the ECU 14 outputs an instruction to the release valves 13a and 13b so that the release valve 13a is closed and the release valve 13b is opened, and then the current control routine is terminated. To do. On the other hand, if it is determined that the temperature is high, the process proceeds to step S19, where the ECU 14 outputs an instruction to the release valves 13a and 13b so that the release valve 13a and the release valve 13b are closed, and then the current control routine is executed. finish.
[0025]
By controlling the operation of the release valves 13a and 13b in this way, CO ₂ CO that is absorbed and released from the absorption and release materials 10a and 10b and supplied to the intake system of the internal combustion engine 1 ₂ The amount can be adjusted. CO ₂ Of CO to start absorption and CO ₂ Of CO that differ from each other at the temperature at which the release of oxygen begins ₂ By providing the absorption / release materials 10a and 10b in the EGR passage 9, the CO ₂ The absorption temperature range and the release temperature range can be expanded. In addition, CO ₂ When the temperature T of the absorption / release materials 10a and 10b is in the range of Ta to Tb in FIG. ₂ It is also possible to switch between absorption and release.
[0026]
In the embodiment of FIG. ₂ The absorption / release materials 10a, 10b to CO ₂ CO is supplied to the intake passage 3 through the EGR passage 9 when ₂ May be insufficient or excessive. 4 and 5 show such CO 2. ₂ The control routine which ECU14 performs in order to control the shortage or excess of quantity is shown. By executing these control routines, the ECU 14 functions as operation control means. Further, the bypass valve 12 and the discharge valves 13a and 13b function as exhaust flow rate adjusting means. These control routines are repeatedly executed at a predetermined cycle during the operation of the internal combustion engine 1. Hereinafter, each control routine will be described.
[0027]
In the bypass valve correction control routine of FIG. ₂ CO of absorption / release materials 10a and 10b ₂ This is executed to control the operation of the bypass valve 12 during absorption. In this control routine, the ECU 14 first determines whether or not the release valves 13a and 13b are open in step S21. If it is determined that the discharge valves 13a and 13b are not in the open state, the current control routine is terminated. On the other hand, if it is determined that it is in the open state, the process proceeds to step S22, where the CO ₂ The temperature of the absorption / release materials 10a and 10b is CO. ₂ It is judged whether it is in the 1st temperature range which absorbs. If it is determined that the temperature is not within the absorption temperature range, the current control routine is terminated. If it is determined that the temperature is within the absorption temperature range, the process proceeds to step S23, where the CO ₂ CO of absorption / release materials 10a and 10b ₂ Calculate the amount of absorption. CO ₂ The amount absorbed is CO ₂ Temperatures of the absorption / release materials 10a and 10b, CO ₂ Exhaust pressure, CO, where the absorption / release materials 10a, 10b are provided ₂ CO of exhaust gas introduced into the absorption / release materials 10a and 10b ₂ Partial pressure, CO ₂ CO absorbed by the absorption / release materials 10a and 10b ₂ It is calculated based on the amount of.
[0028]
In the next step S24, the ECU 14 passes the EGR passage 9 and supplies CO to the intake passage 3 in the exhaust gas. ₂ The amount of change in density is calculated. CO ₂ The amount of change in concentration is the calculated CO ₂ It is calculated based on the absorption amount and the air-fuel ratio of the exhaust gas in the exhaust passage 4. In step S25, the ECU 14 calculates the calculated CO. ₂ The correction operation amount of the bypass valve 12 is calculated so that the amount of change in concentration is offset by the flow rate of the exhaust gas that passes through the bypass passage 11 and is supplied to the intake passage 3. In the next step S26, the ECU 14 calculates the air-fuel ratio of the internal combustion engine 1 after executing the correction operation of the bypass valve 12, and determines whether this air-fuel ratio is equal to or higher than the lower limit value. The lower limit value is set to an air-fuel ratio that does not reach a specific air-fuel ratio range where a large amount of PM is generated. If it is determined that the air-fuel ratio is equal to or greater than the lower limit value, the process proceeds to step S27, the calculated correction operation amount is instructed to the bypass valve 12, and then the current control routine is terminated. On the other hand, when it is determined that the air-fuel ratio is equal to or lower than the lower limit value, the process proceeds to step S28, and the correction operation amount of the bypass valve 12 is calculated again so that the air-fuel ratio of the internal combustion engine 1 is equal to or higher than the lower limit value. The bypass valve 12 is instructed. Thereafter, the current control routine is terminated.
[0029]
In this way, CO ₂ CO of absorption / release materials 10a and 10b ₂ By controlling the operation of the bypass valve 12 according to the amount of absorption, CO supplied to the intake passage 3 ₂ The amount can be maintained at an appropriate amount.
[0030]
In FIG. 4, the concept of “offset” is CO ₂ Not only when the amount of change in concentration is completely canceled, but the amount of change is partially or incompletely canceled, such as CO. ₂ This includes the case where the amount of change in density is decreased.
[0031]
The release valve correction control routine of FIG. ₂ The absorption / release materials 10a, 10b to CO ₂ Is discharged to the intake passage 3 ₂ Is executed by the ECU 14 to suppress the excessive supply of. In FIG. 5, the same processes as those in FIGS. 3 and 4 are denoted by the same reference numerals, and the description thereof is omitted.
[0032]
In the control routine of FIG. 5, the ECU 14 first performs CO in step S11. ₂ It is determined whether or not there is a release request. CO ₂ If it is determined that there is no release request, the current control routine is terminated. CO ₂ If it is determined that there is a release request, the process proceeds to step S31, where the ECU 14 ₂ CO released from the absorption / release materials 10a and 10b ₂ Calculate the amount. CO ₂ The amount released is CO ₂ Temperatures of the absorption / release materials 10a and 10b, CO ₂ Exhaust pressure, CO, where the absorption / release materials 10a, 10b are provided ₂ CO of exhaust gas introduced into the absorption / release materials 10a and 10b ₂ Partial pressure, CO ₂ CO absorbed by the absorption / release materials 10a and 10b ₂ It is calculated based on the amount of. In the subsequent step S24, the ECU 14 passes through the EGR passage 9 and supplies CO to the intake passage 3 in the exhaust gas. ₂ The amount of change in density is calculated. CO ₂ The amount of change in concentration is the calculated CO ₂ It is calculated based on the discharge amount and the air-fuel ratio of the exhaust gas in the exhaust passage 4. In the next step S32, the ECU 14 calculates the correction operation amount of the release valves 13a and 13b. CO ₂ Excess CO from intake / release materials 10a, 10b to intake passage 3 ₂ May be misfired, the internal combustion engine 1 may misfire. Therefore, CO expected to be supplied excessively ₂ The corrected operation amount of the discharge valves 13a and 13b is calculated so as to suppress the amount. In the subsequent step S33, the ECU 14 instructs the corrected operation amount to the release valves 13a and 13b. Thereafter, the current control routine is terminated.
[0033]
By controlling the release valves 13a and 13b in this way, the CO to the intake passage 3 is controlled. ₂ Excessive supply of the fuel can be suppressed, and misfire of the internal combustion engine 1 can be prevented.
[0034]
In the above embodiment, CO ₂ Two absorption / release materials were used, but as shown in FIG. ₂ One absorption / release material may be used. In FIG. 6, the same reference numerals are given to portions common to FIG. 1.
[0035]
In the example of FIG. 6, as a flow rate adjusting means for the exhaust gas passing through the EGR passage 9, in addition to the bypass valve 12 and the discharge valve 13a, CO ₂ Flow rate ratio adjusting valves 13c and 13d capable of adjusting the ratio of the exhaust gas flow rate passing through the absorption / release material 10a and the bypass passage 11 are provided. The operations of the flow rate adjusting valves 13c and 13d are also controlled by the ECU 14.
[0036]
For example, CO ₂ The absorption / release material 10a is CO ₂ Is absorbed, the CO supplied to the intake passage 3 ₂ The amount decreases. Therefore, the flow rate ratio adjusting valves 13c and 13d are operated in the direction of arrow A in FIG. 6 so that the flow rate of the exhaust gas that passes through the bypass passage 11 and is supplied to the intake passage 3 increases. Further, when the air-fuel ratio of the internal combustion engine 1 is rapidly reduced, CO 2 ₂ CO released from the absorption / release material 10a ₂ Is operated in the direction of arrow B in FIG. 6 such that the flow rate adjustment valves 13c and 13d are supplied to the intake passage 3.
[0037]
The CO supplied to the intake passage 3 can also be controlled by controlling the operations of the flow rate adjusting valves 13c and 13d in this way. ₂ The amount can be adjusted. Note that the exhaust flow rate does not need to be adjusted using all of the bypass valve 12, the discharge valve 13a, and the flow rate adjustment valves 13c and 13d. CO ₂ The flow rate of the exhaust gas passing through the absorption / release material 10a and the bypass passage 11 can be adjusted by one of these valves. Accordingly, it is sufficient that at least one of the bypass valve 12, the discharge valve 13a, and the flow rate adjustment valves 13c and 13d is provided.
[0038]
In the above embodiment, CO ₂ All the exhaust gas that has passed through the absorption / release materials 10a and 10b has been introduced into the intake passage 3, but as shown in FIG. ₂ The absorption / release materials 10a, 10b to CO ₂ And CO ₂ In the case of absorbing CO ₂ You may change the position which introduce | transduces the exhaust_gas | exhaustion which passed the absorption / release material 10a, 10b. In FIG. 7, the same reference numerals are given to the portions common to FIG.
[0039]
FIG. 7A shows CO. ₂ The absorption / release materials 10a, 10b to CO ₂ FIG. 7 (b) shows the case where CO is released. ₂ CO to absorption / release material 10a, 10b ₂ Each of the cases is absorbed. In order to change the exhaust introduction position, the example of FIG. 7 is provided with switching valves 15a and 15b and a metering valve 15c. The operation of the switching valves 15a and 15b and the metering valve 15c is also controlled by the ECU 14.
[0040]
As is clear from FIG. ₂ The absorption / release materials 10a, 10b to CO ₂ Is released, the position of the switching valves 15a, 15b and the opening of the metering valve 15c are changed so that the exhaust flows in the direction of the arrow in FIG. 7A, and the exhaust is supplied to the intake passage 3 To do. In the case of the embodiment of FIG. ₂ The flow rate of the exhaust gas that passes through the suction / release materials 10a and 10b and is supplied to the intake passage 3 can be adjusted by changing the opening of the metering valve 15c in addition to the release valves 13a and 13b. On the other hand, CO ₂ CO to absorption / release material 10a, 10b ₂ Is absorbed, the switching valves 15 a and 15 b and the metering valve 15 c are operated so that the exhaust flows in the direction of the arrow in FIG. 7B, and the exhaust is introduced into the exhaust passage 4.
[0041]
By changing the flow of exhaust in this way, CO ₂ CO of absorption / release materials 10a and 10b ₂ Exhaust CO supplied to the intake passage 3 generated during absorption ₂ Concentration fluctuations can be eliminated. Therefore, the control routine of FIG. 4 implemented in the embodiment of FIG. 1 can be omitted.
[0042]
In the example of FIG. ₂ The number of absorption / release materials is not limited to two, and more CO ₂ An absorption / release material may be provided. Further, the turbocharger 8 may not be provided.
[0043]
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. However, in each figure, the same code | symbol is attached | subjected to the part which is common in FIG. 1, FIG. 5, and those description is abbreviate | omitted.
[0044]
The second embodiment shown in FIG. 8 differs from the first embodiment in that an air-fuel ratio sensor 16 that is an air-fuel ratio acquisition means for acquiring the air-fuel ratio of exhaust gas is provided in the EGR passage 9. The output of the air-fuel ratio sensor 16 is sent to the ECU 14 and CO 2 ₂ CO absorbed and released from the absorption / release material 10a ₂ Used for quantity estimation. FIG. 9 illustrates the CO in the embodiment of FIG. ₂ From the absorption / release material 10a to CO ₂ Is released to the internal combustion engine 1 ₂ This is a control routine executed by the ECU 14 in order to suppress the excessive supply of. The control routine of FIG. 9 is repeatedly executed at a predetermined cycle during the operation of the internal combustion engine 1.
[0045]
In the control routine of FIG. 9, the ECU 14 first performs CO in step S11. ₂ It is determined whether or not there is a release request. CO ₂ If it is determined that there is no release request, the current control routine is terminated. CO ₂ If it is determined that there is a release request, the process proceeds to step S41 and the CO ₂ From the absorption / release material 10a to CO ₂ Of exhaust gas in the EGR passage 9 before and after the release ₂ Get density change.
[0046]
CO ₂ The change in concentration is acquired by controlling the operation of the air-fuel ratio sensor switching valve 17 provided in the EGR passage 9 and changing the exhaust gas introduced into the air-fuel ratio sensor 16, for example. When the air-fuel ratio sensor switching valve 17 is at the position A shown in FIG. ₂ Exhaust gas that has passed through the absorption / release material 10 a is not introduced into the air-fuel ratio sensor 16. Therefore, the released CO ₂ It is possible to obtain the air-fuel ratio of the exhaust gas that is not affected by this. On the other hand, when the air-fuel ratio sensor switching valve 17 is at the position B shown in FIG. ₂ CO released from the absorption / release material 10a ₂ Is introduced. Therefore, the released CO ₂ It is possible to acquire the air-fuel ratio of the exhaust gas containing From the change in the air-fuel ratio obtained by changing the position of the air-fuel ratio sensor switching valve 17 in this way, the CO ₂ Get density change.
[0047]
In the next step S42, the ECU 14 performs the CO ₂ CO released from the absorption / release material 10a ₂ Calculate the amount. CO ₂ The amount released is the CO ₂ Calculated based on density change. CO ₂ After calculating the amount, the process proceeds to step S24 and subsequent steps, and the same processing as in FIG. 5 is performed.
[0048]
In this way, the CO / CO ratio is obtained based on the change in the air / fuel ratio acquired by the air / fuel ratio sensor 16. ₂ Calculates the amount of emission, so it is more accurate to CO ₂ The amount released can be estimated. Therefore, the control accuracy of the discharge valve 13a can be improved. CO ₂ CO to absorption / release material 10a ₂ In the case where the air-fuel ratio is absorbed, the air-fuel ratio sensor 16 acquires the change in the air-fuel ratio of the exhaust gas, ₂ The amount of absorption can be estimated more accurately. Thereby, the control accuracy of the correction operation of the bypass valve 12 can be improved. The position where the air-fuel ratio sensor 16 is disposed is not limited to the position shown in FIG. CO ₂ From the absorption / release material 10a to CO ₂ As long as the air-fuel ratio of the exhaust before and after the intake and release can be acquired before and after the intake and release, the exhaust gas may be disposed anywhere. The means for acquiring the air-fuel ratio is not limited to the air-fuel ratio sensor, and an oxygen concentration sensor may be used.
[0049]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. 10 that are the same as those in FIG. 1 are assigned the same reference numerals, and descriptions thereof are omitted.
[0050]
The embodiment shown in FIG. 10 includes an EGR cooler 18 as a heat exchanger that cools the exhaust gas by exchanging heat with the exhaust gas, and an EGR cooler bypass channel that bypasses the EGR cooler 18 and guides the exhaust gas downstream. 19 and an EGR cooler metering valve 20 that adjusts the flow rate of the exhaust gas introduced into the EGR cooler 18.
[0051]
The operation of the EGR cooler metering valve 20 is controlled by the ECU 14. FIG. 11 is a flowchart showing a control routine executed by the ECU 14 to control the operation of the EGR cooler metering valve 20. By executing the control routine of FIG. 11, the ECU 14 functions as a heat exchange amount control means. The control routine of FIG. 11 is repeatedly executed at a predetermined cycle during the operation of the internal combustion engine 1.
[0052]
In the control routine of FIG. 11, the ECU 14 first acquires the exhaust gas temperature in step S51. The temperature of the exhaust may be calculated and acquired based on the amount of fuel supplied to the combustion chamber 2 or may be acquired by a temperature sensor provided in the exhaust passage 4. In the next step S52, the ECU 14 performs the CO ₂ CO to absorption / release material 10a, 10b ₂ It is determined whether or not there is a request for absorption. CO ₂ The absorption request is, for example, CO ₂ CO required for rapidly reducing the air-fuel ratio of the internal combustion engine 1 in the absorption / release materials 10a and 10b ₂ It is determined that the amount is not absorbed. CO ₂ If it is determined that there is an absorption request, the process proceeds to step S53, and it is determined whether or not the acquired exhaust temperature is higher than the temperature Ta in FIG. FIG. 12 shows CO ₂ CO of absorption / release material 10a ₂ The absorption / release characteristics are shown. As is apparent from FIG. 12, CO ₂ The absorption / release material 10a is CO at a temperature lower than Ta. ₂ In the range of higher temperature than Ta ₂ Release. When it is determined that the exhaust temperature is higher than Ta, the process proceeds to step S54, and the EGR cooler metering valve 20 is opened. Thereafter, the current control routine is terminated.
[0053]
On the other hand, in step S52, CO ₂ When it is determined that there is no absorption request and when it is determined in step S53 that the exhaust temperature is not higher than Ta, the process proceeds to step S55, and the EGR cooler metering valve 20 is closed. Thereafter, the current control routine is terminated.
[0054]
In this way, CO ₂ By adjusting the temperature of the exhaust gas introduced into the absorption / release materials 10a and 10b, even if the exhaust gas temperature in the exhaust passage 4 is high, CO ₂ CO to absorption / release material 10a ₂ Can be absorbed. Also, for example, CO in exhaust ₂ CO with higher concentration and higher exhaust pressure ₂ CO that absorbs a lot ₂ When the absorption / release material is used, the CO in the exhaust when the internal combustion engine 1 is operated in a state where the exhaust temperature is high. ₂ Since the concentration is high and the pressure of the exhaust gas is also high, ₂ By introducing it into the absorption / release material, CO ₂ CO to absorption / release materials ₂ Can be absorbed efficiently.
[0055]
CO ₂ Multiple COs with different absorption start temperatures ₂ When the absorption / release material is disposed in the EGR passage 9, for example, the plurality of CO ₂ The lowest CO among the absorption and release materials ₂ By controlling the EGR cooler metering valve 20 based on the absorption start temperature, all CO ₂ CO to absorption / release materials ₂ Can be absorbed.
[0056]
FIG. 13 shows the CO used in the embodiment of FIG. ₂ CO of absorption / release material 10a ₂ The other example of the absorption / release characteristic is shown. As is apparent from FIG. 13, this CO ₂ The absorption / release material 10a is the most CO at the temperature T-max. ₂ To absorb. Therefore, by changing the opening of the EGR cooler metering valve 20 and setting the exhaust temperature to T-max, the CO ₂ The absorption efficiency of can be improved.
[0057]
FIG. 14 shows the CO in FIG. ₂ CO with absorption / release characteristics ₂ It is a flowchart which shows the control routine which ECU14 performs in order to change the opening degree of the metering valve 20 for EGR coolers when an absorption / release material is used for embodiment of FIG. The control routine of FIG. 14 is repeatedly executed at a predetermined cycle during operation of the internal combustion engine 1.
[0058]
In the control routine of FIG. 14, the ECU 14 first obtains the temperature of the exhaust gas in step S51. In the next step S52, the ECU 14 performs the CO ₂ CO to absorption / release material 10a ₂ It is determined whether or not there is a request for absorption. CO ₂ If it is determined that there is an absorption request, the process proceeds to step S61, and it is determined whether or not the acquired exhaust temperature is higher than the temperature T-max in FIG. When it is determined that the exhaust temperature is higher than T-max, the process proceeds to step S62, and the ECU 14 performs CO 2 ₂ The correction operation amount of the EGR cooler metering valve 20 is calculated so that the temperature of the exhaust gas introduced into the intake / release material 10a becomes T-max. The correction operation amount can be obtained by, for example, obtaining a correspondence relationship between the opening degree of the EGR cooler metering valve 20 and the exhaust temperature in advance by experiment, storing it in the ROM of the ECU 14 as a map, and referring to the map. it can. In step S63, the ECU 14 instructs the calculated correction operation amount to the EGR cooler metering valve 20, and thereafter ends the current control routine.
[0059]
On the other hand, in step S52, CO ₂ If it is determined that there is no absorption request, or if it is determined in step S61 that the exhaust temperature is not higher than T-max, the process proceeds to step S55, and the EGR cooler metering valve 20 is closed. Thereafter, the current control routine is terminated.
[0060]
In this way CO ₂ CO to absorption / release material 10a ₂ To absorb CO ₂ By setting the temperature of the exhaust gas introduced into the absorption / release material 10a to T-max, CO ₂ The absorption efficiency of can be further improved.
[0061]
The method of adjusting the exhaust temperature in the third embodiment is not limited to the method of adjusting the exhaust flow rate by the EGR cooler metering valve 20. For example, when the EGR cooler 18 performs heat exchange using the cooling water of the internal combustion engine 1, the flow rate of the cooling water may be changed to adjust the exhaust temperature. Further, the exhaust gas temperature may be adjusted by using both the adjustment of the exhaust gas flow rate and the adjustment of the cooling water flow rate. The heat exchanger is not limited to the one that cools the exhaust, such as an EGR cooler, and may be provided with a heater that heats the exhaust.
[0062]
The position where the EGR cooler 18 is arranged is not limited to the position shown in FIG. For example, as shown in FIG. 15, after branching from the bypass passage 11 and CO ₂ You may arrange | position in the EGR channel | path 9 of the upstream of the absorption / release material 10a, 10b. Further, as shown in FIG. 15, a bypass passage EGR cooler 21 that cools the exhaust gas that passes through the bypass passage and is supplied to the intake passage 3 may be arranged in the bypass passage 11 separately from the EGR cooler 18. Good.
[0063]
The present invention is not limited to the above-described embodiments, and may be implemented in various forms. For example, CO ₂ The number of the absorption / release materials is not limited to two, and may be one or three or more CO. ₂ An absorption / release material may be disposed. Also, multiple CO ₂ The absorption / release material is CO ₂ The first state that absorbs CO and CO ₂ It is not limited to the thing in which at least one is matched with the mutually different temperature range among the 2nd states which discharge | release. For example, CO ₂ Absorption / release rate and CO ₂ CO such as absorption capacity ₂ Multiple CO with different absorption / release characteristics ₂ Absorption / release materials may be used. Further, if the same effect as the above-described embodiment can be obtained, various COs can be obtained. ₂ CO with absorption / release characteristics ₂ A combination of a plurality of absorption / release materials may be used.
[0064]
【The invention's effect】
As explained above, according to the present invention, CO ₂ CO released from absorption / release materials ₂ Can be supplied to the intake system of the internal combustion engine to reduce the air-fuel ratio of the internal combustion engine. CO ₂ The first state that absorbs CO and CO ₂ A plurality of COs at least one of which is different from the second state in which ₂ By using absorption / release materials, CO can be expanded over a wider range. ₂ Can be absorbed and released to control the combustion of the internal combustion engine.
[Brief description of the drawings]
FIG. 1 is a diagram showing a main part of an internal combustion engine to which a combustion control device according to a first embodiment of the present invention is applied.
FIG. 2 shows CO in FIG. ₂ CO of absorption / release materials ₂ The figure which shows the absorption / release characteristic.
FIG. 3 is a diagram showing a control routine executed by the ECU of FIG. 1 to control the operation of the release valve.
FIG. 4 is a diagram showing a control routine executed by the ECU of FIG. 1 to control the operation of the bypass valve.
FIG. 5 is a view showing a control routine executed by the ECU of FIG. 1 to perform a correction operation of the release valve.
FIG. 6 is a view showing a modification of the combustion control device according to the first embodiment of the present invention.
FIG. 7 is a view showing another modification of the combustion control device according to the first embodiment of the present invention.
FIG. 8 is a view showing a main part of an internal combustion engine to which a combustion control device according to a second embodiment of the present invention is applied.
FIG. 9 is a view showing a control routine executed by the ECU shown in FIG. 8 to perform a discharge valve correction operation;
FIG. 10 is a view showing a main part of an internal combustion engine to which a combustion control device according to a third embodiment of the present invention is applied.
FIG. 11 is a view showing a control routine executed by the ECU of FIG. 10 to control the operation of the EGR cooler metering valve.
FIG. 12 shows CO in FIG. ₂ CO of absorption / release materials ₂ The figure which shows the absorption / release characteristic.
13 is another CO used in the combustion control device of FIG. ₂ CO of absorption / release materials ₂ The figure which shows the absorption / release characteristic.
FIG. 14 shows CO in FIG. ₂ CO with absorption / release characteristics ₂ The figure which shows the control routine which ECU of FIG. 10 performs in order to control the operation | movement of the metering valve for EGR coolers when an absorption / release material is used for a combustion control apparatus.
FIG. 15 is a view showing a modification of the combustion control device according to the third embodiment of the present invention.
[Explanation of symbols]
1 Internal combustion engine
2 Combustion chamber
3 Intake passage
4 Exhaust passage
10a, 10b CO ₂ Absorption / release materials (CO ₂ Intake and release means)
11 Bypass passage
12 Bypass valve (exhaust flow rate adjusting means)
13a, 13b Release valve (exhaust flow rate adjusting means)
13c, 13d Flow rate adjusting valve (exhaust flow rate adjusting means)
14 Engine control unit (operation control means, heat exchange amount control means)
16 Air-fuel ratio sensor (Air-fuel ratio acquisition means)
18 EGR cooler (heat exchanger)
20 EGR cooler metering valve (heat exchange control means)

Claims

Applied to an internal combustion engine provided with CO ₂ absorption and release means for absorbing CO ₂ in the first state and releasing CO ₂ absorbed in the second state;
When the supply to the combustion chamber of inert gas is required, the CO ₂ absorbing and releasing means to release CO ₂ in the second state, the CO ₂ that is the release to the intake system of the internal combustion engine A combustion control method for an internal combustion engine, characterized by comprising:

Applied to an internal combustion engine provided with CO ₂ absorption and release means for absorbing CO ₂ in the first state and releasing CO ₂ absorbed in the second state;
The CO ₂ absorbing and releasing means, an internal combustion engine, characterized in that said connected an intake passage of the internal combustion engine to the CO ₂ released from the CO ₂ absorbing and releasing means can be supplied to the intake system of the internal combustion engine Combustion control device.

_{3. The} internal combustion engine according to claim 2, wherein the CO ₂ absorption / release means is connected to an exhaust passage of the internal combustion engine so that the exhaust of the internal combustion engine can be introduced into the CO ₂ absorption / release means. Combustion control device.

The combustion control device for an internal combustion engine according to claim 3, further comprising a bypass passage that connects the exhaust passage and the intake passage so as to bypass the CO ₂ intake / release means.

An exhaust flow rate adjusting means for adjusting the flow rate of the exhaust gas supplied to the intake system through at least one of the bypass passage and the CO ₂ absorbing and releasing means, CO ₂ absorbing volume of the CO ₂ absorbing and releasing means The combustion control apparatus for an internal combustion engine according to claim 4, further comprising operation control means for controlling the operation of the exhaust flow rate adjusting means based on

With the air-fuel ratio acquiring means for acquiring an air-fuel ratio of the exhaust gas passing through the CO ₂ absorbing and releasing means it is located downstream of the CO ₂ absorbing and releasing means,
6. The combustion control apparatus for an internal combustion engine according to claim 5, wherein the operation control unit controls the operation of the exhaust gas flow rate adjusting unit based on the air-fuel ratio acquired by the air-fuel ratio acquisition unit.

Wherein the first state and the second state is that associated with a different temperature range from each other, the exhaust heat that is disposed upstream of the CO ₂ absorbing and releasing means is introduced into the CO ₂ absorbing and releasing means A heat exchanger for exchanging and adjusting the temperature of the exhaust, and a heat exchange amount control means for controlling the heat exchange amount of the heat exchanger,
The heat exchange amount control means controls the heat exchange amount of the heat exchanger based on the amount of CO ₂ absorbed by the CO ₂ absorption / release means. A combustion control device for an internal combustion engine according to the item.

A plurality of the CO ₂ absorption / release means are provided, and each of the plurality of CO ₂ absorption / release means is connected to the intake passage so as to supply CO ₂ released from itself to the intake system. A combustion control device for an internal combustion engine according to any one of claims 2 to 7.

Combustion control device for each of the internal combustion engine according to claim 8 wherein at least one of the first state and the second state is characterized by being different from each other of the plurality of CO ₂ absorption and release means.