JP4026505B2 - Control device for internal combustion engine - Google Patents

Description

但し、δCgは、δCg（Ga，Temp，φost(t，N))と表されるべき関数、つまり、吸入空気量Ga、触媒温度Temp、および時刻tにおける第N段のブロックの酸素吸蔵率φost（t, N）の関数である。ECU４０は、Ga、Temp、およびφostと、δCgとの関係を定めたマップ或いは演算式を記憶しており、そのマップ或いは演算式を用いてδCgを算出する。
【００３４】
δCgは、物理的には、触媒３０が、単位時間および単位長あたりに吸蔵或いは放出する酸素の量を意味している。δCgの符号は、第N段のブロックが酸素を吸蔵する場合には正に設定され、一方、酸素を放出する場合には負に設定される。具体的には、第N段のブロックに流れ込む排気ガスがリーンであり、そのブロックが酸素を吸蔵する状況下ではδCgの符号は正とされ（δCg＞０）、反対に、第N段のブロックに流れ込む排気ガスがリッチであり、そのブロックが酸素を放出する状況下ではδCgの符号は負とされる（δCg＜０）。
【００３５】
従って、上記（１）式中、右辺第２項「δCg×Δt×Δx」は、第N段のブロック（幅Δx）において、Δtの時間の間に吸蔵または放出される酸素量に相当している。そして、上記（１）式によれば、時刻t＋Δtにおいて、第N−1段のブロックから流出してくる排気ガスがリーンである場合は、その排気ガス中の酸素量Cgout(t＋Δt, N−1)から、第N段のブロックで吸蔵される酸素量δCgを減じた値が第N段のブロックから流出する排気ガス中の酸素量Cgout(t＋Δt, N)として求められる。一方、時刻t＋Δtにおいて、第N−1段のブロックから流出してくる排気ガスがリッチである場合は、その排気ガス中の酸素不足量Cgout(t＋Δt, N−1)（符号は負）に、第N段のブロックから放出される酸素量δCgを加えた値が第N段のブロックから流出する排気ガス中の酸素不足量Cgout(t＋Δt, N)として求められる。
【００３６】
δCgを決定する３つの因子のうち、吸入空気量Gaと触媒温度Tempは、それぞれエアフロメータ１６および触媒温度センサ３６により検知することができる。残る１つの因子、すなわち、酸素吸蔵率φost（t，N)は、次式（２）に示す通り、時刻tにおける第N段のブロックの酸素吸蔵量ost(t，N)と、第N段のブロックの酸素吸蔵容量OSC(N)との比である。
φost（t，N)＝ost(t，N)／OSC(N) ・・・（２）
【００３７】
酸素吸蔵容量OSC(N)は、触媒３０の酸素吸蔵量OSCを求めるための公知の手法と同様の手法により求めることができる。例えば、その値OSC(N)は、以下のような手法で求めることができる。すなわち、先ず、第N段のブロックに吸蔵されている全ての酸素が放出されるまで、そのブロックに流入する排気ガスの空燃比をリッチに維持する。全ての酸素が放出されたと判断できたら（第N段のブロックの下流にリッチな排気ガスが流出してきたら）、次にそのブロックに流入する排気ガスの空燃比をリーンに変化させる。以後、第N段のブロックに容量一杯の酸素が吸蔵されるまで（第N段のブロックの下流にリーンな排気ガスが流出してくるまで）、そのブロックに流入する排気ガス中の酸素量を積算する。この手法によれば、酸素量の積算値の最終的な値を、第N段のブロックにおける酸素吸蔵容量OSC(N)として扱うことができる。尚、OSC(N)を求める手法はこれに限定されるものではなく、より単純には、触媒３０のOSCを、ブロック数（本実施形態では１０）で割った値をOSC(N)としてもよい。
【００３８】
上記（２）式に含まれるost (t，N)は、次式（３）に示す関係式により求めることができる。但し、ここでは、説明の便宜上、時刻t＋Δtにおける第N段のブロックの酸素吸蔵量ost(t＋Δt，N)を求める形式で式（３）を表している。また、次式（３）中、右辺第２項に含まれるKは適合係数である。
ost(t＋Δt, N)＝ost(t, N)＋K×δCg×Δt×Δx ・・・（３）
【００３９】
上記（３）式によれば、第N段のブロックに流入する排気ガスがリーンである場合は（従って、δCgは正）、時刻tにける酸素吸蔵量ost(t, N)に、時間Δtの間に新たに吸蔵された酸素量（厳密には適合係数Kで補正された値）を加えた値が時刻t＋Δtにおける酸素吸蔵量ost(t＋Δt, N)として算出される。また、第N段のブロックに流入する排気ガスがリッチである場合は（従って、δCgは負）、時刻tにける酸素吸蔵量ost(t, N)から、時間Δtの間に放出された酸素量（厳密には適合係数Kで補正された値）を減じた値が時刻t＋Δtにおける酸素吸蔵量ost(t＋Δt, N)として算出される。
【００４０】
以上説明した通り、ECU４０は、上述した触媒モデルを用いることにより、第N段のブロックにおける酸素過不足量Cgout(N)、酸素吸蔵率φost(N)、および酸素吸蔵量ost(N)等を求めることができる。そして、ECU４０は、個々のブロックに対して上記の処理を繰り返し適用することにより、AブロックからJブロックまで、全てのブロックにつき、それらの値を算出することができる。
【００４１】
［触媒モデルを用いた運転状態切り換え許否の判断手法の説明］
既述した通り、本実施形態のシステムは、内燃機関１０の運転領域に応じて、全筒運転と減筒運転とを切り換える機能を有している。このような運転状態の切り換えには、発明が解決しようとする課題の欄において説明した通り、一時的な空燃比荒れが伴う。
【００４２】
図３は、内燃機関１０から流出する排気ガス中の空燃比が一時的に荒れた場合に、つまり、その排気ガス中の酸素過不足量E/Goutが一時的に荒れた場合に、その荒れが触媒３０内部にどのように伝達されるかを説明するための図である。
内燃機関１０から流出する排気ガス中の酸素過不足量E/Goutが図３（Ａ）に示すような時間的変化を示した場合、その変化の影響は、図３（Ｂ）に示すようにAブロックから流出する排気ガス中の酸素過不足量にも表れる。そして、その影響は、順次下流のブロックに伝達され、触媒３０がその影響を吸収することができると、Jブロックから流出する排気ガス中の酸素過不足量Cgout(J)は図３（Ｃ）に示すようにほぼゼロのまま維持される。これに対して、触媒３０が、E/Goutの影響を吸収することができない場合は、Cgout(J)にも何らかの変化が生ずる。つまり、触媒３０の下流に酸素が過剰な排気ガス、或いは酸素の不足した排気ガスが流出することになる。
【００４３】
触媒３０の下流には、常に清浄な排気ガスが流出することが望ましい。この要求を満たす意味では、Jブロックから流出する排気ガス中の酸素過不足量Cgout(J)がゼロのまま維持される状況下では全筒運転と減筒運転の切り換えを許容するとしても、Cgout(J)がゼロでない値に変化するような状況下では、その切り換えを禁止することが望ましい。
【００４４】
既述した通り、本実施形態のシステムでは、上述した触媒モデルを用いることにより、内燃機関１０から流出する排気ガス中の酸素過不足量E/Goutに基づいて、個々のブロックから流出する排気ガス中の酸素過不足量Cgout(N)を順次繰り返し計算により求めることができる。従って、内燃機関１０の運転状態を切り換える要求が生じた時点で、E/Goutにどのような荒れが生ずるかが判れば、その荒れが個々のブロックにどのように伝達され、触媒３０から流出する排気ガス中の酸素過不足量Cgout(J)がどのような挙動を示すかを予測することが可能である。そして、その予測が可能であれば、触媒３０の下流に空燃比荒れの影響が及ばない場合に限り運転状態の切り換えを許可することが可能である。
【００４５】
内燃機関１０において、全筒運転と減筒運転とが切り換えられた際に、内燃機関１０から流出する排気ガス中の酸素過不足量E/Goutがどのような荒れを示すかは、ほぼその切り換え時における内燃機関１０の回転数NEと負荷KLとで決定される。従って、運転状態に切り換えに伴ってE/Goutに生ずる変化の様子は、NEとKLとの関係で、予めマップ化しておくことが可能である。
【００４６】
図４（Ａ）は、運転状態に切り換えに伴ってE/Goutに生ずる時間的変化と、その切り換え時における回転数NEおよび負荷KLとの関係を定めたマップの一例である。また、図４（Ｂ）は、同様のマップの他の例である。ECU４０は、このようなマップを記憶しており、運転状態の切り換え要求が生じた際には、現実にその切り換えを行う以前に、そのマップを参照して、その切り換えに伴って生ずるE/Goutの時間的変化を予測する。そして、ECU４０は、予測したE/Goutの時間的変化に基づいて、運転状態の切り換えを許可するか否かを判断する。
【００４７】
［ECU４０が実行する具体的処理の説明］
図５は、上記の機能を実現するためにECU４０が実行するルーチンのフローチャートを示す。尚、このルーチンは、内燃機関１０に対して、全筒運転と減筒運転の切り換えが要求される毎に起動されるものとする。
【００４８】
図５に示すルーチンでは、先ず、切り換え要求が生じた時点での内燃機関１０の運転状態、つまり、その時点での回転数NEおよび負荷KLが取得される（ステップ１００）。
回転数NEは、クランク角センサ２９の出力に基づいて検知することができる。また、負荷KLは、スロットルバルブ１８が全開（WOT：Wide Open Throttle)である場合に生ずるべき吸入空気量（回転数NE、スロットル開度TAなどに基づいて決定される）に対する現実の吸入空気量Gaの比として求めることができる。尚、本ステップ１００において、負荷KLは、内燃機関１０の発生トルクやスロットル開度TAで代用してもよい。
【００４９】
次に、触媒３０に流入する排気ガス中の酸素過不足量Cgin、つまり、内燃機関１０から排出される排気ガス中の酸素過不足量E/Goutが予測される（ステップ１０２）。
既述した通り、ECU４０は、E/Goutと、NEおよびKLとの関係を定めたマップを記憶している。本ステップでは、そのマップを参照して、E/Goutを、すなわち触媒３０に流入する排気ガス中の酸素過不足量Cginを予測する。ところで、図４を参照して説明した通り、本実施形態においてECU４０に記憶されているE/Goutのマップは、E/Goutの時間的変化を定めたマップである。このマップは、厳密には、所定時間Δt毎のE/Goutを意味する複数の離散値により構成されている。本ステップ１０２では、その処理が繰り返される毎に、それらの離散値が時系列で順次E/Goutの予測値、つまり、Cginの予測値として設定される。
【００５０】
図５に示すルーチンでは、次に、上記ステップ１０２において予測されたCginに基づいて、上述した触媒モデルに従って、触媒３０の最終ブロックから流出する排気ガス中の酸素過不足量Cgoutが算出される（ステップ１０４）。
【００５１】
次いで、上記ステップ１０４において算出された酸素過不足量Cgoutの絶対値を積算することにより、酸素過不足量積算値sumCgout＝Σ│Cgout│が算出される（ステップ１０６）。
触媒３０に入力する排気ガスの空燃比に荒れが生じた場合、触媒３０の下流には、酸素不足のリッチな排気ガスが流出することも、また、酸素過多のリーンな排気ガスが流出することも、更には、空燃比がリッチとリーンの両側に荒れる排気ガスが流出することもある。この場合、大気に排出される排気ガスのエミッションは、未浄化成分の総量、つまり、酸素不足量と酸素過多量の総量で判断することが適切である。上記の如くCgoutの絶対値を積算してsumCgoutを求めることによれば、そのような判断を適切に行うことができる。
【００５２】
酸素過不足量の積算値sumCgoutの算出が終わると、次に、全てのCgin予測値について（従って、全てのE/Gout予測値について）上記ステップ１０２〜１０６の処理が実行されたか否かが判断される（ステップ１０８）。
上述した通り、Cgin予測値は（つまりE/Goutの予測値は）、マップを参照することにより求められる。このマップには、E/Goutの時間的変化に対応した複数の離散値が定められている。本ステップ１０８では、今回のサイクルで処理されたCgin予測値が、それら複数の離散値の最後の値に対応するものであるかが判断される。その結果、未だ最後のCgin予測値が処理されていないと判断された場合は、Cgin予測値が時系列的に次のCgin予測値に変更された後、上記ステップ１０２以降の処理が再び実行される。
【００５３】
一方、上記ステップ１０８において、全てのCgin予測値につき処理が終了していると判断された場合は、次に、酸素過不足量の積算値sumCgoutが、所定の判定値αより小さいか否かが判別される（ステップ１１０）。
【００５４】
判定値αは正の値であり、運転状態の切り換えに伴って触媒３０の下流に流出する未浄化の成分の許容上限値を定めた値である。従って、上記ステップ１１０においてsumCgout＜αが成立すると判別される場合は、全筒運転と減筒運転の切り換えを許可して差し支えないと判断することができる。図５に示すルーチンでは、この場合、全筒運転と減筒運転との切り換え実行が許可された後、今回の処理サイクルが終了される（ステップ１１２）。
【００５５】
一方、上記ステップ１１０においてsumCgout＜αが成立しないと判別される場合は、運転状態の切り換えを許可すべきでないと判断することができる。図５に示すルーチンによれば、この場合、以後、全筒運転と減筒運転の切り換え実行が禁止された後、今回の処理サイクルが終了される（ステップ１１４）。
【００５６】
以上説明した通り、図５に示すルーチンによれば、内燃機関１０に対して運転状態の切り換えが要求される毎に、その切り換えに伴ってE/Goutに生ずる変化が予測され、かつ、その予測に基づいて更に、触媒３０の下流に流出する排気ガスの挙動が推定される。そして、このようにして推定された挙動が許容できるものであるか否かにより、全筒運転と減筒運転の切り換え許否を判断することができる。このため、本実施形態のシステムによれば、排気エミッションを悪化させることのない状況下に限り内燃機関１０の運転状態の切り換えを許可することができ、運転状態に切り換えに伴うエミッションの悪化を確実に防ぐことができる。
【００５７】
ところで、上述した実施の形態１では、触媒３０の最終ブロックから流出する排気ガス中の酸素過不足量の積算値sumCgoutに基づいて運転状態の切り換え許否を判断することとしているが、その判断の基礎となり得るパラメータは、sumCgoutに限定されるものではない。つまり、上記の判断は、積算処理に付される以前のCgoutに基づいて直接的に行うこととしてもよい。
【００５８】
更に、上記判断の基礎とするパラメータは、最終ブロックから流出する排気ガス中の酸素過不足量Cgout、或いはその積算値sumCgoutに限定されるものでもない。つまり、運転状態の切り換え許否は、触媒３０の下流に未浄化の成分がどの程度流出するかに基づいて判断すればよく、その判断は、触媒３０の酸素吸蔵状態に関するパラメータに基づいて、例えば個々のブロックの酸素吸蔵率φost(N)に基づいて実行することが可能である。より具体的には、最終ブロックの酸素吸蔵率φost(J)が、その下流に未浄化の排気ガスを流出させることのない範囲（所定の上限判定値以下、かつ、所定の下限判定値以上）であるか否かに基づいて上記判断を行うことも可能である。触媒３０に対してリーンな排気ガスが流入している状況下で最終ブロックの酸素吸蔵率φost(J)が上限判定値を超えている場合は、その下流にリーンな排気ガスが吹き抜ける可能性があると判断できる。また、触媒３０に対してリッチな排気ガスが流入している状況下で最終ブロックの酸素吸蔵率φost(J)が下限判定値を下回っている場合は、その下流にリッチな排気ガスが吹き抜ける可能性があると判断できる。そして、それらの条件が何れも成立しない場合は、触媒３０の下流に未浄化の排気ガスが流出する可能性は十分に低いと判断することができる。加えて、個々のブロックの酸素吸蔵率φost(N)は、上述した（２）式を用いることで算出することができる。従って、本実施形態のシステムにおいては、運転状態の切り換え許否を最終ブロックの酸素吸蔵率φost(J)に基づいて実行することが可能であり、かつ、そのような構成を採用しても、実施の形態１のシステムが奏する優れた効果を達成することができる。
【００５９】
また、上述した実施の形態１においては、触媒モデルを用いた処理を通して、全筒運転と減筒運転の切り換え許否を判断することとしているが、その判断の対象は、全筒運転と減筒運転の切り換え許否に限定されるものではない。すなわち、その判断の対象は、排気空燃比の荒れを伴う運転状態の切り換えであればよく、例えば、吸排気弁の開閉タイミングの切り換え許否などを、その判断の対象としてもよい。
【００６０】
尚、上述した実施の形態１（変形例を含む）においては、酸素過不足量Cgout、その積算値sumCgout、或いは酸素吸蔵率φostが、前記第１の発明における「酸素吸蔵状態に関わるパラメータ」に相当している。また、ECU４０が、上記ステップ１０２の処理を実行することにより前記第１の発明における「流入酸素過不足量予測手段」が、上記ステップ１０４〜１０８の処理を実行することにより前記第１の発明における「パラメータ推定手段」が、上記ステップ１１０〜１１４の処理を実行することにより前記第１の発明における「切り換え可否判断手段」が、それぞれ実現されている。
また、上述した実施の形態１においては、内燃機関１０の吸気弁２６および排気弁２８の状態を切り換えるアクチュエータが前記第１の発明における「気筒数切り換え手段」に相当している。
また、上述した実施の形態１においては、ECU４０が、上記ステップ１００の処理を実行することにより前記第２の発明における「回転数検出手段」および「負荷検出手段」が実現されている。
また、上述した実施の形態１においては、触媒３０の最終ブロックの位置が前記第３の発明における「特定位置」に相当しており、ECU４０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「特定位置パラメータ推定手段」が実現されている。
【００６１】
実施の形態２．
次に、図６を参照して本発明の実施の形態２について説明する。本実施形態のシステムは、実施の形態１のシステムにおいて、ECU４０に、上記図５に示すルーチンに代えて、図６に示すルーチンを実行させることにより実現することができる。
【００６２】
上述した実施の形態１のシステムは、触媒３０の最終ブロックから流出する排気ガス中の酸素過不足量Cgoutを予測し、その予測値に基づいて運転状態の切り換え許否を判断することとしている。このような判断手法によれば、内燃機関１０から流出する排気ガスの空燃比荒れを触媒３０が全体として吸収することができる場合に運転状態の切り換えを許可することができるため、比較的その切り換えを緩やかに許可することができる。
【００６３】
しかしながら、上記の判断手法は、触媒３０の最終ブロックの状態に着目するものであるため、制御誤差に対するマージンを十分に確保することができない。このため、このような判断手法による場合は、排気ガスの絶対量が多大となる内燃機関１０の高負荷運転時や、触媒３０の劣化時において全筒運転と減筒運転の切り換えが行われた場合に、触媒３０の下流に未浄化の成分が吹き抜け易い。
【００６４】
そこで、本実施形態では、最終ブロックに限定せず、触媒３０内の特定のブロックに着目して（そのブロックの状態や、その下流に流出する排気ガス中の酸素過不足量に着目して）内燃機関１０の運転状態の切り換え許否を判断すると共に、その特定のブロックを、内燃機関１０の運転状態や触媒３０の劣化状態に応じて、上流側或いは下流側に適宜移動させることとした。
【００６５】
図６は、上記の機能を実現するために本実施形態においてECU４０が実行する制御ルーチンのフローチャートを示す。尚、このルーチンは、上記図５に示すルーチンと同様に、内燃機関１０に対して、全筒運転と減筒運転の切り換えが要求される毎に起動されるものとする。
【００６６】
図６に示すルーチンでは、先ず、切り換え要求が生じた時点での内燃機関１０の運転状態、つまり、その時点での回転数NEおよび負荷KLが取得される（ステップ１２０）。
本ステップ１２０の処理は、実質的に図５におけるステップ１００の処理と同一であるため、その詳細な説明は省略する。
【００６７】
次に、触媒３０の劣化状態が検知される（ステップ１２２）。
触媒３０の劣化状態は、例えば触媒３０の酸素吸蔵容量OSCに基づいて判断することができる。酸素吸蔵容量OSCは、触媒３０が吸蔵することのできる最大酸素量であり、その容量は、触媒３０の劣化が進むにつれて少なくなる。本実施形態において、ECU４０は、図６に示すルーチンとは別のルーチンにより、公知の手法で酸素吸蔵容量OSCを適宜算出している。本ステップ１２２では、現時点で算出されている最新のOSCを読み出すことにより、その値が検知される。
【００６８】
図６に示すルーチンでは、次に、判定の対象とする特定ブロックの番号Xが取得される（ステップ１２４）。
ECU４０は、内燃機関１０の回転数NEおよび負荷KL、並びに触媒３０の劣化状態との関係で、特定ブロックの番号Xを定めたマップが記憶されている。本ステップ１２４では、このマップを参照することにより、判定の対象とする特定ブロックの番号Xが決定される。このマップによれば、高回転高負荷運転であるほど、特定ブロックは上流側に設定され、また、触媒３０の劣化が進んでいるほど特定ブロックは上流側に設定される。
【００６９】
次に、触媒３０に流入する排気ガス中の酸素過不足量Cgin、つまり、内燃機関１０から排出される排気ガス中の酸素過不足量E/Goutが予測される（ステップ１２６）。
本ステップ１２６の処理は、実質的に図５に示す上記ステップ１０２の処理と同一であるため、その詳細な説明は省略する。
【００７０】
図６に示すステップでは、次に、上記ステップ１２６において予測されたCginに基づいて、上述した触媒モデルに従って、上記ステップ１２４において決定された特定ブロックから流出する排気ガス中の酸素過不足量Cgout(X)が算出される（ステップ１２８）。
【００７１】
次いで、そのようにして算出された特定ブロックのCgout(X)が、所定の範囲に収まっているか、具体的には、β＜Cgout＜γが成立するかが判別される（ステップ１３０）。
判定値βは負の符号を有する値であり、運転状態の切り換えに伴い特定ブロックの下流に流出させることを許容する酸素不足量の限界値である。一方、判定値γは正の符号を有する値であり、運転状態の切り換えに伴い特定ブロックの下流に流出させることを許容する酸素過多量の限界値である。
【００７２】
上記ステップ１３０において、β＜Cgout＜γが成立すると判別された場合は、運転状態の切り換えに伴って招ずるE/Goutの荒れが、触媒３０の内部において、特定ブロック以前の領域において吸収できていると判断できる。そして、この場合は、特定ブロックの下流に未浄化の排気ガスが流出することはなく、運転状態の切り換えを禁止する理由がないと判断できる。図６に示すルーチンでは、この場合、次に全てのCgin予測値について（従って、全てのE/Gout予測値について）上記ステップ１２６〜１３０の処理が実行されたか否かが判断される（ステップ１３２）。
Cgin予測値は（つまりE/Goutの予測値は）、実施の形態１の場合と同様にマップを参照することで求められる。このマップには、E/Goutの時間的変化に対応した複数の離散値が定められている。本ステップ１３２では、今回のサイクルで処理されたCgin予測値が、それら複数の離散値の最後の値に対応するものであるかが判断される。その結果、未だ最後のCgin予測値が処理されていないと判断された場合は、Cgin予測値が時系列的に次のCgin予測値に変更された後、上記ステップ１２６以降の処理が再び実行される。
【００７３】
一方、上記ステップ１３２において、全てのCgin予測値につき上記ステップ１２６〜１３０の処理が終了していると判別された場合は、E/Goutの荒れが収まるまでの間、その荒れは常に触媒３０内の特定ブロック以前の領域において吸収できていたと判断することができる。図６に示すルーチンでは、この場合、全筒運転と減筒運転との切り換え実行が許可された後、今回の処理サイクルが終了される（ステップ１３４）。
【００７４】
上記ステップ１３４において、全てのCgin予測値につき所望の処理が終了したと判断されるまでの間には、上記ステップ１３０において、β＜Cgout＜γが成立しないと判断されることがある。この場合、当該サイクルにおいて処理の対象とされたCgin予測値に対して、特定ブロックから流出する排気ガス中の酸素過不足量Cgoutが、流出許容値を超えたと判断することができる。このような判断がなされた場合、図６に示すルーチンによれば、以後、速やかに全筒運転と減筒運転の切り換え実行が禁止され、その後今回の処理サイクルが終了される（ステップ１３６）。
【００７５】
以上説明した通り、図６に示すルーチンによれば、内燃機関１０の回転数NEが高いほど、またその負荷KLが高いほど、つまり、内燃機関１０から排出される排気ガス量の絶対量が多大であるほと、判定の対象となる特定ブロックを上流側に移行させることができる。更に、このルーチンによれば、触媒３０の劣化が進むにつれ、その特定ブロックを上流側に移行させることができる。そして、このようにして設定された特定ブロックの下流に未浄化の成分が吹き抜けないと判断できる場合に限り、内燃機関１０の運転状態の切り換えを許可することができる。
【００７６】
このような処理によれば、排気ガスの絶対量が多い場合や、触媒３０の劣化が進んでいる場合など、触媒３０の下流に未浄化の成分が吹き抜け易い状況下では、特定ブロックを上流側に移行させ、そのような吹き抜けに対するマージンを大きく確保することができる。また、未浄化の成分が吹き抜ける可能性の低い状況下では、特定ブロックを下流側に移行させ、運転状態の切り換えが許可される頻度を高めることができる。従って、本実施形態のシステムによれば、運転状態の切り換えを不必要に禁止することなく、内燃機関１０のエミッション特性を常に良好に保つことができる。
【００７７】
ところで、上述した実施の形態２においては、特定ブロックから流出する排気ガス中の酸素過不足量Cgoutに基づいて、運転状態の切り換え許否を判断することとしているが、その判断の基礎となるパラメータは、Cgoutに限定されるものではない。すなわち、上記の判断は、特定ブロックの酸素吸蔵率φostが上限側判定値を超えているか否か、或いは下限側判定値を下回っているか否かに基づいて行うこととしてもよい。
【００７８】
また、上述した実施の形態２においては、特定ブロックにおける酸素過不足量Cgoutの値から、直接的に運転状態の切り換え許否を判断することとしているが、その判断は、Cgoutに代えて、その積分値sumCgoutに基づいて行うこととしても良い。
【００７９】
尚、上述した実施の形態２（変形例を含む）においては、酸素過不足量Cgout、その積算値sumCgout、或いは酸素吸蔵率φostが、前記第１の発明における「酸素吸蔵状態に関わるパラメータ」に相当している。また、ECU４０が、上記ステップ１２６の処理を実行することにより前記第１の発明における「流入酸素過不足量予測手段」が、上記ステップ１２８の処理を実行することにより前記第１の発明における「パラメータ推定手段」が、上記ステップ１３０〜１３６の処理を実行することにより前記第１の発明における「切り換え可否判断手段」が、それぞれ実現されている。
また、上述した実施の形態２においては、ECU４０が、上記ステップ１２０の処理を実行することにより前記第２の発明における「回転数検出手段」および「負荷検出手段」が実現されている。
また、上述した実施の形態２においては、特定ブロックの位置が前記第３の発明における「特定位置」に相当しており、ECU４０が、上記ステップ１２８の処理を実行することにより前記第３の発明における「特定位置パラメータ推定手段」が実現されている。
また、上述した実施の形態２においては、ECU４０が、上記ステップ１２０の処理を実行することにより前記第６の発明における「回転数検出手段」、および「負荷検出手段」が、上記ステップ１２２の処理を実行することにより前記第６の発明における「触媒劣化検出手段」が、上記ステップ１２４の処理を実行することにより前記第６の発明における「特定位置決定手段」が、それぞれ実現されている。
【００８０】
【発明の効果】
この発明は以上説明したように構成されているので、以下に示すような効果を奏する。
第１の発明によれば、運転状態の切り換えが要求された際に、その切り換えの後に触媒の内部において実現される酸素吸蔵状態に関わるパラメータを推定し、そのパラメータに基づいて、その切り換え可否を判断することができる。従って、本発明によれば、上記パラメータが、エミッションの悪化を生じさせない値であると判断できる場合にのみ、運転状態の切り換えを許可することができる。
【００８１】
また、この発明によれば、上記パラメータが、エミッションの悪化を生じさせない値であると判断できる場合にのみ、全筒運転と減筒運転の切り換えを許可することができる。
【００８２】
第２の発明によれば、内燃機関の運転状態の切り換え後に触媒に流入する排気ガス中の酸素過不足量（流入酸素過不足量）を、内燃機関の運転状態と負荷とに基づいて、精度良く予測することができる。
【００８３】
第３の発明によれば、触媒内の、排気ガスの流れ方向における特定位置での酸素吸蔵状態に関わるパラメータに基づいて、運転状態の切り換え可否を判断することができる。このため、本発明によれば、触媒の内部状態を考慮して、運転状態の切り換えを、真に必要な場合に限って禁止することができる。
【００８４】
第４の発明によれば、特定位置における酸素過不足量が判定値を超えている場合に切り換えを禁止することができる。このため、本発明によれば、特定位置より下流に未浄化のガスが流出すると予想される状況下で、適切に運転状態の切り換えを禁止することができる。
【００８５】
第５の発明によれば、特定位置における酸素吸蔵率が、上限判定値を超えている場合或いは下限判定値に満たない場合に限り切り換えを禁止することができる。このため、本発明によれば、特定位置より下流に未浄化のガスが流出すると予想される状況下で、適切に運転状態の切り換えを禁止することができる。
【００８６】
第６の発明によれば、パラメータを推定すべき特定位置を、内燃機関の回転数や負荷、或いは触媒の劣化状態に基づいて決定することができる。このため、本発明によれば、内燃機関の状態や触媒の状態に応じて、真に必要な場合にのみ運転状態の切り換えを禁止することができる。
【００８７】
第７の発明によれば、触媒の最終位置におけるパラメータに基づいて、運転状態の切り換えを許可するか否かを判断することができる。このため、本発明によれば、触媒の下流に未浄化のガスが流出すると予測される場合に限り、運転状態の切り換えを禁止することができる。
【図面の簡単な説明】
【図１】 本発明の実施の形態１の構成を説明するための図である。
【図２】 本発明の実施の形態１において用いられる触媒モデルを説明するための図である。
【図３】 本発明の実施の形態１において内燃機関の運転状態が切り換えられることにより発生する排気ガスの空燃比荒れが触媒の内部をどのように伝達されるのかを説明するための図である。
【図４】 本発明の実施の形態１においてECUが記憶するべきマップの例である。
【図５】 本発明の実施の形態１において実行される制御ルーチンのフローチャートである。
【図６】 本発明の実施の形態２において実行される制御ルーチンのフローチャートである。
【符号の説明】
１０ 内燃機関
１２ 吸気通路
１４ 排気通路
３０ 触媒
４０ ECU(Electronic Control Unit)
E/Gout 内燃機関から流出する排気ガス中の酸素過不足量
Cgin 触媒に流入する排気ガス中の酸素過不足量
Cgout 触媒から流出する排気ガス中の酸素過不足量
Cgout(N) 第N段のブロックから流出する排気ガス中の酸素過不足量
Cgin(N) 第N段のブロックに流入する排気ガス中の酸素過不足量
Cgout(X) 特定ブロックから流出する排気ガス中の酸素過不足量[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for maintaining good emission characteristics in an internal combustion engine capable of switching operating states.
[0002]
[Prior art]
Conventionally, for example, as disclosed in Japanese Patent Laid-Open No. 2001-140664, there is a function of switching between all-cylinder operation in which all cylinders are operated and reduced-cylinder operation in which some cylinders are deactivated according to the operation region. Internal combustion engines are known. According to such an internal combustion engine, all-cylinder operation can be appropriately performed in a region suitable for all-cylinder operation, and reduced-cylinder operation can be appropriately performed in a region suitable for reduced-cylinder operation. Therefore, according to the conventional internal combustion engine, it is possible to realize excellent fuel consumption characteristics and excellent emission characteristics as compared with the case where the operating state is limited to all-cylinder operation.
[0003]
By the way, in the conventional internal combustion engine, the reduced-cylinder operation is realized by closing the intake / exhaust valve of the cylinder to be stopped and stopping the air flow in the cylinder. Under circumstances where the engine speed does not vary greatly, the amount of air flowing through the intake passage is substantially determined by the opening of the throttle valve. For this reason, in this internal combustion engine, when switching from all-cylinder operation to reduced-cylinder operation or vice versa, the total amount of air sucked into the internal combustion engine, that is, the amount of air that is subjected to combustion There is no big change in the total amount.
[0004]
In an internal combustion engine that switches the number of cylinders, normally, the total amount of fuel supplied to the internal combustion engine, that is, the total amount of fuel injected into the operating cylinder, so that a large torque change does not occur before and after the switching of the operating state. Is controlled so as not to change before and after the change of the number of cylinders. If the total amount of intake air and the total amount of fuel injection do not change before and after switching the number of cylinders, a constant torque can be obtained regardless of whether or not there is a deactivated cylinder. For this reason, in the conventional internal combustion engine, it is possible to prevent a large torque change from occurring before and after switching the number of cylinders.
[0005]
[Patent Document 1]
JP 2001-140664 A
[Patent Document 2]
JP 2002-195080 A
[0006]
[Problems to be solved by the invention]
However, before and after switching between the all-cylinder operation and the reduced-cylinder operation, a change occurs in the air amount itself sucked into the individual cylinders in operation. In an internal combustion engine, fuel adhesion, usually referred to as port wet, occurs around an intake port and an intake valve. This amount of port wet is in an equilibrium state when the amount of air sucked into each cylinder is stable, but increases and decreases when the amount of air changes. For this reason, even if the total amount of air sucked into the internal combustion engine and the total amount of fuel injected into the operating cylinder are the same, combustion occurs in each cylinder before and after switching between full cylinder operation and reduced cylinder operation. A change occurs in the air-fuel ratio of the air-fuel mixture applied to the fuel cell.
[0007]
Further, strictly speaking, the amount of air taken into each cylinder is affected by the pulsation of intake air. Since the pulsation that occurs during all-cylinder operation and the pulsation that occurs during reduced-cylinder operation are different, even if the amount of air flowing through the intake passage is almost determined by the opening of the throttle valve, the amount of air drawn into each cylinder The total amount is not exactly the same before and after switching the number of cylinders. The air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine also changes due to such a cause before and after switching the number of cylinders.
[0008]
In addition, switching between all-cylinder operation and reduced-cylinder operation requires mechanical switching for moving or stopping the intake / exhaust valve of the idle cylinder. Since such mechanical switching involves a delay, the timing for completing the switching may not coincide with the timing for switching between the fuel injection amount for all-cylinder operation and the fuel injection amount for reduced-cylinder operation. If the two timings do not match, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine will be rough.
[0009]
As described above, when the operating state of the internal combustion engine is switched between the all-cylinder operation and the reduced-cylinder operation, the air-fuel ratio of the air-fuel mixture may temporarily become rough before and after the switching. In the case where the catalyst can absorb such air-fuel ratio roughness, the emission does not deteriorate due to the air-fuel ratio roughness. However, when the catalyst cannot absorb such air-fuel ratio roughness, a situation occurs in which the emission deteriorates as the operating state is switched. Therefore, in order to maintain good emission characteristics at all times, it is desirable to prohibit switching under conditions where the catalyst cannot absorb the air-fuel ratio roughness accompanying switching of the operating state.
[0010]
The present invention has been made in view of the above points, and when a request for switching to an operating state occurs, the internal combustion engine that permits the switching only when it can be determined that the emission does not deteriorate with the switching. An object is to provide a control device.
[0011]
[Means for Solving the Problems]
  A first aspect of the invention is a control device for an internal combustion engine capable of switching an operating state in order to achieve the above object,
  Cylinder number switching means for switching between all cylinder operation in which all cylinders operate and reduced cylinder operation in which some cylinders are deactivated;
  Between the all-cylinder operation and the reduced-cylinder operationOperating stateButswitchingWasThe inflowing oxygen excess / deficiency prediction means for predicting the inflowing oxygen excess / deficiency amount that is the oxygen excess / deficiency amount in the exhaust gas flowing into the catalyst after the switching,
  Parameter estimation means for estimating a parameter related to the oxygen storage state of the catalyst after switching of the operation state based on the inflowing oxygen excess / deficiency amount;
  Based on the estimated parameter, a switchability determination unit that determines whether the operation state can be switched;
  It is characterized by providing.
[0013]
  The second2The invention of the1'sIn the invention,
  A rotational speed detecting means for detecting the rotational speed of the internal combustion engine;
  Load detecting means for detecting the load of the internal combustion engine,
  The inflowing oxygen excess / deficiency prediction means predicts the inflowing oxygen excess / deficiency based on the rotation speed and the load.
[0014]
  The second3The invention of the firstOr the second inventionThe parameter estimation means comprises specific position parameter estimation means for estimating a parameter related to the oxygen storage state at a specific position in the exhaust gas flow direction in the catalyst,
  The switchability determination means determines whether the operation state can be switched based on the parameter at the specific position.
[0015]
  The second4The invention of the3In the invention of
  The parameter related to the oxygen storage state at the specific position is oxygen excess / deficiency at the specific position,
  The switchability determination unit is characterized by prohibiting the switchover when an oxygen excess / deficiency amount at the specific position exceeds a predetermined determination value.
[0016]
  The second5The invention of the3In the invention of
  The parameter related to the oxygen storage state at the specific position is the oxygen storage rate at the specific position,
  The switchability determination unit is characterized in that the switching is prohibited when the oxygen storage rate at the specific position exceeds an upper limit determination value or does not reach a lower limit determination value.
[0017]
  The second6The invention of the3Thru5In any of the inventions of
  At least one of a rotational speed detecting means for detecting the rotational speed of the internal combustion engine, a load detecting means for detecting a load of the internal combustion engine, and a catalyst deterioration detecting means for detecting a deterioration state of the catalyst;
  Specific position determining means for determining the specific position in the catalyst based on at least one of the rotational speed, the load, and the catalyst deterioration state;
  It is characterized by providing.
[0018]
  The second7The invention of the3Thru5In any one of the inventions, the specific position is a final position of the catalyst in a flow direction of the exhaust gas.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.
[0020]
Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the present embodiment includes an internal combustion engine 10. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10.
An air flow meter 16 that detects the amount of air flowing through the intake passage 12, that is, the amount of intake air Ga flowing into the internal combustion engine 10, is arranged. A throttle valve 18 is disposed downstream of the air flow meter 16. The throttle valve 18 is an electronically controlled valve that is driven by the throttle motor 20 based on the accelerator opening. A throttle position sensor 22 for detecting the throttle opening and an accelerator position sensor 24 for detecting the accelerator opening are arranged in the vicinity of the throttle valve 18.
[0021]
The internal combustion engine 10 is a multi-cylinder engine having a plurality of cylinders, and FIG. 1 shows a cross section of one of the cylinders. Each cylinder included in the internal combustion engine 10 is provided with an intake port that communicates with the intake passage 12 and an exhaust port that communicates with the exhaust passage 14. Each intake port is provided with a fuel injection valve 25 for injecting fuel therein. Each intake port and exhaust port is provided with an intake valve 26 and an exhaust valve 28 for conducting or blocking the intake passage 12 or the exhaust passage 14 and the combustion chamber of the internal combustion engine 10, respectively.
[0022]
Actuators (not shown) are connected to the intake valve 26 and the exhaust valve 28, respectively. In this actuator, the intake valve 26 and the exhaust valve 28 are opened and closed with the rotation of the camshaft (hereinafter referred to as “operating state”), and they are maintained in the closed position regardless of the rotation of the camshaft. A state (hereinafter referred to as “stop state”) can be selectively realized for each cylinder. When the intake valve 26 and the exhaust valve 28 are stopped in a specific cylinder, neither air nor fuel is supplied to the cylinder, and as a result, the cylinder is in a resting state. Therefore, the internal combustion engine 10 can be realized by appropriately switching between all-cylinder operation in which all cylinders are in the operating state and reduced-cylinder operation in which some cylinders are in the inactive state.
[0023]
The internal combustion engine 10 includes a crank angle sensor 29 in the vicinity of the crankshaft. The crank angle sensor 29 can detect the rotational position of the crankshaft, the rotational speed of the crankshaft, that is, the rotational speed NE of the internal combustion engine 10 and the like.
[0024]
A catalyst 30 for purifying exhaust gas is disposed in the exhaust passage 14 of the internal combustion engine 10. The catalyst 30 occludes oxygen when lean exhaust gas containing oxygen is supplied, and releases oxygen occluded therein when exhaust gas lacking oxygen is supplied. This is a three-way catalyst that purifies the exhaust gas. An upstream air-fuel ratio sensor 32 and a downstream air-fuel ratio sensor 34 for detecting the exhaust air-fuel ratio A / F at respective positions are disposed upstream and downstream of the catalyst 30. Further, the catalyst 30 is provided with a catalyst temperature sensor 36 for detecting an internal temperature Temp.
[0025]
The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. The ECU 40 is a unit that controls the operating state of the internal combustion engine 10. The various sensors and actuators described above are driven by the ECU 40 and supply output signals and the like to the ECU 40.
[0026]
[Description of catalyst model]
As described above, the catalyst 30 purifies the exhaust gas rich in oxygen shortage by releasing the oxygen stored therein, and when the exhaust gas is lean, the excess oxygen in the gas Purify by purifying it. Therefore, the catalyst 30 cannot purify the rich exhaust gas in a situation where oxygen is not occluded in the interior of the catalyst 30, and in the situation where there is no room for occlusion of oxygen in the interior of the catalyst 30, the exhaust gas is lean. It cannot be purified. For this reason, in order for the catalyst 30 to exhibit a desired purification capacity, the oxygen storage state inside the catalyst 30 is accurately monitored, and the air-fuel ratio A / F of the exhaust gas flowing into the catalyst 30 is determined according to the oxygen storage state. Therefore, it is necessary to control to rich or lean as appropriate. Hereinafter, a method in which the ECU 40 estimates the oxygen storage state of the catalyst 30 will be described.
[0027]
FIG. 2 is a conceptual diagram for explaining a catalyst model used by the ECU 40 for estimating the oxygen storage state inside the catalyst 30 in the present embodiment. That is, in the present embodiment, the ECU 40 estimates the oxygen storage state inside the catalyst 30 using the catalyst model shown in FIG. Hereinafter, the contents of the model and the method for estimating the oxygen storage state using the model will be described in detail with reference to FIG.
[0028]
As shown in FIG. 2, the catalyst model used in the present embodiment is based on the premise that the catalyst 30 is virtually divided into a plurality of blocks arranged in the exhaust gas flow direction. Here, for the sake of convenience, these blocks are designated as A block, B block,..., H block, I block, and J block in order from the upstream side to the downstream side, and each block has a width of Δx. Shall.
[0029]
Assuming that the amount of a specific component (for example, oxygen) in the exhaust gas discharged from the internal combustion engine 10 is E / Gout, the value E / Gout becomes the amount Cgin (A) of the specific component flowing into the A block as it is. Further, if the amount of a specific component (for example, oxygen) in the exhaust gas discharged from the A block is Cgout (A), the value Cgout (A) is the amount of the specific component flowing into the B block as it is Cgin (B) It becomes. Hereinafter, for the convenience of explanation, it is assumed that this characteristic component is oxygen. Cgout and Cgin mean the oxygen amount (excess oxygen amount) contained in the exhaust gas when it is lean, and the oxygen deficiency in the gas when the exhaust gas is rich. Shall. That is, in the following description, Cgout and Cgin both mean oxygen excess / deficiency in the exhaust gas.
[0030]
In the present embodiment, the ECU 40 calculates the oxygen excess / deficiency Cgout (N) in the exhaust gas flowing out from the block based on the oxygen excess / deficiency Cgin (N) in the exhaust gas flowing into each block. A model is stored (details will be described later). According to this model, Cgout (A) can be obtained based on E / Gout, that is, Cgin (A), and Cgout (B) can be obtained based on Cgout (A), that is, Cgin (B). . Then, by repeating the same calculation, the oxygen excess / deficiency Cgout (N) in the exhaust gas flowing out from the individual blocks can be obtained sequentially. By performing the calculation up to the J block, downstream of the catalyst 30 is obtained. The oxygen excess / deficiency Cgout in the exhaust gas flowing out can be obtained as Cgout (J).
[0031]
According to the system shown in FIG. 1, the exhaust air-fuel ratio A / F detected by the upstream air-fuel ratio sensor 32 and the intake air amount Ga detected by the air flow meter 16 (or the fuel calculated based on the Ga) Based on the injection amount), the oxygen excess / deficiency E / Gout in the exhaust gas flowing out from the internal combustion engine 10 can be obtained. Therefore, the ECU 40 obtains the oxygen excess / deficiency Cgout (N) in the exhaust gas discharged from these blocks for all of the blocks A to J by repeatedly performing calculations using the catalyst model described above. be able to.
[0032]
If an exhaust gas rich in air-fuel ratio flows into a block and that block can release the oxygen deficiency, then the exhaust gas with an excess / deficiency Cgout (N) of zero is located downstream of it, that is, The stoichiometric air-fuel ratio exhaust gas flows out. Also, if lean air-fuel ratio exhaust gas flows into a block, and that block can store excess oxygen, then the exhaust gas with oxygen excess / deficiency Cgout (N) of zero is also downstream. Gas flows out. Therefore, the oxygen excess / deficiency Cgout (N) in the exhaust gas flowing out downstream of each block can be recognized as a parameter having a correlation with the oxygen storage state in that block. In the present embodiment, the ECU 40 estimates the oxygen storage state inside the catalyst 30 based on such a principle.
[0033]
Next, the ECU 40 obtains the oxygen excess / deficiency Cgout (N) in the exhaust gas flowing out from the block based on the oxygen excess / deficiency Cgin (N) in the exhaust gas flowing into the N-th stage block. A specific method will be described.
The following expression (1) is an arithmetic expression used by the ECU 40 to estimate the oxygen excess / deficiency Cgout (t + Δt, N) in the exhaust gas flowing out from the N-th block at time t + Δt.

However, δCg is a function to be expressed as δCg (Ga, Temp, φost (t, N)), that is, the intake air amount Ga, the catalyst temperature Temp, and the oxygen storage rate φost of the N-th block at time t. It is a function of (t, N). The ECU 40 stores a map or an arithmetic expression that defines the relationship between Ga, Temp, and φost, and δCg, and calculates δCg using the map or the arithmetic expression.
[0034]
δCg physically means the amount of oxygen that the catalyst 30 occludes or releases per unit time and unit length. The sign of ΔCg is set to be positive when the Nth stage block occludes oxygen, while it is set to be negative when oxygen is released. Specifically, the exhaust gas flowing into the Nth stage block is lean, and the sign of δCg is positive (δCg> 0) under the condition that the block occludes oxygen, on the contrary, the Nth stage block The sign of δCg is negative (δCg <0) when the exhaust gas flowing into is rich and the block releases oxygen.
[0035]
Therefore, in the above equation (1), the second term “δCg × Δt × Δx” on the right side corresponds to the amount of oxygen occluded or released during the time Δt in the N-th block (width Δx). Yes. According to the above equation (1), when the exhaust gas flowing out from the (N−1) -th block is lean at time t + Δt, the oxygen amount Cgout (t + Δt, N−1) in the exhaust gas ), The value obtained by subtracting the oxygen amount ΔCg stored in the Nth stage block is obtained as the oxygen amount Cgout (t + Δt, N) in the exhaust gas flowing out from the Nth stage block. On the other hand, when the exhaust gas flowing out from the block of the (N−1) -th stage is rich at time t + Δt, the oxygen deficiency Cgout (t + Δt, N−1) (sign is negative) in the exhaust gas is A value obtained by adding the amount of oxygen ΔCg released from the N-th block is obtained as an oxygen deficiency Cgout (t + Δt, N) in the exhaust gas flowing out from the N-th block.
[0036]
Of the three factors that determine δCg, the intake air amount Ga and the catalyst temperature Temp can be detected by the air flow meter 16 and the catalyst temperature sensor 36, respectively. The remaining one factor, that is, the oxygen storage rate φost (t, N), is expressed by the following equation (2): the oxygen storage amount ost (t, N) of the N-th block at time t and the N-th stage It is a ratio with the oxygen storage capacity OSC (N) of the block.
φost (t, N) = ost (t, N) / OSC (N) (2)
[0037]
The oxygen storage capacity OSC (N) can be obtained by a method similar to a known method for obtaining the oxygen storage amount OSC of the catalyst 30. For example, the value OSC (N) can be obtained by the following method. That is, first, the air-fuel ratio of the exhaust gas flowing into the block is kept rich until all the oxygen stored in the N-th block is released. If it can be determined that all the oxygen has been released (if rich exhaust gas flows out downstream of the Nth stage block), then the air-fuel ratio of the exhaust gas flowing into that block is changed to lean. Thereafter, the oxygen amount in the exhaust gas flowing into the N-th block until the full oxygen is stored in the N-th block (until lean exhaust gas flows out downstream of the N-th block). Accumulate. According to this method, the final value of the integrated value of the oxygen amount can be handled as the oxygen storage capacity OSC (N) in the N-th block. Note that the method for obtaining OSC (N) is not limited to this, and more simply, the value obtained by dividing the OSC of the catalyst 30 by the number of blocks (10 in the present embodiment) may be referred to as OSC (N). Good.
[0038]
The ost (t, N) included in the above equation (2) can be obtained from the relational equation shown in the following equation (3). However, here, for convenience of explanation, Expression (3) is expressed in a form for obtaining the oxygen storage amount ost (t + Δt, N) of the N-th block at time t + Δt. In the following equation (3), K included in the second term on the right side is a fitness coefficient.
ost (t + Δt, N) = ost (t, N) + K × δCg × Δt × Δx (3)
[0039]
According to the above equation (3), when the exhaust gas flowing into the N-th stage block is lean (thus, δCg is positive), the oxygen storage amount ost (t, N) at time t is set to the time Δt. A value obtained by adding the amount of oxygen newly stored during this period (strictly, the value corrected by the fitness coefficient K) is calculated as the oxygen storage amount ost (t + Δt, N) at time t + Δt. In addition, when the exhaust gas flowing into the Nth stage block is rich (thus, δCg is negative), the oxygen released during time Δt from the oxygen storage amount ost (t, N) at time t A value obtained by subtracting the amount (strictly, the value corrected by the fitness coefficient K) is calculated as the oxygen storage amount ost (t + Δt, N) at time t + Δt.
[0040]
As described above, the ECU 40 uses the catalyst model described above to obtain the oxygen excess / deficiency Cgout (N), oxygen storage rate φost (N), oxygen storage amount ost (N), etc. in the Nth stage block. Can be sought. The ECU 40 can calculate the values for all the blocks from the A block to the J block by repeatedly applying the above processing to each block.
[0041]
[Explanation of operation status switching judgment method using catalyst model]
As described above, the system of the present embodiment has a function of switching between all-cylinder operation and reduced-cylinder operation according to the operation region of the internal combustion engine 10. As described in the section of the problem to be solved by the invention, such switching of the operating state is accompanied by temporary air-fuel ratio roughening.
[0042]
FIG. 3 shows the roughening when the air-fuel ratio in the exhaust gas flowing out from the internal combustion engine 10 is temporarily roughened, that is, when the oxygen excess / deficiency E / Gout in the exhaust gas is temporarily roughened. FIG. 4 is a diagram for explaining how is transmitted to the inside of a catalyst 30;
When the oxygen excess / deficiency E / Gout in the exhaust gas flowing out from the internal combustion engine 10 shows a temporal change as shown in FIG. 3A, the influence of the change is as shown in FIG. 3B. It also appears in the oxygen excess and deficiency in the exhaust gas flowing out from the A block. Then, the influence is sequentially transmitted to the downstream block, and when the catalyst 30 can absorb the influence, the oxygen excess / deficiency Cgout (J) in the exhaust gas flowing out from the J block is shown in FIG. As shown in FIG. On the other hand, when the catalyst 30 cannot absorb the influence of E / Gout, some change also occurs in Cgout (J). That is, exhaust gas with excess oxygen or exhaust gas with insufficient oxygen flows downstream of the catalyst 30.
[0043]
It is desirable that clean exhaust gas always flows out downstream of the catalyst 30. In the sense of satisfying this requirement, even if switching between all-cylinder operation and reduced-cylinder operation is allowed under the condition that the oxygen excess / deficiency Cgout (J) in the exhaust gas flowing out from the J block is maintained at zero, Cgout In situations where (J) changes to a non-zero value, it is desirable to prohibit the switching.
[0044]
As described above, in the system of the present embodiment, the exhaust gas flowing out from each block is based on the oxygen excess / deficiency E / Gout in the exhaust gas flowing out from the internal combustion engine 10 by using the catalyst model described above. The oxygen excess / deficiency amount Cgout (N) can be obtained by repeated calculation in sequence. Accordingly, when it is determined what kind of roughening occurs in E / Gout when a request to switch the operating state of the internal combustion engine 10 occurs, how the roughening is transmitted to the individual blocks and flows out of the catalyst 30. It is possible to predict how the oxygen excess / deficiency Cgout (J) in the exhaust gas will behave. If the prediction is possible, switching of the operating state can be permitted only when the influence of the air-fuel ratio roughness does not affect the downstream of the catalyst 30.
[0045]
In the internal combustion engine 10, when the all-cylinder operation and the reduced-cylinder operation are switched, it is almost the switching that the oxygen excess / deficiency E / Gout in the exhaust gas flowing out from the internal combustion engine 10 shows. This is determined by the rotational speed NE of the internal combustion engine 10 and the load KL. Therefore, the state of the change that occurs in E / Gout as the operation state is switched can be mapped in advance in relation to NE and KL.
[0046]
FIG. 4A is an example of a map that defines the relationship between the temporal change that occurs in E / Gout with switching to the operating state and the rotational speed NE and load KL at the time of switching. FIG. 4B is another example of a similar map. The ECU 40 stores such a map, and when an operation state change request is generated, the ECU 40 refers to the map before actually changing the operation state, and generates an E / Gout generated by the change. Predict changes over time. Then, the ECU 40 determines whether or not to permit switching of the operation state based on the predicted temporal change in E / Gout.
[0047]
[Description of specific processing executed by ECU 40]
FIG. 5 shows a flowchart of a routine executed by the ECU 40 to realize the above function. This routine is started every time the internal combustion engine 10 is requested to switch between all-cylinder operation and reduced-cylinder operation.
[0048]
In the routine shown in FIG. 5, first, the operating state of the internal combustion engine 10 at the time when the switching request is made, that is, the rotational speed NE and the load KL at that time are acquired (step 100).
The rotational speed NE can be detected based on the output of the crank angle sensor 29. The load KL is an actual intake air amount with respect to the intake air amount (determined based on the rotational speed NE, the throttle opening TA, etc.) that should be generated when the throttle valve 18 is fully open (WOT: Wide Open Throttle). It can be determined as the ratio of Ga. In step 100, the load KL may be replaced with the torque generated by the internal combustion engine 10 or the throttle opening TA.
[0049]
Next, the oxygen excess / deficiency Cgin in the exhaust gas flowing into the catalyst 30, that is, the oxygen excess / deficiency E / Gout in the exhaust gas discharged from the internal combustion engine 10 is predicted (step 102).
As described above, the ECU 40 stores a map that defines the relationship between E / Gout and NE and KL. In this step, referring to the map, E / Gout, that is, the oxygen excess / deficiency Cgin in the exhaust gas flowing into the catalyst 30 is predicted. By the way, as described with reference to FIG. 4, the map of E / Gout stored in the ECU 40 in the present embodiment is a map that defines the temporal change of E / Gout. Strictly speaking, this map is composed of a plurality of discrete values that mean E / Gout every predetermined time Δt. In this step 102, each time the process is repeated, these discrete values are sequentially set as a predicted value of E / Gout in time series, that is, a predicted value of Cgin.
[0050]
In the routine shown in FIG. 5, the oxygen excess / deficiency Cgout in the exhaust gas flowing out from the final block of the catalyst 30 is then calculated according to the catalyst model described above based on the Cgin predicted in step 102 ( Step 104).
[0051]
Next, by integrating the absolute value of the oxygen excess / deficiency Cgout calculated in step 104, the oxygen excess / deficiency integrated value sumCgout = Σ | Cgout | is calculated (step 106).
When the air-fuel ratio of the exhaust gas input to the catalyst 30 becomes rough, a rich exhaust gas lacking oxygen flows out downstream of the catalyst 30 or a lean exhaust gas rich in oxygen flows out. In addition, exhaust gas that has a rough air-fuel ratio on both sides of the lean and lean sides may flow out. In this case, it is appropriate to determine the emission of exhaust gas discharged to the atmosphere based on the total amount of unpurified components, that is, the total amount of oxygen deficiency and oxygen excess. As described above, by summing up the absolute value of Cgout to obtain sumCgout, such a determination can be made appropriately.
[0052]
When calculation of the integrated value sumCgout of the oxygen excess / deficiency is finished, it is next determined whether or not the processing of steps 102 to 106 has been executed for all Cgin prediction values (and therefore for all E / Gout prediction values). (Step 108).
As described above, the Cgin predicted value (that is, the E / Gout predicted value) is obtained by referring to the map. In this map, a plurality of discrete values corresponding to temporal changes in E / Gout are defined. In step 108, it is determined whether the Cgin predicted value processed in the current cycle corresponds to the last value of the plurality of discrete values. As a result, if it is determined that the last Cgin predicted value has not yet been processed, the Cgin predicted value is changed to the next Cgin predicted value in time series, and then the processing from step 102 onward is executed again. The
[0053]
On the other hand, if it is determined in step 108 that the process has been completed for all Cgin predicted values, then whether or not the integrated value sumCgout of the oxygen excess / deficiency is smaller than a predetermined determination value α. A determination is made (step 110).
[0054]
The determination value α is a positive value, and is a value that defines an allowable upper limit value of an unpurified component that flows downstream of the catalyst 30 when the operating state is switched. Therefore, if it is determined in step 110 that sumCgout <α is established, it can be determined that switching between all-cylinder operation and reduced-cylinder operation may be permitted. In the routine shown in FIG. 5, in this case, after the execution of switching between the all-cylinder operation and the reduced-cylinder operation is permitted, the current processing cycle is ended (step 112).
[0055]
On the other hand, if it is determined in step 110 that sumCgout <α is not satisfied, it can be determined that switching of the operating state should not be permitted. According to the routine shown in FIG. 5, in this case, after the execution of switching between all-cylinder operation and reduced-cylinder operation is prohibited, the current processing cycle is terminated (step 114).
[0056]
As described above, according to the routine shown in FIG. 5, every time the internal combustion engine 10 is requested to switch the operating state, a change occurring in the E / Gout with the switching is predicted, and the prediction Further, the behavior of the exhaust gas flowing out downstream of the catalyst 30 is estimated. Whether or not the behavior estimated in this way is acceptable can be determined as to whether or not to switch between the all-cylinder operation and the reduced-cylinder operation. For this reason, according to the system of the present embodiment, it is possible to permit switching of the operating state of the internal combustion engine 10 only in a situation where exhaust emission is not deteriorated, and the deterioration of emissions accompanying switching to the operating state is ensured. Can be prevented.
[0057]
By the way, in the first embodiment described above, whether to permit switching of the operating state is determined based on the integrated value sumCgout of the oxygen excess / deficiency in the exhaust gas flowing out from the final block of the catalyst 30. The possible parameters are not limited to sumCgout. That is, the above determination may be made directly based on Cgout before being subjected to integration processing.
[0058]
Further, the parameter on which the above judgment is based is not limited to the oxygen excess / deficiency Cgout in the exhaust gas flowing out from the final block, or its integrated value sumCgout. In other words, whether or not to permit switching of the operating state may be determined based on how much unpurified components flow out downstream of the catalyst 30, and the determination may be based on, for example, individual parameters regarding the oxygen storage state of the catalyst 30. It is possible to carry out based on the oxygen storage rate φost (N) of the block. More specifically, the range in which the oxygen storage rate φost (J) of the final block does not cause unpurified exhaust gas to flow downstream (below a predetermined upper limit determination value and above a predetermined lower limit determination value). It is also possible to make the above determination based on whether or not. If the oxygen storage rate φost (J) of the final block exceeds the upper limit judgment value when lean exhaust gas flows into the catalyst 30, there is a possibility that lean exhaust gas will blow through downstream. It can be judged that there is. Further, when the exhaust gas is flowing into the catalyst 30 and the oxygen storage rate φost (J) of the final block is lower than the lower limit judgment value, the rich exhaust gas can be blown down downstream. It can be judged that there is sex. If none of these conditions is satisfied, it can be determined that the possibility that unpurified exhaust gas flows downstream of the catalyst 30 is sufficiently low. In addition, the oxygen storage rate φost (N) of each block can be calculated by using the above-described equation (2). Therefore, in the system of the present embodiment, it is possible to execute whether or not to switch the operating state based on the oxygen storage rate φost (J) of the final block, and even if such a configuration is adopted, the operation is performed. The outstanding effect which the system of the form 1 shows can be achieved.
[0059]
In the first embodiment described above, whether or not to switch between the all cylinder operation and the reduced cylinder operation is determined through the processing using the catalyst model. It is not limited to whether or not switching is allowed. That is, the determination target may be switching of the operation state accompanied by the rough exhaust air-fuel ratio. For example, whether the switching of the intake / exhaust valve opening / closing timing is permitted may be determined.
[0060]
  In the first embodiment described above (including the modification), the oxygen excess / deficiency Cgout, the integrated value sumCgout, or the oxygen storage rate φost is the “parameter related to the oxygen storage state” in the first invention. It corresponds. Further, when the ECU 40 executes the process of step 102, the “inflowing oxygen excess / deficiency prediction means” in the first invention performs the processes of steps 104 to 108 in the first invention. The “parameter estimation means” executes the processes of steps 110 to 114 described above, thereby realizing the “switchability determination means” in the first invention.
  In the first embodiment described above, the actuator that switches the states of the intake valve 26 and the exhaust valve 28 of the internal combustion engine 10 is the first actuator.1"Switching the number of cylinders"meansIs equivalent to.
  Further, in the first embodiment described above, the ECU 40 executes the process of step 100 described above, thereby causing the first.2The “rotation speed detecting means” and the “load detecting means” in the present invention are realized.
  In the first embodiment described above, the position of the last block of the catalyst 30 is the first position.3This corresponds to the “specific position” in the invention of FIG.3The “specific position parameter estimating means” in the present invention is realized.
[0061]
Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 40 to execute the routine shown in FIG. 6 instead of the routine shown in FIG. 5 in the system of the first embodiment.
[0062]
The system of the first embodiment described above predicts the oxygen excess / deficiency Cgout in the exhaust gas flowing out from the final block of the catalyst 30, and determines whether to permit switching of the operating state based on the predicted value. According to such a determination method, when the catalyst 30 can absorb the rough air-fuel ratio of the exhaust gas flowing out from the internal combustion engine 10 as a whole, the switching of the operation state can be permitted. Can be allowed moderately.
[0063]
However, since the above determination method focuses on the state of the last block of the catalyst 30, a sufficient margin for the control error cannot be ensured. For this reason, in the case of such a determination method, switching between the all-cylinder operation and the reduced-cylinder operation is performed at the time of high-load operation of the internal combustion engine 10 where the absolute amount of exhaust gas becomes large or when the catalyst 30 is deteriorated. In this case, unpurified components are easily blown downstream of the catalyst 30.
[0064]
Thus, in the present embodiment, not limited to the final block, focus on a specific block in the catalyst 30 (focus on the state of that block and the oxygen excess / deficiency in the exhaust gas flowing downstream thereof). Whether or not switching of the operating state of the internal combustion engine 10 is permitted is determined, and the specific block is appropriately moved upstream or downstream depending on the operating state of the internal combustion engine 10 or the deterioration state of the catalyst 30.
[0065]
FIG. 6 shows a flowchart of a control routine executed by the ECU 40 in the present embodiment in order to realize the above function. Note that this routine is started every time when the internal combustion engine 10 is requested to switch between all-cylinder operation and reduced-cylinder operation, similarly to the routine shown in FIG.
[0066]
In the routine shown in FIG. 6, first, the operating state of the internal combustion engine 10 at the time when the switching request is made, that is, the rotational speed NE and the load KL at that time are acquired (step 120).
Since the process of step 120 is substantially the same as the process of step 100 in FIG. 5, detailed description thereof is omitted.
[0067]
Next, the deterioration state of the catalyst 30 is detected (step 122).
The deterioration state of the catalyst 30 can be determined based on, for example, the oxygen storage capacity OSC of the catalyst 30. The oxygen storage capacity OSC is the maximum amount of oxygen that the catalyst 30 can store, and the capacity decreases as the deterioration of the catalyst 30 progresses. In the present embodiment, the ECU 40 appropriately calculates the oxygen storage capacity OSC by a known method by a routine different from the routine shown in FIG. In step 122, the latest OSC calculated at the present time is read to detect the value.
[0068]
In the routine shown in FIG. 6, next, the number X of the specific block to be determined is acquired (step 124).
The ECU 40 stores a map that defines a specific block number X in relation to the rotational speed NE and load KL of the internal combustion engine 10 and the deterioration state of the catalyst 30. In this step 124, the number X of the specific block to be determined is determined by referring to this map. According to this map, the specific block is set on the upstream side as the high-speed and high-load operation is performed, and the specific block is set on the upstream side as the deterioration of the catalyst 30 progresses.
[0069]
Next, the oxygen excess / deficiency Cgin in the exhaust gas flowing into the catalyst 30, that is, the oxygen excess / deficiency E / Gout in the exhaust gas discharged from the internal combustion engine 10 is predicted (step 126).
Since the process of this step 126 is substantially the same as the process of the said step 102 shown in FIG. 5, the detailed description is abbreviate | omitted.
[0070]
In the step shown in FIG. 6, next, based on the Cgin predicted in the step 126, the oxygen excess / deficiency Cgout (in the exhaust gas flowing out from the specific block determined in the step 124 is determined according to the catalyst model described above. X) is calculated (step 128).
[0071]
Next, it is determined whether Cgout (X) of the specific block thus calculated is within a predetermined range, specifically, whether β <Cgout <γ is satisfied (step 130).
The determination value β is a value having a negative sign, and is a limit value of the oxygen deficiency that allows the flow to flow downstream of the specific block in accordance with the switching of the operation state. On the other hand, the determination value γ is a value having a positive sign, and is a limit value of an excessive oxygen amount that allows the gas to flow downstream of the specific block when the operation state is switched.
[0072]
If it is determined in the above step 130 that β <Cgout <γ holds, the rough E / Gout caused by the switching of the operating state can be absorbed in the catalyst 30 in the region before the specific block. Can be judged. In this case, unpurified exhaust gas does not flow downstream of the specific block, and it can be determined that there is no reason to prohibit switching of the operation state. In the routine shown in FIG. 6, in this case, it is next determined whether or not the processing of steps 126 to 130 has been executed for all Cgin prediction values (and therefore for all E / Gout prediction values) (step 132). ).
The Cgin prediction value (that is, the prediction value of E / Gout) is obtained by referring to the map in the same manner as in the first embodiment. In this map, a plurality of discrete values corresponding to temporal changes in E / Gout are defined. In step 132, it is determined whether the Cgin predicted value processed in the current cycle corresponds to the last value of the plurality of discrete values. As a result, if it is determined that the last Cgin prediction value has not yet been processed, the Cgin prediction value is changed to the next Cgin prediction value in time series, and then the processing from step 126 onward is executed again. The
[0073]
On the other hand, if it is determined in step 132 that the processes in steps 126 to 130 have been completed for all Cgin predicted values, the roughness is always within the catalyst 30 until the roughness of E / Gout is settled. It can be determined that absorption was possible in the area before the specific block. In the routine shown in FIG. 6, in this case, after the execution of switching between all-cylinder operation and reduced-cylinder operation is permitted, the current processing cycle is terminated (step 134).
[0074]
Until it is determined in step 134 that desired processing has been completed for all Cgin prediction values, it may be determined in step 130 that β <Cgout <γ is not satisfied. In this case, it is possible to determine that the oxygen excess / deficiency Cgout in the exhaust gas flowing out from the specific block exceeds the outflow allowable value with respect to the Cgin predicted value that is the target of processing in the cycle. When such a determination is made, according to the routine shown in FIG. 6, thereafter, the execution of switching between the all-cylinder operation and the reduced-cylinder operation is prohibited immediately, and then the current processing cycle is ended (step 136).
[0075]
As described above, according to the routine shown in FIG. 6, the higher the rotational speed NE of the internal combustion engine 10 and the higher the load KL, that is, the greater the absolute amount of exhaust gas discharged from the internal combustion engine 10 is. As a result, the specific block to be determined can be shifted to the upstream side. Furthermore, according to this routine, the specific block can be shifted upstream as the deterioration of the catalyst 30 progresses. The switching of the operating state of the internal combustion engine 10 can be permitted only when it can be determined that unpurified components are not blown downstream of the specific block set in this way.
[0076]
According to such a process, when the absolute amount of exhaust gas is large, or when the deterioration of the catalyst 30 is progressing, the specific block is placed on the upstream side in a situation where unpurified components are easily blown downstream of the catalyst 30. It is possible to secure a large margin for such a blow-by. Further, under a situation where there is a low possibility that unpurified components will blow through, the specific block can be shifted to the downstream side to increase the frequency at which switching of the operating state is permitted. Therefore, according to the system of the present embodiment, the emission characteristics of the internal combustion engine 10 can always be kept good without unnecessarily prohibiting switching of the operating state.
[0077]
By the way, in Embodiment 2 described above, it is determined whether or not switching of the operating state is permitted based on the oxygen excess / deficiency Cgout in the exhaust gas flowing out from the specific block. It is not limited to Cgout. That is, the above determination may be made based on whether or not the oxygen storage rate φost of the specific block exceeds the upper limit side determination value or is lower than the lower limit side determination value.
[0078]
In the above-described second embodiment, whether or not switching of the operating state is permitted is directly determined from the value of the oxygen excess / deficiency Cgout in the specific block. This may be performed based on the value sumCgout.
[0079]
  In the above-described second embodiment (including the modification), the oxygen excess / deficiency Cgout, the integrated value sumCgout, or the oxygen storage rate φost is the “parameter related to the oxygen storage state” in the first invention. It corresponds. Further, when the ECU 40 executes the process of step 126, the “inflowing oxygen excess / deficiency predicting means” in the first aspect of the invention executes the process of step 128 of “parameters” of the first aspect of the invention. The “estimating means” executes the processing of the above steps 130 to 136, thereby realizing the “switchability determination means” in the first invention.
  Further, in the above-described second embodiment, the ECU 40 executes the process of the above step 120 to execute the first step.2The “rotation speed detecting means” and the “load detecting means” in the present invention are realized.
  In the second embodiment described above, the position of the specific block is the first position.3This corresponds to the “specific position” in the invention of FIG.3The “specific position parameter estimating means” in the present invention is realized.
  Further, in the above-described second embodiment, the ECU 40 executes the process of the above step 120 to execute the first step.6The “rotation speed detecting means” and the “load detecting means” in the present invention execute the process of step 122 described above, thereby6The “catalyst deterioration detecting means” in the present invention executes the process of step 124, thereby6Each of the “specific position determining means” in the present invention is realized.
[0080]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
According to the first invention, when switching of the operating state is requested, the parameter related to the oxygen storage state realized in the inside of the catalyst after the switching is estimated, and based on the parameter, whether the switching is possible or not is estimated. Judgment can be made. Therefore, according to the present invention, it is possible to permit switching of the operating state only when it can be determined that the parameter is a value that does not cause the emission to deteriorate.
[0081]
  Also thisAccording to the invention, switching between the all-cylinder operation and the reduced-cylinder operation can be permitted only when it can be determined that the parameter is a value that does not cause the emission deterioration.
[0082]
  First2According to this invention, the oxygen excess / deficiency in the exhaust gas flowing into the catalyst after switching the operation state of the internal combustion engine (inflow oxygen excess / deficiency) is accurately predicted based on the operation state and load of the internal combustion engine. can do.
[0083]
  First3According to this invention, it is possible to determine whether or not the operating state can be switched based on the parameter related to the oxygen storage state at a specific position in the exhaust gas flow direction in the catalyst. For this reason, according to the present invention, it is possible to prohibit the switching of the operating state only when it is truly necessary in consideration of the internal state of the catalyst.
[0084]
  First4According to this invention, switching can be prohibited when the oxygen excess / deficiency at the specific position exceeds the determination value. For this reason, according to the present invention, it is possible to appropriately prohibit switching of the operating state under a situation where unpurified gas is expected to flow downstream from the specific position.
[0085]
  First5According to the invention, switching can be prohibited only when the oxygen storage rate at the specific position exceeds the upper limit determination value or does not satisfy the lower limit determination value. For this reason, according to the present invention, it is possible to appropriately prohibit switching of the operating state under a situation where unpurified gas is expected to flow downstream from the specific position.
[0086]
  First6According to this invention, the specific position where the parameter should be estimated can be determined based on the rotational speed and load of the internal combustion engine or the deterioration state of the catalyst. For this reason, according to the present invention, switching of the operating state can be prohibited only when it is truly necessary, depending on the state of the internal combustion engine and the state of the catalyst.
[0087]
  First7According to this invention, it is possible to determine whether or not switching of the operating state is permitted based on the parameter at the final position of the catalyst. Therefore, according to the present invention, switching of the operating state can be prohibited only when it is predicted that unpurified gas will flow out downstream of the catalyst.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the configuration of a first embodiment of the present invention.
FIG. 2 is a diagram for explaining a catalyst model used in Embodiment 1 of the present invention.
FIG. 3 is a diagram for explaining how the air-fuel ratio roughness of exhaust gas generated by switching the operating state of the internal combustion engine in Embodiment 1 of the present invention is transmitted through the inside of the catalyst. .
FIG. 4 is an example of a map that the ECU should store in the first embodiment of the present invention.
FIG. 5 is a flowchart of a control routine executed in the first embodiment of the present invention.
FIG. 6 is a flowchart of a control routine executed in the second embodiment of the present invention.
[Explanation of symbols]
10 Internal combustion engine
12 Intake passage
14 Exhaust passage
30 Catalyst
40 ECU (Electronic Control Unit)
E / Gout Excess and deficiency of oxygen in exhaust gas flowing out from internal combustion engine
Excess and deficiency of oxygen in exhaust gas flowing into Cgin catalyst
Cgout Excess and deficiency of oxygen in exhaust gas flowing out from catalyst
Cgout (N) Excess or deficiency of oxygen in the exhaust gas flowing out from the Nth stage block
Cgin (N) Excess or deficiency of oxygen in exhaust gas flowing into the Nth stage block
Cgout (X) Excess or deficiency of oxygen in exhaust gas flowing out from a specific block

Claims (7)

Cylinder number switching means for switching between all cylinder operation in which all cylinders operate and reduced cylinder operation in which some cylinders are deactivated;
Wherein when the operating state is switched between the reduced-cylinder operation and all-cylinder operation, the inflow of oxygen to predict the flow of oxygen deficiency amount of oxygen deficiency amount of the exhaust gas flowing into the catalyst after the switching Excess and deficiency prediction means,
And parameter estimation means on the basis of the inflowing oxygen deficiency amount, to estimate the parameters related to the oxygen storage state of the catalyst after the switching of the operating state,
Based on the estimated parameter, a switchability determination unit that determines whether the operation state can be switched;
A control device for an internal combustion engine, comprising: A rotational speed detecting means for detecting the rotational speed of the internal combustion engine;
Load detecting means for detecting the load of the internal combustion engine,
The inflowing oxygen deficiency amount predicting means, on the basis of the rotational speed and the load, the control apparatus for an internal combustion engine according to claim 1, wherein the predicting the inflowing oxygen deficiency amount. The parameter estimation means comprises specific position parameter estimation means for estimating a parameter related to the oxygen storage state at a specific position in the exhaust gas flow direction in the catalyst,
3. The control device for an internal combustion engine according to claim 1, wherein the switchability determination unit determines whether the operation state can be switched based on the parameter at the specific position. The parameter related to the oxygen storage state at the specific position is oxygen excess / deficiency at the specific position,
4. The control apparatus for an internal combustion engine according to claim 3, wherein the switchability determination unit prohibits the switchover when an oxygen excess / deficiency amount at the specific position exceeds a predetermined determination value. The parameter related to the oxygen storage state at the specific position is the oxygen storage rate at the specific position,
4. The internal combustion engine according to claim 3, wherein the switchability determination unit prohibits the switching when the oxygen storage rate at the specific position exceeds an upper limit determination value or does not satisfy a lower limit determination value. 5. Control device. At least one of a rotational speed detecting means for detecting the rotational speed of the internal combustion engine, a load detecting means for detecting a load of the internal combustion engine, and a catalyst deterioration detecting means for detecting a deterioration state of the catalyst;
Specific position determining means for determining the specific position in the catalyst based on at least one of the rotational speed, the load, and the catalyst deterioration state;
The control device for an internal combustion engine according to any one of claims 3 to 5 , further comprising: The control device for an internal combustion engine according to any one of claims 3 to 5 , wherein the specific position is a final position of the catalyst in a flow direction of exhaust gas.

Images