JP3832137B2 - Engine fuel supply control device - Google Patents

Description

ただし、Ｔsample：サンプル周期（空燃比をサンプリングする周期）、
Ｔ₁ ：低周波成分の時定数、
Ｔ₂ ：高周波成分の時定数、
ｋ₁ ：低周波成分のゲイン、
ｋ₂ ：高周波成分のゲイン、
Ａ₁ ：ｅ^-Tsample/T1、
Ａ₂ ：ｅ^-Tsample/T2、
Ｂ₁ ：ｋ₁、
Ｂ₂ ：ｋ₂、
数２式において、１番目の式（連続値系）を離散値系に変換したものが２番目の式、この２番目の式にｚ＝ｅ^sTsampleを代入して整理したものが３番目の式である。また、３番目の式をブロック図で示したのが図５である。
【００７１】
なお、燃料挙動に伴う無駄時間については燃料挙動の数学モデルに取り込まず、出力信号を時系列的にオフセットさせることで、モデル次数の上昇を抑える（詳細は１．３で後述する）。
【００７２】
１．２排気モデル
排気モデルは、図６のように各気筒毎の排気ダイナミクス、排気マニフォールド集合部におけるガス混合ダイナミクス、センサ特性の３要素から構成されると考える。これらを総合すると、「無駄時間＋遅れ系」の物理モデルで表すことができる。遅れ系としては、排気ガス輸送遅れ＋ガス混合遅れ＋センサ応答遅れが考えられ、それぞれが１次遅れ以上のモデルである。ただし、今回はオンボードで（ＥＣＭ２上で）プラントモデルを同定することを考えると、なるべく高次となることを避ける必要があり、排気モデルとして１つの時定数で代表し、次のように１次遅れ系の数学モデルで記述する。
【００７３】
【数３】
Ｇ_ex(ｓ)＝１／(ｓＴ_ex＋１)
Ｇ_ex(ｚ)＝(１−ｅ^-Tsample/Tex)／(ｚ−ｅ^-Tsample/Tex)
Ｇ_ex(ｚ)＝(１−Ａ₃)／(ｚ−Ａ₃)
ただし、Ｇ_ex ：排気動特性の伝達関数、
Ｔ_ex ：蒸発時定数、
Ｔsample：サンプル周期、
Ａ₃ ：ｅ^-Tsample/Tex、
数３式においても、１番目の式を離散値系に変換したものが２番目の式、２番目の式にｚ＝ｅ^sTsampleを代入して整理したものが３番目の式である。
【００７４】
また、無駄時間については、燃料挙動モデルと同様に時系列的にオフセットさせることとし、排気モデルに取り込まない（１．３で後述する）。
【００７５】
１．３無駄時間モデル
本プラントモデル３１は、入力に実噴射パルス幅ＣＴＩｎ、出力にＡ／Ｆセンサ３出力電圧読み込み値とおいているため、図３に示したように、実噴射パルス幅ＣＴＩｎを演算してからＡ／Ｆセンサ出力値をＥＣＭ２が読み込むまでにはいくつかの無駄時間（図では「Delay」で表示）が存在する。そこで、改めて入出力間の無駄時間を図７に詳細に示す。
【００７６】
ここで、各無駄時間を説明する。
【００７７】
１）Delay１：噴射量演算から実噴射タイミングまでのディレイ、
実噴射パルス幅ＣＴＩｎは１０ｍｓ毎に演算しており、実際に燃料を噴射するタイミングまでは必ずしも毎サイクル同一ではない。そこで演算された噴射タイミング（燃料噴き始め）角度とそのときの回転数より、パルス幅演算タイミングからの時間を算出することにより無駄時間Delay１を求める。
【００７８】
２）Delay２：実噴射タイミングからＩＶＯ（吸気弁開）までのディレイ、
これは、燃料を噴射し、吸気弁が開いて燃料がシリンダに吸入されるまでの時間である。本ディレイは燃料挙動特性により決まり、各運転条件および燃料性状によって設定する。たとえば、市販されている燃料のうち揮発性がほぼ中間の燃料を用いて、各運転条件（たとえばエンジン回転数と負荷）毎に燃料をステップ的に変化させて実際に応答時間を計測しながら適切な値を設定する。
【００７９】
３）Delay３：ＩＶＯからＥＶＯ（排気弁開）まで（吸入→圧縮→燃焼→排気）のディレイ、
これは、燃料が吸気弁よりシリンダ内に吸入され、燃焼ガスが排気弁から排出されるまでの時間である。このディレイは回転数およびカムプロフィールから求めることができ、設計仕様より求められる。
【００８０】
４）Delay４：燃焼ガスが排気弁を出てからＡ／Ｆセンサに到達するまでのディレイ、
これは、シリンダ内の燃焼ガスが排気弁より排出されてから排気管を通りＡ／Ｆセンサ部に到達するまでの時間である。排気の流速（回転数、負荷等に依存）と排気長さ、Ａ／Ｆセンサ取り付け位置等によって設定する。なお、計算が複雑になるが、運転条件およびハードスペックから求めてもよい。
【００８１】
５）Delay５：センサ応答ディレイ、
これは、Ａ／Ｆセンサ部にガスが到達してからＡ／Ｆセンサが電圧を出力するまでの時間である。Ａ／Ｆセンサ自体は酸素量が変動すると、数ｍｓで反応するが、センサカバーによるガス混合遅れが支配的であり、その時間はセンサカバーの形状により大きく異なる。このため、本ディレイはDelay４と同様にして適切な値を設定する。
【００８２】
６）Delay６：センサ出力値をＡ／Ｄ変換しＥＣＭ２に取り込むまでのディレイ、
これは、Ａ／Ｆセンサが出力する電圧をＥＣＭ２に取り込むためにＡ／Ｄ変換を行うことによるディレイである。現在のハード構成ではＡ／Ｆセンサ３のＡ／Ｄ変換は２ｍｓ毎に行っており、最大無駄時間は２ｍｓである。
【００８３】
７）Delay７：センサ出力値をメモリにバッファリングするまでのディレイ、
Ａ／Ｆセンサ出力値を１０ｍｓでサンプリングする場合に、サンプリングタイミングによっては最大１０ｍｓの無駄時間が生じるおそれがある。このため２ｍｓでＡ／Ｄ変換した値より算出した応答開始からサンプリングタイミングまでの無駄時間をDelay７として算出する。
【００８４】
８）Delay８：バラツキ分、
これは、Delay１〜７より求めた無駄時間以外に生じるバラツキ分である。機種間バラツキや適合のバラツキ等が考えられ、運転毎にも不確定であるため、Delay１〜７経過後の空燃比信号の立ち上がりを判定し決定する。
【００８５】
これで、各無駄時間の説明を終える。
【００８６】
上記のDelay１〜８を分析すると、無駄時間は
▲１▼運転条件により決定する項、
▲２▼演算タイミングより決定する事項、
▲３▼燃料性状等により変動する項
に分類することができる（図８参照）。よって、実際の無駄時間は、次の式で表すことができる。
【００８７】

２．プラントモデルの同定
２．１同定するモデルの作成
実際のエンジンは強い非線形性を有するが、本制御では、ある動作点近傍では線形でありかつ時不変である、いわゆる線形時不変システム（ＬＴＩ：Linear Time-Invariant System）であると仮定する。
【００８８】
また、離散時間系ＬＴＩシステムを、Ｚ領域ではなく時間領域で入出力を記述するため、シフトオペレータｑ^-1を以下のように定義する。
【００８９】
【数４】
ｑ^-1ｘ(ｋ)＝ｘ(ｋ−１)
ただし、離散時間＝ｋＴ（Ｔ：サンプリング周期、ｋ＝０，１，２，・・・）である。
【００９０】
これを用いて、離散値系の入力ｕ(ｔ)、出力ｙ(ｔ)のシステム伝達関数を記述すると、
【００９１】
【数５】
ｙ(ｋ)＝Ｇ(ｑ，θ)・ｕ(ｋ)
となる。θはモデルを記述するパラメータにより構成される。しかし、これは理想的な入出力であり、外部からの雑音を考慮すると、
【００９２】
【数６】
ｙ(ｋ)＝Ｇ(ｑ，θ)・ｕ(ｋ)＋Ｈ(ｑ，θ)・ｗ(ｋ)
と記述できる。ここで、Ｈ(ｑ，θ)は雑音モデルであり、一般的な離散時間系ＬＴＩシステムは、数６式で表すことができる。同システムのブロック図は図９である。
【００９３】
ここで、同システムの伝達関数Ｇ(ｑ)は、数２式の３番目の式と数３式の３番目の式の積であり、さらにＺ^-1で記述されたものをシフトオペレータｑ^-1で記述したものとなって、
【００９４】
【数７】

と表せる。このシステムの伝達関数Ｇ(ｑ)を、
【００９５】
【数８】
Ｇ(ｑ，θ)＝Ｂ(ｑ，θ)／Ａ(ｑ，θ)
の式で定義すると、システムの出力値ｙ(ｋ)は、
【００９６】
【数９】
ｙ(ｋ，θ)＝｛Ｂ(ｑ，θ)／Ａ(ｑ，θ)｝・ｕ(ｋ)＋Ｈ(ｑ，θ)・ｗ(ｋ)
と表すことができる。このように、同定するモデルとしては、プラントモデルであるＧ(ｑ)と、雑音モデルであるＨ(ｑ)を適切な形としたものとを組み合わせたものを採用する。
【００９７】
２．２同定手法
数６式で定義した離散時間系ＬＴＩシステムにおいて、時刻(ｋ−１)までに測定された入出力データに基づいた出力ｙ(ｋ)の一段先予測値ｙ(ｋ｜θ)は、
【００９８】
【数１０】
ｙ(ｋ｜θ)＝［１−Ｈ^-1(ｑ，θ)］ｙ(ｋ)＋Ｈ^-1(ｑ，θ)Ｇ(ｑ，θ)ｕ(ｋ)
の式で表される。これにより、時刻ｋにおける出力を(ｋ−１)までに取得したデータで記述することができる。
【００９９】
予測誤差ε(ｋ｜θ)は
【０１００】
【数１１】
ε(ｋ｜θ)＝ｙ(ｋ)−ｙ(ｋ｜θ)
の式で表すことができる。
【０１０１】
さて、パラメータ推定のための評価規範Ｊ_N(θ)として、
【０１０２】
【数１２】

を設定する。ここで、関数ｌ(ｋ，θ，ε(ｋ，θ))は予測誤差ε(ｋ，θ)の大きさを測る任意のスカラ値関数であり、どのようなノルムを選択するかは、同定結果の利用目的に依存する（２乗ノルムや対数尤度など）。このような評価規範を定義することによって、未知パラメータθの推定値（θ(Ｎ)とする）が決定される。つまり、
【０１０３】
【数１３】

となるθを求めることである。
【０１０４】
一般的に同定手法には様々な手法が提案されているが、エンジンのようなものは間欠的なイベント（燃焼サイクル等）であり、非常に非線形性が強い制御対象である。しかしながら、本制御ではアルゴリズムの簡略化のため、動作点周りでは線形時不変（ＬＴＩ）システムであると仮定している。
【０１０５】
今回は演算量の少なさ、同定精度、対外乱性能を考慮し、線形モデルの同定手法の代表的なものである「パラメトリックモデル同定であるＡＲＸモデルを用いた一括同定手法」を採用する。
【０１０６】
２．３ＡＲＸモデルの同定手法
ＡＲＸモデルは式誤差モデルと呼ばれ、次のように差分方程式の右辺に外乱項ｅ(ｋ)（ＡＲＸモデルでは白色雑音として仮定しており、ｗ(ｋ)とする）が入っている。
【０１０７】
【数１４】
ｙ(ｋ)＋ａ₁・ｙ(ｋ−１)＋・・・＋ａ_na・ｙ(ｋ−ｎａ)＝ｂ₁・ｕ(ｋ−１)＋・・・＋ｂ_nb・ｕ(ｋ−ｎｂ)＋ｅ(ｋ)モデルを記述するパラメータベクトルθは、
【０１０８】
【数１５】
θ＝［ａ₁，・・・，ａ_na，ｂ₁，・・・，ｂ_nb］^T
となる。データベクトル（回帰ベクトル）ψ(ｋ)を、
【０１０９】
【数１６】
ψ(ｋ)＝［−ｙ(ｋ−１)，・・・，−ｙ(ｋ−ｎａ)，ｕ(ｋ−１)，・・・，ｕ(ｋ−ｎｂ)］^T
と定義すると、出力ｙ(ｋ)は次式のように表現できる。
【０１１０】
【数１７】
ｙ(ｋ)＝θ^Tψ(ｋ)＋ｗ(ｋ)
ＡＲＸモデルの一段先予測値ｙ(ｋ｜θ)は、数１０式より求めると、θに関して線形であり、
【０１１１】
【数１８】
ｙ(ｋ｜θ)＝θ^Tψ(ｋ)
と表される。このときの予測誤差ε(ｋ，θ)は、
【０１１２】
【数１９】
ε(ｋ，θ)＝ｙ(ｋ)−θ^Tψ(ｋ)
と表わすことができる。この線形回帰モデルに対して最小２乗法を適用すると、スカラ値関数ｌ(ｋ，θ，ε(ｋ，θ))は、
【０１１３】
【数２０】
ｌ(ｋ，θ，ε(ｋ，θ))＝ε²(ｋ，θ)
となり、パラメータ推定の評価規範Ｊ_N(θ)は、
【０１１４】
【数２１】

となる。数２１式をさらに計算すると、
【０１１５】
【数２２】

【０１１６】
【数２３】
Ｊ_N(θ)＝ｃ(Ｎ)−２θ^Tｆ(Ｎ)＋θ^TＲ(Ｎ)θ
とおくことができる。
【０１１７】
ただし、数２３式のｃ(Ｎ)、ｆ(Ｎ)、Ｒ(Ｎ)は次の通りである。
【０１１８】
【数２４】

【０１１９】
【数２５】

【０１２０】
【数２６】

評価規範Ｊ_N(θ)が最小となるのは、Ｊ_N(θ)がθに関する二次関数であるため、最高次の係数が正であれば、Ｊ_N(θ)の微分値がゼロとなるところである。数２３式の微分値＝０とすると、次の正規方程式（θに関する連立一次方程式）が得られる。
【０１２１】
【数２７】

これより、Ｒ(Ｎ)が正定値行列であれば、Ｊ_N(θ)は微分値がゼロのとき最小となり（Ｊ_N(θ)は下に凸の関数、図１０参照）、
【０１２２】
【数２８】

の式によりパラメータθ(Ｎ)を推定することができる。以上の同定手順を図１１に示す。
【０１２３】
なお、上記の正定値行列の条件には次の３つがある。
【０１２４】
１）同定対象がｎ次の場合は、入力信号ｕ(ｋ)はｎ個以上の正弦波を含んでいなければならない（ステップ入力信号に十分な周波数成分を含ませる）。
【０１２５】
２）同定対象は安定である（エンジンは定常では安定系と考えて差し支えない）。
【０１２６】
３）同定対象は可観測である。すなわち、Ａ(ｑ，θ)とＢ(ｑ，θ)は共通因子を持たない（本モデルは離散系であるためＢ(ｑ，θ)のほうが次数が高いが問題なし）。
【０１２７】
２．４実際のＡＲＸモデルの同定
本モデルは、数７式より分母３次、分子３次の離散系モデルであり、
【０１２８】
【数２９】
Ａ(ｑ)＝１＋ａ₁・ｑ^-1＋ａ₂・ｑ^-2＋ａ₃・ｑ^-3
【０１２９】
【数３０】
Ｂ(ｑ)＝ｂ₁・ｑ^-1＋ｂ₂・ｑ^-2＋ｂ₃・ｑ^-3
と表すことができる。よってパラメータベクトルθおよびデータベクトルψ(ｋ)は、以下のように表すことができる。
【０１３０】
【数３１】
θ＝［ａ₁，ａ₂，ａ₃，ｂ₁，ｂ₂，ｂ₃］^T
【０１３１】
【数３２】
ψ(ｋ)＝［−ｙ(ｋ−１)，−ｙ(ｋ−２)，−ｙ(ｋ−３)，
ｕ(ｋ−１)，ｕ(ｋ−２)，ｕ(ｋ−３)］^T
エンジン回転数が1200rpm時のサンプリング総数ＮをＮ＝128（1280ｍｓ）とすると、数２４式〜数２６式は、
【０１３２】
【数３３】

【０１３３】
【数３４】

【０１３４】
【数３５】

と表すことができる。
【０１３５】
２．５プラントモデル同定に必要な入力信号
システムの同定を行うためには、入力信号が、対象のもつ全てのモードを励起している必要がある。つまり、入力信号が多数の周波数成分を含んでいる必要がある。システムの同定においては、理想的には白色性入力が望ましいが、実際には疑似白色２値信号（Ｍ系列）が用いられる。しかし、エンジンの壁流応答のようなものでは、有効な周波数帯域は非常に低いところであり（応答が遅い）、Ｍ系列のような入力を加えてもほとんど応答波形を得ることができない。そこで、ステップ入力を与えることにより得られる波形（図１２参照）をもとに、システムを同定する。なお、ステップ入力のラプラス変換は１／ｓであるので、周波数ゲインは周波数に対して反比例で減少するため、パワースペクトルより有効な周波数域を決めておく必要がある。
【０１３６】
２．６実験結果
このようにして求めたパラメータθを用いれば、システムの伝達関数Ｇ(ｑ，θ)が定まるので、同定結果と実データを重ねたボード線図を図１３に示す（燃料性状が軽質であるほどカットオフ周波数が高くなる傾向がある）。実験結果によれば、吸気ポートに設けたスワールコントロールバルブが開状態、エンジン回転数が1200rpm近傍、冷却水温が４０℃近傍かつ低負荷域において±３σで燃料性状の異なる２つのガソリンを分離することができた。
【０１３７】
これで、項分け説明を終える。
【０１３８】
次に、ＥＣＭ２で実行される制御内容を、フローチャートにしたがって説明する。
【０１３９】
図１４は燃料性状を推定するためのもので、一定時間毎（１０ｍｓ毎）に実行する。ここでは、図１４をメインルーチン、図１５、図１６を図１４のサブルーチンとして構成しており、したがって、以下ではメインルーチンの説明途中でサブルーチンのあるステップになると、サブルーチンを説明する。
【０１４０】
図１４においてステップ１では燃料性状判定済みフラグをみる。まだ燃料性状を判定していないときは、ステップ２以降に進む。
【０１４１】
ステップ２〜６は排気の空燃比（出力データ）をサンプリングする部分である。ステップ２では、Ａ／Ｆセンサ３で検出される空燃比を読み込み、ステップ３でこの空燃比の読み込み数（サンプリング数）Ｓ１とサンプリング総数Ｎ（たとえば128）を比較する。Ｓ１≦Ｎであるときは、ステップ４に進んで、空燃比をバッファリングして今回の処理を終了する。Ｓ１＞Ｎとなる前はステップ２、４の処理を繰り返す。
【０１４２】
Ｓ１＞Ｎとなったタイミングでステップ３よりステップ５に進む。このとき、バッファにはＮ個の出力データが格納されている。たとえば、今回値をｙ(１)に、前回値をｙ(２)に、２回前の値をｙ(３)に、・・・、Ｎ−１回前の値をｙ(Ｎ)にというようにして、合計でＮ個の出力データが格納されている。
【０１４３】
ステップ５、６ではＮ回前の出力データをバッファから捨て、今回読み込んだ空燃比をバッファリングする。つまり、今回値をｙ(１)に格納する。なお、過去の出力データは１回ずつ古い側にシフトして格納されることはいうまでもない。
【０１４４】
図示しないが、ステップ応答時の実噴射パルス幅ＣＴＩｎ（入力データ）も、今回値をｕ(１)に、前回値をｕ(２)に、２回前の値をｕ(３)に、・・・、Ｎ−１回前の値をｕ(Ｎ)にというようにして合計でＮ個の入力データが格納されており、これらの入力データと上記の出力データとは前述した遅れ時間を考慮して対応付けられる。
【０１４５】
ステップ７、８では、これらＮ個ずつの入出力データを用いて実噴射パルス幅がステップ変化したときの排気空燃比の応答波形を解析し、その解析結果から使用燃料の燃料性状を推定する。
【０１４６】
ここで、「排気空燃比の応答波形の解析」とは、前述の表現によれば、入出力データに基づいてＡＲＸモデル（プラントモデル）のパラメータθを規範モデルとの予測誤差が最小となるように調整してＡＲＸモデルを同定することである。そこでＡＲＸモデルの同定を図１５のサブルーチンにより、また燃料性状の推定について図１６のサブルーチンにより説明する。
【０１４７】
まず図１５において、ステップ２１では、バッファにある入出力データ（入力についてｕ(１)〜ｕ(128)、出力について−ｙ(１)〜−ｙ(128)）より数３２式を用いてデータベクトルψ(ｋ)を作成する。
【０１４８】
ステップ２２ではこのデータベクトルψ(ｋ)から上記の数３３式を用いてＲ(Ｎ)を、またステップ２３では出力データｙ(ｋ)とこのデータベクトルψ(ｋ)から上記の数３４式を用いてｆ(Ｎ)を演算し、これらＲ(Ｎ)、ｆ(Ｎ)からステップ２４において上記の数２８式を用いてモデルパラメータθを演算する。
【０１４９】
次に、図１６に移り、このようにして求めたモデルパラメータθからステップ３１において離散時間系ＬＴＩシステムの伝達関数Ｇ(ｑ，θ)を演算する（θから上記の数２９式、数３０式を用いてＡ(ｑ)、Ｂ(ｑ)を作成し、この２つよりＧ(ｑ，θ)（＝Ｂ(ｑ)／Ａ(ｑ)）を算出する）。
【０１５０】
このシステム伝達関数Ｇ(ｑ，θ)からステップ３２においてＡＲＸモデルのカットオフ周波数ｆｃ_Realを演算する。ステップ３３ではこのカットオフ周波数ｆｃ_Realと規範モデルのカットオフ周波数ｆｃ_Refを比較する。
【０１５１】
ここで、基準燃料に重質ガソリンを用いているので、軽質ガソリンが使用されていればｆｃ_Real＞ｆｃ_Refとなり、重質ガソリンが使用されているときはｆｃ_{R eal}≦ｆｃ_Refとなる。したがって、ｆｃ_Real＞ｆｃ_Refのとき（軽質ガソリンの使用時）はステップ３４に進んで燃料性状切換フラグ＝１とし、これに対して、ｆｃ_Real≦ｆｃ_Refのとき（重質ガソリンの使用時）は、ステップ３３よりステップ３５に進んで燃料性状切換フラグ＝０とする。
【０１５２】
このようにしていずれの燃料が使用されているのかの判定が終了したら、図１４のステップ９に進み、燃料性状切換フラグの値（燃料性状の判定結果）をＥＥＰＲＯＭに格納したあと、ステップ１０において燃料性状判定済みフラグ＝１とする。この燃料性状判定済みフラグ＝１の処理により、次回以降は、図１４のステップ２以降に進むことができない（燃料性状の判定回数が１回だけとなる）。
【０１５３】
このようにして燃料性状の判定が可能になると、燃料噴射量の各種補正量や始動時燃料噴射量を燃料性状の違いに応じて与えることができる。これを具体的にＫＡＳの場合で説明する。
【０１５４】
図１７は、始動後増量補正係数ＫＡＳを演算するためのもので、一定時間毎（たとえば１０ｍｓ毎）に実行する。
【０１５５】
ステップ４１でＥＥＰＲＯＭに格納されている燃料性状切換フラグを読み込む。ステップ４２ではスタータスイッチをみてこれがＯＮのときは、ステップ４３に進み、冷却水温ＴＷと回転数Ｎｅを読み込む。このうち冷却水温ＴＷと燃料性状切換フラグの値から、ステップ４４、４５においてそれぞれ図１８、図１９を内容とするテーブルを検索することにより始動後増量水温補正値ＴＫＡＳ、第２始動後増量補正係数ＫＡＳＳを、また回転数Ｎｅと燃料性状切換フラグの値からステップ４６において図２０を内容とするテーブルを検索することにより始動後増量回転補正値ＴＮＫＡＳを演算し、これらの値を用いステップ４７において
【０１５６】
【数３６】
ＫＡＳ＝ＴＫＡＳ×ＴＮＫＡＳ＋ＫＡＳＳ
の式により始動後増量補正係数ＫＡＳを算出する。
【０１５７】
ここで、ＴＫＡＳ、ＫＡＳ、ＴＮＫＡＳの値は、図１８、図１９、図２０に示したように、同一の条件で燃料性状切換フラグ＝１のとき（つまり軽質ガソリンの使用時）のほうが燃料性状切換フラグ＝０のとき（つまり重質ガソリンの使用時）より小さくなる値である。
【０１５８】
ステップ４８では、スタータスイッチがＯＦＦになってからの処理に備えるため、ＴＫＡＳの値をＴＫＡＳ_n-1に、ＫＡＳＳの値をＫＡＳＳ_n-1に移して今回の処理を終了する。ＴＫＡＳ_n-1、ＫＡＳＳ_n-1は前回値を保持するためのメモリである。
【０１５９】
やがてスタータスイッチがＯＦＦになると（始動完爆）、ステップ４２よりステップ４９以降の減衰操作に進む。
【０１６０】
ステップ４９では、燃料性状切換フラグの値と始動後時間ｔとから図２１を内容とするテーブルを検索することにより始動後増量減少時間割合ＴＭＫＡＳを演算し、ステップ５０でこの値だけ前回値を減少させた値を今回のＴＫＡＳ（＝ＴＫＡＳ_n-1−ＴＭＫＡＳ）として算出する。スタータスイッチがＯＦＦになった直後はＴＫＡＳ＞０であるので、そのままステップ５３に進む。
【０１６１】
ステップ５３〜５６はステップ４９〜５２と同様である。ステップ５３で燃料性状判定フラグの値と始動後時間ｔから図２２を内容とするテーブルを検索することにより第２始動後増量減少時間割合ＴＭＫＡＳＳを演算し、ステップ５４でこの値だけ前回値を減少させた値を今回のＫＡＳＳ（＝ＫＡＳＳ_n-1−ＴＭＫＡＳＳ）として算出する。このときも、ＫＡＳＳ＞０であるので、そのままステップ４６に進んでステップ４６以降の処理を実行する。
【０１６２】
上記のＴＭＫＡＳ、ＴＭＫＡＳＳも、図２１、図２２に示したように、同一の条件で比較したとき軽質ガソリンの使用時のほうが重質ガソリンの使用時より小さくなる値である。
【０１６３】
次回以降はステップ４９、５０、５３、５４を繰り返すことになるので、やがてＴＫＡＳやＫＡＳＳが０以下となり、このときはステップ５２やステップ５６に進んでＴＫＡＳやＫＡＳＳを０に制限する。
【０１６４】
この結果、ＴＫＡＳ、ＫＡＳＳとも、スタータスイッチのＯＦＦ時の値を初期値として、スタータスイッチのＯＦＦ後に一定の割合で減衰して０になる（ただし、ＴＮＫＡＳが一定のとき）。ただし、ＴＫＡＳの初期値のほうがＫＡＳＳの初期値より大きく、かつＴＫＡＳの減少時間割合のほうがＫＡＳＳの減少時間割合より大きい。したがって、ＴＫＡＳとＫＡＳＳを加算した値であるＫＡＳは、スタータスイッチＯＦＦ時のＴＫＡＳの値とＫＡＳＳの値の合計を初期値として、スタータスイッチＯＦＦ後にまず急激な勾配で小さくなり、ＴＫＡＳが０になったタイミングからは緩やかな勾配に切換わって減少していく。
【０１６５】
この場合に、軽質ガソリンの使用時のほうが重質ガソリンの使用時よりもＴＫＡＳ、ＫＡＳＳの各初期値（図１８、図１９のテーブル値）を小さく、かつＴＫＡＳ、ＫＡＳＳの各減少時間割合（図２１、図２２のテーブル値）を大きくしているので、軽質ガソリン使用時のＫＡＳは、重質ガソリン使用時のＫＡＳより小さくなる（図２３参照）。つまり、燃料性状の判定を行っていないものでは、軽質ガソリンの使用時にも、重質ガソリンに対してマッチングしたテーブル値を用いることによる空燃比のリッチ化を招くのであるが、このように、軽質ガソリンの使用であることを判定したときは、次回の始動時のＫＡＳの演算に際して、軽質ガソリン用のＫＡＳを演算することで、軽質ガソリンの使用時にも空燃比がリッチ側に偏ることがなくなるのである。
【０１６６】
図２４のフローチャートは第２実施形態で、第１実施形態の図１６に対応する。図１６と同一部分には同一のステップ番号を付している。
【０１６７】
基準燃料に重質ガソリンを用いた第１実施形態に対して、第２実施形態は、市販されている燃料のうち揮発性が悪くもなく良くもないほぼ中間の燃料を基準燃料として、またこの基準燃料よりも揮発性の良い燃料を軽質ガソリン、この逆に基準燃料よりも揮発性の悪い燃料を重質ガソリンとして設定しておき、プラントモデルのカットオフ周波数と規範モデルのカットオフ周波数（つまり基準燃料に対するカットオフ周波数）の差を演算し、この周波数差と許容範囲とを比較して使用されている燃料の燃料性状を判定するようにしたもので、これによって、基準燃料に対するカットオフ周波数がバラツクことがあっても、燃料性状の推定を安定して行うことができる。
【０１６８】
図２４において、図１６と相違する部分を主に述べると、ステップ６１で
【０１６９】
【数３７】
Δｆｃ＝ｆｃ_Real−ｆｃ_Ref
の式により基準燃料とのカットオフ周波数差Δｆｃを計算し、この周波数差Δｆｃの絶対値と許容範囲を定める所定値ａ（＞０）、あるいはΔｆｃとａをステップ６２、６３において比較する。｜Δｆｃ｜≦ａ（つまり基準燃料が使用されている）であれば、ステップ６２よりステップ６４に進んで燃料性状切換２フラグ＝０とし、｜Δｆｃ｜＞ａかつΔｆｃ＞ａ（つまり軽質ガソリンが使用されている）であるときはステップ６３よりステップ６５に進んで燃料性状切換２フラグ＝１とし、それ以外（つまり重質ガソリンが使用されている）のときはステップ６３よりステップ６６に進んで燃料性状切換２フラグ＝２とする。
【０１７０】
このように第２実施形態では、使用されている燃料が、基準燃料、軽質ガソリン、重質ガソリンのいずれであるかが判定された。
【０１７１】
ただし、第２実施形態のように、燃料性状判定値が３つの値になると、始動後増量補正係数ＫＡＳを演算するに際し、図１８〜図２２に対応して３種類のテーブル値を用意する必要がある。
【０１７２】
次に、図２５、図２６、図２８のフローチャートは第３実施形態で、それぞれ第１実施形態の図１４、図１６、図１７に対応する。図２５において図１４と同一部分に、図２６において図１６と同一部分に、また図２８において図１７と同一部分にそれぞれ同一のステップ番号を付している。
【０１７３】
前述の２つの実施形態が燃料性状判定値（つまり燃料性状切換フラグや燃料性状切換２フラグの値）が２値あるいは３値であったのに対して、第３実施形態は、連続値としての燃料性状推定値を演算し、これをＥＥＰＲＯＭに格納するとともに（図２５のステップ７１、７２）、次回の始動時よりこの燃料性状推定値を用いて始動後増量補正係数ＫＡＳを演算するようにしたものである。
【０１７４】
燃料性状推定値の演算について具体的に図２６により説明すると、ステッ３１、３２で第１実施形態と同じにプラントモデルのカットオフ周波数を演算し、その演算したカットオフ周波数からステップ８１において図２７を内容とするテーブルを検索することにより燃料性状推定値を演算する。プラントモデルのカットオフ周波数と燃料性状推定値との関係は図２７のようになるので、同特性を予めマッチングにより定めておけば、プラントモデルのカットオフ周波数から使用燃料の燃料性状を推定できるのである。
【０１７５】
次に、図２８において、図１７と異なる部分を主に説明すると、ステップ９１で燃料性状推定値ＦＣを読み込み、スタータスイッチのＯＮ時はこの値ＦＣと冷却水温ＴＷ、回転数Ｎeからステップ９２、９３、９４において図２９、図３０、図３１を内容とするマップを検索することにより、始動後増量水温補正値ＴＫＡＳ、第２始動後増量補正係数ＫＡＳＳ、始動後増量回転補正値ＴＮＫＡＳを、またスタータスイッチのＯＦＦ時には燃料性状推定値ＦＣと冷却水温ＴＷからステップ９５、９６において図３２、図３３を内容とするマップを検索することにより、始動後増量減少時間割合ＴＭＫＡＳ、第２始動後増量減少時間割合ＴＭＫＡＳＳをそれぞれ演算する。
【０１７６】
ここで、ＴＫＡＳ、ＫＡＳＳは、図２９、図３０に示したように同一のＦＣであれば冷却水温ＴＷが低いほど、またＴＷが同じであるとき燃料性状が重質になるほど大きくなる値、ＴＭＫＡＳ、ＴＭＫＡＳＳは、図３２、図３３のように同一のＦＣであれば冷却水温ＴＷが高くなるほど、またＴＷが同じであるとき燃料性状が軽質になるほど大きくなる値である。
【０１７７】
なお、燃料性状推定値とＴＷが同一であれば、ＴＫＡＳのほうがＫＡＳＳより大きく、かつＴＭＫＡＳのほうがＴＭＫＡＳＳより大きくなることはいうまでもない。
【０１７８】
この第３実施形態によれば、連続値としての燃料性状推定値ＦＣに応じて始動後増量補正係数ＫＡＳの演算に用いるデータ（マップ値）を割り付けているので、先の２つの実施形態よりも、始動後増量補正係数ＫＡＳの演算精度が向上する。
【０１７９】
図３４のフローチャートは第４実施形態で、第３実施形態の図２８と置き換わるものである。なお、図２８と同一部分には同一のステップ番号を付している。
【０１８０】
さて、ＫＡＳを演算するのに用いるデータを、図２９〜図３３のようにマップ値で与えるのでは、マッチングの工数が莫大なものとなってしまう。そこでこの第４実施形態は、燃料性状推定値ＦＣに応じた燃料性状補正値ＫＦＣを導入してこの補正値ＫＦＣで最重質ガソリンに対してマッチングしたデータ（テーブル値）を補正し、この補正したデータに基づいて始動後増量補正係数ＫＡＳを演算することにより、マッチングの工数を減らすようにしたものである。
【０１８１】
具体的に説明すると、図２８の場合と異なるのは、ステップ１０１、１０２〜１１５である。まずステップ１０１で燃料性状推定値ＦＣから図３５を内容とするテーブルを検索することにより、燃料性状補正値ＫＦＣを演算する。図３５に示したように、ＫＦＣは、最重質ガソリン（燃料性状が最重質）のときを最大の１．０として燃料性状が軽質になるほど小さくなる値である。
【０１８２】
ステップ１０２、１０３では冷却水温ＴＷから図３６、図３７を内容とするテーブルを検索することにより、ＴＫＡＳ、ＴＭＫＡＳ（いずれも最重質ガソリンに対してマッチングした値である）を演算し、これらと上記のＫＦＣとを用いステップ１０４において、
【０１８３】
【数３８】
ＴＫＡＳＦ＝ＴＫＡＳ×ＫＦＣ
ＴＭＫＡＳＦ＝ＴＭＫＡＳ×ＫＦＣ
の式により、燃料性状対応の始動後増量水温補正値ＴＫＡＳＦと燃料性状対応の始動後増量減少時間割合ＴＭＫＡＳＦを計算する。ステップ１０５、１０６、１０７ではステップ１０２、１０３、１０４と同様にして、冷却水温ＴＷから図３８、図３９を内容とするテーブルを検索することにより、ＫＡＳＳ、ＴＭＫＡＳＳ（これらも最重質ガソリンに対してマッチングした値である）を演算し、
【０１８４】
【数３９】
ＫＡＳＳＦ＝ＫＡＳＳ×ＫＦＣ
ＴＭＫＡＳＳＦ＝ＴＭＫＡＳＳ×ＫＦＣ
の式により、燃料性状対応の第２始動後増量補正係数ＫＡＳＳＦと燃料性状対応の第２始動後増量減少時間割合ＴＭＫＡＳＳＦを計算する。そして、これらの値を用いて、上記の数３６式と同様の式である、
【０１８５】
【数４０】
ＫＡＳ＝ＴＫＡＳＦ×ＴＮＫＡＳ＋ＫＡＳＳＦ
の式により始動後増量補正係数ＫＡＳを算出する（ステップ１０８）。
【０１８６】
そしてステップ１０９ではスタータスイッチがＯＦＦになってからの処理に備えるため、ＴＫＡＳＦの値をＴＫＡＳＦ_n-1に、ＫＡＳＳＦの値をＫＡＳＳＦ_n-1に移して今回の処理を終了する。ステップ１１０〜１１５は、スタータスイッチのＯＦＦ後にＴＫＡＳＦ、ＫＡＳＳＦについて図１７のステップ４９〜５６と同様に減衰操作を行う部分である。
【０１８７】
たとえば、最重質ガソリンよりも燃料性状が軽質側のガソリンが使用されるときには、ＫＦＣが１．０より小さな値となるため、ＴＫＡＳＦ＜ＴＫＡＳ、ＴＭＫＡＳＦ＜ＴＭＫＡＳ、ＫＡＳＳＦ＜ＫＡＳＳ、ＴＭＫＡＳＳＦ＜ＴＭＫＡＳＳとなることから、最重質ガソリンに対するＫＡＳよりも小さなＫＡＳが算出され、これによって、図２８の場合と同様に、最重質ガソリンよりも燃料性状が軽質側のガソリンに対しても最適な始動後増量補正係数が与えられるのである。なお、最重質ガソリンの使用時は、ＫＦＣ＝１．０より、ＴＫＡＳＦ＝ＴＫＡＳ、ＴＭＫＡＳＦ＝ＴＭＫＡＳ、ＫＡＳＳＦ＝ＫＡＳＳ、ＴＭＫＡＳＳＦ＝ＴＭＫＡＳＳとなり、従来装置と変わらない。
【０１８８】
この場合に、ＫＡＳの演算に用いるデータを得るに際しては、図３６〜図３９に示す特性を最重質ガソリンに対してマッチングするだけで済むので、第４実施形態によれば、第３実施形態の場合よりマッチングの工数を低減できるのである。
【０１８９】
次に、図４０、図４８、図５１のフローチャートは、第５、第６、第７の各実施形態で、それぞれ図１７、図２８、図３４に対応する。なお、図４０において図１７と同一部分、図４８において図２８と同一部分、図５１において図３４と同一部分には同一のステップ番号を付している。
【０１９０】
前述の図１７、図２８、図３４の３つの実施形態は、燃料性状切換フラグや燃料性状推定値に基づいて始動後増量補正係数ＫＡＳを演算するものであったが、第５、第６、第７の各実施形態は、燃料性状切換フラグや燃料性状推定値に基づいて未燃分増量補正係数ＫＵＢを演算するようにしたものである。なお、未燃分増量補正係数ＫＵＢの演算方法そのものついては特開平１０−１８８８３号公報により提案している。
【０１９１】
図４０から説明すると、ステップ４１、１２１でＥＥＰＲＯＭに格納されている燃料性状切換フラグの値のほか、吸入負圧、回転数Ｎｅ、冷却水温ＴＷを読み込み、ステップ１２２で空燃比フィードバック制御条件（図では「空燃比Ｆ／Ｂ条件」で略記）であるかどうかの判定を行う。空燃比フィードバック制御を禁止する条件は、公知のように、始動時、高負荷時、減速時（フュエルカット時）、Ｏ₂センサ３出力に異常があるとき、Ｏ₂センサ３が未活性状態にあるときのいずれかに該当するときである。
【０１９２】
空燃比フィードバック制御を禁止する条件では、ステップ１２３、１２４に進み、冷却水温ＴＷと燃料性状切換フラグの値から図４１を内容とするテーブルを検索して水温増量補正係数の基本値ＫＴＷ０を、また吸入負圧と回転数Ｎｅより図４２を内容とするマップを検索して水温増量補正係数の負荷回転補正率ＲＫＴＷを求め、ステップ１２５において
【０１９３】
【数４１】
ＫＴＷ＝ＫＴＷ０×ＲＫＴＷ
の式により水温増量補正係数ＫＴＷを計算する。
【０１９４】
ここで、ＫＴＷ０の値は、図４１に示したように同一の冷却水温ＴＷでも軽質ガソリンの使用時（燃料燃料性状切換フラグ＝１）のほうが、重質ガソリンの使用時（燃料燃料性状切換フラグ＝０）よりも小さくなる値である。
【０１９５】
なお、図４２は、軽質ガソリン、重質ガソリンに共通の特性を示しており、実際には、軽質ガソリン用と重質ガソリン用の別々のマップがあり、同一の回転数、同一の吸入負圧でみると、軽質ガソリン用のマップ値のほうが重質ガソリン用のマップ値より小さくなっている。
【０１９６】
最後にステップ１２６では未燃分増量補正係数ＫＵＢに０を入れる。このとき（空燃比フィードバック制御を禁止する条件）はＫＵＢがないのと同じであり、従来と同様に水温増量補正係数ＫＴＷによる燃料増量を行うためである。
【０１９７】
これに対して、空燃比フィードバック制御条件の成立時になると、ステップ１２２よりステップ１２７に進み、水温増量補正係数ＫＴＷに０を入れるとともに、ステップ１２８、１２９で冷却水温ＴＷと燃料性状切換フラグの値より図４３を内容とするテーブルを検索して未燃分増量補正係数の基本値ＫＵＢＡＳを、また吸入負圧と回転数Ｎｅより図４４を内容とするマップを検索して未燃分増量補正係数の負荷回転補正率ＲＫＵＢを求め、ステップ１３０において
【０１９８】
【数４２】
ＫＵＢ＝ＫＵＢＡＳ×ＲＫＵＢ
の式により未燃分増量補正係数ＫＵＢを計算する。
【０１９９】
ＫＵＢＡＳの値も、図４３のようにＫＴＷ０と同様に同一の冷却水温ＴＷであれば軽質ガソリンの使用時（燃料燃料性状切換フラグ＝１）のほうが、重質ガソリンの使用時（燃料燃料性状切換フラグ＝０）よりも小さくなる値である。なお、図４４も、図４２と同様に軽質ガソリン、重質ガソリンに共通の特性を示しており、実際には、軽質ガソリン用と重質ガソリン用の独立したマップがあり、同一の回転数、同一の吸入負圧でみると、軽質ガソリン用のマップ値のほうが重質ガソリン用のマップ値より小さくなっている。
【０２００】
なお、エンジン冷間時は未燃分がエンジン暖機完了後よりも増えるためベース空燃比が理論空燃比とならない（理論空燃比よりもリーン側にくる）ことを前述したが、エンジン冷間時に未燃分が増えた状態でも空燃比が理論空燃比となるようにＫＵＢを適合している。
【０２０１】
詳細には、冷却水温ＴＷだけをパラメータとしてＫＴＷを演算するのではなく、負荷と回転数をもパラメータとしてＫＴＷを演算するのは次の理由からである。従来のＫＴＷはアイドル条件でのエンジンの安定度を主に考慮し、高回転、高負荷側ではそもそも安定度は問題ないと考え、冷却水温だけに対して適合していたのであるが、実際には図４５に示したように、同一の冷却水温、同一の回転数でも吸入負圧（つまりエンジン負荷）が違えばＫＴＷに対する要求値も違ってくる。したがって、スロットルバルブ５が全閉位置にあるときの吸入負圧（たとえばＡ点の吸入負圧）でエンジン安定度を満足する空燃比となるようにＫＴＷを適合したのでは、同じ冷却水温と回転数でもアクセルペダルを踏み込むことによりスロットルバルブ５が所定開度まで開いた状態での吸入負圧（たとえばＢ点の吸入負圧）になると、ＫＴＷが不足することになってしまうのである。同様にして、図４６のように同一の冷却水温、同一の吸入負圧でも回転数が異なると、ＫＴＷに対する要求値が違ってくるので、スロットルバルブ５が全閉位置かつアイドル時の回転数（たとえばＣ点の回転数）でエンジン安定度を満足する空燃比となるようにＫＴＷを適合したのでは、同じ冷却水温と吸入負圧でも高回転（たとえばＤ点の回転数）のときＫＴＷの精度が落ちる。なお、回転数に対する空燃比の特性は一様でなく、右上がりのときと左上がりのときの両方がある。
【０２０２】
なお、図４５は同じ燃料性状の燃料において、エンジン冷間時に冷却水温と回転数を一定に保ったまま吸入負圧を変化させたときのベース空燃比とエンジン安定度を満足する空燃比の、また図４６は燃料性状が同じでありながらエンジン冷間時に冷却水温と吸入負圧を一定に保ったまま回転数を変化させたときのベース空燃比とエンジン安定度を満足する空燃比の各特性を示したものである。
【０２０３】
そこで、重質ガソリン、軽質ガソリンのそれぞれに対して、たとえばアイドル時の吸入負圧と回転数の条件で冷却水温を相違させて水温増量補正係数の基本値ＫＴＷ０を適合した後で、基本値ＫＴＷ０を適合したときの吸入負圧と回転数より外れたときにも、エンジン安定度を満足する空燃比となるように吸入負圧と回転数を相違させて水温増量補正係数の負荷回転補正率ＲＫＴＷを適合するのである。
【０２０４】
また、図４５に示したように、同一の冷却水温、同一の回転数でも吸入負圧が違えばＫＵＢに対する要求値が違ってくることから、Ａ点の吸入負圧で理論空燃比となるようにＫＵＢを適合したのでは、同じ冷却水温と回転数でもＢ点の吸入負圧になると、ＫＵＢが不足することになってしまい、また図４６のように、同一の冷却水温、同一の吸入負圧でも回転数が異なればＫＵＢに対する要求値が違ってくることから、Ｃ点の回転数で理論空燃比となるようにＫＵＢを適合したのでは、同じ冷却水温と吸入負圧でもＤ点の回転数のとき、ＫＵＢの精度が低下するので、重質ガソリン、軽質ガソリンのそれぞれに対して、たとえばアイドル時の吸入負圧と回転数の条件で冷却水温を相違させて未燃分増量補正係数の基本値ＫＵＢＡＳを適合するとともに、基本値ＫＵＢＡＳを適合したときの吸入負圧と回転数より外れたときにも、理論空燃比となるように吸入負圧と回転数を相違させて未燃分増量補正係数の負荷回転補正率ＲＫＵＢを適合する。
【０２０５】
図４２、図４４にＲＫＴＷ、ＲＫＵＢの一例を示したが、ＲＫＴＷ、ＲＫＵＢの各特性はエンジンの機種毎に異なるので、最終的にはエンジンの機種毎に適合する。なお、図４５、図４６においては見やすくするためＡ点、Ｂ点やＣ点、Ｄ点から少し離してＫＴＷ、ＫＵＢを示している。したがって、冷却水温と吸入負圧、回転数が同一の条件でＫＵＢ＜ＫＴＷとなることはいうまでもない。
【０２０６】
上記の吸入負圧については、エアフローメータからの吸入空気量Ｑａと回転数Ｎｅより所定のマップを検索することにより求めることができる。吸入負圧を吸気マニホールドのコレクタ部に設けた圧力センサにより検出することもできる。また、吸入負圧に代えて、基本噴射パルス幅Ｔｐ（あるいはＱａ）を用いることもできる。
【０２０７】
未燃分増量補正係数ＫＵＢの時系列イメージを図２３に対応させて図４７に示す。軽質ガソリンの使用時のほうが重質ガソリンの使用時よりもＫＵＢＡＳの値（図４３のテーブル値）を小さく、かつＲＫＵＢの値（図４４のテーブル値）を小さくしているので、図４７のように軽質ガソリン使用時のＫＵＢは、重質ガソリン使用時のＫＵＢより小さくなる。つまり、燃料性状の判定を行っていないものでは、軽質ガソリンの使用時にも、重質ガソリンに対してマッチングしたテーブル値を用いることによる空燃比のリッチ化を招くのであるが、このように、軽質ガソリンの使用であることを判定したときは、次回の始動時のＫＵＢの演算に際して、重質ガソリン使用時よりも少ない値を軽質ガソリン用のＫＵＢとして演算することで、軽質ガソリンの使用時にも空燃比がリッチ側に偏ることがなくなるのである。
【０２０８】
次に、図４８（第６実施形態）に移ると、図４８では簡単のため図４０で示した負荷回転補正率ＲＫＴＷ、ＲＫＵＢを省略している。図４８において、第５実施形態の図４０と異なるのはステップ１４１、１４３であり、空燃比フィードバック制御を禁止する条件ではステップ１４１において冷却水温ＴＷと燃料性状推定値ＦＣとから図４９を内容とするマップを検索することにより、水温増量補正係数の基本値ＫＴＷ０を演算し、その演算値をステップ１４２で水温増量補正係数ＫＴＷに移し、これに対して空燃比フィードバック制御条件の成立時になると、ステップ１４３に進んで冷却水温ＴＷと燃料性状推定値ＦＣとから今度は図５０を内容とするマップを検索することにより、未燃分増量補正係数の基本値ＫＵＢＡＳを演算し、その演算値をステップ１４４で未燃分増量補正係数ＫＵＢに移している。図４９、図５０において同一の冷却水温、同一の燃料性状推定値ＦＣに対して、ＫＵＢＡＳの値のほうがＫＴＷ０の値より小さいことはいうまでもない。
【０２０９】
この第６実施形態によれば、連続値としての燃料性状推定値ＦＣに応じて、水温増量補正係数ＫＴＷ、未燃分増量補正係数ＫＵＢの演算に用いるデータ（マップ値）を割り付けているので、第５実施形態よりも、水温増量補正係数ＫＴＷ、未燃分増量補正係数ＫＵＢの演算精度が向上する。
【０２１０】
次に、図５１（第７実施形態）に移ると、図５１でも簡単のため図４０で示した負荷回転補正率ＲＫＴＷ、ＲＫＵＢを省略している。図５１において、第６実施形態の図４８と異なるのは、ステップ１０１、１５１〜１５４である。
【０２１１】
まずステップ１０１で燃料性状推定値ＦＣから図３５を内容とするテーブルを検索することにより、燃料性状補正値ＫＦＣを演算した後、空燃比フィードバック制御を禁止する条件ではステップ１５１で冷却水温ＴＷから図５２を内容とするテーブルを検索することにより、ＫＴＷ０（最重質ガソリンに対してマッチングした値である）を演算し、これと上記のＫＦＣとを用いステップ１５２において、
【０２１２】
【数４３】
ＫＴＷ＝ＫＴＷ０×ＫＦＣ
の式により、水温増量補正係数ＫＴＷを計算する。
【０２１３】
これに対して空燃比フィードバック制御条件の成立時になると、ステップ１５３、１５４において、ステップ１５１、１５２と同様にして冷却水温ＴＷから図５３を内容とするテーブルを検索することにより、ＫＵＢＡＳ（これも最重質ガソリンに対してマッチングした値である）を演算し、
【０２１４】
【数４４】
ＫＵＢ＝ＫＵＢＡＳ×ＫＦＣ
の式により、未燃分増量補正係数ＫＵＢを計算する。
【０２１５】
第７実施形態では、たとえば最重質ガソリンよりも燃料性状が軽質側のガソリンが使用されるときには、ＫＦＣが１．０より小さな値となるため、ＫＴＷ＜ＫＴＷ０、ＫＵＢ＜ＫＵＢＡＳとなることから、最重質ガソリンに対するＫＴＷ、ＫＵＢよりも小さなＫＴＷ、ＫＵＢが算出され、これによって、第６実施形態と同様に、最重質ガソリンよりも燃料性状が軽質側のガソリンに対しても、最適な水温増量補正係数と未燃分増量補正係数が与えられるのである。なお、最重質ガソリンの使用時は、ＫＦＣ＝１．０より、ＫＴＷ＝ＫＴＷ０、ＫＵＢ＝ＫＵＢＡＳとなり、従来装置と変わらない。
【０２１６】
この場合に、第７実施形態によれば、ＫＴＷ、ＫＵＢの演算に用いるデータを得るに際して図５２、図５３に示す特性を最重質ガソリンに対してマッチングするだけで済むので、第６実施形態の場合よりマッチングの工数を低減できる。
【０２１７】
前述の第１、第３、第４の各実施形態では噴射量補正量としての始動後増量補正係数ＫＡＳを対象として、また第５、第６、第７の各実施形態では噴射量補正量としての水温増量補正係数ＫＴＷおよび未燃分増量補正係数ＫＵＢを対象として、（Ａ）燃料性状切換フラグを用いる場合、（Ｂ）燃料性状推定値ＦＣを用いる場合、（Ｃ）燃料性状補正値ＫＦＣを用いる場合で説明したが、これに限られるものでない。たとえば、次の（１）、（２）の噴射量補正量や（３）、（４）の燃料噴射量を対象として、上記（Ａ）〜（Ｃ）の３つの場合とも適用できる。
【０２１８】
（１）低周波成分（壁流燃料）。
【０２１９】
（２）高周波成分（壁流燃料）。
【０２２０】
（３）始動時燃料噴射量。
【０２２１】
（４）加速時割り込み噴射量。
【０２２２】
以下では、（１）〜（４）を対象として（Ｃ）を適用する場合を項を分けて説明する。
（１）低周波成分が噴射量補正量の場合
（1-1）付着倍率Ｍｆｈｔｖｏの求め方
上記の付着倍率Ｍｆｈｔｖｏは、単位噴射弁部流量相当パルス幅当たり、かつ１シリンダ当たりの平衡付着量のことであり、これは上記の特開平１０−１８８８２号公報によれば、負荷（Ａｖｔｐ）と回転数Ｎｅと燃料付着部の温度予測値Ｔｆを用いて求めている。なお、燃料付着部の温度予測値Ｔｆの演算については、特開平１−３０５１４２号公報に詳しいので説明は省略する。
【０２２３】
Ｍｆｈｔｖｏの求め方について具体的に説明すると、これは、次のようにして演算している。まず、温度予測値Ｔｆの上下各基準温度Ｔｆ_iとＴｆ_i+1（ｉは１から４（あるいは５）までの整数）に対する基準付着倍率データＭｆｈｔｆ_iとＭｆｈｔｆ_i+1を用い、Ｔｆ、Ｔｆ_i、Ｔｆ_i+1による補間計算で求める。たとえば、Ｍｆｈｔｆ₁、Ｍｆｈｔｆ₂と、基準温度Ｔｆ₁、Ｔｆ₂、現在の温度予測値Ｔｆを用いて
【０２２４】
【数４５】
Ｍｆｈｔｖｏ＝Ｍｆｈｔｆ₁＋（Ｍｆｈｔｆ₂−Ｍｆｈｔｆ₁）
×（Ｔｆ₁−Ｔｆ）／（Ｔｆ₁−Ｔｆ₂）
の式（直線補間計算式）によりＭｆｈｔｖｏを計算する。
【０２２５】
上記の基準付着倍率データＭｆｈｔｆ_iは
【０２２６】
【数４６】
Ｍｆｈｔｆ_i＝Ｍｆｈｑ_i×Ｍｆｈｎ_i
ただし、Ｍｆｈｑ_i：基準付着倍率負荷項、
Ｍｆｈｎ_i：基準付着倍率回転項、
の式により計算する。
【０２２７】
ここで、Ｍｆｈｑ_iはα−Ｎ流量Ｑｈ０と温度予測値Ｔｆを用い補間計算付きで所定のマップを検索して求める。なお、Ｑｈ０は絞り弁開度ＴＶＯと回転数Ｎｅから求められる絞り弁部の空気流量で、既に公知のものである。Ｍｆｈｎ_iは回転数Ｎｅから補間計算付きで所定のテーブルを検索して求める。Ｍｆｈｑ_iのマップ（図５４参照）とＭｆｈｎ_iのテーブル（図５５参照）は、後述するＫｍｆａｔのマップとＫｍｆｎのテーブルとともに、理論空燃比のときにマッチングしたデータが格納されている。また、図５４と後述する図５６の各マップは本来、冷却水温ＴＷに対してマッチングしたものであるが、このマップ検索する際に、冷却水温ＴＷに代えて温度予測値Ｔｆを用いるわけである。
【０２２８】
（1-2）分量割合Ｋｍｆの求め方
上記の分量割合Ｋｍｆは、平衡付着量Ｍｆｈに対して、現時点での付着量（予測変数）Ｍｆが単位周期当たり（たとえばクランク軸１回転毎）にどの程度の割合で接近するかの割合を表す係数のことであり、これは、上記の特開平１０−１８８８２号公報によれば、基本分量割合Ｋｍｆａｔと分量割合回転補正率Ｋｍｆｎの積から演算している。
【０２２９】
ここで、Ｋｍｆａｔは温度予測値Ｔｆを用いて求める。たとえば、α−Ｎ流量Ｑｈ０と温度予測値Ｔｆとを用い、補間計算付きで所定のマップ（図５６参照）を検索する。Ｋｍｆｎは回転数Ｎｅから補間計算付きで所定のテーブル（図５７参照）を検索する。
【０２３０】
なお、基準付着倍率回転項Ｍｆｈｎ_iと分量割合回転補正率Ｋｍｆｎに添付されたｎは気筒番号としてのｎではなく、回転数Ｎｅを意味させている。
【０２３１】
（1-3）燃料性状の反映
低周波数成分を演算するのに用いる４つのデータ（基準付着倍率負荷項Ｍｆｈｑ_iのマップ値、基準付着倍率回転項Ｍｆｈｎ_iのテーブル値、基本分量割合Ｋｍｆａｔのマップ値、分量割合回転補正率Ｋｍｆｎのテーブル値）を最重質ガソリンに対してマッチングしておき、この最重質ガソリンにマッチングしたデータを上記の燃料性状補正値ＫＦＣで補正する。
（２）高周波成分が噴射量補正量の場合
上記の気筒別壁流補正量Ｃｈｏｓｎ¹ の演算に用いる増量ゲインＧｚｔｗｐ、減量ゲインＧｚｔｗｍは、上記の特開平１０−１８８８２号公報によれば、水温ＴＷから図５８、図５９を内容とするテーブルを検索することにより求められる値である。したがって、Ｃｈｏｓｎ¹ の演算に用いる２つのデータ（増量ゲインＧｚｔｗｐのテーブル値と減量ゲインＧｚｔｗｍのテーブル値）を最重質ガソリンに対してマッチングしておき、この最重質ガソリンにマッチングしたデータを上記の燃料性状補正値ＫＦＣで補正する。
（３）始動時燃料噴射量が燃料噴射量の場合
（3-1）始動時燃料噴射パルス幅ＴＩＳＴの求め方
始動時燃料噴射パルス幅ＴＩＳＴは、特開昭７−６３０８２号公報等によれば、
【０２３２】
【数４７】
ＴＩＳＴ＝ＴＳＴ×ＫＴＳＴ×ＫＮＳＴ
ただし、ＴＳＴ ：始動時基本噴射パルス幅、
ＫＴＳＴ：時間補正係数、
ＫＮＳＴ：回転数補正係数、
の式により算出している。ＴＳＴ、ＫＴＳＴ、ＫＮＳＴは、図６０、図６１、図６２を内容とするテーブルを検索して求める値である。
【０２３３】
（3-2）燃料性状の反映
始動時燃料噴射パルス幅を演算するのに用いる３つのデータ（ＴＳＴ、ＫＴＳＴ、ＫＮＳＴの各テーブル値）を最重質ガソリンに対してマッチングしておき、この最重質ガソリンにマッチングしたデータを上記の燃料性状補正値ＫＦＣで補正する。
（４）加速時割り込み噴射量が燃料噴射量の場合
（4-1）加速時割り込み噴射パルス幅の求め方
加速時割り込み噴射パルス幅ＩＪＳＥＴｎは、特開昭６４−３２４５号公報によれば、噴射弁部空気量相当パルス幅Ａｖｔｐの前回開噴射からの変化量であるΔＡｖｔｐｎ（ｎは気筒番号）を用いて、
【０２３４】
【数４８】
ＩＪＳＥＴｎ＝ΔＡｖｔｐｎ×Ｇｗｔｗｐ×Ｇｚｃｙｌｎ＋Ｔｓ
ただし、Ｇｗｔｗｐ：増量ゲインＧｚｔｗｐ、
Ｇｚｃｙｌｎ：気筒別補正率、
の式により算出している。
【０２３５】
ここで、Ｇｚｃｙｌｎ（ｎは気筒番号）が割り込み噴射が行われるサイクル位置から吸気行程までのクランク角差に応じて吸気系燃料の挙動が相違するので、これを考慮するため、図６３を内容とするテーブルを検索して求める値である。
【０２３６】
なお、ＳＰＩ（シングルポイントインジェクション）方式に対する演算式を記載してある特開昭６４−３２４５号公報に対して、数４８式は、ＭＰＩ（マルチポイントインジェクション）方式に書き換えたものである。
【０２３７】
（4-2）燃料性状の反映
加速時割り込み噴射パルス幅を演算するのに用いるデータ（Ｇｗｔｗｐ、Ｇｚｃｙｌｎの各テーブル値）を最重質ガソリンに対してマッチングしておき、この最重質ガソリンにマッチングしたデータを上記の燃料性状補正値ＫＦＣで補正する。
【０２３８】
このようにして、低周波成分、高周波成分といった噴射量補正量や始動時燃料噴射量、加速時割り込み噴射量といった燃料噴射量の演算に燃料性状補正値ＫＦＣを用いることで、各種の噴射量補正量や燃料噴射量の演算精度を高めることができ、これによって使用燃料の燃料性状が相違しても、適切な各種の噴射量補正量や燃料噴射量を与えることができるほか、各種の噴射量補正量や燃料噴射量の演算に用いるデータを得るに際して最重質ガソリンに対してマッチングするだけで済むので、マッチングの工数を低減できる。
【０２３９】
最後に、各種の噴射量や燃料噴射量は実施形態のものに限られるものでなく、燃料性状の影響を受けるものであれば、適用があることはいうまでもない。
【０２４０】
実施形態では、過渡時に燃料噴射量に対する排気空燃比の応答波形をサンプリングし、これら過渡時データに基づいて、予めＥＣＭ上に構築したプラントモデルのパラメータを、基準燃料に対するプラントモデルである規範モデルとの予測誤差が最小となるように調整することにより、使用燃料に対するプラントモデルを同定する場合で説明したが、これに限られるものでなく、燃料噴射量に代えて燃料供給量を用いることもできる。また、予測誤差が最小となるように調整するほか、予測誤差が小さくなるように調整することでもかまわない。
【図面の簡単な説明】
【図１】エンジン制御の制御システム図。
【図２】燃料性状の推定に関係する制御システム図。
【図３】エンジンプラントモデルのブロック図。
【図４】燃料挙動のモデル図。
【図５】燃料挙動のパラレルパスブロック図。
【図６】排気モデル図。
【図７】入出力間の無駄時間を表す波形図。
【図８】無駄時間を分類した表図。
【図９】ＬＴＩシステムの一般的なブロック図。
【図１０】評価関数（評価規範）の特性図。
【図１１】ＡＲＸモデルの同定手法を示すフローチャート。
【図１２】モデル同定に必要な入力信号とその応答を示す波形図。
【図１３】同定結果と実データを重ねて示すボード線図。
【図１４】燃料性状の推定を説明するためのフローチャート。
【図１５】ＡＲＸモデルの同定を説明するためのフローチャート。
【図１６】燃料性状の切換判定を説明するためのフローチャート。
【図１７】始動後増量補正係数ＫＡＳの演算を説明するためのフローチャート。
【図１８】始動後増量水温補正値（初期値）の特性図。
【図１９】第２始動後増量補正係数（初期値）の特性図。
【図２０】始動後増量回転補正値の特性図。
【図２１】始動後増量減少時間割合の特性図。
【図２２】第２始動後増量減少時間割合の特性図。
【図２３】始動後増量補正係数ＫＡＳの時系列イメージを示す波形図。
【図２４】第２実施形態の燃料性状の切換判定を説明するためのフローチャート。
【図２５】第３実施形態の燃料性状の推定を説明するためのフローチャート。
【図２６】第３実施形態の燃料性状推定値の演算を説明するためのフローチャート。
【図２７】カットオフ周波数に対する燃料性状推定値の特性図。
【図２８】第３実施形態の始動後増量補正係数ＫＡＳの演算を説明するためのフローチャート。
【図２９】第３実施形態の始動後増量水温補正値（初期値）の特性図。
【図３０】第３実施形態の第２始動後増量補正係数（初期値）の特性図。
【図３１】第３実施形態の始動後増量回転補正値の特性図。
【図３２】第３実施形態の始動後増量減少時間割合の特性図。
【図３３】第３実施形態の第２始動後増量減少時間割合の特性図。
【図３４】第３実施形態の始動後増量補正係数ＫＡＳの演算を説明するためのフローチャート。
【図３５】第３実施形態の燃料性状補正値の特性図。
【図３６】第３実施形態の始動後増量水温補正値（初期値）の特性図。
【図３７】第３実施形態の始動後増量減少時間割合の特性図。
【図３８】第３実施形態の第２始動後増量補正係数（初期値）の特性図。
【図３９】第３実施形態の第２始動後増量減少時間割合の特性図。
【図４０】第３実施形態の水温増量補係数ＫＴＷ、未燃分増量補正係数ＫＵＢの演算を説明するためのフローチャート。
【図４１】第３実施形態の水温増量補係数の基本値の特性図。
【図４２】第３実施形態の水温増量補係数の負荷回転補正率の特性図。
【図４３】第３実施形態の未燃分増量補正係数の基本値の特性図。
【図４４】第３実施形態の未燃分増量補正係数の負荷回転補正率の特性図。
【図４５】吸入負圧に対する水温増量補係数と未燃分増量補正係数の適合を説明するための空燃比特性図。
【図４６】回転数に対する水温増量補係数と未燃分増量補正係数の適合を説明するための空燃比特性図。
【図４７】第３実施形態の未燃分増量補正係数ＫＵＢの時系列イメージを示す波形図。
【図４８】第４実施形態の水温増量補係数ＫＴＷ、未燃分増量補正係数ＫＵＢの演算を説明するためのフローチャート。
【図４９】第４実施形態の水温増量補係数の基本値の特性図。
【図５０】第４実施形態の未燃分増量補正係数の基本値の特性図。
【図５１】第５実施形態の水温増量補係数ＫＴＷ、未燃分増量補正係数ＫＵＢの演算を説明するためのフローチャート。
【図５２】第５実施形態の水温増量補係数の基本値の特性図。
【図５３】第５実施形態の未燃分増量補正係数の基本値の特性図。
【図５４】基準付着倍率負荷項の特性図。
【図５５】基準付着倍率回転項の特性図。
【図５６】基本分量割合の特性図。
【図５７】分量割合回転補正率の特性図。
【図５８】増量ゲインの特性図。
【図５９】減量ゲインの特性図。
【図６０】始動時基本噴射パルス幅の特性図。
【図６１】回転数補正係数の特性図。
【図６２】時間補正係数の特性図。
【図６３】気筒別補正率の特性図。
【図６４】第１の発明のクレーム対応図。
【図６５】第２の発明のクレーム対応図。
【図６６】第３の発明のクレーム対応図。
【符号の説明】
２ ＥＣＭ
３ Ａ／Ｆセンサ
７ 燃料噴射弁
１４ ＥＥＰＲＯＭ
１５ 燃料噴射量演算手段
２１ プラント同定部
２２ 燃料性状推定部
２３ トリガリング機能
２４ コントローラ
３１ プラントモデル
３７ 規範モデル
３８ 比較手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine fuel supply control device, and more particularly to an apparatus for detecting a fuel property of a fuel for a gasoline engine and utilizing it for calculation of a fuel supply amount.
[0002]
[Prior art]
During cold start when the engine becomes unstable, the fuel is increased by an increase correction coefficient after starting, and the engine is stabilized by setting the air-fuel ratio to a value on the rich side of the stoichiometric air-fuel ratio. (See Kaihei 6-105129).
Further, if the air-fuel ratio feedback control is started as soon as possible after the start, the range in which the three-way catalyst is used is expanded and the exhaust performance is improved. Therefore, even when the fuel increase by the water temperature increase correction coefficient KTW is being performed, O₂In some cases, when the sensor output is activated, the fuel increase by the water temperature increase correction coefficient KTW is stopped and the air-fuel ratio feedback control is started. In this case, the actual air-fuel ratio becomes leaner than the rich side immediately after the start of the air-fuel ratio feedback control. In order to avoid this, the actual air-fuel ratio is quickly increased to the stoichiometric air-fuel ratio immediately after the start of the air-fuel ratio feedback control by avoiding this. Some have converged to the vicinity (see JP-A-10-18883).
[0003]
[Problems to be solved by the invention]
Incidentally, the reason why the injection amount correction using the post-startup increase correction coefficient is necessary is as follows. More specifically, the fuel injection valve provided in front of the intake port, the injected fuel from the injection valve is not entirely injected into the cylinder while being sprayed, It adheres to the part and intake port wall and becomes liquid. The fuel adhering to the intake port wall reaches the cylinder while slowly passing through the port wall while being in a liquid state. That is, only this amount of fuel (wall flow fuel) causes a delay in fuel supply, and the air-fuel ratio leans to the lean side.
[0004]
The reason why the injection amount correction based on the unburned component increase correction coefficient is necessary is that there is a fuel component that does not contribute to combustion (that is, the unburned component), and the air-fuel ratio is inclined to the lean side by this amount. Here, the unburned portion includes, for example, a fuel portion that is discharged as unburned HC without being burned, or a fuel portion that is discharged from the inside of the cylinder into the crankcase through the gap of the piston ring and is dissolved in the oil. Although the above-mentioned wall flow fuel has a response delay, it always enters the cylinder and most of it contributes to combustion, whereas the unburned portion does not contribute to combustion.
[0005]
In this case, the amount of the wall flow fuel and unburned fuel also depends on the properties (particularly volatile) of the fuel, and the amount of the wall flow fuel and unburned fuel increases as the volatility of the fuel decreases. Taking into account the difference in the fuel wall flow and unburned fuel amount due to the difference in volatility of these fuels, the conventional various injection amount corrections have the least volatile fuel (the heaviest gasoline) on the market. Even when is used, it is matched so that the engine rotation in the cold state does not become unstable. If the above-mentioned post-startup increase correction coefficient and unburned fuel increase correction coefficient are used, data used when calculating the post-startup increase correction coefficient and unburned fuel increase correction coefficient is matched with the heaviest gasoline.
[0006]
However, when fuel with better volatility than the heaviest gasoline is used, the injection amount correction amount becomes too large when the injection amount correction amount is for wall flow fuel. Exhaust emissions (especially CO and HC) become worse because the air-fuel ratio is inclined to the richer side than when gasoline is used. In addition, when the fuel injection amount correction amount is intended for unburned fuel, when the fuel having better volatility than the heaviest gasoline is used, the fuel injection amount correction amount is substantially increased. Exhaust emissions (especially CO and HC) are worsened because the air-fuel ratio is inclined richer than when heaviest gasoline is used.
[0007]
Therefore, the present invention samples the response waveform of the exhaust air-fuel ratio with respect to the fuel supply amount at the time of transition, and based on the data at the time of transition, the parameters of the plant model previously built on the ECM (Electronic Control Module) are used as the plant for the reference fuel. Identify the plant model for the fuel used by adjusting the prediction error with the model reference model to the minimum, and compare the cutoff frequency of the identified plant model with the cutoff frequency for the reference model Accordingly, it is possible to estimate the fuel property of the fuel used, and to provide an optimum fuel supply amount according to the fuel property by utilizing the estimation result for calculation of the fuel supply amount.
[0008]
[Means for Solving the Problems]
  As shown in FIG. 64, the first invention is a means 51 for supplying the engine with a fuel supply amount corresponding to the engine operating conditions, a means 52 for detecting the exhaust air-fuel ratio of the engine, and the fuel supply amount at the time of transition. And means 53 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount of the currently used fuel by using the exhaust air / fuel ratio as an output, and a plant model constructed in advance based on these input / output data By adjusting the parameters so that the prediction error with the reference model is reduced, the means 54 for identifying the plant model for the fuel used, and the cutoff frequency fc of the identified plant model_RealMeans 55 for calculatingIf the reference model is matched to the reference fuel,Cutoff frequency fc of this plant model_RealAnd the cut-off frequency fc of the reference model_RefCompare with, Cutoff frequency fc of plant model _Real Is the cut-off frequency fc of the reference model _Ref When higher,Fuel properties of the fuel usedIs lighter than the above, and the cut-off frequency fc of the plant model _Real Is the cut-off frequency fc of the reference model _Ref When lower, the fuel property of the fuel used is heavier than the reference fuelMeans 56 for estimating and means 57 for calculating the fuel supply amount based on the estimation result of the fuel property are provided.
[0009]
  As shown in FIG. 65, the second invention has means 51 for supplying the engine with a fuel supply amount corresponding to the engine operating conditions, means 52 for detecting the exhaust air-fuel ratio of the engine, and the fuel supply amount during the transition. And means 53 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount of the currently used fuel by using the exhaust air / fuel ratio as an output, and a plant model constructed in advance based on these input / output data By adjusting the parameters so that the prediction error with the reference model is reduced, the means 54 for identifying the plant model for the fuel used, and the cutoff frequency fc of the identified plant model_RealMeans 55 for calculatingIf the reference model is matched to the reference fuel,Cutoff frequency fc of this plant model_RealAnd the cut-off frequency fc of the reference model_RefThe difference betweenOf the reference fuelCompare with tolerance, Cutoff frequency fc of plant model _Real And the cut-off frequency fc of the reference model _Ref Is outside the allowable range of the reference fuel, and the cutoff frequency fc of the plant model _Real Is the cut-off frequency fc of the reference model _Ref When bigger thanFuel properties of the fuel usedIs lighter than the reference fuel, and the cutoff frequency fc of the plant model _Real And the cut-off frequency fc of the reference model _Ref Is outside the allowable range of the reference fuel, and the cutoff frequency fc of the plant model _Real Is the cut-off frequency fc of the reference model _Ref When smaller, the fuel property of the fuel used is heavier than the reference fuelMeans 61 for estimating and means 62 for calculating the fuel supply amount based on the estimation result of the fuel property are provided.
[0010]
  As shown in FIG. 66, the third invention has means 51 for supplying the engine with a fuel supply amount corresponding to the engine operating conditions, means 52 for detecting the exhaust air-fuel ratio of the engine, and the fuel supply amount during the transition. And means 53 for sampling the response waveform data of the exhaust air / fuel ratio with respect to the fuel supply amount of the currently used fuel by using the exhaust air / fuel ratio as an output, and a plant model constructed in advance based on these input / output data By adjusting the parameters so that the prediction error with the reference model is reduced, the means 54 for identifying the plant model for the fuel used, and the cutoff frequency fc of the identified plant model_RealMeans 55 for calculatingIf the reference model is matched to the reference fuel, the plant modelCharacteristics of estimated fuel properties with respect to cutoff frequency, Cutoff frequency fc of plant model _Real Is lighter the greater the cutoff frequency of the reference model, and the cutoff frequency fc of the plant model _Real To be heavier the smaller the cutoff frequency of the reference model isMeans 71 for presetting and the calculatedPlant modelCut-off frequency fc_RealMeans for calculating a fuel property estimated value by searching for this characteristic, and means 73 for calculating the fuel supply amount based on the fuel property estimated value.
[0011]
According to a fourth aspect, in the first or second aspect, the estimation result of the fuel property is stored in a nonvolatile memory (for example, EEPROM).
[0012]
In a fifth invention, the estimated fuel property value is stored in a nonvolatile memory (for example, EEPROM) in the third invention.
[0013]
  According to a sixth aspect, in the first aspect, the estimation of the fuel property is based on the reference model.Heavy gasolineAnd when the cut-off frequency of the identified plant model is higher than the cut-off frequency of the reference model,Heavy gasolineIt is to estimate that it is lighter than.
[0014]
  According to a seventh aspect, in the second aspect, the estimation of the fuel property is based on the reference model.Almost intermediate fuel that is neither volatile nor good among commercially available fuelsThe difference between the cut-off frequency of the identified plant model and the cut-off frequency of the reference modelOf reference fuelWhen it is outside the allowable range and the cutoff frequency of the plant model is larger than the cutoff frequency of the reference model,Middle fuelTo be lighter thanAnd when the difference between the cutoff frequency of the identified plant model and the cutoff frequency of the reference model is outside the allowable range of the reference fuel, and the cutoff frequency of the plant model is smaller than the cutoff frequency of the reference model, Heavier than intermediate fuelIs to estimate.
[0015]
In an eighth aspect of the invention, when the fuel supply amount in the first or second aspect comprises a basic fuel injection amount Tp determined from an engine load and a rotational speed and an injection amount correction amount, the estimation result of the fuel property Based on this, the injection amount correction amount is calculated.
[0016]
In a ninth aspect, in the third aspect, when the fuel supply amount is composed of a basic fuel injection amount Tp determined from an engine load and a rotational speed and an injection amount correction amount, an injection is performed based on the estimated fuel property value. The amount correction amount is calculated.
[0017]
According to a tenth aspect, in the eighth or ninth aspect, the injection amount correction amount is a post-startup increase correction amount (post-startup increase correction coefficient KAS).
[0018]
In an eleventh aspect of the invention, in the eighth or ninth aspect, the injection amount correction amount is a water temperature increase correction amount (water temperature increase correction coefficient KTW).
[0019]
In a twelfth aspect, in the eighth or ninth aspect, the injection amount correction amount is an unburned amount increase correction amount (unburned amount increase correction coefficient KUB).
[0020]
In a thirteenth aspect, in the eighth or ninth aspect, the injection amount correction amount is a wall flow correction amount.
[0021]
In a fourteenth aspect based on the thirteenth aspect, the wall flow correction amount is a low frequency component.
[0022]
In a fifteenth aspect, in the thirteenth aspect, the wall flow correction amount is a high frequency component.
[0023]
In a sixteenth aspect of the invention, in any one of the first to third aspects, the fuel supply amount is a starting injection amount (starting fuel injection pulse width TIST).
[0024]
In a seventeenth aspect of the invention, in any one of the first to third aspects, the fuel supply amount is an acceleration interruption injection amount (acceleration interruption injection pulse width IJSETn).
[0025]
In the eighteenth aspect of the invention, adjusting so that the prediction error becomes small in any one of the first to seventeenth aspects is adjusting so that the prediction error is minimized.
[0026]
  In the first, eighth, and ninth inventions, the first parameter is adjusted by adjusting the parameters of the plant model based on the input / output data so that the prediction error with the reference model is reduced.8'sIn the invention, the plant model is identified by adjusting the parameters of the plant model based on the input / output data so that the prediction error with the reference model is minimized. The transfer function of the plant model is known from the parameters at this time, and the cutoff frequency of the plant model is determined from this.
[0027]
Here, when the reference model is matched with the reference fuel and the fuel used is lighter than the reference fuel, the cutoff frequency of the plant model is higher than that for the reference fuel (and vice versa). When the fuel used is heavier than the reference fuel, the cutoff frequency of the plant model is lower than that for the reference fuel). This is because the lighter fuel than the reference fuel has a smaller fuel transport delay than the reference fuel, so that the fuel response becomes higher and the response gain can be maintained up to a higher frequency range than the reference fuel.
[0028]
  Therefore, according to the first, eighth, ninth, and fourteenth inventions, it is possible to estimate the fuel property of the fuel used by comparing the cutoff frequency of the plant model with the cutoff frequency of the reference model. It becomes. For example, RegulationIf the model model is matched to the reference fuel and the cut-off frequency of the identified plant model is higher than the cut-off frequency of the reference model,RulerWhen the reference model is matched to the reference fuel, the difference between the identified plant model cutoff frequency and the reference model cutoff frequency is outside the allowable range, and the plant model cutoff frequency is When the frequency is higher than the cut-off frequency, it can be estimated that the fuel used is lighter than the reference fuel.
[0029]
When the fuel property can be estimated in this way, the fuel supply amount corresponding to the fuel property of the used fuel is calculated by calculating the fuel supply amount based on the estimation result of the fuel property and the estimated fuel property value. Can be given without excess or deficiency.
[0030]
For example, if the fuel property is not judged, even when the fuel is lighter than the reference fuel, the amount of increase correction after starting, the correction amount of water temperature increase, the amount of increase in unburned fuel are calculated using data matched to the reference fuel. The calculation of the correction amount, the wall flow correction amount, the low frequency component, the high frequency component, the starting fuel injection amount, and the acceleration interruption injection amount causes the air-fuel ratio to become richer. According to the twelfth, thirteenth, fourteenth, fifteenth, sixteenth, and seventeenth inventions, when the fuel is lighter than the reference fuel, the post-startup increase correction amount and the water temperature increase are smaller than when the reference fuel is used. Correction amount, unburned amount increase correction amount, wall flow correction amount, low-frequency component, high-frequency component, start-up fuel injection amount, acceleration interrupt injection amount are given, so it is empty even when lighter fuel than the reference fuel is used. The fuel ratio is not biased toward the rich side That.
[0031]
According to the second invention, even when the cutoff frequency with respect to the reference fuel varies, the estimation of the fuel property can be performed stably.
[0032]
According to the third aspect, the calculation accuracy of the fuel supply amount can be increased.
[0033]
According to the fourth and fifth inventions, the estimation result of the fuel property and the estimated value of the fuel property can be used from the beginning of the start in the next operation.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 1 denotes an engine body, and intake air is supplied from an air cleaner through an intake pipe 8 to a cylinder. The fuel is injected from the fuel injection valve 7 toward the intake port of the engine 1 based on an injection signal from the ECM 2 so as to have a predetermined air-fuel ratio according to the operating conditions.
[0035]
The ECM 2 includes a REF signal from the crank angle sensor 4 (a signal for identifying a cylinder generated every 180 ° for four cylinders and every 120 ° for six cylinders), a 1 ° signal, and an intake air amount signal from the air flow meter 6. , An air-fuel ratio signal from a wide-range air-fuel ratio sensor (hereinafter simply referred to as “A / F sensor”) 3 installed on the upstream side (exhaust manifold assembly) of the three-way catalyst 10, a cooling water temperature signal from the water temperature sensor 11, a throttle sensor Based on these, the ECM 2 calculates the basic injection pulse width Tp from the intake air amount Qa and the engine speed Ne, and transiently corrects this Tp during acceleration / deceleration. Correction for wall flow fuel is performed by adding the amount Kathos. The transient correction amount Kathos works not only at the time of acceleration / deceleration, but also at the time of start-up when the wall flow fuel changes greatly, at the time of fuel recovery, and at the time of switching a target equivalent ratio Tfbya described later.
[0036]
The ECM 2 also performs fuel correction using the target equivalence ratio Tfbya in order to improve engine stability during cold start and respond to the required output at high load, as well as a gear position signal from the gear position sensor 13 of the transmission, The lean air-fuel ratio and the stoichiometric air-fuel ratio are controlled according to the conditions while judging the driving state based on a vehicle speed signal from a vehicle speed sensor (not shown). A three-way catalyst 10 is installed in the exhaust pipe 9 to reduce NOx in the exhaust and oxidize HC and CO with maximum conversion efficiency during operation at the stoichiometric air-fuel ratio. When the three-way catalyst 10 has a lean air-fuel ratio, HC and CO are oxidized, but NOx reduction efficiency is low. However, the more the air-fuel ratio shifts to the lean side, the smaller the amount of NOx generated. When the air-fuel ratio exceeds a predetermined air-fuel ratio, it can be reduced to the same level as that purified by the three-way catalyst 10, and at the same time the lean air-fuel ratio. The better the fuel economy is. Therefore, in a predetermined operation region where the load is not so large, the target equivalence ratio Tfbya is set to a value smaller than 1.0, and the lean air-fuel ratio is operated, and in other operation regions, Tfbya is set to 1.0. Thus, the air-fuel ratio is controlled to the stoichiometric air-fuel ratio.
[0037]
As described above, the target equivalent ratio Tfbya is switched according to the change in the operating condition. However, if the above transient correction amount Kathos is calculated as a value for Tfbya = 1.0 (that is, the theoretical air-fuel ratio), the output When switching from Tfbya, such as when decelerating from the air-fuel ratio range (Tfbya is greater than 1.0 at this time), the transient correction amount Katos becomes insufficient, causing the air-fuel ratio to temporarily become overrich or overlean, and the control air-fuel ratio In order to cope with this, the followability deteriorates. In ECM2, the equilibrium adhesion amount Mfh is calculated using the target equivalent ratio Tfbya as a parameter. If this is expressed by an arithmetic expression,
Mfh = Avtp × Mfhtvo × Tfbya × CYLDRN #
Where Mfh: the amount of equilibrium adhesion for all cylinders,
Avtp: injection valve part air amount equivalent pulse width,
Mfhtvo: Adhesion magnification,
CYLDRN #: Number of cylinders
(See Japanese Patent Laid-Open No. 10-18882). The difference between the equilibrium adhesion amount (the equilibrium value of the wall flow fuel) Mfh and the current adhesion amount Mf is multiplied by the quantity ratio Kmf, that is,
Vmf = (Mfh−Mf) × Kmf
The deposition rate (the amount of deposition per unit cycle) Vmf (value per cycle) is calculated by the following formula. When the equilibrium deposition amount Mfh increases (for example, during acceleration), this is set as a transient correction amount Kathos.
CTIn = (Avtp × Tfbya + Kathos) × α × 2 + Ts + Chosn¹
However, Kathos: transient correction amount (value per cycle),
α: Air-fuel ratio feedback correction coefficient,
Ts: Invalid injection pulse width,
Chosn¹: Cylinder wall flow correction amount (value per cycle for each cylinder),
The actual injection pulse width CTIn given to the fuel injection valve at the time of sequential injection (in the case of four cylinders, once every two engine revolutions, in accordance with the ignition order of each cylinder) is calculated for each cylinder. The “value for each cycle” is a value for each input of the 1REF signal, and the “value for each cycle of each cylinder” is a value for each input of the 4REF signal (in the case of 4 cylinders). CTIn and Chosn¹“N” represents a cylinder number.
[0038]
Here, the cylinder-specific wall flow correction amount Chosn will be described. The wall flow fuel has a small amount of direct flow into the cylinder and is relatively slow in response (referred to as a low frequency component), and directly into the cylinder. There is a part that is mainly responsive (referred to as a high-frequency component), and the above Vmf is a wall flow correction amount targeting a low-frequency component, whereas Chosn is a correction targeting a high-frequency component. Amount. That is, since Vmf alone cannot cope with high frequency components, it is necessary to introduce Chosn, which is a correction amount for high frequency components. Specifically, if Avtp is increasing (during acceleration) using ΔAvtpn, which is the amount of change in the injection valve portion air amount equivalent pulse width Avtp from the previous injection,
Chosn = ΔAvtpn × Gztwp
Where Gztwp: increase gain,
When Avtp is decreasing (during deceleration)
Chosn = ΔAvtpn × Gztwm
Where Gztwm: weight loss gain,
The wall flow correction for the high-frequency component is performed by adding the value to the fuel injection pulse width of the synchronous injection for each cylinder. The increase gain Gztwp and the decrease gain Gztwm are for performing water temperature correction. Further, n attached at the end of ΔAvtpn represents the cylinder number as in the case of CTIn.
[0039]
Even in the case where the wall flow correction amount for the high frequency component is introduced in addition to the wall flow correction amount for the low frequency component as described above, if Tfbya is not taken into account in Chosn calculation, particularly from the output air-fuel ratio range. Since Chosn is deficient when Tfbya is switched such as when decelerating and temporarily overrich or overlean occurs, ECM2 also deals with Chosn, which is a wall flow correction amount for high frequency components, in accordance with Tfbya. (Refer to Japanese Patent Laid-Open No. 10-18882). If this is expressed by an arithmetic expression,
Chosn¹= (Kathos-Kathos_-4Ref) × (Gztwc-1) / A
However, Chosn¹: Chosn in the first cycle,
Kathos_-4Ref: Kathos 1 cycle before each cylinder (before 4REF signal),
Gztwc: increase gain Gztwp or decrease gain Gztwm,
A: Response gain of the first cycle of the low frequency component,
It is.
[0040]
It should be noted that the amount of wall flow correction (Chosn) at the time of fuel recovery in consideration of fuel cut (fuel cut may be performed for each cylinder or may be performed simultaneously for all cylinders)¹, Vmf), an optimum wall flow correction amount may be given even during fuel recovery accompanied by switching of the target equivalent ratio Tfbya (see Japanese Patent Laid-Open No. 10-18882).
[0041]
On the other hand, at the time of cold start when the engine becomes unstable, the fuel is increased by the post-startup increase correction coefficient KAS, and the engine is stabilized by setting the air-fuel ratio to a richer value than the stoichiometric air-fuel ratio (Japanese Patent Laid-Open No. Hei. 6-101529). For example, KAS is calculated according to equation 36, which will be described later, and KAS at this time generally decreases linearly with a steep slope from the start timing of the starter switch, with the value when the starter switch is turned on as an initial value. Is a value that decreases with a gentler slope, and finally becomes zero.
[0042]
Also, O as soon as possible after starting₂When the air-fuel ratio feedback control based on the output of the sensor 3 is entered, the area in which the three-way catalyst 10 is used is expanded and the exhaust performance is improved. Therefore, even while the fuel increase by the water temperature increase correction coefficient KTW is being performed. O₂When the sensor 3 output is activated, the fuel increase by KTW is stopped and the air-fuel ratio feedback control is started, but immediately after the air-fuel ratio feedback control starts, the actual air-fuel ratio changes from the rich side to the lean side at once. In order to avoid this, the actual air-fuel ratio is quickly converged to the vicinity of the theoretical air-fuel ratio immediately after the start of the air-fuel ratio feedback control by increasing the fuel by the unburned fuel increase correction amount KUB. I am letting.
[0043]
Here, the unburned portion is a fuel portion that does not contribute to combustion. For example, the unburned portion is discharged as unburned HC without being burned, or is discharged from the cylinder into the crankcase through the gap of the piston ring. There is a fuel that dissolves in the oil. Although wall flow fuel has a response delay, it always enters the cylinder and contributes to combustion, whereas the unburned component does not contribute to combustion.
[0044]
The unburned component increase correction coefficient KUB, the water temperature increase correction coefficient KTW, and the post-startup increase correction coefficient KAS are part of the target equivalent ratio Tfbya.
Tfbya = Kml + KAS + KTW + KUB
Where Dml: fuel-air ratio correction coefficient,
The target equivalent ratio Tfbya is calculated by the following formula.
[0045]
Here, Kml determines a target air-fuel ratio according to operating conditions, and is obtained by searching a map using the engine speed and load as parameters. In some cases, when a target air-fuel ratio is switched, a predetermined damper operation is performed after retrieving a map value of Kml.
[0046]
Further, a special fuel injection pulse width TIST is set at the time of starting (see Japanese Patent Laid-Open No. 7-63082). When a particularly large torque is required, such as during rapid acceleration, the acceleration interrupt injection pulse width IJSETn is calculated, and interrupt injection may be performed even during synchronous injection.
[0047]
The reason why the post-startup increase correction coefficient KAS is required is that a fuel supply delay corresponding to the wall flow fuel occurs, and this wall flow fuel amount is further reduced in fuel properties (particularly volatile). ), The fuel with lower volatility increases the amount of wall flow fuel. Taking into account the difference in fuel flow due to the difference in fuel volatility, various conventional injection amount corrections (for example, conventional post-startup increase corrections) can be used even when the heaviest gasoline is used. The table values used for the KAS calculation are matched so that the rotation does not become unstable. The reason why the injection amount correction using the unburned component increase correction coefficient KUB is necessary is that there is a fuel component that does not contribute to combustion (that is, an unburned component).
[0048]
In this case, the amount of the wall flow fuel and unburned fuel also depends on the properties (particularly volatile) of the fuel, and the amount of the wall flow fuel and unburned fuel increases as the volatility of the fuel decreases. Taking into account the difference in the fuel wall flow and unburned fuel amount due to the difference in volatility of these fuels, the conventional various injection amount corrections have the least volatile fuel (the heaviest gasoline) on the market. Even when is used, it is matched so that the engine rotation in the cold state does not become unstable. If it is said KAS and KUB, the data used when calculating KAS and KUB are matched with the heaviest gasoline.
[0049]
However, when fuel with better volatility than the heaviest gasoline is used, the injection amount correction amount becomes too large when the injection amount correction amount is for wall flow fuel. Exhaust emissions (especially CO and HC) become worse because the air-fuel ratio is inclined to the richer side than when gasoline is used. In addition, when the fuel injection amount correction amount is for unburned fuel, when the fuel with better volatility than the heaviest gasoline is used, the fuel injection amount correction amount is substantially increased. Since the air-fuel ratio tends to be richer than when using the heaviest gasoline, fuel efficiency is worsened.
[0050]
Therefore, at the time of transition in a region where there is a large amount of wall flow fuel and unburned fuel, the response waveform of the exhaust air / fuel ratio with respect to the fuel injection amount is sampled, and the parameters of the plant model previously constructed on the ECM 2 based on these transient data Is adjusted so that an estimation error with the reference model is minimized, and a cutoff frequency of the plant model is obtained based on the adjusted parameter, and this is compared with a reference fuel (Ref fuel). The fuel property is estimated by comparing the cut-off frequency of the reference model, which is a plant model, and the post-startup increase correction coefficient and the unburned component increase correction coefficient are calculated according to the estimated fuel property.
[0051]
This optimization control executed in ECM2 will be described next.
[0052]
FIG. 2 is a block diagram of a control system for optimization control.
[0053]
This control system is roughly divided into a plant identification unit 21, a fuel property estimation unit 22, a triggering function 23, and a controller 24.
[0054]
The outline of the control will be described with reference to FIG. 2 and then plant identification will be described in detail.
[0055]
First, main components of the plant identification unit 21 are a plant model 31, an error detection unit 32, an optimization calculation unit 33, an input (actual injection pulse width) buffering unit 34, and an output (exhaust air / fuel ratio) buffering. The actual injection pulse width CTIn and the A / F sensor 3 output voltage are sampled from the trigger determined from the engine parameters, and the plant model 31 in that region is used as an input / output signal of the plant model 31. Identification. The model format (order) is set in advance from the physical model, and the model parameters are adjusted so as to be optimal for actual input / output signals.
[0056]
Here, the plant model 31 is a discrete cascade coupling model (a denominator 3 having a denominator secondary and denominator second-order lag system model and an exhaust dynamic characteristic being a denominator first-order lag system model. Next, a molecular tertiary physical model). The identification method is a batch process least square method using the most common ARX model.
[0057]
The fuel property estimation unit 22 includes a reference model 37 that is a plant model with respect to a reference fuel (Ref fuel), and a cutoff frequency comparison unit 38, and a cutoff frequency fc of the plant model 31 identified by the plant identification unit 21._RealAnd the cut-off frequency fc of the reference model 37_RefIs compared by the comparison means 38 to determine the fuel property.
[0058]
Here, for simplicity of explanation, if there are only two types of fuel (heavier gasoline with lower volatility is assumed to be heavy gasoline and lighter fuel with better volatility is assumed to be light gasoline) When the reference model matched with gasoline is used, when the cut-off frequency of the identified plant model 31 is higher than the cut-off frequency of the reference model, it can be determined that light gasoline is being used. This is because light gasoline has a smaller fuel transport delay than heavy gasoline, so light gasoline has higher fuel response and can maintain a response gain up to a higher frequency range than heavy gasoline. Note that the fuel property determination value is initially set to heavy gasoline before the fuel property is estimated.
[0059]
In this control, the fuel property is estimated once, for example, during one trip (from the start to the stop of the engine operation), and the estimation result is stored in a non-volatile memory (in this embodiment, EEPROM 14, see FIG. 1). The controller 24 reflects this in the fuel control at the next start.
[0060]
The triggering function 23 samples input / output signals necessary for plant identification and determines a condition for generating a trigger for starting plant identification.
[0061]
Here, in general, in order to identify a system, an input including a wide frequency band is required. In the engine, since it is not realistic to generate an input such as an M-sequence, a point where the input changes stepwise is set as a sampling trigger. It is also necessary to eliminate conditions that greatly affect fuel behavior such as EGR (exhaust gas recirculation) and swirl control. Conditions as described above must exist in the mode for identification or generate an input signal for identification.
[0062]
Specifically, the controller 24 is a post-startup increase correction coefficient adjusting means that sets the post-startup increase correction amount KAS immediately after the next start to an appropriate value according to the fuel property estimated during one trip. Items to be adjusted are the initial value of KAS and the attenuation ratio.
[0063]
Here, for simplification of the control as described above, binary switching for heavy gasoline or light gasoline will be described (thus, the post-startup increase correction coefficient adjusting means 40 is the post-startup increase correction coefficient switching means 40. Therefore, the number of stages for switching the fuel property may be determined from the separation performance of the fuel property and the requirements of the engine.
[0064]
The fuel injection amount calculation means 15 is used for Vmf, CTIn, Chosn described above.¹Is calculated.
[0065]
Next, the identification of the plant model 31 will be described in detail with separate terms.
[0066]
1. Plant model
In order to estimate the fuel properties, it is necessary to extract only the dynamics of the fuel behavior from the dynamics of the engine. The 4-cycle engine (plant) is considered to be composed of the elements shown in FIG. The input / output that can be observed is the actual injection pulse width CTIn obtained by calculating the basic injection pulse width Tp based on the intake air amount Qa and performing various corrections on the basic injection pulse width Tp. IJSETn at the time of interruption injection) and the A / F sensor output value of the exhaust manifold aggregate part subjected to A / D conversion. The plant model obtained from this input / output is
1.1: Fuel behavior model (dead time + delay system),
1.2: Exhaust model (dead time + delay system) and
1.3: Waste time depending on various operations and combustion cycle
It consists of three.
[0067]
1.1 Fuel behavior model
The behavior of the fuel injected from the fuel injection valve can be modeled as shown in FIG. 4 and the mathematical model is expressed as follows.
[0068]
[Expression 1]
F_fc= (1-k_WW) ・ F_fi+ F_fe
F_fe= E^{-t / TWW}・ K_WW・ F_fi/ T_WW
G_WW(s) = (1-k_WW) + K_WW/ (ST_WW+1)
However, G_WW: Transfer function of fuel behavior,
F_fi: Fuel injection,
F_fe: Fuel evaporation,
F_fc: Cylinder intake fuel,
k_WW: Adhesion rate,
T_WW: Time constant of evaporation,
This mathematical model has one time constant (T_WW) And one gain (k_WWThe behavior of fuel is generally divided into a time constant due to fuel adhesion and evaporation, and a time constant due to cylinder suction delay. In terms of the above expression, the slower the response, the lower the frequency. The component and the faster the response are high frequency components.
[0069]
Therefore, the mathematical model of Equation 1 may be connected in parallel for the behavior of two types of fuels with different responses. The mathematical model at this time can be expressed as follows.
[0070]
[Expression 2]

Where Tsample: sampling period (period for sampling the air-fuel ratio),
T₁: Time constant of low frequency component,
T₂: Time constant of high frequency component,
k₁: Gain of low frequency component,
k₂: Gain of high frequency component,
A₁: E^{-Tsample / T1},
A₂: E^{-Tsample / T2},
B₁: K₁,
B₂: K₂,
In Formula 2, the first formula (continuous value system) converted to the discrete value system is the second formula, and this second formula is expressed as z = e^sTsampleThe third formula is obtained by substituting and organizing. FIG. 5 is a block diagram showing the third equation.
[0071]
Note that the dead time associated with the fuel behavior is not taken into the mathematical model of the fuel behavior, and the output signal is offset in time series to suppress the increase in the model order (details will be described later in 1.3).
[0072]
1.2 Exhaust model
As shown in FIG. 6, the exhaust model is considered to be composed of three elements: exhaust dynamics for each cylinder, gas mixing dynamics in the exhaust manifold assembly, and sensor characteristics. When these are combined, they can be represented by a physical model of “dead time + delay system”. As the delay system, exhaust gas transport delay + gas mixing delay + sensor response delay can be considered, and each is a model having a first-order delay or more. However, considering that the plant model is identified on board (on the ECM2) this time, it is necessary to avoid being higher order as much as possible, and the exhaust model is represented by one time constant. Describe with a mathematical model of the next delay system.
[0073]
[Equation 3]
G_ex(s) = 1 / (sT_ex+1)
G_ex(z) = (1-e^{-Tsample / Tex}) / (Ze^{-Tsample / Tex})
G_ex(z) = (1-A_Three) / (Z-A_Three)
However, G_ex: Transfer function of exhaust dynamic characteristics,
T_ex: Evaporation time constant,
Tsample: sample period,
A_Three: E^{-Tsample / Tex},
Also in Equation 3, the first equation converted into a discrete value system is the second equation and the second equation z = e^sTsampleThe third formula is obtained by substituting and organizing.
[0074]
In addition, the dead time is offset in time series like the fuel behavior model, and is not taken into the exhaust model (described later in 1.3).
[0075]
1.3 Waste time model
Since the plant model 31 has the actual injection pulse width CTIn as the input and the output voltage read value of the A / F sensor 3 as the output, as shown in FIG. There is some dead time (indicated by “Delay” in the figure) before the ECM 2 reads the F sensor output value. Therefore, the dead time between input and output is shown again in detail in FIG.
[0076]
Here, each dead time will be described.
[0077]
1) Delay1: Delay from injection amount calculation to actual injection timing,
The actual injection pulse width CTIn is calculated every 10 ms, and is not necessarily the same every cycle until the actual fuel injection timing. The dead time Delay1 is obtained by calculating the time from the pulse width calculation timing based on the calculated injection timing (fuel injection start) angle and the rotation speed at that time.
[0078]
2) Delay 2: Delay from actual injection timing to IVO (intake valve open)
This is the time from when the fuel is injected until the intake valve is opened and the fuel is sucked into the cylinder. This delay is determined by the fuel behavior characteristics and is set according to each operating condition and fuel properties. For example, using commercially available fuel that is almost in the middle of volatility, changing the fuel stepwise for each operating condition (for example, engine speed and load) and measuring the response time Set a correct value.
[0079]
3) Delay 3: Delay from IVO to EVO (exhaust valve open) (intake → compression → combustion → exhaust),
This is the time from when the fuel is drawn into the cylinder through the intake valve until the combustion gas is discharged from the exhaust valve. This delay can be obtained from the rotational speed and the cam profile, and is obtained from the design specifications.
[0080]
4) Delay 4: Delay from when the combustion gas leaves the exhaust valve until it reaches the A / F sensor,
This is the time from when the combustion gas in the cylinder is discharged from the exhaust valve until it reaches the A / F sensor section through the exhaust pipe. It is set according to the exhaust flow velocity (depending on the number of revolutions, load, etc.), the exhaust length, the A / F sensor mounting position, etc. In addition, although calculation becomes complicated, you may obtain | require from an operating condition and a hardware specification.
[0081]
5) Delay5: Sensor response delay,
This is the time from when the gas reaches the A / F sensor section until the A / F sensor outputs a voltage. When the oxygen amount fluctuates, the A / F sensor itself reacts in a few ms, but the gas mixing delay due to the sensor cover is dominant, and the time varies greatly depending on the shape of the sensor cover. For this reason, this delay is set to an appropriate value in the same manner as Delay 4.
[0082]
6) Delay 6: Delay until the sensor output value is A / D converted and loaded into ECM 2.
This is a delay caused by performing A / D conversion in order to capture the voltage output from the A / F sensor into the ECM 2. In the current hardware configuration, A / D conversion of the A / F sensor 3 is performed every 2 ms, and the maximum dead time is 2 ms.
[0083]
7) Delay 7: Delay until the sensor output value is buffered in the memory.
When the A / F sensor output value is sampled at 10 ms, there is a possibility that a maximum dead time of 10 ms may occur depending on the sampling timing. Therefore, the dead time from the response start to the sampling timing calculated from the A / D converted value in 2 ms is calculated as Delay7.
[0084]
8) Delay8: Variation
This is a variation that occurs in addition to the dead time obtained from Delays 1-7. Variations between models, variations in conformity, and the like are conceivable and are uncertain for each operation. Therefore, the rise of the air-fuel ratio signal after the delays 1 to 7 are determined and determined.
[0085]
This completes the explanation of each dead time.
[0086]
When the above Delays 1 to 8 are analyzed, the wasted time is
(1) Terms determined by operating conditions
(2) Matters determined from calculation timing,
(3) Terms that vary depending on fuel properties
(See FIG. 8). Therefore, the actual dead time can be expressed by the following equation.
[0087]

2. Plant model identification
2.1 Creating a model to identify
Although an actual engine has a strong non-linearity, it is assumed in this control that it is a so-called linear time-invariant system (LTI) that is linear and time-invariant near a certain operating point.
[0088]
In addition, since the discrete-time LTI system describes input / output in the time domain instead of the Z domain, the shift operator q^-1Is defined as follows.
[0089]
[Expression 4]
q^-1x (k) = x (k-1)
However, discrete time = kT (T: sampling period, k = 0, 1, 2,...).
[0090]
Using this, a system transfer function of an input u (t) and an output y (t) of a discrete value system is described.
[0091]
[Equation 5]
y (k) = G (q, θ) · u (k)
It becomes. θ is composed of parameters describing the model. However, this is an ideal input / output, and considering external noise,
[0092]
[Formula 6]
y (k) = G (q, θ) · u (k) + H (q, θ) · w (k)
Can be described. Here, H (q, θ) is a noise model, and a general discrete-time LTI system can be expressed by Equation 6. A block diagram of the system is shown in FIG.
[0093]
Here, the transfer function G (q) of the system is the product of the third equation of Equation 2 and the third equation of Equation 3, and Z^-1Is the shift operator q^-1Which is described in
[0094]
[Expression 7]

It can be expressed. The transfer function G (q) of this system is
[0095]
[Equation 8]
G (q, θ) = B (q, θ) / A (q, θ)
The system output value y (k) is defined as
[0096]
[Equation 9]
y (k, θ) = {B (q, θ) / A (q, θ)} · u (k) + H (q, θ) · w (k)
It can be expressed as. Thus, as a model to identify, what combined G (q) which is a plant model, and H (q) which is a noise model in the appropriate form is employ | adopted.
[0097]
2.2 Identification method
In the discrete-time LTI system defined by Equation 6, the one-step predicted value y (k | θ) of the output y (k) based on the input / output data measured up to time (k−1) is
[0098]
[Expression 10]
y (k | θ) = [1-H^-1(q, θ)] y (k) + H^-1(q, θ) G (q, θ) u (k)
It is expressed by the following formula. Thereby, the output at time k can be described by the data acquired up to (k−1).
[0099]
The prediction error ε (k | θ) is
[0100]
## EQU11 ##
ε (k | θ) = y (k) −y (k | θ)
It can be expressed by the following formula.
[0101]
Now, the evaluation criteria J for parameter estimation_N(θ)
[0102]
[Expression 12]

Set. Here, the function l (k, θ, ε (k, θ)) is an arbitrary scalar value function for measuring the magnitude of the prediction error ε (k, θ), and what norm to select is identified. Depends on the purpose of the result (square norm, log likelihood, etc.) By defining such an evaluation criterion, an estimated value of unknown parameter θ (referred to as θ (N)) is determined. That means
[0103]
[Formula 13]

Is to obtain θ.
[0104]
In general, various methods have been proposed as an identification method, but an engine-like object is an intermittent event (combustion cycle or the like), and is a control object with very strong nonlinearity. However, this control assumes a linear time invariant (LTI) system around the operating point to simplify the algorithm.
[0105]
This time, in consideration of the small amount of calculation, the identification accuracy, and the disturbance performance, the “collective identification method using the ARX model, which is parametric model identification”, which is a representative linear model identification method, is adopted.
[0106]
2.3 Identification method of ARX model
The ARX model is called an equation error model, and includes a disturbance term e (k) (assumed as white noise in the ARX model and assumed as w (k)) on the right side of the difference equation as follows.
[0107]
[Expression 14]
y (k) + a₁・ Y (k-1) + ... + a_na・ Y (k−na) = b₁・ U (k-1) + ... + b_nbThe parameter vector θ describing the u (k−nb) + e (k) model is
[0108]
[Expression 15]
θ = [a₁, ..., a_na, B₁, ..., b_nb]^T
It becomes. Data vector (regression vector) ψ (k)
[0109]
[Expression 16]
ψ (k) = [− y (k−1),..., −y (k−na), u (k−1),..., u (k−nb)]^T
The output y (k) can be expressed as follows:
[0110]
[Expression 17]
y (k) = θ^Tψ (k) + w (k)
The one-step predicted value y (k | θ) of the ARX model is linear with respect to θ when calculated from equation (10).
[0111]
[Formula 18]
y (k | θ) = θ^Tψ (k)
It is expressed. The prediction error ε (k, θ) at this time is
[0112]
[Equation 19]
ε (k, θ) = y (k) −θ^Tψ (k)
Can be expressed as When the least square method is applied to this linear regression model, the scalar value function l (k, θ, ε (k, θ)) becomes
[0113]
[Expression 20]
l (k, θ, ε (k, θ)) = ε²(k, θ)
The parameter estimation evaluation norm J_N(θ) is
[0114]
[Expression 21]

It becomes. Further calculating equation (21)
[0115]
[Expression 22]

[0116]
[Expression 23]
J_N(θ) = c (N) −2θ^Tf (N) + θ^TR (N) θ
It can be said.
[0117]
However, c (N), f (N), and R (N) in Equation 23 are as follows.
[0118]
[Expression 24]

[0119]
[Expression 25]

[0120]
[Equation 26]

Evaluation standard J_N(θ) is minimized when J_NSince (θ) is a quadratic function related to θ, if the highest order coefficient is positive, J_NThis is where the differential value of (θ) becomes zero. When the differential value of Equation 23 is set to 0, the following normal equation (simultaneous linear equation relating to θ) is obtained.
[0121]
[Expression 27]

Thus, if R (N) is a positive definite matrix, J_N(θ) is the minimum when the differential value is zero (J_N(θ) is a downward convex function, see FIG.
[0122]
[Expression 28]

The parameter θ (N) can be estimated by the following equation. The above identification procedure is shown in FIG.
[0123]
There are the following three conditions for the positive definite matrix.
[0124]
1) When the identification target is n-th order, the input signal u (k) must include n or more sine waves (a step input signal includes a sufficient frequency component).
[0125]
2) The identification target is stable (the engine can be considered as a stable system in a steady state).
[0126]
3) The identification target is observable. That is, A (q, θ) and B (q, θ) do not have a common factor (since this model is a discrete system, B (q, θ) has a higher order, but there is no problem).
[0127]
2.4 Identification of the actual ARX model
This model is a discrete system model of denominator 3rd order and numerator 3rd order from Equation 7.
[0128]
[Expression 29]
A (q) = 1 + a₁・ Q^-1+ A₂・ Q^-2+ A_Three・ Q^-3
[0129]
[30]
B (q) = b₁・ Q^-1+ B₂・ Q^-2+ B_Three・ Q^-3
It can be expressed as. Therefore, the parameter vector θ and the data vector ψ (k) can be expressed as follows.
[0130]
[31]
θ = [a₁, A₂, A_Three, B₁, B₂, B_Three]^T
[0131]
[Expression 32]
ψ (k) = [− y (k−1), −y (k−2), −y (k−3),
u (k-1), u (k-2), u (k-3)]^T
Assuming that the total number of samplings N when the engine speed is 1200 rpm is N = 128 (1280 ms), Equations 24 to 26 are
[0132]
[Expression 33]

[0133]
[Expression 34]

[0134]
[Expression 35]

It can be expressed as.
[0135]
2.5 Input signals required for plant model identification
In order to identify the system, the input signal needs to excite all modes of the object. That is, the input signal needs to include a large number of frequency components. In system identification, whiteness input is ideally ideal, but in practice a pseudo-white binary signal (M series) is used. However, in the case of the engine wall flow response, the effective frequency band is very low (the response is slow), and even when an input such as an M-sequence is added, a response waveform can hardly be obtained. Therefore, the system is identified based on the waveform (see FIG. 12) obtained by giving the step input. Since the Laplace transform of the step input is 1 / s, the frequency gain decreases in inverse proportion to the frequency. Therefore, it is necessary to determine an effective frequency range from the power spectrum.
[0136]
2.6 Experimental results
Since the transfer function G (q, θ) of the system is determined by using the parameter θ thus obtained, a Bode diagram in which the identification result and the actual data are superimposed is shown in FIG. 13 (the lighter the fuel property, the more light the fuel property is). The cut-off frequency tends to be higher). According to the experimental results, two gasolines with different fuel properties are separated by ± 3σ in the low load range when the swirl control valve provided at the intake port is open, the engine speed is around 1200 rpm, the cooling water temperature is around 40 ° C and the low load range. I was able to.
[0137]
This concludes the description of the itemization.
[0138]
Next, the control content executed by the ECM 2 will be described according to a flowchart.
[0139]
FIG. 14 is for estimating the fuel property, and is executed at regular intervals (every 10 ms). Here, FIG. 14 is configured as the main routine, and FIGS. 15 and 16 are configured as the subroutine of FIG. 14. Therefore, in the following, the subroutine will be described when a step of the subroutine occurs during the description of the main routine.
[0140]
In FIG. 14, in step 1, the fuel property determined flag is viewed. When the fuel property has not been determined yet, the process proceeds to step 2 and subsequent steps.
[0141]
Steps 2 to 6 are parts for sampling the air-fuel ratio (output data) of the exhaust. In step 2, the air-fuel ratio detected by the A / F sensor 3 is read, and in step 3, the read number (sampling number) S1 of this air-fuel ratio is compared with the total sampling number N (for example, 128). When S1 ≦ N, the routine proceeds to step 4 where the air-fuel ratio is buffered and the current processing is terminated. Steps 2 and 4 are repeated before S1> N.
[0142]
The process proceeds from step 3 to step 5 when S1> N. At this time, N pieces of output data are stored in the buffer. For example, the current value is y (1), the previous value is y (2), the previous value is y (3), ..., and the N-1 previous value is y (N). In this way, a total of N pieces of output data are stored.
[0143]
In steps 5 and 6, the output data N times before is discarded from the buffer, and the air / fuel ratio read this time is buffered. That is, the current value is stored in y (1). Needless to say, the past output data is shifted to the old side and stored once.
[0144]
Although not shown, the actual injection pulse width CTIn (input data) at the time of step response is also set to u (1), the previous value is u (2), the previous value is u (3), .., a total of N input data is stored in such a way that the value N-1 times before is u (N), and these input data and the above output data take into account the delay time described above Are associated with each other.
[0145]
In steps 7 and 8, the response waveform of the exhaust air / fuel ratio when the actual injection pulse width changes stepwise is analyzed using these N pieces of input / output data, and the fuel property of the fuel used is estimated from the analysis result.
[0146]
Here, “analysis of the response waveform of the exhaust air / fuel ratio” means that, according to the above expression, the prediction error between the parameter θ of the ARX model (plant model) and the reference model is minimized based on the input / output data. To identify the ARX model. Therefore, the identification of the ARX model will be described with reference to the subroutine of FIG. 15, and the estimation of fuel properties will be described with reference to the subroutine of FIG.
[0147]
First, in FIG. 15, in step 21, input / output data in the buffer (u (1) to u (128) for input, −y (1) to −y (128) for output) is used to calculate data using Equation 32. A vector ψ (k) is created.
[0148]
In step 22, R (N) is calculated from the data vector ψ (k) using the above equation 33, and in step 23, the above equation 34 is calculated from the output data y (k) and this data vector ψ (k). To calculate f (N), and from these R (N) and f (N), in step 24, the model parameter θ is calculated using the above equation (28).
[0149]
Next, moving to FIG. 16, the transfer function G (q, θ) of the discrete-time LTI system is calculated from the model parameter θ thus obtained in step 31 (from the above equations 29 and 30). Are used to create A (q) and B (q), and G (q, θ) (= B (q) / A (q)) is calculated from the two.
[0150]
From this system transfer function G (q, θ), in step 32, the cutoff frequency fc of the ARX model._RealIs calculated. In step 33, this cutoff frequency fc_RealAnd the cut-off frequency fc of the reference model_RefCompare
[0151]
Here, since heavy gasoline is used as the reference fuel, if light gasoline is used, fc_Real> Fc_RefAnd fc when heavy gasoline is used_{R eal}≤fc_RefIt becomes. Therefore, fc_Real> Fc_Ref(When light gasoline is used), the routine proceeds to step 34, where the fuel property switching flag = 1 is set._Real≤fc_Ref(When heavy gasoline is used), the routine proceeds from step 33 to step 35, where the fuel property switching flag = 0.
[0152]
When the determination of which fuel is being used is completed in this way, the process proceeds to step 9 in FIG. 14, where the value of the fuel property switching flag (result of determination of the fuel property) is stored in the EEPROM, and then in step 10 The fuel property determined flag = 1. Due to the processing of the fuel property determination flag = 1, it is not possible to proceed to step 2 and subsequent steps in FIG. 14 after the next time (the number of times of determination of the fuel property is only one).
[0153]
When the fuel property can be determined in this way, various correction amounts of the fuel injection amount and the starting fuel injection amount can be given according to the difference in the fuel property. This will be specifically described in the case of KAS.
[0154]
FIG. 17 is for calculating the post-startup increase correction coefficient KAS, and is executed at regular time intervals (for example, every 10 ms).
[0155]
In step 41, the fuel property switching flag stored in the EEPROM is read. In step 42, when the starter switch is viewed and it is ON, the process proceeds to step 43, and the coolant temperature TW and the rotational speed Ne are read. Of these, the post-startup increase water temperature correction value TKAS and the second post-startup increase correction coefficient are obtained by searching the tables having the contents shown in FIGS. 18 and 19 in steps 44 and 45 from the values of the cooling water temperature TW and the fuel property switching flag. In step 46, KASS is calculated from the rotation speed Ne and the value of the fuel property switching flag, and a post-start-up increasing rotation correction value TNKAS is calculated in step 46, and these values are used in step 47.
[0156]
[Expression 36]
KAS = TKAS x TNKAS + KASS
The post-startup increase correction coefficient KAS is calculated by the following formula.
[0157]
Here, as shown in FIGS. 18, 19, and 20, the values of TKAS, KAS, and TNKAS are the same when the fuel property switching flag = 1 under the same conditions (that is, when light gasoline is used). This value is smaller than when the switching flag = 0 (that is, when heavy gasoline is used).
[0158]
In step 48, in order to prepare for the processing after the starter switch is turned OFF, the value of TKAS is set to TKAS._n-1The KASS value to KASS_n-1To end the current process. TKAS_n-1, KASS_n-1Is a memory for holding the previous value.
[0159]
Eventually, when the starter switch is turned off (startup complete explosion), the operation proceeds from step 42 to the attenuation operation after step 49.
[0160]
In step 49, a post-start increase / decrease time ratio TMKAS is calculated by searching a table having the contents shown in FIG. 21 from the value of the fuel property switching flag and the post-start time t. In step 50, the previous value is decreased by this value. This value is the current TKAS (= TKAS_n-1-TMKAS). Immediately after the starter switch is turned off, TKAS> 0, so the process proceeds to step 53 as it is.
[0161]
Steps 53 to 56 are the same as steps 49 to 52. In step 53, the second post-startup increase / decrease time ratio TMKASS is calculated by searching a table having the contents shown in FIG. 22 from the value of the fuel property determination flag and the post-startup time t. In step 54, the previous value is decreased by this value. This value is the current KASS (= KASS_n-1-TMKASS). Also at this time, since KASS> 0, the process proceeds to step 46 as it is and the processing after step 46 is executed.
[0162]
As shown in FIGS. 21 and 22, the above TMKAS and TMKASS are also smaller values when using light gasoline than when using heavy gasoline when compared under the same conditions.
[0163]
Since the steps 49, 50, 53, and 54 are repeated from the next time onward, TKAS and KASS eventually become 0 or less. At this time, the process proceeds to step 52 and step 56 to limit TKAS and KASS to 0.
[0164]
As a result, both TKAS and KASS are initially set to the value when the starter switch is OFF, and are attenuated at a constant rate to 0 after the starter switch is turned OFF (however, when TNKAS is constant). However, the initial value of TKAS is larger than the initial value of KASS, and the decrease time ratio of TKAS is larger than the decrease time ratio of KASS. Therefore, KAS, which is a value obtained by adding TKAS and KASS, first decreases with a steep slope after turning off the starter switch, with the initial value being the sum of the TKAS value and KASS value when the starter switch is turned off, and TKAS becomes zero. From this timing, it changes to a gentle slope and decreases.
[0165]
In this case, when light gasoline is used, the initial values of TKAS and KASS (table values in FIGS. 18 and 19) are smaller than when heavy gasoline is used, and the respective reduction time ratios of TKAS and KASS (FIG. 21 and the table values in FIG. 22) are increased, so that KAS when light gasoline is used is smaller than KAS when heavy gasoline is used (see FIG. 23). In other words, when the fuel property is not judged, the air-fuel ratio is enriched by using a table value matched to heavy gasoline even when light gasoline is used. When it is determined that gasoline is being used, the KAS for light gasoline is calculated when calculating KAS at the next start, so that the air-fuel ratio will not be biased to the rich side even when light gasoline is used. is there.
[0166]
The flowchart of FIG. 24 is a second embodiment and corresponds to FIG. 16 of the first embodiment. The same steps as those in FIG. 16 are denoted by the same step numbers.
[0167]
In contrast to the first embodiment in which heavy gasoline is used as the reference fuel, the second embodiment uses an almost intermediate fuel that is neither bad nor bad among commercially available fuels as a reference fuel. The fuel that is more volatile than the reference fuel is set as light gasoline, and conversely, the fuel that is less volatile than the reference fuel is set as heavy gasoline, and the cutoff frequency of the plant model and the cutoff frequency of the reference model (that is, The difference between the cutoff frequency and the reference fuel is calculated, and the difference between the frequency difference and the allowable range is compared to determine the fuel properties of the fuel being used. Even if there is a variation, fuel property estimation can be performed stably.
[0168]
In FIG. 24, the part different from FIG.
[0169]
[Expression 37]
Δfc = fc_Real-Fc_Ref
The cut-off frequency difference Δfc with respect to the reference fuel is calculated by the following formula, and the absolute value of this frequency difference Δfc and a predetermined value a (> 0) that defines an allowable range, or Δfc and a are compared in steps 62 and 63. If | Δfc | ≦ a (that is, the reference fuel is used), the routine proceeds from step 62 to step 64 where the fuel property switching 2 flag = 0, and | Δfc |> a and Δfc> a (that is, light gasoline is Is used), the process proceeds from step 63 to step 65 to set the fuel property switching 2 flag = 1. Otherwise (that is, heavy gasoline is used), the process proceeds from step 63 to step 66. The fuel property switching 2 flag = 2.
[0170]
Thus, in 2nd Embodiment, it was determined whether the fuel currently used is a reference fuel, light gasoline, or heavy gasoline.
[0171]
However, when the fuel property determination value becomes three values as in the second embodiment, it is necessary to prepare three types of table values corresponding to FIGS. 18 to 22 when calculating the post-startup increase correction coefficient KAS. There is.
[0172]
Next, the flowcharts of FIGS. 25, 26, and 28 are the third embodiment, and correspond to FIGS. 14, 16, and 17 of the first embodiment, respectively. In FIG. 25, the same step numbers are assigned to the same portions as FIG. 14, the same portions as FIG. 16 in FIG. 26, and the same portions as FIG.
[0173]
Whereas in the above-described two embodiments, the fuel property determination value (that is, the value of the fuel property switching flag or the fuel property switching 2 flag) is binary or ternary, the third embodiment is a continuous value. The estimated fuel property value is calculated and stored in the EEPROM (steps 71 and 72 in FIG. 25), and the post-startup increase correction coefficient KAS is calculated using the estimated fuel property value at the next start. Is.
[0174]
The calculation of the fuel property estimated value will be specifically described with reference to FIG. 26. In steps 31 and 32, the cutoff frequency of the plant model is calculated in the same manner as in the first embodiment, and in FIG. The fuel property estimation value is calculated by searching a table having the contents of. Since the relationship between the cut-off frequency of the plant model and the estimated fuel property value is as shown in FIG. 27, the fuel property of the fuel used can be estimated from the cut-off frequency of the plant model if the same characteristic is determined in advance by matching. is there.
[0175]
Next, in FIG. 28, the difference from FIG. 17 will be mainly explained. In step 91, the fuel property estimation value FC is read. 93, 94, a map containing the contents of FIGS. 29, 30 and 31 is searched to obtain the post-startup increase water temperature correction value TKAS, the second post-startup increase correction coefficient KASS, the post-startup increase rotation correction value TNKAS, and When the starter switch is turned OFF, the fuel property estimated value FC and the coolant temperature TW are searched from the maps having the contents shown in FIGS. 32 and 33 in steps 95 and 96, so that the increase / decrease time ratio TMKAS after the start and the increase / decrease after the second start. Each time ratio TMKASS is calculated.
[0176]
Here, as shown in FIG. 29 and FIG. 30, TKAS and KASS are values that increase as the cooling water temperature TW decreases and the fuel properties become heavier when the TW is the same, TMKAS TMKASS is a value that increases as the cooling water temperature TW increases for the same FC as shown in FIGS. 32 and 33, and as the fuel property becomes lighter when the TW is the same.
[0177]
Needless to say, if the fuel property estimated value and the TW are the same, TKAS is larger than KASS and TMKAS is larger than TMKASS.
[0178]
According to the third embodiment, since the data (map value) used for the calculation of the post-startup increase correction coefficient KAS is assigned according to the fuel property estimated value FC as the continuous value, it is more than the previous two embodiments. Thus, the calculation accuracy of the post-startup increase correction coefficient KAS is improved.
[0179]
The flowchart of FIG. 34 is the fourth embodiment, which replaces FIG. 28 of the third embodiment. The same steps as those in FIG. 28 are denoted by the same step numbers.
[0180]
Now, if the data used to calculate KAS is given as map values as shown in FIGS. 29 to 33, the number of matching steps becomes enormous. Therefore, in the fourth embodiment, a fuel property correction value KFC corresponding to the fuel property estimation value FC is introduced, and the data (table value) matched with the heaviest gasoline is corrected by this correction value KFC. By calculating the post-startup increase correction coefficient KAS based on the obtained data, the number of matching man-hours is reduced.
[0181]
Specifically, steps 101 and 102 to 115 are different from the case of FIG. First, in step 101, a fuel property correction value KFC is calculated by searching a table having the contents shown in FIG. 35 from the fuel property estimation value FC. As shown in FIG. 35, KFC is a value that becomes smaller as the fuel property becomes lighter with 1.0 being the maximum when the fuel is the heaviest gasoline (fuel property is the most heavy).
[0182]
In steps 102 and 103, a table containing the contents of FIG. 36 and FIG. 37 is searched from the coolant temperature TW to calculate TKAS and TMKAS (both are values matched to the heaviest gasoline). In step 104 using the above KFC,
[0183]
[Formula 38]
TKASF = TKAS × KFC
TMKASF = TMKAS × KFC
The post-startup increase water temperature correction value TKASF corresponding to the fuel property and the post-startup increase decrease time ratio TMKASF corresponding to the fuel property are calculated by the following equation. In Steps 105, 106, and 107, as in Steps 102, 103, and 104, by searching the table containing the contents of FIGS. 38 and 39 from the cooling water temperature TW, KASS and TMKASS Is a matching value)
[0184]
[39]
KASSF = KASS × KFC
TMKASSF = TMKASS × KFC
The second post-startup increase correction coefficient KASSF corresponding to the fuel property and the second post-startup increase decrease time ratio TMKASF corresponding to the fuel property are calculated by the following equation. And using these values, it is the same formula as the above-mentioned formula 36,
[0185]
[Formula 40]
KAS = TKASF × TNKAS + KASSF
The post-startup increase correction coefficient KAS is calculated by the following equation (step 108).
[0186]
In step 109, in order to prepare for the processing after the starter switch is turned OFF, the value of TKASF is set to TKASF._n-1The value of KASSF to KASSF_n-1To end the current process. Steps 110 to 115 are parts for performing a damping operation on TKASF and KASSF in the same manner as steps 49 to 56 in FIG. 17 after the starter switch is turned off.
[0187]
For example, when gasoline having a lighter fuel property than the heaviest gasoline is used, the KFC becomes a value smaller than 1.0, so that TKASF <TKAS, TMKASF <TMKAS, KASSF <KASS, TMKAASSF <TMKASS. Therefore, a KAS smaller than the KAS for the heaviest gasoline is calculated, and as a result, as in the case of FIG. 28, the optimum post-start-up increase is also obtained for the lighter fuel property than the heaviest gasoline. A correction factor is given. When the heaviest gasoline is used, from KFC = 1.0, TKASF = TKAS, TMKASF = TMKAS, KASSF = KASS, and TMKASF = TMKASS, which are the same as the conventional apparatus.
[0188]
In this case, when obtaining the data used for the calculation of KAS, it is only necessary to match the characteristics shown in FIG. 36 to FIG. 39 with the heaviest gasoline, so according to the fourth embodiment, the third embodiment. The matching man-hour can be reduced as compared with the case of (1).
[0189]
Next, the flowcharts of FIGS. 40, 48, and 51 correspond to FIGS. 17, 28, and 34 in the fifth, sixth, and seventh embodiments, respectively. In FIG. 40, the same step numbers are assigned to the same parts as in FIG. 17, the same parts in FIG. 48 as in FIG. 28, and the same parts in FIG.
[0190]
In the above-described three embodiments shown in FIGS. 17, 28, and 34, the post-startup increase correction coefficient KAS is calculated based on the fuel property switching flag and the fuel property estimated value. In each of the seventh embodiments, the unburned component increase correction coefficient KUB is calculated based on the fuel property switching flag and the fuel property estimated value. Incidentally, the calculation method of the unburned amount increase correction coefficient KUB itself is proposed in Japanese Patent Laid-Open No. 10-18883.
[0191]
40, in addition to the value of the fuel property switching flag stored in the EEPROM in steps 41 and 121, the intake negative pressure, the rotation speed Ne, and the cooling water temperature TW are read. In step 122, the air-fuel ratio feedback control condition (FIG. Then, it is abbreviated as “air-fuel ratio F / B condition”). The conditions for prohibiting air-fuel ratio feedback control are, as is well known, starting, high load, deceleration (fuel cut), O₂When the sensor 3 output is abnormal,₂This is when the sensor 3 falls into any of the inactive states.
[0192]
In the condition for prohibiting the air-fuel ratio feedback control, the process proceeds to steps 123 and 124, a table containing the contents of FIG. 41 is searched from the cooling water temperature TW and the value of the fuel property switching flag, and the basic value KTW0 of the water temperature increase correction coefficient is set. A map having the contents shown in FIG. 42 is retrieved from the suction negative pressure and the rotational speed Ne to obtain the load rotation correction factor RKTW of the water temperature increase correction coefficient.
[0193]
[Expression 41]
KTW = KTW0 × RKTW
The water temperature increase correction coefficient KTW is calculated by the following formula.
[0194]
Here, as shown in FIG. 41, the value of KTW0 is equal to that when light gasoline is used (fuel fuel property switching flag = 1) even when the same cooling water temperature TW is used (fuel fuel property switching flag). = 0)).
[0195]
FIG. 42 shows characteristics common to light gasoline and heavy gasoline. Actually, there are separate maps for light gasoline and heavy gasoline, the same rotation speed, and the same suction negative pressure. If you look at it, the map value for light gasoline is smaller than the map value for heavy gasoline.
[0196]
Finally, at step 126, 0 is set to the unburned amount increase correction coefficient KUB. At this time (conditions for prohibiting the air-fuel ratio feedback control) is the same as when there is no KUB, and the fuel increase by the water temperature increase correction coefficient KTW is performed as in the conventional case.
[0197]
On the other hand, when the air-fuel ratio feedback control condition is satisfied, the routine proceeds from step 122 to step 127, where 0 is entered in the water temperature increase correction coefficient KTW, and in steps 128 and 129, the values of the cooling water temperature TW and the fuel property switching flag are set. 43 is searched to search the basic value KUBAS of the unburned fuel increase correction coefficient, and the map of FIG. 44 is searched from the suction negative pressure and the rotational speed Ne to search for the unburned fuel increase correction coefficient. In step 130, the load rotation correction factor RKUB is obtained.
[0198]
[Expression 42]
KUB = KUBAS × RKUB
The unburned amount increase correction coefficient KUB is calculated by the following formula.
[0199]
If the value of KUBAS is the same cooling water temperature TW as in KTW0 as shown in FIG. 43, light gasoline is used (fuel fuel property switching flag = 1) when heavy gasoline is used (fuel fuel property switching). Flag = 0). 44 also shows the characteristics common to light gasoline and heavy gasoline as in FIG. 42. Actually, there are independent maps for light gasoline and heavy gasoline, and the same rotation speed, At the same negative suction pressure, the map value for light gasoline is smaller than the map value for heavy gasoline.
[0200]
As described above, when the engine is cold, the unburnt amount increases after the completion of engine warm-up, so the base air-fuel ratio does not become the stoichiometric air-fuel ratio (which is leaner than the stoichiometric air-fuel ratio). KUB is adapted so that the air-fuel ratio becomes the stoichiometric air-fuel ratio even in a state where the unburned amount has increased.
[0201]
Specifically, the KTW is not calculated using only the cooling water temperature TW as a parameter, but the KTW is calculated using the load and the rotation speed as parameters for the following reason. The conventional KTW mainly considers the stability of the engine under idle conditions, and on the high-speed, high-load side, there is no problem with stability in the first place. As shown in FIG. 45, if the suction negative pressure (that is, the engine load) is different even at the same cooling water temperature and the same rotation speed, the required value for KTW also differs. Therefore, if the KTW is adapted so that the air-fuel ratio satisfying the engine stability is satisfied with the suction negative pressure (for example, the suction negative pressure at the point A) when the throttle valve 5 is in the fully closed position, the same cooling water temperature and rotation If the intake negative pressure (for example, intake negative pressure at point B) is reached with the throttle valve 5 opened to a predetermined opening by depressing the accelerator pedal, the KTW will be insufficient. Similarly, as shown in FIG. 46, if the rotational speed is different even at the same cooling water temperature and the same suction negative pressure, the required value for KTW is different, so that the rotational speed (when the throttle valve 5 is in the fully closed position and idling ( For example, if the KTW is adapted so that the air-fuel ratio satisfying the engine stability at the rotation speed at the point C), the accuracy of the KTW at the same cooling water temperature and suction negative pressure at a high rotation speed (for example, the rotation speed at the D point). Falls. Note that the characteristics of the air-fuel ratio with respect to the rotational speed are not uniform, and there are both a case of rising to the right and a case of rising to the left.
[0202]
Note that FIG. 45 shows the air-fuel ratio of the fuel with the same fuel properties that satisfies the base air-fuel ratio and the engine stability when the intake negative pressure is changed while the cooling water temperature and the rotation speed are kept constant when the engine is cold. FIG. 46 shows the characteristics of the base air-fuel ratio and the air-fuel ratio satisfying the engine stability when the engine speed is cold and the engine speed is changed while the cooling water temperature and the suction negative pressure are kept constant. Is shown.
[0203]
Therefore, for each of heavy gasoline and light gasoline, for example, the basic value KTW0 is adjusted after the cooling water temperature is made different under the conditions of the suction negative pressure and the rotational speed at the time of idling to adapt the basic value KTW0 of the water temperature increase correction coefficient. Even when the intake negative pressure and the rotational speed deviate from the above, the intake negative pressure and the rotational speed are made different so that the air-fuel ratio satisfies the engine stability, and the load rotation correction factor RKTW of the water temperature increase correction coefficient is set. Is suitable.
[0204]
Further, as shown in FIG. 45, if the suction negative pressure is different even at the same cooling water temperature and the same rotation speed, the required value for KUB is different, so that the stoichiometric air-fuel ratio is obtained at the suction negative pressure at point A. If KUB is adapted to KUB, if the suction negative pressure at point B is reached even at the same cooling water temperature and rotation speed, the KUB will be insufficient. Also, as shown in FIG. 46, the same cooling water temperature and the same suction negative pressure are used. Since the required value for KUB will be different if the rotational speed is different even at pressure, if KUB is adapted so that the theoretical air-fuel ratio is obtained at the rotational speed at point C, the rotational speed at point D is the same even at the same cooling water temperature and negative suction pressure. Since the accuracy of the KUB is reduced when the number is low, the unburned fuel increase correction coefficient is set differently for heavy gasoline and light gasoline, for example, by making the cooling water temperature different under the conditions of the suction negative pressure and the rotational speed during idling. Adapt basic value KUBAS In both cases, when the basic value KUBAS is met, the suction negative pressure and the rotational speed are different from each other so that the stoichiometric air-fuel ratio becomes the theoretical air-fuel ratio. Fit rate RKUB.
[0205]
42 and 44 show an example of RKTW and RKUB. Since the characteristics of RKTW and RKUB are different for each engine model, they are finally adapted for each engine model. 45 and 46 show KTW and KUB slightly apart from the points A, B, C, and D for easy viewing. Therefore, it goes without saying that KUB <KTW is satisfied under the same conditions of the cooling water temperature, the suction negative pressure, and the rotational speed.
[0206]
The intake negative pressure can be obtained by searching a predetermined map from the intake air amount Qa from the air flow meter and the rotational speed Ne. The negative suction pressure can also be detected by a pressure sensor provided at the collector portion of the intake manifold. Further, the basic injection pulse width Tp (or Qa) can be used instead of the suction negative pressure.
[0207]
FIG. 47 shows a time-series image of the unburned component increase correction coefficient KUB corresponding to FIG. Since the KUBAS value (table value in FIG. 43) is smaller and the RKUB value (table value in FIG. 44) is smaller when light gasoline is used than when heavy gasoline is used, as shown in FIG. In particular, the KUB when using light gasoline is smaller than the KUB when using heavy gasoline. In other words, when the fuel property is not judged, the air / fuel ratio is enriched by using a table value matched to heavy gasoline even when light gasoline is used. When it is determined that gasoline is being used, the KUB for the next start-up is calculated as a KUB for light gasoline by calculating a smaller value than when using heavy gasoline. The fuel ratio is not biased toward the rich side.
[0208]
Next, turning to FIG. 48 (sixth embodiment), the load rotation correction factors RKTW and RKUB shown in FIG. 40 are omitted for simplicity in FIG. In FIG. 48, steps 141 and 143 are different from FIG. 40 of the fifth embodiment. Under the conditions for prohibiting the air-fuel ratio feedback control, the contents of FIG. 49 are calculated from the coolant temperature TW and the fuel property estimated value FC in step 141. The basic value KTW0 of the water temperature increase correction coefficient is calculated by searching the map to be transferred, and the calculated value is transferred to the water temperature increase correction coefficient KTW in step 142. When the air-fuel ratio feedback control condition is satisfied, Proceeding to 143, the basic value KUBAS of the unburned amount increase correction coefficient is calculated from the coolant temperature TW and the fuel property estimated value FC by searching a map having the contents shown in FIG. 50 as the calculated value. The unburned amount increase correction coefficient KUB is moved to. 49 and 50, it goes without saying that the KUBAS value is smaller than the KTW0 value for the same cooling water temperature and the same fuel property estimation value FC.
[0209]
According to the sixth embodiment, the data (map value) used for calculating the water temperature increase correction coefficient KTW and the unburned fuel increase correction coefficient KUB is allocated according to the fuel property estimation value FC as a continuous value. Compared with the fifth embodiment, the calculation accuracy of the water temperature increase correction coefficient KTW and the unburned fuel increase correction coefficient KUB is improved.
[0210]
Next, moving to FIG. 51 (seventh embodiment), the load rotation correction factors RKTW and RKUB shown in FIG. 40 are omitted for simplicity in FIG. In FIG. 51, steps 101 and 151 to 154 are different from FIG. 48 of the sixth embodiment.
[0211]
First, in step 101, a fuel property correction value KFC is calculated by searching a table having the contents shown in FIG. 35 from the fuel property estimated value FC. Then, in the condition for prohibiting the air-fuel ratio feedback control, the cooling water temperature TW is calculated in step 151. By searching a table having the contents of 52, KTW0 (a value matched to the heaviest gasoline) is calculated, and using this and the above KFC, in step 152,
[0212]
[Equation 43]
KTW = KTW0 × KFC
The water temperature increase correction coefficient KTW is calculated by the following formula.
[0213]
On the other hand, when the air-fuel ratio feedback control condition is satisfied, in steps 153 and 154, a table containing FIG. 53 is searched from the coolant temperature TW in the same manner as in steps 151 and 152, whereby KUBAS (this is also the maximum). (Matched value for heavy gasoline)
[0214]
(44)
KUB = KUBAS × KFC
The unburned amount increase correction coefficient KUB is calculated by the following formula.
[0215]
In the seventh embodiment, for example, when gasoline whose fuel property is lighter than the heaviest gasoline is used, since KFC is a value smaller than 1.0, KTW <KTW0 and KUB <KUBAS. KTW and KUB smaller than KTW and KUB for the heaviest gasoline are calculated. As a result, the optimal water temperature is obtained for the gasoline whose fuel properties are lighter than the heaviest gasoline as in the sixth embodiment. An increase correction coefficient and an unburned increase correction coefficient are provided. When using the heaviest gasoline, KFC = 1.0, KTW = KTW0, KUB = KUBAS, which is the same as the conventional apparatus.
[0216]
In this case, according to the seventh embodiment, it is only necessary to match the characteristics shown in FIGS. 52 and 53 with the heaviest gasoline when obtaining data used for the calculation of KTW and KUB. The number of matching steps can be reduced as compared with the case of.
[0217]
In the first, third, and fourth embodiments described above, the post-startup increase correction coefficient KAS as the injection amount correction amount is targeted, and in the fifth, sixth, and seventh embodiments, the injection amount correction amount is used. (A) When using the fuel property switching flag, (B) When using the fuel property estimation value FC, (C) The fuel property correction value KFC Although described in the case of using, it is not limited to this. For example, the following three cases (A) to (C) can be applied to the following injection amount correction amounts (1) and (2) and fuel injection amounts (3) and (4).
[0218]
(1) Low frequency component (wall flow fuel).
[0219]
(2) High frequency component (wall flow fuel).
[0220]
(3) Fuel injection amount at start-up.
[0221]
(4) Interruption injection amount during acceleration.
[0222]
Hereinafter, the case where (C) is applied to (1) to (4) will be described separately.
(1) When the low frequency component is the injection amount correction amount
(1-1) How to find the adhesion magnification Mfhtvo
The above-mentioned adhesion magnification Mfhtvo is the amount of equilibrium adhesion per unit injection valve portion flow rate equivalent pulse width and per cylinder. According to the above-mentioned Japanese Patent Laid-Open No. 10-18882, this is the load (Avtp). It is obtained using the rotational speed Ne and the predicted temperature Tf of the fuel adhering portion. The calculation of the temperature predicted value Tf of the fuel adhering portion is detailed in Japanese Patent Laid-Open No. 1-305142, and the description thereof is omitted.
[0223]
Specifically, how to obtain Mfhtvo will be described as follows. First, each reference temperature Tf above and below the predicted temperature value Tf_iAnd Tf_{i + 1}Reference adhesion magnification data Mfhtf for (i is an integer from 1 to 4 (or 5))_iAnd Mfhtf_{i + 1}Tf, Tf_i, Tf_{i + 1}Obtained by interpolation calculation using. For example, Mfhtf₁, Mfhtf₂And the reference temperature Tf₁, Tf₂Using the current temperature predicted value Tf
[0224]
[Equation 45]
Mfhtvo = Mfhtf₁+ (Mfhtf₂-Mfhtf₁)
× (Tf₁-Tf) / (Tf₁-Tf₂)
Mfhtvo is calculated by the following formula (linear interpolation calculation formula).
[0225]
The reference adhesion magnification data Mfhtf_iIs
[0226]
[Equation 46]
Mfhtf_i= Mfhq_i× Mfhn_i
However, Mfhq_i: Reference adhesion magnification load term,
Mfhn_i: Reference adhesion magnification rotation term,
Calculate with the following formula.
[0227]
Where Mfhq_iIs obtained by searching a predetermined map with interpolation calculation using the α-N flow rate Qh0 and the temperature predicted value Tf. Qh0 is an air flow rate of the throttle valve portion obtained from the throttle valve opening TVO and the rotational speed Ne, and is already known. Mfhn_iIs obtained by searching a predetermined table from the rotational speed Ne with interpolation calculation. Mfhq_iMap (see Fig. 54) and Mfhn_iThe table (see FIG. 55) stores data matched at the stoichiometric air-fuel ratio together with a Kmfat map and a Kmfn table, which will be described later. 54 and FIG. 56, which will be described later, are originally matched with the cooling water temperature TW, but when searching for this map, the predicted temperature value Tf is used instead of the cooling water temperature TW. .
[0228]
(1-2) How to find the proportion Kmf
The above-mentioned quantity ratio Kmf represents the ratio at which the current adhesion amount (predictive variable) Mf approaches the equilibrium adhesion amount Mfh per unit cycle (for example, every rotation of the crankshaft). This is a coefficient, which is calculated from the product of the basic quantity ratio Kmfat and the quantity ratio rotation correction factor Kmfn according to the above-mentioned Japanese Patent Application Laid-Open No. 10-18882.
[0229]
Here, Kmfat is obtained using the predicted temperature value Tf. For example, a predetermined map (see FIG. 56) is searched with interpolation calculation using the α-N flow rate Qh0 and the predicted temperature value Tf. Kmfn searches a predetermined table (see FIG. 57) with interpolation calculation from the rotational speed Ne.
[0230]
Reference adhesion magnification rotation term Mfhn_iAnd n attached to the quantity ratio rotation correction factor Kmfn means not the cylinder number n but the rotation speed Ne.
[0231]
(1-3) Reflecting fuel properties
Four data used to calculate the low frequency component (reference adhesion magnification load term Mfhq_iMap value, reference adhesion magnification rotation term Mfhn_iTable value, basic quantity ratio Kmfat map value, quantity ratio rotation correction factor Kmfn table value) are matched with the heaviest gasoline, and the data matched with the heaviest gasoline is corrected for the above fuel properties. Correct with the value KFC.
(2) When the high frequency component is the injection amount correction amount
Cylinder wall flow correction amount Chosn¹The increase gain Gztwp and the decrease gain Gztwm used in the calculation of the above are values obtained by searching the tables having the contents shown in FIGS. 58 and 59 from the water temperature TW according to the above-mentioned Japanese Patent Laid-Open No. 10-18882. Therefore Chosn¹2 data (table value of increase gain Gztwp and table value of decrease gain Gztwm) are matched with the heaviest gasoline and the data matched with the heaviest gasoline is used for the above fuel property correction. Correct with the value KFC.
(3) When the fuel injection amount at start is the fuel injection amount
(3-1) How to determine the fuel injection pulse width TIST at start
According to Japanese Patent Application Laid-Open No. 7-63082, the fuel injection pulse width TIST at start-up
[0232]
[Equation 47]
TIST = TST × KTST × KNST
Where TST: basic injection pulse width at start,
KTST: Time correction coefficient,
KNST: rotational speed correction coefficient,
It is calculated by the formula of TST, KTST, and KNST are values obtained by searching the tables having the contents shown in FIGS.
[0233]
(3-2) Reflecting fuel properties
Three data (TST, KTST, KNST table values) used to calculate the fuel injection pulse width at start-up are matched with the heaviest gasoline, and the data matched with the heaviest gasoline is the above-mentioned data Is corrected with the fuel property correction value KFC.
(4) When the acceleration interrupt injection amount is the fuel injection amount
(4-1) How to determine the interrupt injection pulse width during acceleration
According to Japanese Unexamined Patent Publication No. 64-3245, the acceleration interruption injection pulse width IJSETn is calculated using ΔAvtpn (n is the cylinder number), which is the amount of change from the previous opening injection of the injection valve portion air amount equivalent pulse width Avtp. ,
[0234]
[Formula 48]
IJSETn = ΔAvtpn × Gwtwp × Gzcyln + Ts
However, Gwtwp: increase gain Gztwp,
Gzcyln: Correction rate for each cylinder,
It is calculated by the formula of
[0235]
Here, since Gzcyln (n is a cylinder number), the behavior of the intake system fuel differs depending on the crank angle difference from the cycle position where the interrupt injection is performed to the intake stroke. This is a value obtained by searching the table to be searched.
[0236]
In contrast to Japanese Patent Application Laid-Open No. 64-3245, which describes an arithmetic expression for the SPI (single point injection) system, Expression 48 is rewritten to the MPI (multipoint injection) system.
[0237]
(4-2) Reflecting fuel properties
The data (Gwtwp and Gzcyln table values) used to calculate the acceleration injection pulse width during acceleration is matched with the heaviest gasoline, and the data matched with the heaviest gasoline is used for the above fuel property correction. Correct with the value KFC.
[0238]
In this way, by using the fuel property correction value KFC for the calculation of the fuel injection amount such as the injection amount correction amount such as the low frequency component and the high frequency component, the fuel injection amount at the start time, and the interrupt injection amount at the time of acceleration, various injection amount corrections The calculation accuracy of the fuel injection amount and the fuel injection amount can be improved, so that even if the fuel properties of the fuel used are different, various appropriate injection amount correction amounts and fuel injection amounts can be given, as well as various injection amounts Since only the matching with the heaviest gasoline is required when obtaining the data used for calculating the correction amount and the fuel injection amount, the number of matching steps can be reduced.
[0239]
Finally, various injection amounts and fuel injection amounts are not limited to those in the embodiment, and needless to say, they are applicable as long as they are affected by the fuel properties.
[0240]
In the embodiment, the response waveform of the exhaust air / fuel ratio with respect to the fuel injection amount at the time of transient is sampled, and based on these transient data, the parameters of the plant model previously constructed on the ECM are converted into the reference model that is the plant model for the reference fuel and However, the present invention is not limited to this, and the fuel supply amount can be used instead of the fuel injection amount. . Further, in addition to adjusting so that the prediction error is minimized, it may be adjusted so as to reduce the prediction error.
[Brief description of the drawings]
FIG. 1 is a control system diagram of engine control.
FIG. 2 is a control system diagram related to estimation of fuel properties.
FIG. 3 is a block diagram of an engine plant model.
FIG. 4 is a model diagram of fuel behavior.
FIG. 5 is a parallel path block diagram of fuel behavior.
FIG. 6 is an exhaust model diagram.
FIG. 7 is a waveform diagram showing dead time between input and output.
FIG. 8 is a table in which dead times are classified.
FIG. 9 is a general block diagram of an LTI system.
FIG. 10 is a characteristic diagram of an evaluation function (evaluation standard).
FIG. 11 is a flowchart showing a method for identifying an ARX model.
FIG. 12 is a waveform diagram showing an input signal necessary for model identification and its response.
FIG. 13 is a Bode diagram showing the identification result and actual data superimposed on each other.
FIG. 14 is a flowchart for explaining estimation of fuel properties.
FIG. 15 is a flowchart for explaining identification of an ARX model.
FIG. 16 is a flowchart for explaining fuel property switching determination;
FIG. 17 is a flowchart for explaining calculation of a post-startup increase correction coefficient KAS.
FIG. 18 is a characteristic diagram of a post-startup increased water temperature correction value (initial value).
FIG. 19 is a characteristic diagram of an increase correction coefficient (initial value) after the second start.
FIG. 20 is a characteristic diagram of an increased rotation correction value after startup.
FIG. 21 is a characteristic diagram of an increase / decrease time ratio after start.
FIG. 22 is a characteristic diagram of the increase / decrease time ratio after the second start.
FIG. 23 is a waveform diagram showing a time-series image of a post-startup increase correction coefficient KAS.
FIG. 24 is a flowchart for explaining fuel property switching determination according to the second embodiment;
FIG. 25 is a flowchart for explaining fuel property estimation according to the third embodiment;
FIG. 26 is a flowchart for explaining calculation of a fuel property estimated value according to the third embodiment.
FIG. 27 is a characteristic diagram of a fuel property estimation value with respect to a cutoff frequency.
FIG. 28 is a flowchart for explaining calculation of a post-startup increase correction coefficient KAS according to the third embodiment.
FIG. 29 is a characteristic diagram of a post-startup increased water temperature correction value (initial value) according to the third embodiment.
FIG. 30 is a characteristic diagram of a second post-startup increase correction coefficient (initial value) of the third embodiment.
FIG. 31 is a characteristic diagram of a post-startup increased rotation correction value of the third embodiment.
FIG. 32 is a characteristic diagram of an increase / decrease time ratio after start of the third embodiment.
FIG. 33 is a characteristic diagram of an increase / decrease time ratio after the second start according to the third embodiment.
FIG. 34 is a flowchart for explaining calculation of a post-startup increase correction coefficient KAS according to the third embodiment.
FIG. 35 is a characteristic diagram of a fuel property correction value according to the third embodiment.
FIG. 36 is a characteristic diagram of a post-startup increased water temperature correction value (initial value) according to the third embodiment.
FIG. 37 is a characteristic diagram of an increase / decrease time ratio after start of the third embodiment.
FIG. 38 is a characteristic diagram of an increase correction coefficient (initial value) after the second start according to the third embodiment.
FIG. 39 is a characteristic diagram of the increase / decrease time ratio after the second start according to the third embodiment.
FIG. 40 is a flowchart for explaining calculation of a water temperature increase supplement coefficient KTW and an unburned component increase correction coefficient KUB of the third embodiment.
FIG. 41 is a characteristic diagram of a basic value of a water temperature increase complementary coefficient according to the third embodiment.
FIG. 42 is a characteristic diagram of a load rotation correction factor of a water temperature increase complementary coefficient according to the third embodiment.
FIG. 43 is a characteristic diagram of a basic value of an unburned amount increase correction coefficient according to the third embodiment.
FIG. 44 is a characteristic diagram of a load rotation correction rate of an unburned component increase correction coefficient according to the third embodiment.
FIG. 45 is an air-fuel ratio characteristic diagram for explaining the adaptation of the water temperature increase supplement coefficient and the unburned fuel increase correction coefficient to the suction negative pressure.
FIG. 46 is an air-fuel ratio characteristic diagram for explaining the adaptation of the water temperature increase supplement coefficient and the unburned fuel increase correction coefficient to the rotation speed.
FIG. 47 is a waveform diagram showing a time-series image of an unburned amount increase correction coefficient KUB of the third embodiment.
FIG. 48 is a flowchart for explaining calculation of a water temperature increase supplement coefficient KTW and an unburned component increase correction coefficient KUB of the fourth embodiment.
FIG. 49 is a characteristic diagram of a basic value of a water temperature increase complementary coefficient according to the fourth embodiment.
FIG. 50 is a characteristic diagram of a basic value of an unburned amount increase correction coefficient according to the fourth embodiment.
FIG. 51 is a flowchart for explaining calculation of a water temperature increase supplement coefficient KTW and an unburned fuel increase correction coefficient KUB according to the fifth embodiment;
FIG. 52 is a characteristic diagram of a basic value of a water temperature increase complementary coefficient according to the fifth embodiment.
FIG. 53 is a characteristic diagram of a basic value of an unburned amount increase correction coefficient according to the fifth embodiment.
FIG. 54 is a characteristic diagram of a reference adhesion magnification load term.
FIG. 55 is a characteristic diagram of a reference adhesion magnification rotation term.
FIG. 56 is a characteristic diagram of a basic quantity ratio.
FIG. 57 is a characteristic diagram of an amount ratio rotation correction factor.
FIG. 58 is a characteristic diagram of an increase gain.
FIG. 59 is a characteristic diagram of the weight loss gain.
FIG. 60 is a characteristic diagram of a basic injection pulse width at start-up.
FIG. 61 is a characteristic diagram of a rotation speed correction coefficient.
FIG. 62 is a characteristic diagram of a time correction coefficient.
FIG. 63 is a characteristic diagram of the correction rate for each cylinder.
FIG. 64 is a diagram corresponding to claims of the first invention.
FIG. 65 is a view corresponding to a claim of the second invention.
FIG. 66 is a diagram corresponding to claims of the third invention.
[Explanation of symbols]
2 ECM
3 A / F sensor
7 Fuel injection valve
14 EEPROM
15 Fuel injection amount calculation means
21 Plant Identification Department
22 Fuel property estimation part
23 Triggering function
24 controller
31 Plant model
37 normative model
38 Comparison means

Claims (18)

Means for supplying the engine with a fuel supply amount corresponding to the engine operating conditions;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the data of the response waveform of the exhaust air / fuel ratio with respect to the fuel supply amount with the currently used fuel, with the fuel supply amount being input during transition and the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
When the reference model is matched with the reference fuel, the cutoff frequency of the plant model is compared with the cutoff frequency of the reference model, and the cutoff frequency of the plant model is higher than the cutoff frequency of the reference model. When the fuel property of the fuel used is lighter than the above, and when the cutoff frequency of the plant model is lower than the cutoff frequency of the reference model, the fuel property of the fuel used is heavier than the reference fuel. Means to estimate that there is,
An engine fuel supply control device, comprising: means for calculating the fuel supply amount based on the estimation result of the fuel property. Means for supplying the engine with a fuel supply amount corresponding to the engine operating conditions;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the data of the response waveform of the exhaust air / fuel ratio with respect to the fuel supply amount with the currently used fuel, with the fuel supply amount being input during transition and the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
When the reference model is matched with the reference fuel, the difference between the cutoff frequency of the plant model and the cutoff frequency of the reference model is compared with the allowable range of the reference fuel, and the cutoff frequency of the plant model is compared. When the difference between the cut-off frequency of the reference model and the reference model is outside the allowable range of the reference fuel, and the cut-off frequency of the plant model is larger than the cut-off frequency of the reference model, the fuel property of the used fuel is higher than that of the reference fuel. If the difference between the cutoff frequency of the plant model and the cutoff frequency of the reference model is outside the allowable range of the reference fuel, and the cutoff frequency of the plant model is smaller than the cutoff frequency of the reference model, Means for estimating that the fuel property of the fuel used is heavier than the reference fuel ;
An engine fuel supply control device, comprising: means for calculating the fuel supply amount based on the estimation result of the fuel property. Means for supplying the engine with a fuel supply amount corresponding to the engine operating conditions;
Means for detecting the exhaust air-fuel ratio of the engine;
Means for sampling the data of the response waveform of the exhaust air / fuel ratio with respect to the fuel supply amount with the currently used fuel, with the fuel supply amount being input during transition and the exhaust air / fuel ratio as an output;
Based on these input / output data, means for identifying the plant model for the fuel used by adjusting the parameters of the plant model constructed in advance so that the prediction error with the reference model is small;
Means for calculating a cutoff frequency of the identified plant model;
When the reference model is matched with the reference fuel, the characteristic of the fuel property estimation value with respect to the cutoff frequency of the plant model is lighter as the cutoff frequency of the plant model becomes larger than the cutoff frequency of the reference model. And means for presetting to represent that the cut-off frequency of the plant model is heavier as the cut-off frequency of the reference model becomes smaller , and
Means for calculating a fuel property estimated value by retrieving this characteristic from the calculated cutoff frequency of the plant model ;
An engine fuel injection control device comprising: means for calculating the fuel supply amount based on the estimated fuel property value. The engine fuel supply control device according to claim 1 or 2, wherein the estimation result of the fuel property is stored in a nonvolatile memory. 4. The engine fuel supply control device according to claim 3, wherein the estimated fuel property value is stored in a nonvolatile memory. The fuel property estimation is lighter than the heavy gasoline when the identified model model has a cutoff frequency higher than the cutoff frequency of the reference model when the reference model is matched with heavy gasoline . The engine fuel supply control device according to claim 1, wherein the engine fuel supply control device is estimated to be present. The estimation of the fuel property is based on the cut-off frequency and the norm of the identified plant model when the normative model is matched with an almost intermediate fuel that is not bad or bad in volatility among commercially available fuels . The identification is also lighter than the intermediate fuel when the difference in model cutoff frequency is outside the acceptable range of the reference fuel and the plant model cutoff frequency is greater than the reference model cutoff frequency. When the difference between the cut-off frequency of the plant model and the cut-off frequency of the reference model is outside the allowable range of the reference fuel and the cut-off frequency of the plant model is smaller than the cut-off frequency of the reference model, the intermediate fuel The fuel supply control device for an engine according to claim 2, wherein the engine fuel supply is estimated to be heavy . When the fuel supply amount is composed of a basic fuel injection amount and an injection amount correction amount determined from an engine load and an engine speed, an injection amount correction amount is calculated based on the estimation result of the fuel property. The fuel supply control device for an engine according to claim 1 or 2. The fuel injection amount correction amount is calculated based on the estimated fuel property value when the fuel supply amount includes a basic fuel injection amount and an injection amount correction amount determined from an engine load and a rotational speed. Item 4. The fuel supply control device for an engine according to Item 3. 10. The engine fuel supply control device according to claim 8, wherein the injection amount correction amount is a post-startup increase correction amount. The engine fuel supply control device according to claim 8 or 9, wherein the injection amount correction amount is a water temperature increase correction amount. The engine fuel supply control device according to claim 8 or 9, wherein the injection amount correction amount is an unburned amount increase correction amount. The engine fuel supply control device according to claim 8 or 9, wherein the injection amount correction amount is a wall flow correction amount. The engine fuel supply control device according to claim 13, wherein the wall flow correction amount is a low-frequency component. The engine fuel supply control device according to claim 13, wherein the wall flow correction amount is a high-frequency component. The engine fuel supply control device according to any one of claims 1 to 3, wherein the fuel supply amount is an injection amount at start-up. The engine fuel supply control device according to any one of claims 1 to 3, wherein the fuel supply amount is an acceleration interrupt injection amount. The engine fuel supply control according to any one of claims 1 to 17, wherein adjusting the prediction error to be small is adjusting the prediction error to be a minimum. apparatus.

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