JP3591270B2

JP3591270B2 - Fuel injection amount control device for multi-cylinder internal combustion engine

Info

Publication number: JP3591270B2
Application number: JP01573098A
Authority: JP
Inventors: 善明渥美
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 1998-01-28
Filing date: 1998-01-28
Publication date: 2004-11-17
Anticipated expiration: 2018-01-28
Also published as: JPH11210523A

Description

【０００１】
【発明の属する技術分野】
本発明は多気筒内燃機関の燃料噴射量制御装置に関し、特に、複数の気筒群毎に設けられた排気通路にそれぞれ空燃比センサが配設され、これら空燃比センサの各出力に応じて機関から排出される排気ガスの空燃比を目標空燃比に一致するように制御する空燃比Ｆ／Ｂ（フィードバック）制御系を複数有し、機関が加速状態のときに所望の気筒へ燃料噴射量を過不足なく供給する多気筒内燃機関の燃料噴射量制御装置に関する。
【０００２】
【従来の技術】
多気筒内燃機関には、複数の気筒を複数の気筒群に分け、気筒群をなすバンク毎に空燃比Ｆ／Ｂ制御を行うものがある。例えばＶ６、Ｖ８等の多気筒内燃機関の場合、複数の気筒を２つのバンクに分け、バンク毎に排気通路を設け、各排気通路にそれぞれ空燃比センサを配設し、各空燃比センサの出力に基づき各バンクに対応した各系統の空燃比Ｆ／Ｂ制御を行っている。
【０００３】
このような複数系統の空燃比Ｆ／Ｂ制御を行う、例えば特開昭５９−１６２３３３号公報に開示された多気筒内燃機関の燃料噴射制御方法は、機関の運転状態に基づいて、例えば機関の回転数ＮＥと吸入空気量ＧＡとから基本燃料噴射量ＴＰを算出し、各空燃比Ｆ／Ｂ制御系の各空燃比センサの出力に基づいて該各空燃比センサにより検出される各空燃比を目標空燃比に一致するように各空燃比Ｆ／Ｂ制御系に属する気筒への各空燃比Ｆ／Ｂ補正係数ＦＡＦをそれぞれ算出し、基本燃料噴射量ＴＰ、各空燃比Ｆ／Ｂ制御系の空燃比Ｆ／Ｂ補正係数ＦＡＦ等に基づいて所定のクランク角に合わせて同期噴射する同期燃料噴射量ＴＡＵを下式から算出し、その同期燃料噴射量を当該気筒へ噴射するよう制御する。
【０００４】
ＴＡＵ＝ＴＰ＊ＦＷＬ＊ＦＡＥ＊α＊（ＦＡＦ＋ＦＧ）＋Ｔｓ
ここで、ＦＷＬは冷間暖機増量補正分、ＦＡＥは加速時に増量される燃料付着補正分、ＦＧは空燃比学習補正係数、αはその他の補正係数、Ｔｓは無効噴射時間である。したがって、同期燃料噴射量ＴＡＵは、空燃比Ｆ／Ｂ制御系に関わらず機関の要求に応じてＴＰ、ＦＷＬ、ＦＡＥおよびαから算出される機関の要求燃料噴射量ＴＡＵＢと空燃比Ｆ／Ｂ制御系毎にＦＡＦおよびＦＧから算出される空燃比補正燃料噴射量ＴＡＵＣとの積と、無効噴射時間Ｔｓとの和として算出される。
【０００５】
また、上記燃料噴射制御方法は、今回同期燃料噴射量が前回同期燃料噴射量より所定量以上増加したとき機関は加速状態にあると判定し、これら同期燃料噴射量の差に応じて加速時に増量する加速補正燃料噴射量を算出し、その加速補正燃料噴射量を吸気行程にある気筒へ噴射するよう制御する。
【０００６】
【発明が解決しようとする課題】
しかしながら、上記特開昭５９−１６２３３３号公報に開示された燃料噴射制御方法は、前回と今回の同期燃料噴射量ＴＡＵを上式から算出し、これらの差から機関の加速状態を判定しているので、前回と今回で燃料噴射する気筒が互いに別系統の空燃比制御系に属するとき、上記空燃比補正燃料噴射量ＴＡＵＣが、前回同期燃料噴射量算出時に減量補正され今回同期燃料噴射量算出時に増量補正されるような前回と今回の空燃比補正燃料噴射量の差が大きい場合、機関が加速状態でないにも関わらず機関は加速状態であると判定してしまい、その差に応じた加速燃料噴射量を今回吸気行程にある噴射終了した気筒に再噴射を実行するので、特に機関が軽負荷のときオーバーリッチとなりエミッションが悪化するという問題が生じる。一方、上記空燃比補正燃料噴射量ＴＡＵＣが、前回同期燃料噴射量算出時に増量補正され今回同期燃料噴射量算出時に減量補正されるような前回と今回の空燃比補正燃料噴射量の差が小さい場合、機関が加速状態であるにも関わらず機関は加速状態でないと判定してしまい、上記再噴射を実行しないので、特に機関が高負荷のときオーバーリーンとなり加速応答性が悪化するという問題がある。
【０００７】
それゆえ、本発明は上記問題を解決し、気筒群毎に設けられた排気通路にそれぞれ配設される空燃比センサの各出力に応じて機関から排出される排気ガスの空燃比を目標空燃比に一致するように制御する空燃比Ｆ／Ｂ制御系を複数有する多気筒内燃機関の燃料噴射量制御装置において、特に機関が加速状態のときに所望の気筒へ燃料噴射量を過不足なく供給する多気筒内燃機関の燃料噴射量制御装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記問題を解決する本発明による多気筒内燃機関の燃料噴射量制御装置は、多気筒内燃機関の気筒群毎に設けられた排気通路にそれぞれ配設される空燃比センサと、該機関の運転状態に基づいて要求燃料噴射量ＴＡＵＢを算出し、該空燃比センサの各出力に基づいて該各空燃比センサにより検出される各空燃比を目標空燃比に一致するように当該気筒へ噴射する前記要求燃料噴射量ＴＡＵＢを補正する各空燃比補正燃料噴射量ＴＡＵＣをそれぞれ算出し、該要求燃料噴射量ＴＡＵＢと該各空燃比補正燃料噴射量ＴＡＵＣとに基づいて所定のクランク角に合わせて同期噴射する同期燃料噴射量ＴＡＵを算出し、当該気筒へ該同期燃料噴射量ＴＡＵを噴射するよう制御する同期燃料噴射手段と、を備えた多気筒内燃機関の燃料噴射量制御装置において、前記内燃機関の加速状態を検出する加速検出手段と、前記加速検出手段により前記内燃機関の加速状態を検出したとき、前回同期噴射を実行した気筒と今回同期噴射を実行する気筒の各要求燃料噴射量の差ΔＴＡＵＢｉ（＝ＴＡＵＢｉ −ＴＡＵＢ）に基づいて加速燃料噴射量ΔＴＡＵＢｉ＊Ｋ_１（Ｋ_１は補正係数）を算出する加速燃料算出手段と、前記算出された加速燃料噴射量を噴射する加速燃料噴射手段と、を備えたことを特徴とする。
【０００９】
本発明による多気筒内燃機関の燃料噴射量制御装置において、前記加速検出手段による加速検出は、前回同期噴射を実行した気筒と今回同期噴射を実行する気筒の各要求燃料噴射量の差から検出される。
上記構成により、別系統の空燃比Ｆ／Ｂ制御系の影響を受けないように機関の加速状態を判定するので、機関の加速判定が正確となり、機関が実際に加速状態のときに適量の加速増量補正を行い、機関が実際には加速状態でないときに不必要な加速増量補正を行わないよう燃料が供給される。
【００１０】
【発明の実施の形態】
図１は本発明による多気筒内燃機関の燃料噴射量制御装置の一実施形態を示す概略図である。図１において、２１はそれぞれ４つのシリンダがＶ字型に２列に配置された構成のＶ型８気筒機関の本体を示す。機関本体２１の吸気通路２２にはエアフローメータ２３が設けられている。エアフローメータ２３は吸入空気量を直接計測するものであって、たとえばポテンショメータを内蔵した可動ベーン式エアフローメータ等が使用され、吸入空気量に比例したアナログ電圧の出力信号を発生する。この出力信号はＥＣＵ（電子制御ユニット）３０のマルチプレクサ内蔵Ａ／Ｄ変換器１０１に入力されている。ディストリビュータ２４には、機関２１のクランクシャフト２回転（７２０°ＣＡ）毎の１番気筒の圧縮行程の上死点ＴＤＣ付近と、この上死点から３６０°ＣＡの位相差をもつ４番気筒の圧縮行程の上死点ＴＤＣ付近とにおいて、各気筒の噴射時期と点火時期を決定するために基準となる２つの基準位置検出用パルス信号を発生するクランク角センサ２５Ａおよびクランク角に換算して３０°毎にクランク角検出用パルス信号を発生するクランク角センサ２５Ｂがそれぞれ設けられている。これらクランク角センサ２５Ａ、２５Ｂのパルス信号はＥＣＵ３０の入出力インターフェイス１０２に供給され、このうちクランク角センサ２５Ｂの出力はＣＰＵ１０３の割込み端子に供給されている。また、気筒判別は基準位置検出用パルス信号を２つ用いて機関２１の始動が開始されてからクランクシャフトが２回転する間に行われる。
【００１１】
また機関２１の吸気管内には吸気管内の圧力を検出する吸気圧センサ２６が設けられ、吸気圧センサ２６はこの吸気圧に比例したアナログ電圧の電気信号を発生し、この出力もＡ／Ｄ変換器１０１に供給されている。
さらに、吸気通路２２には各気筒毎に燃料供給系から加圧燃料を吸気ポートへ供給するための燃料噴射弁２７Ａ、２７Ｂが設けられている。
【００１２】
また、機関２１のシリンダブロックのウォータジャケット（図示せず）には、冷却水の温度を検出するための水温センサ２９が設けられている。水温センサ２９は冷却水の温度に応じたアナログ電圧の電気信号を発生する。この出力もＡ／Ｄ変換器１０１に供給されている。
機関２１の右バンク（以下、Ａバンクという）及び左バンク（以下Ｂバンクという）の排気マニホールド３１Ａ、３１Ｂより下流の排気系には、それぞれ排気ガス中の３つの有害成分ＨＣ、ＣＯ、ＮＯ_Ｘを同時に浄化する三元触媒を収容する触媒コンバータ３２Ａ、３２Ｂが設けられている。この触媒コンバータ（スタートキャタリスト）３２Ａ、３２Ｂは機関始動時の触媒暖機を短時間で行えるように、比較的小容量とされ、エンジンルーム内に設けられている。
【００１３】
Ａバンクの排気マニホールド３１Ａには、すなわち触媒コンバータ３２Ａの上流側の排気管３１ＡにはＡバンク用の第１空燃比センサ３３Ａが設けられ、またＢバンクの排気マニホールド３１Ｂには、すなわち触媒コンバータ３２Ｂの上流側の排気管３１Ｂには同様にＢバンク用の第１空燃比センサ３３Ｂが設けられている。
【００１４】
さらに、２つの排気管３４Ａ、３４Ｂはその下流において集合部３５ａにおいて合流しており、この集合部３５ａ下流側の排気管には三元触媒を収容する触媒コンバータ（メインキャタリスト）３６が配置されている。この触媒コンバータ３６は比較的容量が大きく、車体の床下に設置されている。触媒コンバータ３６の下流側には集合排気管３５が連結されている。また、２つの排気管３４Ａ、３４Ｂには好ましくはそれぞれＡバンク、Ｂバンク用の第２空燃比センサ３７Ａ、３７Ｂが設けられている。
【００１５】
本実施例では、第１空燃比センサ３３Ａ、３３Ｂとしては、排気中の酸素成分濃度と広い空燃比範囲で一対一に対応する、つまり排気空燃比と一対一に対応する出力信号を発生するリニア型の全域空燃比センサ（Ａ／Ｆセンサ）が使用されている。第１空燃比センサ３３Ａ、３３Ｂは、機関２１の排気ガスに含まれる酸素濃度と略比例する出力電圧を発生し、この出力電圧はＥＣＵ３０のＡ／Ｄ変換器１０１に供給されている。一方、第２空燃比センサ３７Ａ、３７Ｂとしては、排気中の酸素成分濃度がリッチのときとリーンのときとで出力が反転するラムダ型の空燃比センサ（Ａ／Ｆセンサ）が使用されている。
【００１６】
本実施例では、ＥＣＵ３０は、たとえばマイクロコンピュータとして構成され、Ａ／Ｄ変換器１０１、入出力（Ｉ／Ｏ）インターフェイス１０２、ＣＰＵ１０３の他に、ＲＯＭ１０４、ＲＡＭ１０５、バックアップＲＡＭ１０６、クロック発生回路１０７等が設けられている。ＥＣＵ３０は、機関２１の燃料噴射制御、点火時期制御、空燃比制御等の基本制御を行う他、後述する本発明による加速時の燃料噴射量の補正制御、すなわち前回同期噴射を実行した気筒と今回同期噴射を実行する気筒の各要求燃料噴射量の差から機関の加速状態を検出する加速検出手段、および前記差に基づいて、加速燃料噴射量を算出する加速燃料算出手段、今回同期噴射時に加速燃料噴射量を噴射する加速燃料噴射手段、として機能する。
【００１７】
ここで、「今回同期噴射」や「前回同期噴射」で使用する「今回」および「前回」は、例えば機関の運転状態から算出された同期燃料噴射量を機関のクランク角に同期して噴射する気筒を「今回」に同期噴射する気筒、すなわち今回同期噴射気筒と位置づけて定義し、その今回同期噴射気筒を基準として、今回噴射する気筒の１つ前の「前回」に同期噴射した、既に同期燃料噴射が完了している気筒を前回同期噴射気筒と定義する。
【００１８】
また、吸気通路２２のスロットル弁３８には、スロットル弁３８が全閉状態か否かを示す信号、すなわちＸＩＤＬ信号を発生するアイドルスイッチ３９が設けられている。このアイドル状態出力信号ＸＩＤＬはＥＣＵ３０の入出力インターフェイス１０２に供給される。
さらに４０Ａ、４０Ｂは２次空気導入制御弁であって、減速時あるいはアイドル時に図示しないエアポンプ等の空気源から２次空気を排気マニホルド３１Ａ、３１Ｂに供給して、ＨＣ、ＣＯエミッションを低減するためのものである。
【００１９】
さらに、ＥＣＵ３０において、ダウンカウンタ１０８Ａ、フリップフロップ１０９Ａ、および駆動回路１１０ＡはＡバンクの燃料噴射弁２７Ａを制御するためのものであり、ダウンカウンタ１０８Ｂ、フリップフロップ１０９Ｂ、駆動回路１１０ＢはＢバンクの燃料噴射弁２７Ｂを制御するためのものである。すなわち、後述のルーチンにおいて、同期燃料噴射量（噴射時間）ＴＡＵ_（Ａ）（ＴＡＵ_（Ｂ））が演算されると、噴射時間ＴＡＵ_（Ａ）（ＴＡＵ_（Ｂ））がダウンカウンタ１０８Ａ（１０８Ｂ）にプリセットされると共にフリップフロップ１０９Ａ（１０９Ｂ）もセットされる。この結果、駆動回路１１０Ａ（１１０Ｂ）が燃料噴射弁２７Ａ（２７Ｂ）の付勢を開始する。他方、ダウンカウンタ１０８Ａ（１０８Ｂ）がクロック信号（図示せず）を計数して最後にその出力端子が“１”レベルとなったときに、フリップフロップ１０９Ａ（１０９Ｂ）がセットされて駆動回路１１０Ａ（１１０Ｂ）は燃料噴射弁２７Ａ（２７Ｂ）の付勢を停止する。つまり、上述の噴射時間ＴＡＵ_（Ａ）（ＴＡＵ_（Ｂ））だけ燃料噴射弁２７Ａ（２７Ｂ）は付勢され、時間ＴＡＵ_（Ａ）（ＴＡＵ_（Ｂ））に応じた量の燃料が機関２１のＡバンク（Ｂバンク）燃焼室に送り込まれることになる。なお、ＣＰＵ１０３の割込みは、Ａ／Ｄ変換器１０１のＡ／Ｄ変換終了後、入出力インターフェイス１０２がクランク角センサ２５Ｂのパルス信号を受信した時、等に発生する。
【００２０】
エアフローメータ２３の吸入空気量データ、吸気圧センサ２６の吸気圧データおよび水温センサ２９の冷却水温データは所定時間もしくは所定クランク角毎に実行されるＡ／Ｄ変換ルーチンによって取込まれてＲＡＭ１０５の所定領域に格納される。つまり、ＲＡＭ１０５における吸入空気量データ、吸気圧データおよび冷却水温データは所定時間毎に更新されている。また、回転速度データはクランク角センサ２５Ｂの３０°ＣＡ（クランク角）毎の割込みによって演算されてＲＡＭ１０５の所定領域に格納される。
【００２１】
次に、本発明による燃料噴射量の制御についてタイムチャートとフローチャートとを用いて以下に説明する。
図２はＶ型８気筒機関における加速時の燃料噴射量制御の説明図である。図２において横軸は時間を示し、縦軸上段の＃に続く数字は噴射および点火気筒の順番を示し、縦軸下段は時刻ｔ_１に加速が開始され変化する同期燃料噴射量ＴＡＵを示す。図２に示すように、Ｖ型８気筒機関では、＃１、＃３、＃５、＃７からなるＡバンクと＃２、＃４、＃６、＃８からなるＢバンクの噴射および点火の順序が、＃１、＃８、＃４、＃３、＃６、＃５、＃７、＃２となっている。図２の上段において、黒帯で示す部分は同期噴射による各気筒の燃料噴射弁の開弁時期を示し、ハッチング（左上から右下への斜線）で示す部分は各気筒の吸気弁の開弁時期を示し、長円で囲まれた中にハッチング（右上から左下への斜線）で示す部分は加速燃料噴射時期を示す。
【００２２】
図３は燃料噴射量算出ルーチンのフローチャートである。図３に示す燃料噴射量算出ルーチンは機関始動後の同期燃料噴射量（ＴＡＵ）を算出するものである。機関始動時の同期燃料噴射量（ＴＡＵＳＴ）は別のルーチンで算出され、機関運転開始後所定の回転数、例えば４００ＲＰＭに到達するまでＴＡＵＳＴが噴射され、４００ＲＰＭ到達以降図３示すルーチンにより算出されたＴＡＵが噴射される。本ルーチンはメインルーチンの中で実行される。
【００２３】
先ずステップＳ３１では機関の運転状態を示す各種信号入力データ、すなわち回転数ＮＥ、吸入空気量ＧＡ、冷却水温ＴＨＷ、スロットル開度ＴＡ、吸気温ＴＨ、等のデータを読み取る。ステップ３２ではステップ３１で読み取った機関の回転数ＮＥと吸入空気量ＧＡのデータに基づきＲＯＭ１０４に格納されている二次元マップから基本燃料噴射量ＴＰを算出する。ステップ３３では冷却水温ＴＨＷ、スロットル開度ＴＡ、吸気温ＴＨ、等により定まる冷間暖機増量補正係数ＦＷＬ、加速時に増量される燃料付着補正係数ＦＡＥおよびその他の補正係数αをそれぞれ算出する。次いで、ステップ３４ではバッテリ電圧ＢＡに基づきＲＯＭ１０４に格納されているマップから無効噴射時間Ｔｓを算出する。
【００２４】
次にステップ３５では空燃比Ｆ／Ｂ制御系毎に、公知の空燃比補正係数算出ルーチンで演算される空燃比補正係数ＦＡＦ_（Ａ）（ＦＡＦ_（Ｂ））および空燃比Ｆ／Ｂ制御の休止中に生じる空燃比のずれ量を補正する空燃比学習補正係数ＦＧ_（Ａ）（ＦＧ_（Ｂ））を読み取る。ここで、ＦＡＦ，ＦＧに続く添字はバンクＡまたはバンクＢを示す。空燃比補正係数ＦＡＦ_（Ａ）（ＦＡＦ_（Ｂ））は第１空燃比センサ３３Ａ（３３Ｂ）の出力値に応じて機関の空燃比が目標空燃比になるように機関へ供給する燃料噴射量を算出するためのフィードバック補正係数であり、空燃比学習補正係数ＦＧ_（Ａ）（ＦＧ_（Ｂ））は空燃比Ｆ／Ｂ制御の休止中に生じる空燃比のずれ量を補正するための補正係数である。ステップ３６ではステップ３２で算出した基本燃料噴射量ＴＰ、ステップ３３で算出した補正係数ＦＷＬ、ＦＡＥ、α、ステップ３４で算出した無効噴射時間Ｔｓおよびステップ３５で読取った空燃比補正係数ＦＡＦ_（Ａ）（ＦＡＦ_（Ｂ））および空燃比学習補正係数ＦＧ_（Ａ）（ＦＧ_（Ｂ））を用いて次式から始動後の同期燃料噴射量ＴＡＵ_（Ａ）（ＴＡＵ_（Ｂ））を算出する。
【００２５】
ＴＡＵ_（Ａ）＝ＴＰ＊ＦＷＬ＊ＦＡＥ＊α＊（ＦＡＦ_（Ａ）＋ＦＧ_（Ａ））＋Ｔｓ
ＴＡＵ_（Ｂ）＝ＴＰ＊ＦＷＬ＊ＦＡＥ＊α＊（ＦＡＦ_（Ｂ）＋ＦＧ_（Ｂ））＋Ｔｓ
上式から、機関のクランク角に応じて同期噴射される同期燃料噴射量ＴＡＵ_（Ａ）（ＴＡＵ_（Ｂ））は、空燃比Ｆ／Ｂ制御系に関わらず機関の要求に応じてＴＰ、ＦＷＬ、ＦＡＥおよびαから算出される機関の要求燃料噴射量ＴＡＵＢと空燃比Ｆ／Ｂ制御系毎にＦＡＦ_（Ａ）（ＦＡＦ_（Ｂ））およびＦＧ_（Ａ）（ＦＧ_（Ｂ））から算出される空燃比補正燃料噴射量ＴＡＵＣ_（Ａ）（ＴＡＵＣ_（Ｂ））との積と無効噴射時間Ｔｓとの和に基づき算出されることが判る。
【００２６】
図４は本発明の燃料噴射ルーチンのフローチャートである。本発明の燃料噴射ルーチンは、クランク角センサ２５Ｂから入出力インターフェイス１０２に入力されるパルス信号を受信する毎に、すなわち３０°ＣＡ毎に実行される。この３０°ＣＡ割込ルーチンの実行はイグニッションスイッチがオンとなったとき開始され、オフとなったとき終了される。先ず、ステップ４０１では、気筒判別が終了したか否かを判定する。すなわち、スタータスイッチをオンにして機関を始動開始した後、クランク角基準センサ２５Ａから出力される２つのパルス信号を受け、クランク軸が２回転して気筒判別が終了したか否かを判定する。３０°ＣＡ割込ルーチンの実行が開始された後、未だ気筒判別が未終了と判定されたときはこの３０°ＣＡ割込ルーチン、すなわち本燃料噴射ルーチンを終了し、気筒判別が終了したと判定されたときからは、ステップ４０２へ進む。
【００２７】
ステップ４０２では、気筒が噴射時期であるか否かをクランク角基準センサ２５Ａとクランク角センサ２５Ｂとから検出して判定し、その判定結果がＹＥＳのときはステップ４０３へ、その判定結果がＮＯのときは本燃料噴射ルーチンを終了する。ステップ４０３では、機関の要求燃料噴射量ＴＡＵＢを次式から算出する。
【００２８】
ＴＡＵＢ＝ＴＰ＊ＦＷＬ＊ＦＡＥ＊α
ステップ４０４では、本ルーチンの前回処理周期の要求燃料噴射量ＴＡＵＢｉに対する今回処理周期の要求燃料噴射量ＴＡＵＢの差分ΔＴＡＵＢｉ（＝ＴＡＵＢｉ −ＴＡＵＢ）を算出する。
ステップ４０５では、ステップ４０４で算出された差分ΔＴＡＵＢｉが所定量Ａより大か否かを判別することにより機関の運転状態が加速状態であるか否かを判定する。すなわち、ΔＴＡＵＢｉ＞Ａのときは機関は加速状態にあるものと判定してステップ４０６へ進み、ΔＴＡＵＢｉ ≦Ａのときは機関は加速状態にないものと判定して本ルーチンを終了する。
【００２９】
ステップ４０６では、ステップ４０４で算出された差分ΔＴＡＵＢｉから燃料噴射弁の性能上最低必要な燃料噴射弁の開弁時間を確保できるか否かを判定し、ΔＴＡＵＢｉ＊Ｋ_１≧Ｂ（Ｂは無効噴射時間Ｔｓ）のときは上記開弁時間を確保できるものと判定してステップ４０７へ進み、ΔＴＡＵＢｉ＊Ｋ_１＜Ｂのときは上記開弁時間を確保できないものと判定して本ルーチンを終了する。ここで、Ｋ_１は再噴射する加速燃料噴射量ΔＴＡＵＢｉ−１の補正係数であり、任意の値、例えば１／２に設定する。
【００３０】
ステップ４０７では、前回処理周期で同期噴射を実行済の気筒で再噴射される加速燃料噴射量ΔＴＡＵＢｉ−１を次式から算出する。
ΔＴＡＵＢｉ−１＝ΔＴＡＵＢｉ＊Ｋ_１
ステップ４０８では、前回に同期噴射済の気筒で再噴射の実行を行う。具体的には、図２に示すように、時刻ｔ_２において、今回の同期噴射気筒が７番気筒（＃７）のときは、前回の同期噴射気筒である５番気筒（＃５）で加速燃料噴射量ΔＴＡＵＢｉ−１を噴射し、時刻ｔ_３において、今回の同期噴射気筒が２番気筒（＃２）のときは、前回の同期噴射気筒である７番気筒（＃７）で加速燃料噴射量ΔＴＡＵＢｉ−１を噴射する。
【００３１】
ステップ４１０では、ステップ４０７で算出された前回の同期噴射気筒への加速燃料噴射量ΔＴＡＵＢｉ−１から燃料噴射弁の性能上最低必要な燃料噴射弁の開弁時間を確保できるか否かを判定し、ΔＴＡＵＢｉ−１＊Ｋ_２≧Ｂ（Ｂは無効噴射時間Ｔｓ）のときは上記開弁時間を確保できるものと判定してステップ４１１へ進み、ΔＴＡＵＢｉ−１＊Ｋ_２＜Ｂのときは上記開弁時間を確保できないものと判定して本ルーチンを終了する。ここで、Ｋ_２は再噴射する加速燃料噴射量ΔＴＡＵＢｉ−２の補正係数であり、任意の値、例えば１／２に設定する。
【００３２】
ステップ４１１では、前々回処理周期で同期噴射を実行済の気筒で再噴射される加速燃料噴射量ΔＴＡＵＢｉ−２を次式から算出する。
ΔＴＡＵＢｉ−２＝ΔＴＡＵＢｉ−１＊Ｋ_２（ΔＴＡＵＢｉ−２＜ΔＴＡＵＢｉ−１）ステップ４１２では、前々回に同期噴射済みの気筒で再噴射の実行を行う。具体的には、図２に示すように、時刻ｔ_２において今回の同期噴射気筒が７番気筒（＃７）のときは、前々回の同期噴射気筒である６番気筒（＃６）で加速燃料噴射量ΔＴＡＵＢｉ−２を噴射し、時刻ｔ_３において、今回の同期噴射気筒が２番気筒（＃２）のときは、前々回の同期噴射気筒である５番気筒（＃５）で加速燃料噴射量ΔＴＡＵＢｉ−２を噴射する。
【００３３】
ステップ４１３では、図２に示すように今回噴射気筒、例えば＃７気筒や、＃２気筒による同期噴射の実行を行う。この今回噴射気筒＃７や＃２による同期燃料噴射量ＴＡＵは、図３を用いて説明した燃料噴射量算出ルーチンの実行により求められたものを使用する。
次いで、ステップ４１４では、ステップ４０３で算出した機関の要求燃料噴射量ＴＡＵＢを前回処理周期の要求燃料噴射量ＴＡＵＢｉに設定する。
【００３４】
なお、上記実施形態以外の機関の加速状態を検出する方法として、機関における、吸入空気量、スロットル開度、回転数、アクセル踏込量等の値から検出する方法を用いてもよい。
また、上記実施形態では、加速燃料を今回の同期噴射と同期して、吸気行程にある気筒、かつ／または吸気行程直前の気筒に噴射する例を示したが、この他に、非同期的に吸気行程にある気筒、かつ／または吸気行程直前の気筒に加速燃料の噴射を実行してもよい。また、各気筒に噴射される加速燃料は各気筒の吸気行程が終了する時間（吸気弁が閉弁するまでの時間）に応じて算出された加速燃料量を減量補正してもよい。
【００３５】
以上、Ｖ型機関を例にとって本発明による燃料噴射制御を説明したが、本発明は空燃比フィードバック制御系を複数設けた直列気筒機関に対しても上記と同様に適用できる。例えば、直列４気筒機関において、＃１と＃４からなる気筒群Ａと＃２と＃３からなる気筒群Ｂがそれぞれ個別の排気管に接続され、各排気管に触媒コンバータが配設され、その触媒コンバータの上流側空燃比センサと好ましくは下流側空燃比センサとが設けられ、これら空燃比センサの出力に基づき各気筒群に対応した各系統の空燃比Ｆ／Ｂ制御を行うとき、噴射気筒の順番が＃１、＃４、＃２、＃３であるので、＃４気筒の噴射後＃２気筒が噴射されるときや、＃３気筒の噴射後＃１気筒が噴射されるときは、前回噴射気筒と今回噴射気筒とは空燃比制御系が異なる。このような直列４気筒機関においても、上述した本発明による燃料噴射量制御を適用すれば、加速増量補正を過不足なく行うことができる。
【００３６】
【発明の効果】
以上説明したように、本発明の多気筒内燃機関の燃料噴射量制御装置によれば、気筒群毎に空燃比Ｆ／Ｂ制御系を複数有する多気筒内燃機関の燃料噴射量制御装置において、空燃比Ｆ／Ｂ制御系とは無関係に機関の加速状態を判定するので、前回噴射気筒と今回噴射気筒とが異なる空燃比制御系のときでも機関の加速状態の判定を正確に行うことができ、空燃比Ｆ／Ｂ制御系とは無関係に機関の加速燃料噴射量を算出するので、機関の加速時に過不足のない燃料噴射量を供給でき、特に、空燃比がリッチのときの加速時における排気エミッションの悪化が抑制でき、空燃比がリーンのときの加速時における加速応答性を向上できる。
【図面の簡単な説明】
【図１】本発明による多気筒内燃機関の燃料噴射量制御装置の一実施形態を示す概略図である。
【図２】Ｖ型８気筒機関における加速時の燃料噴射量制御の説明図である。
【図３】燃料噴射量算出ルーチンのフローチャートである。
【図４】本発明の燃料噴射ルーチンのフローチャートである。
【符号の説明】
２１…機関
２３…エアフローメータ
２５Ａ、２５Ｂ…クランク角センサ
２７Ａ、２７Ｂ…燃料噴射弁
２９…水温センサ
３０…電子制御ユニット（ＥＣＵ）
３１Ａ、３１Ｂ…排気管
３２Ａ、３２Ｂ、３６…触媒コンバータ
３３Ａ、３３Ｂ…第１空燃比センサ
３７Ａ、３７Ｂ…第２空燃比センサ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection amount control device for a multi-cylinder internal combustion engine, and in particular, an air-fuel ratio sensor is provided in each of exhaust passages provided for each of a plurality of cylinder groups, and the engine is controlled in accordance with each output of these air-fuel ratio sensors. It has a plurality of air-fuel ratio F / B (feedback) control systems for controlling the air-fuel ratio of the exhaust gas to be exhausted so as to match the target air-fuel ratio. The present invention relates to a fuel injection amount control device for a multi-cylinder internal combustion engine that supplies a sufficient amount.
[0002]
[Prior art]
Some multi-cylinder internal combustion engines divide a plurality of cylinders into a plurality of cylinder groups and perform air-fuel ratio F / B control for each bank forming the cylinder groups. For example, in the case of a multi-cylinder internal combustion engine such as V6 or V8, a plurality of cylinders are divided into two banks, an exhaust passage is provided for each bank, an air-fuel ratio sensor is provided in each exhaust passage, and an output of each air-fuel ratio sensor is provided. , The air-fuel ratio F / B control of each system corresponding to each bank is performed.
[0003]
A fuel injection control method for a multi-cylinder internal combustion engine that performs such air-fuel ratio F / B control of a plurality of systems, for example, disclosed in Japanese Patent Application Laid-Open No. 59-162333, is based on the operating state of the engine. A basic fuel injection amount TP is calculated from the rotational speed NE and the intake air amount GA, and each air-fuel ratio detected by each air-fuel ratio sensor based on the output of each air-fuel ratio sensor of each air-fuel ratio F / B control system is calculated. An air-fuel ratio F / B correction coefficient FAF for each cylinder belonging to each air-fuel ratio F / B control system is calculated to match the target air-fuel ratio, and the basic fuel injection amount TP and the air-fuel ratio F / B control system are calculated. Based on the air-fuel ratio F / B correction coefficient FAF or the like, a synchronous fuel injection amount TAU for synchronous injection in accordance with a predetermined crank angle is calculated from the following equation, and control is performed so that the synchronous fuel injection amount is injected into the cylinder.
[0004]
TAU = TP * FWL * FAE * α * (FAF + FG) + Ts
Here, FWL is a correction amount for increasing the amount of cold warm-up, FAE is a correction amount for increasing the amount of fuel attached during acceleration, FG is a correction coefficient for learning the air-fuel ratio, α is another correction coefficient, and Ts is an invalid injection time. Accordingly, the synchronous fuel injection amount TAU is calculated from the TP, FWL, FAE, and α according to the engine request, regardless of the air-fuel ratio F / B control system. It is calculated as the sum of the product of the air-fuel ratio corrected fuel injection amount TAUC calculated from FAF and FG for each system and the invalid injection time Ts.
[0005]
Further, the fuel injection control method determines that the engine is in an accelerating state when the current synchronous fuel injection amount has increased by a predetermined amount or more from the previous synchronous fuel injection amount, and increases the amount during acceleration according to the difference between these synchronous fuel injection amounts. Then, the acceleration correction fuel injection amount to be calculated is calculated, and the acceleration correction fuel injection amount is controlled so as to be injected into the cylinder in the intake stroke.
[0006]
[Problems to be solved by the invention]
However, in the fuel injection control method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 59-162333, the previous and current synchronous fuel injection amounts TAU are calculated from the above equation, and the acceleration state of the engine is determined from the difference between the two. Therefore, when the cylinders that inject fuel in the previous time and the current time belong to different air-fuel ratio control systems, the air-fuel ratio corrected fuel injection amount TAUC is reduced and corrected at the time of the previous synchronous fuel injection amount calculation, and at the time of the current synchronous fuel injection amount calculation. If the difference between the previous and current air-fuel ratio corrected fuel injection amounts at which the increase is corrected is large, the engine is determined to be in an accelerated state even though the engine is not in an accelerated state. Since the re-injection is performed for the cylinder whose injection amount has been completed during the current intake stroke, there is a problem that the engine becomes over-rich and the emission deteriorates, especially when the engine is lightly loaded. On the other hand, when the difference between the previous and current air-fuel ratio corrected fuel injection amounts is small such that the air-fuel ratio corrected fuel injection amount TAUC is increased when the previous synchronous fuel injection amount is calculated and reduced when the current synchronous fuel injection amount is calculated. In spite of the fact that the engine is in an accelerating state, it is determined that the engine is not in an accelerating state, and the re-injection is not executed. Therefore, there is a problem that the engine becomes over-lean and the acceleration responsiveness is deteriorated particularly when the engine is under a high load. .
[0007]
Therefore, the present invention solves the above-described problem, and changes the air-fuel ratio of the exhaust gas discharged from the engine in accordance with each output of the air-fuel ratio sensors provided in the exhaust passages provided for each cylinder group to the target air-fuel ratio. In a fuel injection amount control device for a multi-cylinder internal combustion engine having a plurality of air-fuel ratio F / B control systems for controlling the fuel injection amount to be equal to, the fuel injection amount is supplied to a desired cylinder without excess or deficiency, particularly when the engine is in an accelerating state. An object of the present invention is to provide a fuel injection amount control device for a multi-cylinder internal combustion engine.
[0008]
[Means for Solving the Problems]
A fuel injection amount control apparatus for a multi-cylinder internal combustion engine according to the present invention that solves the above-described problems includes an air-fuel ratio sensor disposed in an exhaust passage provided for each cylinder group of the multi-cylinder internal combustion engine, and an operating state of the engine. The required fuel injection amount TAUB is calculated on the basis of the air-fuel ratio sensor, and each air-fuel ratio detected by each air-fuel ratio sensor is injected to the corresponding cylinder so as to match the target air-fuel ratio based on each output of the air-fuel ratio sensor. Each air-fuel ratio corrected fuel injection amount TAUC for correcting the fuel injection amount TAUB is calculated, and synchronous injection is performed at a predetermined crank angle based on the required fuel injection amount TAUB and the air-fuel ratio corrected fuel injection amount TAUC. A synchronous fuel injection means for calculating the synchronous fuel injection amount TAU and controlling the injection of the synchronous fuel injection amount TAU to the cylinder; Acceleration detection means for detecting the acceleration state of the internal combustion engine; and, when the acceleration detection means detects the acceleration state of the internal combustion engine, a request for a cylinder that has previously executed synchronous injection and a request for a cylinder that has executed synchronous injection this time. Acceleration fuel calculating means for calculating an acceleration fuel injection amount ΔTAUBi * K ₁ (K ₁ is a correction coefficient) based on a difference ΔTAUBi (= TAUBi−TAUB) of the fuel injection amount, and injecting the calculated acceleration fuel injection amount And accelerating fuel injection means.
[0009]
In the fuel injection amount control device for a multi-cylinder internal combustion engine according to the present invention, the acceleration detection by the acceleration detection means is detected from a difference between each required fuel injection amount of a cylinder that has performed the previous synchronous injection and a cylinder that has performed the current synchronous injection. You.
According to the above configuration, the acceleration state of the engine is determined so as not to be affected by the air-fuel ratio F / B control system of another system. Therefore, the acceleration determination of the engine becomes accurate, and an appropriate amount of acceleration is performed when the engine is actually in the acceleration state. Fuel is supplied so as to perform an increase correction and prevent unnecessary increase correction when the engine is not actually accelerating.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic diagram showing an embodiment of a fuel injection amount control device for a multi-cylinder internal combustion engine according to the present invention. In FIG. 1, reference numeral 21 denotes a main body of a V-type eight-cylinder engine in which four cylinders are arranged in two rows in a V-shape. An air flow meter 23 is provided in an intake passage 22 of the engine body 21. The air flow meter 23 is for directly measuring the amount of intake air. For example, a movable vane type air flow meter having a built-in potentiometer or the like is used, and generates an output signal of an analog voltage proportional to the amount of intake air. This output signal is input to an A / D converter 101 with a built-in multiplexer of an ECU (electronic control unit) 30. The distributor 24 has a compression stroke near the top dead center TDC of the first cylinder every two rotations (720 ° CA) of the crankshaft of the engine 21 and a fourth cylinder having a phase difference of 360 ° CA from the top dead center. Around the top dead center TDC of the compression stroke, a crank angle sensor 25A that generates two reference position detection pulse signals serving as references for determining the injection timing and the ignition timing of each cylinder and a crank angle of 30 A crank angle sensor 25B that generates a pulse signal for detecting a crank angle for each degree is provided. The pulse signals of the crank angle sensors 25A and 25B are supplied to an input / output interface 102 of the ECU 30, and the output of the crank angle sensor 25B is supplied to an interrupt terminal of the CPU 103. The cylinder discrimination is performed during two revolutions of the crankshaft after the start of the engine 21 using two reference position detection pulse signals.
[0011]
An intake pressure sensor 26 for detecting a pressure in the intake pipe is provided in an intake pipe of the engine 21. The intake pressure sensor 26 generates an electric signal of an analog voltage proportional to the intake pressure. Is supplied to the vessel 101.
Further, the intake passage 22 is provided with fuel injection valves 27A and 27B for supplying pressurized fuel from a fuel supply system to an intake port for each cylinder.
[0012]
A water temperature sensor 29 for detecting the temperature of the cooling water is provided on a water jacket (not shown) of the cylinder block of the engine 21. The water temperature sensor 29 generates an analog voltage electric signal corresponding to the temperature of the cooling water. This output is also supplied to the A / D converter 101.
The exhaust systems downstream of the exhaust manifolds 31A and 31B of the right bank (hereinafter referred to as A bank) and the left bank (hereinafter referred to as B bank) of the engine 21 respectively have three harmful components HC, CO, and NO _{X in the} exhaust gas. Catalytic converters 32A and 32B accommodating a three-way catalyst for purifying the catalyst at the same time. The catalytic converters (start catalysts) 32A and 32B have a relatively small capacity and are provided in the engine room so that the catalyst can be warmed up at the time of starting the engine in a short time.
[0013]
A first air-fuel ratio sensor 33A for the A bank is provided in the exhaust manifold 31A of the A bank, that is, the exhaust pipe 31A on the upstream side of the catalytic converter 32A, and the exhaust manifold 31B of the B bank is provided with the catalytic converter 32B. Similarly, a first air-fuel ratio sensor 33B for the B bank is provided in the exhaust pipe 31B on the upstream side of the fuel cell.
[0014]
Further, the two exhaust pipes 34A and 34B join at a gathering portion 35a downstream thereof, and a catalytic converter (main catalyst) 36 containing a three-way catalyst is arranged in the exhaust pipe downstream of the gathering portion 35a. ing. The catalytic converter 36 has a relatively large capacity and is installed under the floor of the vehicle body. A collective exhaust pipe 35 is connected downstream of the catalytic converter 36. The two exhaust pipes 34A and 34B are preferably provided with second air-fuel ratio sensors 37A and 37B for Bank A and Bank B, respectively.
[0015]
In the present embodiment, the first air-fuel ratio sensors 33A and 33B correspond to one-to-one correspondences between the oxygen component concentration in the exhaust gas and the air-fuel ratio in a wide air-fuel ratio range. A full-range air-fuel ratio sensor (A / F sensor) is used. The first air-fuel ratio sensors 33A and 33B generate an output voltage that is substantially proportional to the concentration of oxygen contained in the exhaust gas of the engine 21, and the output voltage is supplied to the A / D converter 101 of the ECU 30. On the other hand, as the second air-fuel ratio sensors 37A and 37B, lambda-type air-fuel ratio sensors (A / F sensors) whose outputs are inverted between when the oxygen component concentration in the exhaust gas is rich and when it is lean are used. .
[0016]
In the present embodiment, the ECU 30 is configured as a microcomputer, for example, and includes an A / D converter 101, an input / output (I / O) interface 102, a CPU 103, a ROM 104, a RAM 105, a backup RAM 106, a clock generation circuit 107, and the like. Is provided. The ECU 30 performs basic control such as fuel injection control, ignition timing control, air-fuel ratio control, and the like of the engine 21, and also performs correction control of a fuel injection amount during acceleration according to the present invention, which will be described later. Acceleration detecting means for detecting the acceleration state of the engine from the difference between the required fuel injection amounts of the cylinders executing the synchronous injection, and accelerating fuel calculating means for calculating the accelerated fuel injection amount based on the difference; It functions as acceleration fuel injection means for injecting the fuel injection amount.
[0017]
Here, “this time” and “last time” used in “current time synchronous injection” and “last time synchronous injection”, for example, inject the synchronous fuel injection amount calculated from the operating state of the engine in synchronization with the crank angle of the engine. A cylinder that is synchronously injected with “this time” is defined as a cylinder that is synchronously injected with the current injection, that is, a cylinder that is synchronously injected with the current injection. A cylinder for which fuel injection has been completed is defined as a previous synchronous injection cylinder.
[0018]
The throttle valve 38 of the intake passage 22 is provided with an idle switch 39 for generating a signal indicating whether the throttle valve 38 is in a fully closed state, that is, an XIDL signal. This idle state output signal XIDL is supplied to the input / output interface 102 of the ECU 30.
Reference numerals 40A and 40B denote secondary air introduction control valves for supplying secondary air from an air source such as an air pump (not shown) to the exhaust manifolds 31A and 31B at the time of deceleration or idling to reduce HC and CO emissions. belongs to.
[0019]
Further, in the ECU 30, the down counter 108A, the flip-flop 109A, and the drive circuit 110A are for controlling the fuel injection valve 27A of the A bank, and the down counter 108B, the flip flop 109B, and the drive circuit 110B are provided for the fuel cell of the B bank. This is for controlling the injection valve 27B. That is, in the routine described later, synchronous fuel injection amount (injection _{_{time) TAU (A) (TAU (}} B)) when is calculated, the injection time _{_{TAU (A) (TAU (B}} )) is down counter 108A (108B) And the flip-flop 109A (109B) is also set. As a result, the drive circuit 110A (110B) starts energizing the fuel injection valve 27A (27B). On the other hand, when the down counter 108A (108B) counts a clock signal (not shown) and its output terminal finally becomes "1" level, the flip-flop 109A (109B) is set and the drive circuit 110A ( 110B) stops the energization of the fuel injection valve 27A (27B). That is, the above-described injection time _{_{TAU (A) (TAU (B}} )) only the fuel injection valve 27A (27B) is energized, the time _{_{TAU (A) (TAU (B}} )) in an amount corresponding to the fuel of the engine 21 It will be sent to the A bank (B bank) combustion chamber. Note that the interrupt of the CPU 103 occurs when the input / output interface 102 receives a pulse signal of the crank angle sensor 25B after the A / D conversion of the A / D converter 101 ends.
[0020]
The intake air amount data of the air flow meter 23, the intake pressure data of the intake pressure sensor 26, and the cooling water temperature data of the water temperature sensor 29 are taken in by an A / D conversion routine executed for a predetermined time or every predetermined crank angle, and stored in the RAM 105 Stored in the area. That is, the intake air amount data, intake pressure data, and cooling water temperature data in the RAM 105 are updated every predetermined time. The rotation speed data is calculated by an interruption of the crank angle sensor 25B at every 30 ° CA (crank angle) and stored in a predetermined area of the RAM 105.
[0021]
Next, control of the fuel injection amount according to the present invention will be described below using a time chart and a flowchart.
FIG. 2 is an explanatory diagram of fuel injection amount control during acceleration in a V-type eight-cylinder engine. In FIG. 2, the horizontal axis represents time, the number following the longitudinal axis upper # indicates the order of injection and ignition cylinder, the vertical axis lower part shows the synchronous fuel injection quantity TAU acceleration at time t ₁ is started changes. As shown in FIG. 2, in the V-type 8-cylinder engine, the injection and ignition of the A bank consisting of # 1, # 3, # 5, and # 7 and the B bank consisting of # 2, # 4, # 6, and # 8 are performed. The order is # 1, # 8, # 4, # 3, # 6, # 5, # 7, # 2. In the upper part of FIG. 2, the portion indicated by a black band indicates the opening timing of the fuel injection valve of each cylinder by synchronous injection, and the portion indicated by hatching (oblique line from upper left to lower right) opens the intake valve of each cylinder. The timing is shown, and the portion indicated by hatching (oblique lines from upper right to lower left) inside the oval indicates the acceleration fuel injection timing.
[0022]
FIG. 3 is a flowchart of a fuel injection amount calculation routine. The fuel injection amount calculation routine shown in FIG. 3 is for calculating a synchronous fuel injection amount (TAU) after the engine is started. The synchronous fuel injection amount (TAUST) at the time of starting the engine is calculated by another routine, TAUST is injected until a predetermined rotational speed is reached, for example, 400 RPM after the engine operation is started, and after the RPM reaches 400 RPM, the routine is calculated by the routine shown in FIG. TAU is injected. This routine is executed in the main routine.
[0023]
First, in step S31, various signal input data indicating the operating state of the engine, that is, data such as the rotational speed NE, the intake air amount GA, the cooling water temperature THW, the throttle opening TA, the intake temperature TH, and the like are read. In step 32, the basic fuel injection amount TP is calculated from the two-dimensional map stored in the ROM 104 based on the data of the engine speed NE and the intake air amount GA read in step 31. In step 33, a cold warm-up increase correction coefficient FWL determined by the coolant temperature THW, the throttle opening TA, the intake air temperature TH, etc., a fuel adhesion correction coefficient FAE increased during acceleration, and another correction coefficient α are calculated. Next, at step 34, the invalid injection time Ts is calculated from the map stored in the ROM 104 based on the battery voltage BA.
[0024]
Next, at step 35, for each air-fuel ratio F / B control system, the air-fuel ratio correction coefficient FAF _(A) (FAF _(B) ) calculated by a known air-fuel ratio correction coefficient calculation routine and the suspension of the air-fuel ratio F / B control An air-fuel ratio learning correction coefficient FG _(A) (FG _(B) ) for correcting the air-fuel ratio deviation amount occurring therein is read. Here, the subscripts following FAF and FG indicate bank A or bank B. The air-fuel ratio correction coefficient FAF _(A) (FAF _(B) ) determines the fuel injection amount supplied to the engine such that the air-fuel ratio of the engine becomes the target air-fuel ratio in accordance with the output value of the first air-fuel ratio sensor 33A (33B). The air-fuel ratio learning correction coefficient FG _(A) (FG _(B) ) is a correction coefficient for correcting a deviation amount of the air-fuel ratio that occurs during suspension of the air-fuel ratio F / B control. is there. In step 36, the basic fuel injection amount TP calculated in step 32, the correction coefficient FWL, FAE, α calculated in step 33, the invalid injection time Ts calculated in step 34, and the air-fuel ratio correction coefficient FAF _(A) read in step 35 Using (FAF _(B) ) and the air-fuel ratio learning correction coefficient FG _(A) (FG _(B) ), the post-start synchronous fuel injection amount TAU _(A) (TAU _(B) ) is calculated from the following equation.
[0025]
TAU _(A) = TP * FWL * FAE * α * (FAF _(A) + FG _(A) ) + Ts
TAU _(B) = TP * FWL * FAE * α * (FAF _(B) + FG _(B) ) + Ts
From the above equation, the synchronous fuel injection amount TAU _(A) (TAU _(B) ) synchronously injected according to the crank angle of the engine is TP, FWL in accordance with the request of the engine regardless of the air-fuel ratio F / B control system. , Calculated from FAF _(A) (FAF _(B) ) and FG _(A) (FG _(B) ) for each required fuel injection amount TAUB of the engine calculated from FAE and α and the air-fuel ratio F / B control system. It can be seen that the calculation is based on the sum of the product of the air-fuel ratio corrected fuel injection amount TAUC _(A) (TAUC _(B) ) and the invalid injection time Ts.
[0026]
FIG. 4 is a flowchart of the fuel injection routine of the present invention. The fuel injection routine of the present invention is executed every time a pulse signal input to the input / output interface 102 from the crank angle sensor 25B is received, that is, every 30 ° CA. The execution of the 30 ° CA interrupt routine is started when the ignition switch is turned on, and is ended when the ignition switch is turned off. First, in step 401, it is determined whether or not the cylinder determination has been completed. That is, after the starter switch is turned on to start the engine, two pulse signals output from the crank angle reference sensor 25A are received, and it is determined whether the crankshaft has rotated twice and the cylinder determination has been completed. After the execution of the 30 ° CA interrupt routine is started, if it is determined that the cylinder discrimination has not been completed yet, the 30 ° CA interrupt routine, that is, the present fuel injection routine is completed, and it is determined that the cylinder discrimination has been completed. After that, the process proceeds to step 402.
[0027]
In step 402, whether or not the cylinder is at the injection timing is detected and determined from the crank angle reference sensor 25A and the crank angle sensor 25B, and if the determination result is YES, the process proceeds to step 403, and the determination result is NO. At this time, the present fuel injection routine ends. In step 403, the required fuel injection amount TAUB of the engine is calculated from the following equation.
[0028]
TAUB = TP * FWL * FAE * α
In step 404, a difference ΔTAUBi (= TAUBi-TAUB) between the required fuel injection amount TAUB in the current processing cycle and the required fuel injection amount TAUBi in the previous processing cycle of this routine is calculated.
In step 405, it is determined whether or not the operation state of the engine is an acceleration state by determining whether or not the difference ΔTAUBi calculated in step 404 is larger than a predetermined amount A. That is, when ΔTAUBi> A, it is determined that the engine is in an accelerating state, and the routine proceeds to step 406. When ΔTAUBi ≦ A, the engine is not in an accelerating state, and this routine is terminated.
[0029]
In step 406, it is determined from the difference ΔTAUBi calculated in step 404 whether it is possible to secure the minimum required opening time of the fuel injection valve in terms of the performance of the fuel injection valve, and ΔTAUBi * K ₁ ≧ B (B is invalid injection) If it is time Ts), it is determined that the valve opening time can be secured, and the routine proceeds to step 407. If ΔTAUBi * K ₁ <B, it is determined that the valve opening time cannot be secured, and this routine ends. Here, _{K 1} is a correction coefficient for the acceleration fuel injection quantity ΔTAUBi-1 to re-injection set arbitrary value, for example, to 1/2.
[0030]
In step 407, the accelerated fuel injection amount ΔTAUBi-1 to be re-injected in the cylinder for which the synchronous injection has been executed in the previous processing cycle is calculated from the following equation.
_ΔTAUBi-1 = ΔTAUBi * _K 1
In step 408, re-injection is performed for the cylinder that has been subjected to synchronous injection last time. Specifically, as shown in FIG. 2, at time t _2, the when the current synchronous injection cylinder 7 cylinder (# 7), the acceleration in the fifth cylinder is the last sync injection cylinder (# 5) injecting fuel injection amount ΔTAUBi-1, at time t _3, when the current synchronous injection cylinder of the second cylinder (# 2), the acceleration fuel injection is 7 cylinder is the last sync injection cylinder (# 7) Inject the amount ΔTAUBi-1.
[0031]
In step 410, it is determined whether or not the minimum required opening time of the fuel injection valve in terms of the performance of the fuel injection valve can be secured from the previous acceleration fuel injection amount ΔTAUBi-1 to the synchronous injection cylinder calculated in step 407. , when the _{ΔTAUBi-1 * K 2 ≧ B} (B is invalid injection time Ts) proceeds to step 411 it is determined that it can secure the valve opening time, the opening when the ΔTAUBi-1 _{* K} 2 <B It is determined that the valve time cannot be secured, and this routine ends. Here, _{K 2} is a correction coefficient for the acceleration fuel injection quantity ΔTAUBi-2 to be re-injected, to set an arbitrary value, for example, to 1/2.
[0032]
In step 411, the accelerated fuel injection amount ΔTAUBi-2 to be re-injected in the cylinder for which the synchronous injection has been executed in the processing cycle two times before is calculated from the following equation.
In ΔTAUBi-2 = ΔTAUBi-1 * K 2 (ΔTAUBi-2 <ΔTAUBi-1) step 412, the execution of the re-injection at synchronous injection already cylinder before last. Specifically, as shown in FIG. 2, when the current synchronous injection cylinder is the seventh cylinder (# 7) at time t2, the accelerated fuel is injected into the sixth cylinder (# 6), which is the synchronous injection cylinder _two times before. the injection quantity DerutaTAUBi-2 was injected at time t _3, when the current synchronous injection cylinder of the second cylinder (# 2), the acceleration fuel injection quantity in the fifth cylinder is a synchronous injection cylinder before the previous (# 5) Inject ΔTAUBi-2.
[0033]
In step 413, as shown in FIG. 2, synchronous injection is performed by the current injection cylinder, for example, the # 7 cylinder or the # 2 cylinder. As the synchronous fuel injection amount TAU for the current injection cylinders # 7 and # 2, the value obtained by executing the fuel injection amount calculation routine described with reference to FIG. 3 is used.
Next, at step 414, the required fuel injection amount TAUB of the engine calculated at step 403 is set to the required fuel injection amount TAUBi of the previous processing cycle.
[0034]
As a method of detecting the acceleration state of the engine other than the above embodiment, a method of detecting from the values of the intake air amount, the throttle opening, the rotation speed, the accelerator pedal depression amount, and the like in the engine may be used.
In the above-described embodiment, the example in which the accelerated fuel is injected into the cylinder in the intake stroke and / or the cylinder immediately before the intake stroke in synchronization with the current synchronous injection has been described. Accelerated fuel may be injected into a cylinder in a stroke and / or a cylinder immediately before an intake stroke. Further, for the accelerated fuel injected into each cylinder, the amount of the accelerated fuel calculated according to the time when the intake stroke of each cylinder ends (the time until the intake valve closes) may be reduced.
[0035]
As described above, the fuel injection control according to the present invention has been described by taking the V-type engine as an example. However, the present invention can be similarly applied to an in-line cylinder engine provided with a plurality of air-fuel ratio feedback control systems. For example, in an in-line four-cylinder engine, a cylinder group A including # 1 and # 4 and a cylinder group B including # 2 and # 3 are respectively connected to individual exhaust pipes, and a catalytic converter is disposed in each exhaust pipe. An upstream air-fuel ratio sensor and preferably a downstream air-fuel ratio sensor of the catalytic converter are provided. When performing air-fuel ratio F / B control of each system corresponding to each cylinder group based on the output of these air-fuel ratio sensors, injection is performed. Since the order of the cylinders is # 1, # 4, # 2, and # 3, when the # 2 cylinder is injected after the injection of the # 4 cylinder, or when the # 1 cylinder is injected after the injection of the # 3 cylinder. The air-fuel ratio control system differs between the previous injection cylinder and the current injection cylinder. Even in such an in-line four-cylinder engine, if the above-described fuel injection amount control according to the present invention is applied, the acceleration increase correction can be performed without excess or deficiency.
[0036]
【The invention's effect】
As described above, according to the fuel injection amount control device for a multi-cylinder internal combustion engine of the present invention, in the fuel injection amount control device for a multi-cylinder internal combustion engine having a plurality of air-fuel ratio F / B control systems for each cylinder group, Since the acceleration state of the engine is determined independently of the fuel ratio F / B control system, it is possible to accurately determine the acceleration state of the engine even when the previous injection cylinder and the current injection cylinder are different air-fuel ratio control systems, Since the acceleration fuel injection amount of the engine is calculated irrespective of the air-fuel ratio F / B control system, a sufficient fuel injection amount can be supplied when the engine is accelerated. In particular, the exhaust gas during acceleration when the air-fuel ratio is rich is increased. Emission deterioration can be suppressed, and acceleration responsiveness during acceleration when the air-fuel ratio is lean can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment of a fuel injection amount control device for a multi-cylinder internal combustion engine according to the present invention.
FIG. 2 is an explanatory diagram of fuel injection amount control during acceleration in a V-type eight-cylinder engine.
FIG. 3 is a flowchart of a fuel injection amount calculation routine.
FIG. 4 is a flowchart of a fuel injection routine of the present invention.
[Explanation of symbols]
21 ... Engine 23 ... Air flow meters 25A and 25B ... Crank angle sensors 27A and 27B ... Fuel injection valve 29 ... Water temperature sensor 30 ... Electronic control unit (ECU)
31A, 31B ... exhaust pipes 32A, 32B, 36 ... catalytic converters 33A, 33B ... first air-fuel ratio sensors 37A, 37B ... second air-fuel ratio sensors

Claims

An air-fuel ratio sensor disposed in an exhaust passage provided for each cylinder group of a multi-cylinder internal combustion engine, and a required fuel injection amount is calculated based on an operation state of the engine. Based on each output of the air-fuel ratio sensor, The air-fuel ratio correction fuel injection amount for correcting the required fuel injection amount to be injected into the cylinder so that each air-fuel ratio detected by each air-fuel ratio sensor matches the target air-fuel ratio is calculated. Synchronous fuel injection for calculating a synchronous fuel injection amount for synchronous injection in accordance with a predetermined crank angle based on the injection amount and each of the air-fuel ratio corrected fuel injection amounts, and controlling to inject the synchronous fuel injection amount to the cylinder. Means, a fuel injection amount control device for a multi-cylinder internal combustion engine comprising:
Acceleration detection means for detecting the acceleration state of the internal combustion engine,
When the acceleration detecting means detects the acceleration state of the internal combustion engine, an acceleration for calculating an accelerated fuel injection amount based on a difference between each required fuel injection amount of a cylinder that has performed the previous synchronous injection and a cylinder that has performed the current synchronous injection. Fuel calculation means;
Acceleration fuel injection means for injecting the calculated acceleration fuel injection amount,
A fuel injection amount control device for a multi-cylinder internal combustion engine, comprising:

2. The fuel injection amount of the multi-cylinder internal combustion engine according to claim 1, wherein the detection of the acceleration by the acceleration detection means is detected from a difference between each required fuel injection amount of a cylinder that has executed the previous synchronous injection and a cylinder that has executed the current synchronous injection. 3. Control device.