JP3944444B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

【００７６】
上記（９）式中、右辺第２項は、層流状況下、すなわち、吸気バルブ３４の閉弁中における燃料の蒸発率を表す数式モデルである。この項に含まれる個々の記号は、それぞれ以下のような物理量である。
ρl：液体燃料の密度（既定値）
h：付着燃料の膜厚
h＝fw／ρl／sとして算出される。但し、ρlは燃料の密度、sは濡れ面積（既定値）。
Sc_１：層流用適合係数（既定値）
D：吸気ポートの径
μg：吸気ポート３０内ガス（空気）の粘性（既定値）
B_１：層流時質量輸送係数（詳細は後述）
Δt_lam：層流期間、すなわち、吸気バルブ３４の閉弁期間
【００７７】
また、上記（９）式中、右辺第３項は、乱流状況下、すなわち、吸気バルブ３４の開弁中の蒸発率を表す数式モデルである。この項にのみ含まれている個々の記号は、それぞれ以下のような物理量である。
Sc_１：乱流用適合係数（既定値）
B_２：乱流時質量輸送係数（詳細は後述）
ρg：空気の密度（既述した通りρg＝Pg／R_const・Tg）
Δt_turb：乱流期間、すなわち、吸気バルブ３４の開弁期間（作用角）
但し、Δt_lam＋Δt_turb＝７２０(deg)
【００７８】
上述した層流時質量輸送係数B_１および乱流時質量輸送係数B_２は、それぞれ、層流時または乱流時における付着燃料の蒸発のし易さを表すパラメータである。それらの値B_１、B_２は、それぞれ次式（１０）のように表すことができる。
【００７９】
【数２】

【００８０】
上記（１０）式において、iは、燃料に含まれる個々の成分に付した識別番号である。つまり、ΣYsi、或いはΣYgiは、それぞれ、燃料に含まれる複数の成分についてのYsiやYgiの積算値である。ここで、値B_１の式に含まれているYgiは、吸気ポート１０内における個々の燃料成分の蒸気濃度（成分毎に既定値）である。層流状態では、Ygiが無視できない値（例えば１０％程度）となるため、層流時質量輸送係数B_１の式には、その項が含まれている。一方、乱流時には、吸気ポート３０内の個々の成分濃度がほぼ０となるため、乱流時質量輸送係数B_２の式からは、その項が省かれている。また、上記（１０）式において、Ysiは、個々の成分の飽和蒸気濃度である。この飽和蒸気濃度Ysiは、次式（１１）により算出することができる。
【００８１】
【数３】

【００８２】
上記（１１）式に含まれる個々の記号は、それぞれ以下のような物理量である。
wi：燃料に含まれる個々の成分のモル質量（既定値）、
wair：空気のモル質量（既定値）
Pvsi：アントンの式による個々の成分の飽和蒸気圧
飽和蒸気濃度Pvsiは、次式（１２）により求めることができる。
【００８３】
【数４】

【００８４】
但し、上記（１２）式中、a_1i、a_2iおよびa_3iは、燃料成分毎に既定のアントン係数である。また、y_fiは、噴射される燃料成分の個々の成分の質量割合である。更に、上記（１２）式中、Tfは、次式（１３）により表される温度である。
Tf＝ε・Tw＋（１−ε）Tg ・・・（１３）
ここで、εは、０＜ε＜１を満たす値である。通常は、空気の方が影響度が高いので、εには０．７程度の値が代入される。
【００８５】
上記（９）式の右辺第２項に含まれるパラメータ（時間を除く）は、付着燃料の膜厚h、および層流時質量輸送係数B_１を除き固定値である。そして、膜厚hは付着燃料量fwに基づいて決定され、層流時質量輸送係数B_１は、ポート内状態量Pg、Tg、およびTwにより決定される値である。従って、上記（９）式によれば、層流状況下での燃料の蒸発率（右辺第２項）を、ポート内状態量Pg、Tg、およびTwに基づいて算出することができる。
【００８６】
上記（９）式の右辺第３項に含まれるパラメータ（時間を除く）は、付着燃料の膜厚h、空気密度ρg、ポート内ガス流速Ug、および乱流時質量輸送係数B_２を除き固定値である。そして、膜厚hは付着燃料量fwに基づいて決定され、空気密度ρgはPgおよびTgにより決定され、乱流時質量輸送係数B_２は、Pg、TgおよびTwにより決定される値である。また、本実施形態においては、付着燃料量fwも、根本的にはポート内状態量Pg、Tg、UgおよびTwに基づいて算出される値である。従って、上記（９）式によれば、乱流状況下での燃料の蒸発率（右辺第３項）を、ポート内状態量Pg、Tg、UgおよびTwに基づいて算出することができる。
【００８７】
［付着率Rの具体的算出方法］
次に、ECU５０が、付着率Rを算出するために使用する数式モデルの具体的内容について説明する。
上記（４）式および（５）式による付着率Rの算出方法は、飛行中蒸発量F2と、付着後蒸発量G2とを別個に求めて、それらの和（蒸発総量Vfi）を燃料噴射量fiから減ずることにより、最終的に壁面に付着する燃料量（fi−Vfi）を求めることとしている。そして、このようにして求められた燃料量（fi−Vfi）をfiで割ることにより、最終的に壁面に付着した状態となる燃料の割合が求められる。
【００８８】
ところで、最終的に壁面に付着する燃料の割合（R）は、上記の手法で求める他、飛行の過程で蒸発せずに壁面まで到達する燃料の割合R1、壁面に到達した後、反射により失われることなく壁面に付着する燃料の割合α、および壁面に付着した後、蒸発により離脱せずに付着状態を維持する燃料の割合R2をそれぞれ算出し、次式（１４）に示すように、それらを掛け合わせることによっても求めることができる。
R＝R1・α・R2 ・・・（１４）
【００８９】
そこで、ECU５０は、具体的には、上記（１４）式の手法で噴射燃料の付着率Rを算出する。ここで、上記（１４）式に含まれるR1、R2およびαは、それぞれ、以下に示す（１５）〜（１７）式により求めることができる。
【００９０】
【数５】

【００９１】
但し、上記（１５）〜（１７）式に含まれる個々の記号は、それぞれ以下のような物理量である。尚、Sc１、Sc２、ρl、μg、ρg、B_１、B_２、およびΔt_turbについては、既述したものと同一であるため、ここでは、それらの説明は省略する。
di：液滴の代表粒径（既定値）
V：液滴飛行速度（既定値）
Δｔ_drop：液滴飛行時間（既定値）＝（燃料噴射弁から吸気バルブまでの距離）／V
We：ウェーバ数
Re：レイノルズ数
σ：燃料の表面張力
θ_Ｉ：噴射方向と衝突壁面のなす角度
【００９２】
尚、上記（１７）式に示すαは、現実には燃料噴射弁３２の性能と、吸気ポート３０の形状とにより決まる値である。従って、個々の内燃機関１０において、上記（１４）式に則って付着率Rを演算する際には、αは固定値として扱うことができる。
【００９３】
上記（１５）式中、右辺第２項は、飛行蒸発により失われる燃料の割合である。この右辺第２項に含まれるパラメータ（時間を除く）は、空気密度ρgおよび層流時質量輸送係数B_１を除き固定値である。そして、空気密度ρgは、上記の如くポート内ガス圧力Pgおよびポート内ガス温度Tgにより特定される値である。また、層流時質量輸送係数B_１は、Pg、Tgおよび壁面温度Twにより特定される値である（上記（１０）〜（１２）式参照）。従って、本実施形態のシステムによれば、飛行蒸発により失われる燃料の割合を、ポート内状態量Pg、Tg、およびTwに基づいて算出することができる。
【００９４】
上記（１６）式中、右辺第２項は、付着後の蒸発により失われる燃料の割合である。この右辺第２項に含まれるパラメータ（時間を除く）は、空気密度ρg、ポート内ガス流訴奥Ug、および乱流時質量輸送係数B_２を除き固定値である。そして、ρgは、上記の如くPgおよびTgにより特定される値である。また、乱流時質量輸送係数B_２は、Pg、TgおよびTwにより特定される値である（上記（１０）〜（１２）式参照）。従って、本実施形態のシステムによれば、付着後の蒸発により失われる燃料の割合を、ポート内状態量Pg、Tg、UgおよびTwに基づいて算出することができる。
【００９５】
以上説明した通り、ECU５０は、噴射燃料の蒸発挙動を表す数式モデル（上記（１４）〜（１７）式）を用いて、ポート内状態量Pg、Tg、UgおよびTwに基づいて、噴射燃料の付着率Rを精度良く推定することができる。また、ECU５０は、付着燃料の蒸発挙動を表す数式モデル（上記（９）〜（１３）式）を用いて、ポート内状態量Pg、Tg、UgおよびTwに基づいて、付着燃料の残留率Pを精度良く推定することができる。
【００９６】
このため、本実施形態の構成によれば、内燃機関１０の機種毎に煩雑な適合作業を行うことなく、過渡運転時を含む全ての運転状況下で精度良く燃料噴射量を制御する装置を実現することができる。このような燃料噴射制御装置によれば、常に空燃比を精度良く所望空燃比に制御することが可能となる。従って、本実施形態の装置は、良好な排気エミッション特性を実現するうえでも有用である。
【００９７】
また、本実施形態では、上述した燃料噴射量制御を内燃機関１０の暖機後に実行することを前提としているが、つまり、上述した数式モデルを、内燃機関１０の暖機後における燃料噴射制御に利用することとしているが、その利用の場面はこれに限定されるものではない。すなわち、本実施形態の装置では、数式モデルを用いて、ポート内ガス温度Tgや壁面温度Twを含むポート内状態量をパラメータとして付着率Rや残留率Pを算出している。このような数式モデルによれば、冷間始動時など、内燃機関１０の温度が低い場合にも、有効に現実の状態を模擬することができる。
【００９８】
更に、ハイブリッド（HV）車両においては、内燃機関に対する燃料噴射が停止された後、数秒間の経過後に内燃機関の停止が図られることがある。上記の数式モデルによれば、そのような数秒間の間も、現実の状態を精度良く模擬することができる。従って、本実施形態の装置が用いる数式モデルは、冷間運転時や、HV車両の機関停止時などに、付着率Rおよび残留率Pを算出する場面でも利用することができる。
【００９９】
これに対して、付着率Rや残留率Pが、内燃機関の運転状態を表す状態量（負荷KL、回転数NEなど）との関係で、適合により定められる場合には、内燃機関１０の運転状態がその適合時の条件から外れる領域では、精度良く付着率Rや残留率Pを定めることはできない。具体的には、暖機後の条件で適合したマップ値などは、冷間運転時や、HV車両の機関停止時には利用することができない。この点、本実施形態の装置は、適合によりPやRを定める装置に比して、より広い領域への展開が可能であるという優位性を有している。
【０１００】
ところで、上述した実施の形態１においては、付着率Rおよび残留率Pを、ポート内状態量をパラメータとする数式モデルに則って算出することとしているが、その算出は、数式モデルを用いる手法に限られるものではない。すなわち、付着率Rや残留率Pは、ポート内状態量との関係で予め設定したマップを参照して特定することとしてもよい。
【０１０１】
尚、上述した実施の形態１においては、付着燃料の残留率Pおよび噴射燃料の付着率Rが前記第１乃至第３の発明における「燃料制御パラメータ」に相当していると共に、ECU５０が、上記ステップ１０２の処理を実行することにより前記第１乃至第３の発明における「ポート内状態量取得手段」が、上記（９）〜（１７）式を記憶していることにより前記第１乃至第３の発明における「モデル記憶手段」が、それらの式を用いてPおよびRを算出することにより、或いは、上記ステップ１０４〜１０８の処理を実行することにより、前記第１乃至第３の発明における「燃料制御パラメータ算出手段」が、上記ステップ１１４の処理を実行することにより前記第１乃至第３の発明における「付着燃料量算出手段」が、上記ステップ１１０の処理を実行することにより前記第１乃至第３の発明における「噴射量補正手段」が、それぞれ実現されている。
【０１０２】
また、上述した実施の形態１においては、上記（１４）〜（１７）式が前記第２の発明における「噴射燃料蒸発挙動モデル」に、上記（９）〜（１３）式が前記第１の発明における「付着燃料蒸発挙動モデル」に、噴射燃料の付着率Rが前記第１及び第２の発明における「第１の燃料制御パラメータ」に、付着燃料の残留率Pが前記第１及び第２の発明における「第２の燃料制御パラメータ」に、それぞれ相当している。また、ECU５０が、上記（１４）式に従って、或いは上記ステップ１０８において付着率Rを演算することにより、前記第１及び第２の発明における「第１算出手段」が、上記（９）式に従って、或いは上記ステップ１０８において残留率Pを演算することにより、前記第１及び第２の発明における「第２算出手段」が、それぞれ実現されている。
【０１０３】
また、上述した実施の形態１においては、上記（１６）式が前記第１の発明における「付着後蒸発挙動モデル」に相当している。
【０１０４】
また、上述した実施の形態１においては、上記（１５）式が前記第１の発明における「飛行蒸発モデル」に、上記（１７）式が前記第１の発明における「反射蒸発モデル」に、それぞれ相当している。
【０１０５】
また、上述した実施の形態１においては、上記（９）式中、右辺第２項および第３項が、それぞれ、前記第２の発明における「閉弁中蒸発挙動モデル」、および「開弁中蒸発挙動モデル」に、それぞれ相当している。
【０１０６】
実施の形態２．
次に、図８を参照して、本発明の実施の形態２について説明する。
本実施形態の装置は、実施の形態１の装置において、ECU５０に、上記図５に示すフローチャートに代えて、図８に示すフローチャートに沿って処理を実行させることにより実現することができる。
【０１０７】
上述した実施の形態１の装置は、噴射燃料の付着後蒸発量G2を算出するにあたり（上記（１６）式のR2を算出するにあたり）、また、付着燃料の開弁時蒸発量G3を算出するにあたり、吸気バルブ３４の開弁時には、ポート内状態量が常にほぼ一定であることを前提としている。しかしながら、吸気バルブ３４がバルブオーバーラップを伴うようなタイミングで開弁される場合は、その開弁の直後にのみ、吸気ポート３０の内部において既燃ガスの吹き返しが生ずる。この場合、ポート内状態量は、特に、ポート内ガス圧力Pg、ポート内ガス温度Tg、およびポート内ガス流速Ugは、吹き返しの発生中と、その消滅後とで大きく異なった値となる。従って、そのような吹き返しが発生する状況下で、精度良く付着率Rおよび残留率Pを算出するためには、吹き返しの有無に応じて、数式モデルに代入するポート内状態量を変化させることが望ましい。
【０１０８】
［実施の形態２における処理の流れ］
図８は、上記の要求に応えつつ、残留率Pおよび付着率Rを算出し、更に、それらの値P、Rを用いて燃料噴射量fiを適正に補正するために、ECU５０が実行する処理の流れを説明するためのフローチャートである。尚、図８において、上記図５に示すステップと同一のステップについては、同一の符号を付してその説明を省略または簡略する。
【０１０９】
図８に示すフローチャートは、ステップ１０２の後に、ステップ１２０〜１３０が挿入されている点を除き、上記図５に示すフローチャートと同様である。すなわち、図８に示すフローチャートによれば、図５に示すフローチャートによる場合と同様に、先ず、ステップ１００において各種パラメータが計測され、次いで、ステップ１０２において、ポート内状態量Pg、Tg、UgおよびTwが推定される。
【０１１０】
これらのポート内状態量のうち、壁面温度Twは、吹き返しの有無に影響されることのない状態量である。これに対して、Pg、TgおよびUgは、上記の如く吹き返しの有無により大きく変化する状態量である。上記ステップ１０２では、吹き返しが発生しない場合のPg、TgおよびUgが推定されるものとする。
【０１１１】
ポート内状態量Pg、Tg、UgおよびTwが推定されると、次に、吸気バルブ３４の開弁タイミングVTが、所定値VT_０より小さいか否かが判別される（ステップ１２０）。
VTは、既述した通り最遅角のタイミングからの進角量である。従って、その値VTが大きい程、バルブオーバーラップが発生し、吹き返しが発生し易くなる。所定値VT_０は、ポート内状態量に有意な変化を生じさせる程度の吹き返しが発生するか否かを区分する開弁タイミングとして設定された値である。従って、VT＜VT_０が成立する場合は、ポート内状態量を切り換えるほどの吹き返しが発生する可能性は低いと判断できる。一方、その条件が成立しない場合は、上記吹き返しが発生する可能性が高いと判断できる。
【０１１２】
図８に示すフローチャートでは、上記ステップ１２０において、VT＜VT_０が成立すると判別された場合、次に、吸気管圧力Pmが、所定値Pm_０より高いか否かが判別される（ステップ１２２）。
既燃ガスの吹き返しの大きさは、バルブオーバーラップの有無或いは長短の他、吸気管圧力Pmの高低にも影響される。つまり、その吹き返しは、吸気管圧力Pmが低圧であるほど大きくなりやすく、一方、Pmが高圧であるほど発生し難くなる。所定値Pm_０は、VT＜VT_０が成立する環境下で、なお吹き返しが発生する可能性があるか否かを判断するための値である。従って、Pm＞Pm_０が成立する場合は、ポート内状態量を切り換えるほどの吹き返しが発生する可能性は低いと判断できる。一方、その条件が成立しない場合は、上記吹き返しが発生する可能性が高いと判断できる。
【０１１３】
図８に示すフローチャートでは、上記ステップ１２２において、Pm＞Pm_０が成立すると判別された場合、以後、図５に示す場合と同様に、ステップ１０４、１０６以降の処理が実行される。この場合、吹き返しの発生しない状況下で、実施の形態１の場合と同様に、ポート内状態量Pg、Tg、UgおよびTwに基づいて精度良く付着率Rおよび残留率Pが算出され、更に、その算出値RおよびPに基づいて、高精度な燃料噴射制御が実現される。
【０１１４】
これに対して、上記ステップ１２０においてVT＜VT_０が成立しないと判別された場合、および上記ステップ１２２においてPm＞Pm_０が成立しないと判別された場合は、次に、吹き返しが発生する場合のポート内状態量Pg_r、Tg_r、およびUg_rが推定される（ステップ１２４）。
【０１１５】
この場合、噴射燃料の付着率Rの基礎となる付着後蒸発量G2は、次式の通り、吹き返しの発生しない期間における蒸発量H2（Pg、Tg、Ug、Tw）と、吹き返しの発生する期間における蒸発量H’2（Pg_r、Tg_r、Ug_r、Tw）との和として推定される（ステップ１２６）。
G2＝H2（Pg、Tg、Ug、Tw）＋H’2（Pg_r、Tg_r、Ug_r、Tw） ・・・（１８）
【０１１６】
また、付着燃料の残留率Pの基礎となる開弁中蒸発量G3は、次式の通り、吹き返しの発生しない期間における蒸発量H3（Pg、Tg、Ug、Tw）と、吹き返しの発生する期間における蒸発量H’3（Pg_r、Tg_r、Ug_r、Tw）との和として推定される（ステップ１２８）。
G3＝H3（Pg、Tg、Ug、Tw）＋H’3（Pg_r、Tg_r、Ug_r、Tw） ・・・（１９）
【０１１７】
上記ステップ１２６および１２８の処理が実行された場合は、次に、今回の処理サイクルでは、付着後蒸発量G2および開弁中蒸発量G3を、それぞれ上記ステップ１２６および１２８で算出された値に補正する旨が指令される（ステップ１３０）。
【０１１８】
その後、ステップ１０４，１０６以降の処理が実行される。この場合、ステップ１０４において算出される蒸発総量Vfiは、飛行中蒸発量F2に、上記ステップ１２６で算出された付着後蒸発量G2を加えた値となる。また、ステップ１０６で算出される蒸発量Vfwは、閉弁中蒸発量F3に、上記ステップ１２８で算出された開弁中蒸発量G3を加えた値となる。このため、図８に示すフローチャートによれば、吸気ポート３０の内部に吹き返しが発生する場合に、その影響を精度良く付着率Rおよび残留率Pに反映させることができ、高精度な燃料噴射制御を実現することができる。
【０１１９】
［吹き返し発生時の残留率Pの具体的算出方法］
以下に示す（２０）式は、吹き返しが発生する状況下で付着燃料の残留率Pを算出するための数式モデルである。ECU５０は、上記ステップ１２０または１２２において、吹き返しが生ずる可能性があると判断した場合は、具体的には、次式（２０）に則って残留率Pを算出する。
【０１２０】
【数６】

【０１２１】
但し、上記（２０）式中、Δt_turb1は、乱流期間Δt_turbのうち、吹き返しの発生しない期間であり、一方、Δt_turb2は吹き返しが発生する期間である。また、ρg_rおよびB_２_rは、それぞれ、吹き返し発生時におけるポート内状態量Pg_r、Tg_rを用いて算出される空気密度（Pg_r／R_const・Tg_r）、および乱流時質量輸送係数（上記（１０）〜（１３）式参照）である。
【０１２２】
［吹き返し発生時の付着率Rの具体的算出方法］
以下に示す（２１）式は、吹き返しが発生する状況下で噴射燃料の付着率Rを算出するための数式モデルの一部、具体的には、上記（１４）式に示す付着率Rの数式モデル（R＝R1・α・R2）のうち、付着後の蒸発割合を意味するR2を算出するための数式モデルである。ECU５０は、上記ステップ１２０または１２２において、吹き返しが生ずる可能性があると判断した場合は、R2の数式モデルを、上記（１５）式に示すモデルから、下記（２１）式に示すモデルに変更して、付着率Rを算出する。尚、下記（２１）式中、Δt_turb1、Δt_turb2、ρg_rおよびB_２_rは、上記（２０）式の但し書きにおいて説明したものと同様である。
【０１２３】
【数７】

【０１２４】
以上説明した通り、本実施形態の装置は、噴射燃料の付着後の蒸発、および付着燃料の開弁中の蒸発を、それぞれ、吹き返しが発生する場合と発生しない場合とで異なる現象として捉えることができる。このため、本実施形態の装置によれば、吹き返しの発生時にも付着率Rおよび残留率Pを精度良く推定して、実施の形態１の場合に費しれ更に高精度な燃料噴射制御を実現することができる。
【０１２６】
実施の形態３．
次に、図９を参照して、本発明の実施の形態３について説明する。
本実施形態の装置は、実施の形態１の装置において、ECU５０に、上記図５に示すフローチャートに代えて、図９に示すフローチャートに沿って処理を実行させることにより実現することができる。
【０１２７】
吸気ポート３０の内壁温度は、内燃機関１０の暖機終了後も、ほぼ冷却水温度THWと等しい８０℃程度である。この程度の温度では、１サイクルの過程で付着燃料が蒸発し切らない。このため、吸気ポート３０の内壁においては、１サイクルを超える付着燃料の持ち越しが生ずる。これに対して、暖機後の吸気バルブ３４の温度は、１６０〜１８０℃となる。そして、壁面温度がこのように高温である場合は、通常、その表面に付着した燃料は１サイクルの過程で全て蒸発する。
【０１２８】
上述した実施の形態１の装置は、上記の現象を前提として付着燃料の残留率Pを算出している。つまり、付着燃料量fwは、その全てが吸気ポート３０の壁面に付着しており、吸気バルブ３４の表面には付着燃料が発生しないものとして残留率Pの算出を行っている。このため、上記（９）式では、残留率Pを算出するための基礎データとして、ポート内状態量Pg、Tg、UgおよびTwが用いられている。
【０１２９】
ところで、吸気バルブ３４の表面に付着燃料が残留しないという前提は、内燃機関１０の暖機終了前、つまり、吸気バルブ３４の温度が十分に高温となる前は成立しない。そして、そのような状況下では、吸気ポート３０の壁面付近と吸気バルブ３４の表面付近とで、燃料の蒸発特性に影響を与える状態量が異なることから、吸気ポート３０の壁面に付着した燃料と、吸気バルブ３４の表面に付着した燃料とは、異なる蒸発挙動を示す。この場合、付着燃料の残留率Pを精度良く推定するためには、吸気ポート３０の壁面における残留割合と、吸気バルブ３４の表面における残留割合とを別々に算出することが望ましい。
【０１３０】
［実施の形態３における処理の流れ］
図９は、上記の要求に応えつつ、残留率Pおよび付着率Rを算出し、更に、それらの値P、Rを用いて燃料噴射量fiを適正に補正するために、ECU５０が実行する処理の流れを説明するためのフローチャートである。
【０１３１】
図９に示すフローチャートは、ステップ１０２の後に、ステップ１４０〜１４８が挿入されている点を除き、上記図５に示すフローチャートと同様である。すなわち、図９において、ステップ１００〜１０６、およびステップ１１０〜１１４は、それぞれ図５に示すステップと同様である。また、図９に示すステップ１０８ａおよび１０８ｂは、図５に示すステップ１０８を分解して示したもので、それぞれのステップでは、ステップ１０８の場合と同様の手法で付着率Rおよび残留率Pが算出される。
【０１３２】
図９に示すフローチャートによれば、ステップ１００および１０２の処理が実行された後、実施の形態１の場合（図５に示す場合）と同様の手順で噴射燃料の付着率Rが算出される（ステップ１０４，１０８ａ）。
【０１３３】
付着燃料の残留率Pを算出する手順においては、ステップ１０２の後に、先ず、壁面温度Twが所定値Tw_０より低いかどうかが判別される（ステップ１４０）。所定値Tw_０は、内燃機関１０の暖機が不十分であるか、より具体的には、吸気バルブ３４の表面に付着燃料が残存する程度にその暖機が不十分であるかを判断するための判定値である。
【０１３４】
従って、上記ステップ１４０において、Tw＜Tw_０が成立しないと判別された場合は、内燃機関１０の暖機が十分に進んでおり、付着燃料の残留率Pを推定するうえでは、もはや吸気バルブ３４の表面における燃料の蒸発を考慮する必要がないと判断できる。図９に示すフローチャートでは、この場合、以後、実施の形態１の場合（図５に示す場合）と同様の手順で付着燃料の残留率Pが算出される（ステップ１０６，１０８ｂ）。
【０１３５】
一方、上記ステップ１４０において、Tw＜Tw_０が成立すると判別された場合は、付着燃料の残留率Pを推定するうえで、吸気バルブ３４の表面に残留する燃料の影響が無視できないことが判断できる。図９に示すフローチャートでは、この場合、ポート部（P）とバルブ部（V）に分けて状態量が推定される（ステップ１４２）。
【０１３６】
ガス圧力とガス温度は、吸気ポート３０の壁面付近と、吸気バルブ３４の表面付近とで大きくは異ならない。このため、ガス圧力とガス温度は、両者に対して共通な値Pg、Tgが推定される。一方、ガス流速と壁面温度は、吸気ポート３０の壁面付近と、吸気バルブ３４の表面付近とで大きく異なることがある。このため、ガス流速と壁面温度については、ポート部（P）とバルブ部（V）につき、それぞれ異なる値Ugp、TwpおよびUgv、Twvが推定される。
【０１３７】
上記ステップ１４２において推定すべき状態量のうち、PgおよびTg、並びにUgpおよびTwpについては、上記ステップ１０２において推定されたポート内状態量Pg、Tg、UgおよびTwをそのまま流用することができる。従って、ステップ１４２では、実質的には、バルブ部ガス流速Ugvとバルブ部壁面温度Twvについての推定が行われる。これらの値UgvおよびTwvは、例えば、机上シミュレーションの結果に基づいて定めた係数を、ベースの状態量（UgまたはTw）に掛け合わせることにより推定することができる。
【０１３８】
上記ステップ１４２の処理が終了すると、次に、燃料付着量fwの分配率βが決定されると共に、その分配率βを用いて、ポート部付着量fwp＝fw・β、およびバルブ部付着量fwv＝fw・（１−β）が算出される（ステップ１４４）。
分配率βは、ポート部とバルブ部にどのような割合で付着しているかを表す値であり、例えば、ポート内壁面温度Tw、吸気管圧力Pm、および付着燃料量fwなどのパラメータから推定することができる。ECU５０は、それらのパラメータTw、Pm、fwとの関係で分配率を定めたマップを記憶しており、本ステップ１４４では、そのマップを参照することで分配率が決定される。
【０１３９】
図９に示すフローチャートでは、次に、ポート部における付着燃料の蒸発量Vfw,pと、バルブ部における付着燃料の蒸発量Vfw,vがそれぞれ推定される（ステップ１４６）。
ポート部蒸発量Vfw,pは、以下に示すように、蒸発量Vfwの数式モデル（上記（６）式）に、ポート部における状態量Pg、Tg、UgpおよびTwpを代入することで求めることができる。
Vfw,p＝F3（Pg、Tg、Twp）＋G3（Pg、Tg、Ugp、Twp） ・・・（２１）
また、バルブ部蒸発量Vfw,vは、以下に示すように、蒸発量Vfwの数式モデル（上記（６）式）に、バルブ部における状態量Pg、Tg、UgvおよびTwvを代入することで求めることができる。
Vfw,p＝F3（Pg、Tg、Twv）＋G3（Pg、Tg、Ugv、Twv） ・・・（２２）
【０１４０】
上記の処理が終了すると、それらの処理により求めた値を次式に代入することで、ポート部残留率Pp、およびバルブ部残留率Pvが算出される（ステップ１４８）。
Pp＝（fwp−Vfw,p）／fwp ・・・（２３）
Pv＝（fwv−Vfw,v）／fwv ・・・（２４）
【０１４１】
上記ステップ１４８では、更に、算出されたPpおよびPvを、次式に代入することで、付着燃料全体の残留率Pが算出される。
P＝Pp・β＋Pv・（１−β） ・・・（２５）
【０１４２】
以上説明した通り、図９に示すフローチャートによれば、壁面温度Twが高温である場合は、実施の形態１の場合と同様に手法で付着燃料の残留率Pを算出（ステップ１０８ｂ参照）することができ、また、壁面温度Twが低温である場合は、バルブ部とポート部を個別に考慮した手法で付着燃料の残留率Pを算出することができる。従って、本実施形態の装置によれば、内燃機関１０の暖機後において精度良く残留率Pが算出できると共に、その暖機の過程においても、残留率Pを精度良く算出することができる。
【０１４３】
図９に示すフローチャートでは、上記ステップ１０８ａにおいて噴射燃料の付着率Rが算出され、かつ、上記ステップ１０８ｂまたは１４８において付着燃料の残留率Pが算出された後、実施の形態１の場合（図５に示す場合）と同様に、燃料噴射量fiの算出等が行われる（ステップ１１０〜１１４）。このため、本実施形態の装置によれば、精度良く算出した付着率Rおよび残留率Pを用いて、高精度な燃料噴射制御を実現することができる。
【０１４４】
［ポート部残留率Ppの具体的算出方法］
以下に示す（２６）式は、ポート部残留率Ppを算出するための数式モデルである。ECU５０は、上記ステップ１４０において壁面温度Twが所定値Tw_０より低いと判断した場合は、次式（２６）に則ってポート部残留率Ppを算出する。
【０１４５】
【数８】

【０１４６】
但し、上記（２６）式中、hpは、吸気ポート３０の壁面に付着している燃料の膜厚であり、上記ステップ１４４において算出されるポート部付着量fwpを燃料密度ρlで除したものを、吸気ポート３０の濡れ面積sp（既定値）で除することにより算出される値fwp／ρl／spである。また、B_１pおよびB_２pは、それぞれ、ポート部の状態量Pg、Tg、UgpおよびTwpを用いて算出される層流時質量輸送係数、および乱流時質量輸送係数（上記（１０）〜（１３）式参照）である。
【０１４７】
［バルブ部残留率Pvの具体的算出方法］
以下に示す（２７）式は、バルブ部残留率Pvを算出するための数式モデルである。ECU５０は、上記ステップ１４０において壁面温度Twが所定値Tw_０より低いと判断した場合は、次式（２７）に則ってバルブ部残留率Pvを算出する。
【０１４８】
【数９】

【０１４９】
但し、上記（２７）式中、hvは、吸気バルブ３４の表面に付着している燃料の膜厚であり、上記ステップ１４４において算出されるバルブ部付着量fwvを燃料密度ρlで除したものを、吸気バルブ３４の濡れ面積sv（既定値）で除することにより算出される値fwv／ρl／svある。また、B_１vおよびB_２vは、それぞれ、バルブ部の状態量Pg、Tg、UgvおよびTwvを用いて算出される層流時質量輸送係数、および乱流時質量輸送係数（上記（１０）〜（１３）式参照）である。
【０１５１】
実施の形態４．
次に、図１０を参照して、本発明の実施の形態４について説明する。
本実施形態の装置は、実施の形態１の装置において、ECU５０に、上記図５に示すフローチャートに代えて、図１０に示すフローチャートに沿って処理を実行させることにより実現することができる。
【０１５２】
上述した実施の形態１の装置は、噴射燃料の壁面付着後の蒸発挙動は、吸気ポート３０の壁面でも、吸気バルブ３４の表面でも同じであるものとして付着率RRを算出している。しかしながら、既述した通り、吸気ポート３０の壁面近傍と吸気バルブ３４の表面近傍とでは、ガス流速や壁面温度などに無視できない差が生ずる。このため、噴射燃料の付着率Rを精度良く算出するためには、その算出の過程においても、ポート部における状態量と、バルブ部における状態量との差を考慮することが望ましい。
【０１５３】
［実施の形態４における処理の流れ］
図１０は、上記の要求に応えつつ、残留率Pおよび付着率Rを算出し、更に、それらの値P、Rを用いて燃料噴射量fiを適正に補正するために、ECU５０が実行する処理の流れを説明するためのフローチャートである。
【０１５４】
図１０に示すフローチャートは、噴射燃料の付着率Rを算出するためのステップが、ステップ１０６および１０８（その一部）から、ステップ１５０〜１５６に置き換えられている点を除き、上記図５に示すフローチャートと同様である。以下、図１０に示すフローチャートの特徴部について説明する。
【０１５５】
図１０に示すフローチャートによれば、噴射燃料の付着率Rを算出する手順では、先ず、ポート部（P）とバルブ部（V）に分けて状態量が推定される（ステップ１５０）。
本ステップ１５０の処理は、図９に示すステップ１４２の処理と同様である。ここでは、具体的には、上記ステップ１０２で推定された状態量Pg、Tg、UgおよびTwが、ポート部とバルブ部とで共通の状態量PgおよびTg、並びにポート部における状態量UgpおよびTwgとして流用される。そして、シミュレーションにより定めた係数をベースの状態量（UgまたはTw）に掛け合わせることにより、バルブ部における状態量UgvおよびTwvが推定される。
【０１５６】
次に、ポート部およびバルブ部に付着する噴射燃料のうち、ポート部に分配される割合（ポート割合γ）が決定される（ステップ１５２）。
ポート割合γは、例えば、機関回転数NEおよび吸気管圧力Pmなどのパラメータから推定することができる。ECU５０は、それらのパラメータNEおよびPmとの関係でポート割合γを定めたマップを記憶している。本ステップ１４４では、そのマップを参照することでポート割合γが決定される。
【０１５７】
次いで、ポート部における蒸発総量Vfi,pと、バルブ部における蒸発総量Vfi,vとが、それぞれ推定される（ステップ１５４）。
ポート部蒸発総量Vfi,pは、以下に示すように、蒸発総量Vfiの数式モデル（上記（４）式）に、ポート部における状態量Pg、Tg、UgpおよびTwpを代入することで求めることができる。
Vfi,p＝F2（Pg、Tg、Twp）＋G2（Pg、Tg、Ugp、Twp） ・・・（２８）
また、バルブ部蒸発総量Vfi,vは、以下に示すように、蒸発総量Vfiの数式モデル（上記（４）式）に、バルブ部における状態量Pg、Tg、UgvおよびTwvを代入することで求めることができる。
Vfi,p＝F2（Pg、Tg、Twv）＋G2（Pg、Tg、Ugv、Twv） ・・・（２９）
【０１５８】
上記の処理が終了すると、それらの処理により求めた値を次式に代入することで、ポート部付着率Rp、およびバルブ部付着率Rvが算出される（ステップ１５６）。
Rp＝（γ・fi−Vfi,p）／（γ・fi） ・・・（３０）
Rv＝｛（１−γ）・fi−Vfi,v｝／（１−γ）fi ・・・（３２）
【０１５９】
上記ステップ１５６では、更に、算出されたRpおよびRvを、次式に代入することで、噴射燃料全体の付着率Rが算出される。
R＝Rp・γ＋Rv・（１−γ） ・・・（３３）
【０１６０】
以上説明した通り、図１０に示すフローチャートによれば、付着燃料の残留率Pを実施の形態１の場合と同様の手法で算出し（ステップ１０８ｂ参照）、かつ、噴射燃料の付着率を、ポート部とバルブ部における蒸発挙動の相違を考慮した手順で算出することができる。このため、本実施形態の装置によれば、実施の形態１の場合に比して、更に精度良く噴射燃料の付着率Rを算出し、その値Rを用いて、更に高精度な燃料噴射制御を実現することができる。
【０１６１】
［ポート部付着率Rpの具体的算出方法］
以下に示す（３４）〜（３６）式は、ポート部付着率Rpを算出するための演算式である。ECU５０は、上記図１０に示すステップ１５０〜１５６の処理を進めるにあたり、具体的には、これら（３４）〜（３６）式を用いてポート部付着率Rpを算出する。
【０１６２】
【数１０】

【０１６３】
但し、上記（３４）式中、αpは、吸気ポート３０の壁面に到達した液滴燃料が、反射により失われずにその壁面に付着する割合（固定値）である。また、上記（３５）式中、B_１pは、ポート部の状態量Pg、Tg、UgpおよびTwpを用いて算出される層流時質量輸送係数（上記（１０）〜（１３）式参照）である。更に、上記（３６）式中、hpは、吸気ポート３０の壁面に付着している燃料の膜厚であり、また、B_２pは、ポート部の状態量Pg、Tg、UgpおよびTwpを用いて算出される乱流時質量輸送係数（上記（１０）〜（１３）式参照）である。尚、燃料の膜厚hpは、実施の形態３の場合と同様の手法で算出するものとする。
【０１６４】
［バルブ部付着率Rvの具体的算出方法］
以下に示す（３７）〜（３９）式は、ポート部付着率Rvを算出するための演算式である。ECU５０は、上記図１０に示すステップ１５０〜１５６の処理を進めるにあたり、具体的には、これら（３７）〜（３９）式を用いてバルブ部付着率Rvを算出する。
【０１６５】
【数１１】

【０１６６】
但し、上記（３７）式中、αvは、吸気バルブ３４の表面に到達した液滴燃料が、反射により失われずにその表面に付着する割合（固定値）である。また、上記（３８）式中、B_１vは、バルブ部の状態量Pg、Tg、UgvおよびTwvを用いて算出される層流時質量輸送係数（上記（１０）〜（１３）式参照）である。更に、上記（３９）式中、hvは、吸気バルブ３４の表面に付着している燃料の膜厚であり、また、B_２vは、バルブ部の状態量Pg、Tg、UgvおよびTwvを用いて算出される乱流時質量輸送係数（上記（１０）〜（１３）式参照）である。尚、燃料の膜厚hvは、実施の形態３の場合と同様の手法で算出するものとする。
【０１６７】
ところで、上述した実施の形態４においては、付着燃料の残留率Pを、実施の形態１の場合と同様の手法で算出することとしているが、その算出の手法はこれに限定されるものではない。すなわち、付着燃料の残留率Pについても、実施の形態３の場合と同様に、ポート部とバルブ部における蒸発挙動の相違を考慮した手法で算出することとしてもよい。
【０１６９】
実施の形態５．
次に、図１１を参照して、本発明の実施の形態５について説明する。
本実施形態の装置は、実施の形態１の装置において、ECU５０に、上記図５に示すフローチャートに代えて、図１１に示すフローチャートに沿って処理を実行させることにより実現することができる。
【０１７０】
上述した実施の形態１の装置は、付着燃料の減少要因として蒸発のみを考慮して、残留率Pを算出している。これに対して、付着燃料量fwが多くなると、液だれによる付着燃料の減少が生じ易くなる。そこで、本実施形態の装置は、付着燃料量fwが多量である状況下では、液だれの影響をも考慮して付着燃料の残留率Pを算出する。
【０１７１】
［実施の形態５における処理の流れ］
図１１は、上記の要求に応えつつ、残留率Pおよび付着率Rを算出し、更に、それらの値P、Rを用いて燃料噴射量fiを適正に補正するために、ECU５０が実行する処理の流れを説明するためのフローチャートである。
【０１７２】
図１１に示すフローチャートは、付着燃料の残留率Pを算出するための処理として、ステップ１６０〜１６４が追加されていると共に、残留率Pを算出するためのステップが、ステップ１０８からステップ１６６に変更されている点を除き、上記図５に示すフローチャートと同様である。以下、図１０に示すフローチャートの特徴部について説明する。
【０１７３】
図１１に示すフローチャートによれば、ステップ１０２においてポート内状態量が推定された後、ステップ１０４および１０６の処理と共に、燃料付着量fwが判定値δより多量であるかが判別される（ステップ１６０）。
【０１７４】
判定値δは、付着燃料に液だれを生ずるか否かを判断するための値である。このため、fw＞δが成立しないと判別された場合は、残留率Pを算出するうえで、液だれの影響が無視できると判断できる。この場合、付着燃料の液だれ量Ffwが０とされる（ステップ１６２）。
【０１７５】
一方、上記ステップ１６０において、燃料付着量fwが判定値δより多量であると判別された場合は、残留率Pを算出するうえで液だれの影響を考慮すべきことが判断できる。この場合、次に、ポート内状態量Pg、Tg、UgおよびTwに基づいて、液だれ量Ffwが算出される（ステップ１６４）。
尚、液だれ量Ffwは、例えば、ケンブリッジ大学文献SAE１９９９−０１−１３１４などに開示される公知の手法で算出することができる。
【０１７６】
図１１に示すフローチャートでは、上記ステップ１０４，１０６および１６０〜１６４の処理が終了した後、実施の形態１の場合と同様の手法で噴射燃料の付着率Rが算出されると共に、以下に示す演算式に従って、付着燃料の残留率Pが算出される。
P＝（fw−Vfw−Ffw）／fw ・・・（３９）
【０１７７】
上記（３９）式によれば、付着燃料量fwが液だれにより減少する場合には、その影響Ffwを考慮して残留率Pを算出することができる。このため、本実施形態の装置によれば、液だれが発生する状況下では、実施の形態１乃至４の装置に比して、更に高精度な燃料噴射制御を実現することができる。
【０１７８】
尚、上述した実施の形態５においては、ECU５０が、上記ステップ１６０〜１６４の処理を実行することにより前記第３の発明における「液だれ量推定手段」が、また、上記ステップ１６６の処理を実行することにより前記第３の発明における「液だれ加味手段」が、それぞれ実現されている。
【０１８３】
【発明の効果】
この発明は以上説明したように構成されているので、以下に示すような効果を奏する。
第１の発明によれば、噴射燃料が吸気ポートの内部に付着する以前の挙動を、飛行過程での蒸発挙動を表す飛行蒸発モデルと、壁面反射による蒸発挙動を表す反射蒸発モデルの双方を用いて捕らえることができる。このため、本発明によれば、壁面に付着する以前に混合気中に失われる燃料の挙動を精度良く推定することができ、その結果、制御パラメータを高い精度で算出することができる。
【０１８４】
第２の発明によれば、吸気ポートの内部に付着した燃料の蒸発挙動を、吸気バルブの閉弁中における閉弁中蒸発挙動モデルと、吸気バルブの開弁中における開弁中蒸発挙動モデルの双方を用いて捕らえることができる。このため、本発明によれば、付着燃料の蒸発挙動を精度良く推定することができ、その結果、制御パラメータを高い精度で算出することができる。
【０１８７】
第３の発明によれば、付着燃料が、液だれにより減少する場合には、その液だれの影響を加味して、精度良く燃料制御パラメータを算出することができる。
【図面の簡単な説明】
【図１】 本発明の実施の形態１の構成を説明するための図である。
【図２】 図１に示す内燃機関の吸気ポート近傍を拡大して表した図である。
【図３】 吸入空気量Vの変化と燃料付着量fwの変化との関係を示す図である。
【図４】 内燃機関の始動直後に噴射された燃料の内訳を、クランク角CAとの関係で示したシミュレーション結果である。
【図５】 実施の形態１の装置において実行される処理の流れを説明するためのフローチャートである。
【図６】 噴射燃料が壁面に付着して付着燃料となるプロセスを説明するための図である。
【図７】 吸気工程の終了時に付着燃料として吸気ポート内に残留していた燃料が、次サイクルの吸気工程終了時までに蒸発するプロセスを説明するための図である。
【図８】 実施の形態２の装置において実行される処理の流れを説明するためのフローチャートである。
【図９】 実施の形態３の装置において実行される処理の流れを説明するためのフローチャートである。
【図１０】 実施の形態４の装置において実行される処理の流れを説明するためのフローチャートである。
【図１１】 実施の形態５の装置において実行される処理の流れを説明するためのフローチャートである。
【符号の説明】
１０ 内燃機関
１２ 吸気通路
２０ エアフロメータ
２２ スロットルバルブ
３２ 燃料噴射弁
３４ 吸気バルブ
３６、４０ 可変バルブタイミング機構
fw 燃料付着量
fi 燃料噴射量
VT 吸気バルブの開弁タイミング
P 残留率
R 付着率
Vfi 噴射燃料の蒸発総量
fw 蒸発量
Pg ポート内ガス圧力
Tg ポート内ガス温度
Ug ポート内ガス流速
Tw ポート内壁面温度[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device suitable for controlling the fuel injection amount of a port injection type internal combustion engine.
[0002]
[Prior art]
In a port injection type internal combustion engine, fuel is injected into an intake port by a fuel injection valve disposed in an intake passage. The fuel injected in this way is sucked into the cylinder together with air by introducing the in-cylinder negative pressure to the intake port as the intake valve opens. Part of the fuel injected into the intake port adheres to the inner wall and the like. In the steady state, the fuel adhesion amount is constant, and the amount of fuel sucked into the cylinder is equal to the amount of fuel injected.
[0003]
However, during the transient operation of the internal combustion engine, the intake air amount and the fuel injection amount change, so that the fuel adhesion amount also increases or decreases. While this increase / decrease occurs, there is a difference between the amount of fuel sucked into the cylinder and the amount of fuel injected. Therefore, in order to draw a desired amount of fuel into the cylinder during the transient operation, it is necessary to correct the fuel injection amount so that the increase and decrease in the fuel adhesion amount are offset.
[0004]
Japanese Patent No. 2754744 discloses a fuel injection amount control device for correcting the fuel injection amount in the port injection type internal combustion engine. This apparatus has a fuel behavior model in which the amount of fuel adhering to the intake port is a state variable. The parameters of the fuel behavior model are updated according to the operating state of the internal combustion engine. This device calculates the fuel adhesion amount in accordance with the fuel behavior model updated in accordance with the operating state of the internal combustion engine, and corrects the fuel injection amount based on the calculated amount.
[0005]
[Patent Document 1]
Japanese Patent No. 2754744
[Patent Document 2]
Japanese Patent No. 2705298
[Patent Document 3]
JP-A-8-21274
[Patent Document 4]
JP-A-6-93528
[0006]
[Problems to be solved by the invention]
In the above conventional apparatus, the parameters of the fuel behavior model are related to the operating state of the internal combustion engine, and more specifically, the operating state of the internal combustion engine, such as the intake pipe pressure Pm, the engine speed NE, or the intake air temperature THA. It is a conforming value determined in relation to the state quantity representing. In order to ensure high accuracy in such a fuel behavior model, it is necessary to spend a great deal of man-hours to improve the accuracy of parameter adaptation. On the other hand, there is a limit to the accuracy of a fuel behavior model that uses a conforming value determined based on the operating state of the internal combustion engine as a parameter. For this reason, the above-described conventional apparatus requires a lot of man-hours for development, but still leaves room for improvement with respect to the correction accuracy of the fuel injection amount.
[0007]
The present invention has been made in order to solve the above-described problems. By calculating the fuel adhesion amount according to a model related to the fuel adhesion amount based on the state quantity inside the intake port, the present invention is always highly accurate. An object of the present invention is to provide a fuel injection control device for an internal combustion engine that can correct the fuel injection amount.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, a first invention is a fuel injection control device for an internal combustion engine,
  A fuel injection valve that injects fuel into the intake port;
  In-port state quantity acquisition means for acquiring an in-port state quantity representing an internal state of the intake port;
  Model storage means for storing a mathematical model described using the in-port state quantity as a parameter in order to represent the evaporation behavior of fuel inside the intake port;
  Fuel control parameter calculation means for calculating a fuel control parameter for calculating the amount of attached fuel remaining inside the intake port at the end of the intake process based on the in-port state quantity, according to the mathematical model;
  An attached fuel amount calculating means for calculating the amount of the attached fuel based on the fuel control parameter;
  Injection amount correction means for correcting the fuel injection amount to eliminate the influence of the adhered fuel;Prepared,  The mathematical model is
  A flight evaporation model representing evaporation behavior of a fuel injected from the fuel injection valve in a flight process inside the intake port;
  A reflection evaporation model representing evaporation behavior due to wall reflection of the injected fuel;
  A post-attachment evaporation behavior model that represents the behavior when the injected fuel evaporates in the air-fuel mixture before the intake step is completed after the inside of the intake port is attached;
  An attached fuel evaporation behavior model representing an evaporation behavior of the attached fuel inside the intake port, and
  The fuel control parameter calculation means includes
  Using the flight evaporation model, the reflection evaporation model, and the post-attachment evaporation behavior modelFirst calculating means for calculating a first fuel control parameter;
  Second calculating means for calculating a second fuel control parameter in accordance with the attached fuel evaporation behavior model.It is characterized by that.
[0009]
  In addition, the second invention,A fuel injection valve that injects fuel into the intake port;
  In-port state quantity acquisition means for acquiring an in-port state quantity representing an internal state of the intake port;
  Model storage means for storing a mathematical model described using the in-port state quantity as a parameter in order to represent the evaporation behavior of fuel inside the intake port;
  Fuel control parameter calculation means for calculating a fuel control parameter for calculating the amount of attached fuel remaining inside the intake port at the end of the intake process based on the in-port state quantity, according to the mathematical model;
  An attached fuel amount calculating means for calculating the amount of the attached fuel based on the fuel control parameter;
  Injection amount correction means for correcting the fuel injection amount to eliminate the influence of the adhered fuel,  The mathematical model is
  An injection fuel evaporation behavior model representing evaporation behavior of the injected fuel injected from the fuel injection valve inside the intake port;
  An evaporation behavior model during valve closing representing evaporation behavior of the adhering fuel during closing of the intake valve;
  An evaporation behavior model during valve opening representing an evaporation behavior of the attached fuel during opening of the intake valve, and
  The fuel control parameter calculation means includes
  First calculation means for calculating a first fuel control parameter in accordance with the injected fuel evaporation behavior model;
  Second calculating means for calculating a second fuel control parameter by using both the evaporation behavior model during valve closing and the evaporation behavior model during valve opening.It is characterized by that.
[0010]
  In addition, the third invention,A fuel injection valve that injects fuel into the intake port;
  In-port state quantity acquisition means for acquiring an in-port state quantity representing an internal state of the intake port;
  Model storage means for storing a mathematical model described using the in-port state quantity as a parameter in order to represent the evaporation behavior of fuel inside the intake port;
  Fuel control parameter calculation means for calculating a fuel control parameter for calculating the amount of attached fuel remaining inside the intake port at the end of the intake process based on the in-port state quantity, according to the mathematical model;
  An attached fuel amount calculating means for calculating the amount of the attached fuel based on the fuel control parameter;
  Injection amount correction means for correcting the fuel injection amount so as to eliminate the influence of the adhered fuel;
  A dripping amount estimating means for estimating an amount by which the adhered fuel decreases due to dripping, and
  The fuel control parameter calculation means includes liquid dripping means for adding the influence of the liquid dripping to the fuel control parameter.It is characterized by that.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.
[0018]
Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. The configuration shown in FIG. 1 includes an internal combustion engine 10. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end. An intake air temperature sensor 18 is assembled to the air filter 16.
[0019]
An air flow meter 20 is disposed downstream of the air filter 16. The air flow meter 20 is a sensor that detects an intake air amount GA flowing through the intake passage 12. A throttle valve 22 is provided downstream of the air flow meter 20. A throttle sensor 24 that detects the throttle opening degree TA and an idle switch 26 that is turned on when the throttle valve 22 is fully closed are disposed in the vicinity of the throttle valve 22.
[0020]
A surge tank 28 is provided downstream of the throttle valve 22. Further, a fuel injection valve 32 for injecting fuel into the intake port 30 of the internal combustion engine 10 is disposed further downstream of the surge tank.
[0021]
The internal combustion engine 10 includes a variable valve timing (VVT) mechanism 36 that drives an intake valve 34 and a VVT mechanism 40 that drives an exhaust valve 38. The internal combustion engine 10 further includes a water temperature sensor 42 that detects the coolant temperature THW and a rotation speed sensor 44 that detects the engine rotation speed NE.
[0022]
The system of this embodiment includes an ECU (Electronic Control Unit) 50. A fuel injection valve 32 and VVT mechanisms 36 and 40 are connected to the ECU 50 together with the various sensors described above. The ECU 50 can drive the fuel injection valve 32 to inject a desired fuel, detect the states of the VVT mechanisms 36 and 40, and drive them appropriately.
[0023]
[Necessity of fuel injection amount correction]
FIG. 2 is an enlarged view of the vicinity of the intake port 30. Hereinafter, as shown in FIG. 2, the amount of fuel injected from the fuel injection valve 32 is referred to as “fuel attachment amount fi”, and the amount of fuel attached to the wall surface of the intake port 30 or the surface of the intake valve 34 is referred to as “fuel attachment amount”. “fw”, and the amount of fuel sucked into the cylinder is referred to as “fuel intake amount fc”.
[0024]
The fuel adhesion amount fi can be classified into the following (1) and (2).
(1): A portion that adheres to the port or valve and becomes a part of the fuel adhesion amount fw.
(2): A portion that is directly sucked into the cylinder and becomes a part of the fuel intake amount fc.
Further, the fuel adhesion amount fw can be classified into (3) and (4) below.
(3) A portion where the fuel adhesion amount fw still remains after one cycle.
{Circle around (4)} A portion that is detached in the course of one cycle and becomes a part of the fuel intake amount fc.
[0025]
According to the above classification, the fuel intake amount fc per cycle can be expressed as (2) + (4). In the steady state, (1) = (4) is established, and the fuel intake amount fc = (2) + (4) is equal to (1) + (2), that is, the fuel adhesion amount fi and the equal amount. Become. Therefore, in the steady state, if the fuel injection valve 32 is controlled so that the fuel adhesion amount fi matches the target fuel intake amount fc without considering the influence of the fuel adhesion amount fw, the desired air-fuel ratio A / F Can be realized.
[0026]
FIG. 3 is a diagram showing the relationship between the intake air amount V and the fuel adhesion amount fw. As shown in FIG. 3, the fuel attachment amount fw changes with the change in the intake air amount V. Therefore, when the operating state of the internal combustion engine 10 changes from A to B, and a change in V (B−A) occurs in the intake air amount V accordingly, a constant air-fuel ratio A / F is maintained before and after that. In order to achieve this, the fuel injection amount fi is changed by an amount commensurate with the change amount V (B−A) of the intake air amount V, and the fuel adhesion amount fw is increased from fw (A) to fw (B). Therefore, it is necessary to correct the fuel injection amount fi to compensate for the increase.
[0027]
[Explanation of basic control concept]
The apparatus according to the present embodiment corrects the fuel injection amount to cancel the change in the fuel adhesion amount fw during the transient operation of the internal combustion engine 10. Hereinafter, a basic concept for realizing the correction will be described with reference to FIG.
[0028]
FIG. 4 is a simulation result showing a breakdown of the fuel injected immediately after starting the internal combustion engine in relation to the crank angle CA. In this figure, the vertical axis represents the ratio (mass ratio) of the mass of each breakdown remaining in the intake port 30 to the fuel injection amount fi. The waveform indicated by reference numeral (1) indicates the mass ratio of the total amount of fuel (Total) remaining in the intake port.
[0029]
All of the injected fuel remains inside the intake port 30 until the intake valve 34 is opened. Therefore, Total (1) is maintained at 1.0 until the intake valve is opened. In FIG. 4, it is a simulation error that Total 1 is slightly smaller than 1.0 before the valve is opened. Total (1) decreases when the intake valve 34 is opened and fuel is sucked into the cylinder. Then, when the intake valve 34 is closed and the intake of fuel is completed, the intake valve 34 is thereafter maintained at a constant value.
[0030]
The waveform indicated by reference numeral (2) is the mass ratio of the fuel (Drop) present in the form of droplets. Drop (2) increases rapidly immediately after fuel injection, and then decreases rapidly due to vaporization of droplets and adhering fuel.
[0031]
The waveform indicated by reference numeral (3) is the mass ratio of the fuel (Film) adhering to the inner wall of the intake port 30 or the surface of the intake valve 34 in a film form. The film {circle around (3)} increases rapidly as the drop {circle around (2)} decreases, and the intake valve 34 is opened, and starts to decrease by generating an intake air flow. The film {circle around (3)} maintains a decreasing tendency as the adhering fuel evaporates even after the intake valve 34 is closed.
[0032]
The waveform indicated by reference numeral (4) is the mass ratio of vaporized fuel (Vapor). Vapor (4) continues to increase gradually until the intake valve 34 is opened after fuel is injected, and shows a rapid decrease after the intake valve 34 is opened. Then, immediately before the intake valve 34 is closed, the fuel tends to increase again as the attached fuel vaporizes.
[0033]
As shown in FIG. 4, when the intake valve 34 is closed, fuel in the form of a liquid film (attached fuel) and fuel in the form of vaporized fuel (Vapor) are contained in the intake port 30. Existing. In the present specification, the above-mentioned “fuel adhesion amount fw” strictly means the sum of the fuel amounts existing in these two forms, that is, the total {circle over (1)} when the intake valve 34 is closed. Suppose you are pointing.
[0034]
More specifically, the film {circle around (3)} present in the form of a liquid film in the intake port 30 includes the amount of port wet attached to the inner wall of the intake port 30 and the valve wet attached to the surface of the intake valve 34. Consists of quantity and. In FIG. 4, the waveform indicated by symbol (5) is the port wet amount (PWET) waveform, and the waveform indicated by symbol (6) is the valve wet amount (VWET). It is a waveform.
[0035]
The result of the simulation shown in FIG. 4 is a result when the fuel is injected with the fuel adhesion amount fw being zero. Therefore, in this result, the value of Total (1) at the time when the intake valve 34 is closed is the ratio of the fuel amount remaining inside the intake port 30 out of the fuel injection amount fi, that is, “attachment”. This is the ratio of the amount of fuel that constitutes the fuel amount fw. Hereinafter, this ratio is referred to as “attachment rate R” of the injected fuel.
[0036]
When the crank angle further rotates beyond 540 ° CA shown in FIG. 4, the next intake process is started. At the start of this intake stroke, the fuel attachment amount fw corresponding to Total (1) determined when the intake valve 34 is closed already exists in the intake port 30. In this case, a part of the fuel adhesion amount fw is sucked into the cylinder by the intake stroke. Then, the fuel that has not been sucked in is carried over to the next cycle as part of the fuel adhesion amount fw. Hereinafter, the ratio of the fuel adhesion amount fw carried over to the next cycle in this way is referred to as “residual rate P” of the adhered fuel.
[0037]
By using the “deposition rate R” and “residual rate P” described above, the fuel adhesion amount fw present at the end of the intake process of each cycle is equal to the fuel adhesion amount fwO generated in the previous cycle and the current cycle. Can be expressed as follows using the fuel injection amount fi.
fw = R ・ fi + P ・ fwO (1)
[0038]
In addition, if the above-mentioned “adhesion rate R” and “residual rate P” and the fuel adhesion amount fwO generated in the previous cycle are known, the fuel injection amount fi generated in the current cycle is actually in the cylinder. The fuel suction strength fc to be sucked can be calculated (predicted) as follows.
fc = (1-R) / fi + (1-P) / fwO (2)
[0039]
Therefore, in each cycle, if the fuel injection amount fi is corrected so that the above fc becomes the target value before fuel injection, the influence of the fuel adhesion amount fw is eliminated, and the desired air-fuel ratio A / F is always obtained. It is possible to obtain
[0040]
[Calculation of residual rate P and adhesion rate R by model]
As described above, in the apparatus of this embodiment, if the adhesion rate R of the injected fuel and the residual rate P of the adhered fuel are known, the fuel adhesion amount fw generated in each cycle can be accurately calculated. Further, it is possible to realize highly accurate fuel injection amount control by eliminating the influence of the fuel adhesion amount fw.
[0041]
The adhesion rate R of the injected fuel and the residual rate P of the adhering fuel can be specified by, for example, preparing a conformity map determined in advance in relation to the operating state of the internal combustion engine 10 and referring to the map. It is. More specifically, the operating state and the adhesion rate of the internal combustion engine 10 using the engine load KL, the engine speed NE, the opening timing (valve timing VT) of the intake valve 34, or the wall surface temperature Tw of the intake port 30 as parameters. The relationship between R and residual rate P is experimentally determined by calibration, and the results are mapped, and in each cycle, the values corresponding to KL, NE, VT, and Tw are read from the map. P and R may be obtained.
[0042]
However, with such a method, a great deal of man-hours is required at the stage of creating the map. If an attempt is made to increase the accuracy of the residual rate P and the adhesion rate R, the matching order increases, and the matching man-hour required for creating the map further increases. Because of these restrictions, when using a method that identifies the residual rate P and adhesion rate R with reference to a map created by adaptation, for example, the fuel adhesion amount fw is significantly smaller than normal fuel. Immediately after returning from the cut or in a scene where the operating conditions of the internal combustion engine 10 change transiently, the control accuracy of the air-fuel ratio is likely to deteriorate.
[0043]
Therefore, in this embodiment, mathematical models relating to the residual rate P and the adhesion rate R are prepared, and P and R are calculated in accordance with this model in each cycle. The main factors that influence the fuel behavior inside the intake port 30 include fuel evaporation, wall flow, and droplet wall behavior (attachment and reflection). Here, assuming that the influence of the wall flow is small, the residual ratio P and the adhesion ratio R are calculated in consideration of the effects of fuel evaporation and droplet reflection.
[0044]
[Flow of fuel injection control]
FIG. 5 is a flowchart for explaining the flow of processing executed by the ECU 50 in order to calculate the residual rate P and the adhesion rate R and further correct the fuel injection amount fi appropriately using these values P and R. It is.
[0045]
As shown in FIG. 5, the ECU 50 first measures various parameters representing the current state of the internal combustion engine 10 (step 100).
Specifically, intake air amount GA, throttle opening degree TA, cooling water temperature THW, engine speed NE, valve timing VT, and the like are measured. In the present specification, the valve timing VT is a physical quantity indicating the opening timing of the intake valve 34, and means an advance amount from the most retarded timing (reference timing).
[0046]
Next, a physical quantity representing the internal state of the intake port 30, that is, an in-port state quantity is estimated (step 102).
In step 102, specifically, the in-port gas pressure Pg, the in-port gas temperature Tg, the in-port gas flow rate Ug, and the wall surface temperature Tw of the intake port 30 are estimated as in-port state quantities. Here, the in-port gas pressure Pg, the in-port gas temperature Tg, and the in-port gas flow rate Ug are the pressure, temperature, and flow rate of the air flowing inside the intake port 30, respectively.
[0047]
The in-port gas pressure Pg can be approximated by, for example, the intake pipe pressure Pm. In the system of the present embodiment, the intake pipe pressure Pm can be estimated by a known method as disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-130041.
[0048]
The in-port gas pressure Pg may be obtained as the sum of the intake pipe pressure Pm and the correction amount ΔP. The correction amount ΔP is a value for filling a deviation generated between the intake pipe pressure Pm and the in-port gas pressure Pg, and can be specified, for example, in relation to the engine speed NE. Therefore, the correction amount ΔP may be read in advance by creating a map in advance in relation to NE.
[0049]
The in-port gas temperature Tg can be estimated based on, for example, the engine speed NE, the engine load KL, and the valve timing VT. More specifically, the relationship between Tg and NE, KL, and VT is mapped in advance, and Tg can be estimated by referring to the map in each cycle.
[0050]
The in-port gas flow rate Ug can be estimated by the following equation, for example.
Ug = (Volvalve / Avalve) x (Aport / Avalve) (3)
However, Volvalve = (Valve flow rate) / ρg
The “valve passing flow rate” is a flow rate of air passing through the throttle valve 22, and the value can be obtained by a known method as disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-130039. “Ρg” is the gas density (air density) in the intake port 30 and is ρg = Pg / (R_const・ Tg). Where R_constIs the gas constant. In this specification, since the symbol R will be used later as the “adhesion rate R”, the gas constant is R in order to distinguish between the two._constWill be described.
[0051]
The wall surface temperature Tw is substantially the same as the temperature of the cylinder block of the internal combustion engine 10, that is, the coolant temperature THW. Therefore, the wall surface temperature Tw can be estimated based on the output of the temperature sensor 42.
[0052]
After the estimation of the in-port state quantity is finished, the ECU 50 thereafter calculates the adhesion rate R of the injected fuel and the residual rate P of the adhering fuel based on the estimated values (steps 104 to 108).
Here, first, the procedure for calculating the adhesion rate R will be described with reference to FIG. 6, and then the procedure for calculating the residual rate P will be described with reference to FIG.
[0053]
FIG. 6 is a diagram for explaining a process in which the injected fuel adheres to the wall surface and becomes the attached fuel. More specifically, FIG. 6 (A) shows a state in which the fuel injected from the fuel injection valve 32 is flying in the form of droplets. FIG. 6B shows a state in which the droplet reaches the wall surface, a part of the droplet adheres to the wall surface, and the remaining part leaves the wall surface by reflection. FIG. 6C shows a state where a part of the fuel attached to the wall surface is vaporized by heat transfer from the wall surface.
[0054]
As shown in FIG. 6A, the amount of droplets injected from the fuel injection valve 32 decreases due to evaporation in the process of traveling toward the wall surface. Hereinafter, the evaporation generated in this process is referred to as “flight evaporation”. Further, as shown in FIG. 6B, some of the droplets that have reached the wall surface are atomized and scattered by collision (reflection). The splashed droplets are then evaporated, or a part thereof directly flows into the cylinder and is lost from the wall surface. The phenomenon in which droplets are lost due to this collision (reflection) is called “reflection evaporation”.
[0055]
As described above, the amount of droplets injected from the fuel injection valve 32 is “flight evaporation” and “reflection evaporation” before being attached to the wall surfaces (the inner wall of the intake port 30 and the surface of the intake valve 34). Is lost. The amount of liquid droplets lost in this way is no longer an attached fuel. Hereinafter, the amount of droplets evaporated before adhering to the wall surface as described above is referred to as “evaporation amount F2 during flight”.
[0056]
As shown in FIG. 6C, the fuel adhering to the wall surface evaporates due to heat transfer from the wall surface until the intake step in each cycle is completed. For this reason, the amount of adhering fuel is reduced by evaporation even after droplets adhere to the wall surface. Hereinafter, the amount of decrease generated in this process is referred to as “post-adhesion evaporation amount G2”.
[0057]
The adhesion rate R is a ratio between the fuel injection amount fi and the fuel amount finally remaining on the wall surface. If the influence of wall flow (decrease in adhering fuel due to shearing, dripping, etc.) can be ignored, the amount of fuel left on the wall will be subtracted from the fuel injection amount fi by the amount of fuel lost due to evaporation. Value.
[0058]
The total amount of fuel lost by evaporation is the sum of the in-flight evaporation amount F2 and the post-adhesion evaporation amount G2. Here, the mechanisms for generating the in-flight evaporation amount F2 and the post-attachment evaporation amount G2 are completely different as described above. Therefore, in order to accurately calculate the total amount of fuel lost due to evaporation, different models are set for each of the in-flight evaporation amount F2 and the post-adhesion evaporation amount G2, and they are estimated as independent. It is desirable.
[0059]
The ECU 50 is a mathematical model F2 (Pg, Tg, Tw) for estimating the in-flight evaporation amount F2 and a mathematical formula for estimating the post-adhesion evaporation amount G2 as models for calculating the adhesion rate R of the injected fuel. Model G2 (Pg, Tg, Ug, Tw). Then, in step 104 shown in FIG. 5, F2 and G2 are calculated according to these models, respectively, and furthermore, as shown in the following equation, by adding these F2 and G2, the fuel lost by evaporation is calculated. A total amount Vfi (hereinafter referred to as “total evaporation amount Vfi”) is calculated.
Vfi = F2 (Pg, Tg, Tw) + G2 (Pg, Tg, Ug, Tw) (4)
[0060]
The in-flight evaporation amount F2 is significantly affected by the port gas pressure Pg, the port gas temperature Tg, and the wall surface temperature Tw, but is not significantly affected by the port gas flow velocity Ug. For this reason, the mathematical model of the in-flight evaporation amount F2 is configured with only Pg, Tg, and Tw as parameters. On the other hand, the post-attachment evaporation amount G2 is significantly affected by all of the above four in-port state quantities. For this reason, the mathematical model of the post-attachment evaporation amount G2 is configured with all of Pg, Tg, Ug, and Tw as parameters.
[0061]
After calculating the total evaporation amount Vfi as described above, the ECU 50 next calculates the adhesion rate R of the injected fuel in step 108 according to the following equation.
R = (fi−Vfi) / fi (5)
As described above, the ECU 50 is based on the in-port state quantities Pg, Tg, Ug and Tw and in accordance with the two mathematical models F2 (Pg, Tg, Tw) and G2 (Pg, Tg, Ug, Tw). Thus, the total evaporation amount Vfi can be calculated with high accuracy, and the adhesion rate R can be calculated with high accuracy based on the total evaporation amount Vfi and the fuel injection amount fi.
[0062]
FIG. 7 is a diagram for explaining a process in which fuel remaining in the intake port 30 as attached fuel at the end of the intake process evaporates by the end of the intake process of the next cycle. More specifically, FIG. 7A shows a state in which the adhered fuel evaporates after the intake process is completed until the intake process of the next cycle is started, that is, while the intake valve 34 is closed. Show. FIG. 7B shows how the attached fuel evaporates in the next cycle while the intake valve 34 is open, that is, while air flows in the intake port 30. FIG. 7C shows the ratio between the amount of attached fuel lost due to evaporation and the amount of attached fuel remaining attached to the wall surface.
[0063]
After that, the fuel adhering to the wall surface at the end of the intake process is evaporated by receiving heat from the wall surface until the intake process of the next cycle is completed. The fuel that has not been lost due to evaporation remains as an adhering fuel until the next cycle. The residual rate P includes the amount of adhesion at the end of the intake process (corresponding to “attachment” shown in FIG. 7C) and the amount of residual at the end of the intake process of the next cycle (“residue” shown in FIG. 7C). Equivalent). The residual amount can be obtained by subtracting the amount of fuel lost by evaporation (corresponding to “evaporation” shown in FIG. 7C) from the adhesion amount.
[0064]
As shown in FIG. 7 (A), after the intake process is finished, the intake process of the next cycle is started, that is, while the intake valve 34 is closed, Little gas flow occurs. Hereinafter, the gas flow in the intake port 30 under this condition is referred to as “laminar flow”. On the other hand, while the intake valve 34 is open, a gas flow is generated inside the intake port 30 as shown in FIG. Hereinafter, the gas flow in the intake port 30 under this condition is referred to as “turbulent flow”.
[0065]
The adhering fuel exhibits different evaporation characteristics when there is a gas flow in the intake port 30 and when there is no such flow. Therefore, in order to accurately determine the evaporation amount of the adhered fuel that occurs in the process of one cycle, the evaporation amount that occurs in a laminar flow environment (hereinafter referred to as “evaporation amount F3 during valve closing”) and the turbulent flow environment. It is desirable to estimate the resulting evaporated fuel (hereinafter referred to as “amount of evaporation during valve opening G3”) using different models.
[0066]
Therefore, in the present embodiment, as a model for calculating the residual rate P of the adhered fuel, a mathematical model F3 (Pg, Tg, Tw) for estimating the evaporation amount F3 during valve closing, and the evaporation amount G3 during valve opening. A mathematical model G3 (Pg, Tg, Ug, Tw) is prepared for estimating the F, and the ECU 50 calculates F3 and G3 according to different models. Specifically, in step 106 shown in FIG. 5, F3 and G3 are calculated in accordance with these two models, respectively, and further, as shown in the following equation, the F3 and G3 are added, thereby adhering fuel. The evaporation amount Vfw is calculated.
Vfw = F3 (Pg, Tg, Tw) + G3 (Pg, Tg, Ug, Tw) (6)
[0067]
Note that the evaporation amount F3 during valve closing is not significantly affected by the gas flow velocity Ug in the port, and therefore the mathematical model is configured with only Pg, Tg, and Tw as parameters. On the other hand, since the evaporation amount G3 during valve opening is significantly influenced by all the four in-port state quantities, the mathematical model is configured with all of Pg, Tg, Ug and Tw as parameters.
[0068]
After calculating the evaporation amount Vfw of the attached fuel as described above, the ECU 50 next calculates a residual rate P of the attached fuel in step 108 according to the following equation.
P = (fw−Vfw) / fw (7)
However, fw used in this equation is a value calculated by the previous processing cycle, that is, fwO in the above equation (2).
[0069]
As described above, the ECU 50 is based on the in-port state quantities Pg, Tg, Ug and Tw, and in accordance with the two mathematical models F3 (Pg, Tg, Tw) and G3 (Pg, Tg, Ug, Tw). Thus, the evaporation amount Vfw can be calculated with high accuracy, and the residual rate P can be calculated with high accuracy based on the evaporation amount Vfw and the fuel adhesion amount fw.
[0070]
As shown in FIG. 5, after completing the calculation of the adhesion rate R and the residual rate P, the ECU 50 next calculates the fuel amount required as the fuel intake amount fc, that is, the target value of the fuel intake amount fc. (Step 110).
[0071]
Next, the relationship of the above equation (2), that is, fc = (1−R) · fi + (1−P) · fwO is established (however, fwO is the fuel adhesion calculated in the previous processing cycle) Amount fw) and fuel injection amount fi are calculated (step 112).
[0072]
Finally, the fuel adhesion amount fw is calculated according to the above equation (1), that is, according to the relational expression fw = R · fi + P · fwO, using the adhesion rate R and the residual rate P calculated in this processing cycle. (Step 114).
[0073]
As described above, in the present embodiment, the ECU 50 uses the two mathematical models F2 (Pg, Tg, Tw) and G2 (Pg, Tg, Ug, Tw) to calculate the adhesion rate R of the injected fuel, and 2 Using the two mathematical models F3 (Pg, Tg, Tw) and G3 (Pg, Tg, Ug, Tw), the residual rate P of the adhered fuel can be accurately calculated based on the in-port state quantity. These mathematical models are created so as to accurately represent the evaporation state of the injected fuel or the adhered fuel (details will be described later). Therefore, according to the system of the present embodiment, the adhesion rate R and the residual rate P are calculated with extremely high accuracy without performing complicated adaptation work for each internal combustion engine 10, and based on the calculated values P and R, The fuel injection amount can always be controlled with high accuracy.
[0074]
[Specific calculation method of residual rate P]
Next, specific contents of the mathematical model used by the ECU 50 to calculate the residual rate P will be described.
The above formulas (6) and (7) described as the calculation formula for calculating the residual rate P can be modified as follows.
P = (fw-Vfw) / fw
= 1-Vfw / fw
= 1- [F3 (Pg, Tg, Tw) / fw]-[G3 (Pg, Tg, Ug, Tw) / fw] (8)
The following formula (9) is a formula that specifically represents the formula (8).
[0075]
[Expression 1]

[0076]
In the above equation (9), the second term on the right side is a mathematical model representing the evaporation rate of fuel under laminar flow conditions, that is, while the intake valve 34 is closed. The individual symbols included in this term are the following physical quantities.
ρl: Liquid fuel density (default)
h: Film thickness of attached fuel
Calculated as h = fw / ρl / s. Where ρl is the fuel density and s is the wetted area (default).
Sc₁: Laminar flow fitness coefficient (default)
D: Diameter of intake port
μg: Viscosity of gas (air) in intake port 30 (default)
B₁: Mass transport coefficient in laminar flow (details are described later)
Δt_lam: Laminar flow period, that is, the valve closing period of the intake valve 34
[0077]
In the above equation (9), the third term on the right side is a mathematical model that represents the evaporation rate under the turbulent flow condition, that is, when the intake valve 34 is open. The individual symbols included only in this term are the following physical quantities.
Sc₁: Conformance factor for turbulent flow (default)
B₂: Mass transport coefficient in turbulent flow (details will be described later)
ρg: air density (ρg = Pg / R as described above_const・ Tg)
Δt_turb: Turbulent flow period, that is, valve opening period (working angle) of the intake valve 34
However, Δt_lam+ Δt_turb= 720 (deg)
[0078]
The laminar mass transport coefficient B mentioned above₁And turbulent mass transport coefficient B₂Are parameters representing the easiness of evaporation of the attached fuel during laminar flow or turbulent flow, respectively. Their value B₁, B₂Can be expressed as in the following formula (10).
[0079]
[Expression 2]

[0080]
In the above formula (10), i is an identification number assigned to each component contained in the fuel. That is, ΣYsi or ΣYgi is an integrated value of Ysi and Ygi for a plurality of components included in the fuel, respectively. Where the value B₁Ygi included in the equation is the vapor concentration of each fuel component in the intake port 10 (default value for each component). In the laminar flow state, Ygi is a value that cannot be ignored (for example, about 10%).₁This term includes that term. On the other hand, during turbulent flow, the concentration of individual components in the intake port 30 is almost zero, so the turbulent mass transport coefficient B₂That term is omitted from the equation. In the above equation (10), Ysi is the saturated vapor concentration of each component. This saturated vapor concentration Ysi can be calculated by the following equation (11).
[0081]
[Equation 3]

[0082]
Each symbol included in the above expression (11) is a physical quantity as follows.
wi: molar mass of each component in the fuel (default),
wair: molar mass of air (default)
Pvsi: Saturated vapor pressure of individual components according to Anton's formula
The saturated vapor concentration Pvsi can be obtained by the following equation (12).
[0083]
[Expression 4]

[0084]
However, in the above formula (12), a_1i, A_2iAnd a_3iIs a predetermined Anton coefficient for each fuel component. Y_fiIs the mass proportion of the individual components of the injected fuel component. Further, in the above equation (12), Tf is a temperature represented by the following equation (13).
Tf = ε · Tw + (1−ε) Tg (13)
Here, ε is a value satisfying 0 <ε <1. Usually, since air has a higher influence, a value of about 0.7 is substituted for ε.
[0085]
The parameters (excluding time) included in the second term on the right side of equation (9) above are the film thickness h of the adhered fuel and the mass transport coefficient B during laminar flow.₁It is a fixed value except for. The film thickness h is determined based on the amount fw of the adhered fuel, and the laminar mass transport coefficient B₁Is a value determined by the in-port state quantities Pg, Tg, and Tw. Therefore, according to the above equation (9), the fuel evaporation rate (second term on the right side) under the laminar flow condition can be calculated based on the in-port state quantities Pg, Tg, and Tw.
[0086]
The parameters (excluding time) included in the third term on the right side of equation (9) above are the film thickness h of the adhered fuel, the air density ρg, the gas flow velocity Ug in the port, and the turbulent mass transport coefficient B₂It is a fixed value except for. The film thickness h is determined on the basis of the adhered fuel amount fw, the air density ρg is determined by Pg and Tg, and the turbulent mass transport coefficient B₂Is a value determined by Pg, Tg and Tw. Further, in the present embodiment, the attached fuel amount fw is also a value that is basically calculated based on the in-port state amounts Pg, Tg, Ug, and Tw. Therefore, according to the equation (9), the fuel evaporation rate (third term on the right side) under the turbulent flow condition can be calculated based on the in-port state quantities Pg, Tg, Ug, and Tw.
[0087]
[Specific calculation method of adhesion rate R]
Next, specific contents of the mathematical model used by the ECU 50 to calculate the adhesion rate R will be described.
The calculation method of the deposition rate R using the above formulas (4) and (5) is to obtain the in-flight evaporation amount F2 and the post-adhesion evaporation amount G2 separately, and calculate the sum (total evaporation amount Vfi) of the fuel injection amount By subtracting from fi, the amount of fuel (fi-Vfi) that finally adheres to the wall surface is determined. Then, by dividing the fuel amount (fi−Vfi) thus determined by fi, the ratio of the fuel that finally becomes attached to the wall surface is determined.
[0088]
By the way, the ratio (R) of the fuel that finally adheres to the wall surface is obtained by the above method, the ratio R1 of the fuel that reaches the wall surface without evaporating in the course of flight, and is lost by reflection after reaching the wall surface. The ratio α of the fuel adhering to the wall surface without being removed and the ratio R2 of the fuel maintaining the adhering state without being detached by evaporation after adhering to the wall surface are calculated, respectively, as shown in the following equation (14): It can also be obtained by multiplying.
R = R1 ・ α ・ R2 (14)
[0089]
Therefore, the ECU 50 specifically calculates the adhesion rate R of the injected fuel by the method of the above equation (14). Here, R1, R2, and α included in the above equation (14) can be obtained by the following equations (15) to (17), respectively.
[0090]
[Equation 5]

[0091]
However, the individual symbols included in the above equations (15) to (17) are the following physical quantities. In addition, Sc1, Sc2, ρl, μg, ρg, B₁, B₂, And Δt_turbSince is the same as described above, the description thereof is omitted here.
di: Droplet representative particle size (default)
V: Droplet flight speed (default)
Δt_drop: Droplet flight time (default) = (distance from fuel injection valve to intake valve) / V
We: Weber number
Re: Reynolds number
σ: Surface tension of fuel
θ_I: Angle between injection direction and collision wall
[0092]
Note that α shown in the equation (17) is actually a value determined by the performance of the fuel injection valve 32 and the shape of the intake port 30. Therefore, in each internal combustion engine 10, when calculating the adhesion rate R according to the above equation (14), α can be treated as a fixed value.
[0093]
In the above equation (15), the second term on the right side is the ratio of fuel lost due to flight evaporation. The parameters (excluding time) included in the second term on the right side are the air density ρg and the laminar mass transport coefficient B.₁It is a fixed value except for. The air density ρg is a value specified by the in-port gas pressure Pg and the in-port gas temperature Tg as described above. Also, laminar mass transport coefficient B₁Is a value specified by Pg, Tg, and wall surface temperature Tw (see the above formulas (10) to (12)). Therefore, according to the system of this embodiment, the proportion of fuel lost due to flight evaporation can be calculated based on the in-port state quantities Pg, Tg, and Tw.
[0094]
In the above equation (16), the second term on the right side is the ratio of fuel lost due to evaporation after adhesion. The parameters (excluding time) included in the second term on the right-hand side are the air density ρg, the gas flow depth Ug in the port, and the turbulent mass transport coefficient B₂It is a fixed value except for. Ρg is a value specified by Pg and Tg as described above. Also, turbulent mass transport coefficient B₂Is a value specified by Pg, Tg and Tw (see the above formulas (10) to (12)). Therefore, according to the system of the present embodiment, the proportion of fuel lost due to evaporation after adhesion can be calculated based on the in-port state quantities Pg, Tg, Ug and Tw.
[0095]
As described above, the ECU 50 uses the mathematical model representing the evaporation behavior of the injected fuel (the above formulas (14) to (17)) based on the in-port state quantities Pg, Tg, Ug and Tw. The adhesion rate R can be accurately estimated. Further, the ECU 50 uses a mathematical model representing the evaporation behavior of the attached fuel (the above equations (9) to (13)), and based on the in-port state quantities Pg, Tg, Ug and Tw, the attached fuel residual rate P Can be estimated with high accuracy.
[0096]
For this reason, according to the configuration of the present embodiment, an apparatus for accurately controlling the fuel injection amount under all operating conditions including during transient operation without performing complicated adaptation work for each model of the internal combustion engine 10 is realized. can do. According to such a fuel injection control device, the air-fuel ratio can always be controlled to the desired air-fuel ratio with high accuracy. Therefore, the apparatus of the present embodiment is useful for realizing good exhaust emission characteristics.
[0097]
Further, in the present embodiment, it is assumed that the above-described fuel injection amount control is executed after the internal combustion engine 10 is warmed up. That is, the above mathematical model is used for the fuel injection control after the internal combustion engine 10 is warmed up. Although it is supposed to use, the scene of the use is not limited to this. That is, in the apparatus according to the present embodiment, the adhesion rate R and the residual rate P are calculated using a mathematical model as a parameter of the in-port state quantity including the in-port gas temperature Tg and the wall surface temperature Tw. According to such a mathematical model, the actual state can be effectively simulated even when the temperature of the internal combustion engine 10 is low, such as during cold start.
[0098]
Further, in a hybrid (HV) vehicle, the internal combustion engine may be stopped after several seconds after fuel injection to the internal combustion engine is stopped. According to the above mathematical model, an actual state can be accurately simulated even for such a few seconds. Therefore, the mathematical model used by the apparatus according to the present embodiment can also be used in the case where the adhesion rate R and the residual rate P are calculated during cold operation or when the engine of the HV vehicle is stopped.
[0099]
On the other hand, when the adhesion rate R and the residual rate P are determined by conformity in relation to state quantities (the load KL, the rotational speed NE, etc.) representing the operation state of the internal combustion engine, the operation of the internal combustion engine 10 is performed. In a region where the state is out of the condition at the time of adaptation, the adhesion rate R and the residual rate P cannot be determined with high accuracy. Specifically, map values that are suitable for conditions after warm-up cannot be used during cold operation or when the HV vehicle is stopped. In this respect, the apparatus of the present embodiment has an advantage that it can be expanded to a wider area than an apparatus that determines P and R by adaptation.
[0100]
In the first embodiment described above, the adhesion rate R and the residual rate P are calculated according to a mathematical model using the in-port state quantity as a parameter. The calculation is performed by a method using a mathematical model. It is not limited. That is, the adhesion rate R and the residual rate P may be specified with reference to a map set in advance in relation to the in-port state quantity.
[0101]
  In the first embodiment described above, the residual rate P of the adhered fuel and the adhesion rate R of the injected fuel are the first value.Thru thirdThe ECU 50 corresponds to the “fuel control parameter” in the invention of FIG.Thru thirdThe "in-port state quantity acquisition means" in the invention of the first aspect stores the above formulas (9) to (17), whereby the firstThru thirdThe "model storage means" in the invention of the first calculates the first and second by calculating P and R using those equations, or by executing the processing of steps 104 to 108 described above.Thru thirdThe "fuel control parameter calculation means" in the invention of the first performs the first step by executing the process of step 114 above.Thru thirdThe “adhered fuel amount calculating means” in the invention of the first embodiment executes the processing of the step 110, whereby the firstThru thirdEach of the “injection amount correction means” in the present invention is realized.
[0102]
  In the first embodiment described above, the above equations (14) to (17) areSecondIn the "injected fuel evaporation behavior model" in the invention of the present invention, the above equations (9) to (13) areIn the first invention,In the `` attached fuel evaporation behavior model '', the adhesion rate R of the injected fuel is1st and 2ndIn the "first fuel control parameter" of the invention, the residual rate P of the adhered fuel is1st and 2ndThis corresponds to the “second fuel control parameter” in the present invention. Further, the ECU 50 calculates the adhesion rate R in accordance with the above equation (14) or in the step 108, whereby1st and 2ndThe “first calculating means” in the present invention calculates the residual rate P in accordance with the above equation (9) or in the above step 108.1st and 2ndEach of the “second calculation means” in the present invention is realized.
[0103]
  In the first embodiment described above,,The above equation (16) isFirst"Evaporation Behavior Model after Adhesion" in Japanese InventionPhaseIt is hit.
[0104]
  In the first embodiment described above, the expression (15) isFirstIn the "flying evaporation model" in the invention of the above, the above equation (17) isFirstThis corresponds to the “reflection evaporation model” in the invention.
[0105]
  In the first embodiment described above, the second term and the third term on the right side in the formula (9) areSecondThis corresponds to the “evaporation behavior model during valve closing” and the “evaporation behavior model during valve opening”, respectively.
[0106]
Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
The apparatus of the present embodiment can be realized by causing the ECU 50 to execute processing according to the flowchart shown in FIG. 8 instead of the flowchart shown in FIG. 5 in the apparatus of the first embodiment.
[0107]
The apparatus according to the first embodiment described above calculates the evaporation amount G2 after adhesion of the injected fuel (when calculating R2 in the above equation (16)), and calculates the evaporation amount G3 when the attached fuel is opened. In this case, it is assumed that the in-port state quantity is always substantially constant when the intake valve 34 is opened. However, when the intake valve 34 is opened at a timing with valve overlap, burned gas blows back inside the intake port 30 only immediately after the valve opening. In this case, the in-port state quantity, in particular, the in-port gas pressure Pg, the in-port gas temperature Tg, and the in-port gas flow rate Ug are greatly different values during the occurrence of blowback and after the disappearance. Therefore, in order to calculate the adhesion rate R and the residual rate P with high accuracy under the situation where such blowback occurs, it is possible to change the in-port state quantity to be substituted into the mathematical model according to the presence or absence of blowback. desirable.
[0108]
[Processing Flow in Embodiment 2]
FIG. 8 shows a process executed by the ECU 50 in order to calculate the residual rate P and the adhesion rate R while responding to the above requirements, and to appropriately correct the fuel injection amount fi using these values P and R. It is a flowchart for demonstrating the flow of this. In FIG. 8, steps that are the same as the steps shown in FIG. 5 are given the same reference numerals, and descriptions thereof are omitted or simplified.
[0109]
The flowchart shown in FIG. 8 is the same as the flowchart shown in FIG. 5 except that steps 120 to 130 are inserted after step 102. That is, according to the flowchart shown in FIG. 8, as in the case of the flowchart shown in FIG. 5, first, various parameters are measured in step 100, and then in step 102, the in-port state quantities Pg, Tg, Ug and Tw are measured. Is estimated.
[0110]
Of these in-port state quantities, the wall surface temperature Tw is a state quantity that is not affected by the presence or absence of blowback. On the other hand, Pg, Tg, and Ug are state quantities that vary greatly depending on the presence or absence of blowback as described above. In step 102, it is assumed that Pg, Tg, and Ug are estimated when no blowback occurs.
[0111]
When the in-port state quantities Pg, Tg, Ug and Tw are estimated, the valve opening timing VT of the intake valve 34 is then set to a predetermined value VT.₀It is determined whether or not it is smaller (step 120).
VT is the advance amount from the most retarded timing as described above. Therefore, the larger the value VT, the more the valve overlap occurs and the more likely the blow-back occurs. Predetermined value VT₀Is a value set as a valve-opening timing for discriminating whether or not a blowback that causes a significant change in the in-port state quantity occurs. Therefore, VT <VT₀When is established, it can be determined that there is a low possibility that blowback will occur to the extent that the in-port state quantity is switched. On the other hand, if the condition is not satisfied, it can be determined that the possibility of occurrence of the above blowback is high.
[0112]
In the flowchart shown in FIG. 8, in step 120, VT <VT₀If it is determined that is established, the intake pipe pressure Pm is then set to the predetermined value Pm.₀It is determined whether or not it is higher (step 122).
The magnitude of the burned gas blow-back is affected by the presence or absence of valve overlap or the length of the valve, as well as the level of the intake pipe pressure Pm. That is, the blowback tends to increase as the intake pipe pressure Pm is lower, while it is less likely to occur as Pm is higher. Predetermined value Pm₀VT <VT₀This is a value for determining whether or not there is a possibility of blowback in an environment in which Therefore, Pm> Pm₀When is established, it can be determined that there is a low possibility that blowback will occur to the extent that the in-port state quantity is switched. On the other hand, if the condition is not satisfied, it can be determined that the possibility of occurrence of the above blowback is high.
[0113]
In the flowchart shown in FIG. 8, in step 122, Pm> Pm₀When it is determined that the above is established, the processes after steps 104 and 106 are executed in the same manner as in the case shown in FIG. In this case, under the condition where no blow-back occurs, the adhesion rate R and the residual rate P are accurately calculated based on the in-port state quantities Pg, Tg, Ug and Tw, as in the case of the first embodiment. Based on the calculated values R and P, highly accurate fuel injection control is realized.
[0114]
In contrast, in step 120 above, VT <VT₀Is determined not to hold, and in step 122 above, Pm> Pm₀If it is determined that is not established, next, in-port state quantities Pg_r, Tg_r, and Ug_r when blowback occurs are estimated (step 124).
[0115]
In this case, the post-adhesion evaporation amount G2, which is the basis of the adhesion rate R of the injected fuel, is the evaporation amount H2 (Pg, Tg, Ug, Tw) in the period in which no blowback occurs and the period in which the blowback occurs as shown in the following equation Is estimated as the sum of the evaporation amount H′2 (Pg_r, Tg_r, Ug_r, Tw) at step 126.
G2 = H2 (Pg, Tg, Ug, Tw) + H′2 (Pg_r, Tg_r, Ug_r, Tw) (18)
[0116]
Further, the evaporation amount G3 during valve opening, which is the basis of the residual rate P of the adhered fuel, is the evaporation amount H3 (Pg, Tg, Ug, Tw) in the period in which no blowback occurs and the period in which the blowback occurs as shown in the following equation: It is estimated as the sum of the evaporation amount H′3 (Pg_r, Tg_r, Ug_r, Tw) at (step 128).
G3 = H3 (Pg, Tg, Ug, Tw) + H′3 (Pg_r, Tg_r, Ug_r, Tw) (19)
[0117]
If the processes in steps 126 and 128 are executed, then, in this processing cycle, the post-attachment evaporation amount G2 and the evaporation amount G3 during valve opening are corrected to the values calculated in steps 126 and 128, respectively. Is commanded (step 130).
[0118]
Thereafter, the processes after steps 104 and 106 are executed. In this case, the total evaporation amount Vfi calculated in step 104 is a value obtained by adding the post-attachment evaporation amount G2 calculated in step 126 to the in-flight evaporation amount F2. Further, the evaporation amount Vfw calculated in step 106 is a value obtained by adding the evaporation amount G3 during valve opening calculated in step 128 to the evaporation amount F3 during valve closing. Therefore, according to the flowchart shown in FIG. 8, when blowback occurs inside the intake port 30, the influence can be accurately reflected in the adhesion rate R and the residual rate P, and highly accurate fuel injection control. Can be realized.
[0119]
[Specific calculation method of residual rate P when blow-off occurs]
The following equation (20) is a mathematical model for calculating the residual rate P of the adhered fuel under a situation where blowback occurs. When the ECU 50 determines in step 120 or 122 that there is a possibility of blowback, specifically, the ECU 50 calculates the residual rate P according to the following equation (20).
[0120]
[Formula 6]

[0121]
However, in the above equation (20), Δt_turb1Is the turbulent period Δt_turbIs a period in which no blow-back occurs, while Δt_turb2Is a period during which blowback occurs. Ρg_r and B₂_r is the air density (Pg_r / R) calculated using the in-port state quantities Pg_r and Tg_r at the time of occurrence of blowback, respectively._constTg_r), and turbulent mass transport coefficient (see the above formulas (10) to (13)).
[0122]
[Specific calculation method of adhesion rate R when blow-back occurs]
Equation (21) shown below is a part of a mathematical model for calculating the adhesion rate R of the injected fuel under a situation where blowback occurs, specifically, the equation for the adhesion rate R shown in the above equation (14). Among the models (R = R1, α, R2), this is a mathematical model for calculating R2 that means the evaporation rate after adhesion. When the ECU 50 determines in step 120 or 122 that there is a possibility of blowback, the ECU 50 changes the R2 mathematical model from the model shown in the above formula (15) to the model shown in the following formula (21). Then, the adhesion rate R is calculated. In the following equation (21), Δt_turb1, Δt_turb2, Ρg_r and B₂_r is the same as that described in the proviso of the above formula (20).
[0123]
[Expression 7]

[0124]
As described above, the apparatus according to the present embodiment can regard the evaporation after adhesion of the injected fuel and the evaporation during the opening of the adhered fuel as different phenomena depending on whether the blowback occurs or not. it can. For this reason, according to the apparatus of the present embodiment, the adhesion rate R and the residual rate P are accurately estimated even when blowback occurs, and more accurate fuel injection control that is spent in the case of the first embodiment is realized. be able to.
[0126]
Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The apparatus of the present embodiment can be realized by causing the ECU 50 to execute processing according to the flowchart shown in FIG. 9 instead of the flowchart shown in FIG. 5 in the apparatus of the first embodiment.
[0127]
The inner wall temperature of the intake port 30 is about 80 ° C. which is substantially equal to the coolant temperature THW even after the warm-up of the internal combustion engine 10 is completed. At such a temperature, the attached fuel does not evaporate completely during one cycle. For this reason, on the inner wall of the intake port 30, the carryover of the adhered fuel exceeding one cycle occurs. On the other hand, the temperature of the intake valve 34 after warm-up is 160 to 180 ° C. When the wall surface temperature is such a high temperature, the fuel adhering to the surface usually evaporates in one cycle.
[0128]
The apparatus of the first embodiment described above calculates the residual rate P of the adhered fuel on the assumption of the above phenomenon. That is, the residual rate P is calculated assuming that all of the attached fuel amount fw is attached to the wall surface of the intake port 30 and no attached fuel is generated on the surface of the intake valve 34. Therefore, in the above equation (9), the in-port state quantities Pg, Tg, Ug and Tw are used as basic data for calculating the residual rate P.
[0129]
By the way, the assumption that no fuel adheres to the surface of the intake valve 34 is satisfied before the warm-up of the internal combustion engine 10, that is, before the temperature of the intake valve 34 becomes sufficiently high. In such a situation, since the state quantity that affects the evaporation characteristics of the fuel differs between the vicinity of the wall surface of the intake port 30 and the surface of the intake valve 34, the fuel adhering to the wall surface of the intake port 30 The fuel adhering to the surface of the intake valve 34 exhibits a different evaporation behavior. In this case, in order to accurately estimate the residual rate P of the adhered fuel, it is desirable to separately calculate the residual rate on the wall surface of the intake port 30 and the residual rate on the surface of the intake valve 34.
[0130]
[Processing Flow in Embodiment 3]
FIG. 9 shows a process executed by the ECU 50 in order to calculate the residual rate P and the adhesion rate R while responding to the above requirements, and to appropriately correct the fuel injection amount fi using these values P and R. It is a flowchart for demonstrating the flow of this.
[0131]
The flowchart shown in FIG. 9 is the same as the flowchart shown in FIG. 5 except that steps 140 to 148 are inserted after step 102. That is, in FIG. 9, steps 100 to 106 and steps 110 to 114 are the same as the steps shown in FIG. Further, steps 108a and 108b shown in FIG. 9 are exploded views of step 108 shown in FIG. 5. At each step, the adhesion rate R and the residual rate P are calculated in the same manner as in step 108. Is done.
[0132]
According to the flowchart shown in FIG. 9, after the processing of steps 100 and 102 is executed, the adhesion rate R of the injected fuel is calculated in the same procedure as in the case of the first embodiment (the case shown in FIG. 5) ( Step 104, 108a).
[0133]
In the procedure for calculating the residual rate P of the adhered fuel, first, after step 102, the wall surface temperature Tw is a predetermined value Tw.₀It is determined whether it is lower (step 140). Predetermined value Tw₀Is a judgment value for judging whether the warm-up of the internal combustion engine 10 is insufficient, or more specifically, whether the warm-up is insufficient to the extent that the attached fuel remains on the surface of the intake valve 34. It is.
[0134]
Therefore, in step 140 above, Tw <Tw₀Is determined not to hold, the internal combustion engine 10 has sufficiently warmed up, and it is no longer necessary to consider the evaporation of fuel on the surface of the intake valve 34 in estimating the residual rate P of the adhered fuel. It can be judged that there is no. In the flowchart shown in FIG. 9, in this case, thereafter, the residual rate P of the adhered fuel is calculated in the same procedure as in the case of Embodiment 1 (shown in FIG. 5) (steps 106 and 108b).
[0135]
On the other hand, in step 140 above, Tw <Tw₀When it is determined that is satisfied, it can be determined that the influence of the fuel remaining on the surface of the intake valve 34 cannot be ignored in estimating the residual rate P of the adhered fuel. In the flowchart shown in FIG. 9, in this case, the state quantity is estimated separately for the port part (P) and the valve part (V) (step 142).
[0136]
The gas pressure and gas temperature are not significantly different between the vicinity of the wall surface of the intake port 30 and the vicinity of the surface of the intake valve 34. For this reason, common values Pg and Tg are estimated for the gas pressure and the gas temperature. On the other hand, the gas flow velocity and the wall surface temperature may be greatly different between the vicinity of the wall surface of the intake port 30 and the vicinity of the surface of the intake valve 34. For this reason, different values Ugp, Twp, Ugv, and Twv are estimated for the gas flow velocity and wall surface temperature for the port portion (P) and the valve portion (V), respectively.
[0137]
Of the state quantities to be estimated in step 142, as for Pg and Tg, Ugp and Twp, the in-port state quantities Pg, Tg, Ug and Tw estimated in step 102 can be used as they are. Accordingly, in step 142, the valve portion gas flow rate Ugv and the valve portion wall surface temperature Twv are substantially estimated. These values Ugv and Twv can be estimated by, for example, multiplying a base state quantity (Ug or Tw) by a coefficient determined based on the result of the desktop simulation.
[0138]
When the processing in step 142 is completed, the distribution rate β of the fuel adhesion amount fw is determined, and the port portion adhesion amount fwp = fw · β and the valve portion adhesion amount fwv are determined using the distribution rate β. = Fw · (1−β) is calculated (step 144).
The distribution ratio β is a value that indicates what ratio is attached to the port portion and the valve portion, and is estimated from parameters such as the port inner wall surface temperature Tw, the intake pipe pressure Pm, and the attached fuel amount fw, for example. be able to. The ECU 50 stores a map in which the distribution ratio is determined in relation to the parameters Tw, Pm, and fw. In this step 144, the distribution ratio is determined by referring to the map.
[0139]
In the flowchart shown in FIG. 9, next, the evaporation amount Vfw, p of the attached fuel at the port portion and the evaporation amount Vfw, v of the attached fuel at the valve portion are estimated (step 146).
As shown below, the port portion evaporation amount Vfw, p can be obtained by substituting the state amounts Pg, Tg, Ugp, and Twp in the port portion into the mathematical model of the evaporation amount Vfw (the above equation (6)). it can.
Vfw, p = F3 (Pg, Tg, Twp) + G3 (Pg, Tg, Ugp, Twp) (21)
Further, as shown below, the valve portion evaporation amount Vfw, v is obtained by substituting the state amounts Pg, Tg, Ugv and Twv in the valve portion into the mathematical model of the evaporation amount Vfw (the above equation (6)). be able to.
Vfw, p = F3 (Pg, Tg, Twv) + G3 (Pg, Tg, Ugv, Twv) (22)
[0140]
When the above processing is completed, the port portion residual rate Pp and the valve portion residual rate Pv are calculated by substituting the values obtained by these processing into the following equations (step 148).
Pp = (fwp−Vfw, p) / fwp (23)
Pv = (fwv−Vfw, v) / fwv (24)
[0141]
In step 148, the remaining rate P of the entire adhered fuel is calculated by substituting the calculated Pp and Pv into the following equation.
P = Pp · β + Pv · (1-β) (25)
[0142]
As described above, according to the flowchart shown in FIG. 9, when the wall surface temperature Tw is high, the residual rate P of the adhered fuel is calculated by the same method as in the first embodiment (see step 108b). In addition, when the wall surface temperature Tw is low, the residual rate P of the adhered fuel can be calculated by a method that considers the valve portion and the port portion individually. Therefore, according to the apparatus of the present embodiment, the residual rate P can be calculated with high accuracy after the internal combustion engine 10 is warmed up, and the residual rate P can be calculated with high accuracy even during the warming up process.
[0143]
In the flowchart shown in FIG. 9, after the adhesion rate R of the injected fuel is calculated in step 108a and the residual rate P of the adhered fuel is calculated in step 108b or 148, the case of the first embodiment (FIG. 5). In the same manner as in (1), the fuel injection amount fi is calculated (steps 110 to 114). For this reason, according to the apparatus of this embodiment, highly accurate fuel injection control can be realized using the adhesion rate R and the residual rate P calculated with high accuracy.
[0144]
[Specific Calculation Method for Port Portion Residual Rate Pp]
The following equation (26) is a mathematical model for calculating the port portion residual rate Pp. In step 140, the ECU 50 determines that the wall surface temperature Tw is a predetermined value Tw.₀If it is determined that it is lower, the port portion residual rate Pp is calculated according to the following equation (26).
[0145]
[Equation 8]

[0146]
However, in the above equation (26), hp is the film thickness of the fuel adhering to the wall surface of the intake port 30, and is obtained by dividing the port portion adhesion amount fwp calculated in step 144 by the fuel density ρl. The value fwp / ρl / sp calculated by dividing by the wetting area sp (predetermined value) of the intake port 30. B₁p and B₂p is a laminar mass transport coefficient and a turbulent mass transport coefficient (see the above formulas (10) to (13)) calculated using the state quantities Pg, Tg, Ugp and Twp of the port part, respectively. is there.
[0147]
[Specific calculation method of valve portion residual ratio Pv]
The following equation (27) is a mathematical model for calculating the valve portion residual rate Pv. In step 140, the ECU 50 determines that the wall surface temperature Tw is a predetermined value Tw.₀When it is determined that the value is lower, the valve portion residual rate Pv is calculated according to the following equation (27).
[0148]
[Equation 9]

[0149]
However, in the above equation (27), hv is the film thickness of the fuel adhering to the surface of the intake valve 34, and is obtained by dividing the valve portion adhesion amount fwv calculated in the above step 144 by the fuel density ρl. The value fwv / ρl / sv calculated by dividing by the wetting area sv (predetermined value) of the intake valve 34. B₁v and B₂v is a laminar mass transport coefficient and a turbulent mass transport coefficient calculated using the state quantities Pg, Tg, Ugv, and Twv, respectively, of the valve section (see the above formulas (10) to (13)). is there.
[0151]
Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIG.
The apparatus of the present embodiment can be realized by causing the ECU 50 to execute processing according to the flowchart shown in FIG. 10 instead of the flowchart shown in FIG. 5 in the apparatus of the first embodiment.
[0152]
In the apparatus of the first embodiment described above, the deposition rate RR is calculated on the assumption that the evaporation behavior of the injected fuel after adhering to the wall surface is the same on the wall surface of the intake port 30 and the surface of the intake valve 34. However, as described above, there is a non-negligible difference in gas flow rate, wall surface temperature, and the like between the vicinity of the wall surface of the intake port 30 and the vicinity of the surface of the intake valve 34. For this reason, in order to accurately calculate the adhesion rate R of the injected fuel, it is desirable to take into account the difference between the state quantity in the port portion and the state quantity in the valve portion in the calculation process.
[0153]
[Processing Flow in Embodiment 4]
FIG. 10 shows a process executed by the ECU 50 in order to calculate the residual rate P and the adhesion rate R while responding to the above request, and to appropriately correct the fuel injection amount fi using these values P and R. It is a flowchart for demonstrating the flow of this.
[0154]
The flowchart shown in FIG. 10 is the same as that shown in FIG. 5 except that the steps for calculating the adhesion rate R of the injected fuel are replaced with steps 150 to 156 from steps 106 and 108 (part thereof). This is the same as the flowchart. Hereinafter, the characteristic part of the flowchart shown in FIG. 10 will be described.
[0155]
According to the flowchart shown in FIG. 10, in the procedure for calculating the adhesion rate R of the injected fuel, first, the state quantity is estimated separately for the port part (P) and the valve part (V) (step 150).
The processing in step 150 is the same as the processing in step 142 shown in FIG. Here, specifically, the state quantities Pg, Tg, Ug, and Tw estimated in step 102 are the state quantities Pg and Tg that are common to the port part and the valve part, and the state quantities Ugp and Twg in the port part. Diverted as Then, the state quantities Ugv and Twv in the valve unit are estimated by multiplying the coefficient determined by the simulation with the base state quantity (Ug or Tw).
[0156]
Next, of the injected fuel adhering to the port part and the valve part, the ratio (port ratio γ) distributed to the port part is determined (step 152).
The port ratio γ can be estimated from parameters such as the engine speed NE and the intake pipe pressure Pm, for example. The ECU 50 stores a map that defines the port ratio γ in relation to these parameters NE and Pm. In step 144, the port ratio γ is determined by referring to the map.
[0157]
Next, the total evaporation amount Vfi, p at the port portion and the total evaporation amount Vfi, v at the valve portion are estimated (step 154).
The port part total evaporation Vfi, p can be obtained by substituting the state quantities Pg, Tg, Ugp and Twp in the port part into the mathematical model of the total evaporation Vfi (Equation (4) above) as shown below. it can.
Vfi, p = F2 (Pg, Tg, Twp) + G2 (Pg, Tg, Ugp, Twp) (28)
Further, the total valve unit evaporation Vfi, v is obtained by substituting the state quantities Pg, Tg, Ugv and Twv in the valve unit into the mathematical model of the total evaporation Vfi (the above equation (4)), as shown below. be able to.
Vfi, p = F2 (Pg, Tg, Twv) + G2 (Pg, Tg, Ugv, Twv) (29)
[0158]
When the above processes are completed, the port part adhesion rate Rp and the valve part adhesion rate Rv are calculated by substituting the values obtained by these processes into the following equations (step 156).
Rp = (γ · fi−Vfi, p) / (γ · fi) (30)
Rv = {(1-γ) · fi−Vfi, v} / (1-γ) fi (32)
[0159]
In step 156, the calculated Rp and Rv are further substituted into the following equation, whereby the adhesion rate R of the entire injected fuel is calculated.
R = Rp · γ + Rv · (1-γ) (33)
[0160]
As described above, according to the flowchart shown in FIG. 10, the residual rate P of the adhered fuel is calculated by the same method as in the first embodiment (see step 108b), and the adhesion rate of the injected fuel is It can be calculated by a procedure that takes into account the difference in evaporation behavior between the valve part and the valve part. For this reason, according to the apparatus of the present embodiment, the adhesion rate R of the injected fuel is calculated with higher accuracy than in the case of the first embodiment, and the fuel injection control with higher accuracy is performed using the value R. Can be realized.
[0161]
[Specific calculation method of port adhesion rate Rp]
Expressions (34) to (36) shown below are arithmetic expressions for calculating the port portion adhesion rate Rp. Specifically, the ECU 50 calculates the port portion adhesion rate Rp using the equations (34) to (36) when proceeding with the processing of steps 150 to 156 shown in FIG.
[0162]
[Expression 10]

[0163]
However, in the above equation (34), αp is a ratio (fixed value) at which the droplet fuel that has reached the wall surface of the intake port 30 adheres to the wall surface without being lost due to reflection. In the above formula (35), B₁p is a laminar mass transport coefficient (see the above formulas (10) to (13)) calculated using the state quantities Pg, Tg, Ugp and Twp of the port portion. Further, in the above equation (36), hp is the film thickness of the fuel adhering to the wall surface of the intake port 30, and B₂p is a turbulent mass transport coefficient (see the above formulas (10) to (13)) calculated using the state quantities Pg, Tg, Ugp and Twp of the port portion. The film thickness hp of the fuel is calculated by the same method as in the third embodiment.
[0164]
[Specific calculation method of valve portion adhesion rate Rv]
Expressions (37) to (39) shown below are arithmetic expressions for calculating the port portion adhesion rate Rv. Specifically, the ECU 50 calculates the valve portion adhesion rate Rv using the equations (37) to (39) when proceeding with the processing of steps 150 to 156 shown in FIG.
[0165]
## EQU11 ##

[0166]
However, in the above equation (37), αv is a ratio (fixed value) at which the droplet fuel that has reached the surface of the intake valve 34 adheres to the surface without being lost due to reflection. In the above formula (38), B₁v is a laminar mass transport coefficient (see the above formulas (10) to (13)) calculated using the state quantities Pg, Tg, Ugv and Twv of the valve portion. Further, in the above equation (39), hv is the film thickness of the fuel adhering to the surface of the intake valve 34, and B₂v is a mass transport coefficient in turbulent flow calculated using the state quantities Pg, Tg, Ugv and Twv of the valve part (see the above formulas (10) to (13)). The film thickness hv of fuel is calculated by the same method as in the third embodiment.
[0167]
By the way, in the above-described fourth embodiment, the residual rate P of the adhered fuel is calculated by the same method as in the first embodiment, but the calculation method is not limited to this. . That is, the residual rate P of the adhered fuel may be calculated by a method that takes into account the difference in evaporation behavior between the port portion and the valve portion as in the case of the third embodiment.
[0169]
Embodiment 5 FIG.
Next, a fifth embodiment of the present invention will be described with reference to FIG.
The apparatus of the present embodiment can be realized by causing the ECU 50 to execute processing according to the flowchart shown in FIG. 11 instead of the flowchart shown in FIG. 5 in the apparatus of the first embodiment.
[0170]
The apparatus of the first embodiment described above calculates the residual rate P in consideration of only evaporation as a factor for reducing the adhered fuel. In contrast, when the amount of attached fuel fw increases, the amount of attached fuel tends to decrease due to dripping. Therefore, the apparatus of the present embodiment calculates the residual rate P of the adhered fuel in consideration of the effect of dripping under the situation where the amount of adhered fuel fw is large.
[0171]
[Processing Flow in Embodiment 5]
FIG. 11 shows a process executed by the ECU 50 in order to calculate the residual rate P and the adhesion rate R while responding to the above request, and to appropriately correct the fuel injection amount fi using these values P and R. It is a flowchart for demonstrating the flow of.
[0172]
In the flowchart shown in FIG. 11, steps 160 to 164 are added as processing for calculating the residual rate P of the adhered fuel, and the step for calculating the residual rate P is changed from step 108 to step 166. Except for these points, the flowchart is the same as that shown in FIG. Hereinafter, the characteristic part of the flowchart shown in FIG. 10 will be described.
[0173]
According to the flowchart shown in FIG. 11, after the in-port state quantity is estimated in step 102, it is determined whether the fuel adhesion amount fw is larger than the judgment value δ together with the processing in steps 104 and 106 (step 160). ).
[0174]
The determination value δ is a value for determining whether or not dripping occurs in the attached fuel. For this reason, when it is determined that fw> δ is not satisfied, it can be determined that the influence of the liquid dripping can be ignored in calculating the residual rate P. In this case, the dripping amount Ffw of the attached fuel is set to 0 (step 162).
[0175]
On the other hand, when it is determined in step 160 that the fuel adhesion amount fw is larger than the determination value δ, it can be determined that the influence of dripping should be considered in calculating the residual rate P. In this case, next, the dripping amount Ffw is calculated based on the in-port state amounts Pg, Tg, Ug and Tw (step 164).
The dripping amount Ffw can be calculated by a known method disclosed in, for example, Cambridge University literature SAE 1999-01-1314.
[0176]
In the flowchart shown in FIG. 11, after the processing of steps 104, 106 and 160 to 164 is completed, the adhesion rate R of the injected fuel is calculated by the same method as in the first embodiment, and the following calculation is performed. The residual rate P of the adhered fuel is calculated according to the equation.
P = (fw−Vfw−Ffw) / fw (39)
[0177]
According to the above equation (39), when the attached fuel amount fw decreases due to dripping, the residual rate P can be calculated in consideration of the influence Ffw. For this reason, according to the apparatus of this embodiment, under conditions where dripping occurs, fuel injection control with higher accuracy can be realized as compared with the apparatuses of Embodiments 1 to 4.
[0178]
  In the above-described fifth embodiment, the ECU 50 executes the processing in steps 160 to 164 described above, therebyThirdThe “drip amount estimation means” in the present invention also executes the process of step 166 described above, therebyThirdIn the present invention, the “drip adding means” is realized.
[0183]
【The invention's effect】
  Since the present invention is configured as described above, the following effects can be obtained.
  FirstAccording to the invention, the behavior before the injected fuel adheres to the inside of the intake port is captured by using both the flight evaporation model representing the evaporation behavior in the flight process and the reflection evaporation model representing the evaporation behavior due to wall reflection. be able to. Therefore, according to the present invention, it is possible to accurately estimate the behavior of the fuel that is lost in the air-fuel mixture before adhering to the wall surface, and as a result, it is possible to calculate the control parameter with high accuracy.
[0184]
  SecondAccording to the invention, the evaporation behavior of the fuel adhering to the inside of the intake port can be determined by both the evaporation behavior model during closing of the intake valve and the evaporation behavior model during opening of the intake valve. Can be used to capture. Therefore, according to the present invention, the evaporation behavior of the adhered fuel can be estimated with high accuracy, and as a result, the control parameter can be calculated with high accuracy.
[0187]
  ThirdAccording to the invention, when the adhered fuel decreases due to dripping, the fuel control parameter can be calculated with high accuracy in consideration of the dripping effect.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the configuration of a first embodiment of the present invention.
FIG. 2 is an enlarged view showing the vicinity of an intake port of the internal combustion engine shown in FIG.
FIG. 3 is a diagram showing a relationship between a change in intake air amount V and a change in fuel adhesion amount fw.
FIG. 4 is a simulation result showing a breakdown of fuel injected immediately after starting the internal combustion engine in relation to a crank angle CA.
FIG. 5 is a flowchart for explaining the flow of processing executed in the apparatus according to the first embodiment;
FIG. 6 is a diagram for explaining a process in which injected fuel adheres to a wall surface to become attached fuel.
FIG. 7 is a diagram for explaining a process in which fuel remaining in the intake port as attached fuel at the end of the intake process evaporates by the end of the intake process of the next cycle.
FIG. 8 is a flowchart for explaining a flow of processing executed in the apparatus according to the second embodiment;
FIG. 9 is a flowchart for explaining a flow of processing executed in the apparatus according to the third embodiment;
FIG. 10 is a flowchart for explaining the flow of processing executed in the apparatus according to the fourth embodiment;
FIG. 11 is a flowchart for explaining the flow of processing executed in the apparatus according to the fifth embodiment;
[Explanation of symbols]
10 Internal combustion engine
12 Intake passage
20 Air flow meter
22 Throttle valve
32 Fuel injection valve
34 Intake valve
36, 40 Variable valve timing mechanism
fw Fuel adhesion amount
fi Fuel injection amount
VT intake valve opening timing
P Residual rate
R adhesion rate
Vfi injection fuel evaporation
fw evaporation
Gas pressure in Pg port
Tg Gas temperature in the port
Gas flow rate in Ug port
Tw Port wall surface temperature

Claims (3)

A fuel injection valve that injects fuel into the intake port;
In-port state quantity acquisition means for acquiring an in-port state quantity representing an internal state of the intake port;
Model storage means for storing a mathematical model described using the in-port state quantity as a parameter in order to represent the evaporation behavior of fuel inside the intake port;
Fuel control parameter calculation means for calculating a fuel control parameter for calculating the amount of attached fuel remaining inside the intake port at the end of the intake process based on the in-port state quantity, according to the mathematical model;
An attached fuel amount calculating means for calculating the amount of the attached fuel based on the fuel control parameter;
And an injection amount correction means for performing correction on the fuel injection amount so as to eliminate the influence of the adhering fuel, the mathematical expression model,
A flight evaporation model representing evaporation behavior of a fuel injected from the fuel injection valve in a flight process inside the intake port;
A reflection evaporation model representing evaporation behavior due to wall reflection of the injected fuel;
A post-attachment evaporation behavior model that represents the behavior when the injected fuel evaporates in the air-fuel mixture before the intake step is completed after the inside of the intake port is attached;
An attached fuel evaporation behavior model representing an evaporation behavior of the attached fuel inside the intake port, and
The fuel control parameter calculation means includes
First calculation means for calculating a first fuel control parameter using the flight evaporation model, the reflection evaporation model, and the post-attachment evaporation behavior model;
A fuel injection control device for an internal combustion engine, comprising: second calculation means for calculating a second fuel control parameter in accordance with the attached fuel evaporation behavior model . A fuel injection valve that injects fuel into the intake port;
In-port state quantity acquisition means for acquiring an in-port state quantity representing an internal state of the intake port;
Model storage means for storing a mathematical model described using the in-port state quantity as a parameter in order to represent the evaporation behavior of fuel inside the intake port;
Fuel control parameter calculation means for calculating a fuel control parameter for calculating the amount of attached fuel remaining inside the intake port at the end of the intake process based on the in-port state quantity, according to the mathematical model;
An attached fuel amount calculating means for calculating the amount of the attached fuel based on the fuel control parameter;
Injection amount correction means for correcting the fuel injection amount so as to eliminate the influence of the adhering fuel, the mathematical model,
An injection fuel evaporation behavior model representing evaporation behavior of the injected fuel injected from the fuel injection valve inside the intake port;
An evaporation behavior model during valve closing representing evaporation behavior of the adhering fuel during closing of the intake valve;
An evaporation behavior model during valve opening representing an evaporation behavior of the attached fuel during opening of the intake valve, and
The fuel control parameter calculation means includes
First calculation means for calculating a first fuel control parameter in accordance with the injected fuel evaporation behavior model;
A fuel injection control device for an internal combustion engine, comprising: a second calculation unit that calculates a second fuel control parameter using both the during-valve evaporation behavior model and the during-valve evaporation behavior model . A fuel injection valve that injects fuel into the intake port;
In-port state quantity acquisition means for acquiring an in-port state quantity representing an internal state of the intake port;
Model storage means for storing a mathematical model described using the in-port state quantity as a parameter in order to represent the evaporation behavior of fuel inside the intake port;
Fuel control parameter calculation means for calculating a fuel control parameter for calculating the amount of attached fuel remaining inside the intake port at the end of the intake process based on the in-port state quantity, according to the mathematical model;
An attached fuel amount calculating means for calculating the amount of the attached fuel based on the fuel control parameter;
Injection amount correction means for correcting the fuel injection amount so as to eliminate the influence of the adhered fuel;
A dripping amount estimating means for estimating an amount by which the adhered fuel decreases due to dripping, and
The fuel injection control device for an internal combustion engine, wherein the fuel control parameter calculation means includes a liquid dripping means for adding the influence of the liquid dripping to the fuel control parameter .

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