JP2004116459A - Cylinder intake air amount estimating device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder intake air amount estimating device for an internal combustion engine capable of effectively reducing a steady error between actual cylinder intake air amount and estimated cylinder intake air amount. <P>SOLUTION: The cylinder intake air amount estimating device obtains cylinder intake air amount Mc by using an electronic controlled throttle model Ma, a throttle model M2, an intake pipe model M3, an intake valve model M4, and a cylinder model M5. An observer OBS corrects throttle passing air flow rate mt estimated by the throttle model Ms and a cylinder intake air flow rate mc estimated by the intake valve model M4 so as to make time integral value SumSA of deviation SA between throttle passing air flow rate mtes based on a value outputted by an air flow meter 61 to present throttle passing air flow mt(t-T0) by the throttle model M2 and present intake air flow rate mtAFM measured by the air flow meter 61 become 0. <P>COPYRIGHT: (C)2004,JPO

Description

【００４４】
【数４】

【００４５】
上記数３及び数４において、θｔは電子制御スロットルモデルＭ１により推定された現時点から所定時間Ｔ０だけ先の時刻ｔにおける推定スロットルバルブ開度である。スロットルモデルＭ２は、スロットルバルブ開度θｔと流量係数Ｃｔ（θｔ）との関係を規定した図８に示すテーブルと前記推定したスロットルバルブ開度θｔとを用いて流量係数Ｃｔ（θｔ）を求めるとともに、スロットルバルブ開度θｔと開口面積Ａｔ（θｔ）との関係を規定した図９に示すテーブルと前記推定したスロットルバルブ開度θｔとを用いて開口面積Ａｔ（θｔ）を求める。なお、スロットルモデルＭ２は、スロットルバルブ開度θｔと、流量係数Ｃｔ（θｔ）と開口面積Ａｔ（θｔ）の積値Ｃｔ（θｔ）・Ａｔ（θｔ）との関係を規定した図１０に示すテーブル、及び前記推定したスロットルバルブ開度θｔを用いて積値Ｃｔ（θｔ）・Ａｔ（θｔ）を一時に求めるように構成してもよい。
【００４６】
また、スロットルモデルＭ２は、スロットルバルブ上流圧力Ｐａ、及び吸気温度Ｔａを大気圧センサ６３、及び吸気温センサ６２からそれぞれ取得するとともに、吸気管内空気圧力Ｐｍと吸気管内空気温度Ｔｍとを後述する吸気管モデルＭ３から取得し、これらの値を用いて上記数３又は数４を計算し、時刻ｔにおけるスロットル通過空気流量ｍｔを推定する。
【００４７】
ここで、上記スロットルモデルＭ２を記述した数３及び数４の導出過程について説明する。いま、スロットルバルブ４３の上流の開口断面積をＡｕ、空気密度をρｕ、空気の流速をｖｕとし、スロットルバルブ４３による吸気管４１の開口断面積をＡｄ、そこでの空気密度をρｄ、スロットルバルブ４３を通過する空気の流速をｖｄとすると、スロットル通過空気流量ｍｔは、下記数５で表される。数５は質量保存則を記述した式と言える。
【００４８】
【数５】
ｍｔ＝Ａｄ・ρｄ・ｖｄ＝Ａｕ・ρｕ・ｖｕ
【００４９】
一方、運動エネルギーは、空気の質量をｍとすると、スロットルバルブ４３の上流でｍ・ｖｕ^２／２であり、スロットルバルブ４３を通過する場所でｍ・ｖｄ^２／２である。他方、熱エネルギーは、スロットルバルブ４３の上流でｍ・Ｃｐ・Ｔｕであり、スロットルバルブ４３を通過する場所でｍ・Ｃｐ・Ｔｄである。従って、エネルギー保存則により、下記数６が得られる。なお、Ｔｕはスロットルバルブ上流の空気温度、Ｔｄはスロットルバルブ下流の空気温度、Ｃｐは定圧比熱である。
【００５０】
【数６】
ｍ・ｖｕ^２／２＋ｍ・Ｃｐ・Ｔｕ＝ｍ・ｖｄ^２／２＋ｍ・Ｃｐ・Ｔｄ
【００５１】
ところで、状態方程式は下記数７、比熱比κは下記数８、マイヤーの関係は下記数９で示されるから、数７〜数９よりＣｐ・Ｔは下記数１０のように表される。なお、Ｐは気体の圧力、ρは気体の密度、Ｔは気体の温度、Ｒは気体定数、Ｃｖは定容比熱である。
【００５２】
【数７】
Ｐ＝ρ・Ｒ・Ｔ
【００５３】
【数８】
κ＝Ｃｐ／Ｃｖ
【００５４】
【数９】
Ｃｐ＝Ｃｖ＋Ｒ
【００５５】
【数１０】
Ｃｐ・Ｔ＝｛κ／（κ−１）｝・（Ｐ／ρ）
【００５６】
上記数１０の関係を用いて上記エネルギー保存則に基づく数６を書換えると、下記数１１が得られる。
【００５７】
【数１１】
ｖｕ^２／２＋｛κ／（κ−１）｝・（Ｐｕ／ρｕ）＝ｖｄ^２／２＋｛κ／（κ−１）｝・（Ｐｄ／ρｄ）
【００５８】
そして、スロットルバルブ４３の無限上流を考えると、Ａｕ＝∞、ｖｕ＝０であるから、エネルギー保存則に基づく上記数１１は下記数１２に書き換えられる。
【００５９】
【数１２】
｛κ／（κ−１）｝・（Ｐｕ／ρｕ）＝ｖｄ^２／２＋｛κ／（κ−１）｝・（Ｐｄ／ρｄ）
【００６０】
次に、運動量について記述する。断面積Ａｕの部分に加わる圧力をＰｕ、断面積Ａｄの部分に加わる圧力をＰｄ、断面積Ａｕの部分と断面積Ａｕの部分との間をつなぐ固定された空間の平均圧力をＰｍｅａｎとすると、下記数１３が得られる。
【００６１】
【数１３】
ρｄ・ｖｄ^２・Ａｄ−ρｕ・ｖｕ^２・Ａｕ＝Ｐｕ・Ａｕ−Ｐｄ・Ａｄ＋Ｐｍｅａｎ・（Ａｄ−Ａｕ）
【００６２】
上記数１３で、Ａｕ＝∞、ｖｕ＝０を考慮すると、下記数１４が得られるので、同数１４と上記数１３とから下記数１５の運動量に関する関係（運動量保存則に基づく関係）が得られる。
【００６３】
【数１４】
Ｐｍｅａｎ＝Ｐｕ
【００６４】
【数１５】
ρｄ・ｖｄ^２＝Ｐｕ−Ｐｄ
【００６５】
従って、上記数５、上記数１２、及び上記数１５から、下記数１６が得られる。
【００６６】
【数１６】

【００６７】
上記数１６において、Ｐｕはスロットルバルブ上流圧力Ｐａであり、Ｐｄは吸気管内空気圧力Ｐｍであるから、流量係数をＣｔ（θｔ）を導入し、開口断面積Ａｄを開口面積Ａｔ（θｔ）とおきなおして整理すると、上記数３が得られる。上記数４の導出過程は、上記数３の導出過程と同様であるので省略する。
【００６８】
（吸気管モデルＭ３）
吸気管モデルＭ３は、質量保存則とエネルギー保存則とにそれぞれ基づいた下記数１７及び下記数１８、（推定）スロットル通過空気流量ｍｔ、スロットル通過空気温度（即ち、吸入空気温度）Ｔａ、及び吸気管から流出する空気流量ｍｃ（即ち、推定吸気弁通過空気流量、筒内吸入空気流量）から、吸気管内空気圧力Ｐｍ、及び吸気管内空気温度Ｔｍを求めるモデルである。なお、下記数１７、及び下記数１８において、Ｖｍはスロットルバルブ４３から吸気弁３２までの吸気管４１（以下、単に「吸気管部」と称呼する。）の容積である。
【００６９】
【数１７】
ｄ（Ｐｍ／Ｔｍ）／ｄｔ＝（Ｒ／Ｖｍ）・（ｍｔ−ｍｃ）
【００７０】
【数１８】
ｄＰｍ／ｄｔ＝κ・（Ｒ／Ｖｍ）・（ｍｔ・Ｔａ−ｍｃ・Ｔｍ）
【００７１】
吸気管モデルＭ３は、上記数１７、及び上記数１８におけるスロットル通過空気流量ｍｔをスロットルモデルＭ２から取得し、筒内吸入空気流量ｍｃを後述する吸気弁モデルＭ４から取得する。そして、数１７及び数１８に基づく計算を行って時刻ｔの吸気管内空気圧力Ｐｍ、及び時刻ｔの吸気管内空気温度Ｔｍを求める。
【００７２】
ここで、上記吸気管モデルＭ３を記述した数１７及び数１８の導出過程について説明する。いま、吸気管部の総空気量をＭとすると、総空気量Ｍの時間的変化は、吸気管部に流入する空気量に相当するスロットル通過空気流量ｍｔと同吸気管部から流出する空気量に相当する筒内吸入空気流量ｍｃの差であるから、質量保存則に基づく下記数１９が得られる。
【００７３】
【数１９】
ｄＭ／ｄｔ＝ｍｔ−ｍｃ
【００７４】
また、状態方程式は下記数２０となるから、上記数１９と下記数２０とから総空気量Ｍを消去することにより、質量保存則に基づく上記数１７が得られる。
【００７５】
【数２０】
Ｐｍ・Ｖｍ＝Ｍ・Ｒ・Ｔｍ
【００７６】
次に、吸気管部に関するエネルギー保存則について検討すると、この場合、吸気管部の容積Ｖｍは変化せず、また、エネルギーの殆どが温度上昇に寄与する（運動エネルギーは無視し得る）と考えられる。従って、吸気管部の空気のエネルギーＭ・Ｃｖ・Ｔｍの時間的変化量は、同吸気管部に流入する空気のエネルギーＣｐ・ｍｔ・Ｔａと同吸気管部から流出する空気のエネルギーＣｐ・ｍｃ・Ｔｍとの差に等しいので、下記数２１が得られる。
【００７７】
【数２１】
ｄ（Ｍ・Ｃｖ・Ｔｍ）／ｄｔ＝Ｃｐ・ｍｔ・Ｔａ−Ｃｐ・ｍｃ・Ｔｍ
【００７８】
この数２１を、上記数８（κ＝Ｃｐ／Ｃｖ）と、上記数２０（Ｐｍ・Ｖｍ＝Ｍ・Ｒ・Ｔｍ）とを用いて変形することにより、上記数１８が得られる。
【００７９】
（吸気弁モデルＭ４）
吸気弁モデルＭ４は、吸気弁３２の周囲を通過する空気流量（即ち、推定吸気弁通過空気流量、筒内吸入空気流量）ｍｃを、エネルギー保存則、運動量保存則、質量保存則、及び状態方程式等に基づいて得られた下記数２２及び下記数２３にしたがって推定するモデルである。数２２，２３の導出過程は、上記スロットルモデルＭ２の場合と同様である。数２２及び数２３において、Ｃｖ（Ｌ）は吸気弁３２のリフト量Ｌに応じて変化する流量係数、Ａｖ（Ｌ）は同リフト量Ｌに応じて変化する吸気弁３２の周囲に形成される開口の面積、及びＰｃは筒内圧力（シリンダ２１内の圧力Ｐｃ）である。吸気弁モデルＭ４は、吸気管内空気圧力Ｐｍが筒内圧力Ｐｃより大きい順流の場合に数２２を使用し、吸気管内空気圧力Ｐｍが筒内圧力Ｐｃより小さい逆流の場合に数２３を使用する。この結果、筒内吸入空気流量（推定吸気弁通過空気流量）ｍｔは、前記順流の場合に正の値を、前記逆流の場合に負の値をそれぞれ採るように計算される。
【００８０】
【数２２】

【００８１】
【数２３】

【００８２】
吸気弁モデルＭ４は、現時点から所定時間Ｔ０だけ先の時刻ｔにおけるバルブリフト量Ｌ（ｔ）を吸気弁リフト量センサ６７が検出している現時点のバルブリフト量Ｌと、エンジン回転速度Ｎｅとに基づいて推定する。そして、バルブリフト量Ｌと積値Ｃｖ（Ｌ）・Ａｖ（Ｌ）との関係を規定した図１１に示したテーブルと、前記推定したバルブリフト量Ｌ（ｔ）とに基づいて、上記数２２及び上記数２３にて使用する積値Ｃｖ（Ｌ）・Ａｖ（Ｌ）を求める。
【００８３】
また、吸気弁モデルＭ４は、吸気管内空気圧力Ｐｍと吸気管内空気温度Ｔｍとを吸気管モデルＭ３から取得するとともに、筒内圧力Ｐｃと筒内空気温度Ｔｃを後述するシリンダモデルＭ５から取得し、これらの変数を用いて上記数２２又は上記数２３を計算することで、時刻ｔにおける筒内吸入空気流量ｍｃを推定する。
【００８４】
（シリンダモデルＭ５）
シリンダモデルＭ５は、シリンダ２１についてのエネルギー保存則に基づいた下記数２４にしたがって、筒内圧力Ｐｃと筒内空気温度Ｔｃを求めるモデルである。図１２に示したように、下記数２４におけるＶｃはシリンダ２１の容積、Ｔｍはシリンダ２１に吸入される空気の温度Ｔｉと等しい吸気管内空気温度、ｍｃはシリンダ２１内（筒内）に吸入される空気流量ｍｉと等しい前記吸気管部から流出する空気流量、Ｑはシリンダ２１と同シリンダ２１外部（シリンダ壁面、吸気ポート等）との間で伝達される熱量（熱量の時間的変化量、熱の流れ）である。
【００８５】
【数２４】

【００８６】
上記数２４における時刻ｔの筒内吸入空気流量ｍｃは吸気弁モデルＭ４（上記数２２又は上記数２３）により与えられ、同時刻ｔの吸気管内空気温度Ｔｍは吸気管モデルＭ３により与えられる。また、時刻ｔのシリンダ容積Ｖｃはクランク角度に基づいて知ることができるので、上記数２４の右辺第３項（熱量の項）を無視すれば、理論上、上記数２４を用いて時刻ｔにおける筒内圧力Ｐｃを得ることができる。
【００８７】
ここで、上記数２４の導出過程について説明する。先ず、Ｅを筒内のエネルギー、ｈをエンタルピー、Ｗをピストンに対する仕事とすると、シリンダ２１についてエネルギー保存則により下記数２５を得ることができる。
【００８８】
【数２５】
ｄＥ／ｄｔ＝ｍｃ・ｈ−ｄＷ／ｄｔ＋Ｑ
【００８９】
いま、内部エネルギーをｕとすれば下記数２６が成立し、状態方程式は下記数２７の通りである。また、比熱比κの式である上記数８（κ＝Ｃｐ／Ｃｖ）と、マイヤーの関係式である上記数９（Ｃｐ＝Ｃｖ＋Ｒ）とから、下記数２８及び下記数２９が成立する。なお、Ｍｃｙをシリンダ２１内の空気量とする。
【００９０】
【数２６】
ｕ＝Ｃｖ・Ｔｃ
【００９１】
【数２７】
Ｍｃｙ・Ｔｃ＝Ｐｃ・Ｖｃ／Ｒ
【００９２】
【数２８】
Ｃｖ＝Ｒ／（κ−１）
【００９３】
【数２９】
Ｃｐ＝κ・Ｒ／（κ−１）
【００９４】
従って、数２６〜数２８から数２５の左辺ｄＥ／ｄｔについて、下記数３０が成立する。
【００９５】
【数３０】
ｄＥ／ｄｔ＝ｄ（Ｍｃｙ・ｕ）／ｄｔ＝ｄ（Ｍｃｙ・Ｃｖ・Ｔｃ）／ｄｔ＝ｄ｛Ｐｃ・Ｖｃ／（κ−１）｝／ｄｔ
【００９６】
一方、数２５の右辺第１項ｍｃ・ｈについて、下記数３１のエンタルピーの定義と上記数２９から、下記３２が成立する。
【００９７】
【数３１】
ｈ＝Ｃｐ・Ｔｍ
【００９８】
【数３２】
ｍｃ・ｈ＝ｍｃ・｛κ・Ｒ／（κ−１）｝・Ｔｍ
【００９９】
更に、仕事Ｗは下記数３３で表されるから、上記数２５の右辺第２項ｄＷ／ｄｔについて下記数３４が成立する。
【０１００】
【数３３】
ｄＷ＝Ｐｃ・ｄＶｃ
【０１０１】
【数３４】
ｄＷ／ｄｔ＝Ｐｃ・ｄＶｃ／ｄｔ
【０１０２】
数３０、数３２、及び数３４で数２５を書き直して整理すると上記数２４が得られる。
【０１０３】
また、シリンダモデルＭ５は、筒内空気温度Ｔｃを状態方程式である下記数３５にしたがって求める。数３５のＭｃ１は、数２２又は数２３の筒内吸入空気流量ｍｃを吸気弁３２が開弁してから筒内空気温度Ｔｃを求める時点まで時間積分して求める。
【０１０４】
【数３５】
Ｔｃ＝（Ｐｃ・Ｖｃ）／（Ｍｃ１・Ｒ）
【０１０５】
上記原理によれば、シリンダモデルＭ５の上記数２４、及び上記数３５により筒内圧力Ｐｃ、及び筒内空気温度Ｔｃがそれぞれ求められ、これらに基づいて数２２又は数２３により筒内吸入空気流量ｍｃが得られる。従って、本燃料噴射量制御装置は、筒内吸入空気流量ｍｃを吸気弁２３が開弁した時刻ｔｏから同吸気弁３２が閉弁する時刻ｔｆまで時間積分することにより一吸気行程にてシリンダ２１内に吸入される筒内吸入空気量Ｍｃ（吸入空気総量Ｓｍｃ）を推定し、この値Ｍｃと上記数２とに基づいて燃料噴射量ｆｃを決定する。
【０１０６】
（電気制御装置８０に実装する上での改良）
上記数２４の右辺第３項の熱伝達Ｑは、値が小さく無視することができるので、通常は上記数２４を下記数３６のように離散化して電気制御装置８０に実装する。ここで、Δｔは筒内圧力Ｐｃの計算時間間隔である。
【０１０７】
【数３６】

【０１０８】
しかしながら、この手法により実際に筒内圧力Ｐｃを求めてみると、図１３の一点鎖線で示したように、同筒内圧力Ｐｃは離散化の影響を受けて大きく変動し、真値と大きく異なってしまうことが判明した。そこで、本実施形態においては、数２４の右辺第３項の値Ｑを無視するとともに、便宜上、（１）シリンダの容積を一定と仮定した場合（ｄＶｃ＝０）、及び（２）筒内吸入空気流量が０である（ｍｃ＝０）と仮定した場合に分け、それぞれの仮定下で数２４を解析的に解くことで筒内圧力Ｐｃを求めることとした。以下、詳述する。
【０１０９】
（１）シリンダの容積を一定と仮定した場合（ｄＶｃ＝０）
この仮定下では、上記数２４は下記数３７の微分方程式となり、同数３７を解くと下記数３８が得られる。
【０１１０】
【数３７】

【０１１１】
【数３８】

【０１１２】
上記数３８において、θ_０＝ｃｏｓ^−１（１）である。この数３８から、筒内圧力Ｐｃは正弦波状に変化することが解る。一方。上記数３７のＥｕｌｅｒ近似は、下記数３９となる。
【０１１３】
【数３９】

【０１１４】
また、筒内圧力Ｐｃが吸気管内空気圧力Ｐｍより大きくなることはないから、下記数４０が成立する。従って、数３９と数４０とから下記数４１が成立する。
【０１１５】
【数４０】

【０１１６】
【数４１】

【０１１７】
更に、θが１に比べて極めて小さい（θ＜＜１）とき、下記数４２が成立するから、上記数４１と下記数４２を上記数３９に適用して下記数４３を得ることができる。なお、下記数４３における筒内吸入空気流量ｍｃは上記数２２、及び上記数２３により求める。
【０１１８】
【数４２】

【０１１９】
【数４３】

【０１２０】
（２）筒内吸入空気量がない（ｍｃ＝０）と仮定した場合
この仮定下では、上記数２４は下記数４４の微分方程式となる。また、この場合、断熱膨張として扱えるから下記数４５が成立する。
【０１２１】
【数４４】

【０１２２】
【数４５】

【０１２３】
以上から、下記数４６が導かれる。
【０１２４】
【数４６】

【０１２５】
上記数４３、及び上記数４６により求められる筒内圧力Ｐｃを、図１３においてそれぞれ実線、及び二点鎖線により示す。筒内圧力Ｐｃは、吸気管内空気圧力Ｐｍに近似した値となると予想されることから、本実施形態においては、吸気管内空気圧力Ｐｍにより近い上記数４３により得られる筒内圧力Ｐ’ｃ（ｔ）を最終的に求める筒内圧力Ｐｃとして採用する。
【０１２６】
また、一吸気行程での筒内吸入空気量Ｍｃは、数２２又は数２３で与えられる筒内吸入空気流量ｍｃを吸気弁２３が開弁した時刻ｔｏから同吸気弁３２が閉弁する時刻ｔｆまで時間積分することにより求められると述べたが、シミュレーションの結果、エネルギー保存則に基づく上記数２４を時刻ｔｏから時刻ｔｆまで時間積分して整理した下記数４７により求めた方が精度が高くなることが判明した。なお、Ｐｃ（ｔｏ）、及びＶｃ（ｔｏ）は、それぞれ吸気弁開弁時の筒内圧力Ｐｃ（ｔ）、及びシリンダ容積Ｖｃ（ｔ）であり、Ｐｃ（ｔｆ）、及びＶｃ（ｔｆ）は、それぞれ吸気弁閉弁時の筒内圧力Ｐｃ（ｔ）、及びシリンダ容積Ｖｃ（ｔ）である。
【０１２７】
【数４７】

【０１２８】
したがって、本実施形態は、数４７を離散化した下記数４８に基づいて筒内吸入空気量Ｍｃを求める。
【０１２９】
【数４８】

【０１３０】
（オブザーバの追加）
本実施形態は、さらに、補正手段としてのオブザーバＯＢＳを追加し、筒内吸入空気量Ｍｃの推定精度を向上させている。上述した図６において、破線にて囲まれた部分が追加されたオブザーバＯＢＳである。
【０１３１】
このオブザーバＯＢＳは、上記エアフローメータ６１と、吸入空気流量推定手段として機能するエアフローメータモデルＭ６とを含んで構成されている。エアフローメータモデルＭ６は、スロットル通過空気流量（実吸入空気流量）が所定の量αである場合に、エアフローメータ６１が出力するであろう値を推定し、この推定値に基づいてスロットル通過空気流量（推定吸入空気流量）ｍｔｅｓを推定するモデルである。この場合、上記所定の量αは、スロットルモデルＭ２が推定した現時点から所定時間Ｔ０だけ先の時刻ｔにおける（推定）スロットル通過空気流量ｍｔを、むだ時間要素により前記所定時間Ｔ０だけ遅延させたスロットル通過空気流量である現時点における（推定）スロットル通過空気流量ｍｔ（ｔ−Ｔ０）である。
【０１３２】
ここで、エアフローメータモデルＭ６について具体的に述べる。エアフローメータモデルＭ６は、先ず、現時点におけるスロットル通過空気流量ｍｔ（ｔ−Ｔ０）に対する完全放熱量Ｗ１，Ｗ２を、同完全放熱量Ｗ１，Ｗ２とスロットル通過空気流量ｍｔとの関係をそれぞれ規定した図１４に示したテーブルと、前記求められた現時点でのスロットル通過空気流量ｍｔ（ｔ−Ｔ０）とに基づいて求める。完全放熱量Ｗ１、及び完全放熱量Ｗ２は、図４に示した熱線計量部６１ａのボビン部６１ａ１、及び同熱線計量部６１ａのサポート部６１ａ２にそれぞれ対応した放熱遅れを含まない放熱量である。
【０１３３】
次に、エアフローメータモデルＭ６は、ボビン部６１ａ１、及びサポート部６１ａ２にそれぞれ対応する放熱量であり、完全放熱量Ｗ１，Ｗ２に対してそれぞれ一次遅れの特性を有する（応答遅れを含む）放熱量（応答放熱量）ｗ１，ｗ２を下記数４９及び下記数５０にしたがって求める。数４９，数５０における添え字（ｋ）は今回の演算値、添え字（ｋ−１）は前回の演算値を表し、Δｔは前回の演算値を求めてから今回の演算値を求めるまでの時間である。
【０１３４】
【数４９】
ｗ１（ｋ）＝Δｔ・（Ｗ１（ｋ）−ｗ１（ｋ−１））／τ１＋ｗ１（ｋ−１）
【０１３５】
【数５０】
ｗ２（ｋ）＝Δｔ・（Ｗ２（ｋ）−ｗ２（ｋ−１））／τ２＋ｗ２（ｋ−１）
【０１３６】
上記数４９，数５０において、τ１、及びτ２は、ボビン部６１ａ１、及びサポート部６１ａ２にそれぞれ対応する上記一次遅れ特性の時定数であり、下記数５１及び下記数５２により求められる。数５１，数５２中の値ｋ１０，ｋ２０、及び値ｍ１，ｍ２には、実験的に求められた値である。また、数５１，数５２中の値ｕはエアフローメータ６１の熱線計量部６１ａにバイパスされた単位断面積当たりの通過空気量であり、図５に示したエアフローメータ６１の出力電圧Ｖｇと実測された吸入空気流量ｍｔＡＦＭとの関係を規定するＶｇ−ｍｔＡＦＭ変換テーブルと、エアフローメータ６１の実際の出力電圧Ｖｇとに基づいて求められた吸入空気流量ｍｔＡＦＭを、前記熱線計量部６１ａのバイパス流路断面積Ｓで除した値（ｍｔＡＦＭ／Ｓ）である。
【０１３７】
【数５１】
τ１＝ｋ１０・ｕ^ｍ１
【０１３８】
【数５２】
τ２＝ｋ２０・ｕ^ｍ２
【０１３９】
そして、エアフローメータモデルＭ６は、応答放熱量ｗ１，ｗ２の和（ｗ１＋ｗ２）とエアフローメータ６１が出力するであろう値に基づくスロットル通過空気流量ｍｔｅｓとの関係を規定した図１５に示したテーブルと、上記数４９〜数５２により求められた応答放熱量ｗ１，ｗ２の和（ｗ１＋ｗ２）とに基づいて、現時点でエアフローメータ６１が出力するであろう値に基づくスロットル通過空気流量ｍｔｅｓを求める。なお、内燃機関がスロットルバルブ開度ＴＡが一定となる定常運転状態にある場合、このスロットル通過空気流量ｍｔｅｓは、スロットルモデルＭ２が推定した現時点から所定時間Ｔ０だけ先の時刻ｔにおける（推定）スロットル通過空気流量ｍｔ（及び、現時点におけるスロットル通過空気流量ｍｔ（ｔ−Ｔ０））と同一となる。
【０１４０】
再び、図６を参照すると、オブザーバＯＢＳはこのスロットル通過空気流量ｍｔｅｓを表す信号を比較要素ＣＯＭの一端に入力する。一方、オブザーバＯＢＳはエアフローメータ６１の出力Ｖｇを図５に示したテーブルにより現時点での吸入空気流量（実吸入空気流量）ｍｔＡＦＭに変換し、同吸入空気流量ｍｔＡＦＭを表す信号を比較要素ＣＯＭの他端に入力する。
【０１４１】
そして、オブザーバＯＢＳは比較要素ＣＯＭにおいてスロットル通過空気流量ｍｔｅｓと吸入空気流量ｍｔＡＦＭとの偏差ＳＡを求め、この偏差ＳＡを積分要素により時間積分して偏差積分値ＳｕｍＳＡを求めるとともに、偏差積分値ＳｕｍＳＡに所定のゲインＧ１（負の一定値）を乗算した値、及び同偏差積分値ＳｕｍＳＡに所定のゲインＧ２（負の一定値）を乗算した値を、それぞれ、スロットルモデルＭ２が推定するスロットル通過空気流量ｍｔ、及び吸気弁モデルＭ４が推定する筒内吸入空気流量ｍｃに加算する（フィードバックする）。即ち、本実施形態における筒内吸入空気量推定装置は、スロットル通過空気流量ｍｔを、上記数３又は上記数４の代わりに下記数５３又は下記数５４に基いて推定する。
【０１４２】
【数５３】

【０１４３】
【数５４】

【０１４４】
また、本筒内吸入空気量推定装置は、筒内吸入空気流量ｍｃを、上記数２２又は上記数２３の代わりに下記数５５又は下記数５６に基いて推定する。
【０１４５】
【数５５】

【０１４６】
【数５６】

【０１４７】
このようにして、上記偏差ＳＡ（上記偏差積分値ＳｕｍＳＡ）が「０」になる（小さくなる）ように、同偏差ＳＡに基いてスロットルモデルＭ２により推定されたスロットル通過空気流量ｍｔ、及び吸気弁モデルＭ４により推定された筒内吸入空気流量ｍｃがそれぞれ直接補正され、この結果、実際の筒内吸入空気量と上記モデルＭ１〜Ｍ５により得られる筒内吸入空気量Ｍｃの定常的な誤差が低減される。
【０１４８】
（実際の作動）
次に、電気制御装置８０が筒内吸入空気量Ｍｃを推定するとともに、燃料噴射量ｆｃを決定する際の実際の作動について説明する。
【０１４９】
（スロットルバルブ制御）
電気制御装置８０のＣＰＵ８１は、図１６にフローチャートにより示したスロットルバルブ開度を制御するためのルーチンを所定時間（１ｍｓｅｃ）の経過毎に実行するようになっている。従って、所定のタイミングとなると、ＣＰＵ８１はステップ１６００から処理を開始し、ステップ１６０５に進んでアクセルペダル操作量Ａｃｃｐ読み込む。次いで、ＣＰＵ８１はステップ１６１０に進み、同ステップ１６１０にて図７と同じテーブルを用いることにより上記読み込んだアクセルペダル操作量Ａｃｃｐに基づく暫定的な目標スロットルバルブ開度θｒ１を求める。
【０１５０】
次に、ＣＰＵ８１はステップ１６１５に進んで変数Ｉを「６４」に設定し、続くステップ１６２０にて記憶値θｒ（Ｉ）にθｒ（Ｉ−１）の値を格納する。現時点では、変数Ｉは「６４」であるから、記憶値θｒ（６４）に記憶値θｒ（６３）の値が格納される。次いで、ＣＰＵ８１はステップ１６２５に進み、変数Ｉが「１」と等しくなったか否かを判定する。この場合、変数Ｉの値は「６４」であるから、ＣＰＵ８１はステップ１６２５にて「Ｎｏ」と判定してステップ１６３０に進み、同ステップ１６３０にて変数Ｉの値を「１」だけ減少し、その後上記ステップ１６２０に戻る。この結果、ステップ１６２０が実行されると、記憶値θｒ（６３）に記憶値θｒ（６２）の値が格納される。このような処理は、変数Ｉの値が「１」となるまで繰り返し実行される。
【０１５１】
その後、ステップ１６３０の処理が繰り返されて変数Ｉの値が「１」となると、ＣＰＵ８１はステップ１６２５にて「Ｙｅｓ」と判定してステップ１６３５に進み、同ステップ１６３５にて前記ステップ１６１０にて求めた現時点における暫定的な目標スロットルバルブ開度θｒ１を記憶値θｒ（０）に格納する。以上により、現時点からＩｍｓｅｃ前（０ｍｓｅｃ≦Ｉｍｓｅｃ≦６４ｍｓｅｃ，Ｉは整数）の暫定的な目標スロットルバルブ開度θｒ（Ｉ）（Ｉ＝６４，６３，６２，・・・，２，１，０）がＲＡＭ８３内に記憶されることになる。
【０１５２】
次に、ＣＰＵ８１はステップ１６４０に進み、同ステップ１６４０にて記憶値θｒ（６４）を最終的な目標スロットルバルブ開度θｒとして設定し、続くステップ１６４５にて実際のスロットルバルブ開度が目標スロットルバルブ開度θｒと等しくなるように、スロットルバルブアクチュエータ４３ａに対し駆動信号を出力し、その後ステップ１６９５にて本ルーチンを一旦終了する。
【０１５３】
以降においても、上記ルーチンの処理は１ｍｓｅｃの経過毎に実行される。この結果、実際のスロットルバルブ開度が、所定時間Ｔ（＝６４ｍｓｅｃ）前のアクセルペダル操作量Ａｃｃｐに基づく目標スロットルバルブ開度θｒと等しくなるように制御される。これにより、上記電子制御スロットルモデルＭ１は、現時点から時間（Ｔ−Ｔ０）前の目標スロットルバルブ開度θ（Ｔ−Ｔ０）を、現時点から所定時間Ｔ０だけ先の時刻ｔにおけるスロットルバルブ開度θｔとして推定する。
【０１５４】
（スロットル通過空気流量ｍｔ、吸気管内空気圧力Ｐｍ、吸気管内空気温度Ｔｍ推定）ＣＰＵ８１は、図１７及びこれに続く図１８にフローチャートにより示したルーチンを所定時間（８ｍｓｅｃ）の経過毎に実行するようになっている。従って、所定のタイミングになると、ＣＰＵ８１はステップ１７００から処理を開始し、ステップ１７０５に進んで、図５に示したテーブルと同じテーブルと、エアフローメータ６１の出力Ｖｇとを用いて吸入空気流量（実吸入空気流量）ｍｔＡＦＭを求める。
【０１５５】
次に、ＣＰＵ８１はステップ１７１０に進み、図１４に示したテーブルと同じテーブルと、前回以前の本ルーチン実行時において後述するステップ１８１０にて既に求められているスロットル通過空気流量ｍｔ（ｋ）を前記所定時間Ｔ０だけ遅延させることにより得られる現時点におけるスロットル通過空気流量ｍｔ（ｋ−Ｔ０）とを用いて完全放熱量Ｗ１（ｋ），Ｗ２（ｋ）をそれぞれを求める。なお、本ルーチンにおいて、添え字（ｋ）が付された値は今回本ルーチンを実行した際に求める値を表し、添え字（ｋ−１）が付された値は前回本ルーチンを実行した際に求めた値を表す。
【０１５６】
次いで、ＣＰＵ８１はステップ１７１５に進んで、上記数５１及び上記数５２に従って時定数τ１、τ２をそれぞれ求めるとともに、続くステップ１７２０にて上記数４９及び上記数５０に従って応答放熱量ｗ１（ｋ），ｗ２（ｋ）をそれぞれ求める。なお、Δｔは本ルーチンの計算周期（即ち、８ｍｓｅｃ）である。次に、ＣＰＵ８１はステップ１７２５に進み、図１５に示したテーブルと同じテーブルと、前記応答放熱量ｗ１（ｋ），ｗ２（ｋ）の和（ｗ１（ｋ）＋ｗ２（ｋ））とを用いて現時点でエアフローメータ６１が出力するであろう値に基づくスロットル通過空気流量（推定吸入空気流量）ｍｔｅｓを求める。
【０１５７】
次に、ＣＰＵ８１はステップ１７３０に進んで、前記スロットル通過空気流量ｍｔｅｓから前記吸入空気流量ｍｔＡＦＭを減じた値を偏差ＳＡ（ｋ）として格納するとともに、続くステップ１７３５にて、その時点での（前回の）偏差積分値ＳｕｍＳＡ（ｋ−１）に前記偏差ＳＡ（ｋ）を加えた値を新たな（今回の）偏差積分値ＳｕｍＳＡ（ｋ）として設定する。
【０１５８】
次いで、ＣＰＵ８１は図１８のステップ１８０５に進んで図１０に示したテーブルと同じテーブルと、現時点から所定時間Ｔ０だけ先の時刻ｔにおける推定スロットルバルブ開度θｔとを用いて流量係数Ｃｔ（θｔ）と開口面積Ａｔ（θｔ）の積値Ｃｔ（θｔ）・Ａｔ（θｔ）を求める。
【０１５９】
次いで、ＣＰＵ８１はステップ１８１０に進み、同ステップ１８１０にて上記数５３、又は上記数５４にしたがってスロットル通過空気流量ｍｔを計算する。この計算で使用されるスロットルバルブ上流圧力Ｐａ、及び吸気温度Ｔａは、それぞれ大気圧センサ６３、及び吸気温センサ６２から取得される。また、吸気管内空気圧力Ｐｍ（ｋ−１）、及び吸気管内空気温度Ｔｍ（ｋ−１）は、前回の本ルーチン実行時において後述するステップ１８１５にて求められた値Ｐｍ（ｋ）、及びＴｍ（ｋ）であり、偏差積分値ＳｕｍＳＡ（ｋ）は前記ステップ１７３５で求められた値である。
【０１６０】
次にＣＰＵ８１はステップ１８１５に進み、上記数１７及び上記数１８を積分して離散化した下記数５７及び下記数５８に基づいて吸気管内空気圧力Ｐｍ（ｋ）、及び吸気管内空気温度Ｔｍ（ｋ）を求めた後、ステップ１８９５に進んで本ルーチンを一旦終了する。なお、下記数５７及び数５８において、Δｔは本ルーチンの計算周期（即ち、８ｍｓｅｃ）である。
【０１６１】
【数５７】

【０１６２】
【数５８】

【０１６３】
実際には、ＣＰＵ８１は、上記数５７にてＰｍ／Ｔｍを求め、これと上記数５８により求めたＰｍとからＴｍを求める。なお、数５７及び数５８におけるｍｃＡＶＥ（ｋ−１）は、後述する１ｍｓｅｃルーチンで求められる筒内吸入空気流量ｍｃの平均値である。
【０１６４】
（筒内圧力Ｐｃ、筒内吸入空気流量ｍｃ、筒内吸入空気量Ｍｃ等の推定）
ＣＰＵ８１は、図１９及びこれに続く図２０にフローチャートにより示したルーチンを所定時間（１ｍｓｅｃ）の経過毎に実行するようになっている。従って、所定のタイミングになると、ＣＰＵ８１はステップ１９００から処理を開始し、ステップ１９０５に進んで前記時刻ｔにおけるバルブリフト量Ｌと、図１１に示したテーブルと同じテーブルとに基づいて、上記数５５及び上記数５６にて使用する積値Ｃｖ（Ｌ）・Ａｖ（Ｌ）を求め、続くステップ１９１０にて同数５５又は同数５６にしたがって筒内吸入空気流量ｍｃ（ｔ）を計算する。
【０１６５】
ここで、Ｐｍ（ｋ）、及びＴｍ（ｋ）は、前述のステップ１８１５にてそれぞれ求められた吸気管内空気圧、及び吸気管内空気温度であり、Ｔｃ（ｔ）は、前回の本ルーチン実行時において後述するステップ２０４５で設定された値である。また、ＳｕｍＳＡ（ｋ）は上述した図１７のステップ１７３５で求められた偏差積分値であり、Ｐｃ（ｔ）は前回の本ルーチン実行時において後述するステップ１９２５で設定された値である。
【０１６６】
次に、ＣＰＵ８１はステップ１９１５に進み、同ステップ１９１５にて上記数４３にしたがって筒内圧力Ｐ’ｃ（ｔ＋Δｔ）を求める。Δｔは本ルーチンの計算周期（即ち、１ｍｓｅｃ）である。また、ｍｃ（ｔ）は前記ステップ１９１０で求められた値である。
【０１６７】
次いで、ＣＰＵ８１はステップ１９２０に進み、上記数４６にしたがって筒内圧力Ｐｃ（ｔ＋Δｔ）を求め、続くステップ１９２５にて今回求めた筒内圧力Ｐ’ｃ（ｔ＋Δｔ）、及び筒内圧力Ｐｃ（ｔ＋Δｔ）を、次回の本ルーチンの演算のためにそれぞれ筒内圧力Ｐ’ｃ（ｔ）、及び筒内圧力Ｐｃ（ｔ）に格納する。
【０１６８】
次いで、ＣＰＵ８１は図２０に示したステップ２００５に進み、時刻ｔが吸気弁２３が閉状態から開状態へと変化した直後の時点であるか否かを判定し、閉状態から開状態へと変化した直後であれば、ステップ２０１０にて変数Ｚの値を「０」として初期化し、ステップ２０１５にてその時点で求められている筒内圧力Ｐｃ’（ｔ）を吸気弁２３が開弁した時（吸気弁開時）の筒内圧力Ｐｃ（ｔｏ）として格納する。そして、ＣＰＵ８１はステップ２０２０にて時刻ｔのシリンダ容積Ｖｃ（ｔ）を吸気弁開時のシリンダ容積Ｖｃ（ｔｏ）として格納し、続くステップ２０２５にて吸気弁開時からの筒内吸入空気量Ｍｃ１の値を値Ｍｃ０（初期値、例えば「０」）に設定してステップ２０３０に進む。一方、時刻ｔが吸気弁２３が閉状態から開状態へと変化した直後の時点でなければ、ＣＰＵ８１はステップ２００５にて「Ｎｏ」と判定して直接２０３０に進む。
【０１６９】
次に、ＣＰＵ８１はステップ２０３０にて時刻ｔにおいて吸気弁２３が開状態にあるか否かを判定する。いま、時刻ｔが吸気弁２３が閉状態から開状態になった直後に相当していれば、ＣＰＵ８１はステップ２０３０にて「Ｙｅｓ」と判定してステップ２０３５に進み、同ステップ２０３５にて変数Ｚに値Ｐｃ’（ｔ）・ｄＶｃ（ｔ）／ｄｔ・Δｔの値を加えて同変数Ｚを更新する。これにより、変数Ｚは値Ｐ’（ｔ）・ｄＶｃ（ｔ）／ｄｔの積分値相当量となる。続いて、ＣＰＵ８１はステップ２０４０にて吸気弁開時からの筒内吸入空気量Ｍｃ１にｍｃ（ｔ）・Δｔを加えた値を新たな筒内吸入空気量Ｍｃ１として格納し、ステップ２０４５に進んで下記数５９に基づき筒内空気温度Ｔｃ（ｔ）を求め、ステップ２０９５にて本ルーチンを一旦終了する。
【０１７０】
【数５９】
Ｔｃ（ｔ）＝Ｐｃ（ｔ）・Ｖｃ（ｔ）／（Ｍｃ１・Ｒ）
【０１７１】
上記ステップ２０３０〜２０４５の処理は、吸気弁２３が開弁している間、継続されるので、値Ｐ’（ｔ）・ｄＶｃ（ｔ）／ｄｔ・Δｔの総和を示す変数Ｚ、吸気弁開時からの筒内吸入空気量Ｍｃ１、及び筒内空気温度Ｔｃ（ｔ）が更新されて行く。
【０１７２】
その後、所定の時間が経過して時刻ｔが吸気弁２３が開状態から閉状態に変化した直後の時刻になると、ＣＰＵ８１はステップ２００５及びステップ２０３０に進んだとき、何れも「Ｎｏ」と判定してステップ２０５０に進み、同ステップ２０５０にて吸気弁２３が開状態から閉状態に変化した直後であるか否かを判定する。そして、この場合、ＣＰＵ８１はステップ２０５０にて「Ｙｅｓ」と判定し、ステップ２０５５に進んで一吸気行程における筒内吸入空気量Ｍｃを上記数４８にしたがって推定する。
【０１７３】
その後、ＣＰＵ８１はステップ２０６０に進み、上記求めた筒内吸入空気量Ｍｃをクランク角１８０°ＣＡに相当する時間Ｔ_{１８０ＣＡ}で除して、筒内吸入空気量Ｍｃの平均値ｍｃＡＶＥ（ｋ−１）を求め、続くステップ２０６５にて筒内吸入空気量Ｍｃの平均値ｍｃＡＶＥ（ｋ−１）に設定空燃比により変化する係数Ｋを乗じて燃料噴射量ｆｃを求める。なお、筒内吸入空気量Ｍｃの平均値ｍｃＡＶＥ（ｋ−１）は、筒内吸入空気量Ｍｃに比例しているから、燃料噴射量ｆｃは数２にしたがって計算されることになる。そして、ＣＰＵ８１はステップ２０９５に進み、本ルーチンを一旦終了する。
【０１７４】
また、時刻ｔが、吸気弁３２が閉状態から開状態に変化した直後の時刻でなく、且つ開状態から閉状態への変化した直後の時刻でなく、且つ同吸気弁３２が閉状態にある時刻である場合、ＣＰＵ８１は図１９のステップ１９００〜１９２５の処理を実行後、図２０のステップ２００５、２０３０、２０５０にて全て「Ｎｏ」と判定してステップ２０９５に進み、本ルーチンを一旦終了する。
【０１７５】
以上により、筒内吸入空気量Ｍｃが各モデルを用いて推定され、これに応じた燃料噴射量ｆｃが決定される。そして、ＣＰＵ８１は、図示しない燃料噴射ルーチンを所定のタイミングにて実行し、前記決定された燃料噴射量ｆｃだけ燃料を噴射する。
【０１７６】
以上説明したように、本発明による筒内吸入空気量推定装置を含む燃料噴射量制御装置の実施形態によれば、シリンダモデルＭ５により筒内圧力Ｐｃと筒内空気温度Ｔｃとが求められ、これらの値が吸気弁モデルＭ４に提供される。従って、吸気弁モデルＭ４は、従来のように多くの変数によるテーブル検索に基づくのではなく、上記数２２，２３（実際には、上記数５５，５６）にしたがった数値計算により筒内吸入空気流量ｍｃ（従って、筒内吸入空気量Ｍｃ）を求めることができる。この結果、テーブル値の適合に要する労力を低減することができるとともに、精度良く燃料噴射量ｆｃを求めることができた。
【０１７７】
また、オブザーバＯＢＳにより、スロットル通過空気流量（推定吸入空気流量）ｍｔｅｓと吸入空気流量（実吸入空気流量）ｍｔＡＦＭとの偏差ＳＡ（上記偏差積分値ＳｕｍＳＡ）が「０」になるように、同偏差ＳＡに基いてスロットルモデルＭ２により推定されたスロットル通過空気流量ｍｔ、及び吸気弁モデルＭ４により推定された筒内吸入空気流量ｍｃがそれぞれ直接補正される。従って、スロットル通過空気流量ｍｔｅｓが吸入空気流量ｍｔＡＦＭよりも小さい場合、上記吸気管モデルＭ３により推定される吸気管内空気圧力Ｐｍを増大せしめることなく、直接的に筒内吸入空気流量（推定吸気弁通過空気流量）ｍｃを増大せしめることができ、その結果、筒内吸入空気量Ｍｃを増大せしめることが可能となる。
【０１７８】
従って、内燃機関がスロットルバルブ開度が最大の開度で一定となるスロットル全開定常運転状態にある場合であっても、スロットル通過空気流量ｍｔｅｓと吸入空気流量ｍｔＡＦＭとの大小関係に拘わらず実際の筒内吸入空気量と推定された筒内吸入空気量Ｍｃとの定常的な誤差を確実に低減することができ、その結果、適正な燃料噴射量ｆｃを得ることで内燃機関により燃焼される混合気の空燃比を精度良く狙いの値とすることができた。
【０１７９】
本発明は上記実施形態に限定されることはなく、本発明の範囲内において種々の変形例を採用することができる。例えば、上記実施形態では、補正手段としてのオブザーバＯＢＳは、スロットルモデルＭ２により推定されたスロットル通過空気流量ｍｔ、及び吸気弁モデルＭ４により推定された筒内吸入空気流量ｍｃをそれぞれ直接補正しているが、スロットル通過空気流量（推定吸入空気流量）ｍｔｅｓと吸入空気流量（実吸入空気流量）ｍｔＡＦＭとの偏差ＳＡ（上記偏差積分値ＳｕｍＳＡ）が「０」になるように、同偏差ＳＡに基いて、上記数３及び数４にて使用する流量係数Ｃｔ（θｔ）と開口面積Ａｔ（θｔ）の積値Ｃｔ（θｔ）・Ａｔ（θｔ）、及び上記数２２及び数２３にて使用する流量係数Ｃｖ（Ｌ）と開口面積Ａｖ（Ｌ）の積値Ｃｖ（Ｌ）・Ａｖ（Ｌ）を補正し、その結果として、上記スロットル通過空気流量ｍｔ、及び上記筒内吸入空気流量ｍｃをそれぞれ補正してもよい。
【０１８０】
また、上記実施形態の各モデルの他、排気弁を介してシリンダ２１内に流入する空気流量ｍｅを推定するための排気弁モデルを追加採用することもできる。この場合、図２１に示したように、排気弁モデルＭ７はシリンダモデルＭ５に対して接続され、吸気弁モデルＭ４と同様な導出過程を経て得られた下記数６０、及び下記数６１により表される。なお、数６０、及び数６１において、Ｐｅは排気管内空気圧力、Ｔｅは排気管内空気温度であり、数６０は排気系からシリンダ２１内に空気が流入する場合（Ｐｃ＜Ｐｅ）、下記数６１はシリンダ２１から排気系に空気が流出する場合（Ｐｃ＞Ｐｅ）に用いられる。この結果、上記空気流量ｍｅは、排気系からシリンダ２１内に空気が流入する場合に正の値を、シリンダ２１から排気系に空気が流出する場合に負の値をそれぞれ採るように計算される。なお、この場合、排気管内空気圧力を検出するセンサ、及び排気管内空気温度を検出するセンサを設けることが望ましい。
【０１８１】
【数６０】

【０１８２】
【数６１】

【０１８３】
また、上記実施形態においては、インジェクタ３９は吸気ポート３１ａ，３１ｂに向けて燃料を噴射するようになっていたが、燃焼室２５内に直接噴射するように構成されていてもよい。
【図面の簡単な説明】
【図１】本発明による筒内吸入空気量推定装置を含む燃料噴射量制御装置を火花点火式多気筒内燃機関に適用したシステムの概略構成図である。
【図２】図１に示した特定の気筒の燃焼室、及び同燃焼室の近傍部分を示す概略平面図である。
【図３】図１に示したエアフローメータの概略斜視図である。
【図４】図３に示したエアフローメータの熱線計量部の拡大斜視図である。
【図５】図１に示したＣＰＵが参照するエアフローメータの出力と吸入空気流量との関係を規定したテーブルを示したグラフである。
【図６】図１に示した電気制御装置が筒内吸入空気量を推定するために採用した各種モデルの接続関係を示した機能ブロック図である。
【図７】図１に示したＣＰＵが参照するアクセルペダル操作量と目標スロットルバルブ開度との関係を規定したテーブルを示したグラフである。
【図８】スロットルバルブ開度と流量係数との関係を規定したテーブルを示したグラフである。
【図９】スロットルバルブ開度と開口面積との関係を規定したテーブルを示したグラフである。
【図１０】スロットルバルブ開度と、流量係数と開口面積の積値との関係を規定したテーブルを示したグラフである。
【図１１】バルブリフト量と、流量係数と開口面積の積値との関係を規定したテーブルを示したグラフである。
【図１２】シリンダモデルを表すために使用する変数を説明するためシリンダ及びその近傍を概念的に示した図である。
【図１３】シリンダモデルによるシリンダ内圧力の計算結果について説明するためのタイムチャートである。
【図１４】図１に示したＣＰＵが参照するスロットル通過空気流量と完全放熱量との関係を規定したテーブルを示したグラフである。
【図１５】図１に示したＣＰＵが参照する応答放熱量の和とエアフローメータが出力するであろう値に基づくスロットル通過空気流量との関係を規定したテーブルを示したグラフである。
【図１６】図１に示したＣＰＵが実行するスロットルバルブを制御するためのルーチンを示したフローチャートである。
【図１７】図１に示したＣＰＵが８ｍｓｅｃ毎に実行するルーチンの前半部を示したフローチャートである。
【図１８】図１に示したＣＰＵが８ｍｓｅｃ毎に実行するルーチンの後半部を示したフローチャートである。
【図１９】図１に示したＣＰＵが１ｍｓｅｃ毎に実行するルーチンの前半部を示したフローチャートである。
【図２０】図１に示したＣＰＵが１ｍｓｅｃ毎に実行するルーチンの後半部を示したフローチャートである。
【図２１】本発明による燃料噴射量制御装置（筒内吸入空気量推定装置）の実施形態の他の変形例を示した機能ブロック図である。
【図２２】本出願人が検討している燃料噴射量制御装置（筒内吸入空気量推定装置）の機能ブロック図である。
【符号の説明】
１０…火花点火式多気筒内燃機関、２０…シリンダブロック部（エンジン本体部）、２５…燃焼室、３１…吸気ポート、３２…吸気弁、３３…可変吸気タイミング装置、３９…インジェクタ、４１…吸気管、４３…スロットルバルブ、４４…スワールコントロールバルブ、４４ａ…ＳＣＶアクチュエータ、６１…エアフローメータ、８０…電気制御装置、８１…ＣＰＵ、Ｍ１…電子制御スロットルモデル、Ｍ２…スロットルモデル、Ｍ３…吸気管モデル、Ｍ４…吸気弁モデル、Ｍ５…シリンダモデル、Ｍ６…エアフローメータモデル。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an in-cylinder intake air amount estimating apparatus for estimating an in-cylinder intake air amount taken into a cylinder of an internal combustion engine based on an intake system model (simulation model, physical model).
[0002]
[Prior art]
In order to set the air-fuel ratio of the air-fuel mixture burned by the internal combustion engine to a predetermined value, the amount of air taken into the cylinders (in the cylinder and the combustion chamber) of the internal combustion engine (hereinafter referred to as “in-cylinder intake air amount”) Mc ”) must be obtained with high accuracy. Usually, an air flow sensor is provided in the intake passage of the internal combustion engine, and the in-cylinder intake air amount Mc is estimated from the output value of the air flow sensor. However, when the internal combustion engine is in a transient operation state such as when the throttle valve opening greatly changes over time, it is difficult to accurately obtain the in-cylinder intake air amount Mc from the output value of the air flow sensor. Thus, in recent years, various attempts have been made to accurately estimate a value corresponding to the in-cylinder intake air amount Mc by using an intake system model represented by an expression based on fluid dynamics or the like (for example, See Patent Document 1 below). FIG. 22 conceptually shows such an in-cylinder intake air amount estimating apparatus which is being studied by the present applicant. This in-cylinder intake air amount estimating apparatus includes an electronic control throttle model M10. , A throttle model M20, an intake valve model M30, and an intake pipe model M40.
[0003]
Incidentally, the in-cylinder intake air amount Mc is determined when the intake valve is closed (when the intake valve is closed), and has a relationship proportional to the cylinder pressure at that time. The pressure in the cylinder when the intake valve is closed can be regarded as being equal to the pressure upstream of the intake valve and downstream of the throttle valve, that is, the air pressure (intake pipe pressure) Pm in the intake pipe. From the above, the in-cylinder intake air amount estimating apparatus shown in FIG. 22 estimates the in-pipe air pressure Pm when the intake valve is closed by using the models M10 to M40, and calculates the in-cylinder intake air pressure from the estimated intake pipe air pressure Pm. The air amount Mc is estimated.
[0004]
More specifically, the electronic control throttle model M10 estimates the throttle valve opening θt when the intake valve is closed. The throttle model M20 estimates an air flow rate (estimated throttle passing air flow rate) mt passing through the throttle valve by a model obtained based on a law of conservation of energy, a law of conservation of momentum, a law of conservation of mass, and a state equation. ing.
[0005]
The intake valve model M30 estimates the in-cylinder intake air flow rate (estimated intake valve passage air flow rate) mc from the intake pipe air pressure Pm, the intake pipe air temperature Tm, the intake temperature Ta, and the like. That is, as described above, since the in-cylinder intake air flow rate mc is considered to be proportional to the intake pipe air pressure Pm, the intake valve model M30 obtains the in-cylinder intake air flow rate mc according to the following equation 1 based on an empirical rule.
[0006]
(Equation 1)
mc = (Ta / Tm) · (c · Pm−d)
[0007]
In the above equation 1, the value c is a proportional coefficient, and the value d is a value representing the burned gas remaining in the cylinder (this value is considered to be the in-cylinder gas amount when the exhaust valve is closed. "The burned gas amount d"). The intake valve model M30 is a table (look-up table) that specifies the relationship between the engine rotation speed Ne, the opening / closing timing VT of the intake valve, the maximum lift amount Lmax of the intake valve, and the like, the proportionality coefficient c, and the burned gas amount d. , Map), the proportional coefficient c, the burned gas amount, and the actual engine speed Ne, the actual intake valve opening / closing timing VT, and the maximum intake valve lift amount Lmax, and the stored table. Find d. Further, at the time of calculation, the intake valve model M30 calculates the intake pipe air pressure Pm and the intake pipe air temperature Tm at the time of closing the intake valve immediately before (latest), which are already estimated by the intake pipe model M40 to be described later, according to the above equation (1). To estimate the in-cylinder intake air flow rate mc.
[0008]
The intake pipe model M40 has a throttle passage air flow rate mt estimated by the throttle model M20 and an in-cylinder intake air flow rate mc estimated by the intake valve model M30 according to equations based on the law of conservation of mass and the law of conservation of energy, respectively. Is used to estimate the intake pipe air pressure Pm when the intake valve is closed. The in-cylinder intake air amount estimating device estimates the in-cylinder intake air amount Mc based on the intake pipe air pressure Pm when the intake valve is closed estimated by the intake pipe model M40.
[0009]
[Patent Document 1]
JP-A-6-74076
[0010]
[Problems to be solved by the invention]
For this type of in-cylinder intake air amount estimating apparatus, the applicant of the present application has reduced the steady-state error between the actual in-cylinder intake air amount Mc and the in-cylinder intake air amount Mc estimated as described above. In order to improve the accuracy of estimating the estimated in-cylinder intake air amount Mc, the following observer is being added (see Japanese Patent Application No. 2001-316350).
[0011]
That is, the observer is disposed in the intake passage of the internal combustion engine and measures an actual intake air flow rate (actual intake air flow rate) mtAFM to be taken into the intake passage. If the actual intake air flow rate is assumed to be the estimated throttle passing air flow rate mt estimated by the throttle model M20 using an air flow meter model that is a model for the meter, the air flow meter will output. An intake air flow rate estimating means for estimating an output value and estimating an intake air flow rate drawn into the intake passage as an estimated intake air flow rate mtes based on the estimated output value; Estimated by the throttle model M20 according to the deviation from the air flow rate mtAFM Throttle passage adapted to correct the air flow rate mt.
[0012]
By adding such an observer, for example, when the estimated intake air flow rate mtes is smaller than the actual intake air flow rate mtAFM, the estimated throttle passage air flow rate mt becomes equal to the deviation between the estimated intake air flow rate mtes and the actual intake air flow rate mtAFM. The intake pipe air pressure Mc is increased by increasing the air pressure Pm in the intake pipe downstream of the throttle valve. Similarly, when the estimated intake air flow rate mtes is larger than the actual intake air flow rate mtAFM, the in-cylinder intake air amount Mc decreases. In this way, the steady error between the actual in-cylinder intake air amount and the estimated in-cylinder intake air amount Mc is reduced.
[0013]
However, when the internal combustion engine is in a throttle fully open steady state in which the throttle valve opening is constant at the maximum opening, the air pressure Pm in the intake pipe downstream of the throttle valve is lower than the pressure upstream of the throttle valve (that is, the atmospheric pressure Pa). Have also increased to slightly smaller values. Therefore, when the internal combustion engine is in the throttle fully open steady-state operating state and the estimated intake air flow rate mtes is smaller than the actual intake air flow rate mtAFM, the observer increases the estimated throttle passing air flow rate mt to increase the intake pipe air pressure Pm. Is increased, the air pressure Pm in the intake pipe immediately becomes larger than the atmospheric pressure Pa, and the estimated throttle passage air flow rate mt estimated by the throttle model M20 immediately becomes a negative value (a value indicating a backflow). Accordingly, since the air pressure Pm in the intake pipe downstream of the throttle valve cannot be increased, the in-cylinder intake air amount Mc does not increase, and as a result, the actual in-cylinder intake air amount and the estimated in-cylinder intake air amount Mc become steady. However, there is a problem that a typical error may remain.
[0014]
Accordingly, an object of the present invention is an in-cylinder intake air amount estimating apparatus for estimating an in-cylinder intake air amount to be taken into a cylinder of an internal combustion engine based on a model of an intake system. It is an object of the present invention to provide a device capable of effectively reducing a steady error between an intake air amount and an estimated in-cylinder intake air amount.
[0015]
[Overview of the present invention]
A feature of the present invention is a throttle passing air flow rate that estimates a flow rate of air passing through a throttle valve as an estimated throttle passing air flow rate using a model of air passing through the throttle valve disposed in an intake passage of an internal combustion engine. Estimating means and an intake valve passing air for estimating an air flow rate passing through the intake valve as an estimated intake valve passing air flow rate using a model of air passing through the intake valve for communicating and blocking the intake passage and the cylinder. Flow rate estimating means, and in-cylinder intake air amount estimating means for estimating an in-cylinder intake air amount to be taken into the cylinder based on at least the estimated throttle passing air flow rate and the estimated intake valve passing air flow rate. An in-cylinder intake air amount estimating device for an internal combustion engine generates an output value corresponding to an actual intake air flow rate sucked into the intake passage and outputs the output value. An air flow sensor that measures the intake air flow rate at the time as an actual intake air flow rate and a model for the air flow rate sensor are used, and it is assumed that the actual intake air flow rate is the estimated throttle passing air flow rate. An intake air flow rate estimating means for estimating an output value that will be output from the air flow rate sensor and estimating an intake air flow rate to be taken into the intake passage as an estimated intake air flow rate based on the estimated output value; A correction means is provided for correcting the intake valve passing air flow rate estimating means so as to correct the estimated intake valve passing air flow rate based on a difference between the intake air flow rate and the actual intake air flow rate.
[0016]
Here, the correction means may be configured to correct the intake valve passing air flow rate estimating means so as to directly correct the estimated intake valve passing air flow rate estimated by the intake valve passing air flow rate estimating means. If the intake valve passing air flow rate estimating means uses a predetermined parameter (coefficient) when estimating the estimated intake valve passing air flow rate, the predetermined parameter is corrected, and as a result, the estimated intake valve passing air flow rate is estimated. The intake valve passing air flow rate estimating means may be configured to correct the passing air flow rate.
[0017]
In this case, the correction means also corrects the throttle passage air flow estimation means so as to correct the estimated throttle passage air flow based on a deviation between the estimated intake air flow rate and the actual intake air flow rate. Preferably, it is configured. Also in this case, even if the correction means is configured to correct the throttle passing air flow estimation means so as to directly correct the estimated throttle passing air flow rate estimated by the throttle passing air flow estimation means, When the throttle passing air flow rate estimating means uses a predetermined parameter (coefficient) when estimating the estimated throttle passing air flow rate, the predetermined parameter is corrected, and as a result, the estimated throttle passing air flow rate is calculated. It may be configured to correct the throttle passage air flow rate estimating means so as to make the correction.
[0018]
According to these, the correction means corrects the intake valve passage air flow estimation means so as to correct the estimated intake valve passage air flow based on the deviation between the estimated intake air flow rate and the actual intake air flow rate. Therefore, when the estimated intake air flow rate is smaller than the actual intake air flow rate, as described in the section of the problem to be solved by the invention, the intake pipe air pressure Pm downstream of the throttle valve is directly increased without being increased. As a result, the estimated intake valve passing air flow rate (in-cylinder intake air flow rate mc) can be increased. As a result, the in-cylinder intake air amount (Mc) drawn into the cylinder estimated by the in-cylinder intake air amount estimating means can be increased. It is possible to increase it.
[0019]
Therefore, even when the internal combustion engine is in the above-described throttle fully open steady-state operation state in which the throttle valve opening is constant at the maximum opening, regardless of the magnitude relationship between the estimated intake air flow rate and the actual intake air flow rate. The steady-state error between the actual in-cylinder intake air amount and the estimated in-cylinder intake air amount (Mc) can be reliably reduced. As a result, the air-fuel ratio of the air-fuel mixture burned by the internal combustion engine can be reduced. The predetermined value can be accurately set.
[0020]
In addition, any of the above-described cylinder intake air amount estimating apparatuses for an internal combustion engine includes a cylinder pressure that estimates the pressure in the cylinder by calculation using a model for the cylinder obtained based on the law of conservation of energy. Estimating means, wherein the intake valve passing air flow rate estimating means is configured to estimate the estimated intake valve passing air flow rate using a model for air passing through the intake valve using the estimated pressure in the cylinder. It is preferred that
[0021]
According to this, the pressure in the cylinder (in-cylinder pressure) is obtained by calculation. If the in-cylinder pressure is obtained, the intake valve passing air flow rate estimating means estimates the intake valve passing air flow rate (in-cylinder intake air flow rate) by using a "model for air passing through the intake valve" using the in-cylinder pressure. mc) can be obtained by calculation. Therefore, it is possible to accurately obtain the in-cylinder intake air amount (Mc) without adapting the table values (the proportionality coefficient c, the burned gas amount d, and the like) for many combinations of parameters.
[0022]
In this case, the model of the air passing through the intake valve used by the intake valve passing air flow rate estimating means is preferably a model obtained based on a law of conservation of energy, a law of conservation of momentum, and a law of conservation of mass. It is. According to this, the estimated intake valve passage air flow rate (in-cylinder intake air flow rate mc) can be calculated by a model (formula) expressed according to a physical law instead of an empirical rule, and therefore, the in-cylinder intake air amount ( It is possible to improve the estimation accuracy of Mc).
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a fuel injection amount control device including a cylinder intake air amount estimation device for an internal combustion engine according to the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a system in which this fuel injection amount control device is applied to a spark ignition type multi-cylinder (for example, four cylinder) internal combustion engine 10.
[0024]
The internal combustion engine 10 includes a cylinder block 20 including a cylinder block, a cylinder block lower case, and an oil pan, a cylinder head 30 fixed on the cylinder block 20, and a gasoline mixture supplied to the cylinder block 20. It includes an intake system 40 for supplying and an exhaust system 50 for discharging exhaust gas from the cylinder block unit 20 to the outside.
[0025]
The cylinder block section 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 via the connecting rod 23, whereby the crankshaft 24 rotates. The heads of the cylinder 21 and the piston 22 together with the cylinder head 30 form a combustion chamber 25.
[0026]
The cylinder head 30 includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 for opening and closing the intake port 31, an intake camshaft for driving the intake valve 32, and a phase angle of the intake camshaft and the intake valve 32. Valve control device 33 capable of continuously changing the valve lift amount (maximum valve lift amount), an actuator 33a of the intake valve control device 33, an exhaust port 34 communicating with the combustion chamber 25, and an exhaust valve for opening and closing the exhaust port 34. 35, an exhaust camshaft 36 for driving the exhaust valve 35, a spark plug 37, an igniter 38 including an ignition coil for generating a high voltage applied to the spark plug 37, and an injector for injecting fuel into the intake port 31 (fuel injection means) 39 are provided.
[0027]
The intake system 40 includes an intake pipe 41 including an intake manifold communicating with the intake port 31 and forming an intake passage together with the intake port 31, an air filter 42 provided at an end of the intake pipe 41, and an intake pipe 41. A throttle valve 43 that makes the opening cross-sectional area of the intake passage variable and a swirl control valve (hereinafter, referred to as “SCV”) 44 are provided. The throttle valve 43 is driven to rotate in the intake pipe 41 by a throttle valve actuator 43a composed of a DC motor. The SCV 44 is rotatably supported by the intake pipe 41 at a position downstream of the throttle valve 43 and upstream of the injector 39, and is driven to rotate by an SCV actuator 44a composed of a DC motor. Has become.
[0028]
FIG. 2 is a schematic plan view of the combustion chamber 25 of one cylinder (specific cylinder) and the vicinity of the combustion chamber 25. As shown in FIG. 2, the intake port 31 is actually composed of a pair of intake ports 31a and 31b provided for each cylinder. The intake port 31a forms a so-called swirl port which is formed in a helical shape so as to generate a swirl (swirl flow) in the combustion chamber 25, and the intake port 31b forms a so-called straight port. A partition wall 41a extending along the longitudinal direction of the intake pipe 41 is formed in a portion of the intake pipe 41 extending from the surge tank (indicated by a symbol SG in FIG. 1) to each combustion chamber 25 (that is, a part of the intake manifold). Thus, the intake pipe 41 is partitioned into a first intake manifold 45 communicating with the intake port 31a and a second intake manifold 46 communicating with the intake port 31b. A communication passage 41b communicating the first and second intake manifolds 45 and 46 is formed at an appropriate position of the partition wall 41a, and the injector 39 is fixed at a position near the communication passage 41b, and is connected to the intake ports 31a and 31b. It is designed to inject fuel.
[0029]
The SCV 44 is provided in a second intake manifold 46. Therefore, when the SCV 44 closes the second intake manifold 46, the air (air-fuel mixture) mainly passes through the intake port 31a and is sucked into the combustion chamber 25, and swirl is generated in the combustion chamber 25. Combustion at the air-fuel ratio becomes possible. On the other hand, when the SCV 44 opens the second intake manifold 46, air passes through both intake ports 31a and 31b and is sucked into the combustion chamber 25, whereby the amount of air sucked into the combustion chamber 25 increases and the engine Can be increased.
[0030]
Referring again to FIG. 1, the exhaust system 50 includes an exhaust manifold 51 connected to the exhaust port 34, an exhaust pipe 52 connected to the exhaust manifold 51, and a catalytic converter (three-way catalyst device) interposed in the exhaust pipe 52. 53 is provided.
[0031]
On the other hand, this system includes a hot wire air flow meter 61 as an air flow rate sensor, an intake air temperature sensor 62, an atmospheric pressure sensor (throttle valve upstream pressure sensor) 63, a throttle position sensor 64, an SCV opening sensor 65, a cam position sensor 66, Intake valve lift amount sensor 67, crank position sensor 68, water temperature sensor 69, O₂A sensor 70 and an accelerator opening sensor 71 are provided.
[0032]
As shown in FIG. 3 which is a schematic perspective view, the air flow meter 61 measures a bypass passage for partially bypassing the intake air flowing through the intake pipe 41 and a mass flow rate of the intake air bypassed to the bypass passage. And a signal processing unit 61b that outputs a voltage Vg (output value) according to the measured mass flow rate. As shown in FIG. 4 which is an enlarged perspective view of the heat ray measuring section 61a, an intake air temperature measuring resistor (bobbin section) 61a1 made of platinum hot wire and the intake air temperature measuring resistor 61a1 are provided to the signal processing section 61b. It includes a support portion 61a2 for connecting and holding, a heating resistor (heater) 61a3, and a support portion 61a4 for connecting and holding the heating resistor 61a3 to the signal processing portion 61b. The signal processing unit 61b has a bridge circuit composed of an intake air temperature measuring resistor 61a1 and a heating resistor 61a3, and the bridge circuit always keeps the temperature difference between the intake air temperature measuring resistor 61a1 and the heating resistor 61a3 constant. The power supplied to the heating resistor 61a3 is adjusted so as to maintain the voltage Vg, and the supplied power is converted into the voltage Vg and output. The relationship between the output Vg of the air flow meter 61 and the intake air flow rate mtAFM as the actual intake air flow rate is as shown in FIG.
[0033]
The intake air temperature sensor 62 is provided in the air flow meter 61, detects the temperature of the intake air, and outputs a signal representing the intake air temperature Ta. The atmospheric pressure sensor 63 detects the pressure upstream of the throttle valve 43 (that is, the atmospheric pressure) and outputs a signal representing the throttle valve upstream pressure Pa. The throttle position sensor 64 detects the opening of the throttle valve 43 (throttle valve opening) and outputs a signal indicating the throttle valve opening TA. The SCV opening sensor 65 detects the opening of the SCV 44 and outputs a signal representing the SCV opening θiv.
[0034]
The cam position sensor 66 generates a signal (G2 signal) having one pulse every time the intake camshaft rotates 90 ° (that is, each time the crankshaft 24 rotates 180 °). The intake valve lift sensor 67 detects the lift of the intake valve 31 and outputs a signal representing the intake valve lift L that takes a value of “0” when the intake valve is fully closed. The crank position sensor 68 outputs a signal having a narrow pulse each time the crankshaft 24 rotates 10 ° and a signal having a wide pulse each time the crankshaft 24 rotates 360 °. This signal indicates the engine speed Ne. The water temperature sensor 69 detects the temperature of the cooling water of the internal combustion engine 10 and outputs a signal indicating the cooling water temperature THW. O₂The sensor 70 outputs a signal corresponding to the oxygen concentration in the exhaust gas flowing into the catalytic converter 53. The accelerator opening sensor 71 outputs a signal indicating the operation amount Accp of the accelerator pedal 82 operated by the driver.
[0035]
The electric control device 80 includes a CPU 81 connected to the CPU 81 via a bus, a ROM 82 pre-stored with programs, tables (maps) and constants executed by the CPU 81, a RAM 83 in which the CPU 81 temporarily stores data as needed, and a power supply. The microcomputer includes a backup RAM 84 that stores data while being turned on and retains the stored data even when the power is turned off, an interface 85 including an AD converter, and the like. The interface 85 is connected to the sensors 61 to 71, supplies signals from the sensors 61 to 71 to the CPU 81, and controls the actuator 33 a of the intake valve control device 33, the igniter 38, the injector 39, and the throttle in accordance with instructions from the CPU 81. A drive signal is transmitted to the valve actuator 43a and the SCV actuator 44a.
[0036]
Next, a method of determining the fuel injection amount (a method of estimating the in-cylinder intake air amount Mc) using the simulation model by the fuel injection amount control device configured as described above will be described. The processing described below is performed by the CPU 81 executing a program.
[0037]
(Method of determining fuel injection amount fc / estimating method of in-cylinder intake air amount Mc)
The fuel injection amount control device must inject fuel to the cylinder in the intake stroke before the intake valve 32 of the cylinder is closed. Further, even in the case of an internal combustion engine in which fuel is directly injected into the combustion chamber 25, it is necessary to inject fuel before the end of the intake stroke. Therefore, in the fuel injection amount control device, the intake valve closes the in-cylinder intake air amount Mc that would be drawn into the same cylinder when the intake valve 32 is closed (that is, when the intake valve is closed). The fuel injection amount (basic injection amount) fc is determined beforehand based on the following equation (2). In Equation 2, K is a coefficient based on the set air-fuel ratio that changes according to the operating state.
[0038]
(Equation 2)
fc = K · Mc
[0039]
More specifically, the fuel injection amount control device (in-cylinder intake air amount estimation device) includes an electronic control throttle model M1, a throttle model M2, an intake pipe model M3, and an intake valve model M4, as shown in FIG. , And a simulation model of the cylinder model M5 to estimate the in-cylinder intake air amount Mc. The throttle model M2 functions as a throttle passing air flow rate estimating means, the intake valve model M4 functions as an intake valve passing air flow estimating means, and the cylinder model M5 functions as an in-cylinder pressure estimating means. M5 constitutes in-cylinder intake air amount estimating means for estimating the in-cylinder intake air amount Mc sucked into the cylinder 21.
[0040]
(Electronic control throttle model M1)
The electronic control throttle model M1 is a model for estimating the throttle valve opening θt at the time t a predetermined time T0 ahead of the current time based on the accelerator pedal operation amount Accp up to the current time. In the present embodiment, the throttle valve electronic control logic A1 calculates the relationship between the accelerator pedal operation amount Accp detected by the accelerator opening sensor 71 and the accelerator pedal operation amount Accp and the target throttle valve opening degree θr shown in FIG. A provisional target throttle valve opening θr1 is determined based on a table that defines the relationship, and a value obtained by delaying the provisional target throttle valve opening θr1 by a predetermined time T (for example, 64 msec) is the final value. It is determined as the target throttle valve opening θr. Then, the throttle valve electronic control logic A1 (electric control unit 80) sends a drive signal to the throttle valve actuator 43a so that the actual throttle valve opening TA becomes the target throttle valve opening θr.
[0041]
As described above, the target throttle valve opening θr is equal to the provisional target throttle valve opening θr1 determined according to the accelerator pedal operation amount Accp at a point in time that is a predetermined time T before the current time. The target throttle valve opening θr at the time t earlier by T0 is equal to the provisional target throttle valve opening θr1 before the time (T−T0) from the current time. Further, the provisional target throttle valve opening θr1 before the time (T−T0) from the present time is equal to the throttle valve opening θt if the operation delay time of the throttle valve actuator 43a is ignored. Based on such a concept, the electronic control throttle model M1 estimates the throttle valve opening θt at a time t earlier by a predetermined time T0 from the current time. That is, the provisional target throttle valve opening θr1 before the current time (T−T0) is estimated as the throttle valve opening θt at the time t that is a predetermined time T0 from the current time. The throttle valve opening θt may be estimated in consideration of the operation delay time of the throttle valve actuator 43a.
[0042]
(Throttle model M2)
The throttle model M2 calculates an air flow rate (estimated throttle passing air flow rate) mt passing through the throttle valve 43 by the following equation obtained based on physical laws such as an energy conservation law, a momentum conservation law, a mass conservation law, and a state equation. 3 and a model estimated based on Equation 4 below. In the following Expressions 3 and 4, Ct (θt) is a flow coefficient that changes according to the throttle valve opening θt, and At (θt) is a throttle opening area (the intake pipe 41 of the intake pipe 41) that changes according to the throttle valve opening θt. Opening area), Pa is the throttle valve upstream pressure (ie, atmospheric pressure), Pm is the intake pipe air pressure (intake pipe pressure), Ta is the intake temperature (atmospheric temperature), Tm is the intake pipe air temperature, R is the gas constant, And κ are specific heat ratios (hereinafter, κ is treated as a constant value). The throttle model M2 uses Equation 3 when the upstream pressure Pa of the throttle valve is larger than the air pressure Pm in the intake pipe, and uses Equation 4 when the upstream pressure Pa of the throttle valve is smaller than the air pressure Pm in the intake pipe. . As a result, the throttle passing air flow rate mt is calculated to take a positive value in the case of the forward flow and a negative value in the case of the reverse flow.
[0043]
(Equation 3)

[0044]
(Equation 4)

[0045]
In Equations 3 and 4, θt is the estimated throttle valve opening at time t that is a predetermined time T0 ahead of the current time estimated by the electronic control throttle model M1. The throttle model M2 calculates the flow coefficient Ct (θt) using the table shown in FIG. 8 defining the relationship between the throttle valve opening θt and the flow coefficient Ct (θt) and the estimated throttle valve opening θt. The opening area At (θt) is obtained using the table shown in FIG. 9 defining the relationship between the throttle valve opening degree θt and the opening area At (θt) and the estimated throttle valve opening degree θt. The throttle model M2 is a table shown in FIG. 10 that defines the relationship between the throttle valve opening θt and the product value Ct (θt) · At (θt) of the flow coefficient Ct (θt) and the opening area At (θt). The product value Ct (θt) · At (θt) may be determined at a time using the estimated throttle valve opening θt.
[0046]
Further, the throttle model M2 acquires the throttle valve upstream pressure Pa and the intake air temperature Ta from the atmospheric pressure sensor 63 and the intake air temperature sensor 62, respectively, and obtains the intake pipe air pressure Pm and the intake pipe air temperature Tm, which will be described later. The above equation (3) or (4) is calculated using the values obtained from the pipe model M3, and the throttle passing air flow rate mt at time t is estimated.
[0047]
Here, the process of deriving Equations 3 and 4 describing the throttle model M2 will be described. Now, the opening cross-sectional area upstream of the throttle valve 43 is Au, the air density is ρu, the flow velocity of air is vu, the opening cross-sectional area of the intake pipe 41 by the throttle valve 43 is Ad, the air density there is ρd, and the throttle valve 43 Assuming that the flow velocity of the air passing through the throttle valve is vd, the throttle-passing air flow rate mt is expressed by the following equation (5). Equation 5 can be said to be an equation describing the law of conservation of mass.
[0048]
(Equation 5)
mt = Ad ・ ρd ・ vd = Au ・ ρu ・ vu
[0049]
On the other hand, assuming that the mass of the air is m, the kinetic energy is m · vu upstream of the throttle valve 43.²/ 2, where m · vd²/ 2. On the other hand, the heat energy is m · Cp · Tu upstream of the throttle valve 43 and m · Cp · Td where the heat energy passes through the throttle valve 43. Therefore, the following equation 6 is obtained according to the law of conservation of energy. Here, Tu is the air temperature upstream of the throttle valve, Td is the air temperature downstream of the throttle valve, and Cp is the constant pressure specific heat.
[0050]
(Equation 6)
m-vu²/ 2 + m · Cp · Tu = m · vd²/ 2 + m · Cp · Td
[0051]
By the way, since the equation of state is expressed by the following equation 7, the specific heat ratio κ is expressed by the following equation 8, and the relationship of Meyer is expressed by the following equation 9, Cp · T is expressed by the following equation 10 from the equations 7 to 9. Here, P is the gas pressure, ρ is the gas density, T is the gas temperature, R is the gas constant, and Cv is the constant volume specific heat.
[0052]
(Equation 7)
P = ρ ・ RT
[0053]
(Equation 8)
κ = Cp / Cv
[0054]
(Equation 9)
Cp = Cv + R
[0055]
(Equation 10)
Cp · T = {κ / (κ-1)} · (P / ρ)
[0056]
By rewriting Equation 6 based on the above energy conservation law using the relation of Equation 10, the following Equation 11 is obtained.
[0057]
[Equation 11]
vu²/ 2 + {κ / (κ-1)}｝ (Pu / ρu) = vd²/ 2 + {κ / (κ-1)}｝ (Pd / ρd)
[0058]
Then, considering infinity upstream of the throttle valve 43, Au = ∞ and vu = 0, so the above equation 11 based on the law of conservation of energy can be rewritten as the following equation 12.
[0059]
(Equation 12)
{Κ / (κ-1)} · (Pu / ρu) = vd²/ 2 + {κ / (κ-1)}｝ (Pd / ρd)
[0060]
Next, the amount of exercise will be described. Assuming that the pressure applied to the section having the cross-sectional area Au is Pu, the pressure applied to the section having the cross-sectional area Ad is Pd, and the average pressure of the fixed space connecting the section having the cross-sectional area Au and the section having the cross-section Au is Pmean, The following Expression 13 is obtained.
[0061]
(Equation 13)
ρd ・ vd²・ Ad-ρu ・ vu²・ Au = Pu ・ Au-Pd ・ Ad + Pmean ・ (Ad-Au)
[0062]
In the above equation 13, when Au = ∞ and vu = 0 are considered, the following equation 14 is obtained. Therefore, the relation (relation based on the law of conservation of momentum) on the momentum of the following equation 15 is obtained from the same equation 14 and the above equation 13. .
[0063]
[Equation 14]
Pmean = Pu
[0064]
[Equation 15]
ρd ・ vd²= Pu-Pd
[0065]
Therefore, the following Expression 16 is obtained from Expression 5, Expression 12, and Expression 15.
[0066]
(Equation 16)

[0067]
In the above equation (16), Pu is the throttle valve upstream pressure Pa and Pd is the air pressure in the intake pipe Pm. Therefore, the flow coefficient Ct (θt) is introduced, and the opening cross-sectional area Ad is set as the opening area At (θt). By rearranging it, the above equation (3) is obtained. The derivation process of the above equation 4 is the same as the derivation process of the above equation 3, and will be omitted.
[0068]
(Intake pipe model M3)
The intake pipe model M3 is based on the law of conservation of mass and the law of conservation of energy, and the following equations (17) and (18), (estimated) throttle-passing air flow rate mt, throttle-passing air temperature (that is, intake air temperature) Ta, and intake air This is a model for determining the intake pipe air pressure Pm and the intake pipe air temperature Tm from the air flow rate mc flowing out of the pipe (that is, the estimated intake valve passing air flow rate, the in-cylinder intake air flow rate). In the following Expressions 17 and 18, Vm is the volume of the intake pipe 41 (hereinafter, simply referred to as “intake pipe portion”) from the throttle valve 43 to the intake valve 32.
[0069]
[Equation 17]
d (Pm / Tm) / dt = (R / Vm) · (mt−mc)
[0070]
(Equation 18)
dPm / dt = κ · (R / Vm) · (mt · Ta−mc · Tm)
[0071]
The intake pipe model M3 acquires the throttle passing air flow rate mt in Expressions 17 and 18 from the throttle model M2, and acquires the in-cylinder intake air flow rate mc from an intake valve model M4 described later. Then, calculations based on Equations 17 and 18 are performed to obtain the intake pipe air pressure Pm at time t and the intake pipe air temperature Tm at time t.
[0072]
Here, the process of deriving Equations 17 and 18 describing the intake pipe model M3 will be described. Now, assuming that the total amount of air in the intake pipe portion is M, the temporal change of the total air amount M is the air flow mt passing through the throttle corresponding to the amount of air flowing into the intake pipe portion and the air amount flowing out of the intake pipe portion. The following equation 19 based on the law of conservation of mass is obtained from the difference of the in-cylinder intake air flow rate mc corresponding to
[0073]
[Equation 19]
dM / dt = mt-mc
[0074]
Further, since the state equation is represented by the following equation 20, the above equation 17 based on the law of conservation of mass is obtained by eliminating the total air amount M from the above equation 19 and the following equation 20.
[0075]
(Equation 20)
Pm ・ Vm = M ・ R ・ Tm
[0076]
Next, considering the energy conservation law regarding the intake pipe, in this case, it is considered that the volume Vm of the intake pipe does not change and most of the energy contributes to the temperature rise (kinetic energy can be ignored). . Therefore, the temporal change of the energy M · Cv · Tm of the air in the intake pipe is determined by the energy Cp · mt · Ta of the air flowing into the intake pipe and the energy Cp · mc of the air flowing out of the intake pipe. Since it is equal to the difference from Tm, the following Expression 21 is obtained.
[0077]
(Equation 21)
d (M · Cv · Tm) / dt = Cp · mt · Ta−Cp · mc · Tm
[0078]
By transforming Equation 21 using Equation 8 (κ = Cp / Cv) and Equation 20 (Pm · Vm = M · R · Tm), Equation 18 is obtained.
[0079]
(Intake valve model M4)
The intake valve model M4 calculates the air flow passing around the intake valve 32 (that is, the estimated intake valve passing air flow, the in-cylinder intake air flow) mc by the energy conservation law, the momentum conservation law, the mass conservation law, and the state equation. This is a model that is estimated in accordance with the following Expressions 22 and 23 obtained based on the above. The derivation process of Equations 22 and 23 is the same as in the case of the throttle model M2. In Equations 22 and 23, Cv (L) is a flow coefficient that varies according to the lift amount L of the intake valve 32, and Av (L) is formed around the intake valve 32 that varies according to the lift amount L. The area of the opening and Pc are the in-cylinder pressure (the pressure Pc in the cylinder 21). The intake valve model M4 uses Equation 22 when the intake pipe air pressure Pm is a forward flow larger than the cylinder pressure Pc, and uses Equation 23 when the intake pipe air pressure Pm is a reverse flow smaller than the cylinder pressure Pc. As a result, the in-cylinder intake air flow rate (estimated intake valve passage air flow rate) mt is calculated so as to take a positive value in the case of the forward flow and a negative value in the case of the reverse flow.
[0080]
(Equation 22)

[0081]
[Equation 23]

[0082]
The intake valve model M4 calculates the valve lift amount L (t) at a time t earlier by a predetermined time T0 from the current time by the intake valve lift amount sensor 67 at the current valve lift amount L and the engine rotation speed Ne. Estimate based on Then, based on the table shown in FIG. 11 defining the relationship between the valve lift amount L and the product value Cv (L) · Av (L), and the estimated valve lift amount L (t), the above equation (22) is obtained. And the product value Cv (L) · Av (L) used in Expression 23 is obtained.
[0083]
In addition, the intake valve model M4 acquires the intake pipe air pressure Pm and the intake pipe air temperature Tm from the intake pipe model M3, and acquires the in-cylinder pressure Pc and the in-cylinder air temperature Tc from a cylinder model M5 described later. The in-cylinder intake air flow rate mc at the time t is estimated by calculating Expression 22 or Expression 23 using these variables.
[0084]
(Cylinder model M5)
The cylinder model M5 is a model for obtaining the in-cylinder pressure Pc and the in-cylinder air temperature Tc according to the following equation 24 based on the energy conservation law for the cylinder 21. As shown in FIG. 12, Vc in the following Expression 24 is the volume of the cylinder 21, Tm is the air temperature in the intake pipe equal to the temperature Ti of the air sucked into the cylinder 21, and mc is sucked into the cylinder 21 (in the cylinder). The air flow rate Q flowing out of the intake pipe portion, which is equal to the air flow rate mi, is the amount of heat transmitted between the cylinder 21 and the outside of the cylinder 21 (cylinder wall surface, intake port, etc.) Flow).
[0085]
(Equation 24)

[0086]
The in-cylinder intake air flow rate mc at time t in Equation 24 is given by the intake valve model M4 (Equation 22 or 23), and the intake pipe air temperature Tm at the same time t is given by the intake pipe model M3. Also, since the cylinder volume Vc at time t can be known based on the crank angle, if the third term (caloric term) on the right side of the above equation 24 is ignored, then theoretically, at the time t using the above equation 24, The cylinder pressure Pc can be obtained.
[0087]
Here, the derivation process of Equation 24 will be described. First, assuming that E is the energy in the cylinder, h is the enthalpy, and W is the work on the piston, the following equation 25 can be obtained for the cylinder 21 by the law of conservation of energy.
[0088]
(Equation 25)
dE / dt = mc · h−dW / dt + Q
[0089]
Now, assuming that the internal energy is u, the following equation 26 holds, and the state equation is as follows. Further, from the above equation 8 (κ = Cp / Cv) which is the equation of the specific heat ratio κ and the above equation 9 (Cp = Cv + R) which is the Meyer's relation equation, the following equations 28 and 29 are established. Note that Mcy is the amount of air in the cylinder 21.
[0090]
(Equation 26)
u = Cv · Tc
[0091]
[Equation 27]
Mcy · Tc = Pc · Vc / R
[0092]
[Equation 28]
Cv = R / (κ-1)
[0093]
(Equation 29)
Cp = κ · R / (κ-1)
[0094]
Therefore, the following Expression 30 is established for the left side dE / dt of Expressions 26 to 28 to Expression 25.
[0095]
[Equation 30]
dE / dt = d (Mcy · u) / dt = d (Mcy · Cv · Tc) / dt = d {Pc · Vc / (κ−1)} / dt
[0096]
On the other hand, for the first term mc · h on the right side of Expression 25, the following Expression 32 is established from the definition of the enthalpy of Expression 31 and the expression 29.
[0097]
(Equation 31)
h = Cp · Tm
[0098]
(Equation 32)
mc · h = mc · {κ · R / (κ-1)} · Tm
[0099]
Further, since the work W is represented by the following Expression 33, the following Expression 34 is established for the second term dW / dt on the right side of Expression 25.
[0100]
[Equation 33]
dW = Pc · dVc
[0101]
(Equation 34)
dW / dt = Pc · dVc / dt
[0102]
By rewriting and rearranging Equation 25 using Equations 30, 32, and 34, Equation 24 is obtained.
[0103]
Further, the cylinder model M5 calculates the in-cylinder air temperature Tc according to the following equation 35 which is a state equation. Mc1 in Equation 35 is obtained by time-integrating the in-cylinder intake air flow rate mc in Equation 22 or 23 from when the intake valve 32 opens until the in-cylinder air temperature Tc is obtained.
[0104]
(Equation 35)
Tc = (Pc · Vc) / (Mc1 · R)
[0105]
According to the above principle, the in-cylinder pressure Pc and the in-cylinder air temperature Tc are respectively obtained from the above Expressions 24 and 35 of the cylinder model M5. mc is obtained. Accordingly, the present fuel injection amount control device integrates the in-cylinder intake air flow rate mc from the time to when the intake valve 23 opens to the time tf when the intake valve 32 closes, thereby obtaining the cylinder 21 in one intake stroke. The in-cylinder intake air amount Mc (total intake air amount Smc) drawn into the cylinder is estimated, and the fuel injection amount fc is determined based on this value Mc and the above equation (2).
[0106]
(Improvement in mounting on electric control device 80)
Since the value of the heat transfer Q of the third term on the right side of the above equation 24 is small and can be ignored, normally the above equation 24 is discretized as in the following equation 36 and mounted on the electric control device 80. Here, Δt is a calculation time interval of the in-cylinder pressure Pc.
[0107]
[Equation 36]

[0108]
However, when the in-cylinder pressure Pc is actually obtained by this method, as shown by the dashed line in FIG. 13, the in-cylinder pressure Pc fluctuates greatly under the influence of discretization and greatly differs from the true value. It turned out to be. Therefore, in the present embodiment, the value Q of the third term on the right side of Expression 24 is ignored, and for convenience, (1) the cylinder volume is assumed to be constant (dVc = 0), and (2) in-cylinder suction The in-cylinder pressure Pc was determined by assuming that the air flow rate was 0 (mc = 0) and solving Equation 24 analytically under each assumption. The details will be described below.
[0109]
(1) Assuming a constant cylinder volume (dVc = 0)
Under this assumption, Equation 24 becomes a differential equation of Equation 37 below, and solving Equation 37 yields Equation 38 below.
[0110]
(37)

[0111]
[Equation 38]

[0112]
In Equation 38 above, θ₀= Cos^-1(1). From this equation 38, it is understood that the in-cylinder pressure Pc changes in a sine wave shape. on the other hand. The Euler approximation of the above equation (37) is as follows (39).
[0113]
[Equation 39]

[0114]
Further, since the in-cylinder pressure Pc does not become higher than the intake pipe air pressure Pm, the following Expression 40 is established. Therefore, the following Expression 41 is established from Expression 39 and Expression 40.
[0115]
(Equation 40)

[0116]
(Equation 41)

[0117]
Further, when θ is extremely smaller than 1 (θ << 1), the following equation 42 holds, so that the following equation 43 can be obtained by applying the above equation 41 and the following equation 42 to the above equation 39. Note that the in-cylinder intake air flow rate mc in Expression 43 below is obtained from Expression 22 and Expression 23 above.
[0118]
(Equation 42)

[0119]
[Equation 43]

[0120]
(2) When it is assumed that there is no in-cylinder intake air amount (mc = 0)
Under this assumption, Equation 24 becomes a differential equation of Equation 44 below. Further, in this case, the following equation 45 holds because the adiabatic expansion can be handled.
[0121]
[Equation 44]

[0122]
[Equation 45]

[0123]
From the above, the following Expression 46 is derived.
[0124]
[Equation 46]

[0125]
The in-cylinder pressure Pc obtained by the above equations 43 and 46 is indicated by a solid line and a two-dot chain line in FIG. 13, respectively. Since the in-cylinder pressure Pc is expected to be a value close to the intake pipe air pressure Pm, in the present embodiment, the in-cylinder pressure P′c (t) obtained from the above Equation 43 closer to the intake pipe air pressure Pm. ) Is adopted as the finally determined in-cylinder pressure Pc.
[0126]
Further, the in-cylinder intake air amount Mc in one intake stroke is changed from the time to when the intake valve 23 opens to the time tf when the intake valve 32 closes from the in-cylinder intake air flow rate mc given by Expression 22 or Expression 23. Although it has been described that it can be obtained by integrating over time, as a result of simulation, the accuracy is higher when the above Expression 24 based on the law of conservation of energy is obtained by the following Expression 47 obtained by integrating over time from time to to time tf and rearranging it. It has been found. Note that Pc (to) and Vc (to) are the in-cylinder pressure Pc (t) and the cylinder volume Vc (t) when the intake valve is opened, respectively, and Pc (tf) and Vc (tf) are Are the in-cylinder pressure Pc (t) and the cylinder volume Vc (t) when the intake valve is closed.
[0127]
[Equation 47]

[0128]
Therefore, in the present embodiment, the in-cylinder intake air amount Mc is obtained based on the following Expression 48 obtained by discretizing Expression 47.
[0129]
[Equation 48]

[0130]
(Add observer)
In the present embodiment, an observer OBS as a correction unit is further added to improve the accuracy of estimating the in-cylinder intake air amount Mc. In FIG. 6 described above, the portion surrounded by the broken line is the added observer OBS.
[0131]
The observer OBS includes the air flow meter 61 and an air flow meter model M6 functioning as intake air flow rate estimating means. The air flow meter model M6 estimates a value that the air flow meter 61 will output when the throttle passing air flow rate (actual intake air flow rate) is a predetermined amount α, and based on the estimated value, the throttle passing air flow rate. This is a model for estimating (estimated intake air flow rate) mtes. In this case, the predetermined amount α is a throttle obtained by delaying the (estimated) throttle-passing air flow rate mt at a time t earlier by a predetermined time T0 from the current time estimated by the throttle model M2 by the predetermined time T0 by a dead time element. It is the (estimated) throttle passing air flow rate mt (t-T0) at the present time, which is the passing air flow rate.
[0132]
Here, the air flow meter model M6 will be specifically described. The air flow meter model M6 first defines the complete heat radiation amounts W1 and W2 with respect to the throttle passing air flow rate mt (t-T0) at the present time, and the relationship between the full heat radiation amounts W1 and W2 and the throttle passing air flow rate mt. 14 and the obtained airflow mt (t-T0) passing through the throttle at the present time. The complete heat radiation amount W1 and the complete heat radiation amount W2 are heat radiation amounts that do not include a heat radiation delay corresponding to the bobbin portion 61a1 of the heat ray measuring portion 61a and the support portion 61a2 of the heat ray measuring portion 61a shown in FIG.
[0133]
Next, the air flow meter model M6 is a heat radiation amount corresponding to each of the bobbin portion 61a1 and the support portion 61a2, and has a first-order delay characteristic (including a response delay) with respect to the complete heat radiation amounts W1 and W2. (Response heat release amount) w1 and w2 are obtained according to the following Expression 49 and Expression 50. In Equations 49 and 50, the suffix (k) represents the current operation value, the suffix (k-1) represents the previous operation value, and Δt represents the time from when the previous operation value was obtained to when the current operation value was obtained. Time.
[0134]
[Equation 49]
w1 (k) = Δt · (W1 (k) −w1 (k−1)) / τ1 + w1 (k−1)
[0135]
[Equation 50]
w2 (k) = Δt · (W2 (k) −w2 (k−1)) / τ2 + w2 (k−1)
[0136]
In Expressions 49 and 50, τ1 and τ2 are time constants of the first-order lag characteristics corresponding to the bobbin portion 61a1 and the support portion 61a2, respectively, and are obtained by Expressions 51 and 52 below. The values k10 and k20 and the values m1 and m2 in Equations 51 and 52 are values obtained experimentally. The value u in the formulas 51 and 52 is the amount of air passing per unit cross-sectional area bypassed by the heat ray measuring unit 61a of the air flow meter 61, and is actually measured as the output voltage Vg of the air flow meter 61 shown in FIG. The Vg-mtAFM conversion table that defines the relationship with the intake air flow rate mtAFM, and the intake air flow rate mtAFM obtained based on the actual output voltage Vg of the air flow meter 61 are converted into the bypass flow path of the hot-wire measuring unit 61a. The value is divided by the area S (mtAFM / S).
[0137]
(Equation 51)
τ1 = k10 · u^m1
[0138]
(Equation 52)
τ2 = k20 · u^m2
[0139]
The air flow meter model M6 is based on the table shown in FIG. 15 that defines the relationship between the sum (w1 + w2) of the response heat radiation amounts w1 and w2 and the throttle passing air flow rate mtes based on the value that the air flow meter 61 will output. Based on the sum (w1 + w2) of the response heat radiation amounts w1 and w2 obtained from the above Expressions 49 to 52, the throttle passing air flow rate mtes based on the value that the air flow meter 61 will output at the present time is obtained. When the internal combustion engine is in a steady operation state in which the throttle valve opening TA is constant, the throttle passing air flow rate mtes is equal to the (estimated) throttle value at the time t that is a predetermined time T0 earlier than the current time estimated by the throttle model M2. It is the same as the passing air flow rate mt (and the current throttle passing air flow rate mt (t-T0)).
[0140]
Referring again to FIG. 6, the observer OBS inputs a signal representing the throttle-passing air flow rate mtes to one end of the comparison element COM. On the other hand, the observer OBS converts the output Vg of the air flow meter 61 into the current intake air flow rate (actual intake air flow rate) mtAFM by using the table shown in FIG. 5, and outputs a signal representing the intake air flow rate mtAFM to the comparison element COM. Enter at the end.
[0141]
Then, the observer OBS obtains a difference SA between the throttle passing air flow rate mtes and the intake air flow rate mtAFM in the comparison element COM, integrates the difference SA with time by an integration element to obtain a deviation integration value SumSA, and obtains the deviation integration value SumSA. The value obtained by multiplying a predetermined gain G1 (constant negative value) and the value obtained by multiplying the same deviation integral value SumSA by a predetermined gain G2 (constant negative value) are respectively used as the throttle passage air flow rate estimated by the throttle model M2. mt and the in-cylinder intake air flow rate mc estimated by the intake valve model M4 (feedback). That is, the in-cylinder intake air amount estimating device in the present embodiment estimates the throttle passing air flow rate mt based on the following Expression 53 or 54 instead of Expression 3 or Expression 4.
[0142]
[Equation 53]

[0143]
(Equation 54)

[0144]
Further, the in-cylinder intake air amount estimating device estimates the in-cylinder intake air flow rate mc based on the following expression 55 or 56 instead of the expression 22 or 23.
[0145]
[Equation 55]

[0146]
[Equation 56]

[0147]
In this manner, the throttle passage air flow rate mt estimated by the throttle model M2 based on the deviation SA and the intake valve so that the deviation SA (the deviation integration value SumSA) becomes “0” (decreases). The in-cylinder intake air flow rate mc estimated by the model M4 is directly corrected, and as a result, a steady error between the actual in-cylinder intake air amount and the in-cylinder intake air amount Mc obtained by the models M1 to M5 is reduced. Is done.
[0148]
(Actual operation)
Next, the actual operation when the electric control device 80 estimates the in-cylinder intake air amount Mc and determines the fuel injection amount fc will be described.
[0149]
(Throttle valve control)
The CPU 81 of the electric control device 80 executes a routine for controlling the throttle valve opening shown by the flowchart in FIG. 16 every time a predetermined time (1 msec) elapses. Therefore, at a predetermined timing, the CPU 81 starts the process from step 1600 and proceeds to step 1605 to read the accelerator pedal operation amount Accp. Next, the CPU 81 proceeds to step 1610, and in step 1610, obtains a provisional target throttle valve opening θr1 based on the read accelerator pedal operation amount Accp by using the same table as in FIG.
[0150]
Next, the CPU 81 proceeds to step 1615, sets the variable I to “64”, and stores the value of θr (I−1) in the stored value θr (I) in the following step 1620. At present, since the variable I is “64”, the value of the stored value θr (63) is stored in the stored value θr (64). Next, the CPU 81 proceeds to step 1625 to determine whether or not the variable I has become equal to “1”. In this case, since the value of the variable I is “64”, the CPU 81 determines “No” in step 1625, proceeds to step 1630, and decreases the value of the variable I by “1” in step 1630. Thereafter, the flow returns to step 1620. As a result, when step 1620 is executed, the value of the stored value θr (62) is stored in the stored value θr (63). Such processing is repeatedly executed until the value of the variable I becomes “1”.
[0151]
Thereafter, when the process of step 1630 is repeated and the value of the variable I becomes “1”, the CPU 81 determines “Yes” in step 1625 and proceeds to step 1635, and in step 1635, the CPU 81 The provisional target throttle valve opening θr1 at the present time is stored in the storage value θr (0). As described above, the provisional target throttle valve opening θr (I) (I = 64, 63, 62,..., 2, 1, 0) Imsec before the current time (0 msec ≦ Imsec ≦ 64 msec, I is an integer) Is stored in the RAM 83.
[0152]
Next, the CPU 81 proceeds to step 1640, in which the stored value θr (64) is set as the final target throttle valve opening θr in step 1640, and in step 1645, the actual throttle valve opening is set to the target throttle valve opening. A drive signal is output to the throttle valve actuator 43a so as to be equal to the opening degree θr, and thereafter, the routine is temporarily ended in step 1695.
[0153]
Hereinafter, the processing of the above routine is executed every elapse of 1 msec. As a result, the actual throttle valve opening is controlled to be equal to the target throttle valve opening θr based on the accelerator pedal operation amount Accp before the predetermined time T (= 64 msec). Accordingly, the electronic control throttle model M1 calculates the target throttle valve opening θ (T-T0) before the time (T-T0) from the current time by using the throttle valve opening θt at the time t that is a predetermined time T0 ahead of the current time. Is estimated as
[0154]
(Estimation of Throttle Passing Air Flow Rate mt, Intake Pipe Air Pressure Pm, Intake Pipe Air Temperature Tm) The CPU 81 executes the routine shown by the flowchart in FIG. 17 and the subsequent FIG. 18 every time a predetermined time (8 msec) elapses. It has become. Therefore, at a predetermined timing, the CPU 81 starts the process from step 1700, proceeds to step 1705, and uses the same table as the table shown in FIG. (Intake air flow rate) mtAFM is obtained.
[0155]
Next, the CPU 81 proceeds to step 1710, and stores the same table as the table shown in FIG. 14 and the throttle-passing air flow rate mt (k) already obtained in step 1810 to be described later at the time of execution of this routine before the previous time. Complete heat radiation amounts W1 (k) and W2 (k) are obtained using the current throttle passage air flow rate mt (k-T0) obtained by delaying by the predetermined time T0. In the present routine, a value with a suffix (k) represents a value obtained when the present routine is executed this time, and a value with a suffix (k-1) represents a value obtained when the previous routine was executed last time. Represents the value obtained in.
[0156]
Next, the CPU 81 proceeds to step 1715, obtains the time constants τ1 and τ2 according to the formulas 51 and 52, respectively, and in a subsequent step 1720, responds to the heat radiation amounts w1 (k) and w2 according to the formulas 49 and 50. (K) is obtained. Note that Δt is the calculation cycle of this routine (that is, 8 msec). Next, the CPU 81 proceeds to step 1725, and uses the same table as the table shown in FIG. 15 and the sum of the response heat radiation amounts w1 (k) and w2 (k) (w1 (k) + w2 (k)). A throttle passing air flow rate (estimated intake air flow rate) mtes based on a value that the air flow meter 61 will output at the present time is obtained.
[0157]
Next, the CPU 81 proceeds to step 1730, stores a value obtained by subtracting the intake air flow rate mtAFM from the throttle passing air flow rate mtes as a deviation SA (k), and, in a subsequent step 1735, stores the value at that time (previous time). A value obtained by adding the deviation SA (k) to the deviation integrated value SumSA (k-1) is set as a new (current) deviation integrated value SumSA (k).
[0158]
Next, the CPU 81 proceeds to step 1805 in FIG. 18 and uses the same table as the table shown in FIG. 10 and the estimated throttle valve opening θt at the time t earlier by the predetermined time T0 from the present time to use the flow coefficient Ct (θt). And a product value Ct (θt) · At (θt) of the opening area At (θt) are obtained.
[0159]
Next, the CPU 81 proceeds to step 1810, and in step 1810, calculates the throttle passing air flow rate mt according to the equation 53 or 54. The throttle valve upstream pressure Pa and the intake air temperature Ta used in this calculation are obtained from the atmospheric pressure sensor 63 and the intake air temperature sensor 62, respectively. The air pressure Pm (k-1) in the intake pipe and the air temperature Tm (k-1) in the intake pipe are the values Pm (k) and Tm obtained in step 1815 described later in the previous execution of this routine. (K), and the deviation integral value SumSA (k) is the value obtained in step 1735.
[0160]
Next, the CPU 81 proceeds to step 1815, in which the intake pipe air pressure Pm (k) and the intake pipe air temperature Tm (k) are calculated based on the following equations 57 and 58 obtained by integrating the above equations 17 and 18 and discretizing. ), The process proceeds to step 1895, and this routine is temporarily ended. In the following Expressions 57 and 58, Δt is the calculation cycle of this routine (that is, 8 msec).
[0161]
[Equation 57]

[0162]
[Equation 58]

[0163]
Actually, the CPU 81 obtains Pm / Tm by the above equation (57), and obtains Tm from this and Pm obtained by the above equation (58). Note that mcAVE (k-1) in Expressions 57 and 58 is an average value of the in-cylinder intake air flow rate mc obtained in a 1 msec routine described later.
[0164]
(Estimation of in-cylinder pressure Pc, in-cylinder intake air flow rate mc, in-cylinder intake air amount Mc, etc.)
The CPU 81 executes the routine shown by the flowcharts in FIGS. 19 and 20 subsequent thereto every time a predetermined time (1 msec) elapses. Therefore, at a predetermined timing, the CPU 81 starts the process from step 1900 and proceeds to step 1905 to calculate the above equation 55 based on the valve lift amount L at the time t and the same table as the table shown in FIG. Then, the product value Cv (L) · Av (L) to be used is obtained in the above equation 56, and in step 1910, the in-cylinder intake air flow rate mc (t) is calculated according to the same equation 55 or 56.
[0165]
Here, Pm (k) and Tm (k) are the air pressure in the intake pipe and the air temperature in the intake pipe obtained in step 1815, respectively, and Tc (t) is the value at the time of the previous execution of this routine. This is the value set in step 2045 described later. In addition, SumSA (k) is the deviation integral value obtained in step 1735 of FIG. 17 described above, and Pc (t) is the value set in step 1925 described later in the previous execution of this routine.
[0166]
Next, the CPU 81 proceeds to step 1915, and in step 1915, calculates the in-cylinder pressure P'c (t + Δt) according to the above equation (43). Δt is a calculation cycle of this routine (that is, 1 msec). Also, mc (t) is the value obtained in step 1910.
[0167]
Next, the CPU 81 proceeds to step 1920 to obtain the in-cylinder pressure Pc (t + Δt) according to the above equation 46, and in the following step 1925 the in-cylinder pressure P′c (t + Δt) and the in-cylinder pressure Pc (t + Δt) obtained this time. Are stored in the in-cylinder pressure P′c (t) and the in-cylinder pressure Pc (t), respectively, for the next calculation of this routine.
[0168]
Next, the CPU 81 proceeds to step 2005 shown in FIG. 20, determines whether or not the time t is immediately after the intake valve 23 changes from the closed state to the open state, and changes the state from the closed state to the open state. Immediately after this, in step 2010, the value of the variable Z is initialized to "0", and in step 2015, when the intake valve 23 opens the in-cylinder pressure Pc '(t) obtained at that time. This is stored as the in-cylinder pressure Pc (to) when the intake valve is open. Then, in step 2020, the CPU 81 stores the cylinder volume Vc (t) at the time t as the cylinder volume Vc (to) when the intake valve is opened, and in a subsequent step 2025, the in-cylinder intake air amount Mc1 from when the intake valve is opened. Is set to a value Mc0 (initial value, for example, “0”), and the process proceeds to step 2030. On the other hand, if the time t is not immediately after the intake valve 23 changes from the closed state to the open state, the CPU 81 determines “No” in step 2005 and proceeds directly to 2030.
[0169]
Next, at step 2030, the CPU 81 determines whether or not the intake valve 23 is open at time t. If the time t corresponds to immediately after the intake valve 23 changes from the closed state to the open state, the CPU 81 determines “Yes” in step 2030 and proceeds to step 2035. Is added to the value of Pc ′ (t) · dVc (t) / dt · Δt to update the same variable Z. As a result, the variable Z becomes an integral equivalent of the value P '(t) .dVc (t) / dt. Subsequently, in step 2040, the CPU 81 stores a value obtained by adding mc (t) · Δt to the in-cylinder intake air amount Mc1 since the intake valve was opened as a new in-cylinder intake air amount Mc1, and proceeds to step 2045. The in-cylinder air temperature Tc (t) is obtained based on the following Expression 59, and this routine is ended once in step 2095.
[0170]
[Equation 59]
Tc (t) = Pc (t) · Vc (t) / (Mc1 · R)
[0171]
Since the processing of steps 2030 to 2045 is continued while the intake valve 23 is open, the variable Z indicating the sum of the values P ′ (t) ・ dVc (t) / dt ・ Δt, the intake valve opening The in-cylinder intake air amount Mc1 and the in-cylinder air temperature Tc (t) from the time are updated.
[0172]
Thereafter, when a predetermined time has elapsed and time t is a time immediately after the intake valve 23 changes from the open state to the closed state, the CPU 81 determines “No” when proceeding to step 2005 and step 2030. In step 2050, it is determined whether the intake valve 23 has just changed from the open state to the closed state. Then, in this case, the CPU 81 determines “Yes” in step 2050 and proceeds to step 2055 to estimate the in-cylinder intake air amount Mc in one intake stroke according to the above equation (48).
[0173]
Thereafter, the CPU 81 proceeds to step 2060, and calculates the in-cylinder intake air amount Mc obtained above for a time T corresponding to a crank angle of 180 ° CA._180CAThe average value mcAVE (k-1) of the in-cylinder intake air amount Mc is obtained, and in the subsequent step 2065, the average value mcAVE (k-1) of the in-cylinder intake air amount Mc is changed according to the set air-fuel ratio. The fuel injection amount fc is obtained by multiplying by the coefficient K. Since the average value mcAVE (k-1) of the in-cylinder intake air amount Mc is proportional to the in-cylinder intake air amount Mc, the fuel injection amount fc is calculated according to Equation 2. Then, the CPU 81 proceeds to step 2095 and ends this routine once.
[0174]
Further, the time t is not the time immediately after the intake valve 32 changes from the closed state to the open state, nor the time immediately after the change from the open state to the closed state, and the intake valve 32 is in the closed state. If it is the time, the CPU 81 executes the processing of steps 1900 to 1925 in FIG. 19, determines “No” in all of steps 2005, 2030, and 2050 in FIG. 20, proceeds to step 2095, and ends this routine once. .
[0175]
As described above, the in-cylinder intake air amount Mc is estimated using each model, and the fuel injection amount fc corresponding to the model is determined. Then, the CPU 81 executes a fuel injection routine (not shown) at a predetermined timing, and injects the fuel by the determined fuel injection amount fc.
[0176]
As described above, according to the embodiment of the fuel injection amount control device including the in-cylinder intake air amount estimation device according to the present invention, the in-cylinder pressure Pc and the in-cylinder air temperature Tc are obtained by the cylinder model M5. Is provided to the intake valve model M4. Therefore, the intake valve model M4 is not based on a table search using many variables as in the related art, but is calculated by numerical calculations according to the above equations 22 and 23 (actually, the above equations 55 and 56). The flow rate mc (accordingly, the in-cylinder intake air amount Mc) can be obtained. As a result, the labor required for adapting the table values can be reduced, and the fuel injection amount fc can be obtained with high accuracy.
[0177]
Also, the observer OBS sets the deviation SA (the above-mentioned deviation integrated value SumSA) between the throttle passing air flow rate (estimated intake air flow rate) mtes and the intake air flow rate (actual intake air flow rate) mtAFM so as to become “0”. The throttle-passing air flow rate mt estimated by the throttle model M2 and the in-cylinder intake air flow rate mc estimated by the intake valve model M4 are directly corrected based on the SA. Therefore, when the throttle passing air flow rate mtes is smaller than the intake air flow rate mtAFM, the in-cylinder intake air flow rate (estimated intake valve passing rate) is directly increased without increasing the intake pipe air pressure Pm estimated by the intake pipe model M3. (Air flow rate) mc can be increased, and as a result, the cylinder intake air amount Mc can be increased.
[0178]
Therefore, even when the internal combustion engine is in the throttle fully open steady-state operation state in which the throttle valve opening is constant at the maximum opening, regardless of the magnitude relationship between the throttle passing air flow rate mtes and the intake air flow rate mtAFM, the actual value is not limited. It is possible to reliably reduce a steady-state error between the in-cylinder intake air amount and the estimated in-cylinder intake air amount Mc. The air-fuel ratio of the gas could be accurately set to the target value.
[0179]
The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, in the above-described embodiment, the observer OBS as a correction unit directly corrects the throttle passage air flow rate mt estimated by the throttle model M2 and the in-cylinder intake air flow rate mc estimated by the intake valve model M4. Is determined based on the throttle passing air flow rate (estimated intake air flow rate) mtes and the intake air flow rate (actual intake air flow rate) mtAFM so that the deviation SA (the above-described deviation integrated value SumSA) becomes “0”. The product value Ct (θt) · At (θt) of the flow coefficient Ct (θt) and the opening area At (θt) used in the above equations 3 and 4, and the flow coefficient used in the above equations 22 and 23 The product value Cv (L) · Av (L) of Cv (L) and the opening area Av (L) is corrected. As a result, the throttle-passing air flow rate mt and the in-cylinder suction air The flow rate mc may be corrected, respectively.
[0180]
Further, in addition to the models of the above embodiment, an exhaust valve model for estimating the air flow rate me flowing into the cylinder 21 via the exhaust valve may be additionally employed. In this case, as shown in FIG. 21, the exhaust valve model M7 is connected to the cylinder model M5, and is represented by the following equations 60 and 61 obtained through the same derivation process as the intake valve model M4. You. In Equations 60 and 61, Pe is the air pressure in the exhaust pipe, Te is the air temperature in the exhaust pipe, and Equation 60 is for the case where air flows into the cylinder 21 from the exhaust system (Pc <Pe). Is used when air flows out of the cylinder 21 to the exhaust system (Pc> Pe). As a result, the air flow rate me is calculated to take a positive value when air flows into the cylinder 21 from the exhaust system, and to take a negative value when air flows from the cylinder 21 to the exhaust system. . In this case, it is desirable to provide a sensor for detecting the air pressure in the exhaust pipe and a sensor for detecting the air temperature in the exhaust pipe.
[0181]
[Equation 60]

[0182]
[Equation 61]

[0183]
Further, in the above embodiment, the injector 39 injects the fuel toward the intake ports 31a and 31b, but may be configured to directly inject the fuel into the combustion chamber 25.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a system in which a fuel injection amount control device including a cylinder intake air amount estimation device according to the present invention is applied to a spark ignition type multi-cylinder internal combustion engine.
FIG. 2 is a schematic plan view showing a combustion chamber of a specific cylinder shown in FIG. 1 and a portion near the combustion chamber.
FIG. 3 is a schematic perspective view of the air flow meter shown in FIG.
FIG. 4 is an enlarged perspective view of a heat ray measuring section of the air flow meter shown in FIG.
FIG. 5 is a graph showing a table defining a relationship between an output of an air flow meter and an intake air flow rate referred to by a CPU shown in FIG. 1;
6 is a functional block diagram showing a connection relationship of various models adopted for estimating the in-cylinder intake air amount by the electric control device shown in FIG. 1;
FIG. 7 is a graph showing a table defining a relationship between an accelerator pedal operation amount and a target throttle valve opening referred to by a CPU shown in FIG. 1;
FIG. 8 is a graph showing a table defining a relationship between a throttle valve opening and a flow coefficient.
FIG. 9 is a graph showing a table defining a relationship between a throttle valve opening and an opening area.
FIG. 10 is a graph showing a table defining a relationship between a throttle valve opening degree and a product value of a flow coefficient and an opening area.
FIG. 11 is a graph showing a table defining a relationship between a valve lift amount and a product value of a flow coefficient and an opening area.
FIG. 12 is a diagram conceptually showing a cylinder and its vicinity for explaining variables used to represent a cylinder model.
FIG. 13 is a time chart for explaining a calculation result of an in-cylinder pressure by a cylinder model.
FIG. 14 is a graph showing a table defining a relationship between a flow rate of air passing through a throttle and a complete heat release amount referred to by the CPU shown in FIG. 1;
FIG. 15 is a graph showing a table defining a relationship between the sum of the responsive heat radiation amounts referred to by the CPU shown in FIG. 1 and the flow rate of air passing through the throttle based on the value that will be output by the air flow meter.
FIG. 16 is a flowchart showing a routine executed by the CPU shown in FIG. 1 for controlling a throttle valve.
FIG. 17 is a flowchart showing a first half of a routine executed by the CPU shown in FIG. 1 every 8 msec.
FIG. 18 is a flowchart showing a latter half of a routine executed by the CPU shown in FIG. 1 every 8 msec.
FIG. 19 is a flowchart showing the first half of a routine executed by the CPU shown in FIG. 1 every 1 msec.
20 is a flowchart showing the latter half of a routine executed by the CPU shown in FIG. 1 every 1 msec.
FIG. 21 is a functional block diagram showing another modified example of the embodiment of the fuel injection amount control device (in-cylinder intake air amount estimation device) according to the present invention.
FIG. 22 is a functional block diagram of a fuel injection amount control device (cylinder intake air amount estimating device) studied by the present applicant.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Spark ignition type multi-cylinder internal combustion engine, 20 ... Cylinder block part (engine main part), 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 33 ... Variable intake timing device, 39 ... Injector, 41 ... Intake Pipe, 43: throttle valve, 44: swirl control valve, 44a: SCV actuator, 61: air flow meter, 80: electric control device, 81: CPU, M1: electronic control throttle model, M2: throttle model, M3: intake pipe model , M4: intake valve model, M5: cylinder model, M6: air flow meter model.

Claims (4)

Throttle passing air flow rate estimating means for estimating an air flow rate passing through the throttle valve as an estimated throttle passing air flow rate using a model for air passing through a throttle valve disposed in an intake passage of the internal combustion engine;
Intake valve passing air flow rate estimating means for estimating an air flow rate passing through the intake valve as an estimated intake valve passing air flow rate using a model for air passing through the intake valve which communicates and shuts off the intake passage and the cylinder; ,
In-cylinder intake air amount estimating means for estimating an in-cylinder intake air amount to be taken into the cylinder based on at least the estimated throttle passage air flow amount and the estimated intake valve passage air flow amount. An intake air amount estimation device,
An air flow sensor that generates an output value corresponding to the actual intake air flow rate drawn into the intake passage and measures the actual intake air flow rate as an actual intake air flow rate, and a model of the air flow rate sensor. An output value that would be output by the air flow rate sensor when the actual intake air flow rate was assumed to be the estimated throttle-passing air flow rate, and based on the estimated output value, suctioned air into the intake passage. Intake air flow rate estimating means for estimating the intake air flow rate to be estimated as the estimated intake air flow rate,
Correction means for correcting the intake valve passing air flow rate estimating means to correct the estimated intake valve passing air flow rate based on a difference between the estimated intake air flow rate and the actual intake air flow rate;
An in-cylinder intake air amount estimation device for an internal combustion engine, comprising: The in-cylinder intake air amount estimating device for an internal combustion engine according to claim 1,
The correcting means is configured to correct the throttle passing air flow rate estimating means to correct the estimated throttle passing air flow rate based on a deviation between the estimated intake air flow rate and the actual intake air flow rate. In-cylinder intake air amount estimation device. The cylinder intake air amount estimating device for an internal combustion engine according to claim 1 or 2, wherein a pressure in the cylinder is calculated by using a model of the cylinder obtained based on an energy conservation law. Equipped with in-cylinder pressure estimating means for estimating,
The intake valve passing air flow rate estimating means is configured to estimate the estimated intake valve passing air flow rate using a model for air passing through the intake valve using the estimated pressure in the cylinder. In-cylinder intake air amount estimation device. An in-cylinder intake air amount estimating device for an internal combustion engine according to claim 3,
The model of the air passing through the intake valve used by the intake valve passing air flow rate estimating means is a model obtained based on a law of conservation of energy, a law of conservation of momentum, and a law of conservation of mass. Air volume estimation device.

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