JP2004108348A - Cylinder gas state acquisition device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder gas state acquisition device of an internal combustion engine capable of accurately acquiring the state of gas in a cylinder based on the output of a cylinder relative pressure sensor. <P>SOLUTION: This cylinder gas state acquisition device sets the quantity N of temporary cylinder absolute pressure set values Pc (H) by adding a temporary pressure correction value ΔP provided by deducting a cylinder relative pressure detection value Pmeas 1 from a temporary cylinder absolute pressure value PO at the same point provided by temporarily setting the state of cylinder gas at the start of a compression stroke to the quantity N of cylinder relative pressure detected values Pmeas H (H = 1, ..., N) during the compression stroke provided from the cylinder relative pressure sensor. On the other hand, by using, as initial conditions, the state of the cylinder gas at the time of the temporary setting, the quantity N of temporary cylinder absolute pressure calculated values Pcm (H) are calculated from a cylinder model based on the law of energy conservation. Then, the state of the cylinder gas at the time of the temporary setting is defined so that the deviation of the quantity N of the temporary cylinder absolute pressure set values Pc (H) and the quantity N of the temporary cylinder absolute pressure calculated values Pcm (H) becomes minimum. <P>COPYRIGHT: (C)2004,JPO

Description

【００４５】
ここで、上記数２は、ｋ１を所定の係数（＝μ・Ａｔ・｛Ｐａ／（Ｒ・Ｔａ）^１／２｝）、ｍｔｓを吸気弁閉時のスロットル通過空気量とするとき下記数４に書き換えられる。また、数４において、内燃機関１０が定常状態にある場合（スロットルバルブ開度が一定である場合）のスロットル通過空気量をｍｔｓＴＡ、及び吸気管圧力をＰｍＴＡとすると、下記数５が得られるので、数４及び数５から係数ｋ１を消去して下記数６を得ることができる。
【００４６】
【数４】
ｍｔｓ＝ｋ１・Φ（Ｐｍ／Ｐａ）
【００４７】
【数５】
ｍｔｓＴＡ＝ｋ１・Φ（ＰｍＴＡ／Ｐａ）
【００４８】
【数６】
ｍｔｓ＝｛ｍｔｓＴＡ／Φ（ＰｍＴＡ／Ｐａ）｝・Φ（Ｐｍ／Ｐａ）
【００４９】
上記数６の右辺における値｛ｍｔｓＴＡ／Φ（ＰｍＴＡ／Ｐａ）｝は、スロットルバルブ開度ＴＡが一定であるときの吸入空気流量（スロットル通過空気量）に関する値であり、スロットルバルブ開度ＴＡ、エンジン回転速度Ｎｅ、吸気弁の開閉タイミングＶＴ、及びスロットルバルブ上流圧力Ｐａが決定されると、実質的に一意に定まる値である。スロットルモデルＭ２は、スロットルバルブ開度ＴＡ、エンジン回転速度Ｎｅ、吸気弁の開閉タイミングＶＴ、及びスロットルバルブ上流圧力Ｐａと、値｛ｍｔｓＴＡ／Φ（ＰｍＴＡ／Ｐａ）｝との関係を規定したテーブルをＲＯＭ８２内に記憶していて、このテーブルと吸気弁閉時の推定スロットルバルブ開度ＴＡＳ、実際のエンジン回転速度Ｎｅ、実際の吸気弁の開閉タイミングＶＴ、及び実際のスロットルバルブ上流圧力Ｐａとに基づいて値｛ｍｔｓＴＡ／Φ（ＰｍＴＡ／Ｐａ）｝を求める。
【００５０】
また、数６の右辺における値Φ（Ｐｍ／Ｐａ）は、上記数３から理解されるように、比熱比κが一定であるとき、吸気管圧力Ｐｍとスロットルバルブ上流圧力Ｐａにより決定される値である。スロットルモデルＭ２は、吸気管圧力Ｐｍ及びスロットルバルブ上流圧力Ｐａと、値Φ（Ｐｍ／Ｐａ）との関係を規定したテーブルをＲＯＭ８２内に記憶していて、このテーブルと、後述するインテークマニホールドモデルＭ４が現時点で既に演算している最新の吸気管圧力Ｐｍ、及び実際のスロットルバルブ上流圧力Ｐａとに基づいて値Φ（Ｐｍ／Ｐａ）を求める。以上により、吸気弁閉時のスロットル通過空気量ｍｔｓが求められる。
【００５１】
（３）吸気弁モデルＭ３
吸気弁モデルＭ３は、吸気管圧力Ｐｍ、吸気管内温度Ｔｍ、及び吸気温度ＴＨＡ等から筒内吸入空気流量ｍｃを推定するモデルである。吸気弁閉時の気筒内圧力は吸気弁３２の上流の圧力、即ち吸気弁閉時の吸気管圧力Ｐｍとみなすことができるので、筒内吸入空気流量ｍｃは吸気弁閉時の吸気管圧力Ｐｍに比例する。そこで、吸気弁モデルＭ３は筒内吸入空気流量ｍｃを、経験則に基づく下記数７にしたがって求める。
【００５２】
【数７】
ｍｃ＝（Ｔａ／Ｔｍ）・（ｃ・Ｐｍ−ｄ）
【００５３】
数７において、値ｃは比例係数、値ｄは筒内に残存していた既燃ガス量である。吸気弁モデルＭ３は、エンジン回転速度Ｎｅ、及び吸気弁の開閉タイミングＶＴと、比例係数ｃ、及び既燃ガス量ｄとの関係をそれぞれ規定するテーブルをＲＯＭ８２内に格納していて、実際のエンジン回転速度Ｎｅと、実際の吸気弁の開閉タイミングＶＴと前記格納しているテーブルとから比例係数ｃ、及び既燃ガス量ｄを求める。また、吸気弁モデルＭ３は、演算時点において、後述するインテークマニホールドモデルＭ４により既に推定されている直前（最新）の吸気弁閉時の吸気管圧力Ｐｍと直前の吸気管内空気温度Ｔｍとを上記数７に適用し、吸気弁閉時の筒内吸入空気流量ｍｃを推定する。
【００５４】
（４）インテークマニホールドモデルＭ４
インテークマニホールドモデルＭ４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８及び下記数９にしたがって、吸気弁閉時の吸気管圧力Ｐｍと、吸気弁閉時の吸気管内温度Ｔｍとを求める。なお、Ｖは吸気管の容積、Ｒは気体定数、ｍｔはスロットル通過空気量、Ｔａはスロットルバルブ通過空気温度（即ち、吸気温度Ｔａ）である。
【００５５】
【数８】
ｄＰｍ／ｄｔ＝κ・（Ｒ／Ｖ）・（ｍｔ・Ｔａ−ｍｃ・Ｔｍ）
【００５６】
【数９】
ｄ（Ｐｍ／Ｔｍ）／ｄｔ＝（Ｒ／Ｖ）・（ｍｔ−ｍｃ）
【００５７】
図２に示したように、インテークマニホールドモデルＭ４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量ｍｔｓを上記数８，数９におけるスロットル通過空気量ｍｔとして使用し、吸気弁モデルＭ３により推定された吸気弁閉時の筒内吸入空気流量ｍｃを上記数８，数９の筒内吸入空気流量ｍｃとして使用する。このインテークマニホールドモデルＭ４により推定された吸気管圧力Ｐｍが、前記吸気弁閉時の推定吸気管圧力ＰＭＦＷＤとなる。
【００５８】
以上のようにして、本燃料噴射量制御装置は、電子制御スロットルモデルＭ１、スロットルモデルＭ２、吸気弁モデルＭ３、インテークマニホールドモデルＭ４の各シミュレーションモデルを用いて吸気弁閉時の吸気管圧力ＰＭＦＷＤを予測・推定し、推定した吸気管圧力ＰＭＦＷＤに対して所定の計算を行うことにより筒内吸入空気量Ｍｃを求め、上記数１に基づいて燃料噴射量ｆｉを決定する。
【００５９】
（圧縮行程開始時点におけるシリンダ内のガス状態の取得）
本燃料噴射量制御装置は、通常、上述したように各種モデルを使用して、各気筒が吸気行程を迎える度に同吸気行程を迎える特定気筒における筒内吸入空気量Ｍｃを求める一方で、本燃料噴射量制御装置に含まれる本発明による筒内ガス状態取得装置は、所定の条件が成立する度に、以下のようにして、同特定気筒における圧縮行程開始時点におけるシリンダ内のガス状態を取得して、同シリンダ内に吸入されている筒内吸入ガス量（質量）、圧縮行程開始時点における同シリンダ内の筒内絶対圧力等を求める。
【００６０】
（１）筒内相対圧力検出値の取得
先ず、本装置は、クランクポジションセンサ６８により得られる信号とカムポジションセンサ６６により得られる上記Ｇ２信号とにより求められる吸気弁３２の開閉タイミング（進角量）ＶＴに基き、上記特定気筒の吸気弁３２が閉弁する（開状態から閉状態に移行する）圧縮行程開始時点（所定の時点）におけるクランク角θｃａを求めて、その値をクランク角θ（１）として設定する。
【００６１】
そして、本装置は、図４に示すように、クランクポジションセンサ６８により得られるクランク角θｃａがクランク角θ（１）になると、その時点における筒内相対圧力センサ７２により得られる筒内相対圧力検出値Ｐｍｅａｓを筒内相対圧力検出値Ｐｍｅａｓ（１）としてＲＡＭ８３に格納する。以降、本装置は、クランク角θｃａが所定の一定間隔（計算間隔）Δθだけ進む度にクランク角θｃａの値を順にクランク角θ（Ｈ）　（Ｈ＝２，３，・・・）として設定していくとともに、クランク角θｃａがクランク角θ（Ｈ）　（Ｈ＝２，３，・・・）になる度にその時点における上記筒内相対圧力検出値Ｐｍｅａｓを筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）　（Ｈ＝２，３，・・・）として順にＲＡＭ８３に格納していく。
【００６２】
本装置は、このような処理を上記特定気筒の点火プラグ３７が点火されて同特定気筒が爆発行程に移行する圧縮行程終了時点まで継続して行い、同圧縮行程終了時点における上記変数Ｈの値をサンプル数Ｎとして設定する。このようにして、本装置は、所定の時点である圧縮行程開始時点から圧縮行程終了時点までの所定の区間内における複数の（Ｎ個の）筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を取得して順次ＲＡＭ８３に記憶する。
【００６３】
（２）筒内吸入ガス量、及び筒内ガス平均温度の仮設定
次に、本装置は、上記複数の筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を取得した上記圧縮行程時（以下、この圧縮行程を「特定圧縮行程」と呼ぶ。）に上記特定気筒のシリンダ内に吸入されている筒内吸入ガス（混合気）量（質量）Ｍｃｍ、及び特定圧縮行程開始時点における同シリンダ内の筒内ガス平均温度Ｔｃｍを、それぞれ下記数１０及び下記数１１により仮設定する。
【００６４】
【数１０】
Ｍｃｍ＝ｆｉ＋Ｍｃ
【００６５】
【数１１】
Ｔｃｍ＝Ｔｍ
【００６６】
上記数１０において、ｆｉは上記特定気筒の上記特定圧縮行程開始時点の直前に同特定気筒内に実際に噴射された燃料噴射量であり、Ｍｃは上記各モデルを用いて推定されている同特定気筒の上記特定圧縮行程時における筒内吸入空気量である。上記数１１において、Ｔｍは上記インテークマニホールドモデルＭ４により推定されている上記特定気筒の吸気弁閉時（上記特定圧縮行程開始時点）の吸気管内温度Ｔｍである。このように、上記数１０及び上記数１１を利用して、筒内吸入ガス量Ｍｃｍ、及び筒内ガス平均温度Ｔｃｍをそれぞれ仮設定する手段が、仮設定手段を構成する。
【００６７】
（３）仮の圧力補正値の算出、及び仮の筒内絶対圧力設定値の設定
次に、本装置は、上記のように仮設定した筒内吸入ガス量Ｍｃｍの値及び筒内ガス平均温度Ｔｃｍの値を利用して、状態方程式に基く下記数１２により上記特定気筒の上記特定圧縮行程開始時点における仮の筒内絶対圧力Ｐ０（上記特定圧縮行程開始時点における上記特定気筒のシリンダ内のガスの状態の一つ）を求める（仮設定する）。
【００６８】
【数１２】
Ｐ０＝（Ｍｃｍ・Ｒｇ・Ｔｃｍ）／Ｖｃｍ（１）
【００６９】
上記数１２において、Ｒｇはガス定数であり（上述した気体定数Ｒとは異なる）、Ｖｃｍ（１）は、上記特定圧縮行程開始時点、即ちクランク角θｃａが上記クランク角θ（１）となる時点における既知のピストン２２の位置を利用して求まるシリンダ容積である。
【００７０】
次に、本装置は、上記のようにして求めた仮の筒内絶対圧力Ｐ０の値と、上記特定圧縮行程開始時点における上記筒内相対圧力検出値Ｐｍｅａｓ（１）とから、下記数１３により図４に示す仮の圧力補正値ΔＰを求める。
【００７１】
【数１３】
ΔＰ＝Ｐ０−Ｐｍｅａｓ（１）
【００７２】
そして、本装置は、上記のようにして求めた仮の圧力補正値ΔＰと、上記Ｎ個の筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）の各々とに基いて、下記数１４により図４に示す上記所定の区間内におけるＮ個の仮の筒内絶対圧力設定値Ｐｃ（Ｈ）（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を求める。このように、上記数１３を利用して仮の圧力補正値ΔＰを求めるとともに、下記数１４を利用して仮の筒内絶対圧力設定値Ｐｃ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を求める手段が、第１計算手段を構成する。
【００７３】
【数１４】
Ｐｃ（Ｈ）＝Ｐｍｅａｓ（Ｈ）＋ΔＰ　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）
【００７４】
（４）仮の筒内絶対圧力計算値の計算
次に、本装置は、上記のようにして仮設定した上記特定圧縮行程開始時点における上記特定気筒のシリンダ内のガスの状態のうちの仮の筒内絶対圧力Ｐ０の値、及び筒内吸入ガス量Ｍｃｍを初期条件として、エネルギー保存則に基づく下記数１５〜下記数１７、及び状態方程式に基いた下記数１８により記述されたシリンダモデルにより、図４に示す上記所定の区間内におけるＮ個の仮の筒内絶対圧力計算値Ｐｃｍ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を求める。
【００７５】
【数１５】

【００７６】
【数１６】

【００７７】
【数１７】

【００７８】
【数１８】

【００７９】
上記数１５はエネルギー保存則に基く基本式であって、上記特定気筒を模式的に表した図５に示すように、同数１５において、Ｐｃｍは仮の筒内絶対圧力計算値、Ｖｃｍはシリンダ容積、Ｑはシリンダ２１外部（シリンダ壁面、吸気ポート等）からシリンダ２１内に伝達される単位時間当たりの熱伝達量、κは比熱比である。上記数１６は、上記数１５における熱伝達量Ｑを表す基本式であって、同数１６において、Ａは筒内表面積、ｈｗは熱伝達率、Ｔｃｍは筒内ガス平均温度、Ｔｗは筒内壁面温度である。
【００８０】
数１７は所謂ウォッシーニ（Ｗｏｓｃｈｎｉ）モデルを使用して上記数１６における熱伝達率ｈｗを表した式であって、同数１７において、ｄｉはシリンダ内径、Ｃ１は定数（本例では、２．２８）、Ｃｗは平均ピストン速度である。上記数１８は上記特定圧縮行程において特定気筒内に密閉されているガス（混合気）に適用される状態方程式に基く式であって、同数１８において、Ｒｇは上述した気体定数Ｒとは異なるガス定数、Ｍｃｍは筒内吸入ガス量（質量）である。
【００８１】
ここで、シリンダ容積Ｖｃｍ、シリンダ容積の時間微分値ｄＶｃｍ／ｄｔ、筒内表面積Ａはクランクポジションセンサ６８により得られるクランク角θｃａに基いて求めることができ、平均ピストン速度Ｃｗはエンジン回転速度Ｎｅに基いて求めることができ、筒内壁面温度Ｔｗは水温センサ６９により得られる冷却水温ＴＨＷにて代用することができる。また、比熱比κは筒内ガス平均温度Ｔｃｍの関数として表すことができる。
【００８２】
従って、上記数１５〜上記数１８により記述されたシリンダモデルは、筒内吸入ガス量Ｍｃｍ、及び時刻ｔにおける仮の筒内絶対圧力計算値Ｐｃｍの値が求められていると、上記数１８により時刻ｔにおける筒内ガス平均温度Ｔｃｍを求めることができ、その結果、上記数１７により時刻ｔにおける熱伝達率ｈｗを求めることができる。そして、上記数１６により時刻ｔにおける熱伝達量Ｑを求めることができ、その結果、理論上、上記数１５により時刻（ｔ＋ｄｔ）における仮の筒内絶対圧力計算値Ｐｃｍを求めることができる。よって、筒内吸入ガス量Ｍｃｍ、及び仮の筒内絶対圧力Ｐ０の値が初期条件（上記特定圧縮行程開始時点における値）として付与されると、上記シリンダモデルは、理論上、上記所定の区間内における仮の筒内絶対圧力計算値Ｐｃｍを順次求めることができる。
【００８３】
実際には、本装置は、以下のようにして、上記所定の区間内におけるＮ個の仮の筒内絶対圧力計算値Ｐｃｍ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を求める。先ず、上記数１５において、ｄ／ｄｔを（ｄ／ｄθ）・（ｄθ／ｄｔ）＝（ｄ／ｄθ）・ω　（θはクランク角，ωはクランクシャフトの角速度（即ち、エンジン回転速度Ｎｅ））に書き改めると、下記数１９が得られる。
【００８４】
【数１９】

【００８５】
上記数１９の両辺に（κ−１）／（ω・Ｖｃｍ）を乗算して整理すると下記数２０が得られる。
【００８６】
【数２０】

【００８７】
ここで、上記数２０を、クランク角θに関して計算間隔Δθをもって離散化するため、数２０の左辺のｄＰｃｍ／ｄθ，ｄκ／ｄθを、それぞれ下記数２１，下記数２２を用いて書き改め、さらに、数２０におけるＰｃｍをＰｃｍ（θ）、κをκ（θ）、ＶｃｍをＶｃｍ（θ）、ｄＶｃｍ／ｄθをｄＶｃｍ（θ）／ｄθ、ωをω（θ）、ＱをＱ（θ）にそれぞれ書き改めると、下記数２３が得られる。
【００８８】
【数２１】

【００８９】
【数２２】

【００９０】
【数２３】

【００９１】
また、上記数１６において、ＡをＡ（θ）、ｈｗをｈｗ（θ）、ＴｃｍをＴｃｍ（θ）にそれぞれ書き改めると、下記数２４が得られる。
【００９２】
【数２４】

【００９３】
また、上記数１７及び上記数１８を書き改めると、それぞれ、下記数２５及び下記数２６が得られる。
【００９４】
【数２５】

【００９５】
【数２６】

【００９６】
そして、本装置は、初期条件として、筒内吸入ガス量Ｍｃｍを上記のように仮設定された筒内吸入ガス量Ｍｃｍに設定し、上記仮の筒内絶対圧力Ｐ０の値を、クランク角θｃａが上記クランク角θ（１）となる上記特定圧縮行程開始時点における仮の筒内絶対圧力計算値Ｐｃｍ（１）に設定することにより、上記数２６によりクランク角θｃａがクランク角θ（１）となるときにおける筒内ガス平均温度Ｔｃｍ（１）を求めることができ、その結果、上記数２５によりクランク角θｃａがクランク角θ（１）となるときにおける熱伝達率ｈｗ（１）を求めることができる。また、上記筒内ガス平均温度Ｔｃｍ（１）によりクランク角θｃａがクランク角θ（１）となるときにおける比熱比κ（１）を求めることができる。なお、κ（０）はκ（１）と同一の値として設定される。
【００９７】
また、本装置は、上記数２４によりクランク角θｃａがクランク角θ（１）となるときにおける熱伝達量Ｑ（１）を求めることができ、その結果、上記数２３によりクランク角θｃａがクランク角θ（２）（クランク角θ（１）＋Δθ）となるときにおける仮の筒内絶対圧力計算値Ｐｃｍ（２）を求めることができる。換言すれば、本装置は、仮の筒内絶対圧力計算値Ｐｃｍ（１）が求まれば、上記数２３〜上記数２６を使用することにより仮の筒内絶対圧力計算値Ｐｃｍ（２）を求めることができる。
【００９８】
従って、上記数２３〜上記数２６を繰り返し使用することにより、本装置は、図４に示すように、上記所定の区間内におけるＮ個の仮の筒内絶対圧力計算値Ｐｃｍ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を順次求めることができる。このように、上記数２３〜上記数２６を利用して仮の筒内絶対圧力計算値Ｐｃｍ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を求める手段が、第２計算手段を構成する。
【００９９】
（５）偏差指標値の計算
次に、本装置は、上記所定の区間におけるＮ個の仮の筒内絶対圧力設定値Ｐｃ（Ｈ）とＮ個の仮の筒内絶対圧力計算値Ｐｃｍ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）との偏差の程度（図４において多数のドットで示された領域の面積に応じて変化する値）を示す偏差指標値として、下記数２７により表される値Ｅを採用する。このように、下記数２７を利用して偏差指標値Ｅを求める手段が、偏差指標値計算手段を構成する。
【０１００】
【数２７】

【０１０１】
（６）筒内吸入ガス量Ｍｃｍ、及び筒内ガス平均温度Ｔｃｍの同定
上述したように偏差指標値Ｅを求めた後、本装置は、上記偏差指標値Ｅが最小になるように、上記した（２）〜（５）の一連の各処理を繰り返し実行することにより、上記数１０及び上記数１１により仮設定した筒内吸入ガス量Ｍｃｍ及び上記特定圧縮行程開始時点での筒内ガス平均温度Ｔｃｍを同定し、同定された筒内吸入ガス量Ｍｃｍの値及び筒内ガス平均温度Ｔｃｍの値を、それぞれ真の値である確定筒内吸入ガス量Ｍｃｆｉｎ及び確定筒内ガス平均温度Ｔｃｆｉｎとして設定する。かかる同定方法の詳細は後述する。
【０１０２】
そして、本装置は、上記数１２において、Ｍｃｍの代わりに確定筒内吸入ガス量Ｍｃｆｉｎの値を、Ｔｃｍの代わりに確定筒内ガス平均温度Ｔｃｆｉｎをそれぞれ適用することにより、上記特定圧縮行程開始時点での筒内絶対圧力の真の値である確定筒内絶対圧力Ｐｃｆｉｎを求め、上記特定圧縮行程開始時点での特定気筒のシリンダ内に吸入されているガスの真の状態を完全に取得する。このようにして、上記特定圧縮行程開始時点での特定気筒のシリンダ内に吸入されているガスの真の状態を取得する手段が、筒内ガス状態取得手段を構成する。
【０１０３】
また、これにより、本装置は、上記確定筒内吸入ガス量Ｍｃｆｉｎから実際の燃料噴射量ｆｉを減じることにより上記特定気筒の上記特定圧縮行程時における真の筒内吸入空気量を求め、この真の筒内吸入空気量の値と、上述した各モデルを用いて推定されている同特定気筒の同特定圧縮行程時における筒内吸入空気量Ｍｃの値との比較により、先に説明した数７における比例係数ｃ及び既燃ガス量ｄをそれぞれ求めるためにＲＯＭ８２に格納されている各テーブルを補正する。
【０１０４】
さらには、本装置は、下記数２８により真の圧力補正値である確定圧力補正値ΔＰｆｉｎを算出する。
【０１０５】
【数２８】
ΔＰｆｉｎ＝Ｐｃｆｉｎ　−　Ｐｍｅａｓ（１）
【０１０６】
従って、本装置は、上記数２８により確定圧力補正値ΔＰｆｉｎを算出した時点以降、筒内相対圧力センサ７２の出力値である筒内相対圧力検出値Ｐｍｅａｓに確定圧力補正値ΔＰｃｆｉｎを加算することにより、シリンダ２１内の筒内絶対圧力を精度良く求めることができるようになり、内燃機関１０の異常燃焼（例えば、ノッキング、ミスファイア等）の発生を精度良く検出できるようになる。このように、上記数２８を利用して確定圧力補正値ΔＰｆｉｎを求める手段が、圧力補正値取得手段を構成する。以上のようにして、上記特定気筒の上記特定圧縮行程開始時点におけるシリンダ内のガス状態が取得される。
【０１０７】
（実際の作動）
次に、以上のように構成された本燃料噴射量制御装置、及び同燃料噴射量制御装置に含まれる本発明による筒内ガス状態取得装置の実際の作動について、電気制御装置８０のＣＰＵ８１が実行するルーチンをフローチャートにより示した図６〜図１２を参照しながら説明する。
【０１０８】
（スロットルバルブ制御）
電気制御装置８０のＣＰＵ８１は、図６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６００から処理を開始し、ステップ６０５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６１０に進み、同ステップ６１０にて図３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。
【０１０９】
次に、ＣＰＵ８１はステップ６１５に進んで変数Ｉを「６４」に設定し、続くステップ６２０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６２５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６２５にて「Ｎｏ」と判定してステップ６３０に進み、同ステップ６３０にて変数Ｉの値を「１」だけ減少し、その後上記ステップ６２０に戻る。この結果、ステップ６２０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。
【０１１０】
その後、ステップ６３０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６２５にて「Ｙｅｓ」と判定してステップ６３５に進み、同ステップ６３５にて前記ステップ６１０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。
【０１１１】
次に、ＣＰＵ８１はステップ６４０に進み、同ステップ６４０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６４５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６９５にて本ルーチンを一旦終了する。
【０１１２】
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による吸気弁閉時のスロットルバルブ開度ＴＡＳの推定が可能となる。
【０１１３】
（燃料噴射量ｆｉの計算、噴射指示）
ＣＰＵ８１は、吸気行程を迎える特定気筒のクランク角θｃａが、その気筒の吸気上死点から所定クランク角度だけ前の角度（例えば、ＢＴＤＣ９０°）になると、図７の燃料噴射量ｆｉの計算ルーチンの処理をステップ７００から開始してステップ７０５に進み、図２に示した各モデルに従って別途計算されている吸気弁閉時の吸気管圧力ＰＭＦＷＤに基づく筒内吸入空気量Ｍｃを読み込む。なお、筒内吸入空気量Ｍｃは、所定時間毎に繰り返し実行される図２に示した各モデルに従う図示しないルーチンにより求められている。
【０１１４】
次に、ＣＰＵ８１はステップ７１０に進んで、ステップ７０５にて読み込んだ筒内吸入空気量Ｍｃの値と上記数１の右辺とに基づいて燃料噴射量ｆｉを計算する。そして、ＣＰＵ８１はステップ７１５に進んで、ステップ７１０にて計算された燃料噴射量ｆｉだけ燃料を噴射するように前記特定気筒に対するインジェクタ３９に駆動信号を送出し、ステップ７９５に進んで本ルーチンを一旦終了する。
【０１１５】
（筒内吸入ガス量の計算開始判定）
ＣＰＵ８１は、図８にフローチャートにより示した筒内吸入ガス量を計算するためのルーチンを所定時間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８００から処理を開始し、ステップ８０５に進んで、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「０」であるか否かを判定する。筒内相対圧力取得処理実行中フラグＸＨＡＮは、その値が「１」のとき筒内相対圧力センサ７２の出力に基いて筒内相対圧力検出値Ｐｍｅａｓの取得処理を実行していることを示し、その値が「０」のとき同筒内相対圧力検出値Ｐｍｅａｓの取得処理を実行していないことを示す。
【０１１６】
いま、後述する筒内吸入ガス量等の計算開始条件が成立しておらず、且つ、前記筒内相対圧力検出値Ｐｍｅａｓの取得処理を実行していないとして説明を続けると、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「０」になっている。従って、ＣＰＵ８１はステップ８０５にて「Ｙｅｓ」と判定してステップ８１０に進み、筒内吸入ガス量等の計算開始条件が成立していて、且つ吸気行程を迎える特定気筒のクランク角θｃａが上記開閉タイミング（進角量）ＶＴに基いて計算される吸気弁閉時の角度より計算間隔Δθ（一定値）だけ前の角度になっているか否かを判定する。
【０１１７】
この筒内吸入ガス量等の計算開始条件は、冷却水温ＴＨＷが所定温度以上であり、図示しない車速センサにより得られた車速が所定の高車速以上であり、スロットル弁開度ＴＡの単位時間あたりの変化量が所定量以下である、機関が定常運転されている場合に成立する。更に、かかる計算開始条件に、前回の筒内吸入ガス量等の計算時点から所定時間以上が経過したこと、前回の筒内吸入ガス量等の計算時点から車両が所定距離以上運転されたこと、前回の筒内吸入ガス量等の計算時点から内燃機関１０が所定時間以上運転されたことの任意の一つ、又は一つ以上を加えても良い。現段階では、上述したように、筒内吸入ガス量等の計算開始条件は成立していないから、ＣＰＵ８１はステップ８１０にて「Ｎｏ」と判定してステップ８９５に進み、本ルーチンを一旦終了する。
【０１１８】
次に、上記筒内吸入ガス量等の計算開始条件が成立したものとして説明を続けると、ＣＰＵ８１はステップ８１０に進んだとき、特定気筒のクランク角θｃａが吸気弁閉時の角度より計算間隔Δθだけ前の角度になっていると同ステップ８１０にて「Ｙｅｓ」と判定してステップ８１５に進み、筒内相対圧力取得処理を開始するため、筒内相対圧力取得処理実行中フラグＸＨＡＮの値を「１」に設定し、続くステップ８２０にて変数Ｈの値を「０」に設定するとともに、続くステップ８２５にて現時点でクランクポジションセンサ６８により得られる前記特定気筒のクランク角θｃａの値を変数θ１に格納した後、ステップ８９５に進んで本ルーチンを一旦終了する。
【０１１９】
以降、ＣＰＵ８１は図８のルーチンをステップ８００から繰り返し実行するが、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「１」になっていることから、ステップ８０５に進んだとき、同ステップ８０５にて「Ｎｏ」と判定してステップ８３０に進み、前記特定気筒の点火プラグ３７が点火される前であるか否か（現時点が特定気筒の特定圧縮行程終了時点より前であるか否か）を判定するようになる。現時点では、前記特定気筒は吸気弁閉時直前（特定圧縮行程開始直前）の状態にあるから、ＣＰＵ８１はステップ８３０にて「Ｙｅｓ」と判定してステップ８９５に進んで本ルーチンを一旦終了する。これにより、特定気筒の特定圧縮行程が終了するまでステップ８００，８０５，８３０，８９５の処理が繰り返し実行されて、筒内相対圧力取得処理実行中フラグＸＨＡＮの値は「１」に維持される。
【０１２０】
（筒内相対圧力等の取得）
一方、ＣＰＵ８１は図９に示した筒内相対圧力等の取得ルーチンを所定時間の経過毎に繰り返し実行している。従って、所定のタイミングになると、ＣＰＵ８１はステップ９００から処理を開始してステップ９０５に進み、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「１」であるか否かを判定する。ここで、ＣＰＵ８１は、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「０」であれば直ちにステップ９９５に進んで本ルーチンを一旦終了するが、現時点では先の図８のステップ８１５の処理により筒内相対圧力取得処理実行中フラグＸＨＡＮの値は「１」になっているので、ステップ９０５にて「Ｙｅｓ」と判定してステップ９１０に進み、現時点でクランクポジションセンサ６８により得られる前記特定気筒のクランク角θｃａの値を変数θ２に格納する。
【０１２１】
次に、ＣＰＵ８１はステップ９１５に進んで、ステップ９１０の処理時点でのクランク角θｃａの値が格納されている変数θ２の値から先の図８のステップ８２５の処理時点でのクランク角θｃａの値が格納されている変数θ１の値を減算した値（角度）が上記計算間隔Δθ以上になっているか否かを判定する。現時点は先の図８のステップ８２５の処理を実行した直後であるから、現時点では変数θ２の値から変数θ１の値を減算した値が上記計算間隔Δθ未満であり、ＣＰＵ８１はステップ９１５にて「Ｎｏ」と判定して直ちにステップ９９５に進んで本ルーチンを一旦終了する。
【０１２２】
以降、ＣＰＵ８１は、変数θ２の値から変数θ１の値を減算した値が上記計算間隔Δθ以上になるまで、上記ステップ９００〜ステップ９１５の処理を繰り返し実行する。そして、ステップ９１０の処理が繰り返されてクランク角θｃａの増大とともに変数θ２の値が増大し、変数θ２の値から変数θ１の値を減算した値が上記計算間隔Δθに到達すると、ＣＰＵ８１はステップ９１５に進んだとき、「Ｙｅｓ」と判定してステップ９２０以降の筒内相対圧力等の取得処理を開始する。なお、この時点は、先の図８のステップ８１０にて「Ｙｅｓ」と判定した時点から計算間隔Δθだけ経過した時点であるので、特定気筒の吸気弁閉時（特定圧縮行程開始時点）に対応している。
【０１２３】
ＣＰＵ８１はステップ９２０に進むと、その時点での変数Ｈの値を「１」だけ増大した値を新たな変数Ｈとして格納する。現時点では、先の図８のステップ８２０の処理により変数Ｈの値は「０」になっているので、この処理により変数Ｈの値は「１」に設定される。次に、ＣＰＵ８１はステップ９２５に進み、現時点でのクランク角θｃａが格納されている変数θ２の値をクランク角θ（Ｈ）に格納する。これにより、上記特定圧縮行程開始時点でのクランク角θｃａの値がクランク角θ（１）に格納される。
【０１２４】
次いで、ＣＰＵ８１はステップ９３０に進み、現時点での筒内相対圧力検出値Ｐｍｅａｓを筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）に格納する。これにより、上記特定圧縮行程開始時点での筒内相対圧力検出値Ｐｍｅａｓが筒内相対圧力検出値Ｐｍｅａｓ（１）に格納される。次に、ＣＰＵ８１はステップ９３５に進み、クランク角θ（Ｈ）の値と、クランク角θｃａの関数ｆ１とに基づいて得られるシリンダ容積の値をシリンダ容積Ｖｃｍ（Ｈ）として設定する。これにより、上記特定圧縮行程開始時点でのシリンダ容積の値がシリンダ容積Ｖｃｍ（１）に格納される。
【０１２５】
次に、ＣＰＵ８１はステップ９４０に進み、クランク角θ（Ｈ）の値と、クランク角θｃａの関数ｆ２とに基づいて得られるシリンダ容積のクランク角についての微分値をシリンダ容積微分値ｄＶｃｍ（Ｈ）／ｄθとして設定する。これにより、上記特定圧縮行程開始時点でのシリンダ容積微分値がシリンダ容積微分値Ｖｃｍ（１）／ｄθに格納される。
【０１２６】
次いで、ＣＰＵ８１はステップ９４５に進み、クランク角θ（Ｈ）の値と、クランク角θｃａの関数ｆ３とに基づいて得られる筒内表面積の値を筒内表面積Ａ（Ｈ）として設定する。これにより、上記特定圧縮行程開始時点での筒内表面積の値が筒内表面積Ａ（１）に格納される。
【０１２７】
次に、ＣＰＵ８１はステップ９５０に進んで、現時点でのエンジン回転速度Ｎｅの値を角速度ω（Ｈ）に格納する。これにより、上記特定圧縮行程開始時点でのエンジン回転速度Ｎｅの値が角速度ω（１）に格納される。そして、ＣＰＵ８１はステップ９５５に進んで、変数θ２の値を変数θ１として格納した後ステップ９９５に進んで本ルーチンを一旦終了する。
【０１２８】
以降、ＣＰＵ８１は、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「１」である限りにおいて、ステップ９１０，９１５の処理を繰り返し実行する。ここで、先に述べたとおり筒内相対圧力取得処理実行中フラグＸＨＡＮの値は特定圧縮行程が終了するまで「１」に維持されている。従って、現時点から特定圧縮行程が終了するまでの間、ステップ９１０の処理が繰り返されてクランク角θｃａの増大とともに変数θ２の値が増大し、同変数θ２の値から既にステップ９５５にて設定されている変数θ１の最新値を減算した値が上記計算間隔Δθに到達する度ごとに、ステップ９２０以降の筒内相対圧力等の取得処理が実行される。
【０１２９】
この結果、特定圧縮行程開始時点以降、同特定圧縮行程終了時点までの間、クランク角θｃａの値が計算間隔Δθだけ増大する毎に、変数Ｈが「１」ずつ増大するとともに、その各々の時点における各値、即ち、クランク角θ（Ｈ）、筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）、シリンダ容積Ｖｃｍ（Ｈ）、シリンダ容積微分値Ｖｃｍ（Ｈ）／ｄθ、筒内表面積Ａ（Ｈ）、角速度ω（Ｈ）　（Ｈ＝１，２，３，・・・）が順次設定されていく。
【０１３０】
そして、上記特定気筒の点火プラグ３７が点火されて上記特定圧縮行程が終了すると、ＣＰＵ８１は図８のステップ８３０に進んだとき、「Ｎｏ」と判定してステップ８３５に進み、現時点での変数Ｈの値をサンプル数Ｎとして格納する。次いで、ＣＰＵ８１はステップ８４０に進み、現時点にて水温センサ６９により得られる冷却水温ＴＨＷの値を筒内壁面温度Ｔｗとして設定し、続くステップ８４５にて、同ステップ８４５内に記載の式に基き、既に図９のステップ９５０にて算出されているＮ個の角速度ω（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）の平均値を平均回転速度Ｎｅｍｅａｎとして設定するとともに、続くステップ８５０にて、平均回転速度Ｎｅｍｅａｎの値と、エンジン回転速度Ｎｅの関数ｆ４とに基いて得られる平均ピストン速度を平均ピストン速度Ｃｗとして格納する。
【０１３１】
次に、ＣＰＵ８１はステップ８５５に進んで、上記特定気筒の上記特定圧縮行程開始時点の直前に同特定気筒内に実際に噴射された燃料噴射量ｆｉの値に、図２に示した各モデルに従う図示しないルーチンにより推定されている同特定気筒の同特定圧縮行程時における筒内吸入空気量Ｍｃの値を加えた値を筒内吸入ガス量Ｍとして仮設定する。
【０１３２】
次いで、ＣＰＵ８１はステップ８６０に進み、図２に示したインテークマニホールドモデルＭ４に従う図示しないルーチンにより推定されている上記特定気筒の吸気弁閉時（上記特定圧縮行程開始時点）の吸気管内温度Ｔｍの値を筒内ガス平均温度Ｔとして仮設定する。そして、ＣＰＵ８１はステップ８６５に進んで、前記筒内吸入ガス量Ｍの値を筒内吸入ガス量Ｍｃｍとして設定するとともに、続くステップ８７０にて前記筒内ガス平均温度Ｔの値を筒内ガス平均温度Ｔｃｍとして設定した後、ステップ８７５に進んで図１０に示した偏差指標値の計算ルーチンを実行する。
【０１３３】
（偏差指標値の計算）
即ち、ＣＰＵ８１はステップ１０００から処理を開始し、ステップ１００５に進んで、先の図８のステップ８６５，８７０にてそれぞれ設定した筒内吸入ガス量Ｍｃｍの値及び筒内ガス平均温度Ｔｃｍの値と、図９のステップ９３５にて既に設定されているシリンダ容積Ｖｃｍ（１）の値と、上記数１２の右辺に相当するステップ１００５内に記載の式とに基いて上記特定圧縮行程開始時点における仮の筒内絶対圧力Ｐ０を算出する。
【０１３４】
次に、ＣＰＵ８１はステップ１０１０に進んで、仮の筒内絶対圧力Ｐ０の値を仮の筒内絶対圧力設定値Ｐｃ（１）として設定するとともに、続くステップ１０１５にて同仮の筒内絶対圧力Ｐ０の値を仮の筒内絶対圧力計算値Ｐｃｍ（１）として設定する。次いで、ＣＰＵ８１は１０２０に進み、筒内絶対圧力設定値Ｐｃ（１）の値と、図９の９３０にて既に設定されている筒内相対圧力検出値Ｐｍｅａｓ（１）と、上記数１３の右辺に相当するステップ１０２０内に記載の式とに基き仮の圧力補正値ΔＰを算出する。
【０１３５】
次に、ＣＰＵ８１はステップ１０２５に進んで、偏差指標値Ｅの値を「０」にクリアするとともに、続くステップ１０３０にて変数Ｉを「１」に設定する。次いで、ステップ１０３５に進んで、図９のステップ９３０にて設定されている筒内相対圧力検出値Ｐｍｅａｓ（Ｉ）の値と、ステップ１０２０にて算出した仮の圧力補正値ΔＰと、上記数１４の右辺に相当するステップ１０３５内に記載の式とに基き仮の筒内絶対圧力設定値Ｐｃ（Ｉ）を算出する。
【０１３６】
次に、ＣＰＵ８１はステップ１０４０に進んで、仮の筒内絶対圧力計算値Ｐｃｍ（Ｉ）の値（現時点では変数Ｉの値は「１」であり、ステップ１０１５にて設定した仮の筒内絶対圧力計算値Ｐｃｍ（１）の値）と、ステップ１００５にて使用した筒内吸入ガス量Ｍｃｍの値と、図９のステップ９３５にて既に設定されているシリンダ容積Ｖｃｍ（Ｉ）の値と、上記数２６の右辺に相当するステップ１０４０内に記載の式とに基き筒内ガス平均温度Ｔｃｍ（Ｉ）を算出する。
【０１３７】
次いで、ＣＰＵ８１はステップ１０４５に進み、前記筒内ガス平均温度Ｔｃｍ（Ｉ）の値と、筒内ガス平均温度Ｔｃｍの関数ｆ５とに基いて得られる比熱比を比熱比κ（Ｉ）として設定し、続くステップ１０５０にて、図８のステップ８５０にて設定した平均ピストン速度Ｃｗの値と、ステップ１０４０にて使用した仮の筒内絶対圧力計算値Ｐｃｍ（Ｉ）の値と、ステップ１０４０にて算出した筒内ガス平均温度Ｔｃｍ（Ｉ）の値と、上記数２５の右辺に相当するステップ１０５０内に記載の式とに基いて熱伝達率ｈｗ（Ｉ）を算出する。
【０１３８】
次に、ＣＰＵ８１はステップ１０５５に進んで、図９のステップ９４５にて設定した筒内表面積Ａ（Ｉ）の値と、前記熱伝達率ｈｗ（Ｉ）の値と、ステップ１０４０にて算出した筒内ガス平均温度Ｔｃｍ（Ｉ）の値と、図８のステップ８４０にて設定した筒内壁面温度Ｔｗの値と、上記数２４の右辺に相当するステップ１０５５内に記載の式とに基いて単位時間当たりの熱伝達量Ｑ（Ｉ）を算出する。
【０１３９】
次いで、ＣＰＵ８１はステップ１０６０に進んで、ステップ１０４５にて設定したκ（Ｉ）の値及びκ（Ｉ−１）の値（現時点では変数Ｉの値は「１」であり、κ（０）の値はκ（１）の値と同一）と、ステップ１０４０にて使用したシリンダ容積Ｖｃｍ（Ｉ）の値と、図９のステップ９４０にて設定したシリンダ容積微分値ｄＶｃｍ（Ｉ）／ｄθと、ステップ１０４０にて使用した仮の筒内絶対圧力計算値Ｐｃｍ（Ｉ）の値と、ステップ１０５５にて算出した熱伝達量Ｑ（Ｉ）の値と、図９のステップ９５０にて設定した角速度ω（Ｉ）の値と、上記数２３の右辺に相当するステップ１０６０内に記載の式とに基いて仮の筒内絶対圧力計算値Ｐｃｍ（Ｉ＋１）を算出する。
【０１４０】
現時点では、変数Ｉの値は「１」であるので、上述したステップ１０３５〜１０６０では、仮の筒内絶対圧力設定値Ｐｃ（１）、筒内ガス平均温度Ｔｃｍ（１）、比熱比κ（１）、熱伝達率ｈｗ（１）、熱伝達量Ｑ（１）、及び仮の筒内絶対圧力計算値Ｐｃｍ（２）が算出・設定される。
【０１４１】
次に、ＣＰＵ８１はステップ１０６５に進み、その時点での偏差指標値Ｅの値に、仮の筒内絶対圧力計算値Ｐｃｍ（Ｉ）から仮の筒内絶対圧力設定値Ｐｃ（Ｉ）を減じた値を二乗した値を加えた値を新たな偏差指標値Ｅとして設定する。現時点では、偏差指標値Ｅの値は「０」であり、変数Ｉの値は「１」であるので、この処理により、偏差指標値Ｅの値は（Ｐｃｍ（１）−Ｐｃ（１））^２となる。
【０１４２】
そして、ＣＰＵ８１はステップ１０７０に進んで変数Ｉの値が図８のステップ８３５にて設定したサンプル数Ｎの値と等しくなったか否かを判定する。現時点では変数Ｉの値は「１」であるので、ＣＰＵ８１はステップ１０７０にて「Ｎｏ」と判定してステップ１０７５に進み、変数Ｉの値を「１」だけ増大し、その後ステップ１０３５に戻る。
【０１４３】
この結果、変数Ｉの値は「２」になり、続くステップ１０３５〜１０６０では、仮の筒内絶対圧力設定値Ｐｃ（２）、筒内ガス平均温度Ｔｃｍ（２）、比熱比κ（２）、熱伝達率ｈｗ（２）、熱伝達量Ｑ（２）、及び仮の筒内絶対圧力計算値Ｐｃｍ（３）が算出・設定される。ここで、ステップ１０４０にて使用される仮の筒内絶対圧力計算値Ｐｃｍ（２）としては、直前にステップ１０６０の処理を実行した際に計算した仮の筒内絶対圧力計算値Ｐｃｍ（２）が使用される。
【０１４４】
次に、ＣＰＵ８１は再びステップ１０６５に進み、その時点での偏差指標値Ｅの値に（Ｐｃｍ（２）−Ｐｃ（２））^２の値を加えた値を新たな偏差指標値Ｅとして設定する。このような処理は、ステップ１０７５の処理が繰り返されて変数Ｉの値がサンプル数Ｎになるまで繰り返し実行される。これにより、偏差指標値Ｅが上記数２７に示した式に基いた値となる。
【０１４５】
そして、変数Ｉの値がサンプル数Ｎになると、ＣＰＵ８１はステップ１０７０にて「Ｙｅｓ」と判定してステップ１０９５に進み、本ルーチンを終了するとともに、図８のステップ８８０に戻る。このように、図１０の偏差指標値の計算ルーチンは、筒内吸入ガス量Ｍｃｍの値及び筒内ガス平均温度Ｔｃｍの値を設定すると、同設定した筒内吸入ガス量Ｍｃｍの値及び筒内ガス平均温度Ｔｃｍの値に基いた偏差指標値Ｅを計算するルーチンである。
【０１４６】
次いで、ＣＰＵ８１はステップ８８０に進むと、上述した図１０のルーチンにより計算された偏差指標値Ｅの値を偏差指標値前回値Ｅ１に格納するとともに、続くステップ８８５にて筒内相対圧力取得処理実行中フラグＸＨＡＮの値を「０」に設定した後、ステップ８９５に進んで図８のルーチンを一旦終了する。
【０１４７】
以降、ＣＰＵ８１は図８のルーチンをステップ８００から繰り返し実行するが、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「０」になっているので、ステップ８０５に進んだとき「Ｙｅｓ」と判定してステップ８１０に進むようになる。この時点では、筒内吸入ガス量等の計算を終了した直後であって先に説明した筒内吸入ガス量等の計算開始条件が成立していないので、ＣＰＵ８１はステップ８１０にて「Ｎｏ」と判定してステップ８９５に進み本ルーチンを一旦終了する。この結果、次回の筒内吸入ガス量等の計算開始条件が成立する時点までステップ８００，８０５，８１０，８９５の処理が繰り返し実行されて、筒内相対圧力取得処理実行中フラグＸＨＡＮの値は「０」に維持される。
【０１４８】
（偏差指標値最小化処理）
また、ＣＰＵ８１は図１１及びこれに続く図１２に示した偏差指標値を最小にするためのルーチンを所定時間の経過毎に繰り返し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１１００から処理を開始し、ステップ１１０２に進んで、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「１」から「０」に変化したか否かをモニタする。このとき、上記特定気筒の上記特定圧縮行程が終了し、上述した図８のステップ８８５にて筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「１」から「０」に変更されると、ＣＰＵ８１はステップ１１０２にて「Ｙｅｓ」と判定してステップ１１０４に進む。なお、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が変化していなければ、ＣＰＵ８１はステップ１１０２から図１２のステップ１１９５に直接進んで本ルーチンを一旦終了する。
【０１４９】
いま、上記特定気筒の上記特定圧縮行程が終了した直後であるとすると、図８のステップ８８５にて筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「１」から「０」に変更された直後であるから、ＣＰＵ８１はステップ１１０２からステップ１１０４に進み、その時点での筒内吸入ガス量Ｍの値に同定用補正量ΔＭを加えた値を筒内吸入ガス量Ｍ（１）として設定するとともにその時点での筒内ガス平均温度Ｔの値を筒内ガス平均温度Ｔ（１）として設定し、続くステップ１１０６にて、その時点での筒内吸入ガス量Ｍの値から同定用補正量ΔＭを値を減じた値を筒内吸入ガス量Ｍ（２）として設定するとともにその時点での筒内ガス平均温度Ｔの値を筒内ガス平均温度Ｔ（２）として設定し、続くステップ１１０８にて、その時点での筒内吸入ガス量Ｍの値を筒内吸入ガス量Ｍ（３）として設定するとともにその時点での筒内ガス平均温度Ｔの値に同定用補正温度ΔＴを加えた値を筒内ガス平均温度Ｔ（３）として設定し、続くステップ１１１０にて、その時点での筒内吸入ガス量Ｍの値を筒内吸入ガス量Ｍ（４）として設定するとともにその時点での筒内ガス平均温度Ｔの値から同定用補正温度ΔＴを減じた値を筒内ガス平均温度Ｔ（４）として設定する（現時点では、筒内吸入ガス量Ｍの値及び筒内ガス平均温度Ｔの値は、それぞれ図８のステップ８５５及びステップ８６０にて設定された値である。）。
【０１５０】
次に、ＣＰＵ８１はステップ１１１２に進んで変数Ｉを「１」に設定してステップ１１１４に進み、筒内吸入ガス量Ｍ（Ｉ）の値及び筒内ガス平均温度Ｔ（Ｉ）の値をそれぞれ筒内吸入ガス量Ｍｃｍ及び筒内ガス平均温度Ｔｃｍとして設定する。現時点では変数Ｉの値は「１」であるので、筒内吸入ガス量Ｍ（１）の値及び筒内ガス平均温度Ｔ（１）の値がそれぞれ筒内吸入ガス量Ｍｃｍ及び筒内ガス平均温度Ｔｃｍとして設定される。
【０１５１】
次いで、ＣＰＵ８１はステップ１１１６に進んで、先に説明した図１０の偏差指標値の計算ルーチンを実行する。これにより、筒内吸入ガス量Ｍ（１）の値及び筒内ガス平均温度Ｔ（１）の値に基いた偏差指標値Ｅが算出される。次に、ＣＰＵ８１はステップ１１１８に進んで、前記偏差指標値Ｅの値を偏差指標値Ｅ（Ｉ）として設定する。現時点では、変数Ｉの値は「１」であるので前記偏差指標値Ｅが偏差指標値Ｅ（１）として設定される。
【０１５２】
次いで、ＣＰＵ８１はステップ１１２０に進み、変数Ｉの値が「４」と等しいか否かを判定する。現時点では、変数Ｉの値は「１」であるので、ＣＰＵ８１はステップ１１２０にて「Ｎｏ」と判定してステップ１１２２に進み、変数Ｉの値を「１」だけ増大し、その後ステップ１１１４に戻る。この結果、続くステップ１１１４〜１１１８にて、筒内吸入ガス量Ｍ（２）の値及び筒内ガス平均温度Ｔ（２）の値に基いた偏差指標値Ｅが算出され、同偏差指標値Ｅが偏差指標値Ｅ（２）として設定される。このような処理は、ステップ１１２２の処理が繰り返されて変数Ｉの値が「４」になるまで繰り返される。この結果、偏差指標値Ｅ（Ｉ）は筒内吸入ガス量Ｍ（Ｉ）の値及び筒内ガス平均温度Ｔ（Ｉ）に基いて計算される値になるように設定される（Ｉ＝１，２，３，４）。
【０１５３】
そして、変数Ｉの値が「４」になると、ＣＰＵ８１はステップ１１２０にて「Ｙｅｓ」と判定して図１２のステップ１１２４に進み、前記偏差指標値Ｅ（Ｉ）　（Ｉ＝１，２，３，４）のうち最小のものに対応する変数Ｉの値をＩｍｉｎとして設定するとともに、ステップ１１２６に進んで、最小偏差指標値Ｅ（Ｉｍｉｎ）からその時点での偏差指標値前回値Ｅ１（現時点では、図８のステップ８８０にて設定されている値）を減じた値を偏差指標値変化量ΔＥとして設定する。
【０１５４】
次に、ＣＰＵ８１はステップ１１２８に進み、前記偏差指標値変化量ΔＥの絶対値が最小化判定基準値ΔＥｒｅｆ以上であるか否かを判定する。いま、偏差指標値変化量ΔＥの絶対値が最小化判定基準値ΔＥｒｅｆ以上であるとして説明を続けると、ＣＰＵ８１はステップ１１２８にて「Ｙｅｓ」と判定してステップ１１３０に進み、筒内吸入ガス量Ｍ（Ｉｍｉｎ）の値及び筒内ガス平均温度Ｔ（Ｉｍｉｎ）の値を、それぞれ筒内吸入ガス量Ｍ及び筒内ガス平均温度Ｔとして再設定するとともに、続くステップ１１３２にて上記最小偏差指標値Ｅ（Ｉｍｉｎ）を偏差指標値前回値Ｅ１として再設定した後、図１１のステップ１１０４に戻る。
【０１５５】
この結果、続くステップ１１０４〜１１１０にて、筒内吸入ガス量Ｍ（Ｉ）及び筒内ガス平均温度Ｔ（Ｉ）　（Ｉ＝１，２，３，４）の各値が先のステップ１１３０にて設定された筒内吸入ガス量Ｍ及び筒内ガス平均温度Ｔに基いて再設定されて、続くステップ１１１２〜１１２６の処理が実行される。これにより、最小偏差指標値Ｅ（Ｉｍｉｎ）が更新されてより小さい値となり、更新された新たな最小偏差指標値Ｅ（Ｉｍｉｎ）から先のステップ１１３２にて設定された偏差指標値前回値Ｅ１を減じた値が新たな偏差指標値変化量ΔＥとして設定される。
【０１５６】
そして、ステップ１１２８にて再度、前記新たな偏差指標値変化量ΔＥの絶対値が上記最小化判定基準値ΔＥｒｅｆ以上であるか否かが判定され、その結果、新たな偏差指標値変化量ΔＥの絶対値が未だ上記最小化判定基準値ΔＥｒｅｆ以上であれば、同新たな偏差指標値変化量ΔＥの絶対値が上記最小化判定基準値ΔＥｒｅｆ未満になるまで上述した処理が繰り返し実行される。
【０１５７】
その結果、偏差指標値変化量ΔＥの絶対値が上記最小化判定基準値ΔＥｒｅｆ未満になると、その時点での最小偏差指標値Ｅ（Ｉｍｉｎ）が偏差指標値Ｅの最小値であることになる。このとき、ＣＰＵ８１はステップ１１２８にて「Ｎｏ」と判定してステップ１１３４に進み、その時点での筒内吸入ガス量Ｍ（Ｉｍｉｎ）の値及び筒内ガス平均温度Ｔ（Ｉｍｉｎ）の値を、それぞれ確定筒内吸入ガス量Ｍｃｆｉｎ及び確定筒内ガス平均温度Ｔｃｆｉｎとして設定するとともに、続くステップ１１３６にて、同確定筒内吸入ガス量Ｍｃｆｉｎの値及び同確定筒内ガス平均温度Ｔｃｆｉｎの値と、上記数１２の右辺に相当するステップ１１３６内に記載の式とに基き確定筒内絶対圧力Ｐｃｆｉｎを算出する。これにより、筒内吸入ガス量Ｍｃｍ及び筒内ガス平均温度Ｔｃｍの同定が完了する。
【０１５８】
次いで、ＣＰＵ８１はステップ１１３８に進んで、前記確定筒内絶対圧力Ｐｃｆｉｎの値と、図９のステップ９３０にて設定されている筒内相対圧力検出値Ｐｍｅａｓ（１）と、上記数２８の右辺に相当するステップ１１３８内に記載の式とに基いて確定圧力補正値ΔＰｆｉｎを算出する。
【０１５９】
次に、ＣＰＵ８１はステップ１１４０に進んで、上記確定筒内吸入ガス量Ｍｃｆｉｎから実際の燃料噴射量ｆｉを減じることにより上記特定気筒の上記特定圧縮行程時における真の筒内吸入空気量を求め、この真の筒内吸入空気量の値と、上述した各モデルを用いて推定されている同特定気筒の同特定圧縮行程時における筒内吸入空気量Ｍｃの値とを比較することにより、先に説明した吸気弁モデルＭ３を記述する上記数７における比例係数ｃ及び既燃ガス量ｄをそれぞれ求めるためにＲＯＭ８２に格納されている各テーブルを補正する。そして、ＣＰＵ８１はステップ１１９５に進んで本ルーチンを一旦終了する。
【０１６０】
以降、ＣＰＵ８１は図１１及びこれに続く図１２のルーチンを繰り返し実行するが、筒内相対圧力取得処理実行中フラグＸＨＡＮの値が「０」に維持されているので、図１１のステップ１１０２にて「Ｎｏ」と判定して図１２のステップ１１９５に直接進んで本ルーチンを一旦終了するようになる。
【０１６１】
以上説明したように、本発明による筒内ガス状態取得装置の実施形態によれば、筒内相対圧力センサ７２の出力に基いて、上記特定気筒の上記特定圧縮行程開始時点におけるシリンダ内のガスの真の状態を精度良く取得することができた。
【０１６２】
また、上述した筒内吸入ガス量等の計算開始条件が成立する毎に、真の筒内吸入ガス量（Ｍｃｆｉｎ−ｆｉ）を求め、同真の筒内吸入ガス量（Ｍｃｆｉｎ−ｆｉ）と上記各モデルにより推定された筒内吸入空気量Ｍｃとを比較して吸気弁モデルＭ３を記述する上記数７における比例係数ｃ及び既燃ガス量ｄをそれぞれ求めるための各テーブルを補正する。この結果、上記各モデルにより構成される筒内吸入空気量推定装置による筒内吸入空気量Ｍｃの推定精度を向上させることができた。
【０１６３】
また、確定圧力補正値ΔＰｆｉｎが取得された後においては、筒内相対圧力センサ７２の出力値である筒内相対圧力検出値Ｐｍｅａｓと同確定圧力補正値ΔＰｆｉｎとに基いてシリンダ２１内の筒内絶対圧力を精度良く求めることができるようになる。従って、内燃機関の異常燃焼（例えば、ノッキング、ミスファイア等）の発生を精度良く検出できるようになった。
【０１６４】
さらには、最初に仮設定される筒内吸入ガス量Ｍｃｍの値は、上記特定気筒の上記特定圧縮行程開始時点の直前に同特定気筒内に実際に噴射された燃料噴射量ｆｉと上記各モデルを用いて推定されている同特定気筒の上記特定圧縮行程時における筒内吸入空気量Ｍｃとを加算した値であり、最初に仮設定される筒内ガス平均温度Ｔｃｍの値は、上記インテークマニホールドモデルＭ４により推定されている上記特定気筒の吸気弁閉時（上記特定圧縮行程開始時点）の吸気管内温度Ｔｍである。従って、最初に仮設定される筒内吸入ガス量Ｍｃｍの値、及び最初に仮設定される筒内ガス平均温度Ｔｃｍの値は、それぞれ、実際の真の値に近い値である可能性が高いので、偏差指標値Ｅが最小となるように筒内吸入ガス量Ｍｃｍの値及び筒内ガス平均温度Ｔｃｍの値を同定する際に実行される処理の繰り返し回数を少なくすることができた。
【０１６５】
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、仮設定手段は、（特定圧縮行程時にシリンダに吸入されている）筒内吸入ガス量Ｍｃｍと、（特定圧縮行程開始時点における）筒内ガス平均温度Ｔｃｍとを仮設定するように構成されているが、前記筒内吸入ガス量Ｍｃｍ及び前記筒内ガス平均温度Ｔｃｍのいずれか一方と、（特定圧縮行程開始時点における）仮の筒内絶対圧力Ｐ０とを仮設定するように構成してもよい。この場合、前記筒内吸入ガス量Ｍｃｍ及び前記筒内ガス平均温度Ｔｃｍの他方の値は、上記数１２を変形した式に基いて求めることができ、これにより、上記特定圧縮行程開始時点における上記特定気筒のシリンダ内のガスの状態が仮設定される。
【０１６６】
また、上記実施形態では、複数の（サンプル数Ｎ個の）仮の筒内絶対圧力設定値Ｐｃ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）等が設定される圧縮行程の所定の区間の終期を特定圧縮行程終了時点（点火プラグにより点火される時点）に設定しているが、内燃機関１０の運転状態に応じて所定の期間（例えば、アクセルペダルの操作量Ａｃｃｐが「０」となる期間）だけ燃料を噴射しない制御（所謂フューエルカット制御）が実行される場合、前記所定の区間の終期を、通常は特定圧縮行程終了時点に設定し、前記所定の期間内はピストンの位置が圧縮上死点に到達した時点に設定してもよい。
【０１６７】
また、上記実施形態では、エネルギー保存則、及び状態方程式に基くシリンダモデルを記述する上記数１５〜上記数１８のうちの熱伝達率ｈｗ（熱伝達量Ｑ）を求めるための上記数１７において、定数Ｃ１を一定値「２．２８」に設定しているが、値Ｃ１を仮設定手段により仮設定し、筒内ガス状態取得手段により同値Ｃ１の真の値を求めるように（偏差指標値Ｅが最小となるように同値Ｃ１を同定するように）構成してもよい。
【０１６８】
また、上記実施形態では、第１計算手段は、筒内ガス状態取得手段が仮設定手段、第１計算手段、第２計算手段、及び偏差指標値計算手段が行う一連の各処理を繰返し実行させる前に予め取得してある圧縮行程の所定の区間内における複数の筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）に基いて、複数の仮の筒内絶対圧力設定値Ｐｃ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を設定するように構成されているが、、前記第１計算手段を、前記筒内ガス状態取得手段が前記一連の各処理を繰返し実行する毎に、前記複数の筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を新たに取得して同新たに取得した複数の筒内相対圧力検出値Ｐｍｅａｓ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）に基いて前記複数の仮の筒内絶対圧力設定値Ｐｃ（Ｈ）　（Ｈ＝１，２，・・・，Ｎ−１，Ｎ）を設定するように構成してもよい。
【図面の簡単な説明】
【図１】本発明による筒内ガス状態取得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３】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す図である。
【図４】図１に示した特定気筒の圧縮行程におけるクランク角に対する、複数の筒内相対圧力検出値、複数の仮の筒内絶対圧力設定値、及び複数の仮の筒内絶対圧力計算値の各々に基く波形の一例を示した図である。
【図５】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６】図１に示したＣＰＵが実行するスロットルバルブ開度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７】図１に示したＣＰＵが実行する燃料噴射量を計算するためのルーチンを示したフローチャートである。
【図８】図１に示したＣＰＵが実行する筒内吸入ガス量の計算を開始するか否かを決定するためのルーチンを示したフローチャートである。
【図９】図１に示したＣＰＵが実行する複数の筒内相対圧力検出値等を取得するためのルーチンを示したフローチャートである。
【図１０】図１に示したＣＰＵが実行する偏差指標値を計算するためのルーチンを示したフローチャートである。
【図１１】図１に示したＣＰＵが実行する偏差指標値を最小化するためのルーチンの前半部を示したフローチャートである。
【図１２】図１に示したＣＰＵが実行する偏差指標値を最小化するためのルーチンの後半部を示したフローチャートである。
【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）、２１…シリンダ、２５…燃焼室、３１…吸気ポート、３２…吸気弁、３９…インジェクタ、４１…吸気管、４３…スロットルバルブ、６８…クランクポジションセンサ、７１…アクセル開度センサ、７２…筒内相対圧力センサ、８０…電気制御装置、８１…ＣＰＵ。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is based on an output value of an in-cylinder relative pressure sensor that detects a pressure in a cylinder of an internal combustion engine as a relative pressure. The present invention relates to an in-cylinder gas state acquisition device for an internal combustion engine that acquires the state of a gas that is flowing.
[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 cylinders (cylinders, combustion chambers) of the internal combustion engine (hereinafter, “in-cylinder intake air amount”) ) Must be obtained with high accuracy. For this reason, for example, an in-cylinder intake air amount detection device for an internal combustion engine disclosed in Patent Literature 1 below includes an in-cylinder absolute pressure sensor that detects an in-cylinder absolute pressure in a cylinder, An intake air temperature sensor that detects the temperature of the exhaust gas, and an exhaust gas temperature sensor that detects the temperature of the exhaust gas discharged from the cylinder. The in-cylinder gas temperature of the gas sucked into the cylinder is estimated, and the estimated in-cylinder gas temperature at the start of the compression stroke and the in-cylinder gas at the start of the compression stroke obtained by the in-cylinder absolute pressure sensor. The in-cylinder intake air amount is detected using an absolute pressure, a state equation, and the like.
[0003]
By the way, an absolute pressure sensor capable of detecting the absolute pressure as described above can generally detect the absolute pressure accurately within a relatively narrow pressure range, but fluctuates within a relatively wide range such as the pressure in a cylinder. The absolute pressure cannot be accurately detected over the entire wide range. Therefore, in order to accurately detect the pressure in the cylinder over a wide range, it is generally preferable to use a relative pressure sensor that can accurately detect the relative pressure (relative pressure from the reference pressure) over a wide range. is there. However, when the pressure in the cylinder is detected by the relative pressure sensor, the value of the relative pressure in the cylinder in the cylinder obtained by the relative pressure sensor is directly applied to the equation of state like the value of the absolute pressure in the cylinder. It is not possible to obtain the in-cylinder intake air amount.
[0004]
For this reason, the cylinder intake air amount detecting device disclosed in Patent Document 2 below assumes that the state of gas in the cylinder during the compression stroke is a polytropic change (reversible change) with a constant polytropic index. The respective relative pressures at two different points during the compression stroke are detected by the in-cylinder relative pressure sensor to determine the pressure difference between the respective pressures. The value of this pressure difference, the engine speed, and the The amount of in-cylinder intake air is detected based on a value and an experimentally determined table that defines the relationship between the engine rotational speed and the amount of in-cylinder intake air.
[0005]
[Patent Document 1]
JP-A-11-166647
[Patent Document 2]
JP-A-2-238149
[0006]
[Problems to be solved by the invention]
However, since the actual operating condition of the internal combustion engine changes every moment, the amount of heat transferred between the cylinder and the outside of the cylinder during the compression stroke also changes every moment, and as a result, during the actual compression stroke, The state of the gas in the cylinder does not always change with a constant polytrope index (it may change irreversibly). Therefore, in the device disclosed in Patent Document 2, the in-cylinder intake air amount is not always accurately detected.
[0007]
Furthermore, in the device disclosed in Patent Document 2, since the in-cylinder intake air amount is estimated based on the in-cylinder relative pressure values of only two points during the compression stroke, the number of detected points is small. Due to the decrease in detection accuracy, the detection accuracy of the pressure difference may decrease, and the in-cylinder intake air amount may not be detected with high accuracy.
[0008]
Further, in order to detect the occurrence of abnormal combustion (for example, knocking, misfire, etc.) of the internal combustion engine, it is necessary to accurately determine the absolute pressure in the cylinder in the cylinder. Here, if the in-cylinder intake air amount in the cylinder can be accurately detected, by applying the state equation to the gas in the cylinder during the compression stroke, the in-cylinder absolute pressure in the cylinder can also be accurately calculated. The difference between the in-cylinder absolute pressure value obtained and the in-cylinder relative pressure value obtained by the in-cylinder relative pressure sensor is set as a pressure correction value (calibration value), and thereafter, the output value of the in-cylinder relative pressure sensor And the same pressure correction value can be used to accurately determine the in-cylinder absolute pressure.
[0009]
However, as described above, in the device disclosed in Patent Document 2, the in-cylinder intake air amount may not be detected with high accuracy, so that the in-cylinder absolute pressure cannot be obtained with high accuracy. That is, in the device disclosed in Patent Document 2, the air is sucked into the cylinder during the compression stroke such as the in-cylinder intake air amount (gas amount) and the in-cylinder absolute pressure based on the output value of the in-cylinder relative pressure sensor. There is a problem that the gas state cannot be obtained with high accuracy.
[0010]
Therefore, an object of the present invention is that the cylinder is suctioned into the cylinder such as the cylinder intake gas amount (air amount) and the cylinder absolute pressure based on the output of the cylinder relative pressure sensor capable of detecting the relative pressure in the cylinder. It is an object of the present invention to provide an in-cylinder gas state acquisition device for an internal combustion engine that can acquire a gas state with high accuracy.
[0011]
[Overview of the present invention]
A feature of the present invention includes a cylinder relative pressure sensor that detects the pressure in the cylinder as a cylinder relative pressure detection value that is a relative pressure from a predetermined reference pressure, and the cylinder based on the cylinder relative pressure detection value. An in-cylinder gas state acquisition device for an internal combustion engine that acquires a state of gas sucked into the cylinder during a compression stroke; an in-cylinder intake gas amount sucked into the cylinder during a compression stroke; By temporarily setting two values of the in-cylinder gas temperature and the in-cylinder absolute pressure in the same cylinder at the same time, the state of the gas sucked into the same cylinder at the same time is determined. A provisional setting means for provisionally setting the value of the provisional in-cylinder absolute pressure in the cylinder at the predetermined time obtained from the state of the gas sucked into the cylinder at the provisional setting at the predetermined time; A temporary pressure correction value is calculated by comparing with the in-cylinder relative pressure detection value at a predetermined time, and a plurality of in-cylinder relative pressure detection values in a predetermined section of the compression stroke including the predetermined time and the tentative pressure correction value are calculated. First calculating means for sequentially setting a plurality of temporary in-cylinder absolute pressure set values in the same cylinder in the same predetermined section from the pressure correction value; and a cylinder at the predetermined time point temporarily set by the temporary setting means. Using the state of the gas in the cylinder as an initial condition, a plurality of temporary in-cylinder absolute pressure calculation values in the cylinder in the predetermined section are sequentially calculated using a model for the same cylinder obtained based on the law of conservation of energy. A second calculating means for calculating a deviation index value indicating a degree of deviation between the plurality of temporary cylinder absolute pressure set values and the plurality of temporary cylinder absolute pressure calculated values in the predetermined section. A standard value calculating unit, and sequentially correcting the two temporarily set values so as to reduce the degree of the deviation indicated by the deviation index value, and providing the temporary setting unit, the first calculating unit, and the second calculating unit And a series of processes performed by the deviation index value calculating means, repeatedly executed until the degree of the deviation is substantially minimized, at the time when the degree of the deviation is substantially minimized, There is provided in-cylinder gas state acquisition means for setting two values as true values and acquiring a true state of the gas sucked into the cylinder at the predetermined time.
[0012]
In this case, the provisional setting means includes an in-cylinder intake gas amount sucked into the cylinder during the compression stroke, a cylinder gas temperature in the cylinder at a predetermined time in the compression stroke, and an in-cylinder gas temperature in the cylinder at a predetermined time in the compression stroke. By temporarily setting two values of the in-cylinder absolute pressures (hereinafter, referred to as “three values”), the two provisionally set values and the known values at the predetermined time point are determined. Calculating and temporarily setting the remaining one value based on the known cylinder volume at the same predetermined time obtained from the piston position and a state equation applicable to the gas sealed in the cylinder during the compression stroke. Can be.
[0013]
Accordingly, the value of the temporary in-cylinder absolute pressure in the cylinder at a predetermined time used by the first calculation means when calculating the temporary pressure correction value is the value of the in-cylinder absolute pressure in the cylinder at the predetermined time. Is temporarily set as one of the two provisionally set values, the value is the provisionally set value, and the value of the in-cylinder absolute pressure in the cylinder at a predetermined time is the provisionally set value. If they are not included in the two set values, the values are calculated based on the two provisionally set values and the above-described state equation, and are provisionally set values.
[0014]
The first calculation means compares the value of the provisional in-cylinder absolute pressure at the predetermined time provisionally set in this way with the detected value of the in-cylinder relative pressure at the predetermined time obtained by the in-cylinder relative pressure sensor. To calculate a temporary pressure correction value. Then, the first calculating means is capable of detecting the relative pressure (relative pressure from a predetermined reference pressure) over a wide range with a plurality of cylinders in a predetermined section of a compression stroke obtained by the in-cylinder relative pressure sensor. By sequentially calculating and setting a plurality of temporary in-cylinder absolute pressure set values in the same predetermined section based on the relative pressure detection value and the temporary pressure correction value calculated as described above, the same predetermined section is obtained. , A waveform of the provisional in-cylinder absolute pressure set value passing through the plurality of provisional in-cylinder absolute pressure set values is obtained.
[0015]
In addition, the second calculating means is capable of taking into consideration the amount of heat transmitted between the cylinder and the outside of the cylinder during the compression stroke, and is capable of handling irreversible changes. Using a model of the inside, a plurality of temporary in-cylinder absolute pressure calculation values in a predetermined section are sequentially calculated with the state of the gas in the cylinder at the predetermined time temporarily set by the temporary setting means as an initial condition. By doing so, a waveform of the calculated temporary in-cylinder absolute pressure value that passes through the plurality of temporary in-cylinder absolute pressure calculated values is obtained in the predetermined section.
[0016]
The deviation index value calculation means calculates a deviation index value indicating the degree of deviation between the plurality of temporary cylinder absolute pressure set values and the plurality of temporary cylinder absolute pressure calculation values in the predetermined section determined as described above. calculate. The deviation index value is, for example, a value obtained by squaring a difference between a provisional in-cylinder absolute pressure set value and a provisional in-cylinder absolute pressure calculation value at the same crank angle in a predetermined section, and integrated over the same predetermined section. It is a value and is not limited to this.
[0017]
Then, the in-cylinder gas state acquiring means identifies the two values temporarily set by the temporary setting means so that the deviation index value becomes substantially minimum, and sets each of the identified two values as a true value. I do. Further, the in-cylinder gas state acquiring means sets the two true values, respectively, to set the two true values, the known cylinder volume at a predetermined time, and the cylinder during the compression stroke. The true value of the remaining one of the three values can be calculated based on an equation of state that can be applied to the gas enclosed therein. Specifically, the true in-cylinder intake gas amount sucked into the cylinder during the compression stroke, the true in-cylinder gas temperature in the cylinder at a predetermined time in the compression stroke, and the same cylinder gas at the same time in the cylinder Can be obtained respectively.
[0018]
The three true values obtained by the in-cylinder gas state acquiring means in this way are the provisional in-cylinder absolute pressure set values based on the in-cylinder relative pressure detection values (actually measured values) obtained over a wide range with high accuracy. Waveform and the amount of heat transmitted between the cylinder and the outside of the cylinder during the compression stroke can be considered, and it is possible to handle irreversible changes. This is a value identified so that the obtained waveform of the calculated in-cylinder absolute pressure calculation value with high calculation accuracy substantially matches.
[0019]
Also, since the waveform of the in-cylinder absolute pressure set value based on the in-cylinder relative pressure detection value (actual measurement value) can be obtained based on a large number of detection values (actual measurement values) in a predetermined section of the compression stroke, the number of detection points This is a waveform that is unlikely to have the effect of a decrease in the detection accuracy due to the small number of waveforms. Therefore, according to the in-cylinder gas state acquisition device of the present invention, based on the output of the in-cylinder relative pressure sensor, the three true values, that is, the values of the gas in the cylinder at the predetermined time based on these values. The true state can be obtained with high accuracy.
[0020]
Further, by this, for example, an in-cylinder intake air amount configured to estimate an in-cylinder intake air amount using a model of an intake system represented by an expression based on fluid dynamics and the like and a predetermined table (map). If the in-cylinder gas state acquiring device according to the present invention is applied to an internal combustion engine having an estimating device, usually, the in-cylinder intake air amount is estimated based on the model and the table, and at every predetermined timing. By obtaining the true in-cylinder intake gas amount by the in-cylinder gas state acquisition device according to the present invention and correcting the above table by comparing the true in-cylinder intake gas amount and the estimated in-cylinder intake air amount, the cylinder The accuracy of estimating the in-cylinder intake air amount by the internal intake air amount estimation device can be improved.
[0021]
In the in-cylinder gas state acquisition device for an internal combustion engine according to the present invention, the in-cylinder gas state acquisition means is configured to acquire a true in-cylinder absolute pressure in the cylinder at the predetermined time, and It is preferable to include a pressure correction value obtaining unit that obtains a true pressure correction value by comparing the value of the in-cylinder absolute pressure with the detected value of the in-cylinder relative pressure at the predetermined time.
[0022]
According to this, after the true pressure correction value is obtained by the pressure correction value obtaining means, the in-cylinder relative pressure detection value which is the output value of the in-cylinder relative pressure sensor and the true pressure correction value are used. The in-cylinder absolute pressure in the cylinder can be accurately obtained. Therefore, the in-cylinder gas state acquisition device according to the present invention may be applied to an internal combustion engine having a device that detects the occurrence of abnormal combustion (for example, knocking, misfire, etc.) of the internal combustion engine based on a change in the in-cylinder absolute pressure. For example, the occurrence of abnormal combustion of the internal combustion engine can be accurately detected.
[0023]
In any one of the in-cylinder gas state acquisition devices, the predetermined time is set to a compression stroke start time at which an intake valve closes, and the predetermined section is started at the compression stroke start time. Preferably, the time is set such that its end is the end of the compression stroke. Here, the end point of the compression stroke is a point in time when the gas in the cylinder starts burning and shifts to an explosion stroke. According to this, the width of the predetermined section can be maximized, and the waveform of the in-cylinder absolute pressure value can be obtained based on a larger number of detected values (actually measured values). It is possible to minimize the influence of the decrease in detection accuracy due to the smallness.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a fuel injection amount control device including an in-cylinder gas state acquisition device of 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.
[0025]
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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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) 53 interposed in the exhaust pipe 52.
[0030]
On the other hand, this system includes a hot wire air flow meter 61, 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, an intake valve lift amount sensor. 67, crank position sensor 68, water temperature sensor 69, O ₂ A sensor 70, an accelerator opening sensor 71, and an in-cylinder relative pressure sensor 72 are provided.
[0031]
The air flow meter 61 outputs a voltage Vg according to the mass flow rate of the intake air flowing through the intake pipe 41. 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.
[0032]
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 crank angle θca and the engine speed Ne.
[0033]
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. O ₂ The 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 operated by the driver. The in-cylinder relative pressure sensor 72 detects the pressure in the cylinder 21 (in the combustion chamber 25) as a relative pressure from a predetermined reference pressure, and outputs a signal representing the in-cylinder relative pressure detection value Pmeas. .
[0034]
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 72, supplies signals from the sensors 61 to 72 to the CPU 81, and in accordance with instructions from the CPU 81, the actuator 33a of the intake valve control device 33, the igniter 38, the injector 39, and the throttle. A drive signal is transmitted to the valve actuator 43a and the SCV actuator 44a.
[0035]
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.
[0036]
(Method of determining fuel injection amount fi / estimating method of cylinder intake air amount Mc)
This fuel injection amount control device (intake air amount estimating device) must inject fuel into the cylinder before the intake valve 32 of the cylinder in the intake stroke closes. It is necessary to predict the intake air amount (in-cylinder (combustion chamber) intake air amount) that would be drawn into the same cylinder (that is, when the intake valve is closed). On the other hand, the intake pipe pressure PMFWD when the intake valve is closed is proportional to the in-cylinder intake air amount Mc sucked into the combustion chamber 25. Therefore, if the intake pipe pressure PMFWD can be predicted, the actual cylinder intake air amount Mc can be estimated.
[0037]
Therefore, the present fuel injection amount control device predicts and estimates the intake pipe pressure PMFWD when the intake valve is closed, and a predetermined coefficient is obtained by dividing the estimated intake pipe pressure PMFWD by the product of the displacement of one cylinder and the air density. To obtain the in-cylinder intake air amount Mc, and determine the fuel injection amount fi based on the following equation (1). In Equation 1, K is a coefficient that changes according to the set air-fuel ratio.
[0038]
(Equation 1)
fi = K · Mc
[0039]
Hereinafter, a method of estimating the intake pipe pressure PMFWD when the intake valve is closed will be described together with a model used for the estimation. As shown in FIG. 2, the intake pipe pressure PMFWD when the intake valve is closed is estimated by the electronic control throttle model M1, the throttle model M2, the intake valve model M3, and the intake manifold model M4.
[0040]
(1) Electronic control throttle model M1
The electronic control throttle model M1 is a model for estimating the throttle valve opening TAS when the intake valve is closed based on the accelerator pedal operation amount Accp up to the present 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 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 determined in accordance with 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 when the valve is closed is equal to the provisional target throttle valve opening θr1 before the time (Tt) from the current time. The target throttle valve opening θr is equal to the throttle valve opening TAS if the operation delay time of the throttle valve actuator 43a is ignored. Based on such a concept, the electronic control throttle model M1 determines the detected engine speed Ne and the intake valve opening / closing timing (advance amount) VT (the signal Ne) which is separately determined according to the operating state of the internal combustion engine 10. And the actual opening / closing timing VT obtained from the above-mentioned G2 signal.) The time t from the current time to the time when the intake valve is closed is obtained based on the time t, and the same time t and the predetermined time T before the current time. The throttle valve opening TAS when the intake valve is closed is estimated based on the history of the change in the accelerator pedal operation amount Accp (or the provisional target throttle valve opening θr1) up to the present time. Note that the throttle valve opening TAS when the intake valve is closed may be estimated in consideration of the operation delay time of the throttle valve actuator 43a.
[0042]
(2) Throttle model M2
The throttle model M2 calculates the amount of air passing through the throttle valve 43 (the amount of air passing through the throttle) mt by using the following equations 2 and 3 obtained based on the law of conservation of energy, the law of conservation of momentum, the law of conservation of mass, and the equation of state. Is a model that is estimated based on In Expressions 2 and 3, μ is a flow coefficient, At is a throttle opening area, ν is a flow velocity of air passing through the throttle valve 43, Pa is a throttle valve upstream pressure, Pm is an intake pipe pressure, Ta is an intake air temperature, ρm is an intake density, R is a gas constant, and κ is a specific heat ratio (hereinafter, κ is treated as a constant value in the present intake air amount estimating apparatus).
[0043]
(Equation 2)
mt = μ · At · ν · ρm = μ · At · ｛Pa / (R · Ta) ^1/2 ｝ ・ Φ (Pm / Pa)
[0044]
[Equation 3]

[0045]
Here, the above equation 2 indicates that k1 is a predetermined coefficient (= μ · At · ｛Pa / (R · Ta) ^1/2 ｝), When mts is the amount of air passing through the throttle when the intake valve is closed, it can be rewritten as the following equation 4. In Equation 4, if the amount of air passing through the throttle is mtsTA and the intake pipe pressure is PmTA when the internal combustion engine 10 is in a steady state (when the throttle valve opening is constant), the following Equation 5 is obtained. , Eq. 4 and Eq. 5 to eliminate the coefficient k1 to obtain Eq.
[0046]
(Equation 4)
mts = k1 · Φ (Pm / Pa)
[0047]
(Equation 5)
mtsTA = k1 · Φ (PmTA / Pa)
[0048]
(Equation 6)
mts = {mtsTA / Φ (PmTA / Pa)} · Φ (Pm / Pa)
[0049]
The value {mtsTA / Φ (PmTA / Pa)} on the right side of Equation 6 above is a value related to the intake air flow rate (throttle passing air amount) when the throttle valve opening TA is constant, and the throttle valve opening TA, When the engine rotation speed Ne, the intake valve opening / closing timing VT, and the throttle valve upstream pressure Pa are determined, the values are substantially uniquely determined. The throttle model M2 is a table that defines the relationship between the value {mtsTA / Φ (PmTA / Pa)} and the throttle valve opening TA, the engine speed Ne, the opening / closing timing VT of the intake valve, and the throttle valve upstream pressure Pa. Stored in the ROM 82, based on this table and the estimated throttle valve opening TAS when the intake valve is closed, the actual engine speed Ne, the actual intake valve opening / closing timing VT, and the actual throttle valve upstream pressure Pa. To obtain the value {mtsTA / Φ (PmTA / Pa)}.
[0050]
The value Φ (Pm / Pa) on the right side of Equation 6 is, as understood from Equation 3, a value determined by the intake pipe pressure Pm and the throttle valve upstream pressure Pa when the specific heat ratio κ is constant. It is. The throttle model M2 stores, in the ROM 82, a table that defines the relationship between the intake pipe pressure Pm, the throttle valve upstream pressure Pa, and the value Φ (Pm / Pa), and stores this table and an intake manifold model M4 described later. Calculates a value Φ (Pm / Pa) based on the latest intake pipe pressure Pm already calculated at the present time and the actual throttle valve upstream pressure Pa. As described above, the throttle passing air amount mts when the intake valve is closed is obtained.
[0051]
(3) Intake valve model M3
The intake valve model M3 is a model that estimates the in-cylinder intake air flow rate mc from the intake pipe pressure Pm, the intake pipe temperature Tm, the intake temperature THA, and the like. The in-cylinder pressure when the intake valve is closed can be regarded as the pressure upstream of the intake valve 32, that is, the intake pipe pressure Pm when the intake valve is closed. Therefore, the in-cylinder intake air flow rate mc is equal to the intake pipe pressure Pm when the intake valve is closed. Is proportional to Thus, the intake valve model M3 calculates the in-cylinder intake air flow rate mc according to the following equation 7 based on an empirical rule.
[0052]
(Equation 7)
mc = (Ta / Tm) · (c · Pm−d)
[0053]
In Equation 7, the value c is a proportional coefficient, and the value d is the amount of burned gas remaining in the cylinder. The intake valve model M3 stores, in the ROM 82, tables respectively defining the relationship between the engine rotation speed Ne, the opening / closing timing VT of the intake valve, the proportionality coefficient c, and the burned gas amount d. The proportional coefficient c and the burned gas amount d are obtained from the rotational speed Ne, the actual intake valve opening / closing timing VT, and the stored table. At the time of calculation, the intake valve model M3 calculates the immediately preceding (latest) intake pipe pressure Pm at the time of closing the intake valve and the immediately preceding intake pipe air temperature Tm estimated by the intake manifold model M4 described later. 7 to estimate the in-cylinder intake air flow rate mc when the intake valve is closed.
[0054]
(4) Intake manifold model M4
The intake manifold model M4 calculates the intake pipe pressure Pm when the intake valve is closed and the intake pipe temperature Tm when the intake valve is closed according to the following equations 8 and 9 based on the law of conservation of mass and the law of conservation of energy, respectively. Ask. Here, V is the volume of the intake pipe, R is the gas constant, mt is the amount of air passing through the throttle, and Ta is the temperature of air passing through the throttle valve (that is, the intake air temperature Ta).
[0055]
(Equation 8)
dPm / dt = κ · (R / V) · (mt · Ta−mc · Tm)
[0056]
(Equation 9)
d (Pm / Tm) / dt = (R / V) · (mt−mc)
[0057]
As shown in FIG. 2, the intake manifold model M4 uses the throttle passing air amount mts estimated by the throttle model M2 as the throttle passing air amount mt in the above equations 8 and 9, and is estimated by the intake valve model M3. The in-cylinder intake air flow rate mc when the intake valve is closed is used as the in-cylinder intake air flow rate mc in Equations 8 and 9. The intake pipe pressure Pm estimated by the intake manifold model M4 becomes the estimated intake pipe pressure PMFWD when the intake valve is closed.
[0058]
As described above, the present fuel injection amount control device calculates the intake pipe pressure PMFWD when the intake valve is closed using each of the simulation models of the electronic control throttle model M1, the throttle model M2, the intake valve model M3, and the intake manifold model M4. Predicted / estimated, a predetermined calculation is performed on the estimated intake pipe pressure PMFWD to determine the in-cylinder intake air amount Mc, and the fuel injection amount fi is determined based on the above equation (1).
[0059]
(Acquisition of the gas state in the cylinder at the start of the compression stroke)
The fuel injection amount control device normally uses the various models as described above to calculate the in-cylinder intake air amount Mc in the specific cylinder that enters the intake stroke each time the cylinder enters the intake stroke. The in-cylinder gas state acquisition device according to the present invention included in the fuel injection amount control device acquires the gas state in the cylinder at the start of the compression stroke in the specific cylinder every time a predetermined condition is satisfied, as follows. Then, an in-cylinder intake gas amount (mass) sucked into the cylinder, an in-cylinder absolute pressure in the cylinder at the start of the compression stroke, and the like are obtained.
[0060]
(1) Acquisition of in-cylinder relative pressure detection value
First, the present device uses the intake valve opening / closing timing (advance amount) VT of the intake valve 32 obtained from the signal obtained by the crank position sensor 68 and the G2 signal obtained by the cam position sensor 66, based on the intake valve of the specific cylinder. The crank angle θca at the compression stroke start time (predetermined time) at which the valve 32 closes (transition from the open state to the closed state) is obtained, and the value is set as the crank angle θ (1).
[0061]
Then, as shown in FIG. 4, when the crank angle θca obtained by the crank position sensor 68 becomes the crank angle θ (1), the in-cylinder relative pressure detection obtained by the in-cylinder relative pressure sensor 72 at that time is performed. The value Pmeas is stored in the RAM 83 as the in-cylinder relative pressure detection value Pmeas (1). Thereafter, the present apparatus sets the value of the crank angle θca in order as the crank angle θ (H) (H = 2, 3,...) Every time the crank angle θca advances by a predetermined constant interval (calculation interval) Δθ. Whenever the crank angle θca becomes the crank angle θ (H) (H = 2, 3,...), The in-cylinder relative pressure detection value Pmeas at that time is replaced with the in-cylinder relative pressure detection value Pmeas (H ) Are sequentially stored in the RAM 83 as (H = 2, 3,...).
[0062]
The present apparatus continuously performs such processing until the end of the compression stroke in which the ignition plug 37 of the specific cylinder is ignited and the specific cylinder shifts to the explosion stroke, and the value of the variable H at the end of the compression stroke is determined. Is set as the number of samples N. In this manner, the present apparatus provides a plurality of (N) in-cylinder relative pressure detection values Pmeas (H) (H = H) in a predetermined section from the start of the compression stroke, which is the predetermined time, to the end of the compression stroke. , N-1, N) and sequentially stores them in the RAM 83.
[0063]
(2) Temporary setting of in-cylinder intake gas amount and in-cylinder gas average temperature
Next, the present apparatus performs the compression stroke (hereinafter, this compression stroke) during which the plurality of in-cylinder relative pressure detection values Pmeas (H) (H = 1, 2,..., N-1, N) are obtained. Is referred to as a “specific compression stroke”.) The in-cylinder intake gas (air-fuel mixture) amount (mass) Mcm sucked into the cylinder of the specific cylinder, and the in-cylinder gas in the cylinder at the start of the specific compression stroke The average temperature Tcm is provisionally set according to the following equations (10) and (11).
[0064]
(Equation 10)
Mcm = fi + Mc
[0065]
[Equation 11]
Tcm = Tm
[0066]
In the above equation (10), fi is the fuel injection amount actually injected into the specific cylinder immediately before the start of the specific compression stroke of the specific cylinder, and Mc is the same fuel injection amount estimated using each of the models. This is the in-cylinder intake air amount during the specific compression stroke of the cylinder. In the above equation 11, Tm is the intake pipe temperature Tm estimated by the intake manifold model M4 when the intake valve of the specific cylinder is closed (at the start of the specific compression stroke). As described above, the means for temporarily setting the in-cylinder intake gas amount Mcm and the in-cylinder gas average temperature Tcm by using the above Equations 10 and 11 constitutes the temporary setting means.
[0067]
(3) Calculation of temporary pressure correction value and setting of temporary in-cylinder absolute pressure set value
Next, the present device uses the value of the in-cylinder intake gas amount Mcm and the value of the in-cylinder gas average temperature Tcm provisionally set as described above to perform the above-described identification of the specific cylinder by the following equation 12 based on a state equation. A temporary in-cylinder absolute pressure P0 at the start of the compression stroke (one of the states of gas in the cylinder of the specific cylinder at the start of the specific compression stroke) is determined (temporarily set).
[0068]
(Equation 12)
P0 = (Mcm · Rg · Tcm) / Vcm (1)
[0069]
In the above equation (12), Rg is a gas constant (different from the gas constant R described above), and Vcm (1) is the time when the specific compression stroke starts, that is, the time when the crank angle θca becomes the crank angle θ (1). Is the cylinder volume obtained by using the known position of the piston 22 in FIG.
[0070]
Next, the present device calculates the in-cylinder relative pressure P0 obtained as described above and the in-cylinder relative pressure detection value Pmeas (1) at the start of the specific compression stroke according to the following Expression 13. A temporary pressure correction value ΔP shown in FIG. 4 is obtained.
[0071]
(Equation 13)
ΔP = P0−Pmeas (1)
[0072]
Then, the present apparatus calculates the temporary pressure correction value ΔP obtained as described above and the N in-cylinder relative pressure detection values Pmeas (H) (H = 1, 2,..., N−1, N), the N temporary in-cylinder absolute pressure set values Pc (H) (H = 1, 2,..., N) in the predetermined section shown in FIG. −1, N). As described above, the temporary pressure correction value ΔP is obtained by using the above equation (13), and the temporary in-cylinder absolute pressure set value Pc (H) (H = 1, 2,...) By using the following equation (14). , N−1, N) constitute a first calculating means.
[0073]
[Equation 14]
Pc (H) = Pmeas (H) + ΔP (H = 1, 2,..., N−1, N)
[0074]
(4) Calculation of temporary cylinder absolute pressure calculation value
Next, the present apparatus sets the value of the temporary in-cylinder absolute pressure P0 of the gas state in the cylinder of the specific cylinder at the start of the specific compression stroke temporarily set as described above, and the in-cylinder intake gas Using the quantity Mcm as an initial condition, a cylinder model described by the following equations 15 to 17 based on the law of conservation of energy and the following equation 18 based on the equation of state and N cylinders in the predetermined section shown in FIG. A temporary in-cylinder absolute pressure calculation value Pcm (H) (H = 1, 2,..., N-1, N) is obtained.
[0075]
[Equation 15]

[0076]
(Equation 16)

[0077]
[Equation 17]

[0078]
(Equation 18)

[0079]
Equation 15 is a basic equation based on the law of conservation of energy. As shown in FIG. 5 schematically showing the specific cylinder, in Equation 15, Pcm is a tentative in-cylinder absolute pressure calculation value, and Vcm is a cylinder volume. , Q is the amount of heat transferred per unit time from the outside of the cylinder 21 (cylinder wall surface, intake port, etc.) into the cylinder 21, and κ is the specific heat ratio. The above equation (16) is a basic equation representing the heat transfer amount Q in the above equation (15). In the same equation (16), A is the cylinder surface area, hw is the heat transfer coefficient, Tcm is the cylinder gas average temperature, and Tw is the cylinder interior wall surface Temperature.
[0080]
Expression 17 is a formula expressing the heat transfer coefficient hw in Expression 16 using a so-called Woschini model. In Expression 17, di is the cylinder inner diameter, and C1 is a constant (2.28 in this example). , Cw is the average piston speed. Equation 18 is an equation based on a state equation applied to a gas (air-fuel mixture) sealed in a specific cylinder in the specific compression stroke. In Equation 18, Rg is a gas different from the gas constant R described above. The constant, Mcm, is the in-cylinder intake gas amount (mass).
[0081]
Here, the cylinder volume Vcm, the time differential value dVcm / dt of the cylinder volume, and the in-cylinder surface area A can be obtained based on the crank angle θca obtained by the crank position sensor 68, and the average piston speed Cw is calculated based on the engine rotation speed Ne. The cylinder inner wall surface temperature Tw can be substituted by the cooling water temperature THW obtained by the water temperature sensor 69. The specific heat ratio κ can be expressed as a function of the in-cylinder gas average temperature Tcm.
[0082]
Therefore, in the cylinder model described by the above Expressions 15 to 18, if the values of the in-cylinder intake gas amount Mcm and the temporary in-cylinder absolute pressure calculation value Pcm at the time t are obtained, the above Expression 18 shows The in-cylinder gas average temperature Tcm at the time t can be obtained, and as a result, the heat transfer coefficient hw at the time t can be obtained from Expression 17 above. Then, the heat transfer amount Q at the time t can be obtained by the equation (16), and as a result, the temporary in-cylinder absolute pressure calculated value Pcm at the time (t + dt) can be theoretically obtained by the equation (15). Therefore, if the values of the in-cylinder intake gas amount Mcm and the provisional in-cylinder absolute pressure P0 are given as initial conditions (the values at the start of the specific compression stroke), the cylinder model theoretically operates in the predetermined section. , The temporary in-cylinder absolute pressure calculation value Pcm can be sequentially obtained.
[0083]
In practice, the present apparatus performs the following calculation of the N provisional in-cylinder absolute pressure values Pcm (H) (H = 1, 2,..., N−1, N). First, in the above equation (15), d / dt is expressed as (d / dθ) · (dθ / dt) = (d / dθ) · ω (θ is the crank angle, ω is the angular speed of the crankshaft (that is, the engine speed Ne). ), The following equation 19 is obtained.
[0084]
[Equation 19]

[0085]
By multiplying both sides of Equation 19 by (κ-1) / (ω · Vcm), the following Equation 20 is obtained.
[0086]
(Equation 20)

[0087]
Here, in order to discretize the above equation 20 with the calculation interval Δθ with respect to the crank angle θ, dPcm / dθ and dκ / dθ on the left side of the equation 20 are rewritten using the following equations 21 and 22, respectively. In Equation 20, Pcm is Pcm (θ), κ is κ (θ), Vcm is Vcm (θ), dVcm / dθ is dVcm (θ) / dθ, ω is ω (θ), and Q is Q (θ). By rewriting each, the following Expression 23 is obtained.
[0088]
(Equation 21)

[0089]
(Equation 22)

[0090]
(Equation 23)

[0091]
In addition, when A is rewritten as A (θ), hw is expressed as hw (θ), and Tcm is expressed as Tcm (θ), the following Expression 24 is obtained.
[0092]
[Equation 24]

[0093]
Also, by rewriting the above Expression 17 and the above Expression 18, the following Expression 25 and the following Expression 26 are obtained, respectively.
[0094]
(Equation 25)

[0095]
(Equation 26)

[0096]
Then, the present apparatus sets the in-cylinder intake gas amount Mcm to the in-cylinder intake gas amount Mcm provisionally set as described above as an initial condition, and sets the value of the provisional in-cylinder absolute pressure P0 to the crank angle θca. Is set to the provisional in-cylinder absolute pressure calculation value Pcm (1) at the start of the specific compression stroke at which the crank angle θ (1) is obtained. Can be obtained, and as a result, the heat transfer coefficient hw (1) when the crank angle θca becomes the crank angle θ (1) can be obtained from the above equation (25). it can. Further, the specific heat ratio κ (1) when the crank angle θca becomes the crank angle θ (1) can be obtained from the in-cylinder gas average temperature Tcm (1). Note that κ (0) is set as the same value as κ (1).
[0097]
Further, the present apparatus can obtain the heat transfer amount Q (1) when the crank angle θca becomes the crank angle θ (1) according to the above equation (24). As a result, the crank angle θca is calculated by the above equation (23). The temporary in-cylinder absolute pressure calculation value Pcm (2) when θ (2) (crank angle θ (1) + Δθ) is obtained can be obtained. In other words, when the temporary in-cylinder absolute pressure calculation value Pcm (1) is obtained, the present apparatus calculates the temporary in-cylinder absolute pressure calculation value Pcm (2) by using Equations 23 to 26 above. You can ask.
[0098]
Therefore, by repeatedly using the above equations 23 to 26, the present apparatus, as shown in FIG. 4, allows the N temporary in-cylinder absolute pressure calculated values Pcm (H) (H , 1, 2,..., N−1, N). As described above, the means for calculating the provisional in-cylinder absolute pressure calculation value Pcm (H) (H = 1, 2,..., N-1, N) using the above equations 23 to 26 is (2) Construct a calculation means.
[0099]
(5) Calculation of deviation index value
Next, the present apparatus performs N temporary in-cylinder absolute pressure set values Pc (H) and N temporary in-cylinder absolute pressure calculated values Pcm (H) (H = 1, 2, .., N−1, N) as a deviation index value indicating the degree of deviation (a value that changes according to the area of a region indicated by a large number of dots in FIG. 4) by the following Expression 27. The value E is adopted. As described above, the means for calculating the deviation index value E using the following Expression 27 constitutes the deviation index value calculation means.
[0100]
[Equation 27]

[0101]
(6) Identification of in-cylinder intake gas amount Mcm and in-cylinder gas average temperature Tcm
After obtaining the deviation index value E as described above, the present apparatus repeatedly executes the series of processes (2) to (5) so that the deviation index value E is minimized. The in-cylinder intake gas amount Mcm and the in-cylinder gas average temperature Tcm at the start of the specific compression stroke, which are temporarily set according to the above Expressions 10 and 11, are identified. The value of the gas average temperature Tcm is set as the determined in-cylinder intake gas amount Mcfin and the determined in-cylinder gas average temperature Tcfin, which are true values, respectively. Details of such an identification method will be described later.
[0102]
Then, the present apparatus applies the value of the determined in-cylinder intake gas amount Mcfin in place of Mcm and the determined in-cylinder gas average temperature Tcfin in place of Tcm in Equation 12 to obtain the specific compression stroke start time. Then, the determined in-cylinder absolute pressure Pcfin, which is the true value of the in-cylinder absolute pressure, is obtained, and the true state of the gas sucked into the cylinder of the specific cylinder at the start of the specific compression stroke is completely obtained. Thus, the means for acquiring the true state of the gas sucked into the cylinder of the specific cylinder at the start of the specific compression stroke constitutes the in-cylinder gas state obtaining means.
[0103]
Thus, the present device obtains the true in-cylinder intake air amount during the specific compression stroke of the specific cylinder by subtracting the actual fuel injection amount fi from the determined in-cylinder intake gas amount Mcfin. Is compared with the value of the in-cylinder intake air amount Mc in the same specific cylinder during the same specific compression stroke, which is estimated by using the above-described models. The tables stored in the ROM 82 are corrected in order to obtain the proportional coefficient c and the burned gas amount d, respectively.
[0104]
Further, the present apparatus calculates a definite pressure correction value ΔPfin, which is a true pressure correction value, according to Equation 28 below.
[0105]
[Equation 28]
ΔPfin = Pcfin−Pmeas (1)
[0106]
Accordingly, the present device adds the determined pressure correction value ΔPcfin to the in-cylinder relative pressure detection value Pmeas, which is the output value of the in-cylinder relative pressure sensor 72, after the point in time when the determined pressure correction value ΔPfin is calculated according to Equation 28. , The absolute pressure in the cylinder 21 can be determined with high accuracy, and the occurrence of abnormal combustion (for example, knocking, misfire, etc.) of the internal combustion engine 10 can be detected with high accuracy. As described above, the means for obtaining the definite pressure correction value ΔPfin using the above equation 28 constitutes a pressure correction value acquisition means. As described above, the gas state in the cylinder at the start of the specific compression stroke of the specific cylinder is obtained.
[0107]
(Actual operation)
Next, the CPU 81 of the electric control device 80 executes the actual operation of the present fuel injection amount control device configured as described above and the in-cylinder gas state acquisition device according to the present invention included in the fuel injection amount control device. This routine will be described with reference to FIGS.
[0108]
(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. 6 every time a predetermined time (1 msec) elapses. Therefore, at a predetermined timing, the CPU 81 starts the process from step 600 and proceeds to step 605 to read the accelerator pedal operation amount Accp. Next, the CPU 81 proceeds to step 610, and in step 610, 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.
[0109]
Next, the CPU 81 proceeds to step 615, sets the variable I to “64”, and stores the value of θr (I−1) in the stored value θr (I) in the following step 620. 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 625, and determines 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 625 and proceeds to step 630, in which the value of the variable I is reduced by “1”. Thereafter, the flow returns to step 620. As a result, when step 620 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”.
[0110]
Thereafter, when the process of step 630 is repeated and the value of the variable I becomes “1”, the CPU 81 determines “Yes” in step 625 and proceeds to step 635, and in step 635, the CPU 81 determines the value in step 610. 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.
[0111]
Next, the CPU 81 proceeds to step 640, in which the stored value θr (64) is set as the final target throttle valve opening θr, and in step 645, 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 695.
[0112]
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). Thus, the electronic control throttle model M1 can estimate the throttle valve opening TAS when the intake valve is closed.
[0113]
(Calculation of fuel injection amount fi, injection instruction)
When the crank angle θca of the specific cylinder that reaches the intake stroke becomes an angle (for example, BTDC 90 °) that is a predetermined crank angle before the intake top dead center of that cylinder, the CPU 81 executes the routine for calculating the fuel injection amount fi in FIG. The process starts from step 700 and proceeds to step 705, in which the in-cylinder intake air amount Mc based on the intake pipe pressure PMFWD when the intake valve is closed, which is separately calculated according to each model shown in FIG. 2, is read. The in-cylinder intake air amount Mc is determined by a routine (not shown) according to each model shown in FIG. 2 that is repeatedly executed at predetermined time intervals.
[0114]
Next, the CPU 81 proceeds to step 710, and calculates the fuel injection amount fi based on the value of the in-cylinder intake air amount Mc read in step 705 and the right side of the above equation (1). Then, the CPU 81 proceeds to step 715, sends a drive signal to the injector 39 for the specific cylinder so as to inject fuel by the fuel injection amount fi calculated in step 710, and proceeds to step 795 to temporarily execute this routine. finish.
[0115]
(Judgment of calculation start of in-cylinder intake gas amount)
The CPU 81 executes a routine for calculating the in-cylinder intake gas amount shown by the flowchart in FIG. 8 every time a predetermined time elapses. Therefore, at a predetermined timing, the CPU 81 starts the process from step 800 and proceeds to step 805 to determine whether or not the value of the in-cylinder relative pressure acquisition process execution flag XHAN is “0”. The in-cylinder relative pressure acquisition process execution flag XHAN indicates that the acquisition process of the in-cylinder relative pressure detection value Pmeas is being executed based on the output of the in-cylinder relative pressure sensor 72 when the value is “1”, When the value is "0", it indicates that the acquisition process of the in-cylinder relative pressure detection value Pmeas is not executed.
[0116]
Now, the description will be continued assuming that the calculation start condition for the in-cylinder intake gas amount and the like described later is not satisfied and the acquisition process of the in-cylinder relative pressure detection value Pmeas is not executed. The value of the process execution flag XHAN is “0”. Accordingly, the CPU 81 determines “Yes” in step 805, and proceeds to step 810, in which the calculation start condition such as the in-cylinder intake gas amount is satisfied, and the crank angle θca of the specific cylinder reaching the intake stroke is adjusted to the above-described opening / closing state. It is determined whether or not the angle before the intake valve closing angle calculated based on the timing (advance amount) VT by a calculation interval Δθ (constant value) is an angle.
[0117]
The conditions for starting the calculation of the in-cylinder intake gas amount and the like are that the cooling water temperature THW is equal to or higher than a predetermined temperature, the vehicle speed obtained by a vehicle speed sensor (not shown) is equal to or higher than a predetermined high vehicle speed, and the throttle valve opening degree TA per unit time. Is established when the engine is operating in a steady state in which the amount of change is equal to or less than a predetermined amount. Further, the calculation start conditions include that a predetermined time or more has elapsed since the previous calculation of the in-cylinder intake gas amount or the like, that the vehicle has been driven for a predetermined distance or more from the previous calculation time of the in-cylinder intake gas amount or the like, Any one or more of the fact that the internal combustion engine 10 has been operated for a predetermined time or more from the previous calculation of the in-cylinder intake gas amount or the like may be added. At this stage, as described above, since the calculation start condition for the in-cylinder intake gas amount and the like is not satisfied, the CPU 81 determines “No” in step 810, proceeds to step 895, and ends this routine once. .
[0118]
Next, the description will be continued assuming that the calculation start condition for the in-cylinder intake gas amount or the like is satisfied. When the CPU 81 proceeds to step 810, the CPU 81 calculates the crank angle θca of the specific cylinder from the angle at the time of closing the intake valve by the calculation interval Δθ. If the angle is just the previous angle, the determination in step 810 is “Yes” and the process proceeds to step 815 to start the in-cylinder relative pressure acquisition process. In step 820, the value of the variable H is set to “0”. In step 825, the value of the crank angle θca of the specific cylinder obtained at this moment by the crank position sensor 68 is set as a variable. After storing the value in θ1, the routine proceeds to step 895, and this routine is temporarily ended.
[0119]
Thereafter, the CPU 81 repeatedly executes the routine of FIG. 8 from step 800. However, since the value of the in-cylinder relative pressure acquisition process execution flag XHAN is “1”, when the process proceeds to step 805, the CPU 81 executes step 805. Is determined to be "No" and the routine proceeds to step 830, where it is determined whether or not the ignition plug 37 of the specific cylinder is ignited (whether or not the current time is before the end of the specific compression stroke of the specific cylinder). Is determined. At this time, since the specific cylinder is in a state immediately before the intake valve is closed (immediately before the start of the specific compression stroke), the CPU 81 determines “Yes” in step 830, proceeds to step 895, and ends this routine once. Thus, the processing of steps 800, 805, 830, and 895 is repeatedly executed until the specific compression stroke of the specific cylinder is completed, and the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is maintained at "1".
[0120]
(Acquisition of in-cylinder relative pressure, etc.)
On the other hand, the CPU 81 repeatedly executes the routine for obtaining the in-cylinder relative pressure shown in FIG. 9 every time a predetermined time elapses. Therefore, at a predetermined timing, the CPU 81 starts the process from step 900 and proceeds to step 905 to determine whether or not the value of the in-cylinder relative pressure acquisition process execution flag XHAN is “1”. Here, if the value of the in-cylinder relative pressure acquisition process execution flag XHAN is “0”, the CPU 81 immediately proceeds to step 995 to temporarily end this routine, but at this time, the process of step 815 in FIG. Since the value of the in-cylinder relative pressure acquisition process execution flag XHAN is “1”, “Yes” is determined in step 905, and the process proceeds to step 910, where the identification obtained by the crank position sensor 68 at the present time is performed. The value of the crank angle θca of the cylinder is stored in a variable θ2.
[0121]
Next, the CPU 81 proceeds to step 915, and calculates the value of the crank angle θca at the time of the processing of step 825 in FIG. 8 from the value of the variable θ2 in which the value of the crank angle θca at the time of the processing of step 910 is stored. It is determined whether or not the value (angle) obtained by subtracting the value of the variable θ1 in which is stored is equal to or longer than the above calculation interval Δθ. Since the current time is immediately after the execution of the process of step 825 in FIG. 8, the value obtained by subtracting the value of the variable θ1 from the value of the variable θ2 is less than the calculation interval Δθ at this time. If the determination is "No", the process immediately proceeds to step 995 to temporarily end the present routine.
[0122]
Thereafter, the CPU 81 repeatedly executes the processing of the steps 900 to 915 until the value obtained by subtracting the value of the variable θ1 from the value of the variable θ2 becomes equal to or longer than the above-mentioned calculation interval Δθ. Then, the processing of step 910 is repeated, and the value of the variable θ2 increases with the increase of the crank angle θca. When the value obtained by subtracting the value of the variable θ1 from the value of the variable θ2 reaches the calculation interval Δθ, the CPU 81 proceeds to step 915. When the process has proceeded to, the determination is “Yes”, and the acquisition processing of the in-cylinder relative pressure and the like from step 920 onward is started. Since this time is a time when the calculation interval Δθ has elapsed from the time when “Yes” is determined in step 810 of FIG. 8 described above, it corresponds to the time when the intake valve of the specific cylinder is closed (the time of starting the specific compression stroke). are doing.
[0123]
When the CPU 81 proceeds to step 920, the CPU 81 stores a value obtained by increasing the value of the variable H at that time by “1” as a new variable H. At this time, the value of the variable H has been set to “0” by the processing of step 820 in FIG. 8 described above, and thus the value of the variable H is set to “1” by this processing. Next, the CPU 81 proceeds to step 925, and stores the value of the variable θ2 in which the current crank angle θca is stored in the crank angle θ (H). As a result, the value of the crank angle θca at the start of the specific compression stroke is stored in the crank angle θ (1).
[0124]
Next, the CPU 81 proceeds to step 930, and stores the in-cylinder relative pressure detection value Pmeas at the present time as the in-cylinder relative pressure detection value Pmeas (H). As a result, the in-cylinder relative pressure detection value Pmeas at the start of the specific compression stroke is stored in the in-cylinder relative pressure detection value Pmeas (1). Next, the CPU 81 proceeds to step 935, and sets a cylinder volume value obtained based on the value of the crank angle θ (H) and the function f1 of the crank angle θca as the cylinder volume Vcm (H). Thus, the value of the cylinder volume at the start of the specific compression stroke is stored in the cylinder volume Vcm (1).
[0125]
Next, the CPU 81 proceeds to step 940, and calculates a cylinder volume differential value dVcm (H) based on the value of the crank angle θ (H) and the cylinder volume crank angle obtained based on the function f2 of the crank angle θca. / Dθ. As a result, the cylinder volume differential value at the start of the specific compression stroke is stored in the cylinder volume differential value Vcm (1) / dθ.
[0126]
Next, the CPU 81 proceeds to step 945, and sets the value of the in-cylinder surface area obtained based on the value of the crank angle θ (H) and the function f3 of the crank angle θca as the in-cylinder surface area A (H). Thus, the value of the in-cylinder surface area at the start of the specific compression stroke is stored in the in-cylinder surface area A (1).
[0127]
Next, the CPU 81 proceeds to step 950, and stores the current value of the engine rotation speed Ne in the angular velocity ω (H). As a result, the value of the engine rotation speed Ne at the start of the specific compression stroke is stored in the angular velocity ω (1). Then, the CPU 81 proceeds to step 955, stores the value of the variable θ2 as the variable θ1, and then proceeds to step 995 to temporarily end the present routine.
[0128]
Thereafter, as long as the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is “1”, the CPU 81 repeatedly executes the processing of steps 910 and 915. Here, as described above, the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is maintained at “1” until the specific compression stroke ends. Therefore, from the present time until the end of the specific compression stroke, the process of step 910 is repeated, and the value of the variable θ2 increases with the increase of the crank angle θca, and the value of the variable θ2 has already been set in step 955 from the value of the variable θ2. Every time a value obtained by subtracting the latest value of the variable θ1 reaches the calculation interval Δθ, an acquisition process of the in-cylinder relative pressure and the like after step 920 is executed.
[0129]
As a result, every time the value of the crank angle θca increases by the calculation interval Δθ from the start of the specific compression stroke to the end of the specific compression stroke, the variable H increases by “1” and , Namely, the crank angle θ (H), the detected in-cylinder relative pressure value Pmeas (H), the cylinder volume Vcm (H), the cylinder volume differential value Vcm (H) / dθ, the in-cylinder surface area A (H), The angular velocity ω (H) (H = 1, 2, 3,...) Is sequentially set.
[0130]
Then, when the ignition plug 37 of the specific cylinder is ignited and the specific compression stroke is completed, when the CPU 81 proceeds to step 830 in FIG. 8, the CPU 81 determines “No” and proceeds to step 835 to execute the variable H at the present time. Is stored as the number of samples N. Next, the CPU 81 proceeds to step 840, sets the value of the cooling water temperature THW obtained by the water temperature sensor 69 at the present time as the cylinder inner wall surface temperature Tw, and in the subsequent step 845, based on the equation described in the step 845, The average value of the N angular velocities ω (H) (H = 1, 2,..., N−1, N) already calculated in step 950 of FIG. 9 is set as the average rotation speed Nemean, In the following step 850, the average piston speed obtained based on the value of the average rotation speed Nemean and the function f4 of the engine rotation speed Ne is stored as the average piston speed Cw.
[0131]
Next, the CPU 81 proceeds to step 855, in which the value of the fuel injection amount fi actually injected into the specific cylinder immediately before the start of the specific compression stroke in accordance with each model shown in FIG. A value obtained by adding the value of the in-cylinder intake air amount Mc during the same specific compression stroke of the specific cylinder estimated by a routine not shown is temporarily set as the in-cylinder intake gas amount M.
[0132]
Next, the CPU 81 proceeds to step 860, in which the value of the intake pipe temperature Tm at the time of closing the intake valve of the specific cylinder (at the start of the specific compression stroke) estimated by a routine (not shown) according to the intake manifold model M4 shown in FIG. Is temporarily set as the in-cylinder gas average temperature T. Then, the CPU 81 proceeds to step 865 to set the value of the in-cylinder intake gas amount M as the in-cylinder intake gas amount Mcm, and in a subsequent step 870, sets the value of the in-cylinder gas average temperature T to the in-cylinder gas average. After the temperature is set as Tcm, the routine proceeds to step 875, where the routine for calculating the deviation index value shown in FIG. 10 is executed.
[0133]
(Calculation of deviation index value)
That is, the CPU 81 starts the process from step 1000 and proceeds to step 1005, where the values of the in-cylinder intake gas amount Mcm and the in-cylinder gas average temperature Tcm set in steps 865 and 870 of FIG. Based on the value of the cylinder volume Vcm (1) already set in step 935 in FIG. 9 and the expression described in step 1005 corresponding to the right side of the above equation 12, the temporary value at the start of the specific compression stroke is calculated. Is calculated.
[0134]
Next, the CPU 81 proceeds to step 1010, sets the value of the temporary in-cylinder absolute pressure P0 as the temporary in-cylinder absolute pressure set value Pc (1), and in the next step 1015, the temporary in-cylinder absolute pressure Pc (1). The value of P0 is set as a provisional cylinder absolute pressure calculation value Pcm (1). Next, the CPU 81 proceeds to 1020, where the value of the in-cylinder absolute pressure set value Pc (1), the in-cylinder relative pressure detection value Pmeas (1) already set at 930 in FIG. The temporary pressure correction value ΔP is calculated based on the equation described in step 1020 corresponding to
[0135]
Next, the CPU 81 proceeds to step 1025, clears the value of the deviation index value E to “0”, and sets the variable I to “1” in the subsequent step 1030. Next, proceeding to step 1035, the value of the in-cylinder relative pressure detection value Pmeas (I) set in step 930 of FIG. 9, the provisional pressure correction value ΔP calculated in step 1020, and the above equation 14 The temporary in-cylinder absolute pressure set value Pc (I) is calculated based on the equation described in step 1035 corresponding to the right side of the above.
[0136]
Next, the CPU 81 proceeds to step 1040 to calculate the value of the temporary in-cylinder absolute pressure calculated value Pcm (I) (the value of the variable I is “1” at this time, and the temporary in-cylinder absolute pressure set in step 1015). The calculated pressure value Pcm (1), the value of the in-cylinder intake gas amount Mcm used in step 1005, the value of the cylinder volume Vcm (I) already set in step 935 of FIG. The in-cylinder gas average temperature Tcm (I) is calculated based on the equation described in step 1040 corresponding to the right side of the equation (26).
[0137]
Next, the CPU 81 proceeds to step 1045, and sets the specific heat ratio obtained based on the value of the in-cylinder gas average temperature Tcm (I) and the function f5 of the in-cylinder gas average temperature Tcm as the specific heat ratio κ (I). In the following step 1050, the value of the average piston speed Cw set in step 850 in FIG. 8, the value of the temporary in-cylinder absolute pressure calculation value Pcm (I) used in step 1040, and The heat transfer coefficient hw (I) is calculated based on the calculated value of the in-cylinder gas average temperature Tcm (I) and the expression described in step 1050 corresponding to the right side of the above equation 25.
[0138]
Next, the CPU 81 proceeds to step 1055, where the value of the in-cylinder surface area A (I) set in step 945 of FIG. 9, the value of the heat transfer coefficient hw (I), and the value of the cylinder calculated in step 1040 are set. The unit based on the value of the internal gas average temperature Tcm (I), the value of the in-cylinder wall surface temperature Tw set in step 840 of FIG. 8, and the expression in step 1055 corresponding to the right side of the above equation 24 The heat transfer amount Q (I) per hour is calculated.
[0139]
Next, the CPU 81 proceeds to step 1060, and sets the value of κ (I) and the value of κ (I-1) set in step 1045 (at this time, the value of the variable I is “1” and the value of κ (0) is The value is the same as the value of κ (1)), the value of the cylinder volume Vcm (I) used in step 1040, the cylinder volume differential value dVcm (I) / dθ set in step 940 in FIG. The value of the calculated in-cylinder absolute pressure value Pcm (I) used in step 1040, the value of the heat transfer amount Q (I) calculated in step 1055, and the angular velocity ω set in step 950 in FIG. The provisional in-cylinder absolute pressure calculation value Pcm (I + 1) is calculated based on the value of (I) and the expression described in Step 1060 corresponding to the right side of the above Expression 23.
[0140]
At this time, the value of the variable I is “1”, so in steps 1035 to 1060 described above, the provisional in-cylinder absolute pressure set value Pc (1), the in-cylinder gas average temperature Tcm (1), and the specific heat ratio κ ( 1), the heat transfer coefficient hw (1), the heat transfer amount Q (1), and the calculated in-cylinder absolute pressure value Pcm (2) are calculated and set.
[0141]
Next, the CPU 81 proceeds to step 1065 and subtracts the provisional in-cylinder absolute pressure set value Pc (I) from the provisional in-cylinder absolute pressure calculated value Pcm (I) to the value of the deviation index value E at that time. A value obtained by adding the squared value is set as a new deviation index value E. At this time, the value of the deviation index value E is “0” and the value of the variable I is “1”, so that the value of the deviation index value E is (Pcm (1) −Pc (1)) by this processing. ² It becomes.
[0142]
Then, the CPU 81 proceeds to step 1070 to determine whether or not the value of the variable I has become equal to the value of the number of samples N set in step 835 in FIG. Since the value of the variable I is “1” at this time, the CPU 81 determines “No” in step 1070 and proceeds to step 1075, increases the value of the variable I by “1”, and thereafter returns to step 1035.
[0143]
As a result, the value of the variable I becomes “2”, and in subsequent steps 1035 to 1060, the provisional in-cylinder absolute pressure set value Pc (2), the in-cylinder gas average temperature Tcm (2), and the specific heat ratio κ (2) , The heat transfer coefficient hw (2), the heat transfer amount Q (2), and the provisional in-cylinder absolute pressure calculation value Pcm (3) are calculated and set. Here, the temporary in-cylinder absolute pressure calculated value Pcm (2) used in step 1040 is the temporary in-cylinder absolute pressure calculated value Pcm (2) calculated when the process of step 1060 is executed immediately before. Is used.
[0144]
Next, the CPU 81 proceeds to step 1065 again, and sets the value of the deviation index value E at that time to (Pcm (2) -Pc (2)). ² Is set as a new deviation index value E. Such processing is repeated until the processing of step 1075 is repeated and the value of the variable I reaches the number of samples N. As a result, the deviation index value E becomes a value based on the equation shown in Expression 27.
[0145]
Then, when the value of the variable I reaches the number of samples N, the CPU 81 determines “Yes” in step 1070, proceeds to step 1095, ends this routine, and returns to step 880 in FIG. As described above, in the routine for calculating the deviation index value in FIG. 10, when the value of the in-cylinder intake gas amount Mcm and the value of the in-cylinder gas average temperature Tcm are set, the value of the in-cylinder intake gas amount Mcm and the in-cylinder intake gas amount Mcm are set. This is a routine for calculating a deviation index value E based on the value of the gas average temperature Tcm.
[0146]
Next, when the CPU 81 proceeds to step 880, it stores the value of the deviation index value E calculated by the above-described routine of FIG. 10 as the previous value of the deviation index value E1, and executes the in-cylinder relative pressure acquisition processing at step 885. After setting the value of the middle flag XHAN to "0", the routine proceeds to step 895, where the routine of FIG.
[0147]
Thereafter, the CPU 81 repeatedly executes the routine of FIG. 8 from step 800. However, since the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is “0”, it is determined “Yes” when the process proceeds to step 805. Then, the process proceeds to step 810. At this time, since the calculation start condition for the in-cylinder intake gas amount and the like described above has not been satisfied immediately after the calculation of the in-cylinder intake gas amount and the like has been completed, the CPU 81 returns “No” in step 810. After making a determination, the process proceeds to step 895, and this routine is once ended. As a result, the processing of steps 800, 805, 810, and 895 is repeatedly executed until the next calculation start condition such as the in-cylinder intake gas amount is satisfied, and the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is set to “ "0" is maintained.
[0148]
(Deviation index value minimization processing)
The CPU 81 repeatedly executes a routine for minimizing the deviation index value shown in FIG. 11 and subsequent FIG. 12 every time a predetermined time elapses. Accordingly, at a predetermined timing, the CPU 81 starts the process from step 1100 and proceeds to step 1102 to determine whether the value of the in-cylinder relative pressure acquisition process execution flag XHAN has changed from “1” to “0”. Monitor At this time, when the specific compression stroke of the specific cylinder ends, and the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is changed from “1” to “0” in step 885 of FIG. The CPU 81 determines “Yes” in step 1102 and proceeds to step 1104. If the value of the in-cylinder relative pressure acquisition processing execution flag XHAN has not changed, the CPU 81 proceeds directly from step 1102 to step 1195 in FIG. 12 to end this routine once.
[0149]
Now, assuming that it is immediately after the end of the specific compression stroke of the specific cylinder, the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is changed from “1” to “0” in step 885 of FIG. Immediately thereafter, the CPU 81 proceeds from step 1102 to step 1104, and sets a value obtained by adding the correction amount for identification ΔM to the value of the in-cylinder intake gas amount M at that time as the in-cylinder intake gas amount M (1). At the same time, the value of the in-cylinder gas average temperature T at that time is set as the in-cylinder gas average temperature T (1), and in the following step 1106, the identification correction amount is calculated from the in-cylinder intake gas amount M at that time. The value obtained by subtracting ΔM is set as the in-cylinder intake gas amount M (2), and the value of the in-cylinder gas average temperature T at that time is set as the in-cylinder gas average temperature T (2). In, the tube at that time The value of the in-cylinder intake gas amount M is set as the in-cylinder intake gas amount M (3), and the value obtained by adding the identification correction temperature ΔT to the value of the in-cylinder gas average temperature T at that time is the in-cylinder gas average temperature T In step 1110, the value of the in-cylinder intake gas amount M at that time is set as the in-cylinder intake gas amount M (4), and the in-cylinder gas average temperature T at that time is set. A value obtained by subtracting the correction temperature for identification ΔT from the value is set as the in-cylinder gas average temperature T (4) (at this time, the value of the in-cylinder intake gas amount M and the value of the in-cylinder gas average temperature T are respectively shown in FIG. Are the values set in steps 855 and 860 of FIG.
[0150]
Next, the CPU 81 proceeds to step 1112, sets the variable I to “1” and proceeds to step 1114, and sets the value of the in-cylinder intake gas amount M (I) and the value of the in-cylinder gas average temperature T (I) respectively. The in-cylinder intake gas amount Mcm and the in-cylinder gas average temperature Tcm are set. At this time, the value of the variable I is “1”, so that the value of the in-cylinder intake gas amount M (1) and the value of the in-cylinder gas average temperature T (1) are respectively equal to the in-cylinder intake gas amount Mcm and the in-cylinder gas average. The temperature is set as Tcm.
[0151]
Next, the CPU 81 proceeds to step 1116 to execute the above-described routine for calculating the deviation index value in FIG. Thereby, the deviation index value E based on the value of the in-cylinder intake gas amount M (1) and the value of the in-cylinder gas average temperature T (1) is calculated. Next, the CPU 81 proceeds to step 1118 to set the value of the deviation index value E as the deviation index value E (I). At this time, the value of the variable I is “1”, so the deviation index value E is set as the deviation index value E (1).
[0152]
Next, the CPU 81 proceeds to step 1120 and determines whether or not the value of the variable I is equal to “4”. At this time, since the value of the variable I is “1”, the CPU 81 determines “No” in step 1120 and proceeds to step 1122, increases the value of the variable I by “1”, and thereafter returns to step 1114. . As a result, in subsequent steps 1114 to 1118, a deviation index value E based on the value of the in-cylinder intake gas amount M (2) and the value of the in-cylinder gas average temperature T (2) is calculated, and the deviation index value E is calculated. Is set as the deviation index value E (2). Such a process is repeated until the process of step 1122 is repeated and the value of the variable I becomes “4”. As a result, the deviation index value E (I) is set to a value calculated based on the value of the in-cylinder intake gas amount M (I) and the in-cylinder gas average temperature T (I) (I = 1). , 2,3,4).
[0153]
Then, when the value of the variable I becomes “4”, the CPU 81 determines “Yes” in step 1120 and proceeds to step 1124 in FIG. 12, where the deviation index value E (I) (I = 1, 2, 3, 3) , 4), the value of the variable I corresponding to the smallest one is set as Imin, and the routine proceeds to step 1126, where the previous value E1 of the deviation index value at that time from the minimum deviation index value E (Imin) (currently, , The value obtained by subtracting the value set in step 880 in FIG. 8) is set as the deviation index value change amount ΔE.
[0154]
Next, the CPU 81 proceeds to step 1128, and determines whether or not the absolute value of the deviation index value change amount ΔE is equal to or greater than the minimization determination reference value ΔEref. Now, assuming that the absolute value of the deviation index value change amount ΔE is equal to or larger than the minimization determination reference value ΔEref, the CPU 81 determines “Yes” in step 1128, proceeds to step 1130, and proceeds to step 1130. The value of M (Imin) and the value of the in-cylinder gas average temperature T (Imin) are reset as the in-cylinder intake gas amount M and the in-cylinder gas average temperature T, respectively. After resetting E (Imin) as the previous value of the deviation index value E1, the process returns to step 1104 in FIG.
[0155]
As a result, in subsequent steps 1104 to 1110, the values of the in-cylinder intake gas amount M (I) and the in-cylinder gas average temperature T (I) (I = 1, 2, 3, 4) are set to the previous step 1130. Based on the in-cylinder intake gas amount M and the in-cylinder gas average temperature T set in advance, the processes in steps S1112 to S126 are performed. As a result, the minimum deviation index value E (Imin) is updated to a smaller value, and the previous value E1 of the deviation index value set in the previous step 1132 is updated from the updated new minimum deviation index value E (Imin). The subtracted value is set as a new deviation index value change amount ΔE.
[0156]
Then, it is determined again in step 1128 whether or not the absolute value of the new deviation index value change amount ΔE is equal to or greater than the minimization determination reference value ΔEref. As a result, the new deviation index value change amount ΔE is determined. If the absolute value is still equal to or greater than the minimization determination reference value ΔEref, the above-described processing is repeatedly executed until the absolute value of the new deviation index value change amount ΔE becomes less than the minimization determination reference value ΔEref.
[0157]
As a result, when the absolute value of the deviation index value change amount ΔE becomes smaller than the minimization determination reference value ΔEref, the minimum deviation index value E (Imin) at that time becomes the minimum value of the deviation index value E. At this time, the CPU 81 determines “No” in step 1128 and proceeds to step 1134, in which the value of the in-cylinder intake gas amount M (Imin) and the value of the in-cylinder gas average temperature T (Imin) at that time are The determined in-cylinder intake gas amount Mcfin and the determined in-cylinder gas average temperature Tcfin are respectively set, and in the following step 1136, the value of the determined in-cylinder intake gas amount Mcfin and the value of the determined in-cylinder gas average temperature Tcfin are set. The determined in-cylinder absolute pressure Pcfin is calculated based on the equation described in step 1136 corresponding to the right side of the above equation (12). Thus, the identification of the in-cylinder intake gas amount Mcm and the in-cylinder gas average temperature Tcm is completed.
[0158]
Next, the CPU 81 proceeds to step 1138, in which the value of the determined in-cylinder absolute pressure Pcfin, the in-cylinder relative pressure detection value Pmeas (1) set in step 930 of FIG. The determined pressure correction value ΔPfin is calculated based on the equation described in the corresponding step 1138.
[0159]
Next, the CPU 81 proceeds to step 1140 to obtain a true in-cylinder intake air amount during the specific compression stroke of the specific cylinder by subtracting the actual fuel injection amount fi from the determined in-cylinder intake gas amount Mcfin, By comparing the value of the true in-cylinder intake air amount with the value of the in-cylinder intake air amount Mc in the same specific compression stroke of the same cylinder estimated using each of the above-described models, Each table stored in the ROM 82 is corrected in order to obtain the proportional coefficient c and the burnt gas amount d in the above equation 7 describing the described intake valve model M3. Then, the CPU 81 proceeds to step 1195 to end this routine once.
[0160]
Thereafter, the CPU 81 repeatedly executes the routine of FIG. 11 and the subsequent routine of FIG. 12, but since the value of the in-cylinder relative pressure acquisition processing execution flag XHAN is maintained at “0”, the CPU 81 proceeds to step 1102 of FIG. If the determination is “No”, the process directly proceeds to step 1195 in FIG. 12 to temporarily end this routine.
[0161]
As described above, according to the embodiment of the in-cylinder gas state acquisition device according to the present invention, based on the output of the in-cylinder relative pressure sensor 72, the gas in the cylinder at the start of the specific compression stroke of the specific cylinder is determined. The true state could be obtained with high accuracy.
[0162]
Also, every time the above-described calculation start condition such as the in-cylinder intake gas amount is satisfied, the true in-cylinder intake gas amount (Mcfin-fi) is obtained, and the true in-cylinder intake gas amount (Mcfin-fi) is calculated. Each table for calculating the proportional coefficient c and the burnt gas amount d in the above equation (7) describing the intake valve model M3 is compared by comparing the in-cylinder intake air amount Mc estimated by each model with each other. As a result, it was possible to improve the accuracy of estimating the in-cylinder intake air amount Mc by the in-cylinder intake air amount estimating device constituted by the above models.
[0163]
Further, after the final pressure correction value ΔPfin is obtained, the in-cylinder in the cylinder 21 based on the in-cylinder relative pressure detection value Pmeas, which is the output value of the in-cylinder relative pressure sensor 72, and the same final pressure correction value ΔPfin. The absolute pressure can be accurately determined. Therefore, the occurrence of abnormal combustion (for example, knocking, misfire, etc.) of the internal combustion engine can be accurately detected.
[0164]
Further, the value of the in-cylinder intake gas amount Mcm temporarily set first is determined by the fuel injection amount fi actually injected into the specific cylinder immediately before the start of the specific compression stroke of the specific cylinder and the above-described model. Is calculated by adding the in-cylinder intake air amount Mc of the specific cylinder at the time of the specific compression stroke, which is estimated by using the intake manifold average temperature Tcm. This is the intake pipe temperature Tm when the intake valve of the specific cylinder is closed (at the start of the specific compression stroke) estimated by the model M4. Therefore, it is highly likely that the initially temporarily set value of the in-cylinder intake gas amount Mcm and the first temporarily set value of the in-cylinder gas average temperature Tcm are values close to the actual true values. Therefore, it was possible to reduce the number of repetitions of the processing executed when identifying the value of the in-cylinder intake gas amount Mcm and the value of the in-cylinder gas average temperature Tcm so that the deviation index value E was minimized.
[0165]
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 embodiment, the provisional setting means provisionally sets the in-cylinder intake gas amount Mcm (inhaled into the cylinder during the specific compression stroke) and the in-cylinder gas average temperature Tcm (at the start of the specific compression stroke). However, one of the in-cylinder intake gas amount Mcm and the in-cylinder gas average temperature Tcm and the tentative in-cylinder absolute pressure P0 (at the start of the specific compression stroke) are provisionally set. It may be configured as follows. In this case, the other value of the in-cylinder intake gas amount Mcm and the in-cylinder gas average temperature Tcm can be obtained based on an equation obtained by modifying the above equation (12). The state of the gas in the cylinder of the specific cylinder is provisionally set.
[0166]
Further, in the above embodiment, a plurality of (in the number of samples N) temporary in-cylinder absolute pressure set values Pc (H) (H = 1, 2,..., N-1, N) and the like are set. Although the end of the predetermined section of the compression stroke is set to the end of the specific compression stroke (the time of ignition by the ignition plug), the predetermined period (for example, the operation amount of the accelerator pedal) depends on the operation state of the internal combustion engine 10. When the control that does not inject fuel (so-called fuel cut control) is performed only during the period when Accp is "0", the end of the predetermined section is usually set to the end of the specific compression stroke, and the predetermined period is set. The inside may be set at the time when the position of the piston reaches the compression top dead center.
[0167]
Further, in the above embodiment, in the above equation (17) for obtaining the heat transfer coefficient hw (heat transfer amount Q) of the above equations (15) to (18) describing the cylinder model based on the energy conservation law and the state equation, Although the constant C1 is set to a constant value “2.28”, the value C1 is provisionally set by the provisional setting means, and the true value of the same value C1 is obtained by the in-cylinder gas state acquisition means (deviation index value E To identify the equivalency C1 such that is minimized).
[0168]
Further, in the above embodiment, the first calculating means causes the in-cylinder gas state obtaining means to repeatedly execute a series of processes performed by the temporary setting means, the first calculating means, the second calculating means, and the deviation index value calculating means. Based on a plurality of in-cylinder relative pressure detection values Pmeas (H) (H = 1, 2,..., N−1, N) in a predetermined section of the compression stroke obtained in advance in advance, The provisional in-cylinder absolute pressure set value Pc (H) (H = 1, 2,..., N-1, N) is configured to be set. Each time the internal gas state acquisition means repeatedly executes the series of processes, the plurality of in-cylinder relative pressure detection values Pmeas (H) (H = 1, 2,..., N-1, N) are newly updated. , And a plurality of newly detected in-cylinder relative pressure values Pmeas (H) (H = 1, 2,..., N−1) , N), the plurality of temporary in-cylinder absolute pressure set values Pc (H) (H = 1, 2,..., N-1, N) may be set.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a system in which a fuel injection amount control device including an in-cylinder gas state acquisition device according to the present invention is applied to a spark ignition type multi-cylinder internal combustion engine.
FIG. 2 is a functional block diagram showing a connection relation of various models adopted for estimating an in-cylinder intake air amount by the electric control device shown in FIG. 1;
FIG. 3 is a diagram 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. 4 shows a plurality of detected in-cylinder relative pressure values, a plurality of provisional in-cylinder absolute pressure set values, and a plurality of provisional in-cylinder absolute pressure calculated values with respect to a crank angle in a compression stroke of a specific cylinder shown in FIG. FIG. 6 is a diagram showing an example of a waveform based on each of the above.
FIG. 5 is a diagram conceptually showing a cylinder and its vicinity for explaining variables used for representing a cylinder model.
FIG. 6 is a flowchart showing a routine for controlling a throttle valve opening executed by the CPU shown in FIG. 1;
FIG. 7 is a flowchart showing a routine for calculating a fuel injection amount executed by a CPU shown in FIG. 1;
FIG. 8 is a flowchart showing a routine for determining whether or not to start calculation of an in-cylinder intake gas amount executed by the CPU shown in FIG. 1;
9 is a flowchart showing a routine executed by the CPU shown in FIG. 1 for acquiring a plurality of detected in-cylinder relative pressure values and the like.
FIG. 10 is a flowchart illustrating a routine for calculating a deviation index value executed by the CPU illustrated in FIG. 1;
FIG. 11 is a flowchart showing a first half of a routine for minimizing a deviation index value executed by the CPU shown in FIG. 1;
FIG. 12 is a flowchart illustrating a latter half of a routine for minimizing a deviation index value executed by the CPU illustrated in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Spark ignition type multi cylinder internal combustion engine, 20 ... Cylinder block part (engine body part), 21 ... Cylinder, 25 ... Combustion chamber, 31 ... Intake port, 32 ... Intake valve, 39 ... Injector, 41 ... Intake pipe, 43 ... throttle valve, 68 ... crank position sensor, 71 ... accelerator opening sensor, 72 ... cylinder relative pressure sensor, 80 ... electric control device, 81 ... CPU.

Claims (3)

A cylinder relative pressure sensor for detecting a pressure in the cylinder as a cylinder relative pressure detection value that is a relative pressure from a predetermined reference pressure, and is sucked into the cylinder based on the cylinder relative pressure detection value An in-cylinder gas state acquisition device for an internal combustion engine that acquires a gas state,
Of the in-cylinder intake gas amount sucked into the cylinder during the compression stroke, the in-cylinder gas temperature in the cylinder at a predetermined time in the compression stroke, and the in-cylinder absolute pressure in the cylinder at the same time. Temporary setting means for temporarily setting the state of gas sucked into the cylinder at the same predetermined time by temporarily setting the two values of:
The value of the temporary in-cylinder absolute pressure in the cylinder at the predetermined time obtained from the state of the gas sucked into the cylinder at the predetermined time and the detection of the relative pressure in the cylinder at the predetermined time Calculating a temporary pressure correction value by comparing the detected pressure value with a plurality of in-cylinder relative pressure detection values in a predetermined section of the compression stroke including the predetermined time and the temporary pressure correction value. First calculating means for sequentially setting a plurality of temporary in-cylinder absolute pressure set values in the same cylinder within the cylinder;
Using the state of the gas in the cylinder at the predetermined time provisionally set by the provisional setting means as an initial condition, the cylinder in the predetermined section using a model for the cylinder determined based on the law of conservation of energy. Second calculating means for sequentially calculating a plurality of temporary in-cylinder absolute pressure calculated values in the
Deviation index value calculation means for calculating a deviation index value indicating a degree of deviation between the plurality of provisional in-cylinder absolute pressure set values and the plurality of provisional in-cylinder absolute pressure calculated values in the predetermined section,
The two provisionally set values are sequentially corrected so that the degree of the deviation indicated by the deviation index value is reduced, and the provisional setting unit, the first calculation unit, the second calculation unit, and the deviation index value A series of processes performed by the calculating means are repeatedly executed until the degree of the deviation is substantially minimized, and the two values provisionally set are true when the degree of the deviation is substantially minimized. In-cylinder gas state acquisition means for setting the value of
An in-cylinder gas state acquisition device for an internal combustion engine, comprising: An in-cylinder gas state acquisition device for an internal combustion engine according to claim 1,
The in-cylinder gas state obtaining means is configured to obtain a true in-cylinder absolute pressure in the cylinder at the predetermined time,
In-cylinder gas state acquisition device for an internal combustion engine, comprising pressure correction value acquisition means for acquiring a true pressure correction value by comparing the value of the true in-cylinder absolute pressure with the detected value of the in-cylinder relative pressure at the predetermined time. . An in-cylinder gas state acquisition device for an internal combustion engine according to claim 1 or 2,
The predetermined time is set at a compression stroke start time at which the intake valve closes,
The in-cylinder gas state acquisition device for an internal combustion engine, wherein the predetermined section is set so that the start is at the start of the compression stroke and the end is at the end of the compression stroke.

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