JP4131185B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

【００９３】
次に、主燃焼期間での層流燃焼速度ＳＬ２の算出について説明する。前記温度センサを用いて圧縮上死点付近の燃焼ガス温度をＴｔを検出し、このときの燃料ａ、ｂのそれぞれの層流燃焼速度をＳＬ２ａ、ＳＬ２ｂとすると、主燃焼期間での層流燃焼速度ＳＬ２は、
【００９４】
【数２５】

【００９５】
で算出できる。
【００９６】
さらに、点火無駄時間ＤＥＡＤＴＩＭＥは、燃料ａ、ｂのそれぞれの点火無駄時間をＤＥＡＤＴＩＭＥａ、ＤＥＡＤＴＩＭＥｂとすると、下式で算出できる。
【００９７】
【数２６】

【００９８】
なお、各燃料の点火無駄時間は、予め燃焼実験等により算出、記憶しておく。
▲２▼算出方法２：燃料濃度検出センサが故障、もしくは酸素濃度検出センサが故障の場合等、予め混合された燃料ａ、ｂのそれぞれの組成割合ｒａ、ｒｂが検出、推定不可能な場合
初期燃焼期間の層流燃焼速度ＳＬ１の算出方法は、まず前記温度センサを用いて、燃焼開始時のシリンダ内の燃焼ガスの温度Ｔｓを検出し、このときの燃料ａ、ｂのそれぞれの層流燃焼速度をＳＬ１ａ、ＳＬ１ｂとすると、混合燃料の層流燃焼速度ＳＬ１は下式で算出される。
【００９９】
【数２７】

【０１００】
次に、主燃焼期間での層流燃焼速度ＳＬ２の算出について説明する。前記温度センサを用いて圧縮上死点付近の燃焼ガス温度をＴｔを検出し、このときの燃料ａ、ｂのそれぞれの層流燃焼速度をＳＬ２ａ、ＳＬ２ｂとすると、主燃焼期間での層流燃焼速度ＳＬ２は、
【０１０１】
【数２８】

【０１０２】
で算出できる。
【０１０３】
さらに、点火無駄時間ＤＥＡＤＴＩＭＥは、燃料ａ、ｂのそれぞれの点火無駄時間をＤＥＡＤＴＩＭＥａ、ＤＥＡＤＴＩＭＥｂとすると、下式で算出できる。
【０１０４】
【数２９】

【０１０５】
なお、各燃料の点火無駄時間は、予め燃焼実験等により算出、記憶しておく。
▲３▼算出方法３：混合燃料に混合されている燃料の種類がわかっている場合
・燃料ａの沸点が燃料ｂの沸点より低い場合（例えば、燃料ａがアルコールで、燃料ｂがガソリンの場合）
初期燃焼期間の層流燃焼速度ＳＬ１の算出方法は、前記温度センサを用いて、燃焼開始時のシリンダ内の燃焼ガスの温度Ｔｓを検出し、このときの燃料ａの層流燃焼速度をＳＬ１ａとすると、混合燃料の層流燃焼速度ＳＬ１は下式で算出される。
【０１０６】
【数３０】

【０１０７】
また主燃焼期間の層流燃焼速度ＳＬ２は、前記温度センサを用いて圧縮上死点付近の燃焼ガス温度をＴｔを検出し、このときの燃料ｂの層流燃焼速度をＳＬ２ｂとすると、主燃焼期間での層流燃焼速度ＳＬ２は、
【０１０８】
【数３１】

【０１０９】
で算出できる。
【０１１０】
さらに、点火無駄時間ＤＥＡＤＴＩＭＥは、燃料ａの点火無駄時間をＤＥＡＤＴＩＭＥａとすると、下式で算出できる。
【０１１１】
【数３２】

【０１１２】
なお、燃料ａの点火無駄時間は、予め燃焼実験等により算出、記憶しておく。
・燃料ａの沸点が燃料ｂの沸点より高い場合（例えば、燃料ａがガソリンで、燃料ｂがアルコールの場合）
初期燃焼期間の層流燃焼速度ＳＬ１の算出方法は、前記温度センサを用いて、燃焼開始時のシリンダ内の燃焼ガスの温度Ｔｓを検出し、このときの燃料ｂの層流燃焼速度をＳＬ１ｂとすると、混合燃料の層流燃焼速度ＳＬ１は下式で算出される。
【０１１３】
【数３３】

【０１１４】
また主燃焼期間の層流燃焼速度ＳＬ２は、前記温度センサを用いて圧縮上死点付近の燃焼ガス温度Ｔｔを検出し、このときの燃料ａの層流燃焼速度をＳＬ２ａとすると、主燃焼期間での層流燃焼速度ＳＬ２は、
【０１１５】
【数３４】

【０１１６】
で算出できる。
【０１１７】
さらに、点火無駄時間ＤＥＡＤＴＩＭＥは、燃料ｂの点火無駄時間をＤＥＡＤＴＩＭＥｂとすると、下式で算出できる。
【０１１８】
【数３５】

【０１１９】
なお、燃料ｂの点火無駄時間は、予め燃焼実験等により算出、記憶しておく。
【０１２０】
ここで、燃料ａ、ｂの層流燃焼速度ＳＬ１ａ、ＳＬ１ｂは一般に以下の式によって表わされることが分かっている。
【０１２１】
ＳＬ１＝ＳＬstd×（Ｔ０×Ｔstd）^2.18×（Ｐ０／Ｐstd）^-0.16…（１５）
基準温度Ｔ０、基準圧力Ｐ０での層流燃焼速度ＳＬ０を各燃料ａ、ｂ毎に実験等により予め検出しておく。
【０１２２】
ここで常用域である２ｂａｒ以上では上記式の圧力の項の値は小さくなるので、圧力感度を一定値として基準温度に対する層流燃焼速度ＳＬ０（ｍ／ｓｅｃ）を算出しても良く、基準温度等は実験で予め算出しておく。例えば基準温度５５０（Ｋ）の時、層流燃焼速度が１．０（ｍ／ｓｅｃ）であった場合、前記ステップＳ２４で算出した雰囲気温度Ｔｓ（Ｋ）を用いて近似的に下記式で求めることができる。
ＳＬ１＝ｆ９（Ｔ０）
＝１．０×０．７×（Ｔ０／５５０）^2.18…（１６）
前述したように層流域に火炎が伝播し、燃焼速度が急速に速くなった初期燃焼期間の後は、圧力、温度に対する感度は鈍くなるため層流燃焼速度ＳＬ２ａ、ＳＬ２ｂは予め実験によって求めた固定値として定めてもよい。
【０１２３】
なお、ガス圧力Ｔｓは、温度センサを用いて直接測定してもよいが、燃焼開始時のシリンダ内圧力をＰｓ、シリンダ内容積をＶｓ、吸入空気量モル数をｎｓとして、下式より算出できる。
【０１２４】
【数３６】

【０１２５】
また、圧縮上死点付近の燃焼ガス温度Ｔｔについても同様に算出できる。
【０１２６】
このように、種類の異なる２種類の燃料を混合した燃料の組成割合を求め、この組成割合と各燃料の層流燃焼速度とから混合燃料の層流燃焼速度を混合燃料の初期燃焼期間と主燃焼期間とに分けて求めることにより、燃焼ガスの層流燃焼速度を精度良く算出することができ、結果としてＭＢＴの得られる点火時期を精度良く算出することができる。
【０１２７】
また、種類の異なる２種類の燃料を混合した燃料の組成割合を求め、この組成割合と各燃料の点火無駄時間とから混合燃料の点火無駄時間を求めることにより、燃焼ガスの点火無駄時間を精度良く算出することができ、結果としてＭＢＴの得られる点火時期を精度良く算出することができる。
【０１２８】
また、混合燃料を構成する各燃料の組成割合が検出できない場合には、各燃料の層流燃焼速度に基づいて混合燃料の層流燃焼速度を算出することができるため、混合燃料を構成する燃料の種類が分かれば混合燃料の層流燃焼速度が算出することができ、組成割合を検出するための濃度センサや組成割合の推定手段を設ける必要がなく、演算負荷を低減しつつ、従来のＭＢＴ算出法より精度良くＭＢＴの点火時期を算出できる。
【０１２９】
別の混合燃料を構成する燃料が分かっている場合の混合燃料の層流燃焼速度算出法としては、燃焼ガスの初期燃焼期間は、構成する燃料のうち最も沸点の低い燃料の層流燃焼速度を混合燃料の層流燃焼速度として用い、圧縮上死点付近での主燃焼期間は沸点の高い燃料の層流燃焼速度を混合燃料の層流燃焼速度として用いて、点火時期を算出することができる。この方法により、濃度センサを用いることなく、またさらに演算負荷を低減しつつ、従来のＭＢＴ算出法より精度良くＭＢＴの点火時期を算出できる。
【０１３０】
さらに本実施の形態における点火時期制御装置においては、ＣＶＴＣバルブ２２の吸気バルブが閉じられた時点のシリンダ内容積ＶＩＶＣとシリンダ内温度ＴＩＮＩが算出される（ステップＳ１２、Ｓ１３）。そして燃焼ガスの燃焼のしやすさを所定条件における燃焼状態を１とした場合における比で示した反応確率ＲＰＲＯＢＡが算出される（ステップＳ１４）。
【０１３１】
燃焼速度は、シリンダ内における雰囲気温度、燃焼速度の他に残留ガス率ＥＧＲＲＥＭ、水温ＴＷＫ、当量比に依存し、燃焼速度がこれらの値により変化する状態を実験で予め求めマップ化して保有しておくことができる。勿論、これらの因子に依存した相関関係を関数式でもつことも可能である。
【０１３２】
次に、ＭＢＴで点火した場合、燃焼ガスの圧力のピーク値である基準クランク角θＰｍａｘは略一定であり、エンジン高回転側で進角側にシフトする傾向があるためステップＳ１５の如く算出する。
【０１３３】
シリンダ内容積Ｖ₀、有効圧縮比Ｅｃから吸気バルブが閉じられた時点のシリンダ内温度ＴＩＮＩからの温度上昇率を算出し（ステップＳ２１〜Ｓ２４）、燃焼ガスが点火される時点の雰囲気温度Ｔ０が算出される（ステップＳ２５）。算出した雰囲気温度Ｔ０に基づいて、層流燃焼速度ＳＬ１を算出する（ステップＳ２６）。
【０１３４】
燃焼速度は層流燃焼速度が早いほど早くなる傾向にあるため、シリンダ内の乱流速度も燃焼速度に大きく依存する。乱流速度は吸気ポート形状等に左右され、一般にエンジン回転数が高くなるほど速くなる。このためこれを乱れ強さＵ１として算出し（ステップＳ２７）、層流燃焼速度と掛け合わせて燃焼速度ＦＬＡＭＥ１を算出する（ステップＳ２８）。
【０１３５】
そして点火してから火炎核が形成されるまでの燃焼期間ＢＵＲＮ１をステップＳ２９で算出する。火炎核の形成には、燃焼ガス質量の内２％の燃焼によってなされることがわかっているため、燃焼ガス質量の２％を算出して用いる。火炎核形成段階では、点火時点のシリンダ内容積が大きいほど形成に時間が長くなるためこれを分子とし、反応確率ＲＰＲＯＢＡが大きいぼど時間が短く、燃焼速度が早いほど時間が短くなるため、これらを分母とした演算式を用いて演算することにより、正確且つ容易に火炎核形成段階の燃焼時間を求めることができる。
【０１３６】
火炎核が形成された後は、燃焼ガスが急速に燃焼される急速燃焼段階となり火炎核は急速に成長する。圧力がピークとなる６０％の燃焼ガスが燃焼される期間が演算される（ステップＳ３１〜ステップＳ３４）。ここでも火炎核の成長時点のシリンダ内容積が大きいほど形成に時間が長くなるためこれを分子とし、反応確率ＲＰＲＯＢＡが大きいほど時間が短く、燃焼速度が早いほど時間が短くなるため、これらを分母とした演算式を用いて演算することにより、正確且つ容易に火炎核成長段階の燃焼時間を求めることができる。
【０１３７】
以上の如く算出した火炎核形成段階の初期燃焼期間と火炎核成長段階の主燃焼期間とを足すことにより燃焼ガス質量６０％の燃焼に必要な期間を算出する事ができる（ステップＳ４２）。そして点火無駄時間とシリンダ内最大圧力となる基準クランク角θＰｍａｘを考慮してＭＢＴ点火時期を算出し、イグニッションコイルに出力指令を出すことができる（ステップＳ４３）。
【０１３８】
本実施の形態によれば、燃焼期間を算出する際に、圧力・温度に対する燃焼期間の感度が大きい火炎核形成段階と、圧力・温度に対する燃焼期間の感度が鈍くなる主燃焼期間とに分けて演算することで、燃焼期間をより正確に演算することができる。この際、分子に燃焼ガス質量、シリンダ容積、分母に反応面積、燃焼速度といった演算式を用いており、同一次元の単位が分子、分母に用いられることが無いので無駄な演算をすることなく正確に算出できる。
【０１３９】
燃焼状態を無次元の反応確率で置き換えて演算に用いており、当該反応確率は実験等で容易に求めることができるため正確な燃焼期間を算出することができる。また、本実施の形態では、吸気バルブの作動角とリフト量を連続的に可変にできる可変動弁機構を備えた内燃機関へ適用した例を示したが、吸気バルブが閉じた時点のシリンダ内容積が変化しても容易にＭＢＴを算出することができるため、例えば、バルブ開閉に電磁石を用い、バルブタイミングを任意に変化させることができるいわゆる電磁駆動吸排気弁等の可変動弁システムへの適用も行える。なお、吸気バルブの作動角とリフト量を連続的に可変にできる可変動弁機構の一例として特開平１１−１０７７２５号公報、特開２００３−４１９７６号公報に記載のものがある。
【０１４０】
本実施形態では燃焼質量割合から燃焼期間を求めるにあたり、燃焼期間ＢＴを初期燃焼期間ＢＵＲＮ１（燃焼質量割合２％まで）と主燃焼期間ＢＵＲＮ２（燃焼質量割合２％から６０％まで）とに分けて演算し、点火時期ＭＢＴＣＡＬを求めたが、さらに細分化してもよく、または細分化を行った上で、燃焼期間（燃焼質量割合）をたとえば、初期燃焼期間ＢＵＲＮ１と主燃焼期間ＢＵＲＮ２とで分けて加算するようにしてもよい。細分化して燃焼期間を求めることによって、燃焼期間の算出精度を向上できる。
【０１４１】
また、燃焼ガスの層流燃焼速度を算出する方法▲１▼で用いた酸素濃度検出センサによって空燃比を算出し、空燃比の変化から組成割合ｒａ、ｒｂを推定する手法について以下に説明する。
【０１４２】
ここでは、アルコールを含む燃料中のアルコール濃度を検出する方法を一例として説明する。アルコールを含む燃料は、Ｃ（炭素）の原子数がガソリンと異なることからガソリンに比べ、同一の当量比を得るには大きな噴射量が要求されることになる。そこで、酸素濃度センサ１７の検出値を利用して、燃料内のアルコール濃度を以下の手順で推定する。図１４は、燃料内のアルコール濃度推定値ＡＬＣを更新演算する制御の流れを示している。
【０１４３】
まず、ステップ（以下、単にＳと表記する）５１では、酸素濃度センサ１７の出力信号を基に算出された空燃比補正量としての空燃比フィードバック補正係数αを読み込む。
【０１４４】
Ｓ５２では、空燃比学習条件が成立しているか否かを判定し、空燃比学習条件が成立している場合には、Ｓ５３に進み、各運転領域領域毎のαｍ算出マップのマップ値の書き換えを行う。空燃比学習条件が成立していない場合には、各αｍ算出マップのマップ値の書き換えを行わずにＳ５４に進む。ここで、αｍは上記αに基づいて算出される空燃比学習補正係数である。尚、空燃比フィードバッ．ク補正係数α及び空燃比学習補正係数αｍは、空燃比のフィードバック制御に用いられるパラメータであり、インジェクタ３からの燃料噴射量がα及びαｍに応じて補正される。また空燃比フィードバック補正係数α及び空燃比学習補正係数αｍの算出方法は、公知のいかなる算出方法でも使用可能であるため、これらの算出方法についての詳細な説明は省略する。
【０１４５】
Ｓ５４では、現在の各運転領域毎のαｍマップを参照し、各運転領域毎に空燃比補正量としての空燃比学習補正係数αｍを求める。続いてＳ５５に進み、アルコール濃度推定を行うための許可条件が成立しているか否かを判定する。すなわち、このＳ５５においては、水温、エンジン始動後時間、空燃比学習制御の進行状況、給油履歴などの条件が整ったか否かを判定し、条件が整っている場合にはＳ５６に進み、条件が整っていない場合にはアルコール濃度推定を行うことなく終了する。
【０１４６】
Ｓ５６では、次式（３７）のように表される空燃比感度補正総量αｔを算出する。
【０１４７】
【数３７】

【０１４８】
ここで、ＥＴＡＨＯＳは前回のアルコール濃度推定値ＡＬＣから算出される燃料性状分補正量であって、後述する図１５を用い、前回のアルコール濃度推定値ＡＬＣから逆引きで算出されるαｔの前回値である。
【０１４９】
また、このＳ５６におけるαｍ’は、Ｓ５４にて求めた各運転領域別のαｍのうち代表的な回転負荷領域のαｍの平均値、換言すればエンジンとしての使用頻度が高い領域程度のαｍの平均値である。
【０１５０】
Ｓ５７では、図１５に示すマップを用い、Ｓ５６にて算出された空燃比感度補正総量αｔからアルコール濃度推定値ＡＬＣを算出する。
【０１５１】
本発明は、上記した実施形態に限定されるものではなく、本発明の技術的思想の範囲内でさまざまな変更がなしうることは明白である。
【図面の簡単な説明】
【図１】本発明の内燃機関のシステム図である。
【図２】エンジンコントローラで実行される点火時期制御のブロック図である。
【図３】燃焼室の圧力変化図である。
【図４】燃焼質量割合の変化を説明する特性図である。
【図５】物理量の算出を説明するためのフローチャートである。
【図６】エンジンのクランクシャフトとコネクティングロッドの位置関係を説明するダイアグラムである。
【図７】水温補正係数の特性図である。
【図８】当量比補正係数の特性図である。
【図９】基準クランク角の特性図である。
【図１０】初期燃焼期間の算出を説明するためのフローチャートである。
【図１１】温度上昇率の特性図である。
【図１２】主燃焼期間の算出を説明するためのフローチャートである。
【図１３】基本点火時期の算出を説明するためのフローチャートである。
【図１４】燃料内のアルコール濃度推定値を算出する制御の流れを示すフローチャートである。
【図１５】空燃比感度補正総量αｔとアルコール濃度推定値ＡＬＣとの相関関係を示す特性図である。
【符号の説明】
１ 内燃機関
２ 吸気コレクタ
３ インジェクタ
４ 吸気マニホールド
５ 排気マニホールド
６ マフラ
７ エアクリーナ
８ 電子制御スロットル
９ 吸気ダクト
２０ コントロールユニット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ignition timing control device for an internal combustion engine, and more particularly to an ignition timing control device for an internal combustion engine using a mixed fuel.
[0002]
[Prior art]
As a conventional ignition timing control device, the air-fuel ratio of actual exhaust gas is detected using an air-fuel ratio sensor, and the stoichiometric air-fuel ratio determined according to the gas composition of the gas fuel is detected from the actual air-fuel ratio. There is a technique for controlling the ignition timing accordingly (for example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-54305
[Problems to be solved by the invention]
However, in the technique described in Patent Document 1, since the ignition timing is corrected by a certain amount according to the composition (ratio) of the gas fuel, the combustion gas in the cylinder is a mixture of two or more types of fuels having different laminar combustion speeds. If there is a concern, the residual gas rate and the equivalence ratio change, and the MBT ignition timing cannot be accurately calculated when the difference between the MBT ignition timing for gasoline and the MBT ignition timing for gas fuel is not constant. is there.
[0005]
Accordingly, an object of the present invention is to provide an ignition timing control device for an internal combustion engine that can solve the above-mentioned problems and can more accurately obtain the MBT ignition timing of a mixed fuel composed of two or more kinds of fuels.
[0006]
[Means for Solving the Problems]
The present invention relates to an ignition timing control device for an internal combustion engine that calculates an ignition timing at which MBT is obtained from a combustion period calculated based on a laminar combustion speed, wherein the combustion gas is a mixture of a plurality of fuels. The laminar burning velocity of the combustion gas mixed with fuel is calculated based on the type and composition ratio of each fuel.
[0007]
【The invention's effect】
In the present invention, the laminar combustion speed of the combustion gas can be accurately calculated from the laminar combustion speed and the composition ratio of each fuel constituting the combustion gas, whereby the combustion gas fuel is composed of a plurality of fuels. Even so, the ignition timing of MBT can be calculated accurately.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic diagram for explaining the system of the present invention. Intake air is introduced into an internal combustion engine 1 via an intake manifold 2 in which an intake collector 2 and an injector 3 are arranged. Exhaust gas is discharged into the atmosphere from the exhaust manifold 5 provided with the three-way catalyst 21 through the muffler 6.
[0009]
Air purified by an air cleaner 7 is supplied to the intake collector 2 through an intake duct 9. An electronically controlled throttle 8 having a throttle opening sensor and a throttle motor is provided upstream of the intake collector 2.
[0010]
The fuel gas evaporated in the fuel tank 10 is sent to the intake collector 2 together with the air introduced into the canister 11 after being introduced into the canister 11. Further, an EGR passage 12 that connects the three-way catalyst 21 downstream and the intake collector 2 is installed, and a part of the exhaust gas is recirculated into the intake air.
[0011]
The internal combustion engine 1 is provided with a position sensor 13 for detecting the position of the crank angle and a water temperature sensor 14 for detecting the cooling water temperature. The intake duct 9 has an air flow meter 16 for detecting the amount of intake air incorporating the intake air temperature sensor. Provided. Instead of the air flow meter 16, a sensor for detecting the temperature and pressure of the intake manifold 4 may be provided, and the intake air amount may be calculated based on these sensors.
[0012]
The exhaust manifold 5 is provided with an oxygen concentration sensor 17 for detecting the oxygen concentration in the exhaust gas. An EGR control valve 18 is provided in the middle of the EGR passage 12, and a canister purge air control valve 19 for controlling the purge air discharged from the canister 11. Is installed.
[0013]
The internal combustion engine 1 is further provided with a variable valve mechanism 22 that can continuously change the operating angle and lift amount of the intake valve, and an operating angle sensor 15 that detects the actual operating angle of the intake valve. Based on the output signal of the angle sensor 15, the opening timing (IVO) and closing timing (IVC) of the intake valve can be calculated.
[0014]
The output signals of the position sensor 13, the water temperature sensor 14, the operating angle sensor 15, the air flow meter 16 and the intake air temperature sensor incorporated therein are input to the control unit 20, and further from the output signal of the oxygen concentration sensor 17 and a battery (not shown). The voltage signal is also input.
[0015]
Based on these input data, the control unit 20 outputs an ignition timing control signal to the ignition coil, an air-fuel ratio control signal to the fuel injector 3, an intake valve operating angle control signal to the variable valve mechanism 22, and canister control. A signal is output to the canister purge control valve 19 and an EGR control signal is output to the EGR control valve 18 to maintain the internal combustion engine 1 in an appropriate operating state.
[0016]
FIG. 2 is a block diagram of the ignition timing control performed in the engine controller 31. The ignition timing control section 51 and the ignition timing control section 61 are mainly composed. The ignition timing calculation unit 51 further includes an initial combustion period calculation unit 52, a main combustion period calculation unit 53, a combustion period calculation unit 54, a basic ignition timing calculation unit 55, a previous combustion start timing calculation unit 56, and an ignition timing command value calculation unit 57. Become.
[0017]
The initial combustion period calculation unit 52 calculates a period from when the air-fuel mixture is ignited until flame nuclei are formed as the initial combustion period BURN1. The main combustion period calculation unit 53 calculates a period from when the flame kernel is formed until the combustion pressure reaches the maximum value Pmax as the main combustion period BURN2. The combustion period calculation unit 54 calculates the sum of the initial combustion period BURN1 and the main combustion period BURN2 as a combustion period BURN from ignition to the maximum combustion pressure Pmax. The basic ignition timing calculation unit 55 calculates an ignition timing (this ignition timing is referred to as “basic ignition timing”) MBTCAL from which MBT is obtained based on the combustion period BURN.
[0018]
The ignition timing control unit 61 controls the energization angle and the non-energization angle to the ignition coil 13 so that the ignition plug 14 ignites the air-fuel mixture in the combustion chamber 5 at the basic ignition timing MBTCAL calculated in this way. To do.
[0019]
As described above, the combustion period BURN is calculated by dividing the combustion period BURN into the initial combustion period BURN1 and the main combustion period BURN2, and the basic ignition timing MBTCAL is obtained according to the combustion period BURN, based on the result obtained from the combustion analysis. Is. Hereinafter, the ignition timing control based on the combustion analysis will be further described.
[0020]
As shown in FIG. 3, the crank angle at which the combustion pressure of the air-fuel mixture reaches the maximum value Pmax when the air-fuel mixture is ignited with MBT (minimum advance angle value at which maximum torque is obtained) is defined as a reference crank angle θPMAX [degATDC]. The reference crank angle θPMAX is substantially constant regardless of the combustion method, and is generally in the range of 12 to 15 degrees after compression top dead center and at most 10 to 20 degrees after compression top dead center.
[0021]
FIG. 4 shows changes in the combustion mass ratio R obtained by the combustion analysis in the combustion chamber in the spark ignition engine. The combustion mass ratio R representing the ratio of the combustion mass to the fuel supplied to the combustion chamber is 0% at the time of ignition and reaches 100% by complete combustion. The combustion mass ratio Rmax at the reference crank angle θPMAX is constant and about 60%.
[0022]
The combustion period until the combustion mass ratio R reaches 0% to approximately 60% corresponding to the reference crank angle θPMAX is an initial combustion period in which there is almost no change in the combustion mass ratio or the combustion pressure immediately after ignition, and the combustion It can be divided into a mass ratio and a main combustion period in which the combustion pressure increases rapidly. The initial combustion period is a stage from the start of combustion until flame nuclei are formed, and the flame nuclei are formed at a timing of 2% to 10% in terms of the combustion mass ratio. During this period, the rate of increase in combustion pressure and combustion temperature is small, and the initial combustion period is long with respect to changes in the combustion mass ratio. The length of the initial combustion period is susceptible to changes in temperature and pressure in the combustion chamber.
[0023]
On the other hand, in the main combustion period, the flame propagates from the flame kernel to the outside, and the combustion speed increases rapidly. Therefore, the change in the combustion mass ratio during the main combustion period is larger than the change in the combustion mass ratio during the initial combustion period.
[0024]
In the engine controller 31, the period until the combustion mass ratio reaches 2% is defined as the initial combustion period BURN1 [deg], and after the end of the initial combustion period BURN1, the interval until the reference crank angle θPMAX is reached (combustion chamber volume ratio is 2). To about 60%) is distinguished as the main combustion period BURN2 [deg]. Then, a combustion period BURN [deg] that is the sum of the initial combustion period BURN1 and the main combustion period BURN2 is calculated, a reference crank angle θPMAX [degATDC] is subtracted from the combustion period BURN, and an ignition dead time equivalent crank described later is further calculated. The crank angle position to which the angle IGNDEAD [deg] is added is set as the basic ignition timing MBTCAL [degBTDC], which is the ignition timing at which MBT is obtained.
[0025]
The pressure and temperature in the combustion chamber 5 during the initial combustion period in which flame nuclei are formed are almost equivalent to the pressure and temperature at the time of ignition, but the ignition timing is calculated from this, but accurate ignition is performed from the beginning. The time cannot be set. Therefore, as shown in FIG. 2, the previous combustion start timing calculation unit 56 calculates the previous value of the basic ignition timing as the previous combustion start timing MBTCYCL [degBTDC], and gives this value to the initial combustion period calculation unit 52. In addition, the initial combustion period calculation unit 52 cyclically repeats the calculation of the initial combustion period so as to obtain a highly accurate result without a time delay.
[0026]
Next, the calculation of the ignition timing command value QADV executed by the engine controller 31 will be described in detail with reference to the following flowchart.
[0027]
FIG. 5 is for calculating various physical quantities necessary for calculating the ignition timing, and is executed at regular time intervals (for example, every 10 msec).
[0028]
First, in step 11, the intake valve closing timing IVC [degBTDC], the collector internal temperature TCOL [K] detected by the temperature sensor 43, the exhaust gas temperature TEXH [K] detected by the temperature sensor 45, and the internal inert gas rate MRESFR [ %], The coolant temperature TWK [K] detected by the temperature sensor 37, the target equivalence ratio TFBYA, the engine speed NRPM [rpm] detected by the crank angle sensor, and the dead time DEADTIME [μsec].
[0029]
Here, the crank angle sensor includes a position sensor 33 that detects the position of the crankshaft 7 and an operating angle sensor 34 that detects the position of the intake camshaft 25. Based on signals from these two sensors 33 and 34, The engine speed NRPM [rpm] is calculated.
[0030]
The intake valve closing timing IVC is known from the command value given to the intake VTC mechanism 27. Alternatively, the actual intake valve closing timing may be detected by the operating angle sensor 34.
[0031]
The internal inert gas ratio MRESFR is a value obtained by dividing the amount of inert gas remaining in the combustion chamber by the total amount of gas in the combustion chamber, and the calculation thereof will be described later. The ignition dead time DEADTIME is a constant value.
[0032]
The target equivalent ratio TFBYA is calculated in a fuel injection amount calculation flow (not shown). The target equivalent ratio TFBYA is an unnamed number, and is a value represented by the following expression when the theoretical air-fuel ratio is 14.7.
[0033]
TFBYA = 14.7 / target air-fuel ratio (1)
For example, from equation (1), when the target air-fuel ratio is the stoichiometric air-fuel ratio, TFBYA = 1.0, and when the target air-fuel ratio is a lean value such as 22.0, TFBYA is a positive value less than 1.0. is there.
[0034]
In step 12, the volume of the combustion chamber 5 at the intake valve closing timing IVC (that is, the volume at the compression start timing) VIVC [m ³ ] is calculated. The volume VIVC of the combustion chamber 5 when the intake valve is closed is determined by the stroke position of the piston 6. The stroke position of the piston 6 is determined by the crank angle position of the engine.
[0035]
Referring to FIG. 6, consider a case where the rotation center 72 of the crankshaft 71 of the engine is offset from the center axis 73 of the cylinder. Assume that the connecting rod 74, the connecting point 74 between the connecting rod 74 and the crankshaft 71, and the piston pin 76 that connects the connecting rod 74 and the piston are in the relationship shown in the figure. At this time, the volume VIVC of the combustion chamber 5 at the closing timing of the intake valve can be expressed by the following equations (2) to (6).
[0036]
VIVC = f1 (θivc)
= Vc + (π / 4) D ² · H (2)
Vc = (π / 4) D ² · H / (ε−1) (3)
^{H = {(CND + ST 2} /2) - (CRoff-PISoff) 2} 1/2
− {(ST / 2) · cos (θivc + θoff)}
+ (CND ² −X ² ) ^1/2 (4)
X = (ST / 2) · sin (θivc + θoff) −CRoff−PISoff
... (5)
θoff = arcsin {(CRoff−PISoff) / (CND · (ST / 2))}
(6)
Where Vc: gap volume [m ³ ],
ε: compression ratio,
D: cylinder bore diameter [m],
ST: Full piston stroke [m],
H: distance [m] of the piston pin 76 from the TDC,
CND: length of connecting rod 74 [m],
CRoff: offset of the nodal point 75 from the cylinder center axis 73
Distance [m],
PISoff: Cylinder center of crankshaft rotation center 72
Offset distance from axis 73 [m],
θivc: Intake valve closing timing crank angle [degATDC],
θoff: piston pin 76 and crankshaft rotation center 7
The angle between the line connecting 2 and the vertical line in TDC
[Deg],
X: horizontal distance [m] between the nodal point 75 and the piston pin 76,
The crank angle ivc at the intake valve closing timing is known because it is determined by the command signal from the engine controller 31 to the intake VTC mechanism 27 as described above. By substituting the crank angle θivc (= IVC) at this time into the equations (2) to (6), the volume VIVC of the combustion chamber 5 at the closing timing of the intake valve can be calculated. Therefore, in practice, the volume VIVC of the combustion chamber 5 at the intake valve closing timing is set by a table using the intake valve closing timing IVC as a parameter. When the intake VTC mechanism 27 is not provided, a constant value can be given.
[0037]
In step 13, the temperature (that is, the compression start timing temperature) TINI [K] of the combustion chamber 5 at the intake valve closing timing IVC is calculated. The temperature TINI of the combustion chamber 5 at the intake valve closing timing IVC is a temperature of a gas in which fresh air flowing into the combustion chamber 5 and inert gas remaining in the combustion chamber 5 are mixed, and fresh air flowing into the combustion chamber 5. Is equal to the fresh air temperature TCOL in the intake collector 2 and the temperature of the inert gas remaining in the combustion chamber 5 can be approximated by the exhaust temperature TEXH in the vicinity of the exhaust port portion. From the TCOL, the exhaust gas temperature TEXH, and the internal inert gas ratio MRESFR which is the ratio of the inert gas remaining in the combustion chamber 5, it can be obtained by the following equation.
[0038]
TINI = TEXH × MRESFR + TCOL × (1−MRESFR) (7)
In step 14, a reaction probability RPROBA [%] representing the flammability of the air-fuel mixture in the combustion chamber 5 is calculated. The reaction probability RPROBA is a dimensionless value and depends on the three parameters of the residual inert gas ratio MRESFR, the cooling water temperature TWK [K], and the target equivalent ratio TFBYA, and can be expressed by the following equation.
[0039]
RPROBA = f3 (MRESFR, TWK, TFBYA) (8)
More specifically, the maximum value of the reaction probability obtained by the combination of the three parameters MRESFR, TWK, and TFBYA is set to 100%, the relationship between these parameters and the reaction probability RPROBA is experimentally obtained, and the obtained reaction probability RPROBA is obtained. Are stored in advance in the memory of the engine controller 31 as a table corresponding to the parameters. In step 14, the reaction probability RPROBA is obtained by searching this table according to the parameters.
[0040]
Specifically, a table of water temperature correction coefficients having characteristics as shown in FIG. 7 according to the cooling water temperature TWK, a table of internal inert gas rate correction coefficients (not shown) set similarly, and a target equivalent ratio A table of equivalence ratio correction coefficients having characteristics as shown in FIG. 8 according to Tfbya is stored in advance in the memory. The maximum value of each correction coefficient is 1.0, and the reaction probability RPROBA is calculated by multiplying the product of the three types of correction coefficients by the maximum value of 100% of the reaction probability.
[0041]
Explaining each table, the water temperature correction coefficient shown in FIG. 7 becomes larger as the cooling water temperature TWK is higher, and becomes 1.0 when the cooling water temperature TWK is 80 ° C. or higher. The equivalence ratio correction coefficient shown in FIG. 8 is the maximum value of 1.0 when the target equivalence ratio TFBYA is 1.0, that is, the stoichiometric air-fuel ratio. The ratio correction factor decreases. Although the internal inert gas rate correction coefficient is not shown, it is 1.0 when the internal inert gas rate MRESFR is zero.
[0042]
In step 15, a reference crank angle θPMAX [degATDC] is calculated. As described above, the reference crank angle θPMAX does not fluctuate very much, but still has a tendency to advance as the engine speed NRPM increases. Therefore, the reference crank angle θPMAX can be expressed by the following equation as a function of the engine speed NRPM. it can.
[0043]
θPMAX = f4 (NRPM) (9)
Specifically, the reference crank angle θPMAX is obtained by searching a table of characteristics shown in FIG. 9 stored in advance in the memory of the engine controller 31 from the engine speed NRPM. In order to facilitate calculation, the reference crank angle θPMAX can be regarded as constant.
[0044]
Finally, in step 16, the ignition dead time equivalent crank angle IGNDEAD [deg] is calculated. The crank angle IGNDEAD corresponding to the ignition dead time is a crank angle section from the timing at which the ignition command signal, that is, the signal for cutting off the primary current of the ignition coil 13 is output from the engine controller 31 until the ignition plug 14 actually ignites. Can be represented by
[0045]
IGNDEAD = f5 (DEADTIME, NRPM) (10)
Here, the ignition dead time DEADTIME is set to 200 μsec. Equation (10) is for calculating the ignition dead time equivalent crank angle IGNDEAD that is the crank angle corresponding to the ignition dead time DEADTIME from the engine speed NRPM.
[0046]
FIG. 10 is for calculating the initial combustion period BURN1 [deg], and FIG. 12 is for calculating the main combustion period BURN2 [deg], which is executed at regular intervals (for example, every 10 msec). 10 and 12 are executed following FIG.
Either of FIGS. 10 and 12 may be executed first.
[0047]
First, referring to FIG. 10, in step 21, the previous combustion start timing MBTCYCL [degBTDC], the volume VIVC [m ³ ] at the intake valve closing timing of the combustion chamber 5 calculated in step 12 of FIG. 5, and the step of FIG. The temperature TINI [K] at the closing timing of the intake valve of the combustion chamber 5 calculated in 13, the engine speed NRPM [rpm], and the reaction probability RPROBA [%] calculated in step 14 of FIG. 5 are read.
[0048]
Here, the previous combustion start timing MBTCYCL is a value one cycle before [degBTDC] of the basic ignition timing MBTCAL, and the calculation thereof will be described later.
[0049]
In step 22, the volume V0 [m ³ ] at the combustion start timing of the combustion chamber 5 is calculated. As described above, the ignition timing (combustion start timing) here is not the basic ignition timing MBTCAL calculated in the current cycle but a value one cycle before the basic ignition timing. That is, the volume V0 at the combustion start timing of the combustion chamber 5 is calculated from MBTCYCL, which is a value one cycle before the basic ignition timing, by the following equation.
[0050]
V0 = f6 (MBTCYCL) (11)
Specifically, the volume V0 of MBTCYCL in the combustion chamber 5 is calculated from the stroke position of the piston 6 at the previous combustion start timing MBTCYCL and the bore diameter of the combustion chamber 5. In step 12 of FIG. 5, the volume VIVC of the combustion chamber 5 at the intake valve closing timing IVC is obtained by searching a table of intake valve closing timing volumes using the intake valve closing timing as a parameter. Here, MBTCYCL is set as a parameter. The volume V0 of the combustion chamber 5 at the previous combustion start time MBTCYCL may be obtained by searching the table of the previous combustion start time volume.
[0051]
In step 23, an effective compression ratio Ec at the combustion start timing is calculated. The effective compression ratio Ec is a dimensionless value, and is a value obtained by dividing the volume V0 of the combustion chamber 5 at the combustion start timing by the volume VIVC of the combustion chamber 5 at the intake valve closing timing, as shown in the following equation.
[0052]
Ec = f7 (V0, VIVC) = V0 / VIVC (12)
In step 24, the temperature increase rate TCOMP in the combustion chamber 5 from the intake valve closing timing IVC to the combustion start timing is calculated based on the effective compression ratio Ec as shown in the following equation.
[0053]
TCOMP = f8 (Ec) = Ec ^ (κ−1) (13)
Where κ: specific heat ratio,
Equation (13) is an equation for the rate of temperature rise of the adiabatic compressed gas. Note that “^” on the right side of the equation (13) represents power calculation.
[0054]
κ is a value obtained by dividing the constant pressure specific heat of the gas adiabatically compressed by the constant volume specific heat. If the gas adiabatically compressed is air, κ = 1.4, and this value may be used simply. However, the calculation accuracy can be further improved by experimentally determining the value of κ for the air-fuel mixture.
[0055]
FIG. 11 illustrates equation (13). Therefore, it is possible to obtain the temperature increase rate TCOMP by storing a table of such characteristics in advance in the memory of the engine controller 31 and searching the table based on the effective compression ratio Ec.
[0056]
In step 25, the temperature T0 [K] at the combustion start timing of the combustion chamber 5 is multiplied by the temperature TINI at the intake valve closing timing of the combustion chamber 5 by the temperature increase rate TCOMP, that is, T0 = TINI × TCOMP (14).
It is calculated by the following formula.
[0057]
In step 26, a laminar combustion speed SL1 [m / sec] is calculated by the following equation (known).
[0058]
SL1 = SLstd × (T0 × Tstd) ^2.18 × (P0 / Pstd) ^−0.16 (15)
Where Tstd: reference temperature [K],
Pstd: Reference pressure [Pa]
SLstd: Reference laminar combustion at reference temperature Tstd and reference pressure Pstd
Speed [m / sec],
T0: temperature [K] at the combustion start timing of the combustion chamber 5;
P0: pressure [Pa] at the combustion start timing of the combustion chamber 5;
The reference temperature Tstd, the reference pressure Pstd, and the reference laminar combustion speed SLstd are values determined in advance by experiments.
[0059]
Under a pressure of 2 bar or higher, which is a normal pressure in the combustion chamber 5, the pressure term (P0 / Pstd) ^−0.16 in the equation (15) becomes a small value. Accordingly, it is also possible to define the reference laminar combustion speed SLstd only by the reference temperature Tstd with the pressure term (P0 / Pstd) ^−0.16 being a constant value.
[0060]
Accordingly, when the reference temperature Tstd is 550 [K], the reference laminar combustion rate SLstd is 1.0 [m / sec], and the pressure term is 0.7, the temperature T0 and the laminar combustion rate at the combustion start timing The relationship with SL1 can be approximately defined by the following equation.
[0061]
SL1 = f9 (T0)
= 1.0 × 0.7 × (T0 / 550) ^2.18 (16)
In step 27, the turbulence intensity U1 of the gas flow in the initial combustion is calculated. The turbulence intensity U1 of the gas flow is a dimensionless value and depends on the flow rate of fresh air flowing into the combustion chamber 5 and the penetration of the injected fuel from the fuel injector 21.
[0062]
The flow rate of fresh air flowing into the combustion chamber 5 depends on the shape of the intake passage, the operating state of the intake valve 15, and the shape of the intake port 4 where the intake valve 15 is provided. The penetration of the injected fuel depends on the injection pressure of the fuel injector 21, the fuel injection period, and the combustion injection timing.
[0063]
Finally, the turbulence intensity U1 of the gas flow in the initial combustion can be expressed by the following equation as a function of the engine speed NRPM.
[0064]
U1 = f10 (NRPM) = C1 × NRPM (17)
Where C1: constant,
It is also possible to obtain the turbulence intensity U1 from a table using the rotational speed NRPM as a parameter.
[0065]
In step 28, the gas combustion rate FLAME1 [m / sec] in the initial combustion is calculated from the laminar combustion rate SL1 and the turbulence intensity U1 by the following equation.
[0066]
FLAME1 = SL1 × U1 (18)
If there is gas turbulence in the combustion chamber 5, the gas combustion speed changes. Equation (18) takes into account the contribution (influence) to the combustion speed associated with this gas turbulence.
[0067]
In step 29, the initial combustion period BURN1 [deg] is calculated by the following equation.
[0068]
BURN1 = {(NRPM × 6) × (BR1 × V0}
/ ( RP BA x AF1 x FLAME1) (19)
However, AF1: Reaction area (fixed value) of flame kernel [m ² ],
Here, BR1 on the right side of the equation (19) is the amount of change in the combustion mass ratio from the combustion start timing to the end timing of the initial combustion period BURN1, and here BR1 = 2% is set. (NRPM × 6) on the right side of equation (19) is a measure for converting the unit from rpm to crank angle (deg). The reaction area AF1 of the flame kernel is set experimentally.
[0069]
Next, in the flow of FIG. 12, in step 31, the rotational speed NRPM and the reaction probability RPROBA calculated in step 14 of FIG. 5 are read.
[0070]
In step 32, the turbulence intensity U2 of the gas flow in the main combustion is calculated. The turbulence intensity U2 of the gas flow can be expressed by the following equation as a function of the engine speed NRPM, similarly to the turbulence intensity U1 of the gas flow in the initial combustion.
[0071]
U2 = f11 (NRPM) = C2 × NRPM (20)
Where C2 is a constant,
It is also possible to obtain the turbulence intensity U2 from a table using the rotation speed as a parameter.
[0072]
In step 33, the combustion speed FLAME2 [m / sec] in the main combustion is calculated from the laminar combustion speed SL2 [m / sec] and the gas flow turbulence intensity U2 in the main combustion by the following equation.
[0073]
FLAME2 = SL2 × U2 (21)
However, SL2: Laminar burning velocity [m / sec],
Equation (21) considers the contribution to the combustion speed associated with gas turbulence, as in Equation (18).
[0074]
As described above, the length of the main combustion period BURN2 is not easily affected by changes in temperature and pressure in the combustion chamber 5. Therefore, a fixed value obtained experimentally in advance is applied to the laminar combustion speed SL2.
[0075]
In step 34, the main combustion period BURN2 [deg] is calculated by the following equation similar to the equation (19).
[0076]
BURN2 = {(NRPM × 6) × (BR2 × V2}
/ ( RP ROBA x AF2 x FLAME2) (22)
V2: Volume at the start of the main combustion period of the combustion chamber 5 [m ³ ],
AF2: Reaction area of flame kernel [m ² ]
Here, BR2 on the right side of Equation (22) is the amount of change in the combustion mass ratio from the start timing to the end timing of the main combustion period. Since the combustion mass ratio becomes 2% at the end of the initial combustion period, and then the main combustion period starts and the combustion mass ratio reaches 60% and the main combustion period ends, BR2 = 60% − 2% = 58% is set. AF2 is an average reaction area in the growth process of the flame kernel, and is set to a fixed value experimentally determined in advance, like AF1 in the equation (19). The volume V2 at the start of the main combustion period of the combustion chamber 5 is also a fixed value.
[0077]
FIG. 13 is for calculating the basic ignition timing MBTCAL [degBTDC], and is executed at regular intervals (for example, every 10 msec). This is executed following the flow that is executed later in FIGS.
[0078]
In step 41, the initial combustion period BURN1 calculated in step 29 of FIG. 10, the main combustion period BURN2 calculated in step 34 of FIG. 12, and the ignition timing dead time equivalent crank calculated in step 16 of FIG. The angle IGNDEAD, the reference crank angle θPMAX calculated in step 15 of FIG. 5, is read.
[0079]
In step 42, the sum of the initial combustion period BURN1 and the main combustion period BURN2 is calculated as the combustion period BURN [deg].
[0080]
In step 43, the basic ignition timing MBTCAL [degBTDC] is calculated by the following equation.
[0081]
MBTCAL = BURN−θPMAX + IGNDEAD (23)
In step 44, the value obtained by subtracting the ignition dead time equivalent crank angle IGNDEAD from the basic ignition timing MBTCAL is calculated as the previous combustion start timing MBTCYCL [degBTDC].
[0082]
The basic ignition timing MBTCAL calculated in this way is transferred to the ignition register, and an ignition signal for cutting off the primary current is output from the engine controller 31 to the ignition coil 13 at a timing when the actual crank angle coincides with the basic ignition timing MBTCAL. The
[0083]
If the basic ignition timing MBTCAL calculated in step 43 is used as the ignition timing command value for the current cycle, the previous combustion start timing MBTCYCL calculated in step 44 is displayed until the ignition timing for the next cycle is reached. 10 steps 22 are used.
[0084]
As described above, in the present embodiment, the basic ignition timing MBTCAL, which is the ignition timing at which MBT is obtained, is calculated without performing mass calculation such as the amount of unburned gas in the combustion chamber 5, so the calculation load is kept small. be able to.
[0085]
Further, as shown in the above equation (19), the initial combustion period BURN1 is expressed as a function of the combustion chamber volume V0 at the combustion start timing, the reaction probability RPROBA indicating the ease of combustion of the air-fuel mixture, and the combustion speed FLAME1. ing. Here, the larger the combustion chamber volume V0 at the combustion start timing, the smaller the reaction probability RPROBA, and the slower the combustion speed FLAME1, the longer the initial combustion period BURN1 and, as a result, the basic ignition timing MBTCAL advances.
[0086]
Similarly, as shown in the above equation (22), the main combustion period BURN2 is a function of the combustion chamber volume V2 at the start timing of the main combustion period, the reaction probability RPROBA indicating the ease of air-fuel mixture, and the combustion rate FLAME2. It is represented by Here, the larger the combustion chamber volume V2 at the start timing of the main combustion period, the smaller the reaction probability RPROBA, and the slower the combustion speed FLAME2, the longer the main combustion period BURN2, and as a result, the ignition timing MBTCAL is advanced.
[0087]
Thus, the combustion periods BURN1 and BURN2 can be accurately calculated by calculating the combustion periods BURN1 and BURN2 as functions of various parameters that affect the combustion period. As a result, the basic ignition timing MBTCAL calculated based on the combustion periods BURN1 and BURN2 can also be calculated with high accuracy. In addition, since the combustion period BURN is calculated by dividing it into an initial combustion period BURN1 corresponding to a flame nucleus growth period in which temperature and pressure are greatly affected and a main combustion period in which the influence of temperature and pressure is small, the combustion period BURN1 is calculated. The calculation accuracy of BURN is improved. The calculation accuracy can be further improved by further dividing the combustion period BURN into three or more.
[0088]
In the embodiment, the combustion speed FLAME1 used for the calculation of the initial combustion period BURN1 is the product of the laminar combustion speed SL1 and the turbulence intensity U1, and the combustion speed FLAME2 used for the calculation of the main combustion period BURN2 is turbulent with the laminar combustion speed SL2. Although calculated as the product of the strength U2, each may be obtained by a calculation method by addition as described in JP-A-10-30535.
[0089]
In the embodiment, the initial combustion period is defined as a combustion mass ratio from zero to 2% (that is, BR1 = 2%), and the main combustion period is defined as a combustion mass ratio from 2 to 60% (that is, BR2 = 58%). The present invention is not necessarily limited to this value.
[0090]
Next, a method of calculating the laminar combustion speed SL1 during the initial combustion period, the laminar combustion speed SL2 during the main combustion period, and the ignition dead time DEADTIME will be described.
[0091]
Here, the mixed fuel constituting the combustion gas combusted in the cylinder is a mixed fuel of two or more kinds of fuels, for example, alcohol and gasoline. For convenience, the fuel having the lower boiling point is a and the fuel having the higher boiling point is The fuel is denoted as b. The composition ratios of the mixed fuel composed of the fuel a and the fuel b are assumed to be ra and rb (where ra + rb = 1).
(1) Calculation method 1: The composition ratios ra and rb can be detected by a fuel concentration detection sensor (not shown), or the air / fuel ratio can be calculated by an oxygen concentration detection sensor and the composition ratios ra and rb can be estimated from changes in the air / fuel ratio. Case (Note that a method for estimating the composition ratios ra and rb from the change in the air-fuel ratio will be described later.)
First, a method for calculating the laminar fuel velocity SL1 during the initial combustion period will be described. A temperature sensor (not shown) is used to detect the temperature Ts of the combustion gas in the cylinder at the start of combustion. When the laminar combustion speeds of the fuels a and b at this time are SL1a and SL1b, the laminar flow of the mixed fuel The combustion speed SL1 is calculated by the following equation.
[0092]
[Expression 24]

[0093]
Next, calculation of the laminar combustion speed SL2 in the main combustion period will be described. If the temperature of the combustion gas near the compression top dead center is detected by using the temperature sensor, and the laminar combustion speeds of the fuels a and b at this time are SL2a and SL2b, laminar combustion in the main combustion period Speed SL2 is
[0094]
[Expression 25]

[0095]
It can be calculated by
[0096]
Further, the dead ignition time DEADTIME can be calculated by the following formula, assuming that the dead ignition times of the fuels a and b are DEADTIMEa and DEADTIMEb.
[0097]
[Equation 26]

[0098]
Note that the ignition dead time of each fuel is calculated and stored in advance by a combustion experiment or the like.
(2) Calculation method 2: Initially, when the composition ratios ra and rb of the premixed fuels a and b cannot be detected or estimated, such as when the fuel concentration detection sensor fails or the oxygen concentration detection sensor fails In the method of calculating the laminar combustion speed SL1 during the combustion period, first, the temperature sensor is used to detect the temperature Ts of the combustion gas in the cylinder at the start of combustion, and the laminar combustion of the fuels a and b at this time is detected. When the speeds are SL1a and SL1b, the laminar combustion speed SL1 of the mixed fuel is calculated by the following equation.
[0099]
[Expression 27]

[0100]
Next, calculation of the laminar combustion speed SL2 in the main combustion period will be described. If the temperature of the combustion gas near the compression top dead center is detected by using the temperature sensor, and the laminar combustion speeds of the fuels a and b at this time are SL2a and SL2b, laminar combustion in the main combustion period Speed SL2 is
[0101]
[Expression 28]

[0102]
It can be calculated by
[0103]
Further, the dead ignition time DEADTIME can be calculated by the following formula, assuming that the dead ignition times of the fuels a and b are DEADTIMEa and DEADTIMEb.
[0104]
[Expression 29]

[0105]
Note that the ignition dead time of each fuel is calculated and stored in advance by a combustion experiment or the like.
(3) Calculation method 3: When the type of fuel mixed with the mixed fuel is known-When the boiling point of fuel a is lower than the boiling point of fuel b (for example, when fuel a is alcohol and fuel b is gasoline) )
The calculation method of the laminar combustion speed SL1 during the initial combustion period uses the temperature sensor to detect the temperature Ts of the combustion gas in the cylinder at the start of combustion, and the laminar combustion speed of the fuel a at this time is SL1a. Then, the laminar combustion speed SL1 of the mixed fuel is calculated by the following equation.
[0106]
[30]

[0107]
The laminar combustion speed SL2 during the main combustion period is determined by detecting the temperature Tt of the combustion gas near the compression top dead center using the temperature sensor and assuming that the laminar combustion speed of the fuel b at this time is SL2b. The laminar combustion speed SL2 in the period is
[0108]
[31]

[0109]
It can be calculated by
[0110]
Further, the dead ignition time DEADTIME can be calculated by the following formula, assuming that the dead ignition time of the fuel a is DEADTIMEa.
[0111]
[Expression 32]

[0112]
The ignition dead time of the fuel a is calculated and stored in advance by a combustion experiment or the like.
When the boiling point of the fuel a is higher than the boiling point of the fuel b (for example, when the fuel a is gasoline and the fuel b is alcohol)
The calculation method of the laminar combustion speed SL1 during the initial combustion period uses the temperature sensor to detect the temperature Ts of the combustion gas in the cylinder at the start of combustion, and the laminar combustion speed of the fuel b at this time is SL1b. Then, the laminar combustion speed SL1 of the mixed fuel is calculated by the following equation.
[0113]
[Expression 33]

[0114]
The laminar combustion speed SL2 in the main combustion period is detected by detecting the combustion gas temperature Tt near the compression top dead center using the temperature sensor, and the laminar combustion speed of the fuel a at this time is SL2a. The laminar combustion speed SL2 at
[0115]
[Expression 34]

[0116]
It can be calculated by
[0117]
Further, the dead ignition time DEADTIME can be calculated by the following equation, assuming that the dead fuel ignition time DEADTIMEb.
[0118]
[Expression 35]

[0119]
Note that the ignition dead time of the fuel b is calculated and stored in advance by a combustion experiment or the like.
[0120]
Here, it is known that the laminar combustion velocities SL1a and SL1b of the fuels a and b are generally expressed by the following equations.
[0121]
SL1 = SLstd × (T0 × Tstd) ^2.18 × (P0 / Pstd) ^−0.16 (15)
The laminar combustion speed SL0 at the reference temperature T0 and the reference pressure P0 is detected in advance for each fuel a and b by experiments or the like.
[0122]
Here, since the value of the pressure term in the above formula is small at the normal range of 2 bar or more, the laminar combustion speed SL0 (m / sec) with respect to the reference temperature may be calculated with the pressure sensitivity as a constant value. Etc. are calculated in advance by experiments. For example, when the laminar combustion speed is 1.0 (m / sec) at the reference temperature 550 (K), the following equation is approximately obtained using the ambient temperature Ts (K) calculated in step S24. be able to.
SL1 = f9 (T0)
= 1.0 × 0.7 × (T0 / 550) ^2.18 (16)
As described above, after the initial combustion period in which the flame has propagated in the laminar flow region and the combustion rate has rapidly increased, the sensitivity to pressure and temperature becomes dull, so the laminar combustion rates SL2a and SL2b are fixed in advance by experiments. It may be determined as a value.
[0123]
The gas pressure Ts may be directly measured using a temperature sensor, but can be calculated from the following equation, assuming that the pressure in the cylinder at the start of combustion is Ps, the volume in the cylinder is Vs, and the number of moles of intake air is ns. .
[0124]
[Expression 36]

[0125]
Further, the combustion gas temperature Tt near the compression top dead center can be calculated in the same manner.
[0126]
Thus, the composition ratio of the fuel obtained by mixing two different types of fuel is obtained, and the laminar combustion speed of the mixed fuel is determined from the composition ratio and the laminar combustion speed of each fuel, and the initial combustion period of the mixed fuel and the main combustion period. By calculating separately from the combustion period, the laminar combustion speed of the combustion gas can be accurately calculated, and as a result, the ignition timing at which MBT is obtained can be accurately calculated.
[0127]
In addition, the composition ratio of the fuel that is a mixture of two different types of fuel is obtained, and the ignition waste time of the mixed fuel is obtained from this composition ratio and the ignition waste time of each fuel, thereby accurately determining the ignition waste time of the combustion gas. As a result, it is possible to accurately calculate the ignition timing at which MBT is obtained.
[0128]
In addition, when the composition ratio of each fuel constituting the mixed fuel cannot be detected, the laminar combustion speed of the mixed fuel can be calculated based on the laminar combustion speed of each fuel. Therefore, the laminar burning velocity of the mixed fuel can be calculated, and it is not necessary to provide a concentration sensor or a composition ratio estimating means for detecting the composition ratio, and the conventional MBT is reduced while reducing the calculation load. The ignition timing of MBT can be calculated with higher accuracy than the calculation method.
[0129]
As a method of calculating the laminar combustion speed of the mixed fuel when the fuel constituting another mixed fuel is known, the initial combustion period of the combustion gas is the laminar combustion speed of the fuel having the lowest boiling point among the constituent fuels. The ignition timing can be calculated by using the laminar combustion speed of the mixed fuel and using the laminar combustion speed of the fuel having a high boiling point as the laminar combustion speed of the mixed fuel during the main combustion period near the compression top dead center. . By this method, the ignition timing of MBT can be calculated more accurately than the conventional MBT calculation method without using a concentration sensor and while further reducing the calculation load.
[0130]
Further, in the ignition timing control apparatus in the present embodiment, the cylinder internal volume VIVC and the cylinder internal temperature TINI at the time when the intake valve of the CVTC valve 22 is closed are calculated (steps S12 and S13). Then, the reaction probability RPROBA indicated by the ratio when the combustion state of the combustion gas is set to 1 when the combustion state under the predetermined condition is 1 is calculated (step S14).
[0131]
The combustion speed depends on the residual gas ratio EGRREM, water temperature TWK, equivalence ratio in addition to the atmospheric temperature and combustion speed in the cylinder, and the state in which the combustion speed changes according to these values is obtained in advance by experiment and mapped and held. I can leave. Of course, it is also possible to have a correlation depending on these factors as a functional expression.
[0132]
Next, when ignition is performed with MBT, the reference crank angle θPmax, which is the peak value of the pressure of the combustion gas, is substantially constant, and tends to shift toward the advance side on the high engine speed side, and is calculated as in step S15.
[0133]
The rate of temperature increase from the cylinder internal temperature TINI when the intake valve is closed is calculated from the cylinder internal volume V ₀ and the effective compression ratio Ec (steps S21 to S24), and the ambient temperature T0 when the combustion gas is ignited is calculated. Calculated (step S25). Based on the calculated atmospheric temperature T0, a laminar combustion speed SL1 is calculated (step S26).
[0134]
Since the combustion speed tends to increase as the laminar combustion speed increases, the turbulent flow speed in the cylinder also greatly depends on the combustion speed. The turbulent velocity depends on the shape of the intake port and the like, and generally increases as the engine speed increases. Therefore, this is calculated as the turbulence intensity U1 (step S27), and is multiplied by the laminar combustion speed to calculate the combustion speed FLAME1 (step S28).
[0135]
In step S29, the combustion period BURN1 from the ignition to the formation of the flame kernel is calculated. Since it is known that the formation of flame nuclei is performed by combustion of 2% of the mass of the combustion gas, 2% of the mass of the combustion gas is calculated and used. In the flame nucleation stage, the larger the cylinder volume at the time of ignition, the longer the formation time, so this is the numerator. By calculating using an arithmetic expression with the denominator as the denominator, it is possible to accurately and easily determine the combustion time at the flame nucleus formation stage.
[0136]
After the flame nuclei are formed, the flame nuclei rapidly grow in a rapid combustion stage in which the combustion gas is rapidly burned. A period during which 60% of the combustion gas at which the pressure reaches a peak is burned is calculated (steps S31 to S34). Again, the larger the volume in the cylinder at the time of growth of the flame kernel, the longer the formation time, so this is the numerator. The larger the reaction probability RPROBA, the shorter the time, and the faster the combustion speed, the shorter the time. Thus, the combustion time at the flame nucleus growth stage can be obtained accurately and easily.
[0137]
By adding the initial combustion period of the flame nucleus formation stage calculated as described above and the main combustion period of the flame nucleus growth stage, it is possible to calculate a period necessary for combustion with a combustion gas mass of 60% (step S42). Then, the MBT ignition timing is calculated in consideration of the dead time for ignition and the reference crank angle θPmax that is the maximum pressure in the cylinder, and an output command can be issued to the ignition coil (step S43).
[0138]
According to the present embodiment, when calculating the combustion period, it is divided into a flame nucleation stage in which the sensitivity of the combustion period with respect to pressure and temperature is large, and a main combustion period in which the sensitivity of the combustion period with respect to pressure and temperature decreases. By calculating, the combustion period can be calculated more accurately. In this case, calculation formulas such as combustion gas mass and cylinder volume for numerator, reaction area and combustion rate for denominator are used, and units of the same dimension are not used for numerator and denominator. Can be calculated.
[0139]
The combustion state is replaced with a dimensionless reaction probability and used for calculation. Since the reaction probability can be easily obtained by experiments or the like, an accurate combustion period can be calculated. Further, in the present embodiment, an example is shown in which the present invention is applied to an internal combustion engine having a variable valve mechanism that can continuously vary the operating angle and lift amount of the intake valve, but the cylinder contents when the intake valve is closed are shown. Since the MBT can be easily calculated even if the product changes, for example, an electromagnet is used to open and close the valve, and the valve timing can be arbitrarily changed. Application is also possible. Examples of a variable valve mechanism that can continuously vary the operating angle and lift amount of the intake valve are disclosed in Japanese Patent Application Laid-Open Nos. 11-107725 and 2003-41976.
[0140]
In this embodiment, when obtaining the combustion period from the combustion mass ratio, the combustion period BT is divided into an initial combustion period BURN1 (up to a combustion mass ratio of 2%) and a main combustion period BURN2 (from a combustion mass ratio of 2% to 60%). The ignition timing MBTCAL was calculated and calculated, but it may be further subdivided, or after subdividing, the combustion period (combustion mass ratio) is divided into, for example, an initial combustion period BURN1 and a main combustion period BURN2. You may make it add. By subdividing and obtaining the combustion period, the calculation accuracy of the combustion period can be improved.
[0141]
A method for calculating the air / fuel ratio by the oxygen concentration detection sensor used in the method (1) for calculating the laminar combustion speed of the combustion gas and estimating the composition ratios ra and rb from the change in the air / fuel ratio will be described below.
[0142]
Here, a method for detecting the alcohol concentration in the fuel containing alcohol will be described as an example. Since fuel containing alcohol is different from gasoline in the number of C (carbon) atoms, a larger injection amount is required to obtain the same equivalent ratio than gasoline. Therefore, the alcohol concentration in the fuel is estimated by the following procedure using the detection value of the oxygen concentration sensor 17. FIG. 14 shows a flow of control for updating the alcohol concentration estimated value ALC in the fuel.
[0143]
First, in step (hereinafter simply referred to as S) 51, an air-fuel ratio feedback correction coefficient α as an air-fuel ratio correction amount calculated based on the output signal of the oxygen concentration sensor 17 is read.
[0144]
In S52, it is determined whether or not the air-fuel ratio learning condition is satisfied. If the air-fuel ratio learning condition is satisfied, the process proceeds to S53, and the map value of the αm calculation map for each operation region is rewritten. Do. If the air-fuel ratio learning condition is not satisfied, the process proceeds to S54 without rewriting the map value of each αm calculation map. Here, αm is an air-fuel ratio learning correction coefficient calculated based on α. Note that the air-fuel ratio feedback. The fuel correction coefficient α and the air-fuel ratio learning correction coefficient αm are parameters used for air-fuel ratio feedback control, and the fuel injection amount from the injector 3 is corrected according to α and αm. The calculation method of the air-fuel ratio feedback correction coefficient α and the air-fuel ratio learning correction coefficient αm can be used by any known calculation method, and detailed description of these calculation methods will be omitted.
[0145]
In S54, an air-fuel ratio learning correction coefficient αm as an air-fuel ratio correction amount is obtained for each operation region with reference to the current αm map for each operation region. Subsequently, the process proceeds to S55, in which it is determined whether a permission condition for estimating the alcohol concentration is satisfied. That is, in S55, it is determined whether conditions such as the water temperature, the time after engine start, the progress of the air-fuel ratio learning control, the refueling history, and the like are satisfied. If the conditions are satisfied, the process proceeds to S56. If not, the process is terminated without estimating the alcohol concentration.
[0146]
In S56, an air-fuel ratio sensitivity correction total amount αt expressed as the following equation (37) is calculated.
[0147]
[Expression 37]

[0148]
Here, ETAHOS is a fuel property correction amount calculated from the previous alcohol concentration estimated value ALC, and the previous value of αt calculated by reverse lookup from the previous alcohol concentration estimated value ALC using FIG. 15 described later. It is.
[0149]
In addition, αm ′ in S56 is an average value of αm in a representative rotational load region among αm for each operation region obtained in S54, in other words, an average of αm in a region where the frequency of use as an engine is high. Value.
[0150]
In S57, the alcohol concentration estimated value ALC is calculated from the air-fuel ratio sensitivity correction total amount αt calculated in S56 using the map shown in FIG.
[0151]
The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea of the present invention.
[Brief description of the drawings]
FIG. 1 is a system diagram of an internal combustion engine of the present invention.
FIG. 2 is a block diagram of ignition timing control executed by an engine controller.
FIG. 3 is a pressure change diagram of a combustion chamber.
FIG. 4 is a characteristic diagram illustrating a change in combustion mass ratio.
FIG. 5 is a flowchart for explaining calculation of a physical quantity.
FIG. 6 is a diagram for explaining the positional relationship between an engine crankshaft and a connecting rod.
FIG. 7 is a characteristic diagram of a water temperature correction coefficient.
FIG. 8 is a characteristic diagram of an equivalence ratio correction coefficient.
FIG. 9 is a characteristic diagram of a reference crank angle.
FIG. 10 is a flowchart for explaining calculation of an initial combustion period.
FIG. 11 is a characteristic diagram of a rate of temperature increase.
FIG. 12 is a flowchart for explaining calculation of a main combustion period.
FIG. 13 is a flowchart for explaining calculation of basic ignition timing.
FIG. 14 is a flowchart showing a flow of control for calculating an estimated value of alcohol concentration in fuel.
FIG. 15 is a characteristic diagram showing a correlation between an air-fuel ratio sensitivity correction total amount αt and an alcohol concentration estimated value ALC.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake collector 3 Injector 4 Intake manifold 5 Exhaust manifold 6 Muffler 7 Air cleaner 8 Electronic control throttle 9 Intake duct 20 Control unit

Claims (18)

Means for calculating the type and composition ratio of the fuel constituting the combustion gas combusted in the cylinder;
Means for calculating a laminar combustion rate, which is a rate at which the combustion gas in the cylinder burns in a laminar state, based on the type and composition ratio of the fuel;
Means for calculating turbulence intensity, which is an index indicating combustion turbulence based on the operating state;
Means for calculating the volume in the cylinder at the start of combustion of the combustion gas;
Means for setting the amount of change in the combustion mass ratio up to a predetermined crank angle;
Means for calculating a reaction probability indicating the ease of combustion of the combustion gas in the cylinder relative to the ease of combustion of the combustion gas under predetermined operating conditions;
A combustion period is calculated based on the laminar flow velocity, the turbulence intensity, the volume in the cylinder, the amount of change in the combustion mass ratio, and the reaction probability, and a basic ignition timing at which MBT is obtained based on the combustion period is calculated. An ignition timing control device for an internal combustion engine, comprising: means for calculating. Reference crank angle calculating means for calculating a crank angle at which the combustion pressure of the combustion gas in the cylinder is maximized;
An ignition dead time equivalent crank angle calculating means for calculating a crank angle section from the timing at which an ignition command signal of an ignition plug for igniting the combustion gas in the cylinder is output until the ignition plug ignites,
2. The ignition timing control device for an internal combustion engine according to claim 1 , wherein the basic ignition timing from which the MBT is obtained is calculated from the combustion period, the calculated reference crank angle, and a crank angle equivalent to the ignition dead time. . The combustion period is divided into an initial combustion period in which flame nuclei are formed and a main combustion period in which the flame propagates, and the type and composition ratio of the fuel mixed in the combustion gas in each of the initial combustion period and the main combustion period 3. The ignition timing control device according to claim 1, wherein a laminar combustion speed of the combustion gas is calculated based on the ignition timing. Concentration detection means for detecting the concentration of fuel in the combustion gas,
4. The laminar burning velocity of the combustion gas is calculated by weighted averaging according to the concentration of each fuel in which the laminar burning velocity of each fuel is detected. 5. Ignition timing control device for internal combustion engine. The ignition timing control device for an internal combustion engine according to any one of claims 1 to 3 , wherein the laminar combustion velocity of the combustion gas is calculated by averaging the laminar combustion velocity of each fuel . The laminar combustion speed of the combustion gas is the laminar combustion speed of the fuel having the lowest boiling point of the fuel in the initial combustion period, and the laminar combustion speed of the fuel having the highest boiling point of the fuel in the main combustion period. The ignition timing control device for an internal combustion engine according to claim 3 , wherein Means for calculating the type and composition ratio of the fuel constituting the combustion gas combusted in the cylinder;
Means for calculating an ignition dead time indicating a delay of the actual ignition time with respect to the target ignition time based on the type and composition ratio of the fuel;
Means for calculating a laminar combustion rate, which is a rate at which the combustion gas in the cylinder burns in a laminar state;
Means for calculating turbulence intensity, which is an index indicating combustion turbulence based on the operating state;
Means for calculating the volume in the cylinder at the start of combustion of the combustion gas;
Means for setting the amount of change in the combustion mass ratio up to a predetermined crank angle;
Means for calculating a reaction probability indicating the ease of combustion of the combustion gas in the cylinder relative to the ease of combustion of the combustion gas under predetermined operating conditions;
A combustion period is calculated based on the ignition dead time, the laminar combustion speed, the turbulence intensity, the cylinder volume, the amount of change in the combustion mass ratio, and the reaction probability, and the MBT is obtained based on the combustion period. Means for calculating the basic ignition timing
Ignition timing control apparatus of the internal combustion engine comprising the. Concentration detection means for detecting the concentration of fuel in the combustion gas,
The ignition timing control device for an internal combustion engine according to claim 7 , wherein the ignition dead time is calculated by weighted averaging according to the concentration of each fuel in which the ignition dead time of each fuel is detected . 9. The ignition timing control device for an internal combustion engine according to claim 8, wherein the ignition dead time is calculated by averaging ignition dead times of the respective fuels . Said combustion period claim 1 or, characterized in that calculated on the basis of the calculated value obtained by dividing the value obtained by multiplying a change amount of the combustion mass proportion and cylinder volume at a value obtained by multiplying the reaction probability and the combustion rate The ignition timing control device according to claim 7 . 11. The reaction probability is set to a value smaller than 1 when the easiness of combustion at a predetermined residual gas ratio is 1, and the larger the predetermined residual gas ratio is, the lower the value is . The ignition timing control device for an internal combustion engine according to one of the above. The reaction probability, the ease of combustion at a given temperature and 1, in any one of claims 1, 7 or 10 and sets a smaller value than 1 as lower than the temperature of Jo Tokoro An ignition timing control device for an internal combustion engine as described. The reaction probability, the ease of combustion at a given equivalent ratio is 1 and richer than a predetermined equivalent ratio, claim and sets at a value smaller than 1 in both the lean side 1,7 or The ignition timing control device for an internal combustion engine according to any one of 10. The amount of change in the combustion mass proportion of up to the predetermined crank angle, claim 1,7 or 13, characterized in that post-ignition combustion pressure of the combustion gas is the amount of change in the combustion mass proportion of up to a maximum The ignition timing control device for an internal combustion engine according to one of the above. A combustion mass ratio change amount up to the predetermined crank angle is divided into a plurality of parts, a combustion period corresponding to each combustion mass ratio change amount is calculated, and all combustion periods are summed to obtain a combustion period. The ignition timing control device for an internal combustion engine according to claim 14 . The amount of change in the combustion mass ratio up to the predetermined crank angle is defined as the amount of change in the combustion mass ratio until the flame nucleus is formed after ignition of the combustion gas, and the combustion pressure after ignition of the combustion gas is maximum after the formation of the flame nucleus. The ignition timing control device for an internal combustion engine according to claim 15 , wherein the ignition timing control device is divided into a change amount of the combustion mass ratio until it becomes . The atmospheric temperature at the start of combustion of the combustion gas in the cylinder and the atmospheric pressure at the start of combustion of the combustion gas in the cylinder are calculated, and the combustion speed of the combustion gas in the cylinder is a predetermined temperature of the combustion gas, 17. The ignition timing control device for an internal combustion engine according to claim 1, wherein the ignition timing control device calculates the basic laminar combustion speed at a predetermined pressure based on the atmospheric temperature and the atmospheric pressure . 18. The temperature of the combustion gas when the intake valve is closed is calculated, and the ambient temperature is calculated by multiplying the calculated temperature by the temperature increase rate calculated based on the effective compression ratio. An ignition timing control device for an internal combustion engine according to claim 1.

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