JP4062729B2

JP4062729B2 - Abnormality diagnosis device for early catalyst warm-up system

Info

Publication number: JP4062729B2
Application number: JP2002223337A
Authority: JP
Inventors: 森永　　修二郎; 摩島　　嘉裕; 達也岡; 飯田　　寿; 山田　　正和; 山下　　幸宏
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2001-11-05
Filing date: 2002-07-31
Publication date: 2008-03-19
Anticipated expiration: 2022-07-31
Also published as: JP2003201906A

Description

【０００１】
【発明の属する技術分野】
本発明は、排出ガス浄化用の触媒を早期に暖機する触媒早期暖機システムの異常診断を行う触媒早期暖機システムの異常診断装置に関するものである。
【０００２】
【従来の技術】
近年、車両に搭載される内燃機関は、冷間始動時に排出ガス浄化用の触媒を早期に活性温度にまで暖機するために、冷間始動時に触媒早期暖機制御を実施するようにしている。この触媒早期暖機制御では、一般に、点火時期を遅角して排気温度を上昇させると共に、通常のアイドル制御時よりも吸入空気量を増量させてアイドル回転速度を上昇させることで、冷間始動時の点火時期遅角によってアイドル回転が不安定になるのを防止しながら排気熱量（触媒に供給される熱量）を増大させて触媒の暖機を促進するようにしている。この触媒早期暖機システムの故障等によって触媒早期暖機制御中の排気熱量が減少して触媒の早期暖機に必要な熱量が触媒に供給されなくなると、冷間始動時に触媒の暖機（活性化）が遅れて、冷間始動時の排気エミッションが悪化してしまうため、触媒早期暖機システムの異常を早期に検出する必要がある。
【０００３】
そこで、特開２００１−１３２４３８号公報に示すように、触媒の温度を検出する触媒温度センサを設け、この触媒温度センサで検出した触媒温度と、始動後の積算吸入空気量に基づいて推定した推定触媒温度とを比較して、触媒早期暖機システムの異常の有無を診断するようにしたものがある。
【０００４】
また、特開２００１−１３２５２６号公報に示すように、触媒早期暖機制御中にエンジン回転速度と点火時期遅角量の少なくとも一方を所定の異常判定値と比較して、触媒早期暖機システムの異常の有無を診断するようにしたものもある。
【０００５】
【発明が解決しようとする課題】
しかし、前者（特開２００１−１３２４３８号公報）では、触媒温度を検出するための触媒温度センサを新たに設ける必要があるため、その分、コストアップしてしまうという欠点がある。
【０００６】
また、内燃機関の排気熱量（触媒に供給される熱量）は、排気温度と排気流量によって変化し、更に、図４に示すように、排気温度は空燃比によって変化し、排気流量は吸入空気量によって変化するため、内燃機関の排気熱量（触媒に供給される熱量）は、吸入空気量や空燃比によって変化することになる。このため、後者（特開２００１−１３２５２６号公報）では、エンジン回転速度や点火時期に基づいて触媒早期暖機システムが正常と診断された場合でも、吸入空気量や空燃比の影響を受けて排気熱量が減少して触媒の早期暖機に必要な熱量が触媒に供給されていない、つまり、触媒早期暖機制御が正常に行われていない可能性があり、触媒早期暖機システムの異常の有無を誤診断する可能性がある。
【０００７】
本発明はこのような事情を考慮してなされたものであり、従ってその目的は、触媒早期暖機システムの異常診断精度を向上することができると共に、低コスト化の要求も満たすことができる触媒早期暖機システムの異常診断装置を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、本発明の請求項１の触媒早期暖機システムの異常診断装置は、触媒早期暖機制御中に内燃機関の運転状態に基づいて該内燃機関の排気熱量又は前記触媒に供給する熱量を推定する排気熱量算出手段と、この排気熱量算出手段で推定した熱量に基づいて触媒早期暖機システムの異常の有無を診断する異常診断手段と、触媒早期暖機制御中の空燃比を推定する空燃比推定手段とを備え、前記異常診断手段は、前記空燃比推定手段で推定した前記触媒早期暖機制御中の空燃比に基づいて異常診断条件を補正することを特徴とするものである。
【００１２】
本発明のように、排気熱量算出手段によって触媒早期暖機制御中に内燃機関の運転状態に基づいて内燃機関の排気熱量又は触媒に供給する熱量を推定し、その熱量に基づいて触媒早期暖機システムの異常の有無を診断するようにすれば、触媒早期暖機制御中の排気熱量が触媒の早期暖機に必要な熱量となっているか否かをより精度良く判定することができる。
【００１３】
この場合、請求項２のように、吸入空気量パラメータと空燃比パラメータとのうちの少なくとも一方に基づいて排気熱量を求めるようにすると良い。前述したように、吸入空気量や空燃比は、内燃機関の排気熱量を変化させるパラメータとなるため、吸入空気量パラメータや空燃比パラメータを用いれば、排気熱量を精度良く求めることができる。
【００１４】
更に、機関回転速度、点火時期、空燃比によって排気温度が変化することを考慮して、請求項３のように、内燃機関の排気熱量を求める際に、機関回転速度、点火時期、空燃比パラメータのうちの少なくとも１つを用いて排気温度を推定し、この推定排気温度と吸入空気量パラメータとに基づいて排気熱量を算出するようにしても良い。このようにすれば、排気熱量の算出精度を更に向上することができる。
【００１５】
また、請求項４のように、吸入空気量パラメータとしては、エアフローメータ等で検出した吸入空気量、スロットル開度、吸気バルブの可変リフト量、吸気圧のうちの少なくとも１つを用いるようにすれば良い。スロットル開度、吸気圧は、いずれも吸入空気量と相関関係があるため、吸入空気量パラメータとして用いることができる。更に、可変バルブリフト機構によって吸気バルブのリフト量を可変して吸入空気量を調整するシステムでは、吸気バルブの可変リフト量を吸入空気量パラメータとして用いることができる。
【００１６】
また、請求項５のように、空燃比パラメータは、排気系の空燃比センサで検出した空燃比、燃料噴射量、燃焼ラフネス値のうちの少なくとも１つを用いるようにすれば良い。燃料噴射量によって空燃比が変化し、空燃比によって燃焼ラフネス値が変化するため、燃料噴射量や燃焼ラフネス値も空燃比パラメータとして用いることができる。尚、始動後に空燃比センサが活性温度に昇温するまでの期間は空燃比を精度良く検出できないため、空燃比センサの出力を空燃比パラメータとして用いる場合は、空燃比センサの活性後にならないと空燃比パラメータを使用できないが、燃料噴射量や燃焼ラフネス値は、始動直後（触媒早期暖機制御開始直後）から空燃比パラメータとして用いることができる利点がある。
【００１７】
ところで、触媒の暖機に関わる熱量には、内燃機関の排気熱量の他に、触媒内部で排出ガス中のリーン成分（酸素等）とリッチ成分（ＨＣ等）とが反応して発生する反応熱量がある。触媒早期暖機制御中の空燃比によって触媒内部で反応するリーン成分量（酸素量等）が変化して触媒内部で発生する反応熱量が変化するため、触媒早期暖機制御中の空燃比よって触媒の早期暖機に必要な排気熱量も異なってくる。
【００１８】
そこで、請求項１に係る発明では、空燃比推定手段によって触媒早期暖機制御中（排気熱量算出中）の空燃比を推定し、排気熱量に基づいて触媒早期暖機システムの異常の有無を診断する際に、空燃比推定手段で推定した触媒早期暖機制御中の空燃比に基づいて異常診断条件を補正するようにしている。このようにすれば、触媒早期暖機制御中の空燃比によって触媒内部で発生する反応熱量が変化するのに対応して異常診断条件（例えば異常判定値又は排気熱量）を補正することができ、触媒早期暖機制御中の排気熱量が触媒の早期暖機に必要な熱量となっているか否かを精度良く判定することができる。
【００１９】
一般に、触媒早期暖機制御中は、内燃機関の温度が低いため、燃料噴射弁から噴射された燃料のうち吸気ポート壁面等に付着する燃料量（ウェット量）が比較的多くなっている。従って、触媒早期暖機制御中は、燃料噴射量と吸入空気量からでは、空燃比を精度良く推定することができない。
【００２０】
そこで、請求項６のように、排気通路に設けられた空燃比センサが活性状態になった時に該空燃比センサで検出した空燃比に基づいて触媒早期暖機制御中の空燃比を推定するようにしても良い。この場合、空燃比センサが活性状態になるまで待つ必要があるが、空燃比センサで検出した実際の空燃比に基づいて触媒早期暖機制御中の空燃比を推定することができるので、燃料噴射量と吸入空気量から触媒早期暖機制御中の空燃比を推定する場合に比べて、触媒早期暖機制御中の空燃比を精度良く推定することができる。
【００２１】
また、空燃比センサの活性後は、空燃比フィードバック制御が開始されて、空燃比センサの検出空燃比に基づいて空燃比フィードバック補正係数が算出されるため、請求項７のように、空燃比フィードバック補正係数に基づいて触媒早期暖機制御中の空燃比を推定するようにしても良い。空燃比フィードバック補正係数は、空燃比センサの検出空燃比に応じて設定されるので、空燃比フィードバック補正係数に基づいて触媒早期暖機制御中の空燃比を推定しても、空燃比センサの活性時の検出空燃比を用いる場合（請求項６）と同様に、触媒早期暖機制御中の空燃比を精度良く推定することができる。
【００２２】
更に、触媒早期暖機制御中に内燃機関の回転挙動に基づいて空燃比をリーン方向に補正するためのリーン化補正係数を算出するシステムの場合には、請求項８のように、触媒早期暖機制御中の空燃比の推定に用いるパラメータとして、前記空燃比センサの活性時の検出空燃比又は前記空燃比フィードバック補正係数に加えて、リーン化補正係数も用いるようにしても良い。つまり、空燃比センサの活性時の検出空燃比（又は空燃比フィードバック補正係数）とリーン化補正係数とに基づいて触媒早期暖機制御中の空燃比を推定するようにしても良い。リーン化補正係数は、触媒早期暖機制御中の空燃比の挙動（リーン方向への変化量）を表すパラメータとなるため、空燃比センサの活性時の検出空燃比（又は空燃比フィードバック補正係数）とリーン化補正係数とを用いれば、触媒早期暖機制御中のリーン化補正も考慮して空燃比を更に精度良く推定することができる。
【００２３】
ところで、車両の走行中は、運転条件の変化に応じて吸入空気量や燃料噴射量が変化し、それに応じて触媒早期暖機システムの異常診断パラメータ（吸入空気量パラメータや空燃比パラメータ）が変化するだけでなく、走行風による触媒の放熱によって触媒の暖機が遅れるため、車両の走行中は、運転条件の変化や走行風の影響を考慮しないと、触媒早期暖機システムの異常診断を精度良く行うことは困難である。
【００２４】
そこで、請求項９のように、触媒早期暖機制御中且つ内燃機関のアイドル運転中に、触媒早期暖機システムの異常診断を実行するようにすると良い。アイドル運転中であれば、内燃機関の運転条件（吸入空気量や燃料噴射量）が比較的安定しているため、触媒早期暖機システムの異常診断パラメータに及ぼす運転条件の影響を少なくできると共に、走行風による触媒の暖機の遅れも発生しない。そのため、アイドル運転中は、運転条件の変化や走行風の影響を考慮せずに、触媒早期暖機システムの異常診断を精度良く行うことができる。
【００２５】
【発明の実施の形態】
［実施形態（１）］
以下、本発明の実施形態（１）を図１乃至図４に基づいて説明する。まず、図１に基づいてエンジン制御システム全体の概略構成を説明する。内燃機関であるエンジン１１の吸気管１２の最上流部には、エアクリーナ１３が設けられ、このエアクリーナ１３の下流側に、吸入空気量を検出するエアフローメータ１４が設けられている。このエアフローメータ１４の下流側には、スロットルバルブ１５とスロットル開度を検出するスロットル開度センサ１６とが設けられている。
【００２６】
更に、スロットルバルブ１５の下流側には、サージタンク１７が設けられ、このサージタンク１７に、吸気管圧力を検出する吸気管圧力センサ１８が設けられている。また、サージタンク１７には、エンジン１１の各気筒に空気を導入する吸気マニホールド１９が設けられ、各気筒の吸気マニホールド１９の吸気ポート近傍に、それぞれ燃料を噴射する燃料噴射弁２０が取り付けられている。また、エンジン１１のシリンダヘッドには、各気筒毎に点火プラグ２１が取り付けられ、各点火プラグ２１の火花放電によって筒内の混合気に点火される。
【００２７】
一方、エンジン１１の排気管２２には、排出ガス中のＣＯ，ＨＣ，ＮＯｘ等を低減させる三元触媒等の触媒２４が設けられ、この触媒２４の上流側に排出ガスの空燃比又はリーン／リッチを検出する空燃比センサ２３（Ａ／Ｆセンサ、酸素センサ等）が設けられている。また、エンジン１１のシリンダブロックには、冷却水温を検出する冷却水温センサ２９や、エンジン回転速度を検出するクランク角センサ３０が取り付けられている。
【００２８】
これら各種のセンサ出力は、エンジン制御回路（以下「ＥＣＵ」と表記する）３１に入力される。このＥＣＵ３１は、マイクロコンピュータを主体として構成され、内蔵されたＲＯＭ（記憶媒体）に記憶された各種の制御プログラムを実行することで、エンジン運転状態に応じて燃料噴射弁２０の燃料噴射量や点火プラグ２１の点火時期を制御する。
【００２９】
また、ＥＣＵは、ＲＯＭに記憶された触媒早期暖機制御プログラム（図示せず）を実行することで、冷間始動時に、触媒２４を早期に活性温度にまで暖機するための触媒早期暖機制御を実行する。この触媒早期暖機制御では、通常のアイドル制御時よりも点火時期を遅角して排出ガスの温度を上昇させると共に、通常のアイドル制御時よりも吸入空気量を増加させてアイドル回転速度を上昇させることで、冷間始動時の点火時期遅角によってアイドル回転が不安定になるのを防止しながら排気熱量（触媒２４に供給される熱量）を増大させて触媒２４の暖機を促進する。
【００３０】
ここで、エンジン１１の排気熱量（触媒２４に供給される熱量）は、排気温度と排気流量によって変化し、更に、図４に示すように、排気温度は空燃比によって変化し、排気流量は吸入空気量によって変化するため、エンジン１１の排気熱量（触媒２４に供給される熱量）は、吸入空気量や空燃比によって変化することになる。ここで、空燃比は、空燃比センサ２３で検出できるが、冷間始動直後（触媒早期暖機制御開始直後）は、空燃比センサ２３が活性化していないため、本実施形態（１）では、空燃比と相関関係のある燃料噴射量ＴＡＵを空燃比パラメータとして用いる。
【００３１】
これらの事情を考慮して、ＥＣＵ３１は、ＲＯＭに記憶された図２の触媒早期暖機システム異常診断プログラムを実行することで、図３に示すように、触媒早期暖機制御中に吸入空気量ＧＡ（吸入空気量パラメータ）と燃料噴射量ＴＡＵ（空燃比パラメータ）をそれぞれ積算し、吸入空気量積算値ＧＡＳＵＭと燃料噴射量積算値ＴＡＵＳＵＭが、それぞれ所定の正常範囲内か否かによって排気熱量が触媒２４の早期暖機に必要な熱量となっているか否かを判定して、触媒早期暖機システムの異常の有無を診断する。
【００３２】
以下、ＥＣＵ３１が実行する図２の触媒早期暖機システム異常診断プログラムの具体的な処理内容を説明する。本プログラムは、所定時間毎又は所定クランク角毎に繰り返し実行され、特許請求の範囲でいう異常診断手段に相当する役割を果たす。本プログラムが起動されると、まず、ステップ１０１で、触媒早期暖機実行条件が成立しているか否かを、例えば冷却水温が所定温度よりも低いか否か等によって判定する。もし、触媒早期暖機実行条件が成立していなければ、そのまま本プログラムを終了する。
【００３３】
一方、触媒早期暖機実行条件が成立していれば、ステップ１０２に進み、アイドル運転状態か否かを判定する。もし、アイドル運転状態でなければ、以降の異常診断処理（ステップ１０３〜１１２）を実行することなく本プログラムを終了する。
【００３４】
これに対して、触媒早期暖機実行条件が成立して触媒早期暖機制御が実行され、且つアイドル運転中であれば、ステップ１０３以降の異常診断処理を次のようにして実行する。まず、ステップ１０３に進み、エアフローメータ１４で検出した吸入空気量ＧＡを読み込んだ後、ステップ１０４に進み、燃料噴射制御プログラム（図示せず）で算出した燃料噴射量ＴＡＵを読み込む。
【００３５】
この後、ステップ１０５に進み、前回までの吸入空気量積算値ＧＡＳＵＭに今回の吸入空気量ＧＡを加算して吸入空気量積算値ＧＡＳＵＭを更新した後、ステップ１０６に進み、前回までの燃料噴射量積算値ＴＡＵＳＵＭに今回の燃料噴射量ＴＡＵを加算して燃料噴射量積算値ＴＡＵＳＵＭを更新する。この後、ステップ１０７に進み、カウンタＣＳＵＭのカウント値を「１」だけカウントアップする。
【００３６】
この後、ステップ１０８に進み、カウンタＣＳＵＭのカウント値が所定値Ｋを越えたか否かを判定し、越えていなければ、ステップ１０１に戻る。これにより、カウンタＣＳＵＭのカウント値が所定値Ｋを越えるまで、吸入空気量積算値ＧＡＳＵＭを算出する処理と、燃料噴射量積算値ＴＡＵＳＵＭを算出する処理を繰り返す。
【００３７】
その後、カウンタＣＳＵＭのカウント値が所定値Ｋを越えた時点で、ステップ１０９に進み、吸入空気量積算値ＧＡＳＵＭが所定の正常範囲内（Ｇmin ＜ＧＡＳＵＭ＜Ｇmax ）であるか否かを判定し、更に、次のステップ１１０で、燃料噴射量積算値ＴＡＵＳＵＭが所定の正常範囲内（Ｔmin ＜ＴＡＵＳＵＭ＜Ｔmax ）か否かを判定する。
【００３８】
ステップ１０９とステップ１１０で共に「Ｙｅｓ」と判定された場合（つまり吸入空気量積算値ＧＡＳＵＭが正常範囲内、且つ、燃料噴射量積算値ＴＡＵＳＵＭが正常範囲内と判定された場合）には、排気熱量が触媒２４の早期暖機に必要な熱量となっていると判断して、ステップ１１１に進み、触媒早期暖機システムが正常と判定して、本プログラムを終了する。
【００３９】
これに対して、ステップ１０９で「Ｎｏ」と判定された場合（吸入空気量積算値ＧＡＳＵＭが正常範囲外と判定された場合）、又は、ステップ１１０で「Ｎｏ」と判定された場合（燃料噴射量積算値ＴＡＵＳＵＭが正常範囲外と判定された場合）には、排気熱量が触媒２４の早期暖機に適正な熱量となっていない（排気熱量が不足又は過剰）と判断して、ステップ１１２に進み、触媒早期暖機システムが異常と判定して、警告ランプ（図示せず）を点灯して運転者に警告すると共に、異常コードをＥＣＵ３１のバックアップＲＡＭ（図示せず）に記憶した後、本プログラムを終了する。
【００４０】
以上説明した本実施形態（１）では、触媒早期暖機制御中に吸入空気量ＧＡ（吸入空気量パラメータ）と燃料噴射量ＴＡＵ（空燃比パラメータ）をそれぞれ積算し、吸入空気量積算値ＧＡＳＵＭと燃料噴射量積算値ＴＡＵＳＵＭが、それぞれ所定の正常範囲内か否かによって触媒早期暖機システムの異常の有無を診断するようにしたので、触媒早期暖機制御中の積算排気熱量（始動後に触媒２４に供給される総熱量）を評価して、触媒早期暖機システムの異常の有無を精度良く診断することができる。しかも、触媒温度を検出するためのセンサを新たに設ける必要がないので、低コスト化の要求も満たすことができる。
【００４１】
尚、本実施形態（１）では、吸入空気量ＧＡと燃料噴射量ＴＡＵの両方を用いて触媒早期暖機システムの異常診断を行うようにしたが、吸入空気量ＧＡと燃料噴射量ＴＡＵのうちのいずれか一方のみを用いて触媒早期暖機システムの異常診断を行うようにしても良い。
【００４２】
ところで、車両の走行中は、エンジン運転条件の変化に応じて吸入空気量や燃料噴射量が変化し、それに応じて触媒早期暖機システムの異常診断パラメータ（吸入空気量パラメータや空燃比パラメータ）が変化するだけでなく、走行風による触媒２４の放熱によって触媒２４の暖機が遅れるため、車両の走行中は、運転条件の変化や走行風の影響を考慮しないと、媒早期暖機システムの異常診断を精度良く行うことは困難である。
【００４３】
その点、本実施形態（１）では、エンジン運転条件（吸入空気量、燃料噴射量等）が比較的安定しているアイドル運転中に、触媒早期暖機システムの異常診断を実行するようにしたので、異常診断パラメータに及ぼすエンジン運転条件の影響を少なくできると共に、走行風による触媒２４の暖機の遅れも発生しない。そのため、本実施形態（１）では、エンジン運転条件の変化や走行風の影響を考慮せずに、触媒早期暖機システムの異常診断を精度良く行うことができる。
【００４４】
尚、本実施形態（１）では、吸入空気量パラメータとしてエアフローメータ１４で検出した吸入空気量ＧＡを用いたが、吸入空気量パラメータとしてスロットル開度や吸気圧を用いるようにしても良い。更に、可変バルブリフト機構によって吸気バルブのリフト量を可変して吸入空気量を調整するシステムでは、吸気バルブの可変リフト量を吸入空気量パラメータとして用いるようにしても良い。或は、スロットル開度、吸気圧、吸気バルブの可変リフト量等を用いて求めた推定吸入空気量を吸入空気量パラメータとして用いても良い。
【００４５】
また、本実施形態（１）では、空燃比パラメータとして燃料噴射量ＴＡＵを用いたが、空燃比パラメータとして燃焼ラフネス値を用いるようにしても良い。或は、燃料噴射量、燃焼ラフネス値等を用いて求めた推定空燃比を空燃比パラメータとして用いても良い。尚、冷間始動時でも早期に活性化可能な空燃比センサを備えたシステムの場合には、空燃比パラメータとして空燃比センサで検出した空燃比を用いても良い。
【００４６】
［実施形態（２）］
前記実施形態（１）では、触媒早期暖機制御中に吸入空気量ＧＡ（吸入空気量パラメータ）と燃料噴射量ＴＡＵ（空燃比パラメータ）を積算し、その積算値に基づいて触媒早期暖機システムの異常の有無を診断するようにしたが、図５及び図６に示す本発明の実施形態（２）では、触媒早期暖機制御中に推定空燃比Ａ／Ｆ（空燃比パラメータ）を監視し、その挙動に基づいて触媒早期暖機システムの異常の有無を診断するようにしている。
【００４７】
以下、本実施形態（２）の触媒早期暖機システムの異常診断を行う図５の触媒早期暖機システム異常診断プログラムの処理内容を説明する。本プログラムでは、触媒早期暖機制御中且つアイドル運転中のときに、吸入空気量ＧＡと燃料噴射量ＴＡＵを読み込む（ステップ２０１〜２０４）。
【００４８】
この後、ステップ２０５に進み、吸入空気量ＧＡを燃料噴射量ＴＡＵで除算して推定空燃比Ａ／Ｆを算出する。
Ａ／Ｆ＝ＧＡ／ＴＡＵ
尚、図６に示すように、推定空燃比Ａ／Ｆの算出は、空燃比Ａ／Ｆが安定し始めるタイミング付近から開始するようにしても良い。
【００４９】
この後、ステップ２０６に進み、カウンタＣＳＵＭのカウント値を「１」だけカウントアップした後、ステップ２０７に進み、推定空燃比Ａ／Ｆが所定空燃比（例えば１４）よりもリッチか否かを判定する。前述したように、排気温度は空燃比によって変化するため（図４参照）、推定空燃比Ａ／Ｆが所定空燃比（例えば１４）よりもリッチであるか否かによって触媒早期暖機制御中に排気温度が異常低下したか否かを判定することができる。推定空燃比Ａ／Ｆが所定空燃比よりもリーンであれば、次のステップ２０８に進み、カウンタＣＳＵＭのカウント値が所定値Ｋを越えたか否かによって異常診断期間が終了したか否かを判定し、異常診断期間の終了前であれば、ステップ２０１に戻る。
【００５０】
一方、上記ステップ２０７で推定空燃比Ａ／Ｆが所定空燃比よりもリッチと判定された場合には、ステップ２１０に進み、リッチカウンタＮのカウント値を「１」だけカウントアップする。このリッチカウンタＮは、推定空燃比Ａ／Ｆが所定空燃比よりもリッチとなった回数をカウントすることで、排気温度が異常低下した回数をカウントする。この後、ステップ２１１に進み、リッチカウンタＮのカウント値が所定値Ｍを越えたか否かを判定し、越えていなければ、ステップ２０８に進む。
【００５１】
上記ステップ２１１で、リッチカウンタＮのカウント値が所定値Ｍを越えることなく、ステップ２０８で、異常診断期間が終了したと判定されれば、ステップ２０９に進み、触媒早期暖機システムが正常と判定して、本プログラムを終了する。
【００５２】
これに対して、異常診断期間が終了する前に、ステップ２１１でリッチカウンタＮのカウント値が所定値Ｍを越えたと判定された場合には、ステップ２１２に進み、触媒早期暖機システムが異常と判定して、警告ランプ（図示せず）を点灯して運転者に警告すると共に、異常コードをＥＣＵ３１のバックアップＲＡＭ（図示せず）に記憶した後、本プログラムを終了する。
【００５３】
以上説明した本実施形態（２）では、触媒早期暖機制御中に推定空燃比Ａ／Ｆ（空燃比パラメータ）を監視し、推定空燃比Ａ／Ｆが所定空燃比よりもリッチになったか否かで、排気温度が異常低下したか否かを判定して触媒早期暖機システムの異常診断を行うようにしたので、触媒早期暖機制御中に一時的に異常状態となった場合でも、その異常を検出して触媒早期暖機システムの異常と診断することができる。
【００５４】
尚、本実施形態（２）では、空燃比パラメータとして推定空燃比Ａ／Ｆを用いたが、空燃比パラメータとして燃料噴射量や燃焼ラフネス値を用いるようにしても良い。また、冷間始動時でも早期に活性化可能な空燃比センサを備えたシステムの場合には、空燃比パラメータとして空燃比センサで検出した空燃比を用いても良い。
【００５５】
また、本実施形態（２）では、空燃比パラメータ（推定空燃比Ａ／Ｆ）の挙動に基づいて触媒早期暖機システムの異常診断を行うようにしたが、吸入空気量パラメータの挙動、或は、空燃比パラメータと吸入空気量パラメータの両方の挙動に基づいて触媒早期暖機システムの異常診断を行うようにしても良い。
【００５６】
［実施形態（３）］
図７に示す本発明の実施形態（３）では、空燃比、点火時期遅角量、エンジン回転速度によって排気温度が変化することを考慮して、触媒早期暖機制御中に推定空燃比（空燃比パラメータ）、点火時期遅角量及びエンジン回転速度に基づいて推定排気温度を算出すると共に、この推定排気温度と吸入空気量（吸入空気量パラメータ）に基づいてエンジン１１の推定排気熱量を算出し、これを積算して求めた推定排気熱量積算値ＱＳＵＭを所定値Ｑmin と比較して触媒早期暖機システムの異常の有無を診断するようにしている。
【００５７】
以下、本実施形態（３）の触媒早期暖機システムの異常診断を行う図７の触媒早期暖機システム異常診断プログラムの処理内容を説明する。本プログラムでは、触媒早期暖機制御中且つアイドル運転中のときに、吸入空気量ＧＡと燃料噴射量ＴＡＵを読み込む（ステップ３０１〜３０４）。
【００５８】
この後、ステップ３０５に進み、吸入空気量ＧＡを燃料噴射量ＴＡＵで除算して推定空燃比Ａ／Ｆ（Ａ／Ｆ＝ＧＡ／ＴＡＵ）を算出した後、ステップ３０６に進み、推定空燃比Ａ／Ｆ、点火時期遅角量Δθ、エンジン回転速度ＮＥを用いて推定排気温度Ｔを次式により算出する。
Ｔ＝Ａ／Ｆ×Ｋ1 ＋Δθ×Ｋ2 ＋ＮＥ×Ｋ3 ＋Ｋ4
ここで、Ｋ1 〜Ｋ4 は係数である。
【００５９】
推定排気温度Ｔの算出後、ステップ３０７に進み、推定排気温度Ｔと吸入空気量ＧＡとを用いて推定排気熱量Ｑを次式により算出する。
Ｑ＝Ｔ×ＧＡ×Ｅ
ここで、Ｅは排出ガスの比熱である。
【００６０】
推定排気熱量Ｑの算出後、ステップ３０８に進み、前回までの推定排気熱量積算値ＱＳＵＭに今回の推定排気熱量Ｑを加算して推定排気熱量積算値ＱＳＵＭを更新する。この後、ステップ３０９に進み、タイマＣＳＵＭのカウント値を「１」だけカウントアップする。
【００６１】
この後、ステップ３１０に進み、カウンタＣＳＵＭのカウント値が所定値Ｋを越えたか否かを判定し、越えていなければ、ステップ３０１に戻る。これにより、カウンタＣＳＵＭのカウント値が所定値Ｋを越えるまで、推定排気熱量積算値ＱＳＵＭを更新する処理を繰り返す（図６参照）。
【００６２】
その後、カウンタＣＳＵＭのカウント値が所定値Ｋを越えた時点で、ステップ３１１に進み、推定排気熱量積算値ＱＳＵＭが所定値Ｑmin よりも大きいか否かを判定する。推定排気熱量積算値ＱＳＵＭが所定値Ｑmin よりも大きいと判定された場合には、排気熱量が触媒２４の早期暖機に必要な熱量となっていると判断して、ステップ３１２に進み、触媒早期暖機システムが正常と判定して、本プログラムを終了する。
【００６３】
これに対して、ステップ３１１で推定排気熱量積算値ＱＳＵＭが所定値Ｑmin 以下と判定された場合には、排気熱量が不足して、触媒２４の早期暖機に必要な熱量が触媒２４に供給されていないと判断して、ステップ３１３に進み、触媒早期暖機システムが異常と判定して、警告ランプ（図示せず）を点灯して運転者に警告すると共に、異常コードをＥＣＵ３１のバックアップＲＡＭ（図示せず）に記憶した後、本プログラムを終了する。
【００６４】
以上説明した本実施形態（３）では、触媒早期暖機制御中に、推定空燃比（空燃比パラメータ）、点火時期遅角量及びエンジン回転速度に基づいて推定排気温度を算出すると共に、この推定排気温度と吸入空気量（吸入空気量パラメータ）に基づいてエンジン１１の推定排気熱量を算出し、これを積算して求めた推定排気熱量積算値ＱＳＵＭを所定値Ｑmin と比較して触媒早期暖機システムの異常の有無を診断するようにしたので、排気熱量が触媒２４の早期暖機に必要な熱量となっているか否かをより精度良く判定することができる。
【００６５】
尚、本実施形態（３）では、空燃比、点火時期遅角量、エンジン回転速度によって排気温度が変化することを考慮して、空燃比、点火時期遅角量、エンジン回転速度の全てを考慮して排気温度を精度良く推定するようにしたが、空燃比、点火時期遅角量、エンジン回転速度のうちのいずれか２つ又は１つのパラメータのみを用いて排気温度を推定するようにしても良い。
【００６６】
また、本実施形態（３）では、吸入空気量パラメータとしてエアフローメータ１４で検出した吸入空気量ＧＡを用いたが、吸入空気量パラメータとしてスロットル開度、吸気圧、吸気バルブの可変リフト量のいずれかを用いるようにしても良い。或は、スロットル開度、吸気圧、吸気バルブの可変リフト量等を用いて求めた推定吸入空気量を吸入空気量パラメータとして用いても良い。
【００６７】
また、本実施形態（３）では、空燃比パラメータとして推定空燃比Ａ／Ｆを用いたが、空燃比パラメータとして燃料噴射量や燃焼ラフネス値を用いるようにしても良い。また、冷間始動時でも早期に活性化可能な空燃比センサを備えたシステムの場合には、空燃比パラメータとして空燃比センサで検出した空燃比を用いても良い。
【００６８】
［実施形態（４）］
ところで、触媒２４の暖機に関わる熱量には、エンジン１１からの排気熱量の他に、触媒２４の内部で排出ガス中のリーン成分（酸素等）とリッチ成分（ＨＣ等）とが反応して発生する反応熱量がある。触媒早期暖機制御中の空燃比によって触媒２４で反応するリーン成分量（酸素量等）が変化して触媒２４内部で発生する反応熱量が変化するため、触媒早期暖機制御中の空燃比よって触媒２４の早期暖機に必要な排気熱量も異なってくる。
【００６９】
そこで、図８乃至図１１に示す本発明の実施形態（４）では、触媒早期暖機制御中（排気熱量算出中）の空燃比を推定し、排気熱量に基づいて触媒早期暖機システムの異常の有無を診断する際に、触媒早期暖機制御中の推定空燃比に基づいて異常診断条件［本実施形態（４）では排気熱量］を補正するようにしている。尚、本実施形態（４）では、空燃比の情報として空気過剰率λを用いるようにしている。
【００７０】
以下、本実施形態（４）の触媒早期暖機システムの異常診断を行う図８の触媒早期暖機システム異常診断プログラムの処理内容を説明する。本プログラムでは、触媒早期暖機制御中且つアイドル運転中のときに、吸入空気量ＧＡを読み込む（ステップ４０１〜４０３）。
【００７１】
この後、ステップ４０４に進み、点火時期遅角量Δθ、エンジン回転速度ＮＥを用いて基準空燃比（例えば空気過剰率λ＝１）における推定排気温度Ｔ0 を次式により算出する。
Ｔ0 ＝Ｋ0 ＋Δθ×Ｋ2 ＋ＮＥ×Ｋ3
ここで、Ｋ0 、Ｋ2 、Ｋ3 は係数である。
【００７２】
この後、ステップ４０５に進み、推定排気温度Ｔ0 と吸入空気量ＧＡと排出ガスの比熱Ｅを用いて推定排気熱量Ｑ0 を次式により算出する。
Ｑ0 ＝Ｔ0 ×ＧＡ×Ｅ
推定排気熱量Ｑ0 の算出後、ステップ４０６に進み、前回までの推定排気熱量積算値ＱＳＵＭ0 に今回の推定排気熱量Ｑ0 を加算して推定排気熱量積算値ＱＳＵＭ0 を更新する。この後、ステップ４０７に進み、タイマＣＳＵＭのカウント値を「１」だけカウントアップする。
【００７３】
この後、ステップ４０８に進み、カウンタＣＳＵＭのカウント値が所定値Ｋを越えたか否かを判定し、越えていなければ、ステップ４０１に戻る。これにより、カウンタＣＳＵＭのカウント値が所定値Ｋを越えるまで、推定排気熱量積算値ＱＳＵＭ0 を更新する処理を繰り返す。
【００７４】
その後、カウンタＣＳＵＭのカウント値が所定値Ｋを越えた時点で、ステップ４０９に進み、空燃比センサ２３が活性状態になった時点ｔ1 で空燃比センサ２３で検出した空気過剰率λs とリーン化補正係数Ｌs とを用いて触媒早期暖機制御中（排気熱量算出中）の推定空気過剰率λg を次式により算出する。
λg ＝λs ×｛１−（１−Ｌs ）×ＫＬＭＤ｝
ここで、リーン化補正係数Ｌs は、触媒早期暖機制御中にエンジン回転変動が大きくならない範囲で空燃比をリーン方向に補正するための補正係数である（図１０参照）。また、ＫＬＭＤは、触媒早期暖機制御中のリーン化補正の影響を平均化するための係数（例えば０．５）である。
【００７５】
この後、ステップ４１０に進み、図９に示す異常診断補正係数ＫＱのマップを検索して、触媒早期暖機制御中の推定空気過剰率λg に応じた異常診断補正係数ＫＱを算出する。
【００７６】
この図９の異常診断補正係数ＫＱのマップは、触媒早期暖機制御中の推定空気過剰率λg が大きくなる（リーンになる）ほど、異常診断補正係数ＫＱが大きくなるように設定されている。また、推定空気過剰率λg ＝１のときには、異常診断補正係数ＫＱ＝１に設定され、推定排気熱量積算値ＱＳＵＭ0 を補正しない。
【００７７】
この後、ステップ４１１に進み、推定排気熱量積算値ＱＳＵＭ0 に異常診断補正係数ＫＱを乗算して異常診断用の排気熱量積算値ＱＱＳＵＭを求める。
ＱＱＳＵＭ＝ＱＳＵＭ×ＫＱ
この後、ステップ４１２に進み、異常診断用の排気熱量積算値ＱＱＳＵＭが異常判定値Ｑmin よりも大きいか否かを判定する。異常診断用の排気熱量積算値ＱＱＳＵＭが異常判定値Ｑmin よりも大きいと判定された場合には、排気熱量が触媒２４の早期暖機に必要な熱量となっていると判断して、ステップ４１３に進み、触媒早期暖機システムが正常と判定して、本プログラムを終了する。
【００７８】
これに対して、ステップ４１２で異常診断用の排気熱量積算値ＱＱＳＵＭが異常判定値Ｑmin 以下と判定された場合には、排気熱量が不足して、触媒２４の早期暖機に必要な熱量が触媒２４に供給されていないと判断して、ステップ４１４に進み、触媒早期暖機システムが異常と判定して、警告ランプ（図示せず）を点灯して運転者に警告すると共に、異常コードをＥＣＵ３１のバックアップＲＡＭ（図示せず）に記憶した後、本プログラムを終了する。
【００７９】
以上説明した本実施形態（４）では、触媒早期暖機制御中（排気熱量算出中）の推定空気過剰率λg を算出し、この推定空気過剰率λg に基づいて補正した異常診断用の排気熱量積算値ＱＱＳＵＭを用いて触媒早期暖機システムの異常の有無を診断するようにしたので、触媒早期暖機制御中の空燃比（空気過剰率）によって触媒２４内部で発生する反応熱量が変化するのに対応して排気熱量積算値を補正することができ、触媒早期暖機制御中の排気熱量積算値が触媒２４の早期暖機に必要な熱量となっているか否かを精度良く判定することができる。
【００８０】
一般に、触媒早期暖機制御中は、エンジン１１の温度が低いため、燃料噴射弁２０から噴射された燃料のうち吸気ポート壁面等に付着する燃料量（ウェット量）が比較的多くなっている。従って、触媒早期暖機制御中は、燃料噴射量ＴＡＵと吸入空気量ＧＡからでは、触媒早期暖機制御中の空燃比（空気過剰率）を精度良く推定することができない。
【００８１】
その点、本実施形態（４）では、図１０のタイムチャートに示すように、空燃比センサ２３が活性状態になった時点ｔ1 で空燃比センサ２３で検出した空気過剰率λs とリーン化補正係数Ｌs とを用いて触媒早期暖機制御中（排気熱量算出中）の推定空気過剰率λg を算出する。リーン化補正係数Ｌs は、触媒早期暖機制御中の空燃比の挙動（リーン方向への変化量）を表すパラメータとなるため、空燃比センサ２３の活性時の検出空気過剰率λs とリーン化補正係数Ｌs とを用いれば、触媒早期暖機制御中にリーン化補正も考慮して、触媒早期暖機制御中の推定空気過剰率λg （推定空燃比）をより一層精度良く算出することができる。
【００８２】
尚、本実施形態（４）では、推定空気過剰率λg に基づいて推定排気熱量積算値ＱＳＵＭ0 を補正するようにしたが、推定空気過剰率λg に基づいて異常判定値Ｑmin を補正するようにしても良く、この場合も、同様の効果が得られる。
【００８３】
また、本実施形態（４）では、空燃比センサ２３の活性時の検出空気過剰率λs とリーン化補正係数Ｌs とを用いて触媒早期暖機制御中の推定空気過剰率λg を算出するようにしたが、図１１に示すように、空燃比センサ２３が活性した時点ｔ1 で空燃比センサ２３で検出した空気過剰率λs （又は活性時点ｔ1 付近の所定期間の空気過剰率λの平均値λav）を触媒早期暖機制御中の推定空気過剰率λg （推定空燃比）としても良い。
【００８４】
また、図１１に示すように、空燃比センサ２３の活性時には、空燃比フィードバック制御が開始されて、空燃比センサ２３で検出した空燃比を目標空燃比に補正するための空燃比フィードバック補正係数Ｆを算出するので、空燃比センサ２３の活性直後の空燃比フィードバック補正係数Ｆs （又は活性直後の所定期間の空燃比フィードバック補正係数Ｆの平均値Ｆav）に基づいて触媒早期暖機制御中の推定空気過剰率λg （推定空燃比）を算出するようにしても良い。
【００８５】
また、空燃比フィードバック補正係数Ｆs とリーン化補正係数Ｌs とを用いて触媒早期暖機制御中の推定空気過剰率λg （推定空燃比）を算出するようにしても良い。
また、上記各実施形態（１）〜（４）を適宜組み合わせて実施するようにしても良い。
【図面の簡単な説明】
【図１】本発明の実施形態（１）を示すエンジン制御システム全体の概略構成図
【図２】実施形態（１）の触媒早期暖機システム異常診断プログラムの処理の流れを示すフローチャート
【図３】実施形態（１）の実行例を示すタイムチャート
【図４】空燃比と排気温度との関係を示す図
【図５】実施形態（２）の触媒早期暖機システム異常診断プログラムの処理の流れを示すフローチャート
【図６】実施形態（２）及び実施形態（３）の実行例を示すタイムチャート
【図７】実施形態（３）の触媒早期暖機システム異常診断プログラムの処理の流れを示すフローチャート
【図８】実施形態（４）の触媒早期暖機システム異常診断プログラムの処理の流れを示すフローチャート
【図９】異常診断補正係数ＫＱのマップを概念的に示す図
【図１０】実施形態（４）の実行例を示すタイムチャート
【図１１】実施形態（４）の変形例を説明するためのタイムチャート
【符号の説明】
１１…エンジン（内燃機関）、１４…エアフローメータ、１５…スロットルバルブ、２０…燃料噴射弁、２１…点火プラグ、２２…排気管、２３…空燃比センサ、２４…触媒、３１…ＥＣＵ（異常診断手段，排気熱量算出手段，空燃比推定手段）。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormality diagnosis device for an early catalyst warm-up system that diagnoses an abnormality in an early catalyst warm-up system that warms up an exhaust gas purifying catalyst early.
[0002]
[Prior art]
2. Description of the Related Art In recent years, an internal combustion engine mounted on a vehicle has been designed to perform early catalyst warm-up control during cold start in order to warm up an exhaust gas purifying catalyst to an active temperature early during cold start. . In this catalyst early warm-up control, in general, the ignition timing is retarded to raise the exhaust temperature, and the intake air amount is increased more than in the normal idle control to increase the idle rotation speed, thereby performing a cold start. While preventing idle rotation from becoming unstable due to the retarded ignition timing at the time, the exhaust heat amount (heat amount supplied to the catalyst) is increased to promote warming up of the catalyst. If the exhaust heat during the early catalyst warm-up control decreases due to the failure of the early catalyst warm-up system and the amount of heat necessary for the early warm-up of the catalyst is no longer supplied to the catalyst, Therefore, it is necessary to detect an abnormality in the early catalyst warm-up system at an early stage.
[0003]
Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2001-132438, a catalyst temperature sensor for detecting the temperature of the catalyst is provided, and the estimation estimated based on the catalyst temperature detected by the catalyst temperature sensor and the integrated intake air amount after starting. Some of them compare with the catalyst temperature to diagnose the presence or absence of abnormality in the catalyst early warm-up system.
[0004]
Further, as disclosed in Japanese Patent Laid-Open No. 2001-132526, during catalyst early warm-up control, at least one of the engine rotation speed and the ignition timing retard amount is compared with a predetermined abnormality determination value, and the catalyst early warm-up system Some have been diagnosed for abnormalities.
[0005]
[Problems to be solved by the invention]
However, the former (Japanese Patent Laid-Open No. 2001-132438) has a drawback in that it is necessary to newly provide a catalyst temperature sensor for detecting the catalyst temperature, which increases the cost accordingly.
[0006]
Further, the exhaust heat amount (heat amount supplied to the catalyst) of the internal combustion engine varies depending on the exhaust temperature and the exhaust flow rate. Further, as shown in FIG. 4, the exhaust temperature varies depending on the air-fuel ratio, and the exhaust flow rate depends on the intake air amount. Therefore, the amount of heat exhausted from the internal combustion engine (the amount of heat supplied to the catalyst) varies depending on the amount of intake air and the air-fuel ratio. For this reason, in the latter (Japanese Patent Laid-Open No. 2001-132526), even when the early catalyst warm-up system is diagnosed as normal based on the engine speed and ignition timing, the exhaust is affected by the intake air amount and the air-fuel ratio. The amount of heat is reduced and the amount of heat necessary for the early warm-up of the catalyst is not supplied to the catalyst.In other words, there is a possibility that the early catalyst warm-up control is not performed normally. May be misdiagnosed.
[0007]
The present invention has been made in consideration of such circumstances, and therefore the object of the present invention is to improve the accuracy of abnormality diagnosis of the early catalyst warm-up system and to satisfy the demand for cost reduction. An object of the present invention is to provide an abnormality diagnosis device for an early warm-up system.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, an abnormality diagnosis device for a catalyst early warm-up system according to claim 1 of the present invention is provided during catalyst early warm-up control.Exhaust heat amount calculation means for estimating the amount of exhaust heat of the internal combustion engine or the amount of heat supplied to the catalyst based on the operating state of the internal combustion engine, and abnormality of the early catalyst warm-up system based on the heat amount estimated by the exhaust heat amount calculation means An abnormality diagnosing means for diagnosing presence / absence, and an air / fuel ratio estimating means for estimating an air / fuel ratio during catalyst early warm-up control, wherein the abnormality diagnosing means is performing the catalyst early warm-up control estimated by the air / fuel ratio estimating means The abnormality diagnosis condition is corrected based on the air-fuel ratio.
[0012]
  The present inventionAs described above, the exhaust heat amount calculation means estimates the exhaust heat amount of the internal combustion engine or the heat amount supplied to the catalyst based on the operating state of the internal combustion engine during the catalyst early warm-up control, and based on the heat amount, the catalyst early warm-up system To diagnose the presence or absence of abnormalitiesToThen, it is possible to determine with higher accuracy whether or not the exhaust heat quantity during the early catalyst warm-up control is the heat quantity necessary for the early warm-up of the catalyst.
[0013]
  In this case, the claim2As described above, the exhaust heat quantity may be obtained based on at least one of the intake air amount parameter and the air-fuel ratio parameter. As described above, since the intake air amount and the air-fuel ratio are parameters that change the exhaust heat amount of the internal combustion engine, the exhaust heat amount can be accurately obtained by using the intake air amount parameter and the air-fuel ratio parameter.
[0014]
  Further, in consideration of the fact that the exhaust temperature varies depending on the engine speed, the ignition timing, and the air-fuel ratio, the claims3As described above, when obtaining the exhaust heat quantity of the internal combustion engine, the exhaust temperature is estimated using at least one of the engine speed, the ignition timing, and the air-fuel ratio parameter, and the estimated exhaust temperature and the intake air amount parameter are The amount of exhaust heat may be calculated based on this. In this way, the calculation accuracy of the exhaust heat quantity can be further improved.
[0015]
  Claims4As described above, as the intake air amount parameter, at least one of the intake air amount detected by the air flow meter or the like, the throttle opening, the variable lift amount of the intake valve, and the intake pressure may be used. Since both the throttle opening and the intake pressure have a correlation with the intake air amount, they can be used as the intake air amount parameter. Further, in a system that adjusts the intake air amount by varying the lift amount of the intake valve by the variable valve lift mechanism, the variable lift amount of the intake valve can be used as the intake air amount parameter.
[0016]
  Claims5As described above, at least one of the air-fuel ratio, the fuel injection amount, and the combustion roughness value detected by the air-fuel ratio sensor of the exhaust system may be used as the air-fuel ratio parameter. Since the air-fuel ratio changes depending on the fuel injection amount and the combustion roughness value changes depending on the air-fuel ratio, the fuel injection amount and the combustion roughness value can also be used as the air-fuel ratio parameter. Since the air-fuel ratio cannot be accurately detected until the air-fuel ratio sensor rises to the activation temperature after startup, when the air-fuel ratio sensor output is used as the air-fuel ratio parameter, the air-fuel ratio sensor must be activated after the air-fuel ratio sensor is activated. Although the fuel ratio parameter cannot be used, there is an advantage that the fuel injection amount and the combustion roughness value can be used as the air fuel ratio parameter immediately after the start (immediately after the start of the catalyst early warm-up control).
[0017]
By the way, the amount of heat related to the warm-up of the catalyst includes the amount of reaction heat generated by the reaction of the lean component (oxygen, etc.) and the rich component (HC, etc.) in the exhaust gas in addition to the exhaust heat amount of the internal combustion engine. There is. Because the amount of lean component (oxygen amount, etc.) reacting inside the catalyst changes depending on the air-fuel ratio during the catalyst early warm-up control, and the amount of reaction heat generated inside the catalyst changes, the catalyst depends on the air-fuel ratio during the catalyst early warm-up control. The amount of exhaust heat required for early warm-up will also vary.
[0018]
  Therefore, the claimIn the invention according to 1,The air-fuel ratio estimating means estimates the air-fuel ratio during catalyst early warm-up control (exhaust heat amount calculation) and diagnoses the presence or absence of abnormality in the catalyst early warm-up system based on the exhaust heat quantity. The abnormality diagnosis condition is corrected based on the estimated air-fuel ratio during early catalyst warm-up control.Have. In this way, the abnormality diagnosis condition (for example, the abnormality determination value or the exhaust heat amount) can be corrected in response to the change in the amount of reaction heat generated inside the catalyst due to the air-fuel ratio during the early catalyst warm-up control. It is possible to accurately determine whether or not the exhaust heat amount during the catalyst early warm-up control is a heat amount necessary for early catalyst warm-up.
[0019]
In general, during the catalyst early warm-up control, the temperature of the internal combustion engine is low, so the amount of fuel (wet amount) adhering to the intake port wall surface and the like out of the fuel injected from the fuel injection valve is relatively large. Therefore, during the early catalyst warm-up control, the air-fuel ratio cannot be accurately estimated from the fuel injection amount and the intake air amount.
[0020]
  Therefore, the claim6As described above, when the air-fuel ratio sensor provided in the exhaust passage is activated, the air-fuel ratio during the early catalyst warm-up control may be estimated based on the air-fuel ratio detected by the air-fuel ratio sensor. In this case, it is necessary to wait until the air-fuel ratio sensor becomes active, but the air-fuel ratio during early catalyst warm-up control can be estimated based on the actual air-fuel ratio detected by the air-fuel ratio sensor. Compared to estimating the air-fuel ratio during early catalyst warm-up control from the amount and the intake air amount, the air-fuel ratio during early catalyst warm-up control can be estimated with higher accuracy.
[0021]
  Further, after the air-fuel ratio sensor is activated, the air-fuel ratio feedback control is started, and the air-fuel ratio feedback correction coefficient is calculated based on the air-fuel ratio detected by the air-fuel ratio sensor.7As described above, the air-fuel ratio during the early catalyst warm-up control may be estimated based on the air-fuel ratio feedback correction coefficient. Since the air-fuel ratio feedback correction coefficient is set according to the air-fuel ratio detected by the air-fuel ratio sensor, even if the air-fuel ratio during early catalyst warm-up control is estimated based on the air-fuel ratio feedback correction coefficient, When the detected air-fuel ratio is used (claim)6), The air-fuel ratio during the catalyst early warm-up control can be accurately estimated.
[0022]
    Further, in the case of a system for calculating a lean correction coefficient for correcting the air-fuel ratio in the lean direction based on the rotational behavior of the internal combustion engine during the catalyst early warm-up control, the claim is provided.8As described above, the leaning correction coefficient is also used in addition to the detected air-fuel ratio when the air-fuel ratio sensor is active or the air-fuel ratio feedback correction coefficient as a parameter used for estimating the air-fuel ratio during early catalyst warm-up control. May be. That is, the air-fuel ratio during the early catalyst warm-up control may be estimated based on the detected air-fuel ratio (or air-fuel ratio feedback correction coefficient) and the lean correction coefficient when the air-fuel ratio sensor is active. The leaning correction coefficient is a parameter representing the air-fuel ratio behavior (change amount in the lean direction) during the early catalyst warm-up control, and therefore the detected air-fuel ratio (or air-fuel ratio feedback correction coefficient) when the air-fuel ratio sensor is active And the leaning correction coefficient, the air-fuel ratio can be estimated with higher accuracy in consideration of the leaning correction during the early catalyst warm-up control.
[0023]
By the way, while the vehicle is running, the intake air amount and the fuel injection amount change according to changes in the driving conditions, and the abnormality diagnosis parameters (intake air amount parameter and air-fuel ratio parameter) of the catalyst early warm-up system change accordingly. In addition, the catalyst warm-up is delayed due to the heat release of the catalyst due to the traveling wind, so the catalyst early warm-up system abnormality diagnosis is accurate without considering changes in operating conditions and the influence of the traveling wind while the vehicle is traveling. It is difficult to do well.
[0024]
  Therefore, the claim9As described above, it is preferable to perform abnormality diagnosis of the catalyst early warm-up system during the catalyst early warm-up control and the idling operation of the internal combustion engine. During idling, the operating conditions (intake air amount and fuel injection amount) of the internal combustion engine are relatively stable, so the influence of the operating conditions on the abnormality diagnosis parameters of the catalyst early warm-up system can be reduced. There is no delay in warming up the catalyst due to running wind. Therefore, during idle operation, abnormality diagnosis of the catalyst early warm-up system can be performed with high accuracy without taking into consideration changes in operating conditions and the influence of traveling wind.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment (1)]
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 15 and a throttle opening sensor 16 for detecting the throttle opening are provided on the downstream side of the air flow meter 14.
[0026]
Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. In addition, a spark plug 21 is attached to each cylinder of the cylinder 11 of the engine 11, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 21.
[0027]
On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 24 such as a three-way catalyst for reducing CO, HC, NOx, etc. in the exhaust gas, and the exhaust gas air-fuel ratio or lean / An air-fuel ratio sensor 23 (A / F sensor, oxygen sensor, etc.) for detecting rich is provided. A cooling water temperature sensor 29 for detecting the cooling water temperature and a crank angle sensor 30 for detecting the engine rotation speed are attached to the cylinder block of the engine 11.
[0028]
These various sensor outputs are input to an engine control circuit (hereinafter referred to as “ECU”) 31. The ECU 31 is mainly composed of a microcomputer, and executes various control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and ignition of the fuel injection valve 20 according to the engine operating state. The ignition timing of the plug 21 is controlled.
[0029]
Further, the ECU executes a catalyst early warm-up control program (not shown) stored in the ROM, so that at the time of cold start, the catalyst early warm-up for warming the catalyst 24 to the activation temperature early. Execute control. In this early catalyst warm-up control, the ignition timing is retarded from the normal idle control to raise the exhaust gas temperature, and the intake air amount is increased to increase the idle rotation speed than in the normal idle control. By doing so, the exhaust heat amount (heat amount supplied to the catalyst 24) is increased while preventing the idling rotation from becoming unstable due to the ignition timing delay at the time of cold start, and the warm-up of the catalyst 24 is promoted.
[0030]
Here, the exhaust heat amount of the engine 11 (the amount of heat supplied to the catalyst 24) varies depending on the exhaust temperature and the exhaust flow rate. Further, as shown in FIG. 4, the exhaust temperature varies depending on the air-fuel ratio, and the exhaust flow rate is the intake air. Since the amount of air varies depending on the amount of air, the amount of exhaust heat of the engine 11 (the amount of heat supplied to the catalyst 24) varies depending on the amount of intake air and the air-fuel ratio. Here, the air-fuel ratio can be detected by the air-fuel ratio sensor 23, but immediately after the cold start (immediately after the start of the catalyst early warm-up control), the air-fuel ratio sensor 23 is not activated. A fuel injection amount TAU having a correlation with the air-fuel ratio is used as an air-fuel ratio parameter.
[0031]
In consideration of these circumstances, the ECU 31 executes the catalyst early warm-up system abnormality diagnosis program of FIG. 2 stored in the ROM, so that the intake air amount during the catalyst early warm-up control as shown in FIG. GA (intake air amount parameter) and fuel injection amount TAU (air-fuel ratio parameter) are integrated, respectively, and the exhaust heat amount depends on whether the intake air amount integrated value GASUM and the fuel injection amount integrated value TAUSUM are within a predetermined normal range, respectively. It is determined whether or not the amount of heat necessary for early warm-up of the catalyst 24 is determined, and the presence or absence of an abnormality in the early catalyst warm-up system is diagnosed.
[0032]
Hereinafter, specific processing contents of the catalyst early warm-up system abnormality diagnosis program of FIG. 2 executed by the ECU 31 will be described. This program is repeatedly executed every predetermined time or every predetermined crank angle, and plays a role corresponding to the abnormality diagnosis means in the claims. When this program is started, first, at step 101, it is determined whether or not the catalyst early warm-up execution condition is satisfied, for example, by whether or not the coolant temperature is lower than a predetermined temperature. If the catalyst early warm-up execution condition is not satisfied, this program is terminated as it is.
[0033]
On the other hand, if the catalyst early warm-up execution condition is satisfied, the routine proceeds to step 102 where it is determined whether or not the engine is in an idling operation state. If it is not in the idle operation state, this program is terminated without executing the subsequent abnormality diagnosis process (steps 103 to 112).
[0034]
On the other hand, if the catalyst early warm-up execution condition is satisfied and the early catalyst warm-up control is executed, and if the idling operation is being performed, the abnormality diagnosis process after step 103 is executed as follows. First, the process proceeds to step 103, the intake air amount GA detected by the air flow meter 14 is read, and then the process proceeds to step 104, where the fuel injection amount TAU calculated by a fuel injection control program (not shown) is read.
[0035]
Thereafter, the process proceeds to step 105, the current intake air amount GASUM is added to the previous intake air amount integrated value GASUM to update the intake air amount integrated value GASUM, and then the process proceeds to step 106 where the fuel injection amount up to the previous time is obtained. The fuel injection amount integrated value TAUSUM is updated by adding the current fuel injection amount TAU to the integrated value TAUSUM. Thereafter, the process proceeds to step 107, and the count value of the counter CSUM is incremented by “1”.
[0036]
Thereafter, the process proceeds to step 108, where it is determined whether or not the count value of the counter CSUM exceeds a predetermined value K. If not, the process returns to step 101. As a result, the process of calculating the intake air amount integrated value GASUM and the process of calculating the fuel injection amount integrated value TAUSUM are repeated until the count value of the counter CSUM exceeds the predetermined value K.
[0037]
Thereafter, when the count value of the counter CSUM exceeds the predetermined value K, the routine proceeds to step 109, where it is determined whether or not the intake air amount integrated value GASUM is within a predetermined normal range (Gmin <GASUM <Gmax). Further, in the next step 110, it is determined whether or not the fuel injection amount integrated value TAUSUM is within a predetermined normal range (Tmin <TAUSUM <Tmax).
[0038]
When it is determined “Yes” in both step 109 and step 110 (that is, when the intake air amount integrated value GASUM is determined to be within the normal range and the fuel injection amount integrated value TAUSUM is determined to be within the normal range), the exhaust gas is exhausted. It is determined that the amount of heat is the amount of heat necessary for the early warm-up of the catalyst 24, the process proceeds to step 111, it is determined that the early catalyst warm-up system is normal, and this program is terminated.
[0039]
On the other hand, when it is determined as “No” in Step 109 (when the intake air amount integrated value GASUM is determined to be outside the normal range), or when it is determined as “No” at Step 110 (fuel injection). If it is determined that the integrated amount TAUSUM is outside the normal range), it is determined that the amount of heat of exhaust is not appropriate for the early warm-up of the catalyst 24 (the amount of heat of exhaust is insufficient or excessive). Then, the catalyst early warming-up system is determined to be abnormal, a warning lamp (not shown) is lit to warn the driver, and the abnormality code is stored in the backup RAM (not shown) of the ECU 31. Exit the program.
[0040]
In the present embodiment (1) described above, the intake air amount GA (intake air amount parameter) and the fuel injection amount TAU (air fuel ratio parameter) are integrated during the early catalyst warm-up control, respectively, and the intake air amount integrated value GASUM is obtained. Since the presence or absence of an abnormality in the catalyst early warm-up system is diagnosed based on whether or not the fuel injection amount accumulated value TAUSUM is within a predetermined normal range, the accumulated exhaust heat amount during the catalyst early warm-up control (the catalyst 24 after starting) The total amount of heat supplied to the catalyst) can be evaluated to accurately diagnose whether there is an abnormality in the early catalyst warm-up system. Moreover, since it is not necessary to newly provide a sensor for detecting the catalyst temperature, it is possible to satisfy the demand for cost reduction.
[0041]
In the present embodiment (1), the abnormality diagnosis of the catalyst early warm-up system is performed using both the intake air amount GA and the fuel injection amount TAU. Of the intake air amount GA and the fuel injection amount TAU, An abnormality diagnosis of the early catalyst warm-up system may be performed using only one of these.
[0042]
By the way, while the vehicle is running, the intake air amount and the fuel injection amount change according to changes in the engine operating conditions, and the abnormality diagnosis parameters (intake air amount parameter and air-fuel ratio parameter) of the catalyst early warm-up system are accordingly changed. In addition to the change, since the warming-up of the catalyst 24 is delayed due to the heat radiation of the catalyst 24 by the traveling wind, the change in the operating conditions and the influence of the traveling wind must be taken into account while the vehicle is traveling. It is difficult to make a diagnosis accurately.
[0043]
In this regard, in the present embodiment (1), abnormality diagnosis of the catalyst early warm-up system is executed during the idling operation in which the engine operation conditions (intake air amount, fuel injection amount, etc.) are relatively stable. Therefore, the influence of the engine operating conditions on the abnormality diagnosis parameter can be reduced, and the warm-up delay of the catalyst 24 due to the traveling wind does not occur. Therefore, in the present embodiment (1), the abnormality diagnosis of the catalyst early warm-up system can be performed with high accuracy without considering the change in engine operating conditions and the influence of traveling wind.
[0044]
In this embodiment (1), the intake air amount GA detected by the air flow meter 14 is used as the intake air amount parameter. However, the throttle opening or intake pressure may be used as the intake air amount parameter. Further, in a system that adjusts the intake air amount by varying the lift amount of the intake valve by the variable valve lift mechanism, the variable lift amount of the intake valve may be used as the intake air amount parameter. Alternatively, an estimated intake air amount obtained using the throttle opening, intake pressure, variable lift amount of the intake valve, or the like may be used as the intake air amount parameter.
[0045]
In the present embodiment (1), the fuel injection amount TAU is used as the air-fuel ratio parameter. However, the combustion roughness value may be used as the air-fuel ratio parameter. Alternatively, an estimated air-fuel ratio obtained using a fuel injection amount, a combustion roughness value, or the like may be used as an air-fuel ratio parameter. In the case of a system including an air-fuel ratio sensor that can be activated early even during cold start, the air-fuel ratio detected by the air-fuel ratio sensor may be used as the air-fuel ratio parameter.
[0046]
[Embodiment (2)]
In the embodiment (1), the intake air amount GA (intake air amount parameter) and the fuel injection amount TAU (air-fuel ratio parameter) are integrated during the catalyst early warm-up control, and the catalyst early warm-up system is based on the integrated value. In the embodiment (2) of the present invention shown in FIGS. 5 and 6, the estimated air-fuel ratio A / F (air-fuel ratio parameter) is monitored during the early catalyst warm-up control. Based on the behavior, the presence or absence of an abnormality in the early catalyst warm-up system is diagnosed.
[0047]
Hereinafter, the processing contents of the catalyst early warm-up system abnormality diagnosis program of FIG. 5 for performing abnormality diagnosis of the catalyst early warm-up system of the present embodiment (2) will be described. In this program, the intake air amount GA and the fuel injection amount TAU are read during the early catalyst warm-up control and the idling operation (steps 201 to 204).
[0048]
Thereafter, the routine proceeds to step 205, where the estimated air-fuel ratio A / F is calculated by dividing the intake air amount GA by the fuel injection amount TAU.
A / F = GA / TAU
As shown in FIG. 6, the calculation of the estimated air-fuel ratio A / F may be started near the timing at which the air-fuel ratio A / F starts to stabilize.
[0049]
Thereafter, the process proceeds to step 206, the count value of the counter CSUM is incremented by “1”, and then the process proceeds to step 207 to determine whether or not the estimated air-fuel ratio A / F is richer than a predetermined air-fuel ratio (for example, 14). To do. As described above, since the exhaust temperature changes depending on the air-fuel ratio (see FIG. 4), the catalyst early warm-up control is performed depending on whether the estimated air-fuel ratio A / F is richer than a predetermined air-fuel ratio (for example, 14). It can be determined whether or not the exhaust temperature has abnormally decreased. If the estimated air-fuel ratio A / F is leaner than the predetermined air-fuel ratio, the routine proceeds to the next step 208, where it is determined whether or not the abnormality diagnosis period has ended by whether the count value of the counter CSUM has exceeded the predetermined value K If it is before the end of the abnormality diagnosis period, the process returns to step 201.
[0050]
On the other hand, if it is determined in step 207 that the estimated air-fuel ratio A / F is richer than the predetermined air-fuel ratio, the process proceeds to step 210 and the count value of the rich counter N is incremented by “1”. The rich counter N counts the number of times that the exhaust temperature has dropped abnormally by counting the number of times that the estimated air-fuel ratio A / F has become richer than the predetermined air-fuel ratio. Thereafter, the process proceeds to step 211, where it is determined whether or not the count value of the rich counter N exceeds a predetermined value M. If not, the process proceeds to step 208.
[0051]
If it is determined in step 211 that the count value of the rich counter N does not exceed the predetermined value M and the abnormality diagnosis period is ended in step 208, the process proceeds to step 209, where it is determined that the catalyst early warm-up system is normal. Then, this program is terminated.
[0052]
On the other hand, if it is determined in step 211 that the count value of the rich counter N has exceeded the predetermined value M before the abnormality diagnosis period ends, the process proceeds to step 212 and the early catalyst warm-up system is abnormal. After the determination, a warning lamp (not shown) is lit to warn the driver, and the abnormality code is stored in the backup RAM (not shown) of the ECU 31, and then the program is terminated.
[0053]
In the present embodiment (2) described above, the estimated air-fuel ratio A / F (air-fuel ratio parameter) is monitored during the early catalyst warm-up control, and whether or not the estimated air-fuel ratio A / F becomes richer than the predetermined air-fuel ratio. However, since it was determined whether or not the exhaust gas temperature had dropped abnormally and the abnormality diagnosis of the catalyst early warm-up system was performed, even if an abnormal state temporarily occurred during the catalyst early warm-up control, Abnormalities can be detected and diagnosed as abnormalities in the early catalyst warm-up system.
[0054]
In this embodiment (2), the estimated air-fuel ratio A / F is used as the air-fuel ratio parameter, but a fuel injection amount or a combustion roughness value may be used as the air-fuel ratio parameter. In the case of a system including an air-fuel ratio sensor that can be activated early even during cold start, the air-fuel ratio detected by the air-fuel ratio sensor may be used as the air-fuel ratio parameter.
[0055]
In this embodiment (2), the abnormality diagnosis of the catalyst early warm-up system is performed based on the behavior of the air-fuel ratio parameter (estimated air-fuel ratio A / F). The abnormality diagnosis of the early catalyst warm-up system may be performed based on the behavior of both the air-fuel ratio parameter and the intake air amount parameter.
[0056]
[Embodiment (3)]
In the embodiment (3) of the present invention shown in FIG. 7, the estimated air-fuel ratio (empty air / fuel ratio) during the early catalyst warm-up control is taken into consideration that the exhaust gas temperature varies depending on the air-fuel ratio, the ignition timing retard amount, and the engine speed. The estimated exhaust temperature is calculated based on the fuel ratio parameter), the ignition timing retardation amount, and the engine speed, and the estimated exhaust heat amount of the engine 11 is calculated based on the estimated exhaust temperature and the intake air amount (intake air amount parameter). The estimated exhaust heat amount integrated value QSUM obtained by integrating these values is compared with a predetermined value Qmin to diagnose the presence or absence of an abnormality in the early catalyst warm-up system.
[0057]
Hereinafter, the processing content of the catalyst early warm-up system abnormality diagnosis program of FIG. 7 that performs abnormality diagnosis of the catalyst early warm-up system of the present embodiment (3) will be described. In this program, the intake air amount GA and the fuel injection amount TAU are read during the early catalyst warm-up control and the idling operation (steps 301 to 304).
[0058]
Thereafter, the process proceeds to step 305, the estimated air-fuel ratio A / F (A / F = GA / TAU) is calculated by dividing the intake air amount GA by the fuel injection amount TAU, and then the process proceeds to step 306, where the estimated air-fuel ratio A The estimated exhaust gas temperature T is calculated by the following equation using / F, the ignition timing retardation amount Δθ, and the engine speed NE.
T = A / F × K1 + Δθ × K2 + NE × K3 + K4
Here, K1 to K4 are coefficients.
[0059]
After calculating the estimated exhaust temperature T, the process proceeds to step 307, where the estimated exhaust heat quantity Q is calculated by the following equation using the estimated exhaust temperature T and the intake air amount GA.
Q = T × GA × E
Here, E is the specific heat of the exhaust gas.
[0060]
After calculating the estimated exhaust heat quantity Q, the routine proceeds to step 308, where the estimated exhaust heat quantity QSUM of this time is added to the previous estimated exhaust heat quantity integrated value QSUM to update the estimated exhaust heat quantity integrated value QSUM. Thereafter, the process proceeds to step 309, and the count value of the timer CSUM is incremented by “1”.
[0061]
Thereafter, the process proceeds to step 310, where it is determined whether or not the count value of the counter CSUM exceeds a predetermined value K. If not, the process returns to step 301. Thus, the process of updating the estimated exhaust heat amount integrated value QSUM is repeated until the count value of the counter CSUM exceeds the predetermined value K (see FIG. 6).
[0062]
Thereafter, when the count value of the counter CSUM exceeds the predetermined value K, the routine proceeds to step 311 where it is determined whether or not the estimated exhaust heat amount integrated value QSUM is larger than the predetermined value Qmin. If it is determined that the estimated exhaust heat amount integrated value QSUM is larger than the predetermined value Qmin, it is determined that the exhaust heat amount is a heat amount necessary for the early warm-up of the catalyst 24, and the routine proceeds to step 312 where the catalyst early It is determined that the warm-up system is normal, and this program ends.
[0063]
On the other hand, if it is determined in step 311 that the estimated exhaust heat amount integrated value QSUM is equal to or less than the predetermined value Qmin, the exhaust heat amount is insufficient and the heat amount necessary for early warming up of the catalyst 24 is supplied to the catalyst 24. If it is determined that the catalyst early warm-up system is abnormal, a warning lamp (not shown) is lit to warn the driver, and the abnormal code is stored in the backup RAM (not shown) of the ECU 31. After storing the program in the not-shown program, the program is terminated.
[0064]
In the present embodiment (3) described above, the estimated exhaust temperature is calculated based on the estimated air-fuel ratio (air-fuel ratio parameter), the ignition timing retardation amount, and the engine speed during the catalyst early warm-up control, and this estimation is performed. The estimated exhaust heat quantity of the engine 11 is calculated based on the exhaust temperature and the intake air quantity (intake air quantity parameter), and the estimated exhaust heat quantity integrated value QSUM obtained by integrating this is compared with a predetermined value Qmin to quickly warm up the catalyst. Since the presence / absence of abnormality of the system is diagnosed, it can be determined with higher accuracy whether or not the exhaust heat quantity is a heat quantity necessary for the early warm-up of the catalyst 24.
[0065]
In this embodiment (3), all of the air-fuel ratio, the ignition timing retard amount, and the engine speed are considered in consideration of the exhaust temperature changing depending on the air-fuel ratio, the ignition timing retard amount, and the engine speed. Thus, the exhaust gas temperature is accurately estimated, but the exhaust gas temperature may be estimated using only two parameters or one of the air-fuel ratio, ignition timing retard amount, and engine speed. good.
[0066]
In this embodiment (3), the intake air amount GA detected by the air flow meter 14 is used as the intake air amount parameter. However, any of the throttle opening, intake pressure, and variable lift amount of the intake valve can be used as the intake air amount parameter. You may make it use these. Alternatively, an estimated intake air amount obtained using the throttle opening, intake pressure, variable lift amount of the intake valve, or the like may be used as the intake air amount parameter.
[0067]
In this embodiment (3), the estimated air-fuel ratio A / F is used as the air-fuel ratio parameter, but a fuel injection amount or a combustion roughness value may be used as the air-fuel ratio parameter. In the case of a system including an air-fuel ratio sensor that can be activated early even during cold start, the air-fuel ratio detected by the air-fuel ratio sensor may be used as the air-fuel ratio parameter.
[0068]
[Embodiment (4)]
By the way, in addition to the amount of exhaust heat from the engine 11, the lean component (oxygen etc.) and the rich component (HC etc.) in the exhaust gas react in the amount of heat related to the warming up of the catalyst 24. There is a reaction heat generated. Since the amount of lean component (oxygen amount, etc.) that reacts with the catalyst 24 changes due to the air-fuel ratio during the catalyst early warm-up control and the amount of reaction heat generated inside the catalyst 24 changes, the air-fuel ratio during the catalyst early warm-up control changes. The amount of exhaust heat necessary for early warming up of the catalyst 24 also varies.
[0069]
Therefore, in the embodiment (4) of the present invention shown in FIGS. 8 to 11, the air-fuel ratio during catalyst early warm-up control (exhaust heat amount calculation) is estimated, and the abnormality of the catalyst early warm-up system is based on the exhaust heat amount. When diagnosing the presence or absence of the exhaust gas, the abnormality diagnosis condition [the exhaust heat quantity in this embodiment (4)] is corrected based on the estimated air-fuel ratio during the catalyst early warm-up control. In this embodiment (4), the excess air ratio λ is used as the air-fuel ratio information.
[0070]
Hereinafter, the processing content of the catalyst early warm-up system abnormality diagnosis program of FIG. 8 that performs abnormality diagnosis of the catalyst early warm-up system of the present embodiment (4) will be described. In this program, the intake air amount GA is read during the early catalyst warm-up control and the idling operation (steps 401 to 403).
[0071]
Thereafter, the routine proceeds to step 404, where the estimated exhaust gas temperature T0 at the reference air-fuel ratio (for example, the excess air ratio λ = 1) is calculated by the following equation using the ignition timing retardation amount Δθ and the engine speed NE.
T0 = K0 + Δθ × K2 + NE × K3
Here, K0, K2, and K3 are coefficients.
[0072]
Thereafter, the process proceeds to step 405, and the estimated exhaust heat quantity Q0 is calculated by the following equation using the estimated exhaust temperature T0, the intake air amount GA, and the specific heat E of the exhaust gas.
Q0 = T0 x GA x E
After calculating the estimated exhaust heat quantity Q0, the routine proceeds to step 406, where the estimated exhaust heat quantity Q0 is added to the previous estimated exhaust heat quantity integrated value QSUM0 to update the estimated exhaust heat quantity integrated value QSUM0. Thereafter, the process proceeds to step 407, and the count value of the timer CSUM is incremented by “1”.
[0073]
Thereafter, the process proceeds to step 408, where it is determined whether or not the count value of the counter CSUM has exceeded a predetermined value K. If not, the process returns to step 401. Thus, the process of updating the estimated exhaust heat amount integrated value QSUM0 is repeated until the count value of the counter CSUM exceeds the predetermined value K.
[0074]
Thereafter, when the count value of the counter CSUM exceeds the predetermined value K, the routine proceeds to step 409, where the excess air ratio .lambda.s detected by the air-fuel ratio sensor 23 at the time t1 when the air-fuel ratio sensor 23 becomes active and the lean correction are performed. Using the coefficient Ls, the estimated excess air ratio λg during the early catalyst warm-up control (exhaust heat amount calculation) is calculated by the following equation.
.lambda.g = .lambda.s.times. {1- (1-Ls) .times.KLMD}
Here, the lean correction coefficient Ls is a correction coefficient for correcting the air-fuel ratio in the lean direction within a range in which the engine rotation fluctuation does not increase during the early catalyst warm-up control (see FIG. 10). Further, KLMD is a coefficient (for example, 0.5) for averaging the influence of the lean correction during the catalyst early warm-up control.
[0075]
Thereafter, the routine proceeds to step 410, where a map of the abnormality diagnosis correction coefficient KQ shown in FIG. 9 is searched to calculate an abnormality diagnosis correction coefficient KQ corresponding to the estimated excess air ratio λg during the catalyst early warm-up control.
[0076]
The map of the abnormality diagnosis correction coefficient KQ in FIG. 9 is set such that the abnormality diagnosis correction coefficient KQ increases as the estimated excess air ratio λg during the catalyst early warm-up control increases (lean). When the estimated excess air ratio λg = 1, the abnormality diagnosis correction coefficient KQ = 1 is set, and the estimated exhaust heat quantity integrated value QSUM0 is not corrected.
[0077]
Thereafter, the process proceeds to step 411, where the estimated exhaust heat amount integrated value QSUM0 is multiplied by the abnormality diagnosis correction coefficient KQ to obtain the exhaust heat amount integrated value QQSUM for abnormality diagnosis.
QQSUM = QSUM × KQ
Thereafter, the routine proceeds to step 412, where it is determined whether or not the exhaust heat amount integrated value QQSUM for abnormality diagnosis is larger than the abnormality determination value Qmin. If it is determined that the exhaust heat amount integrated value QQSUM for abnormality diagnosis is larger than the abnormality determination value Qmin, it is determined that the exhaust heat amount is a heat amount necessary for the early warm-up of the catalyst 24, and the process proceeds to step 413. Proceed, determine that the early catalyst warm-up system is normal, and terminate this program.
[0078]
On the other hand, if it is determined in step 412 that the exhaust heat amount integrated value QQSUM for abnormality diagnosis is equal to or less than the abnormality determination value Qmin, the exhaust heat amount is insufficient, and the amount of heat necessary for early warm-up of the catalyst 24 is reduced to the catalyst. 24, the process proceeds to step 414, where the early catalyst warm-up system is determined to be abnormal, a warning lamp (not shown) is lit to warn the driver, and an abnormal code is assigned to the ECU 31. After the program is stored in the backup RAM (not shown), the program is terminated.
[0079]
In the embodiment (4) described above, the estimated excess air ratio λg during the early catalyst warm-up control (exhaust heat amount calculation) is calculated, and the exhaust heat quantity for abnormality diagnosis corrected based on the estimated excess air ratio λg. Since the integrated value QQSUM is used to diagnose the presence or absence of an abnormality in the early catalyst warm-up system, the amount of reaction heat generated in the catalyst 24 changes depending on the air-fuel ratio (excess air ratio) during early catalyst warm-up control. Therefore, it is possible to accurately determine whether the exhaust heat amount integrated value during the early catalyst warm-up control is a heat amount necessary for the early warm-up of the catalyst 24. it can.
[0080]
In general, during the catalyst early warm-up control, the temperature of the engine 11 is low, so that the amount of fuel (wet amount) adhering to the intake port wall surface or the like out of the fuel injected from the fuel injection valve 20 is relatively large. Therefore, during the early catalyst warm-up control, the air-fuel ratio (excess air ratio) during the early catalyst warm-up control cannot be accurately estimated from the fuel injection amount TAU and the intake air amount GA.
[0081]
In this regard, in the present embodiment (4), as shown in the time chart of FIG. 10, the excess air ratio λs detected by the air-fuel ratio sensor 23 at the time t1 when the air-fuel ratio sensor 23 is activated and the leaning correction coefficient Ls is used to calculate an estimated excess air ratio λg during early catalyst warm-up control (exhaust heat amount calculation). The lean correction coefficient Ls is a parameter representing the air-fuel ratio behavior (change amount in the lean direction) during the early catalyst warm-up control. Therefore, the detected excess air ratio λs when the air-fuel ratio sensor 23 is active and the lean correction are performed. If the coefficient Ls is used, the estimated excess air ratio λg (estimated air-fuel ratio) during the catalyst early warm-up control can be calculated with higher accuracy in consideration of the lean correction during the catalyst early warm-up control.
[0082]
In this embodiment (4), the estimated exhaust heat quantity integrated value QSUM0 is corrected based on the estimated excess air ratio λg, but the abnormality determination value Qmin is corrected based on the estimated excess air ratio λg. In this case, the same effect can be obtained.
[0083]
In the present embodiment (4), the estimated excess air ratio λg during the early catalyst warm-up control is calculated using the detected excess air ratio λs and the lean correction coefficient Ls when the air-fuel ratio sensor 23 is active. However, as shown in FIG. 11, the excess air ratio λs detected by the air / fuel ratio sensor 23 at the time t1 when the air / fuel ratio sensor 23 is activated (or the average value λav of the excess air ratio λ during a predetermined period near the activation time t1). May be the estimated excess air ratio λg (estimated air-fuel ratio) during early catalyst warm-up control.
[0084]
As shown in FIG. 11, when the air-fuel ratio sensor 23 is active, air-fuel ratio feedback control is started, and an air-fuel ratio feedback correction coefficient F for correcting the air-fuel ratio detected by the air-fuel ratio sensor 23 to the target air-fuel ratio. Therefore, the estimated air during the early catalyst warm-up control based on the air-fuel ratio feedback correction coefficient Fs immediately after the activation of the air-fuel ratio sensor 23 (or the average value Fav of the air-fuel ratio feedback correction coefficient F for a predetermined period immediately after the activation) is calculated. An excess ratio λg (estimated air-fuel ratio) may be calculated.
[0085]
Further, the estimated excess air ratio λg (estimated air-fuel ratio) during the early catalyst warm-up control may be calculated using the air-fuel ratio feedback correction coefficient Fs and the leaning correction coefficient Ls.
Moreover, you may make it implement combining said each embodiment (1)-(4) suitably.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.
FIG. 2 is a flowchart showing a flow of processing of a catalyst early warm-up system abnormality diagnosis program according to the embodiment (1).
FIG. 3 is a time chart showing an execution example of the embodiment (1).
FIG. 4 is a graph showing the relationship between air-fuel ratio and exhaust temperature
FIG. 5 is a flowchart showing the flow of processing of a catalyst early warm-up system abnormality diagnosis program according to the embodiment (2).
FIG. 6 is a time chart showing an execution example of the embodiment (2) and the embodiment (3).
FIG. 7 is a flowchart showing the flow of processing of a catalyst early warming-up system abnormality diagnosis program of embodiment (3).
FIG. 8 is a flowchart showing the flow of processing of a catalyst early warm-up system abnormality diagnosis program of embodiment (4).
FIG. 9 is a diagram conceptually showing a map of an abnormality diagnosis correction coefficient KQ.
FIG. 10 is a time chart showing an execution example of the embodiment (4).
FIG. 11 is a time chart for explaining a modification of the embodiment (4).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 14 ... Air flow meter, 15 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 23 ... Air-fuel ratio sensor, 24 ... Catalyst, 31 ... ECU (abnormality diagnosis) Means, exhaust heat quantity calculation means, air-fuel ratio estimation means).

Claims

In a catalyst early warm-up system that performs catalyst early warm-up control to increase the exhaust heat amount of an internal combustion engine and promote warm-up of a catalyst for exhaust gas purification,
Exhaust heat amount calculating means for estimating an exhaust heat amount of the internal combustion engine or a heat amount supplied to the catalyst based on an operating state of the internal combustion engine during the catalyst early warm-up control;
An abnormality diagnosing means for diagnosing the presence or absence of an abnormality in the catalyst early warming-up system based on the heat quantity estimated by the exhaust heat quantity calculating means ;
Air-fuel ratio estimation means for estimating the air-fuel ratio during the catalyst early warm-up control,
The abnormality diagnosis device for a catalyst early warm-up system, wherein the abnormality diagnosis means corrects an abnormality diagnosis condition based on the air-fuel ratio during the catalyst early warm-up control estimated by the air-fuel ratio estimation means .

The exhaust heat amount calculation means includes an intake air amount or a parameter correlated therewith (hereinafter collectively referred to as “intake air amount parameter”), an air-fuel ratio or a parameter correlated therewith (hereinafter referred to as “air-fuel ratio parameter”). 2. The abnormality diagnosis device for an early catalyst warm-up system according to claim 1 , wherein the exhaust heat quantity of the internal combustion engine is obtained based on at least one of the following.

The exhaust heat quantity calculating means estimates an exhaust temperature using at least one of an engine speed, an ignition timing, and the air-fuel ratio parameter when obtaining the exhaust heat quantity of the internal combustion engine, and the estimated exhaust temperature and the intake air The abnormality diagnosis device for an early catalyst warm-up system according to claim 2 , wherein the exhaust heat quantity is calculated based on the quantity parameter.

4. The catalyst early warm-up according to claim 2 , wherein at least one of intake air amount, throttle opening, intake valve variable lift amount, and intake pressure is used as the intake air amount parameter. System abnormality diagnosis device.

4. The catalyst early warming according to claim 2, wherein the air-fuel ratio parameter is at least one of an air-fuel ratio detected by an air-fuel ratio sensor of an exhaust system, a fuel injection amount, and a combustion roughness value. Machine system abnormality diagnosis device.

The air-fuel ratio estimation means estimates the air-fuel ratio during the early catalyst warm-up control based on the air-fuel ratio detected by the air-fuel ratio sensor when the air-fuel ratio sensor provided in the exhaust passage of the internal combustion engine is activated. The abnormality diagnosis device for a catalyst early warm-up system according to any one of claims 1 to 5 .

The air-fuel ratio estimation means is based on an air-fuel ratio feedback correction coefficient when air-fuel ratio feedback control is executed based on the air-fuel ratio detected by the air-fuel ratio sensor after activation of an air-fuel ratio sensor provided in the exhaust passage of the internal combustion engine. abnormality diagnosis apparatus for fast catalyst warm-up system according to any one of claims 1 to 5, characterized in that for estimating the air-fuel ratio of the catalyst early warm-up control during.

The air-fuel ratio estimation means is a parameter used for estimating the air-fuel ratio during the catalyst early warm-up control, in addition to the detected air-fuel ratio when the air-fuel ratio sensor is activated or the air-fuel ratio feedback correction coefficient, and the catalyst early warm-up. The abnormality diagnosis device for a catalyst early warm-up system according to claim 6 or 7 , wherein a leaning correction coefficient for correcting the air-fuel ratio in the lean direction based on the rotational behavior of the internal combustion engine during engine control is also used. .

The abnormality diagnosis means during idle operation of the catalyst early warm-up control during and engine, according to any one of claims 1 to 8, characterized in that performing the abnormality diagnosis of the catalyst early warm-up system Abnormality diagnosis device for early catalyst warm-up system.