JP2004245118A

JP2004245118A - Diagnostic device of egr system and control device of egr system

Info

Publication number: JP2004245118A
Application number: JP2003035130A
Authority: JP
Inventors: Hidenori Imamura; 秀徳今村
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2003-02-13
Filing date: 2003-02-13
Publication date: 2004-09-02

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diagnostic device of an EGR system (an exhaust gas recirculation system) provided in a speed-density type gasoline injection engine which can judge the plugging of the EGR system without an air flow meter, and a control device of an EGR system which uses the judgement result. <P>SOLUTION: The EGR system recirculates part of exhaust gas to inhalation air. There are provided a basic fuel quantity calculation means 70 which presumes an inhalation air amount based on the pressure of an inlet pipe and the engine rotational speed so as to calculate a basic fuel quantity; an air-fuel ratio feedback control means 70 which computes an amount of air-fuel ratio feedback amendment so that the air-fuel ratio of the exhaust gas may be a target air-fuel ratio and which amends the basic fuel quantity on the air-fuel ratio feedback amendment amount, and a plugging judgement means 70 which judges whether plugging occurs in the EGR system or not based on the air-fuel ratio feedback amendment amount obtained when the EGR system is operated as well as at the time of such an operation hysteresis that there is no possibility of plugging of the EGR system and the air-fuel ratio feedback amendment amount obtained when the EGR system is operated as well as at the time of such an operation hysteresis that there is a possibility of plugging of the EGR system. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、排気還流装置（ＥＧＲ装置）の診断装置及びＥＧＲ装置の制御装置に関するものである。
【０００２】
【従来の技術】
吸入空気量を直接的に検出するマスフロー方式のガソリン噴射機関に備えられるＥＧＲ装置において、ＥＧＲ装置に詰まりがあるか否かを診断するようにしたものがある（特許文献１参照）。
【０００３】
【特許文献１】
特開２００１−１６４９９９号公報
【０００４】
【発明が解決しようとする課題】
ところで、最近では一層の燃費向上のためＥＧＲ装置を積極的に利用することが行われている。これは、ＥＧＲ装置の作動時にＥＧＲガス（不活性ガス）が吸気管に加わり、ポンピングロスが減って燃費がよくなるためである。
【０００５】
一方、排気中には煤や未燃分が含まれ、これがＥＧＲ装置に付着したり堆積したりして有効流路面積を小さくする、いわゆる詰まりが発生する。この詰まりにより、ＥＧＲ装置の作動は正常でも要求されているＥＧＲガス流量が吸気管に導入されなくなり、ポンピングロスがその分大きくなり燃費が悪化する。
【０００６】
そこで、上記の従来装置のようにＥＧＲ装置に詰まりがあるか否かを診断する必要が生じるわけであるが、吸気管圧力と機関回転速度で吸入空気量を推定して基本燃料量を演算するスピードデンシティ方式のガソリン噴射機関に備えられるＥＧＲ装置に対しては、上記の従来装置をそのまま適用することができない。
【０００７】
これについて説明すると、従来装置では、ＥＧＲ装置の作動域において、アクセル開度と機関回転速度をパラメータとする目標吸入空気量のマップを持たせており、エアフローメータで検出した実際の吸入空気量とこの目標吸入空気量とを比較し、実際の吸入空気量が目標吸入空気量より一定量以上少なくなったときＥＧＲ装置に詰まりがあると判定し、ＥＧＲ装置によるＥＧＲ流量を増す側に補正している。ところが、スピードデンシティ方式のガソリン噴射機関にはエアフローメータは基本的に備えられていないので、従来装置をそのまま適用することはできない。かといってエアフローメータを新たに設けるとすればコストアップになる。
【０００８】
本発明は、このような従来の問題点に着目してなされたものであり、スピードデンシティ方式のガソリン噴射機関に備えられるＥＧＲ装置においてもエアフローメータを備えることなくＥＧＲ装置の詰まり判定を行い得る診断装置及びその判定結果を用いるＥＧＲ装置の制御装置を提供することを目的としている。
【０００９】
【課題を解決するための手段】
本発明は、以下のような解決手段により、前記課題を解決する。
【００１０】
本発明は、排気の一部を吸気に還流するＥＧＲ装置において、吸気管圧力と機関回転速度で吸入空気量を推定して基本燃料量を演算する基本燃料量演算手段と、排気の空燃比が目標空燃比となるように空燃比フィードバック補正量を算出し、その空燃比フィードバック補正量で前記基本燃料量を補正する空燃比フィードバック制御手段と、前記ＥＧＲ装置の作動時かつ前記ＥＧＲ装置に詰まりの可能性のない運転履歴のときに得られる前記空燃比フィードバック補正量と、前記ＥＧＲ装置の作動時かつ前記ＥＧＲ装置に詰まりの可能性のある運転履歴のときに得られる前記空燃比フィードバック補正量とに基づいて前記ＥＧＲ装置に詰まりがあるか否かを判定する詰まり判定手段とを備えることを特徴とする。
【００１１】
【作用・効果】
ＥＧＲ装置に詰まりがあると、ＥＧＲガス流量はＥＧＲ装置に詰まりがないときより減り、排気の空燃比が目標空燃比よりもリーン側にずれる。空燃比のフィードバック制御中には、このリーン側にずれた空燃比を目標空燃比に戻そうと空燃比フィードバック補正量が変化する。すなわち、ＥＧＲ装置に詰まりがあるときとないときとで空燃比フィードバック補正量が異なるため、ＥＧＲ装置に詰まりがあるときの空燃比フィードバック補正量とＥＧＲ装置に詰まりがないときの空燃比フィードバック補正量とに基づけばＥＧＲ装置に詰まりがあるか否かを判定することができる。
【００１２】
また、詰まりは、機関の運転時間が長くなりあるいは機関を搭載する車両の走行距離が長くなったときに発生するので、ＥＧＲ装置の作動時かつＥＧＲ装置に詰まりの可能性のない運転履歴のときの空燃比フィードバック補正量と、ＥＧＲ装置の作動時かつＥＧＲ装置に詰まりの可能性のある運転履歴のときの空燃比フィードバック補正量とを比較すればよい。
【００１３】
このようにすることによって本発明ではスピードデンシティ方式のガソリン噴射機関に備えられるＥＧＲ装置においてもエアフローメータを備えることなくＥＧＲ装置の詰まり判定を行い得ることになった。
【００１４】
【発明の実施の形態】
以下、図面等を参照して、本発明の実施の形態について、さらに詳しく説明する。
【００１５】
図１は、本発明によるスピードデンシティ方式のガソリン噴射機関のＥＧＲ制御装置の一実施形態を示す図である。
【００１６】
機関１０の吸気系には、上流側からエアクリーナ２１、スロットルバルブ２２、吸気管２３が配置されている。スロットルバルブ２２は、アクセルペダルの踏み込み量に応動して開き、機関１０が吸入する空気の流量を制御する。
【００１７】
吸気管２３には、吸気圧センサ２４が設けられており、スロットル下流の吸気管２３内の圧力に基づいて内燃機関の負荷を検知する。また、吸気管２３には、燃料噴射弁３１と、燃料ポンプ３２と、レギュレータ３３とを有する燃料噴射装置が設けられており、この燃料噴射弁３１は各気筒ごとに設けられている。
【００１８】
また、機関１０の排気系には、排気マニホールド４１、三元触媒４２、排気管４３、消音器４４が設けられている。三元触媒４２の上流にはフロント酸素センサ４５が設けられ、下流にはリヤ酸素センサ４６が設けられている。フロント酸素センサ４５及びリヤ酸素センサ４６は排気中の酸素濃度を検出する。フロント酸素センサ４５及びリヤ酸素センサ４６の信号はコントロールユニット７０に出力される。
【００１９】
三元触媒４２は、流入する排気の空燃比が理論空燃比（空気過剰率λ＝１）を中心とするいわゆるウィンドウにあるときに、最大の転化効率をもってその排気中に含まれるＣＯ、ＨＣ、ＮＯｘを浄化する。これらの成分を同時に浄化するためには排気中の酸素に過不足がないように理論空燃比付近にコントロールする必要がある。そのため、フロント酸素センサ４５及びリヤ酸素センサ４６によって検出した酸素濃度に基づいて燃料噴射量（燃料噴射弁３１の開時間）を補正して排気が理論空燃比付近になるようにコントロールする。
【００２０】
また、排気マニホールド４１には、排気再循環通路（ＥＧＲ通路）５１が接続されている。このＥＧＲ通路５１の他端は吸気管２３に接続されている。
【００２１】
ＥＧＲ通路５１の途中にはＥＧＲクーラ５２及びＥＧＲバルブ５３が設けられている。ＥＧＲクーラ５２は、吸気管２３に戻す排気（ＥＧＲガス）を冷却する。ＥＧＲバルブ５３は、ＥＧＲクーラ５２によって冷却されたＥＧＲガスの流量をコントロールする。ＥＧＲバルブ５３は、電磁弁などで構成され、印加電力の大きさに応じて開度を変更する。
【００２２】
また、機関１０には、クランク角センサ１２及び水温センサ１３が取り付けられている。クランク角センサ１２はクランク軸の回転角度を検出する。クランク角センサ１２の信号はコントロールユニット７０に出力される。コントロールユニット７０では、この信号に基づいて機関回転速度を演算する。また、水温センサ１３の信号もコントロールユニット７０に出力される。
【００２３】
また、機関１０に連結したトランスミッション１４には、走行速度を測定するための車速センサ１５が設けられている。
【００２４】
コントロールユニット７０は、吸気圧センサ２４の信号と、クランク角センサ１２の信号とに基づいて吸入空気量を推定して基本燃料量Ｔｐを演算する。また、コントロールユニット７０は、フロント酸素センサ４５及びリヤ酸素センサ４６からの信号に基づいて、排気の空燃比が目標空燃比（ここでは理論空燃比）となるように空燃比フィードバック補正係数αを算出する。さらに、コントロールユニット７０は、ＥＧＲ装置に詰まりが生じているか否かを空燃比フィードバック補正量に基づいて判定する。ＥＧＲ装置に詰まりがあると、ＥＧＲガス流量はＥＧＲ装置に詰まりがないときより減り、排気の空燃比が理論空燃比よりもリーン側にずれる。空燃比のフィードバック制御中には、このリーン側にずれた空燃比を理論空燃比に戻そうと空燃比フィードバック補正量が変化する。すなわち、ＥＧＲ装置に詰まりがあるときとないときとで空燃比フィードバック補正量が異なるため、ＥＧＲ装置に詰まりがあるときの空燃比フィードバック補正量とＥＧＲ装置に詰まりがないときの空燃比フィードバック補正量とに基づけばＥＧＲ装置に詰まりがあるか否かを判定することができる。
【００２５】
以下、フローチャートに沿ってコントロールユニット７０で行われるＥＧＲ故障診断の具体的な制御について説明する。
【００２６】
図２は空燃比学習値の更新制御を示すフローチャートである。
【００２７】
ステップＳ１１では、ＥＧＲ作動状態であるか否かを判断し、ＥＧＲ作動状態でなければステップＳ１２に進む。ステップＳ１２では、ＥＧＲ非作動時の空燃比学習値（ＫＢＬＲＣ０）を次式により更新する。
【００２８】

ここで、αａｖｅは空燃比フィーバック補正係数αの半周期当たりの平均値である。
【００２９】
そして、ＥＧＲ作動状態になったらステップＳ１３に進んで、ＥＧＲ詰まり判定を行う必要があるか否かを判断する。これは走行距離が所定距離（ＥＧＲ詰まりが発生する可能性のある走行距離）を超えたか否かで判断する。走行距離が短い間はステップＳ１４へ進んで、ＥＧＲ作動時であってＥＧＲ詰まり判定不要時の空燃比学習値（ＫＢＬＲＣｅ）を更新する。
【００３０】
ステップＳ１５では、ＥＧＲ非作動時の空燃比学習値（ＫＢＬＲＣ０）と、ＥＧＲ作動時であってＥＧＲ詰まり判定不要時の空燃比学習値（ＫＢＬＲＣｅ）との空燃比学習値の差分（ΔＫＢＬＲＣ１）を求める。このようにＥＧＲ作動時であってＥＧＲ詰まり判定不要時の空燃比学習値（ＫＢＬＲＣｅ）がＥＧＲ非作動時の空燃比学習値（ＫＢＬＲＣ０）に対してどのように変化するかを検出し続ける。
【００３１】
続いて、ＥＧＲ詰まりが発生する可能性のある走行距離を超えたら（ステップＳ１３においてＹ）、ステップＳ１６に進んで、ＥＧＲ作動時であってＥＧＲ詰まり判定必要時の空燃比学習値（ＫＢＬＲＣｅ’）を更新する。
【００３２】
ステップＳ１７では、ＥＧＲ非作動時の空燃比学習値（ＫＢＬＲＣ０）と、ＥＧＲ作動時であってＥＧＲ詰まり判定必要時の空燃比学習値（ＫＢＬＲＣｅ’）との空燃比学習値の差分（ΔＫＢＬＲＣ２）を求める。このようにＥＧＲ作動時であってＥＧＲ詰まり判定必要時の空燃比学習値（ＫＢＬＲＣｅ’）がＥＧＲ非作動時の空燃比学習値（ＫＢＬＲＣ０）に対してどのように変化するかを検出し続ける。
【００３３】
図３はＥＧＲ詰まりフラグの設定処理を示すフローチャートである。
【００３４】
ステップＳ２１では、ＥＧＲ詰まりフラグが０（ＥＧＲ詰まり無し）か、１（ＥＧＲ詰まり有り）かを判断し、ステップＳ２２ではＥＧＲ詰まりの可能性のある走行距離を超えたか否かを判断する。ＥＧＲ詰まりフラグが０（ＥＧＲ詰まり無し）であって、所定の走行距離を超えていればステップＳ２３以降の処理を行うが、ＥＧＲ詰まりフラグが１（ＥＧＲ詰まり有り）である場合又は所定の走行距離に達していない場合には、ステップＳ２６へ進んで本処理を終了する。
【００３５】
ステップＳ２３では空燃比学習値の差分（ΔＫＢＬＲＣ１，ΔＫＢＬＲＣ２）を読み込み、ステップＳ２４では両差分の絶対値がＥＧＲ詰まり判定値εよりも大きいか否かを判断する。大きければステップＳ２５へ進んでＥＧＲ詰まりフラグを１に設定し、小さければステップＳ２６へ進んで本処理を終了する。
【００３６】
図４はＥＧＲバルブ開度学習値θの更新処理を示すフローチャートである。
【００３７】
ステップＳ３１では、ＥＧＲ詰まりフラグが１であるか否か（ＥＧＲ詰まり状態であるか否か）を判断する。１であれば（すなわちＥＧＲ詰まりあり状態）ステップＳ３２以降へ進む。１でなければ（すなわちＥＧＲ詰まりなし状態）ステップＳ３６へ進んで本処理を終了する。
【００３８】
ステップＳ３２では空燃比学習値の差分（ΔＫＢＬＲＣ１，ΔＫＢＬＲＣ２）を読み込む。
【００３９】
ステップＳ３３では読み込んだ両差分（ΔＫＢＬＲＣ１，ΔＫＢＬＲＣ２）に基づいてθｈを求め、ステップＳ３４ではθｈによりＥＧＲバルブ開度学習値θを更新し、ステップＳ３５ではＥＧＲ詰まりフラグを０に設定する。
【００４０】
このように本処理を行うことで、ＥＧＲ詰まり状態のときには（ステップＳ３１でＹ）、ＥＧＲバルブ開度学習値θを更新してから（ステップＳ３４）、ＥＧＲ詰まりフラグをリセットする（ステップＳ３５）。
【００４１】
図５はＥＧＲバルブ開度の演算処理を示すフローチャートである。
【００４２】
ステップＳ４１ではＥＧＲ作動域であるか否かを判断する。ＥＧＲ作動域であればＥＧＲバルブ開度θの演算を行う（ステップＳ４２）。具体的には本実施形態では上述のステップＳ３４で更新した学習値を利用する。一方、ＥＧＲ作動域でなければＥＧＲバルブ開度θ＝０とする（ステップＳ４３）。
【００４３】
図６は燃料噴射量Ｔｉの演算を示すフローチャートである。
【００４４】
ステップＳ５１では吸気圧と回転速度を読み込み、ステップＳ５２でこれらに基づいて基本噴射量Ｔｐを演算する。
【００４５】
ステップＳ５３ではフロント酸素センサ４５及びリヤ酸素センサ４６からの出力に基づいて空燃比フィードバック補正係数αを演算する。
【００４６】
ステップＳ５４、Ｓ５８では、図２のステップＳ１１、Ｓ１３と同様に、ＥＧＲ作動状態であるか否か、また走行距離が所定距離を超えたか否かを判定する。ステップＳ５５、Ｓ５９、Ｓ６１ではそれらの判定結果に応じてそれぞれの空燃比学習値ＫＢＬＲＣ０、ＫＢＬＲＣｅ、ＫＢＬＲＣｅ’を読み出し、ステップＳ５６、Ｓ６０、Ｓ６２でその読み出した空燃比学習値を空燃比学習値ＫＢＬＲＣに入れる。ステップＳ５７では例えばシーケンシャル噴射時の燃料噴射量Ｔｉを次式により演算する。
【００４７】
Ｔｉ＝Ｔｐ×（α＋ＫＢＬＲＣ−１）×２＋Ｔｓ
ただし、Ｔｓは無効噴射量である。
【００４８】
なお、上記においては、ある運転状態、すなわち内燃機関の回転速度及び負荷が所定範囲にあるときを例示して説明を行った。運転状態が変わった場合であっても、その運転状態ごとに同様の処理を行うことで、ＥＧＲ作動領域全域に渡って効果を得ることができる。
【００４９】
ＥＧＲガス流量が減ると新気が増えて空燃比が理論空燃比よりもリーン側にずれる。すると、空燃比フィードバック補正係数αは理論空燃比に戻そうと大きくなる方向にずれていき、このαに基づいて更新される空燃比学習値が１．０よりも大きな値になる。そこで、本発明ではＥＧＲ装置の作動時であってＥＧＲ装置に詰まりの可能性のない走行距離のときの第１の空燃比学習値ＫＢＬＲＣｅ、ＥＧＲ装置の作動時であってＥＧＲ装置に詰まりの可能性のある走行距離のときの第２の空燃比学習値ＫＢＬＲＣｅ’に着目し、それぞれ、ＥＧＲ非作動時の空燃比学習値ＫＢＬＲＣ０との差分（ΔＫＢＬＲＣ１，ΔＫＢＬＲＣ２１）を求め（ステップＳ１５，Ｓ１７）、その差分を比較してＥＧＲ詰まりが発生しているか否かを判定する（ステップＳ２４）。そして、ＥＧＲ詰まりが発生しているときはＥＧＲバルブを開くようにした（ステップＳ３４）。このようにしたので、本実施形態によれば、エアフローメータを設けることなくＥＧＲバルブの詰まり判定を行うことができるようになった。
【００５０】
以上説明した実施形態に限定されることなく、その技術的思想の範囲内において種々の変形や変更が可能であり、それらも本発明と均等であることは明白である。
【００５１】
例えば、上記実施形態では、空燃比学習値の差分（ΔＫＢＬＲＣ１，ΔＫＢＬＲＣ２）によってＥＧＲ詰まりが発生しているか否かを判断しているが（ステップＳ２４）、例えば、ＥＧＲ作動時であってＥＧＲ詰まり判定必要時の空燃比学習値（ＫＢＬＲＣｅ’）と、ＥＧＲ作動時であってＥＧＲ詰まり判定不要時の空燃比学習値（ＫＢＬＲＣｅ）との差分によってＥＧＲ詰まりが発生しているか否か、すなわち（｜ＫＢＬＲＣｅ’−ＫＢＬＲＣｅ｜＞ε）が成立するか否かによって判断してもよい。
【００５２】
また、上記実施形態では空燃比フィードバック制御を酸素センサ出力に基づいて行っているが、いわゆる広域空燃比センサ出力に基づいて空燃比フィードバック制御を行ってもよい。
【００５３】
さらに、実施形態では空燃比学習値に基づいてＥＧＲ装置に詰まりが生じた否かを判定する場合で説明したが、空燃比フィードバック補正係数αの平均値（例えば空燃比フィードバック制御中における半周期周当たりの平均値や空燃比フィードバック制御中における所定期間当たりの平均値）に基づいてＥＧＲ装置に詰まりが生じた否かを判定することもできる。
【００５４】
さらにまた、実施形態では運転履歴が車両の走行距離である場合で説明したが、これに限られるものでないことはいうまでもない。
【図面の簡単な説明】
【図１】本発明による内燃機関のＥＧＲ制御装置の一実施形態を示す図である。
【図２】本発明による内燃機関のＥＧＲ制御装置の空燃比学習値の更新制御を示すフローチャートである。
【図３】ＥＧＲ詰まりフラグの設定処理を示すフローチャートである。
【図４】ＥＧＲバルブ開度学習値の更新処理を示すフローチャートである。
【図５】ＥＧＲバルブ開度の演算処理を示すフローチャートである。
【図６】燃料噴射量Ｔｉの演算を示すフローチャートである。
【符号の説明】
１０内燃機関
１１燃焼室
１５車速センサ
２２スロットルバルブ
２３吸気管
３１燃料噴射弁
４１排気マニホールド
４２三元触媒
４５フロント酸素センサ
４６リヤ酸素センサ
５１ＥＧＲ通路
５３ＥＧＲバルブ
７０コントロールユニット[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a diagnostic device for an exhaust gas recirculation device (EGR device) and a control device for the EGR device.
[0002]
[Prior art]
2. Description of the Related Art Among EGR devices provided in a mass flow type gasoline injection engine that directly detects an intake air amount, there is an EGR device that diagnoses whether or not the EGR device is clogged (see Patent Document 1).
[0003]
[Patent Document 1]
JP 2001-164999 A
[Problems to be solved by the invention]
By the way, recently, the EGR device has been actively used to further improve the fuel efficiency. This is because the EGR gas (inert gas) is added to the intake pipe when the EGR device is operated, so that pumping loss is reduced and fuel efficiency is improved.
[0005]
On the other hand, soot and unburned matter are contained in the exhaust gas, which adheres or accumulates on the EGR device to cause a so-called clogging that reduces the effective flow path area. Due to this clogging, even if the operation of the EGR device is normal, the required EGR gas flow rate is not introduced into the intake pipe, so that the pumping loss is increased correspondingly and fuel efficiency is deteriorated.
[0006]
Therefore, it is necessary to diagnose whether or not the EGR device is clogged as in the above-mentioned conventional device. However, the basic fuel amount is calculated by estimating the intake air amount based on the intake pipe pressure and the engine speed. The above-described conventional device cannot be directly applied to an EGR device provided in a speed density type gasoline injection engine.
[0007]
Explaining this, the conventional device has a map of the target intake air amount using the accelerator opening and the engine speed as parameters in the operating range of the EGR device. The target intake air amount is compared with the target intake air amount, and when the actual intake air amount becomes smaller than the target intake air amount by a certain amount or more, it is determined that the EGR device is clogged, and the EGR device is corrected to increase the EGR flow rate. I have. However, a gasoline injection engine of the speed density system is basically not provided with an air flow meter, so that the conventional device cannot be applied as it is. However, if an air flow meter is newly provided, the cost will increase.
[0008]
SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and a diagnosis capable of performing clogging determination of an EGR device without an air flow meter even in an EGR device provided in a speed density type gasoline injection engine. It is an object of the present invention to provide a device and a control device for an EGR device using the determination result.
[0009]
[Means for Solving the Problems]
The present invention solves the above problem by the following means.
[0010]
According to the present invention, in an EGR device that recirculates a part of exhaust gas to intake air, a basic fuel amount calculating means for estimating an intake air amount based on an intake pipe pressure and an engine rotation speed to calculate a basic fuel amount, and an air-fuel ratio of the exhaust gas. An air-fuel ratio feedback control means for calculating an air-fuel ratio feedback correction amount so as to attain the target air-fuel ratio, and correcting the basic fuel amount with the air-fuel ratio feedback correction amount; and when the EGR device is operating and the EGR device is clogged. The air-fuel ratio feedback correction amount obtained at the time of the operation history with no possibility, and the air-fuel ratio feedback correction amount obtained at the time of operation of the EGR device and at the time of the operation history in which the EGR device may be clogged. Clogging determining means for determining whether or not the EGR device is clogged based on the condition.
[0011]
[Action / Effect]
When the EGR device is clogged, the flow rate of the EGR gas is smaller than when the EGR device is not clogged, and the air-fuel ratio of the exhaust gas is shifted to a leaner side than the target air-fuel ratio. During the air-fuel ratio feedback control, the air-fuel ratio feedback correction amount changes to return the lean-side air-fuel ratio to the target air-fuel ratio. That is, since the air-fuel ratio feedback correction amount differs depending on whether the EGR device is clogged or not, the air-fuel ratio feedback correction amount when the EGR device is clogged and the air-fuel ratio feedback correction amount when the EGR device is not clogged. Based on the above, it can be determined whether or not the EGR device is clogged.
[0012]
Also, clogging occurs when the operating time of the engine is prolonged or the traveling distance of the vehicle equipped with the engine is prolonged. Therefore, when the EGR device is operated and the driving history is such that the EGR device is not likely to be clogged. May be compared with the air-fuel ratio feedback correction amount during the operation of the EGR device and during the operation history in which the EGR device may be clogged.
[0013]
By doing so, according to the present invention, even in an EGR device provided in a speed-density type gasoline injection engine, it is possible to determine whether the EGR device is clogged without having an air flow meter.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings and the like.
[0015]
FIG. 1 is a diagram showing an embodiment of an EGR control device of a speed density type gasoline injection engine according to the present invention.
[0016]
In the intake system of the engine 10, an air cleaner 21, a throttle valve 22, and an intake pipe 23 are arranged from the upstream side. The throttle valve 22 opens in response to the depression amount of the accelerator pedal, and controls the flow rate of the air taken in by the engine 10.
[0017]
An intake pressure sensor 24 is provided in the intake pipe 23, and detects the load of the internal combustion engine based on the pressure in the intake pipe 23 downstream of the throttle. Further, the intake pipe 23 is provided with a fuel injection device having a fuel injection valve 31, a fuel pump 32, and a regulator 33. The fuel injection valve 31 is provided for each cylinder.
[0018]
The exhaust system of the engine 10 includes an exhaust manifold 41, a three-way catalyst 42, an exhaust pipe 43, and a muffler 44. A front oxygen sensor 45 is provided upstream of the three-way catalyst 42, and a rear oxygen sensor 46 is provided downstream. The front oxygen sensor 45 and the rear oxygen sensor 46 detect the oxygen concentration in the exhaust gas. The signals of the front oxygen sensor 45 and the rear oxygen sensor 46 are output to the control unit 70.
[0019]
When the air-fuel ratio of the inflowing exhaust gas is in a so-called window centered on the stoichiometric air-fuel ratio (excess air ratio λ = 1), the three-way catalyst 42 has CO, HC, Purify NOx. In order to purify these components at the same time, it is necessary to control the oxygen in the exhaust gas to near the stoichiometric air-fuel ratio so that there is no excess or deficiency. Therefore, the fuel injection amount (opening time of the fuel injection valve 31) is corrected based on the oxygen concentrations detected by the front oxygen sensor 45 and the rear oxygen sensor 46, and the exhaust gas is controlled so as to be near the stoichiometric air-fuel ratio.
[0020]
Further, an exhaust gas recirculation passage (EGR passage) 51 is connected to the exhaust manifold 41. The other end of the EGR passage 51 is connected to the intake pipe 23.
[0021]
An EGR cooler 52 and an EGR valve 53 are provided in the middle of the EGR passage 51. The EGR cooler 52 cools exhaust gas (EGR gas) returned to the intake pipe 23. The EGR valve 53 controls the flow rate of the EGR gas cooled by the EGR cooler 52. The EGR valve 53 is configured by an electromagnetic valve or the like, and changes the opening degree according to the magnitude of the applied power.
[0022]
The engine 10 is provided with a crank angle sensor 12 and a water temperature sensor 13. The crank angle sensor 12 detects the rotation angle of the crank shaft. The signal of the crank angle sensor 12 is output to the control unit 70. The control unit 70 calculates the engine speed based on this signal. Further, the signal of the water temperature sensor 13 is also output to the control unit 70.
[0023]
The transmission 14 connected to the engine 10 is provided with a vehicle speed sensor 15 for measuring a traveling speed.
[0024]
The control unit 70 estimates the intake air amount based on the signal of the intake pressure sensor 24 and the signal of the crank angle sensor 12, and calculates the basic fuel amount Tp. Further, the control unit 70 calculates the air-fuel ratio feedback correction coefficient α based on the signals from the front oxygen sensor 45 and the rear oxygen sensor 46 such that the air-fuel ratio of the exhaust gas becomes the target air-fuel ratio (here, the stoichiometric air-fuel ratio). I do. Further, the control unit 70 determines whether the EGR device is clogged based on the air-fuel ratio feedback correction amount. When the EGR device is clogged, the flow rate of the EGR gas is smaller than when the EGR device is not clogged, and the air-fuel ratio of the exhaust gas is shifted to a leaner side than the stoichiometric air-fuel ratio. During the air-fuel ratio feedback control, the air-fuel ratio feedback correction amount changes to return the lean-side air-fuel ratio to the stoichiometric air-fuel ratio. That is, since the air-fuel ratio feedback correction amount differs depending on whether the EGR device is clogged or not, the air-fuel ratio feedback correction amount when the EGR device is clogged and the air-fuel ratio feedback correction amount when the EGR device is not clogged. Based on the above, it can be determined whether or not the EGR device is clogged.
[0025]
Hereinafter, specific control of the EGR failure diagnosis performed by the control unit 70 will be described with reference to a flowchart.
[0026]
FIG. 2 is a flowchart showing the update control of the air-fuel ratio learning value.
[0027]
In step S11, it is determined whether or not the vehicle is in the EGR operation state, and if not, the process proceeds to step S12. In step S12, the air-fuel ratio learning value (KBLRC0) when the EGR is not operated is updated by the following equation.
[0028]

Here, αave is an average value of the air-fuel ratio feedback correction coefficient α per half cycle.
[0029]
Then, when the EGR operation state is established, the process proceeds to step S13, and it is determined whether or not it is necessary to perform EGR blockage determination. This is determined based on whether or not the traveling distance exceeds a predetermined distance (a traveling distance at which EGR blockage may occur). While the traveling distance is short, the process proceeds to step S14, and the air-fuel ratio learning value (KBLRCe) at the time of EGR operation and when EGR clogging determination is unnecessary is updated.
[0030]
In step S15, a difference (ΔKBRRC1) between the air-fuel ratio learning value (KBRRC0) when the EGR is not operated and the air-fuel ratio learning value (KBLRCe) when the EGR operation is performed and the EGR clogging determination is unnecessary is determined. . In this way, it is continuously detected how the air-fuel ratio learning value (KBLRCe) when the EGR operation is performed and the EGR clogging determination is unnecessary does not change with respect to the air-fuel ratio learning value (KBLRC0) when the EGR is not operating.
[0031]
Subsequently, when the travel distance exceeds the possibility that EGR clogging may occur (Y in step S13), the process proceeds to step S16, and the air-fuel ratio learning value (KBLRCe ') at the time of EGR operation and EGR clogging determination is required. To update.
[0032]
In step S17, the difference (ΔKBRRC2) between the air-fuel ratio learning value (KBRRC0) when the EGR is not operated and the air-fuel ratio learning value (KBLRCe ′) when the EGR is operating and EGR clogging determination is required is calculated. Ask. In this way, it is continuously detected how the air-fuel ratio learning value (KBLRCe ') at the time of EGR operation and EGR clogging determination is required is changed with respect to the air-fuel ratio learning value (KBLRC0) at the time of EGR non-operation.
[0033]
FIG. 3 is a flowchart showing a setting process of the EGR clogging flag.
[0034]
In step S21, it is determined whether the EGR clogging flag is 0 (no EGR clogging) or 1 (EGR clogging is present), and in step S22, it is determined whether or not the running distance exceeds the possibility of EGR clogging. If the EGR clogging flag is 0 (no EGR clogging) and exceeds a predetermined traveling distance, the processing after step S23 is performed. However, if the EGR clogging flag is 1 (EGR clogging is present) or the predetermined traveling distance If not, the process proceeds to step S26, and this process ends.
[0035]
In step S23, the difference between the air-fuel ratio learning values (ΔKBLRC1, ΔKBLRC2) is read, and in step S24, it is determined whether or not the absolute value of both the differences is greater than the EGR blockage determination value ε. If it is larger, the process proceeds to step S25, and the EGR blockage flag is set to 1. If it is smaller, the process proceeds to step S26, and the present process is terminated.
[0036]
FIG. 4 is a flowchart showing an update process of the EGR valve opening learning value θ.
[0037]
In step S31, it is determined whether or not the EGR clogging flag is 1 (whether or not the EGR is clogged). If it is 1, that is, if the EGR is clogged, the process proceeds to step S32. If it is not 1 (ie, no EGR clogging), the process proceeds to step S36 to end this processing.
[0038]
In step S32, the difference (ΔKBLRC1, ΔKBLRC2) between the air-fuel ratio learning values is read.
[0039]
In step S33, θh is determined based on the two differences (ΔKBLRC1, ΔKBLRC2) read. In step S34, the EGR valve opening learning value θ is updated by θh, and in step S35, the EGR blockage flag is set to 0.
[0040]
By performing this processing in this way, when the EGR is clogged (Y in step S31), the EGR valve opening learning value θ is updated (step S34), and the EGR clogging flag is reset (step S35).
[0041]
FIG. 5 is a flowchart showing the calculation processing of the EGR valve opening.
[0042]
In step S41, it is determined whether or not it is in the EGR operation range. If it is in the EGR operation range, the EGR valve opening θ is calculated (step S42). Specifically, in the present embodiment, the learning value updated in step S34 is used. On the other hand, if it is not the EGR operation range, the EGR valve opening θ is set to 0 (step S43).
[0043]
FIG. 6 is a flowchart showing the calculation of the fuel injection amount Ti.
[0044]
In step S51, the intake pressure and the rotational speed are read, and in step S52, the basic injection amount Tp is calculated based on these.
[0045]
In step S53, the air-fuel ratio feedback correction coefficient α is calculated based on the outputs from the front oxygen sensor 45 and the rear oxygen sensor 46.
[0046]
In steps S54 and S58, similarly to steps S11 and S13 in FIG. 2, it is determined whether the vehicle is in the EGR operation state and whether the traveling distance exceeds a predetermined distance. In steps S55, S59, and S61, the respective air-fuel ratio learning values KBLRC0, KBLRCe, and KBLRCe 'are read in accordance with the determination results. In steps S56, S60, and S62, the read air-fuel ratio learning values are used as the air-fuel ratio learning values KBLRC. Put in. In step S57, for example, the fuel injection amount Ti at the time of sequential injection is calculated by the following equation.
[0047]
Ti = Tp × (α + KBLRC−1) × 2 + Ts
Here, Ts is an invalid injection amount.
[0048]
In the above, the description has been given by exemplifying a certain operating state, that is, when the rotational speed and the load of the internal combustion engine are within a predetermined range. Even when the operating state changes, by performing the same processing for each operating state, an effect can be obtained over the entire EGR operation region.
[0049]
When the EGR gas flow rate decreases, fresh air increases and the air-fuel ratio shifts to a leaner side than the stoichiometric air-fuel ratio. Then, the air-fuel ratio feedback correction coefficient α shifts in a direction to increase to return to the stoichiometric air-fuel ratio, and the air-fuel ratio learning value updated based on this α becomes a value larger than 1.0. Therefore, in the present invention, the first air-fuel ratio learning value KBLRCe when the EGR device is in operation and the running distance is such that there is no possibility of clogging in the EGR device. Attention is paid to the second air-fuel ratio learning value KBLRCe 'at the time of the traveling distance having the characteristic, and the differences (ΔKBRRC1, ΔKBLRC21) from the air-fuel ratio learning value KBLRC0 when the EGR is not operated are obtained (steps S15, S17), respectively. The difference is compared to determine whether or not EGR clogging has occurred (step S24). When the EGR clogging has occurred, the EGR valve is opened (step S34). Thus, according to the present embodiment, it is possible to determine whether the EGR valve is clogged without providing an air flow meter.
[0050]
Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is apparent that they are equivalent to the present invention.
[0051]
For example, in the above embodiment, it is determined whether or not EGR clogging has occurred based on the difference between the air-fuel ratio learning values (ΔKBRRC1 and ΔKBRRC2) (step S24). The difference between the air-fuel ratio learning value (KBLRCe ') when it is necessary and the air-fuel ratio learning value (KBLRCe) when the EGR operation is performed and the EGR clogging determination is not necessary is determined as to whether or not EGR clogging has occurred, that is, (| KBRRCe). '−KBLRCe |> ε).
[0052]
In the above embodiment, the air-fuel ratio feedback control is performed based on the output of the oxygen sensor. However, the air-fuel ratio feedback control may be performed based on the output of a so-called wide-range air-fuel ratio sensor.
[0053]
Further, in the embodiment, the case has been described where it is determined whether or not the EGR device is clogged based on the air-fuel ratio learning value. However, the average value of the air-fuel ratio feedback correction coefficient α (for example, the half-cycle It is also possible to determine whether or not clogging has occurred in the EGR device based on the average value per unit time or the average value per predetermined period during the air-fuel ratio feedback control.
[0054]
Furthermore, in the embodiment, the case where the driving history is the traveling distance of the vehicle has been described, but it is needless to say that the driving history is not limited to this.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an EGR control device for an internal combustion engine according to the present invention.
FIG. 2 is a flowchart showing an update control of an air-fuel ratio learning value of the EGR control device for an internal combustion engine according to the present invention.
FIG. 3 is a flowchart illustrating a setting process of an EGR blockage flag.
FIG. 4 is a flowchart showing an update process of an EGR valve opening learning value.
FIG. 5 is a flowchart showing an EGR valve opening calculation process.
FIG. 6 is a flowchart showing a calculation of a fuel injection amount Ti.
[Explanation of symbols]
Reference Signs List 10 internal combustion engine 11 combustion chamber 15 vehicle speed sensor 22 throttle valve 23 intake pipe 31 fuel injection valve 41 exhaust manifold 42 three-way catalyst 45 front oxygen sensor 46 rear oxygen sensor 51 EGR passage 53 EGR valve 70 control unit

Claims

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback control means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio, and correcting the basic fuel amount with the air-fuel ratio feedback correction amount;
The air-fuel ratio feedback correction amount obtained when the EGR device is operating and the operation history is such that the EGR device is not likely to be clogged, and the operation is performed when the EGR device is operating and the EGR device is possibly clogged. Clogging determination means for determining whether the EGR device is clogged based on the air-fuel ratio feedback correction amount obtained at the time of history,
A diagnostic device for an EGR device, comprising:

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback correction amount calculation means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio;
First air-fuel ratio learning value updating means for updating the first air-fuel ratio learning value based on the air-fuel ratio feedback correction amount at the time of operation of the EGR device and at the time of an operation history in which there is no possibility of clogging of the EGR device;
Second air-fuel ratio learning value updating means for updating the second air-fuel ratio learning value based on the air-fuel ratio feedback correction amount when the EGR device is operating and when the EGR device is in an operation history with a possibility of clogging;
Clogging determination means for determining whether or not the EGR device is clogged based on the first air-fuel ratio learning value and the second air-fuel ratio learning value;
A diagnostic device for an EGR device, comprising:

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback control means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio, and correcting the basic fuel amount with the air-fuel ratio feedback correction amount;
The air-fuel ratio feedback correction amount obtained when the EGR device is operating and the operation history is such that the EGR device is not likely to be clogged, and the operation is performed when the EGR device is operating and the EGR device is possibly clogged. Clogging judging means for judging whether or not the EGR device is clogged based on the air-fuel ratio feedback correction amount obtained at the time of history and the air-fuel ratio feedback correction amount obtained when the EGR device is not operating; ,
A diagnostic device for an EGR device, comprising:

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback correction amount calculation means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio;
First air-fuel ratio learning value updating means for updating the first air-fuel ratio learning value based on the air-fuel ratio feedback correction amount at the time of operation of the EGR device and at the time of an operation history in which there is no possibility of clogging of the EGR device;
Second air-fuel ratio learning value updating means for updating the second air-fuel ratio learning value based on the air-fuel ratio feedback correction amount when the EGR device is operating and when the EGR device is in an operation history with a possibility of clogging;
Third air-fuel ratio learning value updating means for updating the third air-fuel ratio learning value based on the air-fuel ratio feedback correction amount when the EGR device is not operating;
Clogging determining means for determining whether or not the EGR device is clogged based on the first air-fuel ratio learning value, the second air-fuel ratio learning value, and the third air-fuel ratio learning value;
A diagnostic device for an EGR device, comprising:

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback control means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio, and correcting the basic fuel amount with the air-fuel ratio feedback correction amount;
The air-fuel ratio feedback correction amount obtained when the EGR device is operating and the operation history is such that the EGR device is not likely to be clogged, and the operation is performed when the EGR device is operating and the EGR device is possibly clogged. Clogging determination means for determining whether the EGR device is clogged based on the air-fuel ratio feedback correction amount obtained at the time of history,
EGR flow correction means for correcting the EGR flow by the EGR device to a side increasing the EGR flow when the EGR device is clogged based on the determination result;
A control device for an EGR device, comprising:

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback correction amount calculation means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio;
First air-fuel ratio learning value updating means for updating the first air-fuel ratio learning value based on the air-fuel ratio feedback correction amount at the time of operation of the EGR device and at the time of an operation history in which there is no possibility of clogging of the EGR device;
Second air-fuel ratio learning value updating means for updating the second air-fuel ratio learning value based on the air-fuel ratio feedback correction amount when the EGR device is operating and when the EGR device is in an operation history with a possibility of clogging;
Clogging determination means for determining whether or not the EGR device is clogged based on the first air-fuel ratio learning value and the second air-fuel ratio learning value;
EGR flow correction means for correcting the EGR flow by the EGR device to a side increasing the EGR flow when the EGR device is clogged based on the determination result;
A control device for an EGR device, comprising:

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback control means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio, and correcting the basic fuel amount with the air-fuel ratio feedback correction amount;
The air-fuel ratio feedback correction amount obtained when the EGR device is operating and the operation history is such that the EGR device is not likely to be clogged, and the operation is performed when the EGR device is operating and the EGR device is possibly clogged. Clogging judging means for judging whether or not the EGR device is clogged based on the air-fuel ratio feedback correction amount obtained at the time of history and the air-fuel ratio feedback correction amount obtained when the EGR device is not operating; ,
EGR flow correction means for correcting the EGR flow by the EGR device to a side increasing the EGR flow when the EGR device is clogged based on the determination result;
A control device for an EGR device, comprising:

In an EGR device that recirculates part of exhaust gas to intake air,
Basic fuel amount calculating means for calculating the basic fuel amount by estimating the intake air amount based on the intake pipe pressure and the engine rotation speed;
Air-fuel ratio feedback correction amount calculation means for calculating an air-fuel ratio feedback correction amount so that the air-fuel ratio of the exhaust becomes the target air-fuel ratio;
First air-fuel ratio learning value updating means for updating the first air-fuel ratio learning value based on the air-fuel ratio feedback correction amount at the time of operation of the EGR device and at the time of an operation history in which there is no possibility of clogging of the EGR device;
Second air-fuel ratio learning value updating means for updating the second air-fuel ratio learning value based on the air-fuel ratio feedback correction amount when the EGR device is operating and when the EGR device is in an operation history with a possibility of clogging;
Third air-fuel ratio learning value updating means for updating the third air-fuel ratio learning value based on the air-fuel ratio feedback correction amount when the EGR device is not operating;
Clogging determining means for determining whether or not the EGR device is clogged based on the first air-fuel ratio learning value, the second air-fuel ratio learning value, and the third air-fuel ratio learning value;
EGR flow correction means for correcting the EGR flow by the EGR device to a side increasing the EGR flow when the EGR device is clogged based on the determination result;
A control device for an EGR device, comprising: