JP3956458B2

JP3956458B2 - Fuel injection control device for internal combustion engine

Info

Publication number: JP3956458B2
Application number: JP00621298A
Authority: JP
Inventors: 啓梅原; 達也藤田; 兼仁中村
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 1998-01-16
Filing date: 1998-01-16
Publication date: 2007-08-08
Anticipated expiration: 2018-01-16
Also published as: JPH11200926A

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関の気筒別の排気酸素濃度を検出して気筒別の燃料噴射量を補正する機能を備えた内燃機関の燃料噴射制御装置に関するものである。
【０００２】
【従来の技術】
この種の燃料噴射制御装置においては、各気筒毎に酸素濃度センサを１つずつ設置すると、コスト高になるため、特開昭５９−１０１５６２号公報に示すように、内燃機関の集合排気管に１つの酸素濃度センサを設け、内燃機関の基準タイミングから各気筒の排気ガスが酸素濃度センサに到達するまでの遅れ時間を運転状態に応じて予め求めておき、それに基づいて１つの酸素濃度センサの出力から気筒別の排気酸素濃度を検出して、それを目標値にフィードバック制御することが提案されている。
【０００３】
しかし、内燃機関の集合排気管を通過する排気ガスは、排気管形状や気筒毎の排気バルブ開放タイミングのオーバラップ等による混ざりが生じるため、上記公報のように、気筒別の排気酸素濃度を１つの酸素濃度センサで検出しようとすると、酸素濃度センサの出力は、常に全気筒の排気酸素濃度を混合した出力となり、１つの気筒の排気酸素濃度を単独で検出することは不可能である。そのため、気筒別の排気酸素濃度を精度良く検出することができず、各気筒の排気酸素濃度を目標値に精度良く制御することが困難である。
【０００４】
この問題を解決するために、特開平５−１８００４０号公報では、酸素濃度センサの出力を各気筒の燃焼履歴に所定の重み係数を乗じた加重平均値からなるものと見なして排気系の挙動を模擬するモデルを構築し、各気筒の排気酸素濃度をオブザーバによって観察し、このオブザーバの出力に基づいて気筒別の排気酸素濃度を推定することで、気筒別の排気酸素濃度を目標値にフィードバック制御する技術が提案されている。
【０００５】
【発明が解決しようとする課題】
上記特開平５−１８００４０号公報では、各気筒の排気ガスが酸素濃度センサで検出されるタイミングは、エンジン回転数と負荷に応じて決定されている。しかし、酸素濃度センサの個体差や経時劣化、過給装置の排気タービンの抵抗等の影響により、酸素濃度センサで検出されるタイミングが変化するため、エンジン回転数と負荷に応じて検出タイミングを決定すると、気筒別の排気酸素濃度を精度良く分離、抽出することが困難である。
【０００６】
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、集合排気管に設置した１つの酸素濃度センサの出力から気筒別の排気酸素濃度を精度良く推定することができ、気筒別の燃料噴射制御を精度良く行うことができる内燃機関の燃料噴射制御装置を提供することにある。
【０００７】
【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の内燃機関の燃料噴射制御装置では、集合排気管に設置した酸素濃度センサの出力を、各気筒の排気酸素濃度に所定の重み係数（各気筒の流量比率に相当）を乗じて加重平均した排気酸素濃度と見なし、この酸素濃度センサの出力から前記重み係数を考慮して気筒別の排気酸素濃度を気筒別排気酸素濃度推定手段により推定する。この際、重み係数を排気酸素濃度検出時のクランク角に応じて重み係数決定手段により決定するが、酸素濃度センサの出力から重み係数が適当でないと判断した場合（つまり気筒別の燃料噴射量のばらつきが大きいと判断した場合）には、重み係数とクランク角との対応関係を補正制御手段により補正する。これにより、各気筒の排気酸素濃度が酸素濃度センサで検出されるタイミングが変化しても、それに応じて重み係数（各気筒の流量比率）とクランク角との対応関係が補正されるため、集合排気管に設置した１つの酸素濃度センサの出力から気筒別の排気酸素濃度を精度良く推定することができ、気筒別の燃料噴射制御を精度良く行うことができる。
【０００８】
ここで、重み係数とクランク角との対応関係を補正する場合には、請求項１のように、特定気筒の燃料噴射量を増量又は減量し、その増量又は減量によって生じる排気酸素濃度の変化が酸素濃度センサで検出されるタイミングをクランク角で検出し、その検出結果に基づいて重み係数とクランク角との対応関係を補正するようにすれば良い。この場合、特定気筒の燃料噴射量を増量又は減量することで、特定気筒の排気酸素濃度を検出するまでの遅れ時間を精度良く検出することができ、この検出結果から各気筒の流量比率を精度良く反映させた重み係数を求めることができる。
【０００９】
この場合、請求項２のように、特定気筒の燃料噴射量を増量又は減量する際に１サイクル当たりの合計燃料噴射量が変化しないように、特定気筒以外の気筒の燃料噴射量を補正するようにしても良い。このようにすれば、特定気筒の燃料噴射量を増減させた時の内燃機関の出力変動を抑制することができ、ドライバビリティを良好に維持できる。
【００１０】
或は、請求項３のように、特定気筒の燃料噴射量を増量する場合に、当該特定気筒の燃料噴射時期を遅角するようにしても良い。このようにすれば、特定気筒の燃料噴射量の増量による出力増加を燃料噴射時期の遅角により抑えることができ、気筒間にトルク差が生じることを防止できて、気筒間のトルク変動による回転変動を抑制できる。これにより、各気筒の排気バルブ開放時間に差が生じることを防止できて、各気筒の流量比率の変化を抑制でき、気筒別の排気酸素濃度の推定精度を向上できる。
【００１１】
また、請求項４のように、特定気筒の燃料噴射量を増量する場合に、その増量分の燃料を当該特定気筒の膨張行程で後噴射することで、当該特定気筒の燃料噴射量を増量するようにしても良い。このように、増量分の燃料を特定気筒の膨張行程で後噴射して燃焼させれば、特定気筒のメイン噴射量を増加させる場合と比較して、特定気筒のトルク上昇を少なくすることができ、気筒間のトルク差を低減することができる。
【００１２】
また、排気ガス還流装置を備えた内燃機関では、各気筒毎の排気ガス還流率のばらつきによって各気筒の流量比率が変動するため、請求項５のように、特定気筒の燃料噴射量を増量又は減量する際に、排気ガス還流装置による排気ガス還流を停止することが好ましい。このようにすれば、排気ガス還流の影響を受けずに気筒別の排気酸素濃度を精度良く推定することができる。
【００１３】
また、ウェイストゲートバルブ付きの過給装置を備えた内燃機関に本発明を適用する場合には、請求項６のように、特定気筒の燃料噴射量を増量又は減量する際に、ウェイストゲートバルブを開放することが好ましい。このように、ウェイストゲートバルブを開放すると、それまで排気タービンで撹拌されていた排気の多くがウェイストゲートに流れるため、排気タービンによる気筒間の排気ガスの撹拌を少なくすることができ、気筒別の排気酸素濃度を精度良く推定することができる。
【００１４】
また、可変ジオメトリターボを備えた内燃機関に本発明を適用する場合には、請求項７のように、特定気筒の燃料噴射量を増量又は減量する際に、排気抵抗を低減するように可変ジオメトリターボのガイド板を開放することが好ましい。このようにすれば、可変ジオメトリターボ内での気筒間の排気ガスの撹拌を少なくすることができる。
【００１５】
【発明の実施の形態】
［実施形態（１）］
以下、本発明をディーゼルエンジンに適用した実施形態（１）を図１乃至図３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。内燃機関であるディーゼルエンジン１１の吸気管１２には、ターボ過給機１３（過給装置）の吸気タービン１４が設置されている。このターボ過給機１３の吸気タービン１４と連結された排気タービン１５がディーゼルエンジン１１の集合排気管１６内に設置され、この排気タービン１５を排気ガスの運動エネルギによって回転駆動することで、吸気タービン１４を回転させて過給圧を発生させる。集合排気管１６には、排気タービン１５の上流側と下流側をバイパスさせるウェイストゲート１７が設けられ、このウェイストゲート１７を通過する排気の流量が電磁式のウェイストゲートバルブ１８によって制御される。集合排気管１６のうちのウェイストゲート１７よりも下流側には、排気酸素濃度を検出する限界電流式の酸素濃度センサ１９が設置されている。
【００１６】
排気タービン１５の上流側の集合排気管１６と吸気タービン１４の下流側の吸気管１２との間にはＥＧＲ配管２０が接続され、このＥＧＲ配管２０の途中に電子制御式のＥＧＲ弁２１が設置され、このＥＧＲ弁２１の弁開度を調整することで、ＥＧＲ配管２０を通過するＥＧＲ流量が制御される。これらＥＧＲ配管２０とＥＧＲ弁２１とから排気ガス還流装置（ＥＧＲ装置）２２が構成されている。ディーゼルエンジン１１の各気筒のシリンダヘッドにはそれぞれ燃料噴射弁２３が取り付けられている。
【００１７】
ターボ過給機１３によって過給される空気は吸気マニホールド２４を介してディーゼルエンジン１１の各気筒に吸入される。各気筒内で圧縮された高温空気中に燃料噴射弁２３から燃料を噴射して自己着火させ、各気筒の排気ガスが排気マニホールド２５を通して１本の集合排気管１６に合流し、大気中に排出される。
【００１８】
ディーゼルエンジン１１の運転状態は、クランク角センサ２６、アクセルセンサ２７、車速センサ２８、酸素濃度センサ１９等によって検出され、これらの出力信号がエンジン制御用の制御回路２９に読み込まれる。この制御回路２９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）には、図２の気筒別噴射量補正プログラム等の各種のエンジン制御プログラムが記憶され、これらのプログラムを実行することで、燃料噴射制御、ＥＧＲ制御及びウェイストゲートバルブ１８の制御を実行する。図２の気筒別噴射量補正プログラム以外のプログラムは、従来と同じであるので、以下、図２の気筒別噴射量補正プログラムのみについて説明する。
【００１９】
図２の気筒別噴射量補正プログラムは、制御回路２９にて所定クランク角毎又は所定時間毎に次のように実行される。まず、ステップ１０１で、アクセルセンサ２７とクランク角センサ２６と車速センサ２８の出力信号を読み込み、次のステップ１０２で、これらの信号から検出されるアクセル開度とエンジン回転数と車速とに基づいて現在の運転状態が定常運転であるか否かを判定する。定常運転でなければ、気筒別の排気酸素濃度の検出が困難であるので、以降の処理を行うことなく、本プログラムを終了する。
【００２０】
一方、定常運転時には、ステップ１０２からステップ１０３に進み、気筒別燃料噴射量制御が必要か否かを判定する。例えば、今までに一度も気筒別燃料噴射量制御が実行されていない時や、前回の気筒別燃料噴射量制御が実行されてから所定の積算走行距離に達している時、或は、定常運転時の酸素濃度センサ１９の出力変化（振幅）が大きい時などは気筒別燃料噴射量制御が必要と判定される。気筒別燃料噴射量制御が必要でないと判定された場合には、以降の処理を行うことなく、本プログラムを終了する。
【００２１】
上記ステップ１０３で、気筒別燃料噴射量制御が必要と判定された場合には、ステップ１０４に進み、特定気筒、例えば気筒＃１の燃料噴射量を所定量△Ｑだけ増量補正し、他の気筒＃２〜＃４の燃料噴射量を△Ｑの３分の１ずつ減量補正して、１サイクル当たりの合計燃料噴射量が変化しないようにする。これにより、気筒＃１のみ排気酸素濃度を低下させると共に、エンジン出力を補正前後で一定に保持する。
【００２２】
この後、ステップ１０５で、ＥＧＲ弁２１を全閉して、排気ガス還流を停止（ＥＧＲカット）すると共に、ウェイストゲートバルブ１８を全開して、排気タービン１５へ向かう排気ガスをウェイストゲート１７へバイパスさせる。この後、ステップ１０６で、酸素濃度センサ１９の出力信号を読み込み、増量補正した気筒＃１の排気酸素濃度が最も良く検出されるタイミングＴa （クランク角）を検出する。つまり、図３に示すように、気筒＃１の燃料噴射量を増量補正すると、気筒＃１の燃焼の際に消費される酸素量が増加して気筒＃１の排気酸素濃度が低下するため、増量補正後に、酸素濃度センサ１９の出力（排気酸素濃度の検出値）が最も低下したタイミングＴa を検出することで、気筒＃１の排気ガスが酸素濃度センサ１９に到達したタイミングＴa を検出する。
【００２３】
この後、ステップ１０７で、燃料噴射量補正を終了した後、ステップ１０８で再び酸素濃度センサ１９の出力信号を読み込む。集合排気管１６を流れる排気ガスは、気筒間の排気バルブのオーバーラップ等の影響により、完全には層状にならず、各気筒の排気ガスが混ざり合った状態で流れるため、酸素濃度センサ１９の出力（排気酸素濃度の検出値）も各気筒の排気酸素濃度が混ざり合った値となる。
【００２４】
そこで、次のステップ１０９で、以下のようにして酸素濃度センサ１９の出力から気筒別の排気酸素濃度を算出する。酸素濃度センサ１９の出力は、各気筒の排気酸素濃度に各気筒の重み係数を乗じて積算した排気酸素濃度と見なすことができる。各気筒の重み係数は、排気酸素濃度検出時に酸素濃度センサ１９部分を通過する各気筒の排気ガスの流量比率である。
【００２５】
（酸素濃度センサ１９の出力）＝Σ（気筒別排気酸素濃度）×（重み係数）
例えば、４気筒エンジンの場合、具体的には、以下の行列式で表すことができる。
【００２６】
【数１】

【００２７】
この行列式において、重み係数Ａn 〜Ｄn は、ステップ１０６で検出したタイミングＴa に応じて次のように補正される。今回検出したタイミングＴa(i)を前回検出したタイミングＴa(i-1)と比較し、Ｔa(i)がＴa(i-1)より遅れている場合には、その遅れ角度ΔＴa を次式により算出する。
ΔＴa ＝Ｔa(i)−Ｔa(i-1)
【００２８】
この後、重み係数Ａn 〜Ｄn とクランク角ｎとの対応関係を次式により補正する。
ｎ（今回値）＝ｎ（前回値）＋ΔＴa
これにより、上記行列式の重み係数Ａn 〜Ｄn を更新し、且つ上記行列式に各クランク角での酸素濃度センサ１９の出力を代入して気筒別の排気酸素濃度を算出する。以上のような処理を行うステップ１０９が、特許請求の範囲でいう気筒別排気酸素濃度推定手段、重み係数決定手段及び補正制御手段としての役割を果たす。
【００２９】
気筒別排気酸素濃度の算出後、ステップ１１０に進み、気筒別排気酸素濃度の算出値を基に、全気筒の排気酸素濃度が同一となるように、気筒別の燃料噴射量の補正量を算出し、この補正量で気筒別の燃料噴射量を補正して、各気筒の燃料噴射を実施する。この後、ステップ１１１で、酸素濃度センサ１９の出力の振幅が所定幅以内であるか否かを判定する。つまり、上記ステップ１１０で行った気筒別の燃料噴射量の補正により気筒別の排気酸素濃度のばらつきが小さくなれば酸素濃度センサ１９の出力の振幅が小さくなるが、気筒別の排気酸素濃度のばらつきが大きければ、酸素濃度センサ１９の出力の振幅が大きくなる。この関係から、酸素濃度センサ１９の出力の振幅が所定幅を越える場合には、気筒別の排気酸素濃度のばらつきが許容値を越えると判断して、ステップ１０１に戻り、上述した処理を繰り返す。つまり、気筒別の排気酸素濃度を算出して、全気筒の排気酸素濃度が同一となるように気筒別の燃料噴射量を補正する処理を繰り返す。
【００３０】
このような気筒別の燃料噴射量の補正により、酸素濃度センサ１９の出力の振幅が所定幅以内になれば、気筒別の排気酸素濃度のばらつきが許容値以内と判断して、ステップ１１２に進み、検出タイミングＴa を前記ステップ１０６で検出したタイミングＴa に更新して本プログラムを終了する。
【００３１】
以上説明した本実施形態（１）によれば、特定気筒の燃料噴射量を増量補正し、その増量補正によって生じる排気酸素濃度の変化が酸素濃度センサ１９で検出されるタイミングＴa をクランク角で検出し、その結果に基づいて重み係数（各気筒の流量比率）とクランク角との対応関係を補正するようにしたので、各気筒の排気酸素濃度が酸素濃度センサ１９で検出されるタイミングが変化しても、それに応じて重み係数とクランク角との対応関係を精度良く補正することができ、集合排気管１６に設置した１つの酸素濃度センサ１９の出力から気筒別の排気酸素濃度を精度良く推定することができ、気筒別の燃料噴射制御を精度良く行うことができる。
【００３２】
更に、本実施形態（１）では、特定気筒の燃料噴射量を増量補正する際に、１サイクル当たりの合計燃料噴射量が変化しないように、特定気筒以外の気筒の燃料噴射量を減量補正するようにしたので、特定気筒の燃料噴射量を増量補正した時のエンジン出力の変動を抑制することができ、ドライバビリティを良好に維持できる。
【００３３】
しかも、特定気筒の燃料噴射量を増量補正する際に、ＥＧＲカットして、各気筒毎のＥＧＲ率のばらつきによる各気筒の流量比率の変動を防止すると共に、ウェイストゲートバルブ１８を全開して過給を停止し、排気タービン１５による気筒間の排気ガスの攪拌を少なくするようにしたので、ＥＧＲやターボ過給機１３の影響を受けずに、気筒別の排気酸素濃度を精度良く推定することができる。
【００３４】
ところで、エンジン１１の運転状態によっては、ＥＧＲカットや過給停止（ウェイストゲートバルブ１８の全開）によってエンジン出力が変化する可能性がある。例えば、エンジン１１が低回転で過給が行われていない状態の時は、ＥＧＲカットによるエンジン出力の上昇が考えられる。また、高負荷時には、もともとＥＧＲ率が低いため、過給停止によるエンジン出力低下が考えられる。このような場合、予めエンジン出力の変化を予測して、それを補正する燃料噴射量のマップを記憶しておき、ＥＧＲカットや過給停止を行う時に、このマップを用いて全気筒の燃料噴射量を同一量補正し、エンジン出力の変動を抑制するようにしても良い。
【００３５】
尚、本実施形態（１）では、特定気筒の燃料噴射量を増量補正したが、減量補正するようにしても良い。特定気筒の燃料噴射量を減量補正する場合には、１サイクル当たりの合計燃料噴射量が変化しないように、他の気筒の燃料噴射量を増量補正すると共に、ステップ１０６において、酸素濃度センサ１９の出力が最も上昇するタイミングＴa を検出するようにすれば良い。
【００３６】
［実施形態（２）］
上記実施形態（１）では、特定気筒＃１の燃料噴射量を増量補正する際に、１サイクル当たりの合計燃料噴射量が変化しないように、特定気筒＃１以外の気筒＃２〜＃４の燃料噴射量を減量補正することで、エンジン出力の変動を抑制するようにしたが、図４及び図５に示す本発明の実施形態（２）では、ステップ１０４ａで、特定気筒＃１の燃料噴射量を増量補正する際に、当該特定気筒＃１の燃料噴射時期を遅角することで、エンジン出力の変動を抑制するようにしている。その他の処理は、前記実施形態（１）で説明した図２の処理と同じであるので、説明を省略する。
【００３７】
このように、特定気筒＃１の燃料噴射量を増量補正する際に、特定気筒＃１の燃料噴射時期を遅角すれば、エンジン出力の変動を抑制できると共に、気筒間のトルク変動による回転変動も抑制でき、各気筒の排気バルブ開放時間に差が生じることを防止できて、各気筒の流量比率の変化を抑制でき、気筒別の排気酸素濃度の推定精度を向上できる。また、回転変動による振動も低減できる。
【００３８】
［実施形態（３）］
図６及び図７に示す本発明の実施形態（３）では、特定気筒＃１の燃料噴射量を増量補正する際に、その増量分の燃料を当該特定気筒＃１の膨張行程で後噴射することで、当該特定気筒＃１の燃料噴射量を増量する（ステップ１０４ｂ）。この場合、特定気筒＃１のメイン噴射量は、他の気筒＃２〜＃４のメイン噴射量と同一である。その他の処理は、前記実施形態（１）で説明した図２の処理と同じであるので、説明を省略する。
【００３９】
このように、増量分の燃料を特定気筒＃１の膨張行程で後噴射して燃焼させれば、特定気筒＃１のメイン噴射量を増加させる場合と比較して、特定気筒＃１のトルク上昇を少なくすることができ、気筒間のトルク差を低減することができて前記実施形態（２）と同じ効果を得ることができる。
【００４０】
［その他の実施形態］
上記各実施形態（１）〜（３）では、いずれもウェイストゲートバルブ１８付きのターボ過給機１３を設けたが、これに代えて、図８に示す可変ジオメトリターボ３０を用いるようにしても良い。この場合には、特定気筒の燃料噴射量を増量（又は減量）する際に、排気抵抗を低減するように可変ジオメトリターボ３０のガイド板３１を開放すれば良い。その他の制御は、上記各実施形態（１）〜（３）のいずれかを採用すれば良い。
【００４１】
可変ジオメトリターボ３０のガイド板３１を開放すれば、可変ジオメトリターボ３０内での排気タービン３２による気筒間の排気ガスの攪拌を少なくすることができ、ウェイストゲートバルブ１８を全開した時とほぼ同様の効果を得ることができる。
【００４２】
また、上記各実施形態（１）〜（３）では、特定気筒＃１の燃料噴射量を増量（又は減量）によって生じる排気酸素濃度の変化が酸素濃度センサ１９で検出されるタイミングＴa を検出し、その検出結果に基づいて重み係数とクランク角との対応関係を補正するようにしたが、エンジン運転中に常に酸素濃度センサ１９の出力をモニタして、重み係数が適当でないと判断した場合（つまり気筒別の燃料噴射量のばらつきが大きいと判断した場合）に、重み係数とクランク角との対応関係を補正するようにしても良い。以下、この補正方法を具体的に説明する。
【００４３】
酸素濃度センサ１９の出力は、排気酸素濃度の他に排気圧力等の影響も受けるため、定常運転で各気筒の排気酸素濃度が一定の場合でも、常に酸素濃度センサ１９の出力が変化する。そこで、予め、定常運転で各気筒の排気酸素濃度が一定の場合の酸素濃度センサ１９の出力の最大変化幅（最大振幅）を想定して、それを許容値として記憶しておき、定常運転時に、所定時間毎に酸素濃度センサ１９の出力の振幅が許容値以下であるか否かを判定し、許容値を越える場合には、気筒別の排気酸素濃度のばらつきが大きい、つまり、重み係数が適当でないと判断する。
【００４４】
この場合には、前記数１の行列式において、重み係数Ａn 〜Ｄn とクランク角ｎとの対応関係を次のようにして補正する。予め、ｎをパラメータとする重み係数Ａn 〜Ｄn のマップを制御回路２９のＲＯＭに記憶しておき、最初に、ｎ＝ｍとして各気筒の排気酸素濃度（実際は燃料噴射量）を補正する。その結果、酸素濃度センサ１９の出力の振幅があまり減少しなければ、ｎ＝ｍ＋Δｍとして、各気筒の排気酸素濃度を再度補正する。これにより、酸素濃度センサ１９の出力の振幅が許容値以下に減少すれば、ｎ＝ｍ＋Δｍとして更新する。反対に、酸素濃度センサ１９の出力の振幅が増加するようであれば、ｎ＝ｍ−Δｍとして、同様の補正を行う。このような補正処理を、酸素濃度センサ１９の出力の振幅が許容値以下に減少するまで繰り返す。
【００４５】
尚、図１のシステム構成例では、ターボ過給機１３とＥＧＲ装置２２の両方を設けているが、いずれか一方のみを持つシステムや、両方とも持たないシステムにも本発明を適用可能である。
【００４６】
その他、本発明は、ディーゼルエンジンに限定されず、ガソリンエンジンにも適用可能である。
【図面の簡単な説明】
【図１】実施形態（１）を示すエンジン制御システム全体の構成図
【図２】実施形態（１）の気筒別噴射量補正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）において特定気筒の燃料噴射量を増量補正した時のエンジン回転数と排気酸素濃度の変化具合を示すタイムチャート
【図４】実施形態（２）の気筒別噴射量補正プログラムの処理の流れを示すフローチャート
【図５】実施形態（２）において特定気筒の燃料噴射量を増量補正した時のエンジン回転数と排気酸素濃度の変化具合を示すタイムチャート
【図６】実施形態（３）の気筒別噴射量補正プログラムの処理の流れを示すフローチャート
【図７】実施形態（３）において特定気筒の燃料噴射量を増量補正した時のエンジン回転数と排気酸素濃度の変化具合を示すタイムチャート
【図８】他の実施形態で用いる可変ジオメトリターボの構成を概略的に示す図
【符号の説明】
１１…ディーゼルエンジン（内燃機関）、１２…吸気管、１３…ターボ過給機、１５…排気タービン、１６…集合排気管、１７…ウェイストゲート、１８…ウェイストゲートバルブ、１９…酸素濃度センサ、２０…ＥＧＲ配管、２１…ＥＧＲ弁、２２…ＥＧＲ装置、２３…燃料噴射弁、２９…制御回路（気筒別排気酸素濃度推定手段，重み係数決定手段，補正制御手段）、３０…可変ジオメトリターボ、３１…ガイド板、３２…排気タービン。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for an internal combustion engine having a function of detecting an exhaust oxygen concentration for each cylinder of the internal combustion engine and correcting a fuel injection amount for each cylinder.
[0002]
[Prior art]
In this type of fuel injection control device, if one oxygen concentration sensor is installed for each cylinder, the cost increases. Therefore, as shown in Japanese Patent Application Laid-Open No. 59-101562, a collective exhaust pipe of an internal combustion engine is provided. One oxygen concentration sensor is provided, and a delay time from the reference timing of the internal combustion engine until the exhaust gas of each cylinder reaches the oxygen concentration sensor is obtained in advance according to the operating state, and based on this, a delay time of one oxygen concentration sensor is obtained. It has been proposed to detect the exhaust oxygen concentration for each cylinder from the output and feedback control it to a target value.
[0003]
However, since the exhaust gas passing through the collective exhaust pipe of the internal combustion engine is mixed due to the exhaust pipe shape and the overlap of the exhaust valve opening timing of each cylinder, the exhaust oxygen concentration for each cylinder is set to 1 as described in the above publication. If an attempt is made to detect with one oxygen concentration sensor, the output of the oxygen concentration sensor is always an output obtained by mixing the exhaust oxygen concentrations of all the cylinders, and it is impossible to detect the exhaust oxygen concentration of one cylinder alone. Therefore, the exhaust oxygen concentration for each cylinder cannot be detected with high accuracy, and it is difficult to accurately control the exhaust oxygen concentration of each cylinder to the target value.
[0004]
In order to solve this problem, Japanese Patent Application Laid-Open No. 5-180040 considers the behavior of the exhaust system by regarding the output of the oxygen concentration sensor as a weighted average value obtained by multiplying the combustion history of each cylinder by a predetermined weighting factor. Build a model to simulate, observe the exhaust oxygen concentration of each cylinder with an observer, and estimate the exhaust oxygen concentration for each cylinder based on the output of this observer, feedback control the exhaust oxygen concentration for each cylinder to the target value Techniques to do this have been proposed.
[0005]
[Problems to be solved by the invention]
In JP-A-5-180040, the timing at which the exhaust gas of each cylinder is detected by the oxygen concentration sensor is determined according to the engine speed and the load. However, because the timing detected by the oxygen concentration sensor changes due to individual differences in oxygen concentration sensors, deterioration over time, resistance of the exhaust turbine of the turbocharger, etc., the detection timing is determined according to the engine speed and load. Then, it is difficult to accurately separate and extract the exhaust oxygen concentration for each cylinder.
[0006]
The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to accurately estimate the exhaust oxygen concentration for each cylinder from the output of one oxygen concentration sensor installed in the collecting exhaust pipe. Another object of the present invention is to provide a fuel injection control device for an internal combustion engine capable of accurately performing fuel injection control for each cylinder.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the fuel injection control device for an internal combustion engine according to claim 1 of the present invention, the output of the oxygen concentration sensor installed in the collective exhaust pipe is set to a predetermined weight coefficient (each The exhaust oxygen concentration is weighted and averaged by multiplying the flow rate ratio of the cylinder), and the exhaust oxygen concentration for each cylinder is estimated from the output of the oxygen concentration sensor by the cylinder-specific exhaust oxygen concentration estimating means in consideration of the weighting factor. . At this time, the weighting factor is determined by the weighting factor determining means according to the crank angle at the time of detecting the exhaust oxygen concentration, but if the weighting factor is determined to be inappropriate from the output of the oxygen concentration sensor (that is, the fuel injection amount of each cylinder) When it is determined that the variation is large), the correspondence between the weighting coefficient and the crank angle is corrected by the correction control means. As a result, even if the timing at which the exhaust oxygen concentration of each cylinder is detected by the oxygen concentration sensor changes, the correspondence between the weighting factor (flow rate ratio of each cylinder) and the crank angle is corrected accordingly. The exhaust oxygen concentration for each cylinder can be accurately estimated from the output of one oxygen concentration sensor installed in the exhaust pipe, and the fuel injection control for each cylinder can be accurately performed.
[0008]
Here, when correcting the correspondence between the weighting coefficient and the crank angle, as in claim 1 , the fuel injection amount of the specific cylinder is increased or decreased, and the change in the exhaust oxygen concentration caused by the increase or decrease is changed. The timing detected by the oxygen concentration sensor may be detected by the crank angle, and the correspondence between the weight coefficient and the crank angle may be corrected based on the detection result. In this case, by increasing or decreasing the fuel injection amount of the specific cylinder, the delay time until the exhaust oxygen concentration of the specific cylinder is detected can be accurately detected, and the flow rate ratio of each cylinder is accurately determined from the detection result. A weighting factor that is well reflected can be obtained.
[0009]
In this case, as in claim 2 , the fuel injection amounts of the cylinders other than the specific cylinder are corrected so that the total fuel injection amount per cycle does not change when the fuel injection amount of the specific cylinder is increased or decreased. Anyway. In this way, output fluctuation of the internal combustion engine when the fuel injection amount of the specific cylinder is increased or decreased can be suppressed, and drivability can be maintained well.
[0010]
Or when increasing the fuel injection amount of a specific cylinder like Claim 3 , you may make it retard the fuel injection timing of the said specific cylinder. In this way, the output increase due to the increase in the fuel injection amount of the specific cylinder can be suppressed by retarding the fuel injection timing, and a torque difference can be prevented from occurring between the cylinders. Variation can be suppressed. Thereby, it is possible to prevent a difference in the exhaust valve opening time of each cylinder, to suppress a change in the flow rate ratio of each cylinder, and to improve the estimation accuracy of the exhaust oxygen concentration for each cylinder.
[0011]
Further, when the fuel injection amount of the specific cylinder is increased as in claim 4 , the fuel injection amount of the specific cylinder is increased by post-injecting the increased amount of fuel in the expansion stroke of the specific cylinder. You may do it. In this way, if the increased amount of fuel is post-injected and combusted in the expansion stroke of the specific cylinder, the increase in torque of the specific cylinder can be reduced compared with the case where the main injection amount of the specific cylinder is increased. The torque difference between the cylinders can be reduced.
[0012]
Further, in an internal combustion engine provided with an exhaust gas recirculation system, the flow rate ratio of each cylinder by the variation of the exhaust gas recirculation ratio of each cylinder is changed, as claimed in claim 5, increasing the fuel injection amount of the specific cylinder or When the amount is reduced, it is preferable to stop the exhaust gas recirculation by the exhaust gas recirculation device. In this way, it is possible to accurately estimate the exhaust oxygen concentration for each cylinder without being affected by the exhaust gas recirculation.
[0013]
Further, when the present invention is applied to an internal combustion engine having a supercharging device with a waste gate valve, the waste gate valve is provided when the fuel injection amount of a specific cylinder is increased or decreased as in claim 6. Opening is preferred. In this way, when the waste gate valve is opened, most of the exhaust gas that has been agitated in the exhaust turbine until then flows to the waste gate, so that the exhaust gas agitation between the cylinders by the exhaust turbine can be reduced. The exhaust oxygen concentration can be accurately estimated.
[0014]
Further, when the present invention is applied to an internal combustion engine having a variable geometry turbo, as in claim 7, when the increase or decrease the fuel injection amount of the specific cylinder, variable geometry so as to reduce the exhaust resistance It is preferable to open the turbo guide plate. In this way, it is possible to reduce the agitation of the exhaust gas between the cylinders in the variable geometry turbo.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment (1)]
Hereinafter, an embodiment (1) in which the present invention is applied to a diesel engine will be described with reference to FIGS. 1 to 3. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An intake turbine 12 of a turbocharger 13 (supercharger) is installed in an intake pipe 12 of a diesel engine 11 that is an internal combustion engine. An exhaust turbine 15 connected to the intake turbine 14 of the turbocharger 13 is installed in a collective exhaust pipe 16 of the diesel engine 11, and the exhaust turbine 15 is rotationally driven by the kinetic energy of the exhaust gas, whereby the intake turbine 14 is rotated to generate a supercharging pressure. The collective exhaust pipe 16 is provided with a waste gate 17 that bypasses the upstream side and the downstream side of the exhaust turbine 15, and the flow rate of the exhaust gas that passes through the waste gate 17 is controlled by an electromagnetic waste gate valve 18. A limiting current type oxygen concentration sensor 19 for detecting the exhaust oxygen concentration is installed downstream of the waste gate 17 in the collective exhaust pipe 16.
[0016]
An EGR pipe 20 is connected between the collective exhaust pipe 16 upstream of the exhaust turbine 15 and the intake pipe 12 downstream of the intake turbine 14, and an electronically controlled EGR valve 21 is installed in the middle of the EGR pipe 20. The EGR flow rate passing through the EGR pipe 20 is controlled by adjusting the valve opening degree of the EGR valve 21. The EGR pipe 20 and the EGR valve 21 constitute an exhaust gas recirculation device (EGR device) 22. A fuel injection valve 23 is attached to each cylinder head of each cylinder of the diesel engine 11.
[0017]
Air supercharged by the turbocharger 13 is drawn into each cylinder of the diesel engine 11 via the intake manifold 24. The fuel is injected from the fuel injection valve 23 into the high-temperature air compressed in each cylinder and self-ignited, and the exhaust gas of each cylinder merges into one collective exhaust pipe 16 through the exhaust manifold 25 and is discharged into the atmosphere. Is done.
[0018]
The operating state of the diesel engine 11 is detected by a crank angle sensor 26, an accelerator sensor 27, a vehicle speed sensor 28, an oxygen concentration sensor 19, and the like, and these output signals are read into a control circuit 29 for engine control. The control circuit 29 is mainly composed of a microcomputer, and a built-in ROM (storage medium) stores various engine control programs such as the cylinder-by-cylinder injection amount correction program of FIG. 2 and executes these programs. Thus, the fuel injection control, the EGR control, and the control of the waste gate valve 18 are executed. Since the programs other than the cylinder-by-cylinder injection amount correction program of FIG. 2 are the same as the conventional ones, only the cylinder-by-cylinder injection amount correction program of FIG. 2 will be described below.
[0019]
The cylinder-by-cylinder injection amount correction program of FIG. 2 is executed by the control circuit 29 as follows every predetermined crank angle or every predetermined time. First, in step 101, output signals of the accelerator sensor 27, the crank angle sensor 26, and the vehicle speed sensor 28 are read, and in the next step 102, based on the accelerator opening, the engine speed, and the vehicle speed detected from these signals. It is determined whether or not the current operation state is a steady operation. If it is not a steady operation, it is difficult to detect the exhaust gas oxygen concentration for each cylinder. Therefore, this program is terminated without performing the subsequent processing.
[0020]
On the other hand, at the time of steady operation, the routine proceeds from step 102 to step 103, where it is determined whether or not the fuel injection amount control for each cylinder is necessary. For example, when cylinder-by-cylinder fuel injection amount control has never been executed, when a predetermined cumulative travel distance has been reached since the previous cylinder-by-cylinder fuel injection amount control was executed, or during steady operation For example, when the output change (amplitude) of the oxygen concentration sensor 19 is large, it is determined that the cylinder fuel injection amount control is necessary. If it is determined that the cylinder-by-cylinder fuel injection amount control is not required, the program is terminated without performing the subsequent processing.
[0021]
If it is determined in step 103 that the cylinder-by-cylinder fuel injection amount control is necessary, the process proceeds to step 104, where the fuel injection amount of a specific cylinder, for example, cylinder # 1, is increased and corrected by a predetermined amount ΔQ. The fuel injection amounts of # 2 to # 4 are corrected to decrease by 1/3 of ΔQ so that the total fuel injection amount per cycle does not change. As a result, the exhaust oxygen concentration is reduced only in cylinder # 1, and the engine output is held constant before and after correction.
[0022]
Thereafter, in step 105, the EGR valve 21 is fully closed to stop the exhaust gas recirculation (EGR cut), and the waste gate valve 18 is fully opened to bypass the exhaust gas toward the exhaust turbine 15 to the waste gate 17. Let Thereafter, in step 106, the output signal of the oxygen concentration sensor 19 is read, and the timing Ta (crank angle) at which the exhaust oxygen concentration of the cylinder # 1 corrected for increase is best detected is detected. That is, as shown in FIG. 3, when the fuel injection amount of the cylinder # 1 is increased and corrected, the amount of oxygen consumed during the combustion of the cylinder # 1 increases and the exhaust oxygen concentration of the cylinder # 1 decreases. After the increase correction, the timing Ta at which the output of the oxygen concentration sensor 19 (the detected value of the exhaust oxygen concentration) has decreased the most is detected, thereby detecting the timing Ta at which the exhaust gas from the cylinder # 1 has reached the oxygen concentration sensor 19.
[0023]
Then, after completing the fuel injection amount correction in step 107, the output signal of the oxygen concentration sensor 19 is read again in step 108. The exhaust gas flowing through the collective exhaust pipe 16 is not completely stratified due to the overlap of exhaust valves between the cylinders and the like, and flows in a mixed state of the exhaust gas of each cylinder. The output (exhaust oxygen concentration detection value) is also a value in which the exhaust oxygen concentration of each cylinder is mixed.
[0024]
Therefore, in the next step 109, the exhaust oxygen concentration for each cylinder is calculated from the output of the oxygen concentration sensor 19 as follows. The output of the oxygen concentration sensor 19 can be regarded as the exhaust oxygen concentration obtained by multiplying the exhaust oxygen concentration of each cylinder by the weighting coefficient of each cylinder and integrating it. The weighting factor of each cylinder is the flow rate ratio of the exhaust gas of each cylinder that passes through the oxygen concentration sensor 19 when the exhaust oxygen concentration is detected.
[0025]
(Output of oxygen concentration sensor 19) = Σ (exhaust oxygen concentration by cylinder) × (weighting factor)
For example, in the case of a four-cylinder engine, specifically, it can be expressed by the following determinant.
[0026]
[Expression 1]

[0027]
In this determinant, the weighting factors An to Dn are corrected as follows according to the timing Ta detected in step 106. The timing Ta (i) detected this time is compared with the timing Ta (i-1) detected last time. If Ta (i) is delayed from Ta (i-1), the delay angle ΔTa is calculated by the following equation. calculate.
ΔTa = Ta (i) −Ta (i−1)
[0028]
Thereafter, the correspondence between the weighting factors An to Dn and the crank angle n is corrected by the following equation.
n (current value) = n (previous value) + ΔTa
Thus, the weighting factors An to Dn of the determinant are updated, and the output of the oxygen concentration sensor 19 at each crank angle is substituted into the determinant to calculate the exhaust oxygen concentration for each cylinder. Step 109 for performing the processing as described above serves as the cylinder-specific exhaust oxygen concentration estimation means, weight coefficient determination means, and correction control means in the claims.
[0029]
After calculating the exhaust oxygen concentration for each cylinder, the process proceeds to step 110, and the correction amount for the fuel injection amount for each cylinder is calculated based on the calculated value for the exhaust oxygen concentration for each cylinder so that the exhaust oxygen concentration for all the cylinders is the same. Then, the fuel injection amount for each cylinder is corrected with this correction amount, and the fuel injection for each cylinder is performed. Thereafter, in step 111, it is determined whether or not the output amplitude of the oxygen concentration sensor 19 is within a predetermined range. That is, if the variation in the exhaust oxygen concentration for each cylinder is reduced by the correction of the fuel injection amount for each cylinder performed in step 110, the amplitude of the output of the oxygen concentration sensor 19 is reduced, but the variation in the exhaust oxygen concentration for each cylinder is reduced. Is larger, the amplitude of the output of the oxygen concentration sensor 19 becomes larger. From this relationship, if the amplitude of the output of the oxygen concentration sensor 19 exceeds the predetermined range, it is determined that the variation in the exhaust oxygen concentration for each cylinder exceeds the allowable value, the process returns to step 101, and the above-described processing is repeated. That is, the process of calculating the exhaust oxygen concentration for each cylinder and correcting the fuel injection amount for each cylinder so that the exhaust oxygen concentration for all the cylinders is the same is repeated.
[0030]
If the amplitude of the output of the oxygen concentration sensor 19 is within a predetermined range due to the correction of the fuel injection amount for each cylinder, it is determined that the variation in the exhaust oxygen concentration for each cylinder is within the allowable value, and the process proceeds to step 112. The detection timing Ta is updated to the timing Ta detected in step 106, and the program is terminated.
[0031]
According to the embodiment (1) described above, the fuel injection amount of the specific cylinder is corrected to increase, and the timing Ta at which the change in the exhaust oxygen concentration caused by the increase correction is detected by the oxygen concentration sensor 19 is detected by the crank angle. Since the correspondence between the weighting coefficient (flow rate ratio of each cylinder) and the crank angle is corrected based on the result, the timing at which the exhaust oxygen concentration of each cylinder is detected by the oxygen concentration sensor 19 changes. However, the correspondence relationship between the weighting coefficient and the crank angle can be corrected with high accuracy accordingly, and the exhaust gas oxygen concentration for each cylinder can be accurately estimated from the output of one oxygen concentration sensor 19 installed in the collective exhaust pipe 16. Therefore, the fuel injection control for each cylinder can be performed with high accuracy.
[0032]
Further, in the present embodiment (1), when the fuel injection amount of the specific cylinder is increased and corrected, the fuel injection amounts of the cylinders other than the specific cylinder are decreased and corrected so that the total fuel injection amount per cycle does not change. Since it did in this way, the fluctuation | variation of the engine output at the time of carrying out the increase correction | amendment of the fuel injection amount of a specific cylinder can be suppressed, and drivability can be maintained favorable.
[0033]
In addition, when the fuel injection amount of the specific cylinder is corrected to be increased, EGR cut is performed to prevent fluctuations in the flow rate ratio of each cylinder due to variations in the EGR rate for each cylinder, and the waste gate valve 18 is fully opened to avoid excessive flow. Since the supply is stopped and the exhaust gas agitation between the cylinders by the exhaust turbine 15 is reduced, the exhaust oxygen concentration for each cylinder can be accurately estimated without being affected by the EGR and the turbocharger 13. Can do.
[0034]
By the way, depending on the operating state of the engine 11, the engine output may change due to EGR cut or supercharging stop (full opening of the waste gate valve 18). For example, when the engine 11 is at a low speed and is not supercharged, an increase in engine output due to EGR cut can be considered. Moreover, since the EGR rate is originally low at the time of high load, it is conceivable that the engine output decreases due to the supercharging stop. In such a case, a change in the engine output is predicted in advance, and a map of the fuel injection amount for correcting the change is stored. When performing EGR cut or supercharging stop, this map is used to inject fuel in all cylinders. The amount may be corrected by the same amount to suppress fluctuations in engine output.
[0035]
In the present embodiment (1), the fuel injection amount of the specific cylinder is corrected to increase, but it may be corrected to decrease. When the fuel injection amount of the specific cylinder is corrected to decrease, the fuel injection amount of other cylinders is increased and corrected so that the total fuel injection amount per cycle does not change. It is only necessary to detect the timing Ta at which the output rises most.
[0036]
[Embodiment (2)]
In the above embodiment (1), when the fuel injection amount of the specific cylinder # 1 is corrected to be increased, the total fuel injection amount per cycle is not changed so that the cylinders # 2 to # 4 other than the specific cylinder # 1 do not change. In the embodiment (2) of the present invention shown in FIGS. 4 and 5, the fuel injection of the specific cylinder # 1 is performed in step 104a in the embodiment (2) of the present invention shown in FIGS. When the amount is corrected to be increased, the fuel injection timing of the specific cylinder # 1 is retarded to suppress fluctuations in the engine output. The other processing is the same as the processing of FIG. 2 described in the above embodiment (1), and thus description thereof is omitted.
[0037]
As described above, when the fuel injection amount of the specific cylinder # 1 is increased and corrected, if the fuel injection timing of the specific cylinder # 1 is retarded, fluctuations in engine output can be suppressed, and rotational fluctuations due to torque fluctuations between the cylinders. Therefore, it is possible to prevent a difference in the exhaust valve opening time of each cylinder, to suppress a change in the flow rate ratio of each cylinder, and to improve the estimation accuracy of the exhaust oxygen concentration for each cylinder. Further, vibration due to rotational fluctuation can be reduced.
[0038]
[Embodiment (3)]
In the embodiment (3) of the present invention shown in FIGS. 6 and 7, when the fuel injection amount of the specific cylinder # 1 is corrected to be increased, the increased amount of fuel is post-injected in the expansion stroke of the specific cylinder # 1. Thus, the fuel injection amount of the specific cylinder # 1 is increased (step 104b). In this case, the main injection amount of the specific cylinder # 1 is the same as the main injection amounts of the other cylinders # 2 to # 4. The other processing is the same as the processing of FIG. 2 described in the above embodiment (1), and thus description thereof is omitted.
[0039]
Thus, if the increased amount of fuel is post-injected and burned in the expansion stroke of the specific cylinder # 1, the torque of the specific cylinder # 1 is increased compared to the case where the main injection amount of the specific cylinder # 1 is increased. The torque difference between the cylinders can be reduced, and the same effect as that of the embodiment (2) can be obtained.
[0040]
[Other Embodiments]
In each of the above embodiments (1) to (3), the turbocharger 13 with the waste gate valve 18 is provided, but instead of this, the variable geometry turbo 30 shown in FIG. 8 may be used. good. In this case, when the fuel injection amount of the specific cylinder is increased (or decreased), the guide plate 31 of the variable geometry turbo 30 may be opened so as to reduce the exhaust resistance. Any other control may employ any one of the above embodiments (1) to (3).
[0041]
If the guide plate 31 of the variable geometry turbo 30 is opened, the agitation of the exhaust gas between the cylinders by the exhaust turbine 32 in the variable geometry turbo 30 can be reduced, which is almost the same as when the waste gate valve 18 is fully opened. An effect can be obtained.
[0042]
In each of the above embodiments (1) to (3), the timing Ta at which the change in the exhaust oxygen concentration caused by increasing (or decreasing) the fuel injection amount of the specific cylinder # 1 is detected by the oxygen concentration sensor 19 is detected. The correspondence relationship between the weighting coefficient and the crank angle is corrected based on the detection result, but the output of the oxygen concentration sensor 19 is constantly monitored during engine operation and it is determined that the weighting coefficient is not appropriate ( That is, when it is determined that the variation in the fuel injection amount for each cylinder is large), the correspondence between the weight coefficient and the crank angle may be corrected. Hereinafter, this correction method will be described in detail.
[0043]
Since the output of the oxygen concentration sensor 19 is influenced by the exhaust pressure and the like in addition to the exhaust oxygen concentration, the output of the oxygen concentration sensor 19 always changes even when the exhaust oxygen concentration of each cylinder is constant in steady operation. Therefore, assuming the maximum change width (maximum amplitude) of the output of the oxygen concentration sensor 19 when the exhaust oxygen concentration of each cylinder is constant in steady operation, it is stored as an allowable value in advance, and at the time of steady operation Then, it is determined whether or not the amplitude of the output of the oxygen concentration sensor 19 is equal to or less than an allowable value every predetermined time. If the amplitude exceeds the allowable value, the variation in exhaust oxygen concentration for each cylinder is large, that is, the weighting factor is Judge that it is not appropriate.
[0044]
In this case, in the determinant of Equation 1, the correspondence relationship between the weighting factors An to Dn and the crank angle n is corrected as follows. A map of weight coefficients An to Dn with n as a parameter is stored in the ROM of the control circuit 29 in advance, and first, the exhaust oxygen concentration (actually the fuel injection amount) of each cylinder is corrected with n = m. As a result, if the amplitude of the output of the oxygen concentration sensor 19 does not decrease so much, n = m + Δm is set and the exhaust oxygen concentration of each cylinder is corrected again. As a result, if the amplitude of the output of the oxygen concentration sensor 19 decreases below the allowable value, it is updated as n = m + Δm. On the other hand, if the amplitude of the output of the oxygen concentration sensor 19 increases, the same correction is performed with n = m−Δm. Such a correction process is repeated until the amplitude of the output of the oxygen concentration sensor 19 decreases below the allowable value.
[0045]
In the system configuration example of FIG. 1, both the turbocharger 13 and the EGR device 22 are provided. However, the present invention can be applied to a system having only one or both of them. .
[0046]
In addition, the present invention is not limited to a diesel engine, but can be applied to a gasoline engine.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an entire engine control system showing an embodiment (1). FIG. 2 is a flowchart showing a processing flow of a cylinder-by-cylinder injection amount correction program of the embodiment (1). FIG. 4 is a time chart showing how the engine speed and the exhaust oxygen concentration change when the fuel injection amount of a specific cylinder is corrected to increase in FIG. 4. FIG. 4 is a flowchart showing the processing flow of a cylinder-by-cylinder injection amount correction program according to the embodiment (2). FIG. 5 is a time chart showing how engine speed and exhaust oxygen concentration change when the fuel injection amount of a specific cylinder is corrected to increase in the embodiment (2). FIG. 6 is an injection amount for each cylinder in the embodiment (3). FIG. 7 is a flowchart showing the processing flow of the correction program. FIG. 7 shows how the engine speed and the exhaust oxygen concentration change when the fuel injection amount of a specific cylinder is increased and corrected in the embodiment (3). It illustrates a variable geometry turbo configuration used in to the time chart 8 with another exemplary embodiment [Description of symbols]
DESCRIPTION OF SYMBOLS 11 ... Diesel engine (internal combustion engine), 12 ... Intake pipe, 13 ... Turbocharger, 15 ... Exhaust turbine, 16 ... Collective exhaust pipe, 17 ... Waste gate, 18 ... Waste gate valve, 19 ... Oxygen concentration sensor, 20 DESCRIPTION OF SYMBOLS ... EGR piping, 21 ... EGR valve, 22 ... EGR apparatus, 23 ... Fuel injection valve, 29 ... Control circuit (exhaust oxygen concentration estimation means according to cylinder, weight coefficient determination means, correction control means), 30 ... Variable geometry turbo, 31 ... guide plate, 32 ... exhaust turbine.

Claims

An oxygen concentration sensor that is installed in a collective exhaust pipe of an internal combustion engine and detects an exhaust oxygen concentration;
The output of the oxygen concentration sensor is regarded as the exhaust oxygen concentration obtained by multiplying the exhaust oxygen concentration of each cylinder by a predetermined weighting factor and weighted and averaged, and the exhaust oxygen concentration for each cylinder is considered from the output of the oxygen concentration sensor in consideration of the weighting factor. A cylinder-specific exhaust oxygen concentration estimating means for estimating
An internal combustion engine fuel injection control device comprising: an injection amount correction unit that corrects a fuel injection amount for each cylinder based on an exhaust oxygen concentration for each cylinder estimated by the exhaust gas concentration estimation unit for each cylinder.
Weighting factor determining means for determining the weighting factor corresponding to the crank angle at the time of exhaust gas oxygen concentration detection;
Correction control means for correcting the correspondence between the weighting factor and the crank angle when it is determined that the weighting factor is not appropriate based on the output of the oxygen concentration sensor ,
The correction control means increases or decreases the fuel injection amount of the specific cylinder, detects a timing at which a change in the exhaust oxygen concentration caused by the increase or decrease is detected by the oxygen concentration sensor by a crank angle, and the detection result A fuel injection control apparatus for an internal combustion engine, wherein the correspondence relationship between the weighting coefficient and the crank angle is corrected based on the correction coefficient .

An oxygen concentration sensor that is installed in a collective exhaust pipe of an internal combustion engine and detects an exhaust oxygen concentration;
The output of the oxygen concentration sensor is regarded as the exhaust oxygen concentration obtained by multiplying the exhaust oxygen concentration of each cylinder by a predetermined weighting factor and weighted and averaged, and the exhaust oxygen concentration for each cylinder is considered from the output of the oxygen concentration sensor in consideration of the weighting factor. A cylinder-specific exhaust oxygen concentration estimating means for estimating
Injection amount correction means for correcting the fuel injection amount for each cylinder based on the exhaust oxygen concentration for each cylinder estimated by the exhaust gas concentration estimation means for each cylinder;
In a fuel injection control device for an internal combustion engine comprising:
Weighting factor determining means for determining the weighting factor corresponding to the crank angle at the time of exhaust gas oxygen concentration detection;
Correction control means for correcting the correspondence between the weight coefficient and the crank angle;
With
The correction control means increases or decreases the fuel injection amount of the specific cylinder, detects a timing at which a change in the exhaust oxygen concentration caused by the increase or decrease is detected by the oxygen concentration sensor by a crank angle, and the detection result And a means for correcting the correspondence between the weighting factor and the crank angle, and the specific cylinder so that the total fuel injection amount per cycle does not change when the fuel injection amount of the specific cylinder is increased or decreased. A fuel injection control device for an internal combustion engine, comprising: means for correcting a fuel injection amount of a cylinder other than the above .

An oxygen concentration sensor that is installed in a collective exhaust pipe of an internal combustion engine and detects an exhaust oxygen concentration;
The output of the oxygen concentration sensor is regarded as the exhaust oxygen concentration obtained by multiplying the exhaust oxygen concentration of each cylinder by a predetermined weighting factor and weighted and averaged, and the exhaust oxygen concentration for each cylinder is considered from the output of the oxygen concentration sensor in consideration of the weighting factor. A cylinder-specific exhaust oxygen concentration estimating means for estimating
Injection amount correction means for correcting the fuel injection amount for each cylinder based on the exhaust oxygen concentration for each cylinder estimated by the exhaust gas concentration estimation means for each cylinder;
In a fuel injection control device for an internal combustion engine comprising:
Weighting factor determining means for determining the weighting factor corresponding to the crank angle at the time of exhaust gas oxygen concentration detection;
Correction control means for correcting the correspondence between the weight coefficient and the crank angle;
With
The correction control means increases or decreases the fuel injection amount of the specific cylinder, detects a timing at which a change in the exhaust oxygen concentration caused by the increase or decrease is detected by the oxygen concentration sensor by a crank angle, and the detection result And a means for correcting the correspondence between the weighting factor and the crank angle, and a means for retarding the fuel injection timing of the specific cylinder when the fuel injection amount of the specific cylinder is increased. The fuel injection control device for an internal combustion engine according to claim 2.

An oxygen concentration sensor that is installed in a collective exhaust pipe of an internal combustion engine and detects an exhaust oxygen concentration;
The output of the oxygen concentration sensor is regarded as the exhaust oxygen concentration obtained by multiplying the exhaust oxygen concentration of each cylinder by a predetermined weighting factor and weighted and averaged, and the exhaust oxygen concentration for each cylinder is considered from the output of the oxygen concentration sensor in consideration of the weighting factor. A cylinder-specific exhaust oxygen concentration estimating means for estimating
Injection amount correction means for correcting the fuel injection amount for each cylinder based on the exhaust oxygen concentration for each cylinder estimated by the exhaust gas concentration estimation means for each cylinder;
In a fuel injection control device for an internal combustion engine comprising:
Weighting factor determining means for determining the weighting factor corresponding to the crank angle at the time of exhaust gas oxygen concentration detection;
Correction control means for correcting the correspondence between the weight coefficient and the crank angle;
With
The correction control means increases or decreases the fuel injection amount of the specific cylinder, detects a timing at which a change in the exhaust oxygen concentration caused by the increase or decrease is detected by the oxygen concentration sensor by a crank angle, and the detection result Based on the means for correcting the correspondence relationship between the weighting factor and the crank angle, and when increasing the fuel injection amount of the specific cylinder, by post-injecting the increased amount of fuel in the expansion stroke of the specific cylinder, A fuel injection control device for an internal combustion engine, comprising: means for increasing the fuel injection amount of the specific cylinder .

Equipped with an exhaust gas recirculation device,
The internal combustion engine according to any one of claims 1 to 4 , wherein the correction control means stops exhaust gas recirculation by the exhaust gas recirculation device when increasing or decreasing the fuel injection amount of the specific cylinder. Engine fuel injection control device.

It has a supercharger with a waste gate valve,
Said correction control means, the fuel injection amount of the specific cylinder when the increase or decrease, the fuel injection control of an internal combustion engine according to any of claims 1 to 5, characterized in that opening the waste gate valve apparatus.

With variable geometry turbo,
Said correction control means, when the increase or decrease the fuel injection amount of the specific cylinder, one of the claims 1 to 5, characterized in that opening the variable geometry turbo of the guide plate to reduce exhaust resistance A fuel injection control device for an internal combustion engine according to claim 1.