JP4048735B2

JP4048735B2 - Control device for internal combustion engine

Info

Publication number: JP4048735B2
Application number: JP2001185163A
Authority: JP
Inventors: 大治磯部; 寛原口
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2001-06-19
Filing date: 2001-06-19
Publication date: 2008-02-20
Anticipated expiration: 2021-06-19
Also published as: JP2003003903A; DE10227177B4; DE10227177A1

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関の排出ガスの酸素濃度を検出する酸素濃度検出手段の出力値と酸素濃度との関係を校正するための大気学習を実施する内燃機関の制御装置に関するものである。
【０００２】
【従来の技術】
近年の電子制御化された自動車では、内燃機関の排気通路に排出ガスの酸素濃度を検出する酸素濃度センサを設置し、この酸素濃度センサの出力値に基づいて空燃比を制御して排気浄化用の触媒の排気浄化率を高めるようにしている。しかし、この酸素濃度センサは、製造ばらつき（個体差）や経時劣化により検出精度が低下する問題がある。
【０００３】
この問題に対して、例えば、特開昭５８−５７０５０号公報、特開平１０−２１２９９９号公報に示すように、燃料カット開始から所定時間経過後に、排気通路内が大気で満たされていると判断して、その時の酸素濃度センサの出力値（酸素濃度検出値）を大気の酸素濃度と見なして、酸素濃度センサの出力値と酸素濃度との関係を校正する大気学習を行うことが提案されている。
【０００４】
【発明が解決しようとする課題】
ところで、近年、より精度の高い空燃比制御や更なる排気エミッション低減を実現するために、酸素濃度センサの検出精度の一層の向上が要求されるようになってきており、そのためには、より精度の高い大気学習を行う必要が生じてきている。大気学習を精度良く行うためには、大気学習時に排気通路内の酸素濃度をできる限り大気の酸素濃度に近付ける必要がある。更に、図１０に示すように、酸素濃度センサの出力値は、排気通路内の酸素濃度センサ周辺の排気圧に応じて変化するため、大気学習時に排気圧をできる限り大気圧に近付けることが望ましい。
【０００５】
上記従来の大気学習方法では、燃料カット開始から所定時間経過後に、排気通路内が大気で満たされていると判断して、大気学習を実施するようにしているが、単に燃料カットしただけでは、排気通路内の雰囲気状態がエンジン運転状態に左右されてしまい、排気通路内の酸素濃度センサ周辺の雰囲気状態が大気状態（大気の酸素濃度及び大気圧）に十分に近付いていない可能性がある。このため、従来の大気学習方法では、エンジン運転状態によっては酸素濃度センサの出力値と酸素濃度との関係を精度良く校正することができない可能性があり、酸素濃度センサの検出精度向上の要求に十分に対応することができない。
【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、酸素濃度検出手段の出力値と酸素濃度との関係を精度良く校正することができ、酸素濃度検出手段の検出精度を向上させることができる内燃機関の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は、排気通路内の酸素濃度検出手段周辺の雰囲気状態がほぼ大気状態になっている期間に、酸素濃度検出手段の出力値と酸素濃度との関係を校正するための大気学習を実施する内燃機関の制御装置において、大気学習を実施するに際して、強制大気状態制御手段によって強制的に排気通路内の酸素濃度を大気の酸素濃度に近付けると共に排気圧を大気圧に近付けるように制御する。このようにすれば、大気学習の際に、排気通路内の酸素濃度検出手段周辺の酸素濃度と排気圧を速やかに大気状態（大気の酸素濃度及び大気圧）に近付けることができ、酸素濃度検出手段の出力値と酸素濃度との関係を精度良く校正することができる。また、請求項１に係る発明では、排気通路から吸気通路への排出ガス環流量を強制的に増加させるようにする。これにより、大気学習の際に、排出ガス環流システム（ＥＧＲシステム）を利用して、排気圧を速やかに低下させることができる。
【００１０】
また、請求項２のように、吸入空気量を強制的に増加させると良い。また、上記目的を達成するために、本発明の請求項３は、排気通路内の酸素濃度検出手段周辺の雰囲気状態がほぼ大気状態になっている期間に、酸素濃度検出手段の出力値と酸素濃度との関係を校正するための大気学習を実施する内燃機関の制御装置において、大気学習を実施するに際して、強制大気状態制御手段によって強制的に排気通路内の酸素濃度を大気の酸素濃度に近付けると共に排気圧を大気圧に近付けるように制御する。このようにすれば、大気学習の際に、排気通路内の酸素濃度検出手段周辺の酸素濃度と排気圧を速やかに大気状態（大気の酸素濃度及び大気圧）に近付けることができ、酸素濃度検出手段の出力値と酸素濃度との関係を精度良く校正することができる。また、請求項３に係る発明では、吸入空気量を強制的に増加させる。また、請求項４のように、可変バルブタイミング調整手段により吸気バルブと排気バルブのバルブオーバーラップ量を強制的に増加させるようにしても良い。また、上記目的を達成するために、本発明の請求項５は、排気通路内の酸素濃度検出手段周辺の雰囲気状態がほぼ大気状態になっている期間に、酸素濃度検出手段の出力値と酸素濃度との関係を校正するための大気学習を実施する内燃機関の制御装置において、大気学習を実施するに際して、強制大気状態制御手段によって強制的に排気通路内の酸素濃度を大気の酸素濃度に近付けると共に排気圧を大気圧に近付けるように制御する。このようにすれば、大気学習の際に、排気通路内の酸素濃度検出手段周辺の酸素濃度と排気圧を速やかに大気状態（大気の酸素濃度及び大気圧）に近付けることができ、酸素濃度検出手段の出力値と酸素濃度との関係を精度良く校正することができる。また、請求項５に係る発明では、可変バルブタイミング調整手段により吸気バルブと排気バルブのバルブオーバーラップ量を強制的に増加させる。これらのように、内燃機関の制御のために備えられているスロットル弁（吸気絞り弁）や可変バルブタイミング調整手段を利用して、大気学習の際に、排気通路への新気導入量を速やかに増加させて排気通路内の酸素濃度を速やかに大気の酸素濃度に近付けることができる。
【００１１】
一方、請求項６に係る発明では、大気学習許可判定手段によって内燃機関の運転状態等に基づいて排気通路内の酸素濃度検出手段周辺の酸素濃度が大気の酸素濃度とほぼ等しくなったと判断したときに大気学習を許可し、その大気学習の許可期間に、予め設定した基準となる酸素濃度検出手段の出力特性に基づいて大気学習時の運転状態に対応した基準出力値を基準出力値算出手段によって算出すると共に、大気学習時の排気圧又はそれを変化させるパラメータを用いて、最終基準出力値算出手段によって基準出力値を補正して最終基準出力値を求める。そして、大気学習の許可期間に補正係数学習手段によって実際の酸素濃度検出手段の出力値と前記最終基準出力値とを比較して、該酸素濃度検出手段の出力値を補正するための補正係数を学習し、内燃機関の運転中に、出力値補正手段によって酸素濃度検出手段の出力値を前記補正係数で補正して排出ガスの酸素濃度を検出する。
【００１２】
この構成では、大気学習の許可期間に、まず、基準となる酸素濃度検出手段（例えば、製造ばらつきや経時劣化のない標準的な酸素濃度検出手段）の出力特性に基づいて大気学習時の運転状態に対応した基準出力値を求める。但し、運転状態が同じでも、排気系の圧力損失の変化や大気圧の変化によって排気圧が変化して酸素濃度検出手段の出力値が変化するため、大気学習時の排気圧又はそれを変化させるパラメータを用いて前記基準出力値を補正して最終基準出力値（大気学習時の最終的な基準出力値）を求める。
【００１３】
このようにして求めた最終基準出力値は、大気学習時に、基準となる酸素濃度検出手段（製造ばらつきや経時劣化のない標準的な酸素濃度検出手段）を用いて酸素濃度を検出した場合の出力値、つまり、大気学習時の標準的な出力値となる。従って、この最終基準出力値と大気学習時の実際の酸素濃度検出手段の出力値とを比較すれば、実際の酸素濃度検出手段の出力値を、基準となる酸素濃度検出手段（製造ばらつきや経時劣化のない標準的な酸素濃度検出手段）の出力値に補正するための補正係数を精度良く学習することができる。この大気学習終了後に、この補正係数を用いて実際の酸素濃度検出手段の出力値を補正すれば、酸素濃度検出手段の製造ばらつきや経時劣化があっても、酸素濃度検出手段の出力値から排出ガスの酸素濃度を精度良く検出することができる。
【００１４】
一般に、大気学習は、減速時等の燃料カット期間中に実施されるが、燃料カット開始当初は、燃料カット前に燃焼したガスが酸素濃度検出手段の上流側に残っているため、その燃焼ガスが排出されて新気（大気）と入れ替わるまでは、排気通路内の酸素濃度検出手段周辺の酸素濃度が大気の酸素濃度に近付かない。従って、燃料カット開始から排気通路内の酸素濃度検出手段周辺の酸素濃度が大気の酸素濃度に近付くまでに遅れが生じる。また、運転状態によっては、燃料カット開始後の新気の導入が遅れたり、排気通路内の酸素濃度が大気の酸素濃度に近付く前に燃料カットが終了してしまうことがある。
【００１５】
また、これらの事情を考慮して、請求項６では、燃料カット期間中に、機関回転速度、車速、変速ギア位置のうちの少なくとも１つが所定の条件を満たし、且つ燃料カット開始から所定のディレー時間が経過した後に、大気学習を許可する。このようにすれば、燃料カット期間中に、運転状態と燃料カット開始後の経過時間に基づいて、排気通路内の酸素濃度検出手段周辺の酸素濃度が大気の酸素濃度に近付いているか否かを簡単且つ精度良く判定することができる。
【００１６】
この場合、燃料カット開始から排気通路内の酸素濃度検出手段周辺の酸素濃度が大気の酸素濃度に近付くまでの時間（ディレー時間）は、運転状態（機関回転速度、車速、変速ギア位置）によって変化するため、このディレー時間を予め設定した固定時間とする場合は、様々な運転状態に対応できるように少し長めのディレー時間に設定する必要があるが、請求項７のように、ディレー時間を機関回転速度、車速、変速ギア位置のうちの少なくとも１つに応じて設定するようにすれば、ディレー時間を運転状態に応じて必要最小限の時間に設定することができる。これにより、例えば、ディレー時間を短く設定する運転状態であれば、燃料カットの時間が少し短くてなっても、大気学習を行うことができ、大気学習の頻度を増加させることができる。
【００１７】
また、請求項８のように、基準となる酸素濃度検出手段として、製造ばらつきの中心の特性を有する標準的な酸素濃度検出手段を用い、予め、この標準的な酸素濃度検出手段を、製造ばらつきの中心の特性を有する標準的な排気浄化手段を設けた排気通路に設置して、該排気浄化手段の目詰り等による圧力損失増加の無い状態で且つ該排気通路内を標準大気圧状態にして測定した標準的な酸素濃度検出手段の出力特性を記憶する記憶手段を設け、この記憶手段に記憶されている出力特性を用いて基準出力値を求めるようにすると良い。このようにすれば、酸素濃度検出手段の製造ばらつきや経時劣化、排気浄化手段の目詰りがあったり、大気圧が標準大気圧からずれていたとしても、常に、それらの影響を排除した基準出力値を簡単に求めることができる。また、請求項９に係る発明では、大気学習許可判定手段によって内燃機関の運転状態等に基づいて排気通路内の酸素濃度検出手段周辺の酸素濃度が大気の酸素濃度とほぼ等しくなったと判断したときに大気学習を許可し、その大気学習の許可期間に、予め設定した基準となる酸素濃度検出手段の出力特性に基づいて大気学習時の運転状態に対応した基準出力値を基準出力値算出手段によって算出すると共に、大気学習時の排気圧又はそれを変化させるパラメータを用いて、最終基準出力値算出手段によって基準出力値を補正して最終基準出力値を求める。そして、大気学習の許可期間に補正係数学習手段によって実際の酸素濃度検出手段の出力値と前記最終基準出力値とを比較して、該酸素濃度検出手段の出力値を補正するための補正係数を学習し、内燃機関の運転中に、出力値補正手段によって酸素濃度検出手段の出力値を前記補正係数で補正して排出ガスの酸素濃度を検出する。また、請求項９では、基準となる酸素濃度検出手段として、製造ばらつきの中心の特性を有する標準的な酸素濃度検出手段を用い、予め、この標準的な酸素濃度検出手段を、製造ばらつきの中心の特性を有する標準的な排気浄化手段を設けた排気通路に設置して、該排気浄化手段の目詰り等による圧力損失増加の無い状態で且つ該排気通路内を標準大気圧状態にして測定した標準的な酸素濃度検出手段の出力特性を記憶する記憶手段を設け、この記憶手段に記憶されている出力特性を用いて基準出力値を求めるようにする。このようにすれば、酸素濃度検出手段の製造ばらつきや経時劣化、排気浄化手段の目詰りがあったり、大気圧が標準大気圧からずれていたとしても、常に、それらの影響を排除した基準出力値を簡単に求めることができる。
【００１８】
更に、請求項１０のように、基準出力値の補正に用いるパラメータとして、大気学習時の大気圧及び／又は排気通路に設けられた排気浄化手段の圧力損失を用いるようにしても良い。排気浄化手段の圧力損失と大気圧は、運転状態以外で、排気圧を変化させる主要なパラメータであるため、排気浄化手段の圧力損失や大気圧を用いて基準出力値を補正すれば、排気浄化手段の目詰り等による圧力損失増加（排気圧上昇）や大気圧の変化による排気圧変化の影響を考慮した最終基準出力値を精度良く求めることができる。しかも、排気圧センサを用いる必要がなく、低コスト化の要求も満たすことができる。また、請求項１１に係る発明では、大気学習許可判定手段によって内燃機関の運転状態等に基づいて排気通路内の酸素濃度検出手段周辺の酸素濃度が大気の酸素濃度とほぼ等しくなったと判断したときに大気学習を許可し、その大気学習の許可期間に、予め設定した基準となる酸素濃度検出手段の出力特性に基づいて大気学習時の運転状態に対応した基準出力値を基準出力値算出手段によって算出すると共に、大気学習時の排気圧又はそれを変化させるパラメータを用いて、最終基準出力値算出手段によって基準出力値を補正して最終基準出力値を求める。そして、大気学習の許可期間に補正係数学習手段によって実際の酸素濃度検出手段の出力値と前記最終基準出力値とを比較して、該酸素濃度検出手段の出力値を補正するための補正係数を学習し、内燃機関の運転中に、出力値補正手段によって酸素濃度検出手段の出力値を前記補正係数で補正して排出ガスの酸素濃度を検出する。請求項１１では、基準出力値の補正に用いるパラメータとして、大気学習時の大気圧及び／又は排気通路に設けられた排気浄化手段の圧力損失を用いるようにする。排気浄化手段の圧力損失と大気圧は、運転状態以外で、排気圧を変化させる主要なパラメータであるため、排気浄化手段の圧力損失や大気圧を用いて基準出力値を補正すれば、排気浄化手段の目詰り等による圧力損失増加（排気圧上昇）や大気圧の変化による排気圧変化の影響を考慮した最終基準出力値を精度良く求めることができる。しかも、排気圧センサを用いる必要がなく、低コスト化の要求も満たすことができる。
【００１９】
この場合、請求項１２のように、大気学習時の大気圧と標準大気圧（１気圧）とのずれによる排気圧変化分に相当する酸素濃度検出手段の出力値変化分及び／又は排気浄化手段の目詰り等による圧力損失増加によって生じる排気圧上昇分に相当する酸素濃度検出手段の出力値変化分を算出し、該出力値変化分によって前記基準出力値を補正して前記最終基準出力値を求めるようにしても良い。このようにすれば、大気圧による影響分と排気浄化手段の目詰り等の圧力損失増加による影響分を、酸素濃度検出手段の出力値変化分に換算することができ、それらの影響を実際の酸素濃度検出手段の出力値から排除して基準出力値を求めることができる。
【００２０】
【発明の実施の形態】
以下、本発明をディーゼルエンジンに適用した一実施形態を図１乃至図１０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、スロットル弁１３が設けられ、このスロットル弁１３の下流側に、吸気温を検出する吸気温センサ１４が設けられている。また、エンジン１１の各気筒の上部には、燃料を筒内に直接噴射する燃料噴射弁１５が取り付けられている。
【００２１】
一方、エンジン１１の排気管１６（排気通路）には、排出ガスの酸素濃度（空燃比）を検出する酸素濃度センサ１７が設けられている。この酸素濃度センサ１７は、排出ガスの酸素濃度（空燃比）に応じてセンサ素子に流れる検出電流が変化し、この検出電流に応じた電圧Ｖafが検出回路１８から出力される。これら酸素濃度センサ１７と検出回路１８とから酸素濃度検出器１９（酸素濃度検出手段）が構成されている。
【００２２】
排気管１６のうちの酸素濃度センサ１７の近傍には、排気温を検出する排気温センサ２０が設置され、この排気温センサ２０の下流側に、排気浄化手段として排出ガス中のＰＭ（粒子状物質）を捕集するＤＰＦ２１（ディーゼルパティキュレートフィルタ）が設けられている。このＤＰＦ２１には、排出ガス中のＮＯｘ、ＨＣ等を浄化する触媒も備えられている。ＤＰＦ２１のＰＭ堆積量の増加に伴ってＤＰＦ２１前後の差圧（圧力損失）が増加し、このＤＰＦ２１の前後の差圧が差圧センサ２２によって検出される。
【００２３】
また、排気管１６のうちの酸素濃度センサ１７の上流側には、ターボ過給機の排気タービン２３が設置され、この排気タービン２３と連結された吸気タービン２４が、吸気管１２のうちのスロットル弁１３の上流側に設置されている。更に、排気管１６のうちの排気タービン２３の上流側と吸気管１２のうちのスロットル弁１３の下流側との間には、排出ガスの一部を吸気側に還流させるためのＥＧＲ配管２５が接続され、このＥＧＲ配管２５の途中に排出ガス還流量（ＥＧＲ量）を制御するＥＧＲ弁２６が設けられている。
【００２４】
また、エンジン１１のシリンダブロックには、冷却水温を検出する冷却水温センサ２７や、エンジン回転速度を検出するクランク角センサ２８が取り付けられている。また、後述するエンジン制御回路（以下「ＥＣＵ」と表記する）２９には、大気圧を検出する大気圧センサ３０が設けられ、アクセルペダル３１の開度（アクセル開度）は、アクセルセンサ３２によって検出される。
【００２５】
上述した各種センサの出力は、ＥＣＵ２９に入力される。このＥＣＵ２９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（記憶手段）に記憶された燃料噴射制御プログラムを実行することで、エンジン運転状態に応じて燃料噴射弁１５の燃料噴射量を制御する。
【００２６】
また、ＥＣＵ２９は、減速時等に燃料カットしたときに、ＥＧＲ弁２６とスロットル弁１３を全開（又は開弁方向）に制御して強制的に排気管１６内の状態を大気状態（大気の酸素濃度、大気圧）に近付ける強制大気状態制御を実施し、燃料カット開始後の経過時間（強制大気状態制御開始後の経過時間）が所定のディレー時間を越えた時点で、排気管１６内の酸素濃度センサ１７周辺の酸素濃度が大気の酸素濃度とほぼ等しくなったと判断して大気学習を許可し、酸素濃度検出器１９の出力値と酸素濃度との関係を校正するための大気学習を次のようにして実施する。
【００２７】
図２に示すように、ＥＣＵ２９は、大気学習の許可期間に、エンジン回転速度ＮＥと変速機のギア位置とをパラメータとする基準出力値Ｖbaseの二次元マップを検索して、大気学習時のエンジン回転速度ＮＥとギア位置（シフト位置）に対応した基準出力値Ｖbaseを求める。
【００２８】
ここで、基準出力値Ｖbaseのマップは、予め基準となる酸素濃度検出器を基準となる排気系に設置して、排気管内の雰囲気状態を標準大気圧状態（１気圧）にして測定した基準となる酸素濃度検出器の出力特性をマップ化してＥＣＵ２９のＲＯＭ（記憶手段）に記憶したものである。ここで、基準となる酸素濃度検出器としては、製造ばらつきの中心の特性を有する標準的な酸素濃度検出器を用い、基準となる排気系としては、排気管とＤＰＦ等が共に製造ばらつきの中心の特性を有し、ＤＰＦがＰＭ堆積無し（目詰り無し）の状態になっている排気系を用いる。これにより、基準となる酸素濃度検出器、つまり、製造ばらつきや経時劣化のない標準的な酸素濃度検出器の大気学習時の運転状態（排気圧）に対応した基準出力値Ｖbase（図９参照）を求める。
【００２９】
一般に、図１０に示すように、酸素濃度検出器１９の出力値は排気圧に応じて変化し、燃料カット時の排気圧は、エンジン回転速度、ギア位置によって異なるため、基準出力値Ｖbaseのマップは、エンジン回転速度に対する基準となる酸素濃度検出器の出力特性がギア位置毎に設定されている。
【００３０】
但し、運転状態が同じでも、ＤＰＦ２１のＰＭ堆積による圧力損失増加や大気圧の変化によって排気圧が変化する。そこで、ＥＣＵ２９は、大気学習の許可期間に、次のようにして大気学習時のＤＰＦ２１の圧力損失と大気圧を用いて基準出力値Ｖbaseを補正して最終基準出力値Ｖstd （大気学習時の最終的な基準出力値）を求める。
【００３１】
まず、差圧センサ２２で検出したＤＰＦ２１の大気学習時の圧力損失（差圧）ΔＰからＤＰＦ２１のＰＭ堆積無しの状態の圧力損失Ｐcat を差し引いて、ＤＰＦ２１のＰＭ堆積による圧力損失増加分（ΔＰ−Ｐcat ）を求める。このＤＰＦ２１の圧力損失増加分（ΔＰ−Ｐcat ）をパラメータとする圧力損失補正値Ｖpmのマップを検索して、大気学習時の圧力損失増加分（ΔＰ−Ｐcat ）に応じた圧力損失補正値Ｖpmを算出する。この圧力損失補正値Ｖpmは、圧力損失増加分（ΔＰ−Ｐcat ）による排気圧上昇分に相当する酸素濃度検出器１９の出力値変化分である。尚、圧力損失補正値Ｖpmのマップは、予め、ＤＰＦ２１のＰＭ堆積による圧力損失増加分（ΔＰ−Ｐcat ）と基準となる酸素濃度検出器の出力値変化分との関係を測定して、それをマップ化してＥＣＵ２９のＲＯＭに記憶したものである。
【００３２】
一方、大気圧Ｐa の影響に関しては、大気圧Ｐa をパラメータとする大気圧補正値Ｖatm のマップを検索して、大気圧センサ３０で検出した大気学習時の大気圧Ｐa に応じた大気圧補正値Ｖatm を算出する。この大気圧補正値Ｖatm は、大気学習時の大気圧Ｐa と標準大気圧（１気圧）とのずれによる排気圧変化分に相当する酸素濃度検出器１９の出力値変化分である。尚、大気圧補正値Ｖatm のマップは、予め大気圧Ｐa と基準となる酸素濃度検出器の出力値変化分との関係を測定して、それをマップ化してＥＣＵ２９のＲＯＭに記憶したものである。
【００３３】
以上のようにして、大気学習時の基準出力値Ｖbase、圧力損失補正値Ｖpm、大気圧補正値Ｖatm を算出した後、これら三者を積算して最終基準出力値Ｖstd を求める。
Ｖstd ＝Ｖbase＋Ｖpm＋Ｖatm
【００３４】
このようにして求めた最終基準出力値Ｖstd （図９参照）は、大気学習時に、基準となる酸素濃度検出器（製造ばらつきや経時劣化のない標準的な酸素濃度検出器）を用いて酸素濃度を検出した場合の出力値、つまり、大気学習時の標準的な出力値となる。
【００３５】
この後、最終基準出力値Ｖstd と実際の酸素濃度検出器１９の出力値Ｖafとの比から補正係数Ｆlearn を算出する。
Ｆlearn ＝Ｖstd ／Ｖaf
【００３６】
これにより、実際の酸素濃度検出器１９の出力値Ｖafを、基準となる酸素濃度検出器の出力値、つまり、製造ばらつきや経時劣化による誤差を含まない真の出力値に補正するための補正係数Ｆlearn を算出し、この補正係数Ｆlearn をＥＣＵ２９のバックアップＲＡＭ等のメモリ（書き換え可能な不揮発性メモリ）に記憶する。
【００３７】
ＥＣＵ２９は、大気学習の許可期間終了後に、次式により実際の酸素濃度検出器１９の出力値Ｖafを、製造ばらつきや経時劣化による誤差を含まない真の出力値Ｖaf（真値）に変換する。
Ｖaf（真値）＝Ｖaf×Ｆlearn
【００３８】
尚、補正係数Ｆlearn を、Ｆlearn ＝Ｖaf／Ｖstd と定義した場合は、真の出力値Ｖaf（真値）を次式により算出すれば良い。
Ｖaf（真値）＝Ｖaf／Ｆlearn
以上説明した大気学習制御は、ＥＣＵ２９によって図３乃至図７の各ルーチンに従って実行される。以下、これら各ルーチンの処理内容を説明する。
【００３９】
［大気学習制御ベースルーチン］
図３に示す大気学習制御ベースルーチンは、ＥＣＵ２９の電源投入後（イグニッションスイッチのオン後）に実行される。本ベースルーチンでは、起動直後に１回のみステップ１００の初期化処理ルーチンを実行して、ＲＡＭの初期化、各種フラグやカウンタのリセット等の初期化処理を行った後、ステップ２００〜５００の処理を所定周期で繰り返し実行する。
【００４０】
まず、ステップ２００で、後述する図４の大気学習許可判定ルーチンを実行して、エンジン運転条件と燃料カット開始後の経過時間に基づいて、強制大気状態制御許可フラグＥＸＫを、強制大気状態制御の許可を意味する「１」又は強制大気状態制御の禁止を意味する「０」にセットすると共に、大気学習許可フラグＥＸＬを、大気学習の許可を意味する「１」又は大気学習の禁止を意味する「０」にセットする。
【００４１】
この後、ステップ３００に進み、後述する図５の強制大気状態制御ルーチンを実行して、強制大気状態許可フラグＥＸＫが「１」にセットされているとき（強制大気状態制御の許可期間）に、強制大気状態制御を実施して強制的に排気管１６内の状態を大気状態（大気の酸素濃度、大気圧）に近付ける。
【００４２】
この後、ステップ４００に進み、後述する図６の大気学習ルーチンを実行して、大気学習許可フラグＥＸＬが「１」にセットされているとき（大気学習の許可期間）に、大気学習を実行して酸素濃度検出器１９の出力値Ｖafと酸素濃度との関係を校正するための補正係数Ｆlearn を学習する。
【００４３】
この後、ステップ５００に進み、後述する図７の酸素濃度検出器出力補正ルーチンを実行して、大気学習許可フラグＥＸＬが「０」にリセットされているとき（大気学習の許可期間終了後）に、補正係数Ｆlearn を用いて酸素濃度検出器１９の出力値Ｖafを製造ばらつきや経時劣化による誤差を含まない真の出力Ｖaf（真値）に補正する。
【００４４】
［大気学習許可判定ルーチン］
図４に示す大気学習許可判定ルーチン（図３のステップ２００）は、例えば１６ｍｓ毎に実行され、特許請求の範囲でいう大気学習許可判定手段に相当する役割を果たす。本ルーチンが起動されると、まず、ステップ２０１で、エンジン回転速度ＮＥが学習許可判定値（例えば２０００ｒｐｍ）よりも高いか否かを判定する。この学習許可判定値は、大気学習を行うのに必要な燃料カット時間を確保できる可能性のあるエンジン回転速度であり、後述する学習終了判定値（例えば１５００ｒｐｍ）よりもある程度高いエンジン回転速度に設定されている。
【００４５】
エンジン回転速度ＮＥが学習許可判定値よりも高いと判定されれば、ステップ２０２に進み、燃料噴射量Ｑが０ｍｍ³／ｓｔ以下であるか否かによって燃料カットされているか否かを判定する。燃料カットされていなければ、強制大気状態制御許可フラグＥＸＫ、後述するカウンタＣlearn 及び大気学習許可フラグＥＸＬを全て「０」に維持する（ステップ２１０〜２１２）。
【００４６】
一方、エンジン回転速度ＮＥが学習許可判定値よりも高い運転状態で、燃料カットされていれば、ステップ２０３に進み、強制大気状態制御許可フラグＥＸＫを強制大気状態制御の許可を意味する「１」にセットする。これにより、後述する図５の強制大気状態制御ルーチンによって強制大気状態制御が開始される。
【００４７】
この後、ステップ２０４に進み、燃料カット開始後（強制大気状態制御の開始後）の経過時間をカウントするカウンタＣlearn をインクリメントして、次のステップ２０５に進み、このカウンタＣlearn のカウント値が所定のディレー時間（例えば５ｓｅｃ）を越えたか否かによって、燃料カット開始後（強制大気状態制御の開始後）の経過時間が所定のディレー時間を越えたか否かを判定する。このディレー時間は、燃料カット及び強制大気状態制御を開始してから排気管１６内の酸素濃度センサ１７の周辺の雰囲気状態が大気状態（大気の酸素濃度、大気圧）に近付くまでに要する時間を確保するための時間であり、予め実験データ等に基づいて設定されている。尚、酸素濃度の変化に対する酸素濃度センサ１７の応答遅れを無視できない場合は、酸素濃度センサ１７の応答遅れもディレー時間に含めるようにすると良い。
【００４８】
燃料カット開始後（強制大気状態制御の開始後）の経過時間が所定のディレー時間に達するまでは、ステップ２１２に進み、大気学習許可フラグＥＸＬを「０」に維持する。
【００４９】
その後、燃料カット開始後（強制大気状態制御の開始後）の経過時間が所定のディレー時間を越えた時点で、ステップ２０５からステップ２０６に進み、カウンタＣlearn のオーバーフロー対策としてカウンタＣlearn の値を６ｓｅｃにセットした後、ステップ２０７に進み、排気管１６内の酸素濃度センサ１７の周辺の雰囲気状態が大気状態に近付いて排気管１６内の酸素濃度センサ１７の周辺の酸素濃度が大気の酸素濃度とほぼ等しくなっていると判断して、大気学習許可フラグＥＸＬを大気学習の許可を意味する「１」にセットする。これにより、後述する図６の大気学習ルーチンによって大気学習が開始される。
【００５０】
一方、上記ステップ２０１で、エンジン回転速度ＮＥが学習許可判定値（例えば２０００ｒｐｍ）以下と判定された場合には、ステップ２０８に進み、エンジン回転速度ＮＥが学習終了判定値（例えば１５００ｒｐｍ）まで低下したか否かを判定する。この学習終了判定値（例えば１５００ｒｐｍ）は、燃料カットを終了するエンジン回転速度（例えば１２００ｒｐｍ）よりも少し高いエンジン回転速度に設定されている。
【００５１】
このステップ２０８で、エンジン回転速度ＮＥが学習終了判定値まで低下していないと判定されれば、ステップ２０９に進み、強制大気状態制御許可フラグＥＸＫが「１」にセットされていることを確認した後、ステップ２０４に進む。
【００５２】
その後、上記ステップ２０８で、エンジン回転速度ＮＥが学習終了判定値以下に低下したと判定された時点で、強制大気状態制御許可フラグＥＸＫ、カウンタＣlearn 、大気学習許可フラグＥＸＬを全て「０」にリセットする（ステップ２１０〜２１２）。
【００５３】
［強制大気状態制御ルーチン］
図５に示す強制大気状態制御ルーチン（図３のステップ３００）は、例えば８ｍｓ毎に実行され、特許請求の範囲でいう強制大気状態制御手段に相当する役割を果たす。本ルーチンが起動されると、まず、ステップ３０１で、強制大気状態制御許可フラグＥＸＫが強制大気状態制御の許可を意味する「１」にセットされているか否かを判定し、強制大気状態制御許可フラグＥＸＫ＝１と判定されれば、ステップ３０２以降の強制大気状態制御を次のようにして実施する。
【００５４】
まず、ステップ３０２で、ＥＧＲ弁２６を強制的に全開（又は開弁方向）に制御してＥＧＲ量を増加させる。これにより、排気管１６内の圧力（排気圧）を強制的に低下させて、速やかに排気圧を大気圧に近付けると共に、シリンダ内の掃気効率を上げる。そして、次のステップ３０３で、スロットル弁１３を強制的に全開（又は開弁方向）に制御して、強制的に新気導入量を増加させて、速やかに排気管１６内の酸素濃度を大気の酸素濃度に近付ける。
【００５５】
その後、上記ステップ３０１で、強制大気状態制御許可フラグＥＸＫ＝０と判定されたときに、ＥＧＲ弁２６とスロットル弁１３を通常制御に戻す（ステップ３０４、３０５）。
【００５６】
［大気学習ルーチン］
図６に示す大気学習ルーチン（図３のステップ４００）は、例えば５００ｍｓ毎に実行される。本ルーチンが起動されると、まず、ステップ４０１で、大気学習許可フラグＥＸＬ＝１が大気学習の許可を意味する「１」にセットされているか否かを判定し、大気学習許可フラグＥＸＬ＝１と判定されれば、ステップ４０２以降の大気学習を次のようにして実施する。
【００５７】
まず、ステップ４０２で、エンジン回転速度ＮＥと変速機のギア位置（シフト位置）を読み込んだ後、ステップ４０３に進み、現在のエンジン回転速度ＮＥとギア位置に応じた基準出力値Ｖbaseをマップにより算出する。このステップ４０２の処理が特許請求の範囲でいう基準出力値算出手段に相当する役割を果たす。
【００５８】
この後、ステップ４０４に進み、現在のＤＰＦ２１のＰＭ堆積による圧力損失増加分（ΔＰ−Ｐcat ）に応じた圧力損失補正値Ｖpmをマップにより算出した後、ステップ４０５に進み、現在の大気圧Ｐa に応じた大気圧補正値Ｖatm をマップにより算出する。そして、次のステップ４０６で、基準出力値Ｖbaseに圧力損失補正値Ｖpmと大気圧補正値Ｖatm を加算して最終基準出力値Ｖstd （大気学習時の標準的な出力値）を求める。
Ｖstd ＝Ｖbase＋Ｖpm＋Ｖatm
このステップ４０６の処理が特許請求の範囲でいう最終基準出力値算出手段に相当する役割を果たす。
【００５９】
そして、次のステップ４０７で、酸素濃度検出器１９の実出力値Ｖafを読み込んだ後、ステップ４０８に進み、最終基準出力値Ｖstd と現在の酸素濃度検出器１９の出力値Ｖafとの比から補正係数Ｆlearn を算出する。
Ｆlearn ＝Ｖstd ／Ｖaf
【００６０】
この後、ステップ４０９に進み、今回算出した補正係数Ｆlearn と前回算出した補正係数Ｆlearn (i-1) との平均値を算出する。
Ｆlearn ＝｛Ｆlearn ＋Ｆlearn (i-1) ｝／２
【００６１】
この後、ステップ４１０に進み、ＥＣＵ２９のバックアップＲＡＭに記憶している前回の補正係数Ｆlearn (i-1) の記憶値を、上記ステップ４０９で平均化した今回の補正係数Ｆlearn で更新する。これらステップ４０８〜４１０の処理が特許請求の範囲でいう補正係数学習手段に相当する役割を果たす。
【００６２】
以上説明したステップ４０１〜４１０の処理を、大気学習許可フラグＥＸＬが「０」にリセットされるまで５００ｍｓ毎に繰り返し実行して補正係数Ｆlearn を学習する。このようにして学習した補正係数Ｆlearn は、ＥＣＵ２９のバックアップＲＡＭ（書き換え可能な不揮発性メモリ）に記憶され、エンジン停止後（イグニッションスイッチのオフ後）も補正係数Ｆlearn の学習値の記憶が保持される。
【００６３】
［酸素濃度検出器出力補正ルーチン］
図７に示す酸素濃度検出器出力補正ルーチン（図３のステップ５００）は、酸素濃度検出器１９の出力値Ｖafの読み込みタイミング毎（例えば２０℃Ａ毎）に実行され、特許請求の範囲でいう出力値補正手段に相当する役割を果たす。
【００６４】
本ルーチンが起動されると、まず、ステップ５０１で、大気学習許可フラグＥＸＬが大気学習禁止を意味する「０」であるか否かを判定し、もし、大気学習許可フラグＥＸＬ＝１（大気学習許可）と判定されれば、そのまま本ルーチンを終了する。
【００６５】
その後、大気学習許可フラグＥＸＬ＝０と判定されたとき、つまり、大気学習の許可期間の終了後にステップ５０２に進み、酸素濃度検出器１９の出力値Ｖafを読み込んだ後、ステップ５０３に進み、酸素濃度検出器１９の出力値Ｖafに補正係数Ｆlearn を乗算して、酸素濃度検出器１９の出力値Ｖafを、製造ばらつきや経時劣化による誤差を含まない真の出力値Ｖaf（真値）に変換する。
Ｖaf（真値）＝Ｖaf×Ｆlearn
【００６６】
尚、エンジン始動後、１回目の大気学習を行う前は、前回のエンジン運転中に学習した補正係数Ｆlearn をＥＣＵ２９のバックアップＲＡＭから読み込んで、この補正係数Ｆlearn を用いて真の出力値Ｖaf（真値）を算出する。
そして、次のステップ５０４で、真の値出力Ｖaf（真値）を酸素濃度に物理値変換する。
【００６７】
以上説明した大気学習制御の実行例を図８のタイムチャートに基づいて説明する。エンジン回転速度ＮＥが学習許可判定値（例えば２０００ｒｐｍ）よりも高い運転状態で、燃料カットされた時点（図８のｔ1 ）で、強制大気状態制御許可フラグＥＸＫを「１」にセットする。これにより、強制大気状態制御を開始してＥＧＲ弁２６を全開（又は開弁方向）に制御して強制的に排気圧を低下させて速やかに排気管１６内を大気圧に近付けると共に、スロットル弁１３を全開（又は開弁方向）に制御して強制的に新気導入量を増加させて速やかに排気管１６内の酸素濃度を大気の酸素濃度に近付ける。
【００６８】
その後、燃料カット開始後の経過時間（強制大気状態制御開始後の経過時間）が所定のディレー時間（例えば５ｓｅｃ）を越えた時点（図８のｔ2 ）で、排気管１６内の雰囲気が大気状態に近付いて排気管１６内の酸素濃度が大気の酸素濃度とほぼ等しくなり、その酸素濃度が酸素濃度検出器１９の出力値に現れていると判断して、大気学習許可フラグＥＸＬ＝１にセットする。この大気学習許可フラグＥＸＬ＝１の期間に、大気学習を実施して、基準となる酸素濃度検出器（製造ばらつきや経時劣化のない標準的な酸素濃度検出器）を用いて酸素濃度を検出した場合の最終基準出力値Ｖstd （＝Ｖbase＋Ｖpm＋Ｖatm ）を算出し、この最終基準出力値Ｖstd と現在の酸素濃度検出器１９の出力値Ｖafとの比から補正係数Ｆlearn を算出して平均化する処理を５００ｍｓ毎に繰り返し実行する。
【００６９】
その後、燃料カットが終了して燃料噴射が再開され、燃料噴射量Ｑ＞０となった時点（図８のｔ3 ）で、又は燃料カットに伴ってエンジン回転速度ＮＥが学習終了判定値（例えば１５００ｒｐｍ）まで低下した時点で、強制大気状態制御許可フラグＥＸＫを「０」にリセットして強制大気状態制御を終了すると共に、大気学習許可フラグＥＸＬを「０」にリセットして大気学習を終了する。
【００７０】
大気学習終了後は、補正係数Ｆlearn を用いて酸素濃度検出器１９の出力値Ｖafを、製造ばらつきや経時劣化による誤差を含まない真の出力値Ｖaf（真値）に補正し、この出力値Ｖaf（真値）を酸素濃度に物理値変換する。
【００７１】
以上説明した本実施形態では、大気学習を実施するに際して、強制大気状態制御を実施して、排気管１６内の状態を強制的に大気状態（大気の酸素濃度及び大気圧）に近付けることができるようにすると共に、大気学習時の最終基準出力値Ｖstd と実際の酸素濃度検出器１９の出力値Ｖafとの比から補正係数Ｆlearn を学習することによって、酸素濃度検出器１９の出力値Ｖafを、基準となる酸素濃度検出器の出力値、つまり、製造ばらつきや経時劣化による誤差を含まない真の出力値Ｖaf（真値）に補正するようにしたので、酸素濃度検出器１９の出力値Ｖafと酸素濃度との関係を精度良く校正することができ、酸素濃度検出器１９の酸素濃度検出精度を向上させることができる。
【００７２】
更に、本実施形態では、エンジン回転速度が学習許可判定値（例えば２０００ｒｐｍ）よりも高い運転状態で燃料カットされたときに、大気学習を許可するようにしたので、燃料カット時間が大気学習を行う時間を確保できると推定されるエンジン回転速度で燃料カットされたときのみに、大気学習を開始することができる。
【００７３】
尚、エンジン回転速度に代えて、車速又はギア位置が所定の条件を満たした燃料カット期間に大気学習を許可するようにしても良い。或は、エンジン回転速度、車速、ギア位置のうちの２つ又は３つが、所定の条件を満たした燃料カット期間に大気学習を許可するようにしても良い。
【００７４】
また、本実施形態では、予め基準となる酸素濃度検出器を、基準となる排気系に設置して標準大気圧の条件で測定した基準となる酸素濃度検出器の出力特性をマップ化してＥＣＵ２９のＲＯＭに記憶しておき、大気学習の許可期間に、このマップを検索して、大気学習時の運転状態（エンジン回転速度ＮＥとギア位置）に対応した基準出力値Ｖbaseを求めるようにしたので、大気学習時に、運転状態に対応した基準出力値Ｖbaseを簡単に算出することができる。
【００７５】
更に、本実施形態では、運転状態以外で、排気圧を変化させる主要なパラメータであるＤＰＦ２１の圧力損失と大気圧を用いて大気学習時の基準出力値Ｖbaseを補正して最終基準出力値Ｖstd を求めるようにしたので、ＤＰＦ２１の目詰り等による圧力損失増加（排気圧上昇）や大気圧の変化による排気圧変化の影響を考慮した最終基準出力値Ｖstd を精度良く求めることができる。しかも、排気圧センサを用いる必要がなく、低コスト化の要求も満たすことができる。
【００７６】
しかしながら、本発明は、排気管１６に排気圧センサを設置して、排気圧センサで検出した排気圧を用いて大気学習時の基準出力値Ｖbaseを補正して最終基準出力値Ｖstd を求めるようにしても良く、この場合でも、本発明の所期の目的を十分に達成することができる。
【００７７】
また、本実施形態では、大気学習時の大気圧と標準大気圧（１気圧）とのずれによる排気圧変化分に相当する酸素濃度検出器１９の出力値変化分を大気圧補正値Ｖatm として算出すると共に、ＤＰＦ２１の圧力損失増加分（ΔＰ−Ｐcat ）による排気圧上昇分に相当する酸素濃度検出器１９の出力値変化分を圧力損失補正値Ｖpmとして算出し、大気学習時の基準出力値Ｖbaseに圧力損失補正値Ｖpmと大気圧補正値Ｖatm を加算して最終基準出力値Ｖstd を求めるようにしたが、大気学習時の基準出力値Ｖbaseを補正するための補正係数のマップとして、大気学習時の大気圧（又は大気圧と標準大気圧との差圧）と、ＤＰＦ２１の圧力損失ΔＰ又は圧力損失増加分（ΔＰ−Ｐcat ）をパラメータとする二次元マップ又は数式等を実験データ等に基づいて作成してＥＣＵ２９のＲＯＭに記憶しておき、大気学習時の大気圧やＤＰＦ２１の圧力損失ΔＰに応じた補正係数を算出して、この補正係数で大気学習時の基準出力値Ｖbaseを補正して最終基準出力値Ｖstd を求めるようにしても良い。
【００７８】
また、ＤＰＦ２１の圧力損失と大気圧のいずれか一方のみに基づいて大気学習時の基準出力値Ｖbaseを補正して最終基準出力値Ｖstd を求めるようにしても良い。
【００７９】
また、本実施形態では、圧力損失補正値Ｖpmを算出する際に用いるＤＰＦ２１のＰＭ堆積無しの状態の圧力損失Ｐcat （以下「初期圧力損失Ｐcat 」という）を固定値としたが、図１１に示すように、ＤＰＦ２１の初期圧力損失Ｐcat は、排気流量に応じて変化する。そこで、排気温センサ２０で検出した排気温度と吸気温センサ１４で検出した吸気温度との温度差（吸入空気の膨脹度合いを表すパラメータ）と吸入空気量とに基づいて排気流量を推定し、図１１に示す排気流量とＤＰＦ２１の初期圧力損失Ｐcat との関係を用いて、排気流量に応じたＤＰＦ２１の初期圧力損失Ｐcat を求めるようにしても良い。このようにすれば、圧力損失補正値Ｖpmの算出精度を向上させて、大気学習時の最終基準出力値Ｖstd をより精度良く求めることができる。
【００８０】
また、本実施形態では、燃料カット開始から大気学習を許可するまでに設けるディレー時間を固定値としたが、このディレー時間をエンジン回転速度、車速、ギア位置のうちの少なくとも１つに応じて設定するようにしても良い。燃料カット開始から排気通路が大気で満たされて、その酸素濃度が酸素濃度検出値の出力値に現れるまでの時間は、エンジン回転速度、車速、ギア位置によって変化するので、ディレー時間をエンジン回転速度、車速、ギア位置に応じて設定すれば、その時の運転状態に応じた最適なディレー時間を設定することができる。
【００８１】
また、本実施形態では、強制大気状態制御の実施時に、ＥＧＲ弁２６とスロットル弁１３を全開（又は開弁方向）に制御するようにしたが、吸気バルブ及び／又は排気バルブのバルブタイミングを可変する可変バルブタイミング調整機構（可変バルブタイミング調整手段）を備えたエンジンの場合には、強制大気状態制御の実施時に、ＥＧＲ弁２６とスロットル弁１３の強制開弁制御に加えて、可変バルブタイミング調整機構を吸気バルブと排気バルブのバルブオーバーラップ量を強制的に増加させるように制御しても良い。或は、強制大気状態制御の実施時に、ＥＧＲ弁２６、スロットル弁１３、可変バルブタイミング調整機構のうちの１つ又は２つのみを制御するようにしても良い。
【００８２】
その他、本発明の適用範囲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適用しても良く、また、排気浄化手段として、ＤＰＦの代わりに、三元触媒、ＮＯｘ触媒等の各種の触媒を設置しても良い等、種々変更して実施することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態を示すエンジン制御システム全体の概略構成図
【図２】ＥＣＵの大気学習機能の構成を示す機能ブロック図
【図３】大気学習制御ベースルーチンの処理の流れを示すフローチャート
【図４】大気学習許可判定ルーチンの処理の流れを示すフローチャート
【図５】強制大気状態制御ルーチンの処理の流れを示すフローチャート
【図６】大気学習ルーチンの処理の流れを示すフローチャート
【図７】酸素濃度検出器出力補正ルーチンの処理の流れを示すフローチャート
【図８】大気学習制御の実行例を示すタイムチャート
【図９】大気学習時の基準出力値Ｖbaseと最終基準出力値Ｖstd と酸素濃度検出器の出力値Ｖafとの関係を示す図
【図１０】排気圧と酸素濃度検出器の出力比との関係を示す図
【図１１】他の実施形態を説明するための排気流量とＤＰＦの初期圧力損失との関係を示す図
【符号の説明】
１１…ディーゼルエンジン（内燃機関）、１２…吸気管、１３…スロットル弁、１５…燃料噴射弁、１６…排気管（排気通路）、１７…酸素濃度センサ、１８…検出回路、１９…酸素濃度検出器（酸素濃度検出手段）、２０…排気温センサ、２１…ＤＰＦ（排気浄化手段）、２２…差圧センサ、２３…排気タービン、２４…吸気タービン、２５…ＥＧＲ配管、２６…ＥＧＲ弁、２９…ＥＣＵ（強制大気状態制御手段，大気学習許可判定手段，基準出力値算出手段，最終基準出力値算出手段，補正係数学習手段，出力値補正手段）、３０…大気圧センサ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine that performs atmospheric learning for calibrating the relationship between the output value of an oxygen concentration detection means for detecting the oxygen concentration of exhaust gas of the internal combustion engine and the oxygen concentration.
[0002]
[Prior art]
In recent electronically controlled automobiles, an oxygen concentration sensor that detects the oxygen concentration of exhaust gas is installed in the exhaust passage of the internal combustion engine, and the air-fuel ratio is controlled based on the output value of the oxygen concentration sensor for exhaust purification. The exhaust gas purification rate of the catalyst is increased. However, this oxygen concentration sensor has a problem that the detection accuracy decreases due to manufacturing variations (individual differences) and deterioration over time.
[0003]
To solve this problem, for example, as shown in JP-A-58-57050 and JP-A-10-2122999, it is determined that the exhaust passage is filled with air after a predetermined time has elapsed since the start of fuel cut. Then, it is proposed to perform atmospheric learning in which the output value (oxygen concentration detection value) of the oxygen concentration sensor at that time is regarded as the oxygen concentration of the atmosphere, and the relationship between the output value of the oxygen concentration sensor and the oxygen concentration is calibrated. Yes.
[0004]
[Problems to be solved by the invention]
By the way, in recent years, in order to achieve more accurate air-fuel ratio control and further reduction of exhaust emission, further improvement in detection accuracy of the oxygen concentration sensor has been required. There is a need to conduct highly atmospheric learning. In order to perform atmospheric learning with high accuracy, it is necessary to make the oxygen concentration in the exhaust passage as close as possible to the atmospheric oxygen concentration at the time of atmospheric learning. Furthermore, as shown in FIG. 10, since the output value of the oxygen concentration sensor changes according to the exhaust pressure around the oxygen concentration sensor in the exhaust passage, it is desirable to make the exhaust pressure as close to the atmospheric pressure as possible when learning the atmosphere. .
[0005]
In the conventional atmospheric learning method, after a predetermined time has elapsed from the start of fuel cut, it is determined that the inside of the exhaust passage is filled with air, and the air learning is performed. There is a possibility that the atmosphere state in the exhaust passage depends on the engine operating state, and the atmosphere state around the oxygen concentration sensor in the exhaust passage is not sufficiently close to the atmospheric state (atmospheric oxygen concentration and atmospheric pressure). For this reason, in the conventional atmospheric learning method, there is a possibility that the relationship between the output value of the oxygen concentration sensor and the oxygen concentration cannot be accurately calibrated depending on the engine operating state. I can't respond enough.
[0006]
The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to accurately calibrate the relationship between the output value of the oxygen concentration detecting means and the oxygen concentration, and to detect the oxygen concentration detecting means. An object of the present invention is to provide a control device for an internal combustion engine capable of improving accuracy.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, claim 1 of the present invention provides an output value and an oxygen concentration of the oxygen concentration detection means during a period in which the atmospheric state around the oxygen concentration detection means in the exhaust passage is substantially atmospheric. In the control device for an internal combustion engine that performs atmospheric learning to calibrate the relationship, the oxygen concentration in the exhaust passage is forcibly brought close to the oxygen concentration in the atmosphere by the forced atmospheric state control means when the atmospheric learning is performed. Control the atmospheric pressure to approach atmospheric pressure. In this way, the oxygen concentration and the exhaust pressure around the oxygen concentration detecting means in the exhaust passage can be quickly brought close to the atmospheric state (atmospheric oxygen concentration and atmospheric pressure) during the air learning, and the oxygen concentration detection The relationship between the output value of the means and the oxygen concentration can be calibrated with high accuracy.In the invention according to claim 1, the exhaust gas ring flow rate from the exhaust passage to the intake passage is forcibly increased. As a result, the exhaust pressure can be quickly reduced by utilizing the exhaust gas recirculation system (EGR system) during atmospheric learning.
[0010]
  Also,Claim 2Forcibly increase the amount of intake airGood. In order to achieve the above object, the third aspect of the present invention provides an output value of the oxygen concentration detection means and the oxygen concentration during a period in which the atmospheric state around the oxygen concentration detection means in the exhaust passage is substantially atmospheric. In an internal combustion engine controller that performs atmospheric learning to calibrate the relationship with concentration, when performing atmospheric learning, the forced atmospheric state control means forcibly brings the oxygen concentration in the exhaust passage close to the atmospheric oxygen concentration. At the same time, the exhaust pressure is controlled to approach the atmospheric pressure. In this way, the oxygen concentration and the exhaust pressure around the oxygen concentration detecting means in the exhaust passage can be quickly brought close to the atmospheric state (atmospheric oxygen concentration and atmospheric pressure) during the air learning, and the oxygen concentration detection The relationship between the output value of the means and the oxygen concentration can be calibrated with high accuracy. In the invention according to claim 3, the amount of intake air is forcibly increased. Further, as in claim 4,The valve overlap amount of the intake valve and the exhaust valve is forcibly increased by the variable valve timing adjustment means.Evengood.In order to achieve the above object, claim 5 of the present invention is characterized in that the output value of the oxygen concentration detection means and the oxygen concentration during the period when the atmosphere state around the oxygen concentration detection means in the exhaust passage is substantially atmospheric. In an internal combustion engine controller that performs atmospheric learning to calibrate the relationship with concentration, when performing atmospheric learning, the forced atmospheric state control means forcibly brings the oxygen concentration in the exhaust passage close to the atmospheric oxygen concentration. At the same time, the exhaust pressure is controlled to approach the atmospheric pressure. In this way, the oxygen concentration and the exhaust pressure around the oxygen concentration detecting means in the exhaust passage can be quickly brought close to the atmospheric state (atmospheric oxygen concentration and atmospheric pressure) during the air learning, and the oxygen concentration detection The relationship between the output value of the means and the oxygen concentration can be calibrated with high accuracy. In the invention according to claim 5, the valve overlap amount of the intake valve and the exhaust valve is forcibly increased by the variable valve timing adjusting means. Like theseBy using a throttle valve (intake throttle valve) and variable valve timing adjusting means provided for control of the internal combustion engine, the amount of fresh air introduced into the exhaust passage can be quickly increased during air learning. The oxygen concentration in the exhaust passage can be quickly brought close to the atmospheric oxygen concentration.
[0011]
On the other hand, in the invention according to claim 6, when it is determined by the atmosphere learning permission determination means that the oxygen concentration around the oxygen concentration detection means in the exhaust passage is substantially equal to the oxygen concentration in the atmosphere based on the operating state of the internal combustion engine. The reference output value corresponding to the operating state at the time of the atmospheric learning based on the output characteristics of the oxygen concentration detection means serving as a reference set in advance during the atmospheric learning permission period. The final reference output value is obtained by correcting the reference output value by the final reference output value calculating means using the exhaust pressure at the time of learning the atmosphere or a parameter that changes the exhaust pressure. Then, the correction coefficient learning means compares the actual output value of the oxygen concentration detection means and the final reference output value by the correction coefficient learning means during the atmospheric learning permission period, and calculates a correction coefficient for correcting the output value of the oxygen concentration detection means. Learning and during operation of the internal combustion engine, the output value correction means corrects the output value of the oxygen concentration detection means with the correction coefficient to detect the oxygen concentration of the exhaust gas.
[0012]
In this configuration, during the air learning permission period, first, the operating state during air learning is based on the output characteristics of the reference oxygen concentration detection means (for example, standard oxygen concentration detection means without manufacturing variations and deterioration over time). A reference output value corresponding to is obtained. However, even if the operating conditions are the same, the exhaust pressure changes due to a change in exhaust system pressure loss or a change in atmospheric pressure, and the output value of the oxygen concentration detection means changes. The reference output value is corrected using a parameter to obtain a final reference output value (final reference output value during atmospheric learning).
[0013]
The final reference output value obtained in this way is the output when the oxygen concentration is detected using the reference oxygen concentration detection means (standard oxygen concentration detection means free from manufacturing variations and deterioration over time) during atmospheric learning. Value, that is, the standard output value during atmospheric learning. Therefore, if this final reference output value is compared with the output value of the actual oxygen concentration detection means during atmospheric learning, the actual output value of the oxygen concentration detection means is converted into the reference oxygen concentration detection means (manufacturing variation and time The correction coefficient for correcting the output value of the standard oxygen concentration detection means without deterioration) can be learned with high accuracy. If the actual output value of the oxygen concentration detection means is corrected using this correction coefficient after the end of the air learning, even if there is manufacturing variation or deterioration with time of the oxygen concentration detection means, the output value from the oxygen concentration detection means is discharged. The oxygen concentration of the gas can be detected with high accuracy.
[0014]
In general, atmospheric learning is performed during a fuel cut period such as during deceleration, but at the beginning of the fuel cut, the gas burned before the fuel cut remains upstream of the oxygen concentration detection means. Until oxygen is discharged and replaced with fresh air (atmosphere), the oxygen concentration around the oxygen concentration detection means in the exhaust passage does not approach the oxygen concentration in the atmosphere. Accordingly, there is a delay from the start of fuel cut until the oxygen concentration around the oxygen concentration detecting means in the exhaust passage approaches the oxygen concentration in the atmosphere. Further, depending on the operating state, the introduction of fresh air after the start of fuel cut may be delayed, or the fuel cut may end before the oxygen concentration in the exhaust passage approaches the oxygen concentration in the atmosphere.
[0015]
  Also,Taking these circumstances into consideration, the claimsIn 6During the fuel cut period, atmospheric learning is permitted after at least one of the engine speed, the vehicle speed, and the transmission gear position satisfies a predetermined condition and a predetermined delay time has elapsed from the start of the fuel cut.Do. In this way, whether or not the oxygen concentration around the oxygen concentration detection means in the exhaust passage is approaching the oxygen concentration in the atmosphere based on the operating state and the elapsed time after the fuel cut starts during the fuel cut period. It can be determined easily and accurately.
[0016]
  In this case, the time from the start of fuel cut until the oxygen concentration around the oxygen concentration detection means in the exhaust passage approaches the oxygen concentration in the atmosphere (delay time) varies depending on the operating state (engine speed, vehicle speed, transmission gear position). Therefore, when this delay time is set to a fixed time set in advance, it is necessary to set a slightly longer delay time so that it can correspond to various operating conditions.7As described above, if the delay time is set according to at least one of the engine speed, the vehicle speed, and the transmission gear position, the delay time can be set to the minimum necessary time according to the driving state. it can. Thereby, for example, in the operating state in which the delay time is set to be short, the air learning can be performed even if the fuel cut time is slightly shortened, and the frequency of air learning can be increased.
[0017]
  Claims8As described above, the standard oxygen concentration detecting means having the characteristic of the center of manufacturing variation is used as the reference oxygen concentration detecting means, and this standard oxygen concentration detecting means is previously set to have the characteristic of the center of manufacturing variation. A standard exhaust gas is installed in an exhaust passage provided with standard exhaust purification means, and is measured in a state where there is no increase in pressure loss due to clogging of the exhaust purification means and the inside of the exhaust passage is in a standard atmospheric pressure state. It is preferable to provide storage means for storing the output characteristics of the oxygen concentration detection means and obtain the reference output value using the output characteristics stored in the storage means. In this way, even if there are manufacturing variations in the oxygen concentration detection means, deterioration with time, clogging of the exhaust purification means, or even if the atmospheric pressure deviates from the standard atmospheric pressure, the reference output that always excludes those effects The value can be easily obtained.In the invention according to claim 9, when the atmosphere learning permission determination means determines that the oxygen concentration around the oxygen concentration detection means in the exhaust passage is substantially equal to the oxygen concentration in the atmosphere based on the operating state of the internal combustion engine, etc. The reference output value corresponding to the operating state at the time of the atmospheric learning based on the output characteristics of the oxygen concentration detection means serving as a reference set in advance during the atmospheric learning permission period. The final reference output value is obtained by correcting the reference output value by the final reference output value calculating means using the exhaust pressure at the time of learning the atmosphere or a parameter that changes the exhaust pressure. Then, the correction coefficient learning means compares the actual output value of the oxygen concentration detection means and the final reference output value by the correction coefficient learning means during the atmospheric learning permission period, and calculates a correction coefficient for correcting the output value of the oxygen concentration detection means. Learning and during operation of the internal combustion engine, the output value correction means corrects the output value of the oxygen concentration detection means with the correction coefficient to detect the oxygen concentration of the exhaust gas. According to a ninth aspect of the present invention, a standard oxygen concentration detecting means having a characteristic of manufacturing variation center is used as a reference oxygen concentration detecting means, and this standard oxygen concentration detecting means is previously set as the center of manufacturing variation. It was installed in an exhaust passage provided with a standard exhaust purification means having the above characteristics, and was measured in a state where there was no increase in pressure loss due to clogging of the exhaust purification means and the inside of the exhaust passage was in a standard atmospheric pressure state. Storage means for storing the output characteristics of the standard oxygen concentration detection means is provided, and the reference output value is obtained using the output characteristics stored in the storage means. In this way, even if there are manufacturing variations in the oxygen concentration detection means, deterioration with time, clogging of the exhaust purification means, or even if the atmospheric pressure deviates from the standard atmospheric pressure, the reference output that always excludes those effects The value can be easily obtained.
[0018]
  Further, as in the tenth aspect, the atmospheric pressure at the time of learning the atmosphere and / or the pressure loss of the exhaust purification means provided in the exhaust passage may be used as the parameter used for correcting the reference output value. Since the pressure loss and atmospheric pressure of the exhaust purification means are the main parameters that change the exhaust pressure outside the operating state, if the reference output value is corrected using the pressure loss and atmospheric pressure of the exhaust purification means, the exhaust purification means It is possible to accurately obtain a final reference output value in consideration of an increase in pressure loss (exhaust pressure increase) due to clogging of the means and an influence of an exhaust pressure change due to a change in atmospheric pressure. Moreover, it is not necessary to use an exhaust pressure sensor, and the demand for cost reduction can be satisfied.In the invention according to claim 11, when the atmosphere learning permission determination means determines that the oxygen concentration around the oxygen concentration detection means in the exhaust passage is substantially equal to the oxygen concentration in the atmosphere based on the operating state of the internal combustion engine. The reference output value corresponding to the operating state at the time of the atmospheric learning based on the output characteristics of the oxygen concentration detection means serving as a reference set in advance during the atmospheric learning permission period. The final reference output value is obtained by correcting the reference output value by the final reference output value calculating means using the exhaust pressure at the time of learning the atmosphere or a parameter that changes the exhaust pressure. Then, the correction coefficient learning means compares the actual output value of the oxygen concentration detection means and the final reference output value by the correction coefficient learning means during the atmospheric learning permission period, and calculates a correction coefficient for correcting the output value of the oxygen concentration detection means. Learning and during operation of the internal combustion engine, the output value correction means corrects the output value of the oxygen concentration detection means with the correction coefficient to detect the oxygen concentration of the exhaust gas. According to the eleventh aspect, the atmospheric pressure at the time of learning the atmosphere and / or the pressure loss of the exhaust purification means provided in the exhaust passage is used as the parameter used for correcting the reference output value. Since the pressure loss and atmospheric pressure of the exhaust purification means are the main parameters that change the exhaust pressure outside the operating state, if the reference output value is corrected using the pressure loss and atmospheric pressure of the exhaust purification means, the exhaust purification means It is possible to accurately obtain a final reference output value in consideration of an increase in pressure loss (exhaust pressure increase) due to clogging of the means and an influence of an exhaust pressure change due to a change in atmospheric pressure. Moreover, it is not necessary to use an exhaust pressure sensor, and the demand for cost reduction can be satisfied.
[0019]
  In this case, the claim12As described above, the change in the output value of the oxygen concentration detection means corresponding to the change in the exhaust pressure due to the difference between the atmospheric pressure during atmospheric learning and the standard atmospheric pressure (1 atm) and / or the pressure due to clogging of the exhaust purification means, etc. A change in output value of the oxygen concentration detection means corresponding to an increase in exhaust pressure caused by an increase in loss may be calculated, and the final reference output value may be obtained by correcting the reference output value based on the change in output value. . In this way, the influence due to atmospheric pressure and the influence due to increased pressure loss such as clogging of the exhaust purification means can be converted into the change in the output value of the oxygen concentration detection means. The reference output value can be obtained by excluding from the output value of the oxygen concentration detecting means.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a diesel engine will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. A throttle valve 13 is provided in an intake pipe 12 of a diesel engine 11 that is an internal combustion engine, and an intake air temperature sensor 14 that detects an intake air temperature is provided downstream of the throttle valve 13. A fuel injection valve 15 for directly injecting fuel into the cylinder is attached to the upper part of each cylinder of the engine 11.
[0021]
On the other hand, the exhaust pipe 16 (exhaust passage) of the engine 11 is provided with an oxygen concentration sensor 17 for detecting the oxygen concentration (air-fuel ratio) of the exhaust gas. In the oxygen concentration sensor 17, the detection current flowing through the sensor element changes according to the oxygen concentration (air / fuel ratio) of the exhaust gas, and the voltage Vaf corresponding to this detection current is output from the detection circuit 18. These oxygen concentration sensor 17 and detection circuit 18 constitute an oxygen concentration detector 19 (oxygen concentration detection means).
[0022]
In the vicinity of the oxygen concentration sensor 17 in the exhaust pipe 16, an exhaust temperature sensor 20 for detecting the exhaust temperature is installed. On the downstream side of the exhaust temperature sensor 20, PM (particulate matter) in the exhaust gas as exhaust purification means. A DPF 21 (diesel particulate filter) that collects the substance is provided. The DPF 21 is also provided with a catalyst for purifying NOx, HC, etc. in the exhaust gas. The differential pressure (pressure loss) before and after the DPF 21 increases with an increase in the amount of PM deposited on the DPF 21, and the differential pressure before and after the DPF 21 is detected by the differential pressure sensor 22.
[0023]
Further, an exhaust turbine 23 of a turbocharger is installed on the upstream side of the oxygen concentration sensor 17 in the exhaust pipe 16, and an intake turbine 24 connected to the exhaust turbine 23 is connected to the throttle in the intake pipe 12. It is installed on the upstream side of the valve 13. Further, an EGR pipe 25 for returning a part of the exhaust gas to the intake side is provided between the upstream side of the exhaust turbine 23 in the exhaust pipe 16 and the downstream side of the throttle valve 13 in the intake pipe 12. An EGR valve 26 that controls the exhaust gas recirculation amount (EGR amount) is provided in the middle of the EGR pipe 25.
[0024]
A cooling water temperature sensor 27 that detects the cooling water temperature and a crank angle sensor 28 that detects the engine rotation speed are attached to the cylinder block of the engine 11. An engine control circuit (hereinafter referred to as “ECU”) 29, which will be described later, is provided with an atmospheric pressure sensor 30 for detecting the atmospheric pressure, and the opening degree of the accelerator pedal 31 (accelerator opening degree) is determined by the accelerator sensor 32. Detected.
[0025]
Outputs of the various sensors described above are input to the ECU 29. The ECU 29 is mainly composed of a microcomputer, and controls the fuel injection amount of the fuel injection valve 15 according to the engine operating state by executing a fuel injection control program stored in a built-in ROM (storage means). To do.
[0026]
Further, the ECU 29 controls the EGR valve 26 and the throttle valve 13 to be fully opened (or in the valve opening direction) when the fuel is cut during deceleration or the like, and forcibly changes the state in the exhaust pipe 16 to the atmospheric state (atmospheric oxygen). The forced atmospheric state control approaching the concentration and the atmospheric pressure is performed, and when the elapsed time after the fuel cut starts (the elapsed time after the forced atmospheric state control starts) exceeds a predetermined delay time, the oxygen in the exhaust pipe 16 It is determined that the oxygen concentration in the vicinity of the concentration sensor 17 is substantially equal to the oxygen concentration in the atmosphere, and the air learning is permitted, and the air learning for calibrating the relationship between the output value of the oxygen concentration detector 19 and the oxygen concentration is performed as follows. It carries out like this.
[0027]
As shown in FIG. 2, the ECU 29 searches the two-dimensional map of the reference output value Vbase using the engine speed NE and the gear position of the transmission as parameters during the atmospheric learning permission period, and A reference output value Vbase corresponding to the rotational speed NE and the gear position (shift position) is obtained.
[0028]
Here, the map of the reference output value Vbase is based on a standard measured by setting a reference oxygen concentration detector in a reference exhaust system in advance and setting the atmospheric state in the exhaust pipe to a standard atmospheric pressure state (1 atm). The output characteristic of the oxygen concentration detector is mapped and stored in the ROM (storage means) of the ECU 29. Here, as the reference oxygen concentration detector, a standard oxygen concentration detector having the characteristics of the center of manufacturing variation is used, and as the reference exhaust system, both the exhaust pipe and the DPF are the center of manufacturing variation. And an exhaust system in which the DPF is in a state of no PM accumulation (no clogging). As a result, the reference output value Vbase corresponding to the operating state (exhaust pressure) at the time of atmospheric learning of the reference oxygen concentration detector, that is, a standard oxygen concentration detector without manufacturing variation or deterioration with time (see FIG. 9). Ask for.
[0029]
In general, as shown in FIG. 10, since the output value of the oxygen concentration detector 19 changes according to the exhaust pressure, and the exhaust pressure at the time of fuel cut varies depending on the engine speed and the gear position, the reference output value Vbase is mapped. The output characteristics of the oxygen concentration detector, which serves as a reference for the engine speed, are set for each gear position.
[0030]
However, even if the operation state is the same, the exhaust pressure changes due to an increase in pressure loss due to PM deposition in the DPF 21 and a change in atmospheric pressure. Therefore, the ECU 29 corrects the reference output value Vbase using the pressure loss and atmospheric pressure of the DPF 21 during atmospheric learning as follows in the permission period for atmospheric learning to obtain the final reference output value Vstd (final during atmospheric learning) Standard output value).
[0031]
First, by subtracting the pressure loss Pcat of the DPF 21 without PM deposition from the pressure loss (differential pressure) ΔP during the atmospheric learning of the DPF 21 detected by the differential pressure sensor 22, an increase in pressure loss (ΔP− Pcat). By searching a map of the pressure loss correction value Vpm using the pressure loss increase (ΔP−Pcat) of the DPF 21 as a parameter, a pressure loss correction value Vpm corresponding to the pressure loss increase (ΔP−Pcat) during atmospheric learning is obtained. calculate. This pressure loss correction value Vpm is a change in the output value of the oxygen concentration detector 19 corresponding to the exhaust pressure increase due to the pressure loss increase (ΔP−Pcat). The map of the pressure loss correction value Vpm is obtained by measuring the relationship between the pressure loss increase (ΔP-Pcat) due to PM deposition of the DPF 21 and the change in the output value of the reference oxygen concentration detector in advance. This is mapped and stored in the ROM of the ECU 29.
[0032]
On the other hand, regarding the influence of the atmospheric pressure Pa, a map of the atmospheric pressure correction value Vatm using the atmospheric pressure Pa as a parameter is searched, and the atmospheric pressure correction value according to the atmospheric pressure Pa detected during atmospheric learning detected by the atmospheric pressure sensor 30. Vatm is calculated. This atmospheric pressure correction value Vatm is a change in the output value of the oxygen concentration detector 19 corresponding to a change in the exhaust pressure due to a difference between the atmospheric pressure Pa and the standard atmospheric pressure (1 atm) during learning of the atmosphere. The map of the atmospheric pressure correction value Vatm is obtained by measuring the relationship between the atmospheric pressure Pa and the change in the output value of the reference oxygen concentration detector in advance, mapping it, and storing it in the ROM of the ECU 29. .
[0033]
As described above, after calculating the reference output value Vbase, the pressure loss correction value Vpm, and the atmospheric pressure correction value Vatm at the time of atmospheric learning, these three are integrated to obtain the final reference output value Vstd.
Vstd = Vbase + Vpm + Vatm
[0034]
The final reference output value Vstd (see FIG. 9) obtained in this way is the oxygen concentration using the reference oxygen concentration detector (standard oxygen concentration detector free from manufacturing variations and deterioration over time) during atmospheric learning. This is the output value when detecting, that is, the standard output value during atmospheric learning.
[0035]
Thereafter, the correction coefficient Flearn is calculated from the ratio between the final reference output value Vstd and the actual output value Vaf of the oxygen concentration detector 19.
Flearn = Vstd / Vaf
[0036]
Thus, the correction coefficient for correcting the actual output value Vaf of the oxygen concentration detector 19 to a reference output value of the oxygen concentration detector, that is, a true output value that does not include errors due to manufacturing variations and deterioration over time. Flearn is calculated, and this correction coefficient Flearn is stored in a memory (a rewritable nonvolatile memory) such as a backup RAM of the ECU 29.
[0037]
The ECU 29 converts the actual output value Vaf of the oxygen concentration detector 19 into a true output value Vaf (true value) that does not include errors due to manufacturing variations or aging deterioration after the atmospheric learning permission period ends.
Vaf (true value) = Vaf × Flearn
[0038]
When the correction coefficient Flearn is defined as Flearn = Vaf / Vstd, the true output value Vaf (true value) may be calculated by the following equation.
Vaf (true value) = Vaf / Flearn
The air learning control described above is executed by the ECU 29 according to the routines shown in FIGS. The processing contents of these routines will be described below.
[0039]
[Atmospheric learning control base routine]
The atmospheric learning control base routine shown in FIG. 3 is executed after the ECU 29 is turned on (after the ignition switch is turned on). In this base routine, the initialization processing routine of step 100 is executed only once immediately after startup to perform initialization processing such as initialization of RAM, reset of various flags and counters, and then processing of steps 200 to 500. Are repeatedly executed in a predetermined cycle.
[0040]
First, in step 200, an atmospheric learning permission determination routine of FIG. 4 described later is executed, and the forced atmospheric state control permission flag EXK is set based on the engine operating conditions and the elapsed time after the start of fuel cut. It is set to “1” meaning permission or “0” meaning prohibition of forced atmospheric state control, and the atmosphere learning permission flag EXL is set to “1” meaning permission of atmosphere learning or prohibition of atmosphere learning. Set to “0”.
[0041]
Thereafter, the process proceeds to step 300, where a forced atmospheric state control routine of FIG. 5 described later is executed, and when the forced atmospheric state permission flag EXK is set to “1” (permitted atmospheric state control permission period), Forced atmospheric state control is performed to forcibly bring the state in the exhaust pipe 16 closer to the atmospheric state (atmospheric oxygen concentration, atmospheric pressure).
[0042]
Thereafter, the process proceeds to step 400, where the atmospheric learning routine of FIG. 6 described later is executed, and the atmospheric learning is executed when the atmospheric learning permission flag EXL is set to “1” (atmospheric learning permission period). Then, a correction coefficient Flearn for calibrating the relationship between the output value Vaf of the oxygen concentration detector 19 and the oxygen concentration is learned.
[0043]
Thereafter, the routine proceeds to step 500, where an oxygen concentration detector output correction routine of FIG. 7 to be described later is executed, and when the atmospheric learning permission flag EXL is reset to “0” (after the atmospheric learning permission period ends). The correction value Flearn is used to correct the output value Vaf of the oxygen concentration detector 19 to a true output Vaf (true value) that does not include errors due to manufacturing variations or deterioration over time.
[0044]
[Atmospheric learning permission judgment routine]
The atmospheric learning permission determination routine (step 200 in FIG. 3) shown in FIG. 4 is executed, for example, every 16 ms, and plays a role corresponding to the atmospheric learning permission determination means in the claims. When this routine is started, first, at step 201, it is determined whether or not the engine speed NE is higher than a learning permission determination value (for example, 2000 rpm). This learning permission determination value is an engine rotation speed that may ensure a fuel cut time necessary for atmospheric learning, and is set to an engine rotation speed that is somewhat higher than a learning end determination value (for example, 1500 rpm) described later. Has been.
[0045]
If it is determined that the engine speed NE is higher than the learning permission determination value, the routine proceeds to step 202 where the fuel injection amount Q is 0 mm.^ThreeIt is determined whether the fuel is cut or not depending on whether it is equal to or less than / st. If the fuel is not cut, the forced atmospheric state control permission flag EXK, a counter Clear described later, and an atmosphere learning permission flag EXL are all maintained at “0” (steps 210 to 212).
[0046]
On the other hand, if the engine speed NE is higher than the learning permission determination value and the fuel is cut off, the routine proceeds to step 203, where the forced atmospheric state control permission flag EXK is “1” which means that the forced atmospheric state control is permitted. Set to. Thus, forced atmospheric state control is started by a forced atmospheric state control routine of FIG.
[0047]
Thereafter, the process proceeds to step 204 where the counter Clear which counts the elapsed time after the start of fuel cut (after the start of forced atmospheric state control) is incremented, and the process proceeds to the next step 205 where the count value of the counter Clear is a predetermined value. It is determined whether or not the elapsed time after the start of fuel cut (after the start of forced atmospheric state control) exceeds a predetermined delay time depending on whether or not a delay time (for example, 5 seconds) has been exceeded. This delay time is the time required from the start of fuel cut and forced atmospheric state control until the atmospheric state around the oxygen concentration sensor 17 in the exhaust pipe 16 approaches the atmospheric state (atmospheric oxygen concentration, atmospheric pressure). This is a time for securing, and is set in advance based on experimental data or the like. If the response delay of the oxygen concentration sensor 17 with respect to the change in oxygen concentration cannot be ignored, the response delay of the oxygen concentration sensor 17 may be included in the delay time.
[0048]
Until the elapsed time after the start of fuel cut (after the start of forced atmospheric state control) reaches a predetermined delay time, the routine proceeds to step 212 and the atmospheric learning permission flag EXL is maintained at “0”.
[0049]
Thereafter, when the elapsed time after the start of fuel cut (after the start of forced atmospheric state control) exceeds a predetermined delay time, the routine proceeds from step 205 to step 206, and the counter Clearn value is set to 6 sec as a counter measure for counter Clearn overflow. After the setting, the routine proceeds to step 207, where the atmosphere state around the oxygen concentration sensor 17 in the exhaust pipe 16 approaches the atmospheric state, and the oxygen concentration around the oxygen concentration sensor 17 in the exhaust pipe 16 is almost equal to the oxygen concentration in the atmosphere. It is determined that they are equal to each other, and the atmospheric learning permission flag EXL is set to “1” which means permission of atmospheric learning. Thereby, atmospheric learning is started by the atmospheric learning routine of FIG.
[0050]
On the other hand, if it is determined in step 201 that the engine rotational speed NE is equal to or lower than the learning permission determination value (for example, 2000 rpm), the process proceeds to step 208, and the engine rotational speed NE is reduced to the learning end determination value (for example, 1500 rpm). It is determined whether or not. The learning end determination value (for example, 1500 rpm) is set to an engine speed that is slightly higher than the engine speed (for example, 1200 rpm) at which the fuel cut ends.
[0051]
If it is determined in step 208 that the engine speed NE has not decreased to the learning end determination value, the process proceeds to step 209, where it has been confirmed that the forced atmospheric state control permission flag EXK is set to “1”. Thereafter, the process proceeds to step 204.
[0052]
Thereafter, when it is determined in step 208 that the engine rotational speed NE has decreased below the learning end determination value, the forced atmospheric state control permission flag EXK, the counter Clear, and the atmospheric learning permission flag EXL are all reset to “0”. (Steps 210 to 212).
[0053]
[Forced atmospheric condition control routine]
The forced atmospheric state control routine (step 300 in FIG. 3) shown in FIG. 5 is executed, for example, every 8 ms, and plays a role corresponding to the forced atmospheric state control means in the claims. When this routine is started, first, in step 301, it is determined whether or not the forced atmospheric state control permission flag EXK is set to “1” which means that the forced atmospheric state control is permitted, and the forced atmospheric state control permission is determined. If it is determined that the flag EXK = 1, the forced atmospheric state control after step 302 is performed as follows.
[0054]
First, in step 302, the EGR valve 26 is forcibly controlled to be fully opened (or in the valve opening direction) to increase the EGR amount. As a result, the pressure (exhaust pressure) in the exhaust pipe 16 is forcibly reduced to quickly bring the exhaust pressure close to the atmospheric pressure and increase the scavenging efficiency in the cylinder. Then, in the next step 303, the throttle valve 13 is forcibly controlled to be fully opened (or in the valve opening direction), the amount of fresh air introduced is forcibly increased, and the oxygen concentration in the exhaust pipe 16 is quickly increased to the atmosphere. Approach the oxygen concentration of
[0055]
Thereafter, when it is determined in step 301 that the forced atmospheric state control permission flag EXK = 0, the EGR valve 26 and the throttle valve 13 are returned to normal control (steps 304 and 305).
[0056]
[Atmospheric learning routine]
The atmospheric learning routine (step 400 in FIG. 3) shown in FIG. 6 is executed every 500 ms, for example. When this routine is started, first, in step 401, it is determined whether or not the atmospheric learning permission flag EXL = 1 is set to “1” meaning permission of atmospheric learning, and the atmospheric learning permission flag EXL = 1. If it is determined, atmospheric learning after step 402 is performed as follows.
[0057]
First, in step 402, the engine speed NE and the gear position (shift position) of the transmission are read, and then the process proceeds to step 403, where the reference output value Vbase corresponding to the current engine speed NE and the gear position is calculated using a map. To do. The process of step 402 plays a role corresponding to the reference output value calculation means in the claims.
[0058]
Thereafter, the process proceeds to step 404, and the pressure loss correction value Vpm corresponding to the pressure loss increase (ΔP-Pcat) due to the current PM deposition in the DPF 21 is calculated from the map. Then, the process proceeds to step 405, where the current atmospheric pressure Pa is set. The corresponding atmospheric pressure correction value Vatm is calculated from the map. Then, in the next step 406, the pressure loss correction value Vpm and the atmospheric pressure correction value Vatm are added to the reference output value Vbase to obtain a final reference output value Vstd (standard output value during atmospheric learning).
Vstd = Vbase + Vpm + Vatm
The processing in step 406 plays a role corresponding to the final reference output value calculation means in the claims.
[0059]
In the next step 407, the actual output value Vaf of the oxygen concentration detector 19 is read, and then the process proceeds to step 408, where the correction is made from the ratio between the final reference output value Vstd and the current output value Vaf of the oxygen concentration detector 19. The coefficient Flearn is calculated.
Flearn = Vstd / Vaf
[0060]
Thereafter, the process proceeds to step 409, where an average value of the correction coefficient Flearn calculated this time and the correction coefficient Flearn (i-1) calculated last time is calculated.
Flearn = {Flearn + Flearn (i-1)} / 2
[0061]
Thereafter, the process proceeds to step 410, and the stored value of the previous correction coefficient Learn (i-1) stored in the backup RAM of the ECU 29 is updated with the current correction coefficient Flearn averaged in step 409. The processing in these steps 408 to 410 plays a role corresponding to the correction coefficient learning means in the claims.
[0062]
The processes in steps 401 to 410 described above are repeatedly executed every 500 ms until the atmospheric learning permission flag EXL is reset to “0” to learn the correction coefficient Flearn. The correction coefficient Flearn learned in this way is stored in the backup RAM (rewritable nonvolatile memory) of the ECU 29, and the stored learning value of the correction coefficient Flearn is retained even after the engine is stopped (after the ignition switch is turned off). .
[0063]
[Oxygen concentration detector output correction routine]
The oxygen concentration detector output correction routine (step 500 in FIG. 3) shown in FIG. 7 is executed at every reading timing (for example, every 20 ° C. A) of the output value Vaf of the oxygen concentration detector 19, and is referred to in the claims. It plays a role corresponding to output value correction means.
[0064]
When this routine is started, first, at step 501, it is determined whether or not the atmospheric learning permission flag EXL is “0” meaning that atmospheric learning is prohibited. If the atmospheric learning permission flag EXL = 1 (atmospheric learning) If it is determined that (permitted), this routine is terminated.
[0065]
Thereafter, when it is determined that the atmospheric learning permission flag EXL = 0, that is, after the end of the atmospheric learning permission period, the process proceeds to step 502, and after reading the output value Vaf of the oxygen concentration detector 19, the process proceeds to step 503. The output value Vaf of the concentration detector 19 is multiplied by the correction coefficient Flearn to convert the output value Vaf of the oxygen concentration detector 19 into a true output value Vaf (true value) that does not include errors due to manufacturing variations and deterioration over time. .
Vaf (true value) = Vaf × Flearn
[0066]
Note that after the engine is started and before the first atmosphere learning is performed, the correction coefficient Learn learned during the previous engine operation is read from the backup RAM of the ECU 29, and the true output value Vaf (true) is read using the correction coefficient Flearn. Value).
In the next step 504, the true value output Vaf (true value) is converted into a physical value into an oxygen concentration.
[0067]
An execution example of the air learning control described above will be described based on the time chart of FIG. The forced atmospheric state control permission flag EXK is set to "1" at the time when the fuel is cut (t1 in FIG. 8) in the operating state where the engine speed NE is higher than the learning permission determination value (for example, 2000 rpm). As a result, the forced atmospheric state control is started and the EGR valve 26 is controlled to be fully opened (or in the valve opening direction) to forcibly reduce the exhaust pressure to quickly bring the exhaust pipe 16 close to the atmospheric pressure, and the throttle valve 13 is fully opened (or in the valve opening direction) to forcibly increase the amount of fresh air introduced to quickly bring the oxygen concentration in the exhaust pipe 16 close to the oxygen concentration in the atmosphere.
[0068]
Thereafter, when the elapsed time after the start of fuel cut (the elapsed time after the start of forced atmospheric state control) exceeds a predetermined delay time (for example, 5 seconds) (at t2 in FIG. 8), the atmosphere in the exhaust pipe 16 is in the atmospheric state. The oxygen concentration in the exhaust pipe 16 becomes almost equal to the oxygen concentration in the atmosphere, and it is determined that the oxygen concentration appears in the output value of the oxygen concentration detector 19, and the atmosphere learning permission flag EXL = 1 is set. To do. During the period when the atmosphere learning permission flag EXL = 1, the atmosphere learning was performed, and the oxygen concentration was detected using a reference oxygen concentration detector (a standard oxygen concentration detector free from manufacturing variations and deterioration over time). In this case, the final reference output value Vstd (= Vbase + Vpm + Vatm) is calculated, and the correction coefficient Flearn is calculated from the ratio between the final reference output value Vstd and the current output value Vaf of the oxygen concentration detector 19 and averaged for 500 ms. Repeat every time.
[0069]
Thereafter, when the fuel cut is completed and the fuel injection is restarted and the fuel injection amount Q> 0 (t3 in FIG. 8) or when the fuel cut occurs, the engine speed NE is determined to be a learning end determination value (for example, 1500 rpm). ), The forced atmospheric state control permission flag EXK is reset to “0” to end the forced atmospheric state control, and the atmospheric learning permission flag EXL is reset to “0” to end the atmospheric learning.
[0070]
After the atmospheric learning is completed, the output value Vaf of the oxygen concentration detector 19 is corrected to a true output value Vaf (true value) that does not include errors due to manufacturing variations and deterioration over time using the correction coefficient Flearn. (True value) is converted into a physical value to oxygen concentration.
[0071]
In the present embodiment described above, when atmospheric learning is performed, forced atmospheric state control is performed, and the state in the exhaust pipe 16 can be forcibly brought close to the atmospheric state (atmospheric oxygen concentration and atmospheric pressure). In addition, by learning the correction coefficient Flearn from the ratio between the final reference output value Vstd at the time of atmospheric learning and the actual output value Vaf of the oxygen concentration detector 19, the output value Vaf of the oxygen concentration detector 19 is Since the output value of the oxygen concentration detector as a reference, that is, the true output value Vaf (true value) that does not include errors due to manufacturing variations and deterioration over time, is corrected, the output value Vaf of the oxygen concentration detector 19 The relationship with the oxygen concentration can be accurately calibrated, and the oxygen concentration detection accuracy of the oxygen concentration detector 19 can be improved.
[0072]
Furthermore, in the present embodiment, since the air learning is permitted when the fuel is cut in the operating state where the engine speed is higher than the learning permission determination value (for example, 2000 rpm), the fuel cut time performs the air learning. Atmospheric learning can be started only when the fuel is cut at the engine speed that is estimated to ensure time.
[0073]
Instead of the engine rotation speed, atmospheric learning may be permitted during a fuel cut period in which the vehicle speed or gear position satisfies a predetermined condition. Or, two or three of the engine rotation speed, the vehicle speed, and the gear position may permit air learning during a fuel cut period that satisfies a predetermined condition.
[0074]
In the present embodiment, the reference oxygen concentration detector is installed in the reference exhaust system in advance, and the output characteristics of the reference oxygen concentration detector measured under the standard atmospheric pressure conditions are mapped to the ECU 29. Since it is stored in ROM and this map is searched during the atmospheric learning permission period, the reference output value Vbase corresponding to the operating state (engine speed NE and gear position) at the time of atmospheric learning is obtained. During the air learning, the reference output value Vbase corresponding to the driving state can be easily calculated.
[0075]
Further, in this embodiment, the final reference output value Vstd is corrected by correcting the reference output value Vbase during atmospheric learning using the pressure loss of the DPF 21 and the atmospheric pressure, which are the main parameters for changing the exhaust pressure, except in the operating state. Since it is obtained, the final reference output value Vstd can be obtained with high accuracy in consideration of the influence of the pressure loss increase (exhaust pressure increase) due to clogging of the DPF 21 and the exhaust pressure change due to the change in atmospheric pressure. Moreover, it is not necessary to use an exhaust pressure sensor, and the demand for cost reduction can be satisfied.
[0076]
However, in the present invention, an exhaust pressure sensor is installed in the exhaust pipe 16, and the reference output value Vbase at the time of atmospheric learning is corrected using the exhaust pressure detected by the exhaust pressure sensor to obtain the final reference output value Vstd. Even in this case, the intended object of the present invention can be sufficiently achieved.
[0077]
In the present embodiment, the change in the output value of the oxygen concentration detector 19 corresponding to the change in the exhaust pressure due to the difference between the atmospheric pressure during atmospheric learning and the standard atmospheric pressure (1 atm) is calculated as the atmospheric pressure correction value Vatm. At the same time, the change in the output value of the oxygen concentration detector 19 corresponding to the increase in exhaust pressure due to the increase in pressure loss (ΔP−Pcat) of the DPF 21 is calculated as the pressure loss correction value Vpm, and the reference output value Vbase during atmospheric learning is calculated. Is added to the pressure loss correction value Vpm and the atmospheric pressure correction value Vatm to obtain the final reference output value Vstd. As a map of correction coefficients for correcting the reference output value Vbase during atmospheric learning, Based on the experimental data or the like based on the experimental data or the like using the atmospheric pressure (or the differential pressure between the atmospheric pressure and the standard atmospheric pressure) and the pressure loss ΔP or the pressure loss increase (ΔP−Pcat) of the DPF 21 as parameters. Create Is stored in the ROM of the ECU 29, and a correction coefficient corresponding to the atmospheric pressure at the time of atmospheric learning and the pressure loss ΔP of the DPF 21 is calculated, and the reference output value Vbase at the time of atmospheric learning is corrected by this correction coefficient to obtain the final reference. The output value Vstd may be obtained.
[0078]
Further, the final reference output value Vstd may be obtained by correcting the reference output value Vbase at the time of atmospheric learning based on only one of the pressure loss of the DPF 21 and the atmospheric pressure.
[0079]
Further, in the present embodiment, the pressure loss Pcat (hereinafter referred to as “initial pressure loss Pcat”) of the DPF 21 without PM accumulation used for calculating the pressure loss correction value Vpm is a fixed value, but is shown in FIG. As described above, the initial pressure loss Pcat of the DPF 21 changes according to the exhaust gas flow rate. Therefore, the exhaust flow rate is estimated based on the temperature difference between the exhaust temperature detected by the exhaust temperature sensor 20 and the intake air temperature detected by the intake air temperature sensor 14 (a parameter indicating the degree of expansion of the intake air) and the intake air amount. 11, the initial pressure loss Pcat of the DPF 21 corresponding to the exhaust flow rate may be obtained using the relationship between the exhaust flow rate and the initial pressure loss Pcat of the DPF 21. In this way, the calculation accuracy of the pressure loss correction value Vpm can be improved, and the final reference output value Vstd during atmospheric learning can be obtained more accurately.
[0080]
Further, in this embodiment, the delay time provided from the start of fuel cut until the learning of the atmosphere is permitted is a fixed value, but this delay time is set according to at least one of the engine rotation speed, the vehicle speed, and the gear position. You may make it do. The time from when the fuel cut starts until the exhaust passage is filled with air and the oxygen concentration appears in the output value of the oxygen concentration detection value varies depending on the engine speed, vehicle speed, and gear position. If it is set according to the vehicle speed and the gear position, the optimum delay time according to the driving state at that time can be set.
[0081]
In the present embodiment, the EGR valve 26 and the throttle valve 13 are controlled to be fully opened (or in the valve opening direction) when the forced atmospheric state control is performed, but the valve timing of the intake valve and / or the exhaust valve is variable. In the case of an engine equipped with a variable valve timing adjustment mechanism (variable valve timing adjustment means) that performs the variable atmospheric timing control, in addition to the forced opening control of the EGR valve 26 and the throttle valve 13, the variable valve timing adjustment is performed. The mechanism may be controlled to forcibly increase the valve overlap amount of the intake valve and the exhaust valve. Alternatively, only one or two of the EGR valve 26, the throttle valve 13, and the variable valve timing adjustment mechanism may be controlled when the forced atmospheric state control is performed.
[0082]
In addition, the scope of application of the present invention is not limited to a diesel engine, and may be applied to a gasoline engine. In addition, as an exhaust purification means, various catalysts such as a three-way catalyst and a NOx catalyst are installed instead of a DPF. It can be implemented with various modifications.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention.
FIG. 2 is a functional block diagram showing a configuration of an atmosphere learning function of the ECU.
FIG. 3 is a flowchart showing a flow of processing of an atmospheric learning control base routine.
FIG. 4 is a flowchart showing a process flow of an atmospheric learning permission determination routine.
FIG. 5 is a flowchart showing a flow of processing of a forced atmospheric state control routine.
FIG. 6 is a flowchart showing the flow of the atmospheric learning routine process.
FIG. 7 is a flowchart showing the flow of processing of an oxygen concentration detector output correction routine.
FIG. 8 is a time chart showing an execution example of atmospheric learning control.
FIG. 9 is a diagram showing the relationship among the reference output value Vbase, the final reference output value Vstd, and the output value Vaf of the oxygen concentration detector during atmospheric learning.
FIG. 10 is a graph showing the relationship between the exhaust pressure and the output ratio of the oxygen concentration detector.
FIG. 11 is a diagram showing the relationship between the exhaust flow rate and the initial pressure loss of the DPF for explaining another embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Diesel engine (internal combustion engine), 12 ... Intake pipe, 13 ... Throttle valve, 15 ... Fuel injection valve, 16 ... Exhaust pipe (exhaust passage), 17 ... Oxygen concentration sensor, 18 ... Detection circuit, 19 ... Oxygen concentration detection 20 (exhaust temperature detection means), 20 ... exhaust temperature sensor, 21 ... DPF (exhaust gas purification means), 22 ... differential pressure sensor, 23 ... exhaust turbine, 24 ... intake turbine, 25 ... EGR piping, 26 ... EGR valve, 29 ... ECU (forced atmospheric state control means, atmosphere learning permission determination means, reference output value calculation means, final reference output value calculation means, correction coefficient learning means, output value correction means), 30 ... atmospheric pressure sensor.

Claims

An oxygen concentration detection means for detecting the oxygen concentration of exhaust gas flowing through the exhaust passage of the internal combustion engine, and the oxygen concentration detection means during a period in which the atmospheric state around the oxygen concentration detection means in the exhaust passage is substantially atmospheric. In the control device for an internal combustion engine that performs atmospheric learning to calibrate the relationship between the output value of the gas and the oxygen concentration,
A forced atmospheric state control means for controlling the exhaust pressure to approach the atmospheric pressure while forcibly bringing the oxygen concentration in the exhaust passage close to the atmospheric oxygen concentration when performing the air learning ;
The control device for an internal combustion engine, wherein the forced atmospheric state control means forcibly increases the exhaust gas flow rate from the exhaust passage to the intake passage to forcibly reduce the exhaust pressure.

2. The internal combustion engine control according to claim 1 , wherein the forced atmospheric state control means forcibly increases the amount of fresh air introduced into the exhaust passage by forcibly increasing the amount of intake air. 3. apparatus.

An oxygen concentration detection means for detecting the oxygen concentration of exhaust gas flowing through the exhaust passage of the internal combustion engine, and the oxygen concentration detection means during a period in which the atmospheric state around the oxygen concentration detection means in the exhaust passage is substantially atmospheric. In the control device for an internal combustion engine that performs atmospheric learning to calibrate the relationship between the output value of the gas and the oxygen concentration,
A forced atmospheric state control means for controlling the exhaust pressure to approach the atmospheric pressure while forcibly bringing the oxygen concentration in the exhaust passage close to the atmospheric oxygen concentration when performing the air learning;
The control apparatus for an internal combustion engine, wherein the forced atmospheric state control means forcibly increases the amount of fresh air introduced into the exhaust passage by forcibly increasing the amount of intake air.

Variable valve timing adjustment means for varying the opening and closing timing of the intake valve and / or the exhaust valve of the internal combustion engine,
The forced atmospheric state control means forcibly increases the amount of fresh air introduced into the exhaust passage by forcibly increasing the valve overlap amount of the intake valve and the exhaust valve by the valve timing adjusting means. The control device for an internal combustion engine according to any one of claims 1 to 3 .

An oxygen concentration detection means for detecting the oxygen concentration of exhaust gas flowing through the exhaust passage of the internal combustion engine, and the oxygen concentration detection means during a period in which the atmospheric state around the oxygen concentration detection means in the exhaust passage is substantially atmospheric. In the control device for an internal combustion engine that performs atmospheric learning to calibrate the relationship between the output value of the gas and the oxygen concentration,
A forced atmospheric state control means for controlling the exhaust pressure to approach the atmospheric pressure while forcibly bringing the oxygen concentration in the exhaust passage close to the atmospheric oxygen concentration when performing the air learning;
Variable valve timing adjustment means for varying the opening and closing timing of the intake valve and / or the exhaust valve of the internal combustion engine,
The forced atmospheric state control means forcibly increases the amount of fresh air introduced into the exhaust passage by forcibly increasing the valve overlap amount of the intake valve and the exhaust valve by the valve timing adjusting means. A control device for an internal combustion engine.

An oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas flowing through the exhaust passage of the internal combustion engine is provided, and atmospheric learning is performed to calibrate the relationship between the output value of the oxygen concentration detection means and the oxygen concentration at a predetermined time. In the internal combustion engine control apparatus,
Atmospheric learning permission determining means for allowing the atmospheric learning when it is determined that the oxygen concentration around the oxygen concentration detecting means in the exhaust passage is substantially equal to the oxygen concentration of the atmosphere based on the operating state of the internal combustion engine, and the like;
A reference output value calculating means for obtaining a reference output value corresponding to an operating state at the time of air learning based on an output characteristic of an oxygen concentration detecting means that is a reference set in advance in the permission period of the air learning;
A final reference output value calculating means for correcting the reference output value using an exhaust pressure at the time of atmospheric learning or a parameter that changes the exhaust pressure during the atmospheric learning permission period to obtain a final reference output value;
A correction coefficient for learning a correction coefficient for correcting the output value of the oxygen concentration detection means by comparing the output value of the oxygen concentration detection means and the final reference output value at the time of atmospheric learning during the atmospheric learning permission period Learning means,
Output value correcting means for detecting the oxygen concentration of the exhaust gas by correcting the output value of the oxygen concentration detecting means with the correction coefficient during operation of the internal combustion engine ,
The atmosphere learning permission determination means is configured to determine whether at least one of the engine rotational speed, the vehicle speed, and the transmission gear position satisfies a predetermined condition during a fuel cut period and a predetermined delay time has elapsed since the start of fuel cut. A control device for an internal combustion engine, which permits atmospheric learning .

The control apparatus for an internal combustion engine according to claim 6 , wherein the air learning permission determination means sets the delay time according to at least one of an engine rotation speed, a vehicle speed, and a transmission gear position.

As the reference oxygen concentration detecting means, a standard oxygen concentration detecting means having a central characteristic of manufacturing variation is used, and this standard oxygen concentration detecting means is previously used as a standard having a central characteristic of manufacturing variation. Standard oxygen concentration detection that is installed in an exhaust passage provided with a simple exhaust purification means, and is measured in a state where there is no increase in pressure loss due to clogging of the exhaust purification means and the inside of the exhaust passage is in a standard atmospheric pressure state Providing storage means for storing the output characteristics of the means;
The control apparatus for an internal combustion engine according to claim 6 or 7 , wherein the reference output value calculation means obtains the reference output value by using the output characteristics stored in the storage means.

An oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas flowing through the exhaust passage of the internal combustion engine is provided, and atmospheric learning is performed to calibrate the relationship between the output value of the oxygen concentration detection means and the oxygen concentration at a predetermined time. In the internal combustion engine control apparatus,
Atmospheric learning permission determining means for allowing the atmospheric learning when it is determined that the oxygen concentration around the oxygen concentration detecting means in the exhaust passage is substantially equal to the oxygen concentration of the atmosphere based on the operating state of the internal combustion engine, and the like;
A reference output value calculating means for obtaining a reference output value corresponding to an operating state at the time of air learning based on an output characteristic of an oxygen concentration detecting means that is a reference set in advance in the permission period of the air learning;
A final reference output value calculating means for correcting the reference output value using an exhaust pressure at the time of atmospheric learning or a parameter that changes the exhaust pressure during the atmospheric learning permission period to obtain a final reference output value;
A correction coefficient for learning a correction coefficient for correcting the output value of the oxygen concentration detection means by comparing the output value of the oxygen concentration detection means and the final reference output value at the time of atmospheric learning during the atmospheric learning permission period Learning means,
Output value correcting means for detecting the oxygen concentration of the exhaust gas by correcting the output value of the oxygen concentration detecting means with the correction coefficient during operation of the internal combustion engine,
As the reference oxygen concentration detecting means, a standard oxygen concentration detecting means having a central characteristic of manufacturing variation is used, and this standard oxygen concentration detecting means is previously used as a standard having a central characteristic of manufacturing variation. Standard oxygen concentration detection that is installed in an exhaust passage provided with a simple exhaust purification means, and is measured in a state where there is no increase in pressure loss due to clogging of the exhaust purification means and the inside of the exhaust passage is in a standard atmospheric pressure state Providing storage means for storing the output characteristics of the means;
The control apparatus for an internal combustion engine, wherein the reference output value calculation means obtains the reference output value using the output characteristics stored in the storage means.

The final reference output value calculation means corrects the reference output value using the atmospheric pressure during atmospheric learning and / or the pressure loss of the exhaust purification means provided in the exhaust passage as a parameter for changing the exhaust pressure. The control device for an internal combustion engine according to any one of claims 6 to 9.

An oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas flowing through the exhaust passage of the internal combustion engine is provided, and atmospheric learning is performed to calibrate the relationship between the output value of the oxygen concentration detection means and the oxygen concentration at a predetermined time. In the internal combustion engine control apparatus,
Atmospheric learning permission determining means for allowing the atmospheric learning when it is determined that the oxygen concentration around the oxygen concentration detecting means in the exhaust passage is substantially equal to the oxygen concentration of the atmosphere based on the operating state of the internal combustion engine, and the like;
A reference output value calculating means for obtaining a reference output value corresponding to an operating state at the time of air learning based on an output characteristic of an oxygen concentration detecting means that is a reference set in advance in the permission period of the air learning;
A final reference output value calculating means for correcting the reference output value using an exhaust pressure at the time of atmospheric learning or a parameter that changes the exhaust pressure during the atmospheric learning permission period to obtain a final reference output value;
A correction coefficient for learning a correction coefficient for correcting the output value of the oxygen concentration detection means by comparing the output value of the oxygen concentration detection means and the final reference output value at the time of atmospheric learning during the atmospheric learning permission period Learning means,
Output value correcting means for detecting the oxygen concentration of the exhaust gas by correcting the output value of the oxygen concentration detecting means with the correction coefficient during operation of the internal combustion engine,
The final reference output value calculating means corrects the reference output value by using atmospheric pressure during atmosphere learning and / or pressure loss of the exhaust purification means provided in the exhaust passage as a parameter for changing the exhaust pressure. A control device for an internal combustion engine.

The final reference output value calculation means includes a change in the output value of the oxygen concentration detection means corresponding to a difference in exhaust pressure due to a difference between the atmospheric pressure and the standard atmospheric pressure during atmospheric learning and / or clogging of the exhaust purification means. Calculating an output value change of the oxygen concentration detecting means corresponding to an increase in exhaust pressure caused by an increase in pressure loss due to, etc., and obtaining the final reference output value by correcting the reference output value by the output value change The control apparatus for an internal combustion engine according to claim 10 or 11 , characterized in that: