JP4169237B2 - Exhaust gas recirculation control device for internal combustion engine - Google Patents
Exhaust gas recirculation control device for internal combustion engine Download PDFInfo
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- JP4169237B2 JP4169237B2 JP2000182540A JP2000182540A JP4169237B2 JP 4169237 B2 JP4169237 B2 JP 4169237B2 JP 2000182540 A JP2000182540 A JP 2000182540A JP 2000182540 A JP2000182540 A JP 2000182540A JP 4169237 B2 JP4169237 B2 JP 4169237B2
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- exhaust gas
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- combustion engine
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/02—EGR systems specially adapted for supercharged engines
- F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
- F02M26/05—High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/02—EGR systems specially adapted for supercharged engines
- F02M26/09—Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine
- F02M26/10—Constructional details, e.g. structural combinations of EGR systems and supercharger systems; Arrangement of the EGR and supercharger systems with respect to the engine having means to increase the pressure difference between the exhaust and intake system, e.g. venturis, variable geometry turbines, check valves using pressure pulsations or throttles in the air intake or exhaust system
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
- F02M26/17—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories in relation to the intake system
- F02M26/19—Means for improving the mixing of air and recirculated exhaust gases, e.g. venturis or multiple openings to the intake system
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Landscapes
- Supercharger (AREA)
- Exhaust-Gas Circulating Devices (AREA)
- Output Control And Ontrol Of Special Type Engine (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
Description
【0001】
【発明の属する技術分野】
本発明は、内燃機関の排気再循環制御装置に関する。
【0002】
【従来の技術】
環境保全の見地から、内燃機関の排出する有害物質に対する規制強化が各地で進んでいる昨今、内燃機関の排気に含まれる有害物質を低減させる方法として排気再循環(通称EGR)が広く知られ、用いられている。燃焼室から排出される排気の一部を排気マニホルドから吸気マニホルドへ還流し吸気に混合させて再度燃焼室に送り込むことで、燃焼を緩慢にし、燃焼最高温度を下げる作用があり、排気に含まれる有害物質特に窒素酸化物(以下NOXと略記)の発生を抑える効果が大きい。
【0003】
図8に従来の形態として、実開平6−1759号公報に記載された、排気再循環装置を有するターボチャージャー付エンジン114の給排気回路図を示す。エンジン114は、ターボチャージャー111と、吸気回路112と、コントローラ113と、排気再循環回路115と、排気回路116とを有する。ターボチャージャー111のコンプレッサ111aで圧縮された吸気は吸気回路112を経てエンジン本体114aに導入される。エンジン本体114aから排出された排気は排気回路116を経てターボチャージャー111に流れ込み、タービン111bを駆動して排出される。
排気再循環回路115は、一端を排気回路116のタービン111bの上流側に分岐接続され、他端を吸気回路112のコンプレッサ111aの下流側に分岐接続される。排気再循環回路115中には、第1アクチュエータ115aによって駆動され排気再循環回路115を開閉自在とするEGR弁115cが設けられている。
吸気回路112には、吸気バイパス回路112aと、第2アクチュエータ112bによって駆動されこの吸気バイパス回路112aへの吸気の流入を選択自在とする三方弁112cとが設けられている。吸気バイパス回路112aにはベンチュリ112dが設けられ、このベンチュリ112dの狭隘部112eに前記排気再循環回路115が接続している。
【0004】
排気の還流を行うとき、コントローラ113は第1アクチュエータ115aを駆動してEGR弁115cを開く。しかし、タービン111b入口の圧力がコンプレッサ111a出口の圧力よりも低い場合にはEGR弁115cを開くだけでは排気を還流できない。そこで図示しない検出手段によりタービン111b入口の圧力がコンプレッサ111a出口の圧力よりも低いことを検出すると、コントローラ113が第2アクチュエータ112bを駆動して三方弁112cを切換え、吸気の大部分を吸気バイパス回路112aに流す。するとベンチュリ112dの狭隘部112eで流速が高まり局所的に圧力が下がるので、タービン111b入口の圧力がコンプレッサ111a出口の圧力よりも低くとも、排気の還流が可能となりNOXの発生を抑えられる。
【0005】
【発明が解決しようとする課題】
しかし、上記従来技術には以下の問題がある。
従来技術のベンチュリ付排気還流システムでは、エンジンの運転条件が変わった場合に不都合が生じる。例えば、急加速時はターボラグのため吸入空気量が過渡的に不足する上に、タービン111b入口の圧力がコンプレッサ111a出口の圧力よりも過渡的に高くなって還流する排気の流量が増大するため、燃焼が緩慢になり、黒煙の排出量が増加するとともに加速性が悪化する。また、エンジン劣化や気圧の変化などによってNOXまたは黒煙の排出量が増加した場合、これを補正するように排気の還流を制御する機能がないので、こういった排気成分の悪化を救済することができない。
【0006】
本発明は、上記の問題点を解決すべくなされたものであり、NOXの排出量、黒煙の排出量、エンジン出力及び燃費のバランスを考慮して排気の還流の制御を行う内燃機関の排気再循環制御装置を提供することを目的としている。
【0007】
【課題を解決するための手段、作用及び効果】
上記の目的を達成するために、本発明は、吸気回路上に配したコンプレッサと排気回路上に配したタービンとを有するターボチャージャと、排気回路のタービン−内燃機関本体間と吸気回路のコンプレッサ−内燃機関本体間とを接続して第1開閉弁によって開閉自在とした排気再循環回路とを設けるとともに、コンプレッサ−内燃機関本体間の吸気の流れを絞る狭隘部を有する絞りを吸気回路に設けて排気再循環回路の接続位置をこの狭隘部略中央とし、この絞りの直上流と直下流とをバイパス接続するとともに第2開閉弁によって開閉自在とされる吸気バイパス回路を設けた内燃機関の排気再循環制御装置において、
回転速度、負荷、排気中のNOX濃度及び排気中の酸素濃度を検出する検出手段と、
内燃機関の回転速度及び負荷に対する目標の空燃比及び排気中のNOX濃度を予め記憶する記憶手段と、
検出手段の検出した酸素濃度から空燃比を求め、この空燃比及び検出手段の検出する排気中のNOX濃度を前記記憶手段の記憶するそれぞれの目標値に近づけるように前記第1開閉弁及び前記第2開閉弁の開度を微調整する制御を行う制御手段とを設けたことを特徴とする。
【0008】
上記構成によれば、排気中のNOX濃度と排気中の酸素濃度との両方の値をフィードバックして内燃機関の回転速度と負荷とに対するNOX濃度及び空燃比の目標値に近づけるように、第1開閉弁と第2開閉弁との開度を制御することによりエンジンの運転状態に最適な値となるようにEGR率を制御できるので、NOXと黒煙との両方の排出量を内燃機関の回転速度と負荷とに応じてバランスよく低減できる。さらに、内燃機関の回転速度と負荷とに対するNOXと黒煙との排出量が内燃機関の劣化や気圧の変化などにより変動しても、上記フィードバック制御によりこれらの変動を補正する制御ができる。
【0009】
また本発明は、吸気回路上に配したコンプレッサと排気回路上に配したタービンとを有するターボチャージャと、排気回路のタービン−内燃機関本体間と吸気回路のコンプレッサ−内燃機関本体間とを接続して第1開閉弁によって開閉自在とした排気再循環回路とを設けるとともに、コンプレッサ−内燃機関本体間の吸気の流れを絞る狭隘部を有する絞りを吸気回路に設けて排気再循環回路の接続位置をこの狭隘部略中央とし、この絞りの直上流と直下流とをバイパス接続するとともに第2開閉弁によって開閉自在とされる吸気バイパス回路を設けた内燃機関の排気再循環制御装置において、
回転速度、負荷、排気中のNOX濃度及び排気中の酸素濃度を検出する検出手段と、
内燃機関の回転速度及び負荷に対する目標の、前記第1開閉弁の開度、前記第2開閉弁の開度、空燃比及び排気中のNOX濃度を予め記憶する記憶手段と、
前記検出手段の検出した回転速度及び負荷に対する前記記憶手段の記憶する目標の開度となるように前記第1開閉弁及び前記第2開閉弁の開度を制御するとともに、検出手段の検出した排気中の酸素濃度から空燃比を求め、この空燃比及び検出手段の検出する排気中のNOX濃度を前記記憶手段の記憶するそれぞれの目標値に近づけるように前記第1開閉弁及び前記第2開閉弁の開度を微調整する制御を行う制御手段とを設けても良い。
【0010】
上記構成によれば、内燃機関の回転速度と負荷とに対する目標の第1開閉弁と第2開閉弁との開度を初期設定するとともに、排気中のNOX濃度と排気中の酸素濃度との両方の値をフィードバックして内燃機関の回転速度と負荷とに対するNOX濃度及び空燃比の目標値に近づけるように、第1開閉弁と第2開閉弁との開度を制御することになる。第1開閉弁と第2開閉弁との開度を初期設定することにより、内燃機関の回転速度と負荷との変動に対する制御系の応答性が向上する。
【0015】
加えて、上記第1又は第2発明の内燃機関の排気再循環制御装置において、前記制御手段は、前記検出手段の検出した運転状態から急加速中と判断したときに、前記第1開閉弁を閉じる制御を行ってもよい。
【0016】
上記構成によれば、急加速時に排気の還流を中止することで、排気の還流による吸気中の酸素濃度の低下を避け、急加速時における出力の低下と排気中の黒煙増加とを防止できる。
【0017】
【発明の実施の形態】
以下、本発明の第1実施形態について、図1、図2を参照して説明する。
図1に第1実施形態の排気再循環装置を有するターボチャージャー付エンジン14の給排気回路図を示す。エンジン14は、ターボチャージャー11と、吸気回路12と、コントローラ13と、排気再循環回路15と、排気回路16とを有する。ターボチャージャー11のコンプレッサ11aで圧縮された吸気は吸気回路12を経てエンジン本体14aに導入される。エンジン本体14aから排出された排気は排気回路16を経てターボチャージャー11に流れ込み、タービン11bを駆動して排出される。
【0018】
排気再循環回路15は、一端を排気回路16の排気マニホルド16a近傍に分岐接続され、他端を吸気回路12の吸気マニホルド12a近傍に分岐接続される。排気再循環回路15中には、図示しないアクチュエータ15aによって駆動され排気再循環回路15を開閉自在とするEGR弁15cが設けられている。EGR弁15cの開度が増加するほど還流する排気の流量は増加し、すなわちEGR率も増加する。
吸気回路12には、ベンチュリ12bと、このベンチュリ12bの直上流と直下流とをバイパス接続する吸気バイパス回路12cと、図示しないアクチュエータによって駆動されこの吸気バイパス回路12cを開閉自在とする吸気バイパス弁12dとが設けられている。ベンチュリ12bの狭隘部にはベンチュリ12b内の上流から下流への流れに合流する接続口が設けられ、この接続口に排気再循環回路15が分岐接続している。吸気バイパス弁12dを絞ると吸気バイパス回路12cの通過流量が減少し、その分ベンチュリ12bの通過流量が増大するので、狭隘部の流速が増大して圧力が下がり、還流する排気の流量は増加し、すなわちEGR率も増加する。
吸気回路12のコンプレッサ11a出口近傍と排気回路16のタービン11b入口近傍との間には、これらを連通する給排気バイパス回路20が設けられ、給排気バイパス回路20には、これを吸気回路12側から排気回路16側への一方向のみ導通自在とする逆止弁20aが設けられている。
【0019】
エンジン14は更に、エンジン14の回転速度を検出する回転速度センサ31a、エンジン14の冷却水の水温を検出する水温センサ31b、出力トルクを検出するトルクメータ31c、排気中の酸素濃度を検出する排気酸素濃度センサ31d、及び排気中のNOX濃度を検出するNOXセンサ31eなどといったエンジン14の運転状態を検出する検出手段31を有する。また、吸気バイパス弁12dの開度の目標値BT、EGR弁15cの開度の目標値ET、NOX濃度の目標値NOXT及び空燃比の目標値RT(A/F)を制御マップとして記憶した記憶手段32を有し、検出手段31の検出した各状態に応じた検出信号と記憶手段32に記憶された制御マップの各目標値データとを入力して後述する演算処理を行い、吸気バイパス弁12d及びEGR弁15cの開度を制御する制御部33を有する。
なお、前記制御マップは、検出手段31が検出する回転速度Nを横の座標、出力トルクTを縦の座標とする座標平面を設定し、この座標平面を格子状に細分し、細分した各領域毎に前記の各目標値を設定するように構成されている。したがって、回転速度及び出力トルクの値が定まれば、これらに対応する前記の各目標値が前記制御マップから一義的に決まる。
【0020】
第1実施形態における制御部33の処理手順を図2に示す制御フローチャート例に基づいて説明する。初期状態となるステップS1では、EGR弁15cは完全に閉じられ、吸気バイパス弁12dは完全に開ききっている。まず制御部33は、ステップS2で、記憶手段32が記憶する制御マップ上において回転速度センサ31aが検出した回転速度Nとトルクメータ31cが検出した出力トルクTとから選択される目標の開度になるように、EGR弁15cを開き吸気バイパス弁12dを閉じる制御を行う。これにより吸気バイパス弁12dの開度は前記目標値BTとなり、EGR弁15cの開度は前記目標値ETとなる。
次にステップS3で、記憶手段32が記憶する制御マップ上において回転速度センサ31aが検出した回転速度N及びトルクメータ31cが検出した出力トルクTに基づいて選択した目標のNOX濃度NOXTと、NOXセンサ31eが検出したNOX濃度NOXOとを比較し、数式「NOXO≧NOXT」が真ならばステップS4へ移行し、偽ならばステップS6へ移行する。
【0021】
ステップS4では、記憶手段32が記憶する制御マップ上において回転速度センサ31aが検出した回転速度N及びトルクメータ31cが検出した出力トルクTから選択した目標の空燃比RT(A/F)と、排気酸素濃度センサ31dが検出した排気中の酸素濃度から算定した空燃比RO(A/F)とを比較し、数式「RO(A/F)≧RT(A/F)」が真ならばステップS5へ移行する。ステップS5ではEGR弁15cの開度を所定値ΔE1だけ増加させるとともに吸気バイパス弁12dの開度を所定値ΔB1だけ減少させ、すなわちEGR率を増加させてステップS3へ戻る。数式「RO(A/F)≧RT(A/F)」が偽ならばステップS7へ移行する。
ステップS6では、記憶手段32が記憶する制御マップ上において回転速度センサ31aが検出した回転速度N及びトルクメータ31cが検出した出力トルクTから選択した目標の空燃比RT(A/F)と、排気酸素濃度センサ31dが検出した排気中の酸素濃度から算定した空燃比RO(A/F)とを比較し、数式「RO(A/F)≧RT(A/F)」が偽ならばステップS8へ移行する。ステップS8では、EGR弁15cの開度を所定値ΔE2だけ減少させるとともに吸気バイパス弁12dの開度を所定値ΔB2だけ増加させ、すなわちEGR率を減少させてステップS3へ戻る。前記ステップS6で数式「RO(A/F)≧RT(A/F)」が真ならばステップS7へ移行する。
ステップS7ではEGR弁15c及び吸気バイパス弁12dの開度を現在値のまま、所定時間保持し、この経過後、S3に戻って以上の処理を繰り返す。
なお、上記処理で、微小開度制御量ΔE1とΔE2、及びΔB1とΔB2は等しい値でも異なった値でもよい。
【0022】
第1実施形態によれば、以上の制御フローチャートにより、まずEGR弁15c及び吸気バイパス弁12dの開度を、エンジン14の回転速度Nと出力トルクTとに対する目標値となるように制御する。通常の運転条件ならば、これだけでもエンジン14の運転状態に最適な値となるようにEGR率を制御できる。さらに排気中のNOX濃度NOXOと空燃比RO(A/F)との両方の値をフィードバックしてエンジン14の回転速度Nと出力トルクTとに対する目標値に近づけるように制御する。これにより、エンジン14の劣化や気圧の変化などによるNOXと黒煙との排出量の変化を補正するようにEGR率を制御できる。したがって、NOXと黒煙との両方の排出量をエンジン14の回転速度と負荷とに応じてバランスよく低減できる。
【0023】
本発明の参考例1として、図3、図4を参照して説明する。図3に参考例1の排気再循環装置を有するターボチャージャー付エンジン14の給排気回路図を示す。第1実施形態との相違は、NOX濃度の替わりにEGR率を状態量として用いることである。このためNOXセンサ31eの替わりに吸気中の酸素濃度を検出する吸気酸素濃度センサ31gを有する。また、記憶手段32の替わりに記憶手段32aを有しており、この記憶手段32aは吸気バイパス弁12dの開度の目標値BT、EGR弁15cの開度の目標値ET、EGR率の目標値EGRT及び空燃比の目標値RT(A/F)を、第1実施形態と同様に制御マップとして記憶する。他のハード構成については第1実施形態と同様である。
【0024】
ここで、実際のEGR率EGROは、排気酸素濃度センサ31dで検出した排気中の酸素濃度と吸気酸素濃度センサ31gで検出した吸気中の酸素濃度とから一義的に求められる。運転状態が決まれば、目標となるNOX排出量NOXTに対応するEGR率EGRTは、一義的に決まるので、EGR率でNOX濃度の代用ができる。したがって参考例1の上記構成によって第1実施形態と等価の制御ができる。
【0025】
参考例1における制御部33の処理手順について、図4に示す制御フローチャートに基づいて説明する。ステップS1及びステップS2の処理までは第1実施形態と同様である(記憶手段32は記憶手段32aに置き換える)。次にステップS2からステップS3aに進み、記憶手段32aが記憶する制御マップ上において回転速度センサ31aが検出した回転速度N及びトルクメータ31cが検出した出力トルクTに基づいて選択した目標のEGR率EGRTと、実際のEGR率EGROとを比較し、数式「EGRO≧EGRT」が真ならばステップS4へ移行し、偽ならばステップS6へ移行する。この先の制御フローチャートは、第1実施形態と同様である(記憶手段32は記憶手段32aに置き換える)。
【0026】
参考例1によれば、以上の制御フローチャートにより、まずEGR弁15c及び吸気バイパス弁12dの開度を、エンジン14の回転速度Nと出力トルクTとに対する目標値となるように制御する。さらに吸気中の酸素濃度及び排気中の酸素濃度から算定したEGR率EGROと排気中の酸素濃度から算定した空燃比RO(A/F)との両方の値をフィードバックしてエンジン14の回転速度Nと出力トルクTとに対する目標のEGR率EGRT及び空燃比RT(A/F)の値に近づけるように制御する。これにより、エンジン14の運転状態に最適な値となるようにEGR率を制御する。したがって、第1実施形態の効果に加えて、NOX濃度を直接検出する必要がなく、これをEGR率で代用するので、高価なNOXセンサ31eが不要になり、製造コストを低減できる。
【0027】
本発明の第2実施形態について、図5を参照して説明する。第1実施形態または参考例1との相違は、暖機運転時及び急加速時に排気の還流を停止する制御が加わることであり、ハード構成については第1実施形態または参考例1と同一である。
【0028】
第2実施形態における制御部33の処理手順について、図5に示す制御フローチャートに基づいて説明する。ステップS1及びステップS2の処理までは第1実施形態または参考例1と同様であり、ステップS2からはステップS9へ移行する。ステップS9では、予め設定した温度値TTと水温センサ31bが検出した冷却水の水温TOとを比較し、数式「TO≦TT」が真ならばステップS12へ移行する。ステップS12ではEGR弁15cを閉じ切るとともに吸気バイパス弁12dを開き切り、すなわちEGR率をゼロにしてステップS9へ戻る。前記ステップS9で数式「TO≦TT」が偽ならばステップS10へ移行する。ステップS10では、予め設定されたエンジンの回転速度の単位時間当りの増加量dNTと、回転速度センサ31aが検出した実際の回転速度Nより得られるエンジンの回転速度の単位時間当り増加量dNOとを比較し、数式「dNO≧dNT」が真ならばステップS13へ移行する。ステップS13ではEGR弁15cを閉じ切るとともに吸気バイパス弁12dを開き切り、すなわちEGR率をゼロにしてステップS10へ戻る。前記ステップS10で数式「dNO≧dNT」が偽ならばステップS11へ移行する。ステップS11ではEGR弁15c及び吸気バイパス弁12dの開度を現在値のまま、所定時間保持し、この経過後ステップS3またはステップS3aへ移行する。この先の制御フローチャートは、第1実施形態または参考例1と同様であり、ステップS5,S7及びS8の処理後はステップS9に戻って以上の処理を繰り返す。
【0029】
第2実施形態によれば、第1実施形態または参考例1の制御に加えて以下の制御を行う。
(1)エンジン14の回転速度の単位時間当りの増加量dNOが所定値dNT以上の場合、EGR率をゼロにして排気の還流を停止する。
(2)エンジン14の冷却水の水温TOが所定値TT以下の場合、EGR率をゼロにして排気の還流を停止する。
したがって第1実施形態または参考例1の効果に加えて、以下の効果が得られる。
(1)エンジン14の回転速度の単位時間当りの増加量dNOが所定値dNT以上の場合すなわち加速時に、排気の還流で吸気中の酸素濃度が低下することによる出力低下と不完全燃焼とを避けられる。したがって、加速時の出力低下を防止して加速性を向上できるとともに、不完全燃焼を防止して黒煙の発生をも抑えられる。
(2)エンジン14の冷却水の水温TOが所定値TT以下の場合すなわち寒冷時に排気の還流を行うと、排気中の水蒸気が排気再循環回路15中で凝結して水になり、各部の腐食作用を招く。特に排気再循環回路15中にEGRクーラが設けてあれば水の凝結量が増え、腐食作用が顕著になる。したがって、寒冷時の排気再循環回路15中での水の凝結を抑えることで、エンジン14各部の腐食を防止できる。
【0030】
本発明の参考例2について、図6、図7を参照して説明する。参考例2は、第2実施形態における加速時に排気の還流を停止する制御処理を、ルーツ形に代表される容積形スーパチャージャで加速時に過給を行う制御処理に置き換えたものである。したがって説明は第2実施形態と相違する箇所に限り、重複する箇所については省略する。図6に参考例2の、排気再循環装置を有するターボチャージャー付エンジン14の給排気回路図を示す。吸気回路12のコンプレッサ11aの直上流に、制御部33からの指令により起動停止自在なスーパチャージャ40と、このスーパチャージャ40の直上流とこのスーパチャージャ40の直下流すなわちコンプレッサ11aの直上流とをバイパスする逆止弁41とが設けられている。制御部33からの指令によりスーパチャージャ40を起動すると、コンプレッサ11aに導入される吸気に過給圧力を与えることができる。スーパチャージャ40を停止しているときは、吸気は逆止弁41を通ってコンプレッサ11aに導入される。
【0031】
参考例2における制御部33の処理手順について、図7に示す制御フローチャートに基づいて説明する。第2実施形態との相違は、ステップS11及びS13の制御処理を、以下に説明するステップS11a及びS13aの制御処理に置き換えたことである。ステップS10では、予め設定されたエンジンの回転速度の単位時間当りの増加量dNTと、回転速度センサ31aが検出した実際の回転速度より得られるエンジンの回転速度の単位時間当り増加量dNOとを第2実施形態と同様に比較する。そして数式「dNO≧dNT」が真ならばステップS13aへ移行する。ステップS13aではスーパチャージャ40を起動してステップS10へ戻る。前記ステップS10で数式「dNO≧dNT」が偽ならばステップS11aへ移行する。ステップS11aではスーパチャージャ40を停止して、ステップS3またはS3aへ移行する。この先の制御フローチャートは、第1実施形態または参考例1と同様であり、ステップS5,S7,S8の処理後はステップS9に戻って以上の処理を繰り返す。
【0032】
参考例2によれば、第1実施形態または参考例1の制御に加えて、以下の制御を行う。
(1)エンジン14の回転速度の単位時間当りの増加量dNOが所定値dNT以上の場合、スーパチャージャ40を起動して過給を行う。
(2)エンジン14の冷却水の水温TOが所定値TT以下の場合、EGR率をゼロにして排気の還流を停止する。
したがって、第1実施形態または参考例1の効果に加えて、以下の効果が得られる。
(1)エンジン14の回転速度の単位時間当りの増加量dNOが所定値dNT以上の場合すなわち加速時に、スーパチャージャ40の過給作用で、排気の還流による吸気中の酸素濃度の低下を補い、出力の低下と不完全燃焼とを防止できる。したがって、排気の還流を停止することなく加速時の出力低下を防止して加速性を向上できるとともに黒煙の発生も抑えられる。
(2)エンジン14の冷却水の水温TOが所定値TT以下の場合すなわち寒冷時に排気の還流を行うと、排気中の水蒸気が排気再循環回路15中で凝結して水になり、各部の腐食作用を招く。特に排気再循環回路15中にEGRクーラが設けてあれば水の凝結量が増え、腐食作用が顕著になる。したがって、寒冷時の排気再循環回路15中での水の凝結を抑えることで、エンジン14各部の腐食を防止できる。
【0033】
なお、本発明は以上に例示した実施形態に限定されるものではない。
例えば前述の給排気バイパス回路20は、吸気の一部を排気回路16に逃がすことで吸気回路12の圧力を下げるとともに排気回路16の圧力を上げて排気の還流を容易にするものであり、本発明にとって必須の構成要件ではない。
また、エンジン14の負荷に相当する状態量として、出力トルクTの替わりに例えば燃料噴射量を用いてもよい。燃料噴射量の検出方法としては、燃料の流量を直接測定してもよいし、コントロールラックの位置から求めてもよい。
さらに、EGR率を求める方法として、例えば吸気中の二酸化炭素濃度と排気中の二酸化炭素濃度とをそれぞれセンサを設けて検出し、各々の二酸化炭素濃度の比率からEGR率を求める方法を用いてもよい。また空燃比を求める他の方法として、吸気流量を直接測定、または吸気回路の圧力及び温度からの演算によって求めるとともに、燃料流量を直接測定、またはコントロールラックの位置からの演算によって求め、この吸気流量と燃料流量とから空燃比を求める方法をとってもよい。
加えて各実施形態の制御フローチャートにおいて、ステップS2の処理を省略し、ステップS1から次のステップに移行する制御を行ってもよい。
【0034】
以上実施形態を例示して説明した通り、本発明によれば、以下の効果が得られる。
(1)排気中のNOX濃度と空燃比との両方の値をフィードバックしてエンジンの回転速度と負荷とに対する目標値に近づけるように、第1開閉弁と吸気バイパス弁との開度を制御することでEGR率を制御している。したがって、NOXと黒煙との両方の排出量をエンジンの回転速度と負荷とに応じてバランスよく低減できる。しかも、エンジンの劣化や気圧の変化などによってNOXと黒煙との排出量が変化しても、この変化を補正して排出量を低減するようにEGR率を制御できる。
(2)急加速時に排気の還流を中止することで、排気の還流による吸気中の酸素濃度の低下を避け、急加速時における出力の低下と排気中の黒煙増加とを防止できる。
【図面の簡単な説明】
【図1】本発明の第1実施形態の給排気回路図である。
【図2】本発明の第1実施形態の制御フローチャート例である。
【図3】本発明の参考例1の給排気回路図である。
【図4】本発明の参考例1の制御フローチャート例である。
【図5】本発明の第2実施形態の制御フローチャート例である。
【図6】本発明の参考例2の給排気回路図である。
【図7】本発明の参考例2の制御フローチャート例である。
【図8】従来技術の給排気回路図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas recirculation control device for an internal combustion engine.
[0002]
[Prior art]
From the standpoint of environmental conservation, regulations on harmful substances emitted by internal combustion engines have been tightened in various places in recent years, and exhaust gas recirculation (commonly known as EGR) is widely known as a method for reducing harmful substances contained in exhaust gas from internal combustion engines. It is used. A part of the exhaust discharged from the combustion chamber is recirculated from the exhaust manifold to the intake manifold, mixed with the intake air, and sent to the combustion chamber again, thereby slowing the combustion and lowering the maximum combustion temperature. The effect of suppressing the generation of harmful substances, particularly nitrogen oxides (hereinafter abbreviated as NO X ) is great.
[0003]
FIG. 8 shows a supply / exhaust circuit diagram of a turbocharged engine 114 having an exhaust gas recirculation device described in Japanese Utility Model Laid-Open No. 6-1759 as a conventional form. The engine 114 includes a turbocharger 111, an intake circuit 112, a controller 113, an exhaust gas recirculation circuit 115, and an exhaust circuit 116. The intake air compressed by the compressor 111a of the turbocharger 111 is introduced into the engine body 114a through the intake circuit 112. The exhaust discharged from the engine main body 114a flows into the turbocharger 111 through the exhaust circuit 116, and is discharged by driving the turbine 111b.
The exhaust gas recirculation circuit 115 has one end branched and connected to the upstream side of the turbine 111 b of the exhaust circuit 116, and the other end branched and connected to the downstream side of the compressor 111 a of the intake circuit 112. An exhaust gas recirculation circuit 115 is provided with an EGR valve 115c that is driven by a first actuator 115a to open and close the exhaust gas recirculation circuit 115.
The intake circuit 112 is provided with an intake bypass circuit 112a and a three-way valve 112c that is driven by the second actuator 112b and allows the inflow of intake air to the intake bypass circuit 112a to be selected. The intake bypass circuit 112a is provided with a venturi 112d, and the exhaust gas recirculation circuit 115 is connected to a narrow portion 112e of the venturi 112d.
[0004]
When the exhaust gas is recirculated, the controller 113 drives the first actuator 115a to open the EGR valve 115c. However, when the pressure at the inlet of the turbine 111b is lower than the pressure at the outlet of the compressor 111a, the exhaust cannot be recirculated only by opening the EGR valve 115c. Therefore, when the detecting means (not shown) detects that the pressure at the inlet of the turbine 111b is lower than the pressure at the outlet of the compressor 111a, the controller 113 drives the second actuator 112b to switch the three-way valve 112c, and a large portion of the intake air is supplied to the intake air bypass circuit. It flows to 112a. Then since locally the pressure flow rate is increased by the narrow portion 112e of the venturi 112d decreases, even pressure turbine 111b inlet is lower than the pressure of the compressor 111a outlet, suppressing the generation of the NO X enables recirculation of exhaust gas.
[0005]
[Problems to be solved by the invention]
However, the above prior art has the following problems.
In the prior art exhaust recirculation system with venturi, inconvenience occurs when the engine operating conditions change. For example, during sudden acceleration, the amount of intake air is transiently insufficient due to a turbo lag, and the pressure at the turbine 111b inlet is transiently higher than the pressure at the compressor 111a outlet, increasing the flow rate of the exhaust gas that is recirculated. Combustion becomes slow, and the amount of black smoke emission increases and the acceleration performance deteriorates. Further, if the discharge amount of the NO X or black smoke, such as by changes in engine degradation and pressure is increased, since there is no function of controlling the recirculation of exhaust gas so as to compensate for this, rescues deterioration of exhaust components saying I can't.
[0006]
The present invention has been made to solve the above problems, and is an internal combustion engine that controls the recirculation of exhaust gas in consideration of the balance of NO X emission, black smoke emission, engine output and fuel consumption. An object of the present invention is to provide an exhaust gas recirculation control device.
[0007]
[Means, actions and effects for solving the problems]
To achieve the above object, the present invention provides a turbocharger having a compressor disposed on an intake circuit and a turbine disposed on an exhaust circuit, a turbine between the exhaust circuit and an internal combustion engine body, and a compressor of the intake circuit. An exhaust gas recirculation circuit connected between the internal combustion engine bodies and freely opened and closed by a first on-off valve is provided, and a throttle having a narrow portion for restricting the flow of intake air between the compressor and the internal combustion engine body is provided in the intake circuit. The exhaust gas recirculation circuit of the internal combustion engine is provided with the intake recirculation circuit provided with an exhaust bypass circuit that is connected to the upstream and the downstream of the throttle by bypass connection and can be opened and closed by the second on-off valve. In the circulation control device,
Speed, load, and detection means for detecting the NO X concentration and the oxygen concentration in the exhaust gas in the exhaust,
Storage means for storing in advance the target air-fuel ratio and the NO x concentration in the exhaust with respect to the rotational speed and load of the internal combustion engine;
Calculated air-fuel ratio from the detected oxygen concentration detection means, the air-fuel ratio and the first on-off valve so as to approach the respective target values to be stored in said storage means concentration of NO X in the exhaust gas detected by the detecting means and the Control means for performing control to finely adjust the opening degree of the second on-off valve is provided.
[0008]
According to the above configuration, the values of both the NO X concentration in the exhaust gas and the oxygen concentration in the exhaust gas are fed back so as to approach the target values of the NO X concentration and the air-fuel ratio for the rotational speed and load of the internal combustion engine. can be controlled the EGR rate to an optimum value to the operating state of the engine by controlling the opening of the first on-off valve and the second on-off valve, an internal combustion emissions of both NO X and black smoke It can be reduced in a well-balanced manner according to the engine speed and load. Furthermore, emissions of NO X and black smoke with respect to the load and the rotational speed of the internal combustion engine be varied due to changes in the degradation and pressure of an internal combustion engine, it is controlled to compensate for these variations by the feedback control.
[0009]
The present invention also provides a turbocharger having a compressor disposed on the intake circuit and a turbine disposed on the exhaust circuit, and connects between the turbine and internal combustion engine body of the exhaust circuit and between the compressor and internal combustion engine body of the intake circuit. And an exhaust gas recirculation circuit that can be opened and closed by the first on-off valve, and a throttle having a narrow portion for restricting the flow of intake air between the compressor and the internal combustion engine body is provided in the intake circuit so that the connection position of the exhaust gas recirculation circuit is provided. In the exhaust gas recirculation control apparatus for an internal combustion engine provided with an intake bypass circuit that is substantially in the center of the narrow portion and bypasses the upstream and downstream of the throttle and can be opened and closed by a second on-off valve.
Speed, load, and detection means for detecting the NO X concentration and the oxygen concentration in the exhaust gas in the exhaust,
Storage means for preliminarily storing the opening degree of the first on-off valve, the opening degree of the second on-off valve, the air-fuel ratio and the NO X concentration in the exhaust gas, with respect to the rotational speed and load of the internal combustion engine;
The opening degree of the first on-off valve and the second on-off valve is controlled so as to be the target opening degree stored in the storage means with respect to the rotational speed and load detected by the detection means, and the exhaust gas detected by the detection means obtains the air-fuel ratio from the oxygen concentration in, the air-fuel ratio and the first on-off valve so as to approach the respective target values to be stored in said storage means concentration of NO X in the exhaust gas detected by the detecting means and the second opening and closing Control means for performing control to finely adjust the opening of the valve may be provided.
[0010]
According to the above configuration, the opening of the first on-off valve and the second on-off valve of the target with respect to the load and the rotational speed of the internal combustion engine as well as the initial setting, the oxygen concentration in the exhaust and concentration of NO X in the exhaust gas by feeding back the both values as close to the target value of the NO X concentration and the air-fuel ratio with respect to the load and the rotational speed of the internal combustion engine, it will control the opening of the first on-off valve and the second on-off valve. By initially setting the opening degree of the first on-off valve and the second on-off valve, the response of the control system to fluctuations in the rotational speed and load of the internal combustion engine is improved.
[0015]
In addition, in the exhaust gas recirculation control device for an internal combustion engine according to the first or second aspect of the invention , when the control means determines that rapid acceleration is being performed from the operating state detected by the detection means, the first on-off valve is Close control may be performed .
[0016]
According to the above configuration, by stopping the exhaust gas recirculation at the time of sudden acceleration, it is possible to avoid a decrease in the oxygen concentration in the intake air due to the exhaust gas recirculation, and to prevent a decrease in output and an increase in black smoke in the exhaust gas at the time of sudden acceleration. .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a supply / exhaust circuit diagram of a turbocharged engine 14 having the exhaust gas recirculation device of the first embodiment. The engine 14 includes a turbocharger 11, an intake circuit 12, a controller 13, an exhaust gas recirculation circuit 15, and an exhaust circuit 16. The intake air compressed by the compressor 11a of the turbocharger 11 is introduced into the engine body 14a through the intake circuit 12. Exhaust gas discharged from the engine body 14a flows into the turbocharger 11 through the exhaust circuit 16, and is discharged by driving the turbine 11b.
[0018]
The exhaust gas recirculation circuit 15 has one end branched and connected near the exhaust manifold 16 a of the exhaust circuit 16, and the other end branched and connected near the intake manifold 12 a of the intake circuit 12. An exhaust gas recirculation circuit 15 is provided with an EGR valve 15c that is driven by an actuator 15a (not shown) to open and close the exhaust gas recirculation circuit 15. As the opening degree of the EGR valve 15c increases, the flow rate of the recirculated exhaust gas increases, that is, the EGR rate also increases.
The intake circuit 12 includes a venturi 12b, an intake bypass circuit 12c that bypass connects the upstream and downstream of the venturi 12b, and an intake bypass valve 12d that is driven by an actuator (not shown) to open and close the intake bypass circuit 12c. And are provided. The narrow portion of the venturi 12b is provided with a connection port that joins the flow from the upstream to the downstream in the venturi 12b, and the exhaust gas recirculation circuit 15 is branched and connected to this connection port. If the intake bypass valve 12d is throttled, the passage flow rate of the intake bypass circuit 12c decreases, and the passage flow rate of the venturi 12b increases accordingly. Therefore, the flow velocity of the narrow portion increases, the pressure decreases, and the flow rate of the recirculated exhaust gas increases. That is, the EGR rate also increases.
A supply / exhaust bypass circuit 20 is provided between the vicinity of the compressor 11a outlet of the intake circuit 12 and the vicinity of the turbine 11b inlet of the exhaust circuit 16, and the intake / exhaust bypass circuit 20 is connected to the intake circuit 12 side. Is provided with a check valve 20a that allows conduction in only one direction from the exhaust circuit 16 to the exhaust circuit 16 side.
[0019]
The engine 14 further includes a rotational speed sensor 31a that detects the rotational speed of the engine 14, a water temperature sensor 31b that detects the coolant temperature of the engine 14, a torque meter 31c that detects output torque, and an exhaust that detects oxygen concentration in the exhaust. having an oxygen concentration sensor 31d, and a detection means 31 for detecting the operating state of the NO X sensor 31e such as such as the engine 14 for detecting the concentration of NO X in the exhaust gas. Further, the target value B T of the opening degree of the intake bypass valve 12d, the target value E T of the opening degree of the EGR valve 15c, the target value NO XT of the NO X concentration, and the target value R T (A / F) of the air-fuel ratio are controlled. A storage unit 32 stored as a map is provided, and a detection signal corresponding to each state detected by the detection unit 31 and each target value data of the control map stored in the storage unit 32 are input to perform arithmetic processing described later. The control unit 33 controls the opening degree of the intake bypass valve 12d and the EGR valve 15c.
The control map sets a coordinate plane in which the rotational speed N detected by the detecting means 31 is a horizontal coordinate and the output torque T is a vertical coordinate. Each target value is set every time. Therefore, if the values of the rotational speed and the output torque are determined, the respective target values corresponding to these values are uniquely determined from the control map.
[0020]
A processing procedure of the control unit 33 in the first embodiment will be described based on a control flowchart example shown in FIG. In step S1, which is an initial state, the EGR valve 15c is completely closed, and the intake bypass valve 12d is completely opened. First, in step S2, the control unit 33 sets the target opening degree selected from the rotation speed N detected by the rotation speed sensor 31a and the output torque T detected by the torque meter 31c on the control map stored in the storage unit 32. Thus, control is performed to open the EGR valve 15c and close the intake bypass valve 12d. Thus the opening degree of the intake bypass valve 12d is the target value B T, and the opening degree of the EGR valve 15c becomes the target value E T.
Next, in step S3, the target NO X concentration NO XT selected based on the rotational speed N detected by the rotational speed sensor 31a and the output torque T detected by the torque meter 31c on the control map stored in the storage means 32, and NO X sensor 31e compares the NO X concentration NO XO detected, the formula "NO XO ≧ NO XT" is shifted to the step S4 if true, the process proceeds and if false to step S6.
[0021]
In step S4, the target air-fuel ratio R T (A / F) selected from the rotational speed N detected by the rotational speed sensor 31a and the output torque T detected by the torque meter 31c on the control map stored in the storage means 32, The air-fuel ratio R O (A / F) calculated from the oxygen concentration in the exhaust gas detected by the exhaust oxygen concentration sensor 31d is compared, and the formula “R O (A / F) ≧ R T (A / F)” is true. If so, the process proceeds to step S5. In step S5, the opening degree of the EGR valve 15c is increased by a predetermined value ΔE1, and the opening degree of the intake bypass valve 12d is decreased by a predetermined value ΔB1, that is, the EGR rate is increased, and the process returns to step S3. If the expression “R O (A / F) ≧ R T (A / F)” is false, the process proceeds to step S7.
In step S6, the target air-fuel ratio R T (A / F) selected from the rotational speed N detected by the rotational speed sensor 31a and the output torque T detected by the torque meter 31c on the control map stored in the storage means 32, The air-fuel ratio R O (A / F) calculated from the oxygen concentration in the exhaust gas detected by the exhaust oxygen concentration sensor 31d is compared, and the formula “R O (A / F) ≧ R T (A / F)” is false. If so, the process proceeds to step S8. In step S8, the opening degree of the EGR valve 15c is decreased by a predetermined value ΔE2, and the opening degree of the intake bypass valve 12d is increased by a predetermined value ΔB2, that is, the EGR rate is decreased, and the process returns to step S3. If the formula “R O (A / F) ≧ R T (A / F)” is true in step S6, the process proceeds to step S7.
In step S7, the opening degrees of the EGR valve 15c and the intake bypass valve 12d are maintained at the current values for a predetermined time, and after this elapse, the process returns to S3 and the above processing is repeated.
In the above process, the minute opening control amounts ΔE1 and ΔE2 and ΔB1 and ΔB2 may be the same value or different values.
[0022]
According to the first embodiment, first, the opening degree of the EGR valve 15c and the intake bypass valve 12d is controlled to be a target value for the rotational speed N and the output torque T of the engine 14 by the above control flowchart. Under normal operating conditions, the EGR rate can be controlled so as to be an optimum value for the operating state of the engine 14 by itself. Further, both values of the NO X concentration NO XO in the exhaust gas and the air-fuel ratio R O (A / F) are fed back and controlled so as to approach the target values for the rotational speed N and the output torque T of the engine 14. This allows control the EGR rate to correct the discharge amount of change of the NO X and black smoke due to changes in the degradation and pressure of the engine 14. Therefore, it is possible to reduce both NO X and black smoke emissions in a well-balanced manner according to the rotational speed and load of the engine 14.
[0023]
Reference Example 1 of the present invention will be described with reference to FIGS. FIG. 3 shows a supply / exhaust circuit diagram of the turbocharged engine 14 having the exhaust gas recirculation device of Reference Example 1 . The difference from the first embodiment is to use the EGR rate as the quantity of state instead of the NO X concentration. For this reason, an intake oxygen concentration sensor 31g for detecting the oxygen concentration in the intake air is provided instead of the NO X sensor 31e. Further, a storage means 32a is provided in place of the storage means 32, and the storage means 32a is provided for the target value B T of the opening degree of the intake bypass valve 12d, the target value E T of the opening degree of the EGR valve 15c, and the EGR rate. The target value EGR T and the target value R T (A / F) of the air-fuel ratio are stored as a control map as in the first embodiment. Other hardware configurations are the same as those in the first embodiment.
[0024]
Here, the actual EGR rate EGR O is uniquely obtained from the oxygen concentration in the exhaust detected by the exhaust oxygen concentration sensor 31d and the oxygen concentration in the intake detected by the intake oxygen concentration sensor 31g. If the operating state is determined, the EGR rate EGR T corresponding to the target NO X emission amount NO XT is uniquely determined, so that the NO X concentration can be substituted by the EGR rate. Therefore, control equivalent to that of the first embodiment can be performed by the above configuration of Reference Example 1 .
[0025]
The processing procedure of the control unit 33 in Reference Example 1 will be described based on the control flowchart shown in FIG. The processes up to step S1 and step S2 are the same as in the first embodiment (storage means 32 is replaced with storage means 32a). Next, the process proceeds from step S2 to step S3a, and the target EGR rate EGR selected based on the rotation speed N detected by the rotation speed sensor 31a and the output torque T detected by the torque meter 31c on the control map stored in the storage means 32a. T is compared with the actual EGR rate EGR O, and if the formula “EGR O ≧ EGR T ” is true, the process proceeds to step S4, and if it is false, the process proceeds to step S6. The previous control flowchart is the same as that in the first embodiment (storage means 32 is replaced with storage means 32a).
[0026]
According to the reference example 1 , first, the opening degree of the EGR valve 15c and the intake bypass valve 12d is controlled to be a target value for the rotational speed N and the output torque T of the engine 14 by the above control flowchart. Further, both the EGR rate EGR O calculated from the oxygen concentration in the intake air and the oxygen concentration in the exhaust gas and the air-fuel ratio R O (A / F) calculated from the oxygen concentration in the exhaust gas are fed back to rotate the engine 14. Control is performed so as to approach the values of the target EGR rate EGR T and the air-fuel ratio R T (A / F) for the speed N and the output torque T. Thereby, the EGR rate is controlled so as to be an optimum value for the operating state of the engine 14. Therefore, in addition to the effect of the first embodiment, it is not necessary to directly detect the NO X concentration, and this is replaced by the EGR rate. Therefore, the expensive NO X sensor 31e is not required, and the manufacturing cost can be reduced.
[0027]
A second embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment or the reference example 1 is that control for stopping the exhaust gas recirculation is added during the warm-up operation and the rapid acceleration, and the hardware configuration is the same as that of the first embodiment or the reference example 1. .
[0028]
The processing procedure of the control unit 33 in the second embodiment will be described based on the control flowchart shown in FIG. The processes up to step S1 and step S2 are the same as those in the first embodiment or the reference example 1, and the process proceeds from step S2 to step S9. In step S9, the preset temperature value T T is compared with the coolant temperature T O detected by the water temperature sensor 31b. If the formula “T O ≦ T T ” is true, the process proceeds to step S12. In step S12, the EGR valve 15c is closed and the intake bypass valve 12d is fully opened, that is, the EGR rate is set to zero, and the process returns to step S9. If the formula “T O ≦ T T ” is false in step S9, the process proceeds to step S10. In step S10, the increment dN T per unit of rotational speed times the preset engine rotation speed sensor 31a per unit time increment of the engine speed is obtained than the actual rotational speed N detected dN O And if the formula “dN O ≧ dN T ” is true, the process proceeds to step S13. In step S13, the EGR valve 15c is closed and the intake bypass valve 12d is fully opened, that is, the EGR rate is set to zero and the process returns to step S10. If the formula “dN O ≧ dN T ” is false in step S10, the process proceeds to step S11. In step S11, the opening degrees of the EGR valve 15c and the intake bypass valve 12d are maintained at the current values for a predetermined time, and after this elapses, the process proceeds to step S3 or step S3a. The previous control flowchart is the same as that of the first embodiment or reference example 1, and after the processing of steps S5, S7 and S8, the processing returns to step S9 and the above processing is repeated.
[0029]
According to the second embodiment, the following control is performed in addition to the control of the first embodiment or the reference example 1 .
(1) When increment dN O per unit rotational speed time of the engine 14 is a predetermined value or more dN T, stops recirculation of exhaust gas by the EGR rate to zero.
(2) When the coolant water temperature T O of the engine 14 is equal to or lower than the predetermined value T T , the EGR rate is set to zero and the exhaust gas recirculation is stopped.
Therefore, in addition to the effects of the first embodiment or the reference example 1 , the following effects can be obtained.
(1) at the time when ie acceleration increment dN O per unit rotational speed time of the engine 14 is a predetermined value or more dN T, the output decreases due to the oxygen concentration in the intake air in recirculation of exhaust gas decreases and incomplete combustion Can be avoided. Therefore, it is possible to improve the acceleration performance by preventing a decrease in output during acceleration, and to prevent the occurrence of black smoke by preventing incomplete combustion.
(2) When the water temperature T O of the cooling water of the engine 14 is equal to or lower than the predetermined value T T , that is, when the exhaust gas is recirculated during cold weather, the water vapor in the exhaust gas condenses in the exhaust gas recirculation circuit 15 and becomes water. Cause corrosive action. In particular, if an EGR cooler is provided in the exhaust gas recirculation circuit 15, the amount of water condensed increases and the corrosive action becomes remarkable. Therefore, corrosion of each part of the engine 14 can be prevented by suppressing condensation of water in the exhaust gas recirculation circuit 15 during cold weather.
[0030]
Reference Example 2 of the present invention will be described with reference to FIGS. The reference example 2 replaces the control process for stopping exhaust gas recirculation during acceleration in the second embodiment with a control process for supercharging during acceleration with a positive displacement supercharger represented by a roots type. Therefore, the description will be omitted only for the portions different from the second embodiment, and overlapping portions will be omitted. FIG. 6 shows a supply / exhaust circuit diagram of the turbocharged engine 14 having the exhaust gas recirculation device according to the second reference example . A supercharger 40 that can be freely started and stopped by a command from the control unit 33, and immediately upstream of the supercharger 40 and immediately downstream of the supercharger 40, that is, immediately upstream of the compressor 11a, are directly upstream of the compressor 11a of the intake circuit 12. A bypass check valve 41 is provided. When the supercharger 40 is activated by a command from the control unit 33, a supercharging pressure can be applied to the intake air introduced into the compressor 11a. When the supercharger 40 is stopped, intake air passes through the check valve 41 and is introduced into the compressor 11a.
[0031]
The processing procedure of the control unit 33 in Reference Example 2 will be described based on the control flowchart shown in FIG. The difference from the second embodiment is that the control processing in steps S11 and S13 is replaced with the control processing in steps S11a and S13a described below. In step S10, the increment dN T per unit of rotational speed times the preset engine, and per unit time increment dN O of the rotational speed of the engine rotational speed sensor 31a is obtained than the actual rotational speed detected Are compared as in the second embodiment. If the formula “dN O ≧ dN T ” is true, the process proceeds to step S13a. In step S13a, the supercharger 40 is activated and the process returns to step S10. If the formula “dN O ≧ dN T ” is false in step S10, the process proceeds to step S11a. In step S11a, the supercharger 40 is stopped and the process proceeds to step S3 or S3a. The previous control flowchart is the same as that in the first embodiment or reference example 1, and after the processing in steps S5, S7, and S8, the process returns to step S9 and the above processing is repeated.
[0032]
According to the reference example 2 , in addition to the control of the first embodiment or the reference example 1 , the following control is performed.
(1) When increment dN O per unit rotational speed time of the engine 14 is a predetermined value or more dN T, performs supercharging Start supercharger 40.
(2) When the coolant water temperature T O of the engine 14 is equal to or lower than the predetermined value T T , the EGR rate is set to zero and the exhaust gas recirculation is stopped.
Therefore, in addition to the effects of the first embodiment or the reference example 1 , the following effects are obtained.
(1) at the time when ie acceleration increment dN O per unit rotational speed time of the engine 14 is a predetermined value or more dN T, in the supercharging effect of the supercharger 40, the decrease in the oxygen concentration in the intake air by recirculation of exhaust gas It is possible to compensate for the decrease in output and incomplete combustion. Accordingly, it is possible to prevent output reduction during acceleration without stopping the exhaust gas recirculation and improve the acceleration performance, and also suppress the generation of black smoke.
(2) When the water temperature T O of the cooling water of the engine 14 is equal to or lower than the predetermined value T T , that is, when the exhaust gas is recirculated during cold weather, the water vapor in the exhaust gas condenses in the exhaust gas recirculation circuit 15 and becomes water. Cause corrosive action. In particular, if an EGR cooler is provided in the exhaust gas recirculation circuit 15, the amount of water condensed increases and the corrosive action becomes remarkable. Therefore, corrosion of each part of the engine 14 can be prevented by suppressing condensation of water in the exhaust gas recirculation circuit 15 during cold weather.
[0033]
In addition, this invention is not limited to embodiment illustrated above.
For example, the above-described supply / exhaust bypass circuit 20 allows a part of the intake air to escape to the exhaust circuit 16 to reduce the pressure of the intake circuit 12 and increase the pressure of the exhaust circuit 16 to facilitate exhaust gas recirculation. It is not an essential component for the invention.
Further, as a state quantity corresponding to the load of the engine 14, for example, a fuel injection quantity may be used instead of the output torque T. As a method for detecting the fuel injection amount, the fuel flow rate may be directly measured or may be obtained from the position of the control rack.
Furthermore, as a method for obtaining the EGR rate, for example, a method of detecting the carbon dioxide concentration in the intake air and the carbon dioxide concentration in the exhaust by providing sensors and obtaining the EGR rate from the ratio of the respective carbon dioxide concentrations may be used. Good. As another method for obtaining the air-fuel ratio, the intake flow rate is directly measured or calculated from the pressure and temperature of the intake circuit, and the fuel flow rate is directly measured or calculated from the position of the control rack. And a method of obtaining the air-fuel ratio from the fuel flow rate.
In addition, in the control flowchart of each embodiment, the process of step S2 may be omitted, and control to move from step S1 to the next step may be performed.
[0034]
As described above by exemplifying the embodiment, according to the present invention, the following effects can be obtained.
(1) The opening degree of the first on-off valve and the intake bypass valve is controlled so that both the NO X concentration in the exhaust gas and the air-fuel ratio are fed back to approach the target values for the engine speed and load. By doing so, the EGR rate is controlled. Therefore, it is possible to reduce a balanced depending both emissions of NO X and black smoke and engine speed and engine load. Moreover, even if the emissions changes in the NO X and black smoke, such as by changes in the degradation and pressure of the engine, can be controlled EGR rate to reduce emissions by correcting this change.
(2) By stopping the recirculation of the exhaust during sudden acceleration, it is possible to avoid a decrease in oxygen concentration in the intake air due to the recirculation of exhaust, and to prevent a decrease in output and an increase in black smoke in the exhaust during sudden acceleration .
[Brief description of the drawings]
FIG. 1 is a supply / exhaust circuit diagram of a first embodiment of the present invention.
FIG. 2 is a control flowchart example of the first embodiment of the present invention.
FIG. 3 is a supply / exhaust circuit diagram of Reference Example 1 of the present invention.
FIG. 4 is a control flowchart example of Reference Example 1 of the present invention.
FIG. 5 is a control flowchart example of a second embodiment of the present invention.
FIG. 6 is a supply / exhaust circuit diagram of Reference Example 2 of the present invention.
FIG. 7 is a control flowchart example of Reference Example 2 of the present invention.
FIG. 8 is a diagram of a conventional air supply / exhaust circuit.
Claims (3)
−内燃機関本体(14a) 間と吸気回路(12)のコンプレッサ(11a) −内燃機関本体(14a) 間とを接続して第1開閉弁(15c) によって開閉自在とした排気再循環回路(15)とを設けるとともに、コンプレッサ(11a) −内燃機関本体(14a) 間の吸気の流れを絞る狭隘部を有する絞り(12b) を吸気回路(12)に設けて排気再循環回路(15)の接続位置をこの狭隘部略中央とし、この絞り(12b) の直上流と直下流とをバイパス接続するとともに第2開閉弁(12d) によって開閉自在とされる吸気バイパス回路(12c) を設けた内燃機関の排気再循環制御装置において、
回転速度、負荷、排気中のNOX濃度及び排気中の酸素濃度を検出する検出手段(31)と、
内燃機関の回転速度及び負荷に対する目標の空燃比及び排気中のNOX濃度を予め記憶する記憶手段(32)と、
前記検出手段(31)の検出した酸素濃度から空燃比を求め、この空燃比及び検出手段(31)の検出する排気中のNOX
濃度を前記記憶手段(32)の記憶するそれぞれの目標値に近づけるように前記第1開閉弁(15c) 及び前記第2開閉弁(12d) の開度を微調整する制御を行う制御手段(33)とを設けた
ことを特徴とする内燃機関の排気再循環制御装置。A turbocharger (11) having a compressor (11a) disposed on the intake circuit (12) and a turbine (11b) disposed on the exhaust circuit (16), and a turbine (11b) of the exhaust circuit (16)
-An exhaust gas recirculation circuit (15) connected between the internal combustion engine body (14a) and the compressor (11a) of the intake circuit (12)-between the internal combustion engine body (14a) and opened and closed by the first on-off valve (15c) ) And a throttle (12b) having a narrow portion for restricting the flow of intake air between the compressor (11a) and the internal combustion engine body (14a) is provided in the intake circuit (12) to connect the exhaust gas recirculation circuit (15). An internal combustion engine provided with an intake bypass circuit (12c) whose position is substantially the center of the narrow portion, bypassing the upstream and downstream of the throttle (12b) and opening and closing by a second on-off valve (12d) In the exhaust gas recirculation control device,
Detection means (31) for detecting the rotational speed, load, NO X concentration in the exhaust gas and oxygen concentration in the exhaust gas;
Storage means (32) for preliminarily storing a target air-fuel ratio and NO X concentration in the exhaust with respect to the rotational speed and load of the internal combustion engine;
The air-fuel ratio is obtained from the oxygen concentration detected by the detecting means (31), and the air-fuel ratio and NO X in the exhaust gas detected by the detecting means (31) are detected.
Control means (33) for finely adjusting the opening degree of the first on-off valve (15c) and the second on-off valve (12d) so that the concentration approaches each target value stored in the storage means (32) And an exhaust gas recirculation control apparatus for an internal combustion engine.
−内燃機関本体(14a) 間と吸気回路(12)のコンプレッサ(11a) −内燃機関本体(14a) 間とを接続して第1開閉弁(15c) によって開閉自在とした排気再循環回路(15)とを設けるとともに、コンプレッサ(11a) −内燃機関本体(14a) 間の吸気の流れを絞る狭隘部を有する絞り(12b) を吸気回路(12)に設けて排気再循環回路(15)の接続位置をこの狭隘部略中央とし、この絞り(12b) の直上流と直下流とをバイパス接続するとともに第2開閉弁(12d) によって開閉自在とされる吸気バイパス回路(12c) を設けた内燃機関の排気再循環制御装置において、
回転速度、負荷、排気中のNOX
濃度及び排気中の酸素濃度を検出する検出手段(31)と、
内燃機関の回転速度及び負荷に対する目標の、前記第1開閉弁(15c) の開度、前記第2開閉弁(12d) の開度、空燃比及び排気中のNOX
濃度を予め記憶する記憶手段(32)と、
前記検出手段(31)の検出した回転速度及び負荷に対する前記記憶手段(32)の記憶する目標の開度となるように前記第1開閉弁(15c) 及び前記第2開閉弁(12d) の開度を制御するとともに、検出手段(31)の検出した酸素濃度から空燃比を求め、この空燃比及び検出手段(31)の検出する排気中のNOX
濃度を前記記憶手段(32)の記憶するそれぞれの目標値に近づけるように前記第1開閉弁(15c) 及び前記第2開閉弁(12d) の開度を微調整する制御を行う制御手段(33)とを設けた
ことを特徴とする内燃機関の排気再循環制御装置。A turbocharger (11) having a compressor (11a) disposed on the intake circuit (12) and a turbine (11b) disposed on the exhaust circuit (16), and a turbine (11b) of the exhaust circuit (16)
-An exhaust gas recirculation circuit (15) connected between the internal combustion engine body (14a) and the compressor (11a) of the intake circuit (12)-between the internal combustion engine body (14a) and opened and closed by the first on-off valve (15c) ) And a throttle (12b) having a narrow portion for restricting the flow of intake air between the compressor (11a) and the internal combustion engine body (14a) is provided in the intake circuit (12) to connect the exhaust gas recirculation circuit (15). An internal combustion engine provided with an intake bypass circuit (12c) whose position is substantially the center of the narrow portion, bypassing the upstream and downstream of the throttle (12b) and opening and closing by a second on-off valve (12d) In the exhaust gas recirculation control device,
Rotational speed, load, NO X in exhaust
Detecting means (31) for detecting the concentration and oxygen concentration in the exhaust;
Targets for the rotational speed and load of the internal combustion engine, the opening degree of the first on-off valve (15c), the opening degree of the second on-off valve (12d), the air-fuel ratio, and NO X in the exhaust gas.
Storage means (32) for storing the concentration in advance;
The first on-off valve (15c) and the second on-off valve (12d) are opened so that the target opening degree stored in the storage means (32) with respect to the rotational speed and load detected by the detection means (31) is obtained. The air-fuel ratio is determined from the oxygen concentration detected by the detection means (31), and the air-fuel ratio and NO X in the exhaust gas detected by the detection means (31) are detected.
Control means (33) for finely adjusting the opening degree of the first on-off valve (15c) and the second on-off valve (12d) so that the concentration approaches each target value stored in the storage means (32) And an exhaust gas recirculation control apparatus for an internal combustion engine.
前記制御手段 (33) は、前記検出手段(31)の検出した運転状態から急加速中と判断したときに、前記第1開閉弁(15c) を閉じる制御を行う
ことを特徴とする内燃機関の排気再循環制御装置。The exhaust gas recirculation control device for an internal combustion engine according to claim 1 or 2 ,
Wherein said control means (33), when it is determined that during rapid acceleration from the detected operating condition of said detecting means (31), and wherein <br/> performing control to close the first on-off valve (15c) An exhaust gas recirculation control device for an internal combustion engine.
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US10794305B2 (en) | 2018-07-12 | 2020-10-06 | Hyundai Motor Company | Valve duty differentiated exhaust gas recirculation control method and exhaust gas recirculation system |
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JP4122913B2 (en) * | 2002-09-26 | 2008-07-23 | トヨタ自動車株式会社 | Hydrogen-utilized internal combustion engine and method for operating the same |
JP4126560B2 (en) * | 2004-09-15 | 2008-07-30 | トヨタ自動車株式会社 | Control device for internal combustion engine |
JP2006152843A (en) * | 2004-11-26 | 2006-06-15 | Sanwa Seiki Co Ltd | Exhaust gas recirculation device |
JP4710666B2 (en) * | 2006-03-16 | 2011-06-29 | いすゞ自動車株式会社 | EGR system control method and EGR system |
JP2009209748A (en) * | 2008-03-04 | 2009-09-17 | Mazda Motor Corp | Exhaust gas recirculation device for engine |
JP5083228B2 (en) * | 2009-01-19 | 2012-11-28 | トヨタ自動車株式会社 | Fuel injection control device |
EP2339152B1 (en) * | 2009-12-23 | 2013-06-19 | FPT Motorenforschung AG | Method and device for controlling an EGR system in a combustion engines |
FR3098255B1 (en) * | 2019-07-03 | 2021-06-04 | Safran Aircraft Engines | Determination of fuel density for metering fuel in a fuel supply system of an aircraft engine |
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US10794305B2 (en) | 2018-07-12 | 2020-10-06 | Hyundai Motor Company | Valve duty differentiated exhaust gas recirculation control method and exhaust gas recirculation system |
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