JP3968999B2 - Diesel engine control device - Google Patents

Description

ただし、ｕ（ｔ）は操作量、ＫＰは比例ゲイン、ＫＩは積分時定数、ＫＤは微分時定数、ｅ（ｔ）は偏差、ｕ（ｔ０）はｕの初期値である。
【００９０】
まず図４０から説明すると、図４０においてステップ１では比例、積分、微分の各ゲインＫＰＭ、ＫＩＭ、ＫＤＭを演算した後ステップ２で積分ゲインＫＩＭと割り当て制御量ＤＮＥＭＩを用いて
【００９１】
【数１０】
ＩｓｃＭＩ＝ＩｓｃＭＩ_n-1＋（ｄＴ／ＫＩＭ）×ＤＮＥＭＩ、
ただし、ｄＴ：演算周期、
ＩｓｃＭＩ_n-1：ＩｓｃＭＩの前回値、
の式で積分補正値ＩｓｃＭＩを演算し、ステップ３でこの値を上下制限値以内に制限した値を改めて積分補正値ＩｓｃＭＩとする。
【００９２】
ステップ４では割り当て制御量ＤＮＥＭＩの変化量と微分ゲインＫＤＭを用いて
【００９３】
【数１１】
ＩｓｃＭＤ＝（ＤＮＥＭＩ−ＤＮＥＭＩ_n-1）×ＫＤＭ／ｄＴ
ただし、ＤＮＥＭＩ_n-1：ＤＮＥＭＩの前回値、
の式で微分補正値ＩｓｃＭＤを演算し、ステップ５で比例ゲインＫＰＭ、割り当て制御量ＤＮＥＭＩ、積分補正値ＩｓｃＭＩ、微分補正値ＩｓｃＭＤを用いて
【００９４】
【数１２】
ＱｆＩｓｃＭ＝ＫＰＭ×（ＤＮＥＭＩ＋ＩｓｃＭＩ＋ＩｓｃＭＤ）＋ＱｆＭｉｎｉ、
ただし、ＱｆＭｉｎｉ：初期値、
の式によりメイン噴射補正量ＱｆＩｓｃＭを算出する。
【００９５】
ここで、積分補正値の初期値であるＱｆＭｉｎｉにはアイドル時の燃料噴射量の１／４〜１／２程度の値を与える。これは積分制御の収束を早くするためである。
【００９６】
上記３つのゲインＫＰＭ、ＫＩＭ、ＫＤＭの演算については図４１により説明する。図４１においてステップ１では比例ゲイン基本値ＫＰＭＢ、空気過剰率補正係数ＫＰＭＬおよびポスト噴射時期補正係数ＫＰＭＰＩＴの積で比例ゲインＫＰＭを算出する。同様にしてステップ２、３では積分ゲイン、微分ゲインの基本値ＫＩＭＢ、ＫＤＭＢ、空気過剰率補正係数ＫＩＭＬ、ＫＤＭＬおよびポスト噴射時期補正係数ＫＩＭＰＩＴ、ＫＤＭＰＩＴの積で積分ゲインＫＩＭ、微分ゲインＫＤＭを算出する。
【００９７】
ただし、基本値、空気過剰率補正係数、ポスト噴射時期補正係数は一定値でなく、基本値ＫＰＭＢ、ＫＩＭＢ、ＫＤＭＢは図４２のように冷却水温Ｔｗに応じて、空気過剰率補正係数ＫＰＭＬ、ＫＩＭＬ、ＫＤＭＬは図４３のように目標空気過剰率に応じて、ポスト噴射時期補正係数ＫＰＭＰＩＴ、ＫＩＭＰＩＴ、ＫＤＭＰＩＴは図４４のようにポスト噴射時期ＴＰＩＴに応じて設定している。
【００９８】
ここで、図４２では暖機完了後に対して低水温時はゲインが小さくなるように設定している（しないとハンチングの恐れあり）。これは後述する図４７においても同様である。
【００９９】
次に、ポスト噴射時期補正量ＩｔＩｓｃＰの演算について図４５のフローにより説明する。ステップ１で比例、積分、微分の各ゲインＫＰＴ、ＫＩＴ、ＫＤＴを演算した後ステップ２で
【０１００】
【数１３】
ＩｓｃＴＩ＝ＩｓｃＴＩ_n-1＋（ｄＴ／ＫＩＴ）×ＤＮＥＰＩ、
ただし、ｄＴ：演算周期、
ＩｓｃＴＩ_n-1：ＩｓｃＭＩの前回値、
の式により積分補正値ＩｓｃＴＩを演算し、ステップ３でこの値を上下制限値以内に制限し、その結果を改めて積分補正値ＩｓｃＴＩとする。ステップ４で
【０１０１】
【数１４】
ＩｓｃＴＤ＝（ＤＮＥＰＩ−ＤＮＥＰＩ_n-1）×ＫＤＴ／ｄＴ、
ただし、ＤＮＥＰＩ_n-1：ＤＮＥＰＩの前回値、
の式により微分補正値ＩｓｃＴＤを演算し、ステップ５で
【０１０２】
【数１５】
ＩｔＩｓｃＰ＝ＫＰＴ×（ＤＮＥＰＩ＋ＩｓｃＴＩ＋ＩｓｃＴＤ）＋ＩＴＰｉｎｉ、
ただし、ＩＴＰｉｎｉ：初期値、
の式によりポスト噴射時期補正量ＩｔＩｓｃＰを算出する。
【０１０３】
ＩＴＰｉｎｉは数１２式のＱｆＭｉｎｉと同様積分補正値の初期値である。
【０１０４】
比例、積分、微分の各ゲインＫＰＴ、ＫＩＴ、ＫＤＴの演算については図４６はフローにより説明する。この処理は図４１と同様である。すなわち、図４６においてステップ１、２、３では比例ゲイン、積分ゲイン、微分ゲインの基本値ＫＰＴＢ、ＫＩＴＢ、ＫＤＴＢ、空気過剰率補正係数ＫＰＴＬ、ＫＩＴＬ、ＫＤＴＬおよびポスト噴射時期補正係数ＫＰＴＰＩＴ、ＫＩＴＰＩＴ、ＫＤＴＰＩＴの積で比例ゲインＫＰＴ、積分ゲインＫＩＴ、微分ゲインＫＤＴを算出する。基本値ＫＰＴＢ、ＫＩＴＢ、ＫＤＴＢは図４７のように冷却水温Ｔｗに応じて、空気過剰率補正係数ＫＰＴＬ、ＫＩＴＬ、ＫＤＴＬは図４８のように空気過剰率に応じて、ポスト噴射時期補正係数ＫＰＴＰＩＴ、ＫＩＴＰＩＴ、ＫＤＴＰＩＴは図４９のようにポスト噴射時期ＴＰＩＴに応じて設定している。
【０１０５】
このようにしてメイン噴射補正量ＱｆＩｓｃＭおよびポスト噴射時期補正量ＩｔＩｓｃＰを演算したら図３５に戻りステップ１０、１１でこれら補正量を用いて
【０１０６】
【数１６】
ＴＱｆＭＩ＝Ｑｆ＋ＱｆＩｓｃＭ、
ＴＩｔＰ＝ＴＰＩＴ＋ＩｔＩｓｃＰ、
の各式によりメイン噴射量ＴＱｆＭＩ、目標ポスト噴射時期ＴＩｔＰを算出する。なお、目標ポスト噴射時期ＴＩｔＰの演算式右辺の「＋」は進角を意味する。
【０１０７】
一方、アイドル回転速度のフィードバック制御域でないときにはステップ１よりステップ１２、１３に進み燃料噴射量Ｑｆをそのままメイン噴射量ＴＱｆＭＩ、ポスト噴射時期ＴＰＩＴをそのまま目標ポスト噴射時期ＴＩｔＰとする。
【０１０８】
なお、ポスト噴射量は目標空気過剰率から算出される噴射量からメイン噴射量を差し引いた値である。例えば図５８に示したように
【０１０９】
【数１７】
ＴＱｆＰ＝Ｑａｃ／Ｔｌａｍｂ−ＴＱｆＭＩ
の式によりポスト噴射量ＴＱｆＰを算出すればよい。
【０１１０】
そして、メイン噴射量ＴＱｆＭＩ、目標メイン噴射時期ＴＭＩＴを用いてメイン噴射を、またポスト噴射量ＴＱｆＰ、目標ポスト噴射時期ＴＩｔＰを用いてポスト噴射を行う。
【０１１１】
次に、本実施形態のアイドル時の作用を図５０を参照しながら説明する。図５０はポスト噴射量に対応して空気過剰率が変化したとき、三方弁に与える噴射パルスがどのように変化するのかをおおよそ３つの場合で示している。同図では左側の段付きパルス（ノズルニードルの開弁動作を早くするため開弁初めにソレノイドに大きな電流を流し、その後は電流を落としてノズルニードルを開弁位置に保持する）によりメイン噴射が、右側のパルス（矩形パルス）によりポスト噴射が行われる。右側のパルスがないのはポスト噴射が行われないことを表す。
【０１１２】
なお、同図では簡単のため３つの場合でメイン噴射開始時期を同じにしており、したがってメイン噴射終了時期を遅らせるとメイン噴射量が増え、この逆にメイン噴射終了時期を進めるとメイン噴射量が減ることになる。
【０１１３】
まず図５０（ａ）はポスト噴射を行わない通常運転時（図３９でλ３以上のとき）の波形である。このときにはメイン噴射量によりトルクが制御される。すなわち、実回転速度Ｎｅが目標値より低下したときにはメイン噴射終了時期を遅らせることによりトルクが増やされ、この逆に実回転速度Ｎｅが目標値より上昇したときにはメイン噴射終了時期を進めることによりトルクが減らされこれによって実回転速度が目標値へと戻される（一点鎖線参照）。これは従来装置と同様である。
【０１１４】
この状態からポスト噴射量が増大するのに伴い空気過剰率が小さくなってゆくので、ポスト噴射時期でトルクを制御する割合が増し、図３９で空気過剰率がλ２の状態となったときが図５０（ｂ）の波形である。この状態ではメイン噴射量はほぼ所定値に固定され、ポスト噴射時期（ポスト噴射開始時期）によりトルクが制御される（一点鎖線参照）。すなわち、ポストトルクの生成により実回転速度Ｎｅが目標値より上昇したときにはポスト噴射開始時期を遅らせることによりトルクが減らされ、この逆に実回転速度Ｎｅが目標値より低下したときにはポスト噴射開始時期を進めることによりトルクが増やされ、これによって実回転速度が目標値へと戻される。
【０１１５】
この場合、ポスト噴射量が大きく設定されていても従来装置のようにメイン噴射量が減らされることはないのでメイン噴射により最低限必要なトルクは確保されており、また目標空気過剰率Ｔｌａｍｂは運転性や排気が悪化しないように予め定めてありポスト噴射量は基本的にこの目標空気過剰率Ｔｌａｍｂを達成する量であるため（数１７式参照）、ポスト噴射により所望の温度にまで排気温度を高めつつ燃焼、運転性や排気の悪化を抑制することができる。
【０１１６】
そして、ポスト噴射量がさらに増大するとポスト噴射時期でトルクを制御する割合が減ってゆき、図３９で空気過剰率が１（＝λ１）の近傍にきたときにはポストルクの発生量が低下するため主にメイン噴射量によりトルクが制御される。このときの波形が図５０（ｃ）の波形である。すなわち、図５０（ａ）と同様に実回転速度Ｎｅが目標値より低下したときにはメイン噴射終了時期を遅らせることによりトルクが増やされ、この逆に実回転速度Ｎｅが目標値より上昇したときにはメイン噴射終了時期を進めることによりトルクが減らされこれによって実回転速度が目標値へと戻される（一点鎖線参照）。
【０１１７】
次に、第２実施形態では第１実施形態に対して、図５１に示す演算フローを追加して構成する。
【０１１８】
可変ノズルを有するターボ過給機を備えるエンジンでは可変ノズル１１ｃを開くことにより過給機の排気タービン１１ａにより回収される熱エネルギが少なくなり、排気タービン１１ａ下流の排気温度を高く保つことができる。そこで、第２実施形態ではアイドル時を含めてポスト噴射を行う場合に可変ノズル１１ｃを開くことにより排気タービン１１ａで回収される熱エネルギを抑制することで、ポスト噴射による排気温度の上昇効果を高めるようにしたものである。
【０１１９】
図５１を具体的に説明すると、ステップ１では従来と同様にして可変ノズルを駆動するアクチュエータに与えるデューディ比ＴＤＴＹＶＮＴを演算する。この演算方法は問わないので、詳細は省略する。
【０１２０】
ステップ２ではポスト噴射フラグＦ ＰＯＳＴをみる。フラグＦ ＰＯＳＴ＝１のとき（ポスト噴射を行う場合）にはステップ３に進み、図５２を内容とするマップを検索することによりポスト噴射時の目標デューティ比ＴＤＴＹＶＮＴＰを演算し、これをステップ４で最終目標デューティ比ＴＤＴＹＶＮＴＦとする。一方フラグＦ ＰＯＳＴ＝０のときにはステップ２よりステップ５に進みデューディ比ＴＤＴＹＶＮＴをそのまま最終目標デューティ比ＴＤＴＹＶＮＴＦとする。
【０１２１】
ここで、図５２の特性をポスト噴射が行われる領域で可変ノズルが開かれる側に設定しておけば、排気タービン１１ａにより回収される熱エネルギが抑制され、その分ポスト噴射による排気温度の上昇効果が高まるので、ＮＯｘ触媒１３やＤＰＦ１４の機能を高めることができる。
【０１２２】
なお図５２の特性はポスト噴射を行わないときの基本値とポスト噴射を行う場合の可変ノズルの開き側への補正量とを加算したものとなっているので、これを分けて構成することもできる。すなわちポスト噴射を行う場合の可変ノズルの開き側への補正量だけのマップを作成しておきこのマップを検索することにより求めた補正量と基本値としてのデューディ比ＴＤＴＹＶＮＴとから最終目標デューティ比を算出するようにしてもかまわない。
【図面の簡単な説明】
【図１】第１実施形態の制御システム図。
【図２】燃料噴射量の演算を説明するためのフローチャート。
【図３】基本燃料噴射量の特性図。
【図４】最大噴射量の特性図。
【図５】シリンダ吸入ＥＧＲ量の演算を説明するためのフローチャート。
【図６】体積効率相当値の演算を説明するためのフローチャート。
【図７】体積効率基本値の特性図。
【図８】体積効率負荷補正値の特性図。
【図９】リッチ運転フラグの設定を説明するためのフローチャート。
【図１０】再生運転フラグの設定を説明するためのフローチャート。
【図１１】ポスト噴射フラグの設定を説明するためのフローチャート。
【図１２】目標主噴射時期の演算を説明するためのフローチャート。
【図１３】目標主噴射時期基本値の特性図（Ｆ ＰＯＳＴ＝０）。
【図１４】目標主噴射時期基本値の特性図（Ｆ ＲＳ＝１）。
【図１５】目標主噴射時期基本値の特性図（Ｆ ＲＧ＝１）。
【図１６】水温補正係数の特性図。
【図１７】吸気温度補正係数の特性図。
【図１８】大気圧補正係数の特性図。
【図１９】最大主噴射時期の特性図。
【図２０】最小主噴射時期の特性図。
【図２１】ポスト噴射時期の演算を説明するためのフローチャート。
【図２２】ポスト噴射時期基本値の特性図（Ｆ ＲＳ＝１）。
【図２３】ポスト主噴射時期基本値の特性図（Ｆ ＲＧ＝１）。
【図２４】水温補正係数の特性図。
【図２５】吸気温度補正係数の特性図。
【図２６】大気圧補正係数の特性図。
【図２７】最大ポスト噴射時期の特性図。
【図２８】最小ポスト噴射時期の特性図。
【図２９】目標空気過剰率の演算を説明するためのフローチャート。
【図３０】再生運転時目標空気過剰率の特性図。
【図３１】リッチ運転時目標空気過剰率の特性図。
【図３２】通常運転時目標空気過剰率の特性図。
【図３３】水温補正係数の特性図。
【図３４】大気圧補正係数の特性図。
【図３５】アイドル回転速度制御を説明するためのフローチャート。
【図３６】目標回転速度の演算を説明するためのフローチャート。
【図３７】目標回転速度基本値の特性図。
【図３８】バッテリ電圧補正量の特性図。
【図３９】制御量分配係数の特性図。
【図４０】主噴射補正量の演算を説明するためのフローチャート。
【図４１】フィードバックゲインの演算を説明するためのフローチャート。
【図４２】ゲイン基本値の特性図。
【図４３】空気過剰率補正係数の特性図。
【図４４】ポスト噴射時期補正係数の特性図。
【図４５】ポスト噴射時期補正量の演算を説明するためのフローチャート。
【図４６】フィードバックゲインの演算を説明するためのフローチャート。
【図４７】ゲイン基本値の特性図。
【図４８】空気過剰率補正係数の特性図。
【図４９】ポスト噴射時期補正係数の特性図。
【図５０】第１実施形態の作用を説明するための波形図。
【図５１】第２実施形態の最終目標デューティ比の演算を説明するためのフローチャート。
【図５２】第２実施形態のポスト噴射時目標デューティ比の特性図。
【図５３】従来装置を制御系で示した図。
【図５４】第１の発明のクレーム対応図。
【図５５】第２の発明のクレーム対応図。
【図５６】ポスト噴射量を大きく設定した場合にポスト噴射の燃費、ポストトルク及び排気（ＨＣ）のそれぞれとポスト噴射時期との関係を示した特性図。
【図５７】制御量分配係数ＫＤＮＥを定めるのに空気過剰率をもってした本発明の制御原理を説明するための特性図。
【図５８】第１実施形態のポスト噴射量の演算を説明するためのフローチャート。
【符号の説明】
６ 燃料噴射弁
１５ コントロールユニット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a diesel engine, and more particularly, to a device that performs idle rotation speed control.
[0002]
[Prior art]
For various purposes, there is what performs so-called post-injection, in which a small amount of fuel is injected in the expansion stroke or exhaust stroke after the end of main injection (see Japanese Patent Laid-Open No. 2000-45828).
[0003]
[Problems to be solved by the invention]
Whereas the conventional post injection amount is only a small amount, there has been a case where a post injection amount that is significantly larger than the conventional post injection amount is set in response to the severe demand for exhaust purification. For example, when post-injection is performed in the expansion stroke after main injection for the purpose of significantly increasing the exhaust temperature to promote warm-up of the catalyst, etc., if the amount is small, most of the post-injected fuel will increase the exhaust temperature. Although it does not reach the point where torque is generated by changing to heat, when the post-injection amount increases, part of the amount changes to torque. That is, new torque (torque generated by the post injection is simply referred to as “post torque” hereinafter) is generated by post injection in the expansion stroke after the main injection.
[0004]
A problem arises when this post torque is generated particularly during idle rotation speed control. For example, the actual engine rotational speed Ne is set so that the predetermined target rotational speed TNE is maintained by the idle rotational speed control at idling when the load is the lowest and therefore the supplied fuel is the least and the engine rotational speed tends to become unstable. When the speed falls below the target rotational speed TNE, a feedback amount based on a deviation from the target value is added to the main injection amount to increase the fuel, and the actual rotational speed is returned to the target value. When this is represented by a control system, the conventional apparatus is as shown in FIG.
(1) The deviation DNE from the target engine speed TNE of the actual engine speed Ne is calculated,
(2) The feedback amount QfIscM is calculated using the deviation DNE and the feedback gain (constant),
(3) The main injection amount TQfMI is calculated by correcting the fuel injection amount with the feedback amount QfIscM.
Is. Even when such post-injection is performed during idle speed control and post torque is generated, resulting in an increase in the engine speed exceeding the target value, the conventional system reduces the main injection amount to reduce the main injection. By reducing the torque (hereinafter simply referred to as “main torque”), the post torque is canceled and the engine rotational speed is maintained at the target value.
[0005]
At this time, especially when the post torque is large, the main injection amount must be reduced to 0 at a minimum in order to offset the increased post torque by the decrease of the main torque. However, post injection cannot replace main injection and perform all the functions of main injection. The main injection amount and the main injection timing are determined so that an optimum torque is generated in the idle state, whereas the post injection timing is set to be retarded from the main injection timing. The in-cylinder temperature at the time of combustion is low and the post-injected fuel burns at a low temperature, soot and nitrogen oxides NOx constituting the exhaust particulates increase, and the emission deteriorates.
[0006]
  Therefore, the present invention maintains the target rotational speed even when post injection is performed during idling.InIn this case, by controlling not only the main injection amount but also the post-injection timing, even when post-injection is performed during idling, the engine speed fluctuation is the same as during normal idling without post-injection. The purpose is to keep on.
[0007]
As a specific configuration, as shown in FIG.
(A1) A control amount distribution coefficient KDNE is determined according to the excess air ratio,
(A2) By distributing the deviation DNE of the actual rotational speed Ne from the target rotational speed TNE with the distribution coefficient KDNE, DNE × KDNE is used as a control amount for the post injection timing, and DNE × (1-KDNE ) As a control amount for the main injection amount,
(A3) After that, feedback amounts ItIscP and QfIscM are calculated using each control amount and feedback gain (constant),
(A4) The target post injection timing TItP and the main injection amount TQfMI are calculated by correcting the corresponding post injection timing and fuel injection amount with the feedback amounts ItIscP and QfIscM.
The configuration. Or as shown in FIG.
(B1) The feedback gain that varies according to the excess air ratio while incorporating the distribution coefficient is set separately for the main injection amount control and the post injection timing control,
(B2) The feedback amounts ItIscP and QfIscM are calculated using the feedback gain and the deviation DNE that change depending on the excess air ratio,
(B3) The target post injection timing TItP and the main injection amount TQfMI are calculated by correcting the corresponding post injection timing and fuel injection amount with the feedback amounts ItIscP and QfIscM.
The configuration.
[0008]
Here, the excess air ratio is used to determine the control amount distribution coefficient KDNE based on the following idea.
[0009]
First, the proportion of post-injected fuel that changes to post-torque changes according to the post-injection timing if the post-injection amount is constant, and increases as the post-injection timing is advanced. Further, if the post injection timing is the same, the post torque increases as the post injection amount increases. Therefore, it is considered that the magnitude of the post torque is determined by the post injection timing and the post injection amount. On the other hand, since the excess air ratio is determined by the sum of the main injection amount and the post injection amount, the excess air ratio changes when the post injection amount changes. Therefore, when the post-injection amount is set to be large, the influence of post-torque was examined using the excess air ratio determined by the post-injection amount and the post-injection timing as parameters, and the result shown in FIG. 56 was obtained. As shown in the middle part of the figure, the post torque decreases as the post injection timing is retarded when the excess air ratio is constant (post injection amount is constant). Therefore, the post torque can be suppressed by retarding the post injection timing.
[0010]
In addition, as shown in the upper part of FIG. 56, generally, when the excess air ratio decreases, the fuel consumption (combustion rate) for post injection deteriorates. That is, when the main injection amount is small (the excess air ratio is large), the post-injected fuel has a sufficient oxygen concentration in the atmosphere, and the reaction between the fuel and oxygen is likely to occur (the combustion speed is high). Almost all of the injected fuel is burned, and the fuel consumption for post injection is improved. On the other hand, when the main injection amount is large (the excess air ratio is small), the post-injection fuel burns with a low oxygen concentration in the atmosphere and the combustion speed is slow, so a part of the post-injection fuel remains unburned. In addition, the heat generated by the post-injected fuel previously burned is used for combustion, so the total amount of heat generated by post-injection is reduced and the post torque is reduced. As a result, as shown in the middle stage of FIG. 56, the smaller the excess air ratio, the smaller the change in post torque with respect to the change in post injection timing (the post torque sensitivity becomes worse).
[0011]
Therefore, when the range indicating the phenomenon that the post torque sensitivity is improved as the excess air ratio is increased when the post injection amount is set large is defined as λ1 to λ2, the conceptual diagram shown in FIG. 57A is obtained. Here, λ1, which is the limit value on the smaller side, is an excess air ratio with poor post-torque sensitivity. Λ2, which is the limit value on the larger side, is the limit excess air ratio that needs to consider the post torque.
[0012]
Next, the control concept of the present invention will be described with reference to FIG. In the figure, the vertical axis is a parameter corresponding to the post torque sensitivity, and represents a share ratio of the post injection with respect to the torque control of the post injection. For example, 0 indicates that the post injection share ratio is 0, that is, torque control is performed only by main injection. As the value increases from this state, the share of post injection increases, and when it becomes 1, this indicates that torque control is performed only by post injection.
[0013]
Note that the torque control by the post injection is performed not by the post injection amount but by the post injection timing. On the other hand, torque control by main injection is performed by controlling the main injection amount.
[0014]
As a result, when the post-injection starts and the engine torque increases, the post-torque can be effectively reduced by retarding the post-injection timing if the excess air ratio is on the λ2 side within the range of λ1 to λ2. The amount by which the main injection amount is reduced is smaller than when the engine torque is reduced only by the conventional main injection amount.
[0015]
Therefore, as shown in FIG. 57 (a), the control of the post-injection timing is given more weight as the air excess ratio is closer to λ2 within the range of λ1 to λ2, that is, the main injection amount and the post injection according to the air excess ratio. By controlling the timing, torque fluctuations can be prevented without causing deterioration of exhaust.
[0016]
57 (a) shows a linear characteristic, but when applied to actual control, the case where the excess air ratio is outside the range of λ1 to λ2 as shown in FIG. 57 (b) is included. Since it is necessary to cope with this, the characteristic of the curve is smoothly connected so that the operating state does not change greatly at the boundary between the range of λ1 to λ2 and the other range.
[0017]
Next, the case where the excess air ratio is outside the range of λ1 to λ2 will be described.
[0018]
First, in the range of λ2 to λ3 where the excess air ratio is larger than λ2, the post injection amount is not so large and is a general amount, so the problem of the present invention (variation in rotational speed when the post injection amount is set large) occurs. It is an area that does not. Therefore, in this region, since the fluctuation of the rotational speed can be sufficiently prevented only by the torque control based on the main injection amount as in the conventional case, as shown in FIG. .
[0019]
Also, in the range where the excess air ratio is smaller than λ1, the post-injection amount is significantly increased, but the post-injection fuel combustion speed is very slow and the post-torque sensitivity is poor, so that the main injection amount control is weighted. (Thus, torque control is performed only by controlling the main injection amount).
[0020]
As the post-injection timing is advanced, the proportion of post-injected fuel that changes to post-torque increases. On the other hand, as the post-injection time is retarded, the fuel efficiency of post-injection worsens (the proportion of fuel that does not burn increases) The post injection timing is controlled within the hatched range in FIG. 56 in consideration of the fact that the exhaust gas deteriorates accordingly (the HC emission amount increases).
[0021]
In addition, the share ratio of the post-injection control is maximized in the vicinity of λ2 in FIG. 57 (b), but in this case, the maximum value is not set to 1 but a little less than 1, leaving room for control by the main injection amount. This is because, for example, when a rotational fluctuation occurs due to a change in the load on the auxiliary machine during idling, torque control is performed with the main injection amount to absorb the rotational fluctuation.
[0022]
In addition, when comparing the case where the post-injection amount, which is the subject of the present invention, is set large with the case where it is set to the general post-injection amount which has been conventionally performed, using FIG. 57 (b), Λ3 in the figure is the excess air ratio of only the main injection before the start of post injection. The general post-injection amount is not so large with respect to the main injection amount, and the excess air ratio after the start of post-injection at that time becomes λ4 and does not deviate so much from λ3. However, when the post-injection amount, which is the subject of the present invention, is set large, the excess air ratio after the start of post-injection is, for example, λ5, which is considerably smaller than λ4 in the general case conventionally performed. .
[0023]
[Means for Solving the Problems]
  According to a first aspect of the present invention, in a diesel engine control apparatus that performs main injection and post-injection in the expansion stroke after the main injection, when performing post-injection during idling, the main injection is performed so that the target rotational speed is maintained. Control the amount and post injection timing togethertorqueWith control means54, the torque control means includes means (not shown) for setting a target excess air ratio Tlamb, means 31 for calculating a deviation DNE of the actual engine speed Ne from the target speed TNE, A control amount distribution coefficient KDNE representing a share ratio of post-injection with respect to torque control is set to a value that increases as the target excess air ratio Tlamb increases in accordance with the target excess air ratio Tlamb, and the deviation DNE with the distribution coefficient KDNE. The control amount for the post injection timing and the control amount for the main injection amount are determined by distributing (for example, DNE × KDNE is a control amount for the post injection timing, and DNE × (1−KDNE) is used as the main injection amount. Means 33), and a control amount for the post injection timing A means 34 for calculating the feedback amount ItIscP of the post injection timing using the feedback gain, a means 35 for calculating the target post injection timing TItP by correcting the post injection timing with the feedback amount ItIscP, and a control amount for the main injection amount And means 36 for calculating the feedback amount QfIscM of the main injection amount using the feedback gain and means 37 for calculating the main injection amount TQfMI by correcting the fuel injection amount Qf with this feedback amount QfIscM.
[0025]
  First2DepartureTomorrow,In a diesel engine control device that performs main injection and post-injection in the expansion stroke after main injection, when performing post-injection during idling, the main injection amount and post-injection timing are set so that the target rotational speed is maintained. Torque control means to control together,As shown in FIG.torqueThe control meansMeans (not shown) for setting the target excess air ratio Tlamb;Means 31 for calculating a deviation DNE of the actual engine speed Ne from the target speed TNE;Incorporating a controlled variable distribution coefficient that represents the share of post-injection for torque controlFeedback gainThe goalExcess air ratioTlambAccording toThe control amount distribution coefficient increases as the target excess air ratio Tlamb increases.Means 41 and 42 for separately setting the main injection amount control and the post injection timing control;GoalExcess air ratioTlambInThis more changingA means 43 for calculating a post injection timing feedback amount ItIscP using the feedback gain for controlling the post injection timing and the deviation DNE, and calculating the target post injection timing TItP by correcting the post injection timing with this feedback amount ItIscP. Means 35 forGoalExcess air ratioTlambInThis more changingA means 44 for calculating the feedback amount QfIscM of the main injection amount using the feedback gain for controlling the main injection amount and the deviation DNE, and the main injection amount TQfMI is calculated by correcting the fuel injection amount Qf with this feedback amount QfIscM. And means 37 for performing.
According to a third aspect, in the first or second aspect, a post torque change with respect to a change in post injection timing is set as a post torque sensitivity, and a range showing a phenomenon in which the post torque sensitivity is improved as the target excess air ratio is increased. When defining from the smaller limit value (λ1) to the larger limit value (λ2), the closer to the larger limit value (λ2), the more weighting is given to the torque control of the post injection timing. Set the control amount distribution coefficient.
[0026]
  In the fourth invention,1In this invention, the feedback gain used to calculate the feedback amount ItIscP of the post injection timing is corrected according to the post injection timing.
[0027]
In the fifth invention, in any one of the first to fourth inventions, a NOx catalyst function for maintaining NOx in an atmosphere with an excess air ratio exceeding 1 and purifying NOx in an atmosphere with an excess air ratio of 1 or less, HC Equipped with an exhaust purification device having an oxidation catalyst function for oxidizing CO or a filter function for capturing exhaust particulates, either alone or in combination.
[0028]
  In a sixth aspect, the turbocharger is provided according to the fifth aspect., Post-injection when idleIn this case, the exhaust energy recovered by the turbocharger is suppressed.
[0029]
【The invention's effect】
  Since the post torque decreases as the post injection timing is retarded when the post injection amount is constant, the post torque can be suppressed by retarding the post injection timing. Therefore, the firstThe secondAccording to the invention, the post injection timing is controlled in addition to the main injection amount, and even if the post injection amount is set to be large at that time, the post injection timing is delayed so that a large post torque is not generated and the rotation fluctuation is not affected. By controlling to the corner side, fluctuations in engine speed can be kept the same as in normal idling without post-injection even when post-injection is performed during idling.
[0030]
  First1The second2According to the invention, since the excess air ratio decreases as the post injection amount increases, the ratio of controlling the torque by the post injection timing is increased in accordance with the decrease of the excess air ratio, and a predetermined excess air ratio is obtained. In this case, the ratio of controlling the torque by the post injection timing can be maximized. In this state, the main injection amount is substantially fixed to a predetermined value, and the torque is controlled by the post injection timing (post injection start timing). That is, when the actual rotational speed increases from the target value due to the generation of the post torque, the torque is reduced by delaying the post injection start timing. Conversely, when the actual rotational speed decreases below the target value, the post injection start timing is advanced. The torque is increased by this, and thereby the actual rotational speed is returned to the target value.
[0031]
  In this case, even if the post-injection amount is set large, the main injection amount is not reduced as in the conventional device, so the minimum necessary torque is ensured by the main injection, andGoalIf the excess air ratio is set in advance so that drivability and exhaust are not deteriorated, the post-injection amount is basically this.GoalSince it becomes the quantity which achieves an excess air ratio, combustion, operativity, and deterioration of exhaust_gas | exhaustion can be suppressed, raising exhaust temperature to desired temperature by post injection.
[0032]
  And the post injection amount further increasedGoalWhen the excess air ratio is close to 1, post itGSince the amount of torque generated decreases, it is possible to minimize the ratio of controlling torque by the post injection timing, that is, to maximize the ratio of controlling torque by the main injection amount. In this state, for example, when the actual rotational speed falls below the target value, the torque is increased by increasing the main injection amount. Conversely, when the actual rotational speed rises above the target value, the torque is reduced by reducing the main injection amount. As a result, the actual rotational speed is returned to the target value.
[0033]
According to the fourth invention, it is possible to control the fluctuation of the rotational speed when performing the post-injection during idling with higher accuracy.
[0034]
  According to the fifth invention, the skyspiritNOx catalyst function for maintaining NOx in an atmosphere with excess ratio exceeding 1 (lean atmosphere) and purifying NOx in an atmosphere with air excess ratio of 1 or more (rich atmosphere), oxidation catalyst function for oxidizing HC / CO, or exhaust particulates By combining the post-injection timing and main injection amount feedback control at the time of idling according to the first, second, third, and fourth inventions, an exhaust gas purification device having a filter function to be captured alone or in combination can be used at the time of idling. NOx purification, filter regeneration, and removal of poisoning are possible, and the performance reliability and durability of the exhaust aftertreatment device can be improved.
[0035]
According to the sixth invention, in the case of an engine equipped with a turbocharger, the exhaust energy is supplied to the exhaust aftertreatment device located downstream of the turbocharger without being recovered by the turbocharger. Moreover, the temperature rise effect by post injection can be utilized efficiently.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic configuration diagram of a diesel engine, in which 1 is an engine body, 2 is an intake passage, and 3 is an exhaust passage.
[0037]
The engine includes a common rail fuel injection device 4. This is mainly composed of a fuel tank (not shown), a supply pump, a common rail (accumulation chamber) 5, and a fuel injection nozzle 6 provided for each cylinder. The high-pressure fuel generated in the high-pressure supply pump is stored in the common rail 5, and the fuel injection nozzle 6 By opening and closing the nozzle needle with the three-way valve 7, the start and end of injection can be freely controlled. The fuel pressure in the common rail 5 is always controlled to the optimum value required by the engine by the pressure sensor and the discharge amount control mechanism of the supply pump.
[0038]
9 is an EGR valve (EGR device) that is provided in a passage 8 that communicates the exhaust passage 3 and the intake passage 2, and 11 is a turbocharger (exhaust turbine 11a, The compressor 11b and the variable nozzle 11c) and 12 are intercoolers.
[0039]
Control of the fuel injection amount, injection timing, fuel pressure, and the like is performed by a control unit 15 constituted by a microprocessor. For this reason, the control unit 15 receives signals from an accelerator opening sensor 16, a sensor 17 for detecting the engine speed and crank angle, a sensor 18 for cylinder discrimination, and a water temperature sensor 19 from an intake air temperature sensor and an atmospheric pressure sensor (not shown). The control unit 15 calculates the target fuel injection amount and the fuel injection timing according to the engine speed and the accelerator opening based on these signals, and in the nozzle corresponding to the target fuel injection amount. The ON time of the three-way valve 7 is controlled, and the ON timing of the three-way valve 7 is controlled corresponding to the target injection timing.
[0040]
The exhaust passage 3 is provided with a NOx catalyst 13 having an oxidation catalyst function. The NOx catalyst 13 adsorbs NOx in the exhaust in a region where the excess air ratio of the exhaust gas exceeds 1, and desorbs the adsorbed NOx when the excess air ratio becomes 1 or less. Reduction and purification is performed using HC and CO existing in an atmosphere with a rate of 1 or less as a reducing agent. In order to regenerate the NOx catalyst 13 by periodically reducing and purifying the adsorbed NOx of the NOx catalyst 13, the control unit 15 performs post-injection in the expansion stroke after the main injection. The purpose of post injection at this time is
(1) Raising the exhaust temperature by rich combustion and thereby raising the temperature of the catalyst;
(2) Promote the reduction of NOx by the catalyst (for that purpose, the excess air ratio must be less than 1)
Therefore, the target excess air ratio is set to 1.0 or less.
[0041]
  A DPF (diesel particulate filter) 14 downstream of the NOx catalyst 13 is for capturing exhaust particulates such as soot. When the exhaust particulate matter trapped in the DPF 14 reaches a predetermined value, the exhaust gas temperature is raised and the exhaust particulate is self-ignited and burned to regenerate the DPF 14 so that the control unit 15 performs an expansion stroke after the main injection under certain conditions. Perform post-injection. The purpose of post-injection at this time is to burn exhaust particulates (that is, oxygen is required, so the excess air ratio must be 1 or more).BecauseFor example, the target excess air ratio is set to 1.2 or less.
[0042]
As described above, both of the post-injections are performed for the regeneration of the NOx catalyst 13 and the DPF 14, but the purpose of the post-injection and the target excess air ratio at that time are different from each other, so the operation of performing the post-injection to regenerate the NOx catalyst 13 is performed. Are distinguished from the rich operation, and the operation of performing the post injection to regenerate the DPF 14 is referred to as the regeneration operation.
[0043]
Although such post-injection is also performed during idling, the post-injection amount when the excess air ratio is 1.2 or less is an amount that is several times the post-injection amount that is generally performed conventionally. Post torque that was outside is generated. Therefore, the target rotational speed TNE is maintained even when post injection is performed in an amount that is several times the post injection amount that is generally performed conventionally, so that the rotational speed does not vary under the influence of the post torque. Thus, the control unit 15 controls the post injection timing in addition to the main injection amount. In particular,
(1) A control amount distribution coefficient KDNE is determined according to a predetermined target excess air ratio Tlamb,
(2) By distributing the deviation DNE from the target rotational speed TNE with this distribution coefficient KDNE, DNE × KDNE is used as a control amount for the post injection timing, whereas DNE × (1-KDNE) is used for the main injection amount. As a controlled variable,
(3) After that, feedback amounts ItIscP and QfIscM are calculated using each control amount and PID gain (feedback gain).
(4) The target post injection timing TItP and the main injection amount QfMI are calculated by correcting the corresponding post injection timing TPIT and fuel injection amount Qf with the feedback amounts ItIscP and QfIscM.
[0044]
The contents of the control including the idle rotation speed control performed by the control unit 15 will be described based on a flowchart.
[0045]
FIG. 2 is a flow for calculating the fuel injection amount Qf. This flow is executed each time a crank angle reference position signal (abbreviated as Ref. In the figure) is input. In step 1, the engine rotational speed Ne and the accelerator opening CL are read, and in step 2, the basic fuel injection amount Mqdrv is calculated by searching a map having the contents shown in FIG. In step 3, various corrections are made to the basic fuel injection amount based on the engine coolant temperature, etc., and the fuel injection amount based on the map containing FIG. 4 in step 4 for the corrected value Qf1. The maximum value Qf1MAX is limited, and the value after the limit is calculated as the fuel injection amount Qf.
[0046]
FIG. 5 is a flow for calculating the cylinder intake fresh air amount Qac.
[0047]
In step 1, the output voltage of the air flow meter (AMF) is read, and in step 2, the intake air amount is calculated from this output voltage by table conversion. In Step 3, a weighted average process is performed on the calculated intake air amount in order to smooth out the influence of the intake pulsation.
[0048]
In step 4, the engine rotational speed Ne is read. In step 5, the intake air amount Qac0 per cylinder is calculated from the rotational speed Ne and the weighted average value Qas0 of the intake air amount.
[0049]
[Expression 1]
Qac0 = (Qas0 / Ne) × KCON #,
Where KCON # is a constant,
Calculate with the following formula.
[0050]
The air flow meter is provided in the intake passage upstream of the compressor, and in order to delay the transport delay from the air flow meter to the collector, in step 6, the value of Qac0 n times (where n is an integer constant) times before the collector inlet position Is obtained as the intake fresh air amount Qacn per cylinder. And in step 7, for this Qacn
[0051]
[Expression 2]
Qac = Qac_n-1× (1-Kvol × Kin) + Qacn × Kvol × Kin,
However, Qac_n-1: The previous value of Qac,
Qac is calculated by the following formula (primary delay formula): the intake fresh air amount per cylinder at the intake valve position (this intake fresh air amount is hereinafter referred to as “cylinder intake fresh air amount”). This is to compensate for the fresh air dynamics from the collector inlet to the intake valve.
[0052]
FIG. 6 is a flow for calculating the volumetric efficiency equivalent value Kin. In step 1, the cylinder intake fresh air amount Qac, the fuel injection amount Qf, and the engine speed Ne are read. In Steps 2 and 3, the volume efficiency basic value KinH1 is retrieved by searching a map containing the content of FIG. 7 from the cylinder intake fresh air amount Qac and the rotational speed Ne, and FIG. 8 is derived from the fuel injection amount Qf and the rotational speed Ne. The volume efficiency load correction value KinH2 is calculated by searching the map to be calculated, and the volume efficiency equivalent value Kin is calculated by multiplying these KinH1 and KinH2 in step 4.
[0053]
FIG. 9 is a flow for setting the rich operation flag based on the operation history. This flow is executed every predetermined time (for example, every 100 ms). First, in step 1, F is the previous value of the rich operation flag. RS_n-1See. F immediately after starting RS_n-1= 0, IntgNES which is the previous value of the variable in Step 2_n-1The value obtained by adding the engine speed Ne at that time to IntgNES, which is the current value of the variable, is similarly set to IntgVSPS, which is the previous value of the variable in Step 3._n-1A value obtained by adding the vehicle speed VSP at that time to IntgVSPS which is a current value of the variable. Thereby, the variables IntgNES and IntgVSPS represent the integrated values of the engine speed and the vehicle speed, respectively.
[0054]
In step 5, the variable IntgNES representing the integrated value of the engine speed is compared with a predetermined value NERS #. When the variable IntgNES exceeds the predetermined value NERS #, the rich operation flag F is set in step 6 in order to perform the rich operation. The process ends with RS = 1. When the variable IntgNES is equal to or smaller than the predetermined value NERS #, the process proceeds from step 5 to step 7, and this time, the variable IntgVSPS representing the integrated value of the vehicle speed is compared with the predetermined value VSPRS #. In order to perform rich operation even when the variable IntgVSPS exceeds the predetermined value VSPRS #, the rich operation flag F in step 6 The process ends with RS = 1.
[0055]
The next time is 100 ms later, and at the next timing when the rich operation flag = 1, F RS_n-1Since = 1, the process proceeds to step 4 and both variables are reset (IntgNES = 0, IntgVSPS = 0). After this, the process proceeds from Steps 5 and 7 to Step 8, and the rich operation flag F The process ends with RS = 0. The next time after 100 ms, the process proceeds from step 1 to steps 2 and 3, and the engine speed and the vehicle speed are added again.
[0056]
In this way, according to FIG. 9, the rich operation flag F RS is a flag that becomes 1 only for 100 ms from the timing when the integrated value of the engine speed or the vehicle speed exceeds a predetermined value.
[0057]
FIG. 10 is a flow for setting the regeneration operation flag based on the operation history. The process of FIG. 10 is the same as the process of FIG. F which is the previous value of the regeneration operation flag in step 1 RG_n-1See. F immediately after startup RG_n-1Since = 0, the process proceeds to step 2 and the previous value of the variable, IntgNEG_n-1The value obtained by adding the engine speed Ne at that time to IntgNEG which is the current value of the variable, and similarly, in step 3, IntgVSPG which is the previous value of the variable._n-1A value obtained by adding the vehicle speed VSP at that time to IntgVSPG which is the current value of the variable. Thereby, IntgNEG and IntgVSPG represent the integrated values of the engine speed and the vehicle speed, respectively.
[0058]
In step 5, a variable IntgNEG representing the integrated value of the engine speed is compared with a predetermined value NERG #. When the variable IntgNEG exceeds the predetermined value NERG #, the regeneration operation flag F is set in step 6 in order to perform the regeneration operation. The process ends with RG = 1. If the variable IntgNEG is less than or equal to the predetermined value NERG #, the process proceeds from step 5 to step 7, and this time, the variable IntgVSPG representing the integrated value of the vehicle speed is compared with the predetermined value VSPRG #. In order to perform the regeneration operation even when the variable IntgVSPG exceeds the predetermined value VSPRG #, the regeneration operation flag F in step 6 is performed. The process ends with RG = 1.
[0059]
The next time is 100 ms later, and at the next timing when flag = 1, F RG_n-1Since = 1, the process proceeds to step 4 to reset both variables (IntgNEG = 0, IntgVSPG = 0). Thereafter, the process proceeds from Steps 5 and 7 to Step 8, and the regeneration operation flag F The process ends with RG = 0. The next time after 100 ms, the process proceeds from step 1 to steps 2 and 3, and the engine speed and the vehicle speed are added again.
[0060]
In this way, according to FIG. 10, the regeneration operation flag F is only given for 100 ms from the timing when the integrated value of the rotational speed or the vehicle speed exceeds the predetermined value. RG = 1.
[0061]
FIG. 11 shows the post injection flag F This is a flow for setting POST. Post injection permission judgment is performed by checking the contents of steps 1 to 7 one by one. When all the items are satisfied, post injection is permitted. . That is,
Step 1) The engine speed Ne and the fuel injection amount Qf are in the post-injection permission region.
[0062]
Step 2) The atmospheric pressure Pa is within a predetermined range.
[0063]
Step 3) The atmospheric temperature Ta is within a predetermined range.
[0064]
Step 4) The cooling water temperature Tw is within a predetermined range.
[0065]
Step 5) The cylinder intake fresh air amount Qac is within a predetermined range.
[0066]
Step 6) Rich operation flag F RS = 1 or regeneration operation flag F RG = 1.
Sometimes post injection flag F to allow post injection operation in step 7 If POST = 1, otherwise, post-injection operation is not permitted. It is assumed that POST = 0.
[0067]
FIG. 12 is a calculation flow of the target main injection timing TMIT. In step 1, the engine speed Ne, the fuel injection amount Qf, the atmospheric pressure Pa, the cooling water temperature Tw, the intake fresh air temperature Ta, the above three flags (post injection flag F POST, rich operation flag F RS, regeneration operation flag F RG) is read, and in step 2, one of the maps shown in FIGS. 13 to 15 is selected according to the three flags, and the selected map is searched from the engine speed Ne and the fuel injection amount Qf. To calculate the basic value TMITB of the target main injection timing.
[0068]
In Steps 3 to 5 in FIG. 12, the water temperature correction coefficient KMITTw of the target main injection timing is obtained by searching the tables having the contents of FIGS. 16, 17, and 18 from the cooling water temperature Tw, the intake fresh air temperature Ta, and the atmospheric pressure Pa. An intake air temperature correction coefficient KMITTA and an atmospheric pressure correction coefficient KMITPa are calculated.
[0069]
[Equation 3]
KM IT = KMITTw × KMITTA × KMITPa
The main injection timing correction amount KM Calculate IT. In step 7, the main injection timing correction amount KM Using IT
[0070]
[Expression 4]
TMIT1 = KM IT x TMITB
The target main injection timing basic value TMITB is corrected by the following formula, and the corrected value is set as the target main injection timing TMIT1.
[0071]
The target main injection timing basic value TMITB is a value (advance amount) measured from the predetermined crank angle position to the advance side. Therefore, the main injection timing is advanced when the correction coefficients KMITTw, KMITTA, and KMITPa are values greater than 1.0. As shown in FIG. 16, the value of the correction coefficient KMITTw is set to a value larger than 1.0 at a low water temperature because the fuel temperature is low and combustion tends to be delayed at a low water temperature. It is for bringing. When the intake fresh air temperature Ta is low as shown in FIG. 17, the correction coefficient KMITTA is set to a value larger than 1.0, and when the atmospheric pressure Pa is low as shown in FIG. 18, the correction coefficient KMITPa is set to a value larger than 1.0. This is because of the same reason.
[0072]
In step 8 of FIG. 12, the maximum main injection timing MITMAX and the minimum main injection timing MITMIN are calculated by searching a map having the contents shown in FIGS. 19 and 20 from the engine speed Ne and the fuel injection amount Qf, and TMIT1 is the maximum. If the value is between the minimum value and the minimum value, the value of TMIT1 is calculated. If TMIT1 exceeds the maximum value, MITMAX is calculated. If TMIT1 is lower than the minimum value, MTMIN is calculated as the target main injection timing TMIT. This is a limiter process.
[0073]
FIG. 21 is a calculation flow of the post injection timing TPIT. The calculation method itself is the same as the target main injection timing. In Step 1, the engine speed Ne, the fuel injection amount Qf, the atmospheric pressure Pa, the cooling water temperature Tw, the intake fresh air temperature Ta, and the rich operation flag F RS, regeneration operation flag F Read RG. In step 2, either one of the maps shown in FIGS. 22 and 23 is selected according to the values of these two flags, and the post-injection timing is searched by searching the selected map from the engine speed Ne and the fuel injection amount Qf. The basic value TPITB is calculated. Although not shown, the post injection flag F When POST = 0, there is no need to perform post injection, so the post injection timing is not calculated.
[0074]
In Steps 3 to 5 of FIG. 21, by searching a table containing the contents of FIGS. 24, 25 and 26 from the cooling water temperature Tw, the intake fresh air temperature Ta, and the atmospheric pressure Pa, the water temperature correction coefficient KPITTw of the post injection timing, the intake air The temperature correction coefficient KPITTa and the atmospheric pressure correction coefficient KPITPa are calculated, and in step 6
[0075]
[Equation 5]
KP IT = KPITTw × KPITTTa × KPITPa
Post injection timing correction amount KP Calculate IT. In step 7, this post injection timing correction amount KP Using IT
[0076]
[Formula 6]
TPIT1 = KP IT x TPITB
The post-injection timing basic value TPITB is corrected by the following formula, and the corrected value is set as the post-injection time TPI1.
[0077]
The post-injection timing basic value TPITB is also a value (advance amount) measured from the predetermined crank angle position to the advance side, similarly to the aforementioned target main injection timing basic value TMITB. Further, when the correction coefficients KPITTw, KPITTTa, KPITPa are larger than 1.0, the post injection timing is advanced. The reason why the post-injection characteristics are shown in FIGS. 24, 25, and 26 is the same as that of the main injection characteristic shown in FIGS. 16, 17, and 18.
[0078]
In step 8 of FIG. 21, the maximum post-injection timing ITPMAX and the minimum post-injection timing ITPMIN are calculated by searching a map having the contents shown in FIGS. 27 and 28 from the engine speed Ne and the fuel injection amount Qf, and TPIT1 is the maximum. If the value is between the minimum value and the minimum value, the value of TPIT1 is calculated. If TPIT1 exceeds the maximum value, ITPMAX is calculated. If TPIT1 is below the minimum value, ITPMIN is calculated as the target post-injection timing TPIT (limiter processing).
[0079]
FIG. 29 is a flow for calculating the target excess air ratio. In this case, since the operation is divided into a regeneration operation, a rich operation, and a normal operation other than that, an optimum excess air ratio is determined for each operation as shown in FIGS. (Even when the speed and the fuel injection amount Qf are the same, the values decrease in the order of normal operation in FIG. 32, regeneration operation in FIG. 30, and rich operation in FIG. 31). For this reason, the target excess air ratio suitable for the operation at that time is calculated by checking which operation is being performed. That is, in steps 1 and 2, the regeneration operation flag F RG or rich operation flag F Look at RS. F When RG = 1 (during the regeneration operation), the target excess air ratio TramRG during the regeneration operation is calculated by searching a map having the contents shown in FIG. Enter the value Tlamb0. Similarly, F When RS = 1 (during rich operation), the map having the contents shown in FIG. 31 is searched in step 4 to obtain the target excess air rate TlambRS during rich operation, and when both flags are 0, in step 5 The target excess air ratio TlambNM during normal operation is calculated by searching a map having the contents shown in FIG. 32, and this is entered into the target excess air ratio basic value Tlamb0 in steps 7 and 8.
[0080]
In Step 9 of FIG. 29, a water temperature correction coefficient KlambTW and an atmospheric pressure correction coefficient KlambPA are calculated by searching a table containing the contents of FIGS. 33 and 34 from the cooling water temperature Tw and the atmospheric pressure Pa, and these are multiplied to excess air. The rate correction amount Klamb is calculated. In step 10, the excess air ratio correction amount Klamb is used.
[0081]
[Expression 7]
Tlamb = Tlamb0 × Klamb
The target excess air ratio Tlamb is calculated by the following formula.
[0082]
In the middle of the experiment, how the correction coefficients KlambTW and KlambPA are to be processed are shown in FIG. 33 and FIG. 34, which incorporate the experimental results up to now. That is, the reason why the excess air ratio is set to be slightly higher at the low water temperature is that white smoke caused by HC is likely to be generated at the low water temperature because the fuel evaporation is slow. The reason why the excess air ratio is set to be low at the low atmospheric pressure is to compensate for the decrease in the torque due to the decrease in the air at the low atmospheric pressure. In any case, the characteristics shown in FIGS. 33 and 34 are not absolute.
[0083]
FIG. 35 is a control flow of the idle rotation speed. In step 1, it is determined from the accelerator opening, the engine speed, etc. whether or not it is within the feedback control range of the idle speed. In the feedback control range of the idle rotation speed, a difference DNE from the target rotation speed TNE of the actual rotation speed Ne is calculated in steps 2 to 4.
[0084]
The calculation of the target rotation speed TNE will be described with reference to the flowchart of FIG. In FIG. 36, the cooling water temperature Tw is read in steps 1 and 2, and a target idle speed basic value TNE0 is calculated by searching a table having the contents shown in FIG. 37 from this value. The basic value TNE0 is a value that increases as the temperature decreases. In step 3, the idle speed correction amount is calculated from the battery voltage or the like. For example, the correction amount corresponding to the battery voltage Bat is as shown in FIG. In step 4, a value obtained by adding the correction amount and the basic value is calculated as the target rotational speed TNE.
[0085]
In step 5 of FIG. 35, the control amount distribution coefficient KDNE is calculated by searching a table having the contents shown in FIG. 39 from the target excess air rate Tlamb (obtained in FIG. 29).
[0086]
[Equation 8]
DNEMI = (1−KDNE) × DNE,
DNEPI = KDNE × DNE,
The respective control amounts DNEMI and DNEI assigned to the main injection amount control and the post injection timing control are calculated by the respective formulas, and the main injection correction amount QfIscM and the post injection timing correction amount are calculated in steps 8 and 9 based on these control amounts DNEMI and DNEI. ItIscP is calculated.
[0087]
Here, the characteristics of the control amount distribution coefficient KDNE in FIG. 39 correspond to those in FIG. That is, when the excess air ratio is λ3 or more, the value of KDNE is 0, and increases as the excess air ratio becomes smaller than λ3, and the excess air ratio reaches a peak of less than 1 at λ2. Furthermore, it becomes smaller as the excess air ratio becomes smaller, and returns to almost 0 below λ1. For this reason, as the value of KDNE approaches 1, the proportion of torque control by the main injection amount decreases corresponding to the increase of the proportion of torque control by post injection timing, and conversely, the value of KDNE approaches 0. Corresponding to the decrease in the ratio of controlling the torque by the post injection timing, the ratio of controlling the torque by the main injection amount is increased. Note that λ1, λ2, and λ3 shown in FIG. 57B are also written here. Further, in the vicinity of λ2 in FIG. 39, the maximum value is not set to 1 but a little less than 1, leaving room for control by the main injection amount when the rotational fluctuation occurs due to a change in the auxiliary load during idling. Needless to say, the control is performed to absorb the rotational fluctuation.
[0088]
The calculation of the main injection correction amount QfIscM will be described with reference to the flow of FIG. 40, and the calculation of the post injection timing correction amount ItIscP will be described with reference to the flow of FIG. Note that these calculations follow an algorithm of the following equation of a proportional / integral / derivative compensator (other control mechanisms may be used).
[0089]
[Equation 9]

However, u (t) is an operation amount, KP is a proportional gain, KI is an integration time constant, KD is a differentiation time constant, e (t) is a deviation, and u (t0) is an initial value of u.
[0090]
First, from FIG. 40, in step 1 in FIG. 40, the proportional, integral, and differential gains KPM, KIM, and KDM are calculated, and then in step 2, the integral gain KIM and the assigned control amount DNEMI are used.
[0091]
[Expression 10]
IscMI = IscMI_n-1+ (DT / KIM) × DNEMI,
Where dT: calculation cycle,
IscMI_n-1: Previous value of IscMI,
The integral correction value IscMI is calculated by the following equation, and the value obtained by limiting this value within the upper and lower limit values in step 3 is again set as the integral correction value IscMI.
[0092]
In step 4, the amount of change in the allocation control amount DNEMI and the differential gain KDM are used.
[0093]
## EQU11 ##
IscMD = (DNEMI-DNEMI_n-1) X KDM / dT
However, DNEMI_n-1: Previous value of DNEMI,
The differential correction value IscMD is calculated by the following equation, and in step 5, the proportional gain KPM, the assigned control amount DNEMI, the integral correction value IscMI, and the differential correction value IscMD are used.
[0094]
[Expression 12]
QfIscM = KPM × (DNEMI + IscMI + IscMD) + QfMini,
Where QfMini: initial value,
The main injection correction amount QfIscM is calculated by the following formula.
[0095]
Here, QfMini, which is the initial value of the integral correction value, is given a value that is about 1/4 to 1/2 of the fuel injection amount during idling. This is to accelerate the convergence of the integral control.
[0096]
The calculation of the three gains KPM, KIM, and KDM will be described with reference to FIG. In FIG. 41, in step 1, the proportional gain KPM is calculated by the product of the proportional gain basic value KPMB, the excess air ratio correction coefficient KPML, and the post injection timing correction coefficient KPMPIT. Similarly, in steps 2 and 3, the integral gain KIM and the differential gain KDM are calculated by the product of the integral gain and the differential gain basic values KIMB and KDMB, the excess air ratio correction coefficients KIML and KDML, and the post injection timing correction coefficients KIMPIT and KDMPIT. .
[0097]
  However, the basic value, the excess air ratio correction coefficient, and the post injection timing correction coefficient are not constant values, and the basic values KPMB, KIMB, and KDMB vary according to the coolant temperature Tw as shown in FIG. KDML is as shown in FIG.GoalAccording to the excess air ratio, the post injection timing correction coefficients KPMITT, KIMPIT, and KDMPIT are set according to the post injection timing TPIT as shown in FIG.
[0098]
Here, in FIG. 42, the gain is set to be smaller at the time of low water temperature than after the warm-up is completed (if not, there is a risk of hunting). The same applies to FIG. 47 described later.
[0099]
Next, the calculation of the post injection timing correction amount ItIscP will be described with reference to the flowchart of FIG. After calculating the proportional, integral and derivative gains KPT, KIT and KDT in step 1, in step 2
[0100]
[Formula 13]
    IscTI = IscTI_n-1+ (DT / KIT) X DNEPI,
      Where dT: calculation cycle,
              IscTI_n-1: Previous value of IscMI,
The integral correction value IscTI is calculated by the following equation, and this value is limited within the upper and lower limit values in step 3, and the result is again set as the integral correction value IscTI. In step 4
[0101]
[Expression 14]
IscTD = (DNEPI-DNEPI_n-1) X KDT / dT,
However, DNEPI_n-1: The previous value of DNEPI,
The differential correction value IscTD is calculated according to the equation
[0102]
[Expression 15]
ItIscP = KPT × (DNEPI + IscTI + IscTD) + ITPini,
However, ITPini: initial value,
The post injection timing correction amount ItIscP is calculated by the following formula.
[0103]
ITPini is the initial value of the integral correction value, similar to QfMini in equation (12).
[0104]
The calculation of the proportional, integral, and differential gains KPT, KIT, and KDT will be described with reference to FIG. This process is the same as in FIG. That is, in steps 1, 2, and 3 in FIG. 46, the basic values KPTB, KITB, KDTB, excess air ratio correction coefficients KPTL, KITL, KDTL, and post-injection timing correction coefficients KPPTIT, KITPIT, KDTPIT in proportional gain, integral gain, and differential gain. The proportional gain KPT, the integral gain KIT, and the differential gain KDT are calculated with the product of The basic values KPTB, KITB, and KDTB are in accordance with the cooling water temperature Tw as shown in FIG. 47, and the excess air ratio correction coefficient KPTL, KITL, and KDTL are in accordance with the excess air ratio as in FIG. KITPIT and KDTPIT are set according to the post injection timing TPIT as shown in FIG.
[0105]
When the main injection correction amount QfIscM and the post injection timing correction amount ItIscP are calculated in this way, returning to FIG. 35, the correction amounts are used in steps 10 and 11.
[0106]
[Expression 16]
TQfMI = Qf + QfIscM,
TItP = TPIT + ItIscP,
The main injection amount TQfMI and the target post-injection timing TItP are calculated by the following equations. In addition, “+” on the right side of the arithmetic expression of the target post injection timing TItP means an advance angle.
[0107]
On the other hand, when it is not in the feedback control range of the idle rotation speed, the process proceeds from step 1 to steps 12 and 13 where the fuel injection amount Qf is used as it is as the main injection amount TQfMI and the post injection timing TPIT is used as the target post injection timing TItP.
[0108]
The post injection amount is a value obtained by subtracting the main injection amount from the injection amount calculated from the target excess air ratio. For example, as shown in FIG.
[0109]
[Expression 17]
TQfP = Qac / Tlamb-TQfMI
The post injection amount TQfP may be calculated by the following formula.
[0110]
Then, the main injection is performed using the main injection amount TQfMI and the target main injection timing TMIT, and the post injection is performed using the post injection amount TQfP and the target post injection timing TItP.
[0111]
Next, the operation during idling of the present embodiment will be described with reference to FIG. FIG. 50 shows how the injection pulse applied to the three-way valve changes when the excess air ratio changes corresponding to the post injection amount in approximately three cases. In the figure, the main injection is performed by a stepped pulse on the left side (a large current is supplied to the solenoid at the beginning of the valve opening in order to speed up the opening operation of the nozzle needle, and then the current is reduced and the nozzle needle is held at the valve opening position). The post injection is performed by the right pulse (rectangular pulse). The absence of the right pulse indicates that no post-injection is performed.
[0112]
In the figure, for simplicity, the main injection start timing is the same in the three cases. Therefore, if the main injection end timing is delayed, the main injection amount increases. Conversely, if the main injection end timing is advanced, the main injection amount increases. Will be reduced.
[0113]
First, FIG. 50A shows a waveform during normal operation without post injection (when λ3 or more in FIG. 39). At this time, the torque is controlled by the main injection amount. That is, when the actual rotational speed Ne falls below the target value, the torque is increased by delaying the main injection end timing. Conversely, when the actual rotational speed Ne rises above the target value, the torque is increased by advancing the main injection end timing. As a result, the actual rotational speed is returned to the target value (see the one-dot chain line). This is the same as the conventional apparatus.
[0114]
As the post injection amount increases from this state, the excess air ratio decreases, so the ratio of controlling the torque at the post injection timing increases, and when the excess air ratio becomes λ2 in FIG. It is a waveform of 50 (b). In this state, the main injection amount is substantially fixed to a predetermined value, and the torque is controlled by the post injection timing (post injection start timing) (see the one-dot chain line). That is, when the actual rotational speed Ne increases from the target value due to the generation of the post torque, the torque is reduced by delaying the post injection start timing, and conversely, when the actual rotational speed Ne decreases from the target value, the post injection start timing is set. The torque is increased by the advancement, and thereby the actual rotational speed is returned to the target value.
[0115]
In this case, even if the post-injection amount is set to be large, the main injection amount is not reduced unlike the conventional device, so the minimum necessary torque is secured by the main injection, and the target excess air rate Tlamb is Since the post-injection amount is basically an amount that achieves this target excess air ratio Tlamb (see Equation 17), the exhaust temperature is reduced to the desired temperature by post-injection. It is possible to suppress deterioration of combustion, drivability and exhaust while increasing.
[0116]
As the post-injection amount further increases, the rate of controlling the torque at the post-injection timing decreases, and when the excess air ratio approaches 1 (= λ1) in FIG. Torque is controlled by the main injection amount. The waveform at this time is the waveform of FIG. That is, as in FIG. 50 (a), when the actual rotational speed Ne decreases from the target value, the torque is increased by delaying the main injection end timing. Conversely, when the actual rotational speed Ne increases from the target value, the main injection is performed. The torque is reduced by advancing the end timing, and the actual rotational speed is thereby returned to the target value (see the alternate long and short dash line).
[0117]
Next, in the second embodiment, a calculation flow shown in FIG. 51 is added to the first embodiment.
[0118]
In an engine equipped with a turbocharger having a variable nozzle, the thermal energy recovered by the exhaust turbine 11a of the supercharger is reduced by opening the variable nozzle 11c, and the exhaust temperature downstream of the exhaust turbine 11a can be kept high. Therefore, in the second embodiment, when post injection is performed including idling, the variable nozzle 11c is opened to suppress the thermal energy recovered by the exhaust turbine 11a, thereby increasing the exhaust temperature increase effect by post injection. It is what I did.
[0119]
51 will be described in detail. In step 1, the duty ratio TDTYVNT given to the actuator that drives the variable nozzle is calculated in the same manner as in the prior art. Since this calculation method does not matter, details are omitted.
[0120]
In step 2, the post injection flag F Watch POST. Flag F When POST = 1 (when post injection is performed), the process proceeds to step 3 and a target duty ratio TDTYVNTP at the time of post injection is calculated by searching a map having the contents shown in FIG. The duty ratio is TDTYVNTF. One flag F When POST = 0, the process proceeds from step 2 to step 5, and the duty ratio TDTYVNT is set as the final target duty ratio TDTYVNTF as it is.
[0121]
Here, if the characteristic of FIG. 52 is set to the side where the variable nozzle is opened in the region where the post injection is performed, the thermal energy recovered by the exhaust turbine 11a is suppressed, and the exhaust temperature rises by the post injection accordingly. Since the effect is enhanced, the functions of the NOx catalyst 13 and the DPF 14 can be enhanced.
[0122]
The characteristics shown in FIG. 52 are obtained by adding the basic value when post-injection is not performed and the correction amount to the opening side of the variable nozzle when post-injection is performed. it can. In other words, the final target duty ratio is determined from the correction amount obtained by searching for this map and the duty ratio TDTYVNT as the basic value by creating a map of only the correction amount to the opening side of the variable nozzle when performing post injection. You may make it calculate.
[Brief description of the drawings]
FIG. 1 is a control system diagram of a first embodiment.
FIG. 2 is a flowchart for explaining calculation of a fuel injection amount.
FIG. 3 is a characteristic diagram of a basic fuel injection amount.
FIG. 4 is a characteristic diagram of a maximum injection amount.
FIG. 5 is a flowchart for explaining calculation of a cylinder suction EGR amount.
FIG. 6 is a flowchart for explaining calculation of a volumetric efficiency equivalent value.
FIG. 7 is a characteristic diagram of volumetric efficiency basic values.
FIG. 8 is a characteristic diagram of a volumetric efficiency load correction value.
FIG. 9 is a flowchart for explaining setting of a rich operation flag.
FIG. 10 is a flowchart for explaining the setting of a regeneration operation flag.
FIG. 11 is a flowchart for explaining setting of a post-injection flag.
FIG. 12 is a flowchart for explaining calculation of a target main injection timing.
FIG. 13 is a characteristic diagram of a target main injection timing basic value (F POST = 0).
FIG. 14 is a characteristic diagram of a target main injection timing basic value (F RS = 1).
FIG. 15 is a characteristic diagram of a target main injection timing basic value (F RG = 1).
FIG. 16 is a characteristic diagram of a water temperature correction coefficient.
FIG. 17 is a characteristic diagram of an intake air temperature correction coefficient.
FIG. 18 is a characteristic diagram of an atmospheric pressure correction coefficient.
FIG. 19 is a characteristic diagram of the maximum main injection timing.
FIG. 20 is a characteristic diagram of the minimum main injection timing.
FIG. 21 is a flowchart for explaining calculation of a post injection timing.
FIG. 22 is a characteristic diagram of the basic value of post injection timing (F RS = 1).
FIG. 23 is a characteristic diagram of the post main injection timing basic value (F RG = 1).
FIG. 24 is a characteristic diagram of a water temperature correction coefficient.
FIG. 25 is a characteristic diagram of an intake air temperature correction coefficient.
FIG. 26 is a characteristic diagram of an atmospheric pressure correction coefficient.
FIG. 27 is a characteristic diagram of the maximum post injection timing.
FIG. 28 is a characteristic diagram of minimum post injection timing.
FIG. 29 is a flowchart for explaining calculation of a target excess air ratio.
FIG. 30 is a characteristic diagram of a target excess air ratio during regeneration operation.
FIG. 31 is a characteristic diagram of a target excess air ratio during rich operation.
FIG. 32 is a characteristic diagram of a target excess air ratio during normal operation.
FIG. 33 is a characteristic diagram of a water temperature correction coefficient.
FIG. 34 is a characteristic diagram of an atmospheric pressure correction coefficient.
FIG. 35 is a flowchart for explaining idle rotation speed control;
FIG. 36 is a flowchart for explaining calculation of a target rotation speed.
FIG. 37 is a characteristic diagram of a target rotation speed basic value.
FIG. 38 is a characteristic diagram of a battery voltage correction amount.
FIG. 39 is a characteristic diagram of a control amount distribution coefficient.
FIG. 40 is a flowchart for explaining calculation of a main injection correction amount.
FIG. 41 is a flowchart for explaining calculation of a feedback gain.
FIG. 42 is a characteristic diagram of a gain basic value.
FIG. 43 is a characteristic diagram of an excess air ratio correction coefficient.
FIG. 44 is a characteristic diagram of a post injection timing correction coefficient.
FIG. 45 is a flowchart for explaining calculation of a post injection timing correction amount;
FIG. 46 is a flowchart for explaining calculation of a feedback gain.
FIG. 47 is a characteristic diagram of a gain basic value.
FIG. 48 is a characteristic diagram of an excess air ratio correction coefficient.
FIG. 49 is a characteristic diagram of a post injection timing correction coefficient.
FIG. 50 is a waveform diagram for explaining the operation of the first embodiment.
FIG. 51 is a flowchart for explaining calculation of a final target duty ratio according to the second embodiment;
FIG. 52 is a characteristic diagram of a post-injection target duty ratio according to the second embodiment.
FIG. 53 is a diagram showing a conventional apparatus in a control system.
FIG. 541FIG.
FIG. 552FIG.
FIG. 56 is a characteristic diagram showing the relationship between post-injection fuel consumption, post-torque and exhaust (HC), and post-injection timing when the post-injection amount is set large.
FIG. 57 is a characteristic diagram for explaining the control principle of the present invention having an excess air ratio to determine the control amount distribution coefficient KDNE.
FIG. 58 is a flowchart for explaining calculation of a post injection amount according to the first embodiment;
[Explanation of symbols]
  6 Fuel injection valve
  15 Control unit

Claims (6)

In a control device for a diesel engine that performs main injection and post-injection in the expansion stroke after the main injection,
When performing post-injection during idling, it is provided with torque control means for controlling the main injection amount and post-injection timing so that the target rotational speed is maintained ,
The torque control means includes
Means for setting a target excess air ratio;
Means for calculating the deviation of the actual engine speed from the target speed;
Means for setting a control amount distribution coefficient representing a share ratio of post-injection with respect to torque control to a value that increases as the target excess air ratio increases according to the target excess air ratio;
Means for determining the control amount for the post injection timing and the control amount for the main injection amount by distributing the deviation by the control amount distribution coefficient;
Means for calculating a post-injection timing feedback amount using a control amount for the post-injection timing and a feedback gain;
Means for correcting the post injection timing by this feedback amount and calculating the target post injection timing;
Means for calculating a feedback amount of the main injection amount using a control amount and a feedback gain for the main injection amount;
Means for correcting the fuel injection amount by this feedback amount and calculating the main injection amount;
Control device for a diesel engine, characterized in that it consists of. In a control device for a diesel engine that performs main injection and post-injection in the expansion stroke after the main injection,
Torque control means for controlling the main injection amount and the post injection timing so that the target rotational speed is maintained when post injection is performed during idling
With
The torque control means includes
Means for setting a target excess air ratio;
Means for calculating the deviation of the actual engine speed from the target speed;
Control of the main injection amount so the control amount distribution coefficient as the target excess air ratio is increased according to feedback gain woven controlled variable distribution coefficient in the target excess air ratio which represents the distribution ratio of the post-injection is increased relative to the torque control And means for setting separately for post injection timing control,
Means for calculating a feedback amount of the post injection timing by using the target excess air ratio to be more changes the feedback gain and the deviation of the control of the post injection timing,
Means for correcting the post injection timing by this feedback amount and calculating the target post injection timing;
Means for calculating a feedback amount of the main injection amount using changes more target excess air ratio and feedback gain control of the main injection amount and said difference,
A diesel engine control device comprising: means for correcting the fuel injection amount by the feedback amount and calculating a main injection amount.   The change in post torque relative to the change in post injection timing is defined as post torque sensitivity, and the range showing the phenomenon that the post torque sensitivity improves as the target excess air ratio increases is from the lower limit value to the larger limit value. 3. The diesel engine according to claim 1, wherein, when defined, the control amount distribution coefficient is set so that the torque control at the post-injection timing is weighted closer to the larger limit value. Control device. The control device for a diesel engine according to claim 1 , wherein a feedback gain used for calculating a feedback amount of the post injection timing is corrected according to the post injection timing.   A single NOx catalyst function that maintains NOx in an atmosphere with an excess air ratio exceeding 1 and purifies NOx in an atmosphere with an excess air ratio of 1 or less, an oxidation catalyst function that oxidizes HC / CO, or a filter function that traps exhaust particulates. 5. The diesel engine control device according to claim 1, further comprising an exhaust emission control device having a combination thereof. 6. The diesel engine control device according to claim 5, further comprising a turbocharger that suppresses exhaust energy recovered by the turbocharger when performing post-injection during idling .

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