JP2004068806A

JP2004068806A - Exhaust emission control device of internal combustion engine

Info

Publication number: JP2004068806A
Application number: JP2003106627A
Authority: JP
Inventors: Shinichiro Okugawa; 奥川　伸一朗; Tsukasa Kuboshima; 窪島　司; Makoto Saito; 斉藤　誠; Shigeto Yabaneta; 矢羽田　茂人
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2002-06-14
Filing date: 2003-04-10
Publication date: 2004-03-04
Anticipated expiration: 2023-04-10
Also published as: JP4352745B2; DE10326784B4; DE10326784A1

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device using a DPF capable of improving detection precision of PM deposit quantity in the middle of reproduction and restraining an aggravation in fuel consumption and a deterioration in the DPF. <P>SOLUTION: The DPF 4 is set between exhaust pipes 2a, 2b of an engine 1, and a first signal processing means to smooth output of a particulate deposit quantity computing means to compute the PM deposit quantity and a second signal processing means to smooth the output of the particulate deposit quantity computing means so that responsibility of the output against input of signal processing becomes higher than the first signal processing means are provided. Slippage with actual PM deposit quantity is reduced by improving the responsiveness by smoothing it by the second signal processing means in the case when time change of the PM deposit quantity is large as in the middle of reproduction. A stabilized detection value is provided by smoothing it by the first signal processing means in the middle of non-reproduction. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関の排出ガスに含まれるパティキュレートを捕集するためのパティキュレートフィルタを備える排気浄化装置に関する。
【０００２】
【従来の技術】
環境対策として、従来より、ディーゼルエンジンから排出されるパティキュレート（粒子状物質；ＰＭ）を低減するための装置が種々提案されている。その代表的なものに、ディーゼルパティキュレートフィルタ（以下ＤＰＦと称する）を備えた排ガス浄化装置があり、排気管内に設置したＤＰＦの多孔質の隔壁を排出ガスが通過する際に、パティキュレートを捕集するように構成されている。
【０００３】
ＤＰＦは、パティキュレートの堆積量が増加すると圧損が増大し、エンジン性能を低下させることから、適正な時期にパティキュレートを燃焼させて、ＤＰＦを再生する必要がある。再生には、バーナやヒータ等の加熱装置を用いることもできるが、近年、例えばポスト噴射や噴射時期の遅角といった噴射制御を行って、ＤＰＦに導入される排気を昇温させる技術が提案され、運転状態に応じた細かな制御が可能となっている。
【０００４】
この時、ＤＰＦのパティキュレート堆積量（以下ＰＭ堆積量と称する）を正確に検出して、ＤＰＦの再生時期の決定を適切に行うことが重要である。再生制御に関する従来技術としては、例えば、特開平８−２１０１２１号公報等があり、ＤＰＦの前後差圧からＰＭ堆積量を算出し、これを基にＤＰＦの再生時期を決定する際に、差圧検出値を平均化して安定化させることが開示されている。
【０００５】
【発明が解決しようとする課題】
しかしながら、差圧検出値を数分間に渡って平均化する信号処理方法は、入力信号変化に対する出力信号変化の応答性が低い。このため、パティキュレートが徐々に堆積していくといったＰＭ堆積量の時間変化が小さい場合には有効な処理であるが、例えば、ＤＰＦ再生中のように、ＰＭ堆積量が急激に減少する場合、図５に示すように、実際のＰＭ堆積量　（実線）とＰＭ堆積量算出値　（点線）とのずれが増大して、精度の高い検出ができない問題がある。さらに、図６に示すように、再生を開始するＰＭ堆積量および再生を終了するＰＭ堆積量をそれぞれ設定し、ＰＭ堆積量算出値を基に再生開始および終了を制御する場合には、図７に示すように、必要以上に長く再生を行うことになり、排気の昇温制御による燃費の悪化およびＤＰＦの劣化をまねくおそれがあった。
【０００６】
そこで、本発明の目的は、ＤＰＦを用いた排気浄化装置において、ＰＭ堆積量の検出精度を高め、再生中のようにＰＭ堆積量の時間変化が大きい場合においても、ＰＭ堆積量を精度良く検出して、ＤＰＦの再生を制御性良く行うことにより、燃費の悪化やＤＰＦの劣化を抑制することにある。
【０００７】
【課題を解決するための手段】
上記課題を解決するために、請求項１の内燃機関の排気浄化装置は、
内燃機関の排気管内に設置されて排気中のパティキュレートを捕集するパティキュレートフィルタと、
上記パティキュレートフィルタによるパティキュレート堆積量を算出するパティキュレート堆積量算出手段と、
上記パティキュレート堆積量算出手段の出力を平滑化または平均化処理する応答性の異なる複数の信号処理手段と、
上記複数の信号処理手段の出力の１つを選択してパティキュレート堆積量を決定するパティキュレート堆積量決定手段と、
上記パティキュレート堆積量決定手段の出力を基に上記パティキュレートフィルタの再生の実施時期を判定する再生実施判定手段と、
上記再生実施判定手段の判定結果を基に上記パティキュレートフィルタを昇温して再生を実施する再生実施手段とを備えている。
【０００８】
請求項１の発明によれば、例えば、上記パティキュレートフィルタの再生中は、応答性の高い信号処理手段を用いて上記パティキュレート堆積量算出手段の出力を平滑化し、通常時（非再生時）は、応答性の低い信号処理手段を用いて上記パティキュレート堆積量算出手段の出力を平滑化する。これにより、再生中は高応答でパティキュレート堆積量を検出して、再生に不必要に長い時間を要することを防止し、通常時（非再生時）は、十分安定したパティキュレート堆積量の算出値を得ることで、検出精度を向上させることができる。よって、パティキュレート堆積量の変化が大きい場合にも、堆積量を精度良く検出し、制御性良く上記パティキュレートフィルタの再生を行うことができ、燃費の悪化やＤＰＦの劣化を抑制できる。
【０００９】
請求項２の内燃機関の排気浄化装置は、上記課題を解決するための他の構成であり、内燃機関の排気管内に設置されて排気中のパティキュレートを捕集するパティキュレートフィルタと、
上記パティキュレートフィルタによるパティキュレート堆積量を算出するパティキュレート堆積量算出手段と、
上記パティキュレート堆積量算出手段の出力を平滑化する第１信号処理手段と、
上記第１信号処理手段よりも信号処理の入力に対する出力の応答性が高くなるように上記パティキュレート堆積量算出手段の出力を平滑化する第２信号処理手段と、
上記第１信号処理手段の出力と上記第２信号処理手段の出力のいずれかを選択してパティキュレート堆積量を決定するパティキュレート堆積量決定手段と、
上記パティキュレート堆積量決定手段の出力を基に上記パティキュレートフィルタの再生の実施時期を判定する再生実施判定手段と、
上記再生実施判定手段の判定結果を基に上記パティキュレートフィルタを昇温して再生を実施する再生実施手段とを備えている。
【００１０】
請求項２の発明によれば、例えば、上記パティキュレートフィルタの再生中は、応答性の高い上記第２信号処理手段を用いて上記パティキュレート堆積量算出手段の出力を平滑化し、通常時（非再生時）は、上記第１信号処理手段を用いて上記パティキュレート堆積量算出手段の出力を平滑化する。これにより、再生中は高応答でパティキュレート堆積量を検出して、再生に不必要に長い時間を要することを防止し、通常時（非再生時）は、十分安定したパティキュレート堆積量の算出値を得ることで、検出精度を向上させることができる。よって、パティキュレート堆積量の変化が大きい場合にも、堆積量を精度良く検出し、制御性良く上記パティキュレートフィルタの再生を行うことができ、燃費の悪化やＤＰＦの劣化を抑制できる。
【００１１】
請求項３の内燃機関の排気浄化装置は、上記課題を解決するための他の構成であり、内燃機関の排気管内に設置されて排気中のパティキュレートを捕集するパティキュレートフィルタと、
上記パティキュレートフィルタによるパティキュレート堆積量を算出するパティキュレート堆積量算出手段と、
上記パティキュレート堆積量算出手段の出力を所定期間に渡り平均化処理する第１信号処理手段と、
上記第１信号処理手段よりも短い所定の期間に渡り上記パティキュレート堆積量算出手段の出力を平均化処理する第２信号処理手段と、
上記第１信号処理手段の出力と上記第２信号処理手段の出力のいずれかを選択してパティキュレート堆積量を決定するパティキュレート堆積量決定手段と、
上記パティキュレート堆積量決定手段の出力を基に上記パティキュレートフィルタの再生の実施時期を判定する再生実施判定手段と、
上記再生実施判定手段の判定結果を基に上記パティキュレートフィルタを昇温して再生を実施する再生実施手段とを有している。
【００１２】
請求項３の発明において、上記第２信号処理手段は、上記第１信号処理手段よりも信号処理を行う期間が短いので、信号入力に対する出力の応答性が高くなる。よって、再生中のようなパティキュレート堆積量の変化が大きい場合に、上記第２信号処理手段を用い、それ以外の場合には、上記第１信号処理手段を用いることで、上記請求項１と同様の効果が得られる。
【００１３】
請求項４の構成において、上記パティキュレート堆積量算出手段は、上記パティキュレートフィルタのパティキュレート堆積量を反映する圧力を検出する圧力検出手段と、内燃機関の排気流量を検出する排気流量検出手段を有している。ある排気流量において、パティキュレート堆積量の増加とともに、上記パティキュレートフィルタの前後差圧等の圧力が増加するので、上記圧力検出手段と上記排気流量検出手段の出力を基に上記パティキュレートフィルタによるパティキュレート堆積量を算出することができる。
【００１４】
請求項５の構成において、上記パティキュレート堆積量決定手段は、上記再生実施手段が作動中である時に、上記第２信号処理手段の出力をパティキュレート堆積量と決定し、それ以外の時には、上記第１信号処理手段の出力をパティキュレート堆積量と決定する。具体的には、上記パティキュレートフィルタが再生中がどうかを、上記再生実施手段が作動中であるかどうかで判定することができ、これを基に信号処理手段を選択することで、ＤＰＦの再生を制御性良く行うことができる。
【００１５】
あるいは、請求項６の構成のように、上記パティキュレート堆積量決定手段が、上記パティキュレートフィルタの温度を検出するＤＰＦ温度検出手段を有し、上記ＤＰＦ温度検出手段の出力が所定値を越えた時に、上記第２信号処理手段の出力をパティキュレート堆積量と決定し、それ以外の時には、上記第１信号処理手段の出力をパティキュレート堆積量と決定するようにしてもよい。上記パティキュレートフィルタの温度を直接検出して、再生中がどうかを判定することもでき、高速走行時の排気温度上昇や、減速時の燃料カットで排気中の酸素濃度が増加するといった理由によって生じる自然燃焼等によりパティキュレート堆積量が急減するような場合にも、精度良い検出が可能になる。
【００１６】
請求項７の構成では、上記ＤＰＦ温度検出手段として、上記パティキュレートフィルタの上流または下流の排気管に設置される排気温度検出手段を設ける。この時、上記パティキュレートフィルタの上流または下流またはその両方の排気温度を基に上記パティキュレートフィルタの温度を検出することができる。
【００１７】
請求項８の構成では、上記ＤＰＦ温度検出手段における上記所定値を６００℃以上とする。上記パティキュレートフィルタの再生中には、通常、６００℃程度ないしそれ以上の温度となるので、上記パティキュレートフィルタが６００℃以上の所定の温度となったか否かで、再生中か否かを判定することができる。
【００１８】
請求項９の構成のように、具体的には、上記再生実施判定手段は、上記パティキュレート堆積量決定手段の出力が第１所定値を越えた時に上記再生実施手段を作動させる。そして、上記パティキュレート堆積量決定手段の出力が第１所定値よりも小さい第２所定値を下回った時に、上記再生実施手段の作動を停止させることで、算出したパティキュレート堆積量を基に、再生制御を容易に行うことができる。
【００１９】
請求項１０の構成において、上記圧力検出手段は、上記パティキュレートフィルタの前後の差圧を検出する。パティキュレート堆積量の増加に伴い、上記パティキュレートフィルタの前後の差圧が増加するので、これを基にパティキュレート堆積量を算出することができる。
【００２０】
あるいは、請求項１１の構成のように、上記圧力検出手段が、上記パティキュレートフィルタの上流の排気圧力を検出するようにしてもよい。上記パティキュレートフィルタの上流の排気圧力とパティキュレート堆積量も同様の関係にあるので、これを基にパティキュレート堆積量を算出することができる。
【００２１】
【発明の実施の形態】
以下、本発明の第１の実施の形態を図１に基づいて説明する。図１（ａ）はディーゼルエンジンの排気浄化装置の全体構成を示すもので、エンジン１から排出された排気ガスは、排気管２ａ、２ｂ間に設置されたディーゼルパティキュレートフィルタ４（ＤＰＦ）を通過してパティキュレートが捕集された後に、外部へ放出される。ＤＰＦ４は公知の構成で、例えば、コーディエライト等の耐熱性セラミックスをハニカム構造に成形してなる。ガス流路となるハニカム構造体の多数のセルは入口側または出口側が互い違いに目封じされており、排気ガス中のパティキュレートは、セルとセルを区画する多孔性の隔壁を通過する際に捕集される。
【００２２】
排気管２ａ、２ｂは、圧力検出手段である差圧センサ５に接続される。差圧センサ１の一端側には、圧力取込管５１を介してＤＰＦ４上流の排気管２ａの圧力が導入され、差圧センサ１の他端側には、圧力取込管５２を介してＤＰＦ４下流の排気管２ｂの圧力が導入されるようになっている。差圧センサ５は、ＥＣＵ６に接続されており、ＤＰＦ４の前後差圧検出値を出力する。また、排気管２ｂには、ＤＰＦ温度検出手段および排気温度検出手段としての排気温センサ８が設置してある。排気管２ａに、ＤＰＦ温度検出手段および排気温度検出手段としての排気温センサ８を設置することもできる。排気温センサ７、８は、ＥＣＵ６に接続されており、ＤＰＦ４の上流側の排気温度または下流側の排気温度を検出して、ＥＣＵ６に出力する。また、エンジン１の吸気管３には、エアフロメータ９が設置してあり、吸気量を検出して、ＥＣＵ６に出力する。
【００２３】
ＥＣＵ６は、差圧センサ５、排気温センサ７、８およびエアフロメータ９の出力値に基づき、エンジン１の排気流量の算出、ＤＰＦ４のパティキュレート堆積量（ＰＭ堆積量）の算出等の演算を行う（排気流量算出手段、パティキュレート堆積量算出手段）。一般に、ある排気流量に対して、ＤＰＦ４に堆積するパティキュレートの量が増加するのに伴い、差圧センサ５で検出されるＤＰＦ４の前後差圧が増加することから、この関係を利用してＰＭ堆積量を算出することができる。
【００２４】
ここで、ＥＣＵ６は、ＰＭ堆積量の算出値を信号処理により安定化させる。例えば、図３のように、ＤＰＦ４の前後差圧等から算出したＰＭ堆積量算出値（信号処理前）を、信号処理を行って平滑化させることで、安定した出力（信号処理後のＰＭ堆積量算出値）を得ることができる。ただし、この方法は、ＰＭ堆積量が短時間で急激に変化しない場合には有効な方法であるものの、再生中のように、ＰＭ堆積量の時間変化が大きい場合には、実際のＰＭ堆積量とのずれが大きくなりやすい（図５）。そこで、本発明では、パティキュレート堆積量算出手段の出力を平滑化または平均化処理する応答性の異なる複数の信号処理手段を設ける。具体的には、従来の方法でＰＭ堆積量の算出値を平滑化処理する第１信号処理手段と、第１信号処理手段よりも信号処理の入力に対する出力の応答性が高くなるように、ＰＭ堆積量の算出値を平滑化処理する第２信号処理手段を設ける。
【００２５】
ＥＣＵ６は、第１信号処理手段と第２信号処理手段の算出値のいずれかを選択して、ＰＭ堆積量を決定する（パティキュレート堆積量決定手段）。さらに、決定されたＰＭ堆積量から上記パティキュレートフィルタの再生を実施する時期かどうかを判定し（再生実施判定手段）、この再生実施判定手段の判定結果を基にＤＰＦ４を昇温して再生させる（再生実施手段）。
【００２６】
ＤＰＦ４の昇温手段として、具体的には、燃料噴射の際に、ポスト噴射や噴射時期の遅角を行ったり、あるいは、吸気スロットルを通常より閉じ側とする等の制御を行うことで、排気を昇温させることができる。例えば、ポスト噴射や遅角を行うと、着火時期の遅れ等により、エネルギーの一部が動力に返還されずに排気の熱エネルギーになるために、通常噴射の場合の排気温度（１５０℃〜４００℃）に対し、より高温（３００℃〜７００℃）の排気がＤＰＦ４内に導入される。吸気スロットルを閉じ側とした場合も同様で、吸気量が減少し、エンジン１の燃焼室内に流入するガスの熱容量が減少するために、排気温度が上昇する。この高温の排気により、ＤＰＦ４内に付着したパティキュレートを燃焼させ、捕集能力を回復させることができる。ＤＰＦ４を昇温させるために、バーナやヒータといった加熱装置を用いることもできる。
【００２７】
このＥＣＵ６の作動の一例を図２に示すフローチャートを用いて説明する。本処理は、ＥＣＵ６において所定の周期で実行され、ＥＣＵ６は、まず、ステップ１０１で、差圧センサ５からＤＰＦ前後差圧Ｐ〔ｋＰａ〕を、エアフロメータ９から吸気量Ｇａ〔ｇ／ｓｅｃ　〕を読み込む。また、排気温センサ７からＤＰＦ４の下流側排気温度を読み込み、ＤＰＦ温度Ｔ〔℃〕を算出する。ここでは、例えば、下流側排気温度をＤＰＦ温度Ｔとしているが、排気温センサ８にて検出されるＤＰＦ４の上流側排気温度を用いたり、上流側排気温度と下流側排気温度の両方を基にＤＰＦ温度Ｔを算出することも可能である。
【００２８】
ステップ１０２では、ＤＰＦ前後差圧Ｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、吸気量Ｇａ〔ｇ／ｓｅｃ　〕から、ＤＰＦ４を通過する排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕を算出する。排気流量Ｖｅｘは、吸気量Ｇａ〔ｇ／ｓｅｃ　〕を、ＤＰＦ温度Ｔ〔℃〕とＤＰＦ前後差圧Ｐ〔ｋＰａ〕を用いて、体積流量に換算することにより求められ、具体的には、下記式（１）を用いて算出する。
Ｖｅｘ＝Ｇａ×２２．４／２８．８×１０１．３／（１０１．３＋Ｐ）｝×（２７３＋Ｔ）／２７３　　　・・・（１）
【００２９】
次に、ステップ１０３に進み、ＤＰＦ前後差圧Ｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、および排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕から、ＤＰＦ４に堆積しているパティキュレートの堆積量（平滑化前ＰＭ堆積量算出値）Ｍａｃｍ（ｉ）を算出する。排気流量に対するＤＰＦ前後差圧の関係は、図４のようになり、ある排気流量に対して、ＰＭ堆積量の増加に応じて差圧が増加することから、この関係を利用して、予め記録してあるマップからＰＭ堆積量を算出することができる。
【００３０】
ステップ１０４では、ＤＰＦ４の再生が実施されているか否かをＤＰＦ再生フラグＸｒｅｇｅｎ　により判定し、その判定結果により平滑化処理方法を選択する。ステップ１０４で、ＤＰＦ４の再生中でないと判定された場合には、ステップ１０５へ進んで、通常の信号処理方法（第１信号処理手段）により、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平滑化処理を行い、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　の算出式を下記式（２）に示す。
ΔＭ＝Ｍａｃｍ（ｉ）−Ｍｐｍ（ｉ−１）
Ｍｐｍ（ｉ）　＝Ｍｐｍ（ｉ−１）　＋ΔＭ／α_１
α_１：定数　　　　　　　　　　　・・・（２）
【００３１】
ＤＰＦ４の再生中と判定された場合には、ステップ１０６へ進み、より応答性の高い信号処理方法（第２信号処理手段）を選択して、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平滑化処理を行い、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　の算出式を下記式（３）に示す。
ΔＭ＝Ｍａｃｍ（ｉ）−Ｍｐｍ（ｉ−１）
Ｍｐｍ（ｉ）　＝Ｍｐｍ（ｉ−１）　＋ΔＭ／β_１
β_１：定数（α_１＞β_１）　　　　・・・（３）
【００３２】
上記ステップ１０５、１０６の信号処理方法において、平滑化処理の応答性は定数α_１または定数β_１により決まり、定数が小さいほど、応答性が高くなる。このため、ＤＰＦ４の再生中の信号処理方法（式（３））における定数β_１を、非再生中の信号処理方法（式（２））における定数α_１より小さくして、再生中の信号処理の応答性を高くすることができる。
【００３３】
ステップ１０７では、算出された平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値を越えたか否かを判定し、第１所定値を越えた場合には、ステップ１０８へ進んで、ＤＰＦ再生フラグをＯＮにし、上述した昇温手段を用いてＤＰＦ４の再生を実施する。ステップ１０７で、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値以下である場合は、ステップ１０９へ進んで、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第２所定値より小さいか否かを判定し、第２所定値より小さい場合には、ステップ１１０でＤＰＦ再生フラグをＯＦＦにして、再生を中止する。この時、第１所定値は、図６における再生開始ＰＭ堆積量に、第２所定値は再生終了ＰＭ堆積量に対応し、第２所定値＜第１所定値である。
【００３４】
以上のように、再生中と、非再生中とで、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）を平滑化するための信号処理方法を変更し、再生中には、高応答の信号処理方法を採用して平滑化後ＰＭ堆積量算出値Ｍｐｍを算出する。これにより、図８に示すように、信号処理後ＰＭ堆積量算出値と実際のＰＭ堆積量からのずれを小さくすることができ、図７のように不必要な再生処理による燃費の悪化等の不具合を解消できる。
【００３５】
図９に本発明の第２の実施の形態を示す。本実施の形態の排気浄化装置の基本構成は、上記図１と同様であり、図示を省略する。上記第１の実施の形態において、ＥＣＵ６は、ＤＰＦ４が再生中か否かをＤＰＦ再生フラグＸｒｅｇｅｎ　のＯＮ、ＯＦＦにより判定したが、ＤＰＦ温度が所定値を越えたか否かを基に判定するようにしてもよい。図９は、この場合の処理を示すフローチャートで、まず、ステップ２０１で、差圧センサ５からＤＰＦ前後差圧Ｐ〔ｋＰａ〕を、エアフロメータ９から吸気量Ｇａ〔ｇ／ｓｅｃ　〕を読み込み、排気温センサ７からＤＰＦ４の下流側排気温度を読み込んでＤＰＦ温度Ｔ〔℃〕を算出する。次に、ステップ２０２で、ＤＰＦ前後差圧Ｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、吸気量Ｇａ〔ｇ／ｓｅｃ　〕から、排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕を算出し、ステップ２０３に進んで、ＤＰＦ前後差圧Ｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、および排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕から、ＤＰＦ４に堆積しているパティキュレートの堆積量（平滑化前ＰＭ堆積量算出値）Ｍａｃｍ（ｉ）を算出する。
【００３６】
ステップ２０４では、ＤＰＦ４の再生が実施されているか否かを、ステップ２０１で算出したＤＰＦ温度Ｔ〔℃〕が所定値を越えたか否かで判定する。一般に、ＤＰＦ４の再生中は、ＤＰＦ温度Ｔ〔℃〕、が６００℃程度、ないしそれ以上となるので、上記所定値を６００℃以上の適当な値とすればよい。ステップ２０４で、ＤＰＦ４の再生中でないと判定された場合には、ステップ２０５へ進んで、通常の信号処理方法（第１信号処理手段）により、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平滑化処理を行い、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。
【００３７】
ステップ２０４で、ＤＰＦ４の再生中と判定された場合には、ステップ２０６へ進み、より応答性の高い信号処理方法（第２信号処理手段）を選択して、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平滑化処理を行い、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。さらに、ステップ２０７では、算出された平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値を越えたか否かを判定し、第１所定値を越えた場合には、ステップ２０８へ進んで、ＤＰＦ再生フラグをＯＮにし、ＤＰＦ４の再生を実施する。ステップ２０７で、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値以下である場合は、ステップ２０９へ進んで、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第２所定値より小さいか否かを判定し、第２所定値より小さい場合には、ステップ２１０でＤＰＦ再生フラグをＯＦＦにして、再生を中止する。
【００３８】
本実施の形態によっても、上記第１の実施の形態と同様の効果が得られ、再生中のように、ＰＭ堆積量の時間変化が大きい場合にも、信号処理の応答性を高くして、精度良くＤＰＦ４の再生制御を行うことができる。また、ＤＰＦ４の温度から再生中か否かを判定することで、自然燃焼等によりパティキュレート堆積量が急減するような場合にも対応でき、精度良い検出が可能になる。
【００３９】
図１０、１１に本発明の第３の実施の形態を示す。図１０に示すように、本実施の形態では、圧力検出手段となる差圧センサ１の役割を圧力センサ５´で代替しており、ＤＰＦ４前後差圧を検出する代わりに、ＤＰＦ４上流の排気圧力を検出する。圧力センサ５´には圧力取り込み管５１を介して、ＤＰＦ４上流の排気管２ａが接続されている。また、上記本実施の形態において、ＥＣＵ６は、ＰＭ堆積量算出手段の出力を所定期間に渡り平均化処理する第１信号処理手段と、これよりも短いＰＭ堆積量算出手段の出力を平均化処理する第２信号処理手段を設けている。この場合も、再生中に第２信号処理手段を、それ以外の場合には、第１信号処理手段を採用することで、同様の効果が得られる。この場合のフローチャートを図１１に示す。
【００４０】
図１１において、まず、ステップ３０１で、圧力センサ５´からＤＰＦ上流排気圧力Ｐｕｐ〔ｋＰａ〕を、エアフロメータ９から吸気量Ｇａ〔ｇ／ｓｅｃ　〕を読み込み、排気温センサ７からＤＰＦ４の下流側排気温度を読み込んでＤＰＦ温度Ｔ〔℃〕を算出する。次に、ステップ３０２で、ＤＰＦ上流排気圧力Ｐｕｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、吸気量Ｇａ〔ｇ／ｓｅｃ　〕から、排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕を算出する。算出には、以下の式（４）を用いる。
Ｖｅｘ＝Ｇａ×２２．４／２８．８×１０１．３／（１０１．３＋Ｐｕｐ）｝×（２７３＋Ｔ）／２７３　　　・・・（４）
【００４１】
ステップ３０３では、ＤＰＦ上流排気圧力Ｐｕｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、および排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕から、ＤＰＦ４に堆積しているパティキュレートの堆積量（平均化前ＰＭ堆積量算出値）Ｍａｃｍ（ｉ）を算出する。次いで、ステップ３０４に進み、ＤＰＦ４の再生が実施されているか否かを、ステップ３０１で算出したＤＰＦ温度Ｔ〔℃〕が所定値を越えたか否かで判定する。ステップ３０４で、ＤＰＦ４の再生中でないと判定された場合には、ステップ３０５へ進んで、通常の信号処理方法（第１信号処理手段）により、平均化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平均化処理を行い、平均化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。平均化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　の算出式を下記式（５）に示す。
【００４２】
【数１】

【００４３】
ＤＰＦ４の再生中と判定された場合には、ステップ３０６へ進み、より応答性の高い信号処理方法（第２信号処理手段）を選択して、平均化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平均化処理を行い、平均化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。平均化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　の算出式を下記式（６）に示す。
【００４４】
【数２】

【００４５】
上記ステップ３０５、３０６の信号処理方法において、平均化処理の応答性は平均化処理期間α_２または平均化処理期間β_２により決定され、期間が短いほど、応答性が高くなる。このため、ＤＰＦ４の再生中の信号処理方法（式（６））における平均化処理期間β_２を、非再生中の信号処理方法（式（５））における平均化処理期間α_２より小さくして、再生中の信号処理の応答性を高くすることができる。
【００４６】
さらに、ステップ３０７では、算出された平均化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値を越えたか否かを判定し、第１所定値を越えた場合には、ステップ３０８へ進んで、ＤＰＦ再生フラグをＯＮにし、ＤＰＦ４の再生を実施する。ステップ３０７で、平均化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値以下である場合は、ステップ３０９へ進んで、平均化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第２所定値より小さいか否かを判定し、第２所定値より小さい場合には、ステップ３１０でＤＰＦ再生フラグをＯＦＦにして、再生を中止する。
【００４７】
本実施の形態によっても、上記第１および第２の実施の形態と同様の効果が得られ、再生中のように、ＰＭ堆積量の時間変化が大きい場合にも、信号処理の応答性を高くして、精度良くＤＰＦの再生制御を行うことができる。
【００４８】
図１２〜図１４に本発明の第４の実施の形態を示す。本実施の形態の排気浄化装置の基本構成は、上記図１と同様であり、図示を省略する。上記第１〜第３の実施の形態では、信号処理手段の応答性を２水準とし、ＥＣＵ６が、再生中か否かに応じて、第１信号処理手段と第２信号処理手段のいずれかを選択するようにしたが、信号処理手段の応答性を３水準以上としてもよい。この場合、例えば、再生中に対応する第２信号処理手段を応答性の異なる複数とし、これらをＤＰＦ４の温度に応じて切替えるようにすることができる。これについて、以下に説明する。
【００４９】
図１２は、ＤＰＦ温度とＰＭ燃焼速度の関係を示す図で、パティキュレートの燃焼速度は、ＤＰＦ４が高温であるほど増加し、逆にＤＰＦ４が低温であるほど減少している。また、再生中のＰＭ堆積量の時間変化は、パティキュレートの燃焼速度に大きく依存する。これはパティキュレートが堆積する速度に対して、パティキュレートの燃焼により堆積量が減少していく速度が十分大きいためである。従って、図１３のように、ＤＰＦ温度が低い時にはＰＭ堆積量の減少はゆるやかであるのに対し、ＤＰＦ温度が高い時にはＰＭ堆積量は急速に減少する。すなわち、ＤＰＦ温度に応じてＰＭ堆積量の時間変化量が異なる。
【００５０】
再生中のＤＰＦ温度は、ＤＰＦ４の安全性や再生の効率を考慮して最適な温度に保たれるが、昇温が困難な運転条件が長時間継続するといった状況や、運転条件の急激な変化といった外乱の影響で、ＤＰＦ温度が最適な温度に対して大きくずれる場合がある。このような場合は、そのＤＰＦ温度でのＰＭ堆積量の時間変化に適した応答性を持つ信号処理手段で、ＰＭ堆積量の算出を行なうことが望ましい。
【００５１】
そこで、本実施の形態では、通常の方法でＰＭ堆積量の算出値を平滑化処理する第１信号処理手段と、これよりも出力の応答性が高い第２信号処理手段を設け、第２信号処理手段は、さらにより出力の応答性が高い、信号処理手段Ａと、これよりも出力の応答性が低い信号処理手段Ｂを有するものとする。そして、ＤＰＦ４の非再生時には第１信号処理手段を選択し、再生中である場合には、ＰＭ堆積量の時間変化の大きいＤＰＦ高温時は、より高応答の信号処理手段Ａを、ＰＭ堆積量の時間変化の小さいＤＰＦ低温時は、より低応答の信号処理手段Ｂを用いる。これにより、再生中の信号処理手段を１水準しか持たない場合に対して、より精度よくＰＭ堆積量算出ができる。
【００５２】
図１４は、この場合の処理を示すフローチャートで、まず、ステップ４０１で、差圧センサ５からＤＰＦ前後差圧Ｐ〔ｋＰａ〕を、エアフロメータ９から吸気量Ｇａ〔ｇ／ｓｅｃ　〕を読み込む。また、排気温センサ７からＤＰＦ４の下流側排気温度を読み込み、ＤＰＦ温度Ｔ〔℃〕を算出する。例えば、下流側排気温度をＴとする。次に、ステップ４０２で、ＤＰＦ前後差圧Ｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、吸気量Ｇａ〔ｇ／ｓｅｃ　〕から、排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕を算出する。ステップ２０３では、ＤＰＦ前後差圧Ｐ〔ｋＰａ〕、ＤＰＦ温度Ｔ〔℃〕、および排気流量Ｖｅｘ〔Ｌ／ｍｉｎ　〕から、上述した図４の関係を利用して、ＤＰＦ４に堆積しているパティキュレートの堆積量（平滑化前ＰＭ堆積量算出値）Ｍａｃｍ（ｉ）を算出する。
【００５３】
ステップ４０４では、ＤＰＦ４の再生が最適な状態で実施されているか否かを、ステップ４０１で算出したＤＰＦ温度Ｔ〔℃〕が、所定値Ａを越えたか否かで判定する。一般に、ＤＰＦ４の再生中は、ＤＰＦ温度Ｔ〔℃〕が６００℃程度、ないしそれ以上となるので、上記所定値Ａを例えば６００℃とし、ＤＰＦ温度Ｔ＞所定値Ａが成立する場合には、ＰＭ堆積量の時間変化の大きいＤＰＦ高温時と判断して、ステップ４０５へ進む。ステップ４０５では、より応答性の高い信号処理方法（信号処理手段Ａ）を選択して、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平滑化処理を行い、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。平滑化処理の応答性は定数β_１によって決定される。
【００５４】
ステップ４０４で、ＤＰＦ温度Ｔが所定値Ａ以下と判定された場合には、ステップ４０６へ進んで、ＤＰＦ温度Ｔ〔℃〕が、所定値Ｂを越えたか否かを判定する。上述したように、ＤＰＦ４の再生中であっても、運転条件によっては、ＤＰＦ温度Ｔ〔℃〕が最適な温度を下回ることがある。そこで、上記所定値Ｂを例えば５００℃とし、ＤＰＦ温度Ｔ＞所定値Ｂが成立する場合には、ＰＭ堆積量の時間変化の小さいＤＰＦ低温時と判断して、ステップ４０７へ進む。ここで、所定値Ａと所定値Ｂの大小関係は、所定値Ａ＞所定値Ｂである。
【００５５】
ステップ４０７では、ＤＰＦ高温時の平滑化処理より応答性の低い信号処理方法（信号処理手段Ｂ）を選択して、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平滑化処理を行い、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。平滑化処理の応答性は定数γ_１によって決定される。
【００５６】
ステップ４０６で、ＤＰＦ温度Ｔが所定値Ｂ以下と判定された場合には、ＤＰＦ４の再生中でないと判定し、ステップ４０８へ進む。ステップ４０８では、通常の信号処理方法（第１信号処理手段）により、平滑化前ＰＭ堆積量算出値Ｍａｃｍ（ｉ）の平滑化処理を行い、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　を算出する。平滑化処理の応答性は定数α_１によって決定される。また、α_１、γ_１、β_１の大小関係はα_１＜γ_１＜β_１である。
【００５７】
ステップ４０９では、算出された平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値を越えたか否かを判定し、第１所定値を越えた場合には、ステップ４１０へ進んで、ＤＰＦ再生フラグをＯＮにし、ＤＰＦ４の再生を実施する。ステップ４０９で、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第１所定値以下である場合は、ステップ４１１へ進んで、平滑化後ＰＭ堆積量算出値Ｍｐｍ（ｉ）　が、第２所定値より小さいか否かを判定し、第２所定値より小さい場合には、ステップ４１２でＤＰＦ再生フラグをＯＦＦにして、再生を中止する。第１所定値と第２所定値の大小関係は、第１所定値＞第２所定値である。
【００５８】
本実施の形態によれば、信号処理手段の応答性を３水準としたので、再生中か非再生中かだけでなく、再生中のＤＰＦ４の温度に応じて、信号処理の応答性を切替えることができる。よって、運転条件によりＤＰＦ温度が最適な再生温度より低く、ＰＭ堆積量の時間変化が小さい場合にも対応できるので、より精度良くＤＰＦ４の再生制御を行うことができる。
【００５９】
なお、上記第３の実施の形態のように、ＰＭ堆積量算出手段の出力を平均化処理する信号処理手段においても、応答性を３水準以上とすることで、同様の効果が得られることはもちろんである。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態における内燃機関の排気浄化装置の全体概略構成図である。
【図２】本発明の第１の実施の形態におけるＥＣＵの制御のフローチャートを示す図である。
【図３】信号処理前のＰＭ堆積量算出値を平滑化処理した結果を示す図である。
【図４】排気流量および差圧とＰＭ堆積量の関係を示す図である。
【図５】ＰＭ堆積量の時間変化と従来の信号処理後のＰＭ堆積量算出値とのずれを示す図である。
【図６】再生によるＰＭ堆積量の時間変化を示す図である。
【図７】信号処理の応答性が低い場合の信号処理後のＰＭ堆積量算出値の時間変化を示す図である。
【図８】信号処理の応答性が高い場合の信号処理後のＰＭ堆積量算出値の時間変化を示す図である。
【図９】本発明の第２の実施の形態におけるＥＣＵの制御のフローチャートを示す図である。
【図１０】本発明の第３の実施の形態における内燃機関の排気浄化装置の全体概略構成図である。
【図１１】本発明の第３の実施の形態におけるＥＣＵの制御のフローチャートを示す図である。
【図１２】ＤＰＦ温度とＰＭ燃焼速度の関係を示す図である。
【図１３】再生中のＤＰＦ温度に応じてＰＭ堆積量の時間変化が異なることを示す図である。
【図１４】本発明の第４の実施の形態におけるＥＣＵの制御のフローチャートを示す図である。
【符号の説明】
１　ディーゼルエンジン（内燃機関）
２ａ、２ｂ　排気管
３　吸気管
４　ＤＰＦ（パティキュレートフィルタ）
５　差圧センサ（圧力検出手段）
６　ＥＣＵ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purification device including a particulate filter for collecting particulates contained in exhaust gas of an internal combustion engine.
[0002]
[Prior art]
As an environmental measure, various devices for reducing particulates (particulate matter; PM) discharged from a diesel engine have been conventionally proposed. A typical example is an exhaust gas purifying apparatus provided with a diesel particulate filter (hereinafter, referred to as DPF). It is configured to gather.
[0003]
Since the pressure loss of the DPF increases as the amount of accumulated particulates increases and the engine performance deteriorates, it is necessary to regenerate the DPF by burning the particulates at an appropriate time. For the regeneration, a heating device such as a burner or a heater can be used. However, in recent years, a technique has been proposed in which the temperature of the exhaust gas introduced into the DPF is increased by performing injection control such as post-injection or retarding the injection timing. In addition, fine control according to the operation state is possible.
[0004]
At this time, it is important to accurately detect the amount of particulate matter accumulated in the DPF (hereinafter referred to as the amount of accumulated PM) and to appropriately determine the DPF regeneration time. As a conventional technique related to regeneration control, for example, there is JP-A-8-210121 and the like. The PM accumulation amount is calculated from the differential pressure across the DPF, and the differential pressure is determined based on the PM accumulation amount. It is disclosed that the detected values are averaged and stabilized.
[0005]
[Problems to be solved by the invention]
However, the signal processing method of averaging the differential pressure detection values over several minutes has low response of an output signal change to an input signal change. For this reason, this is an effective process when the time change of the PM accumulation amount such that the particulates gradually accumulate is small. However, for example, when the PM accumulation amount sharply decreases, such as during DPF regeneration, As shown in FIG. 5, there is a problem that the deviation between the actual PM accumulation amount (solid line) and the PM accumulation amount calculation value (dotted line) increases, so that highly accurate detection cannot be performed. Further, as shown in FIG. 6, when the PM accumulation amount at which the regeneration is started and the PM accumulation amount at which the regeneration is ended are set, and the start and the end of the regeneration are controlled based on the PM accumulation amount calculation value, FIG. As shown in (1), the regeneration is performed for an unnecessarily long time, and there is a fear that the fuel efficiency is deteriorated and the DPF is deteriorated due to the control of the temperature rise of the exhaust gas.
[0006]
Therefore, an object of the present invention is to improve the detection accuracy of the amount of accumulated PM in an exhaust gas purification apparatus using a DPF, and to accurately detect the amount of accumulated PM even when the amount of change in the amount of accumulated PM over time is large, such as during regeneration. Then, by performing DPF regeneration with good controllability, it is to suppress deterioration of fuel efficiency and deterioration of DPF.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, an exhaust gas purification device for an internal combustion engine according to claim 1 is
A particulate filter installed in an exhaust pipe of the internal combustion engine to collect particulates in the exhaust gas;
Particulate accumulation amount calculation means for calculating the amount of particulate accumulation by the particulate filter,
A plurality of signal processing means having different responsiveness for smoothing or averaging the output of the particulate accumulation amount calculation means,
A particulate deposition amount determining means for selecting one of the outputs of the plurality of signal processing means to determine the particulate deposition amount;
Regeneration execution determination means for determining an execution time of regeneration of the particulate filter based on an output of the particulate deposition amount determination means,
A regeneration executing means for increasing the temperature of the particulate filter and performing regeneration based on the judgment result of the regeneration execution judging means.
[0008]
According to the first aspect of the present invention, for example, during the regeneration of the particulate filter, the output of the particulate accumulation amount calculating means is smoothed by using a signal processing means having a high responsiveness. Smoothes the output of the particulate accumulation amount calculating means using signal processing means having low responsiveness. In this way, the amount of accumulated particulates is detected with a high response during regeneration to prevent an unnecessarily long time from being used for regeneration, and a sufficiently stable amount of particulates is calculated during normal times (during non-regeneration). By obtaining the value, the detection accuracy can be improved. Therefore, even when the change in the particulate accumulation amount is large, the accumulation amount can be detected with high accuracy, the particulate filter can be regenerated with good controllability, and deterioration in fuel efficiency and DPF can be suppressed.
[0009]
An exhaust gas purification apparatus for an internal combustion engine according to claim 2 is another configuration for solving the above-mentioned problem, and a particulate filter installed in an exhaust pipe of the internal combustion engine to collect particulates in exhaust gas;
Particulate accumulation amount calculation means for calculating the amount of particulate accumulation by the particulate filter,
First signal processing means for smoothing the output of the particulate accumulation amount calculation means,
Second signal processing means for smoothing the output of the particulate accumulation amount calculation means so that the response of the output to the input of the signal processing is higher than that of the first signal processing means;
Particulate deposition amount determining means for selecting one of the output of the first signal processing means and the output of the second signal processing means to determine the particulate deposition amount;
Regeneration execution determination means for determining an execution time of regeneration of the particulate filter based on an output of the particulate deposition amount determination means,
A regeneration executing means for increasing the temperature of the particulate filter and performing regeneration based on the judgment result of the regeneration execution judging means.
[0010]
According to the second aspect of the present invention, for example, during the regeneration of the particulate filter, the output of the particulate accumulation amount calculating means is smoothed using the second signal processing means having a high response, and the output is normally (non- During reproduction), the output of the particulate accumulation amount calculation means is smoothed using the first signal processing means. In this way, the amount of accumulated particulates is detected with a high response during regeneration to prevent an unnecessarily long time from being used for regeneration, and a sufficiently stable amount of particulates is calculated during normal times (during non-regeneration). By obtaining the value, the detection accuracy can be improved. Therefore, even when the change in the particulate accumulation amount is large, the accumulation amount can be detected with high accuracy, the particulate filter can be regenerated with good controllability, and deterioration in fuel efficiency and DPF can be suppressed.
[0011]
An exhaust gas purification apparatus for an internal combustion engine according to claim 3 is another configuration for solving the above-mentioned problem, and a particulate filter installed in an exhaust pipe of the internal combustion engine to collect particulates in exhaust gas;
Particulate accumulation amount calculation means for calculating the amount of particulate accumulation by the particulate filter,
First signal processing means for averaging the output of the particulate accumulation amount calculation means over a predetermined period;
A second signal processing means for averaging the output of the particulate accumulation amount calculating means over a predetermined period shorter than the first signal processing means;
Particulate deposition amount determining means for selecting one of the output of the first signal processing means and the output of the second signal processing means to determine the particulate deposition amount;
Regeneration execution determination means for determining an execution time of regeneration of the particulate filter based on an output of the particulate deposition amount determination means,
A regeneration execution means for performing regeneration by raising the temperature of the particulate filter based on the determination result of the regeneration execution determination means.
[0012]
According to the third aspect of the present invention, the second signal processing means performs a shorter signal processing period than the first signal processing means, so that the response of the output to the signal input is improved. Therefore, the second signal processing means is used when the change in the amount of particulates deposited is large, such as during reproduction, and in other cases, the first signal processing means is used. Similar effects can be obtained.
[0013]
In the configuration of claim 4, the particulate accumulation amount calculation means includes a pressure detection means for detecting a pressure reflecting the particulate accumulation amount of the particulate filter, and an exhaust flow rate detection means for detecting an exhaust flow rate of the internal combustion engine. Have. At a certain exhaust flow rate, the pressure, such as the differential pressure across the particulate filter, increases with the increase in the amount of accumulated particulates. Therefore, based on the outputs of the pressure detection means and the exhaust flow rate detection means, the particulate matter generated by the particulate filter is reduced. The amount of curated deposition can be calculated.
[0014]
In the configuration of claim 5, the particulate accumulation amount determining means determines the output of the second signal processing means as the particulate accumulation amount when the regeneration performing means is operating, and otherwise, the particulate accumulation amount determining means determines the output. The output of the first signal processing means is determined as a particulate accumulation amount. Specifically, it can be determined whether or not the particulate filter is being regenerated, based on whether or not the regenerating unit is operating. Based on this, by selecting the signal processing unit, the DPF can be regenerated. Can be performed with good controllability.
[0015]
Alternatively, the particulate deposition amount determining means has a DPF temperature detecting means for detecting a temperature of the particulate filter, and an output of the DPF temperature detecting means exceeds a predetermined value. In some cases, the output of the second signal processing means may be determined as the particulate deposition amount, and at other times, the output of the first signal processing means may be determined as the particulate deposition amount. It is also possible to directly detect the temperature of the particulate filter to determine whether regeneration is in progress or not, and this is caused by reasons such as an increase in exhaust gas temperature during high-speed running and an increase in oxygen concentration in exhaust gas due to fuel cut during deceleration. Accurate detection is possible even when the amount of accumulated particulates suddenly decreases due to spontaneous combustion or the like.
[0016]
In the configuration of claim 7, an exhaust gas temperature detecting device provided in an exhaust pipe upstream or downstream of the particulate filter is provided as the DPF temperature detecting device. At this time, the temperature of the particulate filter can be detected based on the exhaust gas temperature at the upstream and / or downstream of the particulate filter.
[0017]
In the configuration of claim 8, the predetermined value in the DPF temperature detecting means is set to 600 ° C. or more. During the regeneration of the particulate filter, the temperature is usually about 600 ° C. or higher. Therefore, it is determined whether the particulate filter has reached a predetermined temperature of 600 ° C. or more to determine whether the particulate filter is being reproduced. can do.
[0018]
Specifically, the regeneration execution determining means activates the regeneration performing means when the output of the particulate accumulation amount determining means exceeds a first predetermined value. Then, when the output of the particulate accumulation amount determining means falls below a second predetermined value smaller than the first predetermined value, the operation of the regeneration performing means is stopped, and based on the calculated particulate accumulation amount, Reproduction control can be easily performed.
[0019]
In the configuration according to claim 10, the pressure detecting means detects a differential pressure across the particulate filter. The differential pressure before and after the particulate filter increases with the increase in the amount of accumulated particulates, so that the amount of accumulated particulates can be calculated based on this.
[0020]
Alternatively, the pressure detecting means may detect an exhaust pressure upstream of the particulate filter. Since the exhaust pressure upstream of the particulate filter and the particulate accumulation amount have a similar relationship, the particulate accumulation amount can be calculated based on this.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIG. FIG. 1A shows an overall configuration of an exhaust gas purification device for a diesel engine. Exhaust gas discharged from the engine 1 passes through a diesel particulate filter 4 (DPF) installed between the

exhaust pipes

2a and 2b. After the particulates are collected, they are released to the outside. The DPF 4 has a known configuration, and is formed by, for example, forming a heat-resistant ceramic such as cordierite into a honeycomb structure. Many cells of the honeycomb structure serving as gas flow passages are alternately plugged on the inlet side or the outlet side, and particulates in the exhaust gas are trapped when passing through the cells and the porous partition walls separating the cells. Gathered.
[0022]
The

exhaust pipes

2a, 2b are connected to a differential pressure sensor 5, which is a pressure detecting means. At one end of the differential pressure sensor 1, the pressure of the exhaust pipe 2 a upstream of the DPF 4 is introduced via a pressure intake pipe 51, and at the other end of the differential pressure sensor 1, the DPF 4 is introduced via a pressure intake pipe 52. The pressure of the downstream exhaust pipe 2b is introduced. The differential pressure sensor 5 is connected to the ECU 6, and outputs a differential pressure detection value before and after the DPF 4. The exhaust pipe 2b is provided with a DPF temperature detecting means and an exhaust gas temperature sensor 8 as an exhaust gas temperature detecting means. The exhaust pipe 2a may be provided with a DPF temperature detecting means and an exhaust gas temperature sensor 8 as an exhaust gas temperature detecting means. The exhaust gas temperature sensors 7 and 8 are connected to the ECU 6 and detect an exhaust gas temperature on the upstream side or an exhaust gas temperature on the downstream side of the DPF 4 and output the detected temperature to the ECU 6. In addition, an air flow meter 9 is installed in the intake pipe 3 of the engine 1, and detects an intake air amount and outputs the detected intake air amount to the ECU 6.
[0023]
The ECU 6 performs calculations such as calculation of the exhaust flow rate of the engine 1 and calculation of the particulate accumulation amount (PM accumulation amount) of the DPF 4 based on the output values of the differential pressure sensor 5, the exhaust gas temperature sensors 7, 8 and the air flow meter 9. (Exhaust flow rate calculation means, particulate accumulation amount calculation means). Generally, as the amount of particulates deposited on the DPF 4 increases with respect to a certain exhaust flow rate, the differential pressure across the DPF 4 detected by the differential pressure sensor 5 increases. The accumulation amount can be calculated.
[0024]
Here, the ECU 6 stabilizes the calculated value of the PM accumulation amount by signal processing. For example, as shown in FIG. 3, the PM accumulation amount calculation value (before signal processing) calculated from the differential pressure across the DPF 4 and the like is subjected to signal processing to be smoothed, thereby providing a stable output (PM accumulation after signal processing). Amount). However, this method is effective when the amount of accumulated PM does not suddenly change in a short time, but when the amount of accumulated PM is largely changed over time, such as during regeneration, the actual amount of accumulated PM is reduced. Deviation tends to be large (FIG. 5). Therefore, in the present invention, a plurality of signal processing units having different responsiveness for smoothing or averaging the output of the particulate accumulation amount calculation unit are provided. Specifically, a first signal processing means for smoothing the calculated value of the amount of accumulated PM by a conventional method, and a PM signal processing means such that the response of the output to the input of the signal processing is higher than that of the first signal processing means. A second signal processing means for smoothing the calculated value of the accumulation amount is provided.
[0025]
The ECU 6 selects one of the calculated values of the first signal processing means and the second signal processing means to determine the PM accumulation amount (particulate accumulation amount determination means). Further, it is determined from the determined amount of accumulated PM whether or not it is time to regenerate the particulate filter (regeneration determining means). Based on the determination result of the regeneration determining means, the DPF 4 is heated and regenerated. (Reproduction implementing means).
[0026]
Specifically, as a means for raising the temperature of the DPF 4, exhaust control is performed by, for example, performing post-injection or retarding the injection timing during fuel injection, or performing control such as closing the intake throttle more than usual. Can be heated. For example, when post-injection or retarding is performed, part of the energy is not returned to the power but becomes thermal energy of the exhaust due to a delay in the ignition timing or the like. Therefore, the exhaust temperature (150 ° C. to 400 ° C.) (° C.), a higher temperature (300 ° C. to 700 ° C.) exhaust gas is introduced into the DPF 4. Similarly, when the intake throttle is closed, the amount of intake air decreases and the heat capacity of gas flowing into the combustion chamber of the engine 1 decreases, so that the exhaust gas temperature rises. By this high-temperature exhaust, the particulates adhering to the inside of the DPF 4 can be burned to recover the trapping ability. In order to raise the temperature of the DPF 4, a heating device such as a burner or a heater may be used.
[0027]
An example of the operation of the ECU 6 will be described with reference to a flowchart shown in FIG. This process is executed at a predetermined cycle in the ECU 6. First, in step 101, the ECU 6 calculates the differential pressure P [kPa] across the DPF from the differential pressure sensor 5 and the intake air Ga [g / sec} from the air flow meter 9. Read. Further, a downstream exhaust temperature of the DPF 4 is read from the exhaust gas temperature sensor 7 to calculate a DPF temperature T [° C.]. Here, for example, the downstream exhaust temperature is set as the DPF temperature T, but the upstream exhaust temperature of the DPF 4 detected by the exhaust temperature sensor 8 is used, or based on both the upstream exhaust temperature and the downstream exhaust temperature. It is also possible to calculate the DPF temperature T.
[0028]
In step 102, the exhaust flow rate Vex [L / min} passing through the DPF 4 is calculated from the pressure difference P [kPa] before and after the DPF, the DPF temperature T [° C], and the intake air amount Ga [g / sec]. The exhaust flow rate Vex is obtained by converting the intake air quantity Ga [g / sec}] into a volume flow rate using the DPF temperature T [° C] and the differential pressure P [kPa] before and after the DPF. It is calculated using equation (1).
Vex = Ga × 22.4 / 28.8 × 101.3 / (101.3 + P) {× (273 + T) / 273} (1)
[0029]
Next, the routine proceeds to step 103, where the amount of particulates deposited on the DPF 4 (before smoothing) is determined based on the differential pressure P [kPa] before and after the DPF, the temperature T [° C.], and the exhaust flow rate Vex [L / min]. The PM accumulation amount calculation value) Macm (i) is calculated. The relationship between the differential pressure of the DPF before and after the exhaust gas flow rate is as shown in FIG. 4. Since the differential pressure increases with an increase in the amount of accumulated PM for a certain exhaust gas flow rate, the relationship is recorded in advance using this relationship. The PM accumulation amount can be calculated from the map.
[0030]
In step 104, it is determined whether or not the regeneration of the DPF 4 is being performed based on the DPF regeneration flag Xregen #, and a smoothing processing method is selected based on the determination result. If it is determined in step 104 that the DPF 4 is not being regenerated, the process proceeds to step 105, and the normal PM signal processing method (first signal processing means) calculates the PM accumulation amount before smoothing Macm (i). A smoothing process is performed, and a post-smoothing PM accumulation amount calculation value Mpm (i) is calculated. The equation for calculating the PM accumulation amount calculation value Mpm (i) （after smoothing is shown in the following equation (2).
ΔM = Macm (i) -Mpm (i-1)
Mpm (i) = Mpm (i−1) + ΔM / α₁
α₁： Constant ・・・ (2)
[0031]
If it is determined that the DPF 4 is being regenerated, the process proceeds to step 106, in which a more responsive signal processing method (second signal processing means) is selected, and the PM deposition amount before smoothing Macm (i) is calculated. A smoothing process is performed, and a post-smoothing PM accumulation amount calculation value Mpm (i) is calculated. The equation for calculating the PM accumulation amount calculation value Mpm (i) after smoothing is shown in the following equation (3).
ΔM = Macm (i) -Mpm (i-1)
Mpm (i) = Mpm (i−1) + ΔM / β₁
β₁: Constant (α₁> Β₁) ・・・ (3)
[0032]
In the signal processing methods of

steps

105 and 106, the responsiveness of the smoothing process is a constant α₁Or the constant β₁The response is higher as the constant is smaller. Therefore, the constant β in the signal processing method (Equation (3)) during the reproduction of the DPF 4₁Is a constant α in the signal processing method during non-reproduction (formula (2)).₁By making it smaller, the responsiveness of signal processing during reproduction can be increased.
[0033]
In step 107, it is determined whether or not the calculated post-smoothing PM accumulation amount calculation value Mpm (i) has exceeded a first predetermined value. If it has exceeded the first predetermined value, the process proceeds to step 108. , The DPF regeneration flag is turned ON, and the regeneration of the DPF 4 is performed by using the above-mentioned temperature raising means. In step 107, when the post-smoothing PM accumulation amount calculation value Mpm (i) 第 is equal to or less than the first predetermined value, the process proceeds to step 109, where the post-smoothing PM accumulation amount calculation value Mpm (i) is set to the second predetermined value. It is determined whether the value is smaller than a predetermined value. If the value is smaller than the second predetermined value, the DPF regeneration flag is turned off in step 110, and the regeneration is stopped. At this time, the first predetermined value corresponds to the regeneration start PM accumulation amount in FIG. 6, and the second predetermined value corresponds to the regeneration end PM accumulation amount, and the second predetermined value <the first predetermined value.
[0034]
As described above, the signal processing method for smoothing the calculated PM accumulation amount before smoothing Macm (i) is changed between during regeneration and during non-regeneration, and during regeneration, high-response signal processing is performed. The PM accumulation amount calculation value Mpm after smoothing is calculated by employing the method. As a result, as shown in FIG. 8, it is possible to reduce the difference between the calculated PM accumulation amount after the signal processing and the actual PM accumulation amount, and to reduce fuel consumption due to unnecessary regeneration processing as shown in FIG. Problems can be resolved.
[0035]
FIG. 9 shows a second embodiment of the present invention. The basic configuration of the exhaust gas purification apparatus of the present embodiment is the same as that of FIG. In the first embodiment, the ECU 6 determines whether or not the DPF 4 is performing regeneration based on whether the DPF regeneration flag Xregen # is ON or OFF. However, the ECU 6 determines whether or not the DPF temperature exceeds a predetermined value. You may. FIG. 9 is a flowchart showing the processing in this case. First, in step 201, the differential pressure P [kPa] before and after the DPF is read from the differential pressure sensor 5 and the intake air amount Ga [g / sec}] is read from the air flow meter 9 and exhausted. The downstream exhaust temperature of the DPF 4 is read from the temperature sensor 7 to calculate the DPF temperature T [° C.]. Next, in step 202, the exhaust flow rate Vex [L / min} is calculated from the pressure difference P [kPa] before and after the DPF, the DPF temperature T [° C], and the intake air amount Ga [g / sec], and the routine proceeds to step 203. , The DPF differential pressure P [kPa], the DPF temperature T [° C.], and the exhaust flow rate Vex [L / min], the amount of particulate matter deposited on the DPF 4 (calculated PM amount before smoothing) Macm (I) is calculated.
[0036]
In step 204, it is determined whether or not the regeneration of the DPF 4 is being performed based on whether or not the DPF temperature T [° C.] calculated in step 201 has exceeded a predetermined value. Generally, during regeneration of the DPF 4, the DPF temperature T [° C.] is about 600 ° C. or more, so the above-mentioned predetermined value may be set to an appropriate value of 600 ° C. or more. If it is determined in step 204 that the DPF 4 is not being regenerated, the process proceeds to step 205 where the normal PM signal processing method (first signal processing means) calculates the PM accumulation amount before smoothing Macm (i). A smoothing process is performed, and a post-smoothing PM accumulation amount calculation value Mpm (i) is calculated.
[0037]
If it is determined in step 204 that the DPF 4 is being reproduced, the process proceeds to step 206, in which a signal processing method (second signal processing means) having higher responsiveness is selected, and the PM accumulation amount before smoothing Macm is calculated. The smoothing process of (i) is performed to calculate a PM accumulation amount calculation value Mpm (i) after smoothing. Further, in step 207, it is determined whether or not the calculated PM accumulated amount calculation value Mpm (i) after smoothing has exceeded a first predetermined value, and if it has exceeded the first predetermined value, the process proceeds to step 208. Then, the DPF regeneration flag is turned ON, and the regeneration of the DPF 4 is performed. In step 207, if the post-smoothing PM accumulation amount calculation value Mpm (i) 以下 is equal to or less than the first predetermined value, the process proceeds to step 209, where the post-smoothing PM accumulation amount calculation value Mpm (i) is set to the second predetermined value. It is determined whether or not the value is smaller than a predetermined value. If the value is smaller than the second predetermined value, the DPF regeneration flag is turned off in step 210, and the regeneration is stopped.
[0038]
According to this embodiment, the same effect as that of the first embodiment can be obtained, and the response of the signal processing can be increased even when the time change of the PM deposition amount is large, such as during reproduction, The regeneration control of the DPF 4 can be accurately performed. Further, by judging whether or not regeneration is being performed from the temperature of the DPF 4, it is possible to cope with a case where the amount of accumulated particulates suddenly decreases due to spontaneous combustion or the like, and accurate detection becomes possible.
[0039]
10 and 11 show a third embodiment of the present invention. As shown in FIG. 10, in the present embodiment, the role of the differential pressure sensor 1 serving as pressure detecting means is replaced by a pressure sensor 5 ', and instead of detecting the differential pressure across the DPF 4, the exhaust pressure upstream of the DPF 4 is reduced. Is detected. An exhaust pipe 2a upstream of the DPF 4 is connected to the pressure sensor 5 'via a pressure intake pipe 51. Further, in the above-described embodiment, the ECU 6 performs the averaging process on the output of the PM accumulation amount calculating unit, the first signal processing unit for averaging the output of the PM accumulation amount calculating unit over a predetermined period, and the averaging process on the output of the PM accumulation amount calculating unit. A second signal processing means for performing the operation. Also in this case, the same effect can be obtained by employing the second signal processing means during reproduction, and otherwise employing the first signal processing means. A flowchart in this case is shown in FIG.
[0040]
11, first, in step 301, the DPF upstream exhaust pressure Pup [kPa] is read from the pressure sensor 5 ', the intake air Ga [g / sec}] is read from the air flow meter 9, and the exhaust gas downstream from the exhaust gas temperature sensor 7 to the DPF 4 is exhausted. The temperature is read and the DPF temperature T [° C.] is calculated. Next, in step 302, the exhaust flow rate Vex [L / min} is calculated from the DPF upstream exhaust pressure Pup [kPa], the DPF temperature T [° C], and the intake air amount Ga [g / sec]. The following equation (4) is used for the calculation.
Vex = Ga × 22.4 / 28.8 × 101.3 / (101.3 + Pup) {× (273 + T) / 273} (4)
[0041]
In step 303, the accumulated amount of particulates accumulated in the DPF 4 (calculation of PM amount before averaging) from the DPF upstream exhaust pressure Pup [kPa], the DPF temperature T [° C.], and the exhaust flow rate Vex [L / min]. Value) Macm (i) is calculated. Next, the routine proceeds to step 304, where it is determined whether or not the DPF 4 is being regenerated by determining whether or not the DPF temperature T [° C.] calculated in step 301 has exceeded a predetermined value. If it is determined in step 304 that the DPF 4 is not being regenerated, the process proceeds to step 305, where the normal PM signal processing method (first signal processing unit) calculates the PM accumulation amount before averaging value Macm (i). An averaging process is performed to calculate a PM accumulation amount calculation value Mpm (i) after averaging. The following equation (5) shows the equation for calculating the averaged PM accumulation amount calculation value Mpm (i) ｉ.
[0042]
(Equation 1)

[0043]
If it is determined that the DPF 4 is being regenerated, the process proceeds to step 306 to select a more responsive signal processing method (second signal processing means) and calculate the PM accumulation amount before averaging value Macm (i). An averaging process is performed to calculate a PM accumulation amount calculation value Mpm (i) after averaging. The equation for calculating the PM accumulation amount calculation value after averaging Mpm (i) is shown in the following equation (6).
[0044]
(Equation 2)

[0045]
In the signal processing methods of steps 305 and 306, the responsiveness of the averaging process is determined by the averaging process period α.₂Or averaging period β₂And the shorter the period, the higher the responsiveness. Therefore, the averaging processing period β in the signal processing method (Equation (6)) during the reproduction of the DPF 4 is performed.₂In the signal processing method (Equation (5)) during non-reproduction.₂By making it smaller, the responsiveness of signal processing during reproduction can be increased.
[0046]
Further, in step 307, it is determined whether or not the calculated averaged PM deposition amount calculation value Mpm (i) has exceeded a first predetermined value. Then, the DPF regeneration flag is turned ON, and the regeneration of the DPF 4 is performed. In step 307, if the averaged PM accumulation amount calculation value Mpm (i) 以下 is equal to or smaller than the first predetermined value, the process proceeds to step 309, where the averaged PM accumulation amount calculation value Mpm (i) is equal to the second PM accumulation amount Mpm (i). It is determined whether or not the value is smaller than a predetermined value. If the value is smaller than the second predetermined value, the DPF regeneration flag is turned off in step 310, and the regeneration is stopped.
[0047]
According to this embodiment, the same effects as those of the first and second embodiments can be obtained, and the responsiveness of signal processing can be improved even when the amount of PM deposition changes over time as during regeneration. Thus, the DPF regeneration control can be accurately performed.
[0048]
12 to 14 show a fourth embodiment of the present invention. The basic configuration of the exhaust gas purification apparatus of the present embodiment is the same as that of FIG. In the above-described first to third embodiments, the responsiveness of the signal processing means is set to two levels, and the ECU 6 switches one of the first signal processing means and the second signal processing means depending on whether or not the reproduction is being performed. Although the selection is made, the responsiveness of the signal processing means may be three or more levels. In this case, for example, a plurality of second signal processing units having different responsivities can be provided during reproduction, and these can be switched according to the temperature of the DPF 4. This will be described below.
[0049]
FIG. 12 is a graph showing the relationship between the DPF temperature and the PM burning speed. The burning speed of the particulate increases as the temperature of the DPF 4 increases, and decreases as the temperature of the DPF 4 decreases. Further, the change over time of the PM accumulation amount during regeneration largely depends on the burning speed of the particulates. This is because the rate at which the amount of accumulation decreases due to the burning of the particulates is sufficiently higher than the rate at which the particulates accumulate. Therefore, as shown in FIG. 13, when the DPF temperature is low, the PM deposition amount decreases slowly, whereas when the DPF temperature is high, the PM deposition amount rapidly decreases. That is, the amount of change over time in the amount of deposited PM differs depending on the DPF temperature.
[0050]
The temperature of the DPF during regeneration is maintained at an optimum temperature in consideration of the safety of the DPF 4 and the efficiency of regeneration. However, operating conditions where it is difficult to raise the temperature continue for a long time, or sudden changes in operating conditions Due to such disturbances, the DPF temperature may deviate significantly from the optimum temperature. In such a case, it is desirable to calculate the amount of accumulated PM by a signal processing unit having a response suitable for a change over time of the amount of accumulated PM at the DPF temperature.
[0051]
Therefore, in the present embodiment, a first signal processing means for smoothing the calculated value of the PM deposition amount by a normal method and a second signal processing means having a higher output response than the first signal processing means are provided. The processing means has a signal processing means A having an even higher output responsiveness and a signal processing means B having a lower output responsiveness. When the DPF 4 is not regenerating, the first signal processing means is selected. When the DPF 4 is being regenerated, the signal processing means A having a higher response is used when the DPF is at a high temperature where the time variation of the PM deposition amount is large. When the DPF is at a low temperature where the time change is small, the signal processing means B having a lower response is used. Thus, the PM accumulation amount can be calculated more accurately than when the signal processing unit during reproduction has only one level.
[0052]
FIG. 14 is a flow chart showing the processing in this case. First, in step 401, the differential pressure sensor 5 reads the pressure difference P [kPa] before and after the DPF, and the air flow meter 9 reads the intake air amount Ga [g / sec}. Further, a downstream exhaust temperature of the DPF 4 is read from the exhaust gas temperature sensor 7 to calculate a DPF temperature T [° C.]. For example, let T be the downstream exhaust temperature. Next, at step 402, the exhaust flow rate Vex [L / min} is calculated from the pressure difference P [kPa] before and after the DPF, the DPF temperature T [° C], and the intake air amount Ga [g / sec]. In step 203, the particulate matter deposited on the DPF 4 is determined from the pressure difference P [kPa] before and after the DPF, the temperature T [° C.] of the DPF, and the exhaust flow rate Vex [L / min] using the relationship shown in FIG. Is calculated (calculated PM accumulation amount before smoothing) Macm (i).
[0053]
In step 404, it is determined whether or not the regeneration of the DPF 4 is performed in an optimum state based on whether or not the DPF temperature T [° C.] calculated in step 401 exceeds a predetermined value A. Generally, during the regeneration of the DPF 4, the DPF temperature T [° C.] is about 600 ° C. or more. Therefore, the predetermined value A is set to, for example, 600 ° C., and when DPF temperature T> predetermined value A is satisfied, It is determined that the DPF is at a high temperature when the PM deposition amount changes greatly with time, and the process proceeds to step 405. In step 405, a signal processing method (signal processing means A) having higher responsiveness is selected, and the PM accumulation amount before smoothing Macm (i) is smoothed, and the PM accumulation amount after smoothing value is calculated. Mpm (i) is calculated. The response of the smoothing process is constant β₁Is determined by
[0054]
If it is determined in step 404 that the DPF temperature T is equal to or lower than the predetermined value A, the process proceeds to step 406, and it is determined whether the DPF temperature T [° C.] exceeds the predetermined value B. As described above, even during the regeneration of the DPF 4, the DPF temperature T [° C.] may be lower than the optimum temperature depending on the operating conditions. Therefore, the predetermined value B is set to, for example, 500 ° C., and when DPF temperature T> predetermined value B is satisfied, it is determined that the DPF is in a low-temperature low state where the time change of the PM accumulation amount is small, and the process proceeds to step 407. Here, the magnitude relationship between the predetermined value A and the predetermined value B is such that the predetermined value A> the predetermined value B.
[0055]
In step 407, a signal processing method (signal processing means B) having lower responsiveness than the smoothing processing at the time of high temperature of the DPF is selected, and the PM accumulation amount calculation value Macm (i) before smoothing is smoothed. Calculated PM accumulation amount calculation value Mpm (i)} is calculated. The response of the smoothing process is a constant γ₁Is determined by
[0056]
If it is determined in step 406 that the DPF temperature T is equal to or lower than the predetermined value B, it is determined that the DPF 4 is not being regenerated, and the process proceeds to step 408. In step 408, the pre-smoothing PM accumulation amount calculation value Macm (i) is smoothed by a normal signal processing method (first signal processing means), and the post-smoothing PM accumulation amount calculation value Mpm (i) is obtained. calculate. The response of the smoothing process is a constant α₁Is determined by Also, α₁, Γ₁, Β₁The relationship of α is α₁<Γ₁<Β₁It is.
[0057]
At step 409, it is determined whether or not the calculated smoothed PM accumulation amount calculation value Mpm (i) has exceeded a first predetermined value. If it has exceeded the first predetermined value, the process proceeds to step 410. , The DPF regeneration flag is turned ON, and the regeneration of the DPF 4 is performed. In step 409, if the post-smoothing PM accumulation amount calculation value Mpm (i) 以下 is equal to or less than the first predetermined value, the process proceeds to step 411, where the post-smoothing PM accumulation amount calculation value Mpm (i) is set to the second It is determined whether or not the value is smaller than a predetermined value. If the value is smaller than the second predetermined value, the DPF regeneration flag is turned off in step 412, and the regeneration is stopped. The magnitude relationship between the first predetermined value and the second predetermined value is such that the first predetermined value> the second predetermined value.
[0058]
According to the present embodiment, the responsiveness of the signal processing means is set to three levels, so that the responsiveness of the signal processing is switched according to the temperature of the DPF 4 during reproduction as well as during reproduction or non-reproduction. Can be. Therefore, it is possible to cope with a case where the DPF temperature is lower than the optimum regeneration temperature depending on the operating conditions and the change over time of the PM deposition amount is small, so that the regeneration control of the DPF 4 can be performed more accurately.
[0059]
In the signal processing means for averaging the output of the PM accumulation amount calculating means as in the third embodiment, the same effect can be obtained by setting the response to three or more levels. Of course.
[Brief description of the drawings]
FIG. 1 is an overall schematic configuration diagram of an exhaust gas purification device for an internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating a flowchart of control of an ECU according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating a result of performing a smoothing process on a PM accumulation amount calculation value before a signal process;
FIG. 4 is a diagram showing a relationship between an exhaust gas flow rate and a differential pressure and a PM deposition amount.
FIG. 5 is a diagram illustrating a difference between a time change of a PM accumulation amount and a calculated value of a PM accumulation amount after a conventional signal processing.
FIG. 6 is a diagram showing a change over time of a PM accumulation amount due to regeneration.
FIG. 7 is a diagram illustrating a temporal change in a PM deposition amount calculation value after signal processing when the response of the signal processing is low.
FIG. 8 is a diagram illustrating a temporal change in a PM accumulation amount calculation value after signal processing when the response of the signal processing is high.
FIG. 9 is a view illustrating a flowchart of control of an ECU according to the second embodiment of the present invention.
FIG. 10 is an overall schematic configuration diagram of an exhaust gas purification device for an internal combustion engine according to a third embodiment of the present invention.
FIG. 11 is a view illustrating a flowchart of control of an ECU according to a third embodiment of the present invention.
FIG. 12 is a diagram showing a relationship between a DPF temperature and a PM burning rate.
FIG. 13 is a diagram showing that the change over time in the amount of deposited PM differs depending on the DPF temperature during regeneration.
FIG. 14 is a view illustrating a flowchart of control of an ECU according to a fourth embodiment of the present invention.
[Explanation of symbols]
1 Diesel engine (internal combustion engine)
2a, 2b exhaust pipe
3 intake pipe
4 DPF (particulate filter)
5 ° differential pressure sensor (pressure detection means)
6 ECU

Claims

A particulate filter installed in an exhaust pipe of the internal combustion engine to collect particulates in the exhaust gas;
Particulate accumulation amount calculation means for calculating the amount of particulate accumulation by the particulate filter,
A plurality of signal processing means having different responsiveness for smoothing or averaging the output of the particulate accumulation amount calculation means,
A particulate deposition amount determining means for selecting one of the outputs of the plurality of signal processing means to determine the particulate deposition amount;
Regeneration execution determination means for determining an execution time of regeneration of the particulate filter based on an output of the particulate deposition amount determination means,
An exhaust purification device for an internal combustion engine, comprising: regeneration means for increasing the temperature of the particulate filter and performing regeneration based on the determination result of the regeneration execution determination means.

A particulate filter installed in an exhaust pipe of the internal combustion engine to collect particulates in the exhaust gas;
Particulate accumulation amount calculation means for calculating the amount of particulate accumulation by the particulate filter,
First signal processing means for smoothing the output of the particulate accumulation amount calculation means,
Second signal processing means for smoothing the output of the particulate accumulation amount calculation means so that the response of the output to the input of the signal processing is higher than that of the first signal processing means;
Particulate deposition amount determining means for selecting one of the output of the first signal processing means and the output of the second signal processing means to determine the particulate deposition amount;
Regeneration execution determination means for determining an execution time of regeneration of the particulate filter based on an output of the particulate deposition amount determination means,
An exhaust purification device for an internal combustion engine, comprising: regeneration means for increasing the temperature of the particulate filter and performing regeneration based on the determination result of the regeneration execution determination means.

A particulate filter installed in an exhaust pipe of the internal combustion engine to collect particulates in the exhaust gas;
Particulate accumulation amount calculation means for calculating the amount of particulate accumulation by the particulate filter,
First signal processing means for averaging the output of the particulate accumulation amount calculation means over a predetermined period;
A second signal processing means for averaging the output of the particulate accumulation amount calculating means over a predetermined period shorter than the first signal processing means;
Particulate deposition amount determining means for selecting one of the output of the first signal processing means and the output of the second signal processing means to determine the particulate deposition amount;
Regeneration execution determination means for determining an execution time of regeneration of the particulate filter based on an output of the particulate deposition amount determination means,
An exhaust purification device for an internal combustion engine, comprising: regeneration means for increasing the temperature of the particulate filter and performing regeneration based on the determination result of the regeneration execution determination means.

The particulate matter accumulation amount calculating means has pressure detecting means for detecting a pressure reflecting the amount of particulate matter accumulated in the particulate filter, and exhaust flow rate detecting means for detecting an exhaust gas flow rate of the internal combustion engine. 4. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the amount of particulates accumulated by the particulate filter is calculated based on outputs of a detecting means and the exhaust flow rate detecting means.

The particulate deposition amount determining means determines the output of the second signal processing means as the particulate deposition amount when the regeneration performing means is operating, and otherwise, the output of the first signal processing means. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the value is determined as a particulate accumulation amount.

The particulate deposition amount determining means has a DPF temperature detecting means for detecting the temperature of the particulate filter, and when the output of the DPF temperature detecting means exceeds a predetermined value, outputs the output of the second signal processing means. 6. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the particulate matter accumulation amount is determined, and in other cases, the output of the first signal processing means is determined as the particulate matter accumulation amount.

As the DPF temperature detecting means, there is provided exhaust temperature detecting means installed in an exhaust pipe upstream or downstream of the particulate filter. 7. The exhaust gas purifying apparatus for an internal combustion engine according to claim 6, wherein the temperature of the filter is detected.

The exhaust gas purifying apparatus for an internal combustion engine according to claim 6 or 7, wherein the predetermined value in the DPF temperature detecting means is equal to or higher than 600 ° C.

The regeneration execution determination means activates the regeneration execution means when the output of the particulate accumulation amount determination means exceeds a first predetermined value, and the output of the particulate accumulation amount determination means is smaller than the first predetermined value. 9. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the operation of the regeneration performing means is stopped when the value falls below a second predetermined value.

10. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the pressure detecting means detects a differential pressure across the particulate filter.

10. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the pressure detecting means detects an exhaust pressure upstream of the particulate filter.