JP3598542B2

JP3598542B2 - Exhaust purification system for diesel internal combustion engine

Info

Publication number: JP3598542B2
Application number: JP24507994A
Authority: JP
Inventors: 隆之戸谷; 信史保浦; 秀治吉田; 恵一加藤; 孝太郎林; 正仁柴田; 誠水谷
Original assignee: Denso Corp; Toyota Motor Corp
Current assignee: Denso Corp; Toyota Motor Corp
Priority date: 1994-10-11
Filing date: 1994-10-11
Publication date: 2004-12-08
Anticipated expiration: 2019-12-08
Also published as: JPH08109818A

Description

【０００１】
【産業上の利用分野】
本発明は、ディーゼル内燃機関の排気浄化装置であって、特に排気ガスが通過するフィルタの層流特性に基づきフィルタに溜まった微粒子捕集量の検出精度を向上させたものに関する。
【０００２】
【従来の技術】
従来、ディーゼル内燃機関において、排気ガスの微粒子（パティキュレイト）の捕集量を検出するものとしてＤＰＦ（ＤｉｅｓｅｌＰａｒｔｉｃｕｌａｔｅＦｉｌｔｅｒ）システムがある。これは、排気ガスが通過するフィルタの層流特性を利用するものであり、フィルタを通過する体積流量が差圧（圧力差）に比例する数１を利用するものである。
【０００３】
【数１】
Ｖ＝Ａ×ΔＰ＝（Ａ０＋Ａｐ）×ΔＰ
ここで、Ｖは体積流量、ΔＰは差圧、Ａは通気抵抗である。但し、通気抵抗はフィルタの初期圧損によるもの（Ａ０）と微粒子捕集量によるもの（Ａｐ）で決められる。
【０００４】
そして、Ａ０＜＜Ａｐならば、実質的にフィルタに溜まった微粒子捕集量は、Ａｐおよびフィルタ間に生じる差圧（圧力差）より算出される。その際、同一捕集量でも運転条件（体積流量の条件）によって、発生差圧が異なるので、これを常に基準状態に補正する必要がある。
このため、ある捕集量のもとで体積流量Ｖがフィルタに流入したときフィルタ間の差圧がΔＰであったとし、またある運転条件を基準としたときの基準体積流量がＶｓｔｄであるとすると、このときの補正された差圧（以下、補正差圧という）ΔＰ１は数２で表される。
【０００５】
【数２】
ΔＰ１＝ΔＰ×Ｖｓｔｄ／Ｖ
このようにして、補正差圧ΔＰ１は、フィルタの微粒子捕集量が一定ならば、体積流量が変化しても一定値になる。かくして、補正差圧ΔＰ１が微粒子捕集量と１対１に対応して補正差圧ΔＰ１から微粒子捕集量が得られる。
【０００６】
しかしながら、フィルタの圧損により排気ガスが通過するフィルタの層流特性が少しずれる場合がある。図２は、フィルタの圧損に起因する層流特性に少しずれがある場合におけるフィルタの体積流量Ｖー差圧ΔＰ特性（フィルタ特性）を示すグラフである。この図において、点線はフィルタの圧損による影響が少ない理想的フィルタ特性（層流性）による体積流量−差圧特性を示し、実線は実際にフィルタによる圧損による影響がある体積流量−差圧特性を示している。このように、フィルタに圧損があると、補正差圧ΔＰ１を上記数２により算出すると、誤差が大きくなる。
【０００７】
そこで、本発明者等は、補正差圧ΔＰ１の算出において、このフィルタ特性を加味することにより、上記問題を解決するものを提案した（特願平５−１７０５８０号）。このものにおける補正差圧ΔＰ１の算出は数３により行われる。
【０００８】
【数３】
ΔＰ１＝ΔＰ×（Ｖｓｔｄ／Ｖ）^１／ａ
ここで、ΔＰは前記のフィルタの差圧、Ｖはフィルタの前記通過体積流量、
Ｖｓｔｄは基準の体積流量、ａは前記通過体積流量Ｖと前記差圧との特性、すなわちフィルタ特性に基ずく係数で、０．５＜ａ＜１である。
【０００９】
【発明が解決しようとする課題】
上記のように補正差圧計算にフィルタ特性を考慮に入れることにより補正差圧の精度を大幅に向上させることができる。
しかしながら、これでも完全に補正することが出来ず、運転条件により補正差圧ΔＰがずれることが判明した。すなわち、フィルタ特性を考慮に入れて補正差圧を求めるようにしても、運転条件を変化させた場合に補正差圧ΔＰ１が変化することが判明した。
【００１０】
この運転条件の変化による補正差圧ΔＰ１の変化について図３を用いて説明する。まず、基準運転条件Ａで運転すると、フィルタには微粒子が捕集されるため補正差圧ΔＰ１値は上昇する。その後、別の運転条件Ｂにし、ある程度、時間が経過したら運転条件を基準運転条件Ａに戻す。この一連の運転中の補正差圧値ΔＰ１は図３（ｂ）に示すように変化する。なお、図３（ａ）はフィルタ特性を考慮に入れない場合の補正差圧ΔＰ１の変化を示している。このように、フィルタ特性を考慮に入れることにより補正差圧の精度を向上させることができるものの、運転条件により補正差圧ΔＰ１にずれが生じてしまう。
【００１１】
従って、微粒子が適切な量になった時に、定期的に燃焼（フィルタの安定再生）させるためには、微粒子の捕集量（補正差圧）を精度よく検出しなければならず、上記数３によるフィルタ特性を考慮に入れた補正差圧の算出では、まだ不十分である。
上記のような運転条件によるずれについて、本発明者等は、種々について検討したところ、フィルタ特性に温度特性があり、フィルタの温度によりフィルタの圧損特性が変化し、補正差圧ΔＰ１の算出に誤差が生じるためであることを見い出した。
【００１２】
図４に、異なる運転条件Ｃ、Ｄ（捕集量は同一の時）で、フィルタに流入する排気ガスの体積流量が同一の場合の、体積流量Ｖ、フィルタ温度Ｔｆ、差圧ΔＰの変化を示す。排気ガスの体積流量が同一であるためフィルタ間に発生する差圧は同一のはずであるが、運転条件が異なるため排気ガス温度が異なり、これによってフィルタ特性も異なり、発生する差圧に違いが出ていることが分かる。
【００１３】
従って、数３において、体積流量Ｖが同一のため、（Ｖｓｔｄ／Ｖ）^{１／ａ}の部分）はそれらの運転条件Ｃ、Ｄにおいて同じになるが、差圧ΔＰが異なるため補正差圧ΔＰ１の値に違いが生じる。
図５に、運転条件を変化（フィルタ温度を変化）させた時の、フィルタ特性のずれの様子を示す。実線は基準運転条件時のフィルタ温度Ｔ０の場合のフィルタ特性である。基準運転条件より負荷の高い運転条件の場合、排気ガス温度は上昇し、フィルタ温度も上昇する。すると、フィルタおよびパティキュレートの温度特性により圧損が減少し、フィルタ特性は点線のように下にずれる。逆に、基準運転条件より負荷の低い運転条件の場合はフィルタ特性は２点鎖線のように上にずれる。但し、ずれ量は温度に対してほぼ線形である。
【００１４】
このように運転条件が変化すると、排気ガス温度が変化し、フィルタの温度も変化する。フィルタには温度特性があるため運転条件が変化するごとにフィルタ特性がずれ、補正差圧に誤差が生じる。
本発明は上記問題に鑑みてなされたもので、フィルタの温度特性を考慮してフィルタに溜まった微粒子の捕集量を示す補正差圧を求め、フィルタの再生処理を行うようにすることを目的とする。
【００１５】
【課題を解決するための手段】
本発明は上記目的を達成するため、請求項１に記載の発明においては、ディーゼル内燃機関（１）の排気系に設置されて排気ガスの微粒子を捕集し、かつ層流特性を有するフィルタ（７）を具備したディーゼル内燃機関の排気浄化装置であって、前記フィルタ（７）を通過する排気ガスの体積流量と、前記フィルタ（７）の間の差圧とを求め、基準の体積流量に対する前記通過排気ガスの体積流量で前記差圧を補正した補正差圧を検出する捕集量検出手段（３，８〜１４，１０２〜１０８）を備え、この検出した補正差圧に基づいて前記フィルタ（７）の再生処理を行うようにしたディーゼル内燃機関の排気浄化装置において、前記捕集量検出手段（３，８〜１４，ステップ１０２〜１０８）は、前記フィルタ（７）の温度を検出するフィルタ温度検出手段（１０，１１，１０５）を有し、この検出したフィルタ温度と基準運転条件時のフィルタ温度とを用いた式で、前記検出したフィルタ温度が前記基準運転条件時のフィルタ温度より高いときに前記補正差圧を大きくし、前記検出したフィルタ温度が前記基準運転条件時のフィルタ温度より低いときに前記補正差圧を小さくするように、前記補正差圧を温度補正することを特徴としている。
【００１６】
請求項２に記載の発明においては、ディーゼル内燃機関（１）の排気系に設置されて排気ガスの微粒子を捕集し、かつ層流特性を有するフィルタ（７）を具備したディーゼル内燃機関の排気浄化装置において、前記フィルタ（７）を通過する体積流量を求める体積流量検出手段（１０４）と、前記フィルタ（７）の間の差圧を求める差圧検出手段（１０３）と、前記フィルタ（７）の温度を検出するフィルタ温度検出手段（１０５）と、前記フィルタ（７）の圧損に起因する体積流量ー差圧特性および前記フィルタ（７）の温度に起因する体積流量ー差圧特性に基づき、前記検出した差圧を、前記検出した体積流量およびフィルタ温度により補正して、補正差圧を演算する補正差圧演算手段（１０６〜１０８）を備え、前記演算した補正差圧に基づいて前記フィルタ（７）の再生処理を行うようになっており、前記補正差圧演算手段は、前記検出したフィルタ温度と基準運転条件時のフィルタ温度とを用いた式で、前記検出したフィルタ温度が前記基準運転条件時のフィルタ温度より高いときに前記検出した差圧を大きくし、前記検出したフィルタ温度が前記基準運転条件時のフィルタ温度より低いときに前記検出した差圧を小さくするように、前記検出した差圧を補正することを特徴としている。
【００１７】
上記の補正差圧ΔＰ１は、後述する実施例においては、以下の数４により求められる。
【００１８】
【数４】
ΔＰ１＝ΔＰ×（Ｖｓｔｄ／Ｖ）^１／ａ×（１＋（Ｔｆ−Ｔ０）×Ｋｔ）
ここで、ΔＰは前述のフィルタ特性、Ｖはフィルタ（７）の通過体積流量、
Ｖｓｔｄは基準の体積流量、ａはフィルタ温度Ｔ０（基準運転条件時のフィルタ温度）時の前記通過体積流量Ｖと前記差圧との特性（フィルタ特性）に基づく係数、Ｔｆはフィルタ温度、Ｔ０は基準運転条件時のフィルタ温度、Ｋｔはフィルタ特性の温度特性を補正する係数である。
【００１９】
請求項３に記載の発明では、請求項２に記載の発明において、前記補正差圧演算手段（１０６〜１０８）は、前記フィルタ（７）の圧損に起因する体積流量ー差圧特性を、体積流量ー基準の差圧に対する差圧特性に規格化して前記フィルタの圧損に対する前記差圧の補正を行う
ことを特徴としている。
【００２０】
請求項４に記載の発明では、請求項１乃至３のいずれか１つに記載の発明において、前記フィルタ温度検出手段（１０５）は、前記フィルタ（７）に流入する排気温度と流出する排気温度の平均値により前記フィルタ（７）の温度を検出する
ことを特徴としている。
【００２１】
なお、上記各手段のカッコ内の符号は、後述する実施例記載の具体的手段との対応関係を示すものである。
【００２２】
【発明の作用効果】
請求項１に記載の発明によれば、フィルタを通過する排気ガスの体積流量と、フィルタの間の差圧とを求め、基準の体積流量に対する前記通過排気ガスの体積流量で差圧を補正した補正差圧を検出し、この検出した補正差圧に基づいてフィルタの再生処理を行うようにしている。
【００２３】
さらに、フィルタの温度を検出し、この検出したフィルタ温度にて前記補正差圧を温度補正している。
従って、フィルタの温度により、補正差圧がずれるのを補正しているから、種々の運転条件によりフィルタ温度が変化する状態が発生しても、それを考慮した補正差圧を得ることにより、運転条件の変化に係わらず正しくフィルタの再生処理を行うことができる。
【００２４】
請求項２に記載の発明によれば、フィルタの圧損に起因する体積流量ー差圧特性およびフィルタの温度に起因する体積流量ー差圧特性に基づき、検出した差圧を、検出した体積流量およびフィルタ温度により補正して補正差圧を演算し、この演算した補正差圧に基づいてフィルタの再生処理を行うようにしている。
従って、フィルタの圧損特性および温度特性を考慮して正確な補正差圧を得るこができ、これによりフィルタの再生処理を正しく行うことができる。
【００２５】
請求項３に記載の発明においては、フィルタの圧損に起因する体積流量ー差圧特性を、体積流量ー基準の差圧に対する差圧特性に規格化してフィルタの圧損に対する差圧の補正を行っている。
従って、このような規格化により、捕集量によらず１つの特性にてフィルタの圧損に対する差圧の補正を行うことができる。
【００２６】
請求項４に記載の発明では、フィルタに流入する排気温度と流出する排気温度の平均値によりフィルタの温度を検出している。
従って、フィルタの平均温度をほぼ正確に把握して、上記請求項１乃至３に記載の発明を適切に実施することができる。
【００２７】
【実施例】
以下、本発明を図に示す実施例について説明する。
図１は、本発明の一実施例を示すディーゼル内燃機関の排気浄化装置の概略構成図である。但し、図１はディーゼルエンジンの排気系に設けられた排気浄化装置の捕集量検出（補正差圧算出）に関する部分のみを抜粋した構成からなる。
【００２８】
ディーゼルエンジン１の吸入側にはエアクリーナ２が設けられており、その吸入流量を検知するための熱線式流量センサ３がエアクリーナ２からディーゼルエンジン１への流路の途中に設けられている。
ディーゼルエンジン１の排気管４には排気浄化装置５が設けられている。排気浄化装置５は排気管４に連結されているハウジング６を有している。ハウジング６の中にはセラミック多孔からなるフィルタ７が設置されており、それに排気ガスが通過することにより排気ガスに含まれる微粒子が捕集される。
【００２９】
フィルタ７の目詰まり防止のため、フィルタ７の微粒子の捕集量が検出され、捕集量がある値に達したら、フィルタ７に捕集された微粒子は図示しない加熱装置で燃焼再生される。
排気浄化装置５には、フィルタ７のディーゼルエンジン１側の絶対圧力（前圧）を検知するための圧力センサ８、フィルタ７の排気側の絶対圧力（後圧）を検知するための圧力センサ９が設けられている。また、ディーゼルエンジン１からフィルタ７に流れ込む排気絶対温度（入ガス温度）を検知するための温度センサ１０、フィルタ７から流出する排気絶対温度（出ガス温度）を検知するための温度センサ１１が設けられている。
【００３０】
そして、各センサからの信号は電子制御ユニット（ＥＣＵ）１２に入力される。このＥＣＵ１２内にはＣＰＵ１３が設けられており、各センサ信号は最終的にはＣＰＵ１３に入力される。また、このＣＰＵ１３には、微粒子の捕集量を演算する捕集量演算部１４が設けられている。
この捕集量演算部１４による演算を詳細に説明する。
【００３１】
まず、捕集量演算部１４ではフィルタ７に流入する体積流量Ｖを熱線式流量センサ３の吸入流量と圧力センサ８の前圧、温度センサ１０の入ガス温度と温度センサ１１の出ガス温度の平均温度より、公知の演算方法を用いて求める。
また、圧力センサ８及び９の前圧から後圧を引くことによりフィルタ７の差圧（ΔＰ）が得られる。フィルタ温度は温度センサ１０及び１１の入ガス温度と出ガス温度の平均温度より得られ、これによりフィルタ７の平均温度をほぼ正確に把握することができる。このようにして捕集量演算部１４で、ある微粒子の捕集量で、ある運転条件下の体積流量と差圧とフィルタ温度が求められる。
【００３２】
体積流量が得られると、フィルタ特性に基づく差圧補正値が求められる。数４における（Ｖｓｔｄ／Ｖ）^１／ａの部分である。この差圧補正値を数５のように定義する。
【００３３】
【数５】
Ｆ＝（Ｖｓｔｄ／Ｖ）^１／ａ
ここで、Ｆは係数であり、フィルタ７に流入する排気ガスの体積流量をパラメータとしたフィルタ特性に基づく差圧補正値と言える。但し、ＣＰＵ１３でこのような演算を行うのは困難であるため体積流量Ｖをパラメータとした２次元マップにより差圧補正値Ｆを求める。マップはフィルタ特性より求める。
【００３４】
図６（ａ）にある捕集量のもとで測定したフィルタ７の体積流量−差圧特性、つまりフィルタ特性を示す。ここで、Ｖｓｔｄは基準運転条件時の体積流量で、そのときに発生した差圧をΔＰｓｔｄとする。この特性を基準運転条件ΔＰｓｔｄで規格化したフィルタ特性を図６（ｂ）に示す。この規格化した値をＫｐとする。
【００３５】
ここで、数３におけるΔＰ１はΔＰｓｔｄであるので、数３より、
ΔＰ／ΔＰｓｔｄ＝１／（Ｖｓｔｄ／Ｖ）^１／ａとなる。また、ΔＰ／ΔＰｓｔｄ＝Ｋｐであるため、これと数５により、Ｋｐ＝１／Ｆとなる。但し、このフィルタ特性は捕集量に依存しない。つまり、フィルタ特性は無次元である。よって、数５は実際の演算では数６のように行う。
【００３６】
【数６】
Ｆ＝１／ＭＡＰ（Ｖ）
ここで、ＭＡＰ（Ｖ）は、体積流量Ｖをパラメータとし、図６（ｂ）に示す関数により求めた差圧補正値Ｋｐである。
上記のような規格化をしない場合には、捕集量毎に図６（ａ）のマップをそれぞれ用意しておく必要があるが、上記のように規格化することにより、捕集量によらず１つのマップで値を求めることができる。
【００３７】
また、捕集量演算部１４では、フィルタ温度（温度センサ１０及び１１の入ガス温度と出ガス温度の平均温度）よりフィルタ特性の温度係数補正値が求められる。数４における１＋（Ｔｆ−Ｔ０）×Ｋｔの部分である。
フィルタ特性は基準運転状態時のもので温度はＴ０である。これよりフィルタ温度Ｔｆが高い場合、つまりＴｆ＞Ｔ０の時、前述したように実際のフィルタ特性値Ｋｐは、ＥＣＵ１２内で持つ基準運転条件時のフィルタ特性値よりも低くなり、補正差圧値ΔＰ１は少なめの値になる。このため、１＋（Ｔｆ−Ｔ０）×Ｋｔの式で、フィルタ特性の温度による変化によって生じる補正差圧ΔＰ１の誤差を補正する。すなわち、Ｔｆ＞Ｔ０の時、１＋（Ｔｆ−Ｔ０）×Ｋｔが＞１となり、マイナス側に発生する補正差圧ΔＰ１の誤差を補正する。Ｔｆ＜Ｔ０の時は前述した場合と逆の方向に補正する。
【００３８】
よって、捕集量演算部１４では数４の計算を数７のように演算することによって実現している。
【００３９】
【数７】
ΔＰ１＝ΔＰ／ＭＡＰ（Ｖ）×（１＋（Ｔｆ−Ｔ０）×Ｋｔ）
ここで、ΔＰは前記フィルタ特性、ＭＡＰ（Ｖ）はフィルタ７の通過体積流量Ｖをパラメータとした関数で基準運転条件時におけるフィルタ温度のもとでのフィルタ特性をもとにした差圧補正係数、Ｔｆはフィルタ温度、Ｔ０は基準運転条件時のフィルタ温度、Ｋｔはフィルタ特性の温度特性を補正する係数を表す。
【００４０】
上記した捕集量演算部１４の処理を含むＣＰＵ１３での演算処理について図７に示すフローチャートを基に説明する。
まず、ステップ１０１にて再生中であるか否かを判定する。後述する再生制御中でなければ、ステップ１０２に進み、センサ３，８〜１１からのセンサ値を取り込む。
【００４１】
次のステップ１０３では、圧力センサ８及び９にてそれぞれ検出した前圧から後圧を引くことによりフィルタ７の差圧ΔＰを求め、ステップ１０４では、熱線式流量センサ３の吸入流量と圧力センサ８の前圧、温度センサ１０の入ガス温度と温度センサ１１の出ガス温度の平均温度より体積流量Ｖを求める。ステップ１０５では、温度センサ１０及び１１の入ガス温度と出ガス温度の平均温度よりフィルタ温度Ｔｆを求める。
【００４２】
この後、ステップ１０６にて、図６（ｂ）に示す関数により体積流量ＶからＭＡＰ（Ｖ）を求め、ステップ１０７にて、フィルタ温度Ｔｆから温度補正値１＋（Ｔｆ−Ｔ０）×Ｋｔを算出する。そして、ステップ１０８に進み、上記数７を用いて補正差圧ΔＰ１を算出する。なお、上記ステップ１０２〜１０８の演算処理が、上述した捕集量演算部１４の処理に該当する。
【００４３】
この補正差圧ΔＰ１を設定値と比較することにより、フィルタ７の再生が必要か否かがステップ１０９にて判定される。この判定がＹＥＳになると、ステップ１１０にて再生制御要求フラグが設定される。このフラグが設定されると、再生制御ルーチン２００では、公知のフィルタ再生制御、すなわち図示しない加熱装置およびエアポンプを所定時間作動させて、フィルタ７に捕集された微粒子を燃焼させる。再生制御フラグが設定されていない間は、この再生制御ルーチン２００では何も制御を行わない。
【００４４】
図３（ｃ）に、上述したフィルタ特性の温度特性を加味した補正差圧ΔＰ１について、運転条件を変化させた場合の測定結果を示す。この図から明らかなように、図３（ａ），（ｂ）に示すものよりかなり精度が向上している。
従って、本実施例によれば、微粒子の捕集量が正確に把握され、微粒子が適切な量で定期的に燃焼できるので、フィルタ７、加熱装置の耐久性を向上させることができる。
【００４５】
なお、上記実施例では、差圧補正とフィルタ温度による補正とを行うものを示したが、フィルタ温度のみによる補正でも十分効果があるものであり、このもののみでも発明を認識しうるものである。
また、図７に示すフローチャートに示す各ステップはそれぞれの機能を実現する機能実現手段として構成されるものであり、これらの機能実現手段により、上記したコンピュータ制御のみならず、ハードロジック構成によっても本発明を構成し得るものである。
【図面の簡単な説明】
【図１】本発明の実施例に係るディーゼル内燃機関の排気浄化装置の概略構成を示す図である。
【図２】フィルタの圧損に起因するフィルタの体積流量ー差圧特性を示すグラフである。
【図３】運転条件を変化させた場合の補正差圧の変化を示す図であり、（ａ）はフィルタ特性を考慮しない場合、（ｂ）はフィルタ特性を考慮した場合、（ｃ）は本実施例による場合を示している。
【図４】異なる運転条件での、体積流量、フィルタ温度、差圧の変化を示す図である。
【図５】フィルタ温度に起因するフィルタの体積流量ー差圧特性を示すグラフである。
【図６】フィルタ特性を示すグラフであり、（ａ）はある捕集量のもとで測定したフィルタの体積流量ー差圧特性を示し、（ｂ）は規格化したフィルタの体積流量ー差圧特性を示している。
【図７】捕集量演算等のＣＰＵで行う演算処理を示すフローチャートである。
【符号の説明】
１ディーゼルエンジン
２エアクリーナ
３熱線式流量センサ
４排気管
５排気浄化装置
６ハウジング
７フィルタ
８，９圧力センサ
１０，１１温度センサ
１２電子制御ユニット（ＥＣＵ）
１３中央演算処理装置（ＣＰＵ）
１４捕集量演算部[0001]
[Industrial applications]
The present invention relates to an exhaust gas purifying apparatus for a diesel internal combustion engine, and more particularly to an apparatus for improving the detection accuracy of the amount of trapped fine particles accumulated in a filter based on laminar flow characteristics of the filter through which exhaust gas passes.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a diesel internal combustion engine, there is a DPF (Diesel Particulate Filter) system as a device that detects an amount of trapped fine particles (particulates) of exhaust gas. This utilizes the laminar flow characteristics of the filter through which the exhaust gas passes, and uses Equation 1 in which the volume flow rate passing through the filter is proportional to the differential pressure (pressure difference).
[0003]
(Equation 1)
V = A × ΔP = (A0 + Ap) × ΔP
Here, V is a volume flow rate, ΔP is a differential pressure, and A is a ventilation resistance. However, the ventilation resistance is determined based on the initial pressure loss of the filter (A0) and the particle collection amount (Ap).
[0004]
If A0 << Ap, the amount of trapped fine particles substantially accumulated in the filter is calculated from the differential pressure (pressure difference) generated between Ap and the filter. At this time, the generated differential pressure varies depending on the operating conditions (conditions of the volume flow rate) even with the same trapping amount, so that it is necessary to always correct this to the reference state.
For this reason, it is assumed that when the volume flow rate V flows into the filter under a certain trapping amount, the differential pressure between the filters is ΔP, and that the reference volume flow rate based on a certain operating condition is Vstd. Then, the corrected differential pressure (hereinafter, referred to as corrected differential pressure) ΔP1 at this time is expressed by Expression 2.
[0005]
(Equation 2)
ΔP1 = ΔP × Vstd / V
In this way, if the amount of trapped fine particles of the filter is constant, the corrected differential pressure ΔP1 becomes a constant value even if the volume flow rate changes. Thus, the corrected differential pressure ΔP1 corresponds to the amount of collected fine particles in a one-to-one correspondence, and the amount of collected fine particles is obtained from the corrected differential pressure ΔP1.
[0006]
However, the laminar flow characteristics of the filter through which the exhaust gas passes may be slightly shifted due to the pressure loss of the filter. FIG. 2 is a graph showing the volume flow rate V-differential pressure ΔP characteristic (filter characteristic) of the filter when the laminar flow characteristic caused by the pressure loss of the filter slightly shifts. In this figure, the dotted line shows the volume flow rate-differential pressure characteristic due to the ideal filter characteristic (laminar flow) that is less affected by the pressure loss of the filter, and the solid line shows the volume flow rate-differential pressure characteristic actually affected by the filter pressure loss. Is shown. As described above, when the filter has a pressure loss, the error increases when the corrected differential pressure ΔP1 is calculated by the above equation (2).
[0007]
The inventors of the present invention have proposed a device that solves the above-described problem by taking this filter characteristic into account when calculating the corrected differential pressure ΔP1 (Japanese Patent Application No. 5-170580). The calculation of the corrected differential pressure ΔP1 in this case is performed according to Equation 3.
[0008]
(Equation 3)
ΔP1 = ΔP × (Vstd / V) ^{1 / a}
Here, ΔP is the differential pressure of the filter, V is the passing volume flow rate of the filter,
Vstd is a reference volume flow rate, and a is a coefficient based on a characteristic between the passing volume flow rate V and the differential pressure, that is, a filter characteristic, and 0.5 <a <1.
[0009]
[Problems to be solved by the invention]
As described above, the accuracy of the corrected differential pressure can be significantly improved by taking the filter characteristics into account in the calculation of the corrected differential pressure.
However, even with this, it was not possible to make a complete correction, and it was found that the corrected differential pressure ΔP was shifted depending on the operating conditions. In other words, it has been found that even when the corrected differential pressure is determined in consideration of the filter characteristics, the corrected differential pressure ΔP1 changes when the operating conditions are changed.
[0010]
The change in the corrected differential pressure ΔP1 due to the change in the operating condition will be described with reference to FIG. First, when the operation is performed under the reference operation condition A, the particulate matter is collected by the filter, so that the value of the corrected differential pressure ΔP1 increases. Thereafter, another operating condition B is set, and after a certain time has elapsed, the operating condition is returned to the reference operating condition A. The corrected differential pressure value ΔP1 during this series of operations changes as shown in FIG. FIG. 3A shows a change in the corrected differential pressure ΔP1 when the filter characteristics are not taken into consideration. As described above, although the accuracy of the corrected differential pressure can be improved by taking the filter characteristics into consideration, a deviation occurs in the corrected differential pressure ΔP1 depending on operating conditions.
[0011]
Therefore, in order to periodically burn (stable regeneration of the filter) when the amount of the fine particles reaches an appropriate amount, the amount of collected fine particles (corrected differential pressure) must be accurately detected. The calculation of the corrected differential pressure taking into account the filter characteristics is still insufficient.
The inventors of the present invention have examined various factors regarding the deviation due to the operating conditions as described above. As a result, the filter characteristic has a temperature characteristic, the pressure loss characteristic of the filter changes depending on the temperature of the filter, and an error occurs in the calculation of the corrected differential pressure ΔP1. Was found to occur.
[0012]
FIG. 4 shows changes in the volume flow rate V, the filter temperature Tf, and the differential pressure ΔP when the exhaust gas flowing into the filter has the same volume flow rate under different operating conditions C and D (when the trapping amounts are the same). Show. Since the volume flow rate of the exhaust gas is the same, the differential pressure generated between the filters should be the same.However, the operating conditions are different, the exhaust gas temperature is different, the filter characteristics are different, and the generated differential pressure is different. You can see that it is out.
[0013]
Therefore, in equation (3), since the volume flow rate V is the same, (Vstd / V) ^{1 / a} is the same under those operating conditions C and D, but since the differential pressure ΔP is different, the corrected differential pressure ΔP1 The values differ.
FIG. 5 shows how the filter characteristics shift when the operating conditions are changed (the filter temperature is changed). The solid line shows the filter characteristics in the case of the filter temperature T0 under the reference operation condition. In the case of an operating condition having a higher load than the reference operating condition, the exhaust gas temperature increases and the filter temperature also increases. Then, the pressure loss decreases due to the temperature characteristics of the filter and the particulates, and the filter characteristics shift downward as indicated by the dotted line. Conversely, in the case of an operating condition having a lower load than the reference operating condition, the filter characteristic shifts upward as indicated by a two-dot chain line. However, the deviation amount is almost linear with respect to the temperature.
[0014]
When the operating conditions change in this way, the exhaust gas temperature changes, and the filter temperature also changes. Since the filter has a temperature characteristic, the filter characteristic shifts each time the operating condition changes, and an error occurs in the corrected differential pressure.
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to obtain a correction differential pressure indicating a trapped amount of fine particles collected in a filter in consideration of a temperature characteristic of the filter, and to perform a regeneration process of the filter. And
[0015]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, there is provided a filter which is installed in an exhaust system of a diesel internal combustion engine (1) to collect fine particles of exhaust gas and have a laminar flow characteristic. 7) An exhaust gas purification apparatus for a diesel internal combustion engine, comprising: a volume flow rate of exhaust gas passing through the filter (7); and a differential pressure between the filters (7). Trapping amount detection means (3, 8 to 14, 102 to 108) for detecting a corrected differential pressure obtained by correcting the differential pressure based on a volume flow rate of the passing exhaust gas, and the filter is provided based on the detected corrected differential pressure. In the exhaust gas purifying apparatus for a diesel internal combustion engine configured to perform the regeneration process (7), the trapped amount detection means (3, 8 to 14, steps 102 to 108) detects the temperature of the filter (7). fill Has a temperature detecting means (10,11,105), the formula using the filter temperature during the detected filter temperature and the reference operating conditions, filter the detected temperature is higher than the filter temperature during the reference operating conditions When the correction differential pressure is increased, the temperature of the correction differential pressure is corrected so as to reduce the correction differential pressure when the detected filter temperature is lower than the filter temperature under the reference operating condition. I have.
[0016]
According to a second aspect of the present invention, the exhaust gas of a diesel internal combustion engine is provided in an exhaust system of the diesel internal combustion engine (1), the filter (7) collecting particulates of exhaust gas and having a laminar flow characteristic. In the purifying apparatus, a volume flow rate detecting means (104) for obtaining a volume flow rate passing through the filter (7), a differential pressure detecting means (103) for obtaining a differential pressure between the filter (7), and the filter (7). A) a filter temperature detecting means (105) for detecting a temperature, and a volume flow-differential pressure characteristic caused by a pressure loss of the filter (7) and a volume flow-differential pressure characteristic caused by a temperature of the filter (7). And a correction differential pressure calculating means (106-108) for correcting the detected differential pressure based on the detected volume flow rate and filter temperature to calculate a corrected differential pressure. Based being adapted to perform the reproduction process of the filter (7), the correction differential pressure calculating means, the formula using the filter temperature during the detected filter temperature and the reference operating conditions, the detected filter The detected differential pressure is increased when the temperature is higher than the filter temperature under the reference operation condition, and the detected differential pressure is reduced when the detected filter temperature is lower than the filter temperature under the reference operation condition. Preferably, the detected differential pressure is corrected .
[0017]
The above-mentioned corrected differential pressure ΔP1 is obtained by the following Expression 4 in an embodiment described later.
[0018]
(Equation 4)
ΔP1 = ΔP × (Vstd / V) ^{1 / a} × (1+ (Tf−T0) × Kt)
Here, ΔP is the above-described filter characteristic, V is the volume flow rate passing through the filter (7),
Vstd is a reference volume flow rate, a is a coefficient based on a characteristic (filter characteristic) between the passing volume flow rate V and the differential pressure at the time of the filter temperature T0 (filter temperature under the reference operation condition), Tf is a filter temperature, and T0 is The filter temperature Kt under the reference operating condition is a coefficient for correcting the temperature characteristics of the filter characteristics.
[0019]
According to a third aspect of the present invention, in the second aspect of the present invention, the correction differential pressure calculating means (106 to 108) calculates a volume flow rate-differential pressure characteristic caused by a pressure loss of the filter (7) by volume. It is characterized in that the differential pressure is corrected for the pressure loss of the filter by normalizing to a differential pressure characteristic with respect to a flow rate-reference differential pressure.
[0020]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the filter temperature detecting means (105) includes an exhaust gas temperature flowing into the filter (7) and an exhaust gas temperature flowing out of the filter (7). The temperature of the filter (7) is detected based on the average value of.
[0021]
In addition, the code | symbol in parenthesis of the said each means shows the correspondence with the concrete means of the Example described later.
[0022]
Operation and Effect of the Invention
According to the first aspect of the present invention, the volume flow rate of the exhaust gas passing through the filter and the differential pressure between the filters are obtained, and the differential pressure is corrected by the volume flow rate of the passing exhaust gas with respect to a reference volume flow rate. A corrected differential pressure is detected, and a filter regeneration process is performed based on the detected corrected differential pressure.
[0023]
Further, the temperature of the filter is detected, and the corrected differential pressure is temperature corrected based on the detected filter temperature.
Therefore, since the deviation of the corrected differential pressure is corrected by the temperature of the filter, even if a state in which the filter temperature changes due to various operating conditions occurs, the operation is performed by obtaining the corrected differential pressure in consideration thereof. The filter regeneration processing can be performed correctly regardless of the change in the condition.
[0024]
According to the invention described in claim 2, based on the volume flow rate-differential pressure characteristic caused by the pressure loss of the filter and the volume flow rate-differential pressure characteristic caused by the temperature of the filter, the detected differential pressure is detected, A correction differential pressure is calculated by correction based on the filter temperature, and a filter regeneration process is performed based on the calculated correction differential pressure.
Therefore, an accurate corrected differential pressure can be obtained in consideration of the pressure loss characteristics and the temperature characteristics of the filter, whereby the filter regeneration process can be performed correctly.
[0025]
In the invention described in claim 3, the volume flow rate-differential pressure characteristic caused by the pressure loss of the filter is normalized to the differential pressure characteristic with respect to the volume flow rate-referenced differential pressure, and the differential pressure for the filter pressure loss is corrected. I have.
Therefore, by such a standardization, it is possible to correct the differential pressure with respect to the pressure loss of the filter with one characteristic regardless of the trapping amount.
[0026]
According to the fourth aspect of the present invention, the temperature of the filter is detected based on the average value of the exhaust gas temperature flowing into the filter and the exhaust gas temperature flowing out of the filter.
Therefore, it is possible to grasp the average temperature of the filter almost accurately, and appropriately carry out the inventions according to the first to third aspects.
[0027]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an exhaust gas purification device for a diesel internal combustion engine, showing one embodiment of the present invention. However, FIG. 1 has a configuration in which only a portion relating to detection of a trapped amount (calculation of a corrected differential pressure) of an exhaust purification device provided in an exhaust system of a diesel engine is extracted.
[0028]
An air cleaner 2 is provided on the intake side of the diesel engine 1, and a hot-wire type flow sensor 3 for detecting the intake flow rate is provided in the middle of a flow path from the air cleaner 2 to the diesel engine 1.
The exhaust pipe 4 of the diesel engine 1 is provided with an exhaust purification device 5. The exhaust gas purification device 5 has a housing 6 connected to the exhaust pipe 4. A filter 7 made of a porous ceramic is provided in the housing 6, and fine particles contained in the exhaust gas are collected by passing the exhaust gas through the filter.
[0029]
In order to prevent the filter 7 from being clogged, the amount of collected fine particles of the filter 7 is detected, and when the collected amount reaches a certain value, the fine particles collected by the filter 7 are burned and regenerated by a heating device (not shown).
The exhaust gas purification device 5 includes a pressure sensor 8 for detecting the absolute pressure (pre-pressure) of the filter 7 on the diesel engine 1 side, and a pressure sensor 9 for detecting the absolute pressure (post-pressure) of the filter 7 on the exhaust side. Is provided. Further, a temperature sensor 10 for detecting the absolute temperature of the exhaust gas (inlet gas temperature) flowing from the diesel engine 1 to the filter 7 and a temperature sensor 11 for detecting the absolute temperature of the exhaust gas (outgas temperature) flowing out of the filter 7 are provided. Have been.
[0030]
Then, signals from the sensors are input to an electronic control unit (ECU) 12. A CPU 13 is provided in the ECU 12, and each sensor signal is finally input to the CPU 13. Further, the CPU 13 is provided with a trapping amount calculation unit 14 that calculates the trapping amount of the fine particles.
The calculation by the collection amount calculator 14 will be described in detail.
[0031]
First, the trapping amount calculation unit 14 calculates the volume flow rate V flowing into the filter 7 as the suction flow rate of the hot wire type flow sensor 3, the pre-pressure of the pressure sensor 8, the incoming gas temperature of the temperature sensor 10, and the outgoing temperature of the temperature sensor 11. It is determined from the average temperature using a known calculation method.
Further, the differential pressure (ΔP) of the filter 7 is obtained by subtracting the post-pressure from the pre-pressure of the pressure sensors 8 and 9. The filter temperature is obtained from the average temperature of the inlet gas temperature and the outlet gas temperature of the temperature sensors 10 and 11, so that the average temperature of the filter 7 can be grasped almost accurately. In this way, the collection amount calculation unit 14 obtains the volume flow rate, the differential pressure, and the filter temperature under certain operation conditions from the collection amount of certain fine particles.
[0032]
When the volume flow rate is obtained, a differential pressure correction value based on the filter characteristics is obtained. This is the portion of (Vstd / V) ^{1 / a in} Equation 4. This differential pressure correction value is defined as in Equation 5.
[0033]
(Equation 5)
F = (Vstd / V) ^{1 / a}
Here, F is a coefficient, which can be said to be a differential pressure correction value based on a filter characteristic using the volume flow rate of the exhaust gas flowing into the filter 7 as a parameter. However, since it is difficult for the CPU 13 to perform such an operation, the differential pressure correction value F is obtained from a two-dimensional map using the volume flow rate V as a parameter. The map is obtained from the filter characteristics.
[0034]
FIG. 6A shows the volume flow rate-differential pressure characteristic of the filter 7 measured under the trapping amount shown in FIG. Here, Vstd is the volume flow rate under the reference operation condition, and the differential pressure generated at that time is defined as ΔPstd. FIG. 6B shows a filter characteristic obtained by standardizing this characteristic under the reference operation condition ΔPstd. This normalized value is defined as Kp.
[0035]
Here, ΔP1 in Equation 3 is ΔPstd.
ΔP / ΔPstd = 1 / (Vstd / V) ^{1 / a} . Further, since ΔP / ΔPstd = Kp, Kp = 1 / F is obtained from this and Expression 5. However, this filter characteristic does not depend on the collection amount. That is, the filter characteristics are dimensionless. Therefore, Equation 5 is performed as in Equation 6 in an actual operation.
[0036]
(Equation 6)
F = 1 / MAP (V)
Here, MAP (V) is a differential pressure correction value Kp obtained by using a function shown in FIG.
In the case where the above-mentioned standardization is not performed, it is necessary to prepare the map of FIG. 6A for each collection amount. The value can be obtained with one map.
[0037]
Further, the trapping amount calculation unit 14 calculates a temperature coefficient correction value of the filter characteristic from the filter temperature (the average temperature of the inlet gas temperature and the outlet gas temperature of the temperature sensors 10 and 11). This is the portion of 1+ (Tf−T0) × Kt in Equation 4.
The filter characteristics are those in the standard operation state, and the temperature is T0. When the filter temperature Tf is higher than this, that is, when Tf> T0, as described above, the actual filter characteristic value Kp becomes lower than the filter characteristic value in the ECU 12 under the reference operation condition, and the corrected differential pressure value ΔP1 Is a small value. Therefore, the error of the correction differential pressure ΔP1 caused by the change in the filter characteristics due to the temperature is corrected by the formula of 1+ (Tf−T0) × Kt. That is, when Tf> T0, 1+ (Tf−T0) × Kt becomes> 1, and the error of the correction differential pressure ΔP1 occurring on the minus side is corrected. When Tf <T0, the correction is made in the direction opposite to that described above.
[0038]
Therefore, the collection amount calculation unit 14 realizes the calculation of Equation 4 by calculating as shown in Equation 7.
[0039]
(Equation 7)
ΔP1 = ΔP / MAP (V) × (1+ (Tf−T0) × Kt)
Here, ΔP is the filter characteristic, and MAP (V) is a function using the passing volume flow rate V of the filter 7 as a parameter, and a differential pressure correction coefficient based on the filter characteristic under the filter temperature under the reference operation condition. , Tf represent the filter temperature, T0 represents the filter temperature under the reference operating condition, and Kt represents a coefficient for correcting the temperature characteristic of the filter characteristic.
[0040]
The calculation processing in the CPU 13 including the processing in the collection amount calculation section 14 described above will be described based on the flowchart shown in FIG.
First, in step 101, it is determined whether or not reproduction is being performed. If the reproduction control described below is not being performed, the process proceeds to step 102, and the sensor values from the sensors 3, 8 to 11 are fetched.
[0041]
In the next step 103, the differential pressure ΔP of the filter 7 is obtained by subtracting the post-pressure from the pre-pressure detected by the pressure sensors 8 and 9, respectively. In step 104, the suction flow rate of the hot wire flow sensor 3 and the pressure sensor 8 The volume flow rate V is determined from the pre-pressure and the average temperature of the incoming gas temperature of the temperature sensor 10 and the outgoing gas temperature of the temperature sensor 11. In step 105, the filter temperature Tf is determined from the average temperature of the incoming gas temperature and the outgoing gas temperature of the temperature sensors 10 and 11.
[0042]
Thereafter, in step 106, MAP (V) is obtained from the volume flow rate V by the function shown in FIG. 6B, and in step 107, a temperature correction value 1+ (Tf-T0) .times.Kt is calculated from the filter temperature Tf. I do. Then, the process proceeds to a step 108, wherein the corrected differential pressure ΔP1 is calculated by using the above equation (7). Note that the calculation processing of steps 102 to 108 corresponds to the processing of the collection amount calculation unit 14 described above.
[0043]
By comparing the corrected differential pressure ΔP1 with a set value, it is determined in step 109 whether or not the regeneration of the filter 7 is necessary. If this determination is YES, a reproduction control request flag is set in step 110. When this flag is set, in the regeneration control routine 200, known filter regeneration control, that is, a heating device and an air pump (not shown) are operated for a predetermined time to burn the particulates collected by the filter 7. While the reproduction control flag is not set, the reproduction control routine 200 performs no control.
[0044]
FIG. 3C shows a measurement result when the operating condition is changed with respect to the corrected differential pressure ΔP1 taking into account the temperature characteristics of the above-described filter characteristics. As is clear from this figure, the accuracy is considerably improved as compared with those shown in FIGS. 3 (a) and 3 (b).
Therefore, according to the present embodiment, the collection amount of the fine particles is accurately grasped, and the fine particles can be periodically burned in an appropriate amount, so that the durability of the filter 7 and the heating device can be improved.
[0045]
In the above-described embodiment, the case where the differential pressure correction and the correction based on the filter temperature are performed has been described. However, the correction based on only the filter temperature is sufficiently effective, and the invention can be recognized by using only this correction. .
Further, each step shown in the flowchart shown in FIG. 7 is configured as a function realizing means for realizing each function, and the functional realizing means enables not only the computer control described above but also a hard logic configuration to implement the present invention. It can constitute the invention.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an exhaust gas purification device for a diesel internal combustion engine according to an embodiment of the present invention.
FIG. 2 is a graph showing a volume flow rate-differential pressure characteristic of a filter caused by a pressure loss of the filter.
3A and 3B are diagrams showing a change in a corrected differential pressure when an operating condition is changed, wherein FIG. 3A shows a case where filter characteristics are not considered, FIG. 3B shows a case where filter characteristics are considered, and FIG. This shows a case according to the embodiment.
FIG. 4 is a diagram showing changes in volume flow rate, filter temperature, and differential pressure under different operating conditions.
FIG. 5 is a graph showing a volume flow rate-differential pressure characteristic of a filter caused by a filter temperature.
6A and 6B are graphs showing filter characteristics. FIG. 6A shows a volume flow rate-differential pressure characteristic of a filter measured under a certain trapping amount, and FIG. 6B shows a volume flow rate-difference of a standardized filter. 9 shows pressure characteristics.
FIG. 7 is a flowchart illustrating a calculation process performed by a CPU, such as a collection amount calculation.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Air cleaner 3 Hot wire type flow sensor 4 Exhaust pipe 5 Exhaust purification device 6 Housing 7 Filter 8, 9 Pressure sensor 10, 11 Temperature sensor 12 Electronic control unit (ECU)
13 Central Processing Unit (CPU)
14 Collection amount calculation unit

Claims

An exhaust purification device for a diesel internal combustion engine, which is provided in an exhaust system of the diesel internal combustion engine, collects particulates of exhaust gas, and includes a filter having laminar flow characteristics,
A collecting method for obtaining a volume flow rate of the exhaust gas passing through the filter and a differential pressure between the filters, and detecting a corrected differential pressure obtained by correcting the differential pressure with the volume flow rate of the passing exhaust gas relative to a reference volume flow rate. An exhaust gas purification device for a diesel internal combustion engine, comprising an amount detection unit, configured to perform a regeneration process of the filter based on the detected corrected differential pressure.
The trapping amount detecting means has a filter temperature detecting means for detecting a temperature of the filter, and an equation using the detected filter temperature and the filter temperature under the standard operation condition, the detected filter temperature is the The correction differential pressure is increased when the filter temperature is higher than the filter temperature under the reference operation condition, and the correction differential pressure is decreased when the detected filter temperature is lower than the filter temperature under the reference operation condition. An exhaust purification device for a diesel internal combustion engine, wherein the pressure is temperature-corrected.

In a diesel internal combustion engine exhaust purification device provided with a filter installed in an exhaust system of a diesel internal combustion engine to collect fine particles of exhaust gas, and having a laminar flow characteristic,
Volume flow detection means for determining the volume flow passing through the filter,
A differential pressure detecting means for obtaining a differential pressure between the filters,
Filter temperature detection means for detecting the temperature of the filter,
Based on the volume flow rate-differential pressure characteristic due to the pressure loss of the filter and the volume flow rate-differential pressure characteristic due to the temperature of the filter, the detected differential pressure is corrected by the detected volume flow rate and the filter temperature, A correction differential pressure calculating means for calculating a correction differential pressure,
The filter regeneration processing is performed based on the calculated corrected differential pressure ,
The correction differential pressure calculating means uses an equation using the detected filter temperature and the filter temperature under the standard operation condition, and calculates the detected difference when the detected filter temperature is higher than the filter temperature under the standard operation condition. A diesel internal combustion engine that corrects the detected differential pressure so as to increase the pressure and reduce the detected differential pressure when the detected filter temperature is lower than the filter temperature under the reference operating condition. Exhaust purification equipment.

The correction differential pressure calculating means corrects the differential pressure with respect to the pressure loss of the filter by normalizing the volume flow rate-differential pressure characteristic due to the pressure loss of the filter into a differential pressure characteristic with respect to the volume flow rate-referenced differential pressure. The exhaust gas purifying apparatus for a diesel internal combustion engine according to claim 2, characterized in that:

4. The diesel internal combustion engine according to claim 1, wherein the filter temperature detection unit detects the temperature of the filter based on an average value of an exhaust gas temperature flowing into the filter and an exhaust gas temperature flowing out of the filter. 5. Engine exhaust purification device.