JP2004340099A

JP2004340099A - Egr device for internal combustion engine and clogging detection device for egr device

Info

Publication number: JP2004340099A
Application number: JP2003140648A
Authority: JP
Inventors: Takao Fukuma; 隆雄福間; Nobuyuki Takahashi; 宜之高橋
Original assignee: Toyota Industries Corp; Toyota Motor Corp
Current assignee: Toyota Industries Corp; Toyota Motor Corp
Priority date: 2003-05-19
Filing date: 2003-05-19
Publication date: 2004-12-02
Anticipated expiration: 2023-05-19
Also published as: JP4299054B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EGR device capable of improving clogging of an EGR cooler without changing a combustion condition of an internal combustion engine. <P>SOLUTION: In the EGR device for the internal combustion engine which is provided with EGR coolers 14L, 14R for cooling exhaust gas on EGR passages 13L, 13R re-circulating exhaust gas to an intake side from an exhaust gas passage 4 in which pressure acting on at least one of the EGR coolers 14L, 14R can be adjusted by a turbocharger 6 as a pressure adjusting means, the turbocharger 6 is operated to keep the pressure on an outlet side at a time of exhaust gas recirculation of the EGR cooler 14L, 14R higher than the pressure on an inlet side at the time of exhaust gas recirculation, and a flow in a reverse direction to the flow at the time of exhaust gas recirculation is generated in the EGR coolers 14L, 14R. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関の排気ガスを吸気通路に還流させるＥＧＲ装置に関する。
【０００２】
【従来の技術】
排気ガスをＥＧＲクーラによって冷却して吸気通路に還流するＥＧＲ装置においては、排気ガス中の煤等がＥＧＲクーラに徐々に堆積して詰まることがある。そこで、ＥＧＲクーラを備えたＥＧＲ装置においては、ＥＧＲクーラの詰まり対策が必要である。
【０００３】
ＥＧＲクーラの詰まり対策を施したＥＧＲ装置としては、ＥＧＲクーラの前後に設置した差圧センサにて詰まりの有無を監視し、詰まりが生じた場合に排気ガス温度が上昇するように内燃機関の燃焼状態を一時的に変更し、排気ガスの熱でＥＧＲクーラに堆積した煤等を燃焼させて詰まりを解消するＥＧＲ装置が提案されている（特許文献１参照）。ＥＧＲクーラの劣化（詰まり）の有無を温度センサにて監視し、劣化が検出された場合にＥＧＲガス量が増加するようにＥＧＲ弁の開度を調整して、劣化前と同等のＥＧＲガス量を確保するＥＧＲ装置も提案されている（特許文献２参照）。その他に本発明に関連する従来技術として特許文献３及び４がある。
【０００４】
【特許文献１】
特開２００２−１７４１４８号公報
【特許文献２】
特開２０００−１３０２６６号公報
【特許文献３】
特開平１０−２８１０１６号公報
【特許文献４】
特開平１１−６２７２２号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、特許文献１のＥＧＲ装置では、排気ガス温度を上昇させるために内燃機関の燃焼状態を排気ガスの浄化性能からみた最適な状態から一時的に変更する必要が生じて排気エミッションが悪化する。排気ガス温度を上昇させるために余計なエネルギが消費される。また、特許文献２のＥＧＲ装置は、ＥＧＲクーラの機能を回復させるわけではないので、ＥＧＲガス量の増加に伴ってＥＧＲガス温度が上昇し、ＥＧＲ効果が低下する。また、いずれのＥＧＲ装置も、ＥＧＲクーラの劣化を検出するために専用の差圧センサ又は温度センサを設ける必要があってコスト増が避けられない。
【０００６】
そこで、本発明は内燃機関の燃焼状態を変更することなくＥＧＲクーラの詰まりを改善できるＥＧＲ装置、及び専用のセンサを使用することなくＥＧＲクーラの詰まりを検出できるＥＧＲ装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明のＥＧＲ装置は、排気通路から吸気側に排気を還流するＥＧＲ通路に排気冷却用のＥＧＲクーラが設けられ、該ＥＧＲクーラの少なくとも一方の側に作用する圧力が圧力調整手段にて調整可能とされた内燃機関のＥＧＲ装置において、前記ＥＧＲクーラの排気還流時における出口側の圧力が前記排気還流時における入口側の圧力よりも高くなるように前記圧力調整手段を操作して、前記ＥＧＲクーラ内に前記排気還流時とは逆方向の流れを生じさせる詰まり解消制御手段が設けられることにより、上述した課題を解決する（請求項１）。
【０００８】
本発明によれば、内燃機関に設けられた圧力調整手段を操作してＥＧＲクーラの入口側と出口側との間の圧力差を変化させることにより、ＥＧＲクーラ内を排気ガスが一定方向に流れることによって堆積した煤等の堆積物を反対方向へガスを流して除去するいわゆる逆洗操作を実施して、比較的容易にＥＧＲクーラの詰まりを解消することができる。このように圧力操作によって堆積物を除去するので、内燃機関の燃焼状態を変更する必要はない。なお、本発明のＥＧＲ装置において、圧力調整手段は内燃機関の運転状態を調整するために排気圧力又は吸気圧力を変化させる手段として設けられているものであればよい。
【０００９】
本発明のＥＧＲ装置は、互いに異なる排気通路に接続される２つのシリンダ群が設けられた内燃機関に好適に適用される。そして、前記ＥＧＲクーラの一端側には一方のシリンダ群の排気側と接続されたＥＧＲ通路の圧力が、他端側には他方のシリンダ群の排気側と接続されたＥＧＲ通路の圧力がそれぞれ導入可能であり、前記詰まり解消制御手段は、前記圧力調整手段を操作して前記シリンダ群に対応する２つのＥＧＲ通路のうち、少なくともいずれか一方のＥＧＲ通路の圧力を変化させることにより、前記ＥＧＲクーラに前記排気還流時とは逆方向の流れを生じさせるようにしてもよい（請求項２）。
【００１０】
２つのシリンダ群のそれぞれが互いに異なる排気通路に接続された内燃機関においては、各シリンダ群から排気ガスを戻すためのＥＧＲ通路が吸気通路に至るまでの少なくとも一部においてシリンダ群毎に分かれている。これらのシリンダ群毎のＥＧＲ通路においては、ＥＧＲ通路や排気通路に設けられた圧力調整手段を操作することにより、ＥＧＲ通路の圧力をシリンダ群毎に別々に調整することができる。このため、ＥＧＲクーラの両端にそれぞれ別々のシリンダ群に対応するＥＧＲ通路の圧力を導入して圧力調整手段を操作すれば、ＥＧＲクーラの両端の圧力の大小関係を変化させ、ＥＧＲクーラ内におけるガスの流れ方向を切り替えられるようになる。なお、互いに異なる３以上のシリンダ群が設けられている内燃機関であっても、２つのシリンダ群が含まれている限りにおいて上記態様に含まれる。
【００１１】
本発明のＥＧＲ装置においては、前記シリンダ群毎のＥＧＲ通路のそれぞれに前記ＥＧＲクーラが設けられ、各ＥＧＲクーラの排気還流時における出口側同士が連絡通路にて接続され、前記シリンダ群毎の排気通路の前記ＥＧＲ通路への分岐位置よりも下流には排気抵抗調整手段が設けられ、前記詰まり解消制御手段は少なくともいずれか一方の排気通路の前記排気抵抗調整手段を前記圧力調整手段として操作して前記逆方向の流れを生じさせてもよい（請求項３）。
【００１２】
この態様によれば、ＥＧＲクーラの出口側同士が連絡通路を介して接続されることにより、各シリンダ群の排気通路がＥＧＲ通路とＥＧＲクーラとを介して相互に接続されることになる。また、各シリンダ群毎の排気抵抗調整手段による排気抵抗を差別化することにより、各シリンダ群の排気圧力に差を設けることができる。そして、排気圧力に差を設けることにより、排気圧力が高い排気通路からＥＧＲ通路、連絡通路及び反対側のＥＧＲ通路を介して反対側の排気圧力が低い排気通路への排気の流れを作り出すことができる。これにより、排気圧力が低いＥＧＲ通路のＥＧＲクーラでは、排気還流時における出口側から入口側へ排気が通過するようになる。なお、排気抵抗調整手段は例えば排気絞り弁のように排気抵抗の調整を目的として設けられている手段に限らず、ターボチャージャのように他の目的（この例では吸気圧力の調整）で設けられていても結果として排気抵抗に変化を生じさせる手段も含む。
【００１３】
本発明のＥＧＲ装置においては、前記シリンダ群毎のＥＧＲ通路が共通のＥＧＲクーラに接続されるとともに当該ＥＧＲクーラの両側にて前記シリンダ群毎のＥＧＲ通路のそれぞれが前記圧力調整手段としてのＥＧＲ弁を介して前記２つのシリンダ群に共通の吸気通路に接続され、前記詰まり解消制御手段は、前記ＥＧＲ通路毎のＥＧＲ弁をそれぞれの開度が差別化されるように操作して前記逆方向の流れを生じさせるようにしてもよい（請求項４）。
【００１４】
この発明によれば、ＥＧＲクーラの両側がＥＧＲ弁を介して吸気通路と接続されるので、一方のＥＧＲ弁を閉じて他方のＥＧＲ弁を開ける場合と、一方のＥＧＲ弁を開いて他方のＥＧＲ弁を閉じる場合とで、ＥＧＲクーラを通過する排気の流れ方向が逆になる。従って、ＥＧＲ弁の開閉状態を適宜切り換えることにより、従前の排気還流時の入口側を出口側に、出口側を入口側に切り換えてＥＧＲクーラ内の堆積物を除去して詰まりを解消することができる。なお、吸気通路が共通であるため、いずれのＥＧＲ弁が開かれても２つのシリンダ群のそれぞれに等しくＥＧＲガスを供給することができる。
【００１５】
本発明のＥＧＲ装置は、吸気を過給する過給器が設けられている内燃機関に適用することもできる。この場合、前記ＥＧＲ通路はＥＧＲ弁を介して前記吸気側に接続され、前記詰まり解消制御手段は、前記ＥＧＲ弁が開かれた状態で前記ＥＧＲクーラの前記排気還流時における入口側の圧力よりも前記排気還流時における出口側の圧力が高くなるよう前記過給器を前記圧力調整手段として操作して前記逆方向の流れを生じさせてもよい（請求項５）。
【００１６】
排気流量が小さくて排気圧力が低下している状態でＥＧＲ弁を開くとともに過給器による過給効果を一時的に増加させて吸気側の圧力を排気圧力よりも増加させることにより、ＥＧＲクーラに排気還流時における出口側から入口側へ吸気を流し、それにより堆積物を除去して詰まりを解消することができる。
【００１７】
本発明のＥＧＲ装置においては前記ＥＧＲクーラの詰まりを検出する詰まり検出手段をさらに具備し、前記詰まり解消制御手段は前記詰まり検出手段にて詰まりが検出された場合に、その検出された詰まりを解消するように前記圧力調整手段を操作して前記逆方向の流れを生じさせてもよい（請求項６）。この態様によればＥＧＲクーラが詰まった場合にこれを確実を解消することができる。
【００１８】
本発明のＥＧＲ装置においては、前記内燃機関にはＥＧＲガスを含まない吸入空気量を検出する吸入空気量検出手段が設けられ、前記詰まり検出手段は、前記ＥＧＲクーラにおける圧力損失が一定と仮定した場合に一定の吸入空気量が前記吸入空気量検出手段にて検出されるように前記吸入空気量に影響する機器類の操作状態を所定の基準状態に設定し、その基準状態にて前記吸入空気量検出手段が検出する吸入空気量の変化に基づいて前記詰まりを検出してもよい（請求項７）。
【００１９】
ＥＧＲクーラにおける圧力損失が一定でかつ内燃機関の吸入空気量に影響する機器類の操作状態が一定であれば、ＥＧＲ量及び排気の量（但し、ＥＧＲガスを除く）は一定となり、吸入空気量検出手段にて検出される吸入空気量はＥＧＲガスを除いた排出空気量に等しくなる。しかしながら、ＥＧＲクーラの詰まりが進行するとＥＧＲガス量が徐々に減少し、ＥＧＲ分を除いた排出空気量が相対的に増加する。このため、吸入空気量に影響する機器類が所定の基準状態に操作されていても吸入空気量検出手段にて検出される吸入空気量は徐々に増加する。このように吸入空気量とＥＧＲクーラの詰まりとは相関関係があるので、吸入空気量検出手段が検出する吸入空気量の変化に基づいてＥＧＲクーラの詰まり状態を判別することができる。なお、吸入空気量検出手段はエアフローメータのように吸入空気量を直接検出する手段に限らず、吸入空気量と相関する吸気圧等の他の物理量を検出することにより、吸入空気量を間接的に検出する手段も含む。吸入空気量に影響する機器類としては、スロットル弁、ＥＧＲ弁、排気通路に設けられた可変ノズル式ターボチャージャの可動ノズル、排気絞り弁、吸排気系の可変動弁機構等が挙げられるが、ＥＧＲクーラの詰まり検出で必要とされる測定精度からみて吸入空気量に与える影響が無視できる機器は基準状態に設定する対象から除外して構わない。
【００２０】
本発明のＥＧＲ装置においては、前記ＥＧＲクーラが前記シリンダ群毎のＥＧＲ通路のそれぞれに設けられ、前記内燃機関には、シリンダ群毎の排気エネルギにて駆動されることにより前記シリンダ群毎に設けられた吸気通路内の吸気を過給するシリンダ群毎の過給器と、前記シリンダ群毎の吸気通路におけるＥＧＲガスを含まない吸入空気量を検出する吸入空気量検出手段とが設けられ、前記ＥＧＲ装置には、前記ＥＧＲクーラにおける圧力損失が一定と仮定した場合に一定の吸入空気量が前記吸入空気量検出手段にて検出されるように前記吸入空気量に影響する機器類の操作状態を所定の基準状態に設定し、その基準状態にて前記吸入空気量検出手段が検出する吸入空気量の変化に基づいて前記ＥＧＲクーラの詰まりを検出する詰まり検出手段が設けられ、前記詰まり検出手段は、前記吸入空気量検出手段が検出したシリンダ群毎の吸入空気量の差に基づいて前記シリンダ群毎のＥＧＲクーラの詰まりの進行度を判別してもよい（請求項８）。
【００２１】
排気エネルギにて駆動されるいわゆるターボチャージャ式の過給器がシリンダ群毎の吸気通路に配置されている構成においては、一方のシリンダ群側のクーラが反対側のＥＧＲクーラよりも相対的に詰まった場合に、その一方のシリンダ群側のＥＧＲ通路を介して戻されるＥＧＲ量が相対的に減少し、当該一方のシリンダ群の排気通路に導かれる排出空気量が増加する。このため、一方のシリンダ群側において、排出空気量の増加に応答して過給効果が高まって当該一方のシリンダ群に対応する側の吸入空気量が増加する。従って、シリンダ群毎に分かれている吸気通路における吸入空気量の差から、シリンダ群側のＥＧＲクーラの詰まりの進行度を判別することができる。
【００２２】
上記のように、シリンダ群毎のＥＧＲクーラの詰まりの進行度を判別する場合において、前記詰まり解消手段は、前記詰まりがより進行していると判別された側のＥＧＲクーラを、反対側のＥＧＲクーラよりも優先して前記排気還流時とは逆方向の流れが生じるように前記圧力調整手段を操作してもよい（請求項９）
【００２３】
内燃機関の運転条件等の制約から圧力調整手段を操作できる時期が限られている場合に、まず詰まりが進行している側のＥＧＲクーラの詰まりを優先して解消する操作を行うようにすれば、限られた期間において高い詰まり解消効果を得ることができる。
【００２４】
本発明の詰まり検出装置は、排気通路から吸気側に排気を還流するＥＧＲ通路に排気冷却用のＥＧＲクーラが設けられた内燃機関のＥＧＲ装置に適用されるＥＧＲクーラの詰まり検出装置において、前記ＥＧＲクーラにおける圧力損失が一定と仮定した場合に一定の吸入空気量が前記吸入空気量検出手段にて検出されるように前記吸入空気量に影響する機器類の操作状態を所定の基準状態に設定する基準状態設定手段と、前記基準状態において前記内燃機関に設けられた吸入空気量検出手段が検出する吸入空気量の変化に基づいて前記詰まりを検出する詰まり検出実行手段とを備えることにより、上述した課題を解決する（請求項１０）。
【００２５】
この検出装置によれば、ＥＧＲクーラの詰まりが進行すれば排出空気量が増加して吸入空気量検出手段が検出する吸入空気量も増加するという上記の相関関係を利用してＥＧＲクーラの詰まりの進行度を判別することができる。吸入空気量検出手段は、一般的な内燃機関には空燃比制等を実行するために設けられているので、詰まり検出専用のセンサが不要となり、部品点数の削減やコストダウンを図ることができる。なお、本発明の詰まり検出装置においても、吸入空気量検出手段はエアフローメータのように吸入空気量を直接検出する手段に限らず、吸入空気量と相関する吸気圧等の他の物理量を検出することにより、吸入空気量を間接的に検出する手段も含む。吸入空気量に影響する機器類としては、スロットル弁、ＥＧＲ弁、排気通路に設けられた可変ノズル式ターボチャージャの可動ノズル、排気絞り弁、吸排気系の可変動弁機構等が挙げられるが、ＥＧＲクーラの詰まり検出で必要とされる測定精度からみて吸入空気量に与える影響が無視できる機器は基準状態に設定する対象から除外して構わない。
【００２６】
【発明の実施の形態】
図１は本発明の一実施形態に係るＥＧＲ装置が組み込まれた内燃機関を示している。この実施形態において、内燃機関は左右のバンク２Ｌ、２Ｒに４つずつシリンダ３が設けられたＶ型８気筒のディーゼルエンジン１として構成されている。左バンク２Ｌのシリンダ３によって一つのシリンダ群が構成され、右バンク２Ｒのシリンダ３によって他の一つのシリンダ群が構成される。なお、一つのシリンダ群は少なくとも一つのシリンダ３が含まれていればよい。
【００２７】
各シリンダ３に吸気を導くための吸気通路４はエアクリーナ５の下流においてバンク毎の分岐路４Ｌ、４Ｒに分かれており、その分岐路４Ｌ、４Ｒにターボチャージャ６のコンプレッサ６ａが配置されている。コンプレッサ６ａの下流において分岐路４Ｌ、４Ｒはインタークーラ７を通過し、吸気通路４の一部を構成する共通のインテークマニホールド８に接続される。一方、各バンクのシリンダ３からの排気は、バンク毎に設けられた排気通路１０Ｌ、１０Ｒのエキゾーストマニホールド１１Ｌ、１１Ｒからターボチャージャ６のタービン６ｂに導かれ、さらにタービン６ｂの下流側に導かれる。タービン６ｂの下流側には触媒や消音器等が設けられるがそれらの図示は省略した。
【００２８】
ターボチャージャ６は、開度調整が可能なノズル装置（不図示）をタービン６ｂ側に備えた可変ノズルターボチャージャ（以下、ＶＮＴと呼ぶことがある。）である。各ターボチャージャ６のノズル開度はエンジンコントロールユニット（ＥＣＵ）１２にて制御される。ＥＣＵ１２は各シリンダ３に対する燃料噴射量等を調整してエンジン１の運転状態を制御する周知のコンピュータである。
【００２９】
エンジン１にはＥＧＲ通路１３が設けられている。ＥＧＲ通路１３は、エキゾーストマニホールド１１Ｌ、１１Ｒにそれぞれ接続されたバンク毎のＥＧＲ通路１３Ｌ、１３Ｒと、ＥＧＲ通路１３Ｌ、１３Ｒを結ぶ連絡通路１３Ｃとを備えている。ＥＧＲ通路１３Ｌ、１３ＲにはＥＧＲガスを冷却するためのＥＧＲクーラ１４Ｌ、１４Ｒが設けられ、連絡通路１３Ｃは各クーラ１４Ｌ、１４Ｒの間に設けられている。このように連絡通路１３Ｃを介してＥＧＲクーラ１４Ｌ、１４Ｒが相互に接続されているため、ＥＧＲクーラ１４Ｌに関してはその排気還流時の入口側（左端側）にＥＧＲ通路１３Ｌの圧力が導入され、排気還流時の出口側（右端側）にはＥＧＲクーラ１４Ｒの出口側におけるＥＧＲ通路１３Ｒの圧力が連絡通路１３Ｃを介して導入される。また、ＥＧＲクーラ１４Ｒに関してはその排気還流時の入口側（右端側）にＥＧＲ通路１３Ｒの圧力が導入され、排気還流時の出口側（左端側）にはＥＧＲクーラ１４Ｌの出口側におけるＥＧＲ通路１３Ｌの圧力が連絡通路１３Ｃを介して導入される。
【００３０】
さらに、連絡通路１３Ｃは一対のＥＧＲ弁１５を介してインテークマニホールド８に接続されている。ＥＧＲ弁１５の開度はＥＣＵ１２によりエンジン１の運転状態に応じて制御される。その開度制御の内容は通常の内燃機関のＥＧＲ制御と同様でよい。
【００３１】
次に、図２を参照してＥＧＲクーラ１４Ｌ、１４Ｒの詰まりを解消する操作を説明する。
【００３２】
左側のバンク２Ｌに対応するＥＧＲクーラ１４Ｌの詰まりを解消するには、各ＥＧＲ弁１５を閉じた状態で図２（ａ）に示すようにバンク２Ｌに対応するターボチャージャ６のノズル開度を、バンク２Ｒに対応するターボチャージャ６のノズル開度よりも増加させる。これにより、エキゾーストマニホールド１１Ｌの排気圧力がエキゾーストマニホールド１１Ｒの排気圧力よりも低下し、ＥＧＲ通路１３には図２（ａ）に矢印で示したように、ＥＧＲ通路１３Ｒから連絡通路１３Ｃを介してＥＧＲ通路１３Ｌに向かう排気ガスの流れが生じる。このため、ＥＧＲクーラ１４Ｌにおいては出口から入口に向かって排気ガスが逆流し、その結果、ＥＧＲクーラ１４Ｌに堆積した煤等の堆積物が除去されてＥＧＲクーラ１４Ｌの詰まりが解消する。
【００３３】
一方、右側のバンク２Ｒに対応するＥＧＲクーラ１４Ｒの詰まりを解消するには、各ＥＧＲ弁１５を閉じた状態で図２（ｂ）に示すようにバンク２Ｒに対応するターボチャージャ６のノズル開度を開け、バンク２Ｌに対応するターボチャージャ６のノズル開度を閉じる。これにより、エキゾーストマニホールド１１Ｒの排気圧力がエキゾーストマニホールド１１Ｌの排気圧力よりも低下し、ＥＧＲ通路１３には図２（ｂ）に矢印で示したように、ＥＧＲ通路１３Ｌから連絡通路１３Ｃを介してＥＧＲ通路１３Ｒに向かう排気ガスの流れが生じる。このため、ＥＧＲクーラ１４Ｒにおいては出口から入口に向かって排気ガスが逆流し、その結果、ＥＧＲクーラ１４Ｒに堆積した煤等の堆積物が除去されてＥＧＲクーラ１４Ｒの詰まりが解消する。
【００３４】
次に、ＥＧＲクーラ１４Ｌ、１４Ｒの詰まりの検出について説明する。図３はＥＣＵ１２がＥＧＲクーラ１４Ｌ、１４Ｒの詰まりを判定するために所定の周期で繰り返し実行するＥＧＲクーラ詰まり判定ルーチンを示すチャートである。ＥＧＲクーラ詰まり判定ルーチンにおいてＥＣＵ１２は、最初のステップＳ１で、詰まりが既に検出されているか否かを判別するための詰まり検出フラグの値が、検出済を示す１にセットされているか否か判断する。検出フラグが１であればステップＳ２以下の処理を省略して今回のルーチンを終える。一方、フラグが１でなければステップＳ２へ進み、ＥＣＵ１２は、詰まりを検出する際の基準状態の一つとして、エンジン１の回転数が所定範囲内か否かを判断する。所定範囲でなければ判定ルーチンを終える。所定範囲であればステップＳ３へ進み、ＥＣＵ１２はＥＧＲ弁１５及びターボチャージャ（ＶＮＴ）６のノズルのそれぞれの開度を所定値にセットする。このときの開度は詰まりを判定する際の基準状態の一つとして定められた開度であって、一定値であれば最大開度〜最小開度の間の任意の開度を選んでよい。この処理により、ＥＣＵ１２は基準状態設定手段として機能する。なお、ステップＳ３ではエンジン１の一回転あたりの吸入空気量に影響する機器類としてターボチャージャ６を対象とし、その操作状態をノズル開度一定という所定の基準状態に設定しているが、これ以外に吸入空気量に影響する機器類が存在する場合にはその操作状態も一定に設定する必要がある。但し、吸入空気量に与える影響がＥＧＲクーラの詰まり判定という目的からみて無視し得る程度に軽微な機器については操作対象から外してよい。
【００３５】
続くステップＳ４では、図１に示す吸気通路４の分岐路４Ｌ、４Ｒに設けられたエアフローメータ１６Ｌ、１６Ｒの出力に基づいて、現在のエンジン１の一回転当たりの吸入空気量を検出してＥＣＵ１２のＲＡＭに測定結果を記憶する。続くステップＳ５において、ＥＣＵ１２は今回のルーチンによる詰まり判定が２回目以降の判定か否か判断する。２回目以降の判定でなければステップＳ５以下をスキップしてルーチンを終える。一方、ステップＳ５で２回目以降の判定であったときはステップＳ６に進み、ＥＣＵ１２はステップＳ４で検出した吸入空気量が１回目のルーチン実行時に検出した吸入空気量に対して所定量以上増加しているか否かを判断する。増加していなければステップＳ６以下をスキップして今回のルーチンを終える。ＥＧＲクーラ１４Ｌ、１４Ｒの少なくともいずれか一方に詰まりが生じると、エンジン１の回転数が一定で、かつターボチャージャ６のノズル開度及びＥＧＲ弁１５の開度が一定の条件下で比較した場合に、ＥＧＲ量が減少して吸入空気量が増加するため、このように吸入空気量を過去の検出値と比較すればＥＧＲクーラ１４Ｌ又は１４Ｒの詰まりの有無が判別できる。
【００３６】
ステップＳ６にて吸入空気量が所定量以上増加しているときは少なくともいずれか一方のＥＧＲクーラ１４Ｌ又は１４Ｒに詰まりが発生したものとしてステップＳ７へ進み、詰まり検出フラグの値に１をセットする。続くステップＳ８ではエアフローメータ１６Ｌ、１６Ｒがそれぞれ検出する吸入空気量を比較し、次のステップＳ９において吸入空気量の多い側のＥＧＲクーラ１４Ｌ又は１４Ｒを詰まりが相対的に進行し、詰まり解消操作において優先して処理されるべき側として判別し、その結果をＥＣＵ１２のＲＡＭに記憶する。ＥＧＲクーラ１４Ｌ、１４Ｒが詰まるほどＥＧＲガス量が減少してタービン６ｂに導かれる排気ガス量が増えるので、その結果としてコンプレッサ６ａによる過給効果が高まってＥＧＲクーラの詰まっている側の分岐路４Ｌ又は４Ｒの吸入空気量が増加する。
【００３７】
その後、ＥＣＵ１２はステップＳ１０にてＥＧＲ弁１５及びターボチャージャ６の開度をそれぞれ元の開度（ステップＳ３の設定前の開度）に戻す。以上により、図３のルーチンを終える。以上のステップＳ４〜Ｓ９によりＥＣＵ１２は詰まり検出実行手段として機能する。
【００３８】
以上の詰まり判定ルーチンにて詰まりが検出されると、ＥＣＵ１２の制御によって図２に示した詰まり解消操作が実施される。図４及び図５は、その詰まり解消操作のためにＥＣＵ１２が実行するＥＧＲクーラ詰まり解消制御ルーチンを示すフローチャートである。ＥＣＵ１２は、エンジン１の運転中に所定の周期で繰り返し図４及び図５のルーチンを実行することにより、本発明の詰まり解消制御手段として機能する。
【００３９】
ＥＧＲクーラ詰まり解消制御ルーチンにおいて、ＥＣＵ１２はまずステップＳ２１において詰まり検出フラグに１がセットされているか否か判断し、１がセットされていなければルーチンを終える。一方、検出フラグが１の場合はステップＳ２２に進み、ＥＣＵ１２はエンジン１に対する燃料噴射量が０となる減速時の燃料カット中か否か判断する。ここではターボチャージャ６のノズル開度を変化させて詰まりを解消するので、エンジン１の運転になるべく影響の少ない状態としてタービン６ｂが回転していてしかも燃料カット中の減速時であることを前提としている。但し、詰まり解消操作を実行する前提としての運転条件はこれに限らず適宜に定めてよい。
【００４０】
続くステップＳ２３では第１解消操作フラグに１がセットされているか否かを判断し、１がセットされていなければステップＳ２４で第２解消操作フラグに１がセットされているか否か判断する。これらのフラグは詰まり解消操作の実行中か否かを判断するためのものである。ステップＳ２３、Ｓ２４のいずれにおいてもフラグに１がセットされていない場合、すなわち、詰まりが検出された後に未だ詰まり解消操作が開始されていない場合にステップＳ２５へ進み、第１解消操作フラグに１をセットするとともに、詰まり解消操作の継続時間のカウントを開始する。その後ステップＳ２６へ進んで各ＥＧＲ弁１５の開度を全閉とし、さらにステップＳ２７にて優先処理側（図３のステップＳ９参照）のＥＧＲクーラ１４Ｌ、又は１４Ｒと同一の側のターボチャージャ６のノズル開度を最大に設定し、続くステップＳ２８にて反対側のターボチャージャ６のノズル開度を最小に設定する。これらの操作により、図２（ａ）又は（ｂ）の状態が実現される。また、第１解消操作フラグは、優先処理側のＥＧＲクーラ１４Ｌ又は１４Ｒに関する詰まり解消操作の実行中か否かを判別するフラグとして機能する。
【００４１】
続くステップＳ２９では、ステップＳ２５で開始された詰まり解消操作の継続時間のカウント値が所定の継続時間に達しているか否か判断する。所定時間に達していなければ今回のルーチンを終え、達していればステップＳ３０へ進んで第１解消操作フラグを０にリセットし、継続時間のカウントを終了する。
【００４２】
続いて図５のステップＳ３１へ進み、第２解消操作フラグに１をセットし、詰まり解消操作の継続時間のカウントを再び初期値から開始する。続くステップＳ３２で各ＥＧＲ弁１５の開度を全閉とし、さらにステップＳ３３にて優先処理側のＥＧＲクーラ１４Ｌ、又は１４Ｒと同一の側のターボチャージャ６のノズル開度を最小に設定し、続くステップＳ２８にて反対側のターボチャージャ６のノズル開度を最大に設定する。これらの操作により、優先処理側のＥＧＲクーラ１４Ｌ又は１４Ｒに対する詰まり解消操作が終了し、反対側のＥＧＲクーラ１４Ｒ又は１４Ｌに対する詰まり解消操作が開始される。第２解消操作フラグは、優先処理側の反対側のＥＧＲクーラ１４Ｒ又は１４Ｌに関する詰まり解消操作の実行中か否かを判別するフラグとして機能する。
【００４３】
続くステップＳ３５では、ステップＳ３１で開始された詰まり解消操作の継続時間のカウント値が所定の継続時間に達しているか否か判断する。所定時間に達していなければ今回のルーチンを終え、達していればステップＳ３６へ進んで第２解消操作フラグを０にリセットし、継続時間のカウントを終了する。その後、ステップＳ３７にて詰まり検出フラグを０にリセットし、ステップＳ３８にてターボチャージャ６のノズル開度及びＥＧＲ弁１５の開度を詰まり解消操作前の元の開度に戻し、これをもってルーチンを終える。以上により、優先処理側の反対側のＥＧＲクーラ１４Ｒ又は１４Ｌに対する詰まり解消操作も終了する。
【００４４】
なお、詰まり解消操作の実行中に図４のルーチンが開始された場合において、エンジン１の運転状態が燃料カット状態から変化したときはステップＳ２２が否定判断される。この場合、ＥＣＵ１２はステップＳ３８にて詰まり解消操作の継続時間のカウントを中断し、ステップＳ３８へ進んでターボチャージャ６のノズル開度及びＥＧＲ弁１５の開度を元に戻して詰まり解消操作を中断させる。このような中断があっても、第１解消操作フラグ又は第２解消操作フラグのいずれかが１にセットされているので、再び燃料カット中に図４のルーチンが開始された場合にステップＳ２３又はステップＳ２４のいずれかが肯定判断される。そして、ステップＳ２３が肯定された場合、ＥＣＵ１２はステップＳ３９にて継続時間のカウントを継続してステップＳ２６に進む。これにより、優先処理側のＥＧＲクーラ１４Ｌ又は１４Ｒに対する詰まり解消操作が再開される。また、ステップＳ２４が肯定判断された場合、ＥＣＵ１２は図５のステップＳ４０にて継続時間のカウントを継続してステップＳ３２に進む。これにより、優先処理側の反対側のＥＧＲクーラ１４Ｒ又は１４Ｌに対する詰まり解消操作が再開される。
【００４５】
図４及び図５の詰まり解消制御ルーチンにおいては、詰まり解消中のターボチャージャ６のノズル開度に関して、ステップＳ２７及びＳ２８においては優先処理側が反対側よりも大きく設定されていればよく、ステップＳ３３及びＳ３４においては優先処理側が反対側よりも小さく設定されていればよい。但し、ＥＧＲクーラ１４Ｌ又は１４Ｒに生じる圧力差をなるべく大きくして逆洗効果を高めるためにはノズル開度を最大と最小とにそれぞれ設定することが望ましい。
【００４６】
また、上記の詰まり解消制御ルーチンでは詰まり解消操作を所定時間継続するようにしたが、詰まり解消操作開始後の吸入空気量の積算値等の他の物理量を参照して詰まり解消操作の終了時期を決めてもよい。
【００４７】
なお、以上の実施形態ではターボチャージャ６が圧力調整手段及び排気抵抗調整手段に相当する。可変ノズル式のターボチャージャに代え、電動発電機によってタービンの回転を調整可能な電動機付きターボチャージャが設けられている場合においても、タービンの回転速度を変化させて排気圧力（排気抵抗）を変えることにより、上記の実施形態と同様にしてＥＧＲクーラの詰まりを解消することができる。
【００４８】
次に、本発明の他の実施形態を説明する。図６は排気通路１０Ｌ、１０Ｒに圧力調整手段及び排気抵抗調整手段として排気絞り弁２０Ｌ、２０Ｒが設けられている例である。この場合には、ターボチャージャ６のノズル開度の操作に代えて、排気絞り弁２０Ｌ、２０Ｒの開度に差を設けることにより、左右の排気通路１０Ｌ、１０Ｒの排気圧力に差を生じさせてＥＧＲクーラ１４Ｌ、１４Ｒの詰まりを解消させることができる。例えば、ＥＧＲクーラ１４Ｌの詰まりを解消する場合には左側の排気絞り弁２０Ｌの開度を大きく、反対側の排気絞り弁２０Ｒの開度をそれよりも小さく設定すればよい。ＥＧＲクーラ１４Ｒの詰まりを解消する場合には排気絞り弁２０Ｌ、２０Ｒの開度を上記と反対に設定すればよい。
【００４９】
図７（ａ）及び（ｂ）はＥＧＲ通路１３Ｌ、１３Ｒを共通のＥＧＲクーラ１４と接続して図１の連絡通路１３Ｃを省略し、ＥＧＲクーラ１４の両側においてＥＧＲ通路１３Ｌ、１３ＲをそれぞれＥＧＲ弁１５Ｌ、１５Ｒを介してインテークマニホールド８に接続した例である。この例においては、ＥＧＲ通路１３Ｌの圧力がＥＧＲクーラ１４の一端側に、ＥＧＲ通路１３Ｒの圧力がＥＧＲクーラ１４の他端側にそれぞれ導入される。
【００５０】
以上の構成においては、左側のＥＧＲ弁１５Ｌを開け、右側のＥＧＲ弁１５Ｒを閉じた場合にはＥＧＲ通路１３Ｌの終端部の圧力がインテークマニホールド８と接続された影響でＥＧＲ通路１３Ｒよりも幾らか低下する。その結果、図７（ａ）にに矢印で示したように、ＥＧＲ通路１３Ｒの排気がＥＧＲクーラ１４を通過してＥＧＲ通路１３Ｌ側に流れ、その排気とＥＧＲ通路１３Ｌの排気とがＥＧＲ弁１５Ｌを介してインテークマニホールド８に流入する。反対に、右側のＥＧＲ弁１５Ｒを開け、左側のＥＧＲ弁１５Ｌを閉じた場合にはＥＧＲ通路１３Ｒの終端部の圧力がインテークマニホールド８と接続された影響でＥＧＲ通路１３Ｌよりも幾らか低下する。その結果、図７（ｂ）に矢印で示したように、ＥＧＲ通路１３Ｌの排気がＥＧＲクーラ１４を通過してＥＧＲ通路１３Ｒ側に流れ、その排気とＥＧＲ通路１３Ｒの排気とがＥＧＲ弁１５Ｒを介してインテークマニホールド８に流入する。
【００５１】
このように、図７（ａ）、（ｂ）の実施形態では、ＥＧＲ弁１５Ｌ、１５Ｒを圧力調整手段として選択的に開閉することにより、ＥＧＲクーラ１４の両端における圧力の大小関係を切り替えてＥＧＲクーラ１４内を通過する排気ガスの流れ方向を適宜に切り替えることができる。従って、ＥＧＲクーラ１４における排気の流れ方向を周期的に切り替えることにより詰まりの進行を一定限度に制限することができる。なお、流れ方向を切り替える目安には継続時間、流量の積算値等を利用してよい。この実施形態では、ターボチャージャ６のノズル開度や排気絞り弁２０Ｌ、２０Ｒ等を操作して詰まりを解消する場合のように特定の運転条件に限って詰まり解消操作を実行するという制約がなく、通常の運転中に適宜方向を切り替えて特定方向への煤等の堆積量の増加を抑えることができるという利点がある。勿論、ターボチャージャ６の開度の差別化による排気圧力の変更を図７の実施形態と組み合わせて詰まり解消を実施してもよい。
【００５２】
図８（ａ）及び（ｂ）はＥＧＲ通路１３Ｌ、１３Ｒを合流させることなく、ＥＧＲ弁１５Ｌ、１５Ｒを介してそれぞれ別々にインテークマニホールド８に接続した例を示している。この例では、ＥＧＲクーラ１４Ｌ、１４Ｒに反対側のＥＧＲ通路１３Ｒ、１３Ｌの圧力を導入することはできないが、ＥＧＲ通路１３Ｌ、１３Ｒとインテークマニホールド８との接続状態をＥＧＲ弁１５Ｌ、１５Ｒを介して互いに独立して制御できるので、排気圧と吸気圧との差を利用してＥＧＲクーラ１４Ｌ、１４Ｒに選択的に逆方向の流れを与えて詰まりを解消することができる。
【００５３】
例えば左側のＥＧＲクーラ１４Ｌの詰まりを解消するためには、同一の側のターボチャージャ６のノズルの開度を増してエキゾーストマニホールド１１Ｌの排気圧力を下げるとともに、反対側のターボチャージャ６のノズル開度を絞ってインテークマニホールド８の圧力をエキゾーストマニホールド１１Ｌの圧力よりも一時的に上昇させ、これに合わせてＥＧＲ弁１５Ｌを開け、ＥＧＲ弁１５Ｒを閉じてＥＧＲクーラ１４の入口側よりも出口側の圧力を高める。これにより、図８（ａ）に示すように、インテークマニホールド８からＥＧＲクーラ１４Ｌを介してＥＧＲ通路１３Ｌに吸気が流れてＥＧＲクーラ１４Ｌに逆洗効果が生じる。右側のＥＧＲクーラ１４Ｒの詰まりを解消するためには上記と逆に右側のターボチャージャ６のノズル開度を増し、左側のターボチャージャ６のノズル開度を減らしてＥＧＲ弁１５Ｌを閉じ、ＥＧＲ弁１５Ｒを開ける。これにより、図８（ｂ）に示すように、インテークマニホールド８からＥＧＲクーラ１４Ｒを介してＥＧＲ通路１３Ｒに吸気が流れてＥＧＲクーラ１４Ｒに逆洗効果が生じる。
【００５４】
なお、図７及び図８のいずれの例においても、ＥＧＲクーラ１４、１４Ｌ、１４Ｒの詰まりが進行するほどＥＧＲガス量が減少して吸入空気量が増えるという関係に変わりはないので、図３のステップＳ２〜Ｓ６の処理によって同様に詰まり判定を行うことができる。
【００５５】
以上の実施形態では、詰まりが検出された場合に限って図４のステップＳ２２以下に進んで詰まり解消操作を実行しているが、エンジン１の運転時間や吸入空気量の積算値のように、詰まりの進行と相関性を有する物理量から詰まり解消操作が必要となる目安が予め判っている場合には、その物理量から詰まり解消操作の時期を特定してステップＳ２３以下の詰まり解消操作を実行してもよい。
【００５６】
本発明の詰まり検出は、ＥＧＲクーラの詰まり解消操作の実行時期を判断する目的に限らず、様々な目的で実行してよい。例えば、詰まりが検出された場合に、その詰まりに伴うＥＧＲ量の減少分を補償して所定量のＥＧＲガスが吸気側に戻されるようにＥＧＲ弁１５の開度を補正してもよい。詰まりに伴うＥＧＲガスの減少に対応して燃料噴射量を補正して排気エミッションの悪化を防止してもよい。
【００５７】
左右のバンク２Ｌ、２Ｒに対してＥＧＲクーラ１４Ｌ、１４Ｒが分けて設けられる図１、図６及び図８の例においては、ターボチャージャ６のノズル開度や排気絞り弁２０Ｌ、２０Ｒの開度が左右均等に制御されている限りにおいて、ＥＧＲクーラ１４Ｌ、１４Ｒの詰まりは等しく進行しているはずであり、それにも関わらず一方のＥＧＲクーラ１４Ｌ又は１４Ｒの詰まりの進行が速い場合には、左右のバンク２Ｌ、２Ｒ間で煤等の堆積物の堆積速度に差を生じさせる何らかの理由が存在する。例えば、一方のバンク２Ｌ又は２Ｒにおいて、各種の誤差により燃料がＥＣＵ１２の指令値よりも多く噴射されている場合、ターボチャージャ６やＥＧＲ弁１５の開度がバンク２Ｌ、２Ｒ間で等しく制御されているはずが実際には一方のバンク２Ｌ又は２ＲにおいてＥＧＲ弁１５の開度が規定よりも大きく設定されている場合には、煤等の堆積速度に差が生じる。
【００５８】
そこで、バンク間におけるＥＧＲクーラ１４Ｌ、１４Ｒの詰まりの進行に関して偏りが検出された場合、進行の速い側のバンク２Ｌ又は２Ｒに関して、煤等の堆積速度が減少するように燃料噴射量やＥＧＲ弁の開度、あるいはターボチャージャの開度を補正してもよい。
【００５９】
以上の実施形態では、Ｖ型エンジンのバンク毎にシリンダ群を構成しているが、本発明はＶ型エンジンに限らない。直列エンジンや水平対向型のエンジンであっても、一部のシリンダ群と他のシリンダ群とをそれぞれ別々の排気通路に接続している限りは本発明を適用することができる。シリンダ群毎の排気通路は後に合流するか否かを問わない。本発明が適用される内燃機関はディーゼルエンジンに限らず、ガソリンエンジンでもよい。
【００６０】
【発明の効果】
以上説明したように、本発明のＥＧＲ装置によれば、内燃機関に設けられた圧力調整手段を操作してＥＧＲクーラの入口側と出口側との間の圧力差を変化させることにより、ＥＧＲクーラ内を排気ガスが一定方向に流れることによって堆積した煤等の堆積物を反対方向へガスを流して除去するいわゆる逆洗操作を実施して、比較的容易にＥＧＲクーラの詰まりを解消することができる。しかも、圧力操作によって堆積物を除去するので、内燃機関の燃焼状態を変更する必要がなく、ＥＧＲクーラの詰まり解消のために、燃焼状態の変更による排気エミッションや燃費の悪化といった不都合が生じるおそれがない。
【００６１】
また、本発明の検出装置によれば、空燃比制御等のために設けられる吸入空気量検出手段を利用してＥＧＲクーラの詰まりの進行度を判別することができるので、詰まり検出専用のセンサが不要となり、部品点数の削減やコストダウンを図ることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係るＥＧＲ装置が設けられた内燃機関の構成を示す図。
【図２】図１のエンジンにおけるＥＧＲクーラの詰まり解消操作を示す図。
【図３】図１のＥＣＵがＥＧＲクーラの詰まりを検出するために実行するＥＧＲクーラ詰まり判定ルーチンを示すフローチャート。
【図４】図１のＥＣＵがＥＧＲクーラの詰まりを解消するために実行するＥＧＲクーラ詰まり解消制御ルーチンを示すフローチャート。
【図５】図４に続くフローチャート。
【図６】排気通路に排気絞り弁が設けられた実施形態を示す図。
【図７】左右のバンクでＥＧＲクーラを共通化した実施形態における詰まり解消操作を示す図。
【図８】ＥＧＲ通路をバンク毎に完全に分離した実施形態における詰まり解消操作を示す図。
【符号の説明】
１ディーゼルエンジン（内燃機関）
２Ｌ、２Ｒバンク
３シリンダ
４吸気通路
６ターボチャージャ（圧力調整手段、排気抵抗調整手段）
７インタークーラ
８インテークマニホールド
１１Ｌ、１１Ｒエキゾーストマニホールド
１２エンジンコントロールユニット（詰まり解消手段、基準状態設定手段、詰まり検出実行手段）
１３ＥＧＲ通路
１３Ｃ連絡通路
１３Ｌ、１３Ｒバンク毎のＥＧＲ通路
１４、１４Ｌ、１４ＲＥＧＲクーラ
１５ＥＧＲ弁
１５Ｌ、１５ＲＥＧＲ弁（圧力調整手段）
１６Ｌ、１６Ｒエアフローメータ
２０Ｌ、２０Ｒ排気絞り弁（圧力調整手段、排気抵抗調整手段）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an EGR device that recirculates exhaust gas of an internal combustion engine to an intake passage.
[0002]
[Prior art]
In an EGR device in which exhaust gas is cooled by an EGR cooler and returned to the intake passage, soot and the like in the exhaust gas may gradually accumulate in the EGR cooler and become clogged. Therefore, in an EGR device including an EGR cooler, it is necessary to take measures against clogging of the EGR cooler.
[0003]
As an EGR device that takes measures against clogging of the EGR cooler, the presence or absence of clogging is monitored by a differential pressure sensor installed before and after the EGR cooler, and combustion of the internal combustion engine is performed so that the exhaust gas temperature rises when clogging occurs. There has been proposed an EGR device in which the state is temporarily changed and soot or the like accumulated in an EGR cooler is burned by heat of exhaust gas to eliminate clogging (see Patent Document 1). The presence or absence of deterioration (clogging) of the EGR cooler is monitored by a temperature sensor, and when the deterioration is detected, the opening degree of the EGR valve is adjusted so that the EGR gas amount is increased. An EGR device has been proposed to ensure the above (see Patent Document 2). Other prior arts related to the present invention include Patent Documents 3 and 4.
[0004]
[Patent Document 1]
JP 2002-174148 A
[Patent Document 2]
JP 2000-130266 A
[Patent Document 3]
JP-A-10-281016
[Patent Document 4]
JP-A-11-62722
[0005]
[Problems to be solved by the invention]
However, in the EGR device of Patent Literature 1, it is necessary to temporarily change the combustion state of the internal combustion engine from an optimum state in view of the exhaust gas purification performance in order to raise the exhaust gas temperature, and the exhaust emission deteriorates. Extra energy is consumed to raise the exhaust gas temperature. Further, since the EGR device of Patent Document 2 does not restore the function of the EGR cooler, the EGR gas temperature increases with an increase in the EGR gas amount, and the EGR effect decreases. Further, in any EGR device, it is necessary to provide a dedicated differential pressure sensor or a temperature sensor in order to detect the deterioration of the EGR cooler, so that an increase in cost cannot be avoided.
[0006]
Therefore, an object of the present invention is to provide an EGR device that can improve the clogging of the EGR cooler without changing the combustion state of the internal combustion engine and an EGR device that can detect the clogging of the EGR cooler without using a dedicated sensor. I do.
[0007]
[Means for Solving the Problems]
In the EGR device of the present invention, an EGR cooler for cooling the exhaust gas is provided in the EGR passage that recirculates the exhaust gas from the exhaust passage to the intake side, and the pressure acting on at least one side of the EGR cooler can be adjusted by the pressure adjusting means. In the EGR device for an internal combustion engine, the pressure adjusting means is operated such that the pressure on the outlet side of the EGR cooler at the time of exhaust gas recirculation is higher than the pressure on the inlet side of the EGR cooler at the time of exhaust gas recirculation. The above-mentioned problem is solved by providing a clog elimination control means for generating a flow in a direction opposite to that at the time of the exhaust gas recirculation (claim 1).
[0008]
According to the present invention, the exhaust gas flows in the EGR cooler in a certain direction by operating the pressure adjusting means provided in the internal combustion engine to change the pressure difference between the inlet side and the outlet side of the EGR cooler. As a result, a so-called back-washing operation of removing the accumulated deposits such as soot by flowing a gas in the opposite direction is performed, so that the clogging of the EGR cooler can be relatively easily eliminated. Since the deposits are removed by the pressure operation in this manner, there is no need to change the combustion state of the internal combustion engine. In the EGR device of the present invention, the pressure adjusting means may be any one provided as a means for changing the exhaust pressure or the intake pressure in order to adjust the operating state of the internal combustion engine.
[0009]
The EGR device of the present invention is preferably applied to an internal combustion engine provided with two cylinder groups connected to different exhaust passages. The pressure of the EGR passage connected to the exhaust side of one cylinder group is introduced to one end of the EGR cooler, and the pressure of the EGR passage connected to the exhaust side of the other cylinder group is introduced to the other end. The clogging elimination control means may control the EGR cooler by operating the pressure adjusting means to change the pressure of at least one of the two EGR passages corresponding to the cylinder group. Then, a flow in a direction opposite to that at the time of the exhaust gas recirculation may be generated (claim 2).
[0010]
In an internal combustion engine in which each of two cylinder groups is connected to a different exhaust passage, an EGR passage for returning exhaust gas from each cylinder group is divided for each cylinder group at least partially until reaching an intake passage. . In the EGR passage for each cylinder group, the pressure in the EGR passage can be separately adjusted for each cylinder group by operating pressure adjusting means provided in the EGR passage and the exhaust passage. For this reason, if the pressure of the EGR passage corresponding to the different cylinder groups is introduced to both ends of the EGR cooler and the pressure adjusting means is operated, the magnitude relationship between the pressures at both ends of the EGR cooler is changed, and the gas in the EGR cooler is changed. Can be switched. Note that even an internal combustion engine provided with three or more cylinder groups different from each other is included in the above embodiment as long as it includes two cylinder groups.
[0011]
In the EGR device of the present invention, the EGR cooler is provided in each of the EGR passages for each of the cylinder groups, and the outlet sides of the EGR coolers at the time of exhaust gas recirculation are connected to each other via a communication passage. Exhaust resistance adjusting means is provided downstream of the branch point of the passage to the EGR passage, and the clogging elimination control means operates the exhaust resistance adjusting means of at least one of the exhaust passages as the pressure adjusting means. The flow in the opposite direction may be generated (claim 3).
[0012]
According to this aspect, since the outlet sides of the EGR coolers are connected via the communication passage, the exhaust passages of the respective cylinder groups are mutually connected via the EGR passage and the EGR cooler. In addition, by differentiating the exhaust resistance by the exhaust resistance adjusting means for each cylinder group, it is possible to provide a difference in the exhaust pressure of each cylinder group. By providing a difference in exhaust pressure, it is possible to create an exhaust flow from the exhaust passage having a high exhaust pressure to the exhaust passage having a low exhaust pressure on the opposite side via the EGR passage, the communication passage, and the EGR passage on the opposite side. it can. Thus, in the EGR cooler in the EGR passage having a low exhaust pressure, the exhaust gas passes from the outlet side to the inlet side during the exhaust gas recirculation. The exhaust resistance adjusting means is not limited to a means provided for the purpose of adjusting exhaust resistance, such as an exhaust throttle valve, but is provided for another purpose (in this example, intake pressure adjustment) such as a turbocharger. However, it also includes means for causing a change in exhaust resistance as a result.
[0013]
In the EGR device according to the present invention, the EGR passage for each cylinder group is connected to a common EGR cooler, and the EGR passage for each cylinder group is provided on both sides of the EGR cooler as an EGR valve as the pressure adjusting means. Connected to an intake passage common to the two cylinder groups, and the clogging elimination control means operates the EGR valves for each of the EGR passages so that the respective opening degrees are differentiated, thereby controlling the EGR valves in the opposite directions. A flow may be generated (claim 4).
[0014]
According to the present invention, since both sides of the EGR cooler are connected to the intake passage via the EGR valve, one EGR valve is closed and the other EGR valve is opened, and one EGR valve is opened and the other EGR valve is opened. When the valve is closed, the flow direction of the exhaust gas passing through the EGR cooler is reversed. Therefore, by appropriately switching the open / close state of the EGR valve, it is possible to remove the deposits in the EGR cooler by switching the inlet side to the outlet side and the outlet side to the inlet side at the time of the previous exhaust gas recirculation to eliminate the clogging. it can. Since the intake passage is common, the EGR gas can be equally supplied to each of the two cylinder groups regardless of which EGR valve is opened.
[0015]
The EGR device of the present invention can also be applied to an internal combustion engine provided with a supercharger for supercharging intake air. In this case, the EGR passage is connected to the intake side via an EGR valve, and the clogging elimination control means sets the EGR cooler to a pressure lower than the pressure on the inlet side during the exhaust gas recirculation of the EGR cooler with the EGR valve opened. The supercharger may be operated as the pressure adjusting means so as to increase the pressure on the outlet side during the exhaust gas recirculation so as to generate the flow in the reverse direction (claim 5).
[0016]
When the exhaust gas flow rate is small and the exhaust pressure is low, the EGR valve is opened, and the supercharging effect of the supercharger is temporarily increased to make the intake pressure higher than the exhaust pressure. The intake air flows from the outlet side to the inlet side at the time of exhaust gas recirculation, thereby removing deposits and eliminating clogging.
[0017]
The EGR device of the present invention further comprises clogging detection means for detecting clogging of the EGR cooler, and the clogging elimination control means removes the detected clogging when the clogging detection means detects clogging. The flow in the opposite direction may be generated by operating the pressure adjusting means so as to perform the flow (claim 6). According to this aspect, when the EGR cooler is clogged, it is possible to surely solve the problem.
[0018]
In the EGR device of the present invention, the internal combustion engine is provided with intake air amount detection means for detecting an intake air amount not containing EGR gas, and the clogging detection means assumes that the pressure loss in the EGR cooler is constant. In such a case, the operation state of the devices affecting the intake air amount is set to a predetermined reference state so that a constant intake air amount is detected by the intake air amount detection means. The clogging may be detected based on a change in the amount of intake air detected by the amount detecting means.
[0019]
If the pressure loss in the EGR cooler is constant and the operating conditions of the devices that affect the intake air amount of the internal combustion engine are constant, the EGR amount and the exhaust amount (excluding EGR gas) are constant, and the intake air amount The amount of intake air detected by the detecting means is equal to the amount of exhaust air excluding EGR gas. However, when the clogging of the EGR cooler progresses, the EGR gas amount gradually decreases, and the exhaust air amount excluding the EGR component relatively increases. For this reason, the intake air amount detected by the intake air amount detecting means gradually increases even if the devices that affect the intake air amount are operated in the predetermined reference state. Since the intake air amount and the clogging of the EGR cooler are correlated, the clogging state of the EGR cooler can be determined based on a change in the intake air amount detected by the intake air amount detecting means. In addition, the intake air amount detecting means is not limited to a means for directly detecting the intake air amount such as an air flow meter, but detects other physical quantities such as an intake pressure correlated with the intake air amount, thereby indirectly detecting the intake air amount. Means for detecting the Examples of devices that affect the amount of intake air include a throttle valve, an EGR valve, a movable nozzle of a variable nozzle turbocharger provided in an exhaust passage, an exhaust throttle valve, and a variable valve mechanism of an intake and exhaust system. Devices that have negligible effect on the intake air amount in view of the measurement accuracy required for detection of clogging of the EGR cooler may be excluded from targets set in the reference state.
[0020]
In the EGR device of the present invention, the EGR cooler is provided in each of the EGR passages for each of the cylinder groups, and the internal combustion engine is provided for each of the cylinder groups by being driven by exhaust energy for each of the cylinder groups. A supercharger for each cylinder group for supercharging intake air in the intake passage provided, and intake air amount detection means for detecting an intake air amount not containing EGR gas in the intake passage for each cylinder group, The EGR device is provided with an operating state of devices that affect the intake air amount so that a constant intake air amount is detected by the intake air amount detection means when the pressure loss in the EGR cooler is assumed to be constant. A clog detection for setting a predetermined reference state and detecting the clogging of the EGR cooler based on a change in the intake air amount detected by the intake air amount detection means in the reference state. Means may be provided, and the clogging detection means may determine the degree of clogging of the EGR cooler for each cylinder group based on a difference in intake air amount for each cylinder group detected by the intake air amount detection means. (Claim 8).
[0021]
In a configuration in which a so-called turbocharger-type supercharger driven by exhaust energy is arranged in the intake passage for each cylinder group, the cooler on one cylinder group side is relatively blocked than the EGR cooler on the opposite side. In this case, the amount of EGR returned through the EGR passage on the one cylinder group side relatively decreases, and the amount of exhaust air guided to the exhaust passage of the one cylinder group increases. For this reason, on one cylinder group side, the supercharging effect increases in response to the increase in the amount of exhaust air, and the intake air amount on the side corresponding to the one cylinder group increases. Therefore, the degree of clogging of the EGR cooler on the cylinder group side can be determined from the difference in the amount of intake air in the intake passage divided for each cylinder group.
[0022]
As described above, when determining the degree of progress of the clogging of the EGR cooler for each cylinder group, the clogging elimination means sets the EGR cooler on the side where the clogging is determined to be more advanced to the EGR cooler on the opposite side. The pressure adjusting means may be operated so that a flow in a direction opposite to that at the time of exhaust gas recirculation occurs prior to a cooler (claim 9).
[0023]
If the time during which the pressure adjusting means can be operated is limited due to restrictions such as the operating conditions of the internal combustion engine, firstly, an operation to clear the clogging of the EGR cooler on the side where clogging is progressing is performed with priority. Thus, a high clogging elimination effect can be obtained in a limited period.
[0024]
The clogging detection device according to the present invention is a clogging detection device for an EGR cooler applied to an EGR device of an internal combustion engine in which an EGR cooler for exhaust gas cooling is provided in an EGR passage that recirculates exhaust gas from an exhaust passage to an intake side. When the pressure loss in the cooler is assumed to be constant, the operation state of the devices affecting the intake air amount is set to a predetermined reference state so that a constant intake air amount is detected by the intake air amount detection means. The reference state setting means and the clogging detection execution means for detecting the clogging based on a change in the amount of intake air detected by the amount of intake air detected by the amount of intake air provided to the internal combustion engine in the reference state are described above. The problem is solved (claim 10).
[0025]
According to this detection device, if the clogging of the EGR cooler progresses, the exhaust air amount increases and the intake air amount detected by the intake air amount detecting means also increases. The degree of progress can be determined. Since the intake air amount detection means is provided in a general internal combustion engine to execute air-fuel ratio control or the like, a sensor dedicated to clog detection is not required, and the number of parts can be reduced and cost can be reduced. . In the clogging detection device of the present invention, the intake air amount detection means is not limited to a means for directly detecting the intake air amount like an air flow meter, but detects another physical amount such as an intake pressure correlated with the intake air amount. Accordingly, a means for indirectly detecting the intake air amount is also included. Examples of devices that affect the amount of intake air include a throttle valve, an EGR valve, a movable nozzle of a variable nozzle turbocharger provided in an exhaust passage, an exhaust throttle valve, and a variable valve mechanism of an intake and exhaust system. Devices that have negligible effect on the intake air amount in view of the measurement accuracy required for detection of clogging of the EGR cooler may be excluded from targets set in the reference state.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an internal combustion engine incorporating an EGR device according to one embodiment of the present invention. In this embodiment, the internal combustion engine is configured as a V-type 8-cylinder diesel engine 1 in which four cylinders 3 are provided in left and right banks 2L, 2R. One cylinder group is constituted by the cylinders 3 of the left bank 2L, and another cylinder group is constituted by the cylinders 3 of the right bank 2R. It is sufficient that one cylinder group includes at least one cylinder 3.
[0027]
An intake passage 4 for guiding intake air to each cylinder 3 is divided into branch passages 4L and 4R for each bank downstream of the air cleaner 5, and a compressor 6a of a turbocharger 6 is arranged in the branch passages 4L and 4R. Downstream of the compressor 6a, the branch passages 4L and 4R pass through the intercooler 7 and are connected to a common intake manifold 8 forming a part of the intake passage 4. On the other hand, the exhaust gas from the cylinders 3 of each bank is guided to the exhaust manifolds 11L and 11R of the exhaust passages 10L and 10R provided for each bank, to the turbine 6b of the turbocharger 6, and further to the downstream side of the turbine 6b. A catalyst, a muffler, and the like are provided on the downstream side of the turbine 6b, but their illustration is omitted.
[0028]
The turbocharger 6 is a variable nozzle turbocharger (hereinafter sometimes referred to as a VNT) having a nozzle device (not shown) capable of adjusting the opening degree on the turbine 6b side. The nozzle opening of each turbocharger 6 is controlled by an engine control unit (ECU) 12. The ECU 12 is a well-known computer that controls the operating state of the engine 1 by adjusting the fuel injection amount and the like for each cylinder 3.
[0029]
The engine 1 is provided with an EGR passage 13. The EGR passage 13 includes EGR passages 13L and 13R for each bank connected to the exhaust manifolds 11L and 11R, respectively, and a communication passage 13C connecting the EGR passages 13L and 13R. EGR passages 13L and 13R are provided with EGR coolers 14L and 14R for cooling EGR gas, and a communication passage 13C is provided between the coolers 14L and 14R. As described above, since the EGR coolers 14L and 14R are connected to each other via the communication passage 13C, the pressure of the EGR passage 13L is introduced to the inlet side (left end side) of the EGR cooler 14L at the time of exhaust gas recirculation, and the exhaust gas is exhausted. The pressure in the EGR passage 13R at the outlet side of the EGR cooler 14R is introduced into the outlet side (right end side) at the time of reflux through the communication passage 13C. Further, with respect to the EGR cooler 14R, the pressure of the EGR passage 13R is introduced to the inlet side (right end side) at the time of exhaust gas recirculation, and the EGR passage 13L at the outlet side of the EGR cooler 14L is introduced to the outlet side (left end side) at the time of exhaust gas recirculation. Is introduced through the communication passage 13C.
[0030]
Further, the communication passage 13C is connected to the intake manifold 8 via a pair of EGR valves 15. The opening of the EGR valve 15 is controlled by the ECU 12 according to the operating state of the engine 1. The content of the opening degree control may be the same as that of the normal EGR control of the internal combustion engine.
[0031]
Next, an operation for eliminating clogging of the EGR coolers 14L and 14R will be described with reference to FIG.
[0032]
In order to eliminate the clogging of the EGR cooler 14L corresponding to the left bank 2L, the nozzle opening of the turbocharger 6 corresponding to the bank 2L is set as shown in FIG. The nozzle opening degree of the turbocharger 6 corresponding to the bank 2R is increased. As a result, the exhaust pressure of the exhaust manifold 11L becomes lower than the exhaust pressure of the exhaust manifold 11R, and the EGR passage 13 is connected to the EGR passage 13R via the communication passage 13C as shown by an arrow in FIG. Exhaust gas flows toward the passage 13L. Therefore, in the EGR cooler 14L, the exhaust gas flows backward from the outlet toward the inlet, and as a result, deposits such as soot deposited on the EGR cooler 14L are removed, and the clogging of the EGR cooler 14L is resolved.
[0033]
On the other hand, in order to eliminate clogging of the EGR cooler 14R corresponding to the right bank 2R, the nozzle opening of the turbocharger 6 corresponding to the bank 2R with the respective EGR valves 15 closed as shown in FIG. Is opened, and the nozzle opening of the turbocharger 6 corresponding to the bank 2L is closed. As a result, the exhaust pressure of the exhaust manifold 11R becomes lower than the exhaust pressure of the exhaust manifold 11L, and the EGR passage 13 is connected to the EGR passage 13L via the communication passage 13C as shown by an arrow in FIG. Exhaust gas flows toward the passage 13R. Therefore, in the EGR cooler 14R, the exhaust gas flows backward from the outlet toward the inlet, and as a result, deposits such as soot deposited on the EGR cooler 14R are removed, and the clogging of the EGR cooler 14R is resolved.
[0034]
Next, detection of clogging of the EGR coolers 14L and 14R will be described. FIG. 3 is a chart showing an EGR cooler clogging determination routine that is repeatedly executed by the ECU 12 at a predetermined cycle in order to determine whether the EGR coolers 14L and 14R are clogged. In the EGR cooler clogging determination routine, in a first step S1, the ECU 12 determines whether or not the value of a clogging detection flag for determining whether or not clogging has already been detected is set to 1 indicating detection has been completed. . If the detection flag is 1, the processing after step S2 is omitted, and the current routine ends. On the other hand, if the flag is not 1, the process proceeds to step S2, and the ECU 12 determines whether or not the rotation speed of the engine 1 is within a predetermined range as one of the reference states for detecting the clogging. If not, the determination routine is terminated. If it is within the predetermined range, the process proceeds to step S3, and the ECU 12 sets the respective opening degrees of the EGR valve 15 and the turbocharger (VNT) 6 to predetermined values. The opening at this time is an opening determined as one of the reference states for determining clogging, and if it is a constant value, any opening between the maximum opening and the minimum opening may be selected. . With this processing, the ECU 12 functions as a reference state setting unit. In step S3, the turbocharger 6 is set as a device that affects the amount of intake air per revolution of the engine 1 and its operation state is set to a predetermined reference state of a constant nozzle opening. If there are devices that affect the amount of intake air, it is necessary to set the operation state to be constant. However, a device whose influence on the intake air amount is negligible for the purpose of determining the clogging of the EGR cooler may be excluded from the operation target.
[0035]
In the following step S4, the ECU 12 detects the current intake air amount per one revolution of the engine 1 based on the outputs of the air flow meters 16L and 16R provided in the branch passages 4L and 4R of the intake passage 4 shown in FIG. The measurement result is stored in the RAM. In the following step S5, the ECU 12 determines whether or not the clogging determination in this routine is the second or subsequent determination. If it is not the second or subsequent determination, the routine skips step S5 and thereafter and ends the routine. On the other hand, if it is the second or subsequent determination in step S5, the process proceeds to step S6, where the ECU 12 increases the intake air amount detected in step S4 by a predetermined amount or more with respect to the intake air amount detected in the first execution of the routine. It is determined whether or not. If it has not increased, step S6 and subsequent steps are skipped and the current routine ends. When clogging occurs in at least one of the EGR coolers 14L and 14R, when the rotation speed of the engine 1 is constant and the nozzle opening of the turbocharger 6 and the opening of the EGR valve 15 are compared under a certain condition. Since the EGR amount decreases and the intake air amount increases, the presence or absence of clogging of the EGR cooler 14L or 14R can be determined by comparing the intake air amount with the past detected value.
[0036]
If the intake air amount has increased by a predetermined amount or more in step S6, it is determined that clogging has occurred in at least one of the EGR coolers 14L or 14R, the process proceeds to step S7, and the value of the clogging detection flag is set to 1. In the following step S8, the intake air amounts detected by the air flow meters 16L and 16R are compared, and in the next step S9, the clogging of the EGR cooler 14L or 14R on the side with the larger intake air relatively progresses. It is determined that the processing should be performed with priority, and the result is stored in the RAM of the ECU 12. As the EGR coolers 14L and 14R become clogged, the amount of EGR gas decreases and the amount of exhaust gas guided to the turbine 6b increases. As a result, the supercharging effect of the compressor 6a increases, and the branch passage 4L on the side where the EGR cooler is clogged is increased. Or, the intake air amount of 4R increases.
[0037]
Thereafter, the ECU 12 returns the opening of the EGR valve 15 and the opening of the turbocharger 6 to the original opening (the opening before setting in step S3) in step S10. Thus, the routine of FIG. 3 ends. Through the above steps S4 to S9, the ECU 12 functions as a clogging detection execution unit.
[0038]
When clogging is detected in the above-described clogging determination routine, the clogging elimination operation shown in FIG. FIGS. 4 and 5 are flowcharts showing an EGR cooler clogging elimination control routine executed by the ECU 12 for the clogging elimination operation. The ECU 12 functions as the clogging elimination control means of the present invention by repeatedly executing the routine of FIGS. 4 and 5 at a predetermined cycle while the engine 1 is operating.
[0039]
In the EGR cooler clogging elimination control routine, the ECU 12 first determines whether or not 1 is set in the clogging detection flag in step S21, and ends the routine if 1 is not set. On the other hand, if the detection flag is 1, the process proceeds to step S22, and the ECU 12 determines whether or not the fuel is being cut during deceleration at which the fuel injection amount to the engine 1 becomes zero. Here, since the clogging is eliminated by changing the nozzle opening of the turbocharger 6, it is premised that the turbine 6b is rotating and the deceleration during the fuel cut is performed in a state where the influence of the operation of the engine 1 is as small as possible. I have. However, the operating condition as a premise for executing the clogging elimination operation is not limited to this, and may be appropriately determined.
[0040]
In a succeeding step S23, it is determined whether or not 1 is set in the first cancellation operation flag. If 1 is not set, it is determined in step S24 whether or not 1 is set in the second cancellation operation flag. These flags are for determining whether or not a clog clearing operation is being performed. If 1 is not set in the flag in any of steps S23 and S24, that is, if the clogging detection operation has not been started yet after the clogging is detected, the process proceeds to step S25, and 1 is set in the first clearing operation flag. At the same time, the counting of the duration of the clog clearing operation is started. Thereafter, the process proceeds to step S26, in which the opening degree of each EGR valve 15 is fully closed. Further, in step S27, the turbocharger 6 on the same side as the EGR cooler 14L or 14R on the priority processing side (see step S9 in FIG. 3). The nozzle opening is set to the maximum, and in the following step S28, the nozzle opening of the turbocharger 6 on the opposite side is set to the minimum. By these operations, the state shown in FIG. 2A or 2B is realized. The first clearing operation flag functions as a flag for determining whether or not the clog clearing operation for the EGR cooler 14L or 14R on the priority processing side is being performed.
[0041]
In a succeeding step S29, it is determined whether or not the count value of the continuation time of the clog clearing operation started in the step S25 has reached a predetermined continuation time. If the predetermined time has not been reached, the current routine is ended. If the time has been reached, the process proceeds to step S30, where the first cancellation operation flag is reset to 0, and the counting of the duration is ended.
[0042]
Subsequently, the process proceeds to step S31 in FIG. 5, in which the second clearing operation flag is set to 1, and the counting of the continuous time of the clogging clearing operation is restarted from the initial value. In the next step S32, the opening of each EGR valve 15 is fully closed, and in step S33, the nozzle opening of the turbocharger 6 on the same side as the EGR cooler 14L or 14R on the priority processing side is set to the minimum, and the process is continued. In step S28, the nozzle opening of the opposite turbocharger 6 is set to the maximum. With these operations, the clog clearing operation for the EGR cooler 14L or 14R on the priority processing side ends, and the clog clearing operation for the EGR cooler 14R or 14L on the opposite side starts. The second clearing operation flag functions as a flag for determining whether or not a clogging clearing operation is being performed on the EGR cooler 14R or 14L on the side opposite to the priority processing side.
[0043]
In a succeeding step S35, it is determined whether or not the count value of the continuous time of the clog clearing operation started in the step S31 has reached a predetermined continuous time. If the predetermined time has not been reached, the current routine is ended. If the time has been reached, the process proceeds to step S36, where the second cancellation operation flag is reset to 0, and the counting of the duration is ended. Then, in step S37, the clogging detection flag is reset to 0, and in step S38, the nozzle opening of the turbocharger 6 and the opening of the EGR valve 15 are returned to the original opening before the clogging operation, and the routine is executed. Finish. Thus, the clog clearing operation for the EGR cooler 14R or 14L on the side opposite to the priority processing side is also ended.
[0044]
When the routine of FIG. 4 is started during the execution of the clog elimination operation, if the operation state of the engine 1 has changed from the fuel cut state, a negative determination is made in step S22. In this case, the ECU 12 suspends the counting of the duration of the clogging elimination operation in step S38, and proceeds to step S38 to restore the nozzle opening of the turbocharger 6 and the opening of the EGR valve 15 to interrupt the clogging elimination operation. Let it. Even if there is such an interruption, since either the first cancellation operation flag or the second cancellation operation flag is set to 1, if the routine of FIG. 4 is started again during the fuel cut, step S23 or An affirmative decision is made in any of the steps S24. If step S23 is affirmed, the ECU 12 continues counting the duration in step S39 and proceeds to step S26. As a result, the clog clearing operation for the EGR cooler 14L or 14R on the priority processing side is restarted. If the determination in step S24 is affirmative, the ECU 12 continues counting the duration in step S40 in FIG. 5 and proceeds to step S32. As a result, the clog clearing operation for the EGR cooler 14R or 14L on the opposite side of the priority processing side is restarted.
[0045]
In the clogging elimination control routine shown in FIGS. 4 and 5, it is sufficient that the priority processing side is set to be larger than the opposite side in steps S27 and S28 with respect to the nozzle opening degree of the turbocharger 6 during clogging elimination. In S34, it is only necessary that the priority processing side is set smaller than the opposite side. However, in order to increase the pressure difference generated in the EGR cooler 14L or 14R as much as possible and to enhance the backwashing effect, it is desirable to set the nozzle opening to the maximum and the minimum, respectively.
[0046]
Further, in the above-described clog elimination control routine, the clog elimination operation is continued for a predetermined time, but the end timing of the clog elimination operation is determined by referring to another physical quantity such as an integrated value of the intake air amount after the clog elimination operation is started. You may decide.
[0047]
In the above embodiment, the turbocharger 6 corresponds to a pressure adjusting unit and an exhaust resistance adjusting unit. Even in the case where a turbocharger with a motor capable of adjusting the rotation of the turbine by a motor generator is provided instead of the variable nozzle type turbocharger, the exhaust pressure (exhaust resistance) is changed by changing the rotation speed of the turbine. Accordingly, clogging of the EGR cooler can be eliminated in the same manner as in the above embodiment.
[0048]
Next, another embodiment of the present invention will be described. FIG. 6 shows an example in which exhaust throttle valves 20L and 20R are provided in the exhaust passages 10L and 10R as pressure adjusting means and exhaust resistance adjusting means. In this case, by providing a difference in the opening degree of the exhaust throttle valves 20L and 20R instead of the operation of the nozzle opening degree of the turbocharger 6, a difference is generated in the exhaust pressure of the left and right exhaust passages 10L and 10R. The clogging of the EGR coolers 14L and 14R can be eliminated. For example, in order to eliminate the clogging of the EGR cooler 14L, the opening of the left exhaust throttle valve 20L may be set to be large, and the opening of the opposite exhaust throttle valve 20R may be set to be smaller. In order to eliminate the clogging of the EGR cooler 14R, the opening degrees of the exhaust throttle valves 20L and 20R may be set opposite to the above.
[0049]
7A and 7B, the EGR passages 13L and 13R are connected to a common EGR cooler 14 to omit the communication passage 13C in FIG. 1, and the EGR passages 13L and 13R are provided on both sides of the EGR cooler 14 with EGR valves. This is an example of connection to the intake manifold 8 via 15L and 15R. In this example, the pressure of the EGR passage 13L is introduced to one end of the EGR cooler 14, and the pressure of the EGR passage 13R is introduced to the other end of the EGR cooler 14.
[0050]
In the above configuration, when the left EGR valve 15L is opened and the right EGR valve 15R is closed, the pressure at the terminal end of the EGR passage 13L is somewhat larger than that of the EGR passage 13R due to the effect of being connected to the intake manifold 8. descend. As a result, as indicated by the arrow in FIG. 7A, the exhaust gas in the EGR passage 13R passes through the EGR cooler 14 and flows toward the EGR passage 13L, and the exhaust gas and the exhaust gas in the EGR passage 13L are exchanged with the EGR valve 15L. Through the intake manifold 8. Conversely, when the right EGR valve 15R is opened and the left EGR valve 15L is closed, the pressure at the end of the EGR passage 13R is somewhat lower than that of the EGR passage 13L due to the effect of being connected to the intake manifold 8. As a result, as indicated by the arrow in FIG. 7B, the exhaust gas in the EGR passage 13L passes through the EGR cooler 14 and flows toward the EGR passage 13R, and the exhaust gas and the exhaust gas in the EGR passage 13R pass through the EGR valve 15R. Through the intake manifold 8.
[0051]
As described above, in the embodiment of FIGS. 7A and 7B, the EGR valves 15L and 15R are selectively opened and closed as pressure adjusting means, thereby switching the magnitude relationship between the pressures at both ends of the EGR cooler 14 to perform the EGR. The flow direction of the exhaust gas passing through the cooler 14 can be appropriately switched. Accordingly, by periodically switching the flow direction of the exhaust gas in the EGR cooler 14, the progress of the clogging can be limited to a certain limit. Note that the duration, the integrated value of the flow rate, or the like may be used as a guide for switching the flow direction. In this embodiment, there is no restriction that the clogging elimination operation is performed only under specific operating conditions, such as when the clogging is eliminated by operating the nozzle opening degree of the turbocharger 6, the exhaust throttle valves 20L, 20R, etc. There is an advantage that the direction can be switched appropriately during normal operation to suppress an increase in the amount of accumulation of soot and the like in a specific direction. Of course, the change of the exhaust pressure by differentiating the opening degree of the turbocharger 6 may be combined with the embodiment of FIG. 7 to eliminate the clogging.
[0052]
FIGS. 8A and 8B show an example in which the EGR passages 13L and 13R are connected to the intake manifold 8 separately via the EGR valves 15L and 15R without merging. In this example, the pressure of the EGR passages 13R, 13L on the opposite side cannot be introduced into the EGR coolers 14L, 14R, but the connection state between the EGR passages 13L, 13R and the intake manifold 8 is changed via the EGR valves 15L, 15R. Since the control can be performed independently of each other, the clogging can be eliminated by selectively applying the reverse flow to the EGR coolers 14L and 14R using the difference between the exhaust pressure and the intake pressure.
[0053]
For example, in order to eliminate the clogging of the left EGR cooler 14L, the opening degree of the nozzle of the turbocharger 6 on the same side is increased to reduce the exhaust pressure of the exhaust manifold 11L, and the nozzle opening degree of the turbocharger 6 on the opposite side. To temporarily raise the pressure of the intake manifold 8 above the pressure of the exhaust manifold 11L, open the EGR valve 15L accordingly, close the EGR valve 15R, and close the pressure on the outlet side of the EGR cooler 14 from the inlet side. Enhance. Thus, as shown in FIG. 8A, the intake air flows from the intake manifold 8 to the EGR passage 13L via the EGR cooler 14L, and a backwash effect is generated in the EGR cooler 14L. To eliminate the clogging of the right EGR cooler 14R, conversely, the nozzle opening of the right turbocharger 6 is increased, the nozzle opening of the left turbocharger 6 is reduced, the EGR valve 15L is closed, and the EGR valve 15R is closed. Open. Thus, as shown in FIG. 8B, the intake air flows from the intake manifold 8 to the EGR passage 13R via the EGR cooler 14R, and a backwash effect is generated in the EGR cooler 14R.
[0054]
7 and 8, the relationship that the amount of EGR gas decreases and the amount of intake air increases as clogging of the EGR coolers 14, 14L, and 14R progresses does not change. The clogging determination can be similarly performed by the processing of steps S2 to S6.
[0055]
In the above embodiment, the clogging elimination operation is performed by proceeding to step S22 and subsequent steps in FIG. 4 only when the clogging is detected. However, as in the operation time of the engine 1 and the integrated value of the intake air amount, If it is known in advance from the physical quantity having a correlation with the progress of clogging that the clogging elimination operation is necessary, the timing of the clogging elimination operation is specified from the physical quantity, and the clogging elimination operation of step S23 and subsequent steps is executed. Is also good.
[0056]
The clogging detection according to the present invention is not limited to the purpose of determining the execution timing of the clogging elimination operation of the EGR cooler, but may be performed for various purposes. For example, when clogging is detected, the opening of the EGR valve 15 may be corrected so that a predetermined amount of EGR gas is returned to the intake side by compensating for a decrease in the EGR amount due to the clogging. The fuel injection amount may be corrected according to the decrease in the EGR gas due to the clogging to prevent deterioration of the exhaust emission.
[0057]
In the examples of FIGS. 1, 6, and 8 in which EGR coolers 14L and 14R are provided separately for the left and right banks 2L and 2R, the opening degree of the nozzle of the turbocharger 6 and the opening degree of the exhaust throttle valves 20L and 20R are different. As long as the right and left sides are controlled equally, the clogging of the EGR coolers 14L and 14R should be progressing equally, and if the clogging of one of the EGR coolers 14L or 14R progresses quickly, There are some reasons for causing a difference in the deposition rate of deposits such as soot between the banks 2L and 2R. For example, when one of the banks 2L or 2R is injecting more fuel than the command value of the ECU 12 due to various errors, the opening degrees of the turbocharger 6 and the EGR valve 15 are controlled equally between the banks 2L and 2R. However, if the opening degree of the EGR valve 15 is set to be larger than the specified value in one of the banks 2L or 2R, a difference occurs in the deposition speed of soot and the like.
[0058]
Therefore, when a deviation is detected with respect to the progress of clogging of the EGR coolers 14L and 14R between the banks, the fuel injection amount and the EGR valve are controlled so that the deposition speed of soot and the like decreases with respect to the bank 2L or 2R on the side of the fast progress. The opening degree or the opening degree of the turbocharger may be corrected.
[0059]
In the above embodiment, the cylinder group is configured for each bank of the V-type engine, but the present invention is not limited to the V-type engine. The present invention can be applied to an in-line engine or a horizontally opposed engine as long as some cylinder groups and other cylinder groups are connected to different exhaust passages. It does not matter whether the exhaust passage for each cylinder group merges later. The internal combustion engine to which the present invention is applied is not limited to a diesel engine, but may be a gasoline engine.
[0060]
【The invention's effect】
As described above, according to the EGR device of the present invention, the pressure difference between the inlet side and the outlet side of the EGR cooler is changed by operating the pressure adjusting means provided in the internal combustion engine, so that the EGR cooler is operated. A so-called backwashing operation is performed in which exhaust gas flows in a certain direction to remove deposits such as soot that have been deposited by flowing gas in the opposite direction, so that clogging of the EGR cooler can be relatively easily eliminated. it can. Moreover, since the deposits are removed by the pressure operation, there is no need to change the combustion state of the internal combustion engine, and in order to eliminate the clogging of the EGR cooler, the change in the combustion state may cause inconvenience such as deterioration of exhaust emission and fuel efficiency. Absent.
[0061]
Further, according to the detecting device of the present invention, the degree of clogging of the EGR cooler can be determined by using the intake air amount detecting means provided for air-fuel ratio control or the like. This is unnecessary, and the number of parts and cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an internal combustion engine provided with an EGR device according to one embodiment of the present invention.
FIG. 2 is a view showing an operation for removing clogging of an EGR cooler in the engine of FIG. 1;
FIG. 3 is a flowchart showing an EGR cooler clogging determination routine executed by the ECU of FIG. 1 to detect clogging of an EGR cooler.
FIG. 4 is a flowchart showing an EGR cooler clogging elimination control routine executed by the ECU of FIG. 1 to eliminate clogging of the EGR cooler.
FIG. 5 is a flowchart following FIG. 4;
FIG. 6 is a diagram showing an embodiment in which an exhaust throttle valve is provided in an exhaust passage.
FIG. 7 is a diagram showing a clog clearing operation in an embodiment in which the right and left banks share an EGR cooler.
FIG. 8 is a diagram showing a clog clearing operation in the embodiment in which the EGR passage is completely separated for each bank.
[Explanation of symbols]
1 diesel engine (internal combustion engine)
2L, 2R bank
3 cylinder
4 Intake passage
6. Turbocharger (pressure adjusting means, exhaust resistance adjusting means)
7 Intercooler
8 Intake manifold
11L, 11R exhaust manifold
12. Engine control unit (clog elimination means, reference state setting means, clog detection execution means)
13 EGR passage
13C access passage
13L, 13R EGR passage for each bank
14, 14L, 14R EGR cooler
15 EGR valve
15L, 15R EGR valve (pressure adjusting means)
16L, 16R air flow meter
20L, 20R Exhaust throttle valve (pressure adjusting means, exhaust resistance adjusting means)

Claims

An EGR cooler for cooling exhaust gas is provided in an EGR passage that recirculates exhaust gas from the exhaust passage to the intake side, and the pressure acting on at least one side of the EGR cooler can be adjusted by pressure adjusting means. In the device,
The pressure adjusting means is operated so that the pressure on the outlet side of the EGR cooler at the time of exhaust gas recirculation is higher than the pressure of the inlet side at the time of exhaust gas recirculation. An EGR device for an internal combustion engine, comprising clogging elimination control means for causing a flow of air.

The internal combustion engine is provided with two cylinder groups connected to different exhaust passages,
The pressure of the EGR passage connected to the exhaust side of one cylinder group can be introduced to one end side of the EGR cooler, and the pressure of the EGR passage connected to the exhaust side of the other cylinder group can be introduced to the other end side. Yes,
The clogging elimination control means operates the pressure adjustment means to change the pressure in at least one of the two EGR passages corresponding to the cylinder group, thereby causing the exhaust gas recirculation to the EGR cooler. 2. The EGR device for an internal combustion engine according to claim 1, wherein a flow is generated in a direction opposite to the time.

The EGR cooler is provided in each of the EGR passages for each of the cylinder groups, and the outlet sides of the EGR coolers at the time of exhaust gas recirculation are connected by communication passages, and the exhaust passage for each of the cylinder groups branches to the EGR passage. Exhaust resistance adjusting means is provided downstream of the position, and the clogging elimination control means operates the exhaust resistance adjusting means of at least one of the exhaust passages as the pressure adjusting means to generate the flow in the reverse direction. The EGR device for an internal combustion engine according to claim 2, wherein:

The EGR passages for each of the cylinder groups are connected to a common EGR cooler, and on each side of the EGR cooler, each of the EGR passages for each of the cylinder groups is connected via an EGR valve as the pressure adjusting means to the two cylinder groups. Wherein the clogging elimination control means operates the EGR valves for each of the EGR passages so that their respective opening degrees are differentiated to generate the flow in the reverse direction. The EGR device for an internal combustion engine according to claim 2, wherein

The internal combustion engine is provided with a supercharger for supercharging intake air, the EGR passage is connected to the intake side via an EGR valve, and the clogging elimination control means performs the operation in a state where the EGR valve is opened. Operating the supercharger as the pressure adjusting means so as to generate the flow in the reverse direction so that the pressure on the outlet side during the exhaust gas recirculation is higher than the pressure on the inlet side during the exhaust gas recirculation of the EGR cooler. The EGR device for an internal combustion engine according to claim 1, wherein:

Clogging detection means for detecting clogging of the EGR cooler, wherein the clogging elimination control means is configured to cancel the detected clogging when the clogging is detected by the clogging detection means. The EGR device for an internal combustion engine according to any one of claims 1 to 5, wherein the EGR device is operated to generate the reverse flow.

The internal combustion engine is provided with intake air amount detection means for detecting an intake air amount not including EGR gas,
The clogging detection unit is configured to operate the devices that affect the intake air amount such that a constant intake air amount is detected by the intake air amount detection unit when the pressure loss in the EGR cooler is assumed to be constant. 7 is set to a predetermined reference state, and the clogging is detected based on a change in the intake air amount detected by the intake air amount detection means in the reference state. EGR device.

The EGR cooler is provided in each of the EGR passages for each of the cylinder groups,
The internal combustion engine includes a supercharger for each cylinder group, which is driven by exhaust energy for each cylinder group to supercharge intake air in an intake passage provided for each cylinder group. Intake air amount detection means for detecting an intake air amount not including EGR gas in the intake passage;
The EGR device has an operating state of devices that affects the intake air amount such that a constant intake air amount is detected by the intake air amount detection means when the pressure loss in the EGR cooler is assumed to be constant. Is set to a predetermined reference state, and clogging detection means for detecting clogging of the EGR cooler based on a change in intake air amount detected by the intake air amount detection means in the reference state is provided,
3. The clogging detection means determines a degree of clogging of an EGR cooler for each cylinder group based on a difference in intake air amount for each cylinder group detected by the intake air amount detection means. An EGR device for an internal combustion engine according to claim 1.

The clogging elimination means is configured to generate the flow in the direction opposite to the exhaust gas recirculation by giving priority to the EGR cooler on the side determined to be more clogged than the EGR cooler on the opposite side. The EGR device for an internal combustion engine according to claim 8, wherein the adjusting means is operated.

An EGR cooler clogging detection device applied to an EGR device of an internal combustion engine in which an EGR cooler for exhaust gas cooling is provided in an EGR passage that recirculates exhaust gas from an exhaust passage to an intake side,
When the pressure loss in the EGR cooler is assumed to be constant, the operation state of the devices affecting the intake air amount is set to a predetermined reference state so that a constant intake air amount is detected by the intake air amount detection means. Reference state setting means to be set;
Clogging detection execution means for detecting the clogging based on a change in the amount of intake air detected by the intake air amount detection means provided in the internal combustion engine in the reference state,
A clogging detection device for an EGR device of an internal combustion engine, comprising: