JP5141430B2 - Exhaust control device and exhaust control method for internal combustion engine - Google Patents

Exhaust control device and exhaust control method for internal combustion engine Download PDF

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JP5141430B2
JP5141430B2 JP2008197382A JP2008197382A JP5141430B2 JP 5141430 B2 JP5141430 B2 JP 5141430B2 JP 2008197382 A JP2008197382 A JP 2008197382A JP 2008197382 A JP2008197382 A JP 2008197382A JP 5141430 B2 JP5141430 B2 JP 5141430B2
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浩一 井上
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Nissan Motor Co Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

この発明は、内燃機関の排気制御に関し、特に、排気還流量（ＥＧＲ量）の制御に関する。   The present invention relates to exhaust control of an internal combustion engine, and more particularly to control of an exhaust gas recirculation amount (EGR amount).

特許文献１にも記載されているように、排気還流（ＥＧＲ）の手法として、ＥＧＲ通路を用いて排気を吸気系へ還流する外部ＥＧＲと、可変動弁装置により吸気弁と排気弁のバルブオーバーラップ量（期間）を調整することで、排気ポートからシリンダへ直接的に排気を逆流させる内部ＥＧＲと、が知られている。   As described in Patent Document 1, as a method of exhaust gas recirculation (EGR), an external EGR that recirculates exhaust gas to an intake system using an EGR passage, and a valve operating system between an intake valve and an exhaust valve by a variable valve device. There is known an internal EGR that adjusts the amount of lap (period) to cause the exhaust gas to directly flow backward from the exhaust port to the cylinder.

ところで、車両の床下などの排気系の比較的下流側にメイン触媒コンバータを配置した構成では、内燃機関の冷間始動後、触媒コンバータの温度が上昇して活性化するまでの間、十分な排気浄化作用を期待することができない。また一方、触媒コンバータを排気系の上流側つまり内燃機関側に近付けるほど、触媒の熱劣化による耐久性低下が問題となる。そのため、特許文献２に開示されているように、メイン触媒コンバータを備えたメイン流路の上流側部分と並列にバイパス流路を設けるとともに、このバイパス流路に、別のバイパス触媒コンバータを介装し、両者を切り換える切換弁によって、冷間始動直後は、バイパス流路側に排気を案内するようにした排気制御装置が、従来から提案されている。この構成では、バイパス触媒コンバータは排気系の中でメイン触媒コンバータよりも相対的に上流側に位置しており、相対的に早期に活性化するので、より早い段階から排気浄化を開始することができる。
特開平１−１８７３５６号公報 特開２００５−１８８３７４号公報 By the way, in the configuration in which the main catalytic converter is disposed on the relatively downstream side of the exhaust system such as under the floor of the vehicle, sufficient exhaust gas is emitted after the internal combustion engine is cold started until the temperature of the catalytic converter rises and is activated. It cannot be expected to have a purification effect. On the other hand, the closer the catalytic converter is to the upstream side of the exhaust system, that is, the internal combustion engine side, the lower the durability due to thermal degradation of the catalyst. Therefore, as disclosed in Patent Document 2, a bypass channel is provided in parallel with the upstream portion of the main channel including the main catalytic converter, and another bypass catalytic converter is interposed in the bypass channel. However, an exhaust control device has been conventionally proposed in which exhaust gas is guided to the bypass flow path side immediately after cold start by a switching valve for switching between the two. In this configuration, the bypass catalytic converter is positioned relatively upstream of the main catalytic converter in the exhaust system and is activated relatively early, so that exhaust purification can be started from an earlier stage. it can.
JP-A-1-187356 JP 2005-188374 A

高回転高負荷域などでは、内部ＥＧＲと外部ＥＧＲとを併用しても、ＥＧＲ量を十分に確保することができないことがある。本発明は、上述したような流路切換弁を利用して、ＥＧＲ量を十分に確保し、燃費向上を図ること主たる目的としている。   In a high rotation / high load range, etc., even if the internal EGR and the external EGR are used in combination, the EGR amount may not be sufficiently secured. The main object of the present invention is to secure a sufficient amount of EGR and improve fuel consumption by using the flow path switching valve as described above.

そこで、本発明は、内燃機関から排出された排気が流れるメイン通路の下流側に設けられたメイン触媒コンバータと、上記メイン通路の上流側部分と並列に設けられたバイパス通路に設けられたバイパス触媒コンバータと、上記メイン通路の上記上流側部分に設けられた流路切換弁と、上記メイン通路又は上記バイパス通路から吸気系へ排気の一部を還流するＥＧＲ通路と、上記ＥＧＲ通路に設けられたＥＧＲ制御弁と、吸気弁と排気弁のバルブオーバーラップ量を変更可能な可変動弁手段と、機関運転状態に基づいて要求ＥＧＲ量を算出する要求ＥＧＲ量算出手段と、この要求ＥＧＲ量に応じて、上記ＥＧＲ制御弁の開度と、上記バルブオーバーラップ量と、上記流路切換弁の開度と、を協調制御するＥＧＲ協調制御手段と、を有することを特徴としている。   Accordingly, the present invention provides a main catalytic converter provided on the downstream side of the main passage through which exhaust gas discharged from the internal combustion engine flows, and a bypass catalyst provided in a bypass passage provided in parallel with the upstream portion of the main passage. A converter, a flow path switching valve provided in the upstream portion of the main passage, an EGR passage for returning a part of exhaust gas from the main passage or the bypass passage to the intake system, and the EGR passage. An EGR control valve, variable valve operating means capable of changing the valve overlap amount of the intake valve and the exhaust valve, requested EGR amount calculating means for calculating the required EGR amount based on the engine operating state, and in accordance with the required EGR amount And EGR cooperative control means for cooperatively controlling the opening degree of the EGR control valve, the valve overlap amount, and the opening degree of the flow path switching valve. It is characterized.

本発明によれば、可変動弁手段によるバルブオーバーラップ量の制御とＥＧＲ制御弁による開度制御に加えて、流路切換弁の開度を協調制御することによって、排気圧力を変化させ、バルブオーバーラップ量による内部ＥＧＲ量やＥＧＲ制御弁による外部ＥＧＲ量を実質的に増減させることができる。従って、機関運転状況に応じてバルブオーバーラップ量とＥＧＲ制御弁の開度と流路切換弁の開度の三者を協調制御することで、機関運転性の悪化やノッキングの発生を招くことなく、幅広い運転領域で十分なＥＧＲ量を確保し、燃費向上を図ることができる。   According to the present invention, in addition to the control of the valve overlap amount by the variable valve means and the opening control by the EGR control valve, the exhaust pressure is changed by cooperatively controlling the opening of the flow path switching valve. The internal EGR amount due to the overlap amount and the external EGR amount due to the EGR control valve can be substantially increased or decreased. Therefore, by coordinating control of the valve overlap amount, the opening degree of the EGR control valve, and the opening degree of the flow path switching valve according to the engine operating condition, the engine operability is not deteriorated and knocking does not occur. It is possible to secure a sufficient EGR amount in a wide driving range and improve fuel efficiency.

以下、この発明を直列４気筒内燃機関の排気制御装置に適用した実施の形態について、図面に基づいて詳細に説明する。図１は、この内燃機関の排気系の配管レイアウトを模式的に示した説明図であり、始めに、この図１に基づいて、排気制御装置全体の構成を説明する。   Hereinafter, an embodiment in which the present invention is applied to an exhaust control device for an in-line four-cylinder internal combustion engine will be described in detail with reference to the drawings. FIG. 1 is an explanatory diagram schematically showing the piping layout of the exhaust system of the internal combustion engine. First, the overall configuration of the exhaust control device will be described with reference to FIG.

直列に配置された♯１気筒〜♯４気筒からなる各気筒１には、気筒毎に上流側メイン通路２が接続されている。４つの気筒の中で、排気行程が連続しない♯１気筒の上流側メイン通路２と♯４気筒の上流側メイン通路２とが１本の中間メイン通路３として合流しており、同様に排気行程が連続しない♯２気筒の上流側メイン通路２と♯３気筒の上流側メイン通路２とが１本の中間メイン通路３として合流している。ここで、各２本の上流側メイン通路２が合流する合流部には、流路切換弁４が設けられている。この流路切換弁４は、冷間時に閉じられるものであって、閉時には、上流側メイン通路２と中間メイン通路３との間の上下の連通を遮断するとともに、２本の上流側メイン通路２の間を非連通状態とする構成となっている。なお、この流路切換弁４は、一対の弁要素５からなり、各弁要素５に含まれる一対の弁体（図示せず）が、２本の上流側メイン通路２の先端部をそれぞれ開閉している。この流路切換弁４（弁要素５）としては、例えば弁体がシール面に接触することにより、漏れを許容せずに流れを完全に遮断することができる形式のものが望ましい。流路切換弁４の下流に位置する２本の中間メイン通路３は、合流点６において互いに合流し、１本の下流側メイン通路７となる。この下流側メイン通路７の途中には、メイン触媒コンバータ８が介装されている。このメイン触媒コンバータ８における触媒としては、三元触媒とＨＣトラップ触媒とを含んでいる。なお、このメイン触媒コンバータ８は、車両の床下に配置される容量の大きなものである。以上の上流側メイン通路２と中間メイン通路３と下流側メイン通路７とメイン触媒コンバータ８とによって、通常の運転時に排気が通流するメイン通路が構成される。このメイン通路は、直列４気筒内燃機関において周知の「４−２−１」の形で集合する配管レイアウトとなっており、従って、排気動的効果を利用した充填効率向上が実現される。   An upstream main passage 2 is connected to each cylinder 1 including # 1 cylinder to # 4 cylinder arranged in series. Among the four cylinders, the upstream main passage 2 of the # 1 cylinder and the upstream main passage 2 of the # 4 cylinder where the exhaust stroke is not continuous merge as one intermediate main passage 3, and the exhaust stroke is similarly performed. The upstream main passage 2 of the # 2 cylinder and the upstream main passage 2 of the # 3 cylinder are joined together as one intermediate main passage 3. Here, a flow path switching valve 4 is provided at a junction where the two upstream main passages 2 join each other. The flow path switching valve 4 is closed when it is cold. When closed, the flow path switching valve 4 blocks the upper and lower communication between the upstream main passage 2 and the intermediate main passage 3, and the two upstream main passages. It is the structure which makes between 2 and a non-communication state. The flow path switching valve 4 includes a pair of valve elements 5, and a pair of valve bodies (not shown) included in each valve element 5 open and close the front ends of the two upstream main passages 2. doing. The flow path switching valve 4 (valve element 5) is preferably of a type that can completely block the flow without allowing leakage, for example, when the valve body contacts the seal surface. The two intermediate main passages 3 positioned downstream of the flow path switching valve 4 merge with each other at a junction 6 to form one downstream main passage 7. A main catalytic converter 8 is interposed in the middle of the downstream main passage 7. The catalyst in the main catalytic converter 8 includes a three-way catalyst and an HC trap catalyst. The main catalytic converter 8 has a large capacity arranged under the floor of the vehicle. The upstream main passage 2, the intermediate main passage 3, the downstream main passage 7, and the main catalytic converter 8 constitute a main passage through which exhaust flows during normal operation. This main passage has a piping layout that gathers in a well-known “4-2-1” form in an in-line four-cylinder internal combustion engine, and therefore, an improvement in charging efficiency utilizing the exhaust dynamic effect is realized.

一方、バイパス通路として、上流側メイン通路２の各々から、上流側バイパス通路１１が分岐している。この上流側バイパス通路１１は、上流側メイン通路２よりも通路断面積が十分に小さなものであって、その上流端となる分岐点１２は、上流側メイン通路２のできるだけ上流側の位置に設定されている。そして、互いに隣接した位置にある♯１気筒の上流側バイパス通路１１と♯２気筒の上流側バイパス通路１１とが合流点１３において１本の中間バイパス通路１４として互いに合流しており、同様に互いに隣接した位置にある♯３気筒の上流側バイパス通路１１と♯４気筒の上流側バイパス通路１１とが合流点１３において１本の中間バイパス通路１４として互いに合流している。なお、各通路を模式的に示した図１では、各上流側バイパス通路１１が比較的長く描かれているが、実際には、可能な限り短くなっている。換言すれば、最短距離でもって中間バイパス通路１４として合流している。２本の中間バイパス通路１４は、合流点１５において１本の下流側バイパス通路１６として互いに合流している。この下流側バイパス通路１６の下流端は、下流側メイン通路７のメイン触媒コンバータ８より上流側の合流点１７において、下流側メイン通路７に合流している。そして、上記下流側バイパス通路１６の途中には、三元触媒を用いたバイパス触媒コンバータ１８が介装されている。このバイパス触媒コンバータ１８は、バイパス流路の中で、可能な限り上流側に配置されている。つまり、中間バイパス通路１４もできるだけ短くなっている。   On the other hand, an upstream bypass passage 11 branches from each of the upstream main passages 2 as bypass passages. The upstream bypass passage 11 has a sufficiently smaller passage cross-sectional area than the upstream main passage 2, and the branch point 12 serving as the upstream end of the upstream bypass passage 11 is set at a position as upstream as possible in the upstream main passage 2. Has been. The upstream bypass passage 11 of the # 1 cylinder and the upstream bypass passage 11 of the # 2 cylinder, which are adjacent to each other, merge with each other as a single intermediate bypass passage 14 at the merge point 13. The upstream bypass passage 11 of the # 3 cylinder and the upstream bypass passage 11 of the # 4 cylinder which are adjacent to each other join each other as a single intermediate bypass passage 14 at the junction 13. In FIG. 1 schematically showing each passage, each upstream bypass passage 11 is drawn relatively long, but in practice it is as short as possible. In other words, it merges as the intermediate bypass passage 14 with the shortest distance. The two intermediate bypass passages 14 join each other as one downstream bypass passage 16 at the junction 15. The downstream end of the downstream bypass passage 16 joins the downstream main passage 7 at a junction 17 upstream of the main catalytic converter 8 in the downstream main passage 7. In the middle of the downstream bypass passage 16, a bypass catalytic converter 18 using a three-way catalyst is interposed. The bypass catalytic converter 18 is disposed as upstream as possible in the bypass flow path. That is, the intermediate bypass passage 14 is as short as possible.

なお、図１の例では、バイパス流路全体の通路長（各気筒のバイパス通路の総和）を短くして、配管自体の熱容量ならびに外気に対する放熱面積を小さくするために、４本の上流側バイパス通路１１を長く引き回さずに上流側で２本の中間バイパス通路１４にまとめているが、このような構成は任意であり、例えば、バイパス触媒コンバータ１８が気筒列の一方に偏って位置する場合などには、他方の端部気筒から直線状に延ばした上流側バイパス通路に残りの気筒の上流側バイパス通路を略直角に接続することにより、全体の通路長を短くすることができる。   In the example of FIG. 1, four upstream bypass passages are used in order to shorten the passage length of the entire bypass passage (the sum of the bypass passages of each cylinder) and reduce the heat capacity of the pipe itself and the heat radiation area for the outside air. Although the passage 11 is not extended for a long time and is grouped into two intermediate bypass passages 14 on the upstream side, such a configuration is arbitrary, for example, the bypass catalytic converter 18 is biased toward one of the cylinder rows. In some cases, the entire passage length can be shortened by connecting the upstream bypass passages of the remaining cylinders at a substantially right angle to the upstream bypass passage extending linearly from the other end cylinder.

上記バイパス触媒コンバータ１８は、周知のモノリス触媒担体を備えており、メイン触媒コンバータ８に比べて容量が小さな小型のものであって、望ましくは、低温活性に優れた触媒が用いられる。また、吸気弁と排気弁のバルブオーバーラップ量を調整可能な可変動弁手段として、吸気弁（又は排気弁）のバルブタイミングを変更可能な可変動弁機構２８が設けられている。このような可変動弁機構２８は周知であり、ここでは説明を省略する。   The bypass catalytic converter 18 includes a well-known monolithic catalyst carrier, and is a small-sized one having a smaller capacity than that of the main catalytic converter 8, and preferably a catalyst excellent in low-temperature activity. In addition, a variable valve mechanism 28 capable of changing the valve timing of the intake valve (or the exhaust valve) is provided as a variable valve mechanism that can adjust the valve overlap amount of the intake valve and the exhaust valve. Such a variable valve mechanism 28 is well known and will not be described here.

そして、吸気系から排気を還流するＥＧＲ通路２０の一端が、バイパス触媒コンバータ１８の下流側の分岐点１９に接続されている。このＥＧＲ通路２０の他端は、ＥＧＲ制御弁２６を介して機関吸気系へと延びている。つまり、上記分岐点１９が、還流排気の取り出し口となっている。そして、ＥＧＲ制御弁２６の開度により、ＥＧＲ通路２０を通る還流排気量、つまり外部ＥＧＲ量が調整される。   One end of the EGR passage 20 that recirculates exhaust gas from the intake system is connected to a branch point 19 on the downstream side of the bypass catalytic converter 18. The other end of the EGR passage 20 extends to the engine intake system via the EGR control valve 26. That is, the branch point 19 serves as a recirculation exhaust outlet. The recirculation exhaust amount passing through the EGR passage 20, that is, the external EGR amount is adjusted by the opening degree of the EGR control valve 26.

また、上記バイパス触媒コンバータ１８の入口側には、上流側空燃比センサ２１が配置され、出口側には、下流側空燃比センサ２２が配置されている。これらの空燃比センサ２１，２２としては、排気空燃比のリッチ，リーンに応じて二値的な信号を出力する所謂酸素センサ、あるいは、排気空燃比の値に対応した連続的に変化する出力が得られる所謂リニア型空燃比センサ、のいずれであってもよい。これらの空燃比センサ２１，２２の検出信号は、周知のように、触媒劣化診断のほか、一般的な空燃比制御（特にバイパス通路側へ排気が案内されているときの空燃比制御）に用いられるので、その精度確保ならびに部品コストの観点から、例えば、上流側空燃比センサ２１にリニア型空燃比センサが用いられ、下流側空燃比センサ２２に酸素センサが用いられている。これらの空燃比センサ２１，２２の検出信号は、エンジンコントロールユニット２３に入力される。なお、メイン通路側へ排気が案内されているときの空燃比制御のために、メイン触媒コンバータ８の入口側および出口側に、同様に空燃比センサ２４，２５を備えている。エンジンコントロールユニット２３は、周知のように、触媒劣化診断，空燃比制御や点火時期制御の他、後述するような流路切換弁４やＥＧＲ制御弁２６の開度制御や、可変動弁機構２８によるバルブオーバーラップ量（期間）の制御などを含む内燃機関の種々の制御を行うものである。なお、ＥＧＲ制御弁２６や流路切換弁４は、いずれも開度を連続的に調整可能なものが用いられている。   An upstream air-fuel ratio sensor 21 is disposed on the inlet side of the bypass catalytic converter 18, and a downstream air-fuel ratio sensor 22 is disposed on the outlet side. As these air-fuel ratio sensors 21 and 22, a so-called oxygen sensor that outputs a binary signal according to the richness or leanness of the exhaust air-fuel ratio, or an output that continuously changes corresponding to the value of the exhaust air-fuel ratio. Any of the so-called linear type air-fuel ratio sensors obtained may be used. As is well known, the detection signals of these air-fuel ratio sensors 21 and 22 are used for general air-fuel ratio control (especially when the exhaust gas is being guided to the bypass passage) in addition to catalyst deterioration diagnosis. Therefore, from the viewpoint of ensuring accuracy and component costs, for example, a linear air-fuel ratio sensor is used for the upstream air-fuel ratio sensor 21, and an oxygen sensor is used for the downstream air-fuel ratio sensor 22. Detection signals of these air-fuel ratio sensors 21 and 22 are input to the engine control unit 23. Note that air-fuel ratio sensors 24 and 25 are similarly provided on the inlet side and the outlet side of the main catalytic converter 8 for air-fuel ratio control when the exhaust gas is guided to the main passage side. As is well known, the engine control unit 23 performs catalyst deterioration diagnosis, air-fuel ratio control, ignition timing control, opening control of the flow path switching valve 4 and EGR control valve 26, which will be described later, and a variable valve mechanism 28. Various controls of the internal combustion engine are performed including control of the valve overlap amount (period) by the control. The EGR control valve 26 and the flow path switching valve 4 are both capable of continuously adjusting the opening degree.

上記のように構成された排気制御装置においては、冷間始動後の機関温度ないしは排気温度が低い段階では、適宜なアクチュエータを介して流路切換弁４が閉じられ、メイン通路が遮断される。そのため、各気筒１から吐出された排気は、その全量が、分岐点１２から上流側バイパス通路１１および中間バイパス通路１４を通してバイパス触媒コンバータ１８へと流れる。バイパス触媒コンバータ１８は、排気系の上流側つまり気筒１に近い位置にあり、かつ小型のものであるので、速やかに活性化し、早期に排気浄化が開始される。また、このとき、流路切換弁４が閉じることで、各気筒１の上流側メイン通路２が互いに非連通状態となる。そのため、ある気筒から吐出された排気が他の気筒の上流側メイン通路２へと回り込む現象が防止され、この回り込みに伴う排気温度の低下が確実に回避される。   In the exhaust control apparatus configured as described above, at the stage where the engine temperature or the exhaust temperature after the cold start is low, the flow path switching valve 4 is closed via an appropriate actuator, and the main passage is shut off. Therefore, the entire amount of exhaust discharged from each cylinder 1 flows from the branch point 12 to the bypass catalytic converter 18 through the upstream bypass passage 11 and the intermediate bypass passage 14. Since the bypass catalytic converter 18 is located upstream of the exhaust system, that is, close to the cylinder 1 and is small in size, the bypass catalytic converter 18 is activated quickly and exhaust purification is started at an early stage. At this time, the flow path switching valve 4 is closed, so that the upstream main passages 2 of the cylinders 1 are not in communication with each other. Therefore, a phenomenon in which the exhaust discharged from a certain cylinder wraps around the upstream main passage 2 of the other cylinder is prevented, and a decrease in the exhaust gas temperature due to this wraparound is surely avoided.

一方、機関の暖機が進行して、機関温度ないしは排気温度が十分に高くなったら、流路切換弁４が開放される。これにより、各気筒１から吐出された排気は、主に、上流側メイン通路２から中間メイン通路３および下流側メイン通路７を通り、メイン触媒コンバータ８を通過する。このときバイパス通路側は特に遮断されていないが、バイパス通路側の方がメイン通路側よりも通路断面積が小さく、かつバイパス触媒コンバータ１８が介在しているので、両者の通路抵抗の差により、排気流の大部分はメイン通路側を通り、バイパス通路側には殆ど流れない。従って、バイパス触媒コンバータ１８の熱劣化は十分に抑制される。またバイパス通路側が完全に遮断されないことから、排気流量が大となる高速高負荷時には、排気流の一部がバイパス通路側を流れることで、背圧による充填効率低下を回避することができる。   On the other hand, when the engine warm-up proceeds and the engine temperature or the exhaust temperature becomes sufficiently high, the flow path switching valve 4 is opened. As a result, the exhaust discharged from each cylinder 1 mainly passes from the upstream main passage 2 through the intermediate main passage 3 and the downstream main passage 7 and through the main catalytic converter 8. At this time, the bypass passage side is not particularly cut off, but the bypass passage side has a smaller passage cross-sectional area than the main passage side, and the bypass catalytic converter 18 is interposed. Most of the exhaust flow passes through the main passage side and hardly flows into the bypass passage side. Therefore, the thermal deterioration of the bypass catalytic converter 18 is sufficiently suppressed. In addition, since the bypass passage side is not completely shut off, at high speed and high load where the exhaust flow rate becomes large, a part of the exhaust flow flows through the bypass passage side, so that a reduction in charging efficiency due to back pressure can be avoided.

またメイン流路側は、前述したように、排気干渉回避を考慮した「４−２−１」の配管レイアウトとなっているので、排気動的効果による充填効率向上効果を得ることができる。ここで、バイパス流路側は、排気干渉回避を特に考慮しない形で連通・集合しているが、上流側バイパス通路１１の通路断面積を十分に小さなものとすることで、各気筒の連通による排気干渉を、実質的に無視し得るレベルにまで低減することが可能である。なお、上流側バイパス通路１１の通路断面積をある上限寸法よりも大きくすると上記の排気干渉による充填効率低下が生じ、また逆にある下限寸法よりも小さくすると、切換弁４が閉状態にある間の排気流量が過度に小さく制限されてしまい、運転可能な領域が過度に狭められる。従って、上流側バイパス通路１１の通路断面積の最適な値は、機関排気量等に応じた所定の上限寸法と下限寸法との範囲内となる。   Further, as described above, the main flow path side has a “4-2-1” piping layout in consideration of avoidance of exhaust interference, so that it is possible to obtain an effect of improving the filling efficiency by the exhaust dynamic effect. Here, the bypass channel side communicates and aggregates in a manner that does not particularly consider exhaust interference avoidance, but by making the cross-sectional area of the upstream bypass passage 11 sufficiently small, exhaust by communication of each cylinder is achieved. Interference can be reduced to a level that is substantially negligible. If the passage cross-sectional area of the upstream bypass passage 11 is larger than a certain upper limit dimension, the charging efficiency is reduced due to the exhaust interference described above, and conversely if smaller than a certain lower limit dimension, the switching valve 4 is in the closed state. The exhaust flow rate is limited to be too small, and the operable region is excessively narrowed. Therefore, the optimum value of the passage cross-sectional area of the upstream bypass passage 11 is within a range between a predetermined upper limit dimension and a lower limit dimension corresponding to the engine displacement.

図２は、ＥＧＲ協調制御の流れを示すフローチャートであり、本ルーチンはエンジンコントロールユニット２３により記憶及び実行される。   FIG. 2 is a flowchart showing the flow of EGR cooperative control, and this routine is stored and executed by the engine control unit 23.

ステップＳ１では、機関運転状態に基づいて要求ＥＧＲ量を算出する。ステップＳ２では、要求ＥＧＲ量等に基づいて、燃焼安定性を算出する。ステップＳ３では、燃焼安定性が所定の燃焼安定限界に達したかを判定する。燃焼安定性が燃焼安定限界に達したと判定すると、ステップＳ４へ進み、要求ＥＧＲ量の増加を禁止する（図３〜図６参照）。   In step S1, the required EGR amount is calculated based on the engine operating state. In step S2, the combustion stability is calculated based on the required EGR amount and the like. In step S3, it is determined whether the combustion stability has reached a predetermined combustion stability limit. If it determines with combustion stability having reached the combustion stability limit, it will progress to step S4 and will prohibit the increase in request | required EGR amount (refer FIGS. 3-6).

ステップＳ５では、例えばノッキングセンサ（図示省略）の信号に基づいてノッキングの発生を検出したかを判定する。ノッキングの発生を検出すると、ステップＳ６へ進み、内部ＥＧＲ量の増加を禁止する。つまり、バルブオーバーラップ量の増加、更には流路切換弁４の開度減少を禁止する。そして、ステップＳ７では、要求ＥＧＲ量に応じて、ＥＧＲ制御弁２６の開度と、可変動弁機構２８によるバルブオーバーラップ量と、流路切換弁４の開度と、を協調制御する。   In step S5, for example, it is determined whether the occurrence of knocking is detected based on a signal from a knocking sensor (not shown). If the occurrence of knocking is detected, the process proceeds to step S6, and an increase in the internal EGR amount is prohibited. That is, an increase in the valve overlap amount and a decrease in the opening degree of the flow path switching valve 4 are prohibited. In step S7, the opening degree of the EGR control valve 26, the valve overlap amount by the variable valve mechanism 28, and the opening degree of the flow path switching valve 4 are cooperatively controlled according to the required EGR amount.

このＥＧＲ協調制御の第１実施例について、図３〜図５のタイミングチャート及び図７を参照して説明する。   A first embodiment of this EGR cooperative control will be described with reference to the timing charts of FIGS. 3 to 5 and FIG.

図７の低回転低負荷域α１のように、要求ＥＧＲ量が小さい状況では、図３に示すように、ＥＧＲ制御弁２６による外部ＥＧＲを付与することなく、要求ＥＧＲ量の増加に応じてバルブオーバーラップ量を大きくして、内部ＥＧＲ量を増加させていく。そして、バルブオーバーラップ量が最大値Ｏ／Ｌｍａｘに達し、かつ、燃焼安定性とノッキングに対して余裕がある場合には、要求ＥＧＲ量の増加に応じて、流路切換弁４の開度を減少させていく。つまり流路切換弁４を閉じていく。このように流路切換弁４の開度を狭くしていくことで、排気圧力を高め、内部ＥＧＲ量を実質的に増加させていくことができる。このように、外部ＥＧＲの付与による燃焼安定性の低下を招くことなく、流路切換弁４を利用して内部ＥＧＲ量を最大限に確保して燃費向上効果を得ることができる。   In a situation where the required EGR amount is small as in the low-rotation low-load region α1 in FIG. 7, as shown in FIG. 3, the valve is adjusted according to the increase in the required EGR amount without applying the external EGR by the EGR control valve 26. The amount of internal EGR is increased by increasing the overlap amount. When the valve overlap amount reaches the maximum value O / Lmax and there is a margin for combustion stability and knocking, the opening degree of the flow path switching valve 4 is increased according to the increase in the required EGR amount. Decrease. That is, the flow path switching valve 4 is closed. Thus, by narrowing the opening degree of the flow path switching valve 4, the exhaust pressure can be increased and the internal EGR amount can be substantially increased. As described above, the fuel consumption improvement effect can be obtained by securing the maximum amount of internal EGR by using the flow path switching valve 4 without reducing the combustion stability due to the application of the external EGR.

そして、図７の高負荷域α２のように、バルブオーバーラップ量が最大値Ｏ／Ｌｍａｘとなり、かつ、流路切換弁４の開度が最小値ＶＯｍｉｎつまり全閉となると、図４に示すように、要求ＥＧＲ量の増加に応じて、ＥＧＲ制御弁２６の開度を増加していき、外部ＥＧＲ量を増加させていく。これによって、要求ＥＧＲ量の増加に応じて内部ＥＧＲ量と外部ＥＧＲ量とを合わせたトータルのＥＧＲ量を増加させていくことができ、更なる燃費向上を図ることができる。   Then, as shown in FIG. 4, when the valve overlap amount becomes the maximum value O / Lmax and the opening degree of the flow path switching valve 4 becomes the minimum value VOmin, that is, fully closed as in the high load region α2 of FIG. Further, the opening degree of the EGR control valve 26 is increased in accordance with the increase in the required EGR amount, and the external EGR amount is increased. As a result, the total EGR amount, which is the sum of the internal EGR amount and the external EGR amount, can be increased in accordance with the increase in the required EGR amount, and fuel efficiency can be further improved.

但し、図７の高回転域α３のように、運転領域によっては、要求ＥＧＲ量の増加に応じて内部ＥＧＲ量を増加させていくと、高温残留ガスの影響で、図５に示すように、燃焼安定性に余裕があってもノッキングを発生してしまうことがある。そこで、ノッキングの発生を検出した場合には、内部ＥＧＲ量の増加、つまりバルブオーバーラップ量の増加や流路切換弁の開度減少を禁止し（図２のステップＳ６参照）、要求ＥＧＲ量の増加に応じて、ＥＧＲ制御弁２６の開度を大きくしていく。これによって、燃焼初期の圧力上昇を抑制してノッキングの発生を有効に回避しつつ、燃焼安定限界までＥＧＲ量を増加させていくことで、十分なＥＧＲ量を確保して燃費効果を最大限に得ることができる。   However, as shown in FIG. 5, when the internal EGR amount is increased in accordance with the increase in the required EGR amount, as shown in FIG. Even if there is a margin in combustion stability, knocking may occur. Therefore, when the occurrence of knocking is detected, an increase in the internal EGR amount, that is, an increase in the valve overlap amount or a decrease in the opening degree of the flow path switching valve is prohibited (see step S6 in FIG. 2). In accordance with the increase, the opening degree of the EGR control valve 26 is increased. As a result, the EGR amount is increased to the combustion stability limit while effectively suppressing the occurrence of knocking by suppressing the pressure increase in the initial stage of combustion, thereby ensuring a sufficient EGR amount and maximizing the fuel consumption effect. Can be obtained.

図６は、ＥＧＲ協調制御の第２実施例を示すタイミングチャートである。この第２実施例では、要求ＥＧＲ量の増加に伴って、先ずバルブオーバーラップ量の増加により内部ＥＧＲ量を増加していき、このバルブオーバーラップ量が最大値Ｏ／Ｌｍａｘに達すると、次に要求ＥＧＲ量の増加に伴ってＥＧＲ制御弁２６の開度つまり外部ＥＧＲ量を増加していく。そして、ＥＧＲ制御弁２６の開度（外部ＥＧＲ量）が最大値ＶＥＧＲｍａｘに達すると、最後に流路切換弁４の開度を低下させていく。これによって、排気圧力の増加に伴い、内部ＥＧＲ量及び外部ＥＧＲ量の双方が実質的に増加していき、全体としてのＥＧＲ量を要求ＥＧＲ量の増加に応じて増加させていくことができる。このような第２実施例では、上記第１実施例と同様、燃焼安定性やノッキングを生じることなくＥＧＲ量を最大限に確保して燃費向上を図ることができることに加え、要求ＥＧＲ量の増加に伴い、バルブオーバーラップ量の増加による内部ＥＧＲ量の増加に続いて、ＥＧＲ制御弁２６の開度増加による外部ＥＧＲ量を増加させ、最後に流路切換弁４の開度を減少させるようにしたので、流路切換弁４の開度減少に伴うバイパス触媒コンバータ１８の熱劣化や通気抵抗の増加を抑制することができる。   FIG. 6 is a timing chart showing a second embodiment of EGR cooperative control. In the second embodiment, as the required EGR amount increases, the internal EGR amount is first increased by increasing the valve overlap amount. When this valve overlap amount reaches the maximum value O / Lmax, As the required EGR amount increases, the opening degree of the EGR control valve 26, that is, the external EGR amount increases. When the opening degree of the EGR control valve 26 (external EGR amount) reaches the maximum value VEGRmax, the opening degree of the flow path switching valve 4 is finally reduced. As a result, as the exhaust pressure increases, both the internal EGR amount and the external EGR amount increase substantially, and the overall EGR amount can be increased in accordance with the increase in the required EGR amount. In the second embodiment, as in the first embodiment, the fuel consumption can be improved by ensuring the maximum EGR amount without causing combustion stability and knocking, and the required EGR amount can be increased. Accordingly, following the increase in the internal EGR amount due to the increase in the valve overlap amount, the external EGR amount due to the increase in the opening degree of the EGR control valve 26 is increased, and finally the opening degree of the flow path switching valve 4 is decreased. Therefore, it is possible to suppress the thermal deterioration of the bypass catalytic converter 18 and the increase in the ventilation resistance due to the decrease in the opening degree of the flow path switching valve 4.

以上の説明より把握し得る本発明の特徴的な構成及び作用効果について、上記実施例を参照して以下に列記する。但し、本発明は上記実施例に限定されるものではなく、その趣旨を逸脱しない範囲で、種々の変形・変更を含むものである。例えば、上記実施例ではＥＧＲ通路２０の排気通路への接続位置つまり排気還流の取り出し口１９を下流側バイパス通路１６としているが、これに限らず、例えば取出し口１９をメイン通路２，３，７に設定してもよい。   The characteristic configurations and operational effects of the present invention that can be understood from the above description will be listed below with reference to the above-described embodiments. However, the present invention is not limited to the above embodiments, and includes various modifications and changes without departing from the spirit of the present invention. For example, in the above embodiment, the connection position of the EGR passage 20 to the exhaust passage, that is, the exhaust outlet 19 for exhaust gas recirculation is used as the downstream bypass passage 16, but the present invention is not limited to this. May be set.

［１］内燃機関から排出された排気が流れるメイン通路（２，３，７）の下流側に設けられたメイン触媒コンバータ８と、上記メイン通路の上流側部分と並列に設けられたバイパス通路（１１，１４，１６）に設けられたバイパス触媒コンバータ１８と、上記メイン通路の上記上流側部分に設けられた流路切換弁４と、上記メイン通路又は上記バイパス通路から吸気系へ排気の一部を還流するＥＧＲ通路２０に設けられたＥＧＲ制御弁２６と、吸気弁と排気弁のバルブオーバーラップ量を変更可能な可変動弁機構２８等の可変動弁手段と、を有する。そして、機関運転状態に基づいて要求ＥＧＲ量を算出する要求ＥＧＲ量算出手段（ステップＳ１）と、この要求ＥＧＲ量に応じて、上記ＥＧＲ制御弁２６の開度と、上記バルブオーバーラップ量と、上記流路切換弁４の開度と、を協調制御するＥＧＲ協調制御手段（ステップＳ７）と、を有することを特徴としている。   [1] A main catalytic converter 8 provided on the downstream side of the main passage (2, 3, 7) through which the exhaust discharged from the internal combustion engine flows, and a bypass passage provided in parallel with the upstream portion of the main passage ( 11, 14, 16) bypass catalytic converter 18, flow switching valve 4 provided in the upstream portion of the main passage, and part of the exhaust from the main passage or the bypass passage to the intake system And an EGR control valve 26 provided in the EGR passage 20 that recirculates gas, and variable valve operating means such as a variable valve mechanism 28 that can change the valve overlap amount of the intake valve and the exhaust valve. Then, a required EGR amount calculating means (step S1) for calculating a required EGR amount based on the engine operating state, and according to the required EGR amount, the opening degree of the EGR control valve 26, the valve overlap amount, EGR cooperative control means (step S7) for cooperatively controlling the opening degree of the flow path switching valve 4 is characterized.

このような構成により、ＥＧＲ制御弁２６の開度を調整することで外部ＥＧＲ量が増減し、バルブオーバーラップ量を調整することで内部ＥＧＲ量が増減する。加えて、流路切換弁４の開度を調整することで、メイン通路とバイパス通路の通気抵抗の差に応じて排気圧力が変化し、これに伴って、内部ＥＧＲ量や外部ＥＧＲ量を実質的に増減させることができる。具体的には、流路切換弁４の開度を減少するほど、つまり流路切換弁４を閉じるほど、通気抵抗の大きいバイパス通路側を通流する排気量が増えることから、排気圧力が上昇し、内部ＥＧＲ量や外部ＥＧＲ量を実質的に増加させることができる。このように、メイン通路とバイパス通路とを切り換える流路切換弁４を利用して、実質的なＥＧＲ量を調整することが可能となることから、ＥＧＲ制御弁２６の開度による外部ＥＧＲ量の調整と、バルブオーバーラップ量による内部ＥＧＲ量の調整に加えて、流路切換弁４の開度を協調制御することで、幅広い運転領域で十分なＥＧＲ量を確保し、燃費向上を図ることができる。   With such a configuration, the external EGR amount increases or decreases by adjusting the opening degree of the EGR control valve 26, and the internal EGR amount increases or decreases by adjusting the valve overlap amount. In addition, by adjusting the opening degree of the flow path switching valve 4, the exhaust pressure changes according to the difference in ventilation resistance between the main passage and the bypass passage, and accordingly, the internal EGR amount and the external EGR amount are substantially reduced. Can be increased or decreased automatically. Specifically, as the opening degree of the flow path switching valve 4 is decreased, that is, as the flow path switching valve 4 is closed, the amount of exhaust gas flowing through the bypass passage having a larger ventilation resistance increases, so the exhaust pressure increases. In addition, the internal EGR amount and the external EGR amount can be substantially increased. Thus, since the substantial EGR amount can be adjusted by using the flow path switching valve 4 for switching between the main passage and the bypass passage, the external EGR amount due to the opening degree of the EGR control valve 26 can be adjusted. In addition to the adjustment and adjustment of the internal EGR amount by the valve overlap amount, the opening degree of the flow path switching valve 4 is coordinated to secure a sufficient EGR amount in a wide range of operation and improve fuel efficiency. it can.

［２］但し、図２のステップＳ２〜Ｓ４や図３〜図６に示すように、燃焼安定性が所定の燃焼安定限界を超えた場合には、要求ＥＧＲ量の増加を禁止することで、燃焼安定性の悪化を回避することができる。   [2] However, as shown in steps S2 to S4 of FIG. 2 and FIGS. 3 to 6, when the combustion stability exceeds a predetermined combustion stability limit, an increase in the required EGR amount is prohibited. Deterioration of combustion stability can be avoided.

［３］また、要求ＥＧＲ量の増加に応じてバルブオーバーラップ量（内部ＥＧＲ量）を増加させていくと、排気ポートより吹き戻される高温残留ガスの影響で、図５に示すように、運転領域（例えば高負荷域α３）によっては燃焼安定性に余裕があってもノッキングを発生してしまうことがある。そこで、ノッキングの発生を検出した場合には、バルブオーバーラップ量の増加を禁止し（ステップＳ６）、要求ＥＧＲ量の増加に応じて、ＥＧＲ制御弁の開度つまり外部ＥＧＲ量を増加していく。これによって、燃焼初期の圧力上昇を抑制してノッキングの発生を回避しつつ、要求ＥＧＲ量の増加に応じてＥＧＲ量を増加させていくことができる。   [3] When the valve overlap amount (internal EGR amount) is increased in accordance with the increase in the required EGR amount, the operation is performed as shown in FIG. 5 due to the influence of the high-temperature residual gas blown back from the exhaust port. Depending on the region (for example, high load region α3), knocking may occur even if there is a margin in combustion stability. Therefore, when the occurrence of knocking is detected, an increase in the valve overlap amount is prohibited (step S6), and the opening degree of the EGR control valve, that is, the external EGR amount is increased in accordance with the increase in the required EGR amount. . As a result, the EGR amount can be increased in accordance with the increase in the required EGR amount while suppressing the occurrence of knocking by suppressing the pressure increase in the early stage of combustion.

［４］燃焼が不安定な低回転低負荷域α１（図７参照）などでは、図３〜図６に示すように、バルブオーバーラップ量が所定値に達するまで、要求ＥＧＲ量の増加に応じてバルブオーバーラップ量を増加することで、外部ＥＧＲの付与による燃焼安定性の低下を招くことなく、要求ＥＧＲ量の増加に応じて内部ＥＧＲ量を増加していくことができる。   [4] In a low-rotation low-load region α1 (see FIG. 7) where combustion is unstable, as shown in FIGS. 3 to 6, the required EGR amount is increased until the valve overlap amount reaches a predetermined value. By increasing the valve overlap amount, the internal EGR amount can be increased in accordance with the increase in the required EGR amount without causing deterioration in combustion stability due to the application of the external EGR.

［５］、上記第１実施例では、図３及び図４に示すように、バルブオーバーラップ量が所定値（最大値Ｏ／Ｌｍａｘ）に達すると、要求ＥＧＲ量の増加に応じて流路切換弁４の開度を減少し、この流路切換弁４の開度が所定値（最小値ＶＯｍｉｎ）まで低下すると、要求ＥＧＲ量の増加に応じてＥＧＲ制御弁２６の開度を増加している。このように、要求ＥＧＲ量の増加に伴って、バルブオーバーラップ量の増加，流路切換弁４の開度減少，及びＥＧＲ制御弁２６の開度増加の順に制御を行い、ＥＧＲ制御弁２６の開度増加による外部ＥＧＲ量の付与を行う前に、内部ＥＧＲ量を最大限に利用することで、外部ＥＧＲの付与による燃焼安定性の低下を最小限に抑制することができる。そして、流路切換弁４の開度が最小値まで低下し、かつ燃焼安定性やノッキングに対して余裕がある場合には、ＥＧＲ制御弁２６の開度増加による外部ＥＧＲ量の付与を行うことで、ＥＧＲ量を最大限に確保して更なる燃費向上を図ることができる。   [5] In the first embodiment, as shown in FIGS. 3 and 4, when the valve overlap amount reaches a predetermined value (maximum value O / Lmax), the flow path is switched according to the increase in the required EGR amount. When the opening degree of the valve 4 is decreased and the opening degree of the flow path switching valve 4 is reduced to a predetermined value (minimum value VOmin), the opening degree of the EGR control valve 26 is increased in accordance with an increase in the required EGR amount. . As described above, as the required EGR amount increases, the valve overlap amount increases, the opening degree of the flow path switching valve 4 decreases, and the opening degree of the EGR control valve 26 increases in order. Before the application of the external EGR amount due to the increase in the opening degree, the internal EGR amount is utilized to the maximum, so that a decrease in combustion stability due to the application of the external EGR can be suppressed to the minimum. When the opening degree of the flow path switching valve 4 is reduced to the minimum value and there is a margin for combustion stability and knocking, an external EGR amount is given by increasing the opening degree of the EGR control valve 26. Therefore, the fuel consumption can be further improved by securing the maximum EGR amount.

［６］但し、ＥＧＲ量を増加するために流路切換弁４の開度を減少すると、バイパス通路を通流する排気量が増加し、バイパス触媒コンバータ１８の熱劣化や通気抵抗の増加等の悪影響が懸念される場合には、図６に示す第２実施例のように、バルブオーバーラップ量が所定値（例えば最大値Ｏ／Ｌｍａｘ）に達すると、要求ＥＧＲ量の増加に応じて先ずＥＧＲ制御弁２６の開度を増加して外部ＥＧＲ量を増加させ、このＥＧＲ制御弁２６の開度が所定値（例えば最大値ＶＥＧＲｍａｘ）に達すると、要求ＥＧＲ量の増加に応じて流路切換弁４の開度を減少している。これによって、ＥＧＲ量の増加の目的で流路切換弁４の開度減少させる機会を最小限に抑制することができる。   [6] However, if the opening degree of the flow path switching valve 4 is decreased in order to increase the EGR amount, the amount of exhaust gas flowing through the bypass passage increases, resulting in thermal deterioration of the bypass catalytic converter 18 or increase in ventilation resistance. When an adverse effect is a concern, as in the second embodiment shown in FIG. 6, when the valve overlap amount reaches a predetermined value (for example, the maximum value O / Lmax), first, EGR is first performed in accordance with the increase in the required EGR amount. When the opening degree of the control valve 26 is increased to increase the external EGR amount, and the opening degree of the EGR control valve 26 reaches a predetermined value (for example, the maximum value VEGRmax), the flow path switching valve is increased according to the increase in the required EGR amount. The opening degree of 4 is decreased. Thereby, the opportunity to reduce the opening degree of the flow path switching valve 4 for the purpose of increasing the EGR amount can be minimized.

この発明に係る排気制御装置の一例を示す構成説明図Configuration explanatory view showing an example of an exhaust control device according to the present invention ＥＧＲ協調制御の流れを示すフローチャート。The flowchart which shows the flow of EGR cooperation control. 第１実施例に係るＥＧＲ協調制御を示すタイミングチャート。The timing chart which shows the EGR cooperative control which concerns on 1st Example. 同じく第１実施例に係るＥＧＲ協調制御を示すタイミングチャート。The timing chart which similarly shows the EGR cooperation control which concerns on 1st Example. 同じく第１実施例に係るノッキング発生時のＥＧＲ協調制御を示すタイミングチャート。The timing chart which shows the EGR cooperation control at the time of the knocking generation which similarly concerns on 1st Example. 第２実施例に係るＥＧＲ協調制御を示すタイミングチャート。The timing chart which shows the EGR cooperative control which concerns on 2nd Example. 上記ＥＧＲ協調制御に関する運転領域を示す説明図。Explanatory drawing which shows the driving | operation area | region regarding the said EGR cooperative control.

符号の説明Explanation of symbols

２…上流側メイン通路
３…中間メイン通路
４…流路切換弁
８…メイン触媒コンバータ
１１…上流側バイパス通路
１４…中間バイパス通路
１６…下流側バイパス通路
１８…バイパス触媒コンバータ
２０…ＥＧＲ通路
２３…エンジンコントロールユニット
２６…ＥＧＲ制御弁
２８…可変動弁機構（可変動弁手段） 2 ... Upstream main passage 3 ... Intermediate main passage 4 ... Flow path switching valve 8 ... Main catalytic converter 11 ... Upstream bypass passage 14 ... Intermediate bypass passage 16 ... Downstream bypass passage 18 ... Bypass catalytic converter 20 ... EGR passage 23 ... Engine control unit 26 ... EGR control valve 28 ... Variable valve mechanism (variable valve means)

Claims (4)

内燃機関から排出された排気が流れるメイン通路の下流側に設けられたメイン触媒コンバータと、
上記メイン通路の上流側部分と並列に設けられたバイパス通路に設けられたバイパス触媒コンバータと、
上記メイン通路の上記上流側部分に設けられた流路切換弁と、
上記メイン通路又は上記バイパス通路から吸気系へ排気の一部を還流するＥＧＲ通路と、
上記ＥＧＲ通路に設けられたＥＧＲ制御弁と、
吸気弁と排気弁のバルブオーバーラップ量を変更可能な可変動弁手段と、
機関運転状態に基づいて要求ＥＧＲ量を算出する要求ＥＧＲ量算出手段と、
この要求ＥＧＲ量に応じて、上記ＥＧＲ制御弁の開度と、上記バルブオーバーラップ量と、上記流路切換弁の開度と、を協調制御するＥＧＲ協調制御手段と、
を有し、
上記ＥＧＲ協調制御手段は、
ノッキングの発生を検出した場合、上記バルブオーバーラップ量の増加を禁止し、上記要求ＥＧＲ量の増加に応じて、上記ＥＧＲ制御弁の開度を増加するとともに、
上記バルブオーバーラップ量が所定値に達するまで、上記要求ＥＧＲ量の増加に応じて上記バルブオーバーラップ量を増加し、
かつ、上記バルブオーバーラップ量が所定値に達すると、上記要求ＥＧＲ量の増加に応じて上記ＥＧＲ制御弁の開度を増加し、上記ＥＧＲ制御弁の開度が所定値に達すると、上記要求ＥＧＲ量の増加に応じて流路切換弁の開度を減少することを特徴とする内燃機関の排気制御装置。 A main catalytic converter provided on the downstream side of the main passage through which the exhaust discharged from the internal combustion engine flows;
A bypass catalytic converter provided in a bypass passage provided in parallel with the upstream portion of the main passage;
A flow path switching valve provided in the upstream portion of the main passage;
An EGR passage that recirculates part of the exhaust gas from the main passage or the bypass passage to the intake system;
An EGR control valve provided in the EGR passage;
Variable valve operating means capable of changing the valve overlap amount of the intake valve and the exhaust valve;
A required EGR amount calculating means for calculating a required EGR amount based on the engine operating state;
EGR cooperative control means for cooperatively controlling the opening of the EGR control valve, the valve overlap amount, and the opening of the flow path switching valve according to the required EGR amount;
Have
The EGR cooperative control means is
When the occurrence of knocking is detected, an increase in the valve overlap amount is prohibited, and the opening degree of the EGR control valve is increased in accordance with the increase in the required EGR amount .
Until the valve overlap amount reaches a predetermined value, the valve overlap amount is increased in accordance with the increase in the required EGR amount,
When the valve overlap amount reaches a predetermined value, the opening degree of the EGR control valve is increased according to the increase in the required EGR amount, and when the opening degree of the EGR control valve reaches a predetermined value, the request An exhaust control device for an internal combustion engine, wherein the opening degree of the flow path switching valve is decreased in accordance with an increase in the EGR amount . 内燃機関から排出された排気が流れるメイン通路の下流側に設けられたメイン触媒コンバータと、
上記メイン通路の上流側部分と並列に設けられたバイパス通路に設けられたバイパス触媒コンバータと、
上記メイン通路の上記上流側部分に設けられた流路切換弁と、
上記メイン通路又は上記バイパス通路から吸気系へ排気の一部を還流するＥＧＲ通路と、
上記ＥＧＲ通路に設けられたＥＧＲ制御弁と、
吸気弁と排気弁のバルブオーバーラップ量を変更可能な可変動弁手段と、
機関運転状態に基づいて要求ＥＧＲ量を算出する要求ＥＧＲ量算出手段と、
この要求ＥＧＲ量に応じて、上記ＥＧＲ制御弁の開度と、上記バルブオーバーラップ量と、上記流路切換弁の開度と、を協調制御するＥＧＲ協調制御手段と、
を有し、
上記ＥＧＲ協調制御手段は、
上記バルブオーバーラップ量が所定値に達するまで、上記要求ＥＧＲ量の増加に応じて上記バルブオーバーラップ量を増加し、
上記バルブオーバーラップ量が所定値に達すると、上記要求ＥＧＲ量の増加に応じて上記ＥＧＲ制御弁の開度を増加し、
上記ＥＧＲ制御弁の開度が所定値に達すると、上記要求ＥＧＲ量の増加に応じて流路切換弁の開度を減少する
ことを特徴とする内燃機関の排気制御装置。 A main catalytic converter provided on the downstream side of the main passage through which the exhaust discharged from the internal combustion engine flows;
A bypass catalytic converter provided in a bypass passage provided in parallel with the upstream portion of the main passage;
A flow path switching valve provided in the upstream portion of the main passage;
An EGR passage that recirculates part of the exhaust gas from the main passage or the bypass passage to the intake system;
An EGR control valve provided in the EGR passage;
Variable valve operating means capable of changing the valve overlap amount of the intake valve and the exhaust valve;
A required EGR amount calculating means for calculating a required EGR amount based on the engine operating state;
EGR cooperative control means for cooperatively controlling the opening of the EGR control valve, the valve overlap amount, and the opening of the flow path switching valve according to the required EGR amount;
Have
The EGR cooperative control means is
Until the valve overlap amount reaches a predetermined value, the valve overlap amount is increased in accordance with the increase in the required EGR amount,
When the valve overlap amount reaches a predetermined value, the opening degree of the EGR control valve is increased in accordance with the increase in the required EGR amount,
An exhaust control device for an internal combustion engine, wherein when the opening degree of the EGR control valve reaches a predetermined value, the opening degree of the flow path switching valve is decreased in accordance with an increase in the required EGR amount. 上記ＥＧＲ協調制御手段は、ノッキングの発生を検出した場合に、上記バルブオーバーラップ量の増加を禁止し、上記要求ＥＧＲ量の増加に応じて、上記ＥＧＲ制御弁の開度を増加することを特徴とする請求項２に記載の内燃機関の排気制御装置。 When the occurrence of knocking is detected, the EGR cooperative control means prohibits an increase in the valve overlap amount, and increases the opening of the EGR control valve in accordance with the increase in the required EGR amount. An exhaust control device for an internal combustion engine according to claim 2 . 内燃機関から排出された排気が流れるメイン通路の下流側に設けられたメイン触媒コンバータと、
上記メイン通路の上流側部分と並列に設けられたバイパス通路に設けられたバイパス触媒コンバータと、
上記メイン通路の上記上流側部分に設けられた流路切換弁と、
上記メイン通路又は上記バイパス通路から吸気系へ排気の一部を還流するＥＧＲ通路と、
上記ＥＧＲ通路に設けられたＥＧＲ制御弁と、
吸気弁と排気弁のバルブオーバーラップ量を変更可能な可変動弁手段と、
を備えた内燃機関の排気制御方法において、
機関運転状態に基づいて要求ＥＧＲ量を算出し、
上記バルブオーバーラップ量が所定値に達するまで、上記要求ＥＧＲ量の増加に応じて上記バルブオーバーラップ量を増加し、
上記バルブオーバーラップ量が所定値に達すると、上記要求ＥＧＲ量の増加に応じて上記ＥＧＲ制御弁の開度を増加し、
上記ＥＧＲ制御弁の開度が所定値に達すると、上記要求ＥＧＲ量の増加に応じて流路切換弁の開度を減少する
ことを特徴とする内燃機関の排気制御方法。 A main catalytic converter provided on the downstream side of the main passage through which the exhaust discharged from the internal combustion engine flows;
A bypass catalytic converter provided in a bypass passage provided in parallel with the upstream portion of the main passage;
A flow path switching valve provided in the upstream portion of the main passage;
An EGR passage that recirculates part of the exhaust gas from the main passage or the bypass passage to the intake system;
An EGR control valve provided in the EGR passage;
Variable valve operating means capable of changing the valve overlap amount of the intake valve and the exhaust valve;
An exhaust control method for an internal combustion engine comprising:
Calculate the required EGR amount based on the engine operating state,
Until the valve overlap amount reaches a predetermined value, the valve overlap amount is increased in accordance with the increase in the required EGR amount,
When the valve overlap amount reaches a predetermined value, the opening degree of the EGR control valve is increased in accordance with the increase in the required EGR amount,
An exhaust control method for an internal combustion engine, wherein when the opening degree of the EGR control valve reaches a predetermined value, the opening degree of the flow path switching valve is decreased in accordance with an increase in the required EGR amount.
JP2008197382A 2008-07-31 2008-07-31 Exhaust control device and exhaust control method for internal combustion engine Expired - Fee Related JP5141430B2 (en)

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