JP2004346796A

JP2004346796A - Recirculation exhaust gas control system for premixed compression ignition combustion internal combustion engine

Info

Publication number: JP2004346796A
Application number: JP2003143244A
Authority: JP
Inventors: Hide Itabashi; 秀板橋
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2003-05-21
Filing date: 2003-05-21
Publication date: 2004-12-09
Anticipated expiration: 2023-05-21
Also published as: JP4059140B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of performing more favorable premixed compression ignition combustion in a wider operating range, in a premixed compression ignition combustion internal combustion engine. <P>SOLUTION: A first intake port 3 for introducing intake air to a central part inside a cylinder, a second intake port 4 for introducing intake air to the vicinity of a wall face inside the cylinder, and an exhaust gas recirculation means 20 for introducing EGR gas to the first intake port 3 and the second intake port 4 are provided. In accordance with an operating condition of the internal combustion engine 1, by controlling the amount of EGR gas introduced to the first intake port 3 and the second intake port 4, respectively, distribution of EGR rate inside the cylinder 2 is controlled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、燃焼室内において、燃焼に供される予混合気が形成される予混合圧縮着火燃焼内燃機関に関する。
【０００２】
【従来の技術】
従来、内燃機関において、吸気行程中または圧縮行程中に気筒内へ燃料を噴射することで、該燃料と吸気（空気）との予混合気を形成し、該予混合気を燃焼に供することによって、ＮＯｘや煙の排出が抑制される予混合圧縮着火燃焼内燃機関の開発が進められている。
【０００３】
このような予混合圧縮着火燃焼内燃機関においては、形成された予混合気が気筒内の温度上昇により圧縮行程上死点近傍となる前に着火燃焼する、いわゆる過早着火が発生する虞がある。そこで、燃焼室に導入される再循環排気量を排気中のＮＯｘ濃度に基づき制御することで、過早着火の発生を防止する技術が知られている（例えば、特許文献１参照）。
【０００４】
【特許文献１】
特開２００１−１５２８５３号公報
【特許文献２】
特開２０００−１２０４５７号公報
【特許文献１】
特開平１０−２７４１０４号公報
【特許文献２】
特開平６−２２９３２５号公報
【０００５】
【発明が解決しようとする課題】
予混合圧縮着火燃焼内燃機関では、機関が高負荷で運転されているときは、気筒内、特に気筒内中央部の温度が高くなるため過早着火が発生し易くなる。また、気筒内において予混合気は略均一に分布している、即ち気筒内での空気と燃料との濃度分布が略均一であるため、高温では予混合気の燃焼は急激なものとなり燃焼騒音が悪化する虞がある。一方、機関が低負荷で運転されているときや機関の暖機前は、気筒内壁面付近の温度が低く該気筒内壁面付近の予混合気において未燃成分が発生する虞がある。
【０００６】
本発明は、上記したような問題に鑑みてなされたものであり、予混合圧縮着火燃焼内燃機関において、より広い運転領域でより好適な予混合圧縮着火燃焼を行うことが可能な技術を提供することを課題とする。
【０００７】
【課題を解決するための手段】
本発明は、上記課題を解決するために以下の手段を採用した。
即ち、本発明は、予混合圧縮着火燃焼内燃機関の再循環排気制御システムであって、複数の吸気ポートを備えており、少なくとも一の吸気ポートに排気の一部を導入し（以下、吸気ポートに導入される排気をＥＧＲガスと称する）、この吸気ポートに導入されるＥＧＲガスの量を制御することで気筒内のＥＧＲガス率の分布を制御するものである。
【０００８】
より詳しくは、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムは、
吸気行程中または／および圧縮行程中に、気筒内に燃料と吸気との予混合気が形成され、該予混合気が燃焼に供される予混合圧縮着火燃焼を行う予混合圧縮着火燃焼内燃機関において、
前記気筒内中央部に吸気を導入する第１吸気ポートと、
前記気筒内壁面付近に吸気を導入する第２吸気ポートと、
前記第１吸気ポートと前記第２吸気ポートとの少なくとも一方にＥＧＲガスを導入する排気再循環手段と、
該排気再循環手段によって前記第１吸気ポートまたは／および前記第２吸気ポートに導入されるＥＧＲガスの量を制御する再循環排気量制御手段と、
前記予混合圧縮着火燃焼内燃機関の運転状態を検出する運転状態検出手段と、
を備え、
前記運転状態検出手段によって検出された前記予混合圧縮着火燃焼内燃機関の運転状態に応じて、前記第１吸気ポートまたは／および前記第２吸気ポートに導入されるＥＧＲガスの量を制御することよって、前記気筒内の再循環排気率の分布を制御することを特徴とする。
【０００９】
ここで、再循環排気率とは、気体（吸気または予混合気）中におけるＥＧＲガス量の割合のことである。以下、この再循環排気率をＥＧＲ率と称する。
【００１０】
本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムによれば、機関の運転状態に応じて、気筒内のＥＧＲ率の分布が制御される。予混合気においては、ＥＧＲ率が高くなると酸素濃度が低下するため該予混合気の着火性は低下し、ＥＧＲ率が低くなると酸素濃度が高くなるため該予混合気の着火性も高くなる。即ち、ＥＧＲ率を制御することで予混合気の着火性を制御することが出来る。更に、気筒内において中央部と壁面付近とでは異なったＥＧＲ率とすることで予混合気の着火遅れを不均一とし、予混合気の急激な燃焼を防止することが出来る。
【００１１】
本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムにおいては、第１吸気ポートまたは第２吸気ポートのいずれか一方にのみＥＧＲガスを導入する場合であっても、気筒内において、ＥＧＲガスが導入された吸気ポートによって吸気が導入された部分のＥＧＲ率は高くなるため、気筒内のＥＧＲ率の分布を制御することが出来る。
【００１２】
また、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムにおいては、第１吸気ポートおよび第２吸気ポートにＥＧＲガスを導入し、第１吸気ポートに導入されるＥＧＲガスの量および第２吸気ポートに導入されるＥＧＲガスの量を、機関の運転状態に応じて、それぞれ制御しても良い。
【００１３】
このような制御によれば、第１吸気ポートに導入されるＥＧＲガスの量および第２吸気ポートに導入されるＥＧＲガスの量をそれぞれ制御することで、第１吸気ポートによって導入される吸気（以下、第１吸気と称する）のＥＧＲ率と第２吸気ポートによって導入される吸気（以下、第２吸気と称する）のＥＧＲ率とをそれぞれ制御することが出来る。そのため、気筒内のＥＧＲ率の分布を機関の運転状態に応じて制御することが可能となる。
【００１４】
そこで、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムにおいては、機関の運転状態が低負荷運転領域にある場合、第１吸気ポートに導入されるＥＧＲガスの量よりも第２吸気ポートに導入されるＥＧＲガスの量を多くしても良い。
【００１５】
低負荷運転領域においては、燃料噴射量は少ないが、このような制御によれば、気筒内中央部のＥＧＲ率は低くなるため該気筒中央部の酸素濃度は高くなるため、該気筒内中央部での予混合気の着火性を確保することが出来る。また、低負荷運転領域においては、気筒内壁面付近の温度は比較的低温となるが、上記のような制御によれば、気筒内壁面付近のＥＧＲ率が高くなりＥＧＲガスの熱によって予混合気の温度を上昇させることが出来る。そのため、該気筒内壁面付近の予混合気における未燃成分の発生を抑制することが可能となる。
【００１６】
一方、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムにおいては、機関の運転状態が高負荷運転領域にある場合、第１吸気ポートに導入されるＥＧＲガスの量よりも第２吸気ポートに導入されるＥＧＲガスの量を少なくしても良い。
【００１７】
高負荷運転領域においては、気筒内中央部の温度が高くなり過早着火が発生し易くなるが、このような制御によれば、気筒内中央部のＥＧＲ率は高くなるため該気筒中央部の酸素濃度は低くなり、該気筒内中央部での予混合気の着火性を抑制することが出来る。以て過早着火を抑制することが可能となる。尚、高負荷運転領域においては、気筒内の温度は高くなっているため、ＥＧＲガスの温度による影響は低負荷時と比較して非常に小さい。また、上記のような制御によれば、気筒内壁面付近のＥＧＲ率は気筒内中央部よりも低くなり、気筒内壁面付近の予混合気と気筒内中央部の予混合気との着火遅れは不均一となる。そのため、予混合気の急激な燃焼が抑制され、以て燃焼騒音の悪化を抑制することが可能となる。
【００１８】
また、本発明に係る内燃機関が、予混合圧縮着火燃焼と、予混合気を形成せずに燃焼を行う通常燃焼とを選択的に切り換える内燃機関であった場合、該内燃機関が通常燃焼を行うときは、第１吸気ポートに導入されるＥＧＲガスの量と第２吸気ポートに導入されるＥＧＲガスの量とが略同一となるよう制御しても良い。即ち、第１吸気と第２吸気とのＥＧＲ率を略同一とすることで気筒内のＥＧＲ率の分布を略均一に制御する。
【００１９】
内燃機関が通常燃焼を行うときは、気筒内のＥＧＲ率の分布を略均一に制御することで、燃焼を安定させ、ドライバビィリティやエミッションの悪化を抑制することが出来る。従って、予混合圧縮着火燃焼と通常燃焼とを切り換える内燃機関であっても、両方の燃焼をより好適に行うことが可能となる。
【００２０】
本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムにおいては、第１吸気ポートまたは／および第２吸気ポートに導入されるＥＧＲガスの量を制御すると共に、第１吸気の導入量と第２吸気の導入量とを、機関の運転状態に応じて、それぞれ制御しても良い。
【００２１】
本発明に係る第２吸気は気筒内壁面付近に導入されるため、該第２吸気が気筒内に流入されることによって、気筒内において壁面に沿った旋回流が生起される。上記のような構成によれば、第１吸気の導入量と第２吸気の導入量とを制御することで、この旋回流のスワール比を制御し、該スワール比を制御することで、気筒内における第１吸気と第２吸気との分布範囲を制御する。
【００２２】
第２吸気の導入量を増加させる、または／および第１吸気の導入量を減少させると、前記旋回流のスワール比が高くなる。該スワール比が高くなると、第２吸気の分布範囲が気筒内壁面付近により集中することになり、それによって第１吸気の分布範囲が気筒内壁面側へ広がることになる。一方、第２吸気の導入量を減少させる、または／および第１吸気の導入量を増加させると、前記旋回流のスワール比が低くなる。該スワール比が低くなると、第２吸気の分布範囲が気筒内中央部側に広がることになり、それによって第１吸気の分布範囲が気筒内中央部により集中することになる。従って、ＥＧＲ率の異なる第１吸気の導入量と第２吸気の導入量とをそれぞれ制御することによって、気筒内壁面に沿った旋回流のスワール比を制御し、以て気筒内のＥＧＲ率分布をより細かく制御することが出来る。
【００２３】
例えば、（１）機関の運転状態が低負荷運転領域においても比較的低い負荷領域にあるときは、第１吸気ポートに導入されるＥＧＲガス量よりも第２吸気ポートに導入されるＥＧＲガス量を多くする、即ち、第１吸気のＥＧＲ率よりも第２吸気のＥＧＲ率を高くすると共に、第２吸気の導入量をより増加させる。そして、（２）低負荷運転領域内において機関負荷が大きくなると共に、第１吸気のＥＧＲガス率より第２吸気のＥＧＲガス率を高くした状態で、第２吸気の導入量をより減少させる。このような制御（１）、（２）によれば、気筒内壁面付近の温度がより低いときは気筒内壁面付近のＥＧＲ率をより集中的に高くすることが出来、効率的に気筒内壁面付近の予混合気の温度を上昇させることが可能となる。また、気筒内中央部においては、機関負荷が大きくなるにつれて、即ち温度上昇に応じてＥＧＲ率の低い範囲を小さくすることで、予混合気の着火性が徐々に抑えられ着火時期をより適正な時期とすることが出来る。
【００２４】
一方、（３）機関の運転状態が高負荷運転領域において比較的低い負荷領域にあるときには、第１吸気ポートに導入されるＥＧＲガス量よりも第２吸気ポートに導入されるＥＧＲガス量を少なくする、即ち、第１吸気のＥＧＲ率より第２吸気のＥＧＲ率を低くすると共に、第２吸気の導入量をより減少させる。そして、（４）機関負荷が大きくなると共に、第１吸気のＥＧＲガス率より第２吸気のＥＧＲガス率を低くした状態で、第２吸気の導入量をより増加させる。このような制御（３）、（４）によれば、気筒内中央部においては、機関負荷が大きくなるにつれて、即ち温度上昇に応じてＥＧＲ率の高い範囲を大きくすることで、予混合気の着火性がより抑制され着火時期をより適正な時期とすることが出来る。
【００２５】
また、機関の運転状態が低負荷運転領域から高負荷運転領域へと移っていくような過渡運転状態にあっても、上記のような（１）、（２）、（３）、（４）の制御を連続的に行うことによって、気筒内のＥＧＲ率の分布を連続的に制御することが出来るため、機関の運転状態に応じて、より好適な予混合圧縮着火燃焼を行うことが可能となる。
【００２６】
また、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムにおいて、第１吸気ポートまたは／および第２吸気ポートに導入されるＥＧＲガスの量を制御すると共に、第１吸気ポートによる吸気時期と、第２吸気ポートによる吸気時期とを、機関の運転状態に応じて、それぞれ制御しても良い。
【００２７】
ここで、吸気時期とは、それぞれの吸気ポートによる吸気の導入が開始される時期および吸気の導入が停止される時期のことである。
【００２８】
吸気行程において、最初に第２吸気ポートによって第２吸気を気筒内に導入し、次に第１吸気ポートによって第１吸気を気筒内に導入することによって、第２吸気が気筒内壁面付近により分布し易くなり、第１吸気が気筒内中央部により分布し易くなる。従って、例えば、第１吸気および第２吸気のＥＧＲ率をそれぞれ制御すると共に、それぞれの吸気時期を制御することによって、前記のような第１吸気の導入量と第２吸気の導入量とをそれぞれ制御した場合と同様、気筒内のＥＧＲ率分布をより細かく制御することが出来る。また、機関の運転状態が低負荷運転領域から高負荷運転領域へと移っていくような過渡運転状態にあっても、気筒内のＥＧＲ率の分布を連続的に制御することが出来るため、機関の運転状態に応じて、より好適な予混合圧縮着火燃焼を行うことが可能となる。
【００２９】
さらに、第１吸気ポートと第２吸気ポートとの少なくとも一方による吸気導入と吸気導入停止とを吸気行程中に複数回繰り返すよう制御しても良い。
【００３０】
このような制御によれば、気筒内において、ＥＧＲ率の高い予混合気とＥＧＲ率の低い予混合気とを多層化することが出来る。そのため、気筒内における予混合気の着火遅れがより不均一となるため、燃焼をより穏やかにすることが出来る。従って、より高い負荷領域で予混合燃焼を行うことが可能となる。
【００３１】
また、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムでは、これまで説明したように各吸気ポートによる吸気導入箇所を気筒内中央部と気筒内壁面付近とに限定することなく、単に複数の吸気ポートと、少なくとも一の吸気ポートにＥＧＲガスを導入する排気再循環手段と、吸気ポートに導入されるＥＧＲガスの量を制御する再循環排気量制御手段と、吸気時期を吸気ポート毎にそれぞれ制御する吸気時期制御手段と、を備え、機関の運転状態に応じて、吸気ポートに導入されるＥＧＲガスの量と、吸気ポート毎の吸気時期とを制御することによって、前記気筒内の再循環排気率の分布を制御しても良い。
【００３２】
吸気行程において、最初に一の吸気ポートにより吸気を気筒内に導入し、次に他の吸気ポートにより吸気を気筒内に導入した場合、最初に導入された吸気は気筒内の下側により分布し易く、次に導入された吸気は気筒内の上側により分布し易くなる。従って、吸気ポート毎の吸気導入箇所が前記第１吸気ポートと前記第２吸気ポートとのように限定されていない場合であっても、ＥＧＲ率の異なる吸気の吸気時期をそれぞれ制御することによって気筒内のＥＧＲ率の分布を制御することが出来る。
【００３３】
また、この場合においても、少なくとも一の吸気ポートによる吸気導入と吸気停止とを、吸気行程中に複数回繰り返すよう制御することで、気筒内において、ＥＧＲ率の高い予混合気とＥＧＲ率の低い予混合気とを多層化することが出来る。そのため、気筒内における予混合気の着火遅れがより不均一となるため、燃焼をより穏やかにすることが出来る。従って、より高い負荷領域で予混合燃焼を行うことが可能となる。
【００３４】
【発明の実施の形態】
＜第１の実施の形態＞
以下、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムの具体的な実施の形態について図面に基づいて説明する。
【００３５】
図１および図２は、本実施の形態に係る内燃機関とその再循環排気制御システムの概略構成を示す図である。
【００３６】
図１に示す内燃機関１は、４つの気筒２（１つの気筒のみ図示）を有する多気筒ディーゼル機関である。気筒２の略中心部には燃焼室に直接燃料を噴射する燃料噴射弁１０が備えられている。また、気筒２には第１吸気ポート３と第２吸気ポート４と２つの排気ポート５が備えられている。
【００３７】
第１吸気ポート３と第２吸気ポート４とは、インテークマニホルド１２と連通されており、インテークマニホルド１２は、吸気通路１１に接続されている。また、２つの排気ポート５はエキゾーストマニホルド１３と連通されており、エキゾーストマニホルド１３は排気通路１４に接続されている。
【００３８】
第１吸気ポート３は、気筒２の軸方向下向きに形成され、且つ該第１吸気ポート３の気筒２への開口部は第２吸気ポート４の気筒２への開口部よりも気筒２の中心により近くなるように設置されている。一方、第２吸気ポート４は、該第２吸気ポートによって導入される吸気によって気筒２の内壁面に沿って横方向旋回流が生起されるよう気筒２に対して接線方向に設置されている。このような構成によって、第１吸気ポート３によって導入される吸気（以下、第１吸気と称する）は気筒２内中央部に導入され、第２吸気ポート４によって導入される吸気（以下、第２吸気と称する）は気筒２内壁面部付近に導入される。
【００３９】
また、２つの排気ポート５には、図示しない排気弁がそれぞれ設けられており、第１吸気ポート３と第２吸気ポート４とには、図２に示すとおり、それぞれ第１吸気弁６と第２吸気弁７とが設けられている。第１吸気弁６と第２吸気弁７とには、各吸気弁６，７の開閉時期やリフト量をそれぞれ制御する第１可変動弁機構８と第２可変動弁機構９とがそれぞれ設けられている。可変動弁機構としては電磁駆動弁等が例示出来る。
【００４０】
また、本実施の形態に係る内燃機関１には、該内燃機関１から排出された排気の一部を吸気系へ再循環させる排気再循環装置２０が備えられている。該排気再循環装置２０は、エキゾーストマニホルド１３と連通されている主排気再循環通路２１と、該主排気再循環通路２１と第１吸気ポート３とを連通する第１ＥＧＲ通路２２と、該主排気再循環通路２１と第２吸気ポート４とを連通する第２ＥＧＲ通路２３と、を備えている。また、第１ＥＧＲ通路２２と第２ＥＧＲ通路２３とには、電磁弁等からなり印加電圧の大きさに応じて第１ＥＧＲ通路２２もしくは第２ＥＧＲ通路２３内を流れる排気（以下、ＥＧＲガスと称する）の流量を調整する第１ＥＧＲ弁２４と第２ＥＧＲ弁２５とがそれぞれ設けられている。
【００４１】
このように構成された排気再循環装置２０では、第１ＥＧＲ弁２４または第２ＥＧＲ弁２５が開弁されると、内燃機関１から排出された排気の一部（ＥＧＲガス）がエキゾーストマニホルド１３を介して主排気再循環通路２１へ流入し、該主排気再循環通路２１を流通するＥＧＲガスが、第１ＥＧＲ通路２２または第２ＥＧＲ通路２３を通って、第１吸気ポート３または第２吸気ポート４へ導入される。各吸気ポート３，４に導入されたＥＧＲガスは新気（空気）と混ざり合って吸気を形成し、該吸気が気筒２内へ導入される。また、第１ＥＧＲ弁２４と第２ＥＧＲ弁２５によって各吸気ポート３，４に導入されるＥＧＲガス量を制御することで、第１吸気と第２吸気とのＥＧＲ率がそれぞれ制御される。
【００４２】
ここで、各吸気のおいてＥＧＲ率が高くなると酸素濃度が低くなり、ＥＧＲ率が低くなると酸素濃度は高くなる。そのため、気筒内において、ＥＧＲ率の高い吸気が導入された部分では予混合気の着火性は抑制され、ＥＧＲ率の低い吸気が導入された部分では予混合気の着火性は向上する。また、ＥＧＲガスの温度は吸気通路１１から導入される新気（空気）の温度よりもかなり高いため、ＥＧＲ率の高い吸気の温度は高くなる。そのため、機関の運転状態が低負荷運転領域にあるときのように気筒２内の温度が低いときは、ＥＧＲ率の高い吸気が導入された部分の予混合気の温度は高くなる。機関の運転状態が高負荷運転領域となると気筒２内の温度はかなり高くなっているため、ＥＧＲガスの温度による影響は小さくなる。
【００４３】
以上述べたように構成された内燃機関１には、該内燃機関１を制御するための電子制御ユニット（ＥＣＵ：ＥｌｅｃｔｒｏｎｉｃＣｏｎｔｒｏｌＵｎｉｔ）３０が併設されている。このＥＣＵ３０は、内燃機関１の運転条件や運転者の要求に応じて内燃機関１の運転状態を制御するユニットである。
【００４４】
ＥＣＵ３０は、内燃機関１の出力軸の回転角に応じた信号を出力するクランクポジションセンサ３１や、アクセル開度に応じた信号を出力するアクセル開度センサ３２等の各種センサと電気的に接続されており、これらセンサの出力信号がＥＣＵ３０に入力される。
【００４５】
一方、ＥＣＵ３０は、燃料噴射弁１０、第１可変動弁機構８、第２可変動弁機構９、第１ＥＧＲ弁２４、第２ＥＧＲ弁２５等と電気的に接続されており、上記各部がＥＣＵ３０によって制御される。
【００４６】
ＥＣＵ３０は、ＣＰＵ、ＲＯＭ、ＲＡＭ等を備えており、例えば、クランクポジションセンサ３１がパルス信号を出力する時間的な間隔等に基づき機関回転数を算出し、アクセル開度センサ３２の出力信号等に基づき機関負荷を算出する。また、ＥＣＵ３０は機関回転数と機関負荷とから内燃機関１の運転状態を判断する。
【００４７】
また、本実施の形態に係る内燃機関１は、吸気行程中または圧縮行程中に燃料噴射弁１０により気筒２内へ燃料を噴射することで、燃料と吸気との予混合気が形成され、該予混合気が燃焼に供される、いわゆる予混合圧縮着火燃焼を行う内燃機関である。
【００４８】
次に、本実施の形態に係る再循環排気システムによる気筒内のＥＧＲガス率の分布制御について説明する。
【００４９】
図３および４は、本実施の形態に係る気筒２内のＥＧＲ率の分布を示す図である。図３および４の一点鎖線はＥＧＲ率分布を示している。
【００５０】
本実施の形態に係る再循環排気システムにおいては、内燃機関１が低負荷運転領域で運転されているときは、第１ＥＧＲ弁２４の開度は第２ＥＧＲ弁２５の開度よりも小さくなるよう制御される。即ち、第１吸気ポート３に導入されるＥＧＲガス量が第２吸気ポートに導入されるＥＧＲガス量よりも少なくなるよう制御される。このため、第１吸気のＥＧＲ率が第２吸気のＥＧＲ率よりも低くなる。
【００５１】
本実施の形態に係る内燃機関１においては、上述したように、第１吸気は気筒２内中央部に導入され、第２吸気は気筒２内壁面付近に導入される。従って、第１吸気のＥＧＲ率が第２吸気のＥＧＲ率よりも低くなると、気筒２内におけるＥＧＲ率の分布は、図３に示すように、中央部のＥＧＲ率が低く、壁面付近のＥＧＲ率が高くなる。
【００５２】
低負荷運転領域においては、燃料噴射量は少ないが、このような制御によれば、気筒２内中央部のＥＧＲ率は低くなる、即ち気筒２内中央部の酸素濃度は比較的高くなるため、該気筒２内中央部での予混合気の着火性を確保することが出来る。また、低負荷運転領域においては、気筒２内壁面付近の温度は比較的低温となるが、上記のような制御によれば、気筒２内壁面付近のＥＧＲ率が高くなるため、ＥＧＲガスの熱によって内壁面付近の予混合気の温度を上昇させることが出来る。そのため、該気筒２内壁面付近の予混合気における未燃成分の発生を抑制することが可能となる。
【００５３】
一方、本実施の形態に係る再循環排気制御システムにおいては、内燃機関１が高負荷運転領域で運転されているときは、第１ＥＧＲ弁２４の開度は第２ＥＧＲ弁２５の開度よりも大きくなるよう制御される。即ち、第１吸気ポート３に導入されるＥＧＲガス量が第２吸気ポートに導入されるＥＧＲガス量よりも多くなるよう制御される。このため、第１吸気のＥＧＲ率が第２吸気のＥＧＲ率よりも高くなる。
【００５４】
第１吸気のＥＧＲ率が第２吸気のＥＧＲ率よりも高くなると、気筒２内におけるＥＧＲ率の分布は、図４に示すように、中央部のＥＧＲ率が高く、壁面付近のＥＧＲ率が低くなる。
【００５５】
高負荷運転領域においては、気筒２内中央部の温度が高くなり過早着火が発生し易くなるが、このような制御によれば、気筒２内中央部のＥＧＲ率は高くなる、即ち気筒２内中央部の酸素濃度は低くなるため、該気筒２内中央部での予混合気の着火性を抑制することが出来、以て過早着火を抑制することが可能となる。また、上記のような制御によれば、気筒２内壁面付近のＥＧＲ率は気筒２内中央部よりも低くなる、即ち気筒２内の酸素分布は不均一となるため、気筒２内壁面付近の予混合気と気筒２内中央部の予混合気との着火遅れは不均一となる。そのため、予混合気の急激な燃焼が抑制され、以て燃焼騒音の悪化を抑制することが可能となる。
【００５６】
尚、第１吸気ポート３と第２吸気ポート４とのいずれか一方にのみＥＧＲガスを導入することで、気筒２内のＥＧＲ率の分布を制御しても良い。また、第１ＥＧＲ通路２２と第２ＥＧＲ通路２３とのいずれか一方が設けられていない構成とした場合であっても、第１吸気ポート３と第２吸気ポート４とのいずれか一方にのみ導入されるＥＧＲガスの量を制御することで、気筒２内のＥＧＲ率の分布を制御することが出来る。
【００５７】
また、本実施の形態に係る内燃機関１を、予混合圧縮着火燃焼と、予混合気を形成せずに燃焼を行う通常燃焼（いわゆる拡散燃焼）とを選択的に切り換える内燃機関とした場合、内燃機関１が通常燃焼を行うときは、第１吸気ポート３に導入されるＥＧＲガスの量と第２吸気ポー４トに導入されるＥＧＲガスの量とが略同一となるよう制御される。即ち、第１吸気と第２吸気とのＥＧＲ率を略同一とすることで気筒２内のＥＧＲ率の分布を略均一に制御する。
【００５８】
通常燃焼時は、気筒２内のＥＧＲ率の分布を略均一に制御することで、燃焼を安定させ、ドライバビィリティやエミッションの悪化を抑制することが出来る。従って、予混合圧縮着火燃焼と通常燃焼とを切り換える内燃機関であっても、両方の燃焼をより好適に行うことが可能となる。
【００５９】
＜第２の実施の形態＞
次に、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムの第２の実施の形態について図面に基づいて説明する。本実施の形態に係る内燃機関と再循環排気制御システムのハード構成は、上述した第１の実施の形態と同様であるため説明を割愛し、本実施の形態に係る再循環排気制御システムによる気筒内のＥＧＲガス率の分布制御について以下に説明する。
【００６０】
図５〜８は、本実施の形態に係る気筒２内のＥＧＲ率の分布を示す図である。図５〜８の一点鎖線はＥＧＲ率分布を示している。一点鎖線の間隔が小さい程ＥＧＲ率分布が密になっていることを示し、一点鎖線の間隔が大きい程ＥＧＲ率分布が疎になっていることを示している。
【００６１】
本実施の形態に係る再循環排気制御システムにおいては、上述した第１の実施の形態と同様、内燃機関１の運転状態に応じて、第１ＥＧＲ弁２４と第２ＥＧＲ弁２５との開度を制御することで、第１吸気と第２吸気とのＥＧＲ率をそれぞれ制御すると共に、吸気行程における第１吸気弁６と第２吸気弁７との閉弁時期を第１可変動弁機構８と第２可変動弁機構９とによってそれぞれ制御することで、気筒２内壁面に沿った旋回流のスワール比を制御する。
【００６２】
本実施の形態に係る第２吸気ポートの配置によれば、第２吸気が気筒２内に導入されると、気筒２内において壁面に沿った旋回流が生起される。この旋回流のスワール比を制御することで、気筒内における第１吸気と第２吸気との分布範囲を制御することが出来る。
【００６３】
第２吸気弁７の閉弁時期を遅角させる、または／および第１吸気弁６の閉弁時期を進角させると、第２吸気の気筒２内への導入量が相対的に増加する。第２吸気の導入量が増加すると、気筒２内壁面に沿った旋回流のスワール比が高くなる。該スワール比が高くなると、第２吸気の分布範囲が気筒２内壁面付近により集中することになり、それによって第１吸気の分布範囲が気筒２内壁面側へ広がることになる。一方、第１吸気弁６の閉弁時期を遅角させる、または／および第２吸気弁７の閉弁時期を進角させると、第２吸気の気筒２内への導入量が相対的に減少する。第２吸気の導入量が減少すると、気筒２内壁面に沿った旋回流のスワール比が低くなる。該スワール比が低くなると、第２吸気の分布範囲が気筒２内中央部側に広がることになり、それによって第１吸気の分布範囲が気筒２内中央部により集中することになる。
【００６４】
そこで、本実施の形態に係る再循環排気制御システムにおいては、（１）内燃機関１の運転状態が低負荷運転領域においても比較的低い負荷領域にあるときは、第１吸気のＥＧＲ率よりも第２吸気のＥＧＲ率を高くすると共に、第２吸気弁７の閉弁時期を遅角させる。そして、（２）低負荷運転領域内において内燃機関１の機関負荷が大きくなると共に、第１吸気のＥＧＲガス率より第２吸気のＥＧＲガス率を高くした状態で、第２吸気弁７の閉弁時期を進角させる。
【００６５】
このような制御（１）、（２）によれば、気筒２内壁面付近の温度がより低いときは、図５に示すように、気筒２内壁面付近のＥＧＲ率をより集中的に高くすることが出来、効率的に気筒２内壁面付近の予混合気の温度を上昇させることが可能となる。また、気筒２内中央部においては、機関負荷が大きくなると、即ち温度が上昇すると、図６に示すように、ＥＧＲ率の低い範囲を小さくすることで、予混合気の着火性が徐々に抑えられ着火時期をより適正な時期とすることが出来る。
【００６６】
一方、（３）内燃機関１の運転状態が高負荷運転領域において比較的低い負荷領域にあるときには、第１吸気のＥＧＲ率より第２吸気のＥＧＲ率を低くすると共に、第２吸気弁７の閉弁時期を進角させる。そして、（４）内燃機関１の機関負荷が大きくなると共に、第１吸気のＥＧＲガス率より第２吸気のＥＧＲガス率を低くした状態で、第２吸気弁７の閉弁時期を遅角させる。このような制御（３）、（４）によれば、機関負荷が比較的小さいときは、図７に示すように、気筒２内中央部におけるＥＧＲ率の高い範囲を小さくし、機関負荷が大きくなるにつれて、即ち温度上昇に応じて、図８に示すように、ＥＧＲ率の高い範囲を大きくすることで、予混合気の着火性がより好適に抑制され着火時期をより適正な時期とすることが出来る。
【００６７】
上記のように、本実施の形態に係る再循環排気制御システムによれば、気筒内のＥＧＲ率分布をより細かく制御することが出来るため、より広い運転領域でより好適な予混合圧縮着火燃焼を行うことが可能となる。
【００６８】
また、本実施の形態に係る再循環排気制御システムにおいては、内燃機関１の運転状態が低負荷運転領域から高負荷運転領域へと移っていくような過渡運転状態にある場合、上記のような（１）、（２）、（３）、（４）の制御を連続的に行うことによって、気筒２内のＥＧＲ率の分布を連続的に制御することが出来るため、内燃機関１の運転状態に応じて、より好適な予混合圧縮着火燃焼を行うことが可能となる。
【００６９】
尚、本実施の形態に係る再循環排気制御システムにおいては、吸気行程における第１吸気弁６と第２吸気弁７とのバルブリフト量を第１可変動弁機構８と第２可変動弁機構９とによってそれぞれ制御することで、第１吸気と第２吸気との気筒２内への導入量をそれぞれ制御し、気筒２内のスワール比を制御しても良い。
【００７０】
＜第３の実施の形態＞
次に、本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムの第３の実施の形態について図面に基づいて説明する。本実施の形態に係る内燃機関と再循環排気制御システムのハード構成は、上述した第１の実施の形態と同様であるため説明を割愛し、本実施の形態に係る再循環排気システムによる気筒内のＥＧＲガス率の分布制御について以下に説明する。
【００７１】
本実施の形態に係る再循環排気制御システムにおいては、上述した第１の実施の形態と同様、内燃機関１の運転状態に応じて、第１ＥＧＲ弁２４と第２ＥＧＲ弁２５との開度を制御することで、第１吸気と第２吸気とのＥＧＲ率をそれぞれ制御すると共に、吸気行程における第１吸気弁６と第２吸気弁７との開弁時期および閉弁時期を第１可変動弁機構８と第２可変動弁機構９とによってそれぞれ制御することで、第１吸気と第２吸気との気筒２内への吸気時期をそれぞれ制御する。
【００７２】
図９は、本実施の形態に係る第１吸気弁６と第２吸気弁７との吸気行程における開弁時期および閉弁時期を示すバルブプロフィールの一例である。点線は吸気行程を示し、実線は開弁時期および閉弁時期を示す。
【００７３】
本実施の形態に係る再循環排気制御システムにおいては、例えば、図９に示すように、吸気行程において、第１吸気弁６の開閉時期を第２吸気弁７の開閉時期よりも遅角させる。このような制御によって、最初に第２吸気が気筒２内導入され、次に第１吸気が気筒２内に導入されるため、第２吸気が気筒２内壁面付近により分布し易くなり、第１吸気が気筒２内中央部により分布し易くなる。
【００７４】
従って、本実施の形態に係る再循環排気制御システムによれば、内燃機関１の運転状態に応じて、第１吸気のＥＧＲ率と第２吸気のＥＧＲ率とをそれぞれ制御すると共に、第１吸気の吸気時期と第２吸気の吸気時期とをそれぞれ制御することによって、上述した第２の実施の形態と同様、気筒２内のＥＧＲ率分布をより細かく制御することが出来る。そのため、より広い運転領域でより好適な予混合圧縮着火燃焼を行うことが可能となる。
【００７５】
また、機関の運転状態が低負荷運転領域から高負荷運転領域へと移っていくような過渡運転状態にあっても、上述した第２の実施の形態と同様、気筒内のＥＧＲ率の分布を連続的に制御することが出来るため、運転状態に応じて、より好適な予混合圧縮着火燃焼を行うことが可能となる。
【００７６】
さらに、本実施の形態に係る再循環排気制御システムにおいては、第１吸気と第２吸気のＥＧＲ率をそれぞれ制御すると共に、第１吸気弁６と第２吸気弁７との少なくとも一方の開弁と閉弁とが吸気行程において複数回繰り返されるよう制御しても良い。
【００７７】
図１０は、このような制御を行った場合の気筒２内のＥＧＲ率の分布の一例を示す図である。図１０の一点鎖線はＥＧＲ率分布を示している。
【００７８】
このような制御によれば、図１０に示すように、気筒２内のＥＧＲ率の分布を多層化することが出来る。そのため、予混合気の着火遅れがより不均一となり、燃焼をより穏やかにすることが出来る。従って、より高い負荷領域で予混合燃焼を行うことが可能となる。
【００７９】
尚、本実施の形態に係る再循環排気制御システムのように、内燃機関１の運転状態に応じて、第１吸気のＥＧＲ率と第２吸気のＥＧＲ率とをそれぞれ制御すると共に、第１吸気と第２吸気との気筒２内への吸気時期をそれぞれ制御することによって、気筒２内のＥＧＲ率分布を制御する場合、第１吸気ポート３と第２吸気ポート４との配置が上述したような配置（即ち、第１吸気は気筒２内中央部に導入され、第２吸気は気筒２内壁面付近に導入されるような配置）となっていなくても、吸気行程において最初に導入された吸気は気筒２内下側により分布し易く、次に導入された吸気は気筒２内上側により分布し易くなるため、気筒２内のＥＧＲ率の分布を制御することが出来る。
【００８０】
また、第１吸気ポート３と第２吸気ポート４との配置を上述したような配置に限定しなくても、第１吸気弁６と第２吸気弁７との少なくともいずれか一方の開弁と閉弁とが吸気行程において複数回繰り返されるよう制御することによって、気筒２内のＥＧＲ率の分布を多層化することが出来る。
【００８１】
【発明の効果】
本発明に係る予混合圧縮着火燃焼内燃機関の再循環排気制御システムによれば、低負荷運転領域においては、着火性を確保しつつ未燃成分の排出を抑制出来、また、高負荷運転領域においては、過早着火や燃焼騒音の悪化を抑制出来るため、より広い運転領域でより好適な予混合圧縮着火燃焼を行うことが可能となる。
【図面の簡単な説明】
【図１】本発明に係る内燃機関とその再循環排気制御システムの概略構成を示す第１の図
【図２】本発明に係る内燃機関とその再循環排気制御システムの概略構成を示す第２の図
【図３】第１の実施の形態に係る気筒内のＥＧＲ率分布を示す第１の図
【図４】第１の実施の形態に係る気筒内のＥＧＲ率分布を示す第２の図
【図５】第２の実施の形態に係る気筒内のＥＧＲ率分布を示す第１の図
【図６】第２の実施の形態に係る気筒内のＥＧＲ率分布を示す第２の図
【図７】第２の実施の形態に係る気筒内のＥＧＲ率分布を示す第３の図
【図８】第２の実施の形態に係る気筒内のＥＧＲ率分布を示す第４の図
【図９】第３の実施の形態に係る第１吸気弁と第２吸気弁との吸気行程における開弁時期および閉弁時期を示すバルブプロフィール
【図１０】第３実施の形態に係る気筒内のＥＧＲ率分布を示す図
【符号の説明】
１・・・内燃機関
２・・・気筒
３・・・第１吸気ポート
４・・・第２吸気ポート
５・・・排気ポート
６・・・第１吸気弁
７・・・第２吸気弁
８・・・第１可変動弁機構
９・・・第２可変動弁機構
１０・・燃料噴射弁
１１・・吸気通路
１２・・インテークマニホルド
１３・・エキゾーストマニホルド
１４・・排気通路
２０・・排気再循環装置
２１・・主排気再循環通路
２２・・第１ＥＧＲ通路
２３・・第２ＥＧＲ通路
２４・・第１ＥＧＲ弁
２５・・第２ＥＧＲ弁
３０・・ＥＣＵ
３１・・クランクポジションセンサ
３２・・アクセル開度センサ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a premixed compression ignition combustion internal combustion engine in which a premixed gas to be used for combustion is formed in a combustion chamber.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an internal combustion engine, by injecting fuel into a cylinder during an intake stroke or a compression stroke, a premixed air of the fuel and intake air (air) is formed, and the premixed air is subjected to combustion. The development of a homogeneous charge compression ignition combustion internal combustion engine that suppresses the emission of NOx and smoke has been promoted.
[0003]
In such a premixed compression ignition combustion internal combustion engine, there is a possibility that so-called premature ignition may occur, in which the formed premixed gas is ignited and burned before reaching the top dead center of the compression stroke due to a temperature rise in the cylinder. . Therefore, a technique for preventing the occurrence of premature ignition by controlling the amount of recirculated exhaust gas introduced into the combustion chamber based on the NOx concentration in the exhaust gas is known (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP 2001-152853 A
[Patent Document 2]
JP-A-2000-120457
[Patent Document 1]
JP-A-10-274104
[Patent Document 2]
JP-A-6-229325
[0005]
[Problems to be solved by the invention]
In a homogeneous charge compression ignition combustion internal combustion engine, when the engine is operated at a high load, premature ignition is likely to occur because the temperature in the cylinder, particularly in the center of the cylinder, increases. Further, the premixed gas is substantially uniformly distributed in the cylinder, that is, since the concentration distribution of the air and the fuel in the cylinder is substantially uniform, the combustion of the premixed gas becomes sharp at a high temperature and the combustion noise is increased. May worsen. On the other hand, when the engine is operating at a low load or before the engine is warmed up, the temperature near the inner wall surface of the cylinder is low and unburned components may be generated in the premixed air near the inner wall surface of the cylinder.
[0006]
The present invention has been made in view of the above-described problems, and provides a technique capable of performing more suitable premixed compression ignition combustion in a wider operating region in a premixed compression ignition combustion internal combustion engine. That is the task.
[0007]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
That is, the present invention is a recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine, which is provided with a plurality of intake ports, and introduces a part of exhaust gas into at least one intake port (hereinafter, intake port). The exhaust gas introduced into the intake port is referred to as EGR gas), and the distribution of the EGR gas rate in the cylinder is controlled by controlling the amount of the EGR gas introduced into the intake port.
[0008]
More specifically, a recirculation exhaust control system for a premixed compression ignition combustion internal combustion engine according to the present invention comprises:
A premixed compression ignition internal combustion engine that performs premixed compression ignition combustion in which a premixed mixture of fuel and intake air is formed in a cylinder during an intake stroke and / or a compression stroke, and the premixed air is used for combustion. At
A first intake port for introducing intake air into a central portion of the cylinder;
A second intake port for introducing intake air near the cylinder inner wall surface,
Exhaust recirculation means for introducing EGR gas into at least one of the first intake port and the second intake port;
Recirculation exhaust amount control means for controlling the amount of EGR gas introduced into the first intake port and / or the second intake port by the exhaust gas recirculation means;
Operating state detecting means for detecting an operating state of the premixed compression ignition combustion internal combustion engine,
With
By controlling the amount of EGR gas introduced into the first intake port and / or the second intake port according to the operating state of the premixed compression ignition combustion internal combustion engine detected by the operating state detecting means. Controlling the distribution of the recirculation exhaust rate in the cylinder.
[0009]
Here, the recirculation exhaust rate is a ratio of the EGR gas amount in the gas (intake air or premixed gas). Hereinafter, this recirculation exhaust rate is referred to as an EGR rate.
[0010]
According to the recirculated exhaust gas control system for a homogeneous charge compression ignition combustion internal combustion engine according to the present invention, the distribution of the EGR rate in the cylinder is controlled according to the operating state of the engine. In the premixed gas, the ignitability of the premixed gas decreases because the oxygen concentration decreases as the EGR rate increases, and the ignitability of the premixed gas increases because the oxygen concentration increases when the EGR rate decreases. That is, the ignitability of the premixed gas can be controlled by controlling the EGR rate. Further, by setting different EGR rates in the center portion and near the wall surface in the cylinder, the ignition delay of the premixed gas is made non-uniform, and rapid combustion of the premixed gas can be prevented.
[0011]
In the recirculation exhaust control system of the premixed compression ignition combustion internal combustion engine according to the present invention, even if EGR gas is introduced only into one of the first intake port and the second intake port, the EGR gas is introduced into the cylinder. Since the EGR rate in the portion where the intake air is introduced by the intake port into which the EGR gas is introduced becomes high, the distribution of the EGR rate in the cylinder can be controlled.
[0012]
In the recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to the present invention, the EGR gas is introduced into the first intake port and the second intake port, and the amount of the EGR gas introduced into the first intake port And the amount of EGR gas introduced into the second intake port may be controlled in accordance with the operating state of the engine.
[0013]
According to such control, by controlling the amount of the EGR gas introduced into the first intake port and the amount of the EGR gas introduced into the second intake port, respectively, the intake air introduced by the first intake port ( Hereinafter, the EGR rate of the first intake and the EGR rate of the intake introduced by the second intake port (hereinafter the second intake) can be controlled. Therefore, it is possible to control the distribution of the EGR rate in the cylinder according to the operating state of the engine.
[0014]
Therefore, in the recirculation exhaust control system for the homogeneous charge compression ignition combustion internal combustion engine according to the present invention, when the operating state of the engine is in the low load operation range, the amount of the EGR gas introduced into the first intake port is smaller than the amount of the EGR gas introduced into the first intake port. (2) The amount of EGR gas introduced into the intake port may be increased.
[0015]
In the low load operation region, the fuel injection amount is small, but according to such control, the EGR rate in the central portion of the cylinder is low, so that the oxygen concentration in the central portion of the cylinder is high. Ignitability of the premixed gas can be ensured. In the low load operation region, the temperature near the cylinder inner wall surface is relatively low. However, according to the above-described control, the EGR rate near the cylinder inner wall surface increases, and the premixed gas is heated by the heat of the EGR gas. Can be raised. Therefore, it is possible to suppress the generation of unburned components in the premixed gas near the inner wall surface of the cylinder.
[0016]
On the other hand, in the recirculation exhaust control system of the homogeneous charge compression ignition combustion internal combustion engine according to the present invention, when the operation state of the engine is in the high load operation range, the amount of EGR gas introduced into the first intake port is smaller than the amount of EGR gas introduced into the first intake port. (2) The amount of the EGR gas introduced into the intake port may be reduced.
[0017]
In the high-load operation region, the temperature in the central portion of the cylinder increases and premature ignition easily occurs. However, according to such control, the EGR rate in the central portion of the cylinder increases, so that the central portion of the cylinder increases. The oxygen concentration becomes low, and the ignitability of the premixed gas at the center of the cylinder can be suppressed. Thus, premature ignition can be suppressed. In the high load operation range, the temperature in the cylinder is high, so the influence of the temperature of the EGR gas is very small as compared with the low load operation. Further, according to the above-described control, the EGR rate near the cylinder inner wall surface becomes lower than that in the central portion of the cylinder, and the ignition delay between the premixed gas near the cylinder inner wall surface and the premixed gas in the central portion of the cylinder is reduced. It becomes uneven. Therefore, abrupt combustion of the premixed gas is suppressed, and deterioration of combustion noise can be suppressed.
[0018]
Further, when the internal combustion engine according to the present invention is an internal combustion engine that selectively switches between premixed compression ignition combustion and normal combustion in which combustion is performed without forming a premixed gas, the internal combustion engine performs normal combustion. When performing the control, the control may be performed such that the amount of the EGR gas introduced into the first intake port and the amount of the EGR gas introduced into the second intake port become substantially the same. That is, the distribution of the EGR rate in the cylinder is controlled to be substantially uniform by making the EGR rates of the first intake air and the second intake air substantially the same.
[0019]
When the internal combustion engine performs normal combustion, by controlling the distribution of the EGR rate in the cylinder substantially uniformly, it is possible to stabilize combustion and suppress deterioration of driver viability and emission. Therefore, even in an internal combustion engine that switches between premixed compression ignition combustion and normal combustion, it is possible to more suitably perform both combustions.
[0020]
In the recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to the present invention, the amount of EGR gas introduced into the first intake port and / or the second intake port is controlled, and the amount of first intake introduced. The amount of the second intake air and the amount of the second intake air may be controlled in accordance with the operating state of the engine.
[0021]
Since the second intake air according to the present invention is introduced near the inner wall surface of the cylinder, a swirling flow along the wall surface is generated in the cylinder by flowing the second intake air into the cylinder. According to the above-described configuration, the swirl flow swirl ratio is controlled by controlling the amount of the first intake air and the amount of the second intake air to be introduced. Is controlled in the distribution range of the first intake and the second intake.
[0022]
Increasing the introduction amount of the second intake air and / or decreasing the introduction amount of the first intake air increases the swirl ratio of the swirling flow. When the swirl ratio increases, the distribution range of the second intake air is more concentrated near the inner wall surface of the cylinder, whereby the distribution range of the first intake air is expanded toward the inner wall surface of the cylinder. On the other hand, when the introduction amount of the second intake air is reduced and / or the introduction amount of the first intake air is increased, the swirl ratio of the swirling flow decreases. When the swirl ratio decreases, the distribution range of the second intake air expands toward the center of the cylinder, whereby the distribution range of the first intake air concentrates on the center of the cylinder. Therefore, the swirl ratio of the swirling flow along the cylinder inner wall surface is controlled by controlling the introduction amount of the first intake and the introduction amount of the second intake having different EGR rates, and thereby the distribution of the EGR rate in the cylinder Can be controlled more finely.
[0023]
For example, (1) when the operating state of the engine is in a relatively low load region even in a low load operation region, the EGR gas amount introduced into the second intake port is more than the EGR gas amount introduced into the first intake port. That is, the EGR rate of the second intake is made higher than the EGR rate of the first intake, and the introduction amount of the second intake is further increased. Then, (2) the amount of second intake air introduced is further reduced in a state where the engine load increases in the low load operation range and the EGR gas rate of the second intake air is higher than the EGR gas rate of the first intake air. According to the controls (1) and (2), when the temperature near the cylinder inner wall surface is lower, the EGR rate near the cylinder inner wall surface can be more intensively increased, and the cylinder inner wall surface can be efficiently made. It is possible to raise the temperature of the nearby premixed gas. Further, in the central portion of the cylinder, as the engine load increases, that is, by reducing the range in which the EGR rate is low in accordance with the temperature rise, the ignitability of the premixed gas is gradually suppressed, and the ignition timing is more appropriately adjusted. It can be time.
[0024]
On the other hand, (3) when the operating state of the engine is in a relatively low load region in the high load operation region, the EGR gas amount introduced into the second intake port is made smaller than the EGR gas amount introduced into the first intake port. That is, the EGR rate of the second intake is made lower than the EGR rate of the first intake, and the introduction amount of the second intake is further reduced. (4) With the engine load increased and the EGR gas rate of the second intake being lower than the EGR gas rate of the first intake, the amount of second intake introduced is further increased. According to such controls (3) and (4), in the central portion of the cylinder, as the engine load increases, that is, by increasing the range in which the EGR rate is high in accordance with the temperature rise, the premixed gas mixture is increased. The ignitability is further suppressed, and the ignition timing can be set to a more appropriate timing.
[0025]
Further, even in the transient operation state where the operation state of the engine shifts from the low load operation area to the high load operation area, the above-mentioned (1), (2), (3), and (4) , The distribution of the EGR rate in the cylinder can be continuously controlled, so that more suitable premixed compression ignition combustion can be performed according to the operating state of the engine. Become.
[0026]
Further, in the recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to the present invention, the amount of EGR gas introduced into the first intake port and / or the second intake port is controlled, and the amount of EGR gas is controlled by the first intake port. The intake timing and the intake timing by the second intake port may be controlled according to the operating state of the engine.
[0027]
Here, the intake timing is a timing at which the introduction of intake air by each intake port is started and a timing at which the introduction of intake air is stopped.
[0028]
In the intake stroke, the second intake is first introduced into the cylinder by the second intake port, and then the first intake is introduced into the cylinder by the first intake port, whereby the second intake is more distributed near the inner wall surface of the cylinder. And the first intake air is more easily distributed to the central portion in the cylinder. Therefore, for example, by controlling the EGR rates of the first intake air and the second intake air, respectively, and controlling the respective intake timings, the introduction amount of the first intake air and the introduction amount of the second intake air are respectively controlled. As in the case of the control, the distribution of the EGR rate in the cylinder can be more finely controlled. Further, even in a transient operation state in which the operation state of the engine shifts from the low load operation area to the high load operation area, the distribution of the EGR rate in the cylinder can be continuously controlled. It is possible to perform more suitable premixed compression ignition combustion in accordance with the operating state of.
[0029]
Further, control may be performed such that the introduction of intake air and the stop of introduction of intake air by at least one of the first intake port and the second intake port are repeated a plurality of times during the intake stroke.
[0030]
According to such control, the premixed gas having a high EGR rate and the premixed gas having a low EGR rate can be multilayered in the cylinder. Therefore, the ignition delay of the premixed gas in the cylinder becomes more non-uniform, so that the combustion can be made more gentle. Therefore, premix combustion can be performed in a higher load region.
[0031]
Further, in the recirculation exhaust control system of the premixed compression ignition combustion internal combustion engine according to the present invention, as described above, the intake introduction position by each intake port is not limited to the central portion in the cylinder and the vicinity of the cylinder inner wall surface. A plurality of intake ports, exhaust recirculation means for introducing EGR gas to at least one intake port, recirculation exhaust quantity control means for controlling the amount of EGR gas introduced to the intake ports, An intake timing control means for controlling each of the ports, and controlling the amount of EGR gas introduced into the intake ports and the intake timing for each intake port in accordance with the operating state of the engine, thereby controlling the cylinder. The distribution of the recirculation exhaust rate in the inside may be controlled.
[0032]
In the intake stroke, when intake air is first introduced into the cylinder by one intake port and then intake air is introduced into the cylinder by the other intake port, the intake air initially introduced is distributed to the lower side of the cylinder. Therefore, the intake air introduced next is more easily distributed to the upper side in the cylinder. Therefore, even when the intake introduction point for each intake port is not limited as in the first intake port and the second intake port, the cylinders are controlled by controlling the intake timings of intakes having different EGR rates. Can control the distribution of the EGR rate in the inside.
[0033]
Also in this case, by controlling the intake and stop of the intake by at least one intake port to be repeated a plurality of times during the intake stroke, the premixed gas having a high EGR rate and the low EGR rate are controlled in the cylinder. The premixed gas can be multilayered. Therefore, the ignition delay of the premixed gas in the cylinder becomes more non-uniform, so that the combustion can be made more gentle. Therefore, premix combustion can be performed in a higher load region.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
<First embodiment>
Hereinafter, a specific embodiment of a recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to the present invention will be described with reference to the drawings.
[0035]
FIG. 1 and FIG. 2 are diagrams showing a schematic configuration of an internal combustion engine and a recirculation exhaust control system thereof according to the present embodiment.
[0036]
The internal combustion engine 1 shown in FIG. 1 is a multi-cylinder diesel engine having four cylinders 2 (only one cylinder is shown). A fuel injection valve 10 for directly injecting fuel into the combustion chamber is provided at a substantially central portion of the cylinder 2. The cylinder 2 has a first intake port 3, a second intake port 4, and two exhaust ports 5.
[0037]
The first intake port 3 and the second intake port 4 communicate with an intake manifold 12, and the intake manifold 12 is connected to an intake passage 11. The two exhaust ports 5 are connected to an exhaust manifold 13, and the exhaust manifold 13 is connected to an exhaust passage 14.
[0038]
The first intake port 3 is formed to face downward in the axial direction of the cylinder 2, and the opening of the first intake port 3 to the cylinder 2 is closer to the center of the cylinder 2 than the opening of the second intake port 4 to the cylinder 2. It is installed so as to be closer. On the other hand, the second intake port 4 is arranged tangentially to the cylinder 2 so that the intake air introduced by the second intake port generates a lateral swirling flow along the inner wall surface of the cylinder 2. With such a configuration, intake air introduced by the first intake port 3 (hereinafter, referred to as first intake) is introduced into a central portion in the cylinder 2, and intake air introduced by the second intake port 4 (hereinafter, second intake). (Referred to as intake air) is introduced near the inner wall surface of the cylinder 2.
[0039]
The two exhaust ports 5 are provided with exhaust valves (not shown), respectively. The first intake port 3 and the second intake port 4 have the first intake valve 6 and the second intake port 4 as shown in FIG. Two intake valves 7 are provided. The first intake valve 6 and the second intake valve 7 are provided with a first variable valve mechanism 8 and a second variable valve mechanism 9 for controlling the opening / closing timing and the lift amount of each of the intake valves 6 and 7, respectively. Have been. An example of the variable valve mechanism is an electromagnetically driven valve.
[0040]
Further, the internal combustion engine 1 according to the present embodiment is provided with an exhaust gas recirculation device 20 that recirculates part of the exhaust gas discharged from the internal combustion engine 1 to the intake system. The exhaust gas recirculation device 20 includes a main exhaust gas recirculation passage 21 communicating with the exhaust manifold 13, a first EGR passage 22 communicating the main exhaust gas recirculation passage 21 with the first intake port 3, A second EGR passage which communicates the recirculation passage with the second intake port; In addition, the first EGR passage 22 and the second EGR passage 23 are provided with exhaust gas (hereinafter, referred to as EGR gas) formed of an electromagnetic valve or the like and flowing through the first EGR passage 22 or the second EGR passage 23 according to the magnitude of the applied voltage. A first EGR valve 24 and a second EGR valve 25 for adjusting the flow rate are provided, respectively.
[0041]
In the exhaust gas recirculation device 20 configured as described above, when the first EGR valve 24 or the second EGR valve 25 is opened, a part of the exhaust gas (EGR gas) discharged from the internal combustion engine 1 passes through the exhaust manifold 13. The EGR gas flowing into the main exhaust gas recirculation passage 21 and flowing through the main exhaust gas recirculation passage 21 passes through the first EGR passage 22 or the second EGR passage 23 to the first intake port 3 or the second intake port 4. be introduced. The EGR gas introduced into each of the intake ports 3 and 4 mixes with fresh air (air) to form intake air, and the intake air is introduced into the cylinder 2. Further, by controlling the amount of EGR gas introduced into each of the intake ports 3 and 4 by the first EGR valve 24 and the second EGR valve 25, the EGR rates of the first intake and the second intake are respectively controlled.
[0042]
Here, in each intake air, as the EGR rate increases, the oxygen concentration decreases, and as the EGR rate decreases, the oxygen concentration increases. Therefore, in the cylinder, the ignitability of the premixed air is suppressed in the portion where the intake air having the high EGR rate is introduced, and the ignitability of the premixed air is improved in the portion where the intake air having the low EGR rate is introduced. Further, since the temperature of the EGR gas is considerably higher than the temperature of fresh air (air) introduced from the intake passage 11, the temperature of intake air having a high EGR rate becomes higher. Therefore, when the temperature in the cylinder 2 is low, such as when the operation state of the engine is in the low load operation region, the temperature of the premixed air in the portion where the intake air with a high EGR rate is introduced becomes high. When the operating state of the engine is in the high load operation range, the temperature in the cylinder 2 is considerably high, so that the influence of the temperature of the EGR gas is small.
[0043]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU: Electronic Control Unit) 30 for controlling the internal combustion engine 1. The ECU 30 is a unit that controls the operating state of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's requirements.
[0044]
The ECU 30 is electrically connected to various sensors such as a crank position sensor 31 that outputs a signal corresponding to the rotation angle of the output shaft of the internal combustion engine 1 and an accelerator opening sensor 32 that outputs a signal corresponding to the accelerator opening. The output signals of these sensors are input to the ECU 30.
[0045]
On the other hand, the ECU 30 is electrically connected to the fuel injection valve 10, the first variable valve mechanism 8, the second variable valve mechanism 9, the first EGR valve 24, the second EGR valve 25, and the like. Controlled.
[0046]
The ECU 30 includes a CPU, a ROM, a RAM, and the like. For example, the ECU 30 calculates an engine speed based on a time interval or the like at which the crank position sensor 31 outputs a pulse signal, and outputs the engine speed to an output signal of the accelerator opening sensor 32 and the like. The engine load is calculated based on the engine load. Further, the ECU 30 determines the operating state of the internal combustion engine 1 from the engine speed and the engine load.
[0047]
Further, in the internal combustion engine 1 according to the present embodiment, by injecting fuel into the cylinder 2 by the fuel injection valve 10 during the intake stroke or the compression stroke, a premixed fuel and intake air is formed. This is an internal combustion engine that performs a so-called premix compression ignition combustion in which a premixed gas is used for combustion.
[0048]
Next, distribution control of the EGR gas rate in the cylinder by the recirculation exhaust system according to the present embodiment will be described.
[0049]
3 and 4 are diagrams showing the distribution of the EGR rate in the cylinder 2 according to the present embodiment. 3 and 4 show the EGR rate distribution.
[0050]
In the recirculation exhaust system according to the present embodiment, when the internal combustion engine 1 is operated in the low load operation range, the opening of the first EGR valve 24 is controlled to be smaller than the opening of the second EGR valve 25. Is done. That is, control is performed such that the amount of EGR gas introduced into the first intake port 3 becomes smaller than the amount of EGR gas introduced into the second intake port. For this reason, the EGR rate of the first intake becomes lower than the EGR rate of the second intake.
[0051]
In the internal combustion engine 1 according to the present embodiment, as described above, the first intake air is introduced into the center of the cylinder 2, and the second intake air is introduced near the inner wall surface of the cylinder 2. Accordingly, when the EGR rate of the first intake is lower than the EGR rate of the second intake, the distribution of the EGR rate in the cylinder 2 is such that the EGR rate in the central portion is low and the EGR rate in the vicinity of the wall surface as shown in FIG. Will be higher.
[0052]
In the low load operation range, the fuel injection amount is small, but according to such control, the EGR rate in the central portion of the cylinder 2 becomes low, that is, the oxygen concentration in the central portion of the cylinder 2 becomes relatively high. The ignitability of the premixed gas at the center of the cylinder 2 can be ensured. In the low load operation region, the temperature near the inner wall surface of the cylinder 2 is relatively low. However, according to the above-described control, the EGR rate near the inner wall surface of the cylinder 2 increases, so that the heat of the EGR gas increases. Thereby, the temperature of the premixed gas near the inner wall surface can be increased. Therefore, it is possible to suppress the generation of unburned components in the premixed gas near the inner wall surface of the cylinder 2.
[0053]
On the other hand, in the recirculation exhaust control system according to the present embodiment, when the internal combustion engine 1 is operated in the high load operation region, the opening of the first EGR valve 24 is larger than the opening of the second EGR valve 25. Is controlled. That is, control is performed such that the amount of EGR gas introduced into the first intake port 3 becomes larger than the amount of EGR gas introduced into the second intake port. For this reason, the EGR rate of the first intake becomes higher than the EGR rate of the second intake.
[0054]
When the EGR rate of the first intake becomes higher than the EGR rate of the second intake, the distribution of the EGR rate in the cylinder 2 is such that the EGR rate in the center is high and the EGR rate in the vicinity of the wall is low, as shown in FIG. Become.
[0055]
In the high-load operation region, the temperature in the central portion of the cylinder 2 increases, and premature ignition easily occurs. However, according to such control, the EGR rate in the central portion of the cylinder 2 increases, that is, the cylinder 2 Since the oxygen concentration in the inner central portion becomes lower, the ignitability of the premixed gas at the central portion in the cylinder 2 can be suppressed, and thus premature ignition can be suppressed. Further, according to the above-described control, the EGR rate near the inner wall surface of the cylinder 2 becomes lower than that at the central portion inside the cylinder 2, that is, the oxygen distribution in the cylinder 2 becomes uneven, so that the vicinity of the inner wall surface of the cylinder 2 becomes The ignition delay between the premixed gas and the premixed gas in the central portion of the cylinder 2 is not uniform. Therefore, abrupt combustion of the premixed gas is suppressed, and deterioration of combustion noise can be suppressed.
[0056]
The distribution of the EGR rate in the cylinder 2 may be controlled by introducing the EGR gas into only one of the first intake port 3 and the second intake port 4. Further, even in the case where either one of the first EGR passage 22 and the second EGR passage 23 is not provided, the gas is introduced into only one of the first intake port 3 and the second intake port 4. By controlling the amount of the EGR gas, the distribution of the EGR rate in the cylinder 2 can be controlled.
[0057]
When the internal combustion engine 1 according to the present embodiment is an internal combustion engine that selectively switches between premixed compression ignition combustion and normal combustion (so-called diffusion combustion) in which combustion is performed without forming a premixed gas, When the internal combustion engine 1 performs normal combustion, control is performed so that the amount of EGR gas introduced into the first intake port 3 and the amount of EGR gas introduced into the second intake port 4 become substantially the same. That is, the distribution of the EGR rate in the cylinder 2 is controlled to be substantially uniform by making the EGR rates of the first intake air and the second intake air substantially the same.
[0058]
During normal combustion, by controlling the distribution of the EGR rate in the cylinder 2 substantially uniformly, combustion can be stabilized, and deterioration of driver viability and emission can be suppressed. Therefore, even in an internal combustion engine that switches between premixed compression ignition combustion and normal combustion, it is possible to more suitably perform both combustions.
[0059]
<Second embodiment>
Next, a second embodiment of a recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to the present invention will be described with reference to the drawings. The hardware configuration of the internal combustion engine and the recirculation exhaust control system according to the present embodiment is the same as that of the above-described first embodiment, and will not be described, and the cylinder by the recirculation exhaust control system according to the present embodiment will be omitted. The control of the distribution of the EGR gas rate in the inside is described below.
[0060]
5 to 8 are diagrams showing distributions of the EGR rate in the cylinder 2 according to the present embodiment. The dashed line in FIGS. 5 to 8 shows the EGR rate distribution. The smaller the interval between dashed lines, the denser the EGR rate distribution, and the larger the interval between dashed lines, the sparser the EGR rate distribution.
[0061]
In the recirculation exhaust control system according to the present embodiment, similarly to the above-described first embodiment, the opening degree of the first EGR valve 24 and the second EGR valve 25 is controlled according to the operating state of the internal combustion engine 1. Accordingly, the EGR rates of the first intake air and the second intake air are respectively controlled, and the closing timing of the first intake valve 6 and the second intake valve 7 during the intake stroke is controlled by the first variable valve mechanism 8 and the second The swirl ratio of the swirling flow along the inner wall surface of the cylinder 2 is controlled by controlling the two variable valve mechanisms 9 respectively.
[0062]
According to the arrangement of the second intake port according to the present embodiment, when the second intake air is introduced into cylinder 2, a swirling flow is generated along the wall surface in cylinder 2. By controlling the swirl ratio of the swirling flow, the distribution range of the first intake and the second intake in the cylinder can be controlled.
[0063]
When the valve closing timing of the second intake valve 7 is retarded and / or the valve closing timing of the first intake valve 6 is advanced, the amount of the second intake air introduced into the cylinder 2 relatively increases. When the amount of the second intake air increases, the swirl ratio of the swirling flow along the inner wall surface of the cylinder 2 increases. When the swirl ratio is increased, the distribution range of the second intake air is more concentrated near the inner wall surface of the cylinder 2, whereby the distribution range of the first intake air is expanded toward the inner wall surface of the cylinder 2. On the other hand, when the closing timing of the first intake valve 6 is retarded and / or when the closing timing of the second intake valve 7 is advanced, the amount of second intake introduced into the cylinder 2 is relatively reduced. I do. When the introduction amount of the second intake air decreases, the swirl ratio of the swirling flow along the inner wall surface of the cylinder 2 decreases. When the swirl ratio decreases, the distribution range of the second intake air expands toward the center of the cylinder 2, whereby the distribution range of the first intake air concentrates on the center of the cylinder 2.
[0064]
Therefore, in the recirculation exhaust control system according to the present embodiment, (1) when the operating state of the internal combustion engine 1 is in a relatively low load region even in the low load operation region, the EGR rate of the first intake air is lower than The EGR rate of the second intake air is increased, and the closing timing of the second intake valve 7 is retarded. Then, (2) closing the second intake valve 7 in a state where the engine load of the internal combustion engine 1 increases in the low load operation region and the EGR gas rate of the second intake is higher than the EGR gas rate of the first intake. The valve timing is advanced.
[0065]
According to the controls (1) and (2), when the temperature near the inner wall surface of the cylinder 2 is lower, the EGR rate near the inner wall surface of the cylinder 2 is intensively increased as shown in FIG. As a result, the temperature of the premixed gas near the inner wall surface of the cylinder 2 can be efficiently increased. Further, in the central portion of the cylinder 2, when the engine load increases, that is, when the temperature rises, the ignitability of the premixed gas is gradually suppressed by reducing the low EGR rate range as shown in FIG. Thus, the ignition timing can be set to a more appropriate timing.
[0066]
On the other hand, (3) when the operation state of the internal combustion engine 1 is in a relatively low load range in the high load operation range, the EGR rate of the second intake is made lower than the EGR rate of the first intake, and The valve closing timing is advanced. (4) With the engine load of the internal combustion engine 1 increased and the EGR gas rate of the second intake lowered from the EGR gas rate of the first intake, the closing timing of the second intake valve 7 is retarded. . According to the controls (3) and (4), when the engine load is relatively small, as shown in FIG. 7, the range in which the EGR rate is high in the central portion of the cylinder 2 is reduced, and the engine load is increased. As shown in FIG. 8, as the temperature rises, the ignitability of the premixed gas is more appropriately suppressed, and the ignition timing is set to a more appropriate timing, as shown in FIG. Can be done.
[0067]
As described above, according to the recirculation exhaust control system according to the present embodiment, since the EGR rate distribution in the cylinder can be controlled more finely, more suitable premixed compression ignition combustion can be performed in a wider operation range. It is possible to do.
[0068]
Further, in the recirculation exhaust control system according to the present embodiment, when the operation state of the internal combustion engine 1 is in a transient operation state in which the internal combustion engine 1 shifts from the low load operation area to the high load operation area, Since the control of (1), (2), (3), and (4) is continuously performed, the distribution of the EGR rate in the cylinder 2 can be continuously controlled. Accordingly, more suitable premixed compression ignition combustion can be performed.
[0069]
In the recirculation exhaust control system according to the present embodiment, the valve lift of the first intake valve 6 and the second intake valve 7 during the intake stroke is controlled by the first variable valve mechanism 8 and the second variable valve mechanism. 9 may control the amount of the first intake air and the second intake air introduced into the cylinder 2, respectively, and control the swirl ratio in the cylinder 2.
[0070]
<Third embodiment>
Next, a third embodiment of a recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to the present invention will be described with reference to the drawings. The hardware configuration of the internal combustion engine and the recirculation exhaust control system according to the present embodiment is the same as that of the above-described first embodiment, and will not be described. The following describes the EGR gas rate distribution control.
[0071]
In the recirculation exhaust control system according to the present embodiment, similarly to the above-described first embodiment, the opening degree of the first EGR valve 24 and the second EGR valve 25 is controlled according to the operating state of the internal combustion engine 1. Thus, the EGR rates of the first intake air and the second intake air are respectively controlled, and the opening timing and closing timing of the first intake valve 6 and the second intake valve 7 in the intake stroke are controlled by the first variable valve. By controlling the mechanism 8 and the second variable valve mechanism 9 respectively, the intake timing of the first intake and the second intake into the cylinder 2 is controlled.
[0072]
FIG. 9 is an example of a valve profile indicating the valve opening timing and the valve closing timing in the intake stroke of the first intake valve 6 and the second intake valve 7 according to the present embodiment. The dotted line indicates the intake stroke, and the solid lines indicate the valve opening timing and the valve closing timing.
[0073]
In the recirculation exhaust control system according to the present embodiment, for example, as shown in FIG. 9, in the intake stroke, the opening and closing timing of the first intake valve 6 is retarded more than the opening and closing timing of the second intake valve 7. By such control, the second intake air is first introduced into the cylinder 2 and then the first intake air is introduced into the cylinder 2, so that the second intake air is more likely to be distributed near the inner wall surface of the cylinder 2, and The intake air is more easily distributed to the central portion in the cylinder 2.
[0074]
Therefore, according to the recirculation exhaust control system according to the present embodiment, the EGR rate of the first intake air and the EGR rate of the second intake air are controlled in accordance with the operating state of the internal combustion engine 1, respectively. By controlling the intake timing of the second intake and the intake timing of the second intake, respectively, it is possible to more finely control the EGR rate distribution in the cylinder 2 as in the above-described second embodiment. Therefore, it is possible to perform more suitable homogeneous charge compression ignition combustion in a wider operation range.
[0075]
Further, even in the transient operation state where the operation state of the engine shifts from the low load operation area to the high load operation area, the distribution of the EGR rate in the cylinder is changed similarly to the above-described second embodiment. Since the control can be continuously performed, it is possible to perform more suitable premixed compression ignition combustion according to the operation state.
[0076]
Furthermore, in the recirculation exhaust control system according to the present embodiment, the EGR rates of the first intake air and the second intake air are respectively controlled, and at least one of the first intake valve 6 and the second intake valve 7 is opened. And the valve closing may be repeated a plurality of times in the intake stroke.
[0077]
FIG. 10 is a diagram illustrating an example of the distribution of the EGR rate in the cylinder 2 when such control is performed. The dashed line in FIG. 10 shows the EGR rate distribution.
[0078]
According to such control, as shown in FIG. 10, the distribution of the EGR rate in the cylinder 2 can be multi-layered. Therefore, the ignition delay of the premixed gas becomes more uneven, and the combustion can be made more gentle. Therefore, premix combustion can be performed in a higher load region.
[0079]
As in the recirculation exhaust control system according to the present embodiment, the EGR rate of the first intake air and the EGR rate of the second intake air are controlled in accordance with the operating state of the internal combustion engine 1, respectively. When the EGR rate distribution in the cylinder 2 is controlled by controlling the intake timing of the second intake port and the second intake port into the cylinder 2, respectively, the arrangement of the first intake port 3 and the second intake port 4 is as described above. (I.e., the first intake air is introduced into the central portion of the cylinder 2 and the second intake air is introduced near the inner wall surface of the cylinder 2). The intake air is more likely to be distributed to the lower side in the cylinder 2 and the next intake air is more likely to be distributed to the upper side in the cylinder 2, so that the distribution of the EGR rate in the cylinder 2 can be controlled.
[0080]
Further, even if the arrangement of the first intake port 3 and the second intake port 4 is not limited to the above-described arrangement, at least one of the first intake valve 6 and the second intake valve 7 may be opened. By performing control such that valve closing is repeated a plurality of times in the intake stroke, the distribution of the EGR rate in the cylinder 2 can be multi-layered.
[0081]
【The invention's effect】
According to the recirculated exhaust gas control system of the homogeneous charge compression ignition combustion internal combustion engine according to the present invention, in the low load operation region, it is possible to suppress the emission of unburned components while ensuring ignitability, and in the high load operation region. Since it is possible to suppress premature ignition and deterioration of combustion noise, it becomes possible to perform more suitable premixed compression ignition combustion in a wider operation range.
[Brief description of the drawings]
FIG. 1 is a first diagram showing a schematic configuration of an internal combustion engine and a recirculation exhaust control system according to the present invention;
FIG. 2 is a second diagram showing a schematic configuration of an internal combustion engine and a recirculation exhaust control system according to the present invention;
FIG. 3 is a first diagram showing an EGR rate distribution in a cylinder according to the first embodiment;
FIG. 4 is a second diagram showing an EGR rate distribution in the cylinder according to the first embodiment;
FIG. 5 is a first diagram showing an EGR rate distribution in a cylinder according to a second embodiment;
FIG. 6 is a second diagram showing an EGR rate distribution in a cylinder according to the second embodiment;
FIG. 7 is a third diagram showing an EGR rate distribution in a cylinder according to the second embodiment;
FIG. 8 is a fourth diagram showing an EGR rate distribution in a cylinder according to the second embodiment;
FIG. 9 is a valve profile showing a valve opening timing and a valve closing timing in an intake stroke of a first intake valve and a second intake valve according to a third embodiment;
FIG. 10 is a diagram showing an EGR rate distribution in a cylinder according to a third embodiment.
[Explanation of symbols]
1 ... internal combustion engine
2 ... cylinder
3 ... First intake port
4 Second intake port
5 ... Exhaust port
6 First intake valve
7 Second intake valve
8 First variable valve mechanism
9 Second variable valve mechanism
10. Fuel injection valve
11 ... Intake passage
12. Intake manifold
13. Exhaust manifold
14. Exhaust passage
20..Exhaust gas recirculation device
21 ·· Main exhaust recirculation passage
22..First EGR passage
23 .. Second EGR passage
24..First EGR valve
25 .. Second EGR valve
30 ECU
31 Crank position sensor
32. Accelerator opening sensor

Claims

A premixed compression ignition internal combustion engine that performs premixed compression ignition combustion in which a premixed mixture of fuel and intake air is formed in a cylinder during an intake stroke and / or a compression stroke, and the premixed air is used for combustion. At
A first intake port for introducing intake air into a central portion of the cylinder;
A second intake port for introducing intake air near the cylinder inner wall surface,
Exhaust recirculation means for introducing a part of exhaust gas into at least one of the first intake port and the second intake port;
Recirculation exhaust amount control means for controlling an amount of exhaust gas introduced into the first intake port and / or the second intake port by the exhaust gas recirculation means;
Operating state detecting means for detecting an operating state of the premixed compression ignition combustion internal combustion engine,
With
By controlling an amount of exhaust gas introduced into the first intake port and / or the second intake port in accordance with an operation state of the homogeneous charge compression ignition combustion internal combustion engine detected by the operation state detection means, A recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine, wherein a distribution of a recirculation exhaust rate in the cylinder is controlled.

The exhaust gas recirculation means introduces a part of exhaust gas into the first intake port and the second intake port,
The recirculation exhaust amount control means is configured to control an amount of exhaust gas introduced into the first intake port and the second intake air in accordance with an operation state of the homogeneous charge compression ignition combustion internal combustion engine detected by the operation state detection means. 2. The system according to claim 1, wherein the amount of exhaust gas introduced into the port is controlled.

When the operation state of the homogeneous charge compression ignition combustion internal combustion engine detected by the operation state detection means is in a low load operation region, the recirculation exhaust gas amount control means controls the amount of exhaust gas introduced into the first intake port. 3. A recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to claim 2, wherein the amount of exhaust gas introduced into said second intake port is made larger than that of said second intake port.

When the operating state of the premixed compression ignition combustion internal combustion engine detected by the operating state detecting means is in a high load operation range, the recirculation exhaust amount control means determines the amount of exhaust gas introduced into the first intake port. 4. The recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to claim 2, wherein the amount of exhaust gas introduced into the second intake port is smaller than that of the second intake port.

The premixed compression ignition combustion internal combustion engine is a premixed compression ignition combustion internal combustion engine that selectively switches between the premixed compression ignition combustion and normal combustion that performs combustion without forming the premixed gas,
When the normal combustion is performed, the recirculated exhaust gas amount control means sets the amount of exhaust gas introduced into the first intake port and the amount of exhaust gas introduced into the second intake port to be substantially the same. The recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to any one of claims 2 to 4, characterized in that:

The amount of intake air introduced by the first intake port and the amount of intake air introduced by the second intake port are respectively determined according to the operating state of the premixed compression ignition combustion internal combustion engine detected by the operating state detecting means. The recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to any one of claims 1 to 4, further comprising an intake air amount control means for controlling.

Intake timing control means for controlling intake timing by the first intake port and intake timing by the second intake port in accordance with an operation state of the premixed compression ignition combustion internal combustion engine detected by the operation state detection means; The recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine according to any one of claims 1 to 4, further comprising:

8. The intake timing control means controls the intake air introduction and the intake air stop by at least one of the first intake port and the second intake port to be repeated a plurality of times during an intake stroke. A recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine as described.

A premixed compression ignition internal combustion engine that performs premixed compression ignition combustion in which a premixed mixture of fuel and intake air is formed in a cylinder during an intake stroke and / or a compression stroke, and the premixed air is used for combustion. At
A plurality of intake ports for introducing intake air into the cylinder,
Exhaust gas recirculation means for introducing a part of exhaust gas into at least one of the intake ports;
Recirculation exhaust amount control means for controlling the amount of exhaust gas introduced into the intake port by the exhaust gas recirculation means,
Intake timing control means for controlling intake timing by the intake port for each intake port,
Operating state detecting means for detecting an operating state of the premixed compression ignition combustion internal combustion engine,
With
According to the operating state of the premixed compression ignition combustion internal combustion engine detected by the operating state detecting means, by controlling the amount of exhaust gas introduced into the intake port and the intake timing for each intake port, A recirculation exhaust control system for a homogeneous charge compression ignition combustion internal combustion engine, wherein a distribution of a recirculation exhaust rate in the cylinder is controlled.