JP3719060B2

JP3719060B2 - In-cylinder internal combustion engine

Info

Publication number: JP3719060B2
Application number: JP24954199A
Authority: JP
Inventors: 博文土田; 祐一入矢; 隆福田; 泰之伊藤
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1999-09-03
Filing date: 1999-09-03
Publication date: 2005-11-24
Anticipated expiration: 2019-09-03
Also published as: JP2001073855A

Description

【０００１】
【産業上の利用分野】
本発明は、ガソリン機関に代表される内燃機関に関し、特に、吸気行程付近で燃料を噴射して均質燃焼を行うとともに、圧縮行程付近で燃料を噴射して成層燃焼を行う筒内噴射式の内燃機関の改良に関する。
【０００２】
【従来の技術】
全開出力時等にシリンダ内に略均質な空燃比の混合気を形成していわゆる均質燃焼を行うとともに、低負荷域では、シリンダ内の一部、つまり点火プラグ近傍のみに比較的濃い混合気を形成して平均的な空燃比を非常に大きく得るようにした成層燃焼を行う筒内噴射式内燃機関が、例えば特開平１１−０３６９５８号公報に記載されている。
【０００３】
更に、この公報に記載された筒内噴射式内燃機関では、均質燃焼領域において、吸気行程早期に燃料が噴射された後に、アクセルの踏み込み等により吸気量が急増した場合に、これに見合う量の追加燃料を圧縮行程前半中に追加噴射して、空燃比の過大化を抑制するように構成されている。
【０００４】
【発明が解決しようとする課題】
しかしながら、上記従来の筒内噴射式内燃機関においては、均質燃焼を行う場合に、吸気行程で噴射された燃料は、吸気ポートから燃焼室内に流入する一定の吸気流に乗って筒内に拡散することから、吸気流の主流の部分と、よどむ領域とで燃料の拡散の程度が不均一となり、筒内における混合気の均質度はあまり良くない。この結果、均質燃焼の中でも空燃比を比較的大きく設定した均質リーン燃焼時に、局所的にリッチの領域で燃焼温度が上昇し、ＮＯｘの排出量が増加するという問題点があった。また空燃比が理論空燃比の近傍に設定された均質ストイキ燃焼時に、局所的にリッチの領域で酸素不足が生じ、ＨＣ，ＣＯ等の排出量の増加を招く等の問題があった。
【０００５】
特に、上記公報の技術のように、均質燃焼時に燃料噴射を複数回に分けて行う場合には、燃焼室内に均質の混合気を形成することが更に困難となり、安定した均質燃焼を行うことができない。
【０００６】
本発明は、このような課題に鑑みてなされたものである。
【０００７】
【課題を解決するための手段】
本発明に係る筒内噴射式内燃機関は、燃焼室内に直接燃料を噴射する燃料噴射弁が吸気側に配置され、吸気行程付近で燃料噴射を行うことにより均質燃焼を実現するとともに、圧縮行程付近で燃料噴射を行うことにより成層燃焼を実現するように構成されている。
【０００８】
そして、請求項１の発明は、均質燃焼時における１回の吸気行程期間中に、燃焼室内への吸気の流入方向を変化させる吸気方向可変手段と、この吸気行程期間中に吸気の流入方向が異なる複数のタイミングに分けて燃料を噴射する燃料噴射制御手段と、を有し、それぞれのタイミングで噴射された燃料を流入方向の異なる吸気の流れに乗せて燃焼室に拡散させることを特徴としている。
【０００９】
このような構成により、それぞれのタイミングで噴射された燃料が流入方向の異なる吸気の流れに乗って燃焼室の全体に良好に拡散され、燃焼室全体に均質な混合気が形成される。この結果、良好な均質燃焼を実現でき、局部的なリッチ状態を生じることが無いため、ＮＯｘ，ＨＣ，ＣＯ等の排出量を大幅に低減することが可能となる。
【００１０】
請求項１の発明をより具体化した請求項２の発明は、上記吸気方向可変手段が、吸気ポートの燃焼室側の開口縁部の周方向一部分に切欠形成された切欠部を有し、均質燃焼時に、吸気弁の低リフト時に主に上記切欠部を通って燃焼室内へ流入する吸気の流入方向が、高リフト時における吸気の流入方向と異なるように設定したことを特徴としている。
【００１１】
この構成によれば、低リフト時における吸気の流入方向が切欠部の形成された方向を指向する形となり、低リフト時と高リフト時で吸気の流入方向を異らせることができる。従って、吸気の流入方向が異なる低リフト時と高リフト時に分けて燃料を噴射することにより、それぞれの吸気の流れに乗って燃料が燃焼室全体に良好に拡散される。
【００１２】
請求項２の発明をより具体化した請求項３の発明は、吸気ポートの途中に設けられた吸気遮断弁と、吸気ポートの吸気遮断弁の上流側と下流側とをバイパスするバイパス通路と、を有し、上記吸気遮断弁で吸気ポートを遮断した均質リーン燃焼時に、吸気弁の低リフト時に上記切欠部を通って燃焼室内へ流入する吸気の流入方向と、高リフト時に主にバイパス通路を通って燃焼室へ流入する吸気の流入方向とが互いに異なるように設定したことを特徴としている。
【００１３】
この構成によれば、均質リーン燃焼時のおける１回の吸気行程期間中に、吸気の流入方向が、低リフト時には切欠部の形成された方向に、高リフト時にはバイパス通路の中心軸に沿う方向に変化する。
【００１４】
また、請求項２の発明をより具体化した請求項４の発明は、各燃焼室の吸気側に一対の吸気ポートが開口しており、かつ、上記燃料噴射弁がシリンダ軸方向視で両吸気ポートの間に配置され、一方の吸気ポートに吸気遮断弁が設けられるとともに、他方の吸気ポートの開口縁部に上記切欠部が形成され、上記吸気遮断弁で一方の吸気ポートを遮断した均質リーン燃焼時に、吸気弁の低リフト時に上記切欠部を通って燃焼室内へ流入する吸気の流入方向と、高リフト時に主に他方の吸気ポートを通って燃焼室へ流入する吸気の流入方向とが互いに異なるように設定したことを特徴としている。
【００１５】
この構成によれば、均質リーン燃焼時における１回の吸気行程期間中に、吸気の流入方向が、低リフト時には切欠部の形成された方向に、高リフト時には他方の吸気ポートの中心軸に沿う方向に変化する。
【００１６】
更に、請求項２の発明をより具体化した請求項５の発明は、各燃焼室の吸気側に一対の吸気ポートが開口しており、かつ、上記燃料噴射弁がシリンダ軸方向視で両吸気ポートの間に配置され、両吸気ポートの開口縁部に上記切欠部がそれぞれ形成され、各切欠部は、高リフト時における吸気の流入方向と略逆方向となる周方向一部分に形成されていることを特徴としている。
【００１７】
この構成によれば、均質燃焼時における１回の吸気行程期間中に、吸気の流入方向が、低リフト時には切欠部の形成された方向に、高リフト時には両吸気ポートの中心軸に沿う方向に変化する。
【００１８】
【発明の効果】
以上のように本発明では、均質燃焼時における１回の吸気行程期間中に、燃焼室への吸気の流入方向を変化させるとともに、吸気の流入方向が異なる複数のタイミングに分けて燃料を噴射する構成としたため、それぞれのタイミングで噴射された燃料が流入方向の異なる吸気の流れに乗って燃焼室内の全域にわたって良好に拡散され、燃焼室内に均質の混合気を形成することができる。この結果、局部的なリッチ状態を生じることが無く、安定した均質燃焼が実現され、ＮＯｘ，ＨＣ、ＣＯの排出量を大幅に低減することができる。
【００１９】
【発明の実施の形態】
以下、この発明の実施の形態を図面を参照して説明する。
【００２０】
図１，２は、本発明の第１実施例に係る筒内噴射式内燃機関を示している。シリンダブロック１０には複数のシリンダ１１が形成されており、その上面を覆うように、シリンダヘッド１２が固定されている。各シリンダ１１には、図外のピストンが摺動可能に嵌合しており、このピストンの上方に、ペントルーフ形の燃焼室１が形成されている。シリンダヘッド１２には、燃焼室１の吸気側（図１，２の左側）の傾斜面１ａに開口する一対の吸気ポート３ａ，３ｂと、排気側（図１，２の右側）の傾斜面１ｂに開口する一対の排気ポート（図示省略）とが形成されるとともに、各吸気ポート３ａ，３ｂを開閉する一対の吸気弁４ａ，４ｂ及び各排気ポートを開閉する一対の排気弁（図示省略）が設けられている。
【００２１】
図１に示すように、これら吸，排気ポートに囲まれたシリンダ１１の略中央には点火プラグ１３が設けられ、この点火プラグ１３の先端が燃焼室１内に臨んでいる。また、電磁式の燃料噴射弁２は、その中心軸が斜め下方へ向かった姿勢で、吸気ポート３ａ，３ｂの下側に設けられている。特に、燃料噴射弁２は、図１に示すシリンダ軸方向視で一対の吸気ポート３ａ，３ｂの間に配置されている。この燃料噴射弁２は、その先端部が燃焼室１内に臨んでおり、燃焼室１内に直接燃焼を噴射するように構成されている。
【００２２】
各吸気ポート３ａ，３ｂの途中には、各吸気ポート３ａ，３ｂを遮断する（絞る）バタフライ式の吸気遮断弁（絞り弁）５ａ，５ｂが設置されている。そして、シリンダヘッド１２には、吸気ポート３ａ，３ｂにおける各吸気遮断弁５ａ，５ｂの上流側と下流側とをバイパスするバイパス通路６が形成されている。つまり、バイパス通路６は、その上流側端部６ｃで吸気遮断弁５ａ，５ｂよりも上流側の吸気ポート３ａ，３ｂの合流部３ｃから分岐しており、途中で二股に分岐して、一方の分岐通路６ａが一方の吸気ポート３ａの開口部近傍に合流しており、他方の分岐通路６ｂが他方の吸気ポート３ｂの開口部近傍に合流している。各分岐通路６ａ，６ｂの中心軸は、図１に示すシリンダ軸方向視で燃焼室１の外周部に沿うように設定されている。
【００２３】
また、吸気弁４ａ，４ｂとの間をシールするバルブシート部８（図３，４）が形成された各吸気ポート３ａ，３ｂの燃焼室１側の開口縁部には、シリンダ中央部寄りの周方向一部分に、切欠部７ａ，７ｂが切欠形成されている。各切欠部７ａ，７ｂは、図３に示すように、バルブシート部８と傾斜面１ａとの間の段部を切り欠くように形成され、かつ、図１に示すシリンダ軸方向視で、シリンダ中央部側へ略三日月状に張り出すように形成されている。
【００２４】
なお、上記燃料噴射弁２，吸気遮断弁５ａ，５ｂ等は図示しないＥＣＵ（エンジン・コントロール・ユニット）に接続されており、このＥＣＵによって、燃料噴射時期及び燃料噴射量が制御されるとともに、吸気遮断弁５ａ，５ｂが開閉制御される。
【００２５】
図３，４は、吸気弁４ａ（４ｂ）が開き始めた直後の状態、つまりリフト量が約１〜２ｍｍ程度の低リフト状態を示しており、図３は、切欠部７ａ（７ｂ）が形成された部分を示す図２のＡ−Ａ断面対応図、図４は、切欠部７ａ，７ｂのない部分を示す図２のＢ−Ｂ断面対応図である。
【００２６】
このような低リフト状態では、主に切欠部７ａ，７ｂを通って吸気が燃焼室１内へ流入する。つまり、図４に示す切欠部７ａ，７ｂの無い部分に比して、切欠部７ａ，７ｂが形成されている部分で、燃焼室１への吸気の流入が促進される。この結果、低リフト時における吸気の流入方向Ｓ１は、切欠部７ａ，７ｂが形成されている方向、すなわちシリンダ軸方向視でシリンダ中心方向となる。
【００２７】
一方、吸気弁４ａ，４ｂが比較的高くリフトした高リフト状態では、切欠部７ａ，７ｂの有無は吸気の流れにほとんど影響せず、従って、燃焼室１へ流入する吸気の流入方向は、吸気遮断弁５ａ，５ｂが閉じていない場合には吸気ポート３ａ，３ｂの中心軸に沿う方向、吸気遮断弁５ａ，５ｂが閉じている場合にはバイパス通路６ａ，６ｂの中心軸に沿う方向Ｓ２（図１）となる。
【００２８】
図５は、エンジン回転数及びエンジン負荷に対して設定された運転領域を表している。同図に示すように、主に低負荷時には成層リーン領域となり、圧縮行程で燃料を噴射して、点火プラグ１３の近傍のみに比較的濃い混合気を形成する成層燃焼が行われる。また、全開出力等の高負荷時には均質ストイキ領域となり、圧縮行程で燃料を噴射して、理論空燃比近傍の混合気を燃焼室１全体に均質に形成する均質ストイキ燃焼が行われる。更に、主に中負荷時には均質リーン領域となり、主に燃費を低減するために、上記の均質ストイキ燃焼時よりも空燃比を大きくした均質リーン燃焼が行われる。
【００２９】
この均質リーン運転領域では、主に燃焼室１内のガス流動を強化するために、吸気遮断弁５ａ，５ｂを閉とし、バイパス通路６ａ，６ｂを通して吸気を燃焼室１へ流入させる。この場合、吸気行程の初期段階では、吸気弁４ａ，４ｂが低リフト状態にあり、吸気は切欠部７ａ，７ｂを通って燃焼室１へ流入するため、前述のように吸気の流入方向Ｓ１は、シリンダ中心方向を指向する。一方、吸気行程の中盤では高リフト状態となるため、燃焼室１へ流入する吸気の流入方向Ｓ２が、バイパス通路６ａ，６ｂの中心軸に沿う方向、すなわち燃焼室１の外周部に沿う方向となる。このように本実施例では、均質リーン燃焼時における１回の吸気行程期間中に、燃焼室１へ流入する吸気の方向を、低リフト時と高リフト時で大きく変化させている。
【００３０】
図６は、この均質リーン燃焼時における燃料噴射時期を示している。本実施例では、必要燃料量を、１回の吸気行程期間中における吸気の方向が異なる複数（ここでは２回）のタイミングに分けて噴射するように制御している。具体的には、１回目の燃料噴射Ｆ１は、吸気弁４ａ，４ｂが低リフト状態にある時期、すなわち吸気の流入方向Ｓ１がシリンダ中心を指向する状態で行われ、２回目の燃料噴射Ｆ２は、吸気弁４ａ，４ｂが高リフト状態にある時期、すなわち吸気の流入方向Ｓ２が燃焼室１の外周部に沿う状態で行われる。
【００３１】
従って、１回目に噴射された燃料と２回目に噴射された燃料とが、それぞれ流入方向の異なる吸気の流れに乗って効果的に拡散され、燃焼室１内での燃料の拡散が促進されるため、燃焼室１全体に均質な可燃混合気を形成することができる。この結果、良好な均質リーン燃焼を実現でき、局部的なリッチ状態を生じることが無いので、ＮＯｘ等の排出量を抑制することが可能となる。
【００３２】
なお、均質ストイキ燃焼時では、吸気遮断弁５ａ，５ｂが開弁されるため、高リフト時における吸気の流入方向は吸気ポート３ａ，３ｂの中心軸に沿う方向となる。この場合でも、１回の吸気行程期間中に、低リフト時の吸入方向Ｓ１と高リフト時の吸入方向とが異なる形となる。従って、このように吸気の流入方向が異なる低リフト時と高リフト時に分けて燃料を噴射することにより、燃焼室１内での燃料の拡散が促進され、燃焼室１全体に均質な可燃混合気を形成することができる。この結果、良好な均質ストイキ燃焼を実現でき、局部的なリッチ状態を生じることが無いので、ＨＣ，ＣＯ等の排出量を抑制することが可能となる。
【００３３】
なお、１回目と２回目の燃料の噴射量は同量である必要は無く、それぞれの噴射期間における流入吸気量に応じた噴射割合が効果的である。更に、この吸気量の割合に対する１回目の噴射割合を２回目よりも大きくする方が望ましい。これは、１回目の方が燃料の拡散する時間を長くとれるため、拡散時間の短い２回目の噴射よりも吸気割合に対する噴射割合を大きくしても、十分に燃料を拡散できることから、より均質の程度を高めることができるからである。
【００３４】
図７，８は、本発明の第２実施例に係る筒内噴射式内燃機関を示している。なお、以下に示す実施例において、上記第１実施例と同一構成部分には同じ参照符号を付して重複する説明を適宜省略する。
【００３５】
この第２実施例は、一方の吸気ポート３ａにのみ、この吸気ポート３ａを遮蔽する吸気遮断弁５ａが設けられるとともに、他方の吸気ポート３ｂの開口縁部にのみ切欠部１７ｂが形成され、かつ、バイパス通路６ａ，６ｂ（図１，２）が設けられていない点で、第１実施例と相違している。上記の切欠部１７ｂは、一方の吸気弁４ａに近接する周方向一部分に形成されている。
【００３６】
均質リーン燃焼時には、吸気遮断弁５ａが閉弁され、主として他方の吸気ポート３ｂから燃焼室１へ吸気が流入する。ここで、吸気行程の初期段階つまり低リフト状態では、主に切欠部１７ｂを通して吸気が燃焼室１へ流入し、その流入方向Ｓ３は、図７で下方へ向かう方向となる。従って、燃焼室１内には、図７で反時計回りのスワール流動が生成される。一方、吸気行程の中盤つまり高リフト状態では、燃焼室１へ流入する吸気の流入方向Ｓ４は、他方の吸気ポート３ｂの中心軸に沿う方向、つまり図７で右方向となり、燃焼室１内に図７で時計回りのスワール流動が生成される。すなわち本実施例では、吸気遮断弁５ａや切欠部７ｂを利用して、１回の吸気行程期間中における吸気の流入方向を、低リフト時と高リフト時で大きく変化させている。
【００３７】
そして、このように吸気の流入方向が異なる低リフト時と高リフト時の２回に分けて燃料を噴射制御することで、それぞれの吸気の流れに乗って燃料を良好に拡散させることができ、第１実施例と同様、燃焼室１全体に均質な混合気を形成することが可能となる。
【００３８】
図９，１０は、本発明の第３実施例に係る筒内噴射式内燃機関を示している。この第３実施例では、バイパス通路６ａ，６ｂや吸気遮断弁５ａ，５ｂ（図１，２）が設けられておらず、かつ、各吸気ポート３ａ，３ｂの開口縁部に形成される切欠部２７ａ，２７ｂが、シリンダ軸方向視で燃料噴射弁２を指向する周方向一部分に配置されている。つまり、各切欠部２７ａ，２７ｂは、高リフト時における吸気の流入方向Ｓ６と略逆方向となる周方向一部分に形成されている。
【００３９】
このように実施例では、吸気遮断弁が無いことから、均質リーン燃焼時及び均質ストイキ燃焼時の双方で、吸気の流入方向は同じように変化する。
【００４０】
詳述すると、均質燃焼時における１回の吸気行程期間中において、吸気行程初期の低リフト時には、両切欠部２７ａ，２７ｂの形成された方向Ｓ５より吸気が燃焼室１内へ流入し、この燃焼室１の外周部に沿って流れる形となる。従って、この低リフト時に噴射された１回目の噴射燃料は、この流れに乗って、主に燃焼室１の外周部に拡散することになる。一方、吸気行程中期の高リフト時には、吸気の流入方向Ｓ６は吸気ポート３ａ，３ｂの中心軸に沿う方向となるため、この期間に噴射された２回目の噴射燃料は、主に燃焼室１の中央部に拡散することになる。この結果、２回に分けて噴射された燃料は、それぞれの吸気の流れに乗って燃焼室１全体に良好に拡散され、上記第１，第２実施例と同様、燃焼室１内に均質な混合気を形成することが可能となる。
【図面の簡単な説明】
【図１】本発明の第１実施例に係る筒内噴射式内燃機関を上方から見た透視対応図。
【図２】上記第１実施例の筒内噴射式内燃機関を示す断面対応図。
【図３】図１のＡ−Ａ断面対応図。
【図４】図１のＢ−Ｂ断面対応図。
【図５】エンジン回転数及びエンジン負荷に対して設定された運転領域を示すグラフ。
【図６】均質燃焼時の燃料噴射時期を示すグラフ。
【図７】本発明の第２実施例に係る筒内噴射式内燃機関を上方から見た透視対応図。
【図８】上記第２実施例の筒内噴射式内燃機関を示す断面対応図。
【図９】本発明の第３実施例に係る筒内噴射式内燃機関を上方から見た透視対応図。
【図１０】上記第３実施例の筒内噴射式内燃機関を示す断面対応図。
【符号の説明】
１…燃焼室
２…燃料噴射弁
３ａ，３ｂ…吸気ポート
５ａ，５ｂ…吸気遮断弁
６…バイパス通路
７ａ，７ｂ…切欠部[0001]
[Industrial applications]
The present invention relates to an internal combustion engine typified by a gasoline engine, and in particular, an in-cylinder injection type internal combustion engine that injects fuel in the vicinity of an intake stroke to perform homogeneous combustion, and injects fuel in the vicinity of a compression stroke to perform stratified combustion. Concerning engine improvement.
[0002]
[Prior art]
A so-called homogeneous combustion is performed by forming a substantially homogeneous air-fuel ratio mixture in the cylinder at the time of fully open output, etc., and in the low load range, a relatively rich mixture is only applied to a part of the cylinder, that is, near the spark plug. An in-cylinder injection internal combustion engine that performs stratified combustion so as to obtain an extremely large average air-fuel ratio is described in, for example, Japanese Patent Application Laid-Open No. 11-036958.
[0003]
Furthermore, in the in-cylinder internal combustion engine described in this publication, in the homogeneous combustion region, after fuel is injected early in the intake stroke, when the intake amount suddenly increases due to depression of the accelerator, etc. The additional fuel is additionally injected during the first half of the compression stroke to suppress an excessive increase in the air-fuel ratio.
[0004]
[Problems to be solved by the invention]
However, in the conventional in-cylinder internal combustion engine, when performing homogeneous combustion, the fuel injected in the intake stroke is diffused into the cylinder by riding on a constant intake flow flowing from the intake port into the combustion chamber. For this reason, the degree of fuel diffusion is non-uniform between the mainstream portion of the intake flow and the stagnation region, and the homogeneity of the air-fuel mixture in the cylinder is not very good. As a result, there is a problem that the combustion temperature rises locally in a rich region and the amount of NOx emission increases during homogeneous lean combustion in which the air-fuel ratio is set to a relatively large value even in homogeneous combustion. Further, during homogeneous stoichiometric combustion in which the air-fuel ratio is set in the vicinity of the stoichiometric air-fuel ratio, there is a problem in that oxygen shortage occurs locally in a rich region, leading to an increase in emissions of HC, CO, and the like.
[0005]
In particular, as in the technique of the above publication, when fuel injection is performed in multiple times during homogeneous combustion, it becomes more difficult to form a homogeneous mixture in the combustion chamber, and stable homogeneous combustion can be performed. Can not.
[0006]
The present invention has been made in view of such problems.
[0007]
[Means for Solving the Problems]
In the cylinder injection internal combustion engine according to the present invention, a fuel injection valve for directly injecting fuel into a combustion chamber is arranged on the intake side, fuel injection is performed in the vicinity of the intake stroke, and homogeneous combustion is realized, and in the vicinity of the compression stroke Is configured to realize stratified combustion by performing fuel injection.
[0008]
According to the first aspect of the present invention, the intake direction varying means for changing the inflow direction of the intake air into the combustion chamber during one intake stroke period during homogeneous combustion, and the inflow direction of the intake air during the intake stroke period are provided. and fuel injection control means for injecting fuel separately in different timing, have a, is characterized in that diffused into the combustion chamber put the fuel injected in the respective timings different intake flow of the inflow direction .
[0009]
With such a configuration, fuel injected at each timing rides on the flow of intake air having different inflow directions and is diffused well throughout the combustion chamber, so that a homogeneous air-fuel mixture is formed throughout the combustion chamber. As a result, good homogeneous combustion can be realized, and a local rich state does not occur, so that it is possible to significantly reduce the amount of NOx, HC, CO, etc. emitted.
[0010]
According to a second aspect of the present invention that further embodies the first aspect of the invention, the intake direction varying means has a notch formed in a portion in the circumferential direction of the opening edge of the intake port on the combustion chamber side. During combustion, the inflow direction of the intake air flowing into the combustion chamber mainly through the notch when the intake valve is low lifted is set to be different from the inflow direction of intake air during the high lift.
[0011]
According to this configuration, the inflow direction of the intake air at the time of low lift is directed to the direction in which the notch is formed, and the inflow direction of the intake air can be different between the low lift time and the high lift time. Therefore, by injecting the fuel separately during the low lift and the high lift in which the inflow direction of the intake air is different, the fuel is favorably diffused throughout the combustion chamber along the flow of each intake air.
[0012]
The invention of claim 3 which more specifically embodies the invention of claim 2 includes an intake cutoff valve provided in the middle of the intake port, a bypass passage bypassing the upstream side and the downstream side of the intake cutoff valve of the intake port, In the homogeneous lean combustion where the intake port is shut off by the intake shut-off valve, the inflow direction of the intake air flowing into the combustion chamber through the notch when the intake valve is low lifted, and the bypass passage mainly during high lift It is characterized in that the inflow directions of the intake air flowing through and into the combustion chamber are different from each other.
[0013]
According to this configuration, during one intake stroke period during homogeneous lean combustion, the intake air inflow direction is in the direction along which the notch is formed during low lift, and along the central axis of the bypass passage during high lift. To change.
[0014]
According to a fourth aspect of the present invention, which further embodies the second aspect of the present invention, a pair of intake ports are opened on the intake side of each combustion chamber, and the fuel injection valve is a double intake as viewed in the cylinder axial direction. A homogeneous lean disposed between the ports, provided with an intake shut-off valve at one intake port, and formed with the notch at the opening edge of the other intake port, and shutting off one intake port with the intake shut-off valve During combustion, the inflow direction of intake air that flows into the combustion chamber through the notch when the intake valve is low lifted and the inflow direction of intake air that flows into the combustion chamber mainly through the other intake port during high lift are mutually It is characterized by being set differently.
[0015]
According to this configuration, during one intake stroke period during homogeneous lean combustion, the intake air inflow direction follows the central axis of the other intake port in the direction in which the notch is formed during low lift and in the high lift. Change direction.
[0016]
Further, according to the invention of claim 5, which is a more specific embodiment of the invention of claim 2, a pair of intake ports are opened on the intake side of each combustion chamber, and the fuel injection valve is a double intake as viewed in the cylinder axial direction. Located between the ports, the notches are formed at the opening edges of both intake ports, and each notch is formed in a portion of the circumferential direction that is substantially opposite to the inflow direction of intake during high lift. It is characterized by that.
[0017]
According to this configuration, during one intake stroke period during homogeneous combustion, the intake air inflow direction is in the direction along which the notch is formed during low lift, and in the direction along the central axis of both intake ports during high lift. Change.
[0018]
【The invention's effect】
As described above, according to the present invention, during one intake stroke period during homogeneous combustion, the direction of intake air flow into the combustion chamber is changed and fuel is injected at a plurality of timings with different intake air inflow directions. Due to the configuration, the fuel injected at each timing rides on the flow of intake air having different inflow directions and is diffused well throughout the combustion chamber, so that a homogeneous air-fuel mixture can be formed in the combustion chamber. As a result, a local rich state is not generated, stable homogeneous combustion is realized, and NOx, HC, and CO emissions can be greatly reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0020]
1 and 2 show a direct injection internal combustion engine according to a first embodiment of the present invention. A plurality of cylinders 11 are formed in the cylinder block 10, and a cylinder head 12 is fixed so as to cover the upper surface thereof. A piston (not shown) is slidably fitted in each cylinder 11, and a pent roof type combustion chamber 1 is formed above the piston. The cylinder head 12 includes a pair of intake ports 3a and 3b that open on an inclined surface 1a on the intake side (left side in FIGS. 1 and 2) of the combustion chamber 1, and an inclined surface 1b on the exhaust side (right side in FIGS. 1 and 2). And a pair of exhaust valves (not shown) for opening and closing the exhaust ports, and a pair of intake valves 4a and 4b for opening and closing the intake ports 3a and 3b. Is provided.
[0021]
As shown in FIG. 1, a spark plug 13 is provided substantially at the center of the cylinder 11 surrounded by the intake and exhaust ports, and the tip of the spark plug 13 faces the combustion chamber 1. The electromagnetic fuel injection valve 2 is provided on the lower side of the intake ports 3a and 3b in a posture in which the central axis is inclined obliquely downward. In particular, the fuel injection valve 2 is disposed between the pair of intake ports 3a and 3b as viewed in the cylinder axial direction shown in FIG. The tip of the fuel injection valve 2 faces the combustion chamber 1 and is configured to inject combustion directly into the combustion chamber 1.
[0022]
In the middle of each intake port 3a, 3b, butterfly-type intake cutoff valves (throttle valves) 5a, 5b that shut off (throttle) the intake ports 3a, 3b are installed. The cylinder head 12 is formed with a bypass passage 6 that bypasses the upstream side and the downstream side of the intake cutoff valves 5a and 5b in the intake ports 3a and 3b. In other words, the bypass passage 6 branches from the merging portion 3c of the intake ports 3a, 3b upstream of the intake shutoff valves 5a, 5b at the upstream end 6c, and branches into a fork in the middle. The branch passage 6a joins near the opening of one intake port 3a, and the other branch passage 6b joins near the opening of the other intake port 3b. The central axis of each of the branch passages 6a and 6b is set along the outer peripheral portion of the combustion chamber 1 as viewed in the cylinder axial direction shown in FIG.
[0023]
Further, the opening edge on the combustion chamber 1 side of each intake port 3a, 3b in which the valve seat portion 8 (FIGS. 3 and 4) for sealing between the intake valves 4a, 4b is formed is close to the center of the cylinder. Cutout portions 7a and 7b are formed in a part in the circumferential direction. As shown in FIG. 3, each notch 7a, 7b is formed so as to cut out a step portion between the valve seat portion 8 and the inclined surface 1a, and the cylinder is viewed in the cylinder axial direction shown in FIG. It is formed so as to project in a substantially crescent shape toward the center side.
[0024]
The fuel injection valve 2, the intake shut-off valves 5a, 5b and the like are connected to an ECU (Engine Control Unit) (not shown). The ECU controls the fuel injection timing and the fuel injection amount, and also controls the intake air. The shutoff valves 5a and 5b are controlled to open and close.
[0025]
3 and 4 show a state immediately after the intake valve 4a (4b) starts to open, that is, a low lift state in which the lift amount is about 1 to 2 mm. FIG. 3 shows the formation of the notch 7a (7b). FIG. 4 is a cross-sectional view corresponding to the AA cross section of FIG. 2 and shows the portion without the notches 7a and 7b.
[0026]
In such a low lift state, the intake air mainly flows into the combustion chamber 1 through the notches 7a and 7b. That is, inflow of the intake air into the combustion chamber 1 is promoted in the portion where the notches 7a and 7b are formed as compared with the portion where the notches 7a and 7b are not shown in FIG. As a result, the intake air inflow direction S1 at the time of low lift is the direction in which the notches 7a and 7b are formed, that is, the cylinder center direction when viewed in the cylinder axial direction.
[0027]
On the other hand, in the high lift state in which the intake valves 4a and 4b are lifted relatively high, the presence or absence of the notches 7a and 7b hardly affects the flow of the intake air, and therefore the inflow direction of the intake air flowing into the combustion chamber 1 is When the shutoff valves 5a and 5b are not closed, the direction along the central axis of the intake ports 3a and 3b. When the shutoff valves 5a and 5b are closed, the direction S2 along the central axis of the bypass passages 6a and 6b ( Fig. 1).
[0028]
FIG. 5 shows the operation region set for the engine speed and the engine load. As shown in the figure, the stratified charge combustion is performed mainly in the stratified lean region at low load, injecting fuel in the compression stroke, and forming a relatively rich mixture only in the vicinity of the spark plug 13. In addition, a homogeneous stoichiometric region is obtained at a high load such as a fully open output, and homogeneous stoichiometric combustion is performed in which fuel is injected in the compression stroke to uniformly form a mixture near the stoichiometric air-fuel ratio in the entire combustion chamber 1. Further, the homogeneous lean region is mainly performed at a medium load, and the homogeneous lean combustion is performed in which the air-fuel ratio is larger than that during the homogeneous stoichiometric combustion in order to mainly reduce the fuel consumption.
[0029]
In this homogeneous lean operation region, in order to mainly strengthen the gas flow in the combustion chamber 1, the intake shutoff valves 5a and 5b are closed, and the intake air flows into the combustion chamber 1 through the bypass passages 6a and 6b. In this case, in the initial stage of the intake stroke, the intake valves 4a and 4b are in a low lift state, and the intake air flows into the combustion chamber 1 through the notches 7a and 7b. , Oriented in the cylinder center direction. On the other hand, in the middle stage of the intake stroke, a high lift state is established. Therefore, the inflow direction S2 of the intake air flowing into the combustion chamber 1 is a direction along the central axis of the bypass passages 6a and 6b, that is, a direction along the outer peripheral portion of the combustion chamber 1. Become. As described above, in this embodiment, the direction of the intake air flowing into the combustion chamber 1 during the single intake stroke period during the homogeneous lean combustion is greatly changed between the low lift time and the high lift time.
[0030]
FIG. 6 shows the fuel injection timing during the homogeneous lean combustion. In this embodiment, the required amount of fuel is controlled to be injected in a plurality of (in this case, two) timings in which the direction of intake air is different during one intake stroke period. Specifically, the first fuel injection F1 is performed when the intake valves 4a and 4b are in a low lift state, that is, in a state where the intake air inflow direction S1 is directed toward the cylinder center, and the second fuel injection F2 is performed. When the intake valves 4a and 4b are in a high lift state, that is, the intake air inflow direction S2 is along the outer peripheral portion of the combustion chamber 1.
[0031]
Therefore, the fuel injected at the first time and the fuel injected at the second time are effectively diffused on the flow of intake air having different inflow directions, and the diffusion of the fuel in the combustion chamber 1 is promoted. Therefore, a homogeneous combustible air-fuel mixture can be formed in the entire combustion chamber 1. As a result, good homogeneous lean combustion can be realized, and a local rich state does not occur, so that it is possible to suppress the discharge amount of NOx and the like.
[0032]
Note that, during homogeneous stoichiometric combustion, the intake shutoff valves 5a and 5b are opened, so that the inflow direction of intake air during high lift is along the central axis of the intake ports 3a and 3b. Even in this case, during one intake stroke period, the suction direction S1 at the time of low lift and the suction direction at the time of high lift are different. Accordingly, by injecting the fuel separately during the low lift and the high lift in which the intake air inflow directions are different in this way, the diffusion of the fuel in the combustion chamber 1 is promoted, and a homogeneous combustible air-fuel mixture in the entire combustion chamber 1 is achieved. Can be formed. As a result, good homogeneous stoichiometric combustion can be realized, and a local rich state does not occur, so it is possible to suppress emissions such as HC and CO.
[0033]
Note that the first and second fuel injection amounts do not have to be the same, and an injection ratio corresponding to the inflow intake air amount in each injection period is effective. Furthermore, it is desirable to make the first injection ratio with respect to the intake amount ratio larger than the second injection ratio. This is because the fuel can be diffused sufficiently even if the injection ratio with respect to the intake ratio is made larger than the second injection with a short diffusion time because the fuel can be diffused longer in the first time. This is because the degree can be increased.
[0034]
7 and 8 show a direct injection internal combustion engine according to a second embodiment of the present invention. In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and repeated description is omitted as appropriate.
[0035]
In the second embodiment, only one intake port 3a is provided with an intake cutoff valve 5a that shields the intake port 3a, and a notch 17b is formed only at the opening edge of the other intake port 3b. The second embodiment is different from the first embodiment in that bypass passages 6a and 6b (FIGS. 1 and 2) are not provided. The notch 17b is formed in a part in the circumferential direction adjacent to the one intake valve 4a.
[0036]
During homogeneous lean combustion, the intake shutoff valve 5a is closed, and intake air mainly flows into the combustion chamber 1 from the other intake port 3b. Here, in the initial stage of the intake stroke, that is, in the low lift state, the intake air mainly flows into the combustion chamber 1 through the notch 17b, and the inflow direction S3 is a downward direction in FIG. Accordingly, a counterclockwise swirl flow in FIG. 7 is generated in the combustion chamber 1. On the other hand, in the middle of the intake stroke, that is, in the high lift state, the inflow direction S4 of the intake air flowing into the combustion chamber 1 is a direction along the central axis of the other intake port 3b, that is, the right direction in FIG. In FIG. 7, a clockwise swirl flow is generated. That is, in the present embodiment, the intake flow direction during one intake stroke period is greatly changed between a low lift and a high lift using the intake cutoff valve 5a and the notch 7b.
[0037]
And, by controlling the fuel injection in two times at the time of low lift and high lift where the inflow direction of the intake air is different in this way, the fuel can be diffused well on the flow of each intake air, As in the first embodiment, a homogeneous air-fuel mixture can be formed in the entire combustion chamber 1.
[0038]
9 and 10 show a direct injection internal combustion engine according to a third embodiment of the present invention. In the third embodiment, the bypass passages 6a and 6b and the intake shut-off valves 5a and 5b (FIGS. 1 and 2) are not provided, and the notches are formed at the opening edges of the intake ports 3a and 3b. 27a and 27b are arranged in a part in the circumferential direction facing the fuel injection valve 2 as viewed in the cylinder axial direction. That is, the notches 27a and 27b are formed in a portion in the circumferential direction that is substantially opposite to the intake air inflow direction S6 during high lift.
[0039]
In this way, in the embodiment, since there is no intake shutoff valve, the intake air inflow direction changes in the same way during both homogeneous lean combustion and homogeneous stoichiometric combustion.
[0040]
More specifically, during one intake stroke period during homogeneous combustion, at the time of low lift at the beginning of the intake stroke, intake air flows into the combustion chamber 1 from the direction S5 in which both the notches 27a and 27b are formed, and this combustion The shape flows along the outer periphery of the chamber 1. Therefore, the first injected fuel injected at the time of this low lift rides on this flow and diffuses mainly to the outer peripheral portion of the combustion chamber 1. On the other hand, at the time of high lift in the middle of the intake stroke, the inflow direction S6 of the intake air is in a direction along the central axis of the intake ports 3a and 3b, so the second injected fuel injected during this period is mainly in the combustion chamber 1. It will diffuse to the center. As a result, the fuel injected in two steps is satisfactorily diffused throughout the combustion chamber 1 along the respective intake flows, and is homogeneous in the combustion chamber 1 as in the first and second embodiments. An air-fuel mixture can be formed.
[Brief description of the drawings]
FIG. 1 is a perspective corresponding view of a direct injection internal combustion engine according to a first embodiment of the present invention as viewed from above.
FIG. 2 is a cross-sectional view showing the direct injection internal combustion engine of the first embodiment.
3 is a cross-sectional view taken along the line AA in FIG.
4 is a cross-sectional view corresponding to BB in FIG. 1;
FIG. 5 is a graph showing an operation region set with respect to an engine speed and an engine load.
FIG. 6 is a graph showing fuel injection timing during homogeneous combustion.
FIG. 7 is a perspective corresponding view of a direct injection internal combustion engine according to the second embodiment of the present invention as viewed from above.
FIG. 8 is a cross-sectional view showing the direct injection internal combustion engine of the second embodiment.
FIG. 9 is a perspective corresponding view of a direct injection internal combustion engine according to the third embodiment of the present invention as viewed from above.
FIG. 10 is a cross-sectional view showing a direct injection internal combustion engine of the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Combustion chamber 2 ... Fuel injection valve 3a, 3b ... Intake port 5a, 5b ... Intake shut-off valve 6 ... Bypass passage 7a, 7b ... Notch

Claims

A fuel injection valve that directly injects fuel into the combustion chamber is arranged on the intake side, and realizes homogeneous combustion by injecting fuel near the intake stroke, and realizes stratified combustion by injecting fuel near the compression stroke In a cylinder injection internal combustion engine,
The intake direction changing means for changing the inflow direction of the intake air into the combustion chamber during one intake stroke period during homogeneous combustion, and the fuel is divided into a plurality of timings in which the inflow direction of the intake air is different during the intake stroke period. and fuel injection control means for injecting, the possess,
An in-cylinder injection internal combustion engine characterized in that fuel injected at each timing is diffused in a combustion chamber on an intake air flow having a different inflow direction .

The intake direction changing means has a notch formed in a part in the circumferential direction of the opening edge on the combustion chamber side of the intake port, and passes through the notch mainly during homogeneous combustion and during low lift of the intake valve. 2. The direct injection internal combustion engine according to claim 1, wherein an inflow direction of intake air flowing into the combustion chamber is set to be different from an inflow direction of intake air during high lift.

An intake cutoff valve provided in the middle of the intake port, and a bypass passage that bypasses the upstream side and the downstream side of the intake cutoff valve of the intake port,
During homogeneous lean combustion with the intake port shut off by the intake shut-off valve, the direction of intake air flowing into the combustion chamber through the notch when the intake valve is lifted low, and the combustion chamber mainly through the bypass passage at high lift 3. The direct injection internal combustion engine according to claim 2, wherein the inflow directions of intake air flowing into the engine are set to be different from each other.

A pair of intake ports are opened on the intake side of each combustion chamber, and the fuel injection valve is disposed between both intake ports as viewed in the cylinder axial direction.
An intake shut-off valve is provided at one intake port, and the notch is formed at the opening edge of the other intake port.
During homogeneous lean combustion in which one intake port is shut off by the intake shut-off valve, the direction of intake air flowing into the combustion chamber through the notch when the intake valve is lifted low, and the other intake port mainly during high lift 3. The direct injection internal combustion engine according to claim 2, wherein the inflow directions of the intake air flowing into the combustion chamber are different from each other.

A pair of intake ports are opened on the intake side of each combustion chamber, and the fuel injection valve is disposed between both intake ports as viewed in the cylinder axial direction.
The notch is formed at each opening edge of both intake ports, and each notch is formed in a portion in the circumferential direction that is substantially opposite to the inflow direction of intake air during high lift. 2. The cylinder injection internal combustion engine according to 2.