JP2004036519A - Direct cylinder injection internal combustion engine - Google Patents

Direct cylinder injection internal combustion engine Download PDF

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Publication number
JP2004036519A
JP2004036519A JP2002195608A JP2002195608A JP2004036519A JP 2004036519 A JP2004036519 A JP 2004036519A JP 2002195608 A JP2002195608 A JP 2002195608A JP 2002195608 A JP2002195608 A JP 2002195608A JP 2004036519 A JP2004036519 A JP 2004036519A
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Japan
Prior art keywords
injection
fuel
fuel injection
internal combustion
combustion engine
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JP2002195608A
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JP4126977B2 (en
Inventor
Akihiko Kakuho
角方　章彦
Tomonori Urushibara
漆原　友則
Koji Hiratani
平谷　康治
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Nissan Motor Co Ltd
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Nissan Motor Co Ltd
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Priority to JP2002195608A priority Critical patent/JP4126977B2/en
Priority to US10/421,874 priority patent/US6739309B2/en
Priority to EP03011365A priority patent/EP1369561A3/en
Publication of JP2004036519A publication Critical patent/JP2004036519A/en
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Publication of JP4126977B2 publication Critical patent/JP4126977B2/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
    • F02B23/10—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder
    • F02B23/101—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder the injector being placed on or close to the cylinder centre axis, e.g. with mixture formation using spray guided concepts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F1/00—Cylinders; Cylinder heads 
    • F02F1/24—Cylinder heads
    • F02F2001/244—Arrangement of valve stems in cylinder heads
    • F02F2001/245—Arrangement of valve stems in cylinder heads the valve stems being orientated at an angle with the cylinder axis
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct cylinder injection internal combustion engine allowing the formation of a relatively larger stratified mixture block with no lean mixture region left in a central portion. <P>SOLUTION: The direct cylinder injection internal combustion engine comprises a combustion chamber 4 having a spark plug 10 and a combustion injection valve 9 at the upper part and an inside cavity 12 located near the approximate center of the crowned face of a piston 3 and an outside cavity 13 encircling the outer periphery of the inside cavity 12, wherein fuel injection is carried out several times in a compression stroke when the operated conditions of the engine are within a specified operation region. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、筒内直接噴射式内燃機関に関する。
【０００２】
【従来の技術】
特開２０００−２６５８４１号公報には、燃焼室上面のほぼ中央に点火プラグおよびインジェクタを配設した筒内直噴エンジンにおいて、ピストン冠面の中央に深皿部を、その周囲に浅皿部を設ける技術が開示されている。この従来技術では、インジェクタからの噴霧形状を中空コーン状にするとともに、中低速運転領域では燃料噴射時期を圧縮行程後半に設定して噴霧を深皿部に当て、高速運転領域では燃料噴射時期を圧縮行程前半に設定して噴霧を浅皿部に当てるようにしている。噴霧を深皿部に当てた場合は深皿部の内部とその上方に混合気塊が形成される強成層状態が得られ、噴霧を浅皿部に当てた場合は浅皿部の内部とその上方に混合気塊が形成される弱成層状態が得られる。
【０００３】
【発明が解決しようとする課題】
しかしながら、噴霧を浅皿部に当てた場合、噴霧は浅皿部の側壁面にガイドされて上方へ巻き上がり、その結果浅皿部の内部とその上方に混合気塊が形成されるのであるが、浅皿部の径や側壁面の形状によっては上方に形成される混合気塊がドーナツ状となり、点火プラグによる着火安定性が低くなる場合がある。また、側壁面を内側へ傾ける（リエントラント形状にする）と巻き上がる噴霧を燃焼室中央へ集めることができるが、傾きを大きくするほど燃焼室のＳ／Ｖ比が悪化して出力・燃費性能が悪化する。また、上方の混合気を燃焼室中央に集めることは弱成層状態を得るという本来の目的にも反している。
【０００４】
【課題を解決するための手段】
そこで、本発明の筒内直接噴射式内燃機関は、燃焼室上部に点火プラグと燃焼噴射弁とを有し、ピストン冠面の略中心付近に位置する内側キャビティと、上記内側キャビティの外周を取り巻く外側キャビティと、を有し、機関運転条件の特定運転領域内あるとき、圧縮行程に複数回の燃料噴射を行うとともに、複数回の燃料噴射のうち少なくとも１回の燃料噴射では燃料が上記内側キャビティに入るよう噴射時期を設定し、残りの燃料噴射では燃料が上記外側キャビティに入るよう噴射時期を設定することを特徴としている。
【０００５】
【発明の効果】
本発明によれば、機関運転条件が特定運転領域にあるときに比較的大きな成層混合気塊が得られ、かつその中央部に希薄な混合気領域残される（混合気塊がドーナツ状となる）のを回避することができる。
【０００６】
【発明の実施の形態】
以下、本発明の一実施例を図面に基づいて詳細に説明する。
【０００７】
図１は、本発明に係る筒内直接噴射式内燃機関の構成を示している。シリンダヘッド１と、シリンダブロック２と、ピストン３とによって画成された燃焼室４は、吸気弁５を介して吸気ポート６と、排気弁７を介して排気ポート８とそれぞれ連通している。吸気弁５と排気弁７は、それぞれ吸気弁用カム（図示せず）と、排気弁用カム（図示せず）とによって開閉駆動される。燃焼室４の上面（シリンダヘッド）の略中央付近には、燃料噴射弁９と、点火プラグ１０とが配置されており、機関コントロールユニット（ＥＣＵ）１１からの信号に基づいて、燃料噴射および点火が行われる。
【０００８】
ピストン３冠面の略中央付近には、内側キャビティ１２と外側キャビティ１３からなる二重キャビティが形成されている。詳述すれば、ピストン３冠面の略中心付近に位置する内側キャビティ１２と、この内側キャビティ１２の外周を取り巻く外側キャビティ１３とによって、径の異なる略同心の２重のキャビティが形成されている。そして、内側キャビティ１２の内径をＲｉ、外側キャビティ１３の外径をＲｏ、ボア径をＲ、とすると、Ｒｉ＜（１／２）Ｒ、（１／２）Ｒ≦Ｒｏ≦（３／４）Ｒｏ、となるよう内側キャビティ１２と外側キャビティ１３とはそれぞれ形成されている。
【０００９】
燃料噴射弁９は、圧縮行程後半における筒内圧力上昇時にも噴霧形状の変化が小さく、指向性の強いものが好ましく、本実施例においては、図２に示すようなホールノズル噴射弁（マルチホール噴射弁）を用いている。
【００１０】
尚、燃料噴射弁９としては、スワール噴霧を噴射し、噴射された燃料の噴霧形状が、略中空円錐状で、かつこの中空円錐の一部が燃料噴射方向に沿って切り欠かれた形状となるスワールノズル噴射弁を用いることも可能である。噴霧円錐の一部をきり欠いた噴霧を噴射するスワールノズル噴射弁としては、例えば特開２０００−３２９０３６に開示されているように、ノズル噴孔部に段差を有した構造とすることで、図３に示すような噴霧を形成することができる。
【００１１】
図４に、本発明の機関負荷に対する燃料噴射時期および燃料噴射量の制御方法の概略図を示す。
【００１２】
機関負荷が所定負荷Ｔ０より低いときは、１回のみの噴射を行い、負荷の上昇に対して燃料噴射開始時期を進角させる。その際、燃料噴霧は内側キャビティ１２に受け止められるように燃料噴射時期が設定される。つまり、圧縮行程に１回のみ燃料噴射を行う場合の燃料噴射量は、燃料噴射開始時期を調整することによって増減する。
【００１３】
そして、機関負荷の増大とともに噴射期間が伸びることで、燃料噴霧が内側キャビティ１２で受け止められないような噴射期間となる前に、圧縮行程中に１回のみ燃料噴射を行う制御から、圧縮行程中に燃料噴射を２回に分けて行う分割噴射に切り換える。
【００１４】
分割噴射を行う場合、２回目の燃料噴射は１回のみ燃料噴射を行うの場合に対して、燃料噴射開始時期を遅角するとともに、燃料噴射量を減じることで、１回のみ燃料噴射する場合と分割噴射する場合の２回目噴射の噴射終了時期は概ね同じ時期となるように設定する。尚、分割噴射を行う場合の２回目の燃料噴射の燃料噴射開始時期は、圧縮行程中に１回のみ燃料噴射を行う場合の燃料噴射開始時期の最進角時期よりも遅角側に設定されている。
【００１５】
また、分割噴射時における機関負荷の増大に対する燃料噴射量の増加は、１回目の燃料噴射量を増やすことによって対応し、その際、１回目の燃料噴射開始時期を進角し、燃料噴射終了時期は概ね同じとする。また、分割噴射を行う場合の１回目の燃料噴射の燃料噴射終了時期は、圧縮行程中に１回のみ燃料噴射を行う場合の燃料噴射開始時期の最進角時期よりも進角側に設定されている。
【００１６】
図５に、成層低負荷運転条件において、１回のみ燃料噴射した場合の燃料挙動を示す。
【００１７】
成層低負荷運転条件における燃料噴射時期は、燃料噴射弁９から噴射された燃料が内側キャビティ１２に受け止められるよう設定され、燃料噴霧は内側キャビティ１２底面に衝突する（図５ａ）。その後噴霧は、噴霧の貫徹力によって内側キャビティ１２底面に沿って進行し、燃焼室４上空へと向かう（図５ｂ）。燃料噴霧はピストン３によってその進行方向を変化させるとともに、燃焼室４上空をうずのように旋回し、周囲の空気を巻き込みながら、キャビティ上空に均質混合気が生成される（図５ｃ）。ここで、１回のみの燃料噴射を内側キャビティ１２を指向して行うために、形成される混合気塊は燃焼室４中央付近の比較的コンパクトな均質混合気となる。
【００１８】
図６に、成層高負荷運転条件における燃料挙動を示す。
【００１９】
成層高負荷運転条件では、２回の燃料噴射を行う。まず、圧縮行程の中期付近において、外側キャビティ１３を指向して１回目の燃料噴射を行う（図６ａ）。この一回目の燃料噴射による燃料噴霧は、外側キャビティ１３底面に衝突し、噴霧の貫徹力によって外側キャビティ１３底面を経由して燃焼室４上空へ向かい、周辺空気を巻き込みつつ、均質混合気を形成する（図６ｂ）。ここで、１回目の燃料噴射により形成される混合気塊の大きさは外側キャビティ１３の大きさに依存し、比較的大きな塊となり、かつ燃焼室４中央部分は希薄となる。
【００２０】
１回目の燃料噴射後、圧縮行程の後半、上死点に近い時期に、２回目の燃料噴射を内側キャビティ１２に向けて行う。つまり、２回目の燃料噴射時期は、１回目と同様な噴射角度であっても、内側キャビティ１２に確実に受け止められるような燃料噴射時期に設定されている。成層低負荷時の１回のみ噴射の場合と同様な混合気形成過程を経て、２回目の燃料噴射により小さな塊の均質混合気が形成され（図６ｃ）、１回目の燃料噴射によって形成された略ドーナツ状に近い混合気塊と２回目の燃料噴射によって形成されたコンパクトな混合気塊によって確実な着火がなされ（図６ｄ）、かつ、均質な混合気塊によって排気、燃費性能を損うことなく性能燃焼を達成することができる。
【００２１】
また、全負荷等の高出力運転時には、吸気行程中に燃料噴射を行い、十分な混合時間をとることで、筒内混合気分布を均質化する、いわゆる均質燃焼を行う。
【００２２】
このような実施形態の筒内直接噴射式内燃機関においては、機関運転条件が特定運転領域内にあるとき、圧縮行程に複数回の燃料噴射を行うとともに、複数回の燃料噴射のうち少なくとも１回の燃料噴射では燃料が内側キャビティ１２に入るよう噴射時期を設定し、残りの燃料噴射では燃料が外側キャビティ１３に入るよう噴射時期を設定したため、機関運転条件が特定運転領域内にあるときに比較的大きな成層混合気塊が得られ、かつ、その中央部に希薄な混合気領域が残される（混合気塊がドーナツ状となる）のを回避することができる。（請求項１に対応）
特に、機関負荷が所定負荷Ｔ０より高いとき、圧縮行程に２回の燃料噴射を行うとともに、１回目の燃料噴射では燃料が外側キャビティ１３に入るよう噴射時期を設定し、２回目の燃料噴射では燃料が内側キャビティ１２に入るよう噴射時期を設定したため、燃料噴射量が多いときに比較的大きな成層混合気塊が得られる。（請求項２に対応）
また、１回目の燃料噴射の噴射量のみを増減させて総燃料噴射量を増減させたため、圧縮行程に２回の燃料噴射を行う場合に内側キャビティ１２を経由した燃料により形成される混合気（点火プラグ１０近傍の混合気）の濃度が総燃料噴射量の増減によらずほぼ一定に保たれ、常に良好な着火性が得られる。（請求項３に対応）
また、燃料噴射開始時期を調整して１回目の燃料噴射を増減させたため、圧縮行程に２回の燃料噴射を行う場合に外側キャビティ１３を経由した燃料により形成される混合気の大きさが噴射量の増加に伴って大きくなり、過濃領域の生成を抑制することが可能となる。（請求項４に対応）
また、機関負荷が所定負荷Ｔ０より低いとき、圧縮行程に１回のみ燃料噴射を行うとともに、噴射した燃料が内側キャビティ１２に入るように噴射時期を設定したため、燃料噴射量が少ないときに比較的小さな成層混合気塊が得られる。（請求項５に対応）
また、圧縮行程に２回の燃料噴射を行う場合の２回目の燃料噴射の噴射量を、圧縮行程に１回のみ燃料噴射を行う場合の噴射量の最大量よりも少なくしたため、圧縮行程に２回の燃料噴射を行う場合に内側キャビティ１２を経由した燃料より形成される混合気と外側キャビティ１３を経由した燃料により形成される混合気とが重複して過濃領域の生成されるのを抑制することが可能となる。すなわち、外側キャビティ１３を経由した燃料により形成される混合気はドーナツ状となるが、時間の経過とともに内外へ拡散し、内側キャビティ１２を経由した燃料により混合気が形成されるべき領域にも広がってくる。この状態で圧縮行程に１回のみの燃料噴射を行う場合の噴射量の最大量と同じ量の燃料を２回目の燃料噴射量として噴射すると、点火プラグ１０近傍の混合気が過濃となる場合がある。従って、圧縮行程に２回の燃料噴射を行う場合の２回目の燃料噴射量を圧縮行程に１回のみの燃料噴射を行う場合の噴射量の最大量よりも少なくすることにより過濃領域の生成を抑制する。（請求項６に対応）
また、１回のみの燃料噴射の噴射開始時期を調整して燃料噴射量を増減させたため、圧縮行程に１回のみの燃料噴射を行う場合に内側キャビティ１２を経由した燃料により形成される混合気の大きさが噴射量の増加に伴って大きくなり、過濃領域の生成を抑制することが可能となる。（請求項７に対応）
また、圧縮行程に２回の燃料噴射を行う場合の２回目の燃料噴射の噴射開始時期を、圧縮行程に１回のみ燃料噴射を行う場合の噴射開始時期の最進角時期よりも遅角側に設定したため、噴射量を少なくして点火プラグ１０近傍に確実に着火可能な混合気を形成することができる。（請求項８に対応）
また、圧縮行程に２回の燃料噴射を行う場合の１回目の燃料噴射の噴射終了時期を、圧縮行程に１回のみ燃料噴射を行う場合の噴射開始時期の最進角時期よりも進角側に設定することにより、内側キャビティ１２と外側キャビティ１３との境界部分に燃料が衝突することが避けられ、２つのキャビティを活用した混合気の形成を良好に達成することができる。（請求項９に対応）
また、内側キャビティ１２及び上記外側キャビティ１３を円形とし、かつこれら２つのキャビティを略同心に配置するとともに、上記内側キャビティの外径をボア径の１／２未満に設定したため、極低負荷（アイドル負荷）から低負荷までの負荷範囲では内側キャビティ１２のみを使用して良好な成層混合気塊を形成し、中負荷から高負荷に負荷範囲では２つのキャビティを使用して良好な成層混合気塊を形成することができる。（請求項１０に対応）
ここで、幅広い負荷範囲において良好な成層燃焼を達成するためには、上述した２重同心のキャビティへ燃料噴射を最適な噴射量で確実に噴射し、受け止めることが重要である。
【００２３】
その場合、燃料噴射は噴霧時期、つまりは筒内圧力によらず所定の方向へ飛翔しなければならない。燃料噴射時期が変わり、筒内圧力が変わった場合に燃料噴霧の噴射角度が変化してしまうと、キャビティ１２，１３で確実に決まった量の燃料を受け止められなくなる虞があるためである。また、内側キャビティ１２への過剰な燃料噴射をさけるために、中空な燃料噴霧であることが望まれる。
【００２４】
そこで、燃料噴射弁９としては、噴射背圧によって燃料噴射角度が変化しないマルチホール噴射弁を用いることによって、燃料噴霧の指向位置を確実にすることができ、２つのキャビティをそれぞれ経由した確実な混合気形成が可能となる。（請求項１１に対応）
また、燃料噴射弁９から噴射された燃料の噴霧形状を、略中空円錐状で、かつこの中空円錐の一部が燃料噴射方向に沿って切り欠かれた形状としても、噴射背圧によって燃料噴霧角度が変化することなく、かつ円周上に比較的均質な噴射が可能となるため、均質な混合気分布を形成しやすい。（請求項１２に対応）
また、燃料噴射弁９としてスワールノズル噴射弁を用いて、噴射された燃料の噴霧形状を、略中空円錐状で、かつこの中空円錐の一部が燃料噴射方向に沿って切り欠かれたスワール噴霧とすれば、噴射背圧によって燃料噴霧角度が変化することなく、より微粒化の進んだ燃料噴霧を噴射することで均質な混合気分布を形成することが出来る。（請求項１３に対応）
尚、キャビティの形状としては、図７に示すような各種形状のものも考えられる。キャビティの側壁を垂直より内側に傾かせることで燃料の集中度を増すことが可能となるが、均質燃焼時の均質度低下あるいはＳ／Ｖ比悪化により、全負荷性能および燃費性能悪化が跳ね返りとして存在し、機関諸元により最適化する必要がある。
【図面の簡単な説明】
【図１】本発明に係る筒内直接噴射式内燃機関の構成を示す説明図。
【図２】ホールノズル噴射弁の説明図。
【図３】スワールノズル噴射弁の説明図。
【図４】本発明の機関負荷に対する燃料噴射時期及び燃料噴射量の制御方法の概略図。
【図５】成層低負荷運転条件において、１回のみ燃料噴射した場合の燃料挙動を示す説明図。
【図６】成層高負荷運転条件における燃料挙動を示す説明図。
【図７】その他のキャビティ形状を示す説明図。
【符号の説明】
３…ピストン
４…燃焼室
９…燃料噴射弁
１２…内側キャビティ
１３…外側キャビティ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a direct injection internal combustion engine.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 2000-265841 discloses a cylinder direct injection engine in which a spark plug and an injector are disposed substantially at the center of the upper surface of a combustion chamber, a deep plate portion at the center of a piston crown surface, and a shallow plate portion around the center. A technique for providing is disclosed. In this conventional technique, the shape of the spray from the injector is made into a hollow cone shape, the fuel injection timing is set in the latter half of the compression stroke in the middle and low speed operation region, and the spray is applied to the deep plate portion. The spray is applied to the shallow plate by setting the compression stroke in the first half. When the spray is applied to the deep dish, a strong stratified state is formed in which a mixed air mass is formed inside and above the deep dish, and when the spray is applied to the shallow dish, the inside of the shallow dish and its A weakly stratified state in which an air-fuel mixture is formed above is obtained.
[0003]
[Problems to be solved by the invention]
However, when the spray is applied to the shallow plate, the spray is guided by the side wall surface of the shallow plate and rolls up, and as a result, an air-fuel mixture is formed inside and above the shallow plate. Depending on the diameter of the shallow plate portion and the shape of the side wall surface, the mixture formed above may have a donut shape, and the ignition stability of the ignition plug may be reduced. In addition, when the side wall surface is inclined inward (into a reentrant shape), the rising spray can be collected at the center of the combustion chamber. However, as the inclination increases, the S / V ratio of the combustion chamber deteriorates, and the output / fuel efficiency performance decreases. Getting worse. Also, collecting the upper mixture in the center of the combustion chamber is contrary to the original purpose of obtaining a weakly stratified state.
[0004]
[Means for Solving the Problems]
Therefore, a direct injection type internal combustion engine of the present invention has a spark plug and a combustion injection valve in an upper portion of a combustion chamber, and surrounds an inner cavity located near the center of a piston crown surface and an outer periphery of the inner cavity. An outer cavity, wherein when the engine operating condition is within a specific operating region, a plurality of fuel injections are performed in a compression stroke, and at least one of the plurality of fuel injections causes the fuel to be injected into the inner cavity. The injection timing is set such that the fuel enters the outer cavity in the remaining fuel injection.
[0005]
【The invention's effect】
According to the present invention, a relatively large stratified air-fuel mixture is obtained when the engine operating condition is in the specific operation region, and a lean air-fuel mixture region is left at the center thereof (the air-fuel mixture becomes donut-shaped). Can be avoided.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
[0007]
FIG. 1 shows a configuration of a direct injection internal combustion engine according to the present invention. A combustion chamber 4 defined by the cylinder head 1, the cylinder block 2, and the piston 3 communicates with an intake port 6 via an intake valve 5 and an exhaust port 8 via an exhaust valve 7, respectively. The intake valve 5 and the exhaust valve 7 are opened and closed by an intake valve cam (not shown) and an exhaust valve cam (not shown), respectively. Near the center of the upper surface (cylinder head) of the combustion chamber 4, a fuel injection valve 9 and a spark plug 10 are arranged, and fuel injection and ignition are performed based on a signal from an engine control unit (ECU) 11. Is performed.
[0008]
Near the center of the crown surface of the piston 3, a double cavity including an inner cavity 12 and an outer cavity 13 is formed. More specifically, the inner cavity 12 located near the center of the crown surface of the piston 3 and the outer cavity 13 surrounding the outer periphery of the inner cavity 12 form substantially concentric double cavities having different diameters. . When the inner diameter of the inner cavity 12 is Ri, the outer diameter of the outer cavity 13 is Ro, and the bore diameter is R, Ri <(1/2) R, (1/2) R ≦ Ro ≦ (3/4) The inner cavity 12 and the outer cavity 13 are each formed to be Ro.
[0009]
The fuel injection valve 9 preferably has a small change in spray shape and a high directivity even when the in-cylinder pressure increases in the latter half of the compression stroke. In the present embodiment, a hole nozzle injection valve (multi-hole injection valve) as shown in FIG. Injection valve).
[0010]
In addition, the fuel injection valve 9 injects swirl spray, and the spray shape of the injected fuel has a substantially hollow cone shape and a shape in which a part of the hollow cone is cut out along the fuel injection direction. It is also possible to use a swirl nozzle injection valve. As a swirl nozzle injection valve that injects a spray with a part of the spray cone cut off, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-329036, a structure having a step in a nozzle injection hole portion is used. A spray as shown in FIG. 3 can be formed.
[0011]
FIG. 4 is a schematic diagram showing a method for controlling the fuel injection timing and the fuel injection amount with respect to the engine load according to the present invention.
[0012]
When the engine load is lower than a predetermined load T 0 performs injection only once, advancing the fuel injection start timing the rise in load. At this time, the fuel injection timing is set so that the fuel spray is received by the inner cavity 12. That is, the amount of fuel injection when fuel injection is performed only once during the compression stroke is increased or decreased by adjusting the fuel injection start timing.
[0013]
Then, since the injection period is extended with an increase in the engine load, before the injection period in which the fuel spray cannot be received by the inner cavity 12, the fuel injection is performed only once during the compression stroke. The fuel injection is switched to the split injection in which the fuel injection is performed twice.
[0014]
In the case of performing the split injection, the second fuel injection is performed only once, while the fuel injection start timing is delayed and the fuel injection amount is reduced to perform the fuel injection only once. The injection end timing of the second injection in the case of split injection is set to be substantially the same. The fuel injection start timing of the second fuel injection in the case of performing the split injection is set to be more retarded than the most advanced timing of the fuel injection start timing in the case of performing the fuel injection only once during the compression stroke. ing.
[0015]
Further, the increase in the fuel injection amount with respect to the increase in the engine load at the time of the split injection is dealt with by increasing the first fuel injection amount, in which case the first fuel injection start timing is advanced and the fuel injection end timing is increased. Are generally the same. Further, the fuel injection end timing of the first fuel injection when performing the split injection is set to be more advanced than the most advanced timing of the fuel injection start timing when performing the fuel injection only once during the compression stroke. ing.
[0016]
FIG. 5 shows the fuel behavior when the fuel is injected only once under the stratified low load operation condition.
[0017]
The fuel injection timing under the stratified low-load operation condition is set so that the fuel injected from the fuel injection valve 9 is received by the inner cavity 12, and the fuel spray collides with the bottom surface of the inner cavity 12 (FIG. 5A). Thereafter, the spray proceeds along the bottom surface of the inner cavity 12 due to the penetration force of the spray, and heads toward the upper space of the combustion chamber 4 (FIG. 5B). The fuel spray is changed in its traveling direction by the piston 3 and swirls over the combustion chamber 4 like an eddy, generating a homogeneous mixture over the cavity while entraining the surrounding air (FIG. 5c). Here, since only one fuel injection is directed toward the inner cavity 12, the formed air-fuel mixture becomes a relatively compact homogeneous air-fuel mixture near the center of the combustion chamber 4.
[0018]
FIG. 6 shows the fuel behavior under stratified high load operation conditions.
[0019]
Under the stratified high load operation condition, two fuel injections are performed. First, near the middle stage of the compression stroke, the first fuel injection is performed toward the outer cavity 13 (FIG. 6A). The fuel spray from the first fuel injection collides with the bottom surface of the outer cavity 13 and travels through the bottom surface of the outer cavity 13 to the upper side of the combustion chamber 4 by the penetration force of the spray to form a homogeneous mixture while entraining the surrounding air. (FIG. 6b). Here, the size of the air-fuel mixture formed by the first fuel injection depends on the size of the outer cavity 13, becomes a relatively large mass, and the central portion of the combustion chamber 4 becomes lean.
[0020]
After the first fuel injection, the second fuel injection is performed toward the inner cavity 12 at a time near the top dead center in the latter half of the compression stroke. That is, the second fuel injection timing is set to a fuel injection timing that can be reliably received by the inner cavity 12 even at the same injection angle as the first fuel injection timing. Through a mixture formation process similar to that of the single injection at the time of stratified low load, a small lump of homogeneous mixture was formed by the second fuel injection (FIG. 6c) and formed by the first fuel injection. Positive ignition is achieved by the mixture mixture having a substantially donut shape and the compact mixture mixture formed by the second fuel injection (FIG. 6d), and the homogeneous mixture mixture impairs exhaust and fuel efficiency. Performance combustion can be attained without the need.
[0021]
In addition, during high-power operation such as full load, fuel injection is performed during the intake stroke, and by taking a sufficient mixing time, so-called homogeneous combustion is performed to homogenize the in-cylinder mixture distribution.
[0022]
In the direct injection type internal combustion engine of such an embodiment, when the engine operating condition is within the specific operation range, the fuel injection is performed a plurality of times during the compression stroke, and at least one of the plurality of fuel injections is performed. In the fuel injection, the injection timing was set so that the fuel entered the inner cavity 12, and the injection timing was set so that the fuel entered the outer cavity 13 in the remaining fuel injection. It is possible to avoid the formation of a stratified mixed gas mass which is large in size, and to leave a lean mixture region in the center of the mixed gas mass (the gas mixture becomes donut-shaped). (Corresponding to claim 1)
In particular, when the engine load is higher than a predetermined load T 0, performs two fuel injection in the compression stroke, the first fuel injection to set the injection timing so that the fuel enters the outer cavity 13, second fuel injection Since the injection timing is set so that the fuel enters the inner cavity 12, a relatively large stratified mixture can be obtained when the fuel injection amount is large. (Corresponding to claim 2)
Further, since the total fuel injection amount is increased or decreased by increasing or decreasing only the injection amount of the first fuel injection, the air-fuel mixture formed by the fuel passing through the inner cavity 12 when performing two fuel injections in the compression stroke ( The concentration of the air-fuel mixture in the vicinity of the spark plug 10 is kept substantially constant irrespective of the increase / decrease of the total fuel injection amount, and good ignitability is always obtained. (Corresponding to claim 3)
Also, since the first fuel injection is increased or decreased by adjusting the fuel injection start timing, the size of the fuel-air mixture formed by the fuel passing through the outer cavity 13 when the fuel injection is performed twice during the compression stroke is increased. It becomes larger with an increase in the amount, and it is possible to suppress the generation of an excessively dense area. (Corresponding to claim 4)
The comparison, when the engine load is lower than a predetermined load T 0, performs fuel injection only once in the compression stroke, when injected fuel for setting the injection timing to enter the inner cavity 12, the fuel injection amount is small An extremely small stratified mixture is obtained. (Corresponding to claim 5)
Further, since the injection amount of the second fuel injection in the case where two fuel injections are performed in the compression stroke is smaller than the maximum amount of the injection amount in the case where the fuel injection is performed only once in the compression stroke, two injections are performed in the compression stroke. In the case of performing the fuel injection twice, the mixture formed by the fuel passing through the inner cavity 12 and the mixture formed by the fuel passing through the outer cavity 13 are prevented from being overlapped to generate the rich region. It is possible to do. That is, the air-fuel mixture formed by the fuel passing through the outer cavity 13 has a donut shape, but diffuses in and out over time, and also spreads to a region where the air-fuel mixture is formed by the fuel passing through the inner cavity 12. Come. In this state, if the same amount of fuel as the maximum amount of injection is injected as the second fuel injection amount when performing only one fuel injection in the compression stroke, the mixture in the vicinity of the ignition plug 10 becomes rich. There is. Therefore, by making the second fuel injection amount when performing two fuel injections during the compression stroke less than the maximum amount of injection amount when performing only one fuel injection during the compression stroke, the rich region is generated. Suppress. (Corresponding to claim 6)
Further, since the fuel injection amount is increased or decreased by adjusting the injection start timing of only one fuel injection, the mixture formed by the fuel passing through the inner cavity 12 when performing only one fuel injection in the compression stroke. Becomes larger with an increase in the injection amount, and it is possible to suppress the generation of the rich region. (Corresponding to claim 7)
Further, the injection start timing of the second fuel injection in the case where the fuel injection is performed twice in the compression stroke is more retarded than the most advanced timing of the injection start timing in the case where the fuel injection is performed only once in the compression stroke. , It is possible to form an air-fuel mixture that can reliably ignite near the spark plug 10 by reducing the injection amount. (Corresponding to claim 8)
Further, the injection end timing of the first fuel injection in the case where the fuel injection is performed twice in the compression stroke is advanced from the most advanced timing of the injection start timing in the case where the fuel injection is performed only once in the compression stroke. With this setting, it is possible to prevent the fuel from colliding with the boundary between the inner cavity 12 and the outer cavity 13, and to achieve the formation of the air-fuel mixture utilizing the two cavities. (Corresponding to claim 9)
Further, since the inner cavity 12 and the outer cavity 13 are circular, and these two cavities are arranged substantially concentrically, and the outer diameter of the inner cavity is set to less than の of the bore diameter, extremely low load (idle In the load range from (load) to low load, a good stratified mixture is formed using only the inner cavity 12, and in the load range from medium to high load, a good stratified mixture is formed using two cavities. Can be formed. (Corresponding to claim 10)
Here, in order to achieve good stratified combustion over a wide load range, it is important to reliably inject and receive the fuel injection into the above-described double concentric cavity with an optimum injection amount.
[0023]
In this case, the fuel injection must fly in a predetermined direction regardless of the spray timing, that is, the cylinder pressure. If the injection angle of the fuel spray changes when the fuel injection timing changes and the in-cylinder pressure changes, the cavities 12 and 13 may not be able to reliably receive a predetermined amount of fuel. In order to avoid excessive fuel injection into the inner cavity 12, a hollow fuel spray is desired.
[0024]
Therefore, by using a multi-hole injection valve in which the fuel injection angle does not change due to the injection back pressure as the fuel injection valve 9, the directivity position of the fuel spray can be ensured, and the reliable position through each of the two cavities can be ensured. A mixture can be formed. (Corresponding to claim 11)
Further, even if the spray shape of the fuel injected from the fuel injection valve 9 is a substantially hollow cone shape and a part of the hollow cone is cut away along the fuel injection direction, the fuel spray by the injection back pressure can be performed. Since a relatively uniform injection can be performed on the circumference without changing the angle, a uniform mixture distribution can be easily formed. (Corresponding to claim 12)
Further, using a swirl nozzle injection valve as the fuel injection valve 9, the spray shape of the injected fuel is substantially hollow conical, and a part of the hollow cone is swirl spray cut out along the fuel injection direction. In this case, a homogeneous fuel-air mixture can be formed by injecting more atomized fuel spray without changing the fuel spray angle due to the injection back pressure. (Corresponding to claim 13)
The cavity may have various shapes as shown in FIG. By inclining the side wall of the cavity inward from the vertical, it is possible to increase the concentration of fuel, but due to the decrease in homogeneity during homogeneous combustion or the deterioration of S / V ratio, the deterioration of full load performance and fuel consumption performance is rebounded. Exists and needs to be optimized according to engine specifications.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a configuration of a direct injection type internal combustion engine according to the present invention.
FIG. 2 is an explanatory view of a hole nozzle injection valve.
FIG. 3 is an explanatory view of a swirl nozzle injection valve.
FIG. 4 is a schematic diagram of a control method of a fuel injection timing and a fuel injection amount with respect to an engine load according to the present invention.
FIG. 5 is an explanatory diagram showing a fuel behavior when fuel is injected only once under a stratified low-load operation condition.
FIG. 6 is an explanatory diagram showing fuel behavior under stratified high load operation conditions.
FIG. 7 is an explanatory view showing another cavity shape.
[Explanation of symbols]
3 Piston 4 Combustion chamber 9 Fuel injection valve 12 Inner cavity 13 Outer cavity

Claims (13)

燃焼室上部に点火プラグと燃焼噴射弁とを有し、ピストン冠面の略中心付近に位置する内側キャビティと、上記内側キャビティの外周を取り巻く外側キャビティと、を備えた筒内直接噴射式内燃機関において、
機関運転条件の特定運転領域内あるとき、圧縮行程に複数回の燃料噴射を行うとともに、複数回の燃料噴射のうち少なくとも１回の燃料噴射では燃料が上記内側キャビティに入るよう噴射時期を設定し、残りの燃料噴射では燃料が上記外側キャビティに入るよう噴射時期を設定することを特徴とする筒内直接噴射式内燃機関。An in-cylinder direct injection internal combustion engine having an ignition plug and a combustion injection valve in the upper part of the combustion chamber, and having an inner cavity located near the center of the piston crown surface, and an outer cavity surrounding the outer periphery of the inner cavity. At
When the engine operation condition is within the specific operation range, the fuel injection is performed a plurality of times in the compression stroke, and the injection timing is set so that the fuel enters the inner cavity in at least one of the plurality of fuel injections. The direct injection type internal combustion engine is characterized in that the injection timing is set so that the remaining fuel is injected into the outer cavity. 機関負荷が所定負荷より高いとき、圧縮行程に２回の燃料噴射を行うとともに、１回目の燃料噴射では燃料が上記外側キャビティに入るよう噴射時期を設定し、２回目の燃料噴射では燃料が上記内側キャビティに入るよう噴射時期を設定することを特徴とする請求項１に記載の筒内直接噴射式内燃機関。When the engine load is higher than the predetermined load, the fuel injection is performed twice in the compression stroke, and the injection timing is set so that the fuel enters the outer cavity in the first fuel injection, and the fuel is injected in the second fuel injection. The direct injection internal combustion engine according to claim 1, wherein the injection timing is set so as to enter the inner cavity. １回目の燃料噴射の噴射量のみを増減させて総燃料噴射量を増減させることを特徴とする請求項２に記載の筒内直接噴射式内燃機関。3. The direct injection internal combustion engine according to claim 2, wherein the total fuel injection amount is increased or decreased by increasing or decreasing only the injection amount of the first fuel injection. 燃料噴射開始時期を調整して１回目の燃料噴射を増減させることを特徴とする請求項３に記載の筒内直接噴射式内燃機関。4. The direct injection internal combustion engine according to claim 3, wherein the first fuel injection is increased or decreased by adjusting a fuel injection start timing. 機関負荷が上記所定負荷より低いとき、圧縮行程に１回のみ燃料噴射を行うとともに、噴射した燃料が上記内側キャビティに入るように噴射時期を設定することを特徴とする請求項２に記載の筒内直接噴射式内燃機関。3. The cylinder according to claim 2, wherein when the engine load is lower than the predetermined load, the fuel is injected only once during the compression stroke, and the injection timing is set so that the injected fuel enters the inner cavity. Internal direct injection type internal combustion engine. 圧縮行程に２回の燃料噴射を行う場合の２回目の燃料噴射の噴射量を、圧縮行程に１回のみ燃料噴射を行う場合の噴射量の最大量よりも少なくすることを特徴とする請求項５に記載の筒内直接噴射式内燃機関。The injection amount of the second fuel injection when performing two fuel injections during the compression stroke is smaller than the maximum injection amount when performing the fuel injection only once during the compression stroke. 6. A direct injection internal combustion engine according to claim 5. １回のみの燃料噴射の噴射開始時期を調整して燃料噴射量を増減させることを特徴とする請求項５に記載の筒内直接噴射式内燃機関。6. The direct injection type internal combustion engine according to claim 5, wherein the fuel injection amount is increased or decreased by adjusting the injection start timing of only one fuel injection. 圧縮行程に２回の燃料噴射を行う場合の２回目の燃料噴射の噴射開始時期を、圧縮行程に１回のみ燃料噴射を行う場合の噴射開始時期の最進角時期よりも遅角側に設定することを特徴とする請求項７に記載の筒内直接噴射式内燃機関。When the fuel injection is performed twice during the compression stroke, the injection start timing of the second fuel injection is set to be more retarded than the most advanced timing of the injection start timing when performing the fuel injection only once during the compression stroke. The direct injection type internal combustion engine according to claim 7, wherein: 圧縮行程に２回の燃料噴射を行う場合の１回目の燃料噴射の噴射終了時期を、圧縮行程に１回のみ燃料噴射を行う場合の噴射開始時期の最進角時期よりも進角側に設定することを特徴とする請求項７に記載の筒内直接噴射式内燃機関。When the fuel injection is performed twice during the compression stroke, the injection end timing of the first fuel injection is set to be more advanced than the most advanced timing of the injection start timing when performing the fuel injection only once during the compression stroke. The direct injection type internal combustion engine according to claim 7, wherein: 上記内側キャビティ及び上記外側キャビティを円形とし、かつこれら２つのキャビティを略同心に配置するとともに、上記内側キャビティの外径をボア径の１／２未満に設定し、上記外側キャビティの外径をボア径の１／２以上３／４未満の範囲に設定することを特徴とする請求項１〜９のいずれかに記載の筒内直接噴射式内燃機関。The inner cavity and the outer cavity are circular, and these two cavities are arranged substantially concentrically. The outer diameter of the inner cavity is set to less than half of the bore diameter, and the outer diameter of the outer cavity is The direct injection type internal combustion engine according to any one of claims 1 to 9, wherein the internal diameter is set to a range of not less than 1/2 and less than 3/4 of the diameter. 上記燃料噴射弁はマルチホール噴射弁であることを特徴とする請求項１〜１０のいずれかに記載の筒内直接噴射式内燃機関。The direct injection internal combustion engine according to any one of claims 1 to 10, wherein the fuel injection valve is a multi-hole injection valve. 上記燃料噴射弁から噴射された燃料の噴霧形状は、略中空円錐状で、かつこの中空円錐の一部が燃料噴射方向に沿って切り欠かれた形状となっていることを特徴とする請求項１〜１０のいずれかに記載の筒内直接噴射式内燃機関。The spray shape of the fuel injected from the fuel injection valve has a substantially hollow cone shape, and a part of the hollow cone is cut away along the fuel injection direction. An in-cylinder direct injection internal combustion engine according to any one of claims 1 to 10. 上記燃料噴射弁はスワール噴霧を噴射するスワールノズル噴射弁であり、このスワールノズル噴射弁から噴射された燃料の噴霧形状は、略中空円錐状で、かつこの中空円錐の一部が燃料噴射方向に沿って切り欠かれた形状となっていることを特徴とする請求項１〜１０のいずれかに記載の筒内直接噴射式内燃機関。The fuel injection valve is a swirl nozzle injection valve that injects swirl spray.The spray shape of the fuel injected from the swirl nozzle injection valve has a substantially hollow cone shape, and a part of the hollow cone is in the fuel injection direction. The direct injection type internal combustion engine according to any one of claims 1 to 10, wherein the internal combustion engine has a shape cut off along the cylinder.
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JP2006118427A (en) * 2004-10-21 2006-05-11 Toyota Motor Corp Compression ignition internal combustion engine
JP2006125388A (en) * 2004-10-28 2006-05-18 Caterpillar Inc Double bowl piston
JP2021050641A (en) * 2019-09-24 2021-04-01 本田技研工業株式会社 Fuel injection control device

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CN102128533B (en) * 2011-03-31 2012-07-18 合肥美的荣事达电冰箱有限公司 Air-cooled freezer

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Publication number Priority date Publication date Assignee Title
JP2006118427A (en) * 2004-10-21 2006-05-11 Toyota Motor Corp Compression ignition internal combustion engine
JP2006125388A (en) * 2004-10-28 2006-05-18 Caterpillar Inc Double bowl piston
JP2021050641A (en) * 2019-09-24 2021-04-01 本田技研工業株式会社 Fuel injection control device
JP7171531B2 (en) 2019-09-24 2022-11-15 本田技研工業株式会社 fuel injection controller

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