JP3777660B2 - In-cylinder direct injection spark ignition internal combustion engine - Google Patents

In-cylinder direct injection spark ignition internal combustion engine Download PDF

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JP3777660B2
JP3777660B2 JP17914596A JP17914596A JP3777660B2 JP 3777660 B2 JP3777660 B2 JP 3777660B2 JP 17914596 A JP17914596 A JP 17914596A JP 17914596 A JP17914596 A JP 17914596A JP 3777660 B2 JP3777660 B2 JP 3777660B2
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combustion chamber
fuel
cylinder
spark plug
fuel injection
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JPH1026024A (en
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憲司朗 柴田
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Nissan Motor Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P15/00—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits
    • F02P15/02—Arrangements having two or more sparking plugs
    • 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
    • F02B75/00—Other engines
    • F02B75/12—Other methods of operation
    • F02B2075/125—Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
    • 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
    • F02B2275/00—Other engines, components or details, not provided for in other groups of this subclass
    • F02B2275/18—DOHC [Double overhead camshaft]
    • 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
    • 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

Description

【０００１】
【発明の属する技術分野】
本発明は、筒内に燃料噴射弁により燃料を直接噴射し、点火プラグによって火花点火を行う筒内直接噴射式火花点火内燃機関に関し、特に、燃料の噴射時期により、均質混合気形成と成層混合気形成とに切り換える筒内直接噴射式火花点火内燃機関に関する。
【０００２】
【従来の技術】
従来、この種の筒内直接噴射式火花点火内燃機関の構造としては、図８に示すようなものがある（特開平５−２４００４４号公報参照）。
即ち、このものは、ピストン２０冠面とシリンダヘッド２１の下面との間に燃焼室２２を形成し、シリンダの中心に沿ったシリンダ軸線２３を含む平面を挟んでシリンダヘッド２１の一側に吸気ポート２４と他側に排気ポート２５とを夫々備えると共に、各ポート２４，２５は夫々吸気バルブ２６と排気バルブ２７を介して燃焼室２２に連通される。
【０００３】
又、吸気ポート２４側のシリンダヘッド２１側壁には、燃料噴射弁２８が取り付けられ、該燃料噴射弁２８の先端噴孔２８ａが燃焼室２２の周縁部から該燃焼室２２内に臨まされ、吸気ポート２４と排気ポート２５間のシリンダヘッド２１下部壁には、点火プラグ２９が取り付けられ、該点火プラグ２９の先端の電極２９ａは燃焼室２２の中央部付近から該燃焼室２２内に臨まされる。
【０００４】
更に、燃焼室２２内における、吸気ポート２４からの吸気の逆タンブル渦流３０の発生を助長するため、ピストン２０冠面の一側（例えば吸気側）部分に、下に凸の曲面を有した凹所２０ａが形成されると共に、この凹所２０ａからなだらかに隆起してピストン２０の上死点においてシリンダヘッド２１下面に近接する隆起部２０ｂが形成される。
【０００５】
かかる機関においては、負荷の高い運転領域では、吸気行程付近の速い時期で燃料を噴射して、できるだけ均質な混合気を形成する一方、負荷の低い運転領域では、圧縮行程付近の遅い時期で点火プラグ２９の電極２９ａ方向に向いた燃料噴射弁２８から噴射された燃料を直立した吸気ポート２４によるガス流動で輸送することにより、点火プラグ２９付近にのみ着火可能な空燃比の混合気を選択的に形成して、燃焼室２２内の他の部分には希薄な混合気を形成するようにしている。
【０００６】
このように、従来の機関は、燃料噴射時期を機関の運転状態に応じて変更することにより、高負荷域の出力性能と低負荷域の燃費性能とを両立する構成となっている。
【０００７】
【発明が解決しようとする課題】
このような従来の筒内直接噴射式火花点火内燃機関にあっては、上述したように、負荷の低い運転領域では圧縮行程の遅い時期にて燃料噴射弁２８から噴射した燃料を点火プラグ２９付近に輸送するガス流動を生成するべく、吸気ポート２４を直立させる構成となっている。
【０００８】
即ち、燃焼室２２に流入する吸気流を、その旋回方向が、吸気バルブ２６→ピストン２０→排気バルブ２７という順序となる、所謂逆タンブル渦流とするため、吸気ポート２４の燃焼室２２に対する連通方向をシリンダヘッド２１上方からとしている。
このため、吸気ポート２４の燃焼室２２に対する連通方向がシリンダヘッド２１側方からである一般的なレイアウトと比較して、機関の全高が高くなる等の問題点があり、機関の車両搭載性が悪化し、又、一般的な従来の機関に対して大幅な変更が必要になるため、生産性の悪化を来すという問題点がある。
【０００９】
更に、負荷の高い運転領域では均質な混合気を形成する必要があるが、燃料噴射弁２８の噴孔２８ａが燃焼室２２の周縁部から燃焼室２２に臨む構成では、均質な混合気の形成が困難である。
又、燃料噴射弁２８の噴孔２８ａは、シリンダ内壁近くに設置されており、ピストン２０によってシリンダ内壁に付着している潤滑油がかき上げられた場合、これが燃料噴射弁２８の噴孔２８ａに付着し、デポジットとなって燃料噴射弁２８の特性に悪影響を与えるという問題点もある。
【００１０】
つまり、筒内直接噴射式火花点火内燃機関において、均質混合気形成と成層混合気形成の両方を可能にするためには、吸気ポート２４の形態並びに点火プラグ２９と燃料噴射弁２８との関係において、次の点を考慮する必要がある。
即ち、成層混合気を形成するには、逆タンブル流を形成する必要があり、このためには、吸気ポート２４の燃焼室２２に対する連通方向をシリンダヘッド２１上方からとする直立した吸気ポート形態が必要がある。
【００１１】
又、均質混合気を形成するためには、点火プラグ２９がシリンダヘッド２１の略中央部に配置されているのが望ましい一方で、成層混合気を形成するためには、燃料噴射弁２８から噴射された燃料がシリンダヘッド２１の略中央部に配置されている点火プラグ２９に対して直接ではなく間接的に向かうように、燃料噴射弁２８の噴孔２８ａ位置を設定する必要がある。
【００１２】
従って、以上のような、吸気ポート２４の形態並びに点火プラグ２９と燃料噴射弁２８との関係ゆえに、上述した種々の問題点が生起するのである。
そこで、本発明は以上のような従来の問題点に鑑み、筒内直接噴射式火花点火内燃機関において、ピストン冠面の形態並びに点火プラグと燃料噴射弁との関係等において工夫を凝らすことにより、均質混合気形成と成層混合気形成の両方を可能にしつつ、従来生起していた問題点を解決することを課題とする。
【００１３】
【課題を解決するための手段】
このため、請求項１に係る発明は、
燃料噴射弁により、ピストン冠面とシリンダボア内周面とシリンダヘッド下面との間に形成された燃焼室内に燃料を直接噴射し、点火プラグによって火花点火を行う筒内直接噴射式火花点火内燃機関であって、機関運転状態に応じて燃料噴射時期を可変することにより、燃焼室内の燃料濃度分布が均質な均質混合気形成と、燃料濃度分布が不均質な成層混合気形成と、に選択的に切り換え可能な筒内直接噴射式火花点火内燃機関において、
前記燃料噴射弁を、その先端噴孔が燃焼室に対応するシリンダヘッド下面の略中央部において該燃焼室内に露出し、かつ燃料噴霧の中心線がシリンダ中心軸に略平行となるように、燃焼室壁に配設する一方、
前記点火プラグを２つ設け、
一方の第１点火プラグを、その先端の電極が各気筒毎に２つずつ設けられた吸気バルブと排気バルブ間位置で、該排気バルブ側の前記燃料噴射弁近傍位置において、燃焼室内に露出するように、燃焼室壁に配設し、
他方の第２点火プラグを、その先端の電極が前記吸気バルブ間位置の燃焼室周縁部において、該燃焼室内に露出するように、燃焼室壁に配設し、
前記ピストン冠面の吸気側に内面が凹曲面の凹所を形成した。
【００１４】
かかる請求項１に係る発明において、
吸気は、往復運動されるピストン動作によって吸入され、吸気ポートを通り燃焼室内に流入する。燃焼室内のガス流動は、吸気行程中には燃焼室内に流れ、圧縮行程中には、ピストン冠面の凹所内底面に沿って第２点火プラグの電極方向へ向かう流れとなる。
【００１５】
ここで、例えば、機関負荷の高い運転領域では、吸気行程付近の早い時期で燃料を噴射し、噴射燃料と吸気とが均質に混合するようにして、燃焼室内の燃料濃度分布が均質な混合気を形成する（均質混合気形成）。
この場合、燃焼室の中心付近に電極が位置する第１点火プラグにより燃焼室内混合気の中心付近に着火し、混合気を良好に燃焼させる。
【００１６】
一方、例えば、機関負荷の低い運転領域では、圧縮行程付近の遅い時期で燃料を噴射することで、燃焼室内のガス流動が、前述したように、ピストン冠面の凹所内底面に沿って第２点火プラグの電極方向へ向かう流れとなるようにし、第２点火プラグの電極付近にのみに、着火可能な燃料濃度となるような成層混合気を形成する（成層混合気形成）。
【００１７】
即ち、先端の電極が吸気バルブ間位置の燃焼室周縁部において、該燃焼室内に露出する第２点火プラグにより成層混合気に着火して燃焼させる。
尚、この場合、燃料噴射弁から噴射された燃料が第２点火プラグの電極を直撃する構成であると、燃料のくすぶり等を生じてしまうため、噴射燃料が間接的に第２点火プラグの電極に向かうことが望ましく、本請求項１に係る発明のように、燃料噴射弁の噴孔と第２点火プラグの電極とが離れた構成が有効である。
【００１８】
請求項２に係る発明は、前記第１点火プラグを、その先端の電極から後端側に向かうに従って前記燃料噴射弁から離れるように前記燃料噴射弁に対して所定角度を有して配設した。また、請求項３に係る発明は、前記第１点火プラグ並びに燃料噴射弁の配設位置に代えて、前記第１点火プラグを、その先端の電極が燃焼室に対応するシリンダヘッド下面の略中央部において該燃焼室内に露出するように、燃焼室壁に配設する一方、前記燃料噴射弁を、その先端噴孔が吸気バルブと排気バルブ間位置で、該排気バルブ側の前記第１点火プラグ近傍位置において、燃焼室内に露出し、かつ燃料噴霧の中心線がシリンダ中心軸と所定の角度を持つように、燃焼室壁に配設した。
【００１９】
かかる請求項３に係る発明において、燃焼室内のガス流動は、圧縮行程中にはピストン冠面の凹所内底面に沿って第２点火プラグの電極方向へ向かう流れとなる。
この発明においても、機関負荷の高い運転領域では、吸気行程付近の早い時期で燃料を噴射し、噴射燃料と吸気とが均質に混合するようにして、燃焼室内の燃料濃度分布が均質な混合気を形成する（均質混合気形成）。
【００２０】
この場合、燃焼室の中心付近に電極が位置する第１点火プラグにより燃焼室内混合気の中心付近に着火し、混合気を良好に燃焼させる。
一方、機関負荷の低い運転領域では、圧縮行程付近の遅い時期で燃料を噴射することで、燃焼室内のガス流動が、前述したように、ピストン冠面の凹所内底面に沿って第２点火プラグの電極方向へ向かう流れとなるようにし、第２点火プラグの電極付近にのみに、着火可能な燃料濃度となるような成層混合気を形成する（成層混合気形成）。
【００２１】
尚、この発明の場合にも、燃料噴射弁の噴孔と第２点火プラグの電極とが離れた構成であるから、噴射燃料が間接的に第２点火プラグの電極に向い、燃料のくすぶり等を生じる虞がない。
請求項４に係る発明は、前記燃料噴射弁を、その先端噴孔から後端側に向かうほど前記第１点火プラグからは離れるように前記第１点火プラグに対して所定角度を有して配設した。また、請求項５に係る発明は、前記燃料噴射弁を、燃料噴霧の中心線が前記吸気バルブが配設されるシリンダヘッドの吸気ポートの中心軸に対して略直角をなすように、燃焼室壁に配設した。
【００２２】
かかる請求項５に係る発明において、吸気行程中において、燃料噴霧に対して吸気の流れが直交するため、燃料の気化がより促進される。
又、燃料噴射弁は、排気バルブ側に傾いて配設されるが、吸気行程噴射では、吸気の流れにより燃料噴霧が排気バルブ側で燃焼室内に均一に拡がる方向に曲げられる。
【００２３】
請求項４に係る発明は、
前記第１及び第２の点火プラグを、機関運転状態に応じて可変される燃料噴射時期によって使用が切り換えられ、夫々機関運転状態に対応して異なる耐久性を持つように構成した。
請求項５に係る発明は、
前記第１点火プラグよりも、第２点火プラグを小型なものとした。
【００２５】
【発明の効果】
請求項１〜４に係る発明によれば、吸気ポートの燃焼室に対する連通方向がシリンダヘッド側方からである一般的なレイアウトにしつつ、均質混合気形成と成層混合気形成とによる、高負荷域の出力性能向上と低負荷域の燃費性能との両立を図れ、機関の全高が高くなる等の問題点がなくなって、機関の車両搭載性が良好となり、又、一般的な従来の機関に対して大幅な変更が不要になるため、生産性の向上を図ることができる。
【００２６】
又、燃料噴射弁の噴孔がシリンダ内壁から離れた位置に配置されているため、運転領域にかかわらず、ピストンによってシリンダ内壁に付着している潤滑油がかき上げられた場合、これが燃料噴射弁の噴孔に付着する虞がなくなり、デポジットによる燃料噴射弁の特性に悪影響を与えるという問題点を解消することができる。
【００２７】
請求項５に係る発明によれば、均質な混合気濃度分布となり、均質混合気形成をより確実なものとできる。
請求項６及び７に係る発明によれば、例えば、第１点火プラグよりも、耐久性が低くとも良い第２点火プラグを小型なものとすることができ、これにより、点火プラグが配設されるシリンダヘッドの設計自由度を高くすることが可能となる。
【００２９】
【発明の実施の形態】
以下、添付された図面を参照して本発明を詳述する。
図１，図２及び図３は、夫々本発明の筒内直接噴射式火花点火内燃機関の一実施形態である４サイクル内燃機関を示す断面図及び平面図であり、図１は、機関が吸気行程中（上死点と下死点の中間付近）のときを示し、図３は、機関が圧縮行程中（上死点付近）のときを示している。
【００３０】
かかる本発明の筒内直接噴射式火花点火内燃機関は、機関運転状態に応じて燃料噴射時期を可変することにより、燃焼室内の燃料濃度分布が均質な均質混合気形成と、燃料濃度分布が不均質な成層混合気形成と、に選択的に切り換え可能な構成となっている。
これらの図において、シリンダブロック２のシリンダボア２Ａ内にて往復運動されるピストン３の冠面３Ａとシリンダボア２Ａ内周面とシリンダヘッド１下面との間には燃焼室１２が形成され、この燃焼室１２の上部のシリンダヘッド１壁、即ち、シリンダヘッド１下部に形成されたシリンダヘッド燃焼室１２Ａの壁には並列する２つの吸気ポート８と並列する２つの排気ポート９とが設けられ、各吸気ポート８には吸気バルブ１０が、各排気ポート９には排気バルブ１１が、夫々配設され、各吸気ポート８及び各排気ポート９には、夫々図示しない吸気マニホールド及び排気マニホールドが接続される。
【００３１】
ここで、燃料噴射弁４は、燃料ギャラリ５から供給される燃料を燃焼室１２内に直接噴射するものであり、その先端噴孔４ａが燃焼室１２に対応するシリンダヘッド１下面の略中央部において該燃焼室１２内に露出し、かつ燃料噴霧の中心線がシリンダ中心軸に略平行となるように、燃焼室１２のピストン３の冠面３Ａと対向するシリンダヘッド１壁、即ち、シリンダヘッド燃焼室１２Ａの壁に配設される。
【００３２】
点火プラグは２つ（６，７）設けられている。
一方の第１点火プラグ６は、その先端の電極６ａが前記吸気バルブ１０と排気バルブ１１間位置で、該排気バルブ１１側の前記燃料噴射弁４近傍位置において、燃焼室１２内に露出するように、シリンダヘッド燃焼室１２Ａの壁に配設される。
【００３３】
他方の第２点火プラグ７は、その先端の電極７ａが前記吸気バルブ１０間位置の燃焼室１２周縁部において、該燃焼室１２内に露出するように、シリンダヘッド燃焼室１２Ａの壁に配設される。
前記ピストン３の冠面３Ａは、機関が圧縮行程中（上死点付近）のときにおいて、燃料噴射弁４から吸気側に噴射された燃料の噴霧を受けて、該燃料噴霧が第２点火プラグ７の電極７ａ方向に向かわしめる形状に形成される。
【００３４】
具体的には、ピストン３の冠面３Ａの吸気側に内面が凹曲面の凹所３ａが形成される。
次に、かかる構成の作用について説明する。
吸気は、シリンダブロック２のシリンダボア２Ａ内にて往復運動されるピストン３動作によって吸入され、吸気マニホールドから吸気ポート８を通り燃焼室１２内に流入する。燃焼室１２内のガス流動は、吸気行程中には図１の矢印１３で示す流れとなり、圧縮行程中には図３の矢印１３で示すように、ピストン３の冠面３Ａの凹所３ａ内底面に沿って第２点火プラグ７の電極７ａ方向へ向かう流れとなる。
【００３５】
ここで、機関負荷の高い運転領域では、図１に示すような吸気行程付近の早い時期で燃料を噴射し、噴射燃料と吸気とが均質に混合するようにして、燃焼室１２内の燃料濃度分布が均質な混合気を形成する（均質混合気形成）。
この場合、燃焼室１２の中心付近に電極６ａが位置する第１点火プラグ６により燃焼室１２内混合気の中心付近に着火し、混合気を良好に燃焼させる。
【００３６】
一方、機関負荷の低い運転領域では、図３に示すような圧縮行程付近の遅い時期で燃料を噴射することで、燃焼室１２内のガス流動が、前述したように、ピストン３の冠面３Ａの凹所３ａ内底面に沿って第２点火プラグ７の電極７ａ方向へ向かう流れとなるようにし、第２点火プラグ７の電極７ａ付近にのみに、着火可能な燃料濃度となるような成層混合気を形成する（成層混合気形成）。
【００３７】
即ち、先端の電極７ａが吸気バルブ１０間位置の燃焼室１２周縁部において、該燃焼室１２内に露出する第２点火プラグ７により成層混合気に着火して燃焼させる。
尚、この場合、燃料噴射弁４から噴射された燃料が第２点火プラグ７の電極７ａを直撃する構成であると、燃料のくすぶり等を生じてしまうため、噴射燃料が間接的に第２点火プラグ７の電極７ａに向かうことが望ましく、本構成のように、燃料噴射弁４の噴孔３ａと第２点火プラグ７の電極７ａとが離れた構成が有効である。
【００３８】
以上説明した実施形態によると、燃料の噴射時期により均質混合気形成と成層混合気形成とを切り換える筒内直接噴射式火花点火内燃機関において、燃料噴射弁４位置に対して、夫々の混合気形成時に適する位置に配置した２つの点火プラグ６，７を設け、成層混合気形成に適したピストン冠面３Ａ形状とするようにしたから、吸気ポート８の燃焼室１２に対する連通方向がシリンダヘッド１側方からである一般的なレイアウトにしつつ、均質混合気形成と成層混合気形成とによる、高負荷域の出力性能向上と低負荷域の燃費性能との両立を図れ、機関の全高が高くなる等の問題点がなくなって、機関の車両搭載性が良好となり、又、一般的な従来の機関に対して大幅な変更が不要になるため、生産性の向上を図ることができる。
【００３９】
又、燃料噴射弁４の噴孔４ａがシリンダ内壁から離れた位置に配置されているため、運転領域にかかわらず、ピストン３によってシリンダ内壁に付着している潤滑油がかき上げられた場合、これが燃料噴射弁４の噴孔４ａに付着する虞がなくなり、デポジットによる燃料噴射弁４の特性に悪影響を与えるという問題点を解消することができる。
【００４０】
尚、上記の各実施形態の説明から明らかなように、第１点火プラグ６は、機関負荷の高い運転領域で用られ、第２点火プラグ７は、機関負荷の低い運転領域で用られる。
このため、第１及び第２の点火プラグ６及び７は、夫々機関運転状態に対応して異なる耐久性を持つように構成しても良い。
【００４１】
即ち、図４及び図５に示すように、第１点火プラグ６よりも、耐久性が低くとも良い第２点火プラグ７を小型なものとすることができ、これにより、点火プラグ６，７が配設されるシリンダヘッド１の設計自由度を高くすることが可能となる。
図６及び図７は、夫々本発明の筒内直接噴射式火花点火内燃機関の他の実施形態である４サイクル内燃機関を示す断面図及び平面図であり、図６は、機関が圧縮行程中（上死点付近）のときを示している。
【００４２】
この実施形態においては、第１点火プラグ６を、その先端の電極６ａが燃焼室１２に対応するシリンダヘッド１下面の略中央部において該燃焼室１２内に露出するように、シリンダヘッド燃焼室１２Ａの壁に配設する。
又、燃料噴射弁４を、その先端噴孔４ａが吸気バルブ１０と排気バルブ１１間位置で、該排気バルブ１１側の前記第１点火プラグ６近傍位置において、燃焼室１２内に露出し、かつ燃料噴霧の中心線がシリンダ中心軸と所定の角度を持つように、シリンダヘッド燃焼室１２Ａの壁に配設する。
【００４３】
この場合、燃料噴射弁４は、その燃料噴霧の中心軸が吸気バルブ１０が配設されるシリンダヘッド１の吸気ポート８の中心軸に対して略直角をなすように配設される。
尚、この実施形態においても、第１点火プラグ６よりも、耐久性が低くとも良い第２点火プラグ７を小型なものとして、点火プラグ６，７が配設されるシリンダヘッド１の設計自由度を高く効果を得るようにしている。
【００４４】
次に、かかる実施形態の作用について説明する。
燃焼室１２内のガス流動は、圧縮行程中には図の矢印１３で示すように、ピストン冠面３Ａの凹所３ａ内底面に沿って第２点火プラグ７の電極７ａ方向へ向かう流れとなる。
この実施形態においても、機関負荷の高い運転領域では、吸気行程付近の早い時期で燃料を噴射し、噴射燃料と吸気とが均質に混合するようにして、燃焼室１２内の燃料濃度分布が均質な混合気を形成する（均質混合気形成）。
【００４５】
この場合、燃焼室１２の中心付近に電極６ａが位置する第１点火プラグ６により燃焼室内混合気の中心付近に着火し、混合気を良好に燃焼させる。
一方、機関負荷の低い運転領域では、図６に示すような圧縮行程付近の遅い時期で燃料を噴射することで、燃焼室１２内のガス流動が、前述したように、ピストン冠面３Ａの凹所３ａ内底面に沿って第２点火プラグ７の電極７ａ方向へ向かう流れとなるようにし、第２点火プラグ７の電極７ａ付近にのみに、着火可能な燃料濃度となるような成層混合気を形成する（成層混合気形成）。
【００４６】
尚、この実施形態の場合にも、燃料噴射弁４の噴孔４ａと第２点火プラグ７の電極７ａとが離れた構成であるから、噴射燃料が間接的に第２点火プラグ７の電極７ａに向い、燃料のくすぶり等を生じる虞がない。
かかる実施形態においても、吸気ポート８の燃焼室１２に対する連通方向がシリンダヘッド１側方からである一般的なレイアウトにしつつ、均質混合気形成と成層混合気形成とによる、高負荷域の出力性能向上と低負荷域の燃費性能との両立を図れ、機関の車両搭載性向上並びに生産性の向上を図ることができる。
【００４７】
又、デポジットによる燃料噴射弁４の特性に悪影響を与えるという問題点を解消することができる。
特に、この実施形態においては、燃料噴射弁４の燃料噴霧の中心軸が吸気ポート８の中心軸に対して略直角をなすようにしたから、吸気行程中において、燃料噴霧に対して吸気の流れが直交するため、燃料の気化がより促進される。
【００４８】
又、燃料噴射弁４は、排気バルブ１１側に傾いて配設されるが、吸気行程噴射では、吸気の流れにより燃料噴霧が排気バルブ１１側で燃焼室１２内に均一に拡がる方向に曲げられる。
従って，これらにより、均質な混合気濃度分布となり、均質混合気形成をより確実なものとできる。
【図面の簡単な説明】
【図１】 本発明の筒内直接噴射式火花点火内燃機関の一実施形態を示す断面図（機関が吸気行程中）
【図２】 同上の実施形態を示すシリンダヘッドの平面図
【図３】 同上の断面図（機関が圧縮行程中）
【図４】 他の実施形態を示す断面図
【図５】 同上の実施形態を示すシリンダヘッドの平面図
【図６】 更に他の実施形態を示す断面図
【図７】 同上の実施形態を示すシリンダヘッドの平面図
【図８】 従来の筒内直接噴射式火花点火内燃機関を示す断面図
【符号の説明】
１ シリンダヘッド
２Ａ シリンダボア
３ ピストン
３Ａ ピストン冠面
３ａ 凹所
４ 燃料噴射弁
４ａ 噴孔
６ 第１点火プラグ
６ａ 電極
７ 第２点火プラグ
７ａ 電極
８ 吸気ポート
９ 排気ポート
１０ 吸気バルブ
１１ 排気バルブ
１２ 燃焼室[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an in-cylinder direct injection type spark ignition internal combustion engine in which fuel is directly injected into a cylinder by a fuel injection valve and spark ignition is performed by an ignition plug, and more particularly, homogeneous mixture formation and stratified mixing are performed depending on fuel injection timing. The present invention relates to an in-cylinder direct injection spark ignition internal combustion engine that is switched to the formation of air.
[0002]
[Prior art]
Conventionally, this type of direct injection spark ignition internal combustion engine of this type is shown in FIG. 8 (see Japanese Patent Laid-Open No. 5-240044).
That is, in this, a combustion chamber 22 is formed between the crown surface of the piston 20 and the lower surface of the cylinder head 21, and an intake air is introduced into one side of the cylinder head 21 across a plane including the cylinder axis 23 along the center of the cylinder. A port 24 and an exhaust port 25 are provided on the other side, and the ports 24 and 25 communicate with the combustion chamber 22 via an intake valve 26 and an exhaust valve 27, respectively.
[0003]
A fuel injection valve 28 is attached to the side wall of the cylinder head 21 on the intake port 24 side, and a tip injection hole 28a of the fuel injection valve 28 is exposed from the peripheral edge of the combustion chamber 22 into the combustion chamber 22. A spark plug 29 is attached to the lower wall of the cylinder head 21 between the port 24 and the exhaust port 25, and an electrode 29 a at the tip of the spark plug 29 faces the combustion chamber 22 from near the center of the combustion chamber 22. .
[0004]
Further, in order to promote the generation of the reverse tumble vortex 30 of the intake air from the intake port 24 in the combustion chamber 22, a concave portion having a downwardly convex curved surface is formed on one side (for example, the intake side) of the piston 20 crown surface. A location 20a is formed, and a raised portion 20b that gently rises from the recess 20a and is close to the bottom surface of the cylinder head 21 at the top dead center of the piston 20 is formed.
[0005]
In such an engine, in a high-load operating region, fuel is injected at a fast timing near the intake stroke to form a homogeneous mixture as much as possible, while in a low-load operating region, ignition is performed at a late timing near the compression stroke. The fuel injected from the fuel injection valve 28 directed toward the electrode 29a of the plug 29 is transported by gas flow through the upright intake port 24, so that an air-fuel ratio mixture that can be ignited only in the vicinity of the spark plug 29 is selectively selected. Thus, a lean air-fuel mixture is formed in the other part of the combustion chamber 22.
[0006]
As described above, the conventional engine has a configuration in which both the output performance in the high load range and the fuel efficiency performance in the low load range are achieved by changing the fuel injection timing according to the operating state of the engine.
[0007]
[Problems to be solved by the invention]
In such a conventional in-cylinder direct injection spark ignition internal combustion engine, as described above, in the operation region where the load is low, the fuel injected from the fuel injection valve 28 at the time when the compression stroke is late is in the vicinity of the spark plug 29. In order to generate a gas flow to be transported to the intake port 24, the intake port 24 is set upright.
[0008]
That is, since the intake flow flowing into the combustion chamber 22 is a so-called reverse tumble vortex flow in which the swirl direction is the order of the intake valve 26 → the piston 20 → the exhaust valve 27, the communication direction of the intake port 24 with respect to the combustion chamber 22 Is from above the cylinder head 21.
For this reason, there is a problem that the overall height of the engine becomes higher compared to a general layout in which the communication direction of the intake port 24 with respect to the combustion chamber 22 is from the side of the cylinder head 21, and the vehicle mountability of the engine is improved. There is a problem that it deteriorates and productivity is deteriorated because a large change is required to a general conventional engine.
[0009]
Furthermore, it is necessary to form a homogeneous air-fuel mixture in an operating region where the load is high, but in a configuration in which the injection hole 28a of the fuel injection valve 28 faces the combustion chamber 22 from the peripheral edge of the combustion chamber 22, formation of a homogeneous air-fuel mixture is required. Is difficult.
The injection hole 28a of the fuel injection valve 28 is installed near the inner wall of the cylinder, and when the lubricating oil adhering to the inner wall of the cylinder is lifted up by the piston 20, this is formed in the injection hole 28a of the fuel injection valve 28. There is also a problem that it adheres and becomes a deposit, which adversely affects the characteristics of the fuel injection valve 28.
[0010]
In other words, in a direct injection type spark ignition internal combustion engine, in order to enable both homogeneous mixture formation and stratified mixture formation, in the form of the intake port 24 and the relationship between the ignition plug 29 and the fuel injection valve 28, It is necessary to consider the following points.
That is, in order to form a stratified mixture, it is necessary to form a reverse tumble flow. For this purpose, an upright intake port configuration in which the communication direction of the intake port 24 to the combustion chamber 22 is from above the cylinder head 21 is used. There is a need.
[0011]
In order to form a homogeneous air-fuel mixture, it is desirable that the spark plug 29 is disposed at a substantially central portion of the cylinder head 21, while in order to form a stratified air-fuel mixture, an injection from the fuel injection valve 28 is performed. It is necessary to set the position of the injection hole 28a of the fuel injection valve 28 so that the injected fuel is directed not indirectly but directly to the spark plug 29 disposed in the substantially central portion of the cylinder head 21.
[0012]
Therefore, the various problems described above occur due to the configuration of the intake port 24 and the relationship between the spark plug 29 and the fuel injection valve 28 as described above.
Therefore, in view of the conventional problems as described above, the present invention provides an in-cylinder direct injection type spark ignition internal combustion engine, by elaborating on the shape of the piston crown surface and the relationship between the spark plug and the fuel injection valve, etc. It is an object of the present invention to solve the problems that have arisen in the past while enabling both homogeneous and stratified mixture formation.
[0013]
[Means for Solving the Problems]
For this reason, the invention according to claim 1
An in-cylinder direct injection spark ignition internal combustion engine in which fuel is directly injected into a combustion chamber formed between a piston crown surface, a cylinder bore inner peripheral surface, and a cylinder head lower surface by a fuel injection valve, and spark ignition is performed by an ignition plug. Therefore, by varying the fuel injection timing according to the engine operating condition, it is possible to selectively form a homogeneous mixture with a homogeneous fuel concentration distribution in the combustion chamber and a stratified mixture with a non-homogeneous fuel concentration distribution. In a switchable in-cylinder direct injection spark ignition internal combustion engine,
Combusting the fuel injection valve so that the tip injection hole is exposed in the combustion chamber at the substantially central portion of the lower surface of the cylinder head corresponding to the combustion chamber, and the fuel spray center line is substantially parallel to the cylinder central axis While arranged on the chamber wall,
Two spark plugs are provided,
One of the first spark plugs is exposed to the combustion chamber at a position between the intake valve and the exhaust valve in which two electrodes at the tip thereof are provided for each cylinder and in the vicinity of the fuel injection valve on the exhaust valve side. Arranged on the combustion chamber wall,
The other second spark plug is disposed on the combustion chamber wall so that the electrode at the tip thereof is exposed in the combustion chamber at the periphery of the combustion chamber between the intake valves,
A recess having a concave curved inner surface was formed on the intake side of the piston crown surface.
[0014]
In the invention according to claim 1,
The intake air is sucked by a reciprocating piston operation and flows into the combustion chamber through the intake port. The gas flow in the combustion chamber flows into the combustion chamber during the intake stroke, and flows toward the electrode of the second spark plug along the bottom surface of the recess of the piston crown during the compression stroke.
[0015]
Here, for example, in an operating region where the engine load is high, the fuel is injected at an early stage near the intake stroke, and the injected fuel and the intake air are uniformly mixed so that the fuel concentration distribution in the combustion chamber is uniform. (Homogeneous gas mixture formation).
In this case, the first spark plug in which the electrode is positioned near the center of the combustion chamber ignites near the center of the mixture in the combustion chamber, and the mixture is burned well.
[0016]
On the other hand, for example, in the operation region where the engine load is low, by injecting fuel at a late time near the compression stroke, the gas flow in the combustion chamber is second along the bottom surface in the recess of the piston crown as described above. A stratified mixture is formed so that the fuel concentration is ignitable only in the vicinity of the electrode of the second spark plug so as to flow toward the electrode of the spark plug (stratified mixture formation).
[0017]
In other words, the stratified mixture is ignited and burned by the second spark plug exposed in the combustion chamber at the peripheral edge of the combustion chamber at the position between the intake valves of the tip electrode.
In this case, if the fuel injected from the fuel injection valve directly hits the electrode of the second spark plug, fuel smoldering or the like occurs, so that the injected fuel is indirectly connected to the electrode of the second spark plug. As in the invention according to claim 1, a configuration in which the nozzle hole of the fuel injection valve and the electrode of the second spark plug are separated is effective.
[0018]
According to a second aspect of the present invention, the first spark plug is disposed at a predetermined angle with respect to the fuel injection valve so as to move away from the fuel injection valve toward the rear end side from the electrode at the tip. . According to a third aspect of the present invention, in place of the position of the first spark plug and the fuel injection valve, the first spark plug is substantially centered on the lower surface of the cylinder head whose tip electrode corresponds to the combustion chamber. The fuel injection valve is disposed on the wall of the combustion chamber so as to be exposed to the combustion chamber at the portion, and the first injection plug on the exhaust valve side is disposed at a position between the intake valve and the exhaust valve. In the vicinity position, it was exposed to the combustion chamber and disposed on the combustion chamber wall so that the center line of the fuel spray had a predetermined angle with the cylinder central axis.
[0019]
In the invention according to claim 3 , the gas flow in the combustion chamber is a flow toward the electrode of the second spark plug along the inner bottom surface of the recess of the piston crown during the compression stroke.
Also in the present invention, in the operating region where the engine load is high, the fuel is injected at an early stage near the intake stroke so that the injected fuel and the intake air are uniformly mixed, so that the fuel concentration distribution in the combustion chamber is uniform. (Homogeneous gas mixture formation).
[0020]
In this case, the first spark plug in which the electrode is positioned near the center of the combustion chamber ignites near the center of the mixture in the combustion chamber, and the mixture is burned well.
On the other hand, in the operation region where the engine load is low, by injecting fuel at a late time near the compression stroke, the gas flow in the combustion chamber is caused to flow along the bottom surface of the recess of the piston crown surface as described above. The stratified mixture is formed only in the vicinity of the electrode of the second spark plug so that the fuel concentration can be ignited (stratified mixture formation).
[0021]
Even in the case of the present invention, since the injection hole of the fuel injection valve and the electrode of the second spark plug are separated from each other, the injected fuel is indirectly directed to the electrode of the second spark plug, so that fuel smoldering, etc. There is no possibility of producing.
According to a fourth aspect of the present invention, the fuel injection valve is disposed at a predetermined angle with respect to the first spark plug so as to move away from the first spark plug toward the rear end side from the front end injection hole. Set up. The invention according to claim 5 is characterized in that the fuel injection valve is disposed in the combustion chamber such that the center line of the fuel spray is substantially perpendicular to the center axis of the intake port of the cylinder head in which the intake valve is disposed. Arranged on the wall.
[0022]
In the invention according to claim 5 , since the flow of the intake air is orthogonal to the fuel spray during the intake stroke, the vaporization of the fuel is further promoted.
Further, the fuel injection valve is disposed to be inclined toward the exhaust valve side, but in the intake stroke injection, the fuel spray is bent in a direction in which the fuel spray spreads uniformly in the combustion chamber on the exhaust valve side by the flow of the intake air.
[0023]
The invention according to claim 4
The use of the first and second spark plugs is switched depending on the fuel injection timing that is varied according to the engine operating state, and each has different durability corresponding to the engine operating state.
The invention according to claim 5
The second spark plug was made smaller than the first spark plug.
[0025]
【The invention's effect】
According to the inventions according to claims 1 to 4 , a high load region is obtained by forming a homogeneous mixture and forming a stratified mixture while adopting a general layout in which the communication direction of the intake port to the combustion chamber is from the side of the cylinder head. The improvement of the output performance of the engine and the fuel efficiency performance in the low load range can be achieved, the problems such as the increase in the overall height of the engine are eliminated, the vehicle mountability of the engine is improved, and the conventional conventional engine is improved. Therefore, productivity can be improved.
[0026]
Further, since the nozzle hole of the fuel injection valve is arranged at a position away from the cylinder inner wall, regardless of the operation region, when the lubricating oil adhering to the cylinder inner wall is lifted up by the piston, this is the fuel injection valve. There is no possibility of adhering to the nozzle hole, and the problem of adversely affecting the characteristics of the fuel injection valve due to deposit can be solved.
[0027]
According to the invention which concerns on Claim 5 , it becomes a homogeneous mixture concentration distribution, and it can make homogeneous mixture formation more reliable.
According to the inventions according to claims 6 and 7 , for example, the second spark plug, which may be lower in durability than the first spark plug, can be made smaller, whereby the spark plug is disposed. It is possible to increase the degree of freedom in designing the cylinder head.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
1, 2 and 3 are a sectional view and a plan view showing a four-cycle internal combustion engine which is an embodiment of a direct injection type spark ignition internal combustion engine of the present invention, respectively. FIG. Fig. 3 shows the time when the engine is in the compression stroke (near the top dead center). Fig. 3 shows the time when the engine is in the compression stroke (near the top dead center).
[0030]
The in-cylinder direct injection spark ignition internal combustion engine of the present invention varies the fuel injection timing according to the engine operating state, thereby forming a homogeneous mixture with a homogeneous fuel concentration distribution in the combustion chamber and a non-uniform fuel concentration distribution. The structure can be selectively switched between the formation of a homogeneous stratified mixture.
In these figures, a combustion chamber 12 is formed between the crown surface 3A of the piston 3 reciprocated in the cylinder bore 2A of the cylinder block 2, the inner peripheral surface of the cylinder bore 2A, and the lower surface of the cylinder head 1, and this combustion chamber. The cylinder head 1 wall at the top of 12, ie, the wall of the cylinder head combustion chamber 12A formed at the bottom of the cylinder head 1, is provided with two intake ports 8 in parallel and two exhaust ports 9 in parallel. An intake valve 10 and an exhaust valve 11 are respectively provided in the port 8 and the exhaust port 9, and an intake manifold and an exhaust manifold (not shown) are connected to the intake port 8 and the exhaust port 9, respectively.
[0031]
Here, the fuel injection valve 4 directly injects the fuel supplied from the fuel gallery 5 into the combustion chamber 12, and its tip injection hole 4 a is substantially at the center of the lower surface of the cylinder head 1 corresponding to the combustion chamber 12. The cylinder head 1 wall facing the crown surface 3A of the piston 3 of the combustion chamber 12, that is, the cylinder head, is exposed in the combustion chamber 12 and the center line of fuel spray is substantially parallel to the cylinder central axis. It is arranged on the wall of the combustion chamber 12A.
[0032]
Two (6, 7) spark plugs are provided.
One of the first spark plugs 6 has an electrode 6a at the tip thereof exposed in the combustion chamber 12 at a position between the intake valve 10 and the exhaust valve 11 and in the vicinity of the fuel injection valve 4 on the exhaust valve 11 side. Further, it is disposed on the wall of the cylinder head combustion chamber 12A.
[0033]
The other second spark plug 7 is disposed on the wall of the cylinder head combustion chamber 12A so that the electrode 7a at the tip of the second spark plug 7 is exposed in the combustion chamber 12 at the periphery of the combustion chamber 12 between the intake valves 10. Is done.
The crown surface 3A of the piston 3 receives the spray of fuel injected from the fuel injection valve 4 to the intake side when the engine is in the compression stroke (near top dead center), and the fuel spray is the second spark plug. 7 is formed in a shape facing toward the electrode 7a.
[0034]
Specifically, a recess 3a having a concave curved inner surface is formed on the intake side of the crown surface 3A of the piston 3.
Next, the operation of this configuration will be described.
The intake air is sucked by the operation of the piston 3 reciprocated in the cylinder bore 2A of the cylinder block 2, and flows into the combustion chamber 12 from the intake manifold through the intake port 8. The gas flow in the combustion chamber 12 becomes a flow indicated by an arrow 13 in FIG. 1 during the intake stroke, and in the recess 3a of the crown surface 3A of the piston 3 as indicated by an arrow 13 in FIG. 3 during the compression stroke. The flow is directed toward the electrode 7a of the second spark plug 7 along the bottom surface.
[0035]
Here, in the operating region where the engine load is high, the fuel concentration in the combustion chamber 12 is such that fuel is injected at an early stage near the intake stroke as shown in FIG. 1 so that the injected fuel and the intake air are homogeneously mixed. A mixture having a uniform distribution is formed (homogeneous mixture formation).
In this case, the first spark plug 6 in which the electrode 6a is located near the center of the combustion chamber 12 ignites near the center of the air-fuel mixture in the combustion chamber 12, and the air-fuel mixture is burned well.
[0036]
On the other hand, in the operation region where the engine load is low, by injecting fuel at a late timing near the compression stroke as shown in FIG. 3, the gas flow in the combustion chamber 12 causes the crown surface 3A of the piston 3 as described above. The stratified mixing is such that the flow is directed toward the electrode 7a of the second spark plug 7 along the inner bottom surface of the recess 3a, and an ignitable fuel concentration is obtained only in the vicinity of the electrode 7a of the second spark plug 7. Form a stratified mixture.
[0037]
That is, the tip electrode 7 a ignites and burns the stratified mixture by the second spark plug 7 exposed in the combustion chamber 12 at the periphery of the combustion chamber 12 at the position between the intake valves 10.
In this case, if the fuel injected from the fuel injection valve 4 directly hits the electrode 7a of the second spark plug 7, a smoldering of the fuel or the like is generated, so that the injected fuel is indirectly in the second ignition. It is desirable to go to the electrode 7a of the plug 7, and a configuration in which the injection hole 3a of the fuel injection valve 4 and the electrode 7a of the second spark plug 7 are separated as in this configuration is effective.
[0038]
According to the embodiment described above, in the in-cylinder direct injection spark ignition internal combustion engine that switches between the homogeneous mixture formation and the stratified mixture formation according to the fuel injection timing, each mixture formation is performed with respect to the fuel injection valve 4 position. Since the two spark plugs 6 and 7 arranged at appropriate positions are provided and the piston crown surface 3A shape suitable for forming the stratified mixture is formed, the direction of communication of the intake port 8 with respect to the combustion chamber 12 is the cylinder head 1 side. The overall layout of the engine can be increased by improving the output performance in the high load range and fuel consumption performance in the low load range by forming a homogeneous mixture and stratified mixture while maintaining a general layout. This eliminates the above-mentioned problem, and makes the vehicle mountability of the engine better, and also makes it unnecessary to make a significant change to a general conventional engine, so that productivity can be improved.
[0039]
In addition, since the nozzle hole 4a of the fuel injection valve 4 is disposed at a position away from the inner wall of the cylinder, when the lubricating oil adhering to the inner wall of the cylinder is lifted up by the piston 3 regardless of the operation region, There is no possibility of adhering to the injection hole 4a of the fuel injection valve 4, and the problem of adversely affecting the characteristics of the fuel injection valve 4 due to deposit can be solved.
[0040]
As is clear from the description of each of the above embodiments, the first spark plug 6 is used in an operation region where the engine load is high, and the second spark plug 7 is used in an operation region where the engine load is low.
For this reason, you may comprise the 1st and 2nd spark plugs 6 and 7 so that it may have different durability corresponding to an engine operation state, respectively.
[0041]
That is, as shown in FIGS. 4 and 5, the second spark plug 7, which may be lower in durability than the first spark plug 6, can be made smaller, so that the spark plugs 6, 7 It becomes possible to increase the degree of freedom of design of the arranged cylinder head 1.
6 and 7 are a cross-sectional view and a plan view, respectively, showing a four-cycle internal combustion engine which is another embodiment of the direct injection type spark ignition internal combustion engine of the present invention. FIG. 6 is a plan view of the engine during the compression stroke. It shows the time (near top dead center).
[0042]
In this embodiment, the first spark plug 6 is connected to the cylinder head combustion chamber 12 </ b> A so that the electrode 6 a at the tip of the first spark plug 6 is exposed in the combustion chamber 12 at a substantially central portion of the lower surface of the cylinder head 1 corresponding to the combustion chamber 12. On the wall.
Further, the fuel injection valve 4 is exposed in the combustion chamber 12 at a position between the intake valve 10 and the exhaust valve 11 and at a position near the first spark plug 6 on the exhaust valve 11 side. The fuel spray is disposed on the wall of the cylinder head combustion chamber 12A so that the center line of the fuel spray has a predetermined angle with the cylinder center axis.
[0043]
In this case, the fuel injection valve 4 is disposed such that the central axis of the fuel spray is substantially perpendicular to the central axis of the intake port 8 of the cylinder head 1 where the intake valve 10 is disposed.
In this embodiment as well, the second spark plug 7 which may be lower in durability than the first spark plug 6 is made smaller, and the degree of freedom in designing the cylinder head 1 in which the spark plugs 6 and 7 are disposed. So that it is highly effective.
[0044]
Next, the operation of this embodiment will be described.
During the compression stroke, the gas flow in the combustion chamber 12 flows toward the electrode 7a of the second spark plug 7 along the inner bottom surface of the recess 3a of the piston crown surface 3A, as indicated by the arrow 13 in the figure. .
Also in this embodiment, in the operating region where the engine load is high, fuel is injected at an early stage near the intake stroke, and the injected fuel and the intake air are uniformly mixed, so that the fuel concentration distribution in the combustion chamber 12 is uniform. A homogeneous mixture (homogeneous mixture formation).
[0045]
In this case, the first spark plug 6 in which the electrode 6a is located near the center of the combustion chamber 12 ignites near the center of the air-fuel mixture in the combustion chamber, and the air-fuel mixture is burned well.
On the other hand, in the operation region where the engine load is low, by injecting the fuel at a late timing near the compression stroke as shown in FIG. 6, the gas flow in the combustion chamber 12 causes the depression of the piston crown 3A as described above. The stratified mixture is designed to flow toward the electrode 7a of the second spark plug 7 along the inner bottom surface of the location 3a, and only in the vicinity of the electrode 7a of the second spark plug 7 Form (stratified mixture formation).
[0046]
Even in this embodiment, since the injection hole 4a of the fuel injection valve 4 and the electrode 7a of the second spark plug 7 are separated from each other, the injected fuel is indirectly connected to the electrode 7a of the second spark plug 7. There is no risk of fuel smoldering.
Also in this embodiment, the output performance in the high load region by the homogeneous mixture formation and the stratified mixture formation, while adopting a general layout in which the communication direction of the intake port 8 to the combustion chamber 12 is from the side of the cylinder head 1. It is possible to achieve both improvement and fuel efficiency performance in a low load range, and it is possible to improve engine mountability and productivity.
[0047]
Further, the problem of adversely affecting the characteristics of the fuel injection valve 4 due to deposit can be solved.
In particular, in this embodiment, since the central axis of the fuel spray of the fuel injection valve 4 is substantially perpendicular to the central axis of the intake port 8, the flow of the intake air with respect to the fuel spray during the intake stroke. Since these are orthogonal, fuel vaporization is further promoted.
[0048]
The fuel injection valve 4 is inclined to the exhaust valve 11 side. In the intake stroke injection, the fuel spray is bent in a direction in which the fuel spray spreads uniformly in the combustion chamber 12 on the exhaust valve 11 side by the flow of intake air. .
Therefore, these results in a homogeneous gas mixture concentration distribution, and the homogeneous gas mixture formation can be made more reliable.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a direct injection type spark ignition internal combustion engine of the present invention (the engine is in the intake stroke)
FIG. 2 is a plan view of a cylinder head showing the same embodiment as above. FIG. 3 is a cross-sectional view of the cylinder head (the engine is in a compression stroke).
FIG. 4 is a cross-sectional view showing another embodiment. FIG. 5 is a plan view of a cylinder head showing the embodiment. FIG. 6 is a cross-sectional view showing still another embodiment. FIG. 8 is a cross-sectional view of a conventional in-cylinder direct injection spark ignition internal combustion engine.
DESCRIPTION OF SYMBOLS 1 Cylinder head 2A Cylinder bore 3 Piston 3A Piston crown surface 3a Recess 4 Fuel injection valve 4a Injection hole 6 First spark plug 6a Electrode 7 Second spark plug 7a Electrode 8 Intake port 9 Exhaust port 10 Intake valve 11 Exhaust valve 12 Combustion chamber

Claims (7)

燃料噴射弁により、ピストン冠面とシリンダボア内周面とシリンダヘッド下面との間に形成された燃焼室内に燃料を直接噴射し、点火プラグによって火花点火を行う筒内直接噴射式火花点火内燃機関であって、機関運転状態に応じて燃料噴射時期を可変することにより、燃焼室内の燃料濃度分布が均質な均質混合気形成と、燃料濃度分布が不均質な成層混合気形成と、に選択的に切り換え可能な筒内直接噴射式火花点火内燃機関において、
前記燃料噴射弁を、その先端噴孔が燃焼室に対応するシリンダヘッド下面の略中央部において該燃焼室内に露出し、かつ燃料噴霧の中心線がシリンダ中心軸に略平行となるように、燃焼室壁に配設する一方、
前記点火プラグを２つ設け、
一方の第１点火プラグを、その先端の電極が各気筒毎に２つずつ設けられた吸気バルブと排気バルブ間位置で、該排気バルブ側の前記燃料噴射弁近傍位置において、燃焼室内に露出するように、燃焼室壁に配設し、
他方の第２点火プラグを、その先端の電極が前記吸気バルブ間位置の燃焼室周縁部において、該燃焼室内に露出するように、燃焼室壁に配設し、
前記ピストン冠面の吸気側に内面が凹曲面の凹所を形成したことを特徴とする筒内直接噴射式火花点火内燃機関。An in-cylinder direct injection spark ignition internal combustion engine in which fuel is directly injected into a combustion chamber formed between a piston crown surface, a cylinder bore inner peripheral surface, and a cylinder head lower surface by a fuel injection valve, and spark ignition is performed by an ignition plug. Therefore, by varying the fuel injection timing according to the engine operating condition, it is possible to selectively form a homogeneous mixture with a homogeneous fuel concentration distribution in the combustion chamber and a stratified mixture with a non-homogeneous fuel concentration distribution. In a switchable in-cylinder direct injection spark ignition internal combustion engine,
Combusting the fuel injection valve so that the tip injection hole is exposed in the combustion chamber at the substantially central portion of the lower surface of the cylinder head corresponding to the combustion chamber, and the fuel spray center line is substantially parallel to the cylinder central axis While arranged on the chamber wall,
Two spark plugs are provided,
One of the first spark plugs is exposed to the combustion chamber at a position between the intake valve and the exhaust valve in which two electrodes at the tip thereof are provided for each cylinder and in the vicinity of the fuel injection valve on the exhaust valve side. Arranged on the combustion chamber wall,
The other second spark plug is disposed on the combustion chamber wall so that the electrode at the tip thereof is exposed in the combustion chamber at the periphery of the combustion chamber between the intake valves,
An in-cylinder direct injection spark ignition internal combustion engine characterized in that a concave surface is formed on the intake side of the piston crown surface. 前記第１点火プラグを、その先端の電極から後端側に向かうほど前記燃料噴射弁から離れるように前記燃料噴射弁に対して所定角度を有して配設したことを特徴とする請求項１記載の筒内直接噴射式火花点火式内燃機関。 2. The first spark plug is disposed at a predetermined angle with respect to the fuel injection valve so as to move away from the fuel injection valve toward a rear end side from an electrode at the front end thereof. An in-cylinder direct injection spark ignition internal combustion engine. 前記第１点火プラグ並びに燃料噴射弁の配設位置に代えて、
前記第１点火プラグを、その先端の電極が燃焼室に対応するシリンダヘッド下面の略中央部において該燃焼室内に露出するように、燃焼室壁に配設する一方、
前記燃料噴射弁を、その先端噴孔が吸気バルブと排気バルブ間位置で、該排気バルブ側の前記第１点火プラグ近傍位置において、燃焼室内に露出し、かつ燃料噴霧の中心線がシリンダ中心軸と所定の角度を持つように、燃焼室壁に配設した、ことを特徴とする請求項１記載の筒内直接噴射式火花点火内燃機関。 In place of the location of the first spark plug and the fuel injection valve,
The first spark plug is disposed on the combustion chamber wall so that the electrode at the tip thereof is exposed in the combustion chamber at a substantially central portion of the lower surface of the cylinder head corresponding to the combustion chamber,
The fuel injection valve is exposed in the combustion chamber at a position between the intake valve and the exhaust valve at the tip injection hole and in the vicinity of the first spark plug on the exhaust valve side, and the center line of the fuel spray is the cylinder center axis The in-cylinder direct injection spark ignition internal combustion engine according to claim 1 , wherein the direct-injection spark ignition internal combustion engine is disposed on the wall of the combustion chamber so as to have a predetermined angle . 前記燃料噴射弁を、その先端噴孔から後端側に向かうほど前記第１点火プラグからは離れるように前記第１点火プラグに対して所定角度を有して配設したことを特徴とする請求項３記載の筒内直接噴射式火花点火内燃機関。 The fuel injection valve is disposed at a predetermined angle with respect to the first spark plug so as to move away from the first spark plug toward the rear end side from the front end injection hole. Item 5. The direct injection type spark ignition internal combustion engine according to item 3 . 前記燃料噴射弁は、燃料噴霧の中心線が前記吸気バルブが配設されるシリンダヘッドの吸気ポートの中心軸に対して略直角をなすように、燃焼室壁に配設したことを特徴とする請求項３又は請求項４記載の筒内直接噴射式火花点火内燃機関。 The fuel injection valve is disposed on the combustion chamber wall so that a center line of fuel spray is substantially perpendicular to a center axis of an intake port of a cylinder head in which the intake valve is disposed. The in-cylinder direct injection spark ignition internal combustion engine according to claim 3 or 4 . 前記第１及び第２の点火プラグは、機関運転状態に応じて可変される燃料噴射時期によって使用が切り換えられ、夫々機関運転状態に対応して異なる耐久性を持つように構成されたことを特徴とする請求項１〜５のうちいずれか１つに記載の筒内直接噴射式火花点火内燃機関。 The use of the first and second spark plugs is switched according to the fuel injection timing that is variable according to the engine operating state, and each of the first and second spark plugs is configured to have different durability corresponding to the engine operating state. An in-cylinder direct injection spark ignition internal combustion engine according to any one of claims 1 to 5 . 前記第１点火プラグよりも、第２点火プラグを小型なものとしたことを特徴とする請求項６記載の筒内直接噴射式火花点火内燃機関。 The in- cylinder direct injection spark ignition internal combustion engine according to claim 6 , wherein the second spark plug is smaller than the first spark plug .
JP17914596A 1996-07-09 1996-07-09 In-cylinder direct injection spark ignition internal combustion engine Expired - Lifetime JP3777660B2 (en)

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