JP4026438B2

JP4026438B2 - Fuel injection valve and fuel injection device

Info

Publication number: JP4026438B2
Application number: JP2002221258A
Authority: JP
Inventors: 恵理子松村; 啓壮武田
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2001-11-27
Filing date: 2002-07-30
Publication date: 2007-12-26
Anticipated expiration: 2022-07-30
Also published as: JP2003227443A

Description

【０００１】
【発明の属する技術分野】
本発明は燃料噴射弁及び燃料噴射装置に関する。
【０００２】
【従来の技術】
従来より、機関負荷が比較的低いときには燃焼室内の限られた領域内に混合気を形成してこの混合気を点火栓により着火し、機関負荷が高くなると燃焼室内を均一混合気により満たしてこの均一混合気を点火栓により着火するようにした筒内噴射式内燃機関が公知である。このような筒内噴射式内燃機関では通常、シリンダヘッド内壁面の中央部に点火栓を配置し、シリンダヘッド内壁面の周辺部に燃料噴射弁を配置し、燃料噴射弁の下方から点火栓の下方まで延びる凹溝をピストン頂面上に形成し、機関負荷が比較的低いときには燃料を凹溝内に向けて噴射し、この噴射燃料を凹溝の内壁面により案内して点火栓周りの限られた領域内に混合気を形成するようにしている。
【０００３】
この場合、点火栓周りに形成される混合気は着火可能である必要があり、即ち噴射燃料を空気と良好に混合させる必要がある。
【０００４】
そこで、燃料噴射弁の噴孔をスリット状に形成した筒内噴射式内燃機関が公知である（特開平９−１５８７３６号公報参照）。このようにすると、凹溝に向かう噴射燃料が偏平扇状に形成されるので噴射燃料と空気との接触面積を大きくすることができ、従って点火栓周りに着火可能な混合気が確実に形成される。
【０００５】
【発明が解決しようとする課題】
このスリット状噴孔はその偏平扇状噴霧の横断面の長軸が凹溝の底壁面に対し概ね平行になるように配置されており、このためスリット状噴孔から噴射された燃料はシリンダ中心軸線方向にはほとんど拡がらない。従って、噴射燃料が確実に凹溝内を進行することが可能になる。
【０００６】
しかしながら、噴射燃料がシリンダ中心軸線方向にほとんど拡がらないので、機関負荷が比較的高いときに燃焼室内に均一混合気を形成するのが困難になるという問題点がある。
【０００７】
なお、特開平９−１２６０９５号公報には一対のスリット状噴孔を具備した燃料噴射弁が開示されているが、これらスリット状噴孔により形成される偏平扇状噴霧の横断面の長軸は共にシリンダ中心軸線に対し垂直であるので、シリンダ中心軸線方向への噴射燃料の拡散はほとんど期待できない。
【０００８】
そこで本発明の目的は、機関負荷が比較的低いときに点火栓周りに着火可能な混合気を確実に形成しつつ、機関負荷が比較的高いときに燃焼室内に均一混合気を確実に形成することができる燃料噴射弁及び燃料噴射装置を提供することにある。
【００１５】
【課題を解決するための手段】
また、前記課題を解決するために１番目の発明によれば、燃焼室頂部のほぼ中央部に点火栓を配置すると共に燃焼室頂部の周縁部に燃料噴射弁を配置し、燃料噴射弁の下方から点火栓の下方まで延びる凹溝をピストン頂面上に形成し、機関圧縮行程に燃料噴射弁から凹溝内に燃料を噴射して該燃料を凹溝の内壁面により点火栓周りに案内し、このとき点火栓周りに形成される混合気を点火栓により着火する第１の燃焼と、機関吸気行程に燃料噴射弁から燃料を噴射して燃焼室内全体を満たす混合気を形成し、該混合気を点火栓により着火する第２の燃焼とを切り替え可能な筒内噴射式内燃機関において、前記燃料噴射弁が一対のスリット状噴孔を具備し、スリット状噴孔の扇状縦断面の中心と、燃料噴射弁のサックの中心との間の距離が互いに異なるようにこれら一対のスリット状噴孔を形成し、該距離が大きい方のスリット状噴孔を、その偏平扇状噴霧の横断面の長軸が凹溝底壁面に対し概ね平行になるように、かつ該距離が小さい方のスリット状噴孔を、その偏平扇状噴霧の扇状縦断面がシリンダ中心軸線に対し概ね平行になるように配置している。
【００１６】
また、前記課題を解決するために２番目の発明によれば、燃焼室頂部のほぼ中央部に点火栓を配置すると共に燃焼室頂部の周縁部に燃料噴射弁を配置し、燃料噴射弁の下方から点火栓の下方まで延びる凹溝をピストン頂面上に形成し、機関圧縮行程に燃料噴射弁から凹溝内に燃料を噴射して該燃料を凹溝の内壁面により点火栓周りに案内し、このとき点火栓周りに形成される混合気を点火栓により着火する第１の燃焼と、機関吸気行程に燃料噴射弁から燃料を噴射して燃焼室内全体を満たす混合気を形成し、該混合気を点火栓により着火する第２の燃焼とを切り替え可能な筒内噴射式内燃機関において、前記燃料噴射弁が一対のスリット状噴孔を具備し、スリット状噴孔の扇状縦断面の中心角に対する噴霧角の比が互いに異なるようにこれら一対のスリット状噴孔を形成し、前記比が大きい方のスリット状噴孔を、その偏平扇状噴霧の横断面の長軸が凹溝底壁面に対し概ね平行になるように、かつ前記比が小さい方のスリット状噴孔を、その偏平扇状噴霧の扇状縦断面がシリンダ中心軸線に対し概ね平行になるように配置している。
【００１７】
また、前記課題を解決するために３番目の発明によれば、燃焼室頂部のほぼ中央部に点火栓を配置すると共に燃焼室頂部の周縁部に燃料噴射弁を配置し、燃料噴射弁の下方から点火栓の下方まで延びる凹溝をピストン頂面上に形成し、機関圧縮行程に燃料噴射弁から凹溝内に燃料を噴射して該燃料を凹溝の内壁面により点火栓周りに案内し、このとき点火栓周りに形成される混合気を点火栓により着火する第１の燃焼と、機関吸気行程に燃料噴射弁から燃料を噴射して燃焼室内全体を満たす混合気を形成し、該混合気を点火栓により着火する第２の燃焼とを切り替え可能な筒内噴射式内燃機関において、前記燃料噴射弁が一対の偏平扇状噴霧形成用噴孔を具備し、筒内圧力が低いときの噴霧角に対する筒内圧力が高いときの噴霧角の比が互いに異なるようにこれら一対の偏平扇状噴霧形成用噴孔を形成し、前記比が大きい方の偏平扇状噴霧形成用噴孔を、その偏平扇状噴霧の横断面の長軸が凹溝底壁面に対し概ね平行になるように、かつ前記比が小さい方の偏平扇状噴霧形成用噴孔を、その偏平扇状噴霧の扇状縦断面がシリンダ中心軸線に対し概ね平行になるように配置している。
【００１８】
また、４番目の発明によれば３番目の発明において、前記比が小さい方の偏平扇状噴霧形成用噴孔をスリット状噴孔から形成し、前記比が大きい方の偏平扇状噴霧形成用噴孔を、それぞれの噴霧が互いに衝突することにより偏平扇状噴霧を形成するように指向される複数の筒状噴孔から形成している。
【００１９】
なお、本明細書においてスリット状噴孔の噴霧角というのは偏平扇状噴霧の扇状縦断面を含んで拡がる平面内における噴霧角をいうものとする。
【００２０】
【発明の実施の形態】
図１から図４は本発明を４ストローク火花点火式内燃機関に適用した場合を示している。図１から図４を参照すると、１は機関本体、２はシリンダブロック、３はシリンダヘッド、４はピストン、５は燃焼室、６は電気制御式燃料噴射弁、７は点火栓、８は一対の吸気弁、９は吸気ポート、１０は一対の排気弁、１１は排気ポートをそれぞれ示す。なお、図２において線Ｍは燃料噴射弁６の中心軸線を示している。
【００２１】
図３に示されるように、一対の吸気弁８及び一対の排気弁９は対称平面Ｌに関しそれぞれ対称的に配置されており、この対称平面Ｌ上に燃料噴射弁６及び点火栓７が配置される。また、点火栓７はシリンダヘッド３の内壁面の中央部、例えばシリンダ中心軸線Ｋ上に配置され、燃料噴射弁６はシリンダヘッド３の内壁面の周縁部に配置される。
【００２２】
また、ピストン４の頂面上には図４に示されるように、燃料噴射弁６の下方から点火栓７の下方まで延びる凹溝４ａが形成される。図１から図４に示される内燃機関では、凹溝４ａの底壁面はシリンダ中心軸線Ｋに対し概ね垂直に拡がっている。
【００２３】
再び図１を参照すると、吸気ポート９は対応する吸気枝管１２を介してサージタンク１３に連結され、サージタンク１３は吸気ダクト１４を介してエアクリーナ１５に連結される。吸気ダクト１４内にはステップモータ１６により駆動されるスロットル弁１７が配置される。一方、排気ポート１１は排気マニホルド１８及び排気管１９を介して触媒２０を内蔵した触媒コンバータ２１に連結される。
【００２４】
電子制御ユニット３０はデジタルコンピュータからなり、双方向性バス３１によって互いに接続されたＲＯＭ（リードオンリメモリ）３２、ＲＡＭ（ランダムアクセスメモリ）３３、ＣＰＵ（マイクロプロセッサ）３４、入力ポート３５及び出力ポート３６を具備する。サージタンク１３には、サージタンク１３内の圧力に比例した出力電圧を発生する圧力センサ３９が取り付けられる。この圧力センサ３９の出力信号は対応するＡＤ変換器３７を介して入力ポート３５に入力される。アクセルペダル４０にはアクセルペダル４０の踏込み量に比例した出力電圧を発生する負荷センサ４１が接続され、負荷センサ４１の出力電圧は対応するＡＤ変換器３７を介して入力ポート３５に入力される。また、入力ポート３５にはクランクシャフトが例えば３０°回転する毎に出力パルスを発生するクランク角センサ４２が接続される。一方、出力ポート３６は対応する駆動回路３８を介して燃料噴射弁６及びステップモータ１６に接続される。
【００２５】
図１から図４に示される内燃機関では、以下に説明する第１の燃焼と第２の燃焼とが選択的に切り替えられるようになっている。即ち、機関運転領域が低負荷側領域と高負荷側領域とに分割されており、低負荷側領域では第１の燃焼が行われ、高負荷側領域では第２の燃焼が行われる。第１の燃焼では図５（Ａ）に示されるように、圧縮行程末期に１回だけ燃料噴射弁６からピストン４の凹溝４ａ内に燃料が噴射される。この場合の噴射燃料ＦＣは凹溝４ａの内壁面により案内されて点火栓７周りに向かい、その結果図５（Ｂ）に示されるように点火栓７周りに混合気Ｇが形成される。このとき、混合気Ｇ周りの燃焼室５内には空気又は空気及びＥＧＲガスの層が形成される。次いで、この混合気Ｇが点火栓７により着火せしめられる。
【００２６】
これに対し第２の燃焼では図５（Ｃ）に示されるように、吸気行程に１回だけ燃料噴射弁６から燃料が噴射される。この場合の噴射燃料ＦＩは燃焼室５内全体をほぼ一様に満たす混合気を形成する。次いでこの混合気は点火栓７により着火せしめられる。なお、高負荷側領域のうちの低負荷側の領域において、燃料を吸気行程と圧縮行程との２回に分けて噴射する、いわゆる二分割噴射を行うこともできる。
【００２７】
次に、図６及び図７を参照して燃料噴射弁６の噴孔について詳しく説明する。図６は燃料噴射弁６の先端部を拡大して示しており、図６（Ａ）は対称平面Ｌ（図３）に沿って見た燃料噴射弁６の部分断面図、図６（Ｂ）は図６（Ａ）の線Ｂに沿って見た燃料噴射弁６の部分断面図、図６（Ｃ）は図６（Ａ）の矢印Ｃの方向から見た燃料噴射弁６の端面図をそれぞれ示している。また、図７はシリンダ中心軸線Ｋを含みかつ対称平面Ｌに垂直な平面に沿って見た内燃機関の断面図を示している。
【００２８】
図６及び図７に示されるように、燃料噴射弁６は一対のスリット状噴孔ＮＬ，ＮＳを具備する。各スリット状噴孔ＮＬ，ＮＳは概略的に言うと、燃料流れ方向に対し平行な縦断面では扇状ないし円弧状をなしており、燃料流れ方向に垂直な横断面では長方形状をなしている。この長方形状断面の長手中心軸線をスリット状噴孔のスリット軸線と称することにする。
【００２９】
スリット状噴孔ＮＬ，ＮＳは偏平扇状噴霧を形成する偏平扇状噴霧形成用噴孔として作用する。ここで、図８を参照してスリット状噴孔により形成される噴霧について簡単に説明する。図８は単一のスリット状噴孔Ｎにより形成される噴霧Ｆを概略的に示しており、図８（Ａ）はスリット状噴孔Ｎのスリット軸線を含む噴霧Ｆの縦断面図、図８（Ｂ）はスリット状噴孔Ｎのスリット軸線に垂直な平面に沿って見た噴霧Ｆの断面図、図８（Ｃ）は噴霧Ｆの横断面図をそれぞれ示している。
【００３０】
図８に示されるように、スリット状噴孔Ｎにより形成される噴霧Ｆは偏平扇状をなし、即ちスリット軸線を含む噴霧Ｆの縦断面Ｊ内では扇状に拡がり、噴霧Ｆの横断面内では長軸Ｔを有する長円状ないし楕円状をなしている。この場合、偏平扇状噴霧Ｆの扇状縦断面Ｊはスリット状噴孔Ｎの扇状縦断面Ｈと概ね平行になり、偏平扇状噴霧Ｆの横断面の長軸Ｔはスリット状噴孔Ｎのスリット軸線に対し概ね平行になる。
【００３１】
再び図６及び図７を参照すると、図６及び図７に示される実施例ではスリット状噴孔ＮＬ，ＮＳのスリット軸線ＡＬ，ＡＳが互いに直交するようにこれらスリット状噴孔ＮＬ，ＮＳが形成されている。特に図６及び図７に示される例では、スリット状噴孔ＮＬ，ＮＳ同士が交差しており、しかもそれぞれの中心において互いに直交している。
【００３２】
言い換えると、スリット状噴孔ＮＬにより形成された偏平扇状噴霧の扇状縦断面を含んで拡がる平面と、スリット状噴孔ＮＳにより形成された偏平扇状噴霧の扇状縦断面を含んで拡がる平面とが、特に燃料流れ下流側で互いに交差し、しかもこれら扇状縦断面同士がそれぞれの中心において互いに直行する。
【００３３】
また、特に図７に示されるように、スリット状噴孔ＮＬはそのスリット軸線ＡＬがピストン４の凹溝４ａの底壁面４ｂに対し概ね平行になるように配置されている。一方、スリット状噴孔ＮＳはそのスリット軸線ＡＳが対称平面Ｌ内にあるように配置されている。言い換えると、スリット状噴孔ＮＬにより形成された偏平扇状噴霧の横断面の長軸が凹溝４ａの底壁面４ｂに対し概ね平行になるようにスリット状噴孔ＮＬが配置され、スリット状噴孔ＮＳにより形成された偏平扇状噴霧の扇状縦断面又はスリット状噴孔ＮＳの扇状縦断面ＨＳがシリンダ中心軸線Ｋに対し概ね平行になるようにスリット状噴孔ＮＳが配置される。
【００３４】
このようにすると、第１の燃焼が行われるときにスリット状噴孔ＮＬにより形成された偏平扇状噴霧が確実に凹溝４ａ内を進行し、従って点火栓７周りに燃料が確実に集められる。また、第２の燃焼が行われるときにスリット状噴孔ＮＳにより形成された偏平扇状噴霧がシリンダ中心軸線Ｋ方向に拡がり、従って均一混合気が形成されやすくなる。
【００３５】
ところが、第１の燃焼が行われるときにスリット状噴孔ＮＳにより形成された偏平扇状噴霧がシリンダ中心軸線Ｋ方向に拡がるとこの燃料は点火栓７周りに集まらず、上述した空気又は空気及びＥＧＲガスの層内に拡散する恐れがある。この燃料には火炎が伝播しにくく、従って燃焼室５から排出される未燃ＨＣを低減するためには噴射燃料がシリンダ中心軸線Ｋ方向にできるだけ拡がらないようにする必要がある。
【００３６】
そこで本発明による実施例では、図８（Ａ）に示されるようにスリット状噴孔Ｎの扇状縦断面の中心角をθｆ、扇状縦断面の中心をＣＳ、燃料噴射弁６のサック６ａの中心をＣＩ、扇状縦断面の中心ＣＳとサック６ａの中心ＣＩとの間の距離をＢでそれぞれ表すものとすると、スリット状噴孔ＮＬの距離Ｂを比較的大きくし、スリット状噴孔ＮＳの距離Ｂを比較的小さくしている。これは次の理由による。
【００３７】
例えば吸気行程における筒内圧力のように噴射場圧力が比較的低いとき（大気圧、０．１ＭＰａ）のときにスリット状噴孔Ｎにより形成された偏平扇状噴霧の噴霧角をθａ、例えば圧縮行程末期における筒内圧力のように噴射場圧力が比較的高いとき（０．５ＭＰａ）のときにスリット状噴孔Ｎにより形成された偏平扇状噴霧の噴霧角をθｐで表すものとすると、図９（Ａ）は距離Ｂを変化させたときの比θａ／θｆの変化を、図９（Ｂ）は距離Ｂを変化させたときの比θｐ／θａの変化をそれぞれ示す実験結果である。なお、いずれの場合も中心角θｆは一定に維持されている。
【００３８】
図９（Ａ）からわかるように、比θａ／θｆは距離Ｂが大きいときにはほぼ１に維持され、距離Ｂが小さくなると１よりもかなり小さくなる。また、距離Ｂが小さくなると距離Ｂの変化に対する比θａ／θｆの変化率が大きくなる。
【００３９】
即ち、距離Ｂを大きくすれば噴霧角が大きくなり、距離Ｂを小さくすれば噴霧角が小さくなる。
【００４０】
従って、スリット状噴孔ＮＬの距離Ｂを大きくすることによりシリンダ中心軸線Ｋに対し垂直な方向に燃料噴霧を拡げることができることになる。また、スリット状噴孔ＮＳの距離Ｂを小さくすることによりシリンダ中心軸線Ｋ方向に燃料噴霧が拡がるのを抑制できることになる。
【００４１】
一方、図９（Ｂ）からわかるように、比θｐ／θａは距離Ｂが大きいときにはほぼ１に維持され、距離Ｂが小さくなると１よりもかなり小さくなる。また、距離Ｂが小さくなると距離Ｂの変化に対する比θｐ／θａの変化率が大きくなる。
【００４２】
即ち、距離Ｂを大きくすれば筒内圧力が高いときにも低いときにも噴霧角が大きくなり、距離Ｂを小さくすれば噴霧角は小さくなり、このとき筒内圧力が高ければ筒内圧力が低いときよりも噴霧角が小さくなる。
【００４３】
従って、スリット状噴孔ＮＬの距離Ｂを大きくすることにより第１の燃焼時にも第２の燃焼時にもシリンダ中心軸線Ｋに対し垂直な方向に燃料噴霧を拡げることができることになる。また、スリット状噴孔ＮＳの距離Ｂを小さくすることにより第１の燃焼時にはシリンダ中心軸線Ｋ方向に燃料噴霧が拡がるのを抑制しながら、第２の燃焼時にはシリンダ中心軸線Ｋ方向に燃料噴霧を拡げることができることになる。
【００４４】
図１０は燃料噴射弁６の中心軸線Ｍに対し垂直な平面即ち横断面における燃料噴霧の外延を概略的に示しており、図１０（Ａ）は圧縮行程末期に燃料を噴射した場合を、図１０（Ｂ）は吸気行程に燃料を噴射した場合をそれぞれ示している。
【００４５】
図１０（Ａ）及び図１０（Ｂ）からわかるように、対称平面Ｌ方向従ってシリンダ中心軸線Ｋ方向では、燃料噴霧が圧縮行程末期に拡がり、吸気行程に収縮されている。これに対し、シリンダ中心軸線Ｋ方向に関し垂直な方向では燃料噴霧形状はほとんど変わらない。
【００４６】
このような現象がいかなるメカニズムで発生するかは必ずしも明らかにされていない。しかしながら、サック６ａ内での燃料の流れ、スリット状噴孔ＮＬ，ＮＳ内を流通するときの燃料の流速、スリット状噴孔ＮＬ，ＮＳ内壁面の抵抗などが関与しているものと考えられる。
【００４７】
従って、一般的に言うと、スリット状噴孔の扇状縦断面の中心ＣＳと、燃料噴射弁６のサック６ａの中心ＣＩとの間の距離Ｂが互いに異なるように一対のスリット状噴孔ＮＬ，ＮＳを形成し、距離Ｂが大きい方のスリット状噴孔ＮＬを、そのスリット軸線ＡＬ又はその偏平扇状噴霧の横断面の長軸が凹溝底壁面４ｂに対し概ね平行になるように、かつ距離Ｂが小さい方のスリット状噴孔ＮＳを、その扇状縦断面ＨＳ又はその偏平扇状噴霧の扇状縦断面がシリンダ中心軸線Ｋに対し概ね平行になるようにそれぞれ配置したということになる。
【００４８】
或いは、スリット状噴孔の扇状縦断面の中心角θｆに対する噴霧角の比θａ／θｆ，θｐ／θｆが互いに異なるように一対のスリット状噴孔ＮＬ，ＮＳを形成し、比θａ／θｆ，θｐ／θｆが大きい方のスリット状噴孔ＮＬを、そのスリット軸線ＡＬ又はその偏平扇状噴霧の横断面の長軸が凹溝底壁面４ｂに対し概ね平行になるように、かつ比θａ／θｆ，θｐ／θｆが小さい方のスリット状噴孔ＮＳを、その扇状縦断面ＨＳ又はその偏平扇状噴霧の扇状縦断面がシリンダ中心軸線Ｋに対し概ね平行になるようにそれぞれ配置したという見方もできる。
【００４９】
更に、筒内圧力が低いときの噴霧角θａに対する筒内圧力が高いときの噴霧角θｐの比θｐ／θａが互いに異なるように一対のスリット状噴孔又は偏平扇状噴霧形成用噴孔ＮＬ，ＮＳを形成し、比θｐ／θａが大きい方のスリット状噴孔ＮＬ又は偏平扇状噴霧形成用噴孔を、そのスリット軸線ＡＬ又はその偏平扇状噴霧の横断面の長軸が凹溝底壁面４ｂに対し概ね平行になるように、かつ比θｐ／θａが小さい方のスリット状噴孔又は偏平扇状噴霧形成用噴孔ＮＳを、その扇状縦断面ＨＳ又はその偏平扇状噴霧の扇状縦断面がシリンダ中心軸線Ｋに対し概ね平行になるようにそれぞれ配置したという見方もできる。
【００５０】
なお、図６及び図７に示される例では、スリット状噴孔ＮＬ，ＮＳの中心角θｆは互いに等しくされており、スリット軸線ＡＬ，ＡＳに対し垂直方向のスリット状噴孔ＮＬ，ＮＳの幅も互いに等しくされている。
【００５１】
図６及び図７に示される例ではスリット状噴孔ＮＬ，ＮＳ同士が互いに交差している。しかしながら図１１に示されるように、スリット軸線ＡＬ，ＡＳは互いに交差するけれどもスリット状噴孔ＮＬ，ＮＳ同士は互いに交差しないようにすることもできる。即ち、図１１（Ａ）に示される例ではスリット状噴孔ＮＬ，ＮＳが互いに離間して配置される。従って、一般的に言うと、偏平扇状噴霧の扇状縦断面を含んで拡がる平面が互いに交差するように一対の偏平扇状噴霧形成用噴孔を配置しているということになる。
【００５２】
一方、図１１（Ｂ）及び図１１（Ｃ）に示される例では一方のスリット状噴孔例えばスリット状噴孔ＮＬがスリット軸線ＡＬ方向に分割された複数例えば一対のスリット状噴孔ＮＬ１，ＮＬ２から形成され、これらスリット状噴孔ＮＬ１，ＮＬ２間にスリット状噴孔ＮＬ１，ＮＬ２から離間して他方のスリット状噴孔ＮＳが配置される。このようにするとスリット状噴孔ＮＬ，ＮＳ同士の交点から多量の燃料が噴射されるのを阻止することができる。
【００５３】
これらスリット状噴孔ＮＬ１，ＮＬ２により形成される噴霧は全体として上述した単一のスリット状噴孔ＮＬと同様の偏平扇状噴霧を形成する。この場合、偏平扇状噴霧の扇状縦断面は各スリット状噴孔ＮＬ１，ＮＬ２の扇状縦断面に対し概ね平行になる。また、スリット状噴孔ＮＬ１により形成される偏平扇状噴霧の扇状縦断面と、スリット状噴孔ＮＬ２により形成される偏平扇状噴霧の扇状縦断面とが共通の平面内に拡がる。
【００５４】
また、偏平扇状噴霧形成用噴孔ＮＬ，ＮＳの少なくとも一方を複数の筒状噴孔から形成することもできる。図１２（Ａ）及び図１２（Ｂ）は偏平扇状噴霧形成用噴孔ＮＬを単一の軸線ＡＬに沿って整列された複数の円筒状噴孔ＮＬＣから形成した場合を示しており、図１２（Ｂ）は偏平扇状噴霧形成用噴孔ＮＬを互いに平行な二つの軸線ＡＬ１，ＡＬ２に沿ってそれぞれ整列された複数の円筒状噴孔ＮＬＣから形成した場合を示している。
【００５５】
この場合、各円筒状噴孔ＮＬＣにより形成される噴霧は円錐状をなし、しかしながら全体としては上述したスリット状噴孔ＮＬにより形成される噴霧と同様の偏平扇状噴霧を形成する。ここで、軸線ＡＬ，ＡＬ１，ＡＬ２は偏平扇状噴霧の横断面の長軸と概ね平行に延びている。また、或る円筒状噴孔ＮＬＣから噴射された燃料が別の円筒状噴孔ＮＬＣ又はスリット状噴孔ＮＳから噴射された燃料と衝突し、従って燃料の微粒化が促進される。
【００５６】
図１３に更に別の実施例を示す。図１３は燃料噴射弁６の先端部を拡大して示しており、図１３（Ａ）は対称平面Ｌ（図３）に沿って見た燃料噴射弁６の部分断面図、図１３（Ｂ）は図１３（Ａ）の線Ｂに沿って見た燃料噴射弁６の部分断面図、図１３（Ｃ）は図１３（Ａ）の矢印Ｃの方向から見た燃料噴射弁６の端面図をそれぞれ示している。
【００５７】
図１３に示される例では、上述したスリット状噴孔ＮＳの一側に複数例えば一対の円筒状噴孔ＮＬＣａが形成され、他側に複数例えば一対の円筒状噴孔ＮＬＣｂが形成される。これら円筒状噴孔ＮＬＣａの中心軸線は概ね点Ｉａに指向されており、円筒状噴孔ＮＬＣｂの中心軸線は概ね点Ｉｂに指向されており、これら点Ｉａ，Ｉｂを結ぶ直線ＩＬはスリット軸線ＡＳ又は対称平面Ｌに対し概ね直行している。
【００５８】
その結果、円筒状噴孔ＮＬＣａにより形成される噴霧同士が互いに衝突し、円筒状噴孔ＮＬＣｂにより形成される噴霧同士が互いに衝突し、図１４に示されるように全体として、スリット状噴孔ＮＬにより形成される噴霧と同様の偏平扇状噴霧を形成する。この場合、この偏平扇状噴霧の横断面の長軸は上述した直線ＩＬに概ね平行になっている。この場合にも燃料の微粒化を促進することができる。
【００５９】
従って、一般的に言うと、筒内圧力が低いときの噴霧角θａに対する筒内圧力が高いときの噴霧角θｐの比θｐ／θａが小さい方の偏平扇状噴霧形成用噴孔をスリット状噴孔ＮＳから形成し、比θｐ／θａが大きい方の偏平扇状噴霧形成用噴孔を、それぞれの噴霧が互いに衝突することにより偏平扇状噴霧を形成するように指向される複数の筒状噴孔ＮＬＣａ，ＮＬＣｂから形成し、筒状噴孔ＮＬＣａ，ＮＬＣｂを、その偏平扇状噴霧の横断面の長軸が凹溝底壁面４ｂに対し概ね平行になるように、かつスリット状噴孔ＮＳを、その扇状縦断面ＨＳ又はその偏平扇状噴霧の扇状縦断面がシリンダ中心軸線Ｋに対し概ね平行になるようにそれぞれ配置したということになる。
【００６０】
なお、図１２及び図１３に示される例では上述した距離Ｂを必ずしも特定することができない。しかしながら、複数の円筒状噴孔ＮＬＣ，ＮＬＣａ，ＮＬＣｂにより形成される偏平扇状噴霧の前記比θａ／θｆ，θｐ／θｆ，θｐ／θａはスリット状噴孔ＮＳの対応する比θａ／θｆ，θｐ／θｆ，θｐ／θａよりも大きくなっている。
【００６１】
このように距離Ｂを特定できない場合でも、図６及び図７に示される例のように距離Ｂを特定できる場合と同様な比θａ／θｆ，θｐ／θｆ，θｐ／θａの挙動が得られる。これは比θａ／θｆ，θｐ／θｆ，θｐ／θａの挙動が単に距離Ｂに依存するものではないことを示しており、即ち距離Ｂに応じて定まるパラメータ例えばスリット状噴孔ＮＬ，ＮＳの流路面積のみに依存していないことを示している。
【００６２】
【発明の効果】
機関負荷が比較的低いときに点火栓周りに着火可能な混合気を確実に形成しつつ、機関負荷が比較的高いときに燃焼室内に均一混合気を確実に形成するすることができる。
【図面の簡単な説明】
【図１】内燃機関の全体図である。
【図２】内燃機関の縦断面図である。
【図３】シリンダヘッドの底面図である。
【図４】ピストンの頂面図である。
【図５】第１及び第２の燃焼を説明するための図である。
【図６】燃料噴射弁の先端部の拡大図である。
【図７】スリット状噴孔と内燃機関の位置関係を説明するための図である。
【図８】燃料噴霧の断面図である。
【図９】距離Ｂの変化に対する比θａ／θｆ，θｐ／θａの変化を示す線図である。
【図１０】燃料噴霧の外延を概略的に示す図である。
【図１１】本発明による別の実施例を示す図である。
【図１２】本発明による別の実施例を示す図である。
【図１３】本発明による別の実施例を示す図である。
【図１４】図１３に示される実施例における燃料噴霧の外延を概略的に示す図である。
【符号の説明】
１…機関本体
６…燃料噴射弁
ＮＬ，ＮＳ…スリット状噴孔
ＡＬ，ＡＳ…スリット軸線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection valve and a fuel injection device.
[0002]
[Prior art]
Conventionally, when the engine load is relatively low, an air-fuel mixture is formed in a limited region in the combustion chamber, and this air-fuel mixture is ignited by a spark plug. When the engine load increases, the combustion chamber is filled with a uniform air-fuel mixture. A cylinder injection type internal combustion engine in which a uniform air-fuel mixture is ignited by a spark plug is known. In such a cylinder injection type internal combustion engine, usually, an ignition plug is arranged at the center of the inner wall surface of the cylinder head, a fuel injection valve is arranged around the inner wall surface of the cylinder head, and the ignition plug is disposed below the fuel injection valve. A concave groove extending downward is formed on the top surface of the piston. When the engine load is relatively low, fuel is injected into the concave groove, and this injected fuel is guided by the inner wall surface of the concave groove to limit the area around the spark plug. An air-fuel mixture is formed in the formed region.
[0003]
In this case, the air-fuel mixture formed around the spark plug needs to be ignitable, that is, the injected fuel needs to be mixed well with the air.
[0004]
Therefore, a cylinder injection type internal combustion engine in which the injection hole of the fuel injection valve is formed in a slit shape is known (see JP-A-9-158736). In this way, since the injected fuel heading toward the concave groove is formed in a flat fan shape, the contact area between the injected fuel and air can be increased, so that an ignitable air-fuel mixture is reliably formed around the spark plug. .
[0005]
[Problems to be solved by the invention]
The slit-shaped nozzle hole is arranged so that the long axis of the cross section of the flat fan-shaped spray is substantially parallel to the bottom wall surface of the concave groove. Therefore, the fuel injected from the slit-shaped nozzle hole is the cylinder center axis. It hardly expands in the direction. Therefore, the injected fuel can surely advance in the concave groove.
[0006]
However, since the injected fuel hardly spreads in the cylinder central axis direction, there is a problem that it becomes difficult to form a uniform air-fuel mixture in the combustion chamber when the engine load is relatively high.
[0007]
Japanese Patent Application Laid-Open No. 9-126095 discloses a fuel injection valve having a pair of slit-shaped nozzle holes. The major axis of the cross section of the flat fan-shaped spray formed by these slit-shaped nozzle holes is the same. Since it is perpendicular to the cylinder center axis, almost no diffusion of the injected fuel in the cylinder center axis direction can be expected.
[0008]
Accordingly, an object of the present invention is to reliably form a uniform air-fuel mixture in the combustion chamber when the engine load is relatively high while reliably forming an air-fuel mixture that can be ignited around the spark plug when the engine load is relatively low. It is an object of the present invention to provide a fuel injection valve and a fuel injection device that can perform the above operation.
[0015]
[Means for Solving the Problems]
In order to solve the above problems 1 According to the second aspect of the invention, the spark plug is disposed at substantially the center of the top of the combustion chamber, the fuel injection valve is disposed at the peripheral edge of the top of the combustion chamber, and the concave groove extending from below the fuel injection valve to below the spark plug is formed. It is formed on the top surface of the piston, and fuel is injected from the fuel injection valve into the concave groove during the engine compression stroke, and the fuel is guided around the spark plug by the inner wall surface of the concave groove. A first combustion for igniting the air-fuel mixture with an ignition plug; and a second air-fuel mixture that fills the entire combustion chamber by injecting fuel from a fuel injection valve in the engine intake stroke and igniting the air-fuel mixture with an ignition plug. In a cylinder injection internal combustion engine capable of switching between combustion, the fuel injection valve includes a pair of slit-shaped injection holes, and a center of a fan-shaped longitudinal section of the slit-type injection hole and a center of a sac of the fuel injection valve A pair of these slips so that the distance between them is different. The slit-shaped nozzle hole having the larger distance is formed so that the long axis of the cross-section of the flat fan-shaped spray is substantially parallel to the bottom wall surface of the groove and the smaller distance is formed. The slit-shaped nozzle holes are arranged so that the fan-shaped longitudinal section of the flat fan-shaped spray is substantially parallel to the cylinder center axis.
[0016]
In order to solve the above problems 2 According to the second aspect of the invention, the spark plug is disposed at substantially the center of the top of the combustion chamber, the fuel injection valve is disposed at the peripheral edge of the top of the combustion chamber, and the concave groove extending from below the fuel injection valve to below the spark plug is formed. It is formed on the top surface of the piston, and fuel is injected from the fuel injection valve into the concave groove during the engine compression stroke, and the fuel is guided around the spark plug by the inner wall surface of the concave groove. A first combustion for igniting the air-fuel mixture with an ignition plug; and a second air-fuel mixture that fills the entire combustion chamber by injecting fuel from a fuel injection valve in the engine intake stroke and igniting the air-fuel mixture with an ignition plug. In a cylinder injection internal combustion engine capable of switching between combustion, the fuel injection valve has a pair of slit-shaped nozzle holes, and the ratio of the spray angle to the central angle of the fan-shaped longitudinal section of the slit-shaped nozzle holes is different from each other. These pair of slit nozzle holes are formed and the front The slit-shaped nozzle hole with the larger ratio is made flat so that the major axis of the cross section of the flat fan-shaped spray is substantially parallel to the bottom wall surface of the groove and the slit-shaped nozzle hole with the smaller ratio is made flat. It arrange | positions so that the fan-shaped vertical cross section of fan-shaped spray may become substantially parallel with respect to a cylinder center axis line.
[0017]
In order to solve the above problems 3 According to the second aspect of the invention, the spark plug is disposed at substantially the center of the top of the combustion chamber, the fuel injection valve is disposed at the peripheral edge of the top of the combustion chamber, and the concave groove extending from below the fuel injection valve to below the spark plug is formed. It is formed on the top surface of the piston, and fuel is injected from the fuel injection valve into the concave groove during the engine compression stroke, and the fuel is guided around the spark plug by the inner wall surface of the concave groove. A first combustion for igniting the air-fuel mixture with an ignition plug; and a second air-fuel mixture that fills the entire combustion chamber by injecting fuel from a fuel injection valve in the engine intake stroke and igniting the air-fuel mixture with an ignition plug. In a cylinder injection type internal combustion engine capable of switching between combustion, the fuel injection valve has a pair of flat fan spray formation nozzle holes, and the spray when the cylinder pressure is high relative to the spray angle when the cylinder pressure is low These pair of flat fans so that the angle ratios are different from each other The spray-forming nozzle hole is formed, the flat fan-shaped spray nozzle having the larger ratio is formed so that the long axis of the cross-section of the flat fan-shaped spray is substantially parallel to the bottom wall surface of the groove, and The flat fan-shaped spray forming nozzle hole with a smaller ratio is arranged so that the fan-shaped longitudinal section of the flat fan-shaped spray is substantially parallel to the cylinder center axis.
[0018]
Also, 4 According to the second invention 3 In the second invention, the flat fan-shaped spray forming nozzle holes with the smaller ratio are formed from slit-shaped nozzle holes, and the sprays collide with each other in the flat fan-shaped spray forming nozzle holes with the larger ratio. Is formed from a plurality of cylindrical nozzle holes directed to form a flat fan-shaped spray.
[0019]
In the present specification, the spray angle of the slit-shaped nozzle hole means the spray angle in a plane extending including the fan-shaped longitudinal section of the flat fan-shaped spray.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
1 to 4 show a case where the present invention is applied to a four-stroke spark ignition type internal combustion engine. 1 to 4, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is a spark plug, and 8 is a pair. , 9 is an intake port, 10 is a pair of exhaust valves, and 11 is an exhaust port. In FIG. 2, a line M indicates the central axis of the fuel injection valve 6.
[0021]
As shown in FIG. 3, the pair of intake valves 8 and the pair of exhaust valves 9 are arranged symmetrically with respect to the symmetry plane L, and the fuel injection valve 6 and the spark plug 7 are arranged on the symmetry plane L. The The spark plug 7 is disposed on the center of the inner wall surface of the cylinder head 3, for example, on the cylinder center axis K, and the fuel injection valve 6 is disposed on the peripheral edge of the inner wall surface of the cylinder head 3.
[0022]
Further, as shown in FIG. 4, a concave groove 4 a extending from the lower side of the fuel injection valve 6 to the lower side of the spark plug 7 is formed on the top surface of the piston 4. In the internal combustion engine shown in FIGS. 1 to 4, the bottom wall surface of the groove 4 a extends substantially perpendicular to the cylinder center axis K.
[0023]
Referring again to FIG. 1, the intake port 9 is connected to the surge tank 13 via the corresponding intake branch pipe 12, and the surge tank 13 is connected to the air cleaner 15 via the intake duct 14. A throttle valve 17 driven by a step motor 16 is disposed in the intake duct 14. On the other hand, the exhaust port 11 is connected to a catalytic converter 21 containing a catalyst 20 via an exhaust manifold 18 and an exhaust pipe 19.
[0024]
The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36. It comprises. A pressure sensor 39 that generates an output voltage proportional to the pressure in the surge tank 13 is attached to the surge tank 13. The output signal of the pressure sensor 39 is input to the input port 35 via the corresponding AD converter 37. A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. The input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 30 °. On the other hand, the output port 36 is connected to the fuel injection valve 6 and the step motor 16 via a corresponding drive circuit 38.
[0025]
In the internal combustion engine shown in FIGS. 1 to 4, a first combustion and a second combustion described below are selectively switched. That is, the engine operation region is divided into a low load side region and a high load side region, and the first combustion is performed in the low load side region, and the second combustion is performed in the high load side region. In the first combustion, as shown in FIG. 5A, fuel is injected into the concave groove 4a of the piston 4 from the fuel injection valve 6 only once at the end of the compression stroke. The injected fuel FC in this case is guided by the inner wall surface of the concave groove 4a and travels around the spark plug 7, and as a result, an air-fuel mixture G is formed around the spark plug 7 as shown in FIG. At this time, a layer of air or air and EGR gas is formed in the combustion chamber 5 around the mixture G. Next, the air-fuel mixture G is ignited by the spark plug 7.
[0026]
On the other hand, in the second combustion, as shown in FIG. 5C, fuel is injected from the fuel injection valve 6 only once in the intake stroke. The injected fuel FI in this case forms an air-fuel mixture that fills the entire combustion chamber 5 almost uniformly. Next, this air-fuel mixture is ignited by the spark plug 7. Note that, in the low load side region of the high load side region, so-called two-split injection, in which the fuel is injected in two steps of an intake stroke and a compression stroke, can be performed.
[0027]
Next, the nozzle hole of the fuel injection valve 6 will be described in detail with reference to FIGS. 6 is an enlarged view of the tip of the fuel injection valve 6. FIG. 6A is a partial cross-sectional view of the fuel injection valve 6 as viewed along the plane of symmetry L (FIG. 3), and FIG. Is a partial cross-sectional view of the fuel injection valve 6 viewed along line B in FIG. 6A, and FIG. 6C is an end view of the fuel injection valve 6 viewed from the direction of arrow C in FIG. Each is shown. FIG. 7 shows a cross-sectional view of the internal combustion engine as viewed along a plane including the cylinder center axis K and perpendicular to the symmetry plane L.
[0028]
As shown in FIGS. 6 and 7, the fuel injection valve 6 includes a pair of slit-shaped injection holes NL and NS. Generally speaking, each of the slit-shaped injection holes NL and NS has a fan shape or an arc shape in a longitudinal section parallel to the fuel flow direction, and a rectangular shape in a transverse section perpendicular to the fuel flow direction. The longitudinal center axis of the rectangular cross section will be referred to as the slit axis of the slit-shaped nozzle hole.
[0029]
The slit-shaped nozzle holes NL and NS act as flat fan-shaped spray forming nozzle holes that form a flat fan-shaped spray. Here, the spray formed by the slit-like nozzle holes will be briefly described with reference to FIG. 8 schematically shows the spray F formed by a single slit-shaped nozzle hole N, and FIG. 8A is a longitudinal sectional view of the spray F including the slit axis of the slit-shaped nozzle hole N. FIG. FIG. 8B is a cross-sectional view of the spray F viewed along a plane perpendicular to the slit axis of the slit-shaped nozzle hole N, and FIG.
[0030]
As shown in FIG. 8, the spray F formed by the slit-shaped nozzle holes N has a flat fan shape, that is, spreads in a fan shape in the longitudinal section J of the spray F including the slit axis, and is long in the transverse section of the spray F. An ellipse or an ellipse having an axis T is formed. In this case, the fan-shaped vertical section J of the flat fan-shaped spray F is substantially parallel to the fan-shaped vertical section H of the slit-shaped nozzle hole N, and the long axis T of the horizontal section of the flat fan-shaped spray F is the slit axis of the slit-shaped nozzle hole N. It is almost parallel to it.
[0031]
Referring to FIGS. 6 and 7 again, in the embodiment shown in FIGS. 6 and 7, the slit injection holes NL and NS are formed so that the slit axes AL and AS of the slit injection holes NL and NS are orthogonal to each other. Has been. In particular, in the example shown in FIGS. 6 and 7, the slit-shaped injection holes NL and NS intersect each other and are orthogonal to each other at the respective centers.
[0032]
In other words, a plane extending including the fan-shaped vertical section of the flat fan-shaped spray formed by the slit-shaped nozzle hole NL and a plane expanding including the fan-shaped vertical section of the flat fan-shaped spray formed by the slit-shaped nozzle hole NS, In particular, they cross each other on the downstream side of the fuel flow, and these fan-shaped longitudinal sections are orthogonal to each other at the center.
[0033]
In particular, as shown in FIG. 7, the slit-like nozzle hole NL is arranged such that its slit axis AL is substantially parallel to the bottom wall surface 4 b of the concave groove 4 a of the piston 4. On the other hand, the slit-shaped nozzle hole NS is arranged such that its slit axis AS is in the symmetry plane L. In other words, the slit-shaped nozzle hole NL is arranged so that the long axis of the cross section of the flat fan-shaped spray formed by the slit-shaped nozzle hole NL is substantially parallel to the bottom wall surface 4b of the groove 4a. The slit-shaped nozzle holes NS are arranged so that the fan-shaped vertical section of the flat fan-shaped spray formed by NS or the fan-shaped vertical section HS of the slit-shaped nozzle holes NS is substantially parallel to the cylinder center axis K.
[0034]
In this way, when the first combustion is performed, the flat fan-shaped spray formed by the slit-shaped nozzle hole NL surely proceeds in the concave groove 4a, and thus the fuel is reliably collected around the spark plug 7. Further, when the second combustion is performed, the flat fan-shaped spray formed by the slit-shaped nozzle hole NS spreads in the cylinder central axis K direction, and therefore, a uniform air-fuel mixture is easily formed.
[0035]
However, when the flat fan-shaped spray formed by the slit-shaped nozzle hole NS spreads in the direction of the cylinder center axis K when the first combustion is performed, this fuel does not collect around the spark plug 7, but the air or air and EGR described above. May diffuse into gas layer. This fuel is difficult for the flame to propagate. Therefore, in order to reduce the unburned HC discharged from the combustion chamber 5, it is necessary to prevent the injected fuel from spreading in the cylinder central axis K direction as much as possible.
[0036]
Therefore, in the embodiment according to the present invention, as shown in FIG. 8A, the center angle of the fan-shaped longitudinal section of the slit-shaped nozzle hole N is θf, the center of the sector-shaped longitudinal section is CS, and the center of the sack 6a of the fuel injection valve 6 , CI, and the distance between the center CS of the fan-shaped longitudinal section and the center CI of the sack 6a respectively represented by B, the distance B of the slit-shaped nozzle hole NL is made relatively large, and the distance of the slit-shaped nozzle hole NS B is relatively small. This is due to the following reason.
[0037]
For example, when the injection field pressure is relatively low (atmospheric pressure, 0.1 MPa), such as the in-cylinder pressure in the intake stroke, the spray angle of the flat fan-shaped spray formed by the slit-shaped nozzle N is θa, for example, the compression stroke When the spray angle of the flat fan-shaped spray formed by the slit-shaped nozzle hole N when the injection field pressure is relatively high (0.5 MPa) as in the in-cylinder pressure at the end stage is represented by θp, FIG. FIG. 9A shows experimental results showing changes in the ratio θa / θf when the distance B is changed, and FIG. 9B shows experimental results showing changes in the ratio θp / θa when the distance B is changed. In any case, the central angle θf is kept constant.
[0038]
As can be seen from FIG. 9A, the ratio θa / θf is maintained at approximately 1 when the distance B is large, and becomes considerably smaller than 1 when the distance B is small. Further, when the distance B is decreased, the rate of change of the ratio θa / θf with respect to the change of the distance B is increased.
[0039]
That is, if the distance B is increased, the spray angle is increased, and if the distance B is decreased, the spray angle is decreased.
[0040]
Therefore, the fuel spray can be expanded in the direction perpendicular to the cylinder center axis K by increasing the distance B of the slit-shaped injection hole NL. Further, by reducing the distance B of the slit-shaped nozzle hole NS, it is possible to suppress the fuel spray from spreading in the direction of the cylinder center axis K.
[0041]
On the other hand, as can be seen from FIG. 9B, the ratio θp / θa is maintained at approximately 1 when the distance B is large, and becomes considerably smaller than 1 when the distance B is small. Further, as the distance B decreases, the rate of change of the ratio θp / θa with respect to the change in the distance B increases.
[0042]
That is, if the distance B is increased, the spray angle is increased when the in-cylinder pressure is high and low, and if the distance B is decreased, the spray angle is decreased. The spray angle is smaller than when it is low.
[0043]
Therefore, by increasing the distance B of the slit-shaped injection hole NL, the fuel spray can be expanded in the direction perpendicular to the cylinder center axis K during both the first combustion and the second combustion. Further, by reducing the distance B of the slit-shaped nozzle hole NS, the fuel spray is prevented from spreading in the cylinder center axis K direction during the first combustion, while the fuel spray is applied in the cylinder center axis K direction during the second combustion. It can be expanded.
[0044]
FIG. 10 schematically shows the extension of fuel spray in a plane perpendicular to the central axis M of the fuel injection valve 6, that is, the cross section, and FIG. 10A shows the case where fuel is injected at the end of the compression stroke. Reference numeral 10 (B) shows a case where fuel is injected during the intake stroke.
[0045]
As can be seen from FIGS. 10A and 10B, in the symmetry plane L direction, that is, the cylinder center axis K direction, the fuel spray spreads at the end of the compression stroke and is contracted in the intake stroke. On the other hand, the fuel spray shape hardly changes in the direction perpendicular to the cylinder center axis K direction.
[0046]
It is not necessarily clarified by what mechanism such a phenomenon occurs. However, it is considered that the flow of fuel in the sac 6a, the flow rate of the fuel when flowing through the slit-shaped nozzle holes NL, NS, the resistance of the inner wall surface of the slit-shaped nozzle holes NL, NS, and the like are involved.
[0047]
Therefore, generally speaking, the pair of slit-shaped nozzle holes NL, NL, the distance B between the center CS of the fan-shaped longitudinal section of the slit-shaped nozzle hole and the center CI of the sac 6a of the fuel injection valve 6 are different from each other. NS is formed, and the slit-shaped nozzle hole NL having the larger distance B is set so that the long axis of the slit axis AL or the cross-section of the flat fan-shaped spray is substantially parallel to the groove bottom wall surface 4b. This means that the slit-shaped nozzle holes NS with smaller B are arranged so that the fan-shaped longitudinal section HS or the fan-shaped longitudinal section of the flat fan-shaped spray is substantially parallel to the cylinder center axis K.
[0048]
Alternatively, the pair of slit-shaped nozzle holes NL and NS are formed so that the spray angle ratios θa / θf and θp / θf to the central angle θf of the fan-shaped longitudinal section of the slit-shaped nozzle holes are different from each other, and the ratio θa / θf, θp The slit-shaped nozzle hole NL having a larger / θf is set so that the longitudinal axis of the slit axis AL or the flat cross-section of the flat fan-shaped spray is substantially parallel to the groove bottom wall surface 4b and the ratio θa / θf, θp. It can also be said that the slit-shaped nozzle holes NS having the smaller / θf are respectively arranged such that the fan-shaped longitudinal section HS or the fan-shaped longitudinal section of the flat fan-shaped spray is substantially parallel to the cylinder center axis K.
[0049]
Further, a pair of slit-shaped nozzle holes or flat fan-shaped spray-forming nozzle holes NL, NS are set so that the ratio θp / θa of the spray angle θp when the cylinder pressure is high with respect to the spray angle θa when the cylinder pressure is low is different from each other. The slit-shaped nozzle hole NL or the flat fan-shaped spray forming nozzle having the larger ratio θp / θa is formed with the slit axis AL or the long axis of the cross-section of the flat fan-shaped spray being in relation to the groove bottom wall surface 4b. The slit-shaped nozzle hole or the flat fan-shaped spray forming nozzle hole NS having a smaller ratio θp / θa so as to be substantially parallel to each other, the fan-shaped vertical section HS or the fan-shaped vertical section of the flat fan-shaped spray is the cylinder center axis K It can also be said that they are arranged so as to be substantially parallel to each other.
[0050]
In the example shown in FIGS. 6 and 7, the central angles θf of the slit-shaped nozzle holes NL and NS are equal to each other, and the width of the slit-shaped nozzle holes NL and NS in the direction perpendicular to the slit axis lines AL and AS. Are also equal to each other.
[0051]
In the example shown in FIGS. 6 and 7, the slit-shaped nozzle holes NL and NS intersect each other. However, as shown in FIG. 11, although the slit axes AL and AS intersect with each other, the slit-shaped injection holes NL and NS may not intersect each other. That is, in the example shown in FIG. 11A, the slit-shaped injection holes NL and NS are arranged apart from each other. Therefore, generally speaking, a pair of flat fan-shaped spray forming nozzle holes are arranged so that planes extending including the fan-shaped longitudinal section of the flat fan-shaped spray intersect each other.
[0052]
On the other hand, in the example shown in FIGS. 11B and 11C, one slit-shaped nozzle hole, for example, a slit-shaped nozzle hole NL is divided into a plurality of, for example, a pair of slit-shaped nozzle holes NL1, NL2. The other slit-shaped nozzle hole NS is arranged between the slit-shaped nozzle holes NL1 and NL2 and spaced from the slit-shaped nozzle holes NL1 and NL2. In this way, it is possible to prevent a large amount of fuel from being injected from the intersection between the slit-shaped injection holes NL and NS.
[0053]
The spray formed by the slit-shaped nozzle holes NL1 and NL2 forms a flat fan-shaped spray similar to the single slit-shaped nozzle hole NL as a whole. In this case, the fan-shaped vertical section of the flat fan-shaped spray is substantially parallel to the fan-shaped vertical sections of the slit-shaped nozzle holes NL1, NL2. In addition, the fan-shaped vertical section of the flat fan-shaped spray formed by the slit-shaped nozzle hole NL1 and the fan-shaped vertical section of the flat fan-shaped spray formed by the slit-shaped nozzle hole NL2 spread in a common plane.
[0054]
In addition, at least one of the flat fan-shaped spray forming nozzle holes NL and NS can be formed from a plurality of cylindrical nozzle holes. 12 (A) and 12 (B) show a case where the flat fan-shaped spray forming nozzle holes NL are formed from a plurality of cylindrical nozzle holes NLC aligned along a single axis AL. (B) shows the case where the flat fan-shaped spray forming nozzle holes NL are formed from a plurality of cylindrical nozzle holes NLC aligned along two parallel axes AL1 and AL2.
[0055]
In this case, the spray formed by each cylindrical nozzle hole NLC has a conical shape. However, as a whole, a flat fan-shaped spray similar to the spray formed by the slit-shaped nozzle hole NL is formed. Here, the axis lines AL, AL1, and AL2 extend substantially parallel to the long axis of the cross section of the flat fan spray. In addition, fuel injected from one cylindrical nozzle hole NLC collides with fuel injected from another cylindrical nozzle hole NLC or slit-shaped nozzle hole NS, and thus atomization of the fuel is promoted.
[0056]
FIG. 13 shows still another embodiment. 13 is an enlarged view of the tip of the fuel injection valve 6. FIG. 13A is a partial cross-sectional view of the fuel injection valve 6 as viewed along the symmetry plane L (FIG. 3), and FIG. Is a partial sectional view of the fuel injection valve 6 as viewed along line B in FIG. 13A, and FIG. 13C is an end view of the fuel injection valve 6 as viewed from the direction of arrow C in FIG. Each is shown.
[0057]
In the example shown in FIG. 13, a plurality of, for example, a pair of cylindrical nozzle holes NLCa are formed on one side of the above-described slit-shaped nozzle hole NS, and a plurality of, for example, a pair of cylindrical nozzle holes NLCb are formed on the other side. The central axis of these cylindrical nozzle holes NLCa is generally directed to the point Ia, the central axis of the cylindrical nozzle hole NLCb is generally directed to the point Ib, and the straight line IL connecting these points Ia and Ib is the slit axis AS. Or it is almost perpendicular to the symmetry plane L.
[0058]
As a result, the sprays formed by the cylindrical nozzle holes NLCa collide with each other, the sprays formed by the cylindrical nozzle holes NLCb collide with each other, and as a whole, as shown in FIG. The flat fan-shaped spray similar to the spray formed by is formed. In this case, the long axis of the cross section of the flat fan spray is substantially parallel to the straight line IL described above. Even in this case, atomization of the fuel can be promoted.
[0059]
Therefore, generally speaking, the flat fan-shaped spray forming nozzle hole with the smaller ratio θp / θa of the spray angle θp when the in-cylinder pressure is high with respect to the spray angle θa when the in-cylinder pressure is low is the slit-shaped nozzle hole. A plurality of cylindrical nozzle holes NLCa, which are formed from NS and are oriented so as to form a flat fan-shaped spray hole when the sprays collide with each other. The cylindrical nozzle holes NLCa and NLCb are formed from the NLCb so that the long axis of the cross section of the flat fan-shaped spray is substantially parallel to the groove bottom wall surface 4b, and the slit-shaped nozzle hole NS is This means that the surface HS or the fan-shaped longitudinal section of the flat fan-shaped spray is arranged so as to be substantially parallel to the cylinder center axis K.
[0060]
In the example shown in FIGS. 12 and 13, the above-described distance B cannot always be specified. However, the ratios θa / θf, θp / θf, θp / θa of the flat fan-shaped spray formed by the plurality of cylindrical nozzle holes NLC, NLCa, NLCb correspond to the corresponding ratios θa / θf, θp / of the slit-shaped nozzle holes NS. It is larger than θf and θp / θa.
[0061]
Even when the distance B cannot be specified as described above, the same behaviors of the ratios θa / θf, θp / θf, and θp / θa as in the example shown in FIGS. 6 and 7 can be obtained. This indicates that the behaviors of the ratios θa / θf, θp / θf, and θp / θa are not merely dependent on the distance B, that is, parameters determined according to the distance B, for example, the flow of the slit-shaped nozzle holes NL and NS. It shows that it does not depend only on the road area.
[0062]
【The invention's effect】
It is possible to reliably form an air-fuel mixture that can be ignited around the spark plug when the engine load is relatively low, and to reliably form a uniform air-fuel mixture in the combustion chamber when the engine load is relatively high.
[Brief description of the drawings]
FIG. 1 is an overall view of an internal combustion engine.
FIG. 2 is a longitudinal sectional view of the internal combustion engine.
FIG. 3 is a bottom view of the cylinder head.
FIG. 4 is a top view of the piston.
FIG. 5 is a diagram for explaining first and second combustion.
FIG. 6 is an enlarged view of a tip portion of a fuel injection valve.
FIG. 7 is a diagram for explaining the positional relationship between the slit-shaped nozzle hole and the internal combustion engine.
FIG. 8 is a cross-sectional view of fuel spray.
9 is a diagram showing changes in ratios θa / θf and θp / θa with respect to changes in distance B. FIG.
FIG. 10 is a diagram schematically showing the extension of fuel spray.
FIG. 11 shows another embodiment according to the present invention.
FIG. 12 is a diagram showing another embodiment according to the present invention.
FIG. 13 shows another embodiment according to the present invention.
14 is a diagram schematically showing the extension of fuel spray in the embodiment shown in FIG. 13. FIG.
[Explanation of symbols]
1 ... Engine body
6 ... Fuel injection valve
NL, NS ... slit-shaped nozzle hole
AL, AS ... Slit axis

Claims

An ignition plug is arranged at the center of the top of the combustion chamber and a fuel injection valve is arranged at the peripheral edge of the top of the combustion chamber. A concave groove extending from below the fuel injection valve to below the ignition plug is formed on the top surface of the piston. In the engine compression stroke, fuel is injected into the groove from the fuel injection valve, and the fuel is guided around the spark plug by the inner wall surface of the groove. At this time, the air-fuel mixture formed around the spark plug is ignited by the spark plug. A cylinder capable of switching between the first combustion to be performed and the second combustion in which fuel is injected from the fuel injection valve in the engine intake stroke to fill the entire combustion chamber and the mixture is ignited by the spark plug In the internal injection internal combustion engine, the fuel injection valve includes a pair of slit-shaped injection holes, and the distance between the center of the fan-shaped longitudinal section of the slit-type injection hole and the center of the sac of the fuel injection valve is different from each other. Forming a pair of slit-like nozzle holes in the The slit-shaped nozzle hole with the larger separation is arranged so that the major axis of the cross section of the flat fan-shaped spray is substantially parallel to the bottom wall surface of the groove and the slit-shaped nozzle hole with the smaller distance is formed with the flat shape. A fuel injection device arranged so that a fan-shaped longitudinal section of fan-shaped spray is substantially parallel to a cylinder central axis.

An ignition plug is arranged at the center of the top of the combustion chamber and a fuel injection valve is arranged at the peripheral edge of the top of the combustion chamber. A concave groove extending from below the fuel injection valve to below the ignition plug is formed on the top surface of the piston. In the engine compression stroke, fuel is injected into the groove from the fuel injection valve, and the fuel is guided around the spark plug by the inner wall surface of the groove. At this time, the air-fuel mixture formed around the spark plug is ignited by the spark plug. A cylinder capable of switching between the first combustion to be performed and the second combustion in which fuel is injected from the fuel injection valve in the engine intake stroke to fill the entire combustion chamber and the mixture is ignited by the spark plug In the internal injection internal combustion engine, the fuel injection valve has a pair of slit-shaped nozzle holes, and the pair of slit-shaped nozzle holes so that the ratio of the spray angle to the central angle of the fan-shaped longitudinal section of the slit-shaped nozzle holes is different from each other. The sleeve with the larger ratio is formed. The slit-shaped nozzle hole having the smaller ratio is arranged so that the major axis of the cross-section of the flat fan-shaped spray is substantially parallel to the bottom surface of the groove, and the fan-shaped longitudinal section of the flat fan-shaped spray is A fuel injection device arranged so that its surface is substantially parallel to the cylinder center axis.

An ignition plug is arranged at the center of the top of the combustion chamber and a fuel injection valve is arranged at the peripheral edge of the top of the combustion chamber. A concave groove extending from below the fuel injection valve to below the ignition plug is formed on the top surface of the piston. In the engine compression stroke, fuel is injected into the groove from the fuel injection valve, and the fuel is guided around the spark plug by the inner wall surface of the groove. At this time, the air-fuel mixture formed around the spark plug is ignited by the spark plug. A cylinder capable of switching between the first combustion to be performed and the second combustion in which fuel is injected from the fuel injection valve in the engine intake stroke to fill the entire combustion chamber and the mixture is ignited by the spark plug In the internal injection internal combustion engine, the fuel injection valve includes a pair of flat fan-shaped spray forming nozzle holes, and the ratio of the spray angle when the in-cylinder pressure is high to the spray angle when the in-cylinder pressure is low is different from each other. A pair of flat fan-shaped spray holes is formed in The flat fan-shaped spray hole having the larger ratio is formed so that the major axis of the cross-section of the flat fan-shaped spray is substantially parallel to the bottom wall surface of the groove and the smaller ratio A fuel injection device in which spray forming nozzle holes are arranged so that the fan-shaped longitudinal section of the flat fan-shaped spray is substantially parallel to the cylinder central axis.

The flat fan-shaped spray forming nozzle hole having the smaller ratio is formed from the slit-shaped nozzle hole, and the flat fan-shaped spray forming nozzle hole having the larger ratio is formed by causing the sprays to collide with each other. The fuel injection device according to claim 3, wherein the fuel injection device is formed from a plurality of cylindrical injection holes directed to form.