JP4099738B2

JP4099738B2 - Fuel injection device

Info

Publication number: JP4099738B2
Application number: JP33080898A
Authority: JP
Inventors: 哲也鳥谷尾
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 1998-11-20
Filing date: 1998-11-20
Publication date: 2008-06-11
Anticipated expiration: 2018-11-20
Also published as: JP2000161174A

Description

【０００１】
【産業上の利用分野】
本発明は、燃料噴射装置に関し、特に電気的に制御されて高圧燃料を内燃機関（以下、「内燃機関」をエンジンという）に噴射する燃料噴射装置に関する。
【０００２】
【従来の技術】
高圧供給ポンプによって加圧圧送される高圧燃料を電気制御によってエンジンに噴射する燃料噴射装置は、ＥＰ０７５３６５８号公報に開示されるようなものが知られている。ＥＰ０７５３６５８号公報に開示される燃料噴射装置を図１２に示す。
【０００３】
この燃料噴射装置は、ノズルニードルと、ノズルニードルと一体或いは別体に配置された制御ピストン４０１と、第１の油圧絞り４０２と、第１の油圧絞り４０２を介して常時高圧燃料通路４０３と連通すると共に制御ピストン４０８の上端面が挿入される制御室４０４と、制御室４０４と低圧燃料通路４０５を連通する第２の油圧絞り４０６と、第２の油圧絞り４０６と低圧燃料通路４０５との間に位置し、電気制御によって両者の連通と遮断をする電磁二方弁４０７とを備える。
【０００４】
この燃料噴射装置によると、所定時刻に所定時間だけ電磁二方弁４０７を開弁させることによってエンジンへの燃料噴射を制御する。すなわち、制御室４０４内の高圧燃料を低圧燃料通路４０５に流通させ、制御ピストン４０１上面に作用する油圧力を低下させてノズルを開くことで噴射が開始される。噴射時以外は、電磁コイル４０９への通電を遮断して制御室４０４と低圧燃料通路４０５の間にある第２の油圧絞り４０６を閉じ、制御室４０４の圧力を噴射圧力と等しい圧力に維持することにより、制御ピストン及びノズルニードルを閉弁させた状態を保つ。したがって電磁二方弁４０７には、制御室４０４内の高圧燃料による開弁方向の油圧力を上回る付勢力が必要となる。
【０００５】
この付勢力は、最大の噴射圧力が制御室内に発生した状態において、油圧力（油圧力≒第２の油圧絞り径×最大噴射圧力）によって電磁二方弁４０７が開弁しない極めて大きな力を発生するスプリング４０８によって提供される。一方、電磁コイル４０９は、この付勢力と油圧力の差を上回る吸引力を発生する必要がある。したがって、制御室４０４内の圧力が低いと電磁二方弁４０７に作用する開弁方向の油圧力が殆ど得られないため、エンジンアイドル時等の噴射圧力が低い運転領域において最も大きな吸引力が必要となる。実用上、約７０Ｎから１００Ｎの吸引力が電磁コイル４０９に必要とされ、約５０Ｎ〜８０Ｎの付勢力がスプリング４０８に必要とされる。
【０００６】
したがって、電磁二方弁４０７のハウジング４１０は、強力な吸引力を発生する電磁コイル４０９を収容するため体格がノズルの体格に対して相対的に大きくなるという問題が生じていた。また、電磁二方弁４０７のハウジング４１０の外径がノズルの外径に対して大きくなりすぎると小型エンジンヘの搭載が極めて困難になるという問題が生じていた。
【０００７】
ＥＰ０７９８４５９号公報に開示される電気制御式の燃料噴射装置を図１３に示す。図１２に示す燃料噴射装置と実質的に同一の部分には同一の符号を付す。この問題を解決するため、ＥＰ０７９８４５９号公報に開示される電気制御式の燃料噴射装置では、電磁二方弁に油圧バランス型のバルブ４２１を採用することで小型化を実現している。この燃料噴射装置によれば、電磁二方弁が開弁状態又は閉弁状態にある時、制御室の油圧によって発生する電磁二方弁への油圧力は開弁方向及び閉弁方向のいずれの方向にも作用しない。したがって、強力なスプリング４２２の付勢力や電磁コイル４２３の吸引力を必要としないため小型化が可能となり、ノズルと電磁二方弁の外径を同等程度まで小さくすることができる。この燃料噴射装置によると、スプリング４２２に必要とされる付勢力及び電磁コイル４２３に必要とされる吸引力は、前述の例に示す燃料噴射装置の約１／２〜１／３である。
【０００８】
【発明が解決しようとする課題】
しかし、上述のＥＰ０７５３６５８号公報及びＥＰ０７９８４５９号公報に示される燃料噴射装置では、制御ピストン及びノズルの閉弁方向に働く油圧力が噴射ノズル先端の弁座部に作用する開弁方向の油圧力より小さくなるまで噴射は開始されない。したがって、制御室の圧力をノズルニードルが開弁するまで減圧させるために所定の時間を要する。このため、電磁二方弁が作動する直後にノズルを開弁させることができず、開弁の遅れが発生する。またノズル閉弁時においても同様に閉弁の後れが発生する。この開弁の遅れは極めて高速で作動する電磁二方弁によっても解消することができない。このため、ディーゼルエンジンにおいて騒音低減やNOx低減のための有効な手段であるパイロット噴射を行う際のパイロット噴射とメイン噴射のインターバルを短くできないという問題があった。
【０００９】
また、エンジン性能を向上させるブーツ状の噴射率波形も得られないという問題があった。さらに、２つの油圧絞りを用いて制御室への高圧燃料の流入と流出を行うため構造が複雑になり、油圧絞りの流量特性のばらつきによる制御室の油圧増減時間にばらつきが発生し、噴射特性がばらつくという問題があった。
【００１０】
本発明は上記の間題を解決するためのものであって、体格が小さく、低い製造コストで製造することが可能で、優れた応答性を備え、かつ噴射特性のばらつきの少ない燃料噴射装置を提供することを目的とする。
【００１１】
【課題を解決するための手段】
本発明の請求項１記載の燃料噴射装置によると、弁座、噴孔及びノズルボデー先端の端面と連通する小径孔がノズルボデーに形成され、ノズルニードルを往復摺動可能に支持するノズルニードル支持部を備える。ノズルニードルに、小径孔に挿入されるガイド部、噴孔近傍の括れ部、弁座に当接する当接部、及びノズルニードル支持部に摺接する摺動部が形成され、ガイド部の外径と、摺動部の外径と、当接部が弁座に当接する部位の外径であるシート径とが実質的に同一であるため、高圧燃料によってノズルニードルに作用する油圧力の合力は、閉弁状態にあるとき開弁方向に作用せず、開弁状態にあるとき閉弁方向に作用しない。したがって、ノズルニードルを開弁させる付勢力及び閉弁させる付勢力を小さくすることができる。このため、燃料噴射装置の体格を小さくすることができるとともに低いコストで製造することができる。また、ノズルニードルは瞬時に電気アクチュエータの動きに追従するため、優れた応答性を備えた燃料噴射装置を提供することができる。
【００１２】
本発明の請求項２記載の燃料噴射装置によると、弁座と噴孔を連通する小径孔がノズルボデーに形成され、ノズルニードルを往復摺動可能に支持するノズルニードル支持部を備える。ノズルニードルに、小径孔に挿入されるガイド部、噴孔近傍の括れ部、弁座に当接する当接部、及びノズルニードル支持部に摺接する摺動部が形成され、ガイド部の外径と、摺動部の外径と、当接部が弁座に当接する部位の外径であるシート径とが実質的に同一である。さらに、ノズルニードルには、ガイド部の先端の端面からノズルニードル支持部側の先端の端面に通ずる低圧燃料流路が内部に形成されるため、低圧リーク燃料を確実に排出することができる。また、小径孔がノズルボデー先端の端面と連通していないため燃焼室の燃焼ガスによってノズルニードルの作動が影響されることが抑制される。
【００１３】
本発明の請求項３記載の燃料噴射装置によると、ガイド部の外径、当接部のシート径、及び摺動部の外径は、０．７ｍｍ以上２．５ｍｍ以下であるため、製造公差や摩耗等によってそれぞれの外径が均等でなくなった場合に外径の差分によってノズルニードルに作用する油圧力の合力は極めて小さい。例えば、シート径と摺動部の外径に１０μｍの差が生じ１６０ＭＰａの噴射圧力である場合、閉弁状態においてノズルニードルに作用する油圧力の合力は、シート径０．７ｍｍのとき１．８Ｎ、シート径２．５ｍｍのとき６．３Ｎである。
【００１４】
本発明の請求項４記載の燃料噴射装置によると、弁座は、下流側から上流側に広がる円錐台状に形成され、上流側の外径は当接部のシート径より０．０１ｍｍ以上０．５ｍｍ以下大きい。上流側の外径とシート径の差が小さいため、当接部の表面に生じる圧力差によってノズルニードルに作用する油圧力の合力は極めて小さい。
【００１５】
本発明の請求項５記載の燃料噴射装置によると、ガイド部は、３μｍ以上１０μｍ以下の径方向クリアランスにて小径孔に挿入され、摺動部は３μｍ以上５μｍ以下の径方向クリアランスにてノズルニードル支持部に摺接するため、径方向クリアランスによって、ノズルニードルに作用する油圧力の合力は極めて小さい。
【００１６】
本発明の請求項６記載の燃料噴射装置によると、ノズルニードルの弁座近傍にノズル室内面に摺接する略円盤状の支持部を設けることにより、ノズルニードルの弁座側の位置決めをする。支持部側面の２、３又は４箇所に支持部の上面から底面に通じる溝が形成され、溝とノズルボデーの間にできる隙間を燃料が流通する。このため、支持部の体格を大きくすることができ、高い加工精度を得ることができる。また、支持部のノズルボデーに摺接する面が摩耗することによってノズルニードルに油圧力の合力が作用することがない。
【００１７】
本発明の請求項８記載の燃料噴射装置によると、括れ部は、下流側から上流側に２段の段差で括れて細くなり、段差面とノズルニードルの軸とでなす角は墳孔とノズルニードルの軸とでなす角と実質的に同一であるため、括れ部から噴孔へ流入する燃料の流量係数を大きくすることができる。
【００１８】
本発明の請求項８記載の燃料噴射装置によると、電気アクチュエータは、高リフト時の開弁速度を低リフト時の開弁速度より相対的に速くしてノズルニードルを摺動させる。
本発明の請求項９記載の燃料噴射装置によると、電気アクチュエータは、開弁直後の略５〜２０μｍの低リフト時に開弁速度を開弁直後の速度の１／３以下の速度に一旦減速させてノズルニードルを摺動させる。
本発明の請求項１０記載の燃料噴射装置によると、ノズルニードルは、所定リフト到達時にノズルニードル支持部の下部平面と当接する当接平面を形成するフランジを有し、当接平面に高圧燃料をノズル室から下部平面に導入するための燃料溝が形成されるため、開弁時においてノズルニードルに油圧力の合力が作用することがない。
【００１９】
本発明の請求項１１記載の燃料噴射装置によると、ガイド部、当接部及び摺動部の表面は、TiN、TiC、TiCN、CrN、DLC又はWC／Cのコーティング処理が施されているため、摩耗によってノズルニードルに油圧力の合力が作用することが抑制される。
【００２０】
本発明の請求項１２記載の燃料噴射装置によると、噴孔内面と小径孔内面との境界は、油脂に砥粒を混合させたスラリーを用い、ノズルボデーの軸線に沿って双方向に流体研磨加工が施されているため、滑らかな連続面を形成している。このため、燃料の流路が変形することがなく同一の噴射特性を長期間維持することができる。
【００２１】
【発明の実施の形態】
以下、本発明の実施の形態を示す複数の実施例について説明する。
（第１実施例）
本発明の第１実施例による燃料噴射装置を図１〜図６に基づいて説明する。
図１に示す電磁制御式の燃料噴射装置は、図示しないディーゼルエンジンの各気筒に設けられ、高圧燃料を蓄圧する図示しないコモンレールから高圧燃料を供給する図示しない燃料配管が接続され、電気的に制御されて燃焼室内に高圧燃料を間欠噴射する。
【００２２】
第１インジェクタボデー１は、電磁コイル３へ通電するハーネスに接続されるコネクタ１１と、燃料配管が接続されるネジ部１２と、インレット１３に圧入固定される燃料フィルタ１４を有し、低圧リーク燃料回収通路１５を形成する棒状中空ボルト１６をねじ固定する。
【００２３】
第２インジェクタボデー２は、第１インジェクタボデー１とリテーニングナット１７によって結合され、電磁コイル３と、電磁コイル３の磁気回路を構成するプラグ３１と、ばね４を係止するばねセット荷重調整部材４１と、高圧燃料通路２１、２２とを有する。電気アクチュエータとしての電磁コイル３は、図５及び図６に示すように、ボビン３２、電磁コイルターミナル３３、及び第２インジェクタボデー２及び第１インジェクタボデー１と絶縁するための樹脂部３４を有し、可能な限り体格を大きくして吸引力を増大するように第２インジェクタボデー２の軸からオフセットして配置される。電磁コイル３の両端には、図１に示すように２つのＯリング３５、３６が設けられ低圧リーク燃料と電磁コイル３がシールされている。ばね４は、一端が後述するアーマチャ５に当接してノズルニードル６を閉弁方向に付勢し、他端に当接するばねセット荷重調整部材４１によって１０Ｎのばね荷重に調整されている。
【００２４】
ノズルニードル支持部７は、軸方向に貫通する高圧燃料通路７１を有し、電磁コイル３とノズルニードル支持部７とのエアギャップを調整するためのエアギャップ調整用スペーサ７２とともにノズルリテーニングナット７３によりノズルボデー８と第２インジェクタボデー２の間に締結される。図２及び図４に示すようにノズルニードル支持部７は、４つの燃料溝７４を下部平面７５に形成する。燃料溝７４は、幅０．７ｍｍ×長さ４ｍｍ×深さ０．５ｍｍである。エアギャップ調整用スペーサ７２は軸方向に貫通する高圧燃料通路７６を有する。高圧燃料通路７１及び高圧燃料通路７６は、図４に示す２本の位置決めピン７７によって位置決めされ連通している。ノズルニードル支持部７及びエアギャップ調整用スペーサ７２の中心を貫通する貫通孔の内面にノズルニードル６が摺接する。
【００２５】
ノズルボデー８は、図３に示すように、底部に弁座８１を形成するノズル室８２を有し、弁座８１から外部先端８３に通じる小径孔８４と、小径孔８４とノズルボデー８外面を連通する噴孔８５が形成される。弁座８１は、円錐台面を有しシート角は１２３°である。噴孔８５の噴孔角度は１５０°である。噴孔８５の内面と小径孔８４の内面の境界は、ナフテン系油脂に炭化珪素砥粒を混合させた粘度５００ＣＰ〜１５００ＣＰ程度のスラリー等を用いて、１００秒から３００秒程度の時間、軸の上下両方向に流体研磨加工が施され滑らかに連続している。
【００２６】
ノズルニードル６は、図２及び図３に示すように主軸６１の一端にガイド部６２、括れ部６３、当接部６４を有し、主軸６１の他端に摺動部６５、フランジ６６を有する。ノズルニードル６のストロークは０．２０ｍｍである。
ガイド部６２は、外径が０．８ｍｍで小径孔８４に径方向クリアランス３〜５μｍで挿入され、ノズルニードル６の噴孔側の位置決めをする。
【００２７】
当接部６４は、円錐台面を有し、上流部の最大外径は０．８３ｍｍ、シート径は０．８ｍｍ、シート角は１１９°である。弁座８１に当接部６４が着座すると燃料供給が遮断される。また、弁座８１、ガイド部６２及び摺動部６５の表面は、TiN、TiC、TiCN、CrN、DLC、WC／C等のコーティング処理が施されている。
【００２８】
括れ部６３は、噴孔８５近傍に位置し、外径は０．５７ｍｍである。当接部６４が弁座８１から離座すると括れ部６３と小径孔８４の隙間から高圧燃料が噴孔８５に流入する。
フランジ６６に、ノズルニードル６が所定リフト到達時にノズルニードル支持部７の下部平面７５と当接する当接平面６７が形成される。フランジ６６は外径３．３ｍｍである。
【００２９】
摺動部６５は外径０．８ｍｍであり、ノズルニードル支持部７の貫通孔に摺接し、径方向クリアランス３〜５μｍにてノズルニードル支持部７に往復摺動可能に支持される。摺動部６５上部に、かしめ接合又はレーザー溶接接合等の機械的接合方法でアーマチャ５が接合される。
【００３０】
次に本実施例による燃料噴射装置の作動を説明する。
高圧燃料は、燃料配管から燃料噴射装置に供給され、燃料フィルタ１４を透過し、高圧燃料通路２１、２２、７６、７１、及び燃料溝７４を通ってノズル室８２に流入する。
【００３１】
このとき高圧燃料は、ノズルニードル６がばね４によって閉弁方向に付勢されているため、噴孔８５から噴射されない。また、当接部６４のシート径、および摺動部６５の外径が等しいため、高圧燃料による油圧力の合力はノズルニードル６に対して軸方向のいずれの方向にも作用しない。
【００３２】
電磁コイル３に通電を開始すると、アーマチャ５が電磁コイル３に吸引され、アーマチャ５に接合されているノズルニードル６がリフトを開始する。当接部６４が弁座８１から離れると高圧燃料がノズルニードルの括れ部６３と小径孔８４の隙間に流入し、噴孔８５から高圧燃料の噴射が開始される。
【００３３】
ノズルニードル６のリフト量が大きくなるに従い、弁座８１と当接部６４の開口面積が大きくなる。噴孔８５の総断面積よりその開口面積が大きくなるあたりから、括れ部６３と小径孔８４の隙間を流通する高圧燃料による油圧力がノズル室８２を流通する高圧燃料による油圧力と等しくなる。この状態において、ガイド部６２の外径、当接部６４のシート径、摺動部６５の外径が全て等しいため、閉弁時と同様に、高圧燃料による油圧力の合力はノズルニードル８に対して軸方向のいずれの方向にも作用しない。
【００３４】
ノズルニードル６が所定リフトに達すると、ノズルニードル６の当接平面６７がノズルニードル支持部７の下部平面７５に当接する。燃料溝７４を通じてノズル室８２から当接平面６７に高圧燃料が導かれるため、ノズル室８２内と等しい油圧力が常に当接平面６７に作用する。また、ガイド部６２の外径、当接部６４のシート径、摺動部６５の外径が全て等しいため、高圧燃料による油圧力の合力はノズルニードル８に対して軸方向のいずれの方向にも作用しない。このため当接平面６７が下部平面７５と当接した状態においても瞬時に閉弁可能である。仮に燃料溝７４がないとすれば、当接平面６７が下部平面７５に当接した場合、当接平面６７に高圧燃料が導かれず高圧燃料による油圧力の均衡状態が崩れ、ノズルニードル６の開弁方向に油圧力の合力が作用する。
【００３５】
ここで、リフト量が非常に小さい状態、すなわち当接部６４と弁座８１の開口面積が非常に小さい状態では、ノズル室８２から括れ部６３と小径孔８４の隙間への燃料供給が絞られるため、括れ部６３と小径孔８４の隙間を流通する高圧燃料による油圧力は、ノズル室８２を流通する高圧燃料による油圧力より低い。このため、当接部６４の表面に沿って圧力差が発生する。しかしながら、当接部６４の最大径は、シート径よりわずかに０．０３ｍｍ大きいだけであるため、高圧燃料による油圧力の合力がノズルニードル６に作用する力は電磁コイルの吸引力に対して極めて小さくノズルニードル６の開閉弁は容易になされる。
【００３６】
所定の噴射時間が経過した後に電磁コイル３への通電を遮断すると、ばね４の付勢力によってノズルニードル６が閉弁を開始し、弁座８１と当接部６４の開口面積が小さくなる。噴孔８５の総断面積よりその開口面積が小さくなるあたりから、括れ部６３と小径孔８４の隙間を流通する高圧燃料による油圧力がノズル室８２を流通する高圧燃料による油圧力より低くなり、高圧燃料による油圧力の均衡状態が崩れる。
【００３７】
ガイド部６２と小径孔８４の径方向クリアランスは３〜５μｍであり、加工ばらつきによって生じるガイド部６２の外径、当接部６４のシート径、及び摺動部６５の外径の３カ所の製造公差は１０μｍ程度であるため、油圧力の均衡状態がクリアランス及び製造公差によって大きく崩れることはない。
【００３８】
また、当接部６４、ガイド部６２、及び摺動部６５には、ＴｉＮ、ＴｉＣ、ＴｉＣＮ、ＣｒＮ、ＤＬＣ、ＷＣ／Ｃ等のコーティング処理が施されているため、寸法の経年変化は１〜２μｍ程度であり、油圧力の均衡状態が経年変化により大きく崩れることはない。
また、噴孔８５と小径孔８４の境界は流体研磨加工により滑らかな連続面を形成しているため、高圧燃料の流通によってエッジが削りとられて噴孔流量特性が変わるといった不具合は発生しない。したがって、同一の噴射特性を長期間維持できる。
【００３９】
（変形例）
図７に示すように、括れ部６３を、２段の段差によって下流側から上流側に括れて細くなるように形成し、かつその段差面の傾斜角度θ２を噴射方向と軸がなす角θ１と実質的に同一とすれば、低リフト状態（図示する中心線より右の状態）において括れ部６３から噴孔８５へと流れる燃料の流量係数を大きくできる。
【００４０】
本実施例による燃料噴射装置によると、開弁及び閉弁時においてノズルニードル６に作用する油圧力の合力が極めて小さいため、ばね４の付勢力を小さくし電磁コイル３の体格を小さくして小型化を実現することができる。
【００４１】
また、ノズルニードル６の作動は電磁コイル３の作動に素早く追従するため、極めて短いインターバルのパイロット噴射、低リフト時の開弁速度を小さくして高リフト時の開弁速度を早くするニードル制御、及び開弁直後の低リフト時に開弁速度を一旦ゼロ近傍まで減速するニードル制御等が可能となる。このため、初期噴射率を小さくしたり、いわゆる周知のブーツ型噴射が実現できる。
また、極めて簡単な構造により噴射制御を行うため、安価である上、噴射特性のばらつきを低減できる。さらにまた、噴射特性の経年変化が極めて小さい。
【００４２】
（第２実施例）
本発明の第２実施例による燃料噴射装置を図８及び図９に示す。第１実施例と実質的に同一の部分には同一符号を付す。本実施例による燃料噴射装置は、ノズルニードル６の噴孔近傍にノズル室８２内面と摺接する第２ノズルニードル支持部が形成される。ノズルニードル６の噴孔側を第２ノズルニードル支持部２００によって位置決めする。
【００４３】
第２ノズルニードル支持部２００の断面は、円周上の３箇所が凹んだ略円形状を有し、凹みから形成される溝２０１が高圧燃料の通路となる。溝２０１は２箇所又は４箇所であってもよい。第２ノズルニードル支持部２００は外径４．０ｍｍで、径方向クリアランス３〜５μｍでノズル室８２内面と摺接する。ノズルニードル６の摺動部６５は、第２ノズルニードル支持部２００の貫通孔に直径方向クリアランス３〜５μｍで摺接する。
【００４４】
ガイド部６２と小径孔８４との径方向クリアランスは５〜１０μｍとし、実質的には第２ノズルニードル支持部２００によってノズルニードル６の噴孔側の位置決めがされる。
本実施例による燃料噴射装置によると、第２ノズルニードル支持部２００は、電磁コイル３の吸引力の大小にかかわらず大径化が図れるため加工精度を得やすい。また、摩耗により第２ノズルニードル支持部２００の外径が変化しても油圧の均衡が崩れることはないため作動の信頼性が高い。
【００４５】
（第３実施例）
本発明の第３実施例による燃料噴射装置を図１０及び図１１に示す。第１実施例と実質的に同一の部分には同一符号を付す。
【００４６】
本実施例による燃料噴射装置は、ノズルニードル３０１と、ノズルニードル３０１を閉弁方向に付勢するためのばね３０２、ノズルニードル３０１とアーマチャ３０３のエアギャップを調整するためのエアギャップ調整部材３０４、電磁コイル３０５、電磁コイルハウジング３０６、電磁コイルターミナルの絶縁と燃料シールを行うための第１ターミナル支持部材３０７及び第２のターミナル支持部材３０８、電磁コイル３０５と第１のターミナル支持部材３０７、及び第２ターミナル支持部材３０８を位置決めするための位置決めピン３０９、３１０を有する。
【００４７】
電磁コイル３０５は、平板型ソレノイドである。平板型ソレノイドは、プランジャ型ソレノイドより吸引力が大きく、確実にノズルニードル３０１を作動させる。電磁コイル３０５はプランジャ型ソレノイドであってもよい。
ノズルニードル３０１は、アーマチャ３０３側の端面と噴孔側の端面を連通する低圧燃料流路３１１を有し、噴孔側の端面から低圧リーク燃料を排出する。
【００４８】
このため、本実施例による燃料噴射装置は、燃焼室の燃焼ガスによる影響が少なく、低圧リーク燃料を確実に回収できニードル先端への耐デポジットを高くすることができ、またノズルニードル６の作動の信頼性が高い。
【図面の簡単な説明】
【図１】本発明の第１実施例による燃料噴射装置を示す部分断面図である。
【図２】図１の部分拡大図である。
【図３】図１の部分拡大図である。
【図４】図１のＡ−Ａ線断面図である
【図５】図１のＢ−Ｂ線断面図である。
【図６】図１のＣ−Ｃ線断面図である。
【図７】第１実施例の変形例によるノズルニードルの作動を説明するための図である。
【図８】本発明の第２実施例による燃料噴射装置を示す部分断面図である。
【図９】図８の部分拡大図である。
【図１０】本発明の第３実施例による燃料噴射装置を示す部分断面図である。
【図１１】図９の部分拡大図である。
【図１２】従来の燃料噴射装置を示す部分断面図である。
【図１３】従来の燃料噴射装置を示す部分断面図である。
【符号の説明】
３電磁コイル（電気アクチュエータ）
６ノズルニードル
６２ガイド部
６３括れ部
６４当接部
６５摺動部
６６フランジ
６７当接平面
７ノズルニードル支持部
７４燃料溝
７５下部平面
８ノズルボデー
８１弁座
８３外部先端（ノズルボデー先端の端面）
８４小径孔
８５噴孔
２００第２ノズルニードル支持部（支持部）
２０１溝
３１１低圧燃料流路[0001]
[Industrial application fields]
The present invention relates to a fuel injection device, and more particularly to a fuel injection device that is electrically controlled to inject high-pressure fuel into an internal combustion engine (hereinafter, “internal combustion engine” is referred to as an engine).
[0002]
[Prior art]
As a fuel injection device that injects high-pressure fuel pressurized and pumped by a high-pressure supply pump into an engine by electric control, a fuel injection device as disclosed in EP0753658 is known. FIG. 12 shows a fuel injection device disclosed in EP0753658.
[0003]
This fuel injection device communicates with a high-pressure fuel passage 403 at all times via a nozzle needle, a control piston 401 arranged integrally with or separate from the nozzle needle, a first hydraulic throttle 402, and a first hydraulic throttle 402. And the control chamber 404 into which the upper end surface of the control piston 408 is inserted, the second hydraulic throttle 406 communicating with the control chamber 404 and the low pressure fuel passage 405, and the second hydraulic throttle 406 and the low pressure fuel passage 405. And an electromagnetic two-way valve 407 that communicates and shuts off both by electrical control.
[0004]
According to this fuel injection device, the fuel injection to the engine is controlled by opening the electromagnetic two-way valve 407 for a predetermined time at a predetermined time. That is, injection is started by causing the high-pressure fuel in the control chamber 404 to flow through the low-pressure fuel passage 405, lowering the oil pressure acting on the upper surface of the control piston 401, and opening the nozzle. Except for the time of injection, the energization to the electromagnetic coil 409 is cut off, the second hydraulic throttle 406 between the control chamber 404 and the low pressure fuel passage 405 is closed, and the pressure in the control chamber 404 is maintained at a pressure equal to the injection pressure. Thus, the control piston and the nozzle needle are kept closed. Therefore, the electromagnetic two-way valve 407 needs an urging force that exceeds the oil pressure in the valve opening direction by the high-pressure fuel in the control chamber 404.
[0005]
This urging force generates an extremely large force that does not open the electromagnetic two-way valve 407 due to the oil pressure (oil pressure≈second hydraulic throttle diameter × maximum injection pressure) in a state where the maximum injection pressure is generated in the control chamber. Provided by a spring 408. On the other hand, the electromagnetic coil 409 needs to generate a suction force that exceeds the difference between the biasing force and the oil pressure. Accordingly, when the pressure in the control chamber 404 is low, the oil pressure in the valve opening direction acting on the electromagnetic two-way valve 407 is hardly obtained, so the greatest suction force is required in the operation region where the injection pressure is low, such as when the engine is idling. It becomes. Practically, an attractive force of about 70N to 100N is required for the electromagnetic coil 409, and an urging force of about 50N to 80N is required for the spring 408.
[0006]
Therefore, since the housing 410 of the electromagnetic two-way valve 407 houses the electromagnetic coil 409 that generates a strong attractive force, there has been a problem that the physique is relatively larger than the physique of the nozzle. In addition, when the outer diameter of the housing 410 of the electromagnetic two-way valve 407 is too large with respect to the outer diameter of the nozzle, there has been a problem that mounting on a small engine becomes extremely difficult.
[0007]
FIG. 13 shows an electrically controlled fuel injection device disclosed in EP0779859. Parts that are substantially the same as those of the fuel injection device shown in FIG. In order to solve this problem, the electrically controlled fuel injection device disclosed in EP 0798459 is downsized by adopting a hydraulically balanced valve 421 as an electromagnetic two-way valve. According to this fuel injection device, when the electromagnetic two-way valve is open or closed, the hydraulic pressure to the electromagnetic two-way valve generated by the hydraulic pressure in the control chamber is either in the valve opening direction or the valve closing direction. Does not affect the direction. Therefore, since the urging force of the strong spring 422 and the attractive force of the electromagnetic coil 423 are not required, the size can be reduced, and the outer diameters of the nozzle and the electromagnetic two-way valve can be reduced to the same level. According to this fuel injection device, the urging force required for the spring 422 and the attractive force required for the electromagnetic coil 423 are about ½ to の of the fuel injection device shown in the above example.
[0008]
[Problems to be solved by the invention]
However, in the fuel injection devices described in the above-mentioned EP 0753658 and EP079859, the oil pressure acting in the valve closing direction of the control piston and the nozzle is smaller than the oil pressure in the valve opening direction acting on the valve seat at the tip of the injection nozzle. The injection is not started until Therefore, a predetermined time is required to reduce the pressure in the control chamber until the nozzle needle is opened. For this reason, the nozzle cannot be opened immediately after the electromagnetic two-way valve is operated, and a delay in opening the valve occurs. Similarly, when the nozzle is closed, the valve closing delay occurs. This delay in valve opening cannot be eliminated even by an electromagnetic two-way valve that operates at an extremely high speed. For this reason, in the diesel engine, there was a problem that the interval between the pilot injection and the main injection when pilot injection, which is an effective means for reducing noise and NOx, cannot be shortened.
[0009]
There is also a problem that a boot-like injection rate waveform that improves engine performance cannot be obtained. In addition, the structure is complicated because high pressure fuel flows into and out of the control chamber using two hydraulic throttles, resulting in variations in the hydraulic pressure increase / decrease time in the control chamber due to variations in the flow rate characteristics of the hydraulic throttle, and the injection characteristics. There was a problem of variation.
[0010]
The present invention is for solving the above problem, and provides a fuel injection device that is small in size, can be manufactured at a low manufacturing cost, has excellent responsiveness, and has little variation in injection characteristics. The purpose is to provide.
[0011]
[Means for Solving the Problems]
According to the fuel injection device of the first aspect of the present invention, the nozzle body is formed with the small-diameter hole communicating with the valve seat, the injection hole, and the end face of the tip of the nozzle body, and supports the nozzle needle so as to be slidable back and forth. Prepare. The nozzle needle is formed with a guide portion that is inserted into the small-diameter hole, a constricted portion near the nozzle hole, a contact portion that contacts the valve seat, and a sliding portion that slidably contacts the nozzle needle support portion. Since the outer diameter of the sliding portion and the seat diameter, which is the outer diameter of the portion where the contact portion contacts the valve seat, are substantially the same, the resultant force of the oil pressure acting on the nozzle needle by the high-pressure fuel is When the valve is closed, it does not act in the valve opening direction, and when it is in the valve open state, it does not act in the valve closing direction. Therefore, the urging force for opening and closing the nozzle needle can be reduced. For this reason, while being able to make the physique of a fuel injection device small, it can manufacture at low cost. Further, since the nozzle needle instantaneously follows the movement of the electric actuator, a fuel injection device having excellent responsiveness can be provided.
[0012]
According to the fuel injection device of the second aspect of the present invention, the small-diameter hole that communicates the valve seat and the injection hole is formed in the nozzle body, and the nozzle needle support portion that supports the nozzle needle so as to be slidable back and forth is provided. The nozzle needle is formed with a guide portion that is inserted into the small-diameter hole, a constricted portion near the nozzle hole, a contact portion that contacts the valve seat, and a sliding portion that slidably contacts the nozzle needle support portion. The outer diameter of the sliding portion and the seat diameter, which is the outer diameter of the portion where the contact portion contacts the valve seat, are substantially the same. Furthermore, since the low pressure fuel flow path leading from the end face at the tip end of the guide portion to the end face at the tip end on the nozzle needle support portion side is formed in the nozzle needle, the low pressure leak fuel can be reliably discharged. Further, since the small-diameter hole is not in communication with the end face of the tip of the nozzle body, the operation of the nozzle needle is suppressed from being affected by the combustion gas in the combustion chamber.
[0013]
According to the fuel injection device of the third aspect of the present invention, the outer diameter of the guide portion, the sheet diameter of the contact portion, and the outer diameter of the sliding portion are 0.7 mm or more and 2.5 mm or less. When the outer diameters are not uniform due to wear or the like, the resultant oil pressure acting on the nozzle needle due to the difference in outer diameter is extremely small. For example, when a difference of 10 μm is generated between the seat diameter and the outer diameter of the sliding portion and the injection pressure is 160 MPa, the resultant force of the oil pressure acting on the nozzle needle in the valve closing state is 1.8 N when the seat diameter is 0.7 mm. When the sheet diameter is 2.5 mm, it is 6.3 N.
[0014]
According to the fuel injection device of the fourth aspect of the present invention, the valve seat is formed in the shape of a truncated cone extending from the downstream side to the upstream side, and the outer diameter on the upstream side is 0. 01 mm or more from the seat diameter of the contact portion. .5mm or less larger. Since the difference between the upstream outer diameter and the seat diameter is small, the resultant force of the oil pressure acting on the nozzle needle due to the pressure difference generated on the surface of the contact portion is extremely small.
[0015]
According to the fuel injector of claim 5 of the present invention, the guide portion is inserted into the small diameter hole with a radial clearance of 3 μm or more and 10 μm or less, and the sliding portion is a nozzle needle with a radial clearance of 3 μm or more and 5 μm or less. Due to the sliding contact with the support portion, the resultant force of the oil pressure acting on the nozzle needle is extremely small due to the radial clearance.
[0016]
According to the fuel injection device of the sixth aspect of the present invention, the nozzle needle is positioned on the valve seat side by providing the substantially disc-shaped support portion that is in sliding contact with the nozzle chamber inner surface in the vicinity of the valve seat of the nozzle needle. Grooves that lead from the upper surface to the bottom surface of the support portion are formed at two, three, or four locations on the side surface of the support portion, and the fuel flows through a gap formed between the groove and the nozzle body. For this reason, the physique of a support part can be enlarged and a high processing precision can be obtained. Moreover, the resultant force of the oil pressure does not act on the nozzle needle due to wear of the surface of the support portion that is in sliding contact with the nozzle body.
[0017]
According to the fuel injection device of the eighth aspect of the present invention, the constricted portion is narrowed by two steps from the downstream side to the upstream side, and the angle formed by the step surface and the axis of the nozzle needle is a hole and a nozzle. Since the angle formed with the needle shaft is substantially the same, the flow coefficient of the fuel flowing from the constricted portion into the nozzle hole can be increased.
[0018]
According to the fuel injection device of the eighth aspect of the present invention, the electric actuator slides the nozzle needle by making the valve opening speed at the time of high lift relatively higher than the valve opening speed at the time of low lift.
According to the fuel injection device of the ninth aspect of the present invention, the electric actuator temporarily reduces the valve opening speed to 1/3 or less of the speed immediately after the valve opening at a low lift of about 5 to 20 μm immediately after the valve opening. And slide the nozzle needle.
According to the fuel injection device of the tenth aspect of the present invention, the nozzle needle has a flange that forms a contact plane that comes into contact with the lower plane of the nozzle needle support portion when the predetermined lift is reached, and high pressure fuel is applied to the contact plane. Since a fuel groove for introduction from the nozzle chamber to the lower plane is formed, the resultant oil pressure does not act on the nozzle needle when the valve is opened.
[0019]
According to the fuel injection device of claim 11 of the present invention, the surfaces of the guide portion, the contact portion and the sliding portion are coated with TiN, TiC, TiCN, CrN, DLC or WC / C. The resultant force of the oil pressure on the nozzle needle due to wear is suppressed.
[0020]
According to the fuel injection device of the twelfth aspect of the present invention, the boundary between the inner surface of the nozzle hole and the inner surface of the small-diameter hole uses a slurry in which oil and fat are mixed with abrasive grains, and fluid polishing is bidirectionally performed along the axis of the nozzle body. As a result, a smooth continuous surface is formed. For this reason, the same injection characteristic can be maintained for a long time without deformation of the fuel flow path.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plurality of examples showing embodiments of the present invention will be described.
(First embodiment)
A fuel injection device according to a first embodiment of the present invention will be described with reference to FIGS.
The electromagnetically controlled fuel injection device shown in FIG. 1 is provided in each cylinder of a diesel engine (not shown) and is electrically connected to a fuel pipe (not shown) for supplying high pressure fuel from a common rail (not shown) for accumulating high pressure fuel. The high pressure fuel is intermittently injected into the combustion chamber.
[0022]
The first injector body 1 includes a connector 11 connected to a harness for energizing the electromagnetic coil 3 , a screw portion 12 to which a fuel pipe is connected, and a fuel filter 14 that is press-fitted and fixed to an inlet 13. A rod-like hollow bolt 16 that forms the collection passage 15 is screwed.
[0023]
The second injector body 2 is coupled to the first injector body 1 by a retaining nut 17, and the electromagnetic coil 3, the plug 31 constituting the magnetic circuit of the electromagnetic coil 3, and the spring set load adjusting member that locks the spring 4. 41 and high-pressure fuel passages 21 and 22. As shown in FIGS. 5 and 6, the electromagnetic coil 3 as an electric actuator has a resin portion 34 for insulation from the bobbin 32, the electromagnetic coil terminal 33, and the second injector body 2 and the first injector body 1. The second injector body 2 is arranged so as to be offset from the axis of the second injector body 2 so as to increase the physique as much as possible to increase the suction force. As shown in FIG. 1, two O-rings 35 and 36 are provided at both ends of the electromagnetic coil 3 to seal the low-pressure leak fuel and the electromagnetic coil 3. The spring 4 is adjusted to a spring load of 10 N by a spring set load adjusting member 41 that contacts one end of an armature 5 to be described later to urge the nozzle needle 6 in the valve closing direction and contacts the other end.
[0024]
The nozzle needle support portion 7 has a high-pressure fuel passage 71 penetrating in the axial direction, and a nozzle retaining nut 73 together with an air gap adjustment spacer 72 for adjusting the air gap between the electromagnetic coil 3 and the nozzle needle support portion 7. Due to this, the nozzle body 8 and the second injector body 2 are fastened. As shown in FIGS. 2 and 4, the nozzle needle support portion 7 forms four fuel grooves 74 in the lower plane 75. The fuel groove 74 is 0.7 mm wide × 4 mm long × 0.5 mm deep. The air gap adjusting spacer 72 has a high-pressure fuel passage 76 penetrating in the axial direction. The high pressure fuel passage 71 and the high pressure fuel passage 76 are positioned and communicated with each other by two positioning pins 77 shown in FIG. The nozzle needle 6 is in sliding contact with the inner surface of the through hole that passes through the centers of the nozzle needle support portion 7 and the air gap adjusting spacer 72.
[0025]
As shown in FIG. 3, the nozzle body 8 has a nozzle chamber 82 that forms a valve seat 81 at the bottom, and communicates the small diameter hole 84 that leads from the valve seat 81 to the external tip 83, and the small diameter hole 84 and the outer surface of the nozzle body 8. A nozzle hole 85 is formed. The valve seat 81 has a truncated cone surface and the seat angle is 123 °. The nozzle hole angle of the nozzle hole 85 is 150 °. The boundary between the inner surface of the nozzle hole 85 and the inner surface of the small-diameter hole 84 is about 100 to 300 seconds using a slurry having a viscosity of about 500 CP to 1500 CP in which silicon carbide abrasive grains are mixed with naphthenic oil and fat. Fluid polishing is applied in both the upper and lower directions and it is smoothly continuous.
[0026]
As shown in FIGS. 2 and 3, the nozzle needle 6 has a guide portion 62, a constricted portion 63, and an abutting portion 64 at one end of the main shaft 61, and a sliding portion 65 and a flange 66 at the other end of the main shaft 61. . The stroke of the nozzle needle 6 is 0.20 mm.
The guide portion 62 has an outer diameter of 0.8 mm and is inserted into the small-diameter hole 84 with a radial clearance of 3 to 5 μm to position the nozzle needle 6 on the nozzle hole side.
[0027]
The abutting portion 64 has a truncated cone surface, the maximum outer diameter of the upstream portion is 0.83 mm, the seat diameter is 0.8 mm, and the seat angle is 119 °. When the contact portion 64 is seated on the valve seat 81, the fuel supply is cut off. Further, the surfaces of the valve seat 81, the guide portion 62, and the sliding portion 65 are subjected to a coating process such as TiN, TiC, TiCN, CrN, DLC, and WC / C.
[0028]
The constricted part 63 is located in the vicinity of the nozzle hole 85 and has an outer diameter of 0.57 mm. When the contact portion 64 is separated from the valve seat 81, high-pressure fuel flows into the injection hole 85 from the gap between the constricted portion 63 and the small diameter hole 84.
The flange 66 is formed with a contact plane 67 that contacts the lower plane 75 of the nozzle needle support 7 when the nozzle needle 6 reaches a predetermined lift. The flange 66 has an outer diameter of 3.3 mm.
[0029]
The sliding portion 65 has an outer diameter of 0.8 mm, is slidably in contact with the through hole of the nozzle needle support portion 7, and is supported by the nozzle needle support portion 7 so as to be slidable back and forth with a radial clearance of 3 to 5 μm. The armature 5 is joined to the upper part of the sliding portion 65 by a mechanical joining method such as caulking joining or laser welding joining.
[0030]
Next, the operation of the fuel injection device according to this embodiment will be described.
The high pressure fuel is supplied from the fuel pipe to the fuel injection device, passes through the fuel filter 14 , flows into the nozzle chamber 82 through the high pressure fuel passages 21, 22, 76, 71 and the fuel groove 74.
[0031]
At this time, the high pressure fuel is not injected from the injection hole 85 because the nozzle needle 6 is biased in the valve closing direction by the spring 4. Further, since the seat diameter of the contact part 64 and the outer diameter of the sliding part 65 are equal, the resultant force of the oil pressure by the high pressure fuel does not act on the nozzle needle 6 in any axial direction.
[0032]
When energization of the electromagnetic coil 3 is started, the armature 5 is attracted to the electromagnetic coil 3 and the nozzle needle 6 joined to the armature 5 starts to lift. When the contact portion 64 is separated from the valve seat 81, the high-pressure fuel flows into the gap between the nozzle needle constricted portion 63 and the small-diameter hole 84, and injection of the high-pressure fuel is started from the injection hole 85.
[0033]
As the lift amount of the nozzle needle 6 increases, the opening area of the valve seat 81 and the contact portion 64 increases. Since the opening area becomes larger than the total cross-sectional area of the nozzle hole 85, the oil pressure by the high pressure fuel flowing through the gap between the constricted portion 63 and the small diameter hole 84 becomes equal to the oil pressure by the high pressure fuel flowing through the nozzle chamber 82. In this state, since the outer diameter of the guide portion 62, the seat diameter of the contact portion 64, and the outer diameter of the sliding portion 65 are all equal, the resultant oil pressure by the high-pressure fuel is applied to the nozzle needle 8 in the same manner as when the valve is closed. On the other hand, it does not act in any axial direction.
[0034]
When the nozzle needle 6 reaches a predetermined lift, the contact plane 67 of the nozzle needle 6 contacts the lower plane 75 of the nozzle needle support portion 7. Since high-pressure fuel is guided from the nozzle chamber 82 to the contact plane 67 through the fuel groove 74, an oil pressure equal to that in the nozzle chamber 82 always acts on the contact plane 67. Further, since the outer diameter of the guide portion 62, the seat diameter of the contact portion 64, and the outer diameter of the sliding portion 65 are all equal, the resultant force of the oil pressure by the high-pressure fuel is in any axial direction with respect to the nozzle needle 8. Does not work. For this reason, even when the contact plane 67 is in contact with the lower plane 75, the valve can be instantaneously closed. If the fuel groove 74 does not exist, when the contact plane 67 contacts the lower plane 75, the high pressure fuel is not guided to the contact plane 67 and the oil pressure balance by the high pressure fuel is lost, and the nozzle needle 6 is opened. The resultant oil pressure acts in the valve direction.
[0035]
Here, in a state where the lift amount is very small, that is, in a state where the opening area of the contact portion 64 and the valve seat 81 is very small, the fuel supply from the nozzle chamber 82 to the gap between the constricted portion 63 and the small diameter hole 84 is restricted. Therefore, the oil pressure by the high pressure fuel flowing through the gap between the constricted portion 63 and the small diameter hole 84 is lower than the oil pressure by the high pressure fuel flowing through the nozzle chamber 82. For this reason, a pressure difference is generated along the surface of the contact portion 64. However, since the maximum diameter of the contact portion 64 is only 0.03 mm larger than the seat diameter, the force acting on the nozzle needle 6 due to the resultant oil pressure by the high-pressure fuel is extremely high relative to the suction force of the electromagnetic coil. The opening / closing valve of the small nozzle needle 6 can be easily made.
[0036]
When the energization of the electromagnetic coil 3 is interrupted after a predetermined injection time has elapsed, the nozzle needle 6 starts to close due to the urging force of the spring 4, and the opening area of the valve seat 81 and the contact portion 64 becomes small. Since the opening area becomes smaller than the total cross-sectional area of the nozzle hole 85, the oil pressure by the high pressure fuel flowing through the gap between the constricted portion 63 and the small diameter hole 84 becomes lower than the oil pressure by the high pressure fuel flowing through the nozzle chamber 82, The oil pressure balance caused by high pressure fuel is lost.
[0037]
The radial clearance between the guide portion 62 and the small-diameter hole 84 is 3 to 5 μm, and is manufactured at three locations: the outer diameter of the guide portion 62 caused by processing variations, the sheet diameter of the contact portion 64, and the outer diameter of the sliding portion 65. Since the tolerance is about 10 μm, the equilibrium state of the oil pressure is not greatly broken by the clearance and the manufacturing tolerance.
[0038]
Further, since the contact portion 64 , the guide portion 62, and the sliding portion 65 are coated with TiN, TiC, TiCN, CrN, DLC, WC / C, etc., the aging change of the dimension is 1 to 1. It is about 2 μm, and the equilibrium state of the oil pressure does not collapse greatly due to aging.
Further, since the boundary between the nozzle hole 85 and the small-diameter hole 84 forms a smooth continuous surface by fluid polishing, there is no problem that the edge is scraped by the flow of high-pressure fuel and the nozzle hole flow rate characteristics change. Therefore, the same injection characteristic can be maintained for a long time.
[0039]
(Modification)
As shown in FIG. 7 , the constricted portion 63 is formed so as to be narrowed from the downstream side to the upstream side by two steps, and the inclination angle θ2 of the step surface is defined as an angle θ1 formed by an injection direction and an axis. If substantially the same, the flow coefficient of the fuel flowing from the constricted portion 63 to the nozzle hole 85 can be increased in a low lift state (a state to the right of the center line shown).
[0040]
According to the fuel injection device according to the present embodiment, the resultant force of the oil pressure acting on the nozzle needle 6 when the valve is opened and closed is extremely small. Therefore, the biasing force of the spring 4 is reduced and the physique of the electromagnetic coil 3 is reduced. Can be realized.
[0041]
In addition, since the operation of the nozzle needle 6 follows the operation of the electromagnetic coil 3 quickly, pilot injection at an extremely short interval, needle control to reduce the valve opening speed at the time of low lift and increase the valve opening speed at the time of high lift, In addition, it is possible to perform needle control or the like for once reducing the valve opening speed to near zero at the time of low lift immediately after the valve opening. For this reason, the initial injection rate can be reduced, or so-called well-known boot type injection can be realized.
Further, since the injection control is performed with an extremely simple structure, it is inexpensive and variation in injection characteristics can be reduced. Furthermore, the change over time in the injection characteristics is extremely small.
[0042]
(Second embodiment)
A fuel injection device according to a second embodiment of the present invention is shown in FIGS. Parts substantially the same as those in the first embodiment are denoted by the same reference numerals. In the fuel injection device according to this embodiment, a second nozzle needle support portion that is in sliding contact with the inner surface of the nozzle chamber 82 is formed in the vicinity of the nozzle hole of the nozzle needle 6. The nozzle hole side of the nozzle needle 6 is positioned by the second nozzle needle support part 200.
[0043]
The cross section of the second nozzle needle support portion 200 has a substantially circular shape with three recesses on the circumference, and a groove 201 formed from the recess serves as a passage for high-pressure fuel. The groove 201 may be two places or four places. The second nozzle needle support portion 200 has an outer diameter of 4.0 mm and is in sliding contact with the inner surface of the nozzle chamber 82 with a radial clearance of 3 to 5 μm. The sliding portion 65 of the nozzle needle 6 is in sliding contact with the through hole of the second nozzle needle support portion 200 with a diametrical clearance of 3 to 5 μm.
[0044]
The radial clearance between the guide portion 62 and the small diameter hole 84 is 5 to 10 μm, and the nozzle nozzle 6 is positioned on the nozzle hole side by the second nozzle needle support portion 200 substantially.
According to the fuel injection device according to the present embodiment, the second nozzle needle support portion 200 can have a large diameter regardless of the attractive force of the electromagnetic coil 3, and therefore it is easy to obtain processing accuracy. Further, even if the outer diameter of the second nozzle needle support portion 200 changes due to wear, the hydraulic pressure balance is not lost, so that the operation reliability is high.
[0045]
(Third embodiment)
A fuel injection device according to a third embodiment of the present invention is shown in FIGS. Parts substantially the same as those in the first embodiment are denoted by the same reference numerals.
[0046]
The fuel injection device according to this embodiment includes a nozzle needle 301, a spring 302 for biasing the nozzle needle 301 in the valve closing direction, an air gap adjusting member 304 for adjusting an air gap between the nozzle needle 301 and the armature 303, Electromagnetic coil 305, electromagnetic coil housing 306, first terminal support member 307 and second terminal support member 308 for insulating and fuel sealing the electromagnetic coil terminal, electromagnetic coil 305 and first terminal support member 307, and Positioning pins 309 and 310 for positioning the two-terminal support member 308 are provided.
[0047]
The electromagnetic coil 305 is a flat plate type solenoid. The flat plate type solenoid has a larger suction force than the plunger type solenoid and reliably operates the nozzle needle 301. The electromagnetic coil 305 may be a plunger type solenoid.
The nozzle needle 301 has a low-pressure fuel flow path 311 that connects the end face on the armature 303 side and the end face on the injection hole side, and discharges low-pressure leak fuel from the end face on the injection hole side.
[0048]
For this reason, the fuel injection device according to the present embodiment is less affected by the combustion gas in the combustion chamber, can reliably collect the low-pressure leak fuel, can increase the deposit resistance to the tip of the needle, and can operate the nozzle needle 6. High reliability.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a fuel injection device according to a first embodiment of the present invention.
FIG. 2 is a partially enlarged view of FIG.
FIG. 3 is a partially enlarged view of FIG. 1;
4 is a cross-sectional view taken along line AA in FIG. 1. FIG. 5 is a cross-sectional view taken along line BB in FIG.
6 is a cross-sectional view taken along the line CC in FIG. 1. FIG.
FIG. 7 is a view for explaining the operation of a nozzle needle according to a modification of the first embodiment.
FIG. 8 is a partial cross-sectional view showing a fuel injection device according to a second embodiment of the present invention.
9 is a partially enlarged view of FIG.
FIG. 10 is a partial sectional view showing a fuel injection device according to a third embodiment of the present invention.
FIG. 11 is a partially enlarged view of FIG. 9;
FIG. 12 is a partial cross-sectional view showing a conventional fuel injection device.
FIG. 13 is a partial cross-sectional view showing a conventional fuel injection device.
[Explanation of symbols]
3 Electromagnetic coil (electric actuator)
6 Nozzle needle 62 Guide part 63 Constricted part 64 Abutting part 65 Sliding part 66 Flange 67 Abutting plane 7 Nozzle needle support part 74 Fuel groove 75 Lower plane 8 Nozzle body 81 Valve seat 83 External tip (end face of nozzle body tip)
84 Small-diameter hole 85 Injection hole 200 Second nozzle needle support part (support part)
201 groove 311 low pressure fuel flow path

Claims

In a fuel injection device that receives supply of fuel from a fuel pipe and intermittently injects fuel into the combustion chamber of the internal combustion engine by electric control,
A nozzle body having a nozzle chamber in which a valve seat is formed at the bottom;
A nozzle needle that shuts off or circulates the fuel flow path by separating from the valve seat or sitting on the valve seat;
A nozzle needle support part for supporting the nozzle needle so as to be reciprocally slidable;
An electric actuator that directly reciprocates the nozzle needle,
The nozzle body has a small-diameter hole communicating the valve seat and the end surface of the nozzle body tip, and an injection hole communicating the small-diameter hole and the nozzle body outer surface,
The nozzle needle has a guide portion that is inserted into the small-diameter hole, a constricted portion near the nozzle hole, a contact portion that contacts the valve seat, and a sliding portion that slides on the nozzle needle support portion. The fuel injection device, wherein an outer diameter of the guide portion, a seat diameter of the contact portion, and an outer diameter of the sliding portion are substantially the same.

In a fuel injection device that receives supply of fuel from a fuel pipe and is electrically controlled to intermittently inject fuel into the combustion chamber of the internal combustion engine,
A nozzle body having a nozzle chamber in which a valve seat is formed at the bottom;
A nozzle needle that blocks or circulates the fuel flow path to the nozzle hole by sitting away from the valve seat or sitting on the valve seat;
A nozzle needle support part for supporting the nozzle needle so as to be reciprocally slidable;
An electric actuator that directly reciprocates the nozzle needle,
The nozzle body has a small diameter hole that does not penetrate the nozzle body in the valve seat, and an injection hole that communicates the small diameter hole and the outer surface of the nozzle body,
The nozzle needle has a guide portion that is inserted into the small-diameter hole, a constricted portion near the nozzle hole, a contact portion that contacts the valve seat, and a sliding portion that slides on the nozzle needle support portion. And a low-pressure fuel flow path that extends from the end surface of the tip of the guide portion to the end surface of the tip on the nozzle needle support portion side is formed inside, the outer diameter of the guide portion, the seat diameter of the contact portion, A fuel injection device characterized in that the outer diameter of the sliding portion is substantially the same.

3. The fuel injection device according to claim 1, wherein an outer diameter of the guide portion, a seat diameter of the contact portion, and an outer diameter of the sliding portion are 0.7 mm or more and 2.5 mm or less. .

The valve seat is formed in a truncated cone shape extending from the downstream side to the upstream side, and the upstream outer diameter is 0.01 mm or more and 0.5 mm or less larger than the seat diameter of the contact portion. Or the fuel-injection apparatus of 3.

The guide portion is inserted into the small diameter hole with a radial clearance of 3 μm or more and less than 10 μm, and the sliding portion is in sliding contact with the nozzle needle support portion with a radial clearance of 3 μm or more and 5 μm or less. The fuel injection device according to any one of claims 1 to 4.

The nozzle needle has a substantially disk-shaped support portion that is in sliding contact with the nozzle chamber inner surface in the vicinity of the valve seat, and a groove that communicates from the top surface to the bottom surface of the support portion at two, three, or four positions of the support portion side surface. It forms, The fuel-injection apparatus as described in any one of Claims 1-5 characterized by the above-mentioned.

The constricted portion is narrowed by two steps from the downstream side to the upstream side, and the angle formed by the step surface and the axis of the nozzle needle is substantially the same as the angle formed by the hole and the axis of the nozzle needle. The fuel injection device according to any one of claims 1 to 6, wherein the fuel injection device is the same.

8. The electric actuator according to claim 1, wherein the nozzle needle is slid by making the valve opening speed during a high lift relatively higher than the valve opening speed during a low lift. The fuel injection device described.

The said electric actuator is once decelerated to the speed of 1/3 or less of the speed immediately after valve opening at the time of a low lift of about 5-20 micrometers just after valve opening , The said nozzle needle is slid. The fuel injection device according to claim 8.

The nozzle needle has a flange that forms a contact plane that comes into contact with the lower plane of the nozzle needle support portion when a predetermined lift is reached, so as to introduce high-pressure fuel from the nozzle chamber to the lower plane on the contact plane. The fuel injection device according to claim 1, wherein a fuel groove is formed.

The surface of the guide part, the contact part, and the sliding part is coated with TiN, TiC, TiCN, CrN, DLC, or WC / C. The fuel injection device according to item.

The boundary between the inner surface of the nozzle hole and the inner surface of the small-diameter hole is formed by using a slurry obtained by mixing oil and fat with abrasive grains, and fluid polishing is performed in both directions along the axis of the nozzle body. Item 12. The fuel injection device according to any one of Items 1 to 3-11.