JP2004052740A

JP2004052740A - Fuel injection apparatus

Info

Publication number: JP2004052740A
Application number: JP2002215283A
Authority: JP
Inventors: Shinji Nakayama; 中山　真治; Yoshiki Tanabe; 田邊　圭樹; Susumu Koketsu; 纐纈　晋
Original assignee: Mitsubishi Fuso Truck and Bus Corp
Current assignee: Mitsubishi Fuso Truck and Bus Corp
Priority date: 2002-07-24
Filing date: 2002-07-24
Publication date: 2004-02-19
Anticipated expiration: 2022-07-24
Also published as: JP3896917B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection apparatus capable of attaining suppression of worsening of fuel consumption and discharge of HC and black smoke and prevention of uneven injection. <P>SOLUTION: This fuel injection apparatus is provided with an injector 5 having a needle valve 12 capable of opening/closing a nozzle hole 8, a pressure receiving chamber 13 applying nozzle hole closing valve force to the needle valve, and a fuel reservoir 6 applying nozzle hole opening valve force to the needle valve; a fuel supply means 9 supplying the fuel reservoir selectively with each pressurized fuel from a high pressure fuel supply part PH and a low pressure fuel supply part PL; a control oil pressure changeover means 58 supplying the pressure receiving chamber selectively with low pressure fuel in the low pressure fuel supply part PL and boosted fuel boosted by a boost mechanism part 30 as control fuel pressure PA; and an injector control valve 22 changing the needle valve to close by shutting off the pressure receiving chamber from an oil pressure discharge line 23 so that the nozzle hole closing valve force exceeds the nozzle hole opening valve force, and changing the needle valve to open by communicating the pressure receiving chamber 13 with the oil pressure discharge line 23 so that the nozzle hole closing valve force is less than the nozzle hole opening valve force. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、内燃機関の燃焼室に燃料噴射する燃料噴射装置、特に、インジェクタの燃料溜に高圧燃料及び低圧燃料を選択的に供給することで、燃焼室への噴射率を変化させることができる燃料噴射装置に関する。
【０００２】
【従来の技術】
内燃機関の燃焼室にインジェクタにより燃料噴射する燃料噴射装置として、蓄圧室を成すコモンレールに燃料供給源からの高圧燃料を供給し、蓄圧室に貯留された高圧燃料をインジェクタの電磁弁の開時に燃焼室に噴霧するコモンレール式燃料噴射装置が知られている。
このコモンレール式燃料噴射装置の内、特に、図７に示すように、インジェクタ１００の燃料溜１１０に高圧燃料供給部１２０の高蓄圧室１２１及び低圧燃料供給部１３０の低蓄圧室１３１の各加圧燃料を切換え手段１４０を切換えることで選択的に供給できるコモンレール式燃料噴射装置が知られている。ここで、インジェクタ１００はインジェクタ本体１０１内の下部に噴口を開閉可能な針弁１０２を収容し、同針弁１０２の上部には針弁に噴口閉弁力を付与するための制御燃料を給排可能に収容する受圧室１０３を形成する。この受圧室１０３には主噴射路１７０より制御燃料が供給され、しかも、インジェクタ電磁弁１８０を介して燃料タンク２００に達する燃圧排出路１９０が接続されている。
【０００３】
このコモンレール式燃料噴射装置は、高蓄圧室１２１に対して高圧ポンプ１２２及び図示しない調圧機構を備えた燃料供給源より高圧燃料を供給し、低蓄圧室１３１の燃料圧を調圧器１６０で調圧している。ここで切換え手段１４０は高圧燃料路１２３の開放時に高蓄圧室１２１の高圧燃料を高圧燃料路１２３及び主噴射路１７０を介し燃料溜１１０に供給し、高噴射率の噴射（図８の符号Ｉｈ）を可能としている。更に、低蓄圧室１３１には流動規制部１５０を備えた低圧燃料路１３２を介し主噴射路１７０の燃料が供給され調圧器１６０で調圧され、切換え手段１４０の閉鎖時には低蓄圧室１３１の低圧燃料が燃料溜１１０に供給され低噴射率の噴射（図８の符号Ｉｌ）を可能としている。
【０００４】
このようにコモンレール式燃料噴射装置は１噴射行程での噴射率を増減切換え可能であり、図８に実線で示すように、インジェクタ電磁弁１８０（図８ではインジェクタ電磁弁Ａと記す）の開弁時期ｔ１ｓに対して切換え手段１４０（図８では切換電磁弁Ｂと記す）の開弁時期ｔ２ｓを所定ずれ時間αだけ遅れるように調整することで、初期噴射率を抑えたブーツ型噴射モードＭ１（ＩｌとＩｈが連続する）を選択できる。あるいは、切換え手段１４０の開弁時期ｔ２ｓ’をインジェクタ電磁弁１８０の開弁時期ｔ１ｓより前にずらすことで、高噴射率（針弁リフトに対応）の矩形噴射モードＭ２（Ｉｈが連続する破線で示すモード）を選択できる。
【０００５】
【発明が解決しようとする課題】
ところで、噴射初期の噴射率を抑制したブーツ型噴射モードＭ１となるように制御する場合、最初の低圧噴射を行なうためには、インジェクタ電磁弁１８０をオンにして、受圧室１０３の制御燃圧を急激に降下させる必要があるが、特に、低圧燃料噴射の場合、低圧燃料路１３２を介し低蓄圧室１３１の燃料が受圧室１０３に供給されており、噴射開始時の受圧室１０３の制御油圧Ｐａの排出に時間がかかる。
【０００６】
その結果、針弁１０２の上昇速度が遅くなり、初期の噴射は針弁１０２と弁座（シート）１０５間の隙間（後述の図３中の符号ｅ１参照）が比較的小さい状態が継続することによる、いわゆるシート絞りの影響を多く受ける。このため、燃料の霧化状態が悪くなり、燃費の悪化や黒煙の排出が多くなっていた。また、燃圧排出路１９０の流出オリフィス１０４の径を大きく設定すれば、開弁速度を早めることは可能だが、閉弁速度が遅くなるため、燃費の悪化やＨＣ、黒煙の排出が多くなる問題がある。
【０００７】
一方、矩形噴射モードＭ２においては、受圧室１０３に高圧燃料路１９０の高圧燃料が供給されており、噴射開始時の受圧室１０３の制御油圧の排出は速やかになされる。しかし、この矩形噴射モードＭ２での閉弁時期ｔ１ｅにおいて、高圧コモンレール１２１から針弁１０２と対向する受圧室１１０に高圧燃料が流入している。ここで生じる噴口閉弁力は針弁１０２の下部側の燃料溜１１０に印加されている噴射圧（開弁圧）とのバランスに打ち勝つことにより、急激に閉弁作動することとなる。
【０００８】
この結果、針弁１０２を急激に閉弁すると、受圧室１０３の制御油圧Ｐａは図８に示すように急増する。このため、針弁１０２が弁座１０５に着座する着座速度が速くなり、着座速度が極度に高いと針弁１０２がバウンドし、例えば、図８に示すように、本来の着座時期ｔｒの後に針弁１０２がバウンドして不斉噴射Ｍｂが生じ、不要な燃料を噴射したり、シート部の耐久性を損ねたりという問題が生じる。
本発明は、以上のような課題に基づき、噴射開始時の針弁の開弁速度を速め、閉弁時の針弁の着座速度の過度な増大化を抑え、これによって、燃費の悪化やＨＣ、黒煙の排出の抑制及び不斉噴射の防止を達成できる燃料噴射装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
請求項１の発明は、インジェクタ本体の噴口を開閉可能な針弁と、同針弁に制御燃料圧相当の噴口閉弁力を付与する受圧室と、上記針弁に噴射燃料圧相当の噴口開弁力を付与する燃料溜とを有したインジェクタと、上記燃料溜に高圧燃料供給部及び低圧燃料供給部の各加圧燃料を選択的に供給する燃料供給手段と、上記低圧燃料供給部の低圧燃料と同低圧燃料の流路に並列接続された増圧機構が低圧燃料の供給を受けて増圧した増圧燃料とを制御燃料圧として選択的に上記受圧室に供給する制御油圧切換え手段と、上記受圧室を同受圧室より延出する油圧排出路と遮断することで針弁に加わる上記噴口閉弁力が上記噴口開弁力を上回るようにして針弁を閉切換えし、上記受圧室を油圧排出路に連通することで針弁に加わる上記噴口閉弁力が上記噴口開弁力を下回るようにして針弁を開切換えするインジェクタ制御弁と、を具備したことを特徴とする。
【００１０】
このように、インジェクタ制御弁の制御油圧切換え手段からの制御油圧を針弁の少なくとも開切換え又は閉切換えに先立って、制御油圧切換え手段からの制御油圧を増減調整して受圧室で受けるようにできる。例えば、閉切換え時の制御油圧を低圧燃料よりも高く高圧燃料よりも低い圧力とすることで、針弁の閉切換えにおける着座速度を比較的遅くして不斉噴射を防止でき、装置の耐久性を向上できる。更に、低圧燃料を用いて噴射開始する場合に、開切換え時の制御油圧を高圧燃料同等、又は前記閉切換え時の制御油圧よりも高い圧力とすることによって針弁の開切換えにおける開放速度が向上し、シート絞りにより霧化状態が悪化することを防止できる。
【００１１】
請求項２の発明は、請求項１記載の燃料噴射装置において、上記受圧室に印加される制御燃料相当の油圧は上記針弁の開切換えに先立つ圧力値の方が閉切換えに先立つ圧力値より高圧に設定されることを特徴とする。
このように、インジェクタ制御弁の制御油圧切換え手段からの制御油圧を針弁の開切換えに先立つ圧力値が閉切換えに先立つ圧力値より大きく、針弁の開切換えにおける開放速度が向上し、霧化状態の悪化を確実に防止でき、しかも、閉切換えに先立つ圧力値は中間圧力となり、着座速度を適度に抑制でき、応答性を保持した上で不斉噴射を抑制できる。
【００１２】
請求項３の発明は、請求項１記載の燃料噴射装置において、上記針弁が開切換え中より閉切換えが行われるに先立ち、上記制御油圧切換え手段の増圧機構が増圧燃料供給作動することを特徴とする。
ここでの制御油圧切換え手段の増圧機構は、針弁が開切換え中より閉切換えする直前に増圧燃料供給作動して中間圧力を受圧室に供給でき、着座速度を適度に抑制でき、応答性を保持した上で不斉噴射を抑制できる。
【００１３】
請求項４の発明は、請求項１記載の燃料噴射装置において、上記制御油圧切換え手段の増圧機構は上記針弁の開切換え及び閉切換えに先立ち増圧燃料供給作動することを特徴とする。
ここでは、針弁の開切換え及び閉切換えに先立ち、増圧機構はそれぞれ増圧燃料供給作動し、これにより噴射時の霧化状態の悪化を防止でき、針弁の着座速度を比較的遅くして不斉噴射を防止でき、装置の耐久性を向上できという装置を比較的簡素な構成で達成できる。
【００１４】
請求項５の発明は、請求項１記載の燃料噴射装置において、上記燃料供給手段が上記インジェクタ制御弁の開切換え後に、前期高圧燃料供給部の加圧燃料を前記燃料溜に供給するように切換えることを特徴とする。
【００１５】
ここではインジェクタ制御弁の開切換え後に初期噴射率を抑えた低圧噴射期間を設定してブーツ型噴射モードでインジェクタを噴射駆動できる。
【００１６】
【発明の実施の形態】
以下、本発明の一実施形態としての燃料噴射装置を図１を参照して説明する。ここでの燃料噴射装置１は高圧と低圧の２つの蓄圧室を備えた燃料噴射装置であり、図示しない車両に搭載された多気筒ディーゼルエンジン（以後単にエンジンと記す）２に装着される。
エンジン２はそのエンジン本体３内の各燃焼室（１つのみ示した）４に燃料噴射装置１により後述のブーツ型噴射モードＭ１或いは矩形型噴射モードＭ２での燃料噴射を行う。
【００１７】
燃料噴射装置１は、各燃焼室４に燃料噴射を行うインジェクタ５と、各インジェクタ５の燃料溜６に高圧燃料供給部ＰＨ、低圧燃料供給部ＰＬ及びインジェクタ切換制御部ＰＳからなる燃料供給手段９と、燃料噴射装置１の噴射制御機能を有するコントローラ７とを備える。
ここで、各インジェクタ５は高圧燃料供給部ＰＨ、低圧燃料供給部ＰＬ及びインジェクタ切換制御部ＰＳに対して並列的に同様に接続されることより、ここでは一つのインジェクタ５との接続構成を主に説明し、他のインジェクタの重複する説明を略す。
【００１８】
インジェクタ５はそのインジェクタ本体１１の下部に噴口８を形成され、同噴口８の内側に燃料溜６が形成される。図３に示すように、噴口８は針弁１２によって開閉されることで燃料溜６の高圧燃料を噴射し、停止することができる。針弁１２の他端である上端には噴射制御部を成す受圧室１３が形成され、受圧室１３には受圧ピストン１４が針弁１２を押圧可能に収容されている。
【００１９】
燃料溜６はインジェクタ本体１１内を貫通して延出する主噴射通路１５に接続される。この主噴射通路１５は高圧管路２０及び低圧管路１７に分岐して連通する。高圧管路２０は切換え手段１６を介し高圧貯留室を成す高圧コモンレール１８に連結され、低圧管路１７は流入規制部４３を介し低蓄圧室を成す低圧コモンレール１９に連結される。
インジェクタ５にはインジェクタ切換制御部ＰＳを成す高圧管路２０側の切換え手段１６、受圧室１３に連結される低圧流入路２１側の制御油圧切換え手段５８、油圧排出路２３側のインジェクタ電磁弁２２が連結される。
【００２０】
図２に示すように、制御油圧切換え手段５８は低圧流入路２１に対して並列状に増圧機構部３０を備える。増圧機構部３０は大小の内径のシリンダ室３０１、３０２を備え、ここに大小の外径で一体化し、或いは２つの円筒で別体に形成された増圧ピストン３０３を収容する。大径のシリンダ室３０１の端部は低圧流入路２１の上流分岐部（低圧コモンレール１９側）ｂ１に小径のシリンダ室３０２の端部は低圧流入路２１の下流分岐部（受圧室１３側）ｂ２に連通する。大径シリンダ室３０１の小径シリンダ室３０２側部位には大径シリンダ室３０１の燃圧を開放する増圧機構作動電磁弁としての増圧電磁弁４０を備えた油圧排出路５０と、低圧流入路２１の中間分岐部ｂ３に絞り５１を介し連通する調圧路５２とが接続される。更に、低圧流入路２１の下流分岐部ｂ２と中間分岐部ｂ３の間にはインジェクタ５側から低圧コモンレール１９側への燃料流動を防止する逆止弁５３が配設される。
【００２１】
増圧電磁弁４０はコントローラ７の駆動信号でオンオフ作動して油圧排出路５０及び大径のシリンダ室３０１間を開閉し、増圧ピストン３０３の大径部の表裏面に圧力差を生じさせて増圧ピストン３０３を図中左側に加圧作動させ、下流分岐部（インジェクタ側）ｂ２側の燃圧を加圧できる。
なお、符号５４は増圧ピストン３０３を上流分岐部（低圧コモンレール１９側）ｂ１に戻す戻しばねを示す。
【００２２】
高圧燃料供給部ＰＨは、燃料タンク２４と、同燃料タンク２４の燃料を高圧コモンレール１８に圧送する供給管２５と、供給管２５上に配備され、燃料タンク２４の燃料をフィルタ２６を介し吸入して高圧化し、高圧コモンレール１８に圧送する燃圧ポンプ２７とを備える。
燃圧ポンプ２７はポンプ本体内に各気筒と連結されるプランジャ室２８及び各プランジャ室２８内で加圧作動する各プランジャ２９を備え、各プランジャ２９はポンプカム軸３１、図示しない回転伝達系を介しエンジンのクランク軸３２により駆動される。
【００２３】
プランジャ室２８は供給管２５の流入部２５１と流出部２５２及び戻し路３３が連結され、戻し路３３は戻し電磁弁３４により開閉される。これにより戻し路３３の戻し燃料量を所定デューティー比Ｄｕｒで調整し、高圧コモンレール１８の高圧燃料を目標燃料圧である高圧コモンレール圧Ｐｈｃｒに増減調整している。
高圧コモンレール１８は気筒配列方向（紙面垂直方向）に向けた状態でエンジン本体３に支持され、供給管２５からの高圧燃料を貯留し、各インジェクタ５に向う高圧管路２０を分岐して延出し、各インジェクタ５の燃料溜６に高圧燃料を供給し、高噴射率の噴射を可能としている。
【００２４】
高圧管路２０の途中の切換え手段１６はインジェクタ切換制御部ＰＳの一部を成し、高圧管路２０を断続可能な弁体３５を備える。この弁体３５はこれに遮断力を付与する遮断ピストン３６が対設され、遮断ピストン３６は切換え圧受室３７に嵌合する。切換え圧受室３７は絞り３８を備えた流入路３９を介し低圧コモンレール１９の低圧管路１７に連通し、しかも切換え弁４６を介し、低圧戻し路４７を経て燃料タンク２４に連通する。
【００２５】
このような切換え手段１６は切換え弁４１がオフ時に、低圧戻し路４２を遮断して低圧コモンレール１９の低圧燃料Ｐｌｃｒを切換え圧受室３７に滞留させ、その燃圧相当の遮断力を遮断ピストン３６を介して弁体３５に付与し、高圧管路２０を遮断し、この際、燃料溜６に低圧管路１７よりの低圧燃料を供給できる。逆に切換え弁４１がオン時に、低圧戻し路４２を開放して切換え圧受室３７の低圧燃料を低圧戻し路４２に排出して弁体３５への遮断力を排除し、高圧管路２０を連通させ、この際、燃料溜６に高圧コモンレール１８よりの高圧燃料を供給できる。
低圧燃料供給部ＰＬは主噴射通路１５より分岐して延出する低圧管路１７と、その低圧管路１７の途中に配備された流入規制部４３と流入端側の低圧コモンレール１９とで構成される。
【００２６】
流入規制部４３は分岐路１７上に絞り４４と逆止弁４５を並列配備している。逆止弁４５は主噴射通路１５の高圧燃料が低圧コモンレール１９に流入するのを阻止し、絞り４４は主噴射通路１５より低圧コモンレール１９に流入する燃料の流入を規制することで、後述の調圧弁４６と協働して低圧コモンレール１９の燃圧を低圧化して保持することを可能としている。更に、低圧コモンレール１９には調圧弁４６を介して燃料タンク２４に達する低圧ドレーン路４７が連結される。この調圧弁４６は流入規制部４３との協働作用により低圧コモンレール２１の燃料圧を所定の低圧値に調圧保持し、しかも、切換え弁４１の遮断時に、低圧燃料を逆止弁４５を通して燃料溜６に供給し、低噴射率の噴射を可能としている。
【００２７】
インジェクタ５の受圧室１３の受圧ピストン１４には低圧コモンレール１９側に連通する低圧流入路２１よりの低圧燃料が制御油圧として導入されている。インジェクタ電磁弁２２のオフ時において、油圧排出路２３が遮断し、受圧ピストン１４は低圧燃料相当の閉弁力を針弁１２に加え、燃料噴射は停止状態に保持される。逆にインジェクタ電磁弁２２のオン時において、低圧戻し路２３が開放され、受圧室１３の燃料は油圧排出路２３に排除され、受圧ピストン１４に加わる閉弁力が開弁力を下回り、針弁１２が開作動して燃料噴射が成される。
【００２８】
コントローラ７はその入出力回路に多数のポートを有し、エンジンの運転情報を検出するための各種センサを接続しており、特に、エンジン２のアクセルペダル開度θａを検出するアクセルペダル開度センサ４８と、クランク角情報Δθを検出するクランク角センサ４９と、水温ｗｔを検出する水温センサ５５と、排気ガス温度Ｔｇを検出する温度センサ５６、大気圧ｐａを検出する大気圧センサ５７とが接続される。ここでクランク角情報Δθはコントローラ７においてエンジン回転数Ｎｅの導出に用いられる。
【００２９】
次に、図１の燃料噴射装置の作動をコントローラ７の制御処理に沿って説明する。
図示しない車両のエンジン２の駆動時において、コントローラ７は複数の制御系、例えば、燃料噴射系、燃料供給系で適宜駆動されている関連機器、センサ類の自己チェック結果を取込み、これが正常であったか否かを確認し、正常（ＯＫ）では図示しないエンジン制御処理ルーチンを実行し、その途中で図６に示す燃料噴射制御ルーチンを実行する。
【００３０】
燃料噴射制御ルーチンのステップｓ１に達すると、最新のデータ、例えば、クランク角度Δθ、エンジン回転数Ｎｅ、排気ガス温度Ｔｇ、水温ｗｔ、大気圧ｐａ等が取り込まれ、それぞれ記憶処理される。
【００３１】
ステップｓ２ではアクセルペダル開度θａ、エンジン回転数Ｎｅに基づき、ブーツ型噴射モードＭ１、又は矩形噴射モードＭ２のいずれかを選択する。ステップｓ３において、選択された噴射モードがいずれかの噴射モードか判定され、矩形型噴射モードＭ２の場合にはステップｓ８に、ブーツ型噴射モードＭ１の場合ステップｓ４に進む。
ステップｓ４では、エンジン回転数Ｎｅとアクセルペダル開度θａに応じた基本燃料噴射量ＩＮＪｂ、水温ｗｔや大気圧ｐａの各補正値ｄｔ（低温域で比較的大きな補正値となる）、ｄｐより目標燃料噴射量ｑｔａｒｇｅｔ（＝ＩＮＪｂ＋ｄｔ＋ｄｐ）を導出する。
【００３２】
ステップｓ５では高低コモンレールの燃圧Ｐｈｃｒ、Ｐｌｃｒをエンジン回転数Ｎｅと目標燃料噴射量ｑｔａｒｇｅｔより図３（ａ）、（ｂ）のコモンレール圧マップｍ１、ｍ２で導出し、これら値相当の出力（デューティー比）を高圧コモンレール１８側の戻し電磁弁３４、低圧コモンレール１９の調圧弁４６の図示しないコモンレール圧ドライバーにセットする。
ステップｓ６ではインジェクタ電磁弁２２の噴射開始時期ｔ１ｓ（図５参照）および切換え弁４１の切換え時期ｔ２ｓ（図５の開弁時期参照）をエンジン回転数Ｎｅに応じて図４（ｃ）の噴射時期マップｍ３で導出する。
【００３３】
更に、導出されたｔ１ｓとｔ２ｓより低圧噴射期間α（＝ｔ１ｓ−ｔ２ｓ）を求め、低圧コモンレールの燃圧Ｐｌｃｒと低圧噴射期間Δｔｉｎｊとより、低圧噴射期間に噴射される低圧燃料噴射量を算出する。そして、目標燃料噴射量ｑｔａｒｇｅｔから低圧燃料噴射量を差し引いた高圧燃料噴射量を求めて、目標高圧燃料噴射量と高圧コモンレール１８の圧力Ｐｈｃｒよりインジェクタ電磁弁２２及び切換弁４１の閉弁時期ｔ１ｅ、ｔ２ｅを導出する。
更に、ステップｓ６ではインジェクタ電磁弁２２駆動後のずれ期間ｇ経過時に増圧電磁弁４０をオフする増圧電磁弁開弁時期ｔａ（＝ｔ１ｓ＋ｇ）と、インジェクタ電磁弁２２の閉弁時期ｔ１ｅに対して先行処理期間ｋだけ先立つ付勢開始時期ｔｂ（＝ｔ１ｅ−ｋ）と、インジェクタ電磁弁２２閉弁後の所定の経過期間γの経過時に増圧電磁弁４０をオンする閉弁付勢開始時期ｔｃ（＝ｔ１ｅ＋γ）とを順次算出する。
【００３４】
ステップｓ７ではインジェクタ電磁弁２２の噴射開始時期ｔ１ｓ、切換え弁４１の切換え時期ｔ２ｓ、今回の低圧噴射期間α及びインジェクタ電磁弁２２及び切換え弁４１の閉弁時期ｔ１ｅ、ｔ２ｅに相当する情報を含む出力が燃料噴射用ドライバ（図示せず）にセットされる。
更に、増圧電磁弁４０の増圧電磁弁開弁時期ｔａ（＝ｔ１ｓ＋ｇ）、付勢開始時期ｔｂ（＝ｔ１ｅ−ｋ）、閉弁付勢開始時期ｔｃ（＝ｔ１ｅ＋γ）に相当する情報を含む出力が増圧用ドライバ（図示せず）にセットされ、この回の制御を終了させ、リターンする。
【００３５】
これに応じて燃料噴射用ドライバはクランク角Δθ信号に基き、インジェクタ電磁弁２２、切換え弁４１及び増圧電磁弁４０の各ドライバを駆動させ、カウントアップに応じて切換え出力を発して、ブーツ型噴射モードＭ１（図５参照）でインジェクタ５が噴射駆動する。
ステップｓ８の通常制御処理では矩形噴射モードＭ２での制御に入る。
ここでは基本燃料噴射量ＩＮＪｂ、目標燃料噴射量ｑｔａｒｇｅｔ（＝ＩＮＪｂ＋ｄｔ＋ｄｐ）を順次算出する。
【００３６】
更に、高コモンレールの燃圧Ｐｈｃｒはエンジン回転数Ｎｅと目標燃料噴射量ｑｔａｒｇｅｔより図示しない通常時コモンレール圧マップで導出し、この値相当の出力（デューティー比）を高圧コモンレール１８側の戻し電磁弁３４（低圧コモンレール１９の調圧弁４６は停止）に出力し、高コモンレールの燃圧Ｐｈｃｒを確保する。
更に、インジェクタ電磁弁２２の噴射開始時期ｔ１ｓ（図５参照）をエンジン回転数Ｎｅに応じて図示しない通常時噴射時期マップで導出する。更に、切換え弁４１の切換え時期ｔ２ｓ’を、図５に示すように、噴射開始時期ｔ１ｓより期間ｊだけ先立つ開弁時期として設定する。更に、高圧噴射期間β及び閉弁時期ｔ１ｅ、ｔ２ｅがブーツ型噴射の場合と同様に導出される。
【００３７】
次いで導出された開弁時期ｔ１ｓ、切換え時期ｔ２ｓ’　、閉弁時期ｔ１ｅ、ｔ２ｅに相当する情報を含む出力が燃料噴射用ドライバ（図示せず）にセットされ、更に、ブーツ型噴射の場合と同様に、増圧電磁弁４０の増圧電磁弁開弁時期ｔａ、付勢開始時期ｔｂ、閉弁付勢開始時期ｔｃが導出され、各時期に相当する情報を含む出力が増圧用ドライバ（図示せず）にセットされ、この回の制御を終了させ、リターンする。
これに応じて燃料噴射用ドライバはクランク角Δθ信号に基き、インジェクタ電磁弁２２、切換え弁４１及び増圧電磁弁４０を駆動し、図５に２点鎖線で示す矩形噴射モードＭ２でインジェクタ５が噴射駆動する。
【００３８】
特に、ブーツ型噴射モードＭ１及び矩形噴射モードＭ２での各インジェクタ５の開駆動時において、増圧電磁弁４０を開切換え時である噴射開始時期ｔ１ｓに先立って、即ち、前行程での閉弁付勢開始時期ｔｃ（＝ｔ１ｅ＋γ）以後オンし、制御油圧切換え手段５８の増圧機構部３０を加圧作動させることで、受圧室（噴射制御部）１３の制御燃圧ＰＡを十分高圧となるように、即ち、高圧コモンレール１８の燃圧Ｐｈｃｒと同等圧、あるいはそれを上回る高圧に加圧作動している。
【００３９】
このように制御油圧を高圧コモンレール１８による高圧燃料（図５ではＰｈｃｒ≒ＰＡ）とすることで、破線で示した低圧コモンレール１９の制御燃圧（Ｐｌｃｒ）と比較して圧力差δが十分に大きくなり、制御燃料の受圧室（噴射制御部）１３からの排出速度が従来より速くなり、針弁下部に印加されている噴射燃料の圧力（開弁圧）とのバランスが応答性良く、いち早く崩れるため、針弁１２の上昇速度（開放速度）が向上する。即ち、図５に破線で示すような低燃料圧Ｐｌｃｒの場合の噴射率（≒針弁リフト）の変化に対し、実線で示すような高圧燃料（図５ではＰｈｃｒ≒ＰＡ）の場合、　針弁１２の上昇速度（開放速度）が十分に早められている。即ち、図３に示すような弁座５０１と針弁１２の隙間ｅ１が比較的速やかに増大することとなる。なお、図５中の符号ｐ１の段部は増圧電磁弁４０のオフがずれ期間ｇ経過することで、この間、受圧室１３の燃圧が下がりきらない状態を示す。
【００４０】
このように、従来のように受圧室１３の開弁時の燃圧が低いことに起因し、針弁がフルリフト途中において、隙間ｅ１が拡大せず、シート絞りが生じて霧化状態が悪化するという不適切な事態の発生を確実に防止でき、針弁の上昇期間が短縮されると共に、フルリフトに至るまでの時間も短縮され、適切な燃料噴射が可能となる。
更に、このようなブーツ型噴射モードＭ１及び矩形噴射モードＭ２でのインジェクタ５の閉弁時期ｔ１ｅにおいて、この閉弁時期ｔ１ｅに対して先行処理期間ｋだけ先立つ付勢開始時期ｔｂ（＝ｔ１ｅ−ｋ）に増圧電磁弁４０をオンする。これにより、受圧室１５の制御燃圧は先行処理期間ｋの期間幅に応じて増加し、中間圧力Ｐｍｃｒとなる。
【００４１】
ここで中間圧力Ｐｍｃｒは低圧コモンレールの燃圧Ｐｌｃｒより大きく、高圧コモンレール１８の圧力Ｐｈｃｒより小さく設定され、ここでは、　中間圧力Ｐｍｃｒ｛≒（Ｐｌｃｒ＋Ｐｈｃｒ）／２｝に設定される。
即ち、ここでの制御燃料相当の油圧ＰＡは針弁１２の開切換え（ｔ１ｓ）に先立つ圧力値（圧力Ｐｈｃｒ）の方が閉切換え（ｔ１ｅ）に先立つ圧力値（中間圧力Ｐｍｃｒ）より高圧に設定される。即ち、　高圧コモンレール１８の圧力Ｐｈｃｒより小さく中間圧力Ｐｍｃｒが設定されるので、　中間圧力Ｐｍｃｒを受けた針弁１２の着座速度を適度に抑制でき、応答性を保持した上で不斉噴射を抑制できる。
【００４２】
なお、図５には、図７の従来装置における受圧室１０３の制御燃圧ＰＡの変動を破線で示した（図７の制御燃圧Ｐａと同一）。ここでは受圧室１０３の制御燃圧が急増し、着座時期ｔｒが本実施形態における着座時期ｔｒ’と比較して速まり、結果として、不斉噴射Ｍｂが発生するという状態を示しているが、このような状態を図１の燃料噴射装置は確実に防止でき、このような針弁１２及び弁座５０１を含む燃料噴射装置１全体としての耐久性が向上する。
【００４３】
更に、図１の燃料噴射装置１の制御油圧切換え手段５８は、針弁１２が開切換え中より閉切換えする直前に増圧燃料供給作動して中間圧力ｐｍｃｒを受圧室１３に供給でき、着座速度を適度に抑制でき、応答性を保持した上で不斉噴射を抑制できる。
更に、　図１の燃料噴射装置１は、針弁１２の開切換え（噴射開始時期ｔ１ｓ、切換え時期ｔ２ｓ）、閉切換え（閉弁時期ｔ１ｅ、ｔ２ｅ）に先立ち、制御油圧切換え手段５８の増圧機構部３０はそれぞれ増圧燃料供給作動し、これにより噴射時の霧化状態の悪化を防止でき、針弁の着座速度を比較的遅くして不斉噴射を防止でき、装置の耐久性を向上できという装置を比較的簡素な構成で達成できる。
【００４４】
【発明の効果】
以上のように、本発明は、インジェクタ制御弁の制御油圧切換え手段からの制御油圧を針弁の少なくとも開切換え又は閉切換えに先立って、制御油圧切換え手段からの制御油圧を増減調整して受圧室で受けるようにできる。例えば、閉切換え時の制御油圧を低圧燃料よりも高く高圧燃料よりも低い圧力とすることで、針弁の閉切換えにおける着座速度を比較的遅くして不斉噴射を防止でき、装置の耐久性を向上できる。
【００４５】
請求項２の発明は、インジェクタ制御弁の制御油圧切換え手段からの制御油圧を針弁の開切換えに先立つ圧力値が閉切換えに先立つ圧力値より大きく、針弁の開切換えにおける開放速度が向上し、霧化状態の悪化を確実に防止でき、しかも、閉切換えに先立つ圧力値は中間圧力となり、着座速度を適度に抑制でき、応答性を保持した上で不斉噴射を抑制できる。
【００４６】
請求項３の発明での制御油圧切換え手段の増圧機構は、針弁が開切換え中より閉切換えする直前に増圧燃料供給作動して中間圧力を受圧室に供給でき、着座速度を適度に抑制でき、応答性を保持した上で不斉噴射を抑制できる。
【００４７】
請求項４の発明は、針弁の開切換え及び閉切換えに先立ち、増圧機構はそれぞれ増圧燃料供給作動し、これにより噴射時の霧化状態の悪化を防止でき、針弁の着座速度を比較的遅くして不斉噴射を防止でき、装置の耐久性を向上できという装置を比較的簡素な構成で達成できる。
【００４８】
請求項５の発明は、インジェクタ制御弁の開切換え後に初期噴射率を抑えた低圧噴射期間を設定してブーツ型噴射モードでインジェクタを噴射駆動できる。
【図面の簡単な説明】
【図１】本発明の一実施形態としての燃料噴射装置の概略構成図である。
【図２】図１の燃料噴射装置が用いる制御油圧切換え手段の概略構成図である。
【図３】図１の燃料噴射装置が用いるインジェクタの部分切欠断面図である。
【図４】図１の燃料噴射装置が用いるマップの特性線図であり、（ａ）のマップは低コモンレール圧Ｐｌｃｒを、（ｂ）のマップは高コモンレール圧Ｐｈｃｒを、（ｃ）のマップは噴射時期の演算に用いる。
【図５】図１の燃料燃料噴射装置の弁駆動特性、噴射率特性説明図である。
【図６】図１の燃料噴射装置の燃料噴射制御ルーチンのフローチャートである。
【図７】従来の燃料噴射装置の概略構成図である。
【図８】燃料噴射装置の弁駆動特性、噴射率特性説明図である。
【符号の説明】
１　　　　　燃料噴射装置
２　　　　　エンジン
４　　　　　燃焼室
５　　　　　インジェクタ
６　　　　　燃料溜
８　　　　　噴口
９　　　　　燃料供給手段
１１　　　　インジェクタ本体
１２　　　　針弁
１３　　　　受圧室
１７　　　　低圧管路
２１　　　　低圧流入路
２２　　　　インジェクタ制御弁
２３　　　　油圧排出路
３０　　　　増圧機構部
５８　　　　制御油圧切換え手段
ＰＡ　　　　制御燃料圧
ＰＨ　　　　高圧燃料供給部
ＰＬ　　　　低圧燃料供給部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention can change an injection rate to a combustion chamber by selectively supplying high-pressure fuel and low-pressure fuel to a fuel reservoir of an injector, particularly, a fuel reservoir of an injector. The present invention relates to a fuel injection device.
[0002]
[Prior art]
As a fuel injection device that injects fuel into the combustion chamber of an internal combustion engine using an injector, high-pressure fuel is supplied from a fuel supply source to a common rail that forms a pressure accumulation chamber, and the high-pressure fuel stored in the pressure accumulation chamber is burned when the injector's solenoid valve is opened. 2. Description of the Related Art A common rail type fuel injection device for spraying a chamber is known.
In this common rail type fuel injection device, in particular, as shown in FIG. 7, each pressurization of a high pressure storage chamber 121 of a high pressure fuel supply unit 120 and a low pressure storage chamber 131 of a low pressure fuel supply unit 130 is performed in a fuel reservoir 110 of an injector 100. There is known a common rail type fuel injection device which can selectively supply fuel by switching fuel switching means 140. Here, the injector 100 accommodates a needle valve 102 capable of opening and closing a nozzle at a lower portion inside the injector body 101, and supplies and discharges control fuel for applying a nozzle closing force to the needle valve at an upper portion of the needle valve 102. A pressure receiving chamber 103 is formed to accommodate the pressure. Control pressure is supplied to the pressure receiving chamber 103 from the main injection path 170, and a fuel pressure discharge path 190 that reaches the fuel tank 200 via an injector solenoid valve 180 is connected.
[0003]
This common rail type fuel injection device supplies high pressure fuel to a high pressure accumulating chamber 121 from a high pressure pump 122 and a fuel supply source having a pressure regulating mechanism (not shown), and regulates a fuel pressure of a low pressure accumulating chamber 131 by a pressure regulator 160. I'm pressing. Here, the switching means 140 supplies the high-pressure fuel in the high-pressure storage chamber 121 to the fuel reservoir 110 via the high-pressure fuel path 123 and the main injection path 170 when the high-pressure fuel path 123 is opened, and injects the fuel at a high injection rate (reference numeral Ih in FIG. 8). ) Is possible. Further, the fuel in the main injection path 170 is supplied to the low pressure accumulating chamber 131 through a low pressure fuel path 132 having a flow restricting section 150 and is regulated by a pressure regulator 160. When the switching means 140 is closed, the low pressure in the low pressure accumulating chamber 131 is reduced. Fuel is supplied to the fuel reservoir 110 to enable low-injection-rate injection (reference numeral Il in FIG. 8).
[0004]
As described above, the common rail type fuel injection device can change the injection rate in one injection stroke by increasing or decreasing. As shown by a solid line in FIG. 8, the injector solenoid valve 180 (in FIG. 8, denoted as injector solenoid valve A) is opened. By adjusting the valve opening timing t2s of the switching means 140 (denoted as the switching solenoid valve B in FIG. 8) with respect to the timing t1s so as to be delayed by a predetermined deviation time α, the boot type injection mode M1 ( Il and Ih continue). Alternatively, by shifting the valve opening timing t2s' of the switching means 140 before the valve opening timing t1s of the injector solenoid valve 180, the rectangular injection mode M2 (Ih with a continuous broken line) having a high injection rate (corresponding to a needle valve lift). Mode shown) can be selected.
[0005]
[Problems to be solved by the invention]
By the way, when controlling to be in the boot type injection mode M1 in which the injection rate at the initial injection is suppressed, in order to perform the first low-pressure injection, the injector solenoid valve 180 is turned on and the control fuel pressure of the pressure receiving chamber 103 is rapidly increased. In particular, in the case of low-pressure fuel injection, the fuel in the low-pressure storage chamber 131 is supplied to the pressure-receiving chamber 103 via the low-pressure fuel path 132, and the control hydraulic pressure Pa of the pressure-receiving chamber 103 at the start of injection is reduced. It takes time to discharge.
[0006]
As a result, the ascending speed of the needle valve 102 becomes slow, and the initial injection continues in a state in which the gap between the needle valve 102 and the valve seat (seat) 105 (see the symbol e1 in FIG. 3 described later) is relatively small. , A lot of the influence of the so-called sheet drawing. For this reason, the atomization state of the fuel has deteriorated, the fuel efficiency has deteriorated, and the emission of black smoke has increased. Further, if the diameter of the outflow orifice 104 in the fuel pressure discharge passage 190 is set to be large, the valve opening speed can be increased, but the valve closing speed is slowed, so that fuel consumption deteriorates and HC and black smoke are increased. There is.
[0007]
On the other hand, in the rectangular injection mode M2, the high-pressure fuel in the high-pressure fuel path 190 is supplied to the pressure receiving chamber 103, and the control oil pressure in the pressure receiving chamber 103 at the start of injection is quickly discharged. However, at the valve closing timing t1e in the rectangular injection mode M2, the high-pressure fuel flows from the high-pressure common rail 121 into the pressure receiving chamber 110 facing the needle valve 102. The orifice closing force generated here overcomes the balance with the injection pressure (valve opening pressure) applied to the fuel reservoir 110 on the lower side of the needle valve 102, whereby the valve closing operation is rapidly performed.
[0008]
As a result, when the needle valve 102 is rapidly closed, the control oil pressure Pa of the pressure receiving chamber 103 is rapidly increased as shown in FIG. For this reason, the seating speed at which the needle valve 102 is seated on the valve seat 105 increases, and if the seating speed is extremely high, the needle valve 102 bounces, for example, as shown in FIG. Asymmetry injection Mb occurs due to the bounce of the valve 102, causing problems such as injecting unnecessary fuel and impairing the durability of the seat portion.
The present invention has been made based on the above-described problems, by increasing the valve opening speed of the needle valve at the start of injection, and suppressing an excessive increase in the seating speed of the needle valve at the time of closing the valve. It is another object of the present invention to provide a fuel injection device capable of achieving suppression of black smoke emission and prevention of asymmetric injection.
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, a needle valve capable of opening and closing an injection port of an injector body, a pressure receiving chamber for applying an injection valve closing force corresponding to a control fuel pressure to the needle valve, and an injection port corresponding to an injection fuel pressure to the needle valve An injector having a fuel reservoir for providing a valve force; a fuel supply means for selectively supplying each of the pressurized fuels of a high-pressure fuel supply unit and a low-pressure fuel supply unit to the fuel reservoir; Control hydraulic pressure switching means for selectively supplying the fuel and the pressure-intensified fuel, which is connected in parallel to the flow path of the low-pressure fuel to the pressure-receiving chamber, with the pressure-increased fuel which has been supplied and increased in pressure by supplying the low-pressure fuel; By closing the pressure receiving chamber from a hydraulic discharge passage extending from the pressure receiving chamber, the needle valve is closed and switched so that the orifice closing force applied to the needle valve exceeds the orifice opening force. Communicating with the hydraulic discharge passage increases the above-mentioned nozzle closing force applied to the needle valve. An injector control valve to open switch the needle valve so as to below the nozzle hole opening valve force, characterized by comprising a.
[0010]
In this manner, the control oil pressure from the control oil pressure switching means of the injector control valve can be received and received by the pressure receiving chamber by increasing or decreasing the control oil pressure from the control oil pressure switching means prior to at least opening or closing the needle valve. . For example, by setting the control oil pressure at the time of closing switching to a pressure higher than the low-pressure fuel and lower than the high-pressure fuel, the seating speed at the time of closing switching of the needle valve can be relatively slow to prevent asymmetric injection, and the durability of the device can be improved. Can be improved. Further, when the injection is started using the low-pressure fuel, the control oil pressure at the time of opening switching is set to a pressure equal to that of the high-pressure fuel or higher than the control oil pressure at the time of closing switching, so that the opening speed in the opening switching of the needle valve is improved. However, it is possible to prevent the atomization state from being deteriorated by the sheet squeezing.
[0011]
According to a second aspect of the present invention, in the fuel injection device according to the first aspect, the hydraulic pressure equivalent to the control fuel applied to the pressure receiving chamber is such that the pressure value prior to the opening switching of the needle valve is higher than the pressure value prior to the closing switching. The high pressure is set.
As described above, the control oil pressure from the control oil pressure switching means of the injector control valve is greater than the pressure value prior to the switching of the needle valve before the switching of the needle valve, and the opening speed in the switching of the opening of the needle valve is improved. The deterioration of the state can be reliably prevented, and the pressure value prior to the close switching becomes the intermediate pressure, the seating speed can be moderately suppressed, and the asymmetric injection can be suppressed while maintaining the responsiveness.
[0012]
According to a third aspect of the present invention, in the fuel injection device according to the first aspect, the pressure increasing mechanism of the control oil pressure switching means operates the pressure increasing fuel supply operation before the needle valve is switched from the open state to the closed state. It is characterized by.
The pressure-intensifying mechanism of the control hydraulic pressure switching means here is capable of supplying intermediate pressure to the pressure receiving chamber by operating the pressure-increasing fuel immediately before the needle valve is switched from the open state to the closed state, so that the seating speed can be suppressed moderately, Asymmetric injection can be suppressed while maintaining the properties.
[0013]
According to a fourth aspect of the present invention, in the fuel injection device according to the first aspect, the pressure-intensifying mechanism of the control hydraulic pressure switching means performs a pressure-increasing fuel supply operation prior to the opening and closing switching of the needle valve.
Here, prior to the switching of the opening and closing of the needle valve, the pressure-intensifying mechanism operates to supply the pressure-increasing fuel, thereby preventing the atomization state from being deteriorated at the time of injection and making the seating speed of the needle valve relatively slow. Asymmetric injection can be prevented, and the durability of the device can be improved, so that the device can be achieved with a relatively simple configuration.
[0014]
According to a fifth aspect of the present invention, in the fuel injection device according to the first aspect, the fuel supply means switches to supply the pressurized fuel of the high-pressure fuel supply unit to the fuel reservoir after the injector control valve is opened. It is characterized by the following.
[0015]
Here, after the opening of the injector control valve is switched, a low-pressure injection period in which the initial injection rate is suppressed can be set to drive the injector in the boot-type injection mode.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a fuel injection device as one embodiment of the present invention will be described with reference to FIG. The fuel injection device 1 here is a fuel injection device having two accumulator chambers of high pressure and low pressure, and is mounted on a multi-cylinder diesel engine (hereinafter simply referred to as engine) 2 mounted on a vehicle (not shown).
The engine 2 performs a fuel injection in a boot type injection mode M1 or a rectangular type injection mode M2 to be described later by the fuel injection device 1 into each combustion chamber (only one is shown) 4 in the engine body 3 thereof.
[0017]
The fuel injection device 1 includes an injector 5 for injecting fuel into each combustion chamber 4, and a fuel supply unit 9 including a high-pressure fuel supply unit PH, a low-pressure fuel supply unit PL, and an injector switching control unit PS in a fuel reservoir 6 of each injector 5. And a controller 7 having an injection control function of the fuel injection device 1.
Here, since each injector 5 is similarly connected in parallel to the high-pressure fuel supply unit PH, the low-pressure fuel supply unit PL, and the injector switching control unit PS, the connection configuration with one injector 5 is mainly used here. And the overlapping description of the other injectors is omitted.
[0018]
The injector 5 has an injection port 8 formed at a lower portion of the injector body 11, and a fuel reservoir 6 is formed inside the injection port 8. As shown in FIG. 3, the injection port 8 is opened and closed by the needle valve 12 to inject high-pressure fuel in the fuel reservoir 6 and stop. A pressure receiving chamber 13 forming an injection control unit is formed at the upper end which is the other end of the needle valve 12, and a pressure receiving piston 14 is housed in the pressure receiving chamber 13 so as to press the needle valve 12.
[0019]
The fuel reservoir 6 is connected to a main injection passage 15 extending through the inside of the injector body 11. The main injection passage 15 branches and communicates with the high-pressure pipe 20 and the low-pressure pipe 17. The high-pressure pipe 20 is connected to a high-pressure common rail 18 forming a high-pressure storage chamber via a switching means 16, and the low-pressure pipe 17 is connected to a low-pressure common rail 19 forming a low-pressure storage chamber via an inflow regulating section 43.
The injector 5 has a switching means 16 on the high-pressure pipe 20 side constituting the injector switching control unit PS, a control oil pressure switching means 58 on the low-pressure inflow path 21 side connected to the pressure receiving chamber 13, and an injector solenoid valve 22 on the hydraulic discharge path 23 side. Are linked.
[0020]
As shown in FIG. 2, the control oil pressure switching means 58 includes a pressure increasing mechanism 30 in parallel with the low pressure inflow passage 21. The pressure-increasing mechanism 30 includes cylinder chambers 301 and 302 having large and small inner diameters, and accommodates a pressure-increasing piston 303 formed integrally with large and small outer diameters or separately formed of two cylinders. The end of the large-diameter cylinder chamber 301 is at the upstream branch portion (the low-pressure common rail 19 side) b1 of the low-pressure inflow passage 21, and the end of the small-diameter cylinder chamber 302 is at the downstream branch portion (the pressure-receiving chamber 13 side) b2 of the low-pressure inflow passage 21. Communicate with A hydraulic discharge passage 50 provided with a pressure-intensifying solenoid valve 40 as a pressure-intensifying mechanism operating solenoid valve for releasing the fuel pressure of the large-diameter cylinder chamber 301 at a portion of the large-diameter cylinder chamber 301 on the side of the small-diameter cylinder chamber 302, and a low-pressure inlet 21. And a pressure regulating path 52 communicating with the intermediate branch part b3 via a throttle 51. Further, a check valve 53 for preventing fuel flow from the injector 5 side to the low-pressure common rail 19 side is provided between the downstream branch portion b2 and the intermediate branch portion b3 of the low-pressure inflow passage 21.
[0021]
The pressure-intensifying solenoid valve 40 is turned on / off by a drive signal of the controller 7 to open and close the hydraulic discharge passage 50 and the large-diameter cylinder chamber 301, and to generate a pressure difference between the front and back surfaces of the large-diameter portion of the pressure-intensifying piston 303. The fuel pressure at the downstream branch portion (injector side) b2 can be increased by operating the pressure-intensifying piston 303 to the left side in the drawing.
Reference numeral 54 denotes a return spring that returns the pressure-intensifying piston 303 to the upstream branch portion (on the low-pressure common rail 19 side) b1.
[0022]
The high-pressure fuel supply unit PH is provided with a fuel tank 24, a supply pipe 25 for pumping the fuel in the fuel tank 24 to the high-pressure common rail 18, and the supply pipe 25, and sucks the fuel in the fuel tank 24 through a filter 26. And a fuel pressure pump 27 for pressure-feeding the fuel to the high-pressure common rail 18.
The fuel pressure pump 27 is provided with a plunger chamber 28 connected to each cylinder in the pump body and each plunger 29 pressurized in each plunger chamber 28. Each plunger 29 is connected to the engine via a pump camshaft 31 and a rotation transmission system (not shown). Driven by the crankshaft 32.
[0023]
The plunger chamber 28 is connected to the inflow part 251 and the outflow part 252 of the supply pipe 25 and the return path 33, and the return path 33 is opened and closed by a return electromagnetic valve 34. As a result, the return fuel amount of the return path 33 is adjusted at the predetermined duty ratio Dur, and the high-pressure fuel of the high-pressure common rail 18 is adjusted to increase or decrease to the high-pressure common rail pressure Phcr, which is the target fuel pressure.
The high-pressure common rail 18 is supported by the engine body 3 in a state of being oriented in the cylinder arrangement direction (perpendicular to the paper surface), stores high-pressure fuel from the supply pipe 25, and branches and extends the high-pressure pipe 20 toward each injector 5. The high-pressure fuel is supplied to the fuel reservoir 6 of each injector 5 to enable injection at a high injection rate.
[0024]
The switching means 16 in the middle of the high-pressure line 20 forms a part of the injector switching control unit PS, and includes a valve body 35 capable of intermittently connecting the high-pressure line 20. The valve body 35 is provided with a shut-off piston 36 for applying a shut-off force thereto, and the shut-off piston 36 is fitted into the switching pressure receiving chamber 37. The switching pressure receiving chamber 37 communicates with the low-pressure line 17 of the low-pressure common rail 19 through an inflow path 39 provided with a throttle 38, and communicates with the fuel tank 24 through a low-pressure return path 47 through a switching valve 46.
[0025]
When the switching valve 41 is turned off, the switching means 16 shuts off the low-pressure return path 42 to cause the low-pressure fuel Plcr of the low-pressure common rail 19 to stay in the switching pressure receiving chamber 37, and the shutoff force corresponding to the fuel pressure is transmitted via the shutoff piston 36. Thus, the high pressure pipe 20 is shut off, and at this time, the low pressure fuel from the low pressure pipe 17 can be supplied to the fuel reservoir 6. Conversely, when the switching valve 41 is on, the low-pressure return path 42 is opened to discharge the low-pressure fuel in the switching pressure receiving chamber 37 to the low-pressure return path 42, thereby eliminating the shut-off force to the valve body 35 and communicating with the high-pressure pipe 20. At this time, high pressure fuel from the high pressure common rail 18 can be supplied to the fuel reservoir 6.
The low-pressure fuel supply section PL is composed of a low-pressure pipe 17 branching and extending from the main injection passage 15, an inflow restricting section 43 provided in the middle of the low-pressure pipe 17, and a low-pressure common rail 19 on the inflow end side. You.
[0026]
The inflow restricting portion 43 has a throttle 44 and a check valve 45 arranged in parallel on the branch path 17. The check valve 45 prevents the high-pressure fuel in the main injection passage 15 from flowing into the low-pressure common rail 19, and the throttle 44 restricts the flow of fuel flowing from the main injection passage 15 into the low-pressure common rail 19, so that a control described later can be performed. In cooperation with the pressure valve 46, the fuel pressure of the low-pressure common rail 19 can be reduced and maintained. Further, a low-pressure drain path 47 reaching the fuel tank 24 via a pressure regulating valve 46 is connected to the low-pressure common rail 19. The pressure regulating valve 46 regulates and holds the fuel pressure of the low-pressure common rail 21 at a predetermined low pressure value in cooperation with the inflow restricting portion 43, and when the switching valve 41 is shut off, the low-pressure fuel passes through the check valve 45. The fuel is supplied to the reservoir 6 to enable low-injection-rate injection.
[0027]
Low-pressure fuel from a low-pressure inflow passage 21 communicating with the low-pressure common rail 19 side is introduced into the pressure-receiving piston 14 of the pressure-receiving chamber 13 of the injector 5 as control oil pressure. When the injector solenoid valve 22 is turned off, the hydraulic discharge path 23 is shut off, the pressure receiving piston 14 applies a valve closing force corresponding to low pressure fuel to the needle valve 12, and the fuel injection is kept stopped. Conversely, when the injector solenoid valve 22 is turned on, the low pressure return path 23 is opened, the fuel in the pressure receiving chamber 13 is removed to the hydraulic discharge path 23, and the valve closing force applied to the pressure receiving piston 14 falls below the valve opening force. 12 is opened to perform fuel injection.
[0028]
The controller 7 has a number of ports in its input / output circuit and is connected to various sensors for detecting engine operation information. In particular, an accelerator pedal opening sensor for detecting the accelerator pedal opening θa of the engine 2 48, a crank angle sensor 49 for detecting crank angle information Δθ, a water temperature sensor 55 for detecting a water temperature wt, a temperature sensor 56 for detecting an exhaust gas temperature Tg, and an atmospheric pressure sensor 57 for detecting an atmospheric pressure pa. Is done. Here, the crank angle information Δθ is used by the controller 7 to derive the engine speed Ne.
[0029]
Next, the operation of the fuel injection device of FIG. 1 will be described along the control processing of the controller 7.
When the engine 2 of the vehicle (not shown) is driven, the controller 7 takes in self-check results of a plurality of control systems, for example, related devices and sensors that are appropriately driven by the fuel injection system and the fuel supply system, and checks whether the results are normal. Whether it is normal or not (OK), an engine control processing routine (not shown) is executed, and a fuel injection control routine shown in FIG. 6 is executed during the routine.
[0030]
When the process reaches step s1 of the fuel injection control routine, the latest data, for example, the crank angle Δθ, the engine speed Ne, the exhaust gas temperature Tg, the water temperature wt, the atmospheric pressure pa, and the like are captured and stored.
[0031]
In step s2, one of the boot type injection mode M1 and the rectangular injection mode M2 is selected based on the accelerator pedal opening θa and the engine speed Ne. In step s3, it is determined whether the selected injection mode is any of the injection modes. In the case of the rectangular injection mode M2, the process proceeds to step s8, and in the case of the boot type injection mode M1, the process proceeds to step s4.
In step s4, the target fuel injection amount INJb according to the engine speed Ne and the accelerator pedal opening θa, the respective correction values dt of the water temperature wt and the atmospheric pressure pa (which are relatively large correction values in a low temperature range), and the target dp. The fuel injection amount qtarget (= INJb + dt + dp) is derived.
[0032]
In step s5, the fuel pressures Phcr and Plcr of the high and low common rails are derived from the engine speed Ne and the target fuel injection amount qtarget using the common rail pressure maps m1 and m2 in FIGS. 3A and 3B, and outputs corresponding to these values (duty ratio) ) Is set to a common rail pressure driver (not shown) of the return solenoid valve 34 on the high pressure common rail 18 side and the pressure regulating valve 46 of the low pressure common rail 19.
In step s6, the injection start timing t1s (see FIG. 5) of the injector solenoid valve 22 and the switching timing t2s (see the valve opening timing of FIG. 5) of the switching valve 41 are changed according to the engine speed Ne in the injection timing of FIG. Derived by map m3.
[0033]
Further, the low pressure injection period α (= t1s−t2s) is obtained from the derived t1s and t2s, and the low pressure fuel injection amount to be injected during the low pressure injection period is calculated from the low pressure common rail fuel pressure Plcr and the low pressure injection period Δtinj. Then, a high-pressure fuel injection amount is obtained by subtracting the low-pressure fuel injection amount from the target fuel injection amount qtarget, and based on the target high-pressure fuel injection amount and the pressure Phcr of the high-pressure common rail 18, the closing timing t1e of the injector solenoid valve 22 and the switching valve 41 is determined. T2e is derived.
Further, in step s6, the pressure-intensifying electromagnetic valve opening timing ta (= t1s + g) for turning off the pressure-intensifying electromagnetic valve 40 when the shift period g has elapsed after the driving of the injector electromagnetic valve 22, and the valve closing timing t1e of the injector electromagnetic valve 22. And the closing start timing for turning on the pressure-intensifying solenoid valve 40 when a predetermined elapsed period γ has elapsed after the closing of the injector solenoid valve 22. tc (= t1e + γ) is sequentially calculated.
[0034]
In step s7, an output including information corresponding to the injection start timing t1s of the injector solenoid valve 22, the switching timing t2s of the switching valve 41, the current low-pressure injection period α, and the closing timings t1e and t2e of the injector solenoid valve 22 and the switching valve 41. Is set in a fuel injection driver (not shown).
Further, it includes information corresponding to the pressure-intensifying electromagnetic valve opening timing ta (= t1s + g), the urging start timing tb (= t1e-k), and the valve-closing urging start timing tc (= t1e + γ) of the pressure-intensifying electromagnetic valve 40. The output is set to a pressure increasing driver (not shown), and the control of this time is terminated, and the process returns.
[0035]
In response to this, the fuel injection driver drives each driver of the injector solenoid valve 22, the switching valve 41, and the pressure increasing solenoid valve 40 based on the crank angle Δθ signal, and issues a switching output in accordance with the count up, and outputs the boot type. In the injection mode M1 (see FIG. 5), the injector 5 performs injection driving.
In the normal control processing in step s8, control in the rectangular injection mode M2 is started.
Here, the basic fuel injection amount INJb and the target fuel injection amount qtarget (= INJb + dt + dp) are sequentially calculated.
[0036]
Further, the fuel pressure Phcr of the high common rail is derived from the engine speed Ne and the target fuel injection amount qtarget in a normal common rail pressure map (not shown), and an output (duty ratio) corresponding to this value is returned to the high pressure common rail 18 by the return solenoid valve 34 ( The pressure regulating valve 46 of the low-pressure common rail 19 is output to stop) to secure the fuel pressure Phcr of the high-common rail.
Further, an injection start timing t1s (see FIG. 5) of the injector solenoid valve 22 is derived from a normal injection timing map (not shown) according to the engine speed Ne. Further, the switching timing t2s ′ of the switching valve 41 is set as a valve opening timing that is earlier than the injection start timing t1s by a period j as shown in FIG. Further, the high pressure injection period β and the valve closing timings t1e and t2e are derived in the same manner as in the case of the boot type injection.
[0037]
Next, an output including information corresponding to the derived valve opening timing t1s, switching timing t2s', and valve closing timings t1e and t2e is set in a fuel injection driver (not shown), and further, as in the case of boot type injection. The pressure-intensifying electromagnetic valve opening timing ta, the urging start timing tb, and the valve-closing urging start timing tc of the pressure-intensifying electromagnetic valve 40 are derived, and an output including information corresponding to each timing is output to a pressure-intensifying driver (not shown). ), The control of this time is ended, and the routine returns.
In response to this, the fuel injection driver drives the injector solenoid valve 22, the switching valve 41, and the pressure-intensifying solenoid valve 40 based on the crank angle Δθ signal, and the injector 5 operates in the rectangular injection mode M2 shown by a two-dot chain line in FIG. Inject drive.
[0038]
In particular, when the injectors 5 are driven to open in the boot-type injection mode M1 and the rectangular injection mode M2, prior to the injection start timing t1s when the pressure-intensifying solenoid valve 40 is switched to open, that is, the valve is closed in the previous stroke. It is turned on after the energization start timing tc (= t1e + γ), and the pressure increasing mechanism 30 of the control oil pressure switching means 58 is pressurized, so that the control fuel pressure PA of the pressure receiving chamber (injection controller) 13 becomes sufficiently high. That is, the pressurizing operation is performed to a pressure equal to or higher than the fuel pressure Phcr of the high-pressure common rail 18.
[0039]
As described above, by setting the control oil pressure to high-pressure fuel (Phr ≒ PA in FIG. 5) by the high-pressure common rail 18, the pressure difference δ becomes sufficiently large as compared with the control fuel pressure (Plcr) of the low-pressure common rail 19 shown by the broken line. In addition, the discharge speed of the control fuel from the pressure receiving chamber (injection control unit) 13 becomes faster than before, and the balance with the pressure of the injected fuel (valve opening pressure) applied to the lower part of the needle valve has good responsiveness and collapses quickly. Thus, the rising speed (opening speed) of the needle valve 12 is improved. That is, the change in the injection rate (弁 needle valve lift) in the case of the low fuel pressure Plcr as shown by the broken line in FIG. 5 is different from that in the case of the high pressure fuel (Phcr ≒ PA in FIG. 5) as shown by the solid line. Twelve ascending speeds (opening speeds) are sufficiently increased. That is, the gap e1 between the valve seat 501 and the needle valve 12 as shown in FIG. 3 increases relatively quickly. 5 indicates a state in which the fuel pressure in the pressure receiving chamber 13 cannot be reduced during this period since the OFF period of the pressure-intensifying solenoid valve 40 has shifted and the period g has elapsed.
[0040]
As described above, because the fuel pressure when the pressure receiving chamber 13 is opened as in the related art is low, the gap e1 does not expand during the full lift of the needle valve, the sheet is throttled, and the atomization state deteriorates. The occurrence of an inappropriate situation can be reliably prevented, the rising period of the needle valve is shortened, and the time required to reach a full lift is also shortened, so that appropriate fuel injection can be performed.
Further, at the valve closing timing t1e of the injector 5 in the boot type injection mode M1 and the rectangular injection mode M2, the energizing start timing tb (= t1e-k) preceding the valve closing timing t1e by the preceding processing period k. ), The pressure-intensifying solenoid valve 40 is turned on. Thus, the control fuel pressure of the pressure receiving chamber 15 increases according to the width of the preceding processing period k, and becomes the intermediate pressure Pmcr.
[0041]
Here, the intermediate pressure Pmcr is set to be larger than the fuel pressure Plcr of the low-pressure common rail and smaller than the pressure Phcr of the high-pressure common rail 18, and is set to the intermediate pressure Pmcr {(Plcr + Phcr) / 2}.
That is, the hydraulic pressure PA corresponding to the control fuel here is set such that the pressure value (pressure Phcr) prior to the opening switching (t1s) of the needle valve 12 is higher than the pressure value (intermediate pressure Pmcr) prior to the closing switching (t1e). Is done. That is, since the intermediate pressure Pmcr is set smaller than the pressure Phcr of the high-pressure common rail 18, the seating speed of the needle valve 12 that has received the intermediate pressure Pmcr can be appropriately suppressed, and the asymmetric injection can be suppressed while maintaining the responsiveness. .
[0042]
In FIG. 5, the fluctuation of the control fuel pressure PA of the pressure receiving chamber 103 in the conventional device of FIG. 7 is shown by a broken line (the same as the control fuel pressure Pa of FIG. 7). Here, a state is shown in which the control fuel pressure of the pressure receiving chamber 103 is rapidly increased, the seating timing tr is faster than the seating timing tr 'in the present embodiment, and as a result, the asymmetric injection Mb is generated. Such a state can be reliably prevented by the fuel injection device of FIG. 1, and the durability of the entire fuel injection device 1 including the needle valve 12 and the valve seat 501 is improved.
[0043]
Further, the control oil pressure switching means 58 of the fuel injection device 1 shown in FIG. 1 can supply the intermediate pressure pmcr to the pressure receiving chamber 13 by operating the pressure-increasing fuel just before the needle valve 12 switches from the open state to the closed state. Can be suppressed moderately and asymmetric injection can be suppressed while maintaining responsiveness.
Further, in the fuel injection device 1 of FIG. 1, prior to the opening switching of the needle valve 12 (injection start timing t1s, switching timing t2s) and the closing switching (valve closing timing t1e, t2e), the pressure increasing mechanism of the control hydraulic pressure switching means 58. Each of the units 30 operates to increase the pressure of the fuel, thereby preventing deterioration of the atomization state at the time of injection, preventing the asymmetric injection by relatively reducing the seating speed of the needle valve, and improving the durability of the device. Can be achieved with a relatively simple configuration.
[0044]
【The invention's effect】
As described above, according to the present invention, the control oil pressure from the control oil pressure switching means of the injector control valve is adjusted by increasing or decreasing the control oil pressure from the control oil pressure switching means prior to at least opening or closing the needle valve. Can be received at For example, by setting the control oil pressure at the time of closing switching to a pressure higher than the low-pressure fuel and lower than the high-pressure fuel, the seating speed at the time of closing switching of the needle valve can be relatively slow to prevent asymmetric injection, and the durability of the device can be improved. Can be improved.
[0045]
According to the second aspect of the present invention, the control oil pressure from the control oil pressure switching means of the injector control valve is such that the pressure value prior to the needle valve opening switching is greater than the pressure value prior to the closing switching, and the opening speed in the needle valve opening switching is improved. In addition, it is possible to reliably prevent the atomization state from deteriorating, and furthermore, the pressure value prior to the switching of the closing becomes the intermediate pressure, the seating speed can be appropriately suppressed, and the asymmetric injection can be suppressed while maintaining the responsiveness.
[0046]
The pressure increasing mechanism of the control oil pressure switching means according to the third aspect of the present invention can supply the intermediate pressure to the pressure receiving chamber by operating the pressure increasing fuel just before the needle valve switches from the open state to the close state, thereby appropriately setting the seating speed. Asymmetric injection can be suppressed while maintaining responsiveness.
[0047]
According to a fourth aspect of the present invention, prior to the switching of the needle valve between the open state and the closed state, the pressure-intensifying mechanism operates to increase the pressure-increased fuel. The device can be achieved with a relatively simple configuration that can prevent asymmetric injection at a relatively slow speed and improve the durability of the device.
[0048]
According to the invention of claim 5, the injector can be driven to be driven in the boot type injection mode by setting the low pressure injection period in which the initial injection rate is suppressed after the injector control valve is switched to open.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fuel injection device as one embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of control oil pressure switching means used by the fuel injection device of FIG.
FIG. 3 is a partially cutaway sectional view of an injector used in the fuel injection device of FIG. 1;
4 is a characteristic line diagram of a map used by the fuel injection device of FIG. 1; FIG. 4A shows a low common rail pressure Plcr, FIG. Used for calculating the injection timing.
FIG. 5 is an explanatory diagram of valve drive characteristics and injection rate characteristics of the fuel-fuel injection device of FIG. 1;
FIG. 6 is a flowchart of a fuel injection control routine of the fuel injection device of FIG. 1;
FIG. 7 is a schematic configuration diagram of a conventional fuel injection device.
FIG. 8 is an explanatory diagram of valve drive characteristics and injection rate characteristics of the fuel injection device.
[Explanation of symbols]
1 fuel injection device
2 Engine
4 Combustion chamber
5 Injector
6 Fuel reservoir
8 spout
9 Fuel supply means
11 Injector body
12 Needle valve
13 Pressure receiving chamber
17 Low pressure pipeline
21 Low pressure inlet
22 Injector control valve
23 Hydraulic discharge path
30 Booster mechanism
58 Control oil pressure switching means
PA control fuel pressure
PH high pressure fuel supply
PL low pressure fuel supply

Claims

A needle valve that can open and close the injection port of the injector body, a pressure receiving chamber that applies the injection valve closing force equivalent to the control fuel pressure to the needle valve, and a fuel reservoir that applies the injection valve opening force equivalent to the injection fuel pressure to the needle valve. An injector having:
Fuel supply means for selectively supplying each pressurized fuel of the high-pressure fuel supply unit and the low-pressure fuel supply unit to the fuel reservoir;
The low-pressure fuel of the low-pressure fuel supply unit and a pressure-intensifying mechanism connected in parallel to the flow path of the low-pressure fuel selectively receive the low-pressure fuel and pressurize the pressure-increased fuel as a control fuel pressure, and selectively supply the control pressure to the pressure-receiving chamber. Control hydraulic pressure switching means for supplying;
By closing the pressure receiving chamber with a hydraulic discharge passage extending from the pressure receiving chamber, the orifice closing force applied to the needle valve is switched to close the needle valve so that the orifice opening force exceeds the orifice opening force, and the pressure receiving chamber is closed. A fuel injection device comprising: an injector control valve that switches the needle valve so that the nozzle closing force applied to the needle valve by communicating with the hydraulic discharge path is less than the nozzle opening force. .

The fuel injection device according to claim 1,
The fuel injection device according to claim 1, wherein the hydraulic pressure equivalent to the control fuel applied to the pressure receiving chamber is set to a higher pressure value prior to the switching of the needle valve than the pressure value prior to the switching of the needle valve.

The fuel injection device according to claim 1,
A fuel injection device characterized in that the pressure-increasing mechanism of the control oil pressure switching means performs a pressure-increasing fuel supply operation before the needle valve is switched to the closed state during the open switching.

The fuel injection device according to claim 1,
A fuel injection device characterized in that the pressure-increasing mechanism of the control oil pressure switching means performs a pressure-increasing fuel supply operation prior to the opening and closing of the needle valve.

The fuel injection device according to claim 1,
A fuel injection device, wherein the fuel supply means switches to supply the pressurized fuel of the high-pressure fuel supply unit to the fuel reservoir after the injector control valve is opened.