JP3796146B2 - DME engine fuel supply system - Google Patents

DME engine fuel supply system Download PDF

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JP3796146B2
JP3796146B2 JP2001244033A JP2001244033A JP3796146B2 JP 3796146 B2 JP3796146 B2 JP 3796146B2 JP 2001244033 A JP2001244033 A JP 2001244033A JP 2001244033 A JP2001244033 A JP 2001244033A JP 3796146 B2 JP3796146 B2 JP 3796146B2
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fuel
engine
temperature
cooler
stopped
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JP2003056410A (en
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晃 齋藤
清治 引野
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Hino Motors Ltd
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Hino Motors Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
    • F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
    • F02M21/0218—Details on the gaseous fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02M21/023—Valves; Pressure or flow regulators in the fuel supply or return system
    • F02M21/0239—Pressure or flow regulators therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/02—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with gaseous fuels
    • F02D19/021—Control of components of the fuel supply system
    • F02D19/022—Control of components of the fuel supply system to adjust the fuel pressure, temperature or composition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/02—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with gaseous fuels
    • F02D19/026—Measuring or estimating parameters related to the fuel supply system
    • F02D19/027—Determining the fuel pressure, temperature or volume flow, the fuel tank fill level or a valve position
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
    • F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
    • F02M21/0203—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels characterised by the type of gaseous fuel
    • F02M21/0209—Hydrocarbon fuels, e.g. methane or acetylene
    • F02M21/0212—Hydrocarbon fuels, e.g. methane or acetylene comprising at least 3 C-Atoms, e.g. liquefied petroleum gas [LPG], propane or butane
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
    • F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
    • F02M21/0218—Details on the gaseous fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02M21/0245—High pressure fuel supply systems; Rails; Pumps; Arrangement of valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
    • F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
    • F02M21/0218—Details on the gaseous fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02M21/0287—Details on the gaseous fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers characterised by the transition from liquid to gaseous phase ; Injection in liquid phase; Cooling and low temperature storage
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M21/00—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form
    • F02M21/02—Apparatus for supplying engines with non-liquid fuels, e.g. gaseous fuels stored in liquid form for gaseous fuels
    • F02M21/0218—Details on the gaseous fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02M21/0248—Injectors
    • F02M21/0275—Injectors for in-cylinder direct injection, e.g. injector combined with spark plug
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/30—Use of alternative fuels, e.g. biofuels

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Fuel-Injection Apparatus (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、ジメチルエーテルを燃料として利用するＤＭＥエンジンの燃料供給装置に関するものである。
【０００２】
【従来の技術】
近年、高セタン価（５５以上）で無煙燃焼するジメチルエーテル（以下ではＤＭＥと略称する）が石油や軽油の代替燃料として注目されており、特にＥＧＲ（排気ガス再循環）や触媒により低ＮＯxを実現し得て将来の厳しい排気規制を満足できるという観点から、ディーゼルエンジンの代替燃料として検討が進められている。
【０００３】
ただし、ＤＭＥは、その沸点が−２５℃と非常に低くて蒸発し易いという特性があるため、ＤＭＥを燃料として利用するＤＭＥエンジンの実用化にあたっては、このようなＤＭＥの特性を十分に考慮した燃料供給装置が必要になるものと考えられており、例えば、図３に示す如きＤＭＥエンジンの燃料供給装置が既に提案されている。
【０００４】
ここに図示している例では、燃料タンク１内に約０.４〜１ＭＰａの圧力で貯えられている燃料（ＤＭＥ）を、前記燃料タンク１内に装備されているフィードポンプ２により燃料供給ライン３を介して高圧ポンプ４に送り出し、該高圧ポンプ４により約２０〜７０ＭＰａに昇圧して圧送ライン５を介しコモンレール６に蓄圧させ、該コモンレール６から噴射ライン７を介し各気筒のインジェクタ８に燃料を導いて開弁制御により燃焼室９内に噴射させ、通常のディーゼルエンジンの場合と同様に圧縮着火により燃焼させるようにしてある。
【０００５】
ここで、前記高圧ポンプ４には、図示しないカムやタペットを介しプランジャ１０をエンジン駆動により昇降させて燃料を圧縮するようにした従来の列型ポンプと類似のピストン式圧送系が採用されており、ポンプ気筒毎に吐出量制御のための電磁弁１１が備えられている。
【０００６】
そして、前記プランジャ１０の下降行程で前記電磁弁１１が開けられてポンプ室１３に燃料が導入されるようになっているが、次のプランジャ１０の上昇行程でも前記電磁弁１１に通電されずに開弁した状態では、燃料ギャラリ１２からポンプ室１３に取り込まれた燃料が前記電磁弁１１を介し昇圧されずに再び燃料ギャラリ１２に排出されることになり、他方、必要吐出量に見合ったタイミングで前記電磁弁１１が通電されて閉弁した状態では、退路を断たれた燃料がポンプ室１３内でプランジャ１０により圧縮されてデリバリバルブ１４（逆止弁）を介しコモンレール６へと圧送されるようになっている。
【０００７】
即ち、前記電磁弁１１の閉弁以降のプランジャ１０のリフト分が吐出量となり、前記電磁弁１１の閉弁のタイミングで吐出量が変わり、コモンレール６の圧力の生成と制御が成されるようになっているのである。
【０００８】
また、高圧ポンプ４内の燃料ギャラリ１２で圧力が所定値を超えた時にオーバーフローバルブ１５（リリーフ弁）により余剰燃料が燃料リターンライン１６に解放されるようになっているが、該燃料リターンライン１６に解放された燃料は、エンジンからの受熱により温度上昇して気泡が発生し易くなっているため、その途中に装備された燃料クーラ１７を介し十分に冷却した後に逆止弁１８を介し前記燃料供給ライン３の途中に再循環させるようにしてある。尚、図中における燃料クーラ１７は、バッテリ駆動の電動ファン１９による空冷方式となっている。
【０００９】
【発明が解決しようとする課題】
しかしながら、斯かる燃料供給装置では、エンジン停止時に高圧ポンプ４が止まって燃料の流れが停滞してしまうと、エンジンや排気系から熱が伝わってきて流路内の燃料が昇温し、ＤＭＥの臨界温度である１２７℃を超えた段階で圧力に関係なく燃焼が気化してしまうため、高圧ポンプ４内の燃料ギャラリ１２に気化ガスが溜まり且つ高圧化してＯリングやオイルシール等のシール手段２０から燃料の気化ガスが外部に漏出（液密性があってもガスの漏出をシールすることは困難）してしまったり、或いは、次にエンジンを始動した時に高圧ポンプ４内が液相状態の燃料で満たされていないことによる焼付きが惹起されてしまう虞れがあった。
【００１０】
また、現状においては、エンジン停止時に燃料供給ライン３及び燃料リターンライン１６と高圧ポンプ４内とから燃料を抜き出す手法が対策として検討されているが、このような手法を採用してしまうと、エンジン停止後に再始動しようとした際に、燃料が燃料供給ライン３及び燃料リターンライン１６と高圧ポンプ４内に充填されるまでに時間を要してしまうため、迅速なエンジンの再始動が行えなくなるという問題があった。
【００１１】
本発明は上述の実情に鑑みてなしたもので、エンジン停止時における高圧ポンプ内からの燃料気化ガスの漏出や該高圧ポンプの焼付きを未然に回避し且つ迅速なＤＭＥエンジンの再始動を実現することを目的としている。
【００１２】
【課題を解決するための手段】
本発明は、燃料タンクの燃料を高圧ポンプにより昇圧してコモンレールに蓄圧させ、該コモンレールからインジェクタに燃料を導いて燃焼室内に噴射させるようにしたＤＭＥエンジンの燃料供給装置において、前記燃料タンクからフィードポンプにより送り出された燃料を前記高圧ポンプへ導く燃料供給ラインと、前記高圧ポンプ内の燃料ギャラリで圧力が所定値を超えた時に解放された余剰燃料を燃料クーラを介し冷却して前記燃料供給ラインの途中に再循環する燃料リターンラインと、該燃料リターンラインの燃料クーラより下流側から適宜に燃料を抜き出して前記燃料タンクに戻すバイパスラインと、該バイパスラインの前記燃料リターンラインに対する接続箇所に装備されて前記燃料クーラを経た燃料を切替指令の入力時にのみ前記バイパスライン側へ選択的に振り分ける流路切替弁と、前記高圧ポンプ内の燃料ギャラリの燃料温度を検出する温度センサと、エンジン停止時に前記流路切替弁に向け切替指令を出力し且つ前記温度センサの検出信号を入力してエンジン停止時に検出温度が所定の設定温度を超えている条件下でのみ前記フィードポンプ及び燃料クーラに向け起動指令を出力する制御装置とを備え、しかも、この制御装置が、エンジン停止時に起動したフィードポンプ及び燃料クーラが温度センサによる検出温度の設定温度下への低下により停止する毎に、次回の起動指令を出力するための設定温度を直前の起動時より高い設定温度に変更するように構成されていることを特徴とするものである。
【００１３】
而して、このようにすれば、エンジン停止時に制御装置から流路切替弁に向け切替指令が出力されて該流路切替弁が切り替わり、燃料クーラを経た燃料がバイパスライン側へ選択的に振り分けられることになる一方、同時にフィードポンプ及び燃料クーラにも適宜に起動指令が出力されて、これらフィードポンプ及び燃料クーラが起動されるので、エンジン停止時においても、フィードポンプにより燃料タンクから燃料が汲み上げられて燃料供給ラインに送り出され、高圧ポンプ内の燃料ギャラリを経由して燃料リターンラインに流れ込む燃料の流れが形成されることになり、該燃料リターンラインに流れ込んだ燃料が燃料クーラを介し冷却された後に流路切替弁を介し燃料タンクに戻されることになる。
【００１４】
ここで、エンジン停止時におけるフィードポンプ及び燃料クーラの起動に関しては、高圧ポンプ内の燃料ギャラリの燃料温度が臨界温度に近い危険温度域まで昇温した段階でフィードポンプ及び燃料クーラを起動させるように制御装置で制御が成されるので、これらフィードポンプ及び燃料クーラの駆動時間を必要最小限に限定して消費電力を大幅に抑制することが可能となる。
【００１５】
しかも、エンジン停止後にエンジンや排気系が冷却して温度的に落ち着いてくるまでは、温度センサによる検出温度が設定温度下へ低下してフィードポンプ及び燃料クーラが停止しても、高圧ポンプの燃料ギャラリ内の燃料温度が再び上昇してくることになるが、次回の起動指令を出力するための設定温度を直前の起動時より高い設定温度に変更するようにしているので、フィードポンプ及び燃料クーラが頻繁に起動停止を繰り返すような事態が回避されることになる。
【００１６】
【発明の実施の形態】
以下本発明の実施の形態を図面を参照しつつ説明する。
【００１７】
図１及び図２は本発明を実施する形態の一例を示すもので、図３と同一の符号を付した部分は同一物を表わしている。
【００１８】
前述した図３と略同様に構成したＤＭＥエンジンの燃料供給装置に関し、本形態例においては、図１に示す如く、燃料リターンライン１６の燃料クーラ１７より下流側から適宜に燃料を抜き出して燃料タンク１に戻すバイパスライン２１が新たに設けられており、該バイパスライン２１の前記燃料リターンライン１６に対する接続箇所には、前記燃料クーラ１７を経た燃料を切替指令２２ａの入力時にのみ前記バイパスライン２１側へ選択的に振り分ける流路切替弁２２が装備されている。
【００１９】
また、高圧ポンプ４に対し燃料ギャラリ１２内の燃料温度を検出する温度センサ２３が新たに装備されており、該温度センサ２３の検出信号２３ａが、所定場所に設けた制御装置２４に入力されるようになっている。
【００２０】
そして、この制御装置２４においては、エンジン停止時に前記流路切替弁２２に向け切替指令２２ａを出力すると共に、前記温度センサ２３からの検出信号２３ａに基づき検出温度が所定の設定温度Ｔ1を超えている条件下でのみフィードポンプ２及び燃料クーラ１７の電動ファン１９に向け適宜に起動指令２ａ，１９ａを出力するようにしてある。
【００２１】
図２は前記制御装置２４での具体的な制御手順を示したものであり、ステップＳ１でエンジン停止が確認されたら、ステップＳ２にて流路切替弁２２が切替指令２２ａにより切り替えられ、次いで、ステップＳ３にて温度センサ２３からの検出信号２３ａに基づき燃料ギャラリ１２内の燃料温度が設定温度Ｔ1を超えているか否かが判定され、設定温度Ｔ1を超えている場合はステップＳ４へと進んでフィードポンプ２及び燃料クーラ１７の電動ファン１９が起動指令２ａ，１９ａにより起動され、これ以降はステップＳ３の判定が繰り返されて検出温度が設定温度Ｔ1下に低下するまでフィードポンプ２及び燃料クーラ１７の電動ファン１９の起動が継続されるようになっており、他方、ステップＳ３における判定で燃料ギャラリ１２内の燃料温度が設定温度Ｔ1を超えていない場合には、ステップＳ５へと進んでフィードポンプ２及び燃料クーラ１７の電動ファン１９が停止されるようになっている。
【００２２】
ここで、ステップＳ３での判定に用いる設定温度Ｔ1は、エンジン停止時に起動したフィードポンプ２及び燃料クーラ１７が温度センサ２３による検出温度の設定温度下への低下により停止する毎に、直前の起動時に用いた設定温度より高い設定温度に変更されるようにしてある。
【００２３】
而して、このように燃料供給装置を構成した場合、エンジン停止時に制御装置２４から流路切替弁２２に向け切替指令２２ａが出力されて該流路切替弁２２が切り替わり、燃料クーラ１７を経た燃料がバイパスライン２１側へ選択的に振り分けられることになる。
【００２４】
そして、エンジン停止時に温度センサ２３の検出信号が所定の設定温度Ｔ1を超えた時に、制御装置２４からフィードポンプ２及び燃料クーラ１７に対し起動指令２ａ，１９ａが出力され、これらフィードポンプ２及び燃料クーラ１７が起動されるので、エンジン停止時においても、フィードポンプ２により燃料タンク１から燃料が汲み上げられて燃料供給ライン３に送り出され、高圧ポンプ４内の燃料ギャラリ１２を経由して燃料リターンライン１６に流れ込む燃料の流れが形成されることになり、該燃料リターンライン１６に流れ込んだ燃料が燃料クーラ１７を介し冷却された後に流路切替弁２２を介し燃料タンク１に戻されることになる。
【００２５】
尚、エンジン停止後にエンジンや排気系が冷却して温度的に落ち着いてくるまでは、温度センサ２３による検出温度が一時的に設定温度Ｔ1下へ低下してフィードポンプ２及び燃料クーラ１７が停止しても、高圧ポンプ４の燃料ギャラリ１２内の燃料温度が再び上昇してくることになるが、次回の起動指令２ａ，１９ａを出力するための設定温度Ｔ1が直前の起動時より高い設定温度に変更されるようになっているので、フィードポンプ２及び燃料クーラ１７が頻繁に起動停止を繰り返すような事態が回避される。
【００２６】
従って、上記形態例によれば、エンジン停止時に高圧ポンプ４が止まっても燃料タンク１と高圧ポンプ４との間で燃料を循環させて該燃焼の流れが停滞してしまうことを回避できるので、高圧ポンプ４内の燃料ギャラリ１２における燃料の気化を著しく抑制することができて、エンジン停止時における高圧ポンプ４内からの燃料気化ガスの漏出や該高圧ポンプ４の焼付きを未然に回避することができ、しかも、エンジン停止後も燃料供給ライン３及び燃料リターンライン１６と高圧ポンプ４内とを燃料で満たした状態のまま維持することができるので、エンジン停止後の迅速なＤＭＥエンジンの再始動を実現することができる。
【００２７】
また、高圧ポンプ４内の燃料ギャラリ１２の燃料温度が臨界温度に近い危険温度域まで昇温した段階でフィードポンプ２及び燃料クーラ１７を起動させるように制御装置２４で制御を行うことで、これらフィードポンプ２及び燃料クーラ１７の駆動時間を必要最小限に限定することができるので、前記フィードポンプ２及び燃料クーラ１７に要する消費電力を大幅に抑制することができる。
【００２８】
更に、フィードポンプ２及び燃料クーラ１７に対し起動指令２ａ，１９ａを出力するための設定温度Ｔ1を、これらフィードポンプ２及び燃料クーラ１７が停止する毎に徐々に高くなるように変更しているので、フィードポンプ２及び燃料クーラ１７が頻繁に起動停止を繰り返すような事態を回避することができる。
【００２９】
尚、本発明のＤＭＥエンジンの燃料供給装置は、上述の形態例にのみ限定されるものではなく、燃料クーラは空冷式に限定されないこと、その他、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。
【００３０】
【発明の効果】
上記した本発明のＤＭＥエンジンの燃料供給装置によれば、下記の如き種々の優れた効果を奏し得る。
【００３１】
（Ｉ）エンジン停止時に高圧ポンプが止まっても燃料タンクと高圧ポンプとの間で燃料を循環させて該燃焼の流れが停滞してしまうことを回避できるので、高圧ポンプ内の燃料ギャラリにおける燃料の気化を著しく抑制することができて、エンジン停止時における高圧ポンプ内からの燃料気化ガスの漏出や該高圧ポンプの焼付きを未然に回避することができ、しかも、エンジン停止後も燃料供給ライン及び燃料リターンラインと高圧ポンプ内とを燃料で満たした状態のまま維持することができるので、エンジン停止後の迅速なＤＭＥエンジンの再始動を実現することができる。
【００３２】
（ＩＩ）高圧ポンプ内の燃料ギャラリの燃料温度が臨界温度に近い危険温度域まで昇温した段階でフィードポンプ及び燃料クーラを起動させるように制御装置で制御を行うことで、これらフィードポンプ及び燃料クーラの駆動時間を必要最小限に限定することができるので、前記フィードポンプ及び燃料クーラに要する消費電力を大幅に抑制することができる。
【００３３】
（ＩＩＩ）フィードポンプ及び燃料クーラに対し起動指令を出力するための設定温度を、これらフィードポンプ及び燃料クーラが停止する毎に徐々に高くなるように変更できるので、フィードポンプ及び燃料クーラが頻繁に起動停止を繰り返すような事態を回避することができる。
【図面の簡単な説明】
【図１】 本発明を実施する形態の一例を示す概略図である。
【図２】 図１の制御装置の制御手順を示すフローチャートである。
【図３】 従来例を示す概略図である。
【符号の説明】
１ 燃料タンク
２ フィードポンプ
２ａ 起動指令
３ 燃料供給ライン
４ 高圧ポンプ
６ コモンレール
８ インジェクタ
９ 燃焼室
１２ 燃料ギャラリ
１６ 燃料リターンライン
１７ 燃料クーラ
１９ 電動ファン
１９ａ 起動指令
２１ バイパスライン
２２ 流路切替弁
２２ａ 切替指令
２３ 温度センサ
２３ａ 検出信号
２４ 制御装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply device for a DME engine using dimethyl ether as a fuel.
[0002]
[Prior art]
In recent years, dimethyl ether (hereinafter abbreviated as DME), which smokelessly burns with a high cetane number (55 or more), has been attracting attention as an alternative fuel for petroleum and light oil, and in particular, achieved low NOx with EGR (exhaust gas recirculation) and catalysts. From the viewpoint of satisfying strict exhaust regulations in the future, studies are underway as alternative fuels for diesel engines.
[0003]
However, since DME has a characteristic that its boiling point is as low as −25 ° C. and is easy to evaporate, the characteristics of DME are fully taken into consideration in the practical use of a DME engine using DME as fuel. It is considered that a fuel supply device is required. For example, a fuel supply device for a DME engine as shown in FIG. 3 has already been proposed.
[0004]
In the example shown here, the fuel (DME) stored in the fuel tank 1 at a pressure of about 0.4 to 1 MPa is supplied to the fuel supply line by the feed pump 2 installed in the fuel tank 1. 3 to the high-pressure pump 4, and the pressure is increased to about 20 to 70 MPa by the high-pressure pump 4 to accumulate pressure on the common rail 6 via the pressure-feed line 5. And is injected into the combustion chamber 9 by valve opening control, and is combusted by compression ignition as in the case of a normal diesel engine.
[0005]
Here, the high-pressure pump 4 employs a piston-type pumping system similar to a conventional row type pump in which the plunger 10 is moved up and down by an engine drive via a cam or tappet (not shown) to compress the fuel. An electromagnetic valve 11 for controlling the discharge amount is provided for each pump cylinder.
[0006]
The solenoid valve 11 is opened during the descending stroke of the plunger 10 and fuel is introduced into the pump chamber 13. However, the solenoid valve 11 is not energized during the next ascent stroke of the plunger 10. In the opened state, the fuel taken into the pump chamber 13 from the fuel gallery 12 is discharged again to the fuel gallery 12 without being increased in pressure through the electromagnetic valve 11, and on the other hand, the timing corresponding to the required discharge amount In the state where the solenoid valve 11 is energized and closed, the retreated fuel is compressed by the plunger 10 in the pump chamber 13 and is pumped to the common rail 6 via the delivery valve 14 (check valve). It is like that.
[0007]
That is, the amount of lift of the plunger 10 after the solenoid valve 11 is closed becomes the discharge amount, and the discharge amount changes at the timing of closing the solenoid valve 11 so that the pressure of the common rail 6 is generated and controlled. It has become.
[0008]
Further, when the pressure exceeds a predetermined value in the fuel gallery 12 in the high-pressure pump 4, excess fuel is released to the fuel return line 16 by the overflow valve 15 (relief valve). Since the temperature of the fuel released in this way rises due to heat received from the engine and bubbles are easily generated, the fuel is sufficiently cooled via the fuel cooler 17 installed in the middle of the fuel and then the fuel is released via the check valve 18. Recirculation is performed in the middle of the supply line 3. In addition, the fuel cooler 17 in the drawing is an air cooling system using a battery-driven electric fan 19.
[0009]
[Problems to be solved by the invention]
However, in such a fuel supply device, when the high-pressure pump 4 is stopped when the engine is stopped and the fuel flow is stagnated, heat is transmitted from the engine or the exhaust system, the temperature of the fuel in the flow path rises, and the DME Since the combustion is vaporized regardless of the pressure when the critical temperature exceeds 127 ° C., the vaporized gas accumulates in the fuel gallery 12 in the high-pressure pump 4 and the pressure is increased, so that the sealing means 20 such as an O-ring or an oil seal is used. The fuel vaporized gas leaks to the outside (it is difficult to seal the gas leak even if it is liquid-tight), or the high pressure pump 4 is in the liquid phase when the engine is started next time. There is a possibility that seizure may be caused by being not filled with fuel.
[0010]
At present, a method for extracting fuel from the fuel supply line 3 and the fuel return line 16 and the high-pressure pump 4 when the engine is stopped has been studied as a countermeasure, but if such a method is adopted, the engine When restarting after stopping, it takes time until the fuel is filled into the fuel supply line 3, the fuel return line 16 and the high-pressure pump 4, which makes it impossible to restart the engine quickly. There was a problem.
[0011]
The present invention has been made in view of the above circumstances, and avoids leakage of fuel vaporized gas from the high-pressure pump and seizure of the high-pressure pump when the engine is stopped, and realizes quick DME engine restart. The purpose is to do.
[0012]
[Means for Solving the Problems]
The present invention relates to a fuel supply device for a DME engine in which fuel in a fuel tank is boosted by a high-pressure pump and accumulated in a common rail, and the fuel is guided from the common rail to an injector and injected into a combustion chamber. A fuel supply line that guides the fuel delivered by the pump to the high-pressure pump; and the fuel supply line that cools excess fuel released when the pressure exceeds a predetermined value in the fuel gallery in the high-pressure pump via the fuel cooler. A fuel return line that is recirculated in the middle of the fuel return line, a bypass line that appropriately draws fuel from the downstream side of the fuel cooler of the fuel return line and returns it to the fuel tank, and a connection point of the bypass line to the fuel return line The fuel that has passed through the fuel cooler is changed only when the switching command is input. A flow path switching valve that selectively distributes to the ipass line side, a temperature sensor that detects a fuel temperature of a fuel gallery in the high-pressure pump, a switching command that is output to the flow path switching valve when the engine is stopped, and the temperature sensor A control device that inputs a detection signal and outputs a start command to the feed pump and the fuel cooler only under a condition that the detected temperature exceeds a predetermined set temperature when the engine is stopped, and the control device comprises: Each time the feed pump and fuel cooler started when the engine is stopped stop due to a decrease in the temperature detected by the temperature sensor, the set temperature for outputting the next start command is set to a higher set temperature than the previous start. It is characterized by being comprised so that it may change.
[0013]
In this way, when the engine is stopped, a switching command is output from the control device to the flow path switching valve, the flow path switching valve is switched, and the fuel that has passed through the fuel cooler is selectively distributed to the bypass line side. At the same time, start commands are also output to the feed pump and fuel cooler at the same time, and the feed pump and fuel cooler are started. Therefore, even when the engine is stopped, fuel is pumped from the fuel tank by the feed pump. The fuel flows into the fuel supply line and flows into the fuel return line via the fuel gallery in the high-pressure pump. The fuel flowing into the fuel return line is cooled through the fuel cooler. After that, it is returned to the fuel tank via the flow path switching valve.
[0014]
Here, regarding the start of the feed pump and the fuel cooler when the engine is stopped, the feed pump and the fuel cooler are started when the fuel temperature of the fuel gallery in the high-pressure pump is raised to a dangerous temperature range close to the critical temperature. Since the control is performed by the control device, it is possible to significantly reduce the power consumption by limiting the drive time of the feed pump and the fuel cooler to the necessary minimum.
[0015]
In addition, even if the temperature detected by the temperature sensor falls below the set temperature and the feed pump and fuel cooler are stopped until the engine or exhaust system cools down after the engine stops, the fuel gallery of the high-pressure pump stops. The fuel temperature in the engine rises again, but the set temperature for outputting the next start command is changed to a set temperature higher than that at the previous start. A situation in which start and stop are frequently repeated is avoided.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
1 and 2 show an example of an embodiment for carrying out the present invention, and portions denoted by the same reference numerals as those in FIG. 3 represent the same items.
[0018]
With respect to the fuel supply device for the DME engine configured in substantially the same manner as in FIG. 3 described above, in this embodiment, as shown in FIG. 1, fuel is appropriately extracted from the downstream side of the fuel cooler 17 of the fuel return line 16 and a fuel tank. The bypass line 21 for returning to 1 is newly provided, and the bypass line 21 is connected to the fuel return line 16 at a position where the fuel that has passed through the fuel cooler 17 is input to the bypass line 21 only when the switching command 22a is input. A flow path switching valve 22 that selectively distributes to each other is provided.
[0019]
Further, the high-pressure pump 4 is newly equipped with a temperature sensor 23 for detecting the fuel temperature in the fuel gallery 12, and a detection signal 23a of the temperature sensor 23 is input to a control device 24 provided at a predetermined location. It is like that.
[0020]
The control device 24 outputs a switching command 22a toward the flow path switching valve 22 when the engine is stopped, and the detected temperature exceeds a predetermined set temperature T 1 based on the detection signal 23a from the temperature sensor 23. The start commands 2a and 19a are appropriately output to the feed pump 2 and the electric fan 19 of the fuel cooler 17 only under the conditions.
[0021]
FIG. 2 shows a specific control procedure in the control device 24. When the engine stop is confirmed in step S1, the flow path switching valve 22 is switched by the switching command 22a in step S2, and then whether the fuel temperature in the fuel gallery 12 based on the detection signal 23a from the temperature sensor 23 at step S3 exceeds the set temperature T 1 is determined, if it exceeds the set temperatures T 1 to step S4 willing electric fan 19 of the feed pump 2 and the fuel cooler 17 is activated command 2a, it is started by 19a, which thereafter feed pump 2 and until drops the lower set temperature T 1 of the detected temperature is repeated determination of the step S3 The start of the electric fan 19 of the fuel cooler 17 is continued, and on the other hand, the fuel in the fuel gallery 12 is determined in step S3. If the temperature does not exceed the set temperatures T 1 is an electric fan 19 of the feed pump 2 and the fuel cooler 17 is adapted to be stopped proceeds to step S5.
[0022]
Here, the set temperature T 1 used for the determination in step S3 is the value immediately before the feed pump 2 and the fuel cooler 17 that are started when the engine is stopped each time the temperature detected by the temperature sensor 23 is lowered to the set temperature. The temperature is changed to a set temperature higher than the set temperature used at the start-up.
[0023]
Thus, when the fuel supply device is configured in this way, the switching command 22a is output from the control device 24 to the flow path switching valve 22 when the engine is stopped, and the flow path switching valve 22 is switched to pass through the fuel cooler 17. The fuel is selectively distributed to the bypass line 21 side.
[0024]
When the detection signal of the temperature sensor 23 exceeds a predetermined set temperature T 1 when the engine is stopped, the control device 24 outputs start commands 2a and 19a to the feed pump 2 and the fuel cooler 17, and the feed pump 2 and Since the fuel cooler 17 is activated, the fuel is pumped up from the fuel tank 1 by the feed pump 2 and sent out to the fuel supply line 3 even when the engine is stopped, and the fuel return is made via the fuel gallery 12 in the high-pressure pump 4. A fuel flow flowing into the line 16 is formed, and the fuel flowing into the fuel return line 16 is cooled via the fuel cooler 17 and then returned to the fuel tank 1 via the flow path switching valve 22. .
[0025]
Note that the temperature detected by the temperature sensor 23 temporarily drops below the set temperature T 1 until the engine and exhaust system cool down and cool down after the engine is stopped, and the feed pump 2 and the fuel cooler 17 are stopped. However, the fuel temperature in the fuel gallery 12 of the high-pressure pump 4 will rise again, but the set temperature T 1 for outputting the next start commands 2a and 19a is higher than the previous set start temperature. Therefore, the situation where the feed pump 2 and the fuel cooler 17 frequently start and stop are avoided.
[0026]
Therefore, according to the above-described embodiment, even if the high pressure pump 4 stops when the engine is stopped, it is possible to prevent the fuel flow from circulating between the fuel tank 1 and the high pressure pump 4 and stagnation of the combustion flow. Fuel vaporization in the fuel gallery 12 in the high-pressure pump 4 can be remarkably suppressed, and leakage of fuel vaporized gas from the high-pressure pump 4 and seizure of the high-pressure pump 4 when the engine is stopped can be avoided. In addition, since the fuel supply line 3, the fuel return line 16, and the high-pressure pump 4 can be kept filled with fuel even after the engine is stopped, the DME engine can be quickly restarted after the engine is stopped. Can be realized.
[0027]
Further, the control device 24 performs control so that the feed pump 2 and the fuel cooler 17 are activated when the fuel temperature of the fuel gallery 12 in the high-pressure pump 4 is raised to a dangerous temperature range close to the critical temperature. Since the drive time of the feed pump 2 and the fuel cooler 17 can be limited to the minimum necessary, the power consumption required for the feed pump 2 and the fuel cooler 17 can be significantly suppressed.
[0028]
Further, the set temperature T 1 for outputting the start commands 2a and 19a to the feed pump 2 and the fuel cooler 17 is changed so as to gradually increase every time the feed pump 2 and the fuel cooler 17 are stopped. Therefore, the situation where the feed pump 2 and the fuel cooler 17 repeatedly start and stop can be avoided.
[0029]
The fuel supply device for the DME engine of the present invention is not limited to the above-described embodiment, and the fuel cooler is not limited to the air-cooled type, and various modifications can be made without departing from the scope of the present invention. Of course, can be added.
[0030]
【The invention's effect】
According to the fuel supply device for a DME engine of the present invention described above, various excellent effects as described below can be obtained.
[0031]
(I) Even if the high-pressure pump is stopped when the engine is stopped, fuel can be circulated between the fuel tank and the high-pressure pump to prevent the combustion flow from stagnation, so that the fuel in the fuel gallery in the high-pressure pump can be prevented. Vaporization can be remarkably suppressed, leakage of fuel vaporized gas from the high-pressure pump when the engine is stopped, and seizure of the high-pressure pump can be avoided in advance, and the fuel supply line and Since the fuel return line and the high-pressure pump can be maintained in a state filled with fuel, the DME engine can be quickly restarted after the engine is stopped.
[0032]
(II) When the fuel temperature in the fuel gallery in the high-pressure pump is raised to a dangerous temperature range close to the critical temperature, the control device controls the feed pump and the fuel cooler to control the feed pump and the fuel. Since the drive time of the cooler can be limited to a necessary minimum, the power consumption required for the feed pump and the fuel cooler can be significantly suppressed.
[0033]
(III) Since the set temperature for outputting the start command to the feed pump and the fuel cooler can be changed so as to gradually increase every time the feed pump and the fuel cooler are stopped, the feed pump and the fuel cooler are frequently used. It is possible to avoid a situation in which start and stop are repeated.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an embodiment of the present invention.
FIG. 2 is a flowchart showing a control procedure of the control device of FIG. 1;
FIG. 3 is a schematic diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Feed pump 2a Start command 3 Fuel supply line 4 High pressure pump 6 Common rail 8 Injector 9 Combustion chamber 12 Fuel gallery 16 Fuel return line 17 Fuel cooler 19 Electric fan 19a Start command 21 Bypass line 22 Flow path switching valve 22a Switch command 23 temperature sensor 23a detection signal 24 control device

Claims (1)

燃料タンクの燃料を高圧ポンプにより昇圧してコモンレールに蓄圧させ、該コモンレールからインジェクタに燃料を導いて燃焼室内に噴射させるようにしたＤＭＥエンジンの燃料供給装置において、
前記燃料タンクからフィードポンプにより送り出された燃料を前記高圧ポンプへ導く燃料供給ラインと、前記高圧ポンプ内の燃料ギャラリで圧力が所定値を超えた時に解放された余剰燃料を燃料クーラを介し冷却して前記燃料供給ラインの途中に再循環する燃料リターンラインと、該燃料リターンラインの燃料クーラより下流側から適宜に燃料を抜き出して前記燃料タンクに戻すバイパスラインと、該バイパスラインの前記燃料リターンラインに対する接続箇所に装備されて前記燃料クーラを経た燃料を切替指令の入力時にのみ前記バイパスライン側へ選択的に振り分ける流路切替弁と、前記高圧ポンプ内の燃料ギャラリの燃料温度を検出する温度センサと、エンジン停止時に前記流路切替弁に向け切替指令を出力し且つ前記温度センサの検出信号を入力してエンジン停止時に検出温度が所定の設定温度を超えている条件下でのみ前記フィードポンプ及び燃料クーラに向け起動指令を出力する制御装置とを備え、
しかも、この制御装置が、エンジン停止時に起動したフィードポンプ及び燃料クーラが温度センサによる検出温度の設定温度下への低下により停止する毎に、次回の起動指令を出力するための設定温度を直前の起動時より高い設定温度に変更するように構成されていることを特徴とするＤＭＥエンジンの燃料供給装置。In a fuel supply device for a DME engine, fuel in a fuel tank is boosted by a high-pressure pump and accumulated in a common rail, and fuel is guided from the common rail to an injector and injected into a combustion chamber.
A fuel supply line that guides fuel delivered from the fuel tank by a feed pump to the high-pressure pump and a fuel gallery in the high-pressure pump cools excess fuel that is released when the pressure exceeds a predetermined value via a fuel cooler. A fuel return line that is recirculated in the middle of the fuel supply line, a bypass line that appropriately draws fuel from the downstream side of the fuel cooler of the fuel return line and returns it to the fuel tank, and the fuel return line of the bypass line A flow path switching valve that is selectively provided to the bypass line only when a switching command is input, and a temperature sensor that detects the fuel temperature of the fuel gallery in the high-pressure pump When the engine is stopped, a switching command is output to the flow path switching valve and the temperature sensor is detected. If the input signal and a control device for detecting the temperature when the engine is stopped and outputs a start command for the feed pump and the fuel cooler only under conditions that exceed the predetermined set temperature,
In addition, every time the feed pump and the fuel cooler started when the engine is stopped are stopped due to a decrease in the temperature detected by the temperature sensor, the set temperature for outputting the next start command is set immediately before. A fuel supply device for a DME engine, wherein the fuel supply device is configured to change to a higher set temperature than at the time of startup.
JP2001244033A 2001-08-10 2001-08-10 DME engine fuel supply system Expired - Fee Related JP3796146B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Applications Claiming Priority (1)

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JP5187228B2 (en) * 2009-02-24 2013-04-24 株式会社デンソー Fuel injection device
NL2003791C2 (en) 2009-11-12 2011-05-16 Vialle Alternative Fuel Systems Bv FUEL FEED SYSTEM AND HIGH PRESSURE PUMP FOR A COMBUSTION ENGINE.
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CN109891078A (en) * 2016-10-24 2019-06-14 罗伯特·博世有限公司 System for liquefied gas to be compressed to goal pressure
CN109891078B (en) * 2016-10-24 2022-09-16 罗伯特·博世有限公司 System for compressing liquefied gas to target pressure

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