JP3830826B2 - Engine LPG supply device - Google Patents

Engine LPG supply device Download PDF

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Publication number
JP3830826B2
JP3830826B2 JP2002035085A JP2002035085A JP3830826B2 JP 3830826 B2 JP3830826 B2 JP 3830826B2 JP 2002035085 A JP2002035085 A JP 2002035085A JP 2002035085 A JP2002035085 A JP 2002035085A JP 3830826 B2 JP3830826 B2 JP 3830826B2
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liquid phase
fuel
lpg
gas phase
fuel system
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JP2003239785A (en
Inventor
博正 大野
平八 安川
智 津坂
真也 山口
正義 田沼
武相 瀧川
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Nikki Co Ltd
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Nikki Co 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
    • F02M21/0203—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
    • 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
    • F02M21/0218—Details on the gaseous fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02M21/0284—Arrangement of multiple injectors or fuel-air mixers per combustion chamber
    • 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
    • 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)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は燃料であるＬＰＧを噴射方式によりエンジンに供給する装置、詳しくは液相のＬＰＧを噴射する系と気相のＬＰＧを噴射する系とをもち、ＬＰＧおよびエンジンの諸状態に応じて系を選択して液相または気相のＬＰＧをエンジンに供給する装置に関するものである。
【０００２】
【従来の技術】
ＬＰＧを燃料に使用するエンジンの高出力化を図るため、減圧気化することなく高圧液相の状態で噴射弁を用いて吸気管路に噴射しエンジンに供給することが提案されている。
【０００３】
周知のように液相のＬＰＧは温度上昇に伴って気化しやすくなる性質をもっており、温度上昇によって燃料タンクから噴射弁に至る液相燃料系内に気相が発生すると圧力が大幅に変動し、また気相燃料も噴射してしまうため噴射弁からの噴射量を狂わせてエンジンを不調または運転不能とする。
【０００４】
その対策として、液相燃料系とは別の噴射弁をもった気相燃料系を具えさせ、液相燃料系内に気相が発生しない状態のときは液相ＬＰＧを噴射するが、気相が発生したときは気相ＬＰＧを噴射するように、使用する燃料系を切換えることが特開昭６３−１８１７２号公報、特開平１１−２１０５５７号公報に提示されている。
【０００５】
図８は前記特開昭６３−１８１７２号公報に記載されているＬＰＧ噴射システムを概略的に示した図であって、エンジン５１の吸気管路５２に液相燃料系５４の液相噴射弁５５と気相燃料系６２の気相噴射弁６３とを設置している。液相燃料系５４は燃料タンク５３から液相噴射弁５５に至る液相燃料通路５６にポンプ５７，圧力センサ５８，温度センサ５９を設けてなり、圧力調整器６１を有する戻し通路６０を具えている。気相燃料系６２は戻し通路６０または燃料タンク５３から気相噴射弁６３に至る気相燃料通路６４に気相貯槽６５を設けたものとしている。
【０００６】
そして、圧力センサ５８と温度センサ５９とによって圧力と温度とを検出して液相燃料通路５６の液相ＬＰＧに気相が発生していると判断したとき、液相噴射弁５５を停止して気相噴射弁６３により気相ＬＰＧをエンジン５１に供給するものである。
【０００７】
図９は前記特開平１１−２１０５５７号公報に記載されているＬＰＧ噴射システムを概略的に示した図であって、図８のものと同様にエンジン５１の吸気管路５２に液相燃料系５４の液相噴射弁５５と気相燃料系６２の気相噴射弁６３とを設置している。液相燃料系５４は燃料タンク５３から液相噴射弁５５に至る液相燃料通路５６にポンプ５７，圧力センサ５８，温度センサ５９を設けてなり、圧力調整器６１を有する戻し通路６０を具えている。一方、気相燃料系６２は燃料タンク５３から気相噴射弁６３に至る気相燃料通路６４に圧力調整器６６，圧力センサ６７，温度センサ６８を設けてなるものとされ、更にエンジン５１の冷却水温度を検出する水温センサ６９を具えている。
【０００８】
そして、圧力センサ５８と温度センサ５９とによって圧力と温度とを検出して液相燃料通路５６の液相ＬＰＧに気相が発生していると判断したとき、液相噴射弁５５を停止して気相噴射弁６３により気相ＬＰＧをエンジン５１に供給する、という基本動作において図８のものと同じである。しかし、図９のものでは、圧力センサ６７と温度センサ６８とによって検出した気相燃料通路６４の気相ＬＰＧの状態、即ち完全気相であるか不完全気相であるかに応じて気相噴射弁６３の制御モードを変えるようにしており、更に水温センサ６９によって高温再始動と判断したときは気相噴射弁６３により気相ＬＰＧをエンジンに供給するようにしている。
【０００９】
【発明が解決しようとする課題】
前記図８，図９のＬＰＧ噴射システムは、前述のように液相燃料系のＬＰＧの状態、即ち液相のみであるか気相を発生しているかの判断を液相燃料通路の圧力と温度とによって行ない、液相ＬＰＧの供給を継続するか気相ＬＰＧの供給に切換えるかを決定している。従って、ＬＰＧの成分比によっては判断の誤差が大きく、正確な制御が困難になる、という問題がある。
【００１０】
また、エンジン始動に際して液相燃料系にＬＰＧが満たされていない場合があり、このような場合は図８のＬＰＧ噴射システムによる始動はもとより、図９のＬＰＧ噴射システムによる冷間始動以外の始動にあたって液相燃料通路のＬＰＧの状態を正確に判断することが困難であり、始動に長時間を要する場合が生じることを避けられない。更に、液相燃料系の液相ＬＰＧの状態のみによって使用する燃料系を選択しているので、液相燃料系のみの使用が継続するとエンジンルーム内の熱で高温となった余剰ＬＰＧが燃料タンクに戻り循環を繰返すことにより、燃料タンク内のＬＰＧの温度・圧力が上昇する。その結果、噴射弁に高精度のものが要求され、且つその制御に複雑なシステムが必要となるばかりか、燃料系を構成する各部品に大きな耐圧強度が必要となり、加えて燃料タンクにＬＰＧを補給する必要を生じたとき内部が高圧であると充填が困難である、という問題を生じる。
【００１１】
本発明は前記従来のＬＰＧ噴射システムがもっている前述の諸問題を解決するためになされたものであって、液相ＬＰＧの噴射と気相ＬＰＧの噴射との切換えを適切に行なわせること、およびこのことに加えてエンジンの始動を容易に安定よく行なわせること、更にこれらに加えて燃料タンクの温度・圧力上昇を抑制して噴射弁、制御システム、耐圧強度に対する要求を軽減させることを目的とし、更にまた切換え時の燃料引継ぎが円滑に行なわれるＬＰＧ噴射システムとすることを目的とする。
【００１２】
【課題を解決するための手段】
本発明は燃料タンクに充填されているＬＰＧの液相部分と気相部分とを個別に吸気管路に噴射しエンジンに供給する液相燃料系と気相燃料系とを有するＬＰＧ噴射システムがもっている前記問題点を次のようにして解決させることとした。
【００１３】
即ち、本発明は前記問題点を解決するための第一手段を、燃料タンクに設置されてその温度を検出するタンク温度センサと；液相燃料系の燃料タンクから液相噴射弁に至る液相燃料通路に設置されてその内部の液相ＬＰＧの圧力および温度を検出する液相圧力センサおよび液相温度センサと；気相燃料系の燃料タンクから気相噴射弁に至る気相燃料通路に設置されてその内部の気相ＬＰＧの圧力および温度を検出する気相圧力センサおよび気相温度センサと；タンク温度センサと気相圧力センサまたは液相温度センサとが検出した各値に基いてＬＰＧの成分比を算出するＬＰＧ成分計算手段と；ＬＰＧ成分計算手段により算出された成分比を基準として、液相圧力センサおよび液相温度センサが検出した各値から液相燃料系内の液相ＬＰＧの状態を判断する液相状態判定手段と；を具え、液相状態判定手段が液相燃料系内の液相ＬＰＧを完全な液相と判断したときは液相燃料系による燃料供給を行なわせ、液相燃料系内に気相を発生していると判断したときは気相燃料系による燃料供給を行なわせるようにした。
【００１４】
このように、液相ＬＰＧと気相ＬＰＧとの切換えを液相燃料系内の液相ＬＰＧの圧力・温度のみによることなく、これらに加えＬＰＧの組成を考慮して決定するものとした第一手段によると、ＬＰＧの成分比の相違による判断誤差がなくなり、正確且つ高精度の制御が可能となって、気相発生後も液相燃料系による燃料供給を行なって混合気過薄となる不都合を回避し、広範囲の運転条件下で安定したエンジン性能を得ることができる。
【００１５】
特に、タンク温度センサが検出した値に基いて燃料の切換えを行なわせる切換指令手段；を具え、切換指令手段は燃料タンクが設定温度以上となったとき、液相状態判定手段が液相燃料系による燃料供給を行なわせる判断をしていても、気相燃料系による燃料供給に切換えさせるものとした。
【００１６】
このように、燃料タンクが設定温度以上となったとき、燃料供給が液相燃料系で行なわれていてもこれを強制的に気相燃料系に切換えさせることを第一手段または第二手段に付加した第三手段によると、これらが有する機能に加えて、燃料タンク内の気相ＬＰＧが消費されて液相ＬＰＧの蒸発量が大幅に増加することによる気化潜熱がもたらす冷却効果が、燃料タンク内の温度・圧力上昇を抑制して噴射弁、制御システム、各部品の耐圧強度に対する要求を軽減させることができる。
【００１７】
更に、本発明はＬＰＧのプロパン比率が高いほど前記基準温度を低温側に移行させて前記気相燃料系による始動燃料供給温度領域を拡張することができる。
【００１８】
【発明の実施の形態】
以下に図面を参照して本発明の実施の形態を説明する。図１は本発明に係るＬＰＧ噴射システムの実施の一形態を示す配置図であって、１はエンジン、２はスロットルボディ３、吸気マニホルド５を含む吸気管路、６は排気管路、７は耐圧容器からなる燃料タンク、８は電子式制御ユニット、ＦＬは液相燃料系、ＦＧは気相燃料系である。
【００１９】
液相燃料系ＦＬは燃料タンク７の液相ＬＰＧに浸漬され、フィルタを通して吸込んだ高圧の液相ＬＰＧを更に加圧する燃料ポンプ１２と、これより送出した液相ＬＰＧを燃料ギャラリ１７に送る液相燃料通路１１と、この通路１１に設置した電磁駆動の液相遮断弁１４，液相圧力センサ１５，液相温度センサ１６と、燃料ギャラリ１７に接続されてエンジン１の各気筒に対応して吸気マニホルド５の枝管のそれぞれに設置した液相噴射弁１８と、液相圧力調整器２０を有し液相燃料通路１１の燃料ギャラリ１７に接近した個所から分岐して燃料タンク７に接続した液相戻し通路１９とを具えている。
【００２０】
液相圧力センサ１５および液相温度センサ１６は燃料ギャラリ１７に近い個所に設置され、また液相噴射弁１８はエンジン１の吸気ポートに接近した個所に設置されており、噴射直前の液相ＬＰＧの状態を検出し且つエンジン入口近くで噴射させることにより、適正量の液相ＬＰＧを応答よくエンジンに供給できるようになっている。
【００２１】
一方、気相燃料系ＦＧは燃料タンク７の気相ＬＰＧに入口を開口させた気相燃料通路２２と、この通路２２に設置した電磁駆動の気相遮断弁２３，気相圧力調整器２４，気相圧力センサ２５，気相温度センサ２６と、吸気マニホルド５の集合部のスロットルボディ３に近い個所に設置した一個の気相噴射弁２７とを具えている。もっとも、気相噴射弁２７は複数個を各気筒に均等分配できるように適宜個所に設置してもよい。
【００２２】
気相圧力センサ２５および気相温度センサ２６は気相噴射弁２７に近い個所に設置されており、噴射直前の気相ＬＰＧの状態を検出して適正量の気相ＬＰＧをエンジンに供給するようになっている。
【００２３】
エンジン１にはその温度、一般には冷却水の温度を検知するエンジン温度センサ３１および回転速度を検知する回転速度センサ３２とが付設され、これらのほかに排気管路６に設置されて排気状態を検知する酸素センサ、吸気管路２の絞り弁４上流側に設置されて吸入空気量を検知する空気流量センサ、絞り弁４の位置を検知するスロットル開度センサなどエンジン１の状態を検知するセンサ類が設置されていて、これらが検出した値が電子式制御ユニット８に送られて液相噴射弁１８，気相噴射弁２７を制御することは、従来の燃料噴射制御システムと同じである。
【００２４】
本実施の形態では、エンジン温度センサ３１，回転速度センサ３２に加えて、燃料タンク７にその内部に充填されているＬＰＧの温度を検知するタンク温度センサ３３を設置している。また、気相圧力調整器２４はエンジン冷却水で加熱するようになっており、温度が低下しても気相を維持して気相噴射弁２７から噴射させることができる。
【００２５】
電子式制御ユニット８にはＬＰＧの成分、具体的には図２に示す圧力−温度線図で表されるプロパン成分比に応じた圧力と温度との関係が記憶させてあり、また通常の空燃比制御のためのコントロール変数入力・演算処理・コントロール信号出力手段のほかに、ＬＰＧ成分計算手段３５，液相状態判定手段３６，始動燃料選定手段３７，切換指令手段３８，遅延時間設定手段３９が含まれている。
【００２６】
通常のエンジン運転において、液相燃料系ＦＬによる燃料供給を行なっているときは液相圧力センサ１５，液相温度センサ１６が検出した液相ＬＰＧの状態とエンジン１の運転状態とに応じて液相噴射弁１８を制御し、気相燃料系ＦＧによる燃料供給を行なっているときは気相圧力センサ２５，気相温度センサ２６が検出した気相ＬＰＧの状態とエンジン１の運転状態に応じて気相噴射弁２７を制御する。
【００２７】
本実施の形態によると、タンク温度センサ３３と気相圧力センサ２５または液相圧力センサ１５とが検出した値に基いて、現在燃料タンク７に充填されているＬＰＧの成分比、本実施の形態ではプロパン成分比をＬＰＧ成分計算手段３５により算出する。この成分比は図２に示す圧力−温度の関係から正確に算出することができる。
【００２８】
そして、算出されたＬＰＧの成分比と液相圧力センサ１５，液相温度センサ１６が検出した液相燃料系ＦＬ内の圧力および温度とを用いて、液相状態判定手段３６により液相燃料系ＦＬ内の液相ＬＰＧの状態、即ち完全な液相であるか気相を発生しているかを判断させる。この場合、成分比によって一定の圧力−温度関係を有しているので、検出した圧力および温度の値がこの関係から逸脱していれば気相を発生している、と判断されて液相燃料系ＦＬによる燃料供給を停止して気相燃料系ＦＧによる燃料供給に切換える。
【００２９】
以上は請求項１に記載した第一手段の実施の形態であり、現在使用しているＬＰＧの組成を液相燃料系ＦＬ内の液相ＬＰＧの状態判断の要素に加えたことにより、ＬＰＧの成分比の相違による判断誤差がなくなり、正確且つ高精度の制御が可能となって、気相発生後も液相燃料系ＦＬによる燃料供給を継続して混合気過薄を生じる、という不都合をなくし広範囲の運転条件下で安定したエンジン性能を得ることができる。
【００３０】
次に、エンジン始動にあたって、ＬＰＧ成分計算手段３５により算出されたＬＰＧの成分比とエンジン温度センサ３１が検出したエンジン温度とを用いて、始動燃料選定手段３７により液相ＬＰＧと気相ＬＰＧのいずれによって始動させるかを選択する。即ち、図３に示すようにエンジン温度が基準温度ＴＥよりも低いときは液相燃料系ＦＬから供給される液相ＬＰＧで始動させ、エンジン温度が基準温度ＴＥよりも高いときは気相燃料系ＦＧから供給される気相ＬＰＧで始動させるものである。このことにより、液相ＬＰＧが気化しにくい低温域で液相ＬＰＧが供給され、あらゆる環境条件下で常にエンジン１を容易に且つ安定よく始動させることが可能となる。尚、エンジン始動後は液相状態判定手段３６の判断に従った燃料供給が行なわれる。
【００３１】
本実施の形態では基準温度ＴＥをＬＰＧの成分比に応じて可変としている。即ち、図４に示すようにＬＰＧ成分計算手段３５によって算出したＬＰＧ成分比の内でプロパンが占める比率が高いほど基準温度ＴＥを低温側へ移行させて気相ＬＰＧによる始動温度領域を拡張する。反対に、プロパンが占める比率が低いほど基準温度ＴＥを高温側に移行させて液相ＬＰＧによる始動温度領域を拡張する。
【００３２】
以上は請求項２に記載した第二手段の実施の形態であり、ＬＰＧ成分比による蒸気圧の相違に応じて基準温度ＴＥを変更することにより、エンジン１の始動性を更に高めることができる。
【００３３】
エンジン１が長時間運転を続けたときや高温雰囲気で運転されたとき、エンジン１の周辺が高温となってこれにより熱せられた余剰液相ＬＰＧが液相戻し通路１９を通って燃料タンク７に戻り、これが循環することによって燃料タンク７の温度が次第に上昇する。燃料タンク７の温度が上昇すると、充填されているＬＰＧの気化が進んで圧力が大幅に上昇する。
【００３４】
燃料タンク７の温度はタンク温度センサ３３によって検出されており、図５に示すように予め設定した基準温度ＴＦよりも低いときは液相燃料系ＦＬによる燃料供給を継続するが、基準温度ＴＦよりも高温となったときは気相燃料系ＦＧによる燃料供給に切換える。この切換えは切換指令手段３８がタンク温度センサ３３によって検出された温度と基準温度ＴＦとを比較して指令を発することによって行なわれ、液相状態判定手段３６が液相燃料系ＦＬ内を完全な液相ＬＰＧと判断していても、この判断よりも優先して切換えを強制的に行なうものとされている。
【００３５】
本実施の形態は、燃料タンク７の気相ＬＰＧを消費することによって燃料タンク７の圧力が低下し、液相ＬＰＧの蒸発量が大幅に増加して蒸発の際の気化潜熱による冷却効果で燃料タンク７の温度が低下する。このように、燃料タンク７の温度・圧力の上昇が抑制されることによって、液相噴射弁１８，気相噴射弁２７に高い加工精度、複雑な動作制御システムを必要としなくなるとともに、液相燃料系ＦＬ、気相燃料系ＦＧの構成部品の耐圧強度に対する要求を軽減することができ、更に燃料タンク７にＬＰＧを補給するときの充填作業を容易に行なうことができるものである。
【００３６】
尚、燃料タンク７の温度が基準温度ＴＦよりも低下したときは、液相状態判定手段３６の判断に従う燃料供給に戻る。尚また、この実施の形態における基準温度ＴＦは一定値に固定しておいてもよいが、ＬＰＧの成分比に応じてプロパン比率が高いほど低温側へ移行させ、気相ＬＰＧに切換える温度領域を拡張させるようにしてもよく、このようにすると燃料タンク７内の温度・圧力の上昇を更に適切に抑制することができる。
【００３７】
更に、図１に示した実施の形態のように、常用する液相燃料系ＦＬの液相噴射弁１８を吸気マニホルド枝管毎にエンジン入口近くに設置し、特定条件で使用する気相燃料系ＦＧの気相噴射弁２７を吸気マニホルド集合部に設置したものにおいて、液相燃料系ＦＬによる燃料供給の停止と気相燃料系ＦＧによる燃料供給の開始とを同時に行なうと、気相噴射弁２７がエンジン１から遠いために供給遅れを生じ、混合気が一時的に過薄となる。また、気相燃料系ＦＧによる燃料供給の停止と液相燃料系ＦＬによる燃料供給の開始とを同時に行なうと、液相噴射弁１８がエンジン１に近いために気相ＬＰＧと液相ＬＰＧとが同時に供給されて混合気を一時的に過濃とする。
【００３８】
図６（Ｂ）はこの様子を示したものであり、切換え時に空燃比がスパイクを発生してエンジン運転性、排気状態を悪化する、という不都合を生じる。
【００３９】
そこで、液相状態判定手段３６および切換指令手段３８が発する指令により切換えを行なうとき、回転速度センサ３２が検出した値に基いて遅延時間設定手段３９により液相燃料系ＦＬの燃料供給停止・開始時期を気相燃料系ＦＧの燃料供給開始・停止時期よりも遅らせる時間を設定し、この設定された遅延時間に従って液相燃料系ＦＬの燃料供給停止と開始とを遅らせるものとした。
【００４０】
即ち、液相燃料系ＦＬから気相燃料系ＦＧに切換えるときは、気相燃料系ＦＧによる燃料供給の開始から少し遅れて液相燃料系ＦＬによる燃料供給を停止させることにより、燃料を途切れることなくエンジン１に供給することができる。また、気相燃料系ＦＧから液相燃料系ＦＬに切換えるときは、気相燃料系ＦＧによる燃料供給の停止から少し遅れて液相燃料系ＦＬによる燃料供給を開始させることにより、これらからの燃料を重複させることなくエンジン１に供給することができる。
【００４１】
尚、遅延時間設定手段３９で遅延時間を設定するにあたり、図７に示すようにエンジン回転速度が高いほど遅延時間を短く設定することが、回転速度の高低にかかわらず燃料の途切れおよび重複を生じさせないために有効である。
【００４２】
以上は請求項４，７に記載した第四手段の実施の形態であり、図６（Ａ）に示したように切換え時における空燃比スパイクの発生がなくなり、一定空燃比の混合気をエンジン１に供給して運転性、排気状態を良好に維持することができる。
【００４３】
【発明の効果】
以上のように、燃料タンクのＬＰＧの液相部分を吸気管路に噴射する液相燃料系と、特定条件下で気相部分を吸気管路に噴射する気相燃料系とを具えたＬＰＧ噴射システムにおいて、各燃料系内のＬＰＧの圧力および温度を検知することに加えて、燃料タンクの温度を検知して使用しているＬＰＧの成分比を算出し、これを基準として液相燃料系内の液相ＬＰＧが完全な液相であるか気相を発生しているかを判断するようにした本発明によると、組成が異なるＬＰＧを用いても常に完全な液相ＬＰＧまたは気相ＬＰＧを噴射させることができ、正確な制御を行なって広範囲の運転条件下で安定したエンジン性能を得ることができるものである。
【００４４】
また、このことにエンジン温度とＬＰＧ成分比とに基いて始動燃料を選定する手段、燃料タンクの温度に基いて液相燃料系による燃料供給を気相燃料系による燃料供給に強制的に切換える手段、エンジン回転速度に応じた時間だけ燃料切換え時の液相燃料系の供給停止・開始を気相燃料系の供給開始・停止よりも遅延させる手段、のいずれかまたは二以上を加えた本発明によると、エンジンの始動を容易且つ安定よく行なうこと、燃料タンクの温度・圧力上昇を抑制して噴射弁、制御システム、各部品に対する諸要求を軽減すること、切換え時の燃料引継ぎを途切れや重複を生じることなく円滑に行なってエンジン運転性、排気状態を損なわないこと、ができるものである。
【図面の簡単な説明】
【図１】 本発明の実施の形態を示す配置図。
【図２】 ＬＰＧの圧力−温度線図。
【図３】 エンジン温度による始動燃料選択を説明する図。
【図４】 始動燃料選択のエンジン基準温度とＬＰＧ成分比との関係を示す図。
【図５】 燃料タンク温度による使用燃料切換えを説明する図。
【図６】 液相ＬＰＧと気相ＬＰＧの切換えと空燃比との関連を説明する図。
【図７】 燃料切換えの遅延時間設定とエンジン回転速度との関係を示す図。
【図８】 従来例の概略配置図。
【図９】 異なる従来例の概略配置図。
【符号の説明】
１ エンジン，２ 吸気管路，７ 燃料タンク，８ 電子式制御ユニット，１１ 液相燃料通路，１５ 液相圧力センサ，１６ 液相温度センサ，１８ 液相噴射弁，２２ 気相燃料通路，２５ 気相圧力センサ，２６ 気相温度センサ，２７ 気相噴射弁，３１ エンジン温度センサ，３２ 回転速度センサ，３３ タンク温度センサ，３５ ＬＰＧ成分計算手段，３６ 液相状態判定手段，３７ 始動燃料選定手段，３８ 切換指令手段，３９ 遅延時間設定手段，ＦＬ 液相燃料系，ＦＧ 気相燃料系，[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for supplying LPG as fuel to an engine by an injection method, and more specifically, a system for injecting LPG in a liquid phase and a system for injecting LPG in a gas phase. Is selected and a liquid phase or gas phase LPG is supplied to the engine.
[0002]
[Prior art]
In order to increase the output of an engine using LPG as fuel, it has been proposed to inject into an intake pipe using an injection valve in a high-pressure liquid phase state without vaporization under reduced pressure and supply the engine to the engine.
[0003]
As is well known, liquid phase LPG tends to vaporize as the temperature rises, and when the gas phase is generated in the liquid phase fuel system from the fuel tank to the injection valve due to the temperature rise, the pressure fluctuates greatly, Further, since the gas phase fuel is also injected, the injection amount from the injection valve is changed to make the engine malfunction or impossible to operate.
[0004]
As a countermeasure, a gas phase fuel system having an injection valve different from the liquid phase fuel system is provided. When no gas phase is generated in the liquid phase fuel system, the liquid phase LPG is injected. JP-A-63-18172 and JP-A-11-210557 suggest that the fuel system to be used should be switched so that gas phase LPG is injected when the gas is generated.
[0005]
FIG. 8 is a diagram schematically showing an LPG injection system described in Japanese Patent Laid-Open No. Sho 63-18172, in which a liquid phase injection valve 55 of a liquid phase fuel system 54 is provided in an intake pipe 52 of an engine 51. And a gas phase injection valve 63 of the gas phase fuel system 62 are installed. The liquid phase fuel system 54 includes a pump 57, a pressure sensor 58, and a temperature sensor 59 in a liquid phase fuel passage 56 extending from the fuel tank 53 to the liquid phase injection valve 55, and includes a return passage 60 having a pressure regulator 61. Yes. The gas phase fuel system 62 is provided with a gas phase storage tank 65 in a gas phase fuel passage 64 extending from the return passage 60 or the fuel tank 53 to the gas phase injection valve 63.
[0006]
Then, when the pressure and temperature are detected by the pressure sensor 58 and the temperature sensor 59 and it is determined that a gas phase is generated in the liquid phase LPG of the liquid phase fuel passage 56, the liquid phase injection valve 55 is stopped. The gas phase LPG is supplied to the engine 51 by the gas phase injection valve 63.
[0007]
FIG. 9 is a diagram schematically showing the LPG injection system described in Japanese Patent Application Laid-Open No. 11-210557, and a liquid-phase fuel system 54 is provided in the intake pipe 52 of the engine 51 in the same manner as in FIG. The liquid phase injection valve 55 and the gas phase injection valve 63 of the gas phase fuel system 62 are provided. The liquid phase fuel system 54 includes a pump 57, a pressure sensor 58, and a temperature sensor 59 in a liquid phase fuel passage 56 extending from the fuel tank 53 to the liquid phase injection valve 55, and includes a return passage 60 having a pressure regulator 61. Yes. On the other hand, the gas phase fuel system 62 is provided with a pressure regulator 66, a pressure sensor 67, and a temperature sensor 68 in a gas phase fuel passage 64 extending from the fuel tank 53 to the gas phase injection valve 63, and further cooling the engine 51. A water temperature sensor 69 for detecting the water temperature is provided.
[0008]
Then, when the pressure and temperature are detected by the pressure sensor 58 and the temperature sensor 59 and it is determined that a gas phase is generated in the liquid phase LPG of the liquid phase fuel passage 56, the liquid phase injection valve 55 is stopped. The basic operation of supplying the gas phase LPG to the engine 51 by the gas phase injection valve 63 is the same as that of FIG. However, in the case of FIG. 9, the gas phase LPG of the gas phase fuel passage 64 detected by the pressure sensor 67 and the temperature sensor 68, that is, the gas phase depends on whether it is a complete gas phase or an incomplete gas phase. The control mode of the injection valve 63 is changed, and when the high temperature restart is determined by the water temperature sensor 69, the gas phase LPG is supplied to the engine by the gas phase injection valve 63.
[0009]
[Problems to be solved by the invention]
The LPG injection system shown in FIGS. 8 and 9 determines the state of the LPG of the liquid phase fuel system, that is, whether the liquid phase is only or whether the gas phase is generated, as described above. This determines whether to continue the supply of the liquid phase LPG or switch to the supply of the gas phase LPG. Therefore, there is a problem that an error in judgment is large depending on the component ratio of LPG, and accurate control becomes difficult.
[0010]
Further, when the engine is started, the liquid phase fuel system may not be filled with LPG. In such a case, not only the start by the LPG injection system of FIG. 8 but also the start other than the cold start by the LPG injection system of FIG. It is difficult to accurately determine the state of the LPG in the liquid phase fuel passage, and it is unavoidable that a long time may be required for starting. Further, since the fuel system to be used is selected only depending on the state of the liquid phase LPG of the liquid phase fuel system, if the use of only the liquid phase fuel system is continued, the surplus LPG that has become hot due to the heat in the engine room is converted into the fuel tank. By returning to step S3 and repeating the circulation, the temperature and pressure of the LPG in the fuel tank rise. As a result, a high-precision injection valve is required, and not only a complicated system is required for its control, but also a large pressure resistance is required for each component of the fuel system. In addition, LPG is added to the fuel tank. When it becomes necessary to replenish, there is a problem that filling is difficult if the inside is at a high pressure.
[0011]
The present invention has been made to solve the above-mentioned problems of the conventional LPG injection system, and appropriately switches between liquid phase LPG injection and gas phase LPG injection, and In addition to this, it is intended to make the engine start easy and stable, and to further reduce the demand for the injection valve, control system, and pressure resistance by suppressing the temperature and pressure rise of the fuel tank. It is another object of the present invention to provide an LPG injection system in which fuel takeover at the time of switching is performed smoothly.
[0012]
[Means for Solving the Problems]
The present invention has an LPG injection system having a liquid phase fuel system and a gas phase fuel system that individually inject a liquid phase portion and a gas phase portion of LPG filled in a fuel tank into an intake pipe and supply them to an engine. The above-described problems were solved as follows.
[0013]
That is, the present invention provides, as a first means for solving the above problems, a tank temperature sensor that is installed in a fuel tank and detects its temperature; a liquid phase from a liquid fuel tank to a liquid injection valve A liquid phase pressure sensor and a liquid phase temperature sensor installed in the fuel passage for detecting the pressure and temperature of the liquid phase LPG inside the fuel passage; installed in the gas phase fuel passage from the fuel tank of the gas phase fuel system to the gas phase injection valve A gas phase pressure sensor and a gas phase temperature sensor for detecting the pressure and temperature of the gas phase LPG therein; and based on the values detected by the tank temperature sensor and the gas phase pressure sensor or the liquid phase temperature sensor, LPG component calculation means for calculating the component ratio; and based on the component ratio calculated by the LPG component calculation means, from the values detected by the liquid phase pressure sensor and the liquid phase temperature sensor, the liquid phase LPG in the liquid phase fuel system Liquid phase state determining means for determining a state; and when the liquid phase state determining means determines that the liquid phase LPG in the liquid phase fuel system is a complete liquid phase, fuel supply by the liquid phase fuel system is performed. When it is judged that a gas phase is generated in the liquid phase fuel system, fuel supply by the gas phase fuel system is performed.
[0014]
As described above, the switching between the liquid phase LPG and the gas phase LPG is determined not only by the pressure and temperature of the liquid phase LPG in the liquid phase fuel system but also by taking into account the composition of the LPG in addition to these. According to the means, there is no determination error due to the difference in the component ratio of LPG, and accurate and highly accurate control is possible. And stable engine performance can be obtained under a wide range of operating conditions.
[0015]
In particular, a switching command means for switching the fuel based on a value detected by the tank temperature sensor is provided. When the fuel tank reaches a set temperature or higher, the switching command means has a liquid phase state judging means for the liquid phase fuel system. Even if it is determined that the fuel supply is performed by the fuel cell, the fuel supply is switched to the gas fuel system.
[0016]
As described above, when the fuel tank reaches the set temperature or higher, the first means or the second means forcibly switch the fuel tank to the gas phase fuel system even if the fuel is supplied by the liquid phase fuel system. According to the added third means, in addition to the functions of these, the cooling effect brought about by the latent heat of vaporization due to the consumption of the vapor phase LPG in the fuel tank and the evaporation amount of the liquid phase LPG significantly increases. It is possible to reduce the temperature and pressure rise in the inside and reduce the demand for pressure resistance of the injection valve, the control system, and each component.
[0017]
Further, according to the present invention, as the propane ratio of LPG is higher, the reference temperature is shifted to a lower temperature side, so that the starting fuel supply temperature range by the gas phase fuel system can be expanded.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a layout view showing an embodiment of an LPG injection system according to the present invention. 1 is an engine, 2 is an intake pipe including a throttle body 3 and an intake manifold 5, 6 is an exhaust pipe, and 7 is an exhaust pipe. A fuel tank comprising a pressure vessel, 8 is an electronic control unit, FL is a liquid phase fuel system, and FG is a gas phase fuel system.
[0019]
The liquid phase fuel system FL is immersed in the liquid phase LPG of the fuel tank 7 and further pressurizes the high pressure liquid phase LPG sucked through the filter, and the liquid phase LPG sent from this is sent to the fuel gallery 17. A fuel passage 11, an electromagnetically driven liquid phase shut-off valve 14, a liquid phase pressure sensor 15, a liquid phase temperature sensor 16, and a fuel gallery 17 that are installed in the passage 11 are connected to a fuel gallery 17 and intake air corresponding to each cylinder of the engine 1. Liquid having a liquid phase injection valve 18 installed in each of the branch pipes of the manifold 5 and a liquid phase pressure regulator 20, branched from a location close to the fuel gallery 17 of the liquid phase fuel passage 11 and connected to the fuel tank 7. And a phase return passage 19.
[0020]
The liquid phase pressure sensor 15 and the liquid phase temperature sensor 16 are installed at a location close to the fuel gallery 17, and the liquid phase injection valve 18 is installed at a location close to the intake port of the engine 1. By detecting this state and injecting near the engine inlet, an appropriate amount of liquid phase LPG can be supplied to the engine with good response.
[0021]
On the other hand, the gas phase fuel system FG includes a gas phase fuel passage 22 having an inlet opening in the gas phase LPG of the fuel tank 7, an electromagnetically driven gas phase shutoff valve 23 installed in the passage 22, a gas phase pressure regulator 24, A gas phase pressure sensor 25, a gas phase temperature sensor 26, and a gas phase injection valve 27 installed at a location near the throttle body 3 in the collection portion of the intake manifold 5 are provided. However, a plurality of gas-phase injection valves 27 may be installed at appropriate locations so that a plurality of gas-phase injection valves 27 can be distributed equally to each cylinder.
[0022]
The gas phase pressure sensor 25 and the gas phase temperature sensor 26 are installed near the gas phase injection valve 27 so as to detect the state of the gas phase LPG immediately before injection and supply an appropriate amount of the gas phase LPG to the engine. It has become.
[0023]
The engine 1 is provided with an engine temperature sensor 31 for detecting the temperature, generally the temperature of the cooling water, and a rotation speed sensor 32 for detecting the rotation speed. A sensor for detecting the state of the engine 1, such as an oxygen sensor for detecting, an air flow sensor for detecting the intake air amount installed upstream of the throttle valve 4 in the intake pipe 2, and a throttle opening sensor for detecting the position of the throttle valve 4. Similar to the conventional fuel injection control system, the values detected by these are sent to the electronic control unit 8 to control the liquid phase injection valve 18 and the gas phase injection valve 27.
[0024]
In this embodiment, in addition to the engine temperature sensor 31 and the rotation speed sensor 32, a tank temperature sensor 33 for detecting the temperature of the LPG filled in the fuel tank 7 is installed. The gas phase pressure regulator 24 is heated by engine cooling water, and can maintain the gas phase and inject from the gas phase injection valve 27 even if the temperature is lowered.
[0025]
The electronic control unit 8 stores the relationship between pressure and temperature in accordance with LPG components, specifically the propane component ratio represented by the pressure-temperature diagram shown in FIG. In addition to control variable input / arithmetic processing / control signal output means for fuel ratio control, LPG component calculation means 35, liquid phase state determination means 36, starting fuel selection means 37, switching command means 38, and delay time setting means 39 are provided. include.
[0026]
In normal engine operation, when fuel is supplied by the liquid phase fuel system FL, the liquid phase LPG detected by the liquid phase pressure sensor 15 and the liquid phase temperature sensor 16 and the operating state of the engine 1 are used for the liquid. When the phase injection valve 18 is controlled and fuel is supplied by the gas phase fuel system FG, the gas phase LPG detected by the gas phase pressure sensor 25 and the gas phase temperature sensor 26 and the operating state of the engine 1 are determined. The gas phase injection valve 27 is controlled.
[0027]
According to the present embodiment, based on the values detected by the tank temperature sensor 33 and the gas phase pressure sensor 25 or the liquid phase pressure sensor 15, the component ratio of the LPG currently filled in the fuel tank 7, the present embodiment Then, the propane component ratio is calculated by the LPG component calculation means 35. This component ratio can be accurately calculated from the pressure-temperature relationship shown in FIG.
[0028]
Then, using the calculated component ratio of LPG and the pressure and temperature in the liquid phase fuel system FL detected by the liquid phase pressure sensor 15 and the liquid phase temperature sensor 16, the liquid phase state determination means 36 uses the liquid phase fuel system. The state of the liquid phase LPG in the FL, that is, whether it is a complete liquid phase or a gas phase is determined. In this case, since there is a constant pressure-temperature relationship depending on the component ratio, if the detected pressure and temperature values deviate from this relationship, it is determined that a gas phase is generated, and the liquid-phase fuel is generated. The fuel supply by the system FL is stopped and switched to the fuel supply by the gas phase fuel system FG.
[0029]
The above is an embodiment of the first means described in claim 1, and by adding the composition of the currently used LPG to the element for determining the state of the liquid phase LPG in the liquid phase fuel system FL, The determination error due to the difference in the component ratios is eliminated, and accurate and highly accurate control is possible, and the inconvenience that the fuel supply by the liquid phase fuel system FL is continued even after the gas phase is generated and the mixture is excessively thin is eliminated. Stable engine performance can be obtained under a wide range of operating conditions.
[0030]
Next, when starting the engine, using the LPG component ratio calculated by the LPG component calculation means 35 and the engine temperature detected by the engine temperature sensor 31, the start fuel selection means 37 selects either the liquid phase LPG or the gas phase LPG. Select whether to start with. That is, as shown in FIG. 3, when the engine temperature is lower than the reference temperature TE, the engine is started with the liquid phase LPG supplied from the liquid fuel system FL, and when the engine temperature is higher than the reference temperature TE, the gas phase fuel system is used. It is started with the gas phase LPG supplied from the FG. As a result, the liquid phase LPG is supplied in a low temperature range where the liquid phase LPG is hard to vaporize, and the engine 1 can always be easily and stably started under all environmental conditions. Note that after the engine is started, fuel is supplied according to the determination of the liquid phase state determination means 36.
[0031]
In the present embodiment, the reference temperature TE is variable according to the LPG component ratio. That is, as shown in FIG. 4, the higher the ratio of propane in the LPG component ratio calculated by the LPG component calculating means 35, the more the reference temperature TE is shifted to the lower temperature side and the starting temperature range by the gas phase LPG is expanded. On the other hand, the lower the ratio of propane, the higher the reference temperature TE is shifted to the higher temperature side, thereby extending the starting temperature range by the liquid phase LPG.
[0032]
The above is the embodiment of the second means described in claim 2, and the startability of the engine 1 can be further improved by changing the reference temperature TE according to the difference in vapor pressure due to the LPG component ratio.
[0033]
When the engine 1 is operated for a long time or in a high temperature atmosphere, the excess liquid phase LPG heated by the surroundings of the engine 1 is heated to the fuel tank 7 through the liquid phase return passage 19. Returning and circulating, the temperature of the fuel tank 7 gradually increases. When the temperature of the fuel tank 7 rises, vaporization of the filled LPG advances and the pressure rises significantly.
[0034]
The temperature of the fuel tank 7 is detected by a tank temperature sensor 33. When the temperature is lower than a preset reference temperature TF as shown in FIG. 5, the fuel supply by the liquid phase fuel system FL is continued, but from the reference temperature TF. When the temperature becomes too high, the fuel supply is switched to the gas phase fuel system FG. This switching is performed by the switching command means 38 comparing the temperature detected by the tank temperature sensor 33 with the reference temperature TF and issuing a command, so that the liquid phase state determining means 36 completes the liquid phase fuel system FL. Even if it is determined as the liquid phase LPG, the switching is forcibly performed in preference to this determination.
[0035]
In this embodiment, the gas phase LPG of the fuel tank 7 is consumed, the pressure of the fuel tank 7 is lowered, the evaporation amount of the liquid phase LPG is greatly increased, and the cooling effect by the latent heat of vaporization at the time of evaporation is used as the fuel. The temperature of the tank 7 decreases. As described above, the increase in the temperature and pressure of the fuel tank 7 is suppressed, so that the liquid phase injection valve 18 and the gas phase injection valve 27 do not require a high processing accuracy and a complicated operation control system, and the liquid phase fuel. It is possible to reduce the requirements for the pressure strength of the components of the system FL and the gas-phase fuel system FG, and it is possible to easily perform the filling operation when the fuel tank 7 is replenished with LPG.
[0036]
When the temperature of the fuel tank 7 falls below the reference temperature TF, the fuel supply is returned to the fuel phase according to the determination of the liquid phase state determination means 36. The reference temperature TF in this embodiment may be fixed to a constant value. However, the higher the propane ratio in accordance with the LPG component ratio, the lower the propane ratio, the lower the temperature range for switching to the gas phase LPG. You may make it expand, and if it does in this way, the rise in the temperature and pressure in the fuel tank 7 can be suppressed further appropriately.
[0037]
Further, as in the embodiment shown in FIG. 1, a liquid-phase injection valve 18 of a liquid-phase fuel system FL that is normally used is installed near the engine inlet for each intake manifold branch pipe, and the gas-phase fuel system used under specific conditions In the case where the FG gas-phase injection valve 27 is installed in the intake manifold assembly, if the fuel supply stop by the liquid-phase fuel system FL and the fuel supply start by the gas-phase fuel system FG are performed simultaneously, the gas-phase injection valve 27 Is far from the engine 1, causing a supply delay, and the air-fuel mixture becomes temporarily thin. Further, when the fuel supply by the gas phase fuel system FG is stopped and the fuel supply by the liquid phase fuel system FL is started at the same time, the gas phase LPG and the liquid phase LPG are generated because the liquid phase injection valve 18 is close to the engine 1. At the same time, the mixture is temporarily over-rich.
[0038]
FIG. 6B shows this situation, and causes the inconvenience that the air-fuel ratio spikes at the time of switching to deteriorate the engine operability and the exhaust state.
[0039]
Therefore, when switching is performed in accordance with commands issued by the liquid phase state determination unit 36 and the switching command unit 38, the delay time setting unit 39 uses the delay time setting unit 39 to stop and start the fuel supply of the liquid phase fuel system FL based on the value detected by the rotation speed sensor 32. A time for delaying the timing from the fuel supply start / stop timing of the gas phase fuel system FG is set, and the fuel supply stop and start of the liquid phase fuel system FL are delayed according to the set delay time.
[0040]
That is, when switching from the liquid phase fuel system FL to the gas phase fuel system FG, the fuel is interrupted by stopping the fuel supply by the liquid phase fuel system FL slightly after the start of fuel supply by the gas phase fuel system FG. Without being supplied to the engine 1. Further, when switching from the gas phase fuel system FG to the liquid phase fuel system FL, the fuel supply from the liquid phase fuel system FL is started by starting the fuel supply by the liquid phase fuel system FL with a slight delay from the stop of the fuel supply by the gas phase fuel system FG. Can be supplied to the engine 1 without overlapping.
[0041]
In setting the delay time by the delay time setting means 39, as shown in FIG. 7, the higher the engine speed, the shorter the delay time is set, resulting in fuel interruption and duplication regardless of the rotational speed. It is effective not to let it.
[0042]
The above is an embodiment of the fourth means described in claims 4 and 7, and as shown in FIG. 6 (A), the occurrence of an air-fuel ratio spike at the time of switching is eliminated, and an air-fuel mixture with a constant air-fuel ratio is supplied to the engine 1. To maintain good operability and exhaust state.
[0043]
【The invention's effect】
As described above, LPG injection comprising a liquid phase fuel system that injects the liquid phase portion of the LPG of the fuel tank into the intake pipe, and a gas phase fuel system that injects the gas phase portion into the intake pipe under specific conditions. In the system, in addition to detecting the pressure and temperature of the LPG in each fuel system, the temperature of the fuel tank is detected and the component ratio of the LPG used is calculated, and this is used as a reference in the liquid phase fuel system According to the present invention, it is determined whether the liquid phase LPG is a complete liquid phase or a gas phase is generated. Even if LPGs having different compositions are used, the liquid phase LPG or the gas phase LPG is always injected. It is possible to obtain a stable engine performance under a wide range of operating conditions by performing accurate control.
[0044]
Further, for this, means for selecting the starting fuel based on the engine temperature and the LPG component ratio, and means for forcibly switching the fuel supply by the liquid phase fuel system to the fuel supply by the gas phase fuel system based on the temperature of the fuel tank. According to the present invention, one or more of means for delaying the supply stop / start of the liquid phase fuel system at the time of fuel switching for a time corresponding to the engine rotation speed is delayed from the supply start / stop of the gas phase fuel system The engine can be started easily and stably, the temperature and pressure rise of the fuel tank is suppressed to reduce various requirements for the injection valve, control system, and parts, and the fuel takeover at the time of switching is interrupted and duplicated. It is possible to carry out smoothly without causing any deterioration in engine operability and exhaust state.
[Brief description of the drawings]
FIG. 1 is a layout view showing an embodiment of the present invention.
FIG. 2 is a pressure-temperature diagram of LPG.
FIG. 3 is a diagram for explaining starting fuel selection based on engine temperature;
FIG. 4 is a diagram showing a relationship between an engine reference temperature for starting fuel selection and an LPG component ratio.
FIG. 5 is a diagram for explaining the use fuel switching according to the fuel tank temperature.
FIG. 6 is a diagram for explaining the relationship between the switching between the liquid phase LPG and the gas phase LPG and the air-fuel ratio.
FIG. 7 is a graph showing a relationship between fuel switching delay time setting and engine speed.
FIG. 8 is a schematic layout diagram of a conventional example.
FIG. 9 is a schematic layout diagram of a different conventional example.
[Explanation of symbols]
1 engine, 2 intake pipe, 7 fuel tank, 8 electronic control unit, 11 liquid phase fuel passage, 15 liquid phase pressure sensor, 16 liquid phase temperature sensor, 18 liquid phase injection valve, 22 gas phase fuel passage, 25 air Phase pressure sensor, 26 gas phase temperature sensor, 27 gas phase injection valve, 31 engine temperature sensor, 32 rotation speed sensor, 33 tank temperature sensor, 35 LPG component calculation means, 36 liquid phase state determination means, 37 start fuel selection means, 38 switching command means, 39 delay time setting means, FL liquid phase fuel system, FG gas phase fuel system,

Claims (2)

燃料タンクに充填されているＬＰＧの液相部分と気相部分とのいずれかを選択して吸気管路に噴射しエンジンに供給する液相燃料系と気相燃料系とを有するものであって、 前記燃料タンクに設置されてその温度を検出するタンク温度センサと、前記液相燃料系の前記燃料タンクから液相噴射弁に至る液相燃料通路に設置されてその内部の液相ＬＰＧの圧力および温度を検出する液相圧力センサおよび液相温度センサと、前記気相燃料系の前記燃料タンクから気相噴射弁に至る気相燃料通路に設置されてその内部の気相ＬＰＧの圧力および温度を検出する気相圧力センサおよび気相温度センサと、前記タンク温度センサと前記気相圧力センサまたは液相圧力センサとが検出した各値に基いてＬＰＧの成分比を算出するＬＰＧ成分計算手段と、前記ＬＰＧ成分計算手段により算出された成分比を基準として、前記液相圧力センサおよび液相温度センサが検出した各値から前記液相燃料系内の液相ＬＰＧの状態を判断する液相状態判定手段と、The fuel tank has a liquid phase fuel system and a gas phase fuel system that select either the liquid phase part or the gas phase part of the LPG filled in the fuel tank, inject it into the intake pipe and supply it to the engine. A tank temperature sensor installed in the fuel tank for detecting the temperature thereof, and a pressure of the liquid phase LPG in the liquid phase fuel passage from the fuel tank of the liquid phase fuel system to the liquid phase injection valve. And a liquid phase pressure sensor and a liquid phase temperature sensor for detecting the temperature, and a pressure and temperature of the gas phase LPG installed in the gas phase fuel passage from the fuel tank of the gas phase fuel system to the gas phase injection valve A gas phase pressure sensor and a gas phase temperature sensor for detecting the LPG component, and an LPG component calculation means for calculating a component ratio of LPG based on each value detected by the tank temperature sensor and the gas phase pressure sensor or the liquid phase pressure sensor; , Liquid phase state determination for determining the state of the liquid phase LPG in the liquid phase fuel system from the values detected by the liquid phase pressure sensor and the liquid phase temperature sensor with reference to the component ratio calculated by the LPG component calculation means. Means,
を具え、前記液相状態判定手段が前記液相燃料系内の液相ＬＰＧを完全な液相と判断したときは前記液相燃料系による燃料供給を行なわせ、前記液相燃料系内に気相を発生していると判断したときは前記気相燃料系による燃料供給を行なわせるようにしたエンジンのＬＰＧ供給装置において、  And when the liquid phase state determining means determines that the liquid phase LPG in the liquid phase fuel system is a complete liquid phase, the fuel supply by the liquid phase fuel system is performed, and the liquid phase fuel system When it is determined that a phase is generated, the engine LPG supply apparatus is configured to perform fuel supply by the gas phase fuel system.
前記タンク温度センサが検出した値に基いて燃料の切換えを行なわせる切換指令手段、を具え、前記切換指令手段は前記燃料タンクが設定温度以上となったとき、前記液相状態判定手段が前記液相燃料系による燃料供給を行なわせる判断をしていても、気相燃料系による燃料供給に切換えさせるようにしたことを特徴とするエンジンのＬＰＧ供給装置。  Switching command means for switching the fuel based on the value detected by the tank temperature sensor, and the switching command means is configured so that when the fuel tank reaches a set temperature or higher, the liquid phase state judging means An LPG supply device for an engine, characterized in that, even if it is determined that fuel supply by a phase fuel system is performed, the fuel supply is switched to fuel supply by a gas phase fuel system. 燃料タンクに充填されているＬＰＧの液相部分と気相部分とのいずれかを選択して吸気管路に噴射しエンジンに供給する液相燃料系と気相燃料系とを有するものであって、 前記燃料タンクに設置されてその温度を検出するタンク温度センサと、前記液相燃料系の前記燃料タンクから液相噴射弁に至る液相燃料通路に設置されてその内部の液相ＬＰＧの圧力および温度を検出する液相圧力センサおよび液相温度センサと、前記気相燃料系の前記燃料タンクから気相噴射弁に至る気相燃料通路に設置されてその内部の気相ＬＰＧの圧力および温度を検出する気相圧力センサおよび気相温度センサと、前記タンク温度センサと前記気相圧力センサまたは液相圧力センサとが検出した各値に基いてＬＰＧの成分比を算出するＬＰＧ成分計算手段と、前記ＬＰＧ成分計算手段により算出された成分比を基準として、前記液相圧力センサおよび液相温度センサが検出した各値から前記液相燃料系内の液相ＬＰＧの状態を判断する液相状態判定手段と、を具え、前記液相状態判定手段が前記液相燃料系内の液相ＬＰＧを完全な液相と判断したときは前記液相燃料系による燃料供給を行なわせ、前記液相燃料系内に気相を発生していると判断したときは前記気相燃料系による燃料供給を行なわせるようにしたエンジンのＬＰＧ供給装置において、It has a liquid phase fuel system and a gas phase fuel system that select either the liquid phase part or the gas phase part of the LPG filled in the fuel tank, inject it into the intake pipe and supply it to the engine. A tank temperature sensor installed in the fuel tank for detecting the temperature thereof, and a pressure of the liquid phase LPG installed in the liquid phase fuel passage from the fuel tank of the liquid phase fuel system to the liquid phase injection valve. And a liquid phase pressure sensor and a liquid phase temperature sensor for detecting the temperature, and a pressure and temperature of the gas phase LPG installed in the gas phase fuel passage from the fuel tank of the gas phase fuel system to the gas phase injection valve. A gas phase pressure sensor and a gas phase temperature sensor for detecting the LPG component, and an LPG component calculation means for calculating a component ratio of LPG based on each value detected by the tank temperature sensor and the gas phase pressure sensor or the liquid phase pressure sensor; , Liquid phase state determination for determining the state of the liquid phase LPG in the liquid phase fuel system from the values detected by the liquid phase pressure sensor and the liquid phase temperature sensor with reference to the component ratio calculated by the LPG component calculation means. And when the liquid phase state determining means determines that the liquid phase LPG in the liquid phase fuel system is a complete liquid phase, fuel is supplied by the liquid phase fuel system, and the liquid phase fuel system When it is determined that a gas phase is generated in the engine, an LPG supply device for an engine in which fuel supply by the gas phase fuel system is performed,
前記始動燃料選定手段はＬＰＧのプロパン比率が高いほど前記基準温度を低温側に移行させて前記気相燃料系による始動燃料供給温度領域を拡張するようにされていることを特徴とするエンジンのＬＰＧ供給装置。  The starter fuel selection means extends the starter fuel supply temperature range by the gas phase fuel system by shifting the reference temperature to a lower temperature side as the propane ratio of LPG is higher. Feeding device.
JP2002035085A 2002-02-13 2002-02-13 Engine LPG supply device Expired - Fee Related JP3830826B2 (en)

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