JP3756995B2

JP3756995B2 - Combustion gas supply method and structure for gas engine

Info

Publication number: JP3756995B2
Application number: JP20051896A
Authority: JP
Inventors: 徹武本
Original assignee: Yanmar Co Ltd
Current assignee: Yanmar Co Ltd
Priority date: 1996-07-30
Filing date: 1996-07-30
Publication date: 2006-03-22
Anticipated expiration: 2016-07-30
Also published as: JPH1047165A

Description

【０００１】
【発明の属する技術分野】
本発明は、希薄燃料ガス混合気を給気とする副室式ガスエンジンにおける、点火栓の燻りの防止及び燃焼効率の向上を図るための燃料ガスの供給方法及び構造に関する。
【０００２】
【従来の技術】
従来、燃焼主室に、給気弁を有して希薄燃料ガス混合気を供給する給気ポートと、排気弁を有する排気ポートとを連通させ、該燃焼主室に連通する燃焼副室に燃料ガス供給弁と点火栓とを臨ませた構造のガスエンジンにおいては、燃料ガス供給弁は、ピストン下降に伴う燃焼主室及び燃焼副室内圧の降下と、燃料ガス設定圧との差圧にて自動的に開弁する自動弁である。
一方、一燃焼行程（ピストンは二往復動する）中において、給気弁及び排気弁の動きに伴い、給気行程、給排気オーバーラップ行程、排気行程、圧縮行程と移行するが、この中で、燃料ガス供給弁は、ピストン上死点付近の給排気オーバーラップ行程の後期より、ピストン下降期に重なる給気行程にかけて、一回のみ開弁する。即ち、燃料ガス供給は以上の一燃焼行程につき一回のみ行われる。
【０００３】
【発明が解決しようとする課題】
このような従来の副室式ガスエンジンにおいては、燃料ガス供給弁の構造上、燃料ガスの供給時期や供給量は制限され、機関の運転範囲、即ち、燃焼副室への燃料供給量の設定幅及び燃焼主室への燃料供給量の設定幅を狭くしていた。そのため、燃焼主室内における燃料ガスの一層の希薄化を図ることができず、排気エミッション（ＮＯ_X）を、ある値以下に低減することが困難であった。
具体的に説明すると、排気中のＮＯ_X低減のためには、点火栓付近（燃焼副室内）に、希薄化されていない状態の燃料ガスがあり、燃焼主室において、燃焼副室に近い側に可燃範囲の混合気、そして、それよりも遠くに超希薄混合気が存在する、混合気の層状態を実現することが理想である。
しかし、従来は、燃料ガス供給弁の開弁が、給気行程の全域にわたり、即ち、燃料ガスの供給期間が長いため、燃料ガスのかなりの量が燃焼主室内の広い範囲に及び、このような混合気の層状化を実現することができないので、排気の低ＮＯ_X化には限界があったのである。
【０００４】
また、もう一つの問題点として、排気ポートに直接連通している燃焼主室からは、排気弁が開弁することで、燃焼ガスが充分に掃気されるものの、燃焼副室内の燃焼ガスは、排気ポートが直接連通していないので、充分に掃気できず、この残留燃焼ガスは、排気行程以後、給排気オーバーラップ行程を経て、給気行程になると、排気弁が閉弁しており、更に、給気弁を介して給気ポートより燃焼主室に供給される希薄燃料ガス混合気圧のため、燃焼主室側には排出されにくく、従って、圧縮行程になって点火栓の点火時期になっても、燃焼副室内に残留し続けるので、点火栓は燻りを生じやすく、点火反応性が悪くなるという不具合があった。
【０００５】
【課題を解決するための手段】
本発明においては、燃焼主室に、給気弁を有して希薄燃料ガス混合気を供給する給気ポートと、排気弁を有する排気ポートとを連通させ、該燃焼主室に連通する燃焼副室に、燃料ガス供給弁と点火栓とを臨ませた構造のガスエンジンにおいて、以上のような課題を解決すべく、次のような手段を用いるものである。
【０００６】
即ち、請求項１においては、給排気オーバーラップ行程の早期と、給気行程の後期に、燃料ガス供給を行う。
【０００７】
また、請求項２においては、給排気オーバーラップ行程の早期と、給気行程の後期に、燃料ガス供給を行う燃料ガス供給方法を行う燃料ガス供給方法を採用するガスエンジンにおいて、燃料ガス供給弁の上流側に供給圧の異なる二つの電磁弁を配設する。
【０００８】
また、請求項３においては、給排気オーバーラップ行程の早期と、給気行程の後期に、燃料ガス供給を行う燃料ガス供給方法を採用するガスエンジンにおいて、該燃料ガス供給弁の動きに連動する弁傘部上流への連通路を設け、該燃料ガス供給弁を内設する弁ケースに、該連通路に連通可能なバイパス通路を設ける。
【０００９】
或いは、請求項４においては、給排気オーバーラップ行程の早期と、給気行程の後期に、燃料ガス供給を行う燃料ガス供給方法を採用するガスエンジンにおいて、該燃料ガス供給弁の弁傘部上部に一体状のシール弁を設け、該燃料ガス供給弁を内設する弁ケースに、該シール弁と着脱可能なシール座を設ける。
【００１０】
或いは、給排気オーバーラップ行程の早期と、給気行程の後期に、燃料ガス供給を行う燃料供給方法において、該燃料ガス供給弁の動きに連動する弁傘部上流への連通路と、該燃料ガス供給弁を内設する弁ケースに設けたバイパス通路とが連通することにより、燃料ガスを副室に供給する。
【００１１】
或いは、給排気オーバーラップ行程の早期と、給気行程の後期に、燃料ガス供給を行う燃料供給方法において、該燃料ガス供給弁の弁傘部上部に一体状のシール弁を設け、該燃料ガス供給弁を内設する弁ケースに、該シール弁と当接可能なシール座を設け、弁の動きに伴う該シール弁と該シール座との着脱により燃料ガスを供給制御する。
【００１２】
【発明の実施の形態】
本発明を、添付の図面を基に説明する。
図１は従来の燃料ガス供給方法による一燃焼行程図、図２は燃料ガスを２回に分けて供給する燃料ガス供給方法を採用する一燃焼行程図、図３は空気供給と燃料ガス供給とを行う燃料ガス供給方法を採用する一燃焼行程図、図４はガスエンジンのシリンダー部分の側面断面図であって、図１における燃料ガス供給時の図、図５は同じく側面断面図であって、（ａ）は図２における一回目の燃料ガス供給時の図、（ｂ）は同じく二回目の燃料ガス供給時の図、図６は同じく側面断面図であって、（ａ）は図３における空気供給時の図、（ｂ）は同じく燃料ガス供給時の図、図７は図２及び図３図示の燃料ガス供給方法を採用した場合における効果を示すグラフ図で、（ａ）は運転可能範囲を示す図、（ｂ）は排出ＮＯ_X特性を示す図、（ｃ）は熱効率を示す図、図８は供給圧の異なる二個の電磁弁より燃料ガス供給弁３に燃料ガスを供給する構造を示す側面略図、図９はバイパス通路２０、環状連通路１８、及び垂直連通路１７ａを設けた構造で、開弁時に燃料ガス供給を二回に分割可能とした燃料ガス供給弁３の側面断面図で、（ａ）は燃料ガス供給弁３の閉弁時の図、（ｂ）は燃料ガス供給弁３が開弁され、燃料ガスＧが燃焼副室５に供給されている時の図、（ｃ）は燃料ガス供給弁３が開弁しつつも、燃料ガスＧが燃焼副室５に供給されない時の図、図１０はシール弁２１とシール座２２ｃを設けた構造で、開弁時に燃料ガス供給を二回に分割可能とした燃料ガス供給弁３の側面断面図で、（ａ）は燃料ガス供給弁３の閉弁時の図、（ｂ）は燃料ガス供給弁３が開弁され、燃料ガスＧが燃焼副室５に供給されている時の図、（ｃ）は燃料ガス供給弁３が開弁しつつも、燃料ガスＧが燃焼副室５に供給されない時の図である。
【００１３】
まず、ガスエンジンの燃焼室及びその周辺構造について、図４等を基に説明する。
シリンダー内において、ピストンＰが上下摺動可能に内設されており、該シリンダー内におけるピストンＰの上方空間が、燃焼主室８となる。燃焼主室８の中央部より上方に、燃焼副室５が連通していて、該燃焼副室５の上端部に燃料ガス供給弁３と点火栓４を臨ませてある。更に、燃焼主室８には、給気ポート１と排気ポート７が連通していて、給気ポート１には給気弁２を、排気ポート７には排気弁６を内装している。給気ポート１には、希薄燃料ガス混合気ＬＧが供給され、燃料ガス供給弁３からは、混合していない通常の燃料ガスＧが供給される。
【００１４】
次に、一燃焼行程中における給気弁２と排気弁６の動きに伴う給・排気行程を図１等にて説明する。
一燃焼行程中に、ピストンＰは上死点ＴＤＣ・下死点ＢＤＣ間を二往復する。まず、給気弁２・排気弁６ともに閉弁した状態で、ピストンＰが上死点ＴＤＣに達し、燃焼主室８及び燃焼副室５内が圧縮されて、点火栓４により、内部に充填された燃焼ガス混合気が燃焼されて、爆発が起こり、ピストンＰを押し下げる膨張行程となる。ピストンＰが下死点ＢＤＣ直前になると、排気弁６が開弁し始め、ピストン上昇中は、排気弁６のみ開弁している排気行程となっている。やがて、ピストンＰが上死点ＴＤＣ直前になると、給気弁２が開弁を開始し、上死点ＴＤＣ付近では、給排気オーバーラップ行程となっている。更に、ピストンＰが下降し、排気弁６は閉弁して、給気弁２のみ開弁している給気行程となる。やがて、ピストンＰが下死点ＢＤＣを過ぎ、上昇し始める時に給気弁２も閉弁し、両弁２・６が閉弁した状態でピストンＰが上昇する圧縮行程となる。そして、ピストンＰが上死点ＴＤＣに達する直前に、前記の圧縮混合気の爆発が起こり、再び膨張行程へと移行する。
【００１５】
以上のような一燃焼行程中において、従来は、図１及び図４の如く、ピストンＰが上死点ＴＤＣより下降することで、燃焼主室８及び燃焼副室５の内圧が低下する、給排気オーバーラップ行程後期より給気行程にかけて、自動弁である燃料ガス供給弁３が開弁して、一回の燃料ガスの供給がなされていた。これに対して本案の燃料ガス供給方法は、一燃焼行程中に、図２の如く、燃料ガスを二回供給する方法、或いは、図３の如く、初期に空気を供給し、後期に燃料ガスを供給する方法となっている。
【００１６】
まず、燃料ガスを二回供給する図２図示の燃料ガス供給方法では、燃料ガス供給が、最初に、排気行程後期より給排気オーバーラップ行程にかけての時期になされ、次に、給気行程の後期になされる。最初の燃料ガス供給期のシリンダーの様子を、図５（ａ）より説明すると、排気弁６は殆ど閉弁しかけている一方、給気弁２が開弁し始めている。この時、燃焼主室８においては、排気弁６の開弁により、排気ポート７に燃焼ガスＢＧが殆ど掃気されてしまっているが、燃焼副室５には燃焼ガスＢＧが充分掃気されずに残留した状態となっている。この燃焼副室５内の残留燃焼ガスＢＧは、これ以後の給排気オーバーラップ行程、給気行程になっても、排気弁６が閉弁してしまっている上に、給気弁２が開弁して、給気ポート１より燃焼主室８内に導入される希薄燃料ガス混合気ＬＧの気圧により、燃焼主室８側に排出されにくくなり、燃焼副室５内に残留し続けるので、圧縮行程における点火栓４の点火時になっても、この残留燃焼ガスＢＧのために、点火栓４が燻ってうまく点火しないという不具合をもたらす。
【００１７】
そこで、この時期に燃料ガス供給弁３を開弁して、燃料ガスＧを燃焼副室５内に供給し、この燃料ガスＧの圧力によって、燃焼副室５内の残留燃焼ガスＢＧを掃気する。燃焼副室５より燃焼主室８へと掃気された残留燃焼ガスＢＧは、閉弁しかけているが僅かに開弁している排気弁６を介して、排気ポート７に掃気されるのである。こうして、燃焼副室５内に燃焼ガスＢＧが残留せず、点火栓４が燻りにくくなる。
【００１８】
次に、給気行程後期に燃料ガスＧを供給するが、この時のシリンダーの様子を図５（ｂ）より説明する。
給気行程前期においては、燃料ガス供給弁３を閉弁したままとしており、従って、燃焼主室８内には、給気弁２を介して、給気ポート１からの希薄燃料ガス混合気ＬＧのみが導入され、ピストンＰが下降した状態における燃焼主室８内全域に希薄燃料ガス混合気ＬＧが充分に拡散する。この状態から給気行程後期の短い期間にて、燃料ガス供給弁３より燃料ガスＧの供給がなされる。そのため、燃焼副室５より燃焼主室８にかけて、点火栓３に近い燃焼副室５内には希薄化されない燃料ガスＧ、その周辺（例えば燃焼副室５より燃焼主室８への連通部分）に可燃範囲の混合気、それより更に遠くの燃焼主室８内に超希薄混合気が存在する、排気中のＮＯ_X低減に理想的な混合気の層状態が実現するのである。
【００１９】
次に、図２図示の如く、一燃焼行程中に燃料ガス供給を二回行うための燃料ガス供給構造の三つの構成例を、図８乃至図１０より説明する。
まず、各構成例の構造において、燃料ガス供給弁３は、基本的には従来と同様のチェック弁構造の自動弁であって、ピストンＰの下降に伴う燃焼主室８及び燃焼副室５内圧の下降に伴って開弁するものであるから、その開弁開始時期と開弁終了時期は、図１にて示す従来の燃料供給方法における燃料ガス供給期間の開始時と終了時期に略一致する。従って、図２図示のように燃料ガス供給時期を分割するには、開弁状態の燃料ガス供給弁３に（詳しくは、その弁傘部３ａの上流に）対して、該燃料ガス供給弁３の上流側の燃料ガス供給路からの燃料ガスを供給・停止制御すればよい。つまり、給排気オーバーラップ行程早期と給気行程後期の二回、燃料ガスＧを燃料ガス供給弁３に供給し、両供給期の間は、燃料ガスＧの供給を停止するのである。
【００２０】
図８図示の構成例においては、燃料ガス供給弁３の上流側（燃料ガス供給弁３の弁傘部３ａより上方）にて、該燃料ガス供給弁３の弁室３ｂより上方に供給ガス通路９を設け、該供給ガス通路９は、電磁弁１０を介設する第一燃料ガス供給路１１と、電磁弁１２を介設する第二燃料ガス供給路１３とに分岐している。一回目の給排気オーバーラップ行程早期には、電磁弁１０を開弁して、第一燃料ガス供給路１１より燃料ガス供給弁３に燃料を供給し、その後、電磁弁１０を閉弁し、給気行程後期に、今度は電磁弁１２を開弁して、第二燃料ガス供給路１３より燃料ガス供給弁３に燃料を供給するのである。
【００２１】
このように、電磁弁を介する燃料ガス供給路を二個、供給ガス通路９に連通させているのは、図２の如く、要求される燃料ガス供給圧が、給排気オーバーラップ行程早期におけるものと、給気行程後期におけるものとで異なるからである。給排気オーバーラップ行程早期においては、燃焼副室５内の残留燃焼ガスＢＧの掃気のため、燃料ガス供給弁３からの燃料ガスＧの噴射を高圧にしたい。そこで電磁弁１０の供給設定圧は高く設定されている。一方、給気行程後期においては燃焼副室５内及び燃焼副室５から燃焼主室８への連通部分にのみ濃燃料ガス混合気を形成するため、燃料ガス供給弁３からの燃料ガスＧは、低圧で噴射したい。そこで、電磁弁１２の供給設定圧を低くしている。このように、両電磁弁１０・１２にて異なる供給設定圧を設定しているのである。
【００２２】
次に、図９図示の燃料ガス供給弁の構造を説明する。
内部に弁室を形成する弁本体１５内に、バネ１４を巻装したチェック弁の燃料ガス供給弁３が上下摺動可能に内設され、その下端は弁傘部３ａとなっていて、弁本体１５下端より下方に突出している。該燃料ガス供給弁３の弁傘部３ａよりも上方には、上部ピストン１６と下部ピストン１７が平行状に環設されていて、両ピストン１６・１７間には本体１５内の弁室にて環状連通路１８が形成されている。また、下部ピストン１７には、環状連通路１８と、弁傘部３ａ上方の弁室内との間を連通する垂直連通路１７ａを貫通状に穿設している。そして、弁本体１５の壁部には、上部ピストン１６上方の弁室の上部に対して燃料ガスＧを常時供給する燃料ガス供給通路１９が穿設され、一方、それより下方位置にて、弁本体１５の壁部に、弁室に対して上部連通路２０ａと下部連通路２０ｂとを連通する側面視コの字状のバイパス通路２０が穿設されており、上部ピストン１６上方の弁室に対して上部連通路２０ａが連通し、また、下部連通路２０ｂは、上部ピストン１６または下部ピストン１７に閉鎖されるか、或いは環状連通路１８に連通するものである。
【００２３】
（ａ）の如く、閉弁状態では、燃料ガス供給弁３が、その往復動域の上死点に位置しているので、ピストン１７の上部がバイパス通路２０の下部連通路２０ｂを閉鎖している。この状態から、給排気オーバーラップ行程掃気になると、燃焼副室５内圧の降下で、燃料ガス供給弁３が下降し始め、それとともに、（ｂ）の如く、環状連通路１８が下部連通路２０ｂに連通し、上部ピストン１６上方の弁室よりバイパス通路２０、環状連通路１８及び垂直連通路１７ａを介して、開弁状態の燃料ガス供給弁３の弁傘部３ａ上部に燃料ガスＧが供給され、一回目の燃料ガスＧの燃焼副室５への供給がなされる。
【００２４】
なおも燃料ガス供給弁３が下降すると、今度は上部ピストン１６が下部連通路２０ｂを閉鎖し始め、やがて（ｃ）の如く、下死点に達して、下部連通路２０ｂは完全に閉鎖される。そして、今度は燃料ガス供給弁３が上昇し、やがて、（ｂ）図示の状態となって、給気行程後期における、二回目の燃料ガスＧの燃焼副室５への供給がなされる。そして燃料ガス供給弁３が上死点に達して、（ａ）の閉弁状態に戻り、燃料ガスＧの燃焼副室５への燃料供給を終了する。
【００２５】
図１０図示の構成例について説明する。燃料ガス供給弁３には、弁傘部３ａよりも上方において、シール弁２１を環設しており、一方、弁ケース２２内の弁室は広幅の上部弁室２２ｂと狭幅の下部弁室２２ｄとを、シール座２２ｃを介して連続状に形成している。弁ケース２２の壁部において、シール弁２１よりも上方部の上部弁室２２ｂに連通する燃料ガス供給通路２２ａが穿設されており、シール座２１の外縁部と上部弁室２２ｂの内壁面との間には隙間がある。
【００２６】
まず、（ａ）の如く、閉弁状態では、燃料ガス供給弁３が上死点にあり、シール弁２１は上部弁室２２ｂ内にて、シール座２２ｃよりも上方に離れた状態で存在している。やがて、（ｂ）の如く、燃料ガス供給弁３が下降して開弁し、シール弁２１より上方の上部弁室２２ｂ内より、シール弁２１と上部弁室２２ｂの内壁面との間の隙間を介して、下部弁室２２ｄに燃料ガスＧが導入され、給排気オーバーラップ行程早期における第一回目の燃焼副室５に向けての燃料ガスＧの供給がなされる。やがて、給排気オーバーラップ行程を過ぎて、給気行程早期になると、（ｃ）の如く、シール弁２１がシール座２２ｃに着座して、この間、上部弁室２２ｂから下部弁室２２ｄへの燃料ガス供給は停止する。給気ガス供給弁３が下死点となった後、給気行程後期にて、再び上昇して（ｂ）の状態となり、二回目の燃料ガスＧの燃焼副室５への供給がなされ、やがて、（ａ）の閉弁状態に戻るのである。
【００２７】
なお、以上の図８乃至図１０図示の三構成例において、燃料ガス供給弁３は、一回目の燃料ガス供給期と、二回目の燃料ガス供給期との間の供給停止期においても、開弁状態（弁傘部３ａが下降した状態）となっているので、完全には燃料ガス供給は停止せず、若干の燃料ガスＧが燃焼副室５に供給され続ける。
【００２８】
次に、図３図示のもう一つの燃料ガス供給方法を説明する。
これは、図２図示の燃料ガス供給方法における一回目の燃料ガスＧの燃焼副室５への供給を、空気の供給に代えるものである。即ち、図２図示の燃料ガス供給方法における給排気オーバーラップ行程早期の燃料ガスＧの供給は、元来の燃料ガス供給の意味よりもむしろ燃焼副室５内の残留燃焼ガスＢＧの掃気を目的としたものである。従って、給気行程後期における二回目の燃料ガスＧの供給量で、目的とする混合気の状態が達成できるのであれば、給排気オーバーラップ行程早期における燃焼ガスＢＧの掃気を、燃料ガスＧで行う必要はない。また、給排気オーバーラップ行程より早い排気行程の後期より掃気を開始すれば、より確実な掃気が可能である。そこで、図３及び図６（ａ）の如く、排気行程の後期より給排気オーバーラップ行程早期においては、空気Ａを燃焼副室５に供給して、残留燃焼ガスＢＧの掃気をするようにしている。
【００２９】
このためには、空気を燃焼副室５に導く構成が必要だが、空気は、図６（ａ）の如く、燃焼ガス供給弁３にて供給可能とすれば、新たに空気供給用の弁等を設ける必要もない。燃料ガス供給弁３に対して、空気Ａと燃料ガスＧとの供給を切り替える構成が必要だが、図８図示の燃料ガス供給構造を用いて、第一燃料ガス供給路１１を空気供給路に代え、電磁弁１０の開弁にて空気を燃料ガス供給弁３に供給する構造とすればよい。なお、燃料ガス供給弁３の上流側の空気圧を高めることで、給排気オーバーラップ行程よりもやや早い排気行程後期より、空気供給を開始することができるのである。
【００３０】
そして、給気行程の後期には、図３及び図６（ｂ）の如く、図２図示の燃料ガス供給方法と同様に、燃料ガス供給弁３より、短期間に少量の燃料ガスＧを燃焼副室５に供給することで、排気中のＮＯ_X低減に理想的な混合気の層状態を形成するのである。
【００３１】
本案に係る図２及び図３図示の燃料ガス供給方法を採用した場合の効果について、図７図示の各グラフより説明する。
各グラフにおいて、Ｘは従来の図１図示の燃料ガス供給方法を採用した場合、Ｙは本構成に係る図２及び図３図示の燃料ガス供給方法を採用した場合を示す。まず、（ａ）の如く、ガスエンジンの運転可能範囲は、燃料ガス供給弁３からの燃料ガスＧの供給量（副室供給ガス流量）と、燃焼主室８内における燃料ガスＧと希薄燃料ガス混合気ＬＧの供給による燃料ガス成分量（主室供給ガス量）との関係において、斜線範囲となっている。この範囲内において、従来は、燃料ガス供給弁３からの供給量が少なくても、燃焼主室８内の燃料ガス成分が多くなってしまうことが判る（（ａ）中Ｘ）。これは、燃料ガス供給弁３より供給された燃料ガスＧが拡散してしまって、燃焼主室８内のガス成分が多くなってしまい、排気の低ＮＯ_X化に理想的な、混合気の層状態となっていないことに由来する。この状態からなおも燃料ガス供給弁３からの燃料ガス供給量を増加しても、主室供給ガス量が多すぎて運転可能範囲を超えてしまう。従って、燃料ガスＧの供給設定量は非常に制限される。また、（ｂ）中Ｘの如く、燃料ガス供給弁３からの燃料ガス供給量（副室供給ガス流量）が少ない状態でも、排気中のＮＯ_X量が高くなる。
【００３２】
対して、図２及び図３図示の燃料ガス供給方法を用いると、（ａ）中Ｙの如く燃料ガス供給弁３からの燃料ガス供給量（副室供給ガス流量）が増大しているにも関わらず、主室供給ガス量が少なくなっており、充分に運転可能範囲に入っている。また、これは、前記の燃焼副室５から燃焼主室８にかけての混合気の層状化に由来するものであり、（ｂ）中Ｙの如く、燃料ガス供給弁３からの燃料ガス供給量が多く設定されているにもかかわらず、排気中のＮＯ_X量も少なくなっている。なお（ｃ）の如く、副室供給ガス流量が増大するにもかかわらず、熱効率は従来のまま維持されている。
【００３３】
【発明の効果】
本発明は、副室式ガスエンジンの燃料ガス供給方法を、以上のようなものとしたので、次のような効果を奏する。
まず、請求項１記載の如き方法を用いることで、給排気オーバーラップ行程早期に燃料ガスを供給することで、燃焼副室内に残留する燃焼ガスを燃焼主室に掃気し、更に、閉弁しかけの排気弁より掃気することができ、このため、点火栓が燻りにくくなり、点火反応性が向上する。そして、後の吸入行程後期の燃料ガス供給までに燃料ガス供給が停止されることで、既に吸入行程で給気ポートより燃焼主室に希薄燃焼ガス混合気が拡散充填され、吸入行程後期における二回目の燃料ガスは、短い期間なので供給される燃料ガスが拡散せず、燃焼副室より燃焼主室にかけて、点火栓に近い所に、略燃料ガスそのままの濃い混合気、その周辺に可燃範囲の混合気、そして更に遠い所に希薄混合気という、混合気の層状態を形成するので、排気中のＮＯ_X低減に貢献するのである。
【００３４】
また、請求項２の如く、供給圧の異なる二個の電磁弁を燃料ガス供給弁の上流に設けることにより、供給圧の高い電磁弁を、給排気オーバーラップ行程早期における燃料ガス供給期、または空気供給期に開弁させることで、燃料ガス或いは空気が高圧で燃焼副室に供給され、燃焼ガスの掃気を良好にすることができ、一方、供給圧の低い電磁弁を、給気行程後期における燃料ガス供給期に開弁することで、低圧の燃料ガスを短期間供給し、排気のＮＯ_X低減に理想的な混合気の層状態を形成することができる。
【００３５】
更に、請求項３の如き燃料ガス供給構造とすることにより、燃料ガス供給弁の開弁時（ピストン下降時の給気行程）の動きの中で、自然に弁傘部上流への連通路とバイパス通路とが連通して燃料ガス供給がなされ、また、連通が閉ざされることで、燃料ガス供給が停止されるものであり、これにより、請求項１の如く、一燃焼行程中に二回の燃料ガス供給がなされ、前記の効果を得るものである。
【００３７】
また、請求項４の如き燃料ガス供給構造とすることにより、燃料ガス供給弁の開弁時（ピストン下降時の給気行程）の動きの中で、自然にシール弁とシール座が離れて燃料ガス供給がなされ、また、シール座に着座することで燃料ガス供給が停止するものであり、これにより、請求項１の如く、一燃焼行程中に二回の燃料ガス供給がなされ、前記の効果を得るものである。
【図面の簡単な説明】
【図１】従来の燃料ガス供給方法による一燃焼行程図である。
【図２】燃料ガスを２回に分けて供給する燃料ガス供給方法を採用する一燃焼行程図である。
【図３】空気供給と燃料ガス供給とを行う燃料ガス供給方法を採用する一燃焼行程図である。
【図４】ガスエンジンのシリンダー部分の側面断面図であって、図１における燃料ガス供給時の図である。
【図５】同じく側面断面図であって、（ａ）は図２における一回目の燃料ガス供給時の図、（ｂ）は同じく二回目の燃料ガス供給時の図である。
【図６】同じく側面断面図であって、（ａ）は図３における空気供給時の図、（ｂ）は同じく燃料ガス供給時の図である。
【図７】図２及び図３図示の燃料ガス供給方法を採用した場合における効果を示すグラフ図で、（ａ）は運転可能範囲を示す図、（ｂ）は排出ＮＯ_X特性を示す図、（ｃ）は熱効率を示す図である。
【図８】供給圧の異なる二個の電磁弁より燃料ガス供給弁３に燃料ガスを供給する構造を示す側面略図である。
【図９】バイパス通路２０、環状連通路１８、及び垂直連通路１７ａを設けた構造で、開弁時に燃料ガス供給を二回に分割可能とした燃料ガス供給弁３の側面断面図で、（ａ）は燃料ガス供給弁３の閉弁時の図、（ｂ）は燃料ガス供給弁３が開弁され、燃料ガスＧが燃焼副室５に供給されている時の図、（ｃ）は燃料ガス供給弁３が開弁しつつも、燃料ガスＧが燃焼副室５に供給されない時の図である。
【図１０】シール弁２１とシール座２２ｃを設けた構造で、開弁時に燃料ガス供給を二回に分割可能とした燃料ガス供給弁３の側面断面図で、（ａ）は燃料ガス供給弁３の閉弁時の図、（ｂ）は燃料ガス供給弁３が開弁され、燃料ガスＧが燃焼副室５に供給されている時の図、（ｃ）は燃料ガス供給弁３が開弁しつつも、燃料ガスＧが燃焼副室５に供給されない時の図である。
【符号の説明】
Ｐピストン
Ｇ燃料ガス
ＬＧ希薄燃料ガス混合気
ＢＧ燃焼ガス
１給気ポート
２給気弁
３燃料ガス供給弁
３ａ弁傘部
３ｂ弁室
４点火栓
５燃焼副室
６排気弁
７排気ポート
８燃焼主室
９供給ガス通路
１０電磁弁
１１第一燃料ガス供給路
１２電磁弁
１３第二燃料ガス供給路
１４バネ
１５弁ケース
１６上部ピストン
１７下部ピストン
１７ａ垂直連通路
１８環状連通路
１９燃料ガス供給通路
２０バイパス通路
２０ａ上部連通路
２０ｂ下部連通路
２１シール弁
２２弁ケース
２２ａ燃料ガス供給通路
２２ｂ上部弁室
２２ｃシール座
２２ｄ下部弁室[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel gas supply method and structure for preventing spark plugs and improving combustion efficiency in a sub-chamber gas engine using a lean fuel gas mixture as a supply air.
[0002]
[Prior art]
Conventionally, an intake port having an intake valve and supplying a lean fuel gas mixture and an exhaust port having an exhaust valve are communicated with the combustion main chamber, and fuel is supplied to the combustion subchamber communicating with the combustion main chamber. In a gas engine having a structure that faces a gas supply valve and a spark plug, the fuel gas supply valve has a differential pressure between the drop in the pressure of the combustion main chamber and the combustion sub chamber as the piston descends and the fuel gas set pressure. It is an automatic valve that opens automatically.
On the other hand, during one combustion stroke (piston reciprocates twice), the movement of the supply valve and exhaust valve shifts to the supply stroke, supply / exhaust overlap stroke, exhaust stroke, and compression stroke. The fuel gas supply valve is opened only once from the latter stage of the supply / exhaust overlap process near the top dead center of the piston to the supply process that overlaps the piston lowering period. That is, the fuel gas is supplied only once per the above-described combustion stroke.
[0003]
[Problems to be solved by the invention]
In such a conventional sub-chamber gas engine, the fuel gas supply timing and supply amount are limited due to the structure of the fuel gas supply valve, and the operating range of the engine, that is, the setting of the fuel supply amount to the combustion sub-chamber is set. The width and the setting range of the fuel supply amount to the main combustion chamber were narrowed. For this reason, the fuel gas in the combustion main chamber cannot be further diluted, and exhaust emission (NO) _X ) Is less than a certain value.
More specifically, NO in exhaust gas _X For reduction, there is undiluted fuel gas in the vicinity of the spark plug (combustion subchamber), in the main combustion chamber, the mixture in the combustible range on the side close to the combustion subchamber, and more However, it is ideal to realize a layered state of an air-fuel mixture in which an ultra-lean air-fuel mixture exists in the distance.
However, conventionally, since the fuel gas supply valve is opened over the entire supply stroke, that is, the fuel gas supply period is long, a considerable amount of the fuel gas extends over a wide range in the combustion main chamber. Because it is not possible to realize a stratified mixture, _X There was a limit to the transformation.
[0004]
Another problem is that although the combustion gas is sufficiently scavenged by opening the exhaust valve from the combustion main chamber directly communicating with the exhaust port, the combustion gas in the combustion sub-chamber is Since the exhaust port is not in direct communication, sufficient scavenging cannot be performed, and this residual combustion gas passes through the supply / exhaust overlap stroke after the exhaust stroke, and when the intake stroke is reached, the exhaust valve is closed. Because of the lean fuel gas mixture pressure supplied from the intake port to the combustion main chamber via the intake valve, it is difficult to discharge to the combustion main chamber side, so the compression stroke becomes the ignition timing of the spark plug However, since it continues to remain in the combustion subchamber, the spark plug is liable to be blown, resulting in poor ignition reactivity.
[0005]
[Means for Solving the Problems]
In the present invention, the combustion main chamber is connected to an air supply port that has an air supply valve and supplies a lean fuel gas mixture, and an exhaust port that has an exhaust valve, and is connected to the combustion main chamber. In a gas engine having a structure in which a fuel gas supply valve and a spark plug are faced in the chamber, the following means are used in order to solve the above problems.
[0006]
That is, In claim 1 The fuel gas is supplied at an early stage of the supply / exhaust overlap process and at a later stage of the supply process.
[0007]
Also, In claim 2 Fuel gas that supplies fuel gas early in the supply / exhaust overlap process and late in the supply process Fuel to perform supply method In a gas engine that employs a gas supply method, two electromagnetic valves having different supply pressures are disposed upstream of a fuel gas supply valve.
[0008]
Also, In claim 3 In a gas engine that employs a fuel gas supply method that supplies fuel gas at an early stage of the supply / exhaust overlap process and at a later stage of the supply process, the connection to the upstream of the valve head portion linked to the movement of the fuel gas supply valve A passage is provided, and a bypass passage capable of communicating with the communication passage is provided in a valve case in which the fuel gas supply valve is provided.
[0009]
Or In claim 4 In a gas engine that employs a fuel gas supply method for supplying fuel gas at an early stage of the supply / exhaust overlap process and at a later stage of the supply process, an integral seal valve is provided on the upper portion of the valve head of the fuel gas supply valve. A seal seat detachable from the seal valve is provided in a valve case provided with the fuel gas supply valve.
[0010]
Alternatively, in a fuel supply method for supplying fuel gas at an early stage of the supply / exhaust overlap process and at a later stage of the supply process, the communication path to the upstream of the valve head portion linked to the movement of the fuel gas supply valve, and the fuel The fuel gas is supplied to the sub chamber by communicating with a bypass passage provided in a valve case in which the gas supply valve is provided.
[0011]
Alternatively, in a fuel supply method in which fuel gas is supplied at an early stage of the supply / exhaust overlap process and at a later stage of the supply process, an integral seal valve is provided on an upper portion of the valve head of the fuel gas supply valve, and the fuel gas is supplied. A seal seat capable of coming into contact with the seal valve is provided in a valve case in which the supply valve is provided, and fuel gas is supplied and controlled by attaching and detaching the seal valve and the seal seat as the valve moves.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described with reference to the accompanying drawings.
FIG. 1 is a one-stroke process diagram according to a conventional fuel gas supply method, FIG. 2 is a one-stroke process diagram that employs a fuel gas supply method that supplies fuel gas in two steps, and FIG. 3 is an air supply and fuel gas supply method. FIG. 4 is a side sectional view of a cylinder portion of a gas engine, FIG. 4 is a side sectional view of the fuel gas supply in FIG. 1, and FIG. 5 is a side sectional view of the same. FIG. 6A is a diagram when the fuel gas is supplied for the first time in FIG. 2, FIG. 6B is a diagram when the fuel gas is supplied for the second time, FIG. 6 is a side sectional view, and FIG. FIG. 7B is a diagram when the fuel gas is supplied, FIG. 7 is a graph showing the effect when the fuel gas supply method shown in FIGS. 2 and 3 is adopted, and FIG. Figure showing possible range, (b) is NO _X FIG. 8C is a diagram showing characteristics, FIG. 8C is a diagram showing thermal efficiency, FIG. 8 is a schematic side view showing a structure for supplying fuel gas to the fuel gas supply valve 3 from two electromagnetic valves having different supply pressures, and FIG. FIG. 6 is a side sectional view of the fuel gas supply valve 3 having a structure in which an annular communication path 18 and a vertical communication path 17a are provided and the fuel gas supply can be divided into two when the valve is opened. FIG. 3 is a view when the valve is closed, (b) is a view when the fuel gas supply valve 3 is opened and the fuel gas G is supplied to the combustion sub-chamber 5, and (c) is a view when the fuel gas supply valve 3 is opened. FIG. 10 shows a structure in which the fuel gas G is not supplied to the combustion sub-chamber 5 while valved. FIG. 10 shows a structure in which a seal valve 21 and a seal seat 22c are provided, and the fuel gas supply can be divided into two when the valve is opened. 2 is a side cross-sectional view of the fuel gas supply valve 3, wherein (a) is a view when the fuel gas supply valve 3 is closed, and (b) is a fuel gas supply valve. FIG. 4C is a view when the valve 3 is opened and the fuel gas G is supplied to the combustion subchamber 5; FIG. 5C is a diagram illustrating a state where the fuel gas G is supplied to the combustion subchamber 5 while the fuel gas supply valve 3 is open. It is a figure when not done.
[0013]
First, the combustion chamber of the gas engine and the surrounding structure will be described with reference to FIG.
In the cylinder, the piston P is installed so as to be vertically slidable, and the space above the piston P in the cylinder is the combustion main chamber 8. The combustion subchamber 5 communicates with the combustion main chamber 8 above the central portion thereof, and the fuel gas supply valve 3 and the spark plug 4 face the upper end of the combustion subchamber 5. In addition, the combustion main chamber 8 communicates with an air supply port 1 and an exhaust port 7. The air supply port 1 is provided with an air supply valve 2, and the exhaust port 7 is provided with an exhaust valve 6. A lean fuel gas mixture LG is supplied to the air supply port 1, and a normal fuel gas G that is not mixed is supplied from the fuel gas supply valve 3.
[0014]
Next, the supply / exhaust stroke associated with the movement of the intake valve 2 and the exhaust valve 6 during one combustion stroke will be described with reference to FIG.
During one combustion stroke, the piston P reciprocates twice between the top dead center TDC and the bottom dead center BDC. First, with both the air supply valve 2 and the exhaust valve 6 closed, the piston P reaches the top dead center TDC, the inside of the combustion main chamber 8 and the combustion sub chamber 5 is compressed, and the inside is filled by the spark plug 4 The combustion gas mixture thus produced is combusted and an explosion occurs, and an expansion stroke is performed to push down the piston P. When the piston P is just before the bottom dead center BDC, the exhaust valve 6 starts to open, and while the piston is rising, only the exhaust valve 6 is open. Eventually, when the piston P is just before the top dead center TDC, the air supply valve 2 starts to open, and in the vicinity of the top dead center TDC, the supply / exhaust overlap stroke is reached. Further, the piston P is lowered, the exhaust valve 6 is closed, and the air supply stroke is performed in which only the air supply valve 2 is opened. Eventually, when the piston P passes the bottom dead center BDC and starts to rise, the air supply valve 2 is also closed, and the compression stroke in which the piston P rises with both the valves 2 and 6 closed. Then, immediately before the piston P reaches the top dead center TDC, the explosion of the compressed air-fuel mixture occurs, and the process proceeds to the expansion stroke again.
[0015]
During the one combustion stroke as described above, conventionally, as shown in FIGS. 1 and 4, the internal pressure of the combustion main chamber 8 and the combustion sub-chamber 5 is reduced by lowering the piston P from the top dead center TDC. From the latter half of the exhaust overlap stroke to the air supply stroke, the fuel gas supply valve 3 that is an automatic valve is opened, and the fuel gas is supplied once. On the other hand, the fuel gas supply method of the present proposal is a method of supplying fuel gas twice as shown in FIG. 2 during one combustion stroke, or supplying air at an early stage as shown in FIG. It has become a method to supply.
[0016]
First, in the fuel gas supply method shown in FIG. 2 in which the fuel gas is supplied twice, the fuel gas is supplied first from the latter half of the exhaust stroke to the supply / exhaust overlap stroke, and then in the latter half of the supply stroke. To be made. The state of the cylinder in the first fuel gas supply period will be described with reference to FIG. 5A. While the exhaust valve 6 is almost closed, the air supply valve 2 starts to open. At this time, in the combustion main chamber 8, the combustion gas BG is almost scavenged in the exhaust port 7 by opening the exhaust valve 6, but the combustion gas BG is not sufficiently scavenged in the combustion subchamber 5. It remains. Even if the residual combustion gas BG in the combustion sub-chamber 5 is in the subsequent supply / exhaust overlap stroke or supply stroke, the exhaust valve 6 is closed and the intake valve 2 is opened. Therefore, it becomes difficult to be discharged to the combustion main chamber 8 side due to the pressure of the lean fuel gas mixture LG introduced into the combustion main chamber 8 from the air supply port 1, and continues to remain in the combustion subchamber 5. Even when the ignition plug 4 is ignited in the compression stroke, the residual combustion gas BG causes a problem that the ignition plug 4 does not ignite well.
[0017]
Therefore, at this time, the fuel gas supply valve 3 is opened, the fuel gas G is supplied into the combustion subchamber 5, and the residual combustion gas BG in the combustion subchamber 5 is scavenged by the pressure of the fuel gas G. . The residual combustion gas BG scavenged from the combustion sub-chamber 5 to the combustion main chamber 8 is scavenged to the exhaust port 7 through the exhaust valve 6 which is being closed but slightly opened. Thus, the combustion gas BG does not remain in the combustion sub-chamber 5 and the spark plug 4 is difficult to burn.
[0018]
Next, the fuel gas G is supplied in the latter half of the supply stroke. The state of the cylinder at this time will be described with reference to FIG.
In the first half of the air supply stroke, the fuel gas supply valve 3 is kept closed. Therefore, the lean fuel gas mixture LG from the air supply port 1 is introduced into the combustion main chamber 8 via the air supply valve 2. Only, and the lean fuel gas mixture LG is sufficiently diffused throughout the combustion main chamber 8 when the piston P is lowered. From this state, the fuel gas G is supplied from the fuel gas supply valve 3 in a short period of the later stage of the air supply stroke. Therefore, from the combustion subchamber 5 to the combustion main chamber 8, the fuel gas G that is not diluted in the combustion subchamber 5 close to the spark plug 3 and its surroundings (for example, a communication portion from the combustion subchamber 5 to the combustion main chamber 8). NO in the exhaust gas, in which there is an air-fuel mixture in the combustible range and an ultra-lean air-fuel mixture in the combustion main chamber 8 farther than that. _X An ideal mixture layer state for reduction is realized.
[0019]
Next, as shown in FIG. 2, three structural examples of the fuel gas supply structure for performing the fuel gas supply twice during one combustion stroke will be described with reference to FIGS.
First, in the structure of each structural example, the fuel gas supply valve 3 is basically an automatic valve having a check valve structure similar to the conventional one, and the internal pressures of the combustion main chamber 8 and the combustion sub chamber 5 when the piston P descends. The valve opening start timing and valve opening end timing substantially coincide with the start timing and end timing of the fuel gas supply period in the conventional fuel supply method shown in FIG. . Therefore, in order to divide the fuel gas supply timing as shown in FIG. 2, the fuel gas supply valve 3 is set to the open fuel gas supply valve 3 (specifically, upstream of the valve head portion 3a). The supply / stop control of the fuel gas from the fuel gas supply path on the upstream side may be performed. That is, the fuel gas G is supplied to the fuel gas supply valve 3 twice in the early stage of the supply / exhaust overlap process and the latter stage of the supply process, and the supply of the fuel gas G is stopped during both supply periods.
[0020]
In the configuration example shown in FIG. 8, the supply gas passage is located upstream of the fuel gas supply valve 3 (above the valve head 3 a of the fuel gas supply valve 3) and above the valve chamber 3 b of the fuel gas supply valve 3. 9, the supply gas passage 9 is branched into a first fuel gas supply passage 11 provided with an electromagnetic valve 10 and a second fuel gas supply passage 13 provided with an electromagnetic valve 12. In the early stage of the first supply / exhaust overlap process, the solenoid valve 10 is opened to supply fuel to the fuel gas supply valve 3 from the first fuel gas supply path 11, and then the solenoid valve 10 is closed, In the latter half of the air supply stroke, the solenoid valve 12 is now opened to supply fuel to the fuel gas supply valve 3 from the second fuel gas supply path 13.
[0021]
As described above, the two fuel gas supply passages through the solenoid valve are connected to the supply gas passage 9 because the required fuel gas supply pressure is in the early stage of the supply / exhaust overlap process as shown in FIG. This is because it differs from that in the later stage of the air supply stroke. In the early stage of the supply / exhaust overlap process, it is desired to increase the injection of the fuel gas G from the fuel gas supply valve 3 in order to scavenge the residual combustion gas BG in the combustion sub chamber 5. Therefore, the supply set pressure of the solenoid valve 10 is set high. On the other hand, in the latter stage of the supply stroke, the rich fuel gas mixture is formed only in the combustion subchamber 5 and in the communication portion from the combustion subchamber 5 to the combustion main chamber 8, so that the fuel gas G from the fuel gas supply valve 3 is I want to inject at low pressure. Therefore, the supply set pressure of the solenoid valve 12 is lowered. In this way, different supply set pressures are set in both solenoid valves 10 and 12.
[0022]
Next, the structure of the fuel gas supply valve shown in FIG. 9 will be described.
Inside the valve body 15 forming a valve chamber, a fuel gas supply valve 3 of a check valve around which a spring 14 is wound is installed so as to be vertically slidable, and its lower end is a valve head portion 3a. Projecting downward from the lower end of the main body 15. Above the valve head portion 3a of the fuel gas supply valve 3, an upper piston 16 and a lower piston 17 are arranged in parallel with each other, and between the pistons 16 and 17 is a valve chamber in the main body 15. An annular communication path 18 is formed. Further, the lower piston 17 is provided with a vertical communication passage 17a that penetrates between the annular communication passage 18 and the valve chamber above the valve head portion 3a. A fuel gas supply passage 19 for constantly supplying the fuel gas G to the upper portion of the valve chamber above the upper piston 16 is formed in the wall portion of the valve main body 15. A U-shaped bypass passage 20 is formed in the wall portion of the main body 15 so that the upper communication passage 20a and the lower communication passage 20b communicate with the valve chamber. The upper communication path 20a communicates with the lower communication path 20b, and the upper communication path 20b is closed by the upper piston 16 or the lower piston 17 or communicated with the annular communication path 18.
[0023]
As shown in (a), in the closed state, the fuel gas supply valve 3 is located at the top dead center of the reciprocating region, so that the upper portion of the piston 17 closes the lower communication passage 20b of the bypass passage 20. Yes. From this state, when the supply / exhaust overlap stroke scavenging is performed, the fuel gas supply valve 3 starts to descend due to a decrease in the internal pressure of the combustion subchamber 5, and at the same time, as shown in FIG. The fuel gas G is supplied from the valve chamber above the upper piston 16 through the bypass passage 20, the annular communication passage 18 and the vertical communication passage 17a to the upper portion of the valve head portion 3a of the opened fuel gas supply valve 3. Then, the fuel gas G is supplied to the combustion subchamber 5 for the first time.
[0024]
When the fuel gas supply valve 3 is lowered, the upper piston 16 starts to close the lower communication path 20b, and finally reaches the bottom dead center as shown in (c), and the lower communication path 20b is completely closed. . Then, this time, the fuel gas supply valve 3 rises, and eventually, the state shown in (b) is reached, and the fuel gas G is supplied to the combustion subchamber 5 for the second time in the latter stage of the supply stroke. Then, the fuel gas supply valve 3 reaches the top dead center, returns to the closed state of (a), and ends the fuel supply of the fuel gas G to the combustion subchamber 5.
[0025]
The configuration example shown in FIG. 10 will be described. The fuel gas supply valve 3 is provided with a seal valve 21 above the valve head portion 3a, while the valve chamber in the valve case 22 has a wide upper valve chamber 22b and a narrow lower valve chamber. 22d is formed continuously through a seal seat 22c. A fuel gas supply passage 22a communicating with the upper valve chamber 22b above the seal valve 21 is formed in the wall portion of the valve case 22, and an outer edge portion of the seal seat 21 and an inner wall surface of the upper valve chamber 22b are formed. There is a gap between them.
[0026]
First, as shown in (a), when the valve is closed, the fuel gas supply valve 3 is at the top dead center, and the seal valve 21 exists in the upper valve chamber 22b in a state separated from the seal seat 22c. ing. Eventually, as shown in (b), the fuel gas supply valve 3 descends and opens, and the gap between the seal valve 21 and the inner wall surface of the upper valve chamber 22b from within the upper valve chamber 22b above the seal valve 21. Then, the fuel gas G is introduced into the lower valve chamber 22d, and the fuel gas G is supplied toward the first combustion subchamber 5 in the early stage of the supply / exhaust overlap stroke. Eventually, when the supply / exhaust overlap stroke is passed and the intake stroke is advanced, the seal valve 21 is seated on the seal seat 22c as shown in (c). During this time, the fuel from the upper valve chamber 22b to the lower valve chamber 22d Gas supply is stopped. After the air supply gas supply valve 3 reaches the bottom dead center, it rises again in the latter stage of the air supply stroke and enters the state (b), and the fuel gas G is supplied to the combustion subchamber 5 for the second time. Eventually, it returns to the closed state of (a).
[0027]
In the above three configuration examples shown in FIGS. 8 to 10, the fuel gas supply valve 3 is opened even in the supply stop period between the first fuel gas supply period and the second fuel gas supply period. Since it is in the valve state (the state in which the valve head portion 3 a is lowered), the fuel gas supply is not completely stopped, and a slight amount of the fuel gas G continues to be supplied to the combustion sub chamber 5.
[0028]
Next, another fuel gas supply method shown in FIG. 3 will be described.
This replaces the first supply of the fuel gas G to the combustion subchamber 5 in the fuel gas supply method shown in FIG. 2 with the supply of air. That is, the supply of the fuel gas G at the early stage of the supply / exhaust overlap process in the fuel gas supply method shown in FIG. 2 is intended to scavenge the residual combustion gas BG in the combustion subchamber 5 rather than the original meaning of the fuel gas supply. It is what. Accordingly, if the target state of the air-fuel mixture can be achieved with the second supply amount of the fuel gas G in the latter half of the supply stroke, the scavenging of the combustion gas BG in the early stage of the supply / exhaust overlap stroke is performed with the fuel gas G. There is no need to do it. Further, if scavenging is started from the latter stage of the exhaust stroke earlier than the supply / exhaust overlap stroke, more reliable scavenging is possible. Therefore, as shown in FIGS. 3 and 6 (a), in the early stage of the supply and exhaust overlap process from the latter stage of the exhaust process, the air A is supplied to the combustion sub chamber 5 to scavenge the residual combustion gas BG. Yes.
[0029]
For this purpose, a structure for guiding the air to the combustion sub-chamber 5 is necessary. However, if the air can be supplied by the combustion gas supply valve 3 as shown in FIG. It is not necessary to provide Although it is necessary to switch the supply of air A and fuel gas G to the fuel gas supply valve 3, the first fuel gas supply path 11 is replaced with an air supply path using the fuel gas supply structure shown in FIG. The structure may be such that air is supplied to the fuel gas supply valve 3 by opening the electromagnetic valve 10. In addition, by increasing the air pressure on the upstream side of the fuel gas supply valve 3, the air supply can be started at the end of the exhaust stroke slightly earlier than the supply / exhaust overlap stroke.
[0030]
Then, in the latter stage of the air supply stroke, as shown in FIGS. 3 and 6B, a small amount of fuel gas G is burned in a short time from the fuel gas supply valve 3 as in the fuel gas supply method shown in FIG. By supplying to the sub chamber 5, NO in the exhaust _X A layer state of an air-fuel mixture ideal for reduction is formed.
[0031]
The effect of adopting the fuel gas supply method shown in FIGS. 2 and 3 according to the present plan will be described with reference to the respective graphs shown in FIG.
In each graph, X represents the case where the conventional fuel gas supply method shown in FIG. 1 is adopted, and Y represents the case where the fuel gas supply method shown in FIGS. 2 and 3 according to this configuration is adopted. First, as shown in (a), the operable range of the gas engine includes the supply amount of fuel gas G from the fuel gas supply valve 3 (subchamber supply gas flow rate), the fuel gas G in the combustion main chamber 8 and the lean fuel. In the relationship with the fuel gas component amount (main chamber supply gas amount) due to the supply of the gas mixture LG, it is in the hatched range. Within this range, conventionally, it can be seen that the fuel gas component in the combustion main chamber 8 increases even if the supply amount from the fuel gas supply valve 3 is small (X in (a)). This is because the fuel gas G supplied from the fuel gas supply valve 3 diffuses and the gas component in the combustion main chamber 8 increases, resulting in low exhaust NO. _X It is derived from the fact that the mixture is not in a layered state that is ideal for conversion. Even if the fuel gas supply amount from the fuel gas supply valve 3 is increased from this state, the main chamber supply gas amount is too large and exceeds the operable range. Therefore, the supply set amount of the fuel gas G is very limited. In addition, as indicated by X in (b), the NO in the exhaust gas even when the amount of fuel gas supplied from the fuel gas supply valve 3 (sub-chamber supply gas flow rate) is small. _X The amount becomes higher.
[0032]
On the other hand, when the fuel gas supply method shown in FIGS. 2 and 3 is used, the fuel gas supply amount (sub chamber supply gas flow rate) from the fuel gas supply valve 3 is increased as indicated by Y in (a). Regardless, the amount of gas supplied to the main room is low and it is well within the operable range. Further, this is due to the stratification of the air-fuel mixture from the combustion sub-chamber 5 to the combustion main chamber 8, and the amount of fuel gas supplied from the fuel gas supply valve 3 is as indicated by Y in (b). Despite many settings, NO in exhaust _X The amount is also decreasing. Note that, as shown in (c), the thermal efficiency is maintained as before even though the sub chamber supply gas flow rate is increased.
[0033]
【The invention's effect】
Since the fuel gas supply method of the sub-chamber gas engine is as described above, the present invention has the following effects.
First, by using the method as set forth in claim 1, the fuel gas is supplied at an early stage of the supply / exhaust overlap process so that the combustion gas remaining in the combustion sub-chamber is scavenged into the combustion main chamber, and then the valve is closed. The exhaust valve can be scavenged, so that the spark plug is less likely to burn and the ignition reactivity is improved. Then, the fuel gas supply is stopped before the fuel gas supply in the later stage of the intake stroke, so that the lean combustion gas mixture is already diffusely filled from the intake port into the combustion main chamber in the intake stroke, and the fuel gas supply in the later stage of the intake stroke is diffused. Since the fuel gas supplied for the second time is a short period, the supplied fuel gas does not diffuse, and from the combustion subchamber to the combustion main chamber, in the vicinity of the spark plug, there is a rich mixture of fuel gas as it is, and there is a combustible range around it. Since the air-fuel mixture, and the lean air-fuel mixture at a further distance, forms a layered state of the air-fuel mixture, NO in the exhaust gas _X It contributes to reduction.
[0034]
Also, As in claim 2 By providing two solenoid valves with different supply pressures upstream of the fuel gas supply valve, the high supply pressure solenoid valve is opened in the fuel gas supply period or the air supply period in the early stage of the supply / exhaust overlap process. As a result, fuel gas or air is supplied to the combustion subchamber at a high pressure, and scavenging of the combustion gas can be improved, while an electromagnetic valve having a low supply pressure is opened in the fuel gas supply period in the latter stage of the supply stroke. By supplying a low-pressure fuel gas for a short period of time, exhaust NO _X A layer state of an air-fuel mixture ideal for reduction can be formed.
[0035]
Further claims 3 With this fuel gas supply structure, the communication path to the upstream of the valve head part and the bypass path naturally communicate with each other when the fuel gas supply valve opens (the supply stroke when the piston descends). Then, the fuel gas is supplied, and the fuel gas supply is stopped by closing the communication, and as a result, the fuel gas is supplied twice during one combustion stroke. The above-mentioned effect is obtained.
[0037]
Claims 4 With such a fuel gas supply structure, the seal valve and the seal seat are naturally separated from each other during the opening of the fuel gas supply valve (the supply stroke when the piston is lowered), and the fuel gas is supplied. Further, the fuel gas supply is stopped by being seated on the seal seat, and as a result, the fuel gas is supplied twice during one combustion stroke as in claim 1 to obtain the above-mentioned effect. .
[Brief description of the drawings]
FIG. 1 is a combustion stroke diagram according to a conventional fuel gas supply method.
FIG. 2 is a combustion stroke diagram that employs a fuel gas supply method that supplies fuel gas in two steps.
FIG. 3 is a combustion stroke diagram that employs a fuel gas supply method that performs air supply and fuel gas supply.
4 is a side cross-sectional view of a cylinder portion of a gas engine, and is a view when fuel gas is supplied in FIG. 1. FIG.
5 is a side sectional view of the same, FIG. 5 (a) is a diagram at the time of the first fuel gas supply in FIG. 2, and FIG. 5 (b) is a diagram at the same time of the second fuel gas supply.
6 is a side cross-sectional view of the same, FIG. 6A is a view when air is supplied in FIG. 3, and FIG. 6B is a view when fuel gas is supplied.
7A and 7B are graphs showing effects when the fuel gas supply method shown in FIGS. 2 and 3 is adopted, wherein FIG. 7A is a diagram showing an operable range, and FIG. 7B is exhaust NO. _X The figure which shows a characteristic, (c) is a figure which shows thermal efficiency.
FIG. 8 is a schematic side view showing a structure for supplying fuel gas to the fuel gas supply valve 3 from two solenoid valves having different supply pressures.
9 is a side cross-sectional view of the fuel gas supply valve 3 having a structure in which a bypass passage 20, an annular communication passage 18 and a vertical communication passage 17a are provided and the fuel gas supply can be divided into two at the time of valve opening; (a) is a diagram when the fuel gas supply valve 3 is closed, (b) is a diagram when the fuel gas supply valve 3 is opened, and fuel gas G is supplied to the combustion sub-chamber 5, (c) It is a figure when the fuel gas G is not supplied to the combustion subchamber 5 while the fuel gas supply valve 3 is opened.
FIG. 10 is a side sectional view of the fuel gas supply valve 3 having a structure in which a seal valve 21 and a seal seat 22c are provided and the fuel gas supply can be divided into two when the valve is opened. 3 is a view when the valve is closed, (b) is a view when the fuel gas supply valve 3 is opened and the fuel gas G is supplied to the combustion sub-chamber 5, and (c) is a view when the fuel gas supply valve 3 is opened. It is a figure when fuel gas G is not supplied to the combustion subchamber 5 while valved.
[Explanation of symbols]
P piston
G Fuel gas
LG Lean fuel gas mixture
BG combustion gas
1 Air supply port
2 Supply valve
3 Fuel gas supply valve
3a Umbrella
3b Valve chamber
4 Spark plugs
5 Combustion subchamber
6 Exhaust valve
7 Exhaust port
8 Combustion main chamber
9 Supply gas passage
10 Solenoid valve
11 First fuel gas supply channel
12 Solenoid valve
13 Second fuel gas supply path
14 Spring
15 Valve case
16 Upper piston
17 Lower piston
17a Vertical communication passage
18 Annular passage
19 Fuel gas supply passage
20 Bypass passage
20a Upper communication passage
20b Lower communication passage
21 Seal valve
22 Valve case
22a Fuel gas supply passage
22b Upper valve chamber
22c Seal seat
22d Lower valve chamber

Claims

An air supply port that supplies a lean fuel gas mixture with an air supply valve to the combustion main chamber and an exhaust port that has an exhaust valve communicate with each other, and a fuel gas is connected to the combustion subchamber that communicates with the combustion main chamber. A fuel gas supply method for a gas engine, characterized in that in a gas engine having a structure in which a supply valve and a spark plug are faced, fuel gas is supplied in an early stage of a supply / exhaust overlap process and in a later stage of an intake process.

A gas engine employing the fuel supply method according to claim 1, wherein two electromagnetic valves having different supply pressures are arranged upstream of the fuel gas supply valve .

2. A gas engine employing the combustion method according to claim 1, wherein a communication passage is provided upstream of the valve head portion linked to the movement of the fuel gas supply valve, and a valve case in which the fuel gas supply valve is provided is provided in the valve case. A fuel gas supply structure for a gas engine, characterized in that a bypass passage capable of communicating with the passage is provided .

A gas engine employing the combustion method according to claim 1, wherein an integral seal valve is provided on an upper portion of a valve head portion of the fuel gas supply valve, and a valve case in which the fuel gas supply valve is provided is provided with the seal valve and A fuel gas supply structure for a gas engine, wherein a detachable seal seat is provided .