JP3956503B2

JP3956503B2 - In-cylinder injection spark ignition engine

Info

Publication number: JP3956503B2
Application number: JP26677398A
Authority: JP
Inventors: 輝行伊東
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1998-09-21
Filing date: 1998-09-21
Publication date: 2007-08-08
Anticipated expiration: 2018-09-21
Also published as: JP2000097032A

Description

【０００１】
【発明の属する技術分野】
本発明は燃焼室に直接燃料を噴射する筒内噴射式火花点火機関に関する。
【０００２】
【従来の技術】
筒内噴射式火花点火機関は、例えば特開平９−７９０７９号公報や特許第２５７７０１９号公報等に示されているように、シリンダヘッドに吸，排気ポートと、これら吸，排気ポートを開閉する吸，排気弁と、燃焼室のほぼ中心に臨む位置に設けた点火プラグと、噴射ノズルが燃焼室に臨む燃料噴射弁と、を配設して、低負荷域では圧縮行程の後期に燃料噴射弁より直接燃料を燃焼室に噴射して成層燃焼を行わせる一方、高負荷域では吸気行程中に前記燃料噴射を行わせて均質燃焼を行わせるようにしている。
【０００３】
【発明が解決しようとする課題】
燃料噴射弁は排気弁配置側に配設すると既燃ガスの熱影響を大きく受けてしまい、また、燃焼室中心部に配設すると排気弁配置側に配設した場合と同様に熱影響を大きく受けてしまうことと、燃料噴射弁の中央設置により点火プラグ配設位置が燃焼室中央からずれて火炎伝播が良好に行われなくなってしまうことから、該燃料噴射弁は吸気弁配置側でしかも燃料と空気との混合性を考慮して吸気弁近傍位置に配設する必要があるため、該燃料噴射弁の配設位置が制約されてしまうばかりでなく、吸気ポート周りの構造によって取付角度にも制約を受けて成層燃焼および均質燃焼に最適な配設レイアウトを採ることが難しくなってしまう。
【０００４】
これは、特に吸，排気弁が多弁化したエンジンコンセプトでは益々顕著となってしまう。
【０００５】
また、このような燃料噴射弁の配設上の問題とは別に、吸気弁の開閉制御によって吸気ポートから吸気を行わせるため、ポンプ損失や動弁系のフリクション損失によるＣＶ値の低下は否めず、特に、筒内噴射式火花点火機関では成層燃焼時に圧縮行程中に噴射された燃料を燃焼室中央の点火プラグ周りに確実に輸送させることが肝要で、このため、吸気ポートには横方向旋回流（スワール）や縦方向旋回流（タンブル流）を生成させるための可変要素を付加する必要があるため、前述のポンプ損失やフリクション損失は更に増大してしまう。
【０００６】
更に、成層燃焼時には前述のように圧縮行程で噴射された燃料を新気の旋回流に乗せて点火プラグ周りに輸送させるのであるが、吸気行程で吸気ポートから吸入される新気は吸気ポートの旋回付与手段により旋回流が形成されても、この旋回流は燃料噴射時期には減衰されて、この減衰された旋回流に対して燃料を噴射して燃料の輸送と燃焼を行わせなければならないため、吸気制御と燃料噴射制御のマッチングが難しく、しかも、ガス流動が弱まるために成層燃焼の向上は大きく期待することはできない。
【０００７】
そこで、本発明は燃料噴射弁の配設レイアウトの自由度を拡大できると共に、吸気タイミングを適切に設定でき、かつ、強いガス流動を生成させることができて成層燃焼はもとより均質燃焼の燃焼性を一段と向上することができる筒内噴射式火花点火機関を提供するものである。
【０００８】
【課題を解決するための手段】
請求項１の発明にあっては、吸気行程で燃焼室に空気を供給する空気供給手段と、燃焼室に直接燃料を噴射する燃料噴射弁と、点火プラグと、ピストン冠面にキャビティ燃焼室とを備え、低負荷域で圧縮行程中に燃料を噴射させて成層燃焼を行わせると共に、高負荷域で吸気行程中に燃料を噴射させて均質燃焼を行わせるようにした筒内噴射式火花点火機関において、前記空気供給手段を、燃焼室に直接空気を噴射する空気噴射弁のみで構成し、成層燃焼時における空気噴射弁の噴射時期を、吸気行程で所定の供給空気量のうち一部を残して噴射させる第１噴射時期と、圧縮行程の前半で残りの空気量を噴射させる第２噴射時期とに多段に設定したことを特徴としている。
【０００９】
請求項２の発明にあっては、請求項１に記載の空気噴射弁を燃料噴射弁配置側に配設してこれらの取付角度を、噴射された燃料をキャビティ燃焼室へ輸送できる角度に設定したことを特徴としている。
【００１０】
請求項３の発明にあっては、請求項２に記載の空気噴射弁と燃料噴射弁の取付角度を、相互の噴射軸線が交差し、かつ、噴射方向が共にキャビティ燃焼室に指向する角度に設定したことを特徴としている。
【００１１】
請求項４の発明にあっては、請求項２および３に記載の空気噴射弁を複数個配設したことを特徴としている。
【００１２】
請求項５の発明にあっては、請求項４に記載の空気噴射弁は、アイドリング時に１つの空気噴射弁から空気噴射を行わせて横向きの旋回流を形成させ、部分負荷および高負荷時に全空気噴射弁から空気噴射を行わせて縦向きの旋回流を形成させるようにしたことを特徴としている。
【００１４】
請求項６の発明にあっては、吸気行程で燃焼室に空気を供給する空気供給手段と、燃焼室に直接燃料を噴射する燃料噴射弁と、点火プラグと、ピストン冠面にキャビティ燃焼室とを備え、低負荷域で圧縮行程中に燃料を噴射させて成層燃焼を行わせると共に、高負荷域で吸気行程中に燃料を噴射させて均質燃焼を行わせるようにした筒内噴射式火花点火機関において、前記空気供給手段を、燃焼室に直接空気を噴射する空気噴射弁のみで構成し、この空気噴射弁を燃料噴射弁配置側に配設してこれらの取付角度を、噴射空気および噴射燃料がキャビティ燃焼室に指向し、かつ、噴射空気の噴射方向が噴射燃料の噴射方向よりも下向きとなって両噴射軸線が交差する角度に設定し、前記成層燃焼時における空気噴射弁の噴射時期を、吸気行程で所定の供給空気量のうち一部を残して噴射させる第１噴射時期と、圧縮行程で燃料噴射直前に残りの空気量を噴射させる第２噴射時期とに多段に設定したことを特徴としている。
【００１６】
請求項７の発明にあっては、請求項１〜６に記載の空気噴射弁を、膨脹行程でも噴射作動させるようにしたことを特徴としている。
【００１７】
請求項８の発明にあっては、請求項１〜７に記載の空気噴射弁を排気行程でも噴射作動させるようにしたことを特徴としている。
【００１８】
請求項９の発明にあっては、請求項１〜８に記載の空気噴射弁の空気通路に、不活性ガス供給通路を接続して、所定量の不活性ガスを混合した空気を噴射させるようにしたことを特徴としている。
【００１９】
請求項１０の発明にあっては、請求項９に記載の不活性ガス供給通路が、空気噴射弁の空気通路と機関排気通路とに跨って接続されて、排気ガスの一部を導入する排気還流通路であることを特徴としている。
【００２０】
【発明の効果】
請求項１に記載の発明によれば、空気供給手段を燃焼室に直接空気を噴射する空気噴射弁で構成して、吸気ポートおよび吸気弁を廃止しているため、燃料噴射弁をこれら吸気ポート，吸気弁に制約されることなく最適な燃料噴射方向が得られる位置および角度に取付けることができる。
【００２１】
また、吸気弁およびその動弁系のフリクション損失がなく、しかも吸気弁，吸気ポートの通気抵抗によるポンプ損失がなくなることと併せて、吸気行程で噴射した高圧の空気がピストンの押し下げ方向に作用するためポンプ損失の低減効果が大きく、ＣＶ値を高めることができる。
【００２２】
更に、高圧の空気噴射によって強いガス流動を形成できるため旋回流付与手段を用いることなく成層燃焼時の点火プラグ周りへの燃料輸送を良好に行わせることができると共に、燃料と空気との干渉を意図的に設定できて燃料の微粒化や成層化を容易に行え、従って、成層燃焼および均質燃焼の燃焼性を向上することができる。
【００２３】
また、燃料の吸気行程噴射を行わせるのに際して、燃料噴射弁から噴射された燃料と吸気弁との干渉に留意する必要がないため、燃料噴霧角度を最適に設定することができるから、均質燃焼はもとより成層燃焼の燃焼性をより一層向上することができる。
しかも、成層燃焼時には圧縮行程の前半でも空気噴射を行わせるため、ガス流動を強化して点火プラグ周りへの燃料の輸送性を高められ、成層燃焼をより一層安定化することができる。
【００２４】
請求項２に記載の発明によれば、請求項１の発明の効果に加えて、空気噴射弁を吸気ポート，吸気弁による制約を受けることなく、成層燃焼時に噴射された燃料をキャビティ燃焼室へ輸送できる最適な角度に設定してあるから、ガス流動の保存性が高く燃料の点火プラグ周りへの輸送性を向上できて成層燃焼の燃焼性を更に向上することができる。
【００２５】
請求項３に記載の発明によれば、請求項２の発明の効果に加えて、空気噴射軸線と燃料噴射軸線とが交差しているため、燃料の吸気行程噴射時に燃料の微粒化を行えると共に、噴射空気より気化潜熱を奮って空気温度を下げられるため、実充填効率を高められて高出力が要求される均質燃焼を行う高負荷域での出力の向上を実現することができ、しかも、噴射空気がキャビティ燃焼室に指向するため、キャビティ燃焼室に燃料が付着するのを抑制できてスモーク発生および未燃ＨＣの発生を低下させることができる。
【００２６】
請求項４に記載の発明によれば、請求項２および３の発明の効果に加えて、空気噴射弁を複数個配設してあるため、１つの空気噴射弁では空気供給量が不十分な場合や、過給のようにより多くの空気が必要とする場合に適切に対応することができる。
【００２７】
請求項５に記載の発明によれば、請求項４の発明の効果に加えて、アイドリング時には１つの空気噴射弁から空気噴射を行わせて横向きの旋回流（スワール）を形成させるため、供給空気量の少ないアイドリング時でもキャビティ燃焼室に確実にスワールを形成できて燃焼の安定化を図ることができ、他方、部分負荷および高負荷時には全空気噴射弁から空気噴射を行わせて縦向きの旋回流（タンブル流，逆タンブル流）を形成させるため、キャビティ燃焼室への燃料付着を抑制してスモーク，未燃ＨＣの発生を低減でき、均質燃焼，成層燃焼の安定化と出力の向上とを実現することができる。
【００２９】
請求項６に記載の発明によれば、空気供給手段を燃焼室に直接空気を噴射する空気噴射弁で構成して、吸気ポートおよび吸気弁を廃止しているため、燃料噴射弁をこれら吸気ポート，吸気弁に制約されることなく最適な燃料噴射方向が得られる位置および角度に取付けることができる。
また、吸気弁およびその動弁系のフリクション損失がなく、しかも吸気弁，吸気ポートの通気抵抗によるポンプ損失がなくなることと併せて、吸気行程で噴射した高圧の空気がピストンの押し下げ方向に作用するためポンプ損失の低減効果が大きく、ＣＶ値を高めることができる。
更に、高圧の空気噴射によって強いガス流動を形成できるため旋回流付与手段を用いることなく成層燃焼時の点火プラグ周りへの燃料輸送を良好に行わせることができると共に、燃料と空気との干渉を意図的に設定できて燃料の微粒化や成層化を容易に行え、従って、成層燃焼および均質燃焼の燃焼性を向上することができる。
また、燃料の吸気行程噴射を行わせるのに際して、燃料噴射弁から噴射された燃料と吸気弁との干渉に留意する必要がないため、燃料噴霧角度を最適に設定することができるから、均質燃焼はもとより成層燃焼の燃焼性をより一層向上することができる。しかも、噴射空気および噴射燃料が共にキャビティ燃焼室に指向し、かつ、噴射空気が噴射燃料よりも下向きに噴射されるため、成層燃焼時はキャビティ燃焼室に空気の膜を早い流れとして形成できて、その上に燃料を噴射させるためにキャビティ燃焼室への燃料付着を回避して成層燃焼の安定化と、スモーク，未燃ＨＣの低減化とを図ることができる。
【００３０】
また、均質燃焼時には噴射空気と噴射燃料との混合，攪拌を積極的に行えると共に燃料の微粒化を行えるから均質燃焼の安定化を図ることができ、しかも、キャビティ燃焼室に高圧の噴射空気が吹き当るため、該キャビティ燃焼室への燃料付着を回避できてスモーク，未燃ＨＣの低減化を図ることができる。
【００３１】
更に、成層燃焼時には圧縮行程で燃料噴射の直前にも空気噴射を行わせるため、キャビティ燃焼室に形成される空気の膜を強化して燃料付着をより確実に防止できると共に、ガス流動を強化できて点火プラグ周りへの燃料の輸送性を高めることができる。
【００３２】
請求項７に記載の発明によれば、請求項１〜６の発明の効果に加えて、膨脹行程でも空気噴射弁からの空気噴射を行わせるため、未燃ＨＣの燃焼を活性化させて熱効率を向上できると共にスモーク，未燃ＨＣの低減化対策を徹底することができる。
【００３３】
請求項８に記載の発明によれば、請求項１〜７の発明の効果に加えて、排気行程でも空気噴射弁からの空気噴射を行わせるため掃気効率を高めることができる。
【００３４】
請求項９に記載の発明によれば、請求項１〜８の発明の効果に加えて、空気噴射弁からは不活性ガスを混合した空気を噴射させるためＮＯx の低減効果を得ることができる。
【００３５】
請求項１０に記載の発明によれば、請求項９の発明の効果に加えて、不活性ガスとして既燃ガスを有効利用するため、排気還流によってコスト的に有利にＮＯx 低減効果を得ることができる。
【００３６】
【発明の実施の形態】
以下、本発明の実施形態を図面と共に詳述する。
【００３７】
図１，２において、１はシリンダブロック、２はピストン、３はシリンダヘッド、４はこれらシリンダブロック１，ピストン２およびシリンダヘッド３で形成された燃焼室を示す。
【００３８】
シリンダヘッド３には燃焼室４のほぼ中央に臨む位置に点火プラグ５を配設してあると共に、図外の排気弁の配置側と反対側の側部に、燃料を直接燃焼室４に噴射する燃料噴射弁６を配設してある。
【００３９】
このシリンダヘッド３には通常のエンジンとは異なって吸気ポートおよび吸気弁はなく、前記燃料噴射弁６の配置側に、高圧ポンプ８で圧縮されて空気通路９により送られてくる高圧の空気を直接燃焼室４に噴射する空気噴射弁７を配設してある。
【００４０】
ピストン２の冠面には前記燃料噴射弁６を配設した側に偏寄した略半部に、成層燃焼時に圧縮行程中に燃料噴射弁６から噴射された燃料を受容するキャビティ燃焼室１０を形成してある。
【００４１】
燃料噴射弁６は、成層燃焼時に圧縮行程中に燃料を噴射した際に、この噴射燃料がキャビティ燃焼室４に指向して該キャビティ燃焼室４に確実に受容される角度で取付けてある一方、空気噴射弁７は吸気行程で噴射された空気が例えば図２に矢印で示すように右旋回して横向きの旋回流（スワール）が形成され、圧縮行程でこのスワールがキャビティ燃焼室１０内に保存されて該圧縮行程中に噴射された燃料を点火プラグ５周りへ確実に輸送し得る角度で取付けてある。
【００４２】
図３は４サイクル行程における成層燃焼時の空気噴射弁７，燃料噴射弁６の各噴射時期と点火プラグ５の点火時期とを示し、また、図４は均質燃焼時のこれら空気噴射弁７，燃料噴射弁６の各噴射時期と点火プラグ５の点火時期とを示しており、Ａは空気の噴射時期を、Ｆは燃料の噴射時期を、Ｓは点火時期をそれぞれ示している。
【００４３】
従って、この第１実施形態の構成によれば、吸気行程で燃焼室４に空気を供給する空気供給手段を、該燃焼室４に直接高圧の空気を供給する空気噴射弁７で構成して、吸気ポートおよび吸気弁を廃止しているため、燃料噴射弁６をこれら吸気ポートや吸気弁に制約を受けることなく最適な燃料噴射方向が得られる位置および角度に取付けることができる。
【００４４】
また、吸気弁およびその動弁系のフリクション損失がなく、しかも吸気弁，吸気ポートの通気抵抗によるポンプ損失がなくなることと併せて、吸気行程で噴射した高圧の空気がピストン２の押し下げ方向に作用するためポンプ損失の低減効果が大きく、ＣＶ値を高めることができる。
【００４５】
更に、高圧の空気噴射によって強いガス流動を形成でき、かつ、空気噴射弁７を吸気ポートや吸気弁による制約を受けずにスワールを形成できる最適な角度で取付けることができるため、旋回流付与手段を用いることなくガス流動の保存性を高めることができ、従って、成層燃焼時に点火プラグ５周りへの燃料の輸送性を高められ、また、空気噴射弁７と燃料噴射弁６との取付角度は燃料と空気との干渉を意図的に設定することもできて燃料の微粒化や成層化を容易に行うことができるから、成層燃焼および均質燃焼の燃焼性を向上することができる。
【００４６】
また、燃料の吸気行程噴射を行わせるのに際して、燃料噴射弁６から噴射された燃料と吸気弁との干渉に留意する必要がないため、燃料噴霧角度を最適に設定することができるから、均質燃焼はもとより成層燃焼の燃焼性をより一層向上することができる。
【００４７】
図５は本発明の第２実施形態を示すもので、この実施形態にあっては前記図１，２に示した第１実施形態の構成において、成層燃焼時における前述の空気噴射弁７の噴射時期を、吸気行程で所定の供給空気量のうち一部を残して噴射させる第１噴射時期Ａ₁と、圧縮行程の前半で残りの空気量を噴射させる第２噴射時期Ａ₂とに多段に設定してある。
【００４８】
従って、この第２実施形態の構成によれば、前記第１実施形態の効果に加えて、成層燃焼時には圧縮行程の前半でも空気噴射を行わせるため、スワールを強化して点火プラグ５周りへの燃料の輸送性を高めることができて、成層燃焼をより一層安定化させることができる。
【００４９】
図６，７は本発明の第３実施形態を示すもので、この実施形態にあっては成層燃焼時（図６）および均質燃焼時（図７）の何れの運転状態時にも、膨脹行程で空気噴射弁７を噴射作動させて所要量の追加空気の噴射Ａ_α ₁を行わせるようにしている。
【００５０】
従って、この第３実施形態の構成によれば、前記第１実施形態および第２実施形態の効果に加えて、膨脹行程でも燃焼温度の高い温度条件下で空気噴射弁７によって所要量の空気噴射Ａ_α ₁を行わせるため、この追加空気によって未燃ＨＣの燃焼を活性化させて熱効率を向上できると共にスモークおよび未燃ＨＣの低減化対策を徹底することができる。
【００５１】
前記第３実施形態では追加空気の噴射を膨脹行程で行わせているが、図８，９に示す第４実施形態のように排気行程でも追加空気の噴射Ａ_α ₂を行わせれば、掃気効率を高めることができる。
【００５２】
また、この排気行程での追加空気の噴射Ａ_α ₂を、鎖線で示すように高い燃焼温度が維持される排気行程の前半で行わせれば、膨脹行程で追加空気の噴射Ａα₁を行った場合と同様に未燃ＨＣの燃焼の活性化を期待することができ、特に該排気行程ではピストンの上昇によって掻き落されるシリンダライナの付着未燃ＨＣの燃焼活性化を図ることもできる。
【００５３】
図１０，１１は本発明の第５実施形態を示すもので、この実施形態にあっては空気噴射弁７と燃料噴射弁６の取付角度を、両噴射軸線が上下方向および水平方向で交差し、かつ、噴射方向が共にキャビティ燃焼室１０に指向する角度に設定してある。
【００５４】
従って、この第５実施形態の構成によれば、前記第１実施形態と同様の効果が得られる他、空気噴射軸線と燃料噴射軸線とが交差しているため、燃料の吸気行程噴射時に燃料の微粒化を行えると共に、噴射空気より気化潜熱を奮って空気温度を下げられるため、実充填効率を高められて高出力が要求される均質燃焼を行う高負荷域での出力の向上を実現することができる。
【００５５】
しかも、噴射空気がキャビティ燃焼室１０に指向するため、キャビティ燃焼室１０に燃料が付着するのを抑制できてスモークおよび未燃ＨＣの発生を低下させることができる。
【００５６】
ここで、この第５実施形態において、空気噴射弁７の成層燃焼時における噴射時期を図５に示した第２実施形態と同様に、吸気行程における第１噴射時期Ａ₁と、圧縮行程前半における第２噴射時期Ａ₂とに多段に設定すれば、該第２噴射時期Ａ₂でキャビティ燃焼室１０に噴射された空気は該キャビティ燃焼室１０で十分にイナーシャーを持ったスワールとなって点火プラグ５周りにより確実に燃料を輸送することが可能となり、成層燃焼の安定性を更に高めることができる。
【００５７】
また、燃料の早噴き・遅点火を実現することもできるから、混合気形成が良好でかつＮＯ_x低減効果が得られ、しかも、燃焼の熱発生時期が遅れるため熱効率を高めることもできる。
【００５８】
図１２，１３は本発明の第６実施形態を示すもので、この実施形態にあっては空気噴射弁７を複数個、具体的には２つの空気噴射弁７，７を燃料噴射弁６の配置側で、平面視して該燃料噴射弁６の噴射軸線を中心に内向きにほぼ線対称に取付けてある。
【００５９】
また、これら２つの空気噴射弁７，７は噴射空気が図１２の矢印で示すように、点火プラグ５の下側を通って図外の排気弁側からピストン２の冠面に向って流れる、所謂順タンブルの縦向き旋回流を形成し得る取付角度で配設してある。
【００６０】
従って、この第６実施形態の構成によれば、前記第１実施形態と同様の効果が得られる他、２つの空気噴射弁７，７を配設してあるため１つの空気噴射弁７では空気供給量が不十分な場合や、過給のようにより多くの空気が必要とする場合に適切に対応することができる。
【００６１】
また、アイドリング時には１つの空気噴射弁７からのみ空気噴射を行わせてスワールを形成させ、部分負荷および高負荷時には両空気噴射弁７，７から同時に空気噴射を行わせて順タンブル流を形成させるようにすれば、供給空気量の少ないアイドリング時でもキャビティ燃焼室１０に確実にスワールを形成できて燃焼の安定化を図ることができ、他方、部分負荷および高負荷時には順タンブル流によってキャビティ燃焼室１０への燃料付着を抑制してスモーク，未燃ＨＣの発生を低減できるため、均質燃焼，成層燃焼の安定化と出力の向上とを実現することができる。
【００６２】
更に、この第６実施形態の場合も図５に示した第２実施形態と同様に、成層燃焼時における２つの空気噴射弁７，７の噴射時期を吸気行程における第１噴射時期Ａ₁と、圧縮行程前半における第２噴射時期Ａ₂とに多段に設定することによって、順タンブル流を強化でき点火プラグ５周りへの燃料の輸送性を高めることができる。
【００６３】
なお、この実施形態では順タンブル流を形成させるようにしているが、逆タンブル流を形成できるように空気噴射弁７，７の取付角度を縦向きにすることも可能である。
【００６４】
図１４，１５は本発明の第７実施形態を示すもので、この実施形態にあっては空気噴射弁７を燃料噴射弁６のほぼ直上位置に配置し、これら空気噴射弁７，燃料噴射弁６の取付角度を、噴射空気および噴射燃料がキャビティ燃焼室１０に指向し、かつ、噴射空気の噴射方向が噴射燃料の噴射方向よりも下向きとなって相互の噴射軸線が上下方向に交差する角度に設定し、噴射空気が図１４の矢印で示すように燃料噴射弁６の前端部分を横切ってキャビティ燃焼室１０に向かい、該キャビティ燃焼室１０で反転して点火プラグ５に向って流れる、所謂逆タンブル流が形成されるようにしてある。
【００６５】
従って、この第７実施形態の構成によれば、前記第１実施形態と同様の効果が得られる他、噴射空気および噴射燃料が共にキャビティ燃焼室１０に指向し、かつ、噴射空気が噴射燃料よりも下向きに噴射されて逆タンブル流が形成されるため、成層燃焼時はキャビティ燃焼室１０に空気の膜を早い流れとして形成できて、その上に燃料を噴射させるためにキャビティ燃焼室１０への燃料付着を回避して成層燃焼の安定化と、スモーク，未燃ＨＣの低減化とを図ることができる。
【００６６】
また、均質燃焼時には噴射空気と噴射燃料との混合，攪拌を積極的に行えると共に燃料の微粒化を行えるから均質燃焼の安定化を図ることができ、しかも、キャビティ燃焼室１０に高圧の噴射空気が吹き当るため、該キャビティ燃焼室１０への燃料付着を回避できてスモーク，未燃ＨＣの低減化を図ることができる。
【００６７】
更に、前記図１０，１１に示した第５実施形態と同様にこの燃料の吸気行程噴射を行う均質燃焼時に、噴射燃料が噴射空気より気化潜熱を奮って空気温度を下げられるため、実充填効率を高められて高出力を得ることができる。
【００６８】
図１６は本発明の第８実施形態を示すもので、この実施形態にあっては前記図１４，１５に示した第７実施形態の構造において、成層燃焼時における前述の空気噴射弁７の噴射時期を、吸気行程で所定の供給空気量のうち一部を残して噴射させる第１噴射時期Ａ₁と、圧縮行程後期の燃料噴射時期Ｆの直前に残りの空気量を噴射させる第２噴射時期に設定してある。
【００６９】
従って、この第８実施形態の構成によれば成層燃焼時には圧縮行程で燃料噴射の直前にも空気噴射を行わせるため、キャビティ燃焼室１０に形成される空気の膜を強化して燃料付着をより確実に防止できるとともに、逆タンブル流を強化でき点火プラグ５周りへの燃料の輸送性を高めることができる。
【００７０】
なお、図１０〜１６に示した各実施形態において、図６，７、又は図８，９に示した実施形態と同様に膨脹行程、および又は排気行程でも空気噴射弁７を噴射作動させて追加の空気を噴射させることによって、未燃ＨＣの低減効果と掃気効率の向上とを図ることができる。
【００７１】
図１７は本発明の第９実施形態を示すもので、この実施形態ではＮＯ_x低減対策のため、空気噴射弁７から不活性ガスを混合した空気を燃焼室４に噴射供給するようにしてある。
【００７２】
図１７では便宜的に図１に示した第１実施形態のエンジンコンセプトに適用した場合を示しており、本実施形態では空気噴射弁７の空気通路９の途中にミキサ室１１を設け、該ミキサ室１１と排気ポート１２とに跨って排気還流通路１３を接続し、該排気還流通路１３に介装した排気還流制御弁装置１４による制御の下に不活性ガスとして吸気量に応じた適正量の還流排気（ＥＧＲ）を行って、ミキサ室１１で新気と混合させて外部ＥＧＲを行わせ、ＮＯ_xの低減効果を得るようにしている。なお、図１７中、１５は排気弁を示す。
【図面の簡単な説明】
【図１】本発明の第１実施形態の構成を概略的に示す断面説明図。
【図２】本発明の第１実施形態の概略的平面説明図。
【図３】本発明の第１実施形態の成層燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図４】本発明の第１実施形態の均質燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図５】本発明の第２実施形態の成層燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図６】本発明の第３実施形態の成層燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図７】本発明の第３実施形態の均質燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図８】本発明の第４実施形態の成層燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図９】本発明の第４実施形態の均質燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図１０】本発明の第５実施形態の構成を概略的に示す断面説明図。
【図１１】本発明の第５実施形態の概略的平面説明図。
【図１２】本発明の第６実施形態の構成を概略的に示す断面説明図。
【図１３】本発明の第６実施形態の概略的平面説明図。
【図１４】本発明の第７実施形態の構成を概略的に示す断面説明図。
【図１５】本発明の第７実施形態の概略的平面説明図。
【図１６】本発明の第８実施形態の成層燃焼時における空気噴射時期，燃料噴射時期および点火時期を示す説明図。
【図１７】本発明の第９実施形態の構成を概略的に示す断面説明図。
【符号の説明】
１シリンダブロック
２ピストン
３シリンダヘッド
４燃焼室
５点火プラグ
６燃料噴射弁
７空気噴射弁
９空気通路
１０キャビティ燃焼室
１２排気ポート（排気通路）
１３排気還流通路（不活性ガス供給通路）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct injection spark ignition engine that injects fuel directly into a combustion chamber.
[0002]
[Prior art]
An in-cylinder injection spark ignition engine, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-79079 and Japanese Patent No. 2577019, has suction and exhaust ports in the cylinder head and suction and exhaust ports that open and close these suction ports. , An exhaust valve, a spark plug provided at a position substantially facing the center of the combustion chamber, and a fuel injection valve with an injection nozzle facing the combustion chamber, and the fuel injection valve at the latter stage of the compression stroke in the low load region While stratified combustion is performed by directly injecting fuel into the combustion chamber, the fuel injection is performed during the intake stroke to perform homogeneous combustion in a high load region.
[0003]
[Problems to be solved by the invention]
If the fuel injection valve is arranged on the exhaust valve arrangement side, it will be greatly affected by the heat of burned gas, and if it is arranged in the center of the combustion chamber, it will have a large thermal effect as if it was arranged on the exhaust valve arrangement side. The fuel injection valve is located on the side of the intake valve and the fuel injection valve is located on the intake valve arrangement side. In consideration of the mixing characteristics of air and air, it is necessary to dispose the fuel injection valve in the vicinity of the intake valve. Due to restrictions, it becomes difficult to adopt an optimal layout for stratified combustion and homogeneous combustion.
[0004]
This becomes more prominent especially in the engine concept with multiple intake and exhaust valves.
[0005]
In addition to the problem of the arrangement of the fuel injection valve, since intake is performed from the intake port by opening / closing control of the intake valve, a decrease in CV value due to pump loss or valve system friction loss cannot be denied. In particular, in a cylinder-injected spark ignition engine, it is important to reliably transport the fuel injected during the compression stroke during stratified combustion around the ignition plug at the center of the combustion chamber. Since it is necessary to add a variable element for generating a flow (swirl) and a longitudinal swirl flow (tumble flow), the aforementioned pump loss and friction loss are further increased.
[0006]
Furthermore, during stratified combustion, as described above, the fuel injected in the compression stroke is transported around the spark plug on the fresh air swirl flow, but the fresh air sucked from the intake port in the intake stroke is Even if a swirl flow is formed by the swirl imparting means, the swirl flow must be attenuated at the fuel injection timing, and fuel must be injected into the attenuated swirl flow to transport and burn the fuel. Therefore, it is difficult to match the intake control and the fuel injection control. Further, since the gas flow is weakened, the improvement of the stratified combustion cannot be expected greatly.
[0007]
Therefore, the present invention can expand the degree of freedom of the layout of the fuel injection valves, can appropriately set the intake timing, and can generate a strong gas flow, so that the flammability of homogeneous combustion as well as stratified combustion can be improved. An in-cylinder injection spark ignition engine that can be further improved is provided.
[0008]
[Means for Solving the Problems]
  In the first aspect of the invention, an air supply means for supplying air to the combustion chamber in the intake stroke, a fuel injection valve for directly injecting fuel into the combustion chamber, a spark plug, a cavity combustion chamber on the piston crown surface, In-cylinder injection spark ignition that injects fuel during the compression stroke in the low load range to perform stratified combustion and injects fuel during the intake stroke in the high load range to perform homogeneous combustion In an engine, an air injection valve for injecting air directly into a combustion chamber as the air supply meansonlyConsists ofThe first injection timing for injecting the air injection valve at the time of stratified combustion leaving a part of the predetermined supply air amount in the intake stroke and the remaining air amount in the first half of the compression stroke are injected. It is characterized in that it is set in multiple stages at two injection timings.
[0009]
In the invention of claim 2, the air injection valve according to claim 1 is arranged on the fuel injection valve arrangement side, and the mounting angle thereof is set to an angle at which the injected fuel can be transported to the cavity combustion chamber. It is characterized by that.
[0010]
In the invention of claim 3, the mounting angle of the air injection valve and the fuel injection valve according to claim 2 is set to an angle at which the injection axes intersect with each other and the injection directions are both directed to the cavity combustion chamber. It is characterized by setting.
[0011]
The invention of claim 4 is characterized in that a plurality of air injection valves according to claims 2 and 3 are provided.
[0012]
In the invention according to claim 5, the air injection valve according to claim 4 causes air to be injected from one air injection valve during idling to form a lateral swirl flow, and the air injection valve is fully operated during partial load and high load. A feature is that air is injected from the air injection valve to form a vertical swirling flow.
[0014]
  Claim6In the invention ofAn air supply means for supplying air to the combustion chamber in the intake stroke, a fuel injection valve for directly injecting fuel into the combustion chamber, a spark plug, and a cavity combustion chamber on the piston crown surface, and during the compression stroke in a low load range In the in-cylinder type spark ignition engine in which fuel is injected into the cylinder and stratified combustion is performed and fuel is injected during the intake stroke in a high load range to perform homogeneous combustion, the air supply means It consists only of air injection valves that inject air directly into the chamber.These air injection valves are arranged on the fuel injection valve arrangement side so that their mounting angles are such that the injection air and the injection fuel are directed to the cavity combustion chamber, and the injection direction of the injection air is lower than the injection direction of the injection fuel Set to the angle at which both injection axes intersectThe first injection timing in which the injection timing of the air injection valve during the stratified combustion is injected while leaving a part of the predetermined supply air amount in the intake stroke, and the remaining air amount immediately before fuel injection in the compression stroke. Set in multiple stages for the second injection timingIt is characterized by that.
[0016]
  Claim7In the present invention, claims 1 to6The air injection valve described in (1) is characterized in that the injection operation is performed even in the expansion stroke.
[0017]
  Claim8In the present invention, claims 1 to7The air injection valve described in (1) is characterized in that the injection operation is performed even in the exhaust stroke.
[0018]
  Claim9In the present invention, claims 1 to8An inert gas supply passage is connected to the air passage of the air injection valve described in the above to inject air mixed with a predetermined amount of inert gas.
[0019]
  Claim10In the invention of claim9The inert gas supply passage described in (1) is an exhaust gas recirculation passage that is connected across the air passage of the air injection valve and the engine exhaust passage and introduces part of the exhaust gas.
[0020]
【The invention's effect】
According to the first aspect of the present invention, the air supply means is constituted by the air injection valve that directly injects air into the combustion chamber, and the intake port and the intake valve are eliminated. Therefore, it can be mounted at a position and an angle at which an optimum fuel injection direction can be obtained without being restricted by the intake valve.
[0021]
In addition, there is no friction loss of the intake valve and its valve system, and pump loss due to ventilation resistance of the intake valve and intake port is eliminated, and high-pressure air injected in the intake stroke acts in the direction of pushing down the piston. Therefore, the effect of reducing pump loss is great, and the CV value can be increased.
[0022]
Furthermore, since a strong gas flow can be formed by high-pressure air injection, fuel can be transported well around the spark plug during stratified combustion without using swirl flow imparting means, and interference between fuel and air can be prevented. It can be set intentionally and the atomization and stratification of the fuel can be easily performed. Therefore, the flammability of stratified combustion and homogeneous combustion can be improved.
[0023]
  In addition, when performing the intake stroke injection of fuel, since it is not necessary to pay attention to the interference between the fuel injected from the fuel injection valve and the intake valve, the fuel spray angle can be optimally set. Besides, the flammability of stratified combustion can be further improved.
  Moreover, since air injection is performed even in the first half of the compression stroke during stratified combustion, the gas flow can be enhanced to improve the transportability of fuel around the spark plug, and stratified combustion can be further stabilized.
[0024]
According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the fuel injected during the stratified combustion is supplied to the cavity combustion chamber without being restricted by the intake port and the intake valve. Since the optimum angle at which the fuel can be transported is set, it is possible to improve the transportability of the fuel around the spark plug and to further improve the combustibility of the stratified combustion because the gas flow is highly conserved.
[0025]
According to the invention described in claim 3, in addition to the effect of the invention of claim 2, since the air injection axis and the fuel injection axis intersect, fuel atomization can be performed at the time of fuel intake stroke injection. Since the air temperature can be lowered by inspiring latent heat of vaporization from the jet air, the actual filling efficiency can be increased and the output can be improved in the high load range where homogeneous combustion is required for high output, Since the injection air is directed to the cavity combustion chamber, it is possible to suppress the fuel from adhering to the cavity combustion chamber, and to reduce the generation of smoke and unburned HC.
[0026]
According to the fourth aspect of the present invention, in addition to the effects of the second and third aspects of the invention, a plurality of air injection valves are provided, so that the air supply amount is insufficient with one air injection valve. It is possible to appropriately cope with the case or when more air is required such as supercharging.
[0027]
According to the fifth aspect of the invention, in addition to the effect of the fourth aspect of the invention, when idling, air is injected from one air injection valve to form a lateral swirl flow (swirl). Even when idling with a small amount, a swirl can be reliably formed in the cavity combustion chamber to stabilize the combustion. On the other hand, during partial load and high load, air injection is performed from the full air injection valve to make a vertical turn Since the flow (tumble flow, reverse tumble flow) is formed, it is possible to reduce the generation of smoke and unburned HC by suppressing fuel adhesion to the cavity combustion chamber, and to stabilize homogeneous combustion and stratified combustion and improve output. Can be realized.
[0029]
  Claim6According to the invention described inSince the air supply means is composed of an air injection valve that injects air directly into the combustion chamber and the intake port and intake valve are eliminated, the fuel injection valve is optimal without being restricted by these intake port and intake valve. It can be mounted at a position and angle where the fuel injection direction is obtained.
In addition, there is no friction loss of the intake valve and its valve system, and pump loss due to the ventilation resistance of the intake valve and intake port is eliminated, and high-pressure air injected in the intake stroke acts in the direction of pushing down the piston. Therefore, the effect of reducing pump loss is great, and the CV value can be increased.
Furthermore, since a strong gas flow can be formed by high-pressure air injection, fuel can be transported well around the spark plug during stratified combustion without using swirl flow imparting means, and interference between fuel and air can be prevented. It can be set intentionally and the atomization and stratification of the fuel can be easily performed. Therefore, the flammability of stratified combustion and homogeneous combustion can be improved.
In addition, when performing the intake stroke injection of fuel, since it is not necessary to pay attention to the interference between the fuel injected from the fuel injection valve and the intake valve, the fuel spray angle can be optimally set. Besides, the flammability of stratified combustion can be further improved. Moreover,Since both the injected air and the injected fuel are directed to the cavity combustion chamber and the injected air is injected downward from the injected fuel, an air film can be formed in the cavity combustion chamber as a fast flow during stratified combustion. In order to inject fuel upward, it is possible to avoid the adhesion of fuel to the cavity combustion chamber to stabilize stratified combustion and to reduce smoke and unburned HC.
[0030]
In addition, during homogeneous combustion, mixing and agitation of injected air and injected fuel can be actively performed and fuel atomization can be performed, so that homogeneous combustion can be stabilized, and high-pressure injected air is introduced into the cavity combustion chamber. Since it blows, fuel adhesion to the cavity combustion chamber can be avoided, and smoke and unburned HC can be reduced.
[0031]
  Furthermore,During stratified combustion, air injection is also performed immediately before fuel injection in the compression stroke, so the air film formed in the cavity combustion chamber can be strengthened to prevent fuel adhesion more reliably, and gas flow can be strengthened to ignite It is possible to improve the transportability of fuel around the plug.
[0032]
  Claim7According to the invention described in claim 1,6In addition to the effects of the present invention, air injection from the air injection valve is performed even in the expansion stroke, so that the combustion of unburned HC can be activated to improve the thermal efficiency and thorough measures to reduce smoke and unburned HC be able to.
[0033]
  Claim8According to the invention described in claim 1,7In addition to the effect of the invention, scavenging efficiency can be improved because air is injected from the air injection valve in the exhaust stroke.
[0034]
  Claim9According to the invention described in claim 1,8In addition to the effect of the present invention, since air mixed with an inert gas is injected from the air injection valve, the effect of reducing NOx can be obtained.
[0035]
  Claim10According to the invention described in claim9In addition to the effect of the present invention, the burned gas is effectively used as the inert gas, so that the NOx reduction effect can be obtained advantageously in terms of cost by the exhaust gas recirculation.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0037]
1 and 2, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, and 4 is a combustion chamber formed by these cylinder block 1, piston 2 and cylinder head 3.
[0038]
The cylinder head 3 is provided with a spark plug 5 at a position substantially facing the center of the combustion chamber 4, and fuel is directly injected into the combustion chamber 4 on the side opposite to the exhaust valve arrangement side (not shown). A fuel injection valve 6 is provided.
[0039]
Unlike the normal engine, the cylinder head 3 does not have an intake port and an intake valve. High-pressure air compressed by a high-pressure pump 8 and sent by an air passage 9 is supplied to the side where the fuel injection valve 6 is disposed. An air injection valve 7 that directly injects into the combustion chamber 4 is provided.
[0040]
A cavity combustion chamber 10 for receiving the fuel injected from the fuel injection valve 6 during the compression stroke at the time of the stratified combustion is formed in a substantially half portion biased to the side where the fuel injection valve 6 is disposed on the crown surface of the piston 2. It is formed.
[0041]
The fuel injection valve 6 is mounted at an angle so that when the fuel is injected during the compression stroke during the stratified combustion, the injected fuel is directed to the cavity combustion chamber 4 and reliably received in the cavity combustion chamber 4. In the air injection valve 7, the air injected in the intake stroke turns right as shown by an arrow in FIG. 2 to form a lateral swirl flow (swirl), and this swirl is stored in the cavity combustion chamber 10 in the compression stroke. Thus, the fuel injected during the compression stroke is mounted at an angle that can reliably transport the fuel around the spark plug 5.
[0042]
FIG. 3 shows the injection timings of the air injection valve 7 and the fuel injection valve 6 and the ignition timing of the spark plug 5 during stratified combustion in the 4-cycle stroke, and FIG. 4 shows the air injection valves 7 and 6 during homogeneous combustion. Each injection timing of the fuel injection valve 6 and the ignition timing of the spark plug 5 are shown. A indicates the air injection timing, F indicates the fuel injection timing, and S indicates the ignition timing.
[0043]
Therefore, according to the configuration of the first embodiment, the air supply means for supplying air to the combustion chamber 4 in the intake stroke is constituted by the air injection valve 7 for supplying high-pressure air directly to the combustion chamber 4, Since the intake port and the intake valve are eliminated, the fuel injection valve 6 can be mounted at a position and an angle at which an optimal fuel injection direction can be obtained without being restricted by the intake port and the intake valve.
[0044]
In addition, there is no friction loss of the intake valve and its valve system, and there is no pump loss due to ventilation resistance of the intake valve and intake port, and high-pressure air injected in the intake stroke acts in the push-down direction of the piston 2 Therefore, the effect of reducing pump loss is great, and the CV value can be increased.
[0045]
Furthermore, since a strong gas flow can be formed by high-pressure air injection, and the air injection valve 7 can be mounted at an optimal angle that can form a swirl without being restricted by the intake port or intake valve, the swirl flow imparting means Therefore, it is possible to improve the storage stability of the gas flow without using the gas, and therefore, it is possible to improve the transportability of the fuel around the spark plug 5 during the stratified combustion, and the mounting angle between the air injector 7 and the fuel injector 6 is Since the interference between the fuel and air can be set intentionally and the fuel can be easily atomized and stratified, the flammability of stratified combustion and homogeneous combustion can be improved.
[0046]
In addition, when performing the intake stroke injection of the fuel, it is not necessary to pay attention to the interference between the fuel injected from the fuel injection valve 6 and the intake valve, so that the fuel spray angle can be set optimally. Combustibility of stratified combustion as well as combustion can be further improved.
[0047]
FIG. 5 shows the second embodiment of the present invention. In this embodiment, in the configuration of the first embodiment shown in FIGS. The first injection timing A in which the timing is injected while leaving a part of the predetermined supply air amount in the intake stroke₁And the second injection timing A for injecting the remaining air amount in the first half of the compression stroke₂Are set in multiple stages.
[0048]
Therefore, according to the configuration of the second embodiment, in addition to the effects of the first embodiment, air injection is performed even in the first half of the compression stroke at the time of stratified combustion. Fuel transportability can be improved, and stratified combustion can be further stabilized.
[0049]
FIGS. 6 and 7 show a third embodiment of the present invention. In this embodiment, the expansion stroke is performed in both the stratified combustion (FIG. 6) and the homogeneous combustion (FIG. 7). Injecting the required amount of additional air A by injecting the air injection valve 7_α ₁I am trying to do.
[0050]
Therefore, according to the configuration of the third embodiment, in addition to the effects of the first embodiment and the second embodiment, a required amount of air injection is performed by the air injection valve 7 under the temperature condition in which the combustion temperature is high even in the expansion stroke. A_α ₁Therefore, the combustion of unburned HC can be activated by this additional air to improve thermal efficiency, and measures for reducing smoke and unburned HC can be thoroughly implemented.
[0051]
In the third embodiment, the injection of additional air is performed in the expansion stroke. However, as in the fourth embodiment shown in FIGS._α ₂If scavenging is performed, scavenging efficiency can be increased.
[0052]
Also, additional air injection A in this exhaust stroke_α ₂Is performed in the first half of the exhaust stroke in which a high combustion temperature is maintained as indicated by a chain line, the additional air injection Aα is performed in the expansion stroke.₁As in the case of performing the above, it is possible to expect the activation of the combustion of the unburned HC, and in particular, in the exhaust stroke, the combustion activation of the unburned HC attached to the cylinder liner that is scraped off by the lift of the piston is also possible. it can.
[0053]
10 and 11 show a fifth embodiment of the present invention. In this embodiment, the mounting angles of the air injection valve 7 and the fuel injection valve 6 are such that both injection axes intersect in the vertical direction and the horizontal direction. In addition, the injection direction is set at an angle that is directed toward the cavity combustion chamber 10.
[0054]
Therefore, according to the configuration of the fifth embodiment, the same effect as that of the first embodiment can be obtained, and the air injection axis and the fuel injection axis intersect each other. Atomization can be performed and the air temperature can be lowered by the latent heat of vaporization from the jet air, so the actual filling efficiency can be increased and the output in a high load range where high power is required to achieve high output can be realized. Can do.
[0055]
Moreover, since the injected air is directed to the cavity combustion chamber 10, it is possible to suppress the fuel from adhering to the cavity combustion chamber 10, and to reduce the generation of smoke and unburned HC.
[0056]
Here, in the fifth embodiment, the injection timing at the time of stratified combustion of the air injection valve 7 is the same as in the second embodiment shown in FIG.₁And the second injection timing A in the first half of the compression stroke₂And the second injection timing A₂In this way, the air injected into the cavity combustion chamber 10 becomes a swirl with sufficient inertia in the cavity combustion chamber 10 so that the fuel can be reliably transported around the spark plug 5 and the stability of stratified combustion is further improved. Can be increased.
[0057]
In addition, it is possible to achieve early fuel injection and late ignition, so that the mixture formation is good and NO_xA reduction effect is obtained, and furthermore, the heat generation time of combustion is delayed, so that the thermal efficiency can be increased.
[0058]
12 and 13 show a sixth embodiment of the present invention. In this embodiment, a plurality of air injection valves 7, specifically, two air injection valves 7 and 7 are connected to the fuel injection valve 6. On the arrangement side, the fuel injection valve 6 is mounted in a substantially line symmetrical manner inward about the injection axis of the fuel injection valve 6 in plan view.
[0059]
Further, these two air injection valves 7, 7, as shown by the arrows in FIG. 12, the injection air flows from the exhaust valve side (not shown) toward the crown surface of the piston 2 through the lower side of the spark plug 5. They are arranged at a mounting angle that can form a so-called forward tumble longitudinal swirl flow.
[0060]
Therefore, according to the configuration of the sixth embodiment, the same effect as that of the first embodiment can be obtained. In addition, since the two air injection valves 7 and 7 are arranged, one air injection valve 7 has air. It is possible to appropriately cope with a case where the supply amount is insufficient or a case where more air is required such as supercharging.
[0061]
Further, during idling, air is injected from only one air injection valve 7 to form a swirl, and during partial load and high load, air injection is simultaneously performed from both air injection valves 7 and 7 to form a forward tumble flow. By doing so, it is possible to reliably form a swirl in the cavity combustion chamber 10 even when idling with a small amount of supply air, and to stabilize the combustion. Since the generation of smoke and unburned HC can be reduced by restraining the fuel from adhering to the fuel cell 10, the homogeneous combustion and the stratified combustion can be stabilized and the output can be improved.
[0062]
Further, in the case of the sixth embodiment, similarly to the second embodiment shown in FIG. 5, the injection timings of the two air injection valves 7 and 7 at the time of stratified combustion are set to the first injection timing A in the intake stroke.₁And the second injection timing A in the first half of the compression stroke₂In addition, the forward tumble flow can be strengthened and the transportability of fuel around the spark plug 5 can be enhanced.
[0063]
In this embodiment, the forward tumble flow is formed. However, the mounting angle of the air injection valves 7 and 7 can be set to be vertical so that the reverse tumble flow can be formed.
[0064]
FIGS. 14 and 15 show a seventh embodiment of the present invention. In this embodiment, the air injection valve 7 is disposed almost directly above the fuel injection valve 6, and the air injection valve 7 and the fuel injection valve are shown. 6 is an angle at which the injected air and the injected fuel are directed to the cavity combustion chamber 10 and the injection direction of the injected air is lower than the injection direction of the injected fuel so that the injection axes intersect each other in the vertical direction. So that the injected air crosses the front end portion of the fuel injection valve 6 toward the cavity combustion chamber 10 as shown by the arrow in FIG. 14, and reverses in the cavity combustion chamber 10 and flows toward the spark plug 5. A reverse tumble flow is formed.
[0065]
Therefore, according to the configuration of the seventh embodiment, the same effects as those of the first embodiment can be obtained, and both the injected air and the injected fuel are directed to the cavity combustion chamber 10 and the injected air is more than the injected fuel. Is also injected downward to form a reverse tumble flow, so that during stratified combustion, an air film can be formed in the cavity combustion chamber 10 as a fast flow, and fuel is injected onto the cavity combustion chamber 10 to be injected onto it. By avoiding fuel adhesion, stratified combustion can be stabilized, and smoke and unburned HC can be reduced.
[0066]
Further, during homogeneous combustion, mixing and agitation of the injected air and the injected fuel can be actively performed and the fuel can be atomized, so that the homogeneous combustion can be stabilized, and the high-pressure injected air is supplied to the cavity combustion chamber 10. Therefore, fuel adhesion to the cavity combustion chamber 10 can be avoided, and smoke and unburned HC can be reduced.
[0067]
Further, as in the fifth embodiment shown in FIGS. 10 and 11, during the homogeneous combustion in which the intake stroke injection of the fuel is performed, the injected fuel is more liable to vaporize latent heat than the injected air, so that the air temperature is lowered. High output can be obtained.
[0068]
FIG. 16 shows an eighth embodiment of the present invention. In this embodiment, in the structure of the seventh embodiment shown in FIGS. 14 and 15, the above-described injection of the air injection valve 7 at the time of stratified combustion is shown. The first injection timing A in which the timing is injected while leaving a part of the predetermined supply air amount in the intake stroke₁And the second injection timing at which the remaining amount of air is injected immediately before the fuel injection timing F in the latter half of the compression stroke.
[0069]
Therefore, according to the configuration of the eighth embodiment, during stratified combustion, air injection is performed immediately before fuel injection in the compression stroke. Therefore, the air film formed in the cavity combustion chamber 10 is strengthened to further adhere to the fuel. While being able to prevent reliably, a reverse tumble flow can be strengthened and the transportability of the fuel around the spark plug 5 can be improved.
[0070]
In addition, in each embodiment shown in FIGS. 10 to 16, as in the embodiment shown in FIGS. 6, 7, or FIGS. 8 and 9, the air injection valve 7 is added during the expansion stroke and / or the exhaust stroke. By injecting the air, it is possible to reduce the unburned HC and improve the scavenging efficiency.
[0071]
FIG. 17 shows a ninth embodiment of the present invention. In this embodiment, NO is shown._xAs a countermeasure for reduction, air mixed with an inert gas is injected from the air injection valve 7 into the combustion chamber 4.
[0072]
FIG. 17 shows a case where it is applied to the engine concept of the first embodiment shown in FIG. 1 for convenience. In this embodiment, a mixer chamber 11 is provided in the middle of the air passage 9 of the air injection valve 7, and the mixer An exhaust gas recirculation passage 13 is connected across the chamber 11 and the exhaust port 12, and an appropriate amount corresponding to the intake air amount as an inert gas is controlled under the control of the exhaust gas recirculation control valve device 14 interposed in the exhaust gas recirculation passage 13. Reflux exhaust (EGR) is performed and mixed with fresh air in the mixer chamber 11 to perform external EGR._xThe reduction effect is obtained. In FIG. 17, reference numeral 15 denotes an exhaust valve.
[Brief description of the drawings]
FIG. 1 is an explanatory cross-sectional view schematically showing a configuration of a first embodiment of the present invention.
FIG. 2 is a schematic plan view illustrating a first embodiment of the present invention.
FIG. 3 is an explanatory diagram showing air injection timing, fuel injection timing, and ignition timing during stratified combustion according to the first embodiment of the present invention.
FIG. 4 is an explanatory diagram showing air injection timing, fuel injection timing, and ignition timing at the time of homogeneous combustion according to the first embodiment of the present invention.
FIG. 5 is an explanatory diagram showing air injection timing, fuel injection timing, and ignition timing during stratified combustion according to the second embodiment of the present invention.
FIG. 6 is an explanatory diagram showing air injection timing, fuel injection timing, and ignition timing during stratified combustion according to the third embodiment of the present invention.
FIG. 7 is an explanatory diagram showing an air injection timing, a fuel injection timing, and an ignition timing at the time of homogeneous combustion according to a third embodiment of the present invention.
FIG. 8 is an explanatory diagram showing air injection timing, fuel injection timing, and ignition timing during stratified combustion according to a fourth embodiment of the present invention.
FIG. 9 is an explanatory diagram showing air injection timing, fuel injection timing, and ignition timing during homogeneous combustion according to the fourth embodiment of the present invention.
FIG. 10 is an explanatory cross-sectional view schematically showing a configuration of a fifth embodiment of the present invention.
FIG. 11 is a schematic plan view illustrating a fifth embodiment of the present invention.
FIG. 12 is a cross-sectional explanatory view schematically showing a configuration of a sixth embodiment of the present invention.
FIG. 13 is a schematic plan view illustrating a sixth embodiment of the present invention.
FIG. 14 is an explanatory cross-sectional view schematically showing a configuration of a seventh embodiment of the present invention.
FIG. 15 is a schematic plan view illustrating a seventh embodiment of the present invention.
FIG. 16 is an explanatory diagram showing air injection timing, fuel injection timing, and ignition timing during stratified combustion according to the eighth embodiment of the present invention.
FIG. 17 is a cross-sectional explanatory view schematically showing a configuration of a ninth embodiment of the present invention.
[Explanation of symbols]
1 Cylinder block
2 piston
3 Cylinder head
4 Combustion chamber
5 Spark plug
6 Fuel injection valve
7 Air injection valve
9 Air passage
10 Cavity combustion chamber
12 Exhaust port (exhaust passage)
13 Exhaust gas recirculation passage (inert gas supply passage)

Claims

An air supply means for supplying air to the combustion chamber in the intake stroke, a fuel injection valve for directly injecting fuel into the combustion chamber, a spark plug, and a cavity combustion chamber on the piston crown surface, and during the compression stroke in a low load range In the in-cylinder type spark ignition engine in which fuel is injected into the cylinder and stratified combustion is performed and fuel is injected during the intake stroke in a high load range to perform homogeneous combustion, the air supply means A first injection timing that includes only an air injection valve that directly injects air into the chamber, and causes the injection timing of the air injection valve during stratified combustion to be injected while leaving a part of a predetermined supply air amount in the intake stroke; An in-cylinder injection spark ignition engine characterized by being set in multiple stages at a second injection timing for injecting the remaining air amount in the first half of the compression stroke.

The in-cylinder injection type according to claim 1, wherein the air injection valve is disposed on the fuel injection valve arrangement side and the mounting angle thereof is set to an angle at which the injected fuel can be transported to the cavity combustion chamber. Spark ignition engine.

3. The in-cylinder injection system according to claim 2, wherein the mounting angle of the air injection valve and the fuel injection valve is set to an angle at which the injection axes intersect with each other and the injection directions are both directed to the cavity combustion chamber. Spark ignition engine.

The in-cylinder injection spark ignition engine according to claim 2 or 3 , wherein a plurality of air injection valves are provided.

During idling, air is injected from one air injection valve to form a sideways swirling flow, and during partial load and high load, air injection is performed from all air injection valves to form a vertical swirling flow. The in-cylinder injection spark ignition engine according to claim 4.

An air supply means for supplying air to the combustion chamber in the intake stroke, a fuel injection valve for directly injecting fuel into the combustion chamber, a spark plug, and a cavity combustion chamber on the piston crown surface, and during the compression stroke in a low load range In the in-cylinder type spark ignition engine in which fuel is injected into the cylinder and stratified combustion is performed and fuel is injected during the intake stroke in a high load range to perform homogeneous combustion, the air supply means The air injection valve that directly injects air into the chamber, the air injection valve is disposed on the fuel injection valve arrangement side, and these mounting angles are set such that the injection air and the injected fuel are directed to the cavity combustion chamber, and The injection direction of the injection air is set to an angle at which both injection axes intersect so that the injection direction of the injected fuel is downward, and the injection timing of the air injection valve during the stratified combustion is set to a predetermined supply air amount in the intake stroke Some of Leaving the first injection timing to inject the in-cylinder injection spark ignition engine, characterized in that set in multiple stages in a second injection timing to inject the remaining amount of air just before the fuel injection in the compression stroke.

Cylinder injection type spark ignition engine according to any one of claims 1-6, characterized in that the air injection valve to also be injected operated in expansion stroke.

Cylinder injection type spark ignition engine according to any one of claims 1-7, characterized in that the air injection valve to also be injected operated in the exhaust stroke.

The air passage of the air injection valve, connects the inert gas supply passage, to any one of claims 1-8, characterized in that so as to inject a predetermined amount of air mixed with an inert gas The in-cylinder injection spark ignition engine described.

The cylinder according to claim 9 , wherein the inert gas supply passage is an exhaust gas recirculation passage connected across the air passage of the air injection valve and the engine exhaust passage to introduce a part of the exhaust gas. An internal injection spark ignition engine.