JP4192633B2

JP4192633B2 - Direct-injection spark ignition internal combustion engine

Info

Publication number: JP4192633B2
Application number: JP2003055976A
Authority: JP
Inventors: 三泰赤木
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2003-03-03
Filing date: 2003-03-03
Publication date: 2008-12-10
Anticipated expiration: 2023-03-03
Also published as: JP2004263641A

Description

【０００１】
【発明の属する技術分野】
本発明は、直噴火花点火式内燃機関に関する。
【０００２】
【従来の技術】
従来より、直噴火花点火式内燃機関では、特許文献１に示されるように、燃焼室の側部に配置される燃料噴射弁から２つの吸気弁の間を経由し燃焼室中心部側へ燃料を噴射している。
【０００３】
【特許文献１】
特開平１１−２９４２０８号公報
【０００４】
【発明が解決しようとする課題】
しかしながら、圧縮行程にて燃料噴射を行う成層運転モードに対し、吸気行程にて燃料噴射を行う均質運転モードでは、吸気弁がリフトしているため、噴射された燃料の一部が吸気弁と干渉することで、筒内での混合気形成を阻害する結果、筒内に液状燃料が多く存在するようになり、機関から排出される未燃燃料（ＨＣ）が多くなるという問題点があった。
【０００５】
特に、筒内に直接燃料を噴射する直噴火花点火式内燃機関の場合、吸気ポート内に燃料を噴射するポート噴射式内燃機関のように、燃料を噴射して点火が行われるまでの混合気形成時間を長くとることができないため、噴射した燃料の吸気弁との干渉は未燃燃料を低減する上で、大きな問題であった。
【０００６】
本発明は、このような従来の問題点に鑑み、吸気行程噴射時に吸気弁と干渉する燃料噴霧を減らして、未燃燃料の排出量を低減することを目的とする。
【０００７】
【課題を解決するための手段】
このため、本発明は、燃焼室の側部に配置される燃料噴射弁から２つの吸気弁の間を経由し燃焼室中心部側へ燃料を噴射すると共に、吸気通路に筒内流動を強化するエアモーションバルブを備える直噴火花点火式内燃機関において、
吸気弁のリフト量を可変制御可能な可変動弁装置を備え、吸気行程にて燃料噴射を行う運転モードの時に、機関の暖機状態と、運転領域とを判別して、
機関の冷機時で、かつ、所定の低回転・低負荷領域の場合には、吸気弁のリフト量を低リフトとし、かつエアモーションバルブを作動させ、
機関の冷機時で、かつ前記低回転・低負荷領域よりも高速・高負荷側の所定の中回転・中負荷領域の場合、および、機関の暖機後で、かつ前記低回転・低負荷領域ないし前記中回転・中負荷領域の場合には、吸気弁のリフト量を高リフトとし、かつエアモーションバルブを作動させ、
前記中回転・中負荷領域よりも高速・高負荷側の高速・高負荷領域の場合には、暖機状態に拘わらず、吸気弁のリフト量を高リフトとし、かつエアモーションバルブを非作動とすることを特徴とする。
又は、吸気行程にて燃料噴射を行う運転モードの時に、運転領域を判別して、
所定の低回転・低負荷領域の場合に、吸気弁のリフト量を低リフトし、かつエアモーションバルブを作動させ、
前記低回転・低負荷領域よりも高速・高負荷側の所定の中回転・中負荷領域の場合には、吸気弁のリフト量を高リフトとし、かつエアモーションバルブを作動させ、
前記中回転・中負荷領域よりも高速・高負荷側の高速・高負荷領域の場合には、吸気弁のリフト量を高リフトとし、かつエアモーションバルブを非作動とする一方、
機関の暖機状態を判別する手段を備え、暖機後は、前記低回転・低負荷領域をより低回転・低負荷側に縮小することを特徴とする。
【０００８】
【発明の効果】
本発明によれば、吸気行程噴射時に吸気弁のリフト量を減少させることで、燃料噴霧と吸気弁との干渉を抑制し、未燃燃料の排出量を低減可能となる。
また、吸気弁のリフト量の制御と、エアモーションバルブの制御とを組み合わせることで、筒内での混合気形成を更に良好なものとすることができる。
【０００９】
【発明の実施の形態】
以下に本発明の実施の形態を図面に基づいて説明する。
図１は本発明の実施形態を示す内燃機関（吸気弁高リフト時）の要部断面図、図２は内燃機関の平面レイアウト図、図３は吸気弁低リフト時の要部断面図である。
【００１０】
内燃機関の燃焼室１には、その上面（シリンダヘッド）側の略中央部に点火プラグ２が配置されている。そして、点火プラグ２を囲むように、２本ずつ吸気ポート３Ａ、３Ｂ及び排気ポート４Ａ、４Ｂが開口し、それぞれに吸気弁５Ａ、５Ｂ及び排気弁６Ａ、６Ｂが装着されている。
【００１１】
燃料噴射弁７は、吸気ポート３Ａ、３Ｂ間に設置され、燃焼室１の吸気弁５Ａ、５Ｂ側の側部にシリンダ中心軸Ｃに対して直角な面に対して所定角度θ傾いて斜め下向きに配置され、２つの吸気弁５Ａ、５Ｂの間を経由し燃焼室１中心部側へ燃料を噴射するようになっている。
【００１２】
また、吸気ポート３Ａ、３Ｂは、それぞれ、仕切板８により上下の分割ポートに分割されており、下側の分割ポートの上流側に、これを閉止可能で、閉止時に筒内流動を強化可能なエアモーションバルブ９が設けられている。本実施形態では、特にタンブル流動を強化するようになっているので、エアモーションバルブ９を、タンブル制御弁（ＴＣＶ）９と称する。
【００１３】
この内燃機関での運転モードには、成層運転モードと均質運転モードとがあり、成層運転モードでは、圧縮行程にて燃料噴射を行い、点火プラグ２の周囲に成層化された混合気塊を形成することで、全体としては極めてリーンな空燃比で成層燃焼を行わせる。これに対し、均質運転モードでは、吸気行程にて燃料噴射を行い、燃焼室１の全体に均質な混合気を形成することで、ストイキ又はリーン空燃比での均質燃焼を行わせる。
【００１４】
ここで、圧縮行程噴射の場合は、吸気弁５Ａ、５Ｂは閉じているため、燃料噴霧と吸気弁５Ａ、５Ｂとの干渉は問題とならないが、吸気行程噴射の場合は、吸気弁５Ａ、５Ｂがリフトしているため、燃料噴霧と吸気弁５Ａ、５Ｂとの干渉が問題となる。図１及び図２には燃料噴霧と吸気弁との干渉部分を黒塗りで示している。
【００１５】
そこで、本発明では、吸気行程にて燃料噴射を行う運転モード（均質運転モード）の時に、図３に示すように、吸気弁５Ａ、５Ｂのリフト量を減少させることにより、燃料噴霧と吸気弁５Ａ、５Ｂとの干渉を防止、あるいは少なくとも減少する。
【００１６】
このため、少なくとも吸気弁５Ａ、５Ｂは、可変動弁装置（図４中の１０）により、リフト量を可変制御可能としてある。この場合の可変動弁装置としては、カム駆動式で油圧によりカムを切換えることでリフト量を変化させるものや、電磁駆動式で任意のリフト特性を得ることができるものを用いることができる。
【００１７】
図４は制御系の構成図であり、点火プラグ２、燃料噴射弁７、タンブル制御弁９などと共に、可変動弁装置１０の作動を制御するエンジンコントロールユニット（ＥＣＵ）１１に、エンジン回転数Ｎを検出可能な回転数センサ１２、負荷（例えばアクセル開度）Ｌを検出可能な負荷センサ１３、エンジン冷却水温Ｔｗを検出可能な水温センサ１４の信号を入力してある。
【００１８】
ここにおいて、ＥＣＵ１１では、各種センサにより検出される運転条件に応じて可変動弁装置１０を制御してリフト量を制御する。
【００１９】
図５は第１実施形態での制御フローであり、均質運転モードにてリフト量制御及びＴＣＶ制御のために実行される。
Ｓ１１では、各種センサより、エンジン回転数Ｎ、負荷Ｌ、水温Ｔｗなどを読込む。
【００２０】
Ｓ１２では、水温Ｔｗを所定値と比較することで、冷機時（Ｔｗ≦所定値）か、暖機後（Ｔｗ＞所定値）かを判定する。
冷機時（Ｔｗ≦所定値）の場合は、Ｓ１３へ進む。
【００２１】
Ｓ１３では、エンジン回転数Ｎが所定のしきい値Ｎ１以下で、かつ負荷Ｌが所定のしきい値Ｌ１以下の低回転・低負荷領域か否かを判定する。この運転領域は、吸気弁の低リフト状態で吸入可能な最大吸入空気量にて運転可能な運転領域である。
【００２２】
低回転・低負荷領域の場合は、Ｓ１４、Ｓ１５へ進む。
Ｓ１４では、冷機時（Ｔｗ≦所定値）で、かつ、低回転・低負荷領域（必要空気量が少ない領域）であるので、吸気弁のリフト量を小さくする（低リフト）。また、Ｓ１５では、ＴＣＶ（タンブル制御弁）を閉じて、筒内流動を強化する。
【００２３】
これに対し、Ｓ１２での判定で、暖機後（Ｔｗ＞所定値）の場合、又は、Ｓ１３での判定で、低回転・低負荷領域でない場合は、Ｓ１６へ進む。
Ｓ１６では、エンジン回転数Ｎが所定のしきい値Ｎ２以下で、かつ負荷Ｌが所定のしきい値Ｌ２以下の低中回転・低中負荷領域か否かを判定する。尚、Ｎ２＞Ｎ１、Ｌ２＞Ｌ１である。
【００２４】
低中回転・低中負荷領域の場合は、Ｓ１７、Ｓ１８へ進む。
Ｓ１７では、吸気弁のリフト量を大きくする（高リフト）。また、Ｓ１８では、ＴＣＶ（タンブル制御弁）を閉じて、筒内流動を強化する。
【００２５】
これに対し、Ｓ１６での判定で、低中回転・低中負荷領域でない場合、すなわち、高回転又は高負荷領域の場合は、Ｓ１９、Ｓ２０へ進む。
Ｓ１９では、吸気弁のリフト量を大きくする（高リフト）。また、Ｓ２０では、ＴＣＶ（タンブル制御弁）を開いて、出力性能を向上させる。
【００２６】
本実施形態によれば、吸気行程にて燃料噴射を行う運転モードで、かつ所定の低回転・低負荷領域の時に、吸気弁のリフト量を減少させることにより、必要空気量を確保できる範囲で、燃料噴霧と吸気弁との干渉を抑制して、混合気形成を良好なものとし、未燃燃料（ＨＣ）の排出量を低減することができる。
【００２７】
また、本実施形態によれば、暖機後は、燃料噴霧と吸気弁とが干渉しても、吸気弁温度、雰囲気温度が高く、気化性が良好なため混合気形成にさほどの支障がない（ＨＣ排出量が少ない）ことから、冷機時のみ低リフトとする一方、暖機後は吸気弁のリフト量の減少を禁止して高リフトとすることにより、吸気の流れをできるだけ阻害しないようにして吸気充填効率の向上とガス流動の悪化防止とを図り、燃焼性能を重視して燃費向上を図ることができる。
【００２８】
また、本実施形態によれば、吸気通路に筒内流動を強化するためのエアモーションバルブ（タンブル制御弁）を備えることにより、吸入空気が吸気弁部の通過する流速を早めて、吸気弁傘部に付着した燃料の気化を促進でき、ガス流動の強化とあわせ、筒内での混合気形成を良好なものとすることができる。
【００２９】
また、暖機後は、燃料噴霧と吸気弁とが干渉しても気化性が良好なため混合気形成にさほどの支障がない（ＨＣ排出量が少ない）ことから、冷機時のみ低リフトとする一方、暖機後は吸気弁のリフト量の減少を禁止して高リフトとすることにより、エアモーションバルブ（タンブル制御弁）によるガス流動の強化をできるだけ阻害しないようにすることができる。すなわち、暖機後はガス流動強化を重視して、混合気分布の更なる均質化を図り、燃費向上を図ることができる。
【００３０】
図６は第２実施形態での制御フローであり、均質運転モードにてリフト量制御及びＴＣＶ制御のために実行される。
Ｓ２１では、各種センサより、エンジン回転数Ｎ、負荷Ｌ、水温Ｔｗなどを読込む。
【００３１】
Ｓ２２では、水温Ｔｗを所定値と比較することで、冷機時（Ｔｗ≦所定値）か、暖機後（Ｔｗ＞所定値）かを判定する。
冷機時（Ｔｗ≦所定値）の場合は、Ｓ２３へ進み、低リフト運転を行う領域を決定する回転数及び負荷のしきい値Ｎ１、Ｌ１を、高回転・高負荷側となるように、比較的大きな値に設定する。尚、ここで設定されるＮ１以下、Ｌ１以下の運転領域が、吸気弁の低リフト状態で吸入可能な最大吸入空気量にて運転可能な運転領域である。
【００３２】
暖機時（Ｔｗ＞所定値）の場合は、Ｓ２４へ進み、低リフト運転を行う領域を決定する回転数及び負荷のしきい値Ｎ１、Ｌ１を、低回転・低負荷側となるように、比較的小さな値に設定する。
【００３３】
Ｓ２３又はＳ２４の実行後は、Ｓ２５へ進む。
Ｓ２５では、エンジン回転数Ｎがしきい値Ｎ１以下で、かつ負荷Ｌがしきい値Ｌ１以下の低回転・低負荷領域か否かを判定する。
【００３４】
低回転・低負荷領域の場合は、Ｓ２６、Ｓ２７へ進む。
Ｓ２６では、冷機時（Ｔｗ≦所定値）で、かつ、低回転・低負荷領域であるので、吸気弁のリフト量を小さくする（低リフト）。また、Ｓ２７では、ＴＣＶ（タンブル制御弁）を閉じて、筒内流動を強化する。
【００３５】
これに対し、Ｓ２５での判定で、低回転・低負荷領域でない場合は、Ｓ２８へ進む。
Ｓ２８では、エンジン回転数Ｎが所定のしきい値Ｎ２以下で、かつ負荷Ｌが所定のしきい値Ｌ２以下の中回転・中負荷領域か否かを判定する。尚、Ｎ２＞Ｎ１、Ｌ２＞Ｌ１である。
【００３６】
中回転・中負荷領域の場合は、Ｓ２９、Ｓ３０へ進む。
Ｓ２９では、吸気弁のリフト量を大きくする（高リフト）。また、Ｓ３０では、ＴＣＶ（タンブル制御弁）を閉じて、筒内流動を強化する。
【００３７】
これに対し、Ｓ２８での判定で、中回転・中負荷領域でない場合、すなわち、高回転又は高負荷領域の場合は、Ｓ３１、Ｓ３２へ進む。
Ｓ３１では、吸気弁のリフト量を大きくする（高リフト）。また、Ｓ３２では、ＴＣＶ（タンブル制御弁）を開いて、出力性能を向上させる。
【００３８】
前記第１実施形態では、暖機後は、吸気弁のリフト量の減少を禁止するのに対し、この第２実施形態では、上記のように制御することで、暖機後は、冷機時に比べ、吸気弁のリフト量を減少させる運転領域をより低回転・低負荷側に縮小している。
【００３９】
すなわち、暖機後は、燃料噴霧と吸気弁とが干渉しても気化性が良好なため混合気形成にさほどの支障がない（ＨＣ排出量が少ない）ことから、エアモーションバルブ（タンブル制御弁）によるガス流動の強化をできるだけ阻害しないようにすることが、燃費向上の観点から望ましい。
【００４０】
しかし、極低回転・低負荷領域では、そもそも吸気流速が低すぎるため、エアモーションバルブ（タンブル制御弁）によるガス流動の強化機能が十分には発揮されない。そこで、極低回転・低負荷領域では、暖機後も低リフトとして、燃料噴霧と吸気弁との干渉防止による未燃燃料（ＨＣ）の排出量低減を図る方が得策と考えられる。
【００４１】
そこで、この第２実施形態では、暖機後は、冷機時に比べ、吸気弁のリフト量を減少させる運転領域をより低回転・低負荷側に縮小し、ガス流動の強化可能な領域ではガス流動の強化を重視し、ガス流動の強化機能が十分に発揮されない領域では燃料噴霧の干渉防止を重視しているのである。
【図面の簡単な説明】
【図１】本発明の実施形態を示す内燃機関（吸気弁高リフト時）の要部断面図
【図２】内燃機関の平面レイアウト図
【図３】吸気弁低リフト時の要部断面図
【図４】制御系の構成図
【図５】第１実施形態の制御フローチャート
【図６】第２実施形態の制御フローチャート
【符号の説明】
１燃焼室
２点火プラグ
３Ａ、３Ｂ吸気ポート
４Ａ、４Ｂ排気ポート
５Ａ、５Ｂ吸気弁
６Ａ、６Ｂ排気弁
７燃料噴射弁
８仕切板
９エアモーションバルブ（タンブル制御弁）
１０可変動弁装置
１１エンジンコントロールユニット（ＥＣＵ）
１２回転数センサ
１３負荷センサ
１４水温センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct injection spark ignition internal combustion engine.
[0002]
[Prior art]
Conventionally, in a direct-injection spark-ignition internal combustion engine, as shown in Patent Document 1, a fuel is injected from a fuel injection valve disposed at a side portion of a combustion chamber to a combustion chamber center side through two intake valves. Is sprayed.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-294208
[Problems to be solved by the invention]
However, in the stratified operation mode in which fuel injection is performed in the compression stroke, in the homogeneous operation mode in which fuel injection is performed in the intake stroke, since the intake valve is lifted, a part of the injected fuel interferes with the intake valve. As a result, as a result of inhibiting the mixture formation in the cylinder, a large amount of liquid fuel is present in the cylinder, and there is a problem that unburned fuel (HC) discharged from the engine increases.
[0005]
In particular, in the case of a direct-injection spark-ignition internal combustion engine that injects fuel directly into a cylinder, the mixture gas until fuel is injected and ignition is performed, as in a port-injection internal combustion engine that injects fuel into an intake port. Since the formation time cannot be made long, the interference of the injected fuel with the intake valve is a big problem in reducing the unburned fuel.
[0006]
The present invention has been made in view of such conventional problems, and an object of the present invention is to reduce the amount of unburned fuel by reducing fuel spray that interferes with the intake valve during intake stroke injection.
[0007]
[Means for Solving the Problems]
For this reason, the present invention injects fuel from the fuel injection valve disposed on the side portion of the combustion chamber to the combustion chamber central portion side through the two intake valves and enhances the in-cylinder flow in the intake passage. In a direct-injection spark ignition internal combustion engine equipped with an air motion valve,
Equipped with a variable valve system that can variably control the lift amount of the intake valve, and in the operation mode in which fuel injection is performed in the intake stroke, the engine warm-up state and the operation region are determined,
In time cold engine, and, in the case of a predetermined low rotation and low-load region, the lift amount of the intake valve is set to a low lift, and actuates the air motion valve,
When the engine is cold, and in a predetermined medium rotation / medium load region at a higher speed / high load side than the low rotation / low load region, and after the engine is warmed up, and the low rotation / low load region Or in the middle rotation / medium load region, the lift amount of the intake valve is set to a high lift, and the air motion valve is operated,
In the case of the high speed / high load area on the high speed / high load side than the medium rotation / medium load area, the lift amount of the intake valve is set to a high lift and the air motion valve is not operated regardless of the warm-up state. It is characterized by doing .
Or, in the operation mode in which fuel injection is performed in the intake stroke, the operation region is determined,
In the specified low rotation / low load range, lower the lift amount of the intake valve and operate the air motion valve.
In the case of a predetermined medium rotation / medium load region on the high speed / high load side than the low rotation / low load region, the lift amount of the intake valve is set to a high lift, and the air motion valve is operated,
In the case of the high speed / high load area on the high speed / high load side than the medium rotation / medium load area, the lift amount of the intake valve is set to a high lift and the air motion valve is not operated ,
Comprising means for determining a warm-up state of the engine, after warm-up is characterized by reducing the low-rotation and low-load region to a lower rotation and low load side.
[0008]
【The invention's effect】
According to the present invention, by reducing the lift amount of the intake valve at the time of intake stroke injection, interference between the fuel spray and the intake valve can be suppressed, and the amount of unburned fuel discharged can be reduced.
Further, by combining the control of the lift amount of the intake valve and the control of the air motion valve, the mixture formation in the cylinder can be further improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view of an essential part of an internal combustion engine (intake valve high lift) showing an embodiment of the present invention, FIG. 2 is a plan layout view of the internal combustion engine, and FIG. .
[0010]
In the combustion chamber 1 of the internal combustion engine, a spark plug 2 is disposed at a substantially central portion on the upper surface (cylinder head) side. Then, two intake ports 3A and 3B and two exhaust ports 4A and 4B are opened so as to surround the spark plug 2, and the intake valves 5A and 5B and the exhaust valves 6A and 6B are mounted respectively.
[0011]
The fuel injection valve 7 is installed between the intake ports 3A and 3B, and is inclined obliquely downward by a predetermined angle θ with respect to a plane perpendicular to the cylinder center axis C on the side of the combustion chamber 1 on the intake valves 5A and 5B side. The fuel is injected into the center of the combustion chamber 1 via the space between the two intake valves 5A and 5B.
[0012]
The intake ports 3A and 3B are each divided into upper and lower divided ports by a partition plate 8, which can be closed upstream of the lower divided port and can enhance the in-cylinder flow when closed. An air motion valve 9 is provided. In this embodiment, since the tumble flow is particularly strengthened, the air motion valve 9 is referred to as a tumble control valve (TCV) 9.
[0013]
The operation mode of the internal combustion engine includes a stratified operation mode and a homogeneous operation mode. In the stratified operation mode, fuel injection is performed in the compression stroke, and a stratified mixture is formed around the spark plug 2. As a result, stratified combustion is performed at a very lean air-fuel ratio as a whole. On the other hand, in the homogeneous operation mode, fuel injection is performed in the intake stroke, and a homogeneous air-fuel mixture is formed in the entire combustion chamber 1, thereby performing homogeneous combustion at a stoichiometric or lean air-fuel ratio.
[0014]
Here, in the case of the compression stroke injection, since the intake valves 5A and 5B are closed, the interference between the fuel spray and the intake valves 5A and 5B does not matter, but in the case of the intake stroke injection, the intake valves 5A and 5B. Therefore, the interference between the fuel spray and the intake valves 5A and 5B becomes a problem. In FIGS. 1 and 2, the interference portion between the fuel spray and the intake valve is shown in black.
[0015]
Therefore, in the present invention, in the operation mode (homogeneous operation mode) in which fuel injection is performed in the intake stroke, as shown in FIG. 3, the fuel spray and the intake valve are reduced by reducing the lift amount of the intake valves 5A and 5B. Interference with 5A, 5B is prevented or at least reduced.
[0016]
For this reason, at least the intake valves 5A and 5B can be variably controlled in lift amount by a variable valve gear (10 in FIG. 4). As the variable valve operating device in this case, a cam drive type that changes the lift amount by switching the cam by hydraulic pressure, or an electromagnetic drive type that can obtain an arbitrary lift characteristic can be used.
[0017]
FIG. 4 is a block diagram of the control system. An engine control unit (ECU) 11 that controls the operation of the variable valve operating apparatus 10 together with the spark plug 2, the fuel injection valve 7, the tumble control valve 9, and the like is connected to the engine speed N. Of the rotation speed sensor 12 capable of detecting the engine load, the load sensor 13 capable of detecting the load (for example, accelerator opening degree) L, and the water temperature sensor 14 capable of detecting the engine cooling water temperature Tw.
[0018]
Here, the ECU 11 controls the variable valve apparatus 10 according to the operating conditions detected by various sensors to control the lift amount.
[0019]
FIG. 5 is a control flow in the first embodiment , which is executed for lift amount control and TCV control in the homogeneous operation mode.
In S11, engine speed N, load L, water temperature Tw, etc. are read from various sensors.
[0020]
In S12, the water temperature Tw is compared with a predetermined value to determine whether it is cold (Tw ≦ predetermined value) or after warming up (Tw> predetermined value).
If it is cold (Tw ≦ predetermined value), the process proceeds to S13.
[0021]
In S13, it is determined whether or not the engine speed N is a low rotation / low load region where the engine speed N is equal to or less than a predetermined threshold value N1 and the load L is equal to or less than the predetermined threshold value L1. This operation region is an operation region in which the operation can be performed with the maximum intake air amount that can be inhaled in a low lift state of the intake valve.
[0022]
In the case of the low rotation / low load region, the process proceeds to S14 and S15.
In S14, when the engine is cold (Tw ≦ predetermined value) and is in a low rotation / low load region (region where the required air amount is small), the lift amount of the intake valve is reduced (low lift). In S15, the TCV (tumble control valve) is closed to enhance the in-cylinder flow.
[0023]
On the other hand, if it is determined in S12 that the engine has been warmed up (Tw> predetermined value), or if it is determined in S13 that it is not in the low rotation / low load region, the process proceeds to S16.
In S16, it is determined whether or not the engine speed N is in a low / medium speed / low / medium load region where the engine speed N is equal to or less than a predetermined threshold value N2 and the load L is equal to or less than the predetermined threshold value L2. Note that N2> N1 and L2> L1.
[0024]
In the case of the low / medium rotation / low / medium load region, the process proceeds to S17 and S18.
In S17, the lift amount of the intake valve is increased (high lift). In S18, the TCV (tumble control valve) is closed to enhance the in-cylinder flow.
[0025]
On the other hand, if it is determined in S16 that the region is not in the low / medium rotation / low / medium load region, that is, in the case of the high rotation or high load region, the process proceeds to S19 and S20.
In S19, the lift amount of the intake valve is increased (high lift). In S20, the TCV (tumble control valve) is opened to improve the output performance.
[0026]
According to the present embodiment, in the operation mode in which fuel injection is performed in the intake stroke, and in a predetermined low rotation / low load region, by reducing the lift amount of the intake valve, the required air amount can be secured. In addition, it is possible to suppress the interference between the fuel spray and the intake valve, to improve the mixture formation, and to reduce the amount of unburned fuel (HC) discharged.
[0027]
In addition, according to the present embodiment, after warm-up, even if the fuel spray and the intake valve interfere with each other, the intake valve temperature and the atmospheric temperature are high and the vaporization property is good, so that there is not much trouble in the mixture formation. (The amount of HC emissions is small.) Therefore, the low lift is only used when the engine is cold. On the other hand, after the engine is warmed up, the lift of the intake valve is prohibited and reduced to a high lift so that the intake flow is not inhibited as much as possible. Thus, it is possible to improve the intake charging efficiency and prevent the gas flow from deteriorating, and to improve the fuel efficiency with emphasis on the combustion performance.
[0028]
In addition, according to the present embodiment, by providing an air motion valve (tumble control valve) for enhancing the in-cylinder flow in the intake passage, the flow velocity of the intake air passing through the intake valve portion is increased, and the intake valve umbrella Vaporization of the fuel adhering to the part can be promoted, and in addition to the enhancement of gas flow, the mixture formation in the cylinder can be made favorable.
[0029]
In addition, after warming up, even if the fuel spray and the intake valve interfere with each other, the vaporization is good, so there is no significant hindrance to the formation of the air-fuel mixture (the amount of HC emissions is small). On the other hand, after the warm-up, the reduction of the lift amount of the intake valve is prohibited and the lift is made high, so that the enhancement of gas flow by the air motion valve (tumble control valve) can be prevented as much as possible. That is, after warming up, emphasis is placed on gas flow enhancement, and the homogenous distribution can be further homogenized to improve fuel efficiency.
[0030]
FIG. 6 is a control flow in the second embodiment , which is executed for lift amount control and TCV control in the homogeneous operation mode.
In S21, engine speed N, load L, water temperature Tw, etc. are read from various sensors.
[0031]
In S22, the water temperature Tw is compared with a predetermined value to determine whether it is cold (Tw ≦ predetermined value) or after warming up (Tw> predetermined value).
When cold (Tw ≦ predetermined value), proceed to S23 and compare the rotation speed and load thresholds N1 and L1 that determine the region for low lift operation so that they are on the high rotation / high load side Set to a large value. In addition, the operation region N1 or less and L1 or less set here is an operation region that can be operated at the maximum intake air amount that can be sucked in the low lift state of the intake valve.
[0032]
In the case of warm-up (Tw> predetermined value), the process proceeds to S24, and the rotation speed and load thresholds N1 and L1 for determining the region for performing the low lift operation are set to the low rotation / low load side. Set to a relatively small value.
[0033]
After execution of S23 or S24, the process proceeds to S25.
In S25, it is determined whether or not the engine speed N is a low rotation / low load region where the engine speed N is equal to or less than the threshold value N1 and the load L is equal to or less than the threshold value L1.
[0034]
In the case of the low rotation / low load region, the process proceeds to S26 and S27.
In S26, since the engine is cold (Tw ≦ predetermined value) and is in a low rotation / low load region, the lift amount of the intake valve is reduced (low lift). In S27, the TCV (tumble control valve) is closed to enhance the in-cylinder flow.
[0035]
On the other hand, if it is determined in S25 that the engine is not in the low rotation / low load region, the process proceeds to S28.
In S28, it is determined whether or not the engine speed N is equal to or less than a predetermined threshold value N2 and the load L is in a medium speed / medium load range equal to or less than the predetermined threshold value L2. Note that N2> N1 and L2> L1.
[0036]
In the middle rotation / medium load region, the process proceeds to S29 and S30.
In S29, the lift amount of the intake valve is increased (high lift). In S30, the TCV (tumble control valve) is closed to enhance the in-cylinder flow.
[0037]
On the other hand, if it is determined in S28 that the region is not in the middle rotation / medium load region, that is, in the case of the high rotation or high load region, the process proceeds to S31 and S32.
In S31, the lift amount of the intake valve is increased (high lift). In S32, the TCV (tumble control valve) is opened to improve the output performance.
[0038]
In the first embodiment , after the warm-up, the reduction of the lift amount of the intake valve is prohibited. In the second embodiment , the control is performed as described above, so that after the warm-up, compared with the cool-down time. The operating range in which the lift amount of the intake valve is reduced is reduced to the low rotation / low load side.
[0039]
That is, after warming up, even if the fuel spray and the intake valve interfere with each other, the vaporization is good, so there is no significant hindrance to the mixture formation (the amount of HC emissions is small). From the viewpoint of improving fuel consumption, it is desirable to prevent the gas flow from being strengthened as much as possible.
[0040]
However, in the extremely low rotation / low load region, the intake air flow velocity is too low in the first place, so that the function of strengthening the gas flow by the air motion valve (tumble control valve) is not fully exhibited. Therefore, in an extremely low rotation / low load region, it is considered better to reduce the amount of unburned fuel (HC) by preventing the fuel spray and the intake valve from interfering with each other by reducing the lift even after warm-up.
[0041]
Therefore, in this second embodiment , after warming up, the operating range in which the lift amount of the intake valve is reduced is reduced to a lower rotation / low load side than when cold, and in the region where gas flow can be enhanced, gas flow is reduced. The emphasis is on the prevention of fuel spray interference in the area where the gas flow enhancement function is not fully exhibited.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part of an internal combustion engine (at the time of high intake valve lift) showing an embodiment of the present invention. FIG. 2 is a plan layout view of the internal combustion engine. FIG. 4 is a block diagram of a control system. FIG. 5 is a control flowchart of the first embodiment. FIG. 6 is a control flowchart of the second embodiment.
1 Combustion chamber
2 Spark plug
3A, 3B Intake port
4A, 4B Exhaust port
5A, 5B Intake valve
6A, 6B Exhaust valve
7 Fuel injection valve
8 Partition plate
9 Air motion valve (tumble control valve)
10 Variable valve gear
11 Engine control unit (ECU)
12 Speed sensor
13 Load sensor
14 Water temperature sensor

Claims

Direct eruption provided with an air motion valve that injects fuel from a fuel injection valve disposed on the side of the combustion chamber to the center of the combustion chamber via the two intake valves and enhances in-cylinder flow in the intake passage In a flower ignition internal combustion engine,
Equipped with a variable valve system that can variably control the lift amount of the intake valve, and in the operation mode in which fuel injection is performed in the intake stroke, the engine warm-up state and the operation region are determined,
In time cold engine, and, in the case of a predetermined low rotation and low load region, the lift amount of the intake valve is set to a low lift, and actuates the air motion valve,
When the engine is cold, and in a predetermined medium rotation / medium load region at a higher speed / high load side than the low rotation / low load region, and after the engine is warmed up, and the low rotation / low load region Or in the middle rotation / medium load region, the lift amount of the intake valve is set to a high lift, and the air motion valve is operated,
In the case of the high speed / high load area on the high speed / high load side than the medium rotation / medium load area, the lift amount of the intake valve is set to a high lift and the air motion valve is not operated regardless of the warm-up state. A direct-injection spark-ignited internal combustion engine.

Direct eruption provided with an air motion valve that injects fuel from a fuel injection valve disposed on the side of the combustion chamber to the center of the combustion chamber via the two intake valves and enhances in-cylinder flow in the intake passage In a flower ignition internal combustion engine,
Equipped with a variable valve system that can variably control the lift amount of the intake valve, and in the operation mode in which fuel injection is performed in the intake stroke, the operation region is determined,
In the specified low rotation / low load range, lower the lift amount of the intake valve and operate the air motion valve.
In the case of a predetermined medium rotation / medium load region on the high speed / high load side than the low rotation / low load region, the lift amount of the intake valve is set to a high lift, and the air motion valve is operated,
In the case of the high speed / high load area on the high speed / high load side than the medium rotation / medium load area, the lift amount of the intake valve is set to a high lift and the air motion valve is not operated ,
Comprising means for determining a warm-up state of the engine, after warming up, straight erupted flowers ignition type internal combustion engine, which comprises reducing the low rotation and low load region to a lower rotation and low load side.