JP3770928B2

JP3770928B2 - Control method and control apparatus for internal combustion engine

Info

Publication number: JP3770928B2
Application number: JP17643594A
Authority: JP
Inventors: 宜茂大山; 護藤枝; 利治野木; 拓也白石; 大須賀　　稔
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1994-07-28
Filing date: 1994-07-28
Publication date: 2006-04-26
Anticipated expiration: 2021-04-26
Also published as: JPH0842381A

Description

【０００１】
【産業上の利用分野】
本発明は、内燃機関、例えば、ガソリンエンジン，ディーゼルエンジン，天然ガスエンジン等のうちの筒内燃料噴射エンジンの制御方法及び制御装置に関する。
【０００２】
【従来の技術】
内燃機関のうち、燃焼室に直接燃料が噴射されるものは筒内燃料噴射エンジンと呼ばれる。筒内燃料噴射エンジンとしては、ディーゼルエンジンが良く知られているが、空気量の変化に対する燃料噴射時期の制御手段は具備していない。また、圧縮行程と膨張行程との比が１以下のエンジンとしては、ミラーサイクルエンジンが知られている。しかし、ミラーサイクルエンジンは上記の空気量の変化に対する燃料噴射時期の制御手段を具備していない。
【０００３】
【発明が解決しようとする課題】
従来の筒内燃料噴射エンジンの制御装置は、空気量が一定の条件で、燃料噴射時期，点火時期を制御するようになっている。したがって、圧縮行程と膨張行程との比が１以下になる筒内燃料噴射エンジンをこの制御装置で制御すると、燃料量が多いとき、局所的に混合気が過濃となり、ディーゼルエンジンのようにすすが発生する。また、燃料量が少ないとき、点火プラグ近くの混合気が過薄になり、燃焼が不安定になる。さらに、空気量が一定の条件で、燃料量を増大すると、空燃比が小さくなり、窒素酸化物（ＮＯｘ）の排出量が増大する。
【０００４】
本発明は、圧縮行程と膨張行程との比が１以下になる筒内燃料噴射エンジンにおいて、上記のすすの発生，燃焼の不安定，ＮＯｘの増大を防止する制御方法及び制御装置を提供することを目的とする。
【０００５】
さらに、空気量可変手段によって、圧縮行程と膨張行程の比が１より小さくなったとき、すなわち、空気量が小さくなったとき、燃焼の不安定を回避することを目的とする。
【０００６】
【課題を解決するための手段】
前記目的を達成すべく、本発明に係る内燃機関の制御方法は、基本的には、内燃機関の燃焼室内に噴射口を備えた燃料噴射装置から噴射される燃料の量と噴射時期を制御するとともに、吸気バルブの開閉時期を制御する内燃機関の制御方法であって、前記噴射される燃料の量の変化に基づいて、前記燃焼室内の燃焼すべき空気量を制御し、該空気量の変化に応じた空燃比とすると共に、空燃比が大きくなるほど前記噴射時期を遅く制御することを特徴とする。
本発明では、空気量を変化させる空気量可変手段、例えば、吸気バルブ可変装置，スロットルバルブ，吸入空気の圧縮機を具備する圧縮行程と膨張行程との比が１以下になる筒内燃料噴射エンジンの制御方法において、変化した空気量に基づいて燃料噴射時期を制御するようにする。また、アクセルペダルの踏み込み量でこの空気量が変化するように制御されるものでは、アクセルペダルの踏み込み量に基づいて燃料噴射時期を制御するようにする。さらに、前記エンジンの制御装置においては、変化した空気量に基づいて燃料噴射時期を制御する手段を付加する。また、アクセルペダルの踏み込み量でこの空気量が変化するように制御されるものでは、アクセルペダルの踏み込み量に基づいて燃料噴射時期を制御する手段を付加する。
【０００７】
【作用】
アクセルペダルの踏み込み量が増大すると、制御装置によって、空気量可変手段が制御され、空気量が増大する。これと連動して、燃料噴射時期制御手段によって噴射時期が制御され、混合気の過濃化によるすすの発生が抑止され、かつ、燃料量の変化に応じて、空気量可変手段が制御されるので、空燃比が１６から１８の値になることがなく、ＮＯｘの排出量が抑制される。
【０００８】
さらに、空気量可変手段によって、圧縮行程と膨張行程の比が１より小さくなったとき、すなわち、空気量が小さくなったとき、燃料噴射時期が制御されるので、燃焼の不安定が回避される。
【０００９】
【実施例】
以下本発明の実施例を図面を用いて説明する。図１において、エンジン１に、凹み燃焼室を有するピストン２，吸気バルブ３，排気バルブ４，燃料噴射弁５，点火プラグ６が取付けられ、吸気管７には、エアークリーナ８が、排気管９には、窒素酸化物浄化用の触媒コンバータ１０が配置される。吸気バルブ３は、低負荷用のカム１１，高負荷用のカム１２で駆動される。排気バルブ４はカム１３で駆動される。カム１１は、ロッカアーム１４を押し、カム１２はロッカアーム１５を押す。このとき、低負荷では電磁ソレノイド１６の作用で、ロッカアーム１４が吸気バルブ３に接続される。高負荷では電磁ソレノイド１７の作用で、ロッカアーム１５が吸気バルブ３に接続される。点火プラグ６，燃料噴射弁５，電磁ソレノイド１６，１７の動作は、制御装置１８によって制御される。アクセルペダル１９の位置は、ポテンショメータ２０によって、エンジンの回転速度は、回転センサ２１によって、排気の空燃比は、空燃比センサ２２によって、制御装置１８に入力される。
【００１０】
アクセルペダル１９の踏み込み量に対し、図２のように、燃料噴射弁５の燃料量を制御する。エンジン回転速度が大きいときの燃料量を小さくするのは、エンジンの暴走を防止するための公知の事項である。燃料量が小さいとき、空気量／燃料量の比が大きくなり、混合気が希薄になるので、図３のごとく、噴射時期を圧縮上死点近くまで遅らせ、点火プラグ６の近くに燃料を集めて、着火を安定にする。燃料量が大きいときは、噴射時期を吸気終りより早くし、燃料と空気の混合を促進することは公知である。点火時期は図３に示すごとく、噴射時期より遅れ、かつ、燃料量が大きいときは、遅れ側に設定されることも公知である。図２，図３の燃料量，噴射時期，点火時期は、制御装置１８によって制御される。これらの制御は公知であるので、ここでは説明を省略する。
【００１１】
高負荷カム１２，低負荷カム１１の形状を図４に示す。低負荷カム１１によって、吸気バルブ３は、圧縮行程の半ばまで開く。これに対し、高負荷カム１２は、従来のものと同じで、圧縮行程の始めに、吸気バルブ３が閉じる。したがって、電磁ソレノイド１６，１７を切換動作し、燃料量が大きいときは、高負荷用カム１２を吸気バルブ３に接続し、燃料量が小さいときは、低負荷用カム１１を吸気バルブ３に接続することによって、図５に示す空気量の特性が得られる。排気バルブ１３は、従来と同じく、排気（膨張）行程の終りに閉じられる。このようにして、燃料量が小さいときの空気量が小さくなるので、図６に示すごとく、燃料量が小さい領域の空燃比の増大が抑止され、燃料量が小さいときの燃焼が安定化する。このとき、図６の燃料量がａのとき、すなわち切換時の空燃比が１６以下にならないよう、空気量を設定する。なぜなら、空燃比１６付近で窒素酸化物の排出量が極大になるためである。このため、図５の吸気弁閉じ時期は、空燃比が上記の条件を満足するように設定される。これにより、図７に示すごとく、燃料量が小さい領域の炭化水素の排出量の増大を低減すると共に、窒素酸化物の排出量の増大が抑止できる。図６の空燃比は、空燃比センサ２２によって検出され、空燃比が、ａの点で１６に近付いたときは、燃料量を小さくするか、吸気弁閉時期を進めて、空燃比の修正動作を行う。これにより、窒素酸化物の排出量の増大を防止する。
【００１２】
図８に示すごとく、吸気弁閉時期を遅らせているので、圧縮ストロークが小さくなり、膨張ストロークは変らないので、膨張圧縮比が２になり、膨張仕事が有効にピストンに伝わるので、燃費率が１０％低減する。このような、吸気弁遅閉じは、ミラーサイクルエンジンとして公知であるが、ここでは、筒内噴射と組合わせた点に新規性がある。すなわち、膨張仕事を有効に活用するミラーサイクルの効果と共に、筒内の空気量の低減による燃料の安定化の効果を重畳したものである。
【００１３】
図１の実施例では、吸気バルブ３の閉時期を制御して、燃料量が大きい領域の空気量を増大する方法を示した。代案として、閉時期を固定したまま、過給圧を高めることによっても、空気量を増大することができる。このときは、膨張／圧縮比が、燃料量が大きい領域でも２になるので、燃費率が全体的に低くなる。
【００１４】
以上のごとく、筒内噴射によって高空気過剰率（高空燃比）での安定運転を可能にすると共に、吸気バルブの遅閉じによって、膨張仕事の有効活用が可能になるので、炭化水素，窒素酸化物の排出量を低減しながら、燃費率を大幅に低減することができる。
【００１５】
吸気バルブ３の遅閉じにおける、空気量の増大は、前述のように、空気の過給圧力を加減するか、吸気バルブ３の閉時期を加減するかによって実施される。図１の実施例では段階的に変化する方法を示したが、これを連続的に変化させることも公知の技術で容易に達成することができる。
【００１６】
従来の筒内噴射システムは、シリンダ内の空気量が一定の条件において、噴射時期，点火時期を設定するようになっていた。しかし、本発明のように、燃料が多い領域において、空気量を増す場合には充分対応することが困難である。空気量が増加した際、噴射時期が一定のままでは、点火プラグ６の近くの燃料の濃度が小さくなり、燃焼が不安定になる。これを回避するためには、空気量の変化に対して、噴射時期，点火時期を制御する必要がある。
【００１７】
すなわち、本発明の要点は、
(1）負荷（燃料量）の変化に対して、空気量を正確に制御し、かつ、噴射時期，点火時期を負荷の変化に対し、正確に制御する。このとき、空燃比センサ２２によって、排気の空燃比を検出し、これによって空気量の制御の誤差を把握し、修正動作を行う。
【００１８】
(2）負荷の変化に対し、噴射時期，点火時期を正確に制御し、かつ、空気量制御信号、例えば、図１の電磁ソレノイド１６，１７の制御信号と同期して、噴射時期，点火時期を制御する。
【００１９】
のいずれかの手段を具備する必要がある。
【００２０】
図９において、空気量がＧ₂のとき、噴射時期は、燃料量が増大するほど、負になる。すなわち、圧縮上死点を零にしているので、噴射時期が進み、−１８０クランク角度、すなわち、圧縮行程の始めまで進む。
【００２１】
ミラーサイクルエンジンでは、過給圧力を低下すると、空気量が低下し、例えば、Ｇ₁になる。このとき、従来のように、燃料量に対する噴射時期を固定していたのでは、理論空燃比近くの噴射時期が−９０度となり、燃料と空気の混合が促進されない。これに対し、本発明では、噴射時期を−１８０度まで進め、混合を促進し、燃焼を安定化することができる。
【００２２】
図１０に本発明による制御のフロー図を示す。図１０のブロック９１でエンジンの回転速度を検出し、ブロック９２でアクセルペダルの踏込量を検出する。両者の値で、ブロック９３で、要求燃料量を演算する。図２の線図をマップ化したテーブルから要求値を読み出す。図８において、燃料量がＦ₁より大きいときは、空気量はＧ₂に、Ｆ₁より小さいときは、Ｇ₁になる。燃料量に対し、空気量を連続的に定めることもできる。ブロック９４で、空燃比センサ２２によって、空燃比を検出する。この値を基に、ブロック９５で、実際の空気量を推定する。この推定値を基に、ブロック９６で、空気量を修正する。これは、過給圧力を加減するか、あるいは、吸気管７にスロットルバルブを設けて吸気管圧力を加減するか、あるいは、吸気弁閉時期を加減することによって行われる。ブロック９７において、図９のような、燃料量と空気量，回転速度に対する噴射時期の表から、噴射時期を決定し、ブロック９８で、実際の燃料噴射を実行する。ブロック９９で、ブロック９７の噴射時期の決定と同じ様に、燃料量，空気量，回転速度に対する点火時期の表から点火時期を決定し、ブロック１００で実際の点火を実行する。
【００２３】
４ストロークエンジンの場合は、図１０に示すブローチャートを２回転に１回、２ストロークエンジンの場合は、１回転に１回実行する。
【００２４】
図１１に空気量の制御装置を示す。まず、第１は、図１に示したごとき、吸気バルブ３の閉時期制御装置１０１を電磁アクチュエータ１０７で制御する。閉時期を遅らせると、空気量が減少し、閉時期を吸気行程の終わりまで進めると、空気量が増加する。第２は、吸気管７にスロットルバルブ１０２を設け、これを電動アクチュエータ１０３で制御する。バルブ１０２を開けると、空気量が増加し、閉じると減少する。第３は、圧縮機１０４を設け、これを電動するか、エンジン１で動かし、空気圧力を高めて、空気量を増す。バイパスバルブ１０５を電動アクチュエータ１０６で動かし、バルブ１０５を開けると、空気量が減少する。空気量は、大気圧，空気温度の変化によって変わるので、温度センサ１０８，圧力センサ１０９の出力信号を、制御装置１８に入力し、所定の修正動作を行う。吸気バルブ３の閉時期の経時変化によっても、空気量が変化する。したがって、空燃比センサ２２の出力信号を制御装置１８に入力し、図１０のブロック９５で、この出力信号を基に、空気量を推定する。
【００２５】
空気量の最大値は、エンジン１の行程容積と圧縮機の容量によって制約される。エンジン１の出力、トルクを増すには、燃料量を、従来のエンジンと同じ様に、図１２のごとく空燃比が１１になるまで、増す必要がある。窒素酸化物ＮＯｘの濃度は、空燃比が１０〜１８で極大値を示すので、この空燃比の領域を避けて、エンジン１は運転される。図１３に示すごとく、空燃量がｆ₁より小さいときは、空気量を小さく設定し、空燃比を１８以上にする。燃料量がｆ₂より大きいときは、空気量を大きく設定し、空燃比を１４.７(理論空燃比）以下に設定する。燃料量がｆ₁とｆ₂の間のときは、空気量を連続的に変えて、空燃比を理論空燃比に制御する。この領域では、三元触媒によって、窒素酸化物を浄化する。
【００２６】
図１４に、空燃比に対するＮＯｘの排出量の変化を示す。噴射時期が遅れるほど、ＮＯｘがピークを示す空燃比が大きくなる。曲線の●印以上の空燃比ではエンジンの燃焼が不安定になる。したがって、●点の右側で運転する。しかし、空燃比が小さくなると、ＮＯｘが増大するので、●点ぎりぎりの空燃比で運転される。すなわち、噴射時期に対する空燃比の設定、あるいは、空燃比に対する噴射時期の設定、あるいは燃料量に対する空燃比の設定（図３）は、図１４のごとき実験データを基に定められる。空燃比が同じで、噴射時期が遅れると、ＮＯｘが増大する。燃料量の増大に対して、空燃比が小さくなる際に、噴射時期の進め制御が遅れると、ＮＯｘが増大する。しかし、本発明においては、燃料噴射弁５は、電気的に制御されるので、遅れがなく、したがって、ＮＯｘの増大が回避できる。
【００２７】
以上、筒内燃料噴射エンジンにおいて、点火プラグで、混合気を着火，燃焼させる場合の実施例を示したが、ディーゼルエンジンのように、自己着火するエンジンにも適用することができる。また、吸気バルブの遅閉じによる、圧縮行程／膨張行程が１以下のミラーサイクルのエンジンの実施例を示したが、吸気バルブ早閉じ、すなわち、吸気バルブと吸気行程の途中で閉じる方法でも、ミラーサイクルを実現することができる。
【００２８】
【発明の効果】
本発明では、筒内燃料噴射エンジンにおいて、シリンダの空気量の変化に応じ、燃料噴射時期を制御できるので、すすの発生，燃焼の不安定，ＮＯｘの増大を防止することができる。
【００２９】
また、圧縮行程／膨張行程を１以下にし、かつ、安定燃焼を達成することによって、圧縮仕事が減少し、エンジンの燃焼経済性が向上する。
【図面の簡単な説明】
【図１】本発明の実施例の構成図。
【図２】アクセルペダルの踏込み量と燃料量との関係図。
【図３】燃料量と噴射時期，点火時期との関係図。
【図４】吸気バルブの開閉カムの動作とクランク角度との関係図。
【図５】燃料量と空気量及び吸気弁閉時期との関係図。
【図６】燃料量と空燃比との関係図。
【図７】燃料量と窒素酸化物，炭化水素の排出量との関係図。
【図８】燃料量と燃費率及び膨張／圧縮比との関係図。
【図９】燃料量と空気量との関係図。
【図１０】本発明の実施例の制御のフロー図。
【図１１】空気量の制御装置の構成図。
【図１２】空燃比とトルク及び窒素酸化物の排出量との関係図。
【図１３】燃料量と空燃比及び空気量との関係図。
【図１４】空燃比と窒素酸化物の排出量との関係図。
【符号の説明】
１…エンジン、３…吸気バルブ、５…燃料噴射弁、１８…制御装置。[0001]
[Industrial application fields]
The present invention relates to a control method and a control device for an in-cylinder fuel injection engine of an internal combustion engine, for example, a gasoline engine, a diesel engine, or a natural gas engine.
[0002]
[Prior art]
Among internal combustion engines, those in which fuel is directly injected into a combustion chamber are called in-cylinder fuel injection engines. A diesel engine is well known as an in-cylinder fuel injection engine, but it does not include means for controlling the fuel injection timing with respect to changes in the air amount. A Miller cycle engine is known as an engine having a ratio of compression stroke to expansion stroke of 1 or less. However, the Miller cycle engine does not have a fuel injection timing control means for the change in the air amount.
[0003]
[Problems to be solved by the invention]
A conventional control device for an in-cylinder fuel injection engine controls fuel injection timing and ignition timing under a condition where the air amount is constant. Therefore, when the control unit controls an in-cylinder fuel injection engine in which the ratio of the compression stroke to the expansion stroke is 1 or less, when the amount of fuel is large, the air-fuel mixture becomes locally rich, so that it becomes like a diesel engine. Will occur. Further, when the amount of fuel is small, the air-fuel mixture near the spark plug becomes excessively thin and the combustion becomes unstable. Furthermore, when the amount of fuel is increased under the condition that the amount of air is constant, the air-fuel ratio decreases, and the amount of nitrogen oxide (NOx) emissions increases.
[0004]
The present invention provides a control method and a control device for preventing the above-mentioned soot generation, combustion instability, and NOx increase in an in-cylinder fuel injection engine in which the ratio of the compression stroke to the expansion stroke is 1 or less. With the goal.
[0005]
Furthermore, it is an object of the present invention to avoid instability of combustion when the ratio of the compression stroke and the expansion stroke becomes smaller than 1, that is, when the air amount becomes small, by the air amount varying means.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the control method for an internal combustion engine according to the present invention basically controls the amount and timing of fuel injected from a fuel injection device having an injection port in the combustion chamber of the internal combustion engine. And an internal combustion engine control method for controlling the opening and closing timing of the intake valve, wherein the amount of air to be combusted in the combustion chamber is controlled based on the change in the amount of injected fuel, and the change in the air amount The injection timing is controlled to be delayed as the air-fuel ratio increases .
In the present invention, an in-cylinder fuel injection engine in which the ratio of the compression stroke to the expansion stroke is 1 or less, which includes an air amount variable means for changing the air amount, for example, an intake valve variable device, a throttle valve, and an intake air compressor. In this control method, the fuel injection timing is controlled based on the changed air amount. In the case where the air amount is controlled so as to change depending on the depression amount of the accelerator pedal, the fuel injection timing is controlled based on the depression amount of the accelerator pedal. Further, in the engine control device, means for controlling the fuel injection timing based on the changed air amount is added. In addition, in the case where the air amount is controlled so as to change according to the depression amount of the accelerator pedal, a means for controlling the fuel injection timing based on the depression amount of the accelerator pedal is added.
[0007]
[Action]
When the amount of depression of the accelerator pedal increases, the air amount variable means is controlled by the control device, and the air amount increases. In conjunction with this, the injection timing is controlled by the fuel injection timing control means, soot generation due to over-concentration of the air-fuel mixture is suppressed, and the air amount variable means is controlled according to the change in the fuel amount. Therefore, the air-fuel ratio does not become a value of 16 to 18, and the NOx emission amount is suppressed.
[0008]
Further, when the ratio of the compression stroke and the expansion stroke becomes smaller than 1, that is, when the air amount becomes small, the fuel injection timing is controlled by the air amount varying means, so that unstable combustion is avoided. .
[0009]
【Example】
Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a piston 2 having an indented combustion chamber, an intake valve 3, an exhaust valve 4, a fuel injection valve 5, and a spark plug 6 are attached to an engine 1, and an air cleaner 8 is connected to an intake pipe 7. Is provided with a catalytic converter 10 for purifying nitrogen oxides. The intake valve 3 is driven by a low load cam 11 and a high load cam 12. The exhaust valve 4 is driven by a cam 13. The cam 11 pushes the rocker arm 14, and the cam 12 pushes the rocker arm 15. At this time, the rocker arm 14 is connected to the intake valve 3 by the action of the electromagnetic solenoid 16 at a low load. At high loads, the rocker arm 15 is connected to the intake valve 3 by the action of the electromagnetic solenoid 17. Operations of the spark plug 6, the fuel injection valve 5, and the electromagnetic solenoids 16 and 17 are controlled by the control device 18. The position of the accelerator pedal 19 is input to the control device 18 by the potentiometer 20, the rotational speed of the engine by the rotation sensor 21, and the air-fuel ratio of the exhaust gas by the air-fuel ratio sensor 22.
[0010]
The fuel amount of the fuel injection valve 5 is controlled with respect to the depression amount of the accelerator pedal 19, as shown in FIG. Reducing the amount of fuel when the engine speed is high is a well-known matter for preventing engine runaway. When the amount of fuel is small, the air amount / fuel amount ratio becomes large and the air-fuel mixture becomes lean. Therefore, as shown in FIG. 3, the injection timing is delayed to near the compression top dead center, and the fuel is collected near the spark plug 6. To stabilize the ignition. It is known that when the amount of fuel is large, the injection timing is made earlier than the end of intake to promote the mixing of fuel and air. As shown in FIG. 3, it is also known that the ignition timing is set to the delay side when the fuel injection is delayed and the fuel amount is large. The fuel amount, injection timing, and ignition timing in FIGS. 2 and 3 are controlled by the control device 18. Since these controls are well-known, description is abbreviate | omitted here.
[0011]
The shapes of the high load cam 12 and the low load cam 11 are shown in FIG. The low load cam 11 opens the intake valve 3 until the middle of the compression stroke. On the other hand, the high load cam 12 is the same as the conventional one, and the intake valve 3 is closed at the beginning of the compression stroke. Accordingly, the electromagnetic solenoids 16 and 17 are switched to connect the high load cam 12 to the intake valve 3 when the fuel amount is large, and connect the low load cam 11 to the intake valve 3 when the fuel amount is small. By doing so, the characteristics of the air amount shown in FIG. 5 are obtained. The exhaust valve 13 is closed at the end of the exhaust (expansion) stroke as in the prior art. In this way, since the air amount when the fuel amount is small becomes small, as shown in FIG. 6, an increase in the air-fuel ratio in a region where the fuel amount is small is suppressed, and combustion when the fuel amount is small is stabilized. At this time, the air amount is set so that the air-fuel ratio at the time of switching does not become 16 or less when the fuel amount in FIG. 6 is a. This is because the emission amount of nitrogen oxides becomes maximum near the air-fuel ratio 16. For this reason, the intake valve closing timing in FIG. 5 is set so that the air-fuel ratio satisfies the above conditions. As a result, as shown in FIG. 7, an increase in the discharge amount of hydrocarbons in a region where the fuel amount is small can be reduced, and an increase in the discharge amount of nitrogen oxides can be suppressed. The air-fuel ratio in FIG. 6 is detected by the air-fuel ratio sensor 22, and when the air-fuel ratio approaches 16 at the point a, the fuel amount is reduced or the intake valve closing timing is advanced to correct the air-fuel ratio. I do. This prevents an increase in nitrogen oxide emissions.
[0012]
As shown in FIG. 8, since the intake valve closing timing is delayed, the compression stroke becomes smaller and the expansion stroke does not change. Therefore, the expansion / compression ratio becomes 2, and the expansion work is effectively transmitted to the piston, so that the fuel consumption rate is increased. Reduce by 10%. Such a slow closing of the intake valve is known as a mirror cycle engine, but here is novel in combination with in-cylinder injection. That is, the effect of stabilizing the fuel by reducing the amount of air in the cylinder is superimposed on the effect of the mirror cycle that effectively uses the expansion work.
[0013]
In the embodiment of FIG. 1, the method of increasing the air amount in the region where the fuel amount is large by controlling the closing timing of the intake valve 3 is shown. As an alternative, the air amount can also be increased by increasing the supercharging pressure while fixing the closing time. At this time, since the expansion / compression ratio becomes 2 even in a region where the amount of fuel is large, the fuel consumption rate is lowered as a whole.
[0014]
As described above, in-cylinder injection enables stable operation at a high excess air ratio (high air-fuel ratio), and the expansion valve can be effectively utilized by slow closing of the intake valve. The fuel consumption rate can be significantly reduced while reducing the amount of emissions.
[0015]
As described above, the increase in the air amount in the slow closing of the intake valve 3 is performed by adjusting the supercharging pressure of the air or by adjusting the closing timing of the intake valve 3. In the embodiment shown in FIG. 1, a method of changing in steps is shown. However, it is also possible to easily change this continuously by a known technique.
[0016]
In the conventional in-cylinder injection system, the injection timing and the ignition timing are set under the condition that the amount of air in the cylinder is constant. However, as in the present invention, when the amount of air is increased in a region where there is a large amount of fuel, it is difficult to cope with it sufficiently. When the air amount increases, if the injection timing remains constant, the concentration of fuel near the spark plug 6 becomes small and combustion becomes unstable. In order to avoid this, it is necessary to control the injection timing and the ignition timing with respect to changes in the air amount.
[0017]
That is, the gist of the present invention is
(1) The amount of air is accurately controlled with respect to changes in load (fuel amount), and the injection timing and ignition timing are accurately controlled with respect to changes in load. At this time, the air-fuel ratio sensor 22 detects the air-fuel ratio of the exhaust gas, thereby grasping an error in the control of the air amount and performing a correction operation.
[0018]
(2) The injection timing and ignition timing are accurately controlled in response to changes in the load, and are synchronized with an air amount control signal, for example, the control signals of the electromagnetic solenoids 16 and 17 in FIG. To control.
[0019]
It is necessary to have one of the following means.
[0020]
In FIG. 9, when the air amount is G ₂ , the injection timing becomes negative as the fuel amount increases. That is, since the compression top dead center is set to zero, the injection timing advances, and advances to the -180 crank angle, that is, the beginning of the compression stroke.
[0021]
In Miller-cycle engine, the lower the supercharging pressure, it reduces the amount of air, for example, in G _1. At this time, if the injection timing relative to the fuel amount is fixed as in the prior art, the injection timing near the stoichiometric air-fuel ratio is -90 degrees, and mixing of fuel and air is not promoted. In contrast, in the present invention, the injection timing can be advanced to -180 degrees, mixing can be promoted, and combustion can be stabilized.
[0022]
FIG. 10 shows a flowchart of control according to the present invention. The engine speed is detected at block 91 in FIG. 10, and the amount of depression of the accelerator pedal is detected at block 92. With both values, the required fuel amount is calculated in block 93. The required value is read from the table in which the diagram of FIG. 2 is mapped. In FIG. 8, the air amount is G ₂ when the fuel amount is larger than F ₁ , and G ₁ when the fuel amount is smaller than F ₁ . The amount of air can also be determined continuously with respect to the amount of fuel. In block 94, the air-fuel ratio is detected by the air-fuel ratio sensor 22. Based on this value, the actual air amount is estimated in block 95. Based on this estimated value, the air quantity is corrected in block 96. This is performed by adjusting the supercharging pressure, or by providing a throttle valve in the intake pipe 7 to increase or decrease the intake pipe pressure, or by adjusting the intake valve closing timing. In block 97, the injection timing is determined from a table of the injection timing with respect to the fuel amount, the air amount, and the rotational speed as shown in FIG. 9, and in block 98, actual fuel injection is executed. In block 99, the ignition timing is determined from the table of the ignition timing with respect to the fuel amount, the air amount, and the rotational speed in the same manner as the injection timing determination in block 97, and actual ignition is executed in block 100.
[0023]
In the case of a 4-stroke engine, the blow chart shown in FIG. 10 is executed once every two revolutions, and in the case of a two-stroke engine, it is executed once per revolution.
[0024]
FIG. 11 shows an air amount control device. First, as shown in FIG. 1, the closing timing control device 101 of the intake valve 3 is controlled by an electromagnetic actuator 107 as shown in FIG. When the closing time is delayed, the air amount decreases, and when the closing time is advanced to the end of the intake stroke, the air amount increases. Second, a throttle valve 102 is provided in the intake pipe 7 and is controlled by an electric actuator 103. The air volume increases when the valve 102 is opened, and decreases when the valve 102 is closed. Thirdly, a compressor 104 is provided, which is electrically driven or moved by the engine 1 to increase the air pressure and increase the amount of air. When the bypass valve 105 is moved by the electric actuator 106 and the valve 105 is opened, the amount of air decreases. Since the amount of air varies depending on changes in atmospheric pressure and air temperature, the output signals of the temperature sensor 108 and pressure sensor 109 are input to the control device 18 and a predetermined correction operation is performed. The amount of air also changes due to the change over time of the closing timing of the intake valve 3. Therefore, the output signal of the air-fuel ratio sensor 22 is input to the control device 18, and the air amount is estimated based on this output signal in block 95 of FIG.
[0025]
The maximum value of the air amount is restricted by the stroke volume of the engine 1 and the capacity of the compressor. In order to increase the output and torque of the engine 1, it is necessary to increase the amount of fuel until the air-fuel ratio becomes 11, as shown in FIG. Since the concentration of nitrogen oxides NOx shows a maximum value when the air-fuel ratio is 10 to 18, the engine 1 is operated avoiding this air-fuel ratio region. As shown in FIG. 13, the air-retarding amount is is smaller than f ₁ is set small air volume, the air-fuel ratio to 18 or more. When the amount of the fuel is greater than f _2, the amount of air largely set, sets the air-fuel ratio to 14.7 (stoichiometric air-fuel ratio) or less. When the fuel amount is between f ₁ and f ₂ , the air amount is continuously changed to control the air-fuel ratio to the stoichiometric air-fuel ratio. In this region, nitrogen oxides are purified by a three-way catalyst.
[0026]
FIG. 14 shows the change in NOx emission with respect to the air-fuel ratio. The later the injection timing, the larger the air-fuel ratio at which NOx peaks. Engine combustion becomes unstable at air-fuel ratios above the ● mark on the curve. Therefore, drive on the right side of the ● point. However, as the air-fuel ratio becomes smaller, NOx increases, so that the operation is performed at the air-fuel ratio just below the dot. That is, the setting of the air-fuel ratio with respect to the injection timing, the setting of the injection timing with respect to the air-fuel ratio, or the setting of the air-fuel ratio with respect to the fuel amount (FIG. 3) is determined based on experimental data as shown in FIG. If the air-fuel ratio is the same and the injection timing is delayed, NOx increases. If the advance control of the injection timing is delayed when the air-fuel ratio decreases with respect to the increase in the fuel amount, NOx increases. However, in the present invention, since the fuel injection valve 5 is electrically controlled, there is no delay, and therefore an increase in NOx can be avoided.
[0027]
As described above, in the in-cylinder fuel injection engine, the embodiment in which the air-fuel mixture is ignited and burned by the spark plug has been described. However, the present invention can also be applied to a self-ignition engine such as a diesel engine. In addition, although an example of a mirror cycle engine in which the compression stroke / expansion stroke is 1 or less due to the slow closing of the intake valve is shown, the intake valve early closing, that is, the method of closing in the middle of the intake valve and the intake stroke, A cycle can be realized.
[0028]
【The invention's effect】
In the present invention, in the cylinder fuel injection engine, the fuel injection timing can be controlled in accordance with the change in the air amount of the cylinder, so that it is possible to prevent soot generation, unstable combustion, and increase in NOx.
[0029]
Further, by reducing the compression stroke / expansion stroke to 1 or less and achieving stable combustion, the compression work is reduced and the combustion economy of the engine is improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment of the present invention.
FIG. 2 is a relationship diagram between an accelerator pedal depression amount and a fuel amount.
FIG. 3 is a relationship diagram of fuel amount, injection timing, and ignition timing.
FIG. 4 is a diagram showing the relationship between the operation of the opening / closing cam of the intake valve and the crank angle.
FIG. 5 is a relationship diagram between the fuel amount, the air amount, and the intake valve closing timing.
FIG. 6 is a relationship diagram between the fuel amount and the air-fuel ratio.
FIG. 7 is a graph showing the relationship between the amount of fuel and the emissions of nitrogen oxides and hydrocarbons.
FIG. 8 is a relationship diagram of fuel amount, fuel consumption rate, and expansion / compression ratio.
FIG. 9 is a relationship diagram between a fuel amount and an air amount.
FIG. 10 is a control flowchart of the embodiment of the present invention.
FIG. 11 is a configuration diagram of an air amount control device.
FIG. 12 is a graph showing the relationship between the air-fuel ratio, torque and nitrogen oxide emissions.
FIG. 13 is a relationship diagram of the fuel amount, the air-fuel ratio, and the air amount.
FIG. 14 is a relationship diagram between the air-fuel ratio and the amount of nitrogen oxide emission.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 3 ... Intake valve, 5 ... Fuel injection valve, 18 ... Control apparatus.

Claims

In a control method for an internal combustion engine for controlling the amount and timing of fuel injected from a fuel injection device having an injection port in a combustion chamber of the internal combustion engine, and for controlling the opening and closing timing of an intake valve,
Based on the change in the amount of fuel to be injected, the amount of air to be combusted in the combustion chamber is controlled to obtain an air-fuel ratio corresponding to the change in the air amount, and the injection timing is delayed as the air-fuel ratio increases. A control method for an internal combustion engine, characterized by controlling.

In a control method for an internal combustion engine for controlling the amount and timing of fuel injected from a fuel injection device having an injection port in a combustion chamber of the internal combustion engine, and for controlling the opening and closing timing of an intake valve,
The amount of fuel to be injected is controlled based on the amount of accelerator pedal depression, the amount of air to be combusted in the combustion chamber is controlled based on the change in the amount of fuel, and the change in the amount of air is And controlling the injection timing later as the air-fuel ratio increases .

The method for controlling an internal combustion engine according to claim 1 or 2, wherein the internal combustion engine is an internal combustion engine having a ratio of a compression stroke to an expansion stroke of 1 or less.

Fuel injection timing control means for controlling the amount and timing of fuel injected from a fuel injection device having an injection port in the combustion chamber of the internal combustion engine, and intake valve opening / closing control means for controlling the opening / closing timing of the intake valve In a control device for an internal combustion engine,
The intake valve opening / closing control means controls the amount of air to be combusted in the combustion chamber based on a change in the amount of fuel to be injected, and the fuel injection timing control means is an air flow according to the change in the air quantity. A control apparatus for an internal combustion engine, characterized by controlling the injection timing later as the air-fuel ratio becomes higher as the fuel ratio becomes higher .

Fuel injection timing control means for controlling the amount and timing of fuel injected from a fuel injection device having an injection port in the combustion chamber of the internal combustion engine, and intake valve opening / closing control means for controlling the opening / closing timing of the intake valve In a control device for an internal combustion engine,
The fuel injection timing control means controls the amount of fuel to be injected based on the depression amount of an accelerator pedal, and the intake valve opening / closing control means controls the inside of the combustion chamber based on a change in the amount of fuel. An internal combustion engine characterized by controlling the amount of air to be burned, wherein the fuel injection timing control means sets the air-fuel ratio according to a change in the air amount, and controls the injection timing later as the air-fuel ratio increases. Control device.

The control apparatus for an internal combustion engine according to claim 4 or 5, wherein the internal combustion engine is an internal combustion engine having a ratio of a compression stroke to an expansion stroke of 1 or less.