JP4075935B2 - Premixed compression self-ignition internal combustion engine - Google Patents

Premixed compression self-ignition internal combustion engine Download PDF

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JP4075935B2
JP4075935B2 JP2006106681A JP2006106681A JP4075935B2 JP 4075935 B2 JP4075935 B2 JP 4075935B2 JP 2006106681 A JP2006106681 A JP 2006106681A JP 2006106681 A JP2006106681 A JP 2006106681A JP 4075935 B2 JP4075935 B2 JP 4075935B2
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友則 漆原
康治 平谷
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Nissan Motor Co Ltd
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Description

本発明は、圧縮された混合気の自己着火現象を利用する予混合圧縮自己着火式内燃機関に関する。 The present invention relates to a premixed compression self-ignition internal combustion engine that utilizes a self-ignition phenomenon of a compressed air- fuel mixture .

ガソリンエンジンの熱効率を改善するために、混合気をリーン化することでポンプ損失を低減すると共に作動ガスの比熱比を大きくして理論熱効率を向上する手法が知られている。しかしながら、従来の火花点火エンジンでは空燃比をリーンにすると燃焼期間が長期化して、燃焼安定度が悪化する。このため、空燃比のリーン化には限界がある。   In order to improve the thermal efficiency of a gasoline engine, a method is known in which the air-fuel mixture is leaned to reduce pump loss and increase the specific heat ratio of the working gas to increase the theoretical thermal efficiency. However, in the conventional spark ignition engine, if the air-fuel ratio is made lean, the combustion period becomes longer and the combustion stability deteriorates. For this reason, there is a limit to the lean air-fuel ratio.

このような燃焼安定度の悪化を避けながら空燃比をリーン化する技術として、圧縮自己着火燃焼が知られている。圧縮自己着火燃焼では、燃焼室内の複数の位置から燃焼反応が起こるため、空燃比がリーン化した場合においても火花点火に比べると燃焼期間が長期化せずに、よりリーンな空燃比でも安定した燃焼が可能となる。また空燃比がリーンのため燃焼温度が低下し、ＮＯｘも大幅に低減できる。   As a technique for leaning the air-fuel ratio while avoiding such deterioration in combustion stability, compression self-ignition combustion is known. In compression self-ignition combustion, combustion reactions occur from multiple positions in the combustion chamber, so even when the air-fuel ratio is lean, the combustion period is not prolonged compared to spark ignition and stable even at a leaner air-fuel ratio. Combustion is possible. Further, since the air-fuel ratio is lean, the combustion temperature is lowered and NOx can be greatly reduced.

従来の圧縮自己着火式ガソリン機関としては、例えば特許文献１記載の第１従来技術が知られている。この例は、吸気ポートに燃料を噴射するエンジンにおいて、圧縮比を直噴ディーゼルエンジン並に高めることによって、圧縮上死点付近のシリンダ内温度及び圧力を高め、これら高温、高圧によりガソリン予混合気に自己着火する条件を成立させ、圧縮自着火燃焼を実現したものである。これによって火花点火ガソリン機関を上回る希薄燃焼限界と低燃費を得ている。   As a conventional compression self-ignition gasoline engine, for example, the first prior art described in Patent Document 1 is known. In this example, in an engine that injects fuel into an intake port, the compression ratio is increased to the same level as that of a direct injection diesel engine, thereby increasing the temperature and pressure in the cylinder near the compression top dead center. The conditions for self-ignition are established, and compression self-ignition combustion is realized. As a result, the lean combustion limit and low fuel consumption that exceed the spark ignition gasoline engine are obtained.

また、従来の燃料噴射を２回に分けた圧縮自己着火式機関としては、例えば特許文献２記載の第２従来技術が知られている。
この従来例は、ディーゼルエンジンにおける高負荷時のノッキングを回避するため、燃料噴射を２回に分け、１回目の噴射を圧縮行程後半の所定の時期にノッキングに至らない程度の噴射量で噴射し、その後の２回目の噴射で燃焼を開始させるという技術である。
特開平７−３３２１４１号公報 特開平１１−７２０３８号公報 Further, as a compression self-ignition engine in which conventional fuel injection is divided into two, for example, a second conventional technique described in Patent Document 2 is known.
In this conventional example, in order to avoid knocking at a high load in a diesel engine, fuel injection is divided into two injections, and the first injection is injected at an injection amount that does not cause knocking at a predetermined time in the second half of the compression stroke. Then, the combustion is started by the second injection thereafter.
JP-A-7-332141 JP-A-11-72038

しかしながら、上記第１従来技術にあっては、単に圧縮比を高めることによって、圧縮自着火する条件を実現したものとなっていた。
このため、理論空燃比付近の混合気で火花点火を行う全負荷運転では、高圧縮比によりノッキングが発生しやすく、ノッキングを回避するためには、点火進角限界を遅角させる必要があり、通常の圧縮比の火花点火式ガソリン機関に比べ大幅にトルクが低下するという問題点があった。 However, in the first prior art, the condition of compression ignition is realized simply by increasing the compression ratio.
For this reason, in full load operation in which spark ignition is performed with a mixture near the stoichiometric air-fuel ratio, knocking is likely to occur due to a high compression ratio, and in order to avoid knocking, it is necessary to retard the ignition advance limit, There is a problem that the torque is greatly reduced as compared with a spark-ignition gasoline engine having a normal compression ratio.

また、上記第２従来技術では、ディーゼルエンジンにおける、早期噴射予混合圧縮自己着火の高負荷時のノッキングを回避するために考案されており、単に１回目の噴射でノッキングに至らない程度の濃さの混合気を作る構成となっていたため、セタン価の低いガソリンを燃料とする圧縮自己着火エンジンにおいては、課題である着火性をかえって悪化させるという逆効果を生じてしまうという問題点があった。   Further, the second prior art is devised in order to avoid knocking at the time of high load of early injection premixed compression self-ignition in a diesel engine, and it is thick enough not to cause knocking simply by the first injection. Therefore, in a compression self-ignition engine using gasoline with a low cetane number as a fuel, there is a problem that an adverse effect of worsening the ignitability, which is a problem, occurs.

上記問題点に鑑み本発明の課題は、高負荷時にノッキングを起こすことなく高出力トルクを得ると共に低負荷時の着火性を安定させ、広範囲の機関回転数及び負荷で安定した圧縮自己着火燃焼を行うことができる内燃機関を提供することである。   In view of the above problems, the object of the present invention is to obtain a high output torque without causing knocking at a high load, stabilize the ignitability at a low load, and achieve a stable compression self-ignition combustion at a wide range of engine speed and load. It is to provide an internal combustion engine that can be performed.

上記課題を解決するため請求項１記載の発明は、燃焼室内に直接燃料を噴射する燃料噴射弁を備え、排気上死点付近で吸気弁及び排気弁がともに閉となる密閉期間を有する予混合圧縮自己着火式内燃機関において、１燃焼サイクルにおける前記密閉期間中と圧縮行程中との両方に前記燃料噴射弁から燃料噴射するとともに、前記密閉期間中の燃料噴射量を負荷の増加に従い減少させ、前記圧縮行程中の燃料噴射量を負荷の増加に従い増加させることを要旨とする。 The invention of claim 1, wherein for solving the above problems is provided with a fuel injection valve for injecting fuel directly into the combustion chamber, premixed with a sealing period in which the intake and exhaust valves are both closed in the vicinity of exhaust top dead center In the compression self-ignition internal combustion engine, fuel is injected from the fuel injection valve during both the sealing period and the compression stroke in one combustion cycle , and the fuel injection amount during the sealing period is decreased as the load increases, The gist is to increase the fuel injection amount during the compression stroke as the load increases.

上記課題を解決するため請求項２記載の発明は、請求項１記載の予混合圧縮自己着火式内燃機関において、前記密閉期間中の燃料噴射は、排気弁閉時期から排気上死点までの間に行われることを要旨とする。 In order to solve the above-mentioned problem, the invention according to claim 2 is the premixed compression self-ignition internal combustion engine according to claim 1, wherein the fuel injection during the sealing period is from the exhaust valve closing timing to the exhaust top dead center. The main point is that

上記課題を解決するため請求項３記載の発明は、請求項１または請求項２記載の予混合圧縮自己着火式内燃機関において、前記圧縮行程中の燃料噴射時期を負荷の増加に従い進角させることを要旨とする。 In order to solve the above-mentioned problems, a third aspect of the present invention is the premixed compression self-ignition internal combustion engine according to the first or second aspect, wherein the fuel injection timing during the compression stroke is advanced according to an increase in load. Is the gist.

上記課題を解決するため請求項４記載の発明は、請求項１ないし請求項３のいずれか１項記載の予混合圧縮自己着火式内燃機関において、前記密閉期間中の燃料噴射量を機関回転数の増加に従い増大させることを要旨とする。 In order to solve the above-mentioned problems, a fourth aspect of the present invention is the premixed compression self-ignition internal combustion engine according to any one of the first to third aspects, wherein the fuel injection amount during the sealing period is determined by the engine speed. The main point is to increase it according to the increase.

上記課題を解決するため請求項５記載の発明は、請求項１ないし請求項３のいずれか１項記載の予混合圧縮自己着火式内燃機関において、前記密閉期間中の燃料噴射時期を機関回転数の増加に従い進角させることを要旨とする。 In order to solve the above-mentioned problems, a fifth aspect of the present invention is the premixed compression self-ignition internal combustion engine according to any one of the first to third aspects, wherein the fuel injection timing during the sealing period is determined by the engine speed. The main point is to advance the angle according to the increase of.

上記課題を解決するため請求項６記載の発明は、請求項１ないし請求項３のいずれか１項記載の予混合圧縮自己着火式内燃機関において、前記圧縮行程中の燃料噴射時期を機関回転数の増加に従い進角させることを要旨とする。 In order to solve the above-mentioned problems, a sixth aspect of the present invention is the premixed compression self-ignition internal combustion engine according to any one of the first to third aspects, wherein the fuel injection timing during the compression stroke is determined by the engine speed. The main point is to advance the angle according to the increase of.

請求項１の発明によれば、燃焼室内に直接燃料を噴射する燃料噴射弁を備え、排気上死点付近で吸気弁及び排気弁がともに閉となる密閉期間を有する予混合圧縮自己着火式内燃機関において、１燃焼サイクルにおける前記密閉期間中と圧縮行程中との両方に前記燃料噴射弁から燃料噴射するとともに、この密閉期間中の燃料噴射量を負荷の増加に従い減少させ、圧縮行程中の燃料噴射量を負荷の増加に従い増加させることとしたので、この密閉期間中の燃料噴射量を最小限におさえたまま、着火に必要な反応性の高い改質物質の量を確保することができるので、圧縮行程中の噴射により形成される濃い混合気塊と合わせて、燃料を安定的に着火させることができる。 According to the first aspect of the present invention, the premixed compression self-ignition internal combustion engine is provided with a fuel injection valve that directly injects fuel into the combustion chamber and has a closed period in which both the intake valve and the exhaust valve are closed near the exhaust top dead center. In the engine, fuel is injected from the fuel injection valve during both the sealing period and the compression stroke in one combustion cycle , and the fuel injection amount during the sealing period is decreased as the load increases, so that the fuel during the compression stroke is reduced. Since the injection amount is increased as the load increases, the amount of highly reactive reforming material necessary for ignition can be secured while keeping the fuel injection amount during this sealing period to a minimum. The fuel can be stably ignited together with the rich air-fuel mixture formed by the injection during the compression stroke.

請求項２の発明によれば、請求項１の発明の効果に加えて、密閉期間中の燃料噴射を、排気弁閉時期から排気上死点までの間に行われることとしたので、密閉期間中の高温高圧による１回目に噴射された燃料の改質度合いを高めるとともに、密閉期間中の燃料噴射量を最小限に抑制して発熱量を小さくおさえることができ、充填効率の低下を少なくできる。   According to the invention of claim 2, in addition to the effect of the invention of claim 1, fuel injection during the sealing period is performed from the exhaust valve closing timing to the exhaust top dead center. The degree of reforming of the fuel injected at the first time due to the high temperature and high pressure inside can be increased, the amount of fuel injection during the sealing period can be minimized, the calorific value can be reduced, and the decrease in filling efficiency can be reduced .

請求項３の発明によれば、請求項１または請求項２の発明の効果に加えて、前記圧縮行程中の燃料噴射時期を負荷の増加に従い進角させることとしたので、圧縮行程中に噴射された燃料が負荷の増加に従って広く拡散することができ、局部的な空燃比の低下を防止し、負荷の増加に伴う粒子状物質（パティキュレート）の発生を抑制することができる。   According to the invention of claim 3, in addition to the effects of the invention of claim 1 or 2, the fuel injection timing during the compression stroke is advanced according to the increase in load, so that the injection during the compression stroke is performed. The dispersed fuel can be diffused widely as the load increases, and the local decrease in the air-fuel ratio can be prevented, and the generation of particulate matter (particulates) accompanying the increase in the load can be suppressed.

請求項４の発明によれば、請求項１ないし請求項３の発明の効果に加えて、前記密閉期間中の燃料噴射量を機関回転数の増加に従い増大させることとしたので、機関回転数の増加に伴ってクランク角当たりの実時間が短縮されても燃料改質の化学反応に寄与する燃料量が増大し、着火に必要な燃料改質物質の量を確保することができる。   According to the invention of claim 4, in addition to the effects of the inventions of claims 1 to 3, the fuel injection amount during the sealing period is increased as the engine speed increases. Even if the actual time per crank angle is shortened along with the increase, the amount of fuel contributing to the chemical reaction of fuel reforming increases, and the amount of fuel reforming substance necessary for ignition can be ensured.

請求項５の発明によれば、請求項１ないし請求項３の発明の効果に加えて、前記密閉期間中の燃料噴射時期を機関回転数の増加に従い進角させることとしたので、機関回転数の増加に伴ってクランク角当たりの実時間が短縮されても燃料改質の化学反応時間が確保され、密閉期間中の燃料噴射量を最小限におさえたまま、機関回転数によらず安定した着火に必要な燃料改質物質の量を確保することができる。   According to the fifth aspect of the invention, in addition to the effects of the first to third aspects of the invention, the fuel injection timing during the sealing period is advanced according to the increase in the engine speed. Even if the actual time per crank angle is shortened as the engine speed increases, the chemical reaction time for fuel reforming is secured, and the fuel injection amount during the sealing period is kept to a minimum and stable regardless of the engine speed. The amount of fuel reforming material necessary for ignition can be secured.

請求項６の発明によれば、請求項１ないし請求項３の発明の効果に加えて、前記圧縮行程中の燃料噴射時期を機関回転数の増加に従い進角させることとしたので、機関回転数の増加に伴ってクランク角当たりの実時間が短縮されても圧縮行程に噴射された燃料から燃料改質の化学反応に寄与する量が増加するようになり、密閉期間中の燃料噴射量を最小限におさえたまま、機関回転数によらず安定した着火に必要な燃料改質物質の量を確保することができる。   According to the invention of claim 6, in addition to the effects of the inventions of claims 1 to 3, the fuel injection timing during the compression stroke is advanced in accordance with the increase of the engine speed. Even if the actual time per crank angle is shortened with an increase in the amount of fuel, the amount that contributes to the chemical reaction of fuel reforming from the fuel injected during the compression stroke will increase, minimizing the fuel injection amount during the sealing period The amount of the fuel reforming material necessary for stable ignition can be ensured regardless of the engine speed.

次に、本発明の実施の形態を図面を参照して詳細に説明する。
図１は、本発明に係る圧縮自己着火式内燃機関の第１実施形態の構成を示すシステム構成図である。 Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a system configuration diagram showing the configuration of a first embodiment of a compression self-ignition internal combustion engine according to the present invention.

図１において、本発明の圧縮自己着火式内燃機関は、電子制御ユニット（以下、ＥＣＵと略す）１と、エンジン本体１０と、燃焼室１１と、ピストン１２と、吸気ポート１３と、吸気弁１４と、吸気弁用可変動弁装置１５と、排気ポート１６と、排気弁１７と、排気弁用可変動弁装置１８と、燃焼室１１に面して設けられた燃料噴射弁１９と、火花点火燃焼時に火花点火を行うための点火プラグ２０と、クランク角センサ２１とを備えている。   1, a compression self-ignition internal combustion engine of the present invention includes an electronic control unit (hereinafter abbreviated as ECU) 1, an engine body 10, a combustion chamber 11, a piston 12, an intake port 13, and an intake valve 14. An intake valve variable valve device 15, an exhaust port 16, an exhaust valve 17, an exhaust valve variable valve device 18, a fuel injection valve 19 provided facing the combustion chamber 11, and spark ignition. A spark plug 20 for performing spark ignition during combustion and a crank angle sensor 21 are provided.

ＥＣＵ１は、負荷及び機関回転速度に応じて火花点火燃焼を行うか圧縮自己着火燃焼を行うかの判定を行う運転領域判定部２と、高負荷または高回転時に火花点火燃焼を行う火花点火燃焼制御部３と、中低負荷かつ中低回転時に自己着火燃焼を行う自己着火燃焼制御部４とを備えている。   The ECU 1 includes an operation region determination unit 2 that determines whether to perform spark ignition combustion or compression self-ignition combustion in accordance with the load and the engine speed, and spark ignition combustion control that performs spark ignition combustion at high load or high speed. And a self-ignition combustion control unit 4 that performs self-ignition combustion during medium-low load and medium-low rotation.

自己着火燃焼制御部４は、低負荷時または低回転時に密閉期間中の燃料噴射を制御する密閉期間中噴射制御部５と、中低負荷または中低回転時に圧縮行程中の燃料噴射を制御する圧縮行程中噴射制御部６と、中負荷または中回転時に吸気行程中の燃料噴射を制御する吸気行程中噴射制御部７とを備えている。   The self-ignition combustion control unit 4 controls the fuel injection during the sealing period at the time of low load or low rotation and the fuel injection during the compression stroke at the time of medium or low load or medium / low rotation. A compression stroke injection control unit 6 and an intake stroke injection control unit 7 that controls fuel injection during the intake stroke during medium load or medium rotation are provided.

また、ＥＣＵ１は、図示しないアクセルペダルに設けられたアクセル開度センサが検出するアクセル開度信号、クランク角センサ２１が検出するクランク角センサ信号を入力する一方、吸気弁用可変動弁装置１５及び排気弁用可変動弁装置１８へバルブタイミング切換信号、燃料噴射弁１９へ燃料噴射制御信号、点火プラグ２０へ点火信号をそれぞれ出力する。   Further, the ECU 1 inputs an accelerator opening signal detected by an accelerator opening sensor provided on an accelerator pedal (not shown) and a crank angle sensor signal detected by a crank angle sensor 21, while an intake valve variable valve gear 15 and A valve timing switching signal is output to the exhaust valve variable valve device 18, a fuel injection control signal is output to the fuel injection valve 19, and an ignition signal is output to the spark plug 20.

図２は、本実施の形態における吸気弁及び排気弁のバルブタイミングの例を示す図である。図２（ａ）のバルブタイミング例（１）に示すように、実線で示した通常の火花点火燃焼時のバルブタイミングと、破線で示した圧縮自己着火燃焼時のバルブタイミングとの２つのバルブタイミングを有している。   FIG. 2 is a diagram illustrating an example of valve timings of the intake valve and the exhaust valve in the present embodiment. As shown in the valve timing example (1) in FIG. 2A, there are two valve timings: a normal spark ignition combustion valve timing indicated by a solid line and a compressed self ignition combustion valve timing indicated by a broken line. have.

図２（ａ）の実線のバルブタイミングは、通常の４行程サイクルのガソリンエンジンのバルブタイミングと同様の火花点火燃焼用の吸気弁リフト及び排気弁リフトであり、排気ＴＤＣ付近で吸気弁１４及び排気弁１７が共に開くオーバーラップ期間がある。   The valve timing of the solid line in FIG. 2 (a) is the intake valve lift and exhaust valve lift for spark ignition combustion similar to the valve timing of a gasoline engine in a normal four-stroke cycle, and the intake valve 14 and the exhaust in the vicinity of the exhaust TDC. There is an overlap period in which the valves 17 open together.

図２（ａ）の破線のバルブタイミングは、圧縮自己着火燃焼用のバルブタイミングを示す吸気弁リフト及び排気弁リフトであり、排気ＴＤＣ付近で排気弁１７及び吸気弁１４がともに閉となる密閉期間（いわば、マイナスオーバラップ期間）を形成するとともに、運転領域が中低負荷、中低回転であることを考慮してリフト量を小さくしていることが特徴である。   The valve timings indicated by broken lines in FIG. 2A are intake valve lift and exhaust valve lift indicating valve timings for compression self-ignition combustion, and a sealing period in which both the exhaust valve 17 and the intake valve 14 are closed near the exhaust TDC. (So-called minus overlap period) is formed, and the lift amount is reduced in consideration of the middle and low loads and the middle and low rotation speed.

図２（ｂ）は、バルブタイミング例（２）を示すもので、実線で示した通常の火花点火燃焼時のバルブタイミングと、破線で示した圧縮自己着火燃焼時のマイナスオーバーラップ期間を有するバルブタイミングとの２つのバルブタイミングを有している点では、図２（ｂ）と同様であるが、最大リフト量は、実線の火花点火燃焼時と等しく、カムプロフィールは変わらずにカムの位相を変えるだけで実現している。   FIG. 2B shows a valve timing example (2), which has a valve timing during normal spark ignition combustion indicated by a solid line and a negative overlap period during compression self-ignition combustion indicated by a broken line. 2b in that it has two valve timings, but the maximum lift amount is equal to that of the solid spark ignition combustion, and the cam profile remains the same without changing the cam profile. It is realized just by changing.

ＥＣＵ１のバルブタイミング制御部５からの制御により、吸排気弁の開閉時期を火花点火用のバルブタイミングと、圧縮自己着火用のバルブタイミングとの間で切り換えるための吸気弁用可変動弁装置１５、排気弁用可変動弁装置１８としては、例えば特開平９−２０３３０７号公報等に示されているようにプロフィールの異なるカムを切り換えるカム切換機構や、電磁力により吸排気弁の開閉を制御する電磁駆動弁が利用可能である。   A variable valve operating device for intake valve 15 for switching the opening / closing timing of the intake and exhaust valves between a valve timing for spark ignition and a valve timing for compression self-ignition by control from the valve timing control unit 5 of the ECU 1; As the exhaust valve variable valve device 18, for example, as disclosed in Japanese Patent Laid-Open No. 9-203307, a cam switching mechanism that switches cams with different profiles, or an electromagnetic that controls opening and closing of the intake and exhaust valves by electromagnetic force. A drive valve is available.

次に本実施形態の動作を説明する。
図３は、本実施形態における部分負荷時のエンジンの作動を説明するエンジンの行程毎の模式断面図であり、（ａ）排気行程、（ｂ）排気ＴＤＣ付近の密閉期間（マイナスオーバラップ）、（ｃ）吸気行程、（ｄ）圧縮行程、（ｅ）圧縮ＴＤＣ付近、をそれぞれ示す。 Next, the operation of this embodiment will be described.
FIG. 3 is a schematic cross-sectional view for each stroke of the engine for explaining the operation of the engine at the partial load in the present embodiment. (A) Exhaust stroke, (b) Sealing period (minus overlap) near the exhaust TDC, (C) The intake stroke, (d) the compression stroke, and (e) the vicinity of the compression TDC are shown.

部分負荷時には、吸気弁用可変動弁装置１５、排気弁用可変動弁装置１８を作動させることによって、排気上死点付近で密閉期間を形成する自己着火燃焼用のバルブタイミングを選択し排気ＴＤＣ付近で密閉期間を形成する。   At the time of partial load, by operating the variable valve device 15 for the intake valve and the variable valve device 18 for the exhaust valve, the valve timing for self-ignition combustion that forms a sealed period near the exhaust top dead center is selected, and the exhaust TDC Form a sealing period in the vicinity.

排気行程前半では図３（ａ）に示すように、通常のエンジンと同じくシリンダの排気ガスは排気弁１７から排気ポート１６へ排出される。   In the first half of the exhaust stroke, as shown in FIG. 3A, the exhaust gas of the cylinder is discharged from the exhaust valve 17 to the exhaust port 16 as in a normal engine.

排気行程後半では図３（ｂ）に示すように、通常のエンジンとは異なり、排気弁１７を閉じてシリンダ内に排気ガスを閉じこめ、再度圧縮を行い、高温、高圧の状態を形成する。   In the latter half of the exhaust stroke, as shown in FIG. 3 (b), unlike the normal engine, the exhaust valve 17 is closed, the exhaust gas is closed in the cylinder, and compression is performed again to form a high temperature and high pressure state.

この高温ガス中に燃料噴射弁１９から１回目のガソリン噴射することによって燃焼の予反応が起こり、ガソリンの組成はアルデヒドを含むより反応性の高い組成に改質される。この改質の程度は高温ガス中にガソリンが保持される時間によって連続的に制御することが可能である。燃料の噴射時期を早めた場合には燃焼開始寸前まで高度に改質され、噴射時期を遅めた場合にはガソリンそのままに近い改質状態となる。   The first gasoline injection from the fuel injection valve 19 into the high-temperature gas causes a combustion prereaction, and the composition of gasoline is reformed to a more reactive composition containing aldehyde. The degree of this reforming can be continuously controlled by the time that gasoline is held in the hot gas. When the fuel injection timing is advanced, the fuel is highly reformed until just before the start of combustion, and when the injection timing is delayed, the reformed state is close to that of gasoline.

吸気行程前半では、吸排気弁を閉じた状態のまま改質された混合気を大気圧近くまで膨脹させ、吸気行程後半では、図３（ｃ）に示すように、吸気弁１４を開けて新気を吸気ポート１３から吸気する。   In the first half of the intake stroke, the reformed air-fuel mixture is expanded to near atmospheric pressure while the intake and exhaust valves are closed, and in the second half of the intake stroke, the intake valve 14 is opened and a new one is opened as shown in FIG. Inhale air from the intake port 13.

圧縮行程では、図３（ｄ）に示すように、高温の改質された混合気と新気が混合された状態で圧縮される。さらに、ここで２回目の燃料噴射を行う。ここで噴射された燃料は、シリンダ内のガスが高密度であるため、拡散が抑制され局所的に濃い混合気が形成される、いわゆる成層化が行われる。   In the compression process, as shown in FIG. 3D, the compressed air is compressed in a mixed state with the high-temperature reformed air-fuel mixture. Further, a second fuel injection is performed here. Since the fuel injected here has a high density of gas in the cylinder, so-called stratification is performed in which diffusion is suppressed and a locally rich mixture is formed.

この結果前記燃料改質の効果と燃料成層化との相乗作用により、公知例の場合の軽油ではなくガソリンを燃料として、さらに、公知例における圧縮比より低い圧縮比にて、図３（ｅ）に示すように圧縮自己着火を達成することができる。このため、火花点火を行う全負荷運転でもノッキング限界に起因するトルク低下が生じにくい。
膨脹行程では図示しないが、自己着火燃焼したガスがピストンを押し下げて軸トルクを発生する。 As a result, due to the synergistic effect of the fuel reforming effect and fuel stratification, gasoline is used instead of light oil in the case of the known example, and at a compression ratio lower than the compression ratio in the known example, FIG. Compressive self-ignition can be achieved as shown in FIG. For this reason, torque reduction due to the knocking limit is less likely to occur even at full load operation with spark ignition.
Although not shown in the expansion stroke, the self-ignited and burned gas pushes down the piston to generate shaft torque.

図４は、本実施形態における全負荷時のエンジンの作動を説明するエンジンの行程毎の断面図であり、（ａ）排気行程、（ｂ）吸気行程、（ｃ）圧縮行程、（ｄ）圧縮ＴＤＣ付近、をそれぞれ示す。   FIG. 4 is a cross-sectional view for each stroke of the engine for explaining the operation of the engine at the full load in this embodiment. (A) Exhaust stroke, (b) Intake stroke, (c) Compression stroke, (d) Compression The vicinity of TDC is shown.

全負荷運転時には、ＥＣＵ１が吸気弁用可変動弁装置１５、排気弁用可変動弁装置１８を作動させることによって、火花点火燃焼用のバルブタイミングを選択し、適切な点火時期に点火プラグ２０の火花により混合気に点火する。この時、４行程にわたって動作は通常の火花点火ガソリンエンジンと同じになる。   During full-load operation, the ECU 1 operates the intake valve variable valve device 15 and the exhaust valve variable valve device 18 to select the valve timing for spark ignition combustion, and to set the spark plug 20 at an appropriate ignition timing. The mixture is ignited by sparks. At this time, the operation is the same as that of a normal spark ignition gasoline engine over four strokes.

次に、部分負荷時の圧縮自着火燃焼に関して詳しく述べる。
前述したような圧縮自己着火は、燃焼室内の温度、圧力、燃料濃度、燃料の改質程度により影響され、これらのいずれも大きいほど圧縮自己着火時期が早まる。一方、エンジンの熱効率の点からは圧縮自己着火の開始時期は圧縮ＴＤＣ付近であることが必要である。 Next, compression auto-ignition combustion at partial load will be described in detail.
The compression self-ignition as described above is affected by the temperature, pressure, fuel concentration, and the degree of reforming of the fuel in the combustion chamber. On the other hand, from the viewpoint of the thermal efficiency of the engine, the start time of compression self-ignition needs to be in the vicinity of compression TDC.

図５は、密閉期間中の燃料の噴射時期と燃料改質の程度の関係を表す概念図である。ここに示したように、密閉期間中の噴射時期を早めるほど燃料が高温高圧に曝される時間が長くなり、燃料の改質度が大きくなる。   FIG. 5 is a conceptual diagram showing the relationship between the fuel injection timing and the degree of fuel reforming during the sealing period. As shown here, the earlier the injection timing during the sealing period, the longer the time during which the fuel is exposed to high temperature and pressure, and the degree of reforming of the fuel increases.

また図６は、密閉期間中の燃料の噴射量と充填効率の関係を示したものである。密閉期間中に燃料を噴射する量が多いほど密閉期間中の熱発生が多くなるため、これに続く吸気行程での吸気量が減少し充填効率が低下する。このため、充填効率の観点からは密閉期間中の燃料噴射量は少ないほど良く、少ない燃料量で大きな改質効果を得るためには、密閉期間中の燃料の噴射時期は排気弁閉時期から排気上死点までの範囲を使うことになる。   FIG. 6 shows the relationship between the fuel injection amount and the charging efficiency during the sealing period. As the amount of fuel injected during the sealing period increases, heat generation during the sealing period increases, so that the intake amount in the subsequent intake stroke decreases and the charging efficiency decreases. Therefore, from the viewpoint of charging efficiency, the smaller the fuel injection amount during the sealing period, the better. In order to obtain a large reforming effect with a small amount of fuel, the fuel injection timing during the sealing period is exhausted from the exhaust valve closing timing. The range up to the top dead center will be used.

図７は、実施形態における負荷と密閉期間中の燃料噴射量および圧縮行程中の燃料噴射量の関係の一例を示したものである。ガソリンは軽油より着火性が低く、また全負荷性能の要求からガソリン機関の圧縮比はディーゼル機関の圧縮比より低くならざるを得ない。このような条件下でガソリンの着火を確保するためには、アルデヒドに代表される燃料改質生成物が、機関速度と圧縮比に応じて、ある一定量必要であることが経験上分かっている。   FIG. 7 shows an example of the relationship between the load, the fuel injection amount during the sealing period, and the fuel injection amount during the compression stroke in the embodiment. Gasoline has lower ignitability than light oil, and the compression ratio of a gasoline engine must be lower than the compression ratio of a diesel engine because of the demand for full load performance. Experience has shown that in order to ensure the ignition of gasoline under such conditions, a certain amount of fuel reforming product represented by aldehyde is required depending on the engine speed and compression ratio. .

図７は、この一定量の改質生成物を確保するために、密閉期間中の燃料噴射量を負荷によらず一定量に保ち、負荷の増加に応じて圧縮行程中の燃料噴射量を増加させる例を示す。この例によれば、図１の密閉期間中噴射制御部５は密閉期間中の燃料噴射量を負荷によらず常に一定量とし、圧縮行程中噴射制御部６は圧縮行程中の燃料噴射量を負荷の増加に従い増加させる制御を行うことになり、自己着火燃焼制御部４全体としての制御構造が簡略化される。   FIG. 7 shows that in order to secure this constant amount of reformed product, the fuel injection amount during the sealing period is kept constant regardless of the load, and the fuel injection amount during the compression stroke is increased as the load increases. An example is shown. According to this example, the injection control unit 5 during the sealing period in FIG. 1 always sets the fuel injection amount during the sealing period to a constant amount regardless of the load, and the injection control unit 6 during the compression stroke sets the fuel injection amount during the compression stroke. The control to be increased according to the increase in load is performed, and the control structure of the self-ignition combustion control unit 4 as a whole is simplified.

図８は、実施形態における負荷と密閉期間中の燃料噴射量および圧縮行程中の燃料噴射量の関係を示した別の例である。負荷の増加に応じて圧縮行程中の燃料噴射量を増加させた場合、これによって混合気の着火性が高まるので、着火に必要な燃料改質生成物の量は減少する。これに合わせて密閉期間中の燃料噴射量を徐々に減らして行く例である。この例によれば、図１の密閉期間中噴射制御部５は密閉期間中の燃料噴射量を負荷の増加に従い減少させ、圧縮行程中噴射制御部６は圧縮行程中の燃料噴射量を負荷の増加に従い増加させる。これにより、密閉期間中噴射制御部５及び圧縮行程中噴射制御部６が共に負荷に応じた燃料噴射量制御を行う必要があるが、吸気充填効率が向上する。   FIG. 8 is another example showing the relationship between the load, the fuel injection amount during the sealing period, and the fuel injection amount during the compression stroke in the embodiment. When the fuel injection amount during the compression stroke is increased in accordance with the increase in the load, the ignitability of the air-fuel mixture is thereby increased, so that the amount of fuel reformed product necessary for ignition is reduced. In accordance with this, the fuel injection amount during the sealing period is gradually reduced. According to this example, the injection control unit 5 during the sealing period in FIG. 1 decreases the fuel injection amount during the sealing period as the load increases, and the injection control unit 6 during the compression stroke reduces the fuel injection amount during the compression stroke to the load. Increase with increase. Thereby, both the injection control unit 5 and the injection control unit 6 during the compression stroke need to perform fuel injection amount control according to the load during the sealing period, but the intake charging efficiency is improved.

図９は、実施形態における負荷に対する燃料噴射時期の設定の一例である。本実施形態の内燃機関は、負荷に応じて４つの運転領域を備えている。即ち、負荷Ｌが小さい領域から大きい領域へ向かって、密閉期間噴射及び圧縮行程噴射による燃料改質自己着火領域（Ｌ＜Ｌ１）、圧縮行程噴射のみのよる成層自己着火領域（Ｌ１＜Ｌ＜Ｌ２）、吸気行程噴射による均質自己着火領域（Ｌ２＜Ｌ＜Ｌ３）、吸気行程噴射と火花点火による均質火花点火領域（Ｌ３＜Ｌ）を備えている。尚、境界負荷Ｌ１，Ｌ２，Ｌ３の付近においては、頻繁な制御の切替を防止するため、以前の燃焼領域を継続するように、燃焼領域の切替制御にある程度のヒステリシス特性を持たせている。   FIG. 9 is an example of setting the fuel injection timing for the load in the embodiment. The internal combustion engine of the present embodiment includes four operation regions according to the load. That is, from the region where the load L is small to the large region, the fuel reforming self-ignition region (L <L1) by the sealing period injection and the compression stroke injection, the stratified self-ignition region (L1 <L <L2) by only the compression stroke injection ), A homogeneous auto-ignition region (L2 <L <L3) by intake stroke injection, and a homogeneous spark ignition region (L3 <L) by intake stroke injection and spark ignition. In the vicinity of the boundary loads L1, L2, and L3, in order to prevent frequent control switching, the combustion region switching control has some hysteresis characteristics so as to continue the previous combustion region.

負荷がＬ１より小さい場合には、１回目の密閉期間中及び２回目の圧縮行程中の燃料噴射を実施し、ガソリンを改質して適正な熱発生時期を得ることができる。   When the load is smaller than L1, fuel injection is performed during the first sealing period and the second compression stroke, and the gasoline is reformed to obtain an appropriate heat generation time.

ある程度エンジンの負荷が高くなり、密閉期間中の燃料改質に頼らなくても混合気を成層化することにより局所的に燃料濃度を高め、圧縮自己着火を起こすことができるようになる。このため、Ｌ１＜Ｌ＜Ｌ２の範囲の負荷Ｌでは、圧縮行程噴射のみの成層自己着火燃焼を行うことができる。   The engine load increases to some extent, and the fuel concentration is locally increased by stratifying the air-fuel mixture without relying on fuel reforming during the sealing period, and compression self-ignition can be caused. For this reason, stratified self-ignition combustion with only compression stroke injection can be performed at the load L in the range of L1 <L <L2.

密閉期間中の燃料改質による圧縮自己着火と、混合気成層化による圧縮自己着火を比較すると、混合気成層化による圧縮自己着火の方が、壁面クエンチングによるＨＣの排出が少ないという利点が有るため、本実施形態では混合気成層化による圧縮自己着火を運転領域に含めてある。   Comparing compression auto-ignition due to fuel reforming during the sealing period and compression auto-ignition due to mixed gas stratification, compressed self-ignition due to mixed gas stratification has the advantage that HC emissions due to wall quenching are less For this reason, in this embodiment, compression self-ignition by mixed gas stratification is included in the operation region.

また、成層自己着火域において、圧縮行程中噴射制御部６は、負荷の増加に従って圧縮行程中の噴射時期を早める制御を行っている。これは、負荷の増加に伴い圧縮行程中の燃料噴射量は増加するが、この時燃料噴射時期を固定しておくと燃焼時の局所空燃比が濃くなりすぎ、ＮＯｘやスモークが発生する。これを回避するためには燃料噴射量を増やすと同時に燃料噴射時期を進角し、圧縮圧力が低く、且つ上死点までの時間的余裕がある時期に燃料を噴射し、噴射した燃料の拡散を容易にして燃焼時の局所空燃比をほぼ一定に保つ必要があるためである。   In the stratified self-ignition region, the injection control unit 6 during the compression stroke performs control to advance the injection timing during the compression stroke as the load increases. This is because the fuel injection amount during the compression stroke increases as the load increases, but if the fuel injection timing is fixed at this time, the local air-fuel ratio at the time of combustion becomes too high, and NOx and smoke are generated. To avoid this, increase the fuel injection amount and simultaneously advance the fuel injection timing, inject the fuel at a time when the compression pressure is low and there is time to the top dead center, and diffusion of the injected fuel This is because it is necessary to make the local air-fuel ratio during combustion almost constant.

さらに負荷が大きくなりＬ２を超えると、吸気行程中の燃料噴射を行って均質混合気による圧縮自己着火へ移る。
更に負荷が大きい領域（Ｌ３＜Ｌ）では、吸排気バルブのタイミングを火花点火用のタイミングに変更するとともに、吸気行程噴射、火花点火を行っている。 When the load further increases and exceeds L2, fuel injection is performed during the intake stroke, and the process proceeds to compression self-ignition with a homogeneous mixture.
In a region where the load is larger (L3 <L), the intake / exhaust valve timing is changed to the timing for spark ignition, and intake stroke injection and spark ignition are performed.

図１０は、本発明の第２実施形態の燃料噴射時期特性を説明する図である。本実施形態の構成は、図１に示した第１実施形態と同様である。
本実施形態は、密閉期間噴射による燃料改質自己着火域（Ｌ＜Ｌ１）において、圧縮行程中の燃料噴射時期を負荷の増加に従い進角させるものである。その他の噴射時期の制御は、図９と同様である。 FIG. 10 is a diagram for explaining the fuel injection timing characteristics of the second embodiment of the present invention. The configuration of this embodiment is the same as that of the first embodiment shown in FIG.
In the present embodiment, the fuel injection timing during the compression stroke is advanced as the load increases in the fuel reforming auto-ignition region (L <L1) by the closed period injection. The other injection timing control is the same as in FIG.

密閉期間噴射による燃料改質自己着火域においても負荷の増加に伴い圧縮行程中の燃料噴射量は増加するが、この時燃料噴射時期を固定しておくと燃焼時の局所空燃比が濃くなりすぎ、ＮＯｘやスモークが発生する。これを回避するためには燃料噴射量を増やすと同時に燃料噴射時期を進角し、燃焼時の局所空燃比をほぼ一定に保つ必要がある。このため、本実施形態においては、密閉期間噴射による燃料改質自己着火域（Ｌ＜Ｌ１）において、圧縮行程中噴射制御部６からの圧縮行程中の燃料噴射時期を負荷の増加に従い進角させている。   Even in the fuel reforming self-ignition region due to closed period injection, the fuel injection amount during the compression stroke increases with the load, but if the fuel injection timing is fixed at this time, the local air-fuel ratio during combustion becomes too dense. NOx and smoke are generated. In order to avoid this, it is necessary to increase the fuel injection amount and simultaneously advance the fuel injection timing to keep the local air-fuel ratio at the time of combustion substantially constant. For this reason, in the present embodiment, in the fuel reforming auto-ignition region (L <L1) by the closed period injection, the fuel injection timing during the compression stroke from the injection control unit 6 during the compression stroke is advanced according to the increase in load. ing.

次に、機関速度と燃料改質の関係について述べる。
エンジンの回転速度を変化させても圧縮自己着火の化学変化の時間は一定であるため、相対的にクランク角に対する圧縮自己着火時期が変化する。すなわち機関速度が遅くなると圧縮自己着火時期が早まり、逆に、機関速度が早くなると圧縮自己着火時期が遅くなる。このため広い範囲の機関速度に対して適正な圧縮自己着火時期を得るためには、燃料の改質程度または改質生成物の量をコントロールする必要が生じる。機関速度の増加に従い前記密閉期間中の燃料噴射量を増大させ、燃料の改質生成物の量を増大させるのはこのための一つの方法である。 Next, the relationship between engine speed and fuel reforming will be described.
Even if the rotational speed of the engine is changed, the time of the chemical change of the compression self-ignition is constant, so that the compression self-ignition timing relative to the crank angle changes relatively. That is, when the engine speed is slowed down, the compression self-ignition timing is advanced. Conversely, when the engine speed is fastened, the compression self-ignition timing is delayed. Therefore, in order to obtain an appropriate compression autoignition timing for a wide range of engine speeds, it is necessary to control the degree of reforming of the fuel or the amount of reformed product. One method for this is to increase the amount of fuel injection during the sealing period and increase the amount of reformed product of the fuel as the engine speed increases.

図１１は、本発明の第３実施形態の燃料噴射特性を説明する図である。本実施形態の構成は、図１に示した第１実施形態と同様である。本実施形態は、機関速度の増加に従い密閉期間中噴射制御部５による密閉期間中の燃料の噴射時期を機関速度の増加に従って進角し、燃料の改質程度を高めた例である。   FIG. 11 is a diagram illustrating the fuel injection characteristics of the third embodiment of the present invention. The configuration of this embodiment is the same as that of the first embodiment shown in FIG. This embodiment is an example in which the fuel injection timing during the sealing period by the injection control unit 5 during the sealing period is advanced according to the increase in the engine speed and the degree of fuel reforming is increased as the engine speed increases.

図１１において、本実施形態の内燃機関は、機関速度に応じて４つの運転領域を備えている。即ち、機関速度Ｖが小さい領域から大きい領域へ向かって、密閉期間噴射及び圧縮行程噴射による燃料改質自己着火領域（Ｖ＜Ｖ１）、圧縮行程噴射のみのよる成層自己着火領域（Ｖ１＜Ｖ＜Ｖ２）、吸気行程噴射による均質自己着火領域（Ｖ２＜Ｖ＜Ｖ３）、吸気行程噴射と火花点火による均質火花点火領域（Ｖ３＜Ｖ）を備えている。尚、境界機関速度Ｖ１，Ｖ２，Ｖ３の付近においては、頻繁な制御の切替を防止するため、以前の燃焼領域を継続するように、燃焼領域の切替制御にある程度のヒステリシス特性を持たせている。   In FIG. 11, the internal combustion engine of the present embodiment has four operating regions according to the engine speed. That is, from the region where the engine speed V is small to the large region, the fuel reforming self-ignition region (V <V1) by the sealed period injection and the compression stroke injection, and the stratified autoignition region (V1 <V <) by only the compression stroke injection. V2), a homogeneous auto-ignition region (V2 <V <V3) by intake stroke injection, and a homogeneous spark ignition region (V3 <V) by intake stroke injection and spark ignition. In the vicinity of the boundary engine speeds V1, V2, and V3, in order to prevent frequent control switching, the combustion region switching control has some hysteresis characteristics so as to continue the previous combustion region. .

機関速度がＶ１より小さい場合には、１回目の密閉期間中及び２回目の圧縮行程中の燃料噴射を実施し、ガソリンを改質して適正な熱発生時期を得ることができる。   When the engine speed is lower than V1, fuel injection can be performed during the first sealing period and the second compression stroke, and the gasoline can be reformed to obtain an appropriate heat generation time.

ある程度エンジンの機関速度が高くなり、密閉期間中の燃料改質に頼らなくても混合気を成層化することにより局所的に燃料濃度を高め、圧縮自己着火を起こすことができるようになる。このため、Ｖ１＜Ｖ＜Ｖ２の範囲の機関速度Ｖでは、圧縮行程噴射のみの成層自己着火燃焼を行うことができる。   The engine speed of the engine increases to some extent, and the fuel concentration can be locally increased by stratifying the air-fuel mixture without relying on fuel reforming during the sealing period, and compression self-ignition can be caused. For this reason, at an engine speed V in the range of V1 <V <V2, stratified self-ignition combustion with only compression stroke injection can be performed.

密閉期間中の燃料改質による圧縮自己着火と、混合気成層化による圧縮自己着火を比較すると、混合気成層化による圧縮自己着火の方が、壁面クエンチングによるＨＣの排出が少ないという利点が有るため、本実施形態では混合気成層化による圧縮自己着火を運転領域に含めてある。   Comparing compression auto-ignition due to fuel reforming during the sealing period and compression auto-ignition due to mixed gas stratification, compressed self-ignition due to mixed gas stratification has the advantage that HC emissions due to wall quenching are less For this reason, in this embodiment, compression self-ignition by mixed gas stratification is included in the operation region.

また、成層自己着火域において、圧縮行程中噴射制御部６は、機関速度の増加に従って圧縮行程中の噴射時期を早める制御を行っている。これは、機関速度の増加に対して圧縮行程中の燃料噴射時期を固定しておくと、燃焼時の局所空燃比が濃くなりすぎ、ＮＯｘやスモークが発生する。これを回避するためには、燃料噴射時期を進角し、圧縮圧力が低く、且つ上死点までの時間的余裕がある時期に燃料を噴射し、噴射した燃料の拡散を容易にすることにより、燃焼時の局所空燃比をほぼ一定に保つことができる。   Further, in the stratified self-ignition region, the injection control unit 6 during the compression stroke performs control to advance the injection timing during the compression stroke as the engine speed increases. This is because if the fuel injection timing during the compression stroke is fixed with respect to the increase in engine speed, the local air-fuel ratio at the time of combustion becomes excessively high, and NOx and smoke are generated. In order to avoid this, the fuel injection timing is advanced, the fuel is injected at a time when the compression pressure is low, and there is sufficient time to top dead center, and the diffusion of the injected fuel is facilitated. The local air-fuel ratio at the time of combustion can be kept substantially constant.

さらに機関速度が大きくなりＶ２を超えると、吸気行程中の燃料噴射を行って均質混合気による圧縮自己着火へ移る。
更に機関速度が大きい領域（Ｖ３＜Ｖ）では、吸排気バルブのタイミングを火花点火用のタイミングに変更するとともに、吸気行程噴射、火花点火を行っている。 When the engine speed further increases and exceeds V2, fuel injection is performed during the intake stroke, and the process proceeds to compression self-ignition with a homogeneous mixture.
Further, in a region where the engine speed is high (V3 <V), the intake / exhaust valve timing is changed to the timing for spark ignition, and intake stroke injection and spark ignition are performed.

図１２は、本発明の第４実施形態の燃料噴射特性を説明する図である。本実施形態の構成は、図１に示した第１実施形態と同様である。本実施形態は、密閉期間噴射による燃料改質自己着火域における圧縮行程中の燃料噴射時期を機関速度の増加に従い進角させる実施形態である。   FIG. 12 is a diagram illustrating the fuel injection characteristics of the fourth embodiment of the present invention. The configuration of this embodiment is the same as that of the first embodiment shown in FIG. This embodiment is an embodiment in which the fuel injection timing during the compression stroke in the fuel reforming auto-ignition region by the sealed period injection is advanced as the engine speed increases.

エンジンの回転速度を変化させても圧縮自己着火に要する化学変化の時間は一定であるため、燃料噴射時期を固定しておくと機関速度の増加に伴い着火時期が遅くなり、ついには失火が発生する。これを回避するためには機関速度の増加にともない圧縮行程中噴射制御部６による圧縮行程中の燃料噴射時期を進角することにより、着火時期を圧縮上死点付近の時期にほぼ一定に保つことができる。   Even if the engine speed is changed, the time of chemical change required for compression self-ignition is constant, so if the fuel injection timing is fixed, the ignition timing is delayed as the engine speed increases, and eventually misfiring occurs. To do. In order to avoid this, the ignition timing is kept substantially constant at the timing near the compression top dead center by advancing the fuel injection timing during the compression stroke by the injection control unit 6 during the compression stroke as the engine speed increases. be able to.

第１の実施形態の構成を示すシステム構成図である。It is a system configuration figure showing the composition of a 1st embodiment. 第１の実施形態におけるバルブタイミングを示す図である。It is a figure which shows the valve timing in 1st Embodiment. 部分負荷時の各行程のエンジン内混合気の状態を説明する模式図である。It is a schematic diagram explaining the state of the air-fuel mixture in the engine in each stroke at the time of partial load. 全負荷時の各行程のエンジン内混合気の状態を説明する模式図である。It is a schematic diagram explaining the state of the engine air-fuel mixture in each stroke at the time of full load. 密閉期間中の燃料噴射時期と燃料改質程度との関係を示すグラフである。It is a graph which shows the relationship between the fuel-injection timing in a sealing period, and a fuel reforming grade. 密閉期間中の燃料噴射量と充填効率との関係を示すグラフである。It is a graph which shows the relationship between the fuel injection quantity and filling efficiency in a sealing period. 第１の実施形態における負荷と各燃料噴射量との関係を示すグラフである。It is a graph which shows the relationship between the load and each fuel injection quantity in 1st Embodiment. 第１の実施形態における負荷と各燃料噴射量との関係の他の例を示すグラフである。It is a graph which shows the other example of the relationship between the load in 1st Embodiment, and each fuel injection quantity. 第１の実施形態における負荷と各燃料噴射時期との関係を示すグラフである。It is a graph which shows the relationship between the load in 1st Embodiment, and each fuel-injection time. 第２の実施形態における負荷と各燃料噴射時期との関係を示すグラフである。It is a graph which shows the relationship between the load in 2nd Embodiment, and each fuel-injection time. 第３の実施形態における機関速度と各燃料噴射時期との関係を示すグラフである。It is a graph which shows the relationship between the engine speed and each fuel injection timing in 3rd Embodiment. 第４の実施形態における機関速度と各燃料噴射時期との関係を示すグラフである。It is a graph which shows the relationship between the engine speed and each fuel-injection time in 4th Embodiment.

符号の説明Explanation of symbols

１ ＥＣＵ
２ 運転領域判定部
３ 火花点火燃焼制御部
４ 自己着火燃焼制御部
５ 密閉期間中噴射制御部
６ 圧縮行程中噴射制御部
７ 吸気行程中噴射制御部
１０ エンジン本体
１１ 燃焼室
１２ ピストン
１３ 吸気ポート
１４ 吸気弁
１５ 吸気弁用可変動弁装置
１６ 排気ポート
１７ 排気弁
１８ 排気弁用可変動弁装置
１９ 燃料噴射弁
２０ 点火プラグ
２１ クランク角センサ 1 ECU
DESCRIPTION OF SYMBOLS 2 Operation area | region determination part 3 Spark ignition combustion control part 4 Self ignition combustion control part 5 Injection control part during sealing period 6 Injection control part during compression stroke 7 Injection control part 10 during intake stroke 10 Engine main body 11 Combustion chamber 12 Piston 13 Intake port 14 Intake valve 15 Intake valve variable valve device 16 Exhaust port 17 Exhaust valve 18 Exhaust valve variable valve device 19 Fuel injection valve 20 Spark plug 21 Crank angle sensor

Claims (6)

燃焼室内に直接燃料を噴射する燃料噴射弁を備え、排気上死点付近で吸気弁及び排気弁がともに閉となる密閉期間を有する予混合圧縮自己着火式内燃機関において、
１燃焼サイクルにおける前記密閉期間中と圧縮行程中との両方に前記燃料噴射弁から燃料噴射するとともに、前記密閉期間中の燃料噴射量を負荷の増加に従い減少させ、前記圧縮行程中の燃料噴射量を負荷の増加に従い増加させることを特徴とする予混合圧縮自己着火式内燃機関。 In a premixed compression self-ignition internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber and having a sealing period in which both an intake valve and an exhaust valve are closed near the exhaust top dead center,
Fuel is injected from the fuel injection valve both during the sealing period and during the compression stroke in one combustion cycle , and the fuel injection amount during the sealing period is decreased as the load increases, so that the fuel injection amount during the compression stroke is reduced. A premixed compression self-ignition internal combustion engine characterized by increasing the engine as the load increases. 前記密閉期間中の燃料噴射は、排気弁閉時期から排気上死点までの間に行われることを特徴とする請求項１記載の予混合圧縮自己着火式内燃機関。 2. The premixed compression self-ignition internal combustion engine according to claim 1, wherein the fuel injection during the sealing period is performed from an exhaust valve closing timing to an exhaust top dead center. 前記圧縮行程中の燃料噴射時期を負荷の増加に従い進角させることを特徴とする請求項１または請求項２記載の予混合圧縮自己着火式内燃機関。 The premixed compression self-ignition internal combustion engine according to claim 1 or 2, wherein the fuel injection timing during the compression stroke is advanced according to an increase in load. 前記密閉期間中の燃料噴射量を機関回転数の増加に従い増大させることを特徴とする請求項１ないし請求項３のいずれか１項記載の予混合圧縮自己着火式内燃機関。 The premixed compression self-ignition internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection amount during the sealing period is increased as the engine speed increases. 前記密閉期間中の燃料噴射時期を機関回転数の増加に従い進角させることを特徴とする請求項１ないし請求項３のいずれか１項記載の予混合圧縮自己着火式内燃機関。 The premixed compression self-ignition internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection timing during the sealing period is advanced in accordance with an increase in engine speed. 前記圧縮行程中の燃料噴射時期を機関回転数の増加に従い進角させることを特徴とする請求項１ないし請求項３のいずれか１項記載の予混合圧縮自己着火式内燃機関。 The premixed compression self-ignition internal combustion engine according to any one of claims 1 to 3, wherein the fuel injection timing during the compression stroke is advanced as the engine speed increases.
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