JP5141807B1 - Combustion control device - Google Patents

Combustion control device Download PDF

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JP5141807B1
JP5141807B1 JP2011189331A JP2011189331A JP5141807B1 JP 5141807 B1 JP5141807 B1 JP 5141807B1 JP 2011189331 A JP2011189331 A JP 2011189331A JP 2011189331 A JP2011189331 A JP 2011189331A JP 5141807 B1 JP5141807 B1 JP 5141807B1
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fuel ratio
air
fuel injection
fuel
injection
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JP2013050092A (en
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裕史 葛山
謹 河合
秀樹 青木
佳央 杉山
努 梅原
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Toyota Industries Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/3011—Controlling fuel injection according to or using specific or several modes of combustion
    • F02D41/3064—Controlling fuel injection according to or using specific or several modes of combustion with special control during transition between modes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
    • F02D41/1458—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio with determination means using an estimation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/3011—Controlling fuel injection according to or using specific or several modes of combustion
    • F02D41/3017—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used
    • F02D41/3035—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used a mode being the premixed charge compression-ignition mode
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/401—Controlling injection timing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

【課題】燃焼切替時等において適切な燃焼を実現することができる燃焼制御装置を提供する。
【解決手段】ＥＣＵは、目標空燃比と検出空燃比との空燃比偏差を算出し、空燃比偏差がリーン側にずれている場合に、空燃比偏差が遅角用閾値よりも小さいときは、１回目及び２回目のメイン燃料噴射の燃料噴射時期を遅角し、更に空燃比偏差がプレ噴射用閾値よりも小さいときは、プレ燃料噴射の燃料噴射量を決定する。また、ＥＣＵは、空燃比偏差がリッチ側にずれている場合に、空燃比偏差が進角用閾値よりも大きいときは、１回目及び２回目のメイン燃料噴射の燃料噴射時期を進角する。そして、ＥＣＵは、必要に応じてプレ燃料噴射を実施するように各インジェクタ５を制御した後、１回目及び２回目のメイン燃料噴射を順次実施するように各インジェクタ５を制御する。
【選択図】図３A combustion control device capable of realizing appropriate combustion at the time of combustion switching or the like is provided.
An ECU calculates an air-fuel ratio deviation between a target air-fuel ratio and a detected air-fuel ratio, and when the air-fuel ratio deviation is deviated to a lean side, when the air-fuel ratio deviation is smaller than a retardation threshold, When the fuel injection timing of the first and second main fuel injections is retarded and the air-fuel ratio deviation is smaller than the pre-injection threshold, the fuel injection amount of the pre-fuel injection is determined. Further, when the air-fuel ratio deviation is shifted to the rich side and the air-fuel ratio deviation is larger than the advance angle threshold, the ECU advances the fuel injection timing of the first and second main fuel injections. The ECU controls each injector 5 so as to perform pre-fuel injection as necessary, and then controls each injector 5 so as to sequentially execute the first and second main fuel injections.
[Selection] Figure 3

Description

本発明は、予混合圧縮着火（ＰＣＣＩ）燃焼を行うエンジンの燃焼制御装置に関するものである。   The present invention relates to a combustion control device for an engine that performs premixed compression ignition (PCCI) combustion.

予混合圧縮着火燃焼を行うエンジンの燃焼制御装置としては、例えば特許文献１に記載されているものが知られている。特許文献１に記載の燃焼制御装置は、低温予混合圧縮着火燃焼に入ってからの経過時間が所定値以下であるときは、通常燃焼から低温予混合圧縮着火燃焼に移行した直後の酸素濃度の高い状態にあると判断し、燃料のパイロット噴射を行うというものである。   As an engine combustion control device that performs premixed compression ignition combustion, for example, the one described in Patent Document 1 is known. In the combustion control device described in Patent Document 1, when the elapsed time after entering the low temperature premixed compression ignition combustion is a predetermined value or less, the oxygen concentration immediately after the transition from the normal combustion to the low temperature premixed compression ignition combustion is achieved. It is determined that the fuel is in a high state, and pilot injection of fuel is performed.

特開２００１−９０５９５号公報JP 2001-90595 A

上記従来技術においては、酸素濃度が高い期間にパイロット噴射を行うことで、燃焼騒音を低減することは可能となる。しかし、パイロット噴射の追加だけでは、ＮＯｘの排出量増加を十分に抑制することはできない。また、上記従来技術では、予混合圧縮着火燃焼から通常燃焼への燃焼切替時等に発生しやすい失火等の不具合については、何ら考慮されていない。   In the above prior art, it is possible to reduce combustion noise by performing pilot injection during a period in which the oxygen concentration is high. However, the addition of pilot injection alone cannot sufficiently suppress an increase in NOx emissions. Moreover, in the said prior art, malfunctions which are easy to generate | occur | produce at the time of the combustion switching from the premixing compression ignition combustion to normal combustion etc. are not taken into consideration at all.

本発明の目的は、燃焼切替時等において適切な燃焼を実現することができる燃焼制御装置を提供することである。   The objective of this invention is providing the combustion control apparatus which can implement | achieve appropriate combustion at the time of combustion switching.

本発明は、予混合圧縮着火燃焼を行うエンジンの燃焼制御装置において、エンジンの燃焼室内に燃料を噴射する燃料噴射弁と、メイン燃料噴射を実施するように燃料噴射弁を制御するメイン噴射制御手段と、メイン燃料噴射を実施する前に補助的なプレ燃料噴射を実施するように燃料噴射弁を制御するプレ噴射制御手段と、燃焼室内の空燃比を検出する空燃比検出手段と、目標空燃比と空燃比検出手段により得られた検出空燃比との偏差を算出する偏差算出手段とを備え、メイン噴射制御手段は、メイン燃料噴射の燃料噴射時期を決定する噴射時期決定手段と、偏差算出手段により算出された目標空燃比と検出空燃比との偏差に応じて、噴射時期決定手段により決定されたメイン燃料噴射の燃料噴射時期を変更する噴射時期変更手段とを有し、噴射時期変更手段は、目標空燃比と検出空燃比との偏差がリーン側にずれている場合に、目標空燃比と検出空燃比との偏差の絶対値が予め決められた遅角用閾値の絶対値よりも大きいかどうかを判断し、目標空燃比と検出空燃比との偏差の絶対値が遅角用閾値の絶対値よりも大きいと判断されると、メイン燃料噴射の燃料噴射時期を遅角する手段であり、プレ噴射制御手段は、目標空燃比と検出空燃比との偏差がリーン側にずれている場合に、目標空燃比と検出空燃比との偏差の絶対値が予め決められたプレ噴射用閾値の絶対値よりも大きいかどうかを判断する手段を有し、目標空燃比と検出空燃比との偏差の絶対値がプレ噴射用閾値の絶対値よりも大きいと判断されたときに、プレ燃料噴射を実施するように燃料噴射弁を制御し、プレ噴射用閾値の絶対値が遅角用閾値の絶対値よりも大きいことを特徴とするものである。 The present invention relates to a combustion control apparatus for an engine that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, and a main injection control means that controls the fuel injection valve to perform main fuel injection. Pre-injection control means for controlling the fuel injection valve so as to perform auxiliary pre-fuel injection before main fuel injection, air-fuel ratio detection means for detecting the air-fuel ratio in the combustion chamber, and target air-fuel ratio And a deviation calculation means for calculating a deviation between the detected air-fuel ratio obtained by the air-fuel ratio detection means, the main injection control means includes an injection timing determination means for determining the fuel injection timing of the main fuel injection, and a deviation calculation means in accordance with the deviation between the calculated target air-fuel ratio and the detected air-fuel ratio by, possess the injection timing changing means for changing the fuel injection timing of the main fuel injection, which is determined by the injection timing determining means When the deviation between the target air-fuel ratio and the detected air-fuel ratio is deviated to the lean side, the injection timing changing means is configured to determine the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio as the absolute value of the predetermined delay angle threshold. If the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is greater than the absolute value of the retard threshold, the fuel injection timing of the main fuel injection is retarded. The pre-injection control means is a pre-injection control means in which the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is predetermined when the deviation between the target air-fuel ratio and the detected air-fuel ratio is shifted to the lean side. Means for determining whether or not the absolute value of the threshold value for injection is larger than the absolute value of the pre-injection threshold value when it is determined that the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is greater than Control the fuel injection valve to perform pre-fuel injection, It is characterized in that the absolute value of the use threshold is greater than the absolute value of the retard threshold.

このように本発明の燃焼制御装置においては、燃焼室内の空燃比を検出し、目標空燃比と検出空燃比との偏差を算出し、その偏差に応じてメイン燃料噴射の燃料噴射時期を変更することにより、燃焼切替時等において適切な燃焼を実現することができる。例えば、通常燃焼から予混合圧縮着火燃焼への燃焼切替時には、燃焼室内の空燃比が予混合圧縮着火燃焼を行う目標空燃比に対してリーンとなる場合があるが、この場合にはメイン燃料噴射の燃料噴射時期を遅角することにより、燃焼騒音を低減しつつ、ＮＯｘの排出量増加を十分に抑制することができる。また、予混合圧縮着火燃焼から通常燃焼への燃焼切替時には、燃焼室内の空燃比が通常燃焼を行う目標空燃比に対してリッチとなる場合があるが、この場合にはメイン燃料噴射の燃料噴射時期を進角することにより、燃料と空気との予混合気の失火を抑制することができる。   Thus, in the combustion control apparatus of the present invention, the air-fuel ratio in the combustion chamber is detected, the deviation between the target air-fuel ratio and the detected air-fuel ratio is calculated, and the fuel injection timing of the main fuel injection is changed according to the deviation. As a result, appropriate combustion can be realized at the time of combustion switching or the like. For example, when switching from normal combustion to premixed compression ignition combustion, the air-fuel ratio in the combustion chamber may be lean relative to the target air-fuel ratio at which premixed compression ignition combustion is performed. In this case, the main fuel injection By delaying the fuel injection timing, it is possible to sufficiently suppress an increase in NOx emission while reducing combustion noise. In addition, when switching from premixed compression ignition combustion to normal combustion, the air-fuel ratio in the combustion chamber may become richer than the target air-fuel ratio for normal combustion. In this case, the fuel injection of the main fuel injection By advancing the timing, misfire of the premixed mixture of fuel and air can be suppressed.

このように目標空燃比と検出空燃比との偏差がリーン側にずれている場合に、目標空燃比と検出空燃比との偏差の絶対値が遅角用閾値の絶対値よりも大きいときは、メイン燃料噴射の燃料噴射時期を遅角することにより、燃料と空気との予混合気の早期着火が抑制される。これにより、通常燃焼から予混合圧縮着火燃焼への燃焼切替時に、燃焼騒音を低減しつつ、ＮＯｘの排出量増加を十分に抑制することができる。   In this way, when the deviation between the target air-fuel ratio and the detected air-fuel ratio is shifted to the lean side, when the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is larger than the absolute value of the retarding threshold value, By retarding the fuel injection timing of the main fuel injection, early ignition of the premixed mixture of fuel and air is suppressed. Thereby, at the time of combustion switching from normal combustion to premixed compression ignition combustion, it is possible to sufficiently suppress an increase in NOx emission while reducing combustion noise.

このように目標空燃比と検出空燃比との偏差がリーン側にずれている場合に、目標空燃比と検出空燃比との偏差の絶対値がプレ噴射用閾値の絶対値よりも大きいときに、補助的なプレ燃料噴射を実施することにより、通常燃焼から予混合圧縮着火燃焼への燃焼切替時に、燃焼騒音を低減することができる。また、燃料と空気との予混合気の失火に対する耐性を高くし、燃焼安定性を向上させることができる。   Thus, when the deviation between the target air-fuel ratio and the detected air-fuel ratio is shifted to the lean side, when the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is larger than the absolute value of the pre-injection threshold value, By performing auxiliary pre-fuel injection, combustion noise can be reduced when switching from normal combustion to premixed compression ignition combustion. In addition, the resistance to misfire of the premixed mixture of fuel and air can be increased, and the combustion stability can be improved.

また、プレ噴射用閾値の絶対値が遅角用閾値の絶対値よりも大きいことにより、目標空燃比と検出空燃比との偏差がリーン側にずれている場合に、目標空燃比と空燃比との偏差の絶対値がプレ噴射用閾値の絶対値よりも大きいときは、メイン燃料噴射の燃料噴射時期を遅角すると共に、プレ燃料噴射を実施することになる。これにより、燃焼騒音を十分に低減しつつ、ＮＯｘの排出量増加を十分に抑制することができると共に、燃料と空気との予混合気の失火に対する耐性を高くし、燃焼安定性を向上させることができる。 Further, by greater than the absolute value of the absolute value of the retard threshold for the pre-injection threshold, if the difference between the target air-fuel ratio and the detected air-fuel ratio is shifted to the lean side, the target air-fuel ratio When the absolute value of the deviation is larger than the absolute value of the pre-injection threshold value, the fuel injection timing of the main fuel injection is retarded and the pre-fuel injection is performed. As a result, it is possible to sufficiently suppress the increase in NOx emissions while sufficiently reducing combustion noise, and to increase the resistance to misfire of the premixed mixture of fuel and air, and to improve the combustion stability. Can do.

また、メイン噴射制御手段は、メイン燃料噴射を複数回に分けて実施するように燃料噴射弁を制御し、プレ噴射制御手段は、１回目のメイン燃料噴射の燃料噴射量を減量して、プレ燃料噴射の燃料噴射量を設定する手段を更に有することが好ましい。この場合には、プレ燃料噴射による燃焼と１回目のメイン燃料噴射による燃焼とが同時に行われる際に生じる燃焼騒音の増加を抑制することができる。   The main injection control means controls the fuel injection valve so that the main fuel injection is performed in a plurality of times, and the pre-injection control means reduces the fuel injection amount of the first main fuel injection, It is preferable to further have means for setting the fuel injection amount of the fuel injection. In this case, it is possible to suppress an increase in combustion noise that occurs when the combustion by the pre-fuel injection and the combustion by the first main fuel injection are performed simultaneously.

さらに、好ましくは、噴射時期変更手段は、目標空燃比と検出空燃比との偏差がリッチ側にずれている場合に、目標空燃比と検出空燃比との偏差の絶対値が予め決められた進角用閾値の絶対値よりも大きいかどうかを判断し、目標空燃比と検出空燃比との偏差の絶対値が進角用閾値の絶対値よりも大きいと判断されると、メイン燃料噴射の燃料噴射時期を進角する手段である。   Further preferably, the injection timing changing means is configured such that when the deviation between the target air-fuel ratio and the detected air-fuel ratio is shifted to the rich side, the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is determined in advance. It is determined whether or not the absolute value of the threshold value for the angle is larger, and if it is determined that the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is greater than the absolute value of the threshold value for the advance angle, the fuel of the main fuel injection It is a means for advancing the injection timing.

このように目標空燃比と検出空燃比との偏差がリッチ側にずれている場合に、目標空燃比と検出空燃比との偏差の絶対値が進角用閾値の絶対値よりも大きいときは、メイン燃料噴射の燃料噴射時期を進角することにより、燃料と空気との予混合気の着火時期の遅角が抑制される。これにより、予混合圧縮着火燃焼から通常燃焼への燃焼切替時に、予混合気の失火を抑制することができる。   Thus, when the deviation between the target air-fuel ratio and the detected air-fuel ratio is shifted to the rich side, when the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is larger than the absolute value of the advance angle threshold, By advancing the fuel injection timing of the main fuel injection, the retard of the ignition timing of the premixed mixture of fuel and air is suppressed. Thereby, the misfire of the premixed gas can be suppressed when switching from premixed compression ignition combustion to normal combustion.

また、好ましくは、エンジンのクランク角を検出するクランク角検出手段を更に備え、偏差算出手段は、クランク角検出手段により検出されたクランク角が所定角度になった時点で、目標空燃比と検出空燃比との偏差を算出する。   Preferably, the engine further comprises a crank angle detecting means for detecting the crank angle of the engine, and the deviation calculating means is configured to detect the target air-fuel ratio and the detected air when the crank angle detected by the crank angle detecting means reaches a predetermined angle. The deviation from the fuel ratio is calculated.

目標空燃比と検出空燃比との偏差の算出を時間同期で周期的に行うと、偏差の算出から燃料噴射までの期間が長く且つ一定でないため、偏差の算出精度が悪化する。そこで、エンジンのクランク角を検出し、クランク角が所定角度になった時点で、目標空燃比と検出空燃比との偏差を算出することにより、偏差の算出から燃料噴射までの期間が短く且つ一定となるため、偏差の算出精度が良くなる。これにより、燃焼切替等において、燃焼騒音の低減効果、ＮＯｘの排出量増加の抑制効果、失火の抑制効果を一層高めることができる。   If the calculation of the deviation between the target air-fuel ratio and the detected air-fuel ratio is periodically performed in time synchronization, the deviation calculation accuracy deteriorates because the period from the deviation calculation to the fuel injection is long and not constant. Therefore, by detecting the engine crank angle and calculating the deviation between the target air-fuel ratio and the detected air-fuel ratio when the crank angle reaches a predetermined angle, the period from the deviation calculation to fuel injection is short and constant. Therefore, the deviation calculation accuracy is improved. Thereby, in combustion switching etc., the reduction effect of combustion noise, the suppression effect of the increase in NOx emission amount, and the suppression effect of misfire can be further enhanced.

本発明によれば、通常燃焼から予混合圧縮着火燃焼への燃焼切替時や、予混合圧縮着火燃焼から通常燃焼への燃焼切替時等において、適切な燃焼を実現することができる。   ADVANTAGE OF THE INVENTION According to this invention, appropriate combustion can be implement | achieved at the time of the combustion switching from normal combustion to premixed compression ignition combustion, the combustion switching from premixed compression ignition combustion to normal combustion, etc.

本発明に係わる燃焼制御装置の一実施形態を備えたディーゼルエンジンを示す概略構成図である。It is a schematic block diagram which shows the diesel engine provided with one Embodiment of the combustion control apparatus concerning this invention. 図１に示したＥＣＵにより実行される処理手順を示すフローチャートである。It is a flowchart which shows the process sequence performed by ECU shown in FIG. 図２に示した予混合圧縮着火燃焼制御の処理手順の詳細を示すフローチャートである。It is a flowchart which shows the detail of the process sequence of the premixing compression ignition combustion control shown in FIG. 図３に示した偏差算出処理手順の詳細を示すフローチャートである。It is a flowchart which shows the detail of the deviation calculation process procedure shown in FIG. 噴射時期調整マップの一例を示すグラフである。It is a graph which shows an example of an injection timing adjustment map. プレ噴射追加マップの一例を示すグラフである。It is a graph which shows an example of a pre-injection addition map. メイン燃料噴射の燃料噴射時期と燃焼騒音及び図示平均有効圧（Ｐｉ）変動率との関係の一例を示すグラフである。It is a graph which shows an example of the relationship between the fuel injection timing of main fuel injection, combustion noise, and the indicated mean effective pressure (Pi) fluctuation rate. プレ燃料噴射の実施時におけるメイン燃料噴射の燃料噴射時期と燃焼騒音、ＮＯｘ排出濃度及び図示平均有効圧（Ｐｉ）変動率との関係の一例を示すグラフである。It is a graph which shows an example of the relationship between the fuel injection timing of main fuel injection at the time of implementation of pre fuel injection, combustion noise, NOx exhaust concentration, and the indicated mean effective pressure (Pi) fluctuation rate. ＥＧＲ率を０％とした場合の熱発生率波形の一例を様々な条件で比較して示すグラフである。It is a graph which compares and shows an example of the heat release rate waveform when an EGR rate is 0% under various conditions. プレ燃料噴射を実施した場合にＥＧＲ率を変更したときの熱発生率波形の一例を比較して示すグラフである。It is a graph which compares and shows an example of the heat release rate waveform when an EGR rate is changed when pre fuel injection is implemented. メイン燃料噴射の燃料噴射時期と図示平均有効圧（Ｐｉ）変動率との関係の一例を示すグラフである。It is a graph which shows an example of the relationship between the fuel injection timing of main fuel injection, and the indicated mean effective pressure (Pi) fluctuation rate. 燃焼モードが通常燃焼から予混合圧縮着火燃焼に切り替わるときの空燃比偏差の算出タイミングの一例を時間同期と角度同期とで比較して示す図である。It is a figure which compares an example of the calculation timing of the air fuel ratio deviation when a combustion mode switches from normal combustion to premixed compression ignition combustion by time synchronization and angle synchronization.

以下、本発明に係わる燃焼制御装置の好適な実施形態について、図面を参照して詳細に説明する。   Hereinafter, a preferred embodiment of a combustion control device according to the present invention will be described in detail with reference to the drawings.

図１は、本発明に係わる燃焼制御装置の一実施形態を備えたディーゼルエンジンを示す概略構成図である。同図において、本実施形態に係るディーゼルエンジン１は、予混合圧縮着火（ＰＣＣＩ）を行う４気筒直列ディーゼルエンジンであり、コモンレール式の燃料噴射装置を備えている。ディーゼルエンジン１はエンジン本体２を備え、このエンジン本体２には４つのシリンダ３が設けられている。   FIG. 1 is a schematic configuration diagram showing a diesel engine equipped with an embodiment of a combustion control device according to the present invention. In the figure, a diesel engine 1 according to this embodiment is a four-cylinder in-line diesel engine that performs premixed compression ignition (PCCI), and includes a common rail fuel injection device. The diesel engine 1 includes an engine body 2, and the engine body 2 is provided with four cylinders 3.

各シリンダ３には、燃焼室４内に燃料を噴射するインジェクタ（燃料噴射弁）５がそれぞれ配設されている。インジェクタ５は、噴射ノズル５ａから放射状に燃料を噴射する。各インジェクタ５はコモンレール６に接続されており、コモンレール６に貯留された高圧燃料が各インジェクタ５に常時供給されている。   Each cylinder 3 is provided with an injector (fuel injection valve) 5 for injecting fuel into the combustion chamber 4. The injector 5 injects fuel radially from the injection nozzle 5a. Each injector 5 is connected to a common rail 6, and high-pressure fuel stored in the common rail 6 is constantly supplied to each injector 5.

エンジン本体２には、燃焼室４内に空気を吸入するための吸気通路７がインテークマニホールド８を介して接続されている。また、エンジン本体２には、燃焼後の排気ガスを排出するための排気通路９がエキゾーストマニホールド１０を介して接続されている。   An intake passage 7 for sucking air into the combustion chamber 4 is connected to the engine body 2 via an intake manifold 8. In addition, an exhaust passage 9 for discharging exhaust gas after combustion is connected to the engine body 2 via an exhaust manifold 10.

吸気通路７には、上流側から下流側に向けてエアクリーナー１１、ターボ過給機１２のコンプレッサ１３、インタークーラー１４及びスロットルバルブ１５が設けられている。スロットルバルブ１５は、吸気通路７の通路面積を絞り、吸気通路７を通過する空気量を減少させると共に下流側の圧力を低下させる。排気通路９には、ターボ過給機１２のタービン１６及び触媒付きＤＰＦ１７が設けられている。   In the intake passage 7, an air cleaner 11, a compressor 13 of the turbocharger 12, an intercooler 14, and a throttle valve 15 are provided from the upstream side toward the downstream side. The throttle valve 15 restricts the passage area of the intake passage 7 to reduce the amount of air passing through the intake passage 7 and lower the downstream pressure. In the exhaust passage 9, a turbine 16 of the turbocharger 12 and a DPF 17 with a catalyst are provided.

また、ディーゼルエンジン１は、燃焼後の排気ガスの一部を排気再循環ガス（ＥＧＲガス）として燃焼室４内に還流する排気再循環（ＥＧＲ）装置１８を備えている。ＥＧＲ装置１８は、吸気通路７とエキゾーストマニホールド１０とを繋ぐように設けられ、ＥＧＲガスを還流するためのＥＧＲ通路１９と、エキゾーストマニホールド１０から吸気通路７へのＥＧＲガスの還流量を調整するＥＧＲバルブ２０と、ＥＧＲ通路１９を通るＥＧＲガスを冷却するＥＧＲクーラ２１と、このＥＧＲクーラ２１をバイパスするようにＥＧＲ通路１９に接続されたバイパス通路２２と、ＥＧＲガスの流路をＥＧＲクーラ２１側またはバイパス通路２２側に切り替える切替弁２３とを有している。   The diesel engine 1 also includes an exhaust gas recirculation (EGR) device 18 that recirculates a part of the exhaust gas after combustion into the combustion chamber 4 as exhaust gas recirculation gas (EGR gas). The EGR device 18 is provided so as to connect the intake passage 7 and the exhaust manifold 10, and an EGR passage 19 for recirculating the EGR gas, and an EGR that adjusts the recirculation amount of the EGR gas from the exhaust manifold 10 to the intake passage 7. The EGR cooler 21 that cools the EGR gas that passes through the valve 20, the EGR passage 19, the bypass passage 22 that is connected to the EGR passage 19 so as to bypass the EGR cooler 21, and the EGR gas passage on the EGR cooler 21 side Or it has the switching valve 23 switched to the bypass channel | path 22 side.

上記の各インジェクタ５、スロットルバルブ１５、ＥＧＲバルブ２０及び切替弁２３は、電子制御ユニット（ＥＣＵ）２４によって制御される。ＥＣＵ２４には、クランク角センサ２５、アクセル開度センサ２６及びエアーフローメータ２７が接続されている。   Each injector 5, throttle valve 15, EGR valve 20 and switching valve 23 are controlled by an electronic control unit (ECU) 24. A crank angle sensor 25, an accelerator opening sensor 26, and an air flow meter 27 are connected to the ECU 24.

クランク角センサ２５は、図示しないピストンが連結されるクランク軸の回転角度（クランク角）を検出することで、エンジン本体２の回転数（エンジン回転数）を算出可能とするためのセンサである。アクセル開度センサ２６は、エンジン本体２の負荷（エンジン負荷）の代替値として、アクセルペダルの踏込み角（アクセル開度）を検出するセンサ（負荷検出手段）である。なお、コモンレール式燃料噴射装置を備えたディーゼルエンジンでは、燃料噴射量を電子制御しており、エンジン負荷の代替値として燃料噴射量を用いることも可能である。エアーフローメータ２７は、燃焼室４内に吸入される空気量を検出するセンサであり、吸気通路７に配置されている。   The crank angle sensor 25 is a sensor that enables calculation of the rotation speed (engine rotation speed) of the engine body 2 by detecting the rotation angle (crank angle) of a crankshaft to which a piston (not shown) is coupled. The accelerator opening sensor 26 is a sensor (load detection means) that detects the depression angle (accelerator opening) of the accelerator pedal as an alternative value for the load (engine load) of the engine body 2. In a diesel engine equipped with a common rail fuel injection device, the fuel injection amount is electronically controlled, and the fuel injection amount can be used as an alternative value for the engine load. The air flow meter 27 is a sensor that detects the amount of air taken into the combustion chamber 4 and is disposed in the intake passage 7.

ＥＣＵ２４は、クランク角センサ２５、アクセル開度センサ２６、エアーフローメータ２７の検出信号を入力し、所定の処理を行い、インジェクタ５、スロットルバルブ１５、ＥＧＲバルブ２０及び切替弁２３を制御する。   The ECU 24 receives detection signals from the crank angle sensor 25, the accelerator opening sensor 26, and the air flow meter 27, performs predetermined processing, and controls the injector 5, the throttle valve 15, the EGR valve 20, and the switching valve 23.

ここで、インジェクタ５、スロットルバルブ１５、排気再循環装置１８、ＥＣＵ２４、クランク角センサ２５、アクセル開度センサ２６及びエアーフローメータ２７は、本実施形態の燃焼制御装置２８を構成している。このような燃焼制御装置２８は、吸気行程、圧縮行程、膨張行程及び排気行程という１サイクルにおいて、燃焼室４内に空気を吸入すると共に各インジェクタ５から燃焼室４内に燃料を複数回に分けて噴射（分割噴射）して、予混合圧縮着火燃焼を行うように制御する。   Here, the injector 5, the throttle valve 15, the exhaust gas recirculation device 18, the ECU 24, the crank angle sensor 25, the accelerator opening sensor 26, and the air flow meter 27 constitute a combustion control device 28 of the present embodiment. Such a combustion control device 28 sucks air into the combustion chamber 4 and divides the fuel into the combustion chamber 4 from each injector 5 in one cycle of the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke. To perform premixed compression ignition combustion.

図２は、ＥＣＵ２４により実行される処理手順を示すフローチャートである。本処理は、クランク角センサ２５、アクセル開度センサ２６及びエアーフローメータ２７の検出信号に基づいてインジェクタ５を制御する処理である。   FIG. 2 is a flowchart showing a processing procedure executed by the ECU 24. This process is a process of controlling the injector 5 based on detection signals of the crank angle sensor 25, the accelerator opening sensor 26, and the air flow meter 27.

同図において、まず燃焼モードが予混合圧縮着火燃焼モードであるかどうかを判断し（手順Ｓ１０１）、燃焼モードが予混合圧縮着火燃焼モードであるときは、予混合圧縮着火燃焼制御を実行し（手順Ｓ１０２）、燃焼モードが予混合圧縮着火燃焼モードでないときは、通常燃焼制御を実行する（手順Ｓ１０３）。   In the figure, first, it is determined whether or not the combustion mode is the premixed compression ignition combustion mode (step S101). When the combustion mode is the premixed compression ignition combustion mode, premixed compression ignition combustion control is executed ( In step S102), when the combustion mode is not the premixed compression ignition combustion mode, normal combustion control is executed (step S103).

図３は、上記の予混合圧縮着火燃焼制御の処理手順の詳細を示すフローチャートである。同図において、まずプレ噴射追加フラグＦを０に初期設定する（手順Ｓ１１１）。続いて、クランク角センサ２５により検出・算出されたエンジン回転数とアクセル開度センサ２６により検出されたアクセル開度（エンジン負荷）とに基づいて、１回目のメイン燃料噴射及びこの後に実施される２回目のメイン燃料噴射の燃料噴射量及び燃料噴射時期を決定する（手順Ｓ１１２）。   FIG. 3 is a flowchart showing details of the processing procedure of the premixed compression ignition combustion control. In the figure, first, a pre-injection addition flag F is initially set to 0 (step S111). Subsequently, on the basis of the engine speed detected and calculated by the crank angle sensor 25 and the accelerator opening (engine load) detected by the accelerator opening sensor 26, the first main fuel injection is performed and thereafter. The fuel injection amount and fuel injection timing of the second main fuel injection are determined (step S112).

続いて、アクセル開度センサ２６により検出されたエンジン負荷が所定値以下であるかどうかを判断する（手順Ｓ１１３）。エンジン負荷が所定値以下であるときは、１回目のメイン燃料噴射の前に実施される補助的なプレ燃料噴射の燃料噴射量を決定する（手順Ｓ１１４）。この時の燃料噴射量は、例えばエンジン負荷に応じた量としても良いし、予め設定された一定量としても良い。そして、プレ噴射追加フラグＦを１にセットする（手順Ｓ１１５）。エンジン負荷が所定値以下でないときは、手順Ｓ１１４，Ｓ１１５を実行しない。   Subsequently, it is determined whether or not the engine load detected by the accelerator opening sensor 26 is equal to or less than a predetermined value (step S113). When the engine load is less than or equal to a predetermined value, the fuel injection amount of auxiliary pre-fuel injection that is performed before the first main fuel injection is determined (step S114). The fuel injection amount at this time may be an amount corresponding to the engine load, for example, or may be a predetermined constant amount. Then, the pre-injection addition flag F is set to 1 (procedure S115). When the engine load is not less than the predetermined value, steps S114 and S115 are not executed.

続いて、目標空燃比（目標Ａ／Ｆ）と検出空燃比（検出Ａ／Ｆ）との空燃比偏差（ΔＡ／Ｆ）を算出する（手順Ｓ１１６）。目標空燃比は、例えば予め設定されたマップを用いて、エンジン回転数及びアクセル開度等から得られる。この空燃比偏差算出処理手順の詳細を図４に示す。   Subsequently, an air-fuel ratio deviation (ΔA / F) between the target air-fuel ratio (target A / F) and the detected air-fuel ratio (detected A / F) is calculated (step S116). The target air-fuel ratio is obtained from the engine speed, the accelerator opening, and the like using a preset map, for example. Details of the air-fuel ratio deviation calculation processing procedure are shown in FIG.

図４において、クランク角センサ２５により検出されたクランク角が燃料噴射を行う角度よりも所定角度（例えば８０度）だけ手前の偏差算出クランク角に達したかどうかを判断する（手順Ｓ１５１）。   In FIG. 4, it is determined whether the crank angle detected by the crank angle sensor 25 has reached a deviation calculation crank angle that is a predetermined angle (for example, 80 degrees) before the fuel injection angle (step S151).

クランク角が偏差算出クランク角に達したときは、次気筒の燃料噴射量を算出する（手順Ｓ１５２）。次気筒の燃料噴射量は、例えば上記手順Ｓ１１２で決定された１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射量から算出する。続いて、エアーフローメータ２７により検出された吸入空気量に基づいて、次気筒の空気量を算出する（手順Ｓ１５３）。そして、次気筒の空気量を次気筒の燃料噴射量で除することで、検出空燃比を算出する（手順Ｓ１５４）。続いて、次気筒における目標空燃比と検出空燃比との空燃比偏差（ΔＡ／Ｆ＝目標Ａ／Ｆ−検出Ａ／Ｆ）を算出する（手順Ｓ１５５）。   When the crank angle reaches the deviation calculation crank angle, the fuel injection amount of the next cylinder is calculated (step S152). The fuel injection amount of the next cylinder is calculated from the fuel injection amounts of the first main fuel injection and the second main fuel injection determined in step S112, for example. Subsequently, the air amount of the next cylinder is calculated based on the intake air amount detected by the air flow meter 27 (step S153). Then, the detected air-fuel ratio is calculated by dividing the air amount of the next cylinder by the fuel injection amount of the next cylinder (step S154). Subsequently, an air-fuel ratio deviation (ΔA / F = target A / F−detected A / F) between the target air-fuel ratio and the detected air-fuel ratio in the next cylinder is calculated (step S155).

図３に戻り、上記の手順Ｓ１１６を実行した後、空燃比偏差がリーン側にずれている（ΔＡ／Ｆ＜０）かどうかを判断する（手順Ｓ１１７）。空燃比偏差がリーン側にずれているときは、空燃比偏差が予め決められた遅角用閾値Ａ０（図５参照）よりも小さいかどうか、つまり空燃比偏差の絶対値が遅角用閾値Ａ０の絶対値よりも大きいかどうかを判断する（手順Ｓ１１８）。 Returning to FIG. 3, after executing step S116, it is determined whether the air-fuel ratio deviation is shifted to the lean side (ΔA / F <0) (step S117). When the air-fuel ratio deviation is deviated to the lean side, whether or not the air-fuel ratio deviation is smaller than a predetermined retardation angle threshold value A 0 (see FIG. 5), that is, the absolute value of the air-fuel ratio deviation is the retardation angle threshold value. determining whether greater than the absolute value of a 0 (Step S118).

空燃比偏差が遅角用閾値Ａ０よりも小さいときは、図５に示す噴射時期調整マップに従って、１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を遅角する（手順Ｓ１１９）。空燃比偏差が遅角用閾値Ａ０よりも小さくないときは、手順Ｓ１１９を実行しない。 When the air-fuel ratio deviation is smaller than the retard threshold A 0 is a view in accordance with the injection timing adjustment map shown in 5, the first main fuel injection and the second retarding the fuel injection timing of the main fuel injection in (Step S119 ). When not smaller than the threshold value A 0 for the air-fuel ratio deviation is retarded does not execute the steps S119.

噴射時期調整マップは、図５に示すように、空燃比偏差と燃料噴射時期との関係を表すマップである。噴射時期調整マップは、空燃比偏差がリーン側にずれている（ΔＡ／Ｆ＜０）ときは、燃料噴射時期を遅角させ、空燃比偏差がリッチ側にずれている（ΔＡ／Ｆ＞０）ときは、燃料噴射時期を進角させるように設定されている。具体的には、噴射時期調整マップは、空燃比偏差が遅角用閾値Ａ０よりも小さいときに、空燃比偏差に応じて遅角量が比例的に大きくなり、空燃比偏差が遅角限界値Ａ１よりも小さくなると、遅角量が一定になるように設定されている。また、噴射時期調整マップは、空燃比偏差が進角用閾値Ｂ０よりも大きときに、空燃比偏差に応じて進角量が比例的に大きくなり、空燃比偏差が進角限界値Ｂ１よりも大きくなると、進角量が一定になるように設定されている。 As shown in FIG. 5, the injection timing adjustment map is a map representing the relationship between the air-fuel ratio deviation and the fuel injection timing. In the injection timing adjustment map, when the air-fuel ratio deviation is shifted to the lean side (ΔA / F <0), the fuel injection timing is retarded and the air-fuel ratio deviation is shifted to the rich side (ΔA / F> 0). ) Is set to advance the fuel injection timing. Specifically, the injection timing adjustment map, when less than the threshold value A 0 for the air-fuel ratio deviation is retarded, the retard amount is proportionally increased in accordance with the air-fuel ratio deviation, retard limit air-fuel ratio difference becomes smaller than the value a 1, the retard amount is set to be constant. Further, in the injection timing adjustment map, when the air-fuel ratio deviation is larger than the advance threshold B 0 , the advance amount increases proportionally according to the air-fuel ratio deviation, and the air-fuel ratio deviation becomes the advance limit B 1. When the value is larger than that, the advance amount is set to be constant.

続いて、空燃比偏差がプレ噴射用閾値Ｃ（図６参照）よりも小さいかどうか、つまり空燃比偏差の絶対値がプレ噴射用閾値Ｃの絶対値よりも大きいかどうかを判断する（手順Ｓ１２０）。プレ噴射用閾値Ｃは、遅角用閾値Ａ０よりも小さな値である。従って、プレ噴射用閾値Ｃの絶対値は、遅角用閾値Ａ０の絶対値よりも大きい。空燃比偏差がプレ噴射用閾値Ｃよりも小さいときは、プレ噴射追加フラグＦが０であるかどうかを判断する（手順Ｓ１２１）。 Subsequently, it is determined whether the air-fuel ratio deviation is smaller than the pre-injection threshold value C (see FIG. 6), that is, whether the absolute value of the air-fuel ratio deviation is larger than the absolute value of the pre-injection threshold value C (step S120). ). For pre-injection threshold C is a value smaller than the threshold value A 0 for retarding. Therefore, the absolute value of the pre-injection threshold C is larger than the absolute value of the retard threshold A 0. When the air-fuel ratio deviation is smaller than the pre-injection threshold C, it is determined whether or not the pre-injection additional flag F is 0 (step S121).

プレ噴射追加フラグＦが０であるときは、図６に示すプレ噴射追加マップを従って、１回目のメイン燃料噴射の前に実施される補助的なプレ燃料噴射の燃料噴射量を決定する（手順Ｓ１２２）。プレ噴射追加マップは、図６に示すように、空燃比偏差と燃料噴射量との関係を表すマップである。プレ噴射追加マップは、空燃比偏差がプレ噴射用閾値Ｃよりも小さいときに、空燃比偏差に応じて燃料噴射量が段階的に大きくなるように設定されている。   When the pre-injection addition flag F is 0, the fuel injection amount of the auxiliary pre-fuel injection to be performed before the first main fuel injection is determined according to the pre-injection addition map shown in FIG. S122). As shown in FIG. 6, the pre-injection addition map is a map representing the relationship between the air-fuel ratio deviation and the fuel injection amount. The pre-injection addition map is set so that when the air-fuel ratio deviation is smaller than the pre-injection threshold C, the fuel injection amount increases stepwise according to the air-fuel ratio deviation.

続いて、プレ噴射追加フラグＦを１にセットする（手順Ｓ１２３）。そして、１回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分を減量する（手順Ｓ１２４）。   Subsequently, the pre-injection addition flag F is set to 1 (procedure S123). Then, the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the first main fuel injection (step S124).

手順Ｓ１２０で空燃比偏差がプレ噴射用閾値Ｃよりも小さくないと判断されたとき、手順Ｓ１２１でプレ噴射追加フラグＦが０でなく１であると判断されたときは、手順Ｓ１２２〜Ｓ１２４を実行しない。   When it is determined in step S120 that the air-fuel ratio deviation is not smaller than the pre-injection threshold value C, when it is determined in step S121 that the pre-injection addition flag F is 1 instead of 0, steps S122 to S124 are executed. do not do.

手順Ｓ１１７で空燃比偏差がリーン側ではなくリッチ側にずれている（ΔＡ／Ｆ＞０）と判断されたときは、空燃比偏差が進角用閾値Ｂ０（図５参照）よりも大きいかどうかを判断する（手順Ｓ１２５）。 If it is determined in step S117 that the air-fuel ratio deviation is shifted from the lean side to the rich side (ΔA / F> 0), is the air-fuel ratio deviation larger than the advance angle threshold B 0 (see FIG. 5)? It is determined whether or not (step S125).

空燃比偏差が進角用閾値Ｂ０よりも大きいときは、図５に示す噴射時期調整マップに従って、１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を進角する（手順Ｓ１２６）。噴射時期調整マップは、上述した通りである。空燃比偏差が進角用閾値Ｂ０よりも大きくないときは、手順Ｓ１２６を実行しない。 When the air-fuel ratio deviation is larger than the advance angle threshold B 0 , the fuel injection timings of the first main fuel injection and the second main fuel injection are advanced according to the injection timing adjustment map shown in FIG. 5 (step S126). ). The injection timing adjustment map is as described above. When the air-fuel ratio deviation is not greater than the advancing threshold B 0 does not execute the steps S126.

手順Ｓ１２４または手順Ｓ１２６を実行した後、プレ噴射追加フラグＦが１であるかどうかを判断する（手順Ｓ１２７）。プレ噴射追加フラグＦが１であるときは、手順Ｓ１１４または手順Ｓ１２２で決定された燃料噴射量に従ってプレ燃料噴射を実施するように、各インジェクタ５を制御する（手順Ｓ１２８）。プレ噴射追加フラグＦが１でなく０であるときは、手順Ｓ１２８を実行しない。   After executing step S124 or step S126, it is determined whether or not the pre-injection addition flag F is 1 (step S127). When the pre-injection addition flag F is 1, each injector 5 is controlled to perform the pre-fuel injection according to the fuel injection amount determined in step S114 or step S122 (step S128). When the pre-injection addition flag F is 0 instead of 1, step S128 is not executed.

続いて、１回目のメイン燃料噴射及び２回目のメイン燃料噴射を順次実施するように、各インジェクタ５を制御する（手順Ｓ１２９）。このとき、手順Ｓ１１９，Ｓ１２４，Ｓ１２６を実行していないときは、手順Ｓ１１２で決定された燃料噴射量及び燃料噴射時期に従って各メイン燃料噴射を実施する。手順Ｓ１１９を実行したときは、手順Ｓ１１９で補正された燃料噴射時期に従って各メイン燃料噴射を実施する。手順Ｓ１２４を実行したときは、手順Ｓ１２４で補正された燃料噴射量に従って１回目のメイン燃料噴射を実施すると共に、手順Ｓ１１２で決定された燃料噴射量に従って２回目のメイン燃料噴射を実施する。手順Ｓ１２６を実行したときは、手順Ｓ１２６で補正された燃料噴射時期に従って各メイン燃料噴射を実施する。   Subsequently, each injector 5 is controlled so as to sequentially perform the first main fuel injection and the second main fuel injection (step S129). At this time, when steps S119, S124, and S126 are not executed, each main fuel injection is performed according to the fuel injection amount and the fuel injection timing determined in step S112. When step S119 is executed, each main fuel injection is performed in accordance with the fuel injection timing corrected in step S119. When step S124 is executed, the first main fuel injection is performed in accordance with the fuel injection amount corrected in step S124, and the second main fuel injection is performed in accordance with the fuel injection amount determined in step S112. When step S126 is executed, each main fuel injection is performed in accordance with the fuel injection timing corrected in step S126.

以上において、ＥＣＵ２４の上記手順Ｓ１１２，Ｓ１１７〜Ｓ１１９，Ｓ１２５，Ｓ１２６，Ｓ１２９は、メイン燃料噴射を実施するように燃料噴射弁５を制御するメイン噴射制御手段を構成する。エアーフローメータ２７及びＥＣＵ２４の上記手順Ｓ１１６の一部（上記手順Ｓ１５１〜Ｓ１５４）は、燃焼室４内の空燃比を検出する空燃比検出手段を構成する。ＥＣＵ２４の上記手順Ｓ１１６の他の一部（上記手順Ｓ１５５）は、目標空燃比と空燃比検出手段により得られた検出空燃比との偏差を算出する偏差算出手段を構成する。ＥＣＵ２４の上記手順Ｓ１１７，Ｓ１２０，Ｓ１２２〜Ｓ１２４，Ｓ１２７，Ｓ１２８は、メイン燃料噴射を実施する前に補助的なプレ燃料噴射を実施するように燃料噴射弁５を制御するプレ噴射制御手段を構成する。クランク角センサ２５は、エンジンのクランク角を検出するクランク角検出手段を構成する。   In the above, the above steps S112, S117 to S119, S125, S126, and S129 of the ECU 24 constitute main injection control means for controlling the fuel injection valve 5 to perform main fuel injection. A part of the procedure S116 of the air flow meter 27 and the ECU 24 (procedures S151 to S154) constitutes an air-fuel ratio detecting means for detecting the air-fuel ratio in the combustion chamber 4. Another part of the procedure S116 of the ECU 24 (procedure S155) constitutes a deviation calculating means for calculating the deviation between the target air-fuel ratio and the detected air-fuel ratio obtained by the air-fuel ratio detecting means. The above steps S117, S120, S122 to S124, S127, and S128 of the ECU 24 constitute pre-injection control means for controlling the fuel injection valve 5 so that auxiliary pre-fuel injection is performed before main fuel injection is performed. . The crank angle sensor 25 constitutes crank angle detection means for detecting the crank angle of the engine.

このとき、上記手順Ｓ１１２は、メイン燃料噴射の燃料噴射時期を決定する噴射時期決定手段を構成し、Ｓ１１７〜Ｓ１１９，Ｓ１２５，Ｓ１２６は、偏差算出手段により算出された目標空燃比と検出空燃比との偏差に応じて、噴射時期決定手段により決定されたメイン燃料噴射の燃料噴射時期を変更する噴射時期変更手段を構成する。また、手順Ｓ１１７，Ｓ１２０は、目標空燃比と検出空燃比との偏差がリーン側にずれている場合に、目標空燃比と検出空燃比との偏差の絶対値が予め決められたプレ噴射用閾値Ｃの絶対値よりも大きいかどうかを判断する手段を構成する。手順Ｓ１２４は、１回目のメイン燃料噴射の燃料噴射量を減量して、プレ燃料噴射の燃料噴射量を設定する手段を構成する。   At this time, the procedure S112 constitutes an injection timing determining means for determining the fuel injection timing of the main fuel injection, and S117 to S119, S125, and S126 include the target air-fuel ratio and the detected air-fuel ratio calculated by the deviation calculating means. An injection timing changing means for changing the fuel injection timing of the main fuel injection determined by the injection timing determining means is configured according to the deviation. In steps S117 and S120, when the deviation between the target air-fuel ratio and the detected air-fuel ratio is shifted to the lean side, the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is determined in advance. A means for determining whether or not the absolute value of C is larger is configured. Step S124 constitutes means for reducing the fuel injection amount of the first main fuel injection and setting the fuel injection amount of the pre-fuel injection.

ところで、通常燃焼から予混合圧縮着火燃焼への燃焼切替時や、減速やシフトチェンジ等の燃料噴射カット時には、ＥＧＲ還流遅れにより燃焼室４内に吸入される空気量が多くなり、燃焼室４内の空燃比がリーンとなる場合があるため、目標空燃比と検出空燃比とのズレが発生し、燃焼騒音やＮＯｘ排出量が増加する可能性がある。一方、予混合圧縮着火燃焼から通常燃焼への燃焼切替時や、加速の際の過給遅れ時には、逆に燃焼室４内の空燃比がリッチとなる場合があるため、目標空燃比と検出空燃比とのズレが発生し、失火が生じる可能性がある。   By the way, at the time of combustion switching from normal combustion to premixed compression ignition combustion, or at the time of fuel injection cut such as deceleration or shift change, the amount of air sucked into the combustion chamber 4 increases due to EGR recirculation delay, and the combustion chamber 4 Since the air-fuel ratio of the engine may become lean, there is a possibility that a deviation between the target air-fuel ratio and the detected air-fuel ratio will occur, resulting in an increase in combustion noise and NOx emission. On the other hand, the air-fuel ratio in the combustion chamber 4 may become rich when the combustion is switched from the premixed compression ignition combustion to the normal combustion or when the supercharging is delayed during acceleration. Misalignment with the fuel ratio may occur and misfire may occur.

これに対し本実施形態では、目標空燃比と検出空燃比との空燃比偏差がリーン側にずれている場合に、空燃比偏差が遅角用閾値Ａ０よりも小さいときは、１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を遅角するようにしたので、燃料と空気との予混合気の早期着火が抑制される。これにより、燃焼騒音を低減すると共に、ＮＯｘの排出量増加を抑制することができる。 In contrast, in the present embodiment, when the air-fuel ratio difference between the target air-fuel ratio and the detected air-fuel ratio is shifted to the lean side, it is smaller than the threshold value A 0 for the air-fuel ratio deviation is retarded, first main Since the fuel injection timing of the fuel injection and the second main fuel injection is retarded, early ignition of the premixed mixture of fuel and air is suppressed. As a result, combustion noise can be reduced and an increase in NOx emission can be suppressed.

また、空燃比偏差がリーン側にずれている場合に、空燃比偏差がプレ噴射用閾値Ｃよりも小さいときは、１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を遅角すると共に、１回目のメイン燃料噴射の前にプレ燃料噴射を実施するようにしたので、上記と同様に、燃焼騒音を低減すると共に、ＮＯｘの排出量増加を抑制することができる。このとき、１回目のメイン燃料噴射の燃料噴射量をプレ燃料噴射の燃料噴射量分だけ減量することにより、プレ燃料噴射による燃焼と１回目のメイン燃料噴射による燃焼が同時に行われる際に発生する燃焼騒音の増大が抑制されるようになる。   Further, when the air-fuel ratio deviation is shifted to the lean side and the air-fuel ratio deviation is smaller than the pre-injection threshold C, the fuel injection timings of the first main fuel injection and the second main fuel injection are retarded. In addition, since the pre-fuel injection is performed before the first main fuel injection, the combustion noise can be reduced and the increase in the NOx emission amount can be suppressed as described above. At this time, the fuel injection amount of the first main fuel injection is reduced by the fuel injection amount of the pre-fuel injection, so that it occurs when the combustion by the pre-fuel injection and the combustion by the first main fuel injection are performed simultaneously. An increase in combustion noise is suppressed.

さらに、上記のプレ燃料噴射を実施することにより、失火耐性が向上するため、燃焼安定性が良くなることに加え、メイン燃料噴射の燃料噴射時期の遅角量を十分確保することができる。従って、燃焼騒音の低減効果及びＮＯｘの排出量増加の抑制効果を高めることができる。   Furthermore, since the pre-fuel injection is performed, the misfire resistance is improved, so that the combustion stability is improved, and the retard amount of the fuel injection timing of the main fuel injection can be sufficiently secured. Therefore, the effect of reducing combustion noise and the effect of suppressing an increase in NOx emissions can be enhanced.

また、空燃比偏差がリッチ側にずれている場合に、空燃比偏差が進角用閾値Ｂ０よりも大きいときは、１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を進角するようにしたので、予混合気の着火時期の遅角が抑制される。これにより、失火を防止し、燃焼安定性を良くすることができる。 Further, when the air-fuel ratio difference is deviated to the rich side, when the air-fuel ratio deviation is greater than the advancing threshold B 0 is the first main fuel injection and fuel injection timing of the second main fuel injection proceeds Since the angle is set, the retard of the ignition timing of the premixed gas is suppressed. Thereby, misfire can be prevented and combustion stability can be improved.

図７は、メイン燃料噴射の燃料噴射時期と燃焼騒音及び図示平均有効圧（Ｐｉ）変動率との関係の一例を示したものである。図中、丸印Ｐ、四角印Ｑ及び三角印Ｒは、ＥＧＲ率つまり空燃比（Ａ／Ｆ）が異なっている。   FIG. 7 shows an example of the relationship between the fuel injection timing of the main fuel injection, the combustion noise, and the indicated mean effective pressure (Pi) fluctuation rate. In the figure, the circle mark P, the square mark Q, and the triangle mark R have different EGR rates, that is, air-fuel ratios (A / F).

図７（ａ）から分かるように、メイン燃料噴射の燃料噴射時期を遅角するに従い、燃焼騒音が低くなる。また、図７（ｂ）から分かるように、メイン燃料噴射の燃料噴射時期をある程度まで遅角しても、Ｐｉ変動率は殆ど変わらない。   As can be seen from FIG. 7A, the combustion noise becomes lower as the fuel injection timing of the main fuel injection is retarded. Further, as can be seen from FIG. 7B, even if the fuel injection timing of the main fuel injection is delayed to some extent, the Pi fluctuation rate hardly changes.

図８は、プレ燃料噴射の実施時におけるメイン燃料噴射の燃料噴射時期と燃焼騒音、ＮＯｘ排出濃度及び図示平均有効圧（Ｐｉ）変動率との関係の一例を示したものである。図中、菱形印Ｓは、プレ燃料噴射を実施せず、ＥＧＲ率を０％としたときのデータを示し、丸印Ｐは、プレ燃料噴射を実施し、ＥＧＲ率を０％としたときのデータを示し、三角印Ｑは、プレ燃料噴射を実施し、ＥＧＲ率を３３％としたときのデータを示し、四角印Ｒは、プレ燃料噴射を実施し、ＥＧＲ率を４２％としたときのデータを示している。   FIG. 8 shows an example of the relationship between the fuel injection timing of the main fuel injection, the combustion noise, the NOx emission concentration, and the indicated mean effective pressure (Pi) fluctuation rate when the pre-fuel injection is performed. In the figure, rhombus S indicates data when pre-fuel injection is not performed and the EGR rate is 0%, and circle P indicates when pre-fuel injection is performed and the EGR rate is 0%. The triangle mark Q indicates the data when the pre-fuel injection is performed and the EGR rate is 33%, and the square mark R indicates the data when the pre-fuel injection is performed and the EGR rate is 42%. Data are shown.

図８（ａ）から分かるように、プレ燃料噴射を実施することで、燃焼騒音が低くなる。また、メイン燃料噴射の燃料噴射時期を遅角するに従い、燃焼騒音が低くなる。また、図８（ｂ）から分かるように、ＥＧＲ率が低い（Ａ／Ｆがリーン側にある）ときは、メイン燃料噴射の燃料噴射時期を遅角するに従い、ＮＯｘの発生率が低くなる。また、図８（ｃ）から分かるように、ＥＧＲ率が低いときは、メイン燃料噴射の燃料噴射時期を遅角しても、Ｐｉ変動率は殆ど変わらず、燃焼安定性が確保されている。   As can be seen from FIG. 8A, the combustion noise is reduced by performing the pre-fuel injection. Further, the combustion noise becomes lower as the fuel injection timing of the main fuel injection is delayed. As can be seen from FIG. 8B, when the EGR rate is low (A / F is on the lean side), the NOx generation rate decreases as the fuel injection timing of the main fuel injection is retarded. Further, as can be seen from FIG. 8C, when the EGR rate is low, the Pi fluctuation rate is hardly changed even if the fuel injection timing of the main fuel injection is retarded, and combustion stability is ensured.

図９は、ＥＧＲ率を０％とした場合の熱発生率波形の一例を様々な条件で比較して示したものである。図中、太実線Ｐは、プレ燃料噴射を実施せず、メイン燃料噴射の燃料噴射時期を遅角しないときの波形を示し、細実線Ｑは、プレ燃料噴射を実施し、メイン燃料噴射の燃料噴射時期を遅角しないときの波形を示し、破線Ｒは、プレ燃料噴射を実施し、更にメイン燃料噴射の燃料噴射時期を遅角したときの波形を示している。   FIG. 9 shows an example of a heat release rate waveform when the EGR rate is 0% and is compared under various conditions. In the figure, a thick solid line P indicates a waveform when the pre-fuel injection is not performed and the fuel injection timing of the main fuel injection is not retarded, and a thin solid line Q indicates that the pre-fuel injection is performed and the fuel of the main fuel injection is A waveform when the injection timing is not retarded is shown, and a broken line R shows a waveform when the pre-fuel injection is performed and the fuel injection timing of the main fuel injection is further retarded.

図９から分かるように、プレ燃料噴射を実施することで、３段着火の状態となり、燃焼騒音が十分低くなる。また、プレ燃料噴射の実施に加え、メイン燃料噴射の燃料噴射時期を遅角することで、着火時期が遅れるため、それに対応して熱発生率波形の山の位置がずれている。   As can be seen from FIG. 9, by performing the pre-fuel injection, a three-stage ignition state is obtained, and the combustion noise is sufficiently reduced. In addition to performing the pre-fuel injection, the ignition timing is delayed by delaying the fuel injection timing of the main fuel injection, and accordingly, the position of the peak of the heat generation rate waveform is shifted accordingly.

図１０は、プレ燃料噴射を実施した場合にＥＧＲ率を変更したときの熱発生率波形の一例を比較して示したものである。図中、太実線Ｐは、ＥＧＲ率を０％としたときの波形を示し、破線Ｑは、ＥＧＲ率を３３％としたときの波形を示し、細実線Ｒは、ＥＧＲ率を４２％としたときの波形を示している。図１０から分かるように、プレ燃料噴射を実施する場合には、ＥＧＲ率が０から高くなる、つまり燃焼室内の空燃比がリッチ側となる（空気量が少なくなる）ほど、熱発生率波形（燃焼状態）が狙いの波形に近づいている。   FIG. 10 shows a comparison of examples of heat release rate waveforms when the EGR rate is changed when pre-fuel injection is performed. In the figure, a thick solid line P indicates a waveform when the EGR rate is 0%, a broken line Q indicates a waveform when the EGR rate is 33%, and a thin solid line R indicates the EGR rate is 42%. Shows the waveform. As can be seen from FIG. 10, when pre-fuel injection is performed, the heat generation rate waveform (as the EGR rate increases from 0, that is, the air-fuel ratio in the combustion chamber becomes richer (the air amount decreases)). The combustion state is approaching the target waveform.

図１１は、メイン燃料噴射の燃料噴射時期と図示平均有効圧（Ｐｉ）変動率との関係の一例を示したものである。図中、黒丸印Ｐは、ＥＧＲ率が所定値であるときのデータを示し、白丸印Ｑは、ＥＧＲ率が所定値よりも３％高いときのデータを示している。図１１から分かるように、ＥＧＲ率が高くなる、つまり燃焼室内の空燃比がリッチ側となると、燃焼安定領域が進角側にシフトしている（矢印参照）。   FIG. 11 shows an example of the relationship between the fuel injection timing of the main fuel injection and the indicated mean effective pressure (Pi) fluctuation rate. In the figure, black circles P indicate data when the EGR rate is a predetermined value, and white circles Q indicate data when the EGR rate is 3% higher than the predetermined value. As can be seen from FIG. 11, when the EGR rate increases, that is, when the air-fuel ratio in the combustion chamber becomes rich, the combustion stable region is shifted to the advance side (see arrow).

ところで、目標空燃比と検出空燃比との空燃比偏差の算出を、時間同期で周期的に行う場合には、図１２に示すように、空燃比偏差の算出から燃料噴射までの期間が長く且つ一定でないため、空燃比偏差の算出精度が悪化する。このため、例えば燃焼モードが通常燃焼から予混合圧縮着火燃焼に切り替わったときに、以下の不具合が生じる。   By the way, when the calculation of the air-fuel ratio deviation between the target air-fuel ratio and the detected air-fuel ratio is periodically performed in time synchronization, the period from the calculation of the air-fuel ratio deviation to the fuel injection is long as shown in FIG. Since it is not constant, the calculation accuracy of the air-fuel ratio deviation deteriorates. For this reason, for example, when the combustion mode is switched from normal combustion to premixed compression ignition combustion, the following problems occur.

即ち、実際の空燃比が目標空燃比に近づいているために本来ならばプレ燃料噴射の実施が不要な状況で、プレ燃料噴射が実施されると、スモークの発生量が多くなる。また、検出空燃比が実際の空燃比より大きい（リーン）側にずれた状況で、空燃比偏差が算出されると、メイン燃料噴射の燃料噴射時期が遅角され過ぎて、燃焼が不安定となり失火する可能性もある。一方、検出空燃比が実際の空燃比より小さい（リッチ）側にずれた状況で、空燃比偏差が算出されると、メイン燃料噴射の燃料噴射時期の遅角量が不足し、燃料と空気との予混合気が早期着火して燃焼音が大きくなる。   That is, since the actual air-fuel ratio is close to the target air-fuel ratio, if the pre-fuel injection is originally performed in a situation where the pre-fuel injection is unnecessary, the amount of smoke generated increases. In addition, when the detected air-fuel ratio is shifted to a larger (lean) side than the actual air-fuel ratio, if the air-fuel ratio deviation is calculated, the fuel injection timing of the main fuel injection is excessively retarded and the combustion becomes unstable. There is a possibility of misfire. On the other hand, if the air-fuel ratio deviation is calculated in a situation where the detected air-fuel ratio is deviated to a smaller (rich) side than the actual air-fuel ratio, the retard amount of the fuel injection timing of the main fuel injection is insufficient, and the fuel and air The premixed gas is ignited early and the combustion noise increases.

これに対し本実施形態では、クランク角センサ２５により検出されたクランク角が燃料噴射を行う角度よりも所定角度だけ手前の偏差算出クランク角に達した時点で、つまりクランク角に同期して、目標空燃比と検出空燃比との空燃比偏差を算出するようにしたので、空燃比偏差の算出から燃料噴射までの期間が短く且つ一定となる。従って、各気筒毎に燃料噴射直前で、空燃比偏差を高精度に算出することができる。これにより、各気筒毎の空気状態に応じて最適な燃料噴射補正（上記のメイン燃料噴射の燃料噴射時期の変更及びプレ燃料噴射の追加）を行うことができる。その結果、空燃比偏差の算出を時間同期で行うときの不具合を解消することが可能となる。   In contrast, in the present embodiment, when the crank angle detected by the crank angle sensor 25 reaches the deviation calculation crank angle that is a predetermined angle before the angle at which fuel injection is performed, that is, in synchronization with the crank angle, Since the air-fuel ratio deviation between the air-fuel ratio and the detected air-fuel ratio is calculated, the period from the calculation of the air-fuel ratio deviation to the fuel injection is short and constant. Therefore, the air-fuel ratio deviation can be calculated with high accuracy immediately before fuel injection for each cylinder. Thereby, optimal fuel injection correction (change of the fuel injection timing of the main fuel injection and addition of pre-fuel injection) can be performed according to the air condition of each cylinder. As a result, it is possible to eliminate the problem in calculating the air-fuel ratio deviation in time synchronization.

以上のように本実施形態によれば、目標空燃比と検出空燃比との空燃比偏差に応じて、メイン燃料噴射の燃料噴射時期の変更及びプレ燃料噴射の追加を行うので、燃焼切替時などに生じる燃焼騒音の増大、失火、エミッションの悪化を抑制することができる。また、空燃比偏差の算出精度が高いので、そのような抑制効果を安定化させることができる。   As described above, according to the present embodiment, the fuel injection timing of the main fuel injection is changed and the pre-fuel injection is added according to the air-fuel ratio deviation between the target air-fuel ratio and the detected air-fuel ratio. Increase in combustion noise, misfire, and emission deterioration can be suppressed. Moreover, since the calculation accuracy of the air-fuel ratio deviation is high, such a suppression effect can be stabilized.

なお、本発明は、上記実施形態に限定されるものではない。例えば上記実施形態では、エンジン負荷が所定値より低いためにプレ燃料噴射を実施する場合には、目標空燃比と検出空燃比との空燃比偏差がプレ噴射用閾値Ｃよりも小さいときに、新たなプレ燃料噴射を実施しないようにしたが、特にそれには限られず、エンジン負荷が所定値より低いためにプレ燃料噴射を実施する場合に、空燃比偏差がプレ噴射用閾値Ｃよりも小さいときは、プレ燃料噴射の燃料噴射量を増やすようにしても良い。この場合には、エンジン負荷が極低負荷状態にあっても、プレ燃料噴射の燃料噴射量が増加するため、燃焼安定性が向上するようになる。   The present invention is not limited to the above embodiment. For example, in the above embodiment, when pre-fuel injection is performed because the engine load is lower than a predetermined value, when the air-fuel ratio deviation between the target air-fuel ratio and the detected air-fuel ratio is smaller than the pre-injection threshold C, a new fuel injection is performed. However, the present invention is not limited to this. When the pre-fuel injection is performed because the engine load is lower than the predetermined value, the air-fuel ratio deviation is smaller than the pre-injection threshold C. The fuel injection amount of pre-fuel injection may be increased. In this case, even when the engine load is in an extremely low load state, the fuel injection amount of the pre-fuel injection is increased, so that the combustion stability is improved.

また、上記実施形態では、目標空燃比と検出空燃比との空燃比偏差以外の要因によるプレ燃料噴射の実施の要否として、エンジン負荷が所定値以下であるか否かを判断したが、これに限られず、プレ燃料噴射を実施するための既知の他の制御内容によってプレ燃料噴射の実施の要否を判断しても良い。   In the above embodiment, whether or not the engine load is equal to or less than the predetermined value is determined as the necessity of performing the pre-fuel injection due to factors other than the air-fuel ratio deviation between the target air-fuel ratio and the detected air-fuel ratio. However, the necessity of performing the pre-fuel injection may be determined based on other known control contents for performing the pre-fuel injection.

また、エンジン負荷が所定値より低いときに、プレ燃料噴射を実施しないこととしても良い。この場合には、空燃比偏差がプレ噴射用閾値Ｃよりも小さいときには、エンジン負荷にかかわらずプレ燃料噴射を実施することとなる。   Alternatively, the pre-fuel injection may not be performed when the engine load is lower than a predetermined value. In this case, when the air-fuel ratio deviation is smaller than the pre-injection threshold C, pre-fuel injection is performed regardless of the engine load.

さらに、上記実施形態では、空燃比偏差が遅角用閾値Ａ０よりも小さいか否かを判断し、空燃比偏差が遅角用閾値Ａ０よりも小さいときに、１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を遅角するように制御したが、遅角用閾値Ａ０を設けずに、空燃比偏差に応じて１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を遅角するようにしても良い。また、上記実施形態では、空燃比偏差が進角用閾値Ｂ０よりも大きいか否かを判断し、空燃比偏差が進角用閾値Ｂ０よりも大きいときに、１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を進角するように制御したが、進角用閾値Ｂ０を設けずに、空燃比偏差に応じて１回目のメイン燃料噴射及び２回目のメイン燃料噴射の燃料噴射時期を進角するようにしても良い。 Furthermore, in the above embodiment, it is determined whether or not the air-fuel ratio or difference is smaller than the retard threshold A 0, when less than the threshold value A 0 for the air-fuel ratio deviation is retarded, the first main fuel injection and the fuel injection timing of the second main fuel injection is controlled so as to retard, but without providing the threshold a 0 for retarding, first main fuel injection and the second main fuel injection in accordance with the air-fuel ratio deviation The fuel injection timing may be retarded. In the above embodiment, it is determined whether the air-fuel ratio deviation is greater than the advancing threshold B 0, when the air-fuel ratio deviation is greater than the advancing threshold B 0, 1 time the main fuel injection and the second fuel injection timing of the main fuel injection is controlled so as to advance, but without providing the advanced angle threshold B 0, 1 st main fuel injection and the second main fuel injection in accordance with the air-fuel ratio deviation The fuel injection timing may be advanced.

また、上記実施形態では、メイン燃料噴射を２回に分けて行うようにしたが、メイン燃料噴射を１回だけ行っても良いし、メイン燃料噴射を３回以上に分けて行うようにしても良い。   In the above embodiment, the main fuel injection is performed twice, but the main fuel injection may be performed only once, or the main fuel injection may be performed three times or more. good.

さらに、上記実施形態では、目標空燃比と検出空燃比との空燃比偏差を算出する際に、エアーフローメータ２７により検出された吸入空気量に基づいて空気量を算出し、その空気量を燃料噴射量で除して検出空燃比を算出するようにしたが、特にそれに限られず、燃焼室４内の空燃比を直接検出する空燃比センサを設け、この空燃比センサにより検出された空燃比を検出空燃比としても良い。   Further, in the above embodiment, when calculating the air-fuel ratio deviation between the target air-fuel ratio and the detected air-fuel ratio, the air amount is calculated based on the intake air amount detected by the air flow meter 27, and the air amount is converted into the fuel amount. The detected air-fuel ratio is calculated by dividing by the injection amount. However, the present invention is not limited to this, and an air-fuel ratio sensor for directly detecting the air-fuel ratio in the combustion chamber 4 is provided, and the air-fuel ratio detected by the air-fuel ratio sensor is calculated. The detected air-fuel ratio may be used.

また、上記実施形態では、エアーフローメータ２７により燃焼室４内への吸入空気量を検出するようにしたが、吸入空気量を含む空気状態を検出するセンサとしては、インテークマニホールド１１に取り付けられる酸素濃度センサを使用することも可能である。   In the above embodiment, the intake air amount into the combustion chamber 4 is detected by the air flow meter 27. However, as a sensor for detecting the air state including the intake air amount, oxygen attached to the intake manifold 11 is used. It is also possible to use a density sensor.

さらに、上記実施形態では、ＥＧＲバルブ２０によりＥＧＲガスの流量を調整することで、燃焼室４内の空燃比を制御するようにしたが、空燃比の制御方法としては特にそれには限られず、例えばターボ過給機１２の過給圧を調整するようにしても良い。   Furthermore, in the above embodiment, the air-fuel ratio in the combustion chamber 4 is controlled by adjusting the flow rate of the EGR gas by the EGR valve 20, but the air-fuel ratio control method is not particularly limited, for example, The supercharging pressure of the turbocharger 12 may be adjusted.

また、本発明は、燃焼切替時、燃料噴射カット時、加速時以外にも、ＬＰＬ（ロープレッシャーループ）ＥＧＲなどＥＧＲ還流遅れが生じるものであれば、適用可能である。   Further, the present invention can be applied as long as an EGR recirculation delay occurs such as LPL (low pressure loop) EGR other than at the time of combustion switching, fuel injection cut, and acceleration.

１…ディーゼルエンジン、４…燃焼室、５…インジェクタ（燃料噴射弁）、２４…ＥＣＵ（メイン噴射制御手段、空燃比検出手段、偏差算出手段、プレ噴射制御手段、噴射時期決定手段、噴射時期変更手段）、２５…クランク角センサ（クランク角検出手段）、２７…エアーフローメータ（空燃比検出手段）、２８…燃焼制御装置。   DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 4 ... Combustion chamber, 5 ... Injector (fuel injection valve), 24 ... ECU (main injection control means, air-fuel ratio detection means, deviation calculation means, pre-injection control means, injection timing determination means, injection timing change Means), 25 ... crank angle sensor (crank angle detection means), 27 ... air flow meter (air-fuel ratio detection means), 28 ... combustion control device.

Claims (4)

予混合圧縮着火燃焼を行うエンジンの燃焼制御装置において、
前記エンジンの燃焼室内に燃料を噴射する燃料噴射弁と、
メイン燃料噴射を実施するように前記燃料噴射弁を制御するメイン噴射制御手段と、
前記メイン燃料噴射を実施する前に補助的なプレ燃料噴射を実施するように前記燃料噴射弁を制御するプレ噴射制御手段と、
前記燃焼室内の空燃比を検出する空燃比検出手段と、
目標空燃比と前記空燃比検出手段により得られた検出空燃比との偏差を算出する偏差算出手段とを備え、
前記メイン噴射制御手段は、前記メイン燃料噴射の燃料噴射時期を決定する噴射時期決定手段と、前記偏差算出手段により算出された前記目標空燃比と前記検出空燃比との偏差に応じて、前記噴射時期決定手段により決定された前記メイン燃料噴射の燃料噴射時期を変更する噴射時期変更手段とを有し、
前記噴射時期変更手段は、前記目標空燃比と前記検出空燃比との偏差がリーン側にずれている場合に、前記目標空燃比と前記検出空燃比との偏差の絶対値が予め決められた遅角用閾値の絶対値よりも大きいかどうかを判断し、前記目標空燃比と前記検出空燃比との偏差の絶対値が前記遅角用閾値の絶対値よりも大きいと判断されると、前記メイン燃料噴射の燃料噴射時期を遅角する手段であり、
前記プレ噴射制御手段は、前記目標空燃比と前記検出空燃比との偏差がリーン側にずれている場合に、前記目標空燃比と前記検出空燃比との偏差の絶対値が予め決められたプレ噴射用閾値の絶対値よりも大きいかどうかを判断する手段を有し、前記目標空燃比と前記検出空燃比との偏差の絶対値が前記プレ噴射用閾値の絶対値よりも大きいと判断されたときに、前記プレ燃料噴射を実施するように前記燃料噴射弁を制御し、
前記プレ噴射用閾値の絶対値が前記遅角用閾値の絶対値よりも大きいことを特徴とする燃焼制御装置。 In an engine combustion control device that performs premixed compression ignition combustion,
A fuel injection valve for injecting fuel into the combustion chamber of the engine;
Main injection control means for controlling the fuel injection valve to perform main fuel injection;
Pre-injection control means for controlling the fuel injection valve to perform auxiliary pre-fuel injection before performing the main fuel injection;
Air-fuel ratio detecting means for detecting an air-fuel ratio in the combustion chamber;
Deviation calculating means for calculating a deviation between the target air-fuel ratio and the detected air-fuel ratio obtained by the air-fuel ratio detecting means;
The main injection control means includes an injection timing determining means for determining a fuel injection timing of the main fuel injection, and the injection according to a deviation between the target air-fuel ratio calculated by the deviation calculating means and the detected air-fuel ratio. possess the injection timing changing means for changing the fuel injection timing of the main fuel injection, which is determined by the timing determining means,
When the deviation between the target air-fuel ratio and the detected air-fuel ratio is deviated to the lean side, the injection timing changing means is configured to delay the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio in advance. It is determined whether or not the absolute value of the angle threshold is larger, and if it is determined that the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is greater than the absolute value of the retard threshold, the main It is a means to retard the fuel injection timing of fuel injection,
When the deviation between the target air-fuel ratio and the detected air-fuel ratio is deviated toward the lean side, the pre-injection control means is configured to pre-determine the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio. Means for determining whether or not the absolute value of the threshold value for injection is larger than the absolute value of the threshold value for injection, and it is determined that the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is larger than the absolute value of the threshold value for pre-injection Sometimes controlling the fuel injection valve to perform the pre-fuel injection,
The combustion control device, wherein an absolute value of the pre-injection threshold is larger than an absolute value of the retardation angle threshold . 前記メイン噴射制御手段は、前記メイン燃料噴射を複数回に分けて実施するように前記燃料噴射弁を制御し、
前記プレ噴射制御手段は、１回目の前記メイン燃料噴射の燃料噴射量を減量して、前記プレ燃料噴射の燃料噴射量を設定する手段を更に有することを特徴とする請求項１記載の燃焼制御装置。 The main injection control means controls the fuel injection valve so that the main fuel injection is performed in a plurality of times,
The pre-injection control means, and reduced fuel injection quantity of the first of the main fuel injection, combustion control according to claim 1, characterized in that it has further means for setting a fuel injection amount of the pre-fuel injection apparatus. 前記噴射時期変更手段は、前記目標空燃比と前記検出空燃比との偏差がリッチ側にずれている場合に、前記目標空燃比と前記検出空燃比との偏差の絶対値が予め決められた進角用閾値の絶対値よりも大きいかどうかを判断し、前記目標空燃比と前記検出空燃比との偏差の絶対値が前記進角用閾値の絶対値よりも大きいと判断されると、前記メイン燃料噴射の燃料噴射時期を進角する手段であることを特徴とする請求項１記載の燃焼制御装置。   When the deviation between the target air-fuel ratio and the detected air-fuel ratio deviates to the rich side, the injection timing changing means is configured to advance the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio in advance. It is determined whether or not the absolute value of the threshold value for angle is larger than the absolute value of the threshold value for advancement, and if the absolute value of the deviation between the target air-fuel ratio and the detected air-fuel ratio is determined to be larger than the absolute value of the threshold value for advancement, 2. The combustion control apparatus according to claim 1, wherein the combustion control apparatus is a means for advancing the fuel injection timing of fuel injection. 前記エンジンのクランク角を検出するクランク角検出手段を更に備え、
前記偏差算出手段は、前記クランク角検出手段により検出された前記クランク角が所定角度になった時点で、前記目標空燃比と前記検出空燃比との偏差を算出することを特徴とする請求項１〜３のいずれか一項記載の燃焼制御装置。 Crank angle detecting means for detecting the crank angle of the engine,
The deviation calculating means calculates a deviation between the target air-fuel ratio and the detected air-fuel ratio when the crank angle detected by the crank angle detecting means reaches a predetermined angle. The combustion control device according to any one of to 3 .
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