JP6763805B2 - Internal combustion engine control device - Google Patents

Internal combustion engine control device Download PDF

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JP6763805B2
JP6763805B2 JP2017035824A JP2017035824A JP6763805B2 JP 6763805 B2 JP6763805 B2 JP 6763805B2 JP 2017035824 A JP2017035824 A JP 2017035824A JP 2017035824 A JP2017035824 A JP 2017035824A JP 6763805 B2 JP6763805 B2 JP 6763805B2
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injection
ignition
period
spark plug
control device
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JP2018009562A (en
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翔太 塚本
翔太 塚本
宏太朗 鈴木
宏太朗 鈴木
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Toyota Motor Corp
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Toyota Motor Corp
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Priority to AU2017203240A priority Critical patent/AU2017203240B2/en
Priority to EP17171707.7A priority patent/EP3267019A1/en
Priority to TW106117422A priority patent/TWI647383B/en
Priority to US15/606,957 priority patent/US10066562B2/en
Priority to CA2970387A priority patent/CA2970387C/en
Priority to BR102017013414-8A priority patent/BR102017013414A2/en
Priority to KR1020170083026A priority patent/KR101928661B1/en
Priority to RU2017123167A priority patent/RU2656071C1/en
Priority to PH12017000195A priority patent/PH12017000195A1/en
Priority to MX2017008841A priority patent/MX370245B/en
Priority to CN201710536989.1A priority patent/CN107575329B/en
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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
    • F02D41/3017—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used
    • F02D41/3023—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used a mode being the stratified charge spark-ignited mode
    • F02D41/3029—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used a mode being the stratified charge spark-ignited mode further comprising a homogeneous charge spark-ignited mode
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M45/00—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship
    • F02M45/02—Fuel-injection apparatus characterised by having a cyclic delivery of specific time/pressure or time/quantity relationship with each cyclic delivery being separated into two or more parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
    • F02B23/10—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
    • F02B23/08—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition
    • F02B23/10—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder
    • F02B23/101—Other engines characterised by special shape or construction of combustion chambers to improve operation with positive ignition with separate admission of air and fuel into cylinder the injector being placed on or close to the cylinder centre axis, e.g. with mixture formation using spray guided concepts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
    • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
    • F02D35/028—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining the combustion timing or phasing
    • 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
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/0245—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus by increasing temperature of the exhaust gas leaving the engine
    • 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
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F02D41/024—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus
    • F02D41/0255—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to increase temperature of the exhaust gas treating apparatus to accelerate the warming-up of the exhaust gas treating apparatus at engine start
    • 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
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
    • F02D41/068—Introducing corrections for particular operating conditions for engine starting or warming up for warming-up
    • 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
    • F02D41/1497—With detection of the mechanical response of the engine
    • F02D41/1498—With detection of the mechanical response of the engine measuring engine roughness
    • 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
    • F02D41/3023—Controlling fuel injection according to or using specific or several modes of combustion characterised by the mode(s) being used a mode being the stratified charge spark-ignited 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
    • F02D41/3011—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
    • F02D41/307—Controlling fuel injection according to or using specific or several modes of combustion with special control during transition between modes to avoid torque shocks
    • 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
    • F02D41/32—Controlling fuel injection of the low pressure type
    • F02D41/34—Controlling fuel injection of the low pressure type with means for controlling injection timing or duration
    • F02D41/345—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
    • F02D41/405—Multiple injections with post injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D43/00—Conjoint electrical control of two or more functions, e.g. ignition, fuel-air mixture, recirculation, supercharging or exhaust-gas treatment
    • F02D43/04—Conjoint electrical control of two or more functions, e.g. ignition, fuel-air mixture, recirculation, supercharging or exhaust-gas treatment using only digital means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P5/00—Advancing or retarding ignition; Control therefor
    • F02P5/04—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions
    • F02P5/145—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using electrical means
    • F02P5/15—Digital data processing
    • F02P5/1502—Digital data processing using one central computing unit
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P5/00—Advancing or retarding ignition; Control therefor
    • F02P5/04—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions
    • F02P5/145—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using electrical means
    • F02P5/15—Digital data processing
    • F02P5/152—Digital data processing dependent on pinking
    • F02P5/1523—Digital data processing dependent on pinking with particular laws of return to advance, e.g. step by step, differing from the laws of retard
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P5/00—Advancing or retarding ignition; Control therefor
    • F02P5/04—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions
    • F02P5/145—Advancing or retarding ignition; Control therefor automatically, as a function of the working conditions of the engine or vehicle or of the atmospheric conditions using electrical means
    • F02P5/15—Digital data processing
    • F02P5/153—Digital data processing dependent on combustion pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/12—Other methods of operation
    • F02B2075/125—Direct injection in the combustion chamber for spark ignition engines, i.e. not in pre-combustion chamber
    • 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
    • F02D2041/389—Controlling fuel injection of the high pressure type for injecting directly into the cylinder
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0802—Temperature of the exhaust gas treatment apparatus
    • 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

Description

この発明は内燃機関の制御装置に関し、詳しくは、筒内インジェクタを備える火花点火式内燃機関に適用される制御装置に関する。 The present invention relates to a control device for an internal combustion engine, and more particularly to a control device applied to a spark ignition type internal combustion engine including an in-cylinder injector.

特許文献１（特開２０１１−１０６３７７号公報）には、複数の噴孔を有するインジェクタと点火プラグを燃焼室上部に備える内燃機関が開示されている。この内燃機関では、点火プラグの放電ギャップの中心位置から、インジェクタの噴孔のうちの点火プラグに最も近い噴孔の中心位置までの距離が、特定の範囲に設定されている。また、この内燃機関では、燃料噴射を開始してから所定時間が経過した後に、当該燃料噴射の終了までの間に亘って、点火プラグへの高電圧の印加を行う制御が行われる。 Patent Document 1 (Japanese Unexamined Patent Publication No. 2011-106377) discloses an internal combustion engine including an injector having a plurality of injection holes and a spark plug in the upper part of the combustion chamber. In this internal combustion engine, the distance from the center position of the discharge gap of the spark plug to the center position of the injection hole closest to the ignition plug among the injection holes of the injector is set in a specific range. Further, in this internal combustion engine, control is performed in which a high voltage is applied to the spark plug after a predetermined time has elapsed from the start of fuel injection until the end of the fuel injection.

上述した制御が行われると、インジェクタによる燃料噴射の期間に、点火プラグへの高電圧の印加期間が重なることになる。ここで、インジェクタには加圧状態の燃料が供給されているので、インジェクタによる燃料噴射が行われると、各噴孔からの燃料噴霧の周囲の空気が持ち去られて低圧部が形成される（エントレインメント）。故に、上述した制御が行われると、上述した点火プラグに最も近い噴孔の周囲に形成された低圧部に、放電ギャップに生じた放電火花が誘引されることになる。よって、この内燃機関によれば、点火プラグの周辺に形成される混合気の着火性を向上できる。 When the above-mentioned control is performed, the period of applying the high voltage to the spark plug overlaps with the period of fuel injection by the injector. Here, since the injector is supplied with fuel in a pressurized state, when fuel injection is performed by the injector, the air around the fuel spray from each injection hole is taken away and a low pressure portion is formed (entrainment). Injection). Therefore, when the above-mentioned control is performed, the discharge spark generated in the discharge gap is attracted to the low-pressure portion formed around the injection hole closest to the above-mentioned spark plug. Therefore, according to this internal combustion engine, the ignitability of the air-fuel mixture formed around the spark plug can be improved.

特開２０１１−１０６３７７号公報Japanese Unexamined Patent Publication No. 2011-106377

特許文献１は更に、上述した誘引作用の適用例として、排気浄化触媒の活性化を紹介している。特許文献１での言及はないが、この排気浄化触媒の活性化は、通常時であれば圧縮上死点の近傍に設定する点火期間（つまり、点火プラグへの高電圧の印加時期）を、当該圧縮上死点よりも遅角側に変更することにより行われるのが一般的である。 Patent Document 1 further introduces activation of an exhaust gas purification catalyst as an application example of the above-mentioned attracting action. Although not mentioned in Patent Document 1, the activation of this exhaust gas purification catalyst normally sets an ignition period (that is, a timing of applying a high voltage to the spark plug) set near the compression top dead center. It is generally performed by changing the compression top dead center to the retard side.

上述した特許文献１の制御を一般的な排気浄化触媒の活性化に適用すると、圧縮上死点よりも遅角側に設定した点火期間を燃料噴射期間と重複させて、点火プラグの周辺に形成される混合気の着火性を向上できることになる。しかし、何らかの要因で着火環境が変化して望ましい範囲から外れた場合には、上述した誘引作用にも関わらず燃焼状態が不安定となる可能性がある。そして、排気浄化触媒の活性化制御中の燃焼サイクルにおいて、このような事態が発生するサイクルが多くなれば、サイクル間の燃焼変動が大きくなるので、ドライバビリティに影響が出てしまう。 When the control of Patent Document 1 described above is applied to the activation of a general exhaust gas purification catalyst, the ignition period set on the retard side of the compression top dead center is overlapped with the fuel injection period and formed around the spark plug. The ignitability of the air-fuel mixture to be produced can be improved. However, if the ignition environment changes for some reason and deviates from the desired range, the combustion state may become unstable despite the above-mentioned attractive action. Then, in the combustion cycle during the activation control of the exhaust gas purification catalyst, if the number of cycles in which such a situation occurs increases, the combustion fluctuation between the cycles becomes large, which affects the drivability.

本発明は、上述した課題に鑑みてなされたものであり、その目的は、インジェクタによる燃料噴射の期間に点火プラグへの高電圧の印加期間を重複させる制御を排気浄化触媒の活性化に適用する場合において、サイクル間の燃焼変動を抑えることにある。 The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to apply a control for overlapping a period of applying a high voltage to a spark plug with a period of fuel injection by an injector to activate an exhaust gas purification catalyst. In some cases, the purpose is to suppress combustion fluctuations between cycles.

本発明に係る内燃機関の制御装置は、インジェクタと、点火プラグと、排気浄化触媒とを備える内燃機関を制御するものである。前記インジェクタは、燃焼室上部に設けられて複数の噴孔から筒内に燃料を噴射するように構成されている。前記点火プラグは、放電火花を用いて筒内の混合気に点火するように構成されており、前記複数の噴孔から噴射される燃料の下流、且つ、前記複数の噴孔から噴射された燃料噴霧のうち前記点火プラグに最も近づく燃料噴霧の外郭面よりも上方に設けられる。前記排気浄化触媒は、前記燃焼室からの排気を浄化するように構成されている。
前記制御装置は、前記排気浄化触媒を活性化させる制御として、圧縮上死点よりも遅角側の点火期間で放電火花が発生するように前記点火プラグを制御すると共に、前記圧縮上死点よりも進角側での第１噴射と、前記圧縮上死点よりも遅角側での第２噴射であって、噴射期間が前記点火期間の少なくとも一部と重複する第２噴射と、を行うように前記インジェクタを制御する。
本発明に係る内燃機関の制御装置は更に、
前記排気浄化触媒を活性化させる制御において、前記点火期間の開始時期から前記第２噴射の噴射期間の終了時期までのインターバルを制御し、
サイクル間の燃焼変動に関連するパラメータが閾値を上回るか否かを判定し、
前記パラメータが前記閾値を上回ると判定された場合は、前記パラメータが前記閾値を下回ると判定された場合に比べて、前記インターバルが拡大するように前記点火プラグと前記インジェクタを制御する。 The internal combustion engine control device according to the present invention controls an internal combustion engine including an injector, a spark plug, and an exhaust gas purification catalyst. The injector is provided in the upper part of the combustion chamber and is configured to inject fuel into the cylinder from a plurality of injection holes. The spark plug is configured to ignite the air-fuel mixture in the cylinder by using a discharge spark, and is downstream of the fuel injected from the plurality of injection holes and the fuel injected from the plurality of injection holes. Of the spray, it is provided above the outer surface of the fuel spray that is closest to the spark plug. The exhaust gas purification catalyst is configured to purify the exhaust gas from the combustion chamber.
As a control for activating the exhaust gas purification catalyst, the control device controls the spark plug so that a discharge spark is generated in an ignition period on the retard side of the compression top dead center, and from the compression top dead center. The first injection on the advance angle side and the second injection on the retard side from the compression top dead center, the injection period of which overlaps with at least a part of the ignition period, are performed. The injector is controlled in such a manner.
Further, the control device for the internal combustion engine according to the present invention
In the control for activating the exhaust gas purification catalyst, the interval from the start time of the ignition period to the end time of the injection period of the second injection is controlled.
Determine if the parameters associated with combustion fluctuations between cycles exceed the threshold
If the parameter is determined to exceed the threshold value, as compared with the case where the parameter is determined to be less than the threshold value, it controls the spark plug and the injector as before hearing Ntabaru is enlarged.

第１噴射での燃料噴霧を含む混合気は、点火期間において初期火炎を生じさせる。噴射期間が点火期間の少なくとも一部と重複する第２噴射が行われると、点火プラグに最も近い噴孔からの燃料噴霧の周囲に形成された低圧部に、少なくとも初期火炎が誘引される。このため、第２噴射が行われると、誘引された初期火炎に第２噴射による燃料噴霧が接触し、初期火炎を成長させる燃焼が促進されるはずである。
しかしながら、この接触が十分でない場合には、初期火炎を成長させる燃焼が不安定となる。初期火炎を成長させる燃焼が不安定となるサイクルが多くなれば、サイクル間の燃焼変動が大きくなる。
この点、サイクル間の燃焼変動に関連するパラメータが閾値を上回ると判定された場合に、当該パラメータが当該閾値を下回ると判定された場合に比べて、点火期間の開始時期から第２噴射の噴射期間の終了時期までのインターバルを拡大させれば、点火期間の開始から第２噴射の終了までのインターバルが長くなり、初期火炎がある程度成長するまで第２噴射の開始が待機されることになる。従って、誘引された初期火炎と放電火花に第２噴射による燃料噴霧の接触が不十分となるような状況が回避される。 The air-fuel mixture containing the fuel spray in the first injection produces an initial flame during the ignition period. When the second injection, in which the injection period overlaps at least a part of the ignition period, is performed, at least the initial flame is attracted to the low pressure portion formed around the fuel spray from the injection hole closest to the spark plug. Therefore, when the second injection is performed, the fuel spray from the second injection comes into contact with the attracted initial flame, and the combustion that grows the initial flame should be promoted.
However, if this contact is not sufficient, the combustion that grows the initial flame becomes unstable. As the number of cycles in which the combustion that grows the initial flame becomes unstable increases, the combustion fluctuation between cycles increases.
In this regard, when it is determined that the parameter related to the combustion fluctuation between cycles exceeds the threshold value, the injection of the second injection is performed from the start time of the ignition period as compared with the case where the parameter is determined to be below the threshold value. If the interval to the end of the period is extended, the interval from the start of the ignition period to the end of the second injection becomes longer, and the start of the second injection is waited until the initial flame grows to some extent. Therefore, a situation in which the contact between the attracted initial flame and the discharged spark by the fuel spray by the second injection is insufficient is avoided.

前記制御装置は、前記パラメータが前記閾値を上回る場合は、前記パラメータと前記閾値の乖離量が増えるほど前記インターバルの拡大量を大きくしてもよい。 Wherein the control device, if the parameter is above the threshold may be increased to expand the amount of the interval as the deviation amount of said parameter and said threshold value is increased.

サイクル間の燃焼変動に関連するパラメータが閾値を上回ると判定された場合に、当該パラメータと当該閾値の乖離量が増えるほどインターバルの拡大量を大きくすれば、誘引された初期火炎に第２噴射による燃料噴霧を確実かつ十分に接触させることが可能となる。
If the parameters related to the combustion variation between cycles is determined to exceed the threshold, by increasing the amount of increase interval as the deviation amount of the parameter and the threshold value is increased, by the second injection to attract initial flame It is possible to ensure and sufficiently contact the fuel spray.

前記第２噴射は、その終了時期を前記点火期間の終了時期よりも進角側としてもよい。 The end time of the second injection may be on the advance side of the end time of the ignition period.

第２噴射の終了時期が点火期間の終了時期よりも遅角側にある場合は、上記低圧部に初期火炎のみが誘引される。これに対し、第２噴射の終了時期が点火期間の終了時期よりも進角側にある場合は、上記低圧部に初期火炎と放電火花の両方が誘引される。そうすると、誘引された初期火炎と放電火花の両方に、第２噴射による燃料噴霧が接触することになる。従って、点火期間の終了時期からみて第２噴射の終了時期が進角側にある場合は、遅角側にある場合に比べて、初期火炎を成長させる燃焼が一層促進される。 When the end time of the second injection is on the retard side of the end time of the ignition period, only the initial flame is attracted to the low pressure portion. On the other hand, when the end time of the second injection is on the advance side of the end time of the ignition period, both the initial flame and the discharge spark are attracted to the low pressure portion. Then, the fuel spray from the second injection comes into contact with both the induced initial flame and the discharged spark. Therefore, when the end time of the second injection is on the advance angle side when viewed from the end time of the ignition period, the combustion for growing the initial flame is further promoted as compared with the case where it is on the retard angle side.

前記パラメータが、クランク軸が所定角度回転するまでに要する時間のばらつき、または、前記点火期間の開始時期から燃焼質量割合が所定割合に到達するまでのクランク角期間のばらつきであってもよい。 The parameter may be a variation in the time required for the crankshaft to rotate by a predetermined angle, or a variation in the crank angle period from the start time of the ignition period to the time when the combustion mass ratio reaches the predetermined ratio.

サイクル間の燃焼変動に関連するパラメータが、クランク軸が所定角度回転するまでに要する時間のばらつき、または、点火期間の開始時期から燃焼質量割合が所定割合に到達するまでのクランク角期間のばらつきである場合は、サイクル間の燃焼変動が精度高く検出される。 The parameters related to the combustion fluctuation between cycles are the variation in the time required for the crankshaft to rotate by a predetermined angle, or the variation in the crank angle period from the start time of the ignition period to the time when the combustion mass ratio reaches the predetermined ratio. In some cases, combustion variations between cycles are detected with high accuracy.

本発明に係る内燃機関の制御装置によれば、インジェクタによる燃料噴射の期間に点火プラグへの高電圧の印加期間を重複させる制御を排気浄化触媒の活性化に適用する場合において、サイクル間の燃焼変動を抑えることができる。 According to the control device of the internal combustion engine according to the present invention, when the control of overlapping the application period of the high voltage to the spark plug during the fuel injection period by the injector is applied to the activation of the exhaust gas purification catalyst, the combustion between cycles Fluctuations can be suppressed.

本発明の実施の形態に係るシステム構成を説明する図である。It is a figure explaining the system configuration which concerns on embodiment of this invention. 触媒暖機制御の概要を説明する図である。It is a figure explaining the outline of the catalyst warm-up control. 膨張行程噴射を説明する図である。It is a figure explaining expansion stroke injection. 膨張行程噴射による放電火花と初期火炎の誘引作用を説明する図である。It is a figure explaining the attracting action of a discharge spark and an initial flame by an expansion stroke injection. 点火期間の開始から膨張行程噴射の終了までのインターバル（点火開始−噴射終了インターバル）と、燃焼変動率との関係を示した図である。It is a figure which showed the relationship between the interval (ignition start-injection end interval) from the start of the ignition period to the end of the expansion stroke injection, and the combustion fluctuation rate. ベース適合値マップの一例を示した図である。It is a figure which showed an example of the base conformity value map. 内燃機関の冷間始動時における、点火プラグ３２による点火時期（より正確には、点火期間の開始時期）とエンジン冷却水温の推移を示した図である。It is a figure which showed the transition of the ignition timing by the spark plug 32 (more accurately, the start timing of the ignition period) and the engine cooling water temperature at the time of cold start of an internal combustion engine. 初期火炎の成長速度が遅くなった場合の筒内状態を説明する図である。It is a figure explaining the in-cylinder state when the growth rate of an initial flame becomes slow. 噴霧外郭面と電極部３４の間の距離が拡大した場合の筒内状態を説明する図である。It is a figure explaining the in-cylinder state when the distance between a spray outer surface and an electrode part 34 is increased. 点火時期を進角する場合の問題を説明する図である。It is a figure explaining the problem in the case of advancing the ignition timing. 点火期間の開始から膨張行程噴射の終了までのインターバルの修正手法を説明する図である。It is a figure explaining the correction method of the interval from the start of the ignition period to the end of the expansion stroke injection. 点火期間の開始から膨張行程噴射の終了までのインターバルが拡大する方向にベース適合値を修正した場合における筒内状態を説明する図である。It is a figure explaining the in-cylinder state when the base conformity value is corrected in the direction which the interval from the start of an ignition period to the end of an expansion stroke injection is expanded. 点火期間の開始から膨張行程噴射の終了までのインターバルが拡大する方向にベース適合値を修正した場合の効果を説明する図である。It is a figure explaining the effect when the base conformity value is corrected in the direction which the interval from the start of an ignition period to the end of an expansion stroke injection is expanded. 本発明の実施の形態においてＥＣＵ４０が実行する処理の一例を示すフローチャートである。It is a flowchart which shows an example of the process which the ECU 40 executes in Embodiment of this invention. 内燃機関の冷間始動時におけるＧａｔ３０と、このＧａｔ３０のばらつきσの推移の一例を示した図である。It is a figure which showed an example of the transition of Gat30 at the time of a cold start of an internal combustion engine and the variation σ of this Gat30. Ｇａｔ３０のばらつきσとクライテリアの差と、インターバル拡大用の補正値との関係を示す図である。It is a figure which shows the relationship between the variation σ of Gat30, the difference of a criterion, and the correction value for interval expansion. 内燃機関の冷間始動時における燃焼変動率とＳＡ−ＣＡ１０のばらつきσとの関係を示す図である。It is a figure which shows the relationship between the combustion fluctuation rate at the time of a cold start of an internal combustion engine, and the variation σ of SA-CA10. ＳＡ−ＣＡ１０のばらつきσの推移の一例を示した図である。It is a figure which showed an example of the transition of the variation σ of SA-CA10.

以下、図面に基づいて本発明の実施の形態について説明する。尚、各図において共通する要素には、同一の符号を付して重複する説明を省略する。また、以下の実施の形態によりこの発明が限定されるものではない。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. The elements common to each figure are designated by the same reference numerals, and duplicate description will be omitted. Further, the present invention is not limited to the following embodiments.

［システム構成の説明］
図１は、本発明の実施の形態に係るシステム構成を説明する図である。図１に示すように、本実施の形態に係るシステムは、車両に搭載される内燃機関１０を備えている。内燃機関１０は４ストローク１サイクルエンジンであり、複数の気筒を有している。但し、図１には、そのうちの１つの気筒１２のみが描かれている。内燃機関１０は、気筒１２が形成されたシリンダブロック１４と、シリンダブロック１４上に配置されるシリンダヘッド１６と、を有している。気筒１２内にはその軸方向（本実施の形態では鉛直方向）に往復動するピストン１８が配置されている。内燃機関１０の燃焼室２０は、少なくともシリンダブロック１４の壁面と、シリンダヘッド１６の下面と、ピストン１８の上面と、によって画定されている。 [Explanation of system configuration]
FIG. 1 is a diagram illustrating a system configuration according to an embodiment of the present invention. As shown in FIG. 1, the system according to the present embodiment includes an internal combustion engine 10 mounted on a vehicle. The internal combustion engine 10 is a 4-stroke, 1-cycle engine and has a plurality of cylinders. However, in FIG. 1, only one of the cylinders 12 is drawn. The internal combustion engine 10 has a cylinder block 14 in which a cylinder 12 is formed, and a cylinder head 16 arranged on the cylinder block 14. A piston 18 that reciprocates in the axial direction (vertical direction in the present embodiment) is arranged in the cylinder 12. The combustion chamber 20 of the internal combustion engine 10 is defined by at least the wall surface of the cylinder block 14, the lower surface of the cylinder head 16, and the upper surface of the piston 18.

シリンダヘッド１６には、燃焼室２０に連通する吸気ポート２２および排気ポート２４が２つずつ形成されている。吸気ポート２２の燃焼室２０に連通する開口部には吸気バルブ２６が設けられ、排気ポート２４の燃焼室２０に連通する開口部には排気バルブ２８が設けられている。また、シリンダヘッド１６には、燃焼室２０の上部の略中央から先端が燃焼室２０を臨むようにインジェクタ３０が設けられている。インジェクタ３０は燃料タンク、コモンレール、サプライポンプ等から構成される燃料供給系に接続されている。また、インジェクタ３０の先端には複数の噴孔が放射状に形成されており、インジェクタ３０を開弁するとこれらの噴孔から燃料が高圧状態で噴射される。 The cylinder head 16 is formed with two intake ports 22 and two exhaust ports 24 communicating with the combustion chamber 20. An intake valve 26 is provided in the opening communicating with the combustion chamber 20 of the intake port 22, and an exhaust valve 28 is provided in the opening communicating with the combustion chamber 20 of the exhaust port 24. Further, the cylinder head 16 is provided with an injector 30 so that the tip of the cylinder head 16 faces the combustion chamber 20 from substantially the center of the upper part of the combustion chamber 20. The injector 30 is connected to a fuel supply system including a fuel tank, a common rail, a supply pump, and the like. Further, a plurality of injection holes are radially formed at the tip of the injector 30, and when the injector 30 is opened, fuel is injected from these injection holes in a high pressure state.

また、シリンダヘッド１６には、インジェクタ３０が設けられた箇所よりも排気バルブ２８の側の燃焼室２０の上部に点火プラグ３２が設けられている。点火プラグ３２は、中心電極と接地電極とからなる電極部３４を先端に備えている。電極部３４は、インジェクタ３０からの燃料噴霧の外郭面（以下「噴霧外郭面」ともいう。）よりも上方になる範囲（すなわち、噴霧外郭面からシリンダヘッド１６の下面までの範囲）に突き出すように配置されている。より詳しく述べると、電極部３４は、インジェクタ３０の噴孔から放射状に噴射された燃料噴霧のうち、点火プラグ３２に最も近づく燃料噴霧の外郭面よりも上方となる範囲に突き出すように配置されている。なお、図１に描かれる外郭線は、インジェクタ３０からの燃料噴霧のうちの点火プラグ３２に最も近づく燃料噴霧の外郭面を表している。 Further, the cylinder head 16 is provided with a spark plug 32 above the combustion chamber 20 on the side of the exhaust valve 28 from the location where the injector 30 is provided. The spark plug 32 is provided with an electrode portion 34 at the tip thereof, which is composed of a center electrode and a ground electrode. The electrode portion 34 is projected to a range above the outer surface of the fuel spray from the injector 30 (hereinafter, also referred to as “spray outer surface”) (that is, a range from the spray outer surface to the lower surface of the cylinder head 16). It is located in. More specifically, the electrode portion 34 is arranged so as to protrude from the fuel spray radially injected from the injection hole of the injector 30 in a range above the outer surface of the fuel spray closest to the spark plug 32. There is. The outer line drawn in FIG. 1 represents the outer surface of the fuel spray closest to the spark plug 32 among the fuel sprays from the injector 30.

吸気ポート２２は、吸気通路側の入口から燃焼室２０に向けてほぼ真っ直ぐに延び、燃焼室２０との接続部分であるスロート３６において流路断面積が絞られている。吸気ポート２２のこのような形状は、吸気ポート２２から燃焼室２０に供給された吸気にタンブル流を生じさせる。タンブル流は燃焼室２０内で旋回する。より詳しく述べると、タンブル流は、燃焼室２０の上部では吸気ポート２２側から排気ポート２４側に向かい、排気ポート２４側では燃焼室２０の上部から下部に向かう。また、タンブル流は、燃焼室２０の下部では排気ポート２４側から吸気ポート２２側に向かい、吸気ポート２２側では燃焼室２０の下部から上方に向かう。燃焼室２０の下部を形成するピストン１８の上面には、タンブル流を保持するための凹みが形成されている。 The intake port 22 extends substantially straight from the inlet on the intake passage side toward the combustion chamber 20, and the cross section of the flow path is narrowed at the throat 36 which is a connecting portion with the combustion chamber 20. Such a shape of the intake port 22 causes a tumble flow in the intake air supplied from the intake port 22 to the combustion chamber 20. The tumble flow swirls in the combustion chamber 20. More specifically, the tumble flow goes from the intake port 22 side to the exhaust port 24 side at the upper part of the combustion chamber 20 and from the upper part to the lower part of the combustion chamber 20 on the exhaust port 24 side. Further, the tumble flow goes from the exhaust port 24 side to the intake port 22 side at the lower part of the combustion chamber 20, and goes upward from the lower part of the combustion chamber 20 at the intake port 22 side. A recess for holding the tumble flow is formed on the upper surface of the piston 18 forming the lower portion of the combustion chamber 20.

また、図１に示すように、本実施の形態に係るシステムは、制御手段としてのＥＣＵ（Electronic Control Unit）４０を備えている。ＥＣＵ４０は、ＲＡＭ（Random Access Memory）、ＲＯＭ（Read Only Memory）、ＣＰＵ（Central Processing Unit）等を備えている。ＥＣＵ４０は、車両に搭載された各種センサの信号を取り込み処理する。各種センサには、ピストン１８に接続されたクランク軸の回転角度を検出するクランク角センサ４２と、車両の運転者によるアクセルペダルの踏み込み量を検出するアクセル開度センサ４４と、内燃機関１０の冷却水温（以下「エンジン冷却水温」ともいう。）を検出する温度センサ４６と、が少なくとも含まれている。ＥＣＵ４０は、取り込んだ各センサの信号を処理して所定の制御プログラムに従って各種アクチュエータを操作する。ＥＣＵ４０によって操作されるアクチュエータには、上述したインジェクタ３０と点火プラグ３２とが少なくとも含まれている。 Further, as shown in FIG. 1, the system according to the present embodiment includes an ECU (Electronic Control Unit) 40 as a control means. The ECU 40 includes a RAM (Random Access Memory), a ROM (Read Only Memory), a CPU (Central Processing Unit), and the like. The ECU 40 takes in and processes signals from various sensors mounted on the vehicle. The various sensors include a crank angle sensor 42 that detects the rotation angle of the crankshaft connected to the piston 18, an accelerator opening sensor 44 that detects the amount of depression of the accelerator pedal by the driver of the vehicle, and cooling of the internal combustion engine 10. At least a temperature sensor 46 for detecting the water temperature (hereinafter, also referred to as "engine cooling water temperature") is included. The ECU 40 processes the signals of the captured sensors and operates various actuators according to a predetermined control program. The actuator operated by the ECU 40 includes at least the injector 30 and the spark plug 32 described above.

［ＥＣＵ４０による始動時制御］
本実施の形態では、図１に示したＥＣＵ４０による内燃機関１０の冷間始動直後の制御として、排気浄化触媒の活性化を促進する制御（以下「触媒暖機制御」ともいう。）が行われる。排気浄化触媒は、内燃機関１０の排気通路に設けられる触媒であり、一例として、活性化状態にある触媒の雰囲気がストイキ近傍にあるときに排気中の窒素酸化物（ＮＯｘ）、炭化水素（ＨＣ）および一酸化炭素（ＣＯ）を浄化する三元触媒が挙げられる。 [Control at start by ECU 40]
In the present embodiment, as the control immediately after the cold start of the internal combustion engine 10 by the ECU 40 shown in FIG. 1, control for promoting activation of the exhaust gas purification catalyst (hereinafter, also referred to as “catalyst warm-up control”) is performed. .. The exhaust purification catalyst is a catalyst provided in the exhaust passage of the internal combustion engine 10. As an example, nitrogen oxides (NOx) and hydrocarbons (HC) in the exhaust when the atmosphere of the activated catalyst is in the vicinity of stoichiometric. ) And a three-way catalyst that purifies carbon monoxide (CO).

ＥＣＵ４０によって実行される触媒暖機制御について、図２乃至図７を参照して説明する。図２には、触媒暖機制御中のインジェクタ３０による噴射時期と、点火プラグ３２による点火期間の開始時期（電極部３４での放電期間の開始時期）と、が描かれている。図２に示すように、触媒暖機制御中は、インジェクタ３０による１回目の噴射（第１噴射）が吸気行程において行われ、圧縮上死点よりも後の膨張行程において、１回目の噴射に比べて少量（一例として５ｍｍ３／ｓｔ程度）の２回目の噴射（第２噴射）が行われる。以下の説明においては、１回目の噴射（第１噴射）を「吸気行程噴射」とも称し、２回目の噴射（第２噴射）を「膨張行程噴射」とも称す。また、図２に示すように、触媒暖機制御中は、点火プラグ３２による点火期間の開始時期が、圧縮上死点よりも遅角側に設定される。なお、図２においては、点火期間の開始時期よりも遅角側で膨張行程噴射が行われているが、膨張行程噴射が点火期間の開始時期よりも進角側で開始されてもよい。これに関して、図３を参照しながら説明する。 The catalyst warm-up control executed by the ECU 40 will be described with reference to FIGS. 2 to 7. In FIG. 2, the injection timing by the injector 30 during the catalyst warm-up control and the start timing of the ignition period by the spark plug 32 (the start timing of the discharge period at the electrode portion 34) are drawn. As shown in FIG. 2, during the catalyst warm-up control, the first injection (first injection) by the injector 30 is performed in the intake stroke, and in the expansion stroke after the compression top dead center, the first injection is performed. A second injection (second injection) of a smaller amount (for example, about 5 mm 3 / st) is performed. In the following description, the first injection (first injection) is also referred to as "intake stroke injection", and the second injection (second injection) is also referred to as "expansion stroke injection". Further, as shown in FIG. 2, during the catalyst warm-up control, the start time of the ignition period by the spark plug 32 is set to the retard side from the compression top dead center. In FIG. 2, the expansion stroke injection is performed on the retard side of the start time of the ignition period, but the expansion stroke injection may be started on the advance side of the start time of the ignition period. This will be described with reference to FIG.

図３は、膨張行程噴射の噴射期間と、点火期間との時期的関係を説明する図である。図３には、開始時期の異なる３つの噴射Ａ，Ｂ，Ｃ，Ｄが描かれている。噴射Ａ，Ｂ，Ｃ，Ｄは開始時期こそ異なるものの、これらの噴射期間は何れも、膨張行程噴射の噴射期間と等しくされている。また、図３に描かれる点火期間は、触媒暖機制御中の点火期間（設定期間）と等しくされている。図３に示すように、点火期間の開始時期を跨ぐように行われる噴射Ｂ、点火期間中に行われる噴射Ｃ、点火期間の終了時期を跨ぐように行われる噴射Ｄが本実施の形態で言うところの膨張行程噴射に該当し、点火期間の開始時期よりも進角側で行われる噴射Ａは、本実施の形態で言うところの膨張行程噴射には該当しない。この理由は、後述する誘引作用を得るためには、膨張行程噴射の噴射期間の少なくとも一部が点火期間と重複している必要があるためである。 FIG. 3 is a diagram for explaining the temporal relationship between the injection period of the expansion stroke injection and the ignition period. In FIG. 3, three injections A, B, C, and D having different start times are drawn. Although the injections A, B, C, and D have different start times, all of these injection periods are equal to the injection period of the expansion stroke injection. Further, the ignition period drawn in FIG. 3 is equal to the ignition period (set period) during catalyst warm-up control. As shown in FIG. 3, the injection B performed so as to straddle the start time of the ignition period, the injection C performed during the ignition period, and the injection D performed so as to straddle the end time of the ignition period are referred to in the present embodiment. However, the injection A which corresponds to the expansion stroke injection and is performed on the advance side from the start time of the ignition period does not correspond to the expansion stroke injection according to the present embodiment. The reason for this is that at least a part of the injection period of the expansion stroke injection needs to overlap with the ignition period in order to obtain the attractive action described later.

［膨張行程噴射による誘引作用］
図４は、膨張行程噴射による放電火花と初期火炎の誘引作用を説明する図である。図４の上段および中段（または下段）には、点火プラグ３２による点火期間中に電極部３４で生じている放電火花、および、この放電火花によって吸気行程噴射による燃料噴霧を含む混合気から生じた初期火炎の２つの異なる状態が描かれている。図４の上段に示される状態が膨張行程噴射を行わない場合での状態に相当し、図４の中段（または下段）に示される状態が膨張行程噴射を行った場合での状態に相当している。なお、説明の便宜上、図４には、膨張行程噴射による燃料噴霧のうち、点火プラグ３２に最も近づく燃料噴霧のみを示す。 [Attractive action by injection of expansion stroke]
FIG. 4 is a diagram for explaining the attraction action of the discharge spark and the initial flame by the expansion stroke injection. The upper and middle (or lower) stages of FIG. 4 are generated from a discharge spark generated at the electrode portion 34 during the ignition period by the spark plug 32 and an air-fuel mixture containing fuel spray by the intake stroke injection due to the discharge spark. Two different states of the initial flame are depicted. The state shown in the upper part of FIG. 4 corresponds to the state when the expansion stroke injection is not performed, and the state shown in the middle stage (or the lower part) of FIG. 4 corresponds to the state when the expansion stroke injection is performed. There is. For convenience of explanation, FIG. 4 shows only the fuel spray closest to the spark plug 32 among the fuel sprays produced by the expansion stroke injection.

図４の上段に示すように、膨張行程噴射を行わない場合は、電極部３４で生じている放電火花および初期火炎がタンブル流の流れ方向に延びる。一方、図４の中段に示すように、膨張行程噴射を行う場合は、燃料噴霧の周囲に低圧部が形成されるので（エントレインメント）、電極部３４で生じている放電火花および初期火炎がタンブル流の流れ方向とは逆の方向に誘引される。そうすると、図４の下段に示すように、誘引された放電火花および初期火炎が膨張行程噴射による燃料噴霧と接触し、これらを巻き込んで一気に成長する。このような放電火花と初期火炎の両方の誘引による初期火炎の成長は、図３の噴射Ｂ，Ｃの場合において起こる。図３の噴射Ｄの場合については後述する。 As shown in the upper part of FIG. 4, when the expansion stroke injection is not performed, the discharge spark and the initial flame generated at the electrode portion 34 extend in the flow direction of the tumble flow. On the other hand, as shown in the middle part of FIG. 4, when the expansion stroke injection is performed, a low pressure portion is formed around the fuel spray (entrainment), so that the discharge spark and the initial flame generated at the electrode portion 34 are tumbled. It is attracted in the direction opposite to the flow direction of the flow. Then, as shown in the lower part of FIG. 4, the induced discharge spark and the initial flame come into contact with the fuel spray by the expansion stroke injection, and they are involved and grow at once. The growth of the initial flame due to the attraction of both the discharge spark and the initial flame occurs in the case of the injections B and C in FIG. The case of injection D in FIG. 3 will be described later.

膨張行程で噴射された燃料噴霧は、タンブル流や筒内圧力の影響を受ける。そのため、点火プラグ３２による点火期間の開始時期よりも進角側の膨張行程において噴射を行った場合は（図３の噴射Ａ参照）、この噴射による燃料噴霧が電極部３４に辿り着く前にその形状が変化してしまう。そのため、点火プラグ周りの混合気の濃度が安定せずサイクル間の燃焼変動が大きくなってしまう。この点、噴射期間の少なくとも一部が点火期間と重複する膨張行程噴射を行えば（図３の噴射Ｂ，Ｃ参照）、図４の中段に示した誘引作用を活用することができる。そのため、膨張行程噴射による燃料噴霧の形状が変化したとしても、初期火炎を成長させる燃焼（以下「初期燃焼」ともいう。）を安定化させて、サイクル間の燃焼変動を抑えることができる。更には、初期燃焼に続く燃焼、すなわち、成長した初期火炎が吸気行程噴射による燃料噴霧を含む混合気を更に巻き込む燃焼（以下「主燃焼」ともいう。）をも安定化させることができる。図３の噴射Ｄの場合は、点火期間の終了に伴い放電火花が消失するものの、初期火炎は残っている。そのため、膨張行程噴射による燃料噴霧よる誘引作用によって、この燃料噴霧と初期火炎を接触させることができる。従って、図３の噴射Ｂ，Ｃの場合と同様に初期燃焼を安定化させて、サイクル間の燃焼変動を抑えることができる。 The fuel spray injected in the expansion stroke is affected by the tumble flow and the in-cylinder pressure. Therefore, when the injection is performed in the expansion stroke on the advance side of the start time of the ignition period by the spark plug 32 (see injection A in FIG. 3), the fuel spray by this injection is before reaching the electrode portion 34. The shape changes. Therefore, the concentration of the air-fuel mixture around the spark plug is not stable, and the combustion fluctuation between cycles becomes large. In this regard, if the expansion stroke injection in which at least a part of the injection period overlaps with the ignition period is performed (see injections B and C in FIG. 3), the attractive action shown in the middle stage of FIG. 4 can be utilized. Therefore, even if the shape of the fuel spray due to the expansion stroke injection changes, it is possible to stabilize the combustion that grows the initial flame (hereinafter, also referred to as “initial combustion”) and suppress the combustion fluctuation between cycles. Further, it is possible to stabilize the combustion following the initial combustion, that is, the combustion in which the grown initial flame further entrains the air-fuel mixture including the fuel spray by the intake stroke injection (hereinafter, also referred to as “main combustion”). In the case of the injection D of FIG. 3, the discharge spark disappears with the end of the ignition period, but the initial flame remains. Therefore, the fuel spray and the initial flame can be brought into contact with each other by the attractive action of the fuel spray by the expansion stroke injection. Therefore, the initial combustion can be stabilized and the combustion fluctuation between cycles can be suppressed as in the case of the injections B and C in FIG.

［インターバル制御］
触媒暖機制御では、点火プラグ３２による点火期間の開始から膨張行程噴射の終了までのインターバルがＥＣＵ４０によって制御される。図５は、点火期間の開始から膨張行程噴射の終了までのインターバル（点火開始−噴射終了インターバル）と、燃焼変動率との関係を示した図である。図５に示す燃焼変動率は、点火期間の開始時期と終了時期を固定しつつ、噴射期間（つまり噴射量）を固定した膨張行程噴射の開始時期を変更することで得られたものである。図５に示すように、「点火開始−噴射終了インターバル」に対して燃焼変動率は下に凸となる。また、図５において、燃焼変動率が最も小さな値を示すのは、点火期間の開始時期（点火開始）と膨張行程噴射の開始時期（噴射開始）を揃える場合（点火開始＝噴射開始）よりも遅角側においてである。 [Interval control]
In the catalyst warm-up control, the ECU 40 controls the interval from the start of the ignition period by the spark plug 32 to the end of the expansion stroke injection. FIG. 5 is a diagram showing the relationship between the interval (ignition start-injection end interval) from the start of the ignition period to the end of the expansion stroke injection and the combustion fluctuation rate. The combustion fluctuation rate shown in FIG. 5 was obtained by changing the start time of the expansion stroke injection in which the injection period (that is, the injection amount) was fixed while fixing the start time and the end time of the ignition period. As shown in FIG. 5, the combustion fluctuation rate becomes convex downward with respect to the “ignition start-injection end interval”. Further, in FIG. 5, the combustion fluctuation rate shows the smallest value than when the start time of the ignition period (ignition start) and the start time of the expansion stroke injection (injection start) are aligned (ignition start = injection start). On the retard side.

ＥＣＵ４０のＲＯＭには、図５に示した燃焼変動率が最も小さな値を示すときの「点火開始−噴射終了インターバル」の値（以下「ベース適合値」ともいう。）を、エンジン運転状態に関連付けたマップ（以下「ベース適合値マップ」ともいう。）が記憶されており、触媒暖機制御の際にはここから読み出される。図６は、ベース適合値マップの一例を示した図である。図６に示すように、ベース適合値マップは、エンジン回転速度とエンジン負荷ｋｌを両軸とする２次元マップとして作成されている。因みにベース適合値マップは、所定の温度刻みで区切ったエンジン冷却水温域ごとに作成されているので、実際にはこのような２次元マップが複数存在している。また、図６に矢印で示すように、ベース適合値は、エンジン回転速度が高くなるほど、または、エンジン負荷が低くなるほど遅角側の値を取るように設定されている。この理由は、エンジン回転速度が高い場合には初期火炎の成長が相対的に遅くなるからであり、エンジン負荷が高い場合には筒内環境の改善により初期火炎の成長が相対的に速くなるからである。 In the ROM of the ECU 40, the value of the "ignition start-injection end interval" (hereinafter, also referred to as "base conforming value") when the combustion fluctuation rate shown in FIG. 5 shows the smallest value is associated with the engine operating state. The map (hereinafter, also referred to as “base conformity value map”) is stored, and is read from here during catalyst warm-up control. FIG. 6 is a diagram showing an example of a base conformity value map. As shown in FIG. 6, the base conformity value map is created as a two-dimensional map having the engine rotation speed and the engine load kl as both axes. By the way, since the base conformity value map is created for each engine cooling water temperature range divided by a predetermined temperature step, there are actually a plurality of such two-dimensional maps. Further, as shown by an arrow in FIG. 6, the base conformity value is set to take a value on the retard side as the engine speed increases or the engine load decreases. The reason for this is that when the engine speed is high, the growth of the initial flame is relatively slow, and when the engine load is high, the growth of the initial flame is relatively fast due to the improvement of the in-cylinder environment. Is.

触媒暖機制御において、点火プラグ３２による点火期間の開始時期と膨張行程噴射の終了時期は、具体的に次のように決定される。先ず、基本点火時期と遅角補正量とに基づいて、点火プラグ３２による点火期間の開始時期が決定される。そして、ベース適合値マップとエンジン運転状態とから求めたベース適合値を、決定した点火期間の開始時期に加算することで、膨張行程噴射の終了時期が決定される。図７は、内燃機関の冷間始動時における、点火プラグ３２による点火時期（より正確には、点火期間の開始時期）とエンジン冷却水温の推移を示した図である。図７に示す時刻ｔ０においてエンジンが始動されたとすると、その直後の時刻ｔ１から触媒暖機制御を実行する運転モード（以下「触媒暖機モード」ともいう。）が開始され、点火時期が徐々に遅角側の値に設定される。そして、エンジン冷却水温がクライテリア（一例として５０℃）に到達した時刻ｔ２において触媒暖機モードが終了され、その後は点火時期が徐々に進角側の値に設定される。 In the catalyst warm-up control, the start time of the ignition period by the spark plug 32 and the end time of the expansion stroke injection are specifically determined as follows. First, the start time of the ignition period by the spark plug 32 is determined based on the basic ignition timing and the retard correction amount. Then, the end time of the expansion stroke injection is determined by adding the base conforming value obtained from the base conforming value map and the engine operating state to the start time of the determined ignition period. FIG. 7 is a diagram showing changes in the ignition timing (more accurately, the start timing of the ignition period) and the engine cooling water temperature by the spark plug 32 at the time of cold start of the internal combustion engine. Assuming that the engine is started at the time t 0 shown in FIG. 7, the operation mode (hereinafter, also referred to as “catalyst warm-up mode”) for executing the catalyst warm-up control is started from the time t 1 immediately after that, and the ignition timing is set. It is gradually set to the value on the retard side. The engine coolant temperature is criteria (50 ° C. for example) catalyst warming mode is terminated at time t 2 has been reached, then is set to the value of the ignition timing is gradually advanced side.

なお、基本点火時期は、エンジン運転条件（主に、吸入空気量およびエンジン回転速度）に応じた値としてＥＣＵ４０のＲＯＭに記憶されている。また、遅角補正量は、遅角補正量をエンジン冷却水温に関連付けたマップ（以下「遅角補正量マップ」ともいう。）に基づいて決定される。因みにこの遅角補正量マップは、ベース適合値マップと同じくＥＣＵ４０のＲＯＭに記憶されており、触媒暖機制御の際にはここから読み出される。 The basic ignition timing is stored in the ROM of the ECU 40 as a value corresponding to the engine operating conditions (mainly the intake air amount and the engine rotation speed). Further, the retard correction amount is determined based on a map in which the retard correction amount is associated with the engine cooling water temperature (hereinafter, also referred to as a “retangle correction amount map”). Incidentally, this retard correction amount map is stored in the ROM of the ECU 40 as well as the base conformity value map, and is read from here during catalyst warm-up control.

［着火環境が望ましい範囲から外れたときの問題点］
ところで、図１に示したシステムにおいて何らかの要因で着火環境が変化して望ましい範囲から外れた場合には、上述した膨張行程噴射による誘引作用にも関わらず燃焼状態が不安定となる可能性がある。例えば、インジェクタ３０の噴孔にデポジットが堆積した場合には、吸気行程噴射での噴射量が少なくなる。また、吸気行程噴射の噴射量を算出する際の空気量を本来よりも少なく読み違えた場合にも、吸気行程噴射での噴射量が少なくなる。そして、吸気行程噴射での噴射量が少なくなれば、点火プラグ３２の周辺の燃料濃度が薄くなり、初期火炎の成長速度（膨張行程噴射による燃料噴霧と接触する前の初期火炎の成長速度をいう。以下同じ。）が遅くなる。また、吸気バルブ２６や排気バルブ２８のバルブタイミングに関する学習が不良の場合には、燃焼室２０内に残留する排気の割合が増加してしまうので、初期火炎の成長速度が遅くなる。初期火炎の成長速度が遅くなれば、膨張行程噴射による燃料噴霧と初期火炎とを接触させることができず、サイクル間の燃焼変動が大きくなる。 [Problems when the ignition environment is out of the desired range]
By the way, in the system shown in FIG. 1, if the ignition environment changes for some reason and deviates from the desired range, the combustion state may become unstable despite the attractive action of the expansion stroke injection described above. .. For example, when a deposit is accumulated in the injection hole of the injector 30, the injection amount in the intake stroke injection is reduced. Further, even if the amount of air when calculating the injection amount of the intake stroke injection is smaller than the original amount and misread, the injection amount in the intake stroke injection is reduced. When the injection amount in the intake stroke injection is reduced, the fuel concentration around the spark plug 32 becomes thin, and the growth rate of the initial flame (the growth rate of the initial flame before contacting with the fuel spray by the expansion stroke injection). The same applies below.) Is slowed down. Further, if the learning about the valve timing of the intake valve 26 and the exhaust valve 28 is poor, the proportion of exhaust gas remaining in the combustion chamber 20 increases, so that the growth rate of the initial flame becomes slow. If the growth rate of the initial flame is slowed down, the fuel spray by the expansion stroke injection cannot be brought into contact with the initial flame, and the combustion fluctuation between cycles becomes large.

図８は、初期火炎の成長速度が遅くなった場合の筒内状態を説明する図である。図８の上段には着火環境が望ましい範囲内にあるときの筒内状態が描かれており、図４の下段に示した筒内状態と同じである。因みにこの場合は、電極部３４で生じている放電火花および初期火炎が膨張行程噴射による燃料噴霧に誘引されてこれと接触し、初期火炎が一気に成長することは既に述べたとおりである。つまりこの場合は、初期火炎の成長速度に特段の問題はないといえる。一方、図８の下段には、初期火炎の成長速度が遅くなった場合の筒内状態が描かれている。この場合、電極部３４で生じている放電火花は膨張行程噴射による燃料噴霧に誘引されるものの、成長速度の遅い初期火炎の誘引が不十分となる。そのため、膨張行程噴射による燃料噴霧と、初期火炎とを接触させることができなくなる。故に、初期燃焼が不安定となり、初期燃焼に続く主燃焼も不安定となってしまう。 FIG. 8 is a diagram illustrating an in-cylinder state when the growth rate of the initial flame is slowed down. The in-cylinder state when the ignition environment is within a desirable range is drawn in the upper part of FIG. 8, which is the same as the in-cylinder state shown in the lower part of FIG. Incidentally, in this case, the discharge spark and the initial flame generated in the electrode portion 34 are attracted to the fuel spray by the expansion stroke injection and come into contact with the discharge spark, and the initial flame grows at a stretch as described above. In other words, in this case, it can be said that there is no particular problem in the growth rate of the initial flame. On the other hand, in the lower part of FIG. 8, the in-cylinder state when the growth rate of the initial flame is slowed down is drawn. In this case, the discharge spark generated at the electrode portion 34 is attracted to the fuel spray by the expansion stroke injection, but the attraction of the initial flame having a slow growth rate is insufficient. Therefore, the fuel spray by the expansion stroke injection and the initial flame cannot be brought into contact with each other. Therefore, the initial combustion becomes unstable, and the main combustion following the initial combustion also becomes unstable.

また、例えば、点火プラグ３２の交換によって電極部３４の燃焼室２０への突き出し量が減少した場合や、インジェクタ３０の噴口へのデポジットの堆積によって噴霧角が変化した場合には、噴霧外郭面と電極部３４の間の距離が拡大する。噴霧外郭面と電極部３４の間の距離が拡大した場合には、膨張行程噴射による燃料噴霧と、初期火炎とを接触させることができず、サイクル間の燃焼変動が大きくなってしまう可能性がある。 Further, for example, when the amount of protrusion of the electrode portion 34 into the combustion chamber 20 is reduced by replacing the spark plug 32, or when the spray angle is changed due to the accumulation of the deposit at the injection port of the injector 30, the spray outer surface is contacted. The distance between the electrode portions 34 is increased. When the distance between the spray outer surface and the electrode portion 34 is increased, the fuel spray by the expansion stroke injection cannot be brought into contact with the initial flame, and there is a possibility that the combustion fluctuation between cycles becomes large. is there.

図９は、噴霧外郭面と電極部３４の間の距離が拡大した場合の筒内状態を説明する図である。図９の上段には着火環境が望ましい範囲内にあるときの筒内状態が描かれており、図４の下段や図８の上段に示した筒内状態と同じである。一方、図９の下段には、噴霧外郭面と電極部３４の間の距離が拡大した場合の筒内状態が描かれている。この場合は、膨張行程噴射による燃料噴霧の周囲に形成された低圧部から、電極部３４で生じている放電火花および初期火炎までの距離が拡大するので、これらの誘引が不十分となる。そのため、膨張行程噴射による燃料噴霧と、初期火炎とを接触させることができなくなる。なお、図９に描かれる外郭線は、インジェクタ３０からの燃料噴霧のうちの点火プラグ３２に最も近づく燃料噴霧の外郭面を表している。 FIG. 9 is a diagram illustrating an in-cylinder state when the distance between the spray outer surface and the electrode portion 34 is increased. The in-cylinder state when the ignition environment is within a desirable range is drawn in the upper part of FIG. 9, which is the same as the in-cylinder state shown in the lower part of FIG. 4 and the upper part of FIG. On the other hand, in the lower part of FIG. 9, the in-cylinder state when the distance between the spray outer surface and the electrode portion 34 is increased is drawn. In this case, the distance from the low-pressure portion formed around the fuel spray by the expansion stroke injection to the discharge spark and the initial flame generated in the electrode portion 34 increases, so that the attraction thereof becomes insufficient. Therefore, the fuel spray by the expansion stroke injection and the initial flame cannot be brought into contact with each other. The outer line drawn in FIG. 9 represents the outer surface of the fuel spray closest to the spark plug 32 among the fuel sprays from the injector 30.

仮に、点火期間の開始時期を進角すれば、筒内環境が改善する。そのため、初期火炎の成長速度が低下している場合には（図８の下段参照）、その低下を緩和して膨張行程噴射による燃料噴霧と初期火炎とを接触させることができる。また、噴霧外郭面と電極部３４の間の距離が拡大している場合には（図９の下段参照）、初期火炎の成長速度を促進して膨張行程噴射による燃料噴霧と初期火炎とを接触させることができる。しかし、点火期間の開始時期を進角すれば、排気浄化触媒に投入できる排気エネルギが減少することから、今度は排気浄化触媒の活性化に時間を要してしまうことになる。 If the start time of the ignition period is advanced, the in-cylinder environment will be improved. Therefore, when the growth rate of the initial flame is reduced (see the lower part of FIG. 8), the decrease can be alleviated and the fuel spray by the expansion stroke injection can be brought into contact with the initial flame. When the distance between the spray outer surface and the electrode portion 34 is increased (see the lower part of FIG. 9), the growth rate of the initial flame is promoted to bring the fuel spray by the expansion stroke injection into contact with the initial flame. Can be made to. However, if the start time of the ignition period is advanced, the exhaust energy that can be input to the exhaust gas purification catalyst decreases, so that it takes time to activate the exhaust gas purification catalyst this time.

この問題について、図１０を参照しながら詳細に説明する。着火環境が望ましい範囲内にある場合は、吸気行程噴射による燃料噴霧から生じた初期火炎が膨張行程噴射による燃料噴霧と接触できる程度の大きさまで成長するまでの期間を、適切な範囲内の値とすることができる。そのため、図１０の中段に実線（正常時）で示すように、点火時期（より正確には、点火期間の開始時期）を遅角側のクランク角ＣＡ１に設定しても、初期火炎の成長速度を適切な範囲内の値（ｖ１）とすることができる。よって、図１０の上段に実線（正常時）で示すように、燃焼変動率をクライテリアよりも小さくすることができる。しかし、着火環境が変化して望ましい範囲から外れた場合には、吸気行程噴射による燃料噴霧から生じた初期火炎が膨張行程噴射による燃料噴霧と接触できる程度の大きさまで成長するまでの期間が長くなる。そのため、図１０の中段に破線（燃焼悪化時）で示すように、クランク角ＣＡ１に設定したままでは初期火炎の成長速度が適切な範囲外の値（ｖ２）まで低下してしまう。よって、図１０の上段に破線（燃焼悪化時）で示すように、燃焼変動率がクライテリアを上回ることになってしまう。 This problem will be described in detail with reference to FIG. If the ignition environment is within the desired range, the period until the initial flame generated from the fuel spray by the intake stroke injection grows to a size that can contact the fuel spray by the expansion stroke injection is set as a value within the appropriate range. can do. Therefore, as shown by the solid line (normal time) in the middle of FIG. 10, even if the ignition timing (more accurately, the start timing of the ignition period) is set to the crank angle CA 1 on the retard side, the growth of the initial flame The speed can be a value within the appropriate range (v 1 ). Therefore, as shown by the solid line (normal state) in the upper part of FIG. 10, the combustion fluctuation rate can be made smaller than that of the criteria. However, if the ignition environment changes and deviates from the desired range, it takes a long time for the initial flame generated from the fuel spray by the intake stroke injection to grow to a size that can come into contact with the fuel spray by the expansion stroke injection. .. Therefore, as shown by the broken line (when combustion deteriorates) in the middle of FIG. 10, the growth rate of the initial flame drops to a value (v 2 ) outside the appropriate range if the crank angle CA 1 is set. Therefore, as shown by the broken line (when combustion deteriorates) in the upper part of FIG. 10, the combustion fluctuation rate exceeds the criteria.

着火環境が望ましい範囲から外れたとしても、点火時期を進角側に変更すれば、初期燃焼の成長速度の傾向を変えることができる。具体的には、点火時期をクランク角ＣＡ１からクランク角ＣＡ２に設定し直せば、図１０の中段に破線（燃焼悪化時）で示すように、初期火炎の成長速度を適切な範囲外の値（ｖ２）から適切な範囲内の値（ｖ１）に戻すことができる。そうすれば、吸気行程噴射による燃料噴霧から生じた初期火炎を、適切な時期に膨張行程噴射による燃料噴霧と初期火炎とを接触させることができるようになるので、燃焼変動率をクライテリアよりも小さくすることが可能となる。しかし、図１０の下段に示すように、点火時期をクランク角ＣＡ２に設定し直した場合には、点火時期をクランク角ＣＡ１に設定した場合よりも排気エネルギが少なくなることから、排気エネルギの減少分だけ排気浄化触媒の活性化に時間を要してしまうことになる。 Even if the ignition environment is out of the desired range, the tendency of the growth rate of the initial combustion can be changed by changing the ignition timing to the advance side. Specifically, if the ignition timing is reset from the crank angle CA 1 to the crank angle CA 2 , the growth rate of the initial flame is out of the appropriate range as shown by the broken line (when combustion deteriorates) in the middle of FIG. The value (v 2 ) can be returned to a value within the appropriate range (v 1 ). By doing so, the initial flame generated from the fuel spray by the intake stroke injection can be brought into contact with the fuel spray by the expansion stroke injection and the initial flame at an appropriate time, so that the combustion fluctuation rate is smaller than that of the criteria. It becomes possible to do. However, as shown in the lower part of FIG. 10, when the ignition timing is reset to the crank angle CA 2 , the exhaust energy is smaller than that when the ignition timing is set to the crank angle CA 1, and therefore the exhaust energy is reduced. It will take time to activate the exhaust gas purification catalyst by the amount of the decrease.

このような事態を避けるため、本実施の形態では、着火環境の変化が原因で膨張行程噴射による燃料噴霧と初期火炎が接触できなくなっていることが予測された場合に、ベース適合値マップから求めたベース適合値を修正することとしている。図１１は、点火期間の開始から膨張行程噴射の終了までのインターバルの修正手法を説明する図である。図５同様、図１１には、「点火開始−噴射終了インターバル」と、燃焼変動率との関係が描かれている。図５と図１１を比べると分かるように、図５では実線で描かれていた関係が、図１１では破線で描かれている。 In order to avoid such a situation, in the present embodiment, when it is predicted that the fuel spray by the expansion stroke injection and the initial flame cannot be contacted due to the change in the ignition environment, it is obtained from the base conformity value map. The base conformity value will be corrected. FIG. 11 is a diagram illustrating a method for correcting an interval from the start of the ignition period to the end of the expansion stroke injection. Similar to FIG. 5, FIG. 11 depicts the relationship between the “ignition start-injection end interval” and the combustion fluctuation rate. As can be seen by comparing FIG. 5 and FIG. 11, the relationship drawn by the solid line in FIG. 5 is drawn by the broken line in FIG.

図８乃至図１０で説明したように、膨張行程噴射による燃料噴霧と初期火炎が接触できなくなっていると、燃焼変動率が大きくなる。つまり、図１１に示すように、「点火開始−噴射終了インターバル」と燃焼変動率との関係が、破線で描かれる関係から実線で描かれる関係へと変化している。それにも関わらず、ベース適合値に設定したまま膨張行程噴射を実行すれば、燃焼変動率がクライテリアを上回ってしまう。この点、変化後の実線で示す関係に従って、「点火開始−噴射終了インターバル」が拡大する方向にベース適合値を修正すれば、燃焼変動率をクライテリアよりも小さくすることができる。 As described with reference to FIGS. 8 to 10, when the fuel spray by the expansion stroke injection and the initial flame cannot come into contact with each other, the combustion fluctuation rate becomes large. That is, as shown in FIG. 11, the relationship between the “ignition start-injection end interval” and the combustion fluctuation rate has changed from the relationship drawn by the broken line to the relationship drawn by the solid line. Nevertheless, if the expansion stroke injection is executed with the base conforming value set, the combustion fluctuation rate exceeds the criteria. In this regard, if the base conformity value is corrected in the direction in which the "ignition start-injection end interval" expands according to the relationship shown by the solid line after the change, the combustion fluctuation rate can be made smaller than that of the criteria.

なお、既に述べたように、ベース適合値は、着火環境が望ましい範囲内にある場合において燃焼変動率が最も小さな値を示すときの「点火開始−噴射終了インターバル」の値である。そのため、修正後の「点火開始−噴射終了インターバル」に基づいて膨張行程噴射を実行した場合であっても、燃焼変動率そのものが、着火環境が望ましい範囲内にある場合に比べて小さくなることはない。しかしながら、「点火開始−噴射終了インターバル」が拡大する方向にベース適合値を修正すれば、燃焼変動率をクライテリアよりも小さくして、着火環境が望ましい範囲内にある場合における燃焼変動率に近づけることができる。 As already described, the base conformity value is the value of the "ignition start-injection end interval" when the combustion fluctuation rate shows the smallest value when the ignition environment is within a desirable range. Therefore, even when the expansion stroke injection is executed based on the corrected "ignition start-injection end interval", the combustion fluctuation rate itself is smaller than that when the ignition environment is within the desired range. Absent. However, if the base conformity value is modified in the direction of expanding the "ignition start-injection end interval", the combustion fluctuation rate can be made smaller than the criteria and closer to the combustion fluctuation rate when the ignition environment is within the desired range. Can be done.

図１２は、点火期間の開始から膨張行程噴射の終了までのインターバルが拡大する方向にベース適合値を修正した場合における筒内状態を説明する図である。図１２の上段および下段には、何れも着火環境が望ましい範囲から外れた場合の筒内状態が描かれている。但し、図１２の上段と下段で異なるのは、上段が「点火開始−噴射終了インターバル」をベース適合値に固定したまま点火時期を進角させた場合を示しており、下段が「点火開始−噴射終了インターバル」が拡大する方向にベース適合値を修正した場合を示している。 FIG. 12 is a diagram illustrating an in-cylinder state when the base conformity value is corrected in the direction in which the interval from the start of the ignition period to the end of the expansion stroke injection is expanded. In both the upper and lower stages of FIG. 12, the in-cylinder state when the ignition environment deviates from the desired range is drawn. However, the difference between the upper row and the lower row in FIG. 12 shows the case where the ignition timing is advanced while the "ignition start-injection end interval" is fixed at the base conforming value, and the lower row shows the "ignition start-". The case where the base conformity value is corrected in the direction of expanding the "injection end interval" is shown.

図１２の上段と下段を比較すると分かるように、「点火開始−噴射終了インターバル」をベース適合値に固定したままでは（上段参照）、膨張行程噴射による燃料噴霧と、成長速度の遅い初期火炎を接触させることができない。これに対し、「点火開始−噴射終了インターバル」が拡大する方向にベース適合値を修正すれば（下段参照）、初期火炎がある程度まで成長した段階で膨張行程噴射による燃料噴霧と接触させることができる。そのため、初期火炎が膨張行程噴射による燃料噴霧と接触する状態を、着火環境が望ましい範囲内にある場合での両者の接触状態に近づけることができる。よって、初期燃焼を安定化させて燃焼変動を抑えることができ、主燃焼をも安定化させることができる。 As can be seen by comparing the upper and lower rows of FIG. 12, with the "ignition start-injection end interval" fixed at the base conforming value (see the upper row), fuel spraying by expansion stroke injection and initial flame with slow growth rate are performed. Cannot be contacted. On the other hand, if the base conformity value is modified in the direction of expanding the "ignition start-injection end interval" (see the lower row), it can be brought into contact with the fuel spray by the expansion stroke injection when the initial flame has grown to a certain extent. .. Therefore, the state in which the initial flame comes into contact with the fuel spray due to the expansion stroke injection can be brought close to the contact state between the two when the ignition environment is within a desirable range. Therefore, the initial combustion can be stabilized and the combustion fluctuation can be suppressed, and the main combustion can also be stabilized.

また、「点火開始−噴射終了インターバル」が拡大する方向にベース適合値を修正すれば、点火時期の大幅な進角を必要としないので、排気浄化触媒に投入する排気エネルギが低下するのを抑えることもできる。図１３は、点火期間の開始から膨張行程噴射の終了までのインターバルが拡大する方向にベース適合値を修正した場合の効果を説明する図である。図１３に示す「ベース適合値（正常時）」は、着火環境が望ましい範囲内にある場合において、ベース適合値に基づいて触媒暖機制御を実行したときに排気浄化触媒に投入される排気エネルギと、その触媒暖機制御での燃焼変動率と、を表している。また、「ベース適合値（燃焼悪化時）」は、着火環境が望ましい範囲から外れた場合において、ベース適合値に基づいて触媒暖機制御を実行したときの同排気エネルギおよび同燃焼変動率に相当している。両者を比較すると分かるように、「ベース適合値（燃焼悪化時）」では、「ベース適合値（正常時）」と同等の排気エネルギが得られるものの、燃焼変動率がクライテリアよりも大きくなってしまう。 In addition, if the base conformity value is corrected in the direction of expanding the "ignition start-injection end interval", a large advance of the ignition timing is not required, so that the exhaust energy input to the exhaust purification catalyst is suppressed from decreasing. You can also do it. FIG. 13 is a diagram illustrating the effect when the base conformity value is modified in the direction in which the interval from the start of the ignition period to the end of the expansion stroke injection is expanded. The “base conformity value (normal state)” shown in FIG. 13 is the exhaust energy input to the exhaust purification catalyst when the catalyst warm-up control is executed based on the base conformity value when the ignition environment is within a desirable range. And the combustion fluctuation rate in the catalyst warm-up control. In addition, the "base conformity value (when combustion deteriorates)" corresponds to the same exhaust energy and the same combustion fluctuation rate when the catalyst warm-up control is executed based on the base conformity value when the ignition environment deviates from the desired range. are doing. As you can see by comparing the two, the "base conformity value (when combustion deteriorates)" provides the same exhaust energy as the "base conformity value (when combustion deteriorates)", but the combustion fluctuation rate becomes larger than the criteria. ..

また、図１３に示す「点火進角（インターバル固定）」は、着火環境が望ましい範囲から外れた場合において、点火時期（より正確には、点火期間の開始時期）を進角しつつ、ベース適合値に基づいて触媒暖機制御を実行したときの同排気エネルギおよび同燃焼変動率に相当している。「点火進角（インターバル固定）」と「ベース適合値（燃焼悪化時）」を比較すると分かるように、「点火進角（インターバル固定）」では燃焼変動率をクライテリアよりも小さくすることができるものの、排気エネルギが減少してしまう。 Further, the "ignition advance angle (fixed interval)" shown in FIG. 13 is suitable for the base while advancing the ignition timing (more accurately, the start timing of the ignition period) when the ignition environment deviates from the desired range. It corresponds to the same exhaust energy and the same combustion fluctuation rate when the catalyst warm-up control is executed based on the values. As you can see by comparing the "ignition advance (fixed interval)" and the "base conformity value (when combustion deteriorates)", the "ignition advance (fixed interval)" can make the combustion fluctuation rate smaller than the criteria. , Exhaust energy is reduced.

図１３に示す「本発明」は、着火環境が望ましい範囲から外れた場合において、修正後のベース適合値に基づいて触媒暖機制御を実行したときの同排気エネルギおよび同燃焼変動率に相当している。「本発明」と他を比較すると分かるように、「本発明」は燃焼変動率をクライテリアよりも小さくすることができ、また、「ベース適合値（正常時）」での排気エネルギよりは低いものの、「点火進角（インターバル固定）」での排気エネルギよりも高い排気エネルギを得ることができる。従って、着火環境が望ましい範囲から外れた場合においても、燃焼変動率が大きくなることを抑えつつ、排気浄化触媒の早期活性化に必要な排気エネルギを確保することができる。 The “present invention” shown in FIG. 13 corresponds to the same exhaust energy and the same combustion fluctuation rate when the catalyst warm-up control is executed based on the corrected base conformance value when the ignition environment is out of the desired range. ing. As can be seen by comparing the "invention" with others, the "invention" can make the combustion fluctuation rate smaller than the criteria, and although it is lower than the exhaust energy at the "base conformity value (normal state)". , It is possible to obtain an exhaust energy higher than the exhaust energy at the "ignition advance angle (fixed interval)". Therefore, even when the ignition environment deviates from the desirable range, it is possible to secure the exhaust energy required for the early activation of the exhaust purification catalyst while suppressing the increase in the combustion fluctuation rate.

［実施の形態での具体的処理］
図１４は、本発明の実施の形態においてＥＣＵ４０が実行する処理の一例を示すフローチャートである。なお、この図に示すルーチンは、内燃機関１０の始動後、各気筒においてサイクルごとに繰り返し実行されるものとする。 [Specific processing in the embodiment]
FIG. 14 is a flowchart showing an example of the process executed by the ECU 40 in the embodiment of the present invention. It is assumed that the routine shown in this figure is repeatedly executed for each cycle in each cylinder after the internal combustion engine 10 is started.

図１４に示すルーチンでは、先ず、エンジン冷却水温がクライテリアに到達しているか否か、または、触媒暖機モードの終了に関するフラグが出されているか否かが判定される（ステップＳ１００）。本ステップＳ１００では具体的に、温度センサ４６の検出値に基づいてエンジン冷却水温がクライテリア（図７参照）に到達しているか否か、または、終了フラグ（ステップＳ１１０参照）が立てられているか否かが判定される。そして、エンジン冷却水温がクライテリアに到達していると判定された場合、または、終了フラグが立てられていると判定された場合（“Ｙｅｓ”の場合）、本ルーチンを抜ける。 In the routine shown in FIG. 14, first, it is determined whether or not the engine cooling water temperature has reached the criteria, or whether or not the flag relating to the end of the catalyst warm-up mode is issued (step S100). Specifically, in this step S100, whether or not the engine cooling water temperature has reached the criteria (see FIG. 7) based on the detected value of the temperature sensor 46, or whether or not the end flag (see step S110) is set. Is judged. Then, when it is determined that the engine cooling water temperature has reached the criteria, or when it is determined that the end flag is set (in the case of "Yes"), this routine is exited.

ステップＳ１００において、エンジン冷却水温がクライテリアに到達していないと判定され、尚且つ、終了フラグも立てられていないと判定された場合（“Ｎｏ”の場合）、エンジン運転状態に基づいて、点火プラグ３２による点火期間の開始時期と、膨張行程噴射の終了時期とが決定される（ステップＳ１０２）。本ステップＳ１０２では先ず、温度センサ４６の検出値に基づくエンジン冷却水温と、遅角補正量マップとに基づいて、遅角補正量が求められる。また、遅角補正量と基本点火時期とに基づいて、点火プラグ３２による点火期間の開始時期が決定される。また、クランク角センサ４２の検出値に基づいて算出されたエンジン回転速度、アクセル開度センサ４４の検出値に基づいて算出されたエンジン負荷、および、温度センサ４６の検出値に基づくエンジン冷却水温と、ベース適合値マップと、に基づいてベース適合値が求められる。そして、求めたベース適合値を、決定した点火プラグ３２による点火期間の開始時期に加算することで、膨張行程噴射の終了時期が決定される。 In step S100, when it is determined that the engine cooling water temperature has not reached the criteria and the end flag is not set (in the case of "No"), the spark plug is based on the engine operating state. The start time of the ignition period according to 32 and the end time of the expansion stroke injection are determined (step S102). In this step S102, first, the retard correction amount is obtained based on the engine cooling water temperature based on the detection value of the temperature sensor 46 and the retard correction amount map. Further, the start time of the ignition period by the spark plug 32 is determined based on the retard correction amount and the basic ignition timing. Further, the engine rotation speed calculated based on the detection value of the crank angle sensor 42, the engine load calculated based on the detection value of the accelerator opening sensor 44, and the engine cooling water temperature based on the detection value of the temperature sensor 46. , The base conformance value map and the base conformity value are obtained based on. Then, by adding the obtained base conformity value to the start time of the ignition period by the determined spark plug 32, the end time of the expansion stroke injection is determined.

ステップＳ１０２に続いて、着火環境の変化に関する判定が行われる（ステップＳ１０４）。本ステップＳ１０４では例えば、触媒暖機制御の開始後におけるＧａｔ３０のばらつき（標準偏差）σがクライテリアを上回るか否かが判定される。クランク角センサ４２のロータには３０°間隔で歯が設けられており、クランク角センサ４２はクランク軸が３０°回転する毎に信号を発するように構成されている。Ｇａｔ３０は、その信号と信号の間の時間、つまりクランク軸が３０°回転するのに要する時間として算出される。図１５は、内燃機関の冷間始動時におけるＧａｔ３０と、このＧａｔ３０のばらつきσの推移の一例を示した図である。図１５の横軸はエンジン始動後の経過時間を表し、時刻ｔ１は触媒暖機制御の開始時期を表している。図１５に示すように、時刻ｔ１から時刻ｔ３までの間はＧａｔ３０の変動が小さい。故に、Ｇａｔ３０のばらつきσがクライテリアよりも小さいと判定される。Ｇａｔ３０のばらつきσがクライテリアよりも小さいと判定された場合（“Ｎｏ”の場合）、ステップＳ１０８に進む。 Following step S102, a determination regarding a change in the ignition environment is made (step S104). In this step S104, for example, it is determined whether or not the variation (standard deviation) σ of Gat 30 after the start of the catalyst warm-up control exceeds the criteria. The rotor of the crank angle sensor 42 is provided with teeth at intervals of 30 °, and the crank angle sensor 42 is configured to emit a signal every time the crankshaft rotates by 30 °. Gat30 is calculated as the time between the signals, that is, the time required for the crankshaft to rotate 30 °. FIG. 15 is a diagram showing an example of the transition of the Gat 30 at the time of cold start of the internal combustion engine and the variation σ of the Gat 30. The horizontal axis of FIG. 15 represents the elapsed time after engine start, the time t 1 denotes the start time of the catalyst warm-up control. As shown in FIG. 15, the fluctuation of Gat 30 is small between the time t 1 and the time t 3 . Therefore, it is determined that the variation σ of Gat 30 is smaller than that of the criteria. If it is determined that the variation σ of Gat 30 is smaller than the criteria (in the case of “No”), the process proceeds to step S108.

一方、図１５に示すように、時刻ｔ３から時刻ｔ４までの間はＧａｔ３０の変動が大きくなる。故に、Ｇａｔ３０のばらつきσがクライテリアよりも大きいと判定される。Ｇａｔ３０のばらつきσがクライテリアを上回ると判定された場合（“Ｙｅｓ”の場合）、何らかの要因で着火環境が変化して望ましい範囲から外れており、膨張行程噴射による燃料噴霧と初期火炎が接触できなくなっている可能性があると判断できる。そのため、点火プラグ３２による点火期間の開始時期と、膨張行程噴射の終了時期とが修正される（ステップＳ１０６）。本ステップＳ１０６では、先ず、エンジン冷却水温と遅角補正量マップとに基づいて、遅角補正量が求められる。また、遅角補正量と基本点火時期とに基づいて、点火プラグ３２による点火期間の開始時期が決定される。また、エンジン回転速度、エンジン負荷およびエンジン冷却水温と、ベース適合値マップと、に基づいて、ベース適合値が求められる。ここまでの処理は、ステップＳ１０２の処理と同じである。本ステップＳ１０６では、求めたベース適合値を、決定した点火プラグ３２による点火期間の開始時期に加算し、更に、インターバル拡大用の補正値（一定値）を更に加算する。これにより、膨張行程噴射の終了時期が決定される。 On the other hand, as shown in FIG. 15, the fluctuation of Gat 30 becomes large from the time t 3 to the time t 4 . Therefore, it is determined that the variation σ of Gat 30 is larger than that of the criteria. If it is determined that the variation σ of Gat30 exceeds the criteria (in the case of “Yes”), the ignition environment has changed for some reason and is out of the desired range, and the fuel spray by the expansion stroke injection and the initial flame cannot contact each other. It can be judged that there is a possibility. Therefore, the start time of the ignition period by the spark plug 32 and the end time of the expansion stroke injection are corrected (step S106). In this step S106, first, the retard correction amount is obtained based on the engine cooling water temperature and the retard correction amount map. Further, the start time of the ignition period by the spark plug 32 is determined based on the retard correction amount and the basic ignition timing. Further, the base conforming value is obtained based on the engine speed, the engine load, the engine cooling water temperature, and the base conforming value map. The processing up to this point is the same as the processing in step S102. In this step S106, the obtained base conformity value is added to the start time of the ignition period by the determined spark plug 32, and a correction value (constant value) for expanding the interval is further added. Thereby, the end time of the expansion stroke injection is determined.

ステップＳ１０６に続いて、ステップＳ１０８では、排気温度がクライテリアＴ１を上回るか否かが判定される。本ステップでは例えば排気浄化触媒の下流に設けた温度センサの検出値に基づいて、排気温度がクライテリアＴ１を上回るか否かが判定される。そして、エンジン冷却水温がクライテリアに到達していると判定された場合（“Ｙｅｓ”の場合）、終了フラグが立てられる（ステップＳ１１０）。 Following step S106, at step S108, the exhaust temperature is whether exceeds the criteria T 1 is determined. In this step based on the detected value of the temperature sensor provided downstream of the example exhaust gas purifying catalyst, whether the exhaust gas temperature exceeds the criteria T 1 is determined. Then, when it is determined that the engine cooling water temperature has reached the criteria (in the case of "Yes"), the end flag is set (step S110).

以上、図１４に示したルーチンによれば、触媒暖機制御の開始後Ｇａｔ３０のばらつきσに基づいて着火環境の変化に関する判定を行うことができる。また、判定の結果、何らかの要因で着火環境が変化して望ましい範囲から外れている可能性があると判断した場合には、点火期間の開始から膨張行程噴射の終了までのインターバルを拡大させることができる。よって、着火環境が望ましい範囲から外れたとしても、サイクル間の燃焼変動を抑えることができる。 As described above, according to the routine shown in FIG. 14, it is possible to determine the change in the ignition environment based on the variation σ of the Gat 30 after the start of the catalyst warm-up control. In addition, if it is determined as a result of the judgment that the ignition environment may change and deviate from the desired range for some reason, the interval from the start of the ignition period to the end of the expansion stroke injection may be extended. it can. Therefore, even if the ignition environment deviates from the desired range, the combustion fluctuation between cycles can be suppressed.

［実施の形態の変形例］
ところで、上記実施の形態では、燃焼室２０に形成されるタンブル流が、排気ポート２４側では燃焼室２０の上部から下部に向かい、且つ、吸気ポート２２側では燃焼室２０の下部から上方に向かうように旋回するとした。しかし、このタンブル流が逆方向、つまり、吸気ポート２２側では燃焼室２０の上部から下方に向かい、且つ、排気ポート２４側では燃焼室２０の下部から上部に向かうように旋回するものであってもよい。但しこの場合は、点火プラグ３２の配置箇所を、排気バルブ２８側から吸気バルブ２６側に変更する必要がある。点火プラグ３２の配置箇所をこのように変更すれば、タンブル流の流れ方向において、インジェクタ３０の下流側に点火プラグ３２が位置することになるので、膨張行程噴射による誘引作用を得ることができる。
更に言えば、燃焼室２０にタンブル流が形成されなくてもよい。上述したサイクル間の燃焼変動はタンブル流の形成の有無に関係なく発生するためである。 [Modified example of the embodiment]
By the way, in the above embodiment, the tumble flow formed in the combustion chamber 20 goes from the upper part to the lower part of the combustion chamber 20 on the exhaust port 24 side, and goes upward from the lower part of the combustion chamber 20 on the intake port 22 side. I decided to turn like this. However, this tumble flow turns in the opposite direction, that is, from the upper part of the combustion chamber 20 to the lower side on the intake port 22 side, and from the lower part to the upper part on the exhaust port 24 side. May be good. However, in this case, it is necessary to change the location of the spark plug 32 from the exhaust valve 28 side to the intake valve 26 side. If the location of the spark plug 32 is changed in this way, the spark plug 32 is located on the downstream side of the injector 30 in the flow direction of the tumble flow, so that an attractive action by the expansion stroke injection can be obtained.
Furthermore, the tumble flow does not have to be formed in the combustion chamber 20. This is because the combustion fluctuation between cycles described above occurs regardless of the presence or absence of the formation of a tumble flow.

また、上記実施の形態では、インジェクタ３０による１回目の噴射（第１噴射）を吸気行程で行い、圧縮上死点よりも後の膨張行程において２回目の噴射（第２噴射）を行った。しかし、この１回目の噴射（第１噴射）を圧縮行程で行ってもよい。また、１回目の噴射（第１噴射）を複数回数に分割して行ってもよいし、分割後の噴射の一部を吸気行程で行い、残りを圧縮行程で行ってもよい。このように、１回目の噴射（第１噴射）の噴射時期および噴射回数については、各種の変形が可能である。 Further, in the above embodiment, the first injection (first injection) by the injector 30 is performed in the intake stroke, and the second injection (second injection) is performed in the expansion stroke after the compression top dead center. However, this first injection (first injection) may be performed in a compression stroke. Further, the first injection (first injection) may be divided into a plurality of times, or a part of the divided injection may be performed in the intake stroke and the rest may be performed in the compression stroke. As described above, various modifications can be made to the injection timing and the number of injections of the first injection (first injection).

また、上記実施の形態では、図１４のステップＳ１０６の処理において、インターバル拡大用の補正値を一定値とした。しかし、インターバル拡大用の補正値は一定値でなくてもよい。例えば、図１５に示したＧａｔ３０のばらつきσとクライテリアの差が大きくなるほどインターバル拡大用の補正値が大きくなるように設定してもよい。このような設定を行う場合は、ＥＣＵ４０のＲＯＭに、Ｇａｔ３０のばらつきσとクライテリアの差と、インターバル拡大用の補正値との関係（図１６参照）を表すマップを記憶しておき、ステップＳ１０６の処理に際してここから読み出せばよい。 Further, in the above embodiment, in the process of step S106 of FIG. 14, the correction value for interval expansion is set to a constant value. However, the correction value for interval expansion does not have to be a constant value. For example, the correction value for interval expansion may be set to increase as the difference between the variation σ of Gat 30 and the criteria shown in FIG. 15 increases. When making such a setting, a map showing the relationship (see FIG. 16) between the variation σ of Gat30 and the difference between the criteria and the correction value for interval expansion is stored in the ROM of the ECU 40, and the map in step S106 is stored. It may be read from here at the time of processing.

また、上記実施の形態では、図１４のステップＳ１０４の処理において、着火環境の変化に関する判定を触媒暖機制御の開始後におけるＧａｔ３０のばらつきσを用いて行った。しかし、このばらつきσの代わりに、点火期間の開始時期から、燃焼質量割合（ＭＦＢ）が１０％に到達するまでのクランク角期間（以下「ＳＡ−ＣＡ１０」ともいう。）のばらつきσを用いて行ってもよい。ＭＦＢは、燃焼室２０に別途設けた筒内圧センサ（図示しない）と、クランク角センサ４２とを利用して得られる筒内圧データの解析結果に基づいて算出され、算出したＭＦＢに基づいてＳＡ−ＣＡ１０が算出される。なお、筒内圧データの解析結果からＭＦＢを算出する手法や、ＳＡ−ＣＡ１０を算出する手法については、例えば特開２０１５−０９４３３９号公報や特開２０１５−０９８７９９号公報に詳述されていることから、本明細書での説明は省略する。 Further, in the above embodiment, in the process of step S104 of FIG. 14, the determination regarding the change in the ignition environment was performed using the variation σ of Gat 30 after the start of the catalyst warm-up control. However, instead of this variation σ, the variation σ of the crank angle period (hereinafter, also referred to as “SA-CA10”) from the start time of the ignition period to the time when the combustion mass ratio (MFB) reaches 10% is used. You may go. The MFB is calculated based on the analysis result of the in-cylinder pressure data obtained by using the in-cylinder pressure sensor (not shown) separately provided in the combustion chamber 20 and the crank angle sensor 42, and the SA- is based on the calculated MFB. CA10 is calculated. The method of calculating the MFB from the analysis result of the in-cylinder pressure data and the method of calculating the SA-CA10 are described in detail in, for example, Japanese Patent Application Laid-Open No. 2015-09439 and Japanese Patent Application Laid-Open No. 2015-098799. , The description in this specification is omitted.

図１７は、燃焼変動率とＳＡ−ＣＡ１０のばらつきσとの関係を示す図である。また、図１８は、内燃機関の冷間始動時におけるＳＡ−ＣＡ１０のばらつきσの推移の一例を示した図である。図１７に示すように、ＳＡ−ＣＡ１０のばらつきσが大きくなるほど、燃焼変動率が大きくなる。つまり、ＳＡ−ＣＡ１０のばらつきσは、燃焼変動率と相関がある。そのため、例えば図１８の時刻ｔ５から時刻ｔ６までの間のように、触媒暖機制御の開始後におけるＳＡ−ＣＡ１０のばらつきσがクライテリアを上回ると判定された場合に、何らかの要因で着火環境が変化して望ましい範囲から外れており、膨張行程噴射による燃料噴霧と初期火炎が接触できなくなっている可能性があると判断して、図１４のステップＳ１０６以降の処理を行ってもよい。
更に言えば、Ｇａｔ３０やＳＡ−ＣＡ１０に限られず、点火期間においてクランク軸が６０°回転するのに要する時間（Ｇａｔ６０）、点火期間の開始時期からＭＦＢが５％に到達するまでのクランク角期間（ＳＡ−ＣＡ５）や、点火期間の開始時期からＭＦＢが１５％に到達するまでのクランク角期間（ＳＡ−ＣＡ１５）を用いてもよい。このように、膨張行程噴射による燃料噴霧と初期火炎の接触状態を判定できるパラメータ（サイクル間の燃焼変動に関連するパラメータ）であれば、上記実施の形態での着火環境の変化に関する判定の指標として用いることができる。 FIG. 17 is a diagram showing the relationship between the combustion fluctuation rate and the variation σ of SA-CA10. Further, FIG. 18 is a diagram showing an example of the transition of the variation σ of SA-CA10 at the time of cold start of the internal combustion engine. As shown in FIG. 17, the larger the variation σ of SA-CA10, the larger the combustion fluctuation rate. That is, the variation σ of SA-CA10 correlates with the combustion fluctuation rate. Therefore, for example, as in the period from time t 5 in FIG. 18 to time t 6, when the variation in SA-CA10 after the start of the catalyst warm-up control σ is determined to exceed the criterion, ignition environment for some reason May change and deviate from the desired range, and it may be determined that there is a possibility that the fuel spray by the expansion stroke injection and the initial flame cannot come into contact with each other, and the processing after step S106 in FIG. 14 may be performed.
Furthermore, it is not limited to Gat30 and SA-CA10, the time required for the crankshaft to rotate 60 ° during the ignition period (Gat60), and the crank angle period from the start time of the ignition period until the MFB reaches 5% (Gat60). SA-CA5) or the crank angle period (SA-CA15) from the start time of the ignition period to the time when the MFB reaches 15% may be used. As described above, if the parameter can determine the contact state between the fuel spray by the expansion stroke injection and the initial flame (parameter related to the combustion fluctuation between cycles), it can be used as an index for determining the change in the ignition environment in the above embodiment. Can be used.

１０ 内燃機関
１２ 気筒
１４ シリンダブロック
１６ シリンダヘッド
１８ ピストン
２０ 燃焼室
２２ 吸気ポート
２４ 排気ポート
３０ インジェクタ
３２ 点火プラグ
３４ 電極部
３６ スロート
４０ ＥＣＵ
４２ クランク角センサ
４４ アクセル開度センサ
４６ 温度センサ 10 Internal combustion engine 12 Cylinder 14 Cylinder block 16 Cylinder head 18 Piston 20 Combustion chamber 22 Intake port 24 Exhaust port 30 Injector 32 Spark plug 34 Electrode part 36 Throat 40 ECU
42 Crank angle sensor 44 Accelerator opening sensor 46 Temperature sensor

Claims (4)

燃焼室上部に設けられて複数の噴孔から筒内に燃料を噴射するインジェクタと、
放電火花を用いて筒内の混合気に点火する点火プラグであって、前記複数の噴孔から噴射される燃料の下流、且つ、前記複数の噴孔から噴射された燃料噴霧のうち前記点火プラグに最も近づく燃料噴霧の外郭面よりも上方に設けられる点火プラグと、
前記燃焼室からの排気を浄化する排気浄化触媒と、を備える内燃機関を制御する内燃機関の制御装置であって、
前記制御装置は、前記排気浄化触媒を活性化させる制御として、圧縮上死点よりも遅角側の点火期間で放電火花が発生するように前記点火プラグを制御すると共に、前記圧縮上死点よりも進角側での第１噴射と、前記圧縮上死点よりも遅角側での第２噴射であって、噴射期間が前記点火期間の少なくとも一部と重複する第２噴射と、を行うように前記インジェクタを制御し、
前記制御装置は更に、
前記排気浄化触媒を活性化させる制御において、前記点火期間の開始時期から前記第２噴射の噴射期間の終了時期までのインターバルを制御し、
サイクル間の燃焼変動に関連するパラメータが閾値を上回るか否かを判定し、
前記パラメータが前記閾値を上回ると判定された場合は、前記パラメータが前記閾値を下回ると判定された場合に比べて、前記インターバルが拡大するように前記点火プラグと前記インジェクタを制御する
ことを特徴とする内燃機関の制御装置。 An injector provided at the top of the combustion chamber that injects fuel into the cylinder from multiple injection holes,
A spark plug that ignites an air-fuel mixture in a cylinder using a discharge spark, and is a spark plug among the fuel sprays injected from the plurality of injection holes downstream of the fuel injected from the plurality of injection holes. The spark plug provided above the outer surface of the fuel spray that is closest to
An internal combustion engine control device that controls an internal combustion engine including an exhaust gas purification catalyst that purifies the exhaust gas from the combustion chamber.
As a control for activating the exhaust gas purification catalyst, the control device controls the spark plug so that a discharge spark is generated in an ignition period on the retard side of the compression top dead center, and from the compression top dead center. The first injection on the advance angle side and the second injection on the retard side from the compression top dead center, the injection period of which overlaps with at least a part of the ignition period, are performed. By controlling the injector so as
The control device further
In the control for activating the exhaust gas purification catalyst, the interval from the start time of the ignition period to the end time of the injection period of the second injection is controlled.
Determine if the parameters associated with combustion fluctuations between cycles exceed the threshold
If the parameter is determined to exceed the threshold value, said parameter is compared with the case where it is determined to be below the threshold value, before hearing Ntabaru controls the spark plug and the injector so as to enlarge A characteristic internal combustion engine control device. 前記制御装置は、前記パラメータが前記閾値を上回ると判定された場合は、前記パラメータと前記閾値の乖離量が増えるほど前記インターバルの拡大量を大きくすることを特徴とする請求項１に記載の内燃機関の制御装置。 Wherein the control device, if the parameter is judged to exceed the threshold, an internal combustion according to claim 1, characterized in that to increase the expansion amount of the interval as the deviation amount of said parameter and said threshold value is increased Engine control device. 前記第２噴射の終了時期が、前記点火期間の終了時期よりも進角側であることを特徴とする請求項１または２に記載の内燃機関の制御装置。 The control device for an internal combustion engine according to claim 1 or 2, wherein the end time of the second injection is on the advance side with respect to the end time of the ignition period. 前記パラメータが、クランク軸が所定角度回転するまでに要する時間のばらつき、または、前記点火期間の開始時期から燃焼質量割合が所定割合に到達するまでのクランク角期間のばらつきであることを特徴とする請求項１乃至３何れか１項に記載の内燃機関の制御装置。 The parameter is characterized by a variation in the time required for the crankshaft to rotate by a predetermined angle, or a variation in the crank angle period from the start time of the ignition period to the time when the combustion mass ratio reaches the predetermined ratio. The control device for an internal combustion engine according to any one of claims 1 to 3.
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