WO2017022630A1 - Internal-combustion engine egr control system, internal-combustion engine, and internal-combustion engine egr control method - Google Patents

Internal-combustion engine egr control system, internal-combustion engine, and internal-combustion engine egr control method Download PDF

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Publication number
WO2017022630A1
WO2017022630A1 PCT/JP2016/072196 JP2016072196W WO2017022630A1 WO 2017022630 A1 WO2017022630 A1 WO 2017022630A1 JP 2016072196 W JP2016072196 W JP 2016072196W WO 2017022630 A1 WO2017022630 A1 WO 2017022630A1
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egr
fuel injection
target value
combustion engine
engine
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PCT/JP2016/072196
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French (fr)
Japanese (ja)
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良文 花村
信夫 青木
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いすゞ自動車株式会社
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Publication of WO2017022630A1 publication Critical patent/WO2017022630A1/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
    • F02D21/00—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas
    • F02D21/06—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air
    • F02D21/08—Controlling engines characterised by their being supplied with non-airborne oxygen or other non-fuel gas peculiar to engines having other non-fuel gas added to combustion air the other gas being the exhaust gas of 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
    • 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
    • F02D41/10—Introducing corrections for particular operating conditions for acceleration
    • 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
    • F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems

Definitions

  • the present invention is an internal combustion engine having an EGR (Exhaust Gas Recirculation) system configured with an EGR valve in an EGR passage, and the opening degree of the EGR valve is set using a NOx target value corresponding to the operating state of the engine.
  • EGR exhaust Gas Recirculation
  • the present invention relates to an EGR control system for an internal combustion engine to be controlled, an internal combustion engine, and an EGR control method for the internal combustion engine.
  • an internal combustion engine such as a diesel engine mounted on a vehicle is provided with an EGR system in order to control the concentration of NOx (nitrogen oxide) contained in exhaust gas to a certain concentration or less.
  • NOx nitrogen oxide
  • the feed-forward control is performed so that the flow rate of the low pressure EGR is constant regardless of the load of the internal combustion engine, and the flow rate of the high pressure EGR is set to the target so that the oxygen concentration in the exhaust gas is constant.
  • An exhaust gas recirculation control device for an internal combustion engine that performs feedback control to a value has been proposed (see, for example, Patent Document 1).
  • an object of the present invention is an internal combustion engine including an EGR system configured to have an EGR valve in an EGR passage, depending on the operating state of the internal combustion engine.
  • the NOx concentration target value is increased without increasing the NOx concentration target value in order to suppress the occurrence of smoke when the engine is operating in an accelerated state. It is an object to provide an EGR control system for an internal combustion engine, an internal combustion engine, and an EGR control method for an internal combustion engine that can perform EGR while avoiding the above.
  • An EGR control system for an internal combustion engine for achieving the above object is an internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage, and corresponds to a target value of NOx concentration of EGR.
  • the control device In an EGR control system for an internal combustion engine provided with a control device that controls the opening degree of the EGR valve based on a target value of the in-cylinder oxygen concentration, the control device is in EGR control and the engine operating state is in an acceleration state.
  • at least one of delaying the fuel injection timing of the in-cylinder fuel injection or lowering the fuel injection pressure is performed without increasing the NOx concentration target value set based on the operating state of the engine. Note that this reduction in fuel injection pressure reduces the fuel injection pressure by reducing the common rail pressure when a common rail system is used.
  • the delay amount of the fuel injection timing and the pressure decrease amount of the combustion injection pressure are experimentally determined beforehand with respect to an index indicating the acceleration state of the engine, for example, a change amount of the accelerator opening, a change amount of the fuel injection amount, It is calculated and stored as map data or the like, and is calculated by referring to this map data when an acceleration state occurs during EGR control.
  • the delay in fuel injection timing and the pressure drop in combustion injection pressure may be only one, but they may be combined, and the optimum ratio of the delay amount and the pressure drop amount in the combination is set experimentally and converted into map data. be able to.
  • the fuel injection timing is delayed or the fuel injection pressure is decreased. Since the generation of smoke is avoided, an increase in NOx emission can be prevented, and deterioration of exhaust gas performance can be suppressed. Also, in the EGR control in the acceleration state, it is not necessary to change the NOx concentration target value set for the steady state to the NOx concentration target value for the acceleration time, and therefore, the same control as the steady state EGR control can be performed. .
  • An internal combustion engine for achieving the above object is configured to include the EGR control system for the internal combustion engine, and can exhibit the same effects as the EGR system for the internal combustion engine.
  • an EGR control method for an internal combustion engine for achieving the above object is an internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage, and the EGR NOx concentration target value.
  • the EGR control method for an internal combustion engine that controls the opening degree of the EGR valve based on the in-cylinder oxygen concentration target value corresponding to the above, when the engine operating state is in the acceleration state during EGR control, the engine operating state
  • at least one of the delay of the fuel injection timing of the in-cylinder fuel injection or the decrease of the fuel injection pressure is performed without increasing the NOx concentration target value set based on the above. According to this method, the same operational effects as the EGR control system for the internal combustion engine can be obtained.
  • an internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage
  • the EGR control system for an internal combustion engine that controls the opening degree of the EGR valve using the NOx concentration target value according to the engine
  • the operating state of the engine is in an accelerated state, and in order to suppress the generation of smoke, based on the operating state of the engine Without increasing the set NOx concentration target value, EGR can be performed while avoiding an increase in the NOx emission amount.
  • FIG. 1 is a diagram schematically showing a configuration of an EGR system in an internal combustion engine according to an embodiment.
  • FIG. 2 is a diagram schematically illustrating a configuration of an EGR control system for an internal combustion engine according to the embodiment.
  • FIG. 3 is a diagram showing the input / output relationship of the NOx concentration target value calculation unit in the second control unit of FIG.
  • FIG. 4 is a diagram schematically showing a configuration of an EGR control system for an internal combustion engine according to a reference technique.
  • the internal combustion engine of the present embodiment is configured to include the EGR control system 40 of the internal combustion engine of the present embodiment, and has the same operational effects as the operational effects of the EGR control system 40 of the internal combustion engine described later. Can do.
  • an internal combustion engine (hereinafter referred to as an engine) 10 includes an EGR system 1 and includes an engine body 11, an intake passage 12, an exhaust passage 13, and an EGR passage 14.
  • the EGR passage 14 is provided by connecting the exhaust passage 13 and the intake passage 12, and is provided with an EGR cooler 15 and an EGR valve 16 that use engine cooling water as a cooling medium in order from the upstream side.
  • fresh air A introduced from the atmosphere is sent to the combustion chamber in the cylinder (cylinder) 11c together with the EGR gas Ge flowing into the intake manifold 11a from the EGR passage 14 as necessary.
  • the engine 10 is mixed and compressed with fuel injected from a fuel injection device (not shown), and the fuel burns to generate power in the engine 10.
  • the exhaust gas G generated by combustion in the engine 10 flows out from the exhaust manifold 11b to the exhaust passage 13.
  • an intake flow sensor (MAF sensor) 21 that detects the intake flow rate
  • an intake pressure sensor 22 that detects the intake pressure
  • an intake temperature sensor 23 that detects the intake temperature, which constitute the intake system sensor group Sg1.
  • an NOx concentration sensor 20 for detecting the NOx concentration in the exhaust gas, which constitutes the exhaust system sensor group Sg2
  • an exhaust lambda sensor (exhaust air excess) for detecting the excess air ratio of the exhaust gas. Rate sensor
  • a control device 30 for controlling the EGR system 1 of the internal combustion engine is provided.
  • the control device 30 calculates the detection values of the sensors 20 to 24 for each preset control time based on the signals transmitted from the sensors 20 to 24 and stores necessary detection value data. To do.
  • the control device 30 is normally incorporated in an engine control unit (ECU) that controls the overall operation state of the engine 10, but may be provided independently.
  • the control device 30 includes a program for executing the EGR control method of the present embodiment, a memory configured to store various data, and a processor (CPU or the like) for executing the program. May be.
  • the control apparatus 30 may be comprised from ASIC (Application
  • ASIC Application
  • FIG. 4 is a diagram schematically showing the configuration of an EGR control system for an internal combustion engine, and is a diagram showing a reference technique for explaining the present embodiment. This reference technique constitutes a part of the present invention.
  • the inventors use the EGR control system 40X as shown in FIG. 4 to set the first NOx concentration target value Nt1 calculated based on the engine operating state such as the engine speed and the fuel injection amount in the actual exhaust gas G. It has been considered to control the opening degree of the EGR valve 16 based on the in-cylinder oxygen concentration so that the NOx concentration becomes equal.
  • the control amount C of the target opening degree that controls the opening degree of the EGR valve 16 is a basic control amount (pre-control) calculated by the feedforward control 44 of the fourth control unit 41 based on the in-cylinder oxygen concentration target value Dt.
  • the first control unit 41 calculates the NOx concentration based on the detection values from the intake system sensor group Sg1 such as the intake flow rate sensor 21, the intake pressure sensor 22, the intake air temperature sensor 23, and the exhaust lambda sensor 24.
  • a value Nc is calculated.
  • the NOx concentration sensor 46 uses the NOx concentration sensor.
  • the first NOx concentration target value Nt1 is calculated by referring to the map data on the basis of the engine speed and the fuel injection amount, and the second control unit 42X performs the smoke on the first NOx concentration target value Nt1.
  • the second NOx concentration target value Nt2 is calculated in consideration of the limit.
  • the third control unit 43 calculates the in-cylinder oxygen concentration target value Dt
  • the fourth control unit 44 calculates a basic control amount that is a target value for feedforward control (pre-control).
  • Pre-control amount) Ca is calculated.
  • the fifth control unit 45 inputs the in-cylinder oxygen concentration target value Dt and the in-cylinder oxygen concentration calculated value Dc calculated by the first control unit 41 to obtain a target value for feedback control (PID control).
  • a certain correction control amount Cb is calculated.
  • the adder 47 adds the basic control amount Ca and the correction control amount Cb to calculate the valve control amount C. With this valve control amount C, the opening degree of the EGR valve 16 is adjusted and controlled.
  • the first NOx concentration target value Nt1 that is the target value of the NOx concentration in the exhaust gas is calculated by referring to the map data based on the engine speed and the fuel injection amount.
  • the first NOx concentration target value Nt1 is set as the NOx concentration target value Nt in the steady state of the engine.
  • the NOx concentration target value (first NOx concentration target value Nt1) set based on the engine operating state is increased, whereby the cylinder
  • the internal oxygen concentration target value Dt is increased to avoid excessive smoke.
  • a lower limit threshold for avoiding smoke generation of the exhaust lambda is set in advance, and the exhaust lambda is set to this lower threshold.
  • the NOx concentration target value is increased so as not to become lower, and the first NOx concentration target value Nt1 used for EGR control is set to a larger value.
  • the control amount C of the target opening degree for controlling the opening degree of the EGR valve 16 is a basic control amount (pre-control amount) Ca calculated by feedforward control of the fourth control unit 44 based on the in-cylinder oxygen concentration target value Dt.
  • the EGR valve 16 is based on the in-cylinder oxygen concentration target value Dt corresponding to the NOx concentration target value Nt1 of EGR. It is the EGR control system 40 of the internal combustion engine provided with the control apparatus 30 which controls the opening degree.
  • the first control unit 41 calculates the NOx concentration based on the detection values from the intake system sensor group Sg1 such as the intake flow rate sensor 21, the intake pressure sensor 22, the intake air temperature sensor 23, the exhaust lambda sensor 24, and the like.
  • the value Nc is calculated.
  • the in-cylinder oxygen concentration calculation value Dc is calculated by taking into account the exhaust gas amount and the oxygen concentration of the internal EGR gas, without calculating only the intake air amount and the oxygen concentration, the exhaust gas amount of the external EGR gas and the inside of the oxygen concentration. It is preferable to calculate.
  • the NOx amount generated in the cylinder and the NOx concentration of the exhaust gas exhausted from the cylinder are calculated from the calculated oxygen concentration value Dc in the cylinder and the estimated value of the combustion chamber temperature, and set as the NOx concentration calculated value Nc.
  • the NOx correction is performed.
  • the first NOx target value Nt1 is calculated by referring to the map data based on the detected value of the exhaust lambda sensor 24, the engine speed Ne and the fuel injection amount q.
  • the second NOx target value Nt1 and the detected value of the exhaust lambda sensor 24 are input to the second control unit 42.
  • the second control unit 42 when the operation state of the engine 10 is in a steady state, smoke is predicted to be generated at the first NOx target value Nt1 from a preset calculation formula, map data, or the like.
  • the NOx concentration that does not cause smoke is set as the second NOx target value Nt2.
  • a so-called smoke limit is performed. If there is no possibility that smoke will occur, the first NOx target value Nt1 is set as the second NOx target value Nt2 as it is.
  • the second control unit 42 calculates the second NOx target value Nt2.
  • the EGR control for suppressing the generation of smoke is based on the operating state of the engine 10 (engine speed Ne or fuel injection amount q (or load Q)).
  • the fuel injection pressure Pcr is lowered by lowering the fuel injection pressure Pcr by lowering the pressure of the common rail.
  • the second NOx concentration target value Nt2 remains the first NOx concentration target value Nt1
  • the correction by the NOx correction coefficient NCf is not performed, and the correction ratio is 1
  • Whether the engine operating state is a steady state or an acceleration state is determined by setting, for example, a rate of change ⁇ Ac of an opening degree Ac of an accelerator pedal (not shown) provided in a driver seat of a vehicle equipped with the engine 10 in advance.
  • a rate of change ⁇ Ac of an opening degree Ac of an accelerator pedal (not shown) provided in a driver seat of a vehicle equipped with the engine 10 in advance.
  • the delay amount ⁇ tf of the fuel injection timing tf and the pressure decrease amount ⁇ Pcr of the combustion injection pressure Pcr are indicators indicating the acceleration state of the engine 10, for example, the change amount ⁇ Ac of the accelerator opening degree Ac and the change amount ⁇ qc of the fuel injection amount q.
  • it is obtained experimentally in advance and stored as map data or the like, and is calculated with reference to this map data when an acceleration state occurs during EGR control.
  • the delay of the fuel injection timing tf and the pressure drop of the combustion injection pressure pcr may be only one, but they may be combined, and the optimum ratio between the delay amount ⁇ tf and the pressure drop amount ⁇ pcr in the combination is set experimentally. Map data can be converted.
  • the NOx concentration Nt is determined by correcting the reference NOx concentration Nt0 by the in-cylinder oxygen concentration D, the correction by the intake manifold temperature (intake air temperature) Ti, and the correction by the engine coolant temperature Tc. It is obtained by correcting with the fuel injection timing tf and correcting with the fuel injection pressure (common rail pressure) Pcr.
  • the delay amount ⁇ tf or the pressure drop amount ⁇ pcr is set based on the relationship of the equation (1).
  • the third control unit 43 inputs the detection values of the intake pressure sensor 22 and the intake temperature sensor 23, and calculates the in-cylinder oxygen concentration target value Dt with respect to the third NOx target value Nt3.
  • the fourth control unit 44 calculates a basic control amount (pre-control amount) Ca that is a target value for feedforward control (pre-control) with respect to the calculated in-cylinder oxygen concentration target value Dt. In calculating the basic control amount Ca, it is preferable to consider the internal EGR gas.
  • the oxygen concentration target value Dto of the external EGR is calculated from the in-cylinder oxygen concentration target value Dt, which is the target value of the oxygen concentration in the cylinder, using the determination of the exhaust gas amount and the oxygen concentration of the external EGR gas.
  • the EGR gas amount Ge in the external EGR is calculated, and the opening degree of the EGR valve 16 that can supply the EGR gas amount Ge is defined as a pre-control amount Ca.
  • the fifth controller 45 calculates the in-cylinder oxygen concentration target value Dt calculated for the third NOx target value Nt3 by the third controller 43 and the in-cylinder calculated by the first controller 41.
  • An oxygen concentration calculation value Dc is input to calculate a correction control amount Cb that is a target value for feedback control (PID control).
  • the adding unit 47 adds the basic control amount Ca and the correction control amount Cb to calculate the valve control amount C.
  • the valve opening amount of the EGR valve 16 is adjusted and controlled by the valve control amount C.
  • This EGR control method for an internal combustion engine is an engine (internal combustion engine) 10 having an EGR system 1 constituted by having an EGR valve 16 in an EGR passage 14, and in-cylinder oxygen corresponding to the NOx concentration target value Nt1 of EGR.
  • the engine (internal combustion engine) 10 and the internal combustion engine EGR control method configured as described above, even when the operating state of the engine 10 is in the acceleration state, the NOx concentration target value Nt1 is not increased.
  • the generation of smoke is avoided by delaying the fuel injection timing tf or lowering the fuel injection pressure Pcr, it is possible to prevent an increase in the NOx emission amount and suppress deterioration of exhaust gas performance.
  • the NOx concentration target value Nt1 set for the steady state need not be changed to the NOx concentration target value for the acceleration, and therefore, the same control as the steady state EGR control is performed. it can.
  • the operation state of the engine is set based on the operation state of the engine in order to suppress smoke generation in the acceleration state. This is useful in that EGR can be performed without increasing the NOx concentration target value without increasing the NOx emission amount.
  • EGR system for internal combustion engine 10
  • Engine internal combustion engine
  • 11 Engine body 11a Intake manifold 11b Exhaust manifold 11c Cylinder 12 Intake passage 13 Exhaust passage 14
  • EGR passage 15 EGR cooler 16
  • NOx concentration sensor 21
  • Intake pressure sensor 23
  • Intake temperature sensor 24
  • Exhaust lambda sensor (exhaust excess ratio sensor) 30 control device 40 40X EGR control system 41 of internal combustion engine 1st control part 42, 42X 2nd control part 43 3rd control part 44 4th control part 45 5th control part 46 NOx correction part 47 addition part A fresh air
  • C EGR valve opening control amount
  • Ca EGR valve opening basic control amount
  • Cb EGR valve opening correction control amount
  • Dt In-cylinder oxygen concentration target value Dc In-cylinder oxygen concentration calculation value
  • G Ga Exhaust gas Ge EGR gas NCf NOx correction coefficient Sg1 Intake system sensor group

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust-Gas Circulating Devices (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)

Abstract

A control device 30 is configured in such a way that if the operating state of an engine 10 is a state of acceleration, while under EGR control for suppressing the generation of smoke, a fuel injection timing tf for injection of fuel into a cylinder is delayed, and/or a fuel injection pressure Pcr is reduced, without increasing a NOx concentration target value Nt1 set on the basis of the operating state of the engine 10.

Description

内燃機関のＥＧＲ制御システム、内燃機関、及び内燃機関のＥＧＲ制御方法EGR control system for internal combustion engine, internal combustion engine, and EGR control method for internal combustion engine
　本発明は、ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲ(Exhaust Gas Recirculation)システムを備えた内燃機関で、エンジンの運転状態に対応したＮＯｘ目標値を使用してＥＧＲバルブの開度を制御する内燃機関のＥＧＲ制御システム、内燃機関、及び内燃機関のＥＧＲ制御方法に関する。 The present invention is an internal combustion engine having an EGR (Exhaust Gas Recirculation) system configured with an EGR valve in an EGR passage, and the opening degree of the EGR valve is set using a NOx target value corresponding to the operating state of the engine. The present invention relates to an EGR control system for an internal combustion engine to be controlled, an internal combustion engine, and an EGR control method for the internal combustion engine.
　一般的に、車両に搭載されるディーゼルエンジン等の内燃機関には、排気ガスに含まれるＮＯｘ（窒素酸化物）の濃度を一定濃度以下に制御するために、ＥＧＲシステムが備えられる。 Generally, an internal combustion engine such as a diesel engine mounted on a vehicle is provided with an EGR system in order to control the concentration of NOx (nitrogen oxide) contained in exhaust gas to a certain concentration or less.
　また、これに関連して、内燃機関の負荷にかかわらず低圧ＥＧＲの流量を一定となるようにフィードフォワード制御するとともに、排気中の酸素濃度が一定となるように、高圧ＥＧＲの流量をその目標値にフィードバック制御する内燃機関の排気還流制御装置が提案されている（例えば、特許文献１参照）。 In this connection, the feed-forward control is performed so that the flow rate of the low pressure EGR is constant regardless of the load of the internal combustion engine, and the flow rate of the high pressure EGR is set to the target so that the oxygen concentration in the exhaust gas is constant. An exhaust gas recirculation control device for an internal combustion engine that performs feedback control to a value has been proposed (see, for example, Patent Document 1).
　しかしながら、この参考技術における過給遅れ対策では、第１ＮＯｘ濃度目標値Ｎｔ１を大きくする変更をしているので、ＮＯｘ排出量が過渡状態の一時的にではあるが増加することになり、排気ガスが悪化することになり、好ましくないという問題がある。 However, in the supercharging delay countermeasure in this reference technique, since the first NOx concentration target value Nt1 is changed, the NOx emission amount temporarily increases in a transient state, and the exhaust gas is increased. There is a problem that it becomes worse and is not preferable.
日本国特開２０１２－２３７２９０号公報Japanese Unexamined Patent Publication No. 2012-237290
　本発明の態様は、上記のことを鑑みてなされたものであり、その目的は、ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲシステムを備えた内燃機関で、内燃機関の運転状態に応じたＮＯｘ濃度目標値を使用してＥＧＲバルブの開度を制御する場合に、エンジンの運転状態が加速状態でスモーク発生の抑制のためにＮＯｘ濃度目標値を大きくすることなく、ＮＯｘ排出量の増加を回避してＥＧＲをすることができる内燃機関のＥＧＲ制御システム、内燃機関及び内燃機関のＥＧＲ制御方法を提供することにある。 An aspect of the present invention has been made in view of the above, and an object of the present invention is an internal combustion engine including an EGR system configured to have an EGR valve in an EGR passage, depending on the operating state of the internal combustion engine. When controlling the opening of the EGR valve using the NOx concentration target value, the NOx concentration target value is increased without increasing the NOx concentration target value in order to suppress the occurrence of smoke when the engine is operating in an accelerated state. It is an object to provide an EGR control system for an internal combustion engine, an internal combustion engine, and an EGR control method for an internal combustion engine that can perform EGR while avoiding the above.
　上記の目的を達成するための本発明の態様の内燃機関のＥＧＲ制御システムは、ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲシステムを備えた内燃機関で、ＥＧＲのＮＯｘ濃度目標値に対応する気筒内酸素濃度目標値に基づいて前記ＥＧＲバルブの開度を制御する制御装置を備えた内燃機関のＥＧＲ制御システムにおいて、前記制御装置が、ＥＧＲ制御中でエンジンの運転状態が加速状態にあるときは、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を増加させることなく、シリンダ内燃料噴射の燃料噴射時期の遅延又は燃料噴射圧力の低下の少なくとも一方を行うように構成される。なお、この燃料噴射圧力の低下は、コモンレールシステムを使用している場合には、コモンレールの圧力を低下することで燃料噴射圧力を低下させる。 An EGR control system for an internal combustion engine according to an aspect of the present invention for achieving the above object is an internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage, and corresponds to a target value of NOx concentration of EGR. In an EGR control system for an internal combustion engine provided with a control device that controls the opening degree of the EGR valve based on a target value of the in-cylinder oxygen concentration, the control device is in EGR control and the engine operating state is in an acceleration state In some cases, at least one of delaying the fuel injection timing of the in-cylinder fuel injection or lowering the fuel injection pressure is performed without increasing the NOx concentration target value set based on the operating state of the engine. Note that this reduction in fuel injection pressure reduces the fuel injection pressure by reducing the common rail pressure when a common rail system is used.
　また、燃料噴射時期の遅延量および燃焼噴射圧力の圧力低下量は、エンジンの加速状態を示す指標、例えば、アクセル開度の変化量や燃料噴射量の変化量等に対して、予め実験的に求めてマップデータ等で記憶しておき、ＥＧＲ制御時に加速状態が発生したときにこのマップデータを参照して算出する。なお、燃料噴射時期の遅延および燃焼噴射圧力の圧力低下は一方のみでもよいが、組み合せでもよく、組み合せの場合の遅延量と圧力低下量の最適な割合は実験的に設定してマップデータ化することができる。 Further, the delay amount of the fuel injection timing and the pressure decrease amount of the combustion injection pressure are experimentally determined beforehand with respect to an index indicating the acceleration state of the engine, for example, a change amount of the accelerator opening, a change amount of the fuel injection amount, It is calculated and stored as map data or the like, and is calculated by referring to this map data when an acceleration state occurs during EGR control. Note that the delay in fuel injection timing and the pressure drop in combustion injection pressure may be only one, but they may be combined, and the optimum ratio of the delay amount and the pressure drop amount in the combination is set experimentally and converted into map data. be able to.
　この構成によれば、エンジンの運転状態が加速状態のときでも、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を増加することなく、燃料噴射時期の遅延又は燃料噴射圧力の低下で、スモークの発生を回避するので、ＮＯｘの排出量の増加を防止でき、排気ガス性能の悪化を抑制することができる。また、加速状態におけるＥＧＲ制御においても、定常時用で設定されるＮＯｘ濃度目標値を加速時用のＮＯｘ濃度目標値に変更しないで済むので、定常状態のＥＧＲ制御と同じ制御で行うことができる。 According to this configuration, even when the engine operating state is the acceleration state, without increasing the NOx concentration target value set based on the engine operating state, the fuel injection timing is delayed or the fuel injection pressure is decreased. Since the generation of smoke is avoided, an increase in NOx emission can be prevented, and deterioration of exhaust gas performance can be suppressed. Also, in the EGR control in the acceleration state, it is not necessary to change the NOx concentration target value set for the steady state to the NOx concentration target value for the acceleration time, and therefore, the same control as the steady state EGR control can be performed. .
　そして、上記の目的を達成するための内燃機関は、上記の内燃機関のＥＧＲ制御システムを備えて構成され、上記の内燃機関のＥＧＲシステムと同様の作用効果を奏することができる。 An internal combustion engine for achieving the above object is configured to include the EGR control system for the internal combustion engine, and can exhibit the same effects as the EGR system for the internal combustion engine.
　また、上記の目的を達成するための本発明の態様の内燃機関のＥＧＲ制御方法は、ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲシステムを備えた内燃機関で、ＥＧＲのＮＯｘ濃度目標値に対応する気筒内酸素濃度目標値に基づいて、前記ＥＧＲバルブの開度を制御する内燃機関のＥＧＲ制御方法において、ＥＧＲ制御中でエンジンの運転状態が加速状態にあるときは、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を増加させることなく、シリンダ内燃料噴射の燃料噴射時期の遅延又は燃料噴射圧力の低下の少なくとも一方を行うことを特徴とする方法である。この方法によれば、上記の内燃機関のＥＧＲ制御システムと同様の作用効果を奏することができる。 Further, an EGR control method for an internal combustion engine according to an aspect of the present invention for achieving the above object is an internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage, and the EGR NOx concentration target value. In the EGR control method for an internal combustion engine that controls the opening degree of the EGR valve based on the in-cylinder oxygen concentration target value corresponding to the above, when the engine operating state is in the acceleration state during EGR control, the engine operating state In this method, at least one of the delay of the fuel injection timing of the in-cylinder fuel injection or the decrease of the fuel injection pressure is performed without increasing the NOx concentration target value set based on the above. According to this method, the same operational effects as the EGR control system for the internal combustion engine can be obtained.
　本発明の内燃機関のＥＧＲ制御システム、内燃機関、及び内燃機関のＥＧＲ制御方法によれば、ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲシステムを備えた内燃機関で、内燃機関の運転状態に応じたＮＯｘ濃度目標値を使用してＥＧＲバルブの開度を制御する内燃機関のＥＧＲ制御システムにおいて、エンジンの運転状態が加速状態でスモーク発生の抑制のために、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を大きくすることなく、ＮＯｘ排出量の増加を回避してＥＧＲをすることができる。 According to an EGR control system for an internal combustion engine, an internal combustion engine, and an EGR control method for an internal combustion engine according to the present invention, an internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage, In the EGR control system for an internal combustion engine that controls the opening degree of the EGR valve using the NOx concentration target value according to the engine, the operating state of the engine is in an accelerated state, and in order to suppress the generation of smoke, based on the operating state of the engine Without increasing the set NOx concentration target value, EGR can be performed while avoiding an increase in the NOx emission amount.
図１は、実施の形態の内燃機関におけるＥＧＲシステムの構成を模式的に示す図である。FIG. 1 is a diagram schematically showing a configuration of an EGR system in an internal combustion engine according to an embodiment. 図２は、実施の形態の内燃機関のＥＧＲ制御システムの構成を模式的に示す図である。FIG. 2 is a diagram schematically illustrating a configuration of an EGR control system for an internal combustion engine according to the embodiment. 図３は、図２の第２制御部におけるＮＯｘ濃度目標値算出部の出入力の関係を示す図である。FIG. 3 is a diagram showing the input / output relationship of the NOx concentration target value calculation unit in the second control unit of FIG. 図４は、参考技術の内燃機関のＥＧＲ制御システムの構成を模式的に示す図である。FIG. 4 is a diagram schematically showing a configuration of an EGR control system for an internal combustion engine according to a reference technique.
　以下、本発明に係る実施の形態の内燃機関のＥＧＲ制御システム、内燃機関、及び内燃機関のＥＧＲ制御方法について、図面を参照しながら説明する。なお、本実施の形態の内燃機関は、本実施の形態の内燃機関のＥＧＲ制御システム４０を備えて構成され、後述する内燃機関のＥＧＲ制御システム４０が奏する作用効果と同様の作用効果を奏することができる。 Hereinafter, an EGR control system for an internal combustion engine, an internal combustion engine, and an EGR control method for an internal combustion engine according to embodiments of the present invention will be described with reference to the drawings. The internal combustion engine of the present embodiment is configured to include the EGR control system 40 of the internal combustion engine of the present embodiment, and has the same operational effects as the operational effects of the EGR control system 40 of the internal combustion engine described later. Can do.
　図１に示すように、本実施の形態の内燃機関（以下エンジン）１０は、ＥＧＲシステム１を備えて構成され、エンジン本体１１と吸気通路１２と排気通路１３とＥＧＲ通路１４を備えている。このＥＧＲ通路１４は、排気通路１３と吸気通路１２とを接続して設けられ、上流側より順に、エンジン冷却水を冷却媒体とするＥＧＲクーラー１５、ＥＧＲバルブ１６が設けられている。 As shown in FIG. 1, an internal combustion engine (hereinafter referred to as an engine) 10 according to the present embodiment includes an EGR system 1 and includes an engine body 11, an intake passage 12, an exhaust passage 13, and an EGR passage 14. The EGR passage 14 is provided by connecting the exhaust passage 13 and the intake passage 12, and is provided with an EGR cooler 15 and an EGR valve 16 that use engine cooling water as a cooling medium in order from the upstream side.
　そして、大気から導入される新気Ａが、必要に応じて、ＥＧＲ通路１４から吸気マニホールド１１ａに流入するＥＧＲガスＧｅを伴って、気筒（シリンダ）１１ｃ内の燃焼室に送られ、燃焼室にて燃料噴射装置（図示しない）より噴射された燃料と混合圧縮されて、燃料が燃焼することで、エンジン１０に動力を発生させる。そして、エンジン１０で燃焼により発生した排気ガスＧが、排気マニホールド１１ｂから排気通路１３に流出するが、その一部はＥＧＲ通路１４にＥＧＲガスＧｅとして流れ、残りの排気ガスＧａ（＝Ｇ－Ｇｅ）は、排気浄化処理装置（図示しない）により浄化処理された後、マフラー（図示しない）を経由して大気へ放出される。 Then, fresh air A introduced from the atmosphere is sent to the combustion chamber in the cylinder (cylinder) 11c together with the EGR gas Ge flowing into the intake manifold 11a from the EGR passage 14 as necessary. The engine 10 is mixed and compressed with fuel injected from a fuel injection device (not shown), and the fuel burns to generate power in the engine 10. Then, the exhaust gas G generated by combustion in the engine 10 flows out from the exhaust manifold 11b to the exhaust passage 13. A part of the exhaust gas G flows into the EGR passage 14 as EGR gas Ge, and the remaining exhaust gas Ga (= G−Ge). ) Is purified by an exhaust purification device (not shown) and then released to the atmosphere via a muffler (not shown).
　また、吸気通路１２には、吸気系センサ群Ｓｇ１を構成する、吸気流量を検出する吸気流量センサ（ＭＡＦセンサ）２１、吸気圧力を検出する吸気圧力センサ２２及び吸気温度を検出する吸気温度センサ２３が設けられるとともに、排気通路１３には、排気系センサ群Ｓｇ２を構成する、排気ガス中のＮＯｘ濃度を検出するＮＯｘ濃度センサ２０と、排気の空気過剰率を検出する排気ラムダセンサ（排気空気過剰率センサ）２４が設けられる。これらのセンサ２０～２４の信号は、予め設定された制御時間毎に、後述する制御装置３０に送信される。 Further, in the intake passage 12, an intake flow sensor (MAF sensor) 21 that detects the intake flow rate, an intake pressure sensor 22 that detects the intake pressure, and an intake temperature sensor 23 that detects the intake temperature, which constitute the intake system sensor group Sg1. Are provided in the exhaust passage 13, and an NOx concentration sensor 20 for detecting the NOx concentration in the exhaust gas, which constitutes the exhaust system sensor group Sg2, and an exhaust lambda sensor (exhaust air excess) for detecting the excess air ratio of the exhaust gas. Rate sensor) 24 is provided. The signals of these sensors 20 to 24 are transmitted to the control device 30 described later at every preset control time.
　また、内燃機関のＥＧＲシステム１を制御する制御装置３０が備えられる。この制御装置３０は、上記のセンサ２０～２４より送信された信号に基づいて、予め設定された制御時間毎に、センサ２０～２４の検出値を算出するとともに、必要な検出値のデータを記憶する。この制御装置３０は、通常は、エンジン１０の運転状態全般を制御するエンジンコントロールユニット（ＥＣＵ）に組み込まれるが、独立して設けてもよい。なお、制御装置３０は、本実施の形態のEGR制御方法を実行するためのプログラムや各種データを記憶するように構成されたメモリとプログラムを実行するためのプロセッサ（CPU等）などから構成されていてもよい。また、制御装置３０は、本実施の形態のEGR制御方法を実行するように設計されたASIC（Application Specific Integrated Circuit）などから構成されていてもよい。 Further, a control device 30 for controlling the EGR system 1 of the internal combustion engine is provided. The control device 30 calculates the detection values of the sensors 20 to 24 for each preset control time based on the signals transmitted from the sensors 20 to 24 and stores necessary detection value data. To do. The control device 30 is normally incorporated in an engine control unit (ECU) that controls the overall operation state of the engine 10, but may be provided independently. The control device 30 includes a program for executing the EGR control method of the present embodiment, a memory configured to store various data, and a processor (CPU or the like) for executing the program. May be. Moreover, the control apparatus 30 may be comprised from ASIC (Application | Specific * Integrated * Circuit) etc. which were designed so that the EGR control method of this Embodiment may be performed.
　以下、実施の形態に係る内燃機関のＥＧＲ制御方法を図２乃至図４を参照しながら説明する。図４は、内燃機関のＥＧＲ制御システムの構成を模式的に示す図であり、本実施の形態を説明するための参考技術を示した図である。なお、この参考技術は本発明の一部を構成するものである。 Hereinafter, an EGR control method for an internal combustion engine according to an embodiment will be described with reference to FIGS. FIG. 4 is a diagram schematically showing the configuration of an EGR control system for an internal combustion engine, and is a diagram showing a reference technique for explaining the present embodiment. This reference technique constitutes a part of the present invention.
　発明者らは、図４に示すようなＥＧＲ制御システム４０Ｘで、エンジン回転数及び燃料噴射量等のエンジン運転状態に基づいて算出される第１ＮＯｘ濃度目標値Ｎｔ１に、実際の排気ガスＧ中のＮＯｘ濃度がなるように、気筒内酸素濃度に基づいて、ＥＧＲバルブ１６の開度を制御することを考えてきた。 The inventors use the EGR control system 40X as shown in FIG. 4 to set the first NOx concentration target value Nt1 calculated based on the engine operating state such as the engine speed and the fuel injection amount in the actual exhaust gas G. It has been considered to control the opening degree of the EGR valve 16 based on the in-cylinder oxygen concentration so that the NOx concentration becomes equal.
　すなわち、ＥＧＲバルブ１６の開度を制御する目標開度の制御量Ｃは、気筒内酸素濃度目標値Ｄｔを基に第４制御部４１のフィードフォワード制御４４で算出される基本制御量（プリ制御量）Ｃａに、気筒内酸素濃度目標値Ｄｔと、各種センサからの入力を基に算出される気筒内酸素濃度の計算値Ｄｃとの差（誤差）ΔＤ（＝Ｄｔ－Ｄｃ）を基に第５制御部４５のフィードバック制御（ＰＩＤ制御）４５で算出される補正制御量Ｃｂを加算してバルブ制御量Ｃが算出される（Ｃ＝Ｃａ＋Ｃｂ）。 That is, the control amount C of the target opening degree that controls the opening degree of the EGR valve 16 is a basic control amount (pre-control) calculated by the feedforward control 44 of the fourth control unit 41 based on the in-cylinder oxygen concentration target value Dt. (Quantity) Ca based on the difference (error) ΔD (= Dt−Dc) between the cylinder oxygen concentration target value Dt and the calculated value Dc of the cylinder oxygen concentration calculated based on the input from various sensors. 5 The valve control amount C is calculated by adding the correction control amount Cb calculated by the feedback control (PID control) 45 of the control unit 45 (C = Ca + Cb).
　より詳細に説明すると、吸気流量センサ２１、吸気圧力センサ２２、吸気温度センサ２３、排気ラムダセンサ２４などの吸気系センサ群Ｓｇ１からの検出値を基に、第１制御部４１で、ＮＯｘ濃度算出値Ｎｃが算出される。それと共に、ＮＯｘ濃度検出値Ｎｄを基本としてＮＯｘ濃度算出値Ｎｃによる算出値を補正する値を用いて、制御用の算出値を補正するとの考えに基づいて、ＮＯｘ補正部４６で、ＮＯｘ濃度センサ２０の検出値であるＮＯｘ濃度検出値Ｎｄが入力され、このＮＯｘ濃度検出値ＮｄとＮＯｘ濃度算出値ＮｃとからＮＯｘ補正係数（補正比率）Ｎｃｆ＝Ｎｄ／Ｎｃが算出される。 More specifically, the first control unit 41 calculates the NOx concentration based on the detection values from the intake system sensor group Sg1 such as the intake flow rate sensor 21, the intake pressure sensor 22, the intake air temperature sensor 23, and the exhaust lambda sensor 24. A value Nc is calculated. At the same time, based on the idea that the calculated value for control is corrected using the value for correcting the calculated value based on the NOx concentration calculated value Nc based on the detected NOx concentration value Nd, the NOx concentration sensor 46 uses the NOx concentration sensor. The NOx concentration detection value Nd, which is 20 detection values, is input, and the NOx correction coefficient (correction ratio) Ncf = Nd / Nc is calculated from the NOx concentration detection value Nd and the NOx concentration calculation value Nc.
　一方、エンジン回転数及び燃料噴射量に基づいてマップデータを参照する等して、第１ＮＯｘ濃度目標値Ｎｔ１が算出され、この第１ＮＯｘ濃度目標値Ｎｔ１に対して、第２制御部４２Ｘで、スモークリミットを考慮して第２ＮＯｘ濃度目標値Ｎｔ２が算出され、更に、内燃機関の運転状態が定常状態であるときに、ＮＯｘ補正係数Ｎｃｆを乗じて、第３ＮＯｘ濃度目標値Ｎｔ３（＝Ｎｔ２×Ｎｃｆ＝Ｎｔ２×Ｎｄ／Ｎｃ）が算出される。また、内燃機関の運転状態が加速状態であるときには、ＮＯｘ補正係数ＮＣｆによる補正を行わず、補正比率を１として、第３ＮＯｘ濃度目標値Ｎｔ３が算出される（Ｎｔ３＝Ｎｔ２×１＝Ｎｔ２）。 On the other hand, the first NOx concentration target value Nt1 is calculated by referring to the map data on the basis of the engine speed and the fuel injection amount, and the second control unit 42X performs the smoke on the first NOx concentration target value Nt1. The second NOx concentration target value Nt2 is calculated in consideration of the limit. Further, when the operating state of the internal combustion engine is in a steady state, the NOx correction coefficient Ncf is multiplied to obtain a third NOx concentration target value Nt3 (= Nt2 × Ncf = Nt2 × Nd / Nc) is calculated. Further, when the operating state of the internal combustion engine is in the acceleration state, the third NOx concentration target value Nt3 is calculated with the correction ratio being 1 without performing correction by the NOx correction coefficient NCf (Nt3 = Nt2 × 1 = Nt2).
　この第３ＮＯｘ濃度目標値Ｎｔ３に対して、第３制御部４３で、気筒内酸素濃度目標値Ｄｔが算出され、第４制御部４４でフィードフォワード制御（プリ制御）の目標値である基本制御量（プリ制御量）Ｃａが算出される。それと共に、第５制御部４５で、気筒内酸素濃度目標値Ｄｔと第１制御部４１で算出された気筒内酸素濃度算出値Ｄｃとを入力して、フィードバック制御（ＰＩＤ制御）の目標値である補正制御量Ｃｂが算出される。加算部４７で、この基本制御量Ｃａと補正制御量Ｃｂとが加算されてバルブ制御量Ｃが算出される。このバルブ制御量ＣでＥＧＲバルブ１６の開度が調整制御される。 With respect to the third NOx concentration target value Nt3, the third control unit 43 calculates the in-cylinder oxygen concentration target value Dt, and the fourth control unit 44 calculates a basic control amount that is a target value for feedforward control (pre-control). (Pre-control amount) Ca is calculated. At the same time, the fifth control unit 45 inputs the in-cylinder oxygen concentration target value Dt and the in-cylinder oxygen concentration calculated value Dc calculated by the first control unit 41 to obtain a target value for feedback control (PID control). A certain correction control amount Cb is calculated. The adder 47 adds the basic control amount Ca and the correction control amount Cb to calculate the valve control amount C. With this valve control amount C, the opening degree of the EGR valve 16 is adjusted and controlled.
　そして、このＥＧＲ制御においては、エンジン回転数及び燃料噴射量に基づいてマップデータを参照する等して、排気ガス中のＮＯｘ濃度の目標値である第１ＮＯｘ濃度目標値Ｎｔ１が算出されているが、この第１ＮＯｘ濃度目標値Ｎｔ１はエンジンの定常状態におけるＮＯｘ濃度目標値Ｎｔで設定されており、エンジンの運転状態が加速状態のときには、このＮＯｘ濃度目標値ＮｔでＥＧＲを行うと、ターボ式過給機の過給遅れ（ターボ遅れ）等により、シリンダ内に送り込まれる新気量及び酸素量が不足し、燃焼状態が悪化してスモークが発生することが予想される。 In the EGR control, the first NOx concentration target value Nt1 that is the target value of the NOx concentration in the exhaust gas is calculated by referring to the map data based on the engine speed and the fuel injection amount. The first NOx concentration target value Nt1 is set as the NOx concentration target value Nt in the steady state of the engine. When the engine operating state is in the acceleration state, if the EGR is performed with this NOx concentration target value Nt, the turbo excess It is expected that the amount of fresh air and oxygen sent into the cylinder will be insufficient due to the supercharging delay (turbo delay) of the charger, and the combustion state will deteriorate and smoke will be generated.
　これに対して、参考技術においては、エンジンの運転状態が加速状態のときでは、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値（第1ＮＯｘ濃度目標値Ｎｔ１）を増加させることで、気筒内酸素濃度目標値Ｄｔを大きくして、過度なスモークの発生を回避している。言い換えれば、過給遅れに伴う排気ラムダ（排気ガスの空気過剰率）の減少を考慮して、排気ラムダのスモーク発生回避のための下限の閾値を予め設けておき、排気ラムダがこの下限の閾値より低くならないようにＮＯｘ濃度目標値を大きくして、ＥＧＲ制御に使用する第１ＮＯｘ濃度目標値Ｎｔ１をより大きい値にしている。 In contrast, in the reference technique, when the engine operating state is the acceleration state, the NOx concentration target value (first NOx concentration target value Nt1) set based on the engine operating state is increased, whereby the cylinder The internal oxygen concentration target value Dt is increased to avoid excessive smoke. In other words, in consideration of a decrease in exhaust lambda (exhaust air excess ratio) due to a delay in supercharging, a lower limit threshold for avoiding smoke generation of the exhaust lambda is set in advance, and the exhaust lambda is set to this lower threshold. The NOx concentration target value is increased so as not to become lower, and the first NOx concentration target value Nt1 used for EGR control is set to a larger value.
　次に、図２および図３を参照しながら本実施の形態を説明する。
　ＥＧＲバルブ１６の開度を制御する目標開度の制御量Ｃは、気筒内酸素濃度目標値Ｄｔを基に第４制御部４４のフィードフォワード制御で算出される基本制御量（プリ制御量）Ｃａに、気筒内酸素濃度目標値Ｄｔと、各種センサからの入力を基に算出される気筒内酸素濃度の計算値Ｄｃとの差（誤差）ΔＤ（＝Ｄｔ－Ｄｃ）を基に第５制御部４５のフィードバック制御（ＰＩＤ制御）で算出される補正制御量Ｃｂを加算してバルブ制御量Ｃが算出される（Ｃ＝Ｃａ＋Ｃｂ）。 Next, the present embodiment will be described with reference to FIGS.
The control amount C of the target opening degree for controlling the opening degree of the EGR valve 16 is a basic control amount (pre-control amount) Ca calculated by feedforward control of the fourth control unit 44 based on the in-cylinder oxygen concentration target value Dt. In addition, the fifth control unit is based on the difference (error) ΔD (= Dt−Dc) between the cylinder oxygen concentration target value Dt and the calculated value Dc of the cylinder oxygen concentration calculated based on inputs from various sensors. The valve control amount C is calculated by adding the correction control amount Cb calculated in the feedback control (PID control) 45 (C = Ca + Cb).
　つまり、ＥＧＲ通路１４にＥＧＲバルブ１６を有して構成されるＥＧＲシステム１を備えたエンジン１０で、ＥＧＲのＮＯｘ濃度目標値Ｎｔ１に対応する気筒内酸素濃度目標値Ｄｔに基づいて、ＥＧＲバルブ１６の開度を制御する制御装置３０を備えた内燃機関のＥＧＲ制御システム４０である。 That is, in the engine 10 including the EGR system 1 configured to include the EGR valve 16 in the EGR passage 14, the EGR valve 16 is based on the in-cylinder oxygen concentration target value Dt corresponding to the NOx concentration target value Nt1 of EGR. It is the EGR control system 40 of the internal combustion engine provided with the control apparatus 30 which controls the opening degree.
　より詳細に説明すると、第１制御部４１では、吸気流量センサ２１、吸気圧力センサ２２、吸気温度センサ２３、排気ラムダセンサ２４などの吸気系センサ群Ｓｇ１からの検出値を基に、ＮＯｘ濃度算出値Ｎｃを算出する。 More specifically, the first control unit 41 calculates the NOx concentration based on the detection values from the intake system sensor group Sg1 such as the intake flow rate sensor 21, the intake pressure sensor 22, the intake air temperature sensor 23, the exhaust lambda sensor 24, and the like. The value Nc is calculated.
　このシリンダ内酸素濃度算出値Ｄｃの算出に際しては内部ＥＧＲガスを考慮することが好ましい。つまり、気筒内で発生するＮＯｘ量に関係するのは、気筒内の全排気ガス量に対する気筒内酸素濃度算出値Ｄｃであるので、気筒内の全排気ガス量に対する気筒内酸素濃度算出値Ｄｃを、吸気量と酸素濃度、外部ＥＧＲガスの排気ガス量と酸素濃度内部とだけで算出せずに、内部ＥＧＲガスの排気ガス量と酸素濃度と考慮に入れて、気筒内酸素濃度算出値Ｄｃを算出することが好ましい。 It is preferable to consider the internal EGR gas when calculating the in-cylinder oxygen concentration calculation value Dc. That is, since the NOx amount generated in the cylinder is related to the in-cylinder oxygen concentration calculation value Dc with respect to the total exhaust gas amount in the cylinder, the in-cylinder oxygen concentration calculation value Dc with respect to the total exhaust gas amount in the cylinder is The in-cylinder oxygen concentration calculation value Dc is calculated by taking into account the exhaust gas amount and the oxygen concentration of the internal EGR gas, without calculating only the intake air amount and the oxygen concentration, the exhaust gas amount of the external EGR gas and the inside of the oxygen concentration. It is preferable to calculate.
　そして、この気筒内酸素濃度算出値Ｄｃと燃焼室温度の推定値などから気筒内で発生するＮＯｘ量及び気筒内から排出される排気ガスのＮＯｘ濃度を算出し、ＮＯｘ濃度算出値Ｎｃとする。 Then, the NOx amount generated in the cylinder and the NOx concentration of the exhaust gas exhausted from the cylinder are calculated from the calculated oxygen concentration value Dc in the cylinder and the estimated value of the combustion chamber temperature, and set as the NOx concentration calculated value Nc.
　それと共に、ＮＯｘ濃度センサ２０で検出されるＮＯｘ濃度検出値Ｎｄを基本としてＮＯｘ濃度算出値Ｎｃによる算出値を補正値を用いて、制御用の算出値を補正するとの考えに基づいて、ＮＯｘ補正部４６で、ＮＯｘ濃度センサ２０の検出値であるＮＯｘ濃度検出値Ｎｄが入力され、このＮＯｘ濃度検出値ＮｄとＮＯｘ濃度算出値ＮｃとからＮＯｘ補正係数（補正比率）Ｎｃｆ＝Ｎｄ／Ｎｃを算出する。 At the same time, based on the idea that the calculated value for control is corrected using the calculated value based on the calculated NOx concentration value Nc based on the detected NOx concentration value Nd detected by the NOx concentration sensor 20, the NOx correction is performed. The NOx concentration detection value Nd, which is a detection value of the NOx concentration sensor 20, is input to the unit 46, and a NOx correction coefficient (correction ratio) Ncf = Nd / Nc is calculated from the NOx concentration detection value Nd and the NOx concentration calculation value Nc. To do.
　一方、排気ラムダセンサ２４の検出値と、エンジン回転数Ｎｅ及び燃料噴射量ｑに基づいてマップデータを参照する等して、第１ＮＯｘ目標値Ｎｔ１が算出される。第２制御部４２には、第１ＮＯｘ目標値Ｎｔ１と排気ラムダセンサ２４の検出値が入力される。第２制御部４２では、エンジン１０の運転状態が定常状態では、この第１ＮＯｘ目標値Ｎｔ１ではスモークが発生することが、予め設定してある計算式やマップデータ等から予測される場合には、スモークが発生しないようなＮＯｘ濃度を第２ＮＯｘ目標値Ｎｔ２とする。所謂スモークリミットを行う。なお、スモークが発生する可能性が無い場合は、そのまま、第１ＮＯｘ目標値Ｎｔ１を第２ＮＯｘ目標値Ｎｔ２とする。これにより第２制御部４２は第２ＮＯｘ目標値Ｎｔ２を算出する。 On the other hand, the first NOx target value Nt1 is calculated by referring to the map data based on the detected value of the exhaust lambda sensor 24, the engine speed Ne and the fuel injection amount q. The second NOx target value Nt1 and the detected value of the exhaust lambda sensor 24 are input to the second control unit 42. In the second control unit 42, when the operation state of the engine 10 is in a steady state, smoke is predicted to be generated at the first NOx target value Nt1 from a preset calculation formula, map data, or the like. The NOx concentration that does not cause smoke is set as the second NOx target value Nt2. A so-called smoke limit is performed. If there is no possibility that smoke will occur, the first NOx target value Nt1 is set as the second NOx target value Nt2 as it is. Thus, the second control unit 42 calculates the second NOx target value Nt2.
　更に、内燃機関の運転状態が定常状態であるときには、ＮＯｘ補正係数Ｎｃｆを乗じて、第３ＮＯｘ目標値Ｎｔ３（＝Ｎｔ２×Ｎｃｆ＝Ｎｔ２×Ｎｄ／Ｎｃ）を算出する。 Furthermore, when the operating state of the internal combustion engine is in a steady state, the NOx correction coefficient Ncf is multiplied to calculate a third NOx target value Nt3 (= Nt2 × Ncf = Nt2 × Nd / Nc).
　そして、エンジン１０の運転状態が加速状態にあるときは、スモークの発生を抑制するためのＥＧＲ制御で、エンジン１０の運転状態（エンジン回転数Ｎｅや燃料噴射量ｑ（若しくは負荷Ｑ））に基づいて設定された第１ＮＯｘ濃度目標値Ｎｔ１を増加させることなく、シリンダ内燃料噴射の燃料噴射時期ｔｆの遅延又は燃料噴射圧力Ｐｃｒの低下の少なくとも一方を行うように構成される。なお、この燃料噴射圧力Ｐｃｒの低下は、コモンレールシステムを使用している場合には、コモンレールの圧力を低下することで燃料噴射圧力Ｐｃｒを低下させる。 When the operating state of the engine 10 is in the acceleration state, the EGR control for suppressing the generation of smoke is based on the operating state of the engine 10 (engine speed Ne or fuel injection amount q (or load Q)). Thus, at least one of delaying the fuel injection timing tf of in-cylinder fuel injection or decreasing the fuel injection pressure Pcr is performed without increasing the first NOx concentration target value Nt1 set in the above. When the common rail system is used, the fuel injection pressure Pcr is lowered by lowering the fuel injection pressure Pcr by lowering the pressure of the common rail.
　また、加速状態であるときには、第２ＮＯｘ濃度目標値Ｎｔ２を第１ＮＯｘ濃度目標値Ｎｔ１のままとし、ＮＯｘ補正係数ＮＣｆによる補正を行わず、補正比率を１として、第３ＮＯｘ目標値Ｎｔ３を算出する（Ｎｔ３＝Ｎｔ２×１＝Ｎｔ２＝Ｎｔ１）。 Further, in the acceleration state, the second NOx concentration target value Nt2 remains the first NOx concentration target value Nt1, the correction by the NOx correction coefficient NCf is not performed, and the correction ratio is 1, and the third NOx target value Nt3 is calculated ( Nt3 = Nt2 × 1 = Nt2 = Nt1).
　このエンジン運転状態が定常状態であるか加速状態で有るかは、例えば、このエンジン１０を備えた車両の運転席に備えたアクセルペダル（図示しない）の開度Ａｃの変化率ΔＡｃが予め設定又は算出される閾値ΔＡｃ０を超えたときは加速状態であるとしたり、エンジン１０の気筒１１ｃ内への燃料噴射量ｑの変化率Δｑが予め設定又は算出される閾値Δｑｃを超えたときは加速状態であるとしたりすることで判定できる。 Whether the engine operating state is a steady state or an acceleration state is determined by setting, for example, a rate of change ΔAc of an opening degree Ac of an accelerator pedal (not shown) provided in a driver seat of a vehicle equipped with the engine 10 in advance. When the calculated threshold value ΔAc0 is exceeded, an acceleration state is assumed, and when the rate of change Δq of the fuel injection amount q into the cylinder 11c of the engine 10 exceeds a preset or calculated threshold value Δqc, the acceleration state is established. Judgment can be made by assuming.
　また、燃料噴射時期ｔｆの遅延量Δｔｆおよび燃焼噴射圧力Ｐｃｒの圧力低下量ΔＰｃｒは、エンジン１０の加速状態を示す指標、例えば、アクセル開度Ａｃの変化量ΔＡｃや燃料噴射量ｑの変化量Δｑｃ等に対して、予め実験的に求めてマップデータ等で記憶しておき、ＥＧＲ制御時に加速状態が発生したときにこのマップデータを参照して算出する。 Further, the delay amount Δtf of the fuel injection timing tf and the pressure decrease amount ΔPcr of the combustion injection pressure Pcr are indicators indicating the acceleration state of the engine 10, for example, the change amount ΔAc of the accelerator opening degree Ac and the change amount Δqc of the fuel injection amount q. For example, it is obtained experimentally in advance and stored as map data or the like, and is calculated with reference to this map data when an acceleration state occurs during EGR control.
　また、燃料噴射時期ｔｆの遅延および燃焼噴射圧力ｐｃｒの圧力低下は一方のみでもよいが、組み合せでもよく、組み合せの場合の遅延量Δｔｆと圧力低下量Δｐｃｒの最適な割合は実験的に設定してマップデータ化することができる。 Further, the delay of the fuel injection timing tf and the pressure drop of the combustion injection pressure pcr may be only one, but they may be combined, and the optimum ratio between the delay amount Δtf and the pressure drop amount Δpcr in the combination is set experimentally. Map data can be converted.
　なお、この燃料噴射時期ｔｆの遅延量Δｔｆと燃焼噴射圧力ｐｃｒの圧力低下量Δｐｃｒと、ＮＯｘ濃度Ｎｔとの関係については、図３のＮＯｘ濃度目標値算出部４２ａの入出力関係で示すように、基準ＮＯｘ濃度Ｎｔ０、シリンダ内酸素濃度をＤ、基準シリンダ内酸素濃度をＤ０、燃料噴射時期をｔｆ、基準燃料噴射量をｔｆ０、燃料噴射圧力をＰｃｒ、基準燃料噴射圧力をＰｃｒ０、エンジン冷却水の水温をＴｃ、基準水温をＴｃ０、吸気マニホールド温度をＴｉ、基準吸気マニホールド温度をＴｉ０とすると、遅延量Δｔｆ（＝θｆ－θｆ０）、圧力低下量ΔＰｃｒ（＝Ｐｃｒ－Ｐｃｒ０）、水温差ΔＴｃ（＝Ｔｃ－Ｔｃ０）と、補正指数のα２、αＴ、補正係数のβｆ、βｃｒ、βｃを用いて、（１）式に示すような関係を用いる。なお、これらの補正指数のα２、αＴ、補正係数のβｆ、βｃｒ、βｃは予め実験などにより設定される値である。 Note that the relationship between the delay amount Δtf of the fuel injection timing tf, the pressure drop amount Δpcr of the combustion injection pressure pcr, and the NOx concentration Nt is shown by the input / output relationship of the NOx concentration target value calculation unit 42a in FIG. , Reference NOx concentration Nt0, cylinder oxygen concentration D, reference cylinder oxygen concentration D0, fuel injection timing tf, reference fuel injection amount tf0, fuel injection pressure Pcr, reference fuel injection pressure Pcr0, engine coolant , Tc0, reference water temperature Tc0, intake manifold temperature Ti, reference intake manifold temperature Ti0, delay amount Δtf (= θf−θf0), pressure drop amount ΔPcr (= Pcr−Pcr0), water temperature difference ΔTc ( = Tc−Tc0), correction indices α2, αT, and correction coefficients βf, βcr, βc, and the relationship shown in the equation (1) is used. These correction indexes α2, αT and correction coefficients βf, βcr, βc are values set in advance by experiments or the like.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
　つまり、この（１）式では、ＮＯｘ濃度Ｎｔは、基準ＮＯｘ濃度Ｎｔ０をシリンダ内酸素濃度Ｄによる補正、吸気マニホールド温度（吸気温度）Ｔｉによる補正、エンジン冷却水の水温Ｔｃによる補正に加えて、燃料噴射時期ｔｆによる補正と燃料噴射圧力（コモンレール圧力］Ｐｃｒによる補正をすることで求められる。 In other words, in this equation (1), the NOx concentration Nt is determined by correcting the reference NOx concentration Nt0 by the in-cylinder oxygen concentration D, the correction by the intake manifold temperature (intake air temperature) Ti, and the correction by the engine coolant temperature Tc. It is obtained by correcting with the fuel injection timing tf and correcting with the fuel injection pressure (common rail pressure) Pcr.
　言い換えれば、ＮＯｘ濃度Ｎｔを固定にした状態で、シリンダ内酸素濃度Ｄが変化しても、遅延量Δｔｆまたは圧力低下量Δｐｃｒの一方の変化又は両方の変化で対応できることを示しており、本実施の形態では、この（１）式の関係に基づいて、遅延量Δｔｆまたは圧力低下量Δｐｃｒを設定する。 In other words, even if the in-cylinder oxygen concentration D changes while the NOx concentration Nt is fixed, it is indicated that one or both of the delay amount Δtf and the pressure drop amount Δpcr can be dealt with. In this embodiment, the delay amount Δtf or the pressure drop amount Δpcr is set based on the relationship of the equation (1).
　そして、第３制御部４３では、吸気圧力センサ２２及び吸気温度センサ２３の検出値を入力して、この第３ＮＯｘ目標値Ｎｔ３に対して、気筒内酸素濃度目標値Ｄｔを算出する。第４制御部４４で、この算出された気筒内酸素濃度目標値Ｄｔに対して、フィードフォワード制御（プリ制御）の目標値である基本制御量（プリ制御量）Ｃａを算出する。この基本制御量Ｃａの算出に際しても、内部ＥＧＲガスを考慮することが好ましい。 Then, the third control unit 43 inputs the detection values of the intake pressure sensor 22 and the intake temperature sensor 23, and calculates the in-cylinder oxygen concentration target value Dt with respect to the third NOx target value Nt3. The fourth control unit 44 calculates a basic control amount (pre-control amount) Ca that is a target value for feedforward control (pre-control) with respect to the calculated in-cylinder oxygen concentration target value Dt. In calculating the basic control amount Ca, it is preferable to consider the internal EGR gas.
　なお、この第４制御部４４では、ＥＧＲバルブ１６の前後に設けた差圧センサ（図示しない）で検出したＥＧＲバルブ１６の前後差圧、ＥＧＲバルブ１６の下流のＥＧＲ通路１４に設けた温度センサ（図示しない）で検出したＥＧＲガスＧｅの温度等を用いて、より正確なＥＧＲガスＧｅの流量とＥＧＲバルブ１６の開度の関係を求めておくことが好ましい。 In the fourth control unit 44, the differential pressure across the EGR valve 16 detected by a differential pressure sensor (not shown) provided before and after the EGR valve 16, the temperature sensor provided in the EGR passage 14 downstream of the EGR valve 16 It is preferable to obtain a more accurate relationship between the flow rate of the EGR gas Ge and the opening degree of the EGR valve 16 using the temperature of the EGR gas Ge detected in (not shown).
　つまり、気筒内で発生するＮＯｘ量に関係する気筒内の全排気ガス量に対する気筒内酸素濃度目標値Ｄｔを、気筒内の排気ガス量と酸素濃度が、内部ＥＧＲガスの排気ガス量と酸素濃度と、外部ＥＧＲガスの排気ガス量と酸素濃度と決まることを利用して、気筒内の酸素濃度の目標値である気筒内酸素濃度目標値Ｄｔから、外部ＥＧＲの酸素濃度目標値Ｄｔｏを算出し、外部ＥＧＲにおけるＥＧＲガス量Ｇｅを算出して、このＥＧＲガス量Ｇｅを供給できるＥＧＲバルブ１６の開度をプリ制御量Ｃａとする。 That is, the in-cylinder oxygen concentration target value Dt with respect to the total exhaust gas amount in the cylinder related to the NOx amount generated in the cylinder, the exhaust gas amount and oxygen concentration in the cylinder, and the exhaust gas amount and oxygen concentration in the internal EGR gas And the oxygen concentration target value Dto of the external EGR is calculated from the in-cylinder oxygen concentration target value Dt, which is the target value of the oxygen concentration in the cylinder, using the determination of the exhaust gas amount and the oxygen concentration of the external EGR gas. Then, the EGR gas amount Ge in the external EGR is calculated, and the opening degree of the EGR valve 16 that can supply the EGR gas amount Ge is defined as a pre-control amount Ca.
　また、それと並行して、第５制御部４５で、第３制御部４３で第３ＮＯｘ目標値Ｎｔ３に対して算出された気筒内酸素濃度目標値Ｄｔと第１制御部４１で算出された気筒内酸素濃度算出値Ｄｃとを入力して、フィードバック制御（ＰＩＤ制御）の目標値である補正制御量Ｃｂを算出する。そして、加算部４７で、この基本制御量Ｃａと補正制御量Ｃｂとを加算してバルブ制御量Ｃを算出する。このバルブ制御量ＣでＥＧＲバルブ１６の開度を調整制御する。 In parallel with this, the fifth controller 45 calculates the in-cylinder oxygen concentration target value Dt calculated for the third NOx target value Nt3 by the third controller 43 and the in-cylinder calculated by the first controller 41. An oxygen concentration calculation value Dc is input to calculate a correction control amount Cb that is a target value for feedback control (PID control). Then, the adding unit 47 adds the basic control amount Ca and the correction control amount Cb to calculate the valve control amount C. The valve opening amount of the EGR valve 16 is adjusted and controlled by the valve control amount C.
　次に、上記の内燃機関のＥＧＲ制御システム４０を用いた、本実施の形態の内燃機関のＥＧＲ制御方法について説明する。この内燃機関のＥＧＲ制御方法は、ＥＧＲ通路１４にＥＧＲバルブ１６を有して構成されるＥＧＲシステム１を備えたエンジン（内燃機関）１０で、ＥＧＲのＮＯｘ濃度目標値Ｎｔ１に対応する気筒内酸素濃度目標値Ｄｔに基づいて、ＥＧＲバルブ１６の開度を制御する内燃機関のＥＧＲ制御方法であり、この内燃機関のＥＧＲ制御方法において、エンジン１１の運転状態が加速状態にあるときは、スモークの発生を抑制するためのＥＧＲ制御で、ＮＯｘ濃度目標値Ｎｔ１を増加させることなく、シリンダ内燃料噴射の燃料噴射時期ｔｆの遅延又は燃料噴射圧力Ｐｃｒの低下の少なくとも一方を行う方法である。 Next, the EGR control method for the internal combustion engine of the present embodiment using the EGR control system 40 for the internal combustion engine will be described. This EGR control method for an internal combustion engine is an engine (internal combustion engine) 10 having an EGR system 1 constituted by having an EGR valve 16 in an EGR passage 14, and in-cylinder oxygen corresponding to the NOx concentration target value Nt1 of EGR. This is an EGR control method for an internal combustion engine that controls the opening of the EGR valve 16 based on the concentration target value Dt. In this EGR control method for the internal combustion engine, when the operating state of the engine 11 is in an acceleration state, the smoke In this EGR control for suppressing the generation, at least one of delaying the fuel injection timing tf of the in-cylinder fuel injection or decreasing the fuel injection pressure Pcr is performed without increasing the NOx concentration target value Nt1.
　上記の構成の内燃機関のＥＧＲ制御システム４０、エンジン（内燃機関）１０、及び内燃機関のＥＧＲ制御方法によれば、エンジン１０の運転状態が加速状態のときでも、ＮＯｘ濃度目標値Ｎｔ１の増加ではなく、燃料噴射時期ｔｆの遅延又は燃料噴射圧力Ｐｃｒの低下で、スモークの発生を回避するので、ＮＯｘの排出量の増加を防止でき、排気ガス性能の悪化を抑制することができる。また、加速状態におけるＥＧＲ制御においても、定常時用で設定されるＮＯｘ濃度目標値Ｎｔ１を加速時用のＮＯｘ濃度目標値に変更しないで済むので、定常状態のＥＧＲ制御と同じ制御で行うことができる。 According to the EGR control system 40, the engine (internal combustion engine) 10, and the internal combustion engine EGR control method configured as described above, even when the operating state of the engine 10 is in the acceleration state, the NOx concentration target value Nt1 is not increased. In addition, since the generation of smoke is avoided by delaying the fuel injection timing tf or lowering the fuel injection pressure Pcr, it is possible to prevent an increase in the NOx emission amount and suppress deterioration of exhaust gas performance. Further, in the EGR control in the acceleration state, the NOx concentration target value Nt1 set for the steady state need not be changed to the NOx concentration target value for the acceleration, and therefore, the same control as the steady state EGR control is performed. it can.
　本出願は、2015年7月31日付で出願された日本国特許出願（2015-151752）に基づくものであり、その内容はここに参照として取り込まれる。 This application is based on a Japanese patent application (2015-151752) filed on July 31, 2015, the contents of which are incorporated herein by reference.
　本発明の内燃機関のＥＧＲ制御システム、内燃機関、及び内燃機関のＥＧＲ制御方法によれば、エンジンの運転状態が加速状態でスモーク発生の抑制のために、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を大きくすることなく、ＮＯｘ排出量の増加を回避してＥＧＲをすることができる点で有用である。 According to the EGR control system for an internal combustion engine, the internal combustion engine, and the EGR control method for an internal combustion engine according to the present invention, the operation state of the engine is set based on the operation state of the engine in order to suppress smoke generation in the acceleration state. This is useful in that EGR can be performed without increasing the NOx concentration target value without increasing the NOx emission amount.
１　内燃機関のＥＧＲシステム
１０　エンジン（内燃機関）
１１　エンジン本体
１１ａ　吸気マニホールド
１１ｂ　排気マニホールド
１１ｃ　気筒
１２　吸気通路
１３　排気通路
１４　ＥＧＲ通路
１５　ＥＧＲクーラー
１６　ＥＧＲバルブ
２０　ＮＯｘ濃度センサ
２１　吸気流量センサ（ＭＡＦセンサ）
２２　吸気圧力センサ
２３　吸気温度センサ
２４　排気ラムダセンサ（排気過剰率センサ）
３０　制御装置
４０、４０Ｘ　内燃機関のＥＧＲ制御システム
４１　第１制御部
４２、４２Ｘ　第２制御部
４３　第３制御部
４４　第４制御部
４５　第５制御部
４６　ＮＯｘ補正部
４７　加算部
Ａ　新気
Ｃ　ＥＧＲバルブの開度の制御量
Ｃａ　ＥＧＲバルブの開度の基本制御量
Ｃｂ　ＥＧＲバルブの開度の補正制御量
Ｄｔ　気筒内酸素濃度目標値
Ｄｃ　気筒内酸素濃度算出値
Ｇ、Ｇａ　排気ガス
Ｇｅ　ＥＧＲガス
ＮＣｆ　ＮＯｘ補正係数
Ｓｇ１　吸気系センサ群 1 EGR system for internal combustion engine 10 Engine (internal combustion engine)
11 Engine body 11a Intake manifold 11b Exhaust manifold 11c Cylinder 12 Intake passage 13 Exhaust passage 14 EGR passage 15 EGR cooler 16 EGR valve 20 NOx concentration sensor 21 Intake flow rate sensor (MAF sensor)
22 Intake pressure sensor 23 Intake temperature sensor 24 Exhaust lambda sensor (exhaust excess ratio sensor)
30 control device 40, 40X EGR control system 41 of internal combustion engine 1st control part 42, 42X 2nd control part 43 3rd control part 44 4th control part 45 5th control part 46 NOx correction part 47 addition part A fresh air C EGR valve opening control amount Ca EGR valve opening basic control amount Cb EGR valve opening correction control amount Dt In-cylinder oxygen concentration target value Dc In-cylinder oxygen concentration calculation value G, Ga Exhaust gas Ge EGR gas NCf NOx correction coefficient Sg1 Intake system sensor group

Claims (6)

  1. 　ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲシステムを備えた内燃機関を制御するＥＧＲ制御システムにおいて、
    ＥＧＲのＮＯｘ濃度目標値に対応する気筒内酸素濃度目標値に基づいて前記ＥＧＲバルブの開度を制御する制御装置を備え、
    　前記制御装置が、ＥＧＲ制御中でエンジンの運転状態が加速状態にあるときは、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を増加させることなく、シリンダ内燃料噴射の燃料噴射時期の遅延又は燃料噴射圧力の低下の少なくとも一方を実行するように構成されたことを特徴とするＥＧＲ制御システム。     In an EGR control system for controlling an internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage,
    A control device for controlling the opening degree of the EGR valve based on the in-cylinder oxygen concentration target value corresponding to the NOx concentration target value of EGR;
    When the control device is in EGR control and the engine operating state is in the acceleration state, the fuel injection timing of the fuel injection in the cylinder is not increased without increasing the NOx concentration target value set based on the engine operating state. An EGR control system configured to perform at least one of a delay and a decrease in fuel injection pressure.
  2. 　前記制御装置が、ＥＧＲ制御中でエンジンの運転状態が加速状態にあるときは、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を増加させることなく、シリンダ内燃料噴射の燃料噴射時期の遅延又は燃料噴射圧力の低下の両方を行うように構成されたことを特徴とする請求項１に記載のＥＧＲ制御システム。 When the control device is in EGR control and the engine operating state is in the acceleration state, the fuel injection timing of the fuel injection in the cylinder is not increased without increasing the NOx concentration target value set based on the engine operating state. The EGR control system according to claim 1, wherein the EGR control system is configured to perform both a delay or a decrease in fuel injection pressure.
  3. 　前記制御装置は、エンジンの加速状態を示す指標と、シリンダ内燃料噴射の燃料噴射時期の遅延量又は燃料噴射圧力の圧力低下量との関係を記憶したマップデータを参照して、シリンダ内燃料噴射の燃料噴射時期の遅延量又は燃料噴射圧力の圧力低下量を算出することを特徴とする請求項１に記載のＥＧＲ制御システム。 The control device refers to map data storing a relationship between an index indicating an acceleration state of the engine and a delay amount of the fuel injection timing of the in-cylinder fuel injection or a pressure drop amount of the fuel injection pressure. 2. The EGR control system according to claim 1, wherein a delay amount of the fuel injection timing or a pressure drop amount of the fuel injection pressure is calculated.
  4. 　エンジンの加速状態を示す前記指標とは、アクセル開度の変化量と燃料噴射量の変化量の少なくとも一方を含むことを特徴とする請求項３に記載のＥＧＲ制御システム。 4. The EGR control system according to claim 3, wherein the index indicating the acceleration state of the engine includes at least one of a change amount of an accelerator opening and a change amount of a fuel injection amount.
  5. 　請求項１に記載のＥＧＲ制御システムを備えたことを特徴とする内燃機関。 An internal combustion engine comprising the EGR control system according to claim 1.
  6. 　ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲシステムを備えた内燃機関で、ＥＧＲのＮＯｘ濃度目標値に対応する気筒内酸素濃度目標値に基づいて、前記ＥＧＲバルブの開度を制御する内燃機関のＥＧＲ制御方法において、
    　ＥＧＲ制御中でエンジンの運転状態が加速状態にあるときは、エンジンの運転状態に基づいて設定されたＮＯｘ濃度目標値を増加させることなく、シリンダ内燃料噴射の燃料噴射時期の遅延又は燃料噴射圧力の低下の少なくとも一方を行うことを特徴とする内燃機関のＥＧＲ制御方法。     An internal combustion engine having an EGR system configured to have an EGR valve in an EGR passage and controlling an opening degree of the EGR valve based on an in-cylinder oxygen concentration target value corresponding to an EGR NOx concentration target value In the EGR control method of the engine,
    When the engine operating state is in the acceleration state during the EGR control, the fuel injection timing delay or the fuel injection pressure of the in-cylinder fuel injection is not increased without increasing the NOx concentration target value set based on the engine operating state. An EGR control method for an internal combustion engine, characterized in that at least one of the reductions is performed.
PCT/JP2016/072196 2015-07-31 2016-07-28 Internal-combustion engine egr control system, internal-combustion engine, and internal-combustion engine egr control method WO2017022630A1 (en)

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Publication number Priority date Publication date Assignee Title
JPH04203453A (en) * 1990-11-30 1992-07-24 Nissan Motor Co Ltd Control device of diesel engine
JPH09151761A (en) * 1995-12-01 1997-06-10 Toyota Motor Corp Fuel control device for internal combustion engine
JPH1136994A (en) * 1997-07-17 1999-02-09 Mazda Motor Corp Exhaust reflux controller of direct injection type engine with turbocharger
JPH11287143A (en) * 1998-04-02 1999-10-19 Denso Corp Internal combustion engine controller
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