WO2012121299A1 - Combustion control device - Google Patents

Combustion control device Download PDF

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Publication number
WO2012121299A1
WO2012121299A1 PCT/JP2012/055860 JP2012055860W WO2012121299A1 WO 2012121299 A1 WO2012121299 A1 WO 2012121299A1 JP 2012055860 W JP2012055860 W JP 2012055860W WO 2012121299 A1 WO2012121299 A1 WO 2012121299A1
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WO
WIPO (PCT)
Prior art keywords
fuel injection
engine
water temperature
combustion
fuel
Prior art date
Application number
PCT/JP2012/055860
Other languages
French (fr)
Japanese (ja)
Inventor
裕史 葛山
田中　剛
謹 河合
Original Assignee
株式会社豊田自動織機
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Filing date
Publication date
Application filed by 株式会社豊田自動織機 filed Critical 株式会社豊田自動織機
Publication of WO2012121299A1 publication Critical patent/WO2012121299A1/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
    • F02D41/38—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
    • 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
    • F02M26/13—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22—Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23—Layout, e.g. schematics
    • F02M26/25—Layout, e.g. schematics with coolers having bypasses
    • 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
    • F02B29/00—Engines characterised by provision for charging or scavenging not provided for in groups F02B25/00, F02B27/00 or F02B33/00 - F02B39/00; Details thereof
    • F02B29/04—Cooling of air intake supply
    • F02B29/0406—Layout of the intake air cooling or coolant circuit
    • 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
    • F02D2200/021—Engine temperature
    • 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
    • F02D41/403—Multiple injections with pilot injections
    • 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
    • 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
    • F02M26/02—EGR systems specially adapted for supercharged engines
    • F02M26/04—EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/05—High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to an engine combustion control apparatus that performs premixed compression ignition (PCCI) combustion.
  • PCCI premixed compression ignition
  • Patent Document 1 As an engine combustion control device that performs premixed compression ignition combustion, for example, the one described in Patent Document 1 is known.
  • the combustion control device described in Patent Document 1 corrects the fuel injection timing to the advance side and lowers the injection pressure when the ignition delay period is prolonged in cold when performing low temperature premixed combustion. By doing so, the fuel injection period is corrected to be extended. This prevents the fuel from diffusing excessively into the combustion chamber and suppresses an increase in unburned HC.
  • An object of the present invention is to provide a combustion control device that can sufficiently suppress an increase in unburned HC and unburned CO even at a low water temperature.
  • the present invention relates to an engine combustion control apparatus that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, and a second fuel injection after the first fuel injection is performed.
  • the first injection valve control means for controlling the fuel injection valve, the water temperature detection means for detecting the water temperature of the engine, and the determination for determining whether or not the engine water temperature detected by the water temperature detection means is lower than a predetermined temperature
  • a second fuel injection valve that controls the fuel injection valve so that the third fuel injection is performed before the first fuel injection is performed when it is determined by the means and the determination means that the water temperature of the engine is lower than the predetermined temperature.
  • Injection valve control means for controlling the fuel injection valve, the water temperature detection means for detecting the water temperature of the engine, and the determination for determining whether or not the engine water temperature detected by the water temperature detection means is lower than a predetermined temperature.
  • the third fuel injection is performed before the first fuel injection is performed, and then the first fuel is injected.
  • the injection and the second fuel injection are sequentially performed.
  • the ignition timing is advanced by preheating by the third fuel injection, the heat generation rate waveform (combustion waveform) approaches the combustion waveform in the warm-up state, and combustion is activated. Therefore, increase in unburned HC and unburned CO can be sufficiently suppressed even at a low water temperature.
  • Load detecting means for detecting engine load is further provided, and the second injection valve control means is configured to select a third temperature according to the engine water temperature detected by the water temperature detecting means and the engine load detected by the load detecting means. You may have a means to determine the fuel injection quantity by fuel injection.
  • the fuel injection amount by the third fuel injection is increased as the water temperature of the engine is lowered. Thereby, ignition can be performed at an appropriate time even at low water temperature. As the engine load increases, the amount of fuel injected by the third fuel injection is reduced. Thereby, excessive combustion at the time of high load can be suppressed.
  • the second injection valve control means compares the engine load with the first predetermined value and the second predetermined value, and when it is determined that the engine load is greater than the first predetermined value, When the fuel injection amount by the third fuel injection is reduced from the fuel injection amount by the first fuel injection and it is determined that the engine load is smaller than the second predetermined value, the fuel by the second fuel injection There may be provided means for reducing the fuel injection amount by the third fuel injection from the injection amount. For example, the first predetermined value and the second predetermined value are equal.
  • the fuel injection amount by the third fuel injection is reduced from the fuel injection amount by the first fuel injection. Thereby, the excessive combustion by 1st fuel injection is suppressed, and a combustion noise can be reduced.
  • the fuel injection amount by the third fuel injection is reduced from the fuel injection amount by the second fuel injection. Thereby, active combustion by the 1st fuel injection is ensured, and unburned HC and unburned CO can be reduced.
  • the second fuel injection has a lower degree of premixing than the first fuel injection. However, since the fuel injection amount by the second fuel injection is reduced, NOx and smoke can be reduced.
  • the second injection valve control means may have means for reducing the fuel injection amount by the third fuel injection from the fuel injection amount by the second fuel injection.
  • the second fuel injection has a lower degree of premixing than the first fuel injection. However, since the fuel injection amount by the second fuel injection is reduced, NOx and smoke can be reduced. Such a configuration is effective when combustion noise can be tolerated even when the engine load is relatively high.
  • An air-fuel ratio control means for controlling the ratio of air and fuel existing in the combustion chamber according to the engine water temperature detected by the water temperature detection means may be further provided.
  • the ratio of air to fuel (air-fuel ratio) existing in the combustion chamber is controlled to become leaner as the engine water temperature becomes lower.
  • the ignition delay time is shortened. Therefore, the combustion waveform can be made closer to the combustion waveform in the warm air state.
  • An exhaust gas recirculation passage that connects the intake and exhaust portions of the combustion chamber, an exhaust gas recirculation passage that is provided in the exhaust gas recirculation passage, and cools the exhaust gas recirculation gas that passes through the exhaust gas recirculation passage, and bypasses the exhaust gas recirculation cooler
  • a bypass passage connected to the exhaust gas recirculation passage, and a flow passage for switching the exhaust gas recirculation gas flow path to the exhaust gas recirculation cooler side or the bypass passage side according to the engine water temperature detected by the water temperature detecting means And a switching unit.
  • the flow path of the exhaust gas recirculation is switched from the exhaust gas recirculation cooler side to the bypass passage side.
  • the exhaust gas recirculation gas in a high temperature state is introduced into the combustion chamber, and the ignition delay time is shortened. Therefore, the combustion waveform can be made closer to the combustion waveform in the warm air state.
  • FIG. 1 is a schematic configuration diagram showing a diesel engine equipped with a combustion control device according to the present embodiment.
  • FIG. 2 is a block diagram showing a configuration of the combustion control device shown in FIG.
  • FIG. 3 is a flowchart showing details of an injector control processing procedure executed by the injector control unit shown in FIG.
  • FIG. 4 is a diagram showing the fuel injection amount and fuel injection timing of the pre-fuel injection, the first main fuel injection, and the second main fuel injection.
  • FIG. 5 is a graph showing an example of a heat release rate waveform.
  • FIG. 6 is a graph showing an example of the in-cylinder average temperature waveform and the heat release rate waveform.
  • FIG. 7 is a diagram illustrating a modification of the fuel injection amount and the fuel injection timing of the pre-fuel injection, the first main fuel injection, and the second main fuel injection.
  • FIG. 1 is a schematic configuration diagram showing a diesel engine provided with a combustion control device according to the present embodiment.
  • the diesel engine 1 according to the present embodiment is a premixed compression ignition (PCCI) type four-cylinder in-line diesel engine.
  • the diesel engine 1 includes an engine body 2, and the engine body 2 is provided with four cylinders 3.
  • Each cylinder 3 is provided with an injector (fuel injection valve) 5 for injecting fuel into the combustion chamber 4.
  • the injector 5 has a plurality of injection holes (not shown) and injects fuel radially from each injection hole.
  • Each injector 5 is connected to a common rail 6, and high-pressure fuel stored in the common rail 6 is constantly supplied to each injector 5.
  • the engine body 2 is connected to an intake passage 7 for sucking air into the combustion chamber 4 via an intake manifold (intake section) 8.
  • An exhaust passage 9 for exhausting exhaust gas after combustion is connected to the engine body 2 via an exhaust manifold (exhaust portion) 10.
  • an air cleaner 11, a compressor 13 of the turbocharger 12, an intercooler 14, and a throttle valve 15 are provided from the upstream side toward the downstream side.
  • the throttle valve 15 restricts the passage area of the intake passage 7 and generates a negative pressure on the downstream side, thereby enabling exhaust gas recirculation (EGR) described later.
  • EGR exhaust gas recirculation
  • a turbine 16 of the turbocharger 12 and a DPF 17 with a catalyst are provided in the exhaust passage 9.
  • the diesel engine 1 includes an exhaust gas recirculation (EGR) device 18 that recirculates a part of the exhaust gas after combustion into the combustion chamber 4.
  • the EGR device 18 includes an EGR passage 19, an EGR valve 20, an EGR cooler 21, a bypass passage 22, and a switching valve 23.
  • the EGR passage 19 connects the intake passage 7 and the exhaust manifold 10.
  • the EGR valve 20 adjusts the recirculation amount of the exhaust gas recirculation gas (EGR gas) from the exhaust manifold 10 to the intake passage 7.
  • the EGR cooler 21 cools the EGR gas passing through the EGR passage 19.
  • the bypass passage 22 is connected to the EGR passage 19 so as to bypass the EGR cooler 21.
  • the switching valve 23 switches the EGR gas flow path to the EGR cooler 21 side or the bypass passage 22 side.
  • Each injector 5, throttle valve 15, EGR valve 20, and switching valve 23 are controlled by an electronic control unit (ECU) (controller) 24.
  • the ECU 24 includes an accelerator opening sensor 25 that detects the accelerator opening, an engine rotation sensor 26 that detects the engine speed, and a crankshaft angle (crank angle) of a piston (not shown). Is connected to a crank angle sensor 27 for detecting the engine water temperature and a water temperature sensor (water temperature detecting means) 28 for detecting the engine water temperature.
  • the injector 5, the throttle valve 15, the EGR valve 20, the switching valve 23, the ECU 24, and the sensors 25 to 28 constitute a combustion control device 29 of the present embodiment.
  • the combustion control device 29 performs control so that premixed compression ignition combustion of split injection in which fuel is injected from each injector 5 in a plurality of times in one cycle of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. .
  • FIG. 2 is a block diagram showing the configuration of the combustion control device 29.
  • the ECU 24 includes an engine load calculation unit 30, an injector control unit 31, and an EGR control unit 32.
  • Engine load calculation unit 30 calculates the engine load based on the accelerator opening detected by accelerator opening sensor 25, the engine speed detected by engine rotation sensor 26, and other conditions.
  • the injector control unit 31 determines basic values of the number of fuel injections, the fuel injection amount, and the fuel injection timing from the engine load and the engine speed calculated by the engine load calculation unit 30.
  • the injector control unit 31 performs correction based on the engine water temperature detected by the water temperature sensor 28, determines the number of fuel injections, the fuel injection amount, and the fuel injection timing, and controls each injector 5. That is, the ECU 24 operates each injector 5 based on the determined number of fuel injections, fuel injection amount, and fuel injection timing.
  • FIG. 3 is a flowchart showing details of the injector control processing procedure executed by the injector control unit 31.
  • the injector control unit 31 performs the first main fuel injection (first fuel injection) and thereafter, as shown in FIG.
  • the fuel injection amount and fuel injection timing for each of the second main fuel injection (second fuel injection) are determined (S101).
  • the fuel injection amount of the second main fuel injection is, for example, smaller than the fuel injection amount of the first main fuel injection.
  • the second main fuel injection starts, for example, at a time when the crank angle is just before the compression top dead center (TDC).
  • FIG. 4 shows the fuel injection amount and fuel injection timing of the pre-fuel injection and the first and second main fuel injections at the time of high load and low load, respectively.
  • the injector control unit 31 determines whether or not the engine water temperature detected by the water temperature sensor 28 is lower than a predetermined temperature (for example, 80 ° C.) (S102).
  • the injector control unit 31 controls the injector 5 so that the first main fuel injection is performed according to the fuel injection amount determined in S101 (S108). . Subsequently, the injector control unit 31 controls the injector 5 to perform the second main fuel injection according to the fuel injection amount determined in S101 (S109).
  • the injector control unit 31 is performed before the first main fuel injection as shown in FIG. 4 based on the engine load and the engine water temperature.
  • the fuel injection amount and fuel injection timing of the pre-fuel injection (third fuel injection) are determined (S103).
  • the fuel injection amount of the pre-fuel injection is smaller than the fuel injection amount of the first and second main fuel injections. The lower the engine water temperature, the greater the fuel injection amount for pre-fuel injection, and the higher the engine load, the smaller the fuel injection amount for pre-fuel injection.
  • the interval between the pre-fuel injection and the first main fuel injection is calculated from the bore, stroke, number of injection holes of the injector 5, the swirl ratio, etc. in order to prevent spray overlap and gaps from adjacent injection holes of the injector 5. Is set to an appropriate interval. As a result, local rich and local lean are avoided, and generation of unburned fuel is suppressed.
  • the injector control unit 31 determines whether the engine load is higher than a predetermined value (S104).
  • the injector control unit 31 determines that the engine load is higher than the predetermined value, as shown in FIG. 4A, the fuel injection amount of the pre-fuel injection is calculated from the fuel injection amount of the first main fuel injection. The weight is reduced (S105). Therefore, the fuel injection amount of the first main fuel injection set in S101 is corrected.
  • the injector control unit 31 determines that the engine load is not higher than the predetermined value, as shown in FIG. 4B, the fuel injection amount of the pre-fuel injection is calculated from the fuel injection amount of the second main fuel injection. Is reduced (S106). Therefore, the fuel injection amount of the second main fuel injection set in S101 is corrected.
  • the injector control unit 31 controls the injector 5 so as to perform pre-fuel injection according to the fuel injection amount set in S103 (S107). Subsequently, the injector control unit 31 controls the injector 5 to perform the first main fuel injection according to the fuel injection amount set in S101 or the fuel injection amount corrected in S105 (S108). Subsequently, the injector control unit 31 controls the injector 5 to perform the second main fuel injection according to the fuel injection amount set in S101 or the fuel injection amount corrected in S106 (S109).
  • the EGR control unit 32 controls the EGR valve 20 and the switching valve 23 according to the engine water temperature. Specifically, the EGR control unit 32 controls the EGR valve 20 so that the flow rate of the EGR gas decreases as the engine water temperature decreases. Further, the EGR control unit 32 determines whether or not the engine water temperature is equal to or lower than a preset reference temperature. The EGR control unit 32 controls the switching valve 23 so that the EGR gas passes through the EGR cooler 21 when the engine water temperature is higher than the reference temperature. The EGR control unit 32 controls the switching valve 23 so that the EGR gas passes through the bypass passage 22 when the engine water temperature is equal to or lower than the reference temperature.
  • the injector control unit 31 of the ECU 24 executes the above-described S101, S108, and S109 so that the first fuel injection is performed and then the second fuel injection is performed (the injector 5). ) Is constituted.
  • the injector control unit 31 constitutes a determination unit that determines whether or not the engine water temperature detected by the water temperature detection unit (water temperature sensor 28) is lower than a predetermined temperature by executing S102.
  • the injector control unit 31 executes the third fuel injection before the first fuel injection when the determination means determines that the engine water temperature is lower than the predetermined temperature by executing S103 to S107.
  • the second injection valve control means for controlling the fuel injection valve is configured to be implemented.
  • the accelerator opening sensor 25, the engine rotation sensor 26, and the engine load calculation unit 30 of the ECU 24 constitute load detection means for detecting the engine load.
  • the EGR control unit 32 and the EGR valve 20 of the ECU 24 constitute air-fuel ratio control means for controlling the ratio of air and fuel existing in the combustion chamber 4 in accordance with the engine water temperature detected by the water temperature detection means. .
  • the EGR control unit 32 and the switching valve 23 of the ECU 24 switch the flow path of the exhaust recirculation gas to the exhaust recirculation cooler 21 side or the bypass passage 22 side according to the engine water temperature detected by the water temperature detecting means.
  • the switching means is configured.
  • the pre-fuel injection is not performed and the first main fuel injection and the second main fuel injection are sequentially performed. . Then, since the ignition of the premixed mixture of fuel and air is started after a predetermined period after the first and second main fuel injections are finished, as shown by the broken line P in FIG. A heat release rate waveform (combustion waveform) is obtained.
  • the combustion waveform is a combustion waveform indicated by a one-dot chain line Q in FIG.
  • FIG. 5 shows a heat generation rate waveform in the case of the warm-up state, when the pre-fuel injection and the EGR gas are not reduced at the low water temperature, and when the pre-fuel injection and the EGR gas are reduced at the low water temperature. An example is shown.
  • the first main fuel injection and the second main fuel injection are sequentially performed after the pre-fuel injection is performed, and the EGR is performed.
  • the combustion waveform substantially coincides with the combustion waveform in the warm-up state, as indicated by the solid line R in FIG. The reason is as follows.
  • the ignition timing is advanced by the pre-heating of the pre-fuel injection. Further, when the flow rate of EGR gas decreases, the ratio of air to fuel (air-fuel ratio) becomes lean. For this reason, good combustibility is ensured and the ignition delay period is shortened. As a result, the ignition timing becomes an appropriate timing, and the combustion waveform substantially matches the combustion waveform in the warm-up state.
  • the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the second main fuel injection.
  • the total amount of the main fuel injection and the fuel injection amount increases.
  • the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the first main fuel injection.
  • the total amount of the main fuel injection and the fuel injection amount does not change.
  • FIG. 6 shows an example of the in-cylinder average temperature waveform and the heat release rate waveform at high load and low load, respectively, when pre-fuel injection is performed at low water temperature.
  • the pre-fuel injection is performed before the first main fuel injection, and then the first main fuel injection and the second main fuel injection are performed.
  • the main fuel injection is sequentially performed.
  • the ignition timing is advanced by preheating by pre-fuel injection, and the combustion waveform approaches the combustion waveform in the warm-up state.
  • the fuel injection amount corresponding to the engine water temperature is set in the pre-fuel injection, combustion by the pre-fuel injection and the first main fuel injection is activated. Thereby, unburned HC and unburned CO can be reduced.
  • the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the second main fuel injection.
  • combustion by the first main fuel injection is activated, and unburned HC / CO can be reduced.
  • the fuel injection amount of the second main fuel injection with a low premixing degree decreases, and the sum of the fuel injection amounts of the pre-fuel injection with a high premixing degree and the first main fuel injection increases. Thereby, NOx and smoke can be reduced.
  • the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the first main fuel injection. Thereby, excessive activation of combustion due to the first main fuel injection is suppressed, and an increase in combustion noise can be suppressed.
  • the flow rate of EGR gas decreases as the engine water temperature decreases. As a result, the air-fuel ratio becomes lean and combustion is activated. Further, when the engine water temperature is equal to or lower than the reference temperature, the switching valve 23 is switched from the EGR cooler 21 side to the bypass passage 22 side. As a result, the EGR gas passes through the bypass passage 22 and the high-temperature EGR gas that is not cooled by the EGR cooler 21 is recirculated into the combustion chamber 4 to stabilize the combustion. As described above, the ignition delay is reduced, and the combustion waveform becomes closer to the combustion waveform in the warm-up state. As a result, an increase in unburned HC and unburned CO can be further suppressed.
  • the present embodiment is an engine combustion control apparatus that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, a water temperature sensor that detects a water temperature of the engine, And a controller for operating the fuel injection valve.
  • the controller operates the fuel injection valve so as to perform the second fuel injection after performing the first fuel injection, and detects the engine detected by the water temperature sensor.
  • the fuel injection valve is operated so that the third fuel injection is performed before the first fuel injection is performed.
  • the combustion control device further includes an accelerator opening sensor that detects the accelerator opening, and an engine rotation sensor that detects the engine speed, and the controller includes the accelerator opening detected by the accelerator opening sensor and the engine.
  • the engine load may be calculated based on information including the engine speed detected by the speed sensor.
  • the combustion control device further includes a valve for adjusting the amount of air present in the combustion chamber, and the controller controls the ratio of air and fuel present in the combustion chamber according to the water temperature detected by the water temperature sensor.
  • the valve may be operated.
  • the valve that adjusts the amount of air present in the combustion chamber may be a valve that adjusts the flow rate of the exhaust gas recirculation gas.
  • this embodiment is a combustion control apparatus for an engine that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, a water temperature sensor that detects a water temperature of the engine, When the fuel injection valve is operated so that the second fuel injection is performed after the first fuel injection is performed and it is determined that the engine water temperature detected by the water temperature sensor is lower than the predetermined temperature, And a controller configured to operate the fuel injection valve to perform a third fuel injection before performing one fuel injection.
  • the injector control unit 31 when the engine load is higher than a predetermined value, the injector control unit 31 reduces the fuel injection amount of the pre-fuel injection from the fuel injection amount of the first main fuel injection (FIG. 4A). reference). Even if the engine load is higher than the predetermined value, if the increase in combustion noise can be tolerated, as shown in FIG. 7, the injector control unit 31 performs pre-fuel injection from the fuel injection amount of the second main fuel injection. The fuel injection amount may be reduced. In this case, since the fuel injection amount of the second main fuel injection with a low premixing degree is reduced, it is possible to contribute to the reduction of smoke.
  • the injector control unit 31 performs the first time based on the comparison result between the engine load and one predetermined value when reducing the fuel injection amount of the pre-fuel injection from the fuel injection amount of the main fuel injection. Alternatively, it is determined whether to reduce the fuel injection amount of the pre-fuel injection from the fuel injection amount of the second main fuel injection.
  • the predetermined value used for comparison with the engine load is not limited to one. As the comparison value, for example, a first predetermined value and a second predetermined value smaller than the first predetermined value may be set.
  • the injector control unit 31 reduces the fuel injection amount of the pre-fuel injection from the fuel injection amount of the first main fuel injection, and the engine load is reduced.
  • the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the second main fuel injection, and the second predetermined value when the engine load is equal to or less than the first predetermined value.
  • the fuel injection amount of the pre-fuel injection may be reduced from both of the fuel injection amounts of the first and second main fuel injections.
  • the injector control unit 31 uniformly reduces the same fuel injection amount when the fuel injection amount of the pre-fuel injection is reduced from both the first and second main fuel injection amounts at medium load. Alternatively, the amount to be reduced from the fuel injection amount of each main fuel injection may be gradually changed.
  • the flow path of the exhaust gas recirculation gas is switched to the exhaust gas recirculation cooler 21 side or the bypass passage 22 side by the switching valve 23.
  • the operation of the switching valve 23 is not limited to simple switching.
  • the switching valve 23 may be operated to include a region where the flow rate of the exhaust gas recirculation gas is gradually changed, for example.
  • the air-fuel ratio in the combustion chamber 4 is controlled by adjusting the flow rate of the EGR gas by the EGR valve 20 according to the engine water temperature. Is not limited to this.
  • the air-fuel ratio in the combustion chamber 4 may be controlled by adjusting the intake amount of air by the throttle valve 15 according to the engine water temperature. Further, both the EGR valve 20 and the throttle valve 15 may be controlled according to the engine water temperature.
  • the main fuel injection is performed twice per cycle, but the main fuel injection may be performed three or more times per cycle.
  • the present invention can be used for a fuel control device of an engine that performs premixed compression ignition combustion.

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

Abstract

A combustion control device is equipped with: a fuel injection valve that injects fuel into the combustion chamber of an engine; a water temperature sensor that detects the engine's water temperature; and an electronic control unit that operates the fuel injection valve. The electronic control unit operates the fuel injection valve so as to execute a second injection of fuel after executing a first injection of fuel, and when it is determined that the engine's water temperature detected by the water temperature sensor is lower than a prescribed temperature, the electronic control unit operates the fuel injection valve so as to execute a third injection of fuel prior to the execution of the first injection of fuel.

Description

燃焼制御装置Combustion control device
　本発明は、予混合圧縮着火（ＰＣＣＩ：Premixed Charge Compression Ignition）燃焼を行うエンジンの燃焼制御装置に関する。 The present invention relates to an engine combustion control apparatus that performs premixed compression ignition (PCCI) combustion.
　予混合圧縮着火燃焼を行うエンジンの燃焼制御装置としては、例えば特許文献１に記載されているものが知られている。特許文献１に記載の燃焼制御装置は、低温予混合燃焼を行う場合、冷間時において着火遅れ期間が長期化するときは、燃料の噴射時期を進角側に補正すると共に、噴射圧力を低下させることで燃料の噴射期間を長期化させる方向に補正する。これにより、燃料が燃焼室内に過度に拡散することが防止され、未燃ＨＣの増加が抑制される。 As an engine combustion control device that performs premixed compression ignition combustion, for example, the one described in Patent Document 1 is known. The combustion control device described in Patent Document 1 corrects the fuel injection timing to the advance side and lowers the injection pressure when the ignition delay period is prolonged in cold when performing low temperature premixed combustion. By doing so, the fuel injection period is corrected to be extended. This prevents the fuel from diffusing excessively into the combustion chamber and suppresses an increase in unburned HC.
特開２００３－１８４６０９号公報JP 2003-184609 A
　しかしながら、上記従来技術のように燃料の噴射期間を長期化させても、早期に噴射された燃料については拡散する時間が長い。このため、燃料の過拡散を十分に防ぐことが困難であり、未燃ＨＣ及び未燃ＣＯの増加を十分抑制できない可能性がある。 However, even if the fuel injection period is extended as in the above-described prior art, it takes a long time for the fuel injected earlier to diffuse. For this reason, it is difficult to sufficiently prevent overdiffusion of fuel, and increase of unburned HC and unburned CO may not be sufficiently suppressed.
　本発明の目的は、低水温時でも、未燃ＨＣ及び未燃ＣＯの増加を十分抑制することができる燃焼制御装置を提供することである。 An object of the present invention is to provide a combustion control device that can sufficiently suppress an increase in unburned HC and unburned CO even at a low water temperature.
　本発明は、予混合圧縮着火燃焼を行うエンジンの燃焼制御装置において、エンジンの燃焼室内に燃料を噴射する燃料噴射弁と、第１の燃料噴射を実施してから第２の燃料噴射を実施するように燃料噴射弁を制御する第１の噴射弁制御手段と、エンジンの水温を検出する水温検出手段と、水温検出手段により検出されたエンジンの水温が所定温度よりも低いかどうかを判断する判断手段と、判断手段によりエンジンの水温が所定温度よりも低いと判断されたときに、第１の燃料噴射を実施する前に第３の燃料噴射を実施するように燃料噴射弁を制御する第２の噴射弁制御手段と、を備える。 The present invention relates to an engine combustion control apparatus that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, and a second fuel injection after the first fuel injection is performed. The first injection valve control means for controlling the fuel injection valve, the water temperature detection means for detecting the water temperature of the engine, and the determination for determining whether or not the engine water temperature detected by the water temperature detection means is lower than a predetermined temperature And a second fuel injection valve that controls the fuel injection valve so that the third fuel injection is performed before the first fuel injection is performed when it is determined by the means and the determination means that the water temperature of the engine is lower than the predetermined temperature. Injection valve control means.
　本発明の燃焼制御装置においては、エンジンの水温が所定温度よりも低いと判断されたときは、第１の燃料噴射を実施する前に第３の燃料噴射を実施し、その後で第１の燃料噴射及び第２の燃料噴射を順次実施する。これにより、第３の燃料噴射による予熱で着火時期が進角し、熱発生率波形（燃焼波形）が暖気状態での燃焼波形に近づき、燃焼が活発化する。したがって、低水温時においても、未燃ＨＣ及び未燃ＣＯの増加を十分抑制することができる。 In the combustion control device of the present invention, when it is determined that the water temperature of the engine is lower than the predetermined temperature, the third fuel injection is performed before the first fuel injection is performed, and then the first fuel is injected. The injection and the second fuel injection are sequentially performed. As a result, the ignition timing is advanced by preheating by the third fuel injection, the heat generation rate waveform (combustion waveform) approaches the combustion waveform in the warm-up state, and combustion is activated. Therefore, increase in unburned HC and unburned CO can be sufficiently suppressed even at a low water temperature.
　エンジンの負荷を検出する負荷検出手段を更に備え、第２の噴射弁制御手段は、水温検出手段により検出されたエンジンの水温及び負荷検出手段により検出されたエンジンの負荷に応じて、第３の燃料噴射による燃料噴射量を決定する手段を有していてもよい。 Load detecting means for detecting engine load is further provided, and the second injection valve control means is configured to select a third temperature according to the engine water temperature detected by the water temperature detecting means and the engine load detected by the load detecting means. You may have a means to determine the fuel injection quantity by fuel injection.
　この場合、エンジンの水温が低くなるほど、第３の燃料噴射による燃料噴射量が多くされる。これにより、低水温時においても適切な時期で着火を行うことができる。エンジンの負荷が高くなるほど、第３の燃料噴射による燃料噴射量が少なくされる。これにより、高負荷時における過度な燃焼を抑制することができる。 In this case, the fuel injection amount by the third fuel injection is increased as the water temperature of the engine is lowered. Thereby, ignition can be performed at an appropriate time even at low water temperature. As the engine load increases, the amount of fuel injected by the third fuel injection is reduced. Thereby, excessive combustion at the time of high load can be suppressed.
　第２の噴射弁制御手段は、エンジンの負荷を第１の所定値及び第２の所定値と比較判断する手段と、エンジンの負荷が第１の所定値よりも大きいと判断されたときは、第１の燃料噴射による燃料噴射量から第３の燃料噴射による燃料噴射量分を減量し、エンジンの負荷が第２の所定値よりも小さいと判断されたときは、第２の燃料噴射による燃料噴射量から第３の燃料噴射による燃料噴射量分を減量する手段とを有していてもよい。例えば、第１の所定値と第２の所定値とは等しい。 The second injection valve control means compares the engine load with the first predetermined value and the second predetermined value, and when it is determined that the engine load is greater than the first predetermined value, When the fuel injection amount by the third fuel injection is reduced from the fuel injection amount by the first fuel injection and it is determined that the engine load is smaller than the second predetermined value, the fuel by the second fuel injection There may be provided means for reducing the fuel injection amount by the third fuel injection from the injection amount. For example, the first predetermined value and the second predetermined value are equal.
　エンジンの負荷が第１の所定値よりも大きいと判断されたときは、第１の燃料噴射による燃料噴射量から第３の燃料噴射による燃料噴射量分が減量される。これにより、第１の燃料噴射による過度な燃焼が抑制され、燃焼騒音を低減することができる。エンジンの負荷が第２の所定値よりも小さいと判断されたときは、第２の燃料噴射による燃料噴射量から第３の燃料噴射による燃料噴射量分が減量される。これにより、第１の燃料噴射による活発な燃焼が確保され、未燃ＨＣ及び未燃ＣＯを低減することができる。第２の燃料噴射は、第１の燃料噴射に比べて予混合度合いが低い。しかしながら、第２の燃料噴射による燃料噴射量が減量されるので、ＮＯｘやスモークを低減することができる。 When it is determined that the engine load is larger than the first predetermined value, the fuel injection amount by the third fuel injection is reduced from the fuel injection amount by the first fuel injection. Thereby, the excessive combustion by 1st fuel injection is suppressed, and a combustion noise can be reduced. When it is determined that the engine load is smaller than the second predetermined value, the fuel injection amount by the third fuel injection is reduced from the fuel injection amount by the second fuel injection. Thereby, active combustion by the 1st fuel injection is ensured, and unburned HC and unburned CO can be reduced. The second fuel injection has a lower degree of premixing than the first fuel injection. However, since the fuel injection amount by the second fuel injection is reduced, NOx and smoke can be reduced.
　第２の噴射弁制御手段は、第２の燃料噴射による燃料噴射量から第３の燃料噴射による燃料噴射量分を減量する手段を有していてもよい。 The second injection valve control means may have means for reducing the fuel injection amount by the third fuel injection from the fuel injection amount by the second fuel injection.
　この場合には、第１の燃料噴射による活発な燃焼が確保されるため、未燃ＨＣ・ＣＯを低減することができる。第２の燃料噴射は、第１の燃料噴射に比べて予混合度合いが低い。しかしながら、第２の燃料噴射による燃料噴射量が減量されるので、ＮＯｘやスモークを低減することができる。このような構成は、エンジンの負荷が比較的高いときでも燃焼騒音が許容できる場合に効果的である。 In this case, since active combustion is ensured by the first fuel injection, unburned HC / CO can be reduced. The second fuel injection has a lower degree of premixing than the first fuel injection. However, since the fuel injection amount by the second fuel injection is reduced, NOx and smoke can be reduced. Such a configuration is effective when combustion noise can be tolerated even when the engine load is relatively high.
　水温検出手段により検出されたエンジンの水温に応じて、燃焼室内に存在する空気と燃料との比率を制御する空燃比制御手段を更に備えていてもよい。 An air-fuel ratio control means for controlling the ratio of air and fuel existing in the combustion chamber according to the engine water temperature detected by the water temperature detection means may be further provided.
　この場合、エンジンの水温が低くなるほど、燃焼室内に存在する空気と燃料との比率（空燃比）がリーン状態となるように制御される。これにより、着火遅れ時間が短縮される。したがって、燃焼波形を更に暖気状態での燃焼波形に近づけることができる。 In this case, the ratio of air to fuel (air-fuel ratio) existing in the combustion chamber is controlled to become leaner as the engine water temperature becomes lower. Thereby, the ignition delay time is shortened. Therefore, the combustion waveform can be made closer to the combustion waveform in the warm air state.
　燃焼室の吸気部と排気部とを繋ぐ排気再循環通路と、排気再循環通路に設けられ、排気再循環通路を通る排気再循環ガスを冷却する排気再循環クーラと、排気再循環クーラをバイパスするように排気再循環通路に接続されたバイパス通路と、水温検出手段により検出されたエンジンの水温に応じて、排気再循環ガスの流路を排気再循環クーラ側またはバイパス通路側に切り替える流路切り替え手段とを更に備えていてもよい。 An exhaust gas recirculation passage that connects the intake and exhaust portions of the combustion chamber, an exhaust gas recirculation passage that is provided in the exhaust gas recirculation passage, and cools the exhaust gas recirculation gas that passes through the exhaust gas recirculation passage, and bypasses the exhaust gas recirculation cooler A bypass passage connected to the exhaust gas recirculation passage, and a flow passage for switching the exhaust gas recirculation gas flow path to the exhaust gas recirculation cooler side or the bypass passage side according to the engine water temperature detected by the water temperature detecting means And a switching unit.
　この場合、エンジンの水温が設定温度よりも低いときは、排気再循環ガスの流路が排気再循環クーラ側からバイパス通路側に切り替えられる。これにより、高温状態の排気再循環ガスが燃焼室内に導入され、着火遅れ時間が短縮される。したがって、燃焼波形を更に暖気状態での燃焼波形に近づけることができる。 In this case, when the engine water temperature is lower than the set temperature, the flow path of the exhaust gas recirculation is switched from the exhaust gas recirculation cooler side to the bypass passage side. Thereby, the exhaust gas recirculation gas in a high temperature state is introduced into the combustion chamber, and the ignition delay time is shortened. Therefore, the combustion waveform can be made closer to the combustion waveform in the warm air state.
　本発明によれば、低水温時でも、未燃ＨＣ及び未燃ＣＯの増加を十分抑制することができる燃焼制御装置を提供することができる。 According to the present invention, it is possible to provide a combustion control device that can sufficiently suppress an increase in unburned HC and unburned CO even at a low water temperature.
図１は、本実施形態に係わる燃焼制御装置を備えたディーゼルエンジンを示す概略構成図である。FIG. 1 is a schematic configuration diagram showing a diesel engine equipped with a combustion control device according to the present embodiment. 図２は、図１に示した燃焼制御装置の構成を示すブロック図である。FIG. 2 is a block diagram showing a configuration of the combustion control device shown in FIG. 図３は、図２に示したインジェクタ制御部により実行されるインジェクタ制御処理手順の詳細を示すフローチャートである。FIG. 3 is a flowchart showing details of an injector control processing procedure executed by the injector control unit shown in FIG. 図４は、プレ燃料噴射、１回目のメイン燃料噴射、及び２回目のメイン燃料噴射の燃料噴射量及び燃料噴射時期を示す図である。FIG. 4 is a diagram showing the fuel injection amount and fuel injection timing of the pre-fuel injection, the first main fuel injection, and the second main fuel injection. 図５は、熱発生率波形の一例を示すグラフである。FIG. 5 is a graph showing an example of a heat release rate waveform. 図６は、筒内平均温度波形及び熱発生率波形の一例を示すグラフである。FIG. 6 is a graph showing an example of the in-cylinder average temperature waveform and the heat release rate waveform. 図７は、プレ燃料噴射、１回目のメイン燃料噴射、及び２回目のメイン燃料噴射の燃料噴射量及び燃料噴射時期の変形例を示す図である。FIG. 7 is a diagram illustrating a modification of the fuel injection amount and the fuel injection timing of the pre-fuel injection, the first main fuel injection, and the second main fuel injection.
　以下、添付図面を参照して、本発明の好適な実施形態について詳細に説明する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
　図１は、本実施形態に係わる燃焼制御装置を備えたディーゼルエンジンを示す概略構成図である。本実施形態に係るディーゼルエンジン１は、予混合圧縮着火（ＰＣＣＩ）式の４気筒直列ディーゼルエンジンである。ディーゼルエンジン１はエンジン本体２を備え、エンジン本体２には４つのシリンダ３が設けられている。 FIG. 1 is a schematic configuration diagram showing a diesel engine provided with a combustion control device according to the present embodiment. The diesel engine 1 according to the present embodiment is a premixed compression ignition (PCCI) type four-cylinder in-line diesel engine. The diesel engine 1 includes an engine body 2, and the engine body 2 is provided with four cylinders 3.
　各シリンダ３には、燃焼室４内に燃料を噴射するインジェクタ（燃料噴射弁）５がそれぞれ配設されている。インジェクタ５は複数の噴孔（図示せず）を有し、各噴孔から放射状に燃料を噴射する。各インジェクタ５はコモンレール６に接続されており、コモンレール６に貯留された高圧燃料が各インジェクタ５に常時供給されている。 Each cylinder 3 is provided with an injector (fuel injection valve) 5 for injecting fuel into the combustion chamber 4. The injector 5 has a plurality of injection holes (not shown) and injects fuel radially from each injection hole. Each injector 5 is connected to a common rail 6, and high-pressure fuel stored in the common rail 6 is constantly supplied to each injector 5.
　エンジン本体２には、燃焼室４内に空気を吸入するための吸気通路７がインテークマニホールド（吸気部）８を介して接続されている。エンジン本体２には、燃焼後の排気ガスを排出するための排気通路９がエキゾーストマニホールド（排気部）１０を介して接続されている。 The engine body 2 is connected to an intake passage 7 for sucking air into the combustion chamber 4 via an intake manifold (intake section) 8. An exhaust passage 9 for exhausting exhaust gas after combustion is connected to the engine body 2 via an exhaust manifold (exhaust portion) 10.
　吸気通路７には、上流側から下流側に向けてエアクリーナー１１、ターボ過給機１２のコンプレッサ１３、インタークーラー１４、及びスロットルバルブ１５が設けられている。スロットルバルブ１５は、吸気通路７の通路面積を絞り、下流側に負圧を発生させ、後述する排気再循環（ＥＧＲ）を可能とする。排気通路９には、ターボ過給機１２のタービン１６及び触媒付きＤＰＦ１７が設けられている。 In the intake passage 7, an air cleaner 11, a compressor 13 of the turbocharger 12, an intercooler 14, and a throttle valve 15 are provided from the upstream side toward the downstream side. The throttle valve 15 restricts the passage area of the intake passage 7 and generates a negative pressure on the downstream side, thereby enabling exhaust gas recirculation (EGR) described later. In the exhaust passage 9, a turbine 16 of the turbocharger 12 and a DPF 17 with a catalyst are provided.
　ディーゼルエンジン１は、燃焼後の排気ガスの一部を燃焼室４内に還流する排気再循環（ＥＧＲ）装置１８を備えている。ＥＧＲ装置１８は、ＥＧＲ通路１９と、ＥＧＲバルブ２０、ＥＧＲクーラ２１、バイパス通路２２、及び切替弁２３を有している。ＥＧＲ通路１９は、吸気通路７とエキゾーストマニホールド１０とを繋ぐ。ＥＧＲバルブ２０は、エキゾーストマニホールド１０から吸気通路７への排気再循環ガス（ＥＧＲガス）の還流量を調整する。ＥＧＲクーラ２１は、ＥＧＲ通路１９を通るＥＧＲガスを冷却する。バイパス通路２２は、ＥＧＲクーラ２１をバイパスするようにＥＧＲ通路１９に接続されている。切替弁２３は、ＥＧＲガスの流路をＥＧＲクーラ２１側またはバイパス通路２２側に切り替える。 The diesel engine 1 includes an exhaust gas recirculation (EGR) device 18 that recirculates a part of the exhaust gas after combustion into the combustion chamber 4. The EGR device 18 includes an EGR passage 19, an EGR valve 20, an EGR cooler 21, a bypass passage 22, and a switching valve 23. The EGR passage 19 connects the intake passage 7 and the exhaust manifold 10. The EGR valve 20 adjusts the recirculation amount of the exhaust gas recirculation gas (EGR gas) from the exhaust manifold 10 to the intake passage 7. The EGR cooler 21 cools the EGR gas passing through the EGR passage 19. The bypass passage 22 is connected to the EGR passage 19 so as to bypass the EGR cooler 21. The switching valve 23 switches the EGR gas flow path to the EGR cooler 21 side or the bypass passage 22 side.
　各インジェクタ５、スロットルバルブ１５、ＥＧＲバルブ２０、及び切替弁２３は、電子制御ユニット（ＥＣＵ）（コントローラ）２４によって制御される。ＥＣＵ２４には、図２にも示されるように、アクセル開度を検出するアクセル開度センサ２５と、エンジン回転数を検出するエンジン回転センサ２６と、図示しないピストンのクランク軸の角度（クランク角）を検出するクランク角センサ２７と、エンジン水温を検出する水温センサ（水温検出手段）２８とが接続されている。 Each injector 5, throttle valve 15, EGR valve 20, and switching valve 23 are controlled by an electronic control unit (ECU) (controller) 24. As shown in FIG. 2, the ECU 24 includes an accelerator opening sensor 25 that detects the accelerator opening, an engine rotation sensor 26 that detects the engine speed, and a crankshaft angle (crank angle) of a piston (not shown). Is connected to a crank angle sensor 27 for detecting the engine water temperature and a water temperature sensor (water temperature detecting means) 28 for detecting the engine water temperature.
　インジェクタ５、スロットルバルブ１５、ＥＧＲバルブ２０、切替弁２３、ＥＣＵ２４及びセンサ２５～２８は、本実施形態の燃焼制御装置２９を構成している。燃焼制御装置２９では、吸気行程、圧縮行程、膨張行程、及び排気行程という１サイクルにおいて、各インジェクタ５から燃料を複数回に分けて噴射する分割噴射の予混合圧縮着火燃焼を行うように制御する。 The injector 5, the throttle valve 15, the EGR valve 20, the switching valve 23, the ECU 24, and the sensors 25 to 28 constitute a combustion control device 29 of the present embodiment. The combustion control device 29 performs control so that premixed compression ignition combustion of split injection in which fuel is injected from each injector 5 in a plurality of times in one cycle of an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. .
　図２は、燃焼制御装置２９の構成を示すブロック図である。ＥＣＵ２４は、エンジン負荷算出部３０と、インジェクタ制御部３１と、ＥＧＲ制御部３２と、を有している。 FIG. 2 is a block diagram showing the configuration of the combustion control device 29. The ECU 24 includes an engine load calculation unit 30, an injector control unit 31, and an EGR control unit 32.
　エンジン負荷算出部３０は、アクセル開度センサ２５により検出されたアクセル開度、エンジン回転センサ２６により検出されたエンジン回転数、及びその他の条件に基づいて、エンジン負荷を算出する。 Engine load calculation unit 30 calculates the engine load based on the accelerator opening detected by accelerator opening sensor 25, the engine speed detected by engine rotation sensor 26, and other conditions.
　インジェクタ制御部３１は、エンジン負荷算出部３０により算出されたエンジン負荷及びエンジン回転数から、燃料噴射回数、燃料噴射量及び燃料噴射時期の基本値を決定する。インジェクタ制御部３１は、水温センサ２８により検出されたエンジン水温に基づいて補正を行い、燃料噴射回数、燃料噴射量、及び燃料噴射時期を決定し、各インジェクタ５を制御する。すなわち、ＥＣＵ２４は、決定した燃料噴射回数、燃料噴射量、及び燃料噴射時期に基づいて、各インジェクタ５を操作する。 The injector control unit 31 determines basic values of the number of fuel injections, the fuel injection amount, and the fuel injection timing from the engine load and the engine speed calculated by the engine load calculation unit 30. The injector control unit 31 performs correction based on the engine water temperature detected by the water temperature sensor 28, determines the number of fuel injections, the fuel injection amount, and the fuel injection timing, and controls each injector 5. That is, the ECU 24 operates each injector 5 based on the determined number of fuel injections, fuel injection amount, and fuel injection timing.
　図３は、インジェクタ制御部３１により実行されるインジェクタ制御処理手順の詳細を示すフローチャートである。 FIG. 3 is a flowchart showing details of the injector control processing procedure executed by the injector control unit 31.
　まず、インジェクタ制御部３１は、エンジン負荷算出部３０により算出されたエンジン負荷に基づいて、図４に示されるように、１回目のメイン燃料噴射（第１の燃料噴射）及びこの後に実施される２回目のメイン燃料噴射（第２の燃料噴射）それぞれの燃料噴射量及び燃料噴射時期を決定する（Ｓ１０１）。このとき、２回目のメイン燃料噴射の燃料噴射量は、例えば１回目のメイン燃料噴射の燃料噴射量よりも少ない。２回目のメイン燃料噴射は、例えばクランク角が圧縮上死点（ＴＤＣ）直前となる時期に開始する。図４は、高負荷時及び低負荷時それぞれにおける、プレ燃料噴射並びに１回目及び２回目のメイン燃料噴射の燃料噴射量及び燃料噴射時期を示す。 First, based on the engine load calculated by the engine load calculation unit 30, the injector control unit 31 performs the first main fuel injection (first fuel injection) and thereafter, as shown in FIG. The fuel injection amount and fuel injection timing for each of the second main fuel injection (second fuel injection) are determined (S101). At this time, the fuel injection amount of the second main fuel injection is, for example, smaller than the fuel injection amount of the first main fuel injection. The second main fuel injection starts, for example, at a time when the crank angle is just before the compression top dead center (TDC). FIG. 4 shows the fuel injection amount and fuel injection timing of the pre-fuel injection and the first and second main fuel injections at the time of high load and low load, respectively.
　続いて、インジェクタ制御部３１は、水温センサ２８により検出されたエンジン水温が所定温度（例えば８０℃）よりも低いかどうかを判断する（Ｓ１０２）。 Subsequently, the injector control unit 31 determines whether or not the engine water temperature detected by the water temperature sensor 28 is lower than a predetermined temperature (for example, 80 ° C.) (S102).
　インジェクタ制御部３１は、エンジン水温が所定温度よりも低くないと判断したときは、Ｓ１０１で決定された燃料噴射量に従って１回目のメイン燃料噴射を実施するように、インジェクタ５を制御する（Ｓ１０８）。続いて、インジェクタ制御部３１は、Ｓ１０１で決定された燃料噴射量に従って２回目のメイン燃料噴射を実施するように、インジェクタ５を制御する（Ｓ１０９）。 When it is determined that the engine water temperature is not lower than the predetermined temperature, the injector control unit 31 controls the injector 5 so that the first main fuel injection is performed according to the fuel injection amount determined in S101 (S108). . Subsequently, the injector control unit 31 controls the injector 5 to perform the second main fuel injection according to the fuel injection amount determined in S101 (S109).
　インジェクタ制御部３１は、Ｓ１０２でエンジン水温が所定温度よりも低いと判断したときは、エンジン負荷及びエンジン水温に基づいて、図４に示されるように、１回目のメイン燃料噴射の前に実施されるプレ燃料噴射（第３の燃料噴射）の燃料噴射量及び燃料噴射時期を決定する（Ｓ１０３）。 When it is determined in S102 that the engine water temperature is lower than the predetermined temperature, the injector control unit 31 is performed before the first main fuel injection as shown in FIG. 4 based on the engine load and the engine water temperature. The fuel injection amount and fuel injection timing of the pre-fuel injection (third fuel injection) are determined (S103).
　プレ燃料噴射の燃料噴射量は、１回目及び２回目のメイン燃料噴射の燃料噴射量よりも少ない。エンジン水温が低くなるほど、プレ燃料噴射の燃料噴射量は多く、エンジン負荷が高くなるほど、プレ燃料噴射の燃料噴射量は少ない。 The fuel injection amount of the pre-fuel injection is smaller than the fuel injection amount of the first and second main fuel injections. The lower the engine water temperature, the greater the fuel injection amount for pre-fuel injection, and the higher the engine load, the smaller the fuel injection amount for pre-fuel injection.
　プレ燃料噴射と１回目のメイン燃料噴射との間隔は、インジェクタ５の隣接する噴孔からの噴霧の重なりや隙間を防ぐために、ボア、ストローク、インジェクタ５の噴孔数、及びスワール比等から算出される適切なインターバルに設定される。これにより、局所リッチ及び局所リーンが回避され、未燃分の燃料の生成が抑えられる。 The interval between the pre-fuel injection and the first main fuel injection is calculated from the bore, stroke, number of injection holes of the injector 5, the swirl ratio, etc. in order to prevent spray overlap and gaps from adjacent injection holes of the injector 5. Is set to an appropriate interval. As a result, local rich and local lean are avoided, and generation of unburned fuel is suppressed.
　続いて、インジェクタ制御部３１は、エンジン負荷が所定値よりも高いかどうかを判断する（Ｓ１０４）。インジェクタ制御部３１は、エンジン負荷が所定値より高いと判断したときは、図４（ａ）に示されるように、１回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分を減量する（Ｓ１０５）。従って、Ｓ１０１で設定された１回目のメイン燃料噴射の燃料噴射量が補正される。インジェクタ制御部３１は、エンジン負荷が所定値より高くないと判断したときは、図４（ｂ）に示されるように、２回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分を減量する（Ｓ１０６）。従って、Ｓ１０１で設定された２回目のメイン燃料噴射の燃料噴射量が補正される。 Subsequently, the injector control unit 31 determines whether the engine load is higher than a predetermined value (S104). When the injector control unit 31 determines that the engine load is higher than the predetermined value, as shown in FIG. 4A, the fuel injection amount of the pre-fuel injection is calculated from the fuel injection amount of the first main fuel injection. The weight is reduced (S105). Therefore, the fuel injection amount of the first main fuel injection set in S101 is corrected. When the injector control unit 31 determines that the engine load is not higher than the predetermined value, as shown in FIG. 4B, the fuel injection amount of the pre-fuel injection is calculated from the fuel injection amount of the second main fuel injection. Is reduced (S106). Therefore, the fuel injection amount of the second main fuel injection set in S101 is corrected.
　インジェクタ制御部３１は、Ｓ１０５及びＳ１０６を実行した後、Ｓ１０３で設定された燃料噴射量に従ってプレ燃料噴射を実施するように、インジェクタ５を制御する（Ｓ１０７）。続いて、インジェクタ制御部３１は、Ｓ１０１で設定された燃料噴射量またはＳ１０５で補正された燃料噴射量に従って１回目のメイン燃料噴射を実施するように、インジェクタ５を制御する（Ｓ１０８）。続いて、インジェクタ制御部３１は、Ｓ１０１で設定された燃料噴射量またはＳ１０６で補正された燃料噴射量に従って２回目のメイン燃料噴射を実施するように、インジェクタ５を制御する（Ｓ１０９）。 After performing S105 and S106, the injector control unit 31 controls the injector 5 so as to perform pre-fuel injection according to the fuel injection amount set in S103 (S107). Subsequently, the injector control unit 31 controls the injector 5 to perform the first main fuel injection according to the fuel injection amount set in S101 or the fuel injection amount corrected in S105 (S108). Subsequently, the injector control unit 31 controls the injector 5 to perform the second main fuel injection according to the fuel injection amount set in S101 or the fuel injection amount corrected in S106 (S109).
　再び図２を参照する。ＥＧＲ制御部３２は、エンジン水温に応じて、ＥＧＲバルブ２０及び切替弁２３を制御する。具体的には、ＥＧＲ制御部３２は、エンジン水温が低くなるほどＥＧＲガスの流量が減少するように、ＥＧＲバルブ２０を制御する。また、ＥＧＲ制御部３２は、エンジン水温が予め設定された基準温度以下であるかどうかを判断する。ＥＧＲ制御部３２は、エンジン水温が基準温度よりも高いときは、ＥＧＲガスがＥＧＲクーラ２１を通るように切替弁２３を制御する。ＥＧＲ制御部３２は、エンジン水温が基準温度以下であるときは、ＥＧＲガスがバイパス通路２２を通るように切替弁２３を制御する。 Refer to FIG. 2 again. The EGR control unit 32 controls the EGR valve 20 and the switching valve 23 according to the engine water temperature. Specifically, the EGR control unit 32 controls the EGR valve 20 so that the flow rate of the EGR gas decreases as the engine water temperature decreases. Further, the EGR control unit 32 determines whether or not the engine water temperature is equal to or lower than a preset reference temperature. The EGR control unit 32 controls the switching valve 23 so that the EGR gas passes through the EGR cooler 21 when the engine water temperature is higher than the reference temperature. The EGR control unit 32 controls the switching valve 23 so that the EGR gas passes through the bypass passage 22 when the engine water temperature is equal to or lower than the reference temperature.
　以上において、ＥＣＵ２４のインジェクタ制御部３１は、上記Ｓ１０１、Ｓ１０８、及びＳ１０９を実行することにより、第１の燃料噴射を実施してから第２の燃料噴射を実施するように燃料噴射弁（インジェクタ５）を制御する第１の噴射弁制御手段を構成する。インジェクタ制御部３１は、Ｓ１０２を実行することにより、水温検出手段（水温センサ２８）により検出されたエンジンの水温が所定温度よりも低いかどうかを判断する判断手段を構成する。インジェクタ制御部３１は、Ｓ１０３～Ｓ１０７を実行することにより、判断手段によりエンジンの水温が所定温度よりも低いと判断されたときに、第１の燃料噴射を実施する前に第３の燃料噴射を実施するように燃料噴射弁を制御する第２の噴射弁制御手段を構成する。 In the above, the injector control unit 31 of the ECU 24 executes the above-described S101, S108, and S109 so that the first fuel injection is performed and then the second fuel injection is performed (the injector 5). ) Is constituted. The injector control unit 31 constitutes a determination unit that determines whether or not the engine water temperature detected by the water temperature detection unit (water temperature sensor 28) is lower than a predetermined temperature by executing S102. The injector control unit 31 executes the third fuel injection before the first fuel injection when the determination means determines that the engine water temperature is lower than the predetermined temperature by executing S103 to S107. The second injection valve control means for controlling the fuel injection valve is configured to be implemented.
　アクセル開度センサ２５とエンジン回転センサ２６とＥＣＵ２４のエンジン負荷算出部３０とは、エンジンの負荷を検出する負荷検出手段を構成する。ＥＣＵ２４のＥＧＲ制御部３２とＥＧＲバルブ２０とは、水温検出手段により検出されたエンジンの水温に応じて、燃焼室４内に存在する空気と燃料との比率を制御する空燃比制御手段を構成する。ＥＣＵ２４のＥＧＲ制御部３２と切替弁２３とは、水温検出手段により検出されたエンジンの水温に応じて、排気再循環ガスの流路を排気再循環クーラ２１側またはバイパス通路２２側に切り替える流路切り替え手段を構成する。 The accelerator opening sensor 25, the engine rotation sensor 26, and the engine load calculation unit 30 of the ECU 24 constitute load detection means for detecting the engine load. The EGR control unit 32 and the EGR valve 20 of the ECU 24 constitute air-fuel ratio control means for controlling the ratio of air and fuel existing in the combustion chamber 4 in accordance with the engine water temperature detected by the water temperature detection means. . The EGR control unit 32 and the switching valve 23 of the ECU 24 switch the flow path of the exhaust recirculation gas to the exhaust recirculation cooler 21 side or the bypass passage 22 side according to the engine water temperature detected by the water temperature detecting means. The switching means is configured.
　本実施形態において、エンジン１が通常の暖気状態（例えば８０℃以上）にあるときは、プレ燃料噴射が実施されずに、１回目のメイン燃料噴射及び２回目のメイン燃料噴射が順に実施される。すると、１回目及び２回目のメイン燃料噴射の終了後にそれぞれ所定期間を経て、燃料と空気との予混合気の着火が開始されるため、図５の破線Ｐで示すように、二山形状の熱発生率波形（燃焼波形）が得られる。 In the present embodiment, when the engine 1 is in a normal warm-up state (for example, 80 ° C. or higher), the pre-fuel injection is not performed and the first main fuel injection and the second main fuel injection are sequentially performed. . Then, since the ignition of the premixed mixture of fuel and air is started after a predetermined period after the first and second main fuel injections are finished, as shown by the broken line P in FIG. A heat release rate waveform (combustion waveform) is obtained.
　エンジン１が低水温状態にあるときに、プレ燃料噴射が実施されずに、１回目のメイン燃料噴射及び２回目のメイン燃料噴射が順に実施された場合には、燃料と空気との予混合気の着火時期が暖気状態に比べて遅れる。したがって、燃焼波形は、図５の一点鎖線Ｑで示される燃焼波形となる。図５は、暖気状態である場合、低水温時においてプレ燃料噴射及びＥＧＲガスの減量を実施しない場合、低水温時においてプレ燃料噴射及びＥＧＲガスの減量を実施する場合それぞれにおける、熱発生率波形の一例を示す。 When the engine 1 is in a low water temperature state, when the first main fuel injection and the second main fuel injection are sequentially performed without performing the pre-fuel injection, the premixed fuel and air are mixed. The ignition timing is delayed compared to the warm-up state. Therefore, the combustion waveform is a combustion waveform indicated by a one-dot chain line Q in FIG. FIG. 5 shows a heat generation rate waveform in the case of the warm-up state, when the pre-fuel injection and the EGR gas are not reduced at the low water temperature, and when the pre-fuel injection and the EGR gas are reduced at the low water temperature. An example is shown.
　これに対し本実施形態のように、エンジン１が低水温状態にあるときに、プレ燃料噴射が実施されてから１回目のメイン燃料噴射及び２回目のメイン燃料噴射が順に実施されると共に、ＥＧＲガスの流量が減少すると、図５の実線Ｒで示されるように、燃焼波形が暖気状態での燃焼波形にほぼ一致する。その理由は、以下の通りである。 In contrast, as in the present embodiment, when the engine 1 is in a low water temperature state, the first main fuel injection and the second main fuel injection are sequentially performed after the pre-fuel injection is performed, and the EGR is performed. When the gas flow rate decreases, the combustion waveform substantially coincides with the combustion waveform in the warm-up state, as indicated by the solid line R in FIG. The reason is as follows.
　プレ燃料噴射が実施されると、そのプレ燃料噴射の予熱によって着火時期が進角する。また、ＥＧＲガスの流量が減少すると、空気と燃料との比率（空燃比）がリーン状態となる。このため、良好な燃焼性が確保され、着火遅れ期間が短縮される。これらにより、着火時期が適切な時期となり、燃焼波形が暖気状態での燃焼波形にほぼ一致する。 When the pre-fuel injection is performed, the ignition timing is advanced by the pre-heating of the pre-fuel injection. Further, when the flow rate of EGR gas decreases, the ratio of air to fuel (air-fuel ratio) becomes lean. For this reason, good combustibility is ensured and the ignition delay period is shortened. As a result, the ignition timing becomes an appropriate timing, and the combustion waveform substantially matches the combustion waveform in the warm-up state.
　エンジン１が低負荷状態にあるときは、上述したように２回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分が減量されるため、プレ燃料噴射の燃料噴射量と１回目のメイン燃料噴射の燃料噴射量との合計量が増加する。エンジン１が高負荷状態にあるときは、上述したように１回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分が減量されるため、プレ燃料噴射の燃料噴射量と１回目のメイン燃料噴射の燃料噴射量との合計量は変わらない。 When the engine 1 is in a low-load state, as described above, the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the second main fuel injection. The total amount of the main fuel injection and the fuel injection amount increases. When the engine 1 is in a high load state, as described above, the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the first main fuel injection. The total amount of the main fuel injection and the fuel injection amount does not change.
　この制御の違いによる作用を、図６により説明する。同量の燃料が低負荷状態の制御パターン（破線Ｘ）で噴射された場合には、高負荷状態の制御パターン（実線Ｙ）で噴射された場合と比較して、筒内平均温度が高くなり、その結果として熱発生率が高くなる。従って、燃料が低負荷状態の制御パターンで噴射されることで、未燃ＨＣ及び未燃ＣＯを低減することができる。図６は、低水温時においてプレ燃料噴射を実施する場合に、高負荷時及び低負荷時それぞれにおける、筒内平均温度波形及び熱発生率波形の一例を示す。 The effect of this control difference will be described with reference to FIG. When the same amount of fuel is injected with a control pattern in a low load state (broken line X), the in-cylinder average temperature is higher than when injected with a control pattern in a high load state (solid line Y). As a result, the heat generation rate is increased. Therefore, unburned HC and unburned CO can be reduced by injecting fuel with a control pattern in a low load state. FIG. 6 shows an example of the in-cylinder average temperature waveform and the heat release rate waveform at high load and low load, respectively, when pre-fuel injection is performed at low water temperature.
　以上のように本実施形態にあっては、エンジン水温が所定温度よりも低いときは、１回目のメイン燃料噴射の前にプレ燃料噴射が実施され、その後に１回目のメイン燃料噴射及び２回目のメイン燃料噴射が順次実施される。このため、プレ燃料噴射による予熱で着火時期が進角し、燃焼波形が暖気状態での燃焼波形に近づく。このとき、プレ燃料噴射ではエンジン水温に応じた燃料噴射量が設定されるので、プレ燃料噴射及び１回目のメイン燃料噴射による燃焼が活発化される。これにより、未燃ＨＣ及び未燃ＣＯを低減することができる。 As described above, in the present embodiment, when the engine water temperature is lower than the predetermined temperature, the pre-fuel injection is performed before the first main fuel injection, and then the first main fuel injection and the second main fuel injection are performed. The main fuel injection is sequentially performed. For this reason, the ignition timing is advanced by preheating by pre-fuel injection, and the combustion waveform approaches the combustion waveform in the warm-up state. At this time, since the fuel injection amount corresponding to the engine water temperature is set in the pre-fuel injection, combustion by the pre-fuel injection and the first main fuel injection is activated. Thereby, unburned HC and unburned CO can be reduced.
　エンジン水温が低い状態においてエンジン負荷が所定値以下であるときは、２回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分が減量される。これにより、１回目のメイン燃料噴射による燃焼が活発化され、未燃ＨＣ・ＣＯを低減することができる。また、予混合度合いが低い２回目のメイン燃料噴射の燃料噴射量が減少すると共に、予混合度合いが高いプレ燃料噴射及び１回目のメイン燃料噴射の燃料噴射量の合計が増加する。これにより、ＮＯｘやスモークを低減することができる。 When the engine load is below a predetermined value when the engine water temperature is low, the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the second main fuel injection. Thereby, combustion by the first main fuel injection is activated, and unburned HC / CO can be reduced. In addition, the fuel injection amount of the second main fuel injection with a low premixing degree decreases, and the sum of the fuel injection amounts of the pre-fuel injection with a high premixing degree and the first main fuel injection increases. Thereby, NOx and smoke can be reduced.
　エンジン水温が低い状態においてエンジン負荷が所定値よりも高いときは、１回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分が減量される。これにより、１回目のメイン燃料噴射による過度な燃焼の活発化が抑えられ、燃焼騒音の増大を抑制することができる。 When the engine load is higher than a predetermined value when the engine water temperature is low, the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the first main fuel injection. Thereby, excessive activation of combustion due to the first main fuel injection is suppressed, and an increase in combustion noise can be suppressed.
　エンジン水温が低くなるほど、ＥＧＲガスの流量が減少する。これにより、空燃比がリーン状態となり、燃焼が活発化する。さらに、エンジン水温が基準温度以下であるときは、切替弁２３がＥＧＲクーラ２１側からバイパス通路２２側に切り替えられる。これにより、ＥＧＲガスがバイパス通路２２を通るようになり、ＥＧＲクーラ２１で冷やされない高温状態のＥＧＲガスが燃焼室４内に再循環され、燃焼が安定化する。以上により、着火遅れが少なくなり、燃焼波形が暖気状態での燃焼波形に更に近づく。その結果、未燃ＨＣ及び未燃ＣＯの増加を一層抑制することができる。 ¡The flow rate of EGR gas decreases as the engine water temperature decreases. As a result, the air-fuel ratio becomes lean and combustion is activated. Further, when the engine water temperature is equal to or lower than the reference temperature, the switching valve 23 is switched from the EGR cooler 21 side to the bypass passage 22 side. As a result, the EGR gas passes through the bypass passage 22 and the high-temperature EGR gas that is not cooled by the EGR cooler 21 is recirculated into the combustion chamber 4 to stabilize the combustion. As described above, the ignition delay is reduced, and the combustion waveform becomes closer to the combustion waveform in the warm-up state. As a result, an increase in unburned HC and unburned CO can be further suppressed.
　以上のように本実施形態によれば、低水温時においても、暖気後と同様な予混合圧縮着火燃焼を実現し、ＨＣやＣＯ、燃焼騒音、及びエミッションの増大を十分抑制することができる。 As described above, according to this embodiment, even when the water temperature is low, premixed compression ignition combustion similar to that after warming-up can be realized, and increase in HC, CO, combustion noise, and emission can be sufficiently suppressed.
　別の観点では、本実施形態は、予混合圧縮着火燃焼を行うエンジンの燃焼制御装置であって、エンジンの燃焼室内に燃料を噴射する燃料噴射弁と、エンジンの水温を検出する水温センサと、燃料噴射弁を操作するコントローラと、を備え、コントローラは、第１の燃料噴射を実施してから第２の燃料噴射を実施するように燃料噴射弁を操作し、水温センサにより検出されたエンジンの水温が所定温度よりも低いと判断したときに、第１の燃料噴射を実施する前に第３の燃料噴射を実施するように燃料噴射弁を操作する。また、燃焼制御装置は、アクセル開度を検出するアクセル開度センサと、エンジン回転数を検出するエンジン回転センサと、を更に備え、コントローラは、アクセル開度センサで検出されたアクセル開度とエンジン回転数センサにより検出されたエンジン回転数とを含む情報に基づいてエンジン負荷を算出してもよい。燃焼制御装置は、燃焼室内に存在する空気の量を調整する弁を更に備え、コントローラは、水温センサにより検出された水温に応じて、燃焼室内に存在する空気と燃料との比率を制御するように弁を操作してもよい。燃焼室内に存在する空気の量を調整する弁が、排気再循環ガスの流量を調整する弁であってもよい。 In another aspect, the present embodiment is an engine combustion control apparatus that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, a water temperature sensor that detects a water temperature of the engine, And a controller for operating the fuel injection valve. The controller operates the fuel injection valve so as to perform the second fuel injection after performing the first fuel injection, and detects the engine detected by the water temperature sensor. When it is determined that the water temperature is lower than the predetermined temperature, the fuel injection valve is operated so that the third fuel injection is performed before the first fuel injection is performed. The combustion control device further includes an accelerator opening sensor that detects the accelerator opening, and an engine rotation sensor that detects the engine speed, and the controller includes the accelerator opening detected by the accelerator opening sensor and the engine. The engine load may be calculated based on information including the engine speed detected by the speed sensor. The combustion control device further includes a valve for adjusting the amount of air present in the combustion chamber, and the controller controls the ratio of air and fuel present in the combustion chamber according to the water temperature detected by the water temperature sensor. The valve may be operated. The valve that adjusts the amount of air present in the combustion chamber may be a valve that adjusts the flow rate of the exhaust gas recirculation gas.
　更に別の観点では、本実施形態は、予混合圧縮着火燃焼を行うエンジンの燃焼制御装置であって、エンジンの燃焼室内に燃料を噴射する燃料噴射弁と、エンジンの水温を検出する水温センサと、第１の燃料噴射を実施してから第２の燃料噴射を実施するように燃料噴射弁を操作し、水温センサにより検出されたエンジンの水温が所定温度よりも低いと判断したときに、第１の燃料噴射を実施する前に第３の燃料噴射を実施するように燃料噴射弁を操作するように構成されたコントローラと、を備える。 In yet another aspect, this embodiment is a combustion control apparatus for an engine that performs premixed compression ignition combustion, a fuel injection valve that injects fuel into a combustion chamber of the engine, a water temperature sensor that detects a water temperature of the engine, When the fuel injection valve is operated so that the second fuel injection is performed after the first fuel injection is performed and it is determined that the engine water temperature detected by the water temperature sensor is lower than the predetermined temperature, And a controller configured to operate the fuel injection valve to perform a third fuel injection before performing one fuel injection.
　なお、本発明は、上記実施形態に限定されるものではない。例えば上記実施形態では、インジェクタ制御部３１は、エンジン負荷が所定値よりも高いとき、１回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分を減量する（図４（ａ）参照）。エンジン負荷が所定値よりも高い場合でも、燃焼騒音の増加が許容できるのであれば、図７に示されるように、インジェクタ制御部３１は、２回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分を減量してもよい。この場合には、予混合度合いが低い２回目のメイン燃料噴射の燃料噴射量が減少するので、スモークの低減に寄与することができる。 Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, when the engine load is higher than a predetermined value, the injector control unit 31 reduces the fuel injection amount of the pre-fuel injection from the fuel injection amount of the first main fuel injection (FIG. 4A). reference). Even if the engine load is higher than the predetermined value, if the increase in combustion noise can be tolerated, as shown in FIG. 7, the injector control unit 31 performs pre-fuel injection from the fuel injection amount of the second main fuel injection. The fuel injection amount may be reduced. In this case, since the fuel injection amount of the second main fuel injection with a low premixing degree is reduced, it is possible to contribute to the reduction of smoke.
　上記実施形態では、インジェクタ制御部３１は、プレ燃料噴射の燃料噴射量分をメイン燃料噴射の燃料噴射量から減量する際に、エンジン負荷と１つの所定値との比較結果に基づいて、１回目または２回目のメイン燃料噴射のいずかの燃料噴射量からプレ燃料噴射の燃料噴射量分を減量するかを決定している。エンジン負荷との比較に用いる所定値は、１つに限定されない。比較値として、例えば、第１の所定値と、この第１の所定値よりも小さい第２の所定値とが設定されてもよい。この場合、インジェクタ制御部３１は、エンジン負荷が第１の所定値よりも大きな高負荷時には、１回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分を減量し、エンジン負荷が第２の所定値よりも小さな低負荷時には、２回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分を減量し、エンジン負荷が第１の所定値以下で第２の所定値以上の中負荷時には、１回目及び２回目のメイン燃料噴射の燃料噴射量の両方からプレ燃料噴射の燃料噴射量分を減量してもよい。つまり、少なくとも、高負荷側に１回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分が減量される領域が設定され、低負荷側に２回目のメイン燃料噴射の燃料噴射量からプレ燃料噴射の燃料噴射量分が減量される領域が設定されていればよい。インジェクタ制御部３１は、中負荷時において、１回目及び２回目のメイン燃料噴射の燃料噴射量の両方からプレ燃料噴射の燃料噴射量分を減量する際に、一律で同じ燃料噴射量を減量してもよく、或いは各メイン燃料噴射の燃料噴射量から減らす量を徐変してもよい。 In the above embodiment, the injector control unit 31 performs the first time based on the comparison result between the engine load and one predetermined value when reducing the fuel injection amount of the pre-fuel injection from the fuel injection amount of the main fuel injection. Alternatively, it is determined whether to reduce the fuel injection amount of the pre-fuel injection from the fuel injection amount of the second main fuel injection. The predetermined value used for comparison with the engine load is not limited to one. As the comparison value, for example, a first predetermined value and a second predetermined value smaller than the first predetermined value may be set. In this case, when the engine load is a high load larger than the first predetermined value, the injector control unit 31 reduces the fuel injection amount of the pre-fuel injection from the fuel injection amount of the first main fuel injection, and the engine load is reduced. At a low load smaller than the second predetermined value, the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the second main fuel injection, and the second predetermined value when the engine load is equal to or less than the first predetermined value. At the above medium load, the fuel injection amount of the pre-fuel injection may be reduced from both of the fuel injection amounts of the first and second main fuel injections. That is, at least a region where the fuel injection amount of the pre-fuel injection is reduced from the fuel injection amount of the first main fuel injection is set on the high load side, and the fuel injection amount of the second main fuel injection is set on the low load side. It is only necessary to set a region where the fuel injection amount of the pre-fuel injection is reduced. The injector control unit 31 uniformly reduces the same fuel injection amount when the fuel injection amount of the pre-fuel injection is reduced from both the first and second main fuel injection amounts at medium load. Alternatively, the amount to be reduced from the fuel injection amount of each main fuel injection may be gradually changed.
　上記実施形態では、切替弁２３により排気再循環ガスの流路が排気再循環クーラ２１側またはバイパス通路２２側に切り替えている。切替弁２３の操作は、単なる切り替えに限定されない。切替弁２３は、例えば排気再循環ガスの流量が徐変される領域を含むように操作されてもよい。 In the above embodiment, the flow path of the exhaust gas recirculation gas is switched to the exhaust gas recirculation cooler 21 side or the bypass passage 22 side by the switching valve 23. The operation of the switching valve 23 is not limited to simple switching. The switching valve 23 may be operated to include a region where the flow rate of the exhaust gas recirculation gas is gradually changed, for example.
　上記実施形態では、エンジン水温に応じて、ＥＧＲバルブ２０によりＥＧＲガスの流量が調整されることにより、燃焼室４内の空燃比が制御されているが、燃焼室４内の空燃比の制御手法はこれに限られない。エンジン水温に応じて、スロットルバルブ１５により空気の吸入量が調整されることにより、燃焼室４内の空燃比が制御されてもよい。また、エンジン水温に応じてＥＧＲバルブ２０及びスロットルバルブ１５の両方が制御されてもよい。 In the above embodiment, the air-fuel ratio in the combustion chamber 4 is controlled by adjusting the flow rate of the EGR gas by the EGR valve 20 according to the engine water temperature. Is not limited to this. The air-fuel ratio in the combustion chamber 4 may be controlled by adjusting the intake amount of air by the throttle valve 15 according to the engine water temperature. Further, both the EGR valve 20 and the throttle valve 15 may be controlled according to the engine water temperature.
　上記実施形態では、１サイクル毎に２回のメイン燃料噴射が実施されているが、１サイクル毎にメイン燃料噴射が３回以上実施されていてもよい。 In the above embodiment, the main fuel injection is performed twice per cycle, but the main fuel injection may be performed three or more times per cycle.
　本発明は、予混合圧縮着火燃焼を行うエンジンの燃料制御装置に利用できる。 The present invention can be used for a fuel control device of an engine that performs premixed compression ignition combustion.
　１…ディーゼルエンジン、４…燃焼室、５…インジェクタ（燃料噴射弁）、８…インテークマニホールド（吸気部）、１０…エキゾーストマニホールド（排気部）、１５…スロットルバルブ（空燃比制御手段）、１９…ＥＧＲ通路（排気再循環通路）、２０…ＥＧＲバルブ（空燃比制御手段）、２１…ＥＧＲクーラ（排気再循環クーラ）、２２…バイパス通路、２３…切替弁（流路切り替え手段）、２４…ＥＣＵ（制御手段）、２５…アクセル開度センサ（負荷検出手段）、２６…エンジン回転センサ（負荷検出手段）、２８…水温センサ（水温検出手段）、２９…燃焼制御装置、３０…エンジン負荷算出部（負荷検出手段）、３１…インジェクタ制御部（第１の噴射弁制御手段、判断手段、第２の噴射弁制御手段）、３２…ＥＧＲ制御部（空燃比制御手段、流路切り替え手段）。 DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 4 ... Combustion chamber, 5 ... Injector (fuel injection valve), 8 ... Intake manifold (intake part), 10 ... Exhaust manifold (exhaust part), 15 ... Throttle valve (air-fuel ratio control means), 19 ... EGR passage (exhaust recirculation passage), 20 ... EGR valve (air-fuel ratio control means), 21 ... EGR cooler (exhaust recirculation cooler), 22 ... bypass passage, 23 ... switching valve (flow passage switching means), 24 ... ECU (Control means), 25 ... accelerator opening sensor (load detection means), 26 ... engine rotation sensor (load detection means), 28 ... water temperature sensor (water temperature detection means), 29 ... combustion control device, 30 ... engine load calculation unit (Load detection means), 31 ... injector control section (first injection valve control means, judgment means, second injection valve control means), 32 ... EGR control section Air-fuel ratio control means, the flow path switching means).

Claims (7)

  1. 　予混合圧縮着火燃焼を行うエンジンの燃焼制御装置であって、
    　前記エンジンの燃焼室内に燃料を噴射する燃料噴射弁と、
    　第１の燃料噴射を実施してから第２の燃料噴射を実施するように前記燃料噴射弁を制御する第１の噴射弁制御手段と、
    　前記エンジンの水温を検出する水温検出手段と、
    　前記水温検出手段により検出された前記エンジンの水温が所定温度よりも低いかどうかを判断する判断手段と、
    　前記判断手段により前記エンジンの水温が前記所定温度よりも低いと判断されたときに、前記第１の燃料噴射を実施する前に第３の燃料噴射を実施するように前記燃料噴射弁を制御する第２の噴射弁制御手段とを備える。     An engine combustion control device that performs premixed compression ignition combustion,
    A fuel injection valve for injecting fuel into the combustion chamber of the engine;
    First injection valve control means for controlling the fuel injection valve so as to perform the second fuel injection after the first fuel injection;
    Water temperature detecting means for detecting the water temperature of the engine;
    Determining means for determining whether the water temperature of the engine detected by the water temperature detecting means is lower than a predetermined temperature;
    When the determination means determines that the water temperature of the engine is lower than the predetermined temperature, the fuel injection valve is controlled so that a third fuel injection is performed before the first fuel injection is performed. Second injection valve control means.
  2. 　請求項１に記載の燃焼制御装置であって、
    　前記エンジンの負荷を検出する負荷検出手段を更に備え、
    　前記第２の噴射弁制御手段は、前記水温検出手段により検出された前記エンジンの水温及び前記負荷検出手段により検出された前記エンジンの負荷に応じて、前記第３の燃料噴射による燃料噴射量を決定する手段を有する。     The combustion control device according to claim 1,
    A load detecting means for detecting the load of the engine;
    The second injection valve control means determines a fuel injection amount by the third fuel injection in accordance with the water temperature of the engine detected by the water temperature detection means and the engine load detected by the load detection means. Has a means to determine.
  3. 　請求項２に記載の燃焼制御装置であって、
    　前記第２の噴射弁制御手段は、前記エンジンの負荷を第１の所定値及び第２の所定値と比較判断する手段と、前記エンジンの負荷が前記第１の所定値よりも大きいと判断されたときは、前記第１の燃料噴射による燃料噴射量から前記第３の燃料噴射による燃料噴射量分を減量し、前記エンジンの負荷が前記第２の所定値よりも小さいと判断されたときは、前記第２の燃料噴射による燃料噴射量から前記第３の燃料噴射による燃料噴射量分を減量する手段とを有する。     The combustion control device according to claim 2,
    The second injection valve control means is determined to compare the engine load with a first predetermined value and a second predetermined value, and to determine that the engine load is greater than the first predetermined value. When it is determined that the fuel injection amount by the third fuel injection is subtracted from the fuel injection amount by the first fuel injection and the engine load is determined to be smaller than the second predetermined value. And a means for reducing the fuel injection amount by the third fuel injection from the fuel injection amount by the second fuel injection.
  4. 　請求項３に記載の燃焼制御装置であって、
    　前記第１の所定値と前記第２の所定値とは等しい。     The combustion control device according to claim 3, wherein
    The first predetermined value and the second predetermined value are equal.
  5. 　請求項２に記載の燃焼制御装置であって、
    　前記第２の噴射弁制御手段は、前記第２の燃料噴射による燃料噴射量から前記第３の燃料噴射による燃料噴射量分を減量する手段を有する。     The combustion control device according to claim 2,
    The second injection valve control means has means for reducing the fuel injection amount by the third fuel injection from the fuel injection amount by the second fuel injection.
  6. 　請求項１～５のいずれか一項に記載の燃焼制御装置であって、
    　前記水温検出手段により検出された前記エンジンの水温に応じて、前記燃焼室内に存在する空気と燃料との比率を制御する空燃比制御手段を更に備える。     A combustion control device according to any one of claims 1 to 5,
    Air-fuel ratio control means is further provided for controlling the ratio of air and fuel existing in the combustion chamber according to the water temperature of the engine detected by the water temperature detection means.
  7. 　請求項１～６のいずれか一項に記載の燃焼制御装置であって、
    　前記燃焼室の吸気部と排気部とを繋ぐ排気再循環通路と、
    　前記排気再循環通路に設けられ、前記排気再循環通路を通る排気再循環ガスを冷却する排気再循環クーラと、
    　前記排気再循環クーラをバイパスするように前記排気再循環通路に接続されたバイパス通路と、
    　前記水温検出手段により検出された前記エンジンの水温に応じて、前記排気再循環ガスの流路を前記排気再循環クーラ側または前記バイパス通路側に切り替える流路切り替え手段と、を更に備える。     The combustion control device according to any one of claims 1 to 6,
    An exhaust gas recirculation passage connecting an intake portion and an exhaust portion of the combustion chamber;
    An exhaust gas recirculation cooler that is provided in the exhaust gas recirculation passage and cools the exhaust gas recirculation gas passing through the exhaust gas recirculation passage;
    A bypass passage connected to the exhaust gas recirculation passage to bypass the exhaust gas recirculation cooler;
    And a flow path switching means for switching the flow path of the exhaust recirculation gas to the exhaust gas recirculation cooler side or the bypass passage side according to the water temperature of the engine detected by the water temperature detection means.
PCT/JP2012/055860 2011-03-10 2012-03-07 Combustion control device WO2012121299A1 (en)

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