WO2012137055A1 - Internal combustion engine starting control device and internal combustion engine starting control method - Google Patents

Internal combustion engine starting control device and internal combustion engine starting control method Download PDF

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Publication number
WO2012137055A1
WO2012137055A1 PCT/IB2012/000660 IB2012000660W WO2012137055A1 WO 2012137055 A1 WO2012137055 A1 WO 2012137055A1 IB 2012000660 W IB2012000660 W IB 2012000660W WO 2012137055 A1 WO2012137055 A1 WO 2012137055A1
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WO
WIPO (PCT)
Prior art keywords
valve
fuel
period
injection
intake
Prior art date
Application number
PCT/IB2012/000660
Other languages
French (fr)
Inventor
Yukinobu Anezaki
Masatoshi Basaki
Motomasa Iizuka
Akihiro Ando
Shinichi Mitani
Hiroshi Nomura
Eiji Murase
Original Assignee
Toyota Jidosha Kabushiki Kaisha
Nippon Soken, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Toyota Jidosha Kabushiki Kaisha, Nippon Soken, Inc. filed Critical Toyota Jidosha Kabushiki Kaisha
Publication of WO2012137055A1 publication Critical patent/WO2012137055A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0261—Controlling the valve overlap
    • F02D13/0265—Negative valve overlap for temporarily storing residual gas in the cylinder
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D13/0203—Variable control of intake and exhaust valves
    • F02D13/0215—Variable control of intake and exhaust valves changing the valve timing only
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/0602—Control of components of the fuel supply system
    • F02D19/0607—Control of components of the fuel supply system to adjust the fuel mass or volume flow
    • F02D19/061—Control of components of the fuel supply system to adjust the fuel mass or volume flow by controlling fuel injectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/0663—Details on the fuel supply system, e.g. tanks, valves, pipes, pumps, rails, injectors or mixers
    • F02D19/0686—Injectors
    • F02D19/0689—Injectors for in-cylinder direct injection
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/08—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed simultaneously using pluralities of fuels
    • F02D19/082—Premixed fuels, i.e. emulsions or blends
    • F02D19/084—Blends of gasoline and alcohols, e.g. E85
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
    • F02D19/08—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed simultaneously using pluralities of fuels
    • F02D19/082—Premixed fuels, i.e. emulsions or blends
    • F02D19/085—Control based on the fuel type or composition
    • F02D19/087—Control based on the fuel type or composition with determination of densities, viscosities, composition, concentration or mixture ratios of fuels
    • 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
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
    • F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
    • F02D41/064—Introducing corrections for particular operating conditions for engine starting or warming up for starting at cold start
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D13/00—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing
    • F02D13/02—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation
    • F02D2013/0292—Controlling the engine output power by varying inlet or exhaust valve operating characteristics, e.g. timing during engine operation in the start-up phase, e.g. for warming-up cold engine or catalyst
    • 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
    • F02D41/0002—Controlling intake air
    • F02D2041/001—Controlling intake air for engines with variable valve actuation
    • 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
    • F02D2200/06—Fuel or fuel supply system parameters
    • F02D2200/0611—Fuel type, fuel composition or fuel quality
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/30—Use of alternative fuels, e.g. biofuels

Definitions

  • the invention relates to an internal combustion engine starting control device and an internal combustion engine starting control method.
  • JP 10-009004 A describes a technique for, at the time of starting an internal combustion engine at an extremely low temperature, lifting exhaust valves by a small amount or completely stopping the exhaust valves and cancelling ignition in an initial fuel injection cycle to transfer fuel to the next cycle to thereby increase the amount of in-cylinder fuel at the time of starting the internal combustion engine.
  • JP 10-009004 A describes a technique for, at the time of starting an internal combustion engine at an extremely low temperature, lifting exhaust valves by a small amount or completely stopping the exhaust valves and cancelling ignition in an initial fuel injection cycle to transfer fuel to the next cycle to thereby increase the amount of in-cylinder fuel at the time of starting the internal combustion engine.
  • the invention provides an internal combustion engine starting control device and internal combustion engine starting control method that further appropriately start an internal combustion engine in a short period of time.
  • a first aspect of the invention provides a starting control device for a direct-injection internal combustion engine.
  • the starting control device includes: a fuel property detecting unit that detects a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; a valve control unit that controls an open/close timing of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; and a first injection control unit that injects fuel from the fuel injection valve in the both valve close period created by the valve control unit, wherein the valve control unit changes the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit,
  • the in-cylinder temperature at which evaporation of fuel having a different property may be facilitated varies. That is, in the case of a fuel having such a property that the evaporation characteristic of the fuel deteriorates with a decrease in the in-cylinder temperature or in the case of a fuel having such a property that the amount of the fuel required for combustion increases with a decrease in the in-cylinder temperature, it is necessary to further increase the in-cylinder temperature.
  • a second aspect of the invention provides a starting control device for a direct-injection internal combustion engine.
  • the starting control device includes: a fuel property detecting unit that detects a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; a valve control unit that controls an open/close tirning of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; and a first injection control unit that injects fuel from the fuel injection valve in the both valve close period created by the valve control unit, wherein the first injection control unit changes an injection parameter of fuel injected in the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit.
  • the injection parameter of fuel at which evaporation of fuel may be facilitated, varies depending on the in-cylinder temperature. That is, at the in-cylinder temperature that is increased by recompression of residual gas, in the case of a fuel having such a property that the evaporation characteristic of the fuel deteriorates or in the case of a fuel having such a property that the amount of the fuel required for combustion increases, the injection parameter of fuel needs to be changed so as to further facilitate evaporation of fuel in coordination with the increased in-cylinder temperature.
  • the injection parameter of fuel injected in the both valve close period is changed on the basis of the property of the fuel.
  • the injection parameter of fuel may be changed so as to achieve the injection parameter of fuel further appropriate for the property of fuel and the in-cylinder temperature determined by the both valve close period, so evaporation of fuel may be facilitated.
  • fuel of which evaporation is facilitated may appropriately combust by ignition in the same cycle as that of fuel injection. Because fuel appropriately combusts in this way, so stable startability may be ensured, and unbumed HC is hard to occur to thereby make it possible to also suppress deterioration of exhaust emissions. Thus, it is possible to further appropriately start the internal combustion engine in a short period of time.
  • the starting control device for an internal combustion engine may further include a second injection control unit that injects fuel from the fuel injection valve after a lapse of the both valve close period.
  • a ratio of an amount of fuel injected by the first injection control unit with respect to a total amount of fuel injected by the first injection control unit and the second injection control unit may be changed on the basis of the property of fuel, detected by the fuel property detecting unit.
  • a ratio of an amount of fuel injected by the second injection control unit with respect to a total amount of fuel injected by the first injection control unit and the second injection control unit may be changed on the basis of the property of fuel, detected by the fuel property detecting unit.
  • the ratio of the amount of fuel injected by the first injection control unit (the amount of fuel injected by the second injection control unit) with respect to the total amount of fuel injected by the first injection control unit and the second injection control unit may be changed on the basis of the property of fuel such that fuel of an amount to which evaporation may be facilitated is injected by the first injection control unit.
  • evaporation of fuel may be facilitated.
  • the valve control unit may set a period from the close timing of the exhaust valve to an intake top dead center within the both valve close period so as to be shorter than a period from the intake top dead center to the open timing of the intake valve within the both valve close period.
  • a negative pressure occurs in the cylinder in a period that exceeds the period from the close timing of the exhaust valve to the intake top dead center within a period from the intake top dead center to the open timing of the intake valve, and the intake valve is opened in a state where a negative pressure is occurring.
  • fuel is injected in a state where a negative pressure is occurring to thereby boil fuel at a reduced pressure.
  • the intake valve by opening the intake valve in a state where a negative pressure is occurring, the flow rate of intake air that flows into the cylinder becomes close to the speed of sound, so it is possible to increase the gas temperature in the cylinder by kinetic energy of intake air.
  • the vaive control unit may change the close timing of the intake valve with respect to an intake bottom dead center after a lapse of the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit.
  • the close timing of the intake valve approaches the intake bottom dead center
  • the engine effective compression ratio in the case where the engine rotation speed is low increases at the time of starting the internal combustion engine to thereby make it possible to increase the gas temperature in the cylinder in the compression stroke.
  • the close timing of the intake valve is changed further appropriately on the basis of the property of fuel to thereby make it possible to facilitate evaporation of fuel.
  • a third aspect of the invention provides a starting control method for a direct-injection internal combustion engine.
  • the starting control method includes: detecting a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; controlling an open/close timing of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; changing at least one of the both valve close period and an injection parameter of fuel injected in the both valve close period on the basis of the detected property of fuel; and injecting fuel from the fuel injection valve in the both valve close period.
  • FIG. 1 is a view that shows the schematic configuration of an internal combustion engine according to a first embodiment of the invention
  • FIG 2A is a view that shows the open/close timing of each intake valve and the open/close timing of each exhaust valve in special starting control according to the first embodiment
  • FIG. 2B is a view that shows the open/close timing of each intake valve and the open/close timing of each exhaust valve in normal starting control according to the first embodiment
  • FIG 3 is a graph that shows an in-cylinder temperature and the percentage of vaporized fuel with respect to the ethanol concentration of fuel according to the first embodiment
  • FIG. 4A is a chart that shows the fuel injection timing in special starting control according to the first embodiment
  • FIG. 4B is a chart that shows the fuel injection timing in normal starting control according to the first embodiment
  • FIG 5 is a graph that shows the correlation between the close timing of each exhaust valve for creating a both valve close period and an in-cylinder temperature according to the first embodiment
  • FIG 6 is a chart that shows the fuel injection timing in special starting control in the case of two-split fuel injection according to the first embodiment
  • FIG. 7 is a flow chart that shows a first special starting control routine according to the first embodiment
  • FIG 8A and FIG 8B are views that respectively show the open/close timing of each exhaust valve and the open/close timing of each intake valve according to a first alternative embodiment
  • FIG 9 is a graph that shows the correlation between a difference Qi-Qe and an in-cylinder temperature according to the first alternative embodiment
  • FIG. 10 is a graph that shows the correlation between the close timing of each intake valve and an in-cylinder temperature according to a second alternative embodiment
  • FIG 11 is a chart that illustrates the case where a fuel injection parameter in a both valve close period is changed such that the number of splits of fuel injection in the both valve close period is increased into two, according to a second embodiment
  • FIG. 12 is a chart that illustrates the case where a fuel injection parameter in a both valve close period is changed by increasing the fuel injection amount in the both valve close period and reducing the fuel injection amount in a compression stroke;
  • FIG. 13 is a graph that shows the correlation between a fuel injection amount in a both valve close period and an exhaust gas temperature according to the second embodiment
  • FIG 14 is a flow chart that shows a second special starting control routine according to the second embodiment.
  • FIG. 15 is a flow chart that shows a third special starting control routine according to a third alternative embodiment.
  • FIG 1 is a view that shows the schematic configuration of an internal combustion engine to which an internal combustion engine starting control device according to a first embodiment of the invention is applied.
  • the internal combustion engine 1 shown in FIG 1 is a direct-injection engine in which fuel is injected directly into each cylinder.
  • Four cylinders 2 are arranged in the internal combustion engine 1.
  • a fuel injection valve 3 is arranged in each of the cylinders 2.
  • An intake passage 4 is connected to the internal combustion engine 1.
  • the intake passage 4 takes intake air into the cylinders 2.
  • a throttle valve 5 is arranged in the middle of the intake passage 4. The opening degree of the throttle valve 5 is adjusted in order to change the volume of intake fresh air.
  • a surge tank 6 is formed in the intake passage 4 downstream of the throttle valve 5.
  • Each fuel injection valve 3 is an electromagnetically-driven injector that directly injects fuei into a corresponding one of the cylinders 2 from the obliquely upper side.
  • Fuel is supplied from a fuel tank 8 to the fuel injection valves 3 via a fuel pipe 7.
  • Multiple types of fuels having different properties may be used in the internal combustion engine 1.
  • the property of the fuel indicates the alcohol concentration (ethanol concentration), and the like, of fuel.
  • Fuels having different properties differ in the evaporation characteristic of fuel with respect to an in-cylinder temperature and the amount of fuel required for combustion with respect to an in-cylinder temperature.
  • the fuels not only include a fuel formed of only gasoline but also may include a composite fuel that mixes ethanol to gasoline or ethanol fuel formed of only ethanol.
  • ethanol concentration is illustrated as the property of fuel; instead, another property may be applied to the aspect of the invention as long as a property that varies the evaporation characteristic of fuel with respect to an in-cylinder temperature and the amount of fuel required for combustion with respect to an in-cylinder temperature.
  • An ethanol concentration sensor 9 is arranged in the fuel pipe 7 between the fuel tank 8 and the fuel injection valves 3. The ethanol concentration sensor 9 detects the ethanol concentration of fuel.
  • the ethanol concentration sensor 9 functions as a fuel property detecting unit.
  • Intake valves 11 are respectively provided in intake ports 10.
  • the intake ports 10 are communicable with the corresponding cylinders 2 of the internal combustion engine 1.
  • the intake ports 10 constitute part of the intake passage 4.
  • Exhaust valves 14 are respectively provided in exhaust ports 13.
  • the exhaust ports 13 are communicable with the corresponding cylinders 2 of the internal combustion engine 1.
  • the exhaust valves 14 constitute part of an exhaust passage 12.
  • a first variable valve timing mechanism (VVT) 15 is provided for the intake valves 11.
  • a second .variable valve timing mechanism (VVT) 16 is provided for the exhaust valves 14.
  • Each of the VVTs 15 and 16 varies the open/close timing (valve timing) of the corresponding valves.
  • valve timing open/close timing
  • the VVTs 15 and 16 in the present embodiment function as a valve control unit.
  • a mechanism, or the like, that is arranged in a power transmission path from a crankshaft to a camshaft and that varies the relative position (phase) of the rotation angle of the camshaft with respect to the rotation angle of the crankshaft may be employed as each of the VVTs 15 and 16.
  • An ignition plug 17 is arranged at the upper portion of each cylinder 2 of the interna! combustion engine 1. High voltage is applied to each ignition plug 17 at ignition timing through an ignition coil, and the like. By so doing, spark discharge occurs toward the opposite electrode of the ignition plug 17 to ignite and combust fuel.
  • a piston 18 is arranged at the lower side of each cylinder 2 of the internal combustion engine 1.
  • An in-cylinder temperature sensor 19 is provided in each piston 18. Each in-cylinder temperature sensor 19 detects the temperature in the corresponding cylinder 2.
  • the in-cylinder temperature sensor 1 directly detects the temperature of the surface of a piston cavity with which fuel injected from the corresponding fuel injection valve 3 collides.
  • a coolant temperature sensor 20 is arranged in a coolant passage through which engine coolant circulates around the cylinders 2 of the internal combustion engine 1.
  • the coolant temperature sensor 20 detects the temperature, of engine coolant.
  • a crank angle sensor 23 is arranged on the crankshaft of the internal combustion engine 1. The crank angle sensor 23 detects the engine rotation speed.
  • the crank angle sensor 23 extracts a crank angle pulse signal from the crankshaft, and then, for example, detects the engine rotation speed, detects the cylinder and detects the stroke of each cylinder 2 at the time of a stop of the cylinders 2.
  • the exhaust passage 12 is connected to the internal combustion engine 1.
  • the exhaust passage 12 allows exhaust gas to be emitted after combustion in each cylinder 2,
  • a catalyst 21 is arranged in the middle of the exhaust passage 12.
  • the catalyst 21 is used to purify exhaust gas.
  • a three-way catalyst, a storage reduction NOx catalyst, or the like, is used as the catalyst 21.
  • An electronic control unit (ECU) 22 is provided for the internal combustion engine 1.
  • Various sensors such as the ethanol concentration sensor 9, the in-cylinder temperature sensors 19, the coolant temperature sensor 20 and the crank angle sensor 23, are connected to the ECU 22 via electric wiring, and signals output from these various sensors are input to the ECU 22.
  • the fuel injection valves 3, the throttle valve 5, the VVTs 15 and 16 and the ignition plugs 17 are connected to the ECU 22 via electric wiring, and these devices are controlled by the ECU 22.
  • the number of cycles until first ignition at the time of starting an internal combustion engine increases by one or more cycles and, as a result, a period of time required for starting the internal combustion engine extends.
  • a load on a starter motor for cranking during a period of the increased cycles until first ignition increases, and the increased load may cause deterioration of the durability of the starter motor.
  • both valve close period a period during which both the intake valve 11 and the exhaust valve 14 are closed
  • fuel is injected during the both valve close period.
  • the both valve close period is created by using the second WT 16 to close the exhaust valve 14 in the middle of the exhaust stroke and using the first WT 15 to open the intake valve 11 in the middle of the intake stroke. That is, the both valve close period is created so as to be a period from a certain timing in the exhaust stroke to a certain timing in the intake stroke, including an intake top dead center.
  • FIG. 2A is a view that shows the open/close timing of each intake valve 11 and the open/close timing of each exhaust valve 14 in special starting control.
  • FIG 2B is a view that shows the open/close timing of each intake valve 11 and the open/close timing of each exhaust valve 14 in normal starting control.
  • normal starting control as shown in FIG 2B, a short valve overlap period during which both valves are opened over a period from before the intake top dead center to after the intake top dead center is provided; whereas, in special starting control, as shown in FIG A, the both valve close period is provided over a period from before the intake top dead center to after the intake top dead center.
  • FIG. 3 is a graph that shows an in-cylinder temperature and the evaporation percentage of fuel with respect to the ethanol concentration of fuel. As shown in FIG. 3, as the ethanol concentration of fuel increases, a higher in-cylinder temperature is required in order to increase the evaporation percentage.
  • the both valve close period is changed through special starting control on the basis of the ethanol concentration of fuel.
  • the ethanol concentration of fuel is detected by the ethanol concentration sensor 9, and then the close timing of each exhaust valve 14, at which each exhaust valve 14 is closed in the middle of the corresponding exhaust stroke, is controlled by the second VVT16 on the basis of the detected ethanol concentration and the open timing of each intake valve 11, at which each intake valve 11 is opened in the middle of the corresponding intake stroke, is controlled by the first WT 15 to thereby change the both valve close period.
  • fuel injection using each fuel injection valve 3 is once completed within the corresponding changed both valve close period.
  • FIG 4A is a chart that shows the fuel injection timing in special starting control by which fuel is injected in the both valve close period.
  • FIG 4B is a chart that shows the fuel injection timing in normal starting control. In normal starting control, as shown in FIG. 4B, a total amount of fuel is injected at a time before a compression top dead center; whereas, in special starting control, as shown in FIG 4A, a total amount of fuel is injected around an intake top dead center in the both valve close period.
  • FIG 5 is a graph that shows the correlation between the close timing of each exhaust valve 14 for creating the both valve close period and an in-cylinder temperature. As shown in FIG 5, as the close timing of each exhaust valve 14 is advanced with respect to the intake top dead center, the in-cylinder temperature more easily increases.
  • the both valve close period may be changed through special starting control so as to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel, so it is possible to facilitate evaporation of fuel.
  • fuel of which evaporation is facilitated may appropriately combust by ignition using the ignition plug 17 in the same cycle as that of fuel injection.
  • the number of cycles until first ignition at the time of starting the internal combustion engine 1 does not increase by one, so a period of time required for starting the internal combustion engine 1 does not extend.
  • a load on the starter motor for cranking also does not increase, so it is possible to suppress deterioration of the durability of the starter motor.
  • FIG 6 is a chart that shows the fuel injection timing of special starting control in the case of two-split fuel injection.
  • special starting control in the case of two-split fuel injection as shown in FIG 6, fuel is injected separately at two points, that is, in the both valve close period and before the compression top dead center.
  • FIG. 7 is a flow chart that shows the first special starting control routine.
  • the routine is executed by the ECU 22.
  • the routine shown in FIG 7 is started when an ignition SW is turned on. As the routine is started, it is determined in S101 whether the in-cylinder temperature detected by each in-cylinder temperature sensor 19 is lower than or equal to a predetermined temperature T.
  • the predetermined temperature T is a temperature at or below which combustion cannot be appropriately performed in normal starting control.
  • S102 it is determined whether the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, is higher than or equal to a predetermined concentration c .
  • the predetermined concentration a is a concentration above which combustion cannot be appropriately performed in normal starting control.
  • a starter SW is turned on to drive the starter motor to thereby start cranking.
  • SI 04 it is determined whether a first exhaust stroke is carried out in each cylinder 2. When affirmative determination is made in S104, the process proceeds to S105. When negative determination is made in S104, the process returns to the same step, and fuel injection and ignition are not carried out until a first exhaust stroke is carried out. This avoids fuel injection and ignition without providing the both valve close period.
  • each fuel injection valve 3 is used to inject fuel in the corresponding both valve close period, and, where necessary, inject the remaining amount of fuel required for combustion in the compression stroke after a lapse of the both valve close period. Then, the corresponding ignition plug 17 is used to ignite fuel near the compression top dead center.
  • S107 it is determined whether the in-cylinder temperature detected by each in-cyiinder temperature sensor 19 is higher than the predetermined temperature T.
  • the predetermined temperature T is a temperature at or below which combustion cannot be appropriately performed in normal starting control.
  • the both valve close period is changed on the basis of the ethanol concentration of fuel as in the case of the first embodiment; however, a period from the close timing of each exhaust valve 14, for creating the both valve close period, to the intake top dead center is shorter than a period from the intake top dead center to the open timing of each intake valve 11.
  • FIG 8A is a view that shows the open/close timing of each exhaust valve 14 according to the first alternative embodiment.
  • FIG 8B is a view that shows the open/close timing of each intake valve 11 according to the first alternative embodiment.
  • a first period (valve close angular range) 9e from the close timing of each exhaust valve 14, for creating the both valve close period, to the intake top dead center is set so as to be shorter than a second period (valve open angular range) ⁇ from the intake top dead center to the open timing of each intake valve 11 (8e ⁇ 6i).
  • the first period 8e is shorter than the second period ⁇ , so the cylinder volume at the time when the intake valve 11 is opened is larger than the cylinder volume at the time when the exhaust valve 14 is closed. Therefore, a negative pressure occurs in the cylinder 2 by the time when the intake valve 11 opens in the both valve close period, and the intake valve 11 opens in a state where a negative pressure is occurring.
  • fuel is injected in the both valve close period during which a negative pressure is occurring to thereby boil the fuel at a reduced pressure.
  • FIG 9 is a graph that shows the correlation between a difference ⁇ - ⁇ and an in-cylinder temperature according to the first alternative embodiment of the invention. As shown in FIG 9, as the difference ⁇ - ⁇ that is obtained by subtracting the first period 6e from the second period 0i increases, the in-cylinder temperature increases. Thus, evaporation of fuel may be facilitated. Particularly, when fuel is injected in the compression stroke after a lapse of the both valve close period described in the first embodiment, it is also possible to facilitate evaporation of fuel injected in the compression stroke.
  • the close timing of each intake valve 11 with respect to the intake bottom dead center after a lapse of the both valve close period is changed on the basis of the ethanol concentration of fuel.
  • FIG. 10 is a graph that shows the correlation between the close timing of each intake valve 11 and an in-cylinder temperature. As shown in FIG 10, as the close timing of each intake valve 11 approaches the intake bottom dead center from any one of an advance side and a retard side, the in-cylinder temperature may be increased.
  • the close timing of each intake valve 11 by changing the close timing of each intake valve 11 with respect to the intake bottom dead center after a lapse of the both valve close period, it is possible to vary the 1 in-cylinder temperature in the compression stroke after the both valve close period.
  • the close timing of each intake valve 11 is changed to further appropriate close timing on the basis of the ethanol concentration of fuel, evaporation of the fuel may be facilitated.
  • the close timing of each intake valve 11 approaches the intake bottom dead center, it is also possible to facilitate evaporation of fuel injected in the compression stroke.
  • the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel. Note that the description of a similar configuration to that of the above described embodiment is omitted.
  • the injection parameter of fuel is a variable, such as the fuel injection amount, the number of splits of fuel injection and the fuel injection timing, that may be varied at the time when fuel is injected.
  • the injection parameter of fuel needs to be changed on the basis of the specific in-cylinder temperature so as to further facilitate evaporation of fuel. For example, in the both valve close period, it is necessary to increase the fuel injection amount, to increase the number of splits of fuel injection or to advance the fuel injection timing.
  • the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel.
  • the ethanol concentration of fuel is detected by the ethanol concentration sensor 9, and then the injection parameter, such as the fuel injection amount, the number of splits and the fuel injection timing of fuel injection in the both valve close period, is changed on the basis of the detected ethanol concentration.
  • fuel injection is carried out with the changed injection parameter so as to once complete fuel injection by the fuel injection valve 3 in the both valve close period.
  • FIG. 11 is a chart that illustrates the case where the injection parameter is changed such that the number of splits of fuel injection in the both valve close period is increased into two. As shown in FIG 11, when the number of splits of fuel injection in the both valve close period is increased into two, it is possible to facilitate evaporation of fuel even when the ethanol concentration of fuel is high.
  • the ratio of the amount of fuel injected in the both valve close period and the ratio of the amount of fuel injected in the compression stroke, with respect to the amount of fuel required for combustion, may be changed on the basis of the ethanol concentration of fuel such that fuel of an amount to which evaporation may be facilitated is injected in the both valve close period on the basis of the ethanol concentration of fuel.
  • FIG. 12 is a chart that illustrates the case where the injection parameter of fuel is changed in the both valve close period so as to increase the amount of fuel injected in the both valve close period and to reduce the amount of fuel injected in the compression stroke.
  • FIG 13 is a graph that shows the correlation between the ratio of the amount of fuel injected in the both valve close period and an exhaust gas temperature.
  • the injection parameter of fuel may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylihder temperature determined by the both valve close period, so evaporation of fuel may be facilitated.
  • fuel of which evaporation is facilitated may appropriately combust by ignition using the ignition plug 17 in the same cycle as that of fuel injection.
  • the number of cycles until first ignition at the time of starting the internal combustion engine 1 does not increase by one, so a period of time required for starting the internal combustion engine 1 does not extend.
  • a load on the starter motor for cranking also does not increase, so it is possible to suppress deterioration of the durability of the starter motor.
  • FIG. 14 is a flow chart that shows the second special starting control routine.
  • the routine is executed by the ECU 22.
  • the second special starting control routine shown in FIG 14 differs from the first special starting control routine shown in FIG 7 in that S105 and S106 are respectively changed to S205 and S206, so only those points will be described.
  • the close timing of each exhaust valve 14, at which each exhaust valve 14 is closed in the middle of the corresponding exhaust stroke, is controlled by the second WT 16 and the open timing of each intake valve 11, at which each intake valve 11 is opened in the middle of the corresponding intake stroke, is controlled by the first VVT 15 to thereby provide a constant both valve close period.
  • the close timing of each exhaust valve 14 is advanced, and the open timing of each intake valve 11 is retarded such that fuel injection is once completed in the both valve close period.
  • each fuel injection valve 3 is used to inject fuel in the both valve close period by changing the injection parameter of fuel on the basis of the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, and, where necessary, to inject fuel of a remaining amount required for combustion in the compression stroke after a lapse of the both valve close period. Then, the corresponding ignition plug 17 is used to ignite fuel near the compression top dead center.
  • the injection parameter of fuel in the both valve close period may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period, so evaporation of fuel may be facilitated.
  • the injection parameter of fuel in the both valve close period may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period, so evaporation of fuel may be facilitated.
  • both the feature of the first embodiment and the feature of the second embodiment are included, and at least any one of the both valve close period and the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel. Note that the description of a similar configuration to those of the above embodiments is omitted.
  • the both valve close period is changed on the basis of the ethanol concentration of fuel in special starting control in order to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel.
  • the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel in order to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period.
  • the both valve close period may be changed in special starting control so as to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel, so evaporation of fuel may be facilitated.
  • the injection parameter of fuel may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period, so evaporation of fuel may be facilitated.
  • fuel of which evaporation is facilitated may appropriately combust by ignition using the ignition plug 17 in the same cycle as that of fuel injection.
  • the number of cycles until first ignition at the time of starting the internal combustion engine 1 does not increase by one, so a period of time required for starting the internal combustion engine 1 does not extend.
  • a load on the starter motor for cranking also does not increase, so it is possible to suppress deterioration of the durability of the starter motor.
  • fuel . appropriately combusts in this way so stable startability may be ensured, and unburned HC is hard to occur to thereby make it possible to also suppress deterioration of exhaust emissions.
  • FIG. 15 is a flow chart that shows the third special starting control routine. The routine is executed by the ECU 22.
  • the third special starting control routine shown in FIG. 15 differs from the first special starting control routine shown in FIG. 7 in that S105 and S106 are respectively changed to S305 and S306, so only those points will be described.
  • each fuel injection valve 3 is used to inject fuel in the both valve close period by changing the injection parameter of fuel on the basis of the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, and, where necessary, to inject fuel of a remaining amount required for combustion in the compression stroke after a lapse of the both valve close period.
  • the both valve close period and the injection parameter of fuel may be changed and the other one may be fixed or the other one may be changed in coordination with the changed one.
  • the injection parameter of fuel in the both valve close period may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period. By so doing, it is possible to appropriately start the internal combustion engine 1 through special starting control.
  • the internal combustion engine starting control device is not limited to the above described embodiments and alternative embodiments; it may be modified in various forms without departing from the scope of the invention. Therefore, the embodiments and alternative embodiments may be combined operably.
  • the above described embodiments and alternative embodiments are also embodiments and alternative embodiments of the internal combustion engine starting control method according to the aspect of the invention.

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  • General Engineering & Computer Science (AREA)
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Abstract

A starting control device for a direct-injection internal combustion engine includes: a fuel property detecting unit (9) that detects a property of fuel injected from a fuel injection valve (3) arranged in a cylinder (2); a valve control unit (15, 16) that controls an open/close timing of an intake valve (11) and an open/close timing of an exhaust valve (14) so as to create a both valve close period, during which both the intake valve (11) and the exhaust valve (14) are closed, within a period from an exhaust stroke to an intake stroke; and a first injection control unit (22) that injects fuel from the fuel injection valve (3) in the both valve close period, wherein the valve control unit (15, 16) changes the both valve close period on the basis of the property of fuel.

Description

INTERNAL COMBUSTION ENGINE STARTING CONTROL DEVICE AND INTERNAL COMBUSTION ENGINE STARTING CONTROL METHOD
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The invention relates to an internal combustion engine starting control device and an internal combustion engine starting control method.
2. Description of Related Art
[0002] For example, Japanese Patent Application Publication No. 10-009004 (JP 10-009004 A) describes a technique for, at the time of starting an internal combustion engine at an extremely low temperature, lifting exhaust valves by a small amount or completely stopping the exhaust valves and cancelling ignition in an initial fuel injection cycle to transfer fuel to the next cycle to thereby increase the amount of in-cylinder fuel at the time of starting the internal combustion engine. With the above technique, it is possible to increase the amount of in-cylinder fuel at the time of starting the internal combustion engine without increasing the fuel injection rate even at a low fuel pressure, and it is also possible to increase the amount of vaporized fuel. In addition, at this time, it is not necessary to use an exclusive fuel pump or injection valve, so costs do not increase.
[0003] However, with the technique described in JP 10-009004 A, the number of cycles until first ignition at the time of starting the internal combustion engine increases and, as a result, a period of time required for starting the internal combustion engine extends.
SUMMARY OF THE INVENTION [0004] The invention provides an internal combustion engine starting control device and internal combustion engine starting control method that further appropriately start an internal combustion engine in a short period of time.
[0005] A first aspect of the invention provides a starting control device for a direct-injection internal combustion engine. The starting control device includes: a fuel property detecting unit that detects a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; a valve control unit that controls an open/close timing of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; and a first injection control unit that injects fuel from the fuel injection valve in the both valve close period created by the valve control unit, wherein the valve control unit changes the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit,
[0006] With the above configuration, fuel is injected from the fuel injection valve in the both valve close period, during which both the intake valve and the exhaust valve are closed, within the period from the exhaust stroke to the intake stroke. When the both valve close period is provided within the period from the exhaust stroke to the intake stroke, gas remaining in the cylinder is recompressed by upward movement of the piston to thereby increase the in-cylinder temperature. Thus, fuel may be injected into the high-temperature cylinder, and evaporation of fuel may be facilitated.
[0007] When the property of fuel varies, the evaporation characteristic of fuel with respect to the in-cylinder temperature and the amount of fuel required for combustion with respect to the in-cylinder temperature vary, so the in-cylinder temperature at which evaporation of fuel having a different property may be facilitated varies. That is, in the case of a fuel having such a property that the evaporation characteristic of the fuel deteriorates with a decrease in the in-cylinder temperature or in the case of a fuel having such a property that the amount of the fuel required for combustion increases with a decrease in the in-cylinder temperature, it is necessary to further increase the in-cylinder temperature. In order to further increase the in-cylinder temperature, it is necessary to advance the close timing of the exhaust valve so as to increase the amount of gas to be recompressed. Then, with the above configuration, the created both valve close period, during which both the intake valve and the exhaust valve are closed, is changed on the basis of the property of fuel. . Thus, it is possible to change the period during which both the intake valve and the exhaust vaJve are closed so as to achieve the in-cylinder temperature further appropriate for the property of fuel, so evaporation of fuel may be facilitated. Fuel of which evaporation is facilitated may appropriately combust by ignition in the same cycle as that of fuel injection. Because fuel appropriately combusts, so stable startability may be ensured, and unburned HC is hard to occur to thereby make it possible to also suppress deterioration of exhaust emissions. Thus, it is possible to further appropriately start the internal combustion engine in a short period of time.
[0008] A second aspect of the invention provides a starting control device for a direct-injection internal combustion engine. The starting control device includes: a fuel property detecting unit that detects a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; a valve control unit that controls an open/close tirning of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; and a first injection control unit that injects fuel from the fuel injection valve in the both valve close period created by the valve control unit, wherein the first injection control unit changes an injection parameter of fuel injected in the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit.
[0009] With the above configuration, fuel is injected from the fuel injection valve in the both valve close period, during which both the intake valve and the exhaust valve are closed, within the period from the exhaust stroke to the intake stroke. When the both valve close period is provided within the period from the exhaust stroke to the intake stroke, gas remaining in the cylinder is recompressed by upward movement of the piston to thereby increase the in-cylinder temperature. Thus, fuel may be injected into the high-temperature cylinder, and evaporation of fuel may be facilitated.
[0010] When the property of fuel varies, the evaporation characteristic of fuel with respect to the in-cylinder temperature and the amount of fuel required for combustion with respect to the in-cylinder temperature vary, so the injection parameter of fuel, at which evaporation of fuel may be facilitated, varies depending on the in-cylinder temperature. That is, at the in-cylinder temperature that is increased by recompression of residual gas, in the case of a fuel having such a property that the evaporation characteristic of the fuel deteriorates or in the case of a fuel having such a property that the amount of the fuel required for combustion increases, the injection parameter of fuel needs to be changed so as to further facilitate evaporation of fuel in coordination with the increased in-cylinder temperature. Then, with the above configuration, the injection parameter of fuel injected in the both valve close period is changed on the basis of the property of the fuel. According to this aspect, the injection parameter of fuel may be changed so as to achieve the injection parameter of fuel further appropriate for the property of fuel and the in-cylinder temperature determined by the both valve close period, so evaporation of fuel may be facilitated. By so doing, fuel of which evaporation is facilitated may appropriately combust by ignition in the same cycle as that of fuel injection. Because fuel appropriately combusts in this way, so stable startability may be ensured, and unbumed HC is hard to occur to thereby make it possible to also suppress deterioration of exhaust emissions. Thus, it is possible to further appropriately start the internal combustion engine in a short period of time.
[0011] The starting control device for an internal combustion engine may further include a second injection control unit that injects fuel from the fuel injection valve after a lapse of the both valve close period.
[0012] With the above configuration, after fuel of an amount to which evaporation may be facilitated is injected by the first injection control unit, fuel of a remaining amount required for combustion may be injected by the second injection control unit. Thus, evaporation of fuel may be facilitated.
[0013] A ratio of an amount of fuel injected by the first injection control unit with respect to a total amount of fuel injected by the first injection control unit and the second injection control unit may be changed on the basis of the property of fuel, detected by the fuel property detecting unit. Alternatively, a ratio of an amount of fuel injected by the second injection control unit with respect to a total amount of fuel injected by the first injection control unit and the second injection control unit may be changed on the basis of the property of fuel, detected by the fuel property detecting unit.
[0014] With the above configuration, the ratio of the amount of fuel injected by the first injection control unit (the amount of fuel injected by the second injection control unit) with respect to the total amount of fuel injected by the first injection control unit and the second injection control unit may be changed on the basis of the property of fuel such that fuel of an amount to which evaporation may be facilitated is injected by the first injection control unit. Thus, evaporation of fuel may be facilitated.
[0015] The valve control unit may set a period from the close timing of the exhaust valve to an intake top dead center within the both valve close period so as to be shorter than a period from the intake top dead center to the open timing of the intake valve within the both valve close period.
[0016] With the above configuration, a negative pressure occurs in the cylinder in a period that exceeds the period from the close timing of the exhaust valve to the intake top dead center within a period from the intake top dead center to the open timing of the intake valve, and the intake valve is opened in a state where a negative pressure is occurring. Thus, fuel is injected in a state where a negative pressure is occurring to thereby boil fuel at a reduced pressure. In addition, by opening the intake valve in a state where a negative pressure is occurring, the flow rate of intake air that flows into the cylinder becomes close to the speed of sound, so it is possible to increase the gas temperature in the cylinder by kinetic energy of intake air. That is, by increasing the gas temperature in the cylinder, it is possible to further increase the in-cylinder temperature after the both valve close period. Thus, evaporation of fuel may be facilitated. [0017] The vaive control unit may change the close timing of the intake valve with respect to an intake bottom dead center after a lapse of the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit.
[0018] As the close timing of the intake valve approaches the intake bottom dead center, the engine effective compression ratio in the case where the engine rotation speed is low increases at the time of starting the internal combustion engine to thereby make it possible to increase the gas temperature in the cylinder in the compression stroke. Thus, with the above configuration, by changing the close timing of the intake valve with respect to the intake bottom dead center after a lapse of the both valve close period, it is possible to vary the in-cylinder temperature after the both valve close period. Thus, the close timing of the intake valve is changed further appropriately on the basis of the property of fuel to thereby make it possible to facilitate evaporation of fuel.
[0019] A third aspect of the invention provides a starting control method for a direct-injection internal combustion engine. The starting control method includes: detecting a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; controlling an open/close timing of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; changing at least one of the both valve close period and an injection parameter of fuel injected in the both valve close period on the basis of the detected property of fuel; and injecting fuel from the fuel injection valve in the both valve close period.
[0020] With the above configuration, as in the case of the first and second aspects, it is possible to further appropriately start the internal combustion engine in a short period of time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
FIG. 1 is a view that shows the schematic configuration of an internal combustion engine according to a first embodiment of the invention;
FIG 2A is a view that shows the open/close timing of each intake valve and the open/close timing of each exhaust valve in special starting control according to the first embodiment;
FIG. 2B is a view that shows the open/close timing of each intake valve and the open/close timing of each exhaust valve in normal starting control according to the first embodiment;
FIG 3 is a graph that shows an in-cylinder temperature and the percentage of vaporized fuel with respect to the ethanol concentration of fuel according to the first embodiment;
FIG. 4A is a chart that shows the fuel injection timing in special starting control according to the first embodiment;
FIG. 4B is a chart that shows the fuel injection timing in normal starting control according to the first embodiment;
FIG 5 is a graph that shows the correlation between the close timing of each exhaust valve for creating a both valve close period and an in-cylinder temperature according to the first embodiment;
FIG 6 is a chart that shows the fuel injection timing in special starting control in the case of two-split fuel injection according to the first embodiment;
FIG. 7 is a flow chart that shows a first special starting control routine according to the first embodiment;
FIG 8A and FIG 8B are views that respectively show the open/close timing of each exhaust valve and the open/close timing of each intake valve according to a first alternative embodiment;
FIG 9 is a graph that shows the correlation between a difference Qi-Qe and an in-cylinder temperature according to the first alternative embodiment; FIG. 10 is a graph that shows the correlation between the close timing of each intake valve and an in-cylinder temperature according to a second alternative embodiment;
FIG 11 is a chart that illustrates the case where a fuel injection parameter in a both valve close period is changed such that the number of splits of fuel injection in the both valve close period is increased into two, according to a second embodiment;
FIG. 12 is a chart that illustrates the case where a fuel injection parameter in a both valve close period is changed by increasing the fuel injection amount in the both valve close period and reducing the fuel injection amount in a compression stroke;
FIG. 13 is a graph that shows the correlation between a fuel injection amount in a both valve close period and an exhaust gas temperature according to the second embodiment;
FIG 14 is a flow chart that shows a second special starting control routine according to the second embodiment; and
FIG. 15 is a flow chart that shows a third special starting control routine according to a third alternative embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
[0022] Hereinafter, specific embodiments of the invention will be described. First Embodiment
[0023] FIG 1 is a view that shows the schematic configuration of an internal combustion engine to which an internal combustion engine starting control device according to a first embodiment of the invention is applied. The internal combustion engine 1 shown in FIG 1 is a direct-injection engine in which fuel is injected directly into each cylinder. Four cylinders 2 are arranged in the internal combustion engine 1. A fuel injection valve 3 is arranged in each of the cylinders 2.
[0024] An intake passage 4 is connected to the internal combustion engine 1. The intake passage 4 takes intake air into the cylinders 2. A throttle valve 5 is arranged in the middle of the intake passage 4. The opening degree of the throttle valve 5 is adjusted in order to change the volume of intake fresh air. A surge tank 6 is formed in the intake passage 4 downstream of the throttle valve 5.
[0025] Each fuel injection valve 3 is an electromagnetically-driven injector that directly injects fuei into a corresponding one of the cylinders 2 from the obliquely upper side. Fuel is supplied from a fuel tank 8 to the fuel injection valves 3 via a fuel pipe 7. Multiple types of fuels having different properties may be used in the internal combustion engine 1. The property of the fuel indicates the alcohol concentration (ethanol concentration), and the like, of fuel. Fuels having different properties differ in the evaporation characteristic of fuel with respect to an in-cylinder temperature and the amount of fuel required for combustion with respect to an in-cylinder temperature. The fuels not only include a fuel formed of only gasoline but also may include a composite fuel that mixes ethanol to gasoline or ethanol fuel formed of only ethanol. By changing the type of fuel, the ethanol concentration of fuel used in the internal combustion engine 1 is changed. In the present embodiment, ethanol concentration is illustrated as the property of fuel; instead, another property may be applied to the aspect of the invention as long as a property that varies the evaporation characteristic of fuel with respect to an in-cylinder temperature and the amount of fuel required for combustion with respect to an in-cylinder temperature. An ethanol concentration sensor 9 is arranged in the fuel pipe 7 between the fuel tank 8 and the fuel injection valves 3. The ethanol concentration sensor 9 detects the ethanol concentration of fuel. The ethanol concentration sensor 9 functions as a fuel property detecting unit.
[0026] Intake valves 11 are respectively provided in intake ports 10. The intake ports 10 are communicable with the corresponding cylinders 2 of the internal combustion engine 1. The intake ports 10 constitute part of the intake passage 4. When each intake valve 11 is opened, intake air is introduced into a conesponding one of the cylinders 2. Exhaust valves 14 are respectively provided in exhaust ports 13. The exhaust ports 13 are communicable with the corresponding cylinders 2 of the internal combustion engine 1. The exhaust valves 14 constitute part of an exhaust passage 12. When each exhaust valve 14 is opened, combusted exhaust gas is emitted to the exhaust passage 12. A first variable valve timing mechanism (VVT) 15 is provided for the intake valves 11. A second .variable valve timing mechanism (VVT) 16 is provided for the exhaust valves 14. Each of the VVTs 15 and 16 varies the open/close timing (valve timing) of the corresponding valves. By controlling the open/close timing of each intake valve 11 and the open/close timing of each exhaust valve 14 with the corresponding WTs 15 and 16, a both valve close period is created within a period from an exhaust stroke to an intake stroke. In the both valve close period, both the intake valve 11 and the exhaust valve 14 are closed. The VVTs 15 and 16 in the present embodiment function as a valve control unit. For example, a mechanism, or the like, that is arranged in a power transmission path from a crankshaft to a camshaft and that varies the relative position (phase) of the rotation angle of the camshaft with respect to the rotation angle of the crankshaft may be employed as each of the VVTs 15 and 16.
[0027] An ignition plug 17 is arranged at the upper portion of each cylinder 2 of the interna! combustion engine 1. High voltage is applied to each ignition plug 17 at ignition timing through an ignition coil, and the like. By so doing, spark discharge occurs toward the opposite electrode of the ignition plug 17 to ignite and combust fuel. In addition, a piston 18 is arranged at the lower side of each cylinder 2 of the internal combustion engine 1. An in-cylinder temperature sensor 19 is provided in each piston 18. Each in-cylinder temperature sensor 19 detects the temperature in the corresponding cylinder 2. The in-cylinder temperature sensor 1 directly detects the temperature of the surface of a piston cavity with which fuel injected from the corresponding fuel injection valve 3 collides. Note that it is also applicable that the correlation between the temperature of engine coolant or the temperature of a cylinder liner and an in-cylinder temperature is obtained in advance and then the temperature of engine coolant or the temperature of the cylinder liner is detected to thereby derive the in-cylinder temperature without using the in-cylinder temperature sensor 19. In addition, a coolant temperature sensor 20 is arranged in a coolant passage through which engine coolant circulates around the cylinders 2 of the internal combustion engine 1. The coolant temperature sensor 20 detects the temperature, of engine coolant. In addition, a crank angle sensor 23 is arranged on the crankshaft of the internal combustion engine 1. The crank angle sensor 23 detects the engine rotation speed. The crank angle sensor 23 extracts a crank angle pulse signal from the crankshaft, and then, for example, detects the engine rotation speed, detects the cylinder and detects the stroke of each cylinder 2 at the time of a stop of the cylinders 2.
[0028] The exhaust passage 12 is connected to the internal combustion engine 1. The exhaust passage 12 allows exhaust gas to be emitted after combustion in each cylinder 2, A catalyst 21 is arranged in the middle of the exhaust passage 12. The catalyst 21 is used to purify exhaust gas. A three-way catalyst, a storage reduction NOx catalyst, or the like, is used as the catalyst 21.
[0029] An electronic control unit (ECU) 22 is provided for the internal combustion engine 1. Various sensors, such as the ethanol concentration sensor 9, the in-cylinder temperature sensors 19, the coolant temperature sensor 20 and the crank angle sensor 23, are connected to the ECU 22 via electric wiring, and signals output from these various sensors are input to the ECU 22. In addition, the fuel injection valves 3, the throttle valve 5, the VVTs 15 and 16 and the ignition plugs 17 are connected to the ECU 22 via electric wiring, and these devices are controlled by the ECU 22.
[0030] Particularly when the internal combustion engine 1 is started at an extremely low temperature, or the like, even when fuel is injected from the fuel injection valves 3 and is then ignited by the corresponding ignition plugs 17 in a first cycle, combustion may not be appropriately performed because misfire or large amounts of unburned HC occurs, for example. Such poor combustion tends to easily occur as the ethanol concentration of fuel increases. This is because, as the ethanol concentration of fuel increases, the fuel is harder to evaporate at a low temperature than gasoline and, as a result, the fuel almost does not vaporize. Therefore, the amount of fuel required for combustion also increases. In order to handle the above problem, there has been suggested, for example, raising the fuel injection pressure or increasing the fuel injection amount on the basis of the ethanol concentration of fuel or advancing the fuel injection timing in order to ensure an evaporation time. However, to raise the fuel injection pressure at the time of starting the internal combustion engine I, a motor-driven pump that obtains power using an electric motor is required instead of a mechanically-driven pump that obtains power from the crankshaft, so costs increase. In addition, to increase the fuel injection amount at the time of starting the internal combustion engine 1, because the fuel injection pressure is low, the fuel injection rate is also low, so a long injection period is required. Thus, an evaporation time for injected fuel cannot be ensured. Therefore, in an existing art, there has also been suggested a technique for lifting exhaust valves by a small amount or completely stopping the exhaust valves and cancelling ignition in an initial fuel injection cycle at the time of starting an internal combustion engine to increase the amount of in-cylinder fuel in the next cycle to thereby carry out first ignition. With this technique, it is possible to increase the amount of in-cylinder fuel at the time of starting an internal combustion engine without increasing the fuel injection rate even at a low fuel pressure, and it is also possible to increase the amount of vaporized fuel. In addition, at this time, it is not necessary to use an exclusive fuel pump or injection valve, so costs do not increase. However, with this technique, the number of cycles until first ignition at the time of starting an internal combustion engine increases by one or more cycles and, as a result, a period of time required for starting the internal combustion engine extends. In addition, a load on a starter motor for cranking during a period of the increased cycles until first ignition increases, and the increased load may cause deterioration of the durability of the starter motor. Thus, it is desired to further appropriately start the internal combustion engine 1 so as to ensure stable and short startability without increasing the number of cycles until first ignition and to make it hard to cause occurrence of unburned HC and suppress deterioration of exhaust emissions.
[0031] According to the embodiment of the invention, within a period from an exhaust stroke to an intake stroke, a period during which both the intake valve 11 and the exhaust valve 14 are closed (referred to as both valve close period) is created, and fuel is injected during the both valve close period. Hereinafter, such starting control is termed special starting control. The both valve close period is created by using the second WT 16 to close the exhaust valve 14 in the middle of the exhaust stroke and using the first WT 15 to open the intake valve 11 in the middle of the intake stroke. That is, the both valve close period is created so as to be a period from a certain timing in the exhaust stroke to a certain timing in the intake stroke, including an intake top dead center. In the both valve close period, because of upward movement of the corresponding piston 18, gas remaining in the cylinder 2 is compressed again and the in-cylinder temperature increases. Therefore, with such special starting control, fuel may be injected from the fuel injection valve 3 into the high-temperature cylinder 2 to thereby make it possible to facilitate evaporation of fuel. The ECU 22 that executes fuel injection control using the fuel injection valves 3 in the corresponding both valve close periods functions as a first injection control unit. Starting control that is normally executed such that the above described special starting control is not executed and fuel is injected in a compression stroke is termed normal starting control. FIG. 2A is a view that shows the open/close timing of each intake valve 11 and the open/close timing of each exhaust valve 14 in special starting control. FIG 2B is a view that shows the open/close timing of each intake valve 11 and the open/close timing of each exhaust valve 14 in normal starting control. In normal starting control, as shown in FIG 2B, a short valve overlap period during which both valves are opened over a period from before the intake top dead center to after the intake top dead center is provided; whereas, in special starting control, as shown in FIG A, the both valve close period is provided over a period from before the intake top dead center to after the intake top dead center.
[0032] However, as in the case of the present embodiment, when fuels having different ethanol concentrations are used for the internal combustion engine 1, because the evaporation characteristic of fuel with respect to an in-cylinder temperature and the amount of fuel required for combustion with respect to an in-cylinder temperature vary depending on the ethanol concentration of fuel, so the amount of increase in in-cylinder temperature in order to facilitate evaporation of fuel varies depending on the ethanol concentration of fuel. FIG. 3 is a graph that shows an in-cylinder temperature and the evaporation percentage of fuel with respect to the ethanol concentration of fuel. As shown in FIG. 3, as the ethanol concentration of fuel increases, a higher in-cylinder temperature is required in order to increase the evaporation percentage.
[0033] Then, in the present embodiment, in order to achieve an in-cylinder temperature further appropriate for the ethanol concentration of fuel, the both valve close period is changed through special starting control on the basis of the ethanol concentration of fuel. Specifically, the ethanol concentration of fuel is detected by the ethanol concentration sensor 9, and then the close timing of each exhaust valve 14, at which each exhaust valve 14 is closed in the middle of the corresponding exhaust stroke, is controlled by the second VVT16 on the basis of the detected ethanol concentration and the open timing of each intake valve 11, at which each intake valve 11 is opened in the middle of the corresponding intake stroke, is controlled by the first WT 15 to thereby change the both valve close period. Then, fuel injection using each fuel injection valve 3 is once completed within the corresponding changed both valve close period. FIG. 4A is a chart that shows the fuel injection timing in special starting control by which fuel is injected in the both valve close period. FIG 4B is a chart that shows the fuel injection timing in normal starting control. In normal starting control, as shown in FIG. 4B, a total amount of fuel is injected at a time before a compression top dead center; whereas, in special starting control, as shown in FIG 4A, a total amount of fuel is injected around an intake top dead center in the both valve close period.
[0034] When only the close timing of each exhaust valve 14 is advanced, the amount of residual gas in the corresponding cylinder 2 increases and the compression end temperature at the time of recompression increases. Thus, only the close timing of each exhaust valve 14, at which each exhaust valve 14 is closed in the middle of the corresponding exhaust stroke, may be controlled by the second VVT 16 to change the both valve close period. FIG 5 is a graph that shows the correlation between the close timing of each exhaust valve 14 for creating the both valve close period and an in-cylinder temperature. As shown in FIG 5, as the close timing of each exhaust valve 14 is advanced with respect to the intake top dead center, the in-cylinder temperature more easily increases. [0035] With the present embodiment, the both valve close period may be changed through special starting control so as to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel, so it is possible to facilitate evaporation of fuel. By so doing, fuel of which evaporation is facilitated may appropriately combust by ignition using the ignition plug 17 in the same cycle as that of fuel injection. Thus, the number of cycles until first ignition at the time of starting the internal combustion engine 1 does not increase by one, so a period of time required for starting the internal combustion engine 1 does not extend. A load on the starter motor for cranking also does not increase, so it is possible to suppress deterioration of the durability of the starter motor. In addition, because fuel appropriately combusts in this way, so stable startability may be ensured, and unburned HC is hard to occur to thereby make it possible to also suppress deterioration of exhaust emissions. Thus, it is possible to further appropriately start the internal combustion engine 1 in a short period of time.
[0036] There is a case where the total amount of fuel required for combustion cannot be injected in the both valve close period, during which both the intake valve 11 and the exhaust valve 14 are closed, within a period from the exhaust stroke to the intake stroke. In this case, fuel of an amount to which evaporation may be facilitated is injected in the both valve close period, and then fuel of a remaining amount required for combustion is injected in the compression stroke after a lapse of the both valve close period. The ECU 22 that executes fuel injection control using the fuel injection valves 3 in the compression stroke after a lapse of the both valve close period functions as a second injection control unit. Such two-split fuel injection is also included in special starting control. FIG. 6 is a chart that shows the fuel injection timing of special starting control in the case of two-split fuel injection. In special starting control in the case of two-split fuel injection, as shown in FIG 6, fuel is injected separately at two points, that is, in the both valve close period and before the compression top dead center.
[0037] A first special starting control routine executed by the ECU 22 will be described with reference to the flow chart shown in FIG 7. FIG. 7 is a flow chart that shows the first special starting control routine. The routine is executed by the ECU 22. [0038] The routine shown in FIG 7 is started when an ignition SW is turned on. As the routine is started, it is determined in S101 whether the in-cylinder temperature detected by each in-cylinder temperature sensor 19 is lower than or equal to a predetermined temperature T. The predetermined temperature T is a temperature at or below which combustion cannot be appropriately performed in normal starting control. When affirmative determination is made in S101, the process proceeds to S102. When negative determination is made in S101, the routine is once ended, and normal starting control is executed.
[0039] In S102, it is determined whether the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, is higher than or equal to a predetermined concentration c . The predetermined concentration a is a concentration above which combustion cannot be appropriately performed in normal starting control. When affirmative determination is made in S102, the process proceeds to S103. When negative determination is made in S102, the routine is once ended, and normal starting control is executed.
[0040] In S103, a starter SW is turned on to drive the starter motor to thereby start cranking.
[0041] In SI 04, it is determined whether a first exhaust stroke is carried out in each cylinder 2. When affirmative determination is made in S104, the process proceeds to S105. When negative determination is made in S104, the process returns to the same step, and fuel injection and ignition are not carried out until a first exhaust stroke is carried out. This avoids fuel injection and ignition without providing the both valve close period.
[0042] In S105, on the basis of the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, the close timing of each exhaust valve 14, at which each exhaust valve 14 is closed in the middle of the corresponding exhaust stroke, is controlled by the second WT 16, and the open timing of each intake valve 11, at which each intake valve 11 is opened in the middle of the corresponding intake stroke, is controlled by the first VVT 15 to thereby change the both valve close period. Specifically, as the ethanol concentration of fuel increases, the close timing of each exhaust valve 14 is advanced, and the open timing of each intake valve 11 is retarded such that fuel injection is once completed in the both valve close period.
[0043] In S106, each fuel injection valve 3 is used to inject fuel in the corresponding both valve close period, and, where necessary, inject the remaining amount of fuel required for combustion in the compression stroke after a lapse of the both valve close period. Then, the corresponding ignition plug 17 is used to ignite fuel near the compression top dead center.
[0044] In S107, it is determined whether the in-cylinder temperature detected by each in-cyiinder temperature sensor 19 is higher than the predetermined temperature T. The predetermined temperature T is a temperature at or below which combustion cannot be appropriately performed in normal starting control. When affirmative determination is made in SI 07, the routine is once ended, and normal starting control is executed or normal operation is carried out. When negative determination is made in S107, the process proceeds to S105, and continues special starting control.
[0045] With the above routine, it is possible to change the both valve close period through special starting control so as to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel. By so doing, it is possible to appropriately start the internal combustion engine 1 through special starting control. First Alternative Embodiment
[0046] In a first alternative embodiment of the invention, the both valve close period is changed on the basis of the ethanol concentration of fuel as in the case of the first embodiment; however, a period from the close timing of each exhaust valve 14, for creating the both valve close period, to the intake top dead center is shorter than a period from the intake top dead center to the open timing of each intake valve 11.
[0047] FIG 8A is a view that shows the open/close timing of each exhaust valve 14 according to the first alternative embodiment. FIG 8B is a view that shows the open/close timing of each intake valve 11 according to the first alternative embodiment. In the first alternative embodiment, as shown in FIG 8A, a first period (valve close angular range) 9e from the close timing of each exhaust valve 14, for creating the both valve close period, to the intake top dead center is set so as to be shorter than a second period (valve open angular range) θί from the intake top dead center to the open timing of each intake valve 11 (8e < 6i).
[0048] With the first alternative embodiment, the first period 8e is shorter than the second period θί, so the cylinder volume at the time when the intake valve 11 is opened is larger than the cylinder volume at the time when the exhaust valve 14 is closed. Therefore, a negative pressure occurs in the cylinder 2 by the time when the intake valve 11 opens in the both valve close period, and the intake valve 11 opens in a state where a negative pressure is occurring. By so doing, in special starting control, fuel is injected in the both valve close period during which a negative pressure is occurring to thereby boil the fuel at a reduced pressure. In addition, by opening the intake valve 11 in a state where a negative pressure is occurring, the flow rate of intake air that flows into the cylinder 2 becomes close to the speed of sound, so it is possible to increase the gas temperature in the cylinder 2 by kinetic energy of intake air. That is, by increasing the gas temperature in the cylinder 2, it is possible to further increase the in-cylinder temperature after the both valve close period. FIG 9 is a graph that shows the correlation between a difference θί-θβ and an in-cylinder temperature according to the first alternative embodiment of the invention. As shown in FIG 9, as the difference θϊ-θβ that is obtained by subtracting the first period 6e from the second period 0i increases, the in-cylinder temperature increases. Thus, evaporation of fuel may be facilitated. Particularly, when fuel is injected in the compression stroke after a lapse of the both valve close period described in the first embodiment, it is also possible to facilitate evaporation of fuel injected in the compression stroke.
Second Alternative Embodiment
[0049] In a second alternative embodiment of the invention, the close timing of each intake valve 11 with respect to the intake bottom dead center after a lapse of the both valve close period is changed on the basis of the ethanol concentration of fuel.
[0050] As the close timing of each intake valve 11 approaches the intake bottom dead center, the engine effective compression ratio in the case where the engine rotation speed is low increases at the time of starting the internal combustion engine 1 to thereby make it possible to increase the gas temperature in the corresponding cylinder 2. FIG. 10 is a graph that shows the correlation between the close timing of each intake valve 11 and an in-cylinder temperature. As shown in FIG 10, as the close timing of each intake valve 11 approaches the intake bottom dead center from any one of an advance side and a retard side, the in-cylinder temperature may be increased. With the second alternative embodiment, by changing the close timing of each intake valve 11 with respect to the intake bottom dead center after a lapse of the both valve close period, it is possible to vary the1 in-cylinder temperature in the compression stroke after the both valve close period. Thus, the close timing of each intake valve 11 is changed to further appropriate close timing on the basis of the ethanol concentration of fuel, evaporation of the fuel may be facilitated. Particularly, when fuel is injected in the compression stroke after a lapse of the both valve close period described in the first embodiment, as the close timing of each intake valve 11 approaches the intake bottom dead center, it is also possible to facilitate evaporation of fuel injected in the compression stroke.
Second Embodiment
[0051] In a second embodiment of the invention, the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel. Note that the description of a similar configuration to that of the above described embodiment is omitted.
[0052] Through special starting control, gas remaining in the cylinder 2 is recompressed by upward movement of the piston 18 to increase the in-cylinder temperature in the both valve close period, so fuel may be injected into the high-temperature cylinder, and evaporation of fuel may be facilitated. However, when fuels having different ethanol concentrations are used in the internal combustion engine 1, the evaporation characteristic of fuel with respect to an in-cylinder temperature and the amount of fuel required for combustion with respect to an in-cylinder temperature vary depending on the ethanol concentration of fuel. Therefore, at a specific in-cylinder temperature that is increased by setting the both valve close period through special starting control, the injection parameter of fuel for facilitating evaporation of fuel varies depending on the ethanol concentration. The injection parameter of fuel is a variable, such as the fuel injection amount, the number of splits of fuel injection and the fuel injection timing, that may be varied at the time when fuel is injected. In the case of a fuel having an ethanol concentration at which the evaporation characteristic of the fuel deteriorates at a specific in-cylinder temperature or in the case of a fuel having an ethanol concentration at which the amount of fuel required for combustion increases at a specific in-cylinder temperature, the injection parameter of fuel needs to be changed on the basis of the specific in-cylinder temperature so as to further facilitate evaporation of fuel. For example, in the both valve close period, it is necessary to increase the fuel injection amount, to increase the number of splits of fuel injection or to advance the fuel injection timing.
[0053] Then, in the present embodiment, in order to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period, the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel. Specifically, the ethanol concentration of fuel is detected by the ethanol concentration sensor 9, and then the injection parameter, such as the fuel injection amount, the number of splits and the fuel injection timing of fuel injection in the both valve close period, is changed on the basis of the detected ethanol concentration. Then, fuel injection is carried out with the changed injection parameter so as to once complete fuel injection by the fuel injection valve 3 in the both valve close period.
[0054] FIG. 11 is a chart that illustrates the case where the injection parameter is changed such that the number of splits of fuel injection in the both valve close period is increased into two. As shown in FIG 11, when the number of splits of fuel injection in the both valve close period is increased into two, it is possible to facilitate evaporation of fuel even when the ethanol concentration of fuel is high.
[0055] In the case of two-split fuel injection in which fuel of an amount to which evaporation may be facilitated is injected in the both valve close period and fuel of a remaining amount required for combustion is injected in the compression stroke after a lapse of the both valve close period, with a change in the injection parameter of fuel in the both valve close period, the injection parameter of fuel in the following compression stroke is also changed. That is, the ratio of the amount of fuel injected in the both valve close period and the ratio of the amount of fuel injected in the compression stroke, with respect to the amount of fuel required for combustion, may be changed on the basis of the ethanol concentration of fuel such that fuel of an amount to which evaporation may be facilitated is injected in the both valve close period on the basis of the ethanol concentration of fuel. FIG. 12 is a chart that illustrates the case where the injection parameter of fuel is changed in the both valve close period so as to increase the amount of fuel injected in the both valve close period and to reduce the amount of fuel injected in the compression stroke. FIG 13 is a graph that shows the correlation between the ratio of the amount of fuel injected in the both valve close period and an exhaust gas temperature. As shown in FIG 13, as the ratio of the amount of fuel injected in the both valve close period with respect to the total amount of fuel injected increases, combustion becomes slow because a homogeneous air-fuel mixture is formed in the cylinder, and afterburning is facilitated, so the exhaust gas temperature in the cylinder increases. Thus, as shown in FIG. 12, when the amount of fuel injected in the both valve close period is increased, the in-cylinder gas temperature in the next and following cycles increases to thereby make it possible to facilitate evaporation of fuel.
[0056] With the present embodiment, the injection parameter of fuel may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylihder temperature determined by the both valve close period, so evaporation of fuel may be facilitated. By so doing, fuel of which evaporation is facilitated may appropriately combust by ignition using the ignition plug 17 in the same cycle as that of fuel injection. Thus, the number of cycles until first ignition at the time of starting the internal combustion engine 1 does not increase by one, so a period of time required for starting the internal combustion engine 1 does not extend. A load on the starter motor for cranking also does not increase, so it is possible to suppress deterioration of the durability of the starter motor. In addition, because fuel appropriately combusts in this way, so stable startability may be ensured, and unburned HC is hard to occur to thereby make it possible to also suppress deterioration of exhaust emissions. Thus, it is possible to further appropriately start the internal combustion engine 1 in a short period of time.
[0057] A second special starting control routine executed by the ECU 22 will be described with reference to the flow chart shown in FIG. 14. FIG. 14 is a flow chart that shows the second special starting control routine. The routine is executed by the ECU 22. The second special starting control routine shown in FIG 14 differs from the first special starting control routine shown in FIG 7 in that S105 and S106 are respectively changed to S205 and S206, so only those points will be described.
[0058] In S205, the close timing of each exhaust valve 14, at which each exhaust valve 14 is closed in the middle of the corresponding exhaust stroke, is controlled by the second WT 16 and the open timing of each intake valve 11, at which each intake valve 11 is opened in the middle of the corresponding intake stroke, is controlled by the first VVT 15 to thereby provide a constant both valve close period. Specifically, as the ethanol concentration of fuel increases, the close timing of each exhaust valve 14 is advanced, and the open timing of each intake valve 11 is retarded such that fuel injection is once completed in the both valve close period.
[0059] In S206, each fuel injection valve 3 is used to inject fuel in the both valve close period by changing the injection parameter of fuel on the basis of the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, and, where necessary, to inject fuel of a remaining amount required for combustion in the compression stroke after a lapse of the both valve close period. Then, the corresponding ignition plug 17 is used to ignite fuel near the compression top dead center.
[0060] With the above routine, the injection parameter of fuel in the both valve close period may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period, so evaporation of fuel may be facilitated. By so doing, it is possible to appropriately start the internal combustion engine 1 through special starting control.
Third Alternative Embodiment
[0061] In a third alternative embodiment of the invention, both the feature of the first embodiment and the feature of the second embodiment are included, and at least any one of the both valve close period and the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel. Note that the description of a similar configuration to those of the above embodiments is omitted.
[0062] In the third alternative embodiment, as in the case of the first embodiment, the both valve close period is changed on the basis of the ethanol concentration of fuel in special starting control in order to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel. Alternatively, as in the case of the second embodiment, the injection parameter of fuel injected in the both valve close period is changed on the basis of the ethanol concentration of fuel in order to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period.
[0063] With the third alternative embodiment, the both valve close period may be changed in special starting control so as to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel, so evaporation of fuel may be facilitated. Alternatively, the injection parameter of fuel may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period, so evaporation of fuel may be facilitated. By so doing, fuel of which evaporation is facilitated may appropriately combust by ignition using the ignition plug 17 in the same cycle as that of fuel injection. Thus, the number of cycles until first ignition at the time of starting the internal combustion engine 1 does not increase by one, so a period of time required for starting the internal combustion engine 1 does not extend. A load on the starter motor for cranking also does not increase, so it is possible to suppress deterioration of the durability of the starter motor. In addition, because fuel . appropriately combusts in this way, so stable startability may be ensured, and unburned HC is hard to occur to thereby make it possible to also suppress deterioration of exhaust emissions. Thus, it is possible to further appropriately start the internal combustion engine in a short period of time.
[0064] A third special starting control routine executed by the ECU 22 will be described with reference to the flow chart shown in FIG. 15. FIG. 15 is a flow chart that shows the third special starting control routine. The routine is executed by the ECU 22. The third special starting control routine shown in FIG. 15 differs from the first special starting control routine shown in FIG. 7 in that S105 and S106 are respectively changed to S305 and S306, so only those points will be described.
[0065] In S305, on the basis of the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, the close timing of each exhaust valve 14, at which each exhaust valve 14 is closed in the middle of the corresponding exhaust stroke, is controlled by the second WT 16, and the open timing of each intake valve 11, at which each intake valve 11 is opened in the middle of the corresponding intake stroke, is controlled by the first VVT 15 to thereby change the both valve close period. Specifically, as the ethanol concentration of fuel increases, the close timing of each exhaust valve 14 is advanced, and the open timing of each intake valve 11 is retarded such that fuel injection is once completed in the both valve close period.
[0066] In S306, each fuel injection valve 3 is used to inject fuel in the both valve close period by changing the injection parameter of fuel on the basis of the ethanol concentration of fuel, detected by the ethanol concentration sensor 9, and, where necessary, to inject fuel of a remaining amount required for combustion in the compression stroke after a lapse of the both valve close period. Note that, in S305 and S306, only one of the both valve close period and the injection parameter of fuel may be changed and the other one may be fixed or the other one may be changed in coordination with the changed one. [0067] With the above routine, it is possible to change the both valve close period in special starting control so as to achieve the in-cylinder temperature further appropriate for the ethanol concentration of fuel. Alternatively, the injection parameter of fuel in the both valve close period may be changed in special starting control so as to achieve the injection parameter of fuel further appropriate for the ethanol concentration of fuel and the in-cylinder temperature determined by the both valve close period. By so doing, it is possible to appropriately start the internal combustion engine 1 through special starting control.
[0068] The internal combustion engine starting control device according to the aspect of the invention is not limited to the above described embodiments and alternative embodiments; it may be modified in various forms without departing from the scope of the invention. Therefore, the embodiments and alternative embodiments may be combined operably. In addition, the above described embodiments and alternative embodiments are also embodiments and alternative embodiments of the internal combustion engine starting control method according to the aspect of the invention.

Claims

CLAIMS:
1. A starting control device for a direct-injection internal combustion engine, comprising:
a fuel property detecting unit that detects a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; a valve control unit that controls an open/close timing of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; and
a first injection control unit that injects fuel from the fuel injection valve in the both valve close period created by the valve control unit, wherein
the valve control unit changes the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit.
2. A starting control device for a direct-injection internal combustion engine, comprising:
a fuel property detecting unit that detects a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine; a valve control unit that controls an open/close timing of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke; and
a first injection control unit that injects fuel from the fuel injection valve in the both valve close period created by the valve control unit, wherein
the first injection control unit changes an injection parameter of fuel injected in the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit.
3. The starting control device according to claim 1 or 2, further comprising:
a second injection control unit that injects fuel from the fuel injection valve after a lapse of the both valve close period.
4. The starting control device according to claim 3, wherein
a ratio of an amount of fuel injected by the first injection control unit
with respect to a total amount of fuel injected by the first injection control unit and the second injection control unit is changed on the basis of the property of fuel, detected by the fuel property detecting unit.
5. The starting control device according to any one of claims 1 to 4, wherein the valve control unit sets a period from the close timing of the exhaust valve to an intake top dead center within the both valve close period so as to be shorter than a period from the intake top dead center to the open timing of the intake valve within the both valve close period.
6. The starting control device according to any one of claims 1 to 5, wherein the valve control unit changes the close timing of the intake valve with respect to an intake bottom dead center after a lapse of the both valve close period on the basis of the property of fuel, detected by the fuel property detecting unit.
7. The starting control device according to any one of claims 1 to 6, wherein the valve control unit controls the open/close timing of the intake valve and the open/close timing of the exhaust valve so as to close the exhaust valve in the middle of the exhaust stroke and to open the intake valve in the middle of the intake stroke to thereby create the both valve close period.
8. A starting control method for a direct-injection internal combustion engine, comprising: detecting a property of fuel injected from a fuel injection valve arranged in a cylinder of the direct-injection internal combustion engine;
controlling an open/close timing of an intake valve and an open/close timing of an exhaust valve so as to create a both valve close period, during which both the intake valve and the exhaust valve are closed, within a period from an exhaust stroke to an intake stroke;
changing at least one of the both valve close period and an injection parameter of fuel injected in the both valve close period on the basis of the detected property of fuel; and injecting fuel from the fuel injection valve in the both valve close period.
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