EP1544443A1 - Méthode d'estimation de la température dans la chambre de combustion après la combustion - Google Patents

Méthode d'estimation de la température dans la chambre de combustion après la combustion Download PDF

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Publication number
EP1544443A1
EP1544443A1 EP04029561A EP04029561A EP1544443A1 EP 1544443 A1 EP1544443 A1 EP 1544443A1 EP 04029561 A EP04029561 A EP 04029561A EP 04029561 A EP04029561 A EP 04029561A EP 1544443 A1 EP1544443 A1 EP 1544443A1
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EP
European Patent Office
Prior art keywords
combustion
temperature
cylinder interior
gas
cylinder
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EP04029561A
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German (de)
English (en)
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EP1544443B1 (fr
Inventor
Teruhiko Miyake
Shigeki Nakayama
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Toyota Motor Corp
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Toyota Motor Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D35/00—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
    • F02D35/02—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions
    • F02D35/025—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining temperatures inside the cylinder, e.g. combustion temperatures
    • F02D35/026—Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for on interior conditions by determining temperatures inside the cylinder, e.g. combustion temperatures using an estimation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F02D41/403—Multiple injections with pilot injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F02D41/405—Multiple injections with post injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P19/00—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition
    • F02P19/02—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition electric, e.g. layout of circuits of apparatus having glowing plugs

Definitions

  • the present invention relates to a combustion temperature estimation method for estimating combustion temperature in a cylinder (in a combustion chamber) of an internal combustion engine.
  • the quantity of emissions such as NO x discharged from an internal combustion engine such as a spark-ignition engine or a diesel engine has a strong correlation with combustion temperature (highest combustion temperature, highest flame temperature) in each cylinder. Therefore, an effective way for reducing the quantity of emissions such as NO x is controlling the combustion temperature to a predetermined temperature. Meanwhile, actual measurement of the combustion temperature is very difficult. Therefore, the combustion temperature must be accurately estimated in order to control the combustion temperature to a predetermined temperature.
  • the combustion chamber temperature condition estimation apparatus for an internal combustion engine described in Japanese Patent Application Laid-Open ( kokai ) No. 2002-54491 includes an exhaust temperature sensor for detecting, at the outside of a combustion chamber of the engine, the temperature of exhaust gas discharged from the combustion chamber, and, on the basis of the detected exhaust gas temperature, estimates the temperature in the combustion chamber after completion of combustion (accordingly, the above-mentioned cylinder interior combustion temperature), which temperature has a strong correlation with the detected exhaust gas temperature.
  • the above-mentioned apparatus estimates the cylinder interior combustion temperature on the assumption that a strong correlation exists between the combustion temperature and the exhaust temperature as measured externally of the combustion chamber. However, in actuality, a strong correlation does not always exist therebetween; therefore, in some cases, the above-mentioned combustion temperature cannot be accurately estimated. In addition, the above-mentioned apparatus has a drawback of increased production cost and a complex structure, because the apparatus includes an exhaust temperature sensor as an essential component.
  • an object of the present invention is to provide a combustion temperature estimation method for an internal combustion engine, which can accurately estimate the temperature of combustion within a cylinder interior (within a combustion chamber) of the internal combustion engine by use of a simple configuration.
  • an ignition-time compressed cylinder interior gas temperature which is a pre-combustion cylinder interior gas temperature at the time of ignition, is first estimated, while utilizing the fact that at least cylinder interior gas present in a cylinder is compressed in the cylinder.
  • the time of ignition refers to a time of ignition by a spark plug.
  • the time of ignition refers to a point in time when a predetermined ignition delay time elapses from a fuel injection timing (a main injection timing in the case where main injection operation is performed after at least one pilot injection operation).
  • the ignition-time compressed cylinder interior gas temperature can be obtained in an accurate and easy manner on the basis of a cylinder interior volume at the time of ignition and a general formula which represents an adiabatic change by use of a politropic index, on the assumption that the state (i.e., temperature and pressure) of cylinder interior gas adiabatically changes before combustion in a compression stroke (and an expansion stroke).
  • a combustion ascribable temperature increase which is an increase in temperature of the cylinder interior gas as a result of combustion, is estimated on the basis of at least the composition of gas taken in the cylinder and the quantity of heat generated as a result of combustion of injected fuel.
  • an increase in temperature of the cylinder interior gas as a result of combustion i.e., the combustion ascribable temperature increase
  • the combustion specific heat and amount by mol (hereinafter may be referred to as "mole amount”) of the cylinder interior gas having participated in combustion change depending on the composition of gas taken into a cylinder (hereinafter may be referred to as "intake gas”); i.e., proportions by concentrations (hereinafter may be referred to as “concentration proportions”) of a plurality of components (e.g., oxygen and inert gases) of intake gas, and increase with, for example, the concentration proportions of inert gases (a detail description will be provided later). Accordingly, the combustion ascribable temperature increase can be accurately obtained on the basis of the constant-pressure specific heat and mole amount of cylinder interior gas having participated in combustion, and the quantity of heat generated as a result of combustion of fuel.
  • injection gas i.e., proportions by concentrations (hereinafter may be referred to as “concentration proportions”) of a plurality of components (e.g., oxygen and inert gases) of intake gas, and increase with, for example
  • combustion speed is an increase in temperature of cylinder interior gas stemming from an increase in combustion speed
  • combustion speed is estimated on the basis of factors which influence combustion speed in a cylinder.
  • the time of ignition is after a point in time corresponding to the compression dead center (i.e., the time of ignition is a point in time in an expansion stroke). In the expansion stroke, the cylinder interior gas temperature decreases with time.
  • the (highest) combustion temperature of cylinder interior gas increases with combustion speed after initiation of combustion.
  • Such an increase in temperature of cylinder interior gas is obtained as the combustion-speed ascribable temperature increase, on the basis of factors which influence the combustion speed.
  • Examples of factors which influence the combustion speed includes fuel injection pressure, engine speed, swirl ratio of gas taken into the cylinder, and boost pressure produced by a supercharger (for the case where the engine is equipped with such a supercharger), and oxygen concentration of gas taken into the cylinder.
  • the (highest) combustion temperature in the cylinder (hereinafter simply referred to as "(highest) combustion temperature”) is estimated from a value obtained through addition of the combustion ascribable temperature increase and the combustion-speed ascribable temperature increase to the ignition-time compressed cylinder interior gas temperature. Accordingly, the highest combustion temperature in the cylinder estimated in this manner can be a value which accurately represents various actual phenomena.
  • the combustion temperature estimation method according to the present invention can accurately estimate the highest combustion temperature by use of a simple configuration to match various actual phenomena.
  • the ignition-time compressed cylinder interior gas temperature is preferably estimated on the basis of the temperature of gas taken into the cylinder, the composition of the taken gas, and an increase in the ignition-time compressed cylinder interior gas temperature estimated on the basis of a factor which increases the pre-combustion cylinder interior gas temperature.
  • the factor which increases the pre-combustion cylinder interior gas temperature include heat generated as a result of combustion of fuel injected by means of pilot injection in the case where such pilot injection is performed before main fuel injection, and heat generated as a result of supply of electricity to a glow plug in the case where electricity is supplied to the glow plug.
  • the ignition-time compressed cylinder interior gas temperature naturally changes with intake temperature. Further, since the politropic index to be used with cylinder interior gas which causes adiabatic change changes depending on the composition of intake gas (accordingly, the composition of cylinder interior gas), the ignition-time compressed cylinder interior gas temperature (based on a general formula representing adiabatic change by use of the politropic index) also changes with the composition of intake gas.
  • the ignition-time compressed cylinder interior gas temperature increases by an amount corresponding to the quantity of the heat.
  • Such an increase in temperature of the cylinder interior gas is obtained as an increase in the ignition-time compressed cylinder interior gas temperature.
  • the temperature of gas (intake gas) taken into the cylinder, the composition of the taken gas (intake gas), and an increase in the ignition-time compressed cylinder interior gas temperature can serve as values (parameters) which influence the ignition-time compressed cylinder interior gas temperature. Accordingly, as described above, in addition to the fact of cylinder interior gas being compressed in a cylinder, the above-described three parameters are taken into consideration when the ignition-time compressed cylinder interior gas temperature is estimated. Thus, the ignition-time compressed cylinder interior gas temperature can be estimated more accurately, and as a result, the (highest) combustion temperature can be estimated more accurately.
  • the ignition-time compressed cylinder interior gas temperature is preferably estimated under the assumption that the time of ignition coincides with the point in time corresponding to the compression top dead center.
  • the cylinder interior gas after ignition i.e., during combustion or after combustion
  • the highest combustion temperature is considered to increase up to a point in time corresponding to the compression top dead center.
  • the highest combustion temperature in this case coincides with the highest combustion temperature in the case where the time of ignition coincides with the point in time corresponding to the compression top dead center.
  • the ignition-time compressed cylinder interior gas temperature is estimated under the assumption that the time of ignition coincides with the point in time corresponding to the compression top dead center, the highest combustion temperature can be estimated more accurately for the case where the time of ignition is prior to the point in time corresponding to the compression top dead center.
  • an control apparatus of an internal combustion engine which apparatus performs a combustion temperature estimation method for an internal combustion engine according to an embodiment of the present invention, and estimates the quantity of NO x generated within a cylinder as a result of combustion, on the basis of the combustion temperature estimated by the method.
  • FIG. 1 schematically shows the entire configuration of a system in which such an engine control apparatus is applied to a four-cylinder internal combustion engine (diesel engine) 10.
  • This system comprises an engine main body 20 including a fuel supply system; an intake system 30 for introducing gas to combustion chambers (cylinder interiors) of individual cylinders of the engine main body 20; an exhaust system 40 for discharging exhaust gas from the engine main body 20; an EGR apparatus 50 for performing exhaust circulation; and an electronic control apparatus 60.
  • Fuel injection valves (injection valves, injectors) 21 are disposed above the individual cylinders of the engine main body 20.
  • the fuel injection valves 21 are connected via a fuel line 23 to a fuel injection pump 22 connected to an unillustrated fuel tank.
  • a glow plug 24 is disposed above each cylinder to be located adjacent to the fuel injection valve 21.
  • Each glow plug 24 is electrically connected to the electronic control apparatus 60.
  • the glow plug 24 generates heat upon receipt of electricity in accordance with a signal from the electronic control apparatus 60 only when the engine is in a predetermined operating state such as a warming up state, so as to supply a predetermined quantity of heat to cylinder interior gas present in each cylinder.
  • the fuel injection pump 22 is electrically connected to the electronic control apparatus 60.
  • the fuel injection pump 22 pressurizes fuel in such a manner that the actual injection pressure (discharge pressure) of fuel becomes equal to the instruction base fuel injection pressure Pcrbase.
  • each of the fuel injection valves 21 opens for a predetermined period of time so as to inject, directly to the combustion chamber of the corresponding cylinder, the fuel pressurized to the instruction base fuel injection pressure Pcrbase, in the instruction fuel injection quantity qfin.
  • the intake system 30 includes an intake manifold 31, which is connected to the respective combustion chambers of the individual cylinders of the engine main body 20; an intake pipe 32, which is connected to an upstream-side branching portion of the intake manifold 31 and constitutes an intake passage in cooperation with the intake manifold 31; a throttle valve 33, which is rotatably held within the intake pipe 32; a throttle valve actuator 33a for rotating the throttle valve 33 in accordance with a drive signal from the electronic control apparatus 60; an intercooler 34, which is interposed in the intake pipe 32 to be located on the upstream side of the throttle valve 33; a compressor 35a of a turbocharger 35, which is interposed in the intake pipe 32 to be located on the upstream side of the intercooler 34; and an air cleaner 36, which is disposed at a distal end portion of the intake pipe 32.
  • the exhaust system 40 includes an exhaust manifold 41, which is connected to the individual cylinders of the engine main body 20; an exhaust pipe 42, which is connected to a downstream-side merging portion of the exhaust manifold 41; a turbine 35b of the turbocharger 35 interposed in the exhaust pipe 42; and a diesel particulate filter (hereinafter referred to as "DPNR") 43, which is interposed in the exhaust pipe 42.
  • the exhaust manifold 41 and the exhaust pipe 42 constitute an exhaust passage.
  • the DPNR 43 is a filter unit which accommodates a filter 43a formed of a porous material such as cordierite and which collects, by means of a porous surface, the particulate matter contained in exhaust gas passing through the filter.
  • a filter 43a formed of a porous material such as cordierite and which collects, by means of a porous surface, the particulate matter contained in exhaust gas passing through the filter.
  • the DPNR 43 also serves as a storage-reduction-type NO x catalyst unit which, after absorption of NO x , releases the absorbed NO x and reduces it.
  • the EGR apparatus 50 includes an exhaust circulation pipe 51, which forms a passage (EGR passage) for circulation of exhaust gas; an EGR control valve 52, which is interposed in the exhaust circulation pipe 51; and an EGR cooler 53.
  • the exhaust circulation pipe 51 establishes communication between an exhaust passage (the exhaust manifold 41) located on the upstream side of the turbine 35b, and an intake passage (the intake manifold 31) located on the downstream side of the throttle valve 33.
  • the EGR control valve 52 responds to a drive signal from the electronic control apparatus 60 so as to change the quantity of exhaust gas to be circulated (exhaust-gas circulation quantity, EGR-gas flow rate).
  • the electronic control apparatus 60 is a microcomputer which includes a CPU 61, ROM 62, RAM 63, backup RAM 64, an interface 65, etc., which are connected to one another by means of a bus.
  • the ROM 62 stores a program to be executed by the CPU 61, tables (lookup tables, maps), constants, etc.
  • the RAM 63 allows the CPU 61 to temporarily store data when necessary.
  • the backup RAM 64 stores data in a state in which the power supply is on, and holds the stored data even after the power supply is shut off.
  • the interface 65 contains A/D converters.
  • the interface 65 is connected to a hot-wire-type airflow meter 71, which serves as air flow rate (new air flow rate) measurement means, and is disposed in the intake pipe 32; an intake gas temperature sensor 72, which is provided in the intake passage to be located downstream of the throttle valve 33 and downstream of a point where the exhaust circulation pipe 51 is connected to the intake passage; an intake pipe pressure sensor 73, which is provided in the intake passage to be located downstream of the throttle valve 33 and downstream of the point where the exhaust circulation pipe 51 is connected to the intake passage; a crank position sensor 74; an accelerator opening sensor 75; and an intake-gas oxygen concentration sensor 76 provided in the intake passage to be located downstream of the throttle valve 33 and downstream of the point where the exhaust circulation pipe 51 is connected to the intake passage.
  • the interface 65 receives respective signals from these sensors, and supplies the received signals to the CPU 61. Further, the interface 65 is connected to the fuel injection valves 21, the fuel injection pump 22, the throttle valve actuator 33a, and the EGR control valve 52; and outputs corresponding drive signals to these components in accordance with instructions from the CPU 61.
  • the hot-wire-type airflow meter 71 measures the mass flow rate of intake gas (new air) passing through the intake passage (intake new air quantity per unit time), and generates a signal indicating the mass flow rate Ga (intake new air flow rate Ga).
  • the intake gas temperature sensor 72 detects the temperature of the above-mentioned intake gas, and generates a signal representing the intake gas temperature Tb.
  • the intake pipe pressure sensor 73 measures the pressure of intake gas (i.e., intake pipe pressure), and generates a signal representing the intake pipe pressure Pb.
  • the crank position sensor 74 detects the absolute crank angle of each cylinder, and generates a signal representing the crank angle CA and engine speed NE; i.e., rotational speed of the engine 10.
  • the accelerator opening sensor 75 detects an amount by which an accelerator pedal AP is operated, and generates a signal representing the accelerator pedal operated amount Accp.
  • the intake-gas oxygen concentration sensor 76 detects the oxygen concentration of intake gas (i.e., intake-gas oxygen concentration), and a signal representing intake-gas oxygen concentration RO2_in.
  • FIG. 2 is a diagram schematically showing a state in which gas (intake gas) is taken from the intake manifold 31 into a certain cylinder (cylinder interior) of the engine 10 and is then discharged to the exhaust manifold 41 after combustion.
  • intake gas (accordingly, cylinder interior gas) includes new air taken from the tip end of the intake pipe 32 via the throttle valve 33, and EGR gas taken from the exhaust circulation pipe 51 via the EGR control valve 52.
  • the mass ratio i.e., EGR ratio
  • EGR ratio EGR ratio of the mass of the taken EGR gas (EGR gas mass) to the sum of the mass of the taken new air (new air mass) and the mass of the taken EGR gas (EGR gas mass) changes depending on the opening of the throttle valve 33 and the opening of the EGR control valve 52, which are properly controlled by the electronic control apparatus 60 (CPU 61) in accordance with the operating condition.
  • the intake gas i.e., gas composed of the new air and the EGR gas
  • the intake valve Vin as the piston moves downward
  • the thus-produced gas mixture serves as cylinder interior gas.
  • the cylinder interior gas is confined within the cylinder when the intake valve Vin closes upon the piston having reached bottom dead center (hereinafter referred to as "ATDC-180°"), and then compressed in a subsequent compression stroke as the piston moves upward.
  • the present apparatus opens the corresponding fuel injection valve 21 for a predetermined period of time corresponding to the instruction fuel injection quantity qfin, to thereby inject fuel directly into the cylinder.
  • the injected fuel disperses in the cylinder with elapse of time, while mixing with the cylinder interior gas to produce a gas mixture.
  • the gas mixture starts combustion by means of self ignition.
  • region B a combustion region
  • region A a non-combustion region
  • region A the remaining portion of the combustion chamber other than the region B.
  • Cylinder interior gas remaining in the combustion chamber after combustion is discharged, as exhaust gas, to the exhaust manifold 41 via the exhaust valve Vout, which is held open during the exhaust stroke, as the piston moves upward.
  • a portion of the exhaust gas is circulated to the intake side as EGR gas via the exhaust circulation pipe 51, and the remaining exhaust gas is discharged to the outside via the exhaust pipe 42.
  • the present apparatus immediately upon arrival of each final fuel injection timing finjfin for a cylinder to which fuel is injected (hereinafter referred to as "fuel injection cylinder"), the highest combustion temperature Tflame of the cylinder interior gas generated as a result of combustion in the region B is estimated immediately after the arrival (after elapse of the above-mentioned ignition delay time).
  • the present apparatus obtains the highest combustion temperature Tflame in accordance with the following Eq. (1).
  • Tflame Tpump + ⁇ Tburn + ⁇ Tb_velo
  • Tpump represents ignition-time compressed cylinder interior gas temperature; i.e., the pre-combustion temperature of cylinder interior gas at the time of ignition.
  • ⁇ Tburn represents a combustion ascribable temperature increase; i.e., an increase in temperature of cylinder interior gas ascribable to combustion.
  • ⁇ Tb_velo represents an increase in temperature of the cylinder interior gas ascribable to an increase in combustion speed.
  • Ta0 represents cylinder interior gas temperature at ATDC-180°; i.e., bottom-dead-center cylinder interior gas temperature.
  • the cylinder interior gas temperature is considered to be substantially equal to the intake temperature Tb. Therefore, the bottom-dead-center cylinder interior gas temperature Ta0 can be obtained as the intake temperature Tb detected by means of the intake temperature sensor 72 at ATDC-180°.
  • Va0 represents cylinder interior volume at ATDC-180°; i.e., bottom-dead-center cylinder interior volume. Since the cylinder interior volume Va can be represented in the form of a function Va(CA) of crank angle CA on the basis of the design specifications of the engine 10, the bottom-dead-center cylinder interior volume Va0 can be obtained on the basis of this function.
  • Vig represents cylinder interior volume at the time of ignition. Since the ignition time is a point in time after passage of a predetermined ignition delay time from a corresponding fuel injection timing, as shown in FIG. 3, a crank angle CAig at the time of ignition can be obtained through addition of a crank angle ⁇ CAdelay, which corresponds to the above-mentioned ignition delay time, to a fuel injection crank angle CAinj corresponding to the above-mentioned final fuel injection timing finjfin. Accordingly, the cylinder interior volume Vig at the time of ignition can be obtained as Va(CAig).
  • ⁇ represents a politropic index.
  • the politropic index ⁇ to be used with the cylinder interior gas which causes adiabatic changes, changes depending on the composition of intake gas (accordingly, the composition of cylinder interior gas).
  • the politropic index ⁇ can be obtained as g(RO2c), where RO2c represents bottom-dead-center intake-gas oxygen concentration; i.e., the intake-gas oxygen concentration RO2_in detected by the intake-gas oxygen concentration sensor 76 (specifically, the intake-gas oxygen concentration RO2_in detected at bottom dead center (ATDC-180°); and g represents a function for obtaining the politropic index from the intake-gas oxygen concentration.
  • the present apparatus obtains the ignition-time compressed cylinder interior gas temperature Tpump in accordance with Eq. (2).
  • the ignition-time compressed cylinder interior gas temperature Tpump increases with a delay in ignition time when the ignition time (ignition-time crank angle CAig) is before a point in time corresponding to the compression top dead center (ATDC0°) (i.e., when the ignition time falls in the compression stroke).
  • the ignition-time compressed cylinder interior gas temperature Tpump decreases with a delay in ignition time when the ignition time is after the point in time corresponding to the compression top dead center (i.e., when the ignition time falls in the expansion stroke).
  • the highest combustion temperature Tflame which a final value to be calculated in accordance with the above-described Eq. (1), is considered to increase up to the point in time corresponding to the compression top dead center. That is, in this case, the highest combustion temperature Tflame is preferably made equal to the highest combustion temperature for the case where the ignition time coincides with the point in time corresponding to the compression top dead center.
  • the present apparatus obtains the ignition-time compressed cylinder interior gas temperature Tpump in accordance with the above-mentioned Eq. (2) while using, as the value of the ignition-time cylinder interior volume Vig, a cylinder interior volume Vtop (const value) at ATDC0° in place of the value of Va(CAig).
  • the ignition-time compressed cylinder interior gas temperature Tpump in this case is estimated as a cylinder interior gas temperature Tal (constant value) at compression top dead center.
  • Tglow constant value in the present example
  • combustion ascribable temperature increase ⁇ Tburn which is an increase in cylinder interior gas temperature ascribable to combustion
  • combustion of 1 mol of injected fuel is considered.
  • the combustion ascribable temperature increase ⁇ Tburn can be represented by the following Eq. (3).
  • ⁇ Tburn Qfuel/(Cp ⁇ ngas)
  • Qfuel represents a quantity of heat generated as a result of combustion of 1 mol of injected fuel, and is a known value (constant) which is univocally determined by the composition of the fuel.
  • Cp represents a post-combustion constant-pressure specific heat of cylinder interior gas involved in the combustion of 1 mol of injected fuel.
  • ngas represents the post-combustion mole amount of cylinder interior gas involved in the combustion of 1 mol of injected fuel. Accordingly, in order to obtain the combustion ascribable temperature increase ⁇ Tburn in accordance with Eq. (3), the above-mentioned constant-pressure specific heat Cp and the above-mentioned mole amount ngas must be obtained.
  • m and n are values univocally determined on the basis of the composition of fuel to be injected.
  • ⁇ , ⁇ , and ⁇ respectively represent the mole amounts of inert gases CO 2 , H 2 O, and N 2 involved in the combustion of fuel of 1 mol. That is, in the present embodiment, four components; i.e., O 2 , CO 2 , H 2 O, and N 2 , are considered as the gas components of the intake gas.
  • O 2 , CO 2 , H 2 O, and N 2 are considered as the gas components of the intake gas.
  • ngas m + n / 2 + ⁇ + ⁇ + ⁇
  • [X] in , [X] egr , and [X] air represent the mass concentration of component X in intake gas, the mass concentration of component X in EGR gas, and the mass concentration of component X in new air, respectively.
  • Gcyl represents the total mass of intake gas taken in a cylinder in a single intake stroke (hereinafter referred to as “cylinder interior total gas quantity Gcyl”); Gegr represents the mass of EGR gas taken from the EGR apparatus 50 into the cylinder in a single intake stroke as a part of intake gas (hereinafter referred to as “EGR gas quantity”); and Gm represents the mass of new air taken from the end portion of the intake pipe 32 into the cylinder in a single intake stroke as a part of intake gas (hereinafter referred to as "intake new air quantity").
  • the cylinder interior total gas quantity Gcyl can be obtained in accordance with the following Eq. (7), which is based on the gas state equation at ATDC-180°.
  • Gcyl (Pa0 ⁇ Va0)/(R ⁇ Ta0)
  • Pa0 represents bottom-dead-center cylinder interior gas pressure; i.e., cylinder interior gas pressure at ATDC-180°. At ATDC-180°, the cylinder interior gas pressure is considered to be substantially equal to the intake pipe pressure Pb. Therefore, the bottom-dead-center cylinder interior gas pressure Pa0 can be obtained from the intake pipe pressure Pb detected by means of the intake pipe pressure sensor 73 at ATDC-180°.
  • R represents a gas constant of cylinder interior gas.
  • Ta0 and Va0 represent bottom-dead-center cylinder interior gas temperature and bottom-dead-center combustion chamber volume, respectively, as in the case of Eq. (2).
  • the intake new air quantity Gm can be calculated on the basis of the intake new air quantity per unit time (intake new air flow rate Ga) measured by means of the airflow meter 71, the engine speed NE based on the output of the crank position sensor 74, and a function f(Ga, NE) which uses the intake new air flow rate Ga and the engine speed NE, as arguments, so as to obtain quantity of intake new air per intake stroke.
  • a bottom-dead-center intake new air flow rate Ga0 and a bottom-dead-center engine speed NE0, which are detected by the corresponding sensors at ATDC-180°, are used as the intake new air flow rate Ga and the engine speed NE, respectively.
  • the EGR gas quantity Gegr can be obtained in accordance with the following Eq. (8) on the basis of the cylinder interior total gas quantity Gcyl and the intake new air quantity Gm, which are obtained in the above-described manner.
  • Gegr Gcyl - Gm
  • intake-gas CO 2 concentration the concentration [CO 2 ] in of CO 2 contained in intake gas. Since the intake-gas CO 2 concentration is equal to the CO 2 concentration of cylinder interior gas taken into a cylinder but not having undergone combustion, the intake-gas CO 2 concentration can be obtained in accordance with the following Eq. (9) as a mass ratio of the "sum of the mass [CO 2 ] air ⁇ Gm of CO 2 contained in new air taken into the cylinder and the mass [CO 2 ] egr ⁇ Gegr of CO 2 contained in EGR gas taken into the cylinder" to the cylinder interior total gas quantity Gcyl.
  • Eq. (9) a mass ratio of the "sum of the mass [CO 2 ] air ⁇ Gm of CO 2 contained in new air taken into the cylinder and the mass [CO 2 ] egr ⁇ Gegr of CO 2 contained in EGR gas taken into the cylinder" to the cylinder interior total gas quantity Gcyl.
  • [CO 2 ] in [CO 2 ] air
  • the concentration [CO 2 ] egr of CO 2 contained in EGR gas is considered to be equal to the concentration of CO 2 contained in exhaust gas (passing through the exhaust valve Vout), and the concentration of CO 2 contained in the exhaust gas is equal to the CO 2 concentration of cylinder interior gas after combustion.
  • the mass of CO 2 generated as a result of combustion can be represented as KCO 2 ⁇ qfinc, where KCO 2 represents the mass of CO 2 generated as a result of combustion of fuel of unit quantity.
  • KCO 2 represents the mass of CO 2 generated as a result of combustion of fuel of unit quantity.
  • the value of KCO 2 ⁇ can be obtained from m ⁇ (MCO 2 /Mfuel).
  • the concentration [CO 2 ] egr of CO 2 contained in EGR gas can be obtained in accordance with the following Eq. (10).
  • Eq. (10) is rearranged, the following Eq. (11) can be obtained.
  • [CO 2 ] egr KCO 2 ⁇ qfinc+[CO 2 ] air G m +[CO 2 ] egr G egr / Gcyl+qfinc
  • [CO 2 ] egr KCO 2 ⁇ qfinc+[CO 2 ] air G m / G m +qfinc
  • Eq. (12) When Eq. (11) is substituted in Eq. (9), the following Eq. (12) can be obtained.
  • the intake-gas CO 2 concentration [CO 2 ] in can be obtained in accordance with Eq. (12).
  • [CO 2 ] in [CO 2 ] air ⁇ (1-R) + KCO 2 ⁇ qfinc+[CO 2 ] air G m / G m +qfinc R
  • intake-gas H 2 O concentration [H 2 O] in of H 2 O contained in the intake gas
  • the intake-gas H 2 O concentration [H 2 O] in can be obtained in the same manner as in the above-described method of obtaining the intake-gas CO 2 concentration [CO 2 ] in with the [CO 2 ] in Eqs. (9) to (12) replaced with [H 2 O] and KCO 2 in Eqs. (9) to (12) with KH 2 O. That is, the intake-gas H 2 O concentration [H 2 O] in can be obtained in accordance with the following Eq. (13).
  • [H 2 O] in [H 2 O] air ⁇ (1-R) + KH 2 O ⁇ qfinc+[H 2 O] air G m / G m +qfinc R
  • KH 2 O represents the mass of H 2 O generated as a result of combustion of a unit quantity of fuel.
  • the intake-gas N 2 concentration [N 2 ] in can be obtained in accordance with Eqs. (9) to (12), with the [CO 2 ] in Eqs. (9) to (12) replaced with [N 2 ] and the terms of KCO 2 in Eqs. (9) to (12) removed. That is, the intake-gas N 2 concentration [N 2 ] in can be obtained in accordance with the following Eq. (14).
  • [N 2 ] in [N 2 ] air ⁇ (1-R) + [N 2 ] air G m / G m + qfinc R
  • intake-gas O 2 concentration a method of obtaining the concentration [O 2 ]in of O 2 contained in the intake gas (hereinafter referred to as "intake-gas O 2 concentration")
  • O 2 contained in the cylinder interior gas is consumed in the cylinder as a result of combustion of fuel (C m H n ).
  • the mass of O 2 consumed as a result of combustion can be represented by KO 2 ⁇ qfinc, where KO 2 represents the mass of O 2 consumed as a result of combustion of a unit quantity of fuel.
  • the intake-gas O 2 concentration [O 2 ] in can be obtained in accordance with Eqs. (9) to (12), with the [CO 2 ] in Eqs.
  • the mass concentration [X] in (X: O 2 , CO 2 , H 2 O, N 2 ) of the above-mentioned four components contained in the intake gas can be obtained.
  • a method of obtaining the above-mentioned mole amounts ⁇ , ⁇ , and ⁇ by use of the thus-obtained mass concentrations will be described.
  • the proportions of the four components in the intake gas are assumed to be maintained as proportions of the four components in cylinder interior gas; i.e., gas taken into a cylinder (more specifically, a gas present in the above-mentioned combustion region (region B)).
  • the proportions of the four components in the cylinder interior gas are equal to those of the four components in the cylinder interior gas.
  • the mass ratio of the four components in the cylinder interior gas can be represented as (m+n/4)MO 2 : ⁇ MCO 2 : ⁇ MH 2 O : ⁇ MN 2 .
  • the following Eq. (18) can be obtained.
  • (m + n / 4)MO 2 : ⁇ MCO 2 : ⁇ MH 2 O: ⁇ MN 2 [O 2 ] in :[CO 2 ] in : [H 2 O] in :[N 2 ] in
  • Eq. (18) Use of Eq. (18) enables the above-mentioned mole amounts ⁇ , ⁇ , and ⁇ to be obtained in accordance with the following Eqs. (19) to (21), respectively.
  • ⁇ [CO 2 ] in / [O 2 ] in MO 2 / MCO 2 (m + n / 4)
  • ⁇ [H 2 O] in / [O 2 ] in MO 2 / MH 2 O(m + n / 4)
  • ⁇ [N 2 ] in / [O 2 ] in MO 2 / MN 2 (m + n / 4)
  • the above-mentioned mole amount ngas and constant-pressure specific heat Cp can be obtained in accordance with the above-mentioned Eqs. (5) and (6).
  • the combustion ascribable temperature increase ⁇ Tburn can be obtained in accordance with the above-mentioned Eq. (3).
  • the present apparatus upon arrival of each final fuel injection timing finjfin, the present apparatus obtains the combustion ascribable temperature increase ⁇ Tburn by use of the above-mentioned Eqs. (3) to (21) and on the basis of at least the composition of intake gas (the concentration proportions of gas components contained in intake gas) and the quantity (Qfuel) of heat generated as a result of combustion of injected fuel.
  • a predetermined period of time (hereinafter referred to as "highest-temperature reaching time") is needed for the cylinder interior gas temperature Ta to increase by the above-mentioned combustion ascribable temperature increase ⁇ Tburn from the temperature at the time of ignition (i.e., ignition-time compressed cylinder interior gas temperature Tpump) and to reach a temperature of (Tpump + ⁇ Tburn) (i.e., reach the highest combustion temperature Tflame).
  • the cylinder interior gas temperature Ta decreases with time because of an increase in the cylinder interior volume Va (an increase in the cylinder interior gas temperature Ta stemming from combustion is suppressed).
  • the shorter the highest-temperature reaching time the higher the highest combustion temperature Tflame.
  • the highest combustion temperature Tflame increases with combustion speed in the cylinder after start of combustion.
  • Such a temperature increase of cylinder interior gas corresponds to the combustion-speed ascribable temperature increase ⁇ Tb_velo.
  • Combustion speed increases with the fuel injection pressure Pcrc for the present operation cycle or the bottom-dead-center engine speed NE0.
  • a combustion speed when the fuel injection pressure Pcrc for the present operation cycle is a reference fuel injection pressure Pcrref and the bottom-dead-center engine speed NE0 is a reference engine speed NEref is defined as ordinary combustion speed.
  • a highest temperature reaching time shorting amount ⁇ tadv with respect to the highest temperature reaching time corresponding to the ordinary combustion speed can be obtained by the following Eq. (22), which is a function of the fuel injection pressure Pcrc for the present operation cycle and the bottom-dead-center engine speed NE0.
  • Eq. (22) is a function of the fuel injection pressure Pcrc for the present operation cycle and the bottom-dead-center engine speed NE0.
  • t0 represents a constant having a negative value
  • Ka and Kb is a constant having a positive value.
  • the values of t0, Ka, and Kb are set in such a manner that ⁇ tadv becomes zero when the fuel injection pressure Pcrc for the present operation cycle is the reference fuel injection pressure Pcrref and the bottom-dead-center engine speed NE0 is the reference engine speed NEref.
  • a ⁇ tadv-corresponding advancing angle ⁇ CAadv which is an advancing amount of crank angle CA corresponding to the highest temperature reaching time shorting amount ⁇ tadv obtained in accordance with Eq.
  • (22) can be obtained on the basis of the highest temperature reaching time shorting amount ⁇ tadv, the bottom-dead-center engine speed NE0, and a function h whose arguments are ⁇ tadv and NE0; i.e., as a value of h( ⁇ tadv, NE0).
  • a value obtained through substation of the above-mentioned highest combustion temperature for ordinary combustion speed Tig from the temperature Tadv can be considered to correspond to an increase in cylinder interior gas temperature (accordingly, the above-mentioned combustion-speed ascribable temperature increase ⁇ Tb_velo) caused by advancement of the time at which the cylinder interior gas temperature reaches the highest combustion temperature Tflame by an amount corresponding to the highest temperature reaching time shorting amount ⁇ tadv, as compared with the case where the combustion speed becomes the ordinary combustion speed.
  • the combustion-speed ascribable temperature increase ⁇ Tb_velo can be obtained in accordance with the following Eq. (23).
  • ⁇ Tb_velo Tig ⁇ (Vig/Vadv) k-1 - Tig
  • the present apparatus upon arrival of each final fuel injection timing finjfin, the present apparatus obtains the combustion-speed ascribable temperature increase ⁇ Tb_velo by use of the above-mentioned Eqs. (22) to (23) and on the basis of the factors which influence the cylinder interior combustion speed; i.e., the fuel injection pressure Pcrc for the present operation cycle and the bottom-dead-center engine speed NE0.
  • the present apparatus estimates the highest combustion temperature Tflame in accordance with the above-mentioned Eq. (1); i.e., from the value obtained through addition of the combustion ascribable temperature increase ⁇ Tburn and the combustion-speed ascribable temperature increase ⁇ Tb_velo to the ignition-time compressed cylinder interior gas temperature Tpump.
  • the above is the outline of the combustion temperature estimation method according to the present invention.
  • NO x generation quantity estimation method upon each arrival of the final fuel injection timing finjfin for a fuel injection cylinder, actual NO x generation quantity NOxact (quantity of NO x generated in the above-mentioned region B as a result of combustion in an explosion (expansion) stoke immediately after the arrival) is estimated.
  • the actual NO x generation quantity NOxact can be obtained in accordance with the following Eq. (24); i.e., by multiplying the quantity of NO x generated as a result of combustion of fuel of unit quantity (hereinafter referred to as "combustion-generated NOx ratio RNOx_burn") by the above-mentioned instruction fuel injection quantity qfinc for the present operation cycle.
  • NOxact RNOx_burn ⁇ qfinc
  • Eq. (25) the combustion generated NOx ratio RNOx_burn in Eq. (24) is estimated by the following Eq. (25).
  • Eq. (25) e is the base of a natural logarithm.
  • RO2c bottom-dead-center intake-gas oxygen concentration
  • qfinc instruction fuel injection quantity for the present operation cycle
  • Tflame represents the highest combustion temperature in the present explosion stroke obtained by the above-described Eq. (1).
  • K0 to K4 are fitting constants which are determined in the manner described below on the basis of typical known multiple regression analysis.
  • RNOx_burn e K0 ⁇ (RO2c) K1 ⁇ (qfinc) K2 ⁇ (Pcrc) K3 ⁇ e (K4/Tflame)
  • Eq. (25) is an empirical formula for obtaining the combustion-generated NO x ratio RNOx_burn.
  • the combustion-generated NO x ratio RNOx_burn estimated by Eq. (25) is a function of the bottom-dead-center intake-gas oxygen concentration RO2c, the instruction fuel injection quantity qfinc in the present operation cycle, the instruction fuel injection pressure Pcrc in the present operation cycle, and the highest combustion temperature Tflame.
  • the combustion-generated NO x ratio RNOx_burn is calculated on the basis of the product of the power of the bottom-dead-center intake-gas oxygen concentration RO2c, the power of the instruction fuel injection quantity qfinc in the present operation cycle, the power of the instruction fuel injection pressure Pcrc in the present operation cycle, and an exponential function whose exponent is determined in accordance with the highest combustion temperature Tflame.
  • the fitting constants K0 to K4 can be determined, for example, through performance of an experiment as follows. That is, first, the engine 10 is operated while the EGR control valve 52 is maintained closed, whereby all the exhaust gas (accordingly, NO x contained in the exhaust gas) discharged via the exhaust valve Vout is discharged to the outside from the exhaust passage.
  • the values of the bottom-dead-center intake-gas oxygen concentration RO2c, the instruction fuel injection quantity qfinc in the present operation cycle, the instruction fuel injection pressure Pcrc in the present operation cycle, and the highest combustion temperature Tflame obtained by the above-described Eq. (1) are successively changed so that combinations of the respective values are attained in various predetermined patterns.
  • the combustion-generated NO x ratio RNOx_burn is successively measured for each pattern.
  • the predetermined known multiple regression analysis is performed on the basis of a large number of data sets regarding the relationship between measured values of the combustion-generated NO x ratio RNOx_burn and the combinations of the above-mentioned respective values, which were obtained as a result of such a work (experiment), whereby the above-mentioned fitting constants K0 to K4 can be obtained.
  • the fitting constants K1 to K3 are determined to assume positive values
  • the fitting constant K4 is determined to assume a negative value.
  • the combustion-generated NO x ratio RNOx_burn (accordingly, actual NO x generation quantity NOxact) calculated and estimated in accordance with Eq. (25) increases with an increase in any one of the bottom-dead-center intake-gas oxygen concentration RO2c, the instruction fuel injection quantity qfinc in the present operation cycle, the instruction fuel injection pressure Pcrc in the present operation cycle, and the highest combustion temperature Tflame. This matches the actual phenomena described below.
  • the actual NO x generation quantity NOxact increases with the intake-gas oxygen concentration RO2_in. This phenomenon occurs because oxygen is a material for generation of NO x , and an increase in the quantity of oxygen within the combustion chamber naturally facilitates generation of NO x .
  • the actual NO x generation quantity NOxact increases with the fuel injection quantity qfin. This phenomenon occurs as follows. When the fuel injection quantity qfin increases, the load of the engine 10 increases, so that the inner wall temperature of the combustion chamber increases. Therefore, the greater the fuel injection quantity qfin (i.e., the greater the load of the engine), the greater the quantity of NO x that is generated.
  • the actual NO x generation quantity NOxact increases with the fuel injection pressure Pcr. This phenomenon occurs as follows. When the fuel injection pressure Pcr is increased, the injection speed of fuel increases with a resultant increase in the degree of atomization of the fuel, whereby the above-mentioned excess air ratio increases. Therefore, the greater the fuel injection pressure Pcr (i.e., the greater the degree of atomization of injected fuel), the greater the quantity of NO x that is generated.
  • the actual NO x generation quantity NOxact increases with the highest combustion temperature Tflame. This phenomenon occurs because increased gas temperature accelerates a chemical reaction of producing NO x from nitrogen.
  • the combustion-generated NO x ratio RNOx_burn can be accurately estimated (thus, the actual NO x generation quantity NOxact can be accurately estimated in accordance with Eq. (24)) in such a manner that the estimated values follow at least the above-described four actual phenomena.
  • the above is the outline of the NO x generation quantity estimation method.
  • the present apparatus which performs the above-mentioned NO x generation quantity estimation method, calculates, at predetermined intervals, a target NO x generation quantity per operation cycle NOxt on the basis of the above-mentioned fuel injection quantity qfin and engine speed NE. Subsequently, the present apparatus feedback-controls the final fuel injection timing finjfin and the opening of the EGR control valve 52 in such a manner that the actual NO x generation quantity NOxact estimated in the previous operation cycle coincides with the target NO x generation quantity NOxt.
  • the final fuel injection timing finjfin to be applied for the fuel injection cylinder in the present operation cycle is delayed from the base fuel injection timing finjbase by a predetermined amount, and the opening of the EGR control valve 52 is increased from the current degree by a predetermined amount.
  • the highest combustion temperature Tflame of the fuel injection cylinder in the present operation cycle is controlled to decrease, whereby the actual NO x generation quantity NOxact; i.e., the quantity of NO x generated in the fuel injection cylinder in the present operation cycle, is rendered coincident with the target NO x generation quantity NOxt.
  • the final fuel injection timing finjfin to be applied for the fuel injection cylinder in the present operation cycle is advanced from the base fuel injection timing finjbase by a predetermined amount, and the opening of the EGR control valve 52 is decreased from the current degree by a predetermined amount.
  • the highest combustion temperature Tflame of the fuel injection cylinder in the present operation cycle is controlled to increase, whereby the actual NO x generation quantity NOxact; i.e., the quantity of NO x discharged from the fuel injection cylinder to the outside in the present operation cycle, is rendered coincident with the target NO x generation quantity NOxt.
  • the above is the outline of fuel injection control.
  • the present apparatus obtains the combustion-generated NO x ratio RNOx_burn on the basis of a table Mapinvlog(log(RNOx_burn)), which is stored in the ROM 62 in order to obtain the combustion-generated NO x ratio RNOx_burn from the "log(RNOx_burn)" obtained in accordance with Eq. (27).
  • This calculation procedure reduces the calculation load of the CPU 61 and prevents deterioration of calculation accuracy.
  • the CPU 61 repeatedly executes, at predetermined intervals, a routine shown by the flowchart of FIG. 5 and adapted to control fuel injection quantity, etc. Therefore, when a predetermined timing has been reached, the CPU 61 starts the processing from step 500, and then proceeds to step 505 so as to obtain an (instruction) fuel injection quantity qfin from an accelerator opening Accp, an engine speed NE, and a table (map) Mapqfin shown in FIG. 6.
  • the table Mapqfin defines the relation between accelerator opening Accp and engine speed NE, and fuel injection quantity qfin; and is stored in the ROM 62.
  • the CPU 61 proceeds to step 510 so as to determine a base fuel injection timing finjbase from the fuel injection quantity qfin, the engine speed NE, and a table Mapfinjbase shown in FIG. 7.
  • the table Mapfinjbase defines the relation between fuel injection quantity qfin and engine speed NE, and base fuel injection timing finjbase; and is stored in the ROM 62.
  • the CPU 61 proceeds to step 515 so as to determine a base fuel injection pressure Pcrbase from the fuel injection quantity qfin, the engine speed NE, and a table MapPcrbase shown in FIG. 8.
  • the table MapPcrbase defines the relation between fuel injection quantity qfin and engine speed NE, and base fuel injection pressure Pcrbase; and is stored in the ROM 62.
  • the CPU 61 proceeds to step 520 so as to determine a target NO x generation quantity NOxt from the fuel injection quantity qfin, the engine speed NE, and a table MapNOxt shown in FIG. 9.
  • the table MapNOxt defines the relation between fuel injection quantity qfin and engine speed NE, and target NOx generation quantity NOxt; and is stored in the ROM 62.
  • step 525 so as to store, as an NO x generation quantity deviation ⁇ NOx, a value obtained through subtraction, from the target NO x generation quantity NOxt, of the latest actual NO x generation quantity NOxact, which is computed at a fuel injection timing in a previous operation cycle by a routine to be described later.
  • the CPU 61 proceeds to step 530 so as to determine an injection-timing correction value ⁇ from the NO x generation quantity deviation ⁇ NOx and a table Map ⁇ shown in FIG. 10.
  • the table Map ⁇ defines the relation between NOx generation quantity deviation ⁇ NOx and injection-timing correction value ⁇ , and is stored in the ROM 62.
  • the CPU 61 proceeds to step 535 so as to correct the base fuel injection timing finjbase by the injection-timing correction value ⁇ to thereby obtain a final fuel injection timing finjfin.
  • the fuel injection timing is corrected in accordance with the NO x generation quantity deviation ⁇ NOx.
  • the injection-timing correction value ⁇ becomes positive, and its magnitude increases with the magnitude of the NO x generation quantity deviation ⁇ NOx, whereby the final fuel injection timing finjfin is shifted toward the advance side.
  • the injection-timing correction value ⁇ becomes negative, and its magnitude increases with the magnitude of the NO x generation quantity deviation ⁇ NOx, whereby the final fuel injection timing finjfin is shifted toward the retard side.
  • step 540 determines whether the injection start timing (i.e., the final fuel injection timing finjfin) is reached for the fuel injection cylinder.
  • the CPU 61 makes a "No" determination in step 540, the CPU 61 proceeds directly to step 595 so as to end the current execution of the present routine.
  • step 540 the CPU 61 proceeds to step 545 so as to inject fuel in an amount of the (instruction) fuel injection quantity qfin into the fuel injection cylinder from the fuel injection valve 21 at the base fuel injection pressure Pcrbase.
  • step 550 the CPU 61 determines whether the NO x generation quantity deviation ⁇ NOx is positive.
  • step 555 the opening of the EGR control valve 52 from the current degree by a predetermined amount. Subsequently, the CPU 61 proceeds to step 570.
  • step 550 the CPU 61 proceeds to step 560 so as to determine whether the NO x generation quantity deviation ⁇ NOx is negative.
  • step 560 determines whether the NO x generation quantity deviation ⁇ NOx is negative.
  • step 565 so as to increase the opening of the EGR control valve 52 from the current degree by a predetermined amount.
  • step 570 the CPU 61 proceeds to step 570 without changing the opening of the EGR control valve 52.
  • step 570 the CPU 61 stores, as the fuel injection quantity qfinc in the present operation cycle, the fuel injection quantity qfin actually injected.
  • step 575 the CPU 61 stores, as the fuel injection pressure Pcrc in the present operation cycle, the base fuel injection pressure Pcrbase at which fuel was actually injected. Subsequently, the CPU 61 proceeds to step 595 so as to end the current execution of the present routine.
  • the CPU 61 repeatedly executes, at predetermined intervals, a routine shown by the flowchart of FIG. 11 and adapted to calculate highest combustion temperature Tflame. Therefore, when a predetermined timing has been reached, the CPU 61 starts the processing from step 1100, and then proceeds to step 1105 so as to determine whether the crank angle CA at the present point in time coincides with ATDC-180°.
  • step 1105 the CPU 61 makes a "No" determination in step 1105, and then proceeds directly to step 1145 so as to determine whether the fuel injection start timing (i.e., the final fuel injection timing finjfin) for the fuel injection cylinder has come. Since the crank angle CA at the present point in time has not yet reached ATDC-180°, the CPU 61 makes a "No" determination in step 1145, and then proceeds directly to step 1195 so as to end the current execution of the present routine.
  • the CPU 61 repeatedly performs the processing of steps 1100, 1105, 1145, and 1195 until the crank angle CA reaches ATDC-180°.
  • the CPU 61 makes a "Yes" determination when it proceeds to step 1105, and then proceeds to step 1110.
  • the CPU 61 stores, as bottom-dead-center cylinder interior gas temperature Ta0, bottom-dead-center cylinder interior gas pressure Pa0, bottom-dead-center intake new air flow rate Ga0, and bottom-dead-center engine speed NE0, respectively, the intake gas temperature Tb, the intake pipe pressure Pb, the intake new air flow rate Ga, and the engine speed NE, which are detected by means of the intake gas temperature sensor 72, the intake pipe pressure sensor 73, the airflow meter 71, and the crank position sensor 74, respectively, at the present point in time (ATDC-180°).
  • the CPU 61 proceeds to step 1115 so as to store, as bottom-dead-center intake-gas oxygen concentration R02c, the intake-gas oxygen concentration RO2_in detected by means of the intake-gas oxygen concentration sensor 76 at the present point in time (ATDC-180°).
  • the CPU 61 computes the cylinder interior total gas quantity Gcyl in accordance with the above-described Eq. (7).
  • the values stored at step 1110 are employed as the bottom-dead-center cylinder interior gas pressure Pa0 and the bottom-dead-center cylinder interior gas temperature Ta0.
  • the CPU 61 proceeds to step 1125 so as to compute an intake new air quantity Gm from the bottom-dead-center intake new air flow rate Ga0 and the bottom-dead-center engine speed NE0 in accordance with the above-defined function f.
  • the CPU 61 computes an EGR gas quantity Gegr on the basis of the cylinder interior total gas quantity Gcyl computed in step 1120 and the intake new air quantity Gm, and in accordance with the above-described Eq. (8).
  • step 1135 so as to obtain an EGR ratio R on the basis of the above-mentioned intake new air quantity Gm, the above-mentioned EGR gas quantity Gegr, and the equation described in the box of step 1135, and then proceeds to step 1140 so as to obtain an excessive air ratio ⁇ on the basis of the above-mentioned intake new air quantity Gm, the fuel injection quantity qfinc in the present operation cycle stored in the above-mentioned step 570, and the equation described in the box of step 1140.
  • step 1145 so as to make a "No" determination, and then proceeds to step 1195 so as to end the current execution of the present routine.
  • the CPU 61 repeatedly performs the processing of steps 1100, 1105, 1145, and 1195 until the fuel injection timing (i.e., the final fuel injection timing finjfin) comes.
  • the CPU 61 makes a "Yes" determination in step 1145 and then proceeds to step 1150 so as to calculate the ignition-time crank angle CAig from the above-mentioned final fuel injection timing finjfin and the above-described ignition delay time.
  • the CPU 61 proceeds via step 1155 to a routine shown in FIG. 12 and adapted to calculate the ignition-time compressed cylinder interior gas temperature Tpump. That is, the CPU 61 starts the processing from step 1200, and then proceeds to step 1205 so as to obtain the politropic index ⁇ from the latest bottom-dead-center intake-gas oxygen concentration RO2c obtained in the above-described step 1115 and the above-mentioned function g.
  • the CPU 61 proceeds to step 1210 so as to determine whether the latest ignition-time crank angle CAig obtained in the above-described step 1150 is delayed from ATDC0°.
  • the CPU 61 makes a "Yes” determination, it proceeds to step 1215 so as to store a cylinder interior volume corresponding to the ignition-time crank angle CAig as the ignition-time cylinder interior volume Vig.
  • the CPU 61 makes a "No" determination in step 1210, it proceeds to step 1220 so as to store a cylinder interior volume Vtop corresponding to the top dead center (ATDC0°) as the ignition-time cylinder interior volume Vig.
  • the CPU 61 proceeds to step 1225 so as to determine whether electricity is supplied to the glow plug 24.
  • the CPU 61 makes a "Yes” determination, it proceeds to step 1230 so as to store the above-mentioned predetermined value Tglow as the cylinder interior gas temperature increase ⁇ Tpump.
  • the CPU 61 makes a "No” determination, it proceeds to step 1235 so as to set the value of the cylinder interior gas temperature increase ⁇ Tpump to zero.
  • the CPU 61 then proceeds to step 1240 so as to obtain the ignition-time compressed cylinder interior gas temperature Tpump on the basis of the latest bottom-dead-center cylinder interior gas temperature Ta0 obtained in the above-described step 1110, the above-mentioned ignition-time cylinder interior volume Vig, the above-mentioned cylinder interior gas temperature increase ⁇ Tpump, and the equation described in the box of step 1240. Subsequently, the CPU 61 proceeds to step 1160 of FIG. 11 via step 1295.
  • the CPU 61 executes a routine shown in FIG. 13 and adapted to calculate the combustion ascribable temperature increase ⁇ Tburn. That is, the CPU 61 starts the processing from step 1300, and then proceeds to step 1305 so as to obtain the intake-gas O 2 concentration [O 2 ] in on the basis of the latest EGR ratio R obtained in the above-described step 1135, the latest excess air ratio ⁇ obtained in the above-described step 1140, and the equation described in the box of step 1305 and corresponding to the above-mentioned Eq. (17).
  • step 1310 so as to obtain the intake-gas CO 2 concentration [CO 2 ] in on the basis of the EGR ratio R, the fuel injection quantity qfinc for the present operation cycle, the latest intake new air quantity Gm obtained in the above-described step 1125, and the equation described in the box of step 1310 and corresponding to the above-mentioned Eq. (12).
  • the CPU 61 proceeds to step 1315 so as to obtain the intake-gas H 2 O concentration [H 2 O] in in accordance with the above-mentioned Eq. (13), and then proceeds to step 1320 so as to obtain the intake-gas N 2 concentration [N 2 ] in in accordance with the above-mentioned Eq. (14).
  • the CPU 61 proceeds to step 1325 so as to obtain the above-described mole amount ⁇ on the basis of the intake-gas CO 2 concentration [CO 2 ] in , the intake-gas O 2 concentration [O 2 ] in , and the above-described Eq. (19). Similarly, the CPU 61 proceeds to step 1330 so as to obtain the above-described mole amount ⁇ in accordance with the above-mentioned Eq. (20), and then proceeds to step 1335 so as to obtain the above-described mole amount ⁇ in accordance with the above-mentioned Eq. (21).
  • the CPU 61 proceeds step 1340 so as to obtain the mole amount ngas of cylinder interior gas after combustion on the basis of the mole amounts ⁇ , ⁇ , ⁇ obtained in the above-described manner, and the above-mentioned Eq. (5).
  • the CPU 61 obtains the constant-pressure specific heat Cp of cylinder interior gas after combustion on the basis of the mole amounts ⁇ , ⁇ , r, and the above-mentioned Eq. (6).
  • the CPU 61 then proceeds to step 1350 so as to obtain the combustion ascribable temperature increase ⁇ Tburn on the basis of the mole amount ngas of cylinder interior gas after combustion, the constant-pressure specific heat Cp of cylinder interior gas after combustion, and the above-mentioned Eq. (3), and then proceeds to step 1165 of FIG. 11 via step 1395.
  • the CPU 61 executes a routine shown in FIG. 14 and adapted to calculate the combustion-speed ascribable temperature increase ⁇ Tb_velo. That is, the CPU 61 starts the processing from step 1400, and then proceeds to step 1405 so as to store, as the highest combustion temperature for ordinary combustion speed Tig, a value obtained through addition of the latest combustion ascribable temperature increase ⁇ Tburn obtained in the above-mentioned step 1350 to the latest ignition-time compressed cylinder interior gas temperature Tpump obtained in the above-mentioned step 1240.
  • the CPU 61 proceeds to step 1410 so as to obtain the highest temperature reaching time shorting amount ⁇ tadv on the basis of the fuel injection pressure Pcrc in the present operation cycle stored in the above-described step 575, the latest bottom-dead-center engine speed NE0 stored in the above-described step 1110, and the above-mentioned Eq. (22).
  • the CPU 61 obtains the ⁇ tadv-corresponding advancing angle ⁇ CAadv on the basis of the highest temperature reaching time shorting amount ⁇ tadv, the bottom-dead-center engine speed NE0, and the above-described function h.
  • the CPU 61 proceeds to step 1420 so as to obtain a corrected ignition-time crank angle CAadv by advancing the latest ignition-time crank angle CAig obtained in the above-described step 1150 by the ⁇ tadv-corresponding advancing angle ⁇ CAadv.
  • the CPU 61 determines whether the corrected ignition-time crank angle CAadv is delayed from ATDC0°.
  • step 1425 When the CPU 61 makes a "Yes” determination in step 1425, it proceeds to step 1430 so as to store a cylinder interior volume corresponding to the corrected ignition-time crank angle CAadv as a corrected ignition-time cylinder interior volume Vadv. Meanwhile, when the CPU 61 makes a "No" determination in step 1425, it proceeds to step 1435 so as to store a cylinder interior volume Vtop corresponding to the top-dead center (ATDC0°) as the corrected ignition-time cylinder interior volume Vadv.
  • ADC0° top-dead center
  • step 1440 so as to obtain the combustion-speed ascribable temperature increase ⁇ Tb_velo on the basis of the ignition-time cylinder interior volume Vig obtained in the above-described step 1215 or 1220, the above-mentioned corrected ignition-time cylinder interior volume Vadv, the above-mentioned highest combustion temperature for ordinary combustion speed Tig, and the above-mentioned Eq. (23).
  • the CPU 61 then proceeds to step 1170 of FIG. 11 via step 1495.
  • the CPU 61 proceeds to step 1170, it obtains the highest combustion temperature Tflame of the cylinder interior gas on the basis of the latest ignition-time compressed cylinder interior gas temperature Tpump obtained in the above-described step 1240, the latest combustion ascribable temperature increase ⁇ Tburn obtained in the above-described step 1350, the latest combustion-speed ascribable temperature increase ⁇ Tb_velo obtained in the above-described step 1440, and the above-described Eq. (1). After that, the CPU 61 proceeds to step 1195 to end the current execution of the present routine.
  • the CPU 61 After that point in time, the CPU 61 repeatedly executes the processing of steps 1100, 1105, 1145, and 1195 until ATDC-180° for the fuel injection cylinder comes again. In the above-described manner, the highest combustion temperature Tflame of cylinder interior gas is newly obtained every time the fuel injection start timing comes.
  • the CPU 61 repeatedly executes, at predetermined intervals, a routine shown by the flowchart of FIG. 15 and adapted to calculate actual NO x generation quantity NOxact. Therefore, when a predetermined timing has been reached, the CPU 61 starts the processing from step 1500, and then proceeds to step 1505 so as to determine whether the fuel injection start timing (i.e., the final fuel injection timing finjfin) has come. When the CPU 61 makes a "No" determination in step 1505, it proceeds directly to step 1595 so as to end the current execution of the present routine.
  • the CPU 61 proceeds to step 1530 so as to obtain "log(RNOx_burn)" in accordance with the above-described Eq. (27).
  • the CPU 61 determines the combustion-generated NO x ratio RNOx_burn on the basis of the log(RNOx_burn) and the above-described table Mapinvlog.
  • the CPU 61 then proceeds to step 1540 so as to obtain the actual NO x generation quantity NOxact in accordance with the above-described Eq. (24) and on the basis of the above-mentioned fuel injection quantity qfinc in the present operation cycle and the above-mentioned combustion-generated NO x ratio RNOx_burn.
  • the CPU 61 proceeds to 1595 so as to end the current execution of the present routine.
  • the CPU 61 repeatedly executes the processing of steps 1500, 1505, and 1595 until the fuel injection start timing for the fuel injection cylinder comes again.
  • a new actual NO x generation quantity NOxact is obtained each time the fuel injection start timing comes.
  • the obtained new actual NO x generation quantity NOxact is used in step 525 of FIG. 5 as described above.
  • the final fuel injection timing finjfin and the opening of the EGR control valve 52 to be applied to the fuel injection cylinder in the next operation cycle are feedback-controlled on the basis of the new actual NO x generation quantity NOxact.
  • the combustion temperature estimation method for an internal combustion engine upon each arrival of fuel injection start timing, the cylinder interior gas temperature (before combustion) at the time of ignition (ignition-time compressed cylinder interior gas temperature Tpump) is estimated, while the fact that the state of cylinder interior gas changes adiabatically is used as a general rule.
  • the quantity Qfuel of heat generated as a result of combustion of fuel is divided by the product of the post-combustion mole amount ngas and constant-pressure specific heat Cp of the cylinder interior gas, which can be obtained from the composition of intake gas (the concentration proportions of gas components), to thereby estimate an increase in temperature of the cylinder interior gas stemming from combustion (combustion ascribable temperature increase ⁇ Tburn).
  • combustion-speed ascribable temperature increase ⁇ Tb_velo an increase in temperature of cylinder interior gas stemming from an increase in combustion speed (combustion-speed ascribable temperature increase ⁇ Tb_velo) is estimated on the basis of fuel injection pressure Pcrc and engine speed NE0, which are factors which influence the combustion speed. Then, the highest combustion temperature Tflame is estimated from a value obtained through addition of the combustion ascribable temperature increase ⁇ Tburn and the combustion-speed ascribable temperature increase ⁇ Tb_velo to the ignition-time compressed cylinder interior gas temperature Tpump. Accordingly, the highest combustion temperature Tflame can be accurately estimated by use of a simple configuration to match various actual phenomena.
  • the present invention is not limited to the above-described embodiment, and may be modified in various manners within the scope of the present invention. For example, the following modifications may be employed.
  • fuel injection pressure and engine speed are employed as factors which influence combustion speed.
  • at least one of the swirl ratio of gas taken into cylinders, the boost pressure produced by a supercharger, and the oxygen concentration of gas taken into cylinders may be employed as a factor which influences combustion speed.
  • heat generated as a result of supply of electricity to a glow plug is employed as a factor which causes an increase in ignition-time compressed cylinder interior gas temperature (cylinder interior gas temperature increase ⁇ Tpump).
  • cylinder interior gas temperature increase ⁇ Tpump cylinder interior gas temperature increase
  • heat generated as a result of combustion of fuel injected by means of the pilot injection may be employed as such a factor.
  • the apparatus according to the present invention is preferably configured to calculate the heat generated as a result of combustion of fuel injected by means of the pilot injection (accordingly, an increase in temperature of cylinder interior gas) on the basis of, for example, the quantity of fuel injected by means of the pilot injection and the timing of the pilot injection (the time span (interval) between the pilot injection and the main injection).
  • the pre-combustion temperature of cylinder interior gas at the time of ignition is estimated on the basis of the fact that the state of the cylinder interior gas changes adiabatically.
  • the quantity of heat generated as a result of combustion of fuel is divided by the product of the post-combustion mole amount and constant-pressure specific heat of the cylinder interior gas, which can be obtained from the concentration proportions of gas components contained in intake gas, to thereby estimate an increase in temperature of the cylinder interior gas stemming from combustion (combustion ascribable temperature increase ⁇ Tburn).
  • combustion-speed ascribable temperature increase ⁇ Tb_velo combustion-speed ascribable temperature increase
EP04029561A 2003-12-16 2004-12-14 Méthode d'estimation de la température dans la chambre de combustion après la combustion Expired - Fee Related EP1544443B1 (fr)

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DE102007006341A1 (de) * 2007-02-08 2008-08-14 Bayerische Motoren Werke Aktiengesellschaft Verfahren zur Steuerung einer Brennkraftmaschine in Kraftfahrzeugen
CN102741533A (zh) * 2010-02-08 2012-10-17 丰田自动车株式会社 内燃机的燃烧控制装置
CN104933226A (zh) * 2015-05-26 2015-09-23 奇瑞汽车股份有限公司 一种发动机机油温度的控制计算方法
DE102008057500B4 (de) 2008-11-15 2019-07-18 Iav Gmbh Ingenieurgesellschaft Auto Und Verkehr Verfahren zum Betrieb einer Verbrennungskraftmaschine
DE102009021793B4 (de) 2009-05-18 2020-08-06 Iav Gmbh Ingenieurgesellschaft Auto Und Verkehr Verfahren zum Bestimmen der Stickoxidemission im Brennraum eines Dieselmotors
DE102006053805B4 (de) * 2006-11-15 2020-12-24 Robert Bosch Gmbh Verfahren zum Betreiben einer Brennkraftmaschine zur Ermittlung einer in einem Brennraum befindlichen Füllung

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JP5252949B2 (ja) * 2008-02-27 2013-07-31 トヨタ自動車株式会社 内燃機関におけるガス濃度計測方法およびガス濃度計測装置
JP4957651B2 (ja) * 2008-05-19 2012-06-20 トヨタ自動車株式会社 内燃機関の吸気制御装置
JP5045575B2 (ja) * 2008-06-25 2012-10-10 トヨタ自動車株式会社 内燃機関の燃焼制御装置
JP5257519B2 (ja) 2009-09-28 2013-08-07 トヨタ自動車株式会社 内燃機関の制御装置
JP5257520B2 (ja) 2009-09-28 2013-08-07 トヨタ自動車株式会社 内燃機関の制御装置
JP6171746B2 (ja) * 2013-09-04 2017-08-02 マツダ株式会社 エンジンの始動制御装置

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006053805B4 (de) * 2006-11-15 2020-12-24 Robert Bosch Gmbh Verfahren zum Betreiben einer Brennkraftmaschine zur Ermittlung einer in einem Brennraum befindlichen Füllung
DE102007006341A1 (de) * 2007-02-08 2008-08-14 Bayerische Motoren Werke Aktiengesellschaft Verfahren zur Steuerung einer Brennkraftmaschine in Kraftfahrzeugen
DE102007006341B4 (de) * 2007-02-08 2018-05-03 Bayerische Motoren Werke Aktiengesellschaft Verfahren zur Steuerung einer Brennkraftmaschine in Kraftfahrzeugen
DE102008057500B4 (de) 2008-11-15 2019-07-18 Iav Gmbh Ingenieurgesellschaft Auto Und Verkehr Verfahren zum Betrieb einer Verbrennungskraftmaschine
DE102009021793B4 (de) 2009-05-18 2020-08-06 Iav Gmbh Ingenieurgesellschaft Auto Und Verkehr Verfahren zum Bestimmen der Stickoxidemission im Brennraum eines Dieselmotors
CN102741533A (zh) * 2010-02-08 2012-10-17 丰田自动车株式会社 内燃机的燃烧控制装置
CN102741533B (zh) * 2010-02-08 2015-09-09 丰田自动车株式会社 内燃机的燃烧控制装置
EP2535545A4 (fr) * 2010-02-08 2018-03-07 Toyota Jidosha Kabushiki Kaisha Dispositif de commande de la combustion pour un moteur à combustion interne
CN104933226A (zh) * 2015-05-26 2015-09-23 奇瑞汽车股份有限公司 一种发动机机油温度的控制计算方法

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EP1544443B1 (fr) 2010-05-19
JP2005180220A (ja) 2005-07-07

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