JP7139936B2 - Engine combustion control device - Google Patents

Description

The technology disclosed herein relates to an engine combustion control device.

Patent Literature 1 describes an engine that burns gasoline fuel by compression ignition. This engine has an in-cylinder pressure sensor that detects the pressure in the combustion chamber. The engine control unit calculates the crank angle at which the mass combustion ratio is 50% from the output of the in-cylinder pressure sensor, and adjusts the combustion start timing so that the crank angle at which the mass combustion ratio is 50% is appropriate.

JP 2001-355484 A

As described in Patent Document 1, in a configuration in which the controller controls the engine based on the output of the in-cylinder pressure sensor, when the air-fuel mixture is normally combusted in the combustion chamber, the output of the in-cylinder pressure sensor Based on this, the engine can be appropriately controlled. However, the reliability of the output of the in-cylinder pressure sensor is low when the air-fuel mixture is abnormally combusting in the combustion chamber. This is because if the air-fuel mixture undergoes abnormal combustion, such as misfiring or pre-ignition, torque corresponding to the amount of fuel supplied to the combustion chamber is not generated. If the engine is controlled based on the output of the unreliable in-cylinder pressure sensor, the operation of the engine may be hindered.

The technology disclosed herein determines the reliability of an in-cylinder pressure sensor.

Specifically, the technology disclosed herein relates to an engine combustion control device. An engine combustion control device includes a plurality of fuel injection units for individually injecting fuel into a plurality of combustion chambers of an engine mounted on an automobile, and measurement signals corresponding to pressure changes in the plurality of combustion chambers. a plurality of in-cylinder pressure sensors that output a control signal related to the amount of fuel injected by the fuel injection unit to each of the plurality of fuel injection units based on at least the measurement signal of the in-cylinder pressure sensor, and injection a control unit that corrects the amount of fuel injected by each of the plurality of fuel injection units so as to suppress variations in the amount of fuel injected between the combustion chambers.

The control unit outputs a control signal to each of the plurality of fuel injection units so that the fuel concentration of the air-fuel mixture in the combustion chamber becomes leaner than the stoichiometric air-fuel ratio, and the control unit measures the in-cylinder pressure sensor. Based on the signal, the control unit calculates the combustion pressure (Pmi) in the combustion chamber, the crank angle position (mfb50) at which the mass combustion ratio becomes a predetermined ratio, and the lower heating value (Qend). Between the ratio (Qend/Pmi) of the lower heating value (Qend) and the combustion pressure (Pmi) and the crank angle position (mfb50) at which the mass combustion ratio is 50%, the mixture in the combustion chamber is performing normal combustion, and a torque corresponding to the amount of fuel supplied to the combustion chamber is generated . When a specific relationship is established, it is determined that the reliability of the measurement signal of the in-cylinder pressure sensor is high, the air-fuel mixture is burning abnormally, and torque corresponding to the amount of fuel supplied to the combustion chamber is not generated. First, if the specific relationship is not established, it is determined that the reliability of the measurement signal of the in-cylinder pressure sensor is low.

When determining that the reliability of the measurement signal of the in-cylinder pressure sensor is high, the control unit corrects the fuel amount and determines that the reliability of the measurement signal of the in-cylinder pressure sensor is low. If so, the correction of the fuel amount is restricted.

According to the study of the inventors of the present application, the combustion pressure calculated using the measurement signal of the in-cylinder pressure sensor, the crank angle position at which the mass combustion ratio becomes a predetermined ratio, and the lower calorific value. It was found that it is possible to determine whether abnormal combustion is occurring or whether abnormal combustion is occurring.

Specifically, a specific relationship is established between Qend/Pmi and mfb50 when the air-fuel mixture is burning normally in the combustion chamber. If the air-fuel mixture is burning abnormally, the specific relationship does not hold. Based on Qend/Pmi and mfb50 calculated from the measurement signal of the in-cylinder pressure sensor, the combustion state of the air-fuel mixture in the combustion chamber can be determined.

When normal combustion is performed in the combustion chamber, the reliability of the measurement signal of the in-cylinder pressure sensor is high. When abnormal combustion occurs in the combustion chamber, the reliability of the measurement signal of the in-cylinder pressure sensor is low. Therefore, the reliability of the measurement signal of the in-cylinder pressure sensor can be determined based on the combustion pressure, the crank angle position at which the mass combustion ratio reaches a predetermined ratio, and the lower heating value.

When the control unit determines that the reliability of the measurement signal of the in-cylinder pressure sensor is high, the control unit controls each of the plurality of fuel injection units so as to suppress variations in the amount of fuel to be injected between the combustion chambers. Correction of the amount of fuel to be injected is performed, and correction of the amount of fuel is limited when it is determined that the reliability of the measurement signal of the in-cylinder pressure sensor is low.

When the reliability of the measurement signal of the in-cylinder pressure sensor is low, the control section does not correct the amount of fuel injected by the fuel injection section. Since it is suppressed to control the engine using the measurement signal with low reliability, it is suppressed to hinder the operation of the engine.

On the other hand, when the reliability of the measurement signal of the in-cylinder pressure sensor is high, the control section corrects the amount of fuel injected by the fuel injection section. The engine operates properly because the variation between combustion chambers in the amount of fuel injected is suppressed.

When the operating state of the engine is in the first region, the control unit makes the fuel concentration of the air-fuel mixture in the combustion chamber leaner than the stoichiometric air-fuel ratio , and the operating state of the engine is in the first region. is in the second region where the load is high , the fuel concentration of the air-fuel mixture in the combustion chamber is set to the stoichiometric air-fuel ratio , and the control unit makes the fuel concentration of the air-fuel mixture in the combustion chamber leaner than the stoichiometric air-fuel ratio When it is determined that the measurement signal of the in-cylinder pressure sensor is highly reliable, the fuel amount may be corrected so as to suppress variations between the combustion chambers.

When the fuel concentration of the air-fuel mixture in the combustion chamber is leaner than the stoichiometric air-fuel ratio, the amount of fuel supplied to the combustion chamber and the torque of the engine have a linear or substantially linear relationship.

When the fuel concentration of the air-fuel mixture in the combustion chamber is leaner than the stoichiometric air-fuel ratio, the torque of the engine can be appropriately adjusted by increasing or decreasing the fuel amount.

As described above, according to the engine combustion control device, the reliability of the in-cylinder pressure sensor can be determined.

FIG. 1 is a diagram illustrating the configuration of an engine. FIG. 2 is a diagram illustrating the configuration of the combustion chamber, the upper diagram being a plan view equivalent of the combustion chamber, and the lower diagram being a sectional view taken along line II-II. FIG. 3 is a block diagram illustrating the configuration of an engine control device. FIG. 4 is a diagram illustrating waveforms of SPCCI combustion. FIG. 5 is a diagram illustrating a control map of the engine when it is warm. FIG. 6 is a flowchart illustrating basic engine control. FIG. 7 is a block diagram illustrating the configuration of an engine control device related to correction of the fuel injection amount. FIG. 8 is a diagram illustrating the relationship between mfb50 and Qend/Pmi. FIG. 9 is a block diagram illustrating a method of calculating the low heat generation amount Qin. FIG. 10 is a flowchart illustrating control related to inter-cylinder correction of the fuel injection amount.

An embodiment of an engine combustion control device will be described in detail below with reference to the drawings. The following description is an example of an engine and a combustion control system for the engine.

FIG. 1 is a diagram illustrating the configuration of a compression ignition engine system. FIG. 2 is a diagram illustrating the configuration of the combustion chamber of the engine. Note that the intake side in FIG. 1 is on the left side of the paper, and the exhaust side is on the right side of the paper. The intake side in FIG. 2 is on the right side of the paper, and the exhaust side is on the left side of the paper. FIG. 3 is a block diagram illustrating the configuration of an engine control device.

The engine 1 is a four-stroke engine that operates by repeating an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke in a combustion chamber 17 . The engine 1 is installed in a four-wheeled vehicle. The automobile runs as the engine 1 operates. The fuel of the engine 1 is gasoline in this configuration example. The fuel may be liquid fuel containing at least gasoline. The fuel may be gasoline, including, for example, bioethanol.

(Engine configuration)
The engine 1 has a cylinder block 12 and a cylinder head 13 mounted thereon. A plurality of cylinders 11 are formed inside the cylinder block 12 . 1 and 2 only one cylinder 11 is shown. The engine 1 is a multi-cylinder engine.

A piston 3 is slidably inserted in each cylinder 11 . Piston 3 is connected to crankshaft 15 via connecting rod 14 . Piston 3 defines combustion chamber 17 together with cylinder 11 and cylinder head 13 . Incidentally, the term "combustion chamber" may be used in a broad sense. In other words, the "combustion chamber" may mean the space formed by the piston 3, the cylinder 11 and the cylinder head 13 regardless of the position of the piston 3.

The lower surface of the cylinder head 13, that is, the ceiling surface of the combustion chamber 17 is composed of an inclined surface 1311 and an inclined surface 1312 as shown in the lower diagram of FIG. The inclined surface 1311 slopes upward from the intake side toward the injection axis X2 of the injector 6, which will be described later. The inclined surface 1312 slopes upward from the exhaust side toward the injection axis X2. The ceiling surface of the combustion chamber 17 has a so-called pent roof shape.

The upper surface of the piston 3 protrudes toward the ceiling surface of the combustion chamber 17 . A cavity 31 is formed in the upper surface of the piston 3 . A cavity 31 is recessed from the upper surface of the piston 3 . The cavity 31 has a shallow plate shape in this configuration example. The center of the cavity 31 is shifted from the center axis X1 of the cylinder 11 toward the exhaust side.

The geometric compression ratio of the engine 1 is set to 10 or more and 30 or less. As will be described later, the engine 1 performs SPCCI combustion, which is a combination of SI combustion and CI combustion, in some operating ranges. SPCCI combustion utilizes the heat generation and pressure increase due to SI combustion to control CI combustion. The engine 1 is a compression ignition engine. However, this engine 1 does not need to increase the temperature of the combustion chamber 17 when the piston 3 reaches the compression top dead center (that is, the compression end temperature). The engine 1 can have a relatively low geometric compression ratio. A lower geometric compression ratio favors lower cooling losses and lower mechanical losses. The geometric compression ratio of the engine 1 is 14 to 17 for regular specifications (low octane fuel with an octane number of about 91) and 15 for high octane specifications (high octane fuel with an octane number of about 96). ~18 may be used.

An intake port 18 is formed in the cylinder head 13 for each cylinder 11 . Although not shown, the intake port 18 has a first intake port and a second intake port. The intake port 18 communicates with the combustion chamber 17 . Although detailed illustration is omitted, the intake port 18 is a so-called tumble port. That is, the intake port 18 has a shape that forms a tumble flow in the combustion chamber 17 .

An intake valve 21 is arranged in the intake port 18 . The intake valve 21 opens and closes between the combustion chamber 17 and the intake port 18 . The intake valve 21 is opened and closed at a predetermined timing by a valve mechanism. The valve mechanism may be a variable valve mechanism that varies valve timing and/or valve lift. In this configuration example, the variable valve mechanism has an electric intake S-VT (Sequential-Valve Timing) 23, as shown in FIG. The electric intake S-VT 23 continuously changes the rotation phase of the intake camshaft within a predetermined angle range. The opening timing and closing timing of the intake valve 21 continuously change. The intake valve mechanism may have a hydraulic S-VT instead of the electric S-VT.

The cylinder head 13 is also formed with an exhaust port 19 for each cylinder 11 . The exhaust port 19 also has a first exhaust port and a second exhaust port. The exhaust port 19 communicates with the combustion chamber 17 .

An exhaust valve 22 is arranged in the exhaust port 19 . The exhaust valve 22 opens and closes between the combustion chamber 17 and the exhaust port 19 . The exhaust valve 22 is opened and closed at a predetermined timing by a valve mechanism. This valve mechanism may be a variable valve mechanism that varies valve timing and/or valve lift. In this configuration example, the variable valve mechanism has an electric exhaust S-VT 24, as shown in FIG. The electric exhaust S-VT 24 continuously changes the rotation phase of the exhaust camshaft within a predetermined angle range. The opening timing and closing timing of the exhaust valve 22 continuously change. The exhaust valve mechanism may have a hydraulic S-VT instead of the electric S-VT.

The electric intake S-VT 23 and the electric exhaust S-VT 24 adjust the length of the overlap period during which both the intake valve 21 and the exhaust valve 22 are open. By increasing the length of the overlap period, residual gases in the combustion chamber 17 can be scavenged. Also, internal EGR (Exhaust Gas Recirculation) gas can be introduced into the combustion chamber 17 by adjusting the length of the overlap period. The internal EGR system is composed of an electric intake S-VT 23 and an electric exhaust S-VT 24 . It should be noted that the internal EGR system is not necessarily composed of S-VT.

An injector 6 is attached to the cylinder head 13 for each cylinder 11 . Injector 6 injects fuel directly into combustion chamber 17 . The injector 6 is an example of a fuel injection section. The injector 6 is arranged in the valley of the pent roof where the inclined surfaces 1311 and 1312 intersect. As shown in FIG. 2, the injection axis X2 of the injector 6 is positioned closer to the exhaust side than the center axis X1 of the cylinder 11. As shown in FIG. The injection axis X2 of the injector 6 is parallel to the central axis X1. The injection axis X2 of the injector 6 and the center of the cavity 31 are aligned. The injector 6 faces the cavity 31 . Note that the injection axis X2 of the injector 6 may coincide with the central axis X1 of the cylinder 11 . In that configuration, the injection axis X2 of the injector 6 and the center of the cavity 31 may coincide.

Although detailed illustration is omitted, the injector 6 is configured by a multi-orifice fuel injection valve having a plurality of orifices. The injector 6 injects the fuel so that the fuel spray spreads radially from the center of the combustion chamber 17, as indicated by the two-dot chain line in FIG. In this configuration example, the injector 6 has ten injection holes, and the injection holes are arranged at equal angles in the circumferential direction.

A fuel supply system 61 is connected to the injector 6 . The fuel supply system 61 includes a fuel tank 63 configured to store fuel, and a fuel supply path 62 connecting the fuel tank 63 and the injector 6 to each other. A fuel pump 65 and a common rail 64 are interposed in the fuel supply path 62 . A fuel pump 65 pumps fuel to the common rail 64 . The fuel pump 65 is a plunger pump driven by the crankshaft 15 in this configuration example. The common rail 64 stores fuel pressure-fed from the fuel pump 65 at high fuel pressure. When the injector 6 opens, the fuel stored in the common rail 64 is injected into the combustion chamber 17 from the injection port of the injector 6 . The fuel supply system 61 is capable of supplying high pressure fuel of 30 MPa or higher to the injector 6 . The pressure of fuel supplied to the injector 6 may be changed according to the operating state of the engine 1 . Note that the configuration of the fuel supply system 61 is not limited to the configuration described above.

A spark plug 25 is attached to the cylinder head 13 for each cylinder 11 . A spark plug 25 forcibly ignites the air-fuel mixture in the combustion chamber 17 . The spark plug 25 is disposed on the intake side of the central axis X1 of the cylinder 11 in this configuration example. A spark plug 25 is positioned between the two intake ports 18 . The spark plug 25 is attached to the cylinder head 13 so as to be tilted from top to bottom toward the center of the combustion chamber 17 . The electrode of the spark plug 25 faces the inside of the combustion chamber 17 and is positioned near the ceiling surface of the combustion chamber 17, as shown in FIG. Note that the spark plug 25 may be arranged on the exhaust side of the central axis X1 of the cylinder 11 . Further, the spark plug 25 may be arranged on the center axis X1 of the cylinder 11. FIG.

An intake passage 40 is connected to one side surface of the engine 1 . The intake passage 40 communicates with the intake port 18 of each cylinder 11 . Gas introduced into the combustion chamber 17 flows through the intake passage 40 . An air cleaner 41 is arranged at the upstream end of the intake passage 40 . The air cleaner 41 filters fresh air. A surge tank 42 is arranged near the downstream end of the intake passage 40 . The intake passage 40 downstream of the surge tank 42 constitutes an independent passage that branches for each cylinder 11 . A downstream end of the independent passage is connected to the intake port 18 of each cylinder 11 .

A throttle valve 43 is arranged between the air cleaner 41 and the surge tank 42 in the intake passage 40 . The throttle valve 43 adjusts the amount of fresh air introduced into the combustion chamber 17 by adjusting the opening of the valve.

A supercharger 44 is also arranged in the intake passage 40 downstream of the throttle valve 43 . The supercharger 44 supercharges the gas introduced into the combustion chamber 17 . In this configuration example, the supercharger 44 is a mechanical supercharger driven by the engine 1 . The mechanical supercharger 44 may be of the Roots, Lysholm, vane, or centrifugal type.

An electromagnetic clutch 45 is interposed between the supercharger 44 and the engine 1 . Between the supercharger 44 and the engine 1 , the electromagnetic clutch 45 transmits driving force from the engine 1 to the supercharger 44 or cuts off transmission of the driving force. As will be described later, the ECU 10 switches between connection and disconnection of the electromagnetic clutch 45 to switch the supercharger 44 between on and off.

An intercooler 46 is arranged downstream of the supercharger 44 in the intake passage 40 . Intercooler 46 cools the gas compressed in supercharger 44 . The intercooler 46 may be configured to be water-cooled or oil-cooled, for example.

A bypass passage 47 is connected to the intake passage 40 . The bypass passage 47 connects the upstream portion of the supercharger 44 and the downstream portion of the intercooler 46 in the intake passage 40 so as to bypass the supercharger 44 and the intercooler 46 . An air bypass valve 48 is arranged in the bypass passage 47 . The air bypass valve 48 adjusts the flow rate of gas flowing through the bypass passage 47 .

The ECU 10 fully opens the air bypass valve 48 when the turbocharger 44 is turned off (that is, when the electromagnetic clutch 45 is disconnected). Gas flowing through the intake passage 40 bypasses the supercharger 44 and is introduced into the combustion chamber 17 of the engine 1 . The engine 1 operates in a non-supercharged state, that is, in a naturally aspirated state.

When the supercharger 44 is turned on, the engine 1 operates in a supercharged state. The ECU 10 adjusts the opening degree of the air bypass valve 48 when the supercharger 44 is turned on (that is, when the electromagnetic clutch 45 is connected). Part of the gas that has passed through the supercharger 44 flows back upstream of the supercharger 44 through the bypass passage 47 . When the ECU 10 adjusts the opening of the air bypass valve 48, the boost pressure of the gas introduced into the combustion chamber 17 changes. It should be noted that the term "supercharging" refers to the time when the pressure in the surge tank 42 exceeds the atmospheric pressure, and the term "non-supercharging" refers to the time when the pressure in the surge tank 42 falls below the atmospheric pressure. good too.

In this configuration example, a supercharging system 49 is configured by the supercharger 44 , the bypass passage 47 and the air bypass valve 48 .

The engine 1 has a swirl generator in the combustion chamber 17 that generates a swirl flow. The swirl flow flows as indicated by white arrows in FIG. The swirl generator has a swirl control valve 56 attached to the intake passage 40 . Although not shown in detail, the swirl control valve 56 is in the secondary passage of the primary passage leading to one of the two intake ports 18 and the secondary passage leading to the other intake port 18. are arranged. The swirl control valve 56 is an opening control valve capable of narrowing the cross section of the secondary passage. If the opening of the swirl control valve 56 is small, the amount of intake air entering the combustion chamber 17 from one intake port 18 is relatively large, and the amount of intake air entering the combustion chamber 17 from the other intake port 18 is relatively small. , the swirl flow in the combustion chamber 17 becomes stronger. When the opening of the swirl control valve 56 is large, the amount of intake air entering the combustion chamber 17 from each of the two intake ports 18 becomes substantially equal, so the swirl flow in the combustion chamber 17 becomes weak. When the swirl control valve 56 is fully opened, no swirl flow occurs.

An exhaust passage 50 is connected to the other side surface of the engine 1 . The exhaust passage 50 communicates with the exhaust port 19 of each cylinder 11 . The exhaust passage 50 is a passage through which the exhaust gas discharged from the combustion chamber 17 flows. An upstream portion of the exhaust passage 50 constitutes an independent passage that branches for each cylinder 11, although detailed illustration is omitted. The upstream end of the independent passage is connected to the exhaust port 19 of each cylinder 11 .

An exhaust gas purification system having a plurality of catalytic converters is arranged in the exhaust passage 50 . Although not shown, the upstream catalytic converter is arranged in the engine room. The upstream catalytic converter has a three-way catalyst 511 and a GPF (Gasoline Particulate Filter) 512 . A downstream catalytic converter is located outside the engine compartment. The downstream catalytic converter has a three-way catalyst 513 . It should be noted that the exhaust gas purification system is not limited to the configuration of the illustrated example. For example, GPF may be omitted. Also, the catalytic converter is not limited to having a three-way catalyst. Furthermore, the order in which the three-way catalyst and GPF are arranged may be changed as appropriate.

An EGR passage 52 that constitutes an external EGR system is connected between the intake passage 40 and the exhaust passage 50 . The EGR passage 52 is a passage for recirculating part of the exhaust gas to the intake passage 40 . The upstream end of the EGR passage 52 is connected between the upstream and downstream catalytic converters in the exhaust passage 50 . A downstream end of the EGR passage 52 is connected to an upstream portion of the supercharger 44 in the intake passage 40 . EGR gas flowing through the EGR passage 52 enters an upstream portion of the supercharger 44 in the intake passage 40 without passing through the air bypass valve 48 of the bypass passage 47 .

A water-cooled EGR cooler 53 is arranged in the EGR passage 52 . The EGR cooler 53 cools the exhaust gas. An EGR valve 54 is also arranged in the EGR passage 52 . The EGR valve 54 adjusts the flow rate of exhaust gas flowing through the EGR passage 52 . By adjusting the opening of the EGR valve 54, the recirculation amount of the cooled exhaust gas, that is, the external EGR gas can be adjusted.

In this configuration example, the EGR system 55 is composed of an external EGR system and an internal EGR system. The external EGR system can supply cooler exhaust gas to the combustion chamber 17 than the internal EGR system.

1 and 3, reference numeral 57 denotes an alternator 57 connected to the crankshaft 15. As shown in FIG. Alternator 57 is driven by engine 1 .

The engine combustion control device includes an ECU (Engine Control Unit) 10 for operating the engine 1 . The ECU 10 is a well-known microcomputer-based controller, and as shown in FIG. (Read Only Memory) for storing programs and data, and an input/output bus 103 for inputting/outputting electric signals. The ECU 10 is an example of a control section.

Various sensors SW1 to SW17 are connected to the ECU 10 as shown in FIGS. The sensors SW1 to SW17 output signals to the ECU 10. FIG. The sensors include the following sensors.

Airflow sensor SW1: arranged downstream of the air cleaner 41 in the intake passage 40, and measures the flow rate of fresh air flowing through the intake passage 40. First intake air temperature sensor SW2: arranged downstream of the air cleaner 41 in the intake passage 40, and , to measure the temperature of fresh air flowing through the intake passage 40. First pressure sensor SW3: arranged downstream of the connecting position of the EGR passage 52 in the intake passage 40 and upstream of the supercharger 44, and Second intake air temperature sensor SW4: arranged downstream of the turbocharger 44 in the intake passage 40 and upstream of the connecting position of the bypass passage 47, and flows out of the turbocharger 44 2nd pressure sensor SW5 for measuring the temperature of the gas: attached to the surge tank 42 and for measuring the pressure of the gas downstream of the supercharger 44. The finger pressure sensor SW6: attached to the cylinder head 13 corresponding to each cylinder 11. and measures the pressure in each combustion chamber 17. Exhaust temperature sensor SW7: arranged in the exhaust passage 50 and measures the temperature of the exhaust gas discharged from the combustion chamber 17. Linear _O2 sensor SW8: an upstream sensor in the exhaust passage 50. Located upstream of the catalytic converter and measures the oxygen concentration in the exhaust gas Lambda _O2 sensor SW9: Located downstream of the three-way catalyst 511 in the upstream catalytic converter and measures the oxygen concentration in the exhaust gas Water temperature sensor SW10: Attached to the engine 1 to measure the temperature of cooling water Crank angle sensor SW11: Attached to the engine 1 to measure the rotation angle of the crankshaft 15 Accelerator position sensor SW12: Attached to the accelerator pedal mechanism and measures the accelerator opening corresponding to the operation amount of the accelerator pedal. Also measures the rotation angle of the exhaust camshaft EGR differential pressure sensor SW15: arranged in the EGR passage 52 and measures the differential pressure upstream and downstream of the EGR valve 54 Fuel pressure sensor SW16: connected to the common rail 64 of the fuel supply system 61 Third intake air temperature sensor SW17 attached to the surge tank 42 for measuring the pressure of the fuel supplied to the injector 6: The temperature of the gas in the surge tank 42, in other words, the temperature of the intake air introduced into the combustion chamber 17 Measure the temperature.

The ECU 10 determines the operating state of the engine 1 based on the signals from these sensors SW1 to SW17, and calculates control amounts for each device according to predetermined control logic. The control logic is stored in memory 102 . The control logic includes using maps stored in memory 102 to compute target and/or control variables.

The ECU 100 transmits electric signals related to the calculated control amount to the injector 6, the spark plug 25, the electric intake S-VT 23, the electric exhaust S-VT 24, the fuel supply system 61, the throttle valve 43, the EGR valve 54, the supercharger 44. , the electromagnetic clutch 45 , the air bypass valve 48 , the swirl control valve 56 and the alternator 57 .

For example, the ECU 10 sets the target torque of the engine 1 and determines the target supercharging pressure based on the signal from the accelerator opening sensor SW12 and the map. Then, the ECU 10 adjusts the opening degree of the air bypass valve 48 based on the target supercharging pressure and the differential pressure across the supercharger 44 obtained from the signals of the first pressure sensor SW3 and the second pressure sensor SW5. By performing feedback control, the supercharging pressure is brought to the target supercharging pressure.

Further, the ECU 10 sets a target EGR rate (that is, the ratio of EGR gas to all gas in the combustion chamber 17) based on the operating state of the engine 1 and the map. Then, the ECU 10 determines the target EGR gas amount based on the target EGR rate and the intake air amount based on the signal of the accelerator opening sensor SW12, and the differential pressure across the EGR valve 54 obtained from the signal of the EGR differential pressure sensor SW15. By performing feedback control for adjusting the opening degree of the EGR valve 54 based on , the amount of external EGR gas introduced into the combustion chamber 17 is made to match the target EGR gas amount.

Furthermore, the ECU 10 executes air-fuel ratio feedback control when a predetermined control condition is satisfied. Specifically, the ECU 10 controls the fuel injection of the injector 6 so that the air-fuel ratio of the air-fuel mixture becomes a desired value based on the oxygen concentration in the exhaust gas measured by the linear _O2 sensor SW8 and the lambda _O2 sensor SW9. Adjust quantity.

Other details of the control of the engine 1 by the ECU 10 will be described later.

(SPCCI combustion concept)
The main purpose of the engine 1 is to improve fuel efficiency and exhaust gas performance. In the self-ignition combustion, if the temperature in the combustion chamber 17 before the start of compression varies, the self-ignition timing changes greatly. Therefore, the engine 1 performs SPCCI combustion, which is a combination of SI combustion and CI combustion.

In the SPCCI combustion, the ignition plug 25 forcibly ignites the air-fuel mixture in the combustion chamber 17, and the air-fuel mixture undergoes SI combustion due to flame propagation, and the heat generated by the SI combustion causes the combustion in the combustion chamber 17. When the temperature rises and the pressure in the combustion chamber 17 rises due to flame propagation, the unburned air-fuel mixture undergoes self-ignition for CI combustion.

By adjusting the calorific value of SI combustion, it is possible to absorb temperature variations in the combustion chamber 17 before the start of compression. By adjusting the ignition timing by the ECU 10, the air-fuel mixture can be self-ignited at the target timing.

In SPCCI combustion, the heat release during SI combustion is milder than that during CI combustion. As illustrated in FIG. 4, the waveform of the heat release rate in SPCCI combustion has a rising slope smaller than that in the waveform of CI combustion. Further, the pressure fluctuation (dp/dθ) in the combustion chamber 17 is also gentler during SI combustion than during CI combustion.

When the unburned air-fuel mixture self-ignites after the start of SI combustion, the slope of the heat release rate waveform may change from small to large at the timing of self-ignition. The heat release rate waveform may have an inflection point X at the timing θci at which CI combustion starts.

After the start of CI combustion, SI combustion and CI combustion are performed in parallel. Since CI combustion generates more heat than SI combustion, the heat release rate is relatively high. However, since the CI combustion is performed after the top dead center of the compression stroke, the slope of the heat release rate waveform is prevented from becoming too large. The pressure fluctuation (dp/dθ) during CI combustion also becomes relatively mild.

Pressure fluctuation (dp/dθ) can be used as an index representing combustion noise. As described above, SPCCI combustion can reduce the pressure fluctuation (dp/dθ), so it is possible to avoid excessive combustion noise. Combustion noise of the engine 1 is suppressed below the permissible level.

The SPCCI combustion ends when the CI combustion ends. CI combustion has a shorter combustion period than SI combustion. The SPCCI combustion has an earlier combustion end timing than the SI combustion.

The heat release rate waveform of SPCCI combustion is formed such that the first heat release rate portion QSI formed by _SI combustion and the second heat release portion QCI formed by _CI combustion are continuous in this order. It is

Here, the SI rate is defined as a parameter that indicates the characteristics of SPCCI combustion. The SI rate is defined as an index related to the ratio of the amount of heat generated by SI combustion to the total amount of heat generated by SPCCI combustion. The SI rate is the heat quantity ratio generated by two combustions with different combustion modes. A high SI rate results in a high proportion of SI combustion, and a low SI rate results in a high proportion of CI combustion. The SI rate may be defined as the ratio of the amount of heat generated by SI combustion to the amount of heat generated by CI combustion. That is, in _SPCCI combustion, the crank angle at which CI combustion starts is defined as the CI combustion start timing θci, and in the waveform 801 shown in FIG. From the area Q _CI of the CI combustion on the side, the SI rate may be set to Q _SI /Q _CI .

(engine operating range)
FIG. 5 exemplifies a map related to control of the engine 1. As shown in FIG. The map is stored in the memory 102 of the ECU 10. FIG. A map 504 illustrated in FIG. 5 is a map when the engine 1 is warm.

The map 504 is defined by the load and speed of the engine 1 . The map 504 is roughly divided into three regions, depending on whether the load is high or low and whether the rotation speed is high or low. Specifically, the three regions are a low load region A1 that includes idling and spreads over low and medium speed regions, medium and high load regions A2, A3 and A4 in which the load is higher than the low load region A1, and a low load region A1. This is a high rotation area A5 in which the rotation speed is higher than the load area A1 and the medium and high load areas A2, A3, and A4. The middle and high load regions A2, A3, and A4 are also divided into a middle load region A2, a high load middle rotation region A3 in which the load is higher than that in the middle load region A2, and a high load low rotation region A3 in which the rotation speed is lower than that in the high load middle rotation region A3. It is divided into area A4.

Here, the low speed region, the middle speed region, and the high speed region are obtained by dividing the entire operating region of the engine 1 in the rotational speed direction into approximately three equal parts: the low speed region, the middle speed region, and the high speed region. , a low rotation area, a middle rotation area, and a high rotation area. In the example of FIG. 5, a rotation speed of less than N1 is low rotation, a rotation speed of N2 or more is high rotation, and a rotation speed of N1 or more and less than N2 is middle rotation. The rotation speed N1 may be, for example, about 1200 rpm, and the rotation speed N2 may be, for example, about 4000 rpm.

Also, the low load range may be a range including a light load operating state, the high load range may be a range including a fully open load operating state, and the medium load may be a range between the low load range and the high load range. In addition, the low load range, the medium load range, and the high load range each divide the entire operating range of the engine 1 in the load direction into approximately three equal parts: the low load range, the medium load range, and the high load range. A low load range, a medium load range, and a high load range may also be used.

A map 504 in FIG. 5 indicates the state of the air-fuel mixture and the combustion mode in each region. The map 504 of FIG. 7 also indicates the driven and non-driven regions of the supercharger 44 . The engine 1 performs SPCCI combustion in a low load range A1, a medium load range A2, a high load medium speed range A3, and a high load low speed range A4. The engine 1 also performs SI combustion in other regions, specifically in the high revolution region A5.

(Engine operation in each area)
Operation of the engine 1 in each area of the map 504 of FIG. 5 will be described in detail below.

(Low load area)
When the engine 1 is operating in the low load region A1, the engine 1 performs SPCCI combustion.

The EGR system 55 introduces EGR gas into the combustion chamber 17 in order to improve fuel efficiency of the engine 1 . Specifically, the electric intake S-VT 23 and the electric exhaust S-VT 24 provide a positive overlap period in which both the intake valve 21 and the exhaust valve 22 are opened near exhaust top dead center.

Also, the swirl generator forms a strong swirl flow in the combustion chamber 17 . The swirl control valve 56 is fully closed or has a predetermined degree of opening on the closing side. When a strong swirl flow is generated in the combustion chamber 17, the swirl flow is strong in the outer peripheral portion of the combustion chamber 17, while the swirl flow in the central portion is relatively weak. The injector 6 injects fuel into the combustion chamber 17 in which a strong swirl flow is formed, so that the air-fuel mixture in the central portion of the combustion chamber 17 is relatively rich in fuel, and the air-fuel mixture in the outer peripheral portion is relatively fuel-rich. Leaning, the mixture can be stratified.

The injector 6 injects fuel into the combustion chamber 17 multiple times during the intake stroke. The multiple fuel injections and the swirl flow in the combustion chamber 17 stratify the air-fuel mixture.

The air-fuel ratio (A/F) of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio throughout the combustion chamber 17 (that is, excess air ratio λ>1). More specifically, the A/F of the air-fuel mixture in the entire combustion chamber 17 is 25 or more and 31 or less. By doing so, the generation of RawNOx can be suppressed, and the exhaust gas performance can be improved.

After the end of fuel injection, the ignition plug 25 ignites the air-fuel mixture in the central portion of the combustion chamber 17 at a predetermined timing before the compression top dead center. The ignition timing may be the end of the compression stroke. The final stage of the compression stroke may be the final stage when the compression stroke is divided into three equal parts, the initial stage, the middle stage, and the final stage.

(medium and high load area)
Even when the engine 1 is operating in the middle and high load ranges A2 to A4, the engine 1 performs SPCCI combustion as in the low load range A1.

EGR system 55 introduces EGR gases into combustion chamber 17 . Specifically, the electric intake S-VT 23 and the electric exhaust S-VT 24 provide a positive overlap period in which both the intake valve 21 and the exhaust valve 22 are opened near exhaust top dead center. Internal EGR gases are introduced into the combustion chamber 17 . Also, the EGR system 55 introduces the exhaust gas cooled by the EGR cooler 53 into the combustion chamber 17 through the EGR passage 52 . That is, the external EGR gas having a lower temperature than the internal EGR gas is introduced into the combustion chamber 17 . External EGR gas regulates the temperature in combustion chamber 17 to a suitable temperature. The EGR system 55 reduces the amount of EGR gas as the load on the engine 1 increases. The EGR system 55 may null EGR gases, including internal EGR gases and external EGR gases, at full load.

The air-fuel ratio (A/F) of the air-fuel mixture in the entire combustion chamber 17 is the stoichiometric air-fuel ratio (A/F≈14.7). By purifying the exhaust gas discharged from the combustion chamber 17 by the three-way catalysts 511 and 513, the exhaust gas performance of the engine 1 is improved. The A/F of the air-fuel mixture should be kept within the purification window of the three-way catalyst. The excess air ratio λ of the mixture may be 1.0±0.2. When the engine 1 is operating in the high-load medium-speed region A3 including full load (that is, maximum load), the A/F of the air-fuel mixture is the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio in the entire combustion chamber 17. It may be made richer than the air-fuel ratio (that is, the excess air ratio λ of the air-fuel mixture is λ≦1).

Since the EGR gas is introduced into the combustion chamber 17, G/F, which is the weight ratio of the total gas and fuel in the combustion chamber 17, becomes leaner than the stoichiometric air-fuel ratio. The G/F of the air-fuel mixture may be 18 or more. By doing so, it is possible to avoid the occurrence of so-called knocking. G/F may be set at 18 or more and 30 or less. Also, G/F may be set at 18 or more and 50 or less.

When the load of the engine 1 is medium load, the injector 6 performs fuel injection multiple times during the intake stroke. The injector 6 may perform the first injection in the first half of the intake stroke and the second injection in the second half of the intake stroke.

Further, when the load of the engine 1 is high, the injector 6 injects fuel during the intake stroke.

The spark plug 25 ignites the air-fuel mixture at a predetermined timing near the compression top dead center after the fuel is injected. When the load of the engine 1 is medium load, the spark plug 25 may ignite before the compression top dead center. When the load of the engine 1 is high, the spark plug 25 may ignite after the compression top dead center.

(Operation of supercharger)
Here, as shown in the map 504 of FIG. 5, the supercharger 44 is off (see S/C OFF) in a portion of the low load region A1 and a portion of the middle and high load region A2. Specifically, the supercharger 44 is off in the low-rotation-side region of the low-load region A1. In the low-load region A1 on the high rotation side, the supercharger 44 is turned on in order to ensure the necessary intake charge amount in response to the increase in the rotation speed of the engine 1 . In addition, the supercharger 44 is off in a part of the low-load, low-rotation side of the middle-to-high load range A2. In the high load region of the medium and high load region A2, the supercharger 44 is turned on in order to secure the required intake charge amount in response to the increase in the fuel injection amount. In addition, the supercharger 44 is also on in the high-rotation-side region in the middle-high load region A2.

Note that the supercharger 44 is on throughout the high load medium speed region A3, the high load low speed region A4, and the high speed speed region A5 (see S/C ON).

(high rotation area)
When the rotation speed of the engine 1 is high, the time required for the crank angle to change by 1° is shortened. It becomes difficult to stratify the air-fuel mixture in the combustion chamber 17 . When the rotation speed of the engine 1 increases, it becomes difficult to perform SPCCI combustion.

Therefore, when the engine 1 is operating in the high speed region A5, the engine 1 performs SI combustion instead of SPCCI combustion. Note that the high rotation region A5 extends over the entire load direction from low load to high load.

EGR system 55 introduces EGR gases into combustion chamber 17 . EGR system 55 reduces the amount of EGR gas as the load increases. The EGR system 55 may zero EGR gas at full load.

Swirl control valve 56 is fully open. A swirl flow is not generated in the combustion chamber 17, and only a tumble flow is generated. By fully opening the swirl control valve 56, it is possible to improve charging efficiency and reduce pump loss.

The air-fuel ratio (A/F) of the air-fuel mixture is basically the stoichiometric air-fuel ratio (A/F≈14.7) in the entire combustion chamber 17 . The excess air ratio λ of the air-fuel mixture may be set to 1.0±0.2. The excess air ratio λ of the air-fuel mixture may be less than 1 when the engine 1 is operating near a fully open load.

The injector 6 starts fuel injection during the intake stroke. The injector 6 injects fuel all at once. A homogeneous or substantially homogeneous mixture is formed in the combustion chamber 17 by initiating fuel injection during the intake stroke. In addition, since it is possible to secure a long vaporization time of the fuel, it is possible to reduce the unburned loss.

The spark plug 25 ignites the air-fuel mixture at an appropriate timing after the end of fuel injection and before the compression top dead center.

(Engine basic control)
FIG. 6 shows a flow of basic control of the engine 1 executed by the ECU 10. As shown in FIG. The ECU 10 operates the engine 1 according to control logic stored in the memory 102 . Specifically, the ECU 10 determines the operating state of the engine 1 based on the signals from the sensors SW1 to SW17, sets a target torque, and adjusts the torque in the combustion chamber 17 so that the engine 1 outputs the target torque. Calculations for adjusting the state quantity, adjusting the injection amount, adjusting the injection timing, and adjusting the ignition timing are performed.

When performing SPCCI combustion, the ECU 10 also controls the SPCCI combustion using two parameters, the SI rate and θci. Specifically, the ECU 10 determines a target SI rate and a target θci corresponding to the operating state of the engine 1, and controls the combustion chamber 17 so that the actual SI rate matches the target SI rate and the actual θci becomes the target θci. It adjusts the internal temperature and adjusts the ignition timing. The ECU 10 sets the target SI rate low when the load on the engine 1 is low, and sets the target SI rate high when the load on the engine 1 is high. When the load of the engine 1 is low, by increasing the proportion of CI combustion in SPCCI combustion, both suppression of combustion noise and improvement of fuel efficiency can be achieved. When the load of the engine 1 is high, increasing the proportion of SI combustion in SPCCI combustion is advantageous for suppressing combustion noise.

In step S121 of the flow of FIG. 6, the ECU 10 reads signals from the sensors SW1 to SW17, and in subsequent step S122, the ECU 10 sets the target acceleration based on the accelerator opening. In step S123, the ECU 10 sets a target torque required to achieve the set target acceleration.

In step S124, the ECU 10 determines the operating state of the engine 1, and determines whether the air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio (that is, the excess air ratio λ=1). . If λ=1, the process proceeds to step S125, and if λ≠1, the process proceeds to step S129.

Steps S125 to S128 set control target values for each device when the engine 1 is operated in the middle load region A2, the high load middle speed region A3, the high load low speed region A4, and the high speed region A5. corresponds to the step of In step S125, the ECU 10 sets the target ignition timing of the spark plug 25 based on the set target torque. In subsequent step S126, the ECU 10 sets a target air amount to fill the combustion chamber 17 based on the set target torque. In step S127, the ECU 10 sets the target injection amount of fuel based on the set target air amount so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio or approximately the stoichiometric air-fuel ratio. Then, in step S128, the ECU 10 sets the target throttle opening of the throttle valve 43, the target SCV opening of the swirl control valve 56, the target EGR valve opening of the EGR valve 54, and the intake air amount based on the set target air amount. A target S-VT phase of the electric S-VT 23 and a target S-VT phase of the exhaust electric S-VT 24 are set.

Steps S129 to S1212 correspond to steps for setting control target values for each device when the engine 1 operates in the low load region A1. In step S129, the ECU 10 sets the target ignition timing of the spark plug 25 based on the set target torque. In subsequent step S1210, the ECU 10 sets the target injection amount of fuel based on the set target torque. In step S1211, the ECU 10 sets the target air amount to fill the combustion chamber 17 based on the set target injection amount so that the air-fuel ratio of the air-fuel mixture becomes a predetermined lean air-fuel ratio. The air-fuel ratio of the air-fuel mixture is between 25 and 31 as described above. Then, in step S1212, the ECU 10 sets the target throttle opening of the throttle valve 43, the target SCV opening of the swirl control valve 56, the target EGR valve opening of the EGR valve 54, and the intake air amount based on the set target air amount. A target S-VT phase of the electric S-VT 23 and a target S-VT phase of the exhaust electric S-VT 24 are set.

In step S1213, the ECU 10 adjusts the throttle opening of the throttle valve 43, the SCV opening of the swirl control valve 56, the EGR valve opening of the EGR valve 54, and the intake The S-VT phase of the electric S-VT 23 and the S-VT phase of the exhaust electric S-VT 24 are adjusted.

In step S1214, the ECU 10 causes the injector 6 to inject fuel at a predetermined timing according to the set target injection amount, and in subsequent step S1215, the ECU 10 causes the ignition plug 25 to perform ignition at the set target ignition timing.

(Cylinder-to-cylinder correction of fuel injection amount)
This engine system is configured to correct variations in the amount of fuel injection between cylinders based on the measurement signal of the in-cylinder pressure sensor SW6 when the engine 1 is operating in the low load region A1. When the engine 1 is operating in the low load region A1, the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. When the fuel concentration of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio, the amount of fuel supplied to the combustion chamber 17 and the torque of the engine 1 have a linear or substantially linear relationship. Variation in the torque of the engine 1 is suppressed by increasing or decreasing the amount of fuel for each cylinder.

FIG. 7 shows the configuration of functional blocks of the ECU 10. As shown in FIG. The functional blocks shown in FIG. 7 are mainly related to control for correcting variations in fuel injection amount between cylinders. The functional blocks include a combustion pressure (Pmi) calculator 10a, a lower calorific value (Qend) calculator 10b, an mfb50 (mass fraction burned) calculator 10c, a reliability determination unit 10d, a fuel injection amount setting unit 10e, and a lower calorific value ( Qin) includes an estimator 10f and a fuel injection amount corrector 10g.

The combustion pressure (Pmi) calculation unit 10a calculates the combustion pressure Pmi associated with the combustion of the air-fuel mixture based on the measurement signal of the in-cylinder pressure sensor SW6. The combustion pressure Pmi is calculated from the indicated mean effective pressure calculated based on the measurement signal of the in-cylinder pressure sensor SW6.

A lower heating value (Qend) calculator 10b calculates a lower heating value Qend based on the measurement signal of the in-cylinder pressure sensor SW6. The lower heating value Qend is calculated from the maximum value of heat generation (the sum of the internal energy dU and the work dW used to move the piston 3) calculated based on the measurement signal of the in-cylinder pressure sensor SW6.

The mfb50 calculator 10c calculates the crank angle at which the mass combustion ratio is 50%, based on the measurement signal of the in-cylinder pressure sensor SW6. mfb50 is calculated based on the combustion waveform based on the measurement signal of the in-cylinder pressure sensor SW6.

The reliability determination unit 10d calculates the combustion pressure Pmi calculated by the combustion pressure (Pmi) calculation unit 10a, the lower heating value Qend calculated by the lower heating value (Qend) calculation unit 10b, and the mfb50 calculated by the mfb50 calculation unit 10c. Based on this, the reliability of the measurement signal of the in-cylinder pressure sensor SW6 is determined. According to studies by the inventors of the present application, when the air-fuel mixture is burning normally in the combustion chamber 17, the ratio (Qend/Pmi) between the lower heating value Qend and the combustion pressure Pmi and mfb50 has a relationship exemplified by the solid line in FIG. Qend/Pmi is related to the torque of the engine 1, and the relationship shown in FIG. 8 means that the torque of the engine 1 decreases when mfb50 is retarded.

When the air-fuel mixture is burning abnormally in the combustion chamber 17, for example, when a misfire or pre-ignition occurs, the relationship between the ratio (Qend/Pmi) of the lower heating value Qend and the combustion pressure Pmi and mfb50 deviates greatly from the solid line in FIG.

The reliability determination unit 10d calculates the combustion pressure Pmi calculated by the combustion pressure (Pmi) calculation unit 10a, the lower heating value Qend calculated by the lower heating value (Qend) calculation unit 10b, and the mfb50 calculated by the mfb50 calculation unit 10c. Based on whether or not the relationship between the ratio (Qend/Pmi) of the lower heating value Qend and the combustion pressure Pmi and mfb50 has a relationship corresponding to the solid line in FIG. Whether or not the measurement signal of SW6 is reliable is determined. Specifically, the reliability determination unit 10d determines that the relationship between the ratio (Qend/Pmi) of the lower heating value Qend and the combustion pressure Pmi and mfb50 is within the reference range between the two dashed lines in FIG. In some cases, it is determined that the air-fuel mixture is normally combusted in the combustion chamber 17 and the measurement signal of the in-cylinder pressure sensor SW6 is highly reliable. On the other hand, if the relationship between the ratio (Qend/Pmi) of the lower heating value Qend and the combustion pressure Pmi and mfb50 is out of the reference range between the two dashed lines in FIG. It is determined that the air-fuel mixture is burning abnormally in the combustion chamber 17 and the measurement signal of the in-cylinder pressure sensor SW6 is unreliable.

The reliability determination unit 10d outputs a signal regarding the reliability of the measurement signal of the in-cylinder pressure sensor SW6 to the fuel injection amount correction unit 10g.

The fuel injection amount setting unit 10e sets the fuel injection amount based on the signals from the sensors SW1 to SW17, as described above. The fuel injection amount setting unit 10e outputs a signal regarding the set fuel injection amount to the fuel injection amount correction unit 10g.

A lower heating value (Qin) estimator 10f estimates the lower heating value (Qin) based on the measurement signal of the in-cylinder pressure sensor SW6. FIG. 9 is a block diagram illustrating the configuration of the lower heating value (Qin) estimator 10f. The lower calorific value (Qin) is the calorific value relative to the amount of fuel supplied into the combustion chamber 17 . A lower heating value (Qin) estimator 10f calculates the ratio of the thermal efficiency of the engine 1 calculated based on a map stored in advance in the ECU 10 to the combustion pressure based on the measurement signal of the in-cylinder pressure sensor SW6, and The lower heating value (Qin) is calculated from the volume. The lower heating value (Qin) estimation unit 10f outputs a signal regarding the calculated lower heating value (Qin) to the fuel injection amount correction unit 10g.

The fuel injection amount correction unit 10g corrects the fuel injection amount for each cylinder set by the fuel injection amount setting unit 10e based on the lower heating value (Qin) from the lower heating value (Qin) estimation unit 10f. Specifically, when the estimated lower heating value (Qin) is small, the fuel injection amount correction unit 10g increases the fuel injection amount so as to increase the heating value. Further, when the estimated lower heating value (Qin) is large, the fuel injection amount correcting unit 10g corrects the fuel injection amount to reduce the heating value. The injector 6 of each cylinder 11 injects fuel according to the fuel injection amount corrected by the fuel injection amount correction unit 10g. As a result, torque variation between cylinders can be suppressed. Engine 1 runs properly.

The fuel injection amount correction unit 10g also does not correct the fuel injection amount described above based on the reliability signal from the reliability determination unit 10d when the reliability of the measurement signal of the in-cylinder pressure sensor SW6 is low. . Control for suppressing variation in fuel injection amount between cylinders is control for suppressing variation in torque generated by combustion in each cylinder 11 on the premise that normal combustion is occurring in the combustion chamber 17 . The measurement signal of the in-cylinder pressure sensor SW6 that is output when abnormal combustion is occurring in the combustion chamber 17 cannot be used for control for suppressing variations in the amount of fuel injection between cylinders.

When the reliability of the measurement signal of the in-cylinder pressure sensor SW6 is low, the fuel injection amount correction unit 10g does not correct the fuel injection amount as described above. .

(Procedure for inter-cylinder correction of fuel injection amount)
FIG. 10 is a flow chart showing the procedure for inter-cylinder correction of the fuel injection amount, which is executed by the abnormality diagnosis device 100 . In step S1 after the start, the abnormality diagnosis device 100 reads detection signals from the sensors SW1 to SW17. In subsequent step S2, the combustion pressure (Pmi) calculation unit 10a calculates the combustion pressure Pmi, the lower heating value (Qend) calculation unit 10b calculates the lower heating value Qend, and the mfb50 calculation unit 10c calculates mfb50. do.

In step S3, the abnormality diagnosis device 100 determines whether or not the air-fuel ratio of the air-fuel mixture is λ≠1. If the engine 1 is operating in the low load region A1, the result in step S3 is YES, so the process proceeds to step S4. If the engine 1 is operating in a region other than the low load region A1, the process returns because step S3 is NO.

In step S4, the reliability determination unit 10d determines whether Qend/Pmi is within the reference range based on Qend/Pmi and mfb50. If Qend/Pmi is within the reference range, the process proceeds to step S5, and if Qend/Pmi is not within the reference range, the process proceeds to step S7.

In step S5, the reliability determination unit 10d determines that the measurement signal of the in-cylinder pressure sensor SW6 is reliable. In subsequent step S6, the fuel injection amount correction unit 10g corrects the fuel injection amount for each cylinder 11 based on the lower heating value (Qin) estimated by the lower heating value (Qin) estimation unit 10gf.

On the other hand, in step S7, the reliability determination unit 10d determines that the measurement signal of the in-cylinder pressure sensor SW6 is unreliable. In subsequent step S8, the fuel injection amount correction unit 10g does not correct the fuel injection amount based on the lower heating value (Qin) estimated by the lower heating value (Qin) estimation unit 10gf.

(Other embodiments)
Note that the technology disclosed herein is not limited to application to the engine 1 having the configuration described above. Various configurations can be adopted for the configuration of the engine 1 .

1 engine 10 ECU (control unit)
17 combustion chamber 6 injector (fuel injection part)
SW6 In-cylinder pressure sensor

Claims (2)

a plurality of fuel injection units for individually injecting fuel into each of a plurality of combustion chambers of an engine mounted on an automobile;
a plurality of in-cylinder pressure sensors that output measurement signals corresponding to pressure changes in the plurality of combustion chambers;
Based on at least a measurement signal of the in-cylinder pressure sensor, a control signal related to the amount of fuel injected by the fuel injection unit is output to each of the plurality of fuel injection units, and variation in the amount of fuel injected between combustion chambers is detected. A control unit that corrects the amount of fuel injected by each of the plurality of fuel injection units so that is suppressed,
The control unit outputs a control signal to each of the plurality of fuel injection units so that the fuel concentration of the air-fuel mixture in the combustion chamber becomes leaner than the stoichiometric air-fuel ratio,
Based on the measurement signal of the in-cylinder pressure sensor, the control unit controls the combustion pressure (Pmi) in the combustion chamber, the crank angle position (mfb50) at which the mass combustion ratio becomes a predetermined ratio, and the lower heating value (Qend). , and
Between the ratio (Qend/Pmi) of the lower heating value (Qend) and the combustion pressure (Pmi) and the crank angle position (mfb50) at which the mass combustion ratio is 50%, the It is a specific relationship corresponding to the fact that the air-fuel mixture is burning normally in the combustion chamber and torque corresponding to the amount of fuel supplied to the combustion chamber is generated . When a specific relationship in which Pmi is large is established, it is determined that the reliability of the measurement signal of the in-cylinder pressure sensor is high, the air-fuel mixture is burning abnormally, and the amount of fuel supplied to the combustion chamber is reduced. determining that the reliability of the measurement signal of the in-cylinder pressure sensor is low when the specific relationship is not established without generating a matching torque ;
The control unit corrects the fuel amount when determining that the reliability of the measurement signal of the in-cylinder pressure sensor is high, and corrects the fuel amount when determining that the reliability of the measurement signal of the in-cylinder pressure sensor is low. is an engine combustion control device for limiting correction of the fuel amount; In the engine combustion control device according to claim 1 ,
When the operating state of the engine is in the first region, the control unit makes the fuel concentration of the air-fuel mixture in the combustion chamber leaner than the stoichiometric air-fuel ratio , and the operating state of the engine is in the first region. when the load is in the second region where the load is high, the fuel concentration of the air-fuel mixture in the combustion chamber is set to the stoichiometric air-fuel ratio,
When the control unit determines that the fuel concentration of the air-fuel mixture in the combustion chamber is leaner than the stoichiometric air-fuel ratio and the reliability of the measurement signal of the in-cylinder pressure sensor is high, the combustion chamber A combustion control device for an engine that corrects the fuel amount so as to suppress variations in fuel consumption.

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