JP7298465B2 - engine controller - Google Patents

Description

The technology disclosed herein relates to an engine control device.

Patent Literature 1 describes an engine control device that performs knocking avoidance control. The controller establishes a first control set defining a first fuel injection timing and a first ignition timing and a second control set defining a second fuel injection timing and a second ignition timing. A first control set is fuel injection timing and ignition timing adapted for high octane fuel, and a second control set is fuel injection timing and ignition timing adapted for low octane fuel. When the knocking sensor detects the occurrence of knocking, the control device described in Patent Document 1 presumes that low-octane fuel is being used, and performs fuel injection and ignition using the second control set. As a result, the control device described in Patent Document 1 avoids the occurrence of knocking.

U.S. Pat. No. 6,200,000 describes an engine that utilizes alcohol-containing fuel. This engine has a fuel property sensor in a fuel passage from the fuel tank to the combustion chamber. The fuel property sensor detects properties of fuel. The engine corrects the air-fuel ratio of the air-fuel mixture according to the properties of the fuel detected by the sensor.

The engine described in Patent Document 2 is also controlled based on the properties of the fuel before refueling until the remaining fuel in the fuel passage is consumed after the fuel tank is refueled. After consumption, control is performed based on the fuel property newly detected by the fuel property sensor. As a result, the engine described in Patent Document 2 can be optimally controlled according to the properties of the fuel actually supplied to the combustion chamber.

JP 2014-105662 A Japanese Patent Application Laid-Open No. 2007-303446

In an engine that can use both high octane fuel and low octane fuel, the octane value of the fuel used may change before and after filling the fuel tank. Specifically, when a high octane fuel was used in the previous refueling, but a low octane fuel was used in the current refueling, or when a low octane fuel was used in the previous refueling, but a high octane fuel was used in the current refueling. , the octane number of the fuel used changes before and after refueling.

As described in Patent Literature 1 and Patent Literature 2, when engine control is changed according to fuel properties, it is important to quickly grasp that the octane number of fuel has changed in order to operate the engine optimally. is preferred.

The technology disclosed herein quickly grasps the octane number of the fuel after refueling.

The technology disclosed herein relates to an engine control device. The controller of this engine is
an engine having cylinders forming a combustion chamber;
a fuel supply unit for supplying fuel in a fuel tank into the combustion chamber;
an igniter attached to the engine and igniting an air-fuel mixture in the combustion chamber;
a measurement unit that outputs measurement signals of parameters related to the engine;
a control unit that stores the octane number of the fuel and outputs a control signal corresponding to the stored octane number to the fuel supply unit and the ignition unit;
The control unit sequentially estimates the octane number based on the measurement signal , performs filtering on the estimated octane number using a first-order lag filter to sequentially update the octane number , stores the updated octane number ,
When the fuel tank is refueled, the control unit, in updating the octane number, minimizes the time constant of the first-order lag filter after refueling the fuel tank, and gradually increases the time constant over time. Make it bigger .

According to this configuration, the control section sequentially estimates the octane number based on the measurement signal from the measurement section. The control unit also filters the estimated octane number with a first-order lag filter , successively updates the octane number, and stores the updated octane number. The controller can accurately grasp the octane number of the fuel while the engine is running. Further, even if the octane number of the fuel changes due to refueling of the fuel in the fuel tank, the control unit determines the octane number after the change, and sends a control signal corresponding to the changed octane number to the fuel supply unit and the ignition. can be output to the The engine is optimally controlled even with varying fuel octane ratings. Further, as will be described later, in an engine in which an air-fuel mixture is combusted by self-ignition, the combustion state of the air-fuel mixture can be appropriately maintained according to the octane number of the fuel.

When the fuel tank is refueled , the control unit minimizes the time constant of the first-order lag filter in updating the octane number . After refueling, the octane number of the fuel may change significantly, but since the time constant is the smallest , the stored octane number can be quickly changed to the octane number of the fuel after refueling. The engine is optimally controlled according to the octane rating of the fuel even after refueling.

The control unit also gradually increases the time constant over time, thereby limiting the period during which the time constant is decreased to a predetermined period after refueling. After a predetermined period of time has passed, the time constant increases . If refueling is not performed, the octane number of the fuel does not change significantly. By increasing the time constant , it is possible to suppress large changes in the stored octane number even if the estimated octane number varies. Since the control signal output by the control unit is prevented from greatly changing due to the estimated octane number variation, the engine can be operated stably except when refueling. Further, by gradually increasing the time constant as time elapses from the time of refueling, it is possible to suppress erroneous determination of the octane number in a situation where the octane number of the fuel cannot change.

The measurement unit outputs a measurement signal corresponding to the amount of fuel in the fuel tank,
The control unit may determine that the fuel tank has been refueled when the amount of fuel in the fuel tank increases by a predetermined amount or more based on the measurement signal.

By doing so, the control unit can determine that fuel has been supplied to the fuel tank to such an extent that the octane number of the fuel can change. When the fuel tank is refueled, the controller can quickly change the stored octane number to the octane number of the fuel after refueling, as described above.

The control unit may filter the estimated octane rating so as not to exceed a predetermined maximum time constant.

The control unit may estimate the octane number based on a combustion parameter related to combustion of the air-fuel mixture obtained from the measurement signal.

The control unit estimates the octane number of the fuel based on combustion parameters related to combustion of the air-fuel mixture,
The control unit minimizes the time constant after fuel is supplied to the fuel tank and after fuel remaining in a supply passage from the fuel tank to the combustion chamber is supplied into the combustion chamber. Moreover, the time constant may be gradually increased as time elapses .

Since the fuel remaining in the supply passage is the fuel before refueling, while the fuel remaining in the supply passage is being supplied into the combustion chamber after refueling, the combustion state of the air-fuel mixture differs from that before refueling. No change, or almost no change. Until the remaining fuel is consumed, the combustion parameter remains the same as before refueling, so the fuel octane value estimated by the control unit also remains the same as before refueling. The controller increases the time constant while fuel remaining in the supply channel is being supplied into the combustion chamber. This suppresses erroneous determination of the octane number.

After the fuel remaining in the supply channel has been fed into the combustion chamber, the fuel fed into the combustion chamber becomes post-fuel fuel. If the octane number of the fuel changes before and after refueling, the combustion parameters will change from before refueling. The control unit reduces the time constant for a predetermined period. As a result, the octane number stored in the control unit is quickly changed to the octane number of the fuel after refueling.

Here, the applicant of the present application has proposed so-called SPCCI (SPark Controlled Compression Ignition) combustion. In SPCCI combustion, the spark plug forcibly ignites the air-fuel mixture in the combustion chamber to start combustion accompanied by flame propagation, and the heat and/or pressure increase due to the combustion causes the unburned air-fuel mixture to self-ignite. It is a form that burns with The heat generated by combustion with flame propagation assists auto-ignition of the unburned mixture.

The inventors of the present application found that in SPCCI combustion, the amount of heat generated in the combustion chamber from the timing when the spark plug ignited the air-fuel mixture to the timing when the unburned air-fuel mixture self-ignited (hereinafter, this heat amount is also referred to as the assist heat amount). ) and the octane rating of the fuel. That is, if the octane number of the fuel is low, the air-fuel mixture tends to self-ignite, so the amount of assist heat is small. The inventors of the present application have found that the octane number of fuel can be determined by calculating the amount of assist heat during SPCCI combustion based on various parameters measured by the measurement unit. The assist heat quantity corresponds to the combustion parameter.

The controller causes the igniter to ignite the air-fuel mixture at a predetermined time so that the engine causes a portion of the air-fuel mixture to begin combustion with flame propagation, followed by remaining unburned mixture. Partial self-ignition combustion is performed in which qi burns by self-ignition,
The control unit receives the measurement signal, calculates the amount of heat generated in the combustion chamber from the timing when the ignition unit ignites to the timing when the unburned air-fuel mixture self-ignites, and calculates the calculated amount of heat estimating the octane number of the fuel based on

According to the above configuration, the ignition section receives the control signal from the control section and ignites the air-fuel mixture at a predetermined timing. A portion of the air-fuel mixture in the combustion chamber begins to burn with flame propagation. Combustion with flame propagation increases the temperature and pressure within the combustion chamber. The remaining unburned air-fuel mixture burns by self-ignition. The engine performs partial self-ignition combustion (that is, SPCCI combustion).

Based on the measurement signal from the measurement unit, the control unit calculates the amount of heat generated in the combustion chamber from the timing when the ignition unit ignites to the timing when the unburned air-fuel mixture self-ignites. This amount of heat is the amount of assist heat. As described above, the assist heat amount has a correlation with the octane number of the fuel. By conducting experiments or simulations, the correlation between the amount of assist heat and the octane number of fuel is examined in advance, and if the correlation is stored as a map or model in the control unit, the control unit calculates The octane number of the fuel can be determined from the amount of assist heat.

The controller having the above configuration can determine the octane number of the fuel if the air-fuel mixture is SPCCI-burned. For example, the technology described in Patent Document 1 cannot determine the octane number of fuel unless knocking occurs. The control device configured as described above can quickly determine the octane number of the fuel. Also, the controller configured as described above can obtain a time-series estimate of the octane number of the fuel while the engine is running.

When the octane number of the fuel changes, the susceptibility to self-ignition of the air-fuel mixture changes. The octane rating of the fuel has a large effect on SPCCI combustion. Accurate knowledge of the octane rating of the fuel at all times allows the engine to properly perform SPCCI combustion.

As described above, the engine control device can quickly grasp the octane number of the fuel after refueling.

FIG. 1 is a configuration diagram illustrating an engine. FIG. 2 is a block diagram illustrating an engine control device. FIG. 3 is a diagram illustrating changes in pressure in the combustion chamber during SPCCI combustion. FIG. 4 is a diagram illustrating an engine control map. FIG. 5 is a diagram illustrating the relationship between the normalized amount of assist heat and the self-ignition timing when the octane number is the same and the operating conditions of the engine are different. FIG. 6 is a diagram illustrating the relationship between the equivalent temperature rise amount and the charging efficiency at different octane numbers and different operating conditions of the engine. FIG. 7 is a block diagram illustrating the configuration of a determination device that determines the octane number of fuel. FIG. 8 is a flowchart illustrating a procedure for determining the octane number of fuel. FIG. 9 is a block diagram illustrating the configuration of a determination device adapted to determine the octane number after refueling. FIG. 10 is a time chart for determining the octane number after refueling. FIG. 11 is a flowchart relating to the procedure for determining the octane number after refueling.

Hereinafter, embodiments of an engine control device will be described with reference to the drawings. The engine and controller described herein are exemplary.

FIG. 1 is a diagram illustrating an engine. FIG. 2 is a block diagram illustrating an engine control device.

The engine 1 has a combustion chamber 17 . The combustion chamber 17 repeats an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke. Engine 1 is a four-stroke engine. The engine 1 is installed in a four-wheeled automobile. The automobile runs as the engine 1 operates. The fuel of the engine 1 is gasoline in this configuration example. This engine 1 can use both high octane fuel and low octane fuel. The octane number of high octane fuel is, for example, 100, and the octane number of low octane fuel is, for example, 91. A user of the vehicle can fill a fuel tank 63, which will be described later, with high octane fuel or low octane fuel. The user can also add low octane fuel to the fuel tank 63 storing high octane fuel, and can add high octane fuel to the fuel tank 63 storing low octane fuel. . When fuel with a different octane number is added, the octane number of the fuel used in the engine 1 becomes an intermediate octane number.

(Engine configuration)
The engine 1 has a cylinder block 12 and a cylinder head 13 . The cylinder head 13 is mounted on the cylinder block 12 .

A plurality of cylinders 11 are formed in the cylinder block 12 . The engine 1 is a multi-cylinder engine. In FIG. 1 only one cylinder 11 is shown.

A piston 3 is inserted in each cylinder 11 . Piston 3 is connected to crankshaft 15 via connecting rod 14 . The piston 3 reciprocates inside the cylinder 11 . The piston 3 , cylinder 11 and cylinder head 13 form a combustion chamber 17 . The "combustion chamber" means a space formed by the piston 3, the cylinder 11 and the cylinder head 13 regardless of the position of the piston 3.

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 (Spark Ignition) combustion and CI (Compression Ignition) combustion, in some operating ranges. SPCCI combustion controls CI combustion through heat generation and/or pressure increase due to SI combustion. The engine 1 is a compression ignition engine. This engine 1 does not need to raise the temperature of the combustion chamber 17 when the piston 3 reaches the compression top dead center. Engine 1 has a low geometric compression ratio. A low geometric compression ratio favors reduced cooling losses and reduced mechanical losses.

An intake port 18 is formed in the cylinder head 13 for each cylinder 11 . 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 generates 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 the intake port 18 . The valve mechanism opens and closes the intake valve 21 at predetermined timings. The valve mechanism may be a variable valve mechanism that varies valve timing and/or valve lift. As shown in FIG. 2, the valve mechanism has an electric intake S-VT (Sequential-Valve Timing) 23 . The electric intake S-VT 23 continuously changes the rotation phase of the intake camshaft within a predetermined angle range. The opening angle of the intake valve 21 does not change. The valve mechanism may have a hydraulic S-VT instead of the electric S-VT.

An exhaust port 19 is formed in the cylinder head 13 for each cylinder 11 . 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 the exhaust port 19 . The valve mechanism opens and closes the exhaust valve 22 at predetermined timings. The valve mechanism may be a variable valve mechanism that varies valve timing and/or valve lift. As shown in FIG. 2, the valve train has an electric exhaust S-VT 24 . The electric exhaust S-VT 24 continuously changes the rotation phase of the exhaust camshaft within a predetermined angle range. The opening angle of the exhaust valve 22 does not change. The 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. Internal EGR gases are introduced into the combustion chamber 17 by adjusting the length of the overlap period.

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 arranged on the ceiling of the combustion chamber 17 (that is, on the bottom surface of the cylinder head 13). Although the detailed illustration is omitted, the injector 6 is of a multiple injection hole type having a plurality of injection holes.

A fuel supply system 61 is connected to the injector 6 . The injector 6 and the fuel supply system 61 constitute a fuel supply section. The fuel supply system 61 includes a fuel tank 63 that stores fuel and a fuel supply path 62 . A fuel supply path 62 connects 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 . Fuel pump 65 delivers fuel to common rail 64 . The fuel pump 65 is a plunger pump driven by the crankshaft 15 in this configuration example. Common rail 64 stores fuel sent from fuel pump 65 . The voltage inside the common rail 64 is high voltage. Injector 6 is connected to common rail 64 . When the injector 6 opens, the high-pressure fuel in the common rail 64 is injected into the combustion chamber 17 through the nozzle hole of the injector 6 . 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 . Electrodes of the ignition plug 25 face the inside of the combustion chamber 17 . The spark plug 25 is an example of an ignition section.

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 . Intake 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 . 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 branches for 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 changing 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 increases the pressure of intake gas introduced into the combustion chamber 17 . In this configuration example, the supercharger 44 is driven by the engine 1 . The 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 . The electromagnetic clutch 45 switches between a state in which driving force is transmitted from the engine 1 to the supercharger 44 and a state in which transmission of the driving force is interrupted. The turbocharger 44 is turned on or off by outputting a control signal to the electromagnetic clutch 45 from the ECU 10, which will be described later.

An intercooler 46 is arranged downstream of the supercharger 44 in the intake passage 40 . The intercooler 46 cools the intake gas compressed by the supercharger 44 . The intercooler 46 is water cooled or oil cooled.

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 to each other. A bypass passage 47 bypasses 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 supercharger 44 is off. Intake gas flowing through the intake passage 40 bypasses the supercharger 44 and the intercooler 46 and reaches 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 on, the engine 1 operates in a supercharged state. The ECU 10 adjusts the opening of the air bypass valve 48 when the supercharger 44 is on. Part of the intake gas that has passed through the supercharger 44 and the intercooler 46 returns to the upstream of the supercharger 44 through the bypass passage 47 . When the ECU 10 adjusts the opening of the air bypass valve 48, the pressure of the intake gas introduced into the combustion chamber 17 changes. "Supercharging" is defined as a state in which the pressure in the surge tank 42 exceeds the atmospheric pressure, and "non-supercharging" is defined as a state in which the pressure in the surge tank 42 is below the atmospheric pressure. You may

The engine 1 has a swirl control valve 56 attached to the intake passage 40 . The swirl control valve 56 generates a swirl flow within the combustion chamber 17 . The swirl control valve 56 is an opening control valve. When the opening degree of the swirl control valve 56 is small, the swirl flow inside the combustion chamber 17 becomes strong. When the opening of the swirl control valve 56 is large, 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 . Exhaust gas discharged from the combustion chamber 17 flows through the exhaust passage 50 . The upstream portion of the exhaust passage 50 branches for each cylinder 11, although detailed illustration is omitted.

An exhaust gas purification system having a plurality of catalytic converters is arranged in the exhaust passage 50 . Although not shown, the exhaust gas purification system is installed in the engine room. The upstream catalytic converter has a three-way catalyst 511 and a GPF (Gasoline Particulate Filter) 512 . 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 is connected between the intake passage 40 and the exhaust passage 50 . The EGR passage 52 is a passage that recirculates part of the exhaust gas to the intake passage 40 . An upstream end of the EGR passage 52 is connected between the two 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 .

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 . The EGR valve 54 adjusts the amount of recirculated external EGR gas.

(Configuration of engine control device)
The engine control device includes an ECU (Engine Control Unit) 10 . The ECU 10 is an example of a control section. The ECU 10 includes a microcomputer 101, a memory 102, and an I/F circuit 103, as shown in FIG. The microcomputer 101 executes programs. Memory 102 stores programs and data. The memory 102 is, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory). The I/F circuit 103 inputs and outputs electrical signals.

Various sensors SW1-SW11 are connected to the ECU 10 as shown in FIGS. The sensors SW1-SW11 output signals to the ECU 10. FIG. The sensors include the following sensors.

The airflow sensor SW1 measures the flow rate of fresh air flowing through the intake passage 40 . The airflow sensor SW1 is arranged downstream of the air cleaner 41 in the intake passage 40 . A first intake air temperature sensor SW2 measures the temperature of fresh air flowing through the intake passage 40 . The first intake air temperature sensor SW2 is arranged downstream of the air cleaner 41 in the intake passage 40 . A second intake air temperature sensor SW3 measures the temperature of intake gas introduced into the combustion chamber 17 . A second intake air temperature sensor SW3 is attached to the surge tank 42 .

The intake pressure sensor SW4 measures the pressure of intake gas introduced into the combustion chamber 17 . The intake pressure sensor SW4 is attached to the surge tank 42 . The in-cylinder pressure sensor SW5 measures the pressure inside each combustion chamber 17 . The in-cylinder pressure sensor SW5 is attached to the cylinder head 13 for each cylinder 11 . A water temperature sensor SW6 measures the temperature of the cooling water. A water temperature sensor SW6 is attached to the engine 1 .

A crank angle sensor SW7 measures the rotation angle of the crankshaft 15 . A crank angle sensor SW7 is attached to the engine 1 . The accelerator opening sensor SW8 measures the accelerator opening corresponding to the amount of operation of the accelerator pedal. The accelerator opening sensor SW8 is attached to the accelerator pedal mechanism. An intake cam angle sensor SW9 measures the rotation angle of the intake camshaft. The intake cam angle sensor SW9 is attached to the engine 1 . The exhaust cam angle sensor SW10 measures the rotation angle of the exhaust camshaft. The exhaust cam angle sensor SW10 is attached to the engine 1 . A level sensor SW11 measures the amount of fuel stored in the fuel tank 63 . The level sensor SW11 is attached to the fuel tank 63 .

The ECU 10 determines the operating state of the engine 1 based on the signals from these sensors SW1-SW11. The ECU 10 also calculates the control amount of each device according to predetermined control logic. The control logic is stored in memory 102 .

The ECU 100 transmits electric signals related to the 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 electromagnetic clutch of the supercharger 44. 45 , air bypass valve 48 and swirl control valve 56 .

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

FIG. 3 illustrates pressure changes 301 within the combustion chamber 17 during SPCCI combustion. The horizontal axis of FIG. 3 is the crank angle. FIG. 3 corresponds to the measurement signal of the in-cylinder pressure sensor SW5. SPCCI combustion is the following form of combustion. That is, the ignition plug 25 forcibly ignites the air-fuel mixture in the combustion chamber 17, whereby the air-fuel mixture starts SI combustion due to flame propagation. After the start of SI combustion, (1) the temperature in the combustion chamber 17 increases due to the heat generated by the SI combustion, and (2) the pressure in the combustion chamber 17 increases due to flame propagation. The unburned air-fuel mixture self-ignites and performs CI combustion. The pressure waveform in SPCCI combustion has a shape in which a peak due to SI combustion is superimposed on a peak due to CI combustion. The pressure waveform has an inflection point at the self-ignition timing θci. By measuring the pressure waveform in the combustion chamber 17 with the in-cylinder pressure sensor SW5, the ECU 10 can determine whether the air-fuel mixture self-ignites and SPCCI combustion is performed based on the shape of the pressure waveform.

By adjusting the amount of SI combustion, it is possible to absorb temperature variations in the combustion chamber 17 before the start of compression. The amount of SI combustion is adjusted by the ECU 10 adjusting the ignition timing. If the ECU 10 adjusts the ignition timing, the air-fuel mixture self-ignites at the target timing. In SPCCI combustion, the amount of SI combustion controls the start timing of CI combustion.

(engine operating range)
FIG. 4 illustrates a control map 401 of engine 1 . The control map 401 is stored in the memory 102 of the ECU 10. FIG. The ECU 10 operates the engine 1 based on the control map 401. FIG.

The control map 401 is defined by the load of the engine 1 and the rotation speed of the engine 1 . The control map 401 is divided into four areas: area A1, area A2, area A3, and area A4. Region A1 is a region where the number of revolutions is higher than that of Na. Area A2 is an area where the load is lower than La among the areas where the rotational speed is equal to or lower than Na. A region A3 is a region in which the load is La or higher among the regions in which the rotational speed is Na or lower. Note that La may be half the maximum load of the engine 1 . Area A4 is a specific area on the low load, low rotation side within area A2. Region A4 corresponds to a specific region of low rotation and low load in the entire operating region of engine 1 . It should be noted that the term "low rotation" as used herein corresponds to the low rotation side when the entire operating range of the engine 1 is divided into the low rotation side and the high rotation side. "Low load" corresponds to the low load side when the entire operating range of the engine 1 is divided into two equal parts, the low load side and the high load side.

When the operating state determined by the load and rotation speed of the engine 1 is within the region A1, the ECU 10 controls the engine 1 to perform SI combustion. The air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio. The air-fuel ratio of the air-fuel mixture may be included in the purification windows of the three-way catalysts 511 and 513 . Note that the air-fuel ratio is the average air-fuel ratio in the entire combustion chamber 17 .

When the operating state of the engine 1 is within the region A2, the ECU 10 controls the engine 1 to perform SPCCI combustion. The air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio. Further, when the operating state of the engine 1 is within the region A2, the supercharger 44 is off. When the operating state of the engine 1 is within region A3, the ECU 10 controls the engine 1 to perform SPCCI combustion. The air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio or substantially the stoichiometric air-fuel ratio. Further, when the operating state of the engine 1 is within the region A3, the supercharger 44 is on.

When the operating state of the engine 1 is within the region A4, the ECU 10 controls the engine 1 to perform SPCCI combustion. The air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. Specifically, the average air-fuel ratio in the entire combustion chamber 17 is 30 or more and 40 or less. When the operating state of the engine 1 is within the region A4, the supercharger 44 is off. Further, when the operating state of the engine 1 is within the region A4, the ECU 10 also provides an overlap period during which both the intake valve 21 and the exhaust valve 22 are open. Internal EGR gases are introduced into the combustion chamber 17 . This causes the temperature in the combustion chamber 17 to rise. In the area A4 where the load of the engine 1 is low, the CI combustion of the SPCCI combustion is stabilized due to the high temperature in the combustion chamber 17 .

The memory 102 of the ECU 10 stores control sets defined for each of the areas A1, A2, A3, and A4. The control set includes at least control amounts for fuel injection timing, ignition timing, the phase angle of the electric intake S-VT 23, the phase angle of the electric exhaust S-VT 24, and the opening of the swirl control valve 56, respectively. The ECU 10 determines the operating state of the engine 1 based on measurement signals from various sensors SW1-SW11. The ECU 10 also operates the injector 6, the spark plug 25, the electric intake S-VT 23, the electric exhaust S-VT 24, and the swirl control valve 56 according to the corresponding control set based on the operating state of the engine 1 and the control map 401. Control.

This engine 1 is also capable of using both high and low octane fuels, as previously described. Memory 102 stores two types of control sets for each region, a first control set corresponding to high octane fuel and a second control set corresponding to low octane fuel. The first control set and the second control set are set so as to optimize fuel consumption and exhaust emission performance corresponding to the octane number of the fuel. For example, the ignition timing of the first control set is set more advanced than the ignition timing of the second control set. The ECU 10 controls the operation of the engine 1 by determining the octane number of the fuel and selecting the control set corresponding to the determined octane number of the fuel through control described later.

(Fuel octane number determination logic)
Next, the logic for determining the octane number of fuel will be described with reference to FIGS. 5 and 6. FIG. This decision logic utilizes the combustion regime of SPCCI combustion. As shown in FIG. 3, in the SPCCI combustion, the ignition plug 25 forcibly ignites the air-fuel mixture in the combustion chamber 17 to start combustion accompanied by flame propagation, and the combustion generates heat and/or pressure rise. , the unburned air-fuel mixture is combusted by self-ignition.

Here, the amount of heat generated in the combustion chamber 17 from the timing when the spark plug ignites the air-fuel mixture to the timing when the unburned air-fuel mixture self-ignites is defined as the assist heat amount. In SPCCI combustion, the unburned air-fuel mixture receives assist heat and self-ignites. If the octane number of the fuel is low, the fuel is likely to self-ignite, so the amount of assist heat is small. Conversely, if the octane number of the fuel is high, the fuel is difficult to self-ignite, so the amount of assist heat is large. There is a correlation between the amount of assist heat and the octane number of the fuel.

FIG. 5 illustrates a graph 501 showing the relationship between the assist heat amount Qsa and the self-ignition timing θci. A graph 501 is a graph obtained by the inventors of the present application by conducting an experiment while changing the operating state of the engine 1 (that is, the load of the engine 1 and the ambient temperature). Graph 501 is a graph when the fuel used is low octane fuel.

The vertical axis of graph 501 is the value obtained by dividing the amount of assist heat Qsa by the amount of gas introduced into combustion chamber 17 . The amount of gas introduced into the combustion chamber 17 changes according to the operating state of the engine 1 . As the load on the engine 1 increases, the amount of gas introduced into the combustion chamber 17 increases. The vertical axis of graph 501 normalizes the amount of assist heat Qsa by the amount of gas introduced into combustion chamber 17 .

The ECU 10 can calculate the amount of heat generated in the combustion chamber 17 based on the measurement signal from the in-cylinder pressure sensor SW5. As shown in FIG. 3, the ECU 10 controls the combustion chamber 17 from the timing at which the spark plug 25 ignites the air-fuel mixture to the timing θci at which the unburned air-fuel mixture self-ignites based on the measurement signal of the in-cylinder pressure sensor SW5. The amount of assist heat Qsa generated inside is calculated.

The horizontal axis of the graph 501 is the timing θci at which the unburned air-fuel mixture self-ignites. When the unburned air-fuel mixture auto-ignites, the pressure change (dP/dθ) changes. The ECU 10 can specify the self-ignition timing θci based on the measurement signal of the in-cylinder pressure sensor SW5.

Further, as described above, the ECU 10 can grasp that the air-fuel mixture self-ignites and SPCCI combustion occurs based on the measurement signal of the in-cylinder pressure sensor SW5.

The circles in the graph 501 are measured values when the ambient temperature in which the engine 1 is operated is normal and the charging efficiency Ce is maximum, and the triangles in the graph 501 are when the ambient temperature is standard and the charging efficiency Ce is high. The diamonds in the graph 501 are the measured values when the ambient temperature is normal and the charging efficiency Ce is low. The squares in the graph 501 are the measured values when the ambient temperature is extremely hot and the charging efficiency Ce is high, and the inverted triangles in the graph 501 are the ambient temperature is extremely hot and the charging efficiency Ce is high. is the measured value when is small.

As indicated by straight lines 5011 to 5015 in graph 501, there is a correlation between normalized assist heat quantity Qsa and self-ignition timing θci. In other words, the straight lines 5011-5015 all rise to the right. When the assist heat quantity Qsa is large, the self-ignition timing θci is retarded, and when the assist heat quantity Qsa is small, the self-ignition timing θci is advanced. Moreover, the correlation is established for each operating state of the engine 1 . That is, the straight lines 5011-5015 differ for each operating state of the engine 1. FIG.

Here, a comparison is made between high and low environmental temperatures. When the environmental temperature is high (straight line 5014), the assist heat quantity Qsa is smaller than when the environmental temperature is low (straight line 5015). When the ambient temperature is high, the temperature of the intake air introduced into the combustion chamber 17 is high. When the intake air temperature is high, the temperature in the combustion chamber 17 rises and the unburned air-fuel mixture tends to self-ignite. Therefore, when the intake air temperature is high, the assist heat quantity Qsa is small.

Next, the magnitude of the charging efficiency Ce will be compared. When the charging efficiency Ce is large, that is, when the torque of the engine 1 is large (lines 5011 and 5012), the assist heat amount Qsa is small. If a large amount of air is introduced into the combustion chamber 17, the temperature in the combustion chamber 17 will be higher as the air is compressed. When the temperature inside the combustion chamber 17 increases, the unburned air-fuel mixture tends to self-ignite. Therefore, when the charging efficiency Ce is high, the assist heat quantity Qsa is small.

In the graph 501, the measured values of the assist heat quantity Qsa and the self-ignition timing θci in each operating state are represented by a straight statistical model, and the intercept of the straight line at a specific crank angle (specific CA, for example, 15° ATDC) is It is defined as the representative value of the model in each operating state. Hereinafter, this representative value will be referred to as "equivalent temperature rise amount (Qsa (specific CA)/cylinder internal gas amount)".

As described above, the graph 501 in FIG. 5 illustrates the relationship between the normalized assist heat amount Qsa and the self-ignition timing θci when the fuel used is the low-octane fuel. Although illustration is omitted, the inventors of the present application found that the correlation between the normalized assist heat amount Qsa and the self-ignition timing θci is established for each operating state of the engine 1 in the same way when the fuel used is a high-octane fuel. Confirmed to do.

FIG. 6 illustrates a graph 601 created based on the graph 501 and the like. The vertical axis of the graph 601 is the aforementioned equivalent temperature rise amount (Qsa (specific CA)/cylinder internal gas amount). The horizontal axis of the graph 601 is the charging efficiency Ce. Graph 601 includes data for various operating conditions of engine 1 . Graph 601 also includes data when the fuel used is a high octane fuel and data when the fuel used is a low octane fuel.

The black circles in the graph 601 are the data when the fuel used is a high octane fuel and the ambient temperature is normal, and the squares in the graph 601 are the data when the fuel used is the high octane fuel and the ambient temperature is extremely hot. be. The white circles in graph 601 are the results when the fuel used is low octane fuel and the ambient temperature is standard, and the triangles in graph 601 are the data when the fuel used is low octane fuel and the ambient temperature is extremely hot. be. The cross marks in the graph 601 are data when the operation of the engine 1 is controlled by the first control set corresponding to the high octane fuel when the fuel used is the high octane fuel.

As indicated by curves 6011 to 6014 in graph 601, there is a correlation between equivalent temperature rise amount (Qsa (specific CA)/cylinder internal gas amount) and charging efficiency Ce. That is, when the charging efficiency Ce is high, the temperature in the combustion chamber 17 rises greatly as the air is compressed, so the equivalent temperature rise is small. Conversely, when the charging efficiency Ce is low, the equivalent temperature rise is growing. Curves 6011-6014 are all downward sloping. Also, the curves 6011 and 6012 when using the high octane fuel are different from the curves 6013 and 6014 when using the low octane fuel. When comparing at the same charging efficiency Ce, when using high octane fuel, the unburned air-fuel mixture is more difficult to self-ignite than when using low octane fuel, so the equivalent temperature rise is larger.

Also, the correlation between the equivalent temperature rise amount and the charging efficiency is established for each environmental temperature. That is, when the curves 6012 and 6014 in extreme heat and the curves 6011 and 6013 in standard time are compared with the same charging efficiency Ce, the temperature in the combustion chamber 17 is higher in extreme heat than in standard time. , the equivalent temperature rise is small.

As shown in graph 601, curves 6011 and 6012 when the fuel used is high octane fuel and curves 6013 and 6014 when the fuel used is low octane fuel are different. Therefore, when the engine 1 is performing SPCCI combustion, the ECU 10 calculates the equivalent temperature rise amount (Qsa (specified CA)/cylinder gas amount) and the charging efficiency based on the measurement signals of various sensors SW1-SW11. Ce and the ECU 10 based on where in the graph 601 the calculated equivalent temperature rise amount (Qsa (specified CA)/cylinder internal gas amount)) and charging efficiency Ce can be plotted. , the octane number of the fuel can be determined.

That is, if the calculated equivalent temperature rise amount (Qsa (specified CA)/cylinder gas amount)) and the charging efficiency Ce are on the curve 6011, for example, the ECU 10 determines that the fuel used is a high octane fuel. It can be determined that there is If the calculated equivalent temperature rise amount (Qsa (specified CA)/cylinder gas amount)) and the charging efficiency Ce are on the curve 6013, for example, the ECU 10 determines that the fuel used is a low octane fuel. It can be determined that there is

In addition, when low octane fuel is added to the fuel tank 63 storing high octane fuel, or when high octane fuel is added to the fuel tank 63 storing low octane fuel, the octane value of the fuel changes to the high octane value. It will have an octane rating that is intermediate between the fuel and the low octane fuel. In this case, the points of the equivalent temperature rise amount (Qsa (specific CA)/cylinder internal gas amount) and the charging efficiency Ce are plotted between the curves in the graph 601 . The ECU 10 can determine the octane number of the fuel, ie, the intermediate octane number, by linear interpolation.

(Octane number determination procedure)
FIG. 7 exemplifies the configuration of a determination device that determines the octane number of fuel. The determination device includes an assist heat quantity calculation unit 105 , a fitting unit 106 , an equivalent temperature rise amount calculation unit 107 , an autoignition characteristic calculation unit 108 , an octane rating determination unit 109 and a control set selection unit 110 . These units are functional blocks of the ECU 10 . The determination device successively determines the octane number while the engine 1 is running.

The assist heat quantity calculation unit 105 calculates the aforementioned assist heat quantity Qsa. The assist heat quantity calculation unit 105 calculates the assist heat quantity Qsa based on the measurement signals of various sensors SW1 to SW11 including the in-cylinder pressure sensor SW5 (see also FIG. 3). The assist heat quantity calculation unit 105 calculates the assist heat quantity Qsa each time combustion is performed in the combustion chamber 17 .

The fitting unit 106 determines the straight line of the statistical model shown in FIG. 5 from the relationship between the assist heat amount Qsa calculated by the assist heat amount calculation unit 105 and the self-ignition timing θci. Specifically, as illustrated in the graph 111, the fitting unit 106 plots the normalized assist heat quantity Qsa on the vertical axis and the self-ignition timing θci on the horizontal axis. A plurality of points indicating the relationship between the assist heat amount Qsa and the self-ignition timing θci are plotted (see black circles in graph 111). A fitting unit 106 defines a straight line, ie, a statistical model, based on the plotted points. The fitting unit 106 may determine the straight line by, for example, the method of least squares. Alternatively, the slope of the straight line may be fixed at a predetermined slope, and the fitting unit 106 may determine only the intercept of the straight line. By doing so, the amount of calculation of the fitting unit 106 is reduced.

Equivalent temperature rise amount calculation unit 107 calculates an equivalent temperature rise amount (Qsa (specific CA)/cylinder gas amount), which is the intercept of specific CA, based on the straight line determined by fitting unit 106 (white circles in graph 111). reference). Specifically, the equivalent temperature rise calculation unit 107 calculates the intersection of the straight line determined by the fitting unit 106 and the vertical line of the specific CA.

The self-ignition characteristic calculator 108 calculates the self-ignition characteristic based on the equivalent temperature rise calculated by the equivalent temperature rise calculator 107 and the map 112 stored in the memory 102 . Map 112 is obtained by rotating graph 601 shown in FIG. 6 counterclockwise by 90°. The map 112 is created in advance by performing experiments or simulations on the engine 1 and is stored in the memory 102 . The map 112 shows the first characteristic line when the fuel used is a high octane fuel and the environmental temperature of the engine 1 is standard conditions, and the fuel used is a low octane fuel and the environmental temperature of the engine 1 is a severe heat condition. and a second characteristic line for the case. The first characteristic line corresponds to the case where the air-fuel mixture is most difficult to self-ignite, and the second characteristic line corresponds to the case where the air-fuel mixture is most likely to self-ignite.

The self-ignition characteristic calculation unit 108 plots points indicating the relationship between the equivalent temperature rise calculated by the equivalent temperature rise calculation unit 107 and the charging efficiency Ce on the map 112 (see black circles in the map 112), and plots the points on the map 112. Compute a curve through (see dashed line in map 112). The curve of the self-ignition characteristic calculated by the self-ignition characteristic calculator 108 is determined between the first characteristic line and the second characteristic line. The self-ignition characteristic curve calculated by the self-ignition characteristic calculator 108 may match the first characteristic line or may match the second characteristic line.

The octane number determination unit 109 determines the octane number of the fuel based on the self-ignition characteristic curve calculated by the self-ignition characteristic calculation unit 108 . More specifically, the octane number determination unit 109 estimates the octane number of the fuel based on the self-ignition characteristic curve calculated by the self-ignition characteristic calculation unit 108 . Octane number determination unit 109 also updates the octane number stored in memory 102 by reflecting the currently estimated octane number in the octane number stored in memory 102 . The octane number determining unit 109 successively updates the octane number while the engine 1 is performing SPCCI combustion.

First, the estimation of the octane number by the octane number determination unit 109 will be described. When the curve of the self-ignition characteristic calculated by the self-ignition characteristic calculation section 108 matches the first characteristic line, the octane number determining section 109 estimates that the fuel used has a high octane number. When the curve of the self-ignition characteristic calculated by the self-ignition characteristic calculation section 108 matches the second characteristic line, the octane number determination unit 109 estimates that the fuel used has a low octane number.

When the curve of the self-ignition characteristics calculated by the self-ignition characteristics calculation unit 108 is positioned between the first characteristic line and the second characteristic line as illustrated by the dashed line in FIG. The octane number of the fuel is calculated by linear interpolation (see arrows in FIG. 7). In this case, the octane number determining unit 109 estimates that the fuel used has an octane number intermediate between the high octane number and the low octane number.

Here, the octane number determining unit 109 performs temperature correction when estimating the octane number. That is, when the intake air temperature is high and/or the water temperature of the engine 1 is high, the temperature of the gas in the combustion chamber 17 is high, so the air-fuel mixture tends to self-ignite. In this case, the octane number of the fuel is apparently lowered. An octane number determination unit 109 corrects the estimated octane number based on the intake air temperature and/or the water temperature of the engine 1 . Specifically, when the intake air temperature and/or the water temperature of the engine 1 are high, the octane number determining unit 109 corrects the estimated octane number to be higher. When the intake air temperature and/or the water temperature of the engine 1 are low, the octane number determination unit 109 corrects the estimated octane number to be low.

Instead of the octane number determination unit 109 correcting the estimated octane number based on the intake air temperature and/or the water temperature of the engine 1, the self-ignition characteristic calculation unit 108 corrects the intake air temperature and/or the water temperature of the engine 1 The self-ignition characteristic may be corrected based on.

After estimating the octane number, the octane number determining unit 109 updates the estimated octane number by filtering the estimated octane number with a first-order lag filter. Memory 102 stores the updated octane rating. By performing the filtering process, the octane value stored in the memory 102 is suppressed from fluctuating greatly. This is advantageous for stabilizing the SPCCI combustion in the engine 1. Although the details will be described later, the octane rating determination unit 109 changes the filter time constant of the first-order lag filter according to the refueling situation.

The control set selection unit 110 selects a control set to be used for controlling the operation of the engine 1 based on the fuel octane value updated by the octane value determination unit 109 , that is, the fuel octane value stored in the memory 102 . Specifically, when the updated fuel octane number is closer to the high octane number than the low octane number, the control set selection unit 110 selects the first control set corresponding to the high octane fuel, and selects the first control set corresponding to the updated fuel octane number. is closer to low octane than high octane, select the second control set corresponding to the low octane fuel.

When the octane number of the fuel stored in the memory 102 is an intermediate octane number, the control set selection unit 110 selects an intermediate value between the control amount of the first control set and the control amount of the second control set. It may be defined as a control amount of the device.

The ECU 10 controls at least the fuel injection timing of the injector 6, the ignition timing of the spark plug 25, the phase angle of the electric intake S-VT 23, the phase angle of the electric exhaust S-VT 24, and the And the opening degree of the swirl control valve 56 is controlled. As a result, the engine 1 always has optimum fuel economy and exhaust emission performance depending on the octane number of the fuel used. In addition, the engine 1 can suppress combustion noise regardless of the octane number of the fuel used.

FIG. 8 shows the control executed by the ECU 10 and exemplifies the procedure for determining the octane number of the fuel. The flow of FIG. 8 starts when the ignition is turned on. In step S<b>1 after the start, the ECU 10 selects the corresponding control set based on the octane number stored in the memory 102 and controls the operation of the engine 1 .

In subsequent step S2, the ECU 10 acquires a measurement signal from the in-cylinder pressure sensor SW5, that is, information on the pressure waveform in the combustion chamber 17. FIG.

In step S3, the ECU 10 calculates the self-ignition timing θci based on the pressure waveform illustrated in FIG. . If the determination in step S4 is YES, the process proceeds to step S5, otherwise the process returns. Determination of fuel octane is only feasible during SPCCI combustion.

The ECU 10 may also determine the octane number of the fuel when the operating state of the engine 1 is in region A2 or region A3 (see FIG. 4). The ECU 10 does not determine the octane number of the fuel when the operating state of the engine 1 is in the region A4, in other words, when the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. By doing so, the ECU 10 can accurately determine the octane number of the fuel.

In step S5, the ECU 10 determines whether or not the charging efficiency Ce is equal to or higher than the lower limit. As illustrated in FIG. 6, in the relationship between the equivalent temperature rise amount and the charging efficiency, when the charging efficiency Ce is low, curves 6011 to 6014 approach each other. In this case, the ECU 10 may erroneously determine the octane rating of the fuel. Therefore, the ECU 10 does not determine the octane number of the fuel when the charging efficiency Ce is smaller than the lower limit value. There is a lower determinable load of octane. If the determination in step S5 is YES, the process proceeds to step S6, and if the determination in step S5 is NO, the process returns. This suppresses erroneous determination of the octane number of the fuel used.

In step S6, the ECU 10 calculates the assist heat quantity Qsa based on the measurement signal of the in-cylinder pressure sensor SW5, as described above. In the subsequent step S7, the ECU 10 defines a linear statistical model based on a plurality of points indicating the relationship between the calculated assist heat amount Qsa and the self-ignition timing θci (see graph 111 in FIG. 7). In other words, the ECU 10 fits a straight line to a plurality of points.

In step S8, the ECU 10 calculates an equivalent temperature rise amount, which is the intercept of the straight line at the specific CA, based on the statistical model of the straight line determined in step S7. Then, in step S9, the ECU 10 calculates the self-ignition characteristics based on the calculated equivalent temperature rise amount and the map 112 stored in the memory 102, and estimates the octane number of the fuel from the self-ignition characteristics ( step S10). In step S<b>11 , the ECU 10 filters the estimated octane number and updates the octane number stored in the memory 102 . In step S12, the ECU 10 selects a control set based on the updated octane rating.

This octane number determination logic utilizes the characteristics of SPCCI combustion. If the mixture is SPCCI combusted, the ECU 10 can determine the octane rating of the fuel used based on combustion parameters related to combustion. Even if knocking does not occur, the ECU 10 can determine the octane number of the used fuel. The ECU 10 can quickly determine the octane number of the fuel used. Further, the ECU 10 can successively determine the octane number of the fuel used while the engine 1 is running.

Further, as shown in FIG. 6, the ECU 10 controls the amount of air introduced into the combustion chamber 17 (that is, charging efficiency Ce) and the amount of assist heat that is calculated (that is, equivalent temperature rise amount (Qsa (specified CA)/in-cylinder The octane number of the fuel is determined based on the relationship with the amount of gas)). This allows the ECU 10 to accurately determine the octane number of the fuel used.

In addition, since the ECU 10 corrects the octane number of the fuel based on the temperature of the intake air introduced into the combustion chamber 17, the ECU 10 can more accurately determine the octane number of the fuel used.

Further, since the ECU 10 corrects the octane number of the used fuel based on the temperature of the cooling water of the engine 1, the ECU 10 can more accurately determine the octane number of the used fuel.

The ECU 10 may correct the octane number of the fuel used based on the amount of EGR gas introduced into the combustion chamber 17 . When there is a large amount of EGR gas, the temperature in the combustion chamber 17 rises, so the unburned air-fuel mixture tends to self-ignite. By correcting the octane number of the used fuel based on the introduction ratio of the EGR gas, the ECU 10 can more accurately determine the octane number of the used fuel.

In addition, when the load of the engine 1 is lower than the lower limit load, the ECU 10 prohibits the determination of the octane number of the used fuel, so that the ECU 10 can suppress erroneous determination of the octane number of the used fuel.

(Structure for promptly judging the octane number after refueling)
As described above, the fuel tank 63 can be filled with either high octane fuel or low octane fuel. When refueling occurs, the octane number of the fuel used can change significantly. After refueling, it is advantageous for stabilization of SPCCI combustion that the ECU 10 promptly and accurately determines the octane number of the fuel.

The ECU 10 can determine the octane number of the fuel if the air-fuel mixture is SPCCI combusted. In other words, the ECU 10 cannot determine the octane number of the fuel if the mixture does not undergo SPCCI combustion.

The control device of the engine 1 is configured so that the ECU 10 quickly and accurately determines the octane number of the fuel after refueling. FIG. 9 illustrates the configuration of a determination device adapted to determine the octane number after refueling. The determination device has a refueling determination section 121 , a remaining fuel determination section 122 , a counter 123 , an octane number estimation section 124 , an octane number update section 125 and a reflection rate setting section 126 . These are functional blocks of the ECU 10 . The octane number estimating section 124 and the octane number updating section 125 correspond to the octane number determining section 109 in FIG. Moreover, FIG. 10 exemplifies the temporal change of each parameter after refueling.

The refueling determination unit 121 determines whether or not the fuel tank 63 has been refueled based on the measurement signal from the level sensor SW11. Specifically, the refueling determination unit 121 determines that refueling has been performed when the amount of fuel in the fuel tank 63 has increased by a predetermined amount or more. As a result, erroneous determination of refueling can be suppressed. Also, the predetermined amount may be appropriately set, for example, as an amount that can change the octane number of the fuel. In the time chart of FIG. 10 , reference numeral 1001 indicates the determination flag of the refueling determination section 121. In the time chart of FIG. Refueling determination unit 121 turns on the determination flag at time t1. Refueling determination unit 121 determines that refueling was performed at time t1.

Remaining fuel determination unit 122 determines whether fuel remaining in fuel supply path 62 from fuel tank 63 to combustion chamber 17 has been consumed after refueling determination unit 121 determines refueling. After the refueling determination unit 121 determines refueling, the remaining fuel determination unit 122 determines whether or not the remaining fuel has been supplied into the combustion chamber 17 by integrating the injection amount of the fuel injected by the injector 6. do. When the integrated value of the injection amount exceeds the volume of the fuel supply passage 62, the remaining fuel is consumed.

In the time chart of FIG. 10 , reference numeral 1002 indicates the determination flag of the remaining fuel determination section 122. In FIG. Remaining fuel determination unit 122 turns on the determination flag at time t2 after time t1. The remaining fuel determination unit 122 determines that the remaining fuel has been consumed at time t2. In the time chart of FIG. 10, the fuel supply determination flag turns off when the remaining fuel determination flag turns on.

Counter 123 is reset to zero when refueling determination unit 121 determines refueling and remaining fuel determination unit 122 determines consumption of remaining fuel. In the time chart of FIG. 10, reference numeral 1003 indicates the value of the counter 123. In FIG. At time t2, the counter 123 is reset. The value of counter 123 is incremented each cycle of engine 1 . In the time chart of FIG. 10, the value of the counter 123 gradually increases after time t2. When the value of counter 123 reaches a predetermined maximum value, counting stops. A counter 123 measures a predetermined period of time after refueling. As will be described later, in the configuration example of FIG. 10, the period from time t2 to time t3 corresponds to the predetermined period after refueling.

As described above, the octane number estimator 124 estimates the octane number of the fuel based on the assist heat amount Qsa and the self-ignition timing θci. In the time chart of FIG. 10 , reference numeral 1004 exemplifies the octane number estimated by the octane number estimation unit 124 . FIG. 10 shows an example in which low octane fuel is supplied to the fuel tank 63 in which high octane fuel has been stored. The octane number estimation unit 124 estimates that the octane number of the fuel is high before refueling at time t1 and before the remaining fuel is consumed at time t2, and after refueling after time t2 and the remaining fuel is consumed. After that, it is assumed that the octane number of the fuel is low.

The octane number updating unit 125 updates the octane number stored in the memory 102 by filtering the octane number estimated by the octane number estimating unit, as described above.

A reflection rate setting unit 126 sets a reflection rate for updating the octane number based on the octane number estimated by the octane number estimation unit 124 . More specifically, the reflection rate setting unit 126 sets the time constant of the first-order lag filter. A reflection rate setting unit 126 sets a reflection rate based on the value of the counter 123 . The reflection rate setting unit 126 increases the reflection rate when the value of the counter 123 is small, and decreases the reflection rate when the value of the counter 123 is large. In other words, the reflection rate setting unit 126 decreases the time constant when the value of the counter 123 is small, and increases the time constant when the value of the counter 123 is large.

As illustrated in the time chart of FIG. 10, the value of the counter 123 is reset to zero at time t2, so the reflection rate is maximized. After time t2, the reflection rate gradually decreases from the maximum as the value of the counter 123 increases. As described above, the value of counter 123 reaches the maximum value at time t3. The reflection rate reaches a minimum at time t3 and remains at a minimum after time t3. That is, after a predetermined period of time has elapsed after refueling, the octane number updating unit 125 reflects the estimated octane number in the stored octane number at the minimum reflection rate.

Reference numeral 1006 in FIG. 10 exemplifies the updated octane number, that is, the change in the octane number stored in memory 102 . Before time t2, the octane number stored in memory 102 is high. After time t2, as the estimated octane number decreases, the octane number stored in memory 102 also decreases. Since the reflection rate is high immediately after time t2, the octane number stored in the memory 102 suddenly drops.

As described above, immediately after refueling (however, after the remaining fuel is consumed), the time constant of the first-order lag filter is small, so the estimated octane rating is strongly reflected in updating the octane rating. The updated octane number is subject to change. That is, when the octane number changes due to refueling, the ECU 10 can quickly change the stored octane number.

In addition, the determination device determines the octane number of the fuel based on the combustion parameters related to the combustion of the air-fuel mixture. Suppressed.

As time passes from refueling and the counter increases, the time constant of the first-order lag filter increases. Estimated octane number is not strongly reflected in octane update. The octane number of the fuel does not change significantly in the situation of not refueling. By making it difficult to reflect the estimated octane number when updating the octane number, fluctuations in the stored octane number are suppressed even if the estimated octane number varies. Since the ECU 10 selects a control set according to the octane number of the fuel used, the operation of the engine 1 is stabilized by suppressing fluctuations in the stored octane number except when refueling. In order to keep the reflection rate at a minimum, the ECU 10 can update the stored octane number by reflecting the estimated octane number in the stored octane number while the engine 1 is running. The ECU 10 can accurately determine the octane rating.

FIG. 11 shows a flowchart relating to octane number update executed by the ECU 10 . First, in step S111 after the start, the ECU 10 controls the engine 1 based on the current octane rating, that is, the octane rating stored in the memory 102, and the ignition timing corresponding to the octane rating. In subsequent step S112, the ECU 10 determines whether fuel has been supplied. If refueled, the process proceeds to step S113; otherwise, the process proceeds to step S115.

In step S113, the ECU 10 determines whether or not the remaining fuel after refueling has been consumed. If the remaining fuel has been consumed, the process proceeds to step S114. If the remaining fuel has not been consumed, the process proceeds to step S115.

The ECCU 10 resets the counter 123 in step S114. In step S115, the ECU 10 determines whether or not the engine 1 has performed SPCCI combustion. As described above, the ECU 10 can determine whether or not the SPCCI combustion is performed based on the measurement signal of the in-cylinder pressure sensor SW5.

If SPCCI combustion has not been performed, the process returns because no octane number estimate can be made. If engine 1 performed SPCCI combustion, the process proceeds to step S116.

In step S116, the ECU 10 determines whether or not the value of the counter 123 is maximum, and if not, the process proceeds to step S117. The ECU 10 increments the value of the counter 123 and then proceeds to step S118. If the value of counter 123 is maximum, the process proceeds to step S118 without proceeding to step S117.

In step S118, the ECU 10 estimates the octane number of the fuel based on the assist heat quantity Qsa and the self-ignition timing θci, and in subsequent step S119, the ECU 10 stores the estimated octane number at a reflection rate according to the counter value. The stored octane number is updated.

It should be noted that the engine control device disclosed herein is not limited to application to the engine 1 having the configuration described above. The engine control device disclosed herein can be applied to engines of various configurations.

1 engine 10 ECU (control unit)
11 Cylinder 17 Combustion Chamber 25 Ignition Plug (Ignition Part)
6 injector (fuel supply unit)
61 fuel supply system (fuel supply unit)
63 Fuel tank SW5 In-cylinder pressure sensor (measurement unit)

Claims (6)

an engine having cylinders forming a combustion chamber;
a fuel supply unit for supplying fuel in a fuel tank into the combustion chamber;
an igniter attached to the engine and igniting an air-fuel mixture in the combustion chamber;
a measurement unit that outputs measurement signals of parameters related to the engine;
a control unit that stores the octane number of the fuel and outputs a control signal corresponding to the stored octane number to the fuel supply unit and the ignition unit;
The control unit sequentially estimates the octane number based on the measurement signal , performs filtering on the estimated octane number using a first-order lag filter, sequentially updates the octane number , and stores the updated octane number ,
When the fuel tank is refueled, the control unit, in updating the octane number, minimizes the time constant of the first-order lag filter after refueling the fuel tank, and gradually increases the time constant over time. Enlarged engine control unit. In the engine control device according to claim 1,
The measurement unit outputs a measurement signal corresponding to the amount of fuel in the fuel tank,
The control device for an engine, wherein the control unit determines that the fuel tank has been refueled when the amount of fuel in the fuel tank increases by a predetermined amount or more based on the measurement signal. In the engine control device according to claim 1 or 2 ,
The control unit for an engine, wherein the control unit filters the estimated octane rating so as not to exceed a predetermined maximum time constant . In the engine control device according to any one of claims 1 to 3 ,
The control unit is an engine control device for estimating the octane number based on a combustion parameter relating to combustion of the air-fuel mixture obtained from the measurement signal. In the engine control device according to claim 3 ,
The control unit estimates the octane number of the fuel based on combustion parameters related to combustion of the air-fuel mixture,
The control unit minimizes the time constant after fuel is supplied to the fuel tank and after fuel remaining in a supply passage from the fuel tank to the combustion chamber is supplied into the combustion chamber. In addition, the engine control device gradually increases the time constant as time elapses . In the engine control device according to claim 4 or 5 ,
The controller causes the igniter to ignite the air-fuel mixture at a predetermined time so that the engine causes a portion of the air-fuel mixture to begin combustion with flame propagation, followed by remaining unburned mixture. Partial self-ignition combustion is performed in which qi burns by self-ignition,
The control unit receives the measurement signal, calculates the amount of heat generated in the combustion chamber from the timing when the ignition unit ignites to the timing when the unburned air-fuel mixture self-ignites, and calculates the calculated amount of heat an engine controller for estimating the octane number of said fuel based on

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