JP2022156452A - engine control system - Google Patents

Abstract

To control the amount of fuel to be injected in a compression stroke while suppressing NOx emissions and stabilizing combustion in a lean burn operation.SOLUTION: A system includes: an engine; a first sensor measuring a concentration of nitrogen oxide in exhaust gas; a second sensor measuring an index value indicating a degree of combustion fluctuation; and a control device. A processor is configured to execute: injecting fuel in an intake stroke; injecting smaller amount of fuel in the compression stroke than that in the intake stroke; adjusting an air-fuel ratio of an air-fuel mixture in the intake stroke when a determination that the concentration of the nitrogen oxide is not within a first target range is made; and adjusting the injection amount in the compression stroke when a determination that the index value is not within a second target range is made.SELECTED DRAWING: Figure 1

Description

The present invention relates to engine control systems.

The engine may be operated in lean burn. Since lean burn uses an air-fuel mixture with a low fuel concentration, a small amount of fuel may be injected during the compression stroke in addition to the intake stroke in order to stabilize ignition. However, since the amount of fuel injected in the compression stroke is very small, it can be difficult to inject the correct amount of fuel. Therefore, in lean burn, various techniques have been proposed for controlling the amount of fuel injected in the compression stroke (for example, Patent Document 1).

For example, Patent Literature 1 discloses a control device for an internal combustion engine having an operation mode in which fuel injection is performed at least twice, including a main injection and a minute injection, in one combustion cycle. In this device, first, in lean burn operation without minute injection, the amount of main injection is controlled so as to correspond to the target amount. Subsequently, in lean burn operation with minute injection, the amount of minute injection is calculated based on the air-fuel ratio, the amount of intake air, and the amount of main injection. The calculated amount of minute injection is compared with the target amount, and the amount of minute injection is adjusted.

Japanese Patent Application Laid-Open No. 2018-3622

In lean-burn operation, in addition to controlling the amount of minute injection in the compression stroke, it is desirable to suppress NOx emissions and stabilize combustion.

In consideration of the above problems, the present invention provides an engine control system that can control the amount of fuel injected in the compression stroke while suppressing NOx emissions and stabilizing combustion in lean burn operation. intended to provide

An engine control system according to one aspect of the present invention includes:
engine and
a first sensor for measuring the concentration of nitrogen oxides in exhaust gas from the engine;
a second sensor that measures an index value indicating the degree of combustion fluctuation of the engine;
a control device that controls the engine;
with
the controller includes one or more processors and one or more storage media storing instructions to be executed by the one or more processors;
The one or more processors, according to the instructions,
injecting fuel into the intake air during the intake stroke;
injecting less fuel into a mixture of air and fuel on a compression stroke than on the intake stroke;
determining whether the concentration of nitrogen oxides measured by the first sensor is within a predetermined first target range;
changing the air-fuel ratio of the air-fuel mixture in the intake stroke so that the concentration of nitrogen oxides is within the first target range when it is determined that the concentration of nitrogen oxides is not within the first target range; to adjust and
Determining whether the index value measured by the second sensor is within a predetermined second target range when the concentration of nitrogen oxides is determined to be within the first target range. and
adjusting the amount of fuel injected in the compression stroke so that the index value is within the second target range when it is determined that the index value is not within the second target range;
configured to run

According to the present invention, in lean-burn operation, the amount of fuel injected in the compression stroke can be controlled while suppressing NOx emissions and stabilizing combustion.

FIG. 1 is a schematic diagram showing an engine control system according to one embodiment of the present invention. FIG. 2 is a functional block diagram of the ECU. FIG. 3 is a schematic diagram for explaining the relationship between the NOx concentration and engine rotation fluctuations in lean burn. FIG. 4 is a flow chart showing the processing of the ECU.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Specific dimensions, materials, numerical values, and the like shown in such embodiments are merely examples for facilitating understanding, and do not limit the present invention unless otherwise specified. In addition, in the specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, thereby omitting redundant description. Elements that are not directly related to the present invention are omitted from the drawing.

FIG. 1 is a schematic diagram showing an engine control system 100 according to one embodiment of the invention. An engine control system (which may also be simply referred to as a "system" in the present disclosure) 100 is applied to a vehicle 500 such as an HEV (Hybrid Electric Vehicle), a gasoline vehicle, or a diesel vehicle, for example. System 100 comprises engine 10 .

In this embodiment, engine 10 is a gasoline engine. In other embodiments, engine 10 may be a diesel engine. The engine 10 has cylinders 11 and pistons 12 . The piston 12 reciprocates within the cylinder 11 . Combustion chamber 13 is defined by cylinder 11 and piston 12 . Piston 12 is connected to crankshaft 18 by connecting rod 14 .

In the engine 10 as described above, a mixture of air and fuel (gasoline) is combusted in the combustion chamber 13 , thereby causing the piston 12 to reciprocate within the cylinder 11 . Linear motion of the piston 12 is transmitted to the crankshaft 18 by the connecting rod 14 and converted into rotary motion of the crankshaft 18 . The rotation speed of the crankshaft 18 (=the rotation speed of the engine 10) is measured by the crank angle sensor Se1. The crank angle sensor Se1 is communicably connected to the ECU 50 (details will be described later). It should be noted that although only one set of cylinders 11 and pistons 12 is shown in FIG. 1 for better understanding, engine 10 may have multiple sets of cylinders 11 and pistons 12 .

The engine 10 has an intake port 15 and an exhaust port 16 . The intake port 15 is provided with an intake valve 15a, and the exhaust port 16 is provided with an exhaust valve 16a. Each operation of the intake valve 15a and the exhaust valve 16a is controlled by, for example, a camshaft (not shown). The camshaft is rotated by a crankshaft 18 via a rotating belt or the like, for example.

The engine 10 has fuel injectors 17 . The injector 17 is provided in the combustion chamber 13, and fuel is injected from the injector 17 into the combustion chamber 13 (so-called direct injection). The injector 17 is communicably connected to the ECU 50 . For example, the ECU 50 controls the injection amount of fuel from the injector 17 by controlling the lift of the needle valve of the injector 17 .

The engine 10 has a spark plug P. A spark plug P is provided in the combustion chamber 13 and ignites a mixture of air and fuel in the combustion chamber 13 . The spark plug P is communicably connected to the ECU 50 . The ECU 50 controls the operation of the spark plug P.

The intake pipe 2 is connected to the intake port 15 . Components such as an air cleaner (not shown) are provided in the intake pipe 2 , and air that has passed through these components is supplied to the combustion chamber 13 through an intake port 15 . The intake pipe 2 is provided with a throttle valve V<b>1 for adjusting the flow rate of air flowing through the intake pipe 2 . The throttle valve V1 is communicably connected to the ECU 50 . The ECU 50 controls the intake air amount by controlling the throttle valve V1.

An exhaust pipe 3 is connected to the exhaust port 16 . The exhaust pipe 3 is provided with an air-fuel ratio (A/F) sensor Se2. The A/F sensor Se<b>2 measures the air-fuel ratio based on the exhaust gas flowing through the exhaust pipe 3 . The A/F sensor Se2 is communicably connected to the ECU 50 . For example, the ECU 50 controls at least one of the injector 17 and the throttle valve V1 based on the air-fuel ratio measured by the A/F sensor Se2.

A front catalyst 4 is provided in the exhaust pipe 3 downstream of the A/F sensor Se2. The front catalyst 4 removes harmful substances (eg, at least one of hydrocarbons (HC), carbon monoxide (CO), or nitrogen oxides (NO _x )) from the exhaust gas. The front catalyst 4 is, for example, a three-way catalyst.

A NOx sensor Se3 is provided downstream of the front catalyst 4 in the exhaust pipe 3 . The NOx sensor Se3 measures the concentration of nitrogen oxides (NOx) in the exhaust gas after passing through the front catalyst 4 . The NOx sensor Se3 is communicably connected to the ECU 50 . For example, the ECU 50 controls at least one of the injector 17 and the throttle valve V1 based on the NOx concentration measured by the NOx sensor Se3.

In the exhaust pipe 3, a particulate filter 5 is provided downstream of the NOx sensor Se3. The particulate filter 5 removes particulate matter (PM) (such as soot) from the exhaust gas. The particulate filter 5 is, for example, a GPF (Gasoline Particulate Filter). In another embodiment, for example, when the engine 10 is a diesel engine, the particulate filter 5 may be a DPF (Diesel Particulate Filter).

In the exhaust pipe 3, a pipe 6 for recirculating the exhaust gas to the intake pipe 2 is connected upstream of the A/F sensor Se2. The pipe 6 is connected downstream of the throttle valve V1 in the intake pipe 2 . The pipe 6 is provided with an EGR (Exhaust Gas Recirculation) valve V2 for adjusting the flow rate of recirculated exhaust gas. The EGR valve V2 is communicably connected to the ECU 50 . The ECU 50 controls the flow rate of recirculated exhaust gas by controlling the EGR valve V2.

The pipe 6 is provided with a differential pressure sensor Se4. The differential pressure sensor Se4 measures the differential pressure between the exhaust gas pressure upstream of the EGR valve V2 and the exhaust gas pressure downstream of the EGR valve V2. The differential pressure sensor Se4 is communicably connected to the ECU 50 . The ECU 50 controls the EGR valve V2 based on the differential pressure measured by the differential pressure sensor Se4.

The system 100 includes an ECU (control device) 50 . The ECU 50 has one or more processors 51 (such as CPU), one or more storage media 52 (such as ROM and RAM), and one or more connectors 53 . The ECU 50 may further have other components. Components of the ECU 50 are communicatively connected to each other by a bus. Storage medium 52 stores one or more programs executed by processor 51 . The program includes instructions for processor 51 . The operation of the ECU 50 shown in this disclosure is realized by the processor 51 executing instructions stored in the storage medium 52 . ECU 50 is communicatively connected to components of system 100 via connector 53 .

The engine 10 of the system 100 as described above is capable of lean burn operation. Lean burn uses a mixture with a high air-fuel ratio compared to the stoichiometric air-fuel ratio (approximately 14.7). When operating at lean burn, the engine 10 first injects fuel into the intake during the intake stroke and then injects a very small amount of fuel into the mixture during the subsequent compression stroke in order to stabilize the ignition of the mixture. Inject fuel. According to such a configuration, an air-fuel mixture having a higher fuel concentration is produced only in a limited area around the spark plug P. In the present disclosure, "main injection" means injecting fuel into the intake air during the intake stroke, and "main injection amount" means the amount of fuel injected in the main injection. Further, in the present disclosure, "assist injection" means injecting fuel into the air-fuel mixture in the compression stroke, and "assist injection amount" means the amount of fuel injected in the assist injection. do.

FIG. 2 is a functional block diagram of the ECU 50. As shown in FIG. When the engine 10 operates in lean burn mode, the processor 51 controls the main injection section 54, the assist injection section 55, the first adjustment section 56, the second adjustment section 57, the third adjustment It functions as a section 58 and a fourth adjustment section 59 .

When functioning as the main injection section 54, the processor 51 controls the injector 17 and the throttle valve V1 so as to inject fuel into the intake air during the intake stroke. The main injection creates a mixture of air and fuel in the combustion chamber 13 . For example, the processor 51 may determine the main injection amount according to factors such as the depression amount of the accelerator pedal. For example, the storage medium 52 may store a table showing the relationship between the amount of depression of the accelerator pedal and the amount of main injection at the start of lean-burn operation. During lean burn operation, the main injection amount or the air-fuel ratio in the main injection may be adjusted (details will be described later).

When functioning as the assist injection unit 55, the processor 51 controls the injector 17 to inject a very small amount of fuel into the air-fuel mixture in the combustion chamber 13 in the compression stroke following the intake stroke. According to such a configuration, an air-fuel mixture having a higher fuel concentration is produced only in a limited area around the spark plug P. For example, the processor 51 may determine the assist injection amount according to factors such as the main injection amount. For example, the storage medium 52 may store a table showing the relationship between the main injection amount and the assist injection amount at the start of lean burn operation. During lean burn operation, the assist injection amount may be adjusted (details will be described later).

FIG. 3 is a schematic diagram for explaining the relationship between the NOx concentration and the rotation fluctuation of the engine 10 in lean burn. In FIG. 3 , the solid line indicates the relationship between the NOx concentration and the rotation fluctuation when the assist injection amount is within the target range, and is the target of the processing by the ECU 50 . Therefore, the relationship between the NOx concentration and the rotational variation shown by the solid line is known. The ECU 50 adjusts the assist injection amount so that the measured NOx concentration and rotation fluctuation approach the solid line (details will be described later). A dashed line shows an example of the relationship between the NOx concentration and the rotation fluctuation when the assist injection amount is outside the target range. The dashed line is merely an example, and the actual relationship between the NOx concentration and the rotation fluctuation when the assist injection amount is out of the target range may differ from the dashed line.

In the lean-burn operation of the present disclosure, both suppression of NOx emissions and stabilization of combustion are required. Specifically, regarding the NOx concentration (horizontal axis), the system 100 suppresses the NOx concentration to the threshold value Th1 or less. Regarding the stability of combustion (vertical axis), the combustion fluctuation (CPi) indicating the stability of combustion has a correlation with the rotation fluctuation of the engine 10, for example. Therefore, in the present embodiment, the processor 51 calculates rotation fluctuations (for example, angular velocity fluctuations) based on the rotation speed of the engine 10 measured by the crank angle sensor Se1. For example, the variation in angular velocity can be calculated from the difference in angular velocity in successive expansion strokes of the same cylinder based on the signal from the crank angle sensor, or from the integrated value of the absolute value of this difference for a predetermined number of consecutive times. The system 100 suppresses the rotation fluctuation to be equal to or less than the threshold Th2.

When the air-fuel ratio is low (fuel rich), the NOx concentration increases while the rpm fluctuation decreases, as shown by both the solid and dashed lines. Also, when the assist injection amount is lower than the target range (broken line), combustion is not stable, so the rotational fluctuation increases compared to when the assist injection amount is within the target range (solid line). Therefore, while executing both the main injection and the assist injection, the system 100 first adjusts the air-fuel ratio to control the NOx concentration within an appropriate range (th1 or less), and then adjusts the assist injection amount. to control the rotational fluctuation to an appropriate range (below Th2). That is, the system 100 sequentially adjusts the air-fuel ratio and the assist injection so that the NOx concentration and rotation fluctuation fall within the regions shown by hatching in FIG. For example, thresholds Th1 and Th2 may be stored in storage medium 52 .

Referring to FIG. 2, processor 51 functions as a first adjuster 56, a second adjuster 57, a third adjuster 58, and a fourth adjuster 59 for this purpose.

When functioning as a first adjuster (which may also be referred to as an "A/F adjuster") 56, the processor 51 controls at least one of the injector 17 and the throttle valve V1 during the intake stroke so that the air-fuel ratio is within the target range. to adjust the air-fuel ratio. Specifically, the processor 51 determines whether the air-fuel ratio received from the A/F sensor Se2 is within the target range. When it is determined that the air-fuel ratio is not within the target range, the ECU 50 controls at least one of the injector 17 and the throttle valve V1 during the intake stroke to adjust the air-fuel ratio so that the air-fuel ratio is within the target range. . For example, the target air-fuel ratio range may be stored in the storage medium 52 .

When functioning as a second adjuster (which may also be referred to as an "EGR adjuster") 57, the processor 51 controls the EGR valve V2 so that the flow rate of recirculated exhaust gas is within a target range. For example, since the flow rate of the recirculated exhaust gas has a correlation with the differential pressure (or pressure ratio) between the pressure on the upstream side and the pressure on the downstream side of the EGR valve V2, this differential pressure (or pressure ratio ), the recirculated exhaust gas flow rate can be measured (estimated). Accordingly, the processor 51 determines whether the differential pressure received from the differential pressure sensor Se4 is within the target range. If it is determined that the differential pressure is not within the target range, the processor 51 controls the EGR output so that the differential pressure is within the target range (i.e., the recirculated exhaust gas flow rate is within the target range). Control valve V2. For example, the target range of differential pressure (or the target range of flow rate) may be stored in the storage medium 52 . A table showing the relationship between the flow rate of the recirculated exhaust gas and the differential pressure may also be stored in the storage medium 52 .

In general, lean burn produces a large amount of NOx due to a large amount of air (oxygen). As such, the system 100 may implement EGR to control NOx emissions. Specifically, since the exhaust gases are rich in inert carbon dioxide, recirculating the exhaust gases into the intake air can reduce the oxygen percentage in the intake air. Therefore, EGR can suppress NOx emissions. However, if NOx emissions can be suppressed to the threshold value Th1 or less only by adjusting the air-fuel ratio, the system 100 does not need to perform EGR.

When functioning as a third adjuster (which may also be referred to as a “NOx adjuster”) 58, the processor 51 adjusts the injector 17 or throttle valve V1 during the intake stroke so that the NOx concentration in the exhaust gas is within the target range. At least one of them is controlled to adjust the air-fuel ratio of the air-fuel mixture. Specifically, the processor 51 determines whether the NOx concentration measured by the NOx sensor Se3 is within the target range. If it is determined that the NOx concentration is not within the target range, the processor 51 controls at least one of the injector 17 and the throttle valve V1 during the intake stroke to adjust the air-fuel ratio so that the NOx concentration is within the target range. do. In this case, the target air-fuel ratio range stored in the storage medium 52 may be updated as well. For example, the target range for NOx concentration may be stored in storage medium 52 .

When functioning as a fourth adjuster (also referred to as a "combustion fluctuation adjuster") 59, the processor 51 controls the injector 17 so that the combustion fluctuation in the engine 10 is within a target range, and the assist injection amount is to adjust. Specifically, the processor 51 determines whether or not the rotation fluctuation measured by the crank angle sensor Se1 is within the target range. When it is determined that the rotational fluctuation is not within the target range, the processor 51 controls the injector 17 in the compression stroke to adjust the assist injection amount so as to be within the target range.

Next, the operation of system 100 will be described.

FIG. 4 is a flow chart showing the processing of the ECU 50. As shown in FIG. For example, the process shown in FIG. 4 may be performed only once after engine 10 starts lean-burn operation, or may be performed at predetermined intervals (eg, ten to several tens of milliseconds, one hundred to several hundred milliseconds). , one to several seconds, ten to several tens of seconds, or one to several minutes).

Processor 51 controls injector 17 and throttle valve V1 to perform main injection (step S100). Processor 51 then controls injector 17 to perform assist injection (step S102).

Subsequently, the processor 51 determines whether the air-fuel ratio received from the A/F sensor (fourth sensor) Se2 is within the target range (fourth target range) (step S104). If it is determined in step S104 that the air-fuel ratio is not within the target range (NO), the processor 51 considers the difference between the actual air-fuel ratio and the target range, and adjusts the air-fuel ratio so that it is within the target range. , the command value to at least one of the injector 17 and the throttle valve V1 in the main injection is corrected (step S106), and the process returns to step S100. At step S100 of the next routine, at least one of the injector 17 and the throttle valve V1 is controlled based on the corrected command value to adjust the air-fuel ratio.

If it is determined in step S104 that the air-fuel ratio is within the target range (YES), the processor 51 determines that the differential pressure received from the differential pressure sensor (third sensor) Se4 is within the target range (third target range). (step S108). In step S108, if it is determined that the differential pressure is not within the target range (NO), the processor 51 considers the difference between the actual differential pressure and the target range so that the differential pressure is within the target range. (That is, so that the flow rate of the recirculated exhaust gas is within the target range), the command value to the EGR valve V2 is adjusted (step S110), and the process returns to step S100.

If it is determined in step S108 that the differential pressure is within the target range (YES), the processor 51 determines that the NOx concentration measured by the NOx sensor (first sensor) Se3 is within the target range (first target range). (step S112). If it is determined in step S112 that the NOx concentration is not within the target range (NO), the processor 51 considers the difference between the actual NOx concentration and the target range, and adjusts the NOx concentration to be within the target range. , the command value to at least one of the injector 17 and the throttle valve V1 in the main injection is corrected (step S114), and the process returns to step S100. At step S100 of the next routine, at least one of the injector 17 and the throttle valve V1 is controlled based on the corrected command value to adjust the air-fuel ratio.

Referring to FIG. 3, for example, the NOx concentration target range (first target range) in step S112 may be Th3 or more and Th4 or less, which is smaller than threshold Th1. For example, this range can be a region in which the rotation fluctuation is equal to or less than the threshold Th2 when the assist injection amount is within the target range (solid line). For example, the lower limit value Th3 can be a lower limit value at which the rotation fluctuation is equal to or less than the threshold value Th2 when the assist injection amount is within the target range (solid line). Further, by setting the upper limit of the target range to Th4, which is smaller than the threshold Th1, it is possible to suppress a situation in which the assist injection amount is outside the target range (broken line) and the rotation fluctuation is equal to or less than the threshold Th2. Therefore, it is possible to prevent a situation in which the assist injection amount is not adjusted even though the assist injection amount is outside the target range (broken line). Note that the target range is not limited to this, and may be another range associated with the threshold Th1. For example, in step S112, if the NOx concentration measured by the NOx sensor Se3 is at a point P1 higher than the upper limit value Th4, the NOx concentration can be reduced to a point P2 between Th3 and Th4.

Referring to FIG. 4, if it is determined in step S112 that the NOx concentration is within the target range (YES), processor 51 determines that the rotational fluctuation measured by crank angle sensor (second sensor) Se1 is within the target range. It is determined whether or not it is within the range (second target range) (step S116). If it is determined in step S116 that the rotation fluctuation is not within the target range (NO), the processor 51 considers the difference between the actual rotation fluctuation and the target range, and adjusts the rotation fluctuation so that the rotation fluctuation is within the target range. , corrects the command value to the injector 17 in the assist injection (step S118), and returns to step S100. In step S102 of the next routine, the injector 17 is controlled based on the corrected command value to adjust the assist injection amount.

Referring to FIG. 3, for example, the target range (second target range) of rotation fluctuation in step S116 may be greater than 0 and equal to or less than threshold Th2. For example, in step S116, if the rotation fluctuation measured by the crank angle sensor Se1 is at a point P2 higher than the threshold Th2, the adjustment (increase) of the assist injection amount in step S102 of the next routine causes the rotation fluctuation to exceed the threshold Th2. It can be reduced to point P3, which is:

If it is determined in step S116 that the rotation fluctuation is within the target range (YES), processor 51 terminates the series of processes. The corrected command value may be stored in storage medium 52 . Subsequent lean-burn operation may be performed based on the data stored in the storage medium 52 .

The system 100 as described above includes an engine 10, a NOx sensor Se3 that measures the NOx concentration in the exhaust gas from the engine 10, a crank angle sensor Se1 that measures rotation fluctuation indicating the degree of combustion fluctuation of the engine 10, and an ECU 50 that controls the engine 10 . ECU 50 includes one or more processors 51 and one or more storage media 52 that store instructions to be executed by one or more processors 51 . The one or more processors 51 are instructed to inject fuel into the intake air during the intake stroke and inject less fuel into the air and fuel mixture during the compression stroke than during the intake stroke. determining whether the NOx concentration measured by the NOx sensor Se3 is within the first target range; and determining that the NOx concentration is not within the first target range. The air-fuel ratio of the air-fuel mixture in the intake stroke is adjusted so as to be within the first target range, and the rotation fluctuation measured by the crank angle sensor Se1 when it is determined that the NOx concentration is within the first target range. is within the second target range, and if it is determined that the rotation fluctuation is not within the second target range, the assist injection amount is adjusted so that the rotation fluctuation is within the second target range. and configured to perform the According to the system 100 as described above, the assist injection amount is controlled so that the NOx concentration is controlled within the first target range and the rotation fluctuation indicating the degree of combustion fluctuation is controlled within the second target range. be. Therefore, in lean-burn operation, the assist injection amount can be controlled while suppressing NOx emissions and stabilizing combustion.

The system 100 also includes a pipe 6 that connects an exhaust pipe 3 and an intake pipe 2 of the engine 10 and recirculates exhaust gas from the exhaust pipe 3 to the intake pipe 2, an EGR valve V2 provided in the pipe 6, and a pipe a differential pressure sensor Se4 for measuring the flow rate of the exhaust gas flowing through 6; Before determining whether the NOx concentration is within the first target range, the one or more processors 51 follow the instruction to determine whether the flow rate of the exhaust gas measured by the differential pressure sensor Se4 is within the third target range. and controlling the EGR valve V2 so that the flow rate of the exhaust gas is within the third target range when it is determined that the flow rate of the exhaust gas is not within the third target range. and further configured to perform: According to such a system 100, EGR can reduce the percentage of oxygen in the intake air. Therefore, NOx emissions can be efficiently suppressed.

Although the embodiments have been described above with reference to the accompanying drawings, the present invention is not limited to such embodiments. It is obvious that a person skilled in the art can conceive of various modifications or modifications within the scope of the claims, and it should be understood that these also belong to the technical scope of the present invention. be done. Further, the steps of the ECU 50 of the above embodiment do not have to be performed in the above order, and may be performed in a different order as long as there is no technical contradiction.

For example, in the above embodiment, differential pressure sensor Se4 is used as the third sensor for measuring the flow rate of recirculated exhaust gas. However, in other embodiments, the third sensor is configured to measure the "pressure ratio" between the exhaust gas pressure upstream of EGR valve V2 and the exhaust gas pressure downstream of EGR valve V2. may be In this case, the ECU 50 may store a table showing the relationship between the pressure ratio and the recirculated exhaust gas flow rate.

Further, in the above embodiment, the rotation fluctuation measured by the crank angle sensor Se1 is used as the index value indicating the degree of combustion fluctuation. However, in other embodiments, other parameters (for example, variations in cylinder pressure during combustion for each ignition cycle) measured by other sensors (for example, cylinder pressure sensors) may be used as index values. .

2 intake pipe 3 exhaust pipe 6 pipe for recirculating exhaust gas 10 engine 17 injector 50 ECU (control device)
51 processor 52 storage medium 100 engine control system Se1 crank angle sensor (second sensor)
Se3 NOx sensor (first sensor)
Se4 differential pressure sensor (third sensor)
V2 EGR valve

Claims (2)

engine and
a first sensor for measuring the concentration of nitrogen oxides in exhaust gas from the engine;
a second sensor that measures an index value indicating the degree of combustion fluctuation of the engine;
a control device that controls the engine;
with
the controller includes one or more processors and one or more storage media storing instructions to be executed by the one or more processors;
The one or more processors, according to the instructions,
injecting fuel into the intake air during the intake stroke;
injecting less fuel into a mixture of air and fuel on a compression stroke than on the intake stroke;
determining whether the concentration of nitrogen oxides measured by the first sensor is within a predetermined first target range;
adjusting the air-fuel ratio of the air-fuel mixture in the intake stroke so that the concentration of nitrogen oxides is within the first target range when it is determined that the concentration of nitrogen oxides is not within the first target range; to adjust and
Determining whether the index value measured by the second sensor is within a predetermined second target range when the concentration of nitrogen oxides is determined to be within the first target range. and
adjusting the amount of fuel injected in the compression stroke so that the index value is within the second target range when it is determined that the index value is not within the second target range;
an engine control system configured to perform a pipe that connects an exhaust pipe and an intake pipe of the engine and recirculates the exhaust gas from the exhaust pipe to the intake pipe;
a valve provided in the pipe;
a third sensor that measures the flow rate of the exhaust gas flowing through the pipe;
further comprising
Before determining whether the concentration of nitrogen oxides is within the first target range, the one or more processors, according to the instructions,
determining whether the flow rate of the exhaust gas measured by the third sensor is within a predetermined third target range;
adjusting the valve so that the flow rate of the exhaust gas is within the third target range when it is determined that the flow rate of the exhaust gas is not within the third target range;
2. The engine control system of claim 1, further configured to perform:

Images