JP7614909B2 - Engine Management System - Google Patents

Description

The present invention relates to an engine control system.

Engines may be operated in lean burn mode. In lean burn, a low fuel mixture is used, so in order to stabilize ignition, a small amount of fuel may be injected in the compression stroke in addition to the intake stroke. However, since the amount of fuel injected in the compression stroke is extremely small, it may be difficult to inject an accurate amount of fuel. Therefore, various techniques have been proposed for controlling the amount of fuel injected in the compression stroke in lean burn (e.g., Patent Document 1).

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

JP 2018-3622 A

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

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

An engine control system according to one aspect of the present invention comprises:
The engine,
a first sensor for measuring a concentration of nitrogen oxides in exhaust gas from the engine;
A second sensor for measuring an index value indicating a degree of combustion fluctuation of the engine;
A control device for controlling the engine;
Equipped with
the control device includes one or more processors and one or more storage media that store instructions executed by the one or more processors;
The one or more processors, in accordance with the instructions,
injecting fuel into the intake air during the intake stroke;
injecting less fuel into the air and fuel mixture during the compression stroke than during the intake stroke;
determining whether the concentration of nitrogen oxides measured by the first sensor is within a predetermined first target range;
when it is determined that the concentration of nitrogen oxides is not within the first target range, adjusting an air-fuel ratio of the 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 the nitrogen oxides is within the first target range, determining whether or not the index value measured by the second sensor is within a predetermined second target range;
When it is determined that the index value is not within the second target range, adjusting an amount of fuel injected during the compression stroke so that the index value is within the second target range;
The apparatus is configured to execute the following steps:

According to the present invention, during lean burn operation, it is possible to control the amount of fuel injected during the compression stroke while suppressing NOx emissions and stabilizing combustion.

FIG. 1 is a schematic diagram showing an engine control system according to an 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 NOx concentration and engine rotation fluctuation in lean burn. FIG. 4 is a flowchart showing the processing of the ECU.

The following describes in detail an embodiment of the present invention with reference to the attached drawings. The specific dimensions, materials, values, etc. shown in the embodiment are merely examples for ease of understanding, and do not limit the present invention unless otherwise specified. In the specification and drawings, elements that have substantially the same functions and configurations are given the same reference numerals to avoid duplicated explanations. Also, elements that are not directly related to the present invention are not shown.

FIG. 1 is a schematic diagram showing an engine control system 100 according to one embodiment of the present invention. The engine control system (which may also be simply referred to as the "system" in this disclosure) 100 is applied to a vehicle 500, such as a hybrid electric vehicle (HEV), a gasoline-powered automobile, or a diesel-powered automobile. The system 100 includes an engine 10.

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

In the engine 10 described above, a mixture of air and fuel (gasoline) is burned in the combustion chamber 13, causing the piston 12 to move back and forth within the cylinder 11. The linear motion of the piston 12 is transmitted to the crankshaft 18 by the connecting rod 14 and converted into the rotational 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 communicatively connected to the ECU 50 (described in detail later). Note that for better understanding, only one pair of cylinders 11 and pistons 12 is shown in FIG. 1, but the engine 10 can have multiple pairs of cylinders 11 and pistons 12.

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

The engine 10 has a fuel injector 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 connected to the ECU 50 so as to be able to communicate with it. For example, the ECU 50 controls the amount of fuel injected from the injector 17 by controlling the lift of a needle valve of the injector 17.

The engine 10 has an ignition plug P. The ignition plug P is provided in the combustion chamber 13 and ignites a mixture of air and fuel in the combustion chamber 13. The ignition plug P is connected to the ECU 50 so as to be able to communicate with it. The ECU 50 controls the operation of the ignition plug P.

The intake pipe 2 is connected to the intake port 15. The intake pipe 2 is provided with components such as an air cleaner (not shown), and air that has passed through these components is supplied to the combustion chamber 13 via the intake port 15. The intake pipe 2 is provided with a throttle valve V1 for adjusting the flow rate of air flowing through the intake pipe 2. The throttle valve V1 is connected to the ECU 50 so as to be able to communicate with it. The ECU 50 controls the amount of intake air by controlling the throttle valve V1.

The exhaust pipe 3 is connected to the exhaust port 16. An air-fuel ratio (A/F) sensor Se2 is provided in the exhaust pipe 3. The A/F sensor Se2 measures the air-fuel ratio based on the exhaust gas flowing through the exhaust pipe 3. The A/F sensor Se2 is connected to the ECU 50 so as to be able to communicate with it. For example, the ECU 50 controls at least one of the injector 17 or the throttle valve V1 based on the air-fuel ratio measured by the A/F sensor Se2.

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

In the exhaust pipe 3, a NOx sensor Se3 is provided downstream of the front catalyst 4. 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 communicatively connected to the ECU 50. For example, the ECU 50 controls at least one of the injector 17 or 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) (e.g., soot) from the exhaust gas. The particulate filter 5 is, for example, a gasoline particulate filter (GPF). In other embodiments, for example, when the engine 10 is a diesel engine, the particulate filter 5 may be a diesel particulate filter (DPF).

In the exhaust pipe 3, upstream of the A/F sensor Se2, a pipe 6 is connected for recirculating exhaust gas to the intake pipe 2. 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 the recirculated exhaust gas. The EGR valve V2 is connected to the ECU 50 so as to be able to communicate with it. The ECU 50 controls the EGR valve V2 to control the flow rate of the recirculated exhaust gas.

A differential pressure sensor Se4 is provided in the pipe 6. 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 communicatively 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 includes one or more processors 51 (e.g., a CPU, etc.), one or more storage media 52 (e.g., a ROM and a RAM, etc.), and one or more connectors 53. The ECU 50 may further include other components. The components of the ECU 50 are communicatively connected to each other via a bus. The storage medium 52 stores one or more programs executed by the processor 51. The programs include instructions for the processor 51. The operation of the ECU 50 shown in this disclosure is realized by the processor 51 executing the instructions stored in the storage medium 52. The ECU 50 is communicatively connected to the components of the system 100 via the connector 53.

The engine 10 of the system 100 described above can be operated in lean burn. Lean burn uses a mixture with a high air-fuel ratio compared to the theoretical air-fuel ratio (approximately 14.7). When operating in lean burn, in order to stabilize the ignition of the mixture, the engine 10 first injects fuel into the intake air during the intake stroke, and then injects a very small amount of fuel into the mixture during the compression stroke. With this configuration, a mixture with a higher fuel concentration is generated only in a limited area around the spark plug P. In this 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. In this disclosure, "assist injection" means injecting fuel into the mixture during the compression stroke, and "assist injection amount" means the amount of fuel injected in the assist injection.

Figure 2 is a functional block diagram of the ECU 50. When the engine 10 is operating in lean burn mode, the processor 51 functions as a main injection unit 54, an assist injection unit 55, a first adjustment unit 56, a second adjustment unit 57, a third adjustment unit 58, and a fourth adjustment unit 59 in accordance with instructions stored in the storage medium 52.

When functioning as the main injection unit 54, the processor 51 controls the injector 17 and the throttle valve V1 to inject fuel into the intake air during the intake stroke. A mixture of air and fuel is generated in the combustion chamber 13 by the main injection. For example, the processor 51 may determine the main injection amount depending on factors such as the amount of depression of the accelerator pedal. For example, a table showing the relationship between the amount of depression of the accelerator pedal at the start of lean burn operation and the main injection amount may be stored in the storage medium 52. During lean burn operation, the main injection amount or the air-fuel ratio in the main injection may be adjusted (described in detail below).

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 mixture in the combustion chamber 13 during the compression stroke following the intake stroke. With this configuration, a mixture with a higher fuel concentration is generated only in a limited area around the spark plug P. For example, the processor 51 may determine the assist injection amount depending on factors such as the main injection amount. For example, a table showing the relationship between the main injection amount and the assist injection amount at the start of lean burn operation may be stored in the storage medium 52. During lean burn operation, the assist injection amount may be adjusted (described in detail below).

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

In the lean burn operation of the present disclosure, it is required to both suppress NOx emissions and stabilize combustion. Specifically, with respect to the NOx concentration (horizontal axis), the system 100 suppresses the NOx concentration to a threshold value Th1 or less. Also, with respect to the combustion stability (vertical axis), the combustion fluctuation (CPi) indicating the stability of combustion is correlated with, for example, the rotation fluctuation of the engine 10. Therefore, in this embodiment, the processor 51 calculates the rotation fluctuation (for example, the angular velocity fluctuation) based on the engine 10 rotation speed measured by the crank angle sensor Se1. For example, the angular velocity fluctuation can be calculated based on the signal from the crank angle sensor by the difference in angular velocity during consecutive expansion strokes of the same cylinder, or 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 a threshold value Th2 or less.

When the air-fuel ratio is low (fuel is rich), as shown by both the solid and dashed lines, the rotational fluctuation decreases while the NOx concentration increases. Also, when the assist injection amount is lower than the target range (dashed line), combustion is not stable, and the rotational fluctuation increases compared to when the assist injection amount is within the target range (solid line). Therefore, while performing both main injection and assist injection, the system 100 first adjusts the air-fuel ratio to control the NOx concentration to an appropriate range (Th1 or less), and then adjusts the assist injection amount to control the rotational fluctuation to an appropriate range (Th2 or less). That is, the system 100 adjusts the air-fuel ratio and the assist injection in order so that the NOx concentration and the rotational fluctuation are in the hatched areas in FIG. 3. For example, the threshold values Th1 and Th2 may be stored in the storage medium 52.

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

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

When functioning as the second adjustment unit (which may also be referred to as the "EGR adjustment unit") 57, the processor 51 controls the EGR valve V2 so that the flow rate of the recirculated exhaust gas falls within a target range. For example, since the flow rate of the recirculated exhaust gas is correlated with the differential pressure (or pressure ratio) between the pressures upstream and downstream of the EGR valve V2, the flow rate of the recirculated exhaust gas can be measured (estimated) by measuring this differential pressure (or pressure ratio). Therefore, 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 valve V2 so that the differential pressure falls within the target range (i.e., so that the flow rate of the recirculated exhaust gas falls within the target range). For example, the target range of the differential pressure (or the target range of the flow rate) may be stored in the storage medium 52. Also, a table showing the relationship between the flow rate of the recirculated exhaust gas and the differential pressure may be stored in the storage medium 52.

Generally, lean burn generates a large amount of NOx because of the large amount of air (oxygen). For this reason, system 100 may implement EGR to suppress NOx emissions. Specifically, exhaust gas contains a large amount of inert carbon dioxide, so the proportion of oxygen in the intake air can be reduced by recirculating exhaust gas into the intake air. Therefore, EGR can suppress NOx emissions. However, if NOx emissions can be suppressed to below threshold value Th1 by adjusting the air-fuel ratio alone, system 100 does not need to implement EGR.

When functioning as the third adjustment unit (which may also be referred to as the "NOx adjustment unit") 58, the processor 51 adjusts the air-fuel ratio of the mixture by controlling at least one of the injector 17 or the throttle valve V1 during the intake stroke so that the NOx concentration in the exhaust gas falls within a target range. 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 adjusts the air-fuel ratio by controlling at least one of the injector 17 or the throttle valve V1 during the intake stroke so that the NOx concentration falls within the target range. In this case, the target range of the air-fuel ratio stored in the storage medium 52 may also be updated. For example, the target range of the NOx concentration may be stored in the storage medium 52.

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

Next, the operation of the system 100 will be explained.

Figure 4 is a flowchart showing the processing of the ECU 50. For example, the processing shown in Figure 4 may be performed only once after the engine 10 starts lean burn operation, or may be repeated at a predetermined interval (for example, tens to tens of milliseconds, a hundred to hundreds of milliseconds, one to several seconds, ten to tens of seconds, or one to several minutes).

The processor 51 controls the injector 17 and the throttle valve V1 to perform a main injection (step S100). Next, the processor 51 controls the injector 17 to perform an assist injection (step S102).

Then, 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 corrects the command value for at least one of the injector 17 or the throttle valve V1 in the main injection, taking into account the difference between the actual air-fuel ratio and the target range, so that the air-fuel ratio is within the target range (step S106), and returns to step S100. In step S100 of the next routine, at least one of the injector 17 or the throttle valve V1 is controlled based on the corrected command value, and the air-fuel ratio is adjusted.

If it is determined in step S104 that the air-fuel ratio is within the target range (YES), the processor 51 determines whether the differential pressure received from the differential pressure sensor (third sensor) Se4 is within the target range (third target range) (step S108). If it is determined in step S108 that the differential pressure is not within the target range (NO), the processor 51 adjusts the command value to the EGR valve V2 (step S110) so that the differential pressure is within the target range (i.e., so that the flow rate of the recirculated exhaust gas is within the target range) while taking into account the difference between the actual differential pressure and the target range, and then returns to step S100.

If it is determined in step S108 that the pressure difference is within the target range (YES), the processor 51 determines whether 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 corrects the command value for at least one of the injector 17 or the throttle valve V1 in the main injection, taking into account the difference between the actual NOx concentration and the target range, so that the NOx concentration is within the target range (step S114), and returns to step S100. In step S100 of the next routine, at least one of the injector 17 or the throttle valve V1 is controlled based on the corrected command value, and the air-fuel ratio is adjusted.

With reference to FIG. 3, for example, the target range (first target range) of the NOx concentration in step S112 may be equal to or greater than Th3 and equal to or less than Th4, which is smaller than the threshold value Th1. For example, this range can be a region in which the rotational fluctuation is equal to or less than the threshold value 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 in which the rotational fluctuation is equal to or less than the threshold value Th2 when the assist injection amount is within the target range (solid line). In addition, by setting the upper limit value of the target range to Th4, which is smaller than the threshold value Th1, it is possible to suppress a situation in which the assist injection amount is outside the target range (dashed line) and the rotational fluctuation is equal to or less than the threshold value Th2. Therefore, it is possible to suppress a situation in which the assist injection amount is not adjusted even though the assist injection amount is outside the target range (dashed line). Note that the target range is not limited to this, and may be another range associated with the threshold value Th1. For example, in step S112, if the NOx concentration measured by the NOx sensor Se3 is at point P1, which is higher than the upper limit value Th4, the NOx concentration can be reduced to point P2 between Th3 and Th4 by adjusting (increasing) the air-fuel ratio (reducing the amount of fuel) in step S100 of the next routine.

Referring to FIG. 4, if it is determined in step S112 that the NOx concentration is within the target range (YES), the processor 51 determines whether the rotational fluctuation measured by the crank angle sensor (second sensor) Se1 is within the target range (second target range) (step S116). If it is determined in step S116 that the rotational fluctuation is not within the target range (NO), the processor 51 corrects the command value to the injector 17 for the assist injection, taking into account the difference between the actual rotational fluctuation and the target range, so that the rotational fluctuation is within the target range (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, and the assist injection amount is adjusted.

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

If it is determined in step S116 that the rotational fluctuation is within the target range (YES), the processor 51 ends the series of processes. The corrected command value may be stored in the storage medium 52. The 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 exhaust gas from the engine 10, a crank angle sensor Se1 that measures rotational fluctuations that indicate the degree of combustion fluctuation in the engine 10, and an ECU 50 that controls the engine 10. The ECU 50 includes one or more processors 51 and one or more storage media 52 that store instructions executed by the one or more processors 51. The one or more processors 51 are configured to execute the following operations according to the instructions: inject fuel into the intake air during the intake stroke; inject less fuel into the air-fuel mixture during the compression stroke than during the intake stroke; determine whether the NOx concentration measured by the NOx sensor Se3 is within a first target range; if it is determined that the NOx concentration is not within the first target range, adjust the air-fuel ratio of the mixture during the intake stroke so that the NOx concentration is within the first target range; if it is determined that the NOx concentration is within the first target range, determine whether the rotational fluctuation measured by the crank angle sensor Se1 is within a second target range; if it is determined that the rotational fluctuation is not within the second target range, adjust the assist injection amount so that the rotational fluctuation is within the second target range. According to the system 100, the assist injection amount is controlled so that the NOx concentration is controlled within the first target range and the rotational fluctuation indicating the degree of combustion fluctuation is controlled within the second target range. Therefore, during lean burn operation, the assist injection amount can be controlled while suppressing NOx emissions and stabilizing combustion.

The system 100 further includes a pipe 6 that connects the exhaust pipe 3 and the 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 differential pressure sensor Se4 that measures the flow rate of exhaust gas flowing through the pipe 6. Before determining whether the NOx concentration is within the first target range, the one or more processors 51 are further configured to determine whether the flow rate of exhaust gas measured by the differential pressure sensor Se4 is within a third target range according to the instruction, and, if it is determined that the flow rate of exhaust gas is not within the third target range, to control the EGR valve V2 so that the flow rate of exhaust gas is within the third target range. According to the system 100, the proportion of oxygen in the intake air can be reduced by EGR. Therefore, the emission of NOx can be efficiently suppressed.

Although the embodiment has been described above with reference to the attached drawings, the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modified or revised examples within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. In addition, the steps of the ECU 50 in the above embodiment do not have to be performed in the above order, and may be performed in a different order as long as no technical contradiction occurs.

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

In addition, in the above embodiment, the rotational fluctuation measured by the crank angle sensor Se1 is used as an index value indicating the degree of combustion fluctuation. However, in other embodiments, other parameters (e.g., fluctuations in in-cylinder pressure during combustion for each ignition cycle) measured by other sensors (e.g., in-cylinder pressure sensor) may be used as the index value.

2 Intake pipe 3 Exhaust pipe 6 Pipe for recirculating exhaust gas 10 Engine 17 Injector 50 ECU (control unit)
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)

The engine,
a first sensor for measuring a concentration of nitrogen oxides in exhaust gas from the engine;
A second sensor for measuring an index value indicating a degree of combustion fluctuation of the engine;
A control device for controlling the engine;
Equipped with
the control device includes one or more processors and one or more storage media that store instructions executed by the one or more processors;
The one or more processors, in accordance with the instructions,
injecting fuel into the intake air during the intake stroke;
injecting less fuel into the air and fuel mixture during the compression stroke than during the intake stroke;
determining whether the concentration of nitrogen oxides measured by the first sensor is within a first predetermined target range;
when it is determined that the concentration of nitrogen oxides is not within the first target range, adjusting an air-fuel ratio of the 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 the nitrogen oxides is within the first target range, determining whether or not the index value measured by the second sensor is within a predetermined second target range;
When it is determined that the index value is not within the second target range, adjusting an amount of fuel injected during the compression stroke so that the index value is within the second target range;
an engine control system configured to: 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 piping;
a third sensor that measures a flow rate of the exhaust gas flowing through the pipe;
Further comprising:
Prior to determining whether the concentration of oxides of nitrogen is within the first target range, the one or more processors, in accordance with the instructions,
determining whether the flow rate of the exhaust gas measured by the third sensor is within a predetermined third target range;
When it is determined that the flow rate of the exhaust gas is not within the third target range, adjusting the valve so that the flow rate of the exhaust gas is within the third target range;
The engine control system of claim 1 further configured to:

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