JP7375696B2 - Internal combustion engine control device and control method - Google Patents

Description

This disclosure relates to a control device and a control method for an internal combustion engine, and particularly to a control device and a control method for an internal combustion engine that includes an injection system that injects fuel at a controlled pressure.

BACKGROUND ART Conventionally, in a diesel engine, when fuel is injected multiple times in one cycle, there has been a combustion method in which main injection is divided into a first stage and a second stage (for example, see Patent Document 1). Hereinafter, this combustion method will be referred to as main two-stage injection combustion. In main two-stage injection combustion, by adjusting the interval between the injection timing of the previous stage of main injection and the injection timing of the latter stage, the pressure waves during combustion in the former stage and the pressure waves during combustion in the latter stage cancel each other out. , noise can be reduced. However, in main two-stage injection combustion, it is known that smoke worsens due to a short ignition delay in the subsequent stage of main injection.

In response to this, smoke characteristics can be improved by increasing the rail pressure of the common rail. Increasing the rail pressure worsens combustion noise. However, in this regard, by keeping the increase in rail pressure to the minimum necessary, it is possible to meet the targets for both combustion noise and smoke.

Japanese Patent Application Publication No. 2015-068284

Here, in the control map for the internal combustion engine, there are regions where main two-stage injection combustion and other combustion methods are suitable and regions where they are not suitable. If a plurality of combustion methods are simply switched on a control map, there is a concern that combustion noise and smoke may worsen at the time of switching.

This disclosure has been made in order to solve the above-mentioned problems, and the purpose is to provide an internal combustion engine control device and control device that can suppress deterioration of combustion noise and smoke when switching between multiple combustion methods. The purpose is to provide a method.

A control device according to this disclosure controls an internal combustion engine. Internal combustion engines include an injection system that injects fuel at controlled pressure. When switching to one of a plurality of combustion methods in an internal combustion engine, the control device calculates each injection amount in multiple stages of fuel injection per cycle according to the switched combustion method, and The injection system is controlled to inject fuel in multiple stages with an injection amount of From this, the injection amount is calculated so as to gradually change to the injection amount of the combustion method after switching.

The plurality of combustion methods may include a first combustion method and a second combustion method. In the region where the combustion method does not exist, the combustion method is switched to the second combustion method in which the predetermined index satisfies the predetermined standard.

The control range of fuel pressure is different between the first combustion method and the second combustion method, and the control device controls the injection system to set the fuel pressure according to the combustion method. During the transition period of switching to the second combustion method, the degree of delay in following the fuel pressure after switching is calculated, and the injection amount of the corresponding stage is gradually changed according to the calculated degree before and after switching. It may be calculated as follows.

For example, in the first combustion method, the main injection in one cycle is in one stage, and in the second combustion method, the main injection in one cycle is in two stages, an earlier stage and a later stage. During the transition period of switching between the combustion method and the second combustion method, the degree of delay in following the fuel pressure after switching is calculated, and the state in which there is no subsequent stage of main injection in the first combustion method, and the state in which there is no subsequent stage of main injection in the first combustion method, and The injection amount of the second stage of the main injection may be calculated to gradually change depending on the calculated degree between the state where the second stage of the main injection of the second combustion method exists.

According to another aspect of this disclosure, an internal combustion engine control method is performed by an internal combustion engine control device. Internal combustion engines include an injection system that injects fuel at controlled pressure. The control method includes, when the control device switches to one of a plurality of combustion methods in an internal combustion engine, calculating the injection amount of each fuel injection in multiple stages per cycle according to the switched combustion method; In the step of controlling the injection system to inject fuel in multiple stages with each injection amount calculated in the cycle, and during the transition period of switching the combustion method, the injection amount of the corresponding stage in the combustion method before and after switching is controlled. The method includes a step of calculating a gradual change from the injection amount of the combustion method before switching to the injection amount of the combustion method after switching.

According to this disclosure, it is possible to provide a control device and a control method for an internal combustion engine that can suppress deterioration of combustion noise and smoke when switching between a plurality of combustion methods.

FIG. 1 is a diagram schematically showing the configuration of a vehicle engine system in an embodiment of the disclosure. FIG. 3 is a diagram showing switching from PCCI (Premixed Charge Compression Ignition) combustion to main two-stage injection combustion using a control map according to the engine rotational speed and the total fuel injection amount in the subject of this disclosure. FIG. 7 is a diagram showing changes in rail pressure when switching from PCCI combustion to main two-stage injection combustion in the subject of this disclosure. FIG. 6 is a diagram showing changes in injection pattern and heat generation when switching from PCCI combustion to main two-stage injection combustion in the subject of this disclosure. FIG. 7 is a diagram showing switching from main two-stage injection combustion to PCCI combustion in a control map according to the rotational speed of the engine 11 and the total injection amount of fuel in the subject of this disclosure. FIG. 6 is a diagram showing changes in rail pressure when switching from main two-stage injection combustion to PCCI combustion in the subject of this disclosure. It is a figure which shows the injection pattern and the change of heat production when switching from main two-stage injection combustion to PCCI combustion in the subject of this disclosure. It is a flowchart which shows the flow of fuel injection processing in this embodiment. It is a flowchart which shows the flow of fuel injection first half processing in this embodiment. It is a flowchart which shows the flow of the fuel injection latter half process in this embodiment. FIG. 7 is a diagram showing switching from PCCI combustion to main two-stage injection combustion using a control map according to the rotational speed of the engine 11 and the total injection amount of fuel in the embodiment of this disclosure. FIG. 6 is a diagram showing changes in rail pressure, follow-up ratio, and injection amount of main two-stage injection when switching from PCCI combustion to main two-stage injection combustion in the embodiment of this disclosure. FIG. 3 is a diagram showing changes in injection pattern and heat generation when switching from PCCI combustion to main two-stage injection combustion in the embodiment of this disclosure. FIG. 3 is a diagram showing switching from main two-stage injection combustion to PCCI combustion in a control map according to the rotational speed of engine 11 and the total injection amount of fuel in the embodiment of this disclosure. FIG. 6 is a diagram showing changes in rail pressure, follow-up ratio, and injection amount of main two-stage injection when switching from main two-stage injection combustion to PCCI combustion in the embodiment of this disclosure. FIG. 3 is a diagram showing changes in injection pattern and heat generation when switching from main two-stage injection combustion to PCCI combustion in the embodiment of this disclosure.

Embodiments of this disclosure will be described below with reference to the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

FIG. 1 is a diagram schematically showing the configuration of an engine system 10 of a vehicle 1 in an embodiment of this disclosure. Referring to FIG. 1, an engine system 10 includes an engine 11, a fuel tank 12, a fuel injection device 13, a fuel pump 14, a common rail 15, an intake passage 8, an exhaust passage 7, and an EGR passage 18. , an EGR valve 19, an air flow meter 2, an intake throttle valve 16, an opening sensor 17, an engine speed sensor 20, a pressure sensor 21, an accelerator opening sensor 22, and a control device 100.

The control device 100 includes a CPU (Central Processing Unit) 110 that performs various processes, a ROM (Read Only Memory) that stores programs and data, and a RAM (Random) that is used as a work memory for the CPU and stores processing results, etc. The control device 100 includes an input port and an output port (none of which are shown) for exchanging information with devices external to the control device 100. An air flow meter 2, an opening sensor 17, an engine speed sensor 20, a pressure sensor 21, an accelerator opening sensor 22, and the like are connected to the input port.

The control device 100 receives signals from each device connected to the input port, executes a predetermined process based on the received signal, and controls the intake throttle valve connected to the output port based on the result of the process. 16, controls the fuel injection device 13, fuel pump 14, EGR valve 19, etc.

An air cleaner (not shown) is provided at one end of the intake passage 8. The other end of the intake passage 8 is connected to the engine 11 (more specifically, the cylinder 11a). An EGR passage 18 is connected to the middle of the intake passage 8 .

The air flow meter 2 is provided between one end of the intake passage 8 and the confluence position of the EGR passage 18. Air flow meter 2 detects the flow rate of fresh air introduced into engine system 10 from intake passage 8 (intake air amount), and outputs a signal indicating the detected intake air amount to control device 100.

The intake throttle valve 16 is provided at a position where the air flow meter 2 and the EGR passage 18 join. The intake throttle valve 16 opens and closes in response to a control signal from the control device 100. The opening sensor 17 is provided at the position of the intake throttle valve 16. The opening sensor 17 detects the opening of the intake throttle valve 16 and outputs a signal indicating the detected opening of the intake throttle valve 16 to the control device 100.

The engine 11 is an internal combustion engine such as a diesel engine. Engine 11 includes multiple cylinders 11a and multiple pistons 11b. For example, when the engine 11 is a four-cylinder engine, the engine 11 is provided with four cylinders 11a. Note that FIG. 1 exemplarily shows the configuration of one of the plurality of cylinders 11a, and the other cylinders have similar configurations. Therefore, detailed explanation thereof will not be repeated.

The fuel injection device 13 is provided at the top of the cylinder 11a. The fuel injection device 13 includes, for example, an injector that has a body in which a nozzle hole is formed and a needle that is provided inside the body and opens and closes the nozzle hole. Fuel injection device 13 is connected to fuel pump 14 and fuel tank 12 via common rail 15 . The fuel pump 14 supplies fuel in the fuel tank 12 to the common rail 15 in response to a control signal from the control device 100 so that the pressure of the fuel in the common rail 15 detected by the pressure sensor 21 becomes a predetermined pressure. . The fuel injection device 13 operates a needle in response to a control signal from the control device 100 to open the nozzle hole (that is, put the nozzle hole in communication with the common rail 15), thereby injecting fuel in the common rail 15. The fuel is injected into the combustion chamber within the cylinder 11a.

The control device 100 determines a control command value corresponding to the total injection amount Q injected during one cycle in the fuel injection device 13 according to the user's operation amount of the accelerator pedal detected by the accelerator opening sensor 22. . Control device 100 controls fuel injection device 13 based on the determined control command value. The control command value is, for example, a value indicating the injection time (injection opening time) or the injection amount of fuel from the fuel injection device 13.

For example, the control device 100 controls the fuel injection device 13 so that the total injection amount Q to be injected during one cycle is divided into multiple injections. Control device 100 controls fuel injection device 13 so that, for example, pilot injection, main injection, and after injection are performed during one cycle. Pilot injection is performed, for example, to suppress the generation of combustion noise and combustion pressure. The main injection is performed, for example, to achieve the torque requested of the engine 11. After-injection is performed, for example, to suppress the occurrence of smoke and the like.

The piston 11b is connected to a crankshaft (not shown) that is an output shaft. The engine rotational speed sensor 20 is provided on the crankshaft and detects the rotational speed of the crankshaft (hereinafter referred to as the rotational speed NE of the engine 11). The engine rotation speed sensor 20 is connected to the control device 100 and transmits a signal indicating the detected rotation speed NE of the engine 11 to the control device 100.

One end of the exhaust passage 7 is connected to the engine 11 (more specifically, the cylinder 11a). The exhaust passage 7 is provided with an exhaust treatment device (not shown) that purifies PM (particulate matter), HC (hydrocarbons), CO (carbon monoxide), and NOx (nitrogen oxides) in the exhaust gas.

The engine 11 is further provided with an EGR (exhaust gas recirculation) system. The EGR system includes an EGR passage 18 and an EGR valve 19. The EGR passage 18 communicates the exhaust passage 7 and the intake passage 8 without passing through the cylinder 11a, and returns a part of the exhaust gas discharged to the exhaust passage 7 to the intake passage 8. The EGR valve 19 adjusts the flow rate of gas circulating through the EGR passage 18 in response to a control signal from the control device 100. Control device 100 controls the opening degree of EGR valve 19 based on the operating state of engine 11.

Specifically, the control device 100 sets the target value of the EGR rate based on the total injection amount Q and the rotational speed NE of the engine 11, for example. For example, a map showing the relationship between the total injection amount Q, the rotational speed NE of the engine 11, and the target value of the EGR rate is stored in the memory 150 of the control device 100, which will be described later. The control device 100 sets a target value of the EGR rate based on the total injection amount Q corresponding to the control command value, the rotational speed NE of the engine 11, and the above-mentioned map. The control device 100 controls the opening degree of the EGR valve 19 so that the EGR rate reaches the target value.

Further, the engine 11 is provided with a supercharger (not shown) that supercharges the air in the intake passage 8 using exhaust energy flowing through the exhaust passage 7 . The supercharger includes, for example, a turbine provided in the exhaust passage 7 and housing turbine blades, a compressor provided in the intake passage 8 and housing the compressor blades, and a shaft connecting the turbine blades and the compressor blades. . When the turbine blades in the turbine are rotated by the exhaust gas flowing through the exhaust passage 7, the shaft connected to the turbine blades and the compressor blades rotate together, and air is force-fed from the compressor to the cylinders, thereby performing supercharging. . Furthermore, a plurality of vanes are provided around the turbine blades in the turbine so as to be able to change the speed at which exhaust gas flows into the turbine blades. The plurality of vanes are operated by actuators. Control device 100 controls the opening degree between the vanes based on the operating state of engine 11.

[assignment]
Conventionally, in the engine 11, when fuel is injected multiple times in one cycle, there has been a combustion method in which main injection is divided into an earlier stage and a later stage. This combustion method is called main two-stage injection combustion. In main two-stage injection combustion, by adjusting the interval between the injection timing of the previous stage of main injection and the injection timing of the latter stage, the pressure waves during combustion in the former stage and the pressure waves during combustion in the latter stage cancel each other out. , noise can be reduced. However, in main two-stage injection combustion, it is known that smoke worsens due to a short ignition delay in the subsequent stage of main injection.

In response to this, the smoke characteristics can be improved by increasing the rail pressure of the common rail 15. Increasing the rail pressure worsens combustion noise. However, in this regard, by keeping the increase in rail pressure to the minimum necessary, it is possible to meet the targets for both combustion noise and smoke.

Here, in the control map for the engine 11, there are regions where main two-stage injection combustion and other combustion methods are suitable and regions where they are not suitable. If a plurality of combustion methods are simply switched on a control map, there is a concern that combustion noise and smoke may worsen at the time of switching.

FIG. 2 is a diagram showing switching from PCCI combustion to main two-stage injection combustion using a control map according to the rotational speed of the engine 11 and the total injection amount of fuel in the subject of this disclosure. PCCI combustion is a combustion method in which a premixture having a constant fuel concentration distribution is compressed and ignited through a premixing period after the end of one main injection. In the embodiment of this disclosure, switching between main two-stage injection combustion and PCCI combustion will be described as an example. Note that a combustion method different from these two combustion methods may be used, or three or more combustion methods may be switched.

Referring to FIG. 2, the horizontal axis represents the rotational speed NE of the engine 11, and the vertical axis represents the total fuel injection amount Q per cycle. An ignitability index τ0 is predetermined for each combination of rotational speed NE and total injection amount Q on this control map. The main 2-stage injection combustion region, which is the area surrounded by the control map, has a large combustion noise when PCCI combustion is used, but a relatively small combustion noise when main 2-stage injection combustion is used. This is an area suitable for injection combustion. The area outside the area enclosed on the control map is the PCCI area.

Here, the combination of rotational speed NE and total injection amount Q is determined from control point (1) in the PCCI region, through control point (2) in the main two-stage injection combustion region, and then to the control point (2) in the main two-stage injection combustion region. The case of switching to (3) will be explained.

FIG. 3 is a diagram showing changes in rail pressure when switching from PCCI combustion to main two-stage injection combustion in the subject of this disclosure. Compared to the rail pressure control range in PCCI combustion, the rail pressure control range in main two-stage injection combustion is high. Therefore, if the indicators used for control, such as the rotational speed NE and the total injection amount Q, are of the same degree, then the control point (1) in the PCCI region, the control point (2) in the main two-stage injection combustion region, and the control point ( When switching to 3), the rail pressure must be increased.

Referring to FIG. 3, when switching from the control point (1) in the PCCI region to the control point (2) in the main two-stage injection combustion region, the PCCI combustion is switched to the main two-stage injection combustion, but at the time of this switching, The target value for rail pressure control is raised from the rail pressure in PCCI combustion to the rail pressure in main two-stage injection combustion, but since the actual rail pressure follows with a delay, at control point (2), the main The rail pressure will be lower than that required for two-stage injection combustion.

FIG. 4 is a diagram showing changes in the injection pattern and heat generation when switching from PCCI combustion to main two-stage injection combustion in the subject of this disclosure. Referring to FIG. 4, at control point (1), since PCCI combustion is performed, the rail pressure is lower than that of main two-stage injection combustion, and pilot 1 injection (PL1), pilot 2 injection (PL2), Fuel is injected in the order of main injection (MAIN). Note that in PCCI combustion, after injection is actually performed after main injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

At control point (2), there is a transition state from PCCI combustion to main two-stage injection combustion, but since the main injection is divided into the first stage main 1 injection and the second stage main 2 injection, the main combustion method is This is a two-stage injection combustion. In the main two-stage injection combustion, fuel is injected in the order of pilot 1 injection (PL1), pilot 2 injection (PL2), main 1 injection (MAIN1), and main 2 injection (MAIN2). Note that in the main two-stage injection combustion, after-injection is actually performed after the main two-stage injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

In a transient state from PCCI combustion to main two-stage injection combustion, such as control point (2), the injection pattern such as the injection timing and injection amount of each injection can be immediately switched to the main two-stage injection combustion injection pattern. It is. However, since the rail pressure is delayed in follow-up, the rail pressure ends up being lower than the rail pressure required for main two-stage injection combustion. For this reason, the amount of smoke generated becomes worse.

At control point (3), the rail pressure rises completely to the main two-stage injection combustion rail pressure. Therefore, the smoke generation state is the original good state of main two-stage injection combustion.

FIG. 5 is a diagram showing switching from main two-stage injection combustion to PCCI combustion in a control map according to the rotational speed of the engine 11 and the total injection amount of fuel in the subject of this disclosure. Referring to FIG. 5, similarly to FIG. 2, the horizontal axis indicates the rotational speed NE of the engine 11, and the vertical axis indicates the total injection amount Q of fuel per cycle. Contrary to FIG. 2, here, the combination of rotational speed NE and total injection amount Q is changed from the control point (4) of the main two-stage injection combustion region to the control point (5) of the PCCI region. The case of switching to control point (6) will be explained.

FIG. 6 is a diagram showing changes in rail pressure when switching from main two-stage injection combustion to PCCI combustion in the subject of this disclosure. The control range of rail pressure in PCCI combustion is lower than the control range of rail pressure in main two-stage injection combustion. For this reason, if the indicators used for control, such as the rotational speed NE and the total injection amount Q, are at the same level, the control point (4) in the main two-stage injection combustion region, the control point (5) in the PCCI region, and the control point ( When switching to 6), the rail pressure must be lowered.

Referring to FIG. 6, when switching from the control point (4) of the main two-stage injection combustion region to the control point (5) of the PCCI region, the main two-stage injection combustion is switched to the PCCI combustion, but at the time of this switching, The target value for rail pressure control is lowered from the rail pressure in main two-stage injection combustion to the rail pressure in PCCI combustion, but since the actual rail pressure follows with a delay, at control point (5), PCCI The rail pressure will be higher than that required for combustion.

FIG. 7 is a diagram showing changes in the injection pattern and heat generation when switching from main two-stage injection combustion to PCCI combustion in the subject of this disclosure. Referring to FIG. 7, at control point (4), since main two-stage injection combustion is performed, the rail pressure is higher than that of PCCI combustion, and pilot 1 injection (PL1), pilot 2 injection (PL2), Fuel is injected in the order of main 1 injection (MAIN1) and main 2 injection (MAIN2). Note that in the main two-stage injection combustion, after-injection is actually performed after the main two-stage injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

At control point (5), there is a transition state from main two-stage injection combustion to PCCI combustion, but since the control has been switched to PCCI, the combustion method is PCCI combustion. In PCCI combustion, fuel is injected in the order of pilot 1 injection (PL1), pilot 2 injection (PL2), and main injection (MAIN). Note that in PCCI combustion, after injection is actually performed after main injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

In a transient state from main two-stage injection combustion to PCCI combustion, such as control point (5), the injection pattern such as the injection timing and injection amount of each injection can be immediately switched to the injection pattern of PCCI combustion. However, since the rail pressure is delayed in follow-up, the rail pressure ends up being higher than the rail pressure required for PCCI combustion. For this reason, the peak of heat generation becomes large, resulting in worsening of combustion noise.

At control point (6), the pressure is completely reduced to the PCCI combustion rail pressure. Therefore, the combustion noise is in the original good state of PCCI combustion.

As shown in FIGS. 2 to 7 described above, simply switching a plurality of combustion methods on a control map will worsen combustion noise and smoke at the time of switching.

[Controls in this disclosure]
Therefore, when switching to one of a plurality of combustion methods in the engine 11, the control device 100 calculates the respective injection amounts in multiple stages of fuel injection per cycle according to the switched combustion method, and calculates each injection amount in each cycle. The fuel injection device 13 is controlled to inject fuel in multiple stages with each injection amount, and during the transition period of switching the combustion method, the injection amount of the corresponding stage in the combustion method before and after switching is changed to the injection amount of the corresponding stage in the combustion method before and after switching. The injection amount is calculated so as to gradually change from the injection amount of the combustion method to the injection amount of the combustion method after switching.

Thereby, deterioration of combustion noise and smoke can be suppressed when switching between a plurality of combustion methods.

Control in this embodiment will be explained below. FIG. 8 is a flowchart showing the flow of fuel injection processing in this embodiment. This fuel injection process is called and executed by the CPU 110 of the control device 100 from a higher level process at every predetermined control cycle. The PCCI combustion and main two-stage injection combustion shown below are known combustion methods, and the injection amount and amount in each injection such as pilot injection, main injection and after injection in one cycle of PCCI combustion and main two-stage injection combustion are Since the methods of calculating the injection timing are publicly known, these calculation methods will not be described in detail.

Referring to FIG. 8, first, CPU 110 of control device 100 executes fuel injection first half processing shown in FIG. 9, which will be described later (step S110).

FIG. 9 is a flowchart showing the flow of the first half of fuel injection processing in this embodiment. Referring to FIG. 9, CPU 110 obtains the accelerator opening detected by accelerator opening sensor 22 and the rotational speed NE of engine 11 detected by engine rotational speed sensor 20 (step S111).

The CPU 110 uses the accelerator opening degree and rotational speed NE to determine the total injection amount Q of fuel in one cycle from a preset map showing the relationship between the accelerator opening degree and rotational speed NE and the total injection amount Q ( Step S112). The CPU 110 calculates the in-cylinder ignitability index τ0 (step S113). The ignitability index τ0 is predetermined in association with the combination of the rotational speed NE and the total injection amount Q, as shown in FIG. 2 and the like.

The CPU 110 calculates a target ignition timing IGtrg that satisfies exhaust and fuel efficiency requirements using the accelerator opening, the total injection amount Q, the rotational speed NE, etc. (step S114). The CPU 110 uses the accelerator opening degree, rotational speed NE, outside temperature, atmospheric pressure, cooling water temperature, etc. to ignite the fuel after fuel injection is started to obtain a target combustion waveform based on a preset map. A target ignition delay τtrg is calculated (step S115). The CPU 110 calculates the ignition delay deviation Δτ (=target ignition delay τtrg−ignitability index τ0) (step S116).

The CPU 110 determines the injection amount of the pilot injection from the calculated ignition delay deviation Δτ (step S117). For example, calculate the required cylinder temperature from the ignition delay deviation Δτ, calculate the desired cylinder temperature by subtracting the current cylinder temperature from the required cylinder temperature, and create a required pilot to achieve the desired cylinder temperature. The amount of heat is calculated, and the injection amount of pilot injection for generating the required amount of pilot heat is calculated. The calculated injection amount of the pilot injection is the sum of the injection amount of the pilot 1 injection and the injection amount of the pilot 2 injection. The ratio of the injection amount of pilot 1 injection and the injection amount of pilot 2 injection is a predetermined constant ratio.

The CPU 110 determines the injection timing of pilot injection (step S118). If the spray from the injector of the fuel injection device 13 touches the wall surface, it will cool down and the HC will worsen. Therefore, the start timing of the injection period of the pilot 1 injection should be advanced as much as possible to the extent that the spray does not touch the wall surface, so that ignition can be achieved. By increasing the delay and making combustion as slow as possible, the initial slope of the combustion waveform is reduced. The length of the injection period of pilot 1 injection is calculated from the injection amount and rail pressure of pilot 1 injection.

In order to reduce the initial slope of the combustion waveform by overlapping the combustion for the pilot 2 injection with the combustion for the main injection, the injection period of the pilot 2 injection is set to be closest to the injection period of the main injection. The length of the injection period of the pilot 2 injection is calculated from the injection amount and rail pressure of the pilot 2 injection.

The CPU 110 determines the injection timing of main injection (main injection in the case of PCCI, main 1 injection in the case of main two-stage injection combustion) (step S119). The main injection timing is determined to adjust the ignition timing to ensure the required degree of isovolume.

First, a temporary main injection timing is calculated by subtracting the target ignition delay τtrg from the target ignition timing IGtrg calculated in step S114. Next, the pilot 1 injection and the pilot 2 injection determined in step S117 and step S118 are executed, and the heat generation shape when injecting the temporary main injection amount at the calculated temporary main injection timing is estimated. Note that the provisional main injection amount is calculated by subtracting the pilot 1 injection amount, the pilot 2 injection amount, and the provisional after injection amount from the total injection amount Q. The tentative after-injection amount is, for example, the after-injection amount in the previous control cycle. If an estimation error occurs between the estimated main ignition timing and the target ignition timing, the main injection timing is corrected by the estimation error. Furthermore, since the ignition timing is advanced by the amount that the pilot combustion overlaps with the main combustion, the start timing of the injection period of the main injection is corrected in order to return the increased amount to the target ignition timing.

After step S119, the CPU 110 returns the process to be executed to the fuel injection process that called the fuel injection first half process. Returning to FIG. 8, after the fuel injection first half process in step S110, the CPU 110 executes the fuel injection second half process shown in FIG. 10, which will be described later (step S120).

FIG. 10 is a flowchart showing the flow of the fuel injection latter half process in this embodiment. Referring to FIG. 10, CPU 110 determines that the current control point is in the PCCI region on the control map shown in FIG. Or, the control point is in the main two-stage injection combustion region, or is in the switching period after the control point is switched from the main two-stage injection combustion region to the PCCI region, or the control point is in the main two-stage injection combustion region from the PCCI region. It is determined whether it is the switching period after switching to the stage injection combustion region (step S121).

If it is determined that the control point is in the PCCI region, the CPU 110 uses the rotational speed NE of the engine 11 and the total injection amount Q to determine the target rail pressure for PCCI (step S122). The target rail pressure for PCCI is predetermined in correspondence with the combination of the rotational speed NE and the total injection amount Q, similar to the ignitability index τ0 in FIG. That is, the rail pressure of PCCI combustion is controlled within a predetermined control range.

The CPU 110 determines the injection amount and injection timing of the PCCI after injection using the rotational speed NE of the engine 11 and the total injection amount Q (step S123). The injection amount and injection timing of the after-injection for PCCI are determined in advance in association with the combination of the rotational speed NE and the total injection amount Q, similar to the ignitability index τ0 in FIG.

The CPU 110 determines the injection amount of the main injection by subtracting the injection amount of the pilot 1 injection, the injection amount of the pilot 2 injection, and the after injection from the total injection amount Q (step S124).

On the other hand, if it is determined that the control point is in the main two-stage injection combustion region or that it is a switching period between the PCCI region and the main two-stage injection combustion region, the CPU 110 controls the rotation speed NE of the engine 11 and the total injection amount Q. The target rail pressure for main two-stage injection is determined using (step S131). The target rail pressure for the main two-stage injection is predetermined in association with the combination of the rotational speed NE and the total injection amount Q, similar to the ignitability index τ0 in FIG. That is, the rail pressure of the main two-stage injection combustion is controlled within a predetermined control range.

The CPU 110 determines the injection amount and injection timing of the main two injections of the main two-stage injection combustion using the rotational speed NE of the engine 11, the total injection amount Q, and the ignitability index τ0 (step S132). The injection amount and injection timing of the main two injections of the main two-stage injection combustion are predetermined in association with the combination of the rotational speed NE and the total injection amount Q, similar to the ignitability index τ0 in FIG.

The CPU 110 determines whether the current time is a switching period between the PCCI region and the main two-stage injection combustion region (step S133). If it is determined that it is the switching period (YES in step S133), the CPU 110 acquires the rail pressure (=actual injection pressure) of the common rail 15 from the pressure sensor 21, and calculates the actual injection pressure with respect to the target rail pressure calculated in step S131. A follow-up ratio is calculated (step S134). The tracking ratio is "1" when the actual injection pressure follows the target injection pressure for main two-stage injection combustion, and "0" when the actual injection pressure follows the target injection pressure for PCCI combustion. It is. The following ratio is calculated using the following formula (1). In other words, 0≦following ratio≦1.

Follow-up ratio = (actual injection pressure - target injection pressure for PCCI combustion) / (target injection pressure for main two-stage injection combustion - target injection pressure for PCCI combustion)... (1)
The CPU 110 corrects the injection amount of the main two injections in the switching period according to the follow-up ratio of the actual injection pressure to the target rail pressure (step S135). The injection amount of the main 2 injection during the switching period is calculated using the following formula (2).

Injection amount of main 2 injection during switching period = Injection amount of main 2 injection of PCCI combustion + (Injection amount of main 2 injection of main 2-stage injection combustion - Injection amount of main 2 injection of PCCI combustion) × Follow-up ratio... (2)
Note that in PCCI combustion, since there is no main 2 injection, the injection amount of the main 2 injection in PCCI combustion is "0". In other words, formula (2) can be expressed as formula (3) below.

Injection amount of main 2 injection during switching period = injection amount of main 2 injection of main 2-stage injection combustion x follow-up ratio... (3)
If it is determined that it is not the switching period (NO in step S133), that is, if the control point is in the main two-stage injection combustion region, or after step S135, the CPU 110 controls the rotational speed NE of the engine 11 and the total injection amount Q. The injection amount and injection timing of after injection for main two-stage injection are determined using (step S136). The injection amount and injection timing of the after injection for the main two-stage injection are predetermined in correspondence with the combination of the rotational speed NE and the total injection amount Q, similar to the ignitability index τ0 in FIG.

The CPU 110 determines the injection amount of the main 1 injection by subtracting the injection amount of the pilot 1 injection, the injection amount of the pilot 2 injection, and the after injection from the total injection amount Q (step S137).

After step S124 or step S137, the CPU 110 controls the fuel injection device 13 to start executing the next cycle of injection control using the calculated rail pressure, injection timing, and injection amount (step S141). After step S141, the CPU 110 returns the process to be executed to the fuel injection process that called the second half of the fuel injection process.

Note that even during the switching period, each parameter such as the rotational speed NE of the engine 11 and the total injection amount Q is not constant, so the rail pressure, the injection amount and injection timing of each injection will change depending on the movement of these parameters. The tracking ratio is calculated based on the calculated rail pressure.

FIG. 11 is a diagram showing switching from PCCI combustion to main two-stage injection combustion using a control map according to the rotational speed of the engine 11 and the total injection amount of fuel in the embodiment of this disclosure. Referring to FIG. 11, since FIG. 11 is similar to FIG. 2, overlapping description will not be repeated.

Here, the combination of rotational speed NE and total injection amount Q is determined from control point (1) in the PCCI region, through control point (2) in the main two-stage injection combustion region, and then to the control point (2) in the main two-stage injection combustion region. The case of switching to (3) will be explained.

FIG. 12 is a diagram showing changes in rail pressure, follow-up ratio, and injection amount of main 2 injection when switching from PCCI combustion to main 2-stage injection combustion in the embodiment of this disclosure. Compared to the rail pressure control range in PCCI combustion, the rail pressure control range in main two-stage injection combustion is high. Therefore, if the indicators used for control, such as the rotational speed NE and the total injection amount Q, are of the same degree, then the control point (1) in the PCCI region, the control point (2) in the main two-stage injection combustion region, and the control point ( When switching to 3), the rail pressure must be increased.

Referring to FIG. 12, when switching from the control point (1) in the PCCI region to the control point (2) in the main two-stage injection combustion region, the PCCI combustion is switched to the main two-stage injection combustion, but at the time of this switching, The target value for rail pressure control is raised from the rail pressure in PCCI combustion to the rail pressure in main two-stage injection combustion, but since the actual rail pressure follows with a delay, at control point (2), the main The rail pressure will be lower than that required for two-stage injection combustion.

For this reason, as shown in FIG. 10, the follow-up ratio of the rail pressure is calculated, and the injection amount of the main 2 injection is calculated using the follow-up ratio. As a result, during the switching period, the follow-up ratio gradually changes from 0 to 1, and accordingly, the injection amount of the main 2 injection also changes. Therefore, the injection amount gradually changes from 0) to the main 2 injection amount of the main 2-stage injection combustion. In the case where the gradual change is not made in this manner, only the injection amount of the main two-stage injection is set as the injection amount of the main two-stage injection combustion in a state where the rail pressure has not risen to the pressure required for the main two-stage injection combustion.

FIG. 13 is a diagram showing changes in the injection pattern and heat generation when switching from PCCI combustion to main two-stage injection combustion in the embodiment of this disclosure. Referring to FIG. 13, at control point (1), since PCCI combustion is performed, the rail pressure is lower than that of main two-stage injection combustion, and pilot 1 injection (PL1), pilot 2 injection (PL2), Fuel is injected in the order of main injection (MAIN). Note that in PCCI combustion, after injection is actually performed after main injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

At control point (2), it is the switching period from PCCI combustion to main two-stage injection combustion, and since the main injection is divided into the first-stage main 1 injection and the second-stage main 2 injection, the combustion method is the main 2-stage injection. This results in staged injection combustion. In the main two-stage injection combustion, fuel is injected in the order of pilot 1 injection (PL1), pilot 2 injection (PL2), main 1 injection (MAIN1), and main 2 injection (MAIN2). Note that in the main two-stage injection combustion, after-injection is actually performed after the main two-stage injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

During the switching period from PCCI combustion to main two-stage injection combustion as shown in control point (2), the injection pattern such as the injection timing and injection amount of each injection can be immediately switched to the main two-stage injection combustion injection pattern. It is. Since the rail pressure is delayed in follow-up, it ends up being lower than the rail pressure required for main two-stage injection combustion. However, in this embodiment, the injection amount of the main two injections is gradually changed depending on the follow-up ratio of the actual rail pressure to the target rail pressure. Therefore, it is possible to prevent the amount of smoke generated from deteriorating.

At control point (3), the rail pressure rises completely to the main two-stage injection combustion rail pressure. As a result, the injection amount of the main two-stage injection also increases to the injection amount of the main two-stage injection combustion.

FIG. 14 is a diagram showing switching from main two-stage injection combustion to PCCI combustion in a control map according to the rotational speed of engine 11 and the total injection amount of fuel in the embodiment of this disclosure. Referring to FIG. 14, since FIG. 14 is similar to FIG. 5, overlapping description will not be repeated.

Contrary to FIG. 11, here, the combination of rotational speed NE and total injection amount Q is changed from the control point (4) of the main two-stage injection combustion region to the control point (5) of the PCCI region, and The case of switching to control point (6) will be explained.

FIG. 15 is a diagram showing changes in rail pressure, follow-up ratio, and injection amount of main two-stage injection when switching from main two-stage injection combustion to PCCI combustion in the embodiment of this disclosure. The control range of rail pressure in PCCI combustion is lower than the control range of rail pressure in main two-stage injection combustion. For this reason, if the indicators used for control, such as the rotational speed NE and the total injection amount Q, are at the same level, the control point (4) in the main two-stage injection combustion region, the control point (5) in the PCCI region, and the control point ( When switching to 6), the rail pressure must be lowered.

Referring to FIG. 15, when switching from the control point (4) of the main two-stage injection combustion region to the control point (5) of the PCCI region, the main two-stage injection combustion is switched to the PCCI combustion, but at the time of this switching, The target value for rail pressure control is lowered from the rail pressure in main two-stage injection combustion to the rail pressure in PCCI combustion, but since the actual rail pressure follows with a delay, at control point (5), PCCI The rail pressure will be higher than that required for combustion.

For this reason, as shown in FIG. 10, the follow-up ratio of the rail pressure is calculated, and the injection amount of the main 2 injection is calculated using the follow-up ratio. As a result, during the switching period, the follow-up ratio gradually changes from 1 to 0, and accordingly, the injection amount of the main 2 injection changes from the injection amount of the main 2 injection of the main 2-stage injection combustion to the injection amount of the main 2 injection of the main 2-stage injection combustion. The injection amount (0 because there is no main 2 injection in PCCI combustion) gradually changes. In the case where the gradual change is not made in this way, only the injection amount of the main 2 injection is set to be the injection amount of the PCCI combustion (that is, 0) in a state where the rail pressure has not decreased to the pressure required for the PCCI combustion.

FIG. 16 is a diagram showing changes in the injection pattern and heat generation when switching from main two-stage injection combustion to PCCI combustion in the embodiment of this disclosure. Referring to FIG. 16, at control point (4), since main two-stage injection combustion is performed, the rail pressure is higher than that of PCCI combustion, and pilot 1 injection (PL1), pilot 2 injection (PL2), Fuel is injected in the order of main 1 injection (MAIN1) and main 2 injection (MAIN2). Note that in the main two-stage injection combustion, after-injection is actually performed after the main two-stage injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

At control point (5), it is a switching period from main two-stage injection combustion to PCCI combustion, and the main injection is divided into the first stage main 1 injection and the second stage main 2 injection, so the combustion method is main 2. This results in staged injection combustion. In the main two-stage injection combustion, fuel is injected in the order of pilot 1 injection (PL1), pilot 2 injection (PL2), main 1 injection (MAIN1), and main 2 injection (MAIN2). Note that in the main two-stage injection combustion, after-injection is actually performed after the main two-stage injection, but this is not shown in the figure. Corresponding to these injections, combustion heat is generated inside the cylinder 11a.

During the switching period from main two-stage injection combustion to PCCI combustion, such as control point (5), the injection pattern such as the injection timing and injection amount of each injection can be immediately switched to the injection pattern of PCCI combustion. Since the rail pressure is delayed in follow-up, the rail pressure ends up being higher than the rail pressure required for PCCI combustion. However, in this embodiment, the injection amount of the main two injections is gradually changed depending on the follow-up ratio of the actual rail pressure to the target rail pressure. Therefore, it is possible to prevent the peak of heat generation from increasing, and it is possible to prevent combustion noise from worsening.

At control point (6), the pressure is completely reduced to the PCCI combustion rail pressure. As a result, the injection amount of the main 2 injection also decreases to the injection amount of PCCI combustion (that is, 0).

[Modified example]
(1) In the embodiment described above, as shown in FIG. 1, the engine 11 is a diesel engine. However, the present invention is not limited to this, and the engine 11 may be configured to be able to change the injection pressure of fuel, and may be a gasoline engine.

(2) In the embodiment described above, two combustion methods are switched as shown in FIGS. 8 to 10. However, the present invention is not limited to this, and three or more combustion methods may be switched.

(3) In the embodiment described above, as shown in FIG. 4 etc., the pilot injection is in two stages, the main injection is in one or two stages, and the after injection is in one stage. However, the present invention is not limited thereto, and may include other injections, such as post injection. Moreover, the number of stages of each injection may be another number of stages.

(4) In the embodiment described above, as shown in FIGS. 8 to 16, the injection amount of the two main injections is gradually changed. However, the invention is not limited to this, and the injection amounts of other injections (for example, main 1 injection, after injection) may be gradually changed.

(5) In the embodiment described above, as shown in FIGS. 10, 12, and 15, the injection amount of the main 2 injection is linearly increased or decreased during the switching period. However, the invention is not limited to this, and if the injection amount is to be changed gradually, it may be increased or decreased non-linearly rather than linearly.For example, as shown in the graph of the main 2 injection amounts in FIG. Instead of changing in a straight line, it may be changed smoothly in a curved line.

(6) In the embodiment described above, it has been shown that the control range of the rail pressure in main two-stage injection combustion is higher than the control range of rail pressure in PCCI combustion. A part of both control ranges may overlap.

(7) The above-mentioned disclosure can be regarded as a disclosure of the control device 100 for the engine 11. Further, the above-mentioned disclosure can be regarded as a disclosure of the engine system 10 or the vehicle 1 including the control device 100, and can also be regarded as a disclosure of a control method or a control program executed by the control device 100.

[summary]
(1) As shown in FIG. 1, the control device 100 controls the engine 11. As shown in FIG. 1, the engine 11 includes an injection system (for example, includes a fuel injection device 13, a fuel pump 14, a common rail 15, and a fuel tank 12) that injects fuel at a controlled pressure. As shown in FIGS. 8 to 10, when switching to one of a plurality of combustion methods (for example, PCCI combustion, main two-stage injection combustion) in the engine 11, the control device 100 controls one combustion method according to the switched combustion method. Calculate each injection amount in multiple stages of fuel injection per cycle (for example, step S117, step S123, step S124, step S132, step S136, step S137), and calculate the fuel injection amount at each injection amount calculated in each cycle. The injection system is controlled to inject in multiple stages (for example, step S141), and during the transition period of switching the combustion method, the injection amount of the corresponding stage in the combustion method before and after switching is changed to the injection amount of the combustion method before and after switching. From the amount, the injection amount is calculated so as to gradually change to the injection amount of the combustion method after switching (for example, steps S132 to S135).

Thereby, deterioration of combustion noise and smoke can be suppressed when switching between a plurality of combustion methods. Furthermore, since the injection amount is gradually changed, changes in the timbre of the combustion sound can also be minimized, and the connection between the timbres of the combustion sound can be improved.

(2) As shown in FIGS. 8 to 16, the plurality of combustion methods include a first combustion method (for example, PCCI combustion) and a second combustion method (for example, main two-stage injection combustion). . As shown in FIGS. 2 and 10, the control device 100 determines that in the first combustion method in the control map for the engine 11, a predetermined index (for example, combustion noise, smoke) is set to a predetermined standard (for example, design standard, In a region where the predetermined index does not satisfy the predetermined criterion, the combustion method is switched to a second combustion method in which the predetermined index satisfies the predetermined criterion (for example, step S121).

Thereby, on the control map, the combustion method can be used in an area where the first combustion method and the second combustion method are advantageous.

(3) As shown in FIG. 3 and the like, the control range of fuel pressure is different between the first combustion method and the second combustion method. As shown in FIGS. 8 to 10, the control device 100 controls the injection system to set the fuel pressure according to the combustion method (for example, step S141), and controls the injection system so that the pressure of the fuel corresponds to the first combustion method and the second combustion method. During the transition period of the switching, the degree of delay in following the fuel pressure after the switching is calculated (for example, step S134), and the injection amount of the corresponding stage is gradually changed before and after the switching according to the calculated degree. (For example, step S135).

Thereby, it is possible to appropriately gradually change the fuel injection amount depending on the degree of follow-up delay of the fuel pressure.

(4) As shown in Fig. 4, etc., in the first combustion method, the main injection in one cycle is in one stage, and in the second combustion method, the main injection in one cycle is in two stages, the first stage and the second stage. It is. As shown in FIGS. 8 to 10, during the transition period of switching between the first combustion method and the second combustion method, the control device 100 calculates the degree of delay in following the fuel pressure after switching. (Step S134), the main injection is changed according to the calculated degree between a state in which there is no post-stage of main injection in the first combustion method and a state in which a post-stage in main injection in the second combustion method is present. Calculation is made so that the injection amount in the latter stage changes gradually (step S135).

Thereby, in PCCI combustion and main two-stage injection combustion, the main injection is important for suppressing combustion noise and smoke, and the injection amount of the main injection can be appropriately controlled.

It is also planned that the embodiments disclosed herein will be implemented in appropriate combinations. The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the description of the embodiments described above, and it is intended that all changes within the meaning and scope equivalent to the claims are included.

1 vehicle, 2 air flow meter, 7 exhaust passage, 8 intake passage, 10 engine system, 11 engine, 11a cylinder, 11b piston, 12 fuel tank, 13 fuel injection device, 14 fuel pump, 15 common rail, 16 intake throttle valve, 17 opening sensor, 18 EGR passage, 19 EGR valve, 20 engine speed sensor, 21 pressure sensor, 22 accelerator opening sensor, 100 control device, 110 CPU, 150 memory.

Claims (3)

A control device for an internal combustion engine,
The internal combustion engine includes an injection system that injects fuel at a controlled pressure;
The plurality of combustion methods in the internal combustion engine include a first combustion method and a second combustion method,
The first combustion method and the second combustion method have different fuel pressure control ranges,
The control device includes:
When switching to any of the plurality of combustion methods, calculate the respective injection amounts in multiple stages of fuel injection per cycle according to the switched combustion method,
controlling the injection system to inject fuel in multiple stages with each injection amount calculated in each cycle;
During the transition period of combustion method switching, the injection amount of the corresponding stage in the combustion method before and after switching is calculated so as to gradually change from the injection amount of the combustion method before switching to the injection amount of the combustion method after switching. ,
In the first combustion method in the control map for the internal combustion engine, in a region where the predetermined index does not satisfy the predetermined criterion, switching to the second combustion method where the predetermined index satisfies the predetermined criterion;
controlling the injection system to provide fuel pressure according to the combustion method;
During the transition period of switching between the first combustion method and the second combustion method, the degree of follow-up delay to the fuel pressure after switching is calculated, and the injection amount of the corresponding stage is calculated before and after switching. A control device for an internal combustion engine that makes calculations that gradually change depending on the degree of change . In the first combustion method, main injection in one cycle is one stage,
In the second combustion method, the main injection in one cycle is in two stages, an earlier stage and a later stage,
During the transition period of switching between the first combustion method and the second combustion method, the control device calculates the degree of delay in following the fuel pressure after switching, and calculates the degree of follow-up delay of the switching between the first combustion method and the second combustion method. The injection amount of the subsequent stage of the main injection is calculated to gradually change according to the calculated degree between a state in which a subsequent stage of the main injection does not exist and a state in which a subsequent stage of the main injection of the second combustion method exists. A control device for an internal combustion engine according to claim 1 . A method for controlling an internal combustion engine executed by a control device for an internal combustion engine, the method comprising:
The internal combustion engine includes an injection system that injects fuel at a controlled pressure;
The plurality of combustion methods in the internal combustion engine include a first combustion method and a second combustion method,
The first combustion method and the second combustion method have different fuel pressure control ranges,
In the control method, the control device:
When switching to one of the plurality of combustion methods, calculating the injection amount of each fuel injection in multiple stages per cycle according to the switched combustion method;
controlling the injection system to inject fuel in multiple stages with each injection amount calculated in each cycle;
During the transition period of switching the combustion method, the injection amount of the corresponding stage in the combustion method before and after switching is calculated so as to gradually change from the injection amount of the combustion method before switching to the injection amount of the combustion method after switching. step and
In the first combustion method in the control map for the internal combustion engine, in a region where the predetermined index does not satisfy the predetermined criterion, switching to the second combustion method in which the predetermined index satisfies the predetermined criterion;
controlling the injection system to provide fuel pressure according to the combustion method;
During the transition period of switching between the first combustion method and the second combustion method, the degree of follow-up delay to the fuel pressure after switching is calculated, and the injection amount of the corresponding stage is calculated before and after switching. A method for controlling an internal combustion engine, the method comprising the step of: calculating the amount gradually depending on the degree of the change .

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