JP2022019210A - Control device of internal combustion engine and control method - Google Patents

Abstract

To suppress the deterioration of combustion noise and smoke at the switching of a plurality of combustion methods.SOLUTION: An engine comprises an injection system (constituted by including a fuel injection device, a fuel pump, a common rail and a fuel tank) for injecting fuel by controlled pressure. When switching any of plurality of combustion methods of the engine (PCCI combustion, two-stage injection combustion), the control device calculates respective injection amounts in the injection of fuel in a plurality of stages per cycle corresponding to the switched combustion method (steps S123, S124, S132, S136 and S137), controls the injection system so as to inject the fuel at the calculated injection amounts of respective cycles in a plurality of the stages (step S141), and in a transition period of the switching of the combustion method, calculates the injection amount of the corresponding stage in the combustion method before and after the switching so that the injection amount is gradually changed to the injection amount of the combustion method after the switching from the injection amount of the combustion method before the switching (steps S132 to S135).SELECTED DRAWING: Figure 10

Description

This disclosure relates to a control device and a control method for an internal combustion engine, and more particularly to a control device and a control method for an internal combustion engine including an injection system for injecting fuel at a controlled pressure.

Conventionally, in a diesel engine, when fuel is injected a plurality of times in one cycle, there has been a combustion method in which the main injection is divided into a front stage and a rear stage (see, for example, Patent Document 1). Hereinafter, this combustion method is referred to as main two-stage injection combustion. In the main two-stage injection combustion, by adjusting the interval between the injection timing of the front stage and the injection timing of the rear stage of the main injection, the pressure wave at the time of combustion at the front stage and the pressure wave at the time of combustion at the rear stage cancel each other out. , Noise can be reduced. However, in the main two-stage injection combustion, it is known that the smoke is deteriorated due to the short ignition delay in the subsequent stage of the main injection.

As a countermeasure, the smoke characteristics can be improved by increasing the rail pressure of the common rail. Increasing the rail pressure worsens the combustion noise. However, for this, by keeping the rail pressure high to the minimum necessary, both combustion noise and smoke can be cleared.

Japanese Unexamined Patent Publication No. 2015-066284

Here, in the control map of the internal combustion engine, there is a region where the main two-stage injection combustion and other combustion methods are suitable and a region where the main two-stage injection combustion method is not suitable. Simply switching between multiple combustion methods on the control map may worsen combustion noise and smoke during switching.

This disclosure is made to solve the above-mentioned problems, and an object thereof is an internal combustion engine control device and control capable of suppressing deterioration of combustion noise and smoke when switching between a plurality of combustion methods. Is to provide a method.

The control device according to this disclosure controls an internal combustion engine. The internal combustion engine comprises an injection system that injects fuel at a controlled pressure. When switching to one of the multiple combustion methods in the internal combustion engine, the control device calculates the injection amount of each of the multiple stages of fuel injection per cycle according to the switched combustion method, and each calculated in each cycle. The injection system is controlled so that the fuel is injected in multiple stages according to the injection amount of Therefore, it 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, and the control device may satisfy a predetermined index in the first combustion method in the control map of the internal combustion engine. In the region where there is no predetermined index, the combustion method is switched to the second combustion method in which the predetermined index satisfies the predetermined standard.

The control range of the fuel pressure differs between the first combustion method and the second combustion method, and the control device controls the injection system so that the fuel pressure is set 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 before and after switching is gradually changed according to the calculated degree. It may be calculated as follows.

For example, in the first combustion method, the main injection in one cycle is one stage, in the second combustion method, the main injection in one cycle is two stages, a front stage and a rear stage, and the control device is the first stage. During the transitional 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 where the latter stage of the main injection of the first combustion method does not exist and the second It may be calculated so that the injection amount of the latter stage of the main injection gradually changes according to the calculated degree between the state where the latter stage of the main injection of the combustion method 2 exists.

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

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

It is a figure which shows the outline of the structure of the engine system of the vehicle in embodiment of this disclosure. It is a figure which shows the switching from PCCI (Premixed Charge Compression Ignition) combustion to the main two-stage injection combustion in the control map according to the engine rotation speed and the total injection amount of fuel in this disclosure subject. It is a figure which shows the change of the rail pressure at the time of switching from PCCI combustion to main two-stage injection combustion in the subject of this disclosure. It is a figure which shows the change of the injection pattern and heat generation at the time of switching from PCCI combustion to main two-stage injection combustion in the subject of this disclosure. It is a figure which shows the switching from the main two-stage injection combustion to PCCI combustion in the control map according to the rotation speed of the engine 11 and the total injection amount of fuel in this disclosure subject. It is a figure which shows the change of the rail pressure at the time of switching from the main two-stage injection combustion to PCCI combustion in the subject of this disclosure. It is a figure which shows the change of the injection pattern and heat generation at the time of switching from the main two-stage injection combustion to PCCI combustion in the subject of this disclosure. It is a flowchart which shows the flow of the fuel injection process in this embodiment. It is a flowchart which shows the flow of the fuel injection first half processing in this embodiment. It is a flowchart which shows the flow of the fuel injection latter half processing in this embodiment. It is a figure which shows the switching from PCCI combustion to the main two-stage injection combustion in the control map according to the rotation speed of the engine 11 and the total injection amount of fuel in the embodiment of this disclosure. It is a figure which shows the change of the rail pressure, the follow-up ratio, and the injection amount of a main 2 injection at the time of switching from PCCI combustion to the main two-stage injection combustion in the embodiment of this disclosure. It is a figure which shows the change of the injection pattern and heat generation at the time of switching from PCCI combustion to main two-stage injection combustion in the embodiment of this disclosure. It is a figure which shows the switching from the main two-stage injection combustion to PCCI combustion in the control map according to the rotation speed of the engine 11 and the total injection amount of fuel in the embodiment of this disclosure. It is a figure which shows the change of the rail pressure, the follow-up ratio, and the injection amount of a main 2 injection at the time of switching from the main two-stage injection combustion to PCCI combustion in the embodiment of this disclosure. It is a figure which shows the change of the injection pattern and the heat generation at the time of switching from the main two-stage injection combustion to PCCI combustion in the embodiment of this disclosure.

Hereinafter, embodiments of this disclosure will be described with reference to the drawings. In the following description, the same parts are designated by the same reference numerals. Their names and functions are the same. Therefore, detailed explanations about them are not repeated.

FIG. 1 is a diagram showing an outline of the configuration of the engine system 10 of the vehicle 1 in the embodiment of this disclosure. With reference to FIG. 1, the 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. , EGR valve 19, air flow meter 2, intake throttle valve 16, opening sensor 17, engine rotation speed sensor 20, pressure sensor 21, accelerator opening sensor 22, and 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 of the CPU and stores processing results and the like. It includes a memory 150 including an Access Memory) and an input port and an output port (neither shown) for exchanging information with an external device of the control device 100. An air flow meter 2, an opening degree sensor 17, an engine rotation speed sensor 20, a pressure sensor 21, an accelerator opening degree sensor 22, and the like are connected to the input port.

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

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 in 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. The air flow meter 2 detects the flow rate (intake air amount) of fresh air introduced into the engine system 10 from the intake passage 8 and outputs a signal indicating the detected intake air amount to the control device 100.

The intake throttle valve 16 is provided at a position between the air flow meter 2 and the confluence position of the EGR passage 18. The intake throttle valve 16 opens and closes according 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 degree of the intake throttle valve 16 and outputs a signal indicating the detected opening degree of the intake throttle valve 16 to the control device 100.

The engine 11 is an internal combustion engine such as a diesel engine. The engine 11 includes a plurality of cylinders 11a and a plurality of pistons 11b. For example, when the engine 11 is a 4-cylinder engine, the engine 11 is provided with four cylinders 11a. Note that FIG. 1 schematically shows the configuration of one of the plurality of cylinders 11a, and the other cylinders have the same configuration. Therefore, the detailed explanation will not be repeated.

The fuel injection device 13 is provided at the top of the cylinder 11a. The fuel injection device 13 is composed of, for example, an injector having a body in which a injection hole is formed and a needle provided inside the body and opening and closing the injection hole. The fuel injection device 13 is connected to the fuel pump 14 and the fuel tank 12 via the common rail 15. The fuel pump 14 supplies the fuel in the fuel tank 12 to the common rail 15 so that the pressure of the fuel in the common rail 15 detected by the pressure sensor 21 becomes a predetermined pressure in response to the control signal from the control device 100. .. The fuel injection device 13 operates the needle in response to a control signal from the control device 100 to open the injection hole (that is, the injection hole and the common rail 15 are in a communicating state), whereby the fuel in the common rail 15 is introduced. It is injected into the combustion chamber in the cylinder 11a.

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

The control device 100 controls the fuel injection device 13 so that, for example, the total injection amount Q injected in one cycle is injected in a plurality of times. The control device 100 controls the fuel injection device 13 so that, for example, the pilot injection, the main injection, and the after injection are executed in 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 required for the engine 11. After injection is performed, for example, to suppress the generation of smoke and the like.

The piston 11b is connected to a crank shaft (not shown) which is an output shaft. The engine rotation speed sensor 20 is provided on the crank shaft and detects the rotation speed of the crank shaft (hereinafter, referred to as the rotation 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) for purifying PM (Particulate Matter), HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) in the exhaust.

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 gas flow rate circulated by the EGR passage 18 in response to a control signal from the control device 100. The control device 100 controls the opening degree of the EGR valve 19 based on the operating state of the engine 11.

Specifically, the control device 100 sets a target value of the EGR rate based on, for example, the total injection amount Q and the rotation speed NE of the engine 11. In the memory 150 described later of the control device 100, for example, a map showing the relationship between the total injection amount Q, the rotation speed NE of the engine 11, and the target value of the EGR rate is stored. The control device 100 sets a target value of the EGR rate from the total injection amount Q corresponding to the control command value, the rotation speed NE of the engine 11, and the map described above. The control device 100 controls the opening degree of the EGR valve 19 so that the EGR rate becomes the target value.

Further, the engine 11 is provided with a supercharger (not shown) that supercharges the air in the intake passage 8 by using the exhaust energy flowing through the exhaust passage 7. The turbocharger includes, for example, a turbine provided in the exhaust passage 7 and accommodating the turbine blades, a compressor provided in the intake passage 8 and accommodating the compressor blades, and a shaft connecting the turbine blades and the compressor blades. .. When the turbine blades in the turbine rotate due to the exhaust flowing through the exhaust passage 7, the shaft connected to the turbine blades and the compressor blades rotate integrally, and air is pumped from the compressor to the cylinder to supercharge. .. Further, around the turbine blades in the turbine, a plurality of vanes configured so as to be able to change the inflow speed of the exhaust gas into the turbine blades are provided. Multiple vanes are actuated by actuators. The control device 100 controls the opening degree between the vanes based on the operating state of the engine 11.

[Task]
Conventionally, in the engine 11, when fuel is injected a plurality of times in one cycle, there has been a combustion method in which the main injection is divided into a front stage and a rear stage. This combustion method is called main two-stage injection combustion. In the main two-stage injection combustion, by adjusting the interval between the injection timing of the front stage and the injection timing of the rear stage of the main injection, the pressure wave at the time of combustion at the front stage and the pressure wave at the time of combustion at the rear stage cancel each other out. , Noise can be reduced. However, in the main two-stage injection combustion, it is known that the smoke is deteriorated due to the short ignition delay in the subsequent stage of the main injection.

As a countermeasure, the smoke characteristic can be improved by increasing the rail pressure of the common rail 15. Increasing the rail pressure worsens the combustion noise. However, for this, by keeping the rail pressure high to the minimum necessary, both combustion noise and smoke can be cleared.

Here, in the control map of the engine 11, there is a region where the main two-stage injection combustion and other combustion methods are suitable and a region where the main two-stage injection combustion method is not suitable. Simply switching between multiple combustion methods on the control map may worsen combustion noise and smoke during switching.

FIG. 2 is a diagram showing switching from PCCI combustion to main two-stage injection combustion in a control map according to the rotation 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 premixed mixture having a constant fuel concentration distribution after a premixing period is compressed and ignited 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 illustrated and described. It should be noted that a combustion method different from these two combustion methods may be used, or three or more combustion methods may be switched.

With reference to FIG. 2, the horizontal axis shows the rotation speed NE of the engine 11, and the vertical axis shows the total fuel injection amount Q per cycle. The ignitability index τ0 is predetermined for each combination of the rotation speed NE and the total injection amount Q on this control map. If the main two-stage injection combustion region, which is the area surrounded on the control map, is PCCI combustion, the combustion noise is large, while if it is the main two-stage injection combustion, the combustion noise is relatively small. This area is suitable for injection combustion. The area outside the area enclosed on the control map is the PCCI area.

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

FIG. 3 is a diagram showing a change in rail pressure when switching from PCCI combustion to main two-stage injection combustion in the subject of this disclosure. The rail pressure control range in the main two-stage injection combustion is higher than the rail pressure control range in PCCI combustion. Therefore, if the indexes used for control such as the rotation speed NE and the total injection amount Q are about the same, the control points (2) and the control points (2) in the main two-stage injection combustion region from the control point (1) in the PCCI region. When switching to 3), the rail pressure must be increased.

With reference 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. The target value for controlling the rail pressure is raised from the rail pressure in PCCI combustion to the rail pressure in main two-stage injection combustion, but the actual rail pressure follows with a delay, so at the control point (2), the main value is used. It will be lower than the rail pressure 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. With reference to FIG. 4, since PCCI combustion is performed at the control point (1), the rail pressure is lower than that of the main two-stage injection combustion, and the pilot 1 injection (PL1), the pilot 2 injection (PL2), and so on. Fuel is injected in the order of main injection (MAIN). In PCCI combustion, after injection is actually performed after the main injection, but it is not shown in the figure. Combustion heat is generated inside the cylinder 11a in response to these injections.

At the 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 main 1 injection in the front stage and the main 2 injection in the rear stage, the main combustion method is It 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). In the main two-stage injection combustion, after injection is actually performed after the main two injection, but it is not shown in the figure. Combustion heat is generated inside the cylinder 11a in response to these injections.

In the transition state from PCCI combustion to main two-stage injection combustion as in control point (2), the injection pattern such as the injection timing and injection amount of each injection can be immediately switched to the injection pattern of main two-stage injection combustion. Is. However, since the rail pressure is delayed in following, the rail pressure becomes lower than the rail pressure required for the main two-stage injection combustion. Therefore, the amount of smoke generated deteriorates.

At the control point (3), the rail pressure of the main two-stage injection combustion is completely increased. Therefore, the smoke generation state is the original good state of the 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 rotation speed of the engine 11 and the total injection amount of fuel in the subject of this disclosure. With reference to FIG. 5, as in FIG. 2, the horizontal axis indicates the rotation speed NE of the engine 11, and the vertical axis indicates the total fuel injection amount Q per cycle. Contrary to FIG. 2, here, the combination of the rotation speed NE and the total injection amount Q is changed from the control point (4) in the main two-stage injection combustion region to the control point (5) in the PCCI region to the PCCI region. The case of switching to the control point (6) of the above will be described.

FIG. 6 is a diagram showing a change in rail pressure when switching from main two-stage injection combustion to PCCI combustion in the subject of this disclosure. The control range of the rail pressure in the PCCI combustion is lower than the control range of the rail pressure in the main two-stage injection combustion. Therefore, if the indexes used for control such as the rotation speed NE and the total injection amount Q are about the same, the control points (5) and the control points (5) in the PCCI region from the control point (4) in the main two-stage injection combustion region ( When switching to 6), the rail pressure must be reduced.

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

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

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

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

At the control point (6), the rail pressure of PCCI combustion is completely reduced. 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 the control map worsens combustion noise and smoke at the time of switching.

[Control in this disclosure]
Therefore, when switching to any of the plurality of combustion methods in the engine 11, the control device 100 calculates each injection amount in the injection of the fuel in a plurality of stages per cycle according to the switched combustion method, and calculates in each cycle. The fuel injection device 13 is controlled so as to inject a plurality of stages of fuel at each of the injected injection amounts, and during the transition period of switching the combustion method, the injection amount of the corresponding stage in the combustion method before and after the switching is set before the switching. It is calculated so that the injection amount of the combustion method gradually changes to the injection amount of the combustion method after switching.

As a result, it is possible to suppress deterioration of combustion noise and smoke when switching between a plurality of combustion methods.

Hereinafter, the control in this embodiment will be described. 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 at predetermined control cycles from the higher-level process. The PCCI combustion and main two-stage injection combustion shown below are known combustion methods, and the injection amount in each injection such as one-cycle pilot injection, main injection, and after injection of PCCI combustion and main two-stage injection combustion, and Since the methods for calculating the injection timing are known, these calculation methods will not be described in detail.

With reference to FIG. 8, first, the CPU 110 of the control device 100 executes the fuel injection first half process shown in FIG. 9 described later (step S110).

FIG. 9 is a flowchart showing the flow of the fuel injection first half process in this embodiment. With reference to FIG. 9, the CPU 110 acquires the accelerator opening degree detected by the accelerator opening degree sensor 22 and the rotation speed NE of the engine 11 detected by the engine rotation speed sensor 20 (step S111).

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

The CPU 110 calculates a target ignition timing IGtrg that satisfies the requirements for exhaust gas and fuel consumption by using the accelerator opening degree, the total injection amount Q, the rotation speed NE, and the like (step S114). The CPU 110 ignites after the fuel injection for obtaining the target combustion waveform is started based on a preset map using the accelerator opening, the rotation speed NE, the outside temperature, the atmospheric pressure, the cooling water temperature, and the like. The target ignition delay τtrg, which is the time until, is calculated (step S115). The CPU 110 calculates the ignition delay deviation Δτ (= target ignition delay τtrg − ignition property 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, the required in-cylinder temperature is calculated from the ignition delay deviation Δτ, the current in-cylinder temperature is subtracted from the required in-cylinder temperature, the desired in-cylinder temperature is calculated, and the required in-cylinder temperature for achieving the desired in-cylinder temperature is achieved. The calorific value is calculated, and the injection amount of the pilot injection for generating the required pilot calorific value 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 the pilot 1 injection and the injection amount of the pilot 2 injection shall be a predetermined constant ratio.

The CPU 110 determines the injection timing of the pilot injection (step S118). When the spray from the injector of the fuel injection device 13 touches the wall surface, it cools down and the HC deteriorates. Therefore, the start timing of the injection period of the pilot 1 injection is ignited by advancing as much as possible so that the spray does not touch the wall surface. By increasing the delay and making the combustion as slow as possible, the initial inclination of the combustion waveform is reduced. The length of the injection period of the pilot 1 injection is calculated from the injection amount and the rail pressure of the pilot 1 injection.

In order to reduce the initial inclination of the combustion waveform by superimposing the combustion for the pilot 2 injection with the combustion for the main injection, the injection period of the pilot 2 injection is in close contact with the injection period of the main injection. The length of the injection period of the pilot 2 injection is calculated as the injection amount and the rail pressure of the pilot 2 injection.

The CPU 110 determines the injection timing of the 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 set to adjust the ignition timing to ensure the required equivalence.

First, the provisional 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 steps S117 and S118 are executed, and the heat generation shape when the temporary main injection amount is injected at the calculated temporary main injection timing is estimated. The temporary main injection amount is calculated by subtracting the pilot 1 injection amount, the pilot 2 injection amount, and the temporary 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 estimated error. In addition, since the ignition timing is earlier because 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 earlier ignition timing to the target ignition timing.

After step S119, the CPU 110 returns the process to be executed to the fuel injection process of the caller of 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 described later (step S120).

FIG. 10 is a flowchart showing the flow of the fuel injection second half processing in this embodiment. With reference to FIG. 10, the CPU 110 has a current control point in the PCCI region on the control map shown in FIG. 2 and the like based on the rotation speed NE of the engine 11, the total injection amount Q, and the ignitability index τ0. Or, it is in the main two-stage injection combustion region, or it is 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 from the PCCI region to the main 2 It is determined whether the switching period is after the switching to the stage injection combustion region (step S121).

When it is determined that the control point is in the PCCI region, the CPU 110 obtains the target rail pressure for PCCI using the rotation speed NE of the engine 11 and the total injection amount Q (step S122). The target rail pressure for PCCI is predetermined in association with the combination of the rotation speed NE and the total injection amount Q, as in the case of the ignitability index τ0 in FIG. That is, the rail pressure of PCCI combustion is controlled within a predetermined control range.

The CPU 110 uses the rotation speed NE of the engine 11 and the total injection amount Q to determine the injection amount and the injection timing of the after injection for PCCI (step S123). The injection amount and the injection timing of the after injection for PCCI are predetermined in association with the combination of the rotation speed NE and the total injection amount Q, as in the ignitability index τ0 of 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 injection amount of the after injection from the total injection amount Q (step S124).

On the other hand, when it is determined that the control point is in the main two-stage injection combustion region or the switching period between the PCCI region and the main two-stage injection combustion region, the CPU 110 determines that the rotation speed NE and the total injection amount Q of the engine 11. Is used to obtain the target rail pressure for main two-stage injection (step S131). The target rail pressure for main two-stage injection is predetermined in association with the combination of the rotation speed NE and the total injection amount Q, as in the case of 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 uses the rotation speed NE of the engine 11, the total injection amount Q, and the ignitability index τ0 to determine the injection amount and the injection timing of the main 2 injections of the main two-stage injection combustion (step S132). The injection amount and injection timing of the main two injections of the main two-stage injection combustion are predetermined in correspondence with the combination of the rotation speed NE and the total injection amount Q, as in the ignitability index τ0 of FIG.

The CPU 110 determines whether or not the current time is the switching period between the PCCI region and the main two-stage injection combustion region (step S133). When 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 the actual injection pressure with respect to the target rail pressure calculated in step S131. The follow-up ratio is calculated (step S134). The follow-up ratio is "1" when the actual injection pressure follows the target injection pressure of the main two-stage injection combustion, and "0" when the actual injection pressure follows the target injection pressure of PCCI combustion. Is. The follow-up ratio is calculated by the following formula (1). That is, 0 ≦ follow-up 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 2 injections during 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 injections during the switching period is calculated by 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)
Since there is no main 2 injection in PCCI combustion, the injection amount of the main 2 injection in PCCI combustion is "0". That is, the mathematical formula (2) can be expressed as the following mathematical formula (3).

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)
When it is determined that it is not the switching period (NO in step S133), that is, when the control point is in the main two-stage injection combustion region, or after step S135, the CPU 110 determines the rotation speed NE and the total injection amount Q of the engine 11. Is used to determine the injection amount and injection timing of the after injection for main two-stage injection (step S136). The injection amount and the injection timing of the after injection for the main two-stage injection are predetermined in accordance with the combination of the rotation speed NE and the total injection amount Q, as in the ignitability index τ0 of 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 injection amount of 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 injection control of the next cycle with 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 of the caller of the fuel injection second half process.

Since each parameter such as the rotation speed NE and the total injection amount Q of the engine 11 is not constant even in the switching period, the rail pressure as soon as these parameters move, and the injection amount and injection timing of each injection are changed. The follow-up 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 in a control map according to the rotation speed of the engine 11 and the total injection amount of fuel in the embodiment of the disclosure. With reference to FIG. 11, FIG. 11 is similar to FIG. 2, so no duplicate description will be repeated.

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

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

With reference 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. The target value for controlling the rail pressure is raised from the rail pressure in PCCI combustion to the rail pressure in main two-stage injection combustion, but the actual rail pressure follows with a delay, so at the control point (2), the main value is used. It will be lower than the rail pressure required for two-stage injection combustion.

Therefore, 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, the follow-up ratio gradually changes from 0 to 1 during the switching period, and accordingly, the injection amount of the main 2 injection is also the injection amount of the main 2 injection of PCCI combustion (there is no main 2 injection in PCCI combustion). Therefore, it gradually changes from 0) to the injection amount of the main 2 injection of the main 2 stage injection combustion. In the case of not gradually changing in this way, only the injection amount of the main two-stage injection was set as the injection amount of the main two-stage injection combustion in a state where the rail pressure did not rise 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. With reference to FIG. 13, since PCCI combustion is performed at the control point (1), the rail pressure is lower than that of the main two-stage injection combustion, and the pilot 1 injection (PL1), pilot 2 injection (PL2), and so on. Fuel is injected in the order of main injection (MAIN). In PCCI combustion, after injection is actually performed after the main injection, but it is not shown in the figure. Combustion heat is generated inside the cylinder 11a in response to these injections.

At the 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 main 1 injection in the front stage and the main 2 injection in the rear stage, the main 2 is used as the combustion method. It becomes 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). In the main two-stage injection combustion, after injection is actually performed after the main two injection, but it is not shown in the figure. Combustion heat is generated inside the cylinder 11a in response to these injections.

In the switching period from PCCI combustion to main two-stage injection combustion as in control point (2), the injection pattern such as the injection timing and injection amount of each injection can be immediately switched to the injection pattern of main two-stage injection combustion. Is. Since the rail pressure is delayed in following, it becomes lower than the rail pressure required for the main two-stage injection combustion. However, in this embodiment, the injection amount of the main 2 injection is gradually changed according to 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 the control point (3), the rail pressure of the main two-stage injection combustion is completely increased. 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 rotation speed of the engine 11 and the total injection amount of fuel in the embodiment of this disclosure. With reference to FIG. 14, FIG. 14 is similar to FIG. 5, so no duplicate description is repeated.

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

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

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

Therefore, 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, the follow-up ratio gradually changes from 1 to 0 during the switching period, and accordingly, the injection amount of the main 2 injection also changes from the injection amount of the main 2 injection of the main two-stage injection combustion to the main 2 of the PCCI combustion. It gradually changes to the injection amount of the injection (0 because there is no main 2 injection in PCCI combustion). In the case of not gradually changing in this way, only the injection amount of the main 2 injection was set as the injection amount of PCCI combustion (that is, 0) in a state where the rail pressure did not drop to the pressure required for PCCI combustion.

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

At the control point (5), it is the switching period from the main two-stage injection combustion to the PCCI combustion, and since the main injection is divided into the main 1 injection in the front stage and the main 2 injection in the rear stage, the main 2 is used as the combustion method. It becomes 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). In the main two-stage injection combustion, after injection is actually performed after the main two injection, but it is not shown in the figure. Combustion heat is generated inside the cylinder 11a in response to these injections.

In the switching period from the main two-stage injection combustion to the PCCI combustion as in the control point (5), the injection pattern such as the injection timing and the injection amount of each injection can be immediately switched to the injection pattern of the PCCI combustion. Since the rail pressure is delayed in following, it becomes higher than the rail pressure required for PCCI combustion. However, in this embodiment, the injection amount of the main 2 injection is gradually changed according to 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 becoming large, and it is possible to prevent the combustion noise from deteriorating.

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

[Modification example]
(1) In the above-described embodiment, 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 a gasoline engine as long as it is configured so that the injection pressure of the fuel can be changed.

(2) In the above-described embodiment, the 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 above-described embodiment, as shown in FIG. 4 and the like, the pilot injection has two stages, the main injection has one or two stages, and the after injection has one stage. However, the present invention is not limited to this, and other injections, for example, post injections may be included. Further, the number of stages of each injection may be another number.

(4) In the above-described embodiment, as shown in FIGS. 8 to 16, the injection amount of the main 2 injection is gradually changed. However, the present invention is not limited to this, and the injection amount of other injections (for example, main 1 injection and after injection) may be gradually changed.

(5) In the above-described embodiment, 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 present invention is not limited to this, and if the injection amount is gradually changed, the injection amount may be increased or decreased non-linearly instead of linearly. For example, as shown in the graph of the main 2 injection amount in FIG. Instead of changing the shape, the shape may be changed smoothly in a curved shape.

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

(7) The above-mentioned disclosure can be regarded as the disclosure of the control device 100 of the engine 11. Further, the above-mentioned disclosure can be regarded as the disclosure of the engine system 10 or the vehicle 1 including the control device 100, and can be regarded as the disclosure of the control method or the 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, including 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 the control device 100 is switched to any of a plurality of combustion methods (for example, PCCI combustion, main two-stage injection combustion) in the engine 11, 1 according to the switched combustion method. Each injection amount in the injection of a plurality of stages of fuel per cycle is calculated (for example, step S117, step S123, step S124, step S132, step S136, step S137), and the fuel is fueled at each injection amount calculated in each cycle. The injection system is controlled to inject a plurality of 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 the switching is set to the injection of the combustion method before the switching. From the amount, it is calculated so as to gradually change to the injection amount of the combustion method after switching (for example, step S132 to step S135).

As a result, it is possible to suppress deterioration of combustion noise and smoke when switching between a plurality of combustion methods. Further, since the injection amount is gradually changed, the change in the timbre of the combustion sound can be minimized, and the connection of the timbre 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, in the control map of the engine 11, in the first combustion method, a predetermined index (for example, combustion noise, smoke) is a predetermined reference (for example, a design standard, a requirement). In the region that does not satisfy the predetermined standard), the combustion method is switched to the second combustion method in which the predetermined index satisfies the predetermined standard (for example, step S121).

Thereby, the combustion method can be used in the advantageous region of the first combustion method and the second combustion method on the control map.

(3) As shown in FIG. 3 and the like, the control range of the 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 so that the pressure of the fuel is set according to the combustion method (for example, step S141), and the first combustion method and the second combustion method are used. During the transition period of switching with, the degree of delay in following the fuel pressure after switching is calculated (for example, step S134), and the injection amount of the corresponding stage before and after switching is gradually changed according to the calculated degree. (For example, step S135).

Thereby, the injection amount of the fuel can be appropriately gradually changed according to the degree of the follow-up delay of the fuel pressure.

(4) As shown in FIG. 4 and the like, in the first combustion method, the main injection in one cycle is one stage, and in the second combustion method, the main injection in one cycle is two stages, a front stage and a rear stage. Is. As shown in FIGS. 8 to 10, the control device 100 calculates the degree of delay in following the pressure of the fuel after switching during the transitional period of switching between the first combustion method and the second combustion method. (Step S134), the main injection is performed according to the calculated degree between the state in which the subsequent stage of the main injection of the first combustion method does not exist and the state in which the subsequent stage of the main injection of the second combustion method exists. It is calculated so that the injection amount in the subsequent stage gradually changes (step S135).

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

It is also planned that the embodiments disclosed this time will be implemented in combination as appropriate. And it should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present disclosure is set forth by the claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims.

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 rotation speed sensor, 21 pressure sensor, 22 accelerator opening sensor, 100 control device, 110 CPU, 150 memory.

Claims (5)

It is a control device for an internal combustion engine.
The internal combustion engine comprises an injection system that injects fuel at a controlled pressure.
The control device is
When switching to any of the plurality of combustion methods in the internal combustion engine, the injection amount of each of the multiple stages of fuel injection per cycle according to the switched combustion method is calculated.
The injection system is controlled to inject multiple stages of fuel with each injection amount calculated in each cycle.
During the transition period of the switching of the combustion method, the injection amount of the corresponding stage in the combustion method before and after the switching is calculated so as to gradually change from the injection amount of the combustion method before the switching to the injection amount of the combustion method after the switching. , Internal combustion engine control device. The plurality of combustion methods include a first combustion method and a second combustion method.
The control device switches to the second combustion method in which the predetermined index satisfies the predetermined standard in the region where the predetermined index does not satisfy the predetermined standard in the first combustion method in the control map of the internal combustion engine. The control device for an internal combustion engine according to claim 1. The control range of the fuel pressure differs between the first combustion method and the second combustion method.
The control device is
The injection system is controlled so that the fuel pressure is set according to the combustion method.
During the transitional period of switching between the first combustion method and 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 before and after switching is calculated. The control device for an internal combustion engine according to claim 2, which is calculated so as to gradually change according to the degree of fuel. In the first combustion method, the main injection in one cycle is one stage.
In the second combustion method, the main injection in one cycle is two stages, a front stage and a rear stage.
The control device calculates the degree of delay in following the pressure of the fuel after the switching during the transitional period of switching between the first combustion method and the second combustion method, and the control device calculates the degree of delay in following the pressure of the fuel after the switching. It is calculated so that the injection amount of the latter stage of the main injection gradually changes according to the calculated degree between the state where the latter stage of the main injection does not exist and the state where the latter stage of the main injection of the second combustion method exists. , The control device for an internal combustion engine according to claim 3. A method for controlling an internal combustion engine, which is executed by a control device for the internal combustion engine.
The internal combustion engine comprises an injection system that injects fuel at a controlled pressure.
In the control method, the control device
When switching to any of the plurality of combustion methods in the internal combustion engine, a step of calculating each injection amount in the injection of a plurality of stages of fuel per cycle according to the switched combustion method, and
A step of controlling the injection system to inject multiple stages of fuel with each injection amount calculated in each cycle, and
During the transition period of the switching of the combustion method, the injection amount of the corresponding stage in the combustion method before and after the switching is calculated so as to gradually change from the injection amount of the combustion method before the switching to the injection amount of the combustion method after the switching. How to control an internal combustion engine, including steps.

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