Control device and control method for an internal combustion engine

Abstract

To suppress combustion noise and deterioration of smoke when switching a plurality of combustion methods.SOLUTION: A control device is a control device for an engine. The engine includes an injection system for injecting fuel with controlled pressure. In the case of switching to any of a plurality of combustion methods in the engine, the control device specifies injection timing of each of a plurality of stages of fuel injection per cycle corresponding to the switched combustion method (Step S113, Step S114), controls the injection system so as to inject the fuel at the plurality of stages at each injection timing calculated in each cycle (Step S123, Step S124, Step S126), and in a transitional period of switching the combustion method, specifies the injection timing at the corresponding stage in the combustion method before and after the switching with regard to at least any stage out of the plurality of stages so as to gradually change from the injection timing in the combustion method before the switching to the injection timing in the combustion method after the switching (Step S125, Step S126).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] 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 that injects fuel at a controlled pressure.

Background Art

[0002] 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 front stage and a rear stage and injected (see, for example, Patent Document 1). Hereinafter, this combustion method is referred to as main two-stage injection combustion. In 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 during the combustion of the front stage and the pressure wave during the combustion of the rear stage can cancel each other out, and noise can be reduced. However, in main two-stage injection combustion, it has been found that smoke deteriorates due to a short ignition delay in the rear stage of the main injection.

[0003] As a countermeasure, by increasing the rail pressure of the common rail, the smoke characteristics can be improved. Increasing the rail pressure deteriorates combustion noise. However, in this regard, by keeping the increase in the rail pressure to the minimum necessary, both combustion noise and smoke can clear the target.

[0004] In the control map of the internal combustion engine, there are regions suitable and not suitable for main two-stage injection combustion and other combustion methods. There is concern that combustion noise and smoke will deteriorate during switching if only a plurality of combustion methods are switched on the control map.

[0005] As a technology to solve these problems, when switching to one of several combustion methods in an internal combustion engine, the injection amount for each of the multiple fuel injection stages per cycle according to the switched combustion method is calculated, and the injection system is controlled to inject fuel in multiple stages with the calculated injection amount in each cycle, and during the transition period of switching combustion methods, the injection amount for the corresponding stage in the combustion method before and after the switch is calculated to gradually change from the injection amount of the combustion method before the switch to the injection amount of the combustion method after the switch (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-19210 [Overview of the project] [Problems that the invention aims to solve]

[0007] According to the technology described in Patent Document 1, it is possible to suppress the deterioration of combustion noise and smoke when switching between multiple combustion methods. However, there was room for further improvement in the technology described in Patent Document 1.

[0008] This disclosure was made to solve the above-mentioned problems, and its purpose is to provide a control device and control method for an internal combustion engine that can further suppress the deterioration of combustion noise and smoke when switching between multiple combustion methods. [Means for solving the problem]

[0009] The control device relating to this disclosure is a control device for an internal combustion engine. The internal combustion engine is equipped with an injection system that injects fuel at a controlled pressure. When switching to one of several combustion methods in the internal combustion engine, the control device identifies the injection timing for each of the multiple fuel injection stages per cycle corresponding to the switched combustion method, controls the injection system to inject fuel in multiple stages at the respective injection timings calculated in each cycle, and during the transition period of switching combustion methods, it identifies the injection timing of the corresponding stage for at least one of the multiple stages in the combustion methods before and after the switch, so as to gradually change from the injection timing of the combustion method before the switch to the injection timing of the combustion method after the switch.

[0010] When the control device determines the injection timing, it further determines the injection amount for each of the multiple fuel injection stages per cycle according to the switched combustion method, and when controlling the injection system, it further controls the injection of fuel in multiple stages with the respective injection amounts calculated in each cycle, and during the transition period of switching combustion methods, it may further determine that the injection amount for the corresponding stage in the combustion methods before and after the switch should be gradually changed from the injection amount of the combustion method before the switch to the injection amount of the combustion method after the switch.

[0011] Multiple combustion methods may include a first combustion method and a second combustion method. The first and second combustion methods have different control ranges for fuel pressure. The control device controls the injection system to set the fuel pressure according to the combustion method, and during the transition period between the first and second combustion methods, it may calculate the degree of delay in following the fuel pressure after the switch, and calculate the injection timing of the corresponding stage before and after the switch to gradually change according to the calculated degree.

[0012] In the first combustion method, there are specific stages in multiple stages of one cycle, and in the second combustion method, there are no specific stages in multiple stages of one cycle. The control device may calculate that the injection timing of the specific stage changes gradually according to the calculated degree between the state in the second combustion method where there are no specific stages and the state in the first combustion method where there are specific stages.

[0013] According to other aspects of this disclosure, a method for controlling an internal combustion engine is performed by a control device for the internal combustion engine. The internal combustion engine includes an injection system that injects fuel at a controlled pressure. The control method includes, when the control device switches to one of a plurality of combustion modes in the internal combustion engine, the steps of: identifying each injection timing in a plurality of fuel injection stages per cycle corresponding to the switched combustion mode; controlling the injection system to inject fuel in a plurality of stages at each injection timing calculated in each cycle; and, during the transition period of switching combustion modes, identifying that for at least one of the plurality of stages, the injection timing of the corresponding stage in the combustion mode before and after the switch should be gradually changed from the injection timing of the combustion mode before the switch to the injection timing of the combustion mode after the switch. [Effects of the Invention]

[0014] This disclosure provides a control device and control method for an internal combustion engine that can further suppress the deterioration of combustion noise and smoke when switching between multiple combustion modes. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows a schematic configuration of the vehicle engine system in an embodiment of this disclosure. [Figure 2] This flowchart shows the flow of the fuel injection process in this embodiment. [Figure 3] This diagram illustrates the switching of the combustion method in this embodiment. [Figure 4] This figure shows the changes in injection pressure and injection parameters when switching between the main single-stage combustion method and the main double-stage combustion method in this embodiment. [Figure 5] This figure shows the changes in combustion pattern, heat generation, and heat generation start timing when switching between the main single-stage combustion method and the main double-stage combustion method in this embodiment. [Figure 6]It is a diagram showing changes in combustion patterns, heat generation, and combustion peaks during the switching between the main single-stage combustion method and the main two-stage combustion method in this embodiment.

Embodiments for Carrying Out the Invention

[0016] <x Hereinafter, embodiments of this disclosure will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0017] FIG. 1 is a diagram showing an outline of the configuration of an engine system 10 of a vehicle 1 in an embodiment of this disclosure. Referring 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, an EGR passage 18, an EGR valve .......

[0018] The control device 100 includes a CPU (Central Processing Unit) 110 that performs various processes, a memory 150 including a ROM (Read Only Memory) that stores programs and data and a RAM (Random Access Memory) that is used as a work memory of the CPU and stores processing results and the like, and input ports and output ports (both not shown) for exchanging information with devices external to the control device 100. The air flow meter 2, the opening sensor 17, the engine speed sensor 20, the pressure sensor 21, the accelerator opening sensor 22, etc. are connected to the input ports.

[0019] The control device 100 receives signals from each device connected to the input port, executes predetermined processing based on the received signals, and controls the intake throttle valve 16, fuel injection device 13, fuel pump 14, EGR valve 19, etc. connected to the output port based on the results of the processing.

[0020] 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). The EGR passage 18 is connected in the middle of the intake passage 8.

[0021] 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 of fresh air (intake air amount) introduced from the intake passage 8 into the engine system 10, and outputs a signal indicating the detected intake air amount to the control device 100.

[0022] 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 performs an opening / closing operation 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 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.

[0023] 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 four-cylinder engine, four cylinders 11a are provided in the engine 11. In FIG. 1, one configuration of the plurality of cylinders 11a is exemplarily shown, and the other cylinders have the same configuration. Therefore, the detailed description thereof will not be repeated.

[0024] The fuel injector 13 is located at the top of the cylinder 11a. The fuel injector 13 is composed of, for example, an injector having a body with a nozzle formed therein and a needle located inside the body that opens and closes the nozzle. The fuel injector 13 is connected to the fuel pump 14 and the fuel tank 12 via the common rail 15. The fuel pump 14 supplies fuel from the fuel tank 12 to the common rail 15 in response to a control signal from the control device 100 so that the fuel pressure in the common rail 15, as detected by the pressure sensor 21, reaches a predetermined pressure. The fuel injector 13 injects fuel from the common rail 15 into the combustion chamber in the cylinder 11a by operating the needle in response to a control signal from the control device 100, thereby opening the nozzle (i.e., connecting the nozzle to the common rail 15).

[0025] The control device 100 determines a control command value corresponding to the total injection amount Q injected in the fuel injector 13 during one cycle, according to the amount of accelerator pedal operation by the user detected by the accelerator pedal position sensor 22. The control device 100 controls the fuel injector 13 based on the determined control command value. The control command value is, for example, a value indicating the fuel injection time (injection opening time) or injection amount from the fuel injector 13.

[0026] The control device 100 controls the fuel injector 13 to inject the total injection amount Q to be injected in one cycle in multiple steps, for example. The control device 100 controls the fuel injector 13 to perform pilot injection, main injection, and after injection in one cycle, for example. Pilot injection is performed, for example, to suppress the generation of combustion noise and combustion pressure. Main injection is performed, for example, to achieve the torque required by the engine 11. After injection is performed, for example, to suppress the generation of smoke, etc.

[0027] The piston 11b is connected to the crankshaft (not shown), which is the output shaft. The engine speed sensor 20 is mounted 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 speed sensor 20 is connected to the control device 100 and transmits a signal indicating the detected rotational speed NE of the engine 11 to the control device 100.

[0028] One end of the exhaust passage 7 is connected to the engine 11 (more specifically, cylinder 11a). The exhaust passage 7 is equipped with an exhaust treatment device (not shown) that purifies PM (Particulate Matter), HC (Hydroxides), CO (Carbon Monoxide), and NOx (Nitrogen Oxides) in the exhaust.

[0029] The engine 11 is further equipped with an EGR (exhaust gas recirculation) system. The EGR system includes an EGR passage 18 and an EGR valve 19. The EGR passage 18 connects the exhaust passage 7 and the intake passage 8 without passing through the cylinder 11a, returning a portion of the exhaust gas discharged into the exhaust passage 7 to the intake passage 8. The EGR valve 19 adjusts the gas flow rate circulating through 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.

[0030] Specifically, the control device 100 sets a target value for the EGR rate based, for example, on the total injection amount Q and the rotational speed NE of the engine 11. The memory 150 of the control device 100, described later, stores, 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 for the EGR rate. The control device 100 sets a target value for the EGR rate from the total injection amount Q, the rotational speed NE of the engine 11, and the map described above, which correspond to the control command value. The control device 100 controls the opening degree of the EGR valve 19 so that the EGR rate reaches the target value.

[0031] Furthermore, the engine 11 is equipped with a supercharger (not shown) that uses exhaust energy flowing through the exhaust passage 7 to supercharge the air in the intake passage 8. 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 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 together, and supercharging is performed by pressurizing air from the compressor to the cylinders. In addition, a plurality of vanes are provided around the turbine blades in the turbine, configured to change the velocity at which the exhaust flows into the turbine blades. The plurality of vanes are operated by actuators. The control device 100 controls the opening degree between the vanes based on the operating state of the engine 11.

[0032] [assignment] Conventionally, in engines 11, when fuel is injected multiple times in one cycle, there was a combustion method in which the main injection was divided into a preceding and succeeding 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 preceding and succeeding main injections, the pressure waves during the combustion of the preceding stage and the pressure waves during the combustion of the succeeding stage can be canceled out, thereby reducing noise. However, it has been found that in main two-stage injection combustion, the smoke is worsened due to the short ignition delay of the succeeding main injection.

[0033] To address 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, by keeping the increase in rail pressure to the minimum necessary, both combustion noise and smoke can be kept within the target limits.

[0034] In the control map of engine 11, there are regions where the main two-stage injection combustion and other combustion methods are suitable, and regions where they are not. Simply switching between multiple combustion methods on the control map raises concerns that combustion noise and smoke will worsen during the switching process.

[0035] As a technology to solve these problems, when switching to one of several combustion methods in the engine 11, the injection amount for each of the multiple fuel injection stages per cycle according to the switched combustion method is calculated, and the injection system is controlled to inject fuel in multiple stages with the calculated injection amount for each cycle, and during the transition period of switching combustion methods, the injection amount for the corresponding stage in the combustion method before and after the switch is calculated to gradually change from the injection amount of the combustion method before the switch to the injection amount of the combustion method after the switch.

[0036] This technology can suppress the deterioration of combustion noise and smoke when switching between multiple combustion methods. However, there was still room for improvement in this technology.

[0037] Therefore, when the control device 100 switches to one of several combustion methods in the engine 11, it identifies the injection timing for each of the multiple fuel injection stages per cycle corresponding to the switched combustion method, and controls the fuel injection device 13 to inject fuel in multiple stages at the respective injection timings calculated in each cycle, and during the transition period of switching combustion methods, it identifies that for at least one of the multiple stages, the injection timing of the corresponding stage in the combustion method before and after the switch should be gradually changed from the injection timing of the combustion method before the switch to the injection timing of the combustion method after the switch.

[0038] This further suppresses the deterioration of combustion noise and smoke when switching between multiple combustion methods.

[0039] The control in this embodiment will now be described. Figure 2 is a flowchart showing the flow of the fuel injection process in this embodiment. Referring to Figure 2, this fuel injection process is called from a higher-level process by the CPU 110 of the control device 100 and executed for each cycle of each cylinder 11a of the engine 11, immediately before the start of that cycle.

[0040] In the engine 11 of this embodiment, the main single-stage combustion method and the main double-stage combustion method are switched. Figure 3 is a diagram illustrating the switching of the combustion method in this embodiment. Referring to Figure 3, as shown in Figure 3(A), in the main single-stage combustion method, in one cycle, the leading pilot injection, proximity pilot injection, main 1 injection, and after injection are performed. As shown in Figure 3(E), in the main double-stage combustion method, in one cycle, the leading pilot injection, proximity pilot injection, main 1 injection, and main 2 injection are performed.

[0041] Returning to Figure 2, the CPU 110 determines the target injection pressure for the main single-stage combustion method of the target cycle and stores it in the memory 150 (step S111), and also determines the target injection pressure for the main double-stage combustion method of the target cycle and stores it in the memory 150 (step S112). The target injection pressure can be determined by known methods described in Japanese Patent Application Publication No. 2022-19210, etc.

[0042] Furthermore, the CPU 110 determines the injection amount and injection timing for each stage of the main single-stage combustion method of the target cycle and stores them in the memory 150 (step S113), and also determines the injection amount and injection timing for each stage of the main double-stage combustion method of the target cycle and stores them in the memory 150 (step S114). The injection amount and injection timing for each combustion method can be determined by known methods described in Japanese Patent Application Publication No. 2022-19210, etc.

[0043] Next, the CPU 110 determines whether the target cycle is in a switching transient (step S121). If it determines that it is not in a switching transient (NO in step S121), the CPU 110 determines whether the combustion method of the target cycle is a main single-stage combustion method or a main double-stage combustion method (step S122).

[0044] If the CPU 110 determines that it is a main single-stage combustion system, it starts injection control for the target cycle using the injection amounts and injection timings for each stage of the main single-stage combustion system stored in memory 150 (step S123), and returns the processing to the higher-level processing that called this fuel injection process.

[0045] If the CPU 110 determines that it is a main two-stage combustion system, it starts injection control for the target cycle using the injection amounts and timings for each stage of the main two-stage combustion system stored in memory 150 (step S124), and returns the processing to the higher-level processing that called this fuel injection process.

[0046] On the other hand, if it is determined that a transitional phase is underway (YES in step S121), the CPU 110 calculates the ratio of the actual injection pressure to the target injection pressure for the target cycle (step S125).

[0047] Figure 4 shows the changes in injection pressure and injection parameters during the switching between the main single-stage combustion system and the main double-stage combustion system in this embodiment. Referring to Figure 4, the follow-up ratio from the start of the switch t1 to the end of the switch t2 is defined as "1" when the actual injection pressure P follows the target injection pressure P2 of the main double-stage combustion system, and as "0" when the actual injection pressure P follows the target injection pressure P1 of the main single-stage combustion system. The follow-up ratio r is calculated, for example, by the following formula (1). That is, 0 ≤ follow-up ratio r ≤ 1.

[0048] Follow-up ratio r = (Actual injection pressure P - Target injection pressure P1 for main 1-stage combustion system) / (Target injection pressure P2 for main 2-stage combustion system - Target injection pressure P1 for main 1-stage combustion system) ... (1) Referring again to Figure 2, the CPU 110 then calculates injection parameters such as the injection amount and injection timing for each stage according to the injection pressure tracking ratio r, starts injection control for the target cycle with the calculated injection parameters for each stage (step S126), and returns the processing to the higher-level processing that called this fuel injection process.

[0049] Referring again to Figure 4, in step S126, the injection parameters such as the injection amount and injection timing for each stage from the start of switching t1 to the end of switching t2 are calculated, for example, using the following formula (2).

[0050] Injection parameter X = Injection parameter X1 for main single-stage combustion system + (Injection parameter X2 for main two-stage combustion system - Injection parameter X1 for main single-stage combustion system) × Tracking ratio r ... (2) Referring again to Figure 3, the injection amount is shown by the width of the rectangle representing each injection (in the time axis direction), and the injection timing is shown by the time of the position on the time axis of the left side of the rectangle representing each injection. By controlling as shown in Figure 2, during the transition transient from the leading pilot injection of the main single-stage combustion system to the leading pilot injection of the main double-stage combustion system, the injection amount remains almost unchanged, while the injection timing gradually changes to an earlier timing.

[0051] During the transition from a close-range pilot injection in a single-stage main combustion system to a close-range pilot injection and main 1 injection in a two-stage main combustion system, the injection volume is first divided into the close-range pilot injection and the main 1 injection. The injection volume of the close-range pilot injection gradually decreases, and the injection timing of the close-range pilot injection gradually becomes earlier. The injection volume of the main 1 injection gradually increases, and the injection timing of the main 1 injection gradually becomes later.

[0052] During the transition from the main 1 injection and after injection of the main single-stage combustion system to the main 2 injection of the main double-stage combustion system, the injection amounts of the main 1 injection and after injection of the main single-stage combustion system gradually decrease, the injection timing of the main 1 injection and after injection of the main single-stage combustion system gradually becomes earlier, and the after injection is integrated into the main 2 injection of the main double-stage combustion system when the injection amount of the after injection becomes 0.

[0053] During the transition from the main two-stage combustion system to the main single-stage combustion system, the change is the reverse of the change shown in Figure 3(A) to Figure 3(E), which is the change from Figure 3(E) to Figure 3(A).

[0054] Figure 5 shows the changes in combustion pattern, heat generation, and heat generation start timing when switching between the main single-stage combustion method and the main double-stage combustion method in this embodiment. Referring to Figure 5, the height of each stage triangle indicates the amount of heat generated at each stage, and the length of the base of each stage triangle indicates the heat generation period at each stage. Note that after injection in the main single-stage combustion method is not shown in Figure 5.

[0055] As shown in Figure 5, for example, a circle is marked at the timing when heat generation for the main 1 injection begins. During the transition from the main single-stage combustion system to the main double-stage combustion system, by controlling the injection parameters of each stage as shown in Figure 2, for example, the timing at which heat generation for the main 1 injection begins can be gradually advanced according to the degree of tracking by the injection pressure. Thus, the timing at which heat generation begins (combustion start-up time) can be cited as an element that prevents abrupt changes in the connection of combustion. With the aim of preventing abrupt changes in the timing at which heat generation begins, injection parameters such as the injection amount and injection timing for each stage may be determined in step S126 of Figure 2.

[0056] Figure 6 shows the changes in combustion pattern, heat generation, and combustion peak when switching between the main single-stage combustion method and the main double-stage combustion method in this embodiment. Referring to Figure 6, the height of each stage triangle indicates the amount of heat generated at each stage, and the length of the base of each stage triangle indicates the heat generation period at each stage. Note that after-injection in the main single-stage combustion method is not shown in Figure 6.

[0057] As shown in Figure 6, during the transition from a single-stage main combustion system to a double-stage main combustion system, by controlling the injection parameters of each stage as shown in Figure 2, for example, the interval Δt between the combustion peaks Δt and the combustion peak height ratio Hp / Hm of the main 1 injection and the main 2 injection are gradually reduced according to the degree of injection pressure tracking. The interval Δt between the combustion peaks Δt and the combustion peak height ratio Hp / Hm are shown, for example, in Japanese Patent Application Publication No. 2021-116773. Thus, the interval Δt between the combustion peaks Δt and the combustion peak height ratio Hp / Hm of the main 1 injection and the main 2 injection can be cited as elements that prevent abrupt changes when connecting combustion. With the aim of preventing abrupt changes in the interval Δt between the combustion peaks Δt and the combustion peak height ratio Hp / Hm, injection parameters such as the injection amount and injection timing of each stage may be determined in step S126 of Figure 2.

[0058] [Differentiation] (1) In the embodiment described above, as shown in Figures 2 and 3, the engine 11 is configured to switch between a main single-stage combustion system and a main double-stage combustion system. However, it is not limited to this, and any combustion system can be switched as long as multiple combustion systems are switched. For example, three or more combustion systems may be switched, or multiple combustion systems included in the main single-stage combustion system may be switched, or multiple combustion systems included in the main double-stage combustion system may be switched.

[0059] (2) In the embodiments described above, as shown in Figures 2 and 3, the injection parameters such as the injection amount and injection timing were gradually changed for all stages of the combustion method before and after switching. However, the invention is not limited to this, and the injection stages in which the injection parameters are gradually changed may be at least some of the stages in one cycle.

[0060] (3) In the embodiments described above, as shown in Figures 2 and 3, the injection parameters to be gradually changed are the injection amount and the injection timing. However, the invention is not limited to this, and the injection parameters to be gradually changed may be other parameters, three or more parameters, or just one of the injection parameters, the injection amount and the injection timing.

[0061] (4) In the embodiment described above, as shown in Figure 4, the injection parameters were linearly increased or decreased during the switching period. However, the invention is not limited to this, and as long as the injection parameters are changed gradually, they may be increased or decreased nonlinearly rather than linearly. For example, instead of changing in a broken line shape as shown in the graph of injection parameters in Figure 4, they may be changed smoothly in a curved shape, or they may be changed in steps.

[0062] (5) In the embodiments described above, it was shown that the control range of the injection pressure for the main two-stage injection combustion is higher than that of the main single-stage combustion system. The control ranges of the two systems may overlap to some extent.

[0063] (6) In the embodiments described above, the engine 11 was assumed to be a diesel engine, as shown in Figure 1. However, it is not limited to this, and the engine 11 may be an internal combustion engine that uses other fuels, such as a gasoline engine, as long as it is configured to be able to change the fuel injection pressure.

[0064] (7) The aforementioned disclosure can be interpreted as a disclosure of the control device 100 for the engine 11. Alternatively, the aforementioned disclosure can be interpreted as a disclosure of an engine system 10 or vehicle 1 equipped with the control device 100, or as a disclosure of a control method or control program executed by the control device 100.

[0065] [summary] (1) As shown in Figures 1 and 2, the control device 100 is a control device for the engine 11. As shown in Figure 1, the engine 11 includes an injection system (for example, a system consisting of a fuel injector 13, a fuel pump 14, a common rail 15, a fuel tank 12, and a pressure sensor 21) that injects fuel at a controlled pressure. As shown in Figures 2 to 6, when the control device 100 switches to one of several combustion methods in the engine 11, it identifies the injection timing for each of the multiple fuel injection stages per cycle corresponding to the switched combustion method (for example, steps S113 and S114), controls the injection system to inject fuel in multiple stages at the respective injection timings calculated in each cycle (for example, steps S123, S124, and S126), and during the transition period of switching the combustion method, it identifies the injection timing for the corresponding stage of at least one of the multiple stages in the combustion method before and after the switch, so as to gradually change from the injection timing of the combustion method before the switch to the injection timing of the combustion method after the switch (for example, steps S125 and S126).

[0066] This suppresses the deterioration of combustion noise and smoke when switching between multiple combustion methods. In addition, because the injection amount is changed gradually, changes in the tone of the combustion sound can be minimized, resulting in a smoother transition between different tonal characteristics.

[0067] (2) As shown in Figure 2, when the control device 100 identifies the injection timing, it further identifies the injection amount for each of the multiple stages of fuel injection per cycle according to the switched combustion method (for example, steps S113 and S114), and when controlling the injection system, it further controls the injection of fuel in multiple stages with the respective injection amounts calculated in each cycle (for example, steps S123, S124, and S126), and during the transition period of switching the combustion method, it further identifies the injection amount for the corresponding stage in the combustion method before and after the switch, so as to gradually change from the injection amount of the combustion method before the switch to the injection amount of the combustion method after the switch (for example, steps S125 and S126).

[0068] This further suppresses the deterioration of combustion noise and smoke when switching between multiple combustion methods. In addition, because the injection amount is changed gradually, changes in the tone of the combustion sound can be minimized, resulting in a smoother transition between different tonal characteristics.

[0069] (3) As shown in Figures 2 to 6, the multiple combustion methods may include a first combustion method and a second combustion method. As shown in Figures 2 and 4, the first combustion method and the second combustion method have different fuel pressure control ranges. As shown in Figure 2, the control device 100 controls the injection system to set the fuel pressure according to the combustion method (for example, steps S123, S124, and S126), and during the transient period of switching between the first and second combustion methods, it may calculate the degree of delay in following the fuel pressure after the switch (for example, step S125), and calculate the injection timing of the corresponding stage before and after the switch to gradually change according to the calculated degree (for example, step S126).

[0070] This allows the fuel injection timing to be appropriately and gradually changed according to the degree of delay in the injection pressure response.

[0071] (4) As shown in Figure 3, in the first combustion method (for example, the main single-stage combustion method), there are specific stages (for example, after-injection stages) in multiple stages of one cycle, while in the second combustion method (for example, the main two-stage combustion method), there are no specific stages in multiple stages of one cycle. As shown in Figures 2 and 3, the control device 100 may calculate (for example, step S125, step S126) that the injection timing of the specific stage will gradually change according to the calculated degree between the state in which there are no specific stages in the second combustion method and the state in which there are specific stages in the first combustion method. This makes it possible to appropriately control the injection timing of the specific stage.

[0072] The embodiments disclosed herein are intended to be implemented in appropriate combinations. Furthermore, the embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the above-described embodiments, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0073] 1 Vehicle, 2 Airflow meter, 7 Exhaust passage, 8 Intake passage, 10 Engine system, 11 Engine, 11a Cylinder, 11b Piston, 12 Fuel tank, 13 Fuel injector, 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 unit, 110 CPU, 150 Memory.

Claims

1. A control device for an internal combustion engine, The internal combustion engine is equipped with an injection system that injects fuel at a controlled pressure, The control device is When switching to one of the multiple combustion methods in the internal combustion engine, the injection timing of each of the multiple fuel injection stages per cycle corresponding to the switched combustion method is specified. The injection system is controlled to inject fuel in multiple stages at each injection timing calculated in each cycle. A control device for an internal combustion engine that, during the transition period when switching combustion modes, calculates the degree of lag in the actual fuel pressure relative to the target fuel pressure, and specifies that for at least one of the multiple stages, the injection timing of the corresponding stage in the combustion mode before and after the switch should be gradually changed from the injection timing of the combustion mode before the switch to the injection timing of the combustion mode after the switch, according to the calculated degree.

2. The control device is When determining the injection timing, the injection amount for each of the multiple fuel injection stages per cycle, corresponding to the switched combustion method, is also determined. When controlling the injection system, the system is further controlled to inject fuel in multiple stages with the respective injection amounts calculated for each cycle. The control device for an internal combustion engine according to claim 1, further specifying that during the transition period of switching combustion methods, the injection amount for the corresponding stage in the combustion methods before and after the switching should be gradually changed from the injection amount of the combustion method before the switching to the injection amount of the combustion method after the switching.

3. The plurality of combustion methods include a first combustion method and a second combustion method, The first combustion method and the second combustion method differ in the control range of the fuel pressure. The control device is The injection system is controlled to adjust the fuel pressure according to the combustion method. A control device for an internal combustion engine according to claim 1 or 2, wherein during the transition period between the first combustion method and the second combustion method, the degree of delay in following the fuel pressure after the switch is calculated, and the injection timing of the corresponding stage before and after the switch is calculated to be gradually changed according to the calculated degree.

4. A control device for an internal combustion engine, The internal combustion engine is equipped with an injection system that injects fuel at a controlled pressure, The control device is When switching to one of the multiple combustion methods in the internal combustion engine, the injection timing of each of the multiple fuel injection stages per cycle corresponding to the switched combustion method is specified. The injection system is controlled to inject fuel in multiple stages at each injection timing calculated in each cycle. During the transition period when switching combustion methods, for at least one of the multiple stages, the injection timing of the corresponding stage in the combustion methods before and after the switch is specified to gradually change from the injection timing of the combustion method before the switch to the injection timing of the combustion method after the switch. The aforementioned multiple combustion methods include a first combustion method and a second combustion method. The first combustion method and the second combustion method differ in the control range of the fuel pressure. The control device is The injection system is controlled to adjust the fuel pressure according to the combustion method. A control device for an internal combustion engine, which calculates the degree of delay in following the fuel pressure after the switch during the transition period between the first combustion method and the second combustion method, and calculates the injection timing of the corresponding stage before and after the switch to gradually change according to the calculated degree.

5. In the first combustion method described above, there is a specific stage in multiple stages within one cycle. In the second combustion method described above, the specific stage does not exist in multiple stages within one cycle. The control device for an internal combustion engine according to claim 4, wherein the control device calculates that the injection timing of the specific stage changes gradually according to a calculated degree between a state in which the specific stage of the second combustion method does not exist and a state in which the specific stage of the first combustion method exists.

6. A method for controlling an internal combustion engine, which is performed by a control device for the internal combustion engine, The internal combustion engine is equipped with an injection system that injects fuel at a controlled pressure, The control method described above involves the control device, When switching to one of the multiple combustion methods in the internal combustion engine, the steps include: identifying the timing of each fuel injection in multiple stages per cycle according to the switched combustion method; A step of controlling the injection system to inject fuel in multiple stages at each injection timing calculated in each cycle, A control method for an internal combustion engine, comprising the steps of: during the transition period of switching between combustion methods, calculating the degree of lag in the actual fuel pressure relative to the target fuel pressure; and specifying that for at least one of multiple stages, the injection timing of the corresponding stage in the combustion method before and after the switch should be gradually changed from the injection timing of the combustion method before the switch to the injection timing of the combustion method after the switch, according to the calculated degree.

7. A method for controlling an internal combustion engine, which is performed by a control device for the internal combustion engine, The internal combustion engine is equipped with an injection system that injects fuel at a controlled pressure, The control method described above involves the control device, When switching to one of the multiple combustion methods in the internal combustion engine, the steps include: identifying the timing of each fuel injection in multiple stages per cycle according to the switched combustion method; A step of controlling the injection system to inject fuel in multiple stages at each injection timing calculated in each cycle, The transition period for switching combustion methods includes a step of calculating the degree of lag in the actual fuel pressure relative to the target fuel pressure, and specifying that for at least one of the multiple stages, the injection timing of the corresponding stage in the combustion method before and after the switch should be gradually changed from the injection timing of the combustion method before the switch to the injection timing of the combustion method after the switch, according to the calculated degree. The aforementioned multiple combustion methods include a first combustion method and a second combustion method. The first combustion method and the second combustion method differ in the control range of the fuel pressure. The control method further includes the control device, The process includes the step of controlling the injection system to set the fuel pressure to a level corresponding to the combustion method, In the aforementioned specific step, the control device calculates the degree of delay in following the fuel pressure after the switch during the transition period between the first combustion method and the second combustion method, and calculates the injection timing of the corresponding stage before and after the switch to gradually change according to the calculated degree, in a method for controlling an internal combustion engine.

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