Fuel injection amount control system and fuel injection amount control method

Abstract

To provide a fuel injection amount control system and a fuel injection amount control method, which can suppress deviation of a pilot heat generation amount from a target pilot heat generation amount in a premixed combustion mode.SOLUTION: A fuel injection amount control system comprises a processing circuit. The processing circuit executes a correction mode for switching a part of a plurality of cylinders from a premixing combustion mode to a diffusion combustion mode at prescribed timing during a period in which each of the plurality of cylinders is controlled in the premixing combustion mode, acquires, in the correction mode, the heat release rate associated with a pilot fuel injection with respect to a first target pilot fuel injection amount in a correction target cylinder in which a fuel injection amount is controlled in the diffusion mode, and corrects the pilot fuel injection amount for the correction target cylinder.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a fuel injection amount control system and a fuel injection amount control method for a dual fuel engine. [Background technology]

[0002] The fuel injection control modes of a dual fuel engine include a diffusion combustion mode in which fuel and intake air are separately supplied to the cylinders of the engine, and a premix combustion mode in which fuel is mixed with the intake air before being supplied to the cylinders. In the diffusion combustion mode, a pilot fuel injection may be performed before the main fuel injection. Similarly, in the premix combustion mode, a pilot fuel injection is performed into the cylinder after the mixture is introduced into the cylinder.

[0003] In an engine having multiple cylinders, it is important to suppress combustion variation among the multiple cylinders in order to ensure stable and efficient operation. Causes of combustion variation include deviation of the heat release amount associated with pilot fuel injection from the target pilot heat release amount.

[0004] The following Patent Document 1 describes a method for suppressing deviation of the amount of heat generation accompanying pilot fuel injection from a target pilot heat generation amount in a diffusion combustion mode. That is, Patent Document 1 describes measuring the heat generation rate during pilot fuel injection, calculating the pilot heat generation amount from the heat generation rate, and correcting the pilot fuel injection amount so that the pilot heat generation amount becomes the target pilot heat generation amount. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-148410 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method of Patent Document 1 cannot be directly applied to the premixed combustion mode, because in the premixed combustion mode, heat generation by the premixed fuel begins immediately after heat generation by the pilot fuel injection, making it difficult to clearly distinguish between the heat generation rate by the pilot fuel injection and the heat generation rate by the premixed fuel.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a fuel injection amount control system and a fuel injection amount control method that can suppress deviation of the pilot heat generation amount from a target pilot heat generation amount in premixed combustion mode. [Means for solving the problem]

[0008] A fuel injection amount control system according to one aspect of the present disclosure is a fuel injection amount control system for an engine having a plurality of cylinders and a plurality of injectors that supply fuel to each of the plurality of cylinders, the system including a processing circuit, the processing circuit being capable of switching between a diffusion combustion mode in which fuel and intake air are individually supplied into each of the plurality of cylinders and a premixed combustion mode in which fuel is mixed with the intake air before being supplied to the cylinder, and each of the plurality of injectors includes a first injector that injects fuel into the corresponding cylinder in the diffusion combustion mode, a second injector that injects fuel into an intake path that supplies intake air to the corresponding cylinder in the premixed combustion mode, and a third injector that injects fuel into the corresponding cylinder to perform a pilot fuel injection before a main fuel injection from the first injector in the diffusion combustion mode and after a main fuel injection from the second injector in the premixed combustion mode, and the processing circuit is configured to control the first injector after a pilot fuel injection from the third injector in the diffusion combustion mode. a first target pilot fuel injection amount in the premixed combustion mode and a second target pilot fuel injection amount in the premixed combustion mode; a first target pilot fuel injection amount in the premixed combustion mode and a second target pilot fuel injection amount in the premixed combustion mode; a first target pilot fuel injection amount in the premixed combustion mode and a second target pilot fuel injection amount in the premixed combustion mode;based on a difference between a target pilot heat generation amount corresponding to the second target pilot fuel injection amount, a target pilot heat generation amount corresponding to the first target pilot fuel injection amount, and the second pilot heat generation amount, the pilot fuel injection amount into the correction target cylinder is corrected so that the second pilot heat generation amount becomes the target pilot heat generation amount,

[0009] A fuel injection amount control method according to another aspect of the present disclosure is a fuel injection amount control method for an engine having a plurality of cylinders and a plurality of injectors that supply fuel to each of the plurality of cylinders, the method being capable of switching between a diffusion combustion mode in which fuel and intake air are individually supplied into each of the plurality of cylinders and a premixed combustion mode in which fuel is mixed with the intake air before being supplied to the cylinder, and each of the plurality of injectors includes a first injector that injects fuel into the corresponding cylinder in the diffusion combustion mode, a second injector that injects fuel into an intake path that supplies intake air to the corresponding cylinder in the premixed combustion mode, and a third injector that injects fuel into the corresponding cylinder to perform a pilot fuel injection before a main fuel injection from the first injector in the diffusion combustion mode and after a main fuel injection from the second injector in the premixed combustion mode, and the fuel injection amount control method further includes controlling a first injector after a pilot fuel injection from the third injector in the diffusion combustion mode, a first target pilot fuel injection amount in a correction target cylinder whose fuel injection amount is controlled by the diffusion mode is calculated based on the heat release rate, and the first pilot heat release amount in the correction target cylinder ... premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on theThe pilot fuel injection amount for the correction target cylinder is corrected based on a difference between a target pilot heat production amount corresponding to the second target pilot fuel injection amount and the second pilot heat production amount so that the second pilot heat production amount becomes the target pilot heat production amount. Effect of the Invention

[0010] According to the present disclosure, it is possible to suppress deviation of the pilot heat production amount from the target pilot heat production amount in the premixed combustion mode. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram showing a schematic configuration of an engine to which a fuel injection amount control system according to an embodiment of the present disclosure is applied. [Diagram 2] FIG. 2 is a conceptual diagram showing a schematic configuration of a fuel injection amount control system according to an embodiment of the present disclosure. [Diagram 3] FIG. 3 is a graph showing the change in heat release rate according to the crank angle associated with pilot fuel injection and main fuel injection in a typical diffusion combustion mode. [Figure 4] FIG. 4 is a graph showing the change in heat release rate with respect to the crank angle associated with pilot fuel injection and main fuel injection in a typical premixed combustion mode. [Diagram 5] FIG. 5 is a flowchart illustrating the flow of processing in the correction mode in this embodiment. [Figure 6] FIG. 6 is a conceptual diagram showing a schematic configuration of a fuel injection amount control system according to a modified example of the embodiment shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments will be described in detail with reference to the drawings. In the following, the same or corresponding elements are denoted by the same reference numerals throughout the drawings, and duplicated descriptions thereof will be omitted.

[0013] Fig. 1 is a schematic diagram showing the configuration of an engine to which a fuel injection amount control system according to an embodiment of the present disclosure is applied. Fig. 2 is a schematic diagram showing the configuration of a fuel injection amount control system according to an embodiment of the present disclosure. Fig. 1 shows a view of an engine 2 as seen from above.

[0014] The engine 2 shown in FIG. 1 includes a cylinder block 4 including a plurality of cylinders. In this embodiment, the engine 2 includes four cylinders 3a, 3b, 3c, and 3d. FIG. 2 shows a cross section of the cylinder 3a perpendicular to the cylinder arrangement direction. The cylinders 3b, 3c, and 3d have a similar configuration. The number of the cylinders may be two or three, or may be more than four. The engine 2 is a dual-fuel engine that can use a plurality of types of fuel. The use of the engine 2 and the type of fuel supplied to the engine 2 are not particularly limited.

[0015] The engine 2 includes a plurality of pistons 5 that reciprocate within the plurality of cylinders 3a, 3b, 3c, and 3d, and a cylinder head 6 that covers the upper parts of the plurality of cylinders 3a, 3b, 3c, and 3d. The engine 2 has a plurality of combustion chambers 7 that are partitioned by the plurality of cylinders 3a, 3b, 3c, and 3d, the plurality of pistons 5, and the cylinder head 6. A crankshaft 8 of the engine 2 is connected to the plurality of pistons 5 via connecting rods 9, and the reciprocating motion of the plurality of pistons 5 causes the crankshaft 8 to rotate.

[0016] The cylinder head 6 has an intake port 10, which is an intake path that supplies intake air to the combustion chamber 7, and an exhaust port 11, which is an exhaust path that discharges exhaust gas from the combustion chamber 7 to the outside. Furthermore, the engine 2 has a plurality of injectors 12, 13, and 14 that supply fuel to the plurality of cylinders 3a, 3b, 3c, and 3d, respectively. The first injector 12 and the third injector 14 are fixed to the cylinder head 6 so as to inject fuel into the cylinders 3a, 3b, 3c, and 3d, i.e., into the combustion chamber 7. The second injector 13 is fixed to the intake port 10 so as to inject fuel into the intake port 10.

[0017] In Fig. 2, for ease of viewing, the arrangement direction of the first injector 12 and the third injector 14 is different from that in Fig. 1. Figs. 1 and 2 merely show that the first injector 12 and the third injector 14 inject fuel into the combustion chamber 7, and their positions are determined appropriately.

[0018] The fuel injection amount control system 1 includes the engine 2 and a controller 20 that controls the engine 2. The controller 20 includes a processing circuit 21 that performs various signal processing. The processing circuit 21 has a computer such as a microcontroller, a personal computer, or a PLC (Programmable Logic Controller). More specifically, the processing circuit 21 includes a processor, a memory, and peripheral circuits. The processor includes, for example, a CPU or an MPU. The memory includes, for example, a ROM, a RAM, a register, a non-volatile storage, and the like. The peripheral circuits include an input / output interface, and the like. The controller 20 can be connected to an operation input device that operates the engine 2, a monitor that displays a control state, a speaker that outputs audio, and the like.

[0019] It should be noted that the functions of the elements disclosed herein can be performed using circuits or processing circuits, including general purpose processors, special purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit, since it includes transistors and other circuits. In this specification, a circuit, unit, means, or part is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed in this specification, or other known hardware that is programmed or configured to perform the recited functions. In the case where the hardware is a processor, which is considered a type of circuit, the circuit, unit, or means is a combination of hardware and software, and the software is used to configure the hardware and / or the processor.

[0020] A control program for controlling the engine 2 is stored in the storage device of the controller 20. The controller 20 controls the engine 2 based on the control program.

[0021] For this purpose, the fuel injection amount control system 1 is equipped with a pressure sensor 15, a crank angle sensor 16, and an exhaust temperature sensor 17. The pressure sensor 15 detects the pressure in the combustion chamber 7. For example, the pressure sensor 15 is fixed to the cylinder head 6. The crank angle sensor 16 detects the rotation angle of the crankshaft 8. The exhaust temperature sensor 17 detects the exhaust temperature at the outlets of the cylinders 3a, 3b, 3c, and 3d. The exhaust temperature sensor 17 is fixed to the exhaust port 11.

[0022] The processing circuit 21 can switch between a diffusion combustion mode and a premixed combustion mode to control the fuel supply to the engine 2 for the multiple cylinders 3a, 3b, 3c, and 3d. The diffusion combustion mode is a control mode in which fuel and intake air are individually supplied to the corresponding cylinders 3a, 3b, 3c, and 3d. The premixed combustion mode is a control mode in which fuel is mixed with intake air before being supplied to the corresponding cylinders 3a, 3b, 3c, and 3d. In the diffusion combustion mode, the engine 2 is mainly supplied with a first fuel, and in the premixed combustion mode, the engine 2 is mainly supplied with a second fuel, the type of which is different from the first fuel. That is, the first fuel is injected from the first injector 12, and the second fuel is injected from the second injector 13. The first fuel is also injected from the third injector 14.

[0023] Furthermore, the processing circuit 21 can set the target fuel injection amount for each of the injectors 12, 13, 14 corresponding to the multiple cylinders 3a, 3b, 3c, 3d. Therefore, even if the target heat generation amount is the same among the multiple cylinders 3a, 3b, 3c, 3d, the processing circuit 21 can make the target fuel injection amount different for each cylinder.

[0024] In the diffusion combustion mode, the processing circuit 21 controls the first injector 12 and the third injector 14 to perform pilot fuel injection from the third injector 14 and then main fuel injection from the first injector 12. In the premixed combustion mode, the processing circuit 21 controls the second injector 13 and the third injector 14 to perform pilot fuel injection from the third injector 14 and then main fuel injection from the second injector 13. In the premixed combustion mode, when premixed fuel, which is a mixture of intake air and fuel, is supplied to the combustion chamber 7, a pilot fuel injection is performed directly into the combustion chamber 7 with an injection amount smaller than the main fuel injection amount. The pilot fuel injection in the premixed combustion mode is performed to ignite the premixed fuel mixed with the intake air in the intake port 10. In general, the second fuel injected from the second injector 13 in the premixed combustion mode has a higher autoignition temperature than the first fuel injected from the first injector 12 and the third injector 14 in the diffusion combustion mode, and does not ignite at the compression end temperature of the piston 5. For this reason, in this embodiment, pilot fuel injection is performed from the third injector 14 to promote ignition of the premixed fuel containing the second fuel.

[0025] On the other hand, in the diffusion combustion mode, pilot fuel injection is performed before the main fuel injection, with the injection amount being smaller than the main fuel injection amount, so that the temperature inside the combustion chamber 7 at the time of the main fuel injection can be raised in advance, and a decrease in the ignition speed at the time of the main fuel injection can be suppressed. Also, the pilot fuel injection suppresses a sudden pressure increase due to the main fuel injection, so that the generation of combustion noise can be reduced.

[0026] When the engine 2 has multiple cylinders 3a, 3b, 3c, and 3d, it is important to suppress the combustion variation among the multiple cylinders 3a, 3b, 3c, and 3d in order to achieve stable and efficient operation. Causes of the combustion variation include the variation in the amount of heat generated by the pilot fuel injection. The variation in the amount of pilot heat generation can be caused by the variation in the amount of heat generated per unit amount of fuel, the initial individual difference of the injectors 12, 13, and 14, aging deterioration, etc.

[0027] Fig. 3 is a graph showing the change in heat release rate according to crank angle associated with pilot fuel injection and main fuel injection in a typical diffusion combustion mode, and Fig. 4 is a graph showing the change in heat release rate according to crank angle associated with pilot fuel injection and main fuel injection in a typical premixed combustion mode.

[0028] In the diffusion combustion mode, the heat release rate FDp generated during pilot fuel injection and the heat release rate FDm generated during main fuel injection are clearly distinguished as shown in Fig. 3. Therefore, it is relatively easy to estimate the amount of heat release during pilot fuel injection by acquiring the heat release rate FDp generated during pilot fuel injection and integrating this heat release rate FDp.

[0029] In contrast, in the premixed combustion mode, it is not possible to clearly distinguish between the heat release rate FPp generated during pilot fuel injection and the heat release rate FPm generated during main fuel injection, as shown in Figure 4. In the premixed combustion mode, heat release associated with main fuel injection occurs immediately after heat release associated with pilot fuel injection.

[0030] This is believed to be because the main fuel injected fuel is mixed with intake air in the intake port 10 before being supplied to the combustion chamber 7, and the flame generated by the pilot fuel injection ignites the air-fuel mixture to cause combustion, so that combustion by pilot fuel injection and combustion by the air-fuel mixture occur consecutively. For this reason, the heat release rate FPp generated by pilot fuel injection in the premixed combustion mode can be affected by not only the pilot fuel injection amount but also the main fuel injection such as the air excess ratio in the premixed fuel.

[0031] Thus, in the diffusion combustion mode, it is relatively easy to associate the pilot fuel injection amount with the heat generation amount generated by the pilot fuel injection, but in the premixed combustion mode, it is difficult to associate the pilot fuel injection amount with the heat generation amount generated by the pilot fuel injection. On the other hand, from the viewpoint of reducing greenhouse gas emissions, it is desirable to operate in the premixed combustion mode, which emits less carbon dioxide, as much as possible. In general, fuels with low autoignition temperatures, such as gasoline, natural gas, and hydrogen, are used for premixed combustion. These fuels have a low ratio of carbon to hydrogen in the fuel, i.e., a low C / H ratio, so that the carbon dioxide emission relative to the calorific value is smaller than that of diesel fuel used in diffusion combustion. Therefore, operation in the premixed combustion mode emits less carbon dioxide.

[0032] Therefore, at a predetermined timing during a period in which each of the multiple cylinders 3a, 3b, 3c, and 3d is controlled in the premixed combustion mode, the processing circuit 21 executes a correction mode in which the combustion mode is switched from the premixed combustion mode to the diffusion combustion mode for some of the multiple cylinders 3a, 3b, 3c, and 3d.

[0033] 5 is a flowchart illustrating the flow of processing in the correction mode in this embodiment. The processing circuit 21 measures the elapsed time t in the premixed combustion mode (step S1). The elapsed time t in the premixed combustion mode indicates the elapsed time from the start of the premixed combustion mode or the elapsed time from the end of a correction mode described later.

[0034] The processing circuit 21 judges whether the elapsed time t has exceeded the reference time ts (step S2). If the elapsed time t has exceeded the reference time ts (Yes in step S2), the processing circuit 21 sets a predetermined cylinder among the multiple cylinders 3a, 3b, 3c, and 3d as a correction target cylinder (step S3). The order in which the multiple cylinders 3a, 3b, 3c, and 3d are set as correction target cylinders is predetermined, and the corresponding cylinders are set as correction target cylinders according to the order. For example, one cylinder among the multiple cylinders 3a, 3b, 3c, and 3d is set as a correction target cylinder in the order of 3a, 3b, 3c, and 3d. Note that two or more cylinders may be set as correction target cylinders at one time.

[0035] The processing circuit 21 switches the fuel injection mode of the cylinder to be corrected from the premixed combustion mode to the diffusion combustion mode (step S4). The period during which the diffusion combustion mode is executed is set to, for example, a period during which the piston 5 in the cylinder to be corrected operates for a predetermined number of cycles. During that time, the premixed combustion mode is maintained for the other cylinders.

[0036] At this time, in order to suppress the output change when switching the fuel injection mode in the correction target cylinder, the processing circuit 21 calculates the fuel injection amount in the diffusion combustion mode based on the lower heating value of the fuel in the premixed combustion mode. That is, the fuel injection amount in the diffusion combustion mode is set so that the lower heating value of the fuel in the diffusion combustion mode is the same as or close to the lower heating value of the fuel in the previous premixed combustion mode.

[0037] In addition, in the correction mode, the target pilot fuel injection amount during pilot fuel injection in the correction target cylinder controlled in the diffusion combustion mode is set to a predetermined first target pilot fuel injection amount. In this embodiment, the first target pilot fuel injection amount is set to the same value as the target pilot fuel injection amount during pilot fuel injection in the premixed combustion mode. Hereinafter, the target pilot fuel injection amount in the premixed combustion mode is referred to as the second target pilot fuel injection amount.

[0038] The processing circuit 21 acquires the pilot heat release rate of the correction target cylinder in which the diffusion combustion mode is executed in the correction mode. The pilot heat release rate dQ / dθ is generally expressed by the following formula.

[0039]

number

[0040] The specific heat ratio κ, the inner diameters of the cylinders 3a, 3b, 3c, 3d, and the positions of the pistons 5 in the cylinders 3a, 3b, 3c, 3d with respect to the crank angle θ are stored in advance in a memory of the controller 20. Therefore, the cylinder volume V can be calculated from the crank angle θ. The crank angle θ is detected by a crank angle sensor 16. The pressure p in the combustion chamber is detected by a pressure sensor 15.

[0041] As described above, the processing circuit 21 acquires the crank angle θ detected by the crank angle sensor 16 and the combustion chamber pressure p detected by the pressure sensor 15 installed in the cylinder to be corrected in the crank angle range Δθ corresponding to the pilot fuel injection, and calculates the pilot heat release rate dQ / dθ using the above formula. The crank angle range Δθ is determined in advance. Note that since dκ / dθ is generally small, the third term in the above formula may be ignored.

[0042] The processing circuit 21 estimates a first pilot heat generation amount in the correction target cylinder from the obtained pilot heat generation rate (step S6). The first pilot heat generation amount is obtained by integrating the pilot heat generation rate over the crank angle range Δθ. When pilot fuel injection is performed multiple times within the execution period of the diffusion combustion mode in one correction target cylinder, the processing circuit 21 may calculate multiple values ​​by integrating the pilot heat generation rate for each period and calculate the average value of these values.

[0043] The processing circuit 21 corrects the second target pilot fuel injection amount into the correction target cylinder based on the estimated first pilot heat production amount (step S7). The processing circuit 21 converts the first pilot heat production amount into a second pilot heat production amount for the second target pilot fuel injection amount based on the correlation between the first target pilot fuel injection amount in the correction mode and the second target pilot fuel injection amount in the premixed combustion mode. As described above, in this embodiment, the first target pilot fuel injection amount is set to the same value as the second target pilot fuel injection amount. Therefore, the second pilot heat production amount is also the same value as the first pilot heat production amount.

[0044] The processing circuit 21 calculates the difference between the target pilot heat generation amount and the second pilot heat generation amount. The target pilot heat generation amount is associated with the second target pilot fuel injection amount in the premixed combustion mode. The relationship between the target pilot heat generation amount and the second target pilot fuel injection amount is stored in the memory of the controller 20 for each of the cylinders 3a, 3b, 3c, and 3d. The target pilot heat generation amount may be a common value among the multiple cylinders 3a, 3b, 3c, and 3d, or may be different values ​​from each other.

[0045] The processing circuit 21 corrects the pilot fuel injection amount into the correction target cylinder based on the difference so that the second pilot heat production amount becomes the target pilot heat production amount.

[0046] The processing circuit 21 calculates a correction amount for the target pilot fuel injection amount according to the difference. For example, the processing circuit 21 determines the correction amount so that the corrected second target pilot fuel injection amount becomes larger as the second pilot heat production amount becomes smaller than the target pilot heat production amount. Also, the processing circuit 21 determines the correction amount so that the corrected second target pilot fuel injection amount becomes smaller as the second pilot heat production amount becomes larger than the target pilot heat production amount. Note that, when the difference between the second pilot heat production amount and the target pilot heat production amount is within a predetermined range including 0, the processing circuit 21 does not correct the second target pilot fuel injection amount, i.e., the correction amount may be set to 0.

[0047] The processing circuit 21 determines whether the above correction process has been performed for all cylinders 3a, 3b, 3c, and 3d (step S8). If there is a cylinder for which the correction process has not been performed (No in step S8), the processing circuit 21 sequentially switches the cylinder to be corrected based on the above switching order (step S9). The processing circuit 21 switches the new cylinder to be corrected from the premixed combustion mode to the diffusion combustion mode, and performs the same correction process (steps S4 to S7).

[0048] At this time, the processing circuit 21 returns the cylinder for which the correction processing has been performed from the diffusion combustion mode to the premixed combustion mode. The target pilot fuel injection amount for the cylinder for which the correction processing has been performed and which has returned to the premixed combustion mode is set to the second target pilot fuel injection amount corrected in the diffusion combustion mode. In this way, the target pilot fuel injection amount for the cylinder to be corrected in the premixed combustion mode is corrected from the first pilot heat generation amount estimated in the diffusion combustion mode.

[0049] When the above correction process has been performed for all cylinders 3a, 3b, 3c, and 3d (Yes in step S8), the processing circuit 21 returns the cylinders to be corrected from the diffusion combustion mode to the premixed combustion mode. Furthermore, the processing circuit 21 resets the elapsed time t and ends the correction mode (step S10).

[0050] According to the above configuration, some of the cylinders 3a, 3b, 3c, and 3d in the engine 2 controlled in the premixed combustion mode are switched to the diffusion combustion mode as cylinders to be corrected. In the diffusion combustion mode, the pilot heat generation amount based on the pilot fuel injection can be estimated, so that the pilot fuel injection amount can be corrected based on the pilot heat generation amount in the some of the cylinders without adding a separate sensor or the like.

[0051] As a result, by using the corrected pilot fuel injection amount as the target pilot fuel injection amount in the premixed combustion mode while continuing the premixed combustion mode for the entire engine 2, it is possible to suppress deviation of the pilot heat generation amount in the premixed combustion mode from the target pilot heat generation amount. Also, by periodically switching to the diffusion combustion mode for some cylinders while maintaining operation in the premixed combustion mode for the entire engine 2, it is possible to reduce carbon dioxide emissions.

[0052] In addition, according to the above configuration, the correction target cylinder is switched in sequence, and the target pilot fuel injection amount in the premixed combustion mode is corrected so that the second pilot heat generation amount becomes the target pilot heat generation amount for each of the multiple cylinders 3a, 3b, 3c, and 3d. This makes it possible to reliably suppress deviation of the pilot heat generation amount from the target pilot heat generation amount for each of the multiple cylinders 3a, 3b, 3c, and 3d.

[0053] Furthermore, with the above configuration, the first target pilot fuel injection amount is set to the same value as the second target pilot fuel injection amount, eliminating the need for a calculation process for converting the first pilot heat production amount to the second pilot heat production amount, thereby improving the accuracy of the correction and reducing the processing load.

[0054] In general, when the operating conditions of the engine 2, such as the compression ratio and the amount of intake air, are the same, the diffusion combustion mode tends to result in slower combustion and poorer thermal efficiency than the premixed combustion mode. When the thermal efficiency is poor, the exhaust temperature at the outlet of the cylinders 3a, 3b, 3c, and 3d is likely to rise. Therefore, in the correction mode, the processing circuit 21 obtains the exhaust temperature at the outlet of the correction target cylinder controlled by the diffusion combustion mode, and when the exhaust temperature becomes equal to or higher than a reference value, changes the fuel injection mode from the first injector 12 corresponding to the correction target cylinder. The exhaust temperature is detected by the exhaust temperature sensor 17 corresponding to the correction target cylinder. The reference value is set based on the heat resistance temperature of the components constituting the exhaust path, etc.

[0055] For example, the processing circuit 21 may advance the fuel injection timing from the first injector 12 corresponding to the cylinder to be corrected when the exhaust temperature becomes equal to or higher than a reference value. This improves the thermal efficiency of the main fuel injection in the cylinder to be corrected. Therefore, it is possible to suppress the increase in the exhaust temperature at the outlet of the cylinder to be corrected without changing the pilot fuel injection amount in the cylinder to be corrected.

[0056] In the premixed combustion mode, there is a risk of a knocking phenomenon occurring, in which premixed fuel in the combustion chamber unexpectedly self-ignites. For this reason, in the premixed combustion mode, the fuel injection timing of the third injector 14 is limited to prevent the occurrence of the knocking phenomenon. In contrast, in the diffusion combustion mode, there is no restriction on the fuel injection timing because the occurrence of the knocking phenomenon does not need to be taken into consideration. For this reason, the fuel injection timing in the diffusion combustion mode can be advanced from the fuel injection timing in the third injector 14 in the premixed combustion mode.

[0057] Also, for example, the processing circuit 21 may reduce the main fuel injection amount from the first injector 12 corresponding to the cylinder to be corrected when the exhaust temperature becomes equal to or higher than a reference value. This reduces the total amount of fuel injection supplied to the cylinder to be corrected. Therefore, it is possible to suppress an increase in the exhaust temperature at the outlet of the cylinder to be corrected without changing the pilot fuel injection amount in the cylinder to be corrected.

[0058] As the process for changing the fuel injection mode, only one of the advancement of the fuel injection timing and the reduction of the main fuel injection amount may be executed, or both may be executed. For example, when the exhaust temperature does not become less than the reference value or does not become less than a predetermined threshold value less than the reference value as a result of executing one of the processes of the advancement of the fuel injection timing and the reduction of the main fuel injection amount, the processing circuit 21 may execute the other process of the advancement of the fuel injection timing and the reduction of the main fuel injection amount. Alternatively, for example, the processing circuit 21 may execute the advancement of the fuel injection timing and the reduction of the main fuel injection amount so that their respective execution periods overlap each other. Also, the advancement of the fuel injection timing may be executed in stages, or the reduction of the fuel injection amount may be executed in stages. For example, when the exhaust temperature remains equal to or higher than the reference value even after the first-stage reduction of the fuel injection amount, a second-stage reduction in which the fuel injection amount is reduced to an amount less than the first stage may be executed.

[0059] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various improvements, changes, and modifications are possible without departing from the spirit and scope of the present disclosure.

[0060] [Other embodiments] For example, in the above embodiment, a configuration is exemplified in which the first injector 12 and the third injector 14 separate from the first injector 12 are provided as injectors for injecting fuel into the multiple cylinders 3a, 3b, 3c, and 3d, i.e., into the combustion chamber 7. Alternatively, the third injector 14 may be a common injector for the first injector 12. FIG. 6 is an image diagram showing a schematic configuration of a fuel injection amount control system according to a modified example of the embodiment shown in FIG. 2. In FIG. 6, the same components as those in the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0061] In the example shown in Fig. 6, the multiple injectors include a first injector 12B that injects fuel into a corresponding cylinder and a second injector 13 that injects fuel into an intake path that supplies intake air to the corresponding cylinder. In the diffusion combustion mode, the processing circuit 21 controls the first injector 12B to perform pilot fuel injection from the first injector 12B and then perform main fuel injection from the same first injector 12B. In addition, in the premixed combustion mode, the processing circuit 21 controls the first injector 12B and the second injector 13 to perform pilot fuel injection from the first injector 12B and then perform main fuel injection from the second injector 13.

[0062] In this modified example, the first injector 12B performs both pilot fuel injection in each mode and main fuel injection in the diffusion combustion mode. Since the first injector 12B needs to perform both pilot fuel injection at a small flow rate and main fuel injection at a large flow rate, the pilot fuel injection amount at a small flow rate is likely to deviate from the target pilot fuel injection amount, and as a result, the pilot heat production amount is likely to deviate from the target pilot heat production amount.

[0063] However, according to the fuel injection amount control system 1 of the present disclosure, the target pilot fuel injection amount is corrected so that the actual pilot heat production amount based on the pilot fuel injection becomes the target pilot heat production amount. Therefore, even in this modified example in which the pilot fuel injection and the main fuel injection in the diffusion combustion mode are performed by the same first injector 12B, it is possible to suppress deviation of the pilot heat production amount in the premixed combustion mode from the target pilot heat production amount.

[0064] In other words, according to the fuel injection amount control system 1 of the present disclosure, the target pilot fuel injection amount is corrected so that the actual pilot heat generation amount based on the pilot fuel injection becomes the target pilot heat generation amount, so that the injector that performs the pilot fuel injection and the injector that performs the main fuel injection in the diffusion combustion mode can be made common while suppressing the deviation of the pilot heat generation amount from the target pilot heat generation amount, thereby reducing the number of parts of the engine 2 that can switch between the diffusion combustion mode and the premixed combustion mode.

[0065] In the above embodiment, the first target pilot fuel injection amount when the correction mode is switched to the diffusion combustion mode is equal to the second target pilot fuel injection amount in the premixed combustion mode. However, the first target pilot fuel injection amount may be a value different from the second target pilot fuel injection amount. In this case, the memory of the controller 20 stores a correlation between the first target pilot fuel injection amount and the second target pilot fuel injection amount. The correlation may be a correlation formula for obtaining one from the other, or a data table in which the first target pilot fuel injection amount and the second target pilot fuel injection amount correspond one-to-one. The correlation may be a correlation between a target pilot heat generation amount associated with the first target pilot fuel injection amount and a target pilot heat generation amount associated with the second target pilot fuel injection amount.

[0066] The processing circuit 21 converts the first pilot heat generation amount estimated in the correction mode into a second pilot heat generation amount for the second target pilot fuel injection amount using such a correlation. For example, the processing circuit 21 converts the first pilot heat generation amount into a second pilot heat generation amount by internalizing or extrapolating using the above correlation. At this time, the processing circuit 21 may change the first target pilot fuel injection amount in the correction mode to obtain a plurality of first pilot heat generation amounts for a plurality of first target pilot fuel injection amounts. The processing circuit 21 calculates the difference between the target pilot heat generation amount and the second pilot heat generation amount, and corrects the pilot fuel injection amount into the correction target cylinder based on the difference so that the second pilot heat generation amount becomes the target pilot heat generation amount. In this way, according to the present disclosure, the pilot fuel injection amount in the premixed combustion mode can be appropriately corrected regardless of whether the first target pilot fuel injection amount and the second target pilot fuel injection amount are different or the same.

[0067] Furthermore, the fuel injection amount control system 1 of the present disclosure is applicable to various engines 2 having multiple cylinders, such as engines mounted on ships, vehicles, and aircraft, or engines installed in facilities such as plants.

[0068] In the above embodiment, the controller 20 of the engine 2 includes the processing circuit 21 of the fuel injection amount control system 1, but the processing circuit 21 that performs arithmetic processing for the fuel injection amount control system 1 may be configured as a processing circuit separate from the controller 20 of the engine 2. For example, the processing circuit 21 may be included in a management system that is higher than the engine 2 in a ship or the like on which the engine 2 is mounted. Also, for example, the processing circuit 21 may be included in an external computer such as a server that is communicatively connected to the controller 20 of the engine 2 via a communication network.

[0069] In addition, the control program for executing the calculation processing in the processing circuit 21 of the fuel injection amount control system 1 in the above embodiment may be configured as a program product provided by downloading from an external computer or recorded on a recording medium, or may be configured as a computer product in which the control program is pre-installed.

[0070] [Summary of this disclosure] [Item 1] A fuel injection amount control system according to one aspect of the present disclosure is a fuel injection amount control system for an engine having a plurality of cylinders and a plurality of injectors that supply fuel to each of the plurality of cylinders, the system including a processing circuit, the processing circuit being capable of switching between a diffusion combustion mode in which fuel and intake air are individually supplied into each of the plurality of cylinders and a premixed combustion mode in which fuel is mixed with the intake air before being supplied to the cylinder, and each of the plurality of injectors includes a first injector that injects fuel into the corresponding cylinder in the diffusion combustion mode, a second injector that injects fuel into an intake path that supplies intake air to the corresponding cylinder in the premixed combustion mode, and a third injector that injects fuel into the corresponding cylinder to perform a pilot fuel injection before a main fuel injection from the first injector in the diffusion combustion mode and after a main fuel injection from the second injector in the premixed combustion mode, and the processing circuit is configured to control the first injector after a pilot fuel injection from the third injector in the diffusion combustion mode. a processing circuit for controlling the plurality of injectors to perform a main fuel injection from the second injector in the premixed combustion mode, and for controlling the plurality of injectors to perform a pilot fuel injection from the third injector in order to ignite the premixed fuel mixed with the intake air in the intake path after performing a main fuel injection from the second injector in the premixed combustion mode; the processing circuit executes a correction mode for switching some of the plurality of cylinders from the premixed combustion mode to the diffusion combustion mode at a predetermined timing during a period during which each of the plurality of cylinders is controlled in the premixed combustion mode; in the correction mode, a heat release rate associated with the pilot fuel injection for a first target pilot fuel injection amount in a correction target cylinder whose fuel injection amount is controlled by the diffusion mode is obtained, an estimation is made of a first pilot heat release amount in the correction target cylinder from the obtained heat release rate, and a correlation between the first target pilot fuel injection amount and a second target pilot fuel injection amount in the premixed combustion mode is obtained.The pilot fuel injection amount for the correction target cylinder is corrected based on a difference between a target pilot heat production amount corresponding to the second target pilot fuel injection amount and the second pilot heat production amount so that the second pilot heat production amount becomes the target pilot heat production amount.

[0071] According to the above configuration, in an engine controlled in a premixed combustion mode, some of the cylinders among a plurality of cylinders are switched to the diffusion combustion mode as cylinders to be corrected. In the diffusion combustion mode, the pilot heat generation amount based on the pilot fuel injection can be estimated, so that the pilot fuel injection amount can be corrected based on the pilot heat generation amount in the some of the cylinders without adding a separate sensor or the like.

[0072] As a result, while continuing the premixed combustion mode for the entire engine, the corrected pilot fuel injection amount is used as the target pilot fuel injection amount in the premixed combustion mode, thereby suppressing deviation of the pilot heat generation amount in the premixed combustion mode from the target pilot heat generation amount. Also, by periodically switching to the diffusion combustion mode for some cylinders while maintaining operation in the premixed combustion mode for the entire engine, it is possible to reduce carbon dioxide emissions.

[0073] [Item 2] In the fuel injection amount control system of item 1, the third injector may be a common injector to the first injector. This makes it possible to reduce the number of parts of an engine capable of switching between a diffusion combustion mode and a premixed combustion mode.

[0074] [Item 3] In the fuel injection amount control system of item 1 or 2, the processing circuit may sequentially switch the correction target cylinder in the correction mode. This causes the target pilot fuel injection amount in the premixed combustion mode to be corrected so that the second pilot heat generation amount becomes the target pilot heat generation amount for each of the multiple cylinders. Therefore, it is possible to reliably suppress the deviation of the pilot fuel generation amount from the target pilot heat generation amount for each of the multiple cylinders.

[0075] [Item 4] In the fuel injection amount control system according to any one of items 1 to 3, the processing circuit may set the first target pilot fuel injection amount to the same value as the second target pilot fuel injection amount, and the second pilot heat production amount to the same value as the first pilot heat production amount. This eliminates the need for a calculation process for converting the first pilot heat production amount to the second pilot heat production amount, thereby improving the accuracy of the correction and reducing the processing load.

[0076] [Item 5] In the fuel injection amount control system according to any one of items 1 to 4, the processing circuit may acquire the exhaust gas temperature at the outlet of the cylinder to be corrected in the correction mode, and advance the fuel injection timing from the first injector corresponding to the cylinder to be corrected when the exhaust gas temperature becomes equal to or higher than a reference value. This improves the thermal efficiency of the main fuel injection in the cylinder to be corrected. Therefore, it is possible to suppress an increase in the exhaust gas temperature at the outlet of the cylinder to be corrected without changing the pilot fuel injection amount in the cylinder to be corrected.

[0077] [Item 6] In the fuel injection amount control system according to any one of items 1 to 5, the processing circuit may acquire an exhaust gas temperature at an outlet of the cylinder to be corrected in the correction mode, and reduce the main fuel injection amount from the first injector corresponding to the cylinder to be corrected when the exhaust gas temperature becomes equal to or higher than a reference value. This reduces the total amount of fuel injection supplied to the cylinder to be corrected. Therefore, it is possible to suppress an increase in the exhaust gas temperature at the outlet of the cylinder to be corrected without changing the pilot fuel injection amount in the cylinder to be corrected.

[0078] [Item 7] A fuel injection amount control method according to another aspect of the present disclosure is a fuel injection amount control method for an engine having a plurality of cylinders and a plurality of injectors that supply fuel to each of the plurality of cylinders, the method being capable of switching between a diffusion combustion mode in which fuel and intake air are individually supplied into each of the plurality of cylinders and a premixed combustion mode in which fuel is mixed with the intake air before being supplied to the cylinder, and each of the plurality of injectors includes a first injector that injects fuel into the corresponding cylinder in the diffusion combustion mode, a second injector that injects fuel into an intake path that supplies intake air to the corresponding cylinder in the premixed combustion mode, and a third injector that injects fuel into the corresponding cylinder to perform a pilot fuel injection before a main fuel injection from the first injector in the diffusion combustion mode and after a main fuel injection from the second injector in the premixed combustion mode, and the fuel injection amount control method further includes controlling a first injector after a pilot fuel injection from the third injector in the diffusion combustion mode, a first target pilot fuel injection amount in a correction target cylinder whose fuel injection amount is controlled by the diffusion mode is calculated based on the heat release rate, and the first pilot heat release amount in the correction target cylinder ... premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the first pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on the heat release rate, and the second pilot heat release amount in the premixed combustion mode is calculated based on theThe pilot fuel injection amount for the correction target cylinder is corrected based on a difference between a target pilot heat production amount corresponding to the second target pilot fuel injection amount and the second pilot heat production amount so that the second pilot heat production amount becomes the target pilot heat production amount. [Explanation of symbols]

[0079] 1. Fuel injection amount control system 2 Engine 3a, 3b, 3c, 3d Cylinders 12,12B First injector 13 Second injector 14 3rd injector 21 Processing circuit

Claims

1. 1. A fuel injection amount control system for an engine having a plurality of cylinders and a plurality of injectors for supplying fuel to each of the plurality of cylinders, comprising: A processing circuit is provided, the processing circuit is capable of switching between and controlling, for each of the plurality of cylinders, a diffusion combustion mode in which fuel and intake air are individually supplied into a corresponding cylinder, and a premixed combustion mode in which fuel is mixed with the intake air before being supplied to the cylinder; Each of the plurality of injectors comprises: a first injector for injecting fuel into a corresponding cylinder in the diffusion combustion mode; a second injector for injecting fuel into an intake passage that supplies intake air to a corresponding cylinder in the premixed combustion mode; a third injector for injecting fuel into a corresponding cylinder to perform a pilot fuel injection before a main fuel injection from the first injector in the diffusion combustion mode and after a main fuel injection from the second injector in the premixed combustion mode; The processing circuitry includes: controlling the plurality of injectors so that, in the diffusion combustion mode, a pilot fuel injection is performed from the third injector, and then a main fuel injection is performed from the first injector; controlling the plurality of injectors so that, in the premixed combustion mode, after a main fuel injection is performed from the second injector, a pilot fuel injection is performed from the third injector in order to ignite the premixed fuel mixed with the intake air in the intake passage; The processing circuitry includes: a correction mode is executed to switch a part of the cylinders from the premixed combustion mode to the diffusion combustion mode at a predetermined timing during a period in which each of the cylinders is controlled in the premixed combustion mode; obtaining a heat release rate associated with the pilot fuel injection relative to a first target pilot fuel injection amount in a correction target cylinder in which a fuel injection amount is controlled in the diffusion mode in the correction mode; A first pilot heat release amount in the cylinder to be corrected is estimated from the obtained heat release rate; converting the first pilot heat generation amount into a second pilot heat generation amount for the second target pilot fuel injection amount based on a correlation between the first target pilot fuel injection amount and a second target pilot fuel injection amount in the premixed combustion mode; a fuel injection amount control system for correcting a pilot fuel injection amount into the cylinder to be corrected based on a difference between a target pilot heat production amount corresponding to the second target pilot fuel injection amount and the second pilot heat production amount so that the second pilot heat production amount becomes the target pilot heat production amount.

2. 2. The fuel injection amount control system according to claim 1, wherein the third injector is a common injector to the first injector.

3. 3. The fuel injection amount control system according to claim 1, wherein the processing circuit sequentially switches the cylinders to be corrected in the correction mode.

4. The processing circuitry includes: Setting the first target pilot fuel injection amount to the same value as the second target pilot fuel injection amount; 3. The fuel injection amount control system according to claim 1, wherein the second pilot heat production amount is set to be equal to the first pilot heat production amount.

5. The processing circuitry includes: In the correction mode, an exhaust temperature at an outlet of the correction target cylinder is acquired; 3. The fuel injection amount control system according to claim 1, further comprising: a step of advancing a fuel injection timing from the first injector corresponding to the cylinder to be corrected when the exhaust gas temperature becomes equal to or higher than a reference value.

6. The processing circuitry includes: In the correction mode, an exhaust temperature at an outlet of the correction target cylinder is acquired; 3. The fuel injection amount control system according to claim 1, further comprising: a step of reducing an amount of main fuel injection from the first injector corresponding to the cylinder to be corrected when the exhaust temperature is equal to or higher than a reference value.

7. 1. A method for controlling a fuel injection amount of an engine having a plurality of cylinders and a plurality of injectors for supplying fuel to each of the plurality of cylinders, comprising: a diffusion combustion mode in which fuel and intake air are individually supplied into each of the plurality of cylinders, and a premixed combustion mode in which fuel is mixed with the intake air before being supplied to the cylinder, and the diffusion combustion mode is switchable between the diffusion combustion mode and the premixed combustion mode. Each of the plurality of injectors comprises: a first injector for injecting fuel into a corresponding cylinder in the diffusion combustion mode; a second injector for injecting fuel into an intake passage that supplies intake air to a corresponding cylinder in the premixed combustion mode; a third injector for injecting fuel into a corresponding cylinder to perform a pilot fuel injection before a main fuel injection from the first injector in the diffusion combustion mode and after a main fuel injection from the second injector in the premixed combustion mode; The fuel injection amount control method includes: controlling the plurality of injectors so that, in the diffusion combustion mode, a pilot fuel injection is performed from the third injector, and then a main fuel injection is performed from the first injector; controlling the plurality of injectors so that, in the premixed combustion mode, after a main fuel injection is performed from the second injector, a pilot fuel injection is performed from the third injector in order to ignite the mixed fuel mixed with the intake air in the intake path; a correction mode is executed to switch some of the cylinders from the premixed combustion mode to the diffusion combustion mode at a predetermined timing during a period in which each of the plurality of cylinders is controlled in the premixed combustion mode; obtaining a heat release rate associated with the pilot fuel injection relative to a first target pilot fuel injection amount in a correction target cylinder in which a fuel injection amount is controlled in the diffusion mode in the correction mode; A first pilot heat release amount in the cylinder to be corrected is estimated from the obtained heat release rate; converting the first pilot heat generation amount into a second pilot heat generation amount for the second target pilot fuel injection amount based on a correlation between the first target pilot fuel injection amount and a second target pilot fuel injection amount in the premixed combustion mode; a pilot fuel injection amount for the cylinder to be corrected based on a difference between a target pilot heat production amount corresponding to the second target pilot fuel injection amount and the second pilot heat production amount so that the second pilot heat production amount becomes the target pilot heat production amount.

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