Control device of internal combustion engine

Abstract

Provided is a control device of an internal combustion engine capable of performing a co-combustion operation using both a liquid fuel and a gaseous fuel as the fuels to be used. The internal combustion engine includes: a cylinder having a combustion chamber for burning the fuels to be used; an injector for injecting the liquid fuel into the combustion chamber; a liquid fuel introduction line for guiding the liquid fuel to the injector; and a gaseous fuel introduction line for guiding the gaseous fuel to the combustion chamber. The control device of the internal combustion engine includes a recovery measure execution part configured to perform a recovery measure for recovering an actual injection amount of the liquid fuel injected from the injector when a reduction amount of output of the internal combustion engine, or the discrepancy between the actual injection amount of the liquid fuel from the injector and an instructed injection amount, exceeds a predetermined threshold in a state in which the internal combustion engine is operated by the co-combustion operation.

Description

Control device for internal combustion engine

[0001] This application claims priority to Japanese Patent Application No. 2023-207065, filed on December 7, 2023, with the Japan Patent Office, the contents of which are incorporated herein by reference.

[0002] BACKGROUND ART It is known that there are internal combustion engines capable of dual combustion operation using gaseous fuel and liquid fuel as fuels (for example, Patent Document 1).

[0003] JP 2011-226741 A

[0004] In an internal combustion engine capable of dual-fuel operation, when a gaseous fuel with relatively low flammability is used, a liquid fuel is required as an ignition source. In recent years, decarbonized fuels such as ammonia gas or methanol gas have been used as the gaseous fuel to reduce environmental impact. When using a decarbonized fuel as the gaseous fuel, the proportion of the decarbonized fuel (gaseous fuel) in the total fuel used is sometimes increased as much as possible. However, this can cause fuel clogging in the injector that injects the liquid fuel, which can lead to a decrease in the output of the internal combustion engine.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure has an object to provide a control device for an internal combustion engine that can suppress fuel clogging in an internal combustion engine capable of dual-fuel operation.

[0006] A control device for an internal combustion engine according to at least one embodiment of the present disclosure is a control device for an internal combustion engine capable of dual combustion operation using both liquid fuel and gaseous fuel as the fuel used, wherein the internal combustion engine includes: a cylinder having a combustion chamber for combusting the fuel used; an injector for injecting liquid fuel into the combustion chamber; a liquid fuel introduction line for guiding the liquid fuel to the injector; and a gaseous fuel introduction line for guiding the gaseous fuel to the combustion chamber, and the control device for the internal combustion engine includes a recovery action execution unit configured to take recovery action to restore the actual injection amount of the liquid fuel injected from the injector when, while the internal combustion engine is operating in the dual combustion operation, the amount of output reduction of the internal combustion engine or the deviation of the actual injection amount of the liquid fuel in the injector from the commanded injection amount exceeds a predetermined threshold.

[0007] According to at least one embodiment of the present disclosure, a control device for an internal combustion engine that can suppress fuel clogging in an internal combustion engine capable of dual-fuel operation is provided.

[0008] Fig. 1 is a schematic diagram of an internal combustion engine system including a control device for an internal combustion engine according to an embodiment of the present disclosure; Fig. 2 is a schematic diagram of an internal combustion engine system including a control device for an internal combustion engine according to an embodiment of the present disclosure; Fig. 3 is a control flow diagram of an internal combustion engine according to an embodiment of the present disclosure; Fig. 4 is a control flow diagram of an internal combustion engine according to an embodiment of the present disclosure; Fig. 5 is an explanatory diagram for explaining recovery measures for an injector according to an embodiment of the present disclosure; Fig. 6 is an explanatory diagram for explaining recovery measures for an injector according to an embodiment of the present disclosure.

[0009] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.

[0010] 1 and 2 are each a schematic diagram of an internal combustion engine system 1 including a control device 3 for an internal combustion engine 2 according to an embodiment of the present disclosure. As shown in FIGS. 1 and 2, the internal combustion engine system 1 includes an internal combustion engine (engine) 2 configured to generate power by burning fuel used therein, and a control device 3 configured to control operation and combustion of the internal combustion engine 2. In the following embodiments, a case will be described in which the internal combustion engine 2 is a four-stroke engine, but some embodiments of the present disclosure are also applicable to cases in which the internal combustion engine 2 is a two-stroke engine.

[0011] 1 and 2, the internal combustion engine 2 includes at least one cylinder 4 (in the illustrated example, a plurality of cylinders 4). Each of the plurality of cylinders 4 has a combustion chamber 40 for combusting a fuel used. Although not shown, the combustion chamber 40 is formed between a cylinder body and a piston housed inside the cylinder body. The internal combustion engine 2 is configured to combust a fuel used and a combustion gas (e.g., air) in each combustion chamber 40 of the plurality of cylinders 4.

[0012] The internal combustion engine 2 is configured to be capable of a mono-fuel operation using liquid fuel as the fuel used, and a multi-fuel operation using both the liquid fuel and gaseous fuel as the fuel used.

[0013] In some embodiments, the liquid fuel is diesel, and the gaseous fuel has a lower methane number than diesel. In one embodiment, the internal combustion engine 2 is a diesel engine. To reduce greenhouse gas emissions, such as carbon dioxide, from the internal combustion engine 2, the proportion of gaseous fuel in the fuel used is increased and the proportion of liquid fuel is decreased. This reduces the flow rate of the liquid fuel injected from the injector 50, which may result in fuel clogging in the injector 50. Furthermore, when the gaseous fuel has a lower methane number than the liquid fuel, it is necessary to increase the temperature inside the cylinder by setting the excess air ratio relatively low to combust the gaseous fuel. Increasing the temperature inside the cylinder may result in excessive heat exposure to the injector 50, which may result in fuel clogging in the injector 50. Because of this high likelihood of fuel clogging in the injector 50, it is necessary to take recovery measures to quickly resolve the fuel clogging in the injector 50.

[0014] In some other embodiments, the liquid fuel may be a fuel oil other than diesel, for example, a renewable fuel oil such as bioethanol.

[0015] In some embodiments, the gaseous fuel is ammonia gas. Because ammonia gas is a gaseous fuel with relatively low combustibility, a liquid fuel must be used as an ignition source. In addition, in order to combust the gaseous fuel with relatively low combustibility, it is necessary to raise the temperature inside the cylinder by setting the excess air ratio relatively low. Note that in some other embodiments, the gaseous fuel may be a gaseous fuel other than ammonia gas, such as hydrogen gas or methanol gas.

[0016] 1 and 2 , the internal combustion engine 2 includes a plurality of injectors 50 for injecting liquid fuel into each combustion chamber 40 of the plurality of cylinders 4, a liquid fuel introduction line 5 for introducing the liquid fuel to the injectors 50, and a gas fuel introduction line 6 for introducing gas fuel to each combustion chamber 40. The injectors 50 are individually provided for each cylinder 4. Each of the plurality of injectors 50 includes a fuel injection valve configured to inject liquid fuel into the corresponding combustion chamber 40.

[0017] In the illustrated embodiment, the internal combustion engine 2 further includes a combustion gas inlet line 7 for introducing combustion gas into each of the plurality of combustion chambers 40, and an exhaust gas discharge line 8 for discharging exhaust gas from each of the plurality of combustion chambers 40, as shown in Figures 1 and 2.

[0018] (Liquid Fuel Introduction Line) The liquid fuel introduction line 5 forms a flow path for supplying liquid fuel to each of the multiple injectors 50, and is not limited to piping. In the illustrated embodiment, as shown in Figures 1 and 2, the liquid fuel introduction line 5 includes a common rail 51 capable of storing liquid fuel, multiple branch pipes 52 for introducing liquid fuel from the common rail 51 to each of the multiple injectors 50, a liquid fuel pipe 54 for introducing liquid fuel from a liquid fuel supply source (e.g., a storage tank for storing liquid fuel) 53 to the common rail 51, and a pressure booster device (e.g., a pressure booster pump) 55 for boosting the pressure of the liquid fuel introduced to the common rail 51.

[0019] One end of each of the branch pipes 52 is connected to the common rail 51, and the other end is connected to the injector 50 corresponding to the branch pipe 52. One end of the liquid fuel pipe 54 is connected to the common rail 51, and the other end is connected to a liquid fuel supply source 53. A pressure booster 55 is provided on the liquid fuel pipe 54.

[0020] 1 , the internal combustion engine 2 may include a pressure acquisition device (a pressure sensor in the illustrated example) 56 configured to acquire the pressure of the liquid fuel guided to the common rail 51. In the illustrated embodiment, the pressure acquisition device 56 is disposed downstream of the pressure booster device 55 in the liquid fuel pipe 54 (on the common rail 51 side), and acquires the pressure of the liquid fuel flowing downstream of the pressure booster device 55 in the liquid fuel pipe 54.

[0021] 2 , the internal combustion engine 2 may include a flow rate obtaining device (a flow rate sensor in the illustrated example) 57 configured to obtain the flow rate of the liquid fuel guided to the common rail 51. In the illustrated embodiment, the flow rate obtaining device 57 is disposed upstream of the booster device 55 in the liquid fuel pipe 54 (on the supply source 53 side) and is configured to obtain the flow rate of the liquid fuel flowing upstream of the booster device 55 in the liquid fuel pipe 54. Note that the flow rate obtaining device 57 may also be disposed downstream of the booster device 55 in the liquid fuel pipe 54 (on the common rail 51 side) and is configured to obtain the flow rate of the liquid fuel flowing downstream of the booster device 55 in the liquid fuel pipe 54.

[0022] (Gaseous Fuel Introduction Line) The gaseous fuel introduction line 6 forms a flow path for supplying gaseous fuel to each of the plurality of combustion chambers 40 and is not limited to piping. In the illustrated embodiment, the gaseous fuel introduction line 6 includes a gaseous fuel pipe 61 for guiding gaseous fuel from a gaseous fuel supply source (e.g., a storage tank for storing gaseous fuel) 63, and a plurality of branch pipes 62 for introducing gaseous fuel from the gaseous fuel pipe 61 to each of the plurality of combustion chambers 40. One end of each of the plurality of branch pipes 62 is connected to the gaseous fuel pipe 61, and the other end is connected to the combustion chamber 40 to which the branch pipe 62 corresponds. The gaseous fuel supply source 63 may store gaseous fuel in a gaseous state or a liquid state.

[0023] (Combustion Gas Introduction Line) The combustion gas introduction line 7 forms a flow path for supplying combustion gas to each of the multiple combustion chambers 40 and is not limited to piping. In the illustrated embodiment, the combustion gas introduction line 7 includes a combustion gas pipe 71 for guiding the combustion gas from a combustion gas supply source, and multiple branch pipes 72 for introducing the combustion gas from the combustion gas pipe 71 into each of the multiple combustion chambers 40. One end of each of the multiple branch pipes 72 is connected to the combustion gas pipe 71 and the other end is connected to the combustion chamber 40 corresponding to the branch pipe 72. One end (upstream end) of the combustion gas pipe 71 may be open to the atmosphere or may be connected to a storage tank that stores the combustion gas.

[0024] In the embodiment shown in FIGS. 1 and 2 , the combustion gas introduction line 7 merges with the gaseous fuel introduction line 6 at a junction P1 provided in the gaseous fuel pipe 61, and the downstream side (combustion chamber 40 side) of the junction P1 is shared with the gaseous fuel introduction line 6. That is, downstream of the junction P1, the gaseous fuel pipe 61 also serves as the combustion gas pipe 71, and each of the branch pipes 62 also serves as a corresponding branch pipe 72. The gaseous fuel is introduced into the combustion chamber 40 in a mixed state with the combustion gas, and the mixed state is burned. To combust the gaseous fuel, the excess air ratio must be kept relatively low to increase the temperature in the cylinder 4. Increasing the temperature in the cylinder 4 may cause excessive heat exposure to the injector 50, which may lead to fuel clogging in the injector 50. Therefore, recovery measures must be taken to quickly resolve the fuel clogging in the injector 50.

[0025] In the embodiment shown in Figures 1 and 2, the gas fuel pipe 61 includes an upstream gas fuel pipe 64 connected at one end to a gas fuel supply source 63 and at the other end to the combustion gas pipe 71 at the junction P1.

[0026] 1 and 2 , the internal combustion engine 2 may further include a flow rate adjustment device (a flow rate adjustment valve in the illustrated example) 65 configured to adjust the flow rate of the gaseous fuel introduced into each of the plurality of combustion chambers 40. The flow rate adjustment device 65 may be provided in the gaseous fuel pipe 61 (the upstream gaseous fuel pipe 64 in the illustrated example), or may be provided in each of the plurality of branch pipes 62.

[0027] 1 and 2, the internal combustion engine 2 may further include a mixer (a static mixer in the illustrated example) 66 that continuously mixes the gaseous fuel and the combustion gas. In the illustrated embodiment, the mixer 66 is provided downstream of the confluence portion P1 of the gaseous fuel pipe 61.

[0028] (Exhaust Gas Discharge Line) The exhaust gas discharge line 8 forms a flow path for discharging exhaust gas from each of the plurality of combustion chambers 40, and is not limited to piping. In the illustrated embodiment, the exhaust gas discharge line 8 includes an exhaust gas pipe 81 and a plurality of branch pipes 82 for discharging exhaust gas from each of the plurality of combustion chambers 40 to the exhaust gas pipe 81. One end of each of the plurality of branch pipes 82 is connected to the exhaust gas pipe 81, and the other end is connected to the combustion chamber 40 corresponding to the branch pipe 82. One end (downstream end) of the exhaust gas pipe 81 may be connected to a chimney (not shown).

[0029] 1 and 2, the internal combustion engine 2 may further include an oxidation catalyst (DOC) 83 that is provided in an exhaust gas pipe 81 and that oxidizes hydrocarbons and carbon monoxide contained in the exhaust gas that flows through the exhaust gas pipe 81. Also, as shown in FIGS. 1 and 2, the exhaust gas pipe 81 may be provided with an orifice 84 that generates back pressure.

[0030] As shown in Figures 1 and 2, the internal combustion engine 2 may further include an analyzer 85 provided in the exhaust gas pipe 81 for obtaining the concentration of nitrogen oxides contained in the exhaust gas flowing through the exhaust gas pipe 81, and an analyzer 86 provided in the exhaust gas pipe 81 for obtaining the concentrations of ammonia gas and nitrous oxide compounds contained in the exhaust gas flowing through the exhaust gas pipe 81.

[0031] (Control Device for Internal Combustion Engine) The control device 3 for the internal combustion engine 2 is an electronic control unit that controls the operation of each device provided in the internal combustion engine 2, such as the injector 50, the boost device 55, and the flow rate adjustment device 65. The control device 3 may be configured as a microcomputer including a central processing unit (CPU) including a processor, a random access memory (RAM), a read-only memory (ROM), an I / O interface, and the like. In the illustrated embodiment, the control device 3 is configured as an engine control unit. Note that in some other embodiments, the control device 3 may be implemented as one of the functions (programs or circuits) provided in the engine control unit. Furthermore, in some other embodiments, the control device 3 may be configured as an electronic control unit separate from the engine control unit.

[0032] The control device 3 of the internal combustion engine 2 includes a control unit 30 configured to perform operation control and combustion control of the internal combustion engine 2 according to the operation mode of the internal combustion engine 2. The internal combustion engine 2 may include a switching device (switch) 10 for manually switching the operation mode of the internal combustion engine 2. The control unit 30 is configured to perform operation control and combustion control of the internal combustion engine 2 according to information (signals) related to the operation mode sent from the switching device 10. When the operation mode of the internal combustion engine 2 is mono-fuel operation, the control unit 30 is configured to close the flow rate adjustment device 65 and control the opening and closing of the injector 50, thereby combusting the liquid fuel and the combustion gas in the combustion chamber 40. Furthermore, when the operation mode of the internal combustion engine 2 is dual-fuel operation, the control unit 30 is configured to open the flow rate adjustment device 65 and control the opening and closing of the injector 50, thereby combusting the liquid fuel and the mixture of the gaseous fuel and the combustion gas in the combustion chamber 40.

[0033] When the operating mode of the internal combustion engine 2 is mono-fuel operation, the control unit 30 is configured to control the combustion of the internal combustion engine 2 so that the proportion of gaseous fuel in the fuel used is as large as possible in order to suppress the generation of greenhouse gases.

[0034] 1 and 2 , a control device 3 for an internal combustion engine 2 according to some embodiments includes a recovery measure execution unit 31. The recovery measure execution unit 31 is configured to monitor the output of the internal combustion engine 2, and to calculate an amount of reduction with respect to a steady-state output, which is the output of the internal combustion engine 2 when the internal combustion engine 2 is operated steadily through dual-fuel combustion. The recovery measure execution unit 31 is configured to take a recovery measure to restore the actual injection amount of liquid fuel injected from the injector 50 when the amount of reduction in the output of the internal combustion engine 2 exceeds a predetermined threshold while the internal combustion engine 2 is operating through dual-fuel combustion.

[0035] Fig. 3 is a control flow diagram of the internal combustion engine 2 according to one embodiment of the present disclosure. The control flow shown in Fig. 3 is executed by the recovery measure execution unit 31. When the internal combustion engine 2 is started (step S1) and is operating in the dedicated combustion operation described above ("No" in step S2), the determination of the output reduction amount (step S4), which will be described later, is not performed, and the dedicated combustion operation of the internal combustion engine 2 continues (step S3).

[0036] When the internal combustion engine 2 is operating in the above-described dual combustion mode ("Yes" in step S2), the amount of output reduction is determined (step S4). If the amount of output reduction does not meet a predetermined threshold ("No" in step S4), it is determined that the injector 50 is not clogged, and the dual combustion mode of the internal combustion engine 2 is continued (step S5). If the amount of output reduction exceeds the predetermined threshold ("Yes" in step S4), it is determined that the injector 50 is clogged, and the above-described recovery measures are taken (step S6).

[0037] If the amount of output reduction of the internal combustion engine 2 exceeds a predetermined threshold, there is a high probability that fuel clogging has occurred in the injector 50. In this case, the recovery measure execution unit 31 performs recovery measures to restore the actual injection amount of liquid fuel injected from the injector 50, thereby quickly eliminating the fuel clogging in the injector 50. The recovery measures (step S6) include issuing a notification to prompt the user to switch the operation mode of the internal combustion engine 2 to mono-fuel operation using liquid fuel as the used fuel, as shown in FIG.

[0038] In the embodiment shown in Fig. 3, when the amount of output reduction of the internal combustion engine 2 exceeds a predetermined threshold ("Yes" in step S4), a notification is issued (step S7) to urge the user to switch the operation mode of the internal combustion engine 2 to mono-fuel operation using liquid fuel as the used fuel. The recovery measure execution unit 31 includes a notification instruction unit 311 (see Figs. 1 and 2). The notification instruction unit 311 is configured to cause the notification device 9 to issue a notification to urge the user to switch the operation mode of the internal combustion engine 2 to mono-fuel operation using liquid fuel as the used fuel when the amount of output reduction of the internal combustion engine 2 exceeds a predetermined threshold ("Yes" in step S4). The notification device 9 issues the notification in response to an instruction to issue the notification from the notification instruction unit 311. The notification device 9 may be a display device (display) that outputs the notification as an image, or may be an audio device (speaker) that outputs the notification as a sound.

[0039] The notification device 9, in response to an instruction from the notification instruction unit 311, can issue a notification urging the user of the internal combustion engine 2 to switch to dedicated combustion operation. The user of the internal combustion engine 2 who has received the notification can switch the operation mode of the internal combustion engine 2 to dedicated combustion operation by operating the switching device 10 at a desired time. Switching the operation mode of the internal combustion engine 2 to dedicated combustion operation makes it possible to increase the amount of liquid fuel injected by the injector 50. Increasing the amount of liquid fuel injected by the injector 50 can directly eliminate fuel clogging in the injector 50.

[0040] In the embodiment shown in FIG. 3, if an operation to switch to exclusive combustion operation is performed after the above notification ("Yes" in step S8), the determination of the amount of output reduction (step S4) is performed again to check whether the exclusive combustion operation has eliminated the clogging of the injector 50.

[0041] In the embodiment shown in Fig. 3, if no operation to switch to exclusive combustion operation is performed after the above notification, the notification device 9 performs the above notification again. The notification by the notification device 9 may be performed at regular intervals. As shown in Fig. 3, in a state in which no operation to switch to exclusive combustion operation is performed and the operating mode of the internal combustion engine 2 is maintained in dual combustion operation (No in step S8), if the notification device 9 performs the above notification (number of notifications N) a predetermined number N1 or more times (Yes in step S9), the output of the internal combustion engine 2 may be forcibly limited to prompt the above operation. The predetermined number N1 is preferably two or more times. The recovery measure execution unit 31 includes a notification instruction unit 311 and an output limiting unit 312 (see Figs. 1 and 2). The output limiting unit 312 is configured to limit the output of the internal combustion engine 2 to a predetermined output or less (for example, 50% or less of the steady-state output) (step S10) when the notification device 9 has issued a notification (number of notifications N) a predetermined number of times or more ("Yes" in step S9 of FIG. 3). By limiting the output of the internal combustion engine 2 to a predetermined output or less by the output limiting unit 312, the user of the internal combustion engine 2 can be strongly urged to switch to mono-fuel operation.

[0042] In some embodiments, the recovery measure execution unit 31 is configured to acquire an actual injection amount of liquid fuel in the injector 50 and calculate a deviation of the actual injection amount of liquid fuel from a command injection amount in the injector 50. The recovery measure execution unit 31 is configured to take a recovery measure to restore the actual injection amount of liquid fuel injected from the injector 50 when the deviation exceeds a predetermined threshold while the internal combustion engine 2 is operating in dual-fuel combustion mode.

[0043] 1 , the recovery measure execution unit 31 is configured to monitor the pressure of the liquid fuel acquired by the pressure acquisition device 56. The recovery measure execution unit 31 acquires the actual injection amount of the liquid fuel from the injector 50 from the change in pressure of the liquid fuel acquired by the pressure acquisition device 56, based on association information that associates the change in pressure (decrease in pressure) of the liquid fuel acquired by the pressure acquisition device 56 with the actual injection amount of the liquid fuel from the injector 50.

[0044] 2 , the recovery measure execution unit 31 is configured to monitor the flow rate of the liquid fuel acquired by the flow rate acquisition device 57. The recovery measure execution unit 31 is configured to acquire the actual injection amount of the liquid fuel in the injector 50 from the change in the flow rate of the liquid fuel acquired by the flow rate acquisition device 57, based on association information that associates the change (increase) in the flow rate of the liquid fuel acquired by the flow rate acquisition device 57 with the actual injection amount of the liquid fuel in the injector 50.

[0045] 4 is a control flow diagram of the internal combustion engine 2 according to an embodiment of the present disclosure. The control flow shown in FIG. 4 is executed by the recovery measure execution unit 31. When the internal combustion engine 2 is started (step S1) and the internal combustion engine 2 is operating in the above-described mono-fuel operation ("No" in step S2), the determination of the deviation amount (step S4) described below is not performed, and the mono-fuel operation of the internal combustion engine 2 is continued (step S3). When the internal combustion engine 2 is operating in the above-described dual-fuel operation ("Yes" in step S2), the determination of the deviation amount of the actual injection amount of liquid fuel from the commanded injection amount is performed (step S4). When the deviation amount does not meet a predetermined threshold ("No" in step S4), it is determined that the injector 50 is not clogged, and the dual-fuel operation of the internal combustion engine 2 is continued (step S5). If the deviation amount exceeds a predetermined threshold value ("Yes" in step S4), it is determined that the injector 50 is clogged, and the above-mentioned recovery measures are taken (step S6).

[0046] Fuel clogging in the injector 50 causes the actual injection amount of liquid fuel in the injector 50 to deviate from the commanded injection amount. This deviation is more directly related to fuel clogging in the injector 50 than a reduction in output of the internal combustion engine 2 caused by various factors. If the deviation amount exceeds a predetermined threshold, there is a high probability that fuel clogging has occurred in the injector 50. In this case, the recovery measure execution unit 31 performs recovery measures to restore the actual injection amount of liquid fuel injected from the injector 50, thereby quickly eliminating the fuel clogging in the injector 50. An example of the recovery measure (step S6) is to increase the proportion of liquid fuel in the fuel used, as shown in FIG. 4.

[0047] In the embodiment shown in FIG. 4 , when the deviation of the actual injection amount of liquid fuel from the instructed injection amount exceeds a predetermined threshold ("Yes" in step S4), the proportion of liquid fuel in the fuel used is increased (step S11). The recovery measure execution unit 31 is configured to increase the proportion of liquid fuel in the fuel used when the deviation exceeds the predetermined threshold ("Yes" in step S4). In one embodiment, the recovery measure execution unit 31 is configured to increase the proportion of liquid fuel in the fuel used to 80% or more as the recovery measure. Increasing the proportion of liquid fuel in the fuel used can increase the amount of liquid fuel injected by the injector 50. Increasing the amount of liquid fuel injected by the injector 50 can directly resolve fuel clogging in the injector 50.

[0048] In the above-described step S11, the operation mode of the internal combustion engine 2 may be switched to mono-fuel operation using liquid fuel as the used fuel, with the aim of increasing the proportion of liquid fuel in the used fuel. In some embodiments, the above-described recovery measure execution unit 31 is configured to switch the operation mode of the internal combustion engine 2 to mono-fuel operation using liquid fuel as the used fuel, with the aim of increasing the proportion of liquid fuel in the used fuel.

[0049] Switching the operation mode of the internal combustion engine 2 to the mono-fuel operation makes it possible to increase the amount of liquid fuel injected by the injector 50. Increasing the amount of liquid fuel injected by the injector 50 directly eliminates fuel clogging in the injector 50.

[0050] The determination of whether the deviation amount exceeds the predetermined threshold value may be performed for each cylinder 4, and the recovery measure may be performed for a cylinder 4 for which the deviation amount exceeds the predetermined threshold value. In other words, the recovery measure does not need to be performed for a cylinder 4 for which the deviation amount does not meet the predetermined threshold value.

[0051] Fig. 5 is a control flow diagram of the internal combustion engine 2 according to an embodiment of the present disclosure. The control flow shown in Fig. 5 is performed by the recovery measure execution unit 31. In the embodiment shown in Fig. 5, when the deviation amount of the actual injection amount of liquid fuel from the instructed injection amount exceeds a predetermined threshold ("Yes" in step S4), the injection amount recovery operation is performed as the above-mentioned recovery measure (step S12). The recovery measure execution unit 31 is configured to execute the injection amount recovery operation when the above-mentioned deviation amount exceeds the predetermined threshold ("Yes" in step S4).

[0052] 6 and 7 are explanatory diagrams for explaining the recovery measures for the injector 50 according to an embodiment of the present disclosure. Each of Fig. 6 and Fig. 7 shows a graph with time T on the horizontal axis and the injection pressure IP of the injector 50 on the vertical axis. L1 shown in Fig. 6 and Fig. 7 indicates the change in the injection pressure IP when the operation mode of the internal combustion engine 2 is mono-fuel operation. L2 and L3 shown in Fig. 6 and Fig. 7 indicate the change in the injection pressure IP during injection amount recovery operation.

[0053] In some embodiments, the recovery measure execution unit 31 is configured to perform the recovery measure (injection amount recovery operation) by increasing the injection pressure IP, which is the pressure of the liquid fuel injected from the injector 50, to a value higher than that during dedicated combustion operation. As shown in Fig. 6, the maximum injection pressure IP2 during injection amount recovery operation is greater than the maximum injection pressure IP1 during dedicated combustion operation. By increasing the injection pressure, which is the pressure of the liquid fuel injected from the injector 50 during injection amount recovery operation, to a value higher than that during dedicated combustion operation, it is possible to directly eliminate fuel clogging in the injector 50.

[0054] In some embodiments, the recovery measure execution unit 31 is configured to pulsate the injection pressure, which is the pressure of the liquid fuel injected from the injector 50, within a predetermined pulsation limit width LW as the recovery measure (injection amount recovery operation). As shown in FIG. 7 , during the injection amount recovery operation, the injection pressure IP is gradually decreased (L3A in FIG. 7 ) or gradually increased (L3B in FIG. 7 ) within the predetermined pulsation limit width LW. Note that during the injection amount recovery operation, there may be a period during which the injection pressure IP is kept constant (L3C in FIG. 7 ). The maximum value IP3 of the injection pressure during the injection amount recovery operation may be the same as or greater than the maximum value IP1 of the injection pressure during the mono-fuel operation. By pulsating the injection pressure, which is the pressure of the liquid fuel injected from the injector 50, within the predetermined pulsation limit width LW during the injection amount recovery operation, the fuel clogging in the injector 50 can be directly resolved.

[0055] In some of the above-described embodiments, the control flows shown in Figures 3 to 5 were performed by the recovery action execution unit 31 of the control device 3, but these control flows may also be partially performed by a part other than the recovery action execution unit 31 of the control device 3, by a device other than the control device 3, or manually.

[0056] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0057] The present disclosure is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and appropriate combinations of these modifications. For example, when the amount of output reduction of the internal combustion engine 2 exceeds a predetermined threshold, the recovery measures shown in Figures 4 and 5 may be implemented. Furthermore, when the amount of deviation described above exceeds a predetermined threshold, the recovery measures shown in Figure 3 may be implemented.

[0058] The contents of the above-described embodiments can be understood, for example, as follows.

[0059] 1) A control device (3) for an internal combustion engine (2) according to at least one embodiment of the present disclosure is a control device (3) for an internal combustion engine (2) capable of dual combustion operation using both liquid fuel and gaseous fuel as fuels in use, wherein the internal combustion engine (2) includes: a cylinder (4) having a combustion chamber (40) for combusting the fuel in use; an injector (50) for injecting liquid fuel into the combustion chamber (40); a liquid fuel introduction line (5) for introducing the liquid fuel to the injector (50); and a gaseous fuel introduction line (6) for introducing gaseous fuel to the combustion chamber (40), and the control device (3) for the internal combustion engine (2) and a recovery measure execution unit (31) configured to take recovery measures to restore the actual injection amount of the liquid fuel injected from the injector (50) when, while the internal combustion engine (2) is operating in the multi-fuel operation, an amount of output reduction of the internal combustion engine (2) or a deviation of the actual injection amount of the liquid fuel in the injector (50) from an instructed injection amount exceeds a predetermined threshold.

[0060] According to the configuration 1) above, when the amount of output reduction of the internal combustion engine (2) or the deviation of the actual injection amount of liquid fuel in the injector (50) from the instructed injection amount exceeds a predetermined threshold, there is a high probability that fuel clogging has occurred in the injector (50). In this case, the recovery measure execution unit (31) performs recovery measures to restore the actual injection amount of liquid fuel injected from the injector (50), thereby enabling early elimination of fuel clogging in the injector (50). This makes it possible to suppress fuel clogging in the injector (50) and suppress a reduction in output of the internal combustion engine (2) due to fuel clogging.

[0061] 2) In some embodiments, in the control device (3) for the internal combustion engine (2) described in 1) above, the recovery measure execution unit (31) is configured to perform the recovery measure when an amount of output reduction of the internal combustion engine (2) exceeds the predetermined threshold value while the internal combustion engine (2) is operating in the dual-fuel combustion operation.

[0062] According to the configuration 2), fuel clogging in the injector (50) leads to a reduction in the output of the internal combustion engine (2). When the amount of reduction in the output of the internal combustion engine (2) exceeds a predetermined threshold, there is a high probability that fuel clogging has occurred in the injector (50), and therefore, by taking the recovery measures, the fuel clogging in the injector (50) can be quickly resolved.

[0063] 3) In some embodiments, in the control device (3) for the internal combustion engine (2) described in 1) above, the recovery measure execution unit (31) is configured to perform the recovery measure when a deviation of an actual injection amount of the liquid fuel in the injector (50) from a commanded injection amount exceeds the predetermined threshold value while the internal combustion engine (2) is operating in the multi-fuel operation.

[0064] According to the configuration 3), fuel clogging in the injector (50) causes a deviation of the actual injection amount of liquid fuel from the injector (50) relative to the commanded injection amount. The deviation is more directly related to fuel clogging in the injector (50) than to a reduction in output of the internal combustion engine (2) caused by various factors. When the deviation exceeds a predetermined threshold, there is a high probability that fuel clogging has occurred in the injector (50), and therefore, by taking the recovery measure, the fuel clogging in the injector (50) can be quickly resolved.

[0065] 4) In some embodiments, in the control device (3) for the internal combustion engine (2) described in any one of 1) to 3) above, the recovery measure execution unit (31) increases the proportion of the liquid fuel in the fuel used as the recovery measure.

[0066] According to the above configuration 4), the proportion of liquid fuel in the fuel used can be increased, thereby increasing the amount of liquid fuel injected from the injector 50. Increasing the amount of liquid fuel injected from the injector 50 can directly eliminate fuel clogging in the injector 50.

[0067] 5) In some embodiments, in the control device (3) for the internal combustion engine (2) described in 4) above, the recovery measure execution unit (31) switches the operation mode of the internal combustion engine to a mono-fuel operation in which the liquid fuel is used as the fuel.

[0068] According to the configuration of 5) above, the operation mode of the internal combustion engine (2) is switched to the mono-fuel operation, thereby increasing the injection amount of liquid fuel in the injector (50). By increasing the injection amount of liquid fuel in the injector (50), fuel clogging in the injector (50) can be directly eliminated.

[0069] 6) In some embodiments, in the control device (3) for the internal combustion engine (2) described in any one of 1) to 5) above, the recovery measure execution unit (31) increases the injection pressure, which is the pressure of the liquid fuel injected from the injector, as the recovery measure, to a pressure higher than that during mono-fuel operation.

[0070] According to the above configuration 6), the injection pressure, which is the pressure of the liquid fuel injected from the injector (50), is increased to a pressure higher than that during mono-fuel operation, thereby directly eliminating fuel clogging in the injector (50).

[0071] 7) In some embodiments, in the control device (3) for the internal combustion engine (2) described in any one of 1) to 6) above, the recovery measure execution unit (31) pulsates the injection pressure, which is the pressure of the liquid fuel injected from the injector, within a predetermined pulsation limit width as the recovery measure.

[0072] According to the above configuration 7), the injection pressure, which is the pressure of the liquid fuel injected from the injector (50), is pulsated within a predetermined pulsation limit width, thereby directly eliminating fuel clogging in the injector (50).

[0073] 8) In some embodiments, in the control device (3) for an internal combustion engine (2) described in any of 1) to 7) above, the recovery measure execution unit (31) includes a notification instruction unit (311) configured to cause the notification device (9) to issue a notification urging the operation mode of the internal combustion engine (2) to be switched to mono-fuel operation using the liquid fuel as the used fuel when, while the internal combustion engine (2) is being operated in the multi-fuel operation, an amount of output reduction of the internal combustion engine (2) or a deviation of an actual injection amount of the liquid fuel in the injector (50) from an instructed injection amount exceeds the predetermined threshold.

[0074] According to the configuration of 8) above, the notification device (9) can issue a notification urging the user of the internal combustion engine (2) to switch to dedicated combustion operation. This allows the user of the internal combustion engine (2) to switch the operation mode of the internal combustion engine (2) to dedicated combustion operation at a time desired by the user. By switching the operation mode of the internal combustion engine (2) to dedicated combustion operation, the injection amount of liquid fuel in the injector (50) can be increased. By increasing the injection amount of liquid fuel in the injector (50), fuel clogging in the injector (50) can be directly eliminated.

[0075] 9) In some embodiments, in the control device (3) for an internal combustion engine (2) described in 8) above, the recovery measure execution unit (31) further includes an output limiting unit (312) configured to limit the output of the internal combustion engine (2) to a predetermined output or less when the alarm device (9) has issued an alarm a predetermined number of times or more.

[0076] According to the configuration of 9) above, the output limiting unit (312) limits the output of the internal combustion engine (2) to a predetermined output or less, so that the user of the internal combustion engine (2) can be strongly urged to switch to mono-fuel operation.

[0077] 10) In some embodiments, there is provided a control device (3) for an internal combustion engine (2) described in any one of 1) to 9) above, wherein the internal combustion engine (2) further includes a combustion gas introduction line (7) for introducing combustion gas into the combustion chamber, the combustion gas introduction line (7) joining the gaseous fuel introduction line (6) at a joining point (P1) and sharing a downstream side of the joining point (P1) with the gaseous fuel introduction line (6).

[0078] According to the configuration of 10), the gaseous fuel is introduced into the combustion chamber (40) in a mixed state with the combustion gas, and the mixed state is burned. In order to burn the gaseous fuel, it is necessary to raise the temperature inside the cylinder (4) by keeping the excess air ratio relatively low. If the temperature inside the cylinder (4) is raised, the injector (50) may be excessively heated, which may lead to fuel clogging in the injector (50). Therefore, it is necessary to take the above recovery measures to quickly clear the fuel clogging in the injector (50).

[0079] 11) In some embodiments, in the control device (3) for an internal combustion engine (2) described in any one of 1) to 10) above, the liquid fuel is diesel, and the gaseous fuel has a lower methane number than the diesel.

[0080] According to the configuration of 11), the proportion of gaseous fuel in the fuel used is increased and the proportion of liquid fuel is decreased in order to reduce greenhouse gas emissions such as carbon dioxide from the internal combustion engine (2). This reduces the flow rate of liquid fuel injected from the injector (50), which may lead to fuel clogging in the injector (50). Furthermore, according to the configuration of 11), when the methane number of the gaseous fuel is lower than that of the liquid fuel, it is necessary to increase the temperature inside the cylinder by setting the excess air ratio relatively low in order to combust the gaseous fuel. Increasing the temperature inside the cylinder may result in excessive heat exposure to the injector (50), which may lead to fuel clogging in the injector (50). Because of this high possibility of fuel clogging in the injector (50), it is necessary to take the above-mentioned recovery measures to quickly resolve the fuel clogging in the injector (50).

[0081] 12) In some embodiments, in the control device (3) for an internal combustion engine (2) according to any one of 1) to 10) above, the gaseous fuel is ammonia gas.

[0082] According to the configuration of 12), ammonia gas is a gas fuel with relatively low combustibility, so a liquid fuel must be used as an ignition source. In addition, in order to combust the gas fuel with relatively low combustibility, it is necessary to raise the temperature inside the cylinder by setting the excess air ratio relatively low.

[0083] REFERENCE SIGNS LIST 1 Internal combustion engine system 2 Internal combustion engine 3 Control device 4 Cylinder 5 Liquid fuel introduction line 6 Gaseous fuel introduction line 7 Combustion gas introduction line 8 Exhaust gas discharge line 9 Notification device 10 Switching device 30 Control unit 31 Recovery measure execution unit 40 Combustion chamber 50 Injector 51 Common rail

Claims

1. A control device for an internal combustion engine capable of multi-fuel operation using both liquid fuel and gaseous fuel as the fuel used, wherein the internal combustion engine includes: a cylinder having a combustion chamber for combusting the fuel used; an injector for injecting liquid fuel into the combustion chamber; a liquid fuel inlet line for guiding the liquid fuel to the injector; and a gaseous fuel inlet line for guiding the gaseous fuel to the combustion chamber, and the control device for the internal combustion engine includes a recovery measure execution unit configured to take recovery measure to restore the actual injection amount of the liquid fuel injected from the injector when the amount of output reduction of the internal combustion engine or the deviation of the actual injection amount of the liquid fuel in the injector from a commanded injection amount exceeds a predetermined threshold value while the internal combustion engine is operating in the multi-fuel operation.

2. The control device for an internal combustion engine as described in claim 1, wherein the recovery measure execution unit is configured to carry out the recovery measure when an amount of output reduction of the internal combustion engine exceeds the predetermined threshold value while the internal combustion engine is operating in the multi-fuel operation.

3. The control device for an internal combustion engine according to claim 1, wherein the recovery action execution unit is configured to carry out the recovery action when a deviation of an actual injection amount of the liquid fuel in the injector from an instructed injection amount exceeds the predetermined threshold value while the internal combustion engine is operating in the multi-fuel operation.

4. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the recovery measure execution unit increases a proportion of the liquid fuel in the fuel used as the recovery measure.

5. The control device for an internal combustion engine according to claim 4, wherein the recovery measure execution unit switches an operation mode of the internal combustion engine to a mono-fuel operation in which the liquid fuel is used as the fuel to be used.

6. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the recovery measure execution unit increases an injection pressure, which is the pressure of the liquid fuel injected from the injector, as the recovery measure, to a pressure higher than that during mono-fuel operation.

7. A control device for an internal combustion engine as claimed in any one of claims 1 to 3, wherein the recovery measure execution unit pulsates an injection pressure, which is the pressure of the liquid fuel injected from the injector, within a predetermined pulsation limit width as the recovery measure.

8. A control device for an internal combustion engine as claimed in any one of claims 1 to 3, wherein the recovery measure execution unit includes a notification instruction unit configured to cause a notification device to issue a notification urging the user to switch the operation mode of the internal combustion engine to mono-fuel operation using the liquid fuel as the used fuel when, while the internal combustion engine is operating in the multi-fuel operation, the amount of output reduction of the internal combustion engine or the deviation of the actual injection amount of the liquid fuel in the injector from the instructed injection amount exceeds the predetermined threshold value.

9. The control device for an internal combustion engine as described in claim 8, wherein the recovery measure execution unit further includes an output limiting unit configured to limit the output of the internal combustion engine to a predetermined output or less when the alarm device has issued an alarm a predetermined number of times or more.

10. A control device for an internal combustion engine as described in any one of claims 1 to 3, wherein the internal combustion engine further includes a combustion gas introduction line for guiding combustion gas to the combustion chamber, the combustion gas introduction line merging with the gaseous fuel introduction line at a junction and sharing a downstream side of the junction with the gaseous fuel introduction line.

11. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the liquid fuel is diesel, and the gaseous fuel has a lower methane number than the diesel.

12. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the gaseous fuel is ammonia gas.

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