Engine control device, engine control method, and program

Abstract

In the present invention, an engine system includes: a fuel tank (32) that supplies gas fuel to a fuel injection valve (50) of an engine (10) via a fuel pipe (31); a pressure sensor (36) provided in the fuel pipe; and a gas sensor (23) that detects a gas component in exhaust gas. An engine control device (60) includes: an air-fuel ratio determination unit that determines, on the basis of a detection result of the gas sensor, whether the air-fuel ratio of an air-fuel mixture is in an excessively rich state in which the air-fuel ratio is excessively rich; a pressure drop determination unit that determines, on the basis of a detection result of the pressure sensor, whether a pressure drop abnormality has occurred in the fuel pipe; and an abnormality identification unit that, when it is determined that the air-fuel ratio is in the excessively rich state and a pressure drop abnormality has occurred, identifies, as an abnormality in the engine system, that an injection hole leakage abnormality, which is a fuel leak in the injection hole of the fuel injection valve, has occurred.

Description

Engine control device, engine control method and program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-126660, filed on August 2, 2024, the contents of which are incorporated herein by reference.

[0002] The disclosure in this specification relates to an engine control device, an engine control method, and a program.

[0003] Fuel injection valves that inject gaseous fuels such as hydrogen have a larger volume of injected fuel per combustion in an engine than fuel injection valves that inject liquid fuels such as gasoline. Therefore, fuel injection valves for gaseous fuels have a larger valve element lift, which raises concerns about fuel leakage due to wear on the valve element seat. Furthermore, in gas engines, there is concern about abnormal combustion due to fuel leakage from the nozzle holes of the fuel injection valve.

[0004] For example, Patent Document 1 describes an open valve malfunction detection device that detects the occurrence of an open valve malfunction in a fuel injection valve that injects gas fuel, where the valve remains open. Specifically, in response to an engine start or stop operation, a shutoff valve provided upstream of the injection valve is opened, closed after a predetermined time has elapsed, and an open valve malfunction of the fuel injection valve is detected based on a change in pressure (a change in pressure in a fuel passage between the fuel injection valve and the shutoff valve) detected after the shutoff valve is closed.

[0005] Japanese Patent Application Laid-Open No. 2006-250141

[0006] In gas engines, it is thought that malfunctions such as abnormal combustion can occur due to gas fuel leakage, but if the cause of the malfunction is not properly understood, there is a concern that when an abnormality occurs, fail-safe measures such as replacing the fuel injection valve for repair or taking the vehicle to an evacuation route cannot be properly implemented.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide an engine control device, an engine control method, and a program that can properly identify abnormalities in an engine system and thereby properly take measures such as replacing a fuel injection valve.

[0008] The engine control device of the present disclosure is applied to an engine system including: an engine having a fuel injection valve that injects gas fuel into a combustion chamber and an ignition device that generates an ignition spark in the combustion chamber at a predetermined ignition timing; a fuel tank that supplies gas fuel to the fuel injection valve through a fuel pipe; a pressure sensor provided in the fuel pipe; and a gas sensor that detects gas components in exhaust gas discharged from the engine, and includes: an air-fuel ratio determination unit that determines whether the air-fuel ratio of the mixture that is burned in the combustion chamber is in an excessively rich state based on the detection result of the gas sensor; a pressure drop determination unit that determines whether a pressure drop abnormality has occurred in the fuel pipe based on the detection result of the pressure sensor; and an abnormality identification unit that, when the air-fuel ratio determination unit determines that the mixture is in the excessively rich state and the pressure drop determination unit determines that the pressure drop abnormality has occurred, identifies an injection hole leakage abnormality, which is a fuel leak at the injection hole of the fuel injection valve, as an abnormality of the engine system.

[0009] In the above configuration, a nozzle hole leakage abnormality of the fuel injector is identified as an engine system abnormality based on a determination that the air-fuel ratio of the mixture burned in the combustion chamber is excessively rich and a determination that a pressure drop abnormality has occurred in the fuel pipe. In this case, the excessively rich air-fuel ratio is considered to be caused by either an excess of fuel due to a nozzle hole leakage abnormality of the fuel injector or an insufficient amount of air entering the combustion chamber. Furthermore, by referring to the determination that a pressure drop abnormality has occurred in the fuel pipe, it is possible to determine that an excess of fuel is the cause of the excessively rich air-fuel ratio, out of either an excess of fuel or an insufficient amount of air. This makes it possible to properly identify a nozzle hole leakage abnormality of the fuel injector as an engine system abnormality. In other words, the above configuration properly identifies an abnormality in the engine system and, ultimately, allows appropriate measures, such as replacing the fuel injector.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of an engine system, Fig. 2 is a cross-sectional view showing the configuration of a fuel injection valve, Fig. 3 is a flowchart showing a procedure for detecting an abnormality while the engine is running, Fig. 4 is a flowchart showing a procedure for identifying an abnormality after the engine is stopped, Fig. 5 is a time chart illustrating an abnormality determination procedure when a nozzle hole leakage abnormality has occurred, Fig. 6 is a time chart illustrating an abnormality determination procedure when an intake system abnormality has occurred, and Fig. 7 is a time chart illustrating an abnormality determination procedure when an ignition system abnormality has occurred.

[0011] An embodiment embodying the present disclosure will be described below with reference to the drawings. This embodiment embodies an engine system equipped with a gas engine that uses, for example, hydrogen gas as a gas fuel. The engine system is mounted on, for example, a vehicle. An overall schematic diagram of the system is shown in FIG.

[0012] 1, an engine 10 is a multi-cylinder internal combustion engine having a plurality of cylinders (e.g., three cylinders), and its intake ports and exhaust ports are connected to an intake system 11 and an exhaust system 12, respectively. The intake system 11 has an intake manifold 13 and an intake pipe 14. The intake pipe 14 is provided with a throttle device 15 as an air amount adjustment device. The throttle device 15 has an electronically controlled throttle valve whose opening is adjusted by a throttle actuator such as a DC motor, and the opening of the throttle valve in the throttle device (throttle opening) is detected by a throttle sensor 16.

[0013] The engine 10 is provided with a rotation sensor 17 that detects the rotation of the crankshaft and a vibration sensor 18 that detects vibrations generated in the engine 10. The detection signal from the rotation sensor 17 makes it possible to calculate the rotation speed of the engine 10 and the crank angle position of the piston in each cylinder. The vibration sensor 18 is provided, for example, in the cylinder block of the engine 10, and outputs a signal with a waveform corresponding to the vibrations generated in the engine 10. The vibration sensor 18 is also generally referred to as a knock sensor.

[0014] The exhaust system 12 has an exhaust manifold 21 and an exhaust pipe 22. The exhaust pipe 22 is provided with a gas sensor 23 that detects gas components in the exhaust and a catalyst 24 that purifies the exhaust. Specifically, the gas sensor 23 is provided with at least one of an oxygen sensor that detects the oxygen concentration in the exhaust, an air-fuel ratio sensor that detects the air-fuel ratio in accordance with the oxygen concentration in the exhaust, and a NOx sensor that detects the NOx concentration in the exhaust.

[0015] A fuel injection valve 50 that injects gas fuel is provided in each cylinder of the engine 10. The fuel injection valve 50 is an in-cylinder injection type fuel injection valve that directly injects gas fuel into a combustion chamber of the engine 10. The fuel injection valve 50 is supplied with gas fuel from the fuel supply unit 30, and the gas fuel is injected into the combustion chamber when the fuel injection valve 50 opens.

[0016] In the fuel supply unit 30, a fuel tank 32 is connected to the fuel injection valve 50 via a fuel pipe 31, and a regulator 33 is provided in the fuel pipe 31 to reduce or adjust the pressure of the gas fuel supplied to the fuel injection valve 50. The regulator 33 has a pressure adjustment function to reduce or adjust the pressure of the gas fuel stored in a high-pressure state in the fuel tank 32 to a predetermined pressure, and the gas fuel after the pressure reduction adjustment is supplied to the fuel injection valve 50 through the fuel pipe 31. In the fuel pipe 31, the upstream side of the regulator 33 is a high-pressure pipe section 31a that forms a high-pressure side passage, and the downstream side is a low-pressure pipe section 31b that forms a low-pressure side passage.

[0017] The low-pressure piping section 31b is provided with a shutoff valve 35. The shutoff valve 35 is opened, for example, by electromagnetic actuation. When the shutoff valve 35 is closed, the flow of gas fuel from the regulator 33 side to the fuel injection valve 50 side is blocked, and when the shutoff valve 35 is open, the flow of gas fuel from the regulator 33 side to the fuel injection valve 50 side is permitted.

[0018] In the fuel pipe 31, a pressure sensor 36 that detects the pressure (fuel pressure) of the gas fuel supplied to the fuel injection valve 50 and a temperature sensor 37 that detects the temperature of the gas fuel are provided in the low-pressure pipe section 31b. Note that a pressure sensor and a temperature sensor may also be provided in the high-pressure pipe section 31a in a similar manner.

[0019] The fuel supply unit 30 is also provided with a leak detection sensor 38 that detects leakage of gas fuel from the fuel pipe 31. The leak detection sensor 38 is, for example, a gas concentration detection device that detects the concentration of a specific component (such as hydrogen concentration) in the atmosphere. The leak detection sensor 38 is provided in an engine compartment where the engine is located in the vehicle or in the installation space for the fuel pipe 31.

[0020] Each cylinder of the engine 10 is provided with a spark plug 40. A high voltage is applied to the spark plug 40 at the desired ignition timing through an ignition device 41, which is comprised of an ignition coil and the like. This application of high voltage generates a spark discharge between the opposing electrodes of each spark plug 40, igniting the gas fuel introduced into the cylinder (combustion chamber) and causing it to burn.

[0021] The configuration of the fuel injection valve 50 will now be described with reference to Figure 2. The fuel injection valve 50 has a cylindrical body 51, and a valve element 52 is housed in the hollow portion of the body 51 so that it can slide axially. The hollow portion of the body 51 forms a passage through which gas fuel flowing in from the fuel pipe 31 passes. A nozzle hole 53 is provided at the tip of the body 51, and the nozzle hole 53 is opened and closed by the valve element 52. The valve element 52 is biased in a valve closing direction, i.e., in a direction that closes the nozzle hole 53, by a spring 54 provided within the body 51.

[0022] The valve element 52 has a fuel passage 52a extending in the axial direction. The valve element 52 also has a core portion 52b. A fuel chamber 55 is formed within the body 51 so as to surround the tip portion of the valve element 52, and the fuel chamber 55 is connected to the fuel passage 52a of the valve element 52. The fuel injection valve 50 has a solenoid 56, which is an electromagnetic drive unit. When the solenoid 56 is energized, the valve element 52 is displaced to an open position against the biasing force of a spring 54, and the nozzle hole 53 is opened. This causes gas fuel to be injected from the nozzle hole 53. When the solenoid 56 is deenergized, the biasing force of the spring 54 returns the valve element 52 to a closed position (seat position), and injection of gas fuel from the nozzle hole 53 is stopped.

[0023] In each cylinder of the engine 10, fuel is injected by the fuel injection valve 50 during the compression stroke, which is one of the four strokes of intake, compression, expansion, and exhaust. Ignition is also performed by the spark plug 40 and the ignition device 41 near the top dead center of the compression stroke, and the gas fuel is burned in the combustion chamber as a result of this ignition.

[0024] The fuel injection valve 50 shown in FIG. 2 has an inward opening valve structure in which the valve element 52 moves inwardly of the body when the valve is opened, but may alternatively have an outward opening valve structure in which the valve element 52 moves outwardly of the body when the valve is opened.

[0025] As shown in FIG. 1 , the ECU 60 (Electronic Control Unit) includes a microcomputer 61 for engine control and a drive circuit 62 for driving injectors. The microcomputer 61 is a computer equipped with a processor and a memory (storage unit) and provides various computational functions. The functions provided by the microcomputer 61 can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, when the microcomputer 61 is provided by a hardware electronic circuit, the function can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer 61 executes programs stored in a non-transitory tangible storage medium serving as a storage unit. The programs include, for example, programs for various processes related to fuel injection control and ignition control. Execution of the programs results in the execution of a method corresponding to the programs. The storage unit is, for example, a non-volatile memory. Note that the programs stored in the storage unit can be updated via a network such as the Internet. In this embodiment, the microcomputer 61 corresponds to an "engine control device."

[0026] The microcomputer 61 calculates a required injection amount, which is the amount of fuel injected per injection, in accordance with the engine operating conditions (e.g., engine rotation speed, engine load, etc.), generates an injection signal from the solenoid current conduction time calculated based on this required injection amount, and outputs the injection signal to the drive circuit 62. The drive circuit 62 applies a voltage to the solenoid 56 in accordance with the injection signal, thereby driving the fuel injection valve 50 to open. As a result, fuel equivalent to the required injection amount is injected from the fuel injection valve 50.

[0027] In an engine system that uses gas fuel such as hydrogen, there are concerns about gas leaks in the fuel injection valve 50 and piping system, as well as abnormal combustion due to gas leaks. In the unlikely event that a gas leak occurs, it is desirable to accurately identify the cause of the abnormality. Possible abnormalities related to fuel combustion in an engine system include a nozzle hole leakage abnormality, which is fuel leakage from the nozzle hole 53 of the fuel injection valve 50; an intake system abnormality, which causes an insufficient amount of air to pass through the throttle device 15; and an ignition system abnormality, which causes the ignition timing of the ignition device 41 to be over-advanced.

[0028] In this embodiment, the outline of the process for identifying abnormalities in the engine system is as follows: - Determine whether pre-ignition has occurred in the engine 10 (pre-ignition determination unit); - Determine whether the air-fuel ratio of the mixture used for combustion in the combustion chamber is excessively rich, based on the detection result of the gas sensor 23 (air-fuel ratio determination unit); - Determine whether a pressure drop abnormality has occurred in the fuel piping 31, based on the detection result of the pressure sensor 36 (pressure drop determination unit).

[0029] When pre-ignition occurs in the engine 10, the abnormality determining unit determines whether the engine system abnormality is a nozzle hole leakage abnormality, an intake system abnormality, or an ignition system abnormality based on the determination result of whether the engine is in an excessively rich state and the determination result of whether a pressure drop abnormality exists (abnormality determining unit). The details of this are described below.

[0030] 3 is a flowchart showing the procedure for detecting an abnormality while the engine is running. This procedure is repeatedly executed by the microcomputer 61 at a predetermined interval while the vehicle power switch (IG switch) is on.

[0031] 3, in step S101, various pieces of information used for abnormality detection are acquired. Specifically, information detected by the rotation sensor 17, the vibration sensor 18, the gas sensor 23, and the leak detection sensor 38 is acquired.

[0032] In step S102, it is determined whether or not an external leakage anomaly, which is a gas leak from the fuel pipe 31, has occurred based on the detection information from the leak detection sensor 38. An external leakage anomaly is an anomaly that indicates that gas fuel has leaked upstream of the fuel injection valve 50 and along a fuel supply path that includes the fuel pipe 31. Specifically, if the concentration of a specific component (e.g., hydrogen concentration) detected by the leak detection sensor 38 is equal to or greater than a predetermined value, it is determined that an external leakage anomaly has occurred. In this case, if it is determined that an external leakage anomaly has occurred, the process proceeds to step S103, and if it is determined that an external leakage anomaly has not occurred, the process proceeds to step S104.

[0033] In step S103, a fail-safe process is executed to deal with the external leakage abnormality. Specifically, the driver is notified to immediately evacuate the vehicle to a safe evacuation location. This notification is made by voice or display. The vehicle's traveling speed may be limited to a predetermined speed or less by limiting the output of the engine 10. After the vehicle is stopped at the evacuation location, the engine 10 is stopped and the shutoff valve 35 is shut off.

[0034] In steps S102 and S103, an external leakage abnormality is identified regardless of the results of the pre-ignition determination, the excessively rich determination, and the pressure drop determination, which will be described later.

[0035] In step S104, it is determined whether pre-ignition has occurred as abnormal combustion in the engine 10. The presence or absence of pre-ignition may be determined based on the detection signal of the vibration sensor 18. Specifically, the presence or absence of pre-ignition is determined based on whether vibrations due to pre-ignition have occurred in each cylinder of the engine 10 during the period from the start of fuel injection by the fuel injection valve 50 to the ignition timing by the ignition device 41.

[0036] Note that any method for determining pre-ignition may be used, and in addition to the above, it is possible to determine whether or not pre-ignition has occurred using, for example, the detection signals of an in-cylinder pressure sensor, an in-cylinder temperature sensor, or the rotation sensor 17. When an in-cylinder pressure sensor is used, a change in in-cylinder pressure due to pre-ignition after fuel injection is detected, and the occurrence of pre-ignition is determined based on this change in in-cylinder pressure. When an in-cylinder temperature sensor is used, a change in in-cylinder temperature due to pre-ignition after fuel injection is detected, and the occurrence of pre-ignition is determined based on this change in in-cylinder temperature. When the rotation sensor 17 is used, a change in instantaneous rotation speed due to pre-ignition is detected, and the occurrence of pre-ignition is determined based on this change in instantaneous rotation speed.

[0037] If it is not determined that pre-ignition has occurred, this process is terminated. If it is determined that pre-ignition has occurred, the process proceeds to step S105, where the pre-ignition flag F1 is set to 1. This flag operation stores the history of pre-ignition occurrences. The pre-ignition flag F1 is a variable that is 0 when pre-ignition has not occurred and is set to 1 when pre-ignition has occurred, and is stored and maintained even after the vehicle's power switch is turned off.

[0038] Then, in step S106, it is determined whether the air-fuel ratio of the mixture to be burned in the combustion chamber is excessively rich, based on the detection signal of the gas sensor 23. In this case, if the actual air-fuel ratio calculated from the detection signal of the gas sensor 23 deviates by a predetermined value or more toward the rich side from the target air-fuel ratio, it is determined that the mixture is in the excessively rich state. Note that, when a NOx sensor is used as the gas sensor 23, it is preferable to determine whether the mixture is in the excessively rich state based on the result of comparing the estimated NOx amount, which is estimated from the required injection amount of the fuel injection valve 50 and the inflow air amount, with the actual NOx amount detected by the gas sensor 23.

[0039] If the air-fuel mixture is in an excessively rich state, the process proceeds to step S107, where the excessively rich flag F2 is set to 1. The excessively rich flag F2 is a variable that is set to 0 when the air-fuel mixture is not in an excessively rich state and is set to 1 when the air-fuel mixture is in an excessively rich state, and is stored and maintained even after the power switch of the vehicle is turned off.

[0040] The pre-ignition determination in step S104 and the excessively rich air-fuel ratio determination in step S106 may be made based on the cumulative number or frequency of occurrences of pre-ignition or excessively rich air-fuel ratio. For example, it may be determined that pre-ignition has occurred when the cumulative number of occurrences of pre-ignition has reached a predetermined number, or when the number of occurrences of pre-ignition within a predetermined period (i.e., the pre-ignition occurrence rate) is equal to or greater than a predetermined number. The same applies to the excessively rich air-fuel ratio determination. The pre-ignition determination and excessively rich air-fuel ratio determination may be made for each cylinder.

[0041] 4 is a flowchart showing the procedure for identifying an abnormality after the engine is stopped. This procedure is executed by the microcomputer 61 after the vehicle's power switch is turned off. In this engine system, power is continuously supplied to the ECU 60 for a predetermined period of time even after the vehicle's power switch is turned off, and the procedure in FIG. 4 is executed during this power supply period.

[0042] In Fig. 4, in step S201, it is determined whether or not the pre-ignition flag F1 is 1. If F1 = 0, that is, if pre-ignition did not occur before the previous engine operation, the process proceeds to step S211. In step S211, it is determined that power to the ECU 60 or the vehicle may be shut off, and then the process ends. Based on this decision to shut off the power, the power to the ECU 60 or the vehicle is shut off. Also, if F1 = 1, that is, if history information indicating that pre-ignition occurred before the previous engine operation is stored, the process proceeds to step S202.

[0043] In step S202, a pressure drop determination is made in the fuel pipe 31. Specifically, with fuel injection by the fuel injection valve 50 stopped and the shutoff valve 35 closed due to the power switch being turned off, a predetermined period (e.g., several minutes) from the closure of the shutoff valve 35 is set as a pressure drop determination period, and it is determined whether or not an abnormal pressure drop due to a fuel leak has occurred based on the amount of pressure drop in the fuel pipe 31 during the pressure drop determination period. In this case, if the amount of pressure drop during the pressure drop determination period is less than a predetermined threshold, it is determined that no abnormal pressure drop due to a fuel leak has occurred, and if the amount of pressure drop is equal to or greater than the threshold, it is determined that an abnormal pressure drop has occurred.

[0044] In step S203, it is determined whether or not the determination result in step S202 indicates a pressure drop abnormality. If a pressure drop abnormality is detected, the process proceeds to step S204, and if no pressure drop abnormality is detected, the process proceeds to step S205.

[0045] In step S204, it is determined whether the excessively rich flag F2 is 1. If F2=1, the process proceeds to step S206, where it is determined that a nozzle hole leakage abnormality has occurred in the fuel injection valve 50 as an abnormality in the engine system. That is, based on the excessively rich state and the occurrence of a pressure drop abnormality, it is determined that a nozzle hole leakage abnormality has occurred. If F2=0, the process proceeds to step S207, where it is determined that a fuel leak has occurred at a location other than the injection hole 53 of the fuel injection valve 50 as an abnormality in the engine system. That is, based on the fact that the excessively rich state is not present and the occurrence of a pressure drop abnormality, it is determined that a fuel leak has occurred, but that the leak location is other than the injection hole.

[0046] Also, in step S205, it is determined whether the excessive-rich flag F2 is 1. If F2=1, the process proceeds to step S208, where it is determined that an intake system abnormality has occurred as an engine system abnormality. In other words, if the engine is in an excessive-rich state and no pressure drop abnormality has occurred, it is believed that the excessive-rich state is caused not by an excess fuel amount but by an insufficient amount of air, and therefore it is determined that an intake system abnormality has occurred. If F2=0, the process proceeds to step S209, where it is determined that an ignition system abnormality has occurred as an engine system abnormality. In other words, if the engine is not in an excessive-rich state and no pressure drop abnormality has occurred, it is believed that the cause of pre-ignition is not a nozzle hole leakage abnormality or an intake system abnormality, and therefore it is determined that an ignition system abnormality has occurred.

[0047] Then, in step S210, fail-safe processing corresponding to steps S206 to S209 is executed. Specifically, to notify the driver of the occurrence of an abnormality, a warning light, a sound, a display, or the like is used. Furthermore, abnormality diagnosis data indicating the occurrence of an abnormality and the cause of the abnormality is stored in the memory of the ECU 60. In this case, the vehicle is allowed to continue traveling, but the driver is warned of the abnormality and is prompted to promptly inspect or replace the part.

[0048] The fail-safe process in step S103 in Fig. 3 and the fail-safe process in step S210 in Fig. 4 both correspond to processes for restricting vehicle travel in order to avoid danger. However, the degree of vehicle travel restriction differs between these fail-safe processes, and the fail-safe process in step S210 (fail-safe process corresponding to a nozzle hole leakage abnormality, etc.) restricts vehicle travel to a lesser extent than the fail-safe process in step S103 (fail-safe process corresponding to an external leakage abnormality).

[0049] Finally, in step S211, it is determined that the power supply to the ECU 60 or the vehicle may be shut off, and then this process ends.

[0050] Identifying an abnormality in the engine system will be described in more detail below using the time charts of Figures 5 to 7. Figure 5 is a time chart illustrating the procedure for determining an abnormality when a nozzle hole leakage abnormality occurs, Figure 6 is a time chart illustrating the procedure for determining an abnormality when an intake system abnormality occurs, and Figure 7 is a time chart illustrating the procedure for determining an abnormality when an ignition system abnormality occurs. In Figures 5 to 7, the first half shows operation while the engine is running (i.e., with the power switch on), and the second half shows operation after the engine has stopped (i.e., after the power switch has been turned off).

[0051] 5 , at timing t1 during engine operation, a pre-ignition flag F1 is set to 1 in response to the occurrence of pre-ignition, and at timing t2, an excessively rich flag F2 is set to 1 in response to an excessively rich air-fuel mixture determination. Subsequently, at timing t3, the engine 10 is stopped in response to the power switch being turned off, and a pressure drop determination is performed from timing t3 onward. This pressure drop determination determines whether or not the fuel pressure in the fuel pipe 31 (more specifically, the low-pressure pipe section 31b) will excessively drop when the fuel injection valve 50 is closed (i.e., fuel injection is stopped) and the shutoff valve 35 is closed. More specifically, during a pressure drop determination period TA starting from the closing of the shutoff valve 35, it is determined whether or not the detected pressure detected by the pressure sensor 36 drops below a pressure threshold value TH obtained by subtracting a predetermined value from the pressure when the shutoff valve 35 is closed.

[0052] When a nozzle hole leakage anomaly has occurred as an engine system anomaly, fuel is leaking from the nozzle hole 53 of the fuel injection valve 50, and the rate of drop in fuel pressure is greater than when no nozzle hole leakage anomaly has occurred (dash-dotted line). Therefore, during the pressure drop determination period TA, the fuel pressure in the fuel pipe 31 drops below the pressure threshold value TH. As a result, at timing t4, it is determined that a pressure drop anomaly has occurred, and the occurrence of a nozzle hole leakage anomaly is identified based on the determination result of the pressure drop anomaly and the determination result of the excessive-rich state.

[0053] In Figure 6, at timing t11 while the engine is running, pre-ignition flag F1 is set to 1 in response to the occurrence of pre-ignition, and at timing t12, excessively rich flag F2 is set to 1 in response to an excessively rich air-mix determination. Subsequently, a pressure drop determination is made at timing t13 or later when the engine 10 is stopped. If an intake system abnormality occurs as an engine system abnormality, an excessively rich air-mix state occurs during engine operation due to an insufficient amount of air, but the rate of pressure drop immediately after the engine is stopped is relatively small. Therefore, at timing t14 when the pressure drop determination period TA has elapsed, it is determined that no pressure drop abnormality has occurred. At timing t14, it is determined that an intake system abnormality has occurred.

[0054] In Figure 7, at timing t21 while the engine is running, pre-ignition occurs and the pre-ignition flag F1 becomes 1. However, unlike Figures 5 and 6, in Figure 7, the excess-rich condition is not met and the excess-rich flag F2 remains 0. Thereafter, a pressure drop determination is made after timing t22 when the power switch is turned off. If an ignition system abnormality has occurred as the engine system abnormality, pre-ignition has occurred in the engine 10 but the excess-rich condition has not been met and the pressure drop rate immediately after the engine is stopped is relatively small. Therefore, at timing t23, it is determined that an ignition system abnormality has occurred.

[0055] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0056] In the above configuration, a nozzle hole leakage abnormality of the fuel injection valve 50 is identified as an engine system abnormality based on a determination result that the air-fuel ratio of the mixture burned in the combustion chamber of the engine 10 is excessively rich and a determination result that a pressure drop abnormality has occurred in the fuel pipe 31. In this case, the excessively rich air-fuel ratio is considered to be caused by either an excess of fuel due to a nozzle hole leakage abnormality of the fuel injection valve 50 or an insufficient amount of air entering the combustion chamber. Furthermore, by referring to the determination result that a pressure drop abnormality has occurred in the fuel pipe 31, it is possible to determine that an excess of fuel is the cause of the excessively rich air-fuel ratio, out of either an excess of fuel or an insufficient amount of air. This makes it possible to properly identify a leakage abnormality of the fuel injection valve 50 as an engine system abnormality. In other words, the above configuration properly identifies an abnormality in the engine system, and ultimately allows appropriate measures, such as replacing the fuel injection valve 50, to be taken.

[0057] When the air-fuel ratio becomes excessively rich and there is no abnormal pressure drop in the fuel pipe 31, it is possible to determine that the engine system is experiencing an insufficient amount of air. This makes it possible to properly identify an intake system abnormality (an abnormality in the throttle device 15) as the abnormality in the engine system.

[0058] When the air-fuel ratio is not excessively rich and there is no abnormal pressure drop in the fuel pipe 31, it is unlikely that there is a nozzle hole leakage abnormality or an intake system abnormality in the engine system, and it is assumed that the ignition timing in the ignition device 41 is over-advanced. This makes it possible to properly identify an ignition system abnormality (an abnormality in the ignition device 41) as an abnormality in the engine system.

[0059] Pre-ignition is a phenomenon that poses significant risk of damage in gas engines that use gas fuels such as hydrogen, and it is desirable to understand the cause of pre-ignition when it occurs. In this regard, the system is configured to identify abnormalities in the engine system on the condition that it is determined that pre-ignition has occurred, making it possible to properly understand the abnormalities that could be the cause of pre-ignition.

[0060] If pre-ignition occurs while the engine is running, its occurrence history is stored, and under conditions in which the pre-ignition occurrence history is stored, a pressure drop determination is made after the engine is stopped. This configuration is such that a pressure drop determination is made after the engine is stopped on the condition that a pre-ignition occurrence history is stored (i.e., the pre-ignition flag F1 is 1). In other words, if a pre-ignition occurrence history is not stored (i.e., the pre-ignition flag F1 is 0), a pressure drop determination is not made after the engine is stopped. In this case, unnecessary pressure drop determinations after the engine is stopped are prevented, and inconveniences such as an increase in power consumption due to a delay in shutting off the power after the engine is stopped can be prevented.

[0061] When it is determined that a nozzle hole leakage abnormality has occurred, a fail-safe process is executed that imposes less restriction on vehicle driving than when it is determined that an external leakage abnormality has occurred. When an external leakage abnormality has occurred, there is a concern that gas fuel may be burned outside the engine, whereas when a nozzle hole leakage abnormality has occurred, there is considered to be almost no concern that gas fuel may be burned outside the engine. The above configuration takes into consideration that when a nozzle hole leakage abnormality has occurred, there is a greater tolerance for continued vehicle driving than when an external leakage abnormality has occurred, and even if a nozzle hole leakage abnormality does occur, the vehicle can be driven to an appropriate evacuation point.

[0062] (Other Embodiments) The above embodiment may be modified as follows, for example.

[0063] In the above embodiment, the excessive-rich determination is made when it is determined that pre-ignition has occurred while the engine is running (when F1 = 1), but this may be changed. For example, the excessive-rich determination may be made regardless of whether pre-ignition has occurred. Furthermore, without making a pre-ignition determination, it may be possible to identify whether an engine system abnormality, such as a nozzle leakage abnormality, an intake system abnormality, or an ignition system abnormality, has occurred based on the determination result of whether or not the engine is in an excessive-rich state and the determination result of whether or not there is a pressure drop abnormality.

[0064] In the above embodiment, whether or not an abnormal pressure drop has occurred in the fuel pipe 31 is determined after the engine has stopped. However, this may be changed. For example, the pressure drop may be determined while the fuel is cut off while the engine is running, or while the engine is stopped due to an idle stop function.

[0065] In the above embodiment, the process of identifying the abnormality location after the engine is stopped (the process in FIG. 4 ) is executed by the microcomputer 61 of the engine control ECU 60. However, this may be modified. For example, the process of identifying the abnormality location (the process in FIG. 4 ) may be executed by an ECU other than the engine ECU that remains active even after the power switch of the vehicle is turned off.

[0066] Gas fuels other than hydrogen gas may also be used. For example, compressed natural gas (CNG) or liquefied natural gas (LP gas) may also be used as the gas fuel.

[0067] In the above embodiment, the present invention is applied to an engine system of a vehicle, but other applications are also possible. For example, the present invention can be applied to engine systems used in construction machinery, agricultural machinery, aircraft, ships, etc.

[0068] In this disclosure and claims, the term "processor" refers to one or more hardware processors configured to execute the processing defined by computer program code (i.e., one or more instructions of a computer program) included in a computer program by loading the computer program code each time. In other words, a "processor" is a hardware device that executes one or more programmed processes. Therefore, computer program code can also be considered software that can define the processing of the processor depending on its content. A "processor" may be a general-purpose or special-purpose processor, such as, but not limited to, a CPU, a microprocessor, a GPU, and a DFP (Data Flow Processor).

[0069] In this disclosure and in the claims, the term "memory" refers to one or more hardware memories that are non-transitory tangible recording media configured to store computer program code and / or data accessible to a processor. The "memory" may be implemented using memory technologies such as SRAM, SDRAM, non-volatile / flash-type memory, or other types of memory. Computer program code constituting a program may be stored in the memory and executed by a processor to cause the processor to perform the various functions described above.

[0070] In this disclosure and in the claims, the term "circuit" refers to one or more hardware logic circuits configured to perform specific processing based on a pre-designed circuit configuration. In other words (and in contrast to "processor"), a "circuit" in this disclosure and in the claims refers to a hardware device that performs specific processing based on circuit configuration, rather than software, such as computer program code. For example, a "circuit" may include custom ICs, such as application-specific integrated circuits (ASICs) and field-programmable gate arrays (FPGAs), designed using a hardware description language (HDL). In other words, a "circuit" in this disclosure and in the claims includes all hardware circuits, except for a processor, which executes processing by loading computer program code.

[0071] In this disclosure or in the claims, the expression "at least one of a circuit and a processor" should be interpreted as a disjunction (logical OR), and not as at least one circuit and at least one processor. Therefore, in this disclosure or in the claims, "at least one of a circuit and a processor causes an engine control unit to perform a function" includes a case where only a circuit causes the engine control unit to perform all of the functions. Also, "at least one of a circuit and a processor causes an engine control unit to perform a function" includes a case where only a processor causes the engine control unit to perform all of the functions. Furthermore, "at least one of a circuit and a processor causes an engine control unit to perform a function" includes a case where a circuit causes the engine control unit to perform some of the functions and a processor causes the engine control unit to perform the remaining functions. In the last example, for example, if an engine control unit performs functions A to C, functions A and B may be implemented by the circuit, and the remaining function C may be implemented by the processor.

[0072] The technical ideas extracted from the above-described embodiments will be described below. an air-fuel ratio determination unit that determines whether an air-fuel ratio of an air-fuel mixture to be combusted in the combustion chamber is excessively rich, based on a detection result of the gas sensor; a pressure drop determination unit that determines whether a pressure drop abnormality has occurred in the fuel pipe; and an abnormality identification unit that, when the air-fuel ratio determination unit determines that the air-fuel ratio is in the excessively rich state and the pressure drop determination unit determines that the pressure drop abnormality has occurred, identifies an abnormality in the engine system as an abnormality in the engine system, where the air-fuel ratio determination unit determines that the air-fuel ratio is in the excessively rich state and the pressure drop determination unit determines that the pressure drop abnormality has occurred. [Configuration 2] The engine control device according to Configuration 1, wherein the engine system includes an air amount regulator (15) that regulates the amount of air supplied to the engine, and when the air-fuel ratio determiner determines that the engine is in the excessively rich state and the pressure drop determiner determines that no pressure drop abnormality has occurred, the abnormality identification unit identifies an intake system abnormality in which an amount of air passing through the air amount regulator is too small as the abnormality of the engine system. [Configuration 3] The engine control device according to Configuration 1 or 2, wherein the engine system includes an ignition device (41) that generates an ignition spark in the combustion chamber and combusts gas fuel injected from the fuel injection valve, and when the air-fuel ratio determiner determines that the engine is not in the excessively rich state and the pressure drop determiner determines that no pressure drop abnormality has occurred, the abnormality identification unit identifies an abnormality in the ignition device as the abnormality of the engine system.[Configuration 4] The engine control device according to any one of Configurations 1 to 3, further comprising a pre-ignition determination unit that determines whether pre-ignition has occurred in the engine, and the abnormality identification unit identifies an abnormality in the engine system on the condition that the pre-ignition determination unit determines that pre-ignition has occurred. [Configuration 5] The engine control device according to any one of Configurations 1 to 4, further comprising a shut-off valve (35) that is provided in the fuel pipe and that, when closed, shuts off fuel supply from the fuel tank to the fuel injection valve, the pressure sensor is provided in the fuel pipe between the fuel injection valve and the shut-off valve, and further comprising a pre-ignition determination unit that determines whether pre-ignition has occurred in the engine, the pre-ignition determination unit stores a history of pre-ignition if it has occurred while the engine is in operation, and the pressure drop determination unit closes the shut-off valve after the engine is stopped under conditions in which the pre-ignition determination unit has stored the history of pre-ignition, and determines whether the pressure drop abnormality has occurred based on a decrease in pressure detected by the pressure sensor within a predetermined period. [Configuration 6] The engine system is mounted on a vehicle, and comprises: an external leakage determination unit that determines whether an external leakage abnormality has occurred, in which gas fuel is leaking, upstream of the fuel injection valve and on a fuel supply path including the fuel pipe; and a failsafe control unit that executes failsafe processing to restrict driving of the vehicle when the abnormality identification unit identifies that the nozzle hole leakage abnormality has occurred and when the external leakage determination unit identifies that the external leakage abnormality has occurred, and when the failsafe control unit identifies that the nozzle hole leakage abnormality has occurred, the engine control device described in any of Configurations 1 to 5, wherein when it is identified that the nozzle hole leakage abnormality has occurred, the failsafe control unit executes the failsafe processing to impose a lesser degree of driving restriction on the vehicle than when it is identified that the external leakage abnormality has occurred.

[0073] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. An engine control device applied to an engine system including an engine (10) having a fuel injection valve (50) that injects gas fuel into a combustion chamber and an ignition device (41) that generates an ignition spark in the combustion chamber at a predetermined ignition timing, a fuel tank (32) that supplies gas fuel to the fuel injection valve through a fuel pipe (31), a pressure sensor (36) provided in the fuel pipe, and a gas sensor (23) that detects gas components in exhaust gas discharged from the engine, the engine control device comprising: an air-fuel ratio determination unit that determines whether the air-fuel ratio of the mixture provided for combustion in the combustion chamber is in an excessively rich state based on the detection result of the gas sensor; a pressure drop determination unit that determines whether a pressure drop abnormality has occurred in the fuel pipe based on the detection result of the pressure sensor; and an abnormality identification unit that identifies, when the air-fuel ratio determination unit determines that the excessively rich state exists and the pressure drop determination unit determines that the pressure drop abnormality has occurred, as an abnormality in the engine system, a nozzle hole leakage abnormality, which is a fuel leak at the nozzle hole of the fuel injection valve.

2. An engine control device as described in claim 1, wherein the engine system is equipped with an air quantity adjustment device (15) that adjusts the amount of air supplied to the engine, and when the air-fuel ratio determination unit determines that the excessively rich state exists and the pressure drop determination unit determines that the pressure drop abnormality has not occurred, the engine system abnormality is an intake system abnormality in which the amount of air passing through the air quantity adjustment device is too small.

3. An engine control device as described in claim 1, wherein the engine system is equipped with an ignition device (41) that generates an ignition spark in the combustion chamber and burns the gas fuel injected from the fuel injection valve, and the abnormality identification unit identifies an abnormality in the ignition device as an abnormality in the engine system when the air-fuel ratio determination unit determines that the air-fuel ratio is not in the excessively rich state and the pressure drop determination unit determines that the pressure drop abnormality has not occurred.

4. An engine control device as described in any one of claims 1 to 3, comprising a pre-ignition determination unit that determines whether pre-ignition has occurred in the engine, and the abnormality identification unit identifies an abnormality in the engine system on the condition that the pre-ignition determination unit determines that pre-ignition has occurred.

5. An engine control device as claimed in any one of claims 1 to 3, wherein the engine system comprises a shut-off valve (35) that is provided in the fuel pipe and that, when closed, shuts off the supply of fuel from the fuel tank to the fuel injection valve, the pressure sensor is provided in the fuel pipe between the fuel injection valve and the shut-off valve, and a pre-ignition determination unit that determines whether or not pre-ignition has occurred in the engine, the pre-ignition determination unit stores a history of pre-ignition if it occurs while the engine is running, and the pressure drop determination unit closes the shut-off valve after the engine is stopped under circumstances in which the pre-ignition determination unit has stored a history of pre-ignition occurrences, and determines whether or not the pressure drop abnormality has occurred based on a decrease in the pressure detected by the pressure sensor within a predetermined period of time.

6. An engine control device according to any one of claims 1 to 3, wherein the engine system is mounted on a vehicle and comprises: an external leakage determination unit that determines that an external leakage abnormality has occurred, in which gas fuel is leaking, upstream of the fuel injection valve and on a fuel supply path including the fuel pipe; and a failsafe control unit that executes failsafe processing to restrict driving of the vehicle when the abnormality identification unit identifies that the nozzle hole leakage abnormality has occurred and when the external leakage determination unit identifies that the external leakage abnormality has occurred, wherein the failsafe control unit executes the failsafe processing to impose a lesser degree of driving restriction on the vehicle when the nozzle hole leakage abnormality has occurred than when the external leakage abnormality has been identified.

7. Applied to an engine system including an engine (10) having a fuel injection valve (50) that injects gas fuel into a combustion chamber and an ignition device (41) that generates an ignition spark in the combustion chamber at a predetermined ignition timing, a fuel tank (32) that supplies gas fuel to the fuel injection valve through a fuel pipe (31), a pressure sensor (36) provided in the fuel pipe, and a gas sensor (23) that detects gas components in exhaust gas discharged from the engine, the system includes at least one of a circuit and a processor: an air-fuel ratio determination process that determines whether the air-fuel ratio of the mixture to be burned in the combustion chamber is in an excessively rich state based on the detection result of the gas sensor; a pressure drop determination process that determines whether a pressure drop abnormality has occurred in the fuel pipe based on the detection result of the pressure sensor; and an abnormality identification process that identifies, when the air-fuel ratio determination process determines the excessively rich state and the pressure drop determination process determines that the pressure drop abnormality has occurred, as an abnormality in the engine system, a nozzle leakage abnormality, which is a fuel leak at the nozzle hole of the fuel injection valve. An engine control method for performing the above.

8. Applied to an engine system including an engine (10) having a fuel injection valve (50) that injects gas fuel into a combustion chamber and an ignition device (41) that generates an ignition spark in the combustion chamber at a predetermined ignition timing, a fuel tank (32) that supplies gas fuel to the fuel injection valve through a fuel pipe (31), a pressure sensor (36) provided in the fuel pipe, and a gas sensor (23) that detects gas components in exhaust gas discharged from the engine, wherein at least one of the circuit and the processor includes: an air-fuel ratio determination process that determines whether the air-fuel ratio of the mixture to be burned in the combustion chamber is in an excessively rich state based on the detection result of the gas sensor; a pressure drop determination process that determines whether a pressure drop abnormality has occurred in the fuel pipe based on the detection result of the pressure sensor; and an abnormality identification process that identifies an injection hole leakage abnormality, which is a fuel leak at the injection hole of the fuel injection valve, as an abnormality in the engine system when the air-fuel ratio determination process determines that the mixture is in the excessively rich state and the pressure drop determination process determines that the pressure drop abnormality has occurred. A program that executes.

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