Engine control device

Abstract

To suppress inflow of combustion gas into an injector.SOLUTION: An electronic control unit 20 suppresses inflow of combustion gas into an injector 18 by lowering a peak of combustion pressure in a cylinder 11 by performing timing delay processing for delaying ignition timing during a decline in the fuel pressure. The electronic control unit 20 suppresses lowering of torque of an engine 10 due to delay of the ignition timing by preforming increase processing for increasing injection amount of hydrogen gas together with the timing delay processing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an engine control device that controls a spark ignition engine including an injector that injects gaseous fuel into a cylinder.

Background Art

[0002] As an engine using gaseous fuel such as hydrogen gas, there is one including a fuel tank that stores gaseous fuel, and a fuel pressure regulator that reduces the gaseous fuel in the fuel tank to a predetermined set pressure and supplies it to an injector. Conventionally, as a control device for such an engine, the device described in Patent Document 1 is known. When the engine is operated at high load in a state where the pressure in the fuel tank is equal to or higher than the set pressure, the control device in the same document starts injecting gaseous fuel from near top dead center of compression, and ignites during the injection period. And thereby, diffusion combustion is performed in the cylinder.

[0003] By the way, in the engine as described above, the internal pressure of the fuel tank decreases as the gaseous fuel in the fuel tank decreases. When the internal pressure of the fuel tank becomes lower than the set pressure, the pressure of the gaseous fuel supplied to the injector becomes lower than the set pressure. And as a result, the injection pressure of the gaseous fuel of the injector also decreases. On the other hand, the pressure in the cylinder during the compression stroke increases as it approaches top dead center of compression. In a state where the injection pressure has decreased, at a time near top dead center of compression, the pressure in the cylinder may exceed the injection pressure, making it difficult to continue injection.

[0004] On the other hand, when the engine is operated at high load in a state where the internal pressure of the fuel tank is lower than the set pressure, the above engine control device advances the injection period of the gaseous fuel, so that fuel injection can be continued even in a state where the injection pressure has decreased. However, when the injection period is advanced, diffusion combustion by igniting during the injection period cannot be continued. Therefore, the above engine control device changes the ignition timing so as to ignite after the injection ends as the injection period is advanced, thereby switching the combustion in the cylinder from diffusion combustion to premixed combustion.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, the injector is configured to inject and stop fuel by opening and closing a nozzle in response to driving of a needle by an electromagnetic solenoid. The needle is biased in a direction to close the nozzle by a spring load and the pressure of gaseous fuel supplied to the injector. During injection stop, these loads keep the nozzle closed to prevent the inflow of combustion gas into the injector.

[0007] However, when the pressure of the gaseous fuel supplied to the injector decreases, the load applied to the needle decreases accordingly. Therefore, when the internal pressure of the fuel tank decreases, the nozzle may open without being able to resist the combustion pressure in the cylinder. As a result, there is a risk that combustion gas may flow into the injector through the opened nozzle.

Means for Solving the Problems

[0008] The engine control device for solving the above problems is a device for controlling a spark ignition engine having an injector for injecting gaseous fuel into a cylinder. When the fuel pressure, which is the pressure of the gaseous fuel supplied to the injector, is lower than a predetermined threshold value, the engine control device performs a retardation process of retarding the ignition timing of the air-fuel mixture in the cylinder after the injection of the gaseous fuel compared to when the fuel pressure is equal to or higher than the threshold value. Further, when the retardation of the ignition timing is being performed by the retardation process, the engine control device performs an increment process of increasing the injection amount of the gaseous fuel by the injector compared to when the retardation is not being performed.

[0009] When the ignition timing is retarded, the combustion becomes slow and the peak of the combustion pressure in the cylinder decreases. Therefore, by performing the retardation process, the inflow of combustion gas into the injector when the combustion pressure decreases can be suppressed. Further, at this time, by increasing the injection amount of the gaseous fuel, the torque reduction associated with the retardation of the ignition timing can be suppressed.

[0010] When the combustion pressure decreases, the injection rate of the gaseous fuel of the injector decreases. Therefore, when the combustion pressure decreases, the injection period of the injector required for injecting the necessary amount of gaseous fuel becomes longer. Further, in the above-described increase process, since the injection amount is increased when the combustion pressure decreases, the injection period of the injector becomes even longer. Thus, in the above engine control device, when the combustion pressure decreases, the injection period of the injector may become significantly longer than when the combustion pressure is not decreasing. Therefore, when the injection amount is increased by the increase process, it is desirable for the engine control device to perform an expansion process of expanding the injection permission period, which is the period for permitting the injection of the gaseous fuel, more than when the injection amount is not increased.

[0011] When the injection start timing of the gaseous fuel is advanced, the time during which the gaseous fuel exists in the cylinder in an unburned state becomes longer. Further, by retarding the ignition timing, the same time also becomes longer. And when this time becomes longer, the amount of heat received by the gaseous fuel after injection from the wall surface of the combustion chamber increases. As a result, due to the temperature rise of the gaseous fuel in the cylinder, the possibility of the gaseous fuel auto-igniting before ignition becomes higher. On the other hand, if the expansion of the injection permission period by the above-described expansion process is performed by delaying the end time of the injection permission period while maintaining the start time of the injection permission period, it becomes difficult for the gaseous fuel to auto-ignite. Also, when the injection amount is increased by the increase process, the occurrence of auto-ignition of the gaseous fuel can be suppressed by delaying the end time of the injection of the gaseous fuel by the injector more than when the injection amount is not increased.

[0012] The above engine control device is preferably applied to an engine including, for example, a fuel tank that stores gaseous fuel and a fuel pressure regulator that reduces the gaseous fuel in the fuel tank to a predetermined set pressure and supplies it to an injector. In the engine configured as described above, when the remaining amount of the gaseous fuel in the fuel tank decreases, the internal pressure of the tank decreases. Then, when the internal pressure of the fuel tank becomes lower than the set pressure, the fuel pressure of the injector also becomes a pressure lower than the set pressure. Therefore, in such an engine, the inflow of combustion gas into the injector due to the decrease in fuel pressure is likely to occur, and the application of the above engine control device is suitable.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0014] Hereinafter, an embodiment of the engine control device will be described in detail with reference to FIGS. 1 to 4. <Configuration of the Engine Control Device> First, with reference to FIG. 1, the configuration of the engine control device of the present embodiment will be described. The engine 10 controlled by the engine control device of the present embodiment is mounted on a vehicle. Further, the engine 10 is configured as a hydrogen gas engine that uses hydrogen gas as fuel.

[0015] The engine 10 has one or more cylinders 11. Inside the cylinder 11, a piston 12 is arranged to reciprocate in the vertical direction in the drawing. And inside the cylinder 11, a combustion chamber 13 for performing combustion is partitioned by the piston 12. An intake port 15 is connected to the upper part of the cylinder 11 via an intake valve 14. Also, an exhaust port 17 is connected to the upper part of the cylinder 11 via an exhaust valve 16. Further, an injector 18 for injecting hydrogen gas into the cylinder 11 and a spark plug 19 for igniting the hydrogen gas injected by the injector 18 are installed in the upper part of the cylinder 11.

[0016] The injector 18 is connected to a fuel tank 28 for storing hydrogen gas via a fuel pressure regulator 29. In the following description, the pressure of the hydrogen gas in the fuel tank 28 is described as the tank internal pressure PT. Also, the pressure of the fuel supplied to the injector 18 through the fuel pressure regulator 29 is described as the fuel pressure PF. The fuel pressure regulator 29 reduces the hydrogen gas in the fuel tank 28 to a predetermined set pressure P0 and supplies it to the injector 18. More specifically, when the tank internal pressure PT is higher than the set pressure P0, the fuel pressure regulator 29 reduces the hydrogen gas in the fuel tank 28 to the set pressure P0 and supplies it to the injector 18. At this time, the fuel pressure PF becomes a pressure equal to the set pressure P0. On the other hand, when the tank internal pressure PT is lower than the set pressure P0, the fuel pressure regulator 29 supplies the hydrogen gas in the fuel tank 28 to the injector 18 without reducing the pressure. At this time, the fuel pressure PF becomes a pressure substantially equal to the tank internal pressure PT. That is, the fuel pressure PF at this time becomes a pressure lower than the set pressure P0. In the following description, when the fuel pressure PF becomes lower than the set pressure P0, it is described as when the fuel pressure PF decreases.

[0017] The electronic control unit 20 that controls such an engine 10 includes an arithmetic processing unit 21 and a storage device 22. Programs and data used for control are stored in the storage device 22. The arithmetic processing unit 21 executes the programs read from the storage device 22 to perform various processes related to the control of the engine 10. In the present embodiment, such an electronic control unit 20 corresponds to an engine control device.

[0018] The electronic control unit 20 is connected to a crank angle sensor 23, an air flow meter 24, a water temperature sensor 25, an accelerator pedal sensor 26, and a tank pressure sensor 27. The crank angle sensor 23 is a sensor that detects the rotational phase of the crankshaft of the engine 10. The air flow meter 24 is a sensor that detects the intake air volume of the engine 10. The water temperature sensor 25 is a sensor that detects the engine water temperature THW, which is the temperature of the cooling water of the engine 10. The accelerator pedal sensor 26 is a sensor that detects the accelerator pedal operation amount ACC of the driver. The tank pressure sensor 27 is a sensor that detects the tank internal pressure PT, which is the pressure of the hydrogen gas in the fuel tank 28. The electronic control unit 20 controls the engine 10 by operating the fuel injection of the injector 18, the ignition timing of the ignition plug 19, etc. based on the detection results of these sensors.

[0019] <Inflow of combustion gas into the injector 18> In the above engine 10, when the remaining amount of hydrogen gas in the fuel tank 28 decreases and the tank internal pressure PT falls below the set pressure P0, the fuel pressure PF supplied to the injector 18 also falls below the set pressure P0. When the fuel pressure PF drops like this, there is a risk that the combustion gas in the combustion chamber 13 will flow into the injector 18. And due to the inflow of the combustion gas, there is a risk that the durability performance of the injector 18 will deteriorate. Also, if the inflowed combustion gas remains in the injector 18 until the next injection, since the remaining combustion gas is injected together with the hydrogen gas, there may be a case where an appropriate amount of hydrogen gas cannot be injected.

[0020] Figure 2 shows a schematic structure of the injector 18. The injector 18 has a needle 30, an electromagnetic solenoid 31, a nozzle 32, and a needle spring 33. Inside the injector 18, hydrogen gas is supplied from the fuel tank 28 through the fuel pressure regulator 29. The nozzle 32 is an outlet for hydrogen gas that communicates the inside and outside of the injector 18. The injector 18 is assembled to the engine 10 with the nozzle 32 exposed in the combustion chamber 13. The needle 30 is a valve body that opens and closes the nozzle 32. The electromagnetic solenoid 31 generates an electromagnetic attractive force for driving the needle 30 toward the side that opens the nozzle 32 in response to energization. The needle spring 33 is a spring that biases the needle 30 toward the side that closes the nozzle 32. In the following description, the load that biases the needle 30 toward the side that closes the nozzle 32 is described as the closing-direction load. Also, the load that biases the needle 30 toward the side that opens the nozzle 32 is described as the opening-direction load.

[0021] When the injector 18 stops hydrogen gas injection, the fuel pressure PF of the hydrogen gas supplied to the injector 18 and the spring load LN of the needle spring 33 are applied as closing-direction loads to the needle 30. On the other hand, the combustion pressure CP of the combustion chamber 13 is applied as an opening-direction load to the tip of the needle 30 when combustion is occurring in the combustion chamber 13.

[0022] When the tank internal pressure PT falls below the set pressure P0 and the fuel pressure PF decreases, the closing-direction load applied to the needle 30 decreases. Therefore, the needle 30 cannot resist the combustion pressure CP and moves in the opening direction, causing the nozzle 32 to open. Then, there is a possibility that the combustion gas in the combustion chamber 13 flows into the inside of the injector 18 through the opened nozzle 32.

[0023] <Ignition Injection Control> The electronic control unit 20 suppresses the inflow of combustion gas into the injector 18 as described above through the control of hydrogen gas injection and ignition in the engine 10. The details of such control will be described below.

[0024] Note that the values at each time period shown below represent the amount of advance from top dead center of compression of the crankshaft, which is the output shaft of the engine 10. Therefore, the time period with a larger value is earlier than the time period with a smaller value. Also, the values for each period shown below represent the change amount of the crankshaft rotation angle during the corresponding period. Therefore, even if the period length is constant, when the engine rotation speed NE is high, the actual time of the corresponding period is shorter than when the engine rotation speed NE is low.

[0025] FIG. 3 shows the processing procedure of an injection ignition control routine executed by the electronic control unit 20 for controlling the injection and ignition of hydrogen gas in the engine 10. The electronic control unit 20 repeatedly executes this routine at a predetermined control cycle during the operation of the engine 10.

[0026] When starting this routine, the electronic control unit 20 first acquires the engine rotation speed NE, the accelerator pedal operation amount ACC, and the tank internal pressure PT in step S100. Subsequently, the electronic control unit 20 calculates the required injection amount QS based on the engine rotation speed NE and the accelerator pedal operation amount ACC in step S110. The required injection amount QS represents the injection amount of hydrogen gas necessary to generate the power demanded by the driver under the condition that the basic ignition timing SAB described later is set as the ignition timing.

[0027] Next, the electronic control unit 20 determines whether the tank internal pressure PT is equal to or higher than the set pressure P0. Then, when the tank internal pressure PT is equal to or higher than the set pressure P0 (YES), the electronic control unit 20 proceeds to step S130, and when the tank internal pressure PT is less than the set pressure P0 (NO), the electronic control unit 20 proceeds to step S200 for processing.

[0028] In step S130, the electronic control unit 20 sets a basic ignition timing SAB as a commanded ignition timing SA which is a command value of the ignition timing. The basic ignition timing SAB may be a fixed value, or may be changed according to the operating condition of the engine 10. In the latter case, the electronic control unit 20 calculates the value of the basic ignition timing SAB based on, for example, the engine rotational speed NE and the required injection amount QS.

[0029] Subsequently, in step S140, the electronic control unit 20 calculates a required injection period TS based on the engine rotational speed NE and the required injection amount QS. The required injection period TS represents the injection period of the hydrogen gas of the injector 18 required for the injection of the hydrogen gas corresponding to the required injection amount QS. As described above, the value of the period here represents the change amount of the crank angle within the period. Therefore, even when the required injection amount QS is the same value, the value of the required injection period TS becomes larger when the engine rotational speed NE is high than when it is low. The required injection period TS also changes depending on the fuel pressure PF. However, at this time, the fuel pressure PF is determined as the set pressure P0 because the tank internal pressure PT is equal to or higher than the set pressure P0. Therefore, the required injection period TS at this time is calculated on the premise that the fuel pressure PF is the set pressure P0.

[0030] Subsequently, in step S150, the electronic control unit 20 sets a predetermined basic injection end timing IE0 as the value of the injection end timing IE. If the time from the end of the hydrogen gas injection to the ignition is too short, the fuel concentration around the ignition plug 19 becomes thin due to insufficient mixing of the intake air and the hydrogen gas. As a result, misfiring may occur. The basic injection end timing IE0 is set to the retard limit of the end timing of the hydrogen gas injection at which ignition performance can be ensured when ignition is performed at the basic ignition timing SAB.

[0031] Next, at step S160, the electronic control unit 20 determines whether the time (= IE + TS) that is TS before the injection end time IE is earlier than the limit injection start time LM. The time that is TS before the injection end time IE represents the start time of the hydrogen gas injection for performing the hydrogen gas injection for the required injection period TS and completing the injection at the injection end time IE. In the following description, this time is referred to as the required injection start time. On the other hand, the limit injection start time LM represents the start time of the injection allowable period during which fuel injection is allowed. If the start time of the hydrogen gas injection is advanced, the time during which the hydrogen gas exists in the cylinder 11 in an unburned state becomes longer. Further, by retarding the ignition timing, this time also becomes longer. And when this time becomes longer, the amount of heat received by the hydrogen gas after injection from the wall surface of the combustion chamber 13 increases. As a result, the possibility of the hydrogen gas self-igniting before ignition in the cylinder 11 becomes higher. The limit injection start time LM is set for the purpose of preventing such self-ignition of the hydrogen gas.

[0032] When the required injection start time is after the limit injection start time LM (S160: YES), the electronic control unit 20 sets the required injection start time as the value of the injection start time IS at step S170. On the other hand, when the required injection start time is earlier than the limit injection start time LM (S160: NO), the electronic control unit 20 sets the limit injection start time LM as the value of the injection start time IS at step S180.

[0033] After the processing of step S170 or S180, the electronic control unit 20 proceeds to the processing of step S190. Then, at step S190, after commanding the hydrogen gas injection for the period from the injection start time IS to the injection end time IE and the ignition at the commanded ignition time SA, the electronic control unit 20 ends the processing of this routine in the current control cycle.

[0034] On the other hand, when the tank internal pressure PT is less than the set pressure P0 (S120: NO) and the process proceeds to step S200, the electronic control unit 20 performs the processes of the following steps S200 to S250 instead of the processes of the above steps S130 to S150. In step S200, the electronic control unit 20 calculates a retard amount ΔSA based on the tank internal pressure PT. The electronic control unit 20 calculates a larger value as the retard amount ΔSA when the tank internal pressure PT is low than when it is high. Then, in the next step S210, the electronic control unit 20 sets the commanded ignition timing SA to a timing that is retarded by the retard amount ΔSA from the basic ignition timing SAB.

[0035] In step S220, the electronic control unit 20 calculates the value of an injection increment ΔQS based on the required injection amount QS and the retard amount ΔSA. Retarding the ignition timing reduces the engine torque. The reduction in engine torque can be compensated for by increasing the hydrogen gas injection amount. The electronic control unit 20 calculates the increment value of the hydrogen gas injection amount required for an increase in engine torque equal to the reduction in engine torque due to the retard of the ignition timing by the retard amount ΔSA as the value of the injection increment ΔQS.

[0036] In step S230, the electronic control unit 20 calculates the required injection period TS based on the required injection amount QS, the injection increment ΔQS, and the tank internal pressure PT. At this time, the electronic control unit 20 calculates the period required for injecting the total amount of the required injection amount QS and the injection increment ΔQS of hydrogen gas under the current tank internal pressure PT as the value of the required injection period TS.

[0037] In step S240, the electronic control unit 20 calculates the value of an expansion amount ΔIE based on the retard amount ΔSA. The electronic control unit 20 calculates the value of the expansion amount ΔIE such that it becomes larger when the retard amount ΔSA is large than when it is small. Then, in the next step S250, after setting the injection end timing IE to a timing that is retarded by the expansion amount ΔIE from the basic injection end timing IE0, the process proceeds to the above step S160.

[0038] <Effects of the Embodiment> The operations and effects of the engine control device of the present embodiment configured as described above will be described.

[0039] When the tank internal pressure PT is equal to or higher than the set pressure P0, the combustion pressure PF of the hydrogen gas supplied to the injector 18 is maintained at the set pressure P0. At this time, in the injection ignition control routine, the electronic control unit 20 operates the spark plug 19 and the injector 18 so as to perform ignition at the basic ignition timing SAB and inject hydrogen gas corresponding to the required injection amount QS.

[0040] On the other hand, when the tank internal pressure PT falls below the set pressure P0, the combustion pressure PF of the hydrogen gas supplied to the injector 18 becomes lower than the set pressure P0. As described above, when the combustion pressure PF decreases, the closing load applied to the needle 30 during injection stop decreases, and the combustion gas in the combustion chamber 13 easily flows into the injector 18. In contrast, when the tank internal pressure PT falls below the set pressure P0, the electronic control unit 20 operates the spark plug 19 to perform ignition at a timing that is retarded by a retard angle ΔSA from the basic ignition timing SAB. In the present embodiment, the ignition timing is set so that ignition is performed after the end of hydrogen gas injection. Therefore, in the present embodiment, when the combustion pressure PF is lower than the set pressure P0, a retard process is performed to retard the ignition timing of the air-fuel mixture in the cylinder 11 after the end of hydrogen gas injection compared to when the combustion pressure PF is equal to or higher than the set pressure P0. In the present embodiment, the retard process is performed through the processes of steps S210 and S220 in FIG. 3.

[0041] In FIG. 4, the transition of the in-cylinder pressure when ignition is performed at the basic ignition timing SAB is shown by a solid line. Also, in FIG. 4, the transition of the in-cylinder pressure when ignition is performed at a timing that is retarded by a retard angle ΔSA from the basic ignition timing SAB under the same conditions except for the ignition timing is shown by a dashed-dotted line. When the ignition timing is retarded, combustion becomes slow, so the peak value of the in-cylinder pressure generated by the combustion after ignition, that is, the combustion pressure CP, decreases. Therefore, even when the combustion pressure PF decreases and the closing load applied to the needle 30 of the injector 18 decreases, it becomes difficult for the combustion gas to flow into the injector 18.

[0042] Further, when the tank internal pressure PT falls below the set pressure P0, the electronic control unit 20 sets the required injection period TS so as to inject hydrogen gas corresponding to the sum of the required injection amount QS and the injection increase amount ΔQS. That is, when the ignition timing is retarded to suppress the inflow of combustion gas into the injector 18, the electronic control unit 20 performs an increment process of increasing the injection amount of hydrogen gas by the injector 18 more than when it is not performed. In the present embodiment, the increment process is performed through the processes of steps S230 to S260 in FIG. 3. By increasing the injection amount of hydrogen gas in this way, a torque drop of the engine 10 accompanying the retardation of the ignition timing can be suppressed.

[0043] By the way, when the tank internal pressure PT is equal to or higher than the set pressure P0, the electronic control unit 20 sets the period T1 from the limit injection start timing LM to the basic injection end timing IE0 as an injection allowable period for allowing hydrogen gas injection. On the other hand, when the fuel pressure PF drops, the injection rate of hydrogen gas from the injector 18 drops. Therefore, when the fuel pressure PF drops, the injection period of the injector 18 required for injecting the required amount of hydrogen gas becomes longer. Further, in the above-described increment process, since the injection amount is increased when the fuel pressure PF drops, the injection period of the injector 18 becomes even longer. Therefore, when the fuel pressure PF drops, in the above period T1, there are many cases where the hydrogen gas corresponding to the required injection amount QS cannot be injected. In contrast, when the fuel pressure PF drops, the electronic control unit 20 performs an expansion process of expanding the injection allowable period from the period T1 to the period T2. Therefore, even when the fuel pressure PF drops, it becomes difficult for the injection amount of hydrogen gas to be insufficient.

[0044] During the enlargement process, the electronic control unit 20 keeps the start time of the injection permission period at the limit injection start time LM and delays the end time of the injection permission period. More specifically, during the enlargement process, the electronic control unit 20 calculates an enlargement amount ΔIE based on the ignition retard amount ΔSA of the ignition timing by the retard process. Then, a time that is delayed by the enlargement amount ΔIE from the basic injection end time IE0 is set as the end time of the injection permission period. In the present embodiment, the enlargement process is performed through the processes of steps S240 and S250 in FIG. 2.

[0045] Note that as described above, the limit injection start time LM is set for the purpose of preventing the spontaneous ignition of hydrogen gas. When the ignition timing is retarded, the period during which hydrogen gas exists in the cylinder 11 in an unburned state becomes longer. At this time, if the start time of injection is advanced, the synchronous period becomes even longer, and the spontaneous ignition of hydrogen gas is likely to occur. On the other hand, the basic injection end time IE0 is set to the time that is the retard limit of the end time of hydrogen gas injection capable of ensuring ignitability when ignition is performed at the basic ignition timing SAB. Such a time that becomes the retard limit becomes later as the ignition timing is retarded. Therefore, by maintaining the start time of the injection permission period and delaying the end time thereof, the injection permission period can be enlarged while suppressing both the spontaneous ignition of hydrogen gas and the deterioration of ignitability.

[0046] According to the engine control device of the present embodiment described above, the following effects can be achieved. (1) When the internal pressure PT of the tank decreases and the fuel pressure PF becomes lower than the set pressure P0, the electronic control unit 20 performs a retardation process of retarding the ignition timing of the air-fuel mixture in the cylinder 11 after the injection end, compared to when the fuel pressure PF is equal to or higher than the set pressure P0. Further, when the retardation of the ignition timing is being performed by the retardation process, the electronic control unit 20 performs an increment process of increasing the injection amount of hydrogen gas by the injector 18 compared to when the retardation is not being performed. When the ignition timing is retarded, the combustion becomes slow and the peak of the combustion pressure CP in the cylinder 11 decreases. Therefore, by implementing the above retardation process, the inflow of combustion gas into the injector 18 when the fuel pressure PF decreases can be suppressed. Further, at this time, by increasing the injection amount of hydrogen gas, the torque reduction of the engine 10 accompanying the retardation of the ignition timing can be suppressed.

[0047] (2) When the injection amount of hydrogen gas is increased by the increment process, the electronic control unit 20 performs an expansion process of expanding the injection permission period for permitting hydrogen gas injection, compared to when the injection amount is not increased. Therefore, even if the period required for the required injection becomes longer due to the decrease in the fuel pressure PF and the increase in the injection amount, it becomes difficult for the injection amount of hydrogen gas to be insufficient.

[0048] (3) The electronic control unit 20 performs the expansion process by delaying the end time of the synchronization period while maintaining the start time of the injection permission period. Therefore, the injection permission period can be expanded while suppressing both the spontaneous ignition of hydrogen gas and the deterioration of the ignitability.

[0049] (4) When the injection amount is increased by the increment process, the electronic control unit 20 delays the end time of the hydrogen gas injection by the injector 18 compared to when the injection amount is not increased. That is, the electronic control unit 20 delays the injection end time IE in conjunction with the ignition timing. Thereby, the change in accordance with the decrease in the fuel pressure PF during the period from injection to ignition can be suppressed. And as a result, it becomes difficult for the ignitability to deteriorate.

[0050] (5) The engine control device of this embodiment is applied to an engine 10 including a fuel tank 28 that stores hydrogen gas, which is a gaseous fuel, and a fuel pressure regulator 29 that reduces the hydrogen gas in the fuel tank 28 to a predetermined set pressure P0 and supplies it to an injector 18. In such an engine 10, when the remaining amount of hydrogen gas in the fuel tank 28 decreases, the tank internal pressure PT decreases. When the tank internal pressure PT becomes lower than the set pressure P0, the fuel pressure PF of the injector 18 also becomes a pressure lower than the set pressure P0. Therefore, in such an engine 10, the inflow of combustion gas into the injector 18 is likely to occur in response to the decrease in the fuel pressure PF. Therefore, in such an engine 10, the effect of the engine control device of this embodiment, which suppresses the inflow of combustion gas into the injector 18 in response to the decrease in the fuel pressure PF, becomes remarkable.

[0051] <Other embodiments> This embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

[0052] The calculation mode of the injection increment ΔQS in step S220 of FIG. 3 may be changed. Even if the increase in engine torque due to the increase in the hydrogen gas injection amount does not exactly match the decrease in engine torque due to the retardation of the ignition timing, if the injection amount is increased, the decrease in engine torque associated with the retardation of the ignition timing can be suppressed.

[0053] · A sensor for detecting the fuel pressure PF may be installed in the engine 10, and in step S120 of FIG. 3, it may be determined whether the detected value of the sensor is equal to or less than the set pressure P0. · When increasing the hydrogen gas injection amount by the increment process, the injection end time IE may not be delayed.

[0054] · The expansion process may be performed by advancing the start time of the injection permission period. Also, the expansion process may be performed by advancing the start time of the injection permission period and delaying the end time of the same period.

[0055] ·It may not be necessary to perform the enlargement process. That is, even when increasing the amount of hydrogen gas injection by the increment process, it may not be necessary to enlarge the injection permission period. ·The engine control in the above embodiment is similarly applicable to an engine using gaseous fuel other than hydrogen gas.

[0056] (Supplementary matters) [Supplementary Note 1] An engine control device for controlling a spark ignition engine having an injector for injecting gaseous fuel into a cylinder, when the fuel pressure, which is the pressure of the gaseous fuel supplied to the injector, is lower than a predetermined threshold value, a retardation process of retarding the ignition timing of the air-fuel mixture in the cylinder after the injection of the gaseous fuel compared to when the fuel pressure is equal to or higher than the threshold value, and when the retardation of the ignition timing is being performed by the retardation process, an increment process of increasing the injection amount of the gaseous fuel by the injector compared to when it is not being performed.

[0057] [Supplementary Note 2] The engine control device according to [Supplementary Note 1], when the injection amount is increased by the increment process, performs an enlargement process of enlarging the injection permission period, which is the period for permitting the injection of the gaseous fuel, compared to when it is not increased.

[0058] [Supplementary Note 3] The enlargement of the injection permission period by the enlargement process is performed by delaying the end time of the injection permission period while maintaining the start time of the injection permission period, according to the engine control device described in [Supplementary Note 2].

[0059] [Supplementary Note 4] The engine control device according to any one of [Supplementary Note 1] to [Supplementary Note 3], when the injection amount is increased by the increment process, delays the end time of the injection of the gaseous fuel by the injector compared to when it is not increased.

[0060] [Supplementary Note 5] The engine includes a fuel tank for storing the gaseous fuel and a fuel pressure adjustment device for reducing the gaseous fuel in the fuel tank to a predetermined set pressure and supplying it to the injector, according to the engine control device described in any one of [Supplementary Note 1] to [Supplementary Note 4].

[0061] [Appendix 6] The increase in the injection amount in the above-described increase process is performed by calculating an increase value of the injection amount of the gaseous fuel required for an increase in engine torque equal to the decrease in engine torque associated with the retardation of the ignition timing by the above-described retardation process. The engine control device according to any one of [Appendix 1] to [Appendix 5].

Explanation of Signs

[0062] 10…Engine 11…Cylinder 12…Piston 13…Combustion chamber 14…Intake valve 15…Intake port 16…Exhaust valve 17…Exhaust port 18…Injector 19…Spark plug 20…Electronic control unit 21…Arithmetic processing unit 22…Storage device 23…Crank angle sensor 24…Airflow meter 25…Intake air temperature sensor 26…Accelerator pedal sensor 27…Tank pressure sensor 28…Fuel tank 29…Fuel pressure regulator 30…Needle 31…Electromagnetic solenoid 32…Nozzle 33…Needle spring

Claims

1. An apparatus for controlling a spark-ignition engine having an injector for injecting gaseous fuel into a cylinder, when a fuel pressure of the gaseous fuel supplied to the injector, which is a combustion pressure, is lower than a predetermined threshold value, a retardation process of retarding an ignition timing of an air-fuel mixture in the cylinder after injection of the gaseous fuel compared to when the combustion pressure is equal to or higher than the threshold value, when the retardation of the ignition timing is being performed by the retardation process, an increment process of increasing an injection amount of the gaseous fuel by the injector compared to when it is not being performed, when the injection amount is being increased by the increment process, an expansion process of expanding an injection permission period, which is a period for permitting injection of the gaseous fuel, compared to when it is not being increased, and the expansion of the injection permission period by the expansion process is performed by delaying an end time of the injection permission period while maintaining a start time of the injection permission period Engine control device.

2. when the injection amount is being increased by the increment process, an end time of injection of the gaseous fuel by the injector is delayed compared to when it is not being increased The engine control device according to claim 1.

3. The engine includes a fuel tank for storing the gaseous fuel and a fuel pressure regulator for reducing the gaseous fuel in the fuel tank to a predetermined set pressure and supplying it to the injector The engine control device according to claim 1.

4. The increment of the injection amount in the increment process is performed by calculating an increment value of the injection amount of the gaseous fuel required to increase the engine torque by an amount equal to a decrease in the engine torque associated with the retardation of the ignition timing by the retardation process The engine control device according to claim 1.

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