Engine System

Abstract

To restrain gas in a cylinder from flowing into a fuel injection valve.SOLUTION: An internal combustion engine includes a cylinder, an intake passage, a throttle valve, an in-cylinder injection valve, a fuel tank, a connecting passage, and an on-off valve. The intake passage introduces intake air into the cylinder. The throttle valve adjusts an amount of the intake air flowing through the intake passage. The in-cylinder injection valve directly injects gas fuel into the cylinder. The fuel tank stores the gas fuel. The connecting passage connects the fuel tank and the in-cylinder injection valve. The on-off valve opens and closes a flow passage of the connecting passage. A control device of the internal combustion engine can execute pre-stop combustion processing in which the on-off valve is closed and then the gas fuel is injected from the in-cylinder injection valve so as to be burned in the cylinder when stopping of the internal combustion engine is required. In the pre-stop combustion processing, an opening of the throttle valve is controlled so that an amount of the intake air introduced into the cylinder is smaller when a fuel pressure which is a pressure of the gas fuel supplied into the in-cylinder injection valve is low than when the fuel pressure is high.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to engine systems. [Background technology]

[0002] The vehicle of Patent Document 1 is equipped with an internal combustion engine that combusts gaseous fuel. The internal combustion engine has cylinders, an intake passage, and a throttle valve. The cylinder is a space for combusting the gaseous fuel. The intake passage introduces intake air into the cylinder. The throttle valve adjusts the amount of intake air flowing through the intake passage. The internal combustion engine also has a fuel injection valve, a fuel tank, a connecting passage, an on-off valve, and a fuel pressure sensor. The fuel injection valve directly injects gaseous fuel into the cylinder. The fuel tank stores gaseous fuel. The connecting passage connects the fuel tank and the fuel injection valve. The on-off valve is located at a portion of the connecting passage where the connecting passage connects to the fuel tank. The on-off valve opens and closes the flow path of the connecting passage. The fuel pressure sensor detects the fuel pressure, which is the pressure of the gaseous fuel supplied to the fuel injection valve.

[0003] The vehicle disclosed in Patent Document 1 is equipped with a control device that controls an internal combustion engine. The control device executes a pre-shutdown combustion process. When a request to stop the internal combustion engine is made, the pre-shutdown combustion process closes an on-off valve and then injects gaseous fuel from a fuel injection valve to combust the fuel in a cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-274312 Summary of the Invention [Problem to be solved by the invention]

[0005] In an internal combustion engine such as that described in Patent Document 1, the pre-shutdown combustion process is performed, which gradually reduces the fuel pressure of the gaseous fuel supplied to the fuel injection valve. As the fuel pressure decreases, the fuel pressure may become lower than the pressure inside the cylinder when the gaseous fuel is injected from the fuel injection valve. In this case, when the fuel injection valve opens to inject the gaseous fuel, gas inside the cylinder may flow into the fuel injection valve. [Means for solving the problem]

[0006] An engine system for solving the above problem includes an internal combustion engine driven by gaseous fuel, and a control device that controls the internal combustion engine, wherein the internal combustion engine has a cylinder that burns the gaseous fuel, an intake passage that introduces intake air into the cylinder, a throttle valve that adjusts the amount of intake air flowing through the intake passage, a fuel injection valve that injects the gaseous fuel directly into the cylinder, a fuel tank that stores the gaseous fuel, a connecting passage that connects the fuel tank and the fuel injection valve, and an on-off valve that opens and closes the flow path of the connecting passage, and when a stop of the internal combustion engine is requested, the control device is capable of executing a pre-stop combustion process in which the on-off valve is closed and the gaseous fuel is injected from the fuel injection valve to be burned in the cylinder, and in the pre-stop combustion process, when a fuel pressure that is the pressure of the gaseous fuel supplied to the fuel injection valve is low, the opening of the throttle valve is controlled so that the amount of intake air introduced into the cylinder is less than when the fuel pressure is high.

[0007] According to the above configuration, when the fuel pressure is low, the amount of intake air introduced from the intake passage into the cylinder is smaller than when the fuel pressure is high. This reduces the pressure inside the cylinder when gaseous fuel is injected from the fuel injection valve. As a result, even when the fuel pressure is low, gas inside the cylinder can be prevented from flowing into the fuel injection valve. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic configuration diagram of an engine system. [Figure 2]10 is a flowchart showing stop control. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Outline of engine system configuration> An embodiment of an engine system 100 including an internal combustion engine 10 and a control device 90 will be described below with reference to Figures 1 and 2. First, a schematic configuration of the engine system 100 applied to a vehicle will be described.

[0010] As shown in Fig. 1, the engine system 100 includes an internal combustion engine 10. The internal combustion engine 10 functions as a drive source for a vehicle. The internal combustion engine 10 uses hydrogen gas as fuel. In this embodiment, hydrogen gas is an example of a gaseous fuel.

[0011] The internal combustion engine 10 includes a plurality of cylinders 11. Each cylinder 11 is a space for burning a mixture of fuel and intake air. In this embodiment, the internal combustion engine 10 includes four cylinders 11. Note that FIG. 1 shows only one representative cylinder 11.

[0012] The internal combustion engine 10 includes a plurality of pistons 16, a plurality of connecting rods 17, and a crankshaft 18. The pistons 16 are located inside the cylinders 11. The pistons 16 are connected to the crankshaft 18 via the connecting rods 17. The pistons 16 reciprocate inside the cylinders 11 as a mixture of fuel and intake air burns in the cylinders 11. The reciprocating motion of the pistons 16 causes the crankshaft 18 to rotate.

[0013] The internal combustion engine 10 includes an intake passage 12, an exhaust passage 13, a plurality of intake valves 21, and a plurality of exhaust valves 22. The intake passage 12 is connected to the cylinders 11. The intake passage 12 introduces intake air from outside the internal combustion engine 10 into each cylinder 11. The exhaust passage 13 is connected to the cylinders 11. The exhaust passage 13 discharges exhaust gas from each cylinder 11 to outside the internal combustion engine 10. The intake valve 21 is located at the downstream end of the intake passage 12. The intake valve 21 opens and closes the downstream end of the intake passage 12 by a driving force from a valve mechanism (not shown). The exhaust valve 22 is located at the upstream end of the exhaust passage 13. The exhaust valve 22 opens and closes the upstream end of the exhaust passage 13 by a driving force from a valve mechanism (not shown).

[0014] The internal combustion engine 10 includes a plurality of in-cylinder injection valves 27, a fuel tank 31, a connecting passage 32, an on-off valve 33, and a regulator 34. The tips of the in-cylinder injection valves 27 are located inside the cylinders 11. The in-cylinder injection valves 27 introduce fuel into the cylinders 11 by injecting hydrogen gas as fuel into the cylinders 11 without passing through the intake passage 12. The internal combustion engine 10 includes four in-cylinder injection valves 27 corresponding to the four cylinders 11. In this embodiment, the in-cylinder injection valves 27 are fuel injection valves that directly inject gaseous fuel into the cylinders 11.

[0015] The fuel tank 31 stores hydrogen gas. A first end of the connection passage 32 is connected to the fuel tank 31. A second end of the connection passage 32 is connected to each in-cylinder injection valve 27. Therefore, the hydrogen gas stored in the fuel tank 31 is supplied to each in-cylinder injection valve 27 via the connection passage 32. The on-off valve 33 is located at the first end of the connection passage 32. The on-off valve 33 opens and closes the flow path of the connection passage 32. The regulator 34 is located in a portion of the connection passage 32 close to the in-cylinder injection valve 27 as viewed from the on-off valve 33. The regulator 34 reduces the pressure of the hydrogen gas supplied to the in-cylinder injection valve 27 to a predetermined specified pressure or lower.

[0016] The internal combustion engine 10 is equipped with a throttle valve 23 and a plurality of ignition devices 24. The throttle valve 23 is located midway through the intake passage 12. The throttle valve 23 adjusts the amount of intake air flowing through the intake passage 12. The tip of the ignition device 24 is located inside the cylinder 11. The ignition device 24 ignites a mixture of fuel and intake air by spark discharge. In other words, the ignition device 24 ignites gaseous fuel inside the cylinder 11. The internal combustion engine 10 is equipped with four ignition devices 24 corresponding to the four cylinders 11.

[0017] The internal combustion engine 10 is equipped with a water jacket 15. The water jacket 15 constitutes a part of a passage through which cooling water circulates. The water jacket 15 surrounds the cylinders 11. The cylinders 11 are cooled by heat exchange with the cooling water flowing through the water jacket 15. In other words, the water jacket 15 is a passage for cooling water to cool the cylinders 11.

[0018] <Electrical configuration of engine system> 1, the engine system 100 includes an accelerator operation amount sensor 81, a vehicle speed sensor 82, a crank angle sensor 83, and a water temperature sensor 84. The engine system 100 also includes an outside air temperature sensor 85, a fuel pressure sensor 86, and an ignition switch 89.

[0019] The accelerator operation amount sensor 81 detects the accelerator operation amount ACC, which is the amount of operation of an accelerator pedal (not shown) operated by the driver. The vehicle speed sensor 82 detects the vehicle speed SP, which is the speed of the vehicle. The crank angle sensor 83 detects the crank angle SC, which is the angular position of the crankshaft 18. The water temperature sensor 84 detects the water temperature TW of the coolant flowing out of the water jacket 15. Specifically, the water temperature sensor 84 detects the temperature of the coolant at the downstream end of the water jacket 15 as the water temperature TW. The outside air temperature sensor 85 detects the outside air temperature TA, which is the air temperature outside the internal combustion engine 10. In this embodiment, the outside air temperature sensor 85 is located near the front bumper of the vehicle. The fuel pressure sensor 86 detects the fuel pressure PF, which is the pressure of hydrogen gas supplied to the direct injection valve 27. Specifically, the fuel pressure sensor 86 detects the pressure in the portion of the connecting passage 32 between the regulator 34 and the direct injection valve 27 as the fuel pressure PF. The ignition switch 89 is located near the driver's seat of the vehicle. The ignition switch 89 is a switch that can be operated by the driver of the vehicle. The driver of the vehicle can start or stop the internal combustion engine 10 by operating the ignition switch 89. The ignition switch 89 is also sometimes called a start switch or the like.

[0020] As shown in FIG. 1, the engine system 100 includes a control device 90. The control device 90 obtains a signal indicating accelerator operation amount ACC from an accelerator operation amount sensor 81. The control device 90 obtains a signal indicating vehicle speed SP from a vehicle speed sensor 82. The control device 90 obtains a signal indicating crank angle SC from a crank angle sensor 83. The control device 90 obtains a signal indicating water temperature TW from a water temperature sensor 84. The control device 90 obtains a signal indicating outside air temperature TA from an outside air temperature sensor 85. The control device 90 obtains a signal indicating fuel pressure PF from a fuel pressure sensor 86. The control device 90 obtains a signal indicating operation of an ignition switch 89 from the ignition switch 89. The control device 90 calculates engine speed NE, which is the rotational speed of the crankshaft 18, based on the crank angle SC.

[0021] The control device 90 calculates a vehicle required driving force, which is a required value of driving force necessary for the vehicle to travel, based on the accelerator operation amount ACC and the vehicle speed SP. The control device 90 calculates a target value for the output of the internal combustion engine 10 and a target engine speed NEA, which is a target value for the engine speed NE, based on the vehicle required driving force. The control device 90 controls the internal combustion engine 10 based on the target value for the output of the internal combustion engine 10 and the target engine speed NEA. Specifically, the control device 90 executes various controls such as adjusting the opening of the throttle valve 23, adjusting the ignition timing of the ignition device 24, adjusting the amount of fuel injected from the direct injection valve 27, and opening and closing the on-off valve 33. In other words, the control device 90 controls the internal combustion engine 10.

[0022] The control device 90 may be configured as a circuit including one or more processors that execute various processes according to a computer program (software). The control device 90 may also be configured as a circuit including one or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), that execute at least some of the various processes, or a combination thereof. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any medium that can be accessed by a general-purpose or dedicated computer.

[0023] <Stop control> Next, a description will be given of the stop control executed by the control device 90. When a request to stop the internal combustion engine 10 is made while the internal combustion engine 10 is being driven, the control device 90 executes the stop control. Here, an example of a request to stop the internal combustion engine 10 is when the ignition switch 89 is operated while the internal combustion engine 10 is being driven.

[0024] 2, when the control device 90 starts the stop control, it executes the process of step S11. In step S11, the control device 90 outputs a control signal to the on-off valve 33 to close the on-off valve 33. That is, when a stop of the internal combustion engine 10 is requested, the control device 90 closes the on-off valve 33. Thereafter, the control device 90 advances the process to step S12.

[0025] In step S12, the control device 90 sets the target engine speed NEA based on the outside air temperature TA. Specifically, the higher the outside air temperature TA, the higher the target engine speed NEA. At this time, the control device 90 sets the target engine speed NEA higher than the target engine speed NEA set during idling of the internal combustion engine 10. In this embodiment, the control device 90 sets the target engine speed NEA to a value within a range of, for example, several hundred rpm to several thousand rpm. Here, the target engine speed NEA during idling is the minimum rotation speed at which the internal combustion engine 10 can continue to drive stably. More specifically, it is the target engine speed NEA of the internal combustion engine 10 when the accelerator depression amount ACC is zero and the vehicle speed SP is zero. After step S12, the control device 90 proceeds to step S13.

[0026] In step S13, the control device 90 sets the injection period, which is the period during which hydrogen gas is injected from the direct injection valve 27, and the ignition timing of the ignition device 24. Specifically, the control device 90 lengthens the injection period of the direct injection valve 27 compared to before the internal combustion engine 10 is requested to be stopped, and retards the ignition timing of the ignition device 24 compared to before the internal combustion engine 10 is requested to be stopped. The control device 90 sets the injection period and ignition timing, for example, as follows: The control device 90 calculates the minimum amount of hydrogen gas required to achieve the target engine speed NEA and the optimal ignition timing based on the target engine speed NEA. The control device 90 also calculates the minimum injection period required by the direct injection valve 27 based on the minimum amount of hydrogen gas. The control device 90 then sets the final injection period of the direct injection valve 27 to a period obtained by adding a predetermined first period to the minimum injection period required by the direct injection valve 27. Furthermore, the control device 90 sets the ignition timing by the ignition device 24 to a timing that is retarded by a predetermined second period from the above-mentioned optimal ignition timing. As a result, the injection period by the direct injection valve 27 that is set in step S13 is longer than before the internal combustion engine 10 is requested to be stopped. Furthermore, the ignition timing by the ignition device 24 that is set in step S13 is retarded compared to before the internal combustion engine 10 is requested to be stopped. Note that the injection period by the direct injection valve 27 is the period from the injection start time at which injection from the direct injection valve 27 starts to the injection end time at which injection from the direct injection valve 27 ends. After step S13, the control device 90 proceeds to step S14.

[0027] In step S14, the control device 90 sets the injection timing for injecting hydrogen gas from the in-cylinder injection valve 27. Specifically, the control device 90 sets the injection start timing for starting injection from the in-cylinder injection valve 27 and the injection end timing for ending injection from the in-cylinder injection valve 27 to timings on the advance side with respect to the top dead center of the compression stroke of the cylinder 11.

[0028] Furthermore, the lower the fuel pressure PF, the more the control device 90 advances the injection start timing and the injection end timing. Specifically, when the fuel pressure PF is higher than a predetermined first threshold, the control device 90 sets the injection start timing within a range from the bottom dead center of the compression stroke of the cylinder 11 to the top dead center of the compression stroke. Therefore, in this case, the injection period by the in-cylinder injection valve 27 is a period that is retarded from the bottom dead center of the compression stroke.

[0029] Furthermore, when the fuel pressure PF is higher than a second threshold value that is smaller than the first threshold value and is equal to or lower than the first threshold value, the control device 90 sets the injection start timing within the range from the top dead center of the intake stroke of the cylinder 11 to the bottom dead center of the intake stroke. At this time, the control device 90 sets the injection start timing so that the injection end timing is set within the range from the bottom dead center of the compression stroke of the cylinder 11 to the top dead center of the compression stroke. Therefore, in this case, the injection period by the in-cylinder injection valve 27 is the period spanning from the intake stroke to the compression stroke.

[0030] When the fuel pressure PF is equal to or lower than the second threshold value, the control device 90 sets the injection start timing and injection end timing within the range from the top dead center of the intake stroke of the cylinder 11 to the bottom dead center of the intake stroke. Therefore, in this case, the injection period by the in-cylinder injection valve 27 is a period on the advance side of the bottom dead center of the compression stroke. After step S14, the control device 90 proceeds to step S15.

[0031] In step S15, the control device 90 controls the opening of the throttle valve 23 based on the fuel pressure PF. Specifically, the control device 90 controls the opening of the throttle valve 23 so that the amount of intake air introduced from the intake passage 12 into the cylinder 11 decreases as the fuel pressure PF decreases. At this time, the control device 90 makes the opening of the throttle valve 23 in step S15 smaller than the opening of the throttle valve 23 before a request to stop the internal combustion engine 10 is made. Note that before a request to stop the internal combustion engine 10 is made, the internal combustion engine 10 is operating, so the opening of the throttle valve 23 is not zero. In this embodiment, the control device 90 controls the opening of the throttle valve 23 to be fully open before a request to stop the internal combustion engine 10 is made, that is, when stop control is not being executed. After step S15, the control device 90 proceeds to step S16.

[0032] In step S16, the control device 90 sets a judgment value A based on the outside air temperature TA and the water temperature TW. In this embodiment, the higher the outside air temperature TA and the higher the water temperature TW, the smaller the judgment value A that the control device 90 sets. Therefore, for example, if the water temperature TW is the same, the higher the outside air temperature TA, the smaller the judgment value A. Similarly, if the outside air temperature TA is the same, the higher the water temperature TW, the smaller the judgment value A. After step S16, the control device 90 proceeds to step S17.

[0033] In step S17, the control device 90 refers to the settings of steps S12 to S14 and executes fuel injection by the in-cylinder injection valve 27 and ignition by the ignition device 24. As a result, the mixture of fuel and intake air is burned in the cylinder 11. In this embodiment, the processes of steps S11 to S15 and step S17 are an example of pre-shutdown combustion processing. Therefore, the control device 90 is able to execute pre-shutdown combustion processing. After step S17, the control device 90 advances the processing to step S21.

[0034] In step S21, the control device 90 determines whether the fuel pressure PF is equal to or less than the determination value A. If the control device 90 determines that the fuel pressure PF is higher than the determination value A (S21: NO), the control device 90 returns the process to step S12. On the other hand, if the control device 90 determines that the fuel pressure PF is equal to or less than the determination value A (S21: YES), the control device 90 proceeds to step S22.

[0035] In step S22, the control device 90 performs a stop process. Specifically, the control device 90 stops the internal combustion engine 10 by terminating fuel injection by the in-cylinder injection valve 27 and ignition by the ignition device 24. After step S22, the control device 90 ends the current stop control.

[0036] <Operation of this embodiment> As shown in FIG. 2, in the engine system 100, the on-off valve 33 is closed in step S11, and then the processes of steps S12 to S17 are repeatedly executed, so that the fuel pressure PF gradually decreases.

[0037] <Effects of this embodiment> (1) In step S15, the control device 90 controls the opening of the throttle valve 23 so that the amount of intake air introduced from the intake passage 12 into the cylinder 11 decreases as the fuel pressure PF decreases. Therefore, the lower the fuel pressure PF, the lower the pressure inside the cylinder 11, for example, at the top dead center of the compression stroke of the cylinder 11. This prevents the fuel pressure PF from becoming lower than the pressure inside the cylinder 11 when hydrogen gas is injected from the in-cylinder injection valve 27. As a result, even if the fuel pressure PF decreases, it is possible to prevent gas inside the cylinder 11 from flowing into the in-cylinder injection valve 27 when the in-cylinder injection valve 27 is open in association with the injection of hydrogen gas from the in-cylinder injection valve 27.

[0038] (2) In step S14, the control device 90 advances the injection start timing at which injection from the in-cylinder injection valve 27 starts and the injection end timing at which injection from the in-cylinder injection valve 27 ends with respect to the top dead center of the compression stroke of the cylinder 11. The lower the fuel pressure PF, the more the control device 90 advances the injection start timing and injection end timing. Generally, in the internal combustion engine 10, the more advanced the timing is with respect to the top dead center of the compression stroke of the cylinder 11, the lower the pressure in the cylinder 11. Therefore, when the fuel pressure PF is low, hydrogen gas is injected from the in-cylinder injection valve 27 at a time when the pressure in the cylinder 11 is low, compared to when the fuel pressure PF is high. That is, in this embodiment, the in-cylinder injection valve 27 can be opened at a time when the pressure in the cylinder 11 is low.

[0039] (3) In step S14, when the fuel pressure PF is higher than a predetermined first threshold, the control device 90 sets the injection start timing within a range from the bottom dead center of the compression stroke of the cylinder 11 to the top dead center of the compression stroke. When the fuel pressure PF is sufficiently high, injecting fuel during the compression stroke makes it less likely to hinder stable fuel combustion in the cylinder 11. On the other hand, when the fuel pressure PF is equal to or lower than the first threshold, the control device 90 sets the injection start timing within a range from the top dead center of the intake stroke of the cylinder 11 to the bottom dead center of the intake stroke. Generally, the pressure in the cylinder 11 during the intake stroke is lower than the pressure in the cylinder 11 during the compression stroke. Therefore, when the fuel pressure PF is equal to or lower than the first threshold, the control device 90 can open the direct injection valve 27 at a time when the pressure in the cylinder 11 is even lower than when the injection start timing is set only within a range from the bottom dead center of the compression stroke of the cylinder 11 to the top dead center of the compression stroke.

[0040] (4) In step S12, the control device 90 sets the target engine speed NEA higher than the target engine speed NEA set during idle operation of the internal combustion engine 10. This increases the number of times per unit time that the cylinder 11 undergoes the combustion stroke. That is, the number of times per unit time that hydrogen gas is injected from the direct injection valve 27 increases. As a result, the fuel pressure PF decreases more quickly than when, for example, the target engine speed NEA set in step S12 is the same as that during idle operation. Here, as shown in FIG. 2 , if it is determined in step S21 that the fuel pressure PF is equal to or lower than the determination value A, the internal combustion engine 10 is stopped in step S22. Therefore, if the fuel pressure PF decreases more quickly, the period from when a request to stop the internal combustion engine 10 is made to stop until the internal combustion engine 10 actually stops is shortened. This reduces the possibility that the driver who requested the internal combustion engine 10 to stop will feel uncomfortable during the period until the internal combustion engine 10 actually stops.

[0041] (5) Generally, if the injection period, which is the period during which hydrogen gas is injected from the in-cylinder injection valve 27, is lengthened, the amount of hydrogen gas injected from the in-cylinder injection valve 27 increases. This increases the amount of hydrogen gas that is burned in the cylinder 11, which tends to increase the output of the internal combustion engine 10. On the other hand, if the ignition timing of the ignition device 24 is retarded, the output of the internal combustion engine 10 tends to decrease.

[0042] In step S13, the control device 90 lengthens the injection period by the direct injection valve 27 compared to before the request to stop the internal combustion engine 10, and retards the ignition timing by the ignition device 24 compared to before the request to stop the internal combustion engine 10. This increases the amount of hydrogen gas injected from the direct injection valve 27, i.e., quickly reduces the fuel pressure PF, while preventing the actual output of the internal combustion engine 10 from increasing relative to the target value of the output of the internal combustion engine 10. In other words, it is possible to shorten the period from when a request to stop the internal combustion engine 10 is made to stop the internal combustion engine 10 until the internal combustion engine 10 actually stops, while preventing the actual output of the internal combustion engine 10 from increasing relative to the target value of the output of the internal combustion engine 10.

[0043] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0044] In the above embodiment, the process for setting the target engine speed NEA may be changed. For example, in step S12, when the outside air temperature TA is equal to or higher than a predetermined specified outside air temperature, the control device 90 may set a higher target engine rotation speed NEA than when the outside air temperature is lower than the specified outside air temperature.

[0045] For example, in step S12, the control device 90 may set the target engine speed NEA to a constant rotation speed regardless of the outside air temperature TA. In this case, the control device 90 may set the target engine speed NEA to the same value as the target engine speed NEA set when the internal combustion engine 10 is idling. In this configuration, it is preferable to set the target engine speed NEA as high as possible from the perspective of quickly reducing the fuel pressure PF.

[0046] In the above embodiment, the process for setting the injection period and ignition timing may be changed. For example, if the rate of decrease of the fuel pressure PF is sufficiently fast, in step S13, the control device 90 may set the injection period by the direct injection valve 27 to the same injection period as before the request to stop the internal combustion engine 10, or may shorten the injection period compared to before the request to stop the internal combustion engine 10. Also, for example, if an increase in the output of the internal combustion engine 10 is acceptable, the control device 90 may set the ignition timing by the ignition device 24 to the same ignition timing as before the request to stop the internal combustion engine 10.

[0047] In the above embodiment, the process for setting the injection timing may be changed. For example, in step S14, the control device 90 may set the injection start timing and the injection end timing within a range from the bottom dead center to the top dead center of the compression stroke of the cylinder 11. Also, for example, in step S14, the control device 90 may set the injection start timing and the injection end timing within a range from the top dead center to the bottom dead center of the intake stroke of the cylinder 11.

[0048] For example, in step S14, the control device 90 may advance the injection start timing and injection end timing only when the fuel pressure PF is equal to or lower than a predetermined specified fuel pressure, compared to when the fuel pressure is higher than the specified fuel pressure.

[0049] For example, in step S14, the control device 90 may set constant injection start and end times regardless of the fuel pressure PF. In this configuration, it is preferable to advance the injection start and end times as much as possible in order to open the direct injection valve 27 when the pressure in the cylinder 11 is low.

[0050] The first threshold value and the second threshold value in step S14 may be the same value. In this modified example, when the fuel pressure PF is higher than the first threshold value, the injection start timing and the injection end timing are retarded from the bottom dead center of the compression stroke. On the other hand, when the fuel pressure PF is equal to or lower than the first threshold value, the injection start timing and the injection end timing are advanced from the bottom dead center of the compression stroke. In other words, in this modified example, the injection period by the direct injection valve 27 is not set as a period spanning from the intake stroke to the compression stroke.

[0051] In the above embodiment, the process for controlling the opening of the throttle valve 23 may be changed. For example, in step S15, when the fuel pressure PF is equal to or lower than a predetermined specified fuel pressure, the control device 90 may control the opening of the throttle valve 23 so that the amount of intake air introduced into the cylinder 11 from the intake passage 12 is reduced compared to when the fuel pressure is higher than the specified fuel pressure. Note that "the amount of intake air is reduced compared to when the fuel pressure PF is high" does not necessarily mean that the amount is reduced gradually, but also means that the amount is reduced in stages. In other words, it is sufficient if there is at least one location where the amount of intake air is reduced when the fuel pressure PF is high, and there is no location where the amount of intake air is increased when the fuel pressure PF is high.

[0052] In the above embodiment, the process of setting the judgment value A may be changed. For example, in step S16, when the water temperature TW is equal to or higher than a predetermined specified water temperature, the control device 90 may set a smaller determination value A than when the water temperature TW is below the specified water temperature.

[0053] For example, in step S16, when the outside air temperature TA is equal to or higher than a predetermined specified outside air temperature, the control device 90 may set a smaller determination value A than when the outside air temperature TA is lower than the specified outside air temperature.

[0054] For example, in step S16, the control device 90 may set the determination value A based only on the outside air temperature TA, regardless of the water temperature TW. Similarly, in step S16, the control device 90 may set the determination value A based only on the water temperature TW, regardless of the outside air temperature TA. Furthermore, for example, in step S16, the control device 90 may set a constant determination value A regardless of the water temperature TW and the outside air temperature TA.

[0055] In the above embodiment, the determination process for stopping the internal combustion engine 10 may be changed. For example, in step S21, the control device 90 may determine whether the period that has elapsed since the execution of the stop-time control began is equal to or greater than a predetermined specified period. In this configuration, if the control device 90 determines that the period that has elapsed since the execution of the stop-time control began is less than the specified period, the control device 90 returns the process to step S12. On the other hand, if the control device 90 determines that the period that has elapsed since the execution of the stop-time control began is equal to or greater than the specified period, the control device 90 proceeds to step S22. Note that in this configuration, the process of step S16 can be omitted.

[0056] In the above embodiment, the configuration of the engine system 100 may be changed. For example, the gaseous fuel of the internal combustion engine 10 is not limited to hydrogen gas. As a specific example, the gaseous fuel of the internal combustion engine 10 may be natural gas or the like.

[0057] For example, the engine system 100 may include, as a fuel injection valve, a port injection valve that injects hydrogen gas into the intake passage 12 in addition to the in-cylinder injection valve 27. In this configuration, the port injection valve injects hydrogen gas into the intake passage 12, thereby introducing the hydrogen gas into the cylinder 11 via the intake passage 12.

[0058] For example, the engine system 100 does not need to be equipped with the outside air temperature sensor 85. As a specific example, the control device 90 may acquire the outside air temperature TA at the location where the vehicle is located by communicating with the outside of the vehicle.

[0059] For example, the engine system 100 does not have to include the fuel pressure sensor 86. As a specific example, the control device 90 may estimate the fuel pressure PF based on an integrated value of the injection period by the direct injection valve 27, or the like.

[0060] <Related technical ideas> The technical ideas that can be understood from the above-described embodiment and modified examples will be described. (Appendix 1) an internal combustion engine driven by gaseous fuel; a control device that controls the internal combustion engine, The internal combustion engine includes: a cylinder that combusts the gaseous fuel; an intake passage that introduces intake air into the cylinder; a throttle valve for adjusting the amount of intake air flowing through the intake passage; a fuel injection valve that directly injects the gaseous fuel into the cylinder; a fuel tank that stores the gaseous fuel; a connecting passage connecting the fuel tank and the fuel injection valve; an on-off valve that opens and closes the flow path of the connecting passage, The control device When a stop of the internal combustion engine is requested, a pre-stop combustion process can be executed in which the on-off valve is closed and the gaseous fuel is injected from the fuel injection valve and burned in the cylinder, In the pre-shutdown combustion process, when the fuel pressure, which is the pressure of the gaseous fuel supplied to the fuel injection valve, is low, the opening of the throttle valve is controlled so that the amount of intake air introduced into the cylinder is smaller than when the fuel pressure is high. Institutional system.

[0061] (Appendix 2) In the pre-shutdown combustion process, the injection start timing at which injection from the fuel injection valve is started is set to a timing on the advance side with respect to the top dead center of the compression stroke of the cylinder, and when the fuel pressure is low, the injection start timing is advanced compared to when the fuel pressure is high. 1. An engine system as described in Appendix 1.

[0062] (Appendix 3) In the pre-shutdown combustion process, when the fuel pressure is higher than a predetermined threshold, the injection start timing is set within a range from the bottom dead center of the compression stroke of the cylinder to the top dead center of the compression stroke, and when the fuel pressure is equal to or lower than the threshold, the injection start timing is set within a range from the top dead center of the intake stroke of the cylinder to the bottom dead center of the intake stroke. 1. An engine system as described in Appendix 2.

[0063] (Appendix 4) When the rotation speed of the crankshaft of the internal combustion engine is defined as the engine rotation speed, In the pre-shutdown combustion process, the target value of the engine rotation speed is set higher than the target value of the engine rotation speed set during idling of the internal combustion engine. An engine system according to any one of Supplementary Notes 1 to 3.

[0064] (Appendix 5) the internal combustion engine has an ignition device that ignites the gaseous fuel in the cylinder, In the pre-stop combustion processing, the period during which the gaseous fuel is injected from the fuel injection valve is made longer than before the stop of the internal combustion engine is requested, and the ignition timing by the ignition device is retarded compared to before the stop of the internal combustion engine is requested. An engine system according to any one of Supplementary Notes 1 to 4. [Explanation of symbols]

[0065] 10...Internal combustion engine 11...cylinder 12...Intake passage 13...Exhaust passage 15...Water jacket 16...Piston 17...Connecting rod 18...Crankshaft 23...Throttle valve 24…Ignition device 27...In-cylinder injection valve 31...Fuel tank 32...Connecting passage 33...Shut-off valve 34...Regulator 81...Accelerator operation amount sensor 82...Vehicle speed sensor 83...Crank angle sensor 84...Water temperature sensor 85...Outside air temperature sensor 86...Fuel pressure sensor 89...Ignition switch 90...Control device 100...Engine System

Claims

1. an internal combustion engine driven by gaseous fuel; a control device that controls the internal combustion engine, The internal combustion engine includes: a cylinder that combusts the gaseous fuel; an intake passage that introduces intake air into the cylinder; a throttle valve for adjusting the amount of intake air flowing through the intake passage; a fuel injection valve that directly injects the gaseous fuel into the cylinder; a fuel tank that stores the gaseous fuel; a connecting passage connecting the fuel tank and the fuel injection valve; an on-off valve that opens and closes the flow path of the connecting passage, The control device When a stop of the internal combustion engine is requested, a pre-stop combustion process can be executed in which the on-off valve is closed and the gaseous fuel is injected from the fuel injection valve and burned in the cylinder, In the pre-shutdown combustion treatment, When a fuel pressure, which is a pressure of the gaseous fuel supplied to the fuel injection valve, is low, the opening degree of the throttle valve is controlled so that the amount of intake air introduced into the cylinder is smaller than when the fuel pressure is high; When the fuel pressure is higher than a predetermined threshold, an injection start timing for starting injection from the fuel injection valve is set within a range from the bottom dead center of the compression stroke of the cylinder to the top dead center of the compression stroke, while when the fuel pressure is equal to or lower than the threshold, the injection start timing is set within a range from the top dead center of the intake stroke of the cylinder to the bottom dead center of the intake stroke. Institutional system.

2. an internal combustion engine driven by gaseous fuel; a control device that controls the internal combustion engine, The internal combustion engine includes: a cylinder that combusts the gaseous fuel; an intake passage that introduces intake air into the cylinder; a throttle valve for adjusting the amount of intake air flowing through the intake passage; a fuel injection valve that directly injects the gaseous fuel into the cylinder; a fuel tank that stores the gaseous fuel; a connecting passage connecting the fuel tank and the fuel injection valve; an on-off valve that opens and closes the flow path of the connecting passage, The control device When a stop of the internal combustion engine is requested, a pre-stop combustion process can be executed in which the on-off valve is closed and the gaseous fuel is injected from the fuel injection valve and burned in the cylinder, When the rotation speed of the crankshaft of the internal combustion engine is defined as the engine rotation speed, In the pre-shutdown combustion treatment, When a fuel pressure, which is a pressure of the gaseous fuel supplied to the fuel injection valve, is low, the opening degree of the throttle valve is controlled so that the amount of intake air introduced into the cylinder is smaller than when the fuel pressure is high; The target value of the engine rotation speed is set higher than the target value of the engine rotation speed set during idling of the internal combustion engine. Institutional system.

3. the internal combustion engine has an ignition device that ignites the gaseous fuel in the cylinder, In the pre-stop combustion processing, the period during which the gaseous fuel is injected from the fuel injection valve is made longer than before the stop of the internal combustion engine is requested, and the ignition timing by the ignition device is retarded compared to before the stop of the internal combustion engine is requested.

3. The engine system according to claim 1 or claim 2.

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