JP2024005628A - engine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to an engine system.

The vehicle of Patent Document 1 includes an internal combustion engine that burns gaseous fuel. An internal combustion engine includes cylinders, an intake passage, and a throttle valve. A cylinder is a space for burning 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. Further, the internal combustion engine includes a fuel injection valve, a fuel tank, a connection passage, an on-off valve, and a fuel pressure sensor. The fuel injection valve injects gaseous fuel directly 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 connecting portion of the connecting passage between the connecting passage and the fuel tank. The on-off valve opens and closes the flow path of the connection passage. The fuel pressure sensor detects fuel pressure, which is the pressure of gaseous fuel supplied to the fuel injection valve.

The vehicle of Patent Document 1 includes a control device that controls an internal combustion engine. The control device executes a pre-shutdown combustion process. The pre-stop combustion process is a process in which, when the internal combustion engine is requested to stop, the on-off valve is closed, and then gaseous fuel is injected from the fuel injection valve and combusted in the cylinder.

Japanese Patent Application Publication No. 2000-274312

In an internal combustion engine such as that disclosed in Patent Document 1, the fuel pressure, which is the pressure of gaseous fuel supplied to the fuel injection valve, gradually decreases by executing the pre-stop combustion process. When the fuel pressure decreases in this way, the fuel pressure may become lower than, for example, the pressure inside the cylinder when gaseous fuel is injected from the fuel injection valve. In this case, if the fuel injection valve opens when injecting gaseous fuel from the fuel injection valve, there is a risk that gas within the cylinder may flow into the fuel injection valve.

An engine system for solving the above problem includes an internal combustion engine that is driven using gaseous fuel as fuel, and a control device that controls the internal combustion engine, and the internal combustion engine has cylinders that burn 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 directly injects the gaseous fuel into the cylinder; and a fuel injection valve that stores the gaseous fuel. The control device includes a fuel tank, a connection passage that connects the fuel tank and the fuel injection valve, and an on-off valve that opens and closes a flow path of the connection passage, and the control device is configured to control the internal combustion engine when a stoppage of the internal combustion engine is requested. At this time, it is possible to perform a pre-shutdown combustion process in which the gaseous fuel is injected from the fuel injection valve and combusted in the cylinder after closing the on-off valve, and in the pre-shutdown combustion process, the gaseous fuel is injected from the fuel injection valve and combusted in the cylinder. When the fuel pressure, which is the pressure of the gaseous fuel supplied to the cylinder, 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.

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 if the fuel pressure becomes low, gas in the cylinder can be prevented from flowing into the fuel injection valve.

1 is a schematic configuration diagram of an engine system. It is a flowchart which shows control at the time of a stop.

<Schematic configuration of the engine system>
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 FIGS. 1 and 2. First, a schematic configuration of an engine system 100 applied to a vehicle will be described.

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

Internal combustion engine 10 includes a plurality of cylinders 11. The 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 in FIG. 1, only one cylinder 11 is shown as a representative.

The internal combustion engine 10 includes a plurality of pistons 16, a plurality of connecting rods 17, and a crankshaft 18. The piston 16 is located inside the cylinder 11. The piston 16 is connected to a crankshaft 18 via a connecting rod 17. The piston 16 reciprocates inside the cylinder 11 as a mixture of fuel and intake air burns in the cylinder 11 . The reciprocating movement of the piston 16 causes the crankshaft 18 to rotate.

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 cylinder 11. The intake passage 12 introduces intake air into each cylinder 11 from the outside of the internal combustion engine 10 . The exhaust passage 13 is connected to the cylinder 11. The exhaust passage 13 discharges exhaust gas from each cylinder 11 to the outside of 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 using a driving force from a valve mechanism (not shown).

The internal combustion engine 10 includes a plurality of in-cylinder injection valves 27 , a fuel tank 31 , a connection passage 32 , an on-off valve 33 , and a regulator 34 . The tip of the in-cylinder injection valve 27 is located within the cylinder 11. The in-cylinder injection valve 27 introduces fuel into the cylinder 11 by injecting hydrogen gas as fuel into the cylinder 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 valve 27 is a fuel injection valve that directly injects gaseous fuel into the cylinder 11 .

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 that is close to the in-cylinder injection valve 27 when viewed from the on-off valve 33 . The regulator 34 reduces the pressure of hydrogen gas supplied to the in-cylinder injection valve 27 to a predetermined pressure or less.

The internal combustion engine 10 includes a throttle valve 23 and a plurality of ignition devices 24 . The throttle valve 23 is located in the middle of 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 within the cylinder 11. The ignition device 24 ignites the mixture of fuel and intake air by spark discharge. That is, the ignition device 24 ignites the gaseous fuel within the cylinder 11 . The internal combustion engine 10 includes four ignition devices 24 corresponding to the four cylinders 11.

Internal combustion engine 10 includes a water jacket 15. The water jacket 15 constitutes a part of a passage through which cooling water circulates. Water jacket 15 surrounds cylinder 11. The cylinder 11 is cooled by heat exchange with cooling water flowing within the water jacket 15. That is, the water jacket 15 is a cooling water passage for cooling the cylinder 11.

<Electrical configuration of engine system>
As shown in FIG. 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 temperature sensor 85, a fuel pressure sensor 86, and an ignition switch 89.

The accelerator operation amount sensor 81 detects an accelerator operation amount ACC, which is the operation amount of an accelerator pedal (not shown) operated by the driver. Vehicle speed sensor 82 detects vehicle speed SP, which is the speed of the vehicle. Crank angle sensor 83 detects crank angle SC, which is the angular position of crankshaft 18 . The water temperature sensor 84 detects the temperature TW of the cooling water flowing out from the water jacket 15. Specifically, the water temperature sensor 84 detects the temperature of the cooling water at the downstream end of the water jacket 15 as the water temperature TW. Outside temperature sensor 85 detects outside temperature TA, which is the temperature outside internal combustion engine 10 . In this embodiment, the outside temperature sensor 85 is located near the front bumper of the vehicle. Fuel pressure sensor 86 detects fuel pressure PF, which is the pressure of hydrogen gas supplied to in-cylinder injection valve 27 . Specifically, the fuel pressure sensor 86 detects the pressure in the portion of the connection passage 32 between the regulator 34 and the in-cylinder injection valve 27 as the fuel pressure PF. 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 a vehicle driver or the like. A vehicle driver or the like can drive or stop the internal combustion engine 10 by operating the ignition switch 89. Note that the ignition switch 89 is sometimes called a start switch or the like.

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

The control device 90 calculates a vehicle required driving force, which is a required value of the 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 of the output of the internal combustion engine 10 and a target engine rotation speed NEA, which is a target value of the engine rotation speed NE, based on the vehicle required driving force. The control device 90 controls the internal combustion engine 10 based on the target value of the output of the internal combustion engine 10 and the target engine rotational speed NEA. Specifically, the control device 90 performs various operations such as adjusting the opening degree of the throttle valve 23, adjusting the ignition timing of the ignition device 24, adjusting the amount of fuel injection from the in-cylinder injection valve 27, and opening and closing the on-off valve 33. Execute control. That is, the control device 90 controls the internal combustion engine 10.

The control device 90 may be configured as a circuit including one or more processors that execute various processes according to computer programs (software). Note that the control device 90 is configured as a circuit that includes one or more dedicated hardware circuits such as an application-specific integrated circuit (ASIC), or a combination thereof, that executes at least some of the various processes. You can. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions configured to cause the CPU to perform processes. Memory or computer-readable media includes any media that can be accessed by a general purpose or special purpose computer.

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

As shown in FIG. 2, when the control device 90 starts the stop control, it executes the process of step S11. In step S11, the control device 90 closes the on-off valve 33 by outputting a control signal to the on-off valve 33. That is, the control device 90 closes the on-off valve 33 when the internal combustion engine 10 is requested to stop. After that, the control device 90 advances the process to step S12.

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

In step S13, the control device 90 sets an injection period, which is a period during which hydrogen gas is injected from the in-cylinder injection valve 27, and an ignition timing by the ignition device 24. Specifically, the control device 90 makes the injection period by the in-cylinder injection valve 27 longer than before the stop of the internal combustion engine 10 is requested, and also makes the injection period longer than before the stop of the internal combustion engine 10 is requested. The ignition timing by the ignition device 24 is retarded. The control device 90 sets the injection period and ignition timing, for example, as follows. Based on the target engine rotation speed NEA, the control device 90 calculates the minimum amount of hydrogen gas required to achieve the target engine rotation speed NEA and the optimal ignition timing. Furthermore, the control device 90 calculates the minimum required injection period by the in-cylinder injection valve 27 based on the minimum required amount of hydrogen gas. Then, the control device 90 sets a period obtained by adding a predetermined first period to the minimum necessary injection period by the direct injection valve 27 as the final injection period by the direct injection valve 27. Further, the control device 90 sets the ignition timing by the ignition device 24 to a timing that is delayed by a predetermined second period from the above-mentioned optimal ignition timing. As a result, the injection period by the direct injection valve 27 set in step S13 becomes longer than before the internal combustion engine 10 is requested to stop. Further, the ignition timing by the ignition device 24 set in step S13 is retarded compared to before the internal combustion engine 10 is requested to stop. The injection period by the in-cylinder injection valve 27 is the period from the injection start time when the in-cylinder injection valve 27 starts injection to the injection end time when the injection from the in-cylinder injection valve 27 ends. After step S13, the control device 90 advances the process to step S14.

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 at which injection from the in-cylinder injection valve 27 is started and the injection end timing at which injection from the in-cylinder injection valve 27 ends, depending on the upper dead end of the compression stroke of the cylinder 11. The period is on the advance side with respect to the point.

Furthermore, the control device 90 advances the injection start timing and the injection end timing as the fuel pressure PF is lower. Specifically, when the fuel pressure PF is higher than a predetermined first threshold value, the control device 90 starts injection 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. Set the time. Therefore, in this case, the injection period by the in-cylinder injection valve 27 is a period on the retard side of the bottom dead center of the compression stroke.

Further, when the fuel pressure PF is higher than a second threshold value that is a smaller value than the first threshold value and is less than or equal to the first threshold value, the control device 90 controls the intake stroke from the top dead center of the intake stroke of the cylinder 11. The injection start timing is set within the range up to the bottom dead center of. 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 a period spanning from the intake stroke to the compression stroke.

Then, when the fuel pressure PF is less than or equal to 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. Set. Therefore, in this case, the injection period by the in-cylinder injection valve 27 is a period on the advance side with respect to the bottom dead center of the compression stroke. After step S14, the control device 90 advances the process to step S15.

In step S15, the control device 90 controls the opening degree of the throttle valve 23 based on the fuel pressure PF. Specifically, the control device 90 controls the opening degree of the throttle valve 23 so that the lower the fuel pressure PF, the smaller the amount of intake air introduced into the cylinder 11 from the intake passage 12. At this time, the control device 90 makes the opening degree of the throttle valve 23 in step S15 smaller than the opening degree of the throttle valve 23 before the stoppage of the internal combustion engine 10 is requested. Note that the opening degree of the throttle valve 23 is not zero because the internal combustion engine 10 is being driven before the stoppage of the internal combustion engine 10 is requested. In the present embodiment, the control device 90 controls the opening degree of the throttle valve 23 to be fully open before the internal combustion engine 10 is requested to stop, that is, when the stop control is not executed. After step S15, the control device 90 advances the process to step S16.

In step S16, the control device 90 sets the determination value A based on the outside air temperature TA and the water temperature TW. In this embodiment, the control device 90 sets a smaller determination value A as the outside air temperature TA and the water temperature TW become higher. Therefore, for example, if the water temperature TW is the same, the higher the outside air temperature TA, the smaller the determination value A becomes. Similarly, if the outside air temperature TA is the same, the higher the water temperature TW, the smaller the determination value A becomes. After step S16, the control device 90 advances the process to step S17.

In step S17, the control device 90 executes fuel injection by the in-cylinder injection valve 27 and ignition by the ignition device 24, with reference to the settings in steps S12 to S14. As a result, the mixture of fuel and intake air is combusted within the cylinder 11. In the present embodiment, the processes in steps S11 to S15 and step S17 are an example of the pre-stop combustion process. Therefore, the control device 90 can execute the pre-shutdown combustion process. After step S17, the control device 90 advances the process to step S21.

In step S21, the control device 90 determines whether the fuel pressure PF is less than or equal to 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 less than or equal to the determination value A (S21: YES), the control device 90 advances the process to step S22.

In step S22, the control device 90 performs a stop process. Specifically, the control device 90 stops the internal combustion engine 10 by ending 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.

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

<Effects of this embodiment>
(1) In step S15, the control device 90 controls the opening degree of the throttle valve 23 so that the lower the fuel pressure PF, the smaller the amount of intake air introduced into the cylinder 11 from the intake passage 12. Therefore, the lower the fuel pressure PF, the lower the pressure within 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 becomes low, when the in-cylinder injection valve 27 is opened due to the injection of hydrogen gas from the in-cylinder injection valve 27, the gas in the cylinder 11 is 27 can be suppressed.

(2) In step S14, the control device 90 determines the injection start timing at which injection from the in-cylinder injection valve 27 is started and the injection end timing at which injection from the in-cylinder injection valve 27 is terminated during the compression stroke of the cylinder 11. The timing is on the advance side with respect to top dead center. Then, the lower the fuel pressure PF is, the more the control device 90 advances the injection start timing and the injection end timing. Generally, in the internal combustion engine 10, the pressure within the cylinder 11 becomes lower as the timing advances relative to the top dead center of the compression stroke of the cylinder 11. Therefore, compared to when the fuel pressure PF is high, 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. That is, in this embodiment, the in-cylinder injection valve 27 can be opened at a time when the pressure inside the cylinder 11 is low.

(3) In step S14, when the fuel pressure PF is higher than a predetermined first threshold value, the control device 90 controls the fuel pressure PF to be 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. Set the injection start time. In this way, when the fuel pressure PF is sufficiently high, by injecting the fuel within the compression stroke, stable combustion of the fuel within the cylinder 11 is less likely to be disturbed. On the other hand, when the fuel pressure PF is below 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. Generally, the pressure inside the cylinder 11 during the intake stroke is lower than the pressure inside the cylinder 11 during the compression stroke. Therefore, for example, compared to a case where the injection start timing is set only 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, when the fuel pressure PF is below the first threshold value, Furthermore, the in-cylinder injection valve 27 can be opened when the pressure inside the cylinder 11 is low.

(4) In step S12, the control device 90 makes the target engine rotation speed NEA higher than the target engine rotation speed NEA set when the internal combustion engine 10 is idling. Therefore, the number of times the cylinder 11 undergoes a combustion stroke per unit time increases. That is, the number of times hydrogen gas is injected from the in-cylinder injection valve 27 per unit time increases. As a result, the fuel pressure PF decreases more quickly than in the case where the target engine rotational speed NEA set in step S12 is the same as that during idling operation, for example. Here, as shown in FIG. 2, if it is determined in step S21 that the fuel pressure PF is less than or equal to the determination value A, the internal combustion engine 10 is stopped in step S22. Therefore, if the fuel pressure PF decreases quickly, the period from when a request to stop the internal combustion engine 10 is issued to when the internal combustion engine 10 actually stops becomes shorter. This reduces the possibility that the driver who requests stopping the internal combustion engine 10 will feel uncomfortable during the period until the internal combustion engine 10 actually stops.

(5) Generally, when 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. Since the amount of hydrogen gas combusted within the cylinder 11 increases, the output of the internal combustion engine 10 tends to increase. On the other hand, if the ignition timing by the ignition device 24 is retarded, the output of the internal combustion engine 10 tends to decrease.

In step S13, the control device 90 lengthens the injection period by the in-cylinder injection valve 27 compared to before the stop of the internal combustion engine 10 is requested, and increases the ignition period compared to before the stop of the internal combustion engine 10 is requested. The ignition timing by the device 24 is retarded. As a result, while suppressing the actual output of the internal combustion engine 10 from becoming larger than the target output value of the internal combustion engine 10, the amount of hydrogen gas injected from the direct injection valve 27 is increased, that is, the fuel pressure PF is increased. It can be lowered quickly. In other words, while suppressing the actual output of the internal combustion engine 10 from increasing with respect to the target value of the output of the internal combustion engine 10, from when a request to stop the internal combustion engine 10 is made to when the internal combustion engine 10 actually stops. period can be shortened.

<Example of change>
This embodiment can be modified and implemented as follows. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

- In the above embodiment, the process for setting the target engine rotational speed NEA may be changed.
For example, in step S12, the control device 90 may set a higher target engine rotational speed NEA when the outside temperature TA is equal to or higher than a predetermined outside temperature than when the outside temperature is below the specified outside temperature. good.

- For example, in step S12, the control device 90 may set the target engine rotational speed NEA to a constant rotational speed regardless of the outside air temperature TA. At this time, the control device 90 may set the target engine rotation speed NEA to the same value as the target engine rotation speed NEA set when the internal combustion engine 10 is idling. Note that in this configuration, from the viewpoint of quickly reducing the fuel pressure PF, it is preferable to set the target engine rotational speed NEA as high as possible.

- In the above embodiment, the process for setting the injection period and ignition timing may be changed.
For example, if the rate of decrease in the fuel pressure PF is sufficiently fast, in step S13, the control device 90 sets the injection period by the in-cylinder injection valve 27 to the same injection period as before the stoppage of the internal combustion engine 10 is requested. , may be shorter than before the stoppage of the internal combustion engine 10 is requested. For example, if it is permissible for the output of the internal combustion engine 10 to increase, the control device 90 may set the ignition timing by the ignition device 24 to the same ignition timing as before the stoppage of the internal combustion engine 10 is requested. good.

- 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 the range from the bottom dead center of the compression stroke of the cylinder 11 to the top dead center of the compression stroke. Further, for example, in step S14, the control device 90 may set the injection start timing and the 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.

- For example, in step S14, the control device 90 advances the injection start timing and the injection end timing only when the fuel pressure PF is below the predetermined fuel pressure, compared to when it is higher than the specified fuel pressure. Good too.

- For example, in step S14, the control device 90 may set constant injection start timing and injection end timing regardless of the fuel pressure PF. In addition, in this configuration, from the viewpoint of opening the in-cylinder injection valve 27 when the pressure in the cylinder 11 is low, it is preferable to set the injection start timing and the injection end timing as advanced as possible.

- The first threshold value and the second threshold value in step S14 may be the same value. In the case of this modification, when the fuel pressure PF is higher than the first threshold value, the injection start timing and injection end timing are on the retard side than the bottom dead center of the compression stroke. On the other hand, when the fuel pressure PF is less than or equal to the first threshold value, the injection start timing and the injection end timing are on the advanced side with respect to the bottom dead center of the compression stroke. That is, in the case of this modification, the injection period by the in-cylinder injection valve 27 is not set as a period spanning from the intake stroke to the compression stroke.

- In the above embodiment, the process for controlling the opening degree of the throttle valve 23 may be changed.
For example, in step S15, the control device 90 controls the amount of intake air introduced into the cylinder 11 from the intake passage 12 to be smaller when the fuel pressure PF is less than or equal to a predetermined fuel pressure than when it is higher than the specified fuel pressure. The opening degree of the throttle valve 23 may be controlled so as to achieve the following. It should be noted that the expression "the amount of intake air becomes smaller than when the fuel pressure PF is high" is not limited to a case where it gradually decreases, but also includes a case where it decreases stepwise. In other words, there must be at least one location where the amount of intake air decreases when the fuel pressure PF increases, and there must also exist a location where the amount of intake air increases when the fuel pressure PF increases. Bye.

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

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

- 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.

- 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 of time that has elapsed since the start of execution of the stop control is equal to or longer than a predetermined period. In this configuration, if the control device 90 determines that the period of time that has elapsed since the start of execution of the stop control 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 of time that has elapsed since the start of execution of the stop control is equal to or longer than the specified period, the control device 90 advances the process to step S22. Note that in this configuration, the process of step S16 can be omitted.

- 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.

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

- For example, the engine system 100 does not need to include the outside temperature sensor 85. As a specific example, the control device 90 may acquire the temperature of the outside air at the point where the vehicle is located as the outside air temperature TA through communication with the outside of the vehicle.

- For example, the engine system 100 may not include the fuel pressure sensor 86. As a specific example, the control device 90 may estimate the fuel pressure PF based on the integrated value of the injection period by the in-cylinder injection valve 27 or the like.

<Related technical ideas>
The technical ideas that can be understood from the above embodiment and modification examples will be described.
(Additional note 1)
an internal combustion engine powered by gaseous fuel;
a control device that controls the internal combustion engine;
The internal combustion engine is
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 directly injects the gaseous fuel into the cylinder;
a fuel tank that stores the gaseous fuel;
a connection passage connecting the fuel tank and the fuel injection valve;
an on-off valve that opens and closes the flow path of the connection passage;
The control device includes:
When the internal combustion engine is requested to stop, it is possible to perform a pre-stop combustion process in which the on-off valve is closed and the gaseous fuel is injected from the fuel injection valve and combusted in the cylinder,
In the pre-stop combustion process, when the fuel pressure, which is the pressure of the gaseous fuel supplied to the fuel injection valve, is low, the amount of intake air introduced into the cylinder is smaller than when the fuel pressure is high. An engine system that controls the opening degree of the throttle valve.

(Additional note 2)
In the pre-stop combustion process, the injection start timing for starting injection from the fuel injector is set to be an advance timing with respect to the top dead center of the compression stroke of the cylinder, and when the fuel pressure is low, the fuel pressure is The engine system according to supplementary note 1, wherein the injection start timing is advanced compared to when the injection start timing is high.

(Additional note 3)
In the pre-stop 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. On the other hand, when the fuel pressure is below 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.

(Additional note 4)
When the rotational speed of the crankshaft of the internal combustion engine is the engine rotational speed,
The engine according to any one of Supplementary notes 1 to 3, wherein in the pre-stop combustion process, the target value of the engine rotational speed is set higher than the target value of the engine rotational speed set during idling operation of the internal combustion engine. system.

(Appendix 5)
The internal combustion engine includes an ignition device that ignites the gaseous fuel in the cylinder,
In the pre-stop combustion process, the period during which the gaseous fuel is injected from the fuel injection valve is made longer than before the internal combustion engine is requested to stop, and The engine system according to any one of Supplementary Notes 1 to 4, wherein the ignition timing of the ignition device is retarded.

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... Connection passage 33... Opening/closing valve 34... Regulator 81... Accelerator operation amount sensor 82... Vehicle speed sensor 83... Crank angle sensor 84... Water temperature sensor 85... Outside temperature sensor 86... Fuel pressure sensor 89... Ignition switch 90... Control device 100... Engine system

Claims (5)

an internal combustion engine powered by gaseous fuel;
a control device that controls the internal combustion engine;
The internal combustion engine is
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 directly injects the gaseous fuel into the cylinder;
a fuel tank that stores the gaseous fuel;
a connection passage connecting the fuel tank and the fuel injection valve;
an on-off valve that opens and closes the flow path of the connection passage;
The control device includes:
When the internal combustion engine is requested to stop, it is possible to perform a pre-stop combustion process in which the on-off valve is closed and the gaseous fuel is injected from the fuel injection valve and combusted in the cylinder,
In the pre-stop combustion process, when the fuel pressure, which is the pressure of the gaseous fuel supplied to the fuel injection valve, is low, the amount of intake air introduced into the cylinder is smaller than when the fuel pressure is high. An engine system that controls the opening degree of the throttle valve. In the pre-stop combustion process, the injection start timing for starting injection from the fuel injector is set to be an advance timing with respect to the top dead center of the compression stroke of the cylinder, and when the fuel pressure is low, the fuel pressure is The engine system according to claim 1, wherein the injection start timing is advanced compared to when the injection start timing is high. In the pre-stop 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. On the other hand, when the fuel pressure is below the threshold value, 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. . When the rotational speed of the crankshaft of the internal combustion engine is the engine rotational speed,
According to any one of claims 1 to 3, in the pre-stop 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 operation of the internal combustion engine. institutional system. The internal combustion engine includes an ignition device that ignites the gaseous fuel in the cylinder,
In the pre-stop combustion process, the period during which the gaseous fuel is injected from the fuel injection valve is made longer than before the internal combustion engine is requested to stop, and The engine system according to claim 1, wherein the ignition timing of the ignition device is retarded.

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