JP2024014305A - engine control device - Google Patents

Abstract

[Problem] To ensure ignitability of fuel. An electronic control unit 20 that controls a spark ignition engine 10 having an injector 18 that injects fuel into a cylinder 11 performs a second injection in the latter half of the compression stroke and a fuel injection before the second injection. When performing a certain first injection, adjustment processing is performed to make the injection speed of the second injection lower than that of the first injection. [Selection diagram] Figure 1

Description

The present invention relates to an engine control device that controls a spark ignition engine that performs in-cylinder injection.

As an engine control device as described above, the device described in Patent Document 1 is conventionally known. The control device described in this document performs the second injection in the latter half of the compression stroke after the first injection, which is the main fuel injection, to increase the fuel concentration in the area near the cylinder bore and the area around the spark plug. A layer of high air-fuel mixture is formed.

Japanese Patent Application Publication No. 2006-22665

Even if the second injection is performed, if the injection force is strong, the spray may not stay around the spark plug. In such a case, the fuel concentration around the spark plug at the time of ignition becomes diluted, and the ignitability of the air-fuel mixture deteriorates.

An engine control device that solves the above problem is a device that controls a spark ignition engine that has an injector that injects fuel into a cylinder. When performing a second injection, which is a fuel injection in the latter half of the compression stroke, and a first injection, which is a fuel injection before the second injection, the engine control device adjusts the injection speed of the second injection to the first injection. Perform adjustment processing to lower the value.

In the engine control device described above, low-speed fuel injection is performed in the latter half of the compression stroke. Since the fuel spray injected at low speed has a small momentum, it tends to stay around the spark plug. Therefore, if low-speed fuel injection is performed in the latter half of the compression stroke, a layer of air-fuel mixture with high fuel concentration is formed around the spark plug during ignition. Therefore, the engine control device has the effect of improving the ignitability of the engine.

An example of the adjustment process is a process in which the first injection is performed with a full-lift injection in which the needle valve fully opens, and the second injection is performed with a partial-lift injection in which the needle valve does not fully open. When the needle valve is not fully open, the resistance during injection is large, so the injection speed of the injector is low. By performing the first injection by full lift injection and the second injection by partial lift injection, the second injection can be performed at a lower injection speed than the first injection.

While fuel injection continues, the injection speed may not be able to be changed. Furthermore, if the injection speed is changed while fuel injection is continued, variations in the fuel injection amount may increase. Even in such a case, if a period in which no fuel injection is performed is set between the first injection and the second injection, the injection speed can be appropriately changed.

Even if the fuel injection amount of the second injection is constant, if the density of the intake air in the cylinder at the time of ignition is high, the fuel concentration around the spark plug at the time of ignition will be lower than if the same density is low. Therefore, it is desirable that the fuel injection amount of the second injection is changed depending on the intake air density within the cylinder. Note that the intake air density within a cylinder changes depending on the intake air filling rate of the same cylinder. Therefore, it is desirable to set the fuel injection amount of the second injection based on the intake air amount of the cylinder. Furthermore, the intake air density within the cylinder also changes depending on the intake air temperature. Therefore, it is desirable to set the fuel injection amount of the second injection based on the intake air temperature of the engine.

1 is a diagram schematically showing the configuration of an embodiment of an engine control device. FIG. 2 is a diagram showing a schematic structure of an injector and a state inside a cylinder immediately before ignition when fuel injection is performed until the latter half of a compression stroke. 3 is a flowchart of a fuel injection control routine executed by the engine control device. (A) shows the change in the implementation status of fuel injection, (B) shows the change in fuel pressure, and (C) shows the change in spray momentum in the above engine control device when the required injection period is longer than the ignition limit injection period. (D) is a time chart showing the implementation status of fuel injection when fuel injection is performed from the earliest injection start time with the fuel pressure maintained at the standard fuel pressure in the above case. In another embodiment of the engine control device, when the required injection period is longer than the ignitability limit injection period, (A) shows the change in the implementation status of fuel injection, (B) shows the change in fuel pressure, and (C ) are time charts showing changes in spray momentum. In another embodiment of the engine control device, when the required injection period is longer than the ignitability limit injection period, (A) shows the change in the implementation status of fuel injection, (B) shows the change in fuel pressure, and (C ) is a time chart showing the change in the lift amount of the needle valve, and (D) is a time chart showing the change in the spray momentum, respectively.

Hereinafter, one embodiment of the engine control device will be described in detail with reference to FIGS. 1 to 4.
<Configuration of engine control device>
First, with reference to FIG. 1, the configuration of the engine control device of this embodiment will be explained. The engine 10 that is controlled by the engine control device of this embodiment is installed in a vehicle. Further, the engine 10 is configured as a hydrogen gas engine that uses hydrogen gas as fuel.

Engine 10 has one or more cylinders 11. A piston 12 is disposed inside the cylinder 11 so as to be able to reciprocate vertically in the figure. Inside the cylinder 11, a combustion chamber 13 in which combustion occurs is defined by a piston 12. An intake port 15 is connected to the upper part of the cylinder 11 via an intake valve 14 . Furthermore, an exhaust port 17 is connected to the upper part of the cylinder 11 via an exhaust valve 16 . Furthermore, an injector 18 that injects hydrogen gas into the cylinder 11 and a spark plug 19 that ignites the hydrogen gas injected by the injector 18 are installed at the top of the cylinder 11.

The injector 18 is connected via a fuel pressure adjustment device 29 to a fuel tank 28 that stores hydrogen gas. The fuel pressure adjustment device 29 is a device that adjusts the fuel pressure PF, which is the pressure of hydrogen gas supplied to the injector 18. The fuel pressure regulator 29 reduces the pressure of hydrogen gas in the fuel tank 28 and supplies it to the injector 18 . The fuel pressure adjustment device 29 is configured to be able to change the fuel pressure PF within a range below the tank internal pressure PT.

As shown in FIG. 2, the injector 18 includes a needle valve 30, an electromagnetic solenoid 31, a spout 32, and a needle spring 33. As described above, hydrogen gas is introduced into the injector 18 from the fuel tank 28 via the fuel pressure regulator 29. The nozzle 32 is a hydrogen gas spout that communicates the inside and outside of the injector 18 . The injector 18 is assembled into the engine 10 with the nozzle 32 exposed within the combustion chamber 13. The needle valve 30 is a valve body that opens and closes the nozzle 32. The electromagnetic solenoid 31 generates electromagnetic attraction force for driving the needle valve 30 toward the side that opens the nozzle 32 in response to energization. The needle spring 33 is a spring that biases the needle valve 30 toward the side that closes the injection port 32. In such an injector 18, the injection speed of fuel from the nozzle 32 when the needle valve 30 is fully open changes in conjunction with the fuel pressure PF.

On the other hand, as shown in FIG. 1, an electronic control unit 20 that controls the engine 10 includes an arithmetic processing unit 21 and a storage device 22. The storage device 22 stores programs and data used for control. The arithmetic processing unit 21 performs various processes related to the control of the engine 10 by executing programs read from the storage device 22 . In this embodiment, such an electronic control unit 20 corresponds to an engine control device.

A crank angle sensor 23, an air flow meter 24, an intake air temperature sensor 25, an accelerator pedal sensor 26, and a tank pressure sensor 27 are connected to the electronic control unit 20. The crank angle sensor 23 is a sensor that detects the rotational phase of the crankshaft of the engine 10. The air flow meter 24 is a sensor that detects the intake air flow rate GA of the engine 10. The intake air temperature sensor 25 is a sensor that detects the intake air temperature THA of the engine 10. The accelerator pedal sensor 26 is a sensor that detects the driver's accelerator pedal operation amount ACC. Tank pressure sensor 27 is a sensor that detects tank internal pressure PT. The electronic control unit 20 determines the engine rotation speed NE, which is the rotation speed of the engine 10, from the detection result of the crank angle sensor 23. Further, the electronic control unit 20 determines the engine load factor KL based on the intake air flow rate GA detected by the air flow meter 24 and the engine rotation speed NE. The engine load rate KL represents the intake air filling rate of the cylinder 11.

<Fuel injection control>
The electronic control unit 20 controls fuel injection of the injector 18 as part of the control of the engine 10. The electronic control unit 20 controls fuel injection through operation of the injector 18 and fuel pressure adjustment device 29.

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

When controlling the fuel injection, the electronic control unit 20 first calculates the required injection amount QS, which is the amount of fuel injection necessary to generate the driving force requested by the driver. Next, the electronic control unit 20 determines the required injection period TS, which is the injection period of fuel necessary for injecting the required injection amount QS. The electronic control unit 20 performs fuel injection control by operating the injector 18 to inject fuel during the required injection period TS. Note that even if the required injection amount QS is constant, the required injection period TS is longer when the engine speed NE is high than when it is low. Further, even if the required injection amount QS is constant, when the fuel pressure PF is low, the required injection period TS is longer than when the fuel pressure PF is high.

On the other hand, there are restrictions on advancing the start timing of fuel injection in order to prevent backflow of fuel into the intake system. Therefore, depending on the operating conditions of the engine 10, the required injection period TS may become longer, and fuel injection may need to be continued until the latter half of the compression stroke immediately before ignition. By the way, the fuel density of hydrogen gas is lower than that of liquid fuel such as gasoline. Therefore, in the engine 10 that uses hydrogen gas as fuel, the operating range of the engine 10 in which the fuel injection ends immediately before ignition is generally wider than in the case of an engine that uses liquid fuel.

FIG. 2 shows the state inside the cylinder 11 immediately before ignition when fuel injection is performed until the latter half of the compression stroke. In such a case, since the time from the end of fuel injection until ignition is short, the mixing of fuel into the intake air does not proceed sufficiently. Furthermore, the fuel spray L is swept away from the vicinity of the spark plug 19 due to the flow field F formed in the cylinder 11 due to the injection. Therefore, when the end timing of fuel injection is in the latter half of the compression stroke, the fuel concentration around the spark plug 19 during ignition becomes low, and the ignitability of hydrogen gas deteriorates. Note that the higher the injection speed of hydrogen gas from the injector 18, the stronger the flow field F formed in the cylinder 11 due to injection. Therefore, the higher the injection speed of hydrogen gas from the injector 18, the more likely deterioration of ignitability occurs when the fuel injection ends at the latter half of the compression stroke.

Note that the electronic control unit 20 basically operates the fuel pressure adjustment device 29 so as to set the fuel pressure PF to a predetermined standard fuel pressure PS. When fuel injection is performed with the fuel pressure PF set to the standard fuel pressure PS, the deterioration of ignition performance as described above occurs when the end time of fuel injection is later than a predetermined time. In the following description, the above-mentioned predetermined time that is the boundary between whether deterioration of ignitability occurs or not will be referred to as ignitability limit injection end time LM. Furthermore, in the following description, the timing that is the limit on the advance side of the fuel injection start timing will be referred to as the earliest injection start timing S0. The period from the earliest injection start time S0 to the ignitability limit injection end time LM is referred to as the ignitability limit injection period TT. If the required injection period TS is longer than the ignitability limit injection period TT, the end timing of fuel injection will be later than the ignitability limit injection end time LM.

<Fuel injection control routine>
The electronic control unit 20 performs fuel injection control to suppress the deterioration of ignitability as described above. Hereinafter, details of fuel injection control for suppressing deterioration of ignitability will be explained.

FIG. 3 shows a processing procedure of a fuel injection control routine executed by the electronic control unit 20 during fuel injection control. The electronic control unit 20 repeatedly executes the same routine at every predetermined control cycle while the engine 10 is operating. Note that the electronic control unit 20 ends the series of processes of this routine in the corresponding control period after completing the process of step S140 in FIG. 3 or after completing the process of step S190.

When this routine starts, the electronic control unit 20 first calculates the required injection amount QS based on the accelerator pedal operation amount ACC and the vehicle speed V in step S100. Next, in step S110, the electronic control unit 20 calculates the required injection period TS based on the required injection amount QS and the engine rotational speed NE. In step S110, the electronic control unit 20 calculates the fuel injection period of the injector 18 that can inject the required injection amount QS of fuel with the fuel pressure PF set to the standard fuel pressure PS as the value of the required injection period TS. ing. Then, in the subsequent step S120, the electronic control unit 20 determines whether the required injection period TS is longer than the ignitability limit injection period TT.

If the required injection period TS is less than or equal to the ignition limit injection period TT (S120: NO), the electronic control unit 20 advances the process to step S130. In step S130, the electronic control unit 20 sets the ignitability limit injection end time LM as the value of the injection end time EC. Further, in step S130, the electronic control unit 20 sets the injection start time SC to a time earlier than the injection end time EC by the necessary injection period TS. Then, in the subsequent step S140, the electronic control unit 20 instructs the injector 18 to perform single-stage injection during the period from the injection start time SC to the injection end time EC. That is, the electronic control unit 20 at this time operates the injector 18 so that the fuel injection for the required injection amount QS by single-stage injection ends at the ignitability limit injection end time LM. Note that the electronic control unit 20 at this time operates the fuel pressure adjustment device 29 so as to maintain the fuel pressure PF at the standard fuel pressure PS.

On the other hand, if the required injection period TS is longer than the ignition limit injection period TT (S120: YES), the electronic control unit 20 advances the process to step S150. In step S150, the electronic control unit 20 calculates the second injection amount QI based on the engine load factor KL and the intake air temperature THA. Further, in step S150, the electronic control unit 20 calculates the difference obtained by subtracting the second injection amount QI from the required injection amount QS as the value of the first injection amount QM. Note that the electronic control unit 20 calculates the value of the second injection amount QI so that when the engine load factor KL is high, it is a larger value than when it is low, and when the intake air temperature THA is low, it is a larger value than when it is high. ing.

Subsequently, in step S160, the electronic control unit 20 calculates the second injection period TI, the second injection start timing SI, and the fuel pressure reduction command timing AP. The second injection period TI is the amount of fuel that is required for the injector 18 to inject the second injection amount QI at the current engine speed NE and with the fuel pressure PF set to a predetermined low fuel pressure PI that is lower than the standard fuel pressure PS. It represents the injection period. The electronic control unit 20 calculates the second injection period TI based on the second injection amount QI and the engine rotation speed NE. Further, the electronic control unit 20 calculates a time earlier than the second injection end time EI by the second injection period TI as the value of the second injection start time SI. The second injection end time EI is set to be earlier than the end time of the compression stroke by a predetermined margin period. The margin period represents the period from when the electronic control unit 20 commands the end of fuel injection until the injector 18 actually stops fuel injection. Further, the electronic control unit 20 calculates a time earlier than the second injection start time SI by a predetermined fuel pressure adjustment period TP as the value of the fuel pressure reduction command time AP. The fuel pressure adjustment period TP is the period from when the electronic control unit 20 instructs the fuel pressure adjustment device 29 to lower the fuel pressure PF from the standard fuel pressure PS to the low fuel pressure PI until the fuel pressure PF actually becomes the low fuel pressure PI. Represents the required period.

Next, in step S170, the electronic control unit 20 calculates a first injection period TM, a first injection end time EM, and a first injection start time SM. The first injection period TM represents the fuel injection period of the injector 18 required to inject the first injection amount QM at the current engine speed NE and with the fuel pressure PF set to the standard fuel pressure PS. The electronic control unit 20 calculates the value of the first injection period TM based on the first injection amount QM and the engine rotational speed NE. Furthermore, the electronic control unit 20 calculates the earlier of the following two times as the value of the first injection end time EM. One of the above two timings is the fuel pressure reduction command timing AP, and the other is a timing earlier than the second injection start timing SI by a predetermined injection interval INT. The injection interval INT represents the period from when the injector 18 stops injecting fuel until it becomes possible to restart fuel injection. Then, the electronic control unit 20 calculates a time earlier than the first injection end time EM by the first injection period TM as the value of the first injection start time SM.

Thereafter, in step S180, the electronic control unit 20 instructs the fuel pressure adjustment device 29 to reduce the fuel pressure during the period from the fuel pressure reduction command timing AP to the second injection end timing EI. In response to this command, the fuel pressure adjustment device 29 lowers the fuel pressure PF from the standard fuel pressure PS to the low fuel pressure PI at the fuel pressure reduction command timing AP. Then, the fuel pressure adjustment device 29 increases the fuel pressure PF from the low fuel pressure PI to the standard fuel pressure PS at the subsequent second injection end time EI. In this embodiment, the process of step S180 corresponds to the adjustment process.

Then, in the next step S190, the electronic control unit 20 instructs the injector 18 to perform the first injection and the second injection. The first injection is fuel injection during the period from the first injection start time SM to the first injection end time EM. The second injection is fuel injection during the period from the second injection start time SI to the second injection end time EI in the latter half of the compression stroke. As described above, the electronic control unit 20 at this time reduces the fuel pressure PF from the standard fuel pressure PS to the low fuel pressure PI at the fuel pressure reduction command timing AP. Therefore, the first injection is performed with the fuel pressure PF set to the standard fuel pressure PS, and the second injection is performed with the fuel pressure PF set to the low fuel pressure PI. The injection speed of hydrogen gas from the injector 18 increases as the fuel pressure PF increases. Therefore, the injection speed of the second injection of hydrogen gas is lower than that of the first injection.

<Actions and effects of the embodiment>
The operation and effects of this embodiment will be explained with reference to FIG. 4. FIGS. 4A to 4C show an example of a control mode of the engine control device of this embodiment when the required injection period TS is longer than the ignition limit injection period TT. FIG. 4(A) shows the transition of the implementation status of fuel injection, FIG. 4(B) shows the transition of the fuel pressure PF, and FIG. 4(C) shows the transition of the momentum of the fuel spray.

In addition, FIG. 4(D) shows that when the required injection period TS is longer than the ignition limit injection period TT, fuel injection is started at the earliest injection start time S0 while maintaining the fuel pressure PF at the standard fuel pressure PS. This shows the implementation status of fuel injection when As described above, in the engine 10, the timing at which fuel injection can be started is limited to the timing after the earliest injection start time S0. On the other hand, the ignitability limit injection period TT is set as a period from the earliest injection start time S0 to the ignitability limit injection end time LM. Therefore, in this case, the time when fuel injection for the required injection amount QS is completed is later than the ignitability limit injection end time LM. That is, in this case, fuel injection is performed at the standard fuel pressure PS until just before ignition, which tends to cause deterioration in ignition performance.

In contrast, in the above case, the engine control device of the present embodiment injects the required injection amount QS of fuel through the first injection and the second injection. The second injection is a small amount of fuel injection performed in the latter half of the compression stroke immediately before ignition. The first injection is a fuel injection in a period before the second injection. The second injection is performed at a lower hydrogen gas injection speed than the first injection. That is, in this embodiment, when the end of fuel injection is in the latter half of the compression stroke immediately before ignition, the second injection with a lower injection speed of hydrogen gas is performed immediately before ignition. Since the fuel spray of the second injection injected at low speed has a small momentum as shown in FIG. 4(C), it tends to remain around the spark plug 19 during ignition. Therefore, even if fuel injection is continued until immediately before ignition, ignitability can be ensured by performing the second injection at a low injection speed in the latter half of the compression stroke.

Note that, as described above, the electronic control unit 20 calculates the second injection amount QI, which is the amount of fuel injected in the second injection, based on the engine load factor KL and the intake air temperature THA. As a result, the electronic control unit 20 sets the value of the second injection amount QI to an amount that can form a layer of air-fuel mixture with an ignitable fuel concentration around the spark plug 19 during ignition. That is, even if the second injection amount QI is constant, if the density of the intake air in the cylinder 11 at the time of ignition is high, the fuel concentration around the spark plug 19 will be lower than if it is low. The density of the intake air in the cylinder 11 increases as the intake air filling rate of the cylinder 11, that is, the engine load factor KL increases. Further, the intake air density within the cylinder 11 increases as the intake air temperature THA decreases. Therefore, by setting the second injection amount QI as an amount that increases as the engine load factor KL increases and increases as the intake air temperature THA decreases, the fuel concentration around the spark plug 19 at the time of ignition can be adjusted to an appropriate level suitable for ignition. concentration.

The engine control device of this embodiment described above has the following effects.
(1) When it is necessary to perform fuel injection until the latter half of the compression stroke, the electronic control unit 20 performs the second injection in the latter half of the compression stroke and the first injection in a period before the second injection. Then, the electronic control unit 20 performs an adjustment process to make the injection speed of the second injection lower than that of the first injection. Therefore, even when fuel injection is performed until immediately before ignition, ignitability is unlikely to deteriorate.

(2) The electronic control unit 20 performs the adjustment process when the required injection period TS, which is the period required to inject fuel for the required injection amount QS, is longer than the predetermined ignitability limit injection period TT. When the required injection period TS is shorter than the ignitability limit injection period TT, fuel injection for the required injection amount QS can be completed earlier than the ignitability limit injection end time LM. In such a case, ignitability can be ensured without performing adjustment processing. Therefore, the adjustment process can be carried out only when the ignitability is likely to deteriorate.

(3) The electronic control unit 20 sets a period in which no fuel injection is performed between the first injection and the second injection. That is, when performing fuel injection until just before ignition, the electronic control unit 20 divides and injects the required injection amount QS of fuel into the first injection and the second injection. If the fuel pressure PF is changed to change the injection speed while fuel injection is continuing, the variation in the fuel injection amount increases. In this regard, if a period in which no fuel injection is performed is set between the first injection and the second injection, the fuel pressure PF can be adjusted during that period. Therefore, an increase in variation in fuel injection amount due to adjustment of fuel pressure PF can be suppressed.

(4) The electronic control unit 20 calculates the second injection amount QI based on the intake air filling rate of the cylinder 11 and the intake air temperature THA. Therefore, in the second injection, an appropriate amount of fuel can be injected to ensure ignitability.

<Other Examples>
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.

- The fuel pressure reduction command timing AP may be set in a manner other than the above. For example, the ignitability limit injection end timing LM may be set as the fuel pressure reduction command timing AP. In any case, if the second injection is performed in the latter half of the compression stroke immediately before ignition at a lower injection speed than the first injection, deterioration in ignitability can be suppressed.

- As shown in FIG. 5, the first injection and the second injection may be performed as a continuous series of fuel injections. FIG. 5 shows an example of an embodiment of fuel injection control when the required injection period TS is longer than the ignition limit injection period TT. More specifically, FIG. 5(A) shows the transition of the implementation status of fuel injection, FIG. 5(B) shows the transition of the fuel pressure PF, and FIG. 5(C) shows the transition of the momentum of the fuel spray. As shown in FIG. 5(A), the electronic control unit 20 starts fuel injection from the earliest injection start time S0. Then, the electronic control unit 20 continues fuel injection until a time later than the ignitability limit injection end time LM. As shown in FIG. 5(B), the electronic control unit 20 lowers the fuel pressure PF from the standard fuel pressure PS to the low fuel pressure PI at the ignition limit injection end timing LM. Therefore, as shown in FIG. 5(C), the momentum of the fuel spray becomes small in the latter half of the compression stroke just before ignition. Therefore, even in such cases, deterioration of ignitability can be suppressed. In this case, the fuel injection in the period before the ignitability limit injection end time LM at which the fuel pressure PF is reduced corresponds to the first injection. The fuel injection in the period after the ignitability limit injection end time LM corresponds to the second injection.

- The second injection amount QI may be calculated based only on either the engine load factor KL or the intake air temperature THA. Further, the second injection amount QI may be calculated without being based on either the engine load factor KL or the intake air temperature THA. Furthermore, the second injection amount QI may be a fixed value.

- The adjustment process may be performed regardless of whether fuel injection is performed in the latter half of the compression stroke immediately before ignition. That is, even when the required injection period TS is shorter than the ignition limit injection period TT, the fuel pressure PF may be adjusted by the adjustment process.

- The injection speed of the second injection may be variably set according to the operating condition of the engine 10. By adjusting the injection speed of the second injection according to the operating condition of the engine 10, a layer with a fuel concentration that can be ignited more reliably can be formed around the spark plug 19 at the time of ignition.

- As shown in FIG. 6, the first injection and the second injection may be performed. 6(A) shows the transition of the implementation status of fuel injection, FIG. 6(B) shows the transition of the fuel pressure PF, FIG. 6(C) shows the transition of the lift amount of the needle valve 30, and FIG. 6(D) shows the transition of the fuel injection status. Each figure shows the change in momentum of the spray. The injector 18 injects fuel by lifting the needle valve 30 and opening the nozzle 32 by the electromagnetic attraction force generated when the electromagnetic solenoid 31 is energized. The needle valve 30 is lifted against the fuel pressure PF in the injector 18 and the spring force of the needle spring 33. Therefore, a certain amount of time is required from the start of energization of the electromagnetic solenoid 31 until the needle valve 30 is fully opened. In the following description, the lift amount of the needle valve 30 when fully open is referred to as full lift amount MAX. Further, the period from the start of fuel injection until the lift amount of the needle valve 30 reaches the full lift amount MAX is referred to as a partial lift period, and the injection period after reaching the full lift amount MAX is referred to as a full lift period. In the case of FIG. 6, the first injection period TM is longer than the partial lift period, and the second injection period TI is shorter than the partial lift period. During the partial lift period, the injection port 32 is not fully opened and the resistance during injection is large, so the fuel injection speed is lower than during the full lift period. Therefore, if the injection is completed within the partial lift period, a small amount of fuel can be injected at a low injection speed. Fuel injection completed within such a partial lift period is called partial lift injection. In contrast, fuel injection that continues until the full-lift period is called full-lift injection. Note that partial lift injection is fuel injection in which the needle valve 30 does not fully open during injection, and full lift injection is fuel injection in which the needle valve 30 does not fully open during injection. In the case of FIG. 6, the first injection is performed by full-lift injection, and the second injection is performed by partial-lift injection. As shown in FIG. 6(D), since the fuel spray of the second injection has a small momentum, it tends to stay around the spark plug 19 during ignition. In this way, by performing the first injection using full lift injection and the second injection using partial lift injection, the second injection can be performed at a lower injection speed than the first injection. In this case, the injection speed can be changed while keeping the fuel pressure PF constant. Therefore, it is possible to carry out an adjustment process in which the injection speed of the second injection is made lower than that of the first injection without providing the fuel pressure adjustment device 29 in the fuel system.

- The fuel injection control in the above embodiment may also be applied to engines that use fuels other than hydrogen gas.
<Additional notes>
The technical ideas that can be understood from the above embodiment and modification examples will be described.

[Additional note 1] A device for controlling a spark ignition engine having an injector that injects fuel into a cylinder, the second injection being the fuel injection in the latter half of the compression stroke, and the fuel in the period before the second injection. An engine control device that performs adjustment processing to make the injection speed of the second injection lower than the first injection when performing the first injection.

[Additional note 2] The adjustment process includes performing the first injection by full lift injection in which the needle valve of the injector fully opens, and performing the second injection by partial lift injection in which the needle valve does not fully open. The engine control device according to [Appendix 1], which is performed in [Appendix 1].

[Additional Note 3] The engine control device according to [Additional Note 1], wherein a period in which fuel injection is not performed is set between the first injection and the second injection.
[Appendix 4] The engine control device according to any one of [Appendix 1] to [Appendix 3], wherein the fuel injection amount of the second injection is set based on the intake air filling rate of the cylinder.

[Appendix 5] The engine control device according to any one of [Appendix 1] to [Appendix 4], wherein the fuel injection amount of the second injection is set based on intake air temperature.

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

Claims (5)

A device for controlling a spark ignition engine having an injector that injects fuel into a cylinder,
When performing a second injection that is fuel injection in the latter half of the compression stroke and a first injection that is fuel injection before the second injection, the injection speed of the second injection is lower than that of the first injection. An engine control device that performs adjustment processing. The adjustment process is performed by performing the first injection by full lift injection in which the needle valve of the injector fully opens, and performing the second injection by partial lift injection in which the needle valve does not fully open. Item 1. The engine control device according to item 1. The engine control device according to claim 1, wherein a period in which no fuel injection is performed is set between the first injection and the second injection. The engine control device according to claim 1, wherein the fuel injection amount of the second injection is set based on the intake air filling rate of the cylinder. The engine control device according to claim 1, wherein the fuel injection amount of the second injection is set based on the intake air temperature of the engine.

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