Engine control unit

Abstract

To secure ignitability of fuel.SOLUTION: An electronic control unit 20 for controlling a spark-ignition type engine 10 including an injector 18 for injecting fuel into a cylinder 11 performs adjustment processing of lowering an injection velocity of second injection so as to be slower than that of first injection when performing the second injection in a latter period of a compression stroke and the first injection that is fuel injection prior to the second injection.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an engine control device for controlling a spark ignition engine with direct cylinder injection. [Background technology]

[0002] A known example of such an engine control device is the device described in Patent Document 1. The control device described in this document performs a second injection later in the compression stroke after the first injection, which is the main fuel injection, to form layers of a mixture with a high fuel concentration near the cylinder bore and near the spark plug. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-22665 Summary of the Invention [Problem to be solved by the invention]

[0004] Even if a second injection is performed, if the injection is too strong, the spray may not remain around the spark plug. In such cases, the fuel concentration around the spark plug at the time of ignition becomes lean, and the ignition ability of the mixture deteriorates. [Means for solving the problem]

[0005] The engine control device that solves the above problem is a device for controlling a spark-ignition engine having an injector that injects fuel into a cylinder. When 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, are performed, the engine control device performs an adjustment process to make the injection velocity of the second injection lower than that of the first injection.

[0006] In the engine control device, low-speed fuel injection is performed in the latter half of the compression stroke. The momentum of the fuel spray injected at low speed is small, so it tends to remain around the spark plug. Therefore, if low-speed fuel injection is performed in the latter half of the compression stroke, a layer of a fuel-rich mixture is formed around the spark plug at the time of ignition. Therefore, the engine control device has the effect of improving the ignition performance of the engine.

[0007] One example of the adjustment process is to perform a first injection using full-lift injection, where the needle valve is fully open, and a second injection using partial-lift injection, where the needle valve is not fully open. When the needle valve is not fully open, the injection resistance is large, which reduces the injection speed of the injector. 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.

[0008] In some cases, it may not be possible to change the injection speed while fuel injection is continuing. Also, changing the injection speed while fuel injection is continuing may result in large variations in the fuel injection amount. Even in such cases, if a period in which fuel is not injected is set between the first and second injections, the injection speed can be changed appropriately.

[0009] Even if the fuel injection amount of the second injection is constant, if the density of 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 density is low. Therefore, it is desirable to change the fuel injection amount of the second injection according to the intake air density in the cylinder. Note that the intake air density in the cylinder changes depending on the intake air filling rate of the 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 in 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. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a schematic configuration of an embodiment of an engine control device; [Figure 2] 1 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 part of the compression stroke. FIG. [Figure 3] 4 is a flowchart of a fuel injection control routine executed by the engine control device. [Figure 4] 10A is a time chart showing the progress of fuel injection in the engine control device when the required injection period is longer than the ignition limit injection period, (B) is a time chart showing the progress of fuel pressure, (C) is a time chart showing the progress of spray momentum, and (D) is a time chart showing the progress of fuel injection when fuel injection is performed from the earliest injection start timing while maintaining the fuel pressure at the standard fuel pressure in the above case. [Figure 5] In another embodiment of the engine control device, (A) is a time chart showing the progress of the fuel injection implementation status, (B) is a time chart showing the progress of the fuel pressure, and (C) is a time chart showing the progress of the spray momentum when the required injection period is longer than the ignition limit injection period. [Figure 6] FIG. 10 is a time chart showing, in another embodiment of the engine control device, the transition of the fuel injection implementation status when the required injection period is longer than the ignition limit injection period. (A) shows the transition of the fuel pressure, (B) shows the transition of the needle valve lift amount, and (D) shows the transition of the spray momentum. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of an engine control device will be described in detail below with reference to FIGS. <Configuration of engine control unit> First, the configuration of the engine control device of this embodiment will be described with reference to Figure 1. An engine 10, which is the object of control by the engine control device of this embodiment, is mounted on a vehicle. The engine 10 is configured as a hydrogen gas engine that uses hydrogen gas as fuel.

[0012] An engine 10 has one or more cylinders 11. A piston 12 is arranged inside the cylinder 11 so that it can reciprocate up and down in the drawing. A combustion chamber 13 where combustion takes place is defined inside the cylinder 11 by the piston 12. An intake port 15 is connected to the top of the cylinder 11 via an intake valve 14. An exhaust port 17 is also connected to the top of the cylinder 11 via an exhaust valve 16. Furthermore, an injector 18 that injects hydrogen gas into the cylinder 11 and an ignition plug 19 that ignites the hydrogen gas injected by the injector 18 are installed above the cylinder 11.

[0013] The injector 18 is connected to a fuel tank 28 that stores hydrogen gas via a fuel pressure regulator 29. The fuel pressure regulator 29 regulates the fuel pressure PF, which is the pressure of the hydrogen gas supplied to the injector 18. The fuel pressure regulator 29 reduces the pressure of the hydrogen gas in the fuel tank 28 and supplies it to the injector 18. The fuel pressure regulator 29 is configured to be able to change the fuel pressure PF within a range equal to or less than the tank internal pressure PT.

[0014] As shown in FIG. 2 , the injector 18 includes a needle valve 30, an electromagnetic solenoid 31, a nozzle 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 outlet that connects the inside and outside of the injector 18. The injector 18 is mounted to the engine 10 with the nozzle 32 exposed in the combustion chamber 13. The needle valve 30 is a valve body that opens and closes the nozzle 32. When energized, the electromagnetic solenoid 31 generates an electromagnetic attractive force that drives the needle valve 30 to open the nozzle 32. The needle spring 33 is a spring that biases the needle valve 30 to close the nozzle 32. In this injector 18, the injection speed of fuel from the nozzle 32 when the needle valve 30 is fully open varies in conjunction with the fuel pressure PF.

[0015] 1, the electronic control unit 20 that controls the engine 10 includes an arithmetic processing device 21 and a storage device 22. The storage device 22 stores programs and data used for control. The arithmetic processing device 21 executes the programs read from the storage device 22 to perform various processes related to the control of the engine 10. In this embodiment, the electronic control unit 20 corresponds to an engine control device.

[0016] The electronic control unit 20 is connected to 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. The crank angle sensor 23 detects the rotational phase of the crankshaft of the engine 10. The air flow meter 24 detects the intake air flow rate GA of the engine 10. The intake air temperature sensor 25 detects the intake air temperature THA of the engine 10. The accelerator pedal sensor 26 detects the accelerator pedal depression amount ACC by the driver. The tank pressure sensor 27 detects the 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. The electronic control unit 20 also determines the engine load factor KL based on the intake air flow rate GA and the engine rotation speed NE detected by the air flow meter 24. The engine load factor KL represents the intake air filling rate of the cylinder 11.

[0017] <Fuel injection control> The electronic control unit 20 controls fuel injection by the injector 18 as part of the control of the engine 10. The electronic control unit 20 controls fuel injection through the operation of the injector 18 and a fuel pressure regulator 29.

[0018] Note that the values ​​for each time period shown below represent the amount of advancement of the rotation angle of the crankshaft, which is the output shaft of the engine 10, from top dead center of the compression stroke. Therefore, times with larger values ​​are earlier than times with smaller values. Also, the values ​​for each period shown below represent the amount of change in the rotation angle of the crankshaft during that period. Therefore, even if the length of the period is constant, when the engine rotation speed NE is high, the actual time of the period will be shorter than when the engine rotation speed NE is low.

[0019] During fuel injection control, the electronic control unit 20 first calculates a required injection amount QS, which is the amount of fuel required to generate the driving force required by the driver. Next, the electronic control unit 20 calculates a required injection period TS, which is the fuel injection period required to inject fuel equivalent to the required injection amount QS. The electronic control unit 20 then controls fuel injection by operating the injector 18 to inject fuel for 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 rotation speed NE is high than when it is low. Furthermore, even if the required injection amount QS is constant, the required injection period TS is longer when the fuel pressure PF is low than when the fuel pressure PF is high.

[0020] On the other hand, there are limitations to accelerating the start of fuel injection, such as preventing backflow of fuel into the intake system. Therefore, depending on the operating conditions of the engine 10, the required injection period TS may be extended, and fuel injection may need to continue until the latter part of the compression stroke just before ignition. Incidentally, hydrogen gas has a lower fuel density than liquid fuels such as gasoline. Therefore, in an engine 10 that uses hydrogen gas as fuel, the operating range of the engine 10 in which fuel injection ends just before ignition is generally wider than in an engine that uses liquid fuel.

[0021] FIG. 2 shows the state inside the cylinder 11 just before ignition when fuel injection continues until the latter part of the compression stroke. In this case, the time between the end of fuel injection and ignition is short, so the fuel is not sufficiently mixed into the intake air. In addition, the flow field F formed inside the cylinder 11 by the injection washes away the fuel spray L from the area around the spark plug 19. Therefore, if fuel injection ends late in the compression stroke, the fuel concentration around the spark plug 19 at the time of ignition decreases, resulting in poor ignition of the hydrogen gas. Note that the higher the injection velocity of the hydrogen gas from the injector 18, the stronger the flow field F formed inside the cylinder 11 by the injection. Therefore, poor ignition when fuel injection ends late in the compression stroke becomes more likely the higher the injection velocity of the hydrogen gas from the injector 18.

[0022] The electronic control unit 20 basically operates the fuel pressure regulator 29 to set the fuel pressure PF to the predetermined standard fuel pressure PS. When fuel injection is performed with the fuel pressure PF set to the standard fuel pressure PS, the above-mentioned deterioration in ignition quality occurs if the fuel injection end timing is later than a predetermined timing. In the following description, the predetermined timing, which is the boundary between whether or not the deterioration in ignition quality occurs, is referred to as the ignition limit injection end timing LM. In the following description, the timing that is the limit on the advance side of the fuel injection start timing is referred to as the earliest injection start timing SO. The period from the earliest injection start timing SO to the ignition limit injection end timing LM is referred to as the ignition limit injection period TT. If the required injection period TS is longer than the ignition limit injection period TT, the fuel injection end timing will be later than the ignition limit injection end timing LM.

[0023] <Fuel injection control routine> The electronic control unit 20 controls fuel injection so as to suppress the deterioration of ignition quality as described above. Hereinafter, the fuel injection control for suppressing the deterioration of ignition quality will be described in detail.

[0024] 3 shows the 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 this routine at each predetermined control cycle while the engine 10 is operating. After completing the processing of step S140 or step S190 in FIG. 3, the electronic control unit 20 ends the series of processing of this routine for the corresponding control cycle.

[0025] When this routine starts, the electronic control unit 20 first calculates the required injection amount QS based on the accelerator pedal depression amount ACC and the vehicle speed V in step S100. Next, the electronic control unit 20 calculates the required injection period TS based on the required injection amount QS and the engine rotation speed NE in step S110. In step S110, the electronic control unit 20 calculates the fuel injection period of the injector 18 that can inject fuel equivalent to the required injection amount QS when the fuel pressure PF is set to the standard fuel pressure PS as the value of the required injection period TS. Then, in the following step S120, the electronic control unit 20 determines whether the required injection period TS is longer than the ignition limit injection period TT.

[0026] If the required injection period TS is equal to or shorter than the ignition limit injection period TT (S120: NO), the electronic control unit 20 proceeds to step S130. In step S130, the electronic control unit 20 sets the ignition limit injection end time LM as the value of the injection end time EC. Also 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 required injection period TS. Then, in the following step S140, the electronic control unit 20 commands the injector 18 to perform single-stage injection from the injection start time SC to the injection end time EC. That is, at this time, the electronic control unit 20 operates the injector 18 so that fuel injection of the required injection amount QS by single-stage injection is completed at the ignition limit injection end time LM. At this time, the electronic control unit 20 operates the fuel pressure regulator 29 to maintain the fuel pressure PF at the standard fuel pressure PS.

[0027] 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 proceeds 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. Furthermore, in step S150, the electronic control unit 20 calculates the difference between the required injection amount QS and the second injection amount QI 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, the value is larger than when it is low, and when the intake air temperature THA is low, the value is larger than when it is high.

[0028] Next, in step S160, the electronic control unit 20 calculates the second injection period TI, the second injection start time SI, and the fuel pressure reduction command time AP. The second injection period TI represents the fuel injection period of the injector 18 required to inject fuel of the second injection amount QI at the current engine speed NE when the fuel pressure PF is set to a predetermined low fuel pressure PI lower than the standard fuel pressure PS. The electronic control unit 20 calculates the second injection period TI based on the second injection amount QI and the engine speed NE. The electronic control unit 20 also calculates the second injection start time SI to be earlier than the second injection end time EI by the second injection period TI. The second injection end time EI is set to be earlier than the end of the compression stroke by a predetermined margin period. The margin period represents the period from when the electronic control unit 20 issues a command to end fuel injection to when the injector 18 actually stops fuel injection. Furthermore, the electronic control unit 20 calculates the fuel pressure decrease command timing AP to be earlier than the second injection start timing SI by a predetermined fuel pressure adjustment period TP. The fuel pressure adjustment period TP represents the period required from when the electronic control unit 20 commands the fuel pressure regulator 29 to decrease the fuel pressure PF from the standard fuel pressure PS to the low fuel pressure PI until the fuel pressure PF actually reaches the low fuel pressure PI.

[0029] 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 fuel of the first injection amount QM when the fuel pressure PF is set to the standard fuel pressure PS at the current engine speed NE. The electronic control unit 20 calculates the value of the first injection period TM based on the first injection amount QM and the engine speed NE. The electronic control unit 20 also calculates the value of the first injection end time EM as the value of the first injection end time EM. One of the two timings is the fuel pressure reduction command timing AP, and the other is a timing earlier than the second injection start time SI by a predetermined injection interval INT. The injection interval INT represents the period from when the injector 18 stops fuel injection until when it can resume fuel injection. The electronic control unit 20 then calculates the value of the first injection start time SM to be earlier than the first injection end time EM by the first injection period TM.

[0030] Then, in step S180, the electronic control unit 20 commands the fuel pressure regulator 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 regulator 29 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. Then, the fuel pressure regulator 29 increases the fuel pressure PF from the low fuel pressure PI to the standard fuel pressure PS at the subsequent second injection end timing EI. In this embodiment, the processing of step S180 corresponds to the adjustment processing.

[0031] Then, in the next step S190, the electronic control unit 20 commands the injector 18 to perform a first injection and a second injection. The first injection is fuel injection during the period from first injection start time SM to first injection end time EM. The second injection is fuel injection during the period from second injection start time SI to second injection end time EI in the latter part 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 time AP. Therefore, the first injection is performed with the fuel pressure PF at the standard fuel pressure PS, and the second injection is performed with the fuel pressure PF at 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 hydrogen gas in the second injection is lower than that in the first injection.

[0032] <Actions and Effects of the Embodiment> The operation and effect of this embodiment will be described with reference to Figure 4. Figures 4(A) to 4(C) show an example of the 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. Figure 4(A) shows the transition of the fuel injection implementation status, Figure 4(B) shows the transition of the fuel pressure PF, and Figure 4(C) shows the transition of the momentum of the fuel spray.

[0033] FIG. 4D also shows the implementation status of fuel injection when fuel injection is started at the earliest injection start time S0 while the fuel pressure PF is maintained at the standard fuel pressure PS when the required injection period TS is longer than the ignition limit injection period TT. As described above, in engine 10, the timing at which fuel injection can start is limited to a time after the earliest injection start time S0. Meanwhile, the ignition limit injection period TT is set to the period from the earliest injection start time S0 to the ignition limit injection end time LM. Therefore, in this case, the timing at which fuel injection of the required injection amount QS is completed is later than the ignition limit injection end time LM. In other words, in this case, fuel injection at the standard fuel pressure PS is performed until just before ignition, which is likely to cause a deterioration in ignition quality.

[0034] In contrast, the engine control device of this embodiment injects fuel equivalent to the required injection amount QS through the first injection and the second injection in the above case. The second injection is a small amount of fuel injected in the latter half of the compression stroke just before ignition. The first injection is a fuel injection performed before the second injection. The second injection is performed with a slower injection speed of hydrogen gas than the first injection. That is, in this embodiment, when fuel injection ends in the latter half of the compression stroke just before ignition, the second injection, with a slower injection speed of hydrogen gas, is performed just before ignition. The fuel spray injected at a low speed in the second injection has a small momentum as shown in FIG. 4(C), and therefore is more likely to remain around the spark plug 19 at the time of ignition. Therefore, even when fuel injection continues until just before ignition, ignition can be ensured by performing the second injection at a low injection speed in the latter half of the compression stroke.

[0035] 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 second injection amount QI to an amount that allows a layer of a mixture with an ignitable fuel concentration to be formed around the spark plug 19 at the time of 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 the density is low. The density of the intake air in the cylinder 11 increases as the intake air filling rate of the cylinder 11, i.e., the engine load factor KL, increases. Furthermore, the intake air density in the cylinder 11 increases as the intake air temperature THA decreases. Therefore, by setting the second injection amount QI to an amount that increases as the engine load factor KL increases and 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 concentration suitable for ignition.

[0036] The engine control device of this embodiment described above has the following advantages. (1) When fuel injection is required until the latter part of the compression stroke, the electronic control unit 20 performs a second injection in the latter part of the compression stroke and a first injection in a period before the second injection. The electronic control unit 20 then performs an adjustment process to make the injection speed of the second injection slower than that of the first injection. Therefore, ignition performance is less likely to deteriorate even when fuel injection is performed until just before ignition.

[0037] (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 ignition limit injection period TT. If the required injection period TS is shorter than the ignition limit injection period TT, fuel injection for the required injection amount QS can be completed earlier than the ignition limit injection end timing LM. In such cases, ignitability can be ensured without performing the adjustment process. Therefore, the adjustment process can be performed only when ignitability is likely to deteriorate.

[0038] (3) The electronic control unit 20 sets a period during which fuel is not injected between the first and second injections. That is, when fuel is injected until just before ignition, the electronic control unit 20 injects fuel in an amount equal to the required injection amount QS in two separate injections, the first injection and the second injection. If the fuel pressure PF is changed to change the injection speed while fuel injection is ongoing, the variation in the fuel injection amount increases. In this regard, if a period during which fuel is not injected between the first and second injections is set, the fuel pressure PF can be adjusted during that period. Therefore, the increase in the variation in the fuel injection amount due to the adjustment of the fuel pressure PF is suppressed.

[0039] (4) The electronic control unit 20 calculates the second injection amount QI based on the intake air filling rate and the intake air temperature THA of the cylinder 11. Therefore, in the second injection, an appropriate amount of fuel that can ensure ignition can be injected.

[0040] <Other Examples> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0041] The fuel pressure reduction command timing AP may be set in a manner other than the above. For example, the ignition limit injection end timing LM may be set as the fuel pressure reduction command timing AP. In any case, if the second injection, which is performed in the latter half of the compression stroke immediately before ignition, is performed at a lower injection speed than the first injection, deterioration of ignition can be suppressed.

[0042] As shown in FIG. 5, the first injection and the second injection may be performed as a continuous series of fuel injections. FIG. 5 illustrates an example of a fuel injection control implementation when the required injection period TS is longer than the ignition limit injection period TT. More specifically, FIG. 5(A) illustrates the transition of the fuel injection implementation status, FIG. 5(B) illustrates the transition of the fuel pressure PF, and FIG. 5(C) illustrates 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. The electronic control unit 20 then continues fuel injection until a time later than the ignition limit injection end time LM. As shown in FIG. 5(B), the electronic control unit 20 reduces the fuel pressure PF from the standard fuel pressure PS to the low fuel pressure PI at the ignition limit injection end time LM. Therefore, as shown in FIG. 5(C), the momentum of the fuel spray decreases in the latter part of the compression stroke immediately before ignition. Therefore, even in this case, deterioration of ignition quality is suppressed. In this case, the fuel injection before the ignition limit injection end time LM at which the fuel pressure PF is reduced corresponds to the first injection, and the fuel injection after the ignition limit injection end time LM corresponds to the second injection.

[0043] The second injection amount QI may be calculated based on only one of the engine load factor KL and the intake air temperature THA. The second injection amount QI may also 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.

[0044] The adjustment process may be performed regardless of whether fuel injection is performed in the latter part of the compression stroke immediately before ignition. In other words, the adjustment process may be performed to adjust the fuel pressure PF even when the required injection period TS is shorter than the ignition limit injection period TT.

[0045] The injection speed of the second injection may be variably set according to the operating conditions of the engine 10. By adjusting the injection speed of the second injection according to the operating conditions of the engine 10, it becomes possible to more reliably form a layer of ignitable fuel concentration around the spark plug 19 at the time of ignition.

[0046] As shown in Figure 6, first and second injections may be performed. Figure 6(A) shows the progress of fuel injection, Figure 6(B) shows the progress of fuel pressure PF, Figure 6(C) shows the progress of lift of needle valve 30, and Figure 6(D) shows the progress of momentum of fuel spray. The injector 18 injects fuel by lifting the needle valve 30 and opening the nozzle 32 using electromagnetic attraction force generated by the electromagnetic solenoid 31 when it 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, it takes some time from the start of energization of the electromagnetic solenoid 31 until the needle valve 30 is fully opened. In the following explanation, the lift of the needle valve 30 when fully opened will be referred to as full lift amount MAX. 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 the partial lift period, and the injection period after the full lift amount MAX is reached is referred to as the full lift period. In 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 open, and resistance during injection is large, resulting in a lower fuel injection speed than during the full lift period. Therefore, if injection is completed within the partial lift period, a small amount of fuel can be injected at a low injection speed. Such fuel injection that is completed within the 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 reach full opening during injection, while full lift injection is fuel injection in which the needle valve 30 reaches full opening during injection. In FIG. 6, the first injection is performed by full lift injection, and the second injection is performed by partial lift injection. As shown in Figure 6(D), the fuel spray in the second injection has a small momentum, so it is more likely to remain around the spark plug 19 during ignition. In this way, 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. In this case, the injection speed can be changed while maintaining the fuel pressure PF constant.Therefore, without providing a fuel pressure regulator 29 in the fuel system, it is possible to carry out an adjustment process to make the injection speed of the second injection slower than that of the first injection.

[0047] 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 concepts that can be understood from the above-described embodiments and modifications will be described below.

[0048] [Appendix 1] An engine control device for controlling a spark ignition engine having an injector that injects fuel into a cylinder, which performs an adjustment process to make the injection speed of the second injection slower than that of the first injection when a second injection, which is a fuel injection in the latter part of the compression stroke, and a first injection, which is a fuel injection in a period before the second injection, are performed.

[0049] [Appendix 2] The engine control device described in [Appendix 1], wherein the adjustment process is performed by performing the first injection by full lift injection in which the needle valve of the injector reaches full opening, and performing the second injection by partial lift injection in which the needle valve does not reach full opening.

[0050] [Appendix 3] The engine control device according to [Appendix 1], wherein a period in which no fuel injection is 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.

[0051] [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 the intake air temperature. [Explanation of symbols]

[0052] 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...Processing device 22…Storage device 23...Crank angle sensor 24...Air flow meter 25...Intake air 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…spout 33...Needle spring

Claims

1. A device for controlling a spark ignition engine having an injector that injects hydrogen gas as fuel into a cylinder, When a second injection, which is a fuel injection in the latter part of the compression stroke, and a first injection, which is a fuel injection prior to the second injection, are performed, an adjustment process is performed to make the injection speed of the second injection lower than that of the first injection, The adjustment process is performed by performing the first injection by full lift injection in which the needle valve of the injector reaches full opening, and by performing the second injection by partial lift injection in which the needle valve does not reach full opening. Engine control device.

2. A device for controlling a spark ignition engine having an injector that injects hydrogen gas as fuel into a cylinder, When a second injection, which is a fuel injection in the latter part of the compression stroke, and a first injection, which is a fuel injection prior to the second injection, are performed, an adjustment process is performed to make the injection speed of the second injection lower than that of the first injection, A required injection amount, which is the amount of fuel injection required to generate the driving force required by the driver, is calculated, and a second injection amount, which is the fuel injection amount of the second injection, is calculated so as to be larger when the engine load factor is high than when it is low, and a first injection amount, which is the fuel injection amount of the first injection, is set to a value obtained by subtracting the second injection amount from the required injection amount. Engine control device.

3. A device for controlling a spark ignition engine having an injector that injects hydrogen gas as fuel into a cylinder, When a second injection, which is a fuel injection in the latter part of the compression stroke, and a first injection, which is a fuel injection prior to the second injection, are performed, an adjustment process is performed to make the injection speed of the second injection lower than that of the first injection, A required injection amount, which is the amount of fuel injection required to generate the driving force required by the driver, is calculated, and a second injection amount, which is the fuel injection amount of the second injection, is calculated so as to be larger when the intake air temperature is low than when it is high, and a first injection amount, which is the fuel injection amount of the first injection, is set to a value obtained by subtracting the second injection amount from the required injection amount. Engine control device.

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