Fuel injection control device and program

Abstract

To properly execute re-energization control when a fuel injection valve is closed.SOLUTION: The fuel injection system includes a fuel injection valve 50 for injecting gas fuel, and a drive circuit for opening the fuel injection valve 50. The drive circuit includes a low-voltage power supply 64 and a boosting power supply 65. The microcomputer 61 of the ECU60 includes a re-energization control unit configured to be capable of executing first re-energization in which re-energization of the solenoid is executed by the low-voltage power source 64 and second re-energization in which re-energization of the solenoid is executed by the boost power source 65 during a valve closing operation of the valve body accompanying the end of injection of the fuel injection valve 50, and a parameter acquiring unit configured to acquire an influence parameter in which variation of a valve closing timing at which the valve body reaches a valve closing position at the time of closing of the fuel injection valve 50 affects an actual injection amount; The re-energization control unit selectively executes the first re-energization and the second re-energization based on the influence parameter acquired by the parameter acquisition unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The disclosure in this specification relates to a fuel injection control device and a program for an internal combustion engine. [Background technology]

[0002] Gas engines that burn gaseous fuel use a fuel injection valve for gaseous fuel, which injects the gaseous fuel. In the fuel injection valve, a valve element is biased to the valve closing side by a spring, and fuel is injected by lifting the valve element to the valve opening side when current is applied to the solenoid. After the solenoid is de-energized following the end of fuel injection, the valve element returns to the valve closing position due to the biasing force of the spring.

[0003] Because gaseous fuel has a lower energy density than liquid fuel, a large flow rate of gaseous fuel must be injected to ensure sufficient engine output. In this case, increasing the injection rate requires increasing the lift of the valve element in the fuel injection valve. Additionally, gaseous fuel has inferior lubricity compared to liquid fuel. For these reasons, concerns remain about wear on the valve element seat and increased driving noise caused by the impact that occurs when the valve closes after fuel injection.

[0004] To address this issue, there is a technology in which the solenoid of the fuel injection valve is re-energized after fuel injection from the fuel injection valve until the valve disc reaches the valve closing position, generating a force in the opposite direction to the valve closing direction, thereby slowing the valve disc closing speed (see, for example, Patent Document 1).This technology mitigates the impact on the valve disc when it closes, reducing wear on the valve disc seat and drive noise. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent Application Publication No. 102022200710 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology for re-energizing the fuel injection valve after fuel injection as described above, there is a concern that if the solenoid is not re-energized at the appropriate timing after the solenoid for fuel injection has stopped being energized, the valve closing speed of the valve disc may not be reduced appropriately. In this regard, the technology described in Patent Document 1 detects the valve closing timing when the valve disc reaches the closed position in the fuel injection valve, and controls the timing of re-energizing the solenoid by feedback control based on that valve closing timing. Specifically, the valve disc in the fuel injection valve has a two-member separate structure with a large overstroke, which increases the change in the current waveform when the valve is closed, and the valve closing timing is detected based on this change point.

[0007] However, fuel injection valves do not necessarily have a configuration for detecting the valve closing timing of the valve body, and if such a configuration is not provided, there is a concern that a deviation in the timing of re-energization will occur.

[0008] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a fuel injection control device and a program that can appropriately execute re-energization control when a fuel injection valve is closed. [Means for solving the problem]

[0009] The present disclosure provides: a fuel injection valve having a solenoid that drives a valve element to open against the biasing force of a spring when energized, and that injects gas fuel when the valve element opens; a drive circuit that applies a voltage to the solenoid to drive the fuel injection valve to open, the drive circuit being applied to a fuel injection system having a low-voltage power supply that can output a battery voltage and a boost power supply that can output a boosted voltage obtained by boosting the battery voltage, and controlling the opening and closing of the fuel injection valve, a re-energization control unit that, when the valve body closes due to the end of injection from the fuel injection valve, enables a first re-energization of the solenoid by the low-voltage power supply during a first energization period, and a second re-energization of the solenoid by the boost power supply during a second energization period that is shorter than the first energization period; a parameter acquisition unit that acquires an influence parameter that indicates an influence of a variation in valve closing timing at which the valve element reaches a valve closing position when the fuel injection valve is closed, on an actual injection amount; Equipped with The reenergization control unit selectively executes the first reenergization and the second reenergization based on the influence parameter acquired by the parameter acquisition unit.

[0010] In the fuel injection control device configured as described above, the solenoid is re-energized when the valve element closes due to the de-energization of the solenoid in the fuel injection valve. This reduces the valve closing speed of the valve element, reducing wear on the valve element seat and drive noise. This effect is thought to be particularly noticeable in fuel injection valves that inject gas fuel, where the valve element has a large valve opening lift.

[0011] Furthermore, in the above configuration, when the valve disc closes following de-energization of the solenoid in the fuel injection valve, a first re-energization (battery energization) in which the solenoid is re-energized by a low-voltage power supply and a second re-energization (boost energization) in which the solenoid is re-energized by a boost power supply can be performed, and these first re-energization and second re-energization can be selectively performed. Comparing the first re-energization and the second re-energization, the first re-energization applies a relatively low attractive force for a relatively long period (first energization period), whereas the second re-energization applies a relatively high attractive force for a relatively short period (second energization period). Therefore, although the first re-energization has a low effect of reducing the velocity of the valve disc at the end of fuel injection, it suppresses a reduction in the velocity reduction effect due to variations in the valve disc closing timing. In contrast, in the second re-energization, unlike the first re-energization, the effect of reducing the velocity of the valve element at the end of fuel injection is enhanced, but there are concerns that the velocity reduction effect may be reduced or the valve element may be lifted again due to variations in the valve closing timing.

[0012] In this regard, an influence parameter indicating the influence of variations in the valve closing timing of the valve disc when the fuel injector is closed on the actual injection amount is acquired, and the first re-energization and the second re-energization are selectively performed based on the influence parameter. In this case, even if variations in the valve closing timing of the fuel injector occur, the influence on the actual injection amount can be reduced while the valve disc speed can be reduced. As a result, the re-energization control can be appropriately performed when the fuel injector is closed.

[0013] In the above fuel injection system, even if the valve closing timing of the valve body in the fuel injection valve is unknown, the influence of variations in valve closing timing can be reduced and the desired effect of reducing the valve closing speed can be obtained. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing the overall configuration of an engine fuel injection system. [Figure 2] FIG. 2 is a cross-sectional view showing the configuration of a fuel injection valve. [Figure 3] 6 is a time chart showing the transition of energization current when battery energization is performed as solenoid re-energization and when boost energization is performed; [Figure 4] 10A and 10B are diagrams for explaining differences in valve closing speed of the valve disc when variations occur in valve closing timing. [Figure 5] 4 is a flowchart showing a control procedure for fuel injection by a fuel injection valve. [Figure 6] FIG. 4 is a diagram showing the relationship between engine rotation speed, injection amount, and re-energization control mode. [Figure 7] FIG. 4 is a diagram showing the relationship between injection amount and interval time. [Figure 8] FIG. 10 is a diagram showing the relationship between the injection amount and the re-energization time. [Figure 9] FIG. 10 is a diagram showing the relationship between the interval time, the re-energization time, and the reduction correction amount. [Figure 10] FIG. 10 is a diagram showing the relationship between engine rotation speed, fuel pressure, and re-energization control mode in another example. [Figure 11]FIG. 4 is a diagram showing the relationship between fuel pressure and interval time. [Figure 12] FIG. 4 is a diagram showing the relationship between fuel pressure and re-energization time. [Figure 13] 10 is a flowchart showing a process for selecting a reenergization control mode. [Figure 14] FIG. 10 is a diagram showing the relationship between temperature and reenergization control mode. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described below with reference to the drawings. This embodiment is embodied as a fuel injection system applied to a gas engine that uses, for example, hydrogen gas as a gas fuel. The fuel injection system and the gas engine are mounted on, for example, a vehicle. An overall schematic diagram of this system is shown in Figure 1.

[0016] In Figure 1, engine 10 is a multi-cylinder internal combustion engine having multiple cylinders (for example, three cylinders), and its intake ports and exhaust ports are connected to an intake system 11 and an exhaust system 12, respectively. Intake system 11 has an intake manifold 13 and an intake pipe 14. Intake pipe 14 is provided with a throttle valve 15 as an air amount adjusting means. Throttle valve 15 is configured as an electronically controlled throttle valve whose opening is adjusted by a throttle actuator such as a DC motor, and the opening of throttle valve 15 (throttle opening) is detected by a throttle sensor 16. Engine 10 is also provided with a rotation sensor 17 that detects the rotation of the crankshaft.

[0017] The exhaust system 12 has an exhaust manifold 21 and an exhaust pipe 22. The exhaust pipe 22 is provided with an exhaust sensor 23 that detects exhaust components and a catalyst 24 that purifies the exhaust. Specifically, the exhaust sensor 23 is provided with an air-fuel ratio sensor that detects the air-fuel ratio from the oxygen concentration in the exhaust.

[0018] A fuel injection valve 50 that injects gas fuel is provided in each cylinder of the engine 10. The fuel injection valve 50 is an in-cylinder injection type fuel injection valve that directly injects gas fuel into a combustion chamber of the engine 10. The fuel injection valve 50 is supplied with gas fuel from the fuel supply unit 30, and the gas fuel is injected into the combustion chamber when the fuel injection valve 50 opens.

[0019] In the fuel supply unit 30, a fuel tank 32 is connected to the fuel injection valve 50 via a fuel pipe 31, and a regulator 33 is provided in the fuel pipe 31 to reduce and adjust the pressure of the gas fuel supplied to the fuel injection valve 50. The regulator 33 has a pressure adjustment function to reduce and adjust the pressure of the gas fuel stored in a high-pressure state in the fuel tank 32 to a predetermined pressure, and the gas fuel after the pressure reduction adjustment is supplied to the fuel injection valve 50 through the fuel pipe 31. In the fuel pipe 31, the upstream side of the regulator 33 is a high-pressure pipe section 31a that forms a high-pressure side passage, and the downstream side is a low-pressure pipe section 31b that forms a low-pressure side passage.

[0020] The low-pressure piping section 31b is provided with a shutoff valve 35. The shutoff valve 35 is opened, for example, by electromagnetic actuation. When the shutoff valve 35 is closed, the flow of gas fuel from the regulator 33 side to the fuel injection valve 50 side is blocked, and when the shutoff valve 35 is open, the flow of gas fuel from the regulator 33 side to the fuel injection valve 50 side is permitted.

[0021] In the fuel pipe 31, a pressure sensor 36 that detects the pressure (fuel pressure) of the gas fuel supplied to the fuel injection valve 50 and a temperature sensor 37 that detects the temperature of the gas fuel are provided in the low-pressure pipe section 31b. Note that a pressure sensor and a temperature sensor may also be provided in the high-pressure pipe section 31a in a similar manner.

[0022] Each cylinder of the engine 10 is provided with an ignition plug 40. A high voltage is applied to the spark plug 40 at the desired ignition timing through an ignition device 41, which is made up of an ignition coil and the like. The application of this high voltage causes a spark discharge between the opposing electrodes of each spark plug 40, igniting and burning gas fuel introduced into the cylinder (combustion chamber).

[0023] The configuration of the fuel injection valve 50 will now be described with reference to Figure 2. The fuel injection valve 50 has a cylindrical body 51, and a valve element 52 is housed in the hollow portion of the body 51 so as to be axially slidable. The hollow portion of the body 51 serves as a passage through which gas fuel flowing in from the fuel pipe 31 passes. A nozzle hole 53 is provided at the tip of the body 51, and the nozzle hole 53 is opened and closed by the valve element 52. The valve element 52 is biased in a valve closing direction, i.e., in a direction that closes the nozzle hole 53, by a spring 54 provided inside the body 51.

[0024] The valve element 52 is provided with a fuel passage 52a extending in the axial direction. The valve element 52 also has a core portion 52b. A fuel chamber 55 is formed within the body 51 so as to surround the tip portion of the valve element 52, and the fuel chamber 55 is connected to the fuel passage 52a of the valve element 52. The fuel injection valve 50 has a solenoid 56, which is an electromagnetic drive unit. When the solenoid 56 is energized in the fuel injection valve 50, the valve element 52 is displaced to an open position against the biasing force of the spring 54, and the nozzle hole 53 is opened. This causes gas fuel to be injected from the nozzle hole 53. When the solenoid 56 is de-energized, the biasing force of the spring 54 returns the valve element 52 to a closed position (seat position), and injection of gas fuel from the nozzle hole 53 is stopped.

[0025] As shown in FIG. 1, an ECU (Electronic Control Unit) 60 includes a microcomputer 61 for engine control, a driving IC 62 for driving the injector, and a power supply circuit 63 that is a driving power source for the fuel injection valve 50.

[0026] The microcomputer 61 is a computer equipped with a processor and a memory (storage unit) and provides various computational functions. The functions provided by the microcomputer 61 can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, when the microcomputer 61 is provided by a hardware electronic circuit, the function can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer 61 executes a program stored in a non-transitory tangible storage medium serving as a storage unit of the microcomputer 61. The program includes, for example, programs for various processes related to fuel injection control and ignition control. When the program is executed, a method corresponding to the program is performed. The storage unit is, for example, a non-volatile memory. Note that the program stored in the storage unit can be updated via a network such as the Internet. In this embodiment, the microcomputer 61 corresponds to a "fuel injection control device."

[0027] The microcomputer 61 calculates a required injection amount, which is the amount of fuel injected per injection, according to the engine operating conditions (for example, engine rotation speed, engine load, etc.), and generates an injection signal from the solenoid current conduction time calculated based on this required injection amount, and outputs it to the drive IC 62. The drive IC 62 and power supply circuit 63 correspond to a "drive circuit," which applies voltage to the solenoid 56 in response to the injection signal, driving the fuel injector 50 to open it. As a result, fuel equivalent to the required injection amount is injected from the fuel injector 50.

[0028] The power supply circuit 63 includes a low-voltage power supply 64 capable of outputting a battery voltage, a boost power supply 65 capable of outputting a boosted voltage obtained by boosting the battery voltage, and a voltage switching circuit 66. The low-voltage power supply 64 is, for example, a low-voltage output circuit that outputs the voltage (low voltage V1) of an in-vehicle 12V battery. The boost power supply 65 is, for example, a high-voltage output circuit that outputs a boosted voltage (high voltage V2) obtained by boosting the output voltage of the low-voltage power supply 64. The boost power supply 65 includes, for example, a capacitor that charges and discharges the boosted voltage obtained by boosting the battery voltage. The low voltage V1 of the low-voltage power supply 64 is, for example, 12V, and the high voltage V2 of the boost power supply 65 is, for example, 60 to 65V.

[0029] The voltage switching circuit 66 is a circuit that switches the drive voltage applied to the fuel injection valve 50 of each cylinder between a low voltage V1 and a high voltage V2. Specifically, by turning on and off a switching element (not shown), a drive current is supplied to the solenoid 56 of the fuel injection valve 50 from either the low voltage power supply 64 or the boost power supply 65.

[0030] When the fuel injector 50 is driven to open by the injection signal, a low voltage V1 and a high voltage V2 are applied to the fuel injector 50 in a time-series manner. In this case, the high voltage V2 is applied at the beginning of the valve opening to ensure the valve opening response of the fuel injector 50, and the low voltage V1 is subsequently applied to maintain the open state of the fuel injector 50.

[0031] However, since gas fuel has a lower energy density than liquid fuel, it is necessary to inject a large flow rate of gas fuel to ensure the output of the engine 10. In this case, to increase the injection rate, it is necessary to increase the lift amount of the valve element 52 in the fuel injection valve 50. In addition, gas fuel has inferior lubricity to liquid fuel. For these reasons, there are concerns that the fuel injection valve 50 for gas fuel may suffer wear of the valve element seat due to the impact when the valve closes after fuel injection, and that driving noise may increase.

[0032] Therefore, in this embodiment, after the solenoid 56 is de-energized at the end of injection from the fuel injection valve 50, the solenoid 56 is re-energized during the valve closing operation period until the valve element 52 reaches the valve closed position, generating a force in the opposite direction to the valve closing direction, thereby reducing the valve closing speed of the valve element 52.

[0033] In this embodiment, the solenoid can be re-energized after the injection signal of the fuel injection valve 50 is turned off by either battery energization (first re-energization) in which the solenoid 56 is re-energized by the low-voltage power supply 64 or boost energization (second re-energization) in which the solenoid 56 is re-energized by the boost power supply 65, and these battery energization and boost energization can be selectively performed.

[0034] 3 is a time chart showing changes in energizing current when battery energization is performed as solenoid re-energization and when boost energization is performed as solenoid re-energization in the fuel injection valve 50. The solid line indicates battery energization, and the dashed dotted line indicates boost energization.

[0035] When battery energization is performed as solenoid re-energization, battery energization by the low-voltage power supply 64 begins when interval time TA1 has elapsed since the end of injection energization (main energization). Battery energization is performed for a re-energization time TB1. On the other hand, when boost energization is performed as solenoid re-energization, boost energization by the boost power supply 65 begins when interval time TA2 has elapsed since the end of injection energization. Boost energization is performed for a re-energization time TB2. Note that the re-energization time TB1 during which battery energization is performed corresponds to the "first energization period," and the re-energization time TB2 during which boost energization is performed corresponds to the "second energization period."

[0036] Comparing battery energization and boost energization, with battery energization, the energization current is relatively low and the re-energization time TB1 is relatively long, so that a relatively low suction force is applied to the fuel injector 50 toward the anti-valve-closing side for a relatively long period of time. In contrast, with boost energization, the energization current is relatively high and the re-energization time TB2 is relatively short, so that a relatively high suction force is applied to the fuel injector 50 toward the anti-valve-closing side for a relatively short period of time. In this case, with battery energization, the speed reduction effect of the valve element 52 at the end of fuel injection is low, but a reduction in the speed reduction effect due to variations in the valve closing timing of the valve element 52 is suppressed. In contrast, with boost energization, contrary to battery energization, the speed reduction effect of the valve element 52 at the end of fuel injection is increased, but there are concerns about a reduction in the speed reduction effect and re-lifting of the valve element 52 due to variations in the valve closing timing of the valve element 52.

[0037] Fig. 4 is a diagram illustrating differences in the valve closing speed of the valve element 52 when variations in the valve closing timing occur in the fuel injection valve 50. In Fig. 4, the horizontal axis represents the magnitude of the variation in the valve closing timing, and the vertical axis represents the magnitude of the valve closing speed of the valve element 52 when the solenoid is re-energized at the end of injection. The valve closing speeds shown in Fig. 4 are the maximum values ​​of the valve closing speeds predicted when the valve element 52 is closed. The solid line represents the characteristics when battery current is applied, and the dashed dotted line represents the characteristics when boost current is applied.

[0038] 4, when the variation in the valve closing timing becomes large, the valve closing timing deviates from the appropriate timing, reducing the effect of reducing the speed of the valve element 52, and the valve closing speed is more likely to be high compared to when the variation in the valve closing timing is small. In this case, when the variation in the valve closing timing is small, the valve closing speed of the valve element 52 is lower with boost energization than with battery energization, while when the variation in the valve closing timing is large, the valve closing speed of the valve element 52 is more likely to be higher with boost energization than with battery energization.

[0039] Furthermore, when the solenoid is re-energized at the end of injection, the actual injection amount from the fuel injection valve 50 fluctuates due to the solenoid re-energization, and the amount of fluctuation in the actual injection amount depends on the valve disc closing speed. Here, when the fuel injection amount is small, the required accuracy of the fuel injection amount is higher than when the fuel injection amount is large, so it is undesirable for the valve disc closing speed to be excessively fast. On the other hand, when the fuel injection amount is large, the required accuracy of the fuel injection amount is lower than when the fuel injection amount is small, so there is a high tolerance for a fast valve disc closing speed. In other words, when variations in the valve closing timing affect the actual injection amount, the degree of the effect on the actual injection amount can vary depending on the fuel injection amount of the fuel injection valve 50.

[0040] Therefore, in this embodiment, an influence parameter that indicates the influence of variations in the valve closing timing of the valve element 52 at the end of fuel injection on the actual injection amount is acquired, and battery energization (first re-energization) and boost energization (second re-energization) are selectively performed based on the influence parameter. In this embodiment, the fuel injection amount per injection by the fuel injection valve 50 is used as the influence parameter. The details will be described below.

[0041] 5 is a flowchart showing a control procedure for fuel injection by the fuel injection valve 50. This process is repeatedly executed by the microcomputer 61 at a predetermined interval.

[0042] 5, in step S101, the engine rotation speed and the engine load are acquired as parameters indicating the engine operating state. The engine rotation speed is calculated from the detection signal of the rotation sensor 17, and the engine load is calculated from the detection signal of the throttle sensor 16. In step S102, a required injection amount is calculated based on the engine operating state using a predetermined map or the like. As is well known, for example, when the engine 10 is idling, the required injection amount is calculated as a minute injection amount, and when the throttle valve 15 is operated to the open side by the driver's accelerator operation or the like, the required injection amount is increased as the engine load increases.

[0043] Thereafter, in step S103, an injection signal is generated based on the required injection amount. The injection signal is generated based on the solenoid energization time determined by time-converting the required injection amount. The injection signal is a solenoid energization signal that energizes the solenoid 56 during the period from the start of valve opening to the start of valve closing after valve opening of the valve body 52 of the fuel injection valve 50.

[0044] Thereafter, in step S104, as an influence parameter, the required injection amount calculated in step S102 is acquired, and a re-energization control mode is determined based on the required injection amount. In the present embodiment, as the re-energization control mode, a non-execution mode in which solenoid re-energization is not executed, a battery energization mode in which solenoid re-energization is performed by battery voltage drive, and a boost energization mode in which solenoid re-energization is performed by boost voltage drive are selectively used, and in step S104, one of these three modes is determined.

[0045] For example, the re-energization control mode may be determined based on the relationship in FIG. 6. In FIG. 6, based on the engine rotational speed and the injection amount, the execution regions X0, X1, X2 of each mode are defined. In FIG. 6, the region where the engine rotational speed is equal to or higher than the threshold value A1 or the injection amount is less than the threshold value B1 is defined as the non-execution mode region X0. In other words, the region where the engine rotational speed is less than the threshold value A1 and the injection amount is equal to or higher than the threshold value B1 is the execution regions X1, X2 of solenoid re-energization.

[0046] Also, in the relationship of FIG. 6, in the execution region of solenoid re-energization (the region where the engine rotational speed < A1 and the injection amount ≧ B1), the region where the engine rotational speed is less than the threshold value A2 and the injection amount is equal to or higher than the threshold value B2 is the region X2 where boost energization is performed in the boost energization mode, and the other region is the region X1 where battery energization is performed in the battery energization mode. The relationship between the threshold values A1 and A2 is A1 > A2, and the relationship between the threshold values B1 and B2 is B1 < B2. It is also possible to determine the re-energization control mode based only on the injection amount among the engine rotational speed and the injection amount.

[0047] The minute injection amount when the engine is idling is preferably included in the region X1 where battery energization is performed. However, the minute injection amount when the engine is idling may also be included in the region X0 where solenoid re-energization is not performed.

[0048] After the process of step S104, in step S105, it is determined whether or not to re-energize the solenoid. At this time, if it is determined in step S104 that the re-energization control mode is the non-execution mode, the result of step S105 is negative and the process proceeds to step S106. In step S106, the injection signal generated in step S103 is output to the drive IC 62. As a result, during fuel injection, the fuel injector 50 is driven to open based on the injection signal generated in step S103.

[0049] If step S105 is positive, the process proceeds to step S107. In step S107, when solenoid re-energization is to be performed, it is determined whether re-energization is to be performed in the battery energization mode or the boost energization mode, depending on the re-energization control mode determined in step S104. In this case, if re-energization is to be performed in the battery energization mode, the process proceeds to step S108, and if re-energization is to be performed in the boost energization mode, the process proceeds to step S110.

[0050] In step S108, the interval time TA1 and the re-energization time TB1 are set as control conditions in the battery energization mode. At this time, the interval time TA1 is set based on the required injection amount using the relationship in Figure 7, and the re-energization time TB1 is set based on the required injection amount using the relationship in Figure 8.

[0051] In the fuel injection valve 50, the magnitude of the residual magnetic flux immediately after de-energization varies depending on the duration of energization of the solenoid 56, and the magnitude of the residual magnetic flux affects the valve closing speed. Specifically, in the region where the injection amount is small, the smaller the injection amount, the smaller the residual magnetic flux, and the faster the valve closing speed. In contrast, once the injection amount exceeds a predetermined amount, the residual magnetic flux saturates, and the effect of the saturated magnetic flux on the injection amount becomes constant. Therefore, in this embodiment, the interval time TA1 is set according to the required injection amount, taking into account that the residual magnetic flux at the time of valve closing changes depending on the required injection amount. In FIG. 7, a relationship is established such that, in the region where the injection amount is less than a predetermined value K, the interval time TA1 becomes shorter as the injection amount decreases, and in the region where the injection amount is equal to or greater than the predetermined value K, the interval time TA1 is constant regardless of the injection amount.

[0052] Furthermore, in the region where the injection amount is small, the tolerance for injection amount variation is small, so from the perspective of injection amount accuracy, it is desirable to reduce the degree of adjustment of the valve closing speed by re-energizing the solenoid. Therefore, in Figure 8, the relationship between the injection amount and the re-energizing time TB1 is defined such that the smaller the injection amount, the shorter the re-energizing time TB1.

[0053] Thereafter, in step S109, the energization time of the injection signal is corrected. In other words, when comparing the case where the solenoid is re-energized with the case where the solenoid is not re-energized, the closing timing of the valve element 52 is delayed when the solenoid is re-energized, and the actual fuel injection amount is increased accordingly. On the other hand, the required injection amount for generating the injection signal is calculated without considering whether the solenoid will be re-energized. Therefore, in step S109, the increase in the actual injection amount due to the solenoid being re-energized is reduced. Specifically, the energization time of the injection signal is corrected to be shorter. The amount of correction by which the energization time of the injection signal is reduced may be determined in advance based on compatibility or the like.

[0054] The amount of reduction correction for reducing the energization time of the injection signal may be variable depending on the degree of decrease in the valve closing speed of the valve element 52 due to the solenoid being re-energized. Specifically, the amount of reduction correction may be set using the relationship shown in FIG. 9. FIG. 9 defines a relationship in which the longer the re-energization time, the greater the amount of reduction correction. Also, FIG. 9 defines a relationship in which the shorter the interval time, the greater the amount of reduction correction.

[0055] In step S110, an interval time TA2 and a re-energization time TB2 are set as control conditions in the boost energization mode. At this time, the interval time TA2 is set based on the required injection amount using the relationship in Figure 7, and the re-energization time TB2 is set based on the required injection amount using the relationship in Figure 8.

[0056] 7, similar to the interval time TA1 in the battery energization mode, the interval time TA2 becomes shorter as the injection amount decreases in the region where the injection amount is less than the predetermined value K, and the interval time TA2 is constant regardless of the injection amount in the region where the injection amount is equal to or greater than the predetermined value K. However, the interval time TA2 is longer than the interval time TA1.

[0057] 8, the relationship between the injection amount and the reenergization time TB2 is defined as follows: the smaller the injection amount, the shorter the reenergization time TB2, similar to the reenergization time TB1 in the battery energization mode. However, the reenergization time TB2 is shorter than the reenergization time TB1. In addition, since the influence of differences in the reenergization time is greater in the boost energization mode than in the battery energization mode, the slope of the reenergization time TB2 with respect to the injection amount is smaller than the slope of the reenergization time TB1 with respect to the injection amount.

[0058] Then, in step S111, the energization time of the injection signal is corrected. At this time, as in step S109, the increase in the actual injection amount due to the re-energization of the solenoid is reduced. Specifically, the energization time of the injection signal is corrected to the shortened side.

[0059] In step S112, the injection signal whose energization time has been corrected in step S109 or step S111 and the re-energization signal corresponding to the control conditions set in step S108 or step S110 are output to the drive IC 62. As a result, during fuel injection, the fuel injector 50 is driven to open based on the injection signal whose energization time has been corrected in step S109 or step S111, and the solenoid is re-energized according to the control conditions set in step S108 or step S110.

[0060] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0061] An influence parameter indicating the influence of variations in the valve closing timing of the valve element 52 when the fuel injection valve 50 is closed on the actual injection amount is acquired, and battery energization (first re-energization) and boost energization (second re-energization) are selectively performed based on the influence parameter. In this case, even if variations occur in the valve closing timing of the fuel injection valve 50, the effect of reducing the speed of the valve element 52 can be obtained while reducing the influence on the actual injection amount. As a result, re-energization control can be appropriately performed when the fuel injection valve 50 is closed.

[0062] In the above fuel injection system, even if the valve closing timing of the valve body of the fuel injection valve 50 is unknown, the influence of variations in the valve closing timing can be reduced and the desired effect of reducing the valve closing speed can be obtained.

[0063] When the injection amount of the fuel injection valve 50 is small, the degree of influence on the actual injection amount due to variations in valve closing timing becomes larger than when the injection amount is large; in other words, the tolerance for variations in valve closing timing becomes smaller. Taking this into consideration, battery energization (first re-energization) is performed when the injection amount is smaller than a predetermined amount, and boost energization (second re-energization) is performed when the injection amount is larger than the predetermined amount. This makes it possible to perform appropriate re-energization control according to the injection amount.

[0064] When the solenoid is re-energized, the appropriate values ​​for the interval time and re-energization time change depending on the injection amount. Taking this into consideration, the interval time and re-energization time are configured to be variably set based on the injection amount at each time. This allows the solenoid to be re-energized appropriately when fuel is injected.

[0065] When the solenoid is re-energized during the valve-closed period at the end of injection, the valve closing timing is delayed compared to when the solenoid is not re-energized, and the actual injection amount of the fuel injector 50 increases accordingly. In consideration of this, when either the battery energization or the boost voltage energization is performed, the solenoid energization time corresponding to the required injection amount is corrected to a decreasing side. This improves the control accuracy of the actual injection amount when the solenoid is re-energized.

[0066] (Other embodiments) The above embodiment may be modified as follows, for example.

[0067] In the above embodiment, the fuel injection amount per injection by the fuel injection valve 50 is used as an influencing parameter indicating that variations in the valve closing timing of the valve element 52 when the fuel injection valve 50 closes affect the actual injection amount. However, this may be changed. For example, the pressure of the fuel injected from the fuel injection valve 50 (fuel pressure) may be used as the influencing parameter. In this configuration, the fuel injection system has a variable pressure of the fuel gas supplied to the fuel injection valve 50. Specifically, in the fuel injection system shown in FIG. 1, the adjustment pressure of the regulator 33 is changeable. In this case, the microcomputer 61 may set a target fuel pressure based on the engine operating state, etc., and adjust the fuel pressure by operating the regulator 33 according to the target fuel pressure.

[0068] Here, when the fuel pressure is high, the degree of influence on the actual injection amount in a state where the variation in the valve closing timing of the valve body 52 is larger than when the fuel pressure is low becomes greater. In view of this point, the microcomputer 61 acquires the fuel pressure of the gaseous fuel as an influence parameter, and selectively executes battery energization and boost energization based on the fuel pressure. The specific process will be described by referring to FIG. 5.

[0069] In FIG. 5, in steps S101 to S103, a required injection amount is calculated based on the engine operating state, and an injection signal is generated based on the required injection amount. Thereafter, in step S104, as an influence parameter, the fuel pressure is acquired, and a re-energization control mode is determined based on the fuel pressure. The fuel pressure may be the detected fuel pressure detected by the pressure sensor 36 provided in the low-pressure pipe portion 31b, or may be the target fuel pressure for fuel pressure control.

[0070] For example, it is preferable to determine the re-energization control mode based on the relationship in FIG. 10. In FIG. 10, based on the engine rotational speed and the fuel pressure, the execution regions X0, X1, X2 of each mode are defined. In FIG. 10, a region where the engine rotational speed is equal to or higher than the threshold value A1 or the fuel pressure is equal to or higher than the threshold value C1 is defined as a non-execution mode region X0. In other words, a region where the engine rotational speed is less than the threshold value A1 and the fuel pressure is less than the threshold value C1 is the execution regions X1, X2 of solenoid re-energization.

[0071] Also, in the relationship of FIG. 10, in the execution region of solenoid re-energization (the region where the engine rotational speed < A1 and the fuel pressure < C1), a region where the engine rotational speed is less than the threshold value A2 and the fuel pressure is less than the threshold value C2 is the region X2 where boost energization is performed in the boost energization mode, and the other regions are the regions X1 where battery energization is performed in the battery energization mode. It is also possible to determine the re-energization control mode based only on the fuel pressure among the engine rotational speed and the fuel pressure.

[0072] Then, in step S107, it is determined whether re-energization is to be performed in the battery energization mode or the boost energization mode. If re-energization is to be performed in the battery energization mode, in step S108, an interval time TA1 and a re-energization time TB1 are set as control conditions in the battery energization mode. At this time, the interval time TA1 is set based on the fuel pressure using the relationship in Figure 11, and the re-energization time TB1 is set based on the fuel pressure using the relationship in Figure 12.

[0073] In the fuel injection valve 50, fuel pressure acts as back pressure on the valve element 52, and the closing speed of the valve element 52 varies depending on the magnitude of the fuel pressure. For example, when the fuel pressure is relatively high, the closing speed of the valve element 52 is faster than when the fuel pressure is relatively low. In this case, it is desirable to increase the speed reduction effect when the valve element 52 closes as the fuel pressure increases. Therefore, in Figure 11, a relationship is established in which the higher the fuel pressure, the shorter the interval time TA1 becomes.

[0074] Furthermore, when the fuel pressure is relatively high, the effect of re-energizing the solenoid to reduce the speed of the valve element 52 is reduced compared to when the fuel pressure is relatively low. Therefore, in Figure 12, the relationship between the fuel pressure and the re-energizing time TB1 is defined such that the higher the fuel pressure, the longer the re-energizing time TB1.

[0075] Thereafter, the energization time of the ejection signal is corrected (step S109), and then the ejection signal and the re-energization signal are output to the driving IC 62 (step S112).

[0076] When re-energization is performed in the boost energization mode, an interval time TA2 and a re-energization time TB2 are set as control conditions in the boost energization mode in step S110. At this time, the interval time TA2 is set based on the fuel pressure using the relationship in Figure 11, and the re-energization time TB2 is set based on the fuel pressure using the relationship in Figure 12.

[0077] 11, the higher the fuel pressure, the shorter the interval TA2, just like the interval TA1 in the battery energization mode, except that the interval TA2 is longer than the interval TA1.

[0078] 12, the relationship between the fuel pressure and the re-energization time TB2 is defined as follows: the higher the fuel pressure, the longer the re-energization time TB2, as in the case of the re-energization time TB1 in the battery energization mode. However, the re-energization time TB2 is shorter than the re-energization time TB1. In addition, because the influence of differences in the re-energization time is greater in the boost energization mode than in the battery energization mode, the slope of the re-energization time TB2 with respect to the fuel pressure is smaller than the slope of the re-energization time TB1 with respect to the fuel pressure.

[0079] Thereafter, the energization time of the ejection signal is corrected (step S111), and then the ejection signal and the re-energization signal are output to the driving IC 62 (step S112).

[0080] When the pressure (fuel pressure) of the fuel injected from the fuel injection valve 50 is high, the effect on the actual injection amount due to variations in valve closing timing becomes greater than when the fuel pressure is low. In consideration of this, battery energization (first re-energization) is performed when the fuel pressure is higher than a predetermined value, and boost energization (second re-energization) is performed when the fuel pressure is lower than the predetermined value. This makes it possible to perform appropriate re-energization control according to the fuel pressure.

[0081] The system may be configured to execute both a process for selecting the re-energization control mode based on the injection amount and a process for selecting the re-energization control mode based on the fuel pressure. In this case, the microcomputer 61 executes the process shown in Fig. 13. The process shown in Fig. 13 is related to the selection between the battery energization mode and the boost energization mode, and may be executed, for example, in step S104 of Fig. 5.

[0082] 13, in step S201, whether to perform battery energization or boost energization when re-energizing the solenoid is selected based on the injection amount as an influencing parameter. For example, using the relationship in FIG. 6, whether to perform battery energization or boost energization is selected based on the engine rotation speed and the injection amount.

[0083] In step S202, whether to perform battery energization or boost energization when re-energizing the solenoid is selected based on the fuel pressure as an influencing parameter. For example, using the relationship in Figure 10, whether to perform battery energization or boost energization is selected based on the engine rotation speed and fuel pressure.

[0084] In step S203, it is determined whether the determination results of steps S201 and S202 match. If the determination results match, the process proceeds to step S204, where it is determined whether battery energization has been selected. If battery energization has been selected, the process proceeds to step S205, where solenoid energization is performed again by battery energization. If boost energization has been selected, the process proceeds to step S206, where solenoid energization is performed again by boost energization.

[0085] If it is determined in step S203 that the determination results do not match, the process proceeds to step S205, where the solenoid is re-energized by energizing the battery. In other words, if the results of the two mode selections do not match and one of them selects to energize the battery, it is determined that the battery will be energized.

[0086] When the re-energization mode selected based on the injection amount differs from the re-energization mode selected based on the fuel pressure, the solenoid re-energization in the battery energization mode is prioritized over the boost energization mode. In this case, the battery re-energization is prioritized over the boost energization mode, thereby appropriately suppressing re-lift of the valve element 52 due to variations in the valve closing timing.

[0087] Temperature information about the fuel injector 50 can also be used as the influencing parameter. The temperature information may be the fuel temperature, the solenoid temperature, or the like. For example, the re-energization control mode may be determined based on the relationship shown in FIG. 14. FIG. 14 illustrates the relationship between the temperature of the fuel or the solenoid 56 and the resistance value of the current path of the fuel injector 50, and defines an execution region X1 of the battery energization mode and an execution region X2 of the boost energization mode according to the temperature region. In FIG. 14, the region where the temperature is less than a threshold D1 or equal to or greater than a threshold D2 corresponds to region X1 where battery energization is performed in the battery energization mode, and the region where the temperature is equal to or greater than the threshold D1 but less than the threshold D2 corresponds to region X2 where boost energization is performed in the boost energization mode. Note that switching the energization mode based on temperature information can also be performed in combination with switching the energization mode based on the injection amount or the fuel pressure.

[0088] In the relationship shown in Figure 6, the injection amount on the vertical axis can be replaced with the engine load. In other words, there is a correlation between the injection amount and the engine load, and the engine load can also be used as an influencing parameter. The engine load can be, for example, the throttle opening or the intake air amount.

[0089] In the above embodiment, when the solenoid is re-energized, both the interval time and the re-energization time are set to be variable depending on the injection amount and fuel pressure, but this may be changed. For example, only one of the interval time and the re-energization time may be set to be variable depending on the injection amount and fuel pressure.

[0090] The condition for re-energizing the solenoid may be that the amount of charge in the battery is equal to or greater than a predetermined value when injection ends, more specifically, that the OC (State of Charge) of the battery is equal to or greater than a predetermined value.

[0091] In the above embodiment, a fuel injection valve having an inward opening structure in which the valve element 52 moves inwardly in the body 51 when the valve is opened is used as the fuel injection valve 50. However, this may be modified to use a fuel injection valve having an outward opening structure in which the valve element 52 moves outwardly in the body 51 when the valve is opened.

[0092] Gas fuels other than hydrogen gas can also be used. For example, compressed natural gas (CNG) and liquefied natural gas (LP gas) can also be used as gas fuels.

[0093] In the above embodiment, the present invention has been described as being applied to a fuel injection system for a vehicle, but other applications are also possible. For example, the present invention can be applied to fuel injection systems used in construction machinery, agricultural machinery, aircraft, ships, etc.

[0094] The control device and method described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control device and method described herein may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the control device and method described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0095] 50...fuel injection valve, 52...valve body, 54...spring, 56...solenoid, 61...microcomputer, 62...drive IC, 63...power supply circuit, 64...low voltage power supply, 65...boosting power supply.

Claims

1. a fuel injection valve (50) having a solenoid (56) that drives a valve element (52) to open against the biasing force of a spring (54) when energized, and that injects gas fuel when the valve element opens; a drive circuit (62, 63) that applies a voltage to the solenoid to drive the fuel injection valve to open, the drive circuit being applied to a fuel injection system having a low-voltage power supply (64) that can output a battery voltage and a boost power supply (65) that can output a boosted voltage obtained by boosting the battery voltage, and the fuel injection control device (61) that controls opening and closing of the fuel injection valve, a re-energization control unit that, when the valve body closes due to the end of injection from the fuel injection valve, enables a first re-energization of the solenoid by the low-voltage power supply during a first energization period, and a second re-energization of the solenoid by the boost power supply during a second energization period that is shorter than the first energization period; a parameter acquisition unit that acquires an influence parameter that indicates an influence of a variation in valve closing timing at which the valve element reaches a valve closing position when the fuel injection valve is closed, on an actual injection amount; Equipped with The re-energization control unit selectively executes the first re-energization and the second re-energization based on the influencing parameter acquired by the parameter acquisition unit.

2. the parameter acquisition unit acquires, as the influencing parameter, a fuel injection amount per injection by the fuel injection valve; 2. The fuel injection control device according to claim 1, wherein the re-energization control unit executes the first re-energization when the fuel injection amount as the influence parameter is smaller than a predetermined amount, and executes the second re-energization when the fuel injection amount is larger than the predetermined amount.

3. The present invention is applied to a fuel injection system having a function of variably controlling the pressure of gas fuel supplied to the fuel injection valve, the parameter acquisition unit acquires, as the influencing parameter, a fuel pressure that is a pressure of gas fuel supplied to the fuel injection valve; 2. The fuel injection control device according to claim 1, wherein the re-energization control unit executes the first re-energization when the fuel pressure as the influence parameter is higher than a predetermined value, and executes the second re-energization when the fuel pressure is lower than the predetermined value.

4. The present invention is applied to a fuel injection system having a function of variably controlling the pressure of gas fuel supplied to the fuel injection valve, the parameter acquisition unit acquires, as the influencing parameters, a fuel injection amount per injection by the fuel injection valve and a fuel pressure which is a pressure of gas fuel supplied to the fuel injection valve; The re-energization control unit selecting whether the first re-energization or the second re-energization is to be performed based on a fuel injection amount as the influencing parameter, and selecting whether the first re-energization or the second re-energization is to be performed based on a fuel pressure as the influencing parameter; 2. The fuel injection control device according to claim 1, wherein when execution of the first re-energization is selected in either one of the selections, it is determined that the first re-energization will be executed.

5. 5. The fuel injection control device according to claim 1, further comprising: a setting unit that, when performing either the first re-energization or the second re-energization, sets at least one of an interval time between a main energization for fuel injection by the fuel injection valve and the re-energization and a re-energization time for performing the re-energization based on the influencing parameter acquired by the parameter acquisition unit.

6. The present invention is applied to a fuel injection system that injects gas fuel to be burned in an internal combustion engine (10) from the fuel injection valve, an injection amount calculation unit that calculates a required injection amount of the fuel injection valve based on an operating state of the internal combustion engine; a correction unit that corrects, when the re-energization control unit executes either the first re-energization or the second re-energization, a current application time of the solenoid corresponding to the required injection amount calculated by the injection amount calculation unit to a decreasing side; The fuel injection control device according to any one of claims 1 to 4, comprising:

7. a fuel injection valve (50) having a solenoid (56) that drives a valve element (52) to open against the biasing force of a spring (54) when energized, and that injects gas fuel when the valve element opens; a drive circuit (62, 63) that applies a voltage to the solenoid to drive the fuel injection valve to open, the drive circuit being applied to a fuel injection system having a low-voltage power supply (64) that can output a battery voltage and a boost power supply (65) that can output a boosted voltage obtained by boosting the battery voltage, and a program for controlling the opening and closing of the fuel injection valve, On the computer, a re-energization control process that enables execution of a first re-energization of the solenoid by the low-voltage power supply during a first energization period and a second re-energization of the solenoid by the boost power supply during a second energization period that is shorter than the first energization period, when the valve body closes following completion of injection from the fuel injection valve; a parameter acquisition process for acquiring an influence parameter that influences an actual injection amount due to a variation in a valve closing timing at which the valve element reaches a valve closing position when the fuel injection valve is closed; Execute a program that, in the reenergization control process, selectively executes the first reenergization and the second reenergization based on the influencing parameter acquired in the parameter acquisition process.

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