Fuel injection control device and program

Abstract

A fuel injection control device (61) is applied to a fuel injection system provided with a drive circuit comprising a low-voltage power supply (64) capable of outputting a battery voltage and a boosted power supply (65) capable of outputting a boosted voltage, and controls opening / closing of a fuel injection valve (50). The fuel injection control device comprises: a re-energization control unit that, during a valve closing operation of a valve body upon the completion of injection by the fuel injection valve, enables execution of first re-energization for re-energizing a solenoid by means of the low-voltage power supply in a first energization period and second re-energization for re-energizing the solenoid by means of the boosted power supply in a second energization period shorter than the first energization period; and a parameter acquisition unit for acquiring an influence parameter indicating an effect on an actual injection amount that results from a variation in the valve closing timing at which the valve body reaches a valve closing position during the closing of the fuel injection valve. The re-energization control unit selectively executes the first re-energization and the second re-energization on the basis of the influence parameter acquired by the parameter acquisition unit.

Description

Fuel injection control device and program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-097395, filed on June 17, 2024, the contents of which are incorporated herein by reference.

[0002] The disclosure in this specification relates to a fuel injection control device and a program for an internal combustion engine.

[0003] 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.

[0004] 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.

[0005] 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 closed 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.

[0006] DE 102022200710

[0007] 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 at which 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 the valve closing timing. Specifically, the fuel injection valve has a valve disc structure made up of two separate members and 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.

[0008] 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.

[0009] 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.

[0010] The present disclosure provides a fuel injection control device that includes: 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; and 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 source capable of outputting battery voltage and a boost power source capable of outputting a boosted voltage obtained by boosting the battery voltage, and that controls opening and closing of the fuel injection valve, the fuel injection control device comprising: a re-energization control unit that, when the valve element closes due to completion of injection from the fuel injection valve, is capable of performing a first re-energization of the solenoid by the low-voltage power source in a first energization period, and a second re-energization of the solenoid by the boost power source in a second energization period that is shorter than the first energization period; and a parameter acquisition unit that acquires an influence parameter that affects an actual injection amount due to variations in valve closing timing at which the valve element reaches a valve closed position when the fuel injection valve is closed, The reenergization control unit selectively executes the first reenergization and the second reenergization based on the influence parameter acquired by the parameter acquisition unit.

[0011] 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.

[0012] In addition, in the above configuration, when the valve disc closes due to 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 is a concern that the velocity reduction effect may be reduced or the valve element may be lifted again due to variations in the valve closing timing.

[0013] In this regard, an influence parameter indicating the influence of variations in the valve closing timing of the valve element 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 element speed can be reduced. As a result, the re-energization control can be appropriately performed when the fuel injector is closed.

[0014] 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.

[0015] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of an engine fuel injection system, Fig. 2 is a cross-sectional view showing the configuration of a fuel injection valve, Fig. 3 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, Fig. 4 is a diagram for explaining the difference in valve closing speed of the valve body when variations in valve closing timing occur, Fig. 5 is a flowchart showing the control procedure for fuel injection by the fuel injection valve, Fig. 6 is a diagram showing the relationship between engine rotation speed, injection amount, and re-energization control mode, and Fig. 7 is a timing chart showing the relationship between engine rotation speed, injection amount, and re-energization control mode. , a diagram showing the relationship between injection amount and interval time, Figure 8 is a diagram showing the relationship between injection amount and re-energization time, Figure 9 is a diagram showing the relationship between interval time, re-energization time and reduction correction amount, Figure 10 is a diagram showing the relationship between engine rotation speed, fuel pressure and re-energization control mode in another example, Figure 11 is a diagram showing the relationship between fuel pressure and interval time, Figure 12 is a diagram showing the relationship between fuel pressure and re-energization time, Figure 13 is a flowchart showing the process of selecting the re-energization control mode, and Figure 14 is a diagram showing the relationship between temperature and re-energization control mode.

[0016] An embodiment embodying the present disclosure 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 FIG.

[0017] In Figure 1, engine 10 is a multi-cylinder internal combustion engine having multiple cylinders (e.g., three cylinders), with intake ports and exhaust ports 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. The 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.

[0018] 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.

[0019] 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.

[0020] 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 or adjust the pressure of the gas fuel supplied to the fuel injection valve 50. The regulator 33 has a pressure adjustment function to reduce or 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.

[0021] 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.

[0022] 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.

[0023] Each cylinder of the engine 10 is provided with a spark plug 40. A high voltage is applied to the spark plug 40 at the desired ignition timing through an ignition device 41, which is comprised of an ignition coil and the like. This application of high voltage generates a spark discharge between the opposing electrodes of each spark plug 40, igniting the gas fuel introduced into the cylinder (combustion chamber) and causing it to burn.

[0024] 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 that it can slide axially. The hollow portion of the body 51 forms 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 within the body 51.

[0025] The valve element 52 has 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, the valve element 52 is displaced to an open position against the biasing force of a 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 deenergized, 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.

[0026] As shown in FIG. 1, the ECU 60 (Electronic Control Unit) 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 .

[0027] The microcomputer 61 is a computer equipped with a processor and a memory (storage unit) and provides various computational functions. The functions of 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 programs stored in a non-transitory tangible storage medium serving as a storage unit of the microcomputer 61. The programs include, for example, programs for various processes related to fuel injection control and ignition control. Execution of the programs results in the execution of methods corresponding to the programs. The storage unit is, for example, a non-volatile memory. Note that the programs stored in the storage unit can be updated, for example, via a network such as the Internet. In this embodiment, the microcomputer 61 corresponds to a "fuel injection control device."

[0028] The microcomputer 61 calculates a required injection amount, which is the amount of fuel injected per injection, according to the engine operating conditions (e.g., 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 to drive the fuel injection valve 50 to open it. As a result, fuel equivalent to the required injection amount is injected from the fuel injection valve 50.

[0029] 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.

[0030] 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.

[0031] When the fuel injection valve 50 is driven to open by the injection signal, a low voltage V1 and a high voltage V2 are applied to the fuel injection valve 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 opening response of the fuel injection valve 50, and the low voltage V1 is subsequently applied to maintain the open state of the fuel injection valve 50.

[0032] 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.

[0033] 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 body 52 reaches the closed position, generating a force in the opposite direction to the valve closing direction, thereby reducing the closing speed of the valve body 52.

[0034] 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.

[0035] 3 is a time chart showing changes in energization current when the solenoid is re-energized by battery energization and when the solenoid is re-energized by boost energization in the fuel injection valve 50. The solid line indicates battery energization, and the dashed dotted line indicates boost energization.

[0036] When battery energization is performed as solenoid re-energization, battery energization by the low-voltage power supply 64 is initiated 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 is initiated 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."

[0037] 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 injection valve 50 as the suction force toward the anti-valve closing side for a relatively long period. 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 injection valve 50 as the suction force toward the anti-valve closing side for a relatively short period. In this case, with battery energization, although the velocity reduction effect of the valve element 52 at the end of fuel injection is low, a reduction in the velocity 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 velocity reduction effect of the valve element 52 at the end of fuel injection is enhanced, but there are concerns about a reduction in the velocity reduction effect due to variations in the valve closing timing of the valve element 52 and re-lifting of the valve element 52.

[0038] Figure 4 is a diagram illustrating differences in the valve closing speed of the valve element 52 when variations in valve closing timing occur in the fuel injection valve 50. In Figure 4, the horizontal axis represents the magnitude of the variation in 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. Note that the valve closing speeds shown in Figure 4 are the maximum values ​​of the valve closing speed 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.

[0039] 4, when the variation in the valve closing timing becomes large, the valve closing timing deviates from the appropriate timing, thereby 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 slower with boost current than with battery current, 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 high with boost current than with battery current.

[0040] 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 large. 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 high 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.

[0041] Therefore, in this embodiment, an influence parameter that indicates the influence of variations in the 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.

[0042] 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.

[0043] 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.

[0044] Then, 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 converting the required injection amount into time. The injection signal is a solenoid energization signal that keeps the solenoid 56 energized during the period from when the valve body 52 of the fuel injection valve 50 starts to open to when it starts to close after the valve opening.

[0045] Then, in step S104, the required injection amount calculated in step S102 is acquired as an influencing parameter, and a re-energization control mode is determined based on the required injection amount. In this embodiment, the re-energization control modes are configured to use a non-execution mode in which solenoid re-energization is not performed, a battery energization mode in which the solenoid is re-energized by battery voltage drive, and a boost energization mode in which the solenoid is re-energized by boost voltage drive, and one of these three modes is determined in step S104.

[0046] For example, the reenergization control mode may be determined based on the relationship shown in Figure 6. In Figure 6, execution regions X0, X1, and X2 for each mode are determined based on the engine speed and the injection amount. In Figure 6, the region where the engine speed is equal to or greater than a threshold A1 or the injection amount is less than a threshold B1 is determined as the non-execution mode region X0. In other words, the regions where the engine speed is less than the threshold A1 and the injection amount is equal to or greater than the threshold B1 are the solenoid reenergization execution regions X1 and X2.

[0047] 6, in the region where solenoid re-energization is performed (the region where engine speed < A1 and injection amount ≥ B1), the region where engine speed is less than threshold value A2 and injection amount is equal to or greater than threshold value B2 is region X2 where boost energization is performed in boost energization mode, and the other region is region X1 where battery energization is performed in battery energization mode. The relationship between threshold values ​​A1 and A2 is A1 > A2, and the relationship between threshold values ​​B1 and B2 is B1 < B2. It is also possible to determine the re-energization control mode based on only the injection amount out of the engine speed and injection amount.

[0048] The minute injection amount during engine idle operation is preferably included in the region X1 where battery energization is performed, but may also be included in the region X0 where solenoid re-energization is not performed.

[0049] After the process of step S104, in step S105, it is determined whether or not to re-energize the solenoid. If it is determined in step S104 that the re-energization control mode is to be 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 injection valve 50 is driven to open based on the injection signal generated in step S103.

[0050] If step S105 is affirmative, 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.

[0051] 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 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.

[0052] 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 Figure 7, a relationship is established where the interval time TA1 becomes shorter as the injection amount decreases in the region where the injection amount is less than a predetermined value K, and the interval time TA1 is constant regardless of the injection amount in the region where the injection amount is equal to or greater than the predetermined value K.

[0053] In addition, in the region where the injection amount is small, the tolerance for injection amount variation is small, so from the viewpoint 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.

[0054] 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 taking into account the solenoid being 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.

[0055] 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. In FIG. 9, the relationship is defined such that the longer the re-energization time, the larger the amount of reduction correction. Also, in FIG. 9, the relationship is defined such that the shorter the interval time, the larger the amount of reduction correction.

[0056] 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.

[0057] 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.

[0058] 8, the relationship between the injection amount and the reenergization time TB2 is set such that 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. Furthermore, since the influence of differences in 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.

[0059] 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 be shorter.

[0060] 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.

[0061] According to the present embodiment described above in detail, the following excellent effects can be obtained.

[0062] 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.

[0063] 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.

[0064] 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 greater than when the injection amount is large. In other words, the tolerance for variations in valve closing timing becomes smaller. In consideration of this, 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.

[0065] 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.

[0066] 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 injection valve 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.

[0067] (Other Embodiments) The above embodiment may be modified as follows, for example.

[0068] In the above embodiment, the fuel injection amount per injection by the fuel injection valve 50 is used as an influencing parameter indicating the influence of variations in the valve closing timing of the valve body 52 on the actual injection amount when the fuel injection valve 50 is closed. 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 in accordance with the target fuel pressure.

[0069] When the fuel pressure is high, the degree of influence on the actual injection amount when the variation in the valve closing timing of the valve element 52 is large becomes greater than when the fuel pressure is low. In consideration of this, the microcomputer 61 acquires the fuel pressure of the gas fuel as an influence parameter, and selectively executes battery energization and boost energization based on the fuel pressure. Specific processing will be described with reference to FIG. 5.

[0070] 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. Then, in step S104, the fuel pressure is acquired as an influencing parameter, and the reenergization 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 piping section 31b, or may be a target fuel pressure for fuel pressure control.

[0071] For example, the reenergization control mode may be determined based on the relationship shown in Figure 10. In Figure 10, execution regions X0, X1, and X2 for each mode are determined based on the engine speed and fuel pressure. In Figure 10, the region where the engine speed is equal to or greater than a threshold A1 or the fuel pressure is equal to or greater than a threshold C1 is defined as the non-execution mode region X0. In other words, the regions where the engine speed is less than the threshold A1 and the fuel pressure is less than the threshold C1 are defined as the solenoid reenergization execution regions X1 and X2.

[0072] 10, in the region where solenoid re-energization is performed (the region where engine speed<A1 and fuel pressure<C1), the region where engine speed is less than threshold value A2 and fuel pressure is less than threshold value C2 is region X2 where boost energization is performed in boost energization mode, and the other region is region X1 where battery energization is performed in battery energization mode. It is also possible to determine the re-energization control mode based on only fuel pressure out of engine speed and fuel pressure.

[0073] 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 for the battery energization mode. At this time, the interval time TA1 is set based on the fuel pressure using the relationship in FIG. 11, and the re-energization time TB1 is set based on the fuel pressure using the relationship in FIG. 12.

[0074] 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 the valve, 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.

[0075] Furthermore, when the fuel pressure is relatively high, the effect of the solenoid re-energization on reducing 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-energization time TB1 is defined such that the higher the fuel pressure, the longer the re-energization time TB1.

[0076] 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).

[0077] 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.

[0078] 11, the higher the fuel pressure, the shorter the interval TA2, similar to the interval TA1 in the battery power supply mode, except that the interval TA2 is longer than the interval TA1.

[0079] 12, the relationship between the fuel pressure and the re-energization time TB2 is defined such that 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. Furthermore, since 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.

[0080] 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).

[0081] 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.

[0082] 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.

[0083] 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.

[0084] In step S202, whether to re-energize the solenoid is selected as either battery energization or boost energization based on the fuel pressure as an influencing parameter. For example, using the relationship in Figure 10, whether to re-energize the solenoid is selected as either battery energization or boost energization based on the engine rotation speed and fuel pressure.

[0085] In step S203, it is determined whether the determination results of steps S201 and S202 are the same. If the determination results are the same, 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 by battery energization. If boost energization has been selected, the process proceeds to step S206, where solenoid energization is performed by boost energization.

[0086] 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 battery energization is selected in one of them, it is determined that battery energization will be performed.

[0087] 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.

[0088] Temperature information related to 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 reenergization control mode may be determined based on the relationship shown in FIG. 14 . FIG. 14 shows 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 current mode and an execution region X2 of the boost current mode depending on 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 current is applied in the battery current mode. 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 current is applied in the boost current mode. Note that switching the current mode based on temperature information can also be performed in combination with the switching of the current mode based on the injection amount or the switching of the current mode based on the fuel pressure.

[0089] 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 be used as an influencing parameter. The engine load can be, for example, the throttle opening or the intake air amount.

[0090] 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 the 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 the fuel pressure.

[0091] The condition for re-energizing the solenoid may be that the amount of charge stored in the battery is equal to or greater than a predetermined value at the end of injection, more specifically, that the OC (State of Charge) of the battery is equal to or greater than a predetermined value.

[0092] In the above embodiment, a fuel injection valve having an inward opening structure in which the valve element 52 moves inwardly into 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 from the body 51 when the valve is opened.

[0093] Gas fuels other than hydrogen gas may also be used. For example, compressed natural gas (CNG) or liquefied natural gas (LP gas) may also be used as the gas fuel.

[0094] In the above embodiment, the present invention is applied to a fuel injection system for a vehicle, but it can also be applied to other applications such as fuel injection systems used in construction machinery, agricultural machinery, aircraft, ships, etc.

[0095] The control device and method described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to execute 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 combination of a processor and memory programmed to execute one or more functions and 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 to be executed by a computer.

[0096] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

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; and 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 source (64) that can output battery voltage and a boost power source (65) that can output a boosted voltage obtained by boosting the battery voltage, and a fuel injection control device (61) that controls the opening and closing of the fuel injection valve, comprising: a re-energization control unit that, when the valve element closes due to the completion of injection from the fuel injection valve, can execute a first re-energization that re-energizes the solenoid using the low-voltage power source during a first energization period, and a second re-energization that re-energizes the solenoid using the boost power source during a second energization period that is shorter than the first energization period; a parameter acquisition unit that acquires an influence parameter that affects an actual injection amount due to a variation in valve closing timing at which the valve element reaches a valve closing position when the fuel injection valve is closed, wherein 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.

2. A fuel injection control device as described in claim 1, wherein the parameter acquisition unit acquires the fuel injection amount for one injection by the fuel injection valve as the influence parameter, and the re-energization control unit executes the first re-energization when the fuel injection amount as the influence parameter is less than a predetermined amount, and executes the second re-energization when the fuel injection amount is greater than the predetermined amount.

3. A fuel injection control device as described in claim 1, which is applied to a fuel injection system having a function of variably controlling the pressure of gas fuel supplied to the fuel injection valve, wherein the parameter acquisition unit acquires the fuel pressure, which is the pressure of the gas fuel supplied to the fuel injection valve, as the influence parameter, and 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. A fuel injection control device as claimed in claim 1, which is applied to a fuel injection system having a function of variably controlling the pressure of gas fuel supplied to the fuel injection valve, wherein the parameter acquisition unit acquires, as the influence parameters, the fuel injection amount for one injection by the fuel injection valve and the fuel pressure, which is the pressure of the gas fuel supplied to the fuel injection valve, and the re-energization control unit selects whether to execute the first re-energization or the second re-energization based on the fuel injection amount as the influence parameter, and selects whether to execute the first re-energization or the second re-energization based on the fuel pressure as the influence parameter, and when it is selected to execute the first re-energization in either of the selections, decides to execute the first re-energization.

5. A fuel injection control device as claimed in any one of claims 1 to 4, comprising a setting unit that, when executing either the first re-energization or the second re-energization, sets at least one of the interval time between the main energization for fuel injection by the fuel injection valve and the re-energization and the re-energization time for executing the re-energization based on the influencing parameter acquired by the parameter acquisition unit.

6. A fuel injection control device as claimed in any one of claims 1 to 4, which 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, and comprises: an injection amount calculation unit that calculates a required injection amount of the fuel injection valve based on the operating state of the internal combustion engine; and a correction unit that corrects the energization time of the solenoid corresponding to the required injection amount calculated by the injection amount calculation unit to a decreasing side when either the first re-energization or the second re-energization is executed by the re-energization control unit.

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; and 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 source (64) capable of outputting battery voltage and a boost power source (65) capable of outputting a boosted voltage obtained by boosting the battery voltage, and a program for controlling the opening and closing of the fuel injection valve, the program comprising: a re-energization control process that enables a computer to execute a first re-energization of the solenoid by the low-voltage power source during a first energization period when the valve element closes due to the completion of injection from the fuel injection valve, and a second re-energization of the solenoid by the boost power source during a second energization period that is shorter than the first energization period; a parameter acquisition process for acquiring an influence parameter that indicates an influence on an actual injection amount caused by a variation in a valve closing timing at which the valve element reaches a valve closing position when the fuel injection valve is closed; and in the re-energization control process, the first re-energization and the second re-energization are selectively executed based on the influence parameter acquired by the parameter acquisition process.

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