FUEL INJECTION CONTROL DEVICE

Abstract

Fuel injection control device comprising: - a high-potential-side switch (SW4) provided for several fuel injectors (INJ1, INJ2, INJ3) common to and between the several fuel injectors and a control voltage source; - low-potential-side switches (SW1, SW2, SW3) that sequentially select a target fuel injector from the several fuel injectors; and - a control unit (10) configured to control the on / off state of the high-potential-side switch and the low-potential-side switches, wherein - the control unit is configured to, while one of the several fuel injectors is selected by the low-potential-side switch, control the high-potential-side switch so that the selected fuel injector performs multi-stage injections, and - the control unit is further configured to: - then,If multi-stage injection for DPF regeneration is requested for a specific fuel injector, and multi-stage injection is not requested for DPF regeneration for the next fuel injector, compare the end timing of the multi-stage injection for DPF regeneration with the start timing of the multi-stage injection not for DPF regeneration based on the requested injection conditions; then, if it is determined that the end timing of the multi-stage injection for DPF regeneration is later than the start timing of the multi-stage injection not for DPF regeneration, change the injection conditions of at least either the multi-stage injection for DPF regeneration or the multi-stage injection not for DPF regeneration so that the multi-stage injection not for DPF regeneration begins in the next fuel injector.after the multi-stage injection for DPF regeneration ends in the specified fuel injector, - to cancel the last fuel injection of the multi-stage injection for DPF regeneration as the change in injection conditions, - furthermore, to increase an injection quantity in at least one fuel injection immediately before the canceled fuel injection in the multi-stage injection for DPF regeneration as the change in injection conditions, - furthermore, to change the injection conditions so that the total amount of the increased injection quantity in the at least one fuel injection immediately before the canceled fuel injection is equal to the injection quantity of the canceled fuel injection, and - to change the injection conditions so that the injection quantities in the two fuel injections immediately before the canceled fuel injection are increased,where, of these two fuel injections, the increase in the injection quantity of the second fuel injection is greater than the increase in the injection quantity of the first fuel injection.

Description

TECHNICAL FIELDThe present disclosure relates to a fuel injection control device.BACKGROUNDJP 2017-89 547 A discloses an exhaust gas purifying apparatus for an internal combustion engine which controls injection timing and the like for post injection in multistage injection in which fuel is injected a plurality of times. In this exhaust gas purifying apparatus, a diesel particulate filter (DPF) is provided in the exhaust passage of the internal combustion engine to promote the combustion of particulates deposited on the DPF. Injection of fuel into the DPF to combust particulates is referred to as "DPF regeneration.". The injection timing of the post injection is determined according to the cetane number of the fuel.At the time of DPF regeneration, there is a need to place the injection timing on the retard side so that the fuel injection can be performed as much as possible during the exhaust stroke. On the other hand, when DPF regeneration is not performed, the fuel injection timing is generally on the advance side as a whole compared to the injection timing during DPF regeneration. Thus, if the in-cylinder fuel injection after the DPF regeneration is on the advance side of the DPF regeneration, the post injection of the DPF regeneration and the pilot injection of the next cylinder may overlap. When the post injection and the first injection overlap, the current may not flow normally to the injection valve of both cylinders. As a result, neither the post injection of the DPF regeneration nor the first injection of the next cylinder can be normally performed.DE 10 2005 017 019 A1 relates to a fuel injection system having a plurality of injectors (injection devices) and, in particular, to a fuel injection system which carries out an overlap injection operation (overlap injection operation) in which firstly one injector from the plurality of injectors is fed for injecting fuel, and a next one of the injectors is fed after the start of the feeding of the one of the injectors, while the one of the injectors continues to be fed.JP 2004-68 606 A relates to a fuel injection control device for an internal combustion engine, in particular a fuel injection control device for an internal combustion engine, which is designed such that, in addition to the main injection for ensuring the driving performance, it can also perform a preinjection for noise suppression and NOx reduction and a post injection for forced regeneration of a particle filter.DE 10 2007 005 361 B3 discloses a method and a device for controlling the fuel injection by means of injectors in a multi-cylinder internal combustion engine (in particular an internal combustion engine with internal mixture formation).DE 10 2008 001 068 A1 teaches a method for operating a fuel injection system for an internal combustion engine, wherein a plurality of injections are provided for execution, which injections can collide with one another in time.A method and a device for controlling an internal combustion engine are known from DE 10 2006 001 368 A1.DE 10 2009 025 480 B3 relates to a method and a device for operating an internal combustion engine having a plurality of cylinders, each of which is assigned an injection valve for metering fuel, at least one end stage being provided for actuating a plurality of injection valves.DE 100 33 343 A1 relates to a fuel injection system for an internal combustion engine, in particular a diesel engine, having at least two cylinders, wherein the fuel injection system has at least two actuator elements, and wherein each cylinder is assigned at least one actuator element each for injecting fuel into the cylinder, and to a method for operating such a fuel injection system.DE 10 2004 016 894 A1 discloses a fuel injection system for an internal combustion engine and a method for operating such a fuel injection system.DE 10 2008 047 384 A1 teaches a method for defining injection time periods for fuel injectors of an internal combustion engine, in particular of a diesel engine, and a corresponding method for controlling fuel injectors for internal combustion engines.SUMMARYIt is an object of the present disclosure to provide a fuel injection control device for executing multistage injections, which prevents the last injection of the DPF regeneration and the first injection of the next cylinder from overlapping each other, and which reliably ensures an effect of the DPF regeneration. The object is achieved by the subject matter of the main claim.According to the present invention, the last injection in the multistage injection for DPF regeneration and the first injection in the next multistage injection can be prevented from overlapping. Further, an effect of the DPF regeneration can be reliably ensured.The aspects disclosed herein apply different technical solutions to achieve their respective objectives. Reference numerals in parentheses in the claims and in this section exemplify corresponding relationships to parts of embodiments described below, and are not intended to limit the technical scope. The objects, features and advantages disclosed herein will become apparent from the following detailed description with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a circuit diagram illustrating an example of a schematic configuration of a fuel injection control device according to a first embodiment. FIG. 2 is a time chart showing an example of the operation of the fuel injection control device 1. FIG. 3 is a diagram illustrating a state in which injection timings before and after the cylinder switching overlap. FIG. 4 is a diagram illustrating an example of the injection timing before and after the cylinder switching. FIG. 5 is a flowchart illustrating an example of a control flow for setting injection conditions according to the first embodiment. FIG. 6 is a flowchart illustrating an example of injection control. FIG. 7 is a flowchart illustrating an example of a control flow for setting injection conditions according to a second embodiment. FIG. 8 is a diagram illustrating the injection timing before and after the cylinder switching according to the second embodiment. FIG. 9 is a flowchart showing an example of a control flow for setting injection conditions according to a third embodiment. FIG. 10 is a diagram illustrating the injection timing before and after the cylinder switching according to the third embodiment.DETAILED DESCRIPTIONHereinafter, embodiments will be described with reference to the drawings, wherein the second and third embodiments are for understanding the present invention embodied in the first embodiment. In some embodiments, parts that functionally and / or structurally correspond to and / or are associated with each other are provided with the same reference numerals or reference numerals having different hundreds or more digits. For corresponding parts and / or associated parts, additional explanations may be given to describe further embodiments.(First Embodiment)A fuel injection control device 1 shown in FIG. 1 is connected to injectors (i.e., injectors) INJ1 to INJ6 of a plurality of cylinders, and sequentially controls the injectors INJ1 to INJ6 (the injectors INJ4 to INJ6 are not shown in the figure). In the first embodiment, the injectors INJ1 to INJ6 are divided into two groups, and each group is driven by a sub-circuit corresponding to this group. The fuel injection control device 1 has a first sub-circuit for driving the injectors INJ 1 to INJ 3 and a second sub-circuit for driving the injectors INJ 4 to INJ 6. For the fuel injection control device 1 shown in FIG. 1, only the first sub-circuit that controls the injection valves INJ 1 to INJ 3 is shown. Further, in the following description, the fuel injection control device 1 will be described only with respect to the first sub-circuit. Since the second sub-circuit has the same circuit configuration as the first sub-circuit and the driving of the injectors INJ 4 to INJ 6 is the same as that of the first sub-circuit, the description of the second sub-circuit is omitted for brevity.The fuel injection control device 1 shown in FIG. 1 includes a drive IC 2, a current detection circuit 3, switches SW 1 to SW 4, a diode D 1, and a resistor R 1. Further, a microcontroller 4 shown in FIG. 1 outputs a control signal to the drive IC 2 of the fuel injection control device 1 to control the fuel injection control device 1. The drive IC 2 and the microcontroller 4 constitute a control unit 10. the microcontroller 4 is connected to and controls both the first sub-circuit and the second sub-circuit of the fuel injection control device 1. The switches SW 1 to SW 4 are n-channel field effect transistors. The switches SW 1 to SW 3 correspond to low-potential side switches. The switch SW 4 corresponds to a high-potential side switch. The drive IC 2 controls the switches SW 1 to SW 4 to be turned on and off according to the control signal from the microcontroller 4.In each of the switches SW 1 to SW 3, the drain terminal is connected to the downstream side of the injectors INJ 1 to INJ 3, and the source terminal is connected to the resistor R 1. Further, the gate terminals of the switches SW 1 to SW 3 are connected to the drive IC 2, and the on / off control of the switches SW 1 to SW 3 is controlled by the drive IC 2. Whenever a certain injection valve is to be controlled by the injection valves INJ1 to INJ3, the corresponding one of the switches SW1 to SW3 is turned on. That is, the switches SW1 to SW3 are used as selection switches to select which one of the fuel injection valves INJ1 to INJ3 is to be driven.As for the switch SW4, its drain is connected to a driving voltage source and its source is connected to the upstream side of the injectors INJ1 to INJ3. An amplified voltage Vboostfrom the driving voltage source is supplied to the drain of the switch SW4. The gate terminal of the switch SW 4 is connected to the drive IC 2, and the on / off control of the switch SW 4 is performed by the drive IC 2. The switch SW 4 outputs the boosted voltage Vboost to a specific injector of (i.e., below) the injectors INJ 1 to INJ 3 selected by the switches SW 1 to SW 3 to drive the specific injector. That is, the switch SW 4 is connected to each of the injectors INJ 1 to INJ 3, and controls the driving of each of the injectors INJ 1 to INJ 3. During two revolutions (720 degrees) of the crankshaft of the internal combustion engine, the injectors INJ1 to INJ3 are sequentially selected at intervals of 240 degrees. Boosted voltage VBo is applied from switch SW4 to the selected injector.In the injectors INJ 1 to INJ 3, when a built-in solenoid is energized, the solenoid moves the valve body to the open state, and the injector is opened. When the energization of the solenoid is stopped, the valve body returns to the closed state. As a result, the injection valve returns to a closed state, and the fuel injection is stopped. By controlling the energization timing and energization duration of the coils of the injectors INJ 1 to INJ 3, the fuel injection amount and the timing of fuel injection into the cylinders can be controlled. In the present embodiment, the fuel injection control device 1 controls the injection valves INJ 1 to INJ 3 of three cylinders, but the number of cylinders is not limited thereto.The diode D 1 is a feedback diode for the injectors INJ 1 to INJ 3, and returns a current to the injectors INJ 1 to INJ 3 when the switch SW 4 is turned from on to off while the switches SW 1 to SW 3 are turned on.The resistor R1 is used to detect the value of the current flowing through the injectors INJ1 to INJ3. In the current detection circuit 3, the current values of the injectors INJ 1 to INJ 3 are detected from the voltage values before and after the resistor R 1.Next, the operation of the fuel injection control device 1 will be described with reference to the time chart shown in FIG. 2. At time T 1, the one of the switches SW 1 to SW 3 corresponding to the drive target of the injectors INJ 1 to INJ 3 is turned on. FIG. 2 shows an example in which the injection valve INJ 1 is the drive target. Therefore, at time T 1, the switch SW 1 corresponding to the injection valve INJ 1 is turned on, and the switches SW 2 and SW 3 corresponding to the injection valves INJ 2 and INJ 3 remain turned off. Further, simultaneously with the switch SW1 being turned on at time T1, the switch SW4 is also turned on, and the boosted voltage VBo is supplied to the injection valve INJ1 to be driven. In the period T 1-T 2, the injector current is increased by the boosted voltage Vboost supplied via the switch SW 4.At time T 2, when the injector current of the to-be-driven injector among the injectors INJ 1 to INJ 3 reaches a peak current, the switch SW 4 is turned off. Subsequently, during the period T 2-T 3, the injector current decreases while receiving the reflux current from the diode D 1. At time T3, the switch SW4 is turned on again and the injector current increases. During the period T 3-T 4, the switch SW 4 is repeatedly turned on and off by an on / off control signal given from the drive IC 2 to the switch SW 4. As a result, the injector current of the injector is maintained at a substantially constant value as it increases and decreases again and again. During this time period, the injector current in T3-T4 maintains the injector open. At time T4, the actuation of the injection valve is completed and all switches SW1 to SW4 are turned off.Hereinafter, the switching timing for normal injections and the switching timing for injections during DPF regeneration will be described with reference to FIGS. 3 and 4. FIG. 3 shows a case where the DPF regeneration is performed before the cylinder is switched, and normal injection is performed after the cylinder is switched. FIG. 4 shows a case where both the injection before and after the cylinder switching are performed during the DPF regeneration.The standard injection condition in normal injection requires a multistage injection with 4 stages and 4 kinds of injections: a first injection, a pilot injection, a main injection, and a post injection. These injections may be performed, for example, as shown in FIG. 2. On the other hand, the standard injection condition during the DPF regeneration requires multistage injection of 5 kinds of injections: a first injection, a pilot injection, a main injection, a post injection, and a post injection. However, in the case of the DPF regeneration, the post injection is performed three times, so that 7 stages of injections in total are required for the multistage injection.In the present embodiment, the number of injections required as the default injection condition at the time of DPF regeneration is assumed to be 7, and the following description is made based on this assumption. During normal injection, the fuel is mainly injected into the cylinder, and the injection is performed on the advance side as a whole as compared with the injections at the time of DPF regeneration. On the other hand, during the DPF regeneration, the injection is performed on the retard side as a whole compared to normal injections, so that the fuel injection is performed at the exhaust timing. Note that Duration_n (where n is an integer from 0 to 7) indicates the time duration from the start of injection to the end of injection of each injection (i.e., the injection duration), and Wait_n (where n is an integer from 0 to 7) indicates the length of the interval between each injection.During DPF regeneration, as described above, injection timing is on the retard side of the crank angle compared to normal injections. Consequently, in the comparative example shown in FIG. 3, when switching from DPF regeneration to normal injection, a problem may occur that the last post injection of the DPF regeneration overlaps with the pilot injection of the normal injection. Although detailed illustration is omitted in FIG. 3, the injector current does not flow normally when the post injection of the previous multistage injection and the pilot injection of the next multistage injection overlap. On the other hand, as shown in FIG. 4, when the DPF regeneration is performed both before and after the cylinder switching, the injection is performed at the timing on the retard side in both cases. Therefore, the last post injection of the DPF regeneration before the switching and the first pilot injection of the DPF regeneration after the switching do not overlap.According to the first embodiment, when switching from the DPF regeneration to the normal injection, the last post injection during the DPF regeneration (the waveform circled by a broken line in FIG. 3 ) is canceled, so that the multistage injection of the DPF regeneration and the multistage injection of the normal injection do not overlap. That is, in the case of switching from DPF regeneration to normal injection, the number of injections during DPF regeneration is changed from the default value of 7 to 6. As a result, the next multistage injection is started after the multistage injection during the DPF regeneration is completed. Therefore, the multistage injection during the DPF regeneration and the multistage injection during the normal operation do not overlap.Next, the controls of the fuel injection control device 1 will be described with reference to the flowcharts shown in FIGS. 5 and 6. The control procedure of FIGS. 5 and 6 is executed by the microcontroller 4. The microcontroller 4 determines the injection conditions (N, Duration_n and Wait_n) based on this control flow and sends them to the drive IC 2. The drive IC 2 controls the turning on / off of the switches SW 1 to SW 4 based on the injection conditions sent from the microcontroller 4. FIG. 5 is a flowchart for setting the injection conditions before the start of injection in each cylinder. The microcontroller 4 acquires information such as engine speed, rail pressure and temperature from various sensors (not shown) of the internal combustion engine before starting fuel injection in each cylinder. Based on this information, the microcontroller 4 determines the injection mode (C_CYL) of the cylinder. Further, the microcontroller 4 calculates the in-cylinder injection end timing based on the above-described information from the various sensors. Moreover, the injection mode (N_CYL) of the next cylinder is also determined based on the above-described information from the various sensors. The injection mode C_CYL and the injection mode N_CYL show a predetermined value (referred to as "DPF" in FIGS. 5 and 6 ) when the injection is a DPF regeneration. The microcontroller 4 sets the injection conditions based on this information.In step S 51, the microcontroller 4 determines whether or not the injection mode C_CYL is "DPF". When the injection mode C_CYL is "DPF", the microcontroller 4 determines whether or not the injection mode N_CYL is "DPF" in step S 52.When it is determined in step S 52 that the injection type N_CYL is "DPF", the number of injections N is set to "7" in step S 510. The injection number N=7 is the number of injections under the standard injection conditions required for the multistage injection for DPF regeneration. The standard injection conditions required for the multistage injection for DPF regeneration are stored in advance in a memory that can be accessed by the microcontroller 4. Similarly, the standard injection conditions required for multistage injections other than those during the DPF regeneration are also stored in advance. Subsequently, in step S 511, the injection durations Duration_ 1 to Duration_ 7 of each injection are set. The injection durations Duration_ 1 to Duration_ 1 show the time from the start to the end of each injection, as described above.Subsequently, in step S 512, the time period between the individual injections is set as the injection waiting periods Wait_ 0 to Wait_ 7. The injection waiting periods Wait_ 1 to Wait_ 16 show the time from the end of injection to the start of the next injection, as described above. Further, the injection waiting period Wait_ 0 indicates the time period until the start of the first pilot injection, and the injection waiting period Wait_ 7 is the time from the end of the last post injection until the switching to the next cylinder.When it is determined in step S 52 that the injection type N_CYL is not "DPF", it is determined in step S 53 whether or not the last in-cylinder injection of the multistage injection before the switching overlaps with the first injection of the next-cylinder injection. If NO is determined in step S 53, then in steps S 510 to S 512, the injection durations Duration_ 1 to Duration_ 7 and the injection waiting durations Wait_ 0 to Wait_ 7 are set while maintaining the standard injection conditions.If YES is determined in step S 53, it is a case where the last in-cylinder injection before switching and the first in-cylinder injection after switching overlap. Thus, when YES is determined in step S 53, in the first embodiment, the injection conditions are changed in steps S 520 to S 522 so that the injections do not overlap at the timing of the cylinder switching.In the first embodiment, if the last in-cylinder injection before the switching and the first in-cylinder injection after the switching were overlapped, the last post in-cylinder injection before the switching is canceled. Therefore, in step S 520, the number of injections N is set to a value of "6" obtained by subtracting 1 from the standard value "7" to cancel the last post injection. Further, in the setting of the injection durations in step S 521 and the setting of the inter-injection waiting durations in step S 522, the injection time Duration_ 7 and the injection waiting duration Wait_ 7 are not set.If NO is determined in step S 51, it means that normal in-cylinder injection is performed before the switching. As described above, the injections performed during the normal injection are four injections in total, i.e., a pilot injection, a pilot injection, a main injection, and a post injection. Therefore, in steps S 530 to S 532, "4" is set for the number of injections N, and in addition, the injection durations Duration_ 1 to Duration_ 4 for each injection and the injection waiting durations Wait_ 0 to Wait_ 4 between each injection are set.Next, injection control will be described with reference to the flowchart shown in FIG. 6. The flowchart shown in FIG. 6 is a flow executed by the microcontroller 4. According to the flow of FIG. 6, the microcontroller 4 sends control signals to the drive IC 2. In step S61, a counter value n is set to "1". In step S62, the apparatus is stopped for the duration of wait_0. Here, for example, in setting the injection conditions shown in FIG. 5, when the value "0" is set in Wait_ 0, the pause does not occur in step S 62, and the process proceeds to step S 63 and on.In step S 63, it is determined whether or not the count value n has reached the number of injections N+1. When the counter value n has reached the number of injections N+1, all the injections in the current cylinder are finished, so that the injection control is finished.If NO is determined in step S63, injection and pause controls are performed. In step S 64, the injection is performed with the injection duration Duration_n (n=1 to 7) set as the injection condition. A control signal for controlling the switches SW 1 to SW 4 is sent from the microcontroller 4 to the drive IC 2, so that injection is performed with the corresponding injection valve having the injection duration Duration_n. Subsequently, in step S 65, the injection control is suspended with the injection waiting period Wait_n (n=1 to 7) set as the injection condition. Thereafter, 1 is added to the count value n in step S 66, the process returns to step S 63 again, and the processes of steps S 64 to S 66 are repeated until the count value n reaches the number of injections N+1.Regarding the cancellation of the last post injection, an exemplary control flow is described above with reference to the flowcharts shown in FIGS. 5 and 6, but the operation of the first embodiment is not limited to this control flow. For example, a method is applicable in which the microcontroller 4 sends a control signal to the drive IC 2 while determining information from various sensors and an injection status during injection control, and dynamically changes the injection conditions.Further, in the above description, there is shown the case that the fuel injection for DPF regeneration is performed before the cylinder switching and the fuel injection after the cylinder switching is the normal injection. However, the application examples of the present disclosure are not limited thereto. The present disclosure is applicable when there is a possibility that the fuel injection into the cylinder after the cylinder in which the DPF regeneration has been performed will be the fuel injection on the advance side of the DPF regeneration.As described above, the control unit 10 has determined that the multistage injection for DPF regeneration is performed before the cylinder switching and the first injection of the multistage injection after the cylinder switching overlaps with the last injection of the multistage injection for DPF regeneration. In this case, the injection conditions are changed to cancel the last fuel injection for DPF regeneration. That is, the number of injections is reduced from the standard number of injections by one to cancel the last post injection, i.e., the last fuel injection during the DPF regeneration. Thereby, it is possible to prevent the post injection before the switching and the pilot injection after the switching from overlapping before and after the switching of the cylinder.Further, in order to compensate for the decrease in the total injection amount due to the cancellation of the post injection, the control unit 10 may increase the injection amount in at least one fuel injection immediately before the cancelled fuel injection. This can be effected, for example, by the values of the injection duration Duration_ 6 and / or of the injection duration Duration_ 5 being increased in step S 521 by the time period corresponding to the canceled seventh injection (Duration_ 7). Thereby, the decrease in the injection amount due to the omission of the last injection of the multistage injections by the other injections of the same multistage injections can be compensated. Thereby, the decrease in the total fuel injection amount due to the omission of the last post injection can be compensated, and the effect of the DPF regeneration can be ensured.In this case, it is preferable that the fuel injection amount in the one or two injections immediately before the canceled fuel injection is increased by the same amount as the injection amount in the canceled fuel injection. For example, in step S 521, the injection duration Duration_ 6 and / or the injection duration Duration_ 5 may be increased by the time period corresponding to the canceled injection duration Duration_ 7. As a result, the decrease in the injection amount due to the omission of the post injection by the other injections in the same multistage injections can be reliably compensated. Thereby, the decrease in the fuel injection amount due to the omission of the post injection can be compensated for, and the effect of the DPF regeneration can be more reliably ensured.Further, to balance the injection amount at the suspended post injection, the injection amounts for the fifth and sixth injections during the DPF regeneration may be increased. Further, in this case, it is preferable that the increase amount of the injection amount in the sixth injection is larger than the increase amount of the injection amount in the fifth injection. For example, in the above example, when both the injection duration Duration_ 6 and the injection duration Duration_ 5 are increased, the injection duration Duration_ 6 is preferably increased more than the increase amount of Duration_ 5. This is because in the multistage injections for executing the DPF regeneration, it is desirable that the post injection be performed as far as possible on the retard side, and it is desirable that the combustion amount be larger on the retard side than on the advance side.(Second Embodiment)Next, a second embodiment of the present disclosure will be described. Note that in the following description, when the same reference numerals as in the first embodiment are used, the same configuration as in the first embodiment is given, and the foregoing description is referred to unless otherwise specified.FIG. 7 describes the control of the fuel injection control device 1 in the second embodiment. The second embodiment is different from the first embodiment in that when switching from the DPF regeneration to the normal injection, the last post injection is not canceled. Therefore, the microcontroller 4 sets the injection number N to 7 in step S 720 as shown in FIG. 7 Along with this, the injection duration Wait_ 7 is set in step S 721 and the injection waiting duration Wait_ 7 is set in step S 722. However, in the second embodiment, the last post injection is not canceled, but the start timing of the last post injection is set to a timing earlier than the default value. That is, in step S 722 of FIG. 7, the microcontroller 4 shortens the injection waiting period Wait_ 6. As a result, the interval between the next to last post injection and the last post injection during the DPF regeneration is shortened. Note that in FIG. 7, steps other than steps S 720 to S 722 are the same as in FIG. 5, so the description of these steps is omitted.FIG. 8 shows the injection timings at the time of switching from the DPF regeneration to the normal injection in the second embodiment. In the waveform diagram of FIG. 8, an example of post injection for the standard DPF regeneration is shown in the upper row, and an example of control of the second embodiment is shown in the middle row. In the second embodiment, the injection conditions are changed to shorten the injection waiting period Wait_ 6, so that the start timing of the last post injection is advanced. This second embodiment is particularly useful when the duration time of the injection waiting period Wait_ 6 at the time of the standard DPF regeneration is long.That is, in the second embodiment, the microcontroller 4 changes the injection conditions to shift the start timing of the last fuel injection from the multistage injections before the switching. This can avoid the problem that the last fuel injection before the switching and the first injection after the switching overlap. Since the post injection of the DPF regeneration is not canceled, there arises an advantage that the effect of the DPF regeneration is high as compared with the first embodiment.The control according to the second embodiment is not limited to the method for shortening the interval between the last injection and the next to last injection of the DPF regeneration. For example, it is possible to advance the start timing of the last injection by shortening the interval between all injections or multiple specific injections in the multistage injections. In this case, realization is possible by shortening all or part of the injection waiting periods Wait_ 0 to Wait_ 6 in step S 722 of FIG. 7.(Third Embodiment)A third embodiment will be described below. Note that in the following description, when the same reference numerals as in the first embodiment are used, the same configuration as in the first embodiment is given, and the foregoing description is referred to unless otherwise specified.In the third embodiment, when the in-cylinder fuel injection before the switching is the DPF regeneration and the post-switching fuel injection is the normal injection, the injection conditions are changed to delay the start timing of the pilot injection of the normal injection. In this way, the last post injection of the DPF regeneration and the first pilot injection of the normal injection can be prevented from overlapping. Therefore, in the third embodiment, the microcontroller 4 stores the injection type P_CYL as data indicating the type of fuel injection into the immediately preceding cylinder. The injection type P_CYL indicates a predetermined value ("DPF") in the case of DPF regeneration, like the injection types C_CYL and N_CYL.FIG. 9 shows a control flow according to the third embodiment. In step S91, it is determined whether or not the injection mode C_CYL in the current target fuel injection cylinder is "DPF". If YES is determined in step S91, the standard DPF regeneration time setting is made in steps S930-S932, whereupon the setting of the injection condition is completed.When NO is determined in step S91, i.e., when the in-cylinder injection mode C_CYL is not "DPF", it is determined in step S92 whether or not the immediately preceding cylinder injection mode (P_CYL) is "DPF". When the injection mode P_CYL is not "DPF", the standard injection conditions for the normal injection are set as the number of injections N, the injection durations Duration_ 1 to Duration_ 4, and the injection waiting durations Wait_ 0 to Wait_ 4 in steps S 910 to S 911.When the determination in step S 92 is YES, that is, when the immediately preceding injection mode P_CYL is "DPF", it is determined in step S 93 whether the last injection of the DPF regeneration and the first injection after the switching overlap. When the determination in step S93 is NO, the standard injection conditions for the normal injection are set in steps S910 to S912.When the determination in step S 93 is YES, the number of injections "4" for the normal injection is set as the number of injections N (step S 920). Further, in steps S 921 and S 922, the injection durations Duration_ 1 to Duration_ 4 and the injection waiting durations Wait_ 0 to Wait_ 4 are set. However, in step S 922, the injection waiting time Wait_ 0 is set to a time longer than the standard value, and the injection waiting time Wait_ 1 is set to a time shorter than the standard value. The injection waiting durations Wait_ 2 to Wait_ 4 are set to the standard waiting time. As a result, the start timing of the pilot injection of the normal injection may be changed to a timing later than the standard injection conditions. Thereby, the last injection of the DPF regeneration before the cylinder switching and the first injection of the normal injection after the cylinder switching can be prevented from overlapping.FIG. 10 shows the injection timings of the DPF regeneration before the cylinder switching and the normal injections after the cylinder switching in the third embodiment. The upper part of FIG. 10 shows the post injection waveform of the DPF regeneration before the cylinder switching. The middle row shows the waveforms of the pilot injection and the pilot injection during the normal injection after the cylinder switching. In the upper and middle waveforms, the last post injection during DPF regeneration and the post injection during normal injection overlap. The lower row shows the waveforms of the pilot injection and the pilot injection of the normal injection after the cylinder switching in which the control of the third embodiment is performed. By the control shown in FIG. 9, the injection waiting period Wait_ 0 is set to be longer than the standard value. In this way, the last injection of the DPF regeneration before the cylinder switching and the first injection at the time of the normal injection after the cylinder switching can be prevented from overlapping. Further, by shortening the injection waiting period Wait_ 1 by increasing the injection waiting period Wait_ 0, the total required time of the normal injection does not change.As described above, in the third embodiment, the microcontroller 4 changes the injection conditions to delay the start timing of the first fuel injection from the fuel injections after the cylinder switching. The injection conditions thus set are sent as a control signal to the drive IC 2, and the drive IC 2 controls the switches SW 1 to SW 4. Thereby, the last injection of the DPF regeneration before the cylinder switching and the first injection in the normal injection after the cylinder switching can be prevented from overlapping. Further, unlike the first and second embodiments, the start timing and the injection amount of the last injection of the DPF regeneration are not changed before the cylinder switching. Therefore, in the third embodiment, the effect of the DPF regeneration can be ensured. Further, regarding the pilot injection of the normal injection after the switching, the pilot injection is not canceled and the start timing is only delayed. By performing the pilot injection without canceling, the effect of reducing the combustion noise can also be obtained.In the above example, the injection waiting time Wait_ 1 has been shortened by the amount by which the injection waiting time Wait_ 0 has been extended. However, not only the injection waiting period Wait_ 1 can be shortened, but also at least two of the injection waiting periods Wait_ 1 to Wait_ 4. This control is effective when the standard value of the injection waiting time Wait_ 1 is short and there is little margin for shortening to catch the extension of the injection waiting time Wait_ 0.Moreover, in the third embodiment, the control is not limited to the control for delaying the start timing of the pilot injection after the cylinder switching. For example, pilot injection may be canceled after the cylinder switching. Thereby, it can be reliably prevented that the last injection of the DPF regeneration before the cylinder switching and the first injection of the normal injection after the cylinder switching overlap.(Other Embodiments)However, the present disclosure including the drawings is not limited to the exemplary embodiments. The disclosure includes the exemplary embodiments and variations thereof that will be apparent to those skilled in the art based thereon. For example, the disclosure is not limited to the combinations of components and / or elements shown in the embodiments.In each of the above-described embodiments, the fuel injection control device 1 includes two sub-circuits each driving three injection valves, and an example of a configuration in which the six-cylinder injection valves INJ 1 to INJ 6 are driven is shown. However, the configuration of the fuel injection control device 1 is not limited thereto. The fuel injection control device 1 may be configured to have only one sub-circuit or three or more sub-circuits, for example. Moreover, the number of injectors driven by a sub-circuit is not limited to three.Further, in each of the above-described embodiments, there is shown a case where a transistor is used as the switches SW 1 to SW 4 of each part. However, switching elements other than transistors may be used as these switches.Further, each of the drive IC 2 and the microcontroller 4 of each of the above-described embodiments is configured of one or more control devices. The control devices may include, for example, a memory and a processor that executes a program stored in the memory. Further, the control device may include, for example, a logic circuit including a digital circuit including a number of programmed logic units (gate circuits).Further, in each of the above embodiments, a configuration example is shown in which the drive IC 2 and the microcontroller 4 are independent blocks. However, the drive IC 2 and the microcontroller 4 may be configured as one element.

Claims

A fuel injection control apparatus comprising: a high potential side switch (SW4) provided to a plurality of fuel injection valves (INJ1, INJ2, INJ3) in common and between the plurality of fuel injection valves and a driving voltage source; a low potential side switch (SW1, SW2, SW3) sequentially selecting a driving target fuel injection valve from the plurality of fuel injection valves; and a control unit (10) configured to control the on / off state of the high potential side switch and the low potential side switches, wherein the control unit is configured to, while one of the plurality of fuel injection valves is selected by the low potential side switch, control the high potential side switch so that the selected fuel injection valve performs multistage injections, and the control unit is further configured to:, when a multistage injection for DPF regeneration is requested for a certain fuel injection valve and a multistage injection for DPF regeneration is not requested for the next fuel injection valve, compare a final timing of the multistage injection for DPF regeneration with a starting timing of the multistage injection for DPF regeneration not based on requested injection conditions, when it is determined that the final timing of the multistage injection for DPF regeneration is later than the starting timing of the multistage injection for DPF regeneration not, change the injection conditions of at least one of the multistage injection for DPF regeneration and the multistage injection for DPF regeneration so that the multistage injection does not start for DPF regeneration in the next fuel injection valve, after the multistage injection for DPF regeneration ends in the specific fuel injection valve, - cancel the last fuel injection of the multistage injection for DPF regeneration as the change in the injection conditions, - further increase an injection amount in at least one fuel injection immediately before the cancelled fuel injection in the multistage injection for DPF regeneration as the change in the injection conditions, - further change the injection conditions such that the total amount of the increased injection amount in the at least one fuel injection immediately before the cancelled fuel injection is equal to the injection amount of the cancelled fuel injection, and - change the injection conditions such that the injection amounts in the two fuel injections immediately before the cancelled fuel injection are increased, wherein, of these two fuel injections, the increase amount of the injection amount of the second fuel injection is larger than the increase amount of the injection amount of the first fuel injection.

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