JP4529892B2 - Fuel injection control device for multi-cylinder engine - Google Patents

Description

  The present invention relates to a fuel injection control device for a multi-cylinder engine.

  In diesel engines, a common rail fuel injection system that accumulates high-pressure fuel equivalent to the fuel injection pressure in the common rail and injects the high-pressure fuel accumulated in the common rail to the engine via the fuel injection valve is practical. It has become. As fuel injection amount control, generally, a basic injection amount is calculated based on an accelerator operation amount by a driver and an engine speed, and various corrections are applied to the basic injection amount to calculate an injection amount command value. . And in the injection period according to the injection amount command value, the electromagnetic solenoid part of the fuel injection valve is energized to perform fuel injection.

  In a multi-cylinder engine, in a configuration in which fuel injection is performed with respect to each cylinder by individual fuel injection valves, the fuel injection amount varies between engine cylinders due to individual differences in fuel injection valves, deterioration with time, and the like. For this reason, various techniques for eliminating variations in the injection amount between cylinders have been proposed. For example, the fuel injection control device of Patent Document 1 is configured to enable so-called multistage injection, in which fuel injection is performed a plurality of times within one fuel cycle by a fuel injection valve, and multistage injection is performed under a predetermined engine operating state. The two fuel injection patterns with different numbers of injections are set, and the fuel injection is performed by equally distributing the injection amount in each injection pattern. Then, each of the injection amount command values is calculated at the time of performing the multi-stage injection by each injection pattern, and the inter-cylinder correction amount is calculated based on these injection amount command values. In addition, since the variation in the injection amount between the cylinders changes as the deterioration of the fuel injection valve progresses, a technique for detecting the deterioration of the fuel injection valve is also being studied.

However, since the patent document 1 sets a special fuel injection pattern, it is considered that the implementation opportunity is restricted by various conditions in consideration of the influence on the engine operating state. In addition, it takes a relatively long time to perform a series of processes. Therefore, an improvement technique for grasping the variation between cylinders is desired.
JP 200419637 A

  The main object of the present invention is to provide a fuel injection control device for a multi-cylinder engine that can easily and accurately grasp variations among cylinders, and thus improve the controllability of fuel injection control.

In the first aspect of the invention, as a premise, fuel injection for each cylinder is performed by performing ISC correction for stabilizing the rotational speed in the idling operation state and inter-cylinder variation correction for correcting variation between cylinders in the engine torque. The amount is calculated, and the driving of the fuel injection valve is controlled based on the calculated fuel injection amount. In particular, 1 to perform the multi-stage injection for performing at least 2 times the fuel injection in the combustion cycle, as well as complete the ISC correction implementation to the ISC correction to the injection of the Saisaki for subsequent injection The inter-cylinder variation correction is performed without performing the ISC correction . Then, the deterioration determination of the fuel injection valve is performed based on the rotational fluctuation amount for each cylinder when the multistage injection is performed.

  According to the said structure, an engine rotation is stabilized by implementing ISC correction | amendment with respect to the previous injection in multistage injection. In addition, by performing the inter-cylinder variation correction for the subsequent injection in that state, when the variation between the cylinders occurs due to the deterioration of the fuel injection valve, the difference in the rotation variation due to the variation between the cylinders is caused. Can be grasped appropriately. Accordingly, it is possible to accurately determine the deterioration of the fuel injection valve. In this case, fuel injection by a special fuel injection pattern is not performed, and the time required for deterioration determination is relatively short. As described above, the variation among the cylinders can be grasped easily and accurately, and the controllability of the fuel injection control can be improved.

  According to the second aspect of the present invention, when the multi-stage injection is performed, an inter-cylinder correction amount for correcting the inter-cylinder variation correction is calculated based on rotation fluctuation information for each cylinder. Then, deterioration determination of the fuel injection valve is performed based on the inter-cylinder correction amount. That is, when a difference in rotation fluctuation occurs between the cylinders due to deterioration of the fuel injection valve, the correction amount between the cylinders varies correspondingly. Therefore, it is possible to determine the deterioration based on the correction amount between cylinders.

  In the third aspect of the present invention, when it is determined that the fuel injection valve has deteriorated, an inter-cylinder correction amount for correcting variation among cylinders is calculated, and the inter-cylinder correction amount is stored as a learning value. To do. In the present invention, since the deterioration determination of the fuel injection valve can be performed with high accuracy as described above, the necessity determination of learning of the correction amount between cylinders can be performed with high accuracy.

On the other hand, in the invention according to claim 4, in the configuration in which the inter-cylinder correction amount for correcting the variation between cylinders is sequentially calculated and stored as a learning value, it is determined whether or not the calculation of the inter-cylinder correction amount is necessary, When it is determined that it is necessary to calculate the intermediate correction amount, multistage injection is performed in which fuel injection is performed at least twice in one combustion cycle, and the ISC correction is performed by performing the ISC correction on the previous injection. And the inter-cylinder variation correction is performed for the subsequent injections without performing the ISC correction . Further, an inter-cylinder correction amount is calculated based on rotation fluctuation information for each cylinder when the multistage injection is performed.

  According to the said structure, an engine rotation is stabilized by implementing ISC correction | amendment with respect to the previous injection in multistage injection. Also, by correcting the variation between cylinders for subsequent injections in that state, when the variation between cylinders occurs due to the deterioration of the fuel injection valve, the difference in rotation fluctuation caused by the variation between the cylinders Can be grasped appropriately. Therefore, the correction amount between cylinders can be calculated with high accuracy. In this case, fuel injection by a special fuel injection pattern is not performed, and the time required for calculating the correction amount between cylinders is relatively short. As described above, the variation among the cylinders can be grasped easily and accurately, and the controllability of the fuel injection control can be improved.

  In the common rail type fuel injection system for injecting high pressure fuel stored in the common rail from the fuel injection valve, as described in claim 5, a plurality of fuel pressure levels in the common rail are set, and the pressure level is set for each pressure level. It is preferable to calculate the correction amount between cylinders. As a result, even if the fuel pressure in the common rail changes according to the engine operating state or the like, it is possible to perform a suitable correction between cylinders in accordance with the fuel pressure at each time.

  Further, as described in claim 6, it is preferable to calculate the inter-cylinder correction amount when the injection amount by the fuel injection valve is relatively small and when it is relatively large. As a result, even when the injection amount by the fuel injection valve changes, it is possible to carry out suitable correction for variation between cylinders in accordance with the injection amount at each time.

  In the seventh aspect of the invention, at least main injection and subsequent post-injection are performed as the multi-stage injection, the ISC correction is performed on the main injection, and the inter-cylinder variations with respect to the post-injection. Make corrections. That is, in the multi-stage injection, it is considered that the fuel amount of the main injection is larger than the other injections. Therefore, the engine rotation can be stabilized more reliably by performing the ISC correction on the main injection. Thereby, the accuracy of deterioration determination and the accuracy of calculating the correction amount between cylinders can be increased.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. The present embodiment embodies the present invention as a common rail fuel injection system for a vehicle diesel engine, and a detailed configuration thereof will be described below.

  FIG. 1 is a configuration diagram showing an outline of a common rail fuel injection system. In FIG. 1, a multi-cylinder diesel engine (hereinafter referred to as an engine) 10 is provided with an electromagnetic injector 11 for each cylinder, and these injectors 11 are connected to a common rail (pressure accumulation pipe) 12 common to each cylinder. A high pressure pump 13 as a fuel supply pump is connected to the common rail 12, and high pressure fuel corresponding to the injection pressure is continuously accumulated in the common rail 12 as the high pressure pump 13 is driven. The high-pressure pump 13 is driven as the engine 10 rotates, and the intake and discharge of fuel are repeatedly performed in synchronization with the engine rotation. The high pressure pump 13 is provided with an electromagnetically driven suction metering valve (SCV) 14 at its fuel suction portion, and the low pressure fuel pumped from the fuel tank 16 by the feed pump 15 passes through the suction metering valve 14. And sucked into the fuel chamber of the pump 13. In practice, the high-pressure pump 13, the suction metering valve 14, and the feed pump 15 are integrated into a pump unit.

  A common rail pressure sensor 17 is provided in the common rail 12, and the fuel pressure (common rail pressure) in the common rail 12 is detected by the common rail pressure sensor 17. Although not shown, the common rail 12 is provided with an electromagnetically driven (or mechanical) pressure reducing valve. When the common rail pressure rises excessively, the pressure reducing valve is opened to perform pressure reduction. It has become.

  The ECU 20 is an electronic control unit including a known microcomputer including a CPU, ROM, RAM, EEPROM, and the like. The ECU 20 detects the engine rotation speed in addition to the detection signal from the common rail pressure sensor 17 described above. A rotation speed sensor 21, an accelerator sensor 22 for detecting an accelerator operation amount (accelerator opening) by a driver, a water temperature sensor 23 for detecting the temperature of engine cooling water, and a fuel temperature in the common rail 12 Detection signals are sequentially input from various sensors such as the fuel temperature sensor 24. Then, the ECU 20 determines an optimal fuel injection amount and injection timing based on engine operation information such as the engine rotation speed and the accelerator opening, and outputs an injection control signal corresponding to the fuel injection amount to the injector 11. Thus, fuel injection from the injector 11 to the combustion chamber is controlled in each cylinder.

  Further, the ECU 20 calculates a target value of the common rail pressure (injection pressure) based on the engine speed and the fuel injection amount at that time, and the fuel discharge amount of the high-pressure pump 13 so that the actual common rail pressure becomes the target common rail pressure. Feedback control. Actually, the target discharge amount of the high-pressure pump 13 is determined based on the deviation between the target value and the actual value of the common rail pressure, and the opening degree of the suction metering valve 14 of the high-pressure pump 13 is controlled accordingly. At this time, by controlling the command current value for the electromagnetic solenoid of the intake metering valve 14, the opening degree of the intake metering valve 14 is increased and decreased, and the fuel discharge amount by the high-pressure pump 13 is adjusted accordingly.

  Here, the fuel injection amount control by the ECU 20 will be described in detail. In the present embodiment, when controlling the fuel injection amount, ISC correction (ISC: Idle Speed Control) for stabilizing the idling rotational speed and FCCB correction (FCCB: Fuel) for eliminating the variation in the fuel injection amount among cylinders. Control Cylinder Balance), and the final fuel injection amount is calculated by performing ISC correction and FCCB correction based on the basic injection amount calculated based on the engine speed and the accelerator opening. Yes.

  FIG. 2 is a time chart showing the state of fluctuation in rotation between cylinders due to variation in the fuel injection amount between cylinders. In FIG. 2, (a) shows the rotational fluctuation of each cylinder when FCCB correction is not executed, and (b) shows the rotational fluctuation of each cylinder when FCCB correction is executed. In (b), the rotational fluctuation shown in (a) is indicated by a dotted line for convenience.

  As shown in FIG. 2 (a), in each of the cylinders # 1 to # 4, a rotational increase and a rotational decrease are repeatedly generated, and the rotational fluctuation varies among the cylinders as illustrated. At this time, the rotational fluctuation amounts of the cylinders # 1 to # 4 are ΔNE1, ΔNE2, ΔNE3, and ΔNE4, respectively. Then, by performing FCCB correction on the fuel injection amount of each cylinder, the rotational fluctuation amount is smoothed almost uniformly as shown in FIG. In such a case, actually, the difference between the average value of the rotational fluctuation amounts ΔNE1 to ΔNE4 of all the cylinders and the rotational fluctuation amount for each cylinder is calculated, and the FCCB correction amount is calculated based on the difference value. .

  FIG. 3 is a control block diagram showing an outline of control logic relating to fuel injection amount control.

  In FIG. 3, first, the basic injection amount Qbase is calculated based on the engine speed and the accelerator opening each time using map data defined in advance. Next, various corrections such as ISC correction and FCCB correction are performed on the basic injection amount Qbase to calculate the final fuel injection amount Qfin. In the case where the ISC correction and the FCCB correction are performed, the final fuel injection amount Qfin is calculated by adding the ISC correction amount Qisc and the FCCB correction amount Qfccb to the basic injection amount Qbase (Qfin = Qbase + Qisc + Qfccb). When calculating the fuel injection amount Qfin, in addition to the ISC correction and FCCB correction, injection amount correction based on the engine water temperature, fuel temperature, common rail pressure, and the like is appropriately performed.

  Further, an injection signal is generated based on the fuel injection amount Qfin. At this time, when performing so-called multistage injection in which fuel injection is performed a plurality of times within one combustion cycle, the fuel injection amount Qfin is divided by the number of injections of multistage injection to determine the injection amount for each injection. . An injection signal is generated based on the injection amount of each injection. Multi-stage injection is performed, for example, with a maximum of five stages, pilot injection and pre-injection are performed prior to main injection, and after injection and post-injection are performed after main injection.

  By the way, it is considered that in the injector 11, the injection characteristics change with time, and the variation in the fuel injection amount among the cylinders changes accordingly. The factors include wear of the sliding part and seating part of the valve body constituting the injector 11 and adhesion of deposits at the nozzle part. In such a case, it is necessary to update the FCCB correction amount Qfccb in accordance with the state of change of the injector 11 with time. Therefore, in the present embodiment, the deterioration determination of the injector 11 is performed when a predetermined condition is satisfied, and the FCCB correction amount Qfccb is newly calculated when the injector is deteriorated, and the previous value is updated with the current value of Qfccb. At this time, the FCCB correction amount Qfccb is stored and held in a backup memory such as an EEPROM (electrically erasable and writable nonvolatile memory) or a backup RAM, and when the FCCB correction amount Qfccb is updated, Data is rewritten in an EEPROM or the like.

  When determining the deterioration of the injector 11, an injection pattern consisting of at least two stages of multi-stage injection is carried out. Among them, ISC correction is performed for the previous fuel injection, and FCCB correction is performed for the subsequent fuel injection. To do. In this case, the engine rotation is stabilized by the ISC correction for the previous fuel injection, and the rotation fluctuation for each cylinder is monitored as a reflection of the variation between the cylinders in this state. Thereby, the dispersion | variation between cylinders can be calculated | required appropriately and the deterioration determination of the injector 11 of each cylinder can be performed accurately.

  FIG. 4 is a time chart showing an injection pattern when determining the deterioration of the injector 11. In FIG. 4A, two-stage fuel injection (f1, f2 in the figure) of main injection and after injection is performed as multi-stage injection, and at that time, ISC correction is performed on the previous main injection. At the same time, FCCB correction is performed for subsequent after injection. Alternatively, as shown in FIG. 4 (b), as the multi-stage injection, three-stage fuel injection (f11, f12, f13 in the figure) of pilot injection, main injection, and after injection is performed. On the other hand, the ISC correction may be performed and the FCCB correction may be performed on the respective injections before and after the main injection.

  When the FCCB correction amount Qfccb is calculated again when it is determined that the injector 11 has deteriorated, an injection pattern consisting of at least two stages of multi-stage injection is performed as in the case of performing the deterioration determination. Among them, ISC correction is performed for the previous fuel injection, and FCCB correction is performed for the subsequent fuel injection (see FIG. 4).

  Next, a processing procedure executed by the ECU 20 to update the FCCB correction amount Qfccb as a learning value will be described in detail. FIG. 5 is a flowchart showing a learning value update processing procedure, and this processing is performed by the ECU 20 at a predetermined time period, for example. By this process, the deterioration determination of the injector 11 of each cylinder and the update of the FCCB correction amount Qfccb for each cylinder are performed in a timely manner.

  In FIG. 5, in step S101, the necessity determination of deterioration determination is performed. For example, if the deterioration determination process has already been performed after the current ECU activation (that is, after the ignition switch is turned on), the process proceeds to step S106 because the deterioration determination is unnecessary. If the deterioration determination process is not performed, it is determined that the deterioration determination is necessary, and the process proceeds to step S102.

  In step S102, it is determined whether or not an execution condition for deterioration determination is satisfied. This execution condition includes, for example, that the engine is in an idle operation state, and that the engine water temperature is equal to or higher than a predetermined temperature (after completion of engine warm-up). It is said. When the execution condition is satisfied, the process proceeds to the subsequent step S103, and when the execution condition is not satisfied, the process is terminated.

  In step S103, fuel injection is performed based on the deterioration determination injection pattern. At this time, fuel injection is performed for each cylinder according to the injection pattern described in FIG. In the subsequent step S104, the deterioration determination of the injector 11 of each cylinder is performed based on the rotational fluctuation amount for each cylinder when the fuel injection based on the deterioration determination injection pattern is performed as described above. At this time, the maximum rotation speed (peak value) and the minimum rotation speed (bottom value) are calculated for each cylinder, and the rotation fluctuation amount (corresponding to ΔNE1 to ΔNE4 in FIG. 2) is calculated based on the difference between the rotation speed fluctuations. The deterioration determination of the injector 11 of each cylinder is performed using the amount as a deterioration determination parameter. For example, when the variation in the amount of rotation fluctuation between cylinders is larger than a predetermined threshold value, it is determined that the injector 11 is in a deteriorated state.

  In step S105, it is determined whether or not the injector 11 is in a deteriorated state in step S104. And if it determines with it being in a degradation state, a series of learning processes after step S106 will be implemented.

  In step S106, it is determined whether a learning condition for the FCCB correction amount Qfccb is satisfied. This condition determination is to determine that the engine operating state is a steady state. Specifically, the learning condition is that there are few engine load fluctuations (for example, accelerator change), and auxiliary equipment such as an air conditioner compressor and an alternator. This includes the fact that the load caused by the operation of the class is small. When the learning condition is satisfied, the process proceeds to the subsequent step S107, and when the learning condition is not satisfied, the present process is terminated.

  In step S107, fuel injection based on the learning injection pattern is performed. At this time, fuel injection is performed for each cylinder according to the injection pattern described in FIG. In the subsequent step S108, the rotation fluctuation amount is calculated for each cylinder, and the FCCB correction amount Qfccb of each cylinder is calculated based on the rotation fluctuation amount. At this time, the difference between the average value of the rotation fluctuation amount of all the cylinders and the rotation fluctuation amount of each cylinder is calculated, and the FCCB correction amount Qfccb is calculated based on the difference value. In step S109, the learning value (Qfccb learning value) stored in the EEPROM or the like is updated based on the FCCB correction amount Qfccb calculated this time.

  Actually, the FCCB correction amount Qfccb calculated in step S108 is a relative FCCB correction value representing the variation amount between cylinders, and the relative FCCB correction value is an absolute FCCB correction value. The FCCB correction value (absolute value) converted into the absolute value is written in the memory as a learning value. Here, the procedure will be described in more detail. That is, after calculating the FCCB correction amount Qfccb for each cylinder by executing the processes in steps S107 and S108, the ECU 20 performs the fuel injection amount control reflecting the FCCB correction amount Qfccb. At this time, ISC control is performed simultaneously, and the control injection amount during idle operation, that is, the deviation of the control injection period is calculated as a result of the control. Then, the FCCB correction amount Qfccb of each cylinder is converted from relative data to absolute data in accordance with the deviation, and the Qfccb value obtained as the absolute data is stored as a new learning value in an EEPROM or the like. .

  After the learning value is updated, in step S110, it is determined whether the calculation of the FCCB correction amount Qfccb for each cylinder has been completed for all the pressure levels with respect to the common rail pressure. In the present embodiment, a plurality of pressure levels are set within the use range of the common rail pressure, and it is determined whether the calculation of the FCCB correction amount Qfccb is completed for each pressure level. If step S110 is NO, the process is terminated as it is. If YES, the process proceeds to step S111, and a series of learning processes is completed (for example, a learning end flag is set).

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

  Since the multistage injection is performed when determining the deterioration of the injector 11, the ISC correction is performed for the previous injection, and the inter-cylinder variation correction is performed for the subsequent injection. Accordingly, when variation between cylinders occurs, it is possible to properly grasp the difference between the cylinders in the rotational fluctuation caused by the variation between the cylinders. Therefore, the deterioration determination of the injector 11 can be performed with high accuracy. In this case, since the fuel injection pattern is a general multistage injection (for example, main injection + after injection), fuel injection by a special fuel injection pattern is not performed, and the time required for deterioration determination is relatively short. It becomes. As described above, the variation among the cylinders can be grasped easily and accurately, and the controllability of the fuel injection control can be improved.

  Further, since the deterioration determination of the injector 11 can be performed with high accuracy as described above, the necessity determination of learning of the FCCB correction amount Qfccb can also be performed with high accuracy.

  Even when the FCCB correction amount Qfccb is learned, similarly to the above, multistage injection is performed, and at that time, ISC correction is performed for the previous injection and inter-cylinder variation correction is performed for the subsequent injection. Therefore, the FCCB correction amount Qfccb can be calculated with high accuracy.

  Since multiple common rail pressure levels are set and the FCCB correction amount Qfccb is calculated for each pressure level, even if the common rail pressure changes depending on the engine operating conditions, etc., it is suitable for each fuel pressure. Correction between cylinders can be performed.

  In addition, this invention is not limited to the content of description of the said embodiment, For example, you may implement as follows.

  In the above-described embodiment, the deterioration determination of the injector 11 of each cylinder is performed based on the rotation fluctuation amount for each cylinder. However, the deterioration determination method is changed. The FCCB correction amount Qfccb of each cylinder may be calculated based on the rotation fluctuation amount for each cylinder, and the deterioration determination of the injector 11 of each cylinder may be performed based on the FCCB correction amount Qfccb. That is, when a difference in rotation fluctuation between cylinders occurs due to deterioration of the injector 11, the FCCB correction amount Qfccb varies corresponding to each cylinder. Therefore, deterioration determination based on the FCCB correction amount Qfccb can be performed.

  In the above embodiment, the difference between the average value of the rotation fluctuation amount of all the cylinders and the rotation fluctuation amount of each cylinder is calculated, and the FCCB correction amount Qfccb is calculated based on the difference value. However, the calculation method is changed. . For example, the fuel injection amount to each cylinder may be individually corrected so as to smooth the rotational fluctuation between the cylinders, and the FCCB correction amount Qfccb may be calculated based on the correction amount at that time.

  The FCCB correction amount Qfccb may be calculated for the case where the injection amount by the injector 11 is relatively small and the case where the injection amount is relatively large. Thereby, even if the injection amount by the injector 11 changes, it becomes possible to carry out inter-cylinder variation correction in accordance with the injection amount at each time.

  In the above embodiment, the deterioration determination injection pattern and the learning injection pattern are the same fuel injection pattern, but this may be changed. For example, as the learning injection pattern, two types of fuel injection patterns with different numbers of multi-stage injections are set, and the fuel injection is performed by equally distributing the injection amount in each injection pattern. And each injection amount command value is calculated at the time of implementation of the multistage injection by each injection pattern, and the correction amount between cylinders may be calculated based on these injection amount command values (refer to JP, 2004-19637, A). .

  In the case of multistage injection at the time of determining the deterioration of the injector 11 or calculating the FCCB correction amount Qfccb, it is also possible to change the forms of ISC correction and FCCB correction for each injection in other ways. In a broad sense, in multi-stage injection, any FCCB correction (inter-cylinder variation correction) may be performed for the last injection, and ISC correction may be performed for an earlier injection.

  In the above embodiment, the deterioration determination of the injector 11 is performed first, and the FCCB correction amount Qfccb is calculated when it is determined that the deterioration has occurred. Instead, the deterioration determination of the injector 11 is a requirement. It is also possible to calculate the FCCB correction amount Qfccb in a timely manner without doing so. For example, the FCCB correction amount Qfccb is calculated (learned) every time the vehicle travel distance becomes a predetermined distance.

It is a block diagram which shows the outline of the engine control system in embodiment of invention. It is a time chart which shows the mode of the rotation fluctuation between cylinders. It is a control block diagram which shows the outline | summary of the control logic regarding fuel injection amount control. It is a time chart for demonstrating the injection pattern at the time of injector deterioration determination. It is a flowchart which shows the process sequence of learning value update.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Injector, 12 ... Common rail, 13 ... High pressure pump, 20 ... ECU.

Claims (7)

The fuel injection amount for each cylinder is calculated by performing the ISC correction for stabilizing the rotational speed in the idling operation state and the inter-cylinder variation correction for correcting the inter-cylinder variation of the engine torque, and the calculated fuel injection In a fuel injection control device for a multi-cylinder engine that controls the drive of a fuel injection valve based on an amount,
We conducted a multi-stage injection for performing at least 2 times the fuel injection in one combustion cycle, as well as complete the ISC correction was performed the ISC correction to the injection of the Saisaki for subsequent injection, the ISC a multi-injection means for executing the cylinder variation correction without performing correction,
Deterioration determining means for performing deterioration determination of the fuel injection valve based on the rotational fluctuation amount for each cylinder when the multistage injection is performed by the multistage injection performing means;
A fuel injection control device for a multi-cylinder engine.   When performing the multi-stage injection by the multi-stage injection execution means, it comprises means for calculating an inter-cylinder correction amount for correcting variation among the cylinders based on rotation fluctuation information for each cylinder, and the deterioration determination means The fuel injection control device for a multi-cylinder engine according to claim 1, wherein the deterioration determination of the fuel injection valve is performed based on a correction amount.   When it is determined by the deterioration determining means that the fuel injection valve has deteriorated, an inter-cylinder correction amount for correcting the inter-cylinder variation correction is calculated, and the inter-cylinder correction amount is stored and held as a learning value. The fuel injection control device for a multi-cylinder engine according to claim 1 or 2. The fuel injection amount for each cylinder is calculated by performing the ISC correction for stabilizing the rotational speed in the idling operation state and the inter-cylinder variation correction for correcting the inter-cylinder variation of the engine torque, and the calculated fuel injection In the fuel injection control device for a multi-cylinder engine that controls the drive of the fuel injection valve based on the amount, and sequentially calculates the inter-cylinder correction amount for correcting the variation among the cylinders and stores it as a learning value,
Necessity determination means for determining necessity of calculation of the correction amount between cylinders;
When it is determined by the necessity determination means that it is necessary to calculate the correction amount between cylinders, multi-stage injection in which fuel injection is performed at least twice in one combustion cycle is performed, and the ISC correction is performed with respect to the previous injection at that time. To complete the ISC correction, and for the subsequent injection, the multistage injection execution means for performing the inter-cylinder variation correction without performing the ISC correction ,
An inter-cylinder correction amount calculating means for calculating the inter-cylinder correction amount based on rotation fluctuation information for each cylinder when the multi-stage injection is performed by the multi-stage injection means;
A fuel injection control device for a multi-cylinder engine. A fuel injection control device that includes a common rail that stores high-pressure fuel corresponding to the injection pressure, adjusts the fuel pressure in the common rail to a target pressure each time, and injects the high-pressure fuel in the common rail into the cylinder by the fuel injection valve Because
The fuel injection for a multi-cylinder engine according to any one of claims 2 to 4, wherein a plurality of fuel pressure levels in the common rail are set and the inter-cylinder correction amount is calculated for each pressure level. Control device.   6. The fuel for a multi-cylinder engine according to claim 2, wherein the inter-cylinder correction amount is calculated for each of a case where the injection amount by the fuel injection valve is relatively small and a case where the injection amount is relatively large. Injection control device.   The multi-stage injection execution means performs at least main injection and subsequent post-injection as the multi-stage injection, performs the ISC correction on the main injection, and varies between the cylinders with respect to the post-injection. The fuel injection control device for a multi-cylinder engine according to any one of claims 1 to 6, wherein correction is performed.

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