JP2010071222A - Fuel injection control device and fuel injection control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dilute lubricating oil in a crankcase CK by scraping injected fuel adhered on an inner wall of a combustion chamber 16 using a piston 30 into the crankcase CK when injecting fuel for regeneration control of a DPF 38a by a fuel injection valve 20 into the fuel chamber 16. <P>SOLUTION: Main injection contributing to generation of torque is performed upon the piston 30 of a diesel engine 10 coming near a compression top dead center. Thereafter, in a latter stage of a compression stroke when the piston 30 is moved down, post injection for regeneration control of a DPF 30a is performed. By opening a pressure-reducing valve 46 between the main injection and the post injection, fuel pressure of the common rail 44 is lowered. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control for an internal combustion engine having a fuel injection device for injecting, via a fuel injection valve, a high pressure fuel stored in a pressure accumulating vessel into a combustion chamber of the internal combustion engine having an aftertreatment device in an exhaust system. The present invention relates to an apparatus and a fuel injection control system.

  For example, in a diesel engine or the like, a diesel particulate filter (DPF) has been put into practical use as a post-treatment device for removing particulate matter (PM) in exhaust gas as regulations are strengthened. . The DPF is a filter having a function of capturing and removing PM in exhaust gas. Specifically, when the trapped amount of PM becomes a predetermined value or more, unburned fuel is added to the exhaust gas, and the PM trapped in the DPF is burned and removed by raising the exhaust gas temperature.

  Here, when a means for adding unburned fuel to the exhaust is provided in the exhaust passage, an increase in cost due to an increase in the number of parts cannot be ignored. For this reason, it has also been proposed and put into practical use, so-called post-injection, which is fuel injection for DPF regeneration, by diverting fuel injection means for generating torque of a diesel engine. Post-injection is to inject fuel into the combustion chamber immediately before the exhaust valve is opened, so that unburned fuel can be supplied into the exhaust passage.

  However, since the fuel injected by the post injection is directly injected into the combustion chamber while preventing the fuel from burning in the combustion chamber, it tends to adhere to the inner wall of the cylinder. The fuel adhering to the inner wall of the cylinder may be scraped off to the crankcase by the piston. When unburned fuel is scraped off the crankcase, the lubricating oil (engine oil) in the crankcase is diluted.

  Therefore, conventionally, it has been proposed to perform post injection a plurality of times during one combustion cycle or to limit the post injection amount itself. These all suppress the amount of injected fuel from reaching the cylinder inner wall by shortening the amount of fuel injection at one time.

As another conventional fuel injection control device, for example, there is one which can be found in the following Patent Document 1.
Japanese Patent No. 3760583

  Incidentally, when post injection is performed a plurality of times during one combustion cycle, the amount of heat generated by the drive circuit of the fuel injection valve increases. This increase in the amount of heat generation can be suppressed by making the drive part of each fuel injection valve as independent as possible, for example, in a multi-cylinder internal combustion engine, but in this case, the cost increase due to an increase in the number of parts is also ignored. Can not. In order to avoid such an increase in the number of parts, there is a demand for limiting pilot injection or the like in order to reduce the amount of heat generated by pilot injection or the like performed prior to main injection.

  Further, when the post injection amount itself is limited, the exhaust gas temperature cannot be sufficiently increased, which may increase the amount of fuel necessary to regenerate the DPF and increase the fuel consumption. There is also.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide high-pressure fuel stored in a pressure accumulating vessel through a fuel injection valve in a combustion chamber of an internal combustion engine provided with an aftertreatment device in an exhaust system. It is an object of the present invention to provide a fuel injection control device and a fuel injection control system for an internal combustion engine that can more appropriately suppress the dilution of engine lubricating oil even when injecting.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  The invention described in claim 1 is directed to a fuel injection device that injects high-pressure fuel stored in a pressure accumulating vessel into a combustion chamber of an internal combustion engine having a post-processing device in an exhaust system via a fuel injection valve. In the case where a request to perform post injection for regeneration of the processing apparatus occurs, there is provided a reduction means for reducing the pressure of the fuel injected from the fuel injection valve as compared with the case where the request does not occur.

  It is considered that the lower the pressure of the fuel injected from the fuel injection valve, the lower the initial velocity of the fuel injected from the fuel injection valve, and the like, so that the amount of fuel adhering to the inner wall of the combustion chamber decreases. In the above invention, in view of this point, when post-injection is performed, the pressure of the fuel injected from the fuel injection valve is reduced to inject the high-pressure fuel stored in the pressure accumulating vessel into the combustion chamber of the internal combustion engine. Even if it exists, dilution of engine lubricating oil can be suppressed more appropriately.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the post injection is performed after the center of the expansion stroke in one combustion cycle.

  In the above invention, by performing the post injection after the center of the compression stroke, the fuel injected by the post injection can be suitably supplied to the exhaust system without burning in the combustion chamber.

  A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the reducing means increases the pressure reduction amount as the post injection amount increases.

  The smaller the fuel injection amount, the shorter the flight distance of the fuel. This means that the smaller the post-injection amount, the smaller the amount of decrease in post-injection injection pressure required to reduce the amount of fuel adhering to the inner wall. In the above invention, in view of this point, the pressure drop amount for the post injection can be suppressed as much as possible by increasing the pressure drop amount as the post injection amount increases.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the lowering means performs the post injection after the main injection for generating the torque of the internal combustion engine is performed. Prior to being performed, the pressure of the fuel injected from the fuel injection valve is reduced.

  In the above invention, in order to perform the pressure reduction process for the post injection while avoiding the main injection period, the injection pressure at the time of main injection is set to the main injection for the purpose of reducing the amount of fuel adhering to the inner wall defining the combustion chamber. For this reason, it is possible to suitably suppress or avoid the situation of deviation from the optimum injection pressure.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, the fuel injection device further comprises outflow means for causing the fuel in the pressure accumulation container to flow out to a fuel tank that stores fuel to be supplied to the pressure accumulation container. The reduction means performs the pressure reduction processing by operating the outflow means prior to the post injection after the main injection is performed.

  According to a sixth aspect of the present invention, in the fourth aspect of the present invention, the fuel injection device includes a fuel tank that stores fuel to be supplied to the pressure accumulating vessel, and the lowering means performs the fuel injection without performing fuel injection. The pressure reduction process is performed by operating the fuel injection valve so that the fuel in the pressure accumulating vessel flows out to the fuel tank through a valve.

  A seventh aspect of the present invention provides the target of the pressure of the fuel injected from the fuel injection valve in the main injection for generating the torque of the internal combustion engine in the first aspect of the present invention. Setting means for setting a value is further provided, wherein the lowering means corrects the target value set by the setting means to be lower when a request to perform post-injection for regeneration of the post-processing device occurs. .

  In the above invention, when the demand for post injection is generated by correcting the target value of the pressure set by the setting means to be reduced, the amount of fuel adhering to the inner wall partitioning the combustion chamber is set rather than the setting of the setting means. Priority can be given to the request to reduce.

  The invention according to claim 8 is the invention according to claim 7, wherein the setting means performs setting processing of the target value based on a parameter indicating an operating state of the internal combustion engine, and the reduction means The reduction amount of the target value is set based on a parameter used for the target value setting process.

  The setting means is adapted according to various required elements such as torque, exhaust characteristics, and noise for each operating state of the internal combustion engine. In the above invention, in view of this point, by setting the amount of reduction based on the parameters used by the setting means, it is possible to perform the reduction processing while taking into account the various required elements.

  An invention according to claim 9 is a fuel injection control system for an internal combustion engine, comprising the fuel injection control device for an internal combustion engine according to any one of claims 1 to 8 and the fuel injection device. is there.

  In the above invention, since the lowering means is provided, it is possible to realize a fuel injection control system that can more appropriately suppress dilution of engine lubricating oil, and thus realize a system with high market value.

(First embodiment)
Hereinafter, a first embodiment in which a fuel injection control device for an internal combustion engine according to the present invention is applied to a fuel injection control device for a diesel engine having four cylinders will be described with reference to the drawings.

  FIG. 1 shows a system configuration according to the present embodiment.

  The illustrated intake passage 12 of the diesel engine 10 communicates with the combustion chamber 16 as the intake valve 14 opens. In the combustion chamber 16, an injection port 22 of the fuel injection valve 20 is disposed so as to protrude. In the combustion chamber 16, the fuel injected from the fuel injection valve 20 and the air sucked from the intake passage 12 are compressed, so that the fuel is ignited and combustion energy is generated. This combustion energy is converted into rotational energy of the crankshaft 32 via the piston 30. On the other hand, the air and fuel used for combustion are discharged into the exhaust passage 36 as exhaust gas as the exhaust valve 34 is opened. The exhaust passage 36 is provided with an exhaust purification device 38 as a post-processing device. The exhaust gas purification device 38 is provided with a diesel particulate filter (DPF 38a) for capturing particulate matter (PM) and burning it out.

  The fuel injection valve 20 is supplied with high-pressure fuel in a pressure accumulating container (common rail 44) common to each cylinder of the diesel engine 10. That is, since the fuel pumped up from the fuel tank 40 by the fuel pump 42 is pressurized (suppressed), the common rail 44 stores the pumped fuel in a high pressure state. The high pressure fuel in the common rail 44 is supplied to the fuel injection valve 20 through the high pressure fuel passage 24.

  The fuel injection valve 20 includes a nozzle needle 21 that opens and closes an injection port 22. A fuel pressure of high pressure fuel supplied from the common rail 44 via the high pressure fuel passage 24 is applied to the nozzle needle 21. Specifically, the fuel pressure is applied to the nozzle needle 21 in both the displacement directions corresponding to the opening and closing of the injection port 22, and a force is applied in the valve closing direction by the elastic body 23. Here, the back pressure chamber 25 filled with fuel for applying pressure to the side that closes the nozzle needle 21 communicates with the low pressure system (fuel tank 40 side) by opening the valve 26 driven by the electromagnetic solenoid 27. Is done. According to such a configuration, the fuel injection valve 20 can be opened and closed by adjusting the relative magnitude relationship between the force applied by the fuel and the elastic body 23 in each of the displacement directions of the nozzle needle 21 by opening and closing the valve 26. it can.

  Incidentally, between the common rail 44 and the low-pressure fuel passage 28, an electronically controlled pressure reducing valve 46 for allowing the fuel in the common rail 44 to flow out to the fuel tank 40 is provided.

  The electronic control unit (ECU 50) is a control unit that controls the diesel engine 10. The ECU 50 includes a crank angle sensor 52 that detects the rotation angle of the crankshaft 32, a fuel pressure sensor 54 that detects the fuel pressure in the common rail 44, an exhaust temperature sensor 56 that detects the exhaust temperature downstream of the exhaust purification device 38, and an accelerator pedal. The output signals of various sensors such as the accelerator sensor 58 for detecting the operation amount are taken in. Based on these, various actuators such as the fuel injection valve 20 and the fuel pump 42 are operated to control the control amount (torque, exhaust characteristics, etc.) of the diesel engine 10.

  Here, the operation of the fuel injection valve 20 is performed via the driver unit (EDU 60). The EDU 60 has a capacitor 60a for supplying electric charge to the electromagnetic solenoid 27 and a switching element for electrically opening and closing between the capacitor 60a and the electromagnetic solenoid 27, as shown in a partial circuit configuration in the figure. 60b, a constant current circuit 60c, and a cylinder selection switch 60d. Here, the capacitor 60a is power supply means for flowing a large current in the initial energization of the electromagnetic solenoid 27, and the constant current circuit 60c is a constant current for maintaining the energization state after the middle energization of the electromagnetic solenoid 27. It is a circuit for flowing. The capacitor 60a, the switching element 60b, and the constant current circuit 60c are shared between the cylinders. On the other hand, the cylinder selection switch 60d is provided separately for each cylinder, and this makes it possible to select which cylinder the electromagnetic solenoid 27 is energized.

  The ECU 50 also controls regeneration of the DPF 38a. This is because the so-called post-injection in which fuel is injected from the fuel injection valve 20 at a timing that is assumed not to be used for combustion in the combustion chamber 16 causes the fuel to be combusted in an exhaust system such as the exhaust purification device 38 and the exhaust. The temperature is raised. By raising the temperature of the exhaust gas flowing into the DPF 38a, the PM trapped by the DPF 38a can be burned and removed, thereby regenerating the DPF 38a.

  FIG. 2 shows a fuel injection control mode during regeneration control of the DPF 38a. As shown in the figure, the main injection m that contributes to the generation of torque of the diesel engine and has the maximum injection amount during the multistage injection is performed in the vicinity of the compression top dead center. Prior to the main injection m, pilot injection pi is performed. The pilot injection pi promotes the mixing of fuel and air immediately before ignition by injecting a very small amount of fuel, and reduces the delay in the ignition timing after the main injection to suppress the generation of nitrogen oxides (NOx). This is done for the purpose of reducing combustion noise and vibration. Here, in the present embodiment, a so-called synchronous system is configured to match the appearance period of the compression top dead center of each cylinder with the appearance period of the pumping top dead center of the fuel pump 42, and the fuel pump before the main injection m. It is set so that the fuel pumping by 42 is completed.

  The post injection po described above is performed after the center of the expansion stroke (for example, “140 ° ATDC”). This is a setting for burning the fuel injected as the post injection po in the exhaust system without burning in the combustion chamber 16.

  Here, the injection amount of the post injection po is set based on a parameter indicating the operation state of the diesel engine 10. Specifically, in this embodiment, a command torque and a rotational speed for the diesel engine 10 are used as this parameter. Here, the command torque is calculated according to the operation amount of the accelerator pedal. Specifically, the final injection amount of the post injection po is calculated by correcting the basic value calculated by the above parameters so that the exhaust temperature detected by the exhaust temperature sensor 56 is feedback controlled to the target value. The When the injection amount of the post injection po is determined in this way, the valve opening time of the fuel injection valve 20 is uniquely determined according to the fuel pressure in the common rail 44. Therefore, by adjusting the valve opening time, desired fuel can be supplied as the post injection po. Can be injected.

  However, when the fuel injected by the post injection po adheres to the inner wall of the cylinder that defines the combustion chamber 16, the fuel may be scraped off by the piston 30 into the crankcase CK and the lubricating oil may be diluted. In order to avoid such a situation, when the post injection po is divided injection, the amount of heat generated by the switching element 60b and the like in the EDU 60 increases. Occurs. Therefore, in the present embodiment, when performing the post injection po, a process for reducing the fuel pressure in the common rail 44 is performed.

  FIG. 3 shows a processing procedure of fuel pressure control (injection pressure control) in the common rail 44 according to the present embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle, for example.

  In this series of processes, if it is determined in step S10 that there is a request for post-injection po, in step S12, the basic injection pressure PBASE is calculated based on a parameter indicating the operating state of the diesel engine 10. This parameter includes a parameter correlated with the load of the diesel engine 10 and the rotational speed. In this embodiment, command torque is used as a parameter having a correlation with the load. Here, as schematically shown in the figure, basically, the basic injection pressure PBASE increases as the rotational speed NE increases. This is because the time required for rotation at a predetermined crank angle interval is shortened as the rotational speed NE is increased. Basically, the basic injection pressure PBASE is increased as the command torque increases. This is because the required injection amount increases as the command torque increases, so that the injection period easily extends. However, in practice, the torque, exhaust characteristics, noise, and the like of the diesel engine 10 are used as required elements within a range that does not greatly contradict such a tendency, and the optimum values for these required elements are adapted.

  In subsequent step S14, an injection pressure correction amount PCOR is calculated. In the present embodiment, this is the product of the correctable amount PCORB and the correction coefficient PCORC. Here, the correctable amount PCORB is calculated based on the parameters used for calculating the basic injection pressure PBASE. This is because the basic injection pressure PBASE is adapted to an optimum value in consideration of various requirements. For this reason, the above parameters are used in order to define an allowable range for each of these required elements. The correction coefficient PCORC is calculated based on the post injection amount and the basic injection pressure PBASE. Here, considering that the flying distance of the injected fuel increases as the post injection amount increases, the correction coefficient PCORC increases as the post injection amount increases. In view of the fact that as the basic injection pressure PBASE increases, the amount of fuel injected by post-injection reaches the cylinder wall surface increases, the correction coefficient PCORC increases as the basic injection pressure PBASE increases.

  In the subsequent step S16, the target injection pressure PFIN is calculated by subtracting the injection pressure correction amount PCOR from the basic injection pressure PBASE. In order to control the fuel pressure in the common rail 44 to the target injection pressure PFIN calculated in this way, the discharge amount of the fuel pump 42 is operated.

  When a negative determination is made in step S10 or when the process of step S16 is completed, this series of processes is temporarily terminated.

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

  (1) When the request | requirement which performs a post injection arises, the pressure of the fuel injected from the fuel injection valve 20 was reduced compared with the case where a request | requirement does not arise. Thereby, dilution of engine lubricating oil can be suppressed more appropriately.

  (2) Post injection was performed after the center of the expansion stroke in one combustion cycle. Thereby, the fuel injected by the post injection can be suitably supplied to the exhaust system without burning in the combustion chamber 16.

  (3) The pressure reduction amount (injection pressure correction amount PCOR) was increased as the post injection amount increased. Thereby, since the pressure drop amount for post injection can be suppressed as much as possible, even under the situation where post injection is performed, the fuel pressure in the common rail 44 can be approximated to the basic injection pressure PBASE as much as possible.

  (4) When a request to perform post injection occurs, the basic injection pressure PBASE is corrected to decrease. Thereby, when the request | requirement which performs post injection arises, the request | requirement which reduces the fuel amount adhering to the inner wall which divides the combustion chamber 16 can be prioritized rather than the request | requirement at the time of adaptation of the basic injection pressure PBASE. .

  (5) A reduction amount of the basic injection pressure PBASE is set based on a parameter used for calculation of the basic injection pressure PBASE. As a result, the reduction process can be performed while taking into consideration various required elements for the adaptation of the basic injection pressure PBASE.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, the main injection is performed in a state where the fuel pressure in the common rail 44 is controlled to the basic injection pressure PBASE, and the fuel pressure in the common rail 44 is decreased after the main injection and before the post injection. Make an empty shot. Here, idling is a process in which fuel flows out from the high-pressure fuel passage 24 to the low-pressure fuel passage 28 via the fuel injection valve 20 without injecting fuel from the injection port 22 of the fuel injection valve 20. This can be performed by opening the valve 26 for an extremely short time by energizing the electromagnetic solenoid 27 for a very short period of time so that the displacement of the nozzle needle 21 is not started.

  FIG. 4 shows a processing procedure of fuel pressure control (injection pressure control) in the common rail 44 according to the present embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle, for example. In FIG. 4, processes corresponding to the processes shown in FIG. 3 are given the same reference numerals for convenience.

  In this series of processes, after the process of step S14 is completed, the target injection pressure PFIN is set to the basic injection pressure PBASE in step S16a. In the subsequent step S20, the number of idle shots N is calculated based on the basic injection pressure PBASE and the injection pressure correction amount PCOR. Here, the larger the injection pressure correction amount PCOR, the larger the number of idle shots N. This is because the amount of decrease in injection pressure increases as the injection pressure correction amount PCOR increases. Further, the higher the basic injection pressure PBASE, the smaller the number of idle shots N. This is because the amount of fuel that can be leaked from the common rail 44 by a single idle shot increases as the fuel pressure of the common rail 44 increases. Incidentally, the fuel pressure appropriate for post-injection is not restricted by the requirements for adapting the basic injection pressure PBASE, but if the fuel pressure is reduced too much during post-injection, the controllability of the fuel pressure immediately after that may decrease. Therefore, in the present embodiment, the number of idle shots N is set based on the injection pressure correction amount PCOR.

  When the process of step S20 is completed, it is determined in step S22 whether or not the blank run execution condition is satisfied. This condition is a logical product condition of the condition that the main injection is completed and the condition that the post injection is not executed. If it is determined that the execution condition is satisfied, the blanking process is performed for the number N of blank shots (steps S24 and S26).

  When a negative determination is made in steps S10, S22, and S24, or when the process of step S26 is completed, this series of processes is temporarily ended.

  FIG. 5 shows a fuel pressure reduction process according to this embodiment. Specifically, FIG. 5A shows the transition of the operation signal, FIG. 5B shows the transition of the injection rate, and FIG. 5C shows the transition of the injection pressure (fuel pressure in the common rail 44). Show. As shown in the figure, by performing idle driving, the injection pressure can be sufficiently reduced prior to the post injection po.

  According to this embodiment described above, the following effects can be obtained in addition to the effects (1) to (3) of the first embodiment.

  (6) After the main injection is performed, the pressure in the common rail 44 is reduced prior to the post injection. Thereby, the situation where the injection pressure at the time of the main injection m deviates from the optimal injection pressure for the main injection m can be suitably suppressed or avoided for the purpose of reducing the amount of fuel adhering to the inner wall defining the combustion chamber 16. .

  (7) After the main injection m was performed, a pressure reduction process was performed by performing an idle shot prior to the post injection po. Thereby, the fuel pressure in the common rail 44 can be reduced after the main injection.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the second embodiment.

  FIG. 6 shows a processing procedure of fuel pressure control (injection pressure control) in the common rail 44 according to the present embodiment. This process is repeatedly executed by the ECU 50 at a predetermined cycle, for example. In FIG. 6, processes corresponding to the processes shown in FIG. 4 are given the same reference numerals for convenience.

  In this series of processes, when the process of step S16a is completed, the driving time T of the pressure reducing valve 46 is calculated based on the basic injection pressure PBASE and the injection pressure correction amount PCOR in step S30. Here, in view of the fact that when the pressure reducing valve 46 is opened for the same period of time, the amount of fuel flowing out from the common rail 44 increases as the fuel pressure in the common rail 44 increases, the drive time T decreases as the basic injection pressure PBASE increases. . In a succeeding step S32, it is determined whether or not a decompression process execution condition is satisfied. This execution condition is the same as that in step S22 of FIG. When the execution condition is satisfied, the pressure reducing valve 46 is opened over the driving time T (steps S34 and S36).

  According to this embodiment described above, in addition to the effects (1) to (3) of the first embodiment and the effect (6) of the second embodiment, the following effects are further obtained. Can be obtained.

  (8) After the main injection m was performed, a pressure reduction process was performed using the pressure reducing valve 46 prior to the post injection po. Thereby, the fuel pressure in the common rail 44 can be reduced after the main injection.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  In the second and third embodiments, the number of idle shots N and the pressure reducing valve drive time T are calculated based on the injection pressure correction amount PCOR. However, the present invention is not limited to this. For example, the post-injection target injection pressure may be set separately from the target injection pressure PFIN, and the idling number N and the pressure reducing valve driving time T may be calculated based on the post-injection target injection pressure. In this case, it is desirable that the target injection pressure at the time of post injection is set to be lower as the post injection amount is larger.

  In each of the above embodiments, the correctable amount PCORB is calculated based on the same parameter as the input parameter for calculating the basic injection pressure PBASE, but is not limited thereto. For example, you may add another parameter to these.

  -Post injection is not limited to that performed during the expansion stroke. For example, it may be performed during the exhaust stroke.

  The fuel injection control system is not limited to a synchronous system, and may be an asynchronous system. Here, for example, in the case of a 4-cylinder engine, when the fuel pumping cycle by the fuel pump 42 is “360 ° CA”, in the second and third embodiments, the group and the pumping for injecting fuel immediately after pumping It is effective to make the number of idle shots N and the pressure reducing valve driving time T different from each other in the group that injects fuel after fuel injection in other cylinders. If the crank angle interval between the top dead center and the top dead center of a specific cylinder varies, the number of idle shots will be taken into account with the crank angle of the nearest top dead center for the specific cylinder. N or a pressure reducing valve driving time T may be set.

  In each of the above embodiments, the command torque is used as a parameter having a correlation with the load used for calculating the basic injection pressure, but the present invention is not limited to this. For example, it may be a command injection amount for the fuel injection valve 20 or an accelerator pedal operation amount.

  As the drive circuit 60 for driving the fuel injection valve 20, a switching element for supplying power to the fuel injection valve 20 (switching element 60b in FIG. 1, switching element of the constant current circuit 60c) is shared by a plurality of cylinders. Not limited to. When switching elements for power supply are provided independently for each cylinder, the temperature rise of the switching element is reduced even if the post injection is divided to avoid the fuel from the post injection adhering to the cylinder inner wall. Although it can be done, the consumption rate of the fuel injection valve 20 may increase as the number of injections increases. For this reason, it is effective to apply the present invention to avoid such a situation.

  The fuel injection valve 20 is not limited to the one that uses the electromagnetic solenoid 27 as an actuator, and may be one that uses a piezoelectric element as an actuator, for example. Further, the structure of the fuel injection valve 20 is not limited to that illustrated in FIG. However, in the second embodiment, the fuel pressure is applied in both the valve opening direction and the valve closing direction of the nozzle needle, and the chamber is filled with fuel that applies pressure in the valve closing direction. It is desirable to open and close the fuel injection valve by communicating with and blocking the fuel tank side.

  The compression ignition type internal combustion engine is not limited to one that uses light oil as a fuel, and may be one that uses heavy oil or biofuel as a fuel, for example. Further, the invention is not limited to the compression ignition type internal combustion engine, and may be, for example, a cylinder injection type gasoline engine. Even in this case, when the fuel is injected into the combustion chamber for regeneration of the post-processing device, the lubricating oil may be diluted, so that the application of the present invention is effective.

1 is a system configuration diagram according to a first embodiment. FIG. The time chart which illustrates the multistage injection aspect concerning the embodiment. The flowchart which shows the procedure of the control process of the injection pressure concerning the embodiment. The flowchart which shows the procedure of the control process of the injection pressure concerning 2nd Embodiment. The time chart which shows the effect of the embodiment. The flowchart which shows the procedure of the control process of the injection pressure concerning 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Diesel engine, 16 ... Combustion chamber, 20 ... Fuel injection valve, 44 ... Common rail, 50 ... ECU (one embodiment of fuel injection control apparatus).

Claims (9)

The fuel injection device for injecting the high-pressure fuel stored in the pressure accumulating vessel into the combustion chamber of the internal combustion engine provided with the aftertreatment device in the exhaust system via the fuel injection valve is an operation target.
When a request to perform post-injection for regeneration of the post-processing device is generated, a reduction means is provided for reducing the pressure of the fuel injected from the fuel injection valve as compared with the case where the request does not occur. A fuel injection control device for an internal combustion engine.   The fuel injection control device for an internal combustion engine according to claim 1, wherein the post-injection is performed after the center of the expansion stroke in one combustion cycle.   3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the lowering unit increases the decrease amount of the pressure as the injection amount of the post injection increases.   The reducing means reduces the pressure of the fuel injected from the fuel injection valve prior to the post-injection after the main injection for generating the torque of the internal combustion engine is performed. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3. The fuel injection device further includes outflow means for flowing out the fuel in the pressure accumulating container to a fuel tank for storing fuel to be supplied to the pressure accumulating container,
5. The fuel injection for an internal combustion engine according to claim 4, wherein the lowering means performs the pressure lowering process by operating the outflow means prior to the post injection after the main injection is performed. Control device. The fuel injection device includes a fuel tank that stores fuel to be supplied to the pressure accumulating vessel,
The reduction means performs the pressure reduction process by operating the fuel injection valve so that the fuel in the pressure accumulating vessel flows out to the fuel tank through the fuel injection valve without performing fuel injection. The fuel injection control device for an internal combustion engine according to claim 4, wherein the fuel injection control device is an internal combustion engine. Further comprising setting means for setting a target value of the pressure of fuel injected from the fuel injection valve during main injection for generating torque of the internal combustion engine;
The reduction means corrects the target value set by the setting means to be reduced when a request to perform post injection for regeneration of the post-processing device occurs. 2. A fuel injection control device for an internal combustion engine according to 1. The setting means performs the setting process of the target value based on a parameter indicating an operating state of the internal combustion engine,
8. The fuel injection control apparatus for an internal combustion engine according to claim 7, wherein the lowering means sets the amount of decrease in the target value based on a parameter used for the target value setting process. A fuel injection control device for an internal combustion engine according to any one of claims 1 to 8,
A fuel injection control system for an internal combustion engine, comprising the fuel injection device.

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