JP5736785B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine including an in-cylinder injector, a port injection injector, and a high-pressure fuel pump that increases a fuel pressure of fuel supplied to the in-cylinder injector.

  2. Description of the Related Art In recent years, as can be seen in Patent Documents 1 to 4, there are known internal combustion engines that include two injectors, an in-cylinder injector and a port injection injector, and use different injectors depending on the situation.

  In this type of internal combustion engine, high fuel pressure is required for fuel injection into a cylinder having a pressure higher than that of the intake port. However, a sufficiently high fuel pressure may not be ensured immediately after engine startup or immediately after switching from low load operation to high load operation. In such a case, if in-cylinder injection of all the fuel is performed, the completion time of the injection enters the compression stroke, leading to deterioration of combustion and emission.

  Therefore, conventionally, in the control apparatus for an internal combustion engine described in Patent Documents 1, 2, and 4, when the fuel pressure is less than the reference pressure, the fuel injection ratio of in-cylinder injection is reduced, and the fuel injection ratio of port injection is reduced accordingly. Increasing. In this way, the completion timing of in-cylinder injection is prevented from becoming too late, and deterioration of combustion and emission is avoided.

JP 2005-248803 A JP 2006-022732 A JP 2006-132396 A JP 2001-107789 A

  Thus, if the fuel injection ratio of in-cylinder injection is reduced when the fuel pressure is insufficient, the deterioration of the combustion state can be suppressed to some extent. However, during the period when the fuel injection ratio of in-cylinder injection is reduced, the fuel that should be injected into the cylinder is originally injected into the intake port, so the optimal combustion state of the soot that is originally obtained is ensured. It will not be possible.

  The present invention has been made in view of such circumstances, and the problem to be solved is to provide a control device for an internal combustion engine that can suppress deterioration of the combustion state due to fuel injection when the fuel pressure is insufficient. There is to do.

In order to solve the above-mentioned problem, the fuel of the fuel supplied to the in-cylinder injector by pressurizing and discharging the fuel supplied from the in-cylinder injector, the port injector, and the feed pump provided in the fuel tank The invention according to claim 1 as a control device for an internal combustion engine including a high-pressure fuel pump for increasing the pressure includes both the in-cylinder injector and the port injection injector in a period until the fuel pressure rises to the reference pressure. The fuel injection is performed from the start, and the pressure increase waiting control for increasing the discharge amount of the high pressure fuel pump is executed.

  In the above configuration, when the fuel pressure necessary for performing only the in-cylinder injection is insufficient, the fuel is injected from both the in-cylinder injector and the port injection injector. In addition, the discharge amount of the high-pressure fuel pump is increased. Therefore, the increase in fuel pressure can be accelerated, and the period during which fuel injection is divided between in-cylinder injection and port injection can be shortened. Therefore, according to the above configuration, it is possible to suppress an increase in the period of fuel injection when the fuel pressure is insufficient, and to suppress deterioration of the combustion state due to the injection.

  If the pressure increase waiting control is performed only by the fuel pressure being low and the fuel injection divided and the high pressure fuel pump discharge amount being increased, the pressure increase waiting control may be executed even when the target fuel pressure is low. . In this regard, as in claim 2, if the pressure increase waiting control is executed on the condition that the deviation between the target fuel pressure and the actual fuel pressure is equal to or greater than the specified value, the target fuel pressure is simply low. The boost wait control is not executed.

  Note that the increase in the fuel discharge amount during the pressure increase waiting control includes the feedback discharge amount set according to the deviation between the target fuel pressure and the actual fuel pressure, and a fixed discharge set in advance as a constant. This can be done by setting the higher of the quantity as the fuel discharge quantity of the high-pressure fuel pump.

  Further, according to claim 4, if the pressure increase waiting control is performed only when there is a history of confirming that the fuel pressure has decreased due to fuel leakage from the high pressure fuel pump, the fuel pressure is actually insufficient. Only in this case, the boost wait control can be executed.

  According to the fifth aspect of the present invention, the reference pressure may be set to the minimum value of the fuel pressure that can complete the fuel injection within the intake stroke when the fuel injection is performed only by the in-cylinder injector. .

1 is a schematic diagram schematically showing the configuration of a fuel system of an internal combustion engine to which an embodiment of the present invention is applied. The time chart which shows an example of the control aspect of the embodiment. The flowchart which shows the process sequence of the pressure | voltage rise waiting control routine applied to the embodiment.

  Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described in detail with reference to FIGS. In the present embodiment, a case where the control device of the present invention is applied to an internal combustion engine having a V-type cylinder arrangement will be described.

First, the configuration of a fuel system of an internal combustion engine to which the control device of the present embodiment is applied will be described with reference to FIG.
As shown in FIG. 1, the feed pump 2 provided in the fuel tank 1 is connected to the low pressure fuel pipe 3 through the low pressure fuel passage 11. The low pressure fuel pipe 3 is connected to a port injection injector 4 for each cylinder.

  On the other hand, the low pressure fuel passage 11 is also connected to a high pressure fuel pump 5 that pressurizes and discharges fuel. The fuel discharge port of the high pressure fuel pump 5 is connected to the high pressure fuel pipe 6 through the high pressure fuel passage 12. An in-cylinder injector 7 for each cylinder is connected to the high-pressure fuel pipe 6. The high-pressure fuel pipe 6 is provided with a fuel pressure sensor 8 that detects the pressure of the fuel stored in the high-pressure fuel pipe 6 and an electromagnetic relief valve 9 that relieves the fuel from the high-pressure fuel pipe 6.

  In such a fuel system of the internal combustion engine, the fuel pumped up from the fuel tank 1 by the feed pump 2 is sent to the low pressure fuel pipe 3 through the low pressure fuel passage 11. The fuel is distributed and supplied from the low-pressure fuel pipe 3 to the port injectors 4 of the respective cylinders, and is injected and supplied to the intake ports of the respective cylinders of the internal combustion engine through the port injectors 4.

  On the other hand, the fuel pumped up by the feed pump 2 is also sent to the high-pressure fuel pump 5 through the low-pressure fuel passage 11. The high pressure fuel pump 5 pressurizes and discharges the introduced fuel. The fuel discharged from the high-pressure fuel pump 5 is sent to the high-pressure fuel pipe 6 through the high-pressure fuel passage 12. The fuel sent to the high-pressure fuel pipe 6 is distributed and supplied to the in-cylinder injectors 7 of each cylinder, and is injected and supplied from the in-cylinder injectors 7 to each cylinder of the internal combustion engine.

  The fuel system of such an internal combustion engine is controlled by the electronic control unit 10. The electronic control unit 10 includes a central processing unit (CPU) that performs arithmetic processing related to various controls of the fuel system, and a read-only memory (ROM) that stores control programs and data. The electronic control unit 10 also includes a random access memory (RAM) that temporarily stores CPU calculation results and sensor detection results, and an input / output port (I / O) that mediates transmission / reception of signals to / from the outside. ing.

  Detection signals from various sensors that detect the engine operating status, including the fuel pressure sensor 8, are input to the input port of the electronic control unit 10. A command signal is output from an output port of the electronic control unit 10 to drive circuits of actuators such as the port injection injector 4, the high pressure fuel pump 5, the in-cylinder injection injector 7, and the electromagnetic relief valve 9.

  Now, in the present embodiment configured as described above, the electronic control unit 10 obtains the injection ratio according to the engine operating condition, and injects fuel from the port injector 4 according to the obtained injection ratio. And the injection ratio of the fuel injection from the in-cylinder injector 7 is controlled. Here, the injection ratio is expressed as a ratio of the port injection amount to the total injection amount. Accordingly, when the value is “1.0”, all fuel is injected into the intake port, and when the value is “0”, all fuel is injected into the cylinder.

  Further, the electronic control unit 10 monitors whether or not the fuel pressure in the high-pressure fuel pipe 6 detected by the fuel pressure sensor 8 is equal to or higher than a reference pressure during engine operation. Here, the reference pressure is the minimum value of the fuel pressure at which fuel injection can be completed within the intake stroke when the required amount of fuel injection is performed only by the in-cylinder injector 7, and this value is the engine rotation speed. Calculated from speed and engine load.

  If the detected value of the fuel pressure (actual fuel pressure) is less than the reference pressure, when all the fuel is injected into the cylinder, the completion timing of the fuel injection enters the compression stroke, and the combustion deteriorates. Therefore, in the present embodiment, when the fuel pressure is insufficient, both the port injection injector 4 and the in-cylinder injection injector 7 are required even when the required injection ratio (requested injection ratio) is “0”. Fuel injection is carried out. The fuel injection amount of the in-cylinder injector 7 at this time is set to an amount that can sufficiently cool the tip of the in-cylinder injector 7 with the injected fuel.

  On the other hand, in the present embodiment, when the actual fuel pressure is less than the reference pressure, the electronic control unit 10 also performs the increase control of the fuel discharge amount of the high-pressure fuel pump 5. In the present embodiment, the higher one of the feedback discharge amount set according to the deviation between the target fuel pressure and the actual fuel pressure and the fixed discharge amount set in advance as a constant is the fuel discharge of the high-pressure fuel pump 5. By setting the amount, the fuel discharge amount at this time is increased. The fixed discharge amount here is set to the value of the fuel discharge amount that can quickly increase the fuel pressure to the reference pressure as long as the actual fuel pressure does not overshoot the target fuel pressure. Note that the fuel discharge amount of the high-pressure fuel pump 5 when the increase control of the fuel discharge amount is not performed is set to the feedback discharge amount.

  As described above, in the present embodiment, when the actual fuel pressure is less than the reference pressure, the pressure increase waiting control by the fuel injection and the increase in the fuel discharge amount as described above is performed. If the pressure increase waiting control is executed simply based on the fact that the actual fuel pressure is low, the pressure increase wait control is executed even when the target fuel pressure is only low. Therefore, in the present embodiment, the pressure increase waiting control is performed only when the target fuel pressure is low by executing the pressure increase wait control on the condition that the deviation between the target fuel pressure and the actual fuel pressure is equal to or greater than a specified value. It is not executed.

  Further, in the present embodiment, the pressure increase waiting control is performed only when there is a history that a decrease in fuel pressure due to fuel leakage (leakage) of the high pressure fuel pump 5 has been confirmed. Only when the fuel pressure is insufficient, the pressure increase waiting control is executed. Here, the decrease in the fuel pressure due to the leak is confirmed by confirming that the amount of decrease in the actual fuel pressure when the fuel discharge amount of the high-pressure fuel pump 5 is “0” is equal to or greater than the prescribed leak judgment value. Yes.

  An example of the control mode of this embodiment is shown in FIG. In the figure, it is confirmed that the fuel pressure is reduced due to the leak at time T0, and the requested injection ratio is set to “0” along with the transition from the idle operation to the normal operation at time T1, and all the fuel is consumed. In-cylinder injection is required.

  However, at this time T1, the actual fuel pressure in the high-pressure fuel pipe 6 has not reached the reference pressure, and the fuel pressure is insufficient to perform in-cylinder injection of all the fuel. Therefore, at this time T1, the electronic control unit 10 does not set the actually set ejection ratio (final ejection ratio) to “0”, turns on the boost waiting control execution flag, and starts the boost waiting control. .

  When the pressurization waiting control is started, the final injection ratio is set to a specified value, and fuel injection is performed by both the port injector 4 and the in-cylinder injector 7. If the feedback discharge amount (F / B discharge amount) is less than the fixed discharge amount, the fuel discharge amount of the high-pressure fuel pump 5 is increased to the fixed discharge amount.

  Then, when the actual fuel pressure rises due to such an increase in the fuel discharge amount, and the actual fuel pressure exceeds the reference pressure at time T2, the final injection ratio is set to “0”, and finally in the cylinder of all the fuel Injection starts. Further, after this time T2, the fuel discharge amount of the high-pressure fuel pump 5 is feedback adjusted in accordance with the deviation between the target fuel pressure and the actual fuel pressure.

  FIG. 3 shows a flowchart of a boost wait control routine applied to this embodiment. The processing of this routine is repeatedly executed by the electronic control unit 10 during engine operation.

  When this routine is started, it is first determined in step S100 whether there is a history of fuel pressure drop due to leakage. Here, if there is no such history (S100: NO), normal fuel injection division control and fuel discharge amount control are executed. That is, in the internal combustion engine at this time, the fuel injection from the port injector 4 and the in-cylinder injector 7 is performed at the injection ratio according to the engine operating condition, and the fuel discharge amount of the high-pressure fuel pump 5 is Feedback control is performed according to the deviation between the target fuel pressure and the actual fuel pressure.

  If there is a history of fuel pressure drop due to leakage (S100: YES), in step S101, it is determined whether or not an execution condition for the pressure increase waiting control is satisfied. The execution condition for the pressure increase waiting control is satisfied when the actual fuel pressure is equal to or lower than the reference pressure, the required injection ratio is “0”, and the deviation between the target fuel pressure and the actual fuel pressure is equal to or greater than a specified value. Is set to Here, if the execution condition of the pressure increase waiting control is not satisfied (S101: NO), in step S102, normal control of fuel injection and fuel discharge amount is executed.

  On the other hand, if the execution condition for the pressure increase waiting control is satisfied (S101: YES), the process proceeds to step S103, and in step S103, both the port injection and the in-cylinder injection at the prescribed injection ratio are performed. Fuel injection is divided. In steps S104 to S106, the larger one of the feedback discharge amount and the fixed discharge amount is set as the fuel discharge amount of the high-pressure fuel pump 5. The processes in steps S103 to S106 described above are continued until the actual fuel pressure reaches the reference pressure (S107: YES).

According to the control apparatus for an internal combustion engine of the present embodiment described above, the following effects can be obtained.
(1) In the present embodiment, fuel injection is performed from both the in-cylinder injector 7 and the port injection injector 4 and the discharge amount of the high-pressure fuel pump 5 until the fuel pressure rises to the reference pressure. The boost wait control for increasing the value is executed. Therefore, the increase in fuel pressure can be accelerated, and the period during which fuel injection is divided between in-cylinder injection and port injection can be shortened. Therefore, according to the present embodiment, it is possible to suppress an increase in the period of fuel injection when the fuel pressure is insufficient, and to suppress deterioration of the combustion state due to the injection.

  (2) In the present embodiment, in-cylinder injection of all the fuel, when the actual fuel pressure is insufficient, an in-cylinder injection amount that can sufficiently cool the tip of the injector with the injected fuel is secured. In addition, fuel injection is performed by both port injection and in-cylinder injection. Therefore, it can be avoided that the tip temperature of the in-cylinder injector 7 becomes too high and deposits are generated or melting damage occurs.

  (3) In the present embodiment, the pressure increase waiting control is executed on condition that the deviation between the target fuel pressure and the actual fuel pressure is equal to or greater than a specified value. Therefore, when the target fuel pressure is merely low, the pressure increase waiting control is not performed unnecessarily.

  (4) In the present embodiment, the pressure increase waiting control is performed only when a decrease in fuel pressure due to fuel leakage from the high pressure fuel pump 5 is confirmed. Therefore, the pressure increase waiting control can be executed only when the fuel pressure is actually insufficient.

  (5) In the present embodiment, the larger one of the feedback discharge amount set in accordance with the deviation between the target fuel pressure and the actual fuel pressure and the fixed discharge amount set in advance as a constant is set as the fuel discharge amount. By setting, the increase control of the fuel discharge amount of the high-pressure fuel pump 5 during the pressure increase waiting control is performed. The fixed discharge amount is set to a fuel discharge amount that can quickly increase the fuel pressure to the reference pressure as long as the actual fuel pressure does not overshoot the target fuel pressure. Therefore, in-cylinder injection of all fuel can be started promptly while preventing overshoot of the fuel pressure.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the pressure increase waiting control is performed only when a decrease in fuel pressure due to fuel leakage from the high pressure fuel pump 5 is confirmed. However, if the suppression of pressure increase is not necessary when the fuel pressure is not actually insufficient, or if this suppression is not necessary, the fuel pressure is not confirmed due to fuel leakage. Instead, the pressure increase waiting control may be performed.

  In the above embodiment, the pressure increase waiting control is executed when the target fuel pressure is simply low by executing the pressure increase wait control on the condition that the deviation between the target fuel pressure and the actual fuel pressure is not less than the specified value. Had to not run. However, if the target fuel pressure is only low and the pressure increase wait control may be executed, the pressure increase wait control is executed regardless of the difference between the target fuel pressure and the actual fuel pressure. Anyway.

  In the above embodiment, the higher one of the feedback discharge amount set according to the deviation between the target fuel pressure and the actual fuel pressure and the fixed discharge amount set in advance as a constant is the fuel of the high-pressure fuel pump 5 By setting the discharge amount, the fuel discharge amount of the high-pressure fuel pump 5 is increased. However, even if the fuel discharge amount of the high-pressure fuel pump 5 is increased by a method other than this, it is possible to suppress the deterioration of the combustion state due to fuel injection when the fuel pressure is insufficient. For example, the fuel discharge amount of the high-pressure fuel pump 5 during the pressure increase waiting control can also be increased by correcting the feedback discharge amount to be increased.

  DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... Feed pump, 3 ... Low pressure fuel piping, 4 ... Port injection injector, 5 ... High pressure fuel pump, 6 ... High pressure fuel piping, 7 ... In-cylinder injection injector, 8 ... Fuel pressure sensor, 9 ... Electromagnetic Relief valve, 10 ... electronic control unit, 11 ... low pressure fuel passage, 12 ... high pressure fuel passage.

Claims (5)

In-cylinder injector, port injector, and high-pressure fuel pump that increases the fuel pressure of the fuel supplied to the in-cylinder injector by pressurizing and discharging the fuel supplied from the feed pump provided in the fuel tank In an internal combustion engine control device comprising:
During the period until the fuel pressure rises to the reference pressure, the pressure increase waiting control is performed to increase the fuel discharge amount of the high-pressure fuel pump while performing fuel injection from both the in-cylinder injector and the port injection injector. A control device for an internal combustion engine. The control device for an internal combustion engine according to claim 1, wherein the pressure increase waiting control is executed on condition that a deviation between a target fuel pressure and an actual fuel pressure is equal to or greater than a specified value. The increase in the fuel discharge amount is the higher of the feedback discharge amount set according to the deviation between the target fuel pressure and the actual fuel pressure or the fixed discharge amount set in advance as a constant, whichever is greater. The control device for an internal combustion engine according to claim 1 or 2, wherein the control device is set as a fuel discharge amount. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the pressure increase waiting control is performed only when there is a history that a fuel pressure drop due to fuel leakage from the high pressure fuel pump has been confirmed. The minimum value of the fuel pressure which can complete fuel injection in the intake stroke is set as the reference pressure when fuel injection is performed only by the in-cylinder injector. The internal combustion engine control device described.

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