JP2016075153A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of suppressing decrease in a rail pressure of a common rail derived from an integral term.SOLUTION: A fuel injection control device includes a common rail 3 for storing fuel supplied to an injector 2, a force-feed pump 4 for force-feeding the fuel to the common rail 3, a PID control section 5 for controlling a fuel force-feed amount of the force-feed pump 4 by PID control in accordance with a deviation between an actual rail pressure and a target rail pressure of the common rail 3 so as to control a rail pressure of the common rail 3 to be the target rail pressure, and a pressure reduction valve 6 provided on the common rail 3 and opened so as to return the fuel in the common rail 3 to a fuel tank 7 when the deviation between the actual rail pressure and the target rail pressure is within a pressure reduction valve operation threshold range set in advance. The PID control section 5 stops calculation of an integral term when the fuel force-feed amount of the force-feed pump 4 is equal to or less than a pressure-feed amount threshold set in advance and a fuel injection amount is equal to or less than an injection amount threshold set in advance.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection control device.

  Depending on the difference between the actual rail pressure of the common rail and the target rail pressure in order to control the common rail rail pressure to the target rail pressure, the common rail that stores the fuel supplied to the injector in a high pressure state, the pump that pumps the fuel to the common rail, There is known a fuel injection control device including a PID control unit that controls a fuel pumping amount of a pump by PID control.

  By the way, in recent years, an injector having no static leak mechanism for returning a part of the supplied fuel to the fuel tank has been used.

  When using an injector that does not have such a static leak mechanism, the fuel injection control device is equipped with a mechanism that reduces the rail pressure, called a pressure reducing valve, in the common rail, and controls the common rail pressure by opening and closing the pressure reducing valve. It is common to do.

  The pressure reducing valve is opened when the deviation between the target rail pressure and the actual rail pressure is within a preset pressure reducing valve operating threshold range (when larger than the preset threshold value), and returns the fuel in the common rail to the fuel tank. It is configured as follows.

  In addition, there exists patent documents 1-4 as prior art document information relevant to the invention of this application.

JP 2007-278169 A JP 2005-113704 A JP 2002-195081 A Japanese Patent Laid-Open No. 05-163994

  However, in the fuel injection control device using the pressure reducing valve as described above, the pressure reducing valve does not operate when the deviation between the target rail pressure and the actual rail pressure is smaller than the threshold value. That is, in the conventional fuel injection control device, when the deviation between the target rail pressure and the actual rail pressure is smaller than the threshold value, the deviation between the target rail pressure and the actual rail pressure remains.

  Therefore, when the fuel pumping amount is controlled by PID control, the remaining deviation is continuously accumulated as an integral term (I term), which may cause a problem.

  Specifically, for example, when the vehicle is downhill due to inertia, fuel injection is not performed and the fuel pumping amount is controlled to be low, so the actual rail pressure is slightly higher than the target rail pressure (the above-described deviation) Higher). In this state, the integral term continues to subtract the deviation between the actual rail pressure and the target rail pressure, the integral term becomes negative, and the fuel pumping amount decreases.

  Therefore, when the fuel injection is resumed after the slope is finished, the fuel pumping amount may be insufficient due to the integrated integral term.

  That is, when fuel injection is restarted with the integral term negative, the rail pressure of the common rail greatly decreases due to the rail pressure drop due to fuel injection and the lack of fuel pumping amount. There is a risk that the engine will stop due to insufficient injection amount.

  Accordingly, an object of the present invention is to provide a fuel injection control device that can solve the above-described problems and can suppress a decrease in rail pressure of a common rail derived from an integral term.

  The present invention has been developed to achieve the above object, and controls a common rail that stores fuel to be supplied to an injector, a pump that pumps fuel to the common rail, and a rail pressure of the common rail to a target rail pressure. Therefore, a PID control unit that controls the fuel pumping amount of the pumping pump by PID control according to a deviation between the actual rail pressure of the common rail and the target rail pressure, and the common rail is provided with the actual rail pressure and the target rail. A pressure reducing valve that is opened when the pressure deviation is within a preset pressure reducing valve operating threshold range and returns the fuel in the common rail to the fuel tank; The fuel pumping amount of the pumping pump is not more than a preset pumping amount threshold, and the fuel injection amount is not more than a preset injection amount threshold. Rutoki a fuel injection control device is configured to stop the operation of the integral term.

  The PID control unit may be configured to stop the calculation of the integral term only when the actual rail pressure is equal to or less than a preset rail pressure threshold.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel-injection control apparatus which can suppress the fall of the rail pressure of the common rail originating in an integral term can be provided.

It is a schematic block diagram of the fuel-injection control apparatus which concerns on one Embodiment of this invention. (A) is a time chart of rail pressure and fuel injection amount in the present invention, and (b) is a time chart of rail pressure and fuel injection amount in the prior art. It is a flowchart which shows the control flow of the PID control part in this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a fuel injection control apparatus according to the present embodiment.

  As shown in FIG. 1, the fuel injection control device 1 includes a common rail 3 that stores fuel to be supplied to an injector 2 in a high pressure state, a pressure feed pump 4 that pumps fuel to the common rail 3, and a rail pressure of the common rail 3 to obtain a target rail pressure. A PID control unit 5 that controls the pressure pump 4 and a pressure reducing valve 6 provided on the common rail 3 are provided.

  In the present embodiment, as the injector 2, one that does not have a static leak mechanism that returns a part of the supplied fuel to the fuel tank 7 is used.

  The PID control unit 5 is mounted on an electronic control unit (hereinafter referred to as ECU) 8 of the vehicle. Various information necessary for fuel injection control, such as the actual rail pressure of the common rail 3, the fuel pumping amount of the pumping pump 4, the fuel injection amount, and the engine speed, is input to the ECU 8 by a sensor or the like (not shown). The target rail pressure is calculated by the ECU 8 based on the fuel injection amount, the engine speed, and the like.

  The PID control unit 5 is configured to control the fuel pumping amount of the pumping pump 4 by PID control in accordance with a deviation between the actual rail pressure of the common rail 3 and the target rail pressure (hereinafter sometimes simply referred to as a deviation). .

  More specifically, the PID control unit 5 multiplies a proportional term (P term) obtained by multiplying a deviation between the actual rail pressure and the target rail pressure by a proportional gain, and a time integral value (cumulative value) of the deviation by an integral gain. The fuel pumping amount of the pumping pump 4 is obtained by adding the integral term (I term) and the differential term (D term) obtained by multiplying the time differential value of the deviation by the differential gain. The PID control unit 5 outputs a drive current corresponding to the obtained fuel pumping amount to the pumping pump 4 so that a desired fuel pumping amount is pumped from the pumping pump 4.

  The pressure reducing valve 6 is opened when the deviation between the actual rail pressure and the target rail pressure is within a preset pressure reducing valve operating threshold value range (when it is larger than the preset threshold value), and the fuel in the common rail 3 is supplied to the fuel tank. It is configured to return to 7. The ECU 8 performs opening / closing control of the pressure reducing valve 6.

  In the fuel injection control device 1 according to the present embodiment, the PID control unit 5 has the fuel pumping amount of the pumping pump 4 equal to or less than a preset pumping amount threshold value, and the fuel injection amount is a preset injection amount threshold value. It is configured to stop the calculation of the integral term when:

  As shown in FIG. 2A, when the vehicle is traveling on a downhill coast, fuel injection is not performed. Therefore, the target rail pressure gradually decreases, and the fuel pumping amount and the fuel injection amount are reduced. Both are controlled very small. The actual rail pressure decreases following the target rail pressure, but the decrease in the actual rail pressure at this time is realized by opening the pressure reducing valve 6.

  Since the pressure reducing valve 6 is opened when the deviation between the actual rail pressure and the target rail pressure is larger than a preset threshold value, the actual rail pressure is higher than the target rail pressure. Therefore, if this state continues, in the prior art, the integral term continues to subtract the deviation between the actual rail pressure and the target rail pressure, and the integral term continues to decrease.

  In this embodiment, in such a case, the calculation of the integral term is stopped. More specifically, the calculation of the integral term is temporarily interrupted, and the PID control is continued using the value of the integral term immediately before the interruption. As a result, it is possible to suppress the integral term from continuing to decrease, and to quickly increase the fuel pumping amount during subsequent acceleration, thereby suppressing a decrease in the rail pressure of the common rail 3.

  In the present embodiment, the PID control is continued using the value of the integral term immediately before the interruption. For example, the PID control unit 5 is set so as to perform the calculation by resetting the integral term or excluding the integral term. It can also be configured. However, in this case, the operation amount (here, fuel pumping amount) by PID control changes abruptly at the timing when the integral term is reset or excluded, which is not preferable.

  Even if the fuel pumping amount is equal to or less than a preset pumping amount threshold value and the fuel injection amount is equal to or less than a preset injection amount threshold value, for example, the integral term is a positive value. The fuel pressure and the operation of the pressure reducing valve 6 are repeated, which may cause the rail pressure hunting of the common rail 3.

  Therefore, in the present embodiment, the PID control unit 5 is further configured to stop the calculation of the integral term only when the actual rail pressure is equal to or less than a preset rail pressure threshold value. This is because when the actual rail pressure is sufficiently small, the actual rail pressure is stable at a value slightly higher than the target rail pressure, and the value of the integral term is considered to be sufficiently small.

  For reference, FIG. 2B shows an example of rail pressure fluctuation in a conventional apparatus that does not stop the calculation of the integral term. As shown in FIG. 2B, when the fuel injection is resumed after the integral term is continuously subtracted, as shown in the area A in FIG. 2, due to the influence of the drop in the rail pressure due to the fuel injection and the insufficient fuel pumping amount. There is a risk that the common rail pressure will drop significantly, causing problems such as engine stoppage.

  Next, the control flow of the fuel injection control device 1 will be described. For example, the fuel injection control device 1 is configured to execute the control flow of FIG. 3 while an ignition switch (not shown) of the vehicle is turned on.

  As shown in FIG. 3, first, in step S1, it is determined whether or not the fuel pumping amount is equal to or less than the pumping amount threshold. If NO is determined in step S1, in step S4, the calculation of the integral term (I term) is resumed or the calculation of the integral term is continued, and the process returns to step S1.

  If YES is determined in step S1, it is determined in step S2 whether the fuel injection amount is equal to or less than an injection amount threshold value. If NO is determined in step S2, the integral term calculation is resumed or the integral term calculation is continued in step S4, and the process returns to step S1.

  If YES is determined in step S2, it is determined in step S3 whether the actual rail pressure of the common rail 3 is equal to or less than the rail pressure threshold value. If NO is determined in step S3, the integral term calculation is resumed or the integral term calculation is continued in step S4, and the process returns to step S1.

  If YES is determined in step S3, the fuel pumping amount is equal to or smaller than the pumping amount threshold, the fuel injection amount is equal to or smaller than the injection amount threshold, and the actual rail pressure is equal to or smaller than the rail pressure threshold. Therefore, in step S5, the calculation of the integral term (I term) is stopped or the calculation of the integral term is stopped, and the process returns to step S1.

  As described above, in the fuel injection control device 1 according to the present embodiment, the fuel pumping amount of the pumping pump 4 is not more than a preset pumping amount threshold value, and the fuel injection amount is not more than a preset injection amount threshold value. At some point, the calculation of the integral term is stopped.

  Thus, the integral term does not continue to subtract the deviation between the actual rail pressure and the target rail pressure. For example, even when the fuel injection is resumed from the state where the fuel is not injected, the rail of the common rail 3 It is possible to suppress a decrease in pressure. As a result, it is possible to suppress problems such as engine stop caused by a decrease in rail pressure.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Fuel injection control apparatus 2 Injector 3 Common rail 4 Pressure feed pump 5 PID control part 6 Pressure reducing valve 7 Fuel tank

Claims (2)

A common rail for storing fuel to be supplied to the injector;
A pump for pumping fuel to the common rail;
A PID control unit for controlling the fuel pumping amount of the pumping pump by PID control according to a deviation between the actual rail pressure of the common rail and the target rail pressure in order to control the rail pressure of the common rail to a target rail pressure;
A pressure reducing valve provided on the common rail and opened when a deviation between the actual rail pressure and the target rail pressure is within a preset pressure reducing valve operating threshold range, and returns the fuel in the common rail to a fuel tank;
In a fuel injection control device comprising:
The PID control unit stops the calculation of the integral term when the fuel pumping amount of the pumping pump is not more than a preset pumping amount threshold and the fuel injection amount is not more than a preset injection amount threshold. A fuel injection control device comprising: The fuel injection control device according to claim 1, wherein the PID control unit is configured to stop the calculation of an integral term only when the actual rail pressure is equal to or less than a preset rail pressure threshold.

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