JP2016217145A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately reduce a rail pressure of a common rail.SOLUTION: A fuel injection control device 1 of this invention includes a common rail 3 for storing fuel to be supplied to an injector 2, a force-feed pump 4 for force-feeding the fuel to the common rail 3, a pressure reduction valve 5 for returning the fuel in the common rail 3 to a fuel tank, a pump control section 6 for feed-back 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, and a pressure reduction valve control section 7 for feed-back controlling an opening of the pressure reduction valve 5 by PID control in accordance with the deviation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection control device.

  The diesel engine includes an injector that directly injects fuel into a cylinder of each cylinder, and a common rail that stores fuel injected from the injector in a high-pressure state.

  In recent years, an injector that does not have a static leak mechanism for returning a part of supplied fuel to a fuel tank has been used. When such an injector is used, it is common to provide a common rail with a pressure reducing valve and open the pressure reducing valve to lower the rail pressure.

  As a technology related to this, for example, a pressure reducing valve and a suction adjusting valve are provided, and feedback for converging the actual rail pressure to the target rail pressure based on a deviation (differential pressure) between the target rail pressure and the actual rail pressure. A fuel injection system that controls the intake amount of an intake adjustment valve by obtaining an amount (feedback gain) is disclosed (see Patent Document 1).

JP 2011-080443 A JP 2007-278169 A JP 2014-051912 A JP2011-111985

  However, in the conventional fuel injection control device, when the rail pressure of the common rail is reduced, feedback control that repeatedly opens and closes the pressure reducing valve is performed, which is insufficient to accurately reduce the rail pressure.

  Therefore, an object of the present invention is to provide a fuel injection control device that can solve the above-described problems and can accurately reduce the rail pressure of a common rail.

  According to one aspect of the present invention, a common rail that stores fuel to be supplied to an injector, a pressure feed pump that pumps fuel to the common rail, a pressure reducing valve that returns fuel in the common rail to a fuel tank, and an actual rail pressure of the common rail A pump control unit that feedback-controls the fuel pumping amount of the pumping pump by PID control according to a deviation between the pressure and the target rail pressure, and a pressure-reducing valve control that feedback-controls the opening degree of the pressure-reducing valve by PID control according to the deviation And a fuel injection control device comprising: a portion.

  Further, it is preferable that the pressure reducing valve control unit executes the feedback control when the deviation exceeds a preset threshold value, and stops the feedback control when the deviation is equal to or less than a preset threshold value. .

  ADVANTAGE OF THE INVENTION According to this invention, the fuel-injection control apparatus which can reduce the rail pressure of a common rail with a sufficient precision can be provided.

It is a schematic block diagram of the fuel-injection control apparatus which concerns on one Embodiment of this invention. It is a figure which shows the control flow of the pressure-reduction valve control part of one Embodiment of this invention. It is a figure where it uses for description of the control condition of the conventional fuel injection control apparatus.

  Hereinafter, an embodiment 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 an embodiment of the present invention.

  As shown in FIG. 1, a fuel injection control device 1 includes an injector 2 that directly injects fuel into a cylinder of each cylinder of a diesel engine (not shown), a common rail 3 that stores fuel supplied to the injector 2 in a high-pressure state, and a common rail 3, a pressure-feed pump 4 that pumps fuel to the pressure pump 3, a pressure-reduction valve 5 that lowers the pressure in the common rail 3, a pump control unit 6 that feedback-controls the fuel pressure-feed amount of the pressure-feed pump 4, and a feedback control of the opening of the pressure-reduction valve 5 And a pressure reducing valve control unit 7 for performing the above operation. The pump control unit 6 and the pressure reducing valve control unit 7 are mounted on a vehicle electronic control unit (hereinafter referred to as ECU) 20 (not shown).

  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 11 is used. Further, the common rail 3 is provided with a common rail pressure sensor 10 for detecting a pressure in the common rail 3 (hereinafter referred to as an actual rail pressure).

  The pressure pump 4 includes a feed pump 12 that pumps fuel from the fuel tank 11, a high-pressure pump 13 that sucks low-pressure fuel from the feed pump 12 and discharges high-pressure fuel, and is discharged from the feed pump 12 and sucked into the high-pressure pump 13. And a suction control valve (hereinafter referred to as SCV) 14 for adjusting the fuel flow rate. The high-pressure pump 13 includes a plunger (not shown) that slides inside the pump cylinder and discharges high-pressure fuel. The SCV 14 is composed of an electromagnetic valve whose opening degree can be changed continuously from fully closed to fully open according to the magnitude of the drive current input from the pump control unit 6.

  The pressure reducing valve 5 is provided on the common rail 3 and is configured to return the fuel in the common rail 3 to the fuel tank 11 when the valve is opened. In particular, the pressure reducing valve 5 of this embodiment is not simply fully closed or fully opened, but is continuously opened from fully closed to fully open according to the magnitude of the drive current input from the pressure reducing valve control unit 7. It consists of a solenoid valve that can be changed.

  The ECU 20 is electrically connected to various sensors such as a common rail pressure sensor 10, an accelerator opening sensor 15 for detecting the accelerator opening, and an engine speed sensor 16 for detecting the engine speed. Various information such as pressure, accelerator opening, and engine speed is input. The target rail pressure is calculated by a target rail pressure calculation unit 21 mounted on the ECU 20 based on the fuel injection amount, the engine speed, and the like.

  More specifically, the target rail pressure calculation unit 21 calculates a target fuel injection amount based on the actual accelerator opening detected by the accelerator opening sensor 15 and the actual engine speed detected by the engine speed sensor 16, A target rail pressure is calculated based on the target fuel injection amount and the actual engine speed.

  The pump control unit 6 and the pressure reducing valve control unit 7 perform PID control on the opening degrees of the SCV 14 and the pressure reducing valve 5, respectively, according to a deviation between the actual rail pressure and the target rail pressure (hereinafter also simply referred to as “deviation”). The deviation in this embodiment means a differential pressure obtained by subtracting the target rail pressure from the actual rail pressure.

Specifically, the pump control unit 6 and the pressure-reducing valve control unit 7, as shown in the following formula, multiply the deviation ΔP (t) between the actual rail pressure and the target rail pressure by a proportional gain K _p ( multiplied by a P term), the time integral value of the deviation [Delta] P (t) and (integral term obtained by multiplying the integral gain K _i to the cumulative value) (I term), the time differential value of the deviation [Delta] P (t) the differential gain K _d By adding the differential term (D term), the opening of the SCV 14 and the opening of the pressure reducing valve 5 are obtained. In obtaining the opening degree of the SCV 14 and the opening degree of the pressure reducing valve 5, the values of the P term, the I term, and the D term are individually set.

  The pump control unit 6 controls the fuel corresponding to the desired opening degree of the SCV 14 to be pumped from the high pressure pump 13 by outputting a driving current corresponding to the obtained opening degree of the SCV 14 to the SCV 14. Further, the pressure reducing valve control unit 7 outputs a drive current corresponding to the obtained opening degree of the pressure reducing valve 5 to the pressure reducing valve 5, thereby supplying fuel corresponding to the desired opening degree of the pressure reducing valve 5 from the common rail 3. Control is made to return to the tank 11.

  Here, when the deviation between the actual rail pressure and the target rail pressure exceeds a preset threshold value, the pressure reducing valve control unit 7 of the present embodiment performs PID control of the pressure reducing valve 5. Feedback control is executed, and when the deviation is less than or equal to this threshold, the feedback control is stopped.

  Further, the pressure reducing valve control unit 7 of the present embodiment closes the pressure reducing valve 5 when the deviation between the actual rail pressure and the target rail pressure is equal to or less than the threshold value, and reduces the pressure when the deviation exceeds the threshold value. Control is performed so that the valve 5 is opened. This is because when the deviation is less than or equal to this threshold value, the actual rail pressure is substantially equal to the target rail pressure, and therefore it is almost unnecessary to feedback control the pressure reducing valve 5. Further, if the pressure reducing valve 5 is opened at this time, fuel leaks from the common rail 3 to prevent the actual rail pressure from increasing.

  Next, the control flow of the pressure reducing valve control unit 7 of the fuel injection control device 1 will be described. For example, the pressure reducing valve control unit 7 performs control so that the control flow in FIG. 2 is repeatedly executed every predetermined calculation cycle (for example, 10 ms) while an ignition switch (not shown) of the vehicle is turned on. .

  As shown in FIG. 2, first, the pressure reducing valve control unit 7 determines whether or not the deviation between the actual rail pressure and the target rail pressure exceeds a preset threshold value in step S101. If it is determined in step S101 that the deviation is less than or equal to this threshold value (NO), feedback control (F / B control) by PID control of the pressure reducing valve 5 is stopped and the pressure reducing valve 5 is closed in step S102. This routine is terminated.

  If it is determined in step S101 that the deviation exceeds a preset threshold value (YES), feedback control (F / B control) is executed by PID control of the pressure reducing valve 5 and the pressure reducing valve 5 is opened in step S103. To end the current routine.

  The fuel injection control device 1 according to the present embodiment described above has the following excellent effects as compared with the conventional fuel injection control device.

  FIG. 3 is a diagram for explaining the control status of a conventional fuel injection control device, in which the solid line (a) is the pressure reducing valve opening, the solid line (b) is the actual rail pressure, and the dotted line (c) is the target rail. Pressure, broken line (d) indicates SCV opening, and solid line (e) indicates fuel injection amount. In the figure, ΔP1 represents a threshold value for opening the pressure reducing valve, and ΔP2 represents a threshold value for closing the pressure reducing valve. In addition, the SCV opening degree of the broken line (d) is such an opening degree that the fuel pumping amount of the high-pressure pump 13 increases toward the upper side.

As shown in FIG. 3, for example, when the fuel injection amount decreases as the vehicle decelerates (time t ₁ ), the ECU performs control to decrease the target rail pressure. On the other hand, the actual rail pressure increases as the fuel injection amount decreases. Further, the ECU controls the opening degree of the SCV so as to reduce the fuel pumping amount as the deviation between the actual rail pressure and the target rail pressure increases (time t _{1 to} t ₂ ).

Here, in the conventional fuel injection control device, when the deviation between the actual rail pressure and the target rail pressure exceeds ΔP1 (time t ₂ ), the pressure reducing valve is opened (fully opened) to reduce the actual rail pressure, When the actual rail pressure decreases and the deviation becomes ΔP2 or less (time t ₃ ), the pressure reducing valve is closed (fully closed) to suppress the decrease in the actual rail pressure.

  That is, in the conventional fuel injection control device, the operation of the pressure reducing valve is only fully closed (off) and fully open (on), so that the actual rail pressure becomes the target rail pressure by repeating the fully open and fully closed operations. Feedback control is performed so that

  However, when the actual rail pressure is reduced using such a pressure reducing valve, when the pressure reducing valve is fully opened, the actual rail pressure rapidly decreases to approach the target rail pressure, and when the actual rail pressure is fully closed, the actual rail pressure is reduced. Is reduced, and the actual rail pressure is separated from the target rail pressure. Therefore, it is insufficient to accurately reduce the actual rail pressure. In addition, there is a problem that the operation noise associated with such full open and full open / close operations is loud.

  On the other hand, the pressure reducing valve 5 in this embodiment is not simply fully closed or fully opened, but is continuously from fully closed to fully opened according to the magnitude of the drive current input from the pressure reducing valve control unit 7. It is possible to change the opening.

  Further, according to the fuel injection control device 1 according to the present embodiment, the opening degree of the pressure reducing valve 5 is feedback controlled by PID control according to the deviation between the actual rail pressure and the target rail pressure. As a result, the actual rail pressure decreases smoothly while approaching the target rail pressure without rapidly decreasing. As a result, the actual rail pressure can be accurately reduced, and the operating noise of the pressure reducing valve can be suppressed.

  Further, according to the fuel injection control device 1 according to the present embodiment, the pressure reducing valve control unit 7 opens the pressure reducing valve 5 to perform feedback control when the deviation exceeds a preset threshold value, and performs the deviation control. Is less than this threshold value, the feedback control is stopped by closing the pressure reducing valve 5 so that the pressure reducing valve 5 is not unnecessarily feedback controlled, and fuel leaks from the common rail 3 and the actual rail pressure is reduced. It is possible to suppress the hindering of the increase.

  The basic embodiment of the present invention has been described in detail above. However, the embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications and examples included in the idea of the present invention defined by the claims. Application examples and equivalents are included in the present invention. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

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

Claims (2)

A common rail for storing fuel to be supplied to the injector;
A pump for pumping fuel to the common rail;
A pressure reducing valve for returning the fuel in the common rail to the fuel tank;
A pump control unit that feedback-controls the fuel pumping amount of the pumping pump by PID control according to the deviation between the actual rail pressure of the common rail and the target rail pressure;
And a pressure-reducing valve control unit that feedback-controls the opening degree of the pressure-reducing valve by PID control in accordance with the deviation. The pressure reducing valve control unit executes the feedback control when the deviation exceeds a preset threshold value, and stops the feedback control when the deviation is equal to or less than a preset threshold value. Fuel injection control device.

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