JP2016217146A - Fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve fuel economy, and to rapidly 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 11, a pressure reduction valve control section 6 for feed-back controlling opening and closing operation of the pressure reduction valve 5 in accordance with a deviation between an actual rail pressure and a target rail pressure of the common rail 3, and a pump control section 7 for feed-back controlling a fuel force-feed amount of the force-feed pump 4 by PID control in accordance with the deviation and stopping force-feeding of the fuel from the force-feed pump 4 during opening of the pressure reduction valve 5 by the pressure reduction valve control section 6.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, a common rail that stores fuel injected from the injector in a high-pressure state, and a pressure-feed pump that supplies high-pressure fuel to the common rail.

  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, based on the deviation between the target rail pressure and the actual rail pressure, feedback control of the opening and closing of the pressure reducing valve and the opening of the suction metering valve of the pressure feed pump is used to adjust the actual rail pressure to a reduced pressure. A fuel injection device is known (see Patent Document 1).

JP 2007-032483 A Japanese Patent Laying-Open No. 2015-010541 JP 2010-265759 A Japanese Patent Laid-Open No. 2005-139928

  However, in the conventional fuel injection control device, even when the pressure reducing valve is opened (fully opened) to reduce the actual rail pressure, the metering valve is controlled so as to pump fuel from the pressure feeding pump to the common rail. . Therefore, useless work of the pressure pump increases, which causes a deterioration in fuel consumption, and can also prevent a rapid rail pressure drop.

  Accordingly, an object of the present invention is to provide a fuel injection control device capable of solving the above-described problems, improving fuel efficiency, and quickly reducing 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 pressure-reducing valve control unit that feedback-controls the opening / closing operation of the pressure-reducing valve according to a deviation between the pressure-feeding pressure and the target rail pressure, and a feedback control of a fuel pumping amount of the pressure-feeding pump by PID control according to the deviation. There is provided a fuel injection control device comprising: a pump control unit that stops pumping of fuel from the pressure pump when the pressure reducing valve is opened by the control unit.

  Further, it is preferable that the pump control unit stops feedback control of the fuel pumping amount when the pressure reducing valve is opened.

  ADVANTAGE OF THE INVENTION According to this invention, while improving a fuel consumption, the fuel injection control apparatus which can reduce the rail pressure of a common rail rapidly 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 fuel-injection control apparatus 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. In the fuel injection device which concerns on one Embodiment of this invention, it is a figure where it uses for description of the control condition when it transfers to normal control from pumping stop control.

  Embodiments of the present invention will be described below 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 3, a pressure reducing valve 5 that reduces the pressure in the common rail 3, a pressure reducing valve control unit 6 that controls the opening / closing operation of the pressure reducing valve 5, and a fuel pressure feed amount of the pressure feeding pump 4. And a pump control unit 7. The pressure reducing valve control unit 6 and the pump control unit 7 are mounted on an electronic control unit (hereinafter referred to as ECU) 20 of a vehicle (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 7.

  The SCV 14 may be configured to adjust the fuel flow rate by restricting the fuel sucked into the high-pressure pump 13, and the high-pressure pump by adjusting the fuel flow rate returned from the SCV 14 to the fuel tank 11. The fuel flow rate drawn into the fuel tank 13 may be adjusted.

  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. Further, the pressure reducing valve 5 is opened (fully opened) while the drive current is being input from the pressure reducing valve control unit 6 (when turned on), and is closed (when turned off) while the drive current is being inputted (fully turned off). It consists of a solenoid valve that is controlled to be closed) and that can only be switched between open and closed.

  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 includes an accelerator opening detected by the accelerator opening sensor 15 (hereinafter referred to as an actual accelerator opening) and an engine speed detected by the engine speed sensor 16 (hereinafter referred to as “actual opening”). The target fuel injection amount is calculated based on the actual engine speed, and the target rail pressure is calculated based on the target fuel injection amount and the actual engine speed.

  The pressure reducing valve control unit 6 feedback-controls the opening / closing operation of the pressure reducing valve 5 in accordance with 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.

  More specifically, the pressure reducing valve controller 6 opens the pressure reducing valve 5 when the deviation exceeds a preset first threshold value ΔP1, and the deviation is equal to or less than a preset second threshold value ΔP2 (<ΔP1). The output of the drive current is controlled so that the pressure reducing valve 5 is sometimes closed.

  The pump control unit 7 refers to a predetermined map (not shown) based on the target rail pressure and the actual engine speed, and feeds the opening of the SCV 14 so that the actual rail pressure becomes approximately the target rail pressure. Calculate the forward term.

Further, the pump control unit 7 calculates a deviation term (P term) obtained by multiplying the deviation ΔP (t) between the actual rail pressure and the target rail pressure by a proportional gain K _p as shown in the following equation, and a deviation ΔP (t ), The integral term (I term) obtained by multiplying the time integral value (cumulative value) by the integral gain K _i, and the differential term (D term) obtained by multiplying the time differential value of the deviation ΔP (t) by the differential gain K _d. By adding together, the feedback term of the opening degree of the SCV 14 is calculated.

  Then, the pump control unit 7 obtains the final target opening of the SCV 14 by adding the feedback term to the feedforward term.

  The pump control unit 7 controls the SCV 14 so that fuel corresponding to the desired target opening degree of the SCV 14 is pumped from the high pressure pump 13 by outputting a driving current corresponding to the obtained target opening degree of the SCV 14 to the SCV 14. To do.

  Thus, the fuel pumping amount of the high-pressure pump 13 is feedback-controlled by PID control according to the deviation (hereinafter also referred to as normal control).

  Further, the pump control unit 7 controls the opening degree of the SCV 14 so as to stop the fuel pumping from the pumping pump 4 when the pressure reducing valve 5 is opened (turned on). Here, “stopping the pumping of fuel” refers to suppressing the pumping so that the fuel pumping amount from the pumping pump 4 is zero or substantially zero.

  More specifically, the pump control unit 7 stores in advance a target opening of the SCV 14 that stops the pumping of fuel (hereinafter referred to as a pumping stop opening). When the deviation exceeds the first threshold value ΔP1, the pump control unit 7 stops the feedback control of the SCV 14 and holds the target opening of the SCV 14 at the pumping stop opening so that the SCV 14 feed forward control (hereinafter referred to as pumping). (Also referred to as stop control).

  At this time, the integral value (cumulative value) of the integral term (I term) or deviation ΔP (t) is held at the value when the pressure reducing valve 5 is fully closed (off) to fully open (on). Used when resuming feedback control.

  In the pumping stop control by the pump control unit 7, the deviation is equal to or smaller than the second threshold value ΔP2, and the target fuel injection amount calculated by the target rail pressure calculation unit 21 is equal to or larger than a predetermined small amount q (> 0) set in advance. Or until the deviation falls below a preset third threshold value ΔP3 (<ΔP2).

  Next, the control flow of the fuel injection control device 1 according to this embodiment will be described. Here, the pressure reducing valve control unit 6 and the pump control unit 7 perform, for example, the control flow of FIG. 2 every predetermined calculation period (for example, 10 ms) while the ignition switch (not shown) of the vehicle is turned on. Control to execute repeatedly. In the initial state, the pressure reducing valve 5 is closed (off).

  In step S101, the pressure reducing valve control unit 6 determines whether or not the flag indicating the open state of the pressure reducing valve is on. If it is determined that the flag is not on (NO), the flow proceeds to step S102. move on.

  In step S102, the pressure reducing valve control unit 6 determines whether or not the deviation ΔP exceeds the first threshold value ΔP1, and if it is determined that the deviation ΔP exceeds the first threshold value ΔP1 (YES), the process proceeds to step S103. move on.

  In step S103, the pressure reducing valve 5 is opened by the pressure reducing valve control unit 6. Next, in step S104, the flag is turned on by the pressure reducing valve control unit 6, and the process proceeds to step S105.

  In step S105, the feedback control of the SCV 14 is stopped by the pump control unit 7, and the feed forward control (pressure feed stop control) for changing the opening of the SCV 14 to the pressure feed stop opening is executed, and this routine is finished. To do.

  If it is determined in step S101 that the flag is on (YES), the process proceeds to step S106.

  In step S106, the pressure reducing valve control unit 6 determines whether or not the deviation ΔP is equal to or smaller than the second threshold value ΔP2, and if it is determined that the deviation ΔP is equal to or smaller than the second threshold value ΔP2 (YES), The process proceeds to S107.

  In step S107, the pressure reducing valve 5 is closed by the pressure reducing valve control unit 6, and then in step S108, the flag is turned off by the pressure reducing valve control unit 6, and the process proceeds to step S109.

  In step S109, the pump control unit 7 determines whether or not the target fuel injection amount Q is equal to or larger than a predetermined amount q (> 0) set in advance, and the target fuel injection amount Q is equal to or larger than the predetermined amount q. If YES is determined (YES), the process proceeds to step S111. In step S111, the opening degree of the SCV 14 is normally controlled by the pump control unit 7, and the current routine ends.

  If it is determined in step S109 that the target fuel injection amount Q is not equal to or greater than the predetermined amount q (NO), the process proceeds to step S110.

  In step S110, the pump control unit 7 determines whether or not the deviation ΔP is equal to or smaller than a preset third threshold value ΔP3, and when it is determined that the deviation ΔP is equal to or smaller than the third threshold value ΔP3 (YES). Advances to step S111, where the opening degree of the SCV 14 is normally controlled in step S111, and the current routine ends.

  If it is determined in step S110 that the deviation ΔP is not equal to or less than the third threshold value ΔP3 (NO), the process proceeds to step S112, and in step S112, the flag is turned on by the pressure reducing valve control unit 6, and step S105 is performed. In step S105, the SCV 14 is controlled to stop pumping, and the current routine ends.

  On the other hand, when it is determined in step S102 that the deviation ΔP does not exceed the first threshold value ΔP1 (NO), the process proceeds to step S113, and in step S113, the pressure reducing valve 5 is closed by the pressure reducing valve control unit 6. Next, in step S114, the flag is turned off by the pressure reducing valve controller 6, and the process proceeds to step S111. In step S111, the opening degree of the SCV 14 is normally controlled, and the current routine ends.

  If it is determined in step S106 that the deviation ΔP is not equal to or smaller than the second threshold value ΔP2 (NO), the process proceeds to step S105. In step S105, the SCV 14 is controlled to stop pumping, and the current routine ends. .

  Here, the control flow in FIG. 2 will be exemplified and briefly described.

  In the initial state (pressure reducing valve closed), first, it is determined in step S101 that the flag is OFF (NO), and then in step S102, until it is determined that the deviation ΔP exceeds the first threshold value ΔP1, step S113. Then, the closed state of the pressure reducing valve 5 is maintained. In this case, flag = off is maintained in step S114, and normal control of the SCV opening is continued in step S111.

  If it is determined in step S102 that the deviation ΔP has exceeded the first threshold value ΔP1, the process proceeds to step S103, and the pressure reducing valve 5 is opened. In this case, the flag is turned on in step S104, and the SCV 14 pumping stop control is executed in step S105.

  When the flag is turned on in step S104, YES is determined in step S101. As a result, the process proceeds to step S105 instead of step S107 until the deviation ΔP is determined to be equal to or smaller than the second threshold value ΔP2 in step S106, so that the open state of the pressure reducing valve 5 is maintained and the SCV 14 is pumped. Stop control continues.

  If it is determined in step S106 that the deviation ΔP is equal to or smaller than the second threshold value ΔP2, the process proceeds to step S107, the pressure reducing valve 5 is closed, and the flag is turned off in step S108. In this case, the normal control of the SCV opening is not immediately executed in step S111, but it is determined in step S109 that the target fuel injection amount Q is equal to or greater than the predetermined amount q, or in step S110. Until it is determined that the deviation ΔP is equal to or smaller than the third threshold value ΔP3, the process proceeds to step S112. In step S112, the flag is turned on, and the pumping stop control of the SCV 14 is continued.

  If it is determined in step S109 that the target fuel injection amount Q is greater than or equal to the predetermined amount q, or if it is determined in step S110 that the deviation ΔP is less than or equal to the third threshold value ΔP3, then the SCV opening is determined in step S111. Normal control is executed.

  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 first threshold value for opening the pressure reducing valve, and ΔP2 represents a second 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.

When the deviation between the actual rail pressure and the target rail pressure exceeds ΔP1 (time t ₂ ), the ECU opens (fully opens) the pressure reducing valve to decrease the actual rail pressure, and the actual rail pressure decreases to cause the deviation. When ΔP2 or less (time t ₃ ), the pressure reducing valve is closed (fully closed) to suppress a decrease in the actual rail pressure.

  That is, the ECU performs feedback control so that the actual rail pressure becomes the target rail pressure by repeating the fully open (on) and fully closed (off) operations of the pressure reducing valve.

Here, regarding the control of SCV, in the conventional fuel injection control device, when the deviation becomes large (time t _{1 to} t ₂ ), the opening degree is feedback-controlled so that the fuel pumping amount becomes small, and the deviation becomes small. As time passes (time t _{2 to} t ₃ ), the opening degree is feedback controlled so that the fuel pumping amount increases.

  However, when the pressure reducing valve is opened (fully opened) to reduce the actual rail pressure, feeding the fuel by feedback-controlling the opening of the SCV increases wasteful work of the pressure pump. It becomes a factor that deteriorates fuel consumption. Further, in such a situation where fuel is being pumped from the pump to the common rail, a rapid decrease in the actual rail pressure is prevented.

  On the other hand, the pump control unit 7 in the present embodiment performs feedforward control on the opening degree of the SCV 14 so as to stop the fuel pumping from the pumping pump 4 when the pressure reducing valve 5 is opened.

  Thereby, in the fuel injection control device 1 according to the present embodiment, useless work of the pressure feed pump 4 is suppressed, fuel efficiency is improved, and the actual rail pressure can be quickly reduced.

  Further, the pump control unit 7 in the present embodiment stops the feedback control of the SCV 14 when the pressure reducing valve 5 is opened.

  Thereby, in the fuel injection control device 1 according to the present embodiment, it is possible to reliably stop the fuel pumping from the pressure pump 4 when the pressure reducing valve 5 is opened.

  On the other hand, in the fuel injection control device 1 according to the present embodiment, when the deviation becomes equal to or smaller than the second threshold value ΔP2, the pressure reducing valve control unit 6 closes the pressure reducing valve 5. At this time, when the pumping stop control is shifted to the normal control, the integral term (I term) held after the start of the pumping stop control is restored in the pump control unit 7 and the feedback control of the SCV 14 is resumed.

  However, since the injector 2 in this embodiment does not have a static leak mechanism, when the deviation becomes equal to or smaller than the second threshold value ΔP2 in a state where the fuel injection amount is zero (or in the vicinity thereof, the same shall apply hereinafter). If the feedback control is resumed immediately, the actual rail pressure will rise rapidly.

  FIG. 4 shows the control of the fuel injection control device when the fuel injection amount is zero and the state immediately shifts from the pressure stop control to the normal control (when the steps S109, S110, and S112 are not present in the control flow of FIG. 2). It is a figure where it uses for description of a condition. In the drawing, the solid line (a) indicates the pressure reducing valve opening, the solid line (b) indicates the actual rail pressure, the dotted line (c) indicates the target rail pressure, and the solid line (Q) indicates the target fuel injection amount. In the figure, ΔP1 represents a first threshold value for opening the pressure reducing valve, and ΔP2 represents a second threshold value for closing the pressure reducing valve.

As shown in FIG. 4, when the deviation between the actual rail pressure and the target rail pressure exceeds ΔP1 (time t ₁ ), the pressure reducing valve 5 is opened (fully opened) and the actual rail pressure is reduced. On the other hand, when the deviation becomes ΔP2 or less (time t ₂ ), the pressure reducing valve 5 is closed (fully closed), but the fuel injection amount is zero and the integral term (I term) is restored. For this reason, the actual rail pressure increases rapidly. Thereafter, when the deviation exceeds the first threshold value ΔP1 (time t ₃ , t ₅ , t ₇ , t ₉ ), the pressure reducing valve 5 is opened (turned on), the actual rail pressure decreases, and the deviation becomes the second When the pressure falls below the threshold (time t ₄ , t ₆ , t ₈ , t ₁₀ ), the pressure reducing valve 5 is closed (turned off). When the on / off operation of the pressure reducing valve 5 is repeated, hunting of the actual rail pressure occurs.

  In view of this, the pump control unit 7 in the present embodiment allows the target fuel injection amount Q to be equal to or greater than the predetermined amount q (a fuel injection amount that suppresses a sudden increase in the actual rail pressure) even when the deviation is equal to or less than the second threshold value ΔP2. Or the pumping stop control is continued until the deviation ΔP is equal to or less than the third threshold value (ΔP3 which is sufficiently small so that the deviation ΔP does not exceed the first threshold value ΔP1 when the actual rail pressure suddenly increases) The ON / OFF repetition of the pressure reducing valve 5 accompanying normal control and the hunting of the actual rail pressure accompanying this are suppressed.

  On the other hand, if the target fuel injection amount Q is equal to or greater than the predetermined amount q, there is no sudden increase in the actual rail pressure due to normal control, and if the deviation ΔP is equal to or less than the third threshold value ΔP3, the deviation ΔP when the actual rail pressure suddenly increases. Does not exceed the first threshold value ΔP1, there is no problem even if the normal control is executed. For this reason, the pump control unit 7 in this embodiment immediately shifts from the pressure stop control to the normal control when these conditions are satisfied.

  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 Pressure reducing valve control part 7 Pump control part 11 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 pressure reducing valve for returning the fuel in the common rail to the fuel tank;
A pressure reducing valve control unit that feedback-controls the opening / closing operation of the pressure reducing valve according to a deviation between the actual rail pressure of the common rail and a target rail pressure;
A pump control unit that feedback-controls a fuel pumping amount of the pumping pump by PID control according to the deviation, and stops pumping of fuel from the pumping pump when the pressure reducing valve is opened by the pressure reducing valve control unit; A fuel injection control device comprising: The fuel injection control device according to claim 1, wherein the pump control unit stops feedback control of the fuel pumping amount when the pressure reducing valve is opened.

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