JP2016079880A - Rail pressure control method and common rail type fuel injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict or prevent rapid changing of a rail pressure when a vehicle running state becomes an over-run state.SOLUTION: When an accelerator opening is rapidly changed from its full-opened state and an indicated injection amount Q2 after changing of the accelerator opening is decreased by a prescribed minimum indicated value Qmin [S102], a rail pressure P just after changing of the accelerator opening exceeds a prescribed maximum pressure Pmax or a differential pressure ΔP across the change of the accelerator opening exceeds a prescribed maximum differential pressure ΔPmax [S104] and when a prescribed elapsing time elapses from a time in which a changing of the accelerator opening occurs [S106], the indicated injection amount is set to zero [S110] and occurrence of over-shooting of the rail pressure is restricted and prevented.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a common rail fuel injection control device, and more particularly to a device that improves the stability and reliability of rail pressure control.

  A so-called common rail type fuel injection control device pressurizes fuel by a high pressure pump, pumps it to a common rail, which is an accumulator, accumulates the pressure, and supplies the accumulated high pressure fuel to the fuel injection valve, so that the internal combustion engine by the fuel injection valve It is well known as one that can inject high-pressure fuel into an engine and is excellent in fuel consumption and emission characteristics.

  In such a common rail type fuel injection control device, it is well known that the controllability of rail pressure control is determined by various factors such as the injection amount of the fuel injection valve. Considering how to realize stable and reliable rail pressure control is an important issue for common rail fuel injection control systems, and various measures have been proposed and put to practical use for rail pressure control. (See, for example, Patent Document 1).

By the way, when the vehicle is in operation, sometimes the accelerator pedal is fully depressed from the fully opened state to suddenly weaken the accelerator pedal to obtain the required accelerator opening. is there.
In such a case, in response to a sudden decrease in the accelerator opening, the indicated value of the fuel injection amount is reduced at a stretch. However, a high-pressure pump or the like that pumps high-pressure fuel to the common rail has a so-called operation delay, so the high-pressure fuel It is well known that the rail pressure overshoot occurs because the pumping amount does not immediately correspond to the changed accelerator opening, and the pumping state before the accelerator opening change is continued.

  Such an overshoot of rail pressure adversely affects the product life of components such as common rails and leads to a decrease in the safety and reliability of the device.For example, when the access opening changes suddenly from the fully open state. Instead of immediately changing the command injection amount to a value corresponding to the changed accelerator opening, the fuel injection amount is maintained at the value before the accelerator opening change for a certain period of time, and then the command injection amount is changed. Thus, there is a case in which a technique for suppressing and reducing rail pressure overshoot due to operation delay of the high pressure pump or the like as described above may be employed.

International Publication No. 2010 / 109967A1

  On the other hand, some vehicles have a function of immediately setting the command injection amount to zero as a so-called overrun state when the accelerator opening is zero or close to that degree. In a vehicle having a function, when the accelerator is suddenly changed from the fully opened state to the fully closed state, the fuel injection amount as described above is maintained for a while to the value before the sudden change of the accelerator opening. In the overrun state, priority is given to the function of setting the command injection amount to zero, which eventually causes the rail pressure overshoot as described above.

  The present invention has been made in view of the above-described circumstances, and suppresses and reduces a sudden change in rail pressure when the running state of the vehicle becomes an overrun state, thereby enabling rail pressure control with high stability and reliability. A rail pressure control method and a common rail fuel injection control device are provided.

In order to achieve the above object of the present invention, a rail pressure control method according to the present invention includes:
Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, and high-pressure fuel can be injected into the engine via a fuel injection valve connected to the common rail, and provided on the upstream side of the high-pressure pump. A rail pressure control method in a common rail fuel injection control device configured such that the rail pressure of the common rail can be controlled by driving control of a metering valve,
When the accelerator opening changes suddenly from the fully open state, and the command injection amount after the accelerator opening change falls below a predetermined minimum instruction value, the rail pressure immediately after the accelerator opening change does not exceed the predetermined maximum pressure, And when the differential pressure | voltage of rail pressure before and behind the said accelerator opening change does not exceed the predetermined maximum differential pressure, it is comprised so that the said instruction | injection amount may be set to zero.
In order to achieve the above object of the present invention, a common rail fuel injection control device according to the present invention includes:
Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump A common rail fuel injection control device configured to be capable of controlling the rail pressure of the common rail by driving control of the metering valve by an electronic control unit,
The electronic control unit is
When it is determined that the accelerator opening suddenly changes from the fully open state and the command injection amount after the accelerator opening change is below a predetermined minimum instruction value, the rail pressure immediately after the accelerator opening change exceeds the predetermined maximum pressure. In addition, when it is determined that the rail pressure differential pressure before and after the accelerator opening change does not exceed the predetermined maximum differential pressure, the command injection amount is set to zero.

  According to the present invention, when the accelerator opening is changed in a decreasing direction, unlike the conventional case, the rail pressure after the accelerator opening change, the magnitude of the differential pressure in the change in the rail pressure before and after the accelerator opening change, and the accelerator opening The command injection amount is set to zero in consideration of the elapsed time after the change in the degree of occurrence, so the rail pressure overshoot due to the command injection amount being zero immediately after the accelerator opening change is made As a result, the occurrence of the rail pressure can be accurately suppressed and prevented, and more stable and reliable rail pressure control can be realized as compared with the prior art.

It is a block diagram which shows the structural example of the common rail type | mold fuel-injection control apparatus in embodiment of this invention. 3 is a subroutine flowchart showing a procedure of rail pressure control processing in the embodiment of the present invention executed by an electronic control unit constituting the common rail fuel injection control device shown in FIG. 1.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.
The members and arrangements described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.
First, a common rail fuel injection control apparatus according to an embodiment of the present invention will be described with reference to FIG.
The common rail fuel injection control device includes a high pressure pump device 50 that pumps high pressure fuel, a common rail 1 that stores the high pressure fuel pumped by the high pressure pump device 50, and high pressure fuel supplied from the common rail 1 to the engine 3. A plurality of fuel injection valves 2-1 to 2-n that inject and supply to the cylinders, and an electronic control unit (indicated as “ECU” in FIG. 1) 4 for executing fuel injection control processing, rail pressure control processing described later, and the like Is the main component.
Such a configuration itself is the same as the basic configuration of this type of fuel injection control apparatus that has been well known.

The high-pressure pump device 50 has a known and well-known configuration in which the supply pump 5, the metering valve 6, and the high-pressure pump 7 are configured as main components.
In this configuration, the fuel in the fuel tank 9 is pumped up by the supply pump 5 and supplied to the high-pressure pump 7 through the metering valve 6. As the metering valve 6, an electromagnetic proportional control valve is used, and the amount of energization is controlled by the electronic control unit 4, so that the flow rate of fuel supplied to the high-pressure pump 7, in other words, the discharge of the high-pressure pump 7. The amount is to be adjusted.

The common rail fuel injection control apparatus according to the embodiment of the present invention is premised on a configuration in which rail pressure control is performed by the electromagnetic metering valve 6 described above.
The common rail 1 is provided with a so-called mechanical safety valve (not shown) on the fuel return passage side. When the rail pressure becomes a predetermined value or more, the safety valve opens and the fuel in the common rail 1 is opened. Is discharged and is designed to be safe.

A return valve 8 is provided between the output side of the supply pump 5 and the fuel tank 9 so that surplus fuel on the output side of the supply pump 5 can be returned to the fuel tank 9.
The supply pump 5 may be provided separately from the high-pressure pump device 50 on the upstream side of the high-pressure pump device 50 or may be provided in the fuel tank 9.
The fuel injection valves 2-1 to 2-n are provided for each cylinder of the engine 3, and are supplied with high-pressure fuel from the common rail 1, and perform fuel injection by injection control by the electronic control unit 4. Yes.

The electronic control unit 4 has, for example, a microcomputer (not shown) having a known and well-known configuration, a storage element (not shown) such as a RAM and a ROM, and a fuel injection valve 2- A drive circuit (not shown) for driving 1 to 2-n and an energization circuit (not shown) for energizing the metering valve 6 are configured as main components. .
In addition to the detection signal of the pressure sensor 11 that detects the pressure of the common rail 1 being input to the electronic control unit 4, various detection signals such as the engine speed, the accelerator opening, the outside air temperature, and the atmospheric pressure, It is input to be used for operation control of the engine 3, fuel injection control, rail pressure control and the like in an embodiment of the present invention to be described later.

Next, the rail pressure control process in the embodiment of the present invention executed by the electronic control unit 4 will be described with reference to the subroutine flowchart shown in FIG.
First, as a premise, the rail pressure control process shown in FIG. 2 is one of various subroutine processes executed in the main routine (not shown) executed in the electronic control unit 4, and in particular, the accelerator opening is to some extent. It is assumed that it is executed when it suddenly changes from, for example, about 80% to a small opening.

Accordingly, when the processing by the electronic control unit 4 is started, it is determined whether or not the command injection amount Q2 is below a predetermined minimum command value Q (see step S102 in FIG. 2).
Here, the command injection amount is determined in the fuel injection valves 2-1 to 2-n based on the engine speed, the accelerator opening, and the like in the fuel injection amount control process executed in the electronic control unit 4 in the same manner as before. The calculated fuel injection amount is calculated as the amount of fuel to be injected.
Further, Q2 is a command injection amount corresponding to the changed accelerator opening.
The predetermined minimum instruction value Q is normally set to a value very close to zero.

If it is determined in step S102 that the command injection amount Q2 is less than the predetermined minimum command value Q (in the case of YES), the process proceeds to step S104 described below, while the command injection amount Q2 is the predetermined minimum If it is determined that the value is not lower than the instruction value Q (in the case of NO), the process proceeds to step S112 described later.
In step S104, whether or not the rail pressure P immediately after the accelerator opening change exceeds a predetermined maximum pressure Pmax (P> Pmax), or the rail pressure P1 and the accelerator opening change before the accelerator opening change. It is determined whether or not the differential pressure ΔP = P2−P1 with the immediately following rail pressure P2 exceeds a predetermined maximum differential pressure ΔPmax (ΔP> ΔPmax).
In this step S104, not only when the value of the rail pressure itself is high, but also when the value of the rail pressure after the accelerator opening change is not so high, from the viewpoint of suppressing a rapid change in the rail pressure, The case where the difference in rail pressure before and after the change in the accelerator opening is large can also be detected, and the process of step S104 described below is executed.

If it is determined in step S104 that P> Pmax or ΔP> ΔPmax (in the case of YES), the process proceeds to the process of step S106 described below, but if it is determined that none of them ( In the case of NO), the process proceeds to step S108 described later.
In step S106, it is determined whether or not a predetermined elapsed time has elapsed since the start of the subroutine processing shown in FIG.

  That is, it is determined whether or not the predetermined elapsed time has elapsed since the sudden change in the accelerator opening described above, and if it is determined that the predetermined elapsed time has elapsed (in the case of YES), From the viewpoint of giving priority to the driver's deceleration request, the process proceeds to step S108 described below. On the other hand, when it is determined that the predetermined elapsed time has not yet elapsed (in the case of NO), the process proceeds to step S112 described later. It will be.

In step S108, overrun is established, that is, in an overrun state, in other words, the instructed injection amount Q is set to zero (see step S110 in FIG. 2), and a series of processing is ended, not shown. Return to the main routine. The command injection amount set to zero is used in a fuel injection control process that is executed in the same manner as before in a main routine (not shown), and the fuel injection amount from the fuel injection valves 2-1 to 2-n becomes zero. Thus, the operation is controlled.
In the embodiment of the present invention, unlike the prior art, even if it is determined in the previous step S102 that the command injection amount Q2 is below the predetermined minimum command value Q, the command injection amount is immediately made zero. Instead, if YES is determined in each of Steps S104 and S106 described above, the command injection amount Q2 is set to zero, so it is determined that the command injection amount Q2 is below the predetermined minimum command value Q. When this is done, the overshoot of the rail pressure, which may occur when the command injection amount is set to zero immediately, is reliably suppressed and prevented.

On the other hand, in step S112, it is determined whether or not the rail pressure overshoot is excessive.
Specifically, the absolute value of the command injection amount difference ΔQ, which is the difference between the command injection amount Q1 immediately before the accelerator opening change and the command injection amount Q2 just after the accelerator opening change, exceeds the predetermined command injection amount difference ΔQmax. If it is determined that the absolute value of the command injection amount difference ΔQ exceeds the predetermined command injection amount difference ΔQmax (in the case of YES), the process proceeds to step S114 described below. When it is determined that the absolute value of the command injection amount difference ΔQ does not exceed the predetermined command injection amount difference ΔQmax (in the case of NO), the process proceeds to step S118 described later.

In step S114, in view of the determination result that the rail pressure overshoot is in an excessive state, the command injection amount Q is set to the command injection amount Q1 immediately before the accelerator opening change. That is, the command injection amount is maintained at a value before the accelerator opening is changed.
Next, it is determined whether or not the number of executions N of step S114 described above has reached the predetermined number of repetitions Nref (see step S116 in FIG. 2), and when it is determined that the number of executions N has reached the predetermined number of repetitions (YES) ), Or when it is determined in step S112 that the overshoot is not excessive (in the case of NO), there is no change in the rail pressure due to the change in the accelerator opening, or it converges to a problem level. As a result, the command injection amount Q is set to the command injection amount Q2 immediately after the accelerator opening change, and a series of processes is terminated, and the process returns to the main routine (not shown).

  On the other hand, when it is determined in step S116 that the number of executions N of step S114 has not yet exceeded the predetermined number of repetitions Nref (in the case of NO), the number of executions N is incremented by one (see step S120 in FIG. 2). ) By returning to the processing of the previous step S114, the command injection amount Q is maintained at Q1.

As described above, when it is determined that the rail pressure overshoot is excessive, the occurrence of rail pressure overshoot is suppressed by maintaining the command injection amount before the accelerator opening change for a while. Can be prevented.
When the accelerator opening changes suddenly from a certain degree of opening to a small opening, the command injection amount is immediately set to a value corresponding to the changed accelerator opening. It is reduced with it. However, since the change in the pumping amount of the high-pressure fuel by the high-pressure pump 7 is accompanied by a slight time delay, even if the command injection amount changes, the common rail 1 is pumped with the same amount of high-pressure fuel as before the accelerator opening change. As a result, an overshoot of rail pressure may occur.

  On the other hand, even after a sudden change in the accelerator opening, the indicated injection amount is set to a value before the sudden change in the accelerator opening for a while, so that the unbalance between the fuel amount pumped to the common rail 1 and the injected fuel amount is unbalanced. As described above, by setting the command injection amount to the original value after the sudden change in the accelerator opening, the state is not generated, and when the pumping state of the high-pressure pump 7 becomes a state that can respond after the sudden change in the accelerator opening. The occurrence of an overshoot of a large rail pressure is suppressed and prevented.

  The present invention can be applied to a common rail fuel injection control device in which the stability and reliability of rail pressure control when the vehicle is overrun is desired.

DESCRIPTION OF SYMBOLS 1 ... Common rail 2-1-2-n ... Fuel injection valve 3 ... Engine 4 ... Electronic control unit 6 ... Metering valve 7 ... High pressure pump 11 ... Pressure sensor

Claims (4)

Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, and high-pressure fuel can be injected into the engine via a fuel injection valve connected to the common rail, and provided on the upstream side of the high-pressure pump. A rail pressure control method in a common rail fuel injection control device configured such that the rail pressure of the common rail can be controlled by driving control of a metering valve,
When the accelerator opening changes suddenly from the fully open state, and the command injection amount after the accelerator opening change falls below a predetermined minimum instruction value, the rail pressure immediately after the accelerator opening change does not exceed the predetermined maximum pressure, The rail pressure control method is characterized in that the indicated injection amount is set to zero when the differential pressure between the rail pressures before and after the accelerator opening change does not exceed a predetermined maximum differential pressure.   When the accelerator opening changes suddenly from the fully open state, and the command injection amount after the accelerator opening change is below a predetermined minimum instruction value, the rail pressure immediately after the accelerator opening change exceeds a predetermined maximum pressure, Alternatively, the command injection is performed when a differential pressure of the rail pressure before and after the change in the accelerator opening exceeds a predetermined maximum differential pressure and a predetermined elapsed time has elapsed since the change in the accelerator opening occurred. The rail pressure control method according to claim 1, wherein the amount is zero. Fuel in the fuel tank is pressurized and pumped to a common rail by a high-pressure pump, enabling high-pressure fuel injection to the engine via a fuel injection valve connected to the common rail, and a metering valve upstream of the high-pressure pump A common rail fuel injection control device configured to be capable of controlling the rail pressure of the common rail by driving control of the metering valve by an electronic control unit,
The electronic control unit is
When it is determined that the accelerator opening suddenly changes from the fully open state and the command injection amount after the accelerator opening change is below a predetermined minimum instruction value, the rail pressure immediately after the accelerator opening change exceeds the predetermined maximum pressure. And when it is determined that the rail pressure differential pressure before and after the accelerator opening change does not exceed a predetermined maximum differential pressure, the command injection amount is set to zero. Common rail fuel injection control device. The electronic control unit is
When it is determined that the accelerator opening suddenly changes from the fully opened state and the command injection amount after the accelerator opening change is below a predetermined minimum instruction value, the rail pressure immediately after the accelerator opening change exceeds the predetermined maximum pressure. Or it is determined that the rail pressure differential pressure before and after the accelerator opening change exceeds a predetermined maximum differential pressure, and a predetermined elapsed time has elapsed since the change in the accelerator opening occurred. In this case, the common rail fuel injection control device according to claim 3, wherein the command injection amount is set to zero.

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