JP4082801B2 - Fuel injection control system for direct injection gasoline engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for a direct injection gasoline engine, and more particularly to a device configured to control fuel pressure by controlling the discharge amount of a fuel pump.
[0002]
[Prior art]
In recent years, fuel injection valves that inject fuel directly into the combustion chamber have been provided, and in the low and medium load regions, fuel is injected in the compression stroke to produce a combustible mixture in the vicinity of the spark plug and perform stratified combustion This enables combustion with a substantially lean air-fuel ratio, while in a high-load region above a predetermined range, fuel is injected in the intake stroke in order to secure the required torque with a limited cylinder volume. A direct-injection gasoline engine has been developed that forms a homogeneous mixture and performs homogeneous combustion.
[0003]
In such a direct-injection gasoline engine, the pressure in the cylinder at the injection timing varies greatly with switching between stratified combustion and homogeneous combustion, and accordingly, it is necessary to switch the fuel supply pressure (injection pressure) to the fuel injection valve accordingly. is there.
[0004]
In order to satisfy such a requirement, the present applicant has previously proposed the following fuel injection device (see Japanese Patent Application No. 10-135576).
[0005]
In other words, a relief is provided to provide a fuel pump (single cylinder pump) that sucks and discharges fuel by a plunger that reciprocates by a cam interposed in the cam shaft of the engine, while communicating the piston chamber of the fuel pump with the suction side. A solenoid valve that opens and closes in a passage is provided in the passage, and the discharge amount of the fuel pump can be controlled by controlling the period during which the relief passage is closed (opened) in the discharge stroke of the fuel pump. .
[0006]
Then, feedback control of the closing period (discharge amount) of the solenoid valve is performed so that the actual fuel pressure detected by the fuel pressure sensor matches the target pressure. On the other hand, when the target pressure does not change, it is supplied to the engine. Since it is sufficient to supply the fuel by the amount of the fuel pump, the feedforward control amount of the discharge amount is determined based on the required fuel injection amount corresponding to the cylinder intake air amount, and the response delay of the feedback control is delayed by the feedforward control amount. Make up.
[0007]
[Problems to be solved by the invention]
By the way, the fuel injection control mode includes an all-cylinder injection mode in which all cylinders are normally sequentially injected, and a half-cylinder injection mode in which fuel is cut in a half-cylinder in order to control the generated torque of the engine.
[0008]
However, conventionally, even in the half cylinder injection mode, if the cylinder intake air amount is the same, the required fuel injection amount of the same amount as that in the all cylinder injection mode is calculated. Thus, a feed-forward control amount is provided, so that, in the feed-forward control, fuel that is twice the amount of fuel that is actually supplied to the engine is supplied from the fuel pump.
[0009]
Therefore, during the half cylinder injection mode, the feedback control amount is accumulated in the reduction correction direction, and when returning from the half cylinder injection mode to the all cylinder injection mode, the feedback control amount accumulated so far is used. Since the discharge amount is corrected to be reduced excessively, it takes time for the fuel pressure to fall significantly below the target and return to the target fuel pressure. During this time, the air / fuel ratio becomes overlean and misfiring occurs. There was a fear.
[0010]
The present invention has been made in view of the above problems, and provides a fuel injection control device for a direct injection gasoline engine that can be stably controlled to a target fuel pressure even when fuel cut is performed in some cylinders. For the purpose.
[0011]
[Means for Solving the Problems]
Therefore, the invention according to claim 1 includes a fuel injection valve that directly injects fuel into the combustion chamber, and the fuel injection valve that is mounted on the combustion chamber of each cylinder from the fuel pressure accumulation chamber connected to the discharge port of the fuel pump. In a direct injection gasoline engine in which a branch passage is extended toward each, a direct injection gasoline that controls a supply pressure of fuel to a fuel injection valve provided for each cylinder by electronically controlling a discharge amount of the fuel pump. a fuel injection control equipment of the engine, and feedback control amount setting means for setting a feedback control of the discharge amount from between the target value and the actual value of the supply pressure of the fuel, the required fuel corresponding to the cylinder intake air quantity Based on the ratio of the feedforward control amount setting means for setting the feedforward control amount of the discharge amount based on the injection amount and the number of cylinders in which fuel injection is stopped. And decrease correction unit that the requested fuel injection quantity decreasing correction to be used for the feed forward control amount setting Te, a discharge amount control means for controlling the discharge amount of the fuel pump based on the feedback control amount and the feedforward control amount , Provided.
[0012]
According to this configuration, the feed-forward control amount of the discharge amount is set on the basis that the fuel injection is performed in all cylinders based on the required fuel injection amount corresponding to the cylinder intake air amount. For example, the fuel injection is performed in half the cylinders. When the engine is stopped, the feedforward control amount is set based on a half of the required fuel injection amount, and as a result, the discharge amount per discharge stroke is corrected to half.
[0013]
According to a second aspect of the present invention, a fuel injection valve for directly injecting fuel into the combustion chamber is provided, and each of the fuel injection valves mounted on the combustion chamber of each cylinder from a fuel pressure accumulation chamber connected to the discharge port of the fuel pump. In a direct-injection gasoline engine with a branch passage extending toward the engine, the fuel pump discharge amount is electronically controlled to control the fuel supply pressure to the fuel injection valve provided for each cylinder. A fuel injection control device, wherein a feedback control amount setting means for setting a feedback control amount of the discharge amount from a target value and an actual value of the fuel supply pressure, and a required fuel injection amount according to a cylinder intake air amount a feed forward control amount setting means for setting a feed-forward control amount of the ejection amount on the basis of the feedback control amount and the feedforward system And discharge amount control means for controlling the discharge amount of the fuel pump based on the amount, the number of times to actually perform the discharge of the fuel to discharge stroke speed in the fuel pump, according to the number of cylinders in which the fuel injection is stopped And a discharge number control means for controlling the discharge .
[0014]
According to such a configuration, it is possible to control whether discharge is normally performed or stopped for each discharge stroke without changing the discharge amount per one time when discharge is performed. The total discharge amount is changed according to the number of stops.
[0015]
The invention according to claim 3 includes a fuel injection valve that directly injects fuel into the combustion chamber, and a fuel pump whose discharge stroke is synchronized with the fuel injection timing of each fuel injection valve, and is connected to the discharge port of the fuel pump. In a direct injection gasoline engine in which a branch passage extends from the fuel pressure accumulation chamber to each of the fuel injection valves attached to the combustion chamber of each cylinder, the discharge amount of the fuel pump is electronically controlled, A fuel injection control device for a direct injection gasoline engine for controlling a fuel supply pressure to a fuel injection valve provided for each cylinder, wherein a feedback control amount of the discharge amount is determined from a target value and an actual value of the fuel supply pressure. a feedback control amount setting means for setting, Fi for setting the feed-forward control amount of the ejection amount on the basis of the required fuel injection amount corresponding to the cylinder intake air quantity A feedforward control amount setting means, and discharge amount control means for controlling the discharge amount of the fuel pump based on the feedback control amount and the feedforward control amount, the cylinder discharge of fuel by the fuel pump is a fuel injection is performed And a discharge stop control means for stopping the discharge at the injection timing of the cylinder in which the fuel injection is stopped, which is performed only at the injection timing.
[0016]
According to this configuration, in the discharge stroke synchronized with the injection timing, when fuel injection is performed at the injection timing, the fuel is discharged from the fuel pump. When the fuel injection is stopped, the fuel from the fuel pump is discharged. Also stop the discharge.
[0017]
【The invention's effect】
According to the first aspect of the present invention, the required fuel injection amount for determining the feed-forward control amount of the discharge amount is corrected to decrease in accordance with the ratio of the number of cylinders where the injection is stopped. There is an effect that the amount of fuel discharged in one discharge stroke can be corrected to decrease in accordance with the number of cylinders in which injection is stopped.
[0018]
According to the second aspect of the present invention, fuel discharge by the fuel pump is discontinuously executed according to the number of cylinders in which injection is stopped, and the total discharge amount is determined in accordance with the number of cylinders in which injection is stopped. It has the effect of being able to lose weight.
[0019]
According to the third aspect of the present invention, since the fuel is discharged from the fuel pump only when the fuel injection is performed, the discharge amount may be excessive even if the fuel injection is stopped in some cylinders. In addition, since the fuel is discharged only when fuel injection is performed, there is an effect that generation of fuel pressure pulsation can be reduced.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 shows the overall configuration of a direct injection gasoline engine according to an embodiment.
[0022]
In FIG. 1, an electric feed pump 2 for pumping the fuel in the tank 1 is provided in the fuel tank 1, and the fuel discharged from the feed pump 2 is sent to the fuel filter 3, the fuel damper 4 and the reverse. The air is sucked into the single cylinder type fuel pump 7 through the low pressure side fuel passage 6 having the stop valve 5 interposed therebetween.
[0023]
The fuel pump 7 has a structure in which fuel is sucked when the piston, which is driven by a pump drive cam provided on the camshaft of the engine, moves up and down, and discharged when it rises.
[0024]
On the other hand, a return passage 8 is provided for connecting the pump chamber of the fuel pump 7 and the low pressure side fuel passage 6 upstream of the check valve 5, and the return passage 8 is opened and closed in the middle of the return passage 8. A solenoid valve 9 is interposed.
[0025]
On the other hand, a high pressure side fuel passage 11 having a check valve 10 is connected to the discharge port of the fuel pump 7, and a fuel pressure accumulation chamber (common rail) 12 is connected to the other end of the high pressure side fuel passage 11. Connected. A branch passage 14 is branched and extended from the fuel pressure accumulation chamber 12 toward each fuel injection valve 13 attached to the combustion chamber of each cylinder.
[0026]
A fuel pressure sensor 15 that detects the fuel pressure in the fuel pressure storage chamber 12 is attached to the fuel pressure storage chamber 12.
[0027]
The solenoid valve 9 is driven and controlled by the control signal from the control unit 16 controls the discharge amount of the fuel pump 7 by controlling the solenoid valve 9, the fuel pressure in the fuel accumulation chamber 12, pulls fuel The fuel injection pressure of the injection valve 13 is controlled.
[0028]
The control unit 16 inputs a fuel pressure signal from the fuel pressure sensor 15, and also inputs signals from sensors that detect various operating states of the engine (engine load, engine speed, etc.). Based on this, the solenoid valve 9 is controlled as described later.
[0029]
Here, an outline of the operation of the electromagnetic valve 9 will be described.
[0030]
As shown in FIG. 2, the solenoid valve 9 is closed at the top dead center (TDC) of the piston of the fuel pump 7, and the pump chamber is being lowered (during the intake stroke) from the top dead center to the bottom dead center. Inhale fuel. When the piston starts to rise, while the solenoid valve 9 is closed and the return passage 8 is closed, fuel is discharged from the fuel pump 7 toward the fuel accumulator chamber 12. When the valve is opened, the fuel is returned from the pump chamber of the fuel pump 7 through the return passage 9 to the low-pressure side fuel passage 6, and the fuel discharge (supply to the fuel pressure accumulation chamber 12) is stopped.
[0031]
Therefore, the period during which fuel is discharged by controlling the valve closing period θ _op (or the valve opening timing before the piston top dead center) after the valve is closed at the piston top dead center until the valve is opened in the discharge stroke. That is, the discharge amount is controlled, and as a result, the fuel pressure in the fuel accumulator chamber 12, that is, the fuel injection pressure is controlled.
[0032]
The solenoid valve 9 is closed during the intake stroke, while the solenoid valve 9 is once opened at the bottom dead center of the piston, and the solenoid valve 9 is closed again in the middle of the discharge stroke. It is good also as a structure which discharges fuel between a piston top dead center and the structure which controls discharge amount by the period from the said piston bottom dead center until the solenoid valve 9 is closed.
[0033]
The flowchart of FIG. 3 shows the state of control of the solenoid valve 9 by the control unit 16, and the routine shown in the flowchart of FIG. 3 is executed every time the piston of the fuel pump 7 becomes top dead center. And
[0034]
In S1, the required fuel injection amount Ti calculated according to the cylinder intake air amount is read.
[0035]
In S2, it is determined whether the mode is a mode in which fuel injection is performed in all cylinders (full cylinder injection mode) or the mode in which fuel injection is performed only in half cylinders for torque control (half cylinder injection mode).
[0036]
In the all cylinder injection mode, the process jumps to S3 and proceeds to S4. However, in the half cylinder injection mode, the process proceeds to S3 (decrease correction means) for the discharge amount control by the valve closing period θ _op. The required fuel injection amount Ti read in S1 is multiplied by 1/2, which is the ratio of the number of cylinders where fuel injection is stopped, to correct the decrease.
[0037]
The fuel injection by the fuel injection valve 13 is performed in accordance with the required fuel injection amount Ti read in S1, and the required fuel injection amount Ti corrected for decrease in S3 is used only for determining the valve closing period θ _op. Used.
[0038]
S4 In (feedforward control amount setting means), referring to the table storing feedforward control amount theta _FF of the closed period theta _op corresponding to the previously required fuel injection amount Ti, the required fuel injection amount Ti of the time The feedforward control amount θ _FF corresponding to is searched.
[0039]
Here, in the all cylinder injection mode, the feedforward control amount θ _FF is set corresponding to the amount of fuel injected from the fuel injection valve 13, but in the half cylinder injection mode, the cylinder that performs fuel injection Therefore, the feedforward control amount θ _FF is set corresponding to half of the amount of fuel injected from the fuel injection valve 13, and as a result, in the half-cylinder injection mode, compared to that in the all-cylinder injection mode. Thus, the discharge amount for each discharge stroke of the fuel pump 7 is reduced by half.
[0040]
Accordingly, it is possible to prevent the fuel pressure from becoming higher than required by performing feedforward control to the same discharge amount as in the full cylinder injection mode in the half cylinder injection mode.
[0041]
In S5, the target fuel pressure is set, and in S6, the actual fuel pressure detected by the fuel pressure sensor 15 is read.
[0042]
In S7 (feedback control amount setting means) , the feedback control amount θ _FB is calculated so that the actual fuel pressure matches the target fuel pressure.
[0043]
In S8, the feedback control amount θ _FB is added to the feedforward control amount θ _FF to determine a final valve closing period θ _op , and in S9, based on the determined valve closing period θ _op , Controls opening and closing of the electromagnetic valve 9 (discharge amount control means) .
[0044]
The flowchart of FIG. 4 shows a second embodiment of control of the solenoid valve 9. When the required fuel injection amount Ti is read in S11, the read required fuel injection is read in S12 (feedforward control amount setting means). The feedforward control amount θ _FF is determined according to the amount Ti.
[0045]
As described above, here, even in the half cylinder injection mode, the feedforward control amount θ _FF is determined without reducing the required fuel injection amount Ti.
[0046]
In S13, the target fuel pressure is set, and in S14, the actual fuel pressure detected by the fuel pressure sensor 15 is read.
[0047]
In S15 (feedback control amount setting means) , the feedback control amount θ _FB is calculated so that the actual fuel pressure matches the target fuel pressure.
[0048]
In S16 (discharge amount control means) , the feedback control amount θ _FB is added to the feedforward control amount θ _FF to determine the final valve closing period θ _op .
[0049]
In S17, it is determined whether the fuel injection is performed in all cylinders or the fuel injection is performed in only half of the cylinders for torque control.
[0050]
When in the all-cylinder injection mode, the routine proceeds to S22, where normal control for controlling the electromagnetic valve 9 is performed based on the valve closing period θ _op determined in S16.
[0051]
On the other hand, when it is the half cylinder injection mode, the process proceeds to S18, and the flag F is determined. When the flag F is 0, the routine proceeds to S19, where the flag F is set to 1, and then the routine proceeds to S22, where normal control is performed to control the electromagnetic valve 9 based on the valve closing period θ _op determined in S16. .
[0052]
On the other hand, when the even was half-cylinder injection mode next time, because 1 the flag F is set, the process proceeds from S18 to S20, after the flag F has been reset to 0, the process proceeds to S21, as the close period theta _op, The same period as the suction stroke is set, the solenoid valve 9 is closed from the bottom dead center of the piston to the top dead center, and the solenoid valve 9 is controlled to be opened during the discharge stroke so that the discharge is not performed.
[0053]
That is, when a half-cylinder injection mode, as the discharge of the fuel with every other shot discharge process is performed, which reduces by half the sum of the discharge amount, the S 18 to S 21 The processing corresponds to the discharge number control means.
[0054]
In the embodiment shown in FIG. 3 and FIG. 4, the fuel injection is performed in all cylinders or half, but the number of cylinders in which fuel injection is stopped is not limited to half. When fuel injection is stopped for only one of the cylinders, the correction calculation of the required fuel injection amount Ti in the flowchart of FIG. 3 may be Ti ← Ti · 3/4, and the flowchart of FIG. Thus, in the case of the configuration in which fuel injection is performed discontinuously, it is only necessary to stop the discharge at a rate of once every four discharge strokes.
[0055]
The flowchart of FIG. 5 shows a third embodiment of control of the electromagnetic valve 9. However, the control shown in the flowchart of FIG. 5 is applied when the fuel pump 7 is driven in synchronism with the injection timing of each cylinder and is configured to have a discharge stroke for each stroke phase difference between the cylinders. The
[0056]
In the flowchart of FIG. 5, from S31 to S36, the same processing as S11 to S16 of the flowchart of FIG. 4 is performed.
[0057]
In S37, it is determined whether the fuel injection mode is performed in all cylinders or the fuel injection mode is performed in only half the cylinders for torque control.
[0058]
When in the all-cylinder injection mode, the process proceeds to S40, and the electromagnetic valve 9 is normally controlled based on the valve closing period θ _op determined in S36.
[0059]
On the other hand, when it is the half cylinder injection mode, the routine proceeds to S38, where it is determined whether or not the current injection timing is for the cylinder in which fuel injection is performed. When it is the injection timing of the cylinder that normally performs fuel injection, the routine proceeds directly to S40, and the electromagnetic valve 9 is normally controlled based on the valve closing period θ _op determined in S36.
[0060]
On the other hand, when it is determined in S38 that the injection timing is in the cylinder where the fuel injection is stopped, the process proceeds to S39 (discharge stop control means) , and the same period as the intake stroke is set as the valve closing period θ _op , and the piston The electromagnetic valve 9 is closed from the bottom dead center to the top dead center, and in the discharge stroke, the electromagnetic valve 9 is controlled to be opened during the entire period, and then the process proceeds to S40.
[0061]
In this case, during the discharge stroke, the electromagnetic valve 9 is controlled to open, the fuel is returned to the low pressure side via the return passage 8, and no fuel is discharged.
[0062]
As described above, if the fuel is discharged from the fuel pump 7 only at the injection timing of the cylinder where the fuel is actually injected, excess fuel is not discharged even in the half-cylinder injection mode. The fuel pressure can be stably controlled to the target pressure, and the pulsation of the fuel pressure can be suppressed by causing the discharge (fuel replenishment) to be performed only when the fuel is injected.
[0063]
In addition, since the above is a structure which does not discharge by the injection timing of the cylinder which stops injection, it is clear that the number of cylinders which stop fuel injection is not limited to half.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration of an embodiment.
FIG. 2 is a time chart showing a state of discharge amount control of the fuel pump according to the embodiment.
FIG. 3 is a flowchart showing control contents according to the first embodiment.
FIG. 4 is a flowchart showing control contents according to the second embodiment.
FIG. 5 is a flowchart showing control contents according to the third embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Fuel tank 2 ... Feed pump 3 ... Fuel filter 4 ... Fuel damper 5, 10 ... Check valve 6 ... Low pressure side fuel passage 7 ... Fuel pump 8 ... Return passage 9 ... Solenoid valve
11… High pressure side fuel passage
12 ... Fuel pressure storage chamber
13 ... Fuel injection valve
14 ... Branch passage
15 ... Fuel pressure sensor
16 ... Control unit

Claims (3)

A fuel injection valve that directly injects fuel into the combustion chamber is provided, and a branch passage extends from the fuel pressure accumulation chamber connected to the discharge port of the fuel pump toward each of the fuel injection valves mounted in the combustion chamber of each cylinder. In the direct injection gasoline engine, the fuel injection control device of the direct injection gasoline engine that controls the supply pressure of the fuel to the fuel injection valve provided for each cylinder by electronically controlling the discharge amount of the fuel pump,
A feedback control amount setting means for setting a feedback control amount of the discharge amount from a target value and an actual value of the supply pressure of the fuel;
A feedforward control amount setting means for setting a feedforward control amount of the discharge amount based on a required fuel injection amount corresponding to a cylinder intake air amount;
A reduction correction means for correcting the reduction of the required fuel injection amount used for setting the feedforward control amount based on the ratio of the number of cylinders in which fuel injection is stopped ;
A discharge amount control means for controlling a discharge amount of the fuel pump based on the feedback control amount and the feedforward control amount;
A fuel injection control device for a direct-injection gasoline engine. A fuel injection valve that directly injects fuel into the combustion chamber is provided, and a branch passage extends from the fuel pressure accumulation chamber connected to the discharge port of the fuel pump toward each of the fuel injection valves mounted in the combustion chamber of each cylinder. In the direct injection gasoline engine, the fuel injection control device of the direct injection gasoline engine that controls the supply pressure of the fuel to the fuel injection valve provided for each cylinder by electronically controlling the discharge amount of the fuel pump,
A feedback control amount setting means for setting a feedback control amount of the discharge amount from a target value and an actual value of the supply pressure of the fuel;
A feedforward control amount setting means for setting a feedforward control amount of the discharge amount based on a required fuel injection amount corresponding to a cylinder intake air amount;
A discharge amount control means for controlling a discharge amount of the fuel pump based on the feedback control amount and the feedforward control amount;
A discharge number control means for controlling the number of times of actually discharging fuel with respect to the number of discharge strokes in the fuel pump according to the number of cylinders in which fuel injection is stopped ;
A fuel injection control device for a direct-injection gasoline engine. A fuel injection valve that directly injects fuel into the combustion chamber; and a fuel pump whose discharge stroke is synchronized with the fuel injection timing of each of the fuel injection valves, and is connected to each cylinder from the fuel pressure accumulation chamber connected to the discharge port of the fuel pump. In a direct-injection gasoline engine in which a branch passage is extended toward each of the fuel injection valves installed in the combustion chamber of the engine, the fuel injection valve provided for each cylinder by electronically controlling the discharge amount of the fuel pump A fuel injection control device for a direct-injection gasoline engine that controls the fuel supply pressure with respect to
A feedback control amount setting means for setting a feedback control amount of the discharge amount from a target value and an actual value of the supply pressure of the fuel;
A feedforward control amount setting means for setting a feedforward control amount of the discharge amount based on a required fuel injection amount corresponding to a cylinder intake air amount;
A discharge amount control means for controlling a discharge amount of the fuel pump based on the feedback control amount and the feedforward control amount;
A discharge stop control means for causing the fuel to be discharged by the fuel pump only at the injection timing of the cylinder where fuel injection is performed, and stopping the discharge at the injection timing of the cylinder where fuel injection is stopped ;
A fuel injection control device for a direct-injection gasoline engine.

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