JP3267217B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, and can be used, for example, in a direct injection gasoline engine that directly injects fuel into each cylinder of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique of supplying an appropriate amount of fuel to each cylinder by controlling an opening period of a fuel injection valve provided in an internal combustion engine in accordance with an operation state of the internal combustion engine. ing. In recent years, a technique has been attempted in which a fuel injection valve for directly injecting fuel into each cylinder of an internal combustion engine is provided, and a fuel injection amount into each cylinder is controlled by controlling a valve opening period of the fuel injection valve. ing.

[0003]

The fuel injection amount per unit time by the fuel injection valve is set according to the maximum value of the fuel injection amount required corresponding to the operating state of the internal combustion engine. In general, when the required fuel injection amount is small, the actual fuel injection amount is not proportional to the injection period, and the linearity tends to deteriorate.

If the internal combustion engine is of the direct injection type,
The fuel injection start timing when injecting fuel directly into the cylinder is
Naturally, the period during which the fuel can be injected is shorter than that of a conventional non-injection type internal combustion engine because it is after the compression stroke. For this reason, the required fuel injection amount (hereinafter, referred to as “required fuel injection amount”) is large, as in the case of a high load. Needs to be increased.

In a system including such a fuel injection valve,
If the required fuel injection amount is small, such as at the time of low load, the linearity deteriorates as described above. The linearity also varies depending on the fuel pressure (hereinafter, referred to as "fuel pressure"). Therefore, if the required fuel injection amount for the internal combustion engine is small, such as when the vehicle is decelerating or during idle operation, the actual fuel injection amount becomes unstable, causing surges or misfires, which are torque fluctuations of the internal combustion engine. There was a problem that occurs.

Accordingly, the present invention has been made to solve such a problem, and a fuel for an internal combustion engine capable of suppressing the occurrence of a surge or a misfire of the internal combustion engine by appropriately controlling a required fuel injection amount for a fuel injection valve. It is an object to provide an injection control device.

[0007]

According to the first aspect of the present invention , fuel is directly injected into each cylinder.
The minimum value of the required fuel injection amount that can be compensated for the required fuel injection amount of the fuel injection valve corresponding to a predetermined operation state of the internal combustion engine including the direct injection gasoline engine is set according to the fuel pressure by the pressure adjusting means. The appropriate fuel injection amount is controlled by the injection amount control means depending on the valve opening period of the fuel injection valve. As a result, when the required fuel injection amount to the fuel injection valve is small and the linearity is degraded and the actual fuel injection amount becomes unstable, an appropriate guard process based on the minimum required fuel injection amount is executed. Also, the internal combustion engine is
Because it is a sorin engine, a large amount within a short fuel injection period
Fuel injection amount per unit time from the need to inject
The fuel injection valve which can increase is adopted. Then, less
When fuel is injected, linearity tends to deteriorate.
Therefore, the required fuel according to the fuel pressure
Guard processing based on the minimum injection amount or invalid injection period or
For the required valve opening period, the maximum valve opening period according to the fuel pressure
Guarding with a small value or invalid injection period is particularly effective.
You. Therefore, the required fuel injection amount or the required valve opening period
The injection accuracy of the fuel injection valve with respect to the interval is improved, and the occurrence of surge or misfire of the internal combustion engine can be suppressed. Furthermore,
In this fuel injection control device, the pressure adjusting means is provided with a high-pressure fuel port.
Pump, reservoir tank and fuel pressure sensor.
Required for the fuel injection valve according to the predetermined operating condition of the Seki
Fuel whose minimum fuel injection amount is detected by the fuel pressure sensor
It is set according to the pressure. As a result, the required fuel injection amount
The injection accuracy of the fuel injection valve with respect to
The occurrence of a surge or a misfire can be suppressed.

In the fuel injection control device for an internal combustion engine according to the second aspect, the minimum value of the valve opening period that can be compensated for the required valve opening period of the fuel injection valve corresponding to the predetermined operating state of the internal combustion engine is the pressure. The fuel injection amount is set according to the fuel pressure by the adjusting means, and the fuel injection amount is controlled by the injection amount control means by an appropriate valve opening period of the fuel injection valve. Thereby, when the required valve opening period of the fuel injection valve is shortened, the linearity is deteriorated, and the actual fuel injection amount becomes unstable, an appropriate guard process based on the minimum value of the valve opening period is executed. For this reason, the injection accuracy of the fuel injection valve for the required valve opening period is improved, and the occurrence of surge or misfire of the internal combustion engine can be suppressed.

In the fuel injection control device for an internal combustion engine according to the third aspect, the invalid injection period which can be compensated for the required valve opening period of the fuel injection valve corresponding to the predetermined operation state of the internal combustion engine is determined by the pressure adjusting means. The fuel injection amount is set according to the fuel pressure, and the injection amount control means controls the fuel injection amount by an appropriate valve opening period of the fuel injection valve. Accordingly, when the required valve opening period of the fuel injection valve is shortened, the linearity is deteriorated, and the actual fuel injection amount becomes unstable, an appropriate guard process based on the invalid injection period is executed. For this reason, the injection accuracy of the fuel injection valve for the required valve opening period is improved, and the occurrence of surge or misfire of the internal combustion engine can be suppressed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples.

FIG. 1 is an overall configuration diagram showing an internal combustion engine to which a fuel injection control device for an internal combustion engine according to one embodiment of the present invention is applied.

In FIG. 1, reference numeral 1 denotes a direct injection type internal combustion engine which injects fuel directly into a cylinder as a four-cylinder gasoline engine;
2 is a surge tank, 3 is an air cleaner, 4 is an intake passage connecting the surge tank 2 and the air cleaner 3, 5 is a spark plug, 6 is a high-pressure fuel injection valve for injecting gasoline fuel into each cylinder, and 7 is a high-pressure fuel injection valve. A reservoir tank, 8 is a high-pressure conduit for guiding high-pressure fuel in the reservoir tank 7 to the fuel injection valve 6;
9 is a high-pressure fuel pump whose discharge pressure is controllable, 10 is a high-pressure pipe for guiding high-pressure fuel from the high-pressure fuel pump 9 to the reservoir tank 7, 11 is a fuel tank, and 12 is a high-pressure fuel tank. This is a low-pressure fuel pump to be supplied to the fuel pump 9.

The ECU (Electronic Control Unit) 20 comprises a digital computer,
CPU 21 as a well-known central processing unit, ROM 22 storing a control program, RAM storing various data
23, etc., are connected as a logical operation circuit via a bidirectional bus 26 to an input port 24 for inputting detection signals from various sensors and an output port 25 for outputting control signals to various actuators. Is done.

A fuel pressure sensor 27 disposed in the reservoir tank 7 detects a fuel pressure PR in the reservoir tank 7, and the fuel pressure PR signal is input to an input port via an A / D (analog-digital) conversion circuit 28 in the ECU 20. 24. Further, a crank angle sensor 29 provided on a crankshaft (not shown) of the internal combustion engine 1 detects the engine speed NE, and an output pulse proportional to the engine speed NE is input to the input port 24. An accelerator opening sensor 3 as a load sensor for detecting a load state of the internal combustion engine 1
0 indicates an accelerator opening Ap corresponding to the depression amount of an accelerator pedal (not shown), and an output voltage proportional to the accelerator opening Ap is input to the input port 24 via the A / D conversion circuit 31 in the ECU 20. Is done.

On the other hand, the fuel injection valve 6 of each cylinder is
Connected to the output port 25 via each drive circuit 34. The ignition plug 5 of each cylinder is connected to the output port 25 via each drive circuit 35 in the ECU 20. The high-pressure fuel pump 9 is connected to the output port 25 via the drive circuit 36.

Next, an EC used in a fuel injection control device for an internal combustion engine according to an embodiment of the present invention will be described.
FIG. 3 will be described based on the flowchart of FIG. 2 showing the processing procedure of the fuel injection control in the CPU 21 in U20. FIG. 3 is a table for obtaining the minimum value Qmin of the required fuel injection amount from the fuel pressure PR. It should be noted that this fuel injection control routine is executed every predetermined time.
It is repeatedly executed in U21.

In FIG. 2, first, at step S101, the accelerator opening Ap from the accelerator opening sensor 30 and the engine speed NE from the crank angle sensor 29 are read. Next, the process proceeds to step S102, and step S10
The required fuel injection amount Qall of each cylinder as a basic fuel injection amount required for one combustion cycle of the internal combustion engine 1 is calculated based on the accelerator opening Ap and the engine speed NE read in step 1. Next, the process proceeds to step S103, where the fuel pressure sensor 2
The fuel pressure PR from 7 is read. Next, step S104
To step S10 based on the table of FIG.
The minimum value Q of the required fuel injection amount from the fuel pressure PR read in step 3
min is calculated. In the table of FIG. 3, the fuel pressure P
The higher the R, the larger the minimum value Qmin of the required fuel injection amount is set, and the intermediate value in this table is obtained by interpolation.

Next, the process proceeds to step S105, in which the required fuel injection amount Qall calculated in step S102 is reduced to the minimum value Qmin of the required fuel injection amount calculated in step S104.
It is determined whether it is less than. When the determination condition of step S105 is satisfied, that is, when Qall <Qmin, the process proceeds to step S106, where Qall = Qmin, and a guard process is performed using the minimum value Qmin of the required fuel injection amount with respect to the required fuel injection amount Qall at this time. Then, this routine ends. Thus, the required fuel injection amount Qall corresponding to the predetermined operating state of the internal combustion engine 1 is less than the minimum value Qmin of the required fuel injection amount that can be compensated by the fuel injection valve 6 set according to the fuel pressure PR. And the required fuel injection amount Q at this time
It is impossible to adapt the actual fuel injection amount from the fuel injection valve 6 to all. Therefore, the required fuel injection amount Qall
Is equal to the minimum value Qmin of the required fuel injection amount that can be compensated, so that the fuel injection amount from the fuel injection valve 6 is stabilized.

On the other hand, if the determination condition of step S105 is not satisfied, that is, if Qall ≧ Qmin, the routine proceeds to step S105.
106 is skipped and the required fuel injection amount Qal at this time is
This routine is terminated without executing the guard process using the minimum value Qmin of the required fuel injection amount with respect to l. At this time, the required fuel injection amount Qall corresponding to the predetermined operating state of the internal combustion engine 1 can be adapted to the actual fuel injection amount from the fuel injection valve 6 set according to the fuel pressure PR. Therefore, the required fuel injection amount Qall is directly reflected on the fuel injection amount from the fuel injection valve 6.

As described above, the fuel injection control apparatus for an internal combustion engine according to the present embodiment has a direct injection that directly injects fuel into each cylinder.
Internal combustion composed of a gasoline engine (cylinder injection internal combustion engine)
CPU in the ECU 20 for controlling the opening period of the fuel injection valve 6 disposed in the engine 1 to control the required fuel injection amount Qall
21. An injection amount control means achieved at 21 and a pressure adjustment comprising a reservoir tank 7 for adjusting the pressure of fuel supplied to the fuel injection valve 6 to a predetermined fuel pressure PR, a high-pressure fuel pump 9, a fuel pressure sensor 27, and the like. Means for determining the minimum value Qmin of the required fuel injection amount required for the fuel injection valve 6 corresponding to a predetermined operating state determined by the accelerator opening Ap of the internal combustion engine 1 and the engine speed NE. Is set in accordance with.

As described above, the fuel injection valve 6 is set according to the maximum value of the required fuel injection amount. If the required fuel injection amount becomes small, the actual fuel injection amount becomes unstable. Therefore, the minimum value Qmin of the required fuel injection amount that can be compensated for the required fuel injection amount Qall corresponding to the predetermined operating state of the internal combustion engine 1 is set according to the fuel pressure PR.

The internal combustion engine 1 is a direct injection gasoline machine.
A large amount of fuel within a short fuel injection period.
Fuel injection amount per unit time can be increased due to injection requirement
An efficient fuel injection valve 6 is employed. Then, you need less fuel
When injecting, linearity tends to deteriorate.
Therefore, the required fuel injection amount Qall must be adjusted according to the fuel pressure PR.
Guard processing by the minimum value of the required fuel injection quantity Qmin is especially provided.
It works. As a result, the injection accuracy of the fuel injection valve 6 with respect to the required fuel injection amount Qall is improved, an air-fuel mixture with good ignition can be generated near the ignition plug 5, and the occurrence of surge and misfire of the internal combustion engine 1 can be suppressed. .

Here, in the above embodiment, the minimum value Qmin of the required fuel injection amount is set in accordance with the fuel pressure PR. However, the present invention is not limited to this. Since the injection amount is correlated with the valve opening period of the fuel injection valve 6, even if the minimum value of the valve opening period of the fuel injection valve 6 is set according to the fuel pressure PR or the invalid injection period is set according to the fuel pressure PR. Good.

Such a fuel injection control device for an internal combustion engine sets a minimum value of a valve opening period required for the fuel injection valve 6 in accordance with a predetermined operating state of the internal combustion engine 1 in accordance with a fuel pressure PR. It is. Further, an invalid injection period required for the fuel injection valve 6 in accordance with a predetermined operating state of the internal combustion engine 1 is set according to the fuel pressure PR. That is, since the minimum value of the valve opening period of the fuel injection valve 6 and the invalid injection period which ultimately determine the required fuel injection amount Qall are set according to the fuel pressure PR, the fuel injection valve 6 with respect to the required fuel injection amount Qall is set. The injection accuracy is improved, and a mixture with good ignition can be generated in the vicinity of the ignition plug 5, so that the occurrence of surge or misfire of the internal combustion engine 1 can be suppressed.

In the above-described embodiment, the minimum value Qmin of the required fuel injection amount is calculated based on the table. However, the present invention is not limited to this. May be multiplied by a correction coefficient corresponding to the fuel pressure PR, that is, the minimum value Qmin of the required fuel injection amount may be calculated from (Qmin set value × correction coefficient).

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an internal combustion engine to which a fuel injection control device for an internal combustion engine according to an embodiment of the present invention is applied.

FIG. 2 is an ECU used in a fuel injection control device for an internal combustion engine according to one embodiment of the present invention.
4 is a flowchart showing a processing procedure of fuel injection control in a CPU inside the CPU.

FIG. 3 is a table for calculating a minimum value of a required fuel injection amount from a fuel pressure in FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 6 (for high pressure) fuel injection valve 7 (for high pressure) reservoir tank 9 high pressure fuel pump 20 ECU (electronic control unit) 27 fuel pressure sensor

Claims (3)

(57) [Claims] 1. Direct injection for directly injecting fuel into each cylinder
An injection quantity control means for controlling the amount of fuel injection by controlling the valve opening period of the fuel injection valve disposed in an internal combustion engine consisting of Formula gasoline engine, a predetermined fuel pressure the pressure of the fuel supplied to the fuel injection valves A high-pressure fuel pump whose discharge pressure can be controlled
Reservoir tank to which high-pressure fuel from the high-pressure fuel pump is guided
And a fuel pressure sensor for detecting a fuel pressure in the reservoir tank.
Corresponding to a predetermined operating state of the internal combustion engine.
To calculate the minimum value of the fuel injection amount required for the fuel injection valve.
Set according to the fuel pressure detected by the fuel pressure sensor
Internal combustion, characterized in that comprising a pressure regulating means for, set according to the minimum value of the required fuel injection amount to the fuel injection valve in response to a predetermined operating state of the internal combustion engine to the fuel pressure Engine fuel injection control device. 2. The fuel injection system according to claim 1, wherein a minimum value of a valve opening period required for the fuel injection valve is set according to the fuel pressure in accordance with a predetermined operation state of the internal combustion engine. A fuel injection control device for an internal combustion engine. 3. The fuel injection valve according to claim 1, wherein an invalid injection period required for the fuel injection valve is set according to the fuel pressure in accordance with a predetermined operation state of the internal combustion engine. A fuel injection control device for an internal combustion engine according to claim 1.