JPH0693914A - Accumulative fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To stabilize a combustion condition by calculating an objective com mon rail pressure from an always stabilized objective engine speed during idle of an engine, and thereby stabilizing an actual common rail pressure. CONSTITUTION:Operation of an injection controlling solenoid valve 3 and a high-pressure pumping valve of a discharge rate control device 1 is controlled according to control signals output from an electronic control unit(ECU) 11. An actual engine speed NE and an accelerator opening thetaAC respectively detected by an engine speed sensor 12 and an accelerator opening sensor 13 are input to an objective injection amount computation circuit 20 inside the ECU 11, and a target injection amount QFIN' is calculated there. In addition, an idling condition judgment circuit 28 is provided. When the idling condition is judged, an objective common rail pressure PFIN is calculated through an objective engine speed NEF of the engine. When other conditions are judged, the target common rail pressure PFIN is calculated from the actual engine speed NE and the objective injection amount QFIN'. An idle speed can be set low, accordingly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation type fuel injection control device for an internal combustion engine, and more particularly, in an internal combustion engine equipped with a pressure-accumulation type unit injector device, fluctuations in the engine speed affect the command injection pressure only at idle. The present invention relates to a pressure-accumulation fuel injection control device for an internal combustion engine, which is designed so as to achieve low idling and low rotation speed without being given.

[0002]

2. Description of the Related Art In recent years, there has been an increasing social demand for increasing the quietness of vehicles equipped with an internal combustion engine. In particular, for vehicles equipped with a diesel engine, the noise during idling was large and the influence on the neighborhood was large. Therefore, to reduce the idle speed of the diesel engine,
There is an advantage that the generated noise can be reduced and the fuel consumption can be improved.

One of the methods for lowering the idle speed of such a diesel engine, that is, a method for achieving a low idling low speed, is to feed back the actual speed of the diesel engine to obtain a constant target speed. Conventionally, a method of controlling the control is known. In addition, JP-A-62-2
No. 3,552, JP-A-58-214631, JP-A-61-14446 and the like disclose a method of correcting the fuel injection amount to keep the engine speed between cylinders constant. It has been shown that this method realizes low idle of a diesel engine.

On the other hand, regarding the structure of the pressure accumulation type fuel injection control device of the diesel engine equipped with the pressure accumulation type unit injector device and the fuel injection pressure control, JP-A-62-62
The control described in Japanese Patent No. 258160 has already been proposed. In this proposal, fuel injection pressure (hereinafter referred to as common rail pressure) control is performed by obtaining a target common rail pressure from a target injection amount and an actual engine speed, and a high pressure pump so that the actual common rail pressure matches the target common rail pressure. The solenoid valve of is controlled.

[0005]

However, if an attempt is made to perform idle control of a diesel engine by using fuel injection pressure control in a pressure accumulation type fuel injection control device for a diesel engine equipped with the pressure accumulation type unit injector device described above. Even if the target injection amount is corrected and controlled according to the deviation between the target rotation speed and the actual rotation speed or the change in the rotation speed between the cylinders, there is still a limit in lowering the idle rotation speed. There is a problem.

The reason for this is that when the diesel engine is idle, even if the actual injection speed is stabilized by correcting the target injection amount, a slight rotation fluctuation remains in the actual rotation speed. That is, as described above, since the target common rail pressure is determined by the actual rotation speed and the target injection amount, if the actual rotation speed changes, the target common rail pressure changes, and as a result, the actual common rail pressure also changes. Then, because the fuel condition changes,
There is a limit to lowering the idle speed, such as hunting of the engine or large engine vibration.

In view of the above, the present invention solves the above-mentioned problems of the prior art and realizes low idling and low engine speed in order to improve the quietness and fuel consumption of a vehicle equipped with a diesel engine during idling. Another object of the present invention is to provide a new pressure-accumulation fuel injection control device for an internal combustion engine.

[0008]

A pressure-accumulation type fuel injection control system for an internal combustion engine according to the present invention which achieves the above-mentioned object, includes a detected value of an engine operating condition parameter such as an engine speed and an accelerator opening and an actual common rail pressure. Based on the detected value, a command fuel injection amount, a fuel injection timing, and a command value of the injection pressure of the cylinder in which fuel is injected next are calculated according to a predetermined program, and a fuel injection period corresponding to the injection pressure command value of the next cylinder In a pressure-accumulation type fuel injection control device for an internal combustion engine that injects fuel with an engine, an idle state determination means for determining an idle state of the engine from an operating state parameter of the engine, and a target engine speed of the engine when the idle state is determined. Idle injection pressure calculation means for calculating the target common rail pressure from the target, and the target injection amount based on the actual engine speed and the target injection amount when it is determined that the engine is not in the idle state. It is characterized by providing a non-idle time injection pressure computing means for calculating the Monreru pressure.

[0009]

According to the pressure-accumulation fuel injection control apparatus for an internal combustion engine of the present invention, when the engine is determined to be in the idle state, the target common rail pressure is calculated from the target revolution speed of the engine, and the engine is not in the idle state. When the determination is made, the target common rail pressure is calculated from the actual engine speed and the target injection amount. As a result, when the engine is idle, the target common rail pressure is always calculated from the stable target speed,
Actual common rail pressure is stable, combustion state is stable

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pressure accumulation type fuel injection control device for an internal combustion engine according to the present invention will be described below with reference to the drawings. First, referring to FIG. 1, a pressure accumulation type fuel injection control device for an internal combustion engine which is the premise of the present invention. The schematic configuration of will be described. Internal combustion engine (engine) 1
Is provided with an injector 2 for injecting high-pressure fuel into the combustion chamber of each cylinder, and fuel injection from the injector 2 to the engine 1 is controlled by opening / closing the injection control solenoid valve 3. . The injector 2 is connected to a high pressure accumulating pipe common to all the cylinders, a so-called common rail 4, and while the injection control solenoid valve 3 is open, the fuel in the common rail 4 is injected from the injector 2 into the combustion chamber of the engine 1. . Therefore, it is necessary for the common rail 4 to continuously accumulate a high predetermined pressure corresponding to the fuel injection pressure. For this reason, the common rail 4 has a supply pipe 6 and a check valve 5.
A high-pressure pump 7 capable of supplying high-pressure fuel is connected via. The high-pressure pump 7 reciprocates the fuel sucked from the fuel tank 8 through the well-known low-pressure supply pump 9 by a cam (not shown) synchronized with the rotation of the engine 1 so as to increase the pressure to a predetermined high pressure required and then the common rail 4 The discharge amount control device 10 is provided.
The discharge amount control device 10 includes a high pressure pump valve that opens and closes an intake port of the high pressure pump 7, and controls the discharge amount by adjusting the effective pressure feeding stroke of the high pressure pump 7 by the high pressure pump valve.

Injection control solenoid valve 3 and discharge amount control device 10
The high-pressure pump valve of the electronic control unit (hereinafter simply referred to as ECU
The operation is controlled by a control signal output from the (11). The ECU 11 includes an engine speed sensor 1
2 and the detection signals from the accelerator opening sensor 13, as well as the input signals from the pressure sensor 14 that detects the actual common rail pressure and various sensors 15 such as water temperature, intake temperature, and intake pressure. The ECU 11 determines the operating state of the engine based on these input signals, performs arithmetic processing according to a predetermined program, and outputs an optimum control signal to the injection control solenoid valve 3 and the discharge amount control device 10. Although not shown, the ECU 11 has a memory (RAM, R) for storing detection data, a control program, and the like.
OM) is provided.

FIG. 2 is a control block diagram of the ECU 11 shown in FIG. In FIG. 2, first, the injection amount control will be described. The actual engine speed NE and the accelerator opening θAC detected by the engine speed sensor 12 and the accelerator opening sensor 13 shown in FIG. 1 are input to the target injection amount calculation circuit 20, where the target injection amount QFI.
N'is calculated. This target injection amount QFIN 'is input to the target injection amount correction circuit 21, and the final target injection amount QFIN is calculated by adding a correction injection amount QC described later here. This final target injection amount QFIN is input to the injector energization time calculation circuit 22, and the injector energization time TQ is obtained by taking into account an actual common rail pressure PC, which will be described later, input therein. Then, the injector drive circuit 23 drives the injector to inject fuel.

Here, the corrected injection amount QC added to the target injection amount correction circuit 21 is calculated as the target injection amount correction circuit 21.
Is determined by the idle state determination circuit 28. The idle state determination circuit 28 determines whether or not the engine is in the idle state according to the operating state parameter of the engine. When the engine is in the idle state, all the three switches SW1 to SW3 are in the ON positions, and when not in the idle state, the three switches are in the ON position. All SW1 to SW3 are O
Set to FF position. When the idle state determination circuit 28 determines that the engine is idle (ON shown in the figure), the target engine speed computing circuit 24 first determines the target idle engine speed NEF based on the engine water temperature. Next, based on the target rotation speed NEF and the actual rotation speed NE, the rotation speed correction injection amount calculation circuit 25 calculates the correction injection amount QC1 according to the deviation.

On the other hand, the inter-cylinder rotational speed time calculation circuit 26 calculates the rotational speed time of each cylinder from the actual rotational speed NE, and the inter-cylinder rotational speed matching correction injection amount calculation circuit 27 calculates the rotation of each cylinder. Corrected injection quantity QC2 to match speeds
Is calculated. Then, the correction injection amount QC2 calculated by the inter-cylinder rotational speed matching correction injection amount calculation circuit 27 and the correction injection amount QC1 calculated by the rotation speed correction injection amount calculation circuit 25 are added by the addition circuit 34. Corrected injection amount QC
Then, the target injection amount correction circuit 21 is turned on through the switch SW1 which is turned on when the idle state determination circuit 28 determines that the engine is idle.

Next, common rail pressure control will be described. The idle state determination circuit 28 determines the idle state (O
N), the target rotation speed NEF calculated by the target rotation speed calculation circuit 24 is input to the target common rail pressure calculation circuit 29 through the switch SW2, where the target common rail pressure PFIN is shown in FIG. 3 (a). It is calculated based on such characteristics. On the other hand, the idle state determination circuit 2
When it is determined in 8 that it is not in the idle state (OFF)
The final target injection amount QFIN and the actual rotational speed NE calculated by the target injection amount correction circuit 21 are respectively set in the switch SW.
3, SW2 is input to the target common rail pressure calculation circuit 29, where the target common rail pressure PFIN is shown in FIG.
It is calculated based on the characteristics shown in (b).

The target common rail pressure PFIN calculated by the target common rail pressure calculation circuit 29 and the actual common rail pressure PC detected by the actual common rail pressure detection circuit 33 are input to the comparison circuit 33. Based on the comparison result, the high pressure pump valve energization is performed. The energization time is calculated by the timing calculation circuit 31, and the high pressure pump valve drive circuit 32 drives the high pressure pump valve. The common rail pressure is the actual common rail pressure detection circuit 3
3, the actual common rail pressure PC is input to the comparison circuit 30 and the injector energization time calculation circuit 22 and reflected in the injector energization time. As described above, the high pressure pump valve is controlled by the comparison circuit 30, the high pressure pump valve energization timing calculation circuit 31, and the high pressure pump valve drive circuit 32 according to the deviation between the actual common rail pressure PC and the target common rail pressure PFIN. ) Be controlled.

Next, the procedure for calculating the target common rail pressure PFIN according to the embodiment of the present invention in the pressure-accumulation type fuel injection control device for an internal combustion engine configured as described above will be described with reference to the flow chart shown in FIG. In step 401, first, engine operating condition parameters such as the actual engine speed NE, accelerator opening θAC, engine water temperature, etc. are read, and in step 402, the target engine speed NEF is calculated from the engine water temperature. In step 403 thereafter, the target injection amount QFIN ′ is calculated from the actual engine speed NE and the accelerator opening θAC, and in step 404, it is determined whether the engine is in the idle state or not by the engine operating state parameter.

If it is determined in step 404 that the engine is in the idle state (YES), the process proceeds to step 405 and, as shown in FIG. 3 (a), the target engine speed NE.
From F, the target common rail pressure PFIN is calculated. On the other hand, when it is determined in step 404 that the engine is not in the idle state (NO), the process proceeds to step 406, the final target injection amount QFIN in which the injection correction amount is added is calculated, and in the subsequent step 407, the final target injection amount QFIN is calculated as shown in FIG. As shown, the target common rail pressure PFIN is calculated from the actual engine speed NE and the target injection amount QFIN.

As described above, according to the embodiment of the present invention, when the engine is idle, the target revolution speed NEF is always stable.
Since the target common rail pressure PFIN is calculated from, the actual common rail pressure PC is stable and the combustion state is stable. Moreover, in combination with the conventional injection amount correction technology at the time of idling, low idling and low engine speed, which can be achieved only by the pressure accumulating unit injector device, can be realized.

In this embodiment, an example in which the invention is applied only to the idle state for the purpose of lowering the low idle speed is shown, but needless to say, it is not limited to low idle and the rotation speed is always constant. In this state, the present invention is effective for stabilizing the rotation speed.

[0021]

As described above, according to the present invention,
When the engine is idle, the target common rail pressure is always calculated from the stable target rotation speed, so that the actual common rail pressure is stable and the combustion state is stable.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a pressure accumulation type fuel injection control device for an internal combustion engine of the present invention.

FIG. 2 is a control block diagram in the ECU of FIG.

3 (a) is a characteristic diagram for calculating the target common rail pressure from the target engine speed in the target common rail pressure calculation circuit in FIG. 2, and FIG. 3 (b) is an actual engine in the target common rail pressure calculation circuit in FIG. FIG. 6 is a characteristic diagram for calculating a target common rail pressure from a rotation speed and a target injection amount.

FIG. 4 is a flowchart showing a procedure for calculating a target common rail pressure according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine (engine) 2 ... Injector 3 ... Injection control solenoid valve 4 ... Common rail (high pressure accumulator pipe) 5 ... Check valve 6 ... Supply pipe 7 ... High pressure pump 8 ... Fuel tank 9 ... Low pressure supply pump 10 ... Discharge amount Control device 11 ... Electronic control unit (ECU) 12 ... Rotation speed sensor 13 ... Accelerator opening sensor 14 ... Pressure sensor 20 ... Target injection amount calculation circuit 21 ... Target injection amount correction circuit 22 ... Injector energization time calculation circuit 23 ... Injector drive Circuit 24 ... Target rotation speed calculation circuit 25 ... Rotation speed correction injection amount calculation circuit 26 ... Inter-cylinder rotation speed time calculation circuit 27 ... Inter-cylinder rotation speed matching correction injection amount calculation circuit 28 ... Idle state determination circuit 29 ... Target common rail pressure calculation Circuit 30 ... Comparison circuit 31 ... High pressure pump valve energization timing calculation circuit 32 ... High pressure pump valve drive circuit 3 ... actual common rail pressure detecting circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiro Itazu 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A command fuel injection amount according to a predetermined program, based on detected values of engine operating state parameters such as engine speed and accelerator opening and detected values of actual common rail pressure,
A fuel injection control device for an internal combustion engine that calculates a fuel injection timing and a command value of an injection pressure of a cylinder in which fuel is next injected, and injects fuel in a fuel injection period according to the injection pressure command value of the next cylinder In (1), an idle state determination means for determining the idle state of the engine from the operating state parameters of the engine, and an idle injection pressure calculation means for calculating the target common rail pressure from the target rotation speed of the engine when the idle state is determined. The non-idle injection pressure calculation means for calculating the target common rail pressure from the actual engine speed and the target injection quantity when it is determined that the engine is not in the idle state is provided. Injection control device.