JPH06299894A - Fuel injection control device for diesel engine - Google Patents

Abstract

PURPOSE:To realize misfire countermeasure at a new high land by using an accumulator type fuel injection pump. CONSTITUTION:The fuel injection control device 200 of a diesel engine 100 in which an accumulator type fuel injection pump 110 for controlling fuel injection pressure is used, is provided with a means 210 for detecting atmosphere pressure, a correcting means 220 for correcting so as to reduce fuel injection pressure in association with reduction of the atmosphere, and additionally it is provided with correcting means 230, 240 for correcting a fuel injection timing to advance side in association with reduction of the atmosphere, or correcting an EGR amount to a reduction side when the atmosphere is a prescribed pressure value and less.

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 a diesel engine, and more particularly to a fuel injection control device for a diesel engine using a pressure accumulation type fuel injection pump.

[0002]

2. Description of the Related Art Recently, a pressure-accumulation type fuel injection pump (hereinafter simply referred to as "accumulation type pump") capable of freely setting and controlling a fuel injection pressure regardless of engine operating conditions such as engine speed and load. ) Has been developed (see, for example, JP-A-62-75025 and JP-A-2-191865). In applying such a pressure accumulating fuel injection pump to a diesel engine, various useful uses are considered.

Various useful uses have been considered in applying such a pressure-accumulation fuel injection pump to a diesel engine, but effective use from the viewpoint of maximizing the advantages of this high-pressure pump. It can be said that the law is almost unclear. On the other hand, when a vehicle equipped with a diesel engine travels in high altitudes, combustion becomes unstable and a large amount of white smoke is generated, engine misfires occur, engine instability (fluctuations in engine speed), engine output drop, poor drivability, etc. The problem of occurs. This is because at high altitudes, the atmospheric pressure is low and the air density drawn by the engine is low, so the pressure of the compressed air in the cylinder is low, the heat capacity is low, and the combustion spray burns due to the low compression pressure. This is because the ignition stability is impaired because the rate of adhesion to the chamber wall surface increases.

In the diesel engine using a so-called jerk type fuel injection pump for each cylinder which is widely used at present, the advance of the fuel injection timing is almost the only means as a measure against the above-mentioned misfire in the highland. For example, there is one that corrects the injection timing to the advance side to prevent a misfire, especially only during light load operation during highland operation (see, for example, Japanese Patent Application Laid-Open No. 61-8426).

[0005]

However, although misfire can be prevented by correcting to the advance side, white smoke, odor, and HC are generated due to increase in fuel adhesion to wall surface and increase in outflow to squish lip. As it gets worse, combustion noise increases, which is not a basic or best solution.

Further, a diesel engine using the above-mentioned pressure-accumulation fuel injection pump has been studied so far, in order to prevent the output reduction of the engine and to improve the fuel consumption rate, the optimum fuel is selected according to the operating condition. The control is to be carried out, but the effective usage from the viewpoint of maximizing the advantages of this accumulator fuel injection pump for optimal control of the diesel engine including exhaust gas purification is insufficient. However, the above-mentioned measures against misfires in highlands have not been examined.

Therefore, the present invention aims to provide a new countermeasure against misfire in high altitudes, and specifically, by using the above-mentioned pressure accumulating fuel injection pump, it is possible to operate in the basic or optimum high altitudes. It is an object of the present invention to provide a fuel injection control device for a diesel engine, which can realize measures against misfire.

[0008]

A fuel injection control device for a diesel engine according to the present invention is capable of controlling a fuel injection pressure as shown in FIG. 1, which is a block diagram showing a conceptual overall configuration thereof. A fuel injection control device (200) for a diesel engine (100) using a pressure-accumulation fuel injection pump (110), comprising means (210) for detecting atmospheric pressure and fuel injection pressure as the atmospheric pressure decreases. A correction means (220) is provided for correcting the fuel injection timing so that the fuel injection timing is advanced toward the advance side as the atmospheric pressure decreases, and / or EGR when the atmospheric pressure is equal to or lower than a predetermined pressure. It is configured to further include a correction unit (230, 240) that corrects the amount to the decreasing side.

[0009]

With the above-mentioned structure, the fuel is injected into the combustion chamber even in the high altitude where the fuel injection pressure is corrected so as to reduce the penetration force of the fuel spray and the compressed air density in the combustion chamber decreases. It is possible to prevent a large amount from adhering to the wall surface, maintain a high concentration of fuel spray in the combustion chamber space, and prevent discharge of white smoke and the like and engine misfire.

At the same time, by correcting the fuel injection timing so as to be advanced, the fuel spray can be held for a long time in the combustion chamber held at high temperature and high pressure, and the ignitability can be further stabilized. . Further, by correcting the EGR amount so as to decrease, it is possible to secure the intake amount of fresh air against the output decrease due to the decrease of the intake air amount and prevent the output decrease.

[0011]

FIG. 2 is a schematic configuration diagram of a fuel injection control device for a diesel engine using a pressure accumulation type fuel injection pump, and FIG. 3 is a sectional view showing a part of the diesel engine. The diesel engine 1 includes a cylinder block 2, a cylinder head 3, a piston 4, a combustion chamber 5, an intake valve 6, an exhaust valve 7, a fuel injection valve 8 arranged in the combustion chamber 5, an intake manifold 9.
And an inlet portion of the intake manifold 9 is connected to the supercharger T. The fuel injection valve 8 is connected via a fuel supply pipe 10 to a fuel accumulator pipe common to each cylinder, that is, a common rail 11. The common rail 11 has a pressure accumulating chamber 12 with a constant volume inside, and the fuel in the pressure accumulating chamber 12 is supplied to the fuel injection valve 8 via the fuel supply pipe 10.

On the other hand, the pressure accumulating chamber 12 is connected to the discharge port of the fuel supply pump 14 via the fuel supply pipe 13, and the suction port of the fuel supply pump 14 is discharged from the auxiliary fuel pump 16 via the flow rate adjusting valve 15. The auxiliary fuel pump 16 is connected to the outlet, and the suction port of the auxiliary fuel pump 16 is connected to the fuel reservoir tank 17. Further, the fuel injection valve 8 is connected to the fuel reservoir tank 17 via a fuel return pipe 18. The fuel supply pump 14 is provided to discharge high-pressure fuel, and the high-pressure fuel is stored in the pressure accumulating chamber 12. The auxiliary fuel pump 16 can be omitted if not necessary.

The fuel pressurized by the fuel supply pump 14 and stored in the pressure accumulating chamber 12 is directly injected into the cylinder from the fuel injection valve 8 whose opening is controlled by the electronic control circuit 70. The electronic control circuit 70 has various sensor outputs for detecting the operating state of the engine in order to form a control signal for controlling the valve opening of the fuel injection valve 8 according to the injection timing and the injection time according to the operating state of the engine. It has been entered. For example, a fuel pressure sensor 75 for detecting the fuel pressure in the pressure accumulating chamber 12 provided at the end of the common rail 11 and an intake pressure sensor 7 for detecting the intake pressure in the intake manifold 9.
6, a water temperature sensor 77 for detecting the engine cooling water temperature, a load sensor 79 for generating an output voltage proportional to the depression amount of the accelerator pedal 78, and disks 81, 82 attached to the engine crankshaft 80, for example, a # 1 cylinder Crank angle sensors 83 and 84 for detecting a pulse indicating that the intake air is at the intake top dead center and a pulse output every time the crankshaft 80 rotates at a constant speed.

As shown in the figure, the electronic control circuit 70 includes a CPU 91, a ROM 92, and a RAM 9 which constitute an arithmetic control unit.
3, a motor drive output circuit 94 for driving and controlling a pump motor that constitutes an input / output unit for inputting / outputting to / from the outside, a valve drive output circuit 95 for driving and controlling the fuel injection valve 8, and a pulse signal from the sensor. It has a pulse input circuit 96 for converting it into a digital signal, an analog input circuit 97 for converting an analog signal from the sensor into a digital signal, and a common bus 98 for mutually connecting them. CPU91
Performs a control main loop for controlling the diesel engine 1 in an optimum operating state periodically or in synchronization with engine rotation. In this control main loop, for example, the following is executed. That is, in the ROM 92,
Control data such as a fuel injection amount at a predetermined load, a predetermined engine speed and an injection start timing at a load and a reference fuel pressure are stored, and signals from various sensors are RA.
The data is taken into M93 at a predetermined timing, the CPU 91 performs necessary arithmetic processing based on these signals and data, and drives the fuel supply pump 14, the flow rate adjusting valve 15, and the auxiliary fuel pump 16 via the motor drive output circuit 94. A signal is output to execute desired fuel pressure control, and a drive signal is output to each fuel injection valve 8 via the valve drive output circuit 95 to execute desired fuel injection control.

As described above, since the air density is low at high altitudes, the density and pressure of compressed air in the combustion chamber of the diesel engine are low, and the amount of heat retained is also low. For this reason, in a diesel engine of a structure in which fuel is injected into the combustion chamber and spontaneously ignited, its ignition becomes unstable at high altitudes, and fluctuations between combustion cycles including incomplete combustion and misfire increase, resulting in unburned or incomplete combustion. There will be problems such as an increase in the amount of white smoke, odor, HC, etc., whose main component is the above fuel, noise deterioration, output reduction, and the like.

However, in the fuel injection control using the pressure-accumulation type fuel injection pump described above, if the fuel injection pressure is lowered, the penetration force of the fuel spray is lowered, so that the density of the compressed air in the combustion chamber is lowered. However, most of the fuel spray does not adhere to the wall surface of the combustion chamber, and is kept at a high concentration in the space inside the combustion chamber. Further, the decrease in the fuel injection pressure also reduces the amount of fuel injected during the normal ignition delay period, and the amount of heat required for heating and evaporating the fuel decreases,
The temperature of the compressed air is also prevented from dropping excessively. As a result, stable ignition can be secured, and the above-mentioned problems can be effectively solved.

FIG. 4 is a characteristic diagram showing the correction control characteristic with respect to the altitude of the fuel injection pressure in the first embodiment of the fuel injection control device for the diesel engine according to the present invention, and FIG. 5 realizes it. 4 is a flowchart showing an example of software for the above. The flowchart of FIG. 5 is incorporated in, for example, an engine control main loop executed by the CPU 91 in the electronic control circuit 70 in FIG. 2 described above.

In this embodiment, in order to control the injection pressure of the pressure accumulation type fuel injection pump, the level ground condition (atmospheric pressure: 76
0mmHg) optimally set injection pressure control map or map (1) and highland conditions (atmospheric pressure: eg 530mmHg) optimally set injection pressure control map or map (2) lower than 10 to 30MPa And are provided. Then, the injection pressure actually used is grasped as the current altitude by detecting the atmospheric pressure by using a sensor for detecting the atmospheric pressure, the intake pressure, the compression pressure, etc., as shown by the solid line in FIG. On the map
It is set by interpolating from the values in (1) and map (2). As a method of interpolation between these two maps, FIG.
In addition to the case of the solid line of, various control modes as shown by the dotted line in the figure can be implemented.

In order to realize this control, in the flow chart of FIG. 5, first, at step a, the operating conditions of the engine are grasped based on the data obtained from various sensors as shown in FIG. It Depending on the obtained operating conditions, in step b
The reference injection pressure is obtained using (1). Next, the intake pressure detected by the sensor is read to detect the atmospheric pressure, and thus the current altitude. Here, in step d, the obtained altitude, map (1) and map
The correction amount of the injection pressure is calculated by interpolation using (2), the actual corrected injection pressure is determined based on the correction amount in step e, and the process returns to the control main loop. As a result, the injection pressure is controlled so as to decrease with an increase in altitude, and the above-described problem in highland operation can be effectively eliminated.

In the second embodiment of the fuel injection control device for the diesel engine according to the present invention, the map (1) in the above-mentioned first embodiment and the formula for calculating the injection pressure correction amount according to the atmospheric pressure, For example, a calculation formula representing the value of the solid line or the dotted line in FIG. 4 is set. For the actual injection pressure, grasp the current altitude, calculate the pressure correction amount, and map
Determined by adding to (1). The correction amount is set to the optimum one for each engine, but a rough guideline is 760 mmHg.
To 530 mmHg, the pressure is reduced by about 10 to 30 MPa. As a control flowchart, for example, the details of step d are different, but the flowchart of FIG. 5 can be basically used.

In the third embodiment of the fuel injection control device for a diesel engine according to the present invention, in addition to the above-described first or second embodiment, the fuel injection timing can be advanced as the altitude increases. It will be implemented together. FIG. 6 is a flow chart for realizing the control, and steps f and g are added to the flow chart of FIG. 5 so that the injection timing is corrected in the advance direction according to the altitude. When the advance angle correction of the injection timing is performed in addition to the correction of the injection pressure in the first and second embodiments as in the present embodiment, the fuel spray is held for a long time in the combustion chamber held at high temperature and high pressure. As a result, the ignition becomes more stable, and the improvement of the ignitability can be made more reliable in combination with the decrease of the injection pressure.

Further, in the fourth embodiment of the fuel injection control device for the diesel engine according to the present invention, the above-mentioned first embodiment is used.
Alternatively, in addition to the second embodiment, the EG
Reduction control of R is also performed. EGR is set to a relatively large amount under flatland conditions, and gradually decreases as the altitude rises, and becomes 0% above a certain altitude. FIG. 7 is a characteristic diagram showing the control characteristic of the present embodiment, and FIG. 8 is a flow chart for realizing the control.

As shown in FIG. 7, in the present embodiment, the injection pressure is reduced as the altitude rises, that is, the atmospheric pressure decreases, and the pressure difference between the flat land and the highland, for example, the highland of about 3000 m is 10. ~ 30 MPa, and
The injection timing is advanced, and the EGR amount is reduced to 0% above a certain altitude. It should be noted that there are various modes of giving the correction at the intermediate altitude, and here, two control modes of a solid line and a dotted line are illustrated.

In the control mode of the EGR control described above, since the combustion improving effect by the high pressure injection is high under the flatland condition, the NOx reducing effect by the EGR is effectively utilized,
Although it is possible to suppress the disadvantages such as smoke increase and output reduction associated with general EGR, under high altitude conditions, the output reduction due to a decrease in the intake air amount becomes large, so the EGR amount is reduced and the amount of fresh air is reduced. It is based on the need to ensure the inhalation volume and prevent the output from decreasing.

The flow chart of FIG. 8 is shown in FIGS.
2 is incorporated in the engine control main loop executed by the electronic control circuit 70 in the fuel injection control system of the diesel engine using the pressure-accumulation fuel injection pump of FIG. From step i, the engine operating conditions are grasped from (1) injection pressure,
Understand the control conditions that serve as the reference for (2) injection timing and (3) EGR amount. Next, in step j, the intake pressure is read to detect the atmospheric pressure, that is, the current altitude, and in step k, (1) is calculated from the obtained reference value and atmospheric pressure.
After calculating the control correction amounts for the injection pressure, (2) injection timing, and (3) EGR amount, determining and outputting those control values, the process returns to the control main loop.

In the above-described embodiment, the diesel engine with a supercharger, that is, the supercharged engine shown in FIG. 2 is used, but it goes without saying that the present invention is also applicable to a non-supercharged engine. .

[0027]

As described above, according to the fuel injection control device of the present invention, the accumulator type fuel injection pump is effectively used to improve the ignitability of the diesel engine at high altitudes, and It is possible to solve the deterioration of engine operating performance such as the deterioration of exhaust of white smoke and the reduction of output, which were inevitable in the operation of a diesel engine.

[Brief description of drawings]

FIG. 1 is a block diagram showing a conceptual overall configuration of a fuel injection control device for a diesel engine according to the present invention.

FIG. 2 is a schematic configuration diagram of a fuel injection control device for a diesel engine using a pressure accumulation type fuel injection pump.

FIG. 3 is a cross-sectional view showing a part of a diesel engine.

FIG. 4 is a characteristic diagram showing the control characteristics of the first embodiment of the fuel injection control device for a diesel engine according to the present invention.

5 is a flowchart showing software for realizing control in the embodiment of FIG.

FIG. 6 is a flow chart for realizing control in a third embodiment of the fuel injection control device for a diesel engine according to the present invention.

FIG. 7 is a characteristic diagram showing control characteristics of a fourth embodiment of the fuel injection control device for a diesel engine according to the present invention.

FIG. 8 is a flowchart showing software for realizing control in the embodiment of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 2 ... Cylinder block 3 ... Cylinder head 4 ... Piston 5 ... Combustion chamber 6 ... Intake valve 7 ... Exhaust valve 8 ... Fuel injection valve 9 ... Intake manifold 10, 13 ... Fuel supply pipe 11 ... Common rail 12 ... Accumulation chamber 14 ... Fuel supply pump 15 ... Flow rate adjusting valve 16 ... Auxiliary fuel pump 17 ... Fuel reservoir tank 70 ... Electronic control circuit 75 ... Fuel pressure sensor 76 ... Intake pressure sensor 77 ... Water temperature sensor 78 ... Accelerator pedal 79 ... Load sensor 83, 84 ... crank angle sensor 91 ... CPU 92 ... ROM 93 ... RAM 94 ... motor drive output circuit 95 ... valve drive output circuit 96 ... pulse input circuit 97 ... analog input circuit 98 ... common bus 100 ... diesel engine 110 ... accumulator fuel injection pump 200 ... Fuel injection control device 210 ... Atmospheric pressure detection means 220 ... Fuel Injection pressure correction means 230 ... fuel injection timing correcting means 240 ... EGR amount correction means

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F02D 43/00 301 N 7536-3G

Claims (3)

[Claims] 1. A fuel injection control device for a diesel engine using a pressure accumulation type fuel injection pump capable of controlling fuel injection pressure, comprising means for detecting atmospheric pressure, and fuel injection pressure as the atmospheric pressure decreases. A fuel injection control device for a diesel engine, comprising: 2. The fuel injection control device for a diesel engine according to claim 1, further comprising a correction unit that corrects the fuel injection timing toward the advance side as the atmospheric pressure decreases. 3. The fuel injection control device for a diesel engine according to claim 1 or 2, further comprising correction means for correcting the EGR amount to a decreasing side when the atmospheric pressure is equal to or lower than a predetermined pressure. .