JPH06307276A - Fuel injection controller of diesel engine - Google Patents

Abstract

PURPOSE:To suppress a quantity of generated black smoke or granular substance by increasing a fuel injection pressure according to an increase in an engine temperature at the time of a high load more than a specified load. CONSTITUTION:A second correction means M7 for correcting a fuel injection pressure to the high pressure side according to an increase in an intake air temperature detected by an intake air temperature detection means M3 when load detected by a load detection means M1 higher than the specified load is provided in a fuel injection pressure control means M4. The fuel injection pressure is increased accoding to the increase in the intake air temperature at the time of the high load more than the specified value, namely in a range where the fuel injection quantity is more than the intake air quantity, and thereby atomization of fuel is promoted and an air in take quantity is increased. Therefore, since combustion is improved, a quantity of generated black smoke or granular substance can be decreased.

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.

[0002]

2. Description of the Related Art As a fuel injection control device for an internal combustion engine, for example, Japanese Patent Laid-Open No. 63-266149 is disclosed.
This fuel injection control device is attached to a fuel supply pump that is connected to a fuel injection valve through a fuel supply passage to supply fuel, a pressure accumulating chamber provided in the fuel supply passage and having a constant volume, and the fuel supply passage. A fuel pressure sensor, a discharge pressure control means for controlling a discharge pressure of fuel supplied from the fuel supply pump to the pressure accumulating chamber in accordance with an output signal from the fuel pressure sensor, and an intake air temperature detecting means for detecting an intake air temperature. The discharge pressure control means has a correction means for correcting the discharge pressure of the fuel supply pump to a higher pressure side as the temperature detected by the intake air temperature detection means is lower. That is, as the intake air temperature is lower, the discharge pressure of the fuel supply pump is corrected to a high pressure side to increase the fuel injection pressure and promote atomization of the fuel.
It improves combustion and suppresses black smoke generation.

[0003]

However, in the above-described fuel injection control device, when the load is higher than the predetermined load, the load is high and the fuel injection amount increases, but the intake air temperature rises. Since the fuel injection pressure is corrected to the low pressure side, the atomization of fuel becomes worse. Moreover, since the intake air density decreases due to the rise in intake air temperature, there is a shortage of air,
There was a risk that the amount of air taken in by the fuel would decrease, combustion would deteriorate, and the amount of black smoke and particulate matter generated would increase.

Therefore, an object of the present invention is to suppress the amount of black smoke and particulate matter generated by increasing the fuel injection pressure as the intake air temperature rises when the load is higher than a predetermined load.

[0005]

As shown in FIG. 1, a fuel injection control device for a diesel engine according to the present invention includes a load detecting means M1 for detecting a load state of the engine, and a load detected by the load detecting means M1. Fuel injection amount control means M2 for increasing the fuel injection amount supplied to the engine as the temperature rises, intake air temperature detection means M3 for detecting the intake air temperature, fuel injection pressure control means M4 for controlling the fuel injection pressure, and the fuel injection An intake air temperature which has a pressure control means M4 and a fuel injection means M5 which injects fuel based on the output of the fuel injection amount control means M2, and the fuel injection pressure control means M4 is detected by the intake air temperature detection means M3. In the fuel injection control device of the diesel engine having the first correction means M6 for correcting the fuel injection pressure to the low pressure side as the load rises, the load detected by the load detection means M1 is located. When the load is higher than the load, the fuel injection pressure control means M4 is provided with a second correction means M7 for correcting the fuel injection pressure to a high pressure side as the intake air temperature detected by the intake air temperature detection means M3 increases. Is characterized by.

[0006]

According to the above means, the load detecting means detects the load state of the engine, and the fuel injection quantity control means increases the fuel injection quantity as the detected load increases. Then, as the intake air temperature detected by the intake air temperature detection means rises, the first correction means of the fuel injection pressure control means corrects the fuel injection pressure to the low pressure side. Fuel is injected by the fuel injection means with the fuel injection amount and the fuel injection pressure thus determined. However, when the load of the engine detected by the load detection means is equal to or more than the predetermined load, the second correction means provided in the fuel injection pressure control means is operated by the second correction means as the intake air temperature detected by the intake air temperature detection means rises. Correct the injection pressure to the high pressure side.

[0007]

2 and 3 relate to a first embodiment of the present invention,
2 is a configuration diagram of the diesel engine according to the present invention, and FIG. 3 is a side sectional view of the diesel engine. 2 is a diesel engine main body, 4 is a cylinder block, 6 is a cylinder head, 8 is a piston, 10 is a combustion chamber, 12 is an intake valve, 14 is an exhaust valve, 16 is a fuel injection valve arranged in the combustion chamber 10, 18 Indicates an intake pipe, and an inlet portion of the intake pipe 18 is connected to the supercharger 20. The fuel injection means is a fuel injection valve 1
6, a fuel supply pump 30, and a path therebetween. The fuel injection valve 16 is connected via a fuel supply pipe 22 to a fuel pressure accumulation pipe 24 common to each cylinder. Fuel pressure accumulator 2
4 has a pressure accumulating chamber 26 having a constant volume therein, and the fuel in the pressure accumulating chamber 26 is supplied to the fuel injection valve 1 via the fuel supply pipe 22.
6 is supplied. On the other hand, the pressure accumulating chamber 26 is connected via a fuel supply pipe 28 to a discharge port of a fuel supply pump 30 whose discharge pressure can be controlled. The suction port of the fuel supply pump 30 is connected to the discharge port of the fuel pump 32, and the suction port of the fuel pump 32 is connected to the fuel reservoir tank 34. Fuel pump 3
2 is provided for feeding the fuel in the fuel reservoir tank 34 to the fuel supply pump 30.
If the fuel can be sucked into the fuel supply pump 30 without the fuel pump 32, the fuel pump 32 need not be provided. On the other hand, the fuel supply pump 30 is provided for discharging high-pressure fuel, and the high-pressure fuel discharged from the fuel supply pump 30 is accumulated in the pressure accumulating chamber 26 via the fuel supply pipe 28. Further, each fuel injection valve 16 is connected to the fuel reservoir tank 34 via a fuel return conduit 36, and the fuel not used for combustion is returned to the fuel reservoir tank 34 via the fuel return conduit 36.

The fuel supply pump 30 supplies the amount of fuel set by the pump discharge amount drive unit 37 into the pressure accumulating chamber 26, and the pump discharge amount drive unit 37 is connected to an electronic control unit 38 for electronic control. According to a command from the device 38, the fuel pressure is set by controlling the discharge amount of the fuel supply pump 30 per one rotation.

The fuel injection valve 16 for injecting fuel is an electrostrictive type using a piezoelectric element, and this fuel injection valve 16 is opened only during a period when a positive voltage is applied. It is injected with the pressure in the pressure accumulating chamber 26. This injection period changes depending on the load.

The electronic control unit 38 as the fuel injection amount control means, the fuel injection pressure control means, the first correction means, and the second correction means includes a well-known CPU 40, RAM 42, ROM 44, and
An input port 46 and an output port 48 are provided and are connected to each other by a bidirectional bus 47. AD converters 50, 52, 54 and 56 are connected to the input port 46, and drive circuits 58, 60, 62, 64 and 66 are connected to the output port 48.
Are connected. The AD converter 50 is connected to the water temperature sensor 68 provided in the diesel engine main body 2, the AD converter 52 is connected to the fuel pressure sensor 70 provided in the pressure accumulating chamber 26, and the AD converter 54 is provided in the intake pipe 18. Is connected to the intake air temperature sensor 72 as the intake air temperature detecting means,
The D converter 56 is connected to a load sensor 74 as a load detecting means provided on the accelerator pedal 76. Further, a rotation angle sensor 80, which is provided near the crankshaft 78, for calculating the engine speed, and a cylinder discrimination sensor 82, for discriminating which fuel injection valve to operate, are also connected to the input port 46. . The driving circuit 58 is connected to the pump discharge amount driving device 37, and driving circuits 60, 62, 64,
Each 66 is connected to the fuel injection valve 16.

The operation of the fuel injection control device for the diesel engine constructed as described above will be described with reference to the flow chart showing the main routine of FIG. 4 stored in the ROM 44 and the flow chart of FIG. 5 for controlling the fuel injection pressure. explain. Rotation angle sensor 80 representing the engine speed N
And the output signal of the cylinder discrimination sensor 82, the accelerator pedal 7
6, the output signal of the load sensor 74 representing the depression amount L of 6, the output signal of the water temperature sensor 68 representing the cooling water temperature Tw of the engine, the output signal of the fuel pressure sensor 70 representing the fuel pressure P in the accumulator 26, the inside of the intake pipe 18. Intake air temperature sensor 72 representing the intake air temperature Ta of
Is inputted into the CPU 40 through the input port 46, and the engine speed N is calculated from the output signals of the rotation angle sensor 80 and the cylinder discrimination sensor 82. The engine speed N, the depression amount L of the accelerator pedal 76, the cooling water temperature Tw, the fuel pressure P, and the intake air temperature Ta are stored in the RAM 42 (step 100).

Next, the depression amount L of the accelerator pedal 76
From the above, the injection amount τ is determined according to the map stored in the ROM 44 in advance (step 200). The injection amount τ is set to increase as the load increases.

Next, the engine speed N and the accelerator pedal 76
The injection timing is determined according to a map stored in advance in the ROM 44 based on the depression amount L of step S30 (step 30).
0).

The fuel injection pressure determined in step 400 will be described with reference to FIG. The reference injection pressure Pdb is determined from the engine speed N and the depression amount L of the accelerator pedal 76 according to a map stored in the ROM 44 in advance (step 401). And ROM44 beforehand
The correction coefficient K is determined according to the graph of the correction coefficient with respect to the load (depression amount L of the accelerator pedal 76) of FIG. This correction coefficient K
Is set to a negative value in the low / medium load range and a positive value in the high load range above a predetermined load. In the figure, Ld is the boundary between the low / medium load range and the high load range. The corrected injection pressure Pdc is obtained by multiplying the correction coefficient K by the intake air temperature Ta (step 403). Thus, the correction coefficient K is set to the intake air temperature T
Since the corrected injection pressure Pdc is obtained by multiplying by a, the absolute value of the corrected injection pressure Pdc increases as the intake air temperature Ta increases at the same rotation speed and the same load. The absolute value is described here because the reference injection pressure Pdb may be corrected to the low pressure side or the high pressure side depending on the load state. The actual injection pressure Pd is determined from the sum of the reference injection pressure Pdb and the corrected injection pressure Pdc (step 404). Next, it is determined whether or not the absolute value of the difference between the fuel pressure P in the pressure accumulating chamber 26 and the actual injection pressure Pd is smaller than ΔP (step 40).
5). When the absolute value is larger than ΔP, the fuel pressure P and the actual injection pressure Pd are compared (step 406). When the fuel pressure P is higher than the actual injection pressure Pd, the discharge amount of the fuel supply pump 30 is controlled by the pump discharge amount drive device 37 in a decreasing direction, and the discharge pressure of the fuel supply pump 30 is reduced to reduce the pressure in the pressure accumulating chamber 26. The fuel pressure P decreases (step 40)
7). When the fuel pressure P is lower than the actual injection pressure Pd, the pump discharge amount driving device 37 controls the discharge amount of the fuel supply pump 30 in the increasing direction, and the discharge pressure of the fuel supply pump 30 is increased to increase the pressure in the accumulator chamber 26. The fuel pressure P increases (step 408). If the absolute value is smaller than ΔP, the process ends. In this way, the fuel pressure P in the accumulator chamber 26
Is maintained at the actual injection pressure Pd.

FIG. 7 is a diagram showing the relationship between the intake air temperature and the actual injection pressure in the low / medium load range according to the present invention when the same load and the same rotational speed are used, and FIG. 8 is the case where the same load and the same rotational speed are used. It is a figure showing the relationship between the intake temperature and the actual injection pressure in the high load region according to the present invention. As described above, since the correction coefficient K is multiplied by the intake air temperature Ta to obtain the corrected injection pressure Pdc, the correction coefficient K becomes a negative value in accordance with FIG. 6 in the low / medium load range, and the actual injection pressure Pd increases as the intake air temperature Ta rises. Is corrected to the low voltage side. In the high load region, the correction coefficient K has a positive value according to FIG. 6, and the actual injection pressure Pd is corrected to the high pressure side as the intake air temperature Ta rises.

As described above, according to the fuel injection control device for the diesel engine in the first embodiment of the present invention, when the load detected by the load sensor 74 is higher than a predetermined load, the intake air temperature sensor 72 detects the intake air. As the temperature Ta rises, the corrected injection pressure Pdc is increased to increase the actual injection pressure Pd and the fuel injection is executed. Therefore, the atomization of the injected fuel is promoted even in the high load region where the fuel injection amount is large. The amount of air taken in by the fuel is increased, combustion is improved, and the amount of black smoke and particulate matter generated is reduced. Although the amount of NOx generated slightly increases due to good combustion, the effect of reducing black smoke and particulate matter is greater.

Further, in the low / medium load range below the predetermined load, the correction injection pressure Pdc is reduced to lower the actual injection pressure Pd as the intake air temperature Ta detected by the intake air temperature sensor 72 increases, and fuel injection is executed. Therefore, the atomization of the fuel is suppressed, the air intake amount of the fuel is reduced, and the combustion becomes slow, so that N
The amount of Ox generated is reduced. It should be noted that in a diesel engine, since the intake air amount is excessive below a predetermined load, the amount of black smoke and particulate matter generated hardly changes even when the intake air temperature changes,
In terms of quantity, it does not matter as much to the left.

FIG. 9 is a graph of the correction coefficient with respect to the load (depression amount L of the accelerator pedal 76) showing the second embodiment of the present invention. The correction coefficient K is set to have a negative value in the low load range, zero in the medium load range, and a positive value in the high load range above a predetermined load. In the figure, Lc is the boundary between the low load region and the medium load region, and Ld is the boundary between the medium load region and the high load region. Other configurations are the same as those of the first embodiment, and the operation is the same as that of the first embodiment except that the reference injection pressure Pdb is not corrected in the medium load range.

FIG. 10 is a graph of the correction coefficient with respect to the load (depression amount L of the accelerator pedal 76) showing the third embodiment of the present invention. The correction coefficient K is set to have a negative value in the low / medium load range and a positive value in the high load range above a predetermined load, and has a slope with respect to the load. In the figure, Ld is the boundary between the low / medium load range and the high load range. Other configurations and operations are the same as those in the first embodiment.

In the above embodiment, the intake air temperature T is used as the intake air temperature.
Although a is used, the reference injection pressure Pdb may be corrected by a temperature change similar to the change of the intake air temperature Ta. For example, it is conceivable that the intake pipe temperature, the atmospheric temperature, the engine cooling water temperature, etc. are detected to estimate the intake temperature, or the atmospheric pressure and the intake pressure are detected and interpolated to improve the accuracy.

[0021]

According to the present invention, when the load of the diesel engine is a high load equal to or higher than the predetermined load, the fuel injection pressure control means is provided with the second correction means for correcting the fuel injection pressure to the high pressure side as the intake air temperature rises. Therefore, at a high load above a certain load, that is, in a region where the fuel injection amount is large relative to the intake air amount, the fuel injection pressure rises as the intake air temperature rises, fuel atomization is promoted, and the air intake amount of fuel is increased. Will increase. Therefore, since the combustion becomes good, it is possible to reduce the generation amount of black smoke and particulate matter.

Further, when the load of the diesel engine is a low / medium load of less than a predetermined load, the fuel injection pressure control means has a first correction means for correcting the fuel injection pressure to a low pressure side as the intake air temperature rises. As a result, the fuel injection pressure becomes lower as the intake air temperature rises in a low / medium load below a predetermined load, that is, in a region where the fuel injection amount is small relative to the intake air amount, and atomization of the fuel is suppressed and fuel Air intake is reduced. Therefore,
The combustion becomes slow, and the amount of NOx generated can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating the configuration of the present invention.

FIG. 2 is a configuration diagram of a diesel engine according to the present invention

[Fig. 3] Side sectional view of a diesel engine

FIG. 4 is a flowchart showing a main routine.

FIG. 5 is a flowchart for controlling the fuel injection pressure.

FIG. 6 is a graph of a correction coefficient with respect to a load in the first embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between intake air temperature and actual injection pressure in a low / medium load range according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between intake air temperature and actual injection pressure in a high load range according to the first embodiment of the present invention.

FIG. 9 is a graph of a correction coefficient with respect to a load in the second embodiment of the present invention.

FIG. 10 is a graph of a correction coefficient with respect to a load in the third embodiment of the present invention.

[Explanation of symbols]

 2 ... Diesel engine body 16 ... Fuel injection valve 22, 28 ... Fuel supply pipe 26 ... Accumulation chamber 30 ... Fuel supply pump 37 ... Pump discharge amount drive device 38 ... Electronic Control device 70 ... Fuel pressure sensor 72 ... Intake air temperature sensor 74 ... Load sensor

Claims (1)

[Claims] 1. A load detection means for detecting a load state of the engine, a fuel injection amount control means for increasing a fuel injection amount supplied to the engine according to a load increase detected by the load detection means, and an intake air temperature detected. Intake air temperature detecting means, fuel injection pressure control means for controlling fuel injection pressure, and fuel injection means for injecting fuel based on the outputs of the fuel injection pressure control means and the fuel injection amount control means. In the fuel injection control device for a diesel engine, the fuel injection pressure control means has a first correction means for correcting the fuel injection pressure to a low pressure side as the intake air temperature detected by the intake air temperature detection means rises. When the detected load is a high load equal to or higher than a predetermined load, the second correction means for correcting the fuel injection pressure to the high pressure side in accordance with the rise in the intake temperature detected by the intake temperature detection means is provided. The fuel injection control apparatus for a diesel engine, characterized in that provided in the fuel injection pressure control means.