JP3765325B2 - Fuel injection control device for diesel engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection control device for a diesel engine.
[0002]
[Prior art]
As a conventional fuel injection control device for a diesel engine, for example, there is one as disclosed in Japanese Patent Application Laid-Open No. 6210210/1987.
[0003]
[Problems to be solved by the invention]
However, in such a conventional fuel injection control device for a diesel engine, particularly in an acceleration transient with a turbocharger composed of a turbocharger, ignition occurs in a region where the intake air amount until the boost pressure rises is small. Since the delay period becomes longer, there is a problem that the combustion noise is deteriorated .
[0004]
The present invention has been made paying attention to such a conventional problem. The intake air amount detecting means for detecting the intake air amount, and the pilot injection amount and the pilot according to the output of the intake air amount detecting means. It aims at solving the said problem by controlling injection timing.
[0005]
That is, in an engine with a supercharger, the amount of intake air is detected during acceleration transients, and when the amount of intake air until the boost pressure rises is small, the pilot injection amount is increased and corrected according to the amount of intake air. By controlling the advance of the injection timing, combustion noise can be reduced even in a low supercharging pressure state.
[0006]
[Means for Solving the Problems]
For this reason, the present invention provides an intake air amount detection means for detecting an intake air amount, and an intake air amount detection means for a diesel engine fuel injection pump provided with a supercharger that performs pilot injection before main injection. Depending on the output, the pilot injection amount and pilot injection timing are controlled, and if it is determined that the intake air amount is less than the target value, the difference between the target intake air amount and the actual intake air amount and the accelerator opening The pilot injection amount calculated based on the accelerator opening is corrected to be increased by the calculated pilot injection amount correction amount that decreases as the accelerator opening increases. In addition, when controlling the pilot injection timing, if it is determined that the intake air amount is smaller than the target value, it is calculated from the difference between the target intake air amount and the actual intake air amount, and the accelerator opening, degree is higher by Rupa pilots injection timing correction amount smaller large, the pilot injection timing advance correction control calculated based on the accelerator opening.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
First, the operation of the invention will be described. In the case of a diesel engine, the fuel injected during the ignition delay period burns rapidly with the ignition, so if the amount of fuel injected during the ignition delay period increases, the combustion noise deteriorates. Tend to.
In the case of a turbocharger, if the supercharging pressure rises, the in-cylinder temperature at the time of fuel injection rises, so the ignition delay period is shortened and combustion noise is reduced. However, until the supercharging pressure rises during the so-called turbo lag period, the ignition delay period becomes longer, so the combustion noise tends to deteriorate. Therefore, until the supercharging pressure rises, pilot injection is performed in order to shorten the post ignition period. And according to the intake air amount at the time of transition, that is, the smaller the intake air amount, the higher the temperature in the cylinder at the time of main injection, so the pilot injection amount is increased and the ignition delay period is long, By correcting the pilot injection timing to advance, combustion noise can be reduced.
[0008]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of the electric fuel injection pump 104. 1 is a pump housing, 2 and 3 are a low-pressure side feed pump and a high-pressure side plunger pump driven by a drive shaft 4. Fuel sucked by a feed pump 2 from a fuel inlet (not shown) is supplied to a pump chamber 5 in the pump housing 1. It is supplied and sent to the plunger pump 3 through a suction passage 6 that opens to the pump chamber 5.
[0009]
The plunger 7 of the plunger pump 3 has the same number of suction grooves 8 as the engine cylinder at the tip and is integrally formed with a face cam 9 having the same number of cam ridges. The face cam 9 rotates together with the drive shaft 4. While moving over the roller 11 disposed on the roller ring 10, it reciprocates by a predetermined cam lift.
[0010]
Therefore, the plunger 7 reciprocates while rotating, and the fuel sucked into the plunger chamber 12 from the suction groove 8 along with the reciprocating rotation passes through a delivery valve from a distribution port (not shown) that leads to the plunger chamber 12. And pumped to the injection nozzle of each cylinder.
[0011]
In order to control the fuel injection timing and the injection amount, a fuel passage 13 that connects the pump chamber 5 and the plunger chamber 12 is formed, and a high-speed electromagnetic valve 14 is interposed in the fuel passage 13. Yes.
[0012]
The electromagnetic valve 14 opens the plunger chamber 12 when the valve is opened, and is closed by a signal from a drive circuit (drive unit) 16 for a predetermined period in the discharge stroke of the plunger pump 3 according to the operating condition of the engine.
[0013]
The fuel injection is started by closing the solenoid valve 14 during the compression stroke of the plunger 7, and the injection is ended by opening the solenoid valve 14. Therefore, the fuel injection start timing is determined by the closing timing of the solenoid valve 14. In addition, the injection amount is controlled according to the valve closing timing. If the solenoid valve 14 is once opened during the fuel injection stroke by the plunger pump 3, pilot injection can be performed prior to the main fuel injection.
Reference numeral 15 denotes a fuel cut valve which is closed when the engine is stopped, etc., and 17 is a distributor head.
[0014]
In the method of performing injection timing and injection amount control by electronic control, for example, experiments on the optimal injection timing and injection amount corresponding to various engine conditions such as rotation speed, accelerator opening, cooling water temperature, fuel temperature, etc. And the value is stored in a storage element such as a ROM of the control device. Then, during actual engine operation, the engine speed is calculated from a signal of one pulse (reference pulse 201) for one rotation of the injection pump and a signal of 36 pulses (scale pulse 202) for one rotation as shown in FIG. The injection timing and injection amount are read out in accordance with the rotational speed, accelerator opening, cooling water temperature, fuel temperature, etc., and the injection timing and injection amount are controlled.
[0015]
As a conventional electric control timer piston, for example, there is one shown in FIG. This is because the fuel of the pump chamber pressure is guided from the pump chamber 5 to the high pressure chamber 22 of the timer piston 20 and the duty ratio of the timing control valve 24 is changed, so that the fuel of the high pressure chamber 22 is supplied to the low pressure chamber 23 side having the timer spring 21. The position of the timer piston 20 is controlled by changing the amount to be extracted. By combining this with an electric pump, the oil feed rate of the pump can be varied. FIG. 4 shows a principle diagram of a sensor that detects the closing timing and the closing period of the electromagnetic valve 14.
[0016]
FIG. 5 is a block diagram showing details of the control unit. A central processing unit (hereinafter referred to as CPU) 502, a read only memory (hereinafter referred to as ROM) 504, a random access memory (hereinafter referred to as RAM) 503, and an input / output circuit (hereinafter referred to as I / O) 501 are configured. ing. The I / O 501 includes an engine speed sensor 117, an accelerator opening sensor 116, a reference pulse 201, a scale pulse 202, an air flow meter 505, a water temperature sensor 506, a fuel temperature sensor 507, an idle switch 508, a DVC sensor 509, and a timer piston position. The output of the sensor 510 is input.
[0017]
The CPU 502 takes in information from the I / O 501 according to a program stored in the ROM 504, performs arithmetic processing, and controls the electromagnetic valve 14 and timing control valve 24 for determining the injection amount, injection timing, and injection rate. Certain data is set in the I / O 501. The RAM 503 is used for temporarily saving data related to the arithmetic processing of the CPU 502. Based on the data output to the CPU 502, the I / O 501 controls the injection amount, injection timing control solenoid valve 14, and injection rate control timing control valve 24.
[0018]
Next, the operation of the CPU will be described based on the flowchart of FIG.
[0019]
First, in step 601, the engine operating conditions such as the engine speed Ne, the accelerator opening Acc, the coolant temperature Tw, the fuel temperature Tf, and the air flow meter output are read. Next, based on the operating conditions read in step 601, in step 602, for example, characteristics as shown in FIGS. 7 to 11 are stored in advance, and the basic injection amount QN, basic injection timing ITN, basic pilot amount QPN are stored. The basic pilot time ITPN and the target intake air amount QaN are calculated. Next, in step 603, the target intake air amount QaN obtained in step 602 is compared with the actual intake air amount Qai . Next, in step 604, based on the comparison result in step 603, for example, characteristics as shown in FIGS. 12 and 13 are stored in advance, and the pilot correction amount ΔQP and the pilot timing correction amount ΔITP are calculated. Next, in step 605, the pilot amount QP and the pilot time ITP are determined, and the process ends.
[0020]
FIG. 14 is a block diagram illustrating details of the control unit according to the second embodiment. FIG. 15 shows a flowchart of the second embodiment. First, in step 1401, engine operating conditions such as the engine speed Ne, the accelerator opening Acc, the coolant temperature Tw, the fuel temperature Tf, and the intake pressure sensor output are read. Next, based on the operation conditions read in step 1401, in step 1402, characteristics such as those shown in FIGS. 7 to 10 and FIG. 16 are stored in advance, and the basic injection amount QN, basic injection timing ITN, basic pilot are stored. The quantity QPN, basic pilot time ITPN, and target intake pressure PaN are calculated.
[0021]
Next, in step 1403, the target intake pressure PaN obtained in step 1402 is compared with the actual intake pressure Pai. Next, in step 1404, for example, characteristics as shown in FIGS. 17 and 18 are stored in advance based on the comparison result in step 1403, and the pilot correction amount ΔQP and the pilot timing correction amount ΔITP are calculated. . Next, in step 1405, the pilot amount QP and the pilot time ITP are determined and the process is terminated.
[0022]
【The invention's effect】
As described above, according to the present invention, the configuration of the intake air amount detection means for detecting the intake air amount, and the pilot injection amount and the pilot injection timing are controlled according to the output of the intake air amount detection means. For example, in a turbocharged engine, the intake air amount is detected during acceleration transients, and when the intake air amount until the boost pressure rises is small, the pilot injection amount is increased and corrected according to the intake air amount. At the same time, by controlling the advance of the pilot injection timing, it is possible to obtain an effect of reducing the combustion noise even in the low supercharging pressure state.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an electric fuel injection pump applied to a first embodiment.
FIG. 2 is a diagram showing a reference pulse and a scale pulse from an injection pump.
FIG. 3 is a sectional view showing a timer piston.
FIG. 4 is a diagram showing a valve closing timing and a valve closing period of an electromagnetic valve.
FIG. 5 is a block diagram of a control unit according to the first embodiment.
FIG. 6 is a flowchart showing the operation of the control unit of the first embodiment.
FIG. 7 is a characteristic diagram of a basic injection amount.
FIG. 8 is a characteristic diagram of basic injection timing.
FIG. 9 is a characteristic diagram of a basic pilot amount.
FIG. 10 is a characteristic diagram of a basic pilot period.
FIG. 11 is a characteristic diagram of a target intake air amount.
FIG. 12 is a characteristic diagram of a pilot correction amount.
FIG. 13 is a characteristic diagram of a pilot timing correction amount.
FIG. 14 is a block diagram showing a control unit in the diesel engine fuel injection control apparatus according to the second embodiment;
FIG. 15 is a flowchart showing the operation of the control unit of the second embodiment.
FIG. 16 is a characteristic diagram of a target intake pressure.
FIG. 17 is a characteristic diagram of a pilot correction amount.
FIG. 18 is a characteristic diagram of a pilot timing correction amount.
[Explanation of symbols]
104 Electric fuel injection pump 505 Air flow meter (intake air amount detection means)
1305 Intake pressure sensor (intake air amount detection means)
502 CPU

Claims (2)

  In a fuel injection pump of a diesel engine equipped with a supercharger that performs pilot injection before main injection, intake air amount detection means for detecting the intake air amount, and pilot injection according to the output of the intake air amount detection means If the intake air amount is determined to be less than the target value by controlling the amount and pilot injection timing, the accelerator opening is calculated from the difference between the target intake air amount and the actual intake air amount and the accelerator opening. A fuel injection control device for a diesel engine, comprising fuel injection control means for increasing and correcting a pilot injection amount calculated based on an accelerator opening by a pilot injection amount correction amount that decreases as the value increases. In a fuel injection pump of a diesel engine equipped with a supercharger that performs pilot injection before main injection, intake air amount detection means for detecting the intake air amount, and pilot injection according to the output of the intake air amount detection means When the intake air amount is determined to be less than the target value by controlling the amount and pilot injection timing, the accelerator opening is calculated from the difference between the target intake air amount and the actual intake air amount and the accelerator opening. as by Rupa pilots injection timing correction amount smaller large, fuel injection control apparatus for a diesel engine comprising the fuel injection control means for correcting advance the pilot injection timing calculated based on the accelerator opening.

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