JPH09228880A - Fuel injection control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce combustion noise in a low super charging state by controlling the quantity of pilot fuel injection and the timing of pilot fuel injection in response to the output of an intake air quantity detecting means in a device where a pilot fuel injection is performed before main fuel injection is made. SOLUTION: When an engine is in operation, a CPU 502 reads in output signals from an engine revolution speed sensor 117, an accelerator opening sensor 116, an air flow meter 505 and the like, and computes the basic quantity of fuel injection, the basic timing of fuel injection, the basic quantity of pilot fuel injection, the basic timing of pilot fuel injection, and the target quantity of intake air. Subsequently, a deviation from the quantity of intake air is obtained, and the quantity of pilot correction, and the corrective quantity of pilot timing, are computed based on the aforesaid deviation, so that the quantity of pilot fuel injection and the timing of pilot fuel injection are thereby determined. The closing of an electromagnetic valve 14 during the compression stroke of a plunger in a fuel injection pump thereby starts injecting fuel, the opening of the electromagnetic valve 14 causes injection to be over, and the opening of the electromagnetic valve 14 once on its halfway permits pilot fuel injection to be performed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a fuel injection control device for a diesel engine.

[0002]

2. Description of the Related Art As a conventional fuel injection control device for a diesel engine, there is, for example, one disclosed in JP-A-62-210227.

[0003]

However, in such a conventional fuel injection control device for a diesel engine, in particular, during the acceleration transition with a turbocharger including a turbocharger, until the boost pressure rises. In a region where the intake air amount is small, the pilot injection characteristic is not optimized, so that not only the effect of pilot injection is not obtained, but also the smoke characteristic is deteriorated.

The present invention has been made by paying attention to such a conventional problem, and it is provided with an intake air amount detecting means for detecting the intake air amount and an output of the intake air amount detecting means.
It is an object of the present invention to solve the above problems by controlling the pilot injection amount and pilot injection timing.

That is, in an engine with a supercharger, the intake air amount is detected during an acceleration transient, 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 pilot injection timing to be advanced, it is possible to obtain the effect of reducing the combustion noise even in the low boost pressure state.

[0006]

Means for Solving the Problems For this reason, the present invention provides
In a fuel injection pump of a diesel engine that performs pilot injection before main injection, the pilot injection amount is reduced when the intake air amount detection means that detects the intake air amount determines that the intake air amount is less than the target value. In addition to the correction, the pilot injection timing is advanced.

[0007]

First, the operation of the present invention will be described. In the case of a diesel engine, the fuel injected during the ignition delay period burns rapidly with ignition, so the amount of fuel injected during the ignition delay period is When it increases, the combustion noise tends to worsen. In the case of a supercharger type, 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 boost pressure rises during the so-called turbo lag period, the ignition delay period becomes long, and combustion noise tends to deteriorate. So, until the boost pressure rises,
Pilot injection is performed to shorten the ignition lag period of the main injection. Then, according to the intake air amount at the time of transition, that is, as the intake air amount is smaller, the temperature in the cylinder at the time of main injection is increased, the pilot injection amount is increased, and the ignition delay period is longer, Combustion noise can be reduced by correcting the pilot injection timing so as to advance.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an electronically controlled fuel injection pump 104
Here is an example. Reference numeral 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, and the fuel sucked by the feed pump 2 from a fuel inlet (not shown) is pump housing 1
It is supplied to the pump chamber 5 inside and is sent to the plunger pump 3 via the suction passage 6 opening to the pump chamber 5.

The plunger 7 of the plunger pump 3 is formed with the same number of suction grooves 8 as the cylinders of the engine at the tip, and a face cam 9 having the same number of cam ridges.
The face cam 9 is integrally formed on the drive shaft 4
While rotating with the roller ring 10, the roller 11 provided over the roller ring 10 is passed over to reciprocate by a predetermined cam lift.

Therefore, the plunger 7 reciprocates while rotating, and the fuel sucked from the suction groove 8 into the plunger chamber 12 by this reciprocating motion is delivered from a distribution port (not shown) communicating with the plunger chamber 12. It is pumped to the injection nozzle of each cylinder through the valve.

A fuel passage 13 that connects the pump chamber 5 and the plunger chamber 12 is formed in order to control the injection timing and injection amount of fuel, and a high-speed solenoid valve 14 is provided in the middle of the fuel passage 13. I am wearing.

The solenoid valve 14 opens the plunger chamber 12 when the valve is opened, and a drive circuit (drive unit).
The signal from 16 causes the plunger pump 3 to be closed for a predetermined period in the discharge stroke of the plunger pump 3 in accordance with the operating conditions of the engine.

The injection of fuel is started by closing the solenoid valve 14 during the compression stroke of the plunger 7, and the injection is ended by further opening the solenoid valve 14. Therefore, the fuel injection is performed depending on the closing timing of the solenoid valve 14. The injection amount is controlled according to the start timing and the valve closing timing. If the solenoid valve 14 is once opened during the fuel injection process by the plunger pump 3, pilot injection can be performed prior to the main injection of fuel. Reference numeral 15 is a fuel cut valve which is closed when the engine is stopped, and 17 is a distributor head.

In the method of controlling the injection timing and the injection amount by electronic control, for example, the number of revolutions, the accelerator opening degree,
The optimum injection timing and injection amount corresponding to various engine conditions such as cooling water temperature and fuel temperature are obtained by experiments and the values are stored in a storage element such as a ROM of the control device. Then, at the time of actual engine operation, a signal of one pulse for one rotation of the injection pump as shown in FIG. 2 (reference pulse 201)
And 36 pulse signals per rotation (scale pulse 202)
From this, the engine speed is calculated, and the injection timing and injection amount are read in accordance with the speed, accelerator opening, cooling water temperature, fuel temperature, etc., and injection timing and injection amount control are performed.

As a conventional electronically controlled timer piston, for example, there is one shown in FIG. This is because the fuel of the pump chamber pressure is introduced 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 to transfer the fuel of the high pressure chamber 22 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 of withdrawal. By combining this with an electronically controlled pump, it is possible to change the oil feed rate of the pump. Further, FIG. 4 shows a principle diagram of a sensor that detects a valve closing timing and a valve closing period of the solenoid valve 14.

FIG. 5 is a block diagram showing the 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. 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.

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 solenoid valve 14 and the timing control valve 24 that determine the injection amount, injection timing, and injection rate. Data that is a control amount is set in the I / O 501. The RAM 503 is used to temporarily save data related to the arithmetic processing of the CPU 502. I / O
501 is based on the data output to the CPU 502,
The solenoid valve 14 for controlling the injection amount and the injection timing and the timing control valve 24 for controlling the injection rate are controlled.

Next, the operation of the CPU will be described with reference to the flowchart of FIG.

First, at step 601, the engine speed Ne, accelerator opening Acc, cooling water temperature Tw, fuel temperature Tf,
Reads engine operating conditions such as air flow meter output. Next, based on the operating conditions read in step 601, the characteristics shown in FIG. 7 to FIG. 11 are stored in advance in step 602, and the basic injection amount QN, the basic injection timing ITN, and the basic pilot amount QPN are stored. , The basic pilot time ITPN and the target intake air amount QaN are calculated. Next, at step 603, the target intake air amount QaN obtained at step 602 is compared with the actual intake air amount Ga. Next, in step 604, based on the comparison result in step 603, for example, the characteristics 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 processing is ended.

FIG. 14 is a block diagram for explaining the details of the control unit according to the second embodiment. FIG.
2 shows a flowchart of the second embodiment. First, at step 1401, engine speed Ne and accelerator opening Ac
The engine operating conditions such as c, cooling water temperature Tw, fuel temperature Tf, and intake pressure sensor output are read. Next, step 1
Based on the operating conditions read in 401, step 1402
Then, for example, the characteristics as shown in FIGS. 7 to 10 and 16 are stored in advance, and the basic injection amount QN, the basic injection timing ITN,
Basic pilot quantity QPN, basic pilot time ITP
N, the target intake pressure PaN is calculated.

Next, in step 1403, step 14
The target intake pressure PaN obtained in 02 is compared with the actual intake pressure Pai. Next, in step 1404, step 1403
Based on the result of the comparison, the characteristics shown in FIGS. 17 and 18 are stored in advance, and the pilot correction amount ΔQP and the pilot timing correction amount ΔITP are calculated. Next, in step 1405, the pilot amount QP and pilot time ITP
And decide.

[0022]

As described above, according to the present invention, the intake air amount detecting means for detecting the intake air amount and the pilot injection amount according to the output of the intake air amount detecting means are provided. By controlling the pilot injection timing, for example, in an engine with a supercharger, the intake air amount is detected during an acceleration transient, and when the intake air amount until the boost pressure rises is small, the pilot air is adjusted according to the intake air amount. By increasing and correcting the injection amount and controlling the pilot injection timing to be advanced, it is possible to obtain the effect of reducing the combustion noise even in the low boost pressure state.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an electronically controlled 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 a solenoid 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 according to 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 a fuel injection control device for a diesel engine according to a second embodiment.

FIG. 15 is a flowchart showing an operation of the control unit according to the second embodiment.

FIG. 16 is a characteristic diagram of 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 detecting means) 1305 intake pressure sensor (intake air amount detecting means) 502 CPU

Claims (6)

[Claims] 1. In a fuel injection pump of a diesel engine that performs pilot injection before main injection, an intake air amount detecting means for detecting an intake air amount, and a pilot injection amount according to an output of the intake air amount detecting means. And a fuel injection timing control device for a diesel engine, which controls pilot injection timing. 2. The fuel for a diesel engine according to claim 1, wherein when the intake air amount detection means determines that the intake air amount is smaller than a target value, the pilot injection amount is corrected to be reduced. Injection control device. 3. The diesel engine according to claim 1, wherein the pilot injection timing is advanced when the intake air amount detecting means determines that the intake air amount is smaller than a target value. Engine fuel injection control device. 4. The fuel injection control device for a diesel engine according to claim 1, wherein the intake air amount detecting means is an air flow meter. 5. The fuel injection control device for a diesel engine according to claim 1, wherein the intake air amount detecting means is performed by an intake pressure sensor. 6. The fuel injection control device for a diesel engine according to claim 1, wherein the diesel engine includes a supercharger.