JPS63277841A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the mechanical noise by adjusting a pulse width of a driving pulse for controlling the operation of a fuel pumping solenoid valve and starting main injection before ending of pilot injection. CONSTITUTION:When an engine is in an operational condition where pilot injection should be executed, a control circuit 5 reads an output signal from a nozzle lift sensor and determines whether or not the output signal has fallen twice in one injection stroke. If NO, stop control of a solenoid valve 20 is increased by a predetermined value, and if YES, the stop control is decreased by a predetermined value. In an actual operation of the solenoid valve 20, a pilot injection time and a main injection time are continuously established under a separate condition. Accordingly, an injection nozzle 10 is seated only once in one injection stroke to thereby reduce a seating noise. Accordingly, a mechanical noise may be reduced as maintaining the effectiveness of the pilot injection.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a fuel injection control device for an internal combustion engine, such as a diesel engine, which is capable of pilot injection performed prior to main fuel injection. It is something.

(Prior Art and its Problems) - Diesel engines generate combustion noise due to a delay in ignition of fuel, and the combustion noise is particularly noticeable when operating at low speeds and low loads.

A conventional fuel injection pump having a pilot injection function is known, for example, from Japanese Patent Laid-Open No. 125754/1983.

This conventional fuel injection pump uses a solenoid valve for fuel overflow, which opens and closes between a high pressure chamber and a low pressure chamber, where fuel is pressurized and pumped to the injection nozzle, depending on the engine operating state. Pilot injection and main injection are performed (FIG. 5(C)) by controlling opening and closing using drive pulses (FIG. 5(a)) (FIG. 5(a)) (FIG. 5(c)). In this case, the lift period (A, B) during each injection of the injection nozzle is detected by the nozzle lift sensor (FIG. 4(d)).

However, when performing the pilot injection in 1. prior to the main injection, the injection nozzle in 1.
Since opening and closing valve operations are performed during pilot injection and main injection, there is a problem in that mechanical noise is large when the valve body is seated, and the combustion noise reduction effect of pilot injection is halved.

(Object of the Invention) The present invention has been made to solve the above-mentioned problems, and is intended to reduce combustion noise due to pilot injection and at the same time reduce mechanical noise in a fuel injection device controlled by a solenoid valve for fuel overflow. Furthermore, it is an object of the present invention to provide a fuel injection control device for an internal combustion engine that is capable of regulating exhaust gas.

(Structure of the Invention) -1. According to the present invention, in order to achieve the above objects, the fuel t'
) addition) 1: In a fuel injection control device that performs pilot injection prior to main injection by controlling opening and closing of a pressure-feeding solenoid valve according to the operating state of the engine, the solenoid valve 01i There is provided a fuel injection control device for an internal combustion engine, characterized in that the main injection is started before the end of the nIj pilot injection by adjusting the pulse width of a drive pulse that controls opening and closing of the main injection.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view showing the main parts of an injection nozzle and a distribution type fuel injection pump connected thereto, implementing the apparatus of the present invention. 10 in the figure is an injection nozzle, and this injection nozzle l
O basically consists of a seat I01) which can come into contact with the seat 10a, 1111 and the seat 10a, and during the lift period of the injection nozzle 10 (nozzle lift period), a nozzle lift sensor (not shown) is used. ) is detected. In this embodiment, it is sufficient for the nozzle lift sensor to simply detect the contact state between the seat 10a and the valve seat 10b, and therefore the nozzle lift sensor uses the seat 10a and the valve seat 10b as a switch. (SOI sensor) is applied, and a lift signal (Sol signal) from the Sol sensor is supplied to the control circuit 5. Note that when the Sol signal is at a high level, it indicates that the injection nozzle 10 is opened, and when it is at a low level, it indicates that the injection nozzle IO is closed (bamboo-shaped @).

1);J The electromagnetic valve 20 for fuel overflow specifically includes a valve housing 22 in which the return passage 21 is bored, and an iron core 24 around which a coil 23 is wound.

The same number of fuel distribution passages 7 and 8 as the number of cylinders are provided in the plunger barrel 4 and the block 3 in which the plunger 6 is fitted, respectively, and the outlet of the passage 8 [1 is the pipe 9a, 9
The injection nozzle 10 is arranged for each cylinder via b.
It is connected to the.

In the figure, 1 is a pump housing, and a feed pump (not shown) is mounted on the pump housing 1, which is driven by a drive shaft (not shown) connected to the output shaft of an engine (not shown). .

The control circuit 5 includes a central processing unit (CPU), a read-only memory (ROM) and a random access memory (ROM) in which an injection control program, which will be described later, is stored in advance.
r<ΔM), etc., and the control circuit 5 includes a rotational speed signal representing the engine rotational speed, a crankshaft reference position signal,
The accelerator opening signal, intake pressure signal, intake temperature signal, and engine coolant temperature signal are each manually input. Based on these input signals, the control circuit 5 outputs a control signal (drive pulse signal) to the electromagnetic valve 20 for fuel overflow to control the injection T11, injection time, and other matters.

Next, injection control by opening/closing control of the electromagnetic valve 20 for fuel overflow according to the present invention will be explained according to the program flowchart shown in FIG.

First, when the ignition switch (not shown) is turned on and the power is turned on, the control circuit is initialized in step 1, and in step 2, the operating parameters of the various sensors representing the engine operating state are determined. Signals are read.

When the reading of this operating parameter signal is completed, in the following step 3, it is determined whether or not the engine is in an operating state in which pilot injection should be performed (for example, idling operating state @). This is done based on the accelerator opening signal and water temperature signal). This step 3
If the determination result is negative (No), proceed to step 4 and inject fuel t1 under normal injection control, that is, inject the required amount of fuel according to the engine operating condition 1 at a time by main injection only. (Fuel injection is performed using a known method.

On the other hand, when the determination result in step 3 is affirmative (Yes), that is, when the engine is in an operating state in which pilot injection should be performed, the mechanical noise when the injection nozzle IO is seated due to the execution of the pilot injection is reduced. In order to reduce this, the following control (control in steps 5 to 9) is executed.

First, in step 5, based on the operating parameters, 1); drive pulse (item C:'!) of control valve 20 is determined;
The drive pulse, the waveform of Fig. 3 (a), that is, the control period (low level period) from the start point to the end point of pilot injection control, Δ, the rest control period (between pilot injection control and main injection control) High level period) i” DPM is determined, and based on these values, the main injection control period AD is further determined.
H is determined.

In step 6, the nozzle lift sensor output value t;(S
ol signal), and in the next step 7, +”+”
+ i The read Sol signal is 2 times\' in one injection stroke
Δi period from the time when the injection nozzle 10 actually starts pilot injection (the first rising of the Sol signal) to the time when the main injection ends (the last falling of the SO1 signal) During this time, it is determined whether or not the S01 signal (S01 signal) has become low level.

If the determination result in step 7 is negative (No), that is, the injection nozzle is seated only once in one injection stroke, the process proceeds to step 9, and the body 11-control 1'orM
is increased by a predetermined value, and then the process returns to step 2.

On the other hand, when the determination result in step 7 is affirmative (Yes), that is, when it is determined that the injection nozzle has been seated twice in one injection stroke, the process proceeds to the next step 8, and the control period 1''llPM is set to a predetermined value. Decrement by the value and then return to step 2.

Drive pulse (target drive pulse) determined as follows:
In the actual operation of the solenoid valve 20 based on (No. 3)
1(1))) Basically, the addition of fuel by the plunger 6 described in η is performed only when the solenoid valve 20 is closed.
However, during the drive pulse for closing the solenoid valve 20, the solenoid valve 20 is
By controlling the valve to open, the pressurization of the fuel is temporarily reduced, and the pilot injection period Δ' and the main injection period B' are performed continuously in a separated state (Fig. 3(c)). ), at this time, the SO signal changes as shown in FIG. 3(d), and the injection nozzle is only seated once in one injection stroke, and the seating noise is reduced.

Therefore, according to the pilot injection control device of this embodiment,
For normal injection, combustion noise peculiar to pilot injection as in the prior art is reduced, while mechanical noise is also reduced, and the same exhaust gas regulation I11 as before can be effectively met.

Here, FIG. 4 shows the engine noise reduction effect according to this embodiment, and shows two cases: normal injection without pilot injection (symbol P) and conventional pilot injection (symbol R). It can be seen that the noise level is the lowest in the case of this example (marked Q) compared to the above.

Note that the injection nozzle is not seated between pilot injection and main injection, and the first valve body of the injection nozzle when seated is
Since jumps in two directions can be prevented, the lift of the injection nozzle (FIG. 3(C)) responds accurately to the drive pulse of the electromagnetic valve 20.

(Effect of the invention) 1]il'l! As described above, according to the present invention, the pilot injection is performed prior to the main injection by controlling the solenoid valve for fuel injection (opening/closing depending on the operating state of the engine). By adjusting the pulse width of the drive pulse that controls the opening and closing of the electromagnetic valve,
Since the main injection is started at j, it is possible to reduce mechanical noise while maintaining the effectiveness of the conventional pilot injection, and of course it is also possible to achieve exhaust gas regulation. Sometimes useful.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of an injection nozzle implementing the device of the present invention and a distribution type fuel injection pump connected thereto;
FIG. 2 is a program flowchart 1 showing injection control by opening/closing control of the solenoid valve shown in FIG. 1, and FIG. 3 is a program flowchart 1.
FIG. 4 is a timing chart illustrating the operation of the injection nozzle by the injection control device, FIG. 4 is a graph showing an experimental example of the effect of reducing engine noise by the control device of the present invention, and FIG. It is a figure similar to figure 3. 5... Control circuit, 10... Injection nozzle, 20...
Solenoid valve for pressurized pressure feeding.

Claims (1)

[Claims] 1. In a fuel injection control device that performs pilot injection prior to main injection by controlling opening and closing of an electromagnetic valve for pressurized fuel feeding according to the operating state of the engine, the electromagnetic valve is controlled to open and close. A fuel injection control device for an internal combustion engine, characterized in that the main injection is started before the end of the pilot injection by adjusting the pulse width of the drive pulse.