JPS58155273A - Fuel injection control device in internal-combustion enging - Google Patents

Abstract

PURPOSE:To make it possible to externally control the back pressure of a nozzle needle in a fuel injection valve, by collecting discharged fuel returned from the fuel injection valve to a fuel tank, in a fuel header, and by arranging a control valve which is operated in accordance with the operating condition of an engine, in a piping passage between the header and the fuel tank. CONSTITUTION:A nozzle needle 17 is lifted overcoming a spring 20 by high pressure fuel which is fed by a fuel injection pump 2 through a fuel passage 16 in a fuel injection valve 3 to the valve seat 18 of the nozzle needle 17, and therefore, a nozzle hole 21 is opened for fuel injection. In such a device, discharged fuel from a nozzle holder 15 is once collected in a fuel header 4, and then, is discharged into a fuel tank 5 through a pipe line disposed therein with a solenoid valve 6 which is controlled by a control device 10 receiving the outputs of a rotary encoder 7 for detecting the rotational speed of an engine crankshaft, a load sensor 8 and a fuel injection timing sensor 9. With this arrangement the back pressure of the nozzle needle 17 is controlled, thereby the characteristics of fuel injection is maintained at a high level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine in which fuel injection pressure can be varied according to engine operating conditions.

Conventionally, in order to vary the fuel injection pressure in an internal combustion engine, an electromagnetic actuator drives a needle holder that receives a spring that biases the nozzle needle of the fuel injection valve in the closing direction to control the valve opening pressure of the nozzle needle. It is known what made it so.

However, when using the conventional method as described above, the position of the needle holder is directly controlled by an electromagnetic actuator, so an electromagnetic actuator must be provided for each cylinder and each fuel injection valve of the internal combustion engine. There was a problem. Furthermore, there is a limit in terms of the power of the needle presser part of the electromagnetic actuator, and there is a problem in that it may not be practical in terms of the driving force that can be obtained.

Another method is to provide a restriction in the exhaust path of leaked fuel from the fuel injection valve nozzle holder and use the restriction to control the back pressure of the nozzle needle. There was a problem with being able to control it.

The present invention has been made in view of the above, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine that solves the above problems by making it possible to control the back pressure of a nozzle needle of a fuel injection valve from the outside. be.

According to the present invention, this purpose is to temporarily collect exhaust fuel discharged from a fuel injection valve and returned to a fuel tank in a fuel header, and to install a control valve driven by an electromagnetic actuator in a piping path connecting the fuel header and the fuel tank. This is achieved by controlling the control valve according to the engine operating conditions.

The present invention will be explained below with reference to Examples.

FIG. 1 is a block diagram of one embodiment of the present invention.

1 is an internal combustion engine, 2 is a fuel injection pump, and fuel from the fuel injection pump 2 is guided to a fuel injection valve 3 provided corresponding to each cylinder of the internal combustion engine 1 and injected into each cylinder. .

The fuel injection valve 3 is constructed as shown in FIG. 2, similar to a conventional fuel injection valve. High pressure fuel from the fuel injection pump 2 is supplied through a fuel passage 16 provided in the nozzle holder 15. When the high-pressure fuel supplied through the fuel passage 16 acts on the valve seat 18 of the nozzle needle 17, a spring installed in the nozzle holder 15 and biasing the nozzle needle 17 in the valve closing direction via the needle presser 19 is activated. 2
0, the nozzle needle 17 moves in the valve closing direction, opens the nozzle hole 21, and starts injecting fuel from the nozzle hole 21.

Furthermore, if the fuel pressure decreases below the pressing force of the nozzle needle 17 from the spring 20, the nozzle needle 17 moves in the valve closing direction and stops fuel injection.

On the other hand, a part of the high-pressure fuel supplied through the fuel passage 16 lubricates between the nozzle needle 17 and the nozzle holder 15,
It is discharged from the top of the nozzle holder 15.

In one embodiment of the present invention, a fuel injection valve nozzle holder 1
The discharged fuel from the fuel tank 5 is concentrated in the fuel ladder 4 and returned to the fuel tank 5 from the fuel ladder 4. An electromagnetic actuator-driven control valve (hereinafter referred to as an electromagnetic valve) that can take an intermediate position in the fuel piping path between the fuel header 4 and the fuel tank 5.
6 is inserted, and by controlling the electromagnetic valve 6, the back pressure of the fuel header 4, that is, the nozzle needle 17 is controlled.

For example, as shown in FIG. 3, the electromagnetic valve 6 includes a valve body 24 forming a valve seat portion (3) 23, a valve portion 25, an electromagnetic actuator 26 for driving the valve portion 25, and a valve body 24 that moves the valve portion 25 in the closing direction. It consists of a spring 27 that urges the Note 2
8 is a fuel bypass passage provided in the valve body 24.

Further, a rotary encoder 7 is attached to the crankshaft of the internal combustion engine 1 to detect the rotational speed of the crankshaft, and generates a number of pulse outputs corresponding to the rotational speed of the crankshaft. The fuel injection pump 2 is provided with a fuel injection timing detector 9 for detecting a point in time before a predetermined time. The fuel injection timing detector 9 may be, for example, a means for detecting a predetermined lift position of a fuel injection pump plunger, or a means for detecting that the pressure of fuel oil near the pump of a fuel injection pipe has reached a predetermined pressure.

The outputs of the rotary encoder 7, load detector 8, and fuel injection timing detector 9 are input to the control device 10, and
The valve opening degree of the solenoid valve 6 is controlled by applying an output of 0 to the solenoid actuator 26 of the solenoid valve 6 (+4).

In the present embodiment shown in FIG. 1, a part of the fuel from the feed pump 11 of the fuel injection pump 2 is guided to another chamber partitioned off by a diaphragm 12 of the fuel header 4. The diaphragm 12 may be removed if the fuel entering the fuel rudder 4 is homogeneous fuel. This is to ensure that the back pressure of the nozzle needle 17 is controlled by the solenoid valve 6 even when the amount of fuel discharged from the fuel injection valve 3 is small. Further, 13 is a throttle inserted into the piping path between the fuel feed pump 11 and the fuel header 4.

The control circuit 10 includes, for example, a gate circuit 30 as shown in FIG.
, counter 31. It has monostable multivibrators 32 and 33, an analog/digital converter (hereinafter referred to as A/D converter) 34, a deducer 35, an address counter 36 consisting of a presettable counter, a decoder 37, a programmable counter 39, and a frequency synthesizer. The device includes a PLL circuit 38, a heptadary counter 40, a gate circuit 41, a storage device 42, a digital/analog converter (hereinafter referred to as a D/A converter) 43, and a drive circuit 44.

The storage device 42 stores the crankshaft rotation speed N as shown in FIG.
On the fuel control characteristic curve defined by
The vertical axis (Q) is divided into predetermined equal parts, in this example, eight parts are divided into equal parts, and the fuel injection valve 3 corresponding to each divided range is divided into eight parts. The pattern of the fuel injection rate during the fuel injection period is stored in advance as a digital value. An example of the pattern of the fuel injection rate is as shown by the solid line in FIG. The fuel injection rate pattern divides one fuel injection period (1) into 7 equal parts, and the nozzle corresponds to the injected fuel amount qpi (i=1 to 7) at each time point to, tll, ... t7 of the 7 equal parts. It is determined by digital values PO, P1, . . . , Pl of the back pressure of the needle.

Note that since FIG. 6 shows the amount of injected fuel qp, the pattern of the back pressure of the nozzle needle 17 is as shown by the broken line in FIG.

Now, the fuel injection rate pattern corresponding to each area where the fuel control characteristics are divided like the eyes of the base is determined by the area (Ni,
Qi) is determined to be the optimal pattern. For example, at 3/4 load, the fuel injection rate is set low to reduce NOx, and at no-load low rotation, the fuel injection rate is set low to reduce noise. Note that FIG. 5 shows an example of the fuel injection rate pattern for each area (Ni, Qi), and in FIG. 5, the arrow indicates that the fuel injection rate is the same as the fuel injection rate shown on the left side of the arrow. Further, the fuel injection rate for each area (Ni, Qi) may be different and can of course be freely determined. Each area (Ni
.
XQB) Po for the area, , Pl,...
PO for P6, Pl, ..., (NA, QH) area
N''1,..., P6, Pl, Po for the (NB, QA) area, 7 I Pl..., P6, Pl,... are stored in advance as digital values of the back pressure of the nozzle needle 17. It is.

Now the output pulse of rotary encoder 7 is sent to gate circuit 3
It is added to the counter 31 via 0.

On the other hand, the output pulse of the injection timing detector 9 triggers the monostable multivibrator 32, which opens the gate circuit 30 for the set time, and the output pulse of the rotary encoder 7 is counted by the counter 31. be done. Therefore, the count value of the counter 31 changes from the time when the output pulse of the injection timing detector 9 occurs to the monostable multivibrator 3.
2 corresponds to the average rotational speed of the crankshaft during the set time. On the other hand, the load of the engine is detected by the load detector 8.
The output signal of the load detector 8 is converted into a digital signal by the A/D converter 34. The output signal of the A/D converter 34 and the count value of the counter 31 are sent by the decoder 35 to an address (NI,
QA) and preset in the address counter 36.

(81 Therefore, the address counter 36 specifies the preset address (Ni, Qi) of the storage device 42.

With this designation, the storage device 42 has the address (N1%Qi)
The digital value Po in the category (Ni, Qi) on the fuel control characteristics, that is, the content stored in , is output. This digital value Po is applied to the D/A converter 43, converted into an analog signal by the D/A converter 43, amplified by the drive circuit 44, and applied to the electromagnetic actuator 26, and is applied to the nozzle by the electromagnetic valve 6. The back pressure of the needle 17 is controlled by 75EPO.

In this case, since the fuel injection timing detector 9 generates an output pulse a predetermined time before the fuel injection timing, the control of the back pressure of the nozzle needle 17 is performed at a predetermined advance timing.

On the other hand, the count value of the counter 31 is applied to a decoder 37 and decoded into three outputs (1). It is applied to the setting terminals of the 100th, 1o, and 1st positions. Therefore, the cycle of the output signal of the frequency synthesizer consisting of the PLL circuit 38 is the fuel injection period for the rotation speed Ni of the crankshaft during the set time of the monostable multivibrator 32 from the generation of the output pulses of the rotary encoder 7 and the fuel injection timing detector 9. It is equal to the time divided into seven equal parts, and corresponding to the rotational speed N1, it is short when the fuel injection period is short and becomes long when the fuel injection period is long.

The output signal of the frequency synthesizer consisting of the PLL circuit 38 is counted by a counter 40, and the gate circuit 41 is opened while the counter 40 is counting 7. Therefore P
The output signal of the frequency synthesizer consisting of the LL circuit 38 passes through the gate circuit 41 and sequentially increments the count value of the address counter 36, and the address designation value of the address counter 36 is set to the value (Ni, Ni, Qi) to every period of the output signal of the PLL circuit 38 (N1% Ql→Ni, Qi, +1)
The storage device 42 stores the address (Ni, Ql) set by the decoder 35.
(Ni,,Q
i+1) is specified, and the digital value POs "1" corresponding to the fuel injection rate pattern for the fuel control characteristic classification (Ni, Qi) shown in FIG.
7 are output sequentially, and the nozzle needle 1 is output by the solenoid valve 6.
The back pressure of 7 is sequentially controlled to Po1P1, fist-5pa, and P7. Therefore, the injection amount is determined by the classification of fuel control characteristics (Nl %
Qi ) is controlled according to a predetermined pattern, and the fuel injection rate is controlled according to the engine load and the crankshaft rotation speed.

Further, when the counter 40 counts 7 output signals output from the PLL circuit 38, the gate of the gate circuit 41 is closed, the output signal of the PLL circuit 38 is not applied to the address counter 36, and the address counter 36 is incremented. There is no need to wait for the next fuel injection timing.

Further, during this waiting period, the count value of the counter 31 is reset by the output of the stable multivibrator 33 triggered by the fuel injection timing detector 9.

Note that the output of the address counter 36 and the memory device 42 is not controlled to be cut off, but this means that once the fuel injection is completed at the -injection timing, the fuel injection pump is connected to the fuel injection valve 3 until the next injection timing is reached. This is because fuel is not supplied from 2.

As described above, according to the present invention, the pressure of the collected fuel discharged from the fuel injection valve is controlled by the electromagnetic valve, so that the conventional fuel injection valve can be used as is. Furthermore, there is no need to provide the electromagnetic valve for each cylinder of the engine, and only one electromagnetic valve is required for one engine, which simplifies the entire system.

Furthermore, since the back pressure of the needle nozzle can be controlled via the solenoid valve, the fuel injection rate characteristics can be controlled from the outside rather than the nozzle itself, and there is no change in the fuel injection rate characteristics over time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. FIG. 2 is a sectional view showing an example of a fuel injection valve C12) used in an embodiment of the present invention. FIG. 3 is a sectional view showing an example of a solenoid valve used in an embodiment of the present invention. FIG. 4 is a block diagram showing an example of a control circuit in an embodiment of the present invention. FIG. 5 and FIG. 6 are a fuel control characteristic diagram and a fuel injection rate characteristic diagram for explaining one embodiment of the present invention. l...engine, 2...fuel injection pump, 3 fuel injection valve, 4...fuel header, 5...fuel tank, 6
... Solenoid valve, 7-- Rotary encoder, 8...
Load detector, 9... Fuel injection timing detector, 10...
・Control charge, 11 Fuel feed pump, 12...
...Diaphragm, 30 and 41...Gate circuit,
35 and 37... decoder, 31 and 40...
Counter, 32 and 33 Monostable multivibrator, 34... Al1) converter, 36... Address counter, 38 - PLL circuit, 39 - Programmable counter, 42... Storage device, 43... D/
A converter. Figure 3 Figure 6 Figure 5
Figure 〒] Figure 4 During injection -- Free 26 *rrrmw 8 Period detection 9
=...-272 44A/D 34 M, M Game 0 ~O45 M M
Rn Unota 31 decoder 35 HA (PO fPl preset □ f) t'y'9 36 P7''°42 P6' Ip6 42 tp=' Eyebrow loss 1 LL 38 PLL P7゛

Claims (1)

[Claims] Exhausted fuel discharged from the fuel injection valve and returned to the fuel tank is once collected in a fuel header, and a control valve driven by an electromagnetic actuator is provided in a piping path connecting the fuel header and the fuel tank, and the control valve is connected to the engine. A fuel injection control device for an internal combustion engine, characterized in that the control is performed according to operating conditions.