JPS5857033A - Fuel injection method of electronically controlled fuel injection device - Google Patents

Abstract

PURPOSE:To increase control stability of injection at low loaded time, when a pulse width of the basic pulse, calculated in accordance with an operational condition, is smaller than a prescribed width, by decreasing a number of injection times for an engine cycle as compared with a case when the above described pulse width is larger than the prescribed width. CONSTITUTION:At operation, a microcomputer 9 firstly performs arithmetic operation of a basic pulse Tp, corresponding to a basic injection quantity, on the basis of outputs of a rotary pulse generator circuit 1 and intake air quantity measuring unit 3. Then in accordance with a content of a flag register, with which of an upper limit value or lower limit value the Tp shall be compared is decided, in accordance with the decision result, a pulse width of the Tp is changed. That is, injection is controlled in such a manner that fuel is injected once a half cycle of an engine when a pulse width of the Tp is larger than a prescribed width while the fuel is injected once a cycle of the engine when the pulse width of the Tp is smaller than the prescribed width. Then the microcomputer 9 correctively calculates an injection pulse on the basis of outputs of a throttle opening sensor 5, water temperature sensor 6, etc. to perform fuel excess correction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection method for an electronically controlled fuel injection device for an internal combustion engine.

An electronically controlled fuel injection system for an internal combustion engine calculates a fuel injection pulse with a pulse width b based on various engine parameters so that the engine always performs proper combustion, and uses the fuel injection pulse to drive an electromagnetic injection valve. It supplies fuel to the engine intermittently.

Such an electronically controlled fuel injection device will be explained with reference to FIG.

In FIG. 1, reference numeral 1 denotes a rotation pulse generation circuit, which shapes the waveform of an ignition signal obtained from the primary side of an ignition coil (not shown) to generate rotation pulses. Basic pulse generation circuit 2 is connected to the output terminal of rotation pulse generation circuit 1.
is connected to the basic pulse generating circuit 2, and the intake pipe (
The output end of an intake air amount measuring device 3 provided in the air conditioner (not shown) is also connected separately. An increase correction circuit 4 is connected to the output end of the basic pulse generation circuit 2. The increase correction circuit 4 includes a throttle opening sensor 5 which detects the operating state of the engine so as to command correction of the pulse width of the basic pulse. Various sensors such as a cooling water temperature sensor 6 are connected. A drive circuit 7 is connected to the output end of the increase correction circuit 4, and the drive circuit 7 drives an electromagnetic injection valve 8 provided for each cylinder.

In the electronically controlled fuel injection system configured as described above, rotation pulses synchronized with engine ignition, that is, rotation of the crankshaft, are supplied from the output end of the rotation pulse generation circuit 1 to the basic pulse generation circuit 2. On the other hand, the intake air amount measuring device 3 generates a voltage according to the intake air amount of the engine. The basic pulse generation circuit 2 generates a basic pulse corresponding to the basic injection amount according to the output voltage and rotation pulse of the intake air amount measuring device 3, and the basic pulse is generated in the increase correction circuit 4 according to the output signals of various sensors. Then, the pulse width is corrected and becomes a fuel injection pulse. The drive circuit 7 drives the electromagnetic injection valve 8 according to the pulse width of the fuel injection pulse generated in this way, and fuel is supplied to the engine.

In such an electronically controlled fuel injection system, a method is adopted in which two injections are made to one cylinder during one engine cycle (intake, compression, explosion, exhaust), and the fuel injection amount is:
The amount of fuel required by the engine is achieved with two injections. Even if the injection capacity of the electromagnetic injection valve is increased, there is a limit, so when the engine is under high load and rotation, the amount of fuel required can be reduced to 1 per engine cycle.
This is because it cannot be supplied with one injection.

However, as shown in FIG. 2, electromagnetic injection valves usually have a non-linear region where the injection amount is not proportional to the applied voltage time due to the fuel injection pulse in a portion where the injection amount is small. However, since it is not possible to easily develop an electromagnetic injection valve with a small injection amount, in small displacement engines, when the injection amount is small such as during idling, the injection amount changes due to the non-linear region due to the pulse of the fuel injection pulse. There was a problem that it was not proportional to the width.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fuel injection method that prevents an electromagnetic injection valve from operating in a non-linear region when the injection amount is small.

The fuel injection method according to the present invention is a method in which when the pulse width of the basic pulse is smaller than a predetermined width, the number of injections per engine cycle is made smaller than when the pulse width of the basic pulse is larger than the predetermined width. It is.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 3 to 5.

FIG. 3 shows a block diagram of an electronically controlled fuel injection system using a microcomputer for a four-cylinder, four-cycle internal combustion engine. In FIG. 3, the same parts as those in FIG. The output ends of each of the sensors, such as the throttle opening sensor 5 and the water temperature sensor 6, are connected to the microcomputer 9 via the A/D converter 10. The microcomputer 9 is a one-chip type, and its output terminal P. Four electromagnetic injection valves 8 are connected via a drive circuit 7 to the four electromagnetic injection valves 8 .

Next, the operation of the microcomputer 9 will be explained with reference to the operation flow diagrams of FIGS. 4 and 5.

First, the microcomputer 9 starts operating (1
01), a basic pulse corresponding to the basic injection amount is calculated from the rotation pulse and the output signal via the A/D converter 10 of the intake air amount measuring device 3 (102). Then, the contents of the seventh flag register A are determined (103).

Flag register A stores 1 if the pulse width of the basic pulse calculated in the previous process was doubled, and 0 if not. If the content of the flag register A is 0, it is determined whether the pulse width of the basic pulse T is larger or smaller than 1°7 mS (104).

If the content of flag register A is .11+, it is determined whether the pulse width of basic pulse T is larger or smaller than 20m8 (105). In this way, since hysteresis is given to the predetermined width to be compared with the pulse width of basic sill 2, it is determined whether to compare with the upper limit value (2,0m5) or the lower limit value (1,7ms) in flag register A. Judge by the content. Next, if T < 1.7 ms, change the contents of flag register A to lII+- (106
), double the pulse width of the basic pulse T (107)
. When Tp < 2.0 m s, the fundamental value (
The pulse width of the pulse T is doubled (107). Also T
”:22.Om s, the content 1 of the flag register A is changed to 0 (lO8).Then, the microcomputer 9 changes the first fuel injection pulse TLt (2T) from the throttle to correct the fuel increase. , +T8).
no). The second fuel injection pulse Tit at low temperature start is also calculated according to the output signal of the water temperature sensor 6 (111
). Then, the first and second fuel injection/crus TLI +
The pulse widths of Tt2 are compared (112).

If Tit≧T, 2, the first fuel injection pulse Tjl is changed to the fuel injection pulse 'r7. ．． = L (113), and the contents of flag register A are determined again (114). When the content of flag register A is .1, the content of flag register B is set to .1 (115). If the content of flag register A is 0, the second fuel injection
When i□ is subjected to fuel injection pulse TLK (116), the contents of flag register B are set to 1+Qn (117).
.

Then, the process returns to step (102) of calculating the basic pulse TP (118). In addition, flag register B
When the final fuel injection method is injection once per engine b cycle, .O. is stored, and when the final fuel injection method is injection once per engine cycle, .1. is stored.

At t'c, the microcomputer 9 starts an interrupt operation in response to the occurrence of the rotation noise ζ (119). When an interrupt operation starts, first, 1 is subtracted from the counter number N (
120). Next, let's judge the value of the counter number N. 12
1), in the case of N4o, interrupt processing is canceled and the program returns to the interrupted program address (122).

If N=0, the contents of flag register B are determined (+23). When the flag register B is 111011, the counter number N is set to 2 (124), and when it is +1111, the counter number N is set to 4 (125). In other words, since it is a 4-cylinder, 4-stroke internal combustion engine, if there is one injection per engine cycle B, two rotational pulses are counted, and if one injection is performed per engine cycle, four rotational pulses are counted. The counter number N is set so that. Then, the fuel injection pulse T, is sent to the output terminal P. 126), and simultaneously drives the electromagnetic injection valves 8 provided in each cylinder via the drive circuit 7. Then, the program returns to the program address where it was interrupted by the interrupt process (122).

Therefore, in the fuel injection method according to the present invention, the rotation pulse is
It is injected every time the engine dies, that is, once every 4 cycles of the engine.
When the basic pulse TPO pulse width becomes smaller than a predetermined width with hysteresis, the basic pulse TPO pulse width is doubled to calculate the fuel injection pulse T. The fuel is injected into all cylinders at the same time. Furthermore, at low temperature startup, even if the basic pulse TPO pulse width is smaller than a predetermined width, the fuel is injected once per engine b cycle using the fuel injection pulse TiK according to the cooling water temperature.

As described above, according to the fuel injection method of the present invention, when the pulse width of the basic pulse is smaller than the predetermined width, the number of injections per engine cycle is increased compared to when the pulse width of the basic pulse is larger than the predetermined width. In order to reduce this, in small-displacement engines, the electromagnetic injector no longer operates in a non-linear region when the injection amount is particularly small, such as when idling, and the injection amount is always proportional to the pulse width of the fuel injection pulse. . As a result,
The fuel injection method can be fully used even in small displacement internal combustion engines.
In addition, control during light loads such as when idling is stable, and it is possible to lower the idling speed, thereby improving fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electronically controlled fuel injection device, FIG. 2 is an injection quantity characteristic diagram of an electromagnetic injection valve, and FIG. 3 is a block diagram of an electronically controlled fuel injection device using the fuel injection method according to the present invention.
4 and 5 are operation flow diagrams showing an embodiment of the present invention by the microcomputer shown in FIG. 3. FIG. Explanation of symbols of main parts 1... Rotating pulse generation circuit 2...
...Basic pulse generation circuit 3...Intake air amount measuring device 4...Increase correction circuit 8...Electromagnetic injection valve 9・・・・・・・・・Microcomputer applicant
Japan Electronics Co., Ltd. Representative Patent Attorney Motohiko Fujimura

Claims (5)

[Claims] (1) A fuel injection method for an electronically controlled fuel injection device for an internal combustion engine that calculates a basic pulse corresponding to a basic injection amount according to the operating state of the engine, when the pulse width of the basic pulse is smaller than a predetermined width. A fuel injection method characterized by reducing the number of injections per engine cycle compared to when the pulse width of the basic pulse is larger than a predetermined width. (2) If the pulse width of the basic pulse is smaller than the predetermined width, fuel is injected once per engine cycle B, and if the pulse width of the basic pulse is smaller than the predetermined width, fuel is injected once per engine cycle. The fuel injection method according to claim 1, characterized in that: (3) If the pulse width of the basic pulse is greater than the predetermined width, engine 1. , /2 cycles, and if the pulse width of the basic pulse is smaller than a predetermined width, fuel is injected simultaneously in all cylinders once per engine cycle. Fuel injection method described in section. (4) Fuel injection according to claim 3, characterized in that when the engine is started at a low temperature, fuel is injected simultaneously in all cylinders once every four cycles of the engine even if the pulse width of the basic pulse is smaller than a predetermined width. Method. (5) Claim 1, characterized in that the sensor means for detecting the predetermined width exhibits a hysteresis characteristic.
Fuel injection method described in section.