JPH0674768B2 - Fuel injection control method for internal combustion engine - Google Patents

Description

The present invention relates to an injection control method for injecting fuel into an intake branch passage corresponding to each cylinder of a multi-cylinder internal combustion engine.

[Conventional technology]

Conventionally, as an electronically controlled fuel injection control method for a multi-cylinder internal combustion engine, a fuel injection valve provided corresponding to each cylinder is used for all cylinders at the same time to reduce the amount of fuel required for each revolution of the crankshaft to 1/2. Of all cylinders in between, a simultaneous injection system that injects into each cylinder, an independent injection system that injects each fuel injection valve individually to inject the required amount of fuel when the corresponding cylinder is in the vicinity of the intake stroke, and half of all cylinders in between. There was a group injection method to perform each.

Also, due to the control device, the fuel injection pulse width can be calculated by the independent injection method (calculated once for every 180 ° crank angle in a 4-cylinder engine), and when the fuel can be injected during the intake stroke, it is determined as the independent injection, and the calculation time is calculated. Japanese Patent Laid-Open No. 56-159527 discloses a device for switching to the simultaneous injection in all cylinders when the injection is not completed during the intake stroke.

Further, there is a case where simultaneous injection is performed at the time of starting when the cylinder of the engine cannot be discriminated by the rotation angle sensor, and the independent injection is switched to when the cylinder discrimination becomes possible.

[Problems to be Solved by the Invention]

However, when the injection method is switched, an excessive amount of fuel is generated and the engine is unstable due to misfire, and a large amount of raw gasoline is discharged.

Therefore, in view of the above problems, the present invention reduces the pulse width of the fuel injection pulse width calculated by normal calculation at the time of switching the injection method and corrects the fuel injection pulse width, so that an appropriate amount of fuel is always drawn into the engine to cause misfire. The purpose is to prevent the above and ensure smooth engine rotation.

[Means for Solving the Problems]

Therefore, in the present invention, in the fuel injection control method for an internal combustion engine in which fuel is intermittently injected in synchronization with the rotation of the internal combustion engine by each fuel injection valve corresponding to each cylinder, the fuel injection control method is performed once for each revolution of the internal combustion engine. It was determined whether the injection method was switched from the simultaneous injection of all cylinders, which is half the amount required for combustion, to the injection of the amount required for combustion for each cylinder independently or once every two revolutions of the internal combustion engine. Later, during the transitional period from this all-cylinder simultaneous injection to each cylinder independent injection or group injection, the fuel required for one combustion is excessively switched in relation to the intake stroke. Fuel injection control method for an internal combustion engine, characterized in that at least one of performing an injection cut of a cylinder of a certain section and correcting a fuel injection pulse width of a part of the cylinders to a half after the switching of the injection method after switching is performed. It is intended to provide.

〔Example〕

The present invention will be described below with reference to the drawings. FIG. 1 shows an overall schematic configuration diagram of an embodiment of a fuel control device according to the present invention. In FIG. 1, reference numeral 1 denotes a main body of a multi-cylinder engine, for example, a 4-cylinder engine. Reference numeral 2 denotes an intake system, which is an air purifier 3, an air flow meter 4 for measuring a flow rate by driving a potentiometer with a dam plate whose opening changes according to an air flow rate, and a stepping on an accelerator pedal 5. It is composed of a throttle valve 6, an intake manifold 7 and the like, the opening of which changes according to the amount of dust.

8 denotes a fuel system, which is a fuel tank 9,
A fuel pump 10 for pressurizing and supplying the fuel in the fuel tank 9 to a distributor 11 described below, a distributor 11 for distributing the pressurized and supplied fuel to the cylinders of the engine body 1, an intake manifold Fuel injectors 12-1 and 12-, which are arranged in No. 7 and inject the fuel distributed by the distributor 11.
2, 12-3, 12-4, and a pressure regulator 13 for keeping the pressure of the fuel pressurized by the fuel pump 10 constant.

Here, each of the fuel injection valves 12-1 to 12-4 is controlled by the following control unit 27 from the fuel injection valves 12-1, 12-2, 12-.
It is a well-known solenoid valve driven by an electric signal separately and independently sent to 3, 12-4. Reference numeral 16 represents an exhaust system, and the exhaust system 16 is composed of an exhaust manifold 17, an air ratio sensor 18 arranged at a collection portion of the exhaust manifold 17, and the like.

Reference numeral 19 denotes a rotation sensor. The rotation sensor 19 has magnetic bodies 21 and 22 which rotate at a speed half that of the crankshaft of the engine, that is, makes one rotation every two rotations of the crankshaft. Electromagnetic pickups 24 and 25 arranged opposite to each other
And detects the induced electromotive force generated when the teeth of the magnetic bodies 21, 22 pass the positions of the electromagnetic pickups 24, 25, and sends a signal, that is, crank angle information, to the control unit 27 described below. The number of teeth of the magnetic bodies 21 and 22 is, for example, 1 and 24.

Reference numeral 26 denotes a potentiometer which is built in the air flow meter 4 and which converts a change in the opening of the dam plate into an electric quantity and sends the signal to the control unit 27 described below.

Reference numeral 27 represents a control unit which receives engine information such as air-fuel ratio information from the air-fuel ratio sensor 18, crank angle information from the rotation sensor 19, intake air amount information from the air flow meter 4, and the like. The fuel injection valves 12-1 and 12-
The fuel injection time for 2, 12-3, 12-4 is calculated, and the corresponding signals are output to the fuel injection valves 12-1, 12-2, 12-3, 12-.
Send to 4.

FIG. 2 shows a block diagram of the control unit 27. Second
In the figure, 28 is an input circuit including an A / D conversion circuit for converting an analog signal such as an air-fuel ratio signal from the air-fuel ratio sensor 18 and an intake air amount signal from the potentiometer 26 into a digital signal, and 29 is a rotation angle sensor 19 An input circuit 30 for shaping a pulse signal from the input circuit, etc., 30 is a microcomputer composed of a one-chip LSI, accepts signals from the input circuits 28, 29, performs an arithmetic process according to a predetermined control program, and outputs an injection pulse signal ( The switching circuit 31 outputs a) shown in the figure and an injection cylinder command signal (b) shown in FIG.
It is what is output. Reference numeral 31 is a switching circuit, which is provided with AND gates 31-1 to 31-4, which divides the injection pulse signal a into each cylinder according to the injection cylinder command signal b and sends it, and 32-1 to 32-4 respectively output A circuit for amplifying the signal from the switching circuit and supplying it to the fuel injection valves 12-1 to 12-4 is shown.

Next, the main processing operation of the control unit 27 will be described with reference to the flowchart of FIG. The flow chart is a schematic representation of the main part of the present invention in the engine control program stored in advance in the ROM of the microcomputer 30. When an ignition key (not shown) is turned on and a constant voltage is applied to the control unit 27 from the stabilized power supply circuit connected to the vehicle-mounted battery via the ignition key, the microcomputer 30 is activated and the frequency of several MHz is reached. The engine control program is executed in synchronization with the clock signal of the crystal unit.

Various initializing processes are performed at the beginning of the program.

The signal G of the electromagnetic pickup 24 is generated for every 720 ° crank angle (two revolutions) of the engine to determine the reference angular position of the engine. The signal NE of the electromagnetic pickup 25 is 30 °
A signal is output for each crank angle. The engine crank angle and engine speed are calculated using G and NE.

After that, when the process shifts to the injection method determination routine, first, at step 100, it is determined whether or not the crank angle is 300 ° C. (calculated by setting the top dead center of the ignition of the first cylinder to be 0 ° C. A).
When it is not ℃ A, it branches to NO and ends. When the temperature is 300 ° C, the process branches to YES and proceeds to step 101 to determine whether the engine speed is 2000 rpm or less. When the engine speed is 2000 rpm or more, NO.
Then, in step 106, a flag for simultaneous injection of two revolutions, which injects fuel once every two revolutions of the engine simultaneously in all cylinders, is set, and the process ends.

If the speed is 2000 rpm or less in step 101, proceed to step 102,
It is determined whether or not the injection pulse signal sent to the fuel injection valve last time is simultaneous injection, and if it is an injection pulse of independent injection, the process branches to NO and proceeds to step 104, sets the flag of independent injection, and ends.

In step 102, if the last time was simultaneous injection (that is, the state where the number of revolutions has decreased from 2000 rpm or more to 2000 rpm or less), Y
Branch to ES and proceed to step 108. The process proceeds to step 108 during the transitional period in which simultaneous injection is switched to independent injection,
As shown in the time chart of FIG. 4, the flag for setting the injection pulse at the end of the simultaneous injection to only the fourth and second cylinders is set and the processing is ended. FIG. 4 shows the injection timing corresponding to each cylinder based on the injection system flag.

That is, as shown in FIG. 4, when switching from one-rotation one-rotation simultaneous injection, which injects 1/2 of the fuel required for one combustion by one injection per one revolution of the engine to independent injection, As shown in the time chart of FIG. (B), the injection pulse at the end of simultaneous injection is injected only into the fourth and second cylinders, and independent injection is performed from the intake stroke of the first cylinder after one rotation.

Alternatively, as shown in FIG. 5, the first injection pulse after the independent injection is stopped (steps 103 and 105 in FIG. 6), the second pulse and the third injection pulse are set to 1/2 of the calculated pulse width (see (Step 109 in FIG. 6) From the fourth pulse, the injection pulse width may be calculated by regular calculation. Further, when switching from one-time one-shot simultaneous injection (step 106 in FIG. 8) to two-group injection (step 111 in FIG. 8), the pulse width of the first two-group injection is changed as shown in FIG. 7 (B). 1/2
(Step 110 in FIG. 8). For the same reason as above, it is possible to switch without misfire.

Although the four-cylinder engine has been described in the above-described embodiments, the same idea can be applied to engines having other numbers of cylinders according to the concept of the present invention, and an excellent effect that the injection system can be switched without engine misfire. .

〔The invention's effect〕

As described above, according to the present invention, once every one revolution of the internal combustion engine, from all cylinder simultaneous injection of half the amount required for combustion, once every two revolutions of the internal combustion engine. It is possible to reliably prevent misfiring due to excess fuel when switching the injection method to each cylinder independent injection or group injection of the amount required for combustion, and it is possible to ensure smooth engine rotation. is there.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a control unit 27, FIG. 3 is a flow chart for determining an injection method, and FIG. 4 is a two-rotation one-time simultaneous injection of FIG. FIG. 5 is an explanatory diagram for switching to group injection, FIG. 5 is an explanatory diagram for switching from one-time, one-time simultaneous injection to independent injection, FIG. 6 is a flowchart for determining the injection method of FIG. 5, and FIG. FIG. 8 is an explanatory diagram of switching from injection to group injection, and FIG. 8 is a flowchart of the injection method determination of FIG. 1 ... Engine body, 4 ... Air flow meter, 6 ... Throttle valve, 12-1 to 12-4 ... Fuel injection valve, 18 ... Air ratio sensor, 19 ... Rotation sensor, 21, 22 ... Magnetism Body, 24, 25
...... Electromagnetic pickup, 27 ...... Control unit

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-137626 (JP, A) JP-A-56-159527 (JP, A) JP-A-58-18530 (JP, A)

Claims (4)

[Claims] 1. A fuel injection method for an internal combustion engine, in which fuel is injected intermittently in synchronization with the rotation of the internal combustion engine by each fuel injection valve corresponding to each cylinder, once for each revolution of the internal combustion engine. Half the amount required for combustion from all cylinders simultaneous injection,
After determining the switching of the injection method to the individual cylinder independent or group injection of the amount required for combustion once every two revolutions of the internal combustion engine, the transition transition from this all-cylinder simultaneous injection to each cylinder independent injection or group injection In the period, the fuel required for one combustion is excessively switched in relation to the intake stroke, the injection cut of some cylinders with respect to the injection method before the switching for the cylinders with the excessive switching, and the injection cut of some cylinders with respect to the injection method after the switching A method for controlling fuel injection in an internal combustion engine, comprising performing at least one of correcting a fuel injection pulse width to be half. 2. The switching of the injection method is from all-cylinder simultaneous injection to each cylinder independent injection method, and the injection pulse in the all-cylinder simultaneous injection method is changed once in relation to the intake stroke during the switching transition period. Claim 1. A fuel injection system according to claim 1, characterized in that only some of the cylinders whose fuel required for combustion becomes excessive after switching are injected and cut, and only the remaining cylinders are injected.
A method for controlling fuel injection in an internal combustion engine according to the above item. 3. The fuel injection method is switched from all-cylinder simultaneous injection to each cylinder independent injection method, and the injection pulse in each cylinder independent injection method is changed once in relation to the intake stroke during the switching transition period. After the fuel required for combustion is switched, the cylinders that are over-combusted once will have injection cut,
The method for controlling fuel injection of an internal combustion engine according to claim 1, wherein the cylinder having a half excess of one combustion is set to a half of the calculated pulse width. 4. The fuel injection method is switched from the cylinder simultaneous injection to the group injection method, and an injection pulse in the group injection method is required for one combustion in relation to the intake process during the switching transition period. 2. The fuel injection control method for an internal combustion engine according to claim 1, wherein the cylinder in which a certain amount of fuel is over half of one combustion after switching is set to half of the calculated pulse width.