JPH0246777B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection amount control method for an internal combustion engine, and more specifically to a fuel injection amount control method during acceleration of an internal combustion engine equipped with an electronically controlled fuel injection device.

Conventional internal combustion engines equipped with electronically controlled fuel injection devices have the disadvantage that the air-fuel ratio temporarily becomes overrich compared to the stoichiometric air-fuel ratio during the initial stage of acceleration, resulting in poor exhaust gas fuel efficiency. This is because the intake air to each cylinder of the engine is delayed due to inertia.
As a result, a difference occurs between the engine rotational speed and the injection timing of the fuel calculated by the air flow meter and injected from the injector.

As a countermeasure to this problem, fuel injection time has conventionally been determined using a value calculated based on the change in Tp. However, during the early stages of rapid acceleration when Tp changes significantly, the engine became overlean, causing misfires and other problems that caused the engine to stagnate. As a countermeasure against this problem, it has been devised to perform fuel injection at the set value when the calculated value is less than the set value.

However, this control method has the disadvantage that the supplied air-fuel ratio becomes overrich immediately after the start of acceleration, and that measures against overrichness during acceleration are not sufficiently taken. Furthermore, as described in JP-A-54-58138 and JP-A-54-111015, it is possible to delay the acceleration increase by a predetermined period of time, but even if this method is adopted as is, the acceleration Sometimes it is impossible to prevent the air-fuel ratio from becoming overrich.

An object of the present invention is to provide a fuel injection amount control method for an internal combustion engine that prevents the air-fuel ratio from becoming overrich during acceleration and improves fuel efficiency.

In order to achieve the above object, the present invention calculates a fuel injection amount based on an output value of an intake air amount detector disposed upstream of an intake system of an internal combustion engine, and uses the fuel injection amount to control the internal combustion engine. A fuel injection amount control method for an internal combustion engine that controls the fuel injection amount of an internal combustion engine, in which the fuel injection amount is increased after the engine has rotated a predetermined number of times after the start of acceleration. .

Embodiments of the present invention will be described below based on the drawings. Figure 1 shows the overall configuration of the engine system, in which 1 is the engine, 2 is the air cleaner, 3 is the throttle chamber, 4 is the intake manifold that sends air to each cylinder, and 6 is the engine. Exhaust pipe 17 transports exhaust gas in each cylinder.
16 is a three-way catalyst. Here, by operating an accelerator pedal (not shown), the opening degree of the throttle valve 5 provided in the throttle chamber 3 is controlled, and thereby the air cleaner 2 is transferred to the engine 1.
The amount of air supplied to each cylinder is controlled. The throttle valve 5 has a throttle sensor 15 that detects whether the throttle valve 5 is fully closed or not, that is, whether the engine is in an idling state.
is provided, and the detection output of the throttle sensor 15 is input to the control circuit 14. When the throttle valve 5 is in the fully closed state, the throttle sensor 15 is in the ON state.

The amount of air controlled by opening and closing the throttle valve 5 is measured by an air flow meter 7 provided upstream of the throttle valve 5 in the throttle chamber 3, and its detection signal is sent to the control circuit 1.
4 is input.

Furthermore, an O ₂ sensor 8 for detecting the residual oxygen concentration in the exhaust gas is provided near the outlet of the exhaust manifold 6. Based on the detection signal of the O ₂ sensor, the air amount detection signal, etc., the control circuit 14 performs various operations. The amount of fuel to be injected so that the air-fuel ratio supplied in the cylinder becomes the optimum air-fuel ratio according to the operating state of the engine is calculated, and the amount of fuel is injected into the injector 20 installed near the inlet of each cylinder of the engine 1 at a predetermined timing for a predetermined period of time. , outputs a control signal for injecting fuel. Further, 12 is an ignition circuit that sends an ignition signal to the ignition plug provided in each cylinder via the distributor 11, and an ignition coil primary signal 13 is inputted from the ignition circuit 12 to the control circuit 14. And this ignition coil primary signal is the control circuit 1
4, it is processed as an engine speed signal and used as basic information in various engine controls including air-fuel ratio control.

Furthermore, 9 is a water temperature sensor that detects the engine cooling water temperature, and 10 is an intake air temperature sensor that detects the temperature of intake air.The detection outputs of these sensors are also taken into the control circuit 14 and used for fuel injection control.

Note that the fuel supply system is not the main point of the present invention, so a description thereof will be omitted.

Next, FIG. 2 shows a specific configuration of the control circuit 14. In the same figure, 30 is a frequency dividing circuit, and the frequency dividing circuit 30 takes in the ignition primary signal 13 and divides it at a predetermined frequency dividing ratio. A pulse signal is output to the basic injection amount calculation circuit 40.

The basic injection amount calculation circuit 40 outputs a basic injection pulse Tp with a pulse width based on the air amount detection signal from the air flow meter 7 to the injection amount correction circuit 50 via the diode 25 at the timing of the pulse signal of the frequency dividing circuit 30. At the same time, it is output to the interrupt control section 52 in the microcomputer 60. The injection amount correction circuit 50 takes in the detection outputs of the water temperature sensor 9 and the intake temperature sensor 10 and the air-fuel ratio correction signal 29 output from the microcomputer 60, and changes the pulse width of the basic injection pulse Tp based on these signals. The injector drive pulse Ti is outputted to the output transistor 24 via the OR gate 23.

Collector and battery of output transistor 24
A current adjustment resistor 22 and a parallel circuit of a solenoid 20A that controls the injection valve of the injector 20 provided in each cylinder are connected in series between the _VB and the injector drive pulse Ti. 24, an excitation current flows through the solenoid 20A of each injector 20, and as a result, the valve opening time of the injector 20 (pulse Ti
In other words, the fuel injection amount is controlled.

Further, the injection amount correction circuit 50 is configured to receive a basic injection pulse cut signal 27, and fuel cut is performed based on this signal 27. Furthermore, an injection amount increase pulse 28 for increasing the fuel injection amount asynchronously with the injector drive pulse Ti is input to the OR gate 23 under specific operating conditions of the engine (for example, during acceleration, idling, etc.). And basic injection pulse cut signal 27
and the injection amount increase pulse 28 are both outputted from a digital output port 58 within the microcomputer 60.

Next, the configuration of the microcomputer 60 will be explained.

42 is a central processing unit (CPU) that performs digital calculation processing related to air-fuel control.
44 is a readable and writable memory element (RAM), and 46 is a memory element (ROM) for storing control programs such as an air-fuel ratio control program and fixed data. Also 4
A timer 8 measures the activation cycle of the interrupt processing program. 52 accepts various interrupts, outputs an interrupt signal to the CPU 42 via the bus line 70, and outputs the basic injection pulse Tp.
This is an interrupt control unit that takes in the basic injection pulse and monitors the rising and falling points of the basic injection pulse. 54 is a digital input port that takes in the detection outputs of various sensors that output digital signals, and this digital input port 54 includes an O ₂ sensor 8 that detects the residual oxygen concentration in exhaust gas and an open/close state of the throttle valve 5. a throttle sensor 15 for detecting the starting state of the engine, and a starter switch 1 for detecting the starting state of the engine.
8. The detection outputs of the clutch switch 19, which detects the depressed state of the clutch, and the shift switch 33, which detects the switching state of the transmission, are input.

Furthermore, 56 is an A/D converter, and the A/D
The detection outputs of the air flow meter 7 and the water temperature sensor 9, which output analog signals, are taken into the converter 56 and converted into digital signals. Reference numeral 58 denotes a digital output port for outputting a digital control signal, and the basic injection pulse 27 and the injection amount increase pulse 28 are outputted from the digital output port 58 as described above. 62 is a D/A converter that outputs an analog control signal;
The converter 62 outputs the air-fuel ratio correction signal 2 described above.
9 is output.

In this way, the input interface 80 composed of the digital input port 54, the digital output port 58, the A/D converter 56, and the D/A converter 62 takes in the detection outputs of various sensors and sends them via the bus line 70. CPU4
At the same time, the CPU 42 performs arithmetic processing based on the control program stored in the ROM 46, and then outputs the control signal to the outside from the digital output port 58 and the D/A converter 62.

Next, an embodiment of the fuel injection amount control method for an internal combustion engine according to the present invention will be described based on FIGS. 3 and 4. FIG. 3 shows the processing contents of the fuel injection control routine.
The basic injection time Tp is taken in. Step 11
At 0, the injection time Tpmax is calculated. That is,
If the current basic injection time is Tp, the previous basic injection time is Tm _-1 , and the average basic injection time is Tm, then Tm=3Tm _-1 +Tp/4...(1) Tpmax=Tm×1.25...(2), Tpmax is calculated from equations (1) and (2). Then, in step 112, the injection time Tpmax is set in the register in the RAM 44. Further, in step 114, after the start of acceleration, it is determined whether the engine rotation speed is within a predetermined value (for example, within 3 rotations).
Here, FIG. 4 shows the fuel injection control characteristics during acceleration, and in the same figure, the curve ABCDE is a plot of the injection time Tpmax obtained in step 110 against the engine rotation speed R _E , and the curve ABCDE is the one plotted in this figure. In the embodiment, fuel injection amount control is performed as shown by the curve ABGDE. In addition, the curve ABFGDE is the conventional control characteristic, T _REF is the reference value of the fuel injection time predetermined so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio at the beginning of acceleration, and Ro is the reference value for the fuel injection time at the start of acceleration, R ₁ ,
R ₂ is the elapsed number of engine rotations at C and D.

After starting acceleration in step 114, if it is determined that the engine speed is within a predetermined value (R ₀ ≦R _E ≦R ₁ ), the process moves to step 118 , and the injection time Tpmax is set at the digital output port 58 . The output register is set, and the task ends at the next step 124. On the other hand, if it is determined in step 114 that the acceleration is not within the predetermined value ( _RE > R ₁ ) from the start of acceleration (point B), the process moves to step 116, where the value is set in the register in the RAM 44 in step 112. A comparison is made between the injection time Tpmax and the previously described reference value. Step 11
If it is determined in step 6 that Tpmax>T _REF , the process moves to step 118, and the same processing as described above is performed.

If it is determined in step 116 that Tpmax≦T _REF , the process moves to step 120, in which T _REF is set as Tpmax in the output register in the digital output port 58, and in the next step 124, the task is Execution ends.

As explained above, according to the present invention, since the fuel injection amount is increased after the engine has rotated to a predetermined value after the start of acceleration, it is possible to prevent the air-fuel ratio from becoming overrich during acceleration, thereby improving fuel efficiency. It becomes possible to contribute.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the engine system, Fig. 2 is a block diagram showing the specific configuration of the control circuit 14, Fig. 3 is a flowchart showing the processing contents of the fuel injection control routine, and Fig. 4 is a flowchart showing the processing contents during acceleration. FIG. 3 is a diagram showing fuel injection control characteristics. 1...Engine, 7...Air flow meter, 2
0...Injector, 40...Basic injection amount calculation circuit, 42...CPU, 44...RAM, 46...
ROM, 58...Digital output port.

Claims (1)

[Claims] 1. A fuel for an internal combustion engine that calculates the fuel injection amount based on the output value of an intake air amount detector disposed upstream of the intake system of the internal combustion engine, and controls the fuel injection amount of the internal combustion engine using the fuel injection amount. In the injection amount control method,
1. A method for controlling a fuel injection amount for an internal combustion engine, comprising increasing the fuel injection amount after the engine rotates a predetermined value after acceleration starts.