JPH0228695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine control method in which the amount of fuel supplied to the internal combustion engine is determined by the pressure and rotational speed of the intake pipe of the internal combustion engine.

In a system that calculates the amount of fuel supplied to an internal combustion engine based on intake pipe pressure and rotational speed, if part of the exhaust gas is recirculated to the intake side (hereinafter referred to as EGR),
Even if the intake pipe pressure and rotational speed are the same, the amount of air taken into the internal combustion engine changes depending on the amount of EGR. Therefore, it is necessary to correct the fuel supply amount calculated from the intake pipe pressure and rotational speed using this EGR amount.

As this correction method, since the amount of EGR is determined by each operating condition, this operating condition is determined by the intake pipe pressure and rotation speed, and the amount of fuel supplied at each intake pipe pressure and rotation speed when EGR control is performed. The correction parameters for are determined experimentally in advance, and these parameters are stored in the memory in the control device of the above system, and if EGR control is being performed,
It is conceivable to correct the fuel supply amount using the above parameters.

However, even under the same operating conditions, when the cooling water temperature is low, this EGR amount is reduced compared to when the water temperature is high, to improve the driving performance of the vehicle when it is cold.

Therefore, even under the same operating conditions, depending on the cooling water temperature,
Since the EGR amount changes, the fuel supply amount correction parameters no longer correspond to the intake pipe pressure and rotation speed.

This invention was made to solve the above-mentioned problems, and it is possible to calculate the amount of fuel supplied to the intake pipe pressure and rotation speed when the EGR amount is zero and when the cooling water temperature is high (for example, 70 degrees Celsius or higher). The first and second parameters for correction are interpolated with the third parameter that changes the EGR amount according to the cooling water temperature, the parameter for correcting the fuel supply amount when EGR is applied is corrected by the cooling water temperature, and the cooling water temperature is An object of the present invention is to provide a fuel control method for an internal combustion engine that can appropriately control the air-fuel ratio of the internal combustion engine even when the EGR amount changes.

Embodiments of the fuel control method for an internal combustion engine according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a fuel control device applied to one embodiment.

1 in FIG. 1 is an internal combustion engine. This internal combustion engine 1 is a four-stroke spark ignition internal combustion engine installed in an automobile, and is designed to take in combustion air through an air cleaner 11, an intake pipe 13, and a throttle valve 14.

Further, fuel is supplied to the intake pipe 13 from a fuel system (not shown).
The fuel is supplied through an electromagnetic injection valve (hereinafter referred to as an injector) 12 that is installed upstream of a throttle valve 14 that is provided midway through the injector.

An intake pipe 13 is located downstream of the throttle valve 14.
A pressure sensor 15 for detecting the pressure is connected. The pressure sensor 15 is, for example, a known semiconductor pressure sensor that converts the absolute pressure of the intake pipe 13 into voltage and outputs it.

Further, the water temperature sensor 16 detects the temperature of the cooling water of the internal combustion engine 1, and uses something like a thermistor whose resistance decreases as the temperature increases.

Further, the ignition coil 18 is adapted to supply high voltage to a spark plug (not shown) provided in each cylinder of the internal combustion engine 1.

On the other hand, 21 is an EGR control valve, and this EGR control valve 21 passes from the exhaust pipe 17 through the EGR input passage 25, through the EGR output passage 26, and then through the intake pipe 13.
The amount of exhaust gas sent downstream of the throttle valve 14 is controlled.

This EGR control valve 21 includes an EGR input passage 25,
A valve 27 connected to the EGR output passage 26, a diaphragm 30 connected to the valve 27,
A spring 31 that biases this diaphragm 30
The diaphragm 30 changes the lift amount of the valve 27 according to the increase or decrease of the negative pressure introduced into the negative pressure chamber 28, and the flow is returned from the exhaust pipe 17 to the intake pipe 13. It is designed to control the amount of exhaust gas released.

The position sensor 22 is connected to the valve 27 and is for detecting the lift amount of the valve 27.
Further, the negative pressure chamber 28 communicates with the upstream side of the throttle valve 14 of the intake pipe 13 via the atmospheric valve 23, and also communicates with the downstream side of the throttle valve 14 of the intake pipe 13 via the negative pressure valve 24. is connected to.

Therefore, by opening and closing the atmospheric valve 23 and the negative pressure valve 24, the pressure in the negative pressure chamber 28 is changed and the lift amount of the valve 27 is changed. The atmospheric valve 23 and the negative pressure valve 24 are connected by a pipe 29, and this pipe 29 communicates with the negative pressure chamber 28.

The control device 3 includes a pressure sensor 15 and a water temperature sensor 1.
6. Inputs signals from the position sensor 22, ignition coil 18, etc., controls the atmospheric valve 23, the negative pressure valve 24, controls the lift amount of the valve 27, controls the injector 12, and supplies it to the internal combustion engine 1. It controls the amount of fuel.

FIG. 2 is a block diagram showing the detailed configuration of this control device 3. As shown in FIG. In FIG. 2, a microcomputer 43 stores a control program and control data in a built-in ROM 44, and also has a built-in RAM 45 for temporarily storing data.

The low-pass filter 32 smoothes the output of the pressure sensor 15, the filter 33 removes noise from the output voltage of the position sensor 22, and the interface 34 converts resistance changes of the water temperature sensor 16 into voltage changes.

These low pass filters 32, filters 3
3. The output of the interface 34 is supplied to a multiplexer 35. The output of the multiplexer 35 is input to the AD converter 36, and the microcomputer 43 inputs the low-pass filter 3 through the multiplexer 35.
2. The outputs of the filter 33 and the interface 34 are sequentially selected, converted into digital codes by the AD converter 36, and taken in.

Further, the comparator 37 is connected to one of the ignition coils 18.
Convert the voltage of the next coil to a logic level signal, D
Flip-flop circuit 38 (hereinafter referred to as FF)
The output is supplied to the clock terminal C of the circuit.

The D terminal of FF38 is grounded, and the FF38
The output becomes "L" in synchronization with the ignition coil 18 generating a high voltage, and generates an interrupt signal to the first interrupt terminal of the microcomputer 43. H”.

The counter 40 is configured to count the "H" period of the output signal of the FF 38 using the oscillator 39 as a basic clock, and the output of the counter 40 is transferred to the microcomputer 43.

The timer 41 is configured to output an interrupt signal to the second interrupt terminal of the microcomputer 43 every 5 msec.

Further, the digital interface 42 converts signals from an idle switch, a start switch, etc. (not shown) into logic level signals, and outputs the signals to the microcomputer 43.

Each of the timers 46 to 48 counts the output signal of the oscillator 49, starts counting down the numerical value set by the microcomputer 43 in response to a trigger signal from this microcomputer 43, and after this trigger signal is input, the count value reaches zero. A signal at the "H" level is output until the time when the "H" level signal is reached.

The outputs of timers 46 to 48 are each output to driver 5.
It is designed to be output from 0 to 52. The driver 50 is connected to the injector 12, the driver 51 is connected to the atmospheric valve 23, and the driver 52 is connected to the atmospheric valve 23.
are connected to the negative pressure valve 24, and the timer 4 is connected to the negative pressure valve 24, respectively.
The connected loads are driven while the outputs 6 to 48 are at the "H" level.

Next, a fuel control method for an internal combustion engine according to the present invention will be explained. The microcomputer 43 is the first
When an interrupt signal from the FF 38 is input to the interrupt terminal of the FF 38, this FF 38 is cleared, a trigger signal is output to the timer 46, and the injector 12 is opened for the time set in advance to the timer 46. , the value of the counter 40, that is, the internal combustion engine 3
The ignition period τ is read and stored in the RAM 45.

In addition, the microcomputer 43 has a timer 41.
When an interrupt signal is input to the second interrupt terminal every 5 msec, the output of the pressure sensor 15 input via the low-pass filter 32, the output of the position sensor 22 input via the filter 33, and the interface Water temperature sensor 16 input via Ace 34
The outputs of are sequentially converted into digital values by the AD converter 36 through the multiplexer 35, and are used as data for the intake pipe pressure P, the valve lift L of the valve 27 of the EGR control valve 21, and the cooling water temperature W, respectively.
Store in RAM45.

Next, every time the interrupt signal every 5 msec is input five times, that is, every 25 msec, the RAM 4 is
Compare the target valve lift L ₀ stored in 5 with the above valve lift L, and calculate this deviation △L as △L=
Let L ₀ −L, and if the deviation △L≧α, set the value of (△L×G1) to the timer 48, and set the value of (△L×G1) to the timer 48.
8, the negative pressure valve 24 is opened, the negative pressure chamber 28 and the downstream side of the throttle valve 14 of the intake pipe 13 are communicated for a predetermined time, and the valve 27 is opened.
moves in the opening direction.

If the deviation △L is △L<-α, the timer 47 is set to a value of (|△L｜×G2), and the timer 47 is triggered.
is opened, the negative pressure chamber 28 and the upstream side of the throttle valve 14 of the intake pipe 13 communicate for a predetermined time, and the valve 27 moves in the closing direction.

Therefore, the valve 27 is feedback-controlled by the control device 3 so as to match the target valve lift.

FIG. 3 is a flowchart showing the calculation of the target valve lift L ₀ and the drive time of the injector 12. When the control device 3 is powered on, the data in the RAM 45 and the timer 4 are stored in step 100.
Initialize 6 to 48 etc.

In step 101, M<τ is calculated from the constant M at the ignition period τ, and the rotational speed N of the internal combustion engine 1 is determined.

In step 102, a target valve lift L ₀ for controlling valve 27 is calculated. The target valve lift L ₀ is determined by using the intake pipe pressure P and rotational speed N as parameters as shown in Fig. 4, and the basic target valve lift C _ij stored in the ROM 44 and the cooling water temperature W as shown in Fig. 5. as a parameter,
Using the water temperature correction coefficient K, which is the third parameter stored in the ROM 44, L ₀ =C _ij ×K is calculated and stored in the RAM 45.

Assuming that the intake pipe pressure is P2, the rotational speed is _N2 , and the water temperature is _W2 , _L0 = _C22 × _K2 .

In addition, in the case of water temperature W ₃ , L ₀ = C ₂₂ × 1.0 = C ₂₂ , and even if the intake pipe pressure and rotation speed are the same, the target valve lift L ₀ changes depending on the water temperature. The amount of exhaust gas flowing back into the pipe 13 also changes.

In step 103, the intake pipe pressure P shown in FIG.
Valve 27 stored in ROM 44 at rotation speed N
When the first parameter A _ij that corrects the drive time of the injector 12 when the valve is fully closed and the lift amount of the valve 27 are water temperature correction coefficient K = 1.0, that is, the target valve lift L ₀ =C _ij is feedback-controlled. In order to correct the driving time _of the injector 12 when , H=A _ij −(A _ij −B _ij )×K. Here, it is assumed that A _ij ≧B _ij .

In step 104, the driving time T of the injector 12 is calculated from T=P×H. step 105
Then, the drive time τ is set in the timer 46, and the process returns to step 101.

Therefore, when the cooling water temperature W is higher than W3, the water temperature correction coefficient K = 1.0, so the above correction coefficient H = B _ij
However, when the cooling water temperature W is below W3, the correction coefficient H is also corrected according to the cooling water temperature W as the target valve lift L ₀ becomes smaller according to the cooling water temperature W.

As described above, according to the fuel control method for an internal combustion engine of the present invention, the first control method for correcting the fuel supply amount with respect to the intake pipe pressure and rotation speed when the ERG is zero and when the cooling water temperature is high, respectively. , second
The parameter is interpolated with the third parameter that changes the EGR amount according to the cooling water temperature, and the parameter that corrects the fuel supply amount when EGR is applied is corrected by the cooling water temperature, so the same intake pipe pressure and rotation Even if the valve lift is changed depending on the cooling water temperature and the EGR amount is reduced at low temperatures,
The injector drive time is corrected according to the lift correction rate based on the cooling water temperature, and if the EGR amount is small, the drive time is lengthened even at the same intake pipe pressure and rotation speed, and the EGR amount is changed depending on the cooling water temperature. It is also possible to optimize the air-fuel ratio of the internal combustion engine.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a fuel control device for an internal combustion engine applied to an embodiment of the fuel control method for an internal combustion engine according to the present invention, and FIG. 2 is a diagram showing a control device in the fuel control device for an internal combustion engine shown in FIG. Fig. 3 is a flowchart showing the microcomputer processing in the control device shown in Fig. 2, and Fig. 4 shows the basic target stored in the ROM using intake pipe pressure and rotation speed as parameters. FIG. 5 is a diagram showing the valve lift, FIG. 5 is a diagram showing the water temperature correction coefficient stored in the ROM using the cooling water temperature as a parameter, and FIGS. 6 and 7 are diagrams showing the injector in the fuel control system of the internal combustion engine shown in FIG. It is a figure showing the correction coefficient of drive time. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 3... Control device, 11... Air cleaner, 12... Injector, 13... Intake pipe, 14... Throttle valve, 15... Pressure sensor, 16... Water temperature sensor, 17... Exhaust pipe,
18...Ignition coil, 21...EGR control valve, 2
2...Position sensor, 23...Atmospheric valve, 24...
... Negative pressure valve, 28 ... Negative pressure chamber, 35 ... Multiplexer, 38 ... D flip-flop circuit,
39, 49...Oscillator, 40...Counter, 41
~48...Timer, 43...Microcomputer, 44...ROM, 45...RAM. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Detecting the pressure in the intake pipe of the internal combustion engine with a pressure sensor, detecting the rotation speed of the internal combustion engine with a rotation speed detection means, and supplying fuel to the internal combustion engine with a fuel supply means provided in the middle of the intake pipe. The cooling water temperature of the internal combustion engine is detected by the water temperature sensor, and the control device controls the fuel supply means based on the outputs of the pressure sensor and rotation speed detection means, and a part of the exhaust gas of the internal combustion engine is controlled. The amount of recirculation to the intake pipe is controlled by a recirculation amount control means according to the operating state of the internal combustion engine, and the pressure sensor and the rotation speed are adjusted respectively when the amount of recirculation is zero and when the cooling water temperature is high. The first and second parameters are set by the output of the detection means, the third parameter is set by the output of the water temperature sensor, and the first, second, and third parameters are stored in a memory in the control device. A fuel control method for an internal combustion engine, characterized in that the recirculation amount is corrected by a third parameter, and the fuel supply amount is corrected according to the first, second, and third parameters.