JPS62247150A - Fuel controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform appropriate control and stable operation, by correcting the quantity of intake to an internal combustion engine in accordance with a prescribed correction formula in which the quantity of intake to the engine per unit time is included as an element, and by changing a constant in the formula depending on the state of the operation of the engine. CONSTITUTION:The t-th quantity Qa(t) of intake to an internal combustion engine 1 per unit time is calculated by a Qa(t) calculation means 20 in accordance with a formula Qa(t)=K.Qa(t-1)+(1-K).Qa where Qa, Qa(t-1) and K denote the result of the detection of the quantity of intake by a sensor 13, the (t-1)-th quantity of intake per unit time and a constant, respectively. The quantity of intake to the engine 1 for a prescribed crank angle thereof is calculated by an AN calculation means 21 on the basis of the calculated quantity Qa(t) of intake. The quantity of fuel to the engine 1 is regulated by a control means 22 on the basis of the output from the AN calculation means 21. The constant K is changed depending on the state of operation of the engine.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is an internal combustion engine that detects the intake air amount of an internal combustion engine using an intake air amount sensor, and controls the fuel supply amount of the internal combustion engine based on the detected output. This relates to an engine fuel control device.

[Conventional technology]

When performing fuel control of an internal combustion engine, an intake air flow sensor (hereinafter abbreviated as AFS) is placed upstream of the throttle valve,
Based on this information and the engine speed, the amount of intake air per intake is determined, and the amount of fuel to be supplied is controlled.

By the way, when trying to detect the intake air amount of an internal combustion engine by placing AFS'Ik upstream of the throttle valve in the air intake passage, when the throttle is suddenly opened,
Since the amount of air filled into the intake passage between the throttle valve and the engine is also measured, the amount of air that is filled into the intake passage between the throttle valve and the engine is measured more than the amount of air that is actually taken into the internal combustion engine, and if the amount of fuel is controlled, it will be over 17. A tool et-arose.

Conventionally, this method is based on the AFS output, that is, the detected intake air amount at a predetermined crank angle. AN(t), the amount of air taken into the internal combustion engine at the n-1st and nth times of a given crank angle are AN (n-1) and AN(n), respectively, and when the filter constant is K, AN(n ) ” KI X AN (n-1) + K
According to the formula s X AN(t)! l) AN(n) t-
There is a system that performs fuel control using this AN(rl)g, which smoothes the amount of intake air for each predetermined crank angle and performs appropriate fuel control.

[Problem that the invention seeks to solve]

However, in the above-mentioned conventional device, since the calculation of the air amount is delayed, the air-fuel ratio changes in a manner that increases the change in the rotational speed, for example, during idling. That is, in FIG. 8, (a)
is the rotational speed Ne, (b) is the intake pipe pressure, (C) is the drive pulse width of the injector 14, and cd) is the air-fuel ratio, %
When the rotational speed Ne changes, the pressure in the intake pipe 15 changes with a slight delay due to the influence of the volume of the intake pipe 15. The amount of air taken into the internal combustion engine 1 is proportional to the intake pipe pressure, and the number of revolutions Ne
If the correction according to the above formula is performed, the intake pipe pressure will be further delayed, and the pulse width signal of the injector 14 will also be delayed.
Delayed as shown. At this time, as shown in g, the air-fuel ratio changes to the rich side when the rotational speed Ne is high, and changes to the lean side when the rotational speed Ne is low. For this reason, due to the characteristics of the internal combustion engine 1 shown in FIG. 9, fluctuations in the rotational speed Ne are promoted, resulting in a problem that the operating state becomes extremely unstable.

This invention has been made to solve the above problems, and provides fuel control for an internal combustion engine that can appropriately control the air-fuel ratio even during transient fluctuations in the amount of intake air and provide a stable rotational speed. The purpose is to obtain equipment.

[Means for solving problems]

The fuel control device for an internal combustion engine according to the present invention provides a result k Qa obtained by the intake air amount sensor, and an intake air amount k Qa (t-1) of the internal combustion engine for the t-1st and tth times per unit time.
, Qa(t), if set as a constant, KQjt) =
K-Qa(t-x) + (1-K) ・Qmt) by the formula of Qa The amount of fuel to be supplied is controlled based on the output of the AN calculation means, and is changed depending on the constant Kt-operating conditions.

[For production]

In the fuel control device for an internal combustion engine according to the present invention, the constant K is changed depending on the operating conditions. For example, during idling operation, the value of K is reduced to reduce the delay in calculating the air amount, and the rotation speed is reduced. Stabilize operation by suppressing fluctuations in

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. By the way, Figure 3 shows the situation when the throttle valve is fully open, where (a) shows the opening of the throttle valve, and (b) shows the AF.
This is the intake air amount Qa passing through St, and overshoots. (C) is 1 t of intake air detected by AFS Qa t
The corrected intake air amount of the internal combustion engine obtained by performing filter processing and selecting ' as the filter constant Qtt)t-indicates (
d) shows the surge tank pressure Pt-.

FIG. 1 shows the configuration of a fuel control system for an internal combustion engine according to the present invention. Reference numeral 1 denotes an internal combustion engine, which has a volume of c per stroke, and which is connected via an AFS 13, a throttle valve 12, a surge tank 11, and an intake pipe 15. Air is sucked in by the injector 14, and fuel is supplied by the injector 14. Further, the volume from the throttle valve 12 to the internal combustion engine 1 is assumed to be t-V. 1
6 is an exhaust pipe.

Reference numeral 10 is a precautionary air cleaner arranged upstream of the AFS 13, and the AFS 13 generates pulses (for example, at a crank angle of 180 degrees from one pulse rise point to the next rise point) according to the amount of air taken into the internal combustion engine 1. ) is output. 20 Fi
Qn(t) calculation means, the result t obtained by AFS 13
Qa is the amount of air taken into the internal combustion engine at the pt-1st time and the tth time per unit time, respectively.

Qbet), Qa when the constant is K) = K・Qa(t-x) + (I K )
・Intake air amount Qa(t) corrected by Qa correction formula
Calculate.

Reference numeral 21 denotes an AN calculation means which receives the outputs of the Qa(t) calculation means 20 and the crank angle sensor 17, and calculates the amount of intake air for a predetermined crank angle. 22 is a control means;
The output of the ANN calculation waveform 21, the output of the water temperature sensor 18 (for example, a thermistor) that detects the cooling water temperature of the internal combustion engine 1, and the output of the idle switch 19 that detects the idle state M' correspond to the amount of air taken in by the internal combustion engine 1. to control the drive time of the injector 14, thereby controlling the internal combustion engine I
Controls the amount of fuel supplied.

FIG. 2 shows the specific structure of this embodiment, and 30 indicates A.
This control device receives output signals from the FS 13, the water temperature sensor 18, the idle switch 19, and the crank angle sensor 17, and controls the four injectors 14 provided for each cylinder of the internal combustion engine 1. Q in Figure 1 (t) corresponds to the calculation means 20 to the control equipment 22, and the RO
It is realized by a microcomputer (hereinafter abbreviated as CPU) 40 having an M41 and a RAM 42. Also, A
The output of FS 13 is connected to counter 33 and input P3 of CPU 40. 34 is an interface connected between the water temperature sensor 18 and the A/D converter 35;
1 is an interface connected between the idle switch 19 and the CPU 40; 36 is a waveform shaping circuit to which the output of the crank angle sensor 17 is input;
is input to the interrupt human power P4 and the counter 37. or,
38 is a timer connected to the interrupt power P5, 39 is an A/D converter that converts the voltage t)-iΦ (not shown) and outputs it to the CPU 40, and 43 is provided between the CPU 40 and the driver 44. With a timer, the output of the driver 44 is connected to each injector 14.

Next, the operation of the above configuration will be explained. The output of the AFS 13 is input to the counter 33. CPU40 is AFS13
The output is input to the interrupt input P3, and interrupt processing is performed every output noser cycle of the AFS 13, and the cycle of the counter 33 is measured. The output of the water temperature sensor 18 is connected to the interface 34
The voltage is converted into a voltage by the converter 35, and converted into a digital value at predetermined time intervals, and then taken into the CPU 40.

The output of the crank angle sensor 17 is inputted to the interrupt input P4 of the CPU 40 and the counter 37 via the waveform shaping circuit 36. The output of the idle switch 19 is input to the CPU 40 via the interface 31f. CPU40
performs interrupt processing every time the crank angle sensor 17 starts up,
The counter 37 measures the cycle between the rising and rising points of the crank angle sensor 17.
Detect from the output of The timer 38 activates the CPU every predetermined time.
An interrupt signal is generated to the interrupt manual P5 of 40. The A/D converter 39 A/D converts the battery voltage t (not shown), and the CPU 40 takes in data of this battery voltage at predetermined time intervals. The timer 43 is preset in the CPU 40,
The output capacitor (P2) of the CPU 40 is triggered to output a predetermined pulse width, and this output drives the injector 14 via the driver 44.

Next, the operation of the CPU 40 will be explained using flowcharts shown in FIG. 4 and FIGS. 6 and 7. First, Figure 4 shows the CPU 40
When a reset signal is input to the CPU 40, the RAM 42, input/output ports, etc. are initialized in step 100, the output of the water temperature sensor 18 is converted from t to A/D in step 101, and is stored in the RAM 42 as WT. do. In step 1.02 the battery voltage t-A
/D conversion and storage in the C'RAM 42 as VB. In step 103, 30/TR is calculated from the period TR of the crank angle sensor 17, and the rotational speed Nek is calculated. In step 105, the output frequency Fa of the AFS 13, which will be described later, is
J: j) Calculate the basic driving time conversion coefficient KP from f□ set for Fa as shown in FIG. In step 106, the correction is performed using the conversion coefficient Kpt-water temperature data WT and stored in the RAM 42 as the driving time conversion coefficient KI. In step 107, the battery voltage data VB is stored in a data table fst' stored in advance in the ROM 41.
The wasted time TDt is calculated and stored in the RAM 42. After the process in step 107, step 101 is performed again.
Repeat the process.

FIG. 6 shows the interrupt processing for the output signal of the interrupt P3, that is, the AFS 13. In step 201, the output TF of the counter 33 is detected and the counter 33 is cleared. This T
F is the pulse period of AFS13. In step 202, the calculation of 1/TF is performed, and the output frequency F of AFS 13 is
a is obtained. In step 203, idle switch 1
It is determined whether 9 is on or off, and if it is on, that is, in the idle state, Fit) = Ks · Fa (
t-z) + (I Km) ・FaO measurement is performed, and if the idle switch 19 is off, step 204
Proceed to F”a(t) = KloFa(t-1) +
(IKx) Perform all calculations of Fa. Kl>K4 and Fi
t) is the corrected intake air amount per unit time.

In addition, FIG. 7 shows that the output of the crank angle sensor 17 causes the CPU to
40 shows an interrupt process when an interrupt signal is generated in the interrupt signal P4. In step 301, the period between the rises of the crank angle sensor 17 is read from the counter 37, stored in the RAM 42 as the period TR, and the counter 37tl is cleared. In step 302, multiplication by Fa-TR is performed to calculate the amount of intake air for a given crank angle, that is, the load data AN. In step 303, the drive time data TI is converted from the load data AN1 drive time conversion coefficient and the wasted time TD.
=AN/K + TD is calculated, and in step 304 the drive time data is set in the Txt timer 43, and in step 3
By triggering the timer 43'lc) at 05, the data T
Four injectors 14 are driven simultaneously in response to I, and the interrupt processing is completed.

In the above embodiment, as described above, the value of K in the correction formula for the intake air amount of the internal combustion engine is made small during idling operation, thereby making it possible to reduce the lag in the intake air amount and shift the phase to the leading side. Can be done. For this reason, the pulse width signal is also on the leading side as shown in f, and the air-fuel ratio can be made thinner when Ne is high and richer when Ne is low, as shown in h, which promotes fluctuations in the rotational speed. A stable rotation speed can be obtained without any problems.

In the above embodiment, the idle state is determined by turning on and off the idle switch 190, but a rotation speed condition and a vehicle stop condition may be added to this. Alternatively, the rotation speed, load, gear ratio, etc. of the internal combustion engine 1 may be detected and the coefficient Kk may be further corrected.

〔Effect of the invention〕

As described above, according to the present invention, the intake air i' of the internal combustion engine is corrected based on the correction formula to obtain the correct intake air it, and proper air-fuel ratio control can be performed. Moreover, by changing the constant Kt in the correction formula according to the operating state, stable operation can be achieved even during idling operation.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a fuel control device according to the present invention, FIG. 2 is a block diagram showing a specific example of the fuel control device for the same internal combustion engine, and FIG. 3 is a block diagram showing a transient state of the internal combustion engine. 4, 6, and 7 are flow charts showing the operation of the fuel control device for an internal combustion engine according to an embodiment of the present invention, and FIG. 5 is a waveform diagram showing changes in the intake air amount. FIG. 8 is an operating waveform diagram of the device according to the present invention, and FIG. 9 is a characteristic diagram of the internal combustion engine. 1... Internal combustion engine, 12... Throttle valve, 13
... Air flow sensor (Karman vortex flowmeter), 14.
...Injector, 15...Intake pipe, 17...Crank angle sensor, 19...Idle switch, 20...
・Qjt) calculation means, 21...AN calculation means, 22.
...Control hand board. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) The intake air amount sensor is placed upstream of the throttle valve and detects the intake air amount of the internal combustion engine. Qa_(_t_-_
1_) and Qa_(_t_), where K is the constant, Qa_(_t_)=K・Qa_(_t_-_1_)+(
Qa_(_t_) calculating means for calculating Qa_(_t_) according to the formula of 1-K)・Qa, and the calculated Qa_(_t_
) for calculating the intake air amount per predetermined crank angle of the internal combustion engine, and a control means for controlling the amount of fuel supplied to the internal combustion engine based on the output of the AN calculation means, and a constant K as an operating condition. A fuel control device for an internal combustion engine, characterized in that the fuel control device changes the fuel accordingly. (2) The fuel control device for an internal combustion engine according to claim 1, wherein the constant K is made small during idling operation.