JPS59196933A - Air-fuel ratio controlling apparatus for internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable to correct deviation of the air-fuel ratio from a preset value within a short while when the operational conditions of an engine are changed drastically, by varying the time constant of O2-feedback control in case that the rate of change in the operational conditions of the engine is greater than a prescribed value. CONSTITUTION:The rate of change in the flow rate of intake air is detected once per one rotation of an engine by a means 10 for detecting the rate of change in the flow rate of intake air. When the rate of change in the flow rate of intake air exceeds a prescribed value, the time constant of O2-feedback control using the output signal of an O2-sensor 3 is varied. By employing such a method, deviation of the air-fuel ratio from an aimed value caused when the operational conditions of an engine are changed drastically can be corrected within a short while.

Description

Detailed Description of the Invention (Technical Field) This invention relates to the air-fuel ratio (mixture ratio of air and fuel) of an internal combustion engine.
Regarding a control device.

(Background Art) As a conventional air-fuel ratio control device for an internal combustion engine, for example, a first
There is something like the one shown in the figure. 1 is an air flow meter that detects the flow rate of intake air taken into the engine, 2 is a rotation speed detector that detects the engine rotation speed, and 3 is a reed in the exhaust gas passage of the engine that outputs according to the oxygen concentration in the exhaust gas. 0□ sensor whose voltage changes and outputs a signal according to the air-fuel ratio, 4 is the engine's crankshaft at the firing interval (18
00. A reference signal generator that generates a signal every 120° for a 4-cycle 6-cylinder engine, 5 a control circuit that inputs the various signals mentioned above, calculates the entire amount of fuel injection (injection time), and outputs it; 6 a control circuit that outputs the fuel injection amount (injection time); A transistor that controls the H close of the injector 7 according to the injection amount, 7 is an injector (fuel injection valve) attached to the innotech muff hold near the intake valve of each cylinder of the engine, 81-1: battery be.

FIG. 2 is a flowchart showing the operation of the conventional air-fuel ratio control device shown in FIG. This processing routine is processed once per engine revolution.

First, in step 11, the control circuit 5 calculates the engine speed N, the output Q of the air flow meter, and the output 02 of the air flow meter.
Read. Next, in step 12, the control circuit 5 calculates 1 for the basic fuel injection amount 'L', .

However, K1 is a constant. Next, in step 13, 02
Compare the output 02 of the sensor 3 and the predetermined value ■(2.02
If >K2, proceed to step 14; if 02≦2, proceed to step 17. Here, F is a flag, F-1 indicates that it was 02>K2 last time (one rotation ago), and F-
0u indicates that O7≦ last time. In Step 4, first check flag Ii"2.F-
When it is 0 (previously (-)2≦2), step 1
Proceed to step 6, set Ii”-1, and α=α-P. Here, α is the feedback control variable determined by the 02 sensor,
P is a time constant. I? When the value is -1, the process proceeds to step 15 and α=α−■ is set. Here ■ is a time constant. On the other hand, in step 17, flag F is checked similarly to step 14. When F=1, proceed to step 19 and p
= 0, α = α + P, and when F = 0, step 18
Proceed to and set α=α+1.

Figures 3(a), 3(b) and 3(c) show the changes in the output of the 02 sensor, 77F, and the feedback control variable α, respectively.

Step 20: Calculate the actual fuel injection amount T2=T,xα using the feedback control variable α obtained in this way.
), the result is output to an output register (not shown), step 21), and the process ends. The output register is composed of a register, a counter, and a comparator, and controls the injector 7 to open for a time corresponding to the value of the register (fuel injection amount T2).

However, in such conventional air-fuel ratio control devices, the time constants P and ■ are kept constant regardless of the engine operating conditions, so when the operating conditions suddenly change due to an error in the air chromator, etc. There is a problem in that it takes time to correct the deviation of the air-fuel ratio from the target value, which adversely affects exhaust performance. An example of this is shown in FIG.

When the vehicle speed suddenly changes as shown in (a) of the same figure, the output of the air chromator will change to the value shown by the broken line in (b) of the same figure relative to the true value, and the feedback control variable α will change as shown in (C) of the same figure. It takes the value shown in . As a result, the air-fuel ratio is the same as the target value (d
) In region A, the air-fuel ratio becomes rich and the emission of Co and )(C becomes constant, and in region B, the air-fuel ratio becomes lean and the emission of NQx becomes constant.

(Objective of the Invention) This invention was made by focusing on such conventional problems, and detects a sudden change in the operating state, and when this is detected, increases the rate of change of the feedback control variable α. The purpose of this invention is to solve the above problems by reducing the total time required to correct the deviation of the air-fuel ratio from the target value.

(Structure and operation of the invention) The present invention will be explained below based on the drawings. FIG. 5 is a diagram showing an embodiment of the present invention. ′=! To explain the configuration, 1 is an air flow meter, 2 is a rotation speed detector, 3 is an O2 safety valve, 4 is a reference signal generator, 5 is a control circuit, 6 is a transistor, 7 is an injector, 8 is a battery, 10
is an intake air flow rate variation width detector. Here, the intake air flow rate change width detector is a characteristic part of the present invention, and inputs each output signal of the reference signal generator 4 and the air flow meter 1, and
In the flowchart shown in the figure, the change in intake air flow rate Q ft
This is a device that detects dQ. In Fig. 6, the output Q of the airflow meter is read by r per engine revolution (step 30), and the difference dQ between this current value Q and the previous value Q' is
Step 3]), and outputs this difference dQ to the control circuit 5. In this embodiment, as described above, a sudden change in the operating state is detected based on a change in the intake air flow rate.

Next, the operation will be explained using the flowchart shown in FIG.

First, in step 40, the control circuit 5 calculates the engine rotation speed N-2 based on the detection signal from the rotation speed detector 2, and also calculates the intake air flow rate Q from the air flow meter 1, the output signal 02 from the 02 sensor 3, and the intake Air flow rate change width detector 1
The amount of change dQ in the intake air flow rate from 0 is read. Next, in step 41, flag FO is checked. Here, the flag i"0 is the absolute value of dQ 1 and dQl is 3 to the predetermined value.
It is a flag to judge whether or not it exceeds 1dQ1>K3, and then it becomes 1 when 1dQ1>K3, and then 2 is set to 2 to the output of O, SE/S3 or the predetermined value.
It becomes O when it passes twice. The broken color is used to reset the flag FOf, (O as described above, and the counter value changes from 2 to 1 to 0 when the output of the sensor passes through 2 to a predetermined value. , the flag FO-0 is set at counter 0. If PO=0 in step 41, the process advances to step 42, and it is determined whether 1dQl>K. If 1dQl<Ig, the process advances to step 47. ,
Calculate the basic injection amount T1. 1dQl>Igu.

If so, it is determined that the operating condition has suddenly changed, and the process proceeds to step 43.
Set FO=1 and set the color/color value to 2,
Proceed to step 46. On the other hand, if it is FO-1 in step 41, the process proceeds to step 44, where it is determined whether or not the counter value is O. If the counter value is not O (counter value O), the process proceeds to step 46, where the time constant ■:= Set L and proceed to step 47. If the cow tie is O (counter 0), step.

The process proceeds to step 45, where the time constant is set to l-11 and FO-0, and the process proceeds to step 47. Furthermore, ■1 and ■2 are l2)I,
There is a relationship between In step 47, the control circuit 5 calculates the basic fuel injection amount T1 - bone K. Next, in step 48,
0, the output value 02 of the sensor 3 is compared with a predetermined value 2.

02) If K2, proceed to step 49; if 02≦2, proceed to step 52. In step 49, the flag F
is checked, and when p=1, α=α−■ is set (step 50), and when p=o, F=1 and α=α−P are set, and the counter value is decremented by 1 (step 51). Similarly, in step 52, all flags lit are checked, and p=Q
If α=α+■ binding (step 53), if do-1, 1F=o, α=α+P, and the counter value is decremented by 1 (step 54). Using the feedback control variable α obtained in this way, the actual fuel injection amount T is determined in step 55.
2-T□×α is calculated and outputted to the output register provided in the control circuit 5 to complete the process. As mentioned above, the output register is composed of a register, a counter, and a comparator, and the output register is a comparator that compares the fuel injection amount T2 written in the register with the counter value of the counter that starts counting clock pulses at the same time as this writing. Compare the two and turn on transistor 6 until the two match, and then turn on injector 7.
Open the door.

Figure 8 shows the same change in vehicle speed as in Figure 4 (a) (Figure 8 (a)
): shows changes in the flag FO value ((existed in the figure)), the feedback control variable α ((C) in the figure), and the air-fuel ratio ((d) in the figure). As is clear from the figure (d), it can be seen that the deviation of the air-fuel ratio from the target value is corrected in an extremely short time.

(Effects of the Invention) As explained above, according to the present invention, it is possible to correct the deviation of the air-fuel ratio from the target value in a short period of time when the operating condition suddenly changes, and the exhaust performance is not adversely affected. You can get the effect of becoming.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional air-fuel ratio control device, Fig. 2 is a flowchart showing the operation of the device, and Fig. 3 shows the relationship between the output value of the 02 sensor, the value of flag F, and the feedback control variable α with respect to the target value. FIG. 4 is a diagram showing the relationship between vehicle speed, airflow meter output, α, and air-fuel ratio in a conventional device; FIG. 5 is a block diagram showing an embodiment of the present invention; FIG.
The figure shows an intake air flow rate variation width detector 1 in the device shown in Figure 5.
7 is a flowchart showing the operation of the device shown in FIG. 5, and FIG. 8 is a diagram showing the relationship between vehicle speed, flag PO, α, and air-fuel ratio in the device shown in FIG. be. 1- Air flow meter 2... Rotation speed detector 3...
・02 sensor 4・・Reference signal generator 5・・Control circuit 6・・Transistor 7・・・Injector 8・・Battery 10・・Intake air flow rate variation width detector N・・Engine rotation speed Q・・Intake air flow rate 02・
・・O2 output value T□・・・Basic fuel injection amount T
2.Actual fuel injection amount K□, K2. K3-・Constant P, I, I,, I2...Time constant F, FO...Flag α...Feedback control variable #/Figure rod, 2

Claims (2)

[Claims] (1) Detect the engine rotation speed N and the intake air flow rate Q, calculate the basic fuel injection amount T, -N (K is a constant), and detect the exhaust gas components of the engine and calculate the detected value. Air-fuel ratio control for an internal combustion engine in which a feedback control variable α is calculated using a predetermined time constant according to The device has means for detecting the amount of change in the operating state, and compares the amount of change with a predetermined value, and when the amount of change exceeds the predetermined value, changes the time constant, and when the amount does not exceed the predetermined value. An air-fuel ratio control device for an internal combustion engine, characterized in that the α is calculated using a time constant. (2) The air-fuel ratio control device according to claim 1, wherein the amount of change in the operating state is determined according to a change in intake air flow rate.