JPS62195433A - Air-fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To prevent fluctuation of a feedback control factor due to failure in ignition, noise for stabilization, by a method wherein, in device which feedback-controls an air-fuel ratio, when a change in an output from an air-fuel ratio sensor exceeds a given value, the differential component of a feedback control factor is corrected to a low value. CONSTITUTION:An air-fuel ratio feedback control factor computing means 9 compares an output Vr from a reference value computing means 8, computing a reference value based on the detecting value of an operating state detecting means 7, with a detecting signal Vs from an air-fuel ratio sensor 13 located in an exhaust gas passage 12. A differential component correcting means 10 is connected to the air-fuel ratio feedback control factor computing means 9, and when the degree of a change in a deviation signal provided resulting from comparison of the reference value Vr with the detecting signal Vs from an O2 sensor exceeds a set value, it is decided to be caused by failure in ignition, noise, a differential component in computation of an air-fuel ratio feedback control factor is corrected to a low value by the differential component correcting means 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention calculates the fuel injection amount according to the operating state of the engine, and feedback-corrects the fuel injection amount according to the detection signal of the air-fuel ratio sensor. This invention relates to an air-fuel ratio control device for an engine.

(Prior art) Conventionally, in engine air-fuel ratio control, in order to improve the control accuracy of the supplied air-fuel ratio, the supplied air-fuel ratio is detected by an air-fuel ratio sensor, this detected air-fuel ratio is compared with a target air-fuel ratio, and the A technique is known in which the fuel injection 11 Flffi is feedback-corrected so that the supplied air-fuel ratio becomes the target air-fuel ratio according to the deviation. In particular, a lean sensor that generates an output signal approximately proportional to the exhaust gas oxygen concentration is used as the air-fuel ratio sensor, and the output of this lean sensor is compared with a reference value corresponding to the target air-fuel ratio, and the difference is determined according to the difference. A known technique is to perform feedback control even when the air-fuel ratio is in a region leaner than the stoichiometric air-fuel ratio, thereby improving fuel efficiency.

Further, when performing feedback correction based on the air-fuel ratio sensor output, there is a technique in which a feedback signal is obtained by PAD control.
No. 14823. Above P
ID control compares the air-fuel ratio sensor output and the MQ value corresponding to the target air-fuel ratio, adds or subtracts Pffi (proportional component) at the time of reversal when the magnitude relationship between the two changes, and also adds or subtracts Pffi (proportional component) to increase or decrease the minute ΔI value. (integral component) is added or subtracted until the next reversal, and a feedback signal is calculated by adding or subtracting the D value (@minute component) according to the degree of change in the deviation between the air-fuel ratio sensor output and the reference value. This is to control the air-fuel ratio so that it quickly matches the target air-fuel ratio.

Therefore, when obtaining a feedback signal that includes a differential component of a signal corresponding to the output of the air-fuel ratio sensor as described above, the degree of change in the feedback signal is determined depending on the magnitude of the change in the air-fuel ratio sensor output. By changing
This improves responsiveness, but on the other hand, if the air-fuel ratio sensor output suddenly changes due to abnormal signals such as noise or misfire, the D value of the differential component becomes a crowded control value due to the influence, and temporarily Therefore, the air-fuel ratio may be controlled to a target value that deviates significantly from the target air-fuel ratio, resulting in a wide range of air-fuel ratio fluctuations.

That is, for example, if a misfire condition occurs in the engine,
The oxygen concentration in the exhaust gas temporarily increases, and the output of the air-fuel ratio sensor detects a significant lean, and a feedback signal containing a differential component corresponding to this output rapidly enriches the air-fuel ratio. It is a matter of fact,
This causes a decrease in control accuracy.

(Object of the Invention) In view of the above-mentioned circumstances, the present invention provides feedback control that includes a differential component of a signal corresponding to the output of an air-fuel ratio sensor, and eliminates the effects of air-fuel ratio fluctuations that do not correspond to operating conditions such as misfires and noise. It is an object of the present invention to provide an air-fuel ratio control device for an engine that performs feedback control with good responsiveness without being affected.

(Structure of the Invention) The air-fuel ratio control device of the present invention includes a basic injection amount calculation means for calculating a basic injection level according to the operating state, and a feedback coefficient including a differential component of a signal corresponding to the output of an air-fuel ratio sensor. feedback coefficient calculation means to obtain; differential component correction means for correcting the differential component of the feedback coefficient to a small value when a change in the signal corresponding to the output of the air-fuel ratio sensor is larger than a predetermined value; and the basic injection amount and the feedback coefficient. The present invention is characterized by comprising a final injection 9A period calculation means for determining the final injection amount tA using the following.

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the present invention. Injector 3 installed in intake passage 2 of engine 1
An air-fuel ratio adjusting means 4 is provided which adjusts the supplied air-fuel ratio by injecting and supplying a predetermined amount of fuel from the air-fuel ratio. This outputs a fuel injection pulse to the injector 3. A signal from a basic injection amount calculation means 6 is input to this final injection amount calculation means 5, and this basic injection amount calculation means 6 receives a signal from an operating state detection means 7 that detects the operating state of the engine, and The basic injection 1 is calculated according to the optimum operating condition.

The signal from the operating state detecting means 7 is output to a reference value calculating means 8, and the reference value calculating means 8 determines a comparison reference signal Vr corresponding to a target air-fuel ratio depending on the operating state.

The feedback coefficient calculation means 9 receives the reference signal Vr of the reference value calculation means 8 and the detection signal Vs of the air-fuel ratio sensor 13 (lean sensor) installed in the exhaust passage 12 of the engine 1.
Then, the detection signal VS of the air-fuel ratio sensor 13 and the reference signal Vr are compared, and according to the deviation between the two, PIDI! containing a differential component corresponding to the degree of change of this deviation is determined. The feedback coefficient is calculated by till.

A differential component correction means 10 is connected to the feedback coefficient calculation means 9, and the differential component correction means 10 performs a comparison with the detection signal VS of the air-fuel ratio hinter 13 or a signal corresponding thereto, for example, a reference signal vr. When the degree of change in the deviation signal becomes larger than a set value, the differential component in the calculation of the feedback coefficient, that is, the D value, is corrected to a smaller value.

The differential component correction means 10 adjusts the output of the air-fuel ratio sensor 13 when the output changes beyond the upper limit corresponding to the upper limit of the air-fuel ratio fluctuation due to air-fuel ratio feedback control, due to misfire, noise, or other abnormalities. In the case of a sudden change, the value of the differential component is set to O or a small value to reduce the influence of this differential component.

the final injection amount calculation means 5 receiving signals from the basic injection amount calculation means 6 and the feedback coefficient calculation means 9;
corrects the basic injection (A) from the basic injection amount calculation means 6 with the feedback coefficient from the feedback coefficient calculation means 9 to correspond to the detection signal of the air-fuel ratio sensor 13 corresponding to the supplied air-fuel ratio and the target air-fuel ratio. The final injection amount is determined so as to match the reference value.

(Effects of the Invention) According to the present invention, there is a difference between the responsiveness of the air-fuel ratio sensor output change due to a change in the target air-fuel ratio and the responsiveness of the air-fuel ratio C sensor output due to misfires, noise, etc. Since the response of , it is possible to improve control accuracy by suppressing fluctuations in the feedback coefficient based on changes in the air-fuel ratio sensor output caused by misfires, noise, and the like.

In addition, responsive control can be performed using feedback coefficients that include differential components, and the output of the air-fuel sensor
By performing accurate air-fuel ratio correction in accordance with the requirements regardless of characteristics, a stable air-fuel ratio can be obtained even in lean control of the air-fuel ratio, which requires particularly high control accuracy.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is an overall configuration diagram of an engine equipped with an air-fuel ratio control device.

An injector 3 is disposed in an intake passage 2 that supplies intake air to a combustion chamber 15 of the engine 1 to supply fuel. In this intake passage 2, an air cleaner 16, an intake sensor 17 for measuring the amount of intake air, and a throttle valve 18 for controlling the amount of intake air are arranged in this order from the upstream side. On the other hand, a catalyst device 19 is interposed in the exhaust passage 12 that discharges exhaust gas from the combustion chamber 15, and purifies harmful components of the exhaust gas including NOx. An air-fuel ratio sensor 13 (lean sensor) is disposed in the exhaust passage 12 upstream of the catalyst device 19.

The air-fuel ratio supplied to the combustion engine 1 is adjusted according to the amount of fuel injected from the injector 3, and the fuel injection by the injector 3 is controlled by the controller 2.
It is controlled by a control signal output from 0. In order to detect the operating state of the engine 1, the controller 20 receives an intake air amount signal from a sensor 17 and a throttle sensor 21 that detects the opening degree of the throttle valve 18.
engine rotation signal (crank angle signal) based on the ignition signal from the distributor 22 and igniter 23, intake air temperature signal from the intake air temperature sensor 24 installed in the air cleaner 16, and water temperature that detects the engine temperature using the cooling water temperature. A water temperature signal from the sensor 25 and an air-fuel ratio signal from the air-fuel ratio sensor 13 are respectively input, and the fuel injection amount and injection timing are controlled according to the operating state of the engine. Note that 26 is a battery.

The controller 20 has the functions of each means shown in FIG. 1, and determines the basic injection group (injection time) and target air-fuel ratio corresponding to the operating state, and in the case of feedback conditions in the lean region, A feedback coefficient using PAD control that includes a differential component is determined from the reference value corresponding to the target air-fuel ratio and the air-fuel ratio sensor output, and the differential component is corrected to a smaller value when the change in the deviation between the air-fuel ratio sensor output and the reference value is large. In addition, various other correction coefficients are determined to calculate the final injection pulse width.

The setting characteristics of the above-mentioned differential components are illustrated in FIG.

Deviation Vr- between air-fuel ratio sensor output signal Vs and reference value Vr
The D value of the differential component is set to increase in the positive or negative direction as the absolute value of the change rate Δ(Vr-S)/Δt of Vs increases. Then, the rate of change of the deviation Δ(Vr −Vs)
When the value of /Δt in the positive or negative direction exceeds the set value vO or -Vo value, the D value of the differential component is set to O. The set value Va is determined in accordance with the upper limit value of the response speed of the air-fuel ratio sensor output corresponding to a change in the air-fuel ratio.

The operation of the controller 20 will be explained based on the flowchart of FIG. 4. This flowchart is based on fuel@
Only the main part of the routine for calculating the injection pulse is shown.

After the start, the controller 20 initializes the system in step S1, and in step S2 detects the operating state of the engine 1 by determining the engine rotation speed Ne, intake air ff1Qa, and air-fuel ratio sensor output VS from the output signals of the various sensors. , throttle pressure lTa, etc. are read respectively.

Then, in step S3, the basic injection pulse width Tp is limited based on the operating state based on the intake air fj4Qa and the engine speed Ne. This basic injection pulse width 1-p
is to find the injection ♀ when controlling at the stoichiometric air-fuel ratio (A/F = 14.7).

Next, in step S4, an air-fuel ratio correction coefficient Caf corresponding to a target air-fuel ratio according to the operating state is calculated.

This air-fuel ratio correction coefficient Caf is the ratio of the target air-fuel ratio to the stoichiometric air-fuel ratio, and when Caf=1, the stoichiometric air-fuel ratio is set as the target air-fuel ratio.

Subsequently, in step S5, it is determined whether the operating state satisfies the feedback condition. This feedback condition is determined based on whether the target air-fuel ratio is 14.7 or more, and when the air-fuel ratio is in the lean region (YES), feedback control is performed, and when the air-fuel ratio is in the rich region (No), oven control is performed.

When performing feedback control, the feedback correction coefficient Cfb is obtained under the control of P f D 1li17 in steps S6 to S14, and the learning correction coefficient C5tdy is obtained in step 815.

To calculate the feedback correction coefficient C[b, first, in step S6, a reference signal Vr, that is, a slice level corresponding to a target air-fuel ratio according to the operating state is determined. This reference signal Vr is obtained by determining a voltage value corresponding to the target air-fuel ratio with a characteristic such that the larger the target air-fuel ratio is, the larger the reference voltage value becomes. In step S7, the deviation vr-vs between the reference signal vr and the output signal Vs of the air-fuel ratio sensor 13 is calculated.

Note that the output of the air-fuel ratio sensor 13 outputs a signal proportional to the oxygen concentration of the exhaust gas, and has a characteristic that the output voltage becomes high when the air-fuel ratio is large and on the lean side.

Then, in step S8, it is determined whether the air-fuel ratio sensor output signal Vs is larger than the reference signal Vr. When the sensor output signal VS is larger (YES), the detected air-fuel ratio is leaner than the target air-fuel ratio, so in step S9, the I value, which is an integral component, is added by a minute value Δ1 to make the supplied air-fuel ratio rich. It is Shino who will migrate. On the other hand, for NOIm where the sensor output signal VS is smaller, the detected air-fuel ratio is richer than the target air-fuel ratio, so in step 810, the I value, which is an integral component, is subtracted by a minute value ΔI to make the supplied air-fuel ratio leaner. It is something that moves to the side.

Subsequently, in step S11, the P value of the proportional component is calculated.

This P value is determined according to the value of the deviation vr - vs determined in step S7, using the P value calculation table described below.

P value calculation table Vr -Vs p value 1, 0 -30 0, 5 -20 0.1 -10 0〇10, 1 10 -0.5 20 -1.0 30 In step 812, the air-fuel ratio sensor 13 To see the rate of change of the output signal VS, the deviation change ω per unit time △
Δ(Vr - Vs), that is, the deviation change rate Δ(V
r −VS ) /Δt is calculated. Then, in step S13, the D value of the differential component is calculated. This D value is determined by the difference change rate Δ(Vr
-Vs)/Δt.

D value calculation table Δ(vr −Vs)/Δ1 0 value 1.0(Vo
) ' 00, 8 -
20 0.5 -10 -0.5 10 -0.8 20 -1.0 (-vo) 0 In the DIN output table above, when the rate of change is O, the D value is also O, and the rate of change is in the positive direction. The D value is set to increase in the negative direction as it increases, and when the rate of change reaches the set value Vo, D#i is set to O. Also, as the rate of change increases from O to a larger value in the negative direction, the D value is set to become a larger value in the positive direction,
Similarly, when the rate of change reaches the set value -Vo, the D value is set to O (see Figure 3).

By adding the P value, 11 points and D value calculated as above, in step 814 the feedback correction coefficient C
[This is where b is calculated.

Further, the calculation of the learning correction coefficient C5tdy in step 815 is based on the feedback correction coefficient C5tdy based on the PID control by comparing the air-fuel ratio sensor output Vs with the reference signal Vr.
fb, each feedback correction coefficient C when the increase/decrease state of b is reversed.
It is obtained by integrating rb and calculating the average value when a predetermined number of integrations is reached. However, if this calculated latest learning correction coefficient C5tdy' is used as is to correct the basic injection time lower ρ, a large air-fuel ratio change will occur if a mistake is made, so it is actually used as the learning correction coefficient Q5tdy. The value to be calculated is the previous learning correction coefficient C5tdy and the latest learning correction coefficient C5tdy'
It is calculated by adding and updating the value of 1/4 of the value.

In step S16, the feedback correction coefficient C[b
, In addition to the learning correction coefficient C5tdy, various correction coefficients,
For example, water temperature correction coefficient CW, intake temperature correction coefficient Ca1r,
The acceleration correction coefficient Cacc, the deceleration correction coefficient CdeC, the invalid injection time Tv based on the battery voltage, etc. are calculated.

Based on the above-mentioned various correction coefficients, the final injection pulse width Ti is determined in step 817, and when the injection timing is set to a predetermined injection timing based on the final injection pulse width Ti, the injection is started based on a YES determination in step 818. Fuel injection is performed for a period of pulse width Ti.

The calculation of the R final injection pulse width T1 in step 817 is performed by calculating the intake temperature correction coefficient Ca1r and the air-fuel ratio correction coefficient Caf with respect to the basic injection pulse width Tp obtained in step S3.
The injection time corresponding to the target air-fuel ratio is obtained by multiplying 1 by the water temperature correction coefficient Qw (warm-up correction) and the acceleration and deceleration correction coefficient Cacc.

Cdec, feedback correction coefficient Crb, and learning correction coefficient (:, 5tdy) are added and multiplied by the above injection time to obtain the corrected injection time, and the invalid injection time TV is added to this to obtain the final injection time, that is, the pulse width T1. This is what we seek.

According to the embodiment described above, the air-fuel ratio can be accurately feedback-controlled in a region leaner than the stoichiometric air-fuel ratio without causing misfires, and moreover, the output signal of the air-fuel ratio sensor 13 may fluctuate rapidly due to misfires, noise, etc. Even if this occurs, by suppressing the influence of DfiiI that accompanies this, stable air-fuel ratio control can be performed, good drivability can be obtained, and fuel efficiency can be improved.

In addition, in the above-mentioned embodiment, various corrections are performed in addition to the feedback correction before and after calculating the final injection pulse, but whether or not to adopt these corrections is determined as necessary.

[Brief explanation of drawings]

Fig. 1 is a block diagram that clearly shows the structure of the present invention, Fig. 2 is an overall block diagram of an engine equipped with an air-fuel ratio illumination device, and Fig. 3 is a characteristic diagram showing the setting characteristics of the differential component of the feedback coefficient. , FIG. 4 is a flowchart for explaining the operation of the controller. 1... Engine 2... Intake passage 3... Injector 4...
Air-fuel ratio adjustment means 5...Final injection amount calculation means 6...Basic injection fJJ amount calculation means 7...
Operating state detection means 8...Reference value calculation means

Claims (1)

[Claims] (1) Calculate the fuel injection amount according to the engine operating condition,
An air-fuel ratio control device for an engine that corrects the fuel injection amount according to a detection signal of an air-fuel ratio sensor, the device comprising: a basic injection amount calculating means for calculating a basic injection amount according to the operating condition; Feedback coefficient calculating means for calculating a feedback coefficient including a differential component of a signal corresponding to the output, and correcting the differential component of the feedback coefficient to a small value when a change in the signal corresponding to the output of the air-fuel ratio sensor is larger than a predetermined value. 1. An air-fuel ratio control device for an engine, comprising: differential component correction means for calculating a final injection amount using the basic injection amount and a feedback coefficient; and final injection amount calculation means for calculating a final injection amount using the basic injection amount and a feedback coefficient.