JPS6355340A - Air-fuel ratio controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the accuracy of feedback control and to prevent fluctuation of torque, by applying delay correction onto a current output from an air-fuel ratio sensor and calculating an air-fuel ratio in current combustion stroke then shifting a target air-fuel ratio corresponding to an operating condition to same combustion timing. CONSTITUTION:A control unit 21 operates a basic fuel injection based on the values detected through an air flow meter 14 and a crank angle sensor 17, and makes feedback control to a target air-fuel ratio being determined according to rotation, basic fuel injection quantity and water temperature based on a value detected through a wide range O2 sensor 19. The value detected through the O2 sensor 19 is corrected in the primary delay system based on a current value and a preceding value so as to calculate the air-fuel ratio of mixture gas in current combustion stroke. The target air-fuel ratio being set according to the rotation, basic fuel injection quantity and water temperature is shifted so as to match its phase with that of an output from the O2 sensor thus calculating an air-fuel ratio feedback correction coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for controlling the air-fuel ratio of an automobile engine.

(Prior Art) In recent years, the demands placed on engines such as automobiles have become more sophisticated, and there is a tendency for mutually contradictory issues such as reduced exhaust gas, high output, and low fuel consumption to be achieved at a high level.

In order to address these issues, combustion control under ultra-lean air-fuel ratios has been attempted, such as "Internal Combustion Engine, Vol. 23, No. 12 J, October 1984 issue, pp. 33-40, published by Sankaido. There is a lean burn device described in .This device achieves the above requirements by performing feedback control of the air-fuel ratio up to the ultra-lean air-fuel ratio region based on the output of a lean sensor that can detect air-fuel ratios over a wide range from rich to lean. Trying to.

In this case, unlike the characteristic where the stoichiometric air-fuel ratio is constant during steady driving, a lean air-fuel ratio is set as the target value even in some acceleration regions. For example, in the normal acceleration range, the air-fuel ratio is 22
．． 5. The air-fuel ratio is 21°5 in the steady running range, and 15.5 during idling. Further, in a full load state, an output air-fuel ratio of 12 to 13 is used to ensure vehicle power performance. As we move to such a lean air-fuel ratio, NO.
x tends to decrease significantly, and in recent years NOxO
This is in line with the reduction of x emissions. However, on the other hand, the air-fuel ratio adaptability range that satisfies both the NOx emission level to satisfy exhaust gas regulations and the allowable torque fluctuation level is narrow (and precise air-fuel ratio control is required).

(Problems to be Solved by the Invention) However, in such conventional air-fuel ratio control devices, although the above-mentioned effects can be obtained by lean combustion, they do not take into account the response delay of the air-fuel ratio sensor. Therefore, there is a risk that an error may occur in the detection of the air-fuel ratio and the accuracy of the air-fuel ratio control may be reduced. In particular, such detection errors become significant when the air-fuel ratio varies depending on operating conditions. As a result, control accuracy decreases and the engine is operated at a richer or leaner side than the target air-fuel ratio, resulting in deterioration of exhaust emission characteristics and deterioration of drivability such as torque fluctuation.

(Objective of the Invention) Therefore, the present invention corrects the current output of the air-fuel ratio sensor using a predetermined delay correction calculation to calculate the air-fuel ratio of the air-fuel mixture in the current combustion stroke, and also shifts the value of the target air-fuel ratio. By aligning the combustion phases of the two so that the combustion timing is the same for the air-fuel ratio of the air-fuel mixture in the current combustion stroke, the accuracy of feedback control of the air-fuel ratio is improved and exhaust emissions and drivability are further improved. The purpose is to improve.

(Means for Solving the Problems) In order to achieve the above object, the air-fuel ratio control device for an internal combustion engine according to the present invention has an air-fuel ratio control system for detecting the air-fuel ratio of an intake air-fuel mixture, as shown in FIG. correcting the current output of the fuel ratio detecting means a, the operating state detecting means for detecting the operating state of the engine, and the air-fuel ratio detecting means a by a predetermined delay correction calculation;
A correction means C that calculates the air-fuel ratio of the air-fuel mixture in the current combustion stroke, a target setting means d that sets a target air-fuel ratio based on the operating state of the engine, and a value of the target air-fuel ratio set by the target setting means d. and a phasing means e which shifts the combustion phases of the two so that the air-fuel ratio of the air-fuel mixture in the current combustion stroke calculated by the correction means C has the same combustion timing. A control means f calculates a control value for feedback correcting the air-fuel ratio based on the target air-fuel ratio and the calculated air-fuel ratio of the correction means C; Operating means g for controlling the air-fuel ratio
It is equipped with.

(Function) In the present invention, the current output of the air-fuel ratio sensor is corrected by a predetermined delay correction calculation, the air-fuel ratio of the air-fuel mixture in the current combustion stroke is calculated, and the value of the target air-fuel ratio is shifted. The combustion phases of both can be matched so that the timing is the same for the air-fuel ratio of the mixture in the combustion stroke. Then, a control value for feeding back and correcting the air-fuel ratio is appropriately calculated based on the target air-fuel ratio when the combustion phases are matched and the air-fuel ratio corrected by the correction calculation. Therefore, feedback control of the air-fuel ratio is executed with high accuracy, and deterioration of exhaust emission characteristics and deterioration of drivability such as torque fluctuation are prevented.

(Example) .

Hereinafter, the present invention will be explained based on the drawings.

2 to 6 are diagrams showing a first embodiment of the present invention. First, the configuration will be explained. In FIG. 2, 1 is an engine, intake air is supplied to each cylinder through an intake pipe 2, and fuel is injected from a fuel tank 3 by a fuel pump 4 through a fuel filter 5, a fuel damper 6, and a fuel supply pipe 7. The injector (operating means) 8 injects based on the signal Si.

Further, the fuel temperature Tf is detected by a fuel temperature sensor 9 disposed in the fuel supply pipe 7, and surplus fuel is returned to the fuel tank 3 via a fuel pressure regulator 10 and a fuel return pipe 11. Then, the air-fuel mixture in the cylinder is ignited and exploded by the discharge action of the spark plug 12, and is discharged as exhaust through the exhaust pipe 13.

The flow rate Qa of the amount of intake air is detected by an air flow meter 14 and controlled by a throttle valve 15 in the intake pipe 2. The opening Cv of the throttle valve 15 is detected by the throttle valve opening sensor 16,
The rotation speed N of the engine 1 is detected by a crank angle sensor 17. Further, the temperature Tw of the cooling water flowing through the water jacket is detected by a water temperature sensor 18. Further, the oxygen concentration in the exhaust gas is detected by an oxygen sensor (air-fuel ratio detection means) 19, and the oxygen sensor 19 is of a type whose output Vi changes uniquely over a wide range of air-fuel ratios from rich to lean regions. is used.

The air flow meter 14, the throttle valve opening sensor 16, and the crank angle sensor 17 constitute an operating state at & output means 20, and the operating state detecting means 20, the fuel temperature sensor 9,
Outputs from the water temperature sensor 18 and oxygen sensor 19 are input to the control unit 21. The control unit 21 has functions as a correction means, a target setting means, a phasing means, and a control means, and as shown in detail in FIG. These are connected to each other by a common bus 27. The A/D converter 25 receives each signal Qa, Tf input as an analog signal.
, Tw and ■i into digital signals, and CPU2
CPU 22 or RA at a predetermined time according to the instructions in
Output to M24. The CPU 22 takes in necessary external data according to the program written in the ROM 23, and also performs arithmetic processing on processing values necessary for air-fuel ratio control, without exchanging data with the RAM 24.
The processed data is output to the I10 boat 26 as necessary. Signals from the sensor group 16.17 are input to the I10 boat 26, and an injection signal Si is output from the I10 boat 26. The ROM 23 stores calculation programs for the CPU 22, and the RAM 24 stores data used in calculations in the form of a map or the like. Note that a part of the RAM 24 is constituted by, for example, a nonvolatile memory, and retains its stored contents (learning values, etc.) even after the calculation is stopped.

Next, the operation will be explained, but first, as pointed out in the conventional problem, the reason why the response delay occurs in the output of the air-fuel ratio sensor will be explained.

Generally, since an air-fuel ratio sensor detects the air-fuel ratio concentration by diffusion and gas exchange of exhaust gas, it is considered that there is a certain delay element in the detection. This delay element changes depending on the diffusion coefficient in the vicinity of the air-fuel ratio sensor, the gas exchange rate, etc., and the factors for this change include (1) engine speed, (2) load, and (3) width of change. Further, although the order of the delay element is considered to be multidimensional, it is also possible to approximate it as a substantially -order delay system. Therefore, when applying correction by the difference method as a method of correcting the -order lag system, the air-fuel ratio A/F after correction is calculated using the following formula 0%. However, A/FO: current air-fuel ratio A/Fl: previous air-fuel ratio α: Correction coefficient (this α corresponds to the approximate −order lag time constant of the air-fuel ratio sensor) To explain this in more detail, this −order lag system is expressed using a differential equation as the following equation 〇. , ゛ Approximating this using a difference gives the 0th equation.

However, y7: current time) 'n-+: previous time (i.e., Δ is y before time,
) T: Time constant of air-fuel ratio sensor Δt: Sample interval (A/F.

and A/F + ) Therefore, the actual output behavior of the air-fuel ratio sensor is shown as a first-order delayed output with a time constant T, as shown in FIG. That is, the response delay of the air-fuel ratio sensor output can be corrected using the differential method.

FIG. 5 is a flowchart showing a program for air-fuel ratio control based on the above basic principle.

~P indicates each step of the flow. This program is executed once every predetermined time. First, the engine speed N is read with PI, and the intake air amount Qa is read with P2.
It is calculated by measuring the interval time of the position signal (signal every 360 degrees) or by measuring the number of pulses in a predetermined time of the position signal (signal every 1 degree). Next, the basic pulse width (basic injection amount) Tp is calculated using P according to the following equation (2).

a'rp=KX□...■ However, K: constant Next, various correction coefficients C0EF are calculated in P4, and invalid pulse width Ts is calculated in Ps. Here, C0EF is a fuel delay correction coefficient, which corrects the fuel amount during a transient period. The value is determined by the vaporization of the fuel and the wall flow rate, but specifically, it is calculated based on the magnitude of acceleration/deceleration, engine warm-up and operating conditions, and whether or not the engine has been started. Further, the above-mentioned various correction coefficients C0EF and invalid pulse width TS are various correction coefficients for correcting the basic pulse width Tp, but since they have little relation to the present invention, a detailed explanation will be omitted.

Next, the injection pulse width Ti is calculated at P according to the following equation.

Ti=TpXCOEFXALPHA+Ts・・・・・・
■ However, ALPHA: Feedback correction coefficient for the air-fuel ratio.
The calculation will be explained in detail in the program described later in FIG.

Furthermore, the injection pulse width Ti is stored in the output register of the I10 port 26 at P, and the injection pulse width Ti is stored at a predetermined crank angle.
An injection signal Si having a fuel injection pulse width corresponding to i is output to the injector 8, and the current process ends.

FIG. 6 is a flowchart showing a program for calculating the air-fuel ratio feedback correction coefficient ALPHA, and this program is executed for each combustion stroke of the engine. First, the target air-fuel ratio TAF under the current operating conditions is determined from a predetermined table map using P, N, Tp, and TW as parameters.

(T A F o =func (N r T p +
Look up T W) ). However, this cooling water temperature Tw is read in another routine (not shown). Next, in order to perform phase matching with the air-fuel ratio sensor output at p+z, the output of the target air-fuel ratio is shifted by two rotations, and Pl,
Then, the memory is rewritten with the previous air-fuel ratio sensor read value A/Fo as A/F. Next, the output of the air-fuel ratio sensor is A/D converted at Pl4, and the A/D converted value is stored in the memory as A/Fo.

Furthermore, in the following p+5-pt't, the above-described difference method is applied to calculate the air-fuel ratio feedback correction coefficient ALPHA. That is, in PIS, calculate the difference correction coefficient α (α=K/N, where K: constant, N: engine speed) according to the following formula (■), and in Pl6 calculate the air-fuel ratio sensor after delay correction according to the above-mentioned formula 0. Calculate output A/F.

T ゛...■ (K/N) Next, the air-fuel ratio feedback correction coefficient ALPHA is calculated by PI (proportional/integral) control according to the following equation (2) using Pl'l, and the process ends.

A L P HA = K p (T A F 4-
A/F) + ΣKl (TAF4-A/F) ・・・・・・■ However, TAFa: Output after phase adjustment calculated with PIz A/F: P Value calculated with lb Kp: Constant In this way, this In the example, the response delay of the output of the air-fuel ratio sensor is appropriately corrected using the differential method, and an accurate air-fuel ratio feedback correction coefficient ALPHA is calculated. Therefore, the accuracy of air-fuel ratio control can be significantly improved, and the exhaust It is possible to improve drivability by preventing deterioration of emission characteristics, torque fluctuation, etc.

Note that in this embodiment, the delay element in the output of the air-fuel ratio sensor is corrected using the differential method, but the present invention is not limited to this. The point is that it is sufficient to appropriately correct the delay element, so it goes without saying that, for example, a mode in which differentiation may be used instead of the difference method is also acceptable. In this case, it becomes possible to perform even more precise correction.

In addition, in this embodiment, as a feedback control method, P
Although I (proportional/integral) control is adopted, the present invention is not limited to this, and other aspects such as P (proportional) control, Pr
D (proportional/integral/derivative) control may be used. That is, in the case of P control, the 0th equation of step Pl'l described above may be changed to the following equation 〇, and in the case of PID system'+TJ, the 0th equation may be changed to the following equation (■).

A L P H A = K p (T A F a
A / F )・・・・・・■ALPHA=Kp (
TAF4 A/F)+ΣK r (TAF a
A/F) 10KI, Δ・・・・・・■ However, Δ: Current (TAF4-A/F) - Previous (TA
F4-A/F) The above first embodiment is an example in which the time constant T of the air-fuel ratio sensor is constant. However, in reality, the time constant T changes depending on the engine speed, load, etc., as described above. This aspect will be illustrated in a second example.

Fig. 7.8 is a diagram showing a second embodiment of the present invention, and this embodiment is similar to the first embodiment except that the calculation of the time constant T is added to the program shown in Fig. 6 above. be. In explaining this embodiment, steps that perform the same processing as in the first embodiment will be given the same numbers and their explanations will be omitted, and steps that are different will be given step numbers circled and their contents will be explained. .

In the program shown in FIG. 7, after passing through PI4, the time constant T is calculated at P2 according to the following equation [phase].

T =func (T p , N) ””@In this way, in this example, the time constant T of the air-fuel ratio is appropriately calculated as a function of the basic pulse width Tp and the engine speed N, so the eighth As shown in the figure, the time constant T of the air-fuel ratio sensor is set to low load (solid line in the figure) in response to the step signal of the air-fuel ratio.
, can be set to a more appropriate value depending on the cases of low load and high rotation (broken line in the same figure) and high load (dotted chain line in the same figure), and the accuracy of the air-fuel ratio feedback correction coefficient ALPHA is increased to The effects of the embodiment can be further improved.

9 to 12 are diagrams showing a third embodiment of the present invention, and since the hardware configuration of this embodiment is the same as that of the first and second embodiments, the hardware configuration will be omitted.

First, the basic concept of this embodiment will be described. In general, the inherent characteristics of an air-fuel ratio sensor are the stoichiometric air-fuel ratio (λ
Although the output is only on the leaner side than = 1), the configuration of the air-fuel ratio sensor in the present invention is to inject a pump current (diffusion current) Ip into zirconia to create a state in which there are few 02 ions on the surface, thereby eliminating the zirconia's original 0□ ion zero. By utilizing the characteristics of sudden changes in output in the vicinity and injecting Ip so that the sudden changes in output are balanced, it is possible to extract output even on the richer side than the stoichiometric air-fuel ratio (see Figure 9 (a)).
. This characteristic is 0zfH degrees in the lean range from the stoichiometric air-fuel ratio, and Co? in the rich range. The output characteristics change depending on the M degree, but the 02 concentration in the lean region is determined by the excess air ratio λ
Since it is proportional to (λ = air-fuel ratio/stoichiometric air-fuel ratio), the output is 1.
As shown in Fig. 9(b), p can be expressed by two broken lines with λ=1 as the boundary for the excess air ratio λ at the fuel-air ratio F/A (reciprocal of the air-fuel ratio A/F). can.

On the other hand, if the target void ratio is TFA and the coefficient of the flow rate characteristic of the injector is KINJ, the constant of the above-mentioned formula 0 can be expressed by the following formula.

K=KINJ XTFA ......0 or more, the output characteristic of the air-fuel ratio sensor is uniformly converted to the fuel-air ratio F/A from the rich region to the lean region, the sensor output characteristic is linearized, and this value is If feedback control (hereinafter referred to as F/B control) is executed so that the current air-fuel ratio becomes the target fuel-air ratio TFA, no matter whether the current air-fuel ratio is rich or lean with respect to the target value, or the target air-fuel ratio TFA Regardless of which side of the stoichiometric air-fuel ratio the position is on, it is possible to make the feedback gain the same on both the rich and lean sides.

However, in the conventional air-fuel ratio F/Bitrl [i method, both the rich and lean sides of the target air-fuel ratio are controlled with the same feedback gain so that the output of the air-fuel ratio sensor itself becomes the target air-fuel ratio. As a result, the result of F/B control may shift from the target value and an offset may occur, resulting in a decrease in control accuracy and deterioration of drivability and exhaust emission characteristics. In addition, in order to avoid such a decrease in control accuracy, it is possible to change the feedback gain depending on the rich side and lean side of the target air-fuel ratio, but the feedback gain may vary depending on the location (target air-fuel ratio). Since the values are different, the arithmetic processing for determining the gain becomes complicated. Therefore, the increase in program capacity and calculation time may lead to higher costs and deterioration in performance.

Therefore, in this embodiment, the output of the air-fuel ratio sensor is changed to the fuel-air ratio F/
Focusing on the fact that it has two broken line characteristics when viewed on the A scale, we find a signal that is completely linear with respect to the fuel/air ratio F/A, as shown by the broken line in Figure 9 (b), and By performing F/B control based on ζ, control offset is avoided by setting the same gain on both the rich side and the dark side of the target value, thereby improving control accuracy. Note that when performing this delay correction, if you execute the delay correction before performing the nearize correction, the slope sensitivity will be different between rich and lean sides of the stoichiometric air-fuel ratio, so the gain of the delay correction will be different between the rich side and the lean side. If the value is not corrected by changing the value, an error will occur instead. Therefore, it is necessary to perform delay correction after linearization.

FIG. 1O111 is a flowchart showing an air-fuel ratio control program based on the above basic principle. In explaining this embodiment, steps that perform the same processing as in the first embodiment are given the same numbers and their explanations are omitted, and different steps are marked with Q.
The contents are explained with the step numbers enclosed by marks. Note that FIGS. 10 and 11 of this embodiment are the same as those of the fifth embodiment of the first embodiment.
This corresponds to Fig. 6 and Fig. 6, respectively.

In the program shown in Fig. 10, after passing through P2, Pill calculates the basic pulse width Tp' according to the following formula @, and P3□ calculates the current pulse width from a predetermined table map with 'rp', N, and 'l'w as parameters. Target fuel-air ratio T under operating conditions
FA (TFA=func (Tp', N, TW
)).

a 'rp' = 、、、X□ ・・・・・・＠However,
Ko: Constant determined by the flow rate characteristics of the injector Next, in P33, the basic fuel pulse width 'rp corresponding to the target fuel-air ratio is calculated according to the following equation.

Figure 11 shows the air-fuel ratio feedback correction coefficient ALPHA.
This is a flowchart showing a program that calculates , and this program is executed for each combustion stroke of the engine.

First, in order to perform phase combination with the air-fuel ratio sensor at Pd2, the TFA signal for four strokes corresponding to the intake stroke to the exhaust stroke is shifted. In other words, in a routine such as this program where calculations are performed for each stroke signal, the air-fuel ratio output can be detected with respect to the target fuel-air ratio TFA determined at the time of injection when fuel is inhaled and compressed during the intake stroke. This is when the exhaust gas is emitted during the explosion and exhaust stroke and reaches the location where the oxygen sensor (air-fuel ratio sensor) 19 is attached. For this reason, here, the signal of the 4-stroke molecule FA corresponding to the intake stroke to the exhaust stroke is shifted and phase-combined with the air-fuel ratio sensor signal. Next, the output of the air-fuel ratio sensor is A/D converted by Pd2, and the A/D converted value is converted to F/A.
Store it in memory as o. In Pd2, in order to obtain the previous linearizer result, the value of KFBAo is transferred to KFBA, and in Pd2, the A/D converted F according to the following formula [phase] is transferred.
/A.

Calculate the linearization correction coefficient KHO3 (first
(See Figure 2).

KHO3=func(F/Ao) −·”■ Next, KFBAo is linearized in P4S according to the following formula [phase].

KFBAo=KHO3xF/Ao ”-...-@Therefore, as shown in Figure 9(b) above, the fuel air ratio F/
The output characteristics of the air-fuel ratio sensor for A (broken line characteristics for air-fuel ratio F/A) can be displayed as one linear straight line over the entire range from rich to lean.
The output of o can be made to have a linear characteristic with respect to the F/A as shown by the chain line in the figure.

In pab to P49 below, the delay correction of the air-fuel ratio sensor is corrected using the difference method as in the first and second embodiments described above, and the air-fuel ratio feedback correction coefficient ALPHF is calculated. In other words, in P4&, the difference correction coefficient (corresponding to the air-fuel ratio sampling interval) is calculated according to the following formula [phase].
α is calculated, and in Pd2, the output KFBA of the air-fuel ratio sensor after linearization and delay correction is calculated according to the following equation.

However, T: first-order lag time constant of the air-fuel ratio sensor m: constant KBFA=KBFAo+α(KBFA,.

-KBFAI) ......O then,
The phase correction signal TFA of the target fuel-air ratio TFA in PdI2 and the fuel-air ratio K obtained by linearizing the output of the air-fuel ratio sensor
Calculate the difference Δ with FBA according to the following formula [phase], and calculate Pd2
The air-fuel ratio feedback correction coefficient ALP is calculated according to the following formula 〇.
Calculate HA and end the process Δ≧TFA, -KFBA River... [phase]
ALPHA=Kp・Δ+Σ(K,・Δ)・・・・・・
・[Phase] In this way, in this example, we focused on the fact that the relationship between the output of the air-fuel ratio sensor and its fuel-air ratio has two broken line characteristics, and the A signal that is completely linear with respect to the air-fuel ratio F/A is obtained, and precise F/B control is performed based on this signal, and the response delay of the air-fuel ratio sensor is appropriately corrected to ensure an accurate air-fuel ratio. Since the feedback correction coefficient ALPHA is calculated, both effects work together to achieve an extremely accurate air-fuel ratio F/B*J'4B, further improving exhaust emission characteristics and drivability. be able to.

Note that in this embodiment, linearization of the air-fuel ratio and correction of the response delay of the air-fuel ratio sensor according to the present invention are performed at the same time, but of course this is not limited to this, and only linearization of the air-fuel ratio is performed independently. Needless to say, the present invention may also be applied to air-fuel ratio control. In this way, if the linearization of this embodiment is applied to a conventional air-fuel ratio control device, etc., there is no need to change the hardware or special sensors, and control accuracy can be improved simply by using software without changing the control gain. It is possible to improve the

(Effects) According to the present invention, the current output of the air-fuel ratio sensor is corrected by a predetermined delay correction calculation to calculate the air-fuel ratio of the air-fuel mixture in the current combustion stroke, and the value of the target air-fuel ratio is shifted. Since both combustion phases are matched so that the combustion timing is the same for the air-fuel ratio of the air-fuel mixture in the current combustion stroke, the accuracy of feedback control of the air-fuel ratio can be increased and torque fluctuations can be prevented. Exhaust emitter.

It is possible to further improve driving performance and drivability.

[Brief Description of the Drawings] Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 6 are diagrams showing a first embodiment of the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a diagram showing a first embodiment of the present invention. A circuit configuration diagram of the control unit, FIG. 4 is a diagram showing the characteristics of the air-fuel ratio sensor, FIG. 5 is a flowchart showing the air-fuel ratio control program, and FIG. 6 is a program for calculating the air-fuel ratio feedback correction coefficient. FIG. 7.8 is a diagram showing the second embodiment of the present invention, and FIG. 7 is a flow chart showing a program for calculating the air-fuel ratio feedback correction coefficient.
Figure 8 is a diagram showing the characteristics of the air-fuel ratio sensor, Figures 9 to 12
The figures are diagrams showing a third embodiment of the present invention, Fig. 9 is a diagram showing the characteristics of the air-fuel ratio sensor, Fig. 10 is a flowchart showing the air-fuel ratio control program, and Fig. 11 is the air-fuel ratio A flowchart showing a program for calculating a feedback correction coefficient, and FIG. 12 is a diagram showing the characteristics of the linearization correction coefficient. 1...Engine, 8...Injector (operating means), 19...
...Oxygen sensor (air-fuel ratio detection means), 20...
- Operating state detection means, 21... Control unit (air-fuel ratio correction means, target setting means, phasing means, control means).

Claims (1)

[Scope of Claims] a) air-fuel ratio detection means for detecting the air-fuel ratio of the intake air-fuel mixture; b) operating state detection means for detecting the operating state of the engine; c) detecting the current output of the air-fuel ratio detection means at a predetermined level. a correction means that calculates the air-fuel ratio of the air-fuel mixture in the current combustion stroke by correcting it by a delay correction calculation; d) a target setting means that sets a target air-fuel ratio based on the operating state of the engine; and e) a target setting means. phasing means that shifts the value of the target air-fuel ratio set by and adjusts the combustion phase of both so that the combustion timing is the same with respect to the air-fuel ratio of the air-fuel mixture in the current combustion stroke calculated by the correction means; and f) a control means for calculating a control value for feedback correcting the air-fuel ratio based on the target air-fuel ratio when the combustion phases are matched and the air-fuel ratio calculated by the correction means; and g) a control value for adjusting the intake air based on the output of the control means. Alternatively, an air-fuel ratio control device for an internal combustion engine, comprising: an operating means for controlling the air-fuel ratio by changing the amount of fuel supplied.