JPS60206953A - Air-fuel ratio control device in internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent the air-fuel ratio of an engine from becoming excessively lean, and therefore to enhance the drivability, by carrying out either an air-fuel ratio feed-back control or an air-fuel ratio open-control in accordance with the operating condition of the engine, and as well by carrying out a compensation for a decrease in air-fuel ratio when the open-control is carried out. CONSTITUTION:In an air-fuel ration control device in an internal-combustion engine M1, the control means 5 determines the supply amount of fuel in accordance with an engine load detected by an operating condition detecting means M2. Further, a selection is made between an air-fuel ratio open-control which controls a fuel supply means M3 in accordance with the above-mentioned fuel supply amount and an air-fuel ratio feed-back control which compensates the fuel supply amount in accordance with an air-fuel ratio detected by an air-fuel ratio detecting means M4. In this arrangement, the control means M5 is provided therein with an air-ratio compensating means M for compensating a decrease in air-fuel ratio when the air-fuel ratio open control is carried out, thereby the air- fuel ratio is controlled to be shifted to the rich side slightly from a desired air- fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an air-fuel ratio control device for an internal combustion engine, and relates to an internal combustion engine that appropriately controls the air-fuel ratio when performing so-called A-fuel ratio control without feedback control of the air-fuel ratio. The present invention relates to an air-fuel ratio control device for an engine.

[Prior Art] Conventionally, in a fuel control device for an internal combustion engine, which controls the fuel supply by determining the amount of fuel supplied to the internal combustion engine by knowing the load of the internal combustion engine from, for example, the intake air m and the engine speed, the exhaust pipe In order to ensure sufficient purification efficiency of the catalytic converter using a three-way catalyst installed in a part of the engine, the air-fuel ratio of the intake air-fuel mixture is estimated based on the exhaust composition, such as the oxygen concentration in the exhaust, and the amount of fuel supplied is determined. Various air-fuel ratio controls have been carried out based on air-fuel ratio control in which the air-fuel ratio of the internal combustion engine is adjusted to the stoichiometric air-fuel ratio. Typical examples of air-fuel ratio control devices for internal combustion engines that use the above-mentioned air-fuel ratio control as the basis of their control are as follows: describes air-fuel ratio control devices for various internal combustion engines that are based on so-called lean burn, in which the air-fuel ratio is partially reduced, instead of control using the stoichiometric air-fuel ratio, for the purpose of improving fuel efficiency. 2) When the air-fuel ratio detection means for performing feedback control of the air-fuel ratio is not operating normally due to completion of warm-up or failure, etc., the so-called open control 911 is used instead of feedback control of the air-fuel ratio of the internal combustion engine. (33) Air-fuel ratio control devices such as air-fuel ratio detection means J
Air-fuel ratio control for various internal combustion engines basically corrects the fuel supply amount using a learning value set according to the air-fuel ratio feedback correction coefficient in order to correct machine differences and changes over time in each part. There are I-wave devices, etc.

In response to strong social demands for improved exhaust gas purification and fuel efficiency, as well as demands for reliable and precise control that minimizes the impact on the entire system caused by malfunctions in one part of the system, we Recently, the above-mentioned air-fuel ratio control has been combined,
In addition to maximizing exhaust gas purification efficiency, depending on the operating status of the internal combustion engine, lean burn improves fuel efficiency and open control is performed to maximize the performance of the internal combustion engine. Fuel ratio control devices have also been proposed and implemented.

However, when open control of the air-fuel ratio is performed in the air-fuel ratio control device of an internal combustion engine that performs such precise air-fuel ratio control, the air-fuel ratio control device 9II may be affected by machine differences or changes over time, or failure of the air-fuel ratio detection means. The air-fuel ratio may deviate from the target air-fuel ratio due to an error in the correction coefficient set due to the imbalance in the fuel supply amount, especially when the air-fuel ratio deviates toward the lean side and becomes over-lean. [Yo, there was the problem of worsening drivability.

This problem is solved by detecting the air-fuel ratio of the internal combustion engine, determining the air-fuel ratio feedback correction coefficient FAF, and learning the C air-fuel ratio using the learning value KG set according to the average (*FAFAV) of the feedback correction coefficient FAF. Even when performing 1r1 control, the response of the learning value KG is relatively slow due to the control property of "learning", and it is not possible to sufficiently follow changes in the load. For several reasons, it has not been completely resolved.Explaining this problem in more detail1-1, the old value control of the air-fuel ratio was originally
Errors in air-fuel ratio 1111 control, such as machine differences of 1!7 and changes over time, are reflected in the learned value K 1 in the vicinity of the value 1 corresponding to
1, and the average value F A F A V of the air-fuel ratio feedback correction coefficient is a predetermined value.
By adding or subtracting G, the air-fuel ratio of the internal combustion engine is determined to be the standard air-fuel ratio.

Therefore, if we shift from air-fuel ratio feedback @ control to open control, the air-fuel ratio feedback correction coefficient FAF no longer has any meaning, so FAF = λ (λ - 1 when control is performed at the stoichiometric air-fuel ratio, λ during lean burn) =0.
6 to 0.8), and if the learning (ifKG) learned during feedback control is used as is to install a fuel injection hanger, even when A-Pun control is implemented, machine differences and There should be no errors due to changes over time.

However, in actual learned value control, since the learning value KG is corrected a predetermined number of times by one learning, (+ > As shown in Fig. 1, the load of the internal combustion engine and the learning value required by the load (!! ii has a unique relationship for each neck and is indicated by broken FILS in the figure), and the learning value on control + (solid line d in the figure) (ii) As shown in Figure 2, when the internal combustion engine's load changes suddenly, the learning that is required in response to the load. ta<indicated by the broken line t in the figure), the learning value of the control tl++ operator (indicated by the solid line e in the figure) cannot keep up with the change and deviates (△1) due to the delay in response. Two problems still remained: G) could occur.

As long as feedback control of the air-fuel ratio is performed, these deviations are absorbed and there is no problem, but the feedback correction coefficient FAF of the air-fuel ratio of 0, 1, and The above (1
) (ii) If the deviation is due to the reason, a.
This appears as a deviation in the air-fuel ratio, which may worsen the drivability of the internal combustion engine. This was particularly a problem during the period [I] in FIG. 2 during J3, as the air-fuel ratio was shifted toward the lean side.

[Objective of the Invention 1 The present invention has been made in view of the above-mentioned points, and its object is to prevent the air-fuel ratio from becoming A-balleen even when performing open control of the air-fuel ratio, and to maintain good drivability. The object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can be realized.

[Configuration 1 of the Invention The configuration of the present invention made to achieve the above object, as shown in FIG. Fuel supply means M for supplying fuel to M1
3, an air-fuel ratio detecting means M4 for detecting an air-fuel ratio based on the internal combustion engine exhaust composition; and determining a fuel supply amount according to the load of the internal combustion engine M1 detected by the operating state detecting means M2; The fuel supply means M3 is controlled according to the supply amount, and the air-fuel ratio of the internal combustion engine M1 is controlled by open control, or the fuel supply amount is corrected according to the air-fuel ratio detected by the air-fuel ratio detection means M4, and the fuel supply means A control means M5 that performs either feedback control to control the air-fuel ratio of the internal combustion engine M1 to the target air-fuel ratio by controlling the air-fuel ratio of the internal combustion engine M3, depending on the operating state of the internal combustion engine M1 detected by the operating state detecting means M2. In the air-fuel ratio control device for an internal combustion engine, the air-fuel ratio control device for an internal combustion engine is characterized in that: 1) the control means M5 described in h above includes an air-fuel ratio correction means M6 that corrects the air-fuel ratio by decreasing it when performing A-pun control of the air-fuel ratio; The gist of this paper is an air-fuel ratio control system for internal combustion engines.

Embodiments] 1. Embodiments of the present invention will be described in detail based on Figure m).

FIG. 114 is a schematic configuration diagram of an air-fuel ratio control device including an internal combustion engine and peripheral devices of the embodiment, in which 1 is a self-contained control unit, and 2 is an electromagnetic fuel injection valve as a fuel supply means. , 41
．． 1 is a well-known lean sensor as an air-fuel ratio detection means for detecting the oxygen content 1α in the exhaust gas from the internal combustion tank 1 from the limit current; 6 is an electronic control circuit including an air-fuel ratio correction means; Each is represented. Further, as a means for detecting the operating state of the internal combustion engine 1, as shown in the figure, an intake (crystal sensor 8) is used.
．． A throttle sensor 12 detects the opening degree of the throttle valve 10, and a semiconductor intake pressure sensor 18 is installed in the surge tank 16 provided in the intake pipe 14 of the internal combustion engine body 1 and detects the intake pipe pressure. A water temperature sensor 20 that detects the temperature of the cooling water of the internal combustion engine 1. Opposed to the rotor 22a inside the distributor 22 is a rotational speed sensor 24 which detects the rotational speed of the internal combustion engine 1 by generating 24 pulses per rotation of a crank (not shown). Similarly, a group of lenses such as a cylinder discrimination sensor 25 which generates one pulse per revolution of the crank is provided.

The high voltage pulse generated by the igniter 26 is supplied to the distributor 22, and the distributor 2
2 is the same as the combustion cycle of each cylinder], and the internal combustion engine 1
The spark plug 3 screwed into the upper part of the cylinder 28 of
0, this high voltage is applied to ignite the air-fuel mixture. Further, 32 is a catalytic converter provided in the exhaust pipe 34 of the internal combustion engine 1.

Next, the internal configuration of the electronic side 011 circuit 6 and the electrical signal system will be explained. The electronic control circuit 6 inputs data and performs data input according to the specified block 1'? A central processing unit (CPU) 60 that performs control, a read-only memory (ROM) 62 that stores control programs, etc. in advance, and a temporary memory (RAM) that can freely store and read data, etc. 64, from the various upper 211 groups that detect the operating state of the internal combustion engine 1 (input port 5 which inputs No. ii), control signal 5J is output to the event control valve 261b, etc. 67, cp
ueo, R.

Data bus (3
8. Connect to the battery 73 via the key switch 71;
The electronic control circuit 6 is provided with a stabilized electric power 114 and an electronic circuit 15; a circuit 75, and the like. The input port 5 includes a pulse input section G5a that inputs pulse signals from the rotation speed sensor 24 and the cylinder discrimination sensor 25, and an intake air temperature sensor 8. Throttle sensor 12, intake Y [Sinza 18.
Leansenza 4. An analog input section 65b for manually inputting analog signals corresponding to each detected value from the water temperature sensor 20 is connected.

-1), the crank angle (not shown) of the internal combustion engine 1 is detected by the signal from the rotation speed sensor 24, and the igniter 26 is driven in synchronization with this. The control signal to open the fuel injection valve 2 and the sensor 4 to detect the oxygen moisture level from the limit current in the fuel sensor (No. 4) A constant voltage signal is outputted via the output horn boat 67.The fuel sentry valve 2 is controlled and controlled by the control signal.
When the valve is opened, the fuel pressure pump J (not shown) supplies fuel (414) so that a fuel noise O1 is supplied to the inside of the intake pipe 14.

Next, the control 911 carried out by the air-fuel ratio control device of the internal combustion engine of this embodiment will be explained based on the flowchart of FIG. 5 showing the processing carried out by the electronic control circuit 6. After the internal combustion engine 1 is started, the water control routine is activated by a pulse input from the cylinder discrimination sensor 25 every 720 degrees of the crank angle, that is, every 2 revolutions.
In Fig. 3, △j, control is entered, and first, in step 100, the intake pipe pressure pu+, which is detected via the input port 5, is determined from the intake pressure sensor to 1B, and the number of rotations Φ is changed to 24j.
, the rotational speed Nc of the internal combustion engine 1 is detected, and the water temperature sensor 20 detects i Ml water IKITWs O.
The process of reading the operating state of the internal combustion engine, such as the opening Op1 of the throttle valve 10 detected by the throttle sensor 12, and the output signal of the sensor 4 is interrupted in line 4f.

In the following step 110, the basic fuel injection time (Tp) is set earlier in accordance with the intake pipe pressure pm which is proportional to the negative front of the internal combustion engine, that is, the intake air ITI per cylinder to the internal combustion engine 1. Processing is performed. That is, with I<1゛ as a constant, the basic fuel injection time T is calculated from Hp=ttrxpm-
I'l is calculated. Step 1 following step 110
In Step 20, from each signal value indicating the operating state read in step 100t, the basic ¥X lit II + 1 riverffl is calculated.
Various correction coefficients are applied to correct 1-1). For example, the transient 11N? determined from the rate of change of the signal 013 from the throttle sensor 12? +Ii positive coefficient F
There are warm-up increase coefficients 1-W, etc., which are determined according to the 11 of water read from the TC and the water temperature sensor 20.

After processing 1■ in step 120, the process proceeds to step 130.
The process proceeds to OPEN 1J to determine whether feedback control of the air-fuel ratio should be performed based on the operating state of the internal combustion engine 1 read in step 100, the output signal of the lean sensor 4, etc.
A determination is made whether 1101I should be performed. The determination in step 130 can be made, for example, when the cooling water temperature Tw is sufficiently high and it can be considered that warm-up has been completed, and when the rate of change in the output horn signal Op of the throttle sensor is within a predetermined range, it can be determined that gradual acceleration is being performed. , and when the output of the lean sensor 4 is within the normal range, the internal combustion engine 1 uses the output of the lean sensor 4 to perform feedback control of the air-fuel ratioll (air-fuel ratio F / [3ilI'l
Assuming that the control is in step 1,
40. If even one of the above three conditions is not met, the determination in step 130 determines that the internal combustion engine 1 is in a state where it should perform A-pun control of the air-fuel ratio, and the control is shifted to step 150.

Since the feedback I11+ is performed in step 140, the A-Pun control operation 1. 'l Correction coefficient K is set to 1<2. In the following step 160, in order to carry out feedback control of the air-fuel ratio, the actual air-fuel ratio determined from the output of Reinron 1 and 4 and the target air; 2I! A feedback correction coefficient FAllIi is obtained by detecting the difference with the ratio. The target air-fuel ratio is normally set to the stoichiometric air-fuel ratio, and is set to a value larger than the stoichiometric air-fuel ratio when performing lean burn.

On the other hand, in step 150, in response to the determination in step 130 that A-sin control is to be performed, the oven 11 and 121
1 implementation 115? +Ii il coefficient K to 1 1-
Place 11! There are 4 results. Here, 1 is slightly larger than 2 (1 - C1 is predetermined according to the fuel injection system of the internal combustion engine, and the air-fuel ratio is set to [1 standard air-fuel ratio J It is used as an air-fuel ratio correction means to control the plowing speed to be slightly richer.

#; 1 <In step 170, the air-fuel ratio feedback correction coefficient rAt2 is set to λ, since the air-fuel ratio foot buckle 11-10 is not rejected.

After completing step 160 in the case where air-fuel ratio feedback control is performed, or after completing step 170 in the case where oven control is performed, the process moves to step 180. The l1fa injection period (fuel injection time) τ is determined. Here τ is already in step 1
Basic fuel injection 61 determined in step 10 Tp1 Each correction coefficient determined in step 120 (representing various correction coefficients such as 100% increase coefficient FWL and transient correction coefficient FTO)
z,...tm).

fl (u+, uz, . . . Ll r+)), in step 140 or step 150
A-Pun control tip opening 4 correction section vIK, smooth 1
J: is calculated from the air-fuel ratio feedback correction coefficient FΔF set in step 60 or step 170 using the following equation.

τ-Tll XFAFXf o (t + , t 2
, -tm)X [+f 1 (u 1 , IJ
2. -IIn) ]+Tv...(1) Here, TV is the invalid injection QJ ll? for correcting the delay in the operation of the m-fuel injection valve. It is between J. In the following step 190, the fuel (fuel) F31 chanting hanger (fuel 1f1
1JJ I+,) +7i1) According to τ, the output cap-
A control signal is output to the fuel injection valve 72 via the fuel injection valve 1-67, and the fuel injection valve 24 is ignited to control the fuel pitch.

After the above processing is completed, the process exits to N and ends this control routine.

1. In J3 of this embodiment configured as above, if either feedback control or A-synth control of the air-fuel ratio is performed depending on the operating state of the internal combustion engine, Operating status fl! (Whether warming is completed or not, etc.) (5) If air-fuel ratio oven control is performed due to an abnormality in Lean-4, etc., the air-fuel ratio feedback correction coefficient F
Let AF be λ, A-Pun control real IM11. ! 1 correction coefficient 1 is set to 1 to a value larger than 1 < 7 when feedback control is performed, and using the correction coefficient 1
4iIS is configured to increase and correct the 31-ring OJ Inτ. Therefore, air-fuel ratio oven control implementation +1i'+
The air-fuel ratio is controlled so that the air-fuel ratio of the internal combustion engine becomes richer than the target air-fuel ratio. For this reason, the problem that the air-fuel ratio of the internal combustion engine shifts to the lean side when A-shin control is performed due to differences in equipment, changes over time, etc., resulting in deterioration of drivability has been sufficiently resolved. .

In particular, during lean burn actual IM, even a slight deviation of the air-fuel ratio toward the lean side has a large effect on drivability.
Control of the air-fuel ratio toward the reach side by setting the correction coefficient at the time of execution is tfj-C as control of the air-fuel ratio when performing lean burn by A-pu control.

Next, a second embodiment of the present invention will be explained. The second embodiment has the same equipment and configuration as the first embodiment, and its control is
As shown in flowcharts 1 to 1 in FIG. 6, there are some differences from the first embodiment. In the second embodiment, each process shown in steps 200 to 290 in FIG. 6 is different from each process in steps 100 to 190 shown in the flowchart in FIG. 5 of the first embodiment, except for the following points. are the same.

(a) Step 2 of setting the learning value KG immediately after step 260 corresponding to step 160 of the first embodiment
65 has been inserted.

(1)) In step 280 corresponding to step 180 of the first embodiment, the fuel injection amount (fuel injection time) τ is calculated as r=Tp x in place of equation (1) as already described in the first embodiment.
KGxFAFxf o (t , , t 2 .

−Lm) x [+f 1 (u + , u
2.・un)]4−l”v...(2) Calculated as follows.

That is, in the second embodiment, so-called learned value control of the air-fuel ratio is adopted in which the combustion single injection Daffi is corrected using the learned value KO set by the air-fuel ratio feedback correction coefficient FAF.

Step 20 excluding steps 265 and 280
Each process from step 0 to step 290 corresponds to each process from step 100 to step 190 of the first embodiment, so a description thereof will be omitted.
The details of the process will be explained based on the flowchart of FIG.

After performing air-fuel ratio feedback control in step 260 and calculating the air-fuel ratio feedback correction coefficient FAF, a process is performed in step 265a to calculate the average value [8FAV] of the feedback correction coefficient FAF.

In the subsequent step 265)b, a value 1 corresponding to the stoichiometric air-fuel ratio is subtracted from the average value FΔFAV of the feedback correction coefficient FAF determined in step 265a, and a process is performed to calculate the deviation amount ΔFAF from the target air-fuel ratio. After the process in step 265b, in step 265G, the deviation amount Δ
FAF is within a predetermined range (here -0°02 to 0.02)
It is determined whether or not it is included. If the deviation amount ΔFAF is within this range, no processing is performed,
Exit to step 280. On the other hand, the deviation amount Δ1:Δ[
is smaller than -0,02, the process proceeds to step 265
Proceed to d and select the predetermined 1n from Gaku W (flKG).
α, for example 0.03, is reduced. Conversely, the deviation amount ΔFA
If F is larger than 0.02 ++, 1N, the process moves to step 265e, and the learning value KG is set to the same predetermined value α(0
,03) is added and overturned. Step 265d, Step 26
After any processing in step 5e, the processing returns to slurry tube 280.

In step 280, as already explained, the above equation (2) is used.
Based on? ,! i $31 Fukawa m1 is calculated.

Therefore, if the air-fuel ratio is controlled by the learned value,
The deviation of the actual air-fuel ratio from the target enhanced fuel ratio is once reflected in the feedback correction coefficient FAF, and then the feedback correction coefficient is transferred to the learning value KG every time the deviation of the average value FAFAV of the coefficient exceeds a predetermined value (1). On a steady basis, the air-fuel ratio noise back coefficient i [coefficient is always kept near the value 1, which corresponds to the stoichiometric air-fuel ratio, and the I difference of each part of the device and the coefficient
□The error caused by one change will be corrected by learning 1ffj K G.

Therefore, in addition to the effects of the first embodiment, the second embodiment also provides the following effects. In other words, learning 1i
Even when f1 control is being performed, the so-called "sensor K G deviation", that is, the response delay of the learned value control causes a learning (ifj K G deviation (see Fig. 2). Actually, there is a broken line (what deviation) between C and C in 1, and when air-fuel ratio η1 control shifts from feedback control (from 11 to A-pun control),
During the period [I] in FIG. 2, the air-fuel ratio does not shift toward the lean side, but in this embodiment, when performing open control of the air-fuel ratio, the correction coefficient K at the time of opening splitter 11 is The value at the time of feedback control is set to 1, which is larger than 2, and the fuel injection malfunction is set to the correction coefficient 1<
As a result of the increase correction, the air-fuel ratio is corrected to the rich side, so even if learning value control is performed, the air-fuel ratio may become lean and drivability may deteriorate when A-bun control of the air-fuel ratio is performed. has been done d′j sufficiently before. In addition, due to abnormal exhaust temperature heating, Lean Hinsa 4
Even in the case where an incorrect learning value KG is learned due to an abnormality in the starting angle, the air-fuel ratio will be corrected to the rich side for the above-mentioned reasons, so there will be no deterioration of drivability due to overleaning. .

In addition, in the two embodiments detailed above, a control correction coefficient is used as the air-fuel ratio correction means, and this is used as the A-JIN 911j Mijitsu III! ! However, instead of using the correction coefficient K when performing open control, the air-fuel ratio is set to a value as large as 1 as the air-fuel ratio feedback correction coefficient to shift the air-fuel ratio to the ridge side. Alternatively, the air-fuel ratio may be extracted by an auxiliary fuel injection means for the auxiliary fuel width so that the air-fuel ratio is corrected to the rich side when the open control U++ is implemented.

In addition, in these embodiments, the combustion is performed once every 2 revolutions of the crank. J'J will be held 131 times 1. Although the present invention has been described using an internal combustion engine in which the II tall is performed, there is no problem in applying the present invention to a multi-cylinder independent fuel internal combustion engine.

In addition, in the above example, when open control is executed, A supplementary iL-failure KLJ A-when control is executed, 1 is uniformly set.
However, the value may be changed depending on the internal combustion engine load, cooling water, etc., and other operating conditions of the internal combustion engine. In this case, when it is necessary to increase the output of the internal combustion engine, such as during acceleration, the correction coefficient 1 is increased to increase the correction amount of the air-fuel ratio from the lean side to the rich side, thereby further improving drivability. This is achieved through precise control such as measuring the improvement of

Although several embodiments of the present invention have been described above, the present invention is not limited to these embodiments in any way, and the gist of the present invention can be implemented in various embodiments within the scope of In2L and fU. Of course you can get it.

[Effects of the Invention] As detailed above, the air-fuel ratio control device for an internal combustion engine of the present invention performs air-fuel ratio control of either air-fuel ratio feedback control or A-bun control depending on the operating state of the internal combustion engine. At the same time, when the A-bun control is executed, the air-fuel ratio is corrected to decrease.

Therefore, when performing A-Pun control of the air-fuel ratio, the air-fuel ratio of the internal combustion engine is controlled slightly to the ridge side compared to the target air-fuel ratio, and as a result, the air-fuel ratio of the internal combustion engine is controlled to be slightly higher than the target air-fuel ratio. The air-fuel ratio of the internal combustion engine does not deviate to the lean side when the control is executed, and good drivability can be ensured, which is an excellent effect.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the relationship between the internal combustion engine load and the internal combustion value in the prior art, Fig. 2 is a schematic diagram of the air-fuel ratio control device including the internal combustion engine and its peripheral devices, and Fig. 5 The figure shows 70-digits representing the control of the first embodiment, FIG. Explain Jrufu 1”-Chit
-1. 1...Internal combustion engine main body 2...Fuel injection valve 4...Lean sensor 18...Intake 1) 1 other person Figure 1 Figure 2 Time FJI

Claims (1)

[Claims] Operating state detection means for detecting the operating state of an internal combustion engine, including the load; an air-fuel ratio detection means for detecting an air-fuel ratio based on the internal combustion engine exhaust composition; and an air-fuel ratio detection means for detecting an air-fuel ratio based on the internal combustion engine exhaust composition; The amount of salt 11 is determined, and the fuel supply means is controlled according to the supply amount of the salt 11, and the air-fuel ratio of the internal combustion engine is controlled by open control, or the fuel supply I is corrected according to the air-fuel ratio detected by the air-fuel ratio detection means. , feedback control that controls the fuel supply means to control the air-fuel ratio of the internal combustion engine to a target air-fuel ratio, or a control means that performs either of the following in accordance with the operating state of the internal combustion engine detected by the operating state detecting means. An air-fuel ratio control device for an internal combustion engine, characterized in that the control means includes an air-fuel ratio correction means for decreasing the air-fuel ratio when performing oven control of the air-fuel ratio. Device.