JPS62121844A - Controller for air-fuel ratio of internal combustion engine - Google Patents

Abstract

PURPOSE:To perform fuel increment control coordinating with vapor content in the fuel in a controller to increase the fuel according to fuel temperature at engine starting by decreasing the fuel increment at a fixed rate, and at a rate larger than the above rate in starting feedback control. CONSTITUTION:A feedback controlling means FB performs the feedback control of fuel quantity to a fixed air-fuel ratio on the basis of the result of detection executed by a detecting means for engine operating state SE to detect operating state of an internal combustion engine EG. In such operating state as the internal combustion engine is restarted under the condition that the temperature of cooling water or suction air is high, a increasing means for fuel quantity at high temperature starting time TF increases the fuel quantity corresponding to vapor content generated in the fuel. A first decreasing means C1 decreases a fuel increment at a first fixed rate from the starting time, and a second decreasing means C2 decreases the fuel increment at a second fixed rate being larger than the first one, when operating conditions for starting the feedback control have been met.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an air-fuel ratio control for an internal combustion engine that can control the amount of fuel supplied to the internal combustion engine and constantly operate the internal combustion engine under optimal conditions. Regarding equipment.

[Prior Art] Conventionally, the amount of fuel supplied to an internal combustion engine mounted on a vehicle or the like has been controlled in order to operate the internal combustion engine under optimal conditions. The same is true when starting the internal combustion engine, and the injection time of the fuel injection device is appropriately set in order to supply an amount of fuel according to the starting characteristics of the internal combustion engine.

However, with the method of determining the amount of fuel to be supplied to the internal combustion engine in proportion to the injection time of the fuel injection device, the fuel in the fuel pipe of the fuel injection device is at a high temperature due to reasons such as high-load long-term operation of the internal combustion engine. In such a case, when paper is generated, the fuel supply is reduced by the amount of paper even if the injection time is the same, resulting in a considerably thinner air-fuel mixture compared to the desired air-fuel ratio. This phenomenon is particularly likely to occur when the internal combustion engine is starting, and there is a possibility that not enough fuel will be supplied to the internal combustion engine, resulting in poor starting performance, or even if the engine does move, the idling state may become unstable. There was sex.

Therefore, as disclosed in JP-A No. 56-81230 or JP-A No. 57-10741, when the internal combustion engine is started while the fuel is at a high temperature, the fuel injection amount is increased for a predetermined period of time. Devices that increase fuel injection amount according to fuel temperature and devices that increase fuel injection amount according to fuel temperature have been proposed.

[Problems to be Solved by the Invention] However, the above-mentioned apparatus also has the following problems, and is still not satisfactory.

In other words, paper generated in fuel piping varies depending on the various internal combustion engine systems and their usage conditions, from those generated very close to the fuel injection valve to those generated near the fuel tank side. The ejection time is not uniquely determined. Therefore, by simply increasing the fuel injection amount based only on the passage of time from the time of fetal movement, it is not possible to determine whether or not the paper has completely disappeared from the fuel pipe, and the paper is still in the fuel pipe. If you stop increasing the amount of fuel injected even though there is paper remaining, paper lock may occur, and conversely, if you continue increasing the amount for too long, the amount will continue to increase even after the paper runs out and the air-fuel ratio will become abnormal. There has been a problem in that this results in a dense condition, leading to deterioration of fuel efficiency and emissions.

Furthermore, although the fuel injection amount is increased according to the fuel temperature, the relationship between the fuel temperature and the amount of paper generated is not unambiguous, and as above, it depends on the internal combustion engine system and its usage conditions. This method has the same problem as described above because it is not possible to determine at what point the generated paper is ejected into the combustion chamber of the internal combustion engine.

In this way, conventionally, starting characteristics have been ensured to a minimum by increasing the amount of fuel by estimating the worst-case condition that occurs in the internal combustion engine system, but how to cancel the boost control is difficult. The question of whether this is a good idea has not yet been resolved.

[Object of the invention] The present invention has been made to solve the above problems,
By correcting the fuel injection amount according to the paper generated in the fuel pipe, the fuel amount 0'J'M when paper is generated is accurately corrected to improve fetal movement characteristics and idle stability. Another object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can improve fuel efficiency and transmission.

[Means for Solving the Problem 1] In order to achieve the above object, the means of the present invention is as shown in the basic configuration diagram of FIG. means SE; feedback control means FB for feedback controlling the amount of fuel injected and supplied to the internal combustion engine EG so that it becomes a predetermined air-fuel ratio when the detection result of the operating state detecting means SE satisfies a predetermined condition; According to the detection result of the state detection means SE, the temperature of the fuel supplied to the internal combustion engine EG is equal to or higher than a predetermined value.

In the air-fuel ratio control device for an internal combustion engine, the air-fuel ratio control device for an internal combustion engine includes a high temperature start increase means TF that increases the amount of fuel injected and supplied from the start of the internal combustion engine EG by a predetermined amount. a first stage reducing means C1 that reduces the increase in fuel by a first predetermined rate from when the internal combustion engine EG is started; The gist of the present invention is an air-fuel ratio control device for an internal combustion engine, comprising: a second stage reduction means C2 that reduces the fuel increase at a second predetermined rate greater than .

[Operation] The first stage reduction means C1 in the present invention functions to reduce the amount of fuel that has been increased more than usual due to the increase control executed by the high temperature start increase means TF at a first predetermined rate.

The increase control executed by the high temperature start increase means TF increases the amount of fuel sufficient to replenish the amount of vapor and increases the amount of fuel in the internal combustion engine E.
It achieves G starting characteristics and stability in idle speed. On the other hand, the paper portion is a finite amount that exists in the piping between the fuel tank that supplies fuel and the fuel injection valve that performs fuel injection, and it is clear that it decreases each time fuel is injected and supplied from the fuel injection valve. It is. Furthermore, the degree of paper reduction can be estimated at the time of designing the internal combustion engine EG system.

Therefore, the present first stage reduction means C1 reduces the fuel that has been increased sufficiently in the initial stage of startup to ensure a good startup at a rate (first predetermined rate) in which the paper portion decreases, thereby increasing the so-called air-fuel ratio of the internal combustion engine EG. It controls the intake.

The second-stage reduction means C2 "acts" when a so-called feedback condition, which is a condition for the air-fuel ratio feedback control means FB to start operating, is established, and the first-stage reduction means C
The amount of fuel increased by the increase control is decreased at a rate greater than the decrease rate executed in step 1. As is well known, internal combustion engine EG
In order to operate the engine at a predetermined air-fuel ratio, it is preferable to measure the actual air-fuel ratio from the exhaust gas and feed back the results. In other words, the air-fuel ratio of the internal combustion engine can be controlled with higher precision and higher responsiveness than through blind control. Therefore, after such an air-fuel ratio feedback condition is established, the second stage reduction is to stop the injection control by the action of the first stage reduction means C1 and more quickly reduce the amount of fuel increased by the increase control that still remains. Means C2
That's why.

Note that the rate of reduction performed by the second stage reduction means C2 changes depending on the rotational speed of the internal combustion engine EG, the temperature of the cooling water, the lubricating oil, etc. at that time, and a sudden change in the operating state of the internal combustion engine EG occurs. Techniques may be added to ensure that this does not occur.

EXAMPLES Hereinafter, in order to explain the present invention more specifically, the present invention will be described in detail by giving examples.

[Embodiment] First, FIG. 2 is an explanatory diagram showing a gasoline engine and its peripheral devices equipped with an air-fuel ratio control device according to an embodiment of the present invention.

1 is the gasoline engine body, 2 is the piston, 3 is the spark plug, 4 is the exhaust manifold, 5 is the exhaust manifold 4
6 is a fuel injection valve that injects fuel into the intake air of the gasoline engine body 1, 7 is an intake manifold, and 8 is an intake valve that is sent to the gasoline engine body 1. An intake air temperature sensor 9 detects the temperature of the air, a water temperature sensor 9 detects the temperature of gasoline engine cooling water, a throttle valve 10 adjusts the intake air amount of the gasoline engine 1, and 11 detects the opening degree of the throttle valve 10. Throttle sensor, 14
15 represents an air flow meter that measures the amount of intake air, and 15 represents a surge tank that absorbs pulsation of the intake air.

16 is an igniter that outputs the high voltage necessary for ignition; 17 is a distributor that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder; and 18 is a distributor 17 A rotation angle sensor 19 is attached to the distributor 17 and outputs 24 pulse signals for one revolution of the distributor 17, that is, two revolutions of the crankshaft.
20 is an electronic control circuit, 21 is a key switch, and 22 is a starter motor. Reference numeral 26 represents a vehicle speed sensor that is interlocked with the axle and generates a pulse signal according to the vehicle speed.

Next, FIG. 3 shows a block diagram of the electronic control circuit 20 and its related parts.

30 is a central processing unit (hereinafter simply referred to as CPU) that inputs and calculates data output from each sensor according to a control program and performs processing to control the operation of various devices; 31 is a control program and a central processing unit (hereinafter simply referred to as CPU); A read-only memory (hereinafter simply referred to as RO'M) in which data is stored, and 32 a random access memory in which data input to the electronic control circuit 20 and data necessary for arithmetic control are temporarily read. (hereinafter simply RAM
33 is a backup random access memory (hereinafter simply referred to as backup RAM) as a non-volatile memory backed up by a battery so as to retain data necessary for subsequent operation of the internal combustion engine even when the key switch 21 is turned off. , 34 to 37 are buffers for the output signals of each sensor, and 38 is a buffer for the output signals of each sensor to the CPU 30.
39 is an A/D converter that converts an analog signal into a digital signal; 40 is an A/D converter that outputs each sensor signal to the CPU 30 via a buffer or via the buffer, multiplexer 38 and A/D converter 39;
and multiplexers 3B and A from the CPU 30.
It represents an input/output port that outputs a control signal for the /D converter 39.

41 converts the output signal of the oxygen sensor 5 into the comparator 4.
2, a buffer 43 represents a shaping circuit that shapes the waveforms of the output signals of the rotation angle sensor 18 and the cylinder discrimination sensor 19. The output of the throttle opening sensor 11 and the operation signal of the key switch 21 are sent to the CPU 3 by an input/output board 46 directly or via a buffer 41 or the like.
Sent to 0.

Additionally, 47.48 connects to CP via output port 49.50.
The drive circuits that drive the fuel injection valve 6 and the igniter 16 by signals from tJ30 are respectively shown. Also, 51 is a path line that serves as a path for signals and data, and 52 is a C
It represents a clock circuit that sends a clock signal serving as a control timing to the PU 30, ROM 31, RAM 32, etc. at predetermined intervals.

Next, the control executed by the electronic control circuit 20 of this embodiment will be described in detail.

The flowchart shown in FIG. 4 is the main control routine. This routine is started when the key switch 21 is turned on, and first performs initialization such as clearing the internal registers of the CPU 30 (step 100), then sets initial values of data used to control the gasoline engine 1, For example, carry out processing such as setting a flag indicating that a fuel cut is in progress to O (step 110).Next, the operating state of the gasoline engine 1, for example, from the air meter 14, rotation angle sensor 18, water temperature sensor 9, etc. Processing to read the signal is performed (step 120), and from the various data read in this way, the intake air ff1Q of the gasoline engine 1 is determined.
A process is performed to calculate various quantities that are the basis of control of the gas engine 1 non-engine 1, such as the engine speed, rotational speed N, or load Q/N (step 130). Thereafter, the well-known ignition control (step 140) is performed based on the various quantities obtained in step 130, and then the gasoline engine 1
Then, the process moves on to calculation of the amount of fuel to be injected and supplied. In order to limit the fuel amount, it is first determined whether the conditions for air-fuel ratio feedback control of the fuel amount exist (step 150), and if the conditions are not met, control is performed that is generally appropriate for the operating state of the gasoline engine 1 at that time. 'The fuel amount correction value is calculated in an open loop (step 160). The conditions for air-fuel ratio feedback are that the gasoline engine 1 is not cold and the oxygen sensor 5 is activated and operating, and that the gasoline engine 1 is not under an extremely high load and that the single signal continues for more than a predetermined time. This is satisfied under so-called steady operating conditions, such as in normal operating ranges where the If these conditions are not satisfied, the operating state of the gasoline engine 1 at that time,
For example, a correction value K for the amount of fuel used is calculated as will be described later in order to supply the optimal amount of fuel to the gasoline engine 1 at any given time, such as during power increase control during high-load operation. Further, at the same time as these calculation processes, a flag FB indicating that air-fuel ratio feedback control is currently being executed is reset, and is set to indicate that open control is currently being executed. When it is determined in step 150 that the air-fuel ratio feedback condition is satisfied, that is, when the gasoline engine 1 is operating stably in a normal steady state, normal feedback control (step 170) is executed. The air-fuel ratio control of the gasoline engine 1 when the above-mentioned severe conditions are satisfied is preferably based on highly accurate and highly responsive control called air-fuel ratio feedback 1J control, which is well known. Therefore, when such conditions are satisfied, the fuel amount correction value FAF based on the output of the oxygen sensor 5 is
is calculated and the aforementioned FB is set. In addition, in this step, as will be described later, in order to ensure a stable air-fuel ratio even if the operating state of the gasoline engine 1 suddenly deviates from the air-fuel ratio feedback control conditions, the air-fuel ratio is calculated from the current output of the oxygen sensor 5. The average value FAFAV of the FAF and the FAF excluded from past data is calculated, and is prepared for subsequent processing. After the optimum control for the operating condition of the gasoline engine 1 is selected in this way and the correction value K or FAF for the amount of fuel to be injected and supplied is calculated, the calculation of the fuel amount 1ffi in step 180 is executed, and the fuel amount 1ffi is actually calculated. The amount of fuel to be supplied to the engine 1 is determined. The calculation of the fuel injection amount executed in step 180 is performed according to the following equation.

T=TB*FAF* (K+Fhot) The value calculated here is the time to open the fuel injection valve 6 (fuel injection time), and TB is Stellar.

The basic fuel injection time is determined from the load, rotation speed, etc. calculated in step 130. As is clear from the above equation, the actual fuel injection time T is the basic fuel injection time TB, which is calculated according to the load and rotation speed, which are the basic operating conditions of the gasoline engine 1, and is optimally corrected for the operating conditions at that time. Calculated by correcting the value. In addition, another correction value Fh used to correct the basic fuel injection time TB in the above equation
Ot is unique to this embodiment, and is calculated by the processing in the flowchart described later. Once the optimal fuel injection time T for the gasoline engine 1 is calculated in this way, another fuel injection execution routine (not shown) executes synchronous injection at a predetermined crank angle synchronized with the rotation of the gasoline engine 1 only during the fuel injection time. , operation under the desired air-fuel ratio is actually achieved.

Next, calculation of the above-mentioned correction value Fhot unique to this embodiment will be explained based on the flowchart of FIG. 5. This Fhot calculation routine is repeatedly executed by the CPU 30 as a part of step 180 in the main routine, or as another predetermined time interrupt routine, so that the latest Fhot calculation routine is always executed when calculating the fuel injection time T.
t is provided.

When the process of this routine is started, it is first determined whether the throttle valve 10 is fully open based on the output of the throttle opening sensor 11 (step 200>, and if it is fully closed, the next step 210 is executed). Otherwise, it is determined that the process of ejecting the correction value FhOt for ensuring idling stability at startup is not necessary, and this routine is ended.

In step 210, the contents of the flag FB described above are determined, and subsequent processing is selected depending on whether air-fuel ratio feedback control has already been started. Here, if the gasoline engine 1 is already in a stable steady-state operating state and FB=1, the process proceeds to the Fhot high-speed reduction process from step 400 described later, and if the gasoline engine 1 is in a transient state such as starting, and FB=O. If so, the process advances to the following step 220.

In step 220, the temperature of the cooling water of the gasoline engine 1 is detected and determined as one method for estimating the temperature of the fuel supplied to the gasoline engine 1. In this step, if the output of the water temperature sensor 9 is higher than 85°C, proceed to the next step 230, and if it is lower than that, proceed to the previous step 230.
This routine ends in the same manner as 00.

In step 230, the temperature of the intake air of the gasoline engine 1, which is another information for estimating the fuel temperature, is detected.
Discern. At this time, the output of the intake air temperature sensor 8 is 65°C.
If it is higher, the process advances to the next step 240, and if it is lower, this routine ends as before.

Therefore, the operating status of the gasoline engine 1 when step 240 is executed is that the accelerator has not been operated yet, and that the water temperature TW>a5°C1 the intake temperature A>65°
A state where the air-fuel ratio feedback condition is not satisfied at C,
That is, when the gasoline engine 1 is restarted at a high temperature in a transient operating state. This step is executed only under such special conditions, and it is determined from the contents of the operated flag "H" whether or not the fuel increase specific to high temperature restart has already been carried out. FH
is reset when the Kallin engine 1 is started, and since FH=O is always set when this routine is executed for the first time, the process proceeds to the next step 250. Step 150
Then, the contents of another flag FSX are determined. This flag FSX is also reset when the gasoline engine 1 is started, and is provided to detect a state in which the once started air-fuel ratio feedback control is interrupted for some reason. Therefore, during normal startup, FBX=O, and the process proceeds to step 260.
0.1 is set to hot, 10% of fuel injection time T
The increase is executed. On the other hand, when FBX=1, step 270 is executed to avoid a sudden change in fuel amount from occurring in the gasoline engine 1, and the average value FAFAV'Ifi of FAF calculated in step 170 described above is
It is set to Fhot. In this way FhO
After t is set, a flag FH indicating that an increase in fuel amount due to Fhot has occurred is set in step 290, and this routine ends.

As described above, once the fuel amount is increased by setting Fhot, the processing of this routine from the next time will flow from step 200 to step 240 until the air-fuel ratio feedback condition of the gasoline engine 1 is satisfied.
F hot low speed reduction processing (step 30)
0 to step 350) are selected.

First, in step 300, a counter C is incremented, and it is determined whether or not the counter C has counted 256 (step 310).

The counter value “256” determined in this step 310
is a value that can be determined theoretically and experimentally based on the repetition execution speed of this routine and the paper reduction speed in the system of the gasoline engine 1 shown in FIG.

The reduction by 1'' corresponds to the increase in the effective injection amount due to the decrease in the amount of paper, and as a result, the window is appropriately set so that changes in the air-fuel ratio of the gasoline engine 1 can be prevented. Therefore, when it is determined that C<256, this routine is ended, and when C=256, the counter C is cleared in step 320 in preparation for the next counting process, and in step 330'""C' F hot 0.01
only decreases. The next steps 340 and 350 are Fho
This is guard processing for t, and in step 340 Fhot is set to O.
The following cases are determined, and only in this case step 350 is executed to set F hot to rOJ again.

By this Fhot low-speed reduction process, after the gasoline engine 1 has had good motion, the fuel is reduced by Fhot as quickly as the paper amount is reduced, and the air-fuel ratio is prevented from becoming abnormally rich.

When the air-fuel ratio feedback control condition is satisfied while the air-fuel ratio open control by the Fho°C low-speed reduction process is being executed and the flag FB is set to "1", the processing of this routine starts from step 200 and step 210. The process proceeds to a reduction process (steps 400 to 430).

Here, first, in step 400, flag FH is reset to indicate the end of the "hot addition 11 process", and in next step 410, flag FSX is set to indicate that the feedback condition described above has once been satisfied. At step 420, the counter C is incremented, and if the counter C reaches "30", the steps 320 to 32 described above are performed.
350 Fhot reduction processing is executed, and if C<30, this routine is ended. In other words, Fhot is reduced approximately eight times faster than the Fiot slow reduction process described above. Even if FhOt is rapidly reduced in this way, the correction value FAF by the air-fuel ratio feedback control is already involved in the calculation during the fuel injection time, and the air-fuel ratio of the gasoline engine 1 can be adjusted to the desired value with high precision and high responsiveness. Since the control is performed in a consistent manner, there will be no effects such as sudden changes in operating conditions.

As described above in detail about the Fhot calculation routine,
According to the processing of this routine, the amount of fuel at the time of high temperature restart is sufficiently increased by F hot so that the starting of the Ganlin engine 1 is smooth, but once the starting is completed, the paper amount of the gasoline engine 1 is reduced. l”hot worth it
Under conditions where Fhot is reduced and air-fuel ratio feedback control is performed, Fhot is reduced at a faster rate and the transition to air-fuel ratio control using only highly accurate and highly responsive air-fuel ratio feedback control occurs in a short time. .

FIG. 6 is an explanatory diagram comparing the above control with conventional control. (A> Figure shows when the air-fuel ratio feedback control condition is not satisfied for a long time and only open control of the air-fuel ratio by F hot is executed, and Figure (B) shows when the air-fuel ratio feedback control condition is satisfied midway through.) , both (
Figure I> shows the conventional control, and Figure (II) shows the control of the embodiment.

First, we will explain the case where the air-fuel ratio feedback condition shown in (A> figure is not satisfied). shifts to the ridge side.6 Also, if Fhot is suddenly set to rOJ in this condition, A/
This will lead to rapid fluctuations in F. However, in this embodiment, in such a case, a low-speed reduction process of Fhot is executed, so after starting the gasoline engine 1, the air-fuel ratio is controlled to gradually approach the stoichiometric air-fuel ratio, as shown in Figure (II). A change in air/fuel ratio is achieved.

In addition, even if the air-fuel ratio feedback condition is satisfied midway through as shown in (B) and FAF is calculated appropriately, in conventional control (1) the air-fuel ratio A is shifted to the -H rich side as shown in the diagram.
/F is off, there is a possibility that a sudden change in the air-fuel ratio will occur. However, in this embodiment, even in such a case, the air-fuel ratio A/F is smoothly controlled to the stoichiometric air-fuel ratio by executing a high-speed reduction process of Fhot within the range of responsiveness by FAF. .

[Effects of the Invention] As described above in detail with reference to embodiments, the air-fuel ratio control device for an internal combustion engine of the present invention includes: an operating state detection means for detecting the operating state of the internal combustion engine; and a detection means for the operating state detection means. Feedback control means for feedback controlling the amount of fuel injected and supplied to the internal combustion engine so that it becomes a predetermined air-fuel ratio when the result satisfies a predetermined condition; In an air-fuel ratio control device for an internal combustion engine, the air-fuel ratio control device for an internal combustion engine has a high-temperature start increasing means for increasing the amount of fuel injected and supplied from the start of the internal combustion engine by a predetermined amount when the fuel temperature is determined to be equal to or higher than a predetermined value. , the fuel increase amount due to the increase control is set to the first level from the time of starting the internal combustion engine.
a first stage reduction means for reducing the amount of fuel at a predetermined rate; and when a predetermined condition that is a condition of the feedback control is satisfied, reducing the fuel increase by a second predetermined rate that is larger than the first predetermined rate; It is characterized by a second stage reduction means, and evaluating the following.

Therefore, it is possible to control the increase in fuel amount in accordance with the amount of paper generated in the internal combustion engine at high temperatures, and not only ensure starting characteristics and idle stability, but also avoid unnecessary increase in fuel amount, thereby reducing the richness deviation of the air-fuel ratio. Moreover, it becomes an excellent air-fuel ratio control device for an internal combustion engine that can prevent the accompanying deterioration of fuel efficiency and emissions.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of the present invention, Fig. 2 is a schematic configuration diagram of a gasoline engine system equipped with an air-fuel ratio control device according to an embodiment, Fig. 3 is a block diagram of its control circuit, and Fig. 4 is an implementation example. A flowchart of the main routine of the example, FIG. 5 is a flowchart of determining the correction value Fhot, and FIG. 6 shows the air-fuel ratio and correction coefficient Fhot according to the conventional control and the embodiment control.
The time chart is shown below. EG...Internal combustion engine SE...Operating state detection means FB...Air-fuel ratio feedback control means TF...High temperature start increase means C1...First stage reduction means C2...Second stage reduction means 1...Gasoline engine 6...Fuel injection valve 8...Intake temperature sensor 9...Water temperature sensor 14...Air flow meter 1B...Rotation angle sensor 20...Electronic control circuit

Claims (1)

[Scope of Claims] Operating state detection means for detecting the operating state of the internal combustion engine; and when the detection result of the operating state detection means satisfies a predetermined condition, the amount of fuel injected and supplied to the internal combustion engine is adjusted to a predetermined air-fuel ratio. feedback control means for performing feedback control so that the temperature of the fuel supplied to the internal combustion engine is equal to or higher than a predetermined value based on the detection result of the operating state detection means; In the air-fuel ratio control device for an internal combustion engine, the air-fuel ratio control device for an internal combustion engine has a high-temperature start increasing means for increasing the amount of fuel by a predetermined amount.
a first stage reduction means for reducing the amount of fuel at a predetermined rate; and when a predetermined condition that is a condition of the feedback control is satisfied, reducing the fuel increase by a second predetermined rate that is larger than the first predetermined rate; An air-fuel ratio control device for an internal combustion engine, comprising: a second stage reduction means;