JPH0223241A - Air-fuel ratio control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent deterioration of exhaust emission and hunting of idle rotational frequency by executing feedback control according to rich lean judgement instead of air-fuel ratio feedback control according to output of O2 sensor during designated operating condition. CONSTITUTION:During operation of an engine, according to the relationship between a deviation between the target air-fuel ratio previously stored in storage means A and the air fuel ratio of air-fuel mixture and an oxygen concentration (O2) sensor output, the first air fuel ratio controlled variable is set corresponding to output of the O2 sensor by the first controlled variable setting means B. When it is detected by air fuel ratio control means F that the engine operating condition is not in a designated condition, the air-fuel ratio is controlled according to the first air-fuel controlled variable, and when it is detected that is in a designated condition, the air-fuel ratio is controlled according to the second air-fuel ratio controlled variable.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention detects the oxygen concentration in exhaust gas from an engine using an oxygen concentration sensor (hereinafter referred to as 02 sensor), and controls the air-fuel ratio based on this detected value. This invention relates to an air-fuel ratio control device for an engine.

[Prior art] Conventionally, the oxygen concentration in the exhaust gas is detected by the 02 sensor installed in the exhaust system, and the detection result by this sensor is rich (
? ! A feedback control method is known in which the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine is adjusted to the stoichiometric air-fuel ratio by determining whether the air-fuel mixture is lean or lean.

Recently, a method has become known in which the air-fuel ratio in the exhaust gas is directly detected from the output characteristics of the 02 sensor relative to the air-fuel ratio, and an air-fuel ratio correction amount is determined based on the deviation from the target air-fuel ratio, thereby performing air-fuel ratio feedback control. (Unexamined Japanese Patent Publication No. 51-14002)
(See Publication No. 1). In this method, since the output characteristics of the 02 sensor relative to the air-fuel ratio are affected by temperature, it is necessary to keep the temperature of the 02 sensor constant.

However, the sensor temperature is rising while the internal combustion engine is warming up, and during high-load operation, the sensor temperature rises too much due to the exhaust temperature, and immediately after high-load operation, the sensor temperature rises.
Due to the heat capacity of the 02 sensor, the sensor temperature does not come down easily, and the deviation from the target air-fuel ratio cannot be detected accurately.If air-fuel ratio feedback control is performed based on the deviation between the target air-fuel ratio and the air-fuel ratio detected by the 02 sensor, the emission The problem was that it worsened.

In addition, if this control method is used when an internal combustion engine is running at idle, since there is no load at idle, it is easily affected by external disturbances such as the operation of an air conditioner, making the idle unstable and causing the feedback frequency to decrease. As a result, there is a problem in that the control amount fluctuates greatly, causing hunting in the engine speed.

The present invention has been made to solve the above-mentioned problems, and its purpose is to detect when the operating state of an internal combustion engine is in a predetermined state, for example, during warm-up of the engine, during high-load operation, or during other predetermined periods. If it is detected that the temperature is not within a predetermined value or the idling state is detected, feedback control based on the deviation between the target air-fuel ratio and the detected air-fuel ratio corresponding to the 02 sensor output is performed. Rich
An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine that can prevent deterioration of emissions, hunting of engine speed, etc. by performing feedback control based on lean determination.

[Means for Solving the Problems] In order to achieve the above object, the present invention, as shown in FIG. Based on the oxygen concentration sensor that outputs a signal corresponding to the air-fuel ratio of the air-fuel mixture supplied to the engine, and the output characteristics of the oxygen concentration sensor with respect to the air-fuel ratio of the air-fuel mixture supplied to the engine, the target air-fuel ratio and the supplied air-fuel ratio are determined. storage means for storing in advance the relationship between the deviation from the air-fuel ratio of the air-fuel mixture and the output of the oxygen concentration sensor; and the relationship stored in the storage means is used to respond to the output of the oxygen concentration sensor. a first control amount setting means for determining an air-fuel ratio deviation and setting an air-fuel ratio control amount according to the deviation; an operating state detecting means for detecting that the operating state of the engine is a predetermined state; rich/lean determining means for determining whether the air-fuel ratio of the air-fuel mixture supplied to the engine is richer or leaner than the target air-fuel ratio based on the output of the oxygen concentration sensor; When the operating state of the engine is not detected to be in the predetermined state by the second control amount setting means for setting the air-fuel ratio control amount according to the determination result and the operating state detection means, the first control amount setting means sets the air-fuel ratio control amount according to the determination result. The air-fuel ratio of the air-fuel mixture supplied to the engine is controlled based on the air-fuel ratio control amount set by the control amount setting means, and when detected, the air-fuel ratio is set by the second control amount setting means. The gist thereof is an air-fuel ratio control device for an internal combustion engine, which includes an air-fuel ratio control means for controlling the air-fuel ratio of an air-fuel mixture supplied to the engine based on a control amount.

The predetermined state detected by the operating state detection means is a warm-up state of the engine.

Further, the predetermined state detected by the operating state detection means may be a high-load operating state of the engine.

Further, the predetermined state detected by the operating state detection means may be within a predetermined period after the engine is released from a high load state.

Furthermore, the predetermined state detected by the operating state detection means may be an idling operating state of the engine.

[Operation] According to the configuration of the air-fuel ratio control device, the first control amount setting means detects the deviation between the target air-fuel ratio stored in the storage means and the air-fuel ratio of the supplied air-fuel mixture and the oxygen concentration sensor. Using the relationship with the output, an air-fuel ratio deviation is determined corresponding to the output of the oxygen concentration sensor, and an air-fuel ratio control amount is set in accordance with the deviation.

The second control amount setting means is a rich/lean determining means for determining whether the air-fuel ratio of the air-fuel mixture supplied to the engine is richer or leaner than the target air-fuel ratio based on the output of the oxygen concentration sensor. The air-fuel ratio control amount is set according to the determination result.

When the operating state detection means does not detect that the operating state of the engine is in a predetermined state, the air-fuel ratio control means controls the engine based on the air-fuel ratio control amount set by the first control amount setting means. and when it is detected that the engine operating state is in a predetermined state, the engine is controlled based on the air-fuel ratio control amount set by the second control amount setting means. controls the air-fuel ratio of the mixture supplied to the

Then, when the engine is warmed up, the air-fuel ratio is controlled according to the rich/lean determination result. Furthermore, the air-fuel ratio is controlled according to the rich/lean determination results when the engine is in a high-load operating state, within a predetermined period after the engine exits the high-load state, or when the engine is in an idling operating state. .

[Example] An example embodying the present invention will be described below with reference to FIGS. 2 to 10.

FIG. 2 is a schematic system diagram showing a vehicle internal combustion engine (hereinafter referred to as engine) equipped with the air-fuel ratio control device of this embodiment and its peripheral devices.

The engine 1 includes an intake system 4 that sucks air from the atmosphere, mixes fuel injected by a fuel injection valve 2 with air, and guides the mixture to an intake boat 3, and an intake system 4 that absorbs air from the atmosphere, mixes the air with fuel injected by a fuel injection valve 2, and guides the mixture to an intake boat 3. It includes a combustion chamber 7 that extracts rotational movement via a piston 6, and an exhaust system 9 that exhausts gas after combustion via an exhaust boat 8.

The intake system 4 includes an air cleaner (path shown) that takes in atmospheric air;
It is comprised of a throttle valve 10 that controls the amount of intake air, a surge tank 11 that smoothes the pulsation of intake air, and the like, and the surge tank 11 is provided with an intake pressure sensor 12 that detects intake pipe negative pressure P. The amount of intake air is controlled by the opening degree of a throttle valve 10 that is linked to an accelerator pedal (not shown). In addition to the intake pressure sensor 12, the intake system 4 includes an opening sensor 13a (see FIG. 3) that outputs a signal according to the opening of the throttle valve 10, and which is turned on when the engine 1 is idling. A throttle position sensor 13 including an idle switch 13b (see FIG. 3), an intake temperature sensor 14, and the like are provided.

The exhaust system 9 is provided with an electromotive force type oxygen concentration sensor (hereinafter referred to as 02 sensor) 15 that detects the oxygen concentration in the exhaust gas. Further, the spark plugs 5 provided in each cylinder of the engine 1 are connected to a distributor 17 that distributes high voltage generated by an igniter 16 in synchronization with the rotation of a crankshaft (not shown). This distributor 17 is provided with a rotational speed sensor 18 that generates a pulse according to the engine 10 rotational speed NE, and a cylinder discrimination sensor 19. The cylinder block la of the engine 1 is cooled by circulating cooling water, and the temperature of this cooling water, which is one of the operating conditions of the engine 1, is detected by a cooling water temperature sensor 20 provided in the cylinder block 1a. Ru.

Each of the above sensor signals for detecting the operating state of the engine 1 is
is input to an electronic control circuit (hereinafter referred to as ECU) 21,
It is used to control the fuel injection amount of the fuel injection valve 2, the ignition timing of the spark plug 5, etc.

As shown in FIG. 3, the ECU 21 is a central processing unit (C
PtJ) 22a, read only memory (ROM)
22b, random access memory (RAM) 22c
It is mainly composed of a one-chip microcomputer 22 that incorporates the following. The rotation speed sensor 1B, the cylinder discrimination sensor 19, and the igniter 16 are directly connected to the input/output boat of the microcomputer 22, and
A/D conversion input circuit 2 inside the microcomputer 22
3, a heater energization control circuit 25 that controls the power supplied to the heater 15b for heating the detection element 15a of the 02 sensor 15 using the battery 24 as a power source, and a drive circuit 26 that drives the fuel injection valve 2 are connected. has been done.

Connected to the A/D conversion input circuit 23 are sensors that output analog signals, such as the intake pressure sensor 12, the opening sensor 13a1 of the throttle position sensor 13, the intake temperature sensor 14, and the coolant temperature sensor 20. Therefore, CPU22
a can read various parameters reflecting the operating state of the engine 1 via the A/D conversion input circuit 23 and know them one by one. Moreover, this A/D conversion input circuit 23 includes:
The output of the heater energization control circuit 25 that applies voltage to the heater 15b of the 02 sensor 15, the terminal voltage output of the current detection resistor 28, and the terminal of the detection element 15a are connected, and the applied voltage of the heater 15b and the detection element The electromotive force generated in the heater 15a and the current flowing in the heater 15b can be detected.

On the other hand, the microcomputer 22 directly controls the igniter 1.
These actuators are driven by outputting a drive signal to the fuel injection valve 2 through the drive circuit 26 or by outputting a control signal to the fuel injection valve 2 via the drive circuit 26.

In the ECU 21 of this embodiment configured in this way,
The operating state of the engine 1 is read and various control processes are executed, but since it is used for fuel injection control, air-fuel ratio control, etc.
The oxygen concentration in the exhaust gas of the engine 1 is being detected.

Next, the control processes executed by this ECU 21 are
This will be explained based on the flowchart shown in FIG.

FIG. 4 shows a warm-up determination process for the engine 1, which is executed at predetermined intervals.

First, in step 100, it is determined whether the engine 1 is starting by checking whether the engine 1 is being started, for example, whether the starter switch (as shown) is being turned on, and determining whether the engine 1 is being started or not. If it is determined that the
Proceed to. If it is determined that the engine is being turned on and is being started, the process proceeds to step 101, where the timer built in the CPU 22a is reset to rOJ to start timing, and the warm-up flag XWUP is set to "O". Reset to .

Next, in step 102, the state of the warm-up flag xwup is determined, and if it is determined that the warm-up flag It is determined whether or not the time measured by is equal to or greater than a predetermined value corresponding to after warm-up. If the time measured by the timer is less than a predetermined value, the process proceeds to step 104 and the warm-up flag The flag xwup is set to "1" and the process ends.

FIG. 5 is a flowchart showing a process executed by the ECU 21 to determine an over-rise state of the 02 sensor temperature due to high-load operation of the engine 1, and this process is also executed at predetermined time intervals. That is, this routine is a process for dealing with a change in the element temperature of the 02 sensor 15 estimated from the engine rotation speed NE detected by the rotation speed sensor 18 in the normal operating state of the engine 1. Here, the temperature of the detection element 15a of the 02 sensor 15 is estimated from the engine speed NE.If the relationship between the engine speed NE and the element temperature of the 02 sensor 15 is expressed as a time chart from an experimental example, the temperature of the detection element 15a of the 02 sensor 15 is estimated as shown in FIG. This is based on the fact that when the engine speed NE continues to be higher than a predetermined time for a predetermined time or more, the element temperature increases accordingly.

In step 110, based on the detection signal from the rotation speed sensor 18, the engine rotation speed NB has been at 4000 rpm or more for more than 4 minutes! Determine whether or not it continues. If the determination is affirmative, the high temperature determination flag XTE is set in step 111.
MP is set to "1", the high load flag XLOAD is set to rlJ in step 112, and this processing is completed. If a negative determination is made in step 110, it is determined in step 113 whether the high load flag XLOAD is set to "1". In the case of an affirmative judgment, that is, immediately after exiting from a state judged to be a high-load operation state,
At step 114, counter C is reset to "O",
At step 115, the high load flag XLOAD is reset to rOJ, and the process ends. Also, step 113
If a negative determination is made in step 116, it is determined whether the counter C is equal to or greater than a predetermined value C1 (a value corresponding to 2 to 3 minutes), and if c<Ct, the counter C is set to "" in step 117. 1” is added to complete this process, and conversely, C≧0
If it is 1, the high temperature determination flag XTEMP is set in step 118.
is reset to rOJ, and in step 119 the counter C
is set to a value obtained by adding "1" to the predetermined value C1, and this processing ends.

According to this process, the high temperature determination flag XTEMP is set to "1" during high load operation and for a predetermined time after high load operation, corresponding to the 02 sensor temperature in FIG. 9.

FIG. 6 is a flowchart showing air-fuel ratio feedback control executed by the ECU 21, and this process is also executed at predetermined time intervals.

In steps 120 and 121, based on the states of the warm-up flag XWUP and the high temperature determination flag A process for determining whether feedback control of the air-fuel ratio should be executed based on the rich/lean determination result of the detected air-fuel ratio is executed.

That is, the warm-up flag xwup is determined in step 120, and the high temperature determination flag XTEMP is determined in step 121.
are determined, and the flag xwup is set to "
1", and the flag The air-fuel ratio deviation Δλ with respect to the target air-fuel ratio (theoretical air-fuel ratio) is calculated based on the o2 sensor output from the map stored in the ROM 22b shown in FIG. In addition,
The map shown in FIG. 7(b) is obtained by reversing the relationship between the 02 sensor output and the air-fuel ratio when the 02 sensor temperature is 600° C. shown in FIG. 7(al).
Then, a proportional correction value PR and an integral correction value IN are determined from the proportional value map shown in FIG. 8(a) and the integral value map shown in FIG. 8(b) stored in the ROM 22b. Then, the process proceeds to step 124 to calculate the air-fuel ratio correction coefficient FAF, and then, in step 125, the proportional correction value PR is set to PRO.
shall be.

On the other hand, in step 120, the warm-up flag XWUP is set to "0".
”, or if it is determined in step 121 that the high temperature determination flag Feedback control determination processing is executed.

In step 126, it is determined that the air-fuel ratio currently detected by the 02 sensor 15 is rich compared to the target air-fuel ratio at that time, and in step 127, it is determined that the previously detected air-fuel ratio was also rich. Then step 1
Proceeding to step 28, the air-fuel ratio correction coefficient FAF is set to (FAF-1).

If it is determined in step 127 that the previously detected air-fuel ratio was lean, then in step 129 the air-fuel ratio correction coefficient FAF is set to (FAF-Rs) (where Rs>
1).

On the other hand, in step 126, it is determined that the currently detected air-fuel ratio is lean compared to the target air-fuel ratio at that time, and in step 130, it is determined that the previously detected air-fuel ratio was also lean. Then, the process proceeds to step 131, where the air-fuel ratio correction coefficient FAF is set to (FAF+1). Further, if it is determined in step 130 that the previously detected air-fuel ratio is low or low, the air-fuel ratio correction coefficient FAF is
AF+Rs).

Then, the air-fuel ratio correction coefficient F obtained by the above processing
Based on AF, the amount of fuel injected from the fuel injection valve 2 is corrected in the fuel injection amount calculation process so that the air-fuel ratio of the air-fuel mixture supplied to the engine 1 becomes the target air-fuel ratio (stoichiometric air-fuel ratio). . Therefore, the air-fuel ratio of the air-fuel mixture is controlled to the target air-fuel ratio.

By the way, when the engine 1 is warmed up, the 02 sensor temperature is low, and the actual 02 sensor output is, for example, 7th
Because it becomes the 500°C pattern shown in figure (a),
If the deviation Δλ is calculated from the map shown in Figure 7 (bl) set based on the 600°C pattern, the value will be different from the actual deviation.When air-fuel ratio control is executed using the deviation Δλ obtained from the map. , causing deterioration of emissions.

However, in this embodiment, when the engine 1 is warmed up, as shown in FIG. Since it is determined based on the judgment, it is possible to prevent the above-mentioned deterioration of emissions during the rise in element temperature during warm-up.

In addition, in this embodiment, as shown in FIG.
00 rpm or more for more than 4 minutes), in other words, the sensor temperature of the 02 sensor 15 becomes higher than the predetermined range as shown in FIG. 10(d) due to an increase in exhaust temperature, and the 02 sensor output characteristic For example, 7 in Figure 7(a)
Even if the pattern changes to 00°C and an accurate air-fuel ratio deviation cannot be obtained, the air-fuel ratio correction coefficient FAF
is determined based on rich/lean judgment, so it is possible to prevent deterioration of emissions.Furthermore, even during periods when the sensor temperature is still judged to be high due to the heat capacity of the 02 sensor 15 even after exiting from high-load operation, Since the air-fuel ratio correction coefficient FAF is determined based on rich/lean determination, deterioration of emissions can be prevented.

Incidentally, in the embodiment described above, the time from startup is used to determine whether the engine is being warmed up or after 11 engines, but the determination may be made based on the coolant temperature of the engine 1.

In addition, although the high-load operating state was determined using rotational speed and time, it may also be determined by intake pipe negative pressure, throttle opening, etc., or even by combining each of the above-mentioned parameters. You may. Furthermore, if the engine has a sensor that measures the amount of intake air, the high load may be determined using the amount of intake air or the amount of intake air and the rotational speed.

Next, a second embodiment of the present invention will be described based on a flowchart shown in FIG. 11 which is executed at predetermined time intervals. In this embodiment, when the engine 1 is in an idling state, the ECU
By performing air-fuel ratio feedback control based on the rich/lean judgment result of the air-fuel ratio detected by the 02 sensor 15, hunting of the idle rotation speed can be prevented even if there is disturbance due to the operation of the air conditioner during this idling operation. This is how it was done.

First, in step 140, the output Ox of the 02 sensor 15 is detected, and in the subsequent step 141, the idle switch 13 is detected.
By detecting the state b, it is determined whether the vehicle is in an idling state. Then, in this step 141, if the idle operation state is not set, that is, the idle switch 13b
If it is determined that is off, the processing from step 142 onwards is executed. The processing after step 142 is the same as the processing after step 122 in the embodiment described above. Also, in step 141, the engine is in an idling state, that is,
If it is determined that the idle switch 13b is on, the processing from step 146 onwards is executed. This step 14
The processing after step 6 is the same as the processing after step 126 in the previous embodiment.

Therefore, according to this example, when the engine 1 is in an idling state, the ECU 21 performs air-fuel ratio feedback control based on the rich/lean judgment result of the air-fuel ratio detected by the 02 sensor 15, as shown in FIG. 12('b). As shown in Figure 12(C), the fluctuations in the air-fuel ratio correction coefficient 1iiFAF are small, and accordingly, as shown in Figure 12 (C), the fluctuations in the idle speed are also small, and idle stabilization is achieved.On the other hand, the air-fuel ratio deviation during idling is When air-fuel ratio control is performed based on Δλ, the air-fuel ratio correction coefficient F
The AF fluctuations are large, and as a result, the idle rotation is also large (hunting occurs, making the idle unstable), as shown in Figure 13 (tc).

In the first embodiment, the element temperature of the 02 sensor 15 is determined by the engine rotation speed NE as the operating state of the engine 1.
However, a thermocouple is attached to the detection element 15a of the 02 sensor 15 to directly detect the temperature, or
The internal resistance of the detection element 15a of the second sensor 15 is measured, and the temperature is determined from the measured internal resistance. Based on this leaching temperature, the air-fuel ratio feed pump/pump control 8 and the air-fuel ratio are performed based on the rich/lean judgment results. The air-fuel ratio feedback control based on the deviation Δλ may be switched.

[Effects of the Invention] As described in detail above, according to the air-fuel ratio control device according to the present invention, the operating state of the internal combustion engine is set to the predetermined operating state, for example,
When the O2 sensor temperature is not within the predetermined value during warm-up of the engine, during high-load operation, or for a predetermined period thereafter, or when the engine is in idle operation, the O2 sensor output characteristics are determined. Based on this relationship, instead of feedback control based on the deviation between the detected air-fuel ratio obtained based on the 02 sensor output and the target air-fuel ratio, feedback control based on rich/lean judgment is performed, which reduces emissions deterioration and idling. This has an excellent effect of preventing idle rotation speed hunting, etc.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of the present invention, Fig. 2 is a configuration diagram showing an engine equipped with an air-fuel pressure control system according to an embodiment of the present invention and its peripheral equipment, and Fig. 3 is an electrical configuration diagram. FIG. 4 is a flowchart showing engine warm-up time-specific processing, FIG. 5 is a flowchart showing processing for determining excessive rise in oxygen concentration sensor temperature due to engine high-load operation, and FIG. 6 is air-fuel ratio Flowchart showing feedback control; FIG. 7(a) is a map showing the relationship between the oxygen concentration sensor output and the air-fuel ratio; FIG. 7(a) is a map showing the relationship between the oxygen concentration sensor output and the air-fuel ratio deviation;
Figure 8(a) is a proportional value map defined by air-fuel ratio deviation,
Fig. 8 (bl is the integral value map defined by the air-fuel ratio deviation,
Fig. 9 is a graph showing the relationship between the engine speed and the element temperature of the oxygen concentration sensor, Fig. 10 is a graph for explaining the action, and Fig. 1B) is the output of the oxygen concentration sensor during warm-up. The graph (in the same figure) is a graph showing the control behavior during warm-up, the IC> in the same figure is a graph showing the output of the oxygen concentration sensor in a high-load operating state, and the figure (d) is a graph showing the temperature of the oxygen concentration sensor. Graph showing the changes; FIG. 11(e) is a graph showing the control behavior in high-load operating conditions; FIG. 11 is a flowchart showing air-fuel ratio feedback control during idling; FIG. 12 explains the operation of this example. FIG. 13 is a waveform diagram for explaining the effects of the conventional wI control method. In the figure, 1 is an engine as an internal combustion engine, 2 is a fuel injection valve, 4 is an intake system, 9 is an exhaust system, 12 is an intake pressure sensor, 13
b is an idle switch, 15 is an oxygen concentration sensor, 15a
is a detection element, 15b is a heater, 18 is a rotation speed sensor, 2
1 is a rich/lean discrimination means, an operating state detection means, and an air-fuel ratio control means. This is an electronic control circuit as first and second control amount setting means. Patent applicant: Nippondenso Co., Ltd. Agent: Patent attorney 1) Time between Hironobu and I

Claims (1)

[Claims] 1. An oxygen concentration sensor that is installed in the exhaust system of an internal combustion engine and that detects the oxygen concentration in the exhaust gas of the internal combustion engine and outputs a signal according to the air-fuel ratio of the air-fuel mixture supplied to the engine. and storing in advance a relationship between the deviation between the target air-fuel ratio and the air-fuel ratio of the supplied air-fuel mixture and the oxygen concentration sensor output, based on the output characteristics of the oxygen concentration sensor with respect to the air-fuel ratio of the air-fuel mixture supplied to the engine. and a storage means for storing the air-fuel ratio, and using the relationship stored in the storage means, determine an air-fuel ratio deviation corresponding to the output of the oxygen concentration sensor, and set an air-fuel ratio control amount according to the deviation. a first control amount setting means for detecting a predetermined operating state of the engine; and an operating state detecting means for detecting that the operating state of the engine is in a predetermined state; rich/lean determining means for determining whether the air-fuel ratio is richer or leaner than the target air-fuel ratio; and second control amount setting means for setting an air-fuel ratio control amount according to the determination result of the rich/lean determining means. When the operating state of the engine is not detected to be in the predetermined state by the operating state detection means, the air-fuel ratio control amount is supplied to the engine based on the air-fuel ratio control amount set by the first control amount setting means. an air-fuel ratio that controls the air-fuel ratio of the air-fuel mixture and, when detected, controls the air-fuel ratio of the air-fuel mixture supplied to the engine based on the air-fuel ratio control amount set by the second control amount setting means; 1. An air-fuel ratio control device for an internal combustion engine, comprising: a control means. 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the predetermined state detected by the operating state detection means is a warm-up state of the engine. 3. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the predetermined state detected by the operating state detection means is a high-load operating state of the engine. 4. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the predetermined state detected by the operating state detection means is within a predetermined period after the engine exits from a high load state. 5. Claim 1, wherein the predetermined state detected by the operating state detection means is an idling operating state of the engine.
The air-fuel ratio control device for the internal combustion engine described above.