JPH084566A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress the occurrence of torque difference in level and a shock during switching of an air-fuel ratio as much as possible, to perform rapid switch of an air-fuel ratio, and to reduce an amount of discharging NOx. CONSTITUTION:An air-fuel ratio control device having an intake air amount control means comprises a means 105 to calculate a fuel injection amount during steady operation based on an intake air amount and the number of revolutions of an engine during steady operation; a means 104 to calculate a fuel injection amount during switching of an air-fuel ratio based on an accelerator pedaling angle and the number of revolutions of an engine during switching of an air-fuel ratio; a means 107 to calculate an throttle opening during steady operation based on an accelerator pedaling angle and the number of revolutions during steady operation; and a means 106 to calculate a throttle opening during switching of an air-fuel ratio based on a fuel injection amount and the number of revolutions during switching of an air-fuel ratio. During steady operation, a fuel injection amount and a throttle opening are calculated by the calculating means 105 and the means 107 to calculate a throttle opening during steady operation, and during switching of an air-fuel ratio, a fuel injection amount and a throttle opening are calculated by the calculating means 104 and the calculating means 106.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control system for an internal combustion engine which switches the air-fuel ratio between stoichiometric and lean.

[0002]

2. Description of the Related Art Generally, in fuel control using a fuel injection device in a gasoline internal combustion engine of an automobile, a fuel injection amount is controlled so that an intake air amount is detected by a sensor and a preset air-fuel ratio is obtained. By the way, there is known a technique for burning the air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine with a leaner air-fuel ratio than the stoichiometric air-fuel ratio (hereinafter, referred to as lean) in order to improve fuel economy of an automobile. In such combustion technology, if the engine is always burned lean, the output will be insufficient compared to when it is burned at the stoichiometric air-fuel ratio (hereinafter referred to as stoichiometry), so in an operating range where a large amount of output is required, The air-fuel ratio is switched to stoichiometry to compensate for the lack of output.

Further, in such an air-fuel ratio control method, conventionally, when the air-fuel ratio is switched, the intake air amount is not changed,
The air-fuel ratio was changed by changing the fuel injection amount. However, in such an air-fuel ratio control system, the output torque changes abruptly when the air-fuel ratio is suddenly switched. That is, when switching from stoichiometric to lean, the fuel amount decreases for the same intake air amount, so the torque sharply decreases (a torque step is generated), and there is a problem that the driver feels shock or discomfort. .

[0004]

Therefore, in order to solve the above problem, it is considered to reduce the shock by gently changing the air-fuel ratio when switching the air-fuel ratio. However, even with this method, since the fuel injection amount changes, the problem that the driver feels uncomfortable even if the throttle is kept constant and the torque gradually changes has not been solved. Further, when the air-fuel ratio is switched, a large number of operations are performed in the air-fuel ratio region where the NOx emission concentration is high, which causes a new problem in terms of exhaust gas purification.

The present invention has been made in view of the above problems, and an object thereof is to suppress a torque step and a shock at the time of switching the air-fuel ratio as much as possible and to provide a quick air-fuel ratio. It is an object of the present invention to provide an air-fuel ratio control device for an internal combustion engine, which can be switched and can reduce the NOx emission amount.

[0006]

In order to achieve the above object, an air-fuel ratio control system for an internal combustion engine according to the present invention is basically an internal combustion engine having means for controlling the intake air amount of the internal combustion engine. The air-fuel ratio control device is characterized by including means for calculating the fuel injection amount when the air-fuel ratio is switched according to the accelerator depression angle and the engine speed. More specifically, it is characterized in that the fuel injection amount is held at the time of switching the air-fuel ratio, and the fuel injection amount is finely adjusted according to the target air-fuel ratio at the time of switching the air-fuel ratio to obtain the air-fuel ratio. It is preferable that an increase in output torque per fuel is suppressed.

According to another aspect of the present invention, in an air-fuel ratio control system for an internal combustion engine, which comprises means for controlling the intake air amount of the internal combustion engine, the fuel injection amount is based on the intake air amount and the engine speed during steady operation. And a steady-state fuel injection amount calculation means for calculating the fuel injection amount, and an air-fuel ratio switching fuel injection amount calculation means for calculating the fuel injection amount based on the accelerator pedal depression angle and the engine speed when the air-fuel ratio is switched. More specifically, at the time of switching the air-fuel ratio, while switching from the calculation value of the steady-state fuel injection amount calculation means to the calculation value of the air-fuel ratio switching fuel injection amount calculation means, when the switching of the air-fuel ratio is completed It is preferable to include a fuel injection amount calculation value selection unit that controls switching of the fuel injection amount calculation value so as to return to the calculation value of the steady-state fuel injection amount calculation unit.

As another aspect, in an air-fuel ratio control system for an internal combustion engine equipped with a means for controlling the intake air amount of the internal combustion engine, the throttle opening is controlled based on the accelerator pedal depression angle and the engine speed during steady operation. The present invention is characterized by comprising a steady-state throttle opening degree calculating means for calculating and an air-fuel ratio switching throttle opening degree calculating means for calculating the throttle opening degree based on the fuel injection amount and the engine speed at the time of air-fuel ratio switching. More specifically, when the air-fuel ratio is switched, the steady state throttle opening calculation means is switched from the calculated value to the air-fuel ratio switching throttle opening calculation means, and when the air-fuel ratio switching is completed, the constant value is set. Equipped with a throttle opening calculated value selection means for switching control of the throttle opening calculated value so as to always return to the calculated value of the throttle opening calculated means. Which is characterized in that is preferred.

Further, as another aspect, in an air-fuel ratio control device for an internal combustion engine equipped with a means for controlling the intake air amount of the internal combustion engine, the fuel injection amount is based on the intake air amount and the engine speed during steady operation. A steady-state fuel injection amount calculation means for calculating, an air-fuel ratio switching fuel injection amount calculation means for calculating the fuel injection amount based on the accelerator depression angle and the engine speed when the air-fuel ratio is switched, and an accelerator depression angle and engine for steady operation A steady-state throttle opening calculation means for determining the throttle opening based on the rotation speed; and an air-fuel ratio switching throttle opening calculation means for determining the throttle opening based on the fuel injection amount and the engine rotation speed when switching the air-fuel ratio. In the steady operation, the steady-state fuel injection amount calculation means calculates the fuel injection amount, and the steady-state throttle opening degree is provided. The throttle opening is calculated by the output means, when the air-fuel ratio is switched, the fuel injection amount is calculated by the air-fuel ratio switching fuel injection amount calculation means, and the throttle opening is calculated by the air-fuel ratio switching throttle opening calculation means. It is characterized by doing so.

Further, as a preferred specific example, the method for calculating the control value of the fuel injection amount in the steady-state fuel injection amount calculation means and the air-fuel ratio switching-time fuel injection amount calculation means is switched, Characterized in that the method for calculating the control value of the throttle opening in the constant throttle opening calculation means and the air-fuel ratio switching throttle opening calculation means is switched, the steady-state fuel injection amount calculation means and the air-fuel ratio switching The calculation method of the control value of the fuel injection amount in the hour fuel injection amount calculation means and the calculation method of the control value of the throttle opening degree in the steady state throttle opening calculation means and the air-fuel ratio switching throttle opening calculation means are switched. The thing characterized by that is mentioned.

[0011]

The air-fuel ratio switching fuel injection amount calculation means calculates the fuel injection amount when the air-fuel ratio is switched by inputting the detected accelerator depression angle and engine speed. The constant fuel injection amount calculation means calculates the fuel injection amount during steady operation by inputting the engine speed and the intake air amount. The air-fuel ratio switching throttle opening calculation means calculates the throttle opening at the air-fuel ratio switching by inputting the engine speed and the accelerator depression angle. The constant throttle opening calculation means calculates the throttle opening during steady operation by inputting the engine speed and the accelerator depression angle. The fuel injection amount calculation value selection means switches the calculated value of the fuel injection amount at the time of switching the air-fuel ratio from the calculation value of the steady-state fuel injection amount calculation means to the calculation value of the air-fuel ratio switching fuel injection amount calculation means, and When the switching is completed, the value is returned to the value calculated by the steady-state fuel injection amount calculation means. Also,
The throttle opening calculated value selection means switches the calculated value of the throttle opening when switching the air-fuel ratio from the calculated value of the steady-state throttle opening calculation means to the calculated value of the throttle opening calculation means when switching the air-fuel ratio, and also switches the air-fuel ratio. When is completed, the value is returned to the value calculated by the steady-state throttle opening calculation means.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the present invention. The target air-fuel ratio calculation means 108 is the accelerator depression angle detection means 10
Accelerator depression angle and intake air amount detection means 10 detected in 1
Intake air amount detected in 2 and engine speed detection means 10
The target air-fuel ratio is calculated by inputting the engine speed detected in 3. Fuel injection amount calculation means 104 during air-fuel ratio switching
Is an accelerator depression angle detected by the accelerator depression angle detecting means 101, an engine speed detected by the engine speed detecting means 103, and a target air-fuel ratio calculated by the target air-fuel ratio calculating means 108. Calculate the amount.

The steady-state fuel injection amount calculation means 105 includes an engine speed detected by the engine speed detection means 103,
The intake air amount detected by the intake air amount detecting means 102 and the target air-fuel ratio calculated by the target air-fuel ratio calculating means 108 are input to calculate the fuel injection amount during steady operation. The air-fuel ratio switching throttle opening calculation means 106 is a target air-fuel ratio calculated by the target air-fuel ratio calculation means 108 and an intake air amount detection means 10.
Intake air amount detected in 2 and engine speed detection means 10
The throttle opening at the time of switching the air-fuel ratio is calculated by inputting the engine speed detected in 3 and the accelerator depression angle detected by the accelerator depression angle detecting means 101.

The steady-state throttle opening calculation means 107 is
The throttle opening during steady operation is input with the engine speed detected by the engine speed detecting means 103, the engine intake air amount detected by the intake air amount detecting means 102, and the accelerator depression angle detected by the accelerator depression angle detecting means 101 as inputs. To calculate. The air-fuel ratio switching time detection unit 111 detects the air-fuel ratio switching time by using the target air-fuel ratio calculated by the target air-fuel ratio calculation unit 108 as an input. Fuel injection amount calculation value selection means 1
Reference numeral 09 indicates that the calculated value of the fuel injection amount at the time of air-fuel ratio switching detected by the air-fuel ratio switching detection means 111 is switched from the calculated value of the steady-state fuel injection amount calculation means 105 to the calculated value of the air-fuel ratio switching fuel injection amount calculation means 104. When the switching of the air-fuel ratio is completed, the value is returned to the calculated value of the steady-state fuel injection amount calculation means 105.
The throttle opening calculation value selection means 110 calculates the throttle opening calculation value at the time of air-fuel ratio switching detected by the air-fuel ratio switching detection means 111 from the calculated value of the steady-state throttle opening calculation means 107 at the air-fuel ratio switching throttle opening calculation. Means 10
The calculated value is changed to the calculated value of 6, and when the change of the air-fuel ratio is completed, the value is returned to the calculated value of the steady state throttle opening calculation means 107. The fuel injection pulse generation means 112 generates a pulse based on the calculated value of the fuel injection amount selected by the fuel injection amount calculated value selection means 109.

The throttle driving means 113 drives the throttle based on the throttle opening calculated value selected by the throttle opening calculated value selecting means 110. In this case,
Not limited to the throttle, the air amount may be controlled by a valve for idle speed control (ISC), a supercharger, a turbo for controlling a motor, or the like.

FIG. 2 is a diagram showing a schematic structure of an internal combustion engine to which the present invention is applied. The intake air amount detecting means 201 detects the intake air amount. The electronic throttle 202 uses the signal from the engine control unit 205 to drive the actuator 206.
Is controlled to open and close the throttle valve to control the intake air flow rate. Further, in response to a signal from the engine control device 205, the fuel injection valve 203 opens the valve to inject fuel when a fuel injection pulse is generated, and the ignition device 204 discharges sparks at a predetermined ignition timing to ignite the air-fuel mixture. .

As described above, in the conventional lean-burn engine, the air-fuel ratio is switched by not changing the throttle when changing the air-fuel ratio, that is, by decreasing or increasing the fuel injection amount without changing the intake air amount. When the air-fuel ratio was switched, the output torque changed, giving shock or discomfort to the driver and passengers. As a countermeasure against this problem, in the present invention, the air-fuel ratio is switched by keeping the fuel injection amount constant when switching the air-fuel ratio and controlling the air amount by opening and closing the throttle. However, when the air-fuel ratio is made thin and the same output is attempted to be generated, the fuel amount required for it is reduced as shown in FIG. Therefore, in order to maintain the output torque when switching the air-fuel ratio, it is necessary to finely adjust the fuel injection amount.

Further, as shown in FIG. 4, the NOx generation amount has a peak value between the air-fuel ratio of 14.7 to 21 to 24. Therefore, when the transition of the air-fuel ratio is performed slowly, the NOx generation amount is increased. Increase and cause deterioration of exhaust gas. Therefore, in order to reduce the amount of NOx produced, the air-fuel ratio must be switched rapidly. FIG. 5 shows the fuel injection amount T when the air-fuel ratio is switched.
It is a figure showing the change of the output torque when holding the value of i.

During a transient state in which the target air-fuel ratio changes from 14.7 to 24, a control signal is output by the air-fuel ratio switching detecting means 111, whereby the control values for the fuel injection amount Ti and the throttle opening TVO are calculated. Are switched. The throttle opening TVO changes similarly to the target air-fuel ratio, and the intake air amount Qa also changes. However, the fuel injection amount Ti is maintained. As a result, the output torque slightly increases due to the increase in the output torque due to the lean air-fuel ratio.

As described above, by maintaining the fuel injection amount Ti and changing the intake air Qa amount at the time of switching the air-fuel ratio, the sudden change of the output torque is suppressed and the switching of the air-fuel ratio can be completed in a short time. Occurrence of can be reduced.
However, even when the fuel injection amount Ti is held in this way, a slight torque fluctuation occurs. Therefore, by reducing the fuel injection amount Ti as the target air-fuel ratio changes and the generated torque per fuel increases, a slight variation in the output torque can be suppressed.

FIG. 6 is a diagram showing a change in the output torque when the increase in the output torque is suppressed by slightly changing the fuel injection amount at the time of switching the air-fuel ratio. When the target air-fuel ratio changes from 14.7 to 24, a control signal is output by the air-fuel ratio switching time detection means 111,
As a result, the fuel injection amount Ti and the throttle opening TV
The calculation method of the control value of O is switched. Throttle opening T
VO changes similarly to the target air-fuel ratio, and the intake air amount Qa also changes similarly. The fuel injection amount Ti is slightly decreased as the target air-fuel ratio increases. Therefore, a slight increase in output torque is suppressed, and torque shock and discomfort do not occur even when the air-fuel ratio is suddenly changed.

FIG. 7 is a diagram showing a calculation flow of the fuel injection amount calculation means 104 at the time of switching the air-fuel ratio. First, step 7
At 01, the accelerator depression angle is detected. Next, step 70.
At 2, the engine speed Ne is detected. In step 703, the target basic fuel injection pulse width Tp is calculated from the map from the engine speed Ne and the accelerator depression angle θth. Next, at step 704, the relative fuel consumption rate η ′ with the fuel consumption rate at the stoichiometric air-fuel ratio of 14.7 as 1 with respect to the target air-fuel ratio is calculated by a map. And step 70
In step 5, the actual fuel injection pulse width Tp 'is calculated by the following equation 1. Tp ′ = Tp × η ′ (Equation 1)

FIG. 8 is a diagram showing a calculation flow of the steady-state fuel injection amount calculation means 105. First, in step 801, the engine speed Ne is detected. Next, in step 802, the intake air amount Qa is detected. Then, in step 803, the basic fuel injection pulse width Tp is obtained by the following equation 2. Tp = Qa / Ne × KA / F × K (Equation 2) where KA / F is a constant determined by the air-fuel ratio and K is a constant not determined by the air-fuel ratio.

Next, at step 804, the basic fuel injection pulse width Tp is multiplied by the relative fuel consumption rate η determined by the target air-fuel ratio by the following equation 3 to obtain the actual fuel injection pulse width Tp '.
Ask for. Tp ′ = η × Tp (Equation 3)

FIG. 9 is a diagram showing a calculation flow of the throttle opening calculation means 106 at the time of switching the air-fuel ratio. First, in step 901, the engine speed Ne is detected. Next, at step 902, the target intake air amount Qa ′ is obtained by multiplying the total fuel injection amount Qf by the target air-fuel ratio A / F by the following equation 4. Qa ′ = Qf × (A / F) (Equation 4) Then, in step 903, the target throttle opening θ is obtained from the engine speed Ne and the target intake air amount Qa ′ by a map.

FIG. 10 shows a steady state throttle opening calculation means 1
It is a figure which shows the flow of calculation of 07. First, step 10
At 01, the accelerator depression angle θth is detected. Then step 1
At 002, the engine speed Ne is obtained. Then, in step 1003, the accelerator depression angle θth and the engine speed N
From e, the target basic intake air amount Qa is obtained from the map. Next, in step 1004, the target intake air amount Qa is obtained by multiplying the target basic intake air amount Qa by the ratio λ between the target air-fuel ratio and the stoichiometric air-fuel ratio by the following equation 5. Qa ′ = Qa × λ (Equation 5) Then, at step 1005, a target throttle opening TVO ′ is obtained from a map from the target intake air amount Qa ′ and the engine speed Ne.

FIG. 11 is a diagram showing the flow of calculation of the air-fuel ratio switching time detection means 111. In step 1101, the current target air-fuel ratio is compared with the previous target air-fuel ratio to check whether the target air-fuel ratio has been switched. If the target air-fuel ratio has been switched, the process proceeds to step 1102, and if not, the process proceeds to step 1103. Yes is output in step 1102, and No is output in step 1103. Then, if the current target air-fuel ratio and the previous target air-fuel ratio match in step 1104, the operation ends.

FIG. 12 shows the calculated fuel injection amount selection means 109.
It is a figure which shows the flow of calculation of. In step 1201, it is checked whether or not the air-fuel ratio is being switched. If the air-fuel ratio is being switched, the procedure proceeds to step 1202, and if not, step 120
Go to 3. In step 1202, the calculated value of the fuel injection amount calculation means at the time of switching the air-fuel ratio is output. In step 1203, the calculated value of the steady-state fuel injection means is output.

FIG. 13 shows a throttle opening calculation value selection means 1
It is a figure which shows the flow of 10 calculations. In step 1301, it is checked whether the air-fuel ratio is being switched. If the air-fuel ratio is being switched, go to step 1302, otherwise step 1
Proceed to 303. In step 1302, the calculated value of the throttle opening calculation means at the time of switching the air-fuel ratio is output. Step 1
At 303, the calculated value of the steady-state throttle opening calculation means is output.

[0030]

As can be understood from the above description, according to the present invention, it is possible to suppress a torque step and a shock at the time of switching the air-fuel ratio as much as possible, and to quickly switch the air-fuel ratio. , NOx emissions can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an air-fuel ratio control device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an internal combustion engine to which the present invention is applied.

FIG. 3 is a diagram showing a fuel consumption rate with respect to an air-fuel ratio of an internal combustion engine.

FIG. 4 is a diagram showing the NOx emission amount with respect to the air-fuel ratio of the internal combustion engine.

FIG. 5 is a diagram showing an operating state of the engine when the air-fuel ratio is switched.

FIG. 6 is a diagram showing an operating state of the engine when switching the air-fuel ratio of the present invention.

FIG. 7 is a diagram showing a calculation flow of a fuel injection amount calculation means at the time of switching the air-fuel ratio of the present invention.

FIG. 8 is a diagram showing a calculation flow of steady-state fuel injection amount calculation means of the present invention.

FIG. 9 is a diagram showing a flow of calculation by a throttle opening calculation means during air-fuel ratio switching of the present invention.

FIG. 10 is a diagram showing a calculation flow of a steady-state throttle opening degree calculation means of the present invention.

FIG. 11 is a diagram showing a flow of calculation of the air-fuel ratio switching time detection means of the present invention.

FIG. 12 is a diagram showing a calculation flow of a fuel injection amount calculation value selection means of the present invention.

FIG. 13 is a diagram showing a calculation flow of a throttle opening calculation value selection means of the present invention.

[Explanation of symbols]

 101 ... Accelerator depression angle detecting means 102 ... Intake air amount detecting means 103 ... Engine speed detecting means 104 ... Air-fuel ratio switching fuel injection amount calculating means 105 ... Steady-time fuel injection amount calculating means 106 ... Air-fuel ratio switching throttle opening Calculating means 107 ... Steady-time throttle opening calculating means 108 ... Target air-fuel ratio calculating means 109 ... Fuel injection amount calculated value selecting means 110 ... Throttle opening calculated value selecting means 111 ... Air-fuel ratio switching detecting means 112 ... Fuel injection pulse generation Means 113 ... Throttle driving means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location F02D 45/00 301 G (72) Inventor Matsuo Amano 2520 Takaba, Katsuta-shi, Ibaraki Hitachi, Ltd. Factory Automotive Equipment Division

Claims (11)

[Claims] 1. An air-fuel ratio control device for an internal combustion engine, comprising means for controlling an intake air amount of an internal combustion engine, comprising means for calculating a fuel injection amount at the time of switching the air-fuel ratio according to an accelerator depression angle and an engine speed. An air-fuel ratio control device for an internal combustion engine, comprising: 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the fuel injection amount is held when the air-fuel ratio is switched. 3. The fuel injection amount is finely adjusted according to the target air-fuel ratio when the air-fuel ratio is switched to suppress an increase in output torque per fuel due to the air-fuel ratio. Air-fuel ratio control device for internal combustion engine. 4. An air-fuel ratio control system for an internal combustion engine, which comprises means for controlling the intake air amount of the internal combustion engine, wherein the fuel injection amount during steady operation is calculated based on the intake air amount and the engine speed during steady operation. An air-fuel ratio control apparatus for an internal combustion engine, comprising: an amount calculation means; and an air-fuel ratio switching fuel injection amount calculation means for calculating a fuel injection amount based on an accelerator depression angle and an engine speed when the air-fuel ratio is switched. 5. The steady-state fuel injection is switched when the air-fuel ratio is switched from the steady-state fuel injection amount calculation means to the calculation value of the air-fuel ratio switching-time fuel injection amount calculation means, and when the air-fuel ratio is switched. 5. The air-fuel ratio control apparatus for an internal combustion engine according to claim 4, further comprising a fuel injection amount calculated value selection unit that controls switching of the fuel injection amount calculated value so as to return to the calculated value of the amount calculation unit. 6. An air-fuel ratio control system for an internal combustion engine comprising means for controlling an intake air amount of the internal combustion engine, wherein a throttle opening at a steady state is calculated for calculating a throttle opening based on an accelerator pedal depression angle and an engine speed during a steady operation. An air-fuel ratio control apparatus for an internal combustion engine, comprising: a degree calculation means; and an air-fuel ratio switching throttle opening calculation means for calculating a throttle opening based on a fuel injection amount and an engine speed when the air-fuel ratio is switched. 7. The steady-state throttle opening degree is switched from the calculated value of the steady-state throttle opening degree calculating means at the time of air-fuel ratio switching to the calculated value of the air-fuel ratio switching throttle opening degree calculating means, and when the air-fuel ratio switching is completed. 7. The air-fuel ratio control device for an internal combustion engine according to claim 6, further comprising throttle opening calculation value selection means for controlling switching of the throttle opening calculation value so as to return to the calculation value of the calculation means. 8. An air-fuel ratio control system for an internal combustion engine, comprising a means for controlling an intake air amount of an internal combustion engine, wherein a fuel injection amount during steady operation is calculated based on an intake air amount and an engine speed during steady operation. A fuel injection amount calculation means for calculating the fuel injection amount based on the accelerator depression angle and the engine speed when the air-fuel ratio is switched, and a throttle amount based on the accelerator depression angle and the engine speed during steady operation. A steady-state throttle opening calculation means for determining the opening, and an air-fuel ratio switching throttle opening calculation means for determining the throttle opening based on the fuel injection amount and the engine speed when the air-fuel ratio is switched are provided. Occasionally, the steady-state fuel injection amount calculation means calculates the fuel injection amount, and the steady-state throttle opening degree calculation means calculates the slot. The opening is calculated, and when the air-fuel ratio is switched, the fuel injection amount is calculated by the air-fuel ratio switching fuel injection amount calculation means, and the throttle opening is calculated by the air-fuel ratio switching throttle opening calculation means. An air-fuel ratio control device for an internal combustion engine. 9. The method for calculating the control value of the fuel injection amount in the steady-state fuel injection amount calculation means and the air-fuel ratio switching fuel injection amount calculation means is switched.
5. An air-fuel ratio control device for an internal combustion engine according to item 5 or 8. 10. The method for calculating the control value of the throttle opening in the steady throttle opening calculating means and the air-fuel ratio switching throttle opening calculating means is switched. Air-fuel ratio controller for internal combustion engine. 11. A method of calculating a control value of a fuel injection amount in the steady-state fuel injection amount calculation means and the air-fuel ratio switching-time fuel injection amount calculation means, and the steady-state throttle opening degree calculation means and the air-fuel ratio switching. 9. The air-fuel ratio control device for an internal combustion engine according to claim 4, wherein the method for calculating the control value of the throttle opening in the hour throttle opening calculation means is switched.