JP2010112353A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device for an internal combustion engine, maintaining appropriate exhaust emission characteristics even if a combination of operating cylinders is changed. <P>SOLUTION: A variable cylinder system is provided for changing the combination of the operating cylinders of a plurality of cylinders. An air-fuel ratio sensor is provided between the merging portion of an exhaust passage and a catalyst downstream of the merging portion. Output of the air-fuel ratio sensor is fed back to the amount of fuel injected so that an air-fuel ratio of exhaust gas led to flow into the catalyst matches with a control target air-fuel ratio. Then, the control target air-fuel ratio or the output of the air-fuel ratio sensor is corrected according to the combination of the operating cylinders. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio control apparatus for an internal combustion engine, and more particularly to an air-fuel ratio control apparatus for an internal combustion engine suitable for executing control of an internal combustion engine mounted on a vehicle.

  Conventionally, as disclosed in, for example, Patent Document 1, an internal combustion engine that includes an air-fuel ratio sensor between a merging portion of an exhaust passage and a catalyst downstream of the merging portion and an oxygen sensor downstream of the catalyst is known. ing. This publication also discloses main feedback control for correcting the fuel injection amount based on the output of the air-fuel ratio sensor upstream of the catalyst and sub-feedback control for correcting the fuel injection amount based on the output of the oxygen sensor downstream of the catalyst. Has been. Further, in this publication, in the sub-feedback control, the control target air-fuel ratio becomes larger as the intake air amount becomes larger in consideration of the air-fuel ratio range (catalyst characteristics) in which the catalyst can efficiently purify the exhaust gas. It is disclosed that the fuel injection amount is corrected to be rich. According to such control, deterioration of exhaust emission can be suppressed in consideration of the characteristics of the catalyst.

JP 2005-48711 A JP 2004-270596 A JP 2008-180230 A JP-A-8-105339

  By the way, when the combination of the operating cylinders is changed by the variable cylinder system, the flow of gas at the merging portion of the exhaust passage changes depending on the combination of the operating cylinders, and the gas hitting characteristic to the air-fuel ratio sensor also changes. Become. For this reason, in the conventional internal combustion engine, when the combination of operating cylinders is changed, the output of the air-fuel ratio sensor does not necessarily become an accurate value due to the change in the gas hitting characteristic, and the feedback that takes into account the above-described catalyst characteristics. Control alone is not sufficient to suppress the deterioration of exhaust emissions.

  The present invention has been made to solve the above-described problems, and provides an air-fuel ratio control apparatus for an internal combustion engine that can suitably suppress deterioration of exhaust emission even when the combination of operating cylinders changes. With the goal.

In order to achieve the above object, a first invention is an air-fuel ratio control apparatus for an internal combustion engine comprising a variable cylinder system capable of changing a combination of operating cylinders among a plurality of cylinders.
An air-fuel ratio sensor disposed between the merging portion of the exhaust passage and the catalyst downstream of the merging portion;
Feedback means for feeding back the output of the air-fuel ratio sensor to the fuel injection amount so that the air-fuel ratio of the exhaust gas flowing into the catalyst matches the control target air-fuel ratio;
And correction means for correcting the control target air-fuel ratio or the output of the air-fuel ratio sensor in accordance with the combination of the operating cylinders.

The second invention is the first invention, wherein
When the combination of the operating cylinders is changed, the correction means switches from the correction method according to the combination before the change to the correction method according to the combination after the change after the exhaust transportation delay time has elapsed. Features.

  According to the first aspect of the invention, the control target air-fuel ratio or the correction amount of the air-fuel ratio sensor output used for feedback control can be switched according to the combination of operating cylinders. Therefore, it is possible to realize a suitable feedback control corresponding to a change in the gas-per-characteristic characteristic of the air-fuel ratio sensor due to the combination of operating cylinders. For this reason, according to the present invention, good exhaust emission characteristics can always be realized regardless of the combination of operating cylinders.

  According to the second invention, after changing the combination of the operating cylinders, the correction amount of the control target air-fuel ratio or the air-fuel ratio sensor output is switched after the exhaust transport delay time from the cylinder to the air-fuel ratio sensor elapses. it can. Therefore, it is possible to realize a suitable feedback control by switching the correction amount after waiting for a change in the per-gas characteristic of the air-fuel ratio sensor due to the combination change of the operating cylinders. For this reason, according to the present invention, it is possible to always achieve a good exhaust emission characteristic by eliminating the influence of the transport delay of the exhaust gas.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. The internal combustion engine 10 is a gasoline engine having a plurality of cylinders (not shown). Each cylinder includes a spark plug 12 and a piston 14. The piston 14 is connected to a crankshaft 16 that is rotationally driven by the reciprocating motion. A crank angle sensor 18 for detecting a crank angle CA of the crankshaft 16 is disposed in the vicinity of the crankshaft 16. A combustion chamber 20 is formed in each cylinder. An intake passage 22 and an exhaust passage 24 are connected to the combustion chamber 20.

  An air flow meter 26 is provided upstream of the intake passage 22. The air flow meter 26 is a sensor for detecting the intake air amount GA flowing through the intake passage 22. A throttle valve 28 is provided downstream of the air flow meter 26. In the vicinity of the throttle valve 28, a throttle sensor 30 for detecting the throttle opening degree TA is disposed. A surge tank 32 is provided downstream of the throttle valve 28. A fuel injection valve 36 for injecting fuel into the intake port 34 downstream of the intake passage 22 is disposed further downstream of the surge tank 32.

  An intake valve 40 that controls a communication state between the intake port 34 and the combustion chamber 20 is provided at a connection portion between the intake port 34 and the combustion chamber 20. The intake valve 40 is driven to open and close by a valve mechanism 42.

  An exhaust valve 46 that controls the state of communication between the exhaust port 44 and the combustion chamber 20 is provided at a connection portion between the exhaust port 44 that is the upstream end of the exhaust passage 24 and the combustion chamber 20. The exhaust valve 46 is driven to open and close by a valve mechanism 48.

  Further, an exhaust manifold 50 common to each cylinder is connected downstream of the exhaust port 44 of each cylinder. An exhaust purification catalyst 52 is provided downstream of the joining portion of the exhaust manifold 50. As the exhaust purification catalyst 52, for example, a three-way catalyst is used. The three-way catalyst has an oxygen storage capacity, adsorbs excess oxygen when the exhaust is lean, and releases deficient oxygen when the exhaust is rich, thereby oxidizing monoxide contained in the exhaust. Purifies carbon (CO), hydrocarbons (HC) and nitrogen oxides (NOx).

  An air-fuel ratio sensor 54 is disposed immediately upstream of the exhaust purification catalyst 52. The air-fuel ratio sensor 54 is a so-called global air-fuel ratio sensor that generates an output voltage corresponding to the air-fuel ratio over a wide air-fuel ratio region. An oxygen sensor 56 is disposed downstream of the exhaust purification catalyst 52. The oxygen sensor 56 is an oxygen sensor whose output value changes stepwise in the vicinity of the theoretical air-fuel ratio.

  The system according to the present embodiment includes an ECU (Electronic Control Unit) 60. The aforementioned crank angle sensor 18, air flow meter 26, throttle sensor 30, air-fuel ratio sensor 54, oxygen sensor 56, etc. are connected to the input side of the ECU 60. The ignition plug 12, the throttle valve 28, the fuel injection valve 36, the valve operating mechanisms 42 and 48, etc. are connected to the output side of the ECU 60. The ECU 60 calculates the engine speed NE based on the crank angle CA.

  The ECU 60 also stores a variable cylinder control routine for changing the combination of operating cylinders according to the operating state of the internal combustion engine 10. Since the specific configuration itself of the variable cylinder control routine is not the main part of the present invention, the detailed description thereof will be omitted here, but can be realized by the following configuration, for example. First, the ECU 60 selects all-cylinder operation or reduced-cylinder operation from each operation information of the internal combustion engine 10. During the reduced-cylinder operation, fuel injection to the cylinders to be stopped is stopped and a control signal is sent to the valve operating mechanisms 42 and 48 to close the intake valve 40 and the exhaust valve 46. Note that the reduced-cylinder operation flag is set to ON during reduced-cylinder operation, and the reduced-cylinder operation flag is set to OFF during all-cylinder operation.

  Hereinafter, air-fuel ratio feedback control in the system of Embodiment 1 will be described with reference to FIGS.

FIG. 2 is a flowchart of a target in-cylinder fuel amount calculation routine executed by the ECU 60 in the present embodiment. This routine is executed at every predetermined crank angle. In this routine, first, in-cylinder air amount MC _i (i = 0, 1,..., N−1) and target in-cylinder fuel amount FCR _i obtained as a result of executing this routine up to the previous time. Is updated (step 100). Specifically, MC _i and FCR _i before i (i = 0, 1,..., N−1) times are updated to MC _{i + 1} and FCR _{i + 1} before i + 1 times. This is because the current in-cylinder air amount MC ₀ and the target in-cylinder fuel amount FCR ₀ are newly calculated in the current routine execution.

Next, at step 110, the engine speed NE and the intake air amount GA are acquired. The engine speed NE is calculated from the crank angle CA based on the output signal of the crank angle sensor 18. The intake air amount GA is calculated based on the output signal of the air flow meter 26. Then, in step 120, from the acquired engine rotational speed NE and the intake air amount GA, and it estimates the cylinder air amount MC ₀ supplied to the cylinder.

Next, in step 130, based on the in-cylinder air amount MC ₀ and the theoretical air-fuel ratio AFT, the calculation of FCR ₀ ← MC0 / AFT is executed, and in order to realize the theoretical air-fuel ratio in the in-cylinder air amount MC ₀ , The target in-cylinder fuel amount FCR ₀ to be supplied to is calculated. Thereafter, this routine is terminated.

  FIG. 3 is a flowchart of a main feedback control routine executed by the ECU 60 in the present embodiment. This routine is executed at every predetermined crank angle. In this routine, first, it is determined whether or not a main feedback execution condition is satisfied (step 200). For example, when the cooling water temperature is equal to or lower than a predetermined temperature, when the internal combustion engine is starting, when the output signal of the air-fuel ratio sensor 54 does not change, when the fuel cut is in progress, it is determined that the condition is not satisfied, and in other cases, the condition is not satisfied It is determined to be established. If the condition is not satisfied, the fuel correction amount DF by feedback control is set to 0 in step 260, and then this routine is terminated.

On the other hand, if it is determined in step 200 that the condition is satisfied, the fuel deviation (the deviation between the actual in-cylinder fuel amount and the target in-cylinder fuel amount) for the past n times obtained as the execution result of this routine until the previous time. ) FD _i (i = 0, 1,..., N−1) is updated (step 210). Specifically, the i (i = 0,1, ..., n-1) the time prior to FD _i, and updates the _{FD i + 1} of the i + 1 times before. This is to calculate the new fuel deviation FD ₀ in the current execution of the routine.

  Next, at step 220, the output voltage value VAF of the air-fuel ratio sensor 54 is calculated. Specifically, a voltage correction value efsfb and a learning value efgsfs calculated by processing similar to the sub-feedback control routine shown in Japanese Patent No. 411041 are added to the output voltage value VAF detected by the air-fuel ratio sensor 54, and further Then, a corrected output voltage value VAF is calculated by adding a voltage correction value efadj calculated by a routine shown in FIG.

  Thereafter, the current air-fuel ratio ABF is determined based on the corrected output voltage value VAF calculated in step 220 (step 230). Note that the ECU 60 stores an air-fuel ratio sensor output conversion map for obtaining the current air-fuel ratio ABF from the corrected output voltage value VAF.

In step 240, based on the cylinder air amount MC _n and target cylinder fuel amount FCR _n has already been calculated by the target cylinder fuel amount calculation routine described in FIG. 2, the _{FD 0 ← MC n / ABF-} FCR n The amount of fuel actually burned in the cylinder, that is, the fuel deviation FD ₀ between the actual in-cylinder fuel quantity and the target in-cylinder fuel quantity is obtained by calculation. Here, an n times before the cylinder air amount MC _n and target cylinder fuel amount FCR _n is to consider transportation delay time of the exhaust gases from the cylinders to the air-fuel ratio sensor 54.

In step 250, the fuel correction amount DF is calculated by calculating DF ← K _fp * FD ₀ + K _fs * ΣFD _i . Here, K _fp is a proportional gain, and K _fs is an integral gain. Thereafter, this routine is terminated.

[Characteristic Control in Embodiment 1]
Next, in the system of the present embodiment, the control routine used for realizing high-precision air-fuel ratio feedback control even when switching between all-cylinder operation and reduced-cylinder operation is described below with reference to FIGS. 5 and will be described.

  FIG. 4 is a flowchart of a routine executed by the ECU 60 to calculate the voltage correction value efadj used in step 220 shown in FIG. 2 in the present embodiment. This routine is executed every predetermined crank angle. In this routine, first, in step 300, it is determined whether or not a predetermined time has elapsed after the engine operating state is in the all-cylinder operation and is switched from the reduced cylinder operation to the all cylinder operation. Here, when the reduced cylinder operation flag is set to OFF by the variable cylinder control routine described above, it is determined that the all cylinder operation is being performed. The predetermined time is a transport delay time of exhaust gas from the cylinder to the air-fuel ratio sensor 54. The ECU 60 stores a map in which the exhaust gas transport delay time is determined in accordance with the engine operating state (all cylinder operation and reduced cylinder operation), the engine speed NE, the throttle opening degree TA, and the like.

  If the condition is satisfied in step 300, that is, if a predetermined time has elapsed after switching from reduced-cylinder operation to all-cylinder operation during all-cylinder operation, a voltage correction value efadj is calculated in step 310. To do. Specifically, the ECU 60 stores a map shown in FIG. The map shown in FIG. 5 determines the voltage correction value of the air-fuel ratio sensor output corresponding to the intake air amount GA for each engine operating state (all cylinder operation and reduced cylinder operation). In this map, the first-order delay from the intake air flow meter 26 to the cylinder is taken into consideration. Further, in the all-cylinder operation correction map f0 and the reduced cylinder operation correction map f1 shown in FIG. 5, the voltage correction value efadj increases as the intake air amount GA increases (that is, the air-fuel ratio becomes richer). As set). In step 310, a voltage correction value efadj corresponding to the intake air amount GA is calculated using the all-cylinder operation correction map f0 shown in FIG. Thereafter, this routine is terminated.

  If the condition is not satisfied in step 300, it is next determined in step 320 whether or not all cylinders are operating. When the reduced cylinder operation flag is OFF, it is determined that all cylinders are operating. If it is determined in step 320 that all-cylinder operation is being performed, that is, if all cylinder operation is being performed and a predetermined time has not yet elapsed after switching from reduced-cylinder operation to all-cylinder operation, then step 330 is performed. The voltage correction value efadj corresponding to the intake air amount GA is calculated based on the above-described reduced-cylinder operation correction map f1 shown in FIG. Thereafter, this routine is terminated.

  If the reduced cylinder operation flag is ON in step 320, it is next determined whether or not a predetermined time has elapsed after switching from all cylinder operation to reduced cylinder operation (step 340). Here, the predetermined time is an exhaust gas transport delay time from the cylinder to the air-fuel ratio sensor 54 described above.

  In step 340, if the condition is satisfied, that is, if the predetermined time has elapsed after switching from all-cylinder operation to reduced-cylinder operation in the reduced-cylinder operation, in step 330, the above-described reduced-cylinder operation shown in FIG. A voltage correction value efadj corresponding to the intake air amount GA is calculated using the correction map f1. Thereafter, this routine is terminated.

  On the other hand, if the condition is not satisfied in step 340, that is, if the predetermined time has not yet elapsed after switching from all-cylinder operation to reduced-cylinder operation, in step 310, the above-described operation for all-cylinder operation shown in FIG. A voltage correction value efadj corresponding to the intake air amount GA is calculated using the correction map f0. Thereafter, this routine is terminated.

As described above, according to the routine shown in FIG. 4, the voltage correction value efadj is used by using the correction maps f0 and f1 that take into account the gas hit characteristics of the air-fuel ratio sensor 54 that changes between the all cylinder operation and the reduced cylinder operation. Can be calculated. Therefore, good exhaust emission characteristics can be realized regardless of all-cylinder operation and reduced-cylinder operation.
In addition, after switching between the all-cylinder operation and the reduced-cylinder operation, after waiting for the exhaust transportation delay time from the cylinder to the air-fuel ratio sensor 54, the voltage is switched by switching between the all-cylinder operation correction map f0 and the reduced-cylinder operation correction map f1. The correction amount efadj can be calculated. Therefore, the correction maps f0 and f1 can be switched after waiting for a change in the gas contact characteristics of the air-fuel ratio sensor due to switching between all-cylinder operation and reduced-cylinder operation. For this reason, according to the system of the present embodiment, it is possible to always achieve a good exhaust emission characteristic by eliminating the influence of the exhaust gas transport delay.

  By the way, in the system of the first embodiment described above, the combination of operating cylinders is two, ie, all cylinder operation and reduced cylinder operation, but this combination of operating cylinders is not limited to this. For example, it is possible to prepare a plurality of patterns of combinations of operating cylinders and idle cylinders that realize the reduced-cylinder operation, and to determine a correction map for reduced-cylinder operation as shown in FIG. 5 according to each combination.

In the first embodiment described above, the merging portion of the exhaust manifold 50 is emptied as the “merging portion of the exhaust passage” in the first invention, and the exhaust purification catalyst 52 is emptied as the “catalyst” in the first invention. The fuel ratio sensor 54 corresponds to the “air-fuel ratio sensor” in the first invention.
In addition, here, the ECU 60 executes the processing of the steps 100 to 260, so that the “feedback means” in the first invention executes the processing of the steps 300 to 340. "Correction means" are realized respectively. Further, in the first embodiment, the VAF calculated in step 220 corresponds to “the output of the air-fuel ratio sensor” in the first invention.

Embodiment 2. FIG.
[System Configuration of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 6 described later in place of the routine shown in FIG. 4 in the configuration shown in FIGS.

[Characteristic Control in Embodiment 2]
In the first embodiment described above, the voltage correction value efadj is switched by switching between the correction maps f0 and f1 according to the switching state between the all-cylinder operation and the reduced-cylinder operation while fixing the control target air-fuel ratio AFT to the theoretical air-fuel ratio. Is calculated and the air-fuel ratio sensor output VAF is corrected to realize highly accurate air-fuel ratio feedback control. On the other hand, in the present embodiment, the air-fuel ratio sensor output VAF is not corrected, but the control target air-fuel ratio AFT is corrected according to the switching state between the all-cylinder operation and the reduced-cylinder operation. It has a feature in realizing the function.

  FIG. 6 is a flowchart of a control routine executed by the ECU 60 in order to realize the above-described function. This routine is the same as the routine shown in FIG. 4 except that the process of step 310 is replaced with step 400 and the process of step 330 is replaced with step 410. Hereinafter, in FIG. 6, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 6, after the condition is satisfied in step 300, the control target air-fuel ratio AFT is calculated in step 400. Specifically, the ECU 60 stores a map shown in FIG. The map shown in FIG. 7 defines the control target air-fuel ratio AFT corresponding to the intake air amount GA for each engine operating state (all cylinder operation and reduced cylinder operation). In this map, the first-order delay from the intake air flow meter 26 to the cylinder is taken into consideration. Further, the all-cylinder operation correction map h0 and the reduced cylinder operation correction map h1 shown in FIG. 7 are set so that the control target air-fuel ratio AFT becomes richer as the intake air amount GA increases. In step 400, the control target air-fuel ratio AFT corresponding to the intake air amount GA is calculated using the all-cylinder operation correction map h0 shown in FIG. Thereafter, this routine is terminated.

  In the routine shown in FIG. 6, if the condition is satisfied in step 320, that is, if the predetermined time has not yet elapsed after switching from reduced-cylinder operation to all-cylinder operation during all-cylinder operation, In step 410, the control target air-fuel ratio AFT corresponding to the intake air amount GA is calculated based on the above-described reduced-cylinder operation correction map h1 shown in FIG. Thereafter, this routine is terminated.

  In the routine shown in FIG. 6, if the condition is satisfied in step 340, that is, if a predetermined time elapses after switching from all-cylinder operation to reduced-cylinder operation during the reduced-cylinder operation, then in step 410. Then, the control target air-fuel ratio AFT corresponding to the intake air amount GA is calculated using the above-described reduced-cylinder operation correction map h1 shown in FIG. Thereafter, this routine is terminated.

  On the other hand, if the condition is not satisfied in step 340, that is, if the predetermined time has not yet elapsed after switching from all-cylinder operation to reduced-cylinder operation, in step 400, for all-cylinder operation shown in FIG. A control target air-fuel ratio AFT corresponding to the intake air amount GA is calculated using the correction map h0. Thereafter, this routine is terminated.

  As described above, according to the routine shown in FIG. 6, the control target air-fuel ratio AFT can be corrected in accordance with the switching state between the all-cylinder operation and the reduced-cylinder operation. For this reason, according to the system of the present embodiment, good emission characteristics can always be realized according to the switching state between the all-cylinder operation and the reduced-cylinder operation, as in the system of the first embodiment.

  By the way, in the system of the second embodiment described above, the combination of operating cylinders is two, that is, all-cylinder operation and reduced cylinder operation, but this combination of operating cylinders is not limited to this. For example, it is possible to prepare a plurality of patterns of combinations of operating cylinders and idle cylinders that realize reduced-cylinder operation, and to determine a reduced-cylinder operation correction map as shown in FIG. 7 according to each combination.

  In the second embodiment described above, the “correction means” according to the first aspect of the present invention is realized by the ECU 60 executing the processing of steps 400 to 410 described above. Further, in the second embodiment, the control target air-fuel ratio AFT calculated in step 400 or 410 corresponds to the “control target air-fuel ratio” in the first invention.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a flowchart of the target cylinder fuel amount calculation routine which ECU60 performs. In Embodiment 1 of this invention, it is a flowchart of the main feedback control routine which ECU60 performs. 3 is a flowchart of a routine executed by an ECU 60 in order to calculate a voltage correction value efadj used in step 220 shown in FIG. 2 in Embodiment 1 of the present invention. FIG. 3 is a map in which a voltage correction value of an air-fuel ratio sensor output corresponding to an intake air amount GA used in Embodiment 1 of the present invention is determined for each engine operating state. In Embodiment 1 of this invention, it is a flowchart of the control routine which ECU60 performs. 3 is a map that defines a control target air-fuel ratio AFT corresponding to an intake air amount GA, which is used in Embodiment 1 of the present invention, for each engine operating state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 18 Crank angle sensor 24 Exhaust passage 26 Air flow meter 36 Fuel injection valve 42, 48 Valve mechanism 50 Exhaust manifold 52 Exhaust purification catalyst 54 Air-fuel ratio sensor 56 Oxygen sensor 60 ECU (Electronic Control Unit)
MC In-cylinder air amount FCR Target in-cylinder fuel amount NE Engine speed GA Intake air amount AFT Theoretical air-fuel ratio, control target air-fuel ratio FD Fuel deviation VAR Air-fuel ratio sensor output efsfb Voltage correction value efgsfsb In sub-feedback control Learning value efadj Voltage correction value ABF Current air-fuel ratio DF Fuel correction amount

Claims (2)

An air-fuel ratio control apparatus for an internal combustion engine comprising a variable cylinder system capable of changing a combination of operating cylinders among a plurality of cylinders,
An air-fuel ratio sensor disposed between the merging portion of the exhaust passage and the catalyst downstream of the merging portion;
Feedback means for feeding back the output of the air-fuel ratio sensor to the fuel injection amount so that the air-fuel ratio of the exhaust gas flowing into the catalyst matches the control target air-fuel ratio;
Correction means for correcting the control target air-fuel ratio or the output of the air-fuel ratio sensor according to the combination of the operating cylinders;
An air-fuel ratio control apparatus for an internal combustion engine, comprising: When the combination of the operating cylinders is changed, the correction means switches from a correction method according to the combination before the change to a correction method according to the combination after the change after the exhaust transportation delay time has elapsed,
The air-fuel ratio control apparatus for an internal combustion engine according to claim 1.

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