JP2007170184A - Air-fuel ratio learning and correcting device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To learn and correct the deviation of air-fuel ratio due to the dispersion of wall flows according to transient operation patterns. <P>SOLUTION: During the transient operation, the maximum deviated amount P1 to the lean side of air-fuel ratio, the maximum deviated amount P2 to the rich side, the timings t1, t2 at which the air-fuel ratio is peak, and the timing t3 at which the air-fuel ratio is converged are detected. Next, these variable indicating the behavior of the air-fuel ratio are converted into the maximum increased amount HP1, the maximum decreased amount HP2, the maximum increased timing Ht1, the maximum decreased timing Ht2, and the correction stop timing Ht3. These variables HP1, HP2, Ht1, Ht2, and Ht3 are stored in a map as the learned values corresponding to the intake air amount Q and the variable amount ΔQ when the behavior of the air-fuel ratio is detected. During the next transient operation with the same intake air amount Q and the variable amount ΔQ, the fuel injection amount is corrected by the characteristics of the variables HP1, HP2, Ht1, Ht2, and Ht3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio learning correction device that learns and corrects an air-fuel ratio shift during engine transient operation.

In Patent Document 1, in order to accurately calculate the basic fuel injection amount at the time of transition in the fuel injection valve unit, a learning value of a coefficient that determines the degree of response at the time of transition is stored using the opening of the intake throttle valve as a parameter. The basic fuel injection amount at the fuel injection valve unit is calculated from the learning value and the detected value of the intake air amount, while the learning value corresponding to the throttle valve opening at that time is calculated based on the change amount of the intake pipe pressure. Has been disclosed.
Japanese Patent Laid-Open No. 9-126011

By the way, according to the above prior art, it is possible to accurately estimate the intake air amount in the injection valve portion at the time of transition.
However, if the characteristics of the so-called wall flow fuel, in which the fuel injected from the fuel injection valve adheres to the wall surface of the intake port and flows as liquid fuel, changes due to variations in engine solids or fuel variations, the intake air amount is accurately estimated. Even if it is possible, an air-fuel mixture having a target air-fuel ratio cannot be formed at the time of transition, and exhaust characteristics and drivability deteriorate due to an air-fuel ratio shift.

Conventionally, learning of an air-fuel ratio learning correction value for bringing the air-fuel ratio closer to the target air-fuel ratio is performed for each condition of engine load and engine speed. In such learning, a correction request for each transient operation pattern is used. There is a problem that the air-fuel ratio shift occurs because the air pressure cannot be satisfied.
The present invention has been made in view of the above problems, and an object thereof is to provide an air-fuel ratio learning correction device for an engine that can learn and correct an air-fuel ratio shift due to wall flow variation corresponding to each transient operation pattern.

  Therefore, the air-fuel ratio learning correction apparatus for an engine according to the present invention detects the characteristic of the air-fuel ratio deviation during the transient operation of the engine, and the learning correction value of the air-fuel ratio based on the characteristic of the air-fuel ratio deviation at that time The engine is stored in correspondence with the amount of change in the amount of air and the amount of intake air, and the engine is based on the learned correction value learned in correspondence with the amount of change in the amount of intake air and the amount of intake air at the time of transient operation of the engine. The air-fuel ratio is corrected and controlled.

  The demand for correction of the fuel amount due to wall flow during transient engine operation differs depending on the amount of intake air and the amount of change in the intake air amount. When the amount of change in the intake air amount is large, the wall flow rate increases and the fuel injection However, if the correction value is learned in accordance with the intake air amount and the amount of change in the intake air amount as in the present invention, the air flow corresponding to the above difference in wall flow rate is required. Fuel ratio correction control can be performed, and air-fuel ratio control accuracy during transient operation can be improved.

Embodiments of the present invention will be described below.
FIG. 1 is a system diagram of a vehicle engine in the embodiment.
In FIG. 1, air that has passed through an air cleaner 2 is sucked into each cylinder of an engine (gasoline internal combustion engine) 1 through an intake duct 3, an intake collector 4, an intake manifold 5, and an intake valve 6.

The intake air amount of the engine 1 is adjusted by the opening TVO of the butterfly throttle valve 7 interposed in the intake duct 3.
The throttle valve 7 is an electronically controlled valve that is driven to open and close by a throttle motor (throttle actuator) 8.
A fuel injection valve 9 is provided in each intake port portion of each cylinder.

The air-fuel mixture formed by the fuel (gasoline) injected from the fuel injection valve 9 is ignited and combusted by spark ignition by an ignition plug (not shown) in the combustion chamber 10.
The combustion exhaust in the combustion chamber 10 is discharged to the atmosphere via an exhaust valve 11, an exhaust manifold 12, and an exhaust duct 13.
The exhaust duct 13 is provided with a catalytic converter 14 for purifying harmful components (NOx, HC, CO) in the exhaust.

The power transistor for controlling the energization of the throttle motor 8, the fuel injection valve 9 and the ignition coil (not shown) is controlled by an engine control unit (ECU) 21 incorporating a microcomputer.
Detection signals from various sensors are input to the engine control unit 21.

  Examples of the various sensors include an air flow meter 22 that detects an intake air flow rate Q (L / min) of the engine 1 on the upstream side of the throttle valve 7, and an oxygen concentration in the exhaust gas that is installed on the upstream side of the catalytic converter 14. An air-fuel ratio sensor 23 for detecting the exhaust air-fuel ratio in a wide range, a rotational speed sensor 24 for detecting the rotational speed Ne (rpm) of the engine 1, and an accelerator for detecting the depression amount (accelerator opening) of the accelerator pedal operated by the driver. An opening sensor 25, a throttle sensor 26 for detecting the opening TPO (deg) of the throttle valve 7, a water temperature sensor 27 for detecting the coolant temperature of the engine 1, and the like are provided.

  The air-fuel ratio sensor 23 includes, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-264340, a sensing electrode that detects rich / lean relative to the stoichiometric air-fuel ratio of the exhaust air-fuel ratio in the gas diffusion layer, A voltage is applied according to a rich / lean discrimination result, and an oxygen pump electrode that moves oxygen ions in the gas diffusion layer is provided. Based on a current (limit current) flowing through the oxygen pump electrode, It is a sensor that can detect the air-fuel ratio of the combustion mixture in a wide area.

However, the sensor for detecting the air-fuel ratio of the engine 1 is not limited to the air-fuel ratio sensor 23 described above, and various known sensors can be applied.
The engine control unit 21 controls the fuel injection amount Ti (injection pulse width) by the fuel injection valve 9 as follows.
First, based on the intake air flow rate Q detected by the air flow meter 22 and the engine rotational speed detected by the rotational speed sensor 24, an air-fuel mixture having a target air-fuel ratio (for example, the theoretical air-fuel ratio) is obtained at the cylinder intake air amount at that time. A basic fuel injection amount Tp (basic injection pulse width) for formation is calculated.

Further, the basic fuel injection amount Tp is corrected by various correction coefficients CO, an air-fuel ratio feedback correction coefficient FAF, an air-fuel ratio learning correction value LAF, a voltage correction amount Ts, and the like to calculate a final fuel injection amount Ti.
The engine control unit 21 individually outputs an injection pulse signal having a pulse width corresponding to the fuel injection amount Ti to each fuel injection valve 9 in synchronization with the intake stroke of each cylinder.

The various correction coefficients CO are correction coefficients for increasing the fuel injection amount when the engine 1 is at a low temperature or during startup, and are set from the coolant temperature, the elapsed time after startup, and the like.
The air-fuel ratio feedback correction coefficient FAF is calculated based on the deviation between the air-fuel ratio detected by the air-fuel ratio sensor 23 and the target air-fuel ratio when a predetermined feedback condition is satisfied.
The air-fuel ratio learning correction value LAF is a value for feedforward correction of the fuel injection amount at the time of transient operation. As will be described later, the intake air amount Q and the change amount ΔQ of the intake air amount Q at the time of transient operation are described. To be learned.

Further, the voltage correction amount Ts is for correcting the invalid injection time by the battery voltage, and is set according to the battery voltage at that time.
Here, the air-fuel ratio learning correction value LAF will be described in detail.
The time chart of FIG. 2 shows the characteristic of the air-fuel ratio learning correction value LAF (ms) detected based on the detection of the air-fuel ratio behavior during transient operation and the detection result.

As shown in FIG. 2, when the engine 1 is accelerated, the air-fuel ratio A / F leans with respect to the target air-fuel ratio due to a delay in the response of the amount of fuel sucked into the cylinder, and then swings back to the rich side. After it occurs, it converges near the target air-fuel ratio.
As a variable indicating the air-fuel ratio behavior during transient operation as described above, the maximum deviation P1 between the actual air-fuel ratio and the target air-fuel ratio when shifted to the lean side (hereinafter, lean-side maximum deviation P1), and the transient determination t0 The time t1 required to reach the lean side maximum deviation P1, and the maximum deviation P2 between the actual air-fuel ratio and the target air-fuel ratio when swinging back to the rich side by leaning back after leaning (hereinafter, rich-side maximum deviation P2) ), A time t2 required from the transition determination t0 to the rich side maximum deviation P2, and a time t3 required from the transition determination t0 to convergence to the vicinity of the target air-fuel ratio.

Instead of the times t1, t2, and t3, the time from the transient determination until the lean side maximum deviation P1 is reached, the time required from the lean side maximum deviation P1 to the rich side maximum deviation P2, the rich side maximum deviation P1 Substantially the same processing can be performed even if the time required from P2 to converge to the vicinity of the target air-fuel ratio is detected.
Then, based on the variables P1, P2, t1, t2, and t3 indicating the air-fuel ratio behavior during the transient operation, variables HP1, HP2, Ht1, Ht2, and Ht3 that determine the air-fuel ratio learning correction value LAF are calculated.

  The variable HP1 is the maximum increase correction value, the variable Ht1 is the time from the transition determination to the timing at which the air-fuel ratio learning correction value LAF is set to the maximum increase correction value HP1, the variable HP2 is the maximum decrease correction value, and the variable Ht2 is the air-fuel ratio from the transient determination Time until the timing at which the learning correction value LAF is set to the maximum reduction correction value HP2, Ht3 is the time from the transient determination to the timing at which correction by the air-fuel ratio learning correction value LAF is made zero (stopped), and the variables HP1, HP2 , Ht1, Ht2, and Ht3 are stored in the learning map in an updatable manner in correspondence with the intake air flow rate Q when the transient operation is detected and the change amount ΔQ of the intake air flow rate Q.

Then, when the transient operation is performed again under the same conditions of the intake air flow rate Q and the change amount ΔQ that have learned the variables HP1, HP2, Ht1, Ht2, and Ht3, the learned variables HP1, HP2, Ht1, Ht2, and so on. The air-fuel ratio learning correction value LAF is changed according to Ht3 to correct the fuel injection amount.
Specifically, the air-fuel ratio learning correction value LAF is increased and changed at a constant speed from 0 to HP1 at time Ht1 from the transient determination. When the maximum increase correction value HP1 is reached, the air-fuel ratio learning correction is performed at time Ht2−time Ht1. The value LAF is decreased and changed from HP1 to HP2 at a constant speed, and when the maximum reduction correction value HP2 is reached, the air-fuel ratio learning correction value LAF is increased from HP2 to 0 in time Ht3-time Ht2.

Next, details of the learning control of the air-fuel ratio learning correction value LAF (variables HP1, HP2, Ht1, Ht2, and Ht3) will be described with reference to the flowchart of FIG.
The routine shown in the flowchart of FIG. 3 is executed every predetermined minute time.
First, in step S11, whether or not the change amount ΔQ per unit time of the intake air flow rate Q detected by the air flow meter 22 (ΔQ = current value−value before unit time) is larger than a threshold for transient determination. Is determined to determine whether or not the engine 1 is accelerating.

If it is determined that the amount of change ΔQ is greater than the threshold value and the engine 1 is in an accelerated operation state, the process proceeds to step S12.
In step S12, for each combination of the intake air flow rate Q and the change amount ΔQ, an intake air flow rate Q at the time of acceleration determination is referred to by referring to a learning map that stores the variables HP1, HP2, Ht1, Ht2, and Ht3 in an updatable manner. Then, variables HP1, HP2, Ht1, Ht2, and Ht3 corresponding to the change amount ΔQ are read, and the air-fuel ratio learning correction value LAF is changed as described above based on the read variables HP1, HP2, Ht1, Ht2, and Ht3. Then, the fuel injection amount (air-fuel ratio) is feedforward corrected.

The initial values of the HP1, HP2, Ht1, Ht2, and Ht3 are 0, and the variables HP1, HP2, Ht1, Ht2, and Ht3 corresponding to the intake air flow rate Q and the change amount ΔQ during the current acceleration have not been learned. When (variables HP1, HP2, Ht1, Ht2, and Ht3 are all 0), correction by the air-fuel ratio learning correction value LAF is not performed.
In the next step S13, the behavior of the air-fuel ratio generated in the current transient (acceleration operation) is specified by detecting the variables P1, P2, t1, t2, and t3.

As described above, the variables P1 and P2 indicate the peak value of the air-fuel ratio shift, and the variables t1, t2, and t3 indicate the time when the air-fuel ratio shift reaches the peak value and the time when the air-fuel ratio converges.
In step S14, a correction request (variables HP1, HP2, Ht1, Ht2, Ht3) under the same acceleration conditions as this time is calculated based on the variables P1, P2, t1, t2, and t3.
Generally, since the response delay time constant τ of the wall flow is correlated with the change amount ΔQ, the time constant τ is determined from the change amount ΔQ when transient operation is detected (see FIG. 4).

τ = f1 (ΔQ)
Further, conversion coefficients α1 to α3 for converting the variables t1, t2 and t3 indicating the timing of the air-fuel ratio deviation into the variables Ht1, Ht2 and Ht3 indicating the timing of the air-fuel ratio correction are determined based on the time constant τ. To do.
α = f2 (τ)
The functions f1 (ΔQ) and f2 (τ) are fixed functions stored in advance.

Based on the conversion coefficients α1 to α3, the variables t1, t2, and t3 indicating the timing of the air-fuel ratio deviation are converted into variables Ht1, Ht2, and Ht3 indicating the timing of the air-fuel ratio correction.
Ht1 = t1 × α1
Ht2 = t2 × α2
Ht3 = t3 × α3
On the other hand, the variables HP1 and HP2 indicating the peak value of the correction amount are calculated as follows.

First, a first coefficient CoefQ used to convert the variables P1 and P2 into the variables HP1 and HP2 is calculated based on a function f4 (Q, ΔQ) having an intake air flow rate Q and a change amount ΔQ as variables. .
CoefQ = f4 (Q, ΔQ)
Further, the second coefficient CoefN is calculated from the function f5 (Ne) having the engine speed Ne as a variable.

CoefN = f5 (Ne)
In general, as the engine speed increases, the air flow rate increases and the port flow velocity increases, so the correction request amount tends to decrease. Therefore, the second correction coefficient CoefN is set with the characteristics shown in FIG. .
Then, a total coefficient CoefTotal is calculated from the first coefficient CoefQ and the second coefficient CoefN.

CoefTotal = CoefQ × CoefN
Here, by multiplying the variables P1 and P2 indicating the air-fuel ratio behavior by the total correction coefficient CoefTotal, the variables HP1 and HP2 indicating the characteristics of the air-fuel ratio learning correction value LAF are converted.
HP1 = P1 × CoefTotal
HP2 = P2 × CoefTotal
As described above, the variables HP1, HP2, Ht1, Ht2, and Ht3 indicating the fuel injection amount correction request for the variables P1, P2, t1, t2, and t3 indicating the current air-fuel ratio behavior are calculated.

In step S15, based on the correction request, the variables HP1, HP2, Ht1, Ht2, and Ht3 stored in the learning map are updated and rewritten corresponding to the current acceleration condition (intake air amount Q and change amount ΔQ). Do.
That is, the stored values in the learning map so far are HP1 ′, HP2 ′, Ht1 ′, Ht2 ′, Ht3 ′, and the newly obtained correction requests are HP1 ″, HP2 ″, Ht1 ″, Ht2 ″, Ht3 ″. Then, the stored value of the corresponding lattice in the learning map is rewritten to HP1 ′ + HP1 ″, HP2 ′ + HP2 ″, Ht1 ′ + Ht1 ″, Ht2 ′ + Ht2 ″, Ht3 ′ + Ht3 ″.

The learning map updates and stores the variables HP1, HP2, Ht1, Ht2, and Ht3 that specify the air-fuel ratio learning correction value LAF for each combination of the intake air amount Q and the change amount ΔQ. The correction request can be learned, and the air-fuel ratio fluctuation during the transient operation can be corrected with high accuracy (see FIG. 6).
In addition, the air-fuel ratio deviation pattern generated during the transient operation is converted into a correction amount change pattern, and further, conversion characteristics are set according to the intake air amount Q, change amount ΔQ, and engine speed Ne. Therefore, it is possible to learn the air-fuel ratio learning correction value LAF that can effectively suppress the air-fuel ratio fluctuation accompanying the transient operation.

In step S16, a characteristic correction coefficient for converting the variables P1, P2, t1, t2, and t3 indicating the air-fuel ratio behavior into variables HP1, HP2, Ht1, Ht2, and Ht3 indicating the fuel injection amount correction request is learned.
In the present embodiment, target values TA1, TA2, TA3 of the variables t1, t2, t3 indicating the timing of the air-fuel ratio deviation change are preset, and the air-fuel ratio based on the variables HP1, HP2, Ht1, Ht2, Ht3 The correction coefficient K1 of the conversion coefficients α1, α2, α3 from the result of learning correction so that the variables t1, t2, t3 as a result of correcting the fuel injection amount with the learning correction value LAF approach the target values TA1, TA2, TA3. , K2, K3.

First, deviations Z1, Z2, and Z3 between the actual values t1, t2, and t3 and the target values TA1, TA2, and TA3 are calculated (see FIG. 7).
Z1 = t1-TA1
Z2 = t2-TA2
Z3 = t3-TA3
Then, correction coefficients K1, K2, and K3 are obtained from the deviations Z1, Z2, and Z3.

K1 = f6 (Z1)
K2 = f6 (Z2)
K3 = f6 (Z3)
In the next and subsequent times, based on the conversion coefficients α1 ′, α2 ′, α3 ′ obtained by correcting the conversion coefficients α1, α2, α3 set based on the change amount ΔQ with the correction coefficients K1, K2, K3, the variables t1, t2 and t3 are converted into variables Ht1, Ht2 and Ht3, and each time the deviations Z1, Z2 and Z3 are detected, the correction coefficients K1, K2 and K3 so far are newly set correction coefficients K1 ′ and K2. The correction is set with “, K3”.

Further, the variables P1 and P2 are reduced in a direction based on the variables P1 and P2 indicating the air-fuel ratio deviation when the fuel injection amount is learned and corrected based on the learned variables HP1, HP2, Ht1, Ht2, and Ht3. Then, a correction coefficient K4 for correcting the total correction coefficient CoefTotal (first coefficient CoefQ, second coefficient CoefN) is calculated.
That is, the fuel injection amount for achieving the target air-fuel ratio based on the variables P1 and P2 indicating the air-fuel ratio deviation when the fuel injection amount is learned and corrected based on the learned variables HP1, HP2, Ht1, Ht2, and Ht3 The correction coefficient K4 for correcting the total correction coefficient CoefTotal is calculated so that the variables HP1 and HP2 satisfying the correction request are calculated.

After learning the correction coefficient K4, the total correction coefficient CoefTotal corrected by the correction coefficient K4 is used when the variables P1 and P2 are converted into the variables HP1 and HP2.
The correction coefficient K4a corresponding to the first coefficient CoefQ and the correction coefficient K4b corresponding to the second coefficient CoefN are individually determined from the characteristics of the required correction amount for the engine speed Ne, the intake air amount Q, and the change amount ΔQ. It is also possible to learn.

As described above, the correction coefficients K1 to K1 for the characteristic of converting the variables P1, P2, t1, t2, and t3 indicating the air-fuel ratio behavior into the variables HP1, HP2, Ht1, Ht2, and Ht3 indicating the correction request for the fuel injection amount. If K4 is learned, the accuracy of estimating the correction request from the air-fuel ratio behavior can be improved, and the convergence of the air-fuel ratio learning correction value LAF can be accelerated.
As a time variable indicating the characteristic of the air-fuel ratio deviation during transient operation, the time when the air-fuel ratio crosses the target air-fuel ratio can be detected instead of the time when the air-fuel ratio shows a peak value.

  Further, as data correlated with the intake air amount Q and the change amount ΔQ, the amount of change in the throttle opening / throttle opening, the intake air amount estimated from the throttle opening and the engine speed, and the change in the intake air amount The amount can be detected.

The system diagram of the engine for vehicles in an embodiment. The time chart which shows the air-fuel ratio behavior at the time of transition in the embodiment, and the air-fuel ratio learning correction value LAF based on the air-fuel ratio behavior. The flowchart which shows the learning control of the air fuel ratio learning correction value in embodiment. The diagram which shows the correlation with the variation | change_quantity (DELTA) Q and the response delay time constant of wall flow in embodiment. The diagram which shows the correlation with the engine speed Ne and conversion coefficient CoefN in embodiment. The figure which shows the correlation with the transient driving | operation pattern in embodiment, and the grid of a corresponding learning map. The time chart which shows an example of the correlation with the timing and target value of the air-fuel ratio behavior at the time of the transition in embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Air cleaner, 3 ... Intake duct, 4 ... Intake collector, 5 ... Intake manifold, 6 ... Intake valve, 7 ... Throttle valve, 8 ... Throttle motor, 9 ... Fuel injection valve, 10 ... Combustion chamber, 11 DESCRIPTION OF SYMBOLS ... Exhaust valve, 12 ... Exhaust manifold, 13 ... Exhaust duct, 14 ... Catalytic converter, 21 ... Engine control unit, 22 ... Air flow meter, 23 ... Air-fuel ratio sensor, 24 ... Rotational speed sensor, 25 ... Accelerator opening sensor, 26 ... Throttle sensor, 27 ... Water temperature sensor

Claims (7)

The characteristic of the air-fuel ratio deviation is detected during the transient operation of the engine, and the learning correction value of the air-fuel ratio based on the characteristic of the air-fuel ratio deviation is stored in correspondence with the intake air amount of the engine and the change amount of the intake air amount at that time. The engine air-fuel ratio is corrected and controlled based on the learned correction value learned in accordance with the intake air amount and the change amount of the intake air amount at the time of the transient operation of the engine. Fuel ratio learning correction device. 2. The air-fuel ratio learning correction apparatus for an engine according to claim 1, wherein the air-fuel ratio deviation characteristic is detected by detecting a peak value of the air-fuel ratio deviation, a time when the peak value is shown, and a time when the air-fuel ratio converges. The peak value of the air-fuel ratio deviation is converted into the peak value of the air-fuel ratio correction amount, the time when the air-fuel ratio deviation shows the peak value is converted into the time when the air-fuel ratio correction amount is the peak value, and the air-fuel ratio becomes The converged timing is converted into a timing for stopping correction by the air-fuel ratio correction amount, and the peak value of the air-fuel ratio correction amount, the timing for setting the air-fuel ratio correction amount as the peak value, and the timing for stopping correction by the air-fuel ratio correction amount are described above. 3. The engine air-fuel ratio learning correction apparatus according to claim 2, wherein learning is performed as a learning correction value. The characteristic for converting the peak value of the air-fuel ratio deviation into the peak value of the air-fuel ratio correction value is determined based on at least one of the engine speed, the intake air amount, and the change amount of the intake air amount. The air-fuel ratio learning correction apparatus for an engine according to claim 3. The characteristic of converting the time when the air-fuel ratio deviation showed a peak value into the time when the air-fuel ratio correction value is a peak value, and / or the time when the air-fuel ratio has converged, the correction by the air-fuel ratio correction amount is stopped. The engine air-fuel ratio learning correction apparatus according to claim 3 or 4, wherein the characteristic to be converted into the timing is determined based on a change amount of the intake air amount. The time when the air-fuel ratio deviation shows the peak value is set to the peak value as the time when the air-fuel ratio deviation shows the peak value and / or the time when the air-fuel ratio converges becomes the target time. 6. The characteristic for converting to a timing and / or the characteristic for converting the timing at which the air-fuel ratio has converged to a timing for stopping correction by the air-fuel ratio correction amount are updated. An air-fuel ratio learning correction apparatus for an engine according to claim 1. The characteristic for converting the peak value of the air-fuel ratio shift into the peak value of the air-fuel ratio correction value is updated in order to reduce the peak value of the air-fuel ratio shift. Engine air-fuel ratio learning correction device.

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