JP3680501B2 - Air-fuel ratio control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for controlling an air-fuel ratio of an intake air-fuel mixture of an internal combustion engine, and particularly to a device having a learning function.
[0002]
[Prior art]
Conventionally, as an air-fuel ratio feedback control device having a learning function, there is one disclosed in JP-A-5-156994.
Here, the air-fuel ratio feedback control is performed by using an oxygen sensor output value and a slice level (target air-fuel ratio equivalent value) in which the rich air-fuel ratio of the actual air-fuel ratio with respect to the target air-fuel ratio (for example, the theoretical air-fuel ratio) is provided in the engine exhaust system The air-fuel ratio feedback correction coefficient α is increased or decreased by proportional / integral control based on the determination result, and is calculated from the intake air flow rate detected by the air flow meter and the engine speed. By correcting the fuel injection amount Tp with the air-fuel ratio feedback correction coefficient α, the deviation of the actual air-fuel ratio from the target air-fuel ratio due to component errors, deterioration with time, environmental changes, etc. is eliminated. is there.
[0003]
Further, the learning function uses a deviation from the reference value (target convergence value) of the air-fuel ratio feedback correction coefficient α as a learning value PHOS, and learning is divided into a plurality for each engine operation region (ie, learning region). The base air-fuel ratio obtained without the air-fuel ratio feedback correction coefficient α is made to substantially match the target value by updating and storing in the map and correcting the basic fuel injection amount Tp with the learning value (air-fuel ratio learning correction value) PHOS. Thus, the convergence of the actual air-fuel ratio to the target air-fuel ratio in the air-fuel ratio feedback control can be accelerated.
[0004]
In other words, by combining the air-fuel ratio feedback control and the learning function, it responds to the fuel injection amount correction request that varies depending on the operating conditions with good responsiveness, and the actual air-fuel ratio can be controlled well in the vicinity of the target air-fuel ratio. It is.
[0005]
[Problems to be solved by the invention]
However, in the conventional air-fuel ratio control apparatus as described above, the search of the learning value PHOS stored in the learning map is a surface search without interpolation based on the rotational speed Ne and the load Tp, and the operation region changes. When the reference area changes, the learned value PHOS changes stepwise.
[0006]
Such a stepwise change in the learned value PHOS changes the fuel supply amount in a stepwise manner, so that the generated torque of the engine may be changed, which may reduce the drivability.
In particular, in a so-called direct fuel injection internal combustion engine that directly injects fuel into a cylinder (inside the cylinder), the fuel is directly fed into the cylinder, so the fuel transportation delay is small and the fuel supply amount changes. In addition, the relationship between the air-fuel ratio (fuel supply amount) and the generated torque is linear during lean operation, so the generated torque changes sensitively with respect to the step change in the fuel supply amount, and the operability The impact on is relatively large.
[0007]
In the so-called intake port internal combustion engine that supplies fuel into the intake port, the fuel transportation delay is relatively large, and the air-fuel ratio (fuel supply amount) changes during operation near the stoichiometric air-fuel ratio. The impact on the operability is small compared to the direct fuel injection internal combustion engine in the cylinder because the sensitivity to torque is low. It is desirable to plan.
[0008]
The present invention has been made in view of such circumstances, and suppresses a change in engine-generated torque caused by a step change in the learning value when the operation region transitions and the reference region of the learning value changes, Accordingly, an object of the present invention is to provide an air-fuel ratio control apparatus for an internal combustion engine that can maintain good operability.
[0009]
[Means for Solving the Problems]
  For this reason, the air-fuel ratio control apparatus for an internal combustion engine according to the first aspect of the present invention, as shown in FIG.
  Basic fuel supply amount calculating means for calculating a basic fuel supply amount based on the engine operating state;
  Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture as a rich lean signal with respect to the theoretical air-fuel ratio;
  Air-fuel ratio feedback correction for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so as to bring the actual air-fuel ratio closer to the theoretical air-fuel ratio based on the detection result detected by the air-fuel ratio detection means Value setting means;
  An air-fuel ratio learning correction value storage means for dividing the engine operation region into a plurality of operation regions, and storing the air-fuel ratio learning correction value for correcting the basic fuel supply amount in a rewritable manner for each operation region;
  An air-fuel ratio learning means for updating and setting the air-fuel ratio learning correction value stored in the air-fuel ratio learning correction value storage means in a direction to decrease the deviation from the reference value of the air-fuel ratio feedback correction value for each operation region;
  With
  The current air-fuel ratio learning correction value searched based on the corresponding operating region and the last fuel supply last timeamountThe air-fuel ratio learning correction value used for the setting of the air-fuel ratio is averaged, and the final fuel supply amount is set using the air-fuel ratio learning correction value after the averaging process, and the set fuel supply is set Drive control of the fuel supply device based on the quantity,
  While the air-fuel ratio learning correction value used for the previous fuel supply amount setting and the air-fuel ratio learning correction value used for the current fuel supply amount setting do not match, the air-fuel ratio by the air-fuel ratio learning means The update setting of the learning correction value is prohibited.
[0010]
With such a configuration, the current air-fuel ratio learning correction value searched based on the corresponding operation region and the air-fuel ratio learning correction value used for the last final fuel supply setting are averaged (for example, weighted). And the final fuel supply amount is set using the air-fuel ratio learning correction value after the averaging process, so that the air-fuel ratio learning correction value used for setting the final fuel supply amount is the step. Change can be suppressed. Therefore, for example, when the operation region transitions and the reference region of the air-fuel ratio learning correction value changes, even if the operation region does not transition, the combustion mode is switched between stratified combustion and homogeneous combustion. However, since the air-fuel ratio learning correction value can be prevented from changing stepwise, the step-wise change in the air-fuel ratio (fuel supply amount) can be suppressed and the change in the torque generated by the engine can be suppressed. Can be maintained well.
Since the air-fuel ratio learning correction value is unstable while the process for suppressing the stepwise change in the air-fuel ratio learning correction value referred to (used for setting the fuel supply amount) is performed, An error may occur in the update learning by the air-fuel ratio learning means performed on the assumption that the air-fuel ratio learning correction value is stable, and the air-fuel ratio learning correction value may be updated to an incorrect value. Can be prevented.
[0011]
  In the invention according to claim 2,
  Basic fuel supply amount calculating means for calculating a basic fuel supply amount based on the engine operating state;
  Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture as a rich lean signal with respect to the theoretical air-fuel ratio;
  Air-fuel ratio feedback correction for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so as to bring the actual air-fuel ratio closer to the theoretical air-fuel ratio based on the detection result detected by the air-fuel ratio detection means Value setting means;
  An air-fuel ratio learning correction value storage means for dividing the engine operation region into a plurality of operation regions, and storing the air-fuel ratio learning correction value for correcting the basic fuel supply amount in a rewritable manner for each operation region;
  An air-fuel ratio learning means for updating and setting the air-fuel ratio learning correction value stored in the air-fuel ratio learning correction value storage means in a direction to decrease the deviation from the reference value of the air-fuel ratio feedback correction value for each operation region;
  Fuel supply amount setting means for setting a final fuel supply amount using the air-fuel ratio learning correction value;
  Drive means for driving and controlling the fuel supply device based on the fuel supply amount set by the fuel supply amount setting means;
  An air-fuel ratio control apparatus for an internal combustion engine configured to include:
  When the operating region transitions and the air-fuel ratio learning correction value used in the fuel supply amount setting means is switched, the air-fuel ratio learning correction value before switching is switched while gradually approaching the air-fuel ratio learning correction value after switching,
  After the transition of the driving area,The air-fuel ratio learning correction value used for the previous fuel supply amount setting matches the air-fuel ratio learning correction value used for the current fuel supply amount setting.UntilDuring the interval, the air-fuel ratio learning correction unit is prohibited from updating the air-fuel ratio learning correction value.
[0012]
According to such a configuration, when the operation region transitions and the reference region of the air-fuel ratio learning correction value changes, primary smoothing processing (averaging processing) or the like is performed without immediately switching to the new air-fuel ratio learning correction value. As a result, the air-fuel ratio learning correction value is gradually changed to a new air-fuel ratio learning correction value. The change is suppressed, and the stepwise change in the air-fuel ratio (fuel supply amount) can be suppressed, so that the change in the torque generated by the engine can be suppressed, and the drivability can be maintained well.
Since the air-fuel ratio learning correction value is unstable while the process for suppressing the stepwise change in the air-fuel ratio learning correction value referred to (used for setting the fuel supply amount) is performed, An error may occur in the update learning by the air-fuel ratio learning means performed on the assumption that the air-fuel ratio learning correction value is stable, and the air-fuel ratio learning correction value may be updated to an incorrect value. Can be prevented.
[0013]
  In invention of Claim 3,
  Basic fuel supply amount calculating means for calculating a basic fuel supply amount based on the engine operating state;
  Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture as a rich lean signal with respect to the theoretical air-fuel ratio;
  Air-fuel ratio feedback correction for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so as to bring the actual air-fuel ratio closer to the theoretical air-fuel ratio based on the detection result detected by the air-fuel ratio detection means Value setting means;
  An air-fuel ratio learning correction value storage means for dividing the engine operation region into a plurality of operation regions, and storing the air-fuel ratio learning correction value for correcting the basic fuel supply amount in a rewritable manner for each operation region;
  An air-fuel ratio learning means for updating and setting the air-fuel ratio learning correction value stored in the air-fuel ratio learning correction value storage means in a direction to decrease the deviation from the reference value of the air-fuel ratio feedback correction value for each operation region;
  Fuel supply amount setting means for setting a final fuel supply amount using the air-fuel ratio learning correction value;
  Drive means for driving and controlling the fuel supply device based on the fuel supply amount set by the fuel supply amount setting means;
  An air-fuel ratio control apparatus for an internal combustion engine configured to include:
  When the air-fuel ratio learning correction value used in the fuel supply amount setting means is switched according to the switching of the combustion mode, the air-fuel ratio learning correction value before switching is switched while gradually approaching the air-fuel ratio learning correction value after switching. ,
  After switching the combustion mode,The air-fuel ratio learning correction value used for the previous fuel supply amount setting matches the air-fuel ratio learning correction value used for the current fuel supply amount setting.UntilDuring the interval, the air-fuel ratio learning correction unit is prohibited from updating the air-fuel ratio learning correction value.
[0014]
  According to such a configuration, for example, when the combustion mode is switched between stratified combustion and homogeneous combustion, and the air-fuel ratio learning correction value changes stepwise, it is immediately switched to a new air-fuel ratio learning correction value. Therefore, the first smoothing process (averaging process) is performed to gradually shift to the new air-fuel ratio learning correction value.ofThe step change is suppressed, and the step change of the air-fuel ratio (fuel supply amount) can be suppressed. As a result, the change of the generated torque of the engine can be suppressed, so that the drivability can be maintained well.
  Since the air-fuel ratio learning correction value is unstable while the process for suppressing the stepwise change in the air-fuel ratio learning correction value referred to (used for setting the fuel supply amount) is performed, An error may occur in the update learning by the air-fuel ratio learning means performed on the assumption that the air-fuel ratio learning correction value is stable, and the air-fuel ratio learning correction value may be updated to an incorrect value. Can be prevented.
[0016]
Claim4In the invention described in (1), the internal combustion engine is an internal combustion engine of a type in which fuel is directly injected into a cylinder.
In particular, in a so-called direct fuel injection internal combustion engine that directly injects fuel into a cylinder (inside the cylinder), the fuel is directly fed into the cylinder, so the fuel transportation delay is small and the fuel supply amount changes. In addition, the relationship between the air-fuel ratio (fuel supply amount) and the generated torque is linear during lean operation, so it is referenced compared to the fuel injection type internal combustion engine in the intake port (for setting the fuel supply amount). Use) The generated torque changes sensitively to the step change of the air-fuel ratio learning correction value and further to the step change of the fuel supply amount, and the influence on the drivability becomes large. Since this possibility can be reliably suppressed, the drivability of the direct fuel injection internal combustion engine in the cylinder can be made equal to the drivability of the fuel injection internal combustion engine in the intake port. Direct fuel injection internal combustion It is possible to improve the marketability of the cough.
[0017]
Claim5In the present invention, the air-fuel ratio learning correction value storage means is configured to divide the engine operation region into a plurality of operation regions in correspondence with the fuel supply amount.
With this configuration, when the air-fuel ratio learning correction value is updated and stored in the air-fuel ratio learning correction value storage means (learning map), the map search value Tib (fuel) is used without using the cylinder charging intake air flow rate as a parameter. Supply amount) is used as a parameter, so that the operating state of the fuel injection valve 4 (actual actual value) is set regardless of whether the target air-fuel ratio (target equivalence ratio) is set to stoichiometric or lean. The learning area corresponding to the fuel supply amount) can be referred to. Accordingly, it is possible to make the learning area during stoichiometric operation and the area to be referred (searched) during lean operation coincide with each other with a simple configuration. Therefore, for example, it is possible to improve the open control accuracy of the air-fuel ratio that is performed by referring to the air-fuel ratio learning correction value during the lean operation.
[0018]
【The invention's effect】
According to the first aspect of the present invention, the current air-fuel ratio learning correction value searched based on the corresponding operation region and the air-fuel ratio learning correction value used for the last final fuel supply setting are averaged. Since the final fuel supply amount is set using the air fuel ratio learning correction value after the averaging process (for example, weighted average), the air / fuel ratio used for setting the final fuel supply amount It is possible to suppress the learning correction value from changing stepwise. Therefore, for example, when the operation region transitions and the reference region of the air-fuel ratio learning correction value changes, even if the operation region does not transition, the combustion mode is switched between stratified combustion and homogeneous combustion. However, since the air-fuel ratio learning correction value can be prevented from changing stepwise, the step-wise change in the air-fuel ratio (fuel supply amount) can be suppressed and the change in the torque generated by the engine can be suppressed. Can be maintained well.
[0019]
According to the second aspect of the present invention, when the operation region transitions and the reference region of the air-fuel ratio learning correction value changes, the primary smoothing process ( Etc., and gradually shifted to a new air-fuel ratio learning correction value. Therefore, even when the operation region transitions and the reference region of the air-fuel ratio learning correction value changes, the air-fuel ratio learning correction is performed. The step change of the value is suppressed, the step change of the air-fuel ratio (fuel supply amount) can be suppressed, and the change of the generated torque of the engine can be suppressed, so that the drivability can be maintained well. it can.
[0020]
According to the third aspect of the present invention, for example, when the combustion mode is switched between stratified combustion and homogeneous combustion, and the air-fuel ratio learning correction value changes stepwise, a new air-fuel ratio learning is performed. Since the first smoothing process (averaging process) is performed without immediately switching to the correction value, and the transition to the new air-fuel ratio learning correction value is made gradually, step-by-step changes in the air-fuel ratio learning correction value As a result, the stepwise change in the air-fuel ratio (fuel supply amount) and the change in the torque generated by the engine can be suppressed, and the drivability can be maintained well.
[0021]
here,Claim1-3Described ineachAccording to the invention, the air-fuel ratio learning correction value is unstable while the processing for suppressing the step change of the air-fuel ratio learning correction value referred to (used for setting the fuel supply amount) is being performed. Therefore, there is a possibility that an error occurs in the update learning by the air-fuel ratio learning means, which is originally performed on the assumption that the air-fuel ratio learning correction value is stable, and the air-fuel ratio learning correction value is updated to an incorrect value. Since this can be prevented, the update learning accuracy by the air-fuel ratio learning means can be kept high.
[0022]
Claim4According to the present invention, the drivability of the in-cylinder direct fuel injection internal combustion engine can be made equivalent to the drivability of the in-cylinder direct fuel injection internal combustion engine. The merchantability of the institution can be improved.
Claim5According to the invention described in (4), the step change of the air-fuel ratio learning correction value is suppressed, the step change of the air-fuel ratio (fuel supply amount) and the change of the generated torque of the engine can be suppressed, Therefore, it is possible to maintain good operability and maintain learning opportunities with a simple configuration even when switching between stoichiometric operation and lean operation (including both stratified combustion and homogeneous combustion). However, highly accurate learning and thus air-fuel ratio feedback control can be performed over the entire operation region, and highly accurate air-fuel ratio open control using the learning result can be performed.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
In FIG. 2 showing the first embodiment of the present invention, the intake air passes through the intake pipe 3 from the air cleaner, the flow rate thereof is controlled by the throttle valve 8 interlocked with the accelerator pedal, and flows into the cylinder (inside the cylinder). The fuel is injected and supplied directly from the injector (fuel injection valve) 4 provided in each cylinder based on the injection signal into the cylinder. In the present embodiment, during the stoichiometric (theoretical air-fuel ratio) operation, the learning value PHOS is updated and stored while performing the air-fuel ratio feedback control based on the output of the oxygen sensor, as described later, while the lean (lean air-fuel ratio) is stored. ) During operation (including lean operation for both homogeneous combustion and stratified combustion), the learning value PHOS updated and stored during stoichiometric operation is referred to (searched) to correct the basic fuel injection amount Tp and perform open control. It is like that.
[0024]
The mixture of the injected fuel and the air flowing into the cylinder burns with the help of ignition sparks in the cylinder, and the burned gas performs the work of pushing down the piston. Thereafter, the combustion gas is discharged to the three-way catalyst 6 through the exhaust pipe 5, where harmful three components (CO, HC, NOx) are cleaned and discharged into the atmosphere.
7 is an air flow meter for detecting the intake air flow rate Qa, 9 is a sensor for detecting the opening TVO of the throttle valve 8, 10 is a crank angle sensor for detecting the engine rotational speed Ne, and 11 is for detecting the cooling water temperature Tw of the water jacket. A water temperature sensor 13 is an ISC (auxiliary air amount control device for idle rotation control etc.) for bypassing the throttle valve 8 and sending air to the cylinder. 14 is a vehicle speed sensor.
[0025]
12A and 12B are O provided in the exhaust pipe before and after the three-way catalyst 6, respectively.₂(Oxygen) sensor that has a characteristic of rich / lean reversal at the stoichiometric air-fuel ratio and outputs a so-called binary value that is richer or leaner than the stoichiometric air-fuel ratio (λ = 1) It is. O₂The (oxygen) sensor is the air-fuel ratio detection means according to the present invention. These two O₂In the control unit 21 in which the output from the sensor is input together with the outputs from the air flow meter 7, the crank angle sensor 10, the water temperature sensor 11, etc., a fuel injection signal is output to the injector 4, and as shown below. In addition, air-fuel ratio feedback control with a learning function is performed.
[0026]
That is, the basic fuel supply amount calculation means, air-fuel ratio feedback correction value setting means, air-fuel ratio learning correction value storage means, air-fuel ratio learning means, fuel supply amount setting means, and drive means of the air-fuel ratio control apparatus according to the present invention. The control unit 21 is provided as software.
3 shows the previous O₂This is a basic routine of air-fuel ratio feedback control based on the sensor output, and is executed in rotation synchronization.
[0027]
First O₂By comparing the sensor output with the slice level corresponding to the theoretical air-fuel ratio, it is determined whether the air-fuel ratio is reversed to rich or lean with respect to this slice level (steps 52 to 54), and depending on the determination result By referring to (searching) the map, the proportional and integral components are read out and stored in registers in the CPU (steps 55, 60, 63, and 68).
[0028]
Each map value P of proportionality and integral_R, P_L, I_R, I_LIs a value given in advance and is a basic control constant for air-fuel ratio feedback control.
Proportional P_R, P_LThe characteristics of the map values are shown in FIG. The map characteristic of FIG. 7 uses the map search value Tib and the engine rotational speed Ne as parameters, but the change amount of Ne can also be used as a parameter.
[0029]
The map search value Tib will be described later.
By the way, in FIG. 7, the area surrounded by a diagonal line is a special zone in which a value much smaller than other areas is entered in order to avoid surging generated in the vehicle.
For the integral, the map value i_R, I_LIt is also possible to obtain a value obtained by multiplying the map search value Tib by the final integrated values IR and IL (steps 61 and 69). This load correction is required because the amplitude of α increases in the operating range where the control cycle of α becomes long, and the exhaust purification performance of the three-way catalyst may deteriorate. This is because it is almost constant regardless of the above.
[0030]
Next, the proportional map value P_R, P_LIs corrected by a learning value PHOS (air-fuel ratio learning correction value) (steps 58 and 66).
As shown in FIG. 6, the learning value PHOS is a value obtained by searching a learning value map and reading a value stored in a learning region to which the current driving condition belongs (steps 57, 112, 113, Steps 65, 112, 113). After O₂If the sensor has a failure, the learning value becomes unreliable, so that the learning function can be removed by setting PHOS = 0 (steps 111 and 114).
[0031]
On the other hand, as shown in FIG. 4 and FIG.₂Updating is performed based on the sensor output (steps 56 and 64). 4 and 5 are the front O₂A cycle in which the sensor output is reversed is executed as a calculation cycle. 4 and 5, it is confirmed in steps 81 to 91 whether the following learning conditions (1) to (7) are satisfied.
[0032]
(1) Rear O₂The sensor is in an active state (step 81).
(2) Rear O₂The sensor is not broken down (abbreviated as “OK” in the figure) (step 82).
(3) The three-way catalyst is in an active state (step 83).
(4) The operating condition is in a region other than the special zone (step 84).
[0033]
Map value P_R, P_LIn this numerical information, there is a bit that is not used as a numerical value and remains “0”, so that only the numerical value stored in the special zone shown in FIG. 1 ”is inserted. By doing this, the value of bit 7 is seen, and if it is “0”, it is determined that the zone is other than the special zone.
[0034]
(5) The air-fuel ratio control has been performed a predetermined number of times in a region other than the special zone (steps 85 and 86).
Since the counter value j in step 85 represents the number of air-fuel ratio inversions since it is determined that it is not in the special zone, this counter value j is compared with a constant value n (for example, 12 times). It can be determined that the air-fuel ratio control has been performed a predetermined number of times in a region other than the zone. The reason for this is that the learning value is updated after the air-fuel ratio control is stabilized.
[0035]
(6) Not in idle state (step 87).
This is because it is preferable to stop the air-fuel ratio feedback control because the engine stability and the like are given priority in the idle state.
(7) Staying in a learning area where the driving conditions are the same for a predetermined number of times (steps 88 to 91).
[0036]
When the learning area is shown in FIG. 8, the area determined from the engine speed Ne and the map search value Tib (obtained from the flowchart of FIG. 10) is divided into a plurality of equal parts, and the learning value PHOS is stored for each area. Yes.
Here, the “map search value Tib” calculation routine according to the present embodiment will be described with reference to the flowchart of FIG.
[0037]
In step 1, the fuel injection pulse width Ti calculated in accordance with the current operating state (target equivalent ratio, various correction coefficients, etc.) is read.
In step 2, a map search value Tib (lean air-fuel ratio operation fuel supply amount) is calculated. The map search value Tib is a parameter dedicated to map search that is different from the fuel injection control.
[0038]
Tib = Ti-Ts
Ts: Invalid injection pulse width
By the way, since this map search value Tib is Ti {≈Tp × TFBYA (target equivalent ratio) −Ts}, it becomes a value correlated with the actual fuel injection amount and the target torque of the engine. For this reason, even if the target air-fuel ratio (target equivalent ratio) is set to stoichiometric or lean, it becomes substantially the same value. Therefore, the “learning region divided by the basic fuel injection amount Tp during stoichiometric operation and the region to be referred to during lean operation are increased by the increase in the basic fuel injection amount Tp accompanying the lean air-fuel ratio. It is possible to surely avoid the fear that “they do not necessarily match”. For this reason, for example, it becomes possible to improve the open control accuracy of the air-fuel ratio during the lean operation. Note that the engine torque during the stoichiometric operation correlates with the basic fuel injection amount Tp (because the target equivalent ratio “λ = 1” is obtained during the stoichiometric operation, this Tp is a value that correlates with the actual fuel injection amount. The engine torque during lean operation is in a state where the intake air flow rate is sufficient, so it does not correlate with the basic fuel injection amount for stoichiometry (that is, the cylinder-filled intake air flow rate) Tp but with the actual fuel injection amount. To do.
[0039]
Then, when the current operating condition belongs to which learning region, and if it is in the same learning region as the previous time, the counter value j_RIs incremented by 1 (steps 88 to 90). This counter value j_RAnd constant value n_RCompare (for example, 6 times) and j_R≧ n_RIf so (step 91), it can be determined that the user has stayed in the same learning area having the same operating condition for a certain number of times.
[0040]
When all of the above (1) to (7) are satisfied, it is determined that the learning condition is satisfied, and is stored in the learning region to which the current operating condition belongs (region determined from the engine speed Ne and the map search value Tib). The learned value PHOS is read and stored in a register in the CPU (step 92).
The update width DPHOS of the learning value includes a post-O₂The air-fuel ratio detected by the sensor gives a negative value on the rich side, and gives a positive value on the lean side. This is corrected by adding the update width DPHOS to the learning value PHOS in step 94 to be described later. Therefore, if the learning value PHOS is reduced by giving a negative value to the update width DPHOS on the rich side, This is because the component PR is large and the other proportional component PL is small, and the air-fuel ratio returns to the lean side. Similarly, by giving a positive value to the learning value DPHOS on the lean side, the air-fuel ratio can be returned to the rich side. Proportional P_RAnd P_LIt doesn't matter if only one of them is not changed.
[0041]
Now, for determining the value (absolute value) of the update range DPHOS of the learning value,₂It is not determined as a constant value according to the comparison result between the sensor output and the slice level.₂The rear O is so large that it deviates greatly from the center value of the sensor output and becomes smaller near the intermediate value.₂Set according to the sensor output (step 93).
[0042]
As shown in FIG.₂Since the output waveform of the sensor has a minimum value of 0V, a maximum value of 1V, and an approximate rotation target centered on an intermediate value of 0.5V,₂A linear function with a downward slope is prepared with the sensor output as the vertical axis and the learning value update width DPHOS as the horizontal axis.₂If the update width DPHOS is determined to be 0 at 0.5 V which is an intermediate value of the sensor output,₂The absolute value of the update width DPHOS increases as the sensor output deviates from the intermediate value.
[0043]
For example, if the points A and B are compared in FIG. 9, the absolute value of the update width DPHOS is larger for the point B further away from the intermediate value.
The update width DPHOS thus obtained is added to the learning value PHOS stored in the register to update the learning value, and the updated learning value PHOS is stored in the same learning region (steps 94 and 95).
[0044]
In this way, the update range of the learning value is set to₂By setting the variable value according to the sensor output, it is possible to prevent air-fuel ratio overshoot and undershoot while improving the convergence of the air-fuel ratio to the window. In this embodiment, the update range of the learning value is set to the rear O₂Although described as a configuration in which a variable value is set according to the sensor output, the present invention is not limited to this, and can also be applied to a case where the update range of the learning value is set to a predetermined value.
[0045]
Finally, the map value P stored in the register in the CPU_L, P_ROf the numerical information, the value of bit 7 is returned to "0" and entered again (step 96). This is because the numerical information bit originally displays a numerical value, so that “1” of bit 7 is treated as a part of the numerical value as it is.
Returning to FIG. 3, the air-fuel ratio feedback control constant (proportional component P_R, P_LAnd an air-fuel ratio feedback correction coefficient (air-fuel ratio feedback correction value) α is calculated on the basis of the integrals IR and IL) (steps 59, 62, 67 and 70). Based on the correction coefficient α thus obtained, the routine of FIG. 11 is executed to calculate the fuel injection pulse width Ti.
[0046]
That is, as shown in FIG. 11, from the intake air flow rate Qa and the rotational speed Ne, the basic injection pulse width Tp (= K · Qa / Ne, where K is a constant, a value that correlates with the cylinder-filled intake air flow rate at the time of stoichiometry). Is calculated using the target equivalent ratio TFBYA (which is set according to the stoichiometric operation or lean operation) or the above-mentioned air-fuel ratio feedback correction coefficient α (α during the stoichiometric operation. The value corrected in “1.0 + learning value PHOS” is calculated as the fuel injection pulse width Ti given to the injector. Co is the sum of 1 and the water temperature increase correction coefficient KTw, and Ts is the invalid injection pulse width.
[0047]
As described above, according to the flowchart of FIG. 10, when the learning value is updated and stored in the map, the stoichiometric basic fuel injection amount (that is, the cylinder-filled intake air flow rate) Tp is used as a parameter as in the prior art. Instead, the map search value Tib (actual fuel injection amount or target torque equivalent value) is used as a parameter, so that even if the target air-fuel ratio (target equivalent ratio) is set to stoichiometric, it is set to lean. However, in any case, it is possible to refer to the learning region corresponding to the operating state (actual fuel injection amount) of the fuel injection valve 4. Therefore, it is possible to make the learning area at the time of stoichiometric operation and the area to be referred (searched) at the time of lean operation coincide with each other with a simple configuration. For this reason, for example, it becomes possible to improve the open control accuracy of the air-fuel ratio during the lean operation.
[0048]
In addition, for example, it may occur when a learning area corresponding to lean operation is newly added separately, i.e., there is a low possibility that learning will be performed in the learning area during stoichiometric operation. There is also a fear that it will not be possible to shift from stoichiometric operation to lean operation because it is not possible to clear "the learning value KL has been acquired (updated and stored) after starting", which is the transition condition to It can also be avoided.
[0049]
In addition, the learning region (one unit) at the time of stoichiometric operation may be expanded to include the region corresponding to the lean operation, that is, the learning accuracy itself may be lowered. It is possible to reliably avoid the fear that the accuracy of the open control during the lean operation performed with reference to the above will be reduced.
In other words, according to the present embodiment, even when switching between stoichiometric operation and lean operation (including both stratified combustion and homogeneous combustion), the entire operation region is maintained while maintaining a learning opportunity with a simple configuration. Thus, highly accurate learning and thus air-fuel ratio feedback control can be performed, and highly accurate air-fuel ratio open control using the learning result can be performed.
[0050]
In the flowchart of FIG. 10, the map search value Tib is set to “Ti-Ts” to obtain the actual fuel injection amount. However, the learning value PHOS and the air-fuel ratio feedback correction coefficient α are set to the reference value (for example, 1.0). Considering the case of a large deviation from the above, Ti itself may change due to the influence, and a learning area different from the learning area that should be referred to may be referred to.
[0051]
Therefore, when calculating the map search value Tib, Ti is divided by the learning value PHOS and, in order to suppress changes due to the air-fuel ratio feedback correction coefficient α and Co (water temperature increase correction coefficient KTw, etc.). You can also
That is, in step 2 of the flowchart of FIG.
Tib = (Ti−Ts) / α / Co
You may make it perform the calculation which becomes.
[0052]
In this way, even if the learning value PHOS and thus the air-fuel ratio feedback correction coefficient α deviates from a reference value (eg, 1.0) over time, for example, it differs from the learning region that should be referred to originally. Since it is possible to reliably avoid the possibility that the learning area will be referred to, the learning accuracy can be further improved and the air-fuel ratio feedback control accuracy can be improved, and the control accuracy of the air-fuel ratio open control using the learning result can be improved. Can be further increased.
[0053]
The routine for calculating the map search value Tib can also be executed according to the flowchart of FIG.
That is,
In step 11, TFBYA and Tp are read.
In step 12, a map search value Tib is calculated.
[0054]
Tib = Tp × TFBYA
Then, using the map search value Tib (learning correction value search fuel supply amount) obtained in this way, the learning value is updated, stored, searched, referenced, and the like.
According to the flowchart of FIG. 12, as in the flowchart of FIG. 10, it is possible to match the learning region during stoichiometric operation with the region to be referred to during lean operation. Therefore, the map search value Tib (target engine torque equivalent value) is not calculated by back-calculating the fuel injection pulse width Ti, but the intake air flow rate Qa (in-cylinder charged intake air flow rate Tp≈Qa / Ne) and the target equivalent Since the calculation is performed by multiplying the ratio, the amount of calculation can be further reduced, and the control logic can be simplified.
[0055]
Further, the map search value Tib according to the flowchart of FIG. 12 is not affected by the learning value PHOS and the air-fuel ratio feedback correction coefficient α, and so on. In addition to realizing control, it is possible to achieve higher accuracy in open control of the air-fuel ratio using the learning result.
[0056]
By the way, in this embodiment, in order to suppress the change of the engine generated torque caused by the step change of the learning value when the operation region transitions and the learning value reference region changes, the following processing ( Perform damper control).
That is, the flowchart (damper control) shown in FIG. 13 is executed. Note that this routine is a routine that is performed when the operation region transitions and the learning value reference region changes.
[0057]
First, in step 21, the current rotational speed Ne and the current map search value Tib are read.
In step 22, a learning map (see FIG. 8) is searched using the rotation speed Ne and map search value Tib read in step 21, the learning value PHOS stored in the corresponding area is read, and this is set in PHOS0. (PHOS0 ← PHOS).
[0058]
In step 23, the primary smoothing process (calculation) of the learning value PHOS is performed as follows.
PHOS_(new)= WT × PHOS0 + (1-WT) × PHOS_(old)
WT; weighting coefficient (0 <WT <1)
In step 24, it is determined whether or not FLRNDP (damper control execution flag) is 1. If it is 1, it is determined that damper control is being executed (primary smoothing process is being executed), and the process proceeds to step 25. On the other hand, if it is 0, it is determined that the damper control is not being executed, and the process proceeds to step 27. Note that FLRNDP is set to 1 immediately after the operation region transitions and the learning value reference region changes.
[0059]
In step 25, | PHOS0-PHOS_(new)It is determined whether or not | <predetermined value KSL (damper control completion determination value). If yes, go to step 26.
In step 26, PHOS0 stored in the learning area corresponding to the current driving area, and the learned value PHOS after the primary smoothing process._(new)Therefore, even if the fuel injection amount is corrected by PHOS0, it is determined that no air-fuel ratio step is generated, FLRNDP is set to 0, and the primary smoothing process is stopped. At the same time, PHOS0 → PHOS in order to use PHOS0 for the processing of steps 58 and 66 in the flowchart of FIG. 3 and the calculation of the fuel injection amount of FIG. 11 (α = 1.0 ± PHOS during lean operation). Then, this flow is finished. That is, the fuel injection amount is corrected based on the learned value PHOS retrieved in step 22.
[0060]
On the other hand, | PHOS0-PHOS_(new)If | ≧ predetermined value KSL, the process proceeds to step 28. In this case, PHOS0 stored in the learning area corresponding to the current driving area and the learned value PHOS after the primary smoothing process are processed._(new)The deviation is still large, and if the fuel injection amount is corrected by PHOS0, there is a possibility that an air-fuel ratio step and a torque step may occur._(new)→ PHOS_(old)| PHOS0-PHOS_(new)| <The primary idle process in step 23 is continued until the predetermined value KSL is reached, and PHOS_(new)3, the processing of steps 58 and 66 in the flowchart of FIG. 3 and the fuel injection amount calculation processing of FIG. 11 (α = 1.0 ± PHOS during lean operation)_(new)).
[0061]
By the way, if it is determined in step 24 that FLRNDP (damper control execution flag) is 0, the learning value reference area has not changed or the damper process has been completed.
In step 27, the learned value PHOS retrieved in step 22 can be used as it is for correcting the fuel injection amount. Therefore, the processing of steps 58 and 66 in the flowchart of FIG. 3 or the fuel injection amount of FIG. This flow is executed in order to perform the calculation processing of the learning value PHOS by executing the flowchart of FIG. 5 when the stoichiometric operation is being performed, while performing the calculation (α = 1.0 ± PHOS during lean operation). finish.
[0062]
As described above, according to the present embodiment, when the driving region changes and the learning value reference region changes, the current learning value PHOS is not immediately switched to the new learning value PHOS, but the first smoothing is performed. Processed value (PHOS_(new)) To correct the fuel injection amount and gradually bring the current learning value PHOS closer to the new learning value PHOS, so that even if the operation region changes and the reference region of the learning value changes, the learning value Therefore, the step change of the fuel supply amount and the change of the generated torque of the engine can be suppressed. Therefore, drivability can be maintained well.
[0063]
Next, a second embodiment of the present invention will be described.
Since the system configuration of the second embodiment is the same as that of the first embodiment, description thereof will be omitted, and only the flowchart of FIG. 14 will be described.
That is, in the second embodiment, in order to suppress the change in the engine generated torque caused by the step change of the learning value when the operation region transitions and the learning value reference region changes, as shown in FIG. Such processing (damper control) is performed. This routine is also a routine that is performed when the operation region transitions and the learning value reference region changes.
[0064]
First, in step 31, the current rotational speed Ne and the current map search value Tib are read.
In step 32, a learning map (see FIG. 8) is searched based on the rotation speed Ne and map search value Tib read in step 31, the learning value PHOS stored in the corresponding area is read, and this is set in PHOS0. (PHOS0 ← PHOS).
[0065]
In step 33, FSTR (stratified combustion switching flag) is read.
In step 34, it is determined whether or not FLRNDP (damper control execution flag) is 1. If 1, the damper control (primary smoothing process) should be executed, and the process proceeds to step 35. On the other hand, if it is 0, it is determined that the damper control is not being executed, and the routine proceeds to step 39.
[0066]
Note that FLRNDP is set to 1 immediately after the operation region transitions and the reference region of the learning value changes, but has a separate learning map for stratified combustion and homogeneous combustion. If the operating range does not change, the learning value PHOS may change stepwise by switching the combustion mode between stratified combustion and homogeneous combustion.
[0067]
Therefore, in this embodiment, in step 39, it is determined whether or not FSTR (stratified combustion switching flag) matches FSTR0 (previous FSTR value). If they do not coincide (FSTR ≠ FSTR0), it is determined that the combustion mode has been changed and the learning map has been changed. If they coincide with each other (FSTR = FSTR0), it is determined that there is no change in the combustion mode and no change in the learning map, and the process proceeds to step 40.
[0068]
In step 35, FLRNDP (damper control execution flag) is set to 1, and the process proceeds to step 36.
In step 36, the primary smoothing process (calculation) of the learning value PHOS is performed as follows.
PHOS_(new)= WT × PHOS0 + (1-WT) × PHOS_(old)
WT; weighting coefficient (0 <WT <1)
In step 37, | PHOS0-PHOS_(new)It is determined whether or not | <predetermined value KSL (damper control completion determination value). If yes, go to step 38.
[0069]
In step 38, PHOS0 stored in the learning area corresponding to the current driving area, and the learned value PHOS after the primary smoothing process._(new)Therefore, even if the fuel injection amount is corrected by PHOS0, it is determined that no air-fuel ratio step is generated, FLRNDP is set to 0, and the primary smoothing process is stopped. At the same time, the learned value PHOS retrieved in step 32 is used for the processing in steps 58 and 66 in the flowchart of FIG. 3 and the calculation of the fuel injection amount in FIG. 11 (α = 1.0 ± PHOS during lean operation). Therefore, this flow is terminated as PHOS0 → PHOS. That is, the fuel injection amount is corrected by the learned value PHOS retrieved in step 32.
[0070]
On the other hand, | PHOS0-PHOS_(new)If | ≧ predetermined value KSL, PHOS0 stored in the learning area corresponding to the current driving area and the learned value PHOS after the primary smoothing process_(new)The deviation is still large, and if the fuel injection amount is corrected by PHOS0, an air-fuel ratio step may occur and a torque step may occur._(new)3, the processing of steps 58 and 66 in the flowchart of FIG. 3 and the fuel injection amount calculation processing of FIG. 11 (α = 1.0 ± PHOS during lean operation)_(new)) | | PHOS0-PHOS_(new)| <The primary idle process in step 36 is continued until the predetermined value KSL is reached (in this case, PHOS_(new)→ PHOS_(old)As the primary annealing process continues).
[0071]
By the way, if it is determined in step 34 that the operation region has not changed or the damper control has been completed, and if it is determined in step 39 that FSTR = FSTR0, stepwise change in the learning value PHOS. If no control is performed, the process proceeds to step 40 without performing damper control (primary smoothing process). In step 40, the following process is performed.
[0072]
In step 40, the learned value PHOS0 searched in step 32 can be used as it is for correcting the fuel injection amount. Therefore, the processing of steps 58 and 66 in the flowchart of FIG. 3 and the fuel injection amount of FIG. This flow is executed in order to perform the calculation processing of the learning value PHOS by executing the flowchart of FIG. 5 if the stoichiometric operation is performed. finish.
[0073]
As described above, according to the second embodiment, combustion is performed between stratified combustion and homogeneous combustion even when the operation region does not transition, as well as when the operation region transitions and the learning value reference region changes. Even when the learning value PHOS changes stepwise, the value obtained by performing the primary smoothing process (PHOS) without immediately switching the current learning value PHOS to the new learning value PHOS._(new)) To correct the fuel injection amount and gradually bring the current learning value PHOS closer to the new learning value PHOS, so that a stepwise change in the learning value is suppressed, so that the fuel supply amount As a result, the change in the torque generated by the engine can be suppressed. Therefore, drivability can be maintained well.
[0074]
In the above embodiments, the internal combustion engine that switches between the stoichiometric operation and the lean operation has been described. However, the present invention is not limited to this, and can be applied to, for example, an internal combustion engine that performs only the stoichiometric operation. is there.
That is, the learning value PHOS to be referred to is switched by the transition of the operation region, switching of the air-fuel ratio, switching of the combustion mode (stratified combustion / homogeneous combustion, etc.), and other factors (for example, evaporative processing or non-processing) In the case of switching, it is included in the scope of the present invention to switch the value before switching so as to gradually approach the value after switching. In each of the above embodiments, the weighted average process is performed as the primary smoothing process. However, the present invention is not limited to this, and the value before switching gradually approaches the value after switching. As long as the process is switched, another method (simple averaging process or the like) can be used.
[0075]
Furthermore, the present invention provides the current learning value PHOS searched based on the corresponding operation region and the previous final fuel supply amount regardless of whether the operation region transitions, the air-fuel ratio or the combustion mode is switched, or the like. The learning value PHOS used for the setting may be always averaged, and the final fuel supply amount of this time may be set using the learning value PHOS after the averaging process. is there. In this case, although the averaging process is always performed, it is not necessary to detect the transition of the operation region, the switching of the air-fuel ratio or the combustion mode, and the control logic can be simplified.
[0076]
AlsoWhile the learned value PHOS used for setting the previous fuel supply amount and the learned value PHOS used for setting the current fuel supply amount do not match, the update setting of the learned value PHOS by the air-fuel ratio learning means BanTheThat is, the learning value PHOS is unstable while processing such as a primary smoothing process for suppressing a stepwise change in the learning value PHOS to be referred to (used for setting the fuel supply amount) is performed. Then, an error occurs in the update learning (control result of the flowchart of FIG. 5) by the air-fuel ratio learning means, which is originally performed on the assumption that the learning value PHOS is stable, and the learning value PHOS may be updated to an incorrect value. This is because such fears can be reliably prevented.
[0077]
In each of the above embodiments, the oxygen sensor is provided before and after the three-way catalyst 6, but the present invention is not limited to this. For example, the oxygen sensor includes any one oxygen sensor. On the basis of the output result, the air-fuel ratio feedback correction coefficient α is given by proportional / integral control (P minutes, I minutes), while the deviation between α and the reference value is updated and stored as a learning value. The present invention can be applied to everything that reflects the learning result.
[Brief description of the drawings]
FIG. 1 is a block diagram of the present invention.
FIG. 2 is a system configuration diagram of the first embodiment of the present invention.
FIG. 3 is a flowchart for explaining calculation of an air-fuel ratio feedback correction coefficient α.
FIG. 4 is a flowchart for explaining learning value PHOS update;
FIG. 5 is a flowchart for explaining update of a learning value PHOS.
FIG. 6 is a flowchart for explaining reading of a learned value PHOS.
[Figure 7] Proportional P⁰¹, P_LFIG.
FIG. 8 is a diagram (table, map) for explaining a learning area;
FIG. 9 Rear O₂It is a characteristic view explaining the relationship of the update width DPHOS with respect to a sensor output.
FIG. 10 is a flowchart for explaining calculation of a map search value Tib.
FIG. 11 is a flowchart for explaining calculation of a fuel injection pulse width Ti.
FIG. 12 is a flowchart for explaining another example of calculation of a map search value Tib.
FIG. 13 is a flowchart for explaining primary smoothing processing (damper control) of a learned value PHOS;
FIG. 14 is a flowchart illustrating primary smoothing processing (damper control) of a learned value PHOS according to the second embodiment of the present invention.
[Explanation of symbols]
4. Injector (fuel supply device)
5 Exhaust pipe
6 Three-way catalyst
7 Air flow meter (engine load sensor)
10 Crank angle sensor (engine speed sensor)
11 Water temperature sensor
12A front O₂Sensor
12B after O₂Sensor
21 Control unit

Claims (5)

Basic fuel supply amount calculating means for calculating a basic fuel supply amount based on the engine operating state;
Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture as a rich lean signal with respect to the theoretical air-fuel ratio;
Air-fuel ratio feedback correction for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so as to bring the actual air-fuel ratio closer to the theoretical air-fuel ratio based on the detection result detected by the air-fuel ratio detection means Value setting means;
An air-fuel ratio learning correction value storage means for dividing the engine operation region into a plurality of operation regions, and storing the air-fuel ratio learning correction value for correcting the basic fuel supply amount in a rewritable manner for each operation region;
An air-fuel ratio learning means for updating and setting the air-fuel ratio learning correction value stored in the air-fuel ratio learning correction value storage means in a direction to decrease the deviation from the reference value of the air-fuel ratio feedback correction value for each operation region;
With
The current air-fuel ratio learning correction value searched based on the corresponding operation region and the air-fuel ratio learning correction value used for setting the final fuel supply amount last time are averaged, and after the averaging process A final fuel supply amount is set using the air-fuel ratio learning correction value, and the fuel supply device is driven and controlled based on the set fuel supply amount.
While the air-fuel ratio learning correction value used for the previous setting of the fuel supply amount and the air-fuel ratio learning correction value used for the current fuel supply amount setting do not match, the air-fuel ratio learning means performs the air-fuel ratio learning correction value. An air-fuel ratio control apparatus for an internal combustion engine, wherein update setting of a fuel ratio learning correction value is prohibited. Basic fuel supply amount calculating means for calculating a basic fuel supply amount based on the engine operating state;
Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture as a rich lean signal with respect to the theoretical air-fuel ratio;
Air-fuel ratio feedback correction for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so as to bring the actual air-fuel ratio closer to the theoretical air-fuel ratio based on the detection result detected by the air-fuel ratio detection means Value setting means;
An air-fuel ratio learning correction value storage means for dividing the engine operation region into a plurality of operation regions, and storing the air-fuel ratio learning correction value for correcting the basic fuel supply amount in a rewritable manner for each operation region;
An air-fuel ratio learning means for updating and setting the air-fuel ratio learning correction value stored in the air-fuel ratio learning correction value storage means in a direction to decrease the deviation from the reference value of the air-fuel ratio feedback correction value for each operation region;
Fuel supply amount setting means for setting a final fuel supply amount using the air-fuel ratio learning correction value;
Drive means for driving and controlling the fuel supply device based on the fuel supply amount set by the fuel supply amount setting means;
An air-fuel ratio control apparatus for an internal combustion engine configured to include:
When the operating region transitions and the air-fuel ratio learning correction value used in the fuel supply amount setting means is switched, the air-fuel ratio learning correction value before switching is switched while gradually approaching the air-fuel ratio learning correction value after switching. West,
After the transition of the operation region, until the air-fuel ratio learning correction value used for setting the previous fuel supply amount matches the air-fuel ratio learning correction value used for setting the current fuel supply amount An air-fuel ratio control apparatus for an internal combustion engine, wherein an update setting of an air-fuel ratio learning correction value by the air-fuel ratio learning means is prohibited. Basic fuel supply amount calculating means for calculating a basic fuel supply amount based on the engine operating state;
Air-fuel ratio detection means for detecting the air-fuel ratio of the engine intake air-fuel mixture as a rich lean signal with respect to the theoretical air-fuel ratio;
Air-fuel ratio feedback correction for setting an air-fuel ratio feedback correction value for correcting the basic fuel supply amount so as to bring the actual air-fuel ratio closer to the theoretical air-fuel ratio based on the detection result detected by the air-fuel ratio detection means Value setting means;
An air-fuel ratio learning correction value storage means for dividing the engine operation region into a plurality of operation regions, and storing the air-fuel ratio learning correction value for correcting the basic fuel supply amount in a rewritable manner for each operation region;
An air-fuel ratio learning means for updating and setting the air-fuel ratio learning correction value stored in the air-fuel ratio learning correction value storage means in a direction to decrease the deviation from the reference value of the air-fuel ratio feedback correction value for each operation region;
Fuel supply amount setting means for setting a final fuel supply amount using the air-fuel ratio learning correction value;
Drive means for driving and controlling the fuel supply device based on the fuel supply amount set by the fuel supply amount setting means;
An air-fuel ratio control apparatus for an internal combustion engine configured to include:
When the air-fuel ratio learning correction value used in the fuel supply amount setting means is switched according to the switching of the combustion mode, the air-fuel ratio learning correction value before switching is switched while gradually approaching the air-fuel ratio learning correction value after switching. And
After switching the combustion mode, until the air-fuel ratio learning correction value used for the previous fuel supply amount setting and the air-fuel ratio learning correction value used for the current fuel supply amount setting match, An air-fuel ratio control apparatus for an internal combustion engine, wherein an update setting of an air-fuel ratio learning correction value by the air-fuel ratio learning means is prohibited.   The air-fuel ratio control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is an internal combustion engine of a type in which fuel is directly injected into a cylinder.   5. The air-fuel ratio learning correction value storage means is configured to divide an engine operation region into a plurality of operation regions corresponding to fuel supply amounts. An air-fuel ratio control apparatus for an internal combustion engine.

Images