JP7040402B2 - Internal combustion engine control device - Google Patents

Description

The present invention is a control device for an internal combustion engine including a fuel injection valve, a catalyst having an oxygen storage capacity provided in an exhaust passage, and an air-fuel ratio sensor provided on the downstream side of the catalyst in the exhaust passage. Regarding.

The air-fuel ratio feedback control that feedback-controls the detection value of the upstream air-fuel ratio sensor provided on the upstream side of the catalyst having an oxygen storage capacity in the exhaust passage to the target value is well known. Further, in Patent Document 1 below, when a downstream air-fuel ratio sensor is provided on the downstream side of the catalyst and the detected value of the downstream air-fuel ratio sensor is leaner than the theoretical air-fuel ratio, the above target value is set to be higher than the theoretical air-fuel ratio. A control device is described in which the target value is leaner than the theoretical air-fuel ratio when it is rich and the detected value of the downstream air-fuel ratio sensor is richer than the theoretical air-fuel ratio (FIG. 11).

Japanese Patent No. 5949957

By the way, the detection value of the downstream air-fuel ratio sensor may deviate due to individual differences, aging deterioration, temperature characteristics, etc. of the downstream air-fuel ratio sensor. Then, for example, when the control for switching the target value is performed as in the above device with the deviation occurring, the oxygen storage amount in the catalyst cannot be maintained at an appropriate value, and the exhaust gas purification capacity by the catalyst is lowered. Inconvenience may occur if the deviation cannot be dealt with, such as when there is a risk.

Hereinafter, means for solving the above problems and their actions and effects will be described.
1. 1. It is applied to an internal combustion engine including a fuel injection valve, a catalyst having an oxygen storage capacity provided in an exhaust passage, and an air-fuel ratio sensor provided on the downstream side of the catalyst in the exhaust passage, and is applied to the catalyst. When the oxygen storage amount is equal to or more than a predetermined amount, the fuel injection valve is operated to allow a fluid containing a larger amount of unburned fuel than the amount that reacts with oxygen in excess or deficiency to flow into the catalyst. Based on the detection value of the air-fuel ratio sensor when the rich control process is performed, the deviation amount calculation process of calculating the deviation amount expression value indicating the deviation amount of the detected value of the air-fuel ratio sensor is executed. In the deviation amount calculation process, even if the detection value is the same, the deviation amount expression value differs depending on the length of time required for the oxygen storage amount of the catalyst to decrease from the maximum value to zero by the rich control process. It is a control device of an internal combustion engine including a process of calculating a value.

When the above fluid flows into the catalyst while the amount of oxygen stored in the catalyst is more than a predetermined amount, the portion of the unburned fuel contained in the fluid that exceeds the amount that reacts with oxygen in just proportion is stored in the catalyst. Since it reacts with the existing oxygen, the unburned fuel flowing out downstream of the catalyst can be ignored. Further, since the amount of oxygen in the fluid is less than the amount that reacts with the unburned fuel in the fluid in just proportion, the amount of oxygen flowing out to the downstream of the catalyst can be ignored. Therefore, as in the above configuration, by starting the rich control process when the oxygen storage amount is equal to or higher than the predetermined amount, the amount of oxygen and the amount of unburned fuel in the fluid flowing out downstream of the catalyst can be ignored. .. Therefore, the fluid to which the air-fuel ratio sensor is exposed at that time is equivalent to that when the air-fuel ratio of the air-fuel mixture to be burned is the theoretical air-fuel ratio. Therefore, the deviation amount expression value can be calculated based on the deviation amount from the detected value assumed when the air-fuel ratio of the air-fuel mixture to be burned is the stoichiometric air-fuel ratio. Therefore, in the above configuration, the deviation amount of the detected value of the air-fuel ratio sensor can be grasped, and the deviation can be dealt with.

However, the detected value when the rich control process is performed tends to be different depending on the length of the required time. Therefore, it is easy to calculate the deviation amount expression value as a different value depending on whether the required time is long or short. Therefore, in the above configuration, the detection value is tentatively the same by changing the mapping that connects the detection value as the input of the deviation amount calculation process and the output of the deviation amount calculation process according to the length of the required time. Even if there is, it is a process of calculating the deviation amount expression value to a different value according to the length of the required time. As a result, the deviation amount expression value can be calculated with higher accuracy as compared with the case where the mapping is not changed.

2. 2. Even if the detected value is the same, the deviation amount calculation process is assumed that the required time is shorter than when the flow rate of the fluid flowing into the catalyst is large when the rich control process is performed, as compared with the case where the flow rate is small. The control device for an internal combustion engine according to 1 above, which includes a process of calculating the deviation amount expression value to a different value according to the flow rate.

When the flow rate of the fluid flowing into the catalyst during the rich control process is large, the amount of oxygen in the catalyst that reacts with the unburned fuel in the fluid is larger than when the flow rate is small. The rate of decrease in oxygen storage is increased, and the required time is shortened. In that case, since the rate of increase in the amount of unburned fuel flowing downstream of the catalyst increases, there is a difference in the detected value when the rich control process is performed between the case where the flow rate of the fluid is large and the case where the flow rate is small. It is easy to occur. Therefore, in the above configuration, by calculating the deviation amount expression value according to the flow rate, the deviation amount expression value can be calculated in consideration of the influence of the flow rate on the detected value, and the deviation amount expression value can be calculated. The deviation amount can be set to a value indicating more appropriately.

3. 3. The maximum storage amount learning process for learning the maximum value of the oxygen storage amount of the catalyst is executed, and the detection value is assumed that the required time is shorter when the maximum value is small than when the maximum value is large. The control device for the internal combustion engine according to 1 or 2 above, which includes a process of calculating the deviation amount expression value to a different value according to the maximum value even if they are the same.

When the maximum value of the oxygen storage amount is small, the time required for the oxygen storage amount of the catalyst to become zero by the rich control process is shorter than when the maximum value is large. In that case, since the rate of increase in the amount of unburned fuel flowing downstream of the catalyst increases, the detection value when the rich control process is performed depends on whether the maximum oxygen storage amount is large or small. Differences are likely to occur. Therefore, in the above configuration, by calculating the deviation amount expression value according to the maximum value of the oxygen storage amount, the deviation amount expression value can be calculated in consideration of the influence of the maximum value on the detected value, and by extension, the deviation amount expression value can be calculated. The deviation amount expression value can be a value that more appropriately indicates the deviation amount.

4. When the rich control process is executed, the fluid flowing into the catalyst is introduced into the fluid, triggered by the fact that the detected value of the air-fuel ratio sensor is equal to or less than the rich determination value indicating that the air-fuel ratio is richer than the theoretical air-fuel ratio. A lean control process for controlling the inclusion of oxygen in an amount larger than the amount that reacts with the unburned fuel in just proportion is executed, and the rich control process is performed by the air-fuel ratio sensor when the lean control process is executed. Is executed as a trigger that is equal to or greater than the lean determination value indicating that is leaner than the stoichiometric air-fuel ratio, and the deviation amount calculation process is performed on a plurality of the detected values in one period in which the rich control process is performed. The deviation amount expression value is updated by the exponential moving average processing of the simple average processing value according to the execution cycle of the simple average processing for calculating the simple average processing value and the rich control processing and the lean control processing. By correcting the simple average processing value that is input to the exponential moving average processing according to the length of the processing and the required time, even if the detected values are the same, the said according to the length of the required time. The control device for an internal combustion engine according to any one of 1 to 3 above, which includes a correction process for calculating a deviation amount expression value to a different value.

When the detected value is equal to or greater than the lean determination value, it can be considered that the amount of oxygen stored is equal to or greater than the predetermined amount. Therefore, in the above configuration, the rich control process is executed with the detection value being equal to or greater than the lean determination value as a trigger. Further, in the above configuration, the simple average processing value is corrected according to the length of the required time. Since the simple average processing value is based on the detection value sampled during one rich control processing period, it can be considered that the simple average processing value is calculated based on the detection value group during the same period of the flow rate of the fluid flowing into the catalyst. .. Therefore, in the case of having the configuration of 2 above, the correction according to the difference in the flow rate can be performed more appropriately as compared with the case where the exponential moving average processing value is the correction target, for example.

5. When the rich control process is executed, the fluid flowing into the catalyst is introduced into the fluid, triggered by the fact that the detected value of the air-fuel ratio sensor is equal to or less than the rich determination value indicating that the air-fuel ratio is richer than the theoretical air-fuel ratio. A lean control process for controlling the amount of oxygen to be contained in an amount larger than the amount that reacts with the unburned fuel in just proportion, and a deviation amount reflection process for reflecting the deviation amount expression value in the lean control process are executed. When the lean control process is executed, the rich control process is executed with the trigger that the detected value of the air-fuel ratio sensor is equal to or greater than the lean determination value indicating that the air-fuel ratio is leaner than the theoretical air-fuel ratio, and the deviation amount is reflected. When the deviation amount expression value is the deviation amount on the lean side, the processing is more actual than the switching timing from the rich control processing to the lean control processing before the deviation amount expression value is reflected in the lean control processing. The control device for an internal combustion engine according to any one of 1 to 4 above, which includes a process of accelerating the switching timing.

When the detected value is equal to or greater than the lean determination value, it can be considered that the amount of oxygen stored is equal to or greater than the predetermined amount. Therefore, in the above configuration, the rich control process is executed with the detection value being equal to or greater than the lean determination value as a trigger.

By the way, when the detected value of the air-fuel ratio sensor is deviated to the lean side, the timing at which the detected value becomes the rich determination value or less is delayed as compared with the case where the detected value is not deviated. Therefore, in the above configuration, by executing the shift amount reflection process, even if the detection value of the air-fuel ratio sensor is shifted to the lean side, the lean control process is performed when the detection value of the air-fuel ratio sensor is not shifted. It is possible to switch to the lean control process at a timing closer to the timing of switching to.

The figure which shows the control device and the drive system of a vehicle which concerns on one Embodiment. The block diagram which shows the process executed by the control device which concerns on the same embodiment. The flow chart which shows the procedure of the sub-feedback process which concerns on the same embodiment. The flow chart which shows the procedure of the stoichiometric point calculation process which concerns on the same embodiment. (A) and (b) are time charts illustrating a sampling method of detected values for calculating a stoichiometric point according to the same embodiment.

Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings.
In the internal combustion engine 10 shown in FIG. 1, the air sucked from the intake passage 12 flows into the combustion chambers 14 of the cylinders # 1 to # 4. In the combustion chamber 14, the mixture of the fuel injected from the fuel injection valve 16 and the air flowing in from the intake passage 12 is used for combustion by the spark discharge of the ignition device 18, and the energy generated by the combustion is the crank shaft 20. Is converted into the rotational energy of. The air-fuel mixture used for combustion is discharged to the exhaust passage 22 as exhaust gas. The exhaust passage 22 is provided with a three-way catalyst 24 on the upstream side and a three-way catalyst 26 on the downstream side. Both the three-way catalysts 24 and 26 have an oxygen storage capacity.

The crank shaft 20 is mechanically connected to the carrier C of the planetary gear mechanism 30 that constitutes the power split mechanism. The rotating shaft 32a of the motor generator 32 is mechanically connected to the sun gear S of the planetary gear mechanism 30, and the rotating shaft 34a of the motor generator 34 and the drive wheel 36 are mechanically connected to the ring gear R of the planetary gear mechanism 30. Are linked together. As a result, the internal combustion engine 10 in the present embodiment is one of the drive sources in the series / parallel hybrid vehicle.

The electric power of the battery 44 is supplied to the motor generator 32 via the inverter 40, and the electric power of the battery 44 is supplied to the motor generator 34 via the inverter 42.

The ECU 50 is required to cooperate with the internal combustion engine 10 and the motor generators 32 and 34 as control targets in addition to the process of controlling the torque and the rotation speed which are the control amounts of the motor generators 32 and 34 as control targets. It is a control device that executes the process for generating the output.

The control device 60 controls the internal combustion engine 10, and operates the operation unit of the internal combustion engine 10 such as the fuel injection valve 16 and the ignition device 18 in order to control the torque, the exhaust component ratio, and the like, which are the controlled amounts thereof. That is, for example, the operation signal MS1 is output to the fuel injection valve 16 to operate the fuel injection valve 16, and the operation signal MS2 is output to the ignition device 18 to operate the ignition device 18.

The control device 60 includes an intake air amount Ga detected by the air flow meter 70, an output signal Scr of the crank angle sensor 72, and an upstream air-fuel ratio sensor provided on the upstream side of the three-way catalyst 24 for controlling the controlled amount. Refer to the detection value Afu according to 74. Further, the control device 60 includes an internal combustion engine 10 detected by a water temperature sensor 78 and a value Afd detected by the downstream air-fuel ratio sensor 76 provided on the downstream side of the three-way catalyst 24 and on the upstream side of the three-way catalyst 26. Refer to the temperature of the cooling water (water temperature THW). The upstream air-fuel ratio sensor 74 and the downstream air-fuel ratio sensor 76 are not so-called oxygen sensors having Z characteristics, but the detected value is linearly increased as the amount of oxygen exceeding the amount of unburned fuel in the exhaust increases. It is a sensor that does. Further, the control device 60 has a function of communicating with the ECU 50 via the communication line 80.

The control device 60 includes a CPU 62, a ROM 64, and a peripheral circuit 66, which are connected by a communication line 68. The peripheral circuit 66 includes a circuit that generates a clock signal that defines internal operation, a power supply circuit, a reset circuit, and the like.

FIG. 2 shows a process executed by the control device 60. The process shown in FIG. 2 is realized by the CPU 62 executing the program stored in the ROM 64.
The base injection amount calculation process M10 is a process of calculating the base injection amount Qb, which is the base value of the fuel amount for setting the air-fuel ratio of the air-fuel mixture in the combustion chamber 14 as the target air-fuel ratio, based on the filling efficiency η. Specifically, in the base injection amount calculation process M10, for example, when the filling efficiency η is expressed as a percentage, the filling efficiency η is set to the fuel amount QTH per 1% of the filling efficiency η for setting the air-fuel ratio as the target air-fuel ratio. The process may be such that the base injection amount Qb is calculated by multiplying. The base injection amount Qb is a fuel amount calculated to control the air-fuel ratio to the target air-fuel ratio based on the amount of air filled in the combustion chamber 14. Incidentally, in the present embodiment, the target air-fuel ratio is the theoretical air-fuel ratio. The filling efficiency η is calculated by the CPU 62 based on the intake air amount Ga and the rotation speed NE. Further, the rotation speed NE is calculated by the CPU 62 based on the output signal Scr.

The main feedback processing M12 adds "1" to the correction ratio δ of the base injection amount Qb as the feedback operation amount, which is the operation amount for feedback-controlling the detected value Afu of the upstream air-fuel ratio sensor 74 to the target value Afu *. This is a process of calculating and outputting the feedback correction coefficient KAF. Specifically, the main feedback process M12 holds and outputs the output values of the proportional element and the differential element that input the difference between the detected value Afu and the target value Afu *, and the integrated value of the values corresponding to the difference. The sum with the output value of the element is defined as the correction ratio δ.

The sub-feedback process M14 is a process of operating the target value Afu * in order to adjust the oxygen storage amount of the three-way catalyst 24 based on the detected value Afd of the downstream air-fuel ratio sensor 76.
The low temperature correction process M16 is a process of calculating the low temperature increase coefficient Kw to a value larger than “1” in order to increase the base injection amount Qb when the water temperature THW is less than the predetermined temperature Tth (for example, 60 ° C.). Specifically, the low temperature increase coefficient Kw is calculated to be a larger value when the water temperature THW is low than when it is high. When the water temperature THW is equal to or higher than the predetermined temperature Tth, the low temperature increase coefficient Kw is set to "1", and the correction amount of the base injection amount Qb by the low temperature increase coefficient Kw is set to zero.

The required injection amount calculation process M18 is a process of calculating the fuel amount (required injection amount Qd) required in one combustion cycle by multiplying the base injection amount Qb by the feedback correction coefficient KAF and the low temperature increase coefficient Kw. ..

The injection valve operation process M20 is a process of outputting an operation signal MS1 to the fuel injection valve 16 in order to operate the fuel injection valve 16. In particular, the injection valve operation process M20 is a process of injecting fuel having a required injection amount Qd from the fuel injection valve 16 within one combustion cycle.

The stoichiometric point calculation process M22 is a process of calculating the detected value Afd of the downstream air-fuel ratio sensor 76 as the stoichiometric point AfL when the air-fuel ratio of the air-fuel mixture to be burned in the combustion chamber 14 is the stoichiometric air-fuel ratio.

The maximum storage amount learning process M24 is a process of learning the maximum value OSmax of the oxygen storage amount OS of the three-way catalyst 24 based on the detection value Afu of the upstream air-fuel ratio sensor 74 and the detection value Afd of the downstream air-fuel ratio sensor 76. be. Specifically, the fuel injection valve 16 is operated so that the detected value Afu becomes lean triggered by the fact that the detected value Afd reverses from lean to rich, and the detected value Afd reverses from rich to lean. The maximum value OSmax of the oxygen storage amount OS is calculated based on the amount of oxygen flowing into the three-way catalyst 24. Specifically, the maximum storage amount learning process M24 includes a process of calculating the oxygen flow rate flowing into the three-way catalyst 24 based on the detected value Afu and the intake air amount Ga.

FIG. 3 shows the procedure of the sub-feedback process M14. The process shown in FIG. 3 is realized by the CPU 62 repeatedly executing the program stored in the ROM 64, for example, at a predetermined cycle. In the following, the step number of each process is represented by a number prefixed with "S".

In the series of processes shown in FIG. 3, the CPU 62 first determines whether or not the lean determination flag Fl is “1” (S10). When the CPU 62 determines that it is "1" (S10: YES), it determines whether or not the detected value Afd is equal to or less than the value obtained by subtracting the rich side sub-offset amount εr from the stoichiometric reference value Afs (S12). .. Here, the stoichiometric reference value Afs is a reference value (reference air-fuel ratio sensor) of the detection value of the downstream air-fuel ratio sensor 76 when the air-fuel ratio of the air-fuel mixture to be burned in the combustion chamber 14 is the stoichiometric air-fuel ratio. Detected value). The process of S12 is a process of determining whether or not the flow rate of the unburned fuel in the fluid flowing out downstream of the three-way catalyst 24 is increasing.

When the CPU 62 determines that the value is equal to or less than the value obtained by subtracting the rich side sub-offset amount εr from the stoichiometric reference value Afs (S12: YES), "0" is substituted for the lean determination flag Fl and "1" is assigned to the rich determination flag Fr. Is substituted (S14).

Next, the CPU 62 substitutes the value obtained by adding the lean side main offset amount δl to the stoichiometric reference value Afs to the target value Afu * (S16).
On the other hand, when the CPU 62 determines that the lean determination flag Fl is “0” (S10: NO), whether or not the detected value Afd is equal to or greater than the value obtained by adding the lean side sub-offset amount εl to the stoichiometric reference value Afs. (S18). This process is a process for determining whether or not the flow rate of oxygen in the fluid flowing out downstream of the three-way catalyst 24 is increasing as the amount of oxygen stored by the three-way catalyst 24 approaches the maximum value OSmax. .. When the CPU 62 determines that the value is less than the value obtained by adding the lean side sub-offset amount εl to the stoichiometric reference value Afs (S18: NO), the process proceeds to the process of S16.

On the other hand, when the CPU 62 determines that the value is equal to or greater than the value obtained by adding the lean side sub-offset amount εl to the stoichiometric reference value Afs (S18: YES), the lean determination flag Fl is set to “1” and the rich determination flag Fr is set to “1”. 0 ”(S20).

When the processing of S20 is completed or when a negative determination is made in the processing of S12, the CPU 62 substitutes the value obtained by subtracting the rich side main offset amount δr from the stoichiometric reference value Afs into the target value Afu * (S22).

By the way, the rich side sub-offset amount εr, the lean side sub-offset amount εl, the rich side main offset amount δr, and the lean side main offset amount δl are the oxygen of the three-way catalyst 24 by one cycle of the treatment of S16 and the treatment of S22. It is said that the value is aimed at the net change in the amount of occlusion.

When the processes of S16 and S22 are completed, the CPU 62 temporarily ends the series of processes shown in FIG.
FIG. 4 shows the procedure of the stoichiometric point calculation process M22. The process shown in FIG. 4 is realized by the CPU 62 repeatedly executing the program stored in the ROM 64, for example, at a predetermined cycle.

In the series of processes shown in FIG. 4, the CPU 62 first determines whether or not the logical product of the following conditions (a) to (e) is true (S30).
Condition (a): It is a condition that the absolute value of the change amount Δη in the predetermined period of the filling efficiency η is equal to or less than the predetermined amount Δηth. Here, the predetermined period may be, for example, a cycle of a series of processes shown in FIG. 4, and in that case, the change amount Δη is a sampling value at the time of the current execution of the series of processes shown in FIG. 4 regarding the filling efficiency η. This value) may be the difference between the sampling value (previous value) at the time of the previous execution. This condition is a condition that the absolute value of the amount of change of the fluid flowing into the three-way catalyst 24 in a predetermined period is not more than a predetermined amount. This condition is provided in view that when the absolute value of the amount of change in the fluid flowing into the three-way catalyst 24 is large, the detected value Afd is more likely to fluctuate than when it is small.

Condition (a): It is a condition that the absolute value of the change amount ΔGa of the intake air amount Ga in a predetermined period is equal to or less than the predetermined amount ΔGath. Here, the predetermined period may be, for example, a series of processing cycles shown in FIG. 4, and in that case, the change amount ΔGa may be the difference between the current value and the previous value regarding the intake air amount Ga. This condition is a condition that the absolute value of the amount of change of the fluid flowing into the three-way catalyst 24 in a predetermined period is not more than a predetermined amount.

Condition (c): It is a condition that the water temperature THW is equal to or higher than the predetermined temperature Tth. This condition is a condition for avoiding the influence of the error of the air-fuel ratio due to the low temperature increase coefficient Kw as the open loop operation amount on the calculation of the stoichiometric point AfL.

Condition (d): It is a condition that the integrated value InG of the intake air amount Ga from the start of the internal combustion engine 10 is equal to or more than the predetermined value InGth. This condition is a condition that the three-way catalyst 24 has an active temperature.

Condition (e): It is a condition that the intake air amount Ga is equal to or more than the lower limit value GaL and is equal to or less than the upper limit value GaH. Here, the upper limit value GaH is set to an upper limit value in which the duration of the processing of S22 is not excessively shortened. Further, the lower limit value GaL is set to a value at the time of idling or the like.

When the CPU 62 determines that the logical product of the above conditions (a) to (e) is true (S30: YES), whether or not the lean determination flag Fl is the time when the lean determination flag Fl is switched from "0" to "1". (S32). When the CPU 62 determines that the value of the lean determination flag Fl at the time of the previous execution of the series of processes shown in FIG. 4 is "0" and the value of the lean determination flag Fl at the time of the current execution is "1". (S32: YES), "1" is assigned to the permission flag Fp (S34).

When the CPU 62 completes the processing of S34 or makes a negative determination in the processing of S32, the CPU 62 determines whether or not the logical product of the following conditions (f) to (c) is true (S36).
Condition (f): It is a condition that the lean determination flag Fl is "1". In this treatment, the amount of unburned fuel in the fluid flowing into the three-way catalyst 24 in a state where the amount of oxygen occluded in the three-way catalyst 24 can be regarded as being equal to or more than a predetermined amount reacts with the unburned fuel in just proportion. It is a condition that the situation is larger than the amount of oxygen to be applied. That is, since the lean determination flag Fl is set to "1" triggered by the fact that the detected value Afd is larger than the stoichiometric reference value Afs by the lean side sub-offset amount εl or more, the lean determination flag Fl is set to "1". When this happens, it can be considered that sufficient oxygen is occluded in the three-way catalyst 24. When the treatment of S22 is performed by setting the lean determination flag Fl to "1", the fluid flowing into the three-way catalyst 24 is larger than the amount of unburned fuel that reacts with oxygen in the fluid in just proportion. Contains an amount of unburned fuel.

Condition (g): It is a condition that the absolute value of the difference between the current value and the previous value of the detected value Afd is equal to or less than the specified amount ΔAfd. In FIG. 4, the current value is indicated by "n" and the previous value is indicated by "n-1".

This condition is a condition that the amount of oxygen and the amount of unburned fuel in the fluid flowing out downstream of the three-way catalyst 24 are negligibly small. That is, after the processing of S22 is started, it takes time for the detected value Afu of the upstream air-fuel ratio sensor 74 to reach the target value Afu * determined by the processing of S22, and during that time, it flows into the three-way catalyst 24. The amount of oxygen in the fluid is decreasing. Therefore, during that period, the amount of oxygen in the fluid flowing out downstream of the three-way catalyst 24 gradually decreases, and the amount of change in the detected value Afd also becomes relatively large. After that, when the detected value Afu of the upstream air-fuel ratio sensor 74 converges to the target value Afu * determined by the processing of S22 and stabilizes, the absolute value of the change amount of the detected value Afd of the downstream air-fuel ratio sensor 76 also becomes small. The condition (g) specifies this point in time.

Condition (c): It is a condition that the permission flag Fp is "1".
When the CPU 62 determines that the logical product of the above conditions (f) to (c) is true (S36: YES), the CPU 62 adds the current sampling value to the integrated value InAfd of the detected value Afd to obtain the integrated value InAfd. Is updated, and the cumulative number N of the detected value Afd is incremented (S38). The CPU 62 determines whether or not the integrated number N is equal to or greater than the reference number NH when the process of S38 is completed or when a negative determination is made in the process of S36 (S40). This process is a process for determining whether or not the stochastic point AfL may be updated using the integrated value InAfd.

When the CPU 62 determines that the number of times is NH or more (S40: YES), the CPU 62 substitutes the integrated value InAfd divided by the integrated number N into the average value Afdave in order to calculate the simple average processing value of the detected value Afd. (S42). Next, the CPU 62 calculates a correction amount Δave according to the intake air amount Ga having a positive correlation with the flow rate of the fluid flowing into the three-way catalyst 24 and the maximum value OSmax, and the average value Afdave according to the correction amount Δave. Is corrected (S43). This process is in view of the fact that the average value Afdave depends on the flow rate of the fluid flowing into the three-way catalyst 24 at the time of executing the process of S22 and the maximum value OSmax. Specifically, the CPU 62 performs a map calculation of the correction amount Δave with the map data having the intake air amount Ga and the maximum value OSmax as the input variables and the correction amount Δave as the output variable stored in the ROM 64 in advance. The map data is a set of data of discrete values of input variables and values of output variables corresponding to the values of the input variables. In the map operation, for example, if the value of the input variable matches any of the values of the input variable of the map data, the value of the output variable of the corresponding map data is used as the operation result, and if they do not match, the value is included in the map data. The processing may be performed using the value obtained by interpolating the values of a plurality of output variables as the calculation result.

Next, the CPU 62 calculates the stoichiometric point AfL by the exponential moving average processing of the average value Afdave (S44). Here, using the smoothing coefficient α having a value larger than “0” and smaller than “1”, the average value Afdave is multiplied by the smoothing coefficient α, and the stoichiometric point AfL is “1-α”. The stoichiometric point AfL is updated by the sum with the value multiplied by. The initial value of the stoichiometric point AfL may be, for example, the stoichiometric reference value Afs.

Next, the CPU 62 subtracts the value obtained by subtracting the stoichiometric reference value Afs from the stoichiometric point AfL from the initial value εr0 of the rich side sub-offset amount εr, and adds it to the initial value εl0 of the lean-side sub-offset amount εl. The rich side sub-offset amount εr and the lean side sub-offset amount εl are updated (S46). When the stochastic point AfL is not calculated, the initial value εr0 may be substituted for the rich side sub-offset amount εr and the initial value εl0 may be substituted for the lean side sub-offset amount εl in the process of FIG.

Then, the CPU 62 initializes the integration number N and the integration value InAfd, and substitutes “0” for the permission flag Fp (S48).
On the other hand, when a negative determination is made in the processing of S40, the CPU 62 determines whether or not the value obtained by subtracting the previous value from the current value of the detected value Afd is smaller than the negative specified amount ΔAfdM (S50). In this treatment, the amount of oxygen occluded by the three-way catalyst 24 is reduced, and whether or not the unburned fuel in the fluid flowing into the three-way catalyst 24 is not sufficiently oxidized by the oxygen stored in the three-way catalyst 24. It is a process for determining. In the present embodiment, the absolute value of the specified amount ΔAfdM is equal to the specified amount ΔAfd. Then, when it is determined that the integration number N is smaller than the specified amount ΔAfdM (S50: YES), the CPU 62 determines whether or not the integration number N is equal to or greater than the lower limit value NL smaller than the reference value NH (S52). The lower limit value NL is set to a lower limit value at which the integrated value InAfd may be reflected in the stoichiometric point AfL.

When the CPU 62 determines that the lower limit value is NL or more (S52: YES), the process proceeds to the process of S42, while when it is determined that the value is less than the lower limit value NL (S52: NO), the process proceeds to the process of S48.

The CPU 62 temporarily ends a series of processes shown in FIG. 4 when a negative determination is made in the processes of S30 and S50 or when the process of S48 is completed.
Here, the operation and effect of this embodiment will be described.

FIG. 5 shows the transition of the detected value Afd of the downstream air-fuel ratio sensor 76. At time t1, the CPU 62 sets the target value Afu * to be richer than the stoichiometric air-fuel ratio, triggered by the detection value Afd exceeding the stoichiometric reference value Afs by a lean side sub-offset amount εl or more (S22). As a result, the air-fuel ratio of the air-fuel mixture to be burned in the combustion chamber 14 becomes richer than the theoretical air-fuel ratio, so that the fluid flowing into the three-way catalyst 24 reacts with oxygen in the fluid in just proportion. It will contain a larger amount of unburned fuel than the amount of unburned fuel. Since this large amount of unburned fuel is oxidized by the oxygen stored in the three-way catalyst 24, the amount of oxygen and the amount of unburned fuel in the fluid flowing downstream from the three-way catalyst 24 are negligible. Become. The CPU 62 detects this by reducing the absolute value of the change amount of the detected value Afd in the processing of S36 (time t2), samples the detected value Afd, and calculates the stoichiometric point AfL based on those sampling values. (S38 to S44).

This stoichiometric point AfL is downstream when the downstream air-fuel ratio sensor 76 is exposed to the fluid flowing out to the downstream of the three-way catalyst 24 when the air-fuel mixture to be burned is constantly set to the stoichiometric air-fuel ratio. It is considered to be the detected value of the side air-fuel ratio sensor 76. Therefore, in the CPU 62, the value obtained by subtracting the stoichiometric reference value Afs from the stoichiometric point AfL is regarded as the amount of deviation of the detected value of the downstream air-fuel ratio sensor 76 from the stoichiometric reference value Afs, and based on this, the rich side sub-offset Update the quantity εr and the lean side sub-offset quantity εl. As a result, one of the oxygen flowing into the three-way catalyst 24 and the unburned fuel in one cycle of the processing of S16 and the processing of S22 is the other due to the deviation of the detected value of the downstream air-fuel ratio sensor 76. It is possible to suppress the amount of reaction with each other in excess of the amount that reacts with each other in just proportion.

By the way, as shown in FIG. 5, the rate of decrease of the detected value Afd after the time t2 when the intake air amount Ga is large (FIG. 5B) is the detected value after the time t2 when the intake air amount Ga is small. It is larger than the rate of decrease of Afd (FIG. 5 (a)). This is because when the treatment of S22 is performed when the intake air amount Ga is large, the flow rate of the unburned fuel in the fluid flowing into the three-way catalyst 24 is larger than when the intake air amount Ga is small. Therefore, the rate of decrease of the oxygen stored in the three-way catalyst 24 increases. Therefore, the average value Afdave may differ depending on the magnitude of the intake air amount Ga. Similarly, even when the maximum value OSmax becomes small due to deterioration of the three-way catalyst 24 or the like, the rate of decrease of the detected value Afd becomes large as compared with the case where the maximum value OSmax is large. Therefore, the CPU 62 corrects the average value Afdave by the correction amount Δave according to the intake air amount Ga and the maximum value OSmax. As a result, the deviation of the average value Afdave can be reduced regardless of the magnitude of the intake air amount Ga and the maximum value OSmax, and the deviation of the stoichiometric point AfL can be reduced.

Incidentally, in the present embodiment, when the deviation of the detected value of the downstream air-fuel ratio sensor 76 is negligibly small, the fluctuation amount of the oxygen storage amount in the three-way catalyst 24 in one cycle of the treatment of S16 and the treatment of S22 is determined. The rich side sub-offset amount εr and the lean side sub-offset amount εl are set so as to be several tens of percent (for example, 10%) or less of the maximum value OSmax. On the other hand, when the detected value Afd of the downstream air-fuel ratio sensor 76 deviates, the detected value Afd becomes the stoichiometric reference value Afs when the air-fuel ratio of the air-fuel mixture to be burned deviates from the stoichiometric air-fuel ratio. Therefore, if the rich side sub-offset amount εr and the lean side sub-offset amount εl are not updated based on the stochastic point AfL, one of the processing of S16 and the processing of S22 becomes excessively long and the other becomes excessively long. It gets shorter. Therefore, in one cycle of the treatment of S16 and the treatment of S22, one of the oxygen flowing into the three-way catalyst 24 and the unburned fuel becomes more than the amount that reacts with the other in just proportion, and the three-way catalyst 24 Oxygen storage may change gradually. In that case, for example, when the fuel cut process or the like is not executed in the middle and the steady operation is performed for a long time, the oxygen storage amount of the three-way catalyst 24 approaches zero or approaches the maximum value OSmax. The purification performance of the exhaust gas by the three-way catalyst 24 may deteriorate.

<Correspondence>
The correspondence between the matters in the above embodiment and the matters described in the above-mentioned "means for solving the problem" column is as follows. In the following, the correspondence is shown for each number of the solution means described in the column of "Means for solving the problem". [1 to 3] The catalyst corresponds to the three-way catalyst 24, and the air-fuel ratio sensor corresponds to the downstream air-fuel ratio sensor 76. The rich control process corresponds to the process of S22. The deviation amount expression value corresponds to the stoichiometric point AfL, and the deviation amount calculation processing corresponds to the processing of S38 and S42 to S44. That is, since the stoichiometric point AfL is a detected value of the target downstream air-fuel ratio sensor 76 when the air-fuel ratio of the air-fuel mixture to be burned is the theoretical air-fuel ratio, the reference downstream air-fuel ratio sensor is used. The difference from the detected value (stoichi reference value Afs) is the deviation amount, which is a parameter expressing the deviation amount. The "process of calculating the deviation amount expression value to a different value according to the length of the required time" corresponds to the process of S43. That is, the mapping with the detected value Afd as the input and the stochastic point AfL as the output is different depending on the required time because the correction amount Δave is different depending on the intake air amount Ga and the maximum value OSmax. When calculating the deviation amount expression value according to different mappings, the output will be different even if the input is the same. [4] The lean control process corresponds to the process of S16, the simple averaging process corresponds to the process of S42, the update process corresponds to the process of S44, and the correction process corresponds to the process of S43. [5] The lean control process corresponds to the process of S16, and the deviation amount reflection process corresponds to the process of S46.

<Other embodiments>
In addition, this embodiment can be changed and carried out as follows. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

・ "About the flow rate of the fluid used to calculate the deviation amount expression value"
In the treatment of S43, the intake air amount Ga was used as the flow rate of the fluid, but the present invention is not limited to this. For example, the exhaust flow rate may be used. Here, the exhaust flow rate may be calculated as the sum of the intake air amount Ga and the required injection amount Qd per predetermined period.

・ "About correction processing"
In the above embodiment, the correction amount Δave of the average value Afdave is calculated based on the intake air amount Ga and the maximum value OSmax, but the present invention is not limited to this. For example, with respect to the two parameters of the intake air amount Ga and the maximum value OSmax, the correction amount Δave may be calculated based on only one of them.

・ "About correction target based on fluid flow rate and maximum value OSmax"
In the above embodiment, the average value Afdave is corrected based on the intake air amount Ga and the maximum value OSmax, but the present invention is not limited to this. For example, the detection value Afd itself used for calculating the stoichiometric point AfL may be corrected.

・ "About rich control processing"
In the above embodiment, the rich control process is configured by the sub-feedback process M14, but the present invention is not limited to this. For example, in view of the fact that the oxygen occlusal amount of the three-way catalyst 24 increases when the fuel cut treatment is performed, the target value Afu * may be made richer than the stoichiometric air-fuel ratio immediately after the fuel cut treatment is performed. good.

However, it is not limited to the process of controlling the air-fuel ratio of the air-fuel mixture to be burned to the target value Afu *, for example, in the fluid flowing into the three-way catalyst 24 by injecting fuel from the fuel injection valve 16 in the exhaust stroke. It may be a process for adjusting the components.

・ "About the deviation amount calculation process"
In the above configuration, the stoichiometric point AfL is calculated as the deviation amount expression value indicating the deviation of the detection value Afd of the air-fuel ratio sensor, but the present invention is not limited to this. For example, it may be the amount of deviation from the detection value (stoichi reference value Afs) of the downstream air-fuel ratio sensor as a reference when the air-fuel ratio of the air-fuel mixture to be burned is the theoretical air-fuel ratio. For example, in the processing of S38, the integrated value of the value obtained by subtracting the stoichiometric reference value Afs from the detected value Afd is obtained, and in the processing of S42, the average value of the values obtained by subtracting the stoichiometric reference value Afs from the detected value Afd is obtained. ,realizable.

It is not essential to calculate the stoichiometric point AfL by simple averaging and exponential moving average processing. For example, when the rich side sub-offset amount εr and the lean side sub-offset amount εl are corrected by the value obtained by multiplying “AfL-Afs” by the gain K by the method described in the column of “Displacement amount reflection processing” below, the stochastic The point AfL may be an average value Afdave. Further, for example, the simple averaging process may be deleted and the exponential moving average process value of the detected value Afd may be set as the stoichiometric point AfL. In that case, as described in the column of "About the correction target based on the fluid flow rate and the maximum value OSmax", it is desirable that the detected value Afd itself is the correction target based on the fluid flow rate and the maximum value OSmax. Furthermore, it is not essential to include at least one of the two processes, the simple averaging process and the exponential moving average process. For example, the low-pass filter processing value such as the first-order lag filter processing in which the time-series data in the predetermined period of the detected value Afd is input may be the processing in which the stochastic point AfL is used.

・ "Execution condition of deviation amount calculation process"
It is not essential that the execution condition of the deviation amount calculation process includes the condition that the logical product of the above conditions (a) to (e) is true. For example, one of the above conditions (a) and (b) may be used as a condition that the absolute value of the change in the flow rate of the fluid flowing into the three-way catalyst 24 is not more than a predetermined amount. Further, for example, the above condition (c) may be deleted. Further, instead of the condition (d), a sensor such as a thermistor that detects the temperature of the three-way catalyst 24 may be provided, and a condition that the detected value is equal to or higher than a predetermined temperature may be provided. Further, for example, instead of reducing the difference between the lower limit value GaL and the upper limit value GaH in the condition (e), the above condition (a) and the condition (b) may be deleted.

Further, for example, instead of the condition (g), a condition that a predetermined time elapses after the lean determination flag Fl is switched to "1" may be used. Further, for example, instead of the above condition (g), a condition that the absolute value of the difference between the detected value Afd and the stoichiometric reference value Afs is equal to or less than a predetermined value may be used.

As described in the column of "About the rich control process", when the rich control process is executed immediately after the fuel cut process, the execution condition may be that it is immediately after the fuel cut process.

・ "About air-fuel ratio control processing"
In the above embodiment, the air-fuel ratio is controlled by the two-degree-of-freedom control of the open loop control by the base injection amount calculation process M10 and the feedback control by the main feedback process M12, but the air-fuel ratio control process is not limited to this. For example, it may be a process of controlling the open loop to the target value Afu * determined by the sub-feedback process.

・ "About the deviation amount reflection process"
The process for correcting "Afs-εr" as the rich determination value and "Afs + εl" as the lean determination value is not limited to the process exemplified as the process of S46. For example, it may be a process of adding "AfL-Afs" to the stoichiometric reference value Afs in the processes of S12 and S18 of FIG.

Instead of the processing of S46, the value obtained by multiplying "AfL-Afs" by the gain K smaller than "1" and larger than "0" is subtracted from the rich side sub-offset amount εr, and the multiplied value is the lean side. It may be added to the sub-offset amount εl.

In the above embodiment, the shift amount reflection process is configured by the process of S46, but the present invention is not limited to this. For example, the value obtained by subtracting "AfL-Afs" from the detected value Afd may be used as the detected value Afd which is the input for the processing of S12 and S18.

The deviation amount reflecting process includes "Afs-εr" as a rich determination value, "Afs + εl" as a lean determination value, and a detection value Afd as a comparison target between the rich determination value and the lean determination value. It is not limited to the process of correcting any of them according to the stoichiometric point AfL. For example, if the output of the downstream air-fuel ratio sensor 76 changes depending on the amount of electricity supplied to the downstream air-fuel ratio sensor 76 (applied voltage, etc.), the stoichiometric point AfL is electrically operated so as to approach the stoichiometric reference value Afs. It may be a process of adjusting a large amount.

・ "About the use of the deviation amount expression value"
The deviation amount expression value is not limited to the one reflected in the sub-feedback process M14. For example, when the fuel injection valve 16 is operated so as to control the air-fuel ratio of the air-fuel mixture to be burned in each of the cylinders # 1 to # 4, the air-fuel mixture to be burned is richer than the others. It may be used for the determination process of the presence or absence of an abnormality (imbalance abnormality). Here, the determination process is small, for example, when the absolute value of the correction amount of the target value Afu * of the main feedback process M12 is large when the absolute value of the difference between the detected value Afd of the downstream air-fuel ratio sensor 76 and the stoichiometric reference value Afs is large. Assuming that the control is made larger than the case, the process may be performed to determine the presence or absence of an imbalance abnormality based on the correction amount. That is, when an imbalance abnormality occurs, the detection value Afu of the upstream air-fuel ratio sensor 74 shifts to the rich side with respect to the air-fuel ratio of the air-fuel ratio collected in one in each of the cylinders. The feedback process M12 controls the air-fuel ratio of the one collected in the above one to be leaner than the theoretical air-fuel ratio. Therefore, since the detected value Afd of the downstream air-fuel ratio sensor 76 is leaner than the theoretical air-fuel ratio, the correction amount includes information on the degree of imbalance abnormality. In order to improve the accuracy of this determination process, the detection value Afd, which is the input of the correction amount calculation process, may be corrected based on the stochastic point AfL in the manner described in the column of "About the shift amount reflection process". In that case, regardless of the air-fuel ratio of the air-fuel ratio to be burned, the corrected detection value Afd becomes the detection value of the reference air-fuel ratio sensor (value presupposed by the control device 60 in control). Since the values are close to each other, it is possible to improve the accuracy of determining the presence or absence of imbalance abnormality based on the correction amount.

・ "About the storage device of the deviation amount expression value"
In the above embodiment, the storage device for storing the stoichiometric point AfL is not particularly specified, but for example, it may be stored in a RAM as a volatile memory. In this case, since the RAM is initialized when the control device 60 is newly started, the stochastic point AfL is not stored in the RAM immediately after the start. However, instead of this, for example, the stoichiometric point AfL may be constantly stored regardless of whether the control device 60 is started or stopped. This can be realized by using, for example, as a storage device, a backup RAM in which power supply is maintained regardless of the state of the main power supply of the control device 60, or a non-volatile memory. Further, for example, as a storage device for storing the stoichiometric point AfL, a device including a RAM as a volatile memory and a non-volatile memory may be used. In this case, the stoichiometric point AfL stored in the RAM may be sequentially updated by the process of S44, and the stoichiometric point AfL may be stored in the non-volatile memory as a post-processing prior to stopping the control device 60. In this case, when the control device 60 is started, the stoichiometric point AfL stored in the non-volatile memory is stored in the volatile memory.

・ "About control device"
The control device is not limited to the one provided with the CPU 62 and the ROM 64 to execute software processing. For example, a dedicated hardware circuit (for example, ASIC or the like) for hardware processing of at least a part of the software processed in the above embodiment may be provided. That is, the control device may have any of the following configurations (a) to (c). (A) A processing device that executes all of the above processing according to a program and a program storage device such as a ROM for storing the program are provided. (B) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit for executing the remaining processing are provided. (C) A dedicated hardware circuit for executing all of the above processes is provided. Here, there may be a plurality of software processing circuits including a processing device and a program storage device, and a plurality of dedicated hardware circuits. That is, the processing may be performed by a processing circuit comprising at least one of one or more software processing circuits and one or more dedicated hardware circuits.

・ "About the vehicle"
The hybrid vehicle is not limited to the series / parallel hybrid vehicle, and may be, for example, a parallel hybrid vehicle or a series hybrid vehicle. However, the vehicle is not limited to the hybrid vehicle, and may be a vehicle in which the drive source of the vehicle is only the internal combustion engine 10.

·"others"
In the above embodiment, the absolute value of the specified amount ΔAfd in the processing of S50 is set to be equal to the specified amount ΔAfd in the processing of S36, but the value is not limited to this and may be larger. Further, the process of S34 is to be executed when the affirmative determination is made in the process of S32 and the above condition (g) is satisfied, and the process of S50 is the process of S52 when the condition (g) is not satisfied. It may be a process of shifting to. In this case, if the condition (g) is not satisfied after the processing of S38 is started, the integrated value InAfd is initialized.

10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Combustion chamber, 16 ... Fuel injection valve, 18 ... Ignition device, 20 ... Crank shaft, 22 ... Exhaust passage, 24, 26 ... Three-way catalyst, 30 ... Planetary gear mechanism, 32 ... motor generator, 32a ... rotary shaft, 34 ... motor generator, 34a ... rotary shaft, 36 ... drive wheel, 40, 42 ... inverter, 44 ... battery, 50 ... ECU, 60 ... control device, 62 ... CPU, 64 ... ROM, 66 ... peripheral circuit, 68 ... communication line, 70 ... air flow meter, 72 ... crank angle sensor, 74 ... upstream air-fuel ratio sensor, 76 ... downstream air-fuel ratio sensor, 78 ... water temperature sensor.

Claims (5)

It is applied to an internal combustion engine including a fuel injection valve, a catalyst having an oxygen storage capacity provided in an exhaust passage, and an air-fuel ratio sensor provided on the downstream side of the catalyst in the exhaust passage.
When the amount of oxygen stored in the catalyst is equal to or greater than a predetermined amount, the fuel injection valve is operated to allow a fluid containing a larger amount of unburned fuel than the amount that reacts with oxygen in just excess or deficiency to flow into the catalyst. Control processing and
Based on the detection value of the air-fuel ratio sensor when the rich control process is performed, the deviation amount calculation process of calculating the deviation amount expression value indicating the deviation amount of the detection value of the air-fuel ratio sensor is executed.
In the shift amount calculation process, even if the detected values are the same, the shift amount expression value differs depending on the length of time required for the oxygen storage amount of the catalyst to decrease from the maximum value to zero by the rich control process. A control device for an internal combustion engine that includes processing to calculate the value. Even if the detected value is the same, the deviation amount calculation process is assumed that the required time is shorter than when the flow rate of the fluid flowing into the catalyst is large when the rich control process is performed, as compared with the case where the flow rate is small. The control device for an internal combustion engine according to claim 1, further comprising a process of calculating the deviation amount expression value to a different value according to the flow rate. The maximum storage amount learning process for learning the maximum value of the oxygen storage amount of the catalyst is executed.
Assuming that the required time is shorter when the maximum value is small than when the maximum value is large, the deviation amount calculation process changes the deviation amount expression value to a different value according to the maximum value even if the detected values are the same. The control device for an internal combustion engine according to claim 1 or 2, which includes a process for calculating. When the rich control process is executed, the fluid flowing into the catalyst is introduced into the fluid, triggered by the fact that the detected value of the air-fuel ratio sensor is equal to or less than the rich determination value indicating that the air-fuel ratio is richer than the theoretical air-fuel ratio. A lean control process is performed to control the oxygen content to be greater than the amount that reacts with the unburned fuel in just proportion.
When the lean control process is executed, the rich control process is executed with the trigger that the detected value of the air-fuel ratio sensor is equal to or greater than the lean determination value indicating that the air-fuel ratio is leaner than the theoretical air-fuel ratio.
The deviation amount calculation process is
A simple averaging process for calculating a simple averaging process value of a plurality of the detected values in one period in which the rich control process is performed, and a simple averaging process.
An update process for updating the deviation amount expression value by an exponential moving average process of the simple average process value according to a cycle in which the rich control process and the lean control process are executed, and an update process.
By correcting the simple average processing value that is input to the exponential moving average processing according to the length of the required time, even if the detected values are the same, the deviation amount is expressed according to the length of the required time. The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising a correction process for calculating values to different values. When the rich control process is executed, the fluid flowing into the catalyst is introduced into the fluid, triggered by the fact that the detected value of the air-fuel ratio sensor is equal to or less than the rich determination value indicating that the air-fuel ratio is richer than the theoretical air-fuel ratio. Lean control processing that controls to contain more oxygen than the amount that reacts with unburned fuel in just proportion.
The deviation amount reflection process for reflecting the deviation amount expression value in the lean control process is executed.
When the lean control process is executed, the rich control process is executed with the trigger that the detected value of the air-fuel ratio sensor is equal to or greater than the lean determination value indicating that the air-fuel ratio is leaner than the theoretical air-fuel ratio.
In the deviation amount reflection process, when the deviation amount expression value is the deviation amount on the lean side, the switching timing from the rich control process to the lean control process before the deviation amount expression value is reflected in the lean control process. The control device for an internal combustion engine according to any one of claims 1 to 4, which includes a process of accelerating the actual switching timing.

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