JP2021085350A - Engine device - Google Patents

Abstract

To obtain a deviation amount of a detection value detected through an exhaust sensor installed at a downstream side of a purification catalyst in an engine exhaust system.SOLUTION: When a detection condition representing detection of a lean state of exhaust at a downstream side of a purification catalyst is met with lean correction in execution, an engine device permits integration of a detected air-fuel ratio detected through an exhaust sensor. Then, when integration conditions that the integration of the detected air-fuel ratio is permitted and the detected air-fuel ratio falls in a first predetermined region including a reference value are met with rich correction in execution, the engine device calculates an integrated air-fuel ratio by integrating the detected air-fuel ratio. Next, when the number of times of the integration of the detected air-fuel ratio becomes equal to or larger than the number of leaning available times, the engine device updates a deviation amount related learned value related to a deviation amount of the detected air-fuel ratio using the integrated air-fuel ratio. Furthermore, when a prohibition condition representing the permission of the integration of the detected air-fuel ratio with the rich correction in execution, the engine device prohibits the integration of the detected air-fuel ratio.SELECTED DRAWING: Figure 6

Description

The present invention relates to an engine device.

Conventionally, as this type of engine device, a purification catalyst arranged in the exhaust system of the engine and capable of absorbing oxygen, a downstream air-fuel ratio sensor arranged downstream of the purification catalyst of the exhaust system, and a purification catalyst A device including an air-fuel ratio control device that controls the air-fuel ratio so that the air-fuel ratio of the exhaust gas flowing into the air-fuel ratio becomes the target air-fuel ratio has been proposed (see, for example, Patent Document 1). In this engine device, the air-fuel ratio controller changes the target air-fuel ratio to the lean set air-fuel ratio when the exhaust air-fuel ratio detected by the downstream air-fuel ratio sensor reaches the rich air-fuel ratio, and then the exhaust air-fuel ratio. Change the target air-fuel ratio to the weak lean set air-fuel ratio before becomes the lean air-fuel ratio. In addition, the air-fuel ratio control device changes the target air-fuel ratio to the rich set air-fuel ratio when the exhaust air-fuel ratio becomes the lean air-fuel ratio, and then sets the target air-fuel ratio before the exhaust air-fuel ratio becomes the rich air-fuel ratio. Change to a weak rich setting air-fuel ratio.

Patent No. 5949957

In such an engine device, the exhaust air-fuel ratio detected by the downstream air-fuel ratio sensor may deviate due to individual differences in the downstream air-fuel ratio sensor, aging deterioration, temperature characteristics, and the like. In this case, if the amount of deviation of the exhaust air-fuel ratio with respect to the air-fuel ratio cannot be grasped, it is possible that appropriate measures cannot be taken and inconveniences such as a decrease in the purification capacity of the purification catalyst may occur.

The main purpose of the engine device of the present invention is to grasp the amount of deviation of the detected value detected by the exhaust sensor mounted on the downstream side of the purification catalyst of the exhaust system of the engine.

The engine device of the present invention has adopted the following means in order to achieve the above-mentioned main object.

The engine device of the present invention
An engine with a fuel injection valve and
A purification catalyst that can be attached to the exhaust system of the engine and can occlude oxygen,
An exhaust sensor mounted on the downstream side of the purification catalyst of the exhaust system,
When operating the engine, if the detected air-fuel ratio detected by the exhaust sensor reaches the rich side threshold or less during the execution of the rich correction for the fuel injection amount of the fuel injection valve, the lean correction for the fuel injection amount is performed. When the detected air-fuel ratio reaches or more than the lean side threshold during the execution of the lean correction, the control device that switches to the execution of the rich correction, and
It is an engine device equipped with
The control device is
If the detection condition for detecting the lean of the exhaust gas downstream of the purification catalyst is satisfied during the execution of the lean correction, the integration of the detected air-fuel ratio is permitted.
An integration condition including the condition that the integration of the detected air-fuel ratio is permitted and the rich correction is being executed and the condition that the detected air-fuel ratio is within the first predetermined range including the reference value is satisfied. If so, the detected air-fuel ratio is integrated to calculate the integrated air-fuel ratio.
When the integrated number of times of the detected air-fuel ratio reaches the learning permitted number of times or more, the deviation amount-related learning value regarding the deviation amount of the detected air-fuel ratio is updated using the integrated air-fuel ratio.
If the prohibition condition is satisfied while the integration of the detected air-fuel ratio is permitted and the rich correction is being executed, the permission for the integration of the detected air-fuel ratio is released.
The gist is that.

In the engine device of the present invention, when the detection condition for detecting the lean of the exhaust gas on the downstream side of the purification catalyst is satisfied during the execution of the lean correction, the integration of the detected air-fuel ratio detected by the exhaust sensor is permitted. Subsequently, an integration condition including the condition that the integration of the detected air-fuel ratio is permitted and the rich correction is being executed and the condition that the detected air-fuel ratio is within the first predetermined range including the reference value is satisfied. If so, the detected air-fuel ratio is integrated to calculate the integrated air-fuel ratio. Then, when the integrated number of times of the detected air-fuel ratio reaches the learning permitted number of times or more, the deviation amount-related learning value regarding the deviation amount of the detected air-fuel ratio is updated using the integrated air-fuel ratio. In this way, the deviation amount-related learning value can be updated (understood). Further, if the prohibition condition is satisfied while the integration of the detected air-fuel ratio is permitted and the rich correction is being executed, the permission for the integration of the detected air-fuel ratio is released. As a result, it is possible to avoid updating the deviation amount-related learning value when the prohibition condition is satisfied. As a result, it is possible to suppress the reliability of the deviation amount-related learning value from becoming low, that is, to make the deviation amount-related learning value a more appropriate value. The integrated air-fuel ratio and the number of integrations may be reset when the permission for integration of the detected air-fuel ratio is released.

Here, as the "reference value", a reference air-fuel ratio (predetermined value), which is a reference value of the detected air-fuel ratio when the air-fuel ratio of the air-fuel mixture in the combustion chamber is the stoichiometric air-fuel ratio, is used. The "deviation amount learning value" is a value related to the detected air-fuel ratio when the detected air-fuel ratio is near the reference value, and is a value that reflects the deviation amount of the detected air-fuel ratio with respect to the reference value. This "deviation amount-related learning value" may be the average air-fuel ratio obtained by dividing the integrated air-fuel ratio by the number of integrations, or the average air-fuel ratio is subjected to slow change processing (smoothing processing or rate processing). It may be the slowly changing air-fuel ratio obtained, or it may be a value obtained by subtracting the reference value from the average air-fuel ratio or the slowly changing air-fuel ratio.

In the engine device of the present invention, the prohibition condition may include a condition in which the deviation amount-related learning value is updated. In this way, it is possible to avoid learning the deviation amount-related learning value a plurality of times between the start of the execution of one rich correction and the end of the execution.

In the engine device of the present invention, the prohibition condition may include a condition in which the integration condition is not satisfied and the number of integrations of the detected air-fuel ratio is less than the number of times of learning permission and is equal to or greater than the number of determinations. In this way, when the integration condition is temporarily unsatisfied due to the disturbance of the detected air-fuel ratio or the detected air-fuel ratio change rate, such as immediately after the start of the establishment of the integration condition, the learning of the deviation amount-related learning value is stopped. Can be avoided.

In this case, the control device may set the number of determinations based on the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst. In this way, the number of times for determination can be set more appropriately.

In the engine device of the present invention, when the total number of times reaches the permitted number of times or more, the integrated air-fuel ratio becomes higher as the number of deviations from which the integration condition is not satisfied after the start of the establishment of the integration condition increases. The degree of reflection may be reduced to update the deviation amount-related learning value. In this way, when the number of deviations is large, it is possible to reduce the influence of the integrated air-fuel ratio on the deviation amount-related learning value, and to avoid reducing the learning opportunity of the deviation amount-related learning value.

In the engine device of the present invention, the integration condition includes a condition in which the operating state of the engine is the steady operating state, and the prohibited condition includes a condition in which the operating state of the engine is no longer in the steady operating state. May be. In this way, it is possible to avoid updating the deviation amount-related learning value when the engine operating state is no longer in the steady operation state and then returns to the steady operation state.

In the engine device of the present invention, the control device may set the learning permission number of times and / or the first predetermined range based on the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst. Good. In this way, the number of times of learning permission and the first predetermined range can be set more appropriately.

In the engine device of the present invention, the integration condition may include a condition in which the detected air-fuel ratio change rate, which is the amount of change in the detected air-fuel ratio per unit time, is within the second predetermined range including the value 0. In this case, the control device may set the second predetermined range based on the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst. In this way, the second predetermined range can be set more appropriately.

In the engine device of the present invention, the detection conditions are a condition in which the lean correction is being executed and a condition in which the detected air-fuel ratio change rate, which is the amount of change in the detected air-fuel ratio per unit time, becomes equal to or higher than a predetermined change rate. It may include at least one of the conditions that the detected air-fuel ratio is equal to or higher than the predetermined air-fuel ratio and the condition that the oxygen storage amount of the purification catalyst is equal to or higher than the predetermined storage amount.

In the engine device of the present invention, the control device may set the rich side threshold value and the lean side threshold value using the deviation amount-related learning value. In this way, the rich side threshold value and the lean side threshold value can be set more appropriately.

It is a block diagram which shows the outline of the structure of the hybrid vehicle 20 which mounts the engine device as an Example of this invention. It is a block diagram which shows the outline of the structure of the engine device 21. It is a control block diagram which shows an example of the control block when the fuel injection control of an engine 22 is performed by an engine ECU 24. It is a flowchart which shows an example of the sub-feedback correction routine executed by the sub-feedback unit 92. It is explanatory drawing which shows an example of the state of the detected air-fuel ratio AFd and the state of a sub-feedback correction. It is a flowchart which shows an example of the deviation amount related learning routine executed by the deviation amount related learning unit 95. It is explanatory drawing which shows an example of the state of the detected air-fuel ratio AFd, the rich correction flag Fr, the steady operation flag Fst, the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integrated number of times Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst. It is explanatory drawing which shows an example of the state of the detected air-fuel ratio AFd, the rich correction flag Fr, the steady operation flag Fst, the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integration number Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst. It is explanatory drawing which shows an example of the state of the detected air-fuel ratio AFd, the rich correction flag Fr, the steady operation flag Fst, the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integration number Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst. It is explanatory drawing which shows an example of the 1st predetermined range setting map. It is explanatory drawing which shows an example of the 2nd predetermined range setting map. It is explanatory drawing which shows an example of the learning permission number setting map. It is explanatory drawing which shows an example of the threshold value setting map. It is a flowchart which shows an example of the deviation amount related learning routine of a modification. It is explanatory drawing which shows an example of the time constant setting map.

Next, a mode for carrying out the present invention will be described with reference to examples.

FIG. 1 is a configuration diagram showing an outline of the configuration of a hybrid vehicle 20 equipped with an engine device 21 as an embodiment of the present invention, and FIG. 2 is a configuration diagram showing an outline of the configuration of the engine device 21. As shown in FIG. 1, the hybrid vehicle 20 of the embodiment includes an engine 22, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a battery 50, and an electronic control unit for hybrid (hereinafter, “HVECU””. ) 70 is provided.

The engine 22 is configured as an internal combustion engine that outputs power using gasoline, light oil, or the like as fuel. As shown in FIG. 2, the engine 22 sucks the air cleaned by the air cleaner 122 into the intake pipe 123 and passes it through the throttle valve 124 and the surge tank 125, and at the downstream side of the surge tank 125 of the intake pipe 123. Fuel is injected from the fuel injection valve 126 to mix air and fuel. Then, the engine 22 sucks the air-fuel mixture into the combustion chamber 129 via the intake valve 128, and explodes and burns the sucked air-fuel mixture by electric sparks from the spark plug 130. The reciprocating motion of the piston 132 pushed down by the energy of the explosive combustion is converted into the rotational motion of the crankshaft 26. The exhaust gas discharged from the combustion chamber 129 to the exhaust pipe 134 via the exhaust valve 133 is discharged to the outside air via the purification devices 136 and 138. The purification devices 136 and 138 have purification catalysts (three-way catalysts) 136a and 138a that purify harmful components of carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) in the exhaust gas, respectively. The purification catalysts 136a and 138a are configured to be able to occlude oxygen, respectively.

The engine 22 is operated and controlled by an electronic control unit for an engine (hereinafter, referred to as "engine ECU") 24. Although not shown, the engine ECU 24 is configured as a microprocessor centered on a CPU, and in addition to the CPU, has a ROM for storing a processing program, a RAM for temporarily storing data, an input / output port, and a communication port. Be prepared.

Signals from various sensors necessary for controlling the operation of the engine 22 are input to the engine ECU 24 via the input port. The signals input to the engine ECU 24 include, for example, a crank angle θcr from the crank position sensor 140 that detects the rotational position of the crankshaft 26 of the engine 22, and a water temperature sensor 142 that detects the temperature of the cooling water of the engine 22. The cooling water temperature Tw can be mentioned. Further, the cam position θca from the cam position sensor 144 that detects the rotational position of the intake camshaft that opens and closes the intake valve 128 and the exhaust camshaft that opens and closes the exhaust valve 133 can also be mentioned. Further, the throttle opening TH from the throttle valve position sensor 124a that detects the position of the throttle valve 124, the intake air amount Qa from the air flow meter 148 attached to the intake pipe 123, and the temperature sensor 149 attached to the intake pipe 123. The intake air temperature Ta from the above and the surge pressure Ps from the pressure sensor 150 attached to the surge tank 125 can also be mentioned. In addition, the air-fuel ratio AFu detected from the upstream air-fuel ratio sensor 152 mounted on the upstream side of the purification device 136 of the exhaust pipe 134, and the downstream side of the purification device 136 of the exhaust pipe 134 and upstream of the purification device 138. The air-fuel ratio AFd detected from the downstream air-fuel ratio sensor 154 mounted on the side can also be mentioned.

From the engine ECU 24, various control signals for controlling the operation of the engine 22 are output via the output port. Examples of the signal output from the engine ECU 24 include a drive control signal to the throttle motor 124b that adjusts the position of the throttle valve 124, a drive control signal to the fuel injection valve 126, and a control signal to the spark plug 130. Can be done.

The engine ECU 24 is connected to the HVECU 70 via a communication port. The engine ECU 24 calculates the rotation speed Ne of the engine 22 based on the crank angle θcr of the engine 22 from the crank position sensor 140. Further, volumetric efficiency (ratio of the volume of air actually sucked in one cycle to the stroke volume per cycle of the engine 22) KL based on the intake air amount Qa from the air flow meter 148 and the rotation speed Ne of the engine 22. Is calculated.

As shown in FIG. 1, the planetary gear 30 is configured as a single pinion type planetary gear mechanism. The rotor of the motor MG1 is connected to the sun gear of the planetary gear 30. A drive shaft 36 connected to the drive wheels 39a and 39b via a differential gear 38 is connected to the ring gear of the planetary gear 30. The crankshaft 26 of the engine 22 is connected to the carrier of the planetary gear 30 via a damper 28.

The motor MG1 is configured as, for example, a synchronous motor generator, and as described above, the rotor is connected to the sun gear of the planetary gear 30. The motor MG2 is configured as, for example, a synchronous motor generator, and a rotor is connected to a drive shaft 36. The inverters 41 and 42 are used to drive the motors MG1 and MG2 and are connected to the battery 50 via the power line 54. The motors MG1 and MG2 are rotationally driven by switching control of a plurality of switching elements (not shown) of the inverters 41 and 42 by an electronic control unit for a motor (hereinafter referred to as "motor ECU") 40.

Although not shown, the motor ECU 40 is configured as a microprocessor centered on a CPU, and in addition to the CPU, includes a ROM for storing a processing program, a RAM for temporarily storing data, an input / output port, and a communication port. Be prepared. Signals from various sensors necessary for driving and controlling the motors MG1 and MG2 are input to the motor ECU 40 via the input port. The signals input to the motor ECU 40 include, for example, the rotation positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotation position sensors 43 and 44 that detect the rotation positions of the rotors of the motors MG1 and MG2, and the motor MG1. , Iu1, Iv1, Iu2, Iv2 of the phase currents of each phase of the motors MG1 and MG2 from the current sensor that detects the phase current flowing in each phase of MG2. From the motor ECU 40, switching control signals and the like to a plurality of switching elements (not shown) of the inverters 41 and 42 are output via the output port. The motor ECU 40 is connected to the HVECU 70 via a communication port. The motor ECU 40 calculates the electric angles θe1, θe2 and the rotation speeds Nm1 and Nm2 of the motors MG1 and MG2 based on the rotation positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotation position sensors 43 and 44.

The battery 50 is configured as, for example, a lithium ion secondary battery or a nickel hydrogen secondary battery, and is connected to the inverters 41 and 42 via the power line 54 as described above. The battery 50 is managed by a battery electronic control unit (hereinafter, referred to as “battery ECU”) 52.

Although not shown, the battery ECU 52 is configured as a microprocessor centered on a CPU, and in addition to the CPU, has a ROM for storing a processing program, a RAM for temporarily storing data, an input / output port, and a communication port. Be prepared. Signals from various sensors necessary for managing the battery 50 are input to the battery ECU 52 via the input port. The signals input to the battery ECU 52 include, for example, the voltage Vb of the battery 50 from the voltage sensor 51a attached between the terminals of the battery 50 and the battery 50 from the current sensor 51b attached to the output terminal of the battery 50. Examples include the current Ib and the temperature Tb of the battery 50 from the temperature sensor 51c attached to the battery 50. The battery ECU 52 is connected to the HVECU 70 via a communication port. The battery ECU 52 calculates the storage ratio SOC based on the integrated value of the battery current Ib from the current sensor 51b. The storage ratio SOC is the ratio of the capacity of electric power that can be discharged from the battery 50 to the total capacity of the battery 50.

Although not shown, the HVECU 70 is configured as a microprocessor centered on a CPU, and includes a ROM for storing a processing program, a RAM for temporarily storing data, an input / output port, and a communication port in addition to the CPU. .. Signals from various sensors are input to the HVECU 70 via the input port. Examples of the signal input to the HVECU 70 include an ignition signal from the ignition switch 80 and a shift position SP from the shift position sensor 82 that detects the operating position of the shift lever 81. Further, the accelerator opening Acc from the accelerator pedal position sensor 84 that detects the depression amount of the accelerator pedal 83, the brake pedal position BP from the brake pedal position sensor 86 that detects the depression amount of the brake pedal 85, and the vehicle speed sensor 88. The vehicle speed V and the outside air temperature Tout from the outside temperature sensor 89 can also be mentioned. As described above, the HVECU 70 is connected to the engine ECU 24, the motor ECU 40, and the battery ECU 52 via a communication port.

The hybrid vehicle 20 of the embodiment configured in this way is in an electric driving mode (EV driving mode) in which the vehicle travels without the operation of the engine 22 and a hybrid driving mode (HV driving mode) in which the hybrid vehicle 20 travels with the operation of the engine 22. Drive.

In the EV traveling mode, the HVECU 70 first sets the required torque Td * required for traveling (required for the drive shaft 36) based on the accelerator opening degree Acc and the vehicle speed V. Subsequently, a value 0 is set in the torque command Tm1 * of the motor MG1, and the torque command Tm2 * of the motor MG2 is set so that the required torque Td * is output to the drive shaft 36, and the set torques of the motors MG1 and MG2 are set. The commands Tm1 * and Tm2 * are transmitted to the motor ECU 40. The motor ECU 40 controls switching of a plurality of switching elements of the inverters 41 and 42 so that the motors MG1 and MG2 are driven by the torque commands Tm1 * and Tm2 *.

In the HV driving mode, the HVECU 70 first sets the required torque Td * as in the EV driving mode. Subsequently, the required power Pd * required for running is calculated by multiplying the required torque Td * by the rotation speed Nd of the drive shaft 36, and the required power Pd * is used to charge / discharge the battery 50. The required power Pe * required for the engine 22 is calculated by subtracting the positive value). Here, as the rotation speed Nd of the drive shaft 36, for example, the rotation speed Nm2 of the motor MG2 or the rotation speed obtained by multiplying the vehicle speed V by a conversion coefficient is used. Then, the target rotation speed Ne * of the engine 22, the target torque Te *, and the torque commands Tm1 of the motors MG1 and MG2 are output so that the required power Pe * is output from the engine 22 and the required torque Td * is output to the drive shaft 36. * And Tm2 * are set, the target rotation speed Ne * and the target torque Te * of the engine 22 are transmitted to 24, and the torque commands Tm1 * and Tm2 * of the motors MG1 and MG2 are transmitted to the motor ECU 40. The engine ECU 24 performs intake air amount control, fuel injection control, ignition control, and the like of the engine 22 so that the engine 22 is operated based on the target rotation speed Ne * and the target torque Te *. The control of the motors MG1 and MG2 (inverters 41 and 42) by the motor ECU 40 has been described above.

Here, the fuel injection control of the engine 22 by the engine ECU 24 will be described. FIG. 3 is a control block diagram showing an example of a control block when fuel injection control of the engine 22 is performed by the engine ECU 24. As shown in the figure, the engine ECU 24 has a base injection amount setting unit 90, a main feedback unit 91, a sub-feedback unit 92, a target injection amount setting unit 93, and injection as a control block for fuel injection control of the engine 22. It has a valve control unit 94, a deviation amount related learning unit 95, and an oxygen storage amount estimation unit 96.

The base injection amount setting unit 90 is a base injection which is a base value of the target injection amount Qf * of the fuel injection valve 126 for setting the air-fuel ratio of the air-fuel mixture in the combustion chamber 129 as the target air-fuel ratio based on the volumetric efficiency KL. Set the quantity Qfb. Here, as the target air-fuel ratio, the theoretical air-fuel ratio (stoichi) is used in the examples. The base injection amount Qfb is calculated by multiplying the unit injection amount (injection amount per 1% of the volumetric efficiency KL) Qfpu for setting the air-fuel ratio of the air-fuel mixture in the combustion chamber 129 as the target air-fuel ratio, for example. Will be done. As described above, the volumetric efficiency KL is based on the intake air amount Qa from the air flow meter 148 and the engine speed Ne calculated based on the crank angle θcr of the engine 22 from the crank position sensor 140. It is calculated.

The main feedback unit 91 calculates a correction value δaf by feedback control for setting the air-fuel ratio AFu detected from the upstream air-fuel ratio sensor 152 to the control air-fuel ratio AFu *, and sets the calculated correction value δaf to a value (-1). Is multiplied and then the value 1 is added to set the correction coefficient Kaf. Here, the control air-fuel ratio AFu * is set by the sub-feedback unit 92. As shown in equation (1), the correction value δaf is calculated using the relational expression of feedback control using the detected air-fuel ratio AFu, the control air-fuel ratio AFu *, the gain Kp of the proportional term, and the gain Ki of the integral term. Will be done. The reason for setting the correction coefficient Kaf by multiplying the correction value δaf by the value (-1) and then adding the value 1 will be described later.

δaf = Kp ・ (AFu * -AFu) + Ki ・ ∫ (AFu * -AFu) dt (1)

The sub-feedback unit 92 sets the rich side value in the control air-fuel ratio AFu * based on the detected air-fuel ratio AFd from the downstream air-fuel ratio sensor 154, and the control air-fuel ratio AFu * on the lean side. Lean correction, which sets the value, is performed alternately. Hereinafter, this process is referred to as "sub-feedback correction". Rich correction and lean correction are performed to adjust the oxygen storage amount of the purification catalyst 136a. The details of the sub-feedback unit 92 will be described later.

The target injection amount setting unit 93 sets a value obtained by multiplying the base injection amount Qfb by the correction coefficient Kaf to the target injection amount Qf * of the fuel injection valve 126. The injection valve control unit 94 controls the fuel injection valve 126 so that the fuel injection of the target injection amount Qf * is performed from the fuel injection valve 126.

Here, the reason why the correction coefficient Kaf is set by multiplying the correction value δaf by the value (-1) and then adding the value 1 in the main feedback unit 91 will be described. During the execution of the lean correction, the detected air-fuel ratio AFu is smaller than the control air-fuel ratio AFu * (on the rich side), and the correction value δaf is basically a positive value according to the equation (1). Therefore, it is necessary to make the correction coefficient Kaf smaller than the value 1 so that the target injection amount Qf * is smaller than the base injection amount Qfb and make the detected air-fuel ratio AF larger than the current value (to the lean side). On the other hand, during the execution of the rich correction, the detected air-fuel ratio AFu is larger than the control air-fuel ratio AFu * (on the lean side), and the correction value δaf is basically negative according to the equation (1). Become a value. Therefore, it is necessary to make the correction coefficient Kaf larger than the value 1 so that the target injection amount Qf * is larger than the base injection amount Qfb and make the detected air-fuel ratio AF smaller than the current value (set to the rich side). For this reason, the correction coefficient Kaf is set by multiplying the correction value δaf by the value (-1) and then adding the value 1.

The deviation amount-related learning unit 95 updates the deviation amount-related learning value regarding the deviation amount of the detected air-fuel ratio AFd from the downstream air-fuel ratio sensor 154 (hereinafter, referred to as “sensor deviation amount”). In the example, the stoichiometric learning value AFdst was used as the deviation amount-related learning value. The stoichiometric learning value AFdst is a learning value regarding the detected air-fuel ratio AFd when the detected air-fuel ratio AFd is near the stoichiometric reference value AFs. The stoichiometric reference values AFs are reference values (preset values) of the detected air-fuel ratio AFd when the air-fuel ratio of the air-fuel mixture in the combustion chamber 129 is the stoichiometric air-fuel ratio. The value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs) is a value that reflects the amount of sensor deviation. The details of the deviation amount-related learning unit 95 will be described later.

The oxygen occlusion estimation unit 96 purifies the purification catalyst based on the air-fuel ratio AFu detected by the upstream air-fuel ratio sensor 152, the air-fuel ratio AFd detected by the downstream air-fuel ratio sensor 154, and the intake air amount Qa from the air flow meter 148. The oxygen storage amount OS of 136a is estimated, and the maximum oxygen storage amount OSmax, which is the maximum value thereof, is estimated. Generally, the maximum oxygen uptake OSmax decreases as the deterioration of the purification catalyst 136a progresses.

Next, the details of the sub-feedback unit 92 will be described. FIG. 4 is a flowchart showing an example of the sub-feedback correction routine executed by the sub-feedback unit 92. This routine is executed repeatedly. In the embodiment, when the repeated execution of this routine is started (when the first execution is started), the value 1 is set in the rich correction flag Fr described later.

In the sub-feedback correction routine of FIG. 4, the sub-feedback unit 92 first inputs the detected air-fuel ratio AFd from the downstream air-fuel ratio sensor 154 (step S100), and examines the value of the rich correction flag Fr (step S110). ). Here, the rich correction flag Fr is a flag indicating which of the rich correction and the lean correction is being executed.

When the rich correction flag Fr is a value 1 in step S110, it is determined that the rich correction is being executed, and the detected air-fuel ratio AFd is the rich side threshold value (AFs-εR) obtained by subtracting the sub-offset amount εR from the stoichiometric reference value AFs. (Step S120). This process is a process for determining whether or not the detected air-fuel ratio AFd has reached a value on the rich side to some extent, that is, whether or not the amount of unburned fuel in the exhaust gas on the downstream side of the purification catalyst 136a has increased to some extent.

When the detected air-fuel ratio AFd is larger than the rich side threshold value (AFs-εR) in step S120, it is determined that the detected air-fuel ratio AFd has not yet reached the rich side value to some extent, and the main offset amount δR is calculated from the stoichiometric reference value AFs. The subtracted value (AFs-δR) is set to the control air-fuel ratio AFu * (step S170), and this routine is terminated. Here, the main offset amount δR is set within the range of the sub-offset amount εR or more. For example, the main offset amount δR is set to a value obtained by adding a margin to the sub-offset amount εR. In this case, the execution of the rich correction is continued.

When the detected air-fuel ratio AFd is equal to or less than the rich side threshold value (AFs-εR) in step S120, it is determined that the detected air-fuel ratio AFd has reached the rich side value to some extent, and the rich correction flag Fr is set to a value 0 (step S130). , The value (AFs + δL) obtained by adding the main offset amount δL to the stoichiometric reference value AFs is set in the control air-fuel ratio AFu * (step S140), and this routine is terminated. Here, the main offset amount δL is set within the range of the sub-offset amount εL or more, which will be described later. For example, the main offset amount δL is set to a value obtained by adding a margin to the sub-offset amount εL. In this way, the execution of the rich correction is switched to the execution of the lean correction.

When the rich correction flag Fr is a value 0 in step S110, it is determined that the lean correction is being executed, and the detected air-fuel ratio AFd is compared with the lean side threshold value (AFs + εL) obtained by adding the sub-offset amount εL to the stoichiometric reference value AFs. (Step S150). This process is a process for determining whether or not the detected air-fuel ratio AFd has reached a value on the lean side to some extent, that is, whether or not the amount of oxygen in the exhaust gas on the downstream side of the purification catalyst 136a has increased to some extent.

When the detected air-fuel ratio AFd is less than the lean side threshold value (AFs + εL) in step S150, it is determined that the detected air-fuel ratio AFd has not yet reached the lean side value to some extent, and the value (AFs + δL) is set by the process of step S140 described above. Set the air-fuel ratio for control to AFu * and end this routine. In this case, the execution of the lean correction is continued.

When the detected air-fuel ratio AFd is equal to or higher than the lean side threshold value (AFs + εL) in step S150, it is determined that the detected air-fuel ratio AFd has reached a lean side value to some extent, and the rich correction flag Fr is set to a value 1 (step S160). By the process of step S170 of the above, the value (AFs-δR) is set to the control air-fuel ratio AFu *, and this routine is terminated. In this way, the execution of the lean correction is switched to the execution of the rich correction.

FIG. 5 is an explanatory diagram showing an example of the detected air-fuel ratio AFd and the state of sub-feedback correction. As shown in the figure, when the detected air-fuel ratio AFd reaches or more than the lean side threshold value (AFs + εL) during the execution of the lean correction (time t1, t3), the execution of the rich correction is switched. Further, when the detected air-fuel ratio AFd reaches the rich side threshold value (AFs-εR) or less during the execution of the rich correction (time t2), the execution of the lean correction is switched. Hereinafter, the period from the start of one of the lean correction and the rich correction to the end of the other (for example, times t1 to t3) is referred to as "one cycle of subfeedback correction".

Since the fuel injection valve 126 is controlled by setting a value larger than the base injection amount Qfb to the target injection amount Qf * during the execution of the rich correction, the exhaust gas flowing into the purification catalyst 136a is in the exhaust gas. It contains more unburned fuel than the amount of unburned fuel that reacts with oxygen in just proportion. Since this large amount of unburned fuel is oxidized by oxygen in the exhaust and oxygen occluded in the purification catalyst 136a, the amount of oxygen and the amount of unburned fuel in the exhaust on the downstream side of the purification catalyst 136a are sufficiently reduced. .. As a result, as shown in the figure, when the detected air-fuel ratio AFd is near the stoichiometric reference value AFs, the absolute value of the detected air-fuel ratio change rate ΔAFd, which is the amount of change in the detected air-fuel ratio AFd per unit time, becomes small.

Next, the details of the deviation amount-related learning unit 95 will be described. FIG. 6 is a flowchart showing an example of a deviation amount-related learning routine executed by the deviation amount-related learning unit 95. This routine is executed repeatedly. In the embodiment, when the repeated execution of this routine is started (the first execution is started), the integrated air-fuel ratio AFdsum, the integrated number Nad, and the integrated permission flag Fad, which will be described later, are set to 0 as initial values. Is set.

In the deviation amount-related learning routine of FIG. 6, the deviation amount-related learning unit 95 first inputs data such as the detected air-fuel ratio AFd, the detected air-fuel ratio change rate ΔAFd, the rich correction flag Fr, and the steady operation flag Fst (step). S200).

Here, as the detected air-fuel ratio AFd, a value detected by the downstream air-fuel ratio sensor 154 is input. As the detected air-fuel ratio change rate ΔAFd, a value calculated as the amount of change per unit time (for example, the execution interval of this routine) of the detected air-fuel ratio AFd is input. A value set by the sub-feedback unit 92 is input to the rich correction flag Fr.

For the steady operation flag Fst, a value set by the steady operation flag setting routine (not shown) is input. In the steady operation flag setting routine, when the operating state of the engine 22 is the steady operation state, the value 1 is set in the steady operation flag Fst, and when the operating state of the engine 22 is not the steady operation state, the value 0 is set in the steady operation flag Fst. Is set.

The conditions under which the operating state of the engine 22 is the steady operating state include, for example, a condition in which the intake air amount change rate ΔQa, which is the amount of change in the intake air amount Qa per unit time, is within the predetermined range Rqa, and the volumetric efficiency KL. Under the condition that the volumetric efficiency change rate ΔKL, which is the amount of change per unit time, is within the predetermined range Rkl, the target torque change rate ΔTe *, which is the amount of change of the target torque Te * of the engine 22 per unit time, is within the predetermined range Rte. At least one of certain conditions and the like is used. The predetermined range Rqa is set as a range in which the rate of change in intake air amount ΔQa can be considered to be near the value 0 (the absolute value is sufficiently small). The predetermined range Rkl is set as a range in which the volumetric efficiency change rate ΔKL can be regarded as a value near 0 (absolute value is sufficiently small). The predetermined range Rte is set as a range in which the target torque change rate ΔTe * can be regarded as being near the value 0 (the absolute value is sufficiently small).

When the data is input in this way, the value of the integration permission flag Fad is checked (step S210). Here, the integration permission flag Fad is a flag indicating whether or not integration of the detected air-fuel ratio AFd (calculation of the integrated air-fuel ratio AFdsum described later) is permitted.

When the integration permission flag Fad has a value of 0, it is determined that the integration of the detected air-fuel ratio AFd is not permitted, and it is determined whether or not the detection condition is satisfied (steps S220 and S230). Here, the detection condition is a condition in which the lean exhaust gas on the downstream side of the purification catalyst 136a is detected during the execution of the lean correction. In the embodiment, the detection condition is a condition in which the rich correction flag Fr is a value 0, that is, a condition in which lean correction is being executed by the sub-feedback unit 92 (step S220), and a threshold value ΔAFdref in which the detected air-fuel ratio change rate ΔAFd is positive. The logical product of the above conditions (step S230) is used. Here, the threshold value ΔAFdref is a threshold value used for determining whether or not the detected air-fuel ratio AFd has changed significantly to the lean side.

When the rich correction flag Fr is a value 1 in step S220, or when the detected air-fuel ratio change rate ΔAFd is less than the threshold value ΔAFdf in step S230, it is determined that the detection condition is not satisfied, and the integration permission flag Fad is not changed. , End this routine.

When the rich correction flag Fr is a value 0 in step S220 and the detected air-fuel ratio change rate ΔAFd is equal to or greater than the threshold value ΔAFdf in step S230, it is determined that the detection condition is satisfied, and the value 1 is set in the integration permission flag Fad. (Step S240), this routine is terminated.

When the integration permission flag Fad is a value 1 in step S210, it is determined that the integration of the detected air-fuel ratio AFd is permitted, and it is determined whether or not the integration condition of the detected air-fuel ratio AFd is satisfied (steps S250 to S280). ). In the embodiment, as the integration condition of the detected air-fuel ratio AFd, the condition that the rich correction flag Fr is a value 1, that is, the condition that the rich correction is being executed by the sub-feedback unit 92 (step S250), and the steady operation flag Fst are values. The condition of 1, that is, the condition that the operating state of the engine 22 is the steady operation state (step S260), the condition that the detected air-fuel ratio AFd is within the predetermined range Raf1 (step S270), and the detected air-fuel ratio change rate ΔAFd are within the predetermined range. It was assumed that the logical product of the condition (step S280) in Raf2 was used.

Here, the predetermined range Raf1 is set as a range in which the detected air-fuel ratio AFd can be regarded as being near the stoichiometric reference value AFs (the difference between the two is sufficiently small). The predetermined range Raf2 is set as a range in which the detected air-fuel ratio change rate ΔAFd can be regarded as being near the value 0 (the absolute value is sufficiently small).

When the rich correction flag Fr is a value 0 in step S250, it is determined that the integration condition of the detected air-fuel ratio AFd is not satisfied, and this routine is terminated. As described above, since the integration permission flag Fad is switched from the value 0 to the value 1 during the execution of the lean correction, assuming that the integration permission flag Fad is a value 1 in step S210 and the rich correction flag Fr is a value 0 in step S250. Can be mentioned from the time when the integration permission flag Fad is switched from the value 0 to the value 1 until the execution of the lean correction to the execution of the rich correction.

The rich correction flag Fr is a value 1 in step S250, the steady operation flag Fst is a value 1 in step S260, and the detected air-fuel ratio AFd is within the predetermined range Raf1 in step S270, and in step S280. When the detected air-fuel ratio change rate ΔAFd is within the predetermined range Raf2, it is determined that the integration condition of the detected air-fuel ratio AFd is satisfied. Then, the value obtained by adding the detected air-fuel ratio AFd to the current integrated air-fuel ratio (current AFdsum) is set in the new integrated air-fuel ratio AFdsum (step S290), and the current integrated number of times (current Nad) is incremented by a value of 1. The value is set to the new integration number Nad (step S300).

Subsequently, the integrated number Nad is compared with the learning permission number Nadlrn (step S310). Here, the learning permission number Nadlrn is set as a number suitable for updating the stoichiometric learning value AFdst. When the total number of times Nad is less than the number of times of learning permitted Nadlrn, it is determined that it is not suitable for updating the stoichiometric learning value AFdst, and this routine is terminated.

When the integrated number Nad is equal to or greater than the learning permitted number Nadlrn in step S310, it is determined that it is suitable for updating the stoichiometric learning value AFdst, and the value obtained by dividing the integrated air-fuel ratio AFdsum by the integrated number Nad is updated as the average air-fuel ratio AFdave ( Step S320), the value obtained by subjecting the average air-fuel ratio AFdave to the smoothing process is updated as the stoichiometric learning value AFdst (step S330).

In the process of step S330, in the embodiment, as shown in the equation (2), the stoichiometric learning value AFdst is updated by the smoothing process using the average air-fuel ratio AFdave, the current stoichiometric point (currently AFdst), and the time constant τ. It is done by doing. In the embodiment, when the repeated execution of this routine is started (the first execution is started), the stoichiometric reference value AFs as the initial value is set in the stoichiometric learning value AFdst.

AFdst = Currently AFdst ・ τ + AFdave ・ (1-τ) (2)

When the stoichiometric learning value AFdst is updated in this way, the sub-offset amount εR and the sub-offset amount εL are updated using the updated learned stoichiometric learning value AFdst (step S340). In the embodiment, as shown in the equation (3), the value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs) is subtracted from the initial value εRini of the sub-offset amount εR to update the sub-offset amount εR. .. Further, as shown in the equation (4), the value (AFdst-AFs) is added to the initial value δ1ini of the sub-offset amount εL to update the sub-offset amount εL. Therefore, when the stoichiometric reference value AFs as the initial value is set in the stoichiometric learning value AFdst, the initial value εRini and the initial value εLini are set in the sub-offset amount εR and the sub-offset amount εL, and the stoichiometric learning value AFdst is updated. When the stoichiometric learning value AFdst deviates from the stoichiometric reference value AFs, the values obtained by the equations (3) and (4) are set in the sub-offset amount εR and the sub-offset amount εL.

εR = εRini-(AFdst-AFs) (3)
εL = εLini + (AFdst-AFs) (4)

As described above, the value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs) is a value reflecting the sensor deviation amount. Then, by the process of step S340, the sub-offset amount εR and the sub-offset amount εL are updated using the value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs). Thereby, in one cycle of the sub-feedback correction, it is possible to prevent one of the oxygen and the unburned fuel flowing into the purification catalyst 136a from becoming excessive in excess of the amount that reacts with the other in just proportion.

The details of this effect will be described below. As a premise, in the embodiment, when the absolute value of the value (AFdst-AFs) is sufficiently small, the upper limit of the fluctuation amount of the oxygen storage amount OS of the purification catalyst 136a in one cycle of the sub-feedback correction is the maximum oxygen storage amount OSmax. The initial value εRini of the sub-offset amount εR and the initial value εLini of the sub-offset amount εL are set so as to be about several% to several tens of% of.

When the absolute value of the value (AFdst-AFs) is large to some extent, the detected air-fuel ratio AFd becomes equal to the stoichiometric reference value AFs when the air-fuel ratio of the air-fuel mixture in the combustion chamber 129 deviates to some extent from the theoretical air-fuel ratio. Therefore, the sub-offset amount εR and the sub-offset amount εL are held at the initial value εRini and the initial value εLini, that is, the rich side threshold value (AFs-εR) and the lean side threshold value (AFs + εL) are set to the value (AFs-εRini) and the value. When held at (AFs + εL), one of the rich correction and the lean correction may be longer than the other to some extent in one cycle of the sub-feedback correction. At this time, one of the oxygen flowing into the purification catalyst 136a and the unburned fuel becomes more than the amount that reacts with the other in just proportion, and the oxygen storage amount OS of the purification catalyst 136a approaches zero or the maximum oxygen. There is a concern that the purification performance of the exhaust of the purification catalyst 136a may deteriorate as the storage amount approaches OSmax. On the other hand, in the embodiment, the sub-offset amount εR and the sub-offset amount εL are updated by using the value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs), that is, the rich side threshold value (AFs). By updating −εR) and the lean threshold (AFs + εL), it is possible to suppress the occurrence of such inconvenience.

When the sub-offset amount εR and the sub-offset amount εL are updated in step S340, the integrated air-fuel ratio AFdsum and the integrated number of times Nad are reset to the value 0 (step S350), and the integrated permission flag Fad is set to the value 0 (step S360). ), End this routine.

When the value 0 is set in the integration permission flag Fad in this way, the integration permission flag Fad is held at the value 0 until the next detection condition is satisfied (steps S220 and S230). Therefore, until the next detection condition is satisfied, the cumulative air-fuel ratio AFdsum and the cumulative number of times Nad are sequentially updated (steps S290 and S300), the average air-fuel ratio AFdave, the stoichiometric learning value AFdst, the sub-offset amount εR, and the sub-offset amount εL. Updates (steps S320 to S340) will be prohibited.

When the integrated condition of the detected air-fuel ratio AFd is satisfied, the integrated air-fuel ratio AFdsum and the average air-fuel ratio AFdave differ depending on whether the detected air-fuel ratio AFd is on the upper limit value side or the lower limit value side within the predetermined range Raf1. , Affects the stoichiometric learning value AFdst. Therefore, during the period from the start of execution of one rich correction to the end of execution, the stoichiometric learning value AFdst is updated a plurality of times when the detected air-fuel ratio AFd is on the upper limit value side and the lower limit value side within the predetermined range Raf1. Then, the reliability of the stoichiometric learning value AFdst may decrease. Based on this, in the embodiment, the stoichiometric learning value AFdst is updated only once between the start of the execution of one rich correction and the end of the execution. As a result, it is possible to prevent the reliability of the stoichiometric learning value AFdst from becoming low.

When the rich correction flag Fr is a value 1 in step S250 and the steady operation flag Fst is a value 0 in step S260, it is determined that the integration condition is not satisfied, and the integrated air-fuel ratio AFdsum and the integrated frequency Nad are set to a value of 0. At the same time as resetting (step S350), the value 0 is set in the integration permission flag Fad (step S360), and this routine is terminated.

When the operating state of the engine 22 is no longer in the steady operation state and then returns to the steady operation state during the execution of the rich correction, the detected air-fuel ratio AFd when the integration condition of the detected air-fuel ratio AFd is satisfied is predetermined. There are cases where the upper limit value side and the lower limit value side are within the range Raf1. As described above, the integrated air-fuel ratio AFdsum and the average air-fuel ratio AFdave are different when the detected air-fuel ratio AFd is on the upper limit value side and the lower limit value side within the predetermined range Raf1, and affects the stoichiometric learning value AFdst. Based on this, in the embodiment, when the operating state of the engine 22 is no longer in the steady operating state during the execution of the rich correction, the update of the stoichiometric learning value AFdst during the execution of the rich correction this time is stopped. As a result, it is possible to prevent the reliability of the stoichiometric learning value AFdst from becoming low.

When the rich correction flag Fr is a value 1 in step S250 and the steady operation flag Fst is a value 0 in step S260, the detected air-fuel ratio AFd is outside the predetermined range Raf1 in step S270, or the detected air is empty in step S280. When the fuel ratio change rate ΔAFd is outside the predetermined range Raf2, it is determined that the integration condition is not satisfied. Then, the integrated number Nad is compared with the threshold value Nadref smaller than the learning permission number Nadlrn (step S370). Here, for the threshold value Nadref, after the integration condition of the detected air-fuel ratio AFd starts to be satisfied, the integration condition is temporarily unsatisfied due to the disturbance of the detected air-fuel ratio AFd and the detected air-fuel ratio change rate ΔAFd, and then the integration condition is re-established. It is set as a value corresponding to the time that may occur or a little longer than that.

When the integrated air-fuel ratio Nad is less than the threshold value Nadref in step S370, the integrated air-fuel ratio AFdsum, the integrated number Nad, and the integrated permission flag Fad are held, and this routine is terminated. As a result, when the integration condition is temporarily unsatisfied due to the disturbance of the detected air-fuel ratio AFd and the detected air-fuel ratio change rate ΔAFd immediately after the start of the establishment of the integrated condition of the detected air-fuel ratio AFd, the stoichiometric learning value AFdst It is possible to avoid canceling the update. As a result, it is possible to suppress a decrease in the chance of updating the stoichiometric learning value AFdst.

When the integrated air-fuel ratio Nad is equal to or greater than the threshold value Nadref in step S370, the integrated air-fuel ratio AFdsum and the integrated number Nad are reset to a value 0 (step S350), and the integrated permission flag Fad is set to a value 0 (step S360). End the routine. In this case, it is decided to cancel the sequential update of the integrated air-fuel ratio AFdsum and the integrated number of times Nad, the average air-fuel ratio AFdave, the stoichiometric learning value AFdst, the sub-offset amount εR, and the sub-offset amount εL during the execution of this rich correction. Become.

When the number of integrations Nad is equal to or greater than the threshold value Nadref, it is usually assumed that there is a low possibility that the integration conditions will not be satisfied due to the disturbance of the detected air-fuel ratio AFd and the detected air-fuel ratio change rate ΔAFd. Based on this, in the embodiment, when the cumulative number of times Nad is equal to or greater than the threshold value Nadref, the detected air-fuel ratio AFd is outside the predetermined range Raf1, or the detected air-fuel ratio change rate ΔAFd is outside the predetermined range Raf2. It was decided to cancel the update of the stoichiometric learning value AFdst during the execution of this rich correction. As a result, it is possible to prevent the reliability of the stoichiometric learning value AFdst from becoming low.

FIG. 7 is an explanatory diagram showing an example of the state of the detected air-fuel ratio AFd, the rich correction flag Fr, the steady operation flag Fst, the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integrated number of times Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst. Is. In the figure, with respect to the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integrated number of times Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst, the solid line shows the state of the example, and the alternate long and short dash line shows the state of the first comparative example. As a first comparative example, it is assumed that the detection condition does not include the condition that the rich correction flag Fr has a value of 0 (lean correction is being executed). In FIG. 7, it is assumed that the steady operation flag Fst is held at a value of 1.

As shown in the figure, when the rich correction flag Fr has a value of 0 and the detected air-fuel ratio AFd reaches the lean side threshold value (AFs + εL) or more (time t12, t22), the rich correction flag Fr is switched to the value 1. Further, when the rich correction flag Fr is a value 1 and the detected air-fuel ratio AFd reaches the rich side threshold value (AFs-εR) or less (time t15, t25), the rich correction flag Fr is switched to a value 0.

Further, when the detection condition is satisfied when the rich correction flag Fr is a value 0 (time t11, t21), the integration permission flag Fad is switched from the value 0 to the value 1. Then, when the integration condition of the detected air-fuel ratio AFd is satisfied when the integration permission flag Fad is a value 1 (time t13, t23), the integrated air-fuel ratio AFdsum and the integration count Nad are sequentially updated, and then the integration count Nad is started. When the number of learning permits Nadlrn or more is reached (time t14, t24), the average air-fuel ratio AFdave and the stoichiometric learning value AFdst are updated, the integrated air-fuel ratio AFdsum and the integrated air-fuel ratio Nad are reset to a value of 0, and the integration permission flag Fad is executed. Is switched from the value 1 to the value 0. In this way, the stoichiometric learning value AFdst can be updated.

In the first comparative example, when the rich correction flag Fr is a value 1 (time t22 to t25), after updating the stoichiometric learning value AFdst and switching the integration permission flag Fad from the value 1 to the value 0 (time t24), When the detected air-fuel ratio AFd suddenly increases (time t31), the detection condition is re-established and the integration permission flag Fad is switched from the value 0 to the value 1. After that, when the integration condition of the detected air-fuel ratio AFd is satisfied (time t32), the cumulative air-fuel ratio AFdsum and the integration count Nad are sequentially updated, and when the integration count Nad reaches the learning permission number Nadlrn or more (time t33). , The average air-fuel ratio AFdave and the stoichiometric learning value AFdst are updated. Therefore, the stoichiometric learning value AFdst is updated twice when the detected air-fuel ratio AFd is on the upper limit value side and the lower limit value side within the predetermined range Raf1 between the start of execution of one rich correction and the end of execution. It will be. Therefore, the reliability of the stoichiometric learning value AFdst may be low.

On the other hand, in the embodiment, when the rich correction flag Fr is a value 1 (time t22 to t25), the stoichiometric learning value AFdst is updated and the integration permission flag Fad is switched from the value 1 to the value 0 (time). Even if the detected air-fuel ratio AFd increases rapidly (time t31), the rich correction flag Fr is set to a value of 1, so that the detection condition is not satisfied and the integration permission flag Fad is held at a value of 0. In this way, it is avoided to sequentially update the integrated air-fuel ratio AFdsum and the integrated number of times Nad, and update the detected air-fuel ratio AFd and the stoichiometric learning value AFdst at times t32 to t33. Therefore, the stoichiometric learning value AFdst is updated only once between the start of execution of one rich correction and the end of execution. As a result, it is possible to prevent the reliability of the stoichiometric learning value AFdst from becoming low.

FIG. 8 shows a state of the detected air-fuel ratio AFd, the rich correction flag Fr, the steady operation flag Fst, the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integrated number of times Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst, as in FIG. It is explanatory drawing which shows an example. In the figure, with respect to the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integrated number of times Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst, the solid line shows the state of the example, and the alternate long and short dash line shows the state of the second comparative example. As a second comparative example, when the integration permission flag Fad is a value 1 and the rich correction flag Fr is a value 1, the integration permission flag Fad is held at a value 1 even if the steady operation flag Fst becomes a value 0. I made it. Further, in the figure, the times t11 to t15, t21 to t23, and t25 are the same as those in FIG.

In the second comparative example, when the rich correction flag Fr is a value 1 (time t22 to t25), even if the steady operation flag Fst becomes a value 0 (time t41), the integration permission flag Fad is held at a value 1. Therefore, after that, when the steady operation flag Fst becomes a value 1 and the integration condition of the detected air-fuel ratio AFd is satisfied (time t42), the cumulative air-fuel ratio AFdsum and the integration count Nad are sequentially updated, and the integration count Nad is permitted to learn. When the number of times Nadlrn or more is reached (time t43), the average air-fuel ratio AFdave and the stoichiometric learning value AFdst are updated. In FIG. 8, the detected air-fuel ratio AFd is sequentially updated from the center to the lower limit within the predetermined range Raf1, and the integrated air-fuel ratio AFdsum and the integrated number of times Nad are sequentially updated, and the average air-fuel ratio AFdave and the stoichiometric learning value AFdst are updated. .. When the operating state of the engine 22 returns to the steady operating state and the integration condition of the detected air-fuel ratio AFd is satisfied, the detected air-fuel ratio AFd is on the upper limit value side and the lower limit value side within the predetermined range Raf1. Occurs. Therefore, if the update of the stoichiometric learning value AFdst is executed, the reliability of the stoichiometric learning value AFdst may decrease.

On the other hand, in the embodiment, when the rich correction flag Fr is a value 1 (time t22 to t25) and the steady operation flag Fst becomes a value 0 (time t41), the integration permission flag Fad is set from a value 1 to a value 0. Switch to. Then, even if the steady-state operation flag Fst becomes a value 1 (time t42) after that, since the rich correction flag Fr is a value 1, the detection condition is not satisfied and the integration permission flag Fad is held at a value 0. In this way, it is avoided to sequentially update the integrated air-fuel ratio AFdsum and the integrated number of times Nad, and update the detected air-fuel ratio AFd and the stoichiometric learning value AFdst at times t42 to t43. As a result, it is possible to prevent the reliability of the stoichiometric learning value AFdst from becoming low.

FIG. 9 shows a state of the detected air-fuel ratio AFd, the rich correction flag Fr, the steady operation flag Fst, the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integrated number of times Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst, as in FIG. It is explanatory drawing which shows an example. In the figure, with respect to the integration permission flag Fad, the integrated air-fuel ratio AFdsum, the integrated number of times Nad, the average air-fuel ratio AFdave, and the stoichiometric learning value AFdst, the solid line shows the state of the example, and the alternate long and short dash line shows the state of the third comparative example. As a third comparative example, the integration conditions for the detected air-fuel ratio AFd are not satisfied because the conditions for the detected air-fuel ratio AFd and the detected air-fuel ratio change rate ΔAFd are not satisfied during the sequential update of the integrated air-fuel ratio AFdsum and the integrated number of times Nad. When the value becomes 0, the integrated air-fuel ratio AFdsum and the integrated air-fuel ratio Nad are reset to a value 0 and the integrated permission flag Fad is switched from a value 1 to a value 0 regardless of the magnitude relationship between the integrated air-fuel ratio Nad and the threshold Nadref. I decided to think about it. Further, in the figure, the times t11 to t15 and t21 to t25 are the same as those in FIG. In FIG. 9, it is assumed that the steady operation flag Fst is held at a value of 1.

In the third comparative example, when the detected air-fuel ratio change rate ΔAFd starts to decrease sharply during the sequential update of the integrated air-fuel ratio AFdsum and the integrated air-fuel ratio AFd and the integrated condition of the detected air-fuel ratio AFd is not satisfied (time t51), the integrated air-fuel ratio Nad and the threshold value. Regardless of the magnitude relationship with Nadref, the integrated air-fuel ratio AFdsum and the integrated number Nad are reset to a value 0, and the integrated permission flag Fad is switched from a value 1 to a value 0. Therefore, the chance of updating the stoichiometric learning value AFdst is reduced.

On the other hand, in the embodiment, when the detected air-fuel ratio change rate ΔAFd starts to decrease sharply during the sequential update of the integrated air-fuel ratio AFdsum and the integrated air-fuel ratio Nad and the integration condition of the detected air-fuel ratio AFd is not satisfied (time t51). When the integrated air-fuel ratio Nad is less than the threshold value Nadref, the integrated air-fuel ratio AFdsum, the integrated air-fuel ratio Nad, and the integrated permission flag Fad are held. After that, when the integration condition of the detected air-fuel ratio AFd is re-established (time t52), the sequential update of the integrated air-fuel ratio AFdsum and the integration number Nad is restarted, and when the integration number Nad reaches the learning permission number Nadlrn or more (time t24). ), Update the average air-fuel ratio AFdave and the stoichiometric learning value AFdst. As a result, it is possible to suppress a decrease in the chance of updating the stoichiometric learning value AFdst.

In the engine device 21 mounted on the hybrid vehicle 20 of the above-described embodiment, a detection condition that is a logical product of a condition in which lean correction is being executed and a condition in which the detected air-fuel ratio change rate ΔAFd is equal to or greater than the threshold value ΔAFdref is satisfied. Then, the integration of the detected air-fuel ratio AFd is permitted. Subsequently, the condition that the integration of the detected air-fuel ratio AFd is permitted and the rich correction is being executed, the condition that the operating state of the engine 22 is the steady operating state, and the detected air-fuel ratio AFd are within the predetermined range Raf1. When the integration condition of the detected air-fuel ratio AFd, which is the logical product of the condition and the condition that the detected air-fuel ratio change rate ΔAFd is within the predetermined range Raf2, is satisfied, the detected air-fuel ratio AFd is integrated to obtain the integrated air-fuel ratio AFdsum. Calculate. Then, when the integrated number Nad reaches the learning permitted number Nadlrn or more, the average air-fuel ratio AFdave is updated using the integrated air-fuel ratio AFdsum, and the stoichiometric learning value AFdst is updated using this detected air-fuel ratio AFd. In this way, the stoichiometric learning value AFdst can be updated.

Further, when the stoichiometric learning value AFdst is updated while the detection air-fuel ratio AFd is permitted to be integrated and the rich correction is being executed, or when the operating state of the engine 22 is no longer in the steady operation state, the integrated number Nad is a threshold value. When it is Nadref or more and the detected air-fuel ratio AFd is out of the predetermined range Raf1 or the detected air-fuel ratio change rate ΔAFd is out of the predetermined range Raf2, the permission for integrating the detected air-fuel ratio AFd is released. Therefore, in these cases, it is prohibited to sequentially update the detected air-fuel ratio AFd and the cumulative number of times Nad, and to update the average air-fuel ratio AFdave and the stoichiometric learning value AFdst until the detection condition is satisfied next time. As a result, it is possible to prevent the reliability of the stoichiometric learning value AFdst from becoming low. That is, the stoichiometric learning value AFdst can be set to a more appropriate value.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 has the detection condition that the rich correction flag Fr is a value 0 and the detected air-fuel ratio change rate ΔAFd is equal to or greater than the threshold value ΔAFdref. The logical product of the conditions was used. However, in place of or in addition to the condition that the detected air-fuel ratio change rate ΔAFd is equal to or greater than the threshold value ΔAFdref, the condition that the detected air-fuel ratio AFd is equal to or greater than the threshold value AFdref or the condition that the oxygen occlusion OS is equal to or greater than the threshold value OSref is used. May be good. Here, as the threshold value AFdref, a value larger than the stoichiometric reference value AFs and smaller than the lean side threshold value (AFs + εL) is used. As the threshold value OSref, a value in which the air-fuel ratio of the air-fuel mixture in the combustion chamber 129 is larger than the oxygen storage amount OS at the stoichiometric air-fuel ratio is used.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 determines that the rich correction flag Fr is a value 1 and the steady operation flag Fst is a value 1 as the integration condition of the detected air-fuel ratio AFd. The logical product of the condition that the detected air-fuel ratio AFd is within the predetermined range Raf1 and the condition that the detected air-fuel ratio change rate ΔAFd is within the predetermined range Raf2 is used. However, at least one of the condition that the steady operation flag Fst is a value 1 and the condition that the detected air-fuel ratio change rate ΔAFd is within the predetermined range Raf2 may not be used.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 has fixed values as predetermined ranges Raf1 and Raf2 used in the processing of steps S270 and S280 of the deviation amount-related learning routine of FIG. Was used. However, the predetermined ranges Raf1 and Raf2 may be set based on at least one of the intake air amount Qa and the maximum oxygen storage amount OSmax. When setting the predetermined range Raf1 and Raf2 based on the intake air amount Qa and the maximum oxygen storage amount OSmax, the predetermined range Raf1 is set using the first predetermined range setting map of FIG. A predetermined range Raf1 may be set using the range setting map.

The first predetermined range setting map of FIG. 10 is preset as a relationship between the intake air amount Qa and the maximum oxygen storage amount OSmax and the predetermined range Raf1, and is stored in a ROM (not shown). The second predetermined range setting map of FIG. 11 is preset as the relationship between the intake air amount Qa and the maximum oxygen storage amount OSmax and the predetermined range Raf2, and is stored in the ROM. As shown in FIGS. 10 and 11, the predetermined ranges Raf1 and Raf2 both become wider as the intake air amount Qa increases (the upper limit value increases and the lower limit value decreases), and the maximum oxygen uptake OSmax The smaller the number, the wider the setting. This is due to the following reasons.

During the execution of the rich correction, the larger the intake air amount Qa, that is, the larger the exhaust amount flowing into the purification catalyst 136a, and the smaller the maximum oxygen occlusion amount OSmax, that is, the greater the degree of deterioration of the purification catalyst 136a, the greater the degree of deterioration of the purification catalyst 136a. The amount of decrease in the oxygen storage amount OS per unit time tends to be large, and the time for establishing the condition that the detected air-fuel ratio AFd is within the predetermined range Raf1 and the condition that the detected air-fuel ratio change rate ΔAFd is within the predetermined range Raf2 becomes short. Cheap. Therefore, by setting the predetermined ranges Raf1 and Raf2 so that the larger the intake air amount Qa is, the wider the maximum oxygen storage amount OSmax is, the larger the intake air amount Qa is, and the smaller the maximum oxygen storage amount OSmax is. Sometimes, it is possible to easily secure the number of detections of the detected air-fuel ratio AFd. As a result, the total number of times Nad can easily reach the number of times of learning permission Nadlrn or more. As a result, it is possible to suppress a decrease in the chance of updating the stoichiometric learning value AFdst.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 uses a fixed value as the learning permission number Nadlrn used in the process of step S310 of the deviation amount-related learning routine of FIG. did. However, the learning permission number Nadlrn may be set based on at least one of the intake air amount Qa and the maximum oxygen storage amount OSmax. When the learning permission number Nadlrn is set based on the intake air amount Qa and the maximum oxygen storage amount OSmax, the learning permission number Nadlrn may be set using the learning permission number setting map of FIG.

The learning permission number setting map of FIG. 12 is preset as a relationship between the intake air amount Qa and the maximum oxygen storage amount OSmax and the learning permission number Nadlrn, and is stored in a ROM (not shown). As shown in FIG. 12, the learning permission number Nadlrn is set so as to decrease as the intake air amount Qa increases and decrease as the maximum oxygen storage amount OSmax decreases. This is due to the following reasons.

As described above, the larger the intake air amount Qa, that is, the larger the displacement that flows into the purification catalyst 136a, and the smaller the maximum oxygen storage amount OSmax, that is, the greater the degree of deterioration of the purification catalyst 136a during the execution of the rich correction. The more the oxygen storage amount OS of the purification catalyst 136a decreases, the greater the rate of decrease. Therefore, by setting the learning permission number Nadlrn so that the larger the intake air amount Qa is, the smaller the maximum oxygen storage amount OSmax is, the larger the intake air amount Qa is, and the smaller the maximum oxygen storage amount OSmax is. In addition, the cumulative number of times Nad can easily reach the number of times of learning permission Nadlrn or more, and it is possible to suppress a decrease in the chance of updating the stoichiometric learning value AFdst.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 uses a fixed value as the threshold value Nadref used in the process of step S370 of the deviation amount-related learning routine of FIG. However, the threshold value Nadref may be set based on at least one of the intake air amount Qa and the maximum oxygen storage amount OSmax. When the threshold value Nadref is set based on the intake air amount Qa and the maximum oxygen storage amount OSmax, the threshold value Nadref may be set using the threshold value setting map of FIG.

The threshold value setting map of FIG. 13 is preset as a relationship between the intake air amount Qa, the maximum oxygen uptake amount OSmax, and the threshold value Nadref, and is stored in a ROM (not shown). As shown in FIG. 13, the threshold value Nadref is set so that the smaller the intake air amount Qa, the larger the threshold value, and the larger the maximum oxygen storage amount OSmax, the larger the threshold value. This is due to the following reasons.

As described above, the larger the intake air amount Qa, that is, the larger the displacement that flows into the purification catalyst 136a, and the smaller the maximum oxygen storage amount OSmax, that is, the greater the degree of deterioration of the purification catalyst 136a during the execution of the rich correction. The more the oxygen storage amount OS of the purification catalyst 136a decreases, the greater the rate of decrease. If the rate of decrease of the oxygen storage amount OS of the purification catalyst 136a is small, the integration condition is temporarily unsatisfied due to the disturbance of the detected air-fuel ratio AFd and the detected air-fuel ratio change rate ΔAFd after the establishment of the detection air-fuel ratio AFd integration condition is started. When becomes, the time until the integration condition is re-established tends to be long. The inventors confirmed this by experiment and analysis. Therefore, by setting the threshold Nadref so that the smaller the intake air amount Qa is, the larger the maximum oxygen storage amount OSmax is, the smaller the intake air amount Qa is, and the larger the maximum oxygen storage amount OSmax is. It is possible to suppress a decrease in the chance of updating the stoiki learning value AFdst.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, when the deviation amount-related learning unit 95 permits the integration of the detected air-fuel ratio AFd and updates the stoichiometric learning value AFdst during the execution of the rich correction. Or, when the operating state of the engine 22 is no longer in the steady operation state, the cumulative number of times Nad is equal to or greater than the threshold Nadref and the detected air-fuel ratio AFd is outside the predetermined range Raf1 or the detected air-fuel ratio change rate ΔAFd is outside the predetermined range Raf2. When this happens, the permission to integrate the detected air-fuel ratio AFd is canceled. However, when the stoichiometric learning value AFdst is updated, when the operating state of the engine 22 is no longer in the steady operation state, the cumulative number of times Nad is equal to or greater than the threshold value Nadref, and the detected air-fuel ratio AFd is out of the predetermined range Raf1 or the detected air-fuel ratio. Only a part of the time when the rate of change ΔAFd falls outside the predetermined range Raf2 may be used. Further, when the detected air-fuel ratio AFd is outside the predetermined range Raf1 or the detected air-fuel ratio change rate ΔAFd is outside the predetermined range Raf2, the detected air-fuel ratio AFd is irrespective of the magnitude relationship between the cumulative number of times Nad and the threshold value Nadref. You may cancel the permission of the accumulation of.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 executes the deviation amount-related learning routine of FIG. However, instead of this, the deviation amount-related learning routine of FIG. 14 may be executed. In the deviation amount-related learning routine of FIG. 14, the process of step S370 is replaced with the process of steps S400 and S410, the process of step S420 is added, and the process of step S350 is replaced with the process of step S430. Except for the above points, it is the same as the deviation amount related learning routine of FIG. Therefore, among the deviation amount-related learning routines of FIG. 14, the same processes as those of the deviation amount-related learning routine of FIG. 6 are assigned the same step numbers, and detailed description thereof will be omitted. In this modification, when the repeated execution of this routine is started (the first execution is started), in addition to the integrated air-fuel ratio AFdsum, the integrated number Nad, and the integrated permission flag Fad, the number of deviations described later is Out. The value 0 as the initial value is set in.

In the deviation amount-related learning routine of FIG. 14, when the deviation amount-related learning unit 95 has a rich correction flag Fr of value 1 in step S250 and a steady operation flag Fst of value 0 in step S260, the deviation amount-related learning unit 95 is set to step S270. When the detected air-fuel ratio AFd is outside the predetermined range Raf1 or when the detected air-fuel ratio change rate ΔAFd is outside the predetermined range Raf2 in step S280, it is determined that the integration condition is not satisfied. Then, it is determined whether or not the integration number Nad is larger than the value 0 (step S400). This process is a process of determining whether the integration condition of the detected air-fuel ratio AFd is before the start of establishment or after the start of establishment.

When the number of integrations Nad is 0 in step S400, it is determined that the integration condition for the detected air-fuel ratio AFd has not yet been satisfied, and this routine is terminated. On the other hand, when the integrated number Nad is larger than the value 0, it is determined that the integrated condition of the detected air-fuel ratio AFd has started to be satisfied, and the current number of deviations (currently Now) is incremented by a value of 1 to obtain the new number of deviations. It is set to Nout (step S410), and this routine is terminated.

When the average air-fuel ratio AFdave was updated in step S320, the time constant τ was set using the number of deviations Nout and the time constant setting map of FIG. 15 (step S420), and the average air-fuel ratio AFdave and the time constant τ were used. The stoichiometric learning value AFdst is updated by the smoothing process of the above equation (2) (step S330). Then, the sub-offset amount εR and the sub-offset amount εL are updated using the stoichiometric learning value AFdst (step S340), and the integrated air-fuel ratio AFdsum, the integrated number Nad, and the number of deviations Nout are reset to values 0 (step S430), and the integrated is performed. The value 0 is set in the permission flag Fad (step S360), and this routine is terminated.

The time constant setting map of FIG. 15 is preset as the relationship between the number of deviations Now and the time constant τ, and is stored in a ROM (not shown). As shown in FIG. 15, the time constant τ is set so as to increase as the number of deviations Out increases. As a result, it is possible to reduce the influence of the average air-fuel ratio AFdave on the stoichiometric learning value AFdst as the number of deviations out increases.

Here, the significance of the difference between the deviation amount-related learning routine of FIG. 6 and the deviation amount-related learning routine of FIG. 14 will be described. In the deviation amount-related learning routine of FIG. 6, after the integration condition for the detected air-fuel ratio AFd starts to be satisfied, the number of integrations Nad is equal to or greater than the threshold value Nadref, and the detected air-fuel ratio AFd falls outside the predetermined range Raf1 or the detected air-fuel ratio change rate ΔAFd When is out of the predetermined range Raf2, the update of the stoichiometric learning value AFdst is stopped, the integrated air-fuel ratio AFdsum and the integrated air-fuel ratio Nad are reset to the value 0, and the integrated permission flag Fad is switched to the value 0.

On the other hand, in the deviation amount-related learning routine of FIG. 14, the detected air-fuel ratio AFd is outside the predetermined range Raf1 or the detected air-fuel ratio change rate ΔAFd is outside the predetermined range Raf2 after the establishment of the integration condition of the detected air-fuel ratio AFd is started. When it becomes, the integrated air-fuel ratio AFdsum, the integrated air-fuel ratio Nad, and the integrated permission flag Fad are held, regardless of the magnitude relationship between the integrated air-fuel ratio Nad and the threshold value Nadref. Then, after that, the integration condition is re-established, and when the integrated air-fuel ratio AFdsum and the integrated air-fuel ratio Nad are sequentially updated and the integrated number Nad reaches the learning permission number Nadlrn or more, the average air-fuel ratio AFdave is updated and the average air-fuel ratio AFdave is set. The value subjected to the smoothing process using the time constant τ based on the number of deviations Nout is updated as the stoichiometric learning value AFdst. As a result, when the number of deviations is large, the influence of the average air-fuel ratio AFdave on the stoichiometric learning value AFdst can be reduced, and the chance of updating the stoichiometric learning value AFdst can be suppressed.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 updates the value obtained by applying the smoothing process to the average air-fuel ratio AFdave as the stoichiometric learning value AFdst. However, the value obtained by subjecting the average air-fuel ratio AFdave to the rate processing may be updated as the stoichiometric learning value AFdst.

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 updates the value obtained by applying the smoothing process to the average air-fuel ratio AFdave as the stoichiometric learning value AFdst. However, the average air-fuel ratio AFdave may be updated as the stoichiometric learning value AFdst. In this case, as shown in the equations (5) and (6), the product of the value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs) and the gains αR and αL smaller than the value 1. It is preferable to update the sub-offset amount εR and the sub-offset amount εL using.

εR = εRini- (AFdst-AFs) ・ αR (5)
εL = εLini + (AFdst-AFs) ・ αL (6)

In the engine device 21 mounted on the hybrid vehicle 20 of the embodiment, the deviation amount-related learning unit 95 updates the stoichiometric learning value AFdst based on the average air-fuel ratio AFdave, and is shown in equations (3) and (4). As described above, the sub-offset amount εR and the sub-offset amount εL were updated using the value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs). However, a value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs) may be updated as the stoichiometric deviation amount ΔAFdst. Further, the value obtained by subjecting the value obtained by subtracting the stoichiometric reference value AFs from the stoichiometric learning value AFdst (AFdst-AFs) by slow change processing (annealing processing or rate processing) may be updated as the stoichiometric deviation amount ΔAFdst. .. Further, a value obtained by subtracting the stoichiometric reference value AFs from the average air-fuel ratio AFdave (AFdave-AFs) may be updated as the stoichiometric deviation amount ΔAFdst. In addition, the value obtained by slowly changing the value obtained by subtracting the stoichiometric reference value AFs from the average air-fuel ratio AFdave (AFdave-AFs) may be updated as the stoichiometric deviation amount ΔAFdst. In these cases, the stoichiometric deviation amount ΔAFdst corresponds to the “deviation amount-related learning value”. Further, in these cases, as shown in the equations (7) and (8), the sub-offset amount εR and the sub-offset amount εL may be updated by using the stoichiometric deviation amount ΔAFdst.

εR = εRini-ΔAFdst (7)
εL = εLini + ΔAFdst (8)

In the embodiment, the engine device 21 mounted on the hybrid vehicle 20 including the engine 22, the planetary gear 30, and the motors MG1 and MG2 is used. However, it may be in the form of an engine device mounted on a so-called one-motor hybrid vehicle including an engine and one motor. Further, it may be in the form of an engine device mounted on an automobile traveling by using only the power from the engine. Further, it may be in the form of an engine device mounted on non-moving equipment such as construction equipment.

The correspondence between the main elements of the examples and the main elements of the invention described in the column of means for solving the problem will be described. In the embodiment, the engine 22 corresponds to the "engine", the purification catalyst 136a corresponds to the "purification catalyst", the downstream air-fuel ratio sensor 154 corresponds to the "exhaust sensor", and the engine ECU 24 corresponds to the "control device". To do.

Regarding the correspondence between the main elements of the examples and the main elements of the invention described in the column of means for solving the problem, the invention described in the column of means for solving the problem in the examples is carried out. Since it is an example for specifically explaining the form for solving the problem, the elements of the invention described in the column of means for solving the problem are not limited. That is, the interpretation of the invention described in the column of means for solving the problem should be performed based on the description in the column, and the examples are the inventions described in the column of means for solving the problem. It is just a concrete example.

Although the embodiments for carrying out the present invention have been described above with reference to examples, the present invention is not limited to these examples, and various embodiments are used without departing from the gist of the present invention. Of course, it can be done.

The present invention can be used in the manufacturing industry of engine devices and the like.

20 hybrid car, 22 engine, 24 engine ECU, 26 crank shaft, 28 damper, 30 planetary gear, 36 drive shaft, 38 differential gear, 39a, 39b drive wheel, 40 motor ECU, 41,42 inverter, 43,44 rotation position sensor , 50 battery, 51a voltage sensor, 51b current sensor, 51c temperature sensor, 52 battery ECU, 54 power line, 70 HVECU, 80 ignition switch, 81 shift lever, 82 shift position sensor, 83 accelerator pedal, 84 accelerator pedal position sensor, 85 Brake pedal, 86 Brake pedal position sensor, 88 Vehicle speed sensor, 89 Outside temperature sensor, 90 Base injection amount setting unit, 91 Main feedback unit, 92 Sub feedback unit, 93 Target injection amount setting unit, 94 Injection valve control unit, 95 Deviation amount related learning unit, 96 oxygen storage amount estimation unit, 122 air cleaner, 123 intake pipe, 124 throttle valve, 124a throttle valve position sensor, 124b throttle motor, 125 surge tank, 126 fuel injection valve, 128 intake valve, 129 combustion chamber , 130 Ignition plug, 132 piston, 133 exhaust valve, 134 exhaust pipe, 136,138 purification device, 136a, 138a purification catalyst, 140 crank position sensor, 142 water temperature sensor, 144 cam position sensor, 148 airflow meter, 149 temperature sensor, 150 pressure sensor, 152 upstream air fuel ratio sensor, 154 downstream air fuel ratio sensor, MG1, MG2 motor.

Claims (11)

An engine with a fuel injection valve and
A purification catalyst that can be attached to the exhaust system of the engine and can occlude oxygen,
An exhaust sensor mounted on the downstream side of the purification catalyst of the exhaust system,
When operating the engine, if the detected air-fuel ratio detected by the exhaust sensor reaches the rich side threshold or less during the execution of the rich correction for the fuel injection amount of the fuel injection valve, the lean correction for the fuel injection amount is performed. When the detected air-fuel ratio reaches or more than the lean side threshold during the execution of the lean correction, the control device that switches to the execution of the rich correction, and
It is an engine device equipped with
The control device is
If the detection condition for detecting the lean of the exhaust gas downstream of the purification catalyst is satisfied during the execution of the lean correction, the integration of the detected air-fuel ratio is permitted.
An integration condition including the condition that the integration of the detected air-fuel ratio is permitted and the rich correction is being executed and the condition that the detected air-fuel ratio is within the first predetermined range including the reference value is satisfied. If so, the detected air-fuel ratio is integrated to calculate the integrated air-fuel ratio.
When the integrated number of times of the detected air-fuel ratio reaches the learning permitted number of times or more, the deviation amount-related learning value regarding the deviation amount of the detected air-fuel ratio is updated by using the integrated air-fuel ratio.
If the prohibition condition is satisfied while the integration of the detected air-fuel ratio is permitted and the rich correction is being executed, the permission for the integration of the detected air-fuel ratio is released.
Engine device. The engine device according to claim 1.
The prohibition condition includes a condition in which the deviation amount-related learning value is updated.
Engine device. The engine device according to claim 1 or 2.
The prohibition condition includes a condition in which the integration condition is not satisfied and the number of integrations of the detected air-fuel ratio is less than the number of times of permission for learning and equal to or greater than the number of determinations.
Engine device. The engine device according to claim 3.
The control device sets the number of determinations based on the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst.
Engine device. The engine device according to claim 1 or 2.
When the number of times of integration reaches the permitted number of times or more, the control device reduces the degree of reflection of the integrated air-fuel ratio as the number of times the integration condition is not satisfied increases after the start of establishment of the integration condition. Update the deviation amount related learning value,
Engine device. The engine device according to any one of claims 1 to 5.
The integration condition includes a condition in which the operating state of the engine is the steady operating state.
The prohibition condition includes a condition in which the operating state of the engine is no longer in the steady operating state.
Engine device. The engine device according to any one of claims 1 to 6.
The control device sets the number of learning permits and / or the first predetermined range based on the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst.
Engine device. The engine device according to any one of claims 1 to 7.
The integration condition includes a condition in which the detected air-fuel ratio change rate, which is the amount of change in the detected air-fuel ratio per unit time, is within the second predetermined range including the value 0.
Engine device. The engine device according to claim 8.
The control device sets the second predetermined range based on the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst.
Engine device. The engine device according to any one of claims 1 to 9.
The detection conditions are a condition in which the lean correction is being executed, a condition in which the detected air-fuel ratio change rate, which is the amount of change in the detected air-fuel ratio per unit time, becomes equal to or higher than a predetermined rate of change, and the detected air-fuel ratio is predetermined. It includes at least one of the conditions that the air-fuel ratio is equal to or higher than the air-fuel ratio and the oxygen storage amount of the purification catalyst is equal to or higher than the predetermined storage amount.
Engine device. The engine device according to any one of claims 1 to 10.
The control device sets the rich side threshold value and the lean side threshold value using the deviation amount-related learning value.
Engine device.

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