JP2021085351A - Engine device - Google Patents

Abstract

To curb a reduction in exhaust purification performance with a catalyst installed in an engine exhaust system.SOLUTION: When an engine is operated under a condition that a detected air-fuel ratio corresponding to an output value of an exhaust sensor becomes equal to or lower than a rich side threshold with rich correction for a fuel injection amount of a fuel injection valve in execution, an engine device switches the rich correction of the fuel injection amount to lean correction. When the engine is operated under a condition that the detected air-fuel ratio becomes equal to or higher than a lean side threshold with the lean correction in execution, the engine device switches the lean correction to the rich correction. Then, when a predetermined time output value, which is the output value of the exhaust sensor in a state of satisfying a predetermined condition for stabilized output value during an engine fuel cut, comes close to a reference output value corresponding to a theoretical air-fuel ratio with respect to a predetermined range, the engine device sets the rich side threshold and the lean side threshold so that the predetermined time output value comes closer to the theoretical air-fuel ratio than when the same is in the predetermined range.SELECTED DRAWING: Figure 8

Description

The present invention relates to an engine device.

Conventionally, this type of engine device includes an engine, a purification catalyst attached to the exhaust system of the engine, and an exhaust sensor provided in the exhaust system of the engine and generating an output according to an exhaust component. It has been proposed (see, for example, Patent Document 1). This engine device includes a detection signal generating means, an air-fuel ratio control means, and an exhaust sensor evaluation means. The detection signal generating means generates a detection signal for multiplying the basic fuel injection amount used during normal operation to obtain the fuel injection amount for determining the state of the exhaust sensor. The air-fuel ratio control means controls the fuel injection amount for determining the state of the exhaust sensor by using the feedback coefficient determined based on the output of the exhaust sensor. The exhaust sensor evaluation means extracts a frequency component corresponding to the detection signal from the output of the exhaust sensor when the fuel injection amount for determining the state of the exhaust sensor is used, and determines the state of the exhaust sensor based on the frequency component. ..

Japanese Unexamined Patent Publication No. 2010-133418

In such an engine device, generally, when the engine is operated, when the detected air-fuel ratio corresponding to the output value of 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 fuel is fueled. While switching to the execution of the lean correction for the injection amount, when the detected air-fuel ratio reaches the lean side threshold value or more during the execution of the lean correction, the execution is switched to the rich correction. When the followability (change amount) of the output value of the exhaust sensor to the change amount of the exhaust component (air-fuel ratio of the exhaust) becomes small, the rich correction and the lean correction are executed when the fuel injection control of the engine is performed. May become difficult to switch, the oxygen storage amount of the catalyst may be excessively reduced or increased, and the exhaust gas purification performance of the catalyst may be deteriorated.

The main object of the engine device of the present invention is to suppress deterioration of exhaust purification performance due to a catalyst attached to 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 first engine device of the present invention is
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 that is attached to the exhaust system and outputs an output value based on the air-fuel ratio of the exhaust,
When operating the engine, if the detected air-fuel ratio corresponding to the output value 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. A control device that switches to execution and switches to execution of the rich correction when the detected air-fuel ratio reaches or more than the lean side threshold during the execution of the lean correction.
It is an engine device equipped with
In the control device, the predetermined output value, which is the output value when a predetermined condition in which the output value is stable is satisfied during the fuel cut of the engine, is a reference output corresponding to the stoichiometric air-fuel ratio with respect to the predetermined range. When the value is approaching, the rich side threshold value and the lean side threshold value are set so as to approach the stoichiometric air-fuel ratio as compared with the case where the predetermined time output value is within the predetermined range.
The gist is that.

In the first engine device of the present invention, the predetermined air-fuel ratio, which is the output value when a predetermined condition in which the output value of the exhaust sensor is stable is satisfied during the fuel cut of the engine, is within a predetermined range. When approaching the reference output value corresponding to, the rich side threshold value and the lean side threshold value are set so as to approach the stoichiometric air-fuel ratio as compared with the case where the predetermined time output value is within the predetermined range. When the predetermined output value is closer to the reference output value than the predetermined range, the change in the output value of the exhaust sensor with respect to the amount of change in the air-fuel ratio of the exhaust compared to when the predetermined output value is within the predetermined range. The amount is assumed to be small. Therefore, by setting the rich side threshold value and the lean side threshold value so as to approach the stoichiometric air-fuel ratio, it is difficult to excessively switch between the execution of the rich correction and the execution of the lean correction when the fuel injection control of the engine is performed. It can be suppressed. As a result, it is possible to prevent the oxygen storage amount of the purification catalyst from being excessively reduced or increased. As a result, it is possible to suppress the deterioration of the exhaust gas purification performance due to the purification catalyst. Here, as the "exhaust sensor", a first sensor in which the output value increases as the air-fuel ratio (oxygen concentration) of the exhaust increases, or a second sensor in which the output value decreases as the air-fuel ratio of the exhaust increases is used. ..

In the first engine device of the present invention, when the predetermined time output value is close to the reference output value with respect to the predetermined range, the predetermined time output value approaches the reference output value. The rich side threshold value and the lean side threshold value may be set so as to be closer to the theoretical air-fuel ratio. In this way, it is possible to more appropriately suppress the deterioration of the exhaust gas purification performance due to the purification catalyst.

In the first engine device of the present invention, when the predetermined time output value is separated from the reference output value with respect to the predetermined range, the control device is within the predetermined range. The rich side threshold value and the lean side threshold value may be set so as to be separated from the stoichiometric air-fuel ratio. When the predetermined output value is separated from the reference output value with respect to the predetermined range, the output value of the exhaust sensor changes with respect to the amount of change in the air-fuel ratio of the exhaust as compared with the case where the predetermined output value is within the predetermined range. The amount is expected to be large. Therefore, by setting the rich side threshold value and the lean side threshold value so as to be separated from the stoichiometric air-fuel ratio, it is easy to excessively switch between the execution of the rich correction and the execution of the lean correction when the fuel injection control of the engine is performed. It can be suppressed. As a result, it is possible to prevent the amount of change (decrease or increase) in the oxygen storage amount of the purification catalyst from becoming excessively small. As a result, it is possible to prevent the purification catalyst from being unable to sufficiently exhibit the exhaust gas purification performance.

In this case, in the control device, when the predetermined time output value is separated from the reference output value with respect to the predetermined range, the more the predetermined time output value is separated from the reference output value, the more the theory The rich side threshold value and the lean side threshold value may be set so as to be further separated from the air-fuel ratio. In this way, it is possible to more appropriately prevent the purification catalyst from being unable to sufficiently exhibit the exhaust gas purification performance.

The second engine device of the present invention is
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 that is attached to the exhaust system and outputs an output value based on the air-fuel ratio of the exhaust,
When the engine is operated, if the detected air-fuel ratio corresponding to the execution output value based on the output value reaches the rich side threshold value or less during the execution of the rich correction for the fuel injection amount of the fuel injection valve, the fuel A control device that switches to the execution of the lean correction for the injection amount and switches to the execution of the rich correction when the detected air-fuel ratio reaches the lean side threshold value or more during the execution of the lean correction.
It is an engine device equipped with
In the control device, the predetermined output value, which is the output value when a predetermined condition in which the output value is stable is satisfied during the fuel cut of the engine, is a reference output corresponding to the stoichiometric air-fuel ratio with respect to the predetermined range. When the value is close to the value, the execution is performed so that the execution output value is separated from the reference output value for the same output value as compared with the case where the predetermined output value is within the predetermined range. Set the output value for
The gist is that.

In the second engine device of the present invention, the predetermined air-fuel ratio, which is the output value when the predetermined condition in which the output value of the exhaust sensor is stable is satisfied during the fuel cut of the engine, is the theoretical air-fuel ratio with respect to the predetermined range. When the output value at a predetermined time is close to the reference output value corresponding to, the execution output value is separated from the reference output value for the same output value as compared with the case where the predetermined output value is within the predetermined range. Set the output value. When the predetermined output value is closer to the reference output value than the predetermined range, the change in the output value of the exhaust sensor with respect to the amount of change in the air-fuel ratio of the exhaust compared to when the predetermined output value is within the predetermined range. The amount is assumed to be small. Therefore, by setting the execution output value so that the execution output value is separated from the reference output value for the same output value, rich correction is executed and lean when fuel injection control of the engine is performed. It is possible to prevent the execution of correction from becoming excessively difficult to switch. As a result, it is possible to prevent the oxygen storage amount of the purification catalyst from being excessively reduced or increased. As a result, it is possible to suppress the deterioration of the exhaust gas purification performance due to the purification catalyst. Here, as the "exhaust sensor", a first sensor in which the output value increases as the air-fuel ratio (oxygen concentration) of the exhaust increases, or a second sensor in which the output value decreases as the air-fuel ratio of the exhaust increases is used. ..

In the second engine device of the present invention, when the predetermined time output value approaches the reference output value with respect to the predetermined range, the predetermined time output value approaches the reference output value. The more the execution output value is, the more the execution output value may be set so that the execution output value is further separated from the reference output value with respect to the same output value. In this way, it is possible to more appropriately suppress the deterioration of the exhaust gas purification performance due to the purification catalyst.

In the second engine device of the present invention, when the predetermined time output value is separated from the reference output value with respect to the predetermined range, the control device is within the predetermined range. The execution output value may be set so that the execution output value approaches the reference output value with respect to the same output value. When the predetermined output value is separated from the reference output value with respect to the predetermined range, the output value of the exhaust sensor changes with respect to the amount of change in the air-fuel ratio of the exhaust as compared with the case where the predetermined output value is within the predetermined range. The amount is expected to be large. Therefore, by setting the execution output value so that the execution output value approaches the reference output value for the same output value, rich correction is executed and lean when fuel injection control of the engine is performed. It is possible to prevent the execution of correction from becoming excessively easy to switch. As a result, it is possible to prevent the amount of change (decrease or increase) in the oxygen storage amount of the purification catalyst from becoming excessively small. As a result, it is possible to prevent the purification catalyst from being unable to sufficiently exhibit the exhaust gas purification performance.

In the second engine device of the present invention, when the predetermined time output value is separated from the reference output value with respect to the predetermined range, the control device is separated from the predetermined range. As the result, the execution output value may be set so that the execution output value is closer to the reference output value with respect to the same output value. In this way, it is possible to more appropriately prevent the purification catalyst from being unable to sufficiently exhibit the exhaust gas purification performance.

The third engine device of the present invention is
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 that is attached to the exhaust system and outputs an output value based on the air-fuel ratio of the exhaust,
When operating the engine, if the detected air-fuel ratio corresponding to the output value 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. A control device that switches to execution and switches to execution of the rich correction when the detected air-fuel ratio reaches or more than the lean side threshold during the execution of the lean correction.
It is an engine device equipped with
In the control device, the predetermined output value, which is the output value when a predetermined condition in which the output value is stable is satisfied during the fuel cut of the engine, is a reference output corresponding to the stoichiometric air-fuel ratio with respect to the predetermined range. When the value is approaching, the execution of the rich correction and the execution of the lean correction are switched using the integrated value of the intake air amount.
The gist is that.

In the third engine device of the present invention, the predetermined air-fuel ratio, which is the output value when the predetermined condition in which the output value of the exhaust sensor is stable is satisfied during the fuel cut of the engine, is the theoretical air-fuel ratio with respect to the predetermined range. When the reference output value corresponding to is approaching, the execution of the rich correction and the execution of the lean correction are switched using the integrated value of the intake air amount. When the predetermined output value is closer to the reference output value than the predetermined range, the change in the output value of the exhaust sensor with respect to the amount of change in the air-fuel ratio of the exhaust compared to when the predetermined output value is within the predetermined range. The amount is assumed to be small. Therefore, by switching between the execution of the rich correction and the execution of the lean correction using the integrated value of the intake air amount, the execution of the rich correction and the execution of the lean correction are excessive when the fuel injection control of the engine is performed. It can be suppressed that it becomes difficult to switch to. As a result, it is possible to prevent the oxygen storage amount of the purification catalyst from being excessively reduced or increased. As a result, it is possible to suppress the deterioration of the exhaust gas purification performance due to the purification catalyst. Here, as the "exhaust sensor", a first sensor in which the output value increases as the air-fuel ratio (oxygen concentration) of the exhaust increases, or a second sensor in which the output value decreases as the air-fuel ratio of the exhaust increases is used. ..

In any of the first to third engine devices of the present invention, the control device considers the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst, and the rich side threshold value and the said. The lean side threshold value may be set. 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 21 as the 1st Example of this invention. It is a block diagram which shows the outline of the structure of the engine device 21. It is explanatory drawing which shows an example of the characteristic of the upstream side air-fuel ratio sensor 152 and the downstream side air-fuel ratio sensor 154. It is explanatory drawing which shows an example of the conversion map. It is a control block diagram which shows an example of the control block at the time of performing the fuel injection control of an engine 22. It is a flowchart which shows an example of a sub-feedback correction routine. 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 sub-offset amount setting routine. It is explanatory drawing which shows an example of the map for setting the basic sub-offset amount. It is explanatory drawing which shows an example of the map for setting the basic sub-offset amount. It is explanatory drawing which shows an example of the map for setting a correction coefficient. It is explanatory drawing which shows an example of the characteristic of the downstream side air-fuel ratio sensor 154. It is a block diagram which shows the outline of the structure of the engine device 21B of a modification. It is explanatory drawing which shows an example of the characteristic of an oxygen sensor 155. It is explanatory drawing which shows an example of the conversion map. It is a flowchart which shows an example of the sub-offset amount setting routine. It is explanatory drawing which shows an example of the map for setting a correction coefficient. It is a flowchart which shows an example of the air-fuel ratio setting routine for execution. It is explanatory drawing which shows an example of the map for setting a correction coefficient. It is a flowchart which shows an example of the air-fuel ratio setting routine for execution. It is explanatory drawing which shows an example of the map for setting a correction coefficient. It is a flowchart which shows an example of a sub-feedback correction routine. It is a flowchart which shows an example of the current low change abnormality flag setting routine. It is a flowchart which shows an example of the voltage change abnormality flag setting routine.

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 the first 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 first 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 a hybrid (hereinafter, "" It is equipped with (called "HVECU") 70.

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.

An upstream air-fuel ratio sensor 152 is attached to the upstream side of the purification device 136 of the exhaust pipe 134 of the engine 22, and is downstream of the purification device 136 of the exhaust pipe 134 and upstream of the purification device 138. , The downstream air-fuel ratio sensor 154 is attached. In the first embodiment, the upstream air-fuel ratio sensor 152 and the downstream air-fuel ratio sensor 154 are assumed to use sensors having the same specifications. FIG. 3 is an explanatory diagram showing an example of the characteristics of the air-fuel ratio (oxygen concentration) -output currents Iafu and Iafd of the upstream air-fuel ratio sensor 152 and the downstream air-fuel ratio sensor 154. As shown in FIG. 3, in the upstream air-fuel ratio sensor 152 and the downstream air-fuel ratio sensor 154, the larger the air-fuel ratio (oxygen concentration) of the exhaust on the upstream side and the downstream side of the purification catalyst 136a, the output current Iafu, respectively. When Iafd increases linearly and the air-fuel ratio of the exhaust is the stoichiometric air-fuel ratio AFth, the output currents Iafu and Iafd are configured as sensors having values of 0 as the reference currents Iafth and Iafdth.

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 output current Iafu from the upstream air-fuel ratio sensor 152 and the output current Iafd from the downstream air-fuel ratio sensor 154 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. Further, using the conversion map of FIG. 4, the output current Iafu from the upstream air-fuel ratio sensor 152 is converted to the detected air-fuel ratio AFu, and the output current Iafd from the downstream air-fuel ratio sensor 154 is converted to the detected air-fuel ratio AFd. .. The conversion map of FIG. 4 is predetermined as the relationship between the output currents Iafu and Iafd and the detected air-fuel ratios AFu and AFd, and is stored in a ROM (not shown).

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

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. 5 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 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 AFth is used in the first embodiment. 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 detected air-fuel ratio AFu corresponding to the output current Iafu from the upstream air-fuel ratio sensor 152 to the control air-fuel ratio AFu *, and calculates the corrected value δaf. Is multiplied by the value (-1) 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 corresponding to the output current Iafd from the downstream air-fuel ratio sensor 154, and the control air-fuel ratio. Lean correction, which sets the lean value in AFu *, 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 sub-offset amount setting unit 95 sets the sub-offset amounts εR and εL used in the sub-feedback unit 92. The details of the sub-offset amount setting unit 95 will be described later. The oxygen occlusion estimation unit 96 is from the detected air-fuel ratio AFu corresponding to the output current Iafu from the upstream air-fuel ratio sensor 152 and the detected air-fuel ratio AFd corresponding to the output current Iafd from the downstream air-fuel ratio sensor 154 and the air flow meter 148. The oxygen storage amount OS of the purification catalyst 136a is estimated based on the intake air amount Qa of the above, 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. 6 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 first 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. 6, the sub-feedback unit 92 first inputs the detected air-fuel ratio AFd corresponding to the output current Iafd from the downstream air-fuel ratio sensor 154 (step S100), and sets the rich correction flag Fr. Check the value (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 (AFth-εR) obtained by subtracting the sub-offset amount εR from the theoretical air-fuel ratio AFth. (Step S120). Here, the sub-offset amount εR is set by the sub-offset amount setting unit 95 as described above. The process of step S120 is a process of 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 downstream of the purification catalyst 136a has increased to some extent. Is.

When the detected air-fuel ratio AFd is larger than the rich side threshold value (AFth-εR) in step S120, it is determined that the detected air-fuel ratio AFd has not yet reached a value on the rich side to some extent, and the main offset amount δR is calculated from the theoretical air-fuel ratio AFth. The subtracted value (AFth-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 (AFth-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 (AFth + δL) obtained by adding the main offset amount δL to the stoichiometric air-fuel ratio AFth 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. For example, the main offset amount δL is set to a value obtained by adding a margin to the sub-offset amount εL. As described above, the sub-offset amount εL is set by the sub-offset amount setting unit 95. 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 (AFth + εL) obtained by adding the sub-offset amount εL to the theoretical air-fuel ratio AFth. (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 (AFth + 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 (AFth + 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 (AFth + 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 (AFth-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. 7 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 (AFth + 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 (AFth-εR) or less (time t2) during the execution of the rich correction, 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 downstream of the purification catalyst 136a are sufficiently small. Become. As a result, as shown in the figure, when the detected air-fuel ratio AFd is near the stoichiometric reference value AFth, 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 sub-offset amount setting unit 95 will be described. FIG. 8 is a flowchart showing an example of a sub-offset amount setting routine executed by the sub-offset amount setting unit 95. This routine is executed repeatedly.

In the sub-offset amount setting routine of FIG. 8, the sub-offset amount setting unit 95 first sets the intake air amount Qa, the output current Iafd, the maximum oxygen storage amount OSmax, the fuel injection control flag Ffi, the first predetermined condition flag Ffc1, and the like. Enter the data (step S200). Here, a value detected by the air flow meter 148 is input as the intake air amount Qa. The value detected by the downstream air-fuel ratio sensor 154 is input to the output current Iafd. The value estimated by the oxygen storage amount estimation unit 96 is input to the maximum oxygen storage amount OSmax.

For the fuel injection control flag Ffi, a value set by the fuel injection control flag setting routine (not shown) is input. In the fuel injection control flag setting routine, the engine ECU 24 sets a value of 1 in the fuel injection control flag Ffi when performing fuel injection control of the engine 22, and a value in the fuel injection control flag Ffi when the fuel injection control of the engine 22 is not performed. 0 is set.

For the first predetermined condition flag Ffc1, a value set by the first predetermined condition flag setting routine (not shown) is input. In the first predetermined condition flag setting routine, the engine ECU 24 sets the value 1 in the first predetermined condition flag Ffc1 when the first predetermined condition is satisfied, and when the first predetermined condition is not satisfied, the engine ECU 24 is the first. A value of 0 is set in the predetermined condition flag Ffc1. As the first predetermined condition, a condition in which the output current Iafd from the downstream air-fuel ratio sensor 154 is stable during the fuel cut of the engine 22 is used. For example, the first predetermined condition includes a condition in which Tfc1 elapses for a predetermined time from the start of the fuel cut of the engine 22, and an output current change rate ΔIafd which is a change amount of the output current Iafd per unit time during the fuel cut of the engine 22. A condition is used in which Tfc2 has elapsed for a predetermined time after the absolute value of is equal to or less than the threshold value ΔIafdref.

The predetermined time Tfc1 is the time required for the output current Iafd to stabilize. The threshold value ΔIafdref is an upper limit value at which it can be determined that the absolute value of the output current change rate ΔIafd has become sufficiently small. The predetermined time Tfc2 is the time required to determine that the absolute value of the output current change rate ΔIafd has become sufficiently small. The predetermined time Tfc1, Tfc2 and the threshold value ΔIafdref are predetermined by experiments and analysis. The fuel cut of the engine 22 is performed, for example, when the accelerator is turned off in the HV driving mode.

When the data is input in this way, the value of the first predetermined condition flag Ffc1 is checked (step S210). Then, when the first predetermined condition flag Ffc1 has a value of 1, it is determined that the first predetermined condition is satisfied, and the output current Iafd is set to the predetermined current Iafdfc (step S220). When the value of the first predetermined condition flag Ffc1 is 0, it is determined that the first predetermined condition is not satisfied, and the process of step S220 is not executed. In this case, the predetermined current Iafdfc is maintained.

Subsequently, the value of the fuel injection control flag Ffi is examined (step S230). When the fuel injection control flag Ffi has a value of 0, it is determined that the fuel injection control of the engine 22 is not performed, and this routine is terminated. When the fuel injection control of the engine 22 is performed, it is not necessary to execute the sub-feedback correction routine of FIG. 6 by the sub-feedback unit 92. Therefore, in the first embodiment, the sub-offset amounts εR and εL are not set.

When the fuel injection control flag Ffi is a value 1 in step S230, it is determined that the fuel injection control of the engine 22 is performed, and the intake air amount Qa, the maximum oxygen storage amount OSmax, and the basic sub-offset amount setting map of FIG. 9 are used. The basic sub-offset amount εRb is set (step S240), and the basic sub-offset amount εLb is set using the intake air amount Qa and the basic sub-offset amount setting map of FIG. 10 (step S250). Subsequently, the correction coefficients αR and αL are set using the predetermined current Iafdfc and the correction coefficient setting map of FIG. 11 (step S260). Then, as shown in the equations (2) and (3), the value obtained by multiplying the basic sub-offset quantities εRb and εLb by the correction coefficients αR and αL is set in the sub-offset quantities εR and εL (step S270). End the routine.

εR = εRb ・ αR (2)
εL = εLb ・ αL (3)

The map for setting the basic sub-offset amount of FIG. 9 is preset as the relationship between the intake air amount Qa and the maximum oxygen storage amount OSmax and the basic sub-offset amount εRb, and is stored in a ROM (not shown). The map for setting the basic sub-offset amount of FIG. 10 is preset as the relationship between the intake air amount Qa and the basic sub-offset amount εLb, and is stored in a ROM (not shown).

As shown in FIG. 9, the basic sub-offset amount εRb is set so as to increase as the intake air amount Qa increases and as the maximum oxygen storage amount OSmax increases. Therefore, as can be seen from the equation (2), the larger the intake air amount Qa and the larger the maximum oxygen storage amount OSmax, the larger the sub-offset amount εR and the smaller the rich side threshold value (AFth-εR) (theoretical air-fuel ratio). Separate from AFth).

As shown in FIG. 10, the basic sub-offset amount εLb is set so as to increase as the intake air amount Qa increases. Therefore, as can be seen from the equation (3), the larger the intake air amount Qa, the larger the sub-offset amount εL and the larger the lean side threshold value (AFth + εL) (away from the theoretical air-fuel ratio AFth).

Hereinafter, the reason why the relationship between the intake air amount Qa and the maximum oxygen storage amount OSmax and the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) will be described. The larger the intake air amount Qa, the larger the amount of decrease or increase in the oxygen storage amount OS of the purification catalyst 136a during execution of rich correction or lean correction per unit time. Further, the larger the maximum oxygen storage amount OSmax, the easier it is for oxygen to be stored in the purification catalyst 136a. Therefore, the larger the intake air amount Qa and the larger the maximum oxygen storage amount OSmax, the smaller the rich side threshold value (AFth-εR), and the larger the intake air amount Qa, the larger the lean side threshold value (AFth + εL). 136a can more fully exhibit the purification performance of the exhaust gas.

The correction coefficient setting map of FIG. 11 is preset as a relationship between the predetermined current Iafdfc and the correction coefficients αR and αL, and is stored in a ROM (not shown). In the figure, the first predetermined range Rfc1 is preset by experiment or analysis as the range of the predetermined current Iafdfc when the downstream air-fuel ratio sensor 154 is normal. As shown in the figure, when the predetermined current Iafdfc is within the first predetermined range Rfc1, the correction coefficients αR and αL are set to values 1. In this case, as can be seen from the equations (2) and (3), the basic sub-offset quantities εRb and εLb and the sub-offset quantities εR and εL are the same.

Further, as shown in the figure, when the predetermined current Iafdfc is smaller than the first predetermined range Rfc1 (when the reference current Iafdt (value 0) is closer to the first predetermined range Rfc1), the correction coefficient The values of αR and αL are set to be smaller than the value 1 as the predetermined current Iafdfc is smaller. In this case, as the predetermined time current Iafdfc is smaller than when the predetermined time current Iafdfc is within the first predetermined range Rfc1, the sub-offset amounts εR and εL are smaller and the rich side threshold value (AFth-εR) is larger. The lean side threshold (AFth + εL) becomes smaller as it becomes larger. That is, the smaller the predetermined current Iafdfc, the closer the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are to the stoichiometric air-fuel ratio AFth.

Further, as shown in the figure, when the predetermined current Iafdfc is larger than the first predetermined range Rfc1 (when it is separated from the reference current Iafdth with respect to the first predetermined range Rfc1), the correction coefficients αR and αL are set. , The larger the predetermined current Ifdfc is, the larger the value is set with respect to the value 1. In this case, as the predetermined time current Iafdfc is larger than when the predetermined time current Iafdfc is within the first predetermined range Rfc1, the sub-offset amounts εR and εL are larger, and the rich side threshold value (AFth-εR) is larger. As it becomes smaller, the lean side threshold value (AFth + εL) becomes larger. That is, the larger the predetermined current Iafdfc, the farther the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are from the stoichiometric air-fuel ratio AFth.

Hereinafter, the reason why the relationship between the predetermined current Iafdfc and the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) will be described. FIG. 12 is an explanatory diagram showing an example of the characteristics of the air-fuel ratio (oxygen concentration) -output current Iafd of the downstream air-fuel ratio sensor 154. In the figure, the solid line shows the characteristics when the downstream air-fuel ratio sensor 154 is normal, the broken line shows the characteristics when the current low change abnormality occurs in the downstream air-fuel ratio sensor 154, and the alternate long and short dash line is the downstream. The characteristics when a high current change abnormality occurs in the side air-fuel ratio sensor 154 are shown. Here, the low current change abnormality and the high current change abnormality are the output current Iafd and the reference current Iafdth (value 0) when the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is different from the stoichiometric air-fuel ratio AFth, respectively. This is an abnormality in which the difference between the two becomes smaller and larger than in the normal state.

As described above, in the first embodiment, as the first predetermined condition, a condition in which the output current Iafd from the downstream air-fuel ratio sensor 154 is stable during the fuel cut of the engine 22 is used. Therefore, when the predetermined current Iafdfc is within the first predetermined range Rfc1, it is assumed that the downstream air-fuel ratio sensor 154 is normal (see the solid line in FIG. 12). In this case, the detected air-fuel ratio AFd (oxygen concentration corresponding to the detected air-fuel ratio AFd) corresponding to the air-fuel ratio (oxygen concentration) of the exhaust gas downstream of the purification catalyst 136a and the output current Iafd from the downstream air-fuel ratio sensor 154). Is almost the same. In this way, the maps of FIGS. 3 and 4 are set.

When the predetermined current Iafdfc is smaller than the first predetermined range Rfc1 (when the reference current Iafdth is closer to the first predetermined range Rfc1), a low current change abnormality occurs in the downstream air-fuel ratio sensor 154. (See the dashed line in FIG. 12). At this time, the difference between the detected air-fuel ratio AFd and the theoretical air-fuel ratio AFth becomes smaller than the difference between the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the theoretical air-fuel ratio AFth. Therefore, if the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set without using the predetermined current Iafdfc, the following inconveniences may occur when the fuel injection control of the engine 22 is performed. There is.

During execution of rich correction, when the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is smaller than the rich side threshold value (AFth-εR), the detected air-fuel ratio AFd becomes the rich side threshold value (AFth-εR). , The oxygen storage amount OS of the purification catalyst 136a may be excessively reduced. Further, during the execution of the lean correction, when the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is larger than the lean side threshold value (AFth + εL), the detected air-fuel ratio AFd becomes the lean side threshold value (AFth + εL) for purification. The oxygen storage amount OS of the catalyst 136a may be excessively increased. That is, it becomes difficult to excessively switch between the execution of the rich correction and the execution of the lean correction, the oxygen storage amount OS of the purification catalyst 136a may be excessively reduced or increased, and the exhaust gas purification performance by the purification catalyst 136a may be deteriorated. There is sex.

In the first embodiment, when the predetermined time current Iafdfc is smaller than the first predetermined range Rfc1, the rich side threshold value (AFth-εR) and lean are compared with the case where the predetermined time current Iafdfc is within the first predetermined range Rfc1. By bringing the side threshold value (AFth + εL) close to the theoretical air-fuel ratio AFth, it is possible to prevent the execution of rich correction and the execution of lean correction from becoming excessively difficult to switch, and the oxygen storage amount OS of the purification catalyst 136a is excessively reduced. It can be suppressed from increasing or increasing. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

Moreover, when the predetermined time current Iafdfc is smaller than the first predetermined range Rfc1, the smaller the predetermined time current Iafdfc is, the closer the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are to the theoretical air-fuel ratio AFth. Therefore, it is possible to more appropriately suppress the deterioration of the exhaust gas purification performance by the purification catalyst 136a.

When the predetermined current Iafdfc is larger than the first predetermined range Rfc1 (when it is separated from the reference current Iath with respect to the first predetermined range Rfc1), a current height change abnormality occurs in the downstream air-fuel ratio sensor 154. (See the alternate long and short dash line in FIG. 12). At this time, the difference between the detected air-fuel ratio AFd and the theoretical air-fuel ratio AFth becomes larger than the difference between the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the theoretical air-fuel ratio AFth. Therefore, if the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set without using the predetermined current Iafdfc, the following inconveniences may occur when the fuel injection control of the engine 22 is performed. There is.

During execution of rich correction, when the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is larger than the rich-side threshold (AFth-εR), the detected air-fuel ratio AFd becomes the rich-side threshold (AFth-εR). There is a possibility that the amount of decrease in the oxygen storage amount OS of the purification catalyst 136a is smaller than that in the case where the downstream air-fuel ratio sensor 154 is normal. Further, during the execution of the lean correction, when the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is smaller than the lean side threshold (AFth + εL), the detected air-fuel ratio AFd becomes the lean side threshold (AFth + εL), and the downstream side becomes the lean side threshold (AFth + εL). There is a possibility that the amount of increase in the oxygen storage amount OS of the purification catalyst 136a is smaller than that when the side air-fuel ratio sensor 154 is normal. That is, the execution of the rich correction and the execution of the lean correction are likely to be excessively switched, the change amount (decrease amount or increase amount) of the oxygen storage amount OS of the purification catalyst 136a becomes excessively small, and the purification catalyst 136a purifies the exhaust gas. There is a possibility that the performance is not fully exhibited.

In the first embodiment, when the predetermined time current Iafdfc is larger than the first predetermined range Rfc1, the rich side threshold value (AFth-εR) and lean are compared with the case where the predetermined time current Iafdfc is within the first predetermined range Rfc1. By separating the side threshold value (AFth + εL) from the theoretical air-fuel ratio AFth, it is possible to prevent the execution of rich correction and the execution of lean correction from being excessively switched, and the amount of change in the oxygen storage amount OS of the purification catalyst 136a is excessive. It can be suppressed to decrease. As a result, it is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

Moreover, when the predetermined time current Iafdfc is larger than the first predetermined range Rfc1, the larger the predetermined time current Iafdfc is, the more the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are separated from the stoichiometric air-fuel ratio AFth. As a result, it is possible to more appropriately prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

In the engine device 21 mounted on the hybrid vehicle 20 of the first embodiment described above, when the predetermined time current Iafdfc is smaller than the first predetermined range Rfc1 (approaching the reference current Iafdth with respect to the first predetermined range Rfc1). When the predetermined time current Iafdfc is within the first predetermined range Rfc1, the rich side threshold value (AFth−εR) and the lean side threshold value (AFth + εL) are brought closer to the stoichiometric air-fuel ratio AFth. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

Further, in the engine device 21 of the first embodiment, when the predetermined current Iafdfc is larger than the first predetermined range Rfc1 (when it is separated from the reference current Iath with respect to the first predetermined range Rfc1), it is predetermined. The rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are separated from the stoichiometric air-fuel ratio AFth as compared with the case where the hourly current Iafdfc is within the first predetermined range Rfc1. As a result, it is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

In the engine device 21 of the first embodiment, when the predetermined time current Iafdfc is smaller than the first predetermined range Rfc1, the smaller the predetermined time current Iafdfc, the richer the threshold value (AFth-εR) and the lean side threshold value (AFth + εL). It was assumed that the air-fuel ratio was closer to AFth. However, the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set to the stoichiometric air-fuel ratio AFth by a predetermined amount γR1 and a predetermined amount γL1 as compared with the case where the predetermined time current Iafdfc is within the first predetermined range Rfc1. It may be brought closer.

In the engine device 21 of the first embodiment, when the predetermined time current Iafdfc is larger than the first predetermined range Rfc1, the larger the predetermined time current Iafdfc is, the richer the threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set. It was set to be farther from the theoretical air-fuel ratio AFth. However, the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set from the stoichiometric air-fuel ratio AFth by a predetermined amount γR2 and a predetermined amount γL2 as compared with the case where the predetermined time current Iafdfc is within the first predetermined range Rfc1. It may be separated. Further, the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) may be set in the same manner as when the predetermined time current Iafdfc is within the first predetermined range Rfc1.

The hybrid vehicle 20 of the first embodiment is provided with the engine device 21 illustrated in FIG. However, instead of this, the engine device 21B of the modified example illustrated in FIG. 13 may be provided. In the engine device 21B of FIG. 13, an oxygen sensor 155 is attached instead of the downstream air-fuel ratio sensor 154 on the downstream side of the purification device 136 of the exhaust pipe 134 and on the upstream side of the purification device 138. It has the same hardware configuration as the engine device 21 of 2. Therefore, among the engine device 21B of FIG. 13, the same hardware configuration as that of the engine device 21 of FIG. 2 is designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 14 is an explanatory diagram showing an example of the characteristics of the air-fuel ratio (oxygen concentration) -output voltage Vo of the oxygen sensor 155. In the figure, the solid line shows the characteristics when the oxygen sensor 155 is normal. As shown in the figure, in the oxygen sensor 155, when the air-fuel ratio (oxygen concentration) of the exhaust gas downstream of the purification catalyst 136a is larger, the output voltage Vo becomes smaller and the air-fuel ratio of the exhaust gas is the stoichiometric air-fuel ratio AFth. It is configured as a sensor in which the output voltage Vo becomes the reference voltage Voth (for example, 0.5 V or the like). Further, in the figure, the broken line shows the characteristic when the voltage low change abnormality occurs in the oxygen sensor 155, and the alternate long and short dash line shows the characteristic when the voltage high change abnormality occurs in the oxygen sensor 155. Here, in the voltage low change abnormality and the voltage high change abnormality, the difference between the output voltage Vo and the reference voltage Voth is normal when the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is different from the stoichiometric air-fuel ratio AFth, respectively. It is an abnormality that becomes smaller and larger than sometimes.

The engine ECU 24 converts the output voltage Vo from the oxygen sensor 155 into the detected air-fuel ratio AFd using the conversion map of FIG. The conversion map of FIG. 15 is predetermined as the relationship between the output voltage Vo and the detected air-fuel ratio AFd when the oxygen sensor 155 is normal, and is stored in a ROM (not shown).

In this modification, the sub-offset amount setting unit 95 executes the sub-offset amount setting routine of FIG. 16 instead of the sub-offset amount setting routine of FIG. The sub-offset amount setting routine of FIG. 16 is the same as the sub-offset amount setting routine of FIG. 8 except that the processing of steps S200, S210, S220, and S260 is replaced with the processing of steps S202, S212, S222, and S262. Is. Therefore, among the sub-offset amount setting routines of FIG. 16, the same processes as those of the sub-offset amount setting routine of FIG. 8 are assigned the same step numbers, and detailed description thereof will be omitted.

In the sub-offset amount setting routine of FIG. 16, the sub-offset amount setting unit 95 first inputs the intake air amount Qa, the maximum oxygen storage amount OSmax, and the fuel injection control flag Ffi, and also inputs the output voltage Vo and the second predetermined condition. The flag Ffc2 is input (step S202). Here, the intake air amount Qa, the maximum oxygen storage amount OSmax, and the fuel injection control flag Ffi are input in the same manner as in the process of step S200 of the sub-offset amount setting routine of FIG. A value detected by the oxygen sensor 155 is input as the output voltage Vo.

For the second predetermined condition flag Ffc2, a value set by the second predetermined condition flag setting routine (not shown) is input. In the second predetermined condition flag setting routine, the engine ECU 24 sets the value 1 in the second predetermined condition flag Ffc2 when the second predetermined condition is satisfied, and when the second predetermined condition is not satisfied, the engine ECU 24 sets the second predetermined condition flag. A value of 0 is set in the predetermined condition flag Ffc2. As the second predetermined condition, a condition in which the output voltage Vo from the oxygen sensor 155 is stable during the fuel cut of the engine 22 is used. For example, the second predetermined condition includes a condition in which Tfc3 elapses for a predetermined time from the start of the fuel cut of the engine 22, and an output voltage change rate ΔVo which is an amount of change in the output voltage Vo per unit time during the fuel cut of the engine 22. A condition is used in which Tfc4 has elapsed for a predetermined time after the absolute value of is equal to or less than the threshold value ΔVolef.

The predetermined time Tfc3 is the time required for the output voltage Vo to stabilize. The threshold value ΔVoref is an upper limit value at which it can be determined that the absolute value of the output voltage change rate ΔVo has become sufficiently small. The predetermined time Tfc4 is the time required to determine that the absolute value of the output voltage change rate ΔVo has become sufficiently small. The predetermined time Tfc3, Tfc4 and the threshold value ΔVoref are predetermined by experiments and analysis.

When the data is input in this way, the value of the second predetermined condition flag Ffc2 is checked (step S212). Then, when the second predetermined condition flag Ffc2 has a value of 1, it is determined that the second predetermined condition is satisfied, and the output voltage Vo is set to the predetermined voltage Vofc (step S222). When the value of the second predetermined condition flag Ffc2 is 0, it is determined that the second predetermined condition is not satisfied, and the process of step S222 is not executed. In this case, the voltage Vofc is maintained at a predetermined time.

Then, when the fuel injection control flag Ffi is a value 1 in step S230, it is determined that the fuel injection control of the engine 22 is performed, and the basic sub-offset amounts εRb and εLb are set by the processing of steps S240 and S250 described above. Subsequently, the correction coefficients αR and αL are set using the predetermined voltage Vofc and the correction coefficient setting map of FIG. 17 (step S262). Then, by the process of step S270 described above, the sub-offset amounts εR and εL are set, and this routine is terminated.

The correction coefficient setting map of FIG. 17 is preset as the relationship between the predetermined voltage Vofc and the correction coefficients αR and αL, and is stored in a ROM (not shown). In the figure, the second predetermined range Rfc2 is preset by experiment or analysis as a range of the predetermined voltage Vofc when the oxygen sensor 155 is normal. As shown in the figure, when the predetermined voltage Vofc is within the second predetermined range Rfc2, the correction coefficients αR and αL are set to values 1. In this case, as can be seen from the equations (2) and (3), the basic sub-offset quantities εRb and εLb and the sub-offset quantities εR and εL are the same.

Further, as shown in the figure, when the predetermined voltage Vofc is larger than the second predetermined range Rfc2 (when the reference voltage Voth is closer to the second predetermined range Rfc2), the correction coefficients αR and αL are set. , The larger the predetermined voltage Vofc is, the smaller the value is set with respect to the value 1. In this case, the larger the predetermined voltage Vofc is, the smaller the sub-offset amounts εR and εL are, and the richer the threshold (AFth-εR) is, as compared with the case where the predetermined voltage Vofc is within the second predetermined range Rfc2. The lean side threshold (AFth + εL) becomes smaller as it becomes larger. That is, the larger the predetermined voltage Vofc, the closer the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are to the stoichiometric air-fuel ratio AFth.

Further, as shown in the figure, when the predetermined voltage Vofc is smaller than the second predetermined range Rfc2 (when it is separated from the reference voltage Voth with respect to the second predetermined range Rfc2), the correction coefficients αR and αL are set. , The smaller the predetermined voltage Vofc is, the larger the value is set with respect to the value 1. In this case, the smaller the predetermined voltage Vofc is, the larger the sub-offset amounts εR and εL are, and the richer the threshold value (AFth-εR) is, as compared with the case where the predetermined voltage Vofc is within the second predetermined range Rfc2. As it becomes smaller, the lean side threshold value (AFth + εL) becomes larger. That is, as the predetermined time voltage Vofc becomes smaller, the rich side threshold value (AFth−εR) and the lean side threshold value (AFth + εL) are further separated from the stoichiometric air-fuel ratio AFth.

Hereinafter, the reason why the relationship between the predetermined voltage Vofc and the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) will be described. In this modification, as the second predetermined condition, a condition in which the output voltage Vo from the oxygen sensor 155 is stable during the fuel cut of the engine 22 is used. Therefore, when the predetermined voltage Vofc is within the second predetermined range Rfc2, it is assumed that the oxygen sensor 155 is normal (see the solid line in FIG. 14). In this case, the air-fuel ratio (oxygen concentration) of the exhaust gas downstream of the purification catalyst 136a and the detected air-fuel ratio AFd (oxygen concentration corresponding to the detected air-fuel ratio AFd) corresponding to the output voltage Vo from the oxygen sensor 155 are abbreviated. Be the same. In this way, the maps of FIGS. 14 and 15 are set.

When the predetermined voltage Vofc is larger than the second predetermined range Rfc2 (when the reference voltage Voth is closer to the second predetermined range Rfc2), it is said that the oxygen sensor 155 has a low voltage change abnormality. Assumed (see dashed line in FIG. 14). At this time, if the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set without using the predetermined voltage Vofc, it is the same as when the current low change abnormality occurs in the downstream air-fuel ratio sensor 154. Challenges can arise.

In this modification, when the predetermined time voltage Vofc is larger than the second predetermined range Rfc2, the rich side threshold value (AFth-εR) and the lean side are compared with the case where the predetermined time voltage Vofc is within the second predetermined range Rfc2. By bringing the threshold value (AFth + εL) close to the theoretical air-fuel ratio AFth, it is possible to prevent the execution of rich correction and the execution of lean correction from becoming excessively difficult to switch, and the oxygen storage amount OS of the purification catalyst 136a is excessively reduced. It can be suppressed from increasing. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

Moreover, when the predetermined time voltage Vofc is larger than the second predetermined range Rfc2, the larger the predetermined time voltage Vofc is, the closer the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are to the theoretical air-fuel ratio AFth. Therefore, it is possible to more appropriately suppress the deterioration of the exhaust gas purification performance by the purification catalyst 136a.

When the predetermined voltage Vofc is smaller than the second predetermined range Rfc2 (when it is separated from the reference voltage Voth with respect to the second predetermined range Rfc2), it is said that the oxygen sensor 155 has a high voltage change abnormality. It is assumed (see the alternate long and short dash line in FIG. 14). At this time, if the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set without using the predetermined voltage Vofc, it is the same as when the current high change abnormality occurs in the downstream air-fuel ratio sensor 154. Challenges can arise.

In this modification, when the predetermined time voltage Vofc is smaller than the second predetermined range Rfc2, the rich side threshold value (AFth-εR) and the lean side are compared with the case where the predetermined time voltage Vofc is within the second predetermined range Rfc2. By separating the threshold value (AFth + εL) from the theoretical air-fuel ratio AFth, it is possible to prevent the execution of rich correction and the execution of lean correction from becoming excessively easy to switch, and the amount of change in the oxygen storage amount OS of the purification catalyst 136a becomes excessive. It is possible to suppress the decrease. As a result, it is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

Moreover, when the predetermined time voltage Vofc is smaller than the second predetermined range Rfc2, the smaller the predetermined time voltage Vofc is, the more the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are separated from the stoichiometric air-fuel ratio AFth. As a result, it is possible to more appropriately prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

In the engine device 21B mounted on the hybrid vehicle 20B of this modified example described above, when the predetermined time voltage Vofc is larger than the second predetermined range Rfc2 (approaching the reference voltage Voth with respect to the second predetermined range Rfc2). When), the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are brought closer to the stoichiometric air-fuel ratio AFth as compared with the case where the predetermined time voltage Vofc is within the second predetermined range Rfc2. As a result, it is possible to prevent the purification catalyst 136a from deteriorating the exhaust gas purification performance of the purification catalyst 136a.

Further, in the engine device 21B of this modification, when the predetermined time voltage Vofc is smaller than the second predetermined range Rfc2 (when it is separated from the reference voltage Voth with respect to the second predetermined range Rfc2), the predetermined time The rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are separated from the stoichiometric air-fuel ratio AFth as compared with the case where the voltage Vofc is within the second predetermined range Rfc2. As a result, it is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

In the engine device 21B of this modification, when the predetermined time voltage Vofc is larger than the second predetermined range Rfc2, the larger the predetermined time voltage Vofc is, the more the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are theoretically determined. The air-fuel ratio was set to be closer to AFth. However, the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set to the stoichiometric air-fuel ratio AFth by a predetermined amount γR3 and a predetermined amount γL3 as compared with the case where the predetermined time voltage Vofc is within the second predetermined range Rfc2. It may be brought closer.

In the engine device 21B of this modification, when the predetermined voltage Vofc is smaller than the second predetermined range Rfc2, the smaller the predetermined voltage Vofc is, the more the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are theoretically determined. The air-fuel ratio was set to be farther from AFth. However, the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) are set from the stoichiometric air-fuel ratio AFth by a predetermined amount γR4 and a predetermined amount γL4 as compared with the case where the predetermined time voltage Vofc is within the second predetermined range Rfc2. It may be separated. Further, the rich side threshold value (AFth-εR) and the lean side threshold value (AFth + εL) may be set in the same manner as when the predetermined time voltage Vofc is within the second predetermined range Rfc2.

Next, the hybrid vehicle 220 equipped with the engine device 221 of the second embodiment will be described. The hybrid vehicle 220 and the engine device 221 of the second embodiment have the same hardware configuration as the hybrid vehicle 20 of the first embodiment illustrated in FIG. 1 and the engine device 21 illustrated in FIG. Therefore, the hardware configurations of the hybrid vehicle 220 and the engine device 221 of the second embodiment are designated by the same reference numerals as those of the hybrid vehicle 20 and the engine device 21 of the first embodiment, and detailed description thereof will be omitted.

The engine device 221 mounted on the hybrid vehicle 220 of the second embodiment differs from the control block of FIG. 5 in the following points as a control block when fuel injection control of the engine 22 is performed by the engine ECU 24. The sub-offset amount setting unit 95 sets the sub-offset amounts εR and εL without using the predetermined current Iafdfc. This can be considered in the same manner as in the case of executing the process of setting the correction coefficients αR and αL to the values 1 regardless of the predetermined current Iafdfc, instead of the process of step S260 of the sub-offset amount setting routine of FIG. it can. Further, the sub-feedback unit 92 executes the sub-feedback correction by using the air-fuel ratio AFd * for execution instead of the detected air-fuel ratio AFd. Here, the air-fuel ratio AFd * for execution is set as follows.

FIG. 18 is a flowchart showing an example of an air-fuel ratio setting routine for execution executed by the engine ECU 24. This routine is executed repeatedly. In the execution air-fuel ratio setting routine of FIG. 18, the engine ECU 24 first inputs data such as the output current Iafd and the first predetermined condition flag Ffc1 (step S300). These data are input in the same manner as in the process of step S200 of the sub-offset amount setting routine of FIG.

When the data is input in this way, the value of the first predetermined condition flag Ffc1 is checked (step S310). Then, when the first predetermined condition flag Ffc1 has a value of 1, it is determined that the first predetermined condition is satisfied, and the output current Iafd is set to the predetermined current Iafdfc (step S320). When the value of the first predetermined condition flag Ffc1 is 0, it is determined that the first predetermined condition is not satisfied, and the process of step S320 is not executed. In this case, the predetermined current Iafdfc is maintained.

Subsequently, the correction coefficient αi was set using the predetermined current Iafdfc and the correction coefficient setting map of FIG. 19 (step S330), and the output current Iafd was multiplied by the correction coefficient αi as shown in the equation (4). The value is set to the execution current Iafd * (step S340). Then, the horizontal axis and the vertical axis of the conversion map of FIG. 4 are replaced with "output current Iafu, Iafd" to "execution current Iafd *" and "detected air-fuel ratio AFd" to "execution air-fuel ratio AFd *", respectively. Is used to convert the execution current Iafd * into the execution air-fuel ratio AFd * (step S350), and this routine is terminated.

Iafd * = Iafd ・ αi (4)

The correction coefficient setting map of FIG. 19 is preset as a relationship between the predetermined current Iafdfc and the correction coefficient αi, and is stored in a ROM (not shown). As shown in the figure, when the predetermined current Iafdfc is within the first predetermined range Rfc1, the correction coefficient αi is set to a value 1. In this case, as can be seen from the equation (4), since the output current Iafd and the execution current Iafd * are the same, the detected air-fuel ratio AFd and the execution air-fuel ratio AFd * are the same.

Further, as shown in the figure, when the predetermined current Iafdfc is smaller than the first predetermined range Rfc1 (when the reference current Iafdt (value 0) is closer to the first predetermined range Rfc1), the correction coefficient A value is set in αi so that the smaller the predetermined current Ifdfc is, the larger the value is with respect to the value 1. In this case, the smaller the predetermined current Iafdfc, the farther the execution current Iafd * is from the reference current Iafdth with respect to the output current Iafd, and the execution air-fuel ratio AFd * is from the theoretical air-fuel ratio AFd with respect to the detected air-fuel ratio AFd. More separated.

Further, as shown in the figure, when the predetermined current Iafdfc is larger than the first predetermined range Rfc1 (when it is separated from the reference current Iafdth with respect to the first predetermined range Rfc1), the correction coefficient αi is set to a predetermined value. The larger the hourly current Iafdfc, the smaller the value is set with respect to the value 1. In this case, the larger the predetermined current Iafdfc is, the closer the execution current Iafd * is to the output current Iafd by the reference current Iafdth, and the execution air-fuel ratio AFd * is closer to the detected air-fuel ratio AFd by the theoretical air-fuel ratio AFth. To do.

Hereinafter, the reason why the relationship between the predetermined current Iafdfc and the air-fuel ratio AFd * for execution will be described will be described. As described above, when the predetermined current Iafdfc is within the first predetermined range Rfc1, it is assumed that the downstream air-fuel ratio sensor 154 is normal (see the solid line in FIG. 12). In this case, by making the air-fuel ratio AFd * for execution the same as the detected air-fuel ratio AFd, the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is substantially the same as the detected air-fuel ratio AFd and the air-fuel ratio AFd * for execution. become.

Further, as described above, when the predetermined current Iafdfc is smaller than the first predetermined range Rfc1 (when the reference current Iafdth is closer to the first predetermined range Rfc1), the downstream air-fuel ratio sensor 154 It is assumed that a low current change abnormality has occurred in (see the broken line in FIG. 12). At this time, in the second embodiment, by separating the air-fuel ratio AFd * for execution from the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd, the air-fuel ratio and the detected air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a The deviation between the air-fuel ratio of the exhaust gas and the air-fuel ratio for execution AFd * can be made smaller than the deviation from the AFd.

By using the air-fuel ratio AFd * for execution for the sub-feedback correction by the sub-feedback unit 92, it is difficult to excessively switch between the execution of the rich correction and the execution of the lean correction as compared with the one using the detected air-fuel ratio AFd. It is possible to suppress the oxygen storage amount OS of the purification catalyst 136a from being excessively decreased or increased. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

Moreover, when the predetermined air-fuel ratio Iafdfc is smaller than the first predetermined range Rfc1, the smaller the predetermined air-fuel ratio AFdfc is, the farther the air-fuel ratio AFd * for execution is from the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd. The deviation between the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the air-fuel ratio for execution AFd * can be made smaller, and the deterioration of the exhaust gas purification performance by the purification catalyst 136a can be more appropriately suppressed.

Further, as described above, when the predetermined current Iafdfc is larger than the first predetermined range Rfc1 (when it is separated from the reference current Iafdth with respect to the first predetermined range Rfc1), the downstream air-fuel ratio sensor 154 It is assumed that an abnormal change in current height has occurred in (see the alternate long and short dash line in FIG. 12). At this time, in the second embodiment, by bringing the air-fuel ratio AFd * for execution closer to the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd, the air-fuel ratio and the detected air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a The deviation between the air-fuel ratio of the exhaust gas and the air-fuel ratio for execution AFd * can be made smaller than the deviation from the AFd.

By using the air-fuel ratio AFd * for execution for the sub-feedback correction by the sub-feedback unit 92, the execution of the rich correction and the execution of the lean correction are more likely to be switched excessively as compared with the one using the detected air-fuel ratio AFd. It is possible to sufficiently change the oxygen storage amount OS of the purification catalyst 136a by suppressing the formation. It is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

Moreover, when the predetermined air-fuel ratio Iafdfc is larger than the first predetermined range Rfc1, the larger the predetermined air-fuel ratio AFdfc is, the closer the air-fuel ratio AFd * for execution is to the detected air-fuel ratio AFd by the theoretical air-fuel ratio AFth. It is possible to make the deviation between the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the air-fuel ratio for execution AFd * smaller, and to more appropriately suppress the purification catalyst 136a from being unable to fully exhibit the exhaust gas purification performance. it can.

In the engine device 221 mounted on the hybrid vehicle 220 of the second embodiment described above, when the predetermined time current Iafdfc is smaller than the first predetermined range Rfc1 (approaching the reference current Feedback with respect to the first predetermined range Rfc1). When), the air-fuel ratio AFd * for execution is separated from the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd, and the sub-feedback correction is executed by the sub-feedback unit 92 using this air-fuel ratio AFd * for execution. To do. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

Further, in the engine device 221 of the second embodiment, when the predetermined time current Iafdfc is larger than the first predetermined range Rfc1 (when it is separated from the reference current Iath with respect to the first predetermined range Rfc1), it is executed. The air-fuel ratio AFd * is brought closer to the theoretical air-fuel ratio AFth with respect to the detected air-fuel ratio AFd, and the sub-feedback correction is executed by the sub-feedback unit 92 using the air-fuel ratio AFd * for execution. As a result, it is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

In the engine device 221 of the second embodiment, when the predetermined time current Iafdfc is smaller than the first predetermined range Rfc1, the smaller the predetermined time current Iafdfc is, the more the air-fuel ratio AFd * for execution is detected. The fuel ratio was set to be farther from AFth. However, the air-fuel ratio AFd * for execution may be separated from the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd by a predetermined amount γ5 as compared with the case where the predetermined time current Iafdfc is within the first predetermined range Rfc1. ..

In the engine device 221 of the second embodiment, when the predetermined air-fuel ratio Iafdfc is larger than the first predetermined range Rfc1, the air-fuel ratio AFd * for execution is brought closer to the detected air-fuel ratio AFd by the theoretical air-fuel ratio AFth. .. However, the air-fuel ratio AFd * for execution may be brought closer to the stoichiometric air-fuel ratio AFth with respect to the detected air-fuel ratio AFd by a predetermined amount γ6 as compared with the case where the predetermined time current Iafdfc is within the first predetermined range Rfc1. .. Further, the air-fuel ratio AFd * for execution may be set in the same manner as when the predetermined current Iafdfc is within the first predetermined range Rfc1.

The hybrid vehicle 220 of the second embodiment is provided with the same engine device 221 as the engine device 21 of the first embodiment illustrated in FIG. However, instead of this, the same engine device 221B as the engine device 21B of the modified example of the first embodiment illustrated in FIG. 13 may be provided. Therefore, the hardware configuration of the engine device 221B is designated by the same reference numerals as the engine device 21B of the modified example of the first embodiment, and detailed description thereof will be omitted.

In this modification, the sub-offset amount setting unit 95 executes the execution air-fuel ratio setting routine of FIG. 20 instead of the execution air-fuel ratio setting routine of FIG. In this routine, the sub-offset amount setting unit 95 first inputs data such as the output voltage Vo and the second predetermined condition flag Ffc2 (step S302). These data are input in the same manner as in the process of step S202 of the sub-offset amount setting routine of FIG.

When the data is input in this way, the value of the second predetermined condition flag Ffc2 is checked (step S312). Then, when the second predetermined condition flag Ffc2 has a value of 1, it is determined that the second predetermined condition is satisfied, and the output voltage Vo is set to the predetermined voltage Vofc (step S322). When the value of the second predetermined condition flag Ffc2 is 0, it is determined that the second predetermined condition is not satisfied, and the process of step S322 is not executed. In this case, the voltage Vofc is maintained at a predetermined time.

Subsequently, the correction coefficient αv is set using the predetermined voltage Vofc and the correction coefficient setting map of FIG. 21 (step S332), and the equation (5) is used using the output voltage Vo, the reference voltage Voth, and the correction coefficient αv. The value calculated by is set to the execution voltage Vo * (step S342). Then, the horizontal axis and the vertical axis of the conversion map of FIG. 15 are replaced with "output voltage Vo" to "execution voltage Vo *" and "detected air-fuel ratio AFd" to "execution air-fuel ratio AFd *", respectively. Then, the execution voltage Vo * is converted into the execution air-fuel ratio AFd * (step S352), and this routine is terminated.

Vo * = Voth + (Vo-Voth) ・ αv (5)

The correction coefficient setting map of FIG. 21 is preset as a relationship between the predetermined voltage Vofc and the correction coefficient αv, and is stored in a ROM (not shown). As shown in the figure, when the predetermined voltage Vofc is within the second predetermined range Rfc2, the correction coefficient αv is set to a value 1. In this case, as can be seen from the equation (5), since the output voltage Vo and the execution voltage Vo * are the same, the detected air-fuel ratio AFd and the execution air-fuel ratio AFd * are the same.

Further, as shown in the figure, when the predetermined voltage Vofc is larger than the second predetermined range Rfc2 (when the reference voltage Voth is closer to the second predetermined range Rfc2), the correction coefficient αv is corrected. The larger the coefficient αv, the larger the value is set with respect to the value 1. In this case, as the predetermined time voltage Vofc is larger, as can be seen from the equation (5), the execution voltage Vo * is further separated from the reference voltage Voth with respect to the output voltage Vo, and the air-fuel ratio AF * becomes the detected air-fuel ratio AFd. On the other hand, it is farther from the theoretical air-fuel ratio AFth.

Further, as shown in the figure, when the predetermined voltage Vofc is smaller than the second predetermined range Rfc2 (when it is separated from the second predetermined range Rfc2), the smaller the predetermined voltage Vofc is in the correction coefficient αv. A value smaller than the value 1 is set. In this case, as the predetermined voltage Vofc becomes smaller, as can be seen from the equation (5), the execution voltage Vo * approaches the output voltage Vo closer to the reference voltage Voth, and the execution air-fuel ratio AFd * becomes the detected air-fuel ratio AFd. It is closer to the theoretical air-fuel ratio AFth.

Hereinafter, the reason for setting the relationship between the predetermined voltage Vofc and the air-fuel ratio AFd * for execution in this way will be described. As described above, when the predetermined voltage Vofc is within the second predetermined range Rfc2, it is assumed that the oxygen sensor 155 is normal (see the solid line in FIG. 14). In this case, by making the air-fuel ratio AFd * for execution the same as the detected air-fuel ratio AFd, the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a is substantially the same as the detected air-fuel ratio AFd and the air-fuel ratio AFd * for execution. become.

Further, as described above, when the predetermined time voltage Vofc is larger than the second predetermined range Rfc2 (when the reference voltage Voth is closer to the second predetermined range Rfc2), the voltage is low on the oxygen sensor 155. It is assumed that a change abnormality has occurred (see the broken line in FIG. 14). At this time, in this modification, by separating the air-fuel ratio AFd * for execution from the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd, the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the detected air-fuel ratio AFd The deviation between the air-fuel ratio of the exhaust gas and the air-fuel ratio for execution AFd * can be made smaller than the deviation from the above.

By using the air-fuel ratio AFd * for execution for the sub-feedback correction by the sub-feedback unit 92, it is difficult to excessively switch between the execution of the rich correction and the execution of the lean correction as compared with the one using the detected air-fuel ratio AFd. It is possible to suppress the oxygen storage amount OS of the purification catalyst 136a from being excessively decreased or increased. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

Moreover, when the predetermined air-fuel ratio Vofc is larger than the second predetermined range Rfc2, the larger the predetermined air-fuel ratio Vofc is, the farther the air-fuel ratio AFd * for execution is from the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd. The deviation between the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the air-fuel ratio for execution AFd * can be made smaller, and the deterioration of the exhaust gas purification performance by the purification catalyst 136a can be more appropriately suppressed.

Further, as described above, when the predetermined time voltage Vofc is smaller than the second predetermined range Rfc2 (when the voltage is separated from the reference voltage Voth with respect to the second predetermined range Rfc2), the voltage is high on the oxygen sensor 155. It is assumed that an abnormal change has occurred (see the alternate long and short dash line in FIG. 14). At this time, in this modification, by bringing the air-fuel ratio AFd * for execution closer to the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd, the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the detected air-fuel ratio AFd The deviation between the air-fuel ratio of the exhaust gas and the air-fuel ratio for execution AFd * can be made smaller than the deviation from the above.

By using the air-fuel ratio AFd * for execution for the sub-feedback correction by the sub-feedback unit 92, the execution of the rich correction and the execution of the lean correction are more likely to be switched excessively as compared with the one using the detected air-fuel ratio AFd. It is possible to sufficiently change the oxygen storage amount OS of the purification catalyst 136a by suppressing the formation. It is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

Moreover, when the predetermined air-fuel ratio Vofc is smaller than the second predetermined range Rfc2, the smaller the predetermined air-fuel ratio Vofc is, the closer the air-fuel ratio AFd * for execution is to the detected air-fuel ratio AFd by the theoretical air-fuel ratio AFth. It is possible to make the deviation between the air-fuel ratio of the exhaust gas downstream of the purification catalyst 136a and the air-fuel ratio for execution AFd * smaller, and to more appropriately suppress the purification catalyst 136a from being unable to fully exhibit the exhaust gas purification performance. it can.

In the engine device 221B mounted on the hybrid vehicle 220B of this modified example described above, when the predetermined time voltage Feedback is larger than the second predetermined range Rfc2 (approaching the reference voltage Feedback with respect to the second predetermined range Rfc2). When), the air-fuel ratio AFd * for execution is separated from the stoichiometric air-fuel ratio AFd with respect to the detected air-fuel ratio AFd, and the sub-feedback correction is executed by the sub-feedback unit 92 using this air-fuel ratio AFd * for execution. .. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

Moreover, when the predetermined time voltage Feedback is smaller than the second predetermined range Rfc2 (when it is separated from the reference voltage Feedback with respect to the second predetermined range Rfc2), the air-fuel ratio AFd * for execution is detected. The air-fuel ratio AFd * for execution is used to perform sub-feedback correction by the sub-feedback unit 92 while approaching the theoretical air-fuel ratio AFth. As a result, it is possible to prevent the purification catalyst 136a from being unable to sufficiently exhibit the exhaust gas purification performance.

In the engine device 221B of this modification, when the predetermined air-fuel ratio Vofc is larger than the second predetermined range Rfc2, the larger the predetermined time voltage Vofc is, the more the air-fuel ratio AFd * for execution is detected. It was designed to be farther away from AFth. However, the air-fuel ratio AFd * for execution may be separated from the stoichiometric air-fuel ratio AFth with respect to the detected air-fuel ratio AFd by a predetermined amount γ7 as compared with the case where the predetermined time voltage Vofc is within the second predetermined range Rfc2. ..

In the engine device 221B of this modification, when the predetermined air-fuel ratio Vofc is smaller than the second predetermined range Rfc2, the smaller the predetermined time voltage Vofc is, the more the air-fuel ratio AFd * for execution is detected. It was decided to bring it closer to AFth. However, the air-fuel ratio AFd * for execution may be brought closer to the stoichiometric air-fuel ratio AFth with respect to the detected air-fuel ratio AFd by a predetermined amount γ8 as compared with the case where the predetermined time voltage Vofc is within the second predetermined range Rfc2. .. Further, the air-fuel ratio AFd * for execution may be set in the same manner as when the predetermined voltage Vofc is within the second predetermined range Rfc2.

Next, the hybrid vehicle 320 equipped with the engine device 321 of the third embodiment will be described. The hybrid vehicle 320 and the engine device 321 of the third embodiment have the same hardware configuration as the hybrid vehicle 20 of the first embodiment illustrated in FIG. 1 and the engine device 21 illustrated in FIG. Therefore, the hardware configurations of the hybrid vehicle 320 and the engine device 321 of the third embodiment are designated by the same reference numerals as those of the hybrid vehicle 20 and the engine device 21 of the first embodiment, and detailed description thereof will be omitted.

The engine device 321 mounted on the hybrid vehicle 320 of the third embodiment differs from the control block of FIG. 5 in the following points as a control block when fuel injection control of the engine 22 is performed by the engine ECU 24. The sub-offset amount setting unit 95 sets the sub-offset amounts εR and εL without using the predetermined current Iafdfc. This can be considered in the same manner as in the case of executing the process of setting the correction coefficients αR and αL to the values 1 regardless of the predetermined current Iafdfc, instead of the process of step S260 of the sub-offset amount setting routine of FIG. it can. Further, the sub-feedback unit 92 executes the sub-feedback correction routine of FIG. 22 instead of the sub-feedback correction routine of FIG. The sub-feedback correction routine of FIG. 22 is the same as the sub-feedback correction routine of FIG. 6 except that the process of step S100 is replaced with the process of step S102 and the process of steps S400 to S410 is added. .. Therefore, among the sub-feedback correction routines of FIG. 22, the same processes as those of the sub-feedback correction routine of FIG. 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the sub-feedback correction routine of FIG. 22, the sub-feedback unit 92 first inputs data such as the detected air-fuel ratio AFd and the current low change abnormality flag Fi (step S102). Here, the detected air-fuel ratio AFd is input in the same manner as in the process of step S100 of the sub-feedback correction routine of FIG. For the current low change abnormality flag Fi, a value set by the current low change abnormality flag setting routine of FIG. 23 is input. Hereinafter, the description of the sub-feedback correction routine of FIG. 22 will be interrupted, and the current low change abnormality flag setting routine of FIG. 23 will be described.

The current low change abnormality flag setting routine of FIG. 23 is repeatedly executed. In this routine, the engine ECU 24 first inputs data such as the output current Iafd and the first predetermined condition flag Ffc1 (step S600). These data are input in the same manner as in the process of step S200 of the sub-offset amount setting routine of FIG.

When the data is input in this way, the value of the first predetermined condition flag Ffc1 is checked (step S610). When the first predetermined condition flag Ffc1 has a value of 1, it is determined that the first predetermined condition is satisfied, and the output current Iafd is set to the predetermined current Iafdfc (step S620).

Subsequently, the predetermined current Iafdfc is compared with the lower limit value Rfc1min of the first predetermined range Rfc1 (step S630). When the predetermined current Iafdfc is equal to or higher than the lower limit value Rfc1min of the first predetermined range Rfc1, the downstream air-fuel ratio sensor 154 does not have a low current change abnormality (normal or a high current change abnormality has occurred). Judgment is made, the value 0 is set to the current low change abnormality flag Fi (step S640), and this routine is terminated.

When the predetermined current Iafdfc is less than the lower limit value Rfc1min of the first predetermined range Rfc1 in step S630, it is determined that the downstream air-fuel ratio sensor 154 has a current low change abnormality, and a value 1 is set to the current low change abnormality flag Fi. After setting (step S650), this routine ends.

When the value of the first predetermined condition flag Ffc1 is 0 in step S610, it is determined that the first predetermined condition is not satisfied, and this routine is terminated. In this case, the fuel injection control flag Ffi is held.

The current low change abnormality flag setting routine of FIG. 23 has been described. Returning to the description of the sub-feedback correction routine of FIG. 22. When data is input in step S102, the value of the current low change abnormality flag Fi is checked (step S400). When the current low change abnormality flag Fi is a value of 0, it is determined that no current low change abnormality has occurred in the downstream air-fuel ratio sensor 154, and the processes of steps S110 to S170 are executed to end this routine. In this case, the same sub-feedback correction as the sub-feedback correction routine of FIG. 6 is executed.

When the current low change abnormality flag Fi is value 1 in step S400, it is determined that the current low change abnormality has occurred in the downstream air-fuel ratio sensor 154, and the intake air amount Qa from the air flow meter 148 is input (step S410). , The value obtained by adding the input intake air amount Qa to the previous integrated intake air amount (previous Qasum) is set in the new integrated intake air amount Qasum (step S420).

Subsequently, the value of the rich correction flag Fr is examined (step S430). When the rich correction flag Fr is a value 1, it is determined that the rich correction is being executed, and the integrated intake air amount Qasum is compared with the threshold value Qref1 (step S440). Here, the threshold value Qref1 is a threshold value used for determining whether or not the amount of unburned fuel in the exhaust gas downstream of the purification catalyst 136a has increased to some extent.

When the integrated intake air amount Qasum is less than the threshold value Qref1 in step S440, it is determined that the amount of unburned fuel in the exhaust on the downstream side of the purification catalyst 136a has not increased to some extent, and the main offset amount δR2 from the stoichiometric air-fuel ratio AFth. The value obtained by subtracting (AFth-δR2) is set to the control air-fuel ratio AFu * (step S510), and this routine is terminated. Here, the main offset amount δR2 is appropriately set. In this case, the execution of the rich correction is continued.

When the integrated intake air amount Qasum is equal to or higher than the threshold value Qref1 in step S440, it is determined that the amount of unburned fuel in the exhaust on the downstream side of the purification catalyst 136a has increased to some extent, and the rich correction flag Fr is set to a value 0 (step). S450), the integrated intake air amount Qasum is reset to a value 0 (step S460), and the value (AFth + δL2) obtained by adding the main offset amount δL2 to the theoretical air-fuel ratio AFth is set as the control air-fuel ratio AFu * (step S470). , End this routine. Here, the main offset amount δL2 is appropriately set. 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 S430, it is determined that the lean correction is being executed, and the integrated intake air amount Qasum is compared with the threshold value Qref2 (step S480). Here, the threshold value Qref2 is a threshold value used for determining 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 integrated intake air amount Qasum is less than the threshold value Qref2 in step S480, it is determined that the oxygen amount in the exhaust gas on the downstream side of the purification catalyst 136a has not increased to some extent, and the value (AFth + δL2) is determined by the processing in step S470 described above. ) Is set to the control air-fuel ratio AFu * (step S470), and this routine is terminated. In this case, the execution of the lean correction is continued.

When the integrated intake air amount Qasum is equal to or higher than the threshold value Qref2 in step S480, it is determined that the amount of oxygen in the exhaust gas downstream of the purification catalyst 136a has increased to some extent, and a value 1 is set in the rich correction flag Fr (step S490). , The integrated intake air amount Qasum is reset to a value 0 (step S500), the value (AFth-δR2) is set to the control air-fuel ratio AFu * by the process of step S510 described above, and this routine is terminated. In this way, the execution of the lean correction is switched to the execution of the rich correction.

As described above, when the predetermined current Iafdfc is less than the lower limit value Rfc1min of the first predetermined range Rfc1, it is assumed that the downstream air-fuel ratio sensor 154 has a current low change abnormality (see the broken line in FIG. 12). At this time, when the fuel injection control of the engine 22 is being performed, it becomes difficult to excessively switch between the execution of the rich correction and the execution of the lean correction, and the oxygen storage amount OS of the purification catalyst 136a may be excessively reduced or increased. However, the purification performance of the exhaust gas by the purification catalyst 136a may be deteriorated.

In the third embodiment, when the predetermined current Iafdfc is less than the lower limit value Rfc1min of the first predetermined range Rfc1, the rich correction is performed by switching between the execution of the rich correction and the execution of the lean correction using the integrated intake air amount Qasum. It is possible to prevent the execution and the execution of the lean correction from becoming excessively difficult to switch, and to suppress the oxygen storage amount OS of the purification catalyst 136a from being excessively decreased or increased. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

In the engine device 321 mounted on the hybrid vehicle 320 of the third embodiment described above, when the predetermined current Iafdfc is less than the lower limit value Rfc1min of the first predetermined range Rfc1, the rich correction is executed using the integrated intake air amount Qasum. To switch between running lean correction and. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

The hybrid vehicle 320 of the third embodiment is provided with the same engine device 321 as the engine device 21 of the first embodiment illustrated in FIG. However, instead of this, the same engine device 321B as the engine device 21B of the modified example of the first embodiment illustrated in FIG. 13 may be provided. Therefore, the hardware configuration of the engine device 221B is designated by the same reference numerals as the engine device 21B of the modified example of the first embodiment, and detailed description thereof will be omitted.

In the engine device 321B of this modification, the sub-feedback unit 92 executes a routine in which the “current low change abnormality flag Fi” of the sub-feedback correction routine of FIG. 22 is replaced with the “voltage low change abnormality flag Fv”. Then, the value set by the voltage low change abnormality flag setting routine of FIG. 24 is input to the voltage low change abnormality flag Fv.

The voltage low change abnormality flag setting routine of FIG. 24 is repeatedly executed. In this routine, the engine ECU 24 first inputs data such as the output voltage Vo and the second predetermined condition flag Ffc2 (step S602), and these data are processed in step S202 of the sub-offset amount setting routine of FIG. It is input in the same way.

When the data is input in this way, the value of the second predetermined condition flag Ffc2 is checked (step S612). When the second predetermined condition flag Ffc2 has a value of 1, it is determined that the second predetermined condition is satisfied, and the output voltage Vo is set to the predetermined voltage Vofc (step S622).

Subsequently, the predetermined voltage Vofc is compared with the upper limit value Rfc2max of the second predetermined range Rfc2 (step S632). When the predetermined voltage Vofc is equal to or less than the upper limit value Rfc2max of the second predetermined range Rfc2, it is determined that the oxygen sensor 155 does not have a low voltage change abnormality (normal or a high voltage change abnormality has occurred). The voltage low change abnormality flag Fv is set to a value of 0 (step S642), and this routine is terminated.

When the predetermined voltage Vofc is larger than the upper limit value Rfc2max of the second predetermined range Rfc2 in step S632, it is determined that the oxygen sensor 155 has a voltage low change abnormality, and the voltage low change abnormality flag Fv is set to a value 1. (Step S652), this routine is terminated.

In the routine executed by the sub-feedback unit 92 in which the "current low change abnormality flag Fi" of the sub-feedback correction routine of FIG. 22 is replaced with the "voltage low change abnormality flag Fv", the voltage low change abnormality flag Fv has a value of 1. Occasionally, it is determined that the oxygen sensor 155 has a low voltage change abnormality, and the above steps S410 to S510 are executed to end this routine.

As described above, when the predetermined voltage Vofc is larger than the upper limit value Rfc2max of the second predetermined range Rfc2, it is assumed that the oxygen sensor 155 has a low voltage change abnormality (see the broken line in FIG. 14). At this time, when the fuel injection control of the engine 22 is being performed, it becomes difficult to excessively switch between the execution of the rich correction and the execution of the lean correction, and the oxygen storage amount OS of the purification catalyst 136a may be excessively reduced or increased. However, the purification performance of the exhaust gas by the purification catalyst 136a may be deteriorated.

In this modification, when the predetermined voltage Vofc is larger than the upper limit value Rfc2max of the second predetermined range Rfc2, the rich correction is performed by switching between the execution of the rich correction and the execution of the lean correction using the integrated intake air amount Qasum. It is possible to prevent the execution and the execution of the lean correction from becoming excessively difficult to switch, and it is possible to suppress the oxygen storage amount OS of the purification catalyst 136a from being excessively decreased or increased. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

In the engine device 321B mounted on the hybrid vehicle 320B of this modified example described above, when the predetermined voltage Vofc is larger than the upper limit value Rfc2max of the second predetermined range Rfc2, the rich correction is executed using the integrated intake air amount Qasum. To switch between running lean correction and. As a result, it is possible to suppress deterioration of the exhaust gas purification performance by the purification catalyst 136a.

In the engine devices 21 and 21B, 221,221B, and 321 and 321B of the first to third embodiments and the modified examples, the sub-offset amount setting unit 95 has the intake air amount Qa and the maximum oxygen storage amount OSmax (first embodiment). In or a modified example thereof, the rich side threshold value (AFth-εR) is further set by using the predetermined time current Iafdfc). However, the rich side threshold value (AFth-εR) may be set by using only one of the intake air amount Qa and the maximum oxygen storage amount OSmax. Further, the rich side threshold value (AFth-εR) may be set without using either the intake air amount Qa or the maximum oxygen storage amount OSmax.

In the engine devices 21 and 21B, 221,221B, and 321 and 321B of the first to third embodiments and the modified examples, the sub-offset amount setting unit 95 sets the intake air amount Qa (in the first embodiment and its variants, the intake air amount Qa). Further, the lean side threshold value (AFth + εL) is set by using the predetermined time current Iafdfc). However, the lean side threshold value (AFth + εL) may be set using the intake air amount Qa and the maximum oxygen storage amount OSmax. Further, the lean side threshold value (AFth + εL) may be set by using the maximum oxygen storage amount OSmax instead of the intake air amount Qa. Further, the lean side threshold value (AFth + εL) may be set without using either the intake air amount Qa or the maximum oxygen storage amount OSmax.

In the engine devices 21, 221 and 321 of the first to third embodiments and the modified examples, sensors having the same specifications are used as the upstream air-fuel ratio sensor 152 and the downstream air-fuel ratio sensor 154. However, sensors with different specifications may be used.

In the first to third embodiments and each modification, the engine devices 21, 21B, 221 mounted on the hybrid vehicles 20, 20B, 220, 220B, 320, 320B including the engine 22, the planetary gear 30, and the motors MG1 and MG2. , 221B, 321 and 321B. 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 first to third embodiments and each modification, the engine 22 corresponds to the "engine", the purification catalyst 136a corresponds to the "purification catalyst", and the downstream air-fuel ratio sensor 154 or the oxygen sensor 155 corresponds to the "exhaust sensor". The engine ECU 24 corresponds to the "control device".

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, 20B, 220, 220B, 320, 320B Hybrid car, 21,21B, 121, 121B, 221,221B engine device, 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 Sub offset amount setting 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 air flow meter, 149 temperature sensor, 150 pressure sensor, 152 upstream air fuel ratio sensor, 154 downstream air fuel ratio sensor, 155 oxygen sensor, MG1, MG2 motor ..

Claims (6)

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 that is attached to the exhaust system and outputs an output value based on the air-fuel ratio of the exhaust,
When operating the engine, if the detected air-fuel ratio corresponding to the output value 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. A control device that switches to execution and switches to execution of the rich correction when the detected air-fuel ratio reaches or more than the lean side threshold during the execution of the lean correction.
It is an engine device equipped with
In the control device, the predetermined output value, which is the output value when a predetermined condition in which the output value is stable is satisfied during the fuel cut of the engine, is a reference output corresponding to the stoichiometric air-fuel ratio with respect to the predetermined range. When the value is approaching, the rich side threshold value and the lean side threshold value are set so as to approach the stoichiometric air-fuel ratio as compared with the case where the predetermined time output value is within the predetermined range.
Engine device. The engine device according to claim 1.
When the predetermined time output value is separated from the reference output value with respect to the predetermined range, the control device is based on the stoichiometric air-fuel ratio as compared with the case where the predetermined time output value is within the predetermined range. The rich side threshold value and the lean side threshold value are set so as to be separated from each other.
Engine device. 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 that is attached to the exhaust system and outputs an output value based on the air-fuel ratio of the exhaust,
When the engine is operated, if the detected air-fuel ratio corresponding to the execution output value based on the output value reaches the rich side threshold value or less during the execution of the rich correction for the fuel injection amount of the fuel injection valve, the fuel A control device that switches to the execution of the lean correction for the injection amount and switches to the execution of the rich correction when the detected air-fuel ratio reaches the lean side threshold value or more during the execution of the lean correction.
It is an engine device equipped with
In the control device, the predetermined output value, which is the output value when a predetermined condition in which the output value is stable is satisfied during the fuel cut of the engine, is a reference output corresponding to the stoichiometric air-fuel ratio with respect to the predetermined range. When the value is close to the value, the execution is performed so that the execution output value is separated from the reference output value for the same output value as compared with the case where the predetermined output value is within the predetermined range. Set the output value for
Engine device. The engine device according to claim 3.
When the predetermined time output value is separated from the reference output value with respect to the predetermined range, the control device has the same output value as compared with the case where the predetermined time output value is within the predetermined range. The execution output value is set so that the execution output value approaches the reference output value.
Engine device. 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 that is attached to the exhaust system and outputs an output value based on the air-fuel ratio of the exhaust,
When operating the engine, if the detected air-fuel ratio corresponding to the output value 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. A control device that switches to execution and switches to execution of the rich correction when the detected air-fuel ratio reaches or more than the lean side threshold during the execution of the lean correction.
It is an engine device equipped with
In the control device, the predetermined output value, which is the output value when a predetermined condition in which the output value is stable is satisfied during the fuel cut of the engine, is a reference output corresponding to the stoichiometric air-fuel ratio with respect to the predetermined range. When the value is approaching, the execution of the rich correction and the execution of the lean correction are switched using the integrated value of the intake air amount.
Engine device. The engine device according to any one of claims 1 to 5.
The control device sets the rich side threshold value and the lean side threshold value in consideration of the intake air amount of the engine and / or the maximum oxygen storage amount of the purification catalyst.
Engine device.

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