Control device for internal combustion engine

When an amount of particulate matter (PM) collected by a gasoline particulate filter (GPF) reaches a predetermined amount, a central processing unit (CPU) executes a regeneration process for regenerating the GPF. That is, the CPU stops supply of fuel to any one of cylinders #1 to #4, while increasing an amount of fuel supplied to remaining cylinders. When a temperature of a three-way catalyst becomes equal to or higher than a first temperature, the CPU increases an injection amount to lower a temperature of exhaust gas. When the temperature of the three-way catalyst becomes equal to or higher than the first temperature during the execution of the regeneration process, the CPU does not increase the injection amount.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2021-122456 filed on Jul. 27, 2021, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a control device for an internal combustion engine.

2. Description of Related Art

For example, the Japanese Unexamined Patent Application Publication No. 2013-249792 (JP 2013-249792 A) describes a control device for an internal combustion engine provided with an exhaust gas control device. This control device estimates the temperature of the exhaust gas control device. When the estimated temperature is equal to or higher than a determination value, the control device increases the amount of fuel injected from the fuel injection valve. This aims at lowering the temperature of the exhaust gas by the heat of vaporization of the fuel.

SUMMARY

The inventors have considered stopping the supply of fuel in some of the plurality of cylinders as a regeneration process for regenerating the exhaust gas control device. This aims at supplying oxygen to the exhaust gas control device. However, in that case, the temperature of the exhaust gas control device rises during the execution of the regeneration process, and when the amount of fuel is increased as described above, the temperature of the exhaust gas control device may rather rise. This is because a large amount of oxygen flowing into the exhaust gas control device from the cylinders in which the fuel supply is stopped reacts with the increased fuel and generates heat.

Hereinafter, means for solving the above issue and its operations and effects will be described.

1. Provided is a control device for an internal combustion engine. The control device is applied to the internal combustion engine including an exhaust gas control device in an exhaust passage. The internal combustion engine includes a plurality of cylinders and a fuel injection valve for supplying fuel to each of the cylinders. The control device executes a stop process, a temperature acquisition process, an increase process, and a prohibition process. The stop process is a process for stopping supply of fuel to some of the cylinders of the internal combustion engine and continuing the supply of the fuel to remaining cylinders. The temperature acquisition process is a process for acquiring a temperature of the exhaust gas control device. The increase process is a process for increasing an injection amount injected by the fuel injection valve when the temperature becomes equal to or higher than a first temperature. The prohibition process is a process for prohibiting both the stop process and the increase process from being executed at the same time.

In the above configuration, the prohibition process prohibits both the stop process and the increase process from being executed at the same time. Thus, when the temperature of the exhaust gas control device becomes equal to or higher than the first temperature during the execution of the stop process, the execution of the increase process is prohibited. Therefore, it is possible to avoid a situation in which a large amount of oxygen flowing into the exhaust gas control device from some cylinders oxidizes a large amount of uncombusted fuel increased by the increase process. Accordingly, it is possible to suppress the temperature of the exhaust gas control device from rising excessively during the execution of the stop process.

2. Provided is the control device for the internal combustion engine according to 1 described above. The prohibition process is a process for prohibiting execution of the increase process when the stop process is being executed. The control device executes a temperature control process when the stop process is executed. The temperature control process includes a process for setting the injection amount injected by the fuel injection valve such that an air-fuel ratio of an air-fuel mixture in the remaining cylinders is richer than a stoichiometric air-fuel ratio when the temperature is lower than a second temperature, and reducing the injection amount injected by the fuel injection valve of the remaining cylinders when the temperature is equal to or higher than the second temperature.

In the above configuration, by making the air-fuel ratio of the air-fuel mixture in the remaining cylinders richer than the stoichiometric air-fuel ratio, the uncombusted fuel flowing into the exhaust gas control device from the remaining cylinders is oxidized by the oxygen flowing into the exhaust gas control device from some cylinders. Therefore, the temperature of the exhaust gas control device can be raised. Further, in the above configuration, when the temperature of the exhaust gas control device becomes equal to or higher than the second temperature, the injection amount injected by the fuel injection valve of the remaining cylinders is reduced. As a result, the amount of uncombusted fuel flowing into the exhaust gas control device from the remaining cylinders can be reduced. Therefore, the amount of heat of oxidation generated by the exhaust gas control device can be reduced. Accordingly, in the above configuration, it is possible to suppress the temperature of the exhaust gas control device from rising excessively.

3. Provided is the control device for the internal combustion engine according to 2 described above. The second temperature is lower than the first temperature. In the above configuration, it is possible to suppress the temperature of the exhaust gas control device from rising significantly beyond the second temperature, which is smaller than the first temperature, by the temperature control process.
4. Provided is the control device for the internal combustion engine according to 2 described above. The second temperature is higher than the first temperature. In the above configuration, it is possible to suppress the temperature of the exhaust gas control device from rising significantly beyond the second temperature by the temperature control process. Therefore, the amount in which the temperature of the exhaust gas control device exceeds the first temperature can be set to about the difference between the second temperature and the first temperature.
5. Provided is the control device for the internal combustion engine according to 1 described above. The prohibition process is a process for prohibiting execution of the stop process when the increase process is executed. In the above configuration, when the increase process is executed, the execution of the stop process is prohibited. Therefore, it is possible to suppress the temperature of the exhaust gas control device from excessively rising beyond the first temperature by the increase process, when the temperature of the exhaust gas control device becomes equal to or higher than the first temperature.

DETAILED DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment will be described with reference to the drawings.

As shown inFIG.1, an internal combustion engine10includes four cylinders #1 to #4. A throttle valve14is provided in an intake passage12of the internal combustion engine10. An intake port12a, which is a downstream portion of the intake passage12, is provided with a port injection valve16for injecting fuel into the intake port12a. The air taken into the intake passage12and the fuel injected from the port injection valve16flow into a combustion chamber20as an intake valve18opens. Fuel is injected into the combustion chamber20from an in-cylinder injection valve22. The air-fuel mixture that is a mixture of the air in the combustion chamber20and the fuel is subjected to combustion with the spark discharge of a spark plug24. The combustion energy generated at that time is converted into the rotation energy of a crank shaft26.

The air-fuel mixture subjected to combustion in the combustion chamber20is discharged to an exhaust passage30as exhaust gas when an exhaust valve28is opened. The exhaust passage30is provided with a three-way catalyst32having an oxygen storage capacity and a gasoline particulate filter (GPF)34. In the present embodiment, as the GPF34, a filter in which a three-way catalyst having an oxygen storage capacity is supported on a filter for collecting particulate matter (PM) is assumed.

The crank shaft26is mechanically connected to a carrier C of a planetary gear mechanism50constituting a power splitting device. A rotation shaft52aof a first motor generator52is mechanically connected to a sun gear S of the planetary gear mechanism50. A rotation shaft54aof a second motor generator54and drive wheels60are mechanically connected to a ring gear R of the planetary gear mechanism50. An alternating current (AC) voltage is applied to a terminal of the first motor generator52by an inverter56. Further, an AC voltage is applied to a terminal of the second motor generator54by an inverter58.

In order to control the torque, the exhaust component ratio, and the like, which are control amounts of the internal combustion engine10as a control target, a control device70operates operation units of the internal combustion engine10such as the throttle valve14, the port injection valve16, the in-cylinder injection valve22, and the spark plug24. The control device70operates the inverter56to control the rotation speed, which is the control amount of the first motor generator52as the control target. The control device70operates the inverter58to control the torque, which is the control amount of the second motor generator54as the control target.FIG.1shows operation signals MS1to MS6of each of the throttle valve14, the port injection valve16, the in-cylinder injection valve22, the spark plug24, and the inverters56,58. The control device70refers to the intake air amount Ga detected by an air flow meter80and the output signal Scr of a crank angle sensor82in order to control the control amount of the internal combustion engine10. Further, the control device70refers to the coolant temperature THW detected by a coolant temperature sensor86and the air-fuel ratio Δf detected by an air-fuel ratio sensor88provided upstream of the three-way catalyst32. The control device70refers to the output signal Sm1of a first rotation angle sensor90that detects the rotation angle of the first motor generator52in order to control the control amount of the first motor generator52. The control device70also refers to the output signal Sm2of a second rotation angle sensor92that detects the rotation angle of the second motor generator54in order to control the control amount of the second motor generator54.

The control device70includes a central processing unit (CPU)72, a read only memory (ROM)74, a peripheral circuit76, and a communication line78. The CPU72, the ROM74, and the peripheral circuit76can communicate with each other by the communication line78. Here, the peripheral circuit76includes a circuit that generates a clock signal defining the internal operation, a power supply circuit, a reset circuit, and the like. The control device70controls the control amount when the CPU72executes the program stored in the ROM74.

The CPU72executes a process for determining whether to execute the regeneration process of the GPF34, a fuel increase process for overheat protection of the three-way catalyst32, and a process for regenerating the GPF34according to the program stored in the ROM74. In the following, the above will be described in order.

Processing Related to Determining Whether to Execute Regeneration Process

FIG.2shows the procedure of the regeneration process. The processes shown inFIG.2are realized when the CPU72repeatedly executes the program stored in the ROM74, for example, at a predetermined cycle. In the following, the step number of each process is represented by a number prefixed with S.

In the series of processes shown inFIG.2, the CPU72first acquires the rotation speed NE, the filling efficiency η, and the coolant temperature THW (S10). The rotation speed NE is calculated by the CPU72based on the output signal Scr. The filling efficiency η is calculated by the CPU72based on the rotation speed NE and the intake air amount Ga. Next, the CPU72calculates the update amount ΔDPM of the accumulated amount DPM based on the rotation speed NE, the filling efficiency and the coolant temperature THW (S12). Here, the accumulated amount DPM is the amount of the PM collected in the GPF34. Specifically, the CPU72calculates the amount of the PM in the exhaust gas discharged to the exhaust passage30based on the rotation speed NE, the filling efficiency and the coolant temperature THW. Further, the CPU72calculates the temperature of the GPF34based on the temperature Tcat of the three-way catalyst32calculated by the process described later, the rotation speed NE, and the filling efficiency η. Then, the CPU72calculates the update amount ΔDPM based on the amount of the PM in the exhaust gas and the temperature of the GPF34. At the time of executing the process of S56described later, the update amount ΔDPM may be calculated in consideration of the fact that the process is under execution.

Next, the CPU72updates the accumulated amount DPM according to the update amount ΔDPM (S14). Subsequently, the CPU72determines whether the flag F is “1” (S16). The flag F being “1” indicates that the regeneration process that is a process for combusting and removing the PM in the GPF34is being executed, while the flag F being “0” indicates that the regeneration process is not being executed. When the CPU72determines that the value is “0” (S16: NO), the CPU72determines whether the accumulated amount DPM is equal to or larger than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is set to a value at which a large amount of the PM is collected by the GPF34and it is desired to remove the PM.

When the CPU72determines that the accumulated amount DPM is equal to or larger than the regeneration execution value DPMH (S18: YES), the CPU72substitutes “1” into the flag F to execute the regeneration process (S20).

When the CPU72determines that the flag F is “1” (S16: YES), the CPU72determines whether the accumulated amount DPM is equal to or smaller than the stop threshold value DPML (S22). The stop threshold value DPML is set to a value at which the amount of the PM collected in the GPF34is sufficiently small and the regeneration process may be stopped. When the CPU72determines that the accumulated amount DPM is larger than the stop threshold value DPML (S22: NO), the CPU72shifts to the process of S20.

On the other hand, when the accumulated amount DPM is equal or smaller than the stop threshold value DPML (S24: YES), the CPU72substitutes “0” into the flag F (S24).

The CPU72temporarily ends the series of processes shown inFIG.2when the processes of S20and S24are completed and when a negative determination is made in the process of S18.

Fuel Increase Process for Overheat Protection of Three-Way Catalyst32

FIG.3shows a procedure for the fuel increase process. The processes shown inFIG.3are realized when the CPU72repeatedly executes the program stored in the ROM74, for example, at a predetermined cycle.

In the series of processes shown inFIG.3, the CPU72first acquires the rotation speed NE of the crank shaft26, the filling efficiency η, the air-fuel ratio Af, the ignition timing aig, the increase coefficient K1, and the regeneration coefficient K2(S30). The increase coefficient K1is a coefficient indicating the ratio of increasing the injection amount when the process of increasing the injection amount is being executed in order to protect the three-way catalyst32from overheating. The increase coefficient K1is “1” when the above-mentioned increase process is not being executed. The regeneration coefficient K2is a coefficient indicating the ratio of increasing the injection amount when the regeneration process of the GPF34is being executed. The regeneration coefficient K2is “1” when the regeneration process of the GPF34is not being executed.

Next, the CPU72calculates the temperature Tcat of the three-way catalyst32based on the rotation speed NE, the filling efficiency η, the air-fuel ratio Af, the ignition timing aig, the increase coefficient K1, and the regeneration coefficient K2(S32). The CPU72calculates the temperature Tcat to a larger value when the filling efficiency η is large than when the filling efficiency η is small. Further, the CPU72calculates the temperature Tcat to a larger value when the amount of a retard angle of the ignition timing aig with respect to the maximum brake torque (MBT) is large than when the amount is small. Further, the CPU72calculates the temperature Tcat to a smaller value when the increase coefficient K1is large than when the increase coefficient K1is small. Further, the CPU72calculates the temperature Tcat to a larger value when the regeneration coefficient K2is large than when the regeneration coefficient K2is small.

Specifically, for example, the CPU72may correct the base value of the temperature Tcat calculated by inputting the rotation speed NE and the filling efficiency η by using the ignition timing aig, the increase coefficient K1, and the regeneration coefficient K2, to calculate the temperature Tcat. In the calculation process of the temperature Tcat, the CPU72takes into account the oxygen storage amount of the three-way catalyst32calculated according to the air-fuel ratio Af. At this time, for example, when the air-fuel ratio Af is larger than the stoichiometric air-fuel ratio in a state where the oxygen storage amount is smaller than the maximum value, it is desirable that the CPU72take into account the temperature rise of the three-way catalyst32that occurs when the oxygen storage amount increases to calculate the temperature Tcat. Further, for example, when the air-fuel ratio Af is smaller than the stoichiometric air-fuel ratio in a state where the oxygen storage amount is equal to or larger than a predetermined amount, it is desirable to take into account the heat of oxidation of the uncombusted fuel in the three-way catalyst32to calculate the temperature Tcat.

Next, the CPU72determines whether the temperature Tcat is equal to or higher than the first temperature Tth1(S34). The first temperature Tth1is set according to the upper limit value of the allowable temperature range of the three-way catalyst32. Specifically, the first temperature Tth1is set to a value smaller than the upper limit value by a predetermined margin amount.

When the CPU72determines that the temperature Tcat is equal to or higher than the first temperature Tth1(S34: YES), the CPU72determines whether the flag F is “0” (S36). The processes of S34and S36are processes for determining whether the execution condition of the process of increasing the injection amount for protecting the three-way catalyst32from overheating is satisfied. That is, the execution condition is a condition that the logical product of the following condition (a) and condition (b) is true.

Condition (a): a condition that the temperature Tcat is equal to or higher than the first temperature Tth1

Condition (b): a condition that the regeneration process of GPF34is not being executed When the CPU72determines that the flag F is “0” (S36: YES), the CPU72calculates the increase coefficient K1by inputting the rotation speed NE and the filling efficiency η that define the operation point of the internal combustion engine10(S38). This considers the fact that the temperature of the exhaust gas differs depending on the operation point. The process of increasing the injection amount by the increase coefficient K1is performed to lower the temperature of the exhaust gas discharged to the exhaust passage30by the heat of vaporization of the fuel. Since the temperature of the exhaust gas is different when the injection amount is not increased, the increase rate required for lowering the temperature of the exhaust gas to a desired temperature differs depending on the operation point.

This process may be a process of performing a map calculation of the increase coefficient K1by the CPU72in a state where the map data is stored in the ROM74, for example. Here, the map data is data in which the rotation speed NE and the filling efficiency η are input variables and the increase coefficient K1is an output variable. The map data is a set data of a discrete value of an input variable and a value of an output variable corresponding to each of the values of the input variable. In the map calculation, when the value of the input variable matches any of the values of the input variable in the map data, the corresponding value of the output variable in the map data may be used as the calculation result. Further, in the map calculation, when the value of the input variable matches none of the values of the input variable in the map data, the value obtained by interpolating the values of a plurality of output variables included in the map data may be used as the calculation result.

Next, the CPU72increases and corrects the required injection amount Qd by the increase coefficient K1(S40). The required injection amount Qd is the amount of fuel required for each of the cylinders #1 to #4 in one combustion cycle. The required injection amount Qd before correction may be, for example, the amount of fuel required to make the air-fuel ratio of the air-fuel mixture in the combustion chamber20the stoichiometric air-fuel ratio. This amount of fuel can be realized, for example, by the operation amount of open loop control obtained by multiplying the filling efficiency η by a predetermined coefficient. Further, for example, the amount of fuel may be realized by correcting the operation amount of the open loop control according to the operation amount required for the feedback control to the target value of the air-fuel ratio Af.

The CPU72temporarily ends the series of processes shown inFIG.3when the process of S40is completed and when a negative determination is made in the processes of S34and S36.

Process Related to Regeneration of GPF34

FIG.4shows a procedure for the process related to regeneration of the GPF34. The processes shown inFIG.4are realized when the CPU72repeatedly executes the program stored in the ROM74, for example, at a predetermined cycle.

In the series of processes shown inFIG.4, the CPU72first determines whether the flag F is “1” (S50). When the CPU72determines that the flag F is “1” (S50: YES), the CPU72substitutes the value obtained by subtracting the temperature Tcat from the target temperature Tcat* into the difference ΔT (S52). The target temperature Tcat* is a target value of the temperature Tcat of the three-way catalyst32at the time of the regeneration process of the GPF34. The target temperature Tcat* is set to a temperature at which the temperature of the GPF34can be raised to a temperature at which the PM can be combusted and removed.

The CPU72calculates the regeneration coefficient K2by inputting the rotation speed NE and the filling efficiency η, which are variables defining the operation point of the internal combustion engine10, and the difference ΔT (S54). The regeneration coefficient K2indicates the rate at which the injection amount is increased during the regeneration process of the GPF34. The regeneration coefficient K2is set to a value equal to or larger than “1”. The CPU72calculates the regeneration coefficient K2to a larger value when the difference ΔT is large than when the difference ΔT is small. Further, the CPU72calculates the value of the regeneration coefficient K2to a different value according to the operation point of the internal combustion engine10even when the magnitude of the difference ΔT is the same. This considers the fact that the temperature of the exhaust gas when the amount is not increased depends on the operation point.

This process may be realized, for example, by calculating the regeneration coefficient K2when the CPU72performs a map calculation on the map data stored in advance in the ROM74. Here, the map data is data in which the difference ΔT, the rotation speed NE, and the filling efficiency η are used as input variables, and the regeneration coefficient K2is used as an output variable.

Then, the CPU72stops the injection of fuel from the port injection valve16and the in-cylinder injection valve22of any one of the cylinders #1 to #4 (S56). Further, the CPU72corrects the required injection amount Qd of the remaining cylinders by the regeneration coefficient K2. That is, the CPU72makes the air-fuel ratio of the air-fuel mixture in the combustion chamber20of the remaining cylinders richer than the stoichiometric air-fuel ratio. This process is a process for raising the temperature of the GPF34by discharging oxygen and uncombusted fuel to the exhaust passage30, and combusting and removing the PM collected by the GPF34. That is, by discharging oxygen and uncombusted fuel to the exhaust passage30, the uncombusted fuel is combusted in the three-way catalyst32and the like to raise the temperature of the exhaust gas. This makes it possible to raise the temperature of the GPF34. Further, by supplying oxygen to the GPF34, the PM collected by the GPF34can be combusted and removed.

The CPU72periodically switches the cylinder for stopping the injection of fuel. The switching cycle is, for example, a predetermined number of times one combustion cycle. Here, the predetermined number may be, for example, a number equal to or larger than 100.

The CPU72temporarily ends the series of processes shown inFIG.4when the process of S56is completed and when a negative determination is made in the process of S50.

Here, the operation and effect of the present embodiment will be described.

FIG.5shows changes in the rotation speed NE, the filling efficiency η, the temperature Tcat, the regeneration coefficient K2, the increase coefficient K1, and the flag F.

As shown inFIG.5, when the regeneration process is not being executed, the CPU72raises the increase coefficient K1to a value larger than “1” at time t1when the temperature Tcat becomes equal to or higher than the first temperature Tth1. As a result, the temperature of the exhaust gas drops due to the heat of vaporization of the injected fuel. Therefore, an increase in the temperature Tcat can be suppressed. InFIG.5, the long dashed double-short dashed lines show a case where the increase coefficient K1is not increased. In that case, the temperature Tcat greatly rises beyond the first temperature Tth1.

When the regeneration process is started at time t2, the CPU72raises the regeneration coefficient K2to a value larger than “1”. The CPU72calculates the regeneration coefficient K2to a larger value as the temperature Tcat is lower than the target temperature Tcat*. Then, the CPU72sets the regeneration coefficient K2to “1” at time t3when the temperature Tcat exceeds the target temperature Tcat*. Further, the CPU72fixes the increase coefficient K1to “1” even at time t4when the temperature Tcat becomes equal to or higher than the first temperature Tth1and after. This is because the above condition (b) is included in the execution condition of the injection amount increase process by the increase coefficient K1.

InFIG.5, the long dashed double-short dashed lines show a case where the above condition (b) is not included in the execution condition of the increase process. In that case, when the temperature Tcat becomes equal to or higher than the first temperature Tth1at time t4, the CPU72executes the increase process by increasing the increase coefficient K1beyond “1”. In that case, the amount of uncombusted fuel discharged into the exhaust gas increases. On the other hand, a large amount of oxygen flows into the three-way catalyst32by the regeneration process. Therefore, the temperature of the three-way catalyst32rises significantly due to the reaction heat when the uncombusted fuel in the exhaust gas is oxidized by the oxygen flowing into the three-way catalyst32.FIG.5shows an example in which the temperature Tcat rises beyond the upper limit value Tot of the allowable temperature of the three-way catalyst32.

In the example shown inFIG.5, the target temperature Tcat* is set to a value smaller than the first temperature Tth1, but the present disclosure is not limited to this.FIG.6shows an example in which the target temperature Tcat* is set to a value larger than the first temperature Tth1.

Even in the example shown inFIG.6, the CPU72maintains the value of the increase coefficient K1at “1” even at time t2when the temperature Tcat becomes equal to or higher than the first temperature Tth1and after. However, the CPU72sets the regeneration coefficient K2to a value larger than “1”, assuming that the temperature Tcat has not yet reached the target temperature Tcat* even at time t2and after. That is, the injection amount is increased. Then, the CPU72sets the regeneration coefficient K2to “1” at time t3when the temperature Tcat reaches the target temperature Tcat*.

As described above, the CPU72does not execute the injection amount increase process aimed at lowering the temperature of the exhaust gas during the regeneration process. Instead, the CPU72performs feedback control so that the temperature Tcat does not exceed the target temperature Tcat* during the regeneration process. Here, the CPU72sets the regeneration coefficient K2to a smaller value when the temperature Tcat is high than when the temperature Tcat is low. That is, the increase amount is set to a smaller value when the temperature Tcat is high than when the temperature Tcat is low. In particular, when the temperature Tcat is equal to or higher than the target temperature Tcat*, the CPU72sets the increase amount to zero.

As a result, it is possible to suppress the temperature of the three-way catalyst32from rising excessively.

Second Embodiment

Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment.

In the first embodiment, during the regeneration process, the injection amount increase process using the increase coefficient K1is prohibited. However, in the present embodiment, when the condition that the temperature Tcat is equal to or higher than the first temperature Tth1, which is the condition for executing the increase process, is satisfied, the execution of the regeneration process is prohibited.

FIG.7shows a procedure for determining whether to execute the regeneration process according to the present embodiment. The processes shown inFIG.7are realized when the CPU72repeatedly executes the program stored in the ROM74, for example, at a predetermined cycle. InFIG.7, for the process corresponding to the process shown inFIG.2, the same step number is assigned and the description thereof will be omitted for convenience of description.

In the series of processes shown inFIG.7, when the CPU72determines that the flag F is “0” (S16: NO), the CPU72determines whether the logical product of the following condition (c) and condition (d) is true (S18a).

Condition (c): a condition that the accumulated amount DPM is equal to or larger than the regeneration execution value DPMH

Condition (d): a determination process that the regeneration process of the GPF34is interrupted

The interruption of the regeneration process is an event caused by a negative determination in the process of S26described later during the execution of the regeneration process.

When the CPU72determines that the logical product is true (S18a: YES) and when the CPU72makes a negative determination in the process of S22, the CPU72determines whether the condition (e) indicating that the temperature Tcat is lower than the first temperature Tth1is satisfied (S26). When the CPU72determines that the condition (e) is satisfied (S26: YES), the CPU72shifts to the process of S20. That is, in the present embodiment, the execution condition of the regeneration process is a condition that the logical product of the condition (c), the condition (d), and the condition (e) is true.

On the other hand, when the CPU72determines that the temperature Tcat is equal to or higher than the first temperature Tth1(S26: NO), the CPU72shifts to the process of S24.

As described above, when the temperature Tcat is equal to or higher than the first temperature Tth1, the CPU72does not execute the regeneration process of the GPF34even when the regeneration request of the CPU72is generated due to the satisfaction of the condition (c). Thus, the fuel is increased by the increase coefficient K1in a state where a large amount of oxygen is not supplied to the three-way catalyst32. Therefore, since the exhaust gas that is limited to a low temperature flows into the three-way catalyst32, it is possible to suppress the temperature of the three-way catalyst32from rising excessively.

Further, the CPU72interrupts the regeneration process when the temperature Tcat of the three-way catalyst32becomes equal to or higher than the first temperature Tth1during the execution of the regeneration process. Thus, the process of supplying a large amount of oxygen to the three-way catalyst32is interrupted. By increasing the amount of fuel by the process ofFIG.3, the temperature of the exhaust gas discharged from each of the cylinders #1 to #4 can be limited to a low temperature. As a result, it is possible to suppress the temperature of the three-way catalyst32from rising excessively.

Correspondence

The correspondence between the matters in the above embodiment and the matters described in the above column of “summary” is as follows. In the following, the correspondence is shown for each number of the solution means described in the column of “summary” [1] The exhaust gas control device corresponds to the three-way catalyst32and the GPF34. The stop process corresponds to the process of S56. The temperature acquisition process corresponds to the process of S32. The increase process corresponds to the process of S40. InFIG.3, the prohibition process corresponds to executing the process of S36as an execution condition of the process of S40. InFIG.7, the prohibition process corresponds to the process of S26. [2] The second temperature corresponds to the target temperature Tcat*. The description in [3] corresponds to the process illustrated inFIG.5. The description in [4] corresponds to the process illustrated inFIG.6. The description in [5] corresponds to the process inFIG.7.

Other Embodiments

The present embodiment can be modified and implemented as follows. The present embodiment and modification examples described below may be carried out in combination of each other within a technically consistent range.

First Temperature and Second Temperature

FIGS.5and6show examples in which the first temperature Tth1and the target temperature Tcat* are values different from each other, but the present disclosure is not limited to this.The second temperature, which is the temperature at which the value of the regeneration coefficient K2is made to be equal to or smaller than “1”, is not limited to the target temperature Tcat*. For example, as described in the column of “Temperature Control Process”, when the temperature Tcat is controlled to be in the region of equal to or higher than the lower limit value and equal to or lower than the upper limit value, the upper limit value may be set as the second temperature.

Temperature Control ProcessIn the above embodiment, the regeneration coefficient K2is variably set according to the difference ΔT, the filling efficiency η as a variable indicating the load, and the rotation speed NE, but the present disclosure is not limited to this. For example, as a variable indicating the load, the accelerator operation amount may be used instead of the filling efficiencyIt is not essential to variably set the regeneration coefficient K2according to the difference ΔT, the variable indicating the load, and the rotation speed NE. For example, the regeneration coefficient K2may be variably set based on the difference ΔT and either one of the variable indicating the load and the rotation speed NE.It is not essential to variably set the regeneration coefficient K2according to at least one of the variable indicating the load and the rotation speed NE. For example, the output value of the proportional element with the difference ΔT as an input may be used as the regeneration coefficient K2. Further, for example, the sum of the output value of the proportional element and the output value of the integrating element with the difference ΔT as an input may be used as the regeneration coefficient K2.In the above embodiment, the minimum value of the regeneration coefficient K2is set to “1”, but the present disclosure is not limited to this. For example, the value may be slightly smaller than “1”. In that case, it is possible to more reliably suppress the amount of uncombusted fuel discharged from the cylinder in which the fuel supply is continued from exceeding the amount of oxygen discharged from the cylinder.The regeneration coefficient K2is not limited to the regeneration coefficient K2set according to the difference between the target temperature Tcat* and the temperature Tcat. For example, the upper limit value and the lower limit value of the temperature Tcat may be set, and the operation amount for controlling the temperature Tcat to be within the region of equal to or higher than the lower limit value and equal to or lower than the upper limit value may be set as the regeneration coefficient K2. In that case, when the temperature Tcat is lower than the lower limit value, the regeneration coefficient K2may be set to a value larger than “1”. Further, when the temperature Tcat is higher than the upper limit value, the regeneration coefficient K2may be set to a value equal to or smaller than “1”. When the temperature Tcat is in the above region, the regeneration coefficient K2may be set to “1”.

Increase ProcessIn the above embodiment, the magnitude of the increase coefficient K1is set according to the rotation speed NE and the filling efficiency η as a variable indicating the load, regardless of the temperature Tcat, but the present disclosure is not limited to this. For example, the magnitude of the increase coefficient K1may be variably set according to the temperature Tcat, the rotation speed NE, and the variable indicating the load. In that case, even when the values of the rotation speed NE and the variable indicating the load are the same, the increase coefficient K1may be set to a larger value when the temperature Tcat is large than when the temperature Tcat is small.In the above embodiment, the increase coefficient K1is set according to the rotation speed NE and the filling efficiency n as the variable indicating the load, but the present disclosure is not limited to this. For example, the accelerator operation amount may be used as the variable indicating the load. Further, the increase coefficient K1may be variably set according to either one of the two values of the rotation speed NE and the variable indicating the load. Furthermore, it is not essential to variably set the increase coefficient K1according to at least one of the two values of the rotation speed NE and the variable indicating the load.

Prohibition ProcessInFIG.7, when the temperature Tcat becomes equal to or higher than the first temperature Tth1during the execution of the regeneration process of GPF34, the regeneration process is interrupted. The increase coefficient K1is thus immediately set to a value larger than “1” by the process shown inFIG.3, but the present disclosure is not limited to this. For example, the process of S40may be prohibited until a predetermined time elapses after the interruption of the regeneration process. In other words, a delay may be provided in the timing of starting the process of S40with respect to the timing of interrupting the regeneration process.

Stop ProcessThe stop process is not limited to the regeneration process. For example, the stop process may be a process of stopping the supply of fuel in some cylinders in order to adjust the output of the internal combustion engine10. In that case, the air-fuel ratio of the air-fuel mixture in a cylinder different from the some cylinders may be set to the stoichiometric air-fuel ratio. Furthermore, for example, the stop process may be a process of stopping the supply of fuel to only some cylinders and executing control to set the air-fuel ratios of the air-fuel mixtures in the remaining cylinders to the stoichiometric air-fuel ratio when the oxygen storage amount of the three-way catalyst32is equal to or smaller than a specified value.

Exhaust Gas Control DeviceThe GPF34is not limited to the GPF provided downstream of the three-way catalyst32in the exhaust passage30. Further, it is not essential that the post-processing device is provided with the GPF34. The GPF34is not limited to a filter on which a three-way catalyst is supported. For example, when a three-way catalyst is provided upstream, the GPF34may be only a filter.

Control DeviceThe control device is not limited to a device that includes the CPU72and the ROM74and executes software processing. For example, the control device may include a dedicated hardware circuit such as an application-specific integrated circuit (ASIC) that performs hardware processing on at least a part of what has been subjected to software-processing in the above embodiment. That is, the control device only needs to include any of the following configurations (a) to (c). (a) A processing device that executes all of the above processes according to a program and a program storage device such as a ROM for storing the program (b) A processing device that executes a part of the above processes according to a program, a program storage device, and a dedicated hardware circuit for executing the remaining processes (c) A dedicated hardware circuit that executes all of the above processes Here, multiple software execution devices provided with the processing device and the program storage device, and multiple dedicated hardware circuits may be provided.