Control device for internal combustion engine

Abstract

The present invention relates to a control device for an internal combustion engine. When the amount of PM trapped by a GPF reaches a predetermined amount, a CPU executes a regeneration process for regenerating the GPF. That is, the CPU stops the supply of fuel to any one of cylinders #1 to #4, and on the other hand, increases the amount of fuel supplied to the remaining cylinders. When the temperature of a three-way catalyst becomes higher than a first temperature, the CPU increases the injection amount in order to lower the temperature of the exhaust gas. When the temperature of the three-way catalyst becomes higher than the first temperature during the execution of the regeneration process, the CPU does not increase the injection amount.

Description

Technical Field

[0001] The present invention relates to a control device for an internal combustion engine. Background Art

[0002] For example, Japanese Patent Application Laid-Open No. 2013-249792 describes a control device for an internal combustion engine equipped with an exhaust gas purification device. The control device estimates the temperature of the exhaust gas purification device. Furthermore, when the estimated temperature is above a judgment value, the control device increases the amount of fuel injected from the fuel injection valve. This is intended to reduce the temperature of the exhaust gas by the heat of vaporization of the fuel. Summary of the invention

[0003] The inventor has studied stopping the supply of fuel to some of the cylinders among the plurality of cylinders as a regeneration process for regenerating the exhaust gas purification device. This is intended to supply oxygen to the exhaust gas purification device. However, in this case, when the temperature of the exhaust gas purification device becomes high during the execution of the regeneration process and the fuel is increased as described above, the temperature of the exhaust gas purification device may rise instead. This is because a large amount of oxygen flowing into the exhaust gas purification device from the cylinder where the fuel supply is stopped reacts with the increased fuel to generate heat.

[0004] Means for solving the above-mentioned problems and their effects are described below.

[0005] 1. A control device for an internal combustion engine, applied to an internal combustion engine equipped with an exhaust purification device in an exhaust passage, the internal combustion engine having a plurality of cylinders and a fuel injection valve for supplying fuel to each of the plurality of cylinders, the control device for the internal combustion engine executing a stop process, a temperature acquisition process, an increment process and a prohibition process, the stop process is a process for stopping the supply of fuel to a part of the cylinders of the internal combustion engine and continuing the supply of fuel to the remaining cylinders, the temperature acquisition process is a process for acquiring the temperature of the exhaust purification device, the increment process is a process for increasing the injection amount of the fuel injection valve when the temperature becomes higher than a first temperature, and the prohibition process is a process for prohibiting both the stop process and the increment process from being executed at the same time.

[0006] In the above structure, the prohibition process prohibits both the stop process and the increase process from being executed simultaneously. Therefore, the increase process is prohibited because the temperature of the exhaust gas purification device becomes higher than the first temperature when the stop process is executed. Therefore, it is possible to avoid a situation where a large amount of oxygen flowing into the exhaust gas purification device from a part of the cylinders oxidizes a large amount of unburned fuel increased by the increase process. Therefore, it is possible to suppress an excessive increase in the temperature of the exhaust gas purification device during the execution of the stop process.

[0007] 2. According to the control device of the internal combustion engine described in 1 above, the prohibition processing is a processing for prohibiting the execution of the incremental processing when the stop processing is being executed, and when the stop processing is being executed, a temperature control processing is executed, and the temperature control processing includes the following processing: when the temperature is lower than a second temperature, the injection amount of the fuel injection valve is set in such a manner that the air-fuel ratio of the mixture in the remaining cylinders is richer than the theoretical air-fuel ratio, and when the temperature becomes higher than the second temperature, the injection amount of the fuel injection valve of the remaining cylinder is reduced.

[0008] In the above structure, by making the air-fuel ratio of the mixture in the remaining cylinders richer than the theoretical air-fuel ratio, the unburned fuel flowing into the exhaust purification device from the remaining cylinders is oxidized by the oxygen flowing into the exhaust purification device from a part of the cylinders. Therefore, the temperature of the exhaust purification device can be increased. In addition, in the above structure, when the temperature of the exhaust purification device becomes higher than the second temperature, the injection amount of the fuel injection valve of the remaining cylinder is reduced. As a result, the amount of unburned fuel flowing into the exhaust purification device from the remaining cylinders can be reduced. Therefore, the amount of oxidation heat generated in the exhaust purification device can be reduced. Therefore, in the above structure, the excessive increase in the temperature of the exhaust purification device can be suppressed.

[0009] 3. According to the control device for the internal combustion engine described in 2 above, the second temperature is lower than the first temperature.

[0010] In the above configuration, by the temperature control process, it is possible to suppress the temperature of the exhaust gas purification device from exceeding the second temperature which is lower than the first temperature and increasing significantly.

[0011] 4. According to the control device for the internal combustion engine described in 2 above, the second temperature is higher than the first temperature.

[0012] In the above configuration, the temperature control process can suppress the temperature of the exhaust gas purification device from exceeding the second temperature and increasing significantly. Therefore, the amount by which the temperature of the exhaust gas purification device exceeds the first temperature can be reduced to the difference between the second temperature and the first temperature.

[0013] 5. According to the control device for the internal combustion engine described in 1 above, the prohibition process is a process of prohibiting execution of the stop process when the amount increase process is executed.

[0014] In the above configuration, when the increasing process is executed, the stopping process is prohibited. Therefore, when the temperature of the exhaust gas purification device reaches the first temperature or higher, the increasing process can suppress the temperature of the exhaust gas purification device from exceeding the first temperature and rising excessively. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Features, advantages and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like numerals represent like elements, and in which:

[0016] Figure 1 It is a diagram showing the configuration of a drive system and a control device according to the first embodiment.

[0017] Figure 2 This is a flowchart showing the procedure of processing executed by the control device according to the first embodiment.

[0018] Figure 3 This is a flowchart showing the procedure of processing executed by the control device according to the first embodiment.

[0019] Figure 4 This is a flowchart showing the procedure of processing executed by the control device according to the first embodiment.

[0020] Figure 5 It is a time chart showing the effect of the first embodiment.

[0021] Figure 6 It is a time chart showing the effect of the first embodiment.

[0022] Figure 7 This is a flowchart showing the procedure of processing executed by the control device according to the second embodiment. DETAILED DESCRIPTION

[0023] <First Embodiment>

[0024] Hereinafter, regarding the first embodiment, Figure 1 Side description.

[0025] like Figure 1 As shown, the internal combustion engine 10 has four cylinders #1 to #4. A throttle valve 14 is provided in the intake passage 12 of the internal combustion engine 10. An intake port injection valve 16 for injecting fuel into the intake port 12a is provided in the downstream portion of the intake passage 12, i.e., the intake port 12a. The air sucked into the intake passage 12 and the fuel injected from the intake port injection valve 16 flow into the combustion chamber 20 as the intake valve 18 is opened. Fuel is injected into the combustion chamber 20 from the in-cylinder injection valve 22. In addition, the mixture of air and fuel in the combustion chamber 20 is used for combustion as the spark discharge of the spark plug 24. The combustion energy generated at this time is converted into the rotational energy of the crankshaft 26.

[0026] The mixture after combustion in the combustion chamber 20 is discharged as exhaust gas to the exhaust passage 30 in accordance with the opening of the exhaust valve 28. A three-way catalyst 32 having oxygen storage capacity and a gasoline particulate filter (GPF) 34 are provided in the exhaust passage 30. It should be noted that in the present embodiment, as the GPF 34, a structure in which a three-way catalyst having oxygen storage capacity is supported on a filter for collecting particulate matter (PM) is assumed.

[0027] The crankshaft 26 is mechanically connected to the gear carrier C of the planetary gear mechanism 50 constituting the power distribution device. The rotating shaft 52a of the first motor generator 52 is mechanically connected to the sun gear S of the planetary gear mechanism 50. In addition, the rotating shaft 54a of the second motor generator 54 and the drive wheel 60 are mechanically connected to the ring gear R of the planetary gear mechanism 50. An AC voltage is applied to the terminals of the first motor generator 52 through the inverter 56. In addition, an AC voltage is applied to the terminals of the second motor generator 54 through the inverter 58.

[0028] The control device 70 operates the operating parts of the internal combustion engine 10, such as the throttle valve 14, the intake port injection valve 16, the in-cylinder injection valve 22, and the spark plug 24, in order to control the control amount of the internal combustion engine 10, i.e., the torque, the exhaust component ratio, etc. The control device 70 also operates the inverter 56 to control the control amount of the first motor generator 52, i.e., the speed. The control device 70 also operates the inverter 58 to control the control amount of the second motor generator 54, i.e., the torque. Figure 1 , operation signals MS1 to MS6 of the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, the spark plug 24, and the inverters 56 and 58 are described. The control device 70 refers to the intake air amount Ga detected by the air flow meter 80 and the output signal Scr of the crank angle sensor 82 in order to control the control amount of the internal combustion engine 10. In addition, the control device 70 refers to the water temperature THW detected by the water temperature sensor 86 and the air-fuel ratio Af detected by the air-fuel ratio sensor 88 provided upstream of the three-way catalyst 32. In addition, the control device 70 refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first motor generator 52 in order to control the control amount of the first motor generator 52. In addition, the control device 70 refers to the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor generator 54 in order to control the control amount of the second motor generator 54.

[0029] The control device 70 includes a CPU 72, a ROM 74, a peripheral circuit 76, and a communication line 78. The CPU 72, the ROM 74, and the peripheral circuit 76 can communicate with each other through the communication line 78. Here, the peripheral circuit 76 includes a circuit for generating a clock signal that specifies the internal operation, a power supply circuit, a reset circuit, etc. The control device 70 controls the control amount by the CPU 72 executing the program stored in the ROM 74.

[0030] The CPU 72 executes processing related to determining whether to execute the regeneration processing of the GPF 34 , fuel increase processing for overheat protection of the three-way catalyst 32 , and processing related to the regeneration of the GPF 34 according to the program stored in the ROM 74 . These are described below in order.

[0031] (Processing Related to Determination of Whether to Execute Regeneration Processing)

[0032] exist Figure 2 The process of the regeneration treatment is shown in FIG. Figure 2 The processing shown is realized by the CPU 72 repeatedly executing, for example, a program stored in the ROM 74 at a predetermined cycle. In the following, the step number of each process is represented by a number with "S" at the beginning.

[0033] exist Figure 2 In the series of processing shown, CPU72 first obtains the rotational speed NE, the filling efficiency η and the water temperature THW (S10). The rotational speed NE is calculated by CPU72 based on the output signal Scr. The filling efficiency η is calculated by CPU72 based on the rotational speed NE and the intake air amount Ga. Next, CPU72 calculates the update amount ΔDPM of the accumulation amount DPM based on the rotational speed NE, the filling efficiency η and the water temperature THW (S12). Here, the accumulation amount DPM is the amount of PM trapped in GPF34. In detail, CPU72 calculates the amount of PM in the exhaust gas discharged to the exhaust passage 30 based on the rotational speed NE, the filling efficiency η and the water temperature THW. In addition, CPU72 calculates the temperature of GPF34 based on the temperature Tcat of the three-way catalyst 32 calculated by the processing described later, the rotational speed NE and the filling efficiency η. Then, CPU72 calculates the update amount ΔDPM based on the amount of PM in the exhaust gas and the temperature of GPF34. It should be noted that, when the process of S56 described later is executed, the update amount ΔDPM may be calculated taking into account that it is the execution time.

[0034] Next, the CPU 72 updates the accumulation amount DPM according to the update amount ΔDPM (S14). Next, the CPU 72 determines whether the flag F is "1" (S16). When the flag F is "1", it means that the process of burning and removing the PM in the GPF 34, that is, the regeneration process, is being executed. On the other hand, when it is "0", it means that it is not the case. When the CPU 72 determines that the flag F is "0" (S16: No), it determines whether the accumulation amount DPM is greater than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is set to a value that is desired to remove the PM when the amount of PM captured by the GPF 34 increases.

[0035] When the CPU 72 determines that the deposition amount DPM is equal to or larger than the regeneration execution value DPMH ( S18 : YES), it substitutes “1” into the flag F in order to execute the regeneration process ( S20 ).

[0036] On the other hand, when the CPU 72 determines that the flag F is "1" (S16: Yes), it determines whether the accumulation amount DPM is less than the stop threshold DPML (S22). The stop threshold DPML is set to a value at which the amount of PM trapped in the GPF 34 is sufficiently reduced to stop the regeneration process. When the CPU 72 determines that the accumulation amount DPM is larger than the stop threshold DPML (S22: No), it moves to the process of S20.

[0037] On the other hand, when the CPU 72 determines that the accumulation amount DPM is equal to or less than the stop threshold value DPML ( S24 : YES), it substitutes “0” into the flag F ( S24 ).

[0038] It should be noted that, when the CPU 72 completes the processing of S20 and S24, or makes a negative determination in the processing of S18, it temporarily terminates the processing. Figure 2 A series of processing is shown.

[0039] (Fuel Increasing Process for Overheat Protection of Three-Way Catalyst 32)

[0040] exist Figure 3 The steps of the fuel increase process are shown in FIG. Figure 3 The processing shown is realized by the CPU 72 repeatedly executing a program stored in the ROM 74 at a predetermined cycle, for example.

[0041] exist Figure 3In the series of processing shown, the CPU 72 first obtains the rotational speed NE of the crankshaft 26, the charging efficiency η, the air-fuel ratio Af, the ignition timing aig, the increment coefficient K1 and the regeneration coefficient K2 (S30). The increment coefficient K1 is a coefficient indicating the ratio of increasing the injection amount when the process of increasing the injection amount in order to protect the three-way catalyst 32 from overheating is being performed. It should be noted that the increment coefficient K1 becomes "1" when the above-mentioned increment process is not performed. The regeneration coefficient K2 is a coefficient indicating the ratio of increasing the injection amount when the regeneration process of the GPF 34 is being performed. It should be noted that the regeneration coefficient K2 becomes "1" when the regeneration process of the GPF 34 is not being performed.

[0042] Next, the CPU 72 calculates the temperature Tcat of the three-way catalyst 32 based on the rotational speed NE, the filling efficiency η, the air-fuel ratio Af, the ignition timing aig, the increment coefficient K1, and the regeneration coefficient K2 (S32). The CPU 72 calculates the temperature Tcat as a larger value when the filling efficiency η is large than when the filling efficiency η is small. In addition, the CPU 72 calculates the temperature Tcat as a larger value when the delay amount of the ignition timing aig relative to the MBT is large than when the delay amount is small. In addition, the CPU 72 calculates the temperature Tcat as a smaller value when the increment coefficient K1 is large than when the increment coefficient K1 is small. In addition, the CPU 72 calculates the temperature Tcat as a larger value when the regeneration coefficient K2 is large than when the regeneration coefficient K2 is small.

[0043] In detail, for example, the CPU 72 may calculate the temperature Tcat by correcting the base value of the temperature Tcat calculated by using the rotation speed NE and the charging efficiency η as inputs using the ignition timing aig, the increment coefficient K1, and the regeneration coefficient K2. In the calculation process of the temperature Tcat, the CPU 72 considers the oxygen storage amount of the three-way catalyst 32 calculated according to the air-fuel ratio Af. At this time, for example, when the air-fuel ratio Af is larger than the theoretical air-fuel ratio in a state where the oxygen storage amount is smaller than the maximum value, the CPU 72 preferably calculates the temperature Tcat by considering the temperature rise of the three-way catalyst 32 generated when the oxygen storage amount increases. In addition, for example, when the air-fuel ratio Af is smaller than the theoretical air-fuel ratio in a state where the oxygen storage amount is greater than a predetermined amount, the temperature Tcat is preferably calculated by considering the oxidation heat of the unburned fuel in the three-way catalyst 32.

[0044] Next, the CPU 72 determines whether the temperature Tcat is equal to or higher than the first temperature Tth1 (S34). The first temperature Tth1 is set according to the upper limit value of the allowable range of the temperature of the three-way catalyst 32. Specifically, the first temperature Tth1 is set to a value smaller than the upper limit value by a predetermined margin.

[0045] When the CPU 72 determines that the temperature Tcat is equal to or higher than the first temperature Tth1 (S34: Yes), it determines whether the flag F is "0" (S36). The processing of S34 and S36 is a process for determining whether the execution condition of the process of increasing the injection amount in order to protect the three-way catalyst 32 from overheating is satisfied. That is, the execution condition is a condition that the logical AND of the following conditions (a) and (b) is true.

[0046] Condition (a): a condition that the temperature Tcat is equal to or higher than the first temperature Tth1.

[0047] Condition (b): A condition in which the regeneration process of the GPF 34 is not executed.

[0048] When the CPU 72 determines that the flag F is "0" (S36: Yes), the rotation speed NE and the charging efficiency η of the operating point of the internal combustion engine 10 are input to calculate the increment coefficient K1 (S38). This is because the temperature of the exhaust gas varies depending on the operating point. The injection amount is increased using the increment coefficient K1 in order to reduce the temperature of the exhaust gas discharged to the exhaust passage 30 by the vaporization heat of the fuel. In addition, since the temperature of the exhaust gas is different when the injection amount is not increased, the increment ratio required to reduce the temperature of the exhaust gas to the desired temperature varies depending on the operating point.

[0049] It should be noted that, for example, the processing may be set to a processing in which the CPU 72 performs a mapping operation on the incremental coefficient K1 in a state in which the mapping data is stored in the ROM 74. Here, the mapping data is data in which the rotational speed NE and the charging efficiency η are set as input variables and the incremental coefficient K1 is set as an output variable. Incidentally, the mapping data is a data set of discrete values ​​of the input variables and values ​​of the output variables corresponding to the values ​​of the input variables. In addition, the mapping operation may be set to a processing in which, when the value of the input variable is consistent with any one of the values ​​of the input variables of the mapping data, the value of the output variable of the corresponding mapping data is set as the result of the operation. In addition, the mapping operation may be set to a processing in which, when the value of the input variable is inconsistent with the value of the input variable of the mapping data, the value obtained by interpolating the values ​​of the plurality of output variables contained in the mapping data is set as the result of the operation.

[0050] Next, the CPU 72 performs an incremental correction on the required injection amount Qd using the incremental 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 can be, for example, the amount of fuel required to make the air-fuel ratio of the mixture in the combustion chamber 20 the theoretical air-fuel ratio. This fuel amount can be achieved, for example, by multiplying the charging efficiency η by a predetermined coefficient to obtain an operation amount of the open-loop control. In addition, for example, it can also be achieved by correcting the operation amount of the open-loop control using an operation amount related to feedback control to a target value of the air-fuel ratio Af.

[0051] It should be noted that the CPU 72 temporarily terminates the process when the process of S40 is completed or when a negative determination is made in the processes of S34 and S36. Figure 3 A series of processing is shown.

[0052] (Processing related to regeneration of GPF 34)

[0053] exist Figure 4 2 shows the process steps related to the regeneration of the GPF 34 . Figure 4 The processing shown is realized by the CPU 72 repeatedly executing a program stored in the ROM 74 at a predetermined cycle, for example.

[0054] exist Figure 4 In the series of processes shown, the CPU 72 first determines whether the flag F is "1" (S50). When the CPU 72 determines that the flag F is "1" (S50: Yes), the value obtained by subtracting the temperature Tcat from the target temperature Tcat* is substituted into the difference ΔT (S52). The target temperature Tcat* is a target value of the temperature Tcat of the three-way catalyst 32 during the regeneration process of the GPF 34. The target temperature Tcat* is set to a temperature that can increase the temperature of the GPF 34 to a temperature that can burn and remove PM.

[0055] The CPU 72 uses the speed NE and the charging efficiency η and the difference ΔT, which are variables that define the operating point of the internal combustion engine 10, as inputs to calculate the regeneration coefficient K2 (S54). The regeneration coefficient K2 represents the ratio of the injection amount to be increased during the regeneration process of the GPF 34. The regeneration coefficient K2 is set to a value greater than "1". The CPU 72 calculates the regeneration coefficient K2 as a larger value when the difference ΔT is large than when the difference ΔT is small. In addition, even if the difference ΔT is the same, the CPU 72 calculates the value of the regeneration coefficient K2 as a different value depending on the operating point of the internal combustion engine 10. This is because the temperature of the exhaust gas without increasing the amount depends on the operating point.

[0056] This process can be realized by, for example, calculating the regeneration coefficient K2 by performing a map operation on map data pre-stored in the ROM 74 by the CPU 72. Here, the map data is data having the difference ΔT, the rotation speed NE, and the charging efficiency η as input variables and having the regeneration coefficient K2 as an output variable.

[0057] Then, CPU72 stops the injection of fuel from the intake port injection valve 16 and the in-cylinder injection valve 22 of any one of the cylinders #1 to #4 (S56). In addition, CPU72 corrects the required injection amount Qd of the remaining cylinders using the regeneration coefficient K2. That is, CPU72 makes the air-fuel ratio of the mixture in the combustion chamber 20 of the remaining cylinders richer than the theoretical air-fuel ratio. This process is used to burn and remove the PM captured by GPF34 by discharging oxygen and unburned fuel into the exhaust passage 30 to increase the temperature of GPF34. That is, by discharging oxygen and unburned fuel into the exhaust passage 30, the unburned fuel is burned in the three-way catalyst 32 and the like to increase the temperature of the exhaust gas. In this way, the temperature of GPF34 can be increased. In addition, by supplying oxygen to GPF34, the PM captured by GPF34 can be burned and removed.

[0058] The CPU 72 periodically switches the cylinders for which fuel injection is stopped. The switching period is set to, for example, a predetermined number of times of one combustion cycle. Here, the predetermined number may be, for example, a number greater than 100.

[0059] It should be noted that the CPU 72 temporarily terminates the process when the process of S56 is completed or a negative determination is made in the process of S50. Figure 4 A series of processing is shown.

[0060] Here, the function and effect of this embodiment will be described.

[0061] exist Figure 5 2 , changes in the rotation speed NE, the charging efficiency η, the temperature Tcat, the regeneration coefficient K2, the increase coefficient K1, and the flag F are shown.

[0062] like Figure 5 As shown in FIG. 1 , when the regeneration process is not executed, at the time t1 when the temperature Tcat becomes higher than the first temperature Tth1, the CPU 72 increases the increment coefficient K1 to a value greater than "1". As a result, the temperature of the exhaust gas is reduced by the heat of vaporization of the injected fuel. Therefore, the increase in the temperature Tcat can be suppressed. It should be noted that Figure 5 In FIG. 1 , the double-dashed line shows a case where the increment coefficient K1 is not increased. In this case, the temperature Tcat exceeds the first temperature Tth1 and rises significantly.

[0063] In addition, when the CPU 72 starts the regeneration process at time t2, the regeneration coefficient K2 is increased to a value greater than "1". The lower the temperature Tcat is than the target temperature Tcat*, the larger the value calculated by the CPU 72 for the regeneration coefficient K2. Then, at time t3 when the temperature Tcat exceeds the target temperature Tcat*, the CPU 72 sets the regeneration coefficient K2 to "1". In addition, after time t4 when the temperature Tcat becomes higher than the first temperature Tth1, the CPU 72 also fixes the increment coefficient K1 to "1". This is because the execution conditions of the increment process of the injection amount based on the increment coefficient K1 include the above-mentioned condition (b).

[0064] exist Figure 5 In the figure, a double-dotted line is used to indicate a case where the above-mentioned condition (b) is not included in the execution conditions of the incremental processing. In this case, if the temperature Tcat becomes higher than the first temperature Tth1 at time t4, the CPU 72 executes the incremental processing by increasing the incremental coefficient K1 to exceed "1". In this case, the amount of unburned fuel discharged into the exhaust gas increases. On the other hand, a large amount of oxygen flows into the three-way catalyst 32 through the regeneration process. Therefore, the temperature of the three-way catalyst 32 rises significantly due to the reaction heat when the unburned fuel in the exhaust gas is oxidized by the oxygen flowing into the three-way catalyst 32. Figure 5 2 shows an example in which the temperature Tcat exceeds the upper limit value Tot of the allowable temperature of the three-way catalyst 32 and rises.

[0065] exist Figure 5 In the example shown, the target temperature Tcat* is set to a value lower than the first temperature Tth1 , but the present invention is not limited to this.

[0066] exist Figure 6 2 shows an example in which the target temperature Tcat* is set to a value greater than the first temperature Tth1.

[0067] exist Figure 6 In the example shown, even after time t2 when the temperature Tcat becomes equal to or higher than the first temperature Tth1, the CPU 72 maintains the value of the increment coefficient K1 at "1". However, even after time t2, the CPU 72 considers that the temperature Tcat has not yet reached the target temperature Tcat* and sets the regeneration coefficient K2 to a value greater than "1". That is, the injection amount is increased. Then, at time t3 when the temperature Tcat reaches the target temperature Tcat*, the CPU 72 sets the regeneration coefficient K2 to "1".

[0068] Thus, the CPU 72 does not perform the injection amount increment process in an attempt to lower the exhaust gas temperature during the regeneration process. Instead, the CPU 72 performs feedback control on the temperature Tcat so that it does not exceed the target temperature Tcat* during the regeneration process. Here, the CPU 72 sets the regeneration coefficient K2 to a smaller value when the temperature Tcat is high than when the temperature Tcat is low. That is, the increment is set to a smaller value when the temperature Tcat is high than when the temperature Tcat is low. In particular, the CPU 72 sets the increment to zero when the temperature Tcat becomes higher than the target temperature Tcat*.

[0069] This can suppress an excessive increase in the temperature of the three-way catalyst 32 .

[0070] <Second Embodiment>

[0071] The second embodiment will be described below with reference to the accompanying drawings, focusing on the differences from the first embodiment. Figure 1 Side description.

[0072] In the first embodiment, the injection amount increase process based on the increase coefficient K1 is prohibited during the regeneration process. In contrast, in the present embodiment, the regeneration process is prohibited when the condition for executing the increase process, that is, the temperature Tcat becomes equal to or higher than the first temperature Tth1, is satisfied.

[0073] exist Figure 7 2 shows the process steps related to the determination of whether or not to execute the regeneration process according to the present embodiment. Figure 7 The processing shown is realized by CPU 72 repeatedly executing a program stored in ROM 74 at a predetermined cycle, for example. Figure 7 In, about Figure 2 For the sake of convenience, the same step numbers are given to the corresponding processes shown in the figure, and their descriptions are omitted.

[0074] exist Figure 7 In the series of processing shown, when the CPU 72 determines that the flag F is "0" (S16: No), it determines whether the logical AND of the following conditions (c) and (d) is true (S18a).

[0075] Condition (c): A condition that the deposition amount DPM is equal to or greater than the regeneration execution value DPMH.

[0076] Condition (d): Determination process to the effect that the regeneration process of the GPF 34 is being interrupted. It should be noted that the interruption of the regeneration process is a phenomenon caused by a negative determination in the process of S26 described later during the execution of the regeneration process.

[0077] When the CPU 72 determines that the logical AND is true (S18a: Yes) and when a negative determination is made in the process of S22, it determines whether the condition (e) that the temperature Tcat is lower than the first temperature Tth1 is satisfied (S26). Furthermore, when the CPU 72 determines that the condition (e) is satisfied (S26: Yes), it moves to the process of S20. That is, in the present embodiment, the execution condition of the regeneration process is set to the condition that the logical AND of the condition (c), the condition (d), and the condition (e) is true.

[0078] On the other hand, when the CPU 72 determines that the temperature Tcat is equal to or higher than the first temperature Tth1 ( S26 : NO), the process proceeds to S24 .

[0079] Thus, when the temperature Tcat is equal to or higher than the first temperature Tth1, even when the CPU 72 generates a regeneration request due to the establishment of the condition (c), the CPU 72 does not execute the regeneration process of the GPF 34. Therefore, the fuel is increased by the increase coefficient K1 without supplying a large amount of oxygen to the three-way catalyst 32. Therefore, the exhaust gas whose temperature is restricted to be low flows into the three-way catalyst 32, so that the temperature of the three-way catalyst 32 can be suppressed from excessively rising.

[0080] In addition, when the temperature Tcat of the three-way catalyst 32 becomes equal to or higher than the first temperature Tth1 during the execution of the regeneration process, the CPU 72 interrupts the regeneration process. As a result, the process of supplying a large amount of oxygen to the three-way catalyst 32 is interrupted. Figure 3 The processing of increasing the fuel can limit the temperature of the exhaust gas discharged from each of the cylinders #1 to #4 to a low level. Therefore, it is possible to suppress an excessive increase in the temperature of the three-way catalyst 32.

[0081] <Correspondence>

[0082] The correspondence between the items in the above-mentioned embodiment and the items recorded in the above-mentioned "Means for Solving the Problem" column is as follows. Below, the correspondence is shown for each number of the solution means recorded in the "Means for Solving the Problem" column. [1] The exhaust gas purification device corresponds to the three-way catalyst 32 and the GPF 34. The stop process corresponds to the process of S56. The temperature acquisition process corresponds to the process of S32. The increment process corresponds to the process of S40. The prohibition process in Figure 3 The processing of S36 is executed in accordance with the execution condition of the processing of S40. Figure 7 [2] The second temperature corresponds to the target temperature Tcat*. [3] Corresponds to Figure 5 The processing illustrated. [4] corresponds to Figure 6 The processing illustrated. [5] corresponds to Figure 7 processing.

[0083] <Other Embodiments>

[0084] It should be noted that the present embodiment can be implemented by modification as follows. The present embodiment and the following modification examples can be implemented in combination with each other within the scope of no technical contradiction.

[0085] "About the First Temperature and the Second Temperature"

[0086] ·exist Figure 5 and Figure 6 2 shows an example in which the first temperature Tth1 and the target temperature Tcat* are different values ​​from each other, but the present invention is not limited to this.

[0087] The second temperature, which is the temperature at which the regeneration coefficient K2 is set to be less than "1", is not limited to the target temperature Tcat*. For example, as described in the "Regarding the temperature control process" column, when the temperature Tcat is controlled so as to be within a range above the lower limit value and below the upper limit value, the upper limit value may be set to the second temperature.

[0088] "About temperature control processing"

[0089] In the above embodiment, the regeneration coefficient K2 is variably set according to the difference ΔT, the charging efficiency η as a variable representing the load, and the rotation speed NE, but the present invention is not limited thereto. For example, the accelerator operation amount may be used as a variable representing the load instead of the charging efficiency η.

[0090] It is not essential to variably set the regeneration coefficient K2 based on the difference ΔT, the variable representing the load, and the rotation speed NE. For example, the regeneration coefficient K2 may be variably set based on any one of the difference ΔT, the variable representing the load, and the rotation speed NE.

[0091] It is not essential to set the regeneration coefficient K2 variably according to at least one of the variable representing the load and the rotation speed NE. For example, the output value of the proportional element with the difference ΔT as input may be set as the regeneration coefficient K2. Also, for example, the sum of the output value of the proportional element with the difference ΔT as input and the output value of the integral element may be set as the regeneration coefficient K2.

[0092] In the above embodiment, the minimum value of the regeneration coefficient K2 is set to "1", but it is not limited to this. For example, it can also be set to a value slightly smaller than "1". In this case, it is possible to more reliably suppress the amount of unburned fuel discharged from the cylinder to which fuel supply continues to be exceeded The amount of oxygen discharged from the cylinder.

[0093] ·The regeneration coefficient K2 is not limited to being set according to the difference between the target temperature Tcat* and the temperature Tcat. For example, the upper limit and lower limit of the temperature Tcat may be set, and the operation amount used to control the temperature Tcat to enter a region above the lower limit and below the upper limit may be set as the regeneration coefficient K2. In this case, when the temperature Tcat is smaller than the lower limit, the regeneration coefficient K2 may be set to a value greater than "1". In addition, when the temperature Tcat is larger than the upper limit, the regeneration coefficient K2 may be set to less than "1". Furthermore, when the temperature Tcat is within this region, the regeneration coefficient K2 may be set to "1".

[0094] About Incremental Processing

[0095] In the above embodiment, the magnitude of the incremental coefficient K1 is set according to the rotation speed NE and the filling efficiency η as a variable representing the load regardless of the temperature Tcat, but the present invention is not limited thereto. For example, the magnitude of the incremental coefficient K1 may be variably set according to the temperature Tcat, the rotation speed NE, and the variable representing the load. In this case, even if the values ​​of the rotation speed NE and the variable representing the load are the same, the incremental coefficient K1 may be set to a larger value when the temperature Tcat is large than when the temperature Tcat is small.

[0096] In the above embodiment, the increment coefficient K1 is set according to the rotation speed NE and the charging efficiency η as a variable representing the load, but the present invention is not limited thereto. For example, the accelerator operation amount may be used as a variable representing the load. In addition, the rotation speed NE and the variable representing the load may be variably set according to either one of them. Moreover, it is not necessary to variably set according to at least one of the rotation speed NE and the variable representing the load.

[0097] "About Prohibition of Processing"

[0098] ·exist Figure 7 In the case where the temperature Tcat during the regeneration process of the GPF 34 becomes equal to or higher than the first temperature Tth1, the regeneration process is interrupted. Figure 3 The increment coefficient K1 is immediately set to a value greater than "1" in the process shown, but the present invention is not limited thereto. For example, the process of S40 may be prohibited until a predetermined time has passed after the regeneration process is interrupted. In other words, the timing of starting the process of S40 relative to the timing of interrupting the regeneration process may be delayed.

[0099] "About stopping processing"

[0100] The stop process is not limited to the regeneration process. For example, it is also possible to stop the supply of fuel to a part of the cylinders in order to adjust the output of the internal combustion engine 10. In this case, the air-fuel ratio of the mixed gas in the cylinder different from the part of the cylinders can also be made to be the theoretical air-fuel ratio. In addition, for example, it is also possible to stop the supply of fuel to only a part of the cylinders when the oxygen storage amount of the three-way catalyst 32 becomes less than a specified value and to control the air-fuel ratio of the mixed gas in the remaining cylinders to be the theoretical air-fuel ratio.

[0101] "About exhaust gas purification equipment"

[0102] The GPF 34 is not limited to being provided downstream of the three-way catalyst 32 in the exhaust passage 30. In addition, it is not essential for the post-processing device to include the GPF 34 itself. The GPF 34 is not limited to being a trap carrying a three-way catalyst. For example, when a three-way catalyst is provided upstream, it may be only a trap.

[0103] About the Control Device

[0104] ·The control device is not limited to having a CPU 72 and a ROM 74 and executing software processing. For example, it may also be provided with a dedicated hardware circuit such as an ASIC that performs hardware processing on at least a part of the software processing in the above-mentioned embodiment. That is, the control device may be any of the following structures (a) to (c). (a) It has a processing device that executes all of the above-mentioned processing according to a program and a program storage device such as a ROM that stores the program. (b) It has a processing device that executes a part of the above-mentioned processing according to a program, a program storage device, and a dedicated hardware circuit that executes the remaining processing. (c) It has a dedicated hardware circuit that executes all of the above-mentioned processing. Here, the software execution device and the dedicated hardware circuit that have the processing device and the program storage device may be multiple.

Claims

1. A control device for an internal combustion engine, applied to an internal combustion engine having an exhaust gas purification 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 plurality of cylinders. The control device of the internal combustion engine executes a stop process, a temperature acquisition process, an increase process and a prohibition process, The stop process is a process of stopping the supply of fuel to a part of the cylinders of the internal combustion engine and continuing the supply of fuel to the remaining cylinders. The temperature acquisition process is a process for acquiring the temperature of the exhaust gas purification device. The increase processing is processing for increasing the injection amount of 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 increment process from being executed at the same time. The prohibition process is a process of prohibiting execution of the increment process while the stop process is being executed, When the stop process is executed, a temperature control process is executed. The temperature control process includes the following processes: when the temperature is lower than a second temperature, the injection amount of the fuel injection valve is set in such a manner that the air-fuel ratio of the mixture in the remaining cylinders is richer than the theoretical air-fuel ratio; and when the temperature becomes higher than the second temperature, the injection amount of the fuel injection valve of the remaining cylinder is reduced.

2. The control device for an internal combustion engine according to claim 1, The second temperature is lower than the first temperature.

3. The control device for an internal combustion engine according to claim 1, The second temperature is greater than the first temperature.

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