Control device for internal combustion engine

Abstract

To increase the accuracy in estimating the temperature of a gas discharged from cylinders, to which fuel supply is stopped, among a plurality of cylinders.SOLUTION: A CPU 72 executes: specific cylinder stop processing of stopping fuel supply to some cylinders among a plurality of cylinders and performing fuel supply to the remaining cylinders other than the some cylinders; all cylinder stop processing of stopping fuel supply to all the cylinders; and temperature calculation processing of calculating a gas temperature, which is the temperature of a gas discharged from the cylinders of the internal combustion engine 10 into an exhaust passage 30. The temperature calculation processing includes processing of calculating the gas temperature on the basis of a temperature of the exhaust passage during execution of the all cylinder stop processing, and processing of calculating the gas temperature of the stopped cylinders, to which fuel supply is stopped, on the basis of a flow rate of the gas discharged from the stopped cylinders and an engine water temperature, during execution of the specific cylinder stop processing.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, Patent Document 1 describes a device that substitutes the temperature of the exhaust passage as the gas temperature, which is the temperature of gas discharged from the internal combustion engine into the exhaust passage, during a so-called fuel cut, in which fuel supply to all cylinders is stopped.

[0003] On the other hand, Patent Document 2 describes an apparatus that performs a specific cylinder stop process to stop fuel supply to some of the multiple cylinders of an internal combustion engine, while supplying fuel to the remaining cylinders other than the some of the cylinders. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-56325 A [Patent Document 2] Patent Publication No. 2021-60027 Summary of the Invention [Problem to be solved by the invention]

[0005] When the specific cylinder stopping process is executed, air is discharged as gas from the stopped cylinders to which fuel supply is stopped, in the same manner as during the execution of the fuel cut described above, and combustion gas is discharged from the combustion cylinders to which fuel is supplied and in which the air-fuel mixture is burned.

[0006] When the specific cylinder stop process is executed, the temperature of the exhaust passage increases due to the combustion gas discharged from the combustion cylinder. Therefore, if the temperature of the exhaust passage is set as the temperature of the gas discharged from the stopped cylinder, the calculated gas temperature will be higher than the actual gas temperature, and there is a risk that the estimation accuracy of the temperature of the gas discharged from the stopped cylinder will decrease. [Means for solving the problem]

[0007] A control device for an internal combustion engine that solves the above problems is applied to an internal combustion engine having a plurality of cylinders. The control device executes a specific cylinder stop process for stopping fuel supply to some of the plurality of cylinders and supplying fuel to the remaining cylinders other than the some of the cylinders, an all-cylinder stop process for stopping fuel supply to all cylinders, and a temperature calculation process for calculating a gas temperature, which is the temperature of gas discharged from a cylinder of the internal combustion engine to an exhaust passage. The temperature calculation process includes a process for calculating the gas temperature based on the temperature of the exhaust passage during the all-cylinder stop process, and a process for calculating the gas temperature of the stopped cylinder based on the flow rate of gas discharged from the stopped cylinder to which fuel supply is stopped and an engine water temperature during the specific cylinder stop process.

[0008] Gas discharged from a stopped cylinder, to which fuel supply has been stopped by execution of the specific cylinder stop process, receives heat from the wall surface of the combustion chamber of the stopped cylinder as it passes through the chamber. The wall surface temperature of the combustion chamber of the stopped cylinder depends on the engine water temperature. In addition, the time during which the gas passing through the combustion chamber of the stopped cylinder receives heat from the wall surface of the combustion chamber depends on the flow rate of gas discharged from the stopped cylinder into the exhaust passage. Therefore, the temperature of gas discharged from the combustion chamber of the stopped cylinder can be estimated based on the engine water temperature and the gas flow rate.

[0009] Therefore, in this configuration, during the execution of the specific cylinder deactivation process, the gas temperature of the deactivated cylinder is calculated based on the flow rate of gas discharged from the deactivated cylinder into the exhaust passage and the engine water temperature, thereby improving the accuracy of estimating the temperature of gas discharged from the deactivated cylinder. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing the configuration of an internal combustion engine, a drive system, and a control device according to an embodiment. [Diagram 2] 4 is a flowchart showing a processing procedure executed by the control device of the embodiment. [Diagram 3] 4 is a flowchart showing a processing procedure executed by the control device of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <Configuration of the internal combustion engine, drive system, and control device> Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings. As shown in FIG. 1, an internal combustion engine 10 includes four cylinders, for example, cylinder #1 to cylinder #4.

[0012] A throttle valve 14 is provided in an intake passage 12 of the internal combustion engine 10. A port injection valve 16 that injects fuel into the intake port 12a is provided in the intake port 12a, which is the downstream portion of the intake passage 12. The air taken into the intake passage 12 and the fuel injected from the port injection valve 16 flow into a combustion chamber 20 when an intake valve 18 opens.

[0013] Further, a cylinder head of the internal combustion engine 10 is provided with an in-cylinder injection valve 22 that injects fuel directly into the combustion chamber 20 . The mixture of air and fuel in the combustion chamber 20 is combusted in response to a spark discharge from an ignition plug 24. The combustion energy generated at that time is converted into rotational energy of a crankshaft 26.

[0014] The air-fuel mixture burned in the combustion chamber 20 of each cylinder is discharged as exhaust gas into an exhaust passage 30 when the exhaust valve 28 opens. A three-way catalyst 32 having an oxygen storage capacity and a gasoline particulate filter (GPF 34) that collects particulate matter (hereinafter referred to as PM) in the exhaust gas are provided in the exhaust passage 30. In this embodiment, the GPF 34 is assumed to be a filter that collects PM and supports a three-way catalyst.

[0015] The crankshaft 26 is mechanically connected to a carrier C of a planetary gear mechanism 50 constituting a power split device. A rotating shaft 52a of a first motor generator 52 is mechanically connected to a sun gear S of the planetary gear mechanism 50. A rotating shaft 54a of a second motor generator 54 and a driving wheel 60 are mechanically connected to a ring gear R of the planetary gear mechanism 50. An AC voltage is applied to terminals of the first motor generator 52 by an inverter 56. An AC voltage is applied to terminals of the second motor generator 54 by an inverter 58.

[0016] The control device 70 controls the internal combustion engine 10, and operates various operating parts of the internal combustion engine 10, such as the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, and the spark plug 24, in order to control the torque, which is a controlled variable, and the ratio of exhaust components, etc. The control device 70 also controls the first motor generator 52, and operates the inverter 56 in order to control the rotation speed, which is a controlled variable. The control device 70 also controls the second motor generator 54, and operates the inverter 58 in order to control the torque, which is a controlled variable. Fig. 1 shows operation signals MS1 to MS6 for the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, the spark plug 24, and the inverters 56, 58, respectively.

[0017] In order to control the control amount of the internal combustion engine 10, the control device 70 refers to the intake air amount Ga detected by the air flow meter 80, the output signal Scr of the crank angle sensor 82, and the temperature of the cooling water (engine water temperature THW) of the internal combustion engine 10 detected by the water temperature sensor 86. The control device 70 also refers to the intake air temperature THA detected by the intake air temperature sensor 84. Here, the intake air temperature THA is referred to as the outside air temperature. The control device 70 also refers to the pressure Pex of the exhaust gas flowing into the GPF 34, which is a value detected by the exhaust pressure sensor 88. The control device 70 also refers to the air-fuel ratio Af detected by an air-fuel ratio sensor 89 upstream of the three-way catalyst 32. In order to control the control amount of the first motor-generator 52 and the second motor-generator 54, the control device 70 also refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first motor-generator 52 and the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor-generator 54.

[0018] The control device 70 includes a CPU 72, a ROM 74, a storage device 75, and a peripheral circuit 76, which are capable of communicating with each other via a communication line 78. Here, the peripheral circuit 76 includes a circuit that generates a clock signal that regulates the internal operation, a power supply circuit, a reset circuit, etc. The control device 70 controls the controlled variable by the CPU 72 executing a program stored in the ROM 74.

[0019] <Processing performed by the control device> The control device 70 calculates the engine speed NE based on the output signal Scr. The control device 70 also calculates an engine load factor KL. The engine load factor KL is a parameter that determines the amount of air filled in the combustion chamber 20, and is the ratio of the amount of inflow air per combustion cycle of one cylinder to a reference amount of inflow air. The reference amount of inflow air may be an amount that is variably set according to the engine speed NE.

[0020] <Regeneration processing> Fig. 2 shows the procedure of the process executed by the control device 70 according to this embodiment. The process shown in Fig. 2 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example, at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "S".

[0021] In the series of processes shown in FIG. 2, the CPU 72 first acquires the engine speed NE, the engine load factor KL, and the engine water temperature THW (S10). Next, the CPU 72 calculates an update amount ΔDPM of the accumulation amount DPM based on the engine speed NE, the engine load factor KL, and the engine water temperature THW (S12). Here, the accumulation amount DPM is the amount of PM trapped in the GPF 34. In detail, the CPU 72 calculates the amount of PM in the exhaust gas discharged into the exhaust passage 30 based on the engine speed NE, the engine load factor KL, and the engine water temperature THW. The CPU 72 also acquires the temperature of the GPF 34, which is calculated in a separate process. The CPU 72 then calculates the update amount ΔDPM based on the amount of PM in the exhaust gas and the temperature of the GPF 34.

[0022] Next, the CPU 72 updates the accumulation amount DPM in accordance with the update amount ΔDPM (S14). Next, the CPU 72 determines whether or not the flag F is "1" (S16). When the flag F is "1", it indicates that the temperature increase process for burning and removing PM in the GPF 34 is being executed, and when the flag F is "0", it indicates that the temperature increase process is not being executed.

[0023] When the CPU 72 determines that the flag F is "0" (S16: NO), it determines whether the accumulation amount DPM is equal to or greater than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is set to a value at which the amount of PM trapped by the GPF 34 is large and it is desired to remove the PM.

[0024] When the CPU 72 determines that the accumulation amount DPM is equal to or greater than the regeneration execution value DPMH (S18: YES), it determines whether or not a condition for executing the temperature increase process is satisfied (S20). Here, the execution condition may be, for example, a condition that the logical product of the following condition (A) and condition (B) is true.

[0025] Condition (A): An engine torque command value Te*, which is a command value of the torque for the internal combustion engine 10, is equal to or greater than a predetermined value Teth. Condition (B): The engine speed NE of the internal combustion engine 10 is equal to or higher than a predetermined speed.

[0026] When the CPU 72 determines that the execution condition for the temperature increase process is met (S20: YES), the CPU 72 executes the temperature increase process and sets flag F to "1" (S22). As the temperature increase process, the CPU 72 executes a specific cylinder stop process.

[0027] The specific cylinder stopping process is a process for stopping the fuel supply to some of the cylinders among a plurality of cylinders and supplying fuel to the remaining cylinders other than the some of the cylinders, and includes a stopping process and an increasing process.

[0028] The stop process is a process for stopping fuel injection from the port injection valve 16 and the direct injection valve 22 of cylinder #1, that is, for stopping the fuel supply to cylinder #1 by performing a fuel cut. Note that, hereinafter, the cylinder for which this stop process is performed is referred to as a stopped cylinder, and the remaining cylinders other than the stopped cylinder, that is, the cylinders to which fuel is supplied and the air-fuel mixture is burned, are referred to as combustion cylinders.

[0029] The amount-increasing process is a process for increasing the amount of fuel supplied to each of the combustion cylinders, namely, cylinders #2, #3, and #4, compared to when the stop process is not executed, in order to supply unburned fuel to the exhaust passage 30. When the amount-increasing process is executed, the amount of fuel injected from the port injection valve 16 and the in-cylinder injection valve 22 is increased so that the air-fuel ratio of the mixture in the combustion cylinder becomes richer than the stoichiometric air-fuel ratio.

[0030] This specific cylinder stop process performs a regeneration process in which oxygen and unburned fuel are supplied to the exhaust passage 30 to raise the temperature of the GPF 34, thereby burning and removing the PM trapped in the GPF 34. That is, oxygen and unburned fuel are discharged into the exhaust passage 30, and the unburned fuel is burned in the three-way catalyst 32 or the like to raise the temperature of the exhaust gas, thereby raising the temperature of the GPF 34. Then, oxygen is supplied to the GPF 34, whereby the PM trapped by the GPF 34 is burned and removed.

[0031] Furthermore, the CPU 72 executes an MG2 torque compensation process to compensate for the reduction in engine output accompanying the execution of the stop process (S24). In this MG2 torque compensation process, the CPU 72 superimposes a compensation torque, which is the output torque for one cylinder, on the torque required for running of the second motor generator 54. Then, the CPU 72 operates the inverter 58 based on the required torque on which the compensation torque has been superimposed.

[0032] On the other hand, in the process of S16, when the CPU 72 determines that the flag F is "1" (S16: YES), the CPU 72 determines whether the accumulation amount DPM is equal to or less than the stop threshold DPML (S26). The stop threshold DPML is set to a value at which the amount of PM trapped in the GPF 34 becomes small enough that the temperature increase process may be stopped. When the CPU 72 determines that the accumulation amount DPM is equal to or less than the stop threshold DPML (S26: YES), the CPU 72 stops the partial cylinder fuel cut process to stop the temperature increase process, and sets the flag F to "0" (S28).

[0033] When the CPU 72 completes the processes of S24 and S28, or when a negative determination is made in the processes of S18 and S20, the CPU 72 temporarily ends the series of processes shown in FIG. <Gas temperature calculation process> The control device 70 executes a temperature calculation process to calculate the gas temperature, which is the temperature of the gas discharged from the cylinders of the internal combustion engine 10 into the exhaust passage 30.

[0034] Fig. 3 shows the procedure of the temperature calculation process executed by the control device 70. The process shown in Fig. 3 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example, at a predetermined interval.

[0035] 3, the CPU 72 first calculates a base outlet gas temperature Toutb (S100), which is a base value of the outlet gas temperature Tout, which is the temperature of gas discharged from the cylinders of the internal combustion engine 10 to the exhaust passage 30. In this embodiment, the operating point of the internal combustion engine 10 is determined by the engine load factor KL and the engine speed NE.

[0036] Specifically, the base output gas temperature Toutb is calculated from the map by the CPU 72 in a state where map data in which the engine speed NE and the engine load factor KL are input variables and the base output gas temperature Toutb is an output variable is stored in advance in the ROM 74. Here, the base output gas temperature Toutb is calculated on the assumption that, for example, the air-fuel ratio is a predetermined air-fuel ratio (assumed to be the stoichiometric air-fuel ratio here), the ignition timing is a predetermined ignition timing (MBT here), the engine water temperature THW is a predetermined temperature, and the intake air temperature THA is a specified temperature.

[0037] Next, the CPU 72 determines whether the logical sum of the fact that all-cylinder fuel cut processing is being executed as an all-cylinder stop processing that stops the fuel supply to all cylinders and the fact that the internal combustion engine 10 is stopped is true (S110).

[0038] If the mixture of air flowing into the combustion chamber 20 via the intake passage 12 and fuel injected from the port injection valve 16 or the in-cylinder injection valve 22 is being combusted by spark discharge from the spark plug 24 (S110: NO), the CPU 72 proceeds to processing of S120.

[0039] In the process of S120, the CPU 72 calculates a first output gas temperature Tout1 by adding the first correction amount ΔT1 and the second correction amount ΔT2 to the base output gas temperature Toutb. This first output gas temperature Tout1 is the temperature of gas discharged from the combustion cylinder.

[0040] The first correction amount ΔT1 is calculated by the CPU 72 based on the engine water temperature THW, the air-fuel ratio Af, the ignition timing aig, and the intake air temperature THA. The first correction amount ΔT1 is a correction amount for correcting the base output gas temperature Toutb based on deviation of the actual state from the condition assumed when the base output gas temperature Toutb is calculated. That is, for example, when the actual air-fuel ratio Af deviates from the assumed air-fuel ratio, the first correction amount ΔT1 is a correction amount for decreasing the base output gas temperature Toutb. Also, for example, when the actual ignition timing aig deviates from the assumed ignition timing to the retard side, the first correction amount ΔT1 is a correction amount for increasing the base output gas temperature Toutb.

[0041] On the other hand, the second correction amount ΔT2 is calculated by the CPU 72 based on the ignition timing aig, the intake air amount Ga, and the air-fuel ratio Af. The second correction amount ΔT2 is the amount of rise in temperature of the exhaust gas caused by the combustion of unburned fuel and oxygen when they are present in the exhaust gas discharged from the combustion chamber 20. The CPU 72 assumes that the more the ignition timing aig is delayed relative to the MBT, the greater the amount of unburned fuel and oxygen present in the exhaust gas discharged from the combustion chamber 20, and calculates the reaction heat therebetween to be a larger value.

[0042] Next, the CPU 72 determines whether the specific cylinder stop process is being executed (S130). If the CPU 72 determines that the specific cylinder stop process is being executed (S130: YES), the CPU 72 calculates a second outlet gas temperature Tout2 (S140). This second outlet gas temperature Tout2 is the temperature of gas discharged from the stopped cylinder.

[0043] Specifically, the CPU 72 calculates the second output gas temperature Tout2 from the map in a state where map data in which the engine water temperature THW and the gas flow rate Ge are input variables and the second output gas temperature Tout2 is an output variable is stored in the ROM 74 in advance. The gas flow rate Ge, which is an input variable in S140, is the flow rate of gas discharged from the stopped cylinder to the exhaust passage 30, and is a value calculated by the CPU 72 based on the intake air amount Ga, the engine rotation speed NE, and the like. Incidentally, the gas flow rate Ge may be directly detected by a flow rate sensor or the like. The CPU 72 calculates the second output gas temperature Tout2 to a larger value (higher temperature) as the engine water temperature THW is higher. The CPU 72 calculates the second output gas temperature Tout2 to a larger value (higher temperature) as the gas flow rate Ge is smaller. The process of S140 corresponds to a process of calculating the gas temperature of the stopped cylinder based on the flow rate of gas discharged from the stopped cylinder to which fuel supply is stopped and the engine water temperature during the execution of the specific cylinder stop process.

[0044] Next, the CPU 72 calculates the output gas temperature Tout based on the first output gas temperature Tout1 and the second output gas temperature Tout2 (S150). Specifically, the CPU 72 assigns the sum of the value obtained by multiplying the first output gas temperature Tout1 by the coefficient K4 and the value obtained by multiplying the second output gas temperature Tout2 by the coefficient K5 to the output gas temperature Tout. The coefficients K4 and K5 are the following values. That is, when the number of cylinders that become stopped cylinders in one combustion cycle when the specific cylinder stop processing is executed is N1, and the total number of cylinders of the internal combustion engine 10 is N, the coefficient K4 is a value indicated by "(N-N1) / N". Here, the value of (N-N1) is the number of cylinders that become burning cylinders in one combustion cycle when the specific cylinder stop processing is executed. Also, the coefficient K5 is a value indicated by "N1 / N". For example, in this embodiment, the coefficient K4 is "(4-1) / 4=0.75", and the coefficient K5 is "1 / 4=0.25".

[0045] When the determination in S130 above is negative, the CPU 72 substitutes the first outlet gas temperature Tout1 calculated in S120 for the outlet gas temperature Tout (S160). In the process of S110, when the CPU 72 determines that the logical sum is true (S110: YES), it assigns the exhaust manifold temperature Texm in the previous control cycle of the process shown in FIG. 3 to the outlet gas temperature Tout (S170). The exhaust manifold temperature Texm is the wall temperature of the exhaust passage 30 on the exhaust upstream side of the three-way catalyst 32. Note that in FIG. 3, in order to distinguish between the current value and the previous value in the series of processes shown in FIG. 3, "n" is written for the current value and "n-1" is written for the previous value. Also, the process of S170 corresponds to the process of calculating the gas temperature based on the temperature of the exhaust passage during execution of the all cylinders stop process.

[0046] When any of the processes of S150, S160, and S170 is completed, the CPU 72 determines whether the internal combustion engine 10 is stopped (S180). When the CPU 72 determines that the internal combustion engine 10 is stopped (S180: YES), the CPU 72 calculates an update amount ΔTexm for the exhaust manifold temperature Texm based on the difference between the exhaust manifold temperature Texm and the engine water temperature THW (S200). In detail, the CPU 72 calculates a smaller update amount ΔTexm as the exhaust manifold temperature Texm is higher than the engine water temperature THW. Specifically, the CPU 72 multiplies the value obtained by subtracting the exhaust manifold temperature Texm from the engine water temperature THW by a predetermined coefficient K1, and assigns the result to the update amount ΔTexm.

[0047] On the other hand, when the CPU 72 determines in the process of S180 that the engine is not stopped (S180: NO), it calculates an update amount ΔTexm based on the difference between the engine water temperature THW and the exhaust manifold temperature Texm as well as the difference between the outlet gas temperature Tout and the exhaust manifold temperature Texm (S220). In detail, the CPU 72 calculates an update amount ΔTexm to be a larger value as the outlet gas temperature Tout is higher than the exhaust manifold temperature Texm. Specifically, the CPU 72 assigns the sum of a value obtained by multiplying the value obtained by subtracting the exhaust manifold temperature Texm from the engine water temperature THW by a predetermined coefficient K1 and a value obtained by multiplying the value obtained by subtracting the exhaust manifold temperature Texm from the outlet gas temperature Tout by a predetermined coefficient K2 to the update amount ΔTexm.

[0048] When the processes of S200 and S220 are completed, the CPU 72 updates the exhaust manifold temperature Texm by adding an update amount ΔTexm to the exhaust manifold temperature Texm (S240). Next, the CPU 72 updates the inlet gas temperature Tin based on the difference between the exhaust manifold temperature Texm and the outlet gas temperature Tout (S260). The inlet gas temperature Tin is the temperature of the gas flowing into the three-way catalyst 32. In detail, the CPU 72 calculates a larger decrease correction amount as the outlet gas temperature Tout is higher than the exhaust manifold temperature Texm, and calculates the inlet gas temperature Tin by decreasing and correcting the outlet gas temperature Tout by the decrease correction amount. Specifically, the CPU 72 calculates the inlet gas temperature Tin by adding a value obtained by subtracting the outlet gas temperature Tout from the exhaust manifold temperature Texm and multiplying the result by a predetermined coefficient K3 to the outlet gas temperature Tout. Note that, when the CPU 72 is executing the process of S170, it does not calculate the inlet gas temperature Tin by the process of S260, but sets the value calculated by the process of S170 as the current inlet gas temperature Tin.

[0049] Next, the CPU 72 calculates the temperature of the three-way catalyst 32 using the inlet gas temperature Tin (S280). Here, when the inlet gas temperature Tin is high, the temperature of the three-way catalyst 32 is calculated to be higher than when the inlet gas temperature Tin is low. Specifically, for example, the correction amount for the temperature of the three-way catalyst 32 may be determined by subtracting the temperature of the three-way catalyst 32 from the inlet gas temperature Tin and multiplying the result by a predetermined coefficient. However, this is not limiting, and for example, the three-way catalyst 32 may be divided into a plurality of regions from the upstream side to the downstream side, and the temperature of each region may be calculated taking into account heat exchange between each of the regions. In this case, the temperature of the most upstream region may be calculated taking into account heat exchange with a fluid having the inlet gas temperature Tin.

[0050] When the process of S280 is completed, the CPU 72 temporarily ends the series of processes shown in FIG. For example, when the temperature of the three-way catalyst 32 calculated by the process of S280 is equal to or lower than a specified temperature while the internal combustion engine 10 is stopped, the CPU 72 starts the internal combustion engine 10. By starting the internal combustion engine 10, the temperature of the three-way catalyst 32 is raised to an activation temperature, thereby ensuring exhaust purification performance.

[0051] <Action and Effects> The operation and effects of this embodiment will be described. (1) The gas discharged from a stopped cylinder, to which fuel supply has been stopped by execution of the specific cylinder stop process, receives heat from the wall surface of the combustion chamber 20 of the stopped cylinder as it passes through the chamber. The wall surface temperature of the combustion chamber 20 of the stopped cylinder is a value that depends on the engine water temperature THW. In addition, the time during which the gas passing through the combustion chamber 20 of the stopped cylinder receives heat from the wall surface of the combustion chamber 20 is a value that depends on the gas flow rate Ge of the gas discharged from the stopped cylinder into the exhaust passage 30. Therefore, the temperature of the gas discharged from the combustion chamber 20 of the stopped cylinder into the exhaust passage 30 can be estimated based on the engine water temperature THW and the gas flow rate Ge.

[0052] Therefore, in this embodiment, during the specific cylinder stop process, the process of S140 shown in Fig. 3 is executed. That is, the second outlet gas temperature Tout2, which is the gas temperature of the stopped cylinder, is calculated based on the gas flow rate Ge of the gas discharged from the stopped cylinder to the exhaust passage 30 and the engine water temperature THW. Therefore, it is possible to improve the accuracy of estimating the temperature of the gas discharged from the stopped cylinder.

[0053] (2) The output gas temperature Tout of the gas discharged from the internal combustion engine 10 to the exhaust passage 30 during execution of the specific cylinder stop process is affected by the ratio between the number of stopped cylinders and the number of burning cylinders in one combustion cycle. Therefore, in this embodiment, during execution of the specific cylinder stop process, the process of S150 shown in FIG. 3 is executed. That is, the first output gas temperature Tout1 and the second output gas temperature Tout2 are weighted by the coefficients K4 and K5, which indicate the ratio between the number of stopped cylinders and the number of burning cylinders, and then the output gas temperature Tout is calculated. Therefore, it is possible to improve the estimation accuracy of the output gas temperature Tout during execution of the specific cylinder stop process.

[0054] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0055] The predetermined conditions for permitting the execution of the above-mentioned temperature increase process are not limited to those exemplified in the above embodiment. For example, the above-mentioned two conditions (A) and (B) may include only one of them. In addition, the predetermined conditions may include conditions other than the above two conditions.

[0056] In order to compensate for the reduction in engine output accompanying the execution of the above-mentioned stop processing, in the processing of S24 shown in Fig. 2, a compensation torque is superimposed on the torque required for the second motor-generator 54. Alternatively, in the case of a vehicle not equipped with such a second motor-generator 54, the amount of air and fuel supplied to the combustion cylinders may be increased compared to when the above-mentioned stop processing is not executed, thereby increasing the output torque of the combustion cylinders and compensating for the reduction in engine output.

[0057] The process for executing the specific cylinder stop process is not limited to the regeneration process described above. For example, the specific cylinder stop process may be executed for catalyst warm-up or sulfur poisoning recovery. Also, for example, the specific cylinder stop process may be executed to increase the amount of oxygen stored in the three-way catalyst 32.

[0058] The process of estimating the deposition amount DPM is not limited to the example shown in Fig. 2. For example, the deposition amount DPM may be estimated based on the intake air amount Ga and the pressure difference between the upstream and downstream sides of the GPF 34. Specifically, the deposition amount DPM may be estimated to be a larger value when the pressure difference is large than when it is small, and even if the pressure difference is the same, the deposition amount DPM may be estimated to be a larger value when the intake air amount Ga is small than when it is large. Here, when the pressure downstream of the GPF 34 is approximately equal to the atmospheric pressure and can be considered to be a generally constant value, the pressure Pex can be used instead of the pressure difference.

[0059] The number of cylinders to be stopped for fuel supply to be stopped in one combustion cycle when the specific cylinder stopping process is being executed is "1". However, the number of cylinders to be stopped can be changed as appropriate with the maximum value being "total number of cylinders - 1". Also, it is not essential to fix the cylinders to be stopped to predetermined cylinders. For example, the cylinders to be stopped for fuel supply to be stopped may be changed for each combustion cycle.

[0060] The GPF 34 is not limited to a filter carrying a three-way catalyst, and may be a filter alone. Furthermore, the GPF 34 is not limited to being provided downstream of the three-way catalyst 32 in the exhaust passage 30. Furthermore, the three-way catalyst 32 may be replaced with an oxidation catalyst that oxidizes components contained in the exhaust gas. Furthermore, it is not essential to provide the GPF 34 as an exhaust purification device.

[0061] The first outlet gas temperature Tout1 may be calculated in a manner different from that in the above embodiment. The control device is not limited to a device equipped with a CPU 72 and a ROM 74 and executing software processing. For example, the control device may be equipped with a dedicated hardware circuit such as an ASIC that performs hardware processing of at least a part of what was processed by software in the above embodiment. That is, the control device may have any of the following configurations (a) to (c). (a) A processing device that executes all of the above processing according to a program, and a program storage device such as a ROM that stores the program. (b) A processing device and program storage device that execute part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, there may be a plurality of software execution devices equipped with a processing device and a program storage device, and a plurality of dedicated hardware circuits.

[0062] The vehicle is not limited to a series-parallel hybrid vehicle, but may be, for example, a parallel hybrid vehicle or a series hybrid vehicle. However, the vehicle is not limited to a hybrid vehicle, and may be, for example, a vehicle in which the power generating device of the vehicle is only the internal combustion engine 10. [Explanation of symbols]

[0063] 10. Internal combustion engine 12…Intake passage 12a…Intake port 14...Throttle valve 16...Port injection valve 18…Intake valve 20…Combustion chamber 22...In-cylinder injection valve 24…Spark plug 26…Crankshaft 28…Exhaust valve 30…Exhaust passage 32...Three-way catalyst 34…GPF 50...Planetary gear mechanism 52…First motor generator 54…Second motor generator 60…Drive wheel 70...Control device 72…CPU 74...ROM 80…Air flow meter 82...Crank angle sensor 86...Water temperature sensor 88...Exhaust pressure sensor

Claims

[Claim 1] When applied to an internal combustion engine having multiple cylinders, a specific cylinder stopping process for stopping fuel supply to some of the cylinders among the plurality of cylinders and supplying fuel to the remaining cylinders other than the some of the cylinders; An all-cylinder shutoff process for stopping fuel supply to all cylinders; A temperature calculation process is executed to calculate a gas temperature, which is the temperature of gas discharged from a cylinder of the internal combustion engine into an exhaust passage. The temperature calculation process includes a process of calculating the gas temperature based on a temperature of the exhaust passage while the all cylinders stop process is being executed, and a process of calculating the gas temperature of the stopped cylinder based on a flow rate of gas discharged from the stopped cylinder to which fuel supply is stopped and an engine water temperature while the specific cylinder stop process is being executed. A control device for an internal combustion engine.

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