Control device for internal combustion engines

Abstract

To suppress an excessive rise in temperature of a catalyst.SOLUTION: A control device 70 executes specific cylinder stop processing of stopping fuel supply to some of a plurality of cylinders provided in an internal combustion engine 10 and performing fuel supply to the remaining cylinders other than the some of the cylinders. The control device 70 stops feedback control of an air-fuel ratio while executing the specific cylinder stopping processing. Then, setting the cylinders to which fuel supply is performed during execution of the specific cylinder stop processing as combustion cylinders, the control device 70 executes processing of reducing and correcting the amount of fuel supplied to the combustion cylinders on the basis of the amount of volatile fuel contained in the blow-by gas introduced into an intake passage 12 while the specific cylinder stop processing is executed.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] For example, Patent Document 1 describes a control device for an internal combustion engine that executes a specific cylinder stop process of stopping fuel supply to some cylinders among a plurality of cylinders of the internal combustion engine and performing fuel supply to the remaining cylinders other than the some cylinders.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, if feedback control of the air-fuel ratio is executed during the execution of the specific cylinder stop process, the controllability of the air-fuel ratio may deteriorate. Therefore, it is conceivable to stop the feedback control of the air-fuel ratio during the execution of the specific cylinder stop process.

[0005] On the other hand, blow-by gas introduced into the intake passage may contain volatile fuel. In a stopped cylinder where combustion stops due to the fuel supply being stopped by the execution of the specific cylinder stop process, such volatile fuel flows into the cylinder and then flows out to the exhaust passage without being burned; therefore, there is a risk that the catalyst provided in the exhaust passage may be overheated due to an excessive amount of fuel being supplied to the catalyst.

Means for Solving the Problems

[0006] The control device for an internal combustion engine that solves the above problems is applied to an internal combustion engine having multiple cylinders, a catalyst provided in the exhaust passage, and a blow-by gas passage that introduces blow-by gas from the crankcase into the intake passage, and is a control device that performs a specific cylinder deactivation process that stops the fuel supply to some of the multiple cylinders and supplies fuel to the remaining cylinders other than the aforementioned some cylinders. This control device stops the air-fuel ratio feedback control while the specific cylinder deactivation process is being executed. death, When the cylinder in which fuel is supplied during the execution of the specified cylinder deactivation process is defined as the combustion cylinder, during the execution of the specified cylinder deactivation process, A process to increase the amount of fuel supplied to the combustion cylinder so that the air-fuel ratio of the mixture in the combustion cylinder becomes richer than the stoichiometric air-fuel ratio, and a process to increase the amount of fuel Weight reduction correction process and, Execute Furthermore, in the reduction correction process, the amount of volatile fuel contained in the blow-by gas introduced into the intake passage that flows into some of the cylinders is reduced from the amount of fuel supplied to the combustion cylinders. . [Effects of the Invention]

[0007] This internal combustion engine control system can suppress the overheating of the catalyst located in the exhaust passage. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing the configuration of an internal combustion engine in one embodiment. [Figure 2] Figure 2 is a flowchart showing the procedure of processing performed by the control device of the same embodiment. [Modes for carrying out the invention]

[0009] Below, one embodiment of a control device for an internal combustion engine will be described with reference to Figures 1 and 2. <Configuration of internal combustion engine and control system> As shown in Figure 1, the internal combustion engine 10 has four cylinders, for example, cylinders #1 to #4. The internal combustion engine 10 is an engine installed in a vehicle.

[0010] The intake passage 12 of the internal combustion engine 10 is equipped with a throttle valve 14. The internal combustion engine 10 is also equipped with a port injection valve 16 that injects fuel into the intake port. The air drawn into the intake passage 12 and the fuel injected from the port injection valve 16 flow into the combustion chamber 20 when the intake valve 18 opens. In addition, the cylinder head of the internal combustion engine 10 is equipped 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 subjected to combustion by the spark discharge of the spark plug 24.

[0011] The fuel-air mixture burned in the combustion chamber 20 of each cylinder is discharged as exhaust into the exhaust passage 30 when the exhaust valve 28 opens. The exhaust passage 30 is equipped with an oxidation catalyst 32 and a gasoline particulate filter (hereinafter referred to as GPF) 34 that collects particulate matter (hereinafter referred to as PM) in the exhaust. A three-way catalyst is supported on the GPF 34.

[0012] The internal combustion engine 10 is equipped with a blow-by gas treatment device for processing blow-by gas. The blow-by gas treatment device is a device that introduces blow-by gas from the crankcase of the internal combustion engine 10 into the intake passage 12, and is equipped with a PCV valve 50. The PCV valve 50 is a valve that adjusts the flow rate of blow-by gas introduced into the intake passage 12, and the opening of the valve changes using the pressure difference between the crankcase and the intake passage 12. The PCV valve 50 and the part of the intake passage 12 downstream of the throttle valve 14 are connected via a blow-by gas passage 51. Blow-by gas from the crankcase is introduced into the intake passage 12 via the blow-by gas passage 51.

[0013] The control device 70 controls the internal combustion engine 10 and operates various control parts of the internal combustion engine 10, such as the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, and spark plug 24, in order to control the torque, exhaust component ratio, and other control quantities. Figure 1 shows the operation signals MS1 to MS4 for the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, and spark plug 24, respectively.

[0014] The control device 70 refers to the output signal Scr from the crank angle sensor 83, the intake air volume GA detected by the airflow meter 84, and the water temperature THW, which is the temperature of the coolant in the internal combustion engine 10, detected by the water temperature sensor 85, in order to control the amount of control of the internal combustion engine 10. The control device 70 also refers to the oil temperature THO, which is the temperature of the lubricating oil in the internal combustion engine 10, detected by the oil temperature sensor 86. The control device 70 also refers to the intake pressure PM, which is the pressure in the intake passage 12 downstream of the throttle valve 14, detected by the pressure sensor 87. The control device 70 also refers to the accelerator pedal operation amount ACCP, which is the amount of accelerator pedal operation detected by the accelerator sensor 88. The control device 70 also refers to the vehicle speed SP, which is detected by the vehicle speed sensor 89. Furthermore, the control device 70 refers to the first air-fuel ratio AF1 detected by the first air-fuel ratio sensor 81 located upstream of the oxidation catalyst 32, and the second air-fuel ratio AF2 detected by the second air-fuel ratio sensor 82 located downstream of the oxidation catalyst 32.

[0015] The control device 70 comprises a CPU 72, a ROM 74, and peripheral circuits 76, which are able to communicate with each other via a communication line 78. Here, the peripheral circuits 76 include circuits that generate clock signals that define internal operation, power supply circuits, reset circuits, etc. The control device 70 performs various controls by having the CPU 72 execute a program stored in the ROM 74.

[0016] As one of various controls, the control device 70 executes well-known air-fuel ratio feedback control. In the air-fuel ratio feedback control, an air-fuel ratio correction value FH, which is a feedback value for making the actual air-fuel ratio coincide with the target air-fuel ratio AFt, is calculated based on the first air-fuel ratio AF1, the second air-fuel ratio AF2, and the target air-fuel ratio AFt of the air-fuel mixture. This air-fuel ratio correction value FH is updated at any time during the execution of the air-fuel ratio feedback control, while the update is stopped when the execution of the air-fuel ratio feedback control is stopped. Then, the amount of fuel injected from the port injection valve 16 and the in-cylinder injection valve 22 is feedback-corrected by the air-fuel ratio correction value FH, so that the actual air-fuel ratio converges to the target air-fuel ratio AFt.

[0017] <Regeneration process of GPF> The control device 70 executes the regeneration process of the GPF 34. FIG. 2 shows the procedure of the regeneration process. The process shown in FIG. 2 is realized by the CPU 72 repeatedly executing the program stored in the ROM 74 at a predetermined cycle. In the following, the step numbers of each process are represented by numbers preceded by "S".

[0018] In the series of processes shown in FIG. 2, the CPU 72 first acquires the engine rotational speed NE, the filling efficiency η, and the coolant temperature THW (S10). The engine rotational speed NE is calculated by the CPU 72 based on the output signal Scr. The filling efficiency η is calculated by the CPU 72 based on the engine rotational speed NE and the intake air amount GA.

[0019] Next, the CPU 72 calculates an update amount ΔDPM of the deposition amount DPM based on the engine rotational speed NE, the filling efficiency η, and the coolant temperature THW (S12). Here, the deposition amount DPM is the amount of PM captured by the GPF 34. Specifically, the CPU 72 calculates the amount of PM in the exhaust gas discharged to the exhaust passage 30 based on the engine rotational speed NE, the filling efficiency η, and the coolant temperature THW. Further, the CPU 72 calculates the temperature of the GPF 34 based on the engine rotational speed NE and the filling efficiency η. Then, the CPU 72 calculates the update amount ΔDPM based on the amount of PM in the exhaust gas and the temperature of the GPF 34. Note that when executing the process of S20 described later, the temperature of the GPF 34 and the update amount ΔDPM may be calculated based on the increment coefficient K.

[0020] Next, the CPU 72 updates the deposition amount DPM according to the update amount ΔDPM (S14). Next, the CPU 72 determines whether the execution flag Fc is "1" (S16). When the execution flag Fc is "1", it indicates that the regeneration process for burning and removing the PM of the GPF 34 is being executed, and when it is "0", it indicates otherwise.

[0021] When the CPU 72 determines that the execution flag Fc is "0" (S16: NO), it determines whether the deposition 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 captured by the GPF 34 is large and it is desirable to remove the PM.

[0022] When the CPU 72 determines that the deposition amount DPM is equal to or greater than the regeneration execution value DPMH (S18: YES), it executes the regeneration process and assigns "1" to the execution flag Fc (S20). Also, as the process in S20, the above-described air-fuel ratio feedback control is stopped. More specifically, the above-described air-fuel ratio correction value FH is held at the current value and the update is stopped.

[0023] As the regeneration process according to this embodiment, the CPU 72 executes the specific cylinder stop process. This specific cylinder deactivation process involves stopping the fuel supply to some of the cylinders among several cylinders, while simultaneously supplying fuel to the remaining cylinders, and includes both deactivation and fuel enrichment processes.

[0024] The shutdown process involves stopping fuel injection from the port injection valve 16 and in-cylinder injection valve 22 of cylinder #1, in other words, performing a fuel cut to stop the fuel supply to cylinder #1. The cylinder on which this shutdown process is performed will be referred to as the shutdown cylinder below, and the remaining cylinders other than the shutdown cylinder, that is, the cylinders to which fuel is supplied and combustion of the fuel-air mixture takes place, will be referred to as the combustion cylinders.

[0025] The enrichment process is a process that increases the amount of fuel supplied to each combustion cylinder, cylinder #2, cylinder #3, and cylinder #4, compared to when the above-mentioned stop process is not performed, in order to supply unburned fuel to the exhaust passage 30. When this enrichment process is performed, 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.

[0026] This specific cylinder deactivation process involves supplying oxygen and unburned fuel to the exhaust passage 30 to raise the temperature of the GPF 34, thereby performing a regeneration process to burn and remove PM collected by the GPF 34. Specifically, by discharging oxygen and unburned fuel into the exhaust passage 30, the unburned fuel is burned in the oxidation catalyst 32, etc., raising the exhaust temperature and thus raising the temperature of the GPF 34. Then, by supplying oxygen to the GPF 34, the PM collected by the GPF 34 is burned and removed.

[0027] Specifically, CPU72 assigns "0" to the required injection amount Qd for the port injection valve 16 and in-cylinder injection valve 22 of cylinder #1. The required injection amount Qd is the target value for the total amount of fuel injected from the port injection valve 16 and in-cylinder injection valve 22 in one combustion cycle.

[0028] On the other hand, the CPU 72 calculates the required injection amounts Qd for cylinder #2, cylinder #3, and cylinder #4 using the following equation (1), based on the enrichment coefficient K, base injection amount Qb, air-fuel ratio correction value FH, and reduction correction value α.

[0029] Qd = K·Qb·FH - α…(1) The enrichment factor K is a value set by the CPU 72 so that the amount of unburned fuel in the exhaust discharged from cylinder #2, cylinder #3, and cylinder #4 into the exhaust passage 30 is less than or equal to the amount that reacts with the oxygen discharged from cylinder #1 without excess or deficiency. For example, in the initial stages of the GPF 34 regeneration process, the CPU 72 sets the air-fuel ratio of the mixture in cylinders #2, #3, and #4 to a value as close as possible to the amount that reacts without excess or deficiency in order to raise the temperature of the oxidation catalyst 32 as quickly as possible. By multiplying by this enrichment factor K, the air-fuel ratio of the mixture in the combustion cylinder becomes richer than the stoichiometric air-fuel ratio.

[0030] The base injection amount Qb is the amount of fuel injected to bring the air-fuel ratio of the fuel mixture to the stoichiometric air-fuel ratio. The CPU72 calculates the base injection amount Qb based on, for example, the volumetric efficiency η and the engine rotational speed NE.

[0031] The weight reduction correction value α is a value calculated by the CPU 72 as follows. First, the CPU 72 calculates the amount of volatile fuel VF in the blow-by gas introduced into the intake passage 12 based on the engine operating conditions. The calculation of this volatile fuel amount VF is similar to the calculation of the outflow fuel amount Qout described in, for example, Japanese Patent Application Publication No. 2006-177288. Then, based on the calculated volatile fuel amount VF and engine rotation speed NE, the CPU 72 calculates the amount of volatile fuel per cylinder VFs, which is the amount of volatile fuel in the blow-by gas drawn into the combustion chamber 20 of one cylinder during the intake stroke. Then, the CPU 72 substitutes the value obtained by multiplying the number of stopped cylinders A in one combustion cycle by the number of burning cylinders B in one combustion cycle by the amount of volatile fuel per cylinder VFs into the weight reduction correction value α. For example, in this embodiment, since number A is "1" and number B is "3", the reduction correction value α becomes "1 / 3 × the amount of volatile fuel per cylinder VFs", or "VFS / 3". When calculating the required injection amount Qd for cylinder #2, cylinder #3, and cylinder #4, this reduction correction value α is subtracted, so that the amount of fuel supplied to the combustion cylinder from the fuel injection valves such as the port injection valve 16 and the in-cylinder injection valve 22 is reduced by the amount of volatile fuel flowing into the stopped cylinder.

[0032] Furthermore, the amount of volatile fuel flowing into the cylinder does not change rapidly. Therefore, the portion of the fuel supplied to the combustion cylinder that corresponds to volatile fuel in the blow-by gas is almost completely offset when calculating the required injection amount Qd by multiplying it by the air-fuel ratio correction value FH, although this value is no longer updated.

[0033] On the other hand, in the S16 process, if the CPU 72 determines that the execution flag Fc is "1" (S16:YES), it determines whether the accumulated DPM is less than or equal to the stop threshold DPML (S22). The stop threshold DPML is set to a value at which the amount of PM collected in the GPF 34 becomes sufficiently small and the regeneration process can be stopped.

[0034] If CPU72 determines that the accumulated amount DPM is greater than the stopping threshold DPML (S22:NO), it continues processing S20. On the other hand, if the CPU 72 determines that the accumulation amount DPM is less than or equal to the stopping threshold DPML (S22: YES), it sets the execution flag Fc to "0" (S28). When the execution flag Fc becomes "0", each process performed in the S20 process is stopped. That is, the regeneration process is stopped, and the air-fuel ratio feedback control is restarted, thereby restarting the updating of the air-fuel ratio correction value FH.

[0035] Furthermore, if CPU72 completes processing S20 or S28, or if it determines that processing S18 is negative, it will terminate the series of processes shown in Figure 2. <Mechanism and Effects> The operation and effects of this embodiment will now be explained.

[0036] In this embodiment, the air-fuel ratio feedback control is stopped while the specific cylinder deactivation process described above is being performed, that is, while the GPF34 regeneration process is being performed. During the specific cylinder deactivation process, a process is performed to reduce the amount of fuel supplied to the combustion cylinder based on the amount of volatile fuel VF contained in the blow-by gas introduced into the intake passage 12. More specifically, when calculating the required injection amount Qd for the combustion cylinder, the amount of fuel is reduced by the amount of the reduction correction value α calculated based on the amount of volatile fuel VF. Therefore, since the amount of fuel reaching the oxidation catalyst 32 is reduced during the specific cylinder deactivation process, the overheating of the oxidation catalyst 32 can be suppressed.

[0037] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0038] The process of performing the specific cylinder deactivation process is not limited to the regeneration process described above. For example, the specific cylinder deactivation process may be performed to warm up the catalyst or recover from sulfur poisoning. Alternatively, for example, the specific cylinder deactivation process may be performed to increase the oxygen storage capacity of the oxidation catalyst 32.

[0039] • While the number of cylinders whose fuel supply is stopped during a combustion cycle when specific cylinder deactivation processing is being performed is "1", the number of cylinders to be deactivated can be changed as appropriate, with a maximum value of "total number of cylinders - 1". Furthermore, it is not necessary to fix the deactivated cylinder to a predetermined cylinder. For example, the cylinder whose fuel supply is stopped may be changed for each combustion cycle.

[0040] • The GPF34 is not limited to a filter supported with a three-way catalyst, but may be a filter alone. Also, the GPF34 is not limited to being installed downstream of the oxidation catalyst 32 in the exhaust passage 30. Furthermore, the oxidation catalyst 32 may be replaced with a three-way catalyst that purifies components contained in the exhaust. [Explanation of Symbols]

[0041] 10...Internal combustion engine, 12...Intake passage, 30...Exhaust passage, 32...Oxidation catalyst, 34...GPF, 50...PCV valve, 51...Blow-by gas passage, 70...Control device

Claims

[Claim 1] A control device applied to an internal combustion engine comprising a plurality of cylinders, a catalyst provided in the exhaust passage, and a blow-by gas passage for introducing blow-by gas from the crankcase into the intake passage, which performs a specific cylinder deactivation process that stops the fuel supply to some of the plurality of cylinders and supplies fuel to the remaining cylinders other than the aforementioned some cylinders, During the execution of the aforementioned specific cylinder deactivation process, the air-fuel ratio feedback control is stopped. When the cylinder to which fuel is supplied during the execution of the specified cylinder deactivation process is designated as the combustion cylinder, during the execution of the specified cylinder deactivation process, the following processes are performed: increasing the amount of fuel supplied to the combustion cylinder so that the air-fuel ratio of the air-fuel mixture in the combustion cylinder becomes richer than the stoichiometric air-fuel ratio; and reducing the amount of fuel compared to the increased amount. In the aforementioned reduction correction process, the amount of volatile fuel contained in the blow-by gas introduced into the intake passage that flows into some of the cylinders is reduced from the amount of fuel supplied to the combustion cylinders. Control device for internal combustion engines.

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