Control device for internal combustion engine

Abstract

To prevent a base opening from being changed to a value deviated from the base opening for performing fuel supply to all cylinders.SOLUTION: A control device is cable of executing: a feedback process to perform feedback correction of an opening of a throttle valve so as to reduce a difference between an actual engine rotation speed and a target engine rotation speed while an internal combustion engine is in idling operation; a learning process to learn operation of the base opening so as to reduce a correction amount of the feedback correction while the internal combustion engine is in the idling operation; and a fuel cut process where a stop pattern to consecutively stop fuel supply to M number of cylinders in the order of proximity to a combustion stroke and a combustion pattern to consecutively supply the fuel to N number of cylinders in the order of proximity to the combustion stroke are alternately repeated with the internal combustion engine continuously operated. When executing the fuel cut process while the internal combustion engine is in the idling operation (Yes in Step S100), the control device prohibits execution of the learning process (Step S110).SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] The internal combustion engine disclosed in Patent Document 1 includes a plurality of cylinders, an intake passage, a throttle valve, and a control device. The intake passage is connected to the plurality of cylinders. The throttle valve adjusts the flow rate of intake air flowing through the intake passage.

[0003] The control device performs so-called idle speed control during idling of the internal combustion engine. That is, the control device feedback corrects the opening of the throttle valve so as to reduce the difference between the actual engine speed and the target engine speed. Also, during idling of the internal combustion engine, the control device stores, as a learned value, the opening of the throttle valve at which the actual engine speed coincides with the target engine speed, based on the result of the feedback correction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-197688 A Summary of the Invention [Problem to be solved by the invention]

[0005] As a technology related to an internal combustion engine, there is known a control in which fuel supply is stopped only to specific cylinders among a plurality of cylinders while the internal combustion engine is idling, and fuel supply is continued to the other cylinders. When this control is executed, the engine speed may decrease due to stopping the fuel supply to the specific cylinders. Therefore, in order to bring the actual engine speed closer to the target engine speed while the above control is being executed, the throttle valve opening is made larger than when fuel is supplied to all cylinders, and the intake amount of intake air is increased.

[0006] However, if the throttle valve opening learning described in Patent Document 1 is executed while the above control is being executed, the learned value of the throttle valve opening will deviate significantly from the opening required to make the actual engine speed match the target engine speed when fuel supply is performed to all cylinders. In this case, in order to quickly make the actual engine speed match the target engine speed when fuel supply to all cylinders is resumed, complex control such as increasing the amount of correction by feedback correction or returning the learned value of the throttle valve opening to its original value is required. [Means for solving the problem]

[0007] A control device for an internal combustion engine to solve the above problem is applied to an internal combustion engine having a plurality of cylinders, an intake passage that introduces intake air into the plurality of cylinders, and a throttle valve that adjusts the flow rate of the intake air flowing through the intake passage, and is capable of executing a feedback process that feedback corrects the opening of the throttle valve so as to reduce the difference between an actual engine speed and a target engine speed during idle operation of the internal combustion engine, a learning process that learns a base opening, which is a value before the feedback correction, during idle operation of the internal combustion engine so that the correction amount by the feedback correction becomes smaller, and a fuel cut process that alternately repeats a stop pattern that stops the supply of fuel to M consecutive cylinders in the order of the cylinders that will reach a combustion stroke, and a combustion pattern that supplies fuel to N consecutive cylinders in the order of the cylinders that will reach a combustion stroke, while continuing operation of the internal combustion engine, where "M" and "N" are integers equal to or greater than 1, and the execution of the learning process is prohibited.

[0008] In the above configuration, when the fuel cut process is executed during idling of the internal combustion engine, learning of the base opening is prohibited, which makes it possible to prevent the base opening from being changed to a value that is significantly different from the base opening when fuel is supplied to all cylinders. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a vehicle. [Diagram 2] FIG. 2 is a flowchart showing the procedure of the prohibition process. [Diagram 3] FIG. 3 is a time chart showing an example of changes over time in (a) engine speed, (b) throttle opening, and (c) learning flag before and after the execution of a fuel cut process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of a control device for an internal combustion engine will be described with reference to the drawings. <General configuration of internal combustion engine> 1, a vehicle 500 has an internal combustion engine 10. The internal combustion engine 10 is a drive source of the vehicle 500.

[0011] The internal combustion engine 10 has an engine body 10A, a crankshaft 31, a crank angle sensor 64, and a water temperature sensor 63. The engine body 10A has four cylinders 11. Each cylinder 11 is a space partitioned in the engine body 10A. Although not shown, each cylinder 11 houses a piston. The piston can reciprocate in the cylinder 11. The piston is connected to the crankshaft 31 via a connecting rod. The crankshaft 31 rotates in response to the reciprocating motion of the piston. The crank angle sensor 64 is located near the crankshaft 31. The crank angle sensor 64 detects a rotational position CR of the crankshaft 31. In this specification, the four cylinders 11 are collectively referred to as cylinders 11, and are individually referred to as a first cylinder #1, a second cylinder #2, a third cylinder #3, and a fourth cylinder #4.

[0012] The engine body 10A has a water jacket 18. The water jacket 18 is a passage through which cooling water flows. The water jacket 18 is positioned around the four cylinders 11. The water temperature sensor 63 is positioned at the outlet of the water jacket 18. The water temperature sensor 63 detects the temperature TW of the cooling water.

[0013] The internal combustion engine 10 has four spark plugs 19. One spark plug 19 is provided for each cylinder 11. The tip of each spark plug 19 is located inside the cylinder 11. The spark plug 19 ignites an air-fuel mixture of intake air and fuel by spark discharge.

[0014] The internal combustion engine 10 has an intake passage 15, an airflow meter 61, a throttle valve 16, an opening sensor 62, and four fuel injection valves 17. The intake passage 15 is a passage for introducing intake air into each cylinder 11. The intake passage 15 is connected to each cylinder 11. The airflow meter 61 is located midway through the intake passage 15. The airflow meter 61 detects the flow rate GA of intake air flowing through the intake passage 15. The throttle valve 16 is located downstream of the airflow meter 61 in the intake passage 15. The throttle valve 16 adjusts the flow rate GA of intake air flowing through the intake passage 15. The opening sensor 62 is located near the throttle valve 16. The opening sensor 62 detects the opening SQ of the throttle valve 16 (hereinafter referred to as throttle opening). The four fuel injection valves 17 are located in the intake passage 15 downstream from the throttle valve 16. A fuel injection valve 17 is provided for each cylinder 11. The fuel injection valve 17 supplies fuel into the cylinder 11 by injecting fuel.

[0015] The internal combustion engine 10 has an exhaust passage 21, a three-way catalyst 22, and a gasoline particulate filter (hereinafter referred to as GPF) 23. The exhaust passage 21 is a passage for discharging exhaust gas from each cylinder 11. The exhaust passage 21 is connected to each cylinder 11. The three-way catalyst 22 is located midway through the exhaust passage 21. The three-way catalyst 22 purifies the exhaust gas. The three-way catalyst 22 has an oxygen storage capacity. The GPF 23 is located downstream of the three-way catalyst 22 in the exhaust passage 21. The GPF 23 collects particulate matter (hereinafter referred to as PM) contained in the exhaust gas.

[0016] The vehicle 500 has a display 501. The display 501 is capable of displaying various information. The display 501 is a touch panel type, and allows input operations from outside.

[0017] <Outline of the control device> The vehicle 500 has a control device 110. The control device 110 may be configured as one or more processors that execute various processes according to a computer program (software). The control device 110 may be configured as one or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that execute at least a part of the various processes, or a circuit including a combination thereof. The processor includes a CPU and memories such as a RAM and a ROM. The memory stores program codes or instructions that are configured to cause the CPU to execute the processes. The memory, i.e., the computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. The control device 110 has a storage device that is an electrically rewritable non-volatile memory.

[0018] The control device 110 controls the display 501. The control device 110 outputs various display signals to the display 501. When an input operation is performed on the display 501, the control device 110 receives a signal related to the input operation.

[0019] The control device 110 controls the internal combustion engine 10. The control device 110 receives detection signals from various sensors in the internal combustion engine 10. Specifically, the control device 110 receives detection signals for the following parameters:

[0020] The intake air flow rate GA detected by the air flow meter 61 Throttle opening SQ detected by the opening sensor 62 - Coolant temperature TW detected by the water temperature sensor 63 The rotational position CR of the crankshaft 31 detected by the crank angle sensor 64 The control device 110 calculates various parameters indicating the engine operating state at any time based on detection signals received from various sensors. Specifically, the control device 110 calculates the engine speed NE based on the rotational position CR of the crankshaft 31. The control device 110 also calculates the engine load KL based on the engine speed NE and the intake air flow rate GA. Furthermore, the control device 110 calculates the accumulation amount W of PM trapped in the GPF 23 based on the engine load KL and the coolant temperature TW.

[0021] The control device 110 has a throttle control unit 111 and a combustion control unit 113. The throttle control unit 111 is a functional unit that is mainly responsible for processing related to the control of the throttle valve 16. The combustion control unit 113 is a functional unit that is mainly responsible for processing related to the combustion of the air-fuel mixture. The combustion control unit 113 is also responsible for processing the setting of a flag related to the aspect of the combustion of the air-fuel mixture.

[0022] The control device 110 switches between a normal mode and a maintenance mode in response to an input operation on the display 501. The normal mode is a processing mode in which the user normally uses the vehicle 500. The maintenance mode is a processing mode exclusively used when the vehicle 500 is maintained, for example, at a maintenance shop. When the maintenance mode is selected, the control device 110 puts the internal combustion engine 10 into an idle operation state. That is, the internal combustion engine 10 enters an engine operation state in which it operates at the minimum engine rotation speed NE at which the internal combustion engine 10 can be driven autonomously. When the maintenance mode is selected, the control device 110 also displays an execution icon on the display 501 for executing a fuel cut process, which will be described later.

[0023] <Fuel cut processing> The combustion control unit 113 can execute a fuel cut process. The fuel cut process is a process for burning the PM collected by the GPF 23 and removing it from the GPF 23. A series of processes in which the four cylinders 11 each undergo a combustion stroke once, that is, a period in which the crankshaft 31 rotates twice, is called one combustion cycle. In the fuel cut process, the combustion control unit 113 repeats a process of stopping the fuel supply to one of the four cylinders 11 in one combustion cycle while supplying fuel to the remaining three cylinders in a plurality of consecutive combustion cycles. Therefore, in the fuel cut process, a stop pattern in which the fuel supply to one cylinder 11 is stopped, and a combustion pattern in which the fuel is continuously supplied to three cylinders 11 in the order of the cylinders 11 undergoing the combustion stroke are alternately repeated while the internal combustion engine 10 continues to operate. In this embodiment, the cylinder 11 to which the fuel supply is stopped during the fuel cut process (hereinafter, referred to as the stopped cylinder) is the second cylinder #2. Furthermore, the cylinders 11 to which fuel is supplied during the fuel cut process (hereinafter, referred to as combustion cylinders) are the first cylinder #1, the third cylinder #3, and the fourth cylinder #4.

[0024] In the fuel cut process, the combustion control unit 113 supplies fuel to the combustion cylinder so that the air-fuel ratio of the mixture in the combustion cylinder becomes richer than the theoretical air-fuel ratio. With the combustion of the mixture in such an air-fuel ratio rich atmosphere, the combustion cylinder discharges unburned fuel to the exhaust passage 21. On the other hand, the stopped cylinder discharges oxygen to the exhaust passage 21. The oxygen discharged by the stopped cylinder to the exhaust passage 21 and the unburned fuel discharged by the combustion cylinder to the exhaust passage 21 eventually reach the three-way catalyst 22. Then, the unburned fuel is burned in the three-way catalyst 22, and the temperature of the exhaust gas rises. Then, when this high-temperature exhaust gas reaches the GPF 23, the temperature of the GPF 23 rises. In this state, when the oxygen discharged by the stopped cylinder to the exhaust passage 21 reaches the GPF 23, the PM captured by the GPF 23 is burned and disappears. Through this process, the PM can be removed from the GPF 23.

[0025] When the control device 110 is in the maintenance mode and an execution icon on the display 501 is operated, the combustion control unit 113 starts the fuel cut process. After the fuel cut process starts, the combustion control unit 113 ends the fuel cut process when the accumulation amount W of PM in the GPF 23 becomes equal to or less than a specified amount WE. The specified amount WE is determined, for example, through an experiment, as a value at which the accumulation amount W of PM in the GPF 23 becomes sufficiently small and the fuel cut process may be ended. Note that the combustion control unit 113 cancels normal processing related to the combustion of the air-fuel mixture during the execution of the fuel cut process. The normal processing is processing in which the mixture is burned in all four cylinders 11. When the fuel cut process ends, the combustion control unit 113 resumes normal processing.

[0026] <Feedback processing> The throttle control unit 111 is capable of executing a feedback process. The feedback process is a process for maintaining the actual engine speed NE at a value close to the target idle speed ENA during the idling operation of the internal combustion engine 10. The target idle speed NEA is a target engine speed during the idling operation of the internal combustion engine 10. The throttle control unit 111 stores the target idle speed NEA in advance.

[0027] As a specific process in the feedback process, the throttle control unit 111 repeatedly calculates a target opening SQ1, which is a target value of the throttle opening SQ. Then, the throttle control unit 111 controls the throttle valve 16 so that the actual throttle opening SQ becomes the target opening SQ1. The throttle control unit 111 calculates the target opening SQ1 by adding a correction value SQ3 to a base opening SQ2, as shown in the following equation (1).

[0028] SQ1 = SQ2 + SQ3 (1) The base opening SQ2 is a throttle opening SQ that can be considered to make the actual engine speed NE coincide with the target idle speed NEA. Even if the base opening SQ2 is set as the target opening SQ1, for example, due to an error in the fuel injection amount, a deviation may occur between the actual engine speed NE and the target idle speed NEA. The correction value SQ3 is a change value of the throttle opening SQ required to compensate for the deviation between the actual engine speed NE obtained by the base opening SQ2 and the target idle speed NEA.

[0029] When the throttle control unit 111 starts the feedback process and calculates the target opening SQ1 for the first time, the throttle control unit 111 calculates the correction value SQ3 as zero. That is, the target opening SQ1 at this time becomes the base opening SQ2. On the other hand, when the throttle control unit 111 calculates the target opening SQ1 for the second time or later, the throttle control unit 111 calculates the correction value SQ3 so as to reduce the difference between the actual engine speed NE and the target idle speed NEA. Specifically, when calculating the correction value SQ3, the throttle control unit 111 calculates a value obtained by adding an adjustment value PH to the previous value SQ3A of the correction value SQ3 as the latest correction value SQ3, as shown in the following equation (2).

[0030] SQ3 = SQ3A + PH (2) The adjustment value PH is a change value of the throttle opening SQ required to eliminate the difference between the current engine speed NE and the target idle speed NEA. A value obtained by subtracting the actual engine speed NE from the target idle speed NEA is called a difference value ΔNE. For example, when the current engine speed NE is lower than the target idle speed NEA and the difference value ΔNE is a positive value, the throttle control unit 111 sets the adjustment value PH to a positive value. At this time, the throttle control unit 111 increases the absolute value of the adjustment value PH as the absolute value of the difference value ΔNE increases. On the other hand, when the actual engine speed NE is higher than the target idle speed NEA and the difference value ΔNE is a negative value, the throttle control unit 111 sets the adjustment value PH to a negative value. At this time, the throttle control unit 111 increases the absolute value of the adjustment value PH as the absolute value of the difference value ΔNE increases. By increasing or decreasing the adjustment value PH in this manner, the throttle control unit 111 performs feedback correction of the throttle opening SQ so as to reduce the difference between the actual engine rotation speed NE and the target idle rotation speed NEA. As described above, the throttle control unit 111 sets the initial target opening SQ1 after the start of the feedback process as the base opening SQ2. In other words, the base opening SQ2 is the target opening SQ1 before the feedback correction is performed.

[0031] Regardless of the processing mode, the throttle control unit 111 starts the feedback processing when the internal combustion engine 10 starts idling. The throttle control unit 111 continues to execute the feedback processing while the internal combustion engine 10 is idling. The throttle control unit 111 ends the feedback processing when the internal combustion engine 10 ends the idling.

[0032] <Guard Information> The throttle control unit 111 prestores first guard information J1 as information to be used in the feedback process. The first guard information J1 is information to be used by the throttle control unit 111 in the feedback process during the above-mentioned normal process in which the mixture is burned in all four cylinders 11. The first guard information J1 includes four parameters, a first adjustment upper limit value, a first adjustment lower limit value, a first target upper limit value, and a first target lower limit value. The first adjustment upper limit value is a positive value. The first adjustment upper limit value is a value that specifies the upper limit of the adjustment value PH calculated by the throttle control unit 111 at each timing. That is, when the adjustment value PH calculated according to the difference value ΔNE is greater than the first adjustment upper limit value, the throttle control unit 111 replaces the adjustment value PH with the first adjustment upper limit value. Then, the first adjustment upper limit value is set as the final adjustment value PH. The first adjustment lower limit value is a negative value, and its absolute value is the same as the first adjustment upper limit value. The first adjustment lower limit value is a value that specifies the lower limit of the adjustment value PH that the throttle control unit 111 calculates at each timing. That is, when the adjustment value PH calculated according to the difference value ΔNE is smaller than the first adjustment lower limit value, the throttle control unit 111 sets this first adjustment lower limit value as the final adjustment value PH. The first target upper limit value is a positive value. The first target upper limit value is a value that specifies the upper limit of the target opening SQ1 that the throttle control unit 111 calculates at each timing. That is, when the target opening SQ1 calculated by adding the correction value SQ3 to the base opening SQ2 is larger than the first target upper limit value, the throttle control unit 111 sets this first target upper limit value as the final target opening SQ1. The first target lower limit value is a positive value. The first target lower limit value is a value that specifies the lower limit of the target opening SQ1 that the throttle control unit 111 calculates at each timing. That is, when the target opening SQ1 calculated by adding the correction value SQ3 to the base opening SQ2 is smaller than the first target lower limit value, the throttle control unit 111 sets this first target lower limit value as the final target opening SQ1.

[0033] Here, the maximum value of the adjustment value PH that can avoid an excessively sudden change in the target opening SQ1 is referred to as the maximum adjustment value. The maximum adjustment value is determined, for example, through experiments. The first adjustment upper limit value is determined as a value that is sufficiently smaller than the predetermined adjustment value. Moreover, the first target upper limit value and the first target lower limit value are determined, for example, through experiments, as the maximum and minimum values ​​that the target opening SQ1 can take when normal processing is executed under a situation in which no abnormality occurs in the internal combustion engine 10.

[0034] The throttle control unit 111 prestores second guard information J2 as information to be used in the feedback process. The second guard information J2 is information to be used by the throttle control unit 111 in the feedback process during the execution of the fuel cut process. The second guard information J2 includes four parameters, a second adjustment upper limit value, a second adjustment lower limit value, a second target upper limit value, and a second target lower limit value. The second adjustment upper limit value is a positive value, similar to the first adjustment upper limit value. The second adjustment upper limit value is a value that defines the upper limit of the adjustment value PH calculated by the throttle control unit 111 at each timing, similar to the first adjustment upper limit value. The second adjustment upper limit value is larger than the first adjustment upper limit value. The second adjustment lower limit value is a negative value, similar to the first adjustment lower limit value. The absolute value of the second adjustment lower limit value is the same as the second adjustment upper limit value. The second adjustment lower limit value is a value that defines the lower limit of the adjustment value PH calculated by the throttle control unit 111 at each timing, similar to the first adjustment lower limit value. The second target upper limit value is a positive value, like the first target upper limit value. The second target upper limit value is a value that specifies the upper limit of the target opening SQ1 calculated by the throttle control unit 111 at each timing, like the first target upper limit value. The second target upper limit value is larger than the first target upper limit value. The second target lower limit value is a positive value, like the first target lower limit value. The second target lower limit value is a value that specifies the lower limit of the target opening SQ1 calculated by the throttle control unit 111 at each timing, like the first target lower limit value. The second target lower limit value is smaller than the first target lower limit value. Thus, in the second guard information J2, the range of the allowable adjustment value PH and the range of the allowable target opening SQ1 are both larger than those in the first guard information J1.

[0035] As will be described later in the section on operation, a sudden change in the engine speed NE occurs when switching between normal processing and fuel cut processing. The second adjustment upper limit value and the second adjustment lower limit value are values ​​that allow feedback correction of the throttle opening SQ in response to the sudden change in the engine speed NE at this time. The absolute value of the second adjustment upper limit value, i.e., the second adjustment lower limit value, is determined, for example, as the above-mentioned predetermined adjustment value. The second target upper limit value and the second target lower limit value are determined, for example, through experiments, as the maximum and minimum values ​​that the target opening SQ1 can take when the fuel cut processing is executed under conditions in which no abnormality occurs in the internal combustion engine 10.

[0036] When executing the feedback process, the throttle control unit 111 selects either the first guard information J1 or the second guard information J2 in accordance with a guard flag FG, which will be described later, and then performs the feedback process based on the upper and lower limits defined by the selected guard information.

[0037] <Learning process> The throttle control unit 111 can execute a learning process. The learning process is a process performed in conjunction with the execution of the feedback process. The learning process is a process for learning the base opening SQ2 so that the correction amount by the feedback correction is reduced. The correction amount by the feedback correction here refers to the absolute value of the correction value SQ3 calculated by the feedback process. In the learning process, the throttle control unit 111 stores the actual engine speed NE, the target opening SQ1 calculated by the feedback process, the correction value SQ3, and the adjustment value PH in chronological order. For example, the throttle control unit 111 stores data for a certain period while overwriting the oldest data with the latest data. Then, the throttle control unit 111 refers to the time series of each parameter, and when the absolute value of the correction value SQ3 is appropriately large and a stable state described later continues for a predetermined judgment period, learns the average value of the target opening SQ1 during that judgment period as a new base opening SQ2. Then, the throttle control unit 111 overwrites the previously stored base opening SQ2 with the new base opening SQ2. The above-mentioned stable state is a state in which the actual engine speed NE falls within the judgment range and the absolute value of the adjustment value PH is equal to or less than the judgment value. The throttle control unit 111 prestores the judgment range, judgment value, and judgment period. The judgment range is determined as a range of the engine speed NE in which the actual engine speed NE can be considered to be substantially equal to the target idle speed NEA. The judgment value is determined as a value in which the absolute value of the adjustment value PH can be considered to be considerably small. The judgment period is determined as a length of time in which the actual engine speed NE can be considered to have converged to the target idle speed NEA when the state in which the actual engine speed NE is within the judgment range continues. The judgment period is determined as a length of time in which the correction value SQ3 and therefore the target opening SQ1 can be considered to be stable when the state in which the absolute value of the adjustment value PH is equal to or less than the judgment value continues. The throttle control unit 111 executes the learning process while the feedback process is being executed, that is, while the internal combustion engine 10 is idling, on the condition that a learning flag FK, which will be described later, is off.

[0038] <Prohibited Processing> The combustion control unit 113 can execute a prohibition process. The prohibition process is a process for specifying whether or not to execute a learning process and guard information to be used in a feedback process. Specifically, in the prohibition process, the combustion control unit 113 prohibits the execution of a learning process when a fuel cut process is being executed. On the other hand, when a fuel cut process is not being executed, that is, when a normal process is being executed, the combustion control unit 113 permits the execution of a learning process. The combustion control unit 113 sets a learning flag FK as a flag for indicating whether or not to execute the above-mentioned learning process. The combustion control unit 113 sets the learning flag FK to "1" or "2." The learning flag FK being "1" means that the execution of the learning process is permitted. The learning flag FK being "2" means that the execution of the learning process is prohibited.

[0039] Also, in the prohibition process, when the fuel cut process is being executed, the combustion control unit 113 designates the second guard information J2 as the guard information to be used in the feedback process. On the other hand, when the fuel cut process is not being executed, that is, when the normal process is being executed, the combustion control unit 113 designates the first guard information J1 as the guard information to be used in the feedback process. The combustion control unit 113 sets a guard flag FG as a flag to indicate the guard information to be designated. The combustion control unit 113 sets the guard flag FG to "1" or "2." The guard flag FG being "1" means that the first guard information J1 should be used in the feedback process. The guard flag FG being "2" means that the second guard information J2 should be used in the feedback process.

[0040] The combustion control unit 113 prohibits the execution of the learning process until a predetermined specified period H has elapsed after the fuel cut process is completed. Furthermore, the combustion control unit 113 designates the second guard information J2 as the guard information to be used in the feedback process until the above-mentioned specified period H has elapsed after the fuel cut process is completed. As described in the section on operation below, when normal processing is resumed after the fuel cut process is completed, a state in which the actual engine speed NE is higher than the target idle speed NEA continues for a while. The specified period H is determined in advance, for example, through an experiment, as the length of time required for the actual engine speed NE to converge to the target idle speed NEA after the fuel cut is completed. The combustion control unit 113 stores the specified period H in advance.

[0041] <Specific processing procedures for prohibition processing> The combustion control unit 113 starts the inhibition process when the maintenance mode is selected by an input operation on the display 501. At the start of the inhibition process, the learning flag FK is "1". Also, at the start of the inhibition process, the guard flag FG is "1". Note that if the control device 110 is switched to the normal mode during the execution of the inhibition process, or if the ignition switch is turned off, the combustion control unit 113 ends the inhibition process at that point.

[0042] 2, when the combustion control unit 113 starts the prohibition process, it first executes the process of step S100. In step S100, the combustion control unit 113 determines whether or not the fuel cut process has started. If the fuel cut process has not started (step S100: NO), the combustion control unit 113 temporarily ends the series of steps of the prohibition process. In this case, the combustion control unit 113 executes the process of step S100 again.

[0043] On the other hand, in step S100, if the fuel cut process has been started (step S100: YES), the combustion control unit 113 advances the process to step S110. In step S110, the combustion control unit 113 prohibits the execution of the learning process. As a specific process of this step S110, the combustion control unit 113 sets the learning flag FK to "2." After this, the combustion control unit 113 advances the process to step S120.

[0044] In step S120, the combustion control unit 113 designates the second guard information J2 as the guard information to be used in the feedback process. As a specific process of this step S120, the combustion control unit 113 sets the guard flag FG to "2." After this, the combustion control unit 113 advances the process to step S130.

[0045] In step S130, the combustion control unit 113 determines whether or not the fuel cut process has ended. If the fuel cut process has not ended (step S130: NO), the combustion control unit 113 executes the process of step S130 again. The combustion control unit 113 repeats the process of step S130 until the fuel cut process ends. Then, when the combustion control unit 113 ends the fuel cut process (step S130: YES), the process proceeds to step S140.

[0046] In step S140, the combustion control unit 113 determines whether or not the specified period H has elapsed since the processing of step S130 was completed. If the specified period H has not elapsed since the processing of step S130 was completed (step S140: NO), the combustion control unit 113 executes the processing of step S140 again. The combustion control unit 113 repeats the processing of step S140 until the specified period H has elapsed since the processing of step S130 was completed. Then, when the specified period H has elapsed since the processing of step S130 was completed (step S140: YES), the combustion control unit 113 advances the processing to step S150.

[0047] In step S150, the combustion control unit 113 permits the execution of the learning process. As a specific process of this step S150, the combustion control unit 113 sets the learning flag FK to "1." After this, the combustion control unit 113 advances the process to step S160.

[0048] In step S160, the combustion control unit 113 designates the first guard information J1 as the guard information to be used in the feedback process. As a specific process of this step S160, the combustion control unit 113 sets the guard flag FG, which is a flag indicating the guard information to be used in the feedback process, to "1". After this, the combustion control unit 113 temporarily ends the series of processes of the inhibition process. Then, the combustion control unit 113 executes the process of step S100 again.

[0049] <Operation of the embodiment> As shown in FIG. 3, at time T1, the maintenance mode is selected and the internal combustion engine 10 is idling. It is assumed that the combustion control unit 113 is not executing a fuel cut process at time T1. Since the internal combustion engine 10 is idling, the throttle control unit 111 is executing a feedback process. That is, as shown in FIG. 3(b), the throttle control unit 111 finely adjusts the throttle opening SQ in the vicinity of the base opening SQ2. As a result, as shown in FIG. 3(a), the throttle control unit 111 maintains the actual engine speed NE at a value close to the target idle speed NEA.

[0050] Assume that the execution icon is operated at time T2, which is later than time T1. In response to the operation of this execution icon, the combustion control unit 113 starts the fuel cut process (step S100: YES). In response to the start of the fuel cut process, the combustion control unit 113 prohibits the execution of the learning process, as shown in FIG. 3(c) (step S110). That is, the combustion control unit 113 sets the learning flag FK to "2". In addition, in response to the start of the fuel cut process, the throttle control unit 111 switches the guard information to be used in the feedback process to the second guard information J2 (step S120). That is, the range of the adjustment value PH allowed in the feedback process is expanded. In addition, as shown by the two-dot chain line in FIG. 3(b), the range of the target opening SQ1 allowed in the feedback process is expanded.

[0051] Now, as shown in FIG. 3(a), when the combustion control unit 113 starts the fuel cut process, the actual engine speed NE drops sharply. This is because the decrease in the engine speed NE caused by the stop of the combustion of the mixture in the stopped cylinder exceeds the increase in the engine speed NE caused by the combustion cylinder being made into an air-fuel rich atmosphere. When the actual engine speed NE drops sharply with the start of the combustion cut process, the throttle control unit 111 adjusts the throttle opening SQ through feedback processing to eliminate the difference between the engine speed NE and the target idle speed NEA. Specifically, the throttle control unit 111 sets the adjustment value PH for feedback correction to a positive value so that the actual engine speed NE is made larger than the current speed. Then, as shown in FIG. 3(b), the throttle control unit 111 makes the throttle opening SQ larger than the base opening SQ2. With the increase in the intake flow rate GA caused by this, the actual engine speed NE increases as shown in FIG. 3(a). Then, the actual engine speed NE approaches the target idle speed NEA. Thereafter, the throttle control unit 111 finely adjusts the throttle opening SQ to a constant value greater than the base opening SQ2, as shown in Fig. 3(b). As a result, the throttle control unit 111 maintains the actual engine speed NE at a value close to the target idle speed NEA, as shown in Fig. 3(a).

[0052] At time T3 after time T2, the combustion control unit 113 ends the fuel cut process and resumes normal processing (step S130: YES). At this time T3, the throttle opening SQ is larger than the base opening SQ2. Here, the base opening SQ2 is a value learned during execution of the normal processing. That is, the base opening SQ2 is the throttle opening SQ for making the actual engine speed NE approximately coincident with the target idle speed NEA when fuel is burned in all four cylinders 11. If normal processing is performed in a state in which the throttle opening SQ is larger than the base opening SQ2, the actual intake air flow rate GA becomes larger than the intake air flow rate GA required to make the actual engine speed NE the target idle speed NEA. As a result, the actual engine speed NE becomes larger than the target idle speed NEA. As described above, the throttle opening SQ at time T3 is larger than the base opening SQ2. Therefore, when normal processing is resumed at time T3, the actual engine speed NE increases rapidly relative to the target idle speed NEA for the reasons described above.

[0053] When the actual engine speed NE increases rapidly after the normal process is resumed, the throttle control unit 111 adjusts the throttle opening SQ through feedback process to eliminate the difference between the engine speed NE and the target idle speed NEA. Specifically, the throttle control unit 111 sets the adjustment value PH for feedback correction to a negative value so as to make the actual engine speed NE smaller than the current value. Then, as shown in FIG. 3(b), the throttle control unit 111 sets the throttle opening SQ to a value close to the base opening SQ2. As the intake flow rate GA decreases accordingly, the actual engine speed NE decreases as shown in FIG. 3(a). Then, the actual engine speed NE becomes close to the target idle speed NEA. Then, at time T4 when the specified period H has elapsed from time T3 (step S140: YES), the actual engine speed NE becomes in a state of approximately converging to the target idle speed NEA.

[0054] At time T4, the combustion control unit 113 permits the learning process (step S150). Also, at time T4, the throttle control unit 111 switches the guard information to be used in the feedback process to the first guard information J1 (step S160). That is, the range of the adjustment value PH permitted in the feedback process is narrowed. Also, as shown by the two-dot chain line in FIG. 3(b), the range of the target opening SQ1 permitted in the feedback process is narrowed.

[0055] After time T4, the throttle control unit 111 finely adjusts the throttle opening SQ to be close to the base opening SQ2, as shown in Fig. 3(b). As a result, the throttle control unit 111 maintains the actual engine speed NE at a value close to the target idle speed NEA, as shown in Fig. 3(a).

[0056] <Effects of the embodiment> (1) As described above, in this embodiment, the throttle opening SQ is maintained at a value greater than the base opening SQ2 during the fuel cut process. If the throttle opening SQ at this time were to be learned as the base opening SQ2, various complex processes would be required when normal processing was resumed, such as increasing the correction amount in the feedback process or relearning the base opening SQ2.

[0057] In this regard, in this embodiment, the learning process is prohibited from being executed while the fuel cut process is being executed. Therefore, it is possible to prevent the base opening SQ2 from deviating significantly from the throttle opening SQ required to realize the target idle rotation speed NEA during the execution of the normal process, as a result of the execution of the fuel cut process. Specifically, the base opening SQ2 at time T2 shown in FIG. 3 is taken over as the base opening SQ2 at time T4 when the specified period H has elapsed after the end of the fuel cut process. Therefore, the throttle opening SQ during the fuel cut process does not affect the base opening SQ2, and the actual engine speed NE quickly converges to the target idle rotation speed NEA during the normal process after time T4.

[0058] (2) As described above, after the fuel cut process is ended and normal process is resumed, it takes a certain amount of time for the actual engine speed NE to converge to the target idle speed NEA. Even if the engine speed NE and the throttle opening SQ happen to stabilize during this period, and conditions for updating the base opening SQ2 are met, a highly reliable learning value cannot be obtained under these circumstances.

[0059] In this regard, in this embodiment, the learning process is prohibited until the specified period H has elapsed after the fuel cut process is completed. Therefore, it is possible to prevent an inappropriate value from being learned as the base opening SQ2 during the period from the end of the fuel cut process until the actual engine speed NE converges to the target idle speed NEA.

[0060] (3) As described above, when the fuel cut process starts, the actual engine speed NE drops suddenly. At this time, in order to quickly return the actual engine speed NE to a value close to the target idle speed NEA, it is necessary to rapidly increase the throttle opening SQ.

[0061] In this embodiment, when the fuel cut process is started, the range of the adjustment value PH that is permissible in the feedback process is expanded. This allows the throttle opening SQ to be rapidly increased to an opening that can achieve the target idle speed NEA. In addition, in this embodiment, the range of the target opening SQ1 that is permissible in the feedback process is also expanded. This allows the target opening SQ1 to be kept within the permissible range even if the adjustment value PH is increased. Therefore, after the fuel cut process is started, the actual engine speed NE can be quickly returned to a value close to the target idle speed NEA.

[0062] (4) As described above, when the fuel cut process is ended and normal process is resumed, the actual engine speed NE increases rapidly. At this time, in order to quickly return the actual engine speed NE to a value close to the target idle speed NEA, it is necessary to rapidly reduce the throttle opening SQ.

[0063] In this embodiment, the range of the adjustment value PH permitted in the feedback process continues to be expanded until the specified period H has elapsed after the fuel cut process is completed. This allows the throttle opening SQ to be rapidly decreased to an opening that can achieve the target idle speed NEA even after the fuel cut process is completed. Therefore, the actual engine speed NE can be quickly returned to a value close to the target idle speed NEA after the fuel cut process is completed.

[0064] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

[0065] In the above embodiment, the throttle control unit 111 is responsible for the feedback process and the learning process, and the combustion control unit 113 is responsible for the fuel cut process and the prohibition process. However, which functional unit in the control device 110 is responsible for which process can be changed as appropriate. A functional unit other than the throttle control unit 111 and the combustion control unit 113 may perform the above processes. It is sufficient that the control device 110 functions so as to appropriately perform each process.

[0066] It is not essential that the execution icon be displayed on the display 501. For example, the fuel cut process may be executed by inputting a specific command using the display 501. Also, for example, a push switch for executing the fuel cut process may be provided inside the vehicle.

[0067] Regardless of the processing mode, the fuel cut processing may be executed while the internal combustion engine 10 is idling. For example, as in the above modified example, a push switch may be provided in the vehicle interior, and when the push switch is operated while the internal combustion engine 10 is idling, the fuel cut processing may be executed regardless of the processing mode. Even in this case, the learning processing may be prohibited while the fuel cut processing is being executed.

[0068] It is not essential to provide two processing modes, the normal mode and the maintenance mode. It is sufficient if the fuel cut processing can be performed while the internal combustion engine 10 is idling. And, the learning processing can be prohibited at that time.

[0069] The fuel cut process may be executed when the internal combustion engine 10 is idling while the vehicle 500 is traveling. If the processing contents of the control device 110 are set so that the fuel cut process is automatically executed when the internal combustion engine 10 is idling and the amount of PM accumulation W in the GPF 23 is appropriately large, the fuel cut process can also be executed while the vehicle 500 is traveling. Even when the fuel cut process is executed while the vehicle 500 is idling while traveling, the learning process may be prohibited while the fuel cut process is being executed.

[0070] The fuel cut process may be performed when the internal combustion engine 10 is not idling. The process contents of the control device 110 may be appropriately set so that the fuel cut process can be performed when the internal combustion engine 10 is not idling.

[0071] The ranges of the adjustment value PH and the target opening SQ1 defined by the first guard information J1 are not limited to those in the above embodiment. The upper and lower limits of each parameter may be set so as to avoid an excessively sudden change in the target opening SQ1 and to keep the target opening SQ1 within an appropriate range of values. The same applies to the second guard information J2. However, the ranges of the adjustment value PH and the target opening SQ1 defined by the second guard information J2 must be such that they can tolerate feedback correction of the throttle opening SQ in response to a sudden change in the engine speed NE when switching between fuel cut processing and normal processing.

[0072] The prohibition of the learning process may be released when the fuel cut process ends. Specifically, in the example shown in Fig. 3, the learning flag FK may be switched to "1" at time T3. If the learning process can be prohibited at least during the fuel cut process, the effect of the fuel cut process on the base opening SQ2 can be reduced.

[0073] It is not necessary to switch the guard information between fuel cut processing and normal processing. If general-purpose upper and lower limits that can be used in both fuel cut processing and normal processing are defined as the range of the adjustment value PH and the target opening SQ1 specified in the guard information, there is no need to switch the guard information.

[0074] The learning process is not limited to the above embodiment. The learning process may be any process that can learn the base opening SQ2 so that the amount of correction by feedback correction is small during idling of the internal combustion engine 10.

[0075] The feedback process is not limited to the above embodiment, but may be any process that feedback corrects the throttle opening SQ so as to reduce the difference between the actual engine speed NE and the target idle speed NEA.

[0076] The stopped cylinders and the combustion cylinders are not limited to the examples in the above embodiment. That is, any of the four cylinders 11 may be a stopped cylinder, or any of the four cylinders 11 may be a combustion cylinder. Also, the stopped cylinders and the combustion cylinders may be changed for each combustion cycle.

[0077] The number of stopped cylinders and the number of combustion cylinders in one combustion cycle may be changed from the example of the above embodiment. Also, the number of stopped cylinders and the number of combustion cylinders may be changed for each combustion cycle. In other words, the stopped cylinders and the combustion cylinders may be set so that the fuel cut process is as follows. "M" and "N" are integers of 1 or more. A stop pattern is a pattern in which fuel supply to M consecutive cylinders 11 is stopped in the order of the cylinders 11 that undergo the combustion stroke. Also, a combustion pattern is a pattern in which fuel supply to N consecutive cylinders 11 is performed in the order of the cylinders 11 that undergo the combustion stroke. The fuel cut process may be a pattern in which the stop pattern and the combustion pattern are alternately repeated while the internal combustion engine 10 continues to operate. Note that the total value of M and N does not need to match the number of cylinders 11. If the total value of M and N does not match the number of cylinders 11, the stopped cylinders and the combustion cylinders may be changed for each combustion cycle, or there may be no stopped cylinders in some combustion cycles.

[0078] The application for which the fuel cut process is performed is not limited to the example of the above embodiment. The stopped cylinders and the combusted cylinders may be set appropriately depending on the application of the fuel cut process. It is not essential to make the air-fuel ratio of the mixture in the combustion cylinder richer than the air-fuel ratio. The air-fuel ratio of the mixture in the combustion cylinder can be set appropriately depending on the application of the fuel cut process.

[0079] The configuration of the internal combustion engine 10 is not limited to the example of the above embodiment. For example, the number of cylinders 11 may be changed. The internal combustion engine only needs to have a plurality of cylinders, an intake passage that introduces intake air into the plurality of cylinders, and a throttle valve that adjusts the flow rate of the intake air flowing through the intake passage.

[0080] The configuration of the vehicle 500 is not limited to the example of the above embodiment. For example, the vehicle may be configured as a hybrid vehicle having an internal combustion engine and a motor generator as a drive source of the vehicle. [Explanation of symbols]

[0081] 11…Cylinder 15…Intake passage 16...Throttle valve 110...Control device

Claims

[Claim 1] The present invention is applied to an internal combustion engine having a plurality of cylinders, an intake passage that introduces intake air into the plurality of cylinders, and a throttle valve that adjusts the flow rate of the intake air flowing through the intake passage, a feedback process for feedback correcting an opening degree of the throttle valve so that a difference between an actual engine rotation speed and a target engine rotation speed is reduced during an idle operation of the internal combustion engine; a learning process for learning a base opening degree, which is a value before the feedback correction, during an idle operation of the internal combustion engine, so that a correction amount by the feedback correction becomes small; a fuel cut process in which a stop pattern in which fuel supply to M consecutive cylinders in the order of the cylinders entering a combustion stroke, where "M" and "N" are integers equal to or greater than 1, is alternately repeated while continuing operation of the internal combustion engine, and a combustion pattern in which fuel supply to N consecutive cylinders in the order of the cylinders entering a combustion stroke, where "M" and "N" are integers equal to or greater than 1; It is possible to execute In the feedback process, an adjustment value for adjusting the correction amount is calculated based on a difference between the actual engine rotation speed and the target engine rotation speed so that the absolute value of the adjustment value is equal to or less than a predetermined adjustment upper limit value, and the calculated adjustment value is added to a previous value of the correction amount to calculate a latest correction amount. When the fuel cut process is executed during idling of the internal combustion engine, execution of the learning process is prohibited, and the adjustment upper limit value is set to a second adjustment upper limit value that is greater than a first adjustment upper limit value that was specified before the fuel cut process is executed, and the adjustment upper limit value is maintained at the second adjustment upper limit value until a predetermined specified period has elapsed after the fuel cut process is completed. A control device for an internal combustion engine.

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