JP7639614B2 - Control device for internal combustion engine - Google Patents

Description

This invention relates to a control device for an internal combustion engine.

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

The control device performs so-called idle speed control while the internal combustion engine is idling. That is, the control device performs feedback correction of the throttle valve opening so as to reduce the difference between the actual engine speed and the target engine speed. In addition, while the internal combustion engine is idling, the control device stores, as a learned value, the throttle valve opening at which the actual engine speed matches the target engine speed, based on the results of the above feedback correction.

JP 2012-197688 A

A known technology related to internal combustion engines is a control that stops fuel supply to only certain cylinders among multiple cylinders while the internal combustion engine is idling, while continuing fuel supply to the other cylinders. When this control is executed, the engine speed may decrease due to stopping fuel supply to certain 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 to increase the amount of intake air compared to when fuel is supplied to all cylinders.

However, if the throttle valve opening learning described in Patent Document 1 is performed while the above control is being performed, 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.

The 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 the actual engine speed and the target engine speed during idle operation of the internal combustion engine, a learning process that learns the base opening, which is the value before the feedback correction, so that the correction amount by the feedback correction becomes smaller during idle operation of the internal combustion engine, 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 reach the combustion stroke, and a combustion pattern that supplies fuel to N consecutive cylinders in the order of the cylinders that reach the combustion stroke, while continuing operation of the internal combustion engine, where "M" and "N" are integers of 1 or more. When the fuel cut process is executed during idle operation of the internal combustion engine, execution of the learning process is prohibited.

In the above configuration, when fuel cut processing is performed while the internal combustion engine is idling, learning of the base opening is prohibited. This 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.

FIG. 1 is a schematic diagram of a vehicle. FIG. 2 is a flowchart showing the procedure of the prohibition process. 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.

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, the vehicle 500 has an internal combustion engine 10. The internal combustion engine 10 is a drive source of the vehicle 500.

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 the rotational position CR of the crankshaft 31. In this specification, when the four cylinders 11 are collectively described, they are referred to as cylinders 11, and when they are described separately, they are referred to as the first cylinder #1, the second cylinder #2, the third cylinder #3, and the fourth cylinder #4.

The engine body 10A has a water jacket 18. The water jacket 18 is a passage through which the 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.

The internal combustion engine 10 has four spark plugs 19. An ignition plug 19 is provided for each cylinder 11. The tip of the spark plug 19 is located inside the cylinder 11. The spark plug 19 ignites the mixture of intake air and fuel by spark discharge.

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 the 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 the 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 the throttle opening). The four fuel injection valves 17 are located downstream of the throttle valve 16 in the intake passage 15. A fuel injection valve 17 is provided for each cylinder 11. The fuel injection valves 17 inject fuel to supply fuel into the cylinders 11.

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.

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 input operations can be performed from outside.

<General configuration 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 (circuitry) including a combination thereof. The processor includes a CPU and memories such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute the processes. The memory, i.e., 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.

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.

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:

The flow rate GA of the intake air detected by the air flow meter 61
Throttle opening SQ detected by the opening sensor 62
The temperature of the cooling water detected by the water temperature sensor 63 (TW)
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 cooling water temperature TW.

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 primarily responsible for processing related to the control of the throttle valve 16. The combustion control unit 113 is a functional unit that is primarily 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 flags related to the manner in which the air-fuel mixture is burned.

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 places the internal combustion engine 10 in an idle operation state. In other words, the internal combustion engine 10 enters an engine operation state in which it operates at the minimum engine rotation speed NE at which it 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 the fuel cut process described below.

<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 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 fuel supply to one cylinder 11 is stopped, and a combustion pattern in which fuel is continuously supplied to three cylinders 11 in the order of the cylinders 11 undergoing a combustion stroke are alternately repeated while the internal combustion engine 10 continues to operate. In this embodiment, the cylinder 11 to which fuel supply is stopped during the fuel cut process (hereinafter, referred to as the stopped cylinder) is the second cylinder #2. 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.

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. As the mixture burns in such an air-fuel ratio rich atmosphere, the combustion cylinder discharges unburned fuel into the exhaust passage 21. On the other hand, the stopped cylinder discharges oxygen into the exhaust passage 21. The oxygen discharged by the stopped cylinder into the exhaust passage 21 and the unburned fuel discharged by the combustion cylinder into the exhaust passage 21 eventually reach the three-way catalyst 22. Then, the unburned fuel burns 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 into the exhaust passage 21 reaches the GPF 23, the PM collected by the GPF 23 is burned and disappears. Through this process, the PM can be removed from the GPF 23.

When the control device 110 is in maintenance mode and the 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 amount of PM accumulation W in the GPF 23 becomes equal to or less than the specified amount WE. The specified amount WE is determined, for example, through experiments, as a value at which the amount of PM accumulation W in the GPF 23 becomes sufficiently small and the fuel cut process may be ended. Note that while the fuel cut process is being executed, the combustion control unit 113 cancels normal processing related to the combustion of the air-fuel mixture. 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.

<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.

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).

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.

When the throttle control unit 111 starts the feedback process and calculates the target opening SQ1 for the first time, it calculates the correction value SQ3 as zero. In other words, 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, it 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 the latest correction value SQ3 by adding the adjustment value PH to the previous value SQ3A of the correction value SQ3, as shown in the following equation (2).

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 the 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 speed NE and the target idle 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.

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

<Guard Information>
The throttle control unit 111 stores in advance the 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 defines the lower limit of the adjustment value PH that the throttle control unit 111 calculates at each timing. In other words, 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 defines the upper limit of the target opening SQ1 that the throttle control unit 111 calculates at each timing. In other words, 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 defines the lower limit of the target opening SQ1 that the throttle control unit 111 calculates at each timing. In other words, 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.

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. In addition, 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 circumstances in which no abnormality has occurred in the internal combustion engine 10.

The throttle control unit 111 prestores the 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 specifies 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 greater 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 specifies 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. 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. 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. 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. The second target lower limit value is smaller than the first target lower limit value. In this way, 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.

As will be explained in the section on operation below, when switching between normal processing and fuel cut processing, a sudden change in engine speed NE occurs. 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 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. In addition, 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 fuel cut processing is executed under conditions in which no abnormality is occurring in the internal combustion engine 10.

When performing 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. Then, the throttle control unit 111 performs the feedback process based on the upper and lower limits defined by the selected guard information.

<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 of time 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 the 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.

<Prohibition processing>
The combustion control unit 113 can execute a prohibition process. The prohibition process is a process for specifying whether or not to execute the learning process and the guard information to be used in the feedback process. Specifically, in the prohibition process, the combustion control unit 113 prohibits the execution of the learning process when the fuel cut process is being executed. On the other hand, when the fuel cut process is not being executed, that is, when normal processing is being executed, the combustion control unit 113 permits the execution of the learning process. The combustion control unit 113 sets a learning flag FK as a flag for indicating whether or not to execute the learning process as described above. 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.

In addition, 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, i.e., when normal processing 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 designated guard information. 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.

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 action section below, when normal processing is resumed after the fuel cut process is completed, the 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 experiments, 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.

<Specific procedure 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 set to "1." Also, at the start of the inhibition process, the guard flag FG is set to "1." 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.

As shown in FIG. 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 been started. If the fuel cut process has not been 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.

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 step S110, the combustion control unit 113 sets the learning flag FK to "2." After that, the combustion control unit 113 advances the process to step S120.

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.

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.

In step S140, the combustion control unit 113 determines whether or not a 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.

In step S150, the combustion control unit 113 allows the learning process to be executed. 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.

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 prohibition process. Then, the combustion control unit 113 executes the process of step S100 again.

<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.

It is assumed 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). In other words, 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.

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 making the combustion cylinder have an air-fuel ratio 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 greater than the current state. Then, as shown in FIG. 3(b), the throttle control unit 111 makes the throttle opening SQ larger than the base opening SQ2. As a result of this, the intake flow rate GA increases, and as shown in FIG. 3(a), the actual engine speed NE increases. Then, the actual engine speed NE approaches the target idle speed NEA. After this, the throttle control unit 111 fine-tunes the throttle opening SQ to a constant value greater than the base opening SQ2, as shown in FIG. 3(b). In this way, 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).

At time T3, which is later than 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 normal processing. In other words, the base opening SQ2 is the throttle opening SQ for making the actual engine speed NE approximately match 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 flow rate GA becomes larger than the intake 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 sharply relative to the target idle speed NEA for the reasons described above.

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 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 negative value so that the actual engine speed NE is smaller than the current state. 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, when the specified period H has elapsed from time T3 to time T4 (step S140: YES), the actual engine speed NE becomes in a state of approximately converging to the target idle speed NEA.

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). In other words, 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.

After time T4, the throttle control unit 111 fine-tunes 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).

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 re-learning the base opening SQ2.

In this regard, in this embodiment, the learning process is prohibited from being executed while the fuel cut process is being executed. This prevents the base opening SQ2 from deviating significantly from the throttle opening SQ required to achieve the target idle speed NEA during normal processing as a result of the execution of the fuel cut process. Specifically, the base opening SQ2 at time T2 shown in FIG. 3 is carried over as the base opening SQ2 at time T4 when the specified period H has elapsed after the fuel cut process ends. 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 speed NEA during normal processing from time T4 onwards.

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

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.

(3) As described above, when the fuel cut process starts, the actual engine speed NE drops sharply. 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.

In this embodiment, when the fuel cut process starts, 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 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 starts, the actual engine speed NE can be quickly returned to a value close to the target idle speed NEA.

(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.

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

<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.

- In the above embodiment, the throttle control unit 111 is responsible for the feedback processing and learning processing, and the combustion control unit 113 is responsible for the fuel cut processing and prohibition processing. However, which functional unit in the control device 110 is responsible for which processing 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 processing. It is sufficient that the control device 110 functions so that each processing can be performed appropriately.

- It is not necessary to display the execution icon 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.

- It may be possible to execute the fuel cut process while the internal combustion engine 10 is idling, regardless of the processing mode. For example, as in the above modified example, a push switch may be provided inside the vehicle cabin, and when the push switch is operated while the internal combustion engine 10 is idling, the fuel cut process may be executed regardless of the processing mode. Even in this case, the learning process may be prohibited while the fuel cut process is being executed.

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

- Fuel cut processing may be performed when the internal combustion engine 10 is idling while the vehicle 500 is traveling. If the processing content of the control device 110 is set to automatically perform fuel cut processing when the internal combustion engine 10 is idling and the amount of PM accumulation W in the GPF 23 is appropriately large, fuel cut processing can also be performed while the vehicle is traveling. Even if fuel cut processing is performed while the vehicle 500 is idling while traveling, the learning process can be prohibited while the fuel cut processing is being performed.

- Fuel cut processing may be performed when the internal combustion engine 10 is not idling. The processing content of the control device 110 may be appropriately set so that fuel cut processing can be performed when the internal combustion engine 10 is not idling.

- The ranges of the adjustment value PH and the target opening SQ1 defined by the first guard information J1 are not limited to the examples in the above embodiment. The upper and lower limits of each parameter can be set so that excessively sudden changes in the target opening SQ1 can be avoided and the target opening SQ1 can be kept within an appropriate value range. 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 need to be such that 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 can be tolerated.

- The prohibition of the learning process may be lifted 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 degree SQ2 can be reduced.

- 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.

The learning process is not limited to the example of 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.

The feedback processing is not limited to the above embodiment. The feedback processing may be any processing 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.

- 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, and any of the cylinders 11 may be a combustion cylinder. In addition, the stopped cylinders and the combustion cylinders may be changed for each combustion cycle.

・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. The stop pattern is a pattern in which fuel supply to M consecutive cylinders 11 is stopped in the order of the cylinders 11 that will undergo the combustion stroke. Also, the combustion pattern is a pattern in which fuel supply to N consecutive cylinders 11 is performed in the order of the cylinders 11 that will undergo the combustion stroke. The fuel cut process may be a process 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.

The purpose of the fuel cut process is not limited to the above embodiment. The stopped cylinders and the combustion cylinders may be appropriately set depending on the purpose 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 may be set appropriately depending on the application of the fuel cut process.

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 multiple cylinders, an intake passage that introduces intake air to the multiple cylinders, and a throttle valve that adjusts the flow rate of the intake air flowing through the intake passage.

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 the drive source of the vehicle.

11: cylinder; 15: intake passage; 16: throttle valve; 110: control device

Claims (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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