Hybrid vehicle control device

Abstract

To suppress a rotation speed of a crank axle from deviating from a target rotation speed.SOLUTION: A control device of a hybrid vehicle can execute: first processing in which a stopping pattern in which fuel supply to M-gas tubes is stopped consecutively in the order in which the gas tubes receive combustion strokes and a combustion pattern in which fuel supply to N-gas tubes is performed consecutively in the order in which the gas tubes receive combustion strokes are alternately repeated while making an internal combustion engine keep on operating; and third processing in which an ignition plug is controlled so that ignition is performed in a target ignition time PF during execution of the first processing. The target ignition time PF at which the first processing is started is referred to as a reference ignition time PB and a rotation speed NE of a crank axle at the time when the first processing is started is referred to as a reference rotation speed NEB. In the third processing, when the reference rotation speed NEB is lower than a target rotation speed NET, a time earlier than the reference ignition time PB is set as the target ignition time PF, and when the reference rotation speed NEB is higher than the target rotation speed NET, a time later than the reference ignition time PB is set as the target ignition time PF.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] The vehicle disclosed in Patent Document 1 has an internal combustion engine, a motor generator, and a control device. The internal combustion engine has a plurality of cylinders and a crankshaft that rotates by combustion of an air-fuel mixture in response to fuel supply to each cylinder. The motor generator is connected to the crankshaft of the internal combustion engine. The motor generator applies torque to the crankshaft and is driven by the crankshaft to operate as a generator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-248698 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology disclosed in Patent Document 1, when controlling an internal combustion engine, fuel supply may be stopped only to a specific portion of a plurality of cylinders while continuing to be supplied to the other cylinders. In this case, stopping the fuel supply to the specific cylinders reduces the torque of the crankshaft. Therefore, a torque may be applied from the motor generator to the crankshaft to compensate for this torque reduction. If the magnitude of the torque is not appropriate, the rotation speed of the crankshaft may deviate from the target rotation speed.

[0005] In addition, when fuel supply to a specific cylinder is stopped as described above, the mixture in the other cylinders may be made richer than the theoretical air-fuel ratio and the ignition timing may be adjusted accordingly. Similar problems may occur not only when the torque applied to the crankshaft from the motor generator as described above is inappropriate, but also when parameters related to the combustion of the mixture, such as the fuel injection amount and ignition timing, are inappropriate. [Means for solving the problem]

[0006] A control device for a hybrid vehicle for solving the above problems is applied to a hybrid vehicle having an internal combustion engine having a plurality of cylinders and a spark plug for each of the cylinders, and a motor generator connected to a crankshaft of the internal combustion engine and capable of rotating the crankshaft, and includes a first process for alternately repeating, while continuing operation of the internal combustion engine, a stop pattern for stopping fuel supply to M consecutive cylinders in the order of the cylinders entering a combustion stroke, and a combustion pattern for supplying fuel to N consecutive cylinders in the order of the cylinders entering a combustion stroke, where "M" and "N" are natural numbers, and a torque of the internal combustion engine associated with the stop pattern during execution of the first process. a second process for applying torque from the motor generator to the crankshaft to compensate for a deficiency in torque, and a third process for controlling the spark plug so that ignition occurs at a target ignition timing during execution of the first process, wherein the target ignition timing when the first process is started is set to a reference ignition timing, and the rotational speed of the crankshaft when the first process is started is set to a reference rotational speed, in the third process, if the reference rotational speed is lower than the target rotational speed, the target ignition timing is set to a timing earlier than the reference ignition timing, and if the reference rotational speed is higher than the target rotational speed, the target ignition timing is set to a timing later than the reference ignition timing.

[0007] If the target ignition timing is delayed, the rotation speed of the crankshaft will decrease. On the other hand, if the target ignition timing is advanced, the rotation speed of the crankshaft will increase. In the above configuration, the target ignition timing is advanced or delayed depending on the difference between the rotation speed of the crankshaft and the target rotation speed. This makes it possible to prevent the rotation speed of the crankshaft from deviating from the target rotation speed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle. [Diagram 2] FIG. 4 is an explanatory diagram of a correction map and a normal map. [Diagram 3] 4 is a diagram showing the relationship between ignition timing, the air-fuel ratio of the mixture, and the generated torque. [Figure 4] 11 is a flowchart showing a processing procedure of a base process. [Diagram 5] 13 is a flowchart showing a processing procedure of a third process. [Figure 6] 11 is a time chart showing an example of changes over time of each parameter in the third process. [Figure 7] 4 is a time chart showing an example of change in generated torque over time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a control device for a hybrid vehicle will be described with reference to the drawings. <Vehicle Overview> As shown in FIG. 1, hybrid vehicle (hereinafter referred to as vehicle) 500 has an internal combustion engine 10, a first motor generator (hereinafter referred to as first MG) 71, a second motor generator (hereinafter referred to as second MG) 72, a first inverter 75, a second inverter 76, and a battery 77.

[0010] The internal combustion engine 10, the first MG 71, and the second MG 72 are the driving sources of the vehicle 500. The internal combustion engine 10 will be described in detail later. The first MG 71 is a generator motor having the functions of both a motor and a generator. The second MG 72 is a generator motor, similar to the first MG 71. The first MG 71 is electrically connected to a battery 77 via a first inverter 75. The second MG 72 is electrically connected to a battery 77 via a second inverter 76. The first inverter 75 and the second inverter 76 perform power conversion of DC to AC. The battery 77 supplies power to the first MG 71 and the second MG 72, and stores the power supplied from the first MG 71 and the second MG 72.

[0011] The vehicle 500 has a power distribution integration mechanism 40 , a reduction gear 50 , a speed reduction mechanism 60 , a differential 61 , and driving wheels 62 . The crankshaft 14, which is the output shaft of the internal combustion engine 10, and the rotating shaft of the first MG 71 are connected to the power distribution integration mechanism 40. In addition, the rotating shaft of the second MG 72 is connected to the power distribution integration mechanism 40 via a reduction gear 50. The power distribution integration mechanism 40 is connected to driving wheels 62 via a reduction gear 60 and a differential 61.

[0012] The power distribution integration mechanism 40 is a planetary gear mechanism. The power distribution integration mechanism 40 has a sun gear 41, a ring gear 42, a plurality of pinion gears 43, and a carrier 44. The sun gear 41 is an external gear. The sun gear 41 rotates on its axis. The ring gear 42 is an internal gear. The ring gear 42 rotates coaxially with the sun gear 41. The plurality of pinion gears 43 are interposed between the sun gear 41 and the ring gear 42. Each pinion gear 43 meshes with both the sun gear 41 and the ring gear 42. The carrier 44 supports each pinion gear 43 in a state in which it can rotate on its axis and revolve around the sun gear 41. The carrier 44 rotates coaxially with the sun gear 41 in accordance with the revolution of each pinion gear 43. The sun gear 41 is connected to a rotation shaft of the first MG 71. The carrier 44 is connected to the crankshaft 14. A ring gear shaft 45 which is an output shaft of the ring gear 42 is connected to both the reduction gear 50 and the reduction mechanism 60 .

[0013] The reduction gear 50 is a planetary gear mechanism. The reduction gear 50 has a sun gear 51, a ring gear 52, and a plurality of pinion gears 53. The sun gear 51 is an external gear. The sun gear 51 rotates on its axis. The ring gear 52 is an internal gear. The ring gear 52 rotates coaxially with the sun gear 51. The plurality of pinion gears 53 are interposed between the sun gear 51 and the ring gear 52. Each pinion gear 53 meshes with both the sun gear 51 and the ring gear 52. Each pinion gear 53 can rotate on its axis, but cannot revolve around the sun gear 51. The sun gear 51 is connected to the rotation shaft of the second MG 72. The ring gear 52 is connected to the ring gear shaft 45 described above.

[0014] When the crankshaft 14 of the internal combustion engine 10 inputs torque to the carrier 44 of the power distribution integration mechanism 40, the power distribution integration mechanism 40 distributes the torque to the sun gear 41 and the ring gear 42. The sun gear 41 inputs the distributed torque to the rotating shaft of the first MG 71. When the rotating shaft of the first MG 71 is rotated by this torque, the first MG 71 can function as a generator.

[0015] On the other hand, when the first MG 71 functions as an electric motor, the rotating shaft of the first MG 71 inputs torque to the sun gear 41 of the power split integration mechanism 40. In this case, the power split integration mechanism 40 distributes the input torque to the carrier 44 and the ring gear 42. The carrier 44 inputs the distributed torque to the crankshaft 14. This torque causes the crankshaft 14 to rotate. In this manner, the first MG 71 can apply torque to the crankshaft 14.

[0016] The ring gear 42 inputs the torque distributed to the ring gear 42 to the drive wheels 62 via the ring gear shaft 45, the reduction mechanism 60, and the differential 61. At this time, the reduction mechanism 60 amplifies and outputs the input torque. The differential 61 also allows a difference in rotation speed to occur between the left and right drive wheels 62.

[0017] Furthermore, when the vehicle 500 decelerates, the second MG 72 is caused to function as a generator, so that a regenerative braking force according to the amount of electricity generated by the second MG 72 is generated in the vehicle 500. On the other hand, when the second MG 72 is caused to function as an electric motor, the second MG 72 inputs torque to the drive wheels 62 via the reduction gear 50, the ring gear shaft 45, the reduction mechanism 60, and the differential 61.

[0018] The vehicle 500 has a first rotation sensor 86, a second rotation sensor 87, an accelerator sensor 83, and a vehicle speed sensor 85. The first rotation sensor 86 is located near the rotation shaft of the first MG 71. The first rotation sensor 86 detects the rotation position of the rotation shaft of the first MG 71 as a first detection position Sm1. The second rotation sensor 87 is located near the rotation shaft of the second MG 72. The second rotation sensor 87 detects the rotation position of the rotation shaft of the second MG 72 as a second detection position Sm2. The accelerator sensor 83 detects an accelerator operation amount ACP, which is an operation amount of an accelerator pedal in the vehicle 500. The vehicle speed sensor 85 is located near the drive wheels 62. The vehicle speed sensor 85 detects a vehicle speed SP, which is the traveling speed of the vehicle 500.

[0019] <General configuration of internal combustion engine> The internal combustion engine 10 includes an engine body 10A, the crankshaft 14, a crank angle sensor 18, and a water temperature sensor .

[0020] 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 each cylinder 11. The piston in each cylinder 11 is connected to a crankshaft 14 via a connecting rod. The crankshaft 14 rotates in response to the reciprocating movement of the piston in each cylinder 11. The crank angle sensor 18 is located near the crankshaft 14. The crank angle sensor 18 detects the rotational position of the crankshaft 14 as a detected crank position Scr. 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.

[0021] The engine body 10A has a water jacket 19. The water jacket 19 is a passage through which cooling water flows. The water jacket 19 is positioned around the four cylinders 11. The water temperature sensor 82 is positioned at the outlet of the water jacket 19. The water temperature sensor 82 detects the temperature of the cooling water as a detected water temperature THW.

[0022] The internal combustion engine 10 has four spark plugs 16. Each spark plug 16 is provided for each cylinder 11. The tip of each spark plug 16 is located within the corresponding cylinder 11. Each spark plug 16 ignites the mixture of intake air and fuel in each cylinder 11 by spark discharge. The four spark plugs 16 ignite in the order of the first cylinder #1, the third cylinder #3, the fourth cylinder #4, and the second cylinder #2. In other words, the four cylinders 11 undergo the combustion stroke in the order of the first cylinder #1, the third cylinder #3, the fourth cylinder #4, and the second cylinder #2.

[0023] The internal combustion engine 10 has an intake passage 15, an airflow meter 81, 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 81 is located midway through the intake passage 15. The airflow meter 81 detects the amount of intake air flowing through the intake passage 15 as a detected intake amount GA. The four fuel injection valves 17 are located downstream of the airflow meter 81 in the intake passage 15. The four fuel injection valves 17 are provided for each cylinder 11. The four fuel injection valves 17 inject fuel for each cylinder 11. Thus, the four fuel injection valves 17 supply fuel to each cylinder 11.

[0024] 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.

[0025] <Outline of the control device> The vehicle 500 has a control device 100. The control device 100 may be configured as one or more processors that execute various processes according to a computer program (software). The control device 100 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 100 has a storage device that is an electrically rewritable non-volatile memory.

[0026] The control device 100 receives detection signals from various sensors mounted on the vehicle 500. Specifically, the control device 100 receives detection signals for the following parameters: The intake air volume detected by the air flow meter 81 is GA The water temperature THW detected by the water temperature sensor 82 The crank angle sensor 18 detects the crank position Scr A first detection position Sm1 detected by the first rotation sensor 86 A second detection position Sm2 detected by the second rotation sensor 87 Accelerator operation amount ACP detected by accelerator sensor 83 Vehicle speed SP detected by the vehicle speed sensor 85 The control device 100 has a hybrid control unit 102, an internal combustion engine control unit 104, and a motor control unit 106. Each of these functional units will be described below in order.

[0027] <Hybrid control unit> The hybrid control unit 102 performs overall control of the vehicle 500. The rotation speed of the crankshaft 14 is referred to as the engine rotation speed NE. Furthermore, the torque of the internal combustion engine 10 is referred to as the engine torque. The hybrid control unit 102 calculates a target value of the engine rotation speed NE (hereinafter referred to as the target engine rotation speed) NET and a target value of the engine torque (hereinafter referred to as the target engine torque) based on the accelerator operation amount ACP and the vehicle speed SP. Furthermore, the hybrid control unit 102 calculates a target value of the torque of the first MG 71 (hereinafter referred to as the target first MG torque) and a target value of the torque of the second MG 72 (hereinafter referred to as the target second MG torque) based on the accelerator operation amount ACP and the vehicle speed SP.

[0028] <Internal combustion engine control unit> The internal combustion engine control unit 104 controls various parts of the internal combustion engine 10 based on the target engine speed NET and target engine torque calculated by the hybrid control unit 102. The internal combustion engine control unit 104 constantly calculates various parameters indicating the engine operating state. Specifically, the internal combustion engine control unit 104 calculates the engine speed NE based on the detected crank position Scr. The internal combustion engine control unit 104 also calculates the engine load KL based on the engine speed NE and the detected intake air amount GA. Furthermore, the internal combustion engine control unit 104 calculates the accumulation amount W of PM trapped in the GPF 23 based on the engine load KL and the detected water temperature THW.

[0029] The internal combustion engine control unit 104 can execute a regeneration process as one of the processes for controlling the internal combustion engine 10. The regeneration process is a process for burning and removing PM trapped by the GPF 23 from the GPF 23. The internal combustion engine control unit 104 can execute a first process as part of the regeneration process. A series of processes in which the four cylinders 11 each undergo a combustion stroke once, that is, a period in which the crankshaft 14 rotates twice, is called one combustion cycle. As the first process, the internal combustion engine control unit 104 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 first 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 first process (hereinafter referred to as the stopped cylinder) is the third cylinder #3. The cylinders 11 to which fuel is supplied during the first process (hereinafter referred to as the combustion cylinders) are the first cylinder #1, the second cylinder #2, and the fourth cylinder #4. In the first process, the internal combustion engine control unit 104 supplies fuel to the combustion cylinders so that the air-fuel ratio of the mixture in the combustion cylinder becomes a rich air-fuel ratio AFR that is a certain amount richer than the stoichiometric air-fuel ratio AFS.

[0030] The internal combustion engine control unit 104 can also execute a third process as part of the regeneration process. The third process is a process for controlling the spark plug 16 during the execution of the first process in accordance with the execution of the first process. The contents of this third process will be explained after the motor control unit 106. The internal combustion engine control unit 104 executes the first process and the third process through the base process of the regeneration process.

[0031] <Motor control unit> The motor control unit 106 controls the first MG 71 and the second MG 72 based on the target first MG torque and the target second MG torque calculated by the hybrid control unit 102. The motor control unit 106 essentially controls the first MG 71 by controlling the first inverter 75. The motor control unit 106 also controls the second MG 72 by controlling the second inverter 76. The motor control unit 106 constantly calculates various parameters indicating the state of each motor generator. Specifically, the motor control unit 106 calculates the rotation speed of the rotating shaft of the first MG 71 based on the first detection position Sm1. The motor control unit 106 also calculates the rotation speed of the rotating shaft of the second MG 72 based on the second detection position Sm2.

[0032] The motor control unit 106 can execute the second process as one of the processes for controlling the first MG 71. As described above, in the first process, the internal combustion engine control unit 104 stops the fuel supply to the third cylinder #3, which is the stopped cylinder. Accordingly, the combustion of the air-fuel mixture in the third cylinder #3 is stopped. The second process is a process for applying torque from the first MG 71 to the crankshaft 14 so as to compensate for the engine torque shortage caused by the stop of the combustion of the air-fuel mixture in the third cylinder #3.

[0033] When the internal combustion engine control unit 104 starts the first process, the motor control unit 106 starts the second process. Then, the motor control unit 106 controls the first MG 71 to apply torque to the crankshaft 14 at the timing when the third cylinder #3 enters the combustion stroke. At that time, the motor control unit 106 calculates a target compensation torque, which is a target value of the torque to be applied to the crankshaft 14. Then, the motor control unit 106 controls the first MG 71 to output the target compensation torque. The target compensation torque is substantially the same in magnitude as the torque generated by the combustion of the mixture in the third cylinder #3. The magnitude of this torque is the magnitude of the torque generated on the crankshaft 14 by the combustion of the mixture in the cylinder 11 when the air-fuel ratio of the mixture in the cylinder 11 is the stoichiometric air-fuel ratio AFS and the target ignition timing PF of the spark plug 16 is the MBT ignition timing. The MBT ignition timing is the ignition timing at which the maximum torque can be obtained in the current engine operating state.

[0034] <Outline of the third process> The internal combustion engine control unit 104 can execute the third process. As described above, the third process is a process for controlling the spark plug 16 during the execution of the first process. In the third process, the internal combustion engine control unit 104 calculates the target ignition timing PF for the combustion cylinder during the execution of the first process. Then, the internal combustion engine control unit 104 controls the spark plug 16 of the combustion cylinder so that ignition is performed at the target ignition timing PF. On the other hand, the internal combustion engine control unit 104 controls the spark plug 16 of the stopped cylinder so that ignition is not performed. Note that the internal combustion engine control unit 104 determines the target ignition timing PF based on the rotational position of the crankshaft 14 relative to the compression top dead center of the cylinder 11 to be ignited. In other words, the compression top dead center of the cylinder 11 to be ignited is set to "0", and the target ignition timing PF set before the compression top dead center is set to a positive value, and the target ignition timing PF set after the compression top dead center is set to a negative value. Therefore, the more the target ignition timing PF is set to the advanced side, the larger the positive value becomes, and the more the target ignition timing PF is set to the retarded side, the smaller the negative value becomes. "Advancing" means to advance the ignition timing. "Retarding" means to delay the ignition timing.

[0035] When the internal combustion engine control unit 104 starts the third process, it first calculates the target ignition timing PF as the reference ignition timing PB. That is, at the start of the first process, the target ignition timing PF becomes the reference ignition timing PB. The reference ignition timing PB will be described later. Here, the engine speed NE when the target ignition timing PF is set to the reference ignition timing PB, that is, the engine speed NE when the first process is started, is referred to as the reference rotation speed NEB. In the third process, the internal combustion engine control unit 104 adjusts the target ignition timing PF according to the magnitude relationship between the target engine rotation speed NET and the reference rotation speed NEB. That is, when the reference rotation speed NEB is lower than the target engine rotation speed NET, the internal combustion engine control unit 104 calculates the ignition timing on the advanced side of the reference ignition timing PB as the target ignition timing PF. On the other hand, when the reference rotation speed NEB is higher than the target engine rotation speed NET, the internal combustion engine control unit 104 calculates the ignition timing on the retarded side of the reference ignition timing PB as the target ignition timing PF.

[0036] The internal combustion engine control unit 104 uses the correction value PH when adjusting the target ignition timing PF as described above. This correction value PH is the amount of change ΔP in the ignition timing required to eliminate the difference between the reference rotation speed NEB and the target engine rotation speed NET. As described later, the correction value PH can take a positive or negative value. The internal combustion engine control unit 104 calculates the target ignition timing PF by adding the correction value PH to the reference ignition timing PB. When the spark plug 16 of the combustion cylinder is controlled based on this target ignition timing PF, the difference between the reference rotation speed NEB and the target engine rotation speed NET is basically eliminated. However, for example, due to an error in the fuel injection amount, the engine rotation speed NE may not change as expected even if the spark plug 16 is controlled by performing correction using the correction value PH. In this case, the difference between the reference rotation speed NEB and the target engine rotation speed NET is not necessarily completely eliminated. Therefore, in the third process, the internal combustion engine control unit 104 continues to perform feedback correction while the first process is being executed so as to eliminate the difference between the engine speed NE and the target engine speed NET. That is, the internal combustion engine control unit 104 calculates the latest target ignition timing PF by adding the correction value PH as the amount of change ΔP in the ignition timing required to eliminate the difference between the engine speed NE and the target engine speed NET to the previous value of the target ignition timing PF.

[0037] <Correction map> The internal combustion engine control unit 104 stores in advance a correction map for calculating the above correction value PH. The correction map represents the relationship between the change amount ΔP of the ignition timing required to change the engine speed NE from the first value to the second value, and the difference value ΔNE, which is a value obtained by subtracting the first value from the second value. The correction map is based on the premise that the first process is being executed. That is, the correction map is based on the premise that only three of the four cylinders 11 are combustion cylinders. The correction map is based on the premise that the air-fuel ratio of the mixture in the combustion cylinder is the above rich air-fuel ratio AFR. Here, there is the following relationship between the ignition timing and the engine speed NE. That is, if the air-fuel ratio in the cylinder 11 is the same, the more the ignition timing is advanced, the higher the engine speed NE becomes, and the more the ignition timing is retarded, the lower the engine speed NE becomes. The correction map reflects this relationship. Specifically, as shown by the solid line in FIG. 2, in the correction map, when the difference value ΔNE is positive, that is, when the second value is greater than the first value, the change amount ΔP of the ignition timing is a positive value, that is, a value that corrects the ignition timing to be advanced. The larger the difference value ΔNE, the larger the change amount ΔP of the ignition timing. On the other hand, in the correction map, when the difference value ΔNE is negative, that is, when the second value is smaller than the first value, the change amount ΔP of the ignition timing is a negative value, that is, a value that corrects the ignition timing to be retarded. The larger the absolute value of the difference value ΔNE, the larger the absolute value of the change amount ΔP. The correction map is created, for example, based on experiments.

[0038] The internal combustion engine control unit 104 stores a normal map as a map of the same type as the correction map. The normal map is for adjusting the ignition timing to change the engine speed NE under a condition where the mixture is burned in all cylinders 11, that is, in the normal processing related to the spark plug 16. The normal map shows the relationship between the change amount ΔP of the ignition timing and the difference value ΔNE, on the premise that the mixture is burned in all cylinders 11 and the air-fuel ratio in all cylinders 11 is the theoretical air-fuel ratio AFS. As shown by the dashed line in FIG. 2, in the normal map, as in the correction map, the change amount ΔP of the ignition timing is basically larger as the difference value ΔNE is larger. When the correction map shown by the solid line in FIG. 2 is compared with the normal map shown by the dashed line in FIG. 2, the absolute value of the change amount ΔP of the ignition timing required to change the engine speed NE by a certain amount is larger in the former than in the latter.

[0039] <Standard ignition timing> As a premise for explaining the reference ignition timing PB, the relationship between the ignition timing of a particular cylinder 11, the air-fuel ratio of the mixture in that particular cylinder 11, and the generated torque, which is the torque generated on the crankshaft 14 when the mixture is combusted in that particular cylinder 11, will be explained.

[0040] Now, assume that the air-fuel ratio of the mixture in the cylinder 11 is set to the stoichiometric air-fuel ratio AFS and the mixture is burned. In this case, as shown by the solid line A1 in Fig. 3, the more the ignition timing is retarded from the MBT ignition timing, the smaller the generated torque becomes. Also, as shown by the solid line A2 in Fig. 3, assume that the air-fuel ratio of the mixture in the cylinder 11 is set to a rich air-fuel ratio AFR and the mixture is burned. In this case, too, the more the ignition timing is retarded from the MBT ignition timing, the smaller the generated torque becomes. Furthermore, in this case, the generated torque becomes larger at the same ignition timing than when the air-fuel ratio of the mixture shown by the solid line A1 in Fig. 1 is the stoichiometric air-fuel ratio AFS.

[0041] Now, as shown by the black circle B1 in FIG. 3, ignition is performed at the MBT ignition timing when the air-fuel ratio in the cylinder 11 is the stoichiometric air-fuel ratio AFS. The torque generated at this time is called the normal torque UN. Also, as shown by the black circle B2 in FIG. 3, ignition is performed at the MBT ignition timing when the air-fuel ratio of the mixture in the cylinder 11 is the rich air-fuel ratio AFR. The torque generated at this time is called the rich torque UR. Due to the relationship between the ignition timing, the air-fuel ratio of the mixture, and the generated torque described above as a premise, the rich torque UR is larger than the normal torque UN. The air-fuel ratio of the mixture in the combustion cylinder during the execution of the first process is the rich air-fuel ratio AFR. Therefore, if the ignition timing of the combustion cylinder during the execution of the first process is the MBT ignition timing, the generated torque of each combustion cylinder becomes the rich torque UR and exceeds the normal torque UN. In this case, the engine torque exceeds the target engine torque due to the following reasons. The generated torque required of each cylinder 11 when the engine torque is set as the target engine torque is the normal torque UN. During the first process, the engine torque decreases due to the combustion of the mixture in the third cylinder #3 being stopped, but the torque equivalent to this decrease is provided by the first MG 71 as described above. As described in relation to the second process, the torque provided by the first MG 71 is approximately equal to the normal torque UN. In other words, during the first process, it appears as if the normal torque UN is being generated from the third cylinder #3. Under such circumstances, when the generated torque of each combustion cylinder becomes the rich torque UR and exceeds the normal torque UN, the total generated torque of the four cylinders 11 becomes larger than when each of the four cylinders 11 generates the normal torque UN. Therefore, the engine torque exceeds the target engine torque.

[0042] In order to avoid the situation where the engine torque exceeds the target engine torque as described above and to make the engine torque approximately equal to the target engine torque, it is necessary to set the ignition timing so that the torque generated by the combustion cylinder becomes the normal torque UN during the execution of the first process. In order to obtain the normal torque UN when the air-fuel ratio in the cylinder 11 is set to a rich air-fuel ratio AFR, the ignition timing needs to be retarded from the MBT ignition timing due to the relationship between the ignition timing, the air-fuel ratio of the mixture, and the generated torque. As shown in the black circle B3 in FIG. 3, among the ignition timings retarded from the MBT ignition timing, the ignition timing at which the normal torque UN can be obtained when the air-fuel ratio of the mixture in the combustion cylinder is set to a rich air-fuel ratio AFR is referred to as the first ignition timing. If the ignition timing of the combustion cylinder is set to the first ignition timing, theoretically, the normal torque UN can be obtained with the combustion of the mixture in the combustion cylinder.

[0043] However, the amount of fuel supplied from the fuel injection valve 17 may have an error due to factors such as product tolerance and aging. Therefore, even if fuel is injected in anticipation of the air-fuel ratio of the mixture in the combustion cylinder becoming a rich air-fuel ratio AFR, the actual air-fuel ratio is not necessarily rich air-fuel ratio AFR. Therefore, as shown by the arrow range B3Q in FIG. 3, even if the mixture is burned with the ignition timing set to the first ignition timing, the actual generated torque is not necessarily the normal torque UN, and the generated torque may be larger or smaller than the normal torque UN. If the actual generated torque becomes smaller than the normal torque UN, the engine speed NE may drop excessively. If such a drop occurs, a process to raise the engine speed NE afterwards is required, which is not preferable. Therefore, as shown by the black circle B4 in FIG. 3, a second ignition timing that is more advanced than the first ignition timing and more retarded than the MBT ignition timing is considered as the ignition timing in the combustion cylinder. As shown by the arrow range B4Q in Fig. 3, this second ignition timing is an ignition timing at which the generated torque does not fall significantly below the normal torque UN even if the generated torque has a certain range due to the above-mentioned product tolerances and the like. Such a second ignition timing can be determined, for example, by experiment. For convenience, the lower limit of the arrow range B4Q in Fig. 3 is set to the normal torque UN. The sizes of the arrow ranges B3Q and B4Q in Fig. 3 are for convenience in explaining the relationship between the first ignition timing and the second ignition timing and the generated torque, and are different from the range of the actual generated torque.

[0044] In this embodiment, the second ignition timing is set to the reference ignition timing PB. The internal combustion engine control unit 104 stores two maps in advance as information for calculating the reference ignition timing PB. The first map is an MBT map. The MBT map represents the MBT ignition timing for each engine operating state defined by the engine speed NE and the engine load KL. The second map is a conversion map. The conversion map represents a relational expression (hereinafter, referred to as a conversion relational expression) for deriving the second ignition timing from the MBT ignition timing for each engine operating state defined by the engine speed NE and the engine load KL. The internal combustion engine control unit 104 calculates the second ignition timing, i.e., the reference ignition timing PB, using these maps. The MBT map and the conversion map are created, for example, based on experiments.

[0045] In the MBT map, the MBT ignition timing is defined as "0" at the compression top dead center of the cylinder 11 to be ignited, and is defined as a positive value if it is advanced from the compression top dead center and a negative value if it is retarded from the compression top dead center. Therefore, the reference ignition timing PB obtained by converting this MBT ignition timing is also based on the compression top dead center of the cylinder 11 to be ignited.

[0046] <Specific processing procedures for recycling> The internal combustion engine control unit 104 repeatedly executes the base processing of the regeneration processing while the ignition switch of the vehicle 500 is on. As shown in Fig. 4, when the internal combustion engine control unit 104 starts the base processing, it executes the processing of step S301.

[0047] In step S301, the internal combustion engine control unit 104 determines whether or not a start condition for the first process is satisfied. The start condition is that a plurality of start requirements are all satisfied. The plurality of start requirements includes the following contents. (A1) The amount W of PM accumulated in the GPF 23 is equal to or greater than a first specified amount W1. (A2) A state in which the target engine speed NET can be regarded as being substantially constant continues for a first set period H1 or longer. (A3) Vehicle speed SP is greater than zero.

[0048] The start requirement (A1) is for determining that removal of PM is necessary in the GPF 23. That is, the first specified amount W1 is a value at which the PM accumulation amount W in the GPF 23 is appropriately large and it is desirable to remove PM from the GPF 23, and is determined in advance, for example, through experiments. Regarding the start requirement (A2), it is not preferable to perform the first process to stop the combustion of the mixture when the target engine speed NET is changing suddenly, such as when there is an acceleration request. Therefore, the above (A2) is determined as one of the start requirements to prohibit the first process when the target engine speed NET is changing suddenly. The first set period H1 is determined in advance, for example, through experiments, as a value at which the target engine speed NET can be considered to be continuing in a stable state. Moreover, regarding the start requirement (A3), it is preferable to stop the operation of the internal combustion engine 10 and set the fuel consumption to "0" while the vehicle 500 is stopped. Therefore, the above (A3) is determined as one of the start requirements from the viewpoint of ensuring that the situation is such that fuel can be injected from each fuel injection valve 17.

[0049] When performing the process of step S301, the internal combustion engine control unit 104 refers to the latest information and past history of parameters required for determining whether each start requirement is satisfied, such as the PM accumulation amount W, the target engine rotation speed NET, and the vehicle speed SP. Then, the internal combustion engine control unit 104 determines whether each start requirement is satisfied based on that information.

[0050] If at least one of the start requirements is not satisfied in step S301, the internal combustion engine control unit 104 determines that the start condition is not established (step S301: NO). In this case, the internal combustion engine control unit 104 temporarily ends the series of processes of the base process. Then, the internal combustion engine control unit 104 executes the process of step S301 again.

[0051] On the other hand, in step S301, if all of the start requirements are satisfied, the internal combustion engine control unit 104 determines that the start condition is established (step S301: YES). In this case, the internal combustion engine control unit 104 advances the process to step S302.

[0052] In step S302, the internal combustion engine control unit 104 cancels normal processing related to fuel supply to the cylinders 11 and starts the first processing. As described above, in the first processing, the internal combustion engine control unit 104 stops fuel supply to the stopped cylinders and supplies fuel to the combustion cylinders so that the air-fuel ratio of the mixture becomes a rich air-fuel ratio AFR. After starting the first processing in step S302, the internal combustion engine control unit 104 advances the processing to step S303.

[0053] In step S303, the internal combustion engine control unit 104 determines whether or not a termination condition for the first process is satisfied. The termination condition is that at least one of a plurality of termination requirements is satisfied. The plurality of termination requirements includes the following contents. (B1) The amount W of PM accumulated in the GPF 23 is equal to or smaller than a second specified amount W2. (B2) The time that has elapsed since the start of the first process is equal to or longer than the second set period H2. (B3) The target engine speed NET has fallen out of a specified range M centered on the target engine speed NET at the time the first process was started. (B4) Vehicle speed SP is zero.

[0054] The termination requirement (B1) is for judging the completion of the removal of PM in the GPF 23. That is, the second specified amount W2 is a value at which the accumulation amount W of PM in the GPF 23 becomes sufficiently small and the first process may be terminated, and is determined in advance, for example, through experiments. The termination requirement (B2) is determined as one of the termination requirements so that the first process is continued only for an allowable period in relation to, for example, other controls. The second set period H2 is determined in advance, for example, through experiments, as a value slightly shorter than the maximum period during which the continuation of the first process is allowed. The termination requirement (B3) is determined as one of the termination requirements from the same viewpoint as the start requirement (A2). The specified range M is determined in advance as a range within which the target engine speed NET can be considered to be stable. The termination requirement (B4) is determined as one of the termination requirements from the same viewpoint as the start requirement (A3). In the process of step S303, similarly to the process of step S301, the internal combustion engine control unit 104 refers to the latest information and past history for parameters required for determining whether each end requirement is satisfied. Then, the internal combustion engine control unit 104 determines whether each end requirement is satisfied based on that information.

[0055] If none of the multiple termination requirements is satisfied in step S303, the internal combustion engine control unit 104 determines that the termination condition is not established (step S303: NO). In this case, the internal combustion engine control unit 104 executes the process of step S303 again. The internal combustion engine control unit 104 repeats the process of step S303 until at least one of the multiple termination requirements is satisfied. Then, when at least one of the multiple termination requirements is satisfied, the internal combustion engine control unit 104 determines that the termination condition is established (step S303: YES). In this case, the internal combustion engine control unit 104 advances the process to step S304.

[0056] In step S304, the internal combustion engine control unit 104 ends the first process. Then, the internal combustion engine control unit 104 resumes normal processing related to the supply of fuel to the cylinder 11. After executing the process of step S304, the internal combustion engine control unit 104 temporarily ends the series of processes of the base process, and executes the process of step S301 again.

[0057] <Specific processing procedure of the third process> When the internal combustion engine control unit 104 starts the first process in the background, it starts the third process in parallel with the first process. That is, even during the execution of the third process, fuel supply to the third cylinder #3 is stopped, and fuel is supplied to the other cylinders 11 so that the air-fuel ratio in the cylinder 11 becomes a rich air-fuel ratio AFR. During the execution of the third process, the internal combustion engine control unit 104 cancels the normal process related to the ignition plug 16.

[0058] As shown in Fig. 5, when the internal combustion engine control unit 104 starts the third process, it executes the process of step S110. In step S110, the internal combustion engine control unit 104 turns on a first flag F. This first flag F is a flag for identifying that it is the first time that the target ignition timing PF is calculated after the start of the third process, i.e., after the start of the first process. After executing the process of step S110, the internal combustion engine control unit 104 advances the process to step S120.

[0059] In step S120, the internal combustion engine control unit 104 determines whether or not the first flag F is off. When the processing of step S120 is performed for the first time after the start of the third process, the first flag is on (step S120: NO). In this case, the internal combustion engine control unit 104 advances the process to step S130.

[0060] In step S130, the internal combustion engine control unit 104 calculates the reference ignition timing PB. As described above, the internal combustion engine control unit 104 uses the MBT map and the conversion map to calculate the reference ignition timing PB. First, the internal combustion engine control unit 104 calculates the MBT ignition timing according to the latest engine operating state by using the MBT map. Specifically, the internal combustion engine control unit 104 refers to the latest engine speed NE and the latest engine load KL together with the MBT map. Then, the internal combustion engine control unit 104 reads out the MBT ignition timing corresponding to the latest engine speed NE and the latest engine load KL from the MBT map. Next, the internal combustion engine control unit 104 converts the MBT ignition timing into the reference ignition timing PB by using the conversion map. Specifically, the internal combustion engine control unit 104 refers to the latest engine speed NE and the latest engine load KL together with the conversion map. Then, the internal combustion engine control unit 104 reads out the conversion relational expression corresponding to the latest engine speed NE and the latest engine load KL from the conversion map. Then, the internal combustion engine control section 104 applies this conversion map to the MBT ignition timing to calculate the reference ignition timing PB. After executing the process of step S130, the internal combustion engine control section 104 advances the process to step S140.

[0061] In step S140, the internal combustion engine control section 104 calculates the reference ignition timing PB calculated in step S130 as the target ignition timing PF. After that, the internal combustion engine control section 104 advances the process to step S150.

[0062] In step S150, the internal combustion engine control section 104 turns off the first flag F. After that, the internal combustion engine control section 104 advances the process to step S180. In step S180, the internal combustion engine control unit 104 controls the spark plugs 16 of the cylinders 11 in the order of the combustion stroke. The internal combustion engine control unit 104 controls the spark plugs 16 of the combustion cylinders so that ignition occurs at the target ignition timing PF determined based on the compression top dead center. The internal combustion engine control unit 104 also controls the spark plugs 16 of the stopped cylinders so that ignition does not occur. The internal combustion engine control unit 104 performs the process of step S180 for a predetermined fixed period. During this fixed period, the combustion cycle is repeated multiple times. For example, when the target ignition timing PF is changed, it takes time for the engine speed NE to change accordingly and for the engine speed NE to stabilize to a certain extent. The above-mentioned fixed period is determined, for example, by experiment, as the time required for the engine speed NE to roughly converge to a value corresponding to the target ignition timing PF, taking this time into consideration. After executing the process of step S180, the internal combustion engine control section 104 advances the process to step S190.

[0063] In step S190, the internal combustion engine control unit 104 determines whether or not the first process that has been executed in the background has been completed. If the internal combustion engine control unit 104 has not completed the first process (step S190: NO), the process returns to step S120.

[0064] As described above, in step S120, the internal combustion engine control unit 104 determines whether or not the first flag F is off. Here, after the target ignition timing PF is calculated once after the start of the third process, the first flag F is turned off by the process of step S150. Therefore, when the process returns to step S120 from the process of step S190, the first flag F is off (step S120: YES). In this case, the internal combustion engine control unit 104 advances the process to step S160.

[0065] In step S160, the internal combustion engine control unit 104 calculates the correction value PH. That is, the internal combustion engine control unit 104 uses the correction map to calculate the change amount ΔP of the ignition timing required to eliminate the difference between the target engine rotation speed NET and the engine rotation speed NE. Specifically, the internal combustion engine control unit 104 refers to the correction map as well as the latest engine rotation speed NE and the latest target engine rotation speed NET. Then, the internal combustion engine control unit 104 subtracts the engine rotation speed NE from the target engine rotation speed NET to calculate the difference value ΔNE. Then, the internal combustion engine control unit 104 reads out the change amount ΔP of the ignition timing corresponding to this difference value ΔNE in the correction map. The internal combustion engine control unit 104 calculates the read change amount ΔP as the correction value PH. Note that, at the stage where the process of step S160 is performed for the first time after the start of the third process, the target ignition timing PF related to the first process has been calculated only once before. As described above, the initial target ignition timing PF is the reference ignition timing PB set in step S140. Therefore, the engine speed NE at the above stage is the engine speed NE when the spark plug 16 of the combustion cylinder is controlled with the target ignition timing PF as the reference ignition timing PB, that is, the reference rotation speed NEB. In this case, the internal combustion engine control unit 104 calculates the amount of change ΔP in the ignition timing required to eliminate the difference between the reference rotation speed NEB and the target engine speed NET as the correction value PH. After calculating the correction value PH, the internal combustion engine control unit 104 advances the process to step S170.

[0066] In step S170, the internal combustion engine control unit 104 calculates the target ignition timing PF. Specifically, the internal combustion engine control unit 104 adds the correction value PH calculated in step S160 to the previous value of the target ignition timing PF. Then, the internal combustion engine control unit 104 sets the resultant value as the latest target ignition timing PF. Note that, when the processing of step S160 is performed for the first time after the start of the third process, the previous value of the target ignition timing PF is the reference ignition timing PB. After executing the processing of step S170, the internal combustion engine control unit 104 advances the processing to step S180. Thereafter, the internal combustion engine control unit 104 performs the processing of steps S180 and S190 in the same manner as described above.

[0067] After that, the internal combustion engine control unit 104 repeats the processes of steps S120, S160, S170, S180, and S190 until the first process executed in the background is completed. During this time, the internal combustion engine control unit 104 repeatedly calculates the correction value PH so that the difference between the latest engine speed NE and the latest target engine speed NET is eliminated. Then, the internal combustion engine control unit 104 adds the calculated correction value PH to the previous value of the target ignition timing PF to calculate the latest target ignition timing PF. When the internal combustion engine control unit 104 finishes the first process executed in the background (step S190: YES), it resumes the normal process related to the spark plug 16 and then finishes the third process. Note that the target ignition timing PF when the normal process related to the spark plug 16 is executed is basically the MBT ignition timing.

[0068] <Operation of the embodiment> (a) Regarding the revival of GPF23 The internal combustion engine control unit 104 can remove PM from the GPF 23 through the execution of the first process and the third process. The mechanism will be described. In the first process, the internal combustion engine control unit 104 stops the fuel supply to the stopped cylinder. In the third process, the internal combustion engine control unit 104 does not ignite the spark plug 16 of the stopped cylinder. Therefore, the combustion of the mixture is stopped in the stopped cylinder. On the other hand, in the first process, the internal combustion engine control unit 104 supplies fuel to the combustion cylinder so that the air-fuel ratio of the mixture becomes a rich air-fuel ratio AFR. In the third process, the internal combustion engine control unit 104 ignites the spark plug 16 of the combustion cylinder. Therefore, in the combustion cylinder, the mixture is burned in a state in which the air-fuel ratio of the mixture is a rich air-fuel ratio AFR. As a result, oxygen is discharged from the stopped cylinder to the exhaust passage 21. On the other hand, unburned fuel is discharged from the combustion cylinder to the exhaust passage 21. When the oxygen and unburned fuel discharged into the exhaust passage 21 reach the three-way catalyst 22, the unburned fuel is burned in the three-way catalyst 22, and the temperature of the exhaust gas rises. When this high-temperature exhaust gas reaches the GPF 23, the temperature of the GPF 23 rises. In this state, when oxygen discharged into the exhaust passage 21 from the deactivated cylinder reaches the GPF 23, the PM captured by the GPF 23 is burned and removed.

[0069] (b) Change in engine speed NE according to target ignition timing PF As shown in FIG. 6, it is assumed that the internal combustion engine control unit 104 starts the third process together with the first process at time T1. Then, as shown in FIG. 6(b), the internal combustion engine control unit 104 sets the target ignition timing PF, which was the MBT ignition timing until then, to the reference ignition timing PB (step S140). Here, the reference ignition timing PB is the second ignition timing as shown by the black circle B4 in FIG. 3. This second ignition timing is a timing on the more advanced side than the first ignition timing as shown by the black circle B3 in FIG. 3. The first ignition timing is an ignition timing that can obtain a normal torque UN when the air-fuel ratio of the mixture in the combustion cylinder is set to a rich air-fuel ratio AFR. When the combustion cylinder is ignited at the second ignition timing that is more advanced than the first ignition timing, theoretically, the generated torque in the combustion cylinder becomes larger than the normal torque UN. As already explained, when the generated torque of the combustion cylinder becomes larger than the normal torque UN, the engine torque exceeds the target engine torque. At the same time, the engine speed NE also exceeds the target engine speed NET. Therefore, as shown in Fig. 6(a), the reference engine speed NEB, which is the engine speed NE when the first process is started with the reference ignition timing PB set as the target ignition timing PF, becomes higher than the target engine speed NET. In this way, the reference engine speed NEB becomes higher than the target engine speed NET in theory because the second ignition timing, which is more advanced than the first ignition timing, is set as the reference ignition timing PB in anticipation of errors in the fuel injection amount, etc.

[0070] Now, suppose that there is no error in the fuel injection amount and the reference rotation speed NEB becomes higher than the target engine rotation speed NET as expected. In this case, the internal combustion engine control unit 104 calculates the change amount ΔP of the ignition timing required to eliminate the difference between the reference rotation speed NEB and the target engine rotation speed NET at time T2 after time T1 as a correction value PH (step S160). In this case, the correction value PH is a negative value because it is necessary to reduce the engine rotation speed NE. Then, the internal combustion engine control unit 104 adds this correction value PH to the reference ignition timing PB to calculate the second target ignition timing PFN. As shown in FIG. 6B, this target ignition timing PFN is a value on the retard side of the reference ignition timing PB. When the spark plug 16 of the combustion cylinder is controlled at this target ignition timing PFN, the engine rotation speed NE decreases as shown in FIG. 6A. Then, the engine rotation speed NE approximately coincides with the target engine rotation speed NET. After that, the internal combustion engine control unit 104 repeatedly calculates the target ignition timing PF while performing feedback correction so that the engine speed NE and the target engine speed NET coincide with each other. Note that, due to the setting of the second target ignition timing PFN, the engine speed NE substantially coincides with the target engine speed NET. Therefore, the correction value PH when calculating the target ignition timing PF for the third time is substantially zero. The third target ignition timing PF is substantially the same as the second target ignition timing PFN. After that, the internal combustion engine control unit 104 maintains the target ignition timing PF at substantially the same value as the second target ignition timing PFN, as shown in FIG. 6(b). In other words, once the internal combustion engine control unit 104 calculates the target ignition timing PFN as a value on the retard side of the reference ignition timing PB, the internal combustion engine control unit 104 maintains the target ignition timing PF at an ignition timing on the retard side of the reference ignition timing PB. When the internal combustion engine control unit 104 ends the first process and the third process at time T3 after time T2, it returns the target ignition timing PF to the MBT ignition timing. Note that the magnitude of the absolute value of the correction value PH shown in Fig. 6 is an example for explaining the change of the target ignition timing PF, and does not necessarily match the actual magnitude. The same is true for the magnitude of the reference rotation speed NEB and the rate of change per unit time of the engine rotation speed NE.

[0071] In the above, the case where the reference rotation speed NEB is higher than the target engine rotation speed NET has been described as an example. However, due to an error in the fuel injection amount or the like, the torque generated by the combustion cylinder may be smaller than the theoretical torque. Accordingly, the reference rotation speed NEB may be lower than the target engine rotation speed NET. In addition, for example, the torque applied from the first MG 71 to the crankshaft 14 may become smaller than the normal torque UN due to some factor, and the reference rotation speed NEB may be lower than the target engine rotation speed NET. In these cases, the internal combustion engine control unit 104 calculates the correction value PH as a positive value to increase the engine rotation speed NE. Then, the internal combustion engine control unit 104 calculates the target ignition timing PFN as a value on the advance side of the reference ignition timing PB. In these cases as well, the engine rotation speed NE can be made to coincide with the target engine rotation speed NET. Once the internal combustion engine control unit 104 calculates the target ignition timing PFN as a value more advanced than the reference ignition timing PB, it thereafter maintains the target ignition timing PF at the ignition timing more advanced than the reference ignition timing PB.

[0072] <Effects of the embodiment> The more the ignition timing of the spark plug 16 is retarded, the lower the engine speed NE becomes. On the other hand, the more the ignition timing of the spark plug 16 is advanced, the higher the engine speed NE becomes. Therefore, in this embodiment, when the reference rotation speed NEB is lower than the target engine speed NET, the reference ignition timing PB is advanced and corrected to calculate the target ignition timing PF so that the difference between the reference rotation speed NEB and the target engine speed NET is eliminated. Also, when the reference rotation speed NEB is higher than the target engine speed NET, the reference ignition timing PB is retarded and corrected to calculate the target ignition timing PF so that the difference between the reference rotation speed NEB and the target engine speed NET is eliminated. By controlling the spark plug 16 of the combustion cylinder based on such a target ignition timing PF, it is possible to suppress the engine speed NE from deviating from the target engine speed NET. Moreover, in this embodiment, the target ignition timing PF is calculated by applying correction using the correction value PH continuously during the execution of the first process so that the difference between the engine speed NE and the target engine speed NET is eliminated. Therefore, the engine speed NE can be maintained in a state where it does not deviate from the target engine speed NET until the first process is completed.

[0073] <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.

[0074] It is not necessary to continue the correction using the correction value PH until the first process ends. It is sufficient to perform the correction using the correction value PH after the start of the first process so that the reference rotation speed NEB and the target engine rotation speed NET coincide. If the spark plug 16 of the combustion cylinder is controlled with the target ignition timing PF obtained by that correction, the engine rotation speed NE should basically coincide with the target engine rotation speed NET. And, if the target ignition timing PF is maintained thereafter, the engine rotation speed NE should generally coincide with the target engine rotation speed NET even without performing the correction using the correction value PH.

[0075] The method of calculating the target ignition timing is not limited to the example of the above embodiment. For example, the correction value PH may be smaller than the absolute value of the change amount ΔP of the ignition timing required to eliminate the difference between the engine speed NE and the target engine speed NET. Even in this case, it is possible to suppress the deviation of the engine speed NE from the target engine speed NET to a certain extent.

[0076] When changing the magnitude of the correction value PH as in the above modified example, the content of the correction map itself may be changed. Also, the correction map may not be changed from that in the above embodiment, and the change amount ΔP of the ignition timing calculated from the correction map may be treated as a provisional correction value. Then, the provisional correction value may be further corrected to calculate the final correction value PH.

[0077] As described in the above modified example, the content of the correction map is not limited to the example of the above embodiment. The correction map is not limited to the graph shown in the above embodiment, but may be, for example, a table showing the correction value PH for each engine operating state, or a relational expression for calculating the correction value PH. In other words, the correction map may be any one that can calculate the correction value PH.

[0078] The correction value PH may be preset as a uniform value. In this case, a positive correction value PH for advance correction and a negative correction value PH for retard correction may be prepared. ·The target ignition timing PF of a plurality of combustion cylinders may not all be the same, but may be changed depending on the combustion cylinder. In this case, the target ignition timing PF may be different for each combustion cylinder, or the target ignition timing PF of only some combustion cylinders may be different from that of the other combustion cylinders. In order to realize such an embodiment, the correction value PH is essentially changed depending on the combustion cylinder. For example, the correction value PH of the combustion cylinders that are before or after the stopped cylinder in terms of the order of the combustion stroke may be set to a different magnitude from the correction value PH of the other combustion cylinders. In the example of the above embodiment, the correction value PH of the first cylinder #1 and the fourth cylinder #4 is set to a different magnitude from the correction value PH of the second cylinder #2. A specific example of the case where such an embodiment is adopted will be described below.

[0079] First, the amount of change ΔP of the ignition timing required to eliminate the difference between the engine speed NE and the target engine speed NET is calculated as a provisional correction value from the correction map of the above embodiment. In this example, the provisional correction value is assumed to be a negative value. Next, an adjustment operation is performed on this provisional correction value to calculate the final correction value PH for each combustion cylinder. At that time, the absolute value of the correction value PH for the first cylinder #1 and the fourth cylinder #4 is set to be larger than the absolute value of the correction value PH for the second cylinder #2. Specifically, the correction value PH for the first cylinder #1 and the fourth cylinder #4 is set to a value obtained by subtracting the first adjustment value from the provisional correction value. The first adjustment value is 0.5 times the specified value. The correction value PH for the second cylinder #2 is set to a value obtained by adding the second adjustment value to the provisional correction value. The second adjustment value is twice the specified value. The specified value is, for example, an arbitrary positive value that is significantly smaller than the absolute value of the provisional correction value. However, the specified value is set as a value such that, when the target ignition timing PF is the value obtained by adding the correction value PH calculated as described above to the reference ignition timing PB, the torque generated in the first cylinder #1 and the fourth cylinder #4 is greater than the normal torque UN, and is smaller than the torque generated when the ignition timing in the second cylinder #2 is set to the reference ignition timing PB.

[0080] When the correction value PH is calculated as described above, the following advantageous effects can be obtained. Assume that the correction value PH is not used at all. The first process is performed with the target ignition timing PF in the combustion cylinder as the reference ignition timing PB. At the timing when the third cylinder #3, which is a stopped cylinder, enters the combustion stroke, the normal torque UN is applied from the first MG 71 to the crankshaft 14, as in the above embodiment. As described in FIG. 3, the generated torque when the ignition timing in the combustion cylinder is set to the reference ignition timing PB is larger than the normal torque UN. Therefore, when the first process is performed with the target ignition timing PF of the combustion cylinder as the reference ignition timing PB, the generated torque at the timing when the first cylinder #1, the fourth cylinder #4, and the second cylinder #2 enter the combustion stroke is larger than the torque provided by the first MG 71 at the timing when the third cylinder #3 enters the combustion stroke, as shown by the solid line in FIG. 7. In FIG. 7, in order to provide a rough guide as to the timing at which the four cylinders 11 undergo the combustion stroke, the numbers of each cylinder 11 are assigned to indicate the rough timing at which each cylinder 11 undergoes the combustion stroke.

[0081] Now, the correction value PH calculated in the above manner is added to the reference ignition timing PB, and the first process is performed with the target ignition timing PF as the value. Since the correction value PH is negative, the target ignition timing PF in the first cylinder #1, the fourth cylinder #4, and the second cylinder #2 is retarded from the reference ignition timing PB. Accordingly, as shown by the dotted line in FIG. 7, the generated torque of each combustion cylinder becomes smaller than the case where the correction by the correction value PH is not performed. Furthermore, for the first cylinder #1 and the fourth cylinder #4, since the first adjustment value is subtracted from the provisional correction value, the generated torque of the first cylinder #1 and the fourth cylinder #4 becomes smaller by the first adjustment value. Then, the generated torque of the first cylinder #1 and the fourth cylinder #4 becomes closer to the normal torque UN than the case where the first adjustment value is not subtracted as shown by the two-dot chain line in FIG. 7. This reduces the difference between the torque generated by the first MG 71 when the third cylinder #3 goes through the combustion stroke and the torque generated by the first cylinder #1 and the fourth cylinder #4 before and after that timing, thereby reducing the torque gap caused by the presence of a stopped cylinder.

[0082] Here, let us suppose that the correction value PH of not only the first cylinder #1 and the fourth cylinder #4 but also the second cylinder #2 is set to a value obtained by subtracting the first adjustment value from the provisional correction value. In this case, the total torque generated from the four cylinders 11 becomes excessively small. In this respect, in the above embodiment, the correction value PH of the second cylinder #2 is set to a value obtained by adding the second adjustment value to the provisional correction value. Therefore, the torque generated by the second cylinder #2 shown by the dotted line in FIG. 7 becomes larger by the amount of this second adjustment value. The torque generated by the second cylinder #2 becomes closer to the torque generated when no correction is performed shown by the solid line in FIG. 7 compared to the torque generated when the second adjustment value is not added shown by the two-dot chain line in FIG. 7. This allows the total torque generated from the four cylinders 11 to be sufficiently secured. Note that the time changes in the torque generated shown by the solid line, dotted line, and two-dot chain line in FIG. 7 are merely schematic for explaining this modified example, and do not necessarily coincide with the time changes in the actual torque generated.

[0083] When adopting an embodiment such as the above modification, the method of calculating the correction value PH can be changed as appropriate. For example, the correction value PH may be calculated by multiplying or dividing the provisional correction value by an arbitrary adjustment value.

[0084] In the above embodiment, the first process and the third process are performed for the purpose of burning and removing PM from the GPF 23. However, the applications of the first process and the third process are not limited to this. The first process and the third process may be performed for any required application.

[0085] Regarding the first process, the manner of fuel supply to the combustion cylinder is not limited to the example of the above embodiment. That is, it is not essential to supply fuel to the combustion cylinder so that the mixture in the combustion cylinder becomes a rich air-fuel ratio AFR. For example, fuel may be injected into the combustion cylinder so that the air-fuel ratio of the mixture in the combustion cylinder becomes the stoichiometric air-fuel ratio AFS. Fuel may be supplied to the combustion cylinder in an appropriate manner depending on the application of the first process.

[0086] 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.

[0087] 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 first process has the following contents. "M" and "N" are natural numbers. The first process may be a process that alternately repeats the following two control patterns while continuing the operation of the internal combustion engine 10. One control pattern is a stop pattern in which fuel supply to M consecutive cylinders 11 is stopped in the order of the cylinders 11 that undergo the combustion stroke. The other control pattern is a combustion pattern in which fuel supply to N consecutive cylinders 11 is performed in the order of the cylinders 11 that undergo the combustion stroke. Note that the sum of M and N does not need to match the total number of cylinders 11. If the sum 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.

[0088] The contents of the start condition and end condition in the first process are not limited to those in the above embodiment. Appropriate contents may be set as the start condition and end condition according to the purpose of the first process.

[0089] Even if the combustion cylinders and the stopped cylinders are changed from those in the above embodiment, in the third process, ignition is performed at the target ignition timing PF for the spark plugs 16 of the combustion cylinders, and ignition is not performed for the spark plugs 16 of the stopped cylinders, as in the above embodiment.

[0090] The reference ignition timing PB calculated in the third process is not limited to the second ignition timing. For example, if fuel is supplied to the combustion cylinder in the first process so that the mixture in the combustion cylinder has a theoretical air-fuel ratio AFS, the reference ignition timing PB may be the MBT ignition timing.

[0091] The magnitude of the target compensation torque is not limited to the example in the above embodiment. The target compensation torque may be any torque that can compensate for at least a part of the shortage of engine torque caused by the stop of combustion of the air-fuel mixture in the stopped cylinder.

[0092] The configuration of the vehicle 500 is not limited to the example of the above embodiment. For example, the vehicle may have only one motor generator. Even in this case, it is sufficient that the motor generator can rotate the crankshaft 14.

[0093] 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 from that of the above embodiment. There may be more than one cylinder 11. The internal combustion engine 10 may have more than one cylinder 11 and a spark plug 16 for each cylinder 11. [Explanation of symbols]

[0094] 10. Internal combustion engine 11…Cylinder 14…Crankshaft 16…Spark plug 71…1st MG 72…2nd MG 100...Control device 102...Hybrid control unit 104...Internal combustion engine control unit 106...Motor control unit 500…Vehicle

Claims

[Claim 1] The present invention is applied to a hybrid vehicle having an internal combustion engine having a plurality of cylinders and a spark plug for each cylinder, and a motor generator connected to a crankshaft of the internal combustion engine and capable of rotating the crankshaft, a first process for alternately repeating, while continuing the operation of the internal combustion engine, a stop pattern in which fuel supply to M consecutive cylinders is stopped in the order of the cylinders entering a combustion stroke, 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 natural numbers; a second process of applying torque from the motor generator to the crankshaft so as to compensate for a torque deficiency of the internal combustion engine caused by the stop pattern during execution of the first process; During execution of the first process, a third process can be executed to control the spark plug so that ignition is performed at a target ignition timing, When the target ignition timing at the time when the first process is started is defined as a reference ignition timing, and the rotation speed of the crankshaft at the time when the first process is started is defined as a reference rotation speed, In the third process, when the reference rotation speed is lower than the target rotation speed, a timing earlier than the reference ignition timing is set as the target ignition timing, and when the reference rotation speed is higher than the target rotation speed, a timing later than the reference ignition timing is set as the target ignition timing. A control device for a hybrid vehicle.

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