Vehicle control device

Abstract

To suppress vibration in a vehicle, and to increase regeneration opportunity of a filter in a low temperature environment.SOLUTION: A control object of a vehicle control device is a vehicle 500 which includes: an internal combustion engine 10 including a filter 25 for capturing particulate substances in an exhaust gas; an automatic transmission 80 connected to the internal combustion engine 10; and a torque converter 50 interposed between the internal combustion engine 10 and the automatic transmission 80. The torque converter 50 includes a lock-up clutch 60 which switches, according to supply / discharge of a hydraulic oil, between a connected state where the internal combustion engine 10 is connected to the automatic transmission 80 and a disconnected state where the internal combustion engine 10 is disconnected from the automatic transmission 80. In the case where the temperature of the hydraulic oil is below a determination temperature, first processing for bringing the lock-up clutch 60 into the disconnected state, and second processing for performing fuel cut in the internal combustion engine 10 on a condition that the lock-up clutch 60 is in the disconnected state and the accumulation amount of the particulate substances captured by the filter 25 is equal to or greater than the determination accumulation amount, during deceleration of the vehicle 500, are executed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a vehicle and a control device therefor. The vehicle has an internal combustion engine, a torque converter with a lock-up clutch, a hydraulic mechanism, and an automatic transmission. The lock-up clutch switches between a connected state, in which the output shaft of the internal combustion engine and the input shaft of the automatic transmission are connected, and a disconnected state, in which they are disconnected, depending on the hydraulic pressure from the hydraulic mechanism.

[0003] Here, when the oil temperature is low, engaging the lockup clutch while the vehicle is decelerating can cause vibrations in the vehicle. Therefore, the control device of Patent Document 1 engages the lockup clutch when the oil temperature is high while the vehicle is decelerating, but disengages the lockup clutch when the oil temperature is low. The control device then cuts fuel to improve fuel economy only when the lockup clutch is engaged during deceleration. When the lockup clutch is engaged, torque from the drive wheels can be transmitted to the internal combustion engine, preventing the internal combustion engine from stalling.

[0004] The internal combustion engine of Patent Document 1 has a filter in the exhaust passage. The filter captures particulate matter contained in the exhaust. When the amount of particulate matter accumulated is large, the control device regenerates the filter by cutting fuel while the vehicle is decelerating. When regenerating the filter, the control device lowers the oil temperature threshold at which the lockup clutch is switched from an engaged state to a disengaged state when the amount of particulate matter accumulated is large compared to normal. Then, when the amount of particulate matter accumulated is large, the control device engages the lockup clutch when the oil temperature is low and cuts fuel. This attempts to regenerate the filter. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-148097 Summary of the Invention [Problem to be solved by the invention]

[0006] As in Patent Document 1, if the lockup clutch is engaged when the oil temperature is low in order to increase the chances of filter regeneration, there is a risk of vehicle vibration. However, if the lockup clutch is disengaged when the oil temperature is low in consideration of vehicle vibration, fuel cut-off, which requires the lockup clutch to be engaged, cannot be performed, reducing the chances of filter regeneration. [Means for solving the problem]

[0007] A vehicle control device for solving the above problem includes a vehicle to be controlled, the vehicle having an internal combustion engine equipped with a filter that captures particulate matter contained in exhaust, an automatic transmission connected to the internal combustion engine, a torque converter interposed between the internal combustion engine and the automatic transmission, a hydraulic mechanism that supplies and discharges hydraulic oil to and from the torque converter, and a temperature sensor that detects the temperature of the hydraulic oil, wherein the torque converter is equipped with a lock-up clutch that switches between a connected state in which an output shaft of the internal combustion engine is connected to an input shaft of the automatic transmission and a disconnected state in which the output shaft is disconnected from the input shaft in response to the supply and discharge of the hydraulic oil, and a first process that switches the lock-up clutch to the disconnected state when the temperature of the hydraulic oil is lower than a predetermined judgment temperature. Continue During deceleration of the vehicle, the lock-up clutch is in the disengaged state, and the amount of particulate matter trapped in the filter is equal to or greater than a predetermined judgment amount. case a second process for cutting fuel in the internal combustion engine; Start .

[0008] When the temperature of the hydraulic oil is below the threshold temperature, the viscosity of the hydraulic oil in the torque converter increases. High viscosity hydraulic oil makes it difficult for the input and output shafts of the torque converter to rotate relative to each other. In other words, even when the lockup clutch is disengaged, a significant proportion of the torque from the drive wheels can be transmitted to the internal combustion engine if the hydraulic oil temperature is low. Focusing on this point, the above configuration cuts fuel while keeping the lockup clutch disengaged during vehicle deceleration when the hydraulic oil temperature is low. Cutting fuel while keeping the lockup clutch disengaged reduces vehicle vibration and increases the chances of filter regeneration in low-temperature environments. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of a vehicle. [Figure 2] FIG. 2 is a flowchart showing a series of processing steps of the specific processing routine. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a vehicle control device will be described with reference to the drawings. <Vehicle Overview> As shown in FIG. 1 , a vehicle 500 includes an internal combustion engine 10, a torque converter 50, an automatic transmission 80, drive wheels 83, and a hydraulic mechanism 70. The internal combustion engine 10 is a drive source for the vehicle 500. A crankshaft 11, which is an output shaft of the internal combustion engine 10, is connected to an input shaft 51 of the torque converter 50. The torque converter 50 is a fluid coupling having a torque amplifying function. An output shaft 52 of the torque converter 50 is connected to an input shaft 81 (hereinafter referred to as a transmission input shaft) of the automatic transmission 80. In other words, the automatic transmission 80 is connected to the internal combustion engine 10 via the torque converter 50. The torque converter 50 is interposed between the internal combustion engine 10 and the automatic transmission 80. The automatic transmission 80 is a stepped transmission that changes the speed ratio in multiple stages by shifting gears. The output shaft of the automatic transmission 80 is connected to drive wheels 83 via a differential or the like. The hydraulic mechanism 70 supplies and discharges hydraulic oil to the torque converter 50 and the automatic transmission 80. The hydraulic mechanism 70 includes a plurality of oil passages, a valve for switching between the oil passages through which the hydraulic oil flows, a pump for supplying the hydraulic oil to the oil passages, and the like.

[0011] <About internal combustion engines> The internal combustion engine 10 has the crankshaft 11 and a plurality of cylinders 12. There are four cylinders 12. Each cylinder 12 is a space for burning a mixture of fuel and intake air. Although not shown, each cylinder 12 houses a piston. The piston reciprocates within the cylinder 12. The crankshaft 11 rotates in response to the reciprocating movement of the piston.

[0012] The internal combustion engine 10 has a plurality of spark plugs 19. One spark plug 19 is provided for each cylinder 12. The spark plug 19 ignites the air-fuel mixture in the cylinder 12. The internal combustion engine 10 has an intake passage 20, a throttle valve 21, and multiple fuel injection valves 22. The intake passage 20 is a passage for introducing intake air into each cylinder 12. The intake passage 20 is connected to each cylinder 12. The throttle valve 21 is located midway through the intake passage 20. The throttle valve 21 adjusts the amount of intake air (hereinafter referred to as intake air amount) GA. The multiple fuel injection valves 22 are located downstream of the throttle valve 21 in the intake passage 20. One fuel injection valve 22 is provided for each cylinder 12. The fuel injection valve 22 injects fuel to supply fuel into the cylinder 12.

[0013] The internal combustion engine 10 has an exhaust passage 23, a three-way catalyst 24, and a gasoline particulate filter (hereinafter simply referred to as the filter) 25. The exhaust passage 23 is a passage for discharging exhaust gas from each cylinder 12. The exhaust passage 23 is connected to each cylinder 12. The three-way catalyst 24 is located midway through the exhaust passage 23. The three-way catalyst 24 purifies the exhaust gas. The filter 25 is located downstream of the three-way catalyst 24 in the exhaust passage 23. The filter 25 collects particulate matter (hereinafter simply referred to as PM) contained in the exhaust gas.

[0014] The internal combustion engine 10 has an air flow meter 13, an intake air temperature sensor 14, a crank position sensor 15, an air-fuel ratio sensor 16, and an exhaust temperature sensor 17. The air flow meter 13 detects the intake air amount GA. The intake air temperature sensor 14 detects the intake air temperature TI. The crank position sensor 15 detects the rotational position CR of the crankshaft 11. The air-fuel ratio sensor 16 detects the air-fuel ratio AF of the exhaust gas upstream of the three-way catalyst 24 in the exhaust passage 23. The exhaust temperature sensor 17 detects the exhaust temperature TO between the three-way catalyst 24 and the filter 25 in the exhaust passage 23. Each sensor repeatedly outputs a signal corresponding to the information detected by that sensor.

[0015] <About the torque converter> In addition to the input shaft 51 and the output shaft 52, the torque converter 50 also has a front cover 56, a pump impeller 53, and a turbine liner 54. The pump impeller 53 is shaped like an impeller. The pump impeller 53 is connected to the input shaft 51 of the torque converter 50 via the front cover 56. The pump impeller 53 rotates integrally with the input shaft 51 together with the front cover 56. The turbine liner 54 is shaped like an impeller. The turbine liner 54 faces the pump impeller 53. The turbine liner 54 is connected to the output shaft 52 of the torque converter 50. The turbine liner 54 rotates integrally with the output shaft 52. The pump impeller 53 and the turbine liner 54 are constantly filled with hydraulic oil supplied from the hydraulic mechanism 70. In the torque converter 50, torque is transmitted between the pump impeller 53 and the turbine liner 54 via the hydraulic oil. Although not shown, the torque converter 50 has a known stator that regulates the flow of hydraulic oil between the pump impeller 53 and the turbine liner 54. The stator is equipped with a one-way clutch.

[0016] The torque converter 50 has a lock-up clutch mechanism (hereinafter simply referred to as a lock-up clutch) 60. The lock-up clutch 60 is a wet-type multi-plate clutch. That is, the lock-up clutch 60 has a plurality of first friction plates 61 and a plurality of second friction plates 62. The first friction plates 61 are annular. The second friction plates 62 are also annular. The first friction plates 61 and the second friction plates 62 are arranged alternately. Adjacent first friction plates 61 and second friction plates 62 face each other. The first friction plates 61 and the second friction plates 62 are movable in the arranging direction. The first friction plates 61 rotate integrally with the pump impeller 53. The second friction plates 62 rotate integrally with the turbine liner 54. Note that, hereinafter, a group of friction plates consisting of a plurality of first friction plates 61 and a plurality of second friction plates 62 will be referred to as a friction plate group.

[0017] The lockup clutch 60 has a lockup piston 67. The lockup piston 67 is disk-shaped. The lockup piston 67 is located on the opposite side of the friction plate group from the front cover 56. The lockup piston 67 moves toward or away from the friction plate group depending on the hydraulic pressure, which will be described later. When the lockup piston 67 approaches the front cover 56, the lockup piston 67 and the front cover 56 sandwich the friction plate group between them. In this case, the adjacent first friction plates 61 and second friction plates 62 come into contact with each other. In other words, the lockup clutch 60 is in a connected state, connecting the input shaft 51 and the output shaft 52 of the torque converter 50. In this connected state, the lockup clutch 60 connects the crankshaft 11 and the transmission input shaft 81. On the other hand, when the lockup piston 67 moves away from the front cover 56, the state in which the friction plate group is sandwiched between the lockup piston 67 and the front cover 56 is released. In this case, the adjacent first friction plates 61 and second friction plates 62 are disposed at positions separated from each other, and a gap exists between them. That is, the lock-up clutch 60 is in a disconnected state in which the input shaft 51 and the output shaft 52 of the torque converter 50 are disconnected. In this disconnected state, the lock-up clutch 60 disconnects the crankshaft 11 from the transmission input shaft 81.

[0018] The torque converter 50 has a first oil chamber 58 and a second oil chamber 59. The first oil chamber 58 and the second oil chamber 59 are separated into two spaces by a lock-up piston 67. The first oil chamber 58 is separated by the front cover 56 and the lock-up piston 67. The friction plates are located in the first oil chamber 58. A first oil passage 71 of a hydraulic mechanism 70 is connected to the first oil chamber 58. Hydraulic oil is supplied to and discharged from the first oil chamber 58 through the first oil passage 71. A second oil passage 72 of the hydraulic mechanism 70 is connected to the second oil chamber 59. Hydraulic oil is supplied to and discharged from the second oil chamber 59 through the second oil passage 72. The lock-up piston 67 operates in response to the pressure difference between the first oil chamber 58 and the second oil chamber 59. When the hydraulic pressure in the second oil chamber 59 becomes higher than the hydraulic pressure in the first oil chamber 58, the lock-up piston 67 moves closer to the front cover 56. In this case, the lock-up clutch 60 is in an engaged state. On the other hand, when the hydraulic pressure in the first oil chamber 58 becomes higher than the hydraulic pressure in the second oil chamber 59, the lock-up piston 67 moves away from the front cover 56. In this case, the lock-up clutch 60 is in a disengaged state. In this way, the lock-up clutch 60 switches between an engaged state and a disengaged state depending on the hydraulic pressure from the hydraulic mechanism 70.

[0019] <Other vehicle configurations> The vehicle 500 has a braking device. The braking device has a brake mechanism 99, a brake pedal 98, and a brake sensor 97. The brake mechanism 99 generates hydraulic pressure according to a brake operation amount N, which is the amount of depression of the brake pedal 98. When this hydraulic pressure becomes high, the brake pads of the brake mechanism 99 are pressed against the drive wheels 83. This causes the drive wheels 83 to be braked. The brake sensor 97 detects the brake operation amount N.

[0020] The vehicle 500 has an accelerator pedal 90, an accelerator sensor 96, a vehicle speed sensor 92, an input shaft rotation sensor 93, a specific temperature sensor 94, and an ignition switch 95. The accelerator sensor 96 detects the depression amount of the accelerator pedal 90 as an accelerator operation amount ACC. The vehicle speed sensor 92 detects the traveling speed of the vehicle 500 as a vehicle speed SP. The input shaft rotation sensor 93 detects the rotation position M of the transmission input shaft 81. The specific temperature sensor 94 detects the temperature L of the hydraulic oil supplied to the torque converter 50. Each sensor repeatedly outputs a signal corresponding to the information detected by it. The ignition switch 95 is a switch for starting the vehicle 500. The ignition switch 95 outputs a signal SS corresponding to the driver's operation.

[0021] <Outline of the control device> The vehicle 500 includes a control device 100. The control device 100 may be configured as one or more processors that execute various processes according to computer programs (software). The control device 100 may also be configured as one or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), that execute at least some of the various processes, or as a circuit including a combination thereof. The processor includes a CPU 102 and memories such as RAM and ROM 104. The memory stores program code or instructions configured to cause the CPU 102 to execute processes. The memory, i.e., computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. The control device 100 also includes an electrically rewritable non-volatile memory 106. The control device 100 performs various processes, described below, by the CPU 102 executing programs stored in the ROM 104.

[0022] The control device 100 receives a signal SS from the ignition switch 95. When the control device 100 receives the signal SS in response to the ignition switch 95 being turned on, the control device 100 starts the internal combustion engine 10. Hereinafter, the period from when the ignition switch 95 is turned on until the next time it is turned off will be referred to as "one trip."

[0023] During one trip, the control device 100 repeatedly receives detection signals from various sensors attached to the vehicle 500. Specifically, the control device 100 receives detection signals for the following parameters:

[0024] The intake air volume GA detected by the air flow meter 13 Intake air temperature TI detected by intake air temperature sensor 14 The crank position sensor 15 detects the rotational position CR of the crankshaft 11 Air-fuel ratio AF detected by air-fuel ratio sensor 16 The exhaust temperature TO detected by the exhaust temperature sensor 17 Vehicle speed SP detected by vehicle speed sensor 92 The rotational position M of the transmission input shaft 81 detected by the input shaft rotation sensor 93 The temperature of the hydraulic oil detected by the specific temperature sensor 94 Acceleration amount ACC detected by accelerator sensor 96 Brake operation amount N detected by the brake sensor 97 The control device 100 calculates the following parameters as needed based on detection signals received from various sensors. The control device 100 calculates the engine rotation speed NE, which is the rotation speed of the crankshaft 11, based on the rotation position CR of the crankshaft 11. The control device 100 also calculates the transmission rotation speed ME, which is the rotation speed of the transmission input shaft 81, based on the rotation position M of the transmission input shaft 81. The unit time defining the engine rotation speed NE and the transmission rotation speed ME is the same.

[0025] The control device 100 controls various parts of the vehicle 500. For example, the control device 100 controls the automatic transmission 80. The control device 100 switches the gear position of the automatic transmission 80 depending on the running conditions of the vehicle 500.

[0026] The control device 100 controls the lockup clutch 60. The control device 100 continuously performs a first process for controlling the lockup clutch 60 during one trip. In the first process, the control device 100 continuously monitors the hydraulic oil temperature L. In the first process, the control device 100 switches the engagement and disengagement of the lockup clutch 60 depending on the latest hydraulic oil temperature L. When the hydraulic oil temperature L is equal to or higher than the threshold temperature LK, the control device 100 engages the lockup clutch 60. That is, the control device 100 controls the hydraulic mechanism 70 so that the hydraulic pressure in the second oil chamber 59 is higher than the hydraulic pressure in the first oil chamber 58. On the other hand, when the hydraulic oil temperature L is lower than the threshold temperature LK, the control device 100 disengages the lockup clutch 60. That is, the control device 100 controls the hydraulic mechanism 70 so that the hydraulic pressure in the first oil chamber 58 is higher than the hydraulic pressure in the second oil chamber 59. The control device 100 stores the above-mentioned threshold temperature LK in advance. In this embodiment, the determination temperature LK is predetermined to be a value slightly higher than zero degrees C. The considerations that are taken into account when determining the determination temperature LK will be explained in the section on operation below.

[0027] As part of the first process, the control device 100 switches the lockup flag on and off depending on the engaged or disengaged state of the lockup clutch 60. The lockup flag is a flag that indicates that the lockup clutch 60 is engaged. That is, the control device 100 turns the lockup flag on when the lockup clutch 60 is engaged. On the other hand, the control device 100 turns the lockup flag off when the lockup clutch 60 is disengaged.

[0028] The control device 100 controls the internal combustion engine 10. During one trip, the control device 100 calculates a target torque for the internal combustion engine 10 based on the accelerator operation amount ACC, the vehicle speed SP, and the like. The control device 100 then adjusts the opening of the throttle valve 21, injects fuel from the fuel injection valve 22, and ignites the spark plug 19 so as to obtain the target torque. As a result, the control device 100 combusts the air-fuel mixture in the cylinders 12. Depending on the situation, the control device 100 may also perform a fuel cut, which stops fuel injection into each cylinder 12. When performing a fuel cut, the control device 100 also stops ignition by the spark plug 19. Depending on the situation, the control device 100 may also cause the internal combustion engine 10 to idle. Idling refers to combusting the air-fuel mixture in each cylinder 12 while maintaining an idle speed NE, which is the minimum engine speed at which the internal combustion engine 10 can operate autonomously.

[0029] <About the accumulation amount calculation process> As the internal combustion engine 10 continues to operate, the amount of PM accumulated in the filter 25 (hereinafter simply referred to as the PM accumulated amount) W gradually increases. The control device 100 continues to perform an accumulation amount calculation process for calculating the PM accumulated amount W during one trip. In the accumulation amount calculation process, the control device 100 repeatedly calculates the PM accumulated amount W. To calculate the PM accumulated amount W, the control device 100 first calculates the PM generation amount and the PM regeneration amount. Next, the control device 100 calculates an updated value by subtracting the PM regeneration amount from the PM generation amount. The control device 100 then adds this updated value to the previous value of the PM accumulated amount W stored in the nonvolatile memory 106. The control device 100 calculates the obtained value as the latest PM accumulated amount W. After calculating the latest PM accumulated amount W, the control device 100 overwrites the previous value stored in the nonvolatile memory 106 with the latest PM accumulated amount W.

[0030] The PM production amount is the amount of PM produced as a result of combustion of the air-fuel mixture in the cylinder 12. The control device 100 calculates the PM production amount based on the intake air amount GA, the fuel injection amount, and the like. The PM regeneration amount is the amount of PM burned by the filter 25. When exhaust gas containing oxygen flows into the filter 25 while the filter temperature TF of the filter 25 is equal to or higher than the ignition point of the PM, the PM accumulated on the filter 25 is burned. Because oxygen is required for PM combustion, the amount of PM burned by the filter 25 is determined by the amount of oxygen in the exhaust gas flowing into the filter 25. Taking this into consideration, the control device 100 calculates the PM regeneration amount based on the oxygen concentration of the exhaust gas flowing into the filter 25 and the filter temperature TF. The control device 100 calculates the oxygen concentration of the exhaust gas based on the air-fuel ratio AF detected by the air-fuel ratio sensor 16. The control device 100 also calculates the filter temperature TF using a heat balance model of the filter 25 based on the temperature and flow rate of the exhaust gas flowing into the filter 25, the outside air temperature, and the like. The temperature of the exhaust gas flowing into the filter 25 can be determined by the exhaust temperature TO detected by the exhaust temperature sensor 17. The flow rate of the exhaust gas flowing into the filter 25 can be calculated from the intake air amount GA and the fuel injection amount. The temperature of the outside air can be the temperature TI of the intake air detected by the intake air temperature sensor 14.

[0031] <Regarding normal processing> The control device 100 can execute normal processing as processing for controlling the internal combustion engine 10 during deceleration of the vehicle 500. In the normal processing, the control device 100 controls the internal combustion engine 10 as follows from the start of deceleration of the vehicle 500 to the end of deceleration. The control device 100 controls the internal combustion engine 10 as follows: and, the control device 100 cuts fuel in the internal combustion engine 10. After starting the fuel cut, the control device 100 ends the fuel cut when the engine rotation speed NE becomes less than the return rotation speed while the vehicle 500 continues to decelerate. In this case, the control device 100 switches the internal combustion engine 10 to idle operation. The control device 100 continues the idle operation until the vehicle 500 finishes deceleration. The return rotation speed is set to a value smaller than the permitted rotation speed. If the engine rotation speed NE is less than the permitted rotation speed at the time the vehicle 500 starts deceleration, the control device 100 causes the internal combustion engine 10 to idle without cutting fuel.

[0032] When performing normal processing, the control device 100 determines the start and end of deceleration of the vehicle 500 as follows. Now, assume that the vehicle speed SP is greater than zero. At this time, when the accelerator operation amount ACC switches from a state in which it is greater than zero to zero, the control device 100 determines that the vehicle 500 has started deceleration. Furthermore, after the vehicle 500 has started deceleration, if the accelerator operation amount ACC becomes greater than zero before the vehicle speed SP reaches zero, or if the vehicle speed SP becomes zero, the control device 100 determines that the vehicle 500 has ended deceleration. The control device 100 determines the start and end of deceleration of the vehicle 500 in the above manner.

[0033] There are two types of normal processing. One normal processing is a normal disengagement processing that is used exclusively when the lockup clutch 60 is in a disengaged state. The other normal processing is a normal engagement processing that is used exclusively when the lockup clutch 60 is in an engaged state. These two normal processings differ in the permitted rotation speed at which fuel cut is permitted. In the normal disengagement processing, the control device 100 uses a predetermined first permitted rotation speed X1 as the permitted rotation speed. On the other hand, in the normal engagement processing, the control device 100 uses a predetermined second permitted rotation speed X2 as the permitted rotation speed. The second permitted rotation speed X2 is set to a value smaller than the first permitted rotation speed X1. As with the permitted rotation speed, the two normal processings differ in the return rotation speed at which fuel cut is discontinued. In the normal disengagement processing, the control device 100 uses a predetermined first return rotation speed Y1 as the return rotation speed. On the other hand, in the normal engagement processing, the control device 100 uses a predetermined second return rotation speed Y2 as the return rotation speed. The second return rotation speed Y2 is set to a value smaller than the first return rotation speed Y1. The control device 100 stores the first permissible rotation speed X1, the second permissible rotation speed X2, the first return rotation speed Y1, and the second return rotation speed Y2 in advance.

[0034] The permitted rotation speed and the return rotation speed are determined taking the following points into consideration. Specifically, when fuel is cut, the engine rotation speed NE decreases. If the engine rotation speed NE decreases excessively, when fuel injection and ignition of the air-fuel mixture are resumed, the engine rotation speed NE cannot be increased to a value at which the internal combustion engine 10 can operate autonomously, which may result in the internal combustion engine 10 stalling. The permitted rotation speed and the return rotation speed are determined to avoid such a stall. The first permitted rotation speed X1 and the second permitted rotation speed X2 are different, and the first return rotation speed Y1 and the second return rotation speed Y2 are different, for the following reasons: When the lock-up clutch 60 is engaged, the crankshaft 11 and the transmission input shaft 81 are mechanically directly coupled. In this case, the torque of the drive wheels 83 can be transmitted to the crankshaft 11 during deceleration of the vehicle 500. The torque of the drive wheels 83 can then rotate the crankshaft 11. In contrast, when the lockup clutch 60 is disengaged, the transmission input shaft 81 and the crankshaft 11 are fluidly connected. Therefore, in this case, torque transmission from the drive wheels 83 to the crankshaft 11 is basically limited. Therefore, if fuel is cut off while the lockup clutch 60 is disengaged, the engine speed NE drops significantly. For this reason, unless the return speed is set relatively high when the lockup clutch 60 is disengaged, the following problem may occur: When terminating the fuel cut, the engine speed NE may drop to a value that makes stalling of the internal combustion engine 10 unavoidable between the determination of the end of the fuel cut and the resumption of combustion of the air-fuel mixture. Therefore, the first return speed Y1 is set to a value greater than the second return speed Y2. Accordingly, the first permitted speed X1 is set to a value greater than the second permitted speed X2. That is, each permitted speed is set to a value greater than the corresponding permitted speed by a predetermined increase. This increase is a value that takes into consideration the decrease in engine speed NE during fuel cut.As described above, when the lock-up clutch 60 is disengaged, the engine rotation speed NE drops significantly during fuel cut. Taking this into consideration, the increase in the first permissible rotation speed X1 relative to the first return rotation speed Y1 is set to be larger than the increase in the second permissible rotation speed X2 relative to the second return rotation speed Y2.

[0035] <Regarding the second treatment> As described above, in normal processing, fuel is cut off under circumstances where stalling of the internal combustion engine 10 can be avoided. Cutting fuel while the vehicle 500 is decelerating can improve the fuel economy of the vehicle 500. Additionally, cutting fuel can supply oxygen to the filter 25 in the internal combustion engine 10. Supplying oxygen to the filter 25 can regenerate the filter 25, as described in relation to the deposition amount calculation process. As described above, the first permissible rotation speed X1 is set to a value greater than the second permissible rotation speed X2. In other words, in a low oil temperature environment where the lock-up clutch 60 is disengaged, there are fewer opportunities to cut fuel compared to a high oil temperature environment where the lock-up clutch 60 is engaged. Accordingly, if there are no opportunities to cut fuel other than during normal processing, there will be fewer opportunities to regenerate the filter 25 in a low oil temperature environment.

[0036] Therefore, the control device 100 can execute a second process as a process for regenerating the filter 25 in a low oil temperature environment with the lock-up clutch 60 in a disengaged state. Similar to the normal disengagement process described above, this second process is a process for cutting fuel while keeping the lock-up clutch 60 in a disengaged state during deceleration of the vehicle 500. However, as will be explained later, the start and end conditions of this second process are different from those of the normal disengagement process.

[0037] The second process is a process for cutting fuel in the internal combustion engine 10 when the following start requirements (A1) to (A5) are all met:

[0038] (A1) Vehicle 500 is decelerating. (A2) The lock-up clutch 60 is in a disengaged state. (A3) The PM accumulation amount W is equal to or greater than the judgment accumulation amount WS.

[0039] (A4) The filter temperature TF is equal to or higher than a specific temperature TFK. (A5) The engine speed NE is equal to or higher than the specific permissible speed XV. The control device 100 pre-stores each initiation requirement and various thresholds included in the initiation requirement. Specifically, the control device 100 pre-stores a threshold accumulation amount WS. The threshold accumulation amount WS is determined, for example, through experiments or simulations, as a value at which the PM accumulation amount W is appropriately large and PM removal from the filter 25 is desirable. The control device 100 pre-stores a specific temperature TFK. The specific temperature TFK is pre-determined as a temperature higher than the ignition point of PM. The control device 100 pre-stores a specific permitted rotation speed XV. The specific permitted rotation speed XV is pre-determined as a value lower than the first permitted rotation speed X1 and higher than the second permitted rotation speed X2. As can be seen from the definition of the specific permitted rotation speed XV, the control device 100 performs fuel cutoff in the second process even at an engine rotation speed NE that would not permit fuel cutoff in the normal disconnection process. The reason why stalling of the internal combustion engine 10 can be avoided with this setting will be explained in the section on operation below. Specifically, the specific permissible rotation speed XV is set to a value closer to the second permissible rotation speed X2 than the median value between the first permissible rotation speed X1 and the second permissible rotation speed X2.

[0040] During the execution of the fuel cut that was initiated in response to the satisfaction of each of the above-mentioned start requirements, i.e., during the execution of the second process, if at least one of the following termination requirements (B1)-(B7) is satisfied, the control device 100 will stop the second process.

[0041] (B1) The rotational speed difference ΔR is equal to or greater than the difference determination value RK. (B2) The depression speed of the brake pedal 98 is equal to or greater than the brake determination value NK. (B3) The engine rotation speed NE is lower than the specific return rotation speed YV.

[0042] (B4) The vehicle speed SP is less than the determination vehicle speed SPK. (B5) The PM accumulation amount W is less than the final accumulation amount WE. (B6) The filter temperature TF is lower than a specific temperature TFK.

[0043] (B7) The accelerator operation amount ACC is greater than zero. The control device 100 stores in advance each termination requirement and various thresholds included in the termination requirement. Specifically, the control device 100 stores in advance a difference determination value RK. Here, the rotational speed difference ΔR specified in the termination requirement (B1) is a value obtained by subtracting the engine rotational speed NE from the transmission rotational speed ME. For example, if fuel is cut off while the vehicle 500 is decelerating and the lock-up clutch 60 is engaged, the transmission rotational speed ME and the engine rotational speed NE will be approximately the same. On the other hand, if fuel is cut off while the vehicle 500 is decelerating and the lock-up clutch 60 is disengaged, the transmission rotational speed ME will be greater than the engine rotational speed NE. Therefore, in this case, the rotational speed difference ΔR will be a positive value. The difference determination value RK is a threshold value for this rotational speed difference ΔR. How the difference determination value RK is determined will be described later in the section on operation.

[0044] The control device 100 stores a brake determination value NK in advance. The brake determination value NK is determined in advance, for example, through experiments or simulations, as the depression speed of the brake pedal 98 at which it can be determined that the occupant has performed an emergency braking operation. The depression speed of the brake pedal 98 is the amount of change in the brake operation amount N per unit time. In this embodiment, this unit time is the interval at which a detection signal is received from the brake sensor 97.

[0045] The control device 100 stores the specific return rotation speed YV in advance. The specific return rotation speed YV is predetermined to be a value smaller than the first return rotation speed Y1 and larger than the second return rotation speed Y2. Specifically, the specific return rotation speed YV is set to a value closer to the second return rotation speed Y2 than the median value between the first return rotation speed Y1 and the second return rotation speed Y2.

[0046] The control device 100 stores a determination vehicle speed SPK in advance. Here, as the vehicle speed SP decreases, the torque that can be transmitted from the drive wheels 83 to the crankshaft 11 also decreases. The determination vehicle speed SPK is determined in advance, for example, through experiments or simulations, as the minimum value of the vehicle speed SP at which sufficient torque can be transmitted to the crankshaft 11 in order to avoid stalling of the internal combustion engine 10.

[0047] The control device 100 stores the end accumulation amount WE in advance. The end accumulation amount WE is determined in advance, for example, through experiments or simulations, as a value at which the PM accumulation amount W becomes sufficiently small and fuel cut can be terminated. The control device 100 stores the end accumulation amount WE in advance. The end accumulation amount WE is smaller than the judgment accumulation amount WS.

[0048] In relation to the above-mentioned start requirement (A3), the following can be said. That is, when the vehicle 500 starts deceleration, if the lock-up clutch 60 is in a disengaged state but the PM accumulation amount W is less than the determination accumulation amount WS, the control device 100 performs normal processing for disengagement. At this time, the control device 100 performs normal processing for disengagement when the engine rotation speed NE is equal to or greater than the first permissible rotation speed X1. and, fuel is cut off. As described above, this first permitted rotation speed X1 is greater than the specific permitted rotation speed XV that is used as a requirement for starting the second process. The magnitude relationship between these speeds can be summarized as follows: The specific permitted rotation speed XV that allows execution of the second process is set to a value smaller than the first permitted rotation speed X1 that allows fuel to be cut off when the lock-up clutch 60 is in a disengaged state and the PM accumulation amount W is less than the determination accumulation amount WS. From a similar perspective, the relationship between the first return rotation speed Y1 that is used in the normal process for disconnection and the specific return rotation speed YV that is used as a requirement for ending the second process can be summarized as follows: The specific return rotation speed YV that stops the second process once it has started is set to a value smaller than the first return rotation speed Y1 that stops fuel to be cut off when the lock-up clutch 60 is in a disengaged state and the PM accumulation amount W is less than the determination accumulation amount WS.

[0049] As described above, when the lockup clutch 60 is in the disengaged state, the control device 100 cuts fuel using the permitted rotation speed and return rotation speed, which vary depending on the amount of PM accumulation W. On the other hand, when the lockup clutch 60 is in the engaged state, the control device 100 always cuts fuel using the same permitted rotation speed and return rotation speed through the normal processing for engagement, regardless of the amount of PM accumulation W.

[0050] <Specific processing routine> The control device 100 starts the specific processing routine when the vehicle 500 starts decelerating. The specific processing routine is a processing routine that controls the implementation of the second processing, including the start and end of the second processing. The method for determining that the vehicle 500 has started decelerating is the same as that already explained in relation to the normal processing. The start of this specific processing routine means that the start requirement (A1) is met.

[0051] As shown in FIG. 2, when the control device 100 starts the specific processing routine, it first performs the processing of step S10. In step S10, the control device 100 determines whether the start requirement (A2) is met. If the lockup flag is on, the control device 100 determines that the start requirement (A2) is not met (step S10: NO). In this case, the control device 100 proceeds to the processing of step S110. Then, in step S110, the control device 100 shifts the control processing currently being performed on the internal combustion engine 10 to normal processing for connection. After this, the control device 100 ends the series of processing of the specific processing routine.

[0052] On the other hand, if the lockup flag is off in step S10, the control device 100 determines that the start requirement (A2) is met (step S10: YES). In this case, the control device 100 advances the process to step S20.

[0053] In step S20, the control device 100 determines whether the start requirement (A3) is met. If the latest PM accumulation amount W calculated in the accumulation amount calculation process is less than the determined accumulation amount WS, the control device 100 determines that the start requirement (A3) is not met (step S20: NO). In this case, the control device 100 proceeds to step S120. Then, in step S120, the control device 100 shifts the control process currently being performed on the internal combustion engine 10 to normal processing for disconnection. After this, the control device 100 ends the series of processes in the specific processing routine.

[0054] On the other hand, in step S20, if the latest PM accumulation amount W is equal to or greater than the determination accumulation amount WS (step S20: YES), the control device 100 determines that the start requirement (A3) is met. In this case, the control device 100 proceeds to step S30.

[0055] In step S30, the control device 100 determines whether the start requirement (A4) is met. If the latest filter temperature TF calculated in the calculation process of the PM accumulation amount W is lower than the specific temperature TFK, the control device 100 determines that the start requirement (A4) is not met (step S30: NO). In this case, the control device 100 proceeds to step S120.

[0056] On the other hand, in step S30, if the latest filter temperature TF is equal to or higher than the specific temperature TFK, the control device 100 determines that the start requirement (A4) is met (step S30: YES). In this case, the control device 100 proceeds to step S40.

[0057] In step S40, the control device 100 determines whether the start requirement (A5) is met. If the latest engine speed NE is less than the specific permission speed XV, the control device 100 determines that the start requirement (A5) is not met (step S40: NO). In this case, the control device 100 proceeds to step S120.

[0058] On the other hand, in step S40, if the latest engine speed NE is equal to or greater than the specific permission speed XV, the control device 100 determines that the start requirement (A5) is met (step S40: YES). In this case, the control device 100 proceeds to step S50.

[0059] In step S50, the control device 100 starts the fuel cut. That is, the control device 100 starts the second process. After that, the control device 100 advances the process to step S60.

[0060] In step S60, the control device 100 determines whether at least one of the multiple termination requirements for the second process is satisfied. In determining whether the termination requirement (B1) is satisfied, the control device 100 first calculates a rotational speed difference ΔR by subtracting the latest engine rotational speed NE from the latest transmission rotational speed ME. The control device 100 then compares this rotational speed difference ΔR with the difference determination value RK. In doing so, the control device 100 determines whether the termination requirement (B1) is satisfied. In determining whether the termination requirement (B2) is satisfied, the control device 100 first calculates a value by subtracting the brake operation amount N received at the immediately previous timing from the latest brake operation amount N as the latest operation speed of the brake pedal 98. The control device 100 then compares this operation speed with the brake determination value NK. In doing so, the control device 100 determines whether the termination requirement (B2) is satisfied. The control device 100 determines whether the termination requirement (B3) is met by comparing the latest engine speed NE with the specific return speed YV. The control device 100 determines whether the termination requirement (B4) is met by comparing the latest vehicle speed SP with the determination vehicle speed SPK. The control device 100 determines whether the termination requirement (B5) is met by comparing the latest PM accumulation amount W with the end accumulation amount WE. The control device 100 determines whether the termination requirement (B6) is met by comparing the latest filter temperature TF with the specific temperature TFK. The control device 100 determines whether the termination requirement (B7) is met by referring to the latest accelerator operation amount ACC. If, after determining whether all the termination requirements are met, none of the termination requirements are met (step S60: NO), the control device 100 executes the process of step S60 again. The control device 100 repeats the process of step S60 until at least one of the multiple termination requirements is met. Then, when at least one of the plurality of termination requirements is met (step S60: YES), the control device 100 advances the process to step S70.

[0061] In step S70, the control device 100 ends the fuel cut. That is, the control device 100 ends the second processing. After this, the control device 100 ends the series of processing of the specific processing routine. Note that, when the control device 100 ends the specific processing routine because a termination requirement other than the termination requirement (B7) is satisfied, the control device 100 temporarily transitions the internal combustion engine 10 to idle operation. A situation in which a termination requirement other than the termination requirement (B7) is satisfied is when the vehicle 500 continues to decelerate or when the vehicle 500 is stopped. After transitioning the internal combustion engine 10 to idle operation, the control device 100 controls the internal combustion engine 10 normally in accordance with the required torque determined from the accelerator operation amount ACC. When the control device 100 ends the specific processing routine because the termination requirement (B7) is satisfied, it resumes control of the internal combustion engine 10 in accordance with the required torque from that point on.

[0062] <Operation of the embodiment> In the second process, the lock-up clutch 60 is kept disengaged and fuel is cut off at an allowable rotation speed and a return rotation speed that are lower than those in the normal disengagement process. The reason why stalling of the internal combustion engine 10 can be avoided even with such settings will now be explained.

[0063] When the temperature L of the hydraulic oil is low, the viscosity of the hydraulic oil in the torque converter 50 increases. When the viscosity of the hydraulic oil is high, it becomes difficult for the input shaft 51 and the output shaft 52 of the torque converter 50 to rotate relative to each other during deceleration of the vehicle 500, even when the lock-up clutch 60 is disengaged. In other words, it becomes difficult for the crankshaft 11 and the transmission input shaft 81 to rotate relative to each other. This is thought to be mainly due to the following two reasons.

[0064] The first reason is related to torque transmission between the first friction plate 61 and the second friction plate 62 in the lock-up clutch 60. The lock-up clutch 60 is a wet type. When the lock-up clutch 60 is disengaged, hydraulic oil is present in the gap between the adjacent first friction plate 61 and second friction plate 62. If fuel is cut off during deceleration of the vehicle 500 under conditions in which the hydraulic oil is highly viscous, the following occurs. Assume that the torque of the drive wheels 83 causes the second friction plate 62 to rotate together with the transmission input shaft 81. If the hydraulic oil is highly viscous, the first friction plate 61 is pulled along by the rotation of the second friction plate 62 via the hydraulic oil. When the first friction plate 61 rotates, the crankshaft 11 rotates together with the pump impeller 53. Through this process, the rotation of the transmission input shaft 81 can be efficiently transmitted to the crankshaft 11.

[0065] The second reason is related to torque transmission between the pump impeller 53 and the turbine liner 54 in the torque converter 50. As described above, suppose that fuel is cut off while the lock-up clutch 60 is disengaged during deceleration of the vehicle 500. Then, suppose that the torque of the drive wheels 83 causes the turbine liner 54 to rotate together with the transmission input shaft 81. At this time, if the viscosity of the hydraulic oil is high, the torque of the turbine liner 54 is more easily transmitted to the pump impeller 53. In other words, when torque is transmitted from the turbine liner 54 to the pump impeller 53 via the hydraulic oil, the higher the viscosity of the hydraulic oil, the stronger the force with which the hydraulic oil pushes the blades of the pump impeller 53. Therefore, the rotation of the turbine liner 54 can be efficiently transmitted to the pump impeller 53 and ultimately to the crankshaft 11.

[0066] For the reasons described above, even when the lockup clutch 60 is disengaged, a significant proportion of the torque from the drive wheels 83 can be transmitted to the crankshaft 11 if the viscosity of the hydraulic oil is high. In light of this, in this embodiment, in order to disengage the lockup clutch 60 when the hydraulic oil has high viscosity, the threshold temperature LK, which is the hydraulic oil temperature L at which the lockup clutch 60 is switched between engaged and disengaged states, is set to a value close to zero degrees. The threshold temperature LK is determined in advance, for example, through experiments or simulations, as the maximum hydraulic oil temperature L that is expected to achieve torque transmission efficiency when the lockup clutch 60 is disengaged that is as close as possible to that when the lockup clutch 60 is engaged. In this way, the threshold temperature LK is determined taking into account the viscosity of the hydraulic oil that can efficiently transmit the torque from the drive wheels 83 to the crankshaft 11 through the above-described effects. By setting the threshold temperature LK in this manner, fuel cutoff can be performed in the second process using an allowable rotational speed and a return rotational speed that are lower than those used in the normal disengagement process.

[0067] However, as long as the lock-up clutch 60 is disengaged, there is some uncertainty as to how high torque transmission efficiency can actually be achieved. Furthermore, even within the category of being below the criterion temperature LK, the viscosity of the hydraulic oil can change if the hydraulic oil temperature L varies. Therefore, even if the permitted rotation speed and return rotation speed are lowered when disengaging the lock-up clutch 60 and performing a fuel cut, it is necessary to set a separate preventative measure to avoid stalling the internal combustion engine 10.

[0068] Therefore, in this embodiment, the termination requirement for determining whether to terminate the second process includes a requirement that is not considered in the normal deceleration process, such as the rotational speed difference ΔR defined in requirement (B1). As described above, the rotational speed difference ΔR is the value obtained by subtracting the engine rotational speed NE from the transmission rotational speed ME. If this rotational speed difference ΔR is small, the torque of the drive wheels 83 is more efficiently transmitted to the crankshaft 11. In other words, the rotational speed difference ΔR is an index of torque transmission efficiency. Regarding the termination requirement (B1) for the second process, the difference determination value RK, which is a threshold value for the rotational speed difference ΔR, is determined in advance, for example, through experiments or simulations, as follows: That is, the difference determination value RK is the minimum value of the rotational speed difference ΔR at which it is estimated that a stall of the internal combustion engine 10 cannot be avoided if the specific allowable rotational speed XV smaller than the first allowable rotational speed X1 and the specific return rotational speed YV smaller than the first return rotational speed Y1 are set. By utilizing the rotational speed difference ΔR, it is possible to properly grasp to what extent the torque of the drive wheels 83 is being transmitted to the crankshaft 11. If the torque of the drive wheels 83 is not being transmitted sufficiently to the crankshaft 11, the fuel cut can be ended at that point.

[0069] Furthermore, in this embodiment, the multiple termination requirements for determining whether to stop the second process include sudden braking of the vehicle 500, as defined by requirement (B2). Here, if the permitted rotation speed for fuel cut is reduced, fuel cut is permitted even when the engine rotation speed NE is relatively low. In this case, the following situation may occur. Suppose that fuel cut is initiated when the vehicle 500 is decelerating and the engine rotation speed NE is relatively low. Then, suppose that sudden braking of the vehicle 500 occurs at that time. If this causes a sudden drop in the transmission rotation speed ME and therefore the engine rotation speed NE, there is a risk that the engine rotation speed NE will drop to a value that makes it impossible to avoid stalling of the internal combustion engine 10. In this regard, in this embodiment, the termination requirement (B2) related to sudden braking of the vehicle 500 is set, so that fuel cut can be terminated when the occupant performs a sudden braking operation, i.e., before the engine rotation speed NE drops excessively.

[0070] <Effects of the embodiment> (1) As described in the above section on operation, when the viscosity of the hydraulic oil increases as the hydraulic oil temperature L decreases, a significant proportion of the torque of the drive wheels 83 can be transmitted to the crankshaft 11. Focusing on this point, in this embodiment, when the hydraulic oil temperature L is low and the PM accumulation amount W is large, the permitted rotation speed and the return rotation speed for performing fuel cutoff while the lockup clutch 60 is disengaged are set lower than those for the normal disengagement process. This increases the chances of regenerating the filter 25 in a low oil temperature environment. Note that, when the lockup clutch 60 is engaged in a low oil temperature environment, vibrations may occur in the vehicle 500. In this regard, if fuel cutoff is performed while the lockup clutch 60 is disengaged, as described above, vibrations do not occur in the vehicle 500. In other words, in this embodiment, vibrations of the vehicle 500 can be suppressed and the chances of regenerating the filter 25 in a low oil temperature environment can be increased.

[0071] (2) When the temperature L of the hydraulic oil is low, the viscosity of the hydraulic oil is expected to be high. However, depending on the situation, the viscosity of the hydraulic oil may not be so high. As a result, the torque of the drive wheels 83 may not be efficiently transmitted to the crankshaft 11. In this embodiment, the permissible rotation speed and the return rotation speed for the fuel cut related to the second process are set low, and an item related to the rotation speed difference ΔR is included as one of the conditions for terminating the fuel cut. As described in the above section on operation, this allows the fuel cut to be terminated at that point when the torque of the drive wheels 83 is not sufficiently transmitted to the crankshaft 11. Therefore, it is possible to prevent the internal combustion engine 10 from stalling while increasing the opportunities for executing the fuel cut and, therefore, for regenerating the filter 25.

[0072] (3) In this embodiment, one of the conditions for ending the fuel cut associated with the second process includes an item related to sudden braking of the vehicle 500. As a result, as described in the above section on operation, when the vehicle 500 is suddenly braked, the fuel cut can be ended before the engine speed NE decreases excessively due to the sudden braking. Therefore, similar to (2) above, it is possible to prevent the internal combustion engine 10 from stalling while increasing the opportunities for executing the fuel cut and thus the regeneration of the filter 25.

[0073] (4) The specific permissible rotation speed XV used in the second process is closer to the second permissible rotation speed X2 than the median between the first permissible rotation speed X1 and the second permissible rotation speed X2. That is, in this embodiment, the permissible rotation speed for performing fuel cutoff to regenerate the filter 25 in a low oil temperature environment is set to a value as close as possible to the permissible rotation speed for performing fuel cutoff in a high oil temperature environment. Therefore, the opportunity for regenerating the filter 25 can be brought closer to a situation where the hydraulic oil temperature L is high.

[0074] <Example of change> The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other within the scope of technical compatibility.

[0075] The threshold temperature LK is not limited to the example in the above embodiment. The threshold temperature LK may be higher or lower than zero degrees. The threshold temperature LK may be any temperature at which the viscosity of the hydraulic oil is expected to increase to a certain degree. Note that even if the threshold temperature LK is set taking into account the viscosity of the hydraulic oil, in some cases the viscosity of the hydraulic oil may not be as high as expected. Even in this case, if appropriate termination requirements are set, stalling of the internal combustion engine 10 can be prevented.

[0076] The specific permission rotation speed XV and the specific return rotation speed YV in the second process are not limited to the examples in the above embodiment. For example, the specific permission rotation speed XV may be a value closer to the first permission rotation speed X1 than the median value between the first permission rotation speed X1 and the second permission rotation speed X2. The same applies to the specific return rotation speed YV. The specific permission rotation speed XV and the specific return rotation speed YV may be set to appropriate values ​​from the viewpoint of avoiding a stall of the internal combustion engine 10.

[0077] The difference determination value RK is not limited to the example in the above embodiment. For example, the difference determination value RK may be smaller than the minimum value described in the above embodiment. The difference determination value RK may be any value that can prevent the internal combustion engine 10 from stalling when fuel cut is performed by the second process.

[0078] The termination requirements are not limited to those described in the above embodiment. Other termination requirements may be set instead of or in addition to those used in the above embodiment. Furthermore, the number of termination requirements may be increased or decreased from that of the above embodiment. For example, a termination requirement may be that the elapsed time since the start of the second process is equal to or greater than a predetermined determination period. In this case, the determination period may be set as a period during which the PM accumulation amount W can be appropriately reduced. The PM dissipation rate may be taken into consideration when determining such a period. When the elapsed time is used as a termination requirement, (B5) and (B6) may be eliminated from the multiple termination requirements used in the above embodiment. The termination requirements may be set as appropriate for avoiding a stall of the internal combustion engine 10. Among the multiple termination requirements used in the above embodiment, termination requirement (B1) may be eliminated. Furthermore, termination requirement (B2) may be eliminated. Eliminating these termination requirements may involve appropriately setting other termination requirements to avoid a stall of the internal combustion engine 10, such as by slightly increasing the specific allowable rotation speed XV.

[0079] The start requirements are not limited to the examples of the above embodiment. Other requirements may be set instead of or in addition to those employed in the above embodiment. Furthermore, the number of start requirements may be increased or decreased from those of the above embodiment. The start requirements may include (A1), (A2), and (A3) of the above embodiment. For example, a start requirement may be that the coolant temperature of the internal combustion engine 10 is equal to or higher than a predetermined threshold water temperature. During a cold start of the internal combustion engine 10, combustion of the air-fuel mixture may be unstable. In light of this, the threshold water temperature may be, for example, the temperature at which the warm-up of the internal combustion engine 10 is completed. Furthermore, among the multiple start requirements employed in the above embodiment, start requirement (A4) may be eliminated. Even in this case, stalling of the internal combustion engine 10 can be avoided by setting an appropriate specific permitted rotation speed XV as end requirement (B3). Furthermore, as in a modified example described below, if the filter 25 can be heated during execution of the second process, start requirement (A5) may be eliminated.

[0080] The fuel cut is not limited to stopping fuel injection for all cylinders 12. That is, when performing the fuel cut, fuel injection may be stopped for some of the cylinders 12 while fuel injection is continued for the remaining cylinders. Even in this case, ignition is suspended for all cylinders 12. Adopting such a configuration can simultaneously raise the temperature of the filter 25 and supply oxygen to the filter 25. That is, the cylinders 12 in which fuel injection is performed discharge unburned fuel into the exhaust passage 23. On the other hand, the cylinders 12 in which fuel injection is stopped discharge oxygen into the exhaust passage 23. When this unburned fuel and oxygen reach the three-way catalyst 24, the unburned fuel is burned in the three-way catalyst 24. This increases the temperature of the exhaust gas. When this high-temperature exhaust gas reaches the filter 25, the temperature of the filter 25 also increases. At this time, when the oxygen discharged into the exhaust passage 23 by the cylinders 12 in which fuel injection is stopped reaches the filter 25, PM is burned in the filter 25.

[0081] The method of determining whether the vehicle 500 has started to decelerate is not limited to the example of the above embodiment. For example, the start of deceleration may be determined based on the history of the vehicle speed SP. That is, it may be determined that the vehicle 500 has started to decelerate when the derivative value of the vehicle speed SP becomes negative. Any method may be used as long as it can appropriately determine whether the vehicle 500 has started to decelerate. The same applies to the method of determining whether the vehicle 500 has finished decelerating.

[0082] The method for calculating the PM accumulation amount W is not limited to the example in the above embodiment. Any calculation method may be used as long as the PM accumulation amount W can be calculated appropriately. For example, the method for calculating the filter temperature TF used to calculate the PM accumulation amount W may be changed from that in the above embodiment. Specifically, the filter temperature TF may be calculated without using the detection value of the exhaust temperature sensor 17. For example, a base value for the filter temperature TF may be calculated based on engine operating conditions such as the engine speed NE and the engine load factor, and the filter temperature TF may be calculated by adjusting the base value taking into account the ignition timing, etc.

[0083] The configuration of the internal combustion engine 10 is not limited to the example of the above embodiment. For example, the number of cylinders 12 may be changed. Any internal combustion engine equipped with a filter can enjoy the above-described effects of the second process.

[0084] The overall configuration of the vehicle 500 is not limited to the example of the above embodiment. A continuously variable automatic transmission may be used. The vehicle only needs to have a torque converter interposed between the internal combustion engine and the automatic transmission, a hydraulic mechanism that supplies and discharges hydraulic oil to and from the torque converter, and a temperature sensor that detects the temperature of the hydraulic oil. The configuration of the torque converter may also change due to changes in the configuration of the lock-up clutch, which will be described later. Even in this case, the torque converter only needs to be configured as a fluid coupling that transmits torque between the pump impeller and the turbine liner via hydraulic oil.

[0085] The configuration of the lockup clutch 60 is not limited to the example in the above embodiment. The lockup clutch may be configured to switch between a connected state, in which the crankshaft 11 and the transmission input shaft 81 are connected, and a disconnected state, in which they are disconnected, in response to the supply and discharge of hydraulic oil. For example, the lockup clutch may be of a type that brings the lockup piston 67 into and out of direct contact with the front cover 56. If the lockup clutch is configured to suppress relative rotation between the crankshaft 11 and the transmission input shaft 81 through the action caused by increased viscosity of the hydraulic oil, stalling of the internal combustion engine 10 can be avoided even if fuel is cut off while the lockup clutch is in the disconnected state. [Explanation of symbols]

[0086] 10...Internal combustion engine 11...Crankshaft 25...Filter 50...Torque converter 60...Lock-up clutch 70...Hydraulic mechanism 80...automatic transmission 81...Transmission input shaft 94...Specific temperature sensor 97...Brake sensor 98...Brake pedal 100...Control device 500...vehicle

Claims

1. an internal combustion engine equipped with a filter that captures particulate matter contained in exhaust gas; an automatic transmission connected to the internal combustion engine; a torque converter interposed between the internal combustion engine and the automatic transmission; a hydraulic mechanism that supplies and discharges hydraulic oil to and from the torque converter; and a temperature sensor that detects the temperature of the hydraulic oil; The torque converter is intended to control a vehicle equipped with a lock-up clutch that switches between a connected state in which an output shaft of the internal combustion engine and an input shaft of the automatic transmission are connected and a disconnected state in which the output shaft and the input shaft are disconnected in response to the supply and discharge of the hydraulic oil, If the temperature of the hydraulic oil is lower than a predetermined judgment temperature, the first process of disengaging the lock-up clutch is continued; When the lock-up clutch is in the disengaged state and the amount of particulate matter trapped in the filter is equal to or greater than a predetermined judgment amount during deceleration of the vehicle, a second process is started to cut fuel in the internal combustion engine. Vehicle control device.

2. During execution of the second process, if the difference between the rotation speed of the output shaft and the rotation speed of the input shaft becomes equal to or greater than a predetermined difference determination value, the second process is stopped. The vehicle control device according to claim 1 .

3. The vehicle has a brake sensor that detects the amount of depression of a brake pedal, If the depression speed of the brake pedal becomes equal to or greater than a predetermined brake determination value during execution of the second process, the second process is stopped. The vehicle control device according to claim 1 .

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