Vehicle control system

Abstract

To prevent excessive rise in a temperature of a filter and prevent repeated change of deceleration in a vehicle.SOLUTION: A control device 100 executes: fuel cut for stopping fuel injection by using a fuel injection valve 22 during deceleration of a vehicle 500; interruption of the fuel cut when a duration from start of the fuel cut becomes longer than an allowable time; and prohibition of start of the fuel cut until a temperature of a filter 34 becomes a determination temperature or lower when frequency of interrupting the fuel cut reaches predetermined frequency within a predetermined time.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a control device for a vehicle.

Background Art

[0002] The internal combustion engine disclosed in Patent Document 1 includes a fuel injection valve and a filter. The fuel injection valve injects fuel for supply into a cylinder. The filter is located in the middle of an exhaust passage. The filter collects particulate matter in the exhaust. When a predetermined execution condition is satisfied, the control device of this internal combustion engine performs a fuel cut that stops the fuel injection from the fuel injection valve. When the control device performs a fuel cut, oxygen is supplied to the filter. Along with this, the particulate matter deposited on the filter burns.

[0003] By the way, when a fuel cut is performed, the temperature of the filter rises as the particulate matter deposited on the filter burns. If the filter overheats at this time, the filter may be damaged. Therefore, the control device interrupts the fuel cut as necessary so as to avoid overheating of the filter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Outline of the Invention

Problems to be Solved by the Invention

[0005] In a technique such as Patent Document 1 that interrupts a fuel cut, when the fuel cut is interrupted, the internal combustion engine outputs torque as the fuel injection resumes. Therefore, the deceleration of the vehicle changes during deceleration of the vehicle. If such changes in deceleration are repeated many times, the passengers will feel discomfort. On the other hand, if the interruption of the fuel cut is not performed, overheating of the filter cannot be avoided.

Means for Solving the Problems

[0006] A vehicle control device for solving the above problems is applied to a vehicle equipped with an internal combustion engine having a fuel injector for injecting fuel into a cylinder and a filter for collecting particulate matter in the exhaust gas discharged from the cylinder, and performs a fuel cut, which stops fuel injection by the fuel injector when the vehicle is decelerating, interrupts the fuel cut if the duration of the fuel cut after it has started exceeds a predetermined allowable time, and if the number of times the fuel cut has been interrupted within a predetermined time reaches a predetermined number of times, the device prohibits the start of the fuel cut until the temperature of the filter falls below a predetermined judgment temperature. [Effects of the Invention]

[0007] The above technical concept prevents the filter from overheating and also prevents repeated changes in deceleration in the vehicle. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of an internal combustion engine. [Figure 2] Figure 2 shows an example of a time map. [Figure 3] Figure 3 is a flowchart illustrating the processing steps for the flag setting process. [Figure 4] Figure 4 is a flowchart illustrating the processing steps for the execution process. [Figure 5] Figure 5 is a time chart showing an example of the time changes of each parameter related to the interruption of fuel cut. [Modes for carrying out the invention]

[0009] <Internal Combustion Engine> Hereinafter, one embodiment of the vehicle control device will be described with reference to the drawings. As shown in Figure 1, the vehicle 500 is equipped with an internal combustion engine 10. The internal combustion engine 10 is the power source for the vehicle 500.

[0010] The internal combustion engine 10 comprises multiple cylinders 12 and a crankshaft 11. Each cylinder 12 is a space partitioned within the engine body 10A for burning a mixture of fuel and intake air. The crankshaft 11 rotates in response to the combustion of the mixture in the cylinders 12. The crankshaft 11 is connected to the wheels 502 via an automatic transmission 501 or the like.

[0011] The internal combustion engine 10 has multiple spark plugs 19. One spark plug 19 is provided for each cylinder 12. The spark plugs 19 ignite the fuel-air mixture in the cylinder 12. The internal combustion engine 10 comprises an intake passage 20, a throttle valve 21, and a plurality of fuel injectors 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 in the middle of the intake passage 20. The throttle valve 21 adjusts the amount of intake air GA. A fuel injector 22 is provided for each cylinder 12. The fuel injector 22 is located downstream of the throttle valve 21 in the intake passage 20. The fuel injector 22 injects fuel. The fuel injected by the fuel injector 22 reaches the cylinder 12 via the intake passage 20. That is, the fuel injector 22 injects fuel to be supplied into the cylinder 12.

[0012] The internal combustion engine 10 includes an exhaust passage 30, a three-way catalytic converter 32, and a gasoline particulate filter (hereinafter simply referred to as the filter) 34. The exhaust passage 30 is a passage for discharging exhaust gas from each cylinder 12. The exhaust passage 30 is connected to each cylinder 12. The three-way catalytic converter 32 is located in the middle of the exhaust passage 30. The three-way catalytic converter 32 purifies hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas. The filter 34 is located downstream of the three-way catalytic converter 32 in the exhaust passage 30. The filter 34 collects particulate matter (hereinafter referred to as PM) in the exhaust gas.

[0013] The internal combustion engine 10 is equipped with an air flow meter 61, an air-fuel ratio sensor 62, an exhaust temperature sensor 63, and a crank position sensor 64. The air flow meter 61 detects the intake air volume GA and the intake air temperature TI. The air-fuel ratio sensor 62 detects the exhaust air-fuel ratio AF, which is the air-fuel ratio of the exhaust gas flowing into the filter 34. The exhaust temperature sensor 63 detects the temperature TO of the exhaust gas flowing into the filter 34. The crank position sensor 64 detects the rotational position CR of the crankshaft 11. Each of these sensors repeatedly outputs a signal corresponding to the information it has detected to the control device 100, which will be described later.

[0014] <Other vehicle configurations> Vehicle 500 is equipped with an accelerator sensor 91, a vehicle speed sensor 92, and an ignition switch 93. The accelerator sensor 91 detects the amount the accelerator pedal is pressed in vehicle 500 as the accelerator operation amount ACC. The vehicle speed sensor 92 detects the vehicle speed of vehicle 500 as the vehicle speed SP. Each of these sensors repeatedly outputs a signal corresponding to the information it has detected to the control device 100, which will be described later. The ignition switch 93 is a switch for starting vehicle 500. The ignition switch 93 outputs a signal Y corresponding to the operation of the occupant to the control device 100, which will be described later.

[0015] <Control device> Vehicle 500 is equipped with a control device 100. The control device 100 includes a CPU 101 and a memory 102. The memory 102 pre-stores various programs that describe the processes to be executed by the CPU 101. The CPU 101 controls the internal combustion engine 10 by executing the programs stored in the memory 102. There are three types of memory 102: RAM, ROM, and an electrically rewritable non-volatile type.

[0016] The CPU 101 receives a signal Y from the ignition switch 93. When the CPU 101 receives a signal Y corresponding to the ignition switch 93 being turned ON, it starts the internal combustion engine 10. Hereinafter, the period from when the ignition switch 93 is turned ON until it is turned OFF will be referred to as "1 trip". During 1 trip, the CPU 101 repeatedly receives detection signals from various sensors attached to the vehicle 500.

[0017] During a single trip, the CPU 101 repeatedly calculates various parameters based on detection signals received from various sensors. For example, the CPU 101 calculates the engine rotation speed, which is the rotational speed of the crankshaft 11, based on the rotational position CR of the crankshaft 11. The CPU 101 also calculates the PM accumulation amount DA as follows. The PM accumulation amount DA is the amount of PM accumulated on the filter 34. In addition, as shown below, the CPU 101 also calculates the filter temperature TF, which is the temperature of the filter 34, during the calculation of the PM accumulation amount DA.

[0018] When calculating the PM deposition amount DA, the CPU 101 calculates the PM generation amount and the PM regeneration amount. Then, the CPU 101 calculates the PM deposition amount DA by updating the PM deposition amount DA. Specifically, the CPU 101 updates the PM deposition amount DA by adding the difference obtained by subtracting the PM regeneration amount from the PM generation amount to the PM deposition amount DA before update. The PM generation amount is the amount of PM generated by the combustion of the air-fuel mixture in the cylinder 12. The CPU 101 calculates the PM generation amount from the intake air amount GA, the fuel injection amount, etc. The PM regeneration amount is the amount of PM burned in the filter 34. The higher the temperature TO of the exhaust gas flowing into the filter 34, the higher the filter temperature TF. Therefore, the filter temperature TF can be obtained from the temperature TO of the exhaust gas detected by the exhaust gas temperature sensor 63. The CPU 101 calculates the filter temperature TF using a heat balance model of the filter 34 based on the temperature TO and flow rate of the exhaust gas flowing into the filter 34 and the temperature of the outside air. The flow rate of the exhaust gas flowing into the filter 34 can be obtained from the intake air amount GA and the fuel injection amount. Also, the temperature of the outside air can use the temperature TI of the intake air detected by the air flow meter 61. When the filter temperature TF is above the ignition point of PM and the exhaust gas containing oxygen flows into the filter 34, the PM deposited on the filter 34 starts to burn. Since oxygen is required for the combustion of PM, the amount of PM burned in the filter 34 at this time is determined according to the amount of oxygen in the exhaust gas flowing into the filter 34. The oxygen concentration of the exhaust gas flowing into the filter 34 can be obtained from the detection result of the air-fuel ratio sensor 62. Therefore, the CPU 101 calculates the PM regeneration amount based on the temperature TO of the exhaust gas detected by the exhaust gas temperature sensor 63, the oxygen concentration detected by the air-fuel ratio sensor 62, that is, the exhaust air-fuel ratio AF, the intake air amount GA, and the fuel injection amount.

[0019] <Normal processing> During one trip, the CPU 101 basically controls the internal combustion engine 10 through normal processing. In normal processing, the CPU 101 calculates the target torque of the internal combustion engine 10 based on the accelerator operation amount ACC, vehicle speed SP, etc. Then, the CPU 101 adjusts the opening degree of the throttle valve 21, injects fuel from the fuel injection valve 22, or performs ignition by the ignition plug 19 so as to obtain the target torque. By doing so, the CPU 101 causes the air-fuel mixture to burn in the cylinder 12. In normal processing, the CPU 101 repeats the calculation of the target torque and the control of various parts based on the target torque. By doing so, the CPU 101 repeats the combustion of the air-fuel mixture in each cylinder 12.

[0020] During deceleration of the vehicle 500, the CPU 101 may cancel the above normal processing and perform a fuel cut to stop the fuel injection by each fuel injection valve 22. Hereinafter, the processing performed by the CPU 101 in relation to the fuel cut will be described.

[0021] <Flag setting process> The CPU 101 is capable of executing a flag setting process. The flag setting process is a process for setting the on / off of a prohibition flag. The prohibition flag is a flag indicating the prohibition of the start of fuel cut. That the prohibition flag is off means permitting the start of fuel cut. That the prohibition flag is on means prohibiting the start of fuel cut.

[0022] During one trip, the CPU 101 repeatedly executes the flag setting process. Note that if the ignition switch 93 is turned off during the execution of the flag setting process, the CPU 101 ends the flag setting process at that time.

[0023] As shown in FIG. 3, when starting the flag setting process, the CPU 101 first performs the process of step S310. In step S310, the CPU 101 sets the prohibition flag to off. After that, the CPU 101 advances the process to step S320.

[0024] In step S320, the CPU 101 resets the number of fuel cut interruptions N to zero. This number of interruptions N is updated periodically in the execution process described later. After this, the CPU 101 proceeds to step S330.

[0025] In step S330, the CPU 101 determines whether the number of interruptions N matches "1". If the number of interruptions N is not "1", the CPU 101 executes the process in step S330 again. The CPU 101 repeats the process in step S330 until the number of interruptions N becomes "1". When the number of interruptions N becomes "1", the CPU 101 starts measuring time and proceeds to step S340.

[0026] In step S340, the CPU 101 determines whether the elapsed time since the interruption count N became "1" has become longer than a predetermined time P. The memory 102 has the predetermined time P stored in advance. In this embodiment, the predetermined time P is 10 seconds. The criteria for determining the predetermined time P will be explained later, along with the predetermined number NK described below. In step S340, if the elapsed time since the interruption count N became "1" is less than or equal to the predetermined time P (step S340: NO), the CPU 101 proceeds to step S350.

[0027] The number one less than the number of interruptions N is called the provisional number of interruptions. In step S350, the CPU 101 determines whether the provisional number of interruptions matches a predetermined number NK. Memory 102 stores the predetermined number NK in advance. In this embodiment, the predetermined number NK is 2. If the provisional number of interruptions does not match the predetermined number NK (step S350: NO), the CPU 101 returns to the process in step S340. Then, the CPU 101 executes the process in step S340 again. After this, if the determination in step S340 is NO and the determination in step S350 is NO, the CPU 101 repeats the processes in steps S340 and S350. During such repetition, if the CPU 101 terminates the series of flag setting processes before the provisional number of interruptions reaches the predetermined number NK (step S350: NO), and the elapsed time since the number of interruptions N became "1" becomes longer than a predetermined time P (step S340: YES). Then, CPU 101 executes the process in step S310 again. Note that if CPU 101 finishes the flag setting process, it also finishes the time measurement that was started in step S330.

[0028] On the other hand, if the CPU 101 finds that the elapsed time since the number of interruptions N became "1" is within a predetermined time P (step S340: NO), and the provisional number of interruptions matches the predetermined number NK (step S350: YES), then proceeds to step S360. In this case, the CPU 101 terminates the time measurement that was started in step S330 at this point.

[0029] In step S360, CPU 101 switches the prohibition flag to ON. Then, CPU 101 proceeds to step S370. In step S370, the CPU 101 determines whether the filter temperature TF is below the determination temperature TK. The memory 102 has the determination temperature TK stored in advance. In this embodiment, the determination temperature TK is 500 degrees. The determination temperature TK is predetermined, for example, through experimentation or simulation, as a temperature that is considerably lower than the temperature at which PM combustion in the filter 34 is possible but the filter 34 is damaged. If the latest filter temperature TF is higher than the determination temperature TK (step S370: NO), the CPU 101 executes the process in step S370 again. The CPU 101 repeats the process in step S370 until the filter temperature TF is below the determination temperature TK. Then, when the filter temperature TF is below the determination temperature TK (step S370: YES), the CPU 101 terminates the series of filter setting processes. Then, the CPU 101 executes the process in step S310 again.

[0030] In the flag setting process described above, CPU 101 performs the following: If the number of provisional interruptions reaches a predetermined number NK while the elapsed time since the number of interruptions N became "1" is within a predetermined time P, CPU 101 turns on the prohibition flag until the filter temperature TF falls below the judgment temperature TK. The number of provisional interruptions is the number of fuel cut interruptions after the first fuel cut interruption.

[0031] <Execution Process> CPU 101 is capable of executing execution processes. These execution processes are for implementing fuel cut-off. During a single trip, CPU 101 starts the execution process when the fuel cut-off execution conditions switch from a false state to a true state. The fuel cut-off execution conditions are that all three of the following requirements are met: The first requirement is that the vehicle 500 is decelerating. The second requirement is that the engine rotation speed is equal to or greater than the recovery rotation speed. The third requirement is that the prohibition flag is off. CPU 101 continuously determines whether the fuel cut-off execution conditions are met based on the latest information of parameters necessary for determining each requirement, such as vehicle speed SP, engine rotation speed, and the prohibition flag. Then, each time the fuel cut-off execution conditions switch to a true state, CPU 101 starts the execution process. Note that CPU 101 may also determine whether the first requirement is met based on the accelerator pedal input (ACC). In this case, the CPU 101 can determine that vehicle 500 has started to decelerate, that is, vehicle 500 is decelerating, when the accelerator pedal input ACC switches from a state greater than zero to zero. The recovery rotational speed in the second requirement is predetermined as a value that can avoid stalling of the internal combustion engine 10 when fuel injection and combustion of the air-fuel mixture are restarted after fuel cut-off.

[0032] As shown in Figure 4, when the CPU 101 starts execution processing, it first executes the process in step S110. In step S110, the CPU 101 calculates the allowable time H. The allowable time H is the length of time that can be sustained for one fuel cut based on the current state of the filter 34. As a prerequisite for the CPU 101 to calculate the allowable time H, the memory 102 has a time map stored in advance. The time map represents the relationship between the filter temperature TF, the PM accumulation amount DA, and the allowable time H. Specifically, the time map is a graph or table that shows the allowable time H for various combinations of filter temperature TF and PM accumulation amount DA. In the example shown in Figure 2, the time map is represented as a graph with the filter temperature TF on the X axis and the PM accumulation amount DA on the Y axis. Note that in Figure 2, only three allowable time H values ​​are shown as representative examples for convenience, in order to make the relationship between the filter temperature TF, the PM accumulation amount DA, and the allowable time H easier to understand. The three allowable time periods H in Figure 2 have the relationship "1st time H1 < 2nd time H2 < 3rd time H3". In the example shown in Figure 2, the contour lines corresponding to the 1st time H1, 2nd time H2, and 3rd time H3 are represented by straight lines, but this is also for convenience. As shown in Figure 2, the filter temperature TF, PM accumulation amount DA, and allowable time period H have the following relationship: For the same filter temperature TF, the larger the PM accumulation amount DA, the shorter the allowable time period H. Also, for the same PM accumulation amount DA, the higher the filter temperature TF, the shorter the allowable time period H. The CPU 101 calculates the allowable time period H based on this time map. Specifically, the CPU 101 refers to the latest PM accumulation amount DA and the latest filter temperature TF along with this time map. Then, based on the time map, the CPU 101 calculates the allowable time period H corresponding to the latest PM accumulation amount DA and the latest filter temperature TF as the allowable time period H for the current fuel cut. Reflecting the contents of the time map, CPU 101 sets the allowable time H shorter as the amount of PM accumulation DA increases, provided the filter temperature TF is the same. Also, CPU 101 sets the allowable time H shorter as the filter temperature TF increases, provided the PM accumulation amount DA is the same.As shown in Figure 4, once the allowable time H is set, the CPU 101 proceeds to step S120.

[0033] In step S120, the CPU 101 cancels normal processing and starts fuel cut-off. That is, the CPU 101 stops fuel injection by each fuel injector 22. The CPU 101 also starts time measurement. After this, the CPU 101 proceeds to step S130.

[0034] In step S130, the CPU 101 determines whether the duration since the start of fuel cut-off has become longer than the allowable time H predetermined in step S110. The duration since the start of fuel cut-off is also called the elapsed time since the start of fuel cut-off. If the above duration is less than or equal to the allowable time H (step S130: NO), the CPU 101 proceeds to step S210.

[0035] In step S210, the CPU 101 determines whether the conditions for executing fuel cut are met at the current time. If the conditions for executing fuel cut are met (step S210: YES), the CPU 101 returns to the process in step S130. The CPU 101 then executes the process in step S130 again. If the judgment in step S130 is NO and the judgment in step S210 is YES, the CPU 101 repeats the processes in steps S130 and S210. During this repetition, if the conditions for executing fuel cut become unmet before the duration since the start of fuel cut exceeds the allowable time H (step S210: NO), the CPU 101 proceeds to step S220. In this case, the CPU 101 terminates the fuel cut in step S220 and resumes normal processing. The CPU 101 then finishes the series of execution processes. When the CPU 101 finishes the execution processes, the time measurement that was started in step S120 also ends. Regarding the processing in step S210, when the CPU 101 recognizes that the fuel cut execution conditions have not been met, it may determine the first requirement of the execution conditions based on the accelerator pedal operation amount ACC. That is, the CPU 101 can determine that deceleration has ended, i.e., that the vehicle 500 is no longer decelerating, when the accelerator pedal operation amount ACC becomes greater than zero.

[0036] Now, if the CPU 101 finds that the conditions for executing the fuel cut have been met and the duration since the fuel cut was started has become longer than the allowable time H (step S130: YES), the process proceeds to step S140. In this case, in step S140, the CPU 101 interrupts the fuel cut. Then, the CPU 101 resumes normal processing. That is, the CPU 101 resumes fuel injection and combustion of the air-fuel mixture. The CPU 101 will keep the internal combustion engine 10 idling until the vehicle 500 has finished decelerating. After interrupting the fuel cut, the CPU 101 proceeds to step S150.

[0037] In step S150, the CPU 101 updates the number of interruptions N. That is, the CPU 101 calculates the new number of interruptions N by adding "1" to the current number of interruptions N. After this, the CPU 101 finishes the processing in step S150. Then, the CPU 101 finishes the series of processes for execution. As described above, once the CPU 101 finishes the execution process, the time measurement that started in step S120 also ends.

[0038] <Regarding the prescribed time and prescribed number of times> Of the various allowable time periods H corresponding to each filter temperature TF and each PM deposit amount DA as defined in the time map above, the longest allowable time period H is referred to as the maximum allowable time. The predetermined time period P is set to be longer than the maximum allowable time.

[0039] Furthermore, the predetermined time P is set taking the following points into consideration. When the CPU 101 interrupts fuel cut-off, fuel injection by each fuel injector 22 and consequently combustion of the air-fuel mixture are resumed during the deceleration of the vehicle 500. When combustion of the air-fuel mixture is resumed, the deceleration of the vehicle 500 changes. This change in deceleration occurs as a result of processing performed by the CPU 101 to protect the filter 34, regardless of the occupant's accelerator operation. Therefore, if the CPU 101 repeatedly interrupts fuel cut-off within a relatively short period of time, the occupant may feel uncomfortable because the change in deceleration will be repeated within that time, regardless of the occupant's accelerator operation. The predetermined time P and the predetermined number of times NK are determined in advance through experiments or simulations in relation to each other so that the start of fuel cut-off can be prohibited before the occupant feels uncomfortable.

[0040] Here, even if fuel cut is interrupted several times over a reasonably long time scale, such as 10 minutes, the frequency of interruptions is low, making it highly unlikely that the occupants will notice anything unusual. Similarly, even if fuel cut is interrupted over a very short time scale, such as 1 millisecond, the occupants will not be able to grasp the interruption of fuel cut, or even the change in deceleration itself, making it highly unlikely that they will notice anything unusual. The predetermined time P is set on a time scale in which, if fuel cut is interrupted multiple times, the occupants can grasp that a change in deceleration is occurring independently of their accelerator operation. The predetermined number of times NK is set as a value that can prevent the start of fuel cut before the occupants notice any unusual sensation associated with the change in deceleration within the predetermined time P defined on this time scale.

[0041] <Operation of the Embodiment> In the following explanation, it is assumed that the second requirement for fuel cut-off is always met during the deceleration of vehicle 500.

[0042] As shown in Figure 5(b), the vehicle 500 repeatedly accelerates and decelerates in response to the occupant's accelerator operation. In Figure 5, the period during which the vehicle 500 is decelerating is represented by dots. Now, let's assume that the prohibition flag is off at time T1 when the vehicle 500 starts to decelerate. In this case, when the vehicle 500 starts to decelerate at time T1, the CPU 101 starts a fuel cut through the execution process as shown in Figure 5(c) (step S120). After the start of the fuel cut, at time T2 while the vehicle 500 is decelerating, if the duration of the fuel cut becomes longer than the allowable time H (step S130: YES), the CPU 101 interrupts the fuel cut (step S140). When the vehicle 500 starts to decelerate again at time T3, the CPU 101 starts a fuel cut. Then, when the duration of the fuel cut becomes longer than the allowable time H, the CPU 101 interrupts the fuel cut at time T4 while the vehicle 500 is decelerating. In the execution process, the CPU 101 sequentially counts the number of times N fuel cuts are interrupted (step S150).

[0043] Here, suppose that the number of provisional interruptions reaches a predetermined number NK at time T5, before a predetermined time P has elapsed since time T2 when the number of fuel cut interruptions N became "1" (step S340: NO). In this case, the CPU 101 switches the prohibition flag to ON in the flag setting process (step S360). Consequently, the third requirement in the conditions for executing fuel cut is no longer met. Therefore, from time T5 onward, the CPU 101 does not perform the execution process and thus the fuel cut even if the vehicle 500 decelerates.

[0044] Here, between time T1 and time T5, the CPU 101 repeatedly performs fuel cut-off. When the CPU 101 performs fuel cut-off, oxygen is supplied to the filter 34, causing the PM accumulated on the filter 34 to burn. Consequently, as shown in Figure 5(a), the filter temperature TF gradually rises. At time T5, the filter temperature TF is quite high. Now, as described above, the CPU 101 in this embodiment does not perform fuel cut-off after time T5. If the situation of the CPU 101 not performing fuel cut-off continues, the filter temperature TF gradually decreases. When the filter temperature TF falls below the judgment temperature TK (step S370: YES), the CPU 101 switches the prohibit flag to off (step S310). Then, when the vehicle 500 decelerates, the CPU 101 will start performing execution processing and, consequently, fuel cut-off again.

[0045] <Effects of the Embodiment> (1) As described in the operation of the above embodiment, under conditions where fuel cut is repeated, the filter temperature TF gradually increases with the combustion of PM. Although an allowable time H for continuing fuel cut is set, if the situation of repeated fuel cut continues, there is a risk that the filter 34 will eventually overheat. Now, setting an allowable time H for continuing fuel cut is advantageous in suppressing overheating of the filter 34, but it also creates opportunities to interrupt fuel cut. If fuel cut is repeatedly interrupted within a relatively short period, the degree of deceleration of the vehicle 500 will change repeatedly during deceleration, even if the occupant does not intend it. For this reason, if fuel cut is repeatedly interrupted within a relatively short period, the occupant may feel uncomfortable.

[0046] Therefore, in this embodiment, if the fuel cut is interrupted a predetermined number of times NK within a predetermined time P, the start of the fuel cut is prohibited. This prevents the filter 34 from overheating and also prevents repeated changes in deceleration in the vehicle 500.

[0047] (2) In order to avoid overheating of the filter 34, as shown in the time map of this embodiment, it is preferable to shorten the allowable time H for continuing fuel cut when the filter temperature TF is high or the PM accumulation amount DA is large. On the other hand, if the allowable time H is short, the possibility of interrupting fuel cut and consequently the possibility of a change in deceleration increases.

[0048] In this embodiment, the initiation of fuel cut is prohibited in situations where setting a shorter allowable time H would result in a higher frequency of fuel cut interruptions. With this configuration, it is possible to set the optimal allowable time H according to the state of the filter 34 while also preventing the occupants from feeling uncomfortable due to changes in the deceleration of the vehicle 500.

[0049] (3) As described above, the predetermined time P is set on a time scale that allows the occupant to become aware when the CPU 101 repeatedly interrupts fuel cut. Setting the fuel cut settings on such a time scale is suitable for designing the control of the internal combustion engine 10 while giving due consideration to the occupant's ride comfort.

[0050] (4) The determination temperature TK for lifting the fuel cut-off ban is a temperature at which PM combustion is possible in the filter 34 without damaging the filter 34. Therefore, after the fuel cut-off ban is lifted, the filter 34 can be regenerated for a reasonably long period of time.

[0051] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0052] The determination temperature TK is not limited to the examples of the above embodiments. From the viewpoint of achieving both PM combustion in the filter 34 and prevention of damage to the filter 34, it is preferable that the determination temperature TK be set within the range of 400 degrees Celsius or more and 600 degrees Celsius or less. However, it is not essential that the determination temperature TK be set to a value within this range. The determination temperature TK may be set to an appropriate temperature for releasing the prohibition on fuel cut-off.

[0053] The predetermined time P is not limited to the examples of the above embodiments. From the viewpoint of a time scale that allows the occupants to perceive the interruption of fuel cut, it is preferable that the predetermined time P is set within the range of 1 second or more and 20 seconds or less. However, it is not essential that the predetermined time P is set to a value within this range. The predetermined time P may be set to an appropriate time scale for deciding whether to prohibit fuel cut. Note that the predetermined time P is set to a time longer than the allowable time H.

[0054] The predetermined number of NK cycles is not limited to the examples of the above embodiment. The predetermined number of NK cycles should be set to a value that prevents the start of fuel cut-off before the occupant notices any discomfort. • The time map can be a table or graph, or it can be a mathematical formula.

[0055] It is not mandatory to define the prohibition of fuel cut based on the elapsed time since the number of interruptions N became "1" or the number of fuel cut interruptions. The timing of when the predetermined time P or the number of interruptions used to determine the prohibition of fuel cut can be changed as appropriate. It is sufficient to configure the system to prohibit fuel cut if the number of fuel cut interruptions reaches a predetermined number NK within the predetermined time P.

[0056] The relationship between the allowable time H, the filter temperature TF, and the PM accumulation amount DA is not limited to the example of the above embodiment. Preferably, the allowable time H is set as follows: For the same filter temperature TF, when the PM accumulation amount DA is the first accumulation amount, the allowable time is shorter than when the PM accumulation amount DA is a second accumulation amount which is less than the first accumulation amount. Also, for the same PM accumulation amount DA, when the filter temperature TF is the first temperature, the allowable time H is shorter than when the filter temperature TK is a second temperature which is lower than the first temperature. However, the relationship is not limited to the one described herein, and the allowable time H may be set appropriately from the viewpoint of preventing damage to the filter 34. The allowable time H may also be determined independently of the filter temperature TF and the PM accumulation amount DA. For example, the allowable time H may be a predetermined fixed value.

[0057] The method for calculating PM accumulation amount DA is not limited to the examples of the above embodiments. Any method for calculating PM accumulation amount DA is acceptable as long as it can be calculated appropriately. The method for calculating the filter temperature TF is not limited to the examples of the embodiments described above. Any method for calculating the filter temperature TF is acceptable as long as it can be calculated appropriately.

[0058] The overall configuration of the internal combustion engine 10 is not limited to the examples of the above embodiments. For example, the fuel injector 22 may be of a type that directly injects fuel into the cylinder 12. [Explanation of symbols]

[0059] 10...Internal combustion engine 12...Cylinder 22...Fuel injector 34...Filter 100...Control device 500...Vehicle

Claims

1. This invention is applied to vehicles equipped with an internal combustion engine having a fuel injector that injects fuel into the cylinder and a filter that collects particulate matter in the exhaust gas discharged from the cylinder. The fuel cut is performed to stop fuel injection by the fuel injector while the vehicle is decelerating. The fuel cut will be interrupted if the duration since the start of the fuel cut exceeds a predetermined allowable time. If the number of times the fuel cut is interrupted within a predetermined time period reaches a predetermined number, the start of the fuel cut will be prohibited until the temperature of the filter falls below a predetermined judgment temperature. Execute Vehicle control system.

2. With respect to the same temperature of the filter, when the amount of particulate matter deposited on the filter is a first deposit amount, the allowable time is set shorter compared to when the amount of deposit is a second deposit amount which is less than the first deposit amount. With respect to the same amount of deposit, the allowable time is set shorter when the filter temperature is at a first temperature compared to when the filter temperature is at a second temperature lower than the first temperature. A vehicle control device according to claim 1.

3. The aforementioned predetermined time is set within the range of 1 second or more and 20 seconds or less. A vehicle control device according to claim 1.

4. The aforementioned determination temperature is set within the range of 400 degrees Celsius or higher and 600 degrees Celsius or lower. A vehicle control device according to claim 1.

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