Vehicle control device

Abstract

To provide a control device of a vehicle capable of suppressing the user's feeling that the responsivity of a vehicle is slow when recovering from fuel cut treatment.SOLUTION: A CPU 72 executes fuel cut treatment of an internal combustion engine 10, under a predetermined condition that an accelerator pedal is released. The CPU 72 limits torque on a small side, by delaying an ignition period when the accelerator pedal is depressed to finish fuel cut treatment. However, the CPU 72 does not limit torque by delaying the ignition period, while a lock-up clutch 42 is released.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, the following Patent Document 1 describes a control device that retards the ignition timing when returning from a fuel cut process. This is aimed at suppressing a sudden increase in the torque transmitted to the drive wheels when returning from a fuel cut. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-353268 Summary of the Invention [Problem to be solved by the invention]

[0004] Some vehicles are equipped with a lock-up clutch that connects the crankshaft of the internal combustion engine and the input shaft of the transmission. If the lock-up clutch is in an engaged state when the vehicle returns from the fuel cut process, the ignition timing can be retarded as described above to reduce shock caused by a sudden change in torque. However, if the lock-up clutch is in a released state when the vehicle returns from the fuel cut process, it takes time for the torque to be transmitted to the drive wheels. Therefore, there is a concern that the user may feel that the vehicle is not responsive when the ignition timing is retarded. [Means for solving the problem]

[0005] Means for solving the above problems and their effects will be described below. 1. A vehicle control device applied to a vehicle in which power from an internal combustion engine is transmitted to driving wheels via a transmission, the crankshaft of the internal combustion engine can be mechanically connected to the input shaft of the transmission by a lock-up clutch, and the vehicle control device executes a stop process that stops combustion control in the internal combustion engine, and a return process that operates a specified operating unit of the internal combustion engine so as to reduce the combustion efficiency of the internal combustion engine in order to limit the torque of the internal combustion engine to a smaller side upon completion of the stop process in response to accelerator operation, the specified operating unit being an operating unit capable of adjusting the combustion efficiency, and the return process includes a process that changes the amount of reduction in accordance with the amount of undercut so that the amount of undercut when the amount of reduction in the combustion efficiency is large is greater than the amount of undercut when the amount of reduction is small, the amount of undercut being the amount by which the rotational speed of the crankshaft of the internal combustion engine falls below the rotational speed of the input shaft of the transmission.

[0006] When the undercut amount is large, the time until the torque of the internal combustion engine is transmitted to the drive wheels is longer than when the undercut amount is small. Therefore, in the above configuration, when the undercut amount is large, the amount of decrease in combustion efficiency is reduced compared to when the undercut amount is small. This makes it possible to prevent the time until the torque of the internal combustion engine is transmitted to the drive wheels from being longer when the undercut amount is large compared to when the undercut amount is small. Therefore, it is possible to prevent the user from feeling that the vehicle is not responsive when returning from the fuel cut process.

[0007] 2. A control device for a vehicle as described in 1 above, which executes a below-travel amount acquisition process for acquiring the below-travel amount, and a status acquisition process for acquiring the status of the lock-up clutch, and the return process includes a process for prohibiting the process of limiting the torque to a smaller side when the below-travel amount is equal to or greater than a predetermined amount and the lock-up clutch is in a released state.

[0008] When the amount of undertravel is large, the time until the torque of the internal combustion engine is transmitted to the drive wheels may feel long to the user. Therefore, in the above configuration, in such a case, the process of limiting the torque to a small side is prohibited. This makes it possible to prevent the time until the torque of the internal combustion engine is transmitted to the drive wheels from feeling long to the user, even if the amount of undertravel is large at the end of the stop process.

[0009] 3. A control device for a vehicle as described in 1 above, which executes a below-travel amount acquisition process to acquire the below-travel amount, and the return process includes a restriction relaxation process to gradually relax the process of limiting the torque of the internal combustion engine to a smaller side as the stop process ends, and the restriction relaxation process includes a process of changing the relaxation speed depending on the below-travel amount so that the below-travel amount when the relaxation speed of the torque restriction is large is larger than the below-travel amount when the relaxation speed is small.

[0010] In the above configuration, the speed at which the restriction is relaxed when the underturning amount is large is increased, so that the torque restriction is quickly lifted when the underturning amount is large, and therefore the time until the torque of the internal combustion engine is transmitted to the drive wheels can be prevented from being felt as long by the user.

[0011] 4. A control device for a vehicle as described in 1 or 3 above, which executes an undercut amount acquisition process to acquire the undercut amount, and the return process includes a process for changing the degree of restriction depending on the undercut amount so that the undercut amount when the degree of restriction to the smaller side is small is greater than the undercut amount when the degree of restriction is large.

[0012] In the above configuration, by reducing the degree of restriction when the underturning amount is large, the torque of the crankshaft becomes larger when the underturning amount is large, so that the time until the torque of the internal combustion engine is transmitted to the drive wheels can be prevented from being felt as long by the user.

[0013] 5. A control device for a vehicle as described in any one of 1 to 4 above, which executes a state acquisition process to acquire the state of the lockup clutch, and the return process includes a process of changing the torque limit of the internal combustion engine in accordance with the amount of deviation when the lockup clutch is not in the released state so that the amount of deviation when the torque limit is loose when the lockup clutch is not in the released state is greater than the amount of deviation when the torque limit is strict when the lockup clutch is not in the released state.

[0014] When the lockup clutch is not in the released state, it includes a slip state in addition to the direct connection state. In the slip state, the time until the torque of the crankshaft is transmitted to the drive wheels tends to be longer than in the direct connection state. This tendency is particularly noticeable when the rotation speed of the crankshaft is large below the rotation speed of the input shaft of the transmission. Therefore, in the above configuration, when the lockup clutch is not in the released state, the torque limit is relaxed when the amount of deviation is large compared to when it is zero. As a result, when the amount of deviation is large, the torque of the crankshaft becomes larger. Therefore, it is possible to prevent the time until the torque of the internal combustion engine is transmitted to the drive wheels from being felt as long by the user.

[0015] 6. A control device for a vehicle described in any one of 1 to 5 above, wherein the specified operating unit is an ignition device, the return processing is a processing for limiting the actual torque of the internal combustion engine relative to the torque that can be achieved by the filling efficiency, and includes a limit torque calculation processing and an ignition retard processing, the limit torque calculation processing includes a processing for calculating the limit torque based on the undercut amount, the limit torque is an upper limit guard value of the torque of the internal combustion engine, and the ignition retard processing is a processing for calculating the amount of retardation of the ignition timing using the limit torque and the filling efficiency of the internal combustion engine as inputs.

[0016] In the above configuration, if the ignition timing is constant, the torque of the internal combustion engine is determined according to the charging efficiency. In the above configuration, if the torque determined according to the charging efficiency exceeds the limit torque, the ignition timing is retarded to limit the actual torque to about the limit torque. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing a configuration of a control device and a drive system of a vehicle according to a first embodiment. [Diagram 2] 4 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Diagram 3] 4 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Figure 4] 4 is a time chart illustrating a transition of a limit torque according to the embodiment; [Diagram 5] 4 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. [Figure 6] 4 is a time chart illustrating a transition of a limit torque according to the embodiment; [Figure 7] 4 is a flowchart showing a procedure of a process executed by a control device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] <First embodiment> Hereinafter, the first embodiment will be described with reference to the drawings. As shown in Fig. 1, a vehicle VC is equipped with an internal combustion engine 10. A throttle valve 14 is provided in an intake passage 12 of the internal combustion engine 10. A fuel injection valve 16 is provided in the intake passage 12 downstream of the throttle valve 14.

[0019] When the intake valve 18 opens, the air-fuel mixture in the intake passage 12 flows into a combustion chamber 24 defined by a cylinder 20 and a piston 22. The mixture in the combustion chamber 24 is combusted by spark discharge from an ignition device 26. Energy generated by the combustion is converted into rotational energy of a crankshaft 28 via the piston 22. Meanwhile, when the exhaust valve 30 opens, the combusted mixture is discharged as exhaust gas into an exhaust passage 32.

[0020] The power of the crankshaft 28 can be transmitted to drive wheels 60 via a torque converter 40 and an automatic transmission 50. More specifically, an input shaft 44 of the torque converter 40 is connected to the crankshaft 28. An output shaft 46 of the torque converter 40 is connected to an input shaft 52 of the automatic transmission 50.

[0021] The torque converter 40 is a fluid transmission mechanism, and includes a pump impeller connected to the input shaft 44 and a turbine impeller connected to the input shaft 52 of the automatic transmission 50. In the torque converter 40, torque is transmitted between the pump impeller and the turbine impeller via fluid, thereby transmitting torque between the input shaft 44 and the output shaft 46 of the torque converter 40.

[0022] The torque converter 40 also includes a lock-up clutch 42. The lock-up clutch 42 is a clutch that can directly connect an input shaft 44 and an output shaft 46 of the torque converter 40. The lock-up clutch 42 can be in any one of a directly connected state, a released state, and a slip state. The directly connected state is a state in which the input shaft 44 and the output shaft 46 are directly connected. The released state is a state in which there is almost no torque transmission between the input shaft 44 and the output shaft 46 via the lock-up clutch 42. The slip state is a state in which the input shaft 44 and the output shaft 46 can rotate relative to each other while torque is transmitted between them via the lock-up clutch 42.

[0023] The automatic transmission 50 is a device that can vary the speed ratio, which is the ratio between the rotation speed of an input shaft 52 and the rotation speed of an output shaft 54 ​​. The control device 70 operates various operating parts of the internal combustion engine 10 to control the torque, exhaust component ratio, and the like, which are control variables of the internal combustion engine 10 as a control object. The control device 70 also operates friction engagement elements of the automatic transmission 50 to control the gear ratio of the automatic transmission 50 as a control object. Furthermore, the control device 70 operates the lock-up clutch 42 to control the engagement state of the torque converter 40 as a control object. Fig. 1 shows operation signals MS1 to MS5 of the throttle valve 14, the fuel injector 16, the ignition device 26, the lock-up clutch 42, and the automatic transmission 50.

[0024] In order to control the controlled variable, the control device 70 refers to the intake air amount Ga detected by the air flow meter 80 and the output signal Scr of the crank angle sensor 82. The control device 70 also refers to the output signal Sin of the input rotation sensor 84 and the accelerator operation amount ACCP, which is the amount of depression of the accelerator pedal, detected by the accelerator sensor 86. The control device 70 also refers to the vehicle speed SPD detected by the vehicle speed sensor 88.

[0025] The control device 70 includes a CPU 72, a ROM 74, a peripheral circuit 76, and a communication line 78. The CPU 72, the ROM 74, and the peripheral circuit 76 are capable of communicating with each other via the communication line 78. Here, the peripheral circuit 76 includes a circuit that generates a clock signal that regulates the internal operation, a power supply circuit, a reset circuit, and the like. The control device 70 controls the controlled variable by the CPU 72 executing a program stored in the ROM 74.

[0026] The CPU 72 operates the engagement state of the lock-up clutch 42 using the accelerator operation amount ACCP and the vehicle speed SPD as inputs. The CPU 72 also operates the opening degree of the throttle valve 14 according to the accelerator operation amount ACCP. The CPU 72 also operates the amount of fuel injected from the fuel injection valve 16 so that the air-fuel ratio of the mixture becomes the target air-fuel ratio. The CPU 72 also operates the ignition device 26 to set the ignition timing according to the basic ignition timing. The basic ignition timing is set to the smaller value of the MBT ignition timing and the knock limit ignition timing, that is, the retarded value. The MBT ignition timing is the maximum torque ignition timing, which is the ignition timing at which the maximum torque can be obtained under the current engine operating conditions. The knock limit ignition timing is the advance limit timing of the ignition timing at which knocking can be kept within an acceptable level under the best assumed conditions.

[0027] Furthermore, the CPU 72 executes a fuel cut process, which is a process for stopping the fuel supply to the internal combustion engine 10 by stopping the fuel injection from the fuel injection valve 16. In the following, among the processes executed by the control device 70, a process related to the fuel cut process and a process related to returning from the fuel cut process will be described in detail.

[0028] (Fuel cut processing) Fig. 2 shows the procedure of the fuel cut process. The process shown in Fig. 2 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example, at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "S".

[0029] 2, the CPU 72 first determines whether or not a flag F is "1" (S10). When the flag F is "1", it indicates that a fuel cut process is being executed, whereas when the flag F is "0", it indicates that a fuel cut process is not being executed. When the CPU 72 determines that the flag F is "0" (S10: NO), it determines whether or not the logical product of the following conditions (A) and (B) is true (S12).

[0030] Condition (A): The accelerator pedal is released. Whether or not this condition is met is determined based on the accelerator depression amount ACCP. Condition (A) is a condition that the engine speed NE, which is the rotation speed of the crankshaft 28, is equal to or higher than a first speed NthH. The engine speed NE is calculated by the CPU 72 based on the output signal Scr. The first speed NthH is set to a value higher than the idle speed when the vehicle VC is stopped.

[0031] When the CPU 72 determines that the logical product is true (S12: YES), it sets flag F to "1" (S14). Then, the CPU 72 executes a fuel cut process (S16).

[0032] On the other hand, when it is determined that the flag F is "1" (S10: YES), the CPU 72 determines whether or not the logical sum of the following conditions (c) and (d) is true (S18). Condition (c): The accelerator pedal is depressed. This condition may be satisfied when the accelerator depression amount ACCP is equal to or greater than a predetermined amount.

[0033] Condition (d): The engine speed NE is equal to or less than a second speed NthL. The second speed NthL is set to a value smaller than the first speed NthH. When the CPU 72 determines that the logical sum is false (S18: NO), the CPU 72 proceeds to the process of S16. On the other hand, when the CPU 72 determines that the logical sum is true (S18: YES), the CPU 72 assigns "0" to the flag F (S20). Then, the CPU 72 starts the fuel supply (S22).

[0034] It should be noted that the CPU 72 temporarily ends the series of processes shown in FIG. 2 when it completes the processes of S16 and S22, or when a negative determination is made in the process of S12. (Processing for recovery from fuel cut processing) The procedure for returning from the fuel cut process is shown in Fig. 3. The process shown in Fig. 3 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example, at a predetermined interval.

[0035] In the series of processes shown in FIG. 3, the CPU 72 first determines whether or not the flag F has switched from "1" to "0" (S30). When the CPU 72 determines that the flag F has switched (S30: YES), the CPU 72 determines whether or not the accelerator pedal has been depressed, in other words, whether or not the accelerator is ON (S32). Next, the CPU 72 assigns a value obtained by subtracting the engine rotation speed NE from the input rotation speed Nin to the undertravel amount ΔN (S34). The input rotation speed Nin is the rotation speed of the input shaft 52 of the automatic transmission 50. The input rotation speed Nin is calculated by the CPU 72 based on the output signal Sin. Next, the CPU 72 acquires a lockup variable Vru (S36). The lockup variable Vru is a variable that indicates the state of the lockup clutch 42.

[0036] Then, the CPU 72 judges whether or not the logical product of the following condition (e) and condition (f) is true (S38). Condition (E): The underturning amount ΔN is equal to or greater than a predetermined amount ΔNth. The predetermined amount ΔNth is set to a value that is assumed to result in an excessively long time until the torque of the internal combustion engine 10 is transmitted to the drive wheels 60 after the fuel cut process is stopped if the process of S40 described below is executed. An excessively long time here is a time that the user feels that the responsiveness of the vehicle VC is low.

[0037] Condition (F): This is a condition that the lock-up clutch 42 is in a released state. When the CPU 72 determines that the logical product is false (S38: NO), it calculates the limit torque Gtrq (S40). The limit torque Gtrq is an upper guard value of the torque of the internal combustion engine 10. The CPU 72 gradually increases the limit torque Gtrq. To this end, the CPU 72 calculates an initial value G0 of the limit torque Gtrq and a gradual increase speed variable ΔG that determines the gradual increase speed of the limit torque Gtrq. In detail, the CPU 72 calculates each of the initial value G0 and the gradual increase speed variable ΔG based on the values ​​of the required torque Trq* and the gear ratio variable Vgr. The required torque Trq* is a required value of the torque of the internal combustion engine 10. The required torque Trq* is calculated by the CPU 72 based on the accelerator operation amount ACCP. The gear ratio variable Vgr is a variable that determines the gear ratio of the automatic transmission 50.

[0038] Specifically, with map data stored in advance in the ROM 74, the CPU 72 performs map calculations to determine an initial value G0. Here, the map data uses the required torque Trq* and the gear ratio variable Vgr as input variables, and the initial value G0 as an output variable. Also, with map data stored in advance in the ROM 74, the CPU 72 performs map calculations to determine a gradual increase speed variable ΔG. Here, the map data uses the required torque Trq* and the gear ratio variable Vgr as input variables, and the gradual increase speed variable ΔG as an output variable.

[0039] Incidentally, map data is a set of data consisting of discrete values ​​of input variables and values ​​of output variables corresponding to each of the input variable values. Furthermore, the map calculation may be a process in which, when the value of an input variable matches any of the input variable values ​​in the map data, the value of the corresponding output variable in the map data is used as the calculation result. Furthermore, when the value of an input variable does not match any of the input variable values ​​in the map data, the map calculation may be a process in which a value obtained by interpolating the values ​​of multiple output variables included in the map data is used as the calculation result.

[0040] When the process of S40 is completed, the CPU 72 calculates the ignition retard amount (S42). That is, when the torque Trqr assumed to be generated based on the charging efficiency η and the basic ignition timing exceeds the limit torque Gtrq, the CPU 72 calculates the ignition retard amount according to the amount of the excess. When the process of S42 is completed or when the process of S38 is judged to be positive, the CPU 72 outputs an operation signal MG3 to the ignition device 26 to operate the ignition device 26 (S44). That is, when the process of S38 is judged to be positive, the CPU 72 outputs an operation signal MS3 according to the above-mentioned basic ignition timing. Also, when the process of S42 is completed, the CPU 72 outputs an operation signal MS3 according to a value obtained by retarding the basic ignition timing by the ignition retard amount.

[0041] When the CPU 72 completes the process of S44 or when a negative determination is made in the processes of S30 and S32, the CPU 72 temporarily ends the series of processes shown in FIG. Here, the operation and effects of this embodiment will be described.

[0042] Fig. 4 shows the transition of the limit torque Gtrq set by the process of S40 in association with the stop of the fuel cut process. Fig. 4 also shows the torque Trqr assumed to be generated based on the charging efficiency η and the basic ignition timing.

[0043] As shown in FIG. 4, when the fuel cut process is stopped at time t1, the CPU 72 sets the limit torque Gtrq to an initial value G0. Then, the CPU 72 gradually increases the limit torque Gtrq. As shown in FIG. 4, the limit torque Gtrq is smaller than the above-mentioned assumed torque Trqr. Therefore, the CPU 72 retards the ignition timing to reduce the combustion efficiency so that the torque of the internal combustion engine 10 becomes the limit torque Gtrq. Here, the combustion efficiency is an amount quantified by the ratio of the indicated torque to the amount of fuel in the air-fuel mixture, etc. This process is intended to suppress the occurrence of a shock to the vehicle VC due to a sudden increase in the torque of the crankshaft 28.

[0044] However, if the torque of the internal combustion engine 10 is limited by the limit torque Gtrq when the lockup clutch 42 is in the released state, the time until the torque is transmitted to the drive wheels 60 will be long. Therefore, the CPU 72 does not impose a limit by the limit torque Gtrq on the condition that the lockup clutch 42 is in the released state. This makes it possible to prevent the time until the torque of the internal combustion engine 10 is transmitted to the drive wheels 60 from becoming a length that is uncomfortable for the user.

[0045] <Second embodiment> The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment.

[0046] In the first embodiment described above, the limit torque Gtrq is not provided under a predetermined condition in which the lockup clutch 42 is in a released state. In contrast, in the present embodiment, the limit torque Gtrq is provided even when the lockup clutch 42 is in a released state.

[0047] Fig. 5 shows the procedure of the process for returning from the fuel cut process according to this embodiment. The process shown in Fig. 5 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example, at a predetermined interval. For convenience, the process shown in Fig. 5 that corresponds to the process shown in Fig. 3 is given the same step number and the description thereof is omitted.

[0048] 5, even if the determination in the process of S38 is affirmative, the CPU 72 calculates the limit torque Gtrq (S50). However, the CPU 72 sets the limit torque Gtrq calculated here to be greater than the value calculated in the process of S40.

[0049] Specifically, the CPU 72 calculates an initial value G0 and a gradual increase speed variable ΔG. The initial value G0 calculated in the process of S50 is greater than the initial value G0 calculated in the process of S40. The gradual increase speed variable ΔG calculated in the process of S50 is also greater than the gradual increase speed variable ΔG calculated in the process of S50. The CPU 72 variably sets the initial value G0 and the gradual increase speed variable ΔG in accordance with the required torque Trq* and the gear ratio variable Vgr.

[0050] Specifically, the CPU 72 performs map calculations on the initial value G0 and the gradual increase speed variable ΔG using map data previously stored in the ROM 74. The map data includes data in which the required torque Trq* and the gear ratio variable Vgr are input variables and the initial value G0 is an output variable, and data in which the required torque Trq* and the gear ratio variable Vgr are input variables and the gradual increase speed variable ΔG is an output variable.

[0051] When the CPU 72 completes the process of S50, the process proceeds to S42. In Fig. 6, the solid line indicates the transition of the limit torque Gtrq calculated by the processing of S50. The two-dot chain line indicates the transition of the limit torque Gtrq calculated by the processing of S40. In Fig. 6, the fuel cut processing is also stopped at time t1. After time t1, the limit torque Gtrq calculated by the processing of S50 is greater than the limit torque Gtrq calculated by the processing of S40. Therefore, when the lock-up clutch 42 is in the released state, the CPU 72 sets the ignition timing after the end of the fuel cut processing to a value closer to the basic ignition timing than when the lock-up clutch 42 is in the directly connected state.

[0052] <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the second embodiment.

[0053] In this embodiment, the below amount ΔN is included in the input for the calculation process of the limit torque Gtrq. Fig. 7 shows the procedure of the process for returning from the fuel cut process. The process shown in Fig. 7 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example, at a predetermined interval. For convenience, the process shown in Fig. 7 that corresponds to the process shown in Fig. 5 is given the same step number and the description thereof is omitted.

[0054] In the series of processes shown in FIG. 7, when the CPU 72 completes the process of S36, it determines whether the above condition (f) is satisfied (S38a). When it determines that the condition (f) is satisfied (S38a: YES), the CPU 72 calculates the limit torque Gtrq based on the required torque Trq*, the gear ratio variable Vgr, and the below-rotation amount ΔN (S50a). Here, the CPU 72 calculates the limit torque Gtrq to a larger value when the below-rotation amount ΔN is large than when it is small. In detail, the CPU 72 calculates the initial value G0 and the gradually increasing speed variable ΔG based on the required torque Trq*, the gear ratio variable Vgr, and the below-rotation amount ΔN.

[0055] Specifically, the initial value G0 and the gradually increasing speed variable ΔG are calculated by map calculation using map data previously stored in the ROM 74. Here, one of the map data has the required torque Trq*, the gear ratio variable Vgr, and the undertravel amount ΔN as input variables, and the initial value G0 as an output variable. The other map data has the required torque Trq*, the gear ratio variable Vgr, and the undertravel amount ΔN as input variables, and the gradually increasing speed variable ΔG as an output variable.

[0056] On the other hand, when it is determined that the condition (f) is not satisfied (S38a: NO), the CPU 72 calculates the limit torque Gtrq exclusively for the case where the condition (f) is not satisfied (S40a). Here, the CPU 72 calculates the limit torque Gtrq based on the required torque Trq*, the gear ratio variable Vgr, and the undertravel amount ΔN. Here, the CPU 72 calculates the limit torque Gtrq to a value larger when the undertravel amount ΔN is large than when it is small. That is, the case where the lockup clutch 42 is not in the released state includes the case where the lockup clutch 42 is in a slipping state. In the slipping state, a difference may occur between the input rotation speed Nin and the engine rotation speed NE. And, it is considered that the larger the undertravel amount ΔN, the weaker the connection between the crankshaft 28 and the input shaft 52. Therefore, the larger the undertravel amount ΔN, the longer the time until the torque of the internal combustion engine 10 is transmitted to the drive wheels 60 after the fuel cut process is completed.

[0057] More specifically, the CPU 72 calculates the initial value G0 and the gradually increasing speed variable ΔG based on the required torque Trq*, the gear ratio variable Vgr, and the undertravel amount ΔN. Specifically, the initial value G0 and the gradually increasing speed variable ΔG are calculated by map calculation using map data previously stored in the ROM 74. Here, one of the map data has the required torque Trq*, the gear ratio variable Vgr, and the undertravel amount ΔN as input variables, and the initial value G0 as an output variable. The other map data has the required torque Trq*, the gear ratio variable Vgr, and the undertravel amount ΔN as input variables, and the gradually increasing speed variable ΔG as an output variable.

[0058] When the required torque Trq*, the gear ratio variable Vgr, and the undertravel amount ΔN are the same, the limit torque Gtrq calculated in S50a is set to be equal to or greater than the limit torque Gtrq calculated in the process of S40a.

[0059] <Correspondence> The correspondence between the matters in the above embodiment and the matters described in the above "Means for solving the problem" column is as follows. In the following, the correspondence is shown for each number of the solving means described in the "Means for solving the problem" column. [1] Stop processing corresponds to the processing of S16. The return processing corresponds to the processing of S36 to S44 in FIG. 3, the processing of S36 to S44, S50 in FIG. 5, and the processing of S36, S38a, S40a, S42, S44, S50a in FIG. 7. [2] Undercut amount acquisition processing corresponds to the processing of S34. The state acquisition processing corresponds to the processing of S36. The prohibition processing corresponds to not setting the limit torque when the processing of S38 in FIG. 3 is judged to be positive. [3] Corresponds to the processing exemplified in FIG. 6. The restriction relaxation processing corresponds to the operation of the ignition timing based on the gradual increase speed variable ΔG calculated in the processing of S40, S50 in FIG. 5 or the processing of S40a, S50a in FIG. 7. [4] This corresponds to the operation of the ignition timing based on the initial value G0 calculated in the processes of S40 and S50 in Fig. 5 or S40a and S50a in Fig. 7. [5] This corresponds to the process of S40a. [6] The limit torque calculation process corresponds to the processes of S40, S40a, S50, and S50a. The ignition retard process corresponds to the process of S42.

[0060] <Other embodiments> This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0061] "Input for calculation of limit torque Gtrq" The inputs for the calculation process of the limit torque Gtrq are not limited to the gear ratio variable Vgr and the required torque Trq*. For example, the accelerator operation amount ACCP may be used as a variable indicating the load instead of the required torque Trq*.

[0062] It is not essential that the input for the calculation process of the limit torque Gtrq includes both the gear ratio variable Vgr and a variable indicating the load. For example, with regard to the two variables indicating the gear ratio variable Vgr and the load, only one of them may be included. However, with regard to the two variables indicating the gear ratio variable Vgr and the load, it is not essential that at least one of them is included.

[0063] In the process of S40a, the undertravel amount ΔN is included in the input in consideration of the case where slippage occurs even when the lock-up clutch 42 is not in the released state, but this is not limiting. "About the limit torque Gtrq" In the above embodiment, it has been described that the limit torque Gtrq is determined based on the initial value G0 and the gradual increase speed variable ΔG. In other words, there is no mention of whether the gradual increase speed variable ΔG is determined to be one value or not. Here, the gradual increase speed variable ΔG may be determined to be one value each time the fuel cut process is stopped, but is not limited to this. For example, after the limit torque Gtrq is increased for a specified time by the gradual increase speed variable ΔG, the limit torque Gtrq may be gradually increased according to the value of the second gradual increase speed variable. In that case, the second gradual increase speed variable may be larger than the gradual increase speed variable ΔG as illustrated in FIG. 4 and FIG. 6.

[0064] The limit torque Gtrq is not limited to a case where both the initial value G0 and the gradual increase speed variable ΔG are variably set based on the input variables of the calculation process of the limit torque Gtrq. For example, only one of the initial value G0 and the gradual increase speed variable ΔG may be variably set.

[0065] "About the restriction relaxation process" It is not essential to gradually increase the limit torque Gtrq according to the gradual increase speed variable ΔG. That is, after the limit torque Gtrq is applied, it may be canceled all at once. In other words, it is not essential to gradually relax the process of limiting the torque of the internal combustion engine 10 to a smaller value.

[0066] "About recovery processing" The return process does not necessarily include a process for calculating the amount of retardation of the ignition timing in accordance with the torque determined according to the limit torque Gtrq. For example, instead of the limit torque Gtrq as a guard value for the torque of the internal combustion engine 10, a reduction correction amount for the torque determined from the accelerator operation amount ACCP or the like may be calculated.

[0067] The process of retarding the ignition timing does not necessarily include a process of calculating the retard amount based on the limited torque and the charging efficiency η. For example, when calculating a reduction correction amount for the torque determined from the accelerator operation amount ACCP or the like as described above, the retard amount may be calculated by inputting the reduction correction amount and the charging efficiency η. Also, for example, the retard amount may be calculated based on the input variable of the calculation process of the limited torque Gtrq and the charging efficiency η.

[0068] "Methods for reducing combustion efficiency" In the above embodiment, the ignition timing is retarded from the MBT ignition timing, but this is not limiting. For example, the ignition timing may be advanced from the MBT ignition timing.

[0069] "Regarding the specified operation parts" The internal combustion engine may be a compression ignition engine, and the predetermined operating unit that reduces the combustion efficiency may be a fuel injection valve. In this case, the process of retarding the ignition timing in the above embodiment may be replaced with a process of retarding the injection timing.

[0070] "About the control device" The control device is not limited to a device having a CPU 72 and a ROM 74 and executing software processing. For example, a dedicated hardware circuit such as an ASIC may be provided to perform hardware processing of at least a part of what was processed by software in the above embodiment. That is, the control device may have any of the following configurations (a) to (c). (a) A processing device that executes all of the above processing according to a program, and a program storage device such as a ROM that stores the program. (b) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, the software execution device having a processing device and a program storage device, and the dedicated hardware circuit may be one or any multiple number. [Explanation of symbols]

[0071] 10. Internal combustion engine 12…Intake passage 14...Throttle valve 16...Fuel injector 26…Ignition device 28…Crankshaft 40…Torque converter 42…Lock-up clutch 50…Automatic transmission 60…Drive wheel 70...Control device

Claims

1. The present invention is applied to a vehicle in which the power of an internal combustion engine is transmitted to drive wheels via a transmission, a crankshaft of the internal combustion engine can be mechanically coupled to an input shaft of the transmission by a lock-up clutch, A stop process for stopping combustion control in the internal combustion engine; a return process for operating a predetermined operating unit of the internal combustion engine so as to reduce the combustion efficiency of the internal combustion engine in order to limit the torque of the internal combustion engine to a smaller value when the stop process corresponding to the accelerator operation is terminated; The predetermined operation unit is an operation unit capable of adjusting the combustion efficiency, The recovery process includes a process of changing the amount of decrease in the combustion efficiency in response to the amount of decrease in the combustion efficiency so that the amount of decrease in the combustion efficiency is greater than the amount of decrease in the combustion efficiency is smaller. A vehicle control device, wherein the undershoot amount is the amount by which the rotation speed of the crankshaft of the internal combustion engine is lower than the rotation speed of the input shaft of the transmission.

2. A process of acquiring the undercut amount; A state acquisition process for acquiring a state of the lock-up clutch is executed, 2. The vehicle control device according to claim 1, wherein the return process includes a process for prohibiting the process of limiting the torque to a smaller value when the undertravel amount is equal to or greater than a predetermined amount and the lock-up clutch is in a released state.

3. Execute a below-limit amount acquisition process to acquire the below-limit amount, the return process includes a restriction easing process that gradually relaxes a process of restricting the torque of the internal combustion engine to a smaller side as the stop process ends, 2. The vehicle control device according to claim 1, wherein the restriction relaxation process includes a process of changing the relaxation speed in accordance with the amount of undertravel so that the amount of undertravel when the relaxation speed of the torque restriction is high is greater than the amount of undertravel when the relaxation speed is low.

4. Execute a below-limit amount acquisition process to acquire the below-limit amount, 4. A vehicle control device as claimed in claim 1 or 3, wherein the return processing includes processing for changing the degree of restriction depending on the amount of undercut so that the amount of undercut when the degree of restriction to the smaller side is small is greater than the amount of undercut when the degree of restriction to the smaller side is large.

5. A state acquisition process is executed to acquire a state of the lock-up clutch. A vehicle control device as claimed in any one of claims 1 to 4, wherein the return processing includes processing for changing the torque limit of the internal combustion engine in accordance with the amount of deviation when the lock-up clutch is not in the released state, so that the amount of deviation when the torque limit is loose when the lock-up clutch is not in the released state is greater than the amount of deviation when the torque limit is strict when the lock-up clutch is not in the released state.

6. the predetermined operation unit is an ignition device, the return process is a process for limiting an actual torque of the internal combustion engine with respect to a torque that can be realized by a charging efficiency, and includes a limit torque calculation process and an ignition retard process, the limit torque calculation process includes a process of calculating a limit torque in accordance with the undertravel amount, the limit torque is an upper guard value of the torque of the internal combustion engine, 6. The control device for a vehicle according to claim 1, wherein the ignition timing retard process calculates an amount of retard of the ignition timing using the limit torque and a charging efficiency of the internal combustion engine as inputs.

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