Vehicle control device

Abstract

To provide a control device of a vehicle, which can suppress shock when an engine is stopped.SOLUTION: When an engine stop request for switching an engine 12 from an operating state to a stopping state is determined, a fuel cut for stopping fuel supply to the engine 12 after operating the engine 12 in a self-sustaining operation state for a prescribed period TE after engine torque Te is made into idle torque Teidl and a K0 clutch 20 is released. Therefore, engine speed Ne becomes stable as compared with engine speed Ne just after the K0 clutch 20 is released, for instance, by operating the engine 12 in the self-sustaining operation for the prescribed period TE after the K0 clutch 20 is released, so that shock when the engine 12 is stopped can be suppressed.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a vehicle control device that cuts fuel after releasing a clutch when an engine stop request is determined, and to a technique that can suppress shock when the engine is stopped. [Background technology]

[0002] There is a well-known control device for a vehicle that includes (a) an engine, (b) an electric motor that is connected to a power transmission path between the engine and drive wheels so that power can be transmitted, and (c) a clutch that is provided between the engine and the electric motor. For example, there is a vehicle control device described in Patent Document 1. The vehicle control device in Patent Document 1 discloses a technology that, when stopping the engine in accordance with an engine stop command to switch from engine running (hybrid running) to motor running, for example, makes the output torque of the engine a predetermined idle torque, and then releases the clutch, and when the torque capacity of the clutch becomes zero, performs a fuel cut to quickly stop the supply of fuel to the engine. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-143307 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the fuel cut is performed immediately after the clutch is released, which means that the fuel cut is performed when the engine speed is not stable, and this could result in a shock when the engine is stopped.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a vehicle control device that can suppress the shock that occurs when the engine is stopped. [Means for solving the problem]

[0006] The gist of a first invention is a control device for a vehicle including: (a) an engine; an electric motor connected to a power transmission path between the engine and drive wheels so as to be capable of transmitting power; and a clutch provided between the engine and the electric motor, and (b) when an engine stop request for switching the engine from a running state to a stopped state is determined, an output torque of the engine is set to a predetermined idle torque, the clutch is released, and then the engine is operated in an autonomous driving state. , the period from when the clutch is released until the engine speed is maintained at a predetermined no-load minimum speed. The fuel supply to the engine is stopped after the engine has been operated for a predetermined period of time, and then a fuel cut is performed.

[0008] Also, 2 The gist of the invention is the first invention. Clearly In this system, (a) the presence or absence of the engine stop request is determined at least during hybrid driving in which the vehicle is driven by driving force from the engine, and (b) when the engine stop request is determined, a torque that is reduced when the output torque of the engine is made to be the idle torque is output from the electric motor.

[0009] Also, 3 The gist of the invention is the first invention. Or the second inventionIn this system, (a) the vehicle is provided with a hydraulic control circuit that controls the clutch hydraulic pressure, which is the hydraulic pressure for switching the control state of the clutch, (b) when the engine stop request is determined, the hydraulic control circuit is controlled so that the clutch hydraulic pressure becomes an engagement maintenance hydraulic pressure that generates a torque capacity of the clutch according to the output torque of the engine while the clutch is maintained in an engaged state, and (c) when the output torque of the engine drops to the idle torque, the hydraulic control circuit reduces the clutch hydraulic pressure from the engagement maintenance hydraulic pressure to release the clutch. Effect of the Invention

[0010] According to the vehicle control device of the first invention, (b) when an engine stop request for switching the engine from a running state to a stopped state is determined, the output torque of the engine is set to a predetermined idle torque, the clutch is released, the engine is operated in an independent operating state for a predetermined period of time, and then a fuel cut is performed to stop the supply of fuel to the engine. Therefore, by operating the engine in an independent operating state for the predetermined period of time after the clutch is released, the rotation speed of the engine is stabilized compared to the rotation speed of the engine immediately after the clutch is released, for example, so that a shock when the engine is stopped can be suppressed. The predetermined period is a period from when the clutch is released until the rotation speed of the engine is maintained at a predetermined no-load minimum rotation speed, so that it is possible to preferably determine that the rotation speed of the engine is stabilized after the clutch is released.

[0012] No. 2 According to the vehicle control device of the invention, (a) the presence or absence of the engine stop request is determined at least during hybrid driving in which the vehicle is driven by the driving force from the engine, and (b) when the engine stop request is determined, a torque that is reduced when the output torque of the engine is made the idle torque is output from the electric motor, thereby making it possible to suitably reduce the fluctuation in the torque transmitted to the drive wheels when the engine is stopped.

[0013] No. 3According to the vehicle control device of the invention, (a) the vehicle is provided with a hydraulic control circuit that controls the clutch hydraulic pressure, which is the hydraulic pressure for switching the control state of the clutch, (b) when the engine stop request is determined, the hydraulic control circuit controls the clutch hydraulic pressure to an engagement maintaining hydraulic pressure that generates a torque capacity of the clutch according to the output torque of the engine while the clutch is maintained in an engaged state, and (c) when the output torque of the engine drops to the idle torque, the hydraulic control circuit lowers the clutch hydraulic pressure from the engagement maintaining hydraulic pressure to release the clutch. This makes it possible to suitably reduce fluctuations in torque transmitted to the drive wheels when the clutch is released. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram for explaining a schematic configuration of a vehicle to which the present invention is applied, and is also a diagram for explaining main parts of control functions and a control system for various controls in the vehicle. [Diagram 2] FIG. 2 is a diagram for explaining a portion of the hydraulic control circuit that is involved in supplying hydraulic pressure to the K0 clutch, and is also a diagram for explaining a hydraulic source that supplies hydraulic oil to the hydraulic control circuit. [Diagram 3] 6 is a time chart illustrating an example of each phase of the K0 clutch during the engine stopping process. [Figure 4] 5 is a time chart illustrating an example of each phase of torque control of the engine and the electric motor during the engine stop process. [Diagram 5] 4 is a flowchart illustrating a main part of the control operation of the electronic control device, and is a flowchart illustrating the control operation for suppressing a shock when the engine is switched from an operating state to a stopped state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0016] Fig. 1 is a diagram illustrating a schematic configuration of a vehicle 10 to which the present invention is applied, and also illustrates the main parts of the control functions and control system for various controls in the vehicle 10. In Fig. 1, the vehicle 10 is a hybrid vehicle equipped with an engine 12 and an electric motor MG, which are driving power sources for traveling. The vehicle 10 also includes driving wheels 14 and a power transmission device 16 provided in a power transmission path between the engine 12 and the driving wheels 14.

[0017] The engine 12 is a known internal combustion engine such as a gasoline engine, a diesel engine, etc. An electronic control device (control device) 90 (described later) controls an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, etc., provided in the vehicle 10, to thereby control an engine torque Te, which is an output torque of the engine 12.

[0018] The electric motor MG is a rotating electric machine having a function as a motor that generates mechanical power from electric power and a function as a generator that generates electric power from mechanical power, and is a so-called motor generator. The electric motor MG is connected to a battery 54 provided in the vehicle 10 via an inverter 52 provided in the vehicle 10. The battery 54 is an electricity storage device that supplies and receives electric power to the electric motor MG. The electric motor MG controls the MG torque Tm, which is the output torque of the electric motor MG, by controlling the inverter 52 by an electronic control device 90 described later. For example, when the rotation direction of the electric motor MG is a positive rotation that is the same as the rotation direction when the engine 12 is in operation, the MG torque Tm is a powering torque when it is a positive torque on the acceleration side, and a regenerative torque when it is a negative torque on the deceleration side. The electric power also means electric energy when there is no particular distinction. The power also means torque and force when there is no particular distinction.

[0019] The power transmission device 16 includes a K0 clutch 20, a torque converter 22, an automatic transmission 24, and the like, in a case 18 that is a non-rotating member attached to the vehicle body. The K0 clutch 20 is a clutch provided between the engine 12 and the electric motor MG in a power transmission path between the engine 12 and the drive wheels 14. The torque converter 22 is connected to the engine 12 via the K0 clutch 20. The automatic transmission 24 is connected to the torque converter 22, and is interposed in the power transmission path between the torque converter 22 and the drive wheels 14. The power transmission device 16 also includes a propeller shaft 28 connected to a transmission output shaft 26 that is an output rotating member of the automatic transmission 24, a differential gear 30 connected to the propeller shaft 28, a pair of drive shafts 32 connected to the differential gear 30, and the like. The power transmission device 16 also includes an engine connecting shaft 34 that connects the engine 12 and the K0 clutch 20, an electric motor connecting shaft 36 that connects the K0 clutch 20 and the torque converter 22, and the like.

[0020] The electric motor MG is connected to the electric motor connecting shaft 36 in the case 18 so as to be capable of transmitting power. That is, the electric motor MG is connected to a power transmission path between the engine 12 and the drive wheels 14, in particular, to a power transmission path between the K0 clutch 20 and the torque converter 22. In other words, the electric motor MG is connected to the torque converter 22 and the automatic transmission 24 so as to be capable of transmitting power without passing through the K0 clutch 20.

[0021] The torque converter 22 includes a pump wheel 22a connected to the motor connecting shaft 36, and a turbine wheel 22b connected to a transmission input shaft 38 that is an input rotating member of the automatic transmission 24. The torque converter 22 is a fluid type power transmission device that transmits driving force from each of the driving force sources (engine 12, electric motor MG) from the motor connecting shaft 36 to the transmission input shaft 38 via fluid. The torque converter 22 includes an LU clutch 40 as a direct clutch that connects the pump wheel 22a and the turbine wheel 22b, that is, that connects the motor connecting shaft 36 and the transmission input shaft 38. The LU clutch 40 is a known lock-up clutch.

[0022] The automatic transmission 24 is a known planetary gear type automatic transmission including, for example, one or more planetary gear devices (not shown) and a plurality of engagement devices CB. The engagement devices CB are, for example, known hydraulic friction engagement devices. The engagement devices CB have their respective torque capacities, or CB torque Tcb, changed by the CB hydraulic pressure PRcb, or regulated hydraulic pressure, supplied from the hydraulic control circuit 56, thereby switching between operating states, such as an engaged state and a released state, i.e., control states.

[0023] The automatic transmission 24 is a stepped transmission in which one of a plurality of gear stages (also called gear stages) with different speed ratios (also called gear ratios) γat (=AT input rotation speed Ni / AT output rotation speed No) is formed by engaging one of the engagement devices CB. The automatic transmission 24 switches between gear stages formed according to the accelerator operation of the driver (=operator) and the vehicle speed V by an electronic control device 90 described later. The AT input rotation speed Ni is the rotation speed of the transmission input shaft 38, and is the input rotation speed of the automatic transmission 24. The AT input rotation speed Ni is the same value as the turbine rotation speed Nt, which is the output rotation speed of the torque converter 22. The AT input rotation speed Ni can be expressed by the turbine rotation speed Nt. The AT output rotation speed No is the rotation speed of the transmission output shaft 26, and is the output rotation speed of the automatic transmission 24.

[0024] The K0 clutch 20 is a hydraulic friction engagement device constituted by, for example, a multi-plate or single-plate clutch. The control state of the K0 clutch 20, such as an engaged state or a released state, is switched by changing the K0 torque Tk0, which is the torque capacity of the K0 clutch 20, by the K0 hydraulic pressure PRk0, which is the hydraulic pressure supplied from the hydraulic control circuit 56. The K0 hydraulic pressure PRk0 is a clutch hydraulic pressure that is a hydraulic pressure for switching the control state of the K0 clutch 20.

[0025] In the vehicle 10, when the K0 clutch 20 is in an engaged state, the engine 12 and the torque converter 22 are connected to each other so as to transmit power. On the other hand, when the K0 clutch 20 is in a disengaged state, power transmission between the engine 12 and the torque converter 22 is interrupted. Since the electric motor MG is connected to the torque converter 22, the K0 clutch 20 functions as a clutch that connects and disconnects the engine 12 from the electric motor MG.

[0026] In the power transmission device 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connecting shaft 34 to the driving wheels 14 via the K0 clutch 20, the electric motor connecting shaft 36, the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order. Moreover, the power output from the electric motor MG is transmitted from the electric motor connecting shaft 36 to the driving wheels 14 via the torque converter 22, the automatic transmission 24, the propeller shaft 28, the differential gear 30, the drive shaft 32, etc. in this order, regardless of the control state of the K0 clutch 20.

[0027] The vehicle 10 includes the MOP 58, which is a mechanical oil pump, the EOP 60, which is an electric oil pump, and a pump motor 62. The MOP 58 is connected to the pump impeller 22a, and is rotated and driven by a driving force source (the engine 12, the electric motor MG) to discharge hydraulic oil OIL used in the power transmission device 16 (see FIG. 2, which will be described later). The pump motor 62 is a motor dedicated to the EOP 60 for rotating and driving the EOP 60. The EOP 60 is rotated and driven by the pump motor 62 to discharge hydraulic oil OIL (see FIG. 2, which will be described later). The hydraulic oil OIL discharged by the MOP 58 and the EOP 60 is supplied to a hydraulic control circuit 56. The hydraulic control circuit 56 supplies the CB hydraulic pressure PRcb, the K0 hydraulic pressure PRk0, and the like, which are adjusted based on the hydraulic oil OIL discharged by the MOP 58 and / or the EOP 60. That is, the hydraulic control circuit 56 controls, for example, the CB hydraulic pressure PRcb and the K0 hydraulic pressure PRk0 based on the hydraulic oil OIL discharged by the MOP 58 and / or the EOP 60.

[0028] FIG. 2 is a diagram for explaining a part of the hydraulic control circuit 56 related to the hydraulic supply to the K0 clutch 20, and is also a diagram for explaining a hydraulic source for supplying the hydraulic oil OIL to the hydraulic control circuit 56. In FIG. 2, the MOP 58 and the EOP 60 are provided in parallel in terms of the configuration of the oil passage through which the hydraulic oil OIL flows. The MOP 58 and the EOP 60 each suck up the hydraulic oil OIL that has returned to the oil pan 100 provided at the bottom of the case 18 through a strainer 102, which is a common suction port, and discharge it to each of the discharge oil passages 104, 106. The discharge oil passages 104, 106 are each connected to an oil passage provided in the hydraulic control circuit 56, for example, a line pressure oil passage 108, which is an oil passage through which the line pressure PL flows. The discharge oil passage 104 through which the hydraulic oil OIL is discharged from the MOP 58 is connected to the line pressure oil passage 108 through a MOP check valve 110 provided in the hydraulic control circuit 56. A discharge oil passage 106 through which the hydraulic oil OIL is discharged from the EOP 60 is connected to a line pressure oil passage 108 via an EOP check valve 112 provided in the hydraulic control circuit 56 .

[0029] In addition to the line pressure oil passage 108, the MOP check valve 110, and the EOP check valve 112, the hydraulic control circuit 56 also includes a regulator valve 114, a pressure regulating oil passage 116, a K0 supply oil passage 118, a PL solenoid valve SLT, a pressure regulating valve SK0, a K0 oil passage switching valve SCK0, and the like.

[0030] The regulator valve 114 adjusts the line pressure PL based on the hydraulic oil OIL discharged from at least one of the MOP 58 and the EOP 60. The PL solenoid valve SLT is, for example, a linear solenoid valve, and is controlled by the electronic control device 90 so as to output a pilot pressure Pslt corresponding to the input torque Tinat to the automatic transmission 24, etc., based on the modulator pressure PM to the regulator valve 114. The modulator pressure PM is, for example, a hydraulic pressure adjusted to a constant value by a modulator valve (not shown) using the line pressure PL as a base pressure.

[0031] The pressure regulating valve SK0 is, for example, a linear solenoid valve, and is controlled by the electronic control device 90 so as to regulate the SK0 oil pressure PRsk0, which is an oil pressure supplied to the pressure regulating oil passage 116, using the line pressure PL as a base pressure. The SK0 oil pressure PRsk0 is a regulated oil pressure obtained by regulating the line pressure PL.

[0032] The K0 oil passage switching valve SCK0 is a switching valve in which an oil passage is switched by the operation of a solenoid. Specifically, in an OFF state in which the solenoid is not energized, the K0 oil passage switching valve SCK0 blocks the oil passage between the pressure adjustment oil passage 116 and the K0 supply oil passage 118, and switches the oil passage so as to connect the line pressure oil passage 108 and the K0 supply oil passage 118. On the other hand, in an ON state in which the solenoid is energized, the K0 oil passage switching valve SCK0 blocks the oil passage between the line pressure oil passage 108 and the K0 supply oil passage 118, and switches the oil passage so as to connect the pressure adjustment oil passage 116 and the K0 supply oil passage 118. The K0 supply oil passage 118 is an oil passage connected to the K0 clutch 20, and is an oil passage through which the K0 oil pressure PRk0 supplied to the K0 clutch 20 flows. Therefore, when the K0 oil passage switching valve SCK0 is in the OFF state, the line pressure PL is set to the K0 oil pressure PRk0. On the other hand, when the K0 oil passage switching valve SCK0 is in the ON state, the SK0 oil pressure PRsk0 is set to the K0 oil pressure PRk0. The K0 oil passage switching valve SCK0 is controlled by the electronic control device 90 so as to switch between the OFF state and the ON state.

[0033] In this way, the hydraulic control circuit 56 selectively supplies to the K0 clutch 20, as the K0 hydraulic pressure PRk0, one of the line pressure PL, which is the base pressure of the K0 hydraulic pressure PRk0, and the SK0 hydraulic pressure PRsk0 obtained by regulating the line pressure PL.

[0034] The vehicle 10 further includes an electronic control device 90 including a control device for the vehicle 10. The electronic control device 90 includes a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, and the like, and the CPU executes various controls of the vehicle 10 by performing signal processing according to a program previously stored in the ROM while utilizing the temporary storage function of the RAM. The electronic control device 90 includes computers for engine control, electric motor control, hydraulic control, and the like as necessary.

[0035] The electronic control device 90 is supplied with various signals based on detection values ​​by various sensors provided in the vehicle 10 (e.g., engine rotation speed sensor 70, turbine rotation speed sensor 72, output rotation speed sensor 74, MG rotation speed sensor 76, accelerator opening sensor 78, throttle valve opening sensor 80, brake switch 82, battery sensor 84, oil temperature sensor 86, etc.) (e.g., engine rotation speed Ne, which is the rotation speed of the engine 12, turbine rotation speed Nt, which is the same value as the AT input rotation speed Ni, AT output rotation speed No corresponding to the vehicle speed V, MG rotation speed Nm, which is the rotation speed of the electric motor MG, accelerator opening θacc, which is the amount of accelerator operation by the driver indicating the magnitude of the driver's acceleration operation, throttle valve opening θth, which is the opening of the electronic throttle valve, brake-on signal Bon, which is a signal indicating a state in which the brake pedal for operating the wheel brakes is being operated by the driver, battery temperature THbat, battery charge / discharge current Ibat, and battery voltage Vbat of the battery 54, and hydraulic oil temperature THoil, which is the temperature of the hydraulic oil OIL in the hydraulic control circuit 56).

[0036] The electronic control device 90 outputs various command signals (e.g., an engine control command signal Se for controlling the engine 12, an MG control command signal Sm for controlling the electric motor MG, a CB hydraulic control command signal Sbc for controlling the engagement device CB, an SK0 hydraulic command value Ssk0 which is a command value for the SK0 hydraulic pressure PRsk0 for controlling the pressure regulating valve SK0 as a command value for controlling the K0 clutch 20, and an SCK0 command signal Ssck0 for controlling the on / off of the K0 oil path switching valve SCK0, an LU hydraulic control command signal Slu for controlling the LU clutch 40, an EOP control command signal Seop for controlling the EOP 60, etc.) to each device (e.g., the engine control device 50, the inverter 52, the hydraulic control circuit 56, the pump motor 62, etc.) provided in the vehicle 10.

[0037] The electronic control unit 90 includes a hybrid control means, i.e., a hybrid control unit 92 , a clutch control means, i.e., a clutch control unit 94 , and a gear shift control means, i.e., a gear shift control unit 96 in order to realize various controls in the vehicle 10 .

[0038] The hybrid control unit 92 includes a function as an engine control means, i.e., an engine control unit 92a, that controls the operation of the engine 12, and a function as an electric motor control means, i.e., an electric motor control unit 92b, that controls the operation of the electric motor MG via the inverter 52, and performs hybrid drive control using the engine 12 and the electric motor MG, etc., using these control functions.

[0039] The hybrid control unit 92 calculates the driving demand amount of the vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a driving demand amount map. The driving demand amount map is a relationship that is experimentally or design-wise obtained and stored in advance, that is, a predetermined relationship. The driving demand amount is, for example, a required driving torque Trdem at the driving wheels 14. In other words, the required driving torque Trdem [Nm] is a required driving power Prdem [W] at the vehicle speed V at that time. As the driving demand amount, a required driving force Frdem [N] at the driving wheels 14, a required AT output torque at the transmission output shaft 26, etc. can also be used. In calculating the driving demand amount, an AT output rotation speed No, etc. may be used instead of the vehicle speed V. The hybrid control unit 92 outputs an engine control command signal Se for controlling the engine 12 and an MG control command signal Sm for controlling the electric motor MG so as to realize the required driving power Prdem, taking into account a transmission loss, an auxiliary load, a gear ratio γat of the automatic transmission 24, etc.

[0040] When the required drive torque Trdem can be satisfied only by the output of the electric motor MG, the hybrid control unit 92 sets the drive mode to the motor drive (=EV drive) mode. In the EV drive mode, the hybrid control unit 92 performs EV drive by outputting drive force only from the electric motor MG among the drive power sources (engine 12, electric motor MG) when the K0 clutch 20 is in the released state. On the other hand, when the required drive torque Trdem cannot be satisfied without using at least the output of the engine 12, the hybrid control unit 92 sets the drive mode to the engine drive mode, i.e., hybrid drive (=HV drive) mode. In the HV drive mode, the hybrid control unit 92 performs engine drive by outputting drive force only from the engine 12 among the drive power sources (engine 12, electric motor MG) when the K0 clutch 20 is in the engaged state, i.e., HV drive. On the other hand, even when the required drive torque Trdem can be satisfied only by the output of the electric motor MG, the hybrid control unit 92 establishes the HV drive mode when, for example, the battery 54 needs to be charged or the engine 12 needs to be warmed up.

[0041] In an operating state of the engine 12 in which the K0 clutch 20 is fully engaged, such as in the HV driving mode, the clutch control unit 94 outputs an SCK0 command signal Ssck0 to control the hydraulic control circuit 56 so that the K0 oil passage switching valve SCK0 is in an off state and the line pressure PL is supplied to the K0 clutch 20. At this time, the clutch control unit 94 may control the hydraulic control circuit 56 by outputting an SK0 hydraulic command value Ssk0 and an SCK0 command signal Ssck0 so that the line pressure PL is supplied to the K0 clutch 20 with the value of the SK0 hydraulic pressure PRsk0 by the pressure regulating valve SK0 set to zero [kPa]. On the other hand, when the engine 12 is stopped and the K0 clutch 20 is in a completely released state, such as in the EV driving mode, the clutch control unit 94 controls the hydraulic control circuit 56 by outputting an SK0 hydraulic pressure command value Ssk0 and an SCK0 command signal Ssck0 so that the SK0 hydraulic pressure PRsk0 is supplied to the K0 clutch 20 by the on state of the K0 oil path switching valve SCK0, with the value of the SK0 hydraulic pressure PRsk0 by the pressure regulating valve SK0 set to zero.

[0042] The hybrid control unit 92 determines whether or not there is an engine start request, which is a request to start the engine 12 by switching the control state of the engine 12 from a stopped state to an operating state. For example, the hybrid control unit 92 determines whether or not there is an engine start request based on whether or not the required driving torque Trdem has increased beyond a range that can be covered only by the output of the electric motor MG during the EV driving mode, whether or not there is a need to warm up the engine 12, or whether or not there is a need to charge the battery 54, etc.

[0043] When the hybrid control unit 92 determines that there is an engine start request, the clutch control unit 94 outputs to the hydraulic control circuit 56 an SK0 oil pressure command value Ssk0 and an SCK0 command signal Ssck0 for controlling the K0 clutch 20 in the released state toward the engaged state with the SK0 oil pressure PRsk0 while keeping the K0 oil passage switching valve SCK0 in the on state so as to obtain a K0 torque Tk0 for transmitting the torque required for cranking the engine 12, which is a torque for increasing the engine rotation speed Ne, to the engine 12 side. In this embodiment, the torque required for cranking the engine 12 is referred to as a required cranking torque Tcrn.

[0044] When the hybrid control unit 92 determines that there is an engine start request, it outputs an MG control command signal Sm to the inverter 52 for causing the electric motor MG to output a required cranking torque Tcrn in accordance with switching of the K0 clutch 20 to the engaged state by the clutch control unit 94. Furthermore, when the hybrid control unit 92 determines that there is an engine start request, it outputs an engine control command signal Se to the engine control device 50 in conjunction with cranking of the engine 12 by the K0 clutch 20 and the electric motor MG for starting fuel supply, engine ignition, and the like.

[0045] After starting of the engine 12 by the hybrid control unit 92 is completed and switching of the K0 clutch 20 to the fully engaged state is completed, the clutch control unit 94 outputs an SCK0 command signal Ssck0 to the hydraulic control circuit 56 for switching the K0 oil passage switching valve SCK0 from the on state to the off state and supplying the line pressure PL to the K0 clutch 20. Thereafter, it is preferable that the clutch control unit 94 outputs an SK0 hydraulic pressure command value Ssk0 to the hydraulic control circuit 56 for setting the value of the SK0 hydraulic pressure PRsk0 to zero.

[0046] The hybrid control unit 92 determines whether or not there is an engine stop request, which is a request to stop the engine 12 by switching the control state of the engine 12 from an operating state to a stopped state. For example, the hybrid control unit 92 determines whether or not there is an engine stop request based on whether or not the required drive torque Trdem is within a range that can be covered only by the output of the electric motor MG during the HV driving mode, i.e., hybrid driving, the warming up of the engine 12 and the like is unnecessary, the charging of the battery 54 is unnecessary, and the like.

[0047] When the hybrid control unit 92 determines that there is an engine stop request, that is, when it determines that there is an engine stop request, it outputs an engine control command signal Se to the engine control device 50 to gradually reduce the engine torque Te to bring the engine 12 into an idling state, that is, an idle torque Teidl described below. After that, the hybrid control unit 92 outputs an engine control command signal Se to the engine control device 50 to perform a fuel cut (=FC) to stop the supply of fuel to the engine 12 after the clutch control unit 94 switches the K0 clutch 20 to a completely released state as described below.

[0048] When the hybrid control unit 92 determines that there is an engine stop request, the clutch control unit 94 outputs an SCK0 command signal Ssck0 to the hydraulic control circuit 56 during the transition in which the engine torque Te is gradually reduced, to switch the K0 oil path switching valve SCK0 from the off state to the on state and supply the SK0 oil pressure PRsk0 to the K0 clutch 20, and outputs an SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56 to gradually reduce the value of the SK0 oil pressure PRsk0 from a value that puts the K0 clutch 20 in an engaged state to zero and switch the K0 clutch 20 to a completely released state.

[0049] The shift control unit 96 judges whether or not to shift the automatic transmission 24 by using, for example, a shift map which is a predetermined relationship, and outputs a CB hydraulic control command signal Sbc to the hydraulic control circuit 56 as necessary to execute shift control of the automatic transmission 24. The shift map is a predetermined relationship having a shift line for judging whether or not to shift the automatic transmission 24 on a two-dimensional coordinate system having, for example, vehicle speed V and required driving torque Trdem as variables. In the shift map, the AT output rotation speed No or the like may be used instead of the vehicle speed V, and the required driving force Frdem, accelerator opening θacc, throttle valve opening θth or the like may be used instead of the required driving torque Trdem.

[0050] Here, in order to control the control state of the K0 clutch 20 when the engine 12 is stopped, a plurality of progress stages, i.e., phases, are defined, which are divided according to the control state of the K0 clutch 20 that is switched during the process of stopping the engine 12.

[0051] Fig. 3 is a time chart illustrating an example of each phase of the K0 clutch 20 during the process of stopping the engine 12. In Fig. 3, "K0 control phase" indicates the transition state of each phase of the K0 clutch 20 during the process of stopping the engine 12. These phases are defined as "stop K0 standby", "standby before K0 pressure adjustment", "pressure adjustment before K0 release", "K0 release transition SW", "K0 complete release transition SW", "SW after K0 release", "K0 complete release", etc. "...SW" indicates "...sweep".

[0052] In Figure 3, time t1 indicates the time when, in HV driving mode, i.e., hybrid driving, it is determined that there is an engine stop request, the stop control request flag is switched from off (= OFF) to on (= ON), and engine stop control is started to stop the engine 12, which is in an operating state.

[0053] After the engine stop control is started, a "stop K0 standby" phase (see time t1-t2) is executed. The "stop K0 standby" phase is a phase in which, in preparation for switching the K0 oil passage switching valve SCK0 from the off state to the on state after the engine stop control is started, that is, in preparation for switching the K0 oil pressure PRk0 from the line pressure PL to the SK0 oil pressure PRsk0, the SK0 oil pressure command value Ssk0 is output to ensure the K0 torque Tk0 according to the engine torque Te in advance, while ensuring that the K0 oil pressure PRk0 is the line pressure PL and the K0 clutch 20 is engaged, until the engine torque Te falls to a predetermined engine torque Tef, and the SK0 oil pressure PRsk0 is the EV steady-state K0 oil pressure PRk0ev. The EV steady-state K0 oil pressure PRk0ev is the SK0 oil pressure PRsk0 in the EV driving mode, and the SK0 oil pressure PRsk0 is zero [kPa].

[0054] The SK0 hydraulic pressure command value Ssk0 for securing the K0 torque Tk0 according to the engine torque Te is the SK0 hydraulic pressure command value Ssk0 for setting the SK0 hydraulic pressure PRsk0 to the engagement maintaining hydraulic pressure PRk0c that generates the K0 torque Tk0 according to the engine torque Te in a state in which the K0 clutch 20 is maintained in an engaged state when the K0 hydraulic pressure PRk0 is set to the SK0 hydraulic pressure PRsk0. For example, the engine torque Te when the engagement maintaining hydraulic pressure PRk0c is set is a value obtained by multiplying the actual engine torque Ter (see thick solid line) that is the actual value of the engine torque Te by a safety factor SF (see long dashed line). Specifically, the value obtained by multiplying the actual engine torque Ter by the safety factor SF is set to the required K0 torque Tk0d (see thin solid line), which is the required value of the K0 torque Tk0, and the total K0 hydraulic pressure PRk0 obtained by adding the equivalent of the pack end pressure of the K0 clutch 20 to the equivalent of the K0 hydraulic pressure PRk0 that generates the required K0 torque Tk0d is set as the engagement maintaining hydraulic pressure PRk0c. The pack end pressure of the K0 clutch 20 is the K0 hydraulic pressure PRk0 when the pack clearance of the K0 clutch 20 is reduced, that is, the K0 hydraulic pressure PRk0 for achieving a state in which the piston in the K0 clutch 20 reaches the stroke end and the K0 torque Tk0 is not generated. The K0 clutch 20 generates the K0 torque Tk0 by further increasing the K0 hydraulic pressure PRk0 from the packing completion state. The safety factor SF is a value larger than 1, and is a predetermined value that makes it easier to maintain the engagement state of the K0 clutch 20 with respect to the actual engine torque Ter, for example, within a range in which the engagement maintenance hydraulic pressure PRk0c is not made too large. The actual engine torque Ter is an estimated value of the engine torque Te calculated by applying the engine rotation speed Ne and the throttle valve opening θth to a predetermined engine torque map, for example.

[0055] The predetermined engine torque Tef is a predetermined threshold value that can suppress or prevent hydraulic vibration in the pressure regulating valve SK0 when the engagement maintaining hydraulic pressure PRk0c is output. The predetermined engine torque Tef may be a threshold value that is compared with the actual engine torque Ter, or may be a threshold value that is compared with a value obtained by multiplying the actual engine torque Ter by a safety factor SF.

[0056] In the "standby for stop K0" phase, when the engine torque Te falls to a predetermined engine torque Tef, the phase is transitioned to a "standby before K0 pressure adjustment" phase (see time t2-t3). The "standby before K0 pressure adjustment" phase is a phase in which the K0 oil pressure PRk0 is set to the line pressure PL, and the SK0 clutch 20 is engaged while ensuring that the K0 oil pressure PRsk0 is switched from the line pressure PL of the K0 oil pressure PRk0 to the SK0 oil pressure PRsk0, and an SK0 oil pressure command value Ssk0 is output to set the SK0 oil pressure PRsk0 to the engagement maintenance oil pressure PRk0c, until the pressure adjustment oil passage 116 to which the SK0 oil pressure PRsk0 is supplied is filled with hydraulic oil OIL. Therefore, until the "standby before K0 pressure adjustment" phase, the actual K0 torque Tk0r (see the short dashed line) is generated by the K0 oil pressure PRk0 set to the line pressure PL while ensuring that the K0 clutch 20 is engaged.

[0057] After the start of the "standby before K0 pressure adjustment" phase, when a predetermined filling time TMfil for filling the pressure adjustment oil passage 116 with hydraulic oil OIL has elapsed, the phase is transitioned to a "pressure adjustment before K0 release" phase (see time points t3-t4). The "pressure adjustment before K0 release" phase is a phase in which an SCK0 command signal Ssck0 is output to switch the K0 oil passage switching valve SCK0 from the OFF state to the ON state, switching the K0 oil pressure PRk0 from the line pressure PL to the SK0 oil pressure PRsk0, and outputting an SK0 oil pressure command value Ssk0 that sets the SK0 oil pressure PRsk0 to the engagement maintenance oil pressure PRk0c. The time t3 is the time when the SCK0 command signal Ssck0 is switched from a non-energized (OFF) signal in which the solenoid of the K0 oil passage switching valve SCK0 is de-energized to an energized (ON) signal in which the solenoid of the K0 oil passage switching valve SCK0 is energized, that is, the SK0 switching start time PTstsk0, which is the time when the hydraulic pressure switching starts from the line pressure PL of the K0 hydraulic pressure PRk0 to the SK0 hydraulic pressure PRsk0. In the "Pressure Adjustment Before K0 Release" phase, the actual K0 torque Tk0r is reduced toward the required K0 torque Tk0d by the SK0 hydraulic pressure PRsk0, that is, the K0 hydraulic pressure PRk0 set to the engagement maintaining hydraulic pressure PRk0c. The "Pressure Adjustment Before K0 Release" phase is executed until the engine torque Te is reduced to a predetermined low torque Telow at which it is determined that the K0 clutch 20 can be switched to the released state. The predetermined low torque Telow is, for example, the engine torque Te output to the engine connecting shaft 34, which is the engine output shaft, in an unloaded operating state in which the K0 clutch 20 is released and the engine 12 is operating independently without a load (for example, an idling rotation state at the lowest rotation speed that is the limit of stability, or a state at the lowest rotation speed at which stable operation is possible without a load), that is, the idle torque Teidl [Nm], and is approximately zero [Nm]. That is, the predetermined low torque Telow is the engine torque Te that is considered to be output from the engine 12 in an unloaded state operating according to a predetermined engine torque command value Ste1 described later. Note that the engine torque Te to be compared with the predetermined low torque Telow may be the actual engine torque Ter, or may be a value obtained by multiplying the actual engine torque Ter by a safety factor SF.

[0058] In the "Pressure Adjustment before K0 Release" phase, when the engine torque Te drops to a predetermined low torque Telow, a transition is made to the "K0 Release Transition SW" phase (see time t4-t5). The "K0 Release Transition SW" phase is a phase in which an SK0 oil pressure command value Ssk0 is output to sweep down (= gradually decrease) the SK0 oil pressure PRsk0 from the engagement maintaining oil pressure PRk0c to the pack end pressure of the K0 clutch 20 at a first gradient SW1 in order to release the K0 clutch 20. The "K0 Release Transition SW" phase is executed until the SK0 oil pressure PRsk0 drops to the pack end pressure at which the K0 torque Tk0 becomes zero [Nm].

[0059] In the "K0 release transition SW" phase, when the SK0 oil pressure PRsk0 drops to the pack end pressure, a transition is made to the "K0 complete release transition SW" phase (see time t5-t6). The "K0 complete release transition SW" phase is a phase in which an SK0 oil pressure command value Ssk0 is output that sweeps down the SK0 oil pressure PRsk0 from the pack end pressure to the release assurance oil pressure PRk0rl at a first gradient SW1. The release assurance oil pressure PRk0rl is, for example, a predetermined SK0 oil pressure PRsk0 value that can guarantee that the K0 clutch 20 is in a released state. The "K0 complete release transition SW" phase is executed until the SK0 oil pressure PRsk0 drops to the release assurance oil pressure PRk0rl.

[0060] In the "K0 complete release transition SW" phase, when the SK0 oil pressure PRsk0 drops to the release guarantee oil pressure PRk0rl, a transition is made to the "K0 post-release SW" phase (see time t6-t7). The "K0 post-release SW" phase is a phase in which the SK0 oil pressure command value Ssk0 is output, which sweeps down the SK0 oil pressure PRsk0 from the release guarantee oil pressure PRk0rl to the EV steady-state K0 oil pressure PRk0ev (=0 [kPa]) at the second gradient SW2. The absolute value of the second gradient SW2 is set to a value greater than the absolute value of the first gradient SW1. The "K0 post-release SW" phase is executed until the SK0 oil pressure PRsk0 drops to the EV steady-state K0 oil pressure PRk0ev.

[0061] In the "SW after K0 release" phase, when the SK0 oil pressure PRsk0 drops to the EV steady-state K0 oil pressure PRk0ev (=0), a transition is made to the "K0 complete release" phase (see time points t7-t9). The "K0 complete release" phase is a phase in which the SK0 oil pressure command value Ssk0 is output to set the SK0 oil pressure PRsk0 to the EV steady-state K0 oil pressure PRk0ev until the engine stop control is completed.

[0062] In the "K0 complete release" phase, for example, the engine 12 is made to wait in an independent operation state as necessary (see time t7-t8). After that, the fuel of the engine 12 is cut off and the engine 12 is stopped (see time t8-t9). When it is determined that the engine speed Ne is zero [rpm], the engine stop control is completed (see time t9).

[0063] In the "Stop K0 standby" phase and the "standby before K0 pressure adjustment" phase, the K0 clutch 20 is in a fully engaged state. In the "K0 pressure adjustment before release" phase, the K0 clutch 20 is in a preparation state before being put into a released state. In the "K0 release transition SW" phase, the K0 clutch 20 is in a state in transition to a released state. In the "K0 complete release transition SW" phase, the K0 clutch 20 is in a state in transition to a completely released state. In the "After K0 release SW" phase and the "K0 complete release" phase, the K0 clutch 20 is in a completely released state.

[0064] In addition, since the torques Te, Tm, etc. of the engine 12 and the electric motor MG are controlled when the engine 12 is stopped, multiple progress stages, i.e., phases, are defined, each divided into stages for controlling the torque of the engine 12 and the electric motor MG that are switched during the process of stopping the engine 12.

[0065] Fig. 4 is a time chart for explaining an example of each phase of the torque control of the engine 12 and the electric motor MG in the process of stopping the engine 12, which is performed in parallel with the K0 control in Fig. 3. In Fig. 4, "torque control phase" indicates a transition state of each phase of the torque control of the engine 12 and the electric motor MG in the process of stopping the engine 12. These phases are defined as "engine torque down," "power switching," "engine self-sustaining," "engine stop," etc.

[0066] After the engine stop control is started, an "engine torque down" phase (see time t1-t4A) is executed. The "engine torque down" phase is a phase in which the engine torque Te is reduced (gradually decreased) to an engine torque Te at which the K0 clutch 20 can be released, for example, an idle torque Teidl (predetermined low torque Telow), while ensuring the required driving torque Trdem required by the driver, after the engine stop control is started. For example, the "engine torque down" phase is a phase in which the engine torque Te is reduced to make the engine torque Teidl the idle torque Teidl, and a torque that is reduced when the engine torque Te is made the idle torque Teidl in order to ensure the required driving torque Trdem is output from the electric motor MG. 4, in the "engine torque down" phase, after the start of the engine stop control, the engine torque command value (dynamic engine torque) Ste [Nm] indicated by the thick solid line is lowered (gradually decreased) to a predetermined engine torque command value Ste1 [Nm], and the MG torque command value (dynamic MG torque) Stm [Nm] indicated by the thin solid line is raised so as to compensate for the decrease in the engine torque command value Ste [Nm]. Note that the "engine torque down" phase is executed until the time when the release of the K0 clutch 20 starts (time t4A), that is, until the time when the K0 torque command value (dynamic K0 torque) Stk0 [Nm] indicated by the long dashed line becomes equal to or less than the engine torque command value Ste [Nm]. Further, the engine torque command value Ste is a torque command value for controlling the engine torque Te, the MG torque command value Stm is a torque command value for controlling the MG torque Tm, and the K0 torque command value Stk0 is a torque command value for controlling the K0 torque Tk0 which is the torque capacity of the K0 clutch 20. Further, the predetermined engine torque command value Ste1 is a torque command value for controlling the engine torque Te to the idle torque Teidl. Note that in Fig. 4, the required driving torque command value (dynamic required driving torque) Stemg [Nm] indicated by the short dashed line is constant during the stopping process of the engine 12.

[0067] In the "engine torque down" phase, when the K0 torque command value Stk0 becomes equal to or less than the engine torque command value Ste (predetermined engine torque command value Ste1), a transition is made to the "power switching" phase (see time t4A to time t6). The "power switching" phase is a phase in which the torque capacity of the K0 clutch 20, that is, the K0 torque Tk0, is reduced, and the driving force source transmitted to the driving wheels 14 is switched from the engine 12 and the electric motor MG to only the electric motor MG by releasing the K0 clutch 20. For example, the "power switching" phase is a phase in which the engine torque Te is maintained at the idle torque Teidl, and the torque (K0 torque Tk0) reduced to release the K0 clutch 20 is output from the electric motor MG. As shown in FIG. 4, in the "power switching" phase, the engine torque command value Ste is maintained at the predetermined engine torque command value Ste1, and the MG torque command value Stm is increased so as to compensate for the reduction in the K0 torque command value Stk0. In the "power switching" phase, the MG torque command value Stm is increased until it matches the required drive torque command value Stetm (Stm=Stetm). The "power switching" phase is executed until the K0 torque command value Stk0 becomes zero [Nm] and the K0 clutch 20 is completely released, that is, until time t6.

[0068] In the "power switching" phase, when the K0 clutch 20 is completely released, the engine 12 is transitioned to the "engine independent" phase (see time t6-t8). The "engine independent" phase is a phase in which the engine 12 is operated in an independent state for a predetermined period TE (t8-t6) [sec] after the K0 clutch 20 is released. The independent operation means that the engine 12 is operated independently while continuously outputting the above-mentioned idle torque Teidl (≒0 Nm) in a state in which the engine 12 is disconnected from the driving force source so that the driving force of the engine 12 is not transmitted to the driving wheels 14 (a state in which the engine 12 is idling). For example, the "engine independent" phase is a phase in which the engine torque Te is maintained at the idle torque Teidl, and the MG torque Tm is controlled so that the required driving torque Trdem is provided only by the output of the electric motor MG. As shown in FIG. 4, in the "engine self-sustaining" phase, the engine torque command value Ste is maintained at a predetermined engine torque command value Ste1, and the MG torque command value Stm is made to coincide with the required drive torque command value Stetm. The "engine self-sustaining" phase is executed until the engine speed Ne becomes equal to or less than a predetermined engine speed Ne1 [rpm] (at time t8). The predetermined engine speed Ne1 is, for example, a judgment value for judging whether the engine speed Ne is stable or not. For example, the predetermined engine speed Ne1 is a minimum engine speed at which the engine 12 can stably rotate when the engine 12 is in an idling state, that is, an idle engine speed (minimum engine speed without load), and is a engine speed at which the catalyst function is not adversely affected by releasing the K0 clutch 20 and performing a fuel cut (FC). That is, the predetermined period TE is a period from when the K0 clutch 20 is completely released until the engine speed Ne becomes equal to or less than the predetermined engine speed Ne1, that is, a period from when the K0 clutch 20 is completely released until the engine speed Ne becomes stable.

[0069] In the "engine self-sustaining" phase, when the engine speed Ne becomes equal to or lower than a predetermined speed Ne1, a transition is made to the "engine stop" phase (see time t8-t9). The "engine stop" phase is a phase in which fuel cut (FC) is performed to stop the engine 12. For example, the "engine stop" phase is a phase in which fuel cut (FC) is performed to stop the engine 12, and the MG torque Tm is controlled so that the required drive torque Trdem is satisfied only by the output of the electric motor MG. As shown in FIG. 4, in the "engine stop" phase, fuel cut is performed, and the MG torque command value Stm is made to match the required drive torque command value Stetm. The "engine stop" phase is executed until the engine speed Ne becomes zero [rpm] (time t9).

[0070] Returning to Figure 1, when the hybrid control unit 92 determines that there is an engine stop request, the clutch control unit 94 outputs an SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56, which sets the SK0 oil pressure PRsk0 to the EV steady-state K0 oil pressure PRk0ev (=0), while keeping the SCK0 command signal Ssck0 as a non-energized (OFF) signal.

[0071] When the hybrid control unit 92 determines that there is an engine stop request, the clutch control unit 94 determines, for example, whether the actual engine torque Ter has become equal to or less than a predetermined engine torque Tef during the transition in which the actual engine torque Ter is gradually reduced.

[0072] When the clutch control unit 94 determines that the actual engine torque Ter has become equal to or less than a predetermined engine torque Tef, it outputs an SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56, changing the SK0 oil pressure PRsk0 from the EV steady-state K0 oil pressure PRk0ev (=0) to the engagement maintenance oil pressure PRk0c, while keeping the SCK0 command signal Ssck0 as a non-energized (OFF) signal.

[0073] The clutch control unit 94 determines whether or not the pressure regulating oil passage 116 to which the SK0 oil pressure PRsk0 is supplied has been filled with hydraulic oil OIL based on whether or not a predetermined filling time TMfil has elapsed from the time (time t2) when the SK0 oil pressure PRsk0 is switched from the EV steady-state K0 oil pressure PRk0ev to the engagement maintenance oil pressure PRk0c.

[0074] When the clutch control unit 94 determines that the pressure regulating oil passage 116 has been filled with hydraulic oil OIL, it outputs the SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56, switching the SCK0 command signal Ssck0 from a non-energized (OFF) signal to an energized (ON) signal (switching the K0 oil pressure PRk0 from the line pressure PL to the SK0 oil pressure PRsk0) while keeping the SK0 oil pressure PRsk0 at the engagement maintenance oil pressure PRk0c.

[0075] The clutch control unit 94 determines whether or not the actual engine torque Ter has decreased to a predetermined low torque Telow during the transition in which the actual engine torque Ter is gradually decreased.

[0076] When the clutch control unit 94 determines that the actual engine torque Ter has decreased to a predetermined low torque Telow, it outputs an SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56 to sweep down the SK0 oil pressure PRsk0, i.e., the K0 oil pressure PRk0, from the engagement maintenance oil pressure PRk0c to the pack end pressure of the K0 clutch 20 at a first gradient SW1.

[0077] When the SK0 oil pressure PRsk0 sweeps down from the engagement maintaining oil pressure PRk0c, the clutch control unit 94 determines whether the SK0 oil pressure PRsk0 has become equal to or lower than the pack end pressure of the K0 clutch 20.

[0078] When the clutch control unit 94 determines that the SK0 oil pressure PRsk0 has become lower than the pack end pressure of the K0 clutch 20, it outputs an SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56 to sweep down the SK0 oil pressure PRsk0 from the pack end pressure to the release guarantee oil pressure PRk0rl at a first gradient SW1.

[0079] When the SK0 oil pressure PRsk0 sweeps down from the pack end pressure, the clutch control unit 94 determines whether the SK0 oil pressure PRsk0 has become equal to or lower than the release assurance oil pressure PRk0rl.

[0080] When the clutch control unit 94 determines that the SK0 oil pressure PRsk0 has become lower than the release guarantee oil pressure PRk0rl, it outputs an SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56 to sweep down the SK0 oil pressure PRsk0 from the release guarantee oil pressure PRk0rl to the EV steady-state K0 oil pressure PRk0ev (=0 [kPa]) at a second gradient SW2.

[0081] When the SK0 oil pressure PRsk0 sweeps down from the release security oil pressure PRk0rl, the clutch control unit 94 determines whether the SK0 oil pressure PRsk0 has become the EV steady-state K0 oil pressure PRk0ev (=0 [kPa]).

[0082] When the clutch control unit 94 determines that the SK0 oil pressure PRsk0 has become the EV steady-state K0 oil pressure PRk0ev (= 0 [kPa]), it outputs an SK0 oil pressure command value Ssk0 to the hydraulic control circuit 56 to maintain the SK0 oil pressure PRsk0 at the EV steady-state K0 oil pressure PRk0ev (= 0 [kPa]).

[0083] When the hybrid control unit 92 determines that there is an engine stop request, it outputs an engine control command signal Se to the engine control device 50 to reduce (gradually decrease) the engine torque Te to the idle torque Teidl in order to bring the engine 12 into an idling state, and outputs an MG control command signal Sm to the inverter 52 to cause the electric motor MG to output a torque that is reduced when the engine torque Te is made to the idle torque Teidl in order to ensure the required drive torque Trdem.

[0084] When the hybrid control unit 92 determines that there is an engine stop request, it determines whether or not the K0 clutch 20 has started to release. For example, when the SK0 hydraulic pressure command value Ssk0 [Nm] becomes equal to or less than the engine torque command value Ste [Nm], that is, when the K0 torque Tk0 [Nm] becomes equal to or less than the engine torque Te [Nm], the hybrid control unit 92 determines that the K0 clutch 20 has started to release.

[0085] When the hybrid control unit 92 determines that the K0 clutch 20 has started to release, it outputs an engine control command signal Se to the engine control device 50 to maintain the engine torque Te at the idle torque Teidl, and outputs an MG control command signal Sm to the inverter 52 to increase the MG torque Tm to compensate for the decrease in the K0 torque Tk0.

[0086] When the hybrid control unit 92 determines that the K0 clutch 20 has started to be released, it determines whether or not the K0 clutch 20 has been released, i.e., completely released. For example, when the K0 torque Tk0 becomes zero, that is, when the SK0 oil pressure PRsk0 becomes equal to or lower than the release guarantee oil pressure PRk0rl, the hybrid control unit 92 determines that the K0 clutch 20 has been completely released.

[0087] When the hybrid control unit 92 determines that the K0 clutch 20 is completely released, it outputs an engine control command signal Se to the engine control device 50 to maintain the engine torque Te at the idle torque Teidl for the predetermined period TE in order to operate the engine 12 in an autonomous operation state for the predetermined period TE, and outputs an MG control command signal Sm to the inverter 52 to set the MG torque Tm to the required drive torque Trdem.

[0088] When the hybrid control unit 92 determines that the K0 clutch 20 is completely released, it determines whether or not a predetermined period of time TE has elapsed since the complete release of the K0 clutch 20. For example, the hybrid control unit 92 determines that the predetermined period of time TE has elapsed when the engine rotation speed Ne becomes equal to or lower than a predetermined rotation speed Ne1 after the K0 clutch 20 is completely released.

[0089] When the hybrid control unit 92 determines that the predetermined period TE has elapsed, it outputs an engine control command signal Se for executing a fuel cut (FC) to the engine control device 50, and outputs an MG control command signal Sm for making the MG torque Tm the required drive torque Trdem to the inverter 52. Note that the hybrid control unit 92 outputs an engine control command signal Se for prohibiting a fuel cut (FC) to the engine control device 50 from the time when it is determined that there is an engine stop request (time t1) to the time when it is determined that the predetermined period TE has elapsed (time t8).

[0090] Fig. 5 is a flow chart for explaining the main part of the control operation of the electronic control device 90, which is a flow chart for explaining the control operation for suppressing the shock when the engine 12 is switched from the operating state to the stopped state, and is executed, for example, repeatedly. Fig. 3 and Fig. 4 are diagrams showing an example of a time chart when the control operation shown in the flow chart of Fig. 5 is executed.

[0091] In FIG. 5, first, in step S10 (hereinafter, step will be omitted) corresponding to the function of the hybrid control unit 92, it is determined whether or not there is an engine stop request. If the determination in S10 is negative, this routine is terminated. If the determination in S10 is positive (time t1 in FIGS. 3 and 4), in S20 corresponding to the function of the hybrid control unit 92, the engine torque Te is reduced while the required driving torque Trdem is secured by the MG torque Tm. Also, fuel cut (FC) is prohibited. Next, in S30 corresponding to the function of the clutch control unit 94, the SCK0 command signal Ssck0 is kept as a non-energized (OFF) signal, and the SK0 oil pressure PRsk0 is set to the EV steady-state K0 oil pressure PRk0ev (=0). Next, in S40 corresponding to the function of the clutch control unit 94, it is determined whether or not the actual engine torque Ter has become equal to or less than a predetermined engine torque Tef. If the determination in S40 is negative, S40 is repeatedly executed. If the determination in S40 is positive (time t2 in FIGS. 3 and 4), in S50 corresponding to the function of the clutch control unit 94, the SK0 oil pressure PRsk0 is changed from the EV steady-state K0 oil pressure PRk0ev (=0) to the engagement maintaining oil pressure PRk0c.

[0092] Next, in S60 corresponding to the function of the clutch control unit 94, it is determined whether or not the hydraulic oil OIL is filled in the pressure adjusting oil passage 116 to which the SK0 hydraulic pressure PRsk0 is supplied. If the determination in S60 is negative, S60 is repeatedly executed. If the determination in S60 is positive (at time t3 in Figs. 3 and 4), in S70 corresponding to the function of the clutch control unit 94, the SCK0 command signal Ssck0 is switched from a non-energized (OFF) signal to an energized (ON) signal, and the K0 hydraulic pressure PRk0 is switched from the line pressure PL to the SK0 hydraulic pressure PRsk0. Next, in S80 corresponding to the function of the clutch control unit 94, it is determined whether or not the actual engine torque Ter has decreased to a predetermined low torque Telow. If the determination in S80 is negative, S80 is repeatedly executed. If the determination in S80 is positive (at time t4 in Figs. 3 and 4), in S90 corresponding to the function of the clutch control unit 94, the SK0 hydraulic pressure PRsk0 is swept down at a first gradient SW1 from the engagement maintaining hydraulic pressure PRk0c to the pack end pressure. Next, in S100, which corresponds to the function of the hybrid control unit 92, it is determined whether or not the release of the K0 clutch 20 has started. If the determination in S100 is negative, S100 is repeatedly executed. If the determination in S100 is positive (time t4A in FIG. 4), in S110, which corresponds to the function of the hybrid control unit 92, the engine torque Te is maintained at the idle torque Teidl, and the MG torque Tm is increased to compensate for the decrease in the K0 torque Tk0.

[0093] Next, in S120 corresponding to the function of the clutch control unit 94, it is determined whether the SK0 oil pressure PRsk0 has become equal to or lower than the pack end pressure of the K0 clutch 20. If the determination in S120 is negative, S120 is repeatedly executed. If the determination in S120 is positive (time t5 in Figs. 3 and 4), in S130 corresponding to the function of the clutch control unit 94, the SK0 oil pressure PRsk0 is swept down from the pack end pressure to the release guarantee oil pressure PRk0rl at a first gradient SW1. Next, in S140 corresponding to the function of the hybrid control unit 92, it is determined whether the K0 clutch 20 has been completely released, that is, whether the SK0 oil pressure PRsk0 has become equal to or lower than the release guarantee oil pressure PRk0rl. If the determination in S140 is negative, S140 is repeatedly executed. If the determination in S140 is positive (time t6 in Figs. 3 and 4), in S150 corresponding to the function of the hybrid control unit 92, the engine 12 is operated in an autonomous operation state.

[0094] Next, in S160 corresponding to the function of the clutch control unit 94, the SK0 oil pressure PRsk0 is swept down from the release guarantee oil pressure PRk0rl to the EV steady-state K0 oil pressure PRk0ev (=0 [kPa]) at the second gradient SW2. Next, in S170 corresponding to the function of the clutch control unit 94, it is determined whether the SK0 oil pressure PRsk0 has become the EV steady-state K0 oil pressure PRk0ev (=0 [kPa]). If the determination in S170 is negative, S170 is repeatedly executed. If the determination in S170 is positive (time t7 in Figs. 3 and 4), it is determined in S180 corresponding to the function of the hybrid control unit 92 whether the engine 12 has been autonomously operated for a predetermined period TE, that is, whether the engine rotation speed Ne has become equal to or lower than a predetermined rotation speed Ne1. If the determination in S180 is negative, S180 is repeatedly executed. If the determination in S180 is positive (time t8 in FIGS. 3 and 4), the fuel cut (FC) is performed in S190, which corresponds to the function of the hybrid control unit 92, to stop the engine 12.

[0095] As described above, according to the electronic control device 90 of the vehicle 10 of this embodiment, when an engine stop request for switching the engine 12 from an operating state to a stopped state is determined, the engine torque Te is set to the idle torque Teidl, the K0 clutch 20 is released, and then the engine 12 is operated in an independent operating state for a predetermined period TE, and then a fuel cut is performed to stop the supply of fuel to the engine 12. For this reason, by operating the engine 12 in an independent operating state for the predetermined period TE after the K0 clutch 20 is released, the engine rotation speed Ne becomes stable compared to, for example, the engine rotation speed Ne immediately after the K0 clutch 20 is released, and therefore it is possible to suppress a shock when the engine 12 is stopped.

[0096] According to the electronic control device 90 of the vehicle 10 of this embodiment, the predetermined period TE is the period from when the K0 clutch 20 is released until the engine rotation speed Ne becomes equal to or lower than a predetermined rotation speed Ne1. Therefore, it is possible to suitably determine that the engine rotation speed Ne has stabilized after the K0 clutch 20 is released.

[0097] According to the electronic control device 90 of the vehicle 10 of this embodiment, the presence or absence of an engine stop request is determined at least during hybrid running in which the vehicle runs using driving force from the engine 12, and when the engine stop request is determined, the torque that is reduced when the engine torque Te is made the idle torque Teidl is output from the electric motor MG. This makes it possible to suitably reduce the fluctuation (step) in the torque transmitted to the drive wheels 14 when the engine 12 is stopped.

[0098] According to the electronic control device 90 of the vehicle 10 of this embodiment, the vehicle 10 is provided with a hydraulic control circuit 56 that controls the K0 hydraulic pressure PRk0, which is a hydraulic pressure for switching the control state of the K0 clutch 20, and when an engine stop request is determined, the hydraulic control circuit 56 is controlled so that the K0 hydraulic pressure PRk0 becomes the engagement maintaining hydraulic pressure PRk0c that generates the torque capacity of the K0 clutch 20 according to the engine torque Te of the engine 12 while the K0 clutch 20 is maintained in the engaged state, and when the engine torque Te of the engine 12 drops to the idle torque Teidl, the hydraulic control circuit 56 lowers the K0 hydraulic pressure PRk0 from the engagement maintaining hydraulic pressure PRk0c to release the K0 clutch 20. Therefore, the fluctuation (step) of the torque transmitted to the drive wheels 14 when the K0 clutch 20 is released can be suitably reduced.

[0099] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the present invention can be applied to other embodiments.

[0100] For example, in the above-described embodiment, the "engine independent" phase is executed from when the K0 clutch 20 is released until the engine rotation speed Ne becomes equal to or lower than the predetermined rotation speed Ne1, but, for example, the "engine independent" phase may be executed until a predetermined period of time [sec] has elapsed since the K0 clutch 20 is released. Note that the above-mentioned predetermined period is a period from when the K0 clutch 20 is released until the engine rotation speed Ne becomes stable, which is set in advance through experiments or the like. Also, the "engine independent" phase may be executed, for example, until the engine rotation speed Ne becomes equal to or lower than the predetermined rotation speed Ne1 for a predetermined period of time from when the K0 clutch 20 is released.

[0101] In the above embodiment, a planetary gear type automatic transmission is exemplified as the automatic transmission 24, but the present invention is not limited to this. The automatic transmission 24 may be a synchronous mesh type parallel two-shaft automatic transmission including a known DCT (Dual Clutch Transmission), a known belt type continuously variable transmission, or the like. Alternatively, the automatic transmission 24 does not necessarily have to be provided.

[0102] In the above embodiment, the torque converter 22 is used as the fluid transmission device, but the present invention is not limited to this. For example, instead of the torque converter 22, another fluid transmission device that does not amplify torque, such as a fluid coupling, may be used as the fluid transmission device. Alternatively, the fluid transmission device does not necessarily have to be provided, and may be replaced with, for example, a starting clutch.

[0103] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0104] 10: Vehicle 12: Engine 14: Drive wheel 20:K0 clutch (clutch) 56: Hydraulic control circuit 90: Electronic control device (control device) 92: Hybrid control unit 94: Clutch control unit MG: Electric motor Ne: Engine speed (rotation speed) Ne1: Predetermined rotation speed PRk0: K0 hydraulic pressure (clutch hydraulic pressure) PRk0c: Engagement maintenance hydraulic pressure TE: Predetermined period Te: Engine torque (output torque) Teidl: Idle torque

Claims

1. A control device for a vehicle including an engine, an electric motor connected to a power transmission path between the engine and a drive wheel so as to be capable of transmitting power, and a clutch provided between the engine and the electric motor, When an engine stop request for switching the engine from an operating state to a stopped state is determined, the output torque of the engine is set to a predetermined idle torque and the clutch is released, and then the engine is operated in an independent operating state for a predetermined period of time from the release of the clutch until the rotation speed of the engine is maintained at a predetermined no-load minimum rotation speed, and then a fuel cut is performed to stop the supply of fuel to the engine. A vehicle control device comprising:

2. The engine stop request is determined to be present or absent at least during hybrid driving in which the vehicle is driven by a driving force from the engine, When the engine stop request is determined, a torque that is reduced when the output torque of the engine is set to the idle torque is output from the electric motor.

2. The vehicle control device according to claim 1.

3. The vehicle is provided with a hydraulic control circuit that controls a clutch hydraulic pressure, which is a hydraulic pressure for switching a control state of the clutch, When the engine stop request is determined, the hydraulic control circuit is controlled so that the clutch hydraulic pressure becomes an engagement maintaining hydraulic pressure that generates a torque capacity of the clutch corresponding to an output torque of the engine while the clutch is maintained in an engaged state, When the output torque of the engine decreases to the idle torque, the hydraulic control circuit reduces the clutch hydraulic pressure from the engagement maintaining hydraulic pressure to release the clutch.

3. The vehicle control device according to claim 1 or 2.

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