Vehicle control system

Abstract

To suppress a shock when starting an engine, and suppress deterioration of energy efficiency when operating regenerative braking by an electric motor.SOLUTION: Since slip control is performed before the start of an engine during motor traveling, the start of the engine can be quickly performed, and a shock due to torque fluctuation accompanying the start of the engine can be suppressed. In addition, when the engine is not started and the input torque to a second clutch is less than a predetermined torque during motor traveling, the slip control is ended and the second clutch is brought into an engaged state, so that when regenerative braking is operated with accelerator-off and brake-on, the second clutch is easily brought into the engaged state. Therefore, it is possible to suppress a shock at the time of starting the engine, and to suppress deterioration of the energy efficiency at the time of operating the regenerative braking by an electric motor.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for a vehicle provided with a clutch between an engine, an electric motor, and drive wheels.

Background Art

[0002] A control device for a vehicle including an engine, an electric motor power-transmissively connected to a power transmission path between the engine and drive wheels, a first clutch provided between the engine and the electric motor in the power transmission path, and a second clutch provided between the electric motor and the drive wheels in the power transmission path is well known. For example, the control device for a vehicle described in Patent Document 1 is such a device. In this Patent Document 1, when starting the engine by controlling the first clutch toward the engaged state during motor running in which only the electric motor is used as a power source in the released state of the first clutch and the engaged state of the second clutch, it is disclosed that the second clutch is set in a slip state or a released state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when starting the engine while the vehicle is running on the motor, it is conceivable to control the second clutch to a slip state from before the engine starts, for example, from the viewpoint of suppressing starting shock and improving response. However, if the engine does not start when the second clutch is controlled to a slip state, and the brake pedal is also pressed, the regenerative braking by the electric motor will be activated while the second clutch remains in a slip state. In this case, a portion of the driven torque from the drive wheels transmitted to the electric motor is lost due to the slip of the second clutch, which reduces the regenerative efficiency and may result in a deterioration of energy efficiency.

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle control device that can suppress shock when starting the engine and suppress deterioration of energy efficiency when regenerative braking by an electric motor is activated. [Means for solving the problem]

[0006] The gist of the first invention is a control device for a vehicle comprising: (a) an engine; an electric motor connected to a power transmission path between the engine and the drive wheels so as to transmit power; a first clutch provided between the engine and the electric motor in the power transmission path; and a second clutch provided between the electric motor and the drive wheels in the power transmission path, wherein (b) the switching from motor-driven driving, in which the vehicle is driven using only the electric motor as a power source when the first clutch is disengaged, to engine-driven driving, in which the vehicle is driven using at least the engine as a power source when the first clutch is engaged, is performed while slip control is being performed to put the second clutch in a slip state; and (c) during motor-driven driving, the slip control is performed from before the engine is started in conjunction with the switching to engine-driven driving, and if the engine is not started during motor-driven driving and the input torque to the second clutch falls below a predetermined torque, the slip control is terminated and the second clutch is put into an engaged state. (d) The slip control is a rotational speed control that controls the output of the electric motor so that the slip amount, which is the rotational speed difference between the input rotational speed and the output rotational speed of the second clutch, becomes a target slip amount which is smaller as the input torque decreases, while the second clutch is controlled with a torque capacity corresponding to the input torque to the second clutch that realizes the required driving torque for the vehicle. It is the matter. Furthermore, the gist of the other invention is a control device for a vehicle comprising: (a) an engine; an electric motor connected to a power transmission path between the engine and the drive wheels so as to transmit power; a first clutch provided between the engine and the electric motor in the power transmission path; and a second clutch provided between the electric motor and the drive wheels in the power transmission path, wherein (b) the switching from motor-driven driving, in which the vehicle is driven using only the electric motor as a power source when the first clutch is disengaged, to engine-driven driving, in which the vehicle is driven using at least the engine as a power source when the first clutch is engaged, is performed while slip control is being performed to put the second clutch in a slip state. (c) While the motor is running, the slip control is performed from before the engine is started when switching to the engine. If the engine is not started while the motor is running and the input torque to the second clutch falls below a predetermined torque, the slip control is terminated and the second clutch is engaged. (d) The torque capacity when controlling the second clutch to a packed state with the pack clearance reduced is set as the lower limit of the torque capacity of the second clutch. (e) The predetermined torque is the lower limit of the torque capacity of the second clutch, or a value obtained by subtracting a predetermined variation from the lower limit. [Effects of the Invention]

[0007] The first invention and each of the other inventions described above According to the system, slip control is performed even before the engine starts during motor-driven operation, allowing for a quick start to the engine and suppressing shocks caused by torque fluctuations associated with engine starting. In addition, if the engine does not start during motor-driven operation and the input torque to the second clutch falls below a predetermined torque, slip control is terminated and the second clutch is engaged. Therefore, when regenerative braking is activated by releasing the accelerator and applying the brakes, the second clutch is more likely to be engaged. Thus, shocks during engine starting can be suppressed, and deterioration of energy efficiency during regenerative braking by the electric motor can be suppressed. Furthermore, according to the first invention, the slip control is a rotational speed control that controls the output of the electric motor so that the slip amount of the second clutch becomes the target slip amount, so that the second clutch is appropriately set to the desired slip state. Furthermore, according to the first invention, the target slip amount is set to a smaller value as the input torque to the second clutch decreases, thereby suppressing the engagement shock of the second clutch when the accelerator operation amount is reduced. Furthermore, according to the other invention described above, the torque capacity when controlling the second clutch to a packed state with reduced pack clearance is set to the lower limit of the torque capacity of the second clutch, so that the torque capacity of the second clutch can be increased quickly. Also, since the predetermined torque is the lower limit of the torque capacity of the second clutch, or a value obtained by subtracting a predetermined variation from the lower limit, the slip control is terminated after the input torque to the second clutch falls below the predetermined torque, thereby suppressing unintended slip of the second clutch. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates the schematic configuration of a vehicle to which the present invention is applied, as well as the main parts of the control functions and control systems for various control functions in the vehicle. [Figure 2] This diagram shows the predetermined relationship between the WSC input torque and the WSC target differential rotational speed. [Figure 3] This flowchart explains the key aspects of the control operation of the electronic control unit, specifically the control operation to suppress shock when starting the engine 12 and to suppress the deterioration of energy efficiency when regenerative braking is performed by the electric motor MG. [Figure 4] This figure shows an example of a time chart when the control operation shown in the flowchart in Figure 3 is performed. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0010] Figure 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied, as well as illustrating the main parts of the control functions and control systems for various controls in the vehicle 10. In Figure 1, the vehicle 10 is a hybrid vehicle equipped with an engine 12 and an electric motor MG that function as a power source. The vehicle 10 also includes drive wheels 14 and a power transmission device 16 provided in the power transmission path between the engine 12 and the drive wheels 14.

[0011] Engine 12 is a known internal combustion engine. The engine torque Te of engine 12 is controlled by an engine control device 50 installed in the vehicle 10, which is controlled by an electronic control device 90, which will be described later.

[0012] The electric motor MG is a known rotating electric machine that has the function of an engine that generates mechanical power from electric power and 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 MG torque Tm of the electric motor MG is controlled by the control of the inverter 52 by an electronic control device 90, which will be described later. The MG torque Tm is, for example, a power torque when the rotation direction of the electric motor MG is forward rotation, which is the same rotation direction as when the engine 12 is running, and it is an acceleration side positive torque that generates power from the electric power from the battery 54. The MG torque Tm is, for example, a regenerative torque when the rotation direction of the electric motor MG is forward rotation, which is the deceleration side negative torque that generates power from the power of the engine 12 or the driven force input from the drive wheels 14 side. Electrical power is synonymous with electrical energy unless otherwise specified. Power is synonymous with driving force, torque, and force unless otherwise specified.

[0013] The power transmission device 16 includes, within a case 18 which is a non-rotating member attached to the vehicle body, a disengagement clutch K0, a starting clutch WSC, an automatic transmission 20, a reduction gear mechanism 22, a differential gear 24 connected to the reduction gear mechanism 22, and the like. The disengagement clutch K0 is a first clutch provided between the engine 12 and the motor MG in the power transmission path between the engine 12 and the drive wheels 14. The starting clutch WSC is a second clutch provided between the motor MG and the drive wheels 14 in the power transmission path between the engine 12 and the drive wheels 14. The reduction gear mechanism 22 is connected to a transmission output gear 26 which is an output rotating member of the automatic transmission 20.

[0014] Furthermore, the power transmission device 16 includes a pair of drive shafts 28 and the like connected to the differential gear 24. Furthermore, within the case 18, the power transmission device 16 includes an engine connecting shaft 30 that connects the engine 12 and the disengagement clutch K0, a motor connecting shaft 32 that connects the disengagement clutch K0 and the starting clutch WSC, and the like. Furthermore, within the case 18, the power transmission device 16 includes a mechanical oil pump 34, a transmission member 36 that connects the motor connecting shaft 32 and the mechanical oil pump 34, and the like. The transmission member 36 is composed of, for example, a sprocket and a chain. The mechanical oil pump 34 is driven by a power source (engine 12, motor MG) to discharge hydraulic oil OIL used in the power transmission device 16.

[0015] The motor MG is connected to the motor connecting shaft 32 within the case 18 such that power can be transmitted. That is, the motor MG is connected to the power transmission path between the engine 12 and the drive wheels 14 such that power can be transmitted.

[0016] The disengagement clutch K0 is, for example, a known friction engagement device. The disengagement clutch K0 has its operating state, that is, its control state, such as an engaged state, a slip state, or a released state, switched by changing the K0 torque capacity Tk0, which is the torque capacity of the disengagement clutch K0, by a regulated K0 hydraulic pressure PRk0 supplied from a hydraulic control circuit 56 provided in the vehicle 10.

[0017] The starting clutch WSC is a wet friction engagement device consisting of a multi-plate clutch pressed by, for example, a hydraulic actuator. The control state of the starting clutch WSC is switched by changing the WSC torque capacity Twsc, which is the torque capacity of the starting clutch WSC, with the regulated WSC hydraulic pressure PRwsc supplied from the hydraulic control circuit 56.

[0018] The input side member of the starting clutch WSC is integrally connected to the motor connection shaft 32. The output side member of the starting clutch WSC is integrally connected to the transmission input shaft 38 which is the input rotating member of the automatic transmission 20. The hydraulic actuator included in the starting clutch WSC is composed of a piston, a return spring, an oil chamber, etc. In the starting clutch WSC, when the WSC hydraulic pressure PRwsc is supplied to the oil chamber, the piston moves in the direction of a plurality of friction plates of the starting clutch WSC against the biasing force of the return spring, and the WSC torque capacity Twsc is changed by the WSC hydraulic pressure PRwsc, whereby the control state is switched. In the starting clutch WSC, when the oil chamber is filled with the working oil OIL and the clearance between the plurality of friction plates is filled by the pressing force of the piston, that is, when the pack clearance of the starting clutch WSC is filled, it is in a so-called pack filling completion state. When the WSC hydraulic pressure PRwsc is further increased from the pack filling completion state in the starting clutch WSC, the WSC torque capacity Twsc is generated. The WSC hydraulic pressure PRwsc for achieving the pack filling completion state is the WSC hydraulic pressure PRwsc for the state where the piston reaches the stroke end and the WSC torque capacity Twsc has not occurred, that is, the pack stroke end (=PSE) pressure PRpse. In this embodiment, the WSC torque capacity Twsc when the WSC hydraulic pressure PRwsc is the PSE pressure PRpse is referred to as the PSE torque Tpse. When the WSC hydraulic pressure PRwsc is set to be not less than the PSE pressure PRpse, the WSC torque capacity Twsc is increased in proportion to the WSC hydraulic pressure PRwsc. Incidentally, since the starting clutch WSC is a wet friction engagement device, in the stroke back region where the WSC hydraulic pressure PRwsc is set to be not more than the PSE pressure PRpse, the WSC torque capacity Twsc corresponding to the sliding loss is generated.

[0019] The automatic transmission 20 is a known planetary gear type automatic transmission, comprising, for example, a planetary gear system and an engagement device CB. The engagement device CB includes, for example, a plurality of known friction engagement devices. Each engagement device CB is switched in a control state by changing its respective torque capacity, the CB torque capacity Tcb, which is supplied by a regulated CB hydraulic pressure PRcb from a hydraulic control circuit 56.

[0020] The automatic transmission 20 forms one of several gear stages with different gear ratios γat (= input rotational speed Ni / output rotational speed No) when any of the engagement devices CB are engaged. The input rotational speed Ni is the rotational speed of the transmission input shaft 38 and is the input rotational speed of the automatic transmission 20. The input rotational speed Ni is also the rotational speed of the output side member of the starting clutch WSC. The output rotational speed No is the rotational speed of the transmission output gear 26 and is the output rotational speed of the automatic transmission 20.

[0021] The hydraulic oil discharged by at least one of the mechanical oil pump 34 and the electric oil pump 58, which is driven by a pump motor 60 installed in the vehicle 10, is supplied to the hydraulic control circuit 56.

[0022] Vehicle 10 is equipped with a wheel brake system 62. Each wheel of vehicle 10, including the drive wheels 14, is equipped with a wheel brake 64. The wheel brake system 62 applies a wheel braking torque TBw, which is the braking torque TB applied by the wheel brake 64, to the wheels according to a command from the electronic control unit 90, which will be described later. Under normal circumstances, the wheel brake system 62 applies a wheel braking torque TBw of a magnitude corresponding to the brake operation amount Bra. On the other hand, when the automatic braking function is activated, or when regenerative control is in operation, for example, the wheel brake system 62 applies a wheel braking torque TBw of a magnitude required for each control. The brake operation amount Bra is a signal that represents the magnitude of the brake pedal operation by the driver, i.e., the magnitude of the brake operation, which corresponds to the force applied to the brake pedal.

[0023] Vehicle 10 is further equipped with an electronic control unit 90, which acts as a controller including the control device for vehicle 10. The electronic control unit 90 is composed of a so-called microcomputer, for example, which includes a CPU, RAM, ROM, input / output interface, etc., and performs various controls on vehicle 10.

[0024] The electronic control unit 90 is supplied with various signals based on detection values ​​from various sensors 70, 72, 74, 76, 78, 80, 82, 84, 86, etc., installed in the vehicle 10 (for example, engine rotation speed Ne, which is the rotation speed of the engine 12; MG rotation speed Nm, which is the rotation speed of the electric motor MG and also the rotation speed of the input side member of the starting clutch WSC; input rotation speed Ni; output rotation speed No, which corresponds to the vehicle speed V; accelerator opening θacc; throttle valve opening θth; brake on signal Bon; brake operation amount Bra; battery temperature THbat; battery charge / discharge current Ibat; battery voltage Vbat; and hydraulic oil temperature THoil, which is the temperature of the hydraulic oil).

[0025] The electronic control unit 90 outputs various command signals (for example, engine control command signal Se, MG control command signal Sm, CB hydraulic control command signal Scb, K0 hydraulic control command signal Sk0, WSC hydraulic control command signal Swsc, electric oil pump control command signal Seop, brake control command signal Sbra, etc.) to each device 50, 52, 56, 60, 62 installed in the vehicle 10.

[0026] The electronic control unit 90 includes a power source control means, i.e., a power source control unit 92, a clutch control means, i.e., a clutch control unit 94, and a braking control means, i.e., a braking control unit 96, in order to realize various controls in the vehicle 10.

[0027] The power source control unit 92 includes functions for controlling the operation of the engine 12 and the operation of the electric motor MG, and these control functions enable hybrid drive control of the engine 12 and the electric motor MG.

[0028] The power source control unit 92 calculates the amount of drive requested by the driver to the vehicle 10 by applying, for example, the accelerator opening θacc and the vehicle speed V to the drive request amount map. The drive request amount map is a predetermined relationship for determining the drive request amount, which has been experimentally or design-driven and stored in advance. The drive request amount is, for example, the requested drive torque Trdem [Nm] at the drive wheel 14. The requested drive torque Trdem is, in other words, the requested drive power Prdem [W] at the vehicle speed V at that time. The requested drive force Frdem [N] at the drive wheel 14 can also be used as the drive request amount. The power source control unit 92 outputs an engine control command signal Se to control the engine 12 and an MG control command signal Sm to control the electric motor MG, taking into account transmission losses, auxiliary loads, the gear ratio γat of the automatic transmission 20, etc., in order to realize the requested drive power Prdem.

[0029] The power source control unit 92 sets the drive mode for driving the vehicle 10 to BEV drive mode when the required drive power Prdem can be supplied by the output of the electric motor MG alone. The BEV drive mode is a motor drive mode in which motor driving (=BEV driving) is possible when the disengaged clutch K0 is released and the vehicle is driven using only the electric motor MG as the power source. On the other hand, the power source control unit 92 sets the drive mode to engine drive mode, i.e., HEV drive mode, when the required drive power Prdem cannot be supplied without using at least the output of the engine 12. The HEV drive mode is a hybrid drive mode in which engine driving (=HEV driving) is possible when the disengaged clutch K0 is engaged and the vehicle is driven using at least the engine 12 as the power source. On the other hand, even when the required drive power Prdem can be supplied by the output of the electric motor MG alone, the power source control unit 92 sets the HEV drive mode when charging the battery 54 is necessary or when warming up the engine 12 is necessary.

[0030] The power source control unit 92 determines whether or not there is an engine start request to switch the control state of the engine 12 from a stopped state to an operating state. For example, in BEV drive mode, the power source control unit 92 determines whether or not there is an engine start request based on whether or not the requested drive power Prdem has increased beyond the range that can be covered by the output of the electric motor MG alone, whether or not the engine 12 etc. needs to be warmed up, or whether or not the battery 54 needs to be charged.

[0031] When the power source control unit 92 determines that there is an engine start request, the clutch control unit 94 controls the disengagement clutch K0 to execute engine start control for the engine 12. For example, the clutch control unit 94 outputs a K0 hydraulic control command signal Sk0 to control the disengagement clutch K0 from the open state toward the engaged state so that a K0 torque capacity Tk0 for transmitting cranking torque Tcr to the engine 12 side is obtained. The cranking torque Tcr is a predetermined torque required to crank the engine 12 in order to increase the engine rotational speed Ne.

[0032] When the power source control unit 92 determines that there is an engine start request, it controls the engine 12 and the electric motor MG to perform engine start control. For example, the power source control unit 92 outputs an MG control command signal Sm for the electric motor MG to output cranking torque Tcr in conjunction with the clutch control unit 94 switching the disengaged clutch K0 to the engaged state. The power source control unit 92 also outputs an engine control command signal Se in conjunction with the cranking of the engine 12 to start fuel supply and engine ignition.

[0033] The clutch control unit 94 makes a gear shift decision for the automatic transmission 20 using, for example, a predetermined relationship called a gear shift map, and outputs a CB hydraulic control command signal Scb to switch the gear of the automatic transmission 20 as needed. The gear shift map is a predetermined relationship having a gear shift line for determining the gear shift of the automatic transmission 20 on a two-dimensional coordinate system with, for example, vehicle speed V and requested drive torque Trdem as variables.

[0034] The braking control unit 96 sets the required braking torque TBdem based on, for example, the driver's accelerator operation (e.g., accelerator opening θacc, rate of decrease of accelerator opening θacc), vehicle speed V, gradient of the downhill road, and the driver's brake operation (e.g., brake operation amount Bra, rate of increase of brake operation amount Bra). During deceleration of the vehicle 10, the braking control unit 96 generates a braking torque TB of the vehicle 10 so that the required braking torque TBdem is obtained. The required braking torque TBdem is basically the required braking torque relative to the wheel braking torque TBw, and is realized by the wheel braking torque TBw, but is preferentially realized by the regenerative braking torque TBr, for example from the viewpoint of improving energy efficiency. The regenerative braking torque TBr is the braking torque TB obtained by regenerative braking by the electric motor MG, i.e., regenerative braking.

[0035] Here, the power source control unit 92 switches from BEV driving to HEV driving while performing slip control CNSlp of the starting clutch WSC. Slip control CNSlp is a control that puts the starting clutch WSC into a slip state. This makes it possible to suppress starting shock caused by torque fluctuations associated with the starting control of the engine 12. Starting shock is caused, for example, by control errors in the engine torque Te when the disengagement clutch K0 is partially engaged, synchronized, and after synchronization.

[0036] During the execution of slip control CNSlp, the clutch control unit 94 controls the starting clutch WSC with a WSC torque capacity Twsc corresponding to the WSC input torque Tinw that realizes the required drive torque Trdem for the vehicle 10. In other words, during the execution of slip control CNSlp, the clutch control unit 94 controls the starting clutch WSC so that a WSC torque capacity Twsc equivalent to the WSC input torque Tinw that realizes the required drive torque Trdem is obtained. The WSC input torque Tinw is the input torque to the starting clutch WSC. The WSC input torque Tinw that realizes the required drive torque Trdem is the torque obtained by converting the required drive torque Trdem onto the motor coupling shaft 32, taking into account losses, etc., i.e., the WSC required torque.

[0037] The power source control unit 92 performs slip control CNSlp by increasing the MG power Pm, which is the output of the electric motor MG that realizes the required drive power Prdem, by a predetermined amount when the starting clutch WSC is controlled so that the WSC torque capacity Twsc is equivalent to the WSC required torque. The increase in MG power Pm is consumed by the starting clutch WSC being put into a slip state, but the portion of MG power Pm that realizes the required drive power Prdem is transmitted to the drive wheels 14.

[0038] When the accelerator is pressed, the electric motor MG alone is insufficient to provide sufficient driving force, so it is necessary to quickly switch to HEV driving. In response to this, the power source control unit 92 performs slip control CNslp during BEV driving, even before starting the engine 12 in conjunction with the switch to HEV driving. In other words, the power source control unit 92 performs slip control CNslp during BEV driving in preparation for starting the engine 12. In this embodiment, the slip control CNslp performed during BEV driving is referred to as BEV-time WSC slip control CNslpev.

[0039] If the engine 12 is started when the accelerator is released or lightly pressed, the electric motor MG alone is less likely to cause insufficient driving force compared to starting when the accelerator is fully pressed. Therefore, after it is determined that there is a request to start the engine, the starting clutch WSC should be slowly brought into a slip state while suppressing shocks and acceleration fluctuations. From another perspective, if the accelerator is released and the brakes are applied while the engine 12 is not started during BEV driving, the regenerative braking by the electric motor MG will be activated while the starting clutch WSC is in a slip state. In this case, the regenerative efficiency may decrease due to the slip of the starting clutch WSC, and the energy efficiency may deteriorate.

[0040] Therefore, the power source control unit 92 executes BEV mode WSC slip control CNslpev when the WSC input torque Tinw is relatively large, and does not execute BEV mode WSC slip control CNslpev when the WSC input torque Tinw is relatively small. In other words, if the engine 12 is not started during BEV driving and the WSC input torque Tinw falls below a predetermined torque Tinf, the power source control unit 92 terminates BEV mode WSC slip control CNslpev and engages the starting clutch WSC.

[0041] The predetermined torque Tinf is, for example, the lower limit of the WSC torque capacity Twsc, or a value obtained by subtracting a predetermined variation from the lower limit of the WSC torque capacity Twsc. From the standpoint of rapidly increasing the WSC torque capacity Twsc, the clutch control unit 94 controls the WSC torque capacity Twsc, i.e., the PSE torque Tpse, when controlling the starting clutch WSC to the packing completion state, as the lower limit of the WSC torque capacity Twsc.

[0042] During BEV operation, the starting clutch WSC switches between an engaged state and a slipped state, with a predetermined torque Tinf as the boundary. In particular, there is concern about the engagement shock when the starting clutch WSC is engaged. To address this, the WSC target differential rotational speed ΔNwsctgt in the BEV WSC slip control CNslpev is changed according to the WSC input torque Tinw. For example, the smaller the WSC input torque Tinw, the smaller the WSC target differential rotational speed ΔNwsctgt is set. The WSC target differential rotational speed ΔNwsctgt is the target value of the WSC differential rotational speed ΔNwsc. The WSC differential rotational speed ΔNwsc is the differential rotational speed of the starting clutch WSC, and is the slip amount which is the difference in rotational speed between the input rotational speed and the output rotational speed of the starting clutch WSC. The WSC target differential rotational speed ΔNwsctgt is the target slip amount. The input rotational speed of the starting clutch WSC is the rotational speed of the input-side member of the starting clutch WSC, and is equal to the MG rotational speed Nm. The output rotational speed of the starting clutch WSC is the rotational speed of the output-side member of the starting clutch WSC, and is equal to the input rotational speed Ni. In other words, the WSC differential rotational speed ΔNwsc is the rotational speed difference between the MG rotational speed Nm and the input rotational speed Ni. In this embodiment, the WSC differential rotational speed ΔNwsc (=Nm-Ni) is defined as the value obtained by subtracting the input rotational speed Ni from the MG rotational speed Nm.

[0043] Figure 2 shows a predetermined relationship between the WSC input torque Tinw and the WSC target differential rotational speed ΔNwsctgt. In Figure 2, the WSC target differential rotational speed ΔNwsctgt is set to a smaller value as the WSC input torque Tinw decreases. When the power source control unit 92 performs BEV WSC slip control CNslpev, it calculates the WSC target differential rotational speed ΔNwsctgt by applying the WSC input torque Tinw to the relationship in Figure 2, for example, and sets the target MG rotational speed Nmtgt, which is the target value of the MG rotational speed Nm. The target MG rotational speed Nmtgt is the value obtained by adding the input rotational speed Ni to the WSC target differential rotational speed ΔNwsctgt (=ΔNwsctgt+Ni). The power source control unit 92 controls the MG power Pm by feedback control so that the MG rotational speed Nm becomes the target MG rotational speed Nmtgt.

[0044] Thus, the slip control CNSlp is a rotational speed control that controls the MG power Pm so that the WSC differential rotational speed ΔNwsc becomes a WSC target differential rotational speed ΔNwsctgt, which is smaller as the WSC input torque Tinw decreases, while the starting clutch WSC is controlled by a WSC torque capacity Twsc corresponding to the WSC input torque Tinw that realizes the required drive torque Trdem.

[0045] When the WSC input torque Tinw decreases and approaches a predetermined torque Tinf, the power source control unit 92 sets the WSC target differential rotational speed ΔNwsctgt to zero and executes BEV-time WSC slip control CNslpev to prevent the starting clutch WSC from slipping unintentionally even if the WSC torque capacity Twsc fluctuates. In this way, when the WSC input torque Tinw decreases to near the predetermined torque Tinf, the power source control unit 92 sets the WSC target differential rotational speed ΔNwsctgt to zero until the WSC input torque Tinw falls below the predetermined torque Tinf.

[0046] The BEV WSC slip control CNslpev can achieve both a reduction in regenerative braking losses due to slippage of the starting clutch WSC and a suppression of engagement shock of the starting clutch WSC.

[0047] Figure 3 is a flowchart illustrating the main parts of the control operation of the electronic control unit 90. This flowchart explains the control operation to suppress shock when starting the engine 12 and to suppress deterioration of energy efficiency when regenerative braking by the electric motor MG is performed. This flowchart is repeatedly executed, for example, during BEV driving.

[0048] In Figure 3, each step in the flowchart corresponds to a function of the power source control unit 92. In step S10 (the step will be omitted hereafter), it is determined whether the WSC input torque Tinw is below a predetermined torque Tinf-α. "α" is a hysteresis component set in the determination of whether or not to execute the BEV WSC slip control CNslpev. If the determination in S10 is negative, in S20 it is determined whether the WSC input torque Tinw is above the predetermined torque Tinf. If the determination in S10 is positive, in S30 the BEV WSC slip control CNslpev is terminated, the starting clutch WSC is transitioned to an engaged state and maintained. If the determination in S20 is positive, in S40 the BEV WSC slip control CNslpev is activated. If the determination in S20 is negative, this routine is terminated. Furthermore, as is clear from the flowchart in Figure 3, the BEV WSC slip control CNslpev may repeatedly switch between operation and non-operation, and terminating the BEV WSC slip control CNslpev is equivalent to stopping the BEV WSC slip control CNslpev.

[0049] Figure 4 shows an example of a time chart when the control operation shown in the flowchart of Figure 3 is performed. Figure 4 shows an example of when the accelerator pedal is released during BEV driving. In Figure 4, the BEV WSC slip request flag, which is a request flag for executing BEV WSC slip control CNslpev, is turned on during BEV driving, and BEV WSC slip control CNslpev is executed in preparation for starting the engine 12 (see [1]). When the accelerator pedal is released, the engine 12 is not started, and the WSC input torque Tinw is reduced. In accordance with the decrease in WSC input torque Tinw, the WSC target differential rotational speed ΔNwsctgt is reduced toward zero, and the command value of the MG rotational speed Nm corresponding to the target MG rotational speed Nmtgt is reduced (see [2]). When the WSC input torque Tinw is reduced to near a predetermined torque Tinf, the WSC target differential rotational speed ΔNwsctgt is set to zero (see [3]). The WSC torque capacity Twsc is reduced with a delay relative to the WSC input torque Tinw due to hydraulic response delays, etc. The lower limit of the WSC torque capacity Twsc is set to the PSE torque Tpse (see [4]). When the WSC input torque Tinw falls below a predetermined torque Tinf, the BEV WSC slip request flag is turned off, the BEV WSC slip control CNslpev is terminated, and a WSC engagement instruction is output to switch the starting clutch WSC to the engaged state (see time t1). Subsequently, the WSC torque capacity Twsc is increased, and the starting clutch WSC is switched to the engaged state (see time t2 and later). When the WSC input torque Tinw is a negative torque, the starting clutch WSC is set to the fully engaged state (see [5]).

[0050] As described above, according to this embodiment, BEV-time WSC slip control CNslpev is performed, so the engine 12 can be started quickly and the engine 12 starting shock can be suppressed. In addition, if the WSC input torque Tinw falls below a predetermined torque Tinf, the BEV-time WSC slip control CNslpev is terminated, so the starting clutch WSC is more likely to be engaged when regenerative braking by the electric motor MG is activated. Therefore, shock can be suppressed when starting the engine 12, and deterioration of energy efficiency can be suppressed when regenerative braking by the electric motor MG is activated.

[0051] Furthermore, according to this embodiment, the BEV-time WSC slip control CNslpev is a rotational speed control that controls the MG power Pm so that the WSC differential rotational speed ΔNwsc becomes the WSC target differential rotational speed ΔNwsctgt, thereby ensuring that the starting clutch WSC is appropriately in the desired slip state.

[0052] Furthermore, according to this embodiment, the WSC target differential rotational speed ΔNwsctgt is set to a smaller value as the WSC input torque Tinw decreases, thereby suppressing the engagement shock of the starting clutch WSC when the accelerator pedal is released.

[0053] Furthermore, according to this embodiment, when the WSC input torque Tinw decreases to near a predetermined torque Tinf, the WSC target differential rotational speed ΔNwsctgt is set to zero, thereby suppressing the engagement shock of the starting clutch WSC and preventing unintended slippage of the starting clutch WSC.

[0054] Furthermore, according to this embodiment, since the PSE torque Tpse is set as the lower limit of the WSC torque capacity Twsc, the WSC torque capacity Twsc can be increased quickly. Also, since the predetermined torque Tinf is the lower limit of the WSC torque capacity Twsc, or a value obtained by subtracting a predetermined variation from the lower limit of the WSC torque capacity Twsc, the BEV-time WSC slip control CNslpev is terminated after the WSC input torque Tinw falls below the predetermined torque Tinf, thereby suppressing unintended slip of the starting clutch WSC.

[0055] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0056] For example, in the above-described embodiment, a starting clutch WSC was exemplified as the second clutch provided between the electric motor MG and the drive wheel 14 in the power transmission path between the engine 12 and the drive wheel 14, but the embodiment is not limited to this. For example, instead of the starting clutch WSC, an engagement device CB that can put the automatic transmission 20 into a power-disabled state, i.e., a neutral state, may be used as the second clutch. Alternatively, if a fluid-type transmission device such as a torque converter is provided in the vehicle 10 instead of the starting clutch WSC, a lock-up clutch provided in the fluid-type transmission device may be used as the second clutch. Note that when a starting clutch WSC is used as the second clutch, an automatic transmission 20 is not necessarily required.

[0057] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of Symbols]

[0058] 10: Vehicles 12: Engine 14: Drive wheels 90: Electronic control unit (control device) K0: Disconnecting clutch (first clutch) MG: Electric motor WSC: Starting Clutch (Second Clutch)

Claims

1. A control device for a vehicle comprising an engine, an electric motor connected to a power transmission path between the engine and the drive wheels so as to transmit power, a first clutch provided between the engine and the electric motor in the power transmission path, and a second clutch provided between the electric motor and the drive wheels in the power transmission path, The switching from motor-driven operation, in which the vehicle is driven using only the electric motor as a power source when the first clutch is disengaged, to engine-driven operation, in which the vehicle is driven using at least the engine as a power source when the first clutch is engaged, is performed while slip control is being performed to put the second clutch in a slip state. During motor-driven operation, the slip control is performed before the engine starts upon switching to engine-driven operation. If the engine does not start during motor-driven operation and the input torque to the second clutch falls below a predetermined torque, the slip control is terminated and the second clutch is engaged. The vehicle control device is characterized in that, while the slip control is being controlled by controlling the second clutch with a torque capacity corresponding to the input torque to the second clutch that realizes the required driving torque for the vehicle, the motor output is controlled so that the slip amount, which is the difference in rotational speed between the input rotational speed and the output rotational speed of the second clutch, becomes a target slip amount which decreases as the input torque decreases.

2. The vehicle control device according to claim 1, characterized in that when the input torque to the second clutch decreases to near the predetermined torque, the target slip amount is set to zero until the input torque falls below the predetermined torque.

3. The torque capacity when controlling the second clutch to a packed state where the pack clearance is reduced is set as the lower limit of the torque capacity of the second clutch. The vehicle control device according to claim 1 or 2, characterized in that the predetermined torque is the lower limit of the torque capacity of the second clutch, or a value obtained by subtracting a predetermined variation from the lower limit.

4. A control device for a vehicle comprising: an engine; an electric motor connected to a power transmission path between the engine and a drive wheel so as to transmit power; a first clutch provided between the engine and the electric motor in the power transmission path; and a second clutch provided between the electric motor and the drive wheel in the power transmission path, The switching from motor-driven operation, in which the vehicle is driven using only the electric motor as a power source when the first clutch is disengaged, to engine-driven operation, in which the vehicle is driven using at least the engine as a power source when the first clutch is engaged, is performed while slip control is being performed to put the second clutch in a slip state. During motor-driven operation, the slip control is performed before the engine starts upon switching to engine-driven operation. If the engine does not start during motor-driven operation and the input torque to the second clutch falls below a predetermined torque, the slip control is terminated and the second clutch is engaged. The torque capacity when controlling the second clutch to a packed state where the pack clearance is reduced is set as the lower limit of the torque capacity of the second clutch. A vehicle control device characterized in that the predetermined torque is the lower limit of the torque capacity of the second clutch, or a value obtained by subtracting a predetermined variation from the lower limit.

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